WO2017138609A1 - Uv curable acrylic polymer and method for producing same, and uv curable hot melt adhesive - Google Patents

Uv curable acrylic polymer and method for producing same, and uv curable hot melt adhesive Download PDF

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Publication number
WO2017138609A1
WO2017138609A1 PCT/JP2017/004736 JP2017004736W WO2017138609A1 WO 2017138609 A1 WO2017138609 A1 WO 2017138609A1 JP 2017004736 W JP2017004736 W JP 2017004736W WO 2017138609 A1 WO2017138609 A1 WO 2017138609A1
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acrylic polymer
group
meth
curable acrylic
molecule
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PCT/JP2017/004736
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French (fr)
Japanese (ja)
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章滋 桑原
川端　和裕
戸田　智基
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積水フーラー株式会社
積水化学工業株式会社
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Priority to JP2017544039A priority Critical patent/JP6275349B2/en
Publication of WO2017138609A1 publication Critical patent/WO2017138609A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers

Definitions

  • the present invention relates to an ultraviolet curable acrylic polymer, a method for producing the same, and an ultraviolet curable hot melt adhesive.
  • Acrylic adhesives are used in adhesive tapes, consumer product labels, sticky notes, and other electronic devices such as personal computers, smartphones, TVs, and digital cameras, taking advantage of their transparency, heat resistance, and weather resistance. It is used for applications such as optical displays. As described above, the acrylic pressure-sensitive adhesive is used in various applications. On the other hand, the tackiness required for the acrylic pressure-sensitive adhesive is different for each use, and the acrylic pressure-sensitive adhesive is required to have desired tackiness depending on the use.
  • hot melt pressure-sensitive adhesive does not require a drying process in the tape and label application process, and therefore does not require equipment for the drying process, and greatly contributes to energy saving.
  • thermoplastic acrylic pressure-sensitive adhesives It is difficult for conventional thermoplastic acrylic pressure-sensitive adhesives to exhibit desired tackiness depending on the application.
  • development of an ultraviolet curable hot-melt pressure-sensitive adhesive that develops desired tackiness according to the application has been promoted using a crosslinking reaction by ultraviolet rays.
  • Patent Document 1 discloses an ultraviolet curable hot melt adhesive containing a vinyl copolymer (A) having a glass transition temperature of ⁇ 5 ° C. or less and a weight average molecular weight of 50,000 to 350,000.
  • An ultraviolet curable hot melt pressure-sensitive adhesive composition is disclosed, which is a composition obtained by polymerizing the vinyl copolymer (A) with a specific monomer component as a constituent component. .
  • Patent Document 2 discloses a composition containing a polyacrylate for processing from a melt and a stabilizer having at least one phosphite group.
  • JP 2006-299017 A Japanese Patent Laid-Open No. 2001-253959
  • the UV curable hot melt pressure-sensitive adhesive is used by being applied on an adherend or a support while maintaining a molten state in use, so that it is exposed to a high temperature melted for a long time. It becomes.
  • the ultraviolet curable hot-melt pressure-sensitive adhesive composition has low thermal stability at the time of melting and is deteriorated by heat at the time of melting. As a result, the UV curable hot melt pressure-sensitive adhesive composition gels, resulting in a problem that coating property is lowered and clogging occurs in piping in the coating machine. Further, the curability of the ultraviolet curable hot melt pressure-sensitive adhesive composition is lowered, and further, there arises a problem that the ultraviolet curable hot melt pressure-sensitive adhesive composition after curing does not exhibit desired tackiness.
  • composition disclosed in Patent Document 2 improves the storage stability of an ultraviolet curable acrylic polymer by adding a stabilizer having a phosphite group to the ultraviolet curable acrylic polymer.
  • a stabilizer has a problem that the curability of the composition by irradiation with ultraviolet rays is lowered, and it also has a problem that the production efficiency is low because a stabilizer mixing step is required.
  • the present invention is an ultraviolet curable acrylic that can be used as an ultraviolet curable hot melt pressure-sensitive adhesive that exhibits excellent thermal stability and coating properties when melted and exhibits desired tackiness upon curing without the need for a stabilizer.
  • a polymer is provided.
  • the ultraviolet curable acrylic polymer of the present invention is an ultraviolet curable acrylic polymer that is cross-linked by irradiation of ultraviolet rays, and the rate of change in weight average molecular weight converted by standard polystyrene after heating at 150 ° C. for 6 hours. Is -20 to 20%.
  • the ultraviolet curable acrylic polymer of the present invention has the above-described configuration, the ultraviolet curable hot melt is excellent in thermal stability at the time of melting and coating properties and exhibits desired tackiness upon curing. It can be used as an adhesive.
  • the ultraviolet curable acrylic polymer of the present invention is characterized in that the change rate of the weight average molecular weight converted to standard polystyrene after being heated at 150 ° C. for 6 hours is ⁇ 20 to 20%.
  • the ultraviolet curable acrylic polymer of the present invention is excellent in thermal stability and coating property when melted by setting the change rate of the weight average molecular weight Mw to ⁇ 20 to 20%, and after curing by ultraviolet irradiation. Expresses desired tackiness.
  • the rate of change of the weight average molecular weight in terms of the standard polystyrene after heating at 150 ° C. for 6 hours in the UV curable acrylic polymer is ⁇ 20 to 20%, preferably ⁇ 15 to 15%, ⁇ 10 ⁇ 10% is more preferred.
  • the weight average molecular weight and the number average molecular weight of the ultraviolet curable acrylic polymer are values measured in the following manner.
  • the weight average molecular weight and the number average molecular weight of the ultraviolet curable acrylic polymer are polystyrene-converted values measured by a GPC (gel permeation chromatography) method. Specifically, an ultraviolet curable acrylic polymer was collected, THF (tetrahydrofuran) was added to dilute the ultraviolet curable acrylic polymer 300 times, and filtering (trade name: Millex-LH ⁇ 0. 45 ⁇ m>) to prepare a measurement sample.
  • GPC gel permeation chromatography
  • the weight average molecular weight and number average molecular weight of the ultraviolet curable acrylic polymer can be measured by the GPC method.
  • the weight average molecular weight and number average molecular weight of the ultraviolet curable acrylic polymer can be measured, for example, with the following measuring apparatus and measurement conditions.
  • the rate of change in weight average molecular weight converted by standard polystyrene after heating at 150 ° C. for 6 hours in an ultraviolet curable acrylic polymer refers to a value measured in the following manner.
  • the weight average molecular weight of the ultraviolet curable acrylic polymer before heating is measured as described above, and the value is defined as the initial weight average molecular weight.
  • the ultraviolet curable acrylic polymer is heated at 150 ° C. for 6 hours. Thereafter, the weight average molecular weight of the ultraviolet curable acrylic polymer is measured as described above, and the value is defined as the weight average molecular weight after heating.
  • the ultraviolet curable acrylic polymer is not particularly limited as long as the above-described change rate of the weight average molecular weight is ⁇ 20 to 20%, and the acrylic polymer is cured by a cross-linking reaction between molecules caused by ultraviolet irradiation.
  • the following acrylic polymers are preferable.
  • (Meth) acrylic acid means acrylic acid or methacrylic acid.
  • (Meth) acrylate means acrylate or methacrylate.
  • (meth) acrylate having no UV-reactive group in the molecule contains 85 to 99.8% by weight of (meth) acrylate having no UV-reactive group in the molecule and 0.1 to 5% by weight of monomer having the UV-reactive group in the molecule, A polymer of a monomer composition containing 70% by mass or more of the main (meth) acrylate in the (meth) acrylate that is not present in the molecule, and having a terminal thiol compound residue as a chain transfer agent A curable acrylic polymer is preferred.
  • (meth) acrylate having no UV-reactive group in the molecule 85 to 99.8% by mass of (meth) acrylate having no UV-reactive group in the molecule, 0.1 to 5% by mass of monomer having an UV-reactive group in the molecule, and 0.1 to 10 (meth) acrylic acid
  • An ultraviolet curable acrylic polymer having a terminal thiol compound residue is preferred.
  • the ultraviolet curable acrylic polymer is a polymer containing a (meth) acrylate unit having no ultraviolet reactive group in the molecule and a monomer unit having an ultraviolet reactive group in the molecule. It is preferable that the molecule does not have an aromatic ring that absorbs light in the ultraviolet region.
  • the ultraviolet curable acrylic polymer is a polymer containing a (meth) acrylate unit having no ultraviolet reactive group in the molecule, a monomer unit having an ultraviolet reactive group in the molecule, and a (meth) acrylic acid unit. It is preferable that none of the monomer units has an aromatic ring that absorbs light in the ultraviolet region in the molecule.
  • the (meth) acrylate having no UV-reactive group in the molecule is not particularly limited.
  • alkyl Preferably contains an acrylate.
  • the alkyl (meth) acrylate having 1 to 8 carbon atoms in the alkyl group is preferably 2-ethylhexyl (meth) acrylate, methyl (meth) acrylate or butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate And butyl (meth) acrylate is more preferable, and 2-ethylhexyl acrylate and butyl acrylate are particularly preferable.
  • the (meth) acrylates that do not have an ultraviolet reactive group in the molecule may be used alone or in combination of two or more.
  • ultraviolet reactive group refers to a functional group that is excited by irradiation of ultraviolet rays to generate radicals, and the radicals generate a hydrogen abstraction reaction, thereby forming a crosslinked structure between ultraviolet curable acrylic polymer molecules.
  • Examples of the ultraviolet reactive group include a benzophenone group, a benzoin group, a maleimide group, and derivatives thereof.
  • the content of the (meth) acrylate unit having no ultraviolet reactive group in the molecule is preferably 85 to 99.8% by mass, more preferably 91.5 to 97% by mass, and 92 It is particularly preferably 5 to 95% by mass.
  • the UV-curable acrylic polymer has an appropriate viscosity when melted, and the UV-curable acrylic polymer The coatability is improved, which is preferable.
  • the ultraviolet curable acrylic polymer after curing by ultraviolet irradiation expresses desired tackiness, which is preferable.
  • the monomer having an ultraviolet reactive group in the molecule is not particularly limited as long as it can be polymerized with a (meth) acrylate having an ultraviolet reactive group in the molecule and no ultraviolet reactive group in the molecule.
  • an ultraviolet reactive group is the same as the above, description is abbreviate
  • a monomer having a UV-reactive group in the molecule it can be polymerized with (meth) acrylate and (meth) acrylic acid having a UV-reactive group in the molecule and having no UV-reactive group in the molecule. Is preferred.
  • the UV-reactive group possessed by the monomer having an UV-reactive group in the molecule is not particularly limited, and examples thereof include a benzophenone group, a benzoin group, a maleimide group, and derivatives thereof. preferable.
  • the UV-reactive group may be contained alone or in combination of two or more in the molecule.
  • the monomer having an ultraviolet reactive group in the molecule is preferably an acrylic monomer having an ultraviolet reactive group in the molecule, more preferably a (meth) acrylate having an ultraviolet reactive group in the molecule, and a benzophenone group in the molecule.
  • (Meth) acrylates in the above are particularly preferred, and 4-acryloyloxybenzophenone is most preferred.
  • numerator may be used independently, or 2 or more types may be used together.
  • the acrylic monomer having an ultraviolet reactive group in the molecule is not particularly limited.
  • the content of the monomer unit having an ultraviolet reactive group in the molecule is preferably 0.1 to 5% by mass, more preferably 0.15 to 1% by mass, and 0.2 to 0%. .6% by mass is particularly preferred.
  • the ultraviolet curable acrylic polymer exhibits desired adhesiveness upon curing by ultraviolet irradiation.
  • monomer units having UV reactive groups in the molecule are all monomer units constituting the main chain (all monomer units constituting the main chain) 350 to It is preferable to have one for every 600.
  • the UV-curable acrylic polymer after curing by UV irradiation exhibits appropriate cohesive strength.
  • the ultraviolet curable acrylic polymer since the ultraviolet curable acrylic polymer has excellent resistance to external force, it can prevent the surroundings from being contaminated by deformation and develops desired tackiness by curing by ultraviolet irradiation. .
  • the number of all monomer units constituting the main chain is calculated in the following manner with respect to one monomer unit having an ultraviolet reactive group in the molecule.
  • the content of the monomer X 0 having an ultraviolet reactive group in the molecule is Y 0 % by mass, and the ultraviolet reactive group is a molecule.
  • the contents of monomers X 1 to Xn other than monomer X 0 are Y 1 to Yn mass%, respectively.
  • the molecular weight of the monomer X 0 having an ultraviolet reactive group in the molecule is defined as M 0 .
  • the molecular weights of the monomers X 1 to Xn other than the monomer X 0 having an ultraviolet reactive group in the molecule are M 1 to Mn, respectively.
  • the number of all monomer units constituting the main chain is calculated with respect to one monomer unit having an ultraviolet reactive group in the molecule in the main chain of the ultraviolet curable acrylic polymer.
  • Y 0 + Y 1 +... + Yn 100.
  • Number of all monomer units constituting the main chain with respect to one monomer unit having an ultraviolet reactive group in the molecule (Y 0 / M 0 + Y 1 / M 1 + Y 2 / M 2 +... + Yn / Mn) / (Y 0 / M 0 )
  • the ultraviolet curable acrylic polymer preferably contains a (meth) acrylic acid unit.
  • the content of the (meth) acrylic acid unit is preferably 0.1 to 10% by mass, and more preferably 4.5 to 8% by mass.
  • the ultraviolet curable acrylic polymer has excellent thermal stability at the time of melting and an appropriate viscosity at the time of melting. It has good coatability.
  • the ultraviolet curable acrylic polymer after curing by irradiation with ultraviolet rays exhibits desired tackiness and high tackiness.
  • the content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet-reactive group in the molecule is preferably 70% by mass or more in the ultraviolet curable acrylic polymer, and 80% by mass. % Or more is more preferable, and 90% by mass or more is particularly preferable.
  • the content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet reactive group in the molecule is preferably 99.8% by mass or less in the ultraviolet curable acrylic polymer.
  • the UV-curable acrylic polymer after curing by UV irradiation has a desired viscosity and has an appropriate viscosity when melted and an excellent coating property.
  • the content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet reactive group in the molecule is 99.8% by mass or less, the ultraviolet curable acrylic system after curing by ultraviolet irradiation The polymer develops the desired tackiness.
  • the main (meth) acrylate unit means the (meth) acrylate unit with the largest content in the (meth) acrylate unit having no ultraviolet-reactive group in the molecule.
  • all of these (meth) acrylates are used as the main (meth) acrylate units.
  • the ultraviolet curable acrylic polymer has a residue of a thiol compound as a chain transfer agent at the molecular end.
  • the chain transfer agent is a thiol compound having no structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group (—OH), a keto group, and a secondary carbon in the molecule.
  • An ultraviolet curable acrylic polymer obtained by polymerization using such a thiol compound as a chain transfer agent is excellent in thermal stability during melting.
  • the tertiary carbon refers to carbon in which three carbons are directly bonded by a covalent bond.
  • Secondary carbon refers to carbon in which two carbons are directly bonded by a covalent bond. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a butoxy group.
  • thiol compound having a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group (—OH), a keto group, or a secondary carbon in the molecule there are no particular limitations on the thiol compound having a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group (—OH), a keto group, or a secondary carbon in the molecule.
  • a monofunctional thiol compound having one thiol group (—SH) in the molecule hereinafter sometimes referred to as a unit “monofunctional thiol compound”
  • a polyfunctional compound having a plurality of thiol groups (—SH) in the molecule hereinafter sometimes referred to as a unit “monofunctional thiol compound”
  • any of functional thiol compounds may be used, but since the adhesive residue can be reduced, a single thiol group (—SH) in the molecule can be reduced. Functional thiol compounds are preferred.
  • R 1 is a monovalent atomic group containing an ester bond in a part of an alkyl group not containing a tertiary carbon or an alkyl group not containing a tertiary carbon.
  • R 1 is preferably a linear alkyl group containing no tertiary carbon, and a monovalent atomic group containing an ester bond in a part of the linear alkyl group containing no tertiary carbon.
  • R 1 has preferably 4 to 18 carbon atoms, more preferably 8 to 18 carbon atoms, and particularly preferably 11 to 18 carbon atoms.
  • alkyl group not containing a tertiary carbon examples include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl, n-heptyl group, n-heptyl group, n -Octyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, lauryl group (n-dodecyl group), n-tridecyl group, n-pentadecyl group, n-hexadecyl group, n- Examples include a heptadecyl group and an n-octadecyl group, and a lauryl group is preferred.
  • Examples of the monovalent atomic group containing an ester bond in a part of the alkyl group not containing a tertiary carbon include an atomic group represented by —R 2 COOR 3 .
  • R 2 is an alkylene group containing no tertiary carbon.
  • R 2 is preferably a linear alkylene group containing no tertiary carbon.
  • R 3 is an alkyl group containing no tertiary carbon.
  • R 3 is preferably a linear alkyl group containing no tertiary carbon.
  • R 2 examples include a methylene group, an ethylene group, an n-butylene group, and an n-pentylene group (isopentylene group), and an ethylene group (—CH 2 CH 2 —) is preferable.
  • R 2 preferably has 1 to 5 carbon atoms, more preferably 2 to 3 carbon atoms.
  • R 3 examples include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl, n-heptyl group, n-heptyl group, n-octyl group, and n-octyl group.
  • R 3 preferably has 4 to 18 carbon atoms, more preferably 11 to 18 carbon atoms.
  • the monofunctional thiol compound for example, lauryl mercaptan, stearyl-3-mercaptopropionate and the like are preferably used.
  • the polyfunctional thiol compound only needs to have a plurality of thiol groups in the molecule, and preferably has a plurality of structural formulas represented by —OCOR 4 —SH in the molecule.
  • R 4 is an alkylene group containing no tertiary carbon.
  • R 4 is preferably a linear alkylene group containing no tertiary carbon. Examples of R 4 include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and an n-pentylene group, and an ethylene group (—CH 2 CH 2 —) is preferable.
  • R 4 preferably has 1 to 5 carbon atoms, more preferably 2 to 3 carbon atoms.
  • polyfunctional thiol compound examples include trimethylolpropane tris (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate) tris (3-mercaptopropionyloxy) ethyl isocyanurate, pentaerythritol tetrakis ( 3-mercaptopropionate), dipentaerythritol hexakis (3-mercaptopropionate) and the like are preferably used.
  • the weight average molecular weight of the ultraviolet curable acrylic polymer is preferably 50,000 to 500,000, more preferably 150,000 to 250,000. When the weight average molecular weight of the ultraviolet curable acrylic polymer is within the above range, the ultraviolet curable acrylic polymer has an appropriate viscosity when melted and has excellent coating properties.
  • the molecular weight distribution (weight average molecular weight / number average molecular weight) of the ultraviolet curable acrylic polymer is preferably 10.0 or less, and more preferably 6.0 or less.
  • the molecular weight distribution of the UV curable acrylic polymer is 10.0 or less, the UV curable acrylic cured by UV irradiation with a low content of low molecular weight components contained in the UV curable acrylic polymer is lowered.
  • the content ratio of the low molecular weight component contained in the polymer can be kept low. Therefore, the ultraviolet curable acrylic polymer cured by ultraviolet irradiation has an excellent cohesive force and is not easily deformed by an external force.
  • the molecular weight distribution (weight average molecular weight / number average molecular weight) of the ultraviolet curable acrylic polymer is preferably 2.0 or more, and more preferably 3.0 or more.
  • the ultraviolet curable acrylic polymer has an appropriate viscosity at the time of melting and excellent coating properties. .
  • the tensile shear strain tan ⁇ after UV curing of the UV curable acrylic polymer is preferably 1.5 or less, more preferably 1.2 or less, and particularly preferably 1.2 to 0.5.
  • the tensile shear strain tan ⁇ is 1.5 or less, the cohesive force of the ultraviolet curable acrylic polymer after being cured by ultraviolet rays is improved, and deformation with respect to external force is difficult.
  • the tensile shear strain tan ⁇ after ultraviolet curing of the ultraviolet curable acrylic polymer is a value measured in the following manner.
  • additives such as a tackifier, an ultraviolet polymerization initiator, a plasticizer, an antioxidant, a colorant, a flame retardant, and an antistatic agent are added to the ultraviolet curable acrylic polymer as long as the physical properties thereof are not impaired. May be added.
  • the ultraviolet curable acrylic polymer comprises a monomer composition containing a (meth) acrylate having no ultraviolet reactive group in the molecule and a monomer having the ultraviolet reactive group in the molecule as the chain transfer agent, It can be produced by radical polymerization in the presence of a polymerization initiator.
  • the monomer composition preferably contains (meth) acrylic acid because the obtained ultraviolet curable acrylic polymer exhibits high tackiness upon curing by ultraviolet irradiation.
  • the polymerization initiator a known polymerization initiator used for radical polymerization may be used.
  • the content of the (meth) acrylate having no UV-reactive group in the molecule is preferably 85 to 99.8% by mass, more preferably 91.5 to 97% by mass, and 92.5 to 95% by mass is particularly preferred.
  • the content of (meth) acrylate having no UV-reactive group in the molecule is 85% by mass or more, the obtained UV-curable acrylic polymer has an appropriate viscosity when melted, and the UV-curable acrylic polymer The coating property is improved, which is preferable.
  • the content of (meth) acrylate having no UV-reactive group in the molecule is 99.8% by mass or less, the UV-curable acrylic polymer after curing by UV irradiation expresses desired tackiness and is preferable.
  • the content of the monomer having an ultraviolet reactive group in the molecule is preferably 0.1 to 5% by mass, more preferably 0.15 to 1% by mass, and 0.2 to 0.6% by mass. % Is particularly preferred.
  • the content of the monomer having an ultraviolet reactive group in the molecule is 0.1 to 5% by mass, the obtained ultraviolet curable acrylic polymer exhibits desired tackiness upon curing by ultraviolet irradiation.
  • the content of (meth) acrylic acid is preferably 0.1 to 10% by mass, and more preferably 4.5 to 8% by mass.
  • the resulting ultraviolet curable acrylic polymer has excellent thermal stability at the time of melting and an appropriate viscosity at the time of melting.
  • the ultraviolet curable acrylic polymer after being cured by irradiation with ultraviolet rays exhibits desired tackiness and high tackiness.
  • the content of the main (meth) acrylate in the (meth) acrylate having no UV-reactive group in the molecule is preferably 70% by mass or more and 80% by mass or more in the monomer composition. More preferably, 90 mass% or more is particularly preferable.
  • the main (meth) acrylate content in the (meth) acrylate having no UV-reactive group in the molecule is preferably 99.8% by mass or less in the monomer composition.
  • the UV-curable acrylic polymer after being cured by UV irradiation has a desired viscosity and has an appropriate viscosity when melted and an excellent coating property.
  • the content of the main (meth) acrylate in the (meth) acrylate having no UV-reactive group in the molecule is 99.8% by mass or less
  • the UV-curable acrylic polymer after curing by UV irradiation is Expresses desired tackiness.
  • the main (meth) acrylate refers to (meth) acrylate having the largest content in (meth) acrylate having no ultraviolet-reactive group in the molecule.
  • all of these (meth) acrylates are the main (meth) acrylates.
  • the amount of the thiol compound used as the chain transfer agent is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 1 part by mass with respect to 100 parts by mass of the monomer composition.
  • the use amount of the thiol compound is within the above range, the obtained ultraviolet curable acrylic polymer has an appropriate viscosity at the time of melting and excellent coating properties.
  • the ultraviolet curable acrylic polymer has an ultraviolet reactive group in its main chain.
  • an ultraviolet curable acrylic polymer is irradiated with ultraviolet rays, radicals are generated in the ultraviolet reactive group and a crosslinking reaction occurs between the ultraviolet curable acrylic polymers, and a crosslinked structure is formed between the ultraviolet curable acrylic polymers and cured.
  • the desired tackiness is exhibited.
  • the ultraviolet curable acrylic polymer can be suitably used as an ultraviolet curable hot melt adhesive.
  • UV curable hot melt adhesive containing an ultraviolet curable acrylic polymer can be easily designed so as to express desired tackiness that varies depending on the application.
  • UV curable hot-melt adhesives should be used suitably for applications (such as sticky notes) that can be peeled off and adhered to an adherend without any adhesive residue, by designing the adhesive after curing to a low level. Can do.
  • UV curable hot melt adhesives are designed for high adhesiveness after curing, so that they can be used in applications such as adhesive tapes, consumer product labels, and electronic devices (such as PCs, smartphones, TVs, and digital cameras). It can be used suitably.
  • Peroxypivalate manufactured by NOF Corporation, trade name “Perhexyl PV”
  • the reaction solution was allowed to stand at 130 ° C. for 2 hours at normal pressure and then desolvated at 110 ° C. for 2 hours under reduced pressure to obtain an ultraviolet curable acrylic polymer.
  • Lauryl mercaptan (LM) and stearyl-3-mercaptopropionate (STMP) have a thiol group directly bonded to the tertiary carbon, alkoxy group, hydroxyl group, keto group, and secondary carbon in the molecular structure. It is a monofunctional thiol compound that does not have the structure.
  • Trimethylolpropane tris (3-mercaptopropionate) (TMMP), tris (3-mercaptopropionyloxy) ethyl isocyanurate (TEMPIC), pentaerythritol tetrakis (3-mercaptopropionate) (PEMP), and dipenta Erythritol hexakis (3-mercaptopropionate) (DPMP) has a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group, a keto group, and a secondary carbon in the molecular structure. It is a polyfunctional thiol compound not possessed.
  • EHMP 2-Ethylhexyl-3-mercaptopropionate
  • MBMP 3-methoxybutyl-3-mercaptopropionate
  • UV-curable acrylic polymer The obtained ultraviolet curable acrylic polymer was collected, and heated in an oven set at 150 ° C. for 6 hours. Then, it was set as the ultraviolet curable acrylic polymer after taking out from oven and heating.
  • the change rate of the weight average molecular weight converted by standard polystyrene after being heated at 150 ° C. for 6 hours, the molecular weight distribution, the SUS peel strength, the SUS peel strength change rate, The adhesive strength against SUS, the tensile shear strain tan ⁇ , the sticking-out property and the melt viscosity were measured as follows, and the results are shown in Tables 1 to 3.
  • the number of monomer units constituting the main chain was measured in the above manner with respect to one monomer unit having an ultraviolet reactive group in the molecule in the main chain. Are shown in the column “Number of monomer units” in Tables 1 to 3.
  • UV-C irradiation intensity about 48 mW / cm 2
  • integrated light quantity about 60 mJ /
  • an ultraviolet irradiation device trade name “Ligth Hammer 6” (H bulb used) manufactured by Heraeus (formerly Fusion UV Systems)
  • UV-C ultraviolet rays
  • a test film was prepared.
  • the test film was cut into a width of 25 mm to prepare a test piece.
  • an SUS plate was prepared, and the surface of the SUS plate was polished with a # 240 water-resistant file and then wiped with a mixed solvent of hexane and acetone for degreasing.
  • a 2 kg hand roller was reciprocated on the test piece. After a curing time of 20 minutes, peeling was performed at an angle of 180 ° at a speed of 300 mm / min using an autograph AGS-100NX manufactured by Shimadzu Corporation, and the peel strength was measured (N / 25 mm).
  • Test film was prepared in the same manner as in the measurement of the SUS peel strength of the ultraviolet curable acrylic polymer before heating.
  • a flat rectangular test piece having a width of 10 mm and a length of 100 mm was cut out from the test film. Under an atmosphere of 23 ° C., 10 mm of one end in the length direction of the test piece was attached to the SUS pedestal.
  • the SUS pedestal was arranged so that the test piece was attached to a vertical surface.
  • a 200 g weight was attached to the other end portion in the length direction of the test piece and held for 3 minutes, and then the displacement width (primary displacement width) at one end in the length direction of the test piece was measured.
  • the vertical downward direction was defined as the plus direction. Based on the following formula, the tensile shear strain tan ⁇ was calculated.
  • Tensile shear strain tan ⁇ Primary displacement width ( ⁇ m) / pressure-sensitive adhesive layer thickness ( ⁇ m)
  • a test film was prepared in the same manner as in the measurement of the SUS peel strength of the ultraviolet curable acrylic polymer before heating.
  • the mold release process was given to one surface of the polyethylene terephthalate film, and the adhesive layer was formed in this mold release process surface.
  • the test body was disposed between two polyethylene terephthalate films, and a 2 kg weight was placed on the test body for 1 hour via the upper polyethylene terephthalate film.
  • the opposing surface of the lower polyethylene terephthalate film with respect to the test body was subjected to release treatment. After 1 hour, the weight on the test specimen was removed, and the end face of the pressure-sensitive adhesive layer of the test specimen was visually observed and evaluated based on the following criteria.
  • melt viscosity With respect to the ultraviolet curable acrylic polymer before heating, the melt viscosity at 130 ° C. of the ultraviolet curable acrylic polymer was measured according to JIS K 6862. Evaluation was made based on the following criteria. A (excellent): Less than 45 Pa ⁇ s, which was very suitable for hot melt coating property. B (good): 45 to 70 Pa ⁇ s, which was suitable for hot melt coating property. C (poor): It exceeded 70 Pa ⁇ s and was not suitable for hot melt coating property.
  • the ultraviolet curable acrylic polymer is excellent in thermal stability and coating property at the time of melting without requiring a stabilizer.
  • the ultraviolet curable acrylic polymer exhibits desired tackiness by curing with ultraviolet irradiation.
  • the ultraviolet curable acrylic polymer can be suitably used as an ultraviolet curable hot melt adhesive.
  • UV curable hot-melt adhesives should be used suitably for applications (such as sticky notes) that can be peeled off and adhered to an adherend without any adhesive residue, by designing the adhesive after curing to a low level. Can do.
  • UV curable hot melt adhesives are designed for high adhesiveness after curing, so that they can be used in applications such as adhesive tapes, consumer product labels, and electronic devices (such as PCs, smartphones, TVs, and digital cameras). It can be used suitably.

Abstract

The present invention provides a UV curable acrylic polymer which can be used as a UV curable hot melt adhesive that exhibits excellent heat stability and coatability when melted, without requiring a stabilizer and that achieves desired adhesiveness by being cured by UV irradiation. The UV curable acrylic polymer according to the present invention crosslinks by UV irradiation, and is characterized in that, after being heated at 150ºC for 6 hours, the rate of change of the weight average molecular expressed in terms of standard polystyrene weight is -20% to 20%.

Description

紫外線硬化型アクリル系ポリマー及びその製造方法並びに紫外線硬化型ホットメルト接着剤UV curable acrylic polymer, method for producing the same, and UV curable hot melt adhesive
　本発明は、紫外線硬化型アクリル系ポリマー及びその製造方法並びに紫外線硬化型ホットメルト接着剤に関する。 The present invention relates to an ultraviolet curable acrylic polymer, a method for producing the same, and an ultraviolet curable hot melt adhesive.
　アクリル系粘着剤は、粘着テープ、消費者向け商品ラベル、付箋などに用いられている他、透明性、耐熱性及び耐候性という特徴を活かして、パソコン、スマートフォン、テレビ及びデジタルカメラなどの電子機器の光学ディスプレイなどの用途に用いられている。このように、アクリル系粘着剤は、様々な用途に用いられている。一方、アクリル系粘着剤に求められる粘着性は用途ごとに相違し、アクリル系粘着剤は、用途に応じて所望の粘着性を有していることが求められる。 Acrylic adhesives are used in adhesive tapes, consumer product labels, sticky notes, and other electronic devices such as personal computers, smartphones, TVs, and digital cameras, taking advantage of their transparency, heat resistance, and weather resistance. It is used for applications such as optical displays. As described above, the acrylic pressure-sensitive adhesive is used in various applications. On the other hand, the tackiness required for the acrylic pressure-sensitive adhesive is different for each use, and the acrylic pressure-sensitive adhesive is required to have desired tackiness depending on the use.
　近年、使用環境の改善の観点から接着剤の無溶剤化が推奨されており、アクリル系粘着剤においてもホットメルト化が進んでいる。ホットメルト粘着剤は、テープ、ラベルへの塗布工程において乾燥工程が必要ないことから、乾燥工程用の設備を必要とせず、省エネルギー化にも大きく寄与する。 In recent years, solvent-free adhesives have been recommended from the viewpoint of improving the usage environment, and hot-melting of acrylic adhesives is also progressing. The hot melt pressure-sensitive adhesive does not require a drying process in the tape and label application process, and therefore does not require equipment for the drying process, and greatly contributes to energy saving.
　従来の熱可塑アクリル系粘着剤は、用途に応じた所望の粘着性を発現させることが難しい。近年では、紫外線による架橋反応を用いて、用途に応じた所望の粘着性を発現する紫外線硬化型ホットメルト粘着剤の開発が進められている。 It is difficult for conventional thermoplastic acrylic pressure-sensitive adhesives to exhibit desired tackiness depending on the application. In recent years, development of an ultraviolet curable hot-melt pressure-sensitive adhesive that develops desired tackiness according to the application has been promoted using a crosslinking reaction by ultraviolet rays.
　紫外線硬化型ホットメルト粘着剤としては、特許文献１に、ガラス転移温度が－５℃以下で重量平均分子量が５００００～３５００００であるビニル系共重合体（Ａ）を含有する紫外線硬化型ホットメルト粘着剤組成物であって、前記ビニル系共重合体（Ａ）が、特定のモノマー成分を構成成分として、重合して得られたものである紫外線硬化型ホットメルト粘着剤組成物が開示されている。 As an ultraviolet curable hot melt adhesive, Patent Document 1 discloses an ultraviolet curable hot melt adhesive containing a vinyl copolymer (A) having a glass transition temperature of −5 ° C. or less and a weight average molecular weight of 50,000 to 350,000. An ultraviolet curable hot melt pressure-sensitive adhesive composition is disclosed, which is a composition obtained by polymerizing the vinyl copolymer (A) with a specific monomer component as a constituent component. .
　また、特許文献２には、溶融物から加工するためのポリアクリレートおよび少なくとも１個の亜リン酸基を有する安定剤を含む組成物が開示されている。 Patent Document 2 discloses a composition containing a polyacrylate for processing from a melt and a stabilizer having at least one phosphite group.
特開２００６－２９９０１７号公報JP 2006-299017 A 特開２００１－２５３９９５号公報Japanese Patent Laid-Open No. 2001-253959
　紫外線硬化型ホットメルト粘着剤は、使用にあたって、溶融状態を維持した状態で被着体又は支持体上に塗工されて用いられることから、長時間に亘って溶融した高温下に晒された状態となる。上記紫外線硬化型ホットメルト粘着剤組成物は、溶融時の熱安定性が低く、溶融時の熱によって劣化してしまう。その結果、紫外線硬化型ホットメルト粘着剤組成物がゲル化することによって塗工性の低下、及び、塗工機内の配管につまりが発生するという問題を生じる。又、紫外線硬化型ホットメルト粘着剤組成物の硬化性が低下し、更に、硬化後の紫外線硬化型ホットメルト粘着剤組成物が所望の粘着性を発現しないという問題を生じる。 The UV curable hot melt pressure-sensitive adhesive is used by being applied on an adherend or a support while maintaining a molten state in use, so that it is exposed to a high temperature melted for a long time. It becomes. The ultraviolet curable hot-melt pressure-sensitive adhesive composition has low thermal stability at the time of melting and is deteriorated by heat at the time of melting. As a result, the UV curable hot melt pressure-sensitive adhesive composition gels, resulting in a problem that coating property is lowered and clogging occurs in piping in the coating machine. Further, the curability of the ultraviolet curable hot melt pressure-sensitive adhesive composition is lowered, and further, there arises a problem that the ultraviolet curable hot melt pressure-sensitive adhesive composition after curing does not exhibit desired tackiness.
　上記特許文献２に開示されている組成物は、紫外線硬化型アクリル系ポリマーに亜リン酸基を有する安定剤を添加することによって紫外線硬化型アクリル系ポリマーの貯蔵安定性を向上させている。 The composition disclosed in Patent Document 2 improves the storage stability of an ultraviolet curable acrylic polymer by adding a stabilizer having a phosphite group to the ultraviolet curable acrylic polymer.
　しかしながら、安定剤の添加によって組成物の紫外線照射による硬化性が低下するという問題点を有していると共に、安定剤の混合工程を必要とするために生産効率が低いという問題も有する。 However, the addition of a stabilizer has a problem that the curability of the composition by irradiation with ultraviolet rays is lowered, and it also has a problem that the production efficiency is low because a stabilizer mixing step is required.
　本発明は、安定剤の必要とすることなく、溶融時の熱安定性及び塗工性に優れ且つ硬化によって所望の粘着性を発現する紫外線硬化型ホットメルト粘着剤として使用可能な紫外線硬化型アクリル系ポリマーを提供する。 The present invention is an ultraviolet curable acrylic that can be used as an ultraviolet curable hot melt pressure-sensitive adhesive that exhibits excellent thermal stability and coating properties when melted and exhibits desired tackiness upon curing without the need for a stabilizer. A polymer is provided.
　本発明の紫外線硬化型アクリル系ポリマーは、紫外線の照射によって架橋する紫外線硬化型アクリル系ポリマーであって、１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率が－２０～２０％であることを特徴とする。 The ultraviolet curable acrylic polymer of the present invention is an ultraviolet curable acrylic polymer that is cross-linked by irradiation of ultraviolet rays, and the rate of change in weight average molecular weight converted by standard polystyrene after heating at 150 ° C. for 6 hours. Is -20 to 20%.
　本発明の紫外線硬化型アクリル系ポリマーは、上述の如き構成を有していることから、溶融時の熱安定性及び塗工性に優れ且つ硬化によって所望の粘着性を発現する紫外線硬化型ホットメルト粘着剤として用いることができる。 Since the ultraviolet curable acrylic polymer of the present invention has the above-described configuration, the ultraviolet curable hot melt is excellent in thermal stability at the time of melting and coating properties and exhibits desired tackiness upon curing. It can be used as an adhesive.
　本発明の紫外線硬化型アクリル系ポリマーは、１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率が－２０～２０％であることを特徴とする。 The ultraviolet curable acrylic polymer of the present invention is characterized in that the change rate of the weight average molecular weight converted to standard polystyrene after being heated at 150 ° C. for 6 hours is −20 to 20%.
　本発明の紫外線硬化型アクリル系ポリマーは、重量平均分子量Ｍｗの変化率を－２０～２０％とすることによって、溶融時の熱安定性及び塗工性に優れていると共に、紫外線照射による硬化後に所望の粘着性を発現する。 The ultraviolet curable acrylic polymer of the present invention is excellent in thermal stability and coating property when melted by setting the change rate of the weight average molecular weight Mw to −20 to 20%, and after curing by ultraviolet irradiation. Expresses desired tackiness.
　紫外線硬化型アクリル系ポリマーにおける１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率は、－２０～２０％であり、－１５～１５％が好ましく、－１０～１０％がより好ましい。 The rate of change of the weight average molecular weight in terms of the standard polystyrene after heating at 150 ° C. for 6 hours in the UV curable acrylic polymer is −20 to 20%, preferably −15 to 15%, −10 ~ 10% is more preferred.
　紫外線硬化型アクリル系ポリマーの重量平均分子量及び数平均分子量は下記の要領で測定された値をいう。 The weight average molecular weight and the number average molecular weight of the ultraviolet curable acrylic polymer are values measured in the following manner.
　紫外線硬化型アクリル系ポリマーの重量平均分子量及び数平均分子量は、ＧＰＣ（ゲルパーミエーションクロマトグラフィー）法によって測定されたポリスチレン換算した値である。具体的には、紫外線硬化型アクリル系ポリマーを採取し、ＴＨＦ（テトラヒドロフラン）を加えて紫外線硬化型アクリル系ポリマーを３００倍に希釈し、フィルタリング（日本ミリポア社製　商品名：Ｍｉｌｌｅｘ－ＬＨ　＜０．４５μｍ＞）を行って、測定試料を作製する。 The weight average molecular weight and the number average molecular weight of the ultraviolet curable acrylic polymer are polystyrene-converted values measured by a GPC (gel permeation chromatography) method. Specifically, an ultraviolet curable acrylic polymer was collected, THF (tetrahydrofuran) was added to dilute the ultraviolet curable acrylic polymer 300 times, and filtering (trade name: Millex-LH <0. 45 μm>) to prepare a measurement sample.
　この測定試料を用いてＧＰＣ法によって紫外線硬化型アクリル系ポリマーの重量平均分子量及び数平均分子量を測定することができる。 Using this measurement sample, the weight average molecular weight and number average molecular weight of the ultraviolet curable acrylic polymer can be measured by the GPC method.
　紫外線硬化型アクリル系ポリマーの重量平均分子量及び数平均分子量は、例えば、下記測定装置及び測定条件にて測定することができる。
測定装置　Ｗａｔｅｒ社製　商品名「ｅ２６９５」
測定条件　カラム：ｓｈｏｄｅｘ社製　ＧＰＣ　ＫＦ－８０６Ｌを２本直列に接続
　　　　　移動相：テトラヒドロフラン使用　１．０ｍＬ／分
　　　　　検出器：ＲＩ検出器（ｅ２４１４）
　　　　　標準物質：ポリスチレン
　　　　　ＳＥＣ温度：４０℃ The weight average molecular weight and number average molecular weight of the ultraviolet curable acrylic polymer can be measured, for example, with the following measuring apparatus and measurement conditions.
Product name “e2695” manufactured by Water
Measurement conditions Column: Two GPC KF-806L manufactured by shodex connected in series Mobile phase: Tetrahydrofuran used 1.0 mL / min Detector: RI detector (e2414)
Standard material: polystyrene SEC temperature: 40 ° C
　紫外線硬化型アクリル系ポリマーにおける１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率は下記の要領で測定された値をいう。 The rate of change in weight average molecular weight converted by standard polystyrene after heating at 150 ° C. for 6 hours in an ultraviolet curable acrylic polymer refers to a value measured in the following manner.
　先ず、加熱前の紫外線硬化型アクリル系ポリマーの重量平均分子量を上記の要領で測定し、その値を初期重量平均分子量とする。次に、紫外線硬化型アクリル系ポリマーを１５０℃にて６時間加熱する。しかる後、紫外線硬化型アクリル系ポリマーの重量平均分子量を上記の要領で測定し、その値を加熱後重量平均分子量とする。下記式に基づいて、紫外線硬化型アクリル系ポリマーにおける１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率を算出する。
　重量平均分子量の変化率（％）
　　＝１００×（加熱後重量平均分子量－初期重量平均分子量）／初期重量平均分子量 First, the weight average molecular weight of the ultraviolet curable acrylic polymer before heating is measured as described above, and the value is defined as the initial weight average molecular weight. Next, the ultraviolet curable acrylic polymer is heated at 150 ° C. for 6 hours. Thereafter, the weight average molecular weight of the ultraviolet curable acrylic polymer is measured as described above, and the value is defined as the weight average molecular weight after heating. Based on the following formula, the change rate of the weight average molecular weight converted by standard polystyrene after heating at 150 ° C. for 6 hours in the ultraviolet curable acrylic polymer is calculated.
Change rate of weight average molecular weight (%)
= 100 × (weight average molecular weight after heating−initial weight average molecular weight) / initial weight average molecular weight
　紫外線硬化型アクリル系ポリマーは、上述した重量平均分子量の変化率が－２０～２０％であって、紫外線の照射によって分子間において架橋反応が生じて硬化するアクリル系ポリマーであれば、特に限定されないが、下記のアクリル系ポリマーが好ましい。 The ultraviolet curable acrylic polymer is not particularly limited as long as the above-described change rate of the weight average molecular weight is −20 to 20%, and the acrylic polymer is cured by a cross-linking reaction between molecules caused by ultraviolet irradiation. However, the following acrylic polymers are preferable.
　即ち、紫外線反応性基を分子内に有しない（メタ）アクリレート単位８５～９９．８質量％及び紫外線反応性基を分子内に有するモノマー単位０．１～５質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位を７０質量％以上含有する重合体であって、連鎖移動剤としてのチオール化合物の残基を末端に有する紫外線硬化型アクリル系ポリマーが好ましい。 That is, it contains 85 to 99.8% by mass of (meth) acrylate units having no UV-reactive group in the molecule and 0.1 to 5% by mass of monomer units having an UV-reactive group in the molecule, and A polymer containing 70% by mass or more of a main (meth) acrylate unit in a (meth) acrylate unit having no group in the molecule, and having a terminal thiol compound residue as a chain transfer agent A curable acrylic polymer is preferred.
　紫外線反応性基を分子内に有しない（メタ）アクリレート単位８５～９９．８質量％、紫外線反応性基を分子内に有するモノマー単位０．１～５質量％及び（メタ）アクリル酸単位０．１～１０質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位を７０質量％以上含有する重合体であって、連鎖移動剤としてのチオール化合物の残基を末端に有する紫外線硬化型アクリル系ポリマーがより好ましい。 85 to 99.8% by mass of (meth) acrylate units having no UV-reactive group in the molecule, 0.1 to 5% by mass of monomer units having an UV-reactive group in the molecule, and 0. A polymer containing 1 to 10% by mass and containing 70% by mass or more of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet reactive group in the molecule, An ultraviolet curable acrylic polymer having a thiol compound residue as a terminal is more preferable.
　なお、（メタ）アクリル酸は、アクリル酸又はメタクリル酸を意味する。（メタ）アクリレートは、アクリレート又はメタクリレートを意味する。 (Meth) acrylic acid means acrylic acid or methacrylic acid. (Meth) acrylate means acrylate or methacrylate.
　また、紫外線反応性基を分子内に有しない（メタ）アクリレート８５～９９．８質量％及び紫外線反応性基を分子内に有するモノマー０．１～５質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートを７０質量％以上含有するモノマー組成物の重合体であって、連鎖移動剤としてのチオール化合物の残基を末端に有する紫外線硬化型アクリル系ポリマーが好ましい。 Further, it contains 85 to 99.8% by weight of (meth) acrylate having no UV-reactive group in the molecule and 0.1 to 5% by weight of monomer having the UV-reactive group in the molecule, A polymer of a monomer composition containing 70% by mass or more of the main (meth) acrylate in the (meth) acrylate that is not present in the molecule, and having a terminal thiol compound residue as a chain transfer agent A curable acrylic polymer is preferred.
　紫外線反応性基を分子内に有しない（メタ）アクリレート８５～９９．８質量％及び紫外線反応性基を分子内に有するモノマー０．１～５質量％及び（メタ）アクリル酸０．１～１０質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートを７０質量％以上含有するモノマー組成物の重合体であって、連鎖移動剤としてのチオール化合物の残基を末端に有する紫外線硬化型アクリル系ポリマーが好ましい。 85 to 99.8% by mass of (meth) acrylate having no UV-reactive group in the molecule, 0.1 to 5% by mass of monomer having an UV-reactive group in the molecule, and 0.1 to 10 (meth) acrylic acid A polymer of a monomer composition containing 70% by mass or more of the main (meth) acrylate in the (meth) acrylate that contains the mass% and does not have the ultraviolet reactive group in the molecule, as a chain transfer agent An ultraviolet curable acrylic polymer having a terminal thiol compound residue is preferred.
　紫外線硬化型アクリル系ポリマーは、紫外線反応性基を分子内に有しない（メタ）アクリレート単位と、紫外線反応性基を分子内に有するモノマー単位とを含む重合体であり、何れのモノマー単位も、分子内に、紫外線領域の光線を吸収する芳香族環を有していないことが好ましい。 The ultraviolet curable acrylic polymer is a polymer containing a (meth) acrylate unit having no ultraviolet reactive group in the molecule and a monomer unit having an ultraviolet reactive group in the molecule. It is preferable that the molecule does not have an aromatic ring that absorbs light in the ultraviolet region.
　紫外線硬化型アクリル系ポリマーは、紫外線反応性基を分子内に有しない（メタ）アクリレート単位と、紫外線反応性基を分子内に有するモノマー単位と、（メタ）アクリル酸単位とを含む重合体であることが好ましく、何れのモノマー単位も、分子内に、紫外線領域の光線を吸収する芳香族環を有していないことが好ましい。 The ultraviolet curable acrylic polymer is a polymer containing a (meth) acrylate unit having no ultraviolet reactive group in the molecule, a monomer unit having an ultraviolet reactive group in the molecule, and a (meth) acrylic acid unit. It is preferable that none of the monomer units has an aromatic ring that absorbs light in the ultraviolet region in the molecule.
　紫外線反応性基を分子内に有しない（メタ）アクリレートとしては、特に限定されず、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｎ－プロピル（メタ）アクリレート、ｎ－ブチル（メタ）アクリレート、イソブチル（メタ）アクリレート、ｓｅｃ－ブチル（メタ）アクリレート、ｎ－ヘキシル（メタ）アクリレート、２－エチルヘキシル（メタ）アクリレート、ｎ－オクチル（メタ）アクリレート、イソオクチル（メタ）アクリレート、ｎ－ノニル（メタ）アクリレート、イソノニル（メタ）アクリレート、ｎ－デシル（メタ）アクリレート、ラウリル（メタ）メタクリレートなどのアルキル（メタ）アクリレートなどのアルキル（メタ）アクリレートが挙げられ、アルキル基の炭素数が１～８のアルキル（メタ）アクリレートを含むことが好ましい。アルキル基の炭素数が１～８のアルキル（メタ）アクリレートは、２－エチルへキシル（メタ）アクリレート、メチル（メタ）アクリレート及びブチル（メタ）アクリレートが好ましく、２－エチルへキシル（メタ）アクリレート及びブチル（メタ）アクリレートがより好ましく、２－エチルヘキシルアクリレート及びブチルアクリレートが特に好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレートは、単独で用いられても二種以上が併用されてもよい。 The (meth) acrylate having no UV-reactive group in the molecule is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) Acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl ( Examples include alkyl (meth) acrylates such as alkyl (meth) acrylates such as (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, and lauryl (meth) methacrylate, and the alkyl group has 1 to 8 carbon atoms. Of alkyl ) Preferably contains an acrylate. The alkyl (meth) acrylate having 1 to 8 carbon atoms in the alkyl group is preferably 2-ethylhexyl (meth) acrylate, methyl (meth) acrylate or butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate And butyl (meth) acrylate is more preferable, and 2-ethylhexyl acrylate and butyl acrylate are particularly preferable. The (meth) acrylates that do not have an ultraviolet reactive group in the molecule may be used alone or in combination of two or more.
　紫外線反応性基とは、紫外線の照射によって励起されてラジカルを発生させ、ラジカルが水素引抜反応を生じることによって、紫外線硬化型アクリル系ポリマー分子間に架橋構造を形成させる官能基をいう。 The term “ultraviolet reactive group” refers to a functional group that is excited by irradiation of ultraviolet rays to generate radicals, and the radicals generate a hydrogen abstraction reaction, thereby forming a crosslinked structure between ultraviolet curable acrylic polymer molecules.
　紫外線反応性基としては、例えば、ベンゾフェノン基、ベンゾイン基、マレイミド基及びこれらの誘導体などが挙げられる。 Examples of the ultraviolet reactive group include a benzophenone group, a benzoin group, a maleimide group, and derivatives thereof.
　紫外線硬化型アクリル系ポリマーにおいて、紫外線反応性基を分子内に有しない（メタ）アクリレート単位の含有量は、８５～９９．８質量％が好ましく、９１．５～９７質量％がより好ましく、９２．５～９５質量％が特に好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート単位の含有量が８５質量％以上であると、紫外線硬化型アクリル系ポリマーは溶融時に適度な粘度を有し、紫外線硬化型アクリル系ポリマーの塗工性が向上し好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート単位の含有量が９９．８質量％以下であると、紫外線照射による硬化後の紫外線硬化型アクリル系ポリマーが所望の粘着性を発現し好ましい。 In the ultraviolet curable acrylic polymer, the content of the (meth) acrylate unit having no ultraviolet reactive group in the molecule is preferably 85 to 99.8% by mass, more preferably 91.5 to 97% by mass, and 92 It is particularly preferably 5 to 95% by mass. When the content of the (meth) acrylate unit having no UV-reactive group in the molecule is 85% by mass or more, the UV-curable acrylic polymer has an appropriate viscosity when melted, and the UV-curable acrylic polymer The coatability is improved, which is preferable. When the content of the (meth) acrylate unit having no ultraviolet reactive group in the molecule is 99.8% by mass or less, the ultraviolet curable acrylic polymer after curing by ultraviolet irradiation expresses desired tackiness, which is preferable. .
　紫外線反応性基を分子内に有するモノマーとしては、分子内に紫外線反応性基を有し且つ紫外線反応性基を分子内に有しない（メタ）アクリレートと重合可能であれば、特に限定されない。なお、紫外線反応性基は、上記と同様であるので説明を省略する。 The monomer having an ultraviolet reactive group in the molecule is not particularly limited as long as it can be polymerized with a (meth) acrylate having an ultraviolet reactive group in the molecule and no ultraviolet reactive group in the molecule. In addition, since an ultraviolet reactive group is the same as the above, description is abbreviate | omitted.
　紫外線反応性基を分子内に有するモノマーとしては、分子内に紫外線反応性基を有し且つ紫外線反応性基を分子内に有しない（メタ）アクリレート及び（メタ）アクリル酸と重合可能であることが好ましい。 As a monomer having a UV-reactive group in the molecule, it can be polymerized with (meth) acrylate and (meth) acrylic acid having a UV-reactive group in the molecule and having no UV-reactive group in the molecule. Is preferred.
　紫外線反応性基を分子内に有するモノマーが有している紫外線反応性基としては、特に限定されないが、ベンゾフェノン基、ベンゾイン基、マレイミド基及びこれらの誘導体などが挙げられ、ベンゾフェノン基及びこの誘導体が好ましい。紫外線反応性基は、分子内に単独で含まれていても二種以上が含まれていてもよい。 The UV-reactive group possessed by the monomer having an UV-reactive group in the molecule is not particularly limited, and examples thereof include a benzophenone group, a benzoin group, a maleimide group, and derivatives thereof. preferable. The UV-reactive group may be contained alone or in combination of two or more in the molecule.
　紫外線反応性基を分子内に有するモノマーとしては、紫外線反応性基を分子内に有するアクリル系モノマーが好ましく、紫外線反応性基を分子内に有する（メタ）アクリレートがより好ましく、ベンゾフェノン基を分子内に有する（メタ）アクリレートが特に好ましく、４－アクリロイルオキシベンゾフェノンが最も好ましい。なお、紫外線反応性基を分子内に有するモノマーは、単独で用いられても二種以上が併用されてもよい。 The monomer having an ultraviolet reactive group in the molecule is preferably an acrylic monomer having an ultraviolet reactive group in the molecule, more preferably a (meth) acrylate having an ultraviolet reactive group in the molecule, and a benzophenone group in the molecule. (Meth) acrylates in the above are particularly preferred, and 4-acryloyloxybenzophenone is most preferred. In addition, the monomer which has an ultraviolet reactive group in a molecule | numerator may be used independently, or 2 or more types may be used together.
　紫外線反応性基を分子内に有するアクリル系モノマーとしては、特に限定されず、例えば、４－アクリロイルオキシベンゾフェノン、４－アクリロイルオキシエトキシベンゾフェノン、４－アクリロイルオキシ－４’－メトキシベンゾフェノン、４－アクリロイルオキシエトキシ－４’－メトキシベンゾフェノン、４－アクリロイルオキシ－４’－ブロモベンゾフェノン、４－アクリロイルオキシエトキシ－４’－ブロモベンゾフェノン、４－メタクリロイルオキシベンゾフェノン、４－メタクリロイルオキシエトキシベンゾフェノン、４－メタクリロイルオキシ－４’－メトキシベンゾフェノン、４－メタクリロイルオキシエトキシ－４’－メトキシベンゾフェノン、４－メタクリロイルオキシ－４’－ブロモベンゾフェノン、４－メタクリロイルオキシエトキシ－４’－ブロモベンゾフェノンなどが挙げられ、４－アクリロイルオキシベンゾフェノンが好ましい。なお、紫外線反応性基を分子内に有するアクリル系モノマーは、単独で用いられても二種以上が併用されてもよい。 The acrylic monomer having an ultraviolet reactive group in the molecule is not particularly limited. For example, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4′-methoxybenzophenone, 4-acryloyloxy Ethoxy-4′-methoxybenzophenone, 4-acryloyloxy-4′-bromobenzophenone, 4-acryloyloxyethoxy-4′-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4 '-Methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-meta Such Leroy oxy ethoxy-4'-bromobenzophenone and the like, 4-acryloyloxy benzophenone are preferred. In addition, the acrylic monomer which has an ultraviolet reactive group in a molecule | numerator may be used independently, or 2 or more types may be used together.
　紫外線硬化型アクリル系ポリマーにおいて、紫外線反応性基を分子内に有するモノマー単位の含有量は、０．１～５質量％が好ましく、０．１５～１質量％がより好ましく、０．２～０．６質量％が特に好ましい。紫外線反応性基を分子内に有するモノマー単位の含有量が０．１～５質量％であると、紫外線硬化型アクリル系ポリマーは、紫外線照射による硬化によって所望の粘着性を発現する。 In the ultraviolet curable acrylic polymer, the content of the monomer unit having an ultraviolet reactive group in the molecule is preferably 0.1 to 5% by mass, more preferably 0.15 to 1% by mass, and 0.2 to 0%. .6% by mass is particularly preferred. When the content of the monomer unit having an ultraviolet reactive group in the molecule is 0.1 to 5% by mass, the ultraviolet curable acrylic polymer exhibits desired adhesiveness upon curing by ultraviolet irradiation.
　紫外線硬化型アクリル系ポリマーの主鎖中において、紫外線反応性基を分子内に有するモノマー単位は、主鎖を構成している全モノマー単位（主鎖を構成している全てのモノマー単位）３５０～６００個に対して１個有していることが好ましい。紫外線硬化型アクリル系ポリマーの主鎖中における紫外線反応性基を分子内に有するモノマー単位の個数が上記範囲であると、紫外線照射による硬化後の紫外線硬化型アクリル系ポリマーが適度な凝集力を発現し、紫外線硬化型アクリル系ポリマーは、外力に対して優れた抵抗力を有することから、変形によって周囲を汚染することを防止することができると共に、紫外線照射による硬化によって所望の粘着性を発現する。 In the main chain of the UV curable acrylic polymer, monomer units having UV reactive groups in the molecule are all monomer units constituting the main chain (all monomer units constituting the main chain) 350 to It is preferable to have one for every 600. When the number of monomer units having UV-reactive groups in the main chain of the UV-curable acrylic polymer is within the above range, the UV-curable acrylic polymer after curing by UV irradiation exhibits appropriate cohesive strength. In addition, since the ultraviolet curable acrylic polymer has excellent resistance to external force, it can prevent the surroundings from being contaminated by deformation and develops desired tackiness by curing by ultraviolet irradiation. .
　なお、紫外線硬化型アクリル系ポリマーの主鎖中において、紫外線反応性基を分子内に有するモノマー単位１個に対する、主鎖を構成している全モノマー単位の数は下記の要領で算出される。 In the main chain of the ultraviolet curable acrylic polymer, the number of all monomer units constituting the main chain is calculated in the following manner with respect to one monomer unit having an ultraviolet reactive group in the molecule.
　紫外線硬化型アクリル系ポリマーの原料となるモノマーＸ0～Ｘｎを含むモノマー組成物中において、紫外線反応性基を分子内に有するモノマーＸ0の含有量をＹ0質量％、紫外線反応性基を分子内に有するモノマーＸ0以外のモノマーＸ1～Ｘｎの含有量をそれぞれＹ1～Ｙｎ質量％とする。紫外線反応性基を分子内に有するモノマーＸ0の分子量をＭ0とする。紫外線反応性基を分子内に有するモノマーＸ0以外のモノマーＸ1～Ｘｎの分子量をそれぞれＭ1～Ｍｎとする。下記式に基づいて、紫外線硬化型アクリル系ポリマーの主鎖中における、紫外線反応性基を分子内に有するモノマー単位１個に対する、主鎖を構成している全モノマー単位の数を算出する。なお、Ｙ0＋Ｙ1＋・・・＋Ｙｎ＝１００となる。
　紫外線反応性基を分子内に有するモノマー単位１個に対する、主鎖を構成している全モノマー単位の数
　＝（Ｙ0／Ｍ0＋Ｙ1／Ｍ1＋Ｙ2／Ｍ2＋・・・＋Ｙｎ／Ｍｎ）／（Ｙ0／Ｍ0） In the monomer composition containing the monomers X 0 to Xn which are the raw materials for the ultraviolet curable acrylic polymer, the content of the monomer X 0 having an ultraviolet reactive group in the molecule is Y 0 % by mass, and the ultraviolet reactive group is a molecule. The contents of monomers X 1 to Xn other than monomer X 0 are Y 1 to Yn mass%, respectively. The molecular weight of the monomer X 0 having an ultraviolet reactive group in the molecule is defined as M 0 . The molecular weights of the monomers X 1 to Xn other than the monomer X 0 having an ultraviolet reactive group in the molecule are M 1 to Mn, respectively. Based on the following formula, the number of all monomer units constituting the main chain is calculated with respect to one monomer unit having an ultraviolet reactive group in the molecule in the main chain of the ultraviolet curable acrylic polymer. Note that Y 0 + Y 1 +... + Yn = 100.
Number of all monomer units constituting the main chain with respect to one monomer unit having an ultraviolet reactive group in the molecule = (Y 0 / M 0 + Y 1 / M 1 + Y 2 / M 2 +... + Yn / Mn) / (Y 0 / M 0 )
　紫外線硬化型アクリル系ポリマーは（メタ）アクリル酸単位が含有されていることが好ましい。紫外線硬化型アクリル系ポリマーにおいて、（メタ）アクリル酸単位の含有量は、０．１～１０質量％が好ましく、４．５～８質量％がより好ましい。（メタ）アクリル酸単位の含有量が０．１～１０質量％であると、紫外線硬化型アクリル系ポリマーは、溶融時の熱安定性に優れていると共に溶融時に適度な粘度を有し、優れた塗工性を有している。更に、紫外線の照射による硬化後の紫外線硬化型アクリル系ポリマーは、所望の粘着性を発現すると共に、高い粘着性を発現する。 The ultraviolet curable acrylic polymer preferably contains a (meth) acrylic acid unit. In the ultraviolet curable acrylic polymer, the content of the (meth) acrylic acid unit is preferably 0.1 to 10% by mass, and more preferably 4.5 to 8% by mass. When the content of the (meth) acrylic acid unit is 0.1 to 10% by mass, the ultraviolet curable acrylic polymer has excellent thermal stability at the time of melting and an appropriate viscosity at the time of melting. It has good coatability. Furthermore, the ultraviolet curable acrylic polymer after curing by irradiation with ultraviolet rays exhibits desired tackiness and high tackiness.
　紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位の含有量は、紫外線硬化型アクリル系ポリマーにおいて、７０質量％以上であることが好ましく、８０質量％以上であることがより好ましく、９０質量％以上であることが特に好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位の含有量は、紫外線硬化型アクリル系ポリマーにおいて、９９．８質量％以下であることが好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位の含有量が７０質量％以上であると、紫外線硬化型アクリル系ポリマーは優れた熱安定性を有し且つ溶融時に適度な粘度を有して優れた塗工性を有していると共に、紫外線照射によって硬化した後の紫外線硬化型アクリル系ポリマーは、所望の粘着性を発現する。紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位の含有量が９９．８質量％以下であると、紫外線照射による硬化後の紫外線硬化型アクリル系ポリマーが所望の粘着性を発現する。なお、主となる（メタ）アクリレート単位とは、紫外線反応性基を分子内に有しない（メタ）アクリレート単位中において、最も含有量の多い（メタ）アクリレート単位をいう。なお、最も含有量の多い（メタ）アクリレート単位が複数種類ある場合には、それら全ての（メタ）アクリレートを主となる（メタ）アクリレート単位とする。 The content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet-reactive group in the molecule is preferably 70% by mass or more in the ultraviolet curable acrylic polymer, and 80% by mass. % Or more is more preferable, and 90% by mass or more is particularly preferable. The content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet reactive group in the molecule is preferably 99.8% by mass or less in the ultraviolet curable acrylic polymer. When the content of the main (meth) acrylate unit in the (meth) acrylate unit having no UV-reactive group in the molecule is 70% by mass or more, the UV-curable acrylic polymer has excellent thermal stability. The UV-curable acrylic polymer after curing by UV irradiation has a desired viscosity and has an appropriate viscosity when melted and an excellent coating property. When the content of the main (meth) acrylate unit in the (meth) acrylate unit having no ultraviolet reactive group in the molecule is 99.8% by mass or less, the ultraviolet curable acrylic system after curing by ultraviolet irradiation The polymer develops the desired tackiness. In addition, the main (meth) acrylate unit means the (meth) acrylate unit with the largest content in the (meth) acrylate unit having no ultraviolet-reactive group in the molecule. In addition, when there are multiple types of (meth) acrylate units with the highest content, all of these (meth) acrylates are used as the main (meth) acrylate units.
　更に、紫外線硬化型アクリル系ポリマーは、分子末端に、連鎖移動剤としてのチオール化合物の残基を有する。連鎖移動剤は、分子内に、第３級炭素、アルコキシ基、水酸基（－ＯＨ）、ケト基及び、第２級炭素にチオール基が直接結合している構造を有しないチオール化合物である。このようなチオール化合物を連鎖移動剤として用いた重合によって得られた紫外線硬化型アクリル系ポリマーは、溶融時の熱安定性に優れている。なお、第３級炭素とは、３個の炭素が共有結合により直接結合している炭素をいう。第２級炭素とは、２個の炭素が共有結合により直接結合している炭素をいう。アルコキシ基としては、例えば、メトキシ基、エトキシ基、ブトキシ基などが挙げられる。 Furthermore, the ultraviolet curable acrylic polymer has a residue of a thiol compound as a chain transfer agent at the molecular end. The chain transfer agent is a thiol compound having no structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group (—OH), a keto group, and a secondary carbon in the molecule. An ultraviolet curable acrylic polymer obtained by polymerization using such a thiol compound as a chain transfer agent is excellent in thermal stability during melting. The tertiary carbon refers to carbon in which three carbons are directly bonded by a covalent bond. Secondary carbon refers to carbon in which two carbons are directly bonded by a covalent bond. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a butoxy group.
　分子内に、第３級炭素、アルコキシ基、水酸基（－ＯＨ）、ケト基及び、第２級炭素にチオール基が直接結合している構造を有しないチオール化合物としては、特に限定されず、分子内に１個のチオール基（－ＳＨ）を有する単官能チオール化合物（以下、単位「単官能チオール化合物」ということがある）、又は、分子内に複数個のチオール基（－ＳＨ）を有する多官能チオール化合物（以下、単に「多官能チオール化合物」ということがある）の何れでもよいが、糊残りの低減を図ることができるので、分子内に１個のチオール基（－ＳＨ）を有する単官能チオール化合物が好ましい。 There are no particular limitations on the thiol compound having a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group (—OH), a keto group, or a secondary carbon in the molecule. A monofunctional thiol compound having one thiol group (—SH) in the molecule (hereinafter sometimes referred to as a unit “monofunctional thiol compound”), or a polyfunctional compound having a plurality of thiol groups (—SH) in the molecule. Any of functional thiol compounds (hereinafter sometimes simply referred to as “polyfunctional thiol compounds”) may be used, but since the adhesive residue can be reduced, a single thiol group (—SH) in the molecule can be reduced. Functional thiol compounds are preferred.
　単官能チオール化合物としては、Ｒ1－ＳＨで表されるチオール化合物が好ましい。Ｒ1は、第３級炭素を含まないアルキル基、又は、第３級炭素を含まないアルキル基の一部にエステル結合を含有する一価の原子団である。Ｒ1は、第３級炭素を含まない直鎖状のアルキル基、及び、第３級炭素を含まない直鎖状のアルキル基の一部にエステル結合を含有する一価の原子団が好ましい。Ｒ1の炭素数は、４～１８個が好ましく、８～１８個がより好ましく、１１～１８個が特に好ましい。 As the monofunctional thiol compound, a thiol compound represented by R 1 —SH is preferable. R 1 is a monovalent atomic group containing an ester bond in a part of an alkyl group not containing a tertiary carbon or an alkyl group not containing a tertiary carbon. R 1 is preferably a linear alkyl group containing no tertiary carbon, and a monovalent atomic group containing an ester bond in a part of the linear alkyl group containing no tertiary carbon. R 1 has preferably 4 to 18 carbon atoms, more preferably 8 to 18 carbon atoms, and particularly preferably 11 to 18 carbon atoms.
　第３級炭素を含まないアルキル基としては、例えば、メチル基、エチル基、ｎ－プロピル基、ｎ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル、ｎ－ヘプチル基、ｎ－ヘプチル基、ｎ－オクチル基、ｎ－オクチル基、ｎ－ノニル基、ｎ－デシル基、ｎ－ウンデシル基、ラウリル基（ｎ－ドデシル基）、ｎ－トリデシル基、ｎ－ペンタデシル基、ｎ－ヘキサデシル基、ｎ－ヘプタデシル基、ｎ－オクタデシル基などが挙げられ、ラウリル基が好ましい。 Examples of the alkyl group not containing a tertiary carbon include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl, n-heptyl group, n-heptyl group, n -Octyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, lauryl group (n-dodecyl group), n-tridecyl group, n-pentadecyl group, n-hexadecyl group, n- Examples include a heptadecyl group and an n-octadecyl group, and a lauryl group is preferred.
　第３級炭素を含まないアルキル基の一部にエステル結合を含有する一価の原子団としては、例えば、－Ｒ2ＣＯＯＲ3で表される原子団が挙げられる。なお、Ｒ2は、第３級炭素を含まないアルキレン基である。Ｒ2は、第３級炭素を含まない直鎖状のアルキレン基が好ましい。Ｒ3は、第３級炭素を含まないアルキル基である。Ｒ3は、第３級炭素を含まない直鎖状のアルキル基が好ましい。 Examples of the monovalent atomic group containing an ester bond in a part of the alkyl group not containing a tertiary carbon include an atomic group represented by —R 2 COOR 3 . R 2 is an alkylene group containing no tertiary carbon. R 2 is preferably a linear alkylene group containing no tertiary carbon. R 3 is an alkyl group containing no tertiary carbon. R 3 is preferably a linear alkyl group containing no tertiary carbon.
　Ｒ2としては、例えば、メチレン基、エチレン基、ｎ－ブチレン基、ｎ－ペンチレン基（イソペンチレン基）などが挙げられ、エチレン基（－ＣＨ2ＣＨ2－）が好ましい。Ｒ2の炭素数は１～５が好ましく、２～３がより好ましい。 Examples of R 2 include a methylene group, an ethylene group, an n-butylene group, and an n-pentylene group (isopentylene group), and an ethylene group (—CH 2 CH 2 —) is preferable. R 2 preferably has 1 to 5 carbon atoms, more preferably 2 to 3 carbon atoms.
　Ｒ3としては、例えば、メチル基、エチル基、ｎ－プロピル基、ｎ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル、ｎ－ヘプチル基、ｎ－ヘプチル基、ｎ－オクチル基、ｎ－オクチル基、ｎ－ノニル基、ｎ－デシル基、ｎ－ウンデシル基、ラウリル基（ｎ－ドデシル基）、ｎ－トリデシル基、ｓｎ－ペンタデシル基、ｎ－ヘキサデシル基、ｎ－ヘプタデシル基、ｎ－オクタデシル基（ステアリル基）などが挙げられ、ｎ－オクタデシル基（ステアリル基）が好ましい。Ｒ3の炭素数は４～１８が好ましく、１１～１８がより好ましい。 Examples of R 3 include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl, n-heptyl group, n-heptyl group, n-octyl group, and n-octyl group. Group, n-nonyl group, n-decyl group, n-undecyl group, lauryl group (n-dodecyl group), n-tridecyl group, sn-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group (Stearyl group) and the like, and n-octadecyl group (stearyl group) is preferable. R 3 preferably has 4 to 18 carbon atoms, more preferably 11 to 18 carbon atoms.
　単官能チオール化合物としては、例えば、ラウリルメルカプタン、ステアリル－３－メルカプトプロピオナートなどが好ましく用いられる。 As the monofunctional thiol compound, for example, lauryl mercaptan, stearyl-3-mercaptopropionate and the like are preferably used.
　多官能チオール化合物としては、分子内に複数個のチオール基を有しておればよく、分子内に－ＯＣＯＲ4－ＳＨで表される構造式を複数個有していることが好ましい。Ｒ4は、第３級炭素を含まないアルキレン基である。Ｒ4は、第３級炭素を含まない直鎖状のアルキレン基が好ましい。Ｒ4としては、例えば、メチレン基、エチレン基、ｎ－プロピレン基、ｎ－ブチレン基、ｎ－ペンチレン基などが挙げられ、エチレン基（－ＣＨ2ＣＨ2－）が好ましい。Ｒ4の炭素数は１～５が好ましく、２～３がより好ましい。 The polyfunctional thiol compound only needs to have a plurality of thiol groups in the molecule, and preferably has a plurality of structural formulas represented by —OCOR 4 —SH in the molecule. R 4 is an alkylene group containing no tertiary carbon. R 4 is preferably a linear alkylene group containing no tertiary carbon. Examples of R 4 include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and an n-pentylene group, and an ethylene group (—CH 2 CH 2 —) is preferable. R 4 preferably has 1 to 5 carbon atoms, more preferably 2 to 3 carbon atoms.
　多官能チオール化合物としては、例えば、トリメチロールプロパントリス（３－メルカプトプロピオナート）、トリメチロールプロパントリス（３－メルカプトプロピオナート）トリス（３－メルカプトプロピオニルオキシ）エチルイソシアヌレート、ペンタエリスリトールテトラキス（３－メルカプトプロピオナート）、ジペンタエリスリトールヘキサキス（３－メルカプトプロピオナート）などが好ましく用いられる。 Examples of the polyfunctional thiol compound include trimethylolpropane tris (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate) tris (3-mercaptopropionyloxy) ethyl isocyanurate, pentaerythritol tetrakis ( 3-mercaptopropionate), dipentaerythritol hexakis (3-mercaptopropionate) and the like are preferably used.
　紫外線硬化型アクリル系ポリマーの重量平均分子量は５００００～５０００００が好ましく、１５００００～２５００００がより好ましい。紫外線硬化型アクリル系ポリマーの重量平均分子量が上記範囲内であると、紫外線硬化型アクリル系ポリマーは、溶融時に適度な粘度を有し優れた塗工性を有する。 The weight average molecular weight of the ultraviolet curable acrylic polymer is preferably 50,000 to 500,000, more preferably 150,000 to 250,000. When the weight average molecular weight of the ultraviolet curable acrylic polymer is within the above range, the ultraviolet curable acrylic polymer has an appropriate viscosity when melted and has excellent coating properties.
　紫外線硬化型アクリル系ポリマーの分子量分布（重量平均分子量／数平均分子量）は１０．０以下が好ましく、６．０以下がより好ましい。紫外線硬化型アクリル系ポリマーの分子量分布が１０．０以下であると、紫外線硬化型アクリル系ポリマー中に含まれている低分子量成分の含有比率を低くして、紫外線照射によって硬化した紫外線硬化型アクリル系ポリマー中に含有されている低分子量成分の含有比率を低く抑えることができる。従って、紫外線照射によって硬化した紫外線硬化型アクリル系ポリマーは、優れた凝集力を有し、外力によって容易に変形しにくい。紫外線硬化型アクリル系ポリマーの分子量分布（重量平均分子量／数平均分子量）は２．０以上が好ましく、３．０以上がより好ましい。紫外線硬化型アクリル系ポリマーの分子量分布（重量平均分子量／数平均分子量）が２．０以上であると、紫外線硬化型アクリル系ポリマーは、溶融時に適度な粘度を有し塗工性に優れている。 The molecular weight distribution (weight average molecular weight / number average molecular weight) of the ultraviolet curable acrylic polymer is preferably 10.0 or less, and more preferably 6.0 or less. When the molecular weight distribution of the UV curable acrylic polymer is 10.0 or less, the UV curable acrylic cured by UV irradiation with a low content of low molecular weight components contained in the UV curable acrylic polymer is lowered. The content ratio of the low molecular weight component contained in the polymer can be kept low. Therefore, the ultraviolet curable acrylic polymer cured by ultraviolet irradiation has an excellent cohesive force and is not easily deformed by an external force. The molecular weight distribution (weight average molecular weight / number average molecular weight) of the ultraviolet curable acrylic polymer is preferably 2.0 or more, and more preferably 3.0 or more. When the molecular weight distribution (weight average molecular weight / number average molecular weight) of the ultraviolet curable acrylic polymer is 2.0 or more, the ultraviolet curable acrylic polymer has an appropriate viscosity at the time of melting and excellent coating properties. .
　紫外線硬化型アクリル系ポリマーの紫外線硬化後の引張せん断ひずみｔａｎθは、１．５以下が好ましく、１．２以下がより好ましく、１．２～０．５が特に好ましい。引張せん断ひずみｔａｎθが１．５以下であると、紫外線によって硬化した後の紫外線硬化型アクリル系ポリマーの凝集力が向上し、外力に対して変形し難くなる。なお、紫外線硬化型アクリル系ポリマーの紫外線硬化後の引張せん断ひずみｔａｎθは下記の要領で測定された値をいう。 The tensile shear strain tanθ after UV curing of the UV curable acrylic polymer is preferably 1.5 or less, more preferably 1.2 or less, and particularly preferably 1.2 to 0.5. When the tensile shear strain tan θ is 1.5 or less, the cohesive force of the ultraviolet curable acrylic polymer after being cured by ultraviolet rays is improved, and deformation with respect to external force is difficult. In addition, the tensile shear strain tanθ after ultraviolet curing of the ultraviolet curable acrylic polymer is a value measured in the following manner.
　上記紫外線硬化型アクリル系ポリマーには、その物性を損なわない範囲内において、粘着付与剤、紫外線重合開始剤、可塑剤、酸化防止剤、着色剤、難燃剤及び帯電防止剤などの他の添加剤が添加されてもよい。 Other additives such as a tackifier, an ultraviolet polymerization initiator, a plasticizer, an antioxidant, a colorant, a flame retardant, and an antistatic agent are added to the ultraviolet curable acrylic polymer as long as the physical properties thereof are not impaired. May be added.
　本発明の紫外線硬化型アクリル系ポリマーの製造方法を説明する。紫外線硬化型アクリル系ポリマーは、上記紫外線反応性基を分子内に有しない（メタ）アクリレート及び上記紫外線反応性基を分子内に有するモノマーを含むモノマー組成物を連鎖移動剤である上記チオール化合物及び重合開始剤の存在下にてラジカル重合させることによって製造することができる。モノマー組成物は、得られる紫外線硬化型アクリル系ポリマーが、紫外線照射による硬化によって高い粘着性を発現するので、（メタ）アクリル酸を含有していることが好ましい。なお、モノマー組成物のラジカル重合は、汎用の重合方法を用いて行えばよい。重合開始剤は、ラジカル重合に用いられる公知の重合開始剤が用いられればよい。 A method for producing the ultraviolet curable acrylic polymer of the present invention will be described. The ultraviolet curable acrylic polymer comprises a monomer composition containing a (meth) acrylate having no ultraviolet reactive group in the molecule and a monomer having the ultraviolet reactive group in the molecule as the chain transfer agent, It can be produced by radical polymerization in the presence of a polymerization initiator. The monomer composition preferably contains (meth) acrylic acid because the obtained ultraviolet curable acrylic polymer exhibits high tackiness upon curing by ultraviolet irradiation. In addition, what is necessary is just to perform radical polymerization of a monomer composition using a general purpose polymerization method. As the polymerization initiator, a known polymerization initiator used for radical polymerization may be used.
　モノマー組成物中において、紫外線反応性基を分子内に有しない（メタ）アクリレートの含有量は、８５～９９．８質量％が好ましく、９１．５～９７質量％がより好ましく、９２．５～９５質量％が特に好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレートの含有量が８５質量％以上であると、得られる紫外線硬化型アクリル系ポリマーは溶融時に適度な粘度を有し、紫外線硬化型アクリル系ポリマーの塗工性が向上し好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレートの含有量が９９．８質量％以下であると、紫外線照射による硬化後の紫外線硬化型アクリル系ポリマーが所望の粘着性を発現し好ましい。 In the monomer composition, the content of the (meth) acrylate having no UV-reactive group in the molecule is preferably 85 to 99.8% by mass, more preferably 91.5 to 97% by mass, and 92.5 to 95% by mass is particularly preferred. When the content of (meth) acrylate having no UV-reactive group in the molecule is 85% by mass or more, the obtained UV-curable acrylic polymer has an appropriate viscosity when melted, and the UV-curable acrylic polymer The coating property is improved, which is preferable. When the content of (meth) acrylate having no UV-reactive group in the molecule is 99.8% by mass or less, the UV-curable acrylic polymer after curing by UV irradiation expresses desired tackiness and is preferable.
　モノマー組成物中において、紫外線反応性基を分子内に有するモノマーの含有量は、０．１～５質量％が好ましく、０．１５～１質量％がより好ましく、０．２～０．６質量％が特に好ましい。紫外線反応性基を分子内に有するモノマーの含有量が０．１～５質量％であると、得られる紫外線硬化型アクリル系ポリマーは、紫外線照射による硬化によって所望の粘着性を発現する。 In the monomer composition, the content of the monomer having an ultraviolet reactive group in the molecule is preferably 0.1 to 5% by mass, more preferably 0.15 to 1% by mass, and 0.2 to 0.6% by mass. % Is particularly preferred. When the content of the monomer having an ultraviolet reactive group in the molecule is 0.1 to 5% by mass, the obtained ultraviolet curable acrylic polymer exhibits desired tackiness upon curing by ultraviolet irradiation.
　モノマー組成物中において、（メタ）アクリル酸の含有量は、０．１～１０質量％が好ましく、４．５～８質量％がより好ましい。（メタ）アクリル酸の含有量が０．１～１０質量％であると、得られる紫外線硬化型アクリル系ポリマーは、溶融時の熱安定性に優れていると共に溶融時に適度な粘度を有し優れた塗工性を有しており、更に、紫外線の照射による硬化後の紫外線硬化型アクリル系ポリマーは、所望の粘着性を発現すると共に、高い粘着性を発現する。 In the monomer composition, the content of (meth) acrylic acid is preferably 0.1 to 10% by mass, and more preferably 4.5 to 8% by mass. When the content of (meth) acrylic acid is 0.1 to 10% by mass, the resulting ultraviolet curable acrylic polymer has excellent thermal stability at the time of melting and an appropriate viscosity at the time of melting. Furthermore, the ultraviolet curable acrylic polymer after being cured by irradiation with ultraviolet rays exhibits desired tackiness and high tackiness.
　紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートの含有量は、モノマー組成物中において、７０質量％以上であることが好ましく、８０質量％以上であることがより好ましく、９０質量％以上が特に好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートの含有量は、モノマー組成物中において、９９．８質量％以下であることが好ましい。紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートの含有量が７０質量％以上であると、得られる紫外線硬化型アクリル系ポリマーは優れた熱安定性を有し且つ溶融時において適度な粘度を有し優れた塗工性を有していると共に、紫外線照射によって硬化した後の紫外線硬化型アクリル系ポリマーは、所望の粘着性を発現する。紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートの含有量が９９．８質量％以下であると、紫外線照射による硬化後の紫外線硬化型アクリル系ポリマーが所望の粘着性を発現する。なお、主となる（メタ）アクリレートとは、紫外線反応性基を分子内に有しない（メタ）アクリレート中において、最も含有量の多い（メタ）アクリレートをいう。なお、最も含有量の多い（メタ）アクリレートが複数種類ある場合には、それら全ての（メタ）アクリレートを主となる（メタ）アクリレートとする。 The content of the main (meth) acrylate in the (meth) acrylate having no UV-reactive group in the molecule is preferably 70% by mass or more and 80% by mass or more in the monomer composition. More preferably, 90 mass% or more is particularly preferable. The main (meth) acrylate content in the (meth) acrylate having no UV-reactive group in the molecule is preferably 99.8% by mass or less in the monomer composition. When the content of the main (meth) acrylate in the (meth) acrylate having no UV-reactive group in the molecule is 70% by mass or more, the obtained UV-curable acrylic polymer has excellent thermal stability. The UV-curable acrylic polymer after being cured by UV irradiation has a desired viscosity and has an appropriate viscosity when melted and an excellent coating property. When the content of the main (meth) acrylate in the (meth) acrylate having no UV-reactive group in the molecule is 99.8% by mass or less, the UV-curable acrylic polymer after curing by UV irradiation is Expresses desired tackiness. The main (meth) acrylate refers to (meth) acrylate having the largest content in (meth) acrylate having no ultraviolet-reactive group in the molecule. In addition, when there are multiple types of (meth) acrylates with the highest content, all of these (meth) acrylates are the main (meth) acrylates.
　連鎖移動剤であるチオール化合物の使用量は、モノマー組成物１００質量部に対して０．０１～５質量部が好ましく、０．０５～１質量部がより好ましい。チオール化合物の使用料が上記範囲内であると、得られる紫外線硬化型アクリル系ポリマーは、溶融時に適度な粘度を有し優れた塗工性を有する。 The amount of the thiol compound used as the chain transfer agent is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 1 part by mass with respect to 100 parts by mass of the monomer composition. When the use amount of the thiol compound is within the above range, the obtained ultraviolet curable acrylic polymer has an appropriate viscosity at the time of melting and excellent coating properties.
　紫外線硬化型アクリル系ポリマーは、その主鎖に紫外線反応性基を有している。紫外線硬化型アクリル系ポリマーに紫外線を照射すると、紫外線反応性基においてラジカルが発生して紫外線硬化型アクリル系ポリマー間において架橋反応が生じ、紫外線硬化型アクリル系ポリマー間に架橋構造が生成されて硬化し所望の粘着性を発現する。紫外線硬化型アクリル系ポリマーは、紫外線硬化型ホットメルト粘着剤として好適に用いることができる。 The ultraviolet curable acrylic polymer has an ultraviolet reactive group in its main chain. When an ultraviolet curable acrylic polymer is irradiated with ultraviolet rays, radicals are generated in the ultraviolet reactive group and a crosslinking reaction occurs between the ultraviolet curable acrylic polymers, and a crosslinked structure is formed between the ultraviolet curable acrylic polymers and cured. The desired tackiness is exhibited. The ultraviolet curable acrylic polymer can be suitably used as an ultraviolet curable hot melt adhesive.
　紫外線硬化型アクリル系ポリマーは、上述の通り、紫外線照射によって硬化して設計通りの粘着性を発現する。従って、紫外線硬化型アクリル系ポリマーを含む紫外線硬化型ホットメルト接着剤は、用途ごとに相違する所望の粘着性を発現するように容易に設計することができる。紫外線硬化型ホットメルト接着剤は、硬化後の粘着性を低く設計することによって、例えば、糊残りなく被着体に対して剥離可能に貼着させる用途（例えば、付箋など）に好適に用いることができる。一方、紫外線硬化型ホットメルト接着剤は、硬化後の粘着性を高く設計することによって、粘着テープ、消費者向け商品ラベル、電子機器（パソコン、スマートフォン、テレビ及びデジタルカメラなど）などの用途にも好適に用いることができる。 As described above, the ultraviolet curable acrylic polymer is cured by ultraviolet irradiation and exhibits the designed tackiness. Therefore, an ultraviolet curable hot melt adhesive containing an ultraviolet curable acrylic polymer can be easily designed so as to express desired tackiness that varies depending on the application. UV curable hot-melt adhesives should be used suitably for applications (such as sticky notes) that can be peeled off and adhered to an adherend without any adhesive residue, by designing the adhesive after curing to a low level. Can do. On the other hand, UV curable hot melt adhesives are designed for high adhesiveness after curing, so that they can be used in applications such as adhesive tapes, consumer product labels, and electronic devices (such as PCs, smartphones, TVs, and digital cameras). It can be used suitably.
　以下に、本発明を実施例を用いてより具体的に説明するが、本発明はこれに限定されない。 Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.
（実施例１～１６、比較例１～５）
　攪拌機、冷却管、温度計及び窒素ガス導入口を備えた２Ｌのセパラブルフラスコに、表１～３に示した所定量のブチルアクリレート（ＢＡ）、２－エチルヘキシルアクリレート（２ＥＨＡ）、アクリル酸（ＡＡｃ）、４－アクリロイルオキシベンゾフェノン（ＢＰＡ）、酢酸エチル、及び、表１～３に記載された所定量の連鎖移動剤を含む反応液を供給して回転速度１００ｒｐｍで攪拌した。なお、表１～３において、「紫外線反応性基を分子内に有するモノマー」を「紫外線反応性基含有モノマー」と表記した。 (Examples 1 to 16, Comparative Examples 1 to 5)
A predetermined amount of butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), acrylic acid (AAc) shown in Tables 1 to 3 was added to a 2 L separable flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen gas inlet. ), 4-acryloyloxybenzophenone (BPA), ethyl acetate, and a predetermined amount of chain transfer agent described in Tables 1 to 3 were supplied and stirred at a rotational speed of 100 rpm. In Tables 1 to 3, “monomer having an ultraviolet reactive group in the molecule” is referred to as “ultraviolet reactive group-containing monomer”.
　セパラブルフラスコ内を窒素ガスで置換した後、ウォーターバスを用いて反応液を還流した。次に、セパラブルフラスコ内に、ｔ－ヘキシルパーオキシ－２－エチルヘキサノエート（日本油脂社製　商品名「パーヘキシルＯ」）及びｔ－ヘキシルパーオキシピバレート（日油社製　商品名「パーヘキシルＰＶ」）を表４の「パーヘキシルＯ」及び「パーヘキシルＰＶ」の「ラジカル重合開始時」の欄のそれぞれに記載された量（質量部）を添加してラジカル重合を開始した。 After replacing the inside of the separable flask with nitrogen gas, the reaction solution was refluxed using a water bath. Next, in a separable flask, t-hexyl peroxy-2-ethylhexanoate (trade name “Perhexyl O” manufactured by NOF Corporation) and t-hexyl peroxypivalate (trade name “Perhexyl” manufactured by NOF Corporation) PV ”) was added in the amounts (parts by mass) described in the columns of“ Perhexyl O ”and“ Perhexyl PV ”in the column of“ At the start of radical polymerization ”in Table 4 to initiate radical polymerization.
　ラジカル重合開始から表４に示した所定の経過時間ごとに所定量（質量部）のｔ－ヘキシルパーオキシ－２－エチルヘキサノエート（日油社製　商品名「パーヘキシルＯ」）及びｔ－ヘキシルパーオキシピバレート（日油社製　商品名「パーヘキシルＰＶ」）を反応液に添加してラジカル重合を６時間に亘って行ない反応終了とした。反応液を常圧で１３０℃にて２時間放置した後、減圧で１１０℃２時間脱溶剤することで、紫外線硬化型アクリル系ポリマーを得た。 A predetermined amount (parts by mass) of t-hexylperoxy-2-ethylhexanoate (trade name “Perhexyl O” manufactured by NOF Corporation) and t-hexyl for each predetermined elapsed time shown in Table 4 from the start of radical polymerization. Peroxypivalate (manufactured by NOF Corporation, trade name “Perhexyl PV”) was added to the reaction solution, and radical polymerization was carried out over 6 hours to complete the reaction. The reaction solution was allowed to stand at 130 ° C. for 2 hours at normal pressure and then desolvated at 110 ° C. for 2 hours under reduced pressure to obtain an ultraviolet curable acrylic polymer.
　なお、ラウリルメルカプタン（ＬＭ）及びステアリル－３－メルカプトプロピオナート（ＳＴＭＰ）は、分子構造中に、第３級炭素、アルコキシ基、水酸基、ケト基及び、第２級炭素にチオール基が直接結合している構造を有していない単官能チオール化合物である。 Lauryl mercaptan (LM) and stearyl-3-mercaptopropionate (STMP) have a thiol group directly bonded to the tertiary carbon, alkoxy group, hydroxyl group, keto group, and secondary carbon in the molecular structure. It is a monofunctional thiol compound that does not have the structure.
　トリメチロールプロパントリス（３－メルカプトプロピオナート）（ＴＭＭＰ）、トリス（３－メルカプトプロピオニルオキシ）エチルイソシアヌレート（ＴＥＭＰＩＣ）、ペンタエリスリトールテトラキス（３－メルカプトプロピオナート）（ＰＥＭＰ）、及び、ジペンタエリスリトールヘキサキス（３－メルカプトプロピオナート）（ＤＰＭＰ）は、分子構造中に、第３級炭素、アルコキシ基、水酸基、ケト基及び、第２級炭素にチオール基が直接結合している構造を有していない多官能チオール化合物である。 Trimethylolpropane tris (3-mercaptopropionate) (TMMP), tris (3-mercaptopropionyloxy) ethyl isocyanurate (TEMPIC), pentaerythritol tetrakis (3-mercaptopropionate) (PEMP), and dipenta Erythritol hexakis (3-mercaptopropionate) (DPMP) has a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group, a keto group, and a secondary carbon in the molecular structure. It is a polyfunctional thiol compound not possessed.
　２－エチルヘキシル－３－メルカプトプロピオナート（ＥＨＭＰ）は、第３級炭素を含む単官能チオール化合物である。３－メトキシブチル－３－メルカプトプロピオナート（ＭＢＭＰ）はアルコキシ基を有する単官能チオール化合物である。 2-Ethylhexyl-3-mercaptopropionate (EHMP) is a monofunctional thiol compound containing a tertiary carbon. 3-methoxybutyl-3-mercaptopropionate (MBMP) is a monofunctional thiol compound having an alkoxy group.
［紫外線硬化型アクリル系ポリマーの加熱条件］
　得られた紫外線硬化型アクリル系ポリマーを採取し、１５０℃に設定されたオーブンに６時間投入して加熱した。その後、オーブンより取り出し加熱後の紫外線硬化型アクリル系ポリマーとした。 [Heating conditions for UV-curable acrylic polymer]
The obtained ultraviolet curable acrylic polymer was collected, and heated in an oven set at 150 ° C. for 6 hours. Then, it was set as the ultraviolet curable acrylic polymer after taking out from oven and heating.
　得られた紫外線硬化型アクリル系ポリマーについて、１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率、分子量分布、対ＳＵＳ剥離強度、対ＳＵＳ剥離強度変化率、対ＳＵＳ糊残り性、引張せん断ひずみｔａｎθ、粘着はみ出し性及び溶融粘度を下記の要領で測定し、その結果を表１～３に示した。 About the obtained ultraviolet curable acrylic polymer, the change rate of the weight average molecular weight converted by standard polystyrene after being heated at 150 ° C. for 6 hours, the molecular weight distribution, the SUS peel strength, the SUS peel strength change rate, The adhesive strength against SUS, the tensile shear strain tanθ, the sticking-out property and the melt viscosity were measured as follows, and the results are shown in Tables 1 to 3.
　得られた紫外線硬化型アクリル系ポリマーについて、主鎖において、紫外線反応性基を分子内に有するモノマー単位１個に対する、主鎖を構成しているモノマー単位の個数を上記要領で測定し、その結果を表１～３の「モノマー単位の個数」の欄に示した。 With respect to the obtained ultraviolet curable acrylic polymer, the number of monomer units constituting the main chain was measured in the above manner with respect to one monomer unit having an ultraviolet reactive group in the molecule in the main chain. Are shown in the column “Number of monomer units” in Tables 1 to 3.
［対ＳＵＳ剥離強度］
　加熱前及び加熱後の紫外線硬化型アクリル系ポリマーのそれぞれを、ポリエチレンテレフタレート（ＰＥＴ）フィルム上に厚み２０μｍとなるように塗工した。次に、紫外線照射装置（ヘレウス（旧フュージョンＵＶシステムズ）社製　商品名「Ｌｉｇｔｈ　Ｈａｍｍｅｒ６」（Ｈバルブ使用））を用いて、ＵＶ－Ｃ照射強度：約４８ｍＷ／ｃｍ2、積算光量：約６０ｍＪ／ｃｍ2となるように紫外線硬化型アクリル系ポリマーに紫外線（ＵＶ－Ｃ）を照射して、紫外線硬化型アクリル系ポリマーを硬化させて、ポリエチレンテレフタレートフィルム上に厚みが２０μｍの粘着剤層が積層一体化されてなる試験フィルムを作製した。試験フィルムを幅２５ｍｍに切断して試験片を作製した。一方、ＳＵＳ板を用意し、このＳＵＳ板の表面を＃２４０の耐水やすりで研磨した後にヘキサンとアセトンの混合溶剤を用いて払拭して脱脂した。ＳＵＳ板の表面に試験片を粘着剤層によって貼着した後、試験片上に２ｋｇハンドローラーを往復させた。２０分の養生時間を置いた後、島津製作所社製のオートグラフＡＧＳ－１００ＮＸを用いて１８０°の角度で３００ｍｍ／ｍｉｎの速度で剥離し、剥離強度を測定（Ｎ／２５ｍｍ）した。 [Against SUS peel strength]
Each of the ultraviolet curable acrylic polymer before heating and after heating was coated on a polyethylene terephthalate (PET) film so as to have a thickness of 20 μm. Next, UV-C irradiation intensity: about 48 mW / cm 2 , integrated light quantity: about 60 mJ /, using an ultraviolet irradiation device (trade name “Ligth Hammer 6” (H bulb used) manufactured by Heraeus (formerly Fusion UV Systems)) An ultraviolet ray curable acrylic polymer is irradiated with ultraviolet rays (UV-C) so as to be cm 2 to cure the ultraviolet ray curable acrylic polymer, and an adhesive layer having a thickness of 20 μm is laminated on the polyethylene terephthalate film. A test film was prepared. The test film was cut into a width of 25 mm to prepare a test piece. On the other hand, an SUS plate was prepared, and the surface of the SUS plate was polished with a # 240 water-resistant file and then wiped with a mixed solvent of hexane and acetone for degreasing. After sticking the test piece to the surface of the SUS plate with an adhesive layer, a 2 kg hand roller was reciprocated on the test piece. After a curing time of 20 minutes, peeling was performed at an angle of 180 ° at a speed of 300 mm / min using an autograph AGS-100NX manufactured by Shimadzu Corporation, and the peel strength was measured (N / 25 mm).
［対ＳＵＳ剥離強度変化率］
　対ＳＵＳ剥離強度において測定された、加熱前の紫外線硬化型アクリル系ポリマーの剥離強度をＸａ、加熱後の紫外線硬化型アクリル系ポリマーの剥離強度をＸｂとして下記式に基づいて対ＳＵＳ剥離強度変化率を算出した。なお、対ＳＵＳ剥離強度変化率が１０％を超え又は－１０％未満であると、紫外線硬化型アクリル系ポリマーは熱安定性が低いと判断できる。
　対ＳＵＳ剥離強度変化率（％）＝１００×（Ｘｂ－Ｘａ）／Ｘａ [Change rate of peel strength against SUS]
Based on the following formula, the rate of change in SUS peel strength was measured with respect to SUS peel strength, where Xa is the peel strength of the ultraviolet curable acrylic polymer before heating, and Xb is the peel strength of the UV curable acrylic polymer after heating. Was calculated. When the rate of change in peel strength with respect to SUS exceeds 10% or less than −10%, it can be determined that the ultraviolet curable acrylic polymer has low thermal stability.
Change rate of SUS peel strength (%) = 100 × (Xb−Xa) / Xa
［対ＳＵＳ糊残り性］
　加熱前の紫外線硬化型アクリル系ポリマーの対ＳＵＳ剥離強度の測定後、ＳＵＳ板の表面を目視観察し、下記基準に基づいて評価した。
　Ａ（excellent）：ＳＵＳ板の表面に紫外線硬化型アクリル系ポリマーの糊残りは全く発生しておらず、凝集力に問題はなかった。
　Ｂ(good)：ＳＵＳ板の表面に紫外線硬化型アクリル系ポリマーの糊残りが僅かに発生していたものの、凝集力に問題ない範囲であった。
　Ｃ(poor)：ＳＵＳ板の表面に紫外線硬化型アクリル系ポリマーの糊残りが全面的に発生し、凝集力に問題があった。 [Resistant to SUS paste]
After measuring the SUS peel strength of the ultraviolet curable acrylic polymer before heating, the surface of the SUS plate was visually observed and evaluated based on the following criteria.
A (excellent): The adhesive residue of the ultraviolet curable acrylic polymer was not generated at all on the surface of the SUS plate, and there was no problem with the cohesive force.
B (good): Although the adhesive residue of the ultraviolet curable acrylic polymer was slightly generated on the surface of the SUS plate, it was in a range where there was no problem with the cohesive force.
C (poor): The adhesive residue of the ultraviolet curable acrylic polymer was entirely generated on the surface of the SUS plate, and there was a problem in the cohesive force.
［引張せん断ひずみｔａｎθ］
　加熱前の紫外線硬化型アクリル系ポリマーについての対ＳＵＳ剥離強度の測定時と同様の要領で試験フィルムを作製した。試験フィルムから幅１０ｍｍ×長さ１００ｍｍの平面長方形状の試験片を切り出した。２３℃の雰囲気下において試験片の長さ方向の一端部１０ｍｍ分をＳＵＳ台座に貼着した。ＳＵＳ台座を試験片の貼着面が垂直となるように配設した。試験片の長さ方向の他端部に２００ｇの錘を取り付けて３分間保持した後、試験片の長さ方向の一端の変位幅（一次変位幅）を測定した。なお、垂直下方方向をプラス方向とした。下記式に基づいて、引張せん断ひずみｔａｎθを算出した。
　引張せん断ひずみｔａｎθ
　　＝一次変位幅（μｍ）／粘着剤層の厚み（μｍ） [Tensile shear strain tanθ]
A test film was prepared in the same manner as in the measurement of the SUS peel strength of the ultraviolet curable acrylic polymer before heating. A flat rectangular test piece having a width of 10 mm and a length of 100 mm was cut out from the test film. Under an atmosphere of 23 ° C., 10 mm of one end in the length direction of the test piece was attached to the SUS pedestal. The SUS pedestal was arranged so that the test piece was attached to a vertical surface. A 200 g weight was attached to the other end portion in the length direction of the test piece and held for 3 minutes, and then the displacement width (primary displacement width) at one end in the length direction of the test piece was measured. The vertical downward direction was defined as the plus direction. Based on the following formula, the tensile shear strain tan θ was calculated.
Tensile shear strain tanθ
= Primary displacement width (μm) / pressure-sensitive adhesive layer thickness (μm)
［粘着はみ出し性］
　加熱前の紫外線硬化型アクリル系ポリマーについての対ＳＵＳ剥離強度の測定時と同様の要領で試験フィルムを作製した。なお、ポリエチレンテレフタレートフィルムの一面に離型処理を施し、この離型処理面に粘着剤層を形成した。 [Adhesive protrusion]
A test film was prepared in the same manner as in the measurement of the SUS peel strength of the ultraviolet curable acrylic polymer before heating. In addition, the mold release process was given to one surface of the polyethylene terephthalate film, and the adhesive layer was formed in this mold release process surface.
　試験フィルムから一辺が２５ｍｍの平面正方形状の試験片を１５個切り出した。１４個の試験片から粘着剤層をポリエチレンテレフタレートフィルムから剥離し、残り１個の試験片の粘着剤層上に積層一体化させた。ポリエチレンテレフタレートフィルム上に３００μｍの粘着剤層が積層されてなる試験体を作製した。 15 Planar square test pieces having a side of 25 mm were cut out from the test film. The pressure-sensitive adhesive layer was peeled from the polyethylene terephthalate film from the 14 test pieces and laminated and integrated on the pressure-sensitive adhesive layer of the remaining one test piece. A test body in which a 300 μm pressure-sensitive adhesive layer was laminated on a polyethylene terephthalate film was prepared.
　試験体を２枚のポリエチレンテレフタレートフィルム間に配設し、上側のポリエチレンテレフタレートフィルムを介して試験体上に２ｋｇの錘を１時間載置した。なお、下側のポリエチレンテレフタレートフィルムにおける試験体に対する対向面は離型処理が施されていた。１時間経過後、試験体上の錘を除去し、試験体の粘着剤層の端面を目視観察し、下記基準に基づいて評価した。
　Ａ（excellent）：粘着剤層にはみ出しが見られず、上側のポリエチレンテレフタレートフィルムの剥離時に粘着剤層によるひっかかりを生じなかった。
　Ｂ(good)：粘着剤層にはみ出しがほとんど見られなかったが、上側のポリエチレンテレフタレートフィルムの剥離時に接触していた粘着剤層により引っかかりを生じた。
　Ｃ(poor)：粘着剤層にはみ出しが見られ、粘着剤層が上側のポリエチレンテレフタレートフィルムに転写しており、上側のポリエチレンテレフタレートフィルムの剥離時に粘着剤層がポリエチレンテレフタレートフィルム側へ移行し粘着欠けを生じた。 The test body was disposed between two polyethylene terephthalate films, and a 2 kg weight was placed on the test body for 1 hour via the upper polyethylene terephthalate film. The opposing surface of the lower polyethylene terephthalate film with respect to the test body was subjected to release treatment. After 1 hour, the weight on the test specimen was removed, and the end face of the pressure-sensitive adhesive layer of the test specimen was visually observed and evaluated based on the following criteria.
A (excellent): No protrusion was observed in the pressure-sensitive adhesive layer, and no catching by the pressure-sensitive adhesive layer occurred when the upper polyethylene terephthalate film was peeled off.
B (good): Almost no protrusion was observed in the pressure-sensitive adhesive layer, but it was caught by the pressure-sensitive adhesive layer that was in contact with the upper polyethylene terephthalate film.
C (poor): The adhesive layer is protruding, the adhesive layer is transferred to the upper polyethylene terephthalate film, and when the upper polyethylene terephthalate film is peeled off, the adhesive layer moves to the polyethylene terephthalate film side and lacks adhesion. Produced.
［溶融粘度］
　加熱前の紫外線硬化型アクリル系ポリマーについて、紫外線硬化型アクリル系ポリマーの１３０℃における溶融粘度をＪＩＳ　Ｋ　６８６２に準拠して測定した。下記基準に基づいて評価した。
　Ａ（excellent）：４５Ｐａ・ｓ未満であり、ホットメルト塗工性に大変適していた。
　Ｂ(good)：４５～７０Ｐａ・ｓであり、ホットメルト塗工性に適していた。
　Ｃ(poor)：７０Ｐａ・ｓを超えており、ホットメルト塗工性に適していなかった。 [Melt viscosity]
With respect to the ultraviolet curable acrylic polymer before heating, the melt viscosity at 130 ° C. of the ultraviolet curable acrylic polymer was measured according to JIS K 6862. Evaluation was made based on the following criteria.
A (excellent): Less than 45 Pa · s, which was very suitable for hot melt coating property.
B (good): 45 to 70 Pa · s, which was suitable for hot melt coating property.
C (poor): It exceeded 70 Pa · s and was not suitable for hot melt coating property.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表１～３の実施例と比較例との比較から、重量平均分子量の変化量が－２０％～２０％の範囲にある場合には、加熱前後の剥離強度の低下が低い（対ＳＵＳ剥離強度変化率は、－１０％以下）ことがわかる。また、塗工性が優れていることも分かる。実施例３～１６においては、加熱前後の何れにおいても剥離強度が高く、粘着性に優れていることが分かる。 From the comparison between the examples in Tables 1 to 3 and the comparative example, when the amount of change in the weight average molecular weight is in the range of −20% to 20%, the decrease in peel strength before and after heating is low (vs. SUS peel strength It can be seen that the rate of change is -10% or less. It can also be seen that the coatability is excellent. In Examples 3 to 16, it can be seen that the peel strength is high and the adhesiveness is excellent before and after heating.
　実施例２、９～１２と実施例１、３～８との対比から、モノマー単位の個数が３５０～６００の範囲に入る場合には、一次変位幅及び引張せん断ひずみｔａｎθが小さく、紫外線硬化型アクリル系ポリマーに凝集力を持たせることができることから、紫外線硬化型アクリル系ポリマーの変形によって周囲を汚染することを防止することができる。 From the comparison between Examples 2 and 9-12 and Examples 1 and 3 to 8, when the number of monomer units falls within the range of 350 to 600, the primary displacement width and the tensile shear strain tanθ are small, and the ultraviolet curable type is used. Since the acrylic polymer can be given cohesive force, it is possible to prevent the surroundings from being contaminated by the deformation of the ultraviolet curable acrylic polymer.
　紫外線硬化型アクリル系ポリマーは、安定剤を必要とすることなく、溶融時の熱安定性及び塗工性に優れている。紫外線硬化型アクリル系ポリマーは、紫外線照射による硬化によって所望の粘着性を発現する。紫外線硬化型アクリル系ポリマーは、紫外線硬化型ホットメルト粘着剤として好適に使用することができる。紫外線硬化型ホットメルト接着剤は、硬化後の粘着性を低く設計することによって、例えば、糊残りなく被着体に対して剥離可能に貼着させる用途（例えば、付箋など）に好適に用いることができる。一方、紫外線硬化型ホットメルト接着剤は、硬化後の粘着性を高く設計することによって、粘着テープ、消費者向け商品ラベル、電子機器（パソコン、スマートフォン、テレビ及びデジタルカメラなど）などの用途にも好適に用いることができる。 The ultraviolet curable acrylic polymer is excellent in thermal stability and coating property at the time of melting without requiring a stabilizer. The ultraviolet curable acrylic polymer exhibits desired tackiness by curing with ultraviolet irradiation. The ultraviolet curable acrylic polymer can be suitably used as an ultraviolet curable hot melt adhesive. UV curable hot-melt adhesives should be used suitably for applications (such as sticky notes) that can be peeled off and adhered to an adherend without any adhesive residue, by designing the adhesive after curing to a low level. Can do. On the other hand, UV curable hot melt adhesives are designed for high adhesiveness after curing, so that they can be used in applications such as adhesive tapes, consumer product labels, and electronic devices (such as PCs, smartphones, TVs, and digital cameras). It can be used suitably.
　（関連出願の相互参照）
　本出願は、２０１６年２月１０日に出願された日本国特許出願第２０１６－２３５７３号に基づく優先権を主張し、この出願の開示はこれらの全体を参照することにより本明細書に組み込まれる。 (Cross-reference of related applications)
This application claims priority based on Japanese Patent Application No. 2016-23573 filed on Feb. 10, 2016, the disclosure of which is incorporated herein by reference in its entirety. .

Claims (12)

  1. 紫外線の照射によって架橋する紫外線硬化型アクリル系ポリマーであって、１５０℃にて６時間加熱された後の標準ポリスチレンにより換算された重量平均分子量の変化率が－２０～２０％であることを特徴とする紫外線硬化型アクリル系ポリマー。 A UV-curable acrylic polymer that is cross-linked by UV irradiation, characterized in that the change rate of the weight average molecular weight converted to standard polystyrene after heating at 150 ° C. for 6 hours is −20 to 20%. UV curable acrylic polymer.
  2. 紫外線反応性基を分子内に有しない（メタ）アクリレート単位８５～９９．８質量％及び紫外線反応性基を分子内に有するモノマー単位０．１～５質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート単位中の主となる（メタ）アクリレート単位を７０質量％以上含有し且つ連鎖移動剤としてのチオール化合物の残基を末端に有する重合体を含むことを特徴とする請求項１に記載の紫外線硬化型アクリル系ポリマー。 The composition contains 85 to 99.8% by mass of (meth) acrylate unit having no UV-reactive group in the molecule and 0.1 to 5% by mass of monomer unit having the UV-reactive group in the molecule, A polymer containing 70% by mass or more of a main (meth) acrylate unit in a (meth) acrylate unit not present in the molecule and having a terminal thiol compound residue as a chain transfer agent is included. The ultraviolet curable acrylic polymer according to claim 1.
  3. 重合体が、（メタ）アクリル酸単位０．１～１０質量％を更に含有することを特徴とする請求項２に記載の紫外線硬化型アクリル系ポリマー。 3. The ultraviolet curable acrylic polymer according to claim 2, wherein the polymer further contains 0.1 to 10% by mass of (meth) acrylic acid units.
  4. 紫外線反応性基を分子内に有するモノマーは、紫外線反応性基を分子内に有する（メタ）アクリレートであることを特徴とする請求項１又は請求項２に記載の紫外線硬化型アクリル系ポリマー。 The ultraviolet curable acrylic polymer according to claim 1 or 2, wherein the monomer having an ultraviolet reactive group in the molecule is a (meth) acrylate having an ultraviolet reactive group in the molecule.
  5. 紫外線反応性基を分子内に有するモノマーは、ベンゾフェノン基を分子内に有する（メタ）アクリレートであることを特徴とする請求項１～４の何れか１項に記載の紫外線硬化型アクリル系ポリマー。 The ultraviolet curable acrylic polymer according to any one of claims 1 to 4, wherein the monomer having an ultraviolet reactive group in the molecule is a (meth) acrylate having a benzophenone group in the molecule.
  6. ベンゾフェノン基を分子内に有する（メタ）アクリレートは、４－アクリロイルオキシベンゾフェノンであることを特徴とする請求項５に記載の紫外線硬化型アクリル系ポリマー。 6. The ultraviolet curable acrylic polymer according to claim 5, wherein the (meth) acrylate having a benzophenone group in the molecule is 4-acryloyloxybenzophenone.
  7. 連鎖移動剤は、分子構造中に、第３級炭素、アルコキシ基、水酸基、ケト基及び、第２級炭素にチオール基が直接結合している構造を有していないチオール化合物であることを特徴とする請求項２～６の何れか１項に記載の紫外線硬化型アクリル系ポリマー。 The chain transfer agent is a thiol compound that does not have a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group, a keto group, or a secondary carbon in the molecular structure. The ultraviolet curable acrylic polymer according to any one of claims 2 to 6.
  8. 主鎖中において、主鎖を構成している全モノマー単位３５０～６００個に対して紫外線反応性基を分子内に有するモノマー単位を１個有しており、且つ、紫外線硬化後の引張せん断ひずみｔａｎθが１．５以下であることを特徴とする請求項２～７の何れか１項に記載の紫外線硬化型アクリル系ポリマー。 The main chain has one monomer unit having an ultraviolet reactive group in the molecule for every 350 to 600 monomer units constituting the main chain, and tensile shear strain after UV curing. 8. The ultraviolet curable acrylic polymer according to claim 2, wherein tan θ is 1.5 or less.
  9. 請求項１～８の何れか１項に記載の紫外線硬化型アクリル系ポリマーを含むことを特徴とする紫外線硬化型ホットメルト粘着剤。 An ultraviolet curable hot-melt pressure-sensitive adhesive comprising the ultraviolet curable acrylic polymer according to any one of claims 1 to 8.
  10. 紫外線反応性基を分子内に有しない（メタ）アクリレート８５～９９．８質量％及び紫外線反応性基を分子内に有するモノマー０．１～５質量％を含み且つ上記紫外線反応性基を分子内に有しない（メタ）アクリレート中の主となる（メタ）アクリレートを７０質量％以上含有するモノマー組成物を連鎖移動剤としてのチオール化合物の存在下にて重合させることを特徴とする紫外線硬化型アクリル系ポリマーの製造方法。 It contains 85-99.8% by mass of (meth) acrylate having no UV-reactive group in the molecule and 0.1-5% by mass of monomer having an UV-reactive group in the molecule, and the above-mentioned UV-reactive group is contained in the molecule. UV-curing acrylic, which is polymerized in the presence of a thiol compound as a chain transfer agent, containing a monomer composition containing 70% by mass or more of the main (meth) acrylate in (meth) acrylate not contained in Method for producing a polymer.
  11. モノマー組成物が、（メタ）アクリル酸０．１～１０質量％を更に含有することを特徴とする請求項１０に記載の紫外線硬化型アクリル系ポリマーの製造方法。 The method for producing an ultraviolet curable acrylic polymer according to claim 10, wherein the monomer composition further contains 0.1 to 10% by mass of (meth) acrylic acid.
  12. 連鎖移動剤は、分子構造中に、第３級炭素、アルコキシ基、水酸基、ケト基及び、第２級炭素にチオール基が直接結合している構造を有していないチオール化合物であることを特徴とする請求項１０又は請求項１１に記載の紫外線硬化型アクリル系ポリマーの製造方法。 The chain transfer agent is a thiol compound that does not have a structure in which a thiol group is directly bonded to a tertiary carbon, an alkoxy group, a hydroxyl group, a keto group, or a secondary carbon in the molecular structure. The method for producing an ultraviolet curable acrylic polymer according to claim 10 or 11.
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