WO2020262646A1 - Adhesive for laminate - Google Patents

Adhesive for laminate Download PDF

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Publication number
WO2020262646A1
WO2020262646A1 PCT/JP2020/025339 JP2020025339W WO2020262646A1 WO 2020262646 A1 WO2020262646 A1 WO 2020262646A1 JP 2020025339 W JP2020025339 W JP 2020025339W WO 2020262646 A1 WO2020262646 A1 WO 2020262646A1
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WO
WIPO (PCT)
Prior art keywords
adhesive
film
laminate
present
component
Prior art date
Application number
PCT/JP2020/025339
Other languages
French (fr)
Inventor
Kenji Matsuda
Hitoshi Ikeda
Original Assignee
Henkel Ag & Co. Kgaa
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Publication date
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Publication of WO2020262646A1 publication Critical patent/WO2020262646A1/en

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    • 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
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes
    • C09J175/08—Polyurethanes from polyethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C08G18/12—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step using two or more compounds having active hydrogen in the first polymerisation step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/34—Carboxylic acids; Esters thereof with monohydroxyl compounds
    • C08G18/343—Polycarboxylic acids having at least three carboxylic acid groups
    • C08G18/345—Polycarboxylic acids having at least three carboxylic acid groups having three carboxylic acid groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4205—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups
    • C08G18/4208—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups
    • C08G18/4211—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups derived from aromatic dicarboxylic acids and dialcohols
    • C08G18/4216—Polycondensates having carboxylic or carbonic ester groups in the main chain containing cyclic groups containing aromatic groups derived from aromatic dicarboxylic acids and dialcohols from mixtures or combinations of aromatic dicarboxylic acids and aliphatic dicarboxylic acids and dialcohols
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4236—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups
    • C08G18/4238—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols
    • C08G18/4241—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols from dicarboxylic acids and dialcohols in combination with polycarboxylic acids and/or polyhydroxy compounds which are at least trifunctional
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4825—Polyethers containing two hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
    • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
    • C08G18/7671—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups containing only one alkylene bisphenyl group
    • 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
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes
    • C09J175/06—Polyurethanes from polyesters

Definitions

  • the present invention relates to an adhesive for laminate, and more specifically to an adhesive for laminate, which is excellent in stability and adhesion, and does not degrade appearance of a film when the film is laminated (or pasted); and to a laminated film using the same.
  • a composite film obtainable by laminating (or pasting) a plastic film e.g., a film made of polyethylene, polypropylene, nylon, polyester, polyimide, etc.
  • a metal deposited film and a metal foil e.g., a foil made of aluminum, copper, etc.
  • an adhesive for bonding the plastic film, the metal deposited film and the metal foil an urethane adhesive obtainable by combining an organic polyol and an organic isocyanate.
  • Patent Literatures 1 to 3 disclose laminated films obtainable by laminating using a urethane adhesive.
  • Patent Literature 1 discloses a method for producing a laminate using a urethane adhesive obtainable by mixing a polyisocyanate, a polyol, and an ester which is liquid at 25°C (see [Claims], [Table 4] to [Table 6]).
  • Patent Literature 2 discloses a method in which polyethylene terephthalate and a metal deposited film are laminated together using a solvent-free urethane adhesive (see [Claims], [0006], [Table 1]).
  • Patent Literature 3 discloses a method for producing a laminated film using a solvent-free adhesive synthesized from a crystalline polyol and a polyisocyanate (see [Claims], [0001], [Table 1]).
  • Patent Literatures 1 to 3 mention that the appearance of the laminated films is improved, however, it could not be said that high demands of consumers are not sufficiently satisfied.
  • the adhesives are required to be excellent in initial adhesive strength to a film after curing.
  • the present inventors thought it important that the adhesive maintains uniformity and hardly causes cloudiness.
  • the present invention was performed so as to solve the above problems and an object thereof is to provide an adhesive for laminate, which is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, and maintains uniformity and is capable of preventing occurrence of cloudiness, when a laminated film is produced by laminating (or pasting) a plastic film, and the laminated film having excellent appearance produced by using the adhesive for laminate.
  • a urethane resin composition comprising a urethane prepolymer prepared from a polyester polyol; a urethane resin obtainable by chain extension of this urethane prepolymer with a polyol component; and a specific plasticizer is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, and is excellent in uniformity and prevention of cloudiness, when the laminated film is produced by laminating a plastic film, thus completing the present invention.
  • An adhesive for laminate which is obtainable by formulating (or combining) (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein the urethane prepolymer (A) is a reaction product of (a1) a polyester polyol and (a2) an isocyanate monomer.
  • the adhesive for laminate according to 1 or 2 wherein the urethane prepolymer (A) has a number average molecular weight 1,500 to 4,000. 4.
  • An adhesive for laminate according to an embodiment of the present invention is an adhesive for laminate, which is obtainable by formulating (or combining) (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein the urethane prepolymer (A) is a urethane resin obtainable by reacting (a1) a polyester polyol with (a2) an isocyanate monomer, and therefore, the adhesive for laminate is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, when a plastic film is laminated to produce a laminated film, and maintains uniformity of the components and cause no cloudiness even when stored at a low temperature over a long period. Since a laminated film according to an embodiment of the present invention is obtainable by using the adhesive for laminate, lamination can be quickly performed and the laminated film is also excellent in appearance.
  • Figure 1 schematically shows a cross-section of a laminated film according to an embodiment of the present invention.
  • Figure 2 schematically shows a cross-section of a laminated film according to another embodiment of the present invention.
  • An adhesive for laminate according to an embodiment of the present invention is obtainable by formulating(or combining) (or mixing) (A) a urethane prepolymer having an isocyanate group at the end (hereinafter also referred to as “component (A)”), (B) a polyol component (hereinafter also referred to as “component (B)”)) and (C) a citric acid ester (or citrate) (hereinafter also referred to as “component (C)”), and comprises the components (A) to (C).
  • component (A) a urethane prepolymer having an isocyanate group at the end
  • component (B) a polyol component
  • component (C) a citric acid ester (or citrate)
  • the adhesive according to the embodiment of the present invention is not particularly limited by the order of formulating and the formulating method of the components (A) to (C) as long as the objective adhesive can be obtainable.
  • the adhesive according to the embodiment of the present invention may be obtainable by simultaneously formulating three components, for example, (A) a urethane prepolymer, (B) a polyol component and (C) a citric acid ester, or obtainable by formulating the component (A) or (C) in advance with the component (B) and formulating with the remaining one component.
  • the adhesive is more preferably obtainable by mixing the components (B) and (C) in advance and formulating the mixture with the component (A).
  • the production of the adhesive by formulating (or mixing) the component (A), the component (B) and the component (C) can be performed by a known method.
  • the adhesive can be obtainable by formulating the components (A) to (C) in a solvent, it is also possible to formulate the components (A) to (C) without using the solvent.
  • the adhesive according to the embodiment of the present invention may be a two-component adhesive which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C), or a two-component adhesive which is obtainable by formulating a first liquid comprising the components (A) and (C) and a second liquid comprising the component (B).
  • the adhesive according to the embodiment of the present invention is more preferably a two-component adhesive comprising a first liquid including the component (A) and a second liquid including the components (B) and (C).
  • the first and second liquids each can appropriately comprise various additives mentioned below.
  • the urethane prepolymer (A) is a urethane resin produced by reacting (a1) a polyester polyol with (a2) an isocyanate monomer.
  • the urethane prepolymer (A) has a chemical structure (e.g., having an ester bond in main chain) based on the polyester polyol (a1), the adhesive for laminate according to the embodiment of the present invention makes it hard to generate air bubbles on a film surface when a plurality of films are laminated together, and thus it is possible to keep a film appearance smooth.
  • the urethane prepolymer (A) preferably has a number average molecular weight of 1,500 to 4,000. When the number average molecular weight of the urethane prepolymer (A) is within the above range, the adhesive for laminate according to the embodiment of the present invention is excellent in adhesion.
  • the number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene standard. Specifically, Mn can be obtained measuring using the following GPC apparatus and measuring method, followed by conversion. HCL-8220GPC manufactured by TOSOH CORPORATION is used as the GPC apparatus and RI is used as a detector. Two TSKgeI SuperMultipore HZM columns manufactured by TOSOH CORPORATION are used as a GPC column. A sample is dissolved in tetrahydrofuran and the solution thus obtained is allowed to flow at a flow rate of 0.35 ml/minute and at a column temperature of 40°C to obtain a measured value.
  • GPC gel permeation chromatography
  • polyester polyol refers to a compound which is “main chain type” polyester and has an ester bond and a hydroxyl group in “main chain”. This hydroxyl group is usually positioned at the end of the main chain, and acts as a functional group reacting with an isocyanate group.
  • the polyester polyol is commonly obtainable by a condensation polymerization reaction of a low molecular polyol with dicarboxylic acid and an anhydride thereof.
  • dicarboxylic acid examples include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, trimesic acid, cyclohexanedicarboxylic acid and the like. These dicarboxylic acids are used alone or in combination.
  • carboxylic anhydride examples include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. These carboxylic anhydrides are used alone or in combination.
  • the low molecular polyol preferably has 1 to 3 functional groups, and particularly preferably a difunctional polyol, that is, a so-called diol.
  • the low molecular polyols can be used alone or in combination.
  • diol examples include low molecular weight diols such as ethylene glycol, 1-methylethylene glycol, 1-ethylethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentyl glycol, 2-methyl-1,3-propanediol, cyclohexanedimethanol, 2,4-dimethyl-1,5-pentanediol and 2,4-dibutyl-1,5-pentanediol. Particularly, at least one selected from ethylene glycol, diethylene glycol, butanediol, hexanediol and neopentyl glycol may be used.
  • polyester polyol preferably has a number average molecular weight of 400 to 1,300.
  • the number average molecular weight of the polyester polyol (a1) is within the above range, the chain length may decrease and thus it becomes easier to crosslink with the isocyanate monomer (a2). Since the unreacted (a2) isocyanate monomer decreases, the adhesive for laminate according to the embodiment of the present invention can include the urethane prepolymer (A) more, and can be more excellent in adhesion.
  • the isocyanate monomer (a2) in the embodiment of the present invention is not particularly limited as long as the objective adhesive for laminate of the present invention can be obtainable, and preferably includes an aromatic isocyanate.
  • the isocyanate monomer (a2) includes the aromatic isocyanate, the adhesion of the adhesive for laminate according to the embodiment of the present invention is improved.
  • the “(a2) isocyanate monomer” does not mean that it is composed of the aromatic isocyanate only.
  • the isocyanate monomer (a2) may include an aliphatic isocyanate and an alicyclic isocyanate.
  • the “aliphatic isocyanate” refers to a compound which has a chain-like hydrocarbon chain to which an isocyanate group is directly bonded, and also has no cyclic hydrocarbon chain.
  • the “aliphatic isocyanate” may have an aromatic ring, but the isocyanate group is not bonded directly to the aromatic ring.
  • the cyclic hydrocarbon chain does not contain aromatic rings.
  • the “alicyclic isocyanate” is a compound which has a cyclic hydrocarbon chain, and may have a chain-like hydrocarbon chain.
  • the isocyanate group may be directly bonded to the cyclic hydrocarbon chain, or may be directly bonded to a chain-like hydrocarbon chain which may be present.
  • the “alicyclic isocyanate” may have an aromatic ring, the isocyanate group is not directly bonded to the aromatic ring.
  • aromatic isocyanate refers to a compound having an aromatic ring in which the isocyanate group is directly bonded to the aromatic ring. Therefore, even though a compound has an aromatic ring in the molecule, when the isocyanate group is not directly bonded to the aromatic ring, the compound is classified into the aliphatic isocyanate or the alicyclic isocyanate.
  • 2,2’-diphenylmethane diisocyanate, 2,4’-diphenylmethane diisocyanate or 4,4’-diphenylmethane diisocyanate corresponds to the aromatic isocyanate, since the isocyanate group is directly bonded to the aromatic ring.
  • xylylene diisocyanate corresponds to the aliphatic isocyanate, although it has an aromatic ring, since the isocyanate group is not directly bonded to the aromatic ring and is bonded to the methylene group.
  • the aromatic ring may have a ring-fused structure in which two or more benzene rings are condensed.
  • aromatic isocyanate examples include 2,2’-diphenylmethane diisocyanate, 2,4’-diphenylmethane diisocyanate, 4,4’-diphenylmethane diisocyanate and the like.
  • aliphatic isocyanate examples include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate) and 1,3-bis(isocyanatomethyl)benzene (xylylene diisocyanate), etc.
  • HDI 1,6-diisocyanatobutane
  • 1,5-diisocyanatopentane 1,6-diisocyanatohexane
  • HDI 1,6-diisocyanato-2,2,4-trimethylhexane
  • methyl 2,6-diisocyanatohexanoate methyl 2,6-diisocyanatohexanoate
  • xylylene diisocyanate
  • alicyclic isocyanate examples include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate: IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate) and 1,4-diisocyanatocyclohexane, etc.
  • IPDI isophorone diisocyanate
  • 1,3-bis(isocyanatomethyl)cyclohexane hydroxylylene diisocyanate
  • bis(4-isocyanatocyclohexyl)methane hydrogenated diphenylmethane diisocyanate
  • 1,4-diisocyanatocyclohexane etc.
  • (B) a polyol component as long as the objective adhesive for laminate according to the embodiment of the present invention can be obtainable and an adverse influence is not exerted on the production of the adhesive.
  • examples thereof include polyester polyols, acrylic polyols, polyether polyols, polyether polyester polyols, polyester polyurethane polyols, polyether polyurethane polyols, or modified products of these polyols.
  • the polyol component (B) may include (a1) a polyester polyol used in the production of the urethane prepolymer (A).
  • the adhesive for laminate according to the embodiment of the present invention comprises (C) a citric acid ester.
  • the citric acid ester (C) acts as a plasticizer.
  • the adhesive for laminate comprises the citric acid ester (C)
  • the adhesion can be improved and the uniformity can be excellent, thus the occurrence of cloudiness can be prevented.
  • a laminated film according to an embodiment of the present invention is obtainable by using the adhesive for laminate, lamination can be quickly performed and the laminated film can be excellent in appearance.
  • citric acid ester (C) examples include triethyl citrate, tributyl citrate, 2-ethylhexyl citrate, acetyl triethyl citrate (or triethyl acetyl citrate), acetyl tributyl citrate (or tributyl acetyl citrate) and acetyl 2-ethylhexyl citrate (or 2-ethylhexyl acetyl citrate).
  • the citric acid ester (C) preferably includes acetyl citric acid esters such as acetyl triethyl citrate, acetyl tributyl citrate, acetyl 2-ethylhexyl citrate, and most preferably tributyl acetyl citrate.
  • acetyl citric acid esters such as acetyl triethyl citrate, acetyl tributyl citrate, acetyl 2-ethylhexyl citrate, and most preferably tributyl acetyl citrate.
  • the adhesive for laminate according to the embodiment of the present invention may be obtainable by formulating (or mixing) other components, in addition to the components (A) to (C).
  • other components include unreacted isocyanate monomers, solvents, tackifier resins, pigments, plasticizers (excluding the above citric acid ester (C)), catalysts and adhesion promoters, etc.
  • the unreacted isocyanate monomer refers to (a2) an isocyanate monomer which did not react with (a1) a polyester polyol, when the polyester polyol (a1) was reacted with the isocyanate monomer (a2) to prepare (A) a urethane prepolymer.
  • the urethane prepolymer (A) is reacted with (B) a polyol component, the unreacted isocyanate monomer can also react with the polyol component (B).
  • tackifier resin examples include styrene-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins and polyester resins (excluding polyester polyols), etc.
  • the tackifier resin commonly has a low molecular weight of less than 1,500 g/mol, and particularly less than 1,000 g/mol.
  • An amount of the tackifier resin to be added is preferably 0 to 50 parts by mass, and more preferably 30 parts by mass or less, based on 100 parts by mass of the total mass (solid content) of the adhesive.
  • pigment examples include nanopigments based on TiO 2 , SiO 2 , Fe 2 O 3 or similar oxides or oxyhydrates. Usually, these pigments preferably have a particle size of 500 nm or less, and more preferably less than 100 nm.
  • plasticizer examples include white oil, naphthenic mineral oil, paraffinic hydrocarbon oil, polypropylene oligomer, polybutene oligomer, polyisoprene oligomer, hydrogenated polyisoprene and/or polybutadiene oligomer, phthalate, adipate, benzoate ester, vegetable oil or animal oil, and derivatives thereof, etc. It is considered that the vegetable oil, the animal oil and derivatives thereof are commonly used in foods and have higher stability, they are more preferable considering that the adhesive for laminate according to the embodiment of the present invention is employed so as to produce food packaging films.
  • Catalyst examples include metal catalysts, for example, tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead catalysts ((lead oleate, lead naphthenate, lead octanoate, etc.), other metal catalysts (naphthenic acid metal salt such as cobalt naphthenate) and the like; and amine-based catalysts, for example, triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, dialkylaminoalkylamines and the like.
  • metal catalysts for example, tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead catalysts ((lead oleate, lead nap
  • adhesion promoter examples include silane compounds. It is possible to use, as the adhesion promoter, known organic functional silanes, for example, (meth)acryloxy functional, epoxy functional, amine functional and non-reactive substituted silanes.
  • Examples thereof include vinyltrialkoxysilane, alkyltrialkoxysilane, tetraalkoxysilane, 3-acryloxypropyltrialkoxysilane, 3-methacryloxypropyltrialkoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane, 2-glycidyloxyethyltrimethoxysilane and the like.
  • the adhesion promoter is preferably included in an amount of 0.1 to 5 parts by mass based on 100 parts by mass of the total mass (solid content) of the adhesive.
  • the adhesive for laminate according to the embodiment of the present invention can be produced by mixing (A) a component, (B) a component and (C) a component.
  • the adhesive for laminate according to the embodiment of the present invention may be a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C), or a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the components (A) and (C) with a second liquid comprising the component (B).
  • other components may be mixed.
  • the first and second liquids each can appropriately comprise various additives mentioned below.
  • the adhesive for laminate according to the embodiment of the present invention is a two-component adhesive
  • the adhesive for laminate is more excellent in storage stability because of using the component (C).
  • the adhesive for laminate according to the embodiment of the present invention is more preferably a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C).
  • the mixing method there is no particular limitation on the mixing method as long as the objective adhesive for laminate of the present invention can be obtainable.
  • the adhesive for laminate according to the embodiment of the present invention can be produced without requiring a special mixing method and a special mixing order, etc.
  • the obtainable adhesive for laminate shows small decrease in initial adhesive strength to a film and small decrease in adhesive strength over time.
  • the adhesive for laminate according to the embodiment of the present invention is applied to a film at 15 to 100°C, the adhesive should have a low viscosity in this temperature range.
  • the viscosity of the adhesive for food packaging film is 300 to 5,000 mPas at 40°C, and preferably 200 to 4,000 mPas at 50°C, as measured using a Brookfield viscometer.
  • the laminated film according to the embodiment of the present invention is a laminate produced by using the above adhesive for laminate.
  • the film to be used to form a laminate is not particularly limited as long as the laminate according to the embodiment of the present invention can be obtainable and includes, for example, a film in which a metal layer is formed on a plastic base material, and a film in which a metal layer is not formed on a plastic base material.
  • the adhesive for laminate according to the embodiment of the present invention is applied to a film.
  • the application can be performed by various methods such as gravure coating, wire bar coating, air knife coating, die coating, lip coating and comma coating methods.
  • the laminated film can be produced by laminating a plurality of films, on which the adhesive for laminate according to the embodiment of the present invention is applied, together.
  • the application amount is preferably 0.5 to 100 g/m 2 , and more preferably 1 to 15 g/m 2 .
  • the laminated film according to the embodiment of the present invention is obtainable by laminating a plurality of films together using the adhesive.
  • An example of the embodiment of the present invention is shown in Figs. 1 and 2, but the present invention is not limited to these embodiments.
  • Figure 1 schematically shows a cross-section of a laminated film according to an embodiment of the present invention.
  • a laminated film 10 is formed of two films and an adhesive for laminated film 13 interposed therebetween, and the two films 11 and 12 are laminated together using the adhesive for laminated sheet 13.
  • the films 11 and 12 may be made of the same or different material.
  • the two films 11 and 12 are laminated together, or three or more films may be laminated together.
  • FIG. 2 A cross-section of a laminated film according to another embodiment of the present invention is schematically shown in Fig. 2.
  • a thin film 11a is formed between a film 11 and an adhesive for laminated film 13.
  • Figure 2 shows an embodiment in which a metal thin film 11a is formed on a surface of the film 11 when the film 11 is a plastic film.
  • the metal thin film 11a can be formed on the surface of the plastic film 11, for example, by vapor deposition, and the laminated film of Fig. 2 can be obtainable by laminating the film 11, on which surface the metal thin film 11a is formed, together with the film 12 by interposing the adhesive for laminated film 13 therebetween.
  • Examples of the metal to be deposited on the plastic film include aluminum, steel, copper and the like. It is possible to impart barrier properties to the plastic film by subjecting the film to vapor deposition. Silicon oxide or aluminum oxide is used as a vapor deposition material.
  • the plastic film 11 as a base material may be either transparent, or white- or black-colored.
  • a plastic film made of polyvinyl chloride, polyester, a fluororesin or an acrylic resin is used as the film 12.
  • a polyethylene terephthalate film or a polybutylene terephthalate film is particularly preferably used.
  • the films 11 and 12 may be either transparent or colored.
  • the deposited thin film 11a of the film 11 and the film 12 are laminated together using the adhesive for laminated film 13 according to the embodiment of the present invention, and the films 11 and 12 are often laminated together by a dry lamination method. Therefore, the adhesive for laminated film 13 is required to be excellent in initial pressure sensitive adhesion to a film during lamination and to be excellent in adhesion to a film after curing.
  • the laminated film according to the embodiment of the present invention is used to produce various packaging bags, outdoor materials, etc.
  • the packaging bag refers to a bag-shaped article obtainable by processing the laminated film so as to contain foods, detergents, shampoo, rinse or the like.
  • Examples of the outdoor material include articles to be used outdoors, such as wall protecting materials, roofing materials, solar battery modules, window materials, outdoor flooring materials, illumination protection materials, automobile members and signboards.
  • the packaging bag and outdoor material take a form including a laminated film obtainable by laminating a plurality of films together.
  • a specific method for producing a urethane prepolymer (A1) will be shown below.
  • Table 1 38.3 parts by mass of a polyester polyol (a1-1) was charged in a reaction vessel, followed by stirring under reduced pressure for 1 hour while heating the reaction vessel in an oil bath at 80°C to remove moisture. Then, 61.7 parts by mass of an isocyanate monomer (a2) was charged, followed by stirring under reduced pressure at 80°C for 1 hour to prepare 100 parts by mass of an isocyanate component.
  • the isocyanate component includes 70 parts by mass of a urethane prepolymer (A1) and 30 parts by mass of an unreacted isocyanate monomer.
  • the number average molecular weight of the urethane prepolymer (A1) is a value measured by GPC.
  • the measured value is a number average molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene standard.
  • GPC gel permeation chromatography
  • the value can be measured using the following GPC apparatus and measuring method.
  • HCL-8220GPC manufactured by TOSOH CORPORATION was used as a GPC apparatus, and RI was used as a detector.
  • Two TSKgel SuperMultipore HZ-M columns manufactured by TOSOH CORPORATION were used as a GPC column.
  • a sample was dissolved in tetrahydrofuran and the solution thus obtained was allowed to flow at a flow rate of 0.35 ml/minute and at a column temperature of 40°C and then the molecular weight was determined by conversion of an observed molecular weight based on a calibration curve obtained by using polystyrene having a monodisperse molecular weight as a standard reference material.
  • Citric acid ester C-1) ATBC (acetyl tributyl citrate, Taoka Chemical Company, Limited) (C-2) ATEC (acetyl triethyl citrate, Jungbunzlauer Japan Co., Ltd.) (C-3) TEC (triethyl citrate, Jungbunzlauer Japan Co., Ltd.) (C-4) TBC (tributyl citrate, Jungbunzlauer Japan Co., Ltd.) (C’-5) TOTM (trimethyl tremellitate, J-PLUS Co., Ltd.) (C’-6) DOA (dioctyl adipate, Taoka Chemical Company, Limited) (C’-7) DOZ (dioctyl azelate, Taoka Chemical Company, Limited)
  • components (A) to (C) were mixed to produce adhesives for laminate of Examples 1 to 9 and Comparative Examples 1 to 7. Specifically, first, a component (B) and a component (C) were mixed in the number of parts shown in Tables 2 and 3, and then a component (A) was added to the mixture. The amount of the component (A) to be added is the number of parts shown in Tables 2 and 3. Then, in accordance with the composition (parts by mass) shown in Table 2 and 3, the components (A) to (C) were stirred at 60°C to prepare adhesives for laminate.
  • each laminated film was cut out into pieces of 15 mm in width in a TD direction, and then a peel test was performed using a tensile strength testing machine (TENSILON RTM-250 (trade name), manufactured by ORIENTEC CORPORATION) and the adhesive strength was measured. After each laminated film was left to stand in an atmosphere at room temperature (23°C) for 24 hours or more, the peel test was performed under conditions of a tensile speed of 300 mm/min and T-type peel.
  • the evaluation criteria are as follows. Regarding the peel position, the measurement was performed at both the white solid print area and the plain area, and the evaluation was performed by the lower measured value. A: 2.0 N/15 mm or more B: 1.0 N/15 mm or more and less than 2.0 N/15 mm C: Less than 1.0 N/15 mm, or not functioning as adhesive
  • the adhesives for laminate of Examples 1 to 9 impart very high level appearance to the film, and are also excellent in adhesion to the film with the print area.
  • the compatibility between the components (B) and (C) was also satisfactory. It is considered that the compatibility between the components (B) and (C) is important with respect to uniformity and the occurrence of cloudiness (or haziness) when three components, for example, the components (A) to (C) are mixed, and exerts an influence on the initial adhesion and the appearance.
  • the compatibility can contribute to an improvement in storage stability.
  • the compatibility is very important with respect to an improvement in storage stability of, for example, a two-component adhesive for laminate, comprising a first liquid including the component (A) and a second liquid including the components (B) and (C).
  • the adhesives for laminate of Examples are excellent in performances mentioned above and are sufficiently useful as an adhesive for laminate of a food packaging bag which is required to have very high level appearance.
  • the adhesives for laminate of Comparative Examples 2 to 4 are inferior in stability because of including no citric acid ester, and the adhesive for laminate of Comparative Example 1 is inferior in appearance of the laminated film.
  • the adhesives for laminate of Comparative Examples 5 to 7 are drastically inferior in appearance of the laminated film since the urethane prepolymers (A) as a raw material are not prepared using a polyester polyol.
  • an adhesive for laminate according to an embodiment of the present invention does not degrade appearance of a film, and is excellent in initial adhesive strength after curing and is excellent in uniformity and prevention of cloudiness.
  • An adhesive for laminate according to an embodiment of the present invention does not degrade appearance of a film when a plurality of films are laminated together and is excellent in initial adhesive strength after curing, and is excellent in uniformity and prevention of cloudiness, thus making it possible to employ in various applications.
  • the adhesive for laminate is particularly suited as an adhesive for laminated film, which is used for packaging foods, detergents, shampoos and rinses, etc.

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  • Organic Chemistry (AREA)
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Abstract

Disclosed is an adhesive for laminate, which is obtainable by formulating (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein the urethane prepolymer (A) is a reaction product of (a1) a polyester polyol and (a2) an isocyanate monomer.

Description

ADHESIVE FOR LAMINATE
The present invention relates to an adhesive for laminate, and more specifically to an adhesive for laminate, which is excellent in stability and adhesion, and does not degrade appearance of a film when the film is laminated (or pasted); and to a laminated film using the same.
When producing packaging materials for such as foods, medical supplies and cosmetics, and substrates such as FPC substrates and TAB substrates, for example, a composite film obtainable by laminating (or pasting) a plastic film (e.g., a film made of polyethylene, polypropylene, nylon, polyester, polyimide, etc.), a metal deposited film and a metal foil (e.g., a foil made of aluminum, copper, etc.) is used. There have been known, as an adhesive for bonding the plastic film, the metal deposited film and the metal foil, an urethane adhesive obtainable by combining an organic polyol and an organic isocyanate.
In recent years, there has been increasing demand for a solvent-free adhesive as the urethane adhesive, considering environment aspect, simple equipment and cost-benefit, etc. Comparing the solvent-free adhesive with a solvent-based adhesive, although there is a merit by using no solvent, air bubbles are easily generated on a film surface because of poor wettability when a plurality of films are laminated together, which may lead to degradation of the film appearance. In particular, an aluminum-deposited polyethylene terephthalate film often causes poor appearance.
Patent Literatures 1 to 3 disclose laminated films obtainable by laminating using a urethane adhesive. Patent Literature 1 discloses a method for producing a laminate using a urethane adhesive obtainable by mixing a polyisocyanate, a polyol, and an ester which is liquid at 25°C (see [Claims], [Table 4] to [Table 6]).
Patent Literature 2 discloses a method in which polyethylene terephthalate and a metal deposited film are laminated together using a solvent-free urethane adhesive (see [Claims], [0006], [Table 1]).
Patent Literature 3 discloses a method for producing a laminated film using a solvent-free adhesive synthesized from a crystalline polyol and a polyisocyanate (see [Claims], [0001], [Table 1]).
Patent Literatures 1 to 3 mention that the appearance of the laminated films is improved, however, it could not be said that high demands of consumers are not sufficiently satisfied. Considering working efficiency in the production of a packaging bag using the laminated film, the adhesives are required to be excellent in initial adhesive strength to a film after curing. Considering excellent initial adhesion to a film and an improvement in the appearance of the film, the present inventors thought it important that the adhesive maintains uniformity and hardly causes cloudiness.
[PTL 1] JP 2018-162420 A
[PTL 2] JP 2006-57089 A
[PTL 2] JP 2002-249745 A
The present invention was performed so as to solve the above problems and an object thereof is to provide an adhesive for laminate, which is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, and maintains uniformity and is capable of preventing occurrence of cloudiness, when a laminated film is produced by laminating (or pasting) a plastic film, and the laminated film having excellent appearance produced by using the adhesive for laminate.
As a result of continued intensive study, the present inventors have found that a urethane resin composition comprising a urethane prepolymer prepared from a polyester polyol; a urethane resin obtainable by chain extension of this urethane prepolymer with a polyol component; and a specific plasticizer is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, and is excellent in uniformity and prevention of cloudiness, when the laminated film is produced by laminating a plastic film, thus completing the present invention.
The present description includes the following embodiments.
1. An adhesive for laminate, which is obtainable by formulating (or combining) (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein
the urethane prepolymer (A) is a reaction product of (a1) a polyester polyol and (a2) an isocyanate monomer.
2. The adhesive for laminate according to 1, wherein the polyester polyol (a1) has a number average molecular weight of 400 to 1,300.
3. The adhesive for laminate according to 1 or 2, wherein the urethane prepolymer (A) has a number average molecular weight 1,500 to 4,000.
4. The adhesive for laminate according to any one of 1 to 3, wherein the citric acid ester (C) comprises an acetyl citric acid ester.
5. The adhesive for laminate according to any one of 1 to 4, wherein the citric acid ester (C) comprises acetyl tributyl citrate (or tributyl acetyl citrate).
6. The adhesive for laminate according to any one of 1 to 5, wherein the components (A) to (C) are formulated (or combined) to a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C) to obtain a two-component adhesive for laminate.
7. A laminated film obtainable by using the adhesive for laminate according to any one of 1 to 6.
An adhesive for laminate according to an embodiment of the present invention is an adhesive for laminate, which is obtainable by formulating (or combining) (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein the urethane prepolymer (A) is a urethane resin obtainable by reacting (a1) a polyester polyol with (a2) an isocyanate monomer, and
therefore, the adhesive for laminate is excellent in initial adhesive strength to a film after curing and does not degrade appearance of a laminated film, when a plastic film is laminated to produce a laminated film, and maintains uniformity of the components and cause no cloudiness even when stored at a low temperature over a long period.
Since a laminated film according to an embodiment of the present invention is obtainable by using the adhesive for laminate, lamination can be quickly performed and the laminated film is also excellent in appearance.
Figure 1 schematically shows a cross-section of a laminated film according to an embodiment of the present invention. Figure 2 schematically shows a cross-section of a laminated film according to another embodiment of the present invention.
An adhesive for laminate according to an embodiment of the present invention is obtainable by formulating(or combining) (or mixing) (A) a urethane prepolymer having an isocyanate group at the end (hereinafter also referred to as “component (A)”), (B) a polyol component (hereinafter also referred to as “component (B)”)) and (C) a citric acid ester (or citrate) (hereinafter also referred to as “component (C)”), and comprises the components (A) to (C).
The adhesive according to the embodiment of the present invention is not particularly limited by the order of formulating and the formulating method of the components (A) to (C) as long as the objective adhesive can be obtainable. The adhesive according to the embodiment of the present invention may be obtainable by simultaneously formulating three components, for example, (A) a urethane prepolymer, (B) a polyol component and (C) a citric acid ester, or obtainable by formulating the component (A) or (C) in advance with the component (B) and formulating with the remaining one component. The adhesive is more preferably obtainable by mixing the components (B) and (C) in advance and formulating the mixture with the component (A).
The production of the adhesive by formulating (or mixing) the component (A), the component (B) and the component (C) can be performed by a known method. Although the adhesive can be obtainable by formulating the components (A) to (C) in a solvent, it is also possible to formulate the components (A) to (C) without using the solvent.
The adhesive according to the embodiment of the present invention may be a two-component adhesive which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C), or a two-component adhesive which is obtainable by formulating a first liquid comprising the components (A) and (C) and a second liquid comprising the component (B). The adhesive according to the embodiment of the present invention is more preferably a two-component adhesive comprising a first liquid including the component (A) and a second liquid including the components (B) and (C). The first and second liquids each can appropriately comprise various additives mentioned below.
In the embodiment of the present invention, the urethane prepolymer (A) is a urethane resin produced by reacting (a1) a polyester polyol with (a2) an isocyanate monomer.
When the urethane prepolymer (A) has a chemical structure (e.g., having an ester bond in main chain) based on the polyester polyol (a1), the adhesive for laminate according to the embodiment of the present invention makes it hard to generate air bubbles on a film surface when a plurality of films are laminated together, and thus it is possible to keep a film appearance smooth.
The urethane prepolymer (A) preferably has a number average molecular weight of 1,500 to 4,000. When the number average molecular weight of the urethane prepolymer (A) is within the above range, the adhesive for laminate according to the embodiment of the present invention is excellent in adhesion.
As used herein, the number average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene standard. Specifically, Mn can be obtained measuring using the following GPC apparatus and measuring method, followed by conversion. HCL-8220GPC manufactured by TOSOH CORPORATION is used as the GPC apparatus and RI is used as a detector. Two TSKgeI SuperMultipore HZM columns manufactured by TOSOH CORPORATION are used as a GPC column. A sample is dissolved in tetrahydrofuran and the solution thus obtained is allowed to flow at a flow rate of 0.35 ml/minute and at a column temperature of 40°C to obtain a measured value. Using a calibration curve obtained by using polystyrene having a monodisperse molecular weight as a standard reference material, the measured value is converted to obtain the objective Mn. The same manner is applied to Mn of the polyester polyol (a1) and Mn of the isocyanate monomer (a2) mentioned below.
As used herein, (a1) “polyester polyol” refers to a compound which is “main chain type” polyester and has an ester bond and a hydroxyl group in “main chain”. This hydroxyl group is usually positioned at the end of the main chain, and acts as a functional group reacting with an isocyanate group.
The polyester polyol is commonly obtainable by a condensation polymerization reaction of a low molecular polyol with dicarboxylic acid and an anhydride thereof.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, trimesic acid, cyclohexanedicarboxylic acid and the like. These dicarboxylic acids are used alone or in combination.
Examples of the carboxylic anhydride include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. These carboxylic anhydrides are used alone or in combination.
The low molecular polyol preferably has 1 to 3 functional groups, and particularly preferably a difunctional polyol, that is, a so-called diol. The low molecular polyols can be used alone or in combination.
Examples of the diol include low molecular weight diols such as ethylene glycol, 1-methylethylene glycol, 1-ethylethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentyl glycol, 2-methyl-1,3-propanediol, cyclohexanedimethanol, 2,4-dimethyl-1,5-pentanediol and 2,4-dibutyl-1,5-pentanediol. Particularly, at least one selected from ethylene glycol, diethylene glycol, butanediol, hexanediol and neopentyl glycol may be used.
In the embodiment of the present invention, (a1) “polyester polyol” preferably has a number average molecular weight of 400 to 1,300. When the number average molecular weight of the polyester polyol (a1) is within the above range, the chain length may decrease and thus it becomes easier to crosslink with the isocyanate monomer (a2). Since the unreacted (a2) isocyanate monomer decreases, the adhesive for laminate according to the embodiment of the present invention can include the urethane prepolymer (A) more, and can be more excellent in adhesion.
The isocyanate monomer (a2) in the embodiment of the present invention is not particularly limited as long as the objective adhesive for laminate of the present invention can be obtainable, and preferably includes an aromatic isocyanate. When the isocyanate monomer (a2) includes the aromatic isocyanate, the adhesion of the adhesive for laminate according to the embodiment of the present invention is improved.
The “(a2) isocyanate monomer” according to the embodiment of the present invention does not mean that it is composed of the aromatic isocyanate only. As long as an adverse influence is not exerted on the adhesion of the adhesive for laminate according to the embodiment of the present invention and the appearance of the film, the isocyanate monomer (a2) may include an aliphatic isocyanate and an alicyclic isocyanate.
As used herein, the “aliphatic isocyanate” refers to a compound which has a chain-like hydrocarbon chain to which an isocyanate group is directly bonded, and also has no cyclic hydrocarbon chain. The “aliphatic isocyanate” may have an aromatic ring, but the isocyanate group is not bonded directly to the aromatic ring.
As used herein, the cyclic hydrocarbon chain does not contain aromatic rings.
The “alicyclic isocyanate” is a compound which has a cyclic hydrocarbon chain, and may have a chain-like hydrocarbon chain. The isocyanate group may be directly bonded to the cyclic hydrocarbon chain, or may be directly bonded to a chain-like hydrocarbon chain which may be present. Although the “alicyclic isocyanate” may have an aromatic ring, the isocyanate group is not directly bonded to the aromatic ring.
The “aromatic isocyanate” refers to a compound having an aromatic ring in which the isocyanate group is directly bonded to the aromatic ring. Therefore, even though a compound has an aromatic ring in the molecule, when the isocyanate group is not directly bonded to the aromatic ring, the compound is classified into the aliphatic isocyanate or the alicyclic isocyanate.
Therefore, for example, 2,2’-diphenylmethane diisocyanate, 2,4’-diphenylmethane diisocyanate or 4,4’-diphenylmethane diisocyanate (OCN-C6H4-CH2-C6H4-NCO) corresponds to the aromatic isocyanate, since the isocyanate group is directly bonded to the aromatic ring.
Meanwhile, for example, xylylene diisocyanate (OCN-CH2-C6H4-CH2-NCO) corresponds to the aliphatic isocyanate, although it has an aromatic ring, since the isocyanate group is not directly bonded to the aromatic ring and is bonded to the methylene group.
The aromatic ring may have a ring-fused structure in which two or more benzene rings are condensed.
Examples of the aromatic isocyanate include 2,2’-diphenylmethane diisocyanate, 2,4’-diphenylmethane diisocyanate, 4,4’-diphenylmethane diisocyanate and the like.
Examples of the aliphatic isocyanate include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate) and 1,3-bis(isocyanatomethyl)benzene (xylylene diisocyanate), etc.
Examples of the alicyclic isocyanate include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate: IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate) and 1,4-diisocyanatocyclohexane, etc.
There is no particular limitation on the method for reacting (a1) a polyester polyol with (a2) an isocyanate monomer as long as (A) a urethane prepolymer according to the embodiment of the present invention can be obtained, and a common urethanation reaction method can be used. For example, it is possible to use bulk polymerization using no solvent and solution polymerization using a solvent, and the polymerization is performed by appropriately heating with stirring and, if necessary, a catalyst can be used. It is also possible to use various additives, for example, a plasticizer when (a1) the polyester polyol is reacted with (a2) the isocyanate monomer.
In the embodiment of the present invention, there is no particular limitation on “(B) a polyol component” as long as the objective adhesive for laminate according to the embodiment of the present invention can be obtainable and an adverse influence is not exerted on the production of the adhesive.
Examples thereof include polyester polyols, acrylic polyols, polyether polyols, polyether polyester polyols, polyester polyurethane polyols, polyether polyurethane polyols, or modified products of these polyols.
The polyol component (B) may include (a1) a polyester polyol used in the production of the urethane prepolymer (A).
The adhesive for laminate according to the embodiment of the present invention comprises (C) a citric acid ester. The citric acid ester (C) acts as a plasticizer. When the adhesive for laminate comprises the citric acid ester (C), the adhesion can be improved and the uniformity can be excellent, thus the occurrence of cloudiness can be prevented.
Since a laminated film according to an embodiment of the present invention is obtainable by using the adhesive for laminate, lamination can be quickly performed and the laminated film can be excellent in appearance.
Examples of the citric acid ester (C) include triethyl citrate, tributyl citrate, 2-ethylhexyl citrate, acetyl triethyl citrate (or triethyl acetyl citrate), acetyl tributyl citrate (or tributyl acetyl citrate) and acetyl 2-ethylhexyl citrate (or 2-ethylhexyl acetyl citrate).
In the embodiment of the present invention, the citric acid ester (C) preferably includes acetyl citric acid esters such as acetyl triethyl citrate, acetyl tributyl citrate, acetyl 2-ethylhexyl citrate, and most preferably tributyl acetyl citrate. When the citric acid ester (C) include the above esters, the adhesive for laminate according to the embodiment of the present invention exhibits more improved adhesive strength and also more improved appearance and uniformity, and can prevent more the occurrence of cloudiness and is more excellent in overall balance.
The adhesive for laminate according to the embodiment of the present invention may be obtainable by formulating (or mixing) other components, in addition to the components (A) to (C). Examples of “other components” include unreacted isocyanate monomers, solvents, tackifier resins, pigments, plasticizers (excluding the above citric acid ester (C)), catalysts and adhesion promoters, etc.
The unreacted isocyanate monomer refers to (a2) an isocyanate monomer which did not react with (a1) a polyester polyol, when the polyester polyol (a1) was reacted with the isocyanate monomer (a2) to prepare (A) a urethane prepolymer.
When the urethane prepolymer (A) is reacted with (B) a polyol component, the unreacted isocyanate monomer can also react with the polyol component (B).
Examples of the “tackifier resin” include styrene-based resins, terpene-based resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins and polyester resins (excluding polyester polyols), etc. The tackifier resin commonly has a low molecular weight of less than 1,500 g/mol, and particularly less than 1,000 g/mol. An amount of the tackifier resin to be added is preferably 0 to 50 parts by mass, and more preferably 30 parts by mass or less, based on 100 parts by mass of the total mass (solid content) of the adhesive.
Examples of the “pigment” include nanopigments based on TiO2, SiO2, Fe2O3 or similar oxides or oxyhydrates. Usually, these pigments preferably have a particle size of 500 nm or less, and more preferably less than 100 nm.
Examples of the “plasticizer” include white oil, naphthenic mineral oil, paraffinic hydrocarbon oil, polypropylene oligomer, polybutene oligomer, polyisoprene oligomer, hydrogenated polyisoprene and/or polybutadiene oligomer, phthalate, adipate, benzoate ester, vegetable oil or animal oil, and derivatives thereof, etc.
It is considered that the vegetable oil, the animal oil and derivatives thereof are commonly used in foods and have higher stability, they are more preferable considering that the adhesive for laminate according to the embodiment of the present invention is employed so as to produce food packaging films.
Examples of the “catalyst” include metal catalysts, for example, tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead catalysts ((lead oleate, lead naphthenate, lead octanoate, etc.), other metal catalysts (naphthenic acid metal salt such as cobalt naphthenate) and the like; and amine-based catalysts, for example, triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, dialkylaminoalkylamines and the like.
Examples of the “adhesion promoter” include silane compounds. It is possible to use, as the adhesion promoter, known organic functional silanes, for example, (meth)acryloxy functional, epoxy functional, amine functional and non-reactive substituted silanes. Examples thereof include vinyltrialkoxysilane, alkyltrialkoxysilane, tetraalkoxysilane, 3-acryloxypropyltrialkoxysilane, 3-methacryloxypropyltrialkoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane, 2-glycidyloxyethyltrimethoxysilane and the like.
In the embodiment of the present invention, the adhesion promoter is preferably included in an amount of 0.1 to 5 parts by mass based on 100 parts by mass of the total mass (solid content) of the adhesive.
As mentioned above, the adhesive for laminate according to the embodiment of the present invention can be produced by mixing (A) a component, (B) a component and (C) a component. The adhesive for laminate according to the embodiment of the present invention may be a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C), or a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the components (A) and (C) with a second liquid comprising the component (B). In some cases, other components may be mixed. The first and second liquids each can appropriately comprise various additives mentioned below.
When the adhesive for laminate according to the embodiment of the present invention is a two-component adhesive, the adhesive for laminate is more excellent in storage stability because of using the component (C). The adhesive for laminate according to the embodiment of the present invention is more preferably a two-component adhesive for laminate, comprising two liquids, which is obtainable by formulating a first liquid comprising the component (A) and a second liquid comprising the components (B) and (C).
There is no particular limitation on the mixing method as long as the objective adhesive for laminate of the present invention can be obtainable. There is also no particular limitation on the order of mixing the components. The adhesive for laminate according to the embodiment of the present invention can be produced without requiring a special mixing method and a special mixing order, etc. Thus, the obtainable adhesive for laminate shows small decrease in initial adhesive strength to a film and small decrease in adhesive strength over time.
Since the adhesive for laminate according to the embodiment of the present invention is applied to a film at 15 to 100°C, the adhesive should have a low viscosity in this temperature range. Considering the coatability, the viscosity of the adhesive for food packaging film is 300 to 5,000 mPas at 40°C, and preferably 200 to 4,000 mPas at 50°C, as measured using a Brookfield viscometer.
The laminated film according to the embodiment of the present invention is a laminate produced by using the above adhesive for laminate. The film to be used to form a laminate is not particularly limited as long as the laminate according to the embodiment of the present invention can be obtainable and includes, for example, a film in which a metal layer is formed on a plastic base material, and a film in which a metal layer is not formed on a plastic base material.
When a laminated film is produced, the adhesive for laminate according to the embodiment of the present invention is applied to a film. The application can be performed by various methods such as gravure coating, wire bar coating, air knife coating, die coating, lip coating and comma coating methods.
The laminated film can be produced by laminating a plurality of films, on which the adhesive for laminate according to the embodiment of the present invention is applied, together. When the adhesive for laminate is applied to the film, the application amount is preferably 0.5 to 100 g/m2, and more preferably 1 to 15 g/m2.
The laminated film according to the embodiment of the present invention is obtainable by laminating a plurality of films together using the adhesive. An example of the embodiment of the present invention is shown in Figs. 1 and 2, but the present invention is not limited to these embodiments.
Figure 1 schematically shows a cross-section of a laminated film according to an embodiment of the present invention. A laminated film 10 is formed of two films and an adhesive for laminated film 13 interposed therebetween, and the two films 11 and 12 are laminated together using the adhesive for laminated sheet 13. The films 11 and 12 may be made of the same or different material.
In Figure 1, the two films 11 and 12 are laminated together, or three or more films may be laminated together.
A cross-section of a laminated film according to another embodiment of the present invention is schematically shown in Fig. 2. In Fig. 2, a thin film 11a is formed between a film 11 and an adhesive for laminated film 13. Figure 2 shows an embodiment in which a metal thin film 11a is formed on a surface of the film 11 when the film 11 is a plastic film. The metal thin film 11a can be formed on the surface of the plastic film 11, for example, by vapor deposition, and the laminated film of Fig. 2 can be obtainable by laminating the film 11, on which surface the metal thin film 11a is formed, together with the film 12 by interposing the adhesive for laminated film 13 therebetween.
Examples of the metal to be deposited on the plastic film include aluminum, steel, copper and the like. It is possible to impart barrier properties to the plastic film by subjecting the film to vapor deposition. Silicon oxide or aluminum oxide is used as a vapor deposition material. The plastic film 11 as a base material may be either transparent, or white- or black-colored.
A plastic film made of polyvinyl chloride, polyester, a fluororesin or an acrylic resin is used as the film 12. To impart heat resistance, weatherability, rigidity, insulating properties and the like, a polyethylene terephthalate film or a polybutylene terephthalate film is particularly preferably used. The films 11 and 12 may be either transparent or colored.
The deposited thin film 11a of the film 11 and the film 12 are laminated together using the adhesive for laminated film 13 according to the embodiment of the present invention, and the films 11 and 12 are often laminated together by a dry lamination method. Therefore, the adhesive for laminated film 13 is required to be excellent in initial pressure sensitive adhesion to a film during lamination and to be excellent in adhesion to a film after curing.
The laminated film according to the embodiment of the present invention is used to produce various packaging bags, outdoor materials, etc.
The packaging bag refers to a bag-shaped article obtainable by processing the laminated film so as to contain foods, detergents, shampoo, rinse or the like. Examples of the outdoor material include articles to be used outdoors, such as wall protecting materials, roofing materials, solar battery modules, window materials, outdoor flooring materials, illumination protection materials, automobile members and signboards.
The packaging bag and outdoor material take a form including a laminated film obtainable by laminating a plurality of films together.
The present invention will be described below in more specific and detailed manner by way of Examples and Comparative Examples. It should be noted that these Examples are intended to describe the present invention and the present invention is not limited thereto. In Examples, unless otherwise specified, parts by mass and percentages by mass are based on the portions where a solvent is not taken into consideration.
<Preparation of (A) Urethane Prepolymer>
Components for synthesizing (A) a urethane prepolymer are shown below.
(a1) Polyester polyol
(a1-1) PES-1 (polyester polyol synthesized from adipic acid, ethylene glycol, 2-methyl-1,3-propanediol and glycerin, Mn: 1,200, hydroxyl value: 180 mgKOH/g)
(a1-2) PES-2 (polyester polyol synthesized from adipic acid, diethylene glycol, 2-methyl-1,3-propanediol and glycerin, Mn: 1,000, hydroxyl value: 210 mgKOH/g)
(a1-3) PES-3 (polyester polyol synthesized from adipic acid, isophthalic acid and diethylene glycol, Mn: 1,100, hydroxyl value: 110 mgKOH/g)
(a1-4) PES-4 (polyester polyol synthesized from adipic acid, isophthalic acid and diethylene glycol, Mn: 2,000, hydroxyl value: 58 mgKOH/g)
(a1’) Polyol other than polyester polyol
(a1’-5) SANNIX PP400 (polypropylene glycol, Mn: 400, hydroxyl value: 281 mgKOH/g, Sanyo Chemical Industries, Ltd.)
(a1’-6) PTMG650 (polytetramethylene ether glycol, Mn: 650, hydroxyl value: 173 mgKOH/g, Mitsubishi Chemical Corporation)
(a1’-7) BP-5P (polyoxypropylene bisphenol A ether, Mn: 530, hydroxyl value: 211 mgKOH/g, Sanyo Chemical Industries, Ltd.)
(a2) Isocyanate monomer
(a2-1) DESMODUR 2460M (55% 2,4-diphenylmethane diisocyanate, 45% 4,4-diphenylmethane diisocyanate, Covestro Japan Ltd.)
(a2-2) Millionate MT (4,4-diphenylmethane diisocyanate, TOSOH CORPORATION)
A specific method for producing a urethane prepolymer (A1) will be shown below.
As shown in Table 1, 38.3 parts by mass of a polyester polyol (a1-1) was charged in a reaction vessel, followed by stirring under reduced pressure for 1 hour while heating the reaction vessel in an oil bath at 80°C to remove moisture. Then, 61.7 parts by mass of an isocyanate monomer (a2) was charged, followed by stirring under reduced pressure at 80°C for 1 hour to prepare 100 parts by mass of an isocyanate component. The isocyanate component includes 70 parts by mass of a urethane prepolymer (A1) and 30 parts by mass of an unreacted isocyanate monomer.
The number average molecular weight of the urethane prepolymer (A1) is a value measured by GPC. The measured value is a number average molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene standard. Specifically, the value can be measured using the following GPC apparatus and measuring method.
HCL-8220GPC manufactured by TOSOH CORPORATION was used as a GPC apparatus, and RI was used as a detector. Two TSKgel SuperMultipore HZ-M columns manufactured by TOSOH CORPORATION were used as a GPC column. A sample was dissolved in tetrahydrofuran and the solution thus obtained was allowed to flow at a flow rate of 0.35 ml/minute and at a column temperature of 40°C and then the molecular weight was determined by conversion of an observed molecular weight based on a calibration curve obtained by using polystyrene having a monodisperse molecular weight as a standard reference material.
Method for Producing ((A2) to (A’9)) Urethane Prepolymers
In the same manner as in the production in the urethane prepolymer (A1), each urethane polymer was produced. Polyols ((a1-1) to (a1’-7)) and isocyanate monomers ((a2-1) to (a2-2)) were formulated according to the composition shown in Table 1 to obtain urethane prepolymers (A2) to (A’9)).

Figure JPOXMLDOC01-appb-T000001
<Production of Adhesive for Laminate>
Components for producing an adhesive composition are shown below.
(A) Urethane prepolymer
(A1) to (A’9) Urethane prepolymers (see Table 1)
(B) Polyol component
(B1) PES-1 (polyester polyol synthesized from adipic acid, ethylene glycol, 2-methyl-1,3-propanediol and glycerin, Mn: 1,200, hydroxyl value: 180 mgKOH/g, which is the same as (a1-1))
(B2) PES-2 (polyester polyol synthesized from adipic acid, diethylene glycol, 2-methyl-1,3-propanediol and glycerin, Mn: 1,000, hydroxyl value: 210 mgKOH/g, which is the same as (a1-2))
(B3) PES-4 (polyester polyol synthesized from adipic acid, isophthalic acid and diethylene glycol, Mn: 2,000, hydroxyl value: 58 mgKOH/g, which is the same as (a1-4))
(B4) PPG1000 (polypropylene glycol, Mn: 1,000, hydroxyl value: 173 mgKOH/g, AGC Inc.)
(C) Citric acid ester
(C-1) ATBC (acetyl tributyl citrate, Taoka Chemical Company, Limited)
(C-2) ATEC (acetyl triethyl citrate, Jungbunzlauer Japan Co., Ltd.)
(C-3) TEC (triethyl citrate, Jungbunzlauer Japan Co., Ltd.)
(C-4) TBC (tributyl citrate, Jungbunzlauer Japan Co., Ltd.)
(C’-5) TOTM (trimethyl tremellitate, J-PLUS Co., Ltd.)
(C’-6) DOA (dioctyl adipate, Taoka Chemical Company, Limited)
(C’-7) DOZ (dioctyl azelate, Taoka Chemical Company, Limited)
As shown in Tables 2 and 3, components (A) to (C) were mixed to produce adhesives for laminate of Examples 1 to 9 and Comparative Examples 1 to 7. Specifically, first, a component (B) and a component (C) were mixed in the number of parts shown in Tables 2 and 3, and then a component (A) was added to the mixture. The amount of the component (A) to be added is the number of parts shown in Tables 2 and 3. Then, in accordance with the composition (parts by mass) shown in Table 2 and 3, the components (A) to (C) were stirred at 60°C to prepare adhesives for laminate.

Figure JPOXMLDOC01-appb-T000002
 *: Numbers in parentheses indicate amounts of the unreacted NCO monomer.
Figure JPOXMLDOC01-appb-T000003
 *: Numbers in parentheses indicate amounts of the unreacted NCO monomer.
<Production of Laminated Film>
Each of adhesives for laminate of Examples was applied to a print surface side of a PET film with a white solid print area and a plain area so that the solid mass became 2 g/m2 and a deposited CPP film was laminated from the deposition surface side, followed by pressure bonding using a hand roller so that air bubbles escape to the outside as much as possible. Then, curing was performed in an atmosphere at 40°C for 24 hours to obtain laminated films of Examples.
<Evaluation>
1. Evaluation of Appearance
The appearance of each laminated film after curing was visually evaluated. The evaluation criteria are as follows.
A: Few dots (air bubbles)
B: Relatively many dots (air bubbles)
C: Noticeably many dots (air bubbles), or not functioning as adhesive
2. Measurement of Adhesive Strength after Curing
After curing, each laminated film was cut out into pieces of 15 mm in width in a TD direction, and then a peel test was performed using a tensile strength testing machine (TENSILON RTM-250 (trade name), manufactured by ORIENTEC CORPORATION) and the adhesive strength was measured.
After each laminated film was left to stand in an atmosphere at room temperature (23°C) for 24 hours or more, the peel test was performed under conditions of a tensile speed of 300 mm/min and T-type peel. The evaluation criteria are as follows. Regarding the peel position, the measurement was performed at both the white solid print area and the plain area, and the evaluation was performed by the lower measured value.
A: 2.0 N/15 mm or more
B: 1.0 N/15 mm or more and less than 2.0 N/15 mm
C: Less than 1.0 N/15 mm, or not functioning as adhesive
3. Evaluation of Solution Stability
Compatibility between (B) a polyol component and (C) a citric acid ester was evaluated. The components (B) and (C) were stirred at normal temperature in accordance with the formulating ratio in Table 2, and then 150 g of the mixture was charged in 225 ml of a bottle. After being left to stand in a thermostatic bath at -5°C for 24 hours, it was visually confirmed whether the compatibility changed as compared with the state at normal temperature. The evaluation criteria are as follows.
A: There was no change in state.
C : Change in state (separation or cloudiness) was observed
-: Evaluation cannot be performed since the components (B) and (C) are not formulated.
As shown in Table 2, the adhesives for laminate of Examples 1 to 9 impart very high level appearance to the film, and are also excellent in adhesion to the film with the print area. To react with (A) a urethane prepolymer, although the polyol component (B) is mixed in advance with the citric acid ester (C) (plasticizer), the compatibility between the components (B) and (C) was also satisfactory. It is considered that the compatibility between the components (B) and (C) is important with respect to uniformity and the occurrence of cloudiness (or haziness) when three components, for example, the components (A) to (C) are mixed, and exerts an influence on the initial adhesion and the appearance. Furthermore, in a two-component adhesive, the compatibility can contribute to an improvement in storage stability. The compatibility is very important with respect to an improvement in storage stability of, for example, a two-component adhesive for laminate, comprising a first liquid including the component (A) and a second liquid including the components (B) and (C).
As seen above, the adhesives for laminate of Examples are excellent in performances mentioned above and are sufficiently useful as an adhesive for laminate of a food packaging bag which is required to have very high level appearance.
To the contrary, as shown in Table 3, the adhesives for laminate of Comparative Examples 2 to 4 are inferior in stability because of including no citric acid ester, and the adhesive for laminate of Comparative Example 1 is inferior in appearance of the laminated film.
The adhesives for laminate of Comparative Examples 5 to 7 are drastically inferior in appearance of the laminated film since the urethane prepolymers (A) as a raw material are not prepared using a polyester polyol.
The results revealed that an adhesive for laminate according to an embodiment of the present invention does not degrade appearance of a film, and is excellent in initial adhesive strength after curing and is excellent in uniformity and prevention of cloudiness.
An adhesive for laminate according to an embodiment of the present invention does not degrade appearance of a film when a plurality of films are laminated together and is excellent in initial adhesive strength after curing, and is excellent in uniformity and prevention of cloudiness, thus making it possible to employ in various applications.
The adhesive for laminate is particularly suited as an adhesive for laminated film, which is used for packaging foods, detergents, shampoos and rinses, etc.
Cross-Reference to Related Application
This application claims priority under Article 4 of the Paris Convention based on Japanese Patent Application No. 2019-120341 filed on June 27, 2019 in Japan. This priority patent application is incorporated herein by reference in its entirety.
Description of Symbols
10 Laminated film
11 Film
11a Deposited thin film
12 Film
13 Adhesive layer

Claims (5)

  1. An adhesive for laminate, which is obtainable by formulating (A) a urethane prepolymer having an isocyanate group at the end, (B) a polyol component and (C) a citric acid ester, wherein
    the urethane prepolymer (A) is a reaction product of (a1) a polyester polyol and (a2) an isocyanate monomer.
  2. The adhesive for laminate according to claim 1, wherein the polyester polyol (a1) has a number average molecular weight of 400 to 1,300.
  3. The adhesive for laminate according to claim 1 or 2, wherein the urethane prepolymer (A) has a number average molecular weight 1,500 to 4,000.
  4. The adhesive for laminate according to any one of claims 1 to 3, wherein the citric acid ester (C) comprises an acetyl citric acid ester.
  5. A laminated film obtainable by using the adhesive for laminate according to any one of claims 1 to 4.
PCT/JP2020/025339 2019-06-27 2020-06-26 Adhesive for laminate WO2020262646A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5130205A (en) * 1989-06-12 1992-07-14 W. R. Grace & Co.-Conn. Laminate and gas permeation module comprising two-component polyurethane adhesive
JP2002249745A (en) 2001-02-27 2002-09-06 Mitsui Takeda Chemicals Inc Two-part curable solventless adhesive composition
JP2006057089A (en) 2004-07-23 2006-03-02 Toyo Mooton Kk Solventless adhesive composition and laminate given by using the same
US20120156507A1 (en) * 2010-12-21 2012-06-21 Pankaj Vinubhai Shah Adhesive compositions
JP2018162420A (en) 2017-03-27 2018-10-18 東洋インキＳｃホールディングス株式会社 Laminate and method for producing the same

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5041517A (en) * 1989-06-12 1991-08-20 W. R. Grace & Co.-Conn. Two-component polyurethane adhesive
JP6747310B2 (en) * 2017-01-20 2020-08-26 東洋インキＳｃホールディングス株式会社 Adhesive and adhesive sheet
JP6519687B1 (en) * 2018-04-12 2019-05-29 東洋インキＳｃホールディングス株式会社 Pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and method for producing hydroxyl terminated urethane prepolymer
JP2021004343A (en) * 2019-06-27 2021-01-14 ヘンケルジャパン株式会社 Adhesive for laminate

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5130205A (en) * 1989-06-12 1992-07-14 W. R. Grace & Co.-Conn. Laminate and gas permeation module comprising two-component polyurethane adhesive
JP2002249745A (en) 2001-02-27 2002-09-06 Mitsui Takeda Chemicals Inc Two-part curable solventless adhesive composition
JP2006057089A (en) 2004-07-23 2006-03-02 Toyo Mooton Kk Solventless adhesive composition and laminate given by using the same
US20120156507A1 (en) * 2010-12-21 2012-06-21 Pankaj Vinubhai Shah Adhesive compositions
JP2018162420A (en) 2017-03-27 2018-10-18 東洋インキＳｃホールディングス株式会社 Laminate and method for producing the same

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