WO2020227535A1 - Reactive polyurethane hot melt adhesive composition, preparation, and use - Google Patents

Reactive polyurethane hot melt adhesive composition, preparation, and use Download PDF

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Publication number
WO2020227535A1
WO2020227535A1 PCT/US2020/031882 US2020031882W WO2020227535A1 WO 2020227535 A1 WO2020227535 A1 WO 2020227535A1 US 2020031882 W US2020031882 W US 2020031882W WO 2020227535 A1 WO2020227535 A1 WO 2020227535A1
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WIPO (PCT)
Prior art keywords
hot melt
melt adhesive
diol
adhesive composition
reactive
Prior art date
Application number
PCT/US2020/031882
Other languages
French (fr)
Inventor
Brent ZHANG
Trump WANG
Original Assignee
H.B. Fuller Company
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Publication date
Application filed by H.B. Fuller Company filed Critical H.B. Fuller Company
Publication of WO2020227535A1 publication Critical patent/WO2020227535A1/en

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    • 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
    • C08G18/67—Unsaturated compounds having active hydrogen
    • C08G18/69—Polymers of conjugated dienes
    • C08G18/698—Mixtures with compounds of group C08G18/40
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    • 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
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    • C08G18/08—Processes
    • C08G18/088—Removal of water or carbon dioxide from the reaction mixture or reaction components
    • C08G18/0885—Removal of water or carbon dioxide from the reaction mixture or reaction components using additives, e.g. absorbing agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • 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
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    • C08G18/18—Catalysts containing secondary or tertiary amines or salts thereof
    • C08G18/20—Heterocyclic amines; Salts thereof
    • C08G18/2081—Heterocyclic amines; Salts thereof containing at least two non-condensed heterocyclic rings
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • 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
    • C—CHEMISTRY; METALLURGY
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    • 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
    • C08G18/4804—Two or more polyethers of different physical or chemical nature
    • C08G18/4808—Mixtures of two or more polyetherdiols
    • 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
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    • 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
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    • C08G18/69—Polymers of conjugated dienes
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    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
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    • 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
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/04—Non-macromolecular additives inorganic
    • 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
    • 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
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    • C09J175/06—Polyurethanes from polyesters
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    • 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
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    • 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
    • C09J175/14—Polyurethanes having carbon-to-carbon unsaturated bonds
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    • C08G2170/00—Compositions for adhesives
    • C08G2170/20—Compositions for hot melt adhesives
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    • C08G2190/00—Compositions for sealing or packing joints

Definitions

  • This disclosure is directed to a reactive polyurethane hot melt adhesive composition, a preparation process, and use thereof.
  • HMMC adhesive compositions are known. They are usually hot melt adhesives based on an isocyanate- terminated polyurethane prepolymer as a main binder.
  • the isocyanate groups in NCO- terminated prepolymers react with moisture (for example, moisture in the air or on an adherend) resulting in crosslinking and bonding while generating CO 2 .
  • Suitable NCO- terminated prepolymers can be obtained by reacting a polymer which is reactive toward isocyanate groups, such as polymer polyols (for example polyether polyols and polyester polyols) with polyisocyanates such as monomeric diisocyanates.
  • Polyurethane hot melt adhesives when free of water and solvent, typically have a solids content of 100%. They can be high-performance environmentally friendly adhesives that cater to the needs of increasing attention to the environment.
  • Reactive polyurethane hot melt adhesives have excellent properties compared to conventional hot melt adhesives. They have the characteristics of conventional hot melt adhesives, i.e., are free of solvent, have high initial viscosity, and rapid positioning when being applied; and once applied, have good resistance to water, heat, coldness, and creep. They can also be applied at temperatures which are normally lower than those used for applying conventional hot melt adhesives (e.g. from 150°C to 180°C) and can be used for bonding and compounding of plastic parts. They are often favored in modem automatic assembly industries.
  • Reactive polyurethane hot melt adhesives are useful in the fields of building materials, furniture and woodworking, electrical, automotive, bookbinding, shoemaking and fabric processing.
  • Certain commercially available fast-drying (losing surface tackiness within a second-order period) reactive polyurethane hot melt adhesives include one-component adhesives that are moisture curable. These adhesives may be suitable for adhesion of wood, metal, and plastic. In the assembly line, they can provide a strong rapid bonding force after the substrate is pressed or rolled. Due to good performance, such adhesives have been tested for use with filters. However, some users of these filters have found that the adhesive becomes brittle after the bonded filters have been used for some period of time. One reason for this is that certain chemicals present in the fluids being filtered have some alkalinity, and currently available adhesives are often not resistant to alkali corrosion.
  • U.S. Patent No. 5,530,085 discloses a polyurethane prepolymer composition including as a binder a prepolymer which is obtained by reacting diphenylmethane diisocyanate (MDI) with a hydroxyl-terminated conjugated diene polymer at a temperature of no more than 100°C, wherein MDI comprises at least 20% of 2,4’ -MDI isomer.
  • MDI diphenylmethane diisocyanate
  • the polyurethane prepolymer composition can be used as a moisture curable hot melt adhesive, which is asserted to be resistant to acidic and basic solutions.
  • the hydroxyl-terminated conjugated diene polymers, especially polybutadiene diols may not be favored in certain applications. And they may be relatively expensive as polymer polyols for the synthesis of polyurethanes.
  • U.S. Patent No. 4,021 ,414 also teaches a polyurethane polymer which is obtained by first reacting diisocyanate with a mixture comprising a 2,6-dialkyl-p-cresol and a polybutadiene polyol to obtain a prepolymer, the obtained prepolymer is dissolved in a solvent to form a sprayable prepolymer solution, which is then cured at a temperature of 25 to 100°C in the presence of 2,2’-diaminodiphenyl disulfide.
  • the disclosed compounds often do not have adequate acid and alkali resistance in certain applications.
  • the polybutadiene polyol required in this patent may be relatively expensive for certain applications.
  • a reactive hot melt adhesive having improved alkali resistance and acid resistance.
  • a reactive hot melt adhesive that has both superior acid resistance and alkali resistance.
  • the reactive polyurethane hot melt adhesive can be economically advantageous.
  • the reactive hot melt adhesive is derived from a composition that after curing, exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in either of an acid solution and an alkaline solution (for example an aqueous solution of HCl and an aqueous solution of NaOH).
  • the reactive hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in either of an aqueous solution with a pH value of 1 and 13 for at least three weeks.
  • the reactive hot melt adhesive can be tack-free witiiin a suitable period of time (e.g. not more than 50 seconds) after application.
  • the reactive hot melt adhesive composition becomes tack-free in no greater than 50 seconds, no greater than 40 seconds, no greater than 30 seconds, or even no greater than 20 seconds, after application of the hot melt adhesive composition.
  • a reactive hot melt adhesive composition having an isocyanate-terminated polyurethane prepolymer derived from diphenylmethane diisocyanate and a polymer polyol mixture including at least one polyester diol and at least one polyether diol.
  • the polyester diol can be a reaction product of one or more C4- C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
  • the polyether diol can be at least one of polypropylene glycol and polytetrahydrofuran diol.
  • the polypropylene glycol can have a molecular weight of from 200 to 2,000, 300 to 800, or even from 350 to 600.
  • the polytetrahydrofuran diol can have a molecular weight of from 200 to 4,000, from 800 to 3,500, or even 2,500 to 3,500.
  • the polytetrahydrofuran diol can have a surface tension of no greater than 42 mN/m, no greater than 33 mN/m, or even no greater than 30 mN/m measured at 50°C according to the national standard GB/T22237-2008 (“Surface active agents. Determination of surface tension”).
  • the weight ratio of polyether diol to polyester diol in the reactive hot melt adhesive composition can be greater than or equal to 1.0:3.0, greater than or equal to 1.1:3.0, or even from 1.2:3.0 to 1.0:1.0.
  • the reactive hot melt adhesive composition can further include an
  • the reactive hot melt adhesive composition can further include an ethylene/vinyl acetate copolymer (EVA) and have a weight ratio of polyether diol to polyester diol greater than or equal to 1.0:4.0.
  • the weight ratio of polyether diol to polyester diol can be greater than or equal to 1.0:4.0, such as from 1.0:4.0 to 1.0:1.0.
  • the reactive hot melt adhesive is derived from a composition having from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.% ethylene/vinyl acetate copolymer (EVA), based on the total weight of the reactive hot melt adhesive composition.
  • the reactive hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one).
  • the hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one) for at least three weeks.
  • the hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one) for at least five weeks. After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13.
  • the hot melt adhesive After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13 for at least three weeks. After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13 for at least five weeks.
  • the reactive hot melt adhesive is derived from a composition having a polyether diol that is a combination of polypropylene glycol and polytetrahydrofuran diol. In some instances, the reactive hot melt adhesive is derived from a composition having a poly ether diol that is a combination of polypropylene glycol and polytetrahydrofuran diol, and the weight ratio of polypropylene glycol to
  • polytetrahydrofuran diol is from 2:1 to 1:2, or even from 1.5:1 to 1.1:1.
  • the reactive hot melt adhesive is derived from a composition that includes diphenylmethane diisocyanate having greater than or equal to 70 wt.%, 80 wt.%, 90 wt.%, or even 100% being of the diphenylmethane diisocyanate being 4,4’ -diphenylmethane diisocyanate.
  • the reactive hot melt adhesive is derived from a composition that includes polytetrahydrofuran diol exhibiting a surface tension of less than 42 mN/m, less than 33 mN/m, or even less than 30 mN/m, as measured at 50°C according to the national standard GB/T22237-2008.
  • the reactive hot melt adhesive is derived from a composition that includes a reaction product of one or more C6-C8 saturated aliphatic diols with one or more C12-C16 saturated aliphatic dicarboxylic acids, a reaction product of one or more C12-C16 saturated aliphatic diols with one or more C6-C8 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
  • the reactive hot melt adhesive is derived from a composition that includes a polymer polyol mixture that includes a hydroxyl-terminated poly butadiene diol having a molecular weight of from 2,000 to 10,000, from 4,000 to 6,000, and/or a partially hydrogenated product in an amount of from five wt.% to 18 wt.%, or from eight wt.% to 14 wt.%, based on the total wdght of the reactive polyurethane hot melt adhesive composition.
  • the reactive hot melt adhesive is derived from a composition having a molar ratio of isocyanate group contained in MDI to hydroxyl group contained in polymer polyols from 1.4:1.0 to 4.0:1.0, from 1.5:1.0 to 3.5:1.0, or even 1.5:1.0 to 1.7:1.0.
  • the reactive hot melt adhesive is derived from a composition having isocyanate-terminated polyurethane prepolymer having from 0.4 wt.% to 4.0 wt.%, 0.6 wt.% to 3.7 wt.%, or even from 0.7 wt.% to 3.3 wt.% unreacted isocyanate groups, based on the total weight of the prepolymer.
  • the reactive hot melt adhesive is derived from a composition having from 20 wt.% to 45 wt.%, or even from 25 wt.% to 35 wt.% of the polyester diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • the reactive hot melt adhesive is derived from a composition having from eight wt% to 35 wt.%, or even from nine wt.% to 30% wt.% of the polyether diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • the reactive hot melt adhesive is derived from a composition having from three wt.% to 20 wt.%, or from five wt.% to 15 wt.% filler, based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • the reactive hot melt adhesive is a one-component moisture curable polyurethane hot melt adhesive composition.
  • a method for preparing a reactive polyurethane hot melt adhesive composition includes reacting
  • diphenylmethane diisocyanate with a polymer polyol mixture having at least one polyester diol and at least one polyether diol to form an isocyanate-terminated polyurethane prepolymer.
  • a reactive polyurethane hot melt adhesive composition as a hot melt adhesive.
  • a reactive polyurethane hot melt adhesive composition as a hot melt adhesive in fields such as building materials, furniture and woodworking, electrical, automobile, bookbinding, shoemaking, filter assembly, and fabric processing.
  • a reactive polyurethane hot melt adhesive composition comprising an isocyanate-terminated polyurethane prepolymer (P) which is obtained from a diphenylmethane diisocyanate and a polymer polyol mixture (M) comprising at least one polyester diol (a) and at least one polyether diol (b).
  • the polyester diol (a) can be a reaction product of one or more C4-C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
  • the at least one poly ether diol (b) can be at least one of polypropylene glycol (b1) and polytetrahydrofuran diol (b2).
  • the polypropylene glycol (b1 ) can have a molecular weight of from 200 to 2,000.
  • the polytetrahydrofuran diol (b2) can be polytetrahydrofuran diol (b2-a) having a molecular weight of from 200 to 4,000. Additionally, or alteratively, the polytetrahydrofuran diol (b2-b) can have a surface tension of less than 42 mN/m measured at 50°C according to the national standard GB/T22237-2008.
  • the reactive polyurethane hot melt adhesive composition can be formulated to meet at least one of the following requirements.
  • the weight ratio of the at least one polyether diol (b) to the at least one polyester diol a) can be greater than 1.0:3.0; the reactive polyurethane hot melt adhesive composition can further include an
  • the weight ratio of the at least one polyether diol (b) to the at least one polyester diol (a) can be equal to or greater than 1.0:4.0, and combinations thereof.
  • the hot melt adhesive composition after curing, exhibits a weight loss of no greater than 2.0 wt% after being placed in at least one of an aqueous solution with a pH value of 1 (one) and an aqueous solution with a pH value 13. In some embodiments, the hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt% after being placed in only one of an aqueous solution with a pH of 1 (one) or an aqueous solution having a pH of 13. In some embodiments, the hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt% after being placed in any one of an aqueous solution with a pH of 1 (one) and an aqueous solution having a pH of 13.
  • the reactive polyurethane hot melt adhesive composition is typically solid at room temperature (i.e. from 22°C to 25°C) and is free of solvent.
  • the reactive polyurethane hot melt adhesive composition typically has a viscosity at 140°C of less than 100,000 cPs, preferably from 3,000 to 80,000 cPs, especially from 3,000 to 50,000 cPs.
  • the polyurethane prepolymer (P) contained therein can be a binder.
  • a binder also called a binding agent, refers to a substance which provides a binding force for adhesives so as to bind ingredients therein together.
  • the binder can also be main film-forming substance and can be referred to in some instances as a film-former.
  • the starting materials for forming the polyurethane prepolymer (P) include diphenylmethane diisocyanate (MDI).
  • MDI diphenylmethane diisocyanate
  • Diphenylmethane diisocyanate mainly has three isomers, including 4,4’-MDI, 2,4’-MDI, and 2,2’-MDI. These isomers are all useful in the present disclosure.
  • the MDI comprises more than 70%, preferably more than 80%, more preferably more than 90%, particularly preferably 100% of 4,4’-MDI.
  • the content of the polyurethane prepolymer (P) can be from 15 wt.% to 95 wt.%, from 50 wt.% to 85 wt.%, or even from 60 wt.% to 75 wt.%, based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • M Polymer Polyol Mixture
  • the polymer polyol mixture (M) can be combined with MDI to form the isocyanate-terminated polyurethane prepolymer (P).
  • the polymer polyol mixture (M) includes at least one polyester diol (a) and at least one polyether diol (b). That is, typically at least one polyester diol (a) and at least one poly ether diol (b) are included, and both react with MDI to form the chain of the polyurethane prepolymer (P).
  • Suitable embodiments of the polyester diol (a) include a reaction product of one or more C4-C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
  • polyester diol (a) is a reaction product of one or more C6-C8 saturated aliphatic diols with one or more C12-C16 saturated aliphatic dicarboxylic acids, a reaction product of one or more C12-C16 saturated aliphatic diols with one or more C6-C8 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
  • Suitable examples of saturated aliphatic diol for forming polyester diol (a) may be butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, tetradecanediol, hexadecanediol, or a combination thereof.
  • Suitable examples of saturated aliphatic dicarboxylic acid for forming polyester diol (a) may be succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, or a combination thereof.
  • polyester diol (a) is poly(hexanediol sebacate) diol, poly(hexanediol dodecanedioate) diol, poly(hexanediol tetradecanedioate) diol, poly(hexanediol hexadecanedioate) diol, poly(octanediol sebacate) diol, poly(octanediol dodecanedioate) diol, poly(octanediol tetradecanedioate) diol, poly(octanediol hexadecanedioate) diol, poly(dodecanediol adipate) diol, poly(tetradecanediol adipate) diol, poly(hexadecanediol adipate) di
  • the reactive polyurethane hot melt adhesive composition includes from 20% to 45% by weight, or from 25% to 35% by weight of the polyester diol (a) in the form of building units incorporated into the polyurethane prepolymer (P), based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • the reactive polyurethane hot melt adhesive composition includes from eight wt.% to 35 wt%, or even from nine wt.% to 30 wt.% of the poly ether diol (b) in the form of building units incorporated into the polyurethane prepolymer (P), based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • polyether diol (b) include at least one of polypropylene glycol (bl) and polytetrahydrofuran diol (b2).
  • Polyether diol (b) may be one or more polypropylene glycols (bl), one or more polytetrahydrofuran diols (b2), or a combination of one or more polypropylene glycols (bl) with one or more polytetrahydrofuran diols
  • Suitable examples of polypropylene glycol (bl) include polypropylene glycol having a molecular weight of from 200 to 2,000, from 300 to 800, or even from 350 to 600.
  • the polypropylene glycol can have a terminal hydroxyl group and can react with MDI to form polyurethane.
  • the polypropylene glycol can be prepared by any suitable process, for example, by ring-opening polymerization of propylene oxide, or any suitable process commercially available.
  • Polypropylene glycol (bl) may be those commercially available under the trade designation DP 400 (molecular weight: 400) obtained from Kukdo Chemical Co., Ltd.
  • polytetrahydrofuran diol (b2) examples include polytetrahydrofuran diol (b2-a) having a molecular weight of from 200 to 4,000.
  • the polytetrahydrofuran diol (b2-b) has a surface tension of less than 42 mN/m measured at 50°C according to the national standard GB/T22237-2008.
  • the polytetrahydrofuran diol (b2) can have a terminal hydroxyl group and can react with MDI to form polyurethane.
  • the molecular weight of polytetrahydrofuran diol (b2-a) is usually from 200 to 4,000, from 800 to 3,500, or even from 2,500 to 3,500.
  • polytetrahydrofuran diol (b2-a) has a surface tension measured at 50°C according to the national standard GB/T22237-2008 of less than 42 mN/m, less than 33 mN/m, or even less than 30 mN/m.
  • polytetrahydrofuran diol (b2-b) may be used.
  • the polytetrahydrofuran diol (b2-b) can have a surface tension determined at 50°C according to the national standard
  • polytetrahydrofuran diol (b2) can be prepared by any suitable process, for example, by ring-opening polymerization of tetrahydrofuran, or any suitable process that is commercially available.
  • suitable examples of polytetrahydrofuran diol (b2) include those commercially available under the trade designations POLY THF 1000 (molecular weight: 1,000) from BASF AG (Ludwigshafen, Germany) and PTG 3,000 (molecular weight: 3,000) from Taiwan Dalian Chemical Industry Company.
  • the at least one poly ether diol (b) is a combination of polypropylene glycol (bl) and polytetrahydrofuran diol (b2).
  • Suitable weight ratios of polypropylene glycol (bl) to polytetrahydrofuran diol (b2) include from 2:1 to 1:2, or even from 1.5:1 to 1.1:1.
  • the weight ratio of the at least one polyether diol (b) to the at least one polyester diol (a) is greater than or equal to 1.0:4.0, greater than 1.0:3.0, or even greater than 1.1:3.0, for example from 1.0:4.0 to 1.0:1.0, or from 1.2:3.0 to 1.0:1.0. In some instances, if the weight ratio is less than 1.0:3.0, the tack-free property of the resulting reactive polyurethane hot melt adhesive composition may be deteriorated. For instance, the surface may be still tacky after the opening time and may need a comparatively long time to achieve tack-free (e.g. more than 50 seconds).
  • the polymer polyol mixture (M) can further include other polymer polyols.
  • the polymer polyol mixture (M) can include one or more of the following polymer polyol compounds.
  • the polymer polyol mixture (M) may be a hydroxyl- terminated polybutadiene diol having a molecular weight of from 2,000 to 10,000, from or even 4,000 to 6,000, and a partially hydrogenated product thereof.
  • the polymer polyol mixture (M) may be a polyester diol based on a dimer of an unsaturated fatty acid containing at least 12 carbon atoms and/or a hydrogenated product thereof.
  • the polymer polyol compound may be either a hydroxyl-terminated polybutadiene diol itself or a partially hydrogenated product of the hydroxyl-terminated polybutadiene diol, or a combination thereof.
  • the polymer polyol can have a molecular weight from 2,000 to 10,000, or even from 4,000 to 6,000. Suitable examples of the polymer polyol may be those commercially available under the trade designations KRASOL LBH-P 2000, KRASOL LBH-P 3000, KRASOL LBH-P 5000 and KRASOL LBH-P 10000 from Cray Valley (Paris, France).
  • the reactive polyurethane hot melt adhesive composition includes from 5 to 18% by weight, or even from 8 to 14% by weight, a hydroxyl-terminated polybutadiene diol and/or a partially hydrogenated product thereof.
  • the polymer polyol mixture (M) may be a hydroxyl- terminated polyester diol having a molecular weight of from 300 to 1,000, or even from 400 to 700, of phthalic acid and/or anhydride thereof with C2-C4 alkylene glycol and/or di(C2-C4 alkylene glycol).
  • the molecular weight of polymer polyol may be from 300 to 1 ,000, of even from 400 to 700.
  • the polymer polyol compound may be a hydroxyl-terminated polyester diol of phthalic acid and/or anhydride thereof with C2-C4 alkylene glycol and/or di(C2-C4 alkylene glycol).
  • C2-C4 alkylene glycol include ethylene glycol, propylene glycol, and butylene glycol.
  • di(C2-C4 alkylene glycol) include diethylene glycol, dipropylene glycol and dibutylene glycol.
  • the polymer polyol compound may be a hydroxyl- terminated polyester diol formed from phthalic anhydride and di(C2-C4 alkylene glycol), such as a hydroxyl-terminated polyester diol formed from phthalic anhydride and diethylene glycol.
  • the polymer polyol compound may be a polyester diol based on a dimer of an unsaturated fatly acid containing at least 12 carbon atoms and/or a hydrogenated product thereof.
  • a dimer of unsaturated fatty acid is a mixture, whose main components contain two carboxylic acid groups.
  • the dimer of unsaturated fatty acid can be obtained by mutual polymerization of unsaturated fatty acids containing at least one, for example, two or three, olefinic double bonds, such as oleic acid and linoleic acid.
  • a dimer of unsaturated fatty acid containing at least 12 carbon atoms can be prepared by refining a vegetable oil (a drying oil or a semi-drying oil), such as natural oils including soybean oil, cottonseed oil, rice bran oil or the like containing a high content of linoleic acid or oleic acid, to obtain a fatty acid, which can be then subjected to batchwise pressurized catalytic polymerization or continuous catalytic polymerization or the like.
  • Common dimers of fatty acid include dimers of octadecadienoic acid. With a dimer of unsaturated fatty acid as a raw material, polyester diols may be synthesized.
  • polyester diols sometimes contain ethylenically unsaturated double bonds depending on the starting materials, and thus may be partially or frilly hydrogenated.
  • polymer polyol compound may be those commertially available under the trade designation SOVERMOL 908 (polyester diol) manufactured by BASF AG, which is a hydrogenated dimeric Cis unsaturated fatty acid dimethyl ester diol.
  • the reactive polyurethane hot melt adhesive composition includes one or more of the polymer polyol compounds disclosed above, and the total amount thereof is less than or equal to 50% by weight of the total amount of the polyester diol (a), or less than or equal to exceed 40% by weight of the total amount of the polyester diol (a).
  • the polyurethane hot melt adhesive composition is reactive.
  • the polyurethane prepolymer (P) contained therein can include terminal isocyanate groups, which, upon curing after application, react with moisture to release carbon dioxide.
  • the molar ratio of the isocyanate group contained in MD1 for forming the polyurethane prepolymer (P) to the hydroxyl group contained in the polymer polyols generally ranges from 1.4:1.0 to 4.0: 1.0, from 1.5:1.0 to 3.5:1.0, or even from 1.5:1.0 to 1.7: 1.0.
  • the isocyanate-terminated polyurethane prepolymer indudes, based on the total weight thereof, from 0.4 wt.% to 4.0 wt.%, from 0.6 wt.% to 3.7 wt.%, or even from 0.7 wt.% to 3.3% wt.% of unreacted (i.e. free) isocyanate groups.
  • the reactive polyurethane hot melt adhesive composition can include an ethylene vinyl acetate copolymer (EVA).
  • EVA ethylene vinyl acetate copolymer
  • polyurethane hot melt adhesive composition based on its total weight, includes from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.% ethylene/vinyl acetate copolymer.
  • the reactive polyurethane hot melt adhesive composition may optionally further comprise a non-reactive polymer.
  • a non-reactive polymer means that the polymer does not participate in the chemical reaction during the preparation, application and curing processes of the reactive polyurethane hot melt adhesive composition.
  • the addition of the non-reactive polymer can increase the strength of the bulk of the cured hot melt adhesive composition.
  • non-reactive polymers include ethylene/vinyl acetate (EVA), thermoplastic polyurethane (TPU), amorphous poly -alpha- olefin (APAO), thermoplastic elastomer (TPE) such as ethylenically thermoplastic elastomer (TPO or TPES) or thermoplastic amide (TP A).
  • the nonreactive polymer can be a thermoplastic polyurethane (TPU), ethylene/vinyl acetate copolymer (EVA), amorphous poly-a-olefin (APAO), or a combination thereof.
  • anon-reactive polymer examples include ethylene/vinyl acetate copolymer.
  • Non-reactive polymers may be, for example, commercially available under the trade designations DESMOCOLL 540/1 (TPU) from Covestro Polymers (China) Co., Ltd., ESCORENE UL7710 (EVA) from Exxon Mobil Corporation (Irving, TX, USA), and VESTOPLAST 508 (APAO) from Evonik Industries.
  • a useful amount of the non-reactive polymer can be selected to help increase the cohesion of the reactive polyurethane hot melt adhesive composition after curing without significantly impairing the resistance to acid, resistance to alkali and fast tack- free property of the hot melt adhesive composition.
  • the non-reactive polymer is generally used in an amount of not more than 40 wt.%, such as from 5 wt.% to 30 wt.%, from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.%, based on the total weight of the reactive polyurethane hot melt adhesive composition.
  • the polyurethane hot melt adhesive composition may further include a curing catalyst for polyurethane, such as a catalyst suitable for one-component moisture curing, to shorten the curing time.
  • a curing catalyst for polyurethane such as a catalyst suitable for one-component moisture curing, to shorten the curing time.
  • Useful curing catalysts comprise ether and morpholine functional groups, examples of which include 2,2’-dimorpholinoethylether, di(2,6- dimethyl morpholinoethyl)ether, and 4,4'-(oxydi-2, 1 -ethanediyl)bis-morpholine.
  • Suitable commercially available catalysts include, e.g., JEFFCAT DMDEE 4,4'-(oxydi-2,l- ethanediyl) bis-morpholine, which is available from Huntsman Corp. (Houston, Texas).
  • metal catalysts include, e.g., catalysts based on tin (e.g. dibutyltin dilaurate and dibutyltin acetate), bismuth, zinc, and potassium
  • the curing catalyst may be present in an amount of from 0.01 wt.% to two wt.%, or even from 0.05 wt.% to one wt.%, based on the total weight of the polyurethane hot melt adhesive composition.
  • the reactive polyurethane hot melt adhesive composition may also include various other conventional additives typically comprised in reactive polyurethane hot melt adhesive compositions.
  • additives include, for example, tackifiers, plasticizers, waxes, stabilizers, antioxidants, fillers (talc, clay, silica, and treated variants thereof, carbon black and mica, microparticles including, for example, microspheres such as glass microspheres, polymer microspheres and combinations thereof), UV scavengers and absorbers, colorants (e.g. pigments and dyes), fluorescents, odor masking agents, biocides, corrosion inhibitors, adhesion promoters, surfactants, defoamers, flame retardants, and combinations thereof.
  • Useful tackifiers include, for example, aromatic, aliphatic and alicyclic hydrocarbon resins, mixed aromatic and aliphatic modified resins, aromatic modified hydrocarbon resins, and hydrogenated variants thereof; teipenes, modified terpenes, and hydrogenated variants thereof; rosin esters; and combinations thereof.
  • Useful waxes include, for example, hydroxyl modified waxes, carbon monoxide modified waxes, hydroxyl stearamide waxes, fatty amide waxes, hydrocarbon waxes including, such as, high-density low-molecular-weight polyethylene waxes, paraffin and microcrystalline waxes, and combinations thereof.
  • Useful stabilizers include carbodiimide stabilizers, such as that available under the trade designation STABAXOL 7000 from Rhein Chemie, Germany.
  • antioxidants examples include those available under the trade desginations IRGANOX 565, 1010 and 1076 hindered phenolic antioxidants from Ciba-Geigy (Basel, Switzerland), and ANOX 20 hindered phenolic antioxidants from Great Lakes Chemicals (West Lafayette, IN, USA). These antioxidants can function as free radical scavengers and can be used alone or in combination with other antioxidants.
  • the reactive polyurethane hot melt adhesive composition optionally includes not more than two wt.% of an antioxidant.
  • the reactive polyurethane hot melt adhesive composition optionally includes from about three, four, five, or about seven, to about 12, 13, 15, or about 20 percent by weight of filler, or a weight percent between any pair of the foregoing values.
  • a process for preparation of a reactive polyurethane hot melt adhesive composition including reacting diphenylmethane diisocyanate with the polymer polyol mixture (M) comprising at least one polyester diol a) and at least one poly ether diol b) as described above to give an isocyanate-terminated polyurethane prepolymer (P).
  • M polymer polyol mixture
  • P isocyanate-terminated polyurethane prepolymer
  • the process for obtaining an isocyanate-terminated polyurethane prepolymer (P) by reacting MDI with a polymer polyol mixture (M) may include any suitable process known to those of skill in the art.
  • the reaction mixture comprising MDI, at least one polyester diol a) and at least one poly ether diol b) is subjected to reaction under the condition of moisture removal at an elevated temperature, typically from 60°C to 160°C, preferably from 80°C to 120°C.
  • the reaction time is usually from 1 to 2 hours.
  • the polymer polyol mixture (M) is firstly introduced into a reactor, heated to a reaction temperature, and dried under vacuum to remove moisture absorbed by the polyol from environment, followed by addition of MDI into the reactor.
  • the reaction of the polymer polyol with MDI may be conducted under vacuum or in an inert atmosphere such as nitrogen.
  • MDI typically can be used in an excessive amount by mole relative to the polymer polyol.
  • the reaction between MDI and polymer polyols is typically carried out at aNCO:OH molar ratio of from 1.4:1.0 to 4.0:1.0, from 1.5:1.0 to 3.5:1.0, or even
  • the reactive polyurethane hot melt adhesive composition readily undergoes a curing reaction with moisture, it is advantageous to store it in a moisture- proof container to inhibit unwanted reactions after the composition is prepared.
  • the reactive polyurethane hot melt adhesive composition can be cured in a variety of mechanisms.
  • the curing reaction occurs mainly between the compound having an available active hydrogen atom and the NCO group of the polyurethane prepolymer (P).
  • Various reactive compounds having free active hydrogen are well known in the art, including water, hydrogen sulfide, polyols, ammonia, and other active compounds.
  • the reactive polyurethane hot melt adhesive composition is preferably cured by moisture out of consideration for cost, environmental protection and operation simplicity.
  • the reactive polyurethane hot melt adhesive composition is a one-component moisture curable hot melt adhesive composition.
  • One-component moisture curable polyurethane adhesives are mainly cured by moisture in air, so suitable air humidity should be maintained, and a slow curing at room temperature (e.g. from about 22°C to about 25°C) is preferred. If air is dry, a small amount of water can be applied onto the surface coated with an adhesive to promote curing. If the adhesive is sandwiched between dry and hard adherends, and the adhesive layer is relatively thick so that moisture from interface and exteral cannot penetrate into the adhesive easily, then the curing will be incomplete. In this case, a small amount of water can be injected into the adhesive. [0076] According to another aspect, there is provided use of a reactive polyurethane hot melt adhesive composition according as a hot melt adhesive.
  • the reactive polyurethane hot melt adhesive composition is useful in all of the commonly known applications of HMMC adhesives.
  • the reactive polyurethane hot melt adhesive composition is used as a hot melt adhesive, especially as a one-component moisture curable hot melt adhesive, in the fields of building materials, furiture and woodworking, electrical, automobile, bookbinding, shoemaking, filter assembly, and fabric processing.
  • the reactive polyurethane hot melt adhesive composition can be applied to a substrate using any suitable application method including, e.g., automatic fine line dispensing, jet dispensing, slot die coating, roll coating, gravure coating, transfer coating, patter coating, screen printing, spray coating, filament coating, extrusion, air knife, trailing blade, brushing, dipping, doctor blade, offset gravure coating, rotogravure coating, and combinations thereof.
  • the moisture curable adhesive composition can be applied as a continuous or discontinuous coating, in single or multiple layers, and combinations thereof.
  • the moisture curable adhesive composition can be applied at any suitable temperature including, e.g., from 60°C to 200°C, from 80°C to 175°C, or even from about 110°C to 150°C.
  • the surface of the substrate on which the reactive polyurethane hot melt adhesive composition is applied is surface-treated to enhance adhesion using any suitable method for enhancing adhesion to the substrate surface including, e.g., corona treatments, chemical treatments (e.g., chemical etching), flame treatments, abrasion, and combinations thereof.
  • any suitable method for enhancing adhesion to the substrate surface including, e.g., corona treatments, chemical treatments (e.g., chemical etching), flame treatments, abrasion, and combinations thereof.
  • Viscosity was determined using a Brookfield Thermosel viscometer
  • the hot melt adhesive composition was melted at a temperature of 140°C and applied to the non-release surface of a PET release film at a thickness of 100 mm, and immediately timed.
  • the surface of the adhesive layer was pressed with a pointing finger every 1 to 2 seconds.
  • the time when the hand no longer felt tackiness is the tack-free time.
  • the testing time is stopped at 60 seconds.
  • the prepared hot melt adhesive composition was coated on a release PET film and cured at room temperature and at ambient humidity (about 50%) for seven days to obtain a 100 mm adhesive film. Using a press vulcanizer, multiple layers of adhesive film were laminated together at 120°C, cut into a sheet sample of 15 mm x 20 mm x 2 mm, and weighed.
  • DP 400 is a polypropylene glycol, Mw of 400, surface tension: 30.324 mN/m, purchased from Kukdo Chemical Co., Ltd.
  • POLY THF 1000 is a polytetrahydrofuran diol, Mw of 1,000, purchased from
  • PTG 3000 is a polytetrahydrofuran diol, Mw of 3,000, surface tension:
  • SOVERMOL 908 is a hydrogenated dimerized C18 unsaturated fatly acid dimethyl ester diol, Mw of 543.7, surface tension: 32.853 mN/m, purchased from BASF
  • PS 2002 is a polyester diol obtained by reacting phthalic anhydride with diethylene glycol, Mw of 575, surface tension: 41.631 mN/m, purchased from Stepan Chemical LLC.
  • KRASOL LBH-P 5000 is a polybutadiene diol, Mw of 5,000, surface tension: 26.581 mN/m, purchased from Cray Valley.
  • DYNACOLL 7380 is a polyester diol, Mw of 3,500, purchased from
  • MISTRON VAPOR is a talc, purchased from Luzenac America, Inc.
  • EVERNOX 10GF is an antioxidant, purchased from Everspring Company.
  • VeESTOPLAST 508 is an amorphous poly-a-olefin, purchased from
  • DESMODUR CD-C is a carbodiimide isocyanate, purchased from Covestro Polymers (China) Co., Ltd.
  • DMDEE is a 4,4’-(oxydi-2, 1 -ethanediyl) bismorpholine, purchased from Huntsman Corp. (Houston, Texas). Preparation of Hot Melt Adhesive Composition Samples
  • HL9810 is a moisture curable polyurethane hot melt adhesive, available from H.B. Fuller of St. Paul, MN USA. This hot melt adhesive was designated as Comparative Example C-l. This hot melt adhesive was tested by the above described testing methods with respect to its various properties. It is noted that the viscosity testing for HL9810 was conducted at a temperature of 163°C instead of 140°C. The results are summarized in the Table 2 below.
  • Examples 1 to 8 shows that the use of MDI as polyisocyanate helped improve resistance to acid and alkali, particularly, improved alkali resistance, compared with the use of carbodiimide diisocyanate.

Abstract

A reactive polyurethane hot melt adhesive composition comprising an isocyanate- terminated polyurethane prepolymer obtained from diphenylmethane diisocyanate and a polymer polyol mixture comprising at least one polyester diol and at least one polyether diol. A reactive polyurethane hot melt adhesive composition that has reduced cost, good performance of becoming tack-free upon application, and excellent alkali and acid resistance after curing.

Description

REACTIVE POLYURETHANE HOT MELT ADHESIVE COMPOSITION,
PREPARATION, AND USE
FIELD
[0001] This disclosure is directed to a reactive polyurethane hot melt adhesive composition, a preparation process, and use thereof.
BACKGROUND
[0002] Polyurethane-based hot melt moisture curable (HMMC) adhesive compositions are known. They are usually hot melt adhesives based on an isocyanate- terminated polyurethane prepolymer as a main binder. The isocyanate groups in NCO- terminated prepolymers react with moisture (for example, moisture in the air or on an adherend) resulting in crosslinking and bonding while generating CO2. Suitable NCO- terminated prepolymers can be obtained by reacting a polymer which is reactive toward isocyanate groups, such as polymer polyols (for example polyether polyols and polyester polyols) with polyisocyanates such as monomeric diisocyanates.
[0003] Polyurethane hot melt adhesives, when free of water and solvent, typically have a solids content of 100%. They can be high-performance environmentally friendly adhesives that cater to the needs of increasing attention to the environment. Reactive polyurethane hot melt adhesives have excellent properties compared to conventional hot melt adhesives. They have the characteristics of conventional hot melt adhesives, i.e., are free of solvent, have high initial viscosity, and rapid positioning when being applied; and once applied, have good resistance to water, heat, coldness, and creep. They can also be applied at temperatures which are normally lower than those used for applying conventional hot melt adhesives (e.g. from 150°C to 180°C) and can be used for bonding and compounding of plastic parts. They are often favored in modem automatic assembly industries. Reactive polyurethane hot melt adhesives are useful in the fields of building materials, furniture and woodworking, electrical, automotive, bookbinding, shoemaking and fabric processing. [0004] Certain commercially available fast-drying (losing surface tackiness within a second-order period) reactive polyurethane hot melt adhesives include one-component adhesives that are moisture curable. These adhesives may be suitable for adhesion of wood, metal, and plastic. In the assembly line, they can provide a strong rapid bonding force after the substrate is pressed or rolled. Due to good performance, such adhesives have been tested for use with filters. However, some users of these filters have found that the adhesive becomes brittle after the bonded filters have been used for some period of time. One reason for this is that certain chemicals present in the fluids being filtered have some alkalinity, and currently available adhesives are often not resistant to alkali corrosion.
[0005] It has been found that existing reactive polyurethane hot melt adhesives often also have insufficient acid resistance in some applications. Often the hot melt adhesive will be gradually degraded over time, so that the adhesive does not function properly and needs to be replaced or re-glued.
[0006] U.S. Patent No. 5,530,085 discloses a polyurethane prepolymer composition including as a binder a prepolymer which is obtained by reacting diphenylmethane diisocyanate (MDI) with a hydroxyl-terminated conjugated diene polymer at a temperature of no more than 100°C, wherein MDI comprises at least 20% of 2,4’ -MDI isomer. The polyurethane prepolymer composition can be used as a moisture curable hot melt adhesive, which is asserted to be resistant to acidic and basic solutions. However, the hydroxyl-terminated conjugated diene polymers, especially polybutadiene diols, may not be favored in certain applications. And they may be relatively expensive as polymer polyols for the synthesis of polyurethanes.
[0007] U.S. Patent No. 4,021 ,414 also teaches a polyurethane polymer which is obtained by first reacting diisocyanate with a mixture comprising a 2,6-dialkyl-p-cresol and a polybutadiene polyol to obtain a prepolymer, the obtained prepolymer is dissolved in a solvent to form a sprayable prepolymer solution, which is then cured at a temperature of 25 to 100°C in the presence of 2,2’-diaminodiphenyl disulfide. However, the disclosed compounds often do not have adequate acid and alkali resistance in certain applications. The polybutadiene polyol required in this patent may be relatively expensive for certain applications.
[0008] There is a need for a reactive hot melt adhesive that is suitably resistant to acid and alkali corrosion.
SUMMARY
[0009] Disclosed herein is a reactive hot melt adhesive having improved alkali resistance and acid resistance. Disclosed herein a reactive hot melt adhesive that has both superior acid resistance and alkali resistance. The reactive polyurethane hot melt adhesive can be economically advantageous.
[0010] Is some embodiments, the reactive hot melt adhesive is derived from a composition that after curing, exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in either of an acid solution and an alkaline solution (for example an aqueous solution of HCl and an aqueous solution of NaOH). In some embodiments, the reactive hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in either of an aqueous solution with a pH value of 1 and 13 for at least three weeks.
[0011] The reactive hot melt adhesive can be tack-free witiiin a suitable period of time (e.g. not more than 50 seconds) after application. In some embodiments, the reactive hot melt adhesive composition becomes tack-free in no greater than 50 seconds, no greater than 40 seconds, no greater than 30 seconds, or even no greater than 20 seconds, after application of the hot melt adhesive composition.
[0012] Disclosed herein is a reactive hot melt adhesive composition having an isocyanate-terminated polyurethane prepolymer derived from diphenylmethane diisocyanate and a polymer polyol mixture including at least one polyester diol and at least one polyether diol. The polyester diol can be a reaction product of one or more C4- C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products. The polyether diol can be at least one of polypropylene glycol and polytetrahydrofuran diol. The polypropylene glycol can have a molecular weight of from 200 to 2,000, 300 to 800, or even from 350 to 600. The polytetrahydrofuran diol can have a molecular weight of from 200 to 4,000, from 800 to 3,500, or even 2,500 to 3,500. The polytetrahydrofuran diol can have a surface tension of no greater than 42 mN/m, no greater than 33 mN/m, or even no greater than 30 mN/m measured at 50°C according to the national standard GB/T22237-2008 (“Surface active agents. Determination of surface tension”). The weight ratio of polyether diol to polyester diol in the reactive hot melt adhesive composition can be greater than or equal to 1.0:3.0, greater than or equal to 1.1:3.0, or even from 1.2:3.0 to 1.0:1.0.
[0013] The reactive hot melt adhesive composition can further include an
ethylene/vinyl acetate copolymer (EVA). The reactive hot melt adhesive composition can further include an ethylene/vinyl acetate copolymer (EVA) and have a weight ratio of polyether diol to polyester diol greater than or equal to 1.0:4.0. The weight ratio of polyether diol to polyester diol can be greater than or equal to 1.0:4.0, such as from 1.0:4.0 to 1.0:1.0. In some instances, the reactive hot melt adhesive is derived from a composition having from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.% ethylene/vinyl acetate copolymer (EVA), based on the total weight of the reactive hot melt adhesive composition.
[0014] After curing, the reactive hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one). After curing the hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one) for at least three weeks. After curing the hot melt adhesive can exhibit a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 1 (one) for at least five weeks. After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13. After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13 for at least three weeks. After curing the hot melt adhesive exhibits a weight loss of no greater than 2.0 wt.%, no greater than 1.5 wt.%, or even no greater than 1.0 wt.%, after being placed in an aqueous solution with a pH value of 13 for at least five weeks.
[0015] In some instances, the reactive hot melt adhesive is derived from a composition having a polyether diol that is a combination of polypropylene glycol and polytetrahydrofuran diol. In some instances, the reactive hot melt adhesive is derived from a composition having a poly ether diol that is a combination of polypropylene glycol and polytetrahydrofuran diol, and the weight ratio of polypropylene glycol to
polytetrahydrofuran diol is from 2:1 to 1:2, or even from 1.5:1 to 1.1:1.
[0016] In some instances, the reactive hot melt adhesive is derived from a composition that includes diphenylmethane diisocyanate having greater than or equal to 70 wt.%, 80 wt.%, 90 wt.%, or even 100% being of the diphenylmethane diisocyanate being 4,4’ -diphenylmethane diisocyanate. In some instances, the reactive hot melt adhesive is derived from a composition that includes polytetrahydrofuran diol exhibiting a surface tension of less than 42 mN/m, less than 33 mN/m, or even less than 30 mN/m, as measured at 50°C according to the national standard GB/T22237-2008.
[0017] In some instances, the reactive hot melt adhesive is derived from a composition that includes a reaction product of one or more C6-C8 saturated aliphatic diols with one or more C12-C16 saturated aliphatic dicarboxylic acids, a reaction product of one or more C12-C16 saturated aliphatic diols with one or more C6-C8 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
[0018] In some instances, the reactive hot melt adhesive is derived from a composition that includes a polymer polyol mixture that includes a hydroxyl-terminated poly butadiene diol having a molecular weight of from 2,000 to 10,000, from 4,000 to 6,000, and/or a partially hydrogenated product in an amount of from five wt.% to 18 wt.%, or from eight wt.% to 14 wt.%, based on the total wdght of the reactive polyurethane hot melt adhesive composition. [0019] In some instances, the reactive hot melt adhesive is derived from a composition having a molar ratio of isocyanate group contained in MDI to hydroxyl group contained in polymer polyols from 1.4:1.0 to 4.0:1.0, from 1.5:1.0 to 3.5:1.0, or even 1.5:1.0 to 1.7:1.0.
[0020] In some instances, the reactive hot melt adhesive is derived from a composition having isocyanate-terminated polyurethane prepolymer having from 0.4 wt.% to 4.0 wt.%, 0.6 wt.% to 3.7 wt.%, or even from 0.7 wt.% to 3.3 wt.% unreacted isocyanate groups, based on the total weight of the prepolymer.
[0021] In some instances, the reactive hot melt adhesive is derived from a composition having from 20 wt.% to 45 wt.%, or even from 25 wt.% to 35 wt.% of the polyester diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition. In some instances, the reactive hot melt adhesive is derived from a composition having from eight wt% to 35 wt.%, or even from nine wt.% to 30% wt.% of the polyether diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
[0022] In some instances, the reactive hot melt adhesive is derived from a composition having from three wt.% to 20 wt.%, or from five wt.% to 15 wt.% filler, based on the total weight of the reactive polyurethane hot melt adhesive composition.
[0023] In some instances, the reactive hot melt adhesive is a one-component moisture curable polyurethane hot melt adhesive composition.
[0024] In another aspect, there is provided a method for preparing a reactive polyurethane hot melt adhesive composition. Disclosed herein is a method for preparation of a reactive polyurethane hot melt adhesive composition including reacting
diphenylmethane diisocyanate with a polymer polyol mixture having at least one polyester diol and at least one polyether diol to form an isocyanate-terminated polyurethane prepolymer.
[0025] In another aspect, there is provided use of a reactive polyurethane hot melt adhesive composition as a hot melt adhesive. Disclosed herein is a use of a reactive polyurethane hot melt adhesive composition as a hot melt adhesive in fields such as building materials, furniture and woodworking, electrical, automobile, bookbinding, shoemaking, filter assembly, and fabric processing.
DETAILED DESCRIPTION
[0026] Disclosed herein is a reactive polyurethane hot melt adhesive composition comprising an isocyanate-terminated polyurethane prepolymer (P) which is obtained from a diphenylmethane diisocyanate and a polymer polyol mixture (M) comprising at least one polyester diol (a) and at least one polyether diol (b). The polyester diol (a) can be a reaction product of one or more C4-C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products. The at least one poly ether diol (b) can be at least one of polypropylene glycol (b1) and polytetrahydrofuran diol (b2). The polypropylene glycol (b1 ) can have a molecular weight of from 200 to 2,000. The polytetrahydrofuran diol (b2) can be polytetrahydrofuran diol (b2-a) having a molecular weight of from 200 to 4,000. Additionally, or alteratively, the polytetrahydrofuran diol (b2-b) can have a surface tension of less than 42 mN/m measured at 50°C according to the national standard GB/T22237-2008.
[0027] The reactive polyurethane hot melt adhesive composition can be formulated to meet at least one of the following requirements. The weight ratio of the at least one polyether diol (b) to the at least one polyester diol a) can be greater than 1.0:3.0; the reactive polyurethane hot melt adhesive composition can further include an
ethylene/vinyl acetate copolymer (EVA); and the weight ratio of the at least one polyether diol (b) to the at least one polyester diol (a) can be equal to or greater than 1.0:4.0, and combinations thereof.
[0028] The hot melt adhesive composition, after curing, exhibits a weight loss of no greater than 2.0 wt% after being placed in at least one of an aqueous solution with a pH value of 1 (one) and an aqueous solution with a pH value 13. In some embodiments, the hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt% after being placed in only one of an aqueous solution with a pH of 1 (one) or an aqueous solution having a pH of 13. In some embodiments, the hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt% after being placed in any one of an aqueous solution with a pH of 1 (one) and an aqueous solution having a pH of 13.
[0029] The reactive polyurethane hot melt adhesive composition is typically solid at room temperature (i.e. from 22°C to 25°C) and is free of solvent. The reactive polyurethane hot melt adhesive composition typically has a viscosity at 140°C of less than 100,000 cPs, preferably from 3,000 to 80,000 cPs, especially from 3,000 to 50,000 cPs.
[0030] Unless otherwise specified, the molecular weights mentioned herein are measured by gel permeation chromatography (GPC), and refer to weight-averaged molecular weight (Mw). Unless otherwise indicated, all parts, ratios, percentages and amounts recited herein are based on weight
[0031] Prepolymer (P)
[0032] In the reactive polyurethane hot melt adhesive composition, the polyurethane prepolymer (P) contained therein can be a binder. As used herein, a binder, also called a binding agent, refers to a substance which provides a binding force for adhesives so as to bind ingredients therein together. The binder can also be main film-forming substance and can be referred to in some instances as a film-former.
[0033] In some embodiments, the starting materials for forming the polyurethane prepolymer (P) include diphenylmethane diisocyanate (MDI). Diphenylmethane diisocyanate mainly has three isomers, including 4,4’-MDI, 2,4’-MDI, and 2,2’-MDI. These isomers are all useful in the present disclosure. In a preferred embodiment, the MDI comprises more than 70%, preferably more than 80%, more preferably more than 90%, particularly preferably 100% of 4,4’-MDI.
[0034] The content of the polyurethane prepolymer (P) can be from 15 wt.% to 95 wt.%, from 50 wt.% to 85 wt.%, or even from 60 wt.% to 75 wt.%, based on the total weight of the reactive polyurethane hot melt adhesive composition. [0035] Polymer Polyol Mixture (M)
[0036] The polymer polyol mixture (M) can be combined with MDI to form the isocyanate-terminated polyurethane prepolymer (P). The polymer polyol mixture (M) includes at least one polyester diol (a) and at least one polyether diol (b). That is, typically at least one polyester diol (a) and at least one poly ether diol (b) are included, and both react with MDI to form the chain of the polyurethane prepolymer (P).
[0037] Polyester Diol (a)
[0038] Suitable embodiments of the polyester diol (a) include a reaction product of one or more C4-C12 saturated aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products. Preferably, polyester diol (a) is a reaction product of one or more C6-C8 saturated aliphatic diols with one or more C12-C16 saturated aliphatic dicarboxylic acids, a reaction product of one or more C12-C16 saturated aliphatic diols with one or more C6-C8 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products. Suitable examples of saturated aliphatic diol for forming polyester diol (a) may be butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, tetradecanediol, hexadecanediol, or a combination thereof. Suitable examples of saturated aliphatic dicarboxylic acid for forming polyester diol (a) may be succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, or a combination thereof. Preferably, polyester diol (a) is poly(hexanediol sebacate) diol, poly(hexanediol dodecanedioate) diol, poly(hexanediol tetradecanedioate) diol, poly(hexanediol hexadecanedioate) diol, poly(octanediol sebacate) diol, poly(octanediol dodecanedioate) diol, poly(octanediol tetradecanedioate) diol, poly(octanediol hexadecanedioate) diol, poly(dodecanediol adipate) diol, poly(tetradecanediol adipate) diol, poly(hexadecanediol adipate) diol, poly(dodecanediol sebacate) diol, poly(tetradecanediol sebacate) diol, poly(hexadecanediol sebacate) diol, or any combination thereof. Polyester diol (a) can be, for example, those commercially available under the trade designation DYNACOLL 7380 (molecular weight: 3,500) from Evonik Industries (Essen, Germany).
[0039] In some embodiments, the reactive polyurethane hot melt adhesive composition includes from 20% to 45% by weight, or from 25% to 35% by weight of the polyester diol (a) in the form of building units incorporated into the polyurethane prepolymer (P), based on the total weight of the reactive polyurethane hot melt adhesive composition.
[0040] Poly ether Diol (b)
[0041] In some embodiments, the reactive polyurethane hot melt adhesive composition includes from eight wt.% to 35 wt%, or even from nine wt.% to 30 wt.% of the poly ether diol (b) in the form of building units incorporated into the polyurethane prepolymer (P), based on the total weight of the reactive polyurethane hot melt adhesive composition.
[0042] Suitable examples of polyether diol (b) include at least one of polypropylene glycol (bl) and polytetrahydrofuran diol (b2). Polyether diol (b) may be one or more polypropylene glycols (bl), one or more polytetrahydrofuran diols (b2), or a combination of one or more polypropylene glycols (bl) with one or more polytetrahydrofuran diols
(b2).
[0043] Suitable examples of polypropylene glycol (bl) include polypropylene glycol having a molecular weight of from 200 to 2,000, from 300 to 800, or even from 350 to 600. The polypropylene glycol can have a terminal hydroxyl group and can react with MDI to form polyurethane. The polypropylene glycol can be prepared by any suitable process, for example, by ring-opening polymerization of propylene oxide, or any suitable process commercially available. Polypropylene glycol (bl) may be those commercially available under the trade designation DP 400 (molecular weight: 400) obtained from Kukdo Chemical Co., Ltd. (Seoul, South Korea), and PPG 2,000 (molecular weight: 2,000, trade designation: VORANOL 2000L) available from Dow Chemical Company (Midland, MI, USA). [0044] Suitable examples of polytetrahydrofuran diol (b2) include polytetrahydrofuran diol (b2-a) having a molecular weight of from 200 to 4,000. In some embodiments, the polytetrahydrofuran diol (b2-b) has a surface tension of less than 42 mN/m measured at 50°C according to the national standard GB/T22237-2008. The polytetrahydrofuran diol (b2) can have a terminal hydroxyl group and can react with MDI to form polyurethane.
[0045] The molecular weight of polytetrahydrofuran diol (b2-a) is usually from 200 to 4,000, from 800 to 3,500, or even from 2,500 to 3,500. Preferably, polytetrahydrofuran diol (b2-a) has a surface tension measured at 50°C according to the national standard GB/T22237-2008 of less than 42 mN/m, less than 33 mN/m, or even less than 30 mN/m.
[0046] Additionally, or alternatively, as polytetrahydrofuran diol (b2),
polytetrahydrofuran diol (b2-b) may be used. The polytetrahydrofuran diol (b2-b) can have a surface tension determined at 50°C according to the national standard
GB/T22237-2008 of less than 42 mN/m, less than 33 mN/m, or even less than 30 mN/m [0047] In some embodiments, polytetrahydrofuran diol (b2) can be prepared by any suitable process, for example, by ring-opening polymerization of tetrahydrofuran, or any suitable process that is commercially available. Suitable examples of polytetrahydrofuran diol (b2) include those commercially available under the trade designations POLY THF 1000 (molecular weight: 1,000) from BASF AG (Ludwigshafen, Germany) and PTG 3,000 (molecular weight: 3,000) from Taiwan Dalian Chemical Industry Company.
[0048] In a preferred embodiment, the at least one poly ether diol (b) is a combination of polypropylene glycol (bl) and polytetrahydrofuran diol (b2). Suitable weight ratios of polypropylene glycol (bl) to polytetrahydrofuran diol (b2) include from 2:1 to 1:2, or even from 1.5:1 to 1.1:1.
[0049] In some instances, the weight ratio of the at least one polyether diol (b) to the at least one polyester diol (a) is greater than or equal to 1.0:4.0, greater than 1.0:3.0, or even greater than 1.1:3.0, for example from 1.0:4.0 to 1.0:1.0, or from 1.2:3.0 to 1.0:1.0. In some instances, if the weight ratio is less than 1.0:3.0, the tack-free property of the resulting reactive polyurethane hot melt adhesive composition may be deteriorated. For instance, the surface may be still tacky after the opening time and may need a comparatively long time to achieve tack-free (e.g. more than 50 seconds).
[0050] The polymer polyol mixture (M) can further include other polymer polyols. For example, the polymer polyol mixture (M) can include one or more of the following polymer polyol compounds. The polymer polyol mixture (M) may be a hydroxyl- terminated polybutadiene diol having a molecular weight of from 2,000 to 10,000, from or even 4,000 to 6,000, and a partially hydrogenated product thereof. The polymer polyol mixture (M) may be a polyester diol based on a dimer of an unsaturated fatty acid containing at least 12 carbon atoms and/or a hydrogenated product thereof.
[0051] In some embodiments, the polymer polyol compound may be either a hydroxyl-terminated polybutadiene diol itself or a partially hydrogenated product of the hydroxyl-terminated polybutadiene diol, or a combination thereof. The polymer polyol can have a molecular weight from 2,000 to 10,000, or even from 4,000 to 6,000. Suitable examples of the polymer polyol may be those commercially available under the trade designations KRASOL LBH-P 2000, KRASOL LBH-P 3000, KRASOL LBH-P 5000 and KRASOL LBH-P 10000 from Cray Valley (Paris, France).
[0052] In some embodiments, the reactive polyurethane hot melt adhesive composition, based on its total weight, includes from 5 to 18% by weight, or even from 8 to 14% by weight, a hydroxyl-terminated polybutadiene diol and/or a partially hydrogenated product thereof. The polymer polyol mixture (M) may be a hydroxyl- terminated polyester diol having a molecular weight of from 300 to 1,000, or even from 400 to 700, of phthalic acid and/or anhydride thereof with C2-C4 alkylene glycol and/or di(C2-C4 alkylene glycol). The molecular weight of polymer polyol may be from 300 to 1 ,000, of even from 400 to 700. In some embodiments, the polymer polyol compound may be a hydroxyl-terminated polyester diol of phthalic acid and/or anhydride thereof with C2-C4 alkylene glycol and/or di(C2-C4 alkylene glycol). Suitable examples of C2-C4 alkylene glycol include ethylene glycol, propylene glycol, and butylene glycol. Suitable example of di(C2-C4 alkylene glycol) include diethylene glycol, dipropylene glycol and dibutylene glycol. For example, the polymer polyol compound may be a hydroxyl- terminated polyester diol formed from phthalic anhydride and di(C2-C4 alkylene glycol), such as a hydroxyl-terminated polyester diol formed from phthalic anhydride and diethylene glycol.
[0053] In some embodiments, the polymer polyol compound, may be a polyester diol based on a dimer of an unsaturated fatly acid containing at least 12 carbon atoms and/or a hydrogenated product thereof. A dimer of unsaturated fatty acid is a mixture, whose main components contain two carboxylic acid groups. The dimer of unsaturated fatty acid can be obtained by mutual polymerization of unsaturated fatty acids containing at least one, for example, two or three, olefinic double bonds, such as oleic acid and linoleic acid. A dimer of unsaturated fatty acid containing at least 12 carbon atoms can be prepared by refining a vegetable oil (a drying oil or a semi-drying oil), such as natural oils including soybean oil, cottonseed oil, rice bran oil or the like containing a high content of linoleic acid or oleic acid, to obtain a fatty acid, which can be then subjected to batchwise pressurized catalytic polymerization or continuous catalytic polymerization or the like. Common dimers of fatty acid include dimers of octadecadienoic acid. With a dimer of unsaturated fatty acid as a raw material, polyester diols may be synthesized. These polyester diols sometimes contain ethylenically unsaturated double bonds depending on the starting materials, and thus may be partially or frilly hydrogenated. As an example, polymer polyol compound may be those commertially available under the trade designation SOVERMOL 908 (polyester diol) manufactured by BASF AG, which is a hydrogenated dimeric Cis unsaturated fatty acid dimethyl ester diol.
[0054] In some embodiments, the reactive polyurethane hot melt adhesive composition includes one or more of the polymer polyol compounds disclosed above, and the total amount thereof is less than or equal to 50% by weight of the total amount of the polyester diol (a), or less than or equal to exceed 40% by weight of the total amount of the polyester diol (a).
[0055] The polyurethane hot melt adhesive composition is reactive. For example, the polyurethane prepolymer (P) contained therein can include terminal isocyanate groups, which, upon curing after application, react with moisture to release carbon dioxide. In some embodiments, the molar ratio of the isocyanate group contained in MD1 for forming the polyurethane prepolymer (P) to the hydroxyl group contained in the polymer polyols generally ranges from 1.4:1.0 to 4.0: 1.0, from 1.5:1.0 to 3.5:1.0, or even from 1.5:1.0 to 1.7: 1.0. In some embodiments, the isocyanate-terminated polyurethane prepolymer indudes, based on the total weight thereof, from 0.4 wt.% to 4.0 wt.%, from 0.6 wt.% to 3.7 wt.%, or even from 0.7 wt.% to 3.3% wt.% of unreacted (i.e. free) isocyanate groups.
[0056] Ethylene Vinyl Acetate
[0057] The reactive polyurethane hot melt adhesive composition can include an ethylene vinyl acetate copolymer (EVA). In some embodiments, the reactive
polyurethane hot melt adhesive composition, based on its total weight, includes from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.% ethylene/vinyl acetate copolymer.
[0058] Optional Components
[0059] The reactive polyurethane hot melt adhesive composition may optionally further comprise a non-reactive polymer. As used herein,“non-reactive” means that the polymer does not participate in the chemical reaction during the preparation, application and curing processes of the reactive polyurethane hot melt adhesive composition. The addition of the non-reactive polymer can increase the strength of the bulk of the cured hot melt adhesive composition. In some embodiments, non-reactive polymers include ethylene/vinyl acetate (EVA), thermoplastic polyurethane (TPU), amorphous poly -alpha- olefin (APAO), thermoplastic elastomer (TPE) such as ethylenically thermoplastic elastomer (TPO or TPES) or thermoplastic amide (TP A). In some embodiments, the nonreactive polymer can be a thermoplastic polyurethane (TPU), ethylene/vinyl acetate copolymer (EVA), amorphous poly-a-olefin (APAO), or a combination thereof.
Particularly suitable examples of anon-reactive polymer include ethylene/vinyl acetate copolymer. Non-reactive polymers may be, for example, commercially available under the trade designations DESMOCOLL 540/1 (TPU) from Covestro Polymers (China) Co., Ltd., ESCORENE UL7710 (EVA) from Exxon Mobil Corporation (Irving, TX, USA), and VESTOPLAST 508 (APAO) from Evonik Industries.
[0060] A useful amount of the non-reactive polymer can be selected to help increase the cohesion of the reactive polyurethane hot melt adhesive composition after curing without significantly impairing the resistance to acid, resistance to alkali and fast tack- free property of the hot melt adhesive composition. The non-reactive polymer is generally used in an amount of not more than 40 wt.%, such as from 5 wt.% to 30 wt.%, from 10 wt.% to 25 wt.%, or even from 15 wt.% to 20 wt.%, based on the total weight of the reactive polyurethane hot melt adhesive composition.
[0061] The polyurethane hot melt adhesive composition may further include a curing catalyst for polyurethane, such as a catalyst suitable for one-component moisture curing, to shorten the curing time. Useful curing catalysts comprise ether and morpholine functional groups, examples of which include 2,2’-dimorpholinoethylether, di(2,6- dimethyl morpholinoethyl)ether, and 4,4'-(oxydi-2, 1 -ethanediyl)bis-morpholine. Suitable commercially available catalysts include, e.g., JEFFCAT DMDEE 4,4'-(oxydi-2,l- ethanediyl) bis-morpholine, which is available from Huntsman Corp. (Houston, Texas).
A variety of metal catalysts are suitable too, which include, e.g., catalysts based on tin (e.g. dibutyltin dilaurate and dibutyltin acetate), bismuth, zinc, and potassium
[0062] When the reactive polyurethane hot melt adhesive composition includes a curing catalyst for polyurethane, the curing catalyst may be present in an amount of from 0.01 wt.% to two wt.%, or even from 0.05 wt.% to one wt.%, based on the total weight of the polyurethane hot melt adhesive composition.
[0063] The reactive polyurethane hot melt adhesive composition may also include various other conventional additives typically comprised in reactive polyurethane hot melt adhesive compositions. These additives include, for example, tackifiers, plasticizers, waxes, stabilizers, antioxidants, fillers (talc, clay, silica, and treated variants thereof, carbon black and mica, microparticles including, for example, microspheres such as glass microspheres, polymer microspheres and combinations thereof), UV scavengers and absorbers, colorants (e.g. pigments and dyes), fluorescents, odor masking agents, biocides, corrosion inhibitors, adhesion promoters, surfactants, defoamers, flame retardants, and combinations thereof.
[0064] Useful tackifiers include, for example, aromatic, aliphatic and alicyclic hydrocarbon resins, mixed aromatic and aliphatic modified resins, aromatic modified hydrocarbon resins, and hydrogenated variants thereof; teipenes, modified terpenes, and hydrogenated variants thereof; rosin esters; and combinations thereof. [0065] Useful waxes include, for example, hydroxyl modified waxes, carbon monoxide modified waxes, hydroxyl stearamide waxes, fatty amide waxes, hydrocarbon waxes including, such as, high-density low-molecular-weight polyethylene waxes, paraffin and microcrystalline waxes, and combinations thereof.
[0066] Useful stabilizers include carbodiimide stabilizers, such as that available under the trade designation STABAXOL 7000 from Rhein Chemie, Germany.
[0067] Examples of useful commercially available antioxidants include those available under the trade desginations IRGANOX 565, 1010 and 1076 hindered phenolic antioxidants from Ciba-Geigy (Basel, Switzerland), and ANOX 20 hindered phenolic antioxidants from Great Lakes Chemicals (West Lafayette, IN, USA). These antioxidants can function as free radical scavengers and can be used alone or in combination with other antioxidants. The reactive polyurethane hot melt adhesive composition optionally includes not more than two wt.% of an antioxidant.
[0068] Examples of useful commercially available fillers include MISTRON VAPOR talc from Luzenac America, Inc. (Englewood, Colorado). The reactive polyurethane hot melt adhesive composition optionally includes from about three, four, five, or about seven, to about 12, 13, 15, or about 20 percent by weight of filler, or a weight percent between any pair of the foregoing values.
[0069] Process for Preparing
[0070] Disclosed herein is a process for preparation of a reactive polyurethane hot melt adhesive composition, including reacting diphenylmethane diisocyanate with the polymer polyol mixture (M) comprising at least one polyester diol a) and at least one poly ether diol b) as described above to give an isocyanate-terminated polyurethane prepolymer (P).
[0071] The process for obtaining an isocyanate-terminated polyurethane prepolymer (P) by reacting MDI with a polymer polyol mixture (M) may include any suitable process known to those of skill in the art. In general, the reaction mixture comprising MDI, at least one polyester diol a) and at least one poly ether diol b) is subjected to reaction under the condition of moisture removal at an elevated temperature, typically from 60°C to 160°C, preferably from 80°C to 120°C. The reaction time is usually from 1 to 2 hours. For example, the polymer polyol mixture (M) is firstly introduced into a reactor, heated to a reaction temperature, and dried under vacuum to remove moisture absorbed by the polyol from environment, followed by addition of MDI into the reactor. The reaction of the polymer polyol with MDI may be conducted under vacuum or in an inert atmosphere such as nitrogen.
[0072] In order to obtain an isocyanate-terminated polyurethane prepolymer (P), MDI typically can be used in an excessive amount by mole relative to the polymer polyol. In one embodiment, the reaction between MDI and polymer polyols is typically carried out at aNCO:OH molar ratio of from 1.4:1.0 to 4.0:1.0, from 1.5:1.0 to 3.5:1.0, or even
1.5:1.0 to 1.7:1.0.
[0073] Since the reactive polyurethane hot melt adhesive composition readily undergoes a curing reaction with moisture, it is advantageous to store it in a moisture- proof container to inhibit unwanted reactions after the composition is prepared.
[0074] The reactive polyurethane hot melt adhesive composition can be cured in a variety of mechanisms. The curing reaction occurs mainly between the compound having an available active hydrogen atom and the NCO group of the polyurethane prepolymer (P). Various reactive compounds having free active hydrogen are well known in the art, including water, hydrogen sulfide, polyols, ammonia, and other active compounds. The reactive polyurethane hot melt adhesive composition is preferably cured by moisture out of consideration for cost, environmental protection and operation simplicity.
Accordingly, in a preferred embodiment, the reactive polyurethane hot melt adhesive composition is a one-component moisture curable hot melt adhesive composition.
[0075] One-component moisture curable polyurethane adhesives are mainly cured by moisture in air, so suitable air humidity should be maintained, and a slow curing at room temperature (e.g. from about 22°C to about 25°C) is preferred. If air is dry, a small amount of water can be applied onto the surface coated with an adhesive to promote curing. If the adhesive is sandwiched between dry and hard adherends, and the adhesive layer is relatively thick so that moisture from interface and exteral cannot penetrate into the adhesive easily, then the curing will be incomplete. In this case, a small amount of water can be injected into the adhesive. [0076] According to another aspect, there is provided use of a reactive polyurethane hot melt adhesive composition according as a hot melt adhesive. The reactive polyurethane hot melt adhesive composition is useful in all of the commonly known applications of HMMC adhesives. Preferably, the reactive polyurethane hot melt adhesive composition is used as a hot melt adhesive, especially as a one-component moisture curable hot melt adhesive, in the fields of building materials, furiture and woodworking, electrical, automobile, bookbinding, shoemaking, filter assembly, and fabric processing.
[0077] The reactive polyurethane hot melt adhesive composition can be applied to a substrate using any suitable application method including, e.g., automatic fine line dispensing, jet dispensing, slot die coating, roll coating, gravure coating, transfer coating, patter coating, screen printing, spray coating, filament coating, extrusion, air knife, trailing blade, brushing, dipping, doctor blade, offset gravure coating, rotogravure coating, and combinations thereof. The moisture curable adhesive composition can be applied as a continuous or discontinuous coating, in single or multiple layers, and combinations thereof. The moisture curable adhesive composition can be applied at any suitable temperature including, e.g., from 60°C to 200°C, from 80°C to 175°C, or even from about 110°C to 150°C.
[0078] Optionally, the surface of the substrate on which the reactive polyurethane hot melt adhesive composition is applied is surface-treated to enhance adhesion using any suitable method for enhancing adhesion to the substrate surface including, e.g., corona treatments, chemical treatments (e.g., chemical etching), flame treatments, abrasion, and combinations thereof.
[0079] For one-component moisture curable adhesives, it is useful to closely control the rate of heating, or reaction of the NCO groups with water in the adhesive or substrate surface and air will be accelerated, the generated CO2 gas fails to diffuse in time, and the viscosity of the adhesive layer increases rapidly, and as a result, there can be bubbles remaining in the adhesive layer. EXAMPLES
[0080] The following non-limiting examples are included to further illustrate various embodiments of the instant disclosure and do not limit the scope of the instant disclosure. Test Methods
[0081] Determination of Surface Tension.
[0082] The surface tensions described herein were measured at 50°C according to the national standard GB/T22237-2008 (“Surface active agents. Determination of surface tension”).
[0083] Viscosity Test.
[0084] Viscosity was determined using a Brookfield Thermosel viscometer
(AMETEK Brookfield, of Middleboro, MA, USA) with a rotor No. 27. The viscosity was measured at 140°C.
[0085] Tack-Free Time Test.
[0086] The hot melt adhesive composition was melted at a temperature of 140°C and applied to the non-release surface of a PET release film at a thickness of 100 mm, and immediately timed. The surface of the adhesive layer was pressed with a pointing finger every 1 to 2 seconds. The time when the hand no longer felt tackiness is the tack-free time. The testing time is stopped at 60 seconds.
[0087] Test for Resistance to Acid and Alkali.
[0088] The prepared hot melt adhesive composition was coated on a release PET film and cured at room temperature and at ambient humidity (about 50%) for seven days to obtain a 100 mm adhesive film. Using a press vulcanizer, multiple layers of adhesive film were laminated together at 120°C, cut into a sheet sample of 15 mm x 20 mm x 2 mm, and weighed.
[0089] An aqueous solution of hydrochloric acid having a pH of 1 (one) and an aqueous solution of sodium hydroxide having a pH of 13 were placed in an oven and heated to 80°C. The sheet samples were then placed in each of the two solutions and soaked. After soaking for the given number of days, the samples were taken out, rinsed, dried, and weighed. The weight loss percentage of each sample was calculated. Raw Materials
[0090] DP 400 is a polypropylene glycol, Mw of 400, surface tension: 30.324 mN/m, purchased from Kukdo Chemical Co., Ltd.
[0091] POLY THF 1000 is a polytetrahydrofuran diol, Mw of 1,000, purchased from
BASF AG.
[0092] PTG 3000 is a polytetrahydrofuran diol, Mw of 3,000, surface tension:
27.951°, purchased from Taiwan Dalian Chemical Industry Company.
[0093] SOVERMOL 908 is a hydrogenated dimerized C18 unsaturated fatly acid dimethyl ester diol, Mw of 543.7, surface tension: 32.853 mN/m, purchased from BASF
AG.
[0094] PS 2002 is a polyester diol obtained by reacting phthalic anhydride with diethylene glycol, Mw of 575, surface tension: 41.631 mN/m, purchased from Stepan Chemical LLC.
[0095] KRASOL LBH-P 5000 is a polybutadiene diol, Mw of 5,000, surface tension: 26.581 mN/m, purchased from Cray Valley.
[0096] DYNACOLL 7380 is a polyester diol, Mw of 3,500, purchased from
Evonik Industries.
[0097] MISTRON VAPOR is a talc, purchased from Luzenac America, Inc.
(Englewood, Colorado).
[0098] EVERNOX 10GF is an antioxidant, purchased from Everspring Company.
[0099] ESCRONE UL7710 in an EVA, VA of 26.7%, MI of 420 g/10min at 190°C, purchased from Exxon Mobil Corporation.
[0100] VeESTOPLAST 508 is an amorphous poly-a-olefin, purchased from
Evonik Industries.
[0101] DESMODUR CD-C is a carbodiimide isocyanate, purchased from Covestro Polymers (China) Co., Ltd.
[0102] DMDEE is a 4,4’-(oxydi-2, 1 -ethanediyl) bismorpholine, purchased from Huntsman Corp. (Houston, Texas). Preparation of Hot Melt Adhesive Composition Samples
[0103] All components except MDI and the curing catalyst DMDEE of each composition formulations as shown in Table 1 were charged into a reactor in the respective amounts shown in Table 1, heated to a temperature of from 130°C to 140°C and evacuated so as to remove moisture. Then the temperature was decreased to 100°C and MDI was added and stirred for one hour while maintaining the temperature. After that, the curing catalyst DMDEE was added in an amount shown in Table 1, and the obtained mixture was stirred for further 20 minutes and cooled to room temperature to obtain the respective polyurethane melt adhesive composition sample.
[0104] The formulas and experimental results of all the hot melt adhesive composition samples except Comparative Example C-1 are summarized in Table 1. Comparative Example C-1 is shown in Table 2.
Figure imgf000023_0001
[0105] HL9810 is a moisture curable polyurethane hot melt adhesive, available from H.B. Fuller of St. Paul, MN USA. This hot melt adhesive was designated as Comparative Example C-l. This hot melt adhesive was tested by the above described testing methods with respect to its various properties. It is noted that the viscosity testing for HL9810 was conducted at a temperature of 163°C instead of 140°C. The results are summarized in the Table 2 below.
Figure imgf000024_0001
[0106] As shown in Table 1 and Table 2, comparison of Comparative Example C-l with Illustrative Examples 1 to 8 demonstrates that hot melt adhesive compositions according to the present disclosure are better than HL9810 in terms of resistance to acid and resistance to alkali. Moreover, the hot melt adhesive compositions according to the present disclosure dried at a faster rate than HL9810.
[0107] Comparison of Comparative Examples C-3 and C-4 with Illustrative
Examples 1 to 8 shows that the use of MDI as polyisocyanate helped improve resistance to acid and alkali, particularly, improved alkali resistance, compared with the use of carbodiimide diisocyanate.
[0108] Comparison of Comparative Examples C-2, C-6, C-7 and C-8 with Illustrative Examples 1 to 8 shows that when polyurethane prepolymer was prepared from other polyester diols and poly butadiene diol, instead of from polyether diol (b) according to the present disclosure, the resulting hot melt adhesive compositions are either not as resistant to acid and alkali, particularly, less resistant to alkali, or are less favorable in achieving tack-free, leaving a tacky surface after 60 seconds.
[0109] Comparison of Comparative Examples C-5 with Illustrative Examples 1 to 8 demonstrates that when polyether diol (b) used according to the present disclosure is used in a small amount and no EVA is used, the resulting hot melt adhesive compositions have less favorable tack-free time, thus having a tacky surface after 60 seconds, and the resistance to alkali is not as good as the hot melt adhesive composition according to the present disclosure.
[0110] In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only examples of the invention and should not be taken as limiting the scope of the invention. Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.

Claims

CLAIMS What is claimed is:
1. A reactive hot melt adhesive composition comprising:
an isocyanate-terminated polyurethane prepolymer derived from diphenylmethane diisocyanate and a polymer polyol mixture having at least one polyester diol and at least one poly ether diol,
the polyester diol being a reaction product of one or more C4-C12 saturated
aliphatic diols with one or more C10-C18 saturated aliphatic dicarboxylic acids, a reaction product of one or more C10-C18 saturated aliphatic diols with one or more C4-C12 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products; and
the polyether diol, being at least one of polypropylene glycol having a molecular weight of from 200 to 2,000 and polytetrahydrofuran diol having a molecular weight of from 200 to 4,000 and a surface tension of less than 42 mN/m;
the reactive hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt% after being placed in at least one of an aqueous solution having a pH of 1 (one) and an aqueous solution having a pH of 13.
2. The reactive hot melt adhesive composition of claim 1, wherein the reactive hot melt adhesive composition exhibits a weight loss of no greater than 2.0 wt.%, after being placed in either of an aqueous solution having a pH of 1 (one) and an aqueous solution having a pH of 13.
3. The reactive hot melt adhesive composition of claim 1, exhibiting one or both of the following:
the weight ratio of the at least one polyether diol to the at least one polyester diol is greater than 1.0:3.0; and the reactive polyurethane hot melt adhesive composition further includes an ethylene/vinyl acetate copolymer and the weight ratio of the at least one polyether diol b) to the at least one polyester diol greater than or equal to
1.0:4.0.
4. The reactive hot melt adhesive composition according to any one of claims 1 to 3, wherein the composition includes from 10 wt.% to 25 wt.% weight ethylene/vinyl acetate copolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
5. The reactive hot melt adhesive composition according to any one of claims 1 to 4, wherein the polyetiier diol includes polypropylene glycol and polytetrahydrofuran diol at a ratio from 2: 1 to 1 :2.
6. The composition according to any of one claims 1 to 5, wherein the
diphenylmethane diisocyanate includes greater than or equal to 70 wt.% 4,4’- diphenylmethane diisocyanate based on the total weight of the diphenylmethane diisocyanate.
7. The composition according to any of one claims 1 to 6, wherein the polyether diol is polytetrahydrofuran diol having a surface tension of no greater than 33 mN/m
8. The composition according to any one of claims 1 to 7, wherein the polyester diol is a reaction product of one or more C6-C8 saturated aliphatic diols with one or more C12- C16 saturated aliphatic dicarboxylic acids, a reaction product of one or more C12-C16 saturated aliphatic diols with one or more C6-C8 saturated aliphatic dicarboxylic acids, or a combination of the foregoing reaction products.
9. The composition according to any one of claims 1 to 8, wherein the polymer polyol mixture includes at least one of a hydroxyl-terminated polybutadiene diol having a molecular weight of from 2,000 to 10,000, a partially hydrogenated product in an amount of from five wt.% to 18 wt.% based on the total weight of the reactive hot melt adhesive composition, and combinations thereof.
10. The composition according to any one of claims 1 to 9, wherein the molar ratio of the isocyanate group contained in MDI to the hydroxyl group contained in the polymer polyols is from 1.4:1.0 to 4.0:1.0.
11. The composition according to any one of claims 1 to 10, wherein the isocyanate- terminated polyurethane prepolymer includes from 0.4 wt.% to 4.0 wt.% unreacted isocyanate groups, based on the total weight of the prepolymer.
12. The composition according to one any of claims 1 to 11, where the composition includes from 20 wt.% to 45 wt.% by weight polyester diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
13. The composition according to any one of claims 1 to 12, where the composition includes from eight wt.% to 35 wt.% polyether diol in the form of building units incorporated into the polyurethane prepolymer, based on the total weight of the reactive polyurethane hot melt adhesive composition.
14. The composition according to any one of claims 1 to 13, where the composition comprises from three wt.% to 20 wt% filler, based on the total weight of the reactive polyurethane hot melt adhesive composition.
15. The composition according to any one of claims 1 to 14 being a one-component moisture curable polyurethane hot melt adhesive composition.
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