CN117794971A

CN117794971A - Moisture curable polyurethane hot melt adhesive with heat and moisture resistance

Info

Publication number: CN117794971A
Application number: CN202180101151.4A
Authority: CN
Inventors: 童鹏; E·延杜比; 龚鸿亮; 张卫明
Original assignee: Sika Technology AG
Current assignee: Sika Technology AG
Priority date: 2021-09-09
Filing date: 2021-09-09
Publication date: 2024-03-29
Also published as: WO2023035194A1

Abstract

The invention relates to a moisture-curable hot-melt adhesive composition comprising at least one isocyanate-functional polyurethane polymer P, which is obtained by reacting: a) Polyol composition comprising a 1) at least one polyester polyol PO1 which is solid at 25 ℃, a 2) at least one first polyester polyol PO2 which is liquid at 25 ℃, a 3) optionally at least one second polyester polyol PO3 which is liquid at 25 ℃, which is different from the at least one first polyester polyol PO2 which is liquid at 25 ℃, and a 4) at least one polycarbonate diol PO4 and/or at least one hydroxyl-terminated polybutadiene PO5, and b) at least one polyisocyanate PI. The invention also relates to the use of the adhesive composition for bonding substrates in the production of white goods, motor vehicles and electronic devices.

Description

Moisture curable polyurethane hot melt adhesive with heat and moisture resistance

Technical Field

The present invention relates to reactive polyurethane hot melt adhesives with improved heat and moisture resistance and the use of the adhesives for bonding substrates in the production of white goods, motor vehicles and electronic devices.

Background

Hot melt adhesives are solvent free adhesives that are solid at room temperature and are applied to the substrates to be bonded in the form of a melt. After cooling, the adhesive solidifies and forms an adhesive bond with the substrate by physically occurring bonds. Conventional hot melt adhesives are non-reactive adhesives which soften again when heated and are therefore unsuitable for use at elevated temperatures. Reactive hot melt adhesives contain polymers having reactive groups that enable the adhesive to be chemically cured, for example by cross-linking of polymer chains. Because of the chemically cured polymer matrix, reactive hot melt adhesives do not soften when heated, and therefore these adhesives are also suitable for use at elevated temperatures. Chemical curing of the polymer may be initiated, for example, by heating or exposing the adhesive composition to water (e.g., atmospheric moisture). Moisture-curable hot melt adhesives generally contain polymers functionalized with isocyanate or silane groups that are capable of crosslinking the polymer chains upon contact with atmospheric moisture.

Moisture-curing polyurethane hotmelt adhesives (PUR-RHM) consist essentially of isocyanate-functional polyurethane polymers obtained by reacting suitable polyols, typically polyester and/or polyether polyols, with polyisocyanates, wherein the reaction is carried out at a molar excess of isocyanate (NCO) groups Over Hydroxyl (OH) groups. The adhesive composition cures by reaction of residual isocyanate groups with water, which results in various chain extension and/or crosslinking reactions of the polymer. The fully cured polyurethane hot melt adhesive contains urea and/or urethane linkages and also ester and/or ether linkages depending on the starting materials used to provide the isocyanate functional polymer. The crosslinked hot melt adhesive does not remelt when subjected to heat. However, the ester linkages will undergo hydrolysis reactions under conditions of high temperature and humidity, for example, 85 ℃ and 85% relative humidity, to produce the corresponding acids and alcohols. The acid formed in the hydrolysis reaction will further accelerate the decomposition of the ester bond. It has been found that conventional polyurethane hot melt adhesives begin to decompose after 200 hours of artificial aging testing at 85 ℃ and 85% relative humidity.

Accordingly, there is a need for a new moisture curable polyurethane hot melt adhesive having improved heat and moisture resistance. Such adhesives are particularly useful for bonding substrates in the production of white goods, motor vehicles and electronic devices.

Summary of The Invention

It is an object of the present invention to provide an adhesive composition which overcomes or at least alleviates the disadvantages of the prior art moisture curable polyurethane hot melt adhesives as described above.

In particular, it is an object of the present invention to provide a moisture curable polyurethane hot melt adhesive composition having improved heat and moisture resistance. The cured adhesive composition should preferably also have excellent mechanical properties, in particular high tensile strength and elongation at break, as well as high adhesive bond strength as measured by lap shear strength.

It has surprisingly been found that these objects are achieved by the features of claim 1.

The core of the present invention is a novel moisture curable polyurethane hot melt adhesive composition comprising at least one isocyanate functional polyurethane polymer obtained by reacting a polyol composition with one or more polyisocyanates, wherein the polyol composition comprises a solid polyester polyol, a liquid polyester polyol and a polycarbonate diol and/or a hydroxyl terminated polybutadiene.

It has surprisingly been found that the addition of polycarbonate diol and/or hydroxyl-terminated polybutadiene to a polyol composition for obtaining at least one isocyanate-functional polyurethane polymer not only improves the thermal and moisture stability of the cured adhesive, but also has a positive effect on mechanical properties and adhesive bond strength.

Further subject matter of the invention is given in the further independent claims. Preferred aspects of the invention are given in the dependent claims.

Detailed Description

The subject of the present invention is an adhesive composition comprising at least one isocyanate-functional polyurethane polymer P obtained by reacting:

a) A polyol composition comprising

a1 At least one polyester polyol PO1 which is solid at 25 ℃,

a2 At least one first polyester polyol PO2 which is liquid at 25 ℃,

a3 Optionally at least one second polyester polyol PO3 which is liquid at 25 ℃ and which is different from the at least one first polyester polyol PO2 which is liquid at 25 ℃, and

a4 At least one polycarbonate diol PO4 and/or at least one hydroxy-terminated polybutadiene PO5, and

b) At least one of the polyisocyanates, PI,

wherein the proportion of component a 4) in the polyol composition a) is from 5 to 50% by weight, preferably from 10 to 40% by weight, more preferably from 15 to 30% by weight, based on the total weight of the polyol composition a).

The prefix "poly" in a substance name such as "polyol" or "polyisocyanate" refers to a substance that formally contains two or more functional groups per molecule that appear in its name. For example, the polyol is a compound having two or more hydroxyl groups, and the polyisocyanate is a compound having two or more isocyanate groups.

The term "polymer" refers to a collection of chemically homogeneous macromolecules produced by polymerization (polyaddition, polycondensation), wherein the macromolecules differ in their degree of polymerization, molecular weight and chain length. The term also includes derivatives of the collection of macromolecules resulting from the polymerization reaction, i.e. compounds obtained by reactions such as addition or substitution of functional groups in the predetermined macromolecules, which may be chemically uniform or chemically non-uniform.

The term "functionalized polymer" refers to a polymer that has been chemically modified to contain functional groups in the polymer backbone. In contrast, the term "nonfunctionalized polymer" refers to a polymer that has not been chemically modified to contain functional groups such as epoxy, silane, sulfonate, amide, or anhydride groups on the polymer backbone.

The term "polyurethane polymer" refers to polymers prepared by the so-called diisocyanate polyaddition process. They also include those polymers which contain little or no urethane groups. Examples of polyurethane polymers are polyether-polyurethanes, polyester-polyurethanes, polyether-polyureas, polyester-polyureas, polyisocyanurates and polycarbodiimides.

The term "isocyanate-functional polyurethane polymer" refers to a polyurethane polymer that contains one or more unreacted isocyanate groups. Polyurethane prepolymers can be obtained by reacting an excess of polyisocyanate with a polyol and are themselves polyisocyanates. The terms "isocyanate functional polyurethane polymer" and "polyurethane prepolymer" are used interchangeably.

The term "molecular weight" refers to the molar mass (g/mol) of a molecule or a portion of a molecule (also referred to as a "portion"). The term "average molecular weight" refers to the number average molecular weight (M) _n ) Or weight average molecular weight (M _w ). Molecular weight can be determined by Gel Permeation Chromatography (GPC) using polystyrene as a standard, styrene-divinylbenzene gels with porosities of 100, 1000 and 10000 angstroms as columns, and depending on the molecule taken at 35 ℃Tetrahydrofuran was used as solvent or 1,2, 4-trichlorobenzene was used as solvent at 160 ℃.

The term "average OH functionality" refers to the average number of hydroxyl (OH) groups per molecule. The average OH functionality of the compounds may be based on the number average molecular weight (M _n ) And hydroxyl value calculation. The hydroxyl number of a compound can be determined by using the method defined in DIN 53 240-2 standard.

The term "open time" refers to the length of time that an adhesive applied to a substrate surface is still capable of forming an adhesive bond after contact with another substrate.

The "amount of the at least one component X" in the composition, e.g. "amount of the at least one polyol" herein refers to the sum of the individual amounts of all polyols contained in the composition. For example, in the case where the at least one polyol is a polyester polyol and the composition comprises 20% by weight of the at least one polyol, the sum of the amounts of all polyester polyols contained in the composition is equal to 20% by weight.

The term "room temperature" refers to a temperature of about 23 ℃.

The adhesive composition comprises at least one isocyanate functional polyurethane polymer P obtained by reacting a polyol composition with at least one polyisocyanate PI. "polyol composition" is understood to include all polyols used to obtain at least one isocyanate-functional polyurethane polymer P.

The adhesive composition is preferably a hot melt adhesive, more preferably a one-component hot melt adhesive. In the context of the present invention, the term "one-component composition" refers to a composition in which all the ingredients of the composition are stored in the same container or compartment in the form of a mixture.

The polyol composition comprises at least one polyester polyol PO1 which is solid at 25 ℃, at least one first polyester polyol PO2 which is liquid at 25 ℃ and optionally at least one second polyester polyol PO3 which is liquid at 25 ℃ different from the at least one first polyester polyol PO2 which is liquid at 25 ℃.

Suitable polyester polyols for use as the at least one polyester polyol PO1, PO2 and PO3 include crystalline, partially crystalline, amorphous and liquid polyester polyols. These can be obtained by reacting di-and tri-alcohols, preferably diols, such as 1, 2-ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, dipropylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 10-decanediol, 1, 12-dodecanediol, dimerized fatty alcohols, neopentyl glycol, glycerol, 1-trimethylol propane, or mixtures of the above alcohols, preferably dicarboxylic acids or their anhydrides or esters, such as succinic acid, glutaric acid, 3-dimethylglutaric acid, adipic acid, suberic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimerized fatty acids, isophthalic acid, terephthalic acid and hexahydrophthalic acid, or mixtures of the above acids. Polyester polyols made from lactones such as epsilon-caprolactone, also known as polycaprolactone, are also suitable.

Preferred polyester polyols include those obtained by reacting adipic acid, sebacic acid or dodecanedicarboxylic acid as dicarboxylic acid with hexanediol or neopentyl glycol as diol. Other examples of suitable polyester polyols include polyester polyols of oleochemical origin. Polyester polyols of this type can be prepared, for example, by complete ring opening of epoxidized triglycerides of fatty mixtures comprising at least partially ethylenically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms, and subsequent partial transesterification of triglycerin derivatives to give alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical. Particularly suitable crystalline and partially crystalline polyester polyols include adipic acid/hexanediol polyesters and dodecanedicarboxylic acid/hexanediol polyesters.

According to one or more embodiments, at least one polyester polyol PO1 which is solid at 25℃has a number average molecular weight (M _n ) 500-10000g/mol, preferably 1000-5000g/mol, and/or a hydroxyl value of 10-75mg KOH/g, preferably 15-50mg KOH/g, determined according to ISO 4629-2 standard, and/or a melting point (T) _m ) Is at 30-100deg.C, preferably 40-70deg.C, more preferably 45-65deg.C。

Suitable partly crystalline and crystalline polyester polyols which are solid at 25℃may be mentioned, for example, under the trade name Dynacol The 7300 series (from Evonik Industries) is commercially available.

Preferably, at least one polyester polyol PO1 which is solid at 25℃comprises at least 2.5% by weight, preferably at least 5% by weight, more preferably at least 10% by weight of the total weight of the polyol composition a).

According to one or more embodiments, the at least one polyester polyol PO1, which is solid at 25℃comprises from 10 to 50% by weight, preferably from 15 to 40% by weight, more preferably from 20 to 35% by weight, based on the total weight of the polyol composition a).

According to one or more embodiments, the at least one first polyester polyol PO2 which is liquid at 25℃has a number average molecular weight (M _n ) 500-10000g/mol, preferably 2500-7500g/mol, and/or a hydroxyl number of 5-50mg KOH/g, preferably 10-35mg KOH/g, determined according to ISO 4629-2 standard, and/or a glass transition temperature of-5℃or below-5℃preferably-15℃or below-15℃more preferably-35℃or below-35℃determined by DSC.

Suitable polyester polyols which are liquid at 25℃may be mentioned, for example, under the trade name Dynacol7200 series (from Evonik Industries) are commercially available.

According to one or more embodiments, the polyol composition a) comprises, in addition to at least one first polyester polyol PO2 which is liquid at 25 ℃, at least one second polyester polyol PO3 which is liquid at 25 ℃ which is different from at least one first polyester polyol PO2 which is liquid at 25 ℃.

According to one or more embodiments, the at least one second polyester polyol PO3 which is liquid at 25℃has a number average molecular weight (M _n ) From 500 to 5000g/mol, preferably from 1000 to 3500g/mol and/or hydroxyl groups measured according to ISO 4629-2 standardThe value is 25 to 150mg KOH/g, preferably 35 to 100mg KOH/g.

According to one or more embodiments, at least one second polyester polyol PO3, which is liquid at 25 ℃, is an aromatic polyester polyol, preferably a phthalic anhydride diethylene glycol polyester polyol.

According to one or more embodiments, the at least one polyester polyol PO3 which is liquid at 25℃comprises from 10 to 50% by weight, preferably from 15 to 40% by weight, more preferably from 20 to 35% by weight, based on the total weight of the polyol composition a).

The polyol composition a) further comprises at least one polycarbonate diol PO4 and/or at least one hydroxyl-terminated polybutadiene PO5.

Suitable polycarbonate diols may be obtained by reacting, for example, the diols or triols described above as suitable for the synthesis of polyester polyols with dialkyl carbonates, diaryl carbonates or phosgene.

Suitable polycarbonate diols are commercially available under the following trade names, for example:

trade nameFor example->UM、/>UH、/>PH、UHC、/>UC and->UT series (all from UBE Industries ltd.);

Trade nameC112 and Oxymer M->(all from Perstorp);

trade nameFor example->C2100、/>C2200、/>XP2613、/>3100XP、/>3200XP、/>XP 2716、/>C1100 and->C1200 (all from Covestro);

trade nameFor example

T5652、/>T5651、/>T5650J、/>G4672、/>T4671、/>T5652、/>T5651、/>T5650J、/>T4692、/>T4691、/>T5650E、/>G3452; and->g3450J (all from Asahi Kasei Chemicals); and

trade name102、/>106 and->107 (all from Caffaro Industrie SpA).

According to one or more embodiments, the number average molecular weight (M of the at least one polycarbonate diol PO4 _n ) 300-10000g/mol, preferably 500-5000g/mol and/or a hydroxyl number of 25-200mg KOH/g, preferably 35-100mg KOH/g, measured according to the ISO 4629-2 standard.

According to one or more preferred embodiments, the at least one polycarbonate diol PO4 is prepared by reacting a first diol selected from the group consisting of 1, 6-hexanediol and 2-methyl-1, 3-propanediol with a second C ₃ -C ₂₀ Transesterification of diols with carbonates.

According to one or more embodiments, the first glycol is 1, 6-hexanediol, and the second C ₃ -C ₂₀ The diol is selected from the group consisting of 1, 3-propanediol, 2-methyl-1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, neopentyl glycol and trimethyl-1, 6-hexanediol.

According to one or more further embodiments, the first glycol is 2-methyl-1, 3-propanediol, and the second C ₃ -C ₂₀ The diol is selected from the group consisting of: 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, neopentyl glycol and trimethyl-1, 6-hexanediol.

According to one or more preferred embodiments, the first glycol is 1, 6-hexanediol, and the second C ₃ -C ₂₀ The diol is selected from 1, 4-butanediol and neopentyl glycol.

According to one or more embodiments, the proportion of the first diol is 20 to 80 mole%, relative to the total amount of diols used to prepare the at least one polycarbonate diol PO4, the second C ₃ -C ₂₀ The proportion of diol is 20-80mol%.

The reaction between the first and second diols and the carbonate may optionally be carried out in the presence of a small amount of polyol. Suitable polyols for this purpose include, for example, trimethylolethane, trimethylolpropane, hexanetriol and pentaerythritol. Preferably, the proportion of polyol (if used) is from 0.1 to 5mol%, more preferably from 0.1 to 2mol% relative to the total amount of diol used to prepare the at least one polycarbonate diol PO 4.

Suitable carbonates include alkylene carbonates, dialkyl carbonates and diaryl carbonates.

According to one or more embodiments, the carbonate is selected from ethylene carbonate, trimethylene carbonate, 1, 2-propylene carbonate, 5-methyl-1, 3-dioxan-2-one, 1, 2-butylene carbonate, 1, 3-butylene carbonate, 1, 2-pentylene carbonate, dimethyl carbonate, diethyl carbonate, di-n-butyl carbonate and diphenyl carbonate, preferably selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate and di-n-butyl carbonate.

According to one or more preferred embodiments, the carbonate is selected from dimethyl carbonate and diethyl carbonate.

Preferably, at least one polycarbonate diol PO4 is a polycarbonate diol that is liquid at 25 ℃.

The polyol composition a) may comprise at least one hydroxyl-terminated polybutadiene PO5 instead of or in addition to at least one polycarbonate diol PO 4.

The term "polybutadiene" refers to an oligomer or polymer of butadiene. The hydroxyl-terminated polybutadiene is a polybutadiene having primary hydroxyl groups. Suitable hydroxy-terminated polybutadiene can be obtained by polymerization of 1, 3-butadiene and allyl alcohol or by oxidation of suitable polybutadiene.

Suitable hydroxy-terminated polybutadiene can be obtained, for example, under the trade name PolyAnd->Commercially available (from Cray Valley), such as +.>LBH-P 2000、/>LBH-P 3000、/>HLBH P 2000、HLBH P2000 CF and Poly->R45V; under the trade name->(from Evonik Industries), e.g.)>HT; trade name->(from Emerald Materials), e.g.)>2800X95 HTB.

According to one or more embodiments, the at least one hydroxyl-terminated polybutadiene PO5 has a number average molecular weight (M _n ) 500-10000g/mol, preferably 1000-5000g/mol, and/or an average hydroxyl functionality of 1.3-2.9, preferably 1.5-2.2, and/or a glass transition temperature of-5 ℃ or below-5 ℃, preferably-15 ℃ or below-15 ℃ as determined by DSC.

According to one or more preferred embodiments, the at least one hydroxy-terminated polybutadiene PO5 is a hydroxy-terminated polybutadiene that is liquid at 25 ℃, preferably a hydrogenated hydroxy-terminated polybutadiene that is liquid at 25 ℃.

According to one or more embodiments, the total amount of polyols in the polyol composition a) which are liquid at 25 ℃ is from 35 to 95 wt%, preferably from 45 to 90 wt%, more preferably from 50 to 85 wt%, based on the total weight of the polyol composition a).

Suitable polyisocyanates for use as the at least one polyisocyanate PI include, for example, aliphatic, cycloaliphatic and aromatic polyisocyanates, in particular diisocyanates, in particular monomeric diisocyanates. Oligomeric and polymeric products of non-monomeric diisocyanates, such as monomeric diisocyanates, for example adducts of monomeric diisocyanates, are also suitable, but monomeric diisocyanates are preferably used.

The term "monomer" refers to a molecule having at least one polymerizable group. Monomeric di-or polyisocyanates are particularly free of urethane groups. In the context of the present invention, the oligomer or polymer product of a diisocyanate monomer, such as an adduct of a monomeric diisocyanate, is not a monomeric diisocyanate.

When the isocyanate groups are directly bonded to aliphatic, cycloaliphatic or arylaliphatic moieties, the isocyanate is referred to as "aliphatic". The corresponding functional groups are therefore referred to as aliphatic isocyanate groups. When the isocyanate groups are directly bonded to an aromatic moiety, the isocyanate is referred to as "aromatic". The corresponding functional groups are therefore referred to as aromatic isocyanate groups.

According to one or more embodiments, at least one polyisocyanate PI is a diisocyanate, preferably a monomeric diisocyanate, more preferably a number average molecular weight (M _n ) Not more than 1000g/mol, preferably not more than 500g/mol, more preferably not more than 400g/mol of monomeric diisocyanate.

Examples of suitable monomeric diisocyanates include, for example, 1, 6-Hexamethylene Diisocyanate (HDI), 2-methylpentamethylene-1, 5-diisocyanate, 2, 4-and 2, 4-trimethyl-1, 6-hexamethylene diisocyanate (TMDI) and mixtures of these isomers, 1, 10-decamethylene diisocyanate, 1, 12-dodecamethylene diisocyanate, lysine ester diisocyanate, cyclohexane-1, 3-diisocyanate and cyclohexane-1, 4-diisocyanate and mixtures of these isomers, 1-methyl-2, 4-and-2, 6-diisocyanatocyclohexane and mixtures of these isomers (HTDI or H6 TDI), 1-isocyanato-3, 5-trimethyl-5-isocyanatomethylcyclohexane (=isophorone diisocyanate or IPDI), perhydro-2, 4 '-and-4, 4' -diphenylmethane diisocyanate (HMDI or H12 MDI) and mixtures of these isomers, 1-methyl-2, 4-and-diisocyanato-1, 4-diisocyanato-and mixtures of these isomers, XD-1-2, 4-diisocyanato-and-m-xylylene (TMDI) and mixtures of these isomers, XD-1-methyl-2, 4-and-diisocyanato-1, 6-diisocyanato-and-m-xylylene (TMDI) and mixtures of these isomers, XD-1-4-and-diisocyanato-1, 3-diisocyanato-m-1-4-diisocyanato-1-3-diisocyanato m-p-and mixtures thereof Bis (1-isocyanato-1-methylethyl) naphthalene, 2, 4-and 2, 6-toluene diisocyanate and mixtures of these isomers (TDI), 4' -, 2,4' -and 2,2' -diphenylmethane diisocyanate and mixtures of these isomers (MDI), 1, 3-and 1, 4-phenylene diisocyanate and mixtures of these isomers, 2,3,5, 6-tetramethyl-1, 4-diisocyanatobenzene, naphthalene-1, 5-diisocyanate (NDI), 3' -dimethyl-4, 4' -diisocyanatobiphenyl (TODI), and dianisidine diisocyanate (DADI).

According to one or more embodiments, the monomeric diisocyanate is selected from the group consisting of 4,4' -, 2,4' -and 2,2' -diphenylmethane diisocyanate and mixtures of these isomers (MDI), 2, 4-and 2, 6-toluene diisocyanate and mixtures of these isomers (TDI), 1, 6-Hexamethylene Diisocyanate (HDI) and 1-isocyanato-3, 5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). Furthermore, it is known to the person skilled in the art that technical grade products of diisocyanates may often contain isomer mixtures or other isomers as impurities. According to one or more embodiments, the monomeric diisocyanate is selected from MDI and IPDI. Suitable monomeric diisocyanates are known, for example, under the trade nameCommercially available (from BASF) and Desmodur (from Covestro).

According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer P has an average isocyanate functionality of not more than 3.5, preferably not more than 3.0. The term "average NCO functionality" in this disclosure refers to the average number of isocyanate (NCO) groups per molecule. The average NCO functionality of a compound can be determined by using the method defined in ISO 14896-2006 Standard method A.

Preferably, the at least one isocyanate functional polyurethane polymer P comprises at least 50 wt%, more preferably at least 65 wt%, even more preferably at least 75 wt%, still more preferably at least 85 wt% of the total weight of the adhesive composition.

According to one or more embodiments, the at least one isocyanate functional polyurethane polymer P comprises 50 to 95 wt%, preferably 60 to 90 wt%, more preferably 65 to 85 wt%, even more preferably 70 to 85 wt%, of the total weight of the adhesive composition.

According to one or more embodiments, the adhesive composition further comprises at least one poly (meth) acrylate AC. In the context of the present invention, the term "(meth) acrylate" means methacrylate or acrylate.

The term "poly (meth) acrylate" refers to homopolymers, copolymers and higher interpolymers of (meth) acrylate monomers with one or more additional (meth) acrylate monomers and/or with one or more additional monomers.

Preferably, the (meth) acrylate monomers do not contain other functional groups such as hydroxyl groups and/or carboxyl groups. However, the (meth) acrylate monomer containing other functional groups, particularly hydroxyl groups, may be used in combination with the (meth) acrylate monomer containing no other functional groups.

Suitable (meth) acrylate monomers include, for example, alkyl (meth) acrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and branched isomers thereof, for example isobutyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate and cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate or 3, 5-dimethyladamantanyl acrylate.

Suitable (meth) acrylate monomers having other functional groups include, for example, hydroxyl-containing (meth) acrylate monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate.

Other suitable comonomers for synthesizing the at least one poly (meth) acrylate AC include vinyl compounds such as ethylenically unsaturated hydrocarbons having functional groups, vinyl esters, vinyl halides, vinylidene halides, nitriles of ethylenically unsaturated hydrocarbons, phosphate esters and zinc salts of (meth) acrylic acid. Examples of other suitable comonomers include, for example, maleic anhydride, styrene compounds, acrylonitrile, vinyl acetate, vinyl propionate, vinyl chloride, (meth) acrylic acid, β -acryloxypropionic acid, vinyl acetic acid, fumaric acid, crotonic acid, aconitic acid, trichloroacrylic acid, itaconic acid and maleic acid and amides thereof.

Particularly suitable poly (meth) acrylates include, for example, homopolymers and copolymers obtained by free radical polymerization of one or more (meth) acrylate monomers optionally in combination with one or more hydroxy-functional (meth) acrylate monomers and/or at least one additional comonomer.

Suitable poly (meth) acrylates can be obtained, for example, under the trade nameAC is commercially available, such asAC 1420、/>AC 1520、/>AC 1631、/>AC 1620、AC 1630、/>AC 1632、/>AC 1750、/>AC 1920、AC 4830 and->AC 2740 (all from Evonik Industries).

According to one or more embodiments, the weight average molecular weight (M _w ) 15000-100000g/mol, preferably 25000-65000g/mol, and/or a glass transition temperature of 0 ℃ or higher, preferably 35 ℃ or higher, as determined according to the ISO 11357-1 standard, and/or a softening point of 75-200 ℃, preferably 125-185 ℃ as determined by the ring and ball method, as determined according to the ISO 4625 standard, and/or an acid value of not more than 25mg KOH/g, preferably not more than 10mg KOH/g, as determined according to the EN ISO 2114 standard.

According to one or more embodiments, the at least one poly (meth) acrylate AC comprises 0.5 to 35 wt%, preferably 1.5 to 25 wt%, more preferably 2.5 to 15 wt%, of the total weight of the adhesive composition.

According to one or more embodiments, the adhesive composition further comprises at least one catalyst CA that catalyzes the reaction of isocyanate groups with water.

Examples of suitable catalysts include metal-based catalysts such as dialkyltin complexes, in particular dibutyltin (IV) or dioctyltin (IV) carboxylates or acetylacetonates, such as dibutyltin dilaurate (DBTDL), dibutyltin diacetylacetonate, dioctyltin dilaurate (DOTDL), further bismuth (III) complexes such as bismuth octoate or bismuth neodecanoate, zinc (II) complexes such as zinc octoate or zinc neodecanoate, and zirconium (IV) complexes such as zirconium octoate or zirconium neodecanoate.

Other examples of suitable catalysts include amine group containing compounds such as dimorpholinodialkylethers and/or dimorpholino substituted polyalkylene glycols such as 2,2' -dimorpholinodiethyl ether and 1, 4-diazabicyclo [2.2.2] -octane. Combinations of two or more catalysts may also be used, with preferred combinations including combinations of one or more metal catalysts with one or more morpholinamine compounds.

According to one or more embodiments, the at least one catalyst CA comprises from 0.005 to 2.00 weight percent, preferably from 0.05 to 1.00 weight percent, based on the total weight of the adhesive composition.

The adhesive composition may further comprise auxiliary substances and additives, for example those selected from the group consisting of fillers, plasticizers, adhesion promoters, UV absorbers, UV and heat stabilizers, optical brighteners, pigments, dyes and drying agents.

Examples of suitable UV stabilizers that may be added to the adhesive composition include, for example, sterically hindered phenols, and suitable UV absorbers include, for example, hydroxybenzophenones, hydroxybenzotriazoles, triazines, anilides, benzoates, cyanoacrylates, phenylformamidines, and mixtures thereof.

Suitable fillers include inorganic and organic fillers, especially natural, ground or precipitated calcium carbonate, which are optionally coated with fatty acids or fatty acid esters, especially stearic acid, barite (precipitated stone), talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieves, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica (including finely divided silica from a pyrogenic process), industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver, steel, polyvinyl chloride powder and hollow spheres.

The total amount of such auxiliary substances and additives is preferably not more than 15 wt%, more preferably not more than 10 wt%, based on the total weight of the adhesive composition.

According to one or more embodiments, the adhesive composition is obtained by a method comprising the steps of:

A) Providing a polyol composition and optionally at least one poly (meth) acrylate AC in a reactor,

b) Adding at least one isocyanate PI to the mixture obtained from step a) and optionally carrying out the reaction in the presence of one or more catalysts, wherein the molar ratio between isocyanate groups and hydroxyl groups is at least 1.1, preferably at least 1.3, to obtain a reaction mixture comprising at least one isocyanate-functional polyurethane polymer P.

C) Optionally adding at least one catalyst CA to the reaction mixture obtained from step B).

According to one or more embodiments, the NCO/OH ratio in step B) of the process is not more than 3.5, preferably not more than 3.0, more preferably not more than 2.75, in particular from 1.3 to 2.5, preferably from 1.5 to 2.2.

The reaction carried out in step B) will convert substantially all of the hydroxyl groups of the polyol composition, for example at least 95%, preferably at least 99% of the hydroxyl groups of the polyol composition.

Preferably, the starting mixture provided in step a) is dehydrated under vacuum at a temperature of 120 ℃ or higher than 120 ℃ before step B) is carried out.

The reaction in step B) may be carried out according to conventional methods for preparing isocyanate-functional polyurethane polymers. The reaction may be carried out, for example, at a temperature of 50 to 160 ℃, preferably 60 to 120 ℃, optionally in the presence of a catalyst. The reaction time depends on the temperature used, but may be, for example, in the range from 30 minutes to 6 hours, in particular from 30 minutes to 3 hours, preferably from 30 minutes to 1.5 hours. Suitable catalysts for use in the reaction of step B) include, for example, metal catalysts, such as 83 (from Vertellus Performance Materials inc.) and tin catalyst.

The adhesive composition of the invention is a moisture curable adhesive composition, i.e. the adhesive composition may be cured by contacting the composition with water, in particular with atmospheric moisture.

Furthermore, the adhesive composition of the invention has good workability under typical application conditions of hot melt adhesives, in particular at temperatures of 85-200 ℃, which means that the adhesive has a sufficiently low viscosity at this application temperature to enable application in the molten state to a substrate. The adhesive composition gives high initial strength upon cooling immediately after application to a substrate even before the crosslinking reaction with water, in particular with atmospheric moisture.

According to one or more embodiments, the viscosity of the adhesive composition at a temperature of 110 ℃ is not more than 25000 mPa-s, preferably not more than 15000 mPa-s, more preferably not more than 10000 mPa-s, even more preferably not more than 7500 mPa-s. The viscosity at a temperature of 110℃can be measured at 5 revolutions per minute using a conventional viscometer, for example by using a Brookfield DV-2 viscometer with a number 27 spindle, preferably with a Thermosel system for temperature control.

According to one or more embodiments, the adhesive composition has a softening point in the range of 40-150 ℃, preferably 45-135 ℃, more preferably 50-100 ℃ as measured by the ring and ball method according to the ISO 4625 standard.

The preferences given above for the polyurethane polymer P, the polyester polyol PO1 which is solid at 25 ℃, the first polyester polyol PO2 which is liquid at 25 ℃, the second polyester polyol PO3 which is liquid at 25 ℃, the at least one polycarbonate diol PO4, the at least one hydroxyl-terminated polybutadiene PO5, the at least one polyisocyanate PI, the at least one poly (meth) acylate AC and the at least one catalyst CA apply equally to all subjects of the invention, unless otherwise indicated.

Another subject of the invention is the use of the adhesive composition according to the invention for bonding substrates in the production of white goods, motor vehicles and electronic devices. Suitable electronic devices include, for example, displays, cell phones, smart watches, and audio devices.

Another subject of the invention is a method for bonding a first substrate to a second substrate, comprising the steps of:

i) The adhesive composition according to the invention is heated to provide a molten adhesive composition,

II) applying the molten adhesive composition to a surface of a first substrate to form an adhesive film,

III) contacting the adhesive film with the surface of the second substrate, and

IV) chemically curing the adhesive film with water, preferably with atmospheric moisture.

The first and second substrates may be sheet-like articles having first and second major surfaces defined by peripheral edges and defining a thickness therebetween, or articles of three-dimensional shape.

In a method of bonding a first substrate to a second substrate, the adhesive composition is heated to a temperature above the softening point of the adhesive composition and applied to the surface of the first substrate in a molten state using any conventional technique (e.g., by using slot die coating, roll coating, extrusion coating, calender coating, or spray coating). The adhesive composition may be, for example, in the range of 25-750g/m ² Preferably 35-650g/m ² More preferably 45-550g/m ² Even more preferably 50-500g/m ² Is applied to the surface of the first substrate.

After the adhesive film has been brought into contact with the surface of the second substrate, the adhesive composition develops a certain initial adhesive strength by physical curing, i.e. upon cooling. Depending on the application temperature and the embodiment of the adhesive composition, in particular depending on the reactivity of the adhesive, the chemical curing reaction may already start during the application of the adhesive composition onto the surface of the first substrate. However, in general, most of the chemical curing occurs after the adhesive has been applied, particularly after the applied adhesive film has been contacted with the surface of the second substrate.

The first and second substrates may be composed of any conventional material including polymeric materials, metals, painted metals, glass, wood-derived materials such as natural fiber polypropylene (NFPP) and fiber materials. Suitable polymeric materials include, for example, polyethylene (PE), particularly High Density Polyethylene (HDPE), polypropylene (PP), glass fiber reinforced polypropylene (GFPP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), acrylonitrile Butadiene Styrene (ABS), polyamide (PA), and combinations thereof. The first and second substrates may be composed of single or multiple layers of different types of materials. The layer composed of the polymeric material may further contain additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes, and biocides.

A further subject of the invention is a composite element obtainable by using the method of the invention for bonding a first substrate to a second substrate.

Examples

The following compounds and products shown in table 1 were used in the examples.

TABLE 1

The adhesive compositions shown in tables 2-4 were prepared according to the procedure shown below.

Preparation of adhesive composition

Solid polyester polyol (PO 1), liquid polyester polyols (PO 2 and PO 3), poly (meth) Acrylate (AC) and polycarbonate diol (PO 4) or hydroxyl terminated polybutadiene (PO 5) are charged into a stainless steel reactor.

The mixture was stirred under vacuum at 140 ℃ for 120 minutes to dehydrate the components and obtain a homogeneously mixed mixture. The temperature of the mixture was reduced to 120 ℃ and polyisocyanate was added to the mixture under a nitrogen blanket. The starting mixture thus obtained was stirred under vacuum at a temperature of 120 ℃ for 45 minutes to obtain a reaction product containing an isocyanate-functional polyurethane polymer. A Catalyst (CA) was then added to the reaction product under a nitrogen blanket. After mixing for 45 minutes under vacuum, the obtained adhesive composition was stored at room temperature with the exclusion of moisture.

Measurement method

The following measurement methods were used to characterize the adhesive compositions.

Viscosity at 110 DEG C

The sample adhesive composition provided in the sealed tube was preheated in an oven at a temperature of 110 ℃ for a period of 20 minutes. After heating, a sample of 12.3g of the adhesive composition was weighed and placed in a disposable cartridge of a viscometer having a 27-gauge spindle equipped with a Thermosel system and measuring viscosity at a temperature of 110℃at a speed of 5 revolutions per minute using a Brookfield DV-2 viscometer. Values obtained by tempering at the measured temperature for 20 minutes and measuring for 5 minutes are recorded as representative viscosities.

Open time

The sample adhesive composition provided in the sealed tube was first preheated in an oven to a temperature of 110 ℃ for a period of 30 minutes. After heating, a 20g sample of the molten adhesive was applied with a spatula to the surface of a silicone paper tape placed on a heated plate (B700 white, laufenberg & Sohn KG). The silicone tape was 30cm by 10cm in size and the adhesive was applied as a film 500 μm thick and 30cm by 6cm in size. The silicone tape and doctor blade were heated to a temperature of 110 ℃ with a heated plate prior to application of the adhesive film.

Immediately after the application of the adhesive, the silicone strip was removed from the hotplate and placed (adhesive film facing upwards) on the plywood sheet at room temperature (23 ℃), the time being recorded as the starting point for the measurement. A short strip of silicone coated paper (non-siliconized surface facing outwards) of 10cm x1cm in size and formed on a roll was placed on the adhesive film every 10 seconds and then slowly removed to separate the strip from the adhesive film. This process is repeated until the paper strap cannot be removed from the adhesive film without damaging the paper strip or the adhesive film. The time interval between the start of the measurement and the last sampling point was recorded as the open time (in seconds) of the adhesive composition.

The values of open time presented in tables 2-4 are obtained as an average of three measurements made with the same adhesive composition.

Tensile Strength and elongation at break

The adhesive composition provided in the sealed tube was preheated in an oven to a temperature of 110 ℃ for 30 minutes. After heating, a 40g sample of the molten adhesive was applied with a spatula to the surface of a silicone paper tape placed on a heated plate (B700 white, laufenberg & Sohn KG). The silicone paper was 60cm by 10cm in size and the adhesive was applied as a film 500 μm thick and 60cm by 6cm in size. Immediately after the adhesive application, the silicone strip was removed from the hotplate and stored for 7 days under standard climatic conditions (23 ℃,55% relative humidity).

The measurement was carried out using a method based on DIN 53504 standard. 5 rectangular specimens having dimensions of 2.0cm by 8.0cm were cut from a cured adhesive film (cured at 23 ℃ C./50% relative humidity for 14 days) having a thickness of 500. Mu.m. The test specimens were clamped in a tensile tester (Zwick Z020) and pulled apart at a speed of 100mm/min (test conditions 23 ℃,50% relative humidity). The tensile strength and elongation at break were determined based on the measured maximum tensile stress.

The values of tensile strength and elongation at break presented in tables 2-4 are obtained as the average of five measurements made with the same adhesive composition.

Tensile Lap Shear Strength (LSS)

The adhesive composition provided in the sealed tube was preheated in an oven to a temperature of 110 ℃ for 30 minutes. After heating, a sample of the molten adhesive was applied to the surface of a Polycarbonate (PC) substrate of dimensions 9cm by 2cm by 5 mm. The adhesive was coated as a film of dimensions 2.5cm by 1cm and thickness 1 mm.

Immediately after the adhesive was applied, a second PC substrate having the same dimensions as the first PC specimen was positioned on the first PC substrate along the edge of the adhesive film to form a test composite. The second PC substrate was firmly pressed against the first PC specimen to remove air from the adhesive bond. A 150g weight was placed on the top surface of the second PC substrate. Any adhesive that was squeezed out of the joint was trimmed with a knife. The test composite was stored under climatic conditions (23 ℃,55% relative humidity) for 7 days and then the lap shear strength was measured.

Lap shear strength was measured according to EN 1465 standard using a material testing device (Zwick Z020) and a test speed of 10 mm/min. The lap shear strength obtained after subjecting the test composite to an artificial aging treatment (500 hours, at 65 ℃ and 85 ℃) was also measured to determine the heat and humidity stability of the test adhesive composition.

The lap shear strength values for each of the adhesive compositions presented in tables 2-4 have been obtained as an average of three measurements made with the same test composite elements prepared by using the same adhesive composition.

TABLE 2

TABLE 3 Table 3

TABLE 4 Table 4

Composition [ wt.%)]	Ex-9	Ex-10	Ex-11	Ex-12
					PO1	24.07	21.73	19.80	18.18
PO2	8.02	7.24	6.60	6.06
					PO3	31.83	28.73	26.17	24.04
PO41
					PO42
PO5	8.92	16.09	22.00	26.93
					AC	11.20	10.11	9.21	8.46
PI	15.87	16.01	16.13	16.23
					CA	0.10	0.10	0.10	0.10
Totals to	100.01	100.01	100.01	100.00
					Measured performance
Viscosity @110 ℃ C[ cps ]]	5200	5300	5500	6000
					Open time [ min]	5	6	6	8
Breaking strength [ MPa ]]	9.5	8.8	8	6.32
					Elongation at break [%]	1300	1400	1400	1600
LSS PC/PC[MPa]
					Before artificial ageing	9.8	8.2	7.5	6.32
@65℃/95％RH,500h	8.1	6.22	6.43	5.54
					@85℃/85％RH,500h	3.38	3.27	3.66	3.86

Claims

1. An adhesive composition comprising at least one isocyanate-functional polyurethane polymer P obtained by reacting:

a) A polyol composition comprising

a1 At least one polyester polyol PO1 which is solid at 25 ℃,

a2 At least one first polyester polyol PO2 which is liquid at 25 ℃,

b) At least one of the polyisocyanates, PI,

wherein the proportion of component a 4) in the polyol composition a) is from 5 to 50% by weight, preferably from 10 to 40% by weight, based on the total weight of the polyol composition.

2. The adhesive composition of claim 1, wherein the at least one polyester polyol PO1 that is solid at 25 ℃ has a number average molecular weight (M _n ) 500-10000g/mol, preferably 1000-5000g/mol, and/or a hydroxyl number of 10-75mg KOH/g, preferably 15-50mg KOH/g, as determined according to ISO 4629-2 standard, and/or a melting point (Tm) of 30-100℃as determined by DSC, preferably 40-70 ℃.

3. The adhesive composition according to claim 1 or 2, wherein the at least one polyester polyol PO1, which is solid at 25 ℃, comprises 10 to 50 wt%, preferably 15 to 40 wt%, of the total weight of the polyol composition a).

4. The adhesive composition according to any of the preceding claims, wherein the at least one first polyester polyol PO2 which is liquid at 25 ℃ has a number average molecular weight (M _n ) 500-10000g/mol, preferably 2500-7500g/mol, and/or a hydroxyl number of 5-50mg KOH/g, preferably 10-35mg KOH/g, as determined according to ISO 4629-2 standard, and/or a glass transition temperature of-5℃or below-5℃preferably-15℃or below-15℃as determined by DSC.

5. The adhesive composition according to any of the preceding claims, wherein the at least one polycarbonate diol PO4 has a number average molecular weight (M) of 300-10000g/mol, preferably 500-5000g/mol _n ) And/or a hydroxyl number of 25 to 200mg KOH/g, preferably 35 to 100mg KOH/g, determined according to ISO 4629-2 standard.

6. The adhesive composition of any of the preceding claims, wherein the at least one polycarbonate diol PO4 is obtainable by a process selected from the group consisting of 1, 6-hexanediol and 2-methyl-1, 3-propanediolFirst and second C ₃ -C ₂₀ Transesterification of diols with carbonates.

7. The adhesive composition of claim 6 wherein the first glycol is 1, 6-hexanediol and the second C ₃ -C ₂₀ The diol is selected from the group consisting of 1, 3-propanediol, 2-methyl-1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, neopentyl glycol and trimethyl-1, 6-hexanediol.

8. The adhesive composition according to claim 6 or 7, wherein the carbonate is selected from the group consisting of ethylene carbonate, dimethyl carbonate, diethyl carbonate and di-n-butyl carbonate.

9. Adhesive composition according to any one of the preceding claims, wherein the at least one hydroxyl-terminated polybutadiene PO5 has a number average molecular weight (M) of 500-10000g/mol, preferably 1000-5000g/mol _n ) And/or an average hydroxyl functionality of from 1.3 to 2.9, preferably from 1.5 to 2.2 and/or a glass transition temperature as determined by DSC at-5℃or below-5℃preferably at-15℃or below-15 ℃.

10. The adhesive composition according to any one of the preceding claims, wherein the at least one hydroxyl-terminated polybutadiene PO5 is a hydroxyl-terminated polybutadiene that is liquid at 25 ℃.

11. The adhesive composition according to any of the preceding claims, wherein the total amount of polyols in the polyol composition a) which are liquid at 25 ℃ is from 35 to 95 wt%, preferably from 45 to 90 wt%, more preferably from 50 to 85 wt%, based on the total weight of the polyol composition a).

12. The adhesive composition according to any of the preceding claims, wherein the at least one polyisocyanate PI is a diisocyanate, preferably a monomeric diisocyanate, preferably having a number of not more than 1000g/mol, preferably not more than 500g/molAverage molecular weight (M) _n )。

13. The adhesive composition according to any of the preceding claims, wherein the at least one isocyanate functional polyurethane polymer P comprises at least 50 wt%, preferably at least 65 wt%, more preferably at least 75 wt% of the total weight of the adhesive composition.

14. The adhesive composition of any of the preceding claims, further comprising at least one poly (meth) acrylate AC.

15. The adhesive composition according to any of the preceding claims, further comprising at least one catalyst CA that catalyzes the reaction of isocyanate groups with water.

16. Use of the adhesive composition according to any one of claims 1-15 for bonding substrates in the production of white goods, motor vehicles and electronic devices.

17. A method for bonding a first substrate to a second substrate, the method comprising the steps of:

i) The adhesive composition according to any one of claims 1-15 is heated to provide a molten adhesive composition,

III) contacting the adhesive film with the surface of the second substrate, and