Moisture-curable polyurethane hot melt adhesives with improved thermal stability

Abstract

The present invention relates to a moisture-curable hot melt adhesive composition comprising at least one isocyanate-functional polyurethane polymer P, i. obtained by reacting a) at least one polyester polyol PO1 solid at 25°C, b) at least one first polyether polyol PO2, c) optionally at least one second polyether polyol PO3 different from the at least one first polyether polyol PO2, and d) at least one polyisocyanate PI, with ii. optionally at least one catalyst CA, wherein the at least one first polyether polyol PO2 is a grafted polyether polyol. The present invention also relates to the use of the adhesive composition for bonding substrates in the manufacture of white goods, automobiles and electronic devices.

Description

[Technical Field]

[0001] The present invention relates to reactive polyurethane hot melt adhesives with improved heat resistance and the use of the adhesives for bonding substrates in the manufacture of white goods, automobiles and electronic devices. [Background technology]

[0002] Hot melt adhesives are solvent-free adhesives that are solid at room temperature and are applied in a molten state to the substrates to be bonded. After cooling, the adhesive solidifies and forms an adhesive bond with the substrate through a physically generated bond. Traditional hot melt adhesives are non-reactive adhesives that soften again when heated and are therefore not suitable for use at high temperatures. Reactive hot melt adhesives contain polymers with reactive groups that allow chemical curing of the adhesive, for example, by crosslinking the polymer chains. Due to the chemically cured polymer matrix, reactive hot melt adhesives do not soften when heated, and therefore these adhesives are also suitable for use at high temperatures. Chemical curing of the polymer can be initiated, for example, by heating the adhesive composition or by exposing it to water, such as atmospheric moisture. Moisture-curing hot melt adhesives typically contain polymers functionalized with isocyanate or silane groups, allowing crosslinking of the polymer chains upon contact with atmospheric moisture.

[0003] Moisture-curing polyurethane hot melt adhesives (PUR-RHM) consist primarily of isocyanate-functional polyurethane polymers. They are obtained by reacting a suitable polyol, typically a polyester and / or polyether polyol, with a polyisocyanate. This reaction is carried out with a molar excess of isocyanate (NCO) groups over hydroxyl (OH) groups. The adhesive composition cures by reaction of the remaining isocyanate groups with water, resulting in various chain extensions and / or crosslinking reactions of the polymer. Fully cured polyurethane hot melt adhesives contain urea and / or urethane linkages, and ester and / or ether linkages depending on the starting materials used to provide the isocyanate-functional polymer. Crosslinked hot melt adhesives do not remelt even when heated. However, compared to adhesives with high crosslink densities, such as epoxy or silicone adhesives, moisture-curing polyurethane hot melt adhesives typically have poor heat resistance. This drawback significantly limits the use of PUR-RHM in many applications, particularly in bonding components in the automotive, white goods, and electronics industries.

[0004] Therefore, there is a need for new types of moisture-curable polyurethane hot melt adhesives with improved heat resistance that are particularly suitable for use in bonding substrates in the manufacture of white goods, automobiles, and electronic devices. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide an adhesive composition which overcomes or at least mitigates the disadvantages of prior art moisture-curable polyurethane hot melt adhesives such as those discussed above.

[0006] In particular, it is an object of the present invention to provide a moisture-curable polyurethane hot melt adhesive composition having improved heat resistance. The cured adhesive composition should preferably also have excellent mechanical properties, in particular high tensile strength and elongation at break, and low viscosity at typical application temperatures of hot melt adhesives. [Means for solving the problem]

[0007] Surprisingly, it has been found that the features of claim 1 make it possible to achieve this object.

[0008] The core of the present invention is a novel type of moisture-curable polyurethane hot melt adhesive composition comprising at least one isocyanate-functional polyurethane polymer obtained by reacting a polyol composition with a polyisocyanate, the polyol composition comprising a polyester polyol that is solid at 25°C, a grafted polyether polyol, and a polyisocyanate.

[0009] Surprisingly, it has been found that the addition of a grafted polyether polyol to an adhesive composition not only improves the thermal stability of the cured adhesive, but also leads to improvements in the mechanical properties, particularly the tensile strength, of the cured adhesive composition.

[0010] Other subject matters of the invention are set out in the other independent claims. Preferred embodiments of the invention are set out in the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0011] The subject of the present invention is i. at least one isocyanate-functional polyurethane polymer P, a) at least one polyester polyol PO1 that is solid at 25°C, b) at least one first polyether polyol PO2, c) optionally at least one second polyether polyol PO3 different from the at least one first polyether polyol PO2, and d) at least one polyisocyanate PI and at least one isocyanate-functional polyurethane polymer P obtained by reacting ii. optionally, at least one catalyst CA; wherein the at least one first polyether polyol PO2 is a grafted polyether polyol.

[0012] The prefix "poly" in a substance designation such as "polyol" or "polyisocyanate" formally refers to a substance containing more than one of the functional groups in the designation per molecule. For example, a polyol is a compound with more than one hydroxyl group, and a polyisocyanate is a compound with more than one isocyanate group.

[0013] The term "polymer" refers to a collection of chemically uniform macromolecules produced by polymerization reactions (polymerization, polyaddition, polycondensation). Macromolecules differ with respect to their degree of polymerization, molecular weight and chain length. The term also includes derivatives of said collection of macromolecules resulting from multiple reactions, i.e., compounds obtained by reactions such as addition or substitution of functional groups in a given macromolecule, which may be chemically uniform or chemically heterogeneous.

[0014] The term "functionalized polymer" refers to a polymer that has been chemically modified to include functional groups on the polymer backbone. In contrast, the term "non-functionalized polymer" refers to a polymer that has not been chemically modified to include functional groups, such as epoxy groups, silane groups, sulfonate groups, amide groups, or anhydride groups, on the polymer backbone.

[0015] The term "polyurethane polymer" refers to polymers prepared by the so-called diisocyanate polyaddition method. These include polymers that are substantially or completely free of urethane groups. Examples of polyurethane polymers are polyether-polyurethanes, polyester-polyurethanes, polyether-polyureas, polyureas, polyester-polyureas, polyisocyanurates, and polycarbodiimides.

[0016] The term "isocyanate-functional polyurethane polymer" refers to a polyurethane polymer containing 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.

[0017] The term "molecular weight" refers to the molar mass (g / mol) of a molecule or a portion of a molecule, also called a "moiety." The term "average molecular weight" refers to the number average molecular weight (M n ) or weight average molecular weight (M w Molecular weights can be determined by gel permeation chromatography (GPC) using polystyrene as the standard, styrene-divinylbenzene gels of porosity 100 Å, 1000 Å, and 10000 Å as the columns, and tetrahydrofuran at 35° C. as the solvent or 1,2,4-trichlorobenzene at 160° C. as the solvent, depending on the molecule.

[0018] The term "average OH functionality" refers to the average number of hydroxyl (OH) groups per molecule. The average OH functionality of a compound is determined by the number average molecular weight (M n ) and the hydroxyl number. The hydroxyl number of a compound can be measured using the method defined in the DIN 53240-2 standard.

[0019] The term "open time" refers to the length of time that an adhesive applied to the surface of a substrate is able to form an adhesive bond after contact with another substrate.

[0020] The "amount of at least one component X" in a composition, e.g., the "amount of at least one polyol," as used herein refers to the sum of the individual amounts of all polyols contained in the composition. For example, if the at least one polyol is a polyester polyol that is solid at 25°C and the composition contains 20 wt% of the at least one polyol, then the sum of the amounts of all polyester polyols that are solid at 25°C contained in the composition is equal to 20 wt%.

[0021] The term "room temperature" refers to a temperature of about 23°C.

[0022] The adhesive composition is preferably a hot melt adhesive, more preferably a one-component hot melt adhesive. The term "one-component composition" in the context of the present invention refers to a composition in which all components of the composition are stored as a mixture in the same container or compartment.

[0023] The adhesive composition comprises at least one isocyanate-functional polyurethane polymer P obtained by reacting a polyol composition comprising at least one polyester polyol PO1 that is solid at 25°C and at least one grafted polyether polyol PO2 with at least one polyisocyanate PI.

[0024] Grafted polyether polyols, also known as "graft polyether polyols," "modified polyether polyols," "copolymer polyether polyols (CPPs)," or polymer polyols (POPs), are polyether polyols containing dispersed polymers of ethylenically unsaturated monomers. Grafted polyether polyols can be obtained, for example, by free-radical graft polymerization of a base polyether polyol with ethylenically unsaturated monomers such as styrene and acrylonitrile. Methods for producing suitable grafted polyether polyols are disclosed, for example, in WO 2008005708 A1 and WO 2017053064 A1.

[0025] The term "solids content" of a grafted polyether polyol, also known as graft density, refers to the ratio of the mass of the grafted portion of the polyether polyol to the total mass of the polyether polyol. The solids content of a grafted polyether polyol can be determined using the method defined in GB / T31062-2014 standard.

[0026] According to one or more embodiments, the at least one first polyether polyol PO2 has a solids content of 25 to 75 wt.-%, preferably 30 to 65 wt.-%, more preferably 30 to 55 wt.-%, even more preferably 35 to 55 wt.-% and / or a hydroxyl number, determined in accordance with the ISO 4629-2 standard, of 10 to 100 mg KOH / g, preferably 15 to 75 mg KOH / g, more preferably 20 to 50 mg KOH / g, even more preferably 25 to 45 mg KOH / g.

[0027] Suitable grafted polyether polyols are commercially available, for example, under the tradenames Voranol®, such as Voranol® 3943A and Voranol® 220-260; Voralux®, such as Voralux® HL400, Voralux® HL431, and Voralux® HL500; and Specflex®, such as Specflex® NC701 and Specflex® NC702 (all from Dow Chemical Company).

[0028] Further suitable grafted polyether polyols are commercially available under the trade names Arcol® (from Covestro), such as Arcol® HS-100, and Pluracol® (from BASF), such as Pluracol® 1365, Pluracol® 1441, and Pluracol® 5132.

[0029] Preferably, the at least one first polyether polyol PO2 constitutes at least 1.5 wt. %, preferably at least 2.5 wt. %, more preferably at least 5 wt. % of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

[0030] According to one or more embodiments, the at least one first polyether polyol PO2 constitutes 2.5 to 65 wt.-%, preferably 5 to 60 wt.-%, more preferably 10 to 55 wt.-%, even more preferably 15 to 50 wt.-%, and even more preferably 15 to 45 wt.-% of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P. Adhesive compositions comprising the at least one first polyether polyol PO2 in an amount falling within the above ranges have been found to exhibit particularly good thermal stability and mechanical properties of the cured adhesive compositions.

[0031] According to one or more embodiments, the at least one first polyether polyol PO2 is obtained by graft copolymerization, preferably free radical graft copolymerization, of at least one base polyether polyol with a composition of one or more ethylenically unsaturated monomers.

[0032] Ethylenically unsaturated monomers suitable for use in the graft copolymerization include, for example, acrylonitrile, styrene, methylstyrene, methyl methacrylate, vinyl acetate, vinylbenzene, and vinyltoluene.

[0033] According to one or more embodiments, the composition of ethylenically unsaturated monomers includes at least one acrylic monomer, preferably an acrylonitrile monomer.

[0034] According to one or more preferred embodiments, the composition of ethylenically unsaturated monomers comprises or consists of at least one acrylic monomer, preferably acrylonitrile, and at least one other ethylenically unsaturated monomer, preferably styrene.

[0035] Preferably, the at least one base polyether polymer is selected from the group consisting of polyoxypropylene polyether polyols, poly(oxyethylene / oxypropylene) polyether polyols, and polyoxyethylene polyether polyols.

[0036] Suitable polyester polyols for use as the at least one polyester polyol PO1 solid at 25° C. include crystalline and partially crystalline polyester polyols, which are dihydric and trihydric, preferably dihydric, alcohols such as 1,2-ethanediol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, dimer fatty alcohols, neopentyl glycol, glycerol, 1,1,1-trimethyl ... These polyols can be obtained by reacting methanol or a mixture of the aforementioned alcohols with an organic dicarboxylic or tricarboxylic acid, preferably a dicarboxylic acid or anhydride or ester thereof, such as succinic acid, glutaric acid, 3,3-dimethylglutaric acid, adipic acid, suberic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimer fatty acid, isophthalic acid, terephthalic acid, and hexahydrophthalic acid, or a mixture of the aforementioned acids. Polyester polyols made from lactones, such as ε-caprolactone, also known as polycaprolactone, are also suitable.

[0037] Preferred polyester polyols include those obtained by reacting adipic acid, sebacic acid, or dodecanedicarboxylic acid as the dicarboxylic acid with hexanediol or neopentyl glycol as the dihydric alcohol. Further examples of suitable polyester polyols include oleochemical-derived polyester polyols. This type of polyester polyol can be prepared, for example, by fully ring-opening epoxidized triglycerides of a fat mixture containing at least partially olefinically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivative to obtain alkyl ester polyols having 1 to 12 carbon atoms in the alkyl group. Particularly suitable crystalline and partially crystalline polyester polyols include adipic acid / hexanediol polyesters and dodecanedicarboxylic acid / hexanediol polyesters.

[0038] According to one or more embodiments, the at least one polyester polyol PO1 solid at 25° C. has a number average molecular weight (M) of 500 to 10,000 g / mol, preferably 1,000 to 5,000 g / mol. n ), and / or a hydroxyl number determined according to the ISO 4629-2 standard of 10 to 75 mg KOH / g, preferably 15 to 50 mg KOH / g, and / or a melting point (T) determined by DSC of 30 to 100°C, preferably 40 to 70°C, more preferably 45 to 65°C. m )

[0039] Suitable polyester polyols that are solid at 25° C. are commercially available, for example, under the trade name Dynacoll® 7300-series (from Evonik Industries).

[0040] Preferably, the at least one polyester polyol PO1 that is solid at 25°C constitutes at least 2.5% by weight, preferably at least 5% by weight, more preferably at least 10% by weight of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

[0041] According to one or more embodiments, the at least one polyester polyol PO1 solid at 25° C. constitutes 5 to 45% by weight, preferably 10 to 40% by weight, more preferably 10 to 35% by weight, and even more preferably 10 to 30% by weight of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

[0042] According to one or more embodiments, the polyol composition used to obtain the at least one isocyanate-functional polyurethane polymer P comprises, in addition to at least one first polyether polyol PO2, at least one second polyether polyol PO3 that is different from the at least one first polyether polyol PO2.

[0043] Suitable polyether polyols, also known as polyoxyalkylene polyols, for use as the at least one second polyether polyol PO3 include the polymerization products of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, tetrahydrofuran or mixtures thereof, optionally with a starter molecule having two or more active hydrogen atoms, such as water, ammonia or a compound having two or more OH- or NH- groups, such as 1,2-ethanediol, 1,2- and 1,3-propanediol. Polyoxyalkylene polyols with low unsaturation (measured in milliequivalents of unsaturation per gram of polyol (meq / g) according to ASTM D-2849-69) produced using double metal cyanide complex catalysts (DMC catalysts) can be used, as well as polyoxyalkylene polyols with relatively high unsaturation (measured in milliequivalents of unsaturation per gram of polyol (meq / g)) produced using anionic catalysts such as NaOH, KOH, or alkali metal alkoxides.

[0044] Particularly suitable polyether polyols include polyoxyalkylene diols or triols, especially polyoxyethylene diols or triols.

[0045] Particularly suitable are polyoxyalkylene diols or polyoxyalkylene triols, more particularly those having a number average molecular weight (M) in the range of 1000 to 30000 g / mol. n) and polyoxypropylene diols and triols having a number average molecular weight (M) of 400 to 8000 g / mol n Suitable polyether polyols are commercially available, for example, under the trade names Acclaim®, Desmophene® and Arcol® (all from Covestro).

[0046] According to one or more embodiments, the at least one second polyether polyol PO3 constitutes 15 to 85 wt. %, preferably 25 to 80 wt. %, more preferably 30 to 75 wt. %, even more preferably 35 to 70 wt. %, and even more preferably 35 to 65 wt. % of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

[0047] According to one or more embodiments, the at least one second polyether polyol PO3 is a polyether polyol that is liquid at 25° C. and preferably has a hydroxyl number, determined according to the ISO 4629-2 standard, of 15 to 100 mg KOH / g, preferably 35 to 75 mg KOH / g, more preferably 45 to 65 mg KOH / g.

[0048] Suitable polyisocyanates for use as the at least one polyisocyanate PI include, for example, aliphatic, cycloaliphatic, and aromatic polyisocyanates, particularly diisocyanates, especially monomeric diisocyanates. Non-monomeric diisocyanates, such as oligomeric and polymeric products of monomeric diisocyanates, for example, adducts of monomeric diisocyanates, are also suitable, although the use of monomeric diisocyanates is preferred.

[0049] The term "monomer" means a molecule having at least one polymerizable group. Monomeric diisocyanates or polyisocyanates specifically do not contain urethane groups. For purposes of this invention, oligomeric or polymeric products of diisocyanate monomers, such as adducts of monomeric diisocyanates, are not monomeric diisocyanates.

[0050] If the isocyanate group is directly attached to an aliphatic, cycloaliphatic, or arylaliphatic moiety, the isocyanate is called "aliphatic." The corresponding functional group is therefore called an aliphatic isocyanate group. If the isocyanate group is directly attached to an aromatic moiety, the isocyanate is called "aromatic." The corresponding functional group is therefore called an aromatic isocyanate group.

[0051] According to one or more embodiments, the at least one polyisocyanate PI is a diisocyanate, preferably a monomeric diisocyanate, more preferably having a number average molecular weight (M) of 1000 g / mol or less, preferably 500 g / mol or less, more preferably 400 g / mol or less. n ) is a monomeric diisocyanate having the formula:

[0052] Examples of suitable monomeric diisocyanates include, for example, 1,6-hexamethylene diisocyanate (HDI), 2-methylpentamethylene 1,5-diisocyanate, 2,2,4- and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate (TMDI) and mixtures of these isomers, 1,10-decamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, lysine diisocyanate, lysine ester diisocyanate, cyclohexane 1,3-diisocyanate, and 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 H6TDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (=isophorone diisocyanate or IPDI), perhydro-2,4'- and -4,4'-diphenylmethane diisocyanate (HMDI or H12MDI) and mixtures of these isomers, 1,4-di Isocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, m- and p-xylylene diisocyanate (m- and p-XDI) and mixtures of these isomers, m- and p-tetramethyl-1,3- and 1,4-xylylene diisocyanate (m- and p-TMXDI) and mixtures of these isomers, bis(1-isocyanato-1-methylethyl)naphthalene, 2,4- and 2,6-tolylene diisocyanate and and mixtures of these isomers (TDI), 4,4'-, 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), 3,3'-dimethyl-4,4'-diisocyanatobiphenyl (TODI), and dianisidine diisocyanate (DADI).

[0053] 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 their isomers (MDI), 2,4- and 2,6-tolylene diisocyanate and mixtures of their isomers (TDI), 1,6-hexamethylene diisocyanate (HDI), and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). Furthermore, those skilled in the art will recognize that technical grade diisocyanate products may frequently contain isomer mixtures or other isomers as impurities. According to one or more embodiments, the monomeric diisocyanate is selected from the group consisting of MDI and IPDI. Suitable monomeric diisocyanates are commercially available, for example, under the trade names Lupranat® (from BASF) and Desmodur (from Covestro).

[0054] According to one or more embodiments, the isocyanate-functional polyurethane polymer P has an average isocyanate functionality of 3.5 or less, preferably 3.0 or less. 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 using the method defined in ISO 14896-2006 Standard Method A.

[0055] Preferably, the at least one isocyanate-functional polyurethane polymer P constitutes at least 50% by weight of the total weight of the adhesive composition, more preferably at least 65% by weight, even more preferably at least 75% by weight, and even more preferably at least 85% by weight.

[0056] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer P constitutes 50 to 95 wt. %, preferably 60 to 90 wt. %, more preferably 65 to 85 wt. %, and even more preferably 70 to 85 wt. % of the total weight of the adhesive composition.

[0057] According to one or more embodiments, the adhesive composition further comprises at least one poly(meth)acrylate AC. The term "(meth)acrylate" in the context of the present invention denotes a methacrylate or an acrylate.

[0058] The term "poly(meth)acrylate" refers to homopolymers, copolymers and higher order interpolymers of a (meth)acrylate monomer with one or more additional (meth)acrylate monomers and / or one or more additional monomers.

[0059] It may be preferred that the (meth)acrylate monomer does not contain further functional groups such as hydroxyl and / or carboxyl groups. However, (meth)acrylate monomers containing further functional groups, especially hydroxyl groups, can be used in combination with (meth)acrylate monomers that do not contain further functional groups.

[0060] Suitable (meth)acrylate monomers include alkyl (meth)acrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and branched isomers thereof such as isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, and also cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate or 3,5-dimethyladamantyl acrylate.

[0061] Suitable (meth)acrylate monomers having further functional groups include, for example, hydroxyl group-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-hydroxy-hexyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate.

[0062] Further suitable comonomers for the synthesis of at least one poly(meth)acrylate AC include vinyl compounds such as functionalized ethylenically unsaturated hydrocarbons, vinyl esters, vinyl halides, vinylidene halides, nitriles of ethylenically unsaturated hydrocarbons, phosphate esters, and zinc salts of (meth)acrylic acid. Examples of further suitable comonomers include, for example, maleic anhydride, styrene, styrenic compounds, acrylonitrile, vinyl acetate, vinyl propionate, vinyl chloride, (meth)acrylic acid, β-acryloyloxypropionic acid, vinylacetic acid, fumaric acid, crotonic acid, aconitic acid, trichloroacrylic acid, itaconic acid, and maleic acid, and their amides.

[0063] 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 hydroxyl-functional (meth)acrylate monomers and / or at least one additional comonomer.

[0064] Suitable poly(meth)acrylates are commercially available, for example, under the trade names Dynacoll® AC, such as Dynacoll® AC1420, Dynacoll® AC1520, Dynacoll® AC1631, Dynacoll® AC1620, Dynacoll® AC1630, Dynacoll® AC1632, Dynacoll® AC1750, Dynacoll® AC1920, Dynacoll® AC4830 and Dynacoll® AC2740 (all from Evonik Industries).

[0065] According to one or more embodiments, the at least one poly(meth)acrylate AC has a weight average molecular weight (M) of 15,000 to 100,000 g / mol, preferably 25,000 to 65,000 g / mol. w ) and / or a glass transition temperature determined in accordance with ISO 11357-1 standard of 0°C or higher, preferably 35°C or higher, and / or a softening point determined by the ring and ball method in accordance with ISO 4625 standard of 75 to 200°C, preferably 125 to 185°C, and / or an acid value determined in accordance with EN ISO 2114 standard of 25 mgKOH / g or lower, preferably 10 mgKOH / g or lower.

[0066] According to one or more embodiments, the at least one poly(meth)acrylate AC constitutes 5 to 55 wt. %, preferably 10 to 45 wt. %, more preferably 15 to 35 wt. % of the total weight of the adhesive composition.

[0067] 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.

[0068] Examples of suitable catalysts include metal-based catalysts, such as dialkyltin complexes, in particular dibutyltin(IV) or dioctyltin(IV) carboxylates or acetoacetonates, such as dibutyltin dilaurate (DBTDL), dibutyltin diacetylacetonate, dioctyltin dilaurate (DOTDL), as well as 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.

[0069] Further examples of suitable catalysts include compounds containing amine groups, such as dimorpholinodialkyl ethers 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 one or more metal catalysts and one or more morpholine amine compounds.

[0070] According to one or more embodiments, the at least one catalyst CA comprises 0.005 to 2.00 wt. %, preferably 0.05 to 1.00 wt. %, of the total weight of the adhesive composition.

[0071] The adhesive composition may further comprise auxiliary substances and additives such as those selected from the group consisting of fillers, plasticizers, adhesion promoters, UV absorbers, UV and heat stabilizers, optical brighteners, pigments, dyes and drying agents.

[0072] Examples of suitable UV stabilizers that can 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.

[0073] Suitable fillers include inorganic and organic fillers, especially natural, ground or precipitated calcium carbonate, optionally coated with a fatty acid or a fatty acid ester, especially stearic acid, barium (baryte), talc, quartz flour, 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 pyrolysis processes, industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver, steel, etc., polyvinyl chloride powder and hollow spheres.

[0074] The total amount of such auxiliary substances and additives is preferably 15% by weight or less, more preferably 10% by weight or less, based on the total weight of the adhesive composition.

[0075] According to one or more embodiments, the adhesive composition comprises: A) feeding polyols a) to c) and optionally at least one poly(meth)acrylate AC into a reactor; B) adding at least one isocyanate PI to the mixture obtained from step A) and carrying out a reaction, optionally in the presence of one or more catalysts, in which the molar ratio of isocyanate groups to 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). The compound is obtained by a method comprising:

[0076] According to one or more embodiments, the NCO / OH ratio in step B) of the process is at most 3.5, preferably at most 3.0, more preferably at most 2.75, in particular between 1.3 and 2.5, preferably between 1.5 and 2.2.

[0077] The reaction carried out in step B) converts 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.

[0078] Preferably, the starting mixture provided in step A) is dehydrated under vacuum at a temperature of 120° C. or higher before carrying out step B).

[0079] The reaction in step B) can be carried out according to conventional methods used to prepare isocyanate-functional polyurethane polymers. The reaction can be carried out, for example, at a temperature ranging from 50 to 160°C, preferably from 60 to 120°C, optionally in the presence of a catalyst. The reaction time depends on the temperature used, but can range, for example, from 30 minutes to 6 hours, particularly from 30 minutes to 3 hours, preferably from 30 minutes to 1.5 hours. Suitable catalysts for use in the reaction in step B) include metal catalysts and tin catalysts, such as Coscat® 83 (available from Vertellus Performance Materials Inc.).

[0080] The adhesive composition of the present invention is a moisture-curable adhesive composition, that is, the adhesive composition can be cured by contacting it with water, especially atmospheric moisture.

[0081] Furthermore, the adhesive composition of the present invention has good workability under typical application conditions for hot melt adhesives, particularly at temperatures in the range of 85-200°C, meaning that at the application temperature the adhesive has a sufficiently low viscosity to allow application to a substrate in the molten state. The adhesive composition develops high early strength upon cooling immediately after application to a substrate, even before the onset of crosslinking reactions with water, particularly atmospheric moisture.

[0082] According to one or more embodiments, the adhesive composition has a viscosity of 25,000 mPa·s or less, preferably 15,000 mPa·s or less, more preferably 12,500 mPa·s or less, at a temperature of 110° C. The viscosity at a temperature of 110° C. can be measured using a conventional viscometer at 5 revolutions per minute, for example, by using a Brookfield DV-2 viscometer with spindle No. 27, preferably equipped with a Thermosel System for temperature control.

[0083] According to one or more embodiments, the adhesive composition has a softening point, measured by the ring and ball method according to ISO 4625 standard, in the range of 40 to 175°C, preferably 45 to 150°C, more preferably 50 to 135°C, and even more preferably 50 to 120°C.

[0084] The preferences stated above with regard to the polyurethane polymer P, the polyester polyol PO1 solid at 25°C, the first polyether polyol PO2, the second polyether polyol PO3, the at least one poly(meth)acrylate AC and the at least one catalyst CA apply equally to all subjects of the present invention, unless otherwise specified.

[0085] Another subject of the present invention is the use of the adhesive composition of the present invention for bonding substrates in the manufacture of white goods, automobiles and electronic devices. Suitable electronic devices include, for example, displays, mobile phones, smart watches and audio devices.

[0086] Another subject of the present invention is a method for adhesively bonding a first substrate to a second substrate, comprising the steps of: I) heating an adhesive composition according to the present invention 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 a surface of a second substrate; IV) chemically curing the adhesive film with water, preferably atmospheric moisture; The method includes:

[0087] The first and second substrates may be sheet-like articles or three-dimensional shaped articles having first and second major surfaces defined by perimeters and defining a thickness therebetween.

[0088] In a method for adhesively 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 in a molten state to the surface of the first substrate using any conventional technique, such as slot die coating, roller coating, extrusion coating, calendar coating, or spray coating. The adhesive composition may be applied in a thickness of, for example, 25 to 750 g / m 2 , preferably 35 to 500 g / m 2 , more preferably 45 to 350 g / m 2 , and more preferably 50 to 250 g / m 2 can be applied to the surface of the first substrate at a coating weight of

[0089] After the adhesive film contacts the surface of the second substrate, the adhesive composition undergoes physical hardening, i.e., cooling, to develop a certain initial adhesive strength. Depending on the application temperature and the embodiment of the adhesive composition, particularly the reactivity of the adhesive, the chemical hardening reaction may already begin during the application of the adhesive composition to the surface of the first substrate. However, typically, most of the chemical hardening occurs after the application of the adhesive, particularly after the applied adhesive film contacts the surface of the second substrate.

[0090] The first and second substrates can be made of any conventional material, including polymeric materials, metal, painted metal, glass, wood, wood-derived materials such as natural fiber polypropylene (NFPP), and fibrous 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 can be made of a single layer or multiple layers of different types of materials. Layers made of polymeric materials can further contain additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes, and biocides.

[0091] Yet another subject of the invention is a composite element obtainable by using the method of the invention for adhesively bonding a first substrate to a second substrate. [Example]

[0092] The compounds and products shown in Table 1 were used in the examples.

[0093] [Table 1]

[0094] The adhesive compositions shown in Table 2 were prepared according to the procedure set forth below.

[0095] Preparation of the tested adhesive compositions Solid polyester polyol (PO1), polyether polyols (PO2 and PO3) and poly(meth)acrylate (AC) were charged into a stainless steel reactor.

[0096] The mixture was held under vacuum with stirring at 140°C for 120 minutes to dehydrate the components and obtain a homogeneously mixed mixture. The temperature of the mixture was reduced to 120°C, and polyisocyanate (PI) was added to the mixture under a nitrogen blanket. The resulting starting mixture was reacted under vacuum at a temperature of 120°C with stirring for 45 minutes to obtain a reaction product containing an isocyanate-functional polyurethane polymer (P). A catalyst (CA) was then added to the reaction product under a nitrogen blanket. After mixing under vacuum for 45 minutes, the resulting adhesive composition was stored at room temperature under the exclusion of moisture.

[0097] Measurement method The adhesive compositions were characterized using the following measurement methods.

[0098] Viscosity at 110℃ The sample adhesive composition, supplied in a sealed tube, was preheated in an oven at 110°C for 20 minutes. After heating, a 12.3g sample of the adhesive composition was weighed, placed in a disposable sleeve, and placed in the viscometer. The viscosity was measured at 110°C and 5 revolutions per minute using a Brookfield DV-2 viscometer with a Thermosel system and spindle No. 27. The sample was tempered at the temperature for 20 minutes, and the value obtained after 5 minutes of measurement was recorded as the representative viscosity.

[0099] Open Time The sample adhesive composition, supplied in a sealed tube, was first preheated in an oven to a temperature of 110°C for 30 minutes. After heating, a 20g sample of the molten adhesive was applied using a doctor blade to the surface of a piece of silicone paper (B700 white, Laufenberg & Sohn KG) placed on a heating plate. The silicone paper piece had dimensions of 30cm x 10cm, and the adhesive was applied as a film 500µm thick and measuring 30cm x 6cm. Before applying the adhesive film, the silicone paper piece and doctor blade were heated to a temperature of 110°C on the heating plate.

[0100] Immediately after applying the adhesive, the silicone paper strip was removed from the heating plate and placed (with the adhesive film facing up) on a sheet of plywood at room temperature (23°C), and this time was recorded as the starting point of the measurement. Every 10 seconds, a strip of silicone-coated paper formed into a roll and measuring 10 cm x 1 cm (with the non-siliconized side facing outward) was placed on the adhesive film and then slowly peeled away to separate the strip from the adhesive film. This procedure was repeated until the paper strip could no longer be peeled from the adhesive film without damaging the paper strip or the adhesive film. The time interval from the starting point of the measurement to the last sampling point was recorded as the open time (seconds) of the adhesive composition.

[0101] The open time values ​​shown in Table 2 were obtained as the average of three measurements carried out on the same adhesive composition.

[0102] Tensile strength and elongation at break The adhesive composition provided in a sealed tube was preheated in an oven to a temperature of 110°C for 30 minutes. After heating, a 40g sample of the molten adhesive was applied using a doctor blade to the surface of a piece of silicone paper (B700 white, Laufenberg & Sohn KG) placed on a heating plate. The silicone paper had dimensions of 60cm x 10cm, and the adhesive was applied as a 500µm thick film measuring 60cm x 6cm. Immediately after application of the adhesive, the silicone paper piece was removed from the heating plate and stored under standard climatic conditions (23°C, 55% relative humidity) for 7 days.

[0103] The measurements were carried out according to the DIN 53504 standard. Five rectangular specimens measuring 2.0 cm x 8.0 cm were cut from a 500 μm thick cured adhesive film (cured for 14 days at 23°C / 50% relative humidity). The specimens were fixed to a tensile testing machine (Zwick Z 020) and peeled at a rate of 100 mm / min (test conditions: 23°C, 50% relative humidity). The tensile strength and elongation at break were determined based on the measured maximum tensile stress.

[0104] The values ​​of tensile strength and elongation at break shown in Table 2 were obtained as the average of five measurements carried out on the same adhesive composition.

[0105] Thermal stability under static load (heat resistance) The adhesive composition provided in a sealed tube was preheated in an oven at a temperature of 110°C for 20 minutes. After heating, a sample of the molten adhesive was applied to the surface of a wood specimen (pine) having dimensions of 9cm x 2cm x 5mm and having 1mm copper wire as a spacer on the surface. The adhesive was applied as a film having dimensions of 2cm x 2cm and a thickness of 1mm.

[0106] Immediately after applying the adhesive, a second wood specimen (pine) with identical dimensions was placed on top of the first wood specimen along the edge of the adhesive film to form a test composite element. The second wood specimen was pressed firmly against the first wood specimen to remove air from the adhesive bond. A 150 g weight was placed on top of the second wood specimen. Any adhesive squeezed out of the joint was cut off with a knife. The test composite element consisting of the bonded wood specimens was then stored for 14 days under standard climatic conditions (23°C, 40-60% relative humidity).

[0107] The test composite elements were then hung vertically from one end of the first wood specimen by a metal hook and placed in the oven. A metal weight equivalent to a static load of 1 kg was attached to the bottom end of the second wood specimen of each composite element. Three composite elements were placed in the oven at a time for thermal stability measurements.

[0108] For thermal stability measurements, the oven was first heated to a temperature 40°C below the expected adhesive bond failure temperature. The composite elements were held at this starting temperature for 60 minutes. If no bond failure occurred, the oven temperature was increased by 10°C and measurements continued for another 60 minutes. The oven temperature was increased in 10°C increments according to the procedure above until bond failure occurred. The last temperature measured before bond failure occurred was recorded as the representative thermal stability temperature.

[0109] The heat resistance value for each adhesive composition shown in Table 2 was obtained as the average of three measurements performed using the same test composite element prepared with the same adhesive composition.

[0110] [Table 2] The present disclosure includes the following aspects. <Aspect 1> i. at least one isocyanate-functional polyurethane polymer P, a) at least one polyester polyol PO1 that is solid at 25°C, b) at least one first polyether polyol PO2, c) optionally at least one second polyether polyol PO3 different from said at least one first polyether polyol PO2, and d) at least one polyisocyanate PI and at least one isocyanate-functional polyurethane polymer P obtained by reacting ii. optionally, at least one catalyst CA; wherein said at least one first polyether polyol PO2 is a grafted polyether polyol. <Aspect 2> 2. The adhesive composition according to claim 1, wherein the at least one first polyether polyol PO2 has a solids content at 40°C of 25 to 75 wt.%, preferably 30 to 65 wt.%, and / or a hydroxyl number, determined in accordance with the ISO 4629-2 standard, of 10 to 100 mg KOH / g, preferably 15 to 75 mg KOH / g. <Aspect 3> 3. The adhesive composition of claim 1 or 2, wherein the at least one first polyether polyol PO2 constitutes 2.5 to 65 wt. %, preferably 5 to 60 wt. %, of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P. <Aspect 4> 4. The adhesive composition of any one of Aspects 1 to 3, wherein the at least one first polyether polyol PO2 is obtained by graft copolymerization of at least one base polyether polyol with a composition of one or more ethylenically unsaturated monomers. <Aspect 5> 5. The adhesive composition of embodiment 4, wherein the composition of ethylenically unsaturated monomers comprises at least one acrylic monomer, preferably an acrylonitrile monomer. <Aspect 6> 6. The adhesive composition of claim 4 or 5, wherein the composition of ethylenically unsaturated monomers comprises or consists of at least one acrylic monomer, preferably acrylonitrile, and at least one other ethylenically unsaturated monomer, preferably styrene. <Aspect 7> 7. The adhesive composition according to any one of Aspects 4 to 6, wherein the at least one base polyether polymer is selected from the group consisting of polyoxypropylene polyether polyols, poly(oxyethylene / oxypropylene) polyether polyols, and polyoxyethylene polyether polyols. <Aspect 8> The at least one polyester polyol PO1 that is solid at 25° C. has a number average molecular weight (M n ), and / or a hydroxyl number determined according to the ISO 4629-2 standard of 10 to 75 mg KOH / g, preferably 15 to 50 mg KOH / g, and / or a melting point (T m 8. The adhesive composition according to any one of embodiments 1 to 7, wherein <Aspect 9> 9. The adhesive composition according to any one of the preceding aspects, wherein the at least one polyester polyol PO1 that is solid at 25°C constitutes 5 to 45 wt. %, preferably 10 to 40 wt. %, of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P. <Aspect 10> 10. The adhesive composition of any one of aspects 1 to 9, wherein the at least one second polyether polyol PO3 constitutes 15 to 85 wt. %, preferably 25 to 80 wt. %, of the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P. <Aspect 11> The at least one polyisocyanate PI preferably has a number average molecular weight (M) of less than or equal to 1000 g / mol, preferably less than or equal to 500 g / mol. n 11. The adhesive composition according to any one of Aspects 1 to 10, wherein the diisocyanate is a diisocyanate having the formula (I), preferably a monomeric diisocyanate. <Aspect 12> 12. The adhesive composition of any of the preceding embodiments, wherein the at least one isocyanate-functional polyurethane polymer P constitutes at least 50 wt.%, preferably at least 65 wt.%, and more preferably at least 75 wt.% of the total weight of the adhesive composition. <Aspect 13> 13. The adhesive composition of any one of aspects 1 to 12, further comprising at least one poly(meth)acrylate AC, preferably comprising 5 to 55 wt. %, preferably 10 to 45 wt. %, of the total weight of the adhesive composition. <Aspect 14> 14. The adhesive composition of any one of aspects 1 to 13, further comprising the at least one catalyst CA that catalyzes the reaction of isocyanate groups with water. <Aspect 15> 15. The adhesive composition according to aspect 14, wherein the at least one catalyst CA comprises 0.005 to 2.00 wt %, preferably 0.05 to 1.00 wt %, of the total weight of the adhesive composition. <Aspect 16> 16. Use of the adhesive composition according to any one of aspects 1 to 15 for bonding substrates in the manufacture of white goods, automobiles and electronic devices. <Aspect 17> 1. A method of adhesively bonding a first substrate to a second substrate, comprising: I) heating the adhesive composition of any one of aspects 1-15 to provide a molten adhesive composition; II) applying the molten adhesive composition to a surface of the first substrate to form an adhesive film; III) contacting the adhesive film with a surface of the second substrate; IV) chemically curing the adhesive film with water, preferably atmospheric moisture; A method comprising:

Claims

1. i. at least one isocyanate-functional polyurethane polymer P, a) at least one polyester polyol PO1 that is solid at 25°C, b) at least one first polyether polyol PO2, c) at least one second polyether polyol PO3 different from said at least one first polyether polyol PO2, and d) at least one polyisocyanate PI and at least one isocyanate-functional polyurethane polymer P obtained by reacting ii. Optionally, at least one catalyst CA; wherein the at least one first polyether polyol PO2 is a grafted polyether polyol obtained by graft copolymerization of styrene and acrylonitrile; the adhesive composition further comprises at least one poly(meth)acrylate AC, comprising 15 to 35 wt. % of the total weight of the adhesive composition; 1. An adhesive composition, wherein the at least one polyester polyol PO1 that is solid at 25°C constitutes 10 to 30% by weight, the at least one first polyether polyol PO2 constitutes 15 to 45% by weight, and the at least one second polyether polyol PO3 constitutes 35 to 65% by weight, each based on the total weight of all polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

2. 2. The adhesive composition according to claim 1, wherein the at least one first polyether polyol PO2 has a solids content at 40°C of 25 to 75% by weight and / or a hydroxyl number, determined in accordance with the ISO 4629-2 standard, of 10 to 100 mg KOH / g.

3. 3. The adhesive composition according to claim 1, wherein the at least one first polyether polyol PO2 is obtained by graft copolymerization of at least one base polyether polyol with one or more ethylenically unsaturated monomers.

4. The adhesive composition of claim 3 , wherein the composition of ethylenically unsaturated monomers comprises at least one acrylic monomer.

5. 5. The adhesive composition of claim 3, wherein the composition of ethylenically unsaturated monomers comprises or consists of at least one acrylic monomer and at least one other ethylenically unsaturated monomer.

6. 6. The adhesive composition according to claim 3, wherein the at least one base polyether polymer is selected from the group consisting of polyoxypropylene polyether polyols, poly(oxyethylene / oxypropylene) polyether polyols, and polyoxyethylene polyether polyols.

7. The at least one polyester polyol PO1 that is solid at 25° C. has a number average molecular weight (M ｎ ), and / or a hydroxyl number determined according to ISO 4629-2 standard of 10 to 75 mg KOH / g, and / or a melting point (T ｍ The adhesive composition according to any one of claims 1 to 6, wherein

8. The adhesive composition according to any one of claims 1 to 7, wherein the at least one polyisocyanate PI is a diisocyanate.

9. Adhesive composition according to any one of the preceding claims, wherein the at least one isocyanate-functional polyurethane polymer P constitutes at least 50% by weight of the total weight of the adhesive composition.

10. The adhesive composition according to any one of claims 1 to 9, further comprising said at least one catalyst CA which catalyzes the reaction of isocyanate groups with water.

11. 11. The adhesive composition of claim 10, wherein the at least one catalyst CA comprises 0.005 to 2.00 wt. % of the total weight of the adhesive composition.

12. Use of the adhesive composition according to any one of claims 1 to 11 for bonding substrates in the manufacture of white goods, automobiles and electronic devices.

13. 1. A method of adhesively bonding a first substrate to a second substrate, comprising: I) heating the adhesive composition according to any one of claims 1 to 11 to provide a molten adhesive composition; II) applying the molten adhesive composition to a surface of the first substrate to form an adhesive film; III) contacting the adhesive film with a surface of the second substrate; IV) chemically curing the adhesive film with water; A method comprising:

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