Moisture-curable polyurethane hot melt adhesives with improved thermal stability

Abstract

The present invention relates to a moisture-curing adhesive composition comprising at least 65% by weight of at least one isocyanate-functional polyurethane polymer P obtained by reacting a) a polyol composition comprising a1) at least one polyester polyol PO1, a2) at least one polyether polyol PO2, and b) at least one polyisocyanate PI, further comprising at least one non-functionalized thermoplastic polymer TP having a softening point, determined by the ring and ball method according to the ISO 4625 standard, of 70-200° C., preferably 75-185° C. The present 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

[Technical field]

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

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

[0003] Moisture-curable polyurethane hot melt adhesives (PUR-RHM) consist of mainly isocyanate-functional polyurethane polymers obtained by reacting suitable polyols, typically polyester and / or polyether polyols, with polyisocyanates, the reaction being 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 extension and / or crosslinking reactions of the polymer. Fully cured polyurethane hot melt adhesives contain urea and / or urethane bonds as well as ester and / or ether bonds depending on the starting materials used to provide the isocyanate-functional polymer. Crosslinked hot melt adhesives do not remelt when subjected to heating. However, compared to adhesives with high crosslink density, such as epoxy or silicone adhesives, moisture-curable polyurethane hot melt adhesives typically have lower heat resistance properties. This disadvantage significantly limits the use of PUR-HM in many applications, especially in bonding components in the automotive, white goods and electronics industries.

[0004] Thus, 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 production of white goods, automotive vehicles, 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 as 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, especially high tensile strength, overlap shear strength and elongation at break, as well as low viscosity at typical application temperatures of hot melt adhesives. [Means for solving the problem]

[0007] Surprisingly, it has been found that these objects can be achieved by means of the features of claim 1.

[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 adhesive composition further comprising at least one non-functionalized thermoplastic polymer having a relatively high softening point.

[0009] Surprisingly, it has been found that the addition of a non-functionalized thermoplastic polymer having a relatively high softening point to an adhesive composition not only improves the thermal stability of the cured adhesive, but also leads to improvements in the mechanical properties of the cured adhesive composition, in particular the tensile and lap shear strength.

[0010] Further subject matter of the invention is set out in the other independent claims. Preferred embodiments of the invention are set out in the dependent claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The subject of the present invention is a) a polyol composition, a1) at least one polyester polyol PO1, and a2) at least one polyether polyol PO2 A polyol composition comprising: b) at least one polyisocyanate PI; and wherein the adhesive composition further comprises at least one non-functionalized thermoplastic polymer TP having a softening point, determined by the ring and ball method according to the ISO 4625-1:2020 standard, of 70 to 200°C, preferably 75 to 185°C, more preferably 85 to 165°C, even more preferably 90 to 145°C, and more preferably 95 to 135°C.

[0012] The prefix "poly" in a material name, such as "polyol" or "polyisocyanate," refers in formal terms to a material that contains more than one per molecule of the functional group present in the name. A polyol, for example, is a compound with two or more hydroxyl groups, and a polyisocyanate is a compound with two or more isocyanate groups.

[0013] The term "polymer" denotes a collection of chemically homogeneous macromolecules produced by polyreactions (polymerization, polyaddition, polycondensation), the macromolecules differing with respect to their degree of polymerization, molecular weight and chain length. The term also includes derivatives of said collection of macromolecules resulting from polyreactions, i.e. compounds obtained by reactions, e.g. addition or substitution, of functional groups on a given macromolecule and which may be chemically homogeneous or chemically non-homogeneous.

[0014] The term "functionalized polymer" refers to a polymer that has been chemically modified to contain functional groups on the polymer backbone. In contrast, the term "non-functionalized 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.

[0015] The term "polyurethane polymer" refers to polymers prepared by the so-called diisocyanate polyaddition process. These also include those polymers which 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 that contains one or more unreacted isocyanate groups. Polyurethane prepolymers can be obtained by reacting an excess of polyisocyanates with polyols, which 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 may be determined by gel permeation chromatography (GPC) using polystyrene as the standard, styrene-divinylbenzene gels with porosity of 100 angstroms, 1000 angstroms and 10000 angstroms as the column, and tetrahydrofuran as the solvent at 35° C. or 1,2,4-trichlorobenzene as the solvent at 160° C. 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 determined by using a method such as that 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 still capable of forming an adhesive bond after coming into contact with another substrate.

[0020] In the present document, the term "amount of at least one component X" in a composition, such as "amount of at least one polyol", refers to the sum of the individual amounts of all polyols contained in the composition.For example, if at least one polyol is a polyester polyol and the composition contains 20% by weight of at least one polyol, the sum of the amounts of all polyester polyols contained in the composition is equal to 20% by weight.

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

[0022] The adhesive composition is preferably a hot melt adhesive composition, more preferably a one-component hot melt adhesive composition. 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 in 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 with at least one polyisocyanate PI. The term "polyol composition" is understood to include all the polyols used to obtain the at least one isocyanate-functional polyurethane polymer P.

[0024] The polyol composition comprises at least one polyester polyol PO1 and at least one polyether polyol PO2.

[0025] Suitable polyester polyols for use as the at least one polyester polyol PO1 include crystalline, partially crystalline, amorphous and liquid polyester polyols, which include dihydric and trihydric alcohols, 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-trimethylol, 1,2,1-triphenylamine ... They can be obtained by reacting thiolpropane or a mixture of the aforementioned alcohols with organic di- or tricarboxylic acids, preferably dicarboxylic acids or their anhydrides or esters, such as succinic acid, glutaric acid, 3,3-dimethylglutaric acid, adipic acid, suberic acid, sebacic acid, undecanediacid, dodecanedicarboxylic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimer fatty acid, isophthalic acid, terephthalic acid and hexahydrophthalic acid or mixtures of the aforementioned acids. Polyester polyols made from lactones, such as ε-caprolactone, also known as polycaprolactone, are also suitable.

[0026] Preferred polyester polyols include those obtained by reacting adipic acid, sebacic acid or dodecanedicarboxylic acid as dicarboxylic acid and hexanediol or neopentyl glycol as dihydric alcohol. Further 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 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 derivatives, 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.

[0027] Preferably, the at least one polyester polyol PO1 is a solid partially crystalline or crystalline polyester polyol at 25°C.

[0028] According to one or more embodiments, the at least one polyester polyol PO1 has a softening point, determined by the ring and ball method according to the ISO 4625-1:2020 standard, of at least 85°C, preferably at least 95°C, more preferably at least 105°C, even more preferably at least 110°C.

[0029] According to one or more embodiments, the at least one polyester polyol PO1 has a softening point, determined by the ring and ball method according to the ISO 4625-1:2020 standard, of 85 to 200°C, preferably 95 to 175°C, more preferably 105 to 155°C, even more preferably 110 to 135°C.

[0030] It has been found that adhesive compositions comprising an isocyanate-functional polyurethane polymer P obtained by reacting a polyisocyanate PI with a polyol composition comprising at least one polyester polyol PO1 having a softening point falling within the above ranges exhibit improved tensile strength and increased heat resistance after curing.

[0031] According to one or more embodiments, the at least one polyester polyol PO1 has a number average molecular weight (M), determined by gel permeation chromatography (GPC) using polystyrene as standard, of 500 to 10,000 g / mol, preferably 1,500 to 5,000 g / mol. n ) and / or has 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.

[0032] Suitable solid partially crystalline and crystalline polyester polyols at 25° C. are commercially available, for example, under the trade name Dynacoll® 7300 series (from Evonik Industries).

[0033] According to one or more embodiments, the polyol composition a) comprises 10 to 50 wt.-%, preferably 15 to 40 wt.-%, more preferably 20 to 35 wt.-% of at least one polyester polyol PO1 solid at 25° C., based on the total weight of the polyol composition a).

[0034] The polyol composition a) further comprises at least one polyether polyol PO2.

[0035] Suitable polyether polyols, also known as polyoxyalkylene polyols, for use as the at least one polyether polyol PO2 are starter molecules having two or more active hydrogen atoms, such as water, ammonia or compounds having two or more OH- or NH- groups, such as 1,2-ethanediol, 1,2- and 1,3-propanediol, neopentyl glycol, diethylene glycol, triethylene glycol, the isomeric dipropylene glycols and tripropylene glycols, the isomeric butanediols, pent ... The polymerization products of ethylene oxide, 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, tetrahydrofuran, or mixtures thereof, optionally polymerized with benzene, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, 1,3- and 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, glycerol, aniline, and mixtures of the foregoing compounds. For example, both polyoxyalkylene polyols having a low degree of unsaturation (measured by ASTM D-2849-69 and expressed as milliequivalents of unsaturation per gram of polyol (meq / g)) produced using double metal cyanide complex catalysts (DMC catalysts) and polyoxyalkylene polyols having a relatively high degree of unsaturation produced, for example, using anionic catalysts such as NaOH, KOH or alkali metal alkoxides can be used.

[0036] Particularly suitable polyether polyols include polyoxyalkylene diols or triols, especially polyoxyethylene diols or triols.

[0037] Particularly suitable are polyoxyalkylene diols or polyoxyalkylene triols, more particularly those having a number average molecular weight (M n) and also polyoxypropylene diols and triols having a number average molecular weight (M n Suitable polyether polyols are commercially available, for example, under the trade names Acclaim®, Desmophene® and Arcol® (all from Covestro).

[0038] According to one or more embodiments, the polyol composition a) comprises 10 to 50 wt.-%, preferably 15 to 40 wt.-%, more preferably 20 to 35 wt.-% of at least one polyether polyol PO2, based on the total weight of the polyol composition a).

[0039] According to one or more embodiments, the at least one polyether polyol PO2 is a liquid polyether polyol at 25° C. having a hydroxyl number, preferably 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.

[0040] The polyol composition a) is a3) at least one liquid polyester polyol PO3 at 25°C It may be preferred to further comprise:

[0041] According to one or more embodiments, at least one liquid polyester polyol PO3 at 25° C. has a number average molecular weight (M) determined by gel permeation chromatography (GPC) using polystyrene as standard of 500 to 5000 g / mol, preferably 1000 to 3500 g / mol. n ) and / or has a hydroxyl number, determined according to the ISO 4629-2 standard, of 25 to 150 mg KOH / g, preferably 35 to 100 mg KOH / g.

[0042] According to one or more embodiments, the at least one liquid polyester polyol PO3 at 25° C. is an aromatic polyester polyol, preferably a phthalic anhydride diethylene glycol polyester polyol.

[0043] According to one or more embodiments, the polyol composition a) comprises 10 to 50 wt.-%, preferably 15 to 40 wt.-%, more preferably 20 to 35 wt.-% of at least one liquid polyester polyol PO3 at 25° C., based on the total weight of the polyol composition a).

[0044] 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. Non-monomeric diisocyanates, such as oligomeric and polymeric products of monomeric diisocyanates, such as adducts of monomeric diisocyanates, are also suitable, but the use of monomeric diisocyanates is preferred.

[0045] The term "monomer" refers to a molecule having at least one polymerizable group. Monomeric diisocyanates or polyisocyanates in particular do not contain urethane groups. In the context of the present invention, oligomeric or polymeric products of diisocyanate monomers, such as adducts of monomeric diisocyanates, are not monomeric diisocyanates.

[0046] An isocyanate is referred to as "aliphatic" when its isocyanate group is directly attached to an aliphatic, cycloaliphatic, or arylaliphatic moiety. The corresponding functional group is therefore referred to as an aliphatic isocyanate group. An isocyanate is referred to as "aromatic" when its isocyanate group is directly attached to an aromatic moiety. The corresponding functional group is therefore referred to as an aromatic isocyanate group.

[0047] 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) determined by gel permeation chromatography (GPC) using polystyrene as standard 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:

[0048] 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 cyclohexane ester diisocyanate. 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-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, isocyanato-2,2,6-trimethylcyclohexane (TMCDI), 1,3- and 1,4-bis(isocyanato-methyl)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 These include 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate 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).

[0049] 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 products of diisocyanates 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).

[0050] Preferably, at least one 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 indicates the average number of isocyanate (NCO) groups per molecule. The average NCO functionality of a compound can be determined by using a method such as that defined in ISO14896-2006 standard method A.

[0051] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer P has an average isocyanate functionality of 1.1 to 3.5, preferably 1.5 to 3, more preferably 1.8 to 2.5.

[0052] Preferably, the adhesive composition comprises at least 50% by weight, more preferably at least 65% by weight, even more preferably at least 75% by weight, and also more preferably at least 85% by weight of at least one isocyanate-functional polyurethane polymer P, based on the total weight of the adhesive composition.

[0053] According to one or more embodiments, the adhesive composition comprises 50-95 wt.-%, preferably 60-90 wt.-%, more preferably 65-85 wt.-%, even more preferably 70-85 wt.-% of at least one isocyanate-functional polyurethane polymer P, based on the total weight of the adhesive composition.

[0054] The adhesive composition comprises at least one isocyanate-functional polyurethane polymer P as well as at least one non-functionalized thermoplastic polymer TP.

[0055] Surprisingly, it has been found that the decrease in storage modulus of the cured polyurethane adhesive composition can be shifted to higher temperatures by using a non-functionalized thermoplastic polymer with a relatively high softening temperature as a rheology modifier in the adhesive composition. The addition of the functionalized thermoplastic polymer not only results in improved thermal stability (which can be seen as improved lap shear strength at higher temperatures), but also has a positive effect on the adhesive properties at normal room temperature, especially with regard to increased tensile strength and lap shear strength.

[0056] According to one or more embodiments, the adhesive composition comprises 2.5-30 wt.-%, preferably 5-25 wt.-%, more preferably 7.5-25 wt.-%, even more preferably 7.5-20 wt.-%, and even more preferably 10-20 wt.-% of at least one non-functionalized thermoplastic polymer TP, based on the total weight of the hot melt adhesive composition.

[0057] According to one or more embodiments, the at least one non-functionalized thermoplastic polymer TP comprises at least one poly(meth)acrylate AC and / or at least one thermoplastic polyurethane TPU.

[0058] In general, the expression "at least one component X comprises at least one component XN", e.g. "at least one thermoplastic polymer TP comprises at least one poly(meth)acrylate AC", is understood in the context of the present disclosure to mean that the composition comprises one or more poly(meth)acrylates AC as representatives of the at least one thermoplastic polymer TP.

[0059] Thermoplastic polyurethanes (TPUs) are polyurethane-based thermoplastic elastomers (TPEs) that are linear, segmented block copolymers composed of alternating hard and soft segments or domains formed by the reaction of (1) diisocyanates with short-chain diols (so-called chain extenders) and (2) diisocyanates with longer-chain diols.

[0060] The term "(meth)acrylate" in the context of the present invention denotes methacrylate or acrylate. The term "poly(meth)acrylate" refers to homopolymers, copolymers and higher interpolymers of (meth)acrylate monomers with one or more further (meth)acrylate monomers and / or one or more further monomers.

[0061] It may be preferred that the (meth)acrylate monomers do 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 have further functional groups.

[0062] Suitable (meth)acrylate monomers include, for example, 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.

[0063] 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.

[0064] Further suitable comonomers for the synthesis of at least one poly(meth)acrylate AC include vinyl compounds, such as ethylenically unsaturated hydrocarbons with functional groups, vinyl esters, vinyl halides, vinylidene halides, nitriles of ethylenically unsaturated hydrocarbons, phosphoric 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, beta-acryloyloxypropionic acid, vinylacetic acid, fumaric acid, crotonic acid, aconitic acid, trichloroacrylic acid, itaconic acid and maleic acid and their amides.

[0065] Particularly suitable poly(meth)acrylates include, for example, homopolymers and copolymers obtained by 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 further comonomer.

[0066] 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).

[0067] According to one or more embodiments, the at least one poly(meth)acrylate AC is an acid number, determined according to the EN ISO 2114 standard, of less than or equal to 25 mg KOH / g, preferably less than or equal to 15 mg KOH / g, more preferably less than or equal to 10 mg KOH / g, and / or - a weight average molecular weight (M) determined by gel permeation chromatography (GPC) using polystyrene as standard of 15000 to 100000 g / mol, preferably 25000 to 65000 g / mol; w ), and / or - a glass transition temperature (T) determined according to the ISO 11357-1:2016 standard, greater than or equal to 0 °C, preferably greater than or equal to 35 °C g ) has.

[0068] According to one or more embodiments, the at least one non-functionalized thermoplastic polymer TP is composed of at least one poly(meth)acrylate AC.

[0069] According to one or more embodiments, the at least one non-functionalized thermoplastic polymer TP comprises at least one thermoplastic polyurethane TPU.

[0070] Thermoplastic polyurethanes have been found to be particularly suitable for use as rheology modifiers to improve the heat resistance of the cured adhesive composition.

[0071] According to one or more embodiments, the at least one thermoplastic polyurethane TPU has a glass transition temperature, determined according to the ISO11357-1:2016 standard, of 0°C or less, preferably -5°C or less, more preferably -10°C or less, even more preferably -15°C or less.

[0072] According to one or more embodiments, the at least one non-functionalized thermoplastic polymer TP is composed of at least one thermoplastic polyurethane TPU.

[0073] According to one or more embodiments, the at least one non-functionalized thermoplastic polymer TP comprises at least one poly(meth)acrylate AC and at least one thermoplastic polyurethane TPU, the weight ratio of the amount of the at least one poly(meth)acrylate AC to the amount of the at least one thermoplastic polyurethane TPU being in the range of 5:1 to 1:5, preferably 3:1 to 1:3, more preferably 2:1 to 1:2.

[0074] 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.

[0075] 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), 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.

[0076] Further examples of suitable catalysts include compounds containing amine groups, such as dimorpholino dialkyl ethers and / or dimorpholino substituted polyalkylene glycols, such as 2,2'-dimorpholino diethyl 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 with one or more morpholine amine compounds.

[0077] According to one or more embodiments, the adhesive composition comprises 0.005-2.00 wt. %, preferably 0.05-1.00 wt. %, of at least one catalyst CA, based on the total weight of the adhesive composition.

[0078] The adhesive composition of the present invention 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 desiccants.

[0079] Examples of suitable ultraviolet light 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.

[0080] Suitable fillers include inorganic and organic fillers, in particular natural, ground or precipitated calcium carbonate, optionally coated with fatty acids or fatty acid esters, in particular stearic acid, barite, 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, polyvinyl chloride powders, and hollow spheres.

[0081] The total amount of such auxiliary substances and additives is preferably not more than 15% by weight, more preferably not more than 10% by weight, based on the total weight of the adhesive composition.

[0082] According to one or more embodiments, the adhesive composition comprises: A) providing a polyol composition a) and at least one non-functionalized thermoplastic polymer TP in a reactor; B) adding at least one isocyanate PI to the mixture obtained from step A) and reacting, optionally 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, and a reaction mixture comprising at least one isocyanate-functional polyurethane polymer P is obtained.

[0083] 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 2.75, preferably between 1.5 and 2.5.

[0084] The reaction carried out in step B) converts substantially all of the hydroxyl groups of the polyol composition a), for example at least 95%, preferably at least 99%, of the hydroxyl groups of the polyol a) composition.

[0085] 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).

[0086] The reaction in step B) may be carried out by conventional methods used for the preparation of isocyanate-functional polyurethane polymers. The reaction may be carried out in the presence of a catalyst at a temperature ranging, for example, from 50 to 160° C., preferably from 60 to 120° C. The reaction time depends on the temperature used and may range, for example, 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 in step B) include, for example, metal catalysts, such as Coscat® 83 (from Vertellus Performance Materials Inc.) and tin catalysts.

[0087] The adhesive composition of the present invention is a moisture-curable adhesive composition, that is, the adhesive composition can be cured by contacting the composition with water, especially atmospheric moisture.

[0088] 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 application temperatures the adhesive has a sufficiently low viscosity in the molten state to allow application to a substrate. The adhesive composition also develops high initial strength upon cooling immediately after application to a substrate, even before the initiation of crosslinking reactions with water, particularly atmospheric moisture.

[0089] According to one or more embodiments, the adhesive composition has a viscosity of 25000 mPa·s or less, preferably 20000 mPa·s or less, more preferably 15000 mPa·s or less, even more preferably 12500 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 number 27, preferably by Thermosel System for temperature control.

[0090] According to one or more embodiments, the adhesive composition has a softening point, measured by the ring and ball method according to standard 4625-1:2020, in the range of 40 to 165°C, preferably 45 to 135°C, more preferably 50 to 105°C.

[0091] The preferences given above for the isocyanate-functional polyurethane polymer P, the polyol composition, the polyester polyol PO1, the polyether polyol PO2, the polyester polyol PO3, the non-functionalized thermoplastic polymer TP and the catalyst CA apply equally to all subjects of the present invention, unless otherwise stated.

[0092] Another subject of the invention is the use of the adhesive composition of the invention for bonding substrates in the production of white goods, motor vehicles and electronic devices. Suitable electronic devices include, for example, displays, mobile phones, smart watches and audio devices.

[0093] Another subject of the invention is a method for adhesively bonding a first substrate to a second substrate, the method 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; Includes.

[0094] The first and second substrates may be sheet-like articles or three-dimensional shaped articles having first and second major surfaces defined by peripheral edges and defining a thickness therebetween.

[0095] In a method of 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, for example, by using slot die coating, roller coating, extrusion coating, calendar coating or spray coating. The adhesive composition may, for example, be applied in a thickness of 25 to 750 g / m 2 , preferably 35 to 650 g / m 2 , more preferably 45 to 550 g / m 2 , and even more preferably 50 to 500 g / m 2 may be applied to the surface of the first substrate with a coating weight of

[0096] After the adhesive film is contacted with the surface of the second substrate, the adhesive composition undergoes physical hardening, i.e., cooling, to produce a certain initial adhesive strength. Depending on the application temperature and the embodiment of the adhesive composition, in particular the reactivity of the adhesive, the chemical hardening reaction may already begin during the application of the adhesive composition on the surface of the first substrate. Typically, however, most of the chemical hardening occurs after the application of the adhesive, in particular after the applied adhesive film is contacted with the surface of the second substrate.

[0097] The first and second substrates may be made of any conventional material, including polymeric materials, metals, painted metals, glass, wood, wood-derived materials, such as natural fiber polypropylene (NFPP), and fibrous materials. Suitable polymeric materials include, for example, polyethylene (PE), in particular 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 made of a single layer or multiple layers of different types of materials. The layers made of polymeric materials may further contain additives, such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes, and biocides.

[0098] Another subject of the invention is a composite component obtainable by using the method of the invention for adhesively bonding a first substrate to a second substrate. EXAMPLES

[0099] The following compounds and products shown in Table 1 were used in the examples.

[0100] [Table 1]

[0101] The adhesive compositions set forth in Table 2 were prepared according to the procedures set forth below.

[0102] Preparation of Adhesive Composition A solid polyester polyol (PO1), a liquid polyether polyol (PO2), a liquid polyester polyol (PO3) and a non-functionalized thermoplastic polymer (TP) were charged into a stainless steel reactor.

[0103] The mixture was kept 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 nitrogen blanket. The starting mixture thus obtained 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. A catalyst (CA) was then added to the reaction product under nitrogen blanket. After mixing under vacuum for 45 minutes, the obtained adhesive composition was stored at room temperature with the exclusion of moisture.

[0104] Measurement method The adhesive compositions were characterized using the following measurement methods:

[0105] Viscosity at 110℃ The sample adhesive composition provided in a sealed tube was preheated in an oven at a temperature of 110° C. for a period of 30 minutes. After heating, a sample of 12.3 g of adhesive composition was weighed and placed in a disposable sleeve of the viscometer. The viscosity was measured at a temperature of 110° C. and 5 revolutions per minute using a Brookfield DV-2 viscometer with spindle number 27 equipped with a Thermosel system. The value obtained after 20 minutes of tempering and 5 minutes of measurement at the measurement temperature was recorded as the representative viscosity.

[0106] Open Time The sample adhesive composition provided in a sealed tube was first preheated in an oven at a temperature of 110° C. for a period of 30 minutes. After heating, a 20 g sample of the molten adhesive was applied with a doctor blade to the surface of a silicone paper strip (B700 white, Laufenberg&Sohn KG) placed on a heated plate. The silicone paper strip had dimensions of 30 cm×10 cm, and the adhesive was applied as a film with a thickness of 500 μm and dimensions of 30 cm×6 cm. Before applying the adhesive film, the silicone paper strip and the doctor blade were heated with a heated plate to a temperature of 110° C.

[0107] Immediately after application of the adhesive, the silicone paper strip was removed from the heating plate and placed on a sheet of plywood at room temperature (23°C) (with the adhesive film facing up), this time was recorded as the starting point of the measurement. Every 10 seconds, a short strip of silicone-coated paper with dimensions of 10 cm x 1 cm and formed into a roll (with the non-siliconized surface facing outwards) was placed on the adhesive film and then slowly removed, separating the strip from the adhesive film. This procedure was repeated until the paper strip could no longer be removed from the adhesive film without damaging the paper strip or the adhesive film. The time interval between the starting point of the measurement and the last sampling point was recorded as the open time (seconds) of the adhesive composition.

[0108] The open time values ​​presented in Table 2 were obtained as the average of three measurements made with the same adhesive composition.

[0109] Tensile strength and elongation at break The adhesive composition provided in a sealed tube was preheated in an oven at a temperature of 110° C. for a period of 30 minutes. After heating, a 40 g sample of the molten adhesive was applied with a doctor blade to the surface of a silicone paper strip (B700 white, Laufenberg&Sohn KG) placed on a hot plate. The silicone paper had dimensions of 60 cm×10 cm and the adhesive was applied as a film with a thickness of 500 μm and dimensions of 60 cm×6 cm. Immediately after application of the adhesive, the silicone paper strip was removed from the hot plate and stored at standard climatic conditions (23° C., 55% relative humidity) for a period of 7 days.

[0110] Measurements were carried out using a method based on the DIN53504 standard. Five rectangular test specimens with dimensions of 2.0 cm x 8.0 cm were cut from the cured adhesive film (cured for 14 days at 23°C / 50% relative humidity) with a thickness of 500 μm. The test specimens were clamped in a tensile tester (Zwick Z020) and pulled apart at a speed 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.

[0111] The tensile strength and elongation at break values ​​presented in Table 2 were obtained as the average of five measurements made on the same adhesive composition.

[0112] Tensile Lap Shear Strength (LSS) The adhesive composition provided in a sealed tube was preheated in an oven at a temperature of 110° C. After heating, a sample of the molten adhesive was applied onto the surface of a polycarbonate (PC) substrate having dimensions of 9 cm×2 cm×5 mm. The adhesive was applied as a film having dimensions of 2.5 cm×1 cm and a thickness of 1 mm.

[0113] Immediately after application of the adhesive, a second PC substrate having the same dimensions as the first PC specimen was placed on the first PC substrate along the edge of the adhesive film to form a test composite. The second PC substrate was pressed firmly against the first PC specimen to remove air from the adhesive bond. A 150 g weight was placed on the upper surface of the second PC substrate. The excess adhesive from the bond was cut off with a knife. The test composite was stored at standard climatic conditions (23° C., 55% relative humidity) for a period of 7 days, after which the overlap shear strength was measured.

[0114] The overlap shear strength was measured according to the EN1465 standard using a material testing machine (Zwick Z020) and a test speed of 10 mm / min. The overlap shear strength obtained after subjecting the test composite components to artificial aging treatment (500 hours at 65°C and 85°C) was also measured to determine the heat and humidity stability of the tested adhesive compositions.

[0115] The overlap shear strength values ​​for each adhesive composition presented in Table 2 were obtained as the average of three measurements made with the same test composite prepared using the same adhesive composition.

[0116] [Table 2]

Claims

1. a) a polyol composition, a1) at least one polyester polyol PO1, a2) at least one polyether polyol PO2 a polyol composition comprising: b) at least one polyisocyanate PI; and 1. An adhesive composition comprising at least 65% by weight of at least one isocyanate-functional polyurethane polymer P obtained by reacting The adhesive composition further comprises at least one non-functionalized thermoplastic polymer TP having a softening point, determined by the ring and ball method according to standard ISO 4625-1:2020, of 70 to 200°C, preferably 75 to 185°C.

2. 2. The adhesive composition according to claim 1, wherein the at least one polyester polyol PO1 has a softening point, determined by the ring and ball method according to standard ISO 4625-1:2020, of at least 85°C, preferably at least 95°C.

3. 3. The adhesive composition according to claim 1, wherein the at least one polyether polyol PO2 is a liquid polyether polyol 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.

4. The polyol composition a) is a3) at least one liquid polyester polyol PO3 at 25°C The adhesive composition of claim 1 or 2, further comprising:

5. 5. The adhesive composition according to claim 4, wherein the at least one liquid polyester polyol PO3 at 25°C is an aromatic polyester polyol, preferably a phthalic anhydride diethylene glycol polyester polyol.

6. The at least one polyisocyanate PI is a diisocyanate, preferably a monomeric diisocyanate, preferably having 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 3. The adhesive composition according to claim 1 or 2, wherein

7. 3. The adhesive composition according to claim 1, comprising at least 75% by weight of said at least one isocyanate-functional polyurethane polymer P, based on the total weight of said adhesive composition.

8. 3. The adhesive composition according to claim 1, comprising 2.5 to 30 wt. %, preferably 5 to 25 wt. %, of said at least one non-functionalized thermoplastic polymer TP, based on the total weight of the hot melt adhesive composition.

9. The adhesive composition according to claim 1 , wherein the at least one non-functionalized thermoplastic polymer TP comprises at least one poly(meth)acrylate AC and / or at least one thermoplastic polyurethane TPU.

10. 10. The adhesive composition according to claim 9, wherein the at least one poly(meth)acrylate AC preferably has an acid number, determined according to the EN ISO 2114 standard, of less than or equal to 25 mg KOH / g, preferably less than or equal to 10 mg KOH / g.

11. 10. The adhesive composition according to claim 9, wherein the at least one thermoplastic polyurethane TPU has a glass transition temperature, determined according to the ISO 11357-1:2016 standard, of 0°C or less, preferably -5°C or less.

12. Adhesive composition according to any one of claims 9 to 11, wherein said at least one non-functionalized thermoplastic polymer TP consists of said at least one thermoplastic polyurethane TPU.

13. 3. The adhesive composition of claim 1, further comprising at least one catalyst CA that catalyzes the reaction of isocyanate groups with water.

14. 14. The adhesive composition of claim 13, comprising 0.005 to 2.00 wt. %, preferably 0.05 to 1.00 wt. %, of said at least one catalyst CA, based on the total weight of the adhesive composition.

15. 3. Use of the adhesive composition according to claim 1 or 2 for bonding substrates in the production of white goods, motor vehicles and electronic devices.

16. 1. A method of adhesively bonding a first substrate to a second substrate, comprising: I) heating the adhesive composition of claim 1 or 2 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:

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