Moisture-curable polyurethane hot melt adhesive with improved early strength

Abstract

The present invention relates to a moisture-curing adhesive composition comprising at least one isocyanate-functional polyurethane polymer P obtained by reacting a) a polyol composition comprising a1) at least one polyester polyol PO1 solid at 25° C. and a2) at least one polyether polyol PO2 with b) at least one polyisocyanate PI, said at least one polyether polyol PO2 having a hydroxyl number of at least 100 mg KOH / g, preferably at least 150 mg KOH / g, measured according to standard ISO 4629-2:2016. The present invention also relates to the use of said adhesive composition as an assembly adhesive, lamination adhesive or as an adhesive for assembling sandwich elements, in particular as an interior lamination adhesive in the automotive industry.

Description

[Technical field]

[0001] The present invention relates to reactive polyurethane hot melt adhesives having improved early strength and the use of the adhesives to bond substrates in the manufacture 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 molten form to the substrates to be joined. After cooling, the adhesive solidifies and forms an adhesive bond with the substrates 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 of the polymer chains. Due to the chemically cured polymer matrix, the reacted 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 or by exposure of the adhesive composition to water, such as atmospheric moisture. Moisture-curing hot melt adhesives typically contain polymers functionalized with isocyanate or silane groups, which allow crosslinking of the polymer chains when exposed to atmospheric moisture.

[0003] Moisture-curable polyurethane hot melt adhesives (PUR-RHM) consist mainly of isocyanate-functional polyurethane polymers, obtained by reaction of suitable polyols, typically polyester and / or polyether polyols, with polyisocyanates, the reaction being carried out with a molar excess of isocyanate (NCO) groups relative to hydroxyl (OH) groups. The adhesive composition cures by reaction of the residual isocyanate groups with water, which leads to various chain extension and / or crosslinking reactions of the polymer. Fully cured polyurethane hot melt adhesives contain urea and / or urethane bonds and, depending on the starting materials used to obtain the isocyanate-functional polymer, ester and / or ether bonds. Crosslinked hot melt adhesives do not remelt when heated and therefore typically have very good thermal stability. However, some PUR-RHM adhesives show a more or less gradual increase in adhesive bond strength, which can be a major disadvantage, especially in automotive lamination applications. Summary of the Invention [Problem to be solved by the invention]

[0004] Thus, there is a need for a new class of moisture-curable polyurethane hot melt adhesives that have improved initial bond strength, which are particularly suitable for use in automotive interior lamination applications. [Means for solving the problem]

[0005] It is an object of the present invention to provide an adhesive composition that overcomes, or at least mitigates, the disadvantages of the prior art moisture-curable polyurethane hot melt adhesives 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 initial adhesive strength. The cured adhesive composition should preferably also have very good properties, in particular high lap shear strength, and low viscosity at typical application temperatures for hot melt adhesives.

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

[0008] The gist of the present invention is a new type of moisture-curable polyurethane hot melt adhesive composition comprising at least one isocyanate-functional polyurethane polymer obtained by the reaction of a polyol composition with a polyisocyanate, the polyol composition comprising a low molecular weight polyether polyol having a high hydroxyl number.

[0009] Surprisingly, it has been found that the addition of a low molecular weight polyether polyol to an adhesive composition significantly improves the initial (green) adhesive strength of the adhesive composition.

[0010] Further subject matter of the invention is set out in the further 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 that is solid at 25° C., and a2) at least one polyether polyol PO2 A polyol composition comprising: b) at least one polyisocyanate PI; an adhesive composition comprising at least one isocyanate-functional polyurethane polymer P obtained by reacting The at least one polyether polyol PO2 has a hydroxyl number of at least 100 mg KOH / g, preferably at least 150 mg KOH / g, measured according to standard ISO 4629-2:2016, of the adhesive composition.

[0012] The prefix "poly" in the names of substances such as "polyol" or "polyisocyanate" refers, in official terms, to substances that contain more than one of the functional groups appearing in the name per molecule. For example, a polyol 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" refers to a set of chemically homogeneous macromolecules produced by polyreactions (polymerization, polyaddition, polycondensation) that differ with respect to their degree of polymerization, molecular weight and chain length. The term also includes derivatives of said set of macromolecules obtained by polyreactions, i.e. compounds obtained by reactions such as, for example, addition or substitution of functional groups in a predetermined macromolecule, which may be chemically homogeneous or chemically heterogeneous.

[0014] The term "polyurethane polymer" refers to polymers prepared by the so-called diisocyanate polyaddition process. These also 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.

[0015] 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.

[0016] The term "molecular weight" refers to the molar mass (g / mol) of a molecule or a part 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 standards, styrene-divinylbenzene gels with porosity of 100 angstroms, 1000 angstroms, and 10000 angstroms as columns, and tetrahydrofuran as a solvent at 35° C. or 1,2,4-trichlorobenzene as a solvent at 160° C., depending on the molecule.

[0017] 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 the method specified in the standard DIN 53 240-2.

[0018] The term "open time" refers to the length of time that an adhesive applied to a substrate surface is still capable of forming an adhesive bond after being contacted with another substrate.

[0019] 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, then the sum of the amounts of all polyester polyols contained in the composition is 20% by weight.

[0020] The term "room temperature" means a temperature of about 23°C.

[0021] 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 means a composition in which all components of the composition are stored as one mixture in the same container or compartment.

[0022] The adhesive composition comprises at least one isocyanate-functional polyurethane polymer P obtained by reaction of 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.

[0023] Preferably, the adhesive composition comprises: c) further comprising at least one thermoplastic polymer TP having a melting point of 45 to 150°C, preferably 50 to 125°C, more preferably 50 to 100°C, even more preferably 55 to 90°C, even more preferably 55 to 80°C, measured by differential scanning calorimetry (DSC) in accordance with standard ISO 11357-3:2018.

[0024] It has been found that adhesive compositions comprising at least one isocyanate-functional polymer P obtained using a polyol composition comprising at least one polyether polyol PO2 and at least one thermoplastic polymer TP have improved initial adhesive strength properties compared to prior art polyurethane-based moisture-curing hot melt adhesives.

[0025] The polyol composition comprises at least one polyester polyol PO1 which is solid at 25° C. and at least one polyether polyol PO2.

[0026] Suitable polyester polyols for use as the at least one polyester polyol PO1 include crystalline, partially crystalline and amorphous 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-trimethylol, 1,1,1-triphenylphosphine ... Polyester polyols can be obtained by reacting dimethylolpropane, or a mixture of 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, undecane diacid, dodecane diacid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimer fatty acid, isophthalic acid, terephthalic acid, and hexahydrophthalic acid, or mixtures of acids. Polyester polyols made from lactones, such as ε-caprolactone, also known as polycaprolactone, are also suitable.

[0027] Preferred polyester polyols include those obtained by reaction of adipic acid, sebacic acid or dodecanedicarboxylic acid as dicarboxylic acid with 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.

[0028] According to one or more embodiments, the at least one polyester polyol PO1 that is solid at 25° C. has a softening point of at least 55° C., preferably at least 65° C., more preferably at least 75° C., measured by the Ring and Ball method according to standard ISO 4625-1:2020.

[0029] According to one or more embodiments, the at least one polyester polyol PO1 solid at 25° C. is: - a hydroxyl number between 10 and 60 mg KOH / g, preferably between 15 and 50 mg KOH / g, measured according to standard ISO 4629-2:2016, and / or - It has a softening point of 55 to 165°C, preferably 65 to 135°C, more preferably 75 to 105°C, as measured by the Ring and Ball method according to standard ISO 4625-1:2020.

[0030] According to one or more embodiments, the at least one polyester polyol PO1 has a number average molecular weight (M) of 500 to 10,000 g / mol, preferably 1,500 to 5,000 g / mol, as measured by gel permeation chromatography (GPC) using polystyrene as a standard. n ), and / or a hydroxyl number of 10 to 75 mg KOH / g, preferably 15 to 55 mg KOH / g, measured according to standard ISO 4629-2.

[0031] Partially crystalline, crystalline, and amorphous polyester polyols solid at 25° C. suitable for use as at least one PO1 are commercially available, for example, under the trade names Dynacoll® 7100- and 7300-series (Evonik Industries).

[0032] According to one or more embodiments, the polyol composition a) comprises at least 35% by weight, preferably at least 50% by weight, more preferably at least 65% by weight, of at least one polyester polyol PO1 that is solid at 25° C., based on the total weight of the polyol composition a).

[0033] The polyol composition a) further comprises at least one polyether polyol PO2 having a hydroxyl number, measured according to standard ISO 4629-2:2016, of at least 100 mg KOH / g, preferably at least 150 mg KOH / g, more preferably at least 200 mg KOH / g, even more preferably at least 250 mg KOH / g.

[0034] According to one or more embodiments, the at least one polyether polyol PO2 has a hydroxyl number, measured according to standard ISO 4629-2:2016, of 150 to 1000 mg KOH / g, preferably 200 to 750 mg KOH / g, more preferably 250 to 500 mg KOH / g, even more preferably 275 to 500 mg KOH / g.

[0035] According to one or more embodiments, the at least one polyether polyol PO2 is a melting point of 45 to 100°C, preferably 50 to 90°C, more preferably 55 to 80°C, measured by differential scanning calorimetry (DSC) according to standard ISO 11357-3:2018, and / or - having a molecular weight of less than or equal to 1000 g / mol, preferably less than or equal to 750 g / mol, more preferably less than or equal to 500 g / mol, in particular between 150 and 1000 g / mol, preferably between 200 and 750 g / mol, more preferably between 250 and 500 g / mol, as measured by gel permeation chromatography (GPC) using polystyrene as the standard.

[0036] According to one or more preferred embodiments, the at least one polyether polyol PO2 is a polyether diol, preferably an aromatic polyether diol. Suitable polyether diols are commercially available, for example, under the trade name Dianol (from Arkema).

[0037] According to one or more embodiments, the at least one polyether polyol PO2 preferably has the formula (I) [ka] (wherein y and y each independently represent an integer in the range of 1 to 5) is an alkylene oxide adduct of bisphenol A.

[0038] Suitable alkylene oxide adducts of bisphenol A of formula (I) are commercially available, for example, under the trade name Dow Resin 565 (from Dow Chemicals), Dianol (from Arkema), and Synfac Polyols (from Milliken Chemicals).

[0039] According to one or more preferred embodiments, the at least one polyether polyol PO2 is a compound of formula (I) in which x and y have the value 1.

[0040] According to one or more embodiments, the polyol composition a) comprises 1.5 to 45 wt.-%, preferably 2.5 to 35 wt.-%, more preferably 5 to 25 wt.-%, even more preferably 10 to 20 wt.-% of at least one polyether polyol PO2, based on the total weight of the polyol composition a).

[0041] According to one or more embodiments, the polyol composition a) comprises: a3) further comprising at least one polyester polyol PO3 which is liquid at 25°C.

[0042] According to one or more embodiments, the at least one polyester polyol PO3 that is liquid at 25° C. is: a hydroxyl number between 10 and 60 mg KOH / g, preferably between 15 and 50 mg KOH / g, measured according to standard ISO 4629-2:2016, and / or - have a glass transition temperature (Tg) of less than or equal to 0°C, preferably less than or equal to -15°C, measured in accordance with standard ISO 11357-1:2016;

[0043] According to one or more embodiments, the polyol composition a) comprises 5 to 50 wt.-%, preferably 10 to 40 wt.-%, more preferably 15 to 45 wt.-%, based on the total weight of the polyol composition a), of at least one polyester polyol PO3 that is liquid at 25° C.

[0044] 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.

[0045] The term "monomer" refers to a molecule having at least one polymerizable group. Monomeric diisocyanates or polyisocyanates specifically do not include urethanes. 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] If the isocyanate group is attached directly 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 attached directly to an aromatic moiety, the isocyanate is called "aromatic." The corresponding functional group is therefore called an aromatic isocyanate group.

[0047] According to one or more embodiments, the at least one polyisocyanate PI has 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, as measured by gel permeation chromatography (GPC) using a diisocyanate, preferably a monomeric diisocyanate, more preferably polystyrene as the standard. 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 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-diiso Cyanato-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 mixtures of these isomers. 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 these isomers (MDI), 2,4- and 2,6-tolylene diisocyanate and mixtures of these isomers (TDI), 1,6-hexamethylene diisocyanate (HDI), and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). Furthermore, the skilled person knows that technical grade products of diisocyanates often 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 less than or equal to 3.5, preferably less than or equal to 3.0. The term "average NCO functionality" in this disclosure means the average number of isocyanate (NCO) groups per molecule. The average NCO functionality of a compound can be determined using the method specified in method A of standard ISO 14896-2006.

[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, even more preferably at least 80% 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 65-90 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 thermoplastic polymer TP.

[0055] According to one or more embodiments, the adhesive composition comprises 2.5-30 wt.-%, preferably 5-30 wt.-%, more preferably 5-25 wt.-%, even more preferably 10-25 wt.-% of at least one thermoplastic polymer TP, based on the total weight of the hot melt adhesive composition.

[0056] According to one or more preferred embodiments, the at least one thermoplastic polymer TP comprises at least one thermoplastic polyurethane TPU.

[0057] In general, the expression "at least one component X comprises at least one component XN", such as "at least one thermoplastic polymer TP comprises at least one thermoplastic polyurethane TPU", is understood in the context of the present disclosure to mean that the composition comprises one or more thermoplastic polyurethanes TPU as representatives of the at least one thermoplastic polymer TP.

[0058] Thermoplastic polyurethanes (TPUs) are polyurethane-based thermoplastic elastomers (TPEs) that are linear segmented block copolymers formed of alternating hard and soft segments or domains formed by the reaction of (1) diisocyanates with short chain diols (so-called chain extenders) with (2) diisocyanates with long chain diols.

[0059] Thermoplastic polyurethanes have been found to be particularly suitable for use as rheology modifiers to improve the heat resistance of the cured adhesive composition.

[0060] According to one or more embodiments, the at least one thermoplastic polyurethane TPU is a polycaprolactone-copolyester polyurethane.

[0061] According to one or more embodiments, the at least one thermoplastic polymer TP is composed of at least one thermoplastic polyurethane TPU.

[0062] 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.

[0063] Examples of suitable catalysts include metal-based catalysts, such as dialkyltin complexes, in particular dibutyltin(IV) or dioctyltin(IV) carboxylates or acetoacetonates, for example dibutyltin dilaurate (DBTDL), dibutyltin diacetylacetonate, dioctyltin dilaurate (DOTDL), further bismuth(III) complexes, for example bismuth octoate or bismuth neodecanoate, zinc(II) complexes, for example zinc octoate or zinc neodecanoate, and zirconium(IV) complexes, for example zirconium octoate or zirconium neodecanoate.

[0064] 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. A combination of two or more catalysts can also be used, with combinations comprising one or more metal catalysts and one or more morpholine amine compounds being preferred.

[0065] 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.

[0066] The adhesive composition of the present invention may further comprise auxiliary substances and additives selected from the group consisting of, for example, fillers, plasticizers, adhesion promoters, UV absorbers, UV and heat stabilizers, flame retardants, optical brighteners, pigments, dyes, and drying agents.

[0067] 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, phenylformiamidines, and mixtures thereof.

[0068] Suitable fillers include inorganic and organic fillers, in particular natural ground or precipitated calcium carbonate, optionally coated with a fatty acid or fatty acid ester, in particular stearic acid, barite, talc, quartz flour, silica sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieves, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica, such as finely divided pyrogenic silica, industrially produced carbon black, graphite, powders of metals such as aluminum, copper, iron, silver, steel, polyvinyl chloride powder, and hollow spheres.

[0069] 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.

[0070] According to one or more embodiments, the adhesive composition comprises: A) feeding a polyol composition a) and at least one thermoplastic polymer TP into a reactor; B) adding at least one isocyanate PI to the mixture obtained in step A) and reacting, optionally in the presence of one or more catalysts, to obtain a reaction mixture comprising at least one isocyanate-functional polyurethane polymer P, the molar ratio between isocyanate groups and hydroxyl groups being at least 1.1, preferably at least 1.3; The method is obtained by a method comprising the steps of:

[0071] 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.

[0072] In the reaction carried out in step B), substantially all the hydroxyl groups of the polyol composition a) are converted, for example at least 95%, preferably at least 99%, of the hydroxyl groups of the polyol a) composition.

[0073] Preferably, the starting mixture provided in step A) is dehydrated under vacuum at a temperature equal to or greater than 120° C. before carrying out step B).

[0074] The reaction in step B) can be carried out by conventional methods used for the preparation of isocyanate-functional polyurethane polymers. The reaction can be carried out, for example, at a temperature in the range of 50 to 160°C, preferably 60 to 120°C, optionally in the presence of a catalyst. The reaction time depends on the temperature used and can be, for example, in the range of 30 minutes to 6 hours, in particular 30 minutes to 3 hours, preferably 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.

[0075] 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.

[0076] 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 95-200°C, meaning that at the application temperature the adhesive has a low enough viscosity to be applicable to a substrate in the molten state. The adhesive composition also has high early strength when cooled immediately after application to a substrate, even before the crosslinking reaction with water, particularly atmospheric moisture, begins.

[0077] According to one or more embodiments, the adhesive composition has a viscosity of 100,000 mPa·s or less, preferably 75,000 mPa·s or less, at a temperature of 130° C. The viscosity at a temperature of 130° C. can be measured using a conventional viscometer at 5 revolutions per minute, for example by using a Brookfield DV-2 viscometer using spindle No. 27, preferably using a Thermosel System for temperature control.

[0078] According to one or more embodiments, the adhesive composition has a softening point in the range of 45 to 115°C, preferably 50 to 105°C, more preferably 55 to 95°C, as measured by the Ring and Ball method according to standard 4625-1:2020.

[0079] What has been stated above as being preferred with regard to the isocyanate-functional polyurethane polymer P, the polyol composition, the polyester polyol PO1, the polyether polyol PO2, the polyester polyol PO3, the thermoplastic polymer TP and the catalyst CA applies equally to all the subject matter of the present invention, unless otherwise stated.

[0080] Another subject of the invention is the use of the adhesive composition according to the invention as an assembly adhesive, lamination adhesive or as an adhesive for assembling sandwich elements, in particular as an interior lamination adhesive in the automotive industry.

[0081] Another subject of the invention is a method for adhesively bonding a first substrate to a second substrate, comprising: I) heating the adhesive composition according to the present invention to obtain 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 using water, preferably atmospheric moisture.

[0082] 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 a thickness defined therebetween.

[0083] 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 a 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 be, for example, from 25 to 750 g / m 2 , preferably 35 to 500 g / m 2 , more preferably 45 to 350 g / m 2 , and even more preferably 50 to 250 g / m 2 can be applied to the surface of the first substrate in a coating amount of

[0084] After the adhesive film is contacted with the surface of the second substrate, the adhesive composition develops a certain initial adhesive strength by physical hardening, i.e., cooling. Depending on the application temperature and the embodiment of the adhesive composition, especially the reactivity of the adhesive, the chemical hardening reaction may already start 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, especially after the applied adhesive film contacts the surface of the second substrate.

[0085] The first and second substrates may be made of any conventional material, such as polymeric materials, metals, painted metals, glass, wood, materials derived from wood, such as natural fiber polypropylene (NFPP), and fiber 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 include additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes, and biocides.

[0086] 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. EXAMPLES

[0087] The following compounds and products shown in Table 1 were used in the examples.

[0088] [Table 1]

[0089] The adhesive compositions shown in Table 2 were prepared according to the procedure set out below.

[0090] Preparation of Adhesive Composition The solid polyester polyol (PO1), the polyether polyol (PO2), the liquid polyester polyol (PO3), and the thermoplastic polymer (TP) were charged into a stainless steel reactor.

[0091] The mixture was maintained under vacuum with stirring at 140°C for 120 minutes to allow for dehydration of the components and to obtain a homogeneously mixed mixture. Polyisocyanate (PI) was then added to the mixture under a nitrogen blanket. The starting mixture thus obtained was reacted under vacuum at a temperature of 140°C with stirring for 60 minutes to obtain a reaction product comprising an isocyanate-functional polyurethane polymer. The resulting adhesive composition was stored at room temperature with the exclusion of moisture.

[0092] Measurement method The adhesive compositions were characterized using the following measurement methods:

[0093] Viscosity at 130℃ The sample adhesive composition placed in a sealed tube was preheated in an oven for 30 minutes at a temperature of 130°C. After heating, a 12.3 g sample of the adhesive composition was weighed out and placed in a disposable sleeve for the viscometer. The viscosity was measured at a temperature of 130°C at 5 revolutions per minute using a Brookfield DV-2 viscometer with spindle No. 27 equipped with a Thermosel system. The values ​​obtained using 20 minutes of tempering at the measurement temperature and the 5 minutes measurement were recorded as the respective viscosities.

[0094] Open Time The sample adhesive composition contained in the sealed tube was first preheated in an oven at a temperature of 110° C. for 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 to a temperature of 110° C. using a heated plate.

[0095] Immediately after application of 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 the time was recorded as the start of the measurement. Every 10 seconds, a short strip of silicone-coated paper, formed into a roll with dimensions of 10 cm x 1 cm (with the surface without silicone facing outwards), was placed on the adhesive film and then the strip was slowly pulled away from the adhesive film to separate it. 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 start of the measurement and the final sampling time was recorded as the open time (in seconds) of the adhesive composition.

[0096] The open time values ​​shown in Table 2 were obtained as the average of three measurements made with the same adhesive composition.

[0097] Lap shear strength (LSS) The adhesive was kept in an oven at 130°C for more than 30 minutes to ensure that the adhesive was obtained in a molten state. After heating, a sample of the molten adhesive was spread on the surface of a wood substrate having dimensions of 9cm x 2cm x 5mm. The adhesive was applied as a coating having dimensions of 2.5cm x 1cm and a thickness of 1mm.

[0098] Immediately after applying the adhesive, a second wood substrate having the same dimensions as the first wood substrate was placed on top of the first wood substrate along the edge of the adhesive film to form a test composite element. The second wood substrate was pressed firmly against the first wood substrate to remove air from the adhesive joint. A 150 g weight was placed on the top surface of the second wood substrate. The adhesive that had extruded from the seam was removed with a knife. The lap shear strength (LSS) of the test composite element was measured according to the standard EN 1465 using a material testing machine (Zwick Z 020) and a test speed of 10 mm / min. The lap shear strength was measured using test composite elements that had been stored for 3 / 6 / 10 / 20 / 30 minutes after bonding the first wood substrate with the second substrate to determine the green (initial) adhesive bond strength obtained with the test adhesive composition.

[0099] Peel strength 90° To ensure that the adhesive was obtained in a molten state, the adhesive was kept in an oven at 130°C for more than 30 minutes. A doctor knife was used to coat a 100 μm thick adhesive film directly onto a PVC film having dimensions of 5 cm x 20 cm (width, length). A test specimen was made by laminating the PVC film to an ABS board having dimensions of 5 cm x 15 cm (width, length) by using a press roll. After 30 minutes, the PVC film was peeled off by hand from the surface of the ABS board and the peel strength was recorded.

[0100] [Table 2]

Claims

1. a) a polyol composition, a1) at least one polyester polyol PO1 that is solid at 25° C., and a2) at least one polyether polyol PO2 A polyol composition comprising: b) at least one polyisocyanate PI, an adhesive composition comprising at least one isocyanate-functional polyurethane polymer P obtained by reacting 1. The adhesive composition, wherein the at least one polyether polyol PO2 has a hydroxyl number, measured according to standard ISO 4629-2:2016, of at least 100 mg KOH / g, preferably at least 150 mg KOH / g.

2. 2. The adhesive composition according to claim 1, further comprising c) at least one thermoplastic polymer TP having a melting point of 45 to 150° C., preferably 50 to 125° C., measured by differential scanning calorimetry (DSC) according to standard ISO 11357-3:2018.

3. 3. The adhesive composition according to claim 1 or 2, wherein the at least one polyether polyol PO2 has a melting point of 45 to 100° C., preferably 50 to 90° C., measured by differential scanning calorimetry (DSC) in accordance with standard ISO 11357-3:2018.

4. 4. The adhesive composition according to claim 1, wherein the at least one polyether polyol PO2 has a molecular weight of less than or equal to 1000 g / mol, preferably less than or equal to 500 g / mol, as measured by gel permeation chromatography (GPC) using polystyrene as standard.

5. The adhesive composition according to any one of claims 1 to 4, wherein the at least one polyether polyol PO2 is a polyether diol, preferably an aromatic polyether diol.

6. The at least one polyether polyol PO2 preferably has the formula (I) 【Chemistry 1】 (In the formula, y and y each independently represent an integer in the range of 1 to 5.) 6. The adhesive composition according to claim 1, wherein the alkylene oxide is an alkylene oxide adduct of bisphenol A.

7. 8. The adhesive composition of claim 7, wherein x and y in formula (I) have a value of 1.

8. The polyol composition a) comprises: The adhesive composition according to any one of claims 1 to 7, further comprising a3) at least one polyester polyol PO3 which is liquid at 25°C. The at least one polyester polyol PO3 liquid at 25° C. has a hydroxyl number of 10 to 60 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to standard ISO 4629-2:2016, and / or a glass transition temperature (T ) of 0° C. or less, preferably −15° C. or less, measured according to standard ISO 11357-1:2016. ｇ 9. The adhesive composition of claim 8, wherein

9. The at least one polyisocyanate PI is a diisocyanate, preferably a monomeric diisocyanate, preferably having a number average molecular weight (M ｎ The adhesive composition according to any one of claims 1 to 8, wherein

10. 10. The adhesive composition according to any one of claims 1 to 9, comprising at least 50% by weight, preferably at least 65% by weight, of said at least one isocyanate-functional polyurethane polymer P, based on the total weight of the adhesive composition.

11. 11. The adhesive composition according to any one of claims 2 to 10, comprising 2.5 to 30 wt.-%, preferably 5 to 30 wt.-%, of said at least one thermoplastic polymer TP, based on the total weight of the hot melt adhesive composition.

12. The adhesive composition according to any one of claims 2 to 11, wherein the at least one thermoplastic polymer TP comprises at least one thermoplastic polyurethane TPU.

13. The adhesive composition according to any one of claims 1 to 12, further comprising at least one catalyst CA which catalyzes the reaction of isocyanate groups with water.

14. Use of the adhesive composition according to any one of claims 1 to 13 as an assembly adhesive, lamination adhesive or as an adhesive for assembling sandwich elements, preferably as an interior lamination adhesive in the automotive industry.

15. 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 13 to obtain 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 using water, preferably atmospheric moisture; The method includes:

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