Reactive hot melt adhesive with low monomeric diisocyanate content

Abstract

The invention relates to an adhesive composition comprising at least one isocyanate-functional polyurethane polymer and having a low monomeric diisocyanate content. The invention also relates to a method for producing the adhesive composition, to the use of the adhesive composition as an assembly adhesive, a lamination adhesive or as an adhesive for building sandwich elements, and to a method for joining substrates to each other.

Description

Technical Field

[0001] The invention relates to reactive polyurethane-based hotmelt adhesives with a low monomeric diisocyanate content and to the use of the adhesives as assembly adhesives, laminating adhesives or as adhesives for building sandwich elements, in particular in the automotive industry. Background Art

[0002] Hot melt adhesives are solvent-free adhesives that are solid at room temperature and are applied to the substrates to be joined in the form of a melt. After cooling, the adhesive solidifies and forms an adhesive bond with the substrate by physically occurring bonding. Conventional hot melt adhesives are non-reactive adhesives that soften again when heated and are therefore not suitable for use at elevated temperatures. Reactive hot melt adhesives contain polymers with reactive groups so that the adhesive can be chemically cured, for example by crosslinking of polymer chains. Due to the cured polymer matrix, reactive hot melts do not soften when heated, so these adhesives are also suitable for use at elevated temperatures. The chemical curing of the polymer can be initiated, for example, by heating the adhesive composition or exposing it to water. Moisture-curing hot melt adhesives typically contain polymers functionalized with isocyanate or silane groups, which allow the polymer chains to crosslink when in contact with water, particularly with atmospheric moisture.

[0003] Typical reactive hot melt adhesives used as assembly adhesives in the automotive industry include moisture-curing polyurethane-based and polyolefin-based hot melt adhesives. Moisture-curing polyurethane hot melt (PUR-RHM) adhesives are mainly composed of isocyanate-terminated polyurethane prepolymers, which are obtained by reacting a suitable polyol, usually a diol, with a stoichiometric excess of a monomeric diisocyanate. When in contact with water, the residual isocyanate groups of the polyurethane prepolymer form carbamic acid, which is unstable and decomposes into amines and carbon dioxide. Amines react rapidly with other isocyanate groups to form urea bonds.

[0004] PU-RHM adhesives typically contain large amounts of unreacted monomeric diisocyanates ("residual monomers"), since the isocyanate-functional prepolymers are obtained by reacting a polyol with a significant stoichiometric excess of monomeric diisocyanates. The application temperature of the hot melt adhesive, such as 85 to 200°C, particularly 120 to 160°C, increases the vapor pressure of the residual monomers and causes them to volatilize. Due to the toxicity of certain diisocyanates, additional steps are usually taken to reduce their atmospheric concentrations in areas where personnel are exposed. In some cases, ventilation structures such as "down draft booths" are provided to minimize personnel exposure to volatile monomers. However, providing such ventilation structures may be expensive and difficult. Chemical regulations and classification standards require that the product be labeled as hazardous if the content of unreacted monomeric diisocyanates in the adhesive exceeds a limit of 0.1% by weight (GHS07 / GHS08). In addition, at concentrations of monomeric MDI>1%, the product must be labeled with an additional hazard statement (stamen) (H351). For these reasons, various efforts have been made to reduce the concentration of residual diisocyanates in PU-RHM adhesives.

[0005] An obvious approach to providing a label-free PUR-RHM adhesive is to subject the reaction product obtained by the reaction of a diisocyanate and a polyol to a physical unit operation, such as a distillation or extraction step, to reduce the content of residual monomers. Methods based on this approach have been disclosed in, for example, WO 01 / 14443A1 and WO 01 / 40340A2. However, reducing the residual monomer content of a reaction product comprising a polyurethane prepolymer obtained by the reaction of a diisocyanate and an amorphous polyol by distillation has proven to be almost impossible due to the high viscosity of such a polyurethane prepolymer. On the other hand, amorphous polyols are generally required in addition to other types of polyols in PUR-RHM adhesives to adjust various adhesive properties, in particular the open time, green strength, viscosity and flexibility of the cured adhesive.

[0006] Another approach is based on the use of distilled (stripped) short-chain polyurethane prepolymers with a low content of monomeric diisocyanates, which are available, for example, under the trade name Purchase, such as LS2397 (from Covestro). Such stripped prepolymers can be used to replace a portion of the monomeric diisocyanate in the reaction mixture or as a "reactive diluent" to reduce the residual monomer content of the final adhesive composition. However, these types of adhesive compositions have been found to have the disadvantages of reduced heat resistance, insufficient storage stability and reduced initial (green) bond strength.

[0007] The concentration of residual monomers can also be reduced by using a two-step production method, which includes a first step in which a polyol of the first type is reacted with a diisocyanate monomer to provide a reaction mixture comprising a polyurethane prepolymer and residual monomers, and then another polyol is added to the reaction mixture to reduce the second step of residual monomer content. An example of this scheme has been disclosed in EP3088435 A1. Another example is a three-step method disclosed in EP 3116930 A1, in which a polyol is first reacted with a diisocyanate monomer to provide a reaction product, which is modified by adding mercaptosilane. The amount of monomer diisocyanates is then further reduced by adding a distilled polyurethane prepolymer before, during and / or after adding mercaptosilane. The approach based on using this stepwise production method has the inherent disadvantage of involving multiple reaction steps, which significantly increases production costs.

[0008] There is therefore a need for new reactive polyurethane hot melt adhesives having a low residual monomer content which can be produced using simple and cost-effective production processes. Summary of the invention SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide a moisture curing polyurethane hot melt adhesive which overcomes or at least alleviates the disadvantages of the prior art moisture curing polyurethane adhesives as discussed above.

[0011] In particular, it is an object of the present invention to provide a moisture-curable polyurethane hot melt adhesive without H351 classification.

[0012] Another object of the present invention is to provide a moisture curable polyurethane hot melt adhesive without H351 classification, which has excellent adhesive joint properties, especially in terms of green (initial) strength, tensile strength, elongation and heat resistance of the cured adhesive.

[0013] The subject of the invention is an adhesive composition as defined in claim 1 .

[0014] Two different approaches based on the same basic principle have been found to achieve the above objectives. According to the first approach, at least one blocked amorphous polyester polyol is added as a non-reactive diluent to a reaction product comprising at least one isocyanate-functional polyurethane polymer with a low residual monomer content to provide an adhesive having the desired properties. Suitable isocyanate-functional polyurethane polymers with a low residual monomer content can be obtained by using a low stoichiometric excess of isocyanate groups relative to the hydroxyl groups in the reaction mixture or by using a high stoichiometric excess of isocyanate groups relative to the hydroxyl groups and then subjecting the reaction product to a treatment, such as distillation, to reduce the residual monomer content.

[0015] The second scheme is based on reacting a polyurethane prepolymer with a low residual monomer content with an amorphous polyol to provide an adhesive composition with a low residual monomer content and containing a polyurethane prepolymer with desired properties. Both of the above schemes can provide a moisture-curable polyurethane hot melt composition with extremely low residual monomer content and good adhesive properties (especially in terms of green (initial) strength, tensile strength, elongation and heat resistance of the cured adhesive). In addition, the present invention is not limited to using only one of the above schemes, and adhesive compositions based on the combination of these two schemes are also considered to fall within the scope of the present invention.

[0016] Further subjects of the invention are set forth in the other independent claims. Preferred aspects of the invention are set forth in the dependent claims. DETAILED DESCRIPTION OF THE INVENTION

[0018] The subject of the invention is an adhesive composition comprising at least one isocyanate-functional polyurethane polymer PU,

[0019] wherein the at least one isocyanate-functional polyurethane polymer PU comprises:

[0020] at least one isocyanate-functional polyurethane polymer PU1 obtained by reacting at least one polyester polyol PO1 and at least one diisocyanate P1 in a molar ratio of isocyanate groups to hydroxyl groups of 1.5 to 2.1, preferably 1.75 to 1.9, and / or

[0021] at least one isocyanate-functional polyurethane polymer PU2 obtained by reacting at least one polyester polyol PO2 and at least one diisocyanate P2 in a molar ratio of at least 3, preferably at least 5, and subjecting the reaction mixture thus obtained to a treatment in order to reduce the amount of residual monomeric diisocyanate, preferably by distillation, and

[0022] The adhesive composition further comprises at least one acetylated amorphous polyester polyol APO

[0023] Or wherein the at least one isocyanate-functional polyurethane polymer PU comprises:

[0024] at least one isocyanate-functional polyurethane polymer PU3 obtained by reacting at least one polyester polyol PO3 and at least one polyurethane prepolymer PUP in a molar ratio of isocyanate groups to hydroxyl groups of 1.9 to 3.5, preferably 2.2 to 2.8, and

[0025] wherein the at least one polyester polyol PO3 comprises at least one amorphous polyester polyol PO31, and wherein the adhesive composition optionally further comprises at least one acetylated amorphous polyester polyol APO.

[0026] The prefix "poly" in a substance name such as "polyol" or "polyisocyanate" refers to a substance that contains, in formal terms, two or more of the functional groups that appear in its name per molecule. For example, a polyol is a compound having two or more hydroxyl groups, while a polyisocyanate is a compound having two or more isocyanate groups.

[0027] The term "α-olefin" means a olefin having the molecular formula C x H 2x (x corresponds to the number of carbon atoms), characterized by a carbon-carbon double bond at the first carbon atom (the α-carbon). Examples of α-olefins include ethylene, propylene, 1-butene, 2-methyl-1-propene (isobutylene), 1-pentene, 1-hexene, 1-heptene, and 1-octene. For example, 1,3-butadiene, 2-butene, and styrene are not referred to as "α-olefins" according to the present disclosure.

[0028] The term "prepolymer" refers to a polymer containing at least one, usually two or more reactive groups, such as isocyanate groups. The prepolymer can be chain-extended, crosslinked or coupled via the reactive groups.

[0029] 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.

[0030] The term "polyurethane polymer" means a polymer prepared by the so-called diisocyanate polyaddition process. These also include those polymers which contain almost or completely no urethane groups. Examples of polyurethane polymers are polyether-polyurethanes, polyester-polyurethanes, polyether-polyureas, polyureas, polyester-polyureas, polyisocyanurates and polycarbodiimides.

[0031] The term "polyurethane prepolymer" means a polyurethane polymer containing one or more unreacted isocyanate groups. Polyurethane prepolymers can be obtained by reacting an excess of polyisocyanates with polyols, and they themselves are polyisocyanates. The terms "isocyanate-functional polyurethane polymer" and "polyurethane prepolymer" are used interchangeably.

[0032] When its isocyanate group is directly bonded to an aliphatic, alicyclic or arylaliphatic moiety, an isocyanate is referred to as "aliphatic". The corresponding functional group is therefore referred to as an aliphatic isocyanate group. In addition, when its isocyanate group is directly bonded to an aromatic moiety, an isocyanate is referred to as "aromatic". The corresponding functional group is therefore referred to as an aromatic isocyanate group.

[0033] The term "molecular weight" refers to the molar mass (g / mol) of a molecule or a portion of a molecule (also referred to as a "moiety"). The term "average molecular weight" may refer to the weight average or number average molecular weight (M) of an oligomeric or polymeric mixture of a molecule or moiety. n 、M w The molecular weight can be determined by conventional methods, preferably by gel permeation chromatography (GPC), using polystyrene as standard, styrene-divinylbenzene gels with porosities of 100 angstroms, 1000 angstroms and 10000 angstroms as columns, and tetrahydrofuran as solvent at 35° C. or 1,2,4-trichlorobenzene as solvent at 160° C., depending on the molecule.

[0034] The term "average OH functionality" refers to the average number of hydroxyl (OH) groups per molecule. The average OH functionality of a compound can be calculated based on the number average molecular weight (M) of the compound. n The hydroxyl value of a compound can be determined using the method defined in EN ISO 4629-2 standard.

[0035] The term "softening point" or "softening temperature" means the temperature at which a compound softens in a rubbery state, or the temperature at which crystalline parts within a compound melt. The softening point can be measured by the ring and ball method according to the DIN EN 1238 standard.

[0036] The term "open time" refers to the length of time that an adhesive applied to a substrate surface is still able to form an adhesive bond after contact with another substrate.

[0037] The "amount or content of at least one component X" in the composition, for example "the amount of the at least one polyisocyanate P" refers to the sum of the individual amounts of all polyisocyanates P contained in the composition. In addition, in the case where the composition contains 20% by weight of at least one polyisocyanate P, the sum of the amounts of all polyisocyanates P contained in the composition is equal to 20% by weight.

[0038] The term "room temperature" refers to a temperature of approximately 23°C.

[0039] The adhesive compositions of the present invention preferably exhibit low levels of monomeric diisocyanates.

[0040] The term "monomeric diisocyanate" in the present disclosure refers to an organic compound having two isocyanate groups separated by a divalent hydrocarbon group, preferably having an average molecular weight of not more than 1000 g / mol, more preferably not more than 500 g / mol, and even more preferably not more than 400 g / mol. In particular, monomeric diisocyanates do not contain urethane groups, and oligomeric or polymeric products of diisocyanate monomers, such as adducts of monomeric diisocyanates, are not considered "monomeric diisocyanates" in the present invention.

[0041] According to one or more embodiments, the adhesive composition has a monomeric diisocyanate content of less than 1.0 wt%, preferably less than 0.85 wt%, more preferably less than 0.65 wt%, even more preferably less than 0.5 wt%, even more preferably less than 0.35 wt%, especially less than 0.15 wt%, and most preferably less than 0.1 wt%, based on the total weight of the adhesive composition. An adhesive composition having a monomeric diisocyanate content of less than 0.1 wt% is safe to use even without special protective measures and can therefore be sold in many countries without being labeled as hazardous (Xn).

[0042] Preferably, the at least one isocyanate-functional polyurethane polymer PU is present in the adhesive composition in an amount of at least 15 wt. %, preferably at least 25 wt. %, more preferably at least 35 wt. %, even more preferably at least 40 wt. %, based on the total weight of the adhesive composition.

[0043] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU is present in the adhesive composition in an amount of 15-85 wt. %, preferably 25-75 wt. %, more preferably 35-70 wt. %, even more preferably 40-70 wt. %, even more preferably 40-65 wt. %, based on the total weight of the adhesive composition.

[0044] According to one or more embodiments, the at least one isocyanate functional polyurethane polymer PU has an average isocyanate functionality determined according to ISO 14896-2009 standard method A in the range of 1.2-2.7, preferably 1.5-2.5 and / or an isocyanate content determined by using the method as defined in ISO 11909:2007 standard in the range of 0.5-30% by weight, preferably 1.0-25% by weight.

[0045] Compounds suitable for use as the at least one acetylated amorphous polyester polyol APO are obtainable by acetylation of amorphous polyester polyols.

[0046] According to one or more embodiments, the at least one acetylated amorphous polyester polyol APO is obtained by a process comprising reacting at least one amorphous polyester polyol with acetic anhydride in a molar ratio of 1.3:1 to 1:1.3, preferably 1.1:1 to 1:1, preferably subsequently subjecting the reaction product to distillation to reduce the amount of residual acetic anhydride. Preferably, the reaction of the at least one amorphous polyester polyol with acetic anhydride is carried out in an acetic acid solution.

[0047] Preferably, if the at least one acetylated amorphous polyester polyol APO is used, it is present in the adhesive composition in an amount of at least 5 wt%, preferably at least 10 wt%, more preferably at least 15 wt%, based on the total weight of the adhesive composition.

[0048] According to one or more embodiments, the at least one acetylated amorphous polyester polyol APO is present in the adhesive composition in an amount of 5-65 wt %, preferably 10-55 wt %, more preferably 10-50 wt %, even more preferably 15-45 wt %, even more preferably 20-45 wt %, based on the total weight of the adhesive composition.

[0049] Suitable polyester polyols for use in the present invention include liquid, amorphous, partially crystalline and crystalline polyester polyols. These can be prepared by mixing diols and triols, preferably diols (e.g., 1,2-ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, dimerized fatty alcohols, neopentyl glycol, glycerol, 1,1,1-trimethylolpropane or mixtures of the above alcohols), with organic diols. Carboxylic acids 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, undecanedioic acid, dodecanedicarboxylic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimer fatty acids, isophthalic acid, terephthalic acid and hexahydrophthalic acid or mixtures of the above acids) are obtained by reaction, and polyester polyols made from lactones such as ε-caprolactone, for example also known as polycaprolactone.

[0050] Preferred polyester polyols include those obtained by reacting adipic acid, sebacic acid or dodecane dicarboxylic acid as dicarboxylic acids with hexanediol or neopentyl glycol as diols. Other examples of suitable polyester polyols include polyester polyols of oleochemical origin. This type of polyester polyol can be prepared, for example, by completely ring-opening an epoxidized triglyceride of a fat mixture comprising at least part of olefinically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms and by subsequent partial transesterification of the triglyceride derivatives to obtain an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl group. Particularly suitable crystalline or semi-crystalline polyester polyols include adipic acid / hexanediol polyesters and dodecane dicarboxylic acid / hexanediol polyesters.

[0051] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU comprises:

[0052] at least one isocyanate-functional polyurethane polymer PU1 obtained by reacting at least one polyester polyol PO1 and at least one diisocyanate P1 in a molar ratio of isocyanate groups to hydroxyl groups of 1.5 to 2.1, preferably 1.75 to 1.9, and / or

[0053] at least one isocyanate-functional polyurethane polymer PU2 obtained by reacting at least one polyester polyol PO2 and at least one diisocyanate P2 in a molar ratio of at least 3, preferably at least 5, and subjecting the reaction mixture thus obtained to a treatment to reduce the amount of residual monomeric diisocyanate, preferably by distillation.

[0054] The reaction between the at least one polyester polyol PO1 and the at least one diisocyanate P1 can be carried out using conventional techniques for preparing polyurethane prepolymers. This means in particular that the hydroxyl groups of the polyester polyol PO1 react with the isocyanate groups of the diisocyanate P1.

[0055] Preferably, the reaction between the at least one polyester polyol PO1 and the at least one diisocyanate P1 will convert substantially all of the hydroxyl groups of the at least one polyester polyol PO1, such as at least 95%, typically at least 99% of the hydroxyl groups of the at least one polyester polyol PO1.

[0056] The reaction between the at least one polyester polyol PO1 and the at least one diisocyanate P1 can be carried out, for example, at a temperature of 60-160° C., preferably 80-140° C., optionally in the presence of a catalyst. As will be appreciated, the reaction time depends on the temperature used, but can be, for example, in the range of 30 minutes to 6 hours, preferably 30 minutes to 3 hours, more preferably 30 minutes to 1.5 hours. Suitable catalysts include, for example, metal catalysts such as 83 (from Vertellus Performance Materials Inc.) and tin catalyst.

[0057] Similar considerations apply to the reaction between the at least one polyester polyol PO2 and the at least one diisocyanate P2.

[0058] According to one or more embodiments, the at least one polyester polyol PO1 comprises at least one polyester polyol PO11 that is solid at 23°C and / or at least one polyester polyol PO12 that is liquid at 23°C.

[0059] Generally, the expression "the at least one component X comprises at least one component XN", such as "the at least one polyester polyol PO1 comprises at least one solid polyester polyol PO11" is understood in the present disclosure to mean that the composition comprises one or more solid polyester polyols PO11 as representatives of the at least one polyester polyol PO1.

[0060] Preferably, the at least one polyester polyol PO11 which is solid at 23° C. is a crystalline polyester polyol which is solid at 23° C., which preferably has:

[0061] - a hydroxyl value of 10 to 100 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0062] - a softening point of 50-100° C., preferably 60-90° C., measured by the ring and ball method according to ISO 4625 standard, and / or

[0063] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (M n ).

[0064] Solid polyester polyols suitable for use as polyester polyol PO11 are commercially available under the trade name of the 7300 series (from Evonik Industries).

[0065] Preferably, the at least one polyester polyol PO12 which is liquid at 23° C. has:

[0066] - a hydroxyl value of 10 to 100 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0067] - a glass transition temperature measured by DCS equal to or lower than -10°C, preferably equal to or lower than -25°C, and / or

[0068] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (M n ).

[0069] Liquid polyester polyols suitable for use as polyester polyol PO12 are available under the trade names of the 7200 series (from Evonik Industries) and under the trade names HM (from DIC Performance Resins), such as HM 2686 was purchased.

[0070] According to one or more preferred embodiments, the at least one polyester polyol PO1 comprises the at least one polyester polyol PO11 which is solid at 23°C and the at least one polyester polyol PO12 which is liquid at 23°C, wherein the weight ratio of the total amount of PO12 to the total amount of PO11 is preferably in the range of 5:1 to 1:5, more preferably 3:1 to 1:3, even more preferably 2:1 to 1:2, even more preferably 1.5:1 to 1:1.5.

[0071] Particularly suitable diisocyanates for use as the at least one diisocyanate P1 and P2 include, for example, monomeric aliphatic, cycloaliphatic and aromatic diisocyanates.

[0072] According to one or more preferred embodiments, the at least one diisocyanate P1 and P2 is a monomeric diisocyanate, preferably having a number average molecular weight (M) of not more than 1000 g / mol, preferably not more than 500 g / mol, more preferably not more than 400 g / mol. n ) of a monomeric diisocyanate.

[0073] Examples of suitable monomeric diisocyanates include aliphatic and aromatic monomeric diisocyanates, 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 1,6-diisocyanate, 1,12-dodecamethylene diisocyanate, 1,10-decamethylene di ...2-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 1,12 ,3-diisocyanate and cyclohexane 1,4-diisocyanate and mixtures of these isomers, 1-methyl-2,4- and -2,6-cyclohexane diisocyanate 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 mixtures, 1,4-diisocyanato-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-Toluene diisocyanate and mixtures of these isomers (TDI), 4,4′-diphenylmethane diisocyanate (MDI), optionally with a certain proportion of 2,4′- and / or 2,2′-diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate (PDI) and mixtures of these isomers, naphthalene 1,5-diisocyanate (NDI), 3,3′-dimethyl-4,4′-biphenyl diisocyanate (TODI) and dianisidine diisocyanate (DADI).

[0074] Suitable aliphatic and aromatic monomeric diisocyanates are commercially available, for example under the trade names (from BASF), Desmodur (from Covestro) and (From Asahi Kasei).

[0075] According to one or more embodiments, the at least one diisocyanate P1 and P2 is selected from 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 2,2'-diphenylmethane diisocyanate (2,2'MDI) or a mixture of these isomers, toluene diisocyanate (TDI), in particular 2,4-toluene diisocyanate (2,4TDI), 2,6-toluene diisocyanate (2,6TDI) or a mixture of these isomers, 1,6-hexamethylene diisocyanate (HDI) and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). In addition, the skilled person knows that technical-grade products of diisocyanates may often contain isomer mixtures or other isomers as impurities.

[0076] According to one or more embodiments, the isocyanate functional polyurethane polymer PU2 has a content of monomeric diisocyanates of not more than 1.0 wt. %, preferably not more than 0.5 wt. %, based on the total weight of the isocyanate functional polyurethane polymer.

[0077] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU2 comprises:

[0078] at least one first isocyanate-functional polyurethane polymer PU21 obtained by reacting at least one polyester polyol PO21 and the at least one diisocyanate P2, and / or

[0079] at least one second isocyanate-functional polyurethane polymer PU22 obtained by reacting at least one polyester polyol PO22 and the at least one diisocyanate P2,

[0080] Wherein the at least one polyester polyol PO21 is a polyester polyol which is solid at 23°C, and the at least one polyester polyol PO22 is a polyester polyol which is liquid at 23°C.

[0081] According to one or more embodiments, the at least one polyester polyol PO21 has:

[0082] - a hydroxyl value of 10 to 100 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0083] - a softening point of 45-100° C., preferably 55-90° C., measured by the ring and ball method according to ISO 4625 standard, and / or

[0084] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (Mn ).

[0085] According to one or more embodiments, the at least one polyester polyol PO22 has:

[0086] - a hydroxyl value of 10 to 100 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0087] - a glass transition temperature measured by DCS equal to or lower than -10°C, preferably equal to or lower than -25°C, and / or

[0088] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (M n ).

[0089] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU2 comprises the at least one isocyanate-functional polyurethane polymer PU21 and the at least one isocyanate-functional polyurethane polymer PU22, wherein the weight ratio of the total amount of polymer PU21 to the total amount of polymer PU22 is preferably in the range of 10:1 to 1:1, more preferably 7:1 to 1.5:1, even more preferably 5:1 to 2:1, and even more preferably 5:1 to 3:1.

[0090] According to one or more embodiments, the at least one diisocyanate P2 comprises at least one diisocyanate P21 and / or at least one diisocyanate P22, wherein the at least one diisocyanate P21 is a monomeric diphenylmethane diisocyanate having a 2,4′-isomer content of at least 25% by weight, preferably at least 35% by weight, based on the total weight of the first diisocyanate P21, and wherein the at least one second diisocyanate P22 is a monomeric diphenylmethane diisocyanate having a 4,4′-isomer content of at least 75% by weight, preferably at least 95% by weight, based on the total weight of the second diisocyanate P22.

[0091] According to one or more embodiments, the at least one diisocyanate P2 comprises or consists of the at least one diisocyanate P21. According to one or more embodiments, the at least one diisocyanate P2 comprises or consists of the at least one diisocyanate P22.

[0092] According to one or more preferred embodiments, the at least one diisocyanate P2 consists of the at least one diisocyanate P22.

[0093] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU comprises:

[0094] at least one isocyanate-functional polyurethane polymer PU3 obtained by reacting at least one polyester polyol PO3 and at least one polyurethane prepolymer PUP in a molar ratio of isocyanate groups to hydroxyl groups of 1.9 to 3.5, preferably 2.2 to 2.8, wherein the at least one polyester polyol PO3 comprises at least one amorphous polyester polyol PO31.

[0095] According to one or more embodiments, the isocyanate functional polyurethane polymer PU3 has a content of monomeric diisocyanates of not more than 1.0 wt.-%, preferably not more than 0.5 wt.-%, based on the total weight of the isocyanate functional polyurethane polymer PU3.

[0096] Preferably, the at least one amorphous polyester polyol PO31 has:

[0097] - a hydroxyl value of 15 to 100 mg KOH / g, preferably 25 to 75 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0098] - a softening point of 55-115°C, preferably 65-105°C, measured by the ring and ball method according to ISO 4625 standard, and / or

[0099] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (M n ), and / or

[0100] - a glass transition temperature measured by DCS of at least 0°C, preferably at least 15°C, more preferably at least 25°C.

[0101] Suitable polyester polyols for use as the at least one amorphous polyester polyol PO31 are commercially available, for example as The trade name of the 7100 series (from Evonik Industries) and Trade name for the HM 1800 series (from DIC Performance Resins).

[0102] According to one or more preferred embodiments, the at least one polyester polyol PO3 comprises the at least one amorphous polyester polyol PO31 and at least one crystalline polyester polyol PO32 which is solid at 23°C.

[0103] Preferably, the at least one crystalline polyester polyol PO32 which is solid at 23° C. has:

[0104] - a hydroxyl value of 10 to 100 mg KOH / g, preferably 15 to 50 mg KOH / g, measured according to EN ISO 4629-2, and / or

[0105] - a softening point of 45-100° C., preferably 55-90° C., measured by the ring and ball method according to ISO 4625 standard, and / or

[0106] -500-10000 g / mol, preferably 1500-7500 g / mol number average molecular weight (M n ).

[0107] Preferably, the at least one polyurethane prepolymer PUP is obtained by reacting at least one polyester polyol PO4 and at least one diisocyanate P2 in a molar ratio of at least 3, preferably at least 4, and subjecting the reaction mixture thus obtained to a treatment to reduce the amount of residual monomeric diisocyanate, preferably by distillation.

[0108] According to one or more embodiments, the polyurethane prepolymer PUP has a content of monomeric diisocyanate of not more than 1.0 wt. %, preferably not more than 0.5 wt. %, based on the total weight of the polyurethane prepolymer PUP.

[0109] Particularly suitable polyester polyols for use as the at least one polyester polyol PO4 include liquid polyester polyols as well as partially crystalline and crystalline polyester polyols which are solid at a temperature of 23°C.

[0110] According to one or more preferred embodiments, the at least one polyester polyol PO4 comprises or consists of poly(tetramethylene ether) glycol, preferably having a number average molecular weight (M) of 250-10000 g / mol, preferably 500-7500 g / mol. n ).

[0111] According to one or more embodiments, the at least one isocyanate-functional polyurethane polymer PU comprises the at least one isocyanate-functional polyurethane polymer PU2 and the at least one isocyanate-functional polyurethane polymer PU3, wherein the weight ratio of the total amount of polyurethane polymer PU2 to the total amount of polyurethane polymer PU3 is preferably in the range of 5:1 to 1:5, more preferably 3:1 to 1:3, and even more preferably 2:1 to 1:2.

[0112] According to one or more further embodiments, the at least one isocyanate-functional polyurethane polymer PU comprises the at least one isocyanate-functional polyurethane polymer PU2 and the at least one isocyanate-functional polyurethane polymer PU3, wherein the weight ratio of the total amount of polyurethane polymer PU2 to the total amount of polyurethane polymer PU3 is preferably in the range of 5:1 to 1:5, more preferably 3:1 to 1:3, and even more preferably 2:1 to 1:2, and wherein the adhesive composition further comprises the at least one acetylated polyester polyol APO.

[0113] According to one or more embodiments, the adhesive composition further comprises at least one additional thermoplastic polymer TP free of isocyanate groups.

[0114] Suitable compounds for use as the at least one additional thermoplastic polymer TP include, for example, thermoplastic polyurethanes (TPU) and thermoplastic polyester resins.

[0115] 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 long-chain diols.

[0116] Suitable thermoplastic polyester resins include, for example, those having a hydroxyl value measured according to EN ISO 4629-2 of not more than 15 mg KOH / g, preferably not more than 12 mg KOH / g and / or a number average molecular weight (M) of at least 5000 g / mol, preferably at least 7500 g / mol. n ) of polyester resin.

[0117] According to one or more embodiments, the at least one additional thermoplastic polymer TP comprises at least one thermoplastic polyurethane, preferably a polycaprolactone-copolyester polyurethane, and / or at least one thermoplastic polyester resin, preferably having a hydroxyl value measured according to EN ISO 4629-2 of not more than 15 mg KOH / g, preferably not more than 12 mg KOH / g.

[0118] According to one or more embodiments, the at least one additional thermoplastic polymer TP is present in the adhesive composition in an amount of 0.5-30 wt%, preferably 2.5-25 wt%, more preferably 3.5-20 wt%, based on the total weight of the adhesive composition.

[0119] According to one or more embodiments, the adhesive composition further comprises at least one crosslinking agent, preferably an oligomeric polyisocyanate.

[0120] According to one or more embodiments, the at least one cross-linking agent has:

[0121] -150-5000 g / mol, preferably 250-3500 g / mol, more preferably 350-2500 g / mol, and even more preferably 350-1500 g / mol number average molecular weight (M n ), and / or

[0122] - a viscosity measured at 23°C according to ISO 3219:1994 standard of 100-5000 MPa·s, preferably 250-4000 MPa·s, more preferably 350-3500 MPa·s, even more preferably 450-2500 MPa·s, even more preferably 500-2000 MPa·s, and / or

[0123] - a content of free NCO groups measured according to ISO 11909:2007 standard of 10 to 35% by weight, preferably 15 to 30% by weight, more preferably 20 to 30% by weight.

[0124] According to one or more embodiments, the at least one crosslinking agent is an aliphatic or aromatic oligomeric polyisocyanate.

[0125] According to one or more embodiments, the at least one crosslinking agent is a trimer of an aliphatic diisocyanate, preferably selected from the group consisting of hexamethylene 1,6-diisocyanate (HDI), 2-methylpentamethylene 1,5-diisocyanate, 2,2,4- and 2,4,4-trimethylhexamethylene 1,6-diisocyanate (TMDI), dodecamethylene 1,12-diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate and any desired mixtures of these isomers, 1-isocyanate The main products include 1,4-diisocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), perhydrodiphenylmethane 2,4'- and 4,4'-diisocyanate (HMDI), 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), xylylene meta- and para-diisocyanate (XDI), tetramethylxylylene 1,3- and 1,4-diisocyanate (TMXDI), and 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane.

[0126] The technical form of trimers of aliphatic diisocyanates is usually a mixture of substances with different degrees of polymerization and chemical structures. Suitable commercially available aliphatic diisocyanate trimers include those having an average NCO functionality of 2.4 to 4.0 and containing in particular isocyanurate, imino In addition, allophanates, carbodiimides, uretonimines or A preferred technical form of the trimer of an aliphatic diisocyanate is an oligomeric mixture comprising a major portion of aliphatic diisocyanate trimers mixed with dimers and higher oligomers. Particularly preferred are oligomeric mixtures comprising small amounts of monomeric diisocyanates, in particular having a content of not more than 1.0% by weight, preferably not more than 0.5% by weight, even more preferably not more than 0.25% by weight, even more preferably not more than 0.25% by weight of monomeric diisocyanates.

[0127] Suitable commercially available technical oligomer mixtures of aliphatic diisocyanates are HDI biuret, for example N 100 and N 3200 (from Coverstro), HDB and HDB-LV (from Vencorex) and 24A-100 (from Asahi Kasei); HDI isocyanurates, such as N 3300, N 3600 and N 3790BA (all from Coverstro), HDT, HDT-LV and HDT-LV2 (all from Vencorex), TPA-100 and THA-100 (from Asahi Kasei) and HX (from Nippon Polyurethanes); HDI uretdione, for example as N3400 (from Covestro); HDI imino Diazinediones, for example as XP 2410 (from Coverstro); HDI allophanates, such as VP LS2102 (from Covestro); and IPDI isocyanurate, for example in solution, such as Z 4470 (from Covestro), or in solid form, such as T1890 / 100 (from Evonik Degussa).

[0128] According to one or more embodiments, the at least one crosslinking agent is present in the adhesive composition in an amount of 0.1-10 wt %, preferably 0.5-5 wt %, based on the total weight of the adhesive composition.

[0129] The adhesive composition may further comprise auxiliary substances and additives, such as those selected from fillers, flame retardants, plasticizers, adhesion promoters, UV absorbers, UV and heat stabilizers, fluorescent brighteners, pigments, dyes and desiccants. Examples of suitable UV stabilizers that may be added to the adhesive composition include, for example, sterically hindered phenols.

[0130] Suitable fillers for the adhesive composition include, for example, inorganic and organic fillers, especially natural calcium carbonate, ground calcium carbonate or precipitated calcium carbonate (which is optionally coated with a fatty acid or a fatty acid ester, especially stearic acid), baryte (heavy spar), talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieves, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silicon dioxide (including finely divided silicon dioxide from pyrogenic processes), industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver or steel, PVC powder or hollow spheres.

[0131] According to one or more embodiments, the adhesive composition further comprises at least one inorganic filler, preferably selected from calcium carbonate, barite, talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica, molecular sieves, alumina, aluminum hydroxide, magnesium hydroxide, silica, carbon black, graphite, metal powder and hollow spheres.

[0132] If used, the at least one inorganic filler is preferably present in the adhesive composition in an amount of 1.5-35 wt %, more preferably 2.5-30 wt %, more preferably 5-25 wt %, even more preferably 5-20 wt %, based on the total weight of the adhesive composition.

[0133] According to one or more embodiments, the adhesive composition further comprises at least one polyolefin resin that is liquid at 23° C. Preferably, the at least one polyolefin resin that is liquid at 25° C. is a non-functionalized polyolefin resin that is liquid at 25° C.

[0134] According to one or more embodiments, the at least one polyolefin resin that is liquid at 23° C. is present in the adhesive composition in an amount of 1-30 wt %, preferably 5-25 wt %, more preferably 10-25 wt %, based on the total weight of the adhesive composition.

[0135] According to one or more embodiments, the at least one polyolefin resin that is liquid at 23°C has:

[0136] - a number average molecular weight (M) in the range of 500-5000 g / mol, preferably 500-3500 g / mol, more preferably 1000-3000 g / mol, more preferably 1500-2500 g / mol n ), and / or

[0137] - Pour point determined according to ISO 3016 standard in the range of -10 to +15°C, preferably -10 to +10°C.

[0138] According to one or more embodiments, the at least one polyolefin resin that is liquid at 23° C. is selected from polyisobutylene (PIB) and polybutene, in particular low molecular weight polyisobutylene and low molecular weight polybutene, preferably having a number average molecular weight (M) in the range of 500-5000 g / mol, more preferably 500-3500 g / mol, even more preferably 1000-3000 g / mol, even more preferably 1500-2500 g / mol. n ) and / or a pour point determined according to ISO 3016 standard in the range of -10 to +15°C, preferably -10 to +10°C. The term "polyisobutylene" refers herein to polyolefins and olefin oligomers of isobutylene or 2-methyl-1-propylene, preferably containing at least 75%, more preferably at least 85% of repeating units derived from isobutylene. The term "polybutene" refers herein to polyolefins and olefin oligomers containing isobutylene and / or 1-butene and / or 2-butene. The ratio of C4-olefin isomers may vary depending on the manufacturer and grade. When the C4-olefin is entirely 1-butene, the material is referred to as "poly-n-butene" or "PNB".

[0139] Suitable commercially available polybutenes and polyisobutylenes which are liquid at 23°C include, for example H-300 and H-1200 (from Ineos); V230, V500 and V700 (from BASF); poly 230 (from Univar GmbH, Germany); and PB 950 (from Daelim Industrial).

[0140] The adhesive composition may further include one or more catalysts for accelerating the reaction of isocyanate groups and moisture. The presence of such a catalyst is not mandatory, but it may be preferred. The example of a suitable catalyst includes a metal-based catalyst, such as a dialkyl tin complex, particularly dibutyltin (IV) or dioctyltin (IV) carboxylate or acetylacetonate, such as dibutyltin dilaurate (DBTDL), dibutyltin diacetylacetonate, dioctyltin dilaurate (DOTDL), other bismuth (III) complex, such as bismuth octoate or bismuth neodecanoate, zinc (II) complex, such as zinc octoate or zinc neodecanoate, and zirconium (IV) complex, such as zirconium octoate or zirconium neodecanoate.

[0141] Further examples of suitable catalysts include compounds containing amine groups, such as dimorpholinodialkyl ethers and / or dimorpholino substituted polyalkylene glycols, for example 2,2'-dimorpholinodiethyl ether and 1,4-diazabicyclo[2.2.2]-octane. Combinations of two or more catalysts may also be used, with preferred combinations comprising one or more metal catalysts in combination with one or more morpholinoamine compounds.

[0142] If present in the adhesive composition, the total amount of catalyst that catalyzes the reaction of isocyanate groups with moisture is preferably 0.005 to 2.00 wt %, more preferably 0.05 to 1.00 wt %, based on the total weight of the adhesive composition.

[0143] The adhesive composition is a moisture curing adhesive composition, ie the adhesive composition can be cured by contacting the composition with water, especially with atmospheric moisture. Preferably, the adhesive composition is a moisture curing hot melt adhesive composition.

[0144] Furthermore, the adhesive composition of the invention has good workability under typical application conditions of hot melt adhesives, in particular at temperatures in the range of 100-180° C., which means that at the application temperature, the viscosity of the adhesive is low enough to be applied to the substrate in the molten state. The adhesive composition also develops high green strength upon cooling immediately after application to the substrate, even before the crosslinking reaction with water, in particular with atmospheric moisture, is initiated.

[0145] According to one or more embodiments, the viscosity of the adhesive composition at a temperature of 130° C. is not greater than 100,000 mPa·s, preferably not greater than 85,000 mPa·s, more preferably not greater than 75,000 mPa·s and / or the viscosity at a temperature of 130° C. is at least 10,000 mPa·s, preferably at least 12,500 mPa·s, more preferably at least 15,000 mPa·s. 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 Thermosel viscometer with a No. 27 spindle.

[0146] According to one or more embodiments, the adhesive composition has a softening point measured by the ring and ball method according to DIN EN 1238 standard in the range of 60-150°C, preferably 65-140°C, more preferably 70-130°C, and even more preferably 75-115°C.

[0147] In addition, the adhesive composition can be provided as a one-component storage-stable composition. According to one or more embodiments, the adhesive composition is a one-component moisture-curing hot melt adhesive composition. The term "storage-stable composition" herein refers to a composition that can be stored in suitable packaging or facilities (such as barrels, bags or barrels) for a period of, for example, several months to more than one year without suffering any service-related changes in the application properties and / or reactivity of the composition, especially in the absence of moisture.

[0148] Unless otherwise stated, the preferences given above for the isocyanate-functional polyurethane polymers PU, PU1, PU2 and PU3, for the polyester polyols PO1, PO2, PO3 and PO4, for the diisocyanates P1 and P2 and for the polyurethane prepolymers PUP apply equally to all subjects of the present invention.

[0149] Another subject of the present invention is a process for producing the adhesive composition of the invention, which comprises mixing the at least one isocyanate-functional polymer PU with the other constituents of the adhesive composition.

[0150] The mixing of the at least one isocyanate functional polymer PU with the other ingredients of the adhesive composition is preferably carried out at a temperature above the softening point of the at least one isocyanate functional polymer PU. According to one or more embodiments, the mixing is carried out at a temperature in the range of 50-200°C, preferably 65-180°C, more preferably 80-175°C, and even more preferably 90-160°C.

[0151] A further subject matter of the present invention is the use of the adhesive composition according to the invention as assembly adhesive, laminating adhesive or as adhesive for the construction of sandwich elements.

[0152] Another subject of the present invention is a method for adhesively joining a first substrate to a second substrate, the method comprising the following steps:

[0153] I) heating the adhesive composition according to the present invention to provide a molten adhesive composition,

[0154] II) applying the molten adhesive composition to the surface of the first substrate to form an adhesive film,

[0155] III) contacting the adhesive film with a surface of a second substrate, and

[0156] IV) Chemical curing of the adhesive film with water, in particular with atmospheric moisture.

[0157] The first substrate and the second substrate are preferably sheet-like articles having first and second major surfaces defined by peripheral edges and defining a thickness therebetween, or are three-dimensionally shaped articles.

[0158] In the method of adhesively joining a first substrate to a second substrate, the adhesive composition is heated to a temperature above the softening point of the adhesive composition and applied in a molten state to the surface of the first substrate using any conventional technique, such as by using a slot die coating, roller coating, extrusion coating, calendar coating or spraying. The adhesive composition can be applied at a rate of, for example, 50-500 g / m 2 , such as 55-350g / m 2 , especially 65-150g / m 2 A coating weight of 10000 is applied to the surface of the first substrate.

[0159] In particular, in adhesive compositions having a viscosity of less than 150 g / m 2 , especially less than 100g / m 2 In the case of a film with a coating weight of 2000 to 5000 W is applied to the surface of the first substrate, the adhesive film formed in step II) can be reactivated by heating before contacting with the surface of the second substrate. The reactivation temperature depends on the embodiment of the adhesive composition. It may be preferred, for example, that the adhesive film is reactivated by heating to a temperature of 60-200°C, in particular 70-180°C, preferably 120-160°C. The heating of the adhesive film can be carried out using any conventional technique, such as heating in an oven, heating by air stream or heating with infrared (IR) radiation. The reactivated adhesive film is preferably contacted with the second substrate within a short time after reaching the reactivation temperature, in any case within the open time of the adhesive composition.

[0160] After the adhesive film is in contact with the surface of the second substrate, the adhesive composition develops a certain initial adhesive strength by physical curing (i.e., when cooled). Depending on the application temperature and according to the embodiment of the adhesive composition, in particular according to the reactivity of the adhesive, the chemical curing reaction may have already begun during the application of the adhesive composition on the surface of the first substrate. However, in general, chemical curing occurs mostly after the adhesive is applied, in particular after the applied adhesive film has been in contact with the surface of the second substrate.

[0161] The first and second substrates can be composed of any conventional materials, 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), particularly high-density polyethylene (HDPE), polypropylene (PP), glass fiber reinforced polypropylene (GFPP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polyamide (PA) and combinations thereof. The first substrate and the second substrate can be composed of a single layer or multiple layers of different types of materials. The layer composed of polymeric materials can further contain additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes and biocides.

[0162] According to one or more embodiments, one of the first substrate and the second substrate is composed of a polar material, wherein the other substrate is composed of a non-polar material.

[0163] According to one or more further embodiments, the first substrate, or, in the case where the first substrate consists of a plurality of layers, the layer constituting the outer external surface onto which the adhesive composition is applied in step II) of the method, consists of a polar material, preferably selected from PMMA, PA, PC, ABS, glass fiber reinforced plastic (GFRP), glass and metal, and the second substrate, or, in the case where the second substrate consists of a plurality of layers, the layer constituting the outer external surface in contact with the adhesive film in step III) of the method, consists of a non-polar material, preferably selected from polypropylene, polyethylene and polystyrene.

[0164] According to one or more further embodiments, the first substrate, or, in the case where the first substrate consists of a plurality of layers, the layer constituting the outer external surface onto which the adhesive composition is applied in step II) of the method, consists of a non-polar material, preferably selected from polypropylene, polyethylene or polystyrene, and the second substrate, or, in the case where the second substrate consists of a plurality of layers, the layer constituting the outer external surface in contact with the adhesive film in step III) of the method, consists of a polar material, preferably selected from PMMA, PA, PC, ABS, glass fiber reinforced plastic (GFRP), glass or metal.

[0165] A further subject matter of the present invention is a composite element obtainable by using the method according to the invention for adhesively joining a first substrate to a second substrate.

[0166] The composite elements of the invention can be used, for example, to produce interior lining components for motor vehicles. Examples of such interior lining components include door panels, switch panels, rear luggage racks, headlinings, sliding roofs, center consoles, glove boxes, sun visors, pillars, door handles, armrests, floor panels, cargo floors and trunk area floors as well as sleeping compartments and rear panels for trucks. DETAILED DESCRIPTION

[0167] Example

[0168] The following compounds and products shown in Table 1 were used in the Examples.

[0169] Table 1

[0170]

[0171] Non-stripped polyurethane prepolymer PU1

[0172] The polyol (PO1X) and the monomeric diisocyanate (P1) were reacted at a temperature of 120°C using a conventional preparation method to obtain a reaction product containing a polyurethane prepolymer and some unreacted monomeric diisocyanate. The compositions of the unstripped polyurethane prepolymers used to prepare adhesive compositions Example 1, Example 2, and Reference Example 2 are shown in Table 3.

[0173] Stripped polyurethane prepolymers PU2 and PUP

[0174] The polyol (PO2X, PO4) and the monomeric diisocyanate (P2X) are reacted at a temperature of 80°C using a common preparation method to obtain a reaction mixture containing a polyurethane prepolymer and unreacted monomeric diisocyanate. The reaction mixture is distilled using a short-path evaporator (jacket temperature 170 to 180°C, pressure 0.05 to 0.002 mbar, condensation temperature 47°C) to reduce the content of volatile compounds, especially the content of unreacted monomeric diisocyanate.

[0175] Distillation 1: 170°C, p = 0.03-0.05 mbar

[0176] Distillation 2: 180°C, p = 0.002-0.003 mbar

[0177] Rotation speed: 400rpm

[0178] Flow rate: 8.05-8.62kg / h

[0179] The composition and properties of the stripped polyurethane prepolymer are shown in Table 2.

[0180] Acetylated polyester polyol APO

[0181] First, amorphous polyester polyol (PO31) was reacted with acetic anhydride in an acetic acid solution at a molar ratio of 1:1. The reaction product thus obtained was distilled to remove the solvent and residual (unreacted) acetic anhydride.

[0182] Table 2 Stripped polyurethane prepolymer

[0183]

[0184] Adhesive composition

[0185] The polyurethane prepolymer (PU1, PU2 or PU3) was mixed with the other ingredients of the adhesive composition and stirred (~80 rpm) for 30 minutes at a temperature of 120° C. The adhesive composition thus obtained was filled in a tube and stored at normal room temperature in the absence of moisture.

[0186] In the case of an adhesive composition with a polyurethane prepolymer PU3, the stripped polyurethane prepolymer (PUP) is first reacted with one or more polyols (PO3X) at a temperature of 80° C. to obtain a reaction product containing a polyurethane prepolymer (PU3). If applicable, the reaction product is mixed with the other ingredients of the adhesive composition and stirred (~80 rpm) at a temperature of 120° C. for 30 minutes.

[0187] The adhesive composition of Example 18 was prepared using a two-step process. In the first step, acetylated polyester polyol (APO) and thermoplastic polyurethane (TPX) were mixed at 160°C with continuous stirring until a homogeneous mixture was obtained. In the second step, the temperature of the mixture was reduced to 120°C, and polyurethane prepolymers (PU2, PU3) were added to the mixture and stirred (~80 rpm) for 30 minutes.

[0188] The ingredients of the adhesive compositions and their properties are shown in Tables 3-6.

[0189] Opening hours

[0190] The sample adhesive composition provided in a sealed tube was first preheated in an oven to a temperature of 110°C for a period of 30 minutes. After heating, a sample of 20 grams of molten adhesive was applied with a spatula to the surface of a silicone paper strip (B700 white, Laufenberg & Sohn KG) placed on a heating plate. The size of the silicone paper strip was 30 cm x 10 cm, and the adhesive was applied as a film with a thickness of 500 μm and a size of 30 cm x 6 cm. Before applying the adhesive film, the silicone paper strip and the spatula were heated to a temperature of 110°C with a heating plate.

[0191] Immediately after applying the adhesive, remove the silicone paper strip from the hot plate and place it (adhesive film facing up) on a piece of plywood at room temperature (23° C.), and record this time as the starting point of the measurement. Every 10 seconds, a short strip of silicone-coated paper (non-silicone-treated surface facing outward) with a size of 10 cm×1 cm and formed in a roll is placed on the adhesive film and then slowly removed to separate the strip from the adhesive film. Repeat this procedure until the paper strip cannot be removed from the adhesive film without damaging the paper strip or the adhesive film. The time interval between the measurement starting point and the last sampling point is recorded as the open time (in seconds) of the adhesive composition.

[0192] The open time values ​​shown in Tables 3-6 were obtained as the average of three measurements made with the same adhesive composition.

[0193] Green strength (tensile lap shear strength)

[0194] The adhesive was kept in an oven at 130°C for more than 30 minutes to ensure that the adhesive was provided in a molten state. After heating, a sample of the molten adhesive was applied to the surface of a wood substrate having dimensions of 9 cm x 2 cm x 5 mm. The adhesive was applied as a coating film having dimensions of 2.5 cm x 1 cm and a thickness of 1 mm.

[0195] After applying adhesive, the second wooden substrate with the same size as the first wooden substrate is placed on the first wooden substrate along the edge of the adhesive film to form the test composite element. The second wooden substrate is tightly pressed on the first wooden substrate to remove air from the adhesive joint (bond). The weight of 150 grams is placed on the end surface of the second wooden substrate. Any adhesive that is squeezed out from the joint is trimmed with a knife. Use material testing device (Zwick Z 020) and the test speed of 10mm / min, according to the lap shear strength (LSS) of EN 1465 standard measurement test composite element. Adopt the test composite element that has stored 6 / 10 / 20 / 30 minutes after the first wooden substrate is bonded with the second substrate to measure the lap shear strength, to study the green blank (initial) adhesive bond strength obtained with the adhesive composition of test.

[0196] Curing time

[0197] A sample of the adhesive composition provided in a sealed tube was preheated in an oven to a temperature of 140°C for 20 minutes. After heating, a sample of 20 grams of the molten adhesive was applied with a spatula to the surface of a silicone paper strip (B700white, Laufenberg & Sohn KG) placed on a heating plate. The size of the silicone paper was 30 cm x 10 cm, and the adhesive was applied as a film with a thickness of 500 μm and a size of 30 cm x 6 cm. Before applying the adhesive film, the silicone paper strip and the spatula were heated to a temperature of 150°C with a heating plate.

[0198] Immediately after applying the adhesive, the silicone paper strip was removed from the hot plate and stored under standard climatic conditions (23°C, 55% relative humidity). The point in time at which the adhesive film solidified was recorded as the starting point of the measurement. At the defined sampling time, a test strip of 10 cm x 1 cm in size was cut from the silicone paper strip and placed on a hot plate at a temperature of 150°C. The procedure was continued until the adhesive film on the test strip no longer melted on the hot plate. The length of the time interval between the starting point and the last sampling point was recorded as the curing time (in hours) of the adhesive composition.

[0199] The values ​​for cure time shown in Tables 3-6 were obtained as the average of three measurements made with the same adhesive composition.

[0200] Tensile strength and elongation at break

[0201] The adhesive composition provided in a sealed tube was preheated in an oven to a temperature of 110° C. for a period of 30 minutes. After heating, a sample of 40 grams of molten adhesive was applied with a spatula to the surface of a silicone paper strip (B700 white, Laufenberg & Sohn KG) placed on a heating plate. The size of the silicone paper was 60 cm×10 cm, and the adhesive was applied as a film with a thickness of 500 μm and a size of 60 cm×6 cm. The silicone paper strip was removed from the heating plate immediately after the adhesive was applied and stored under standard climatic conditions (23° C., 55% relative humidity) for 7 days.

[0202] The measurement was performed using a method based on the DIN 53504 standard. Five rectangular specimens of 2.0 cm × 8.0 cm were cut from a cured adhesive film (cured for 14 days at 23°C / 50% relative humidity) with a thickness of 500 μm. The specimens were clamped in a tensile tester (Zwick Z 020) 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.

[0203] The values ​​of tensile strength and elongation at break shown in Tables 3-6 were obtained as averages of five measurements made with the same adhesive composition.

[0204] Viscosity

[0205] All viscosities were measured using a rotational viscometer Rheotec RC30 (cone diameter 25 mm, cone angle 1°, cone tip-plate distance 0.05 m, shear rate 50 s -1 ) determination.

[0206] The viscosity values ​​in Tables 3-6 were obtained as the average of three measurements made with the same adhesive composition.

[0207] Heat resistance (thermal stability under static load)

[0208] The adhesive composition provided in a sealed tube was preheated in an oven at a temperature of 130° C. for a period of 20 minutes. After heating, a sample of the molten adhesive was applied on the surface of a wood specimen (pine) having dimensions of 9 cm×2 cm×5 mm and having 1 mm copper wires as spacers on its surface. The adhesive was applied as a film having dimensions of 2 cm×2 cm and a thickness of 1 mm.

[0209] Immediately after applying adhesive, a second wood sample (pine) having the same size as the first wood sample was placed on the first wood sample along the edge of the adhesive film to form a test composite element. The second wood sample was tightly pressed on the first wood sample to remove air from the adhesive joint. A weight of 150 grams was placed on the top surface of the second wood sample. Any adhesive squeezed out from the joint was trimmed with a knife. The test composite element composed of the wood samples of the joint was then stored for 14 days under standard climate conditions (23°C, 40-60% relative humidity).

[0210] The test composite element was then suspended vertically from one end of the first wood specimen on a metal hook and placed in an oven. A metal weight corresponding to a 1 kg dead load was attached to the lower end of the second wood specimen of each composite element. Three composite elements were placed in the oven at a time for thermal stability measurements.

[0211] In the thermal stability measurement, the oven is first heated to a temperature 40°C below the expected adhesive joint failure temperature. The composite element is kept at this starting temperature for 60 minutes. In the case that no joint failure occurs, the temperature of the oven is increased by 10°C and the measurement is continued for another 60 minutes. The temperature of the oven is increased in steps of 10°C according to the procedure described above until joint failure occurs. The last measured temperature before joint failure occurs is recorded as a representative thermal stability temperature.

[0212] The values ​​of heat resistance of each adhesive composition shown in Tables 3 to 6 were obtained as the average of three measurements performed with the same test composite member prepared using the same adhesive composition.

[0213] Residual monomeric diisocyanate content

[0214] The residual monomeric diisocyanate content was determined using high pressure liquid chromatography (HPLC) with a photodiode array, 0.04 M sodium acetate / acetonitrile as mobile phase and N-propyl-4-nitrobenzylamine as derivatizing agent.

[0215] Table 3

[0216]

[0217] * SikaMelt-632

[0218]

[0219] Table 5

[0220]

[0221] Table 6

[0222]

Claims

1. An adhesive composition comprising at least one isocyanate-functional polyurethane polymer PU, wherein the at least one isocyanate-functional polyurethane polymer PU comprises: at least one isocyanate-functional polyurethane polymer PU1 obtained by reacting at least one polyester polyol PO1 and at least one diisocyanate P1 in a molar ratio of isocyanate groups to hydroxyl groups of 1.5 to 2.1, preferably 1.75 to 1.9, and / or at least one isocyanate-functional polyurethane polymer PU2 obtained by reacting at least one polyester polyol PO2 and at least one diisocyanate P2 in a molar ratio of at least 3, preferably at least 5, and subjecting the reaction mixture thus obtained to a treatment to reduce the amount of residual monomeric diisocyanate, preferably by distillation, and The adhesive composition further comprises at least one acetylated amorphous polyester polyol APO Or wherein the at least one isocyanate-functional polyurethane polymer PU comprises: at least one isocyanate-functional polyurethane polymer PU3 obtained by reacting at least one polyester polyol PO3 and at least one polyurethane prepolymer PUP in a molar ratio of isocyanate groups to hydroxyl groups of 1.9 to 3.5, preferably 2.2 to 2.8, and wherein the at least one polyester polyol PO3 comprises at least one amorphous polyester polyol PO31, and wherein the adhesive composition optionally further comprises at least one acetylated amorphous polyester polyol APO.

2. The adhesive composition according to claim 1, wherein the composition has a monomeric diisocyanate content of not more than 0.85 wt. %, preferably not more than 0.65 wt. %, based on the total weight of the adhesive composition.

3. Adhesive composition according to any one of the preceding claims, wherein the at least one acetylated polyester polyol APO is obtained by a process comprising reacting at least one amorphous polyester polyol with acetic anhydride in a molar ratio of 1.3:1 to 1:1.3, preferably subsequently subjecting the reaction product to a distillation in order to reduce the amount of residual acetic anhydride.

4. The adhesive composition according to any one of the preceding claims, wherein the at least one acetylated polyester polyol APO is present in the adhesive composition in an amount of at least 5 wt.-%, preferably at least 10 wt.-%, based on the total weight of the adhesive composition.

5. The adhesive composition according to claim 1, wherein the composition comprises at least 15 wt. %, preferably at least 35 wt. %, of the at least one isocyanate-functional polyurethane polymer PU, based on the total weight of the adhesive composition.

6. Adhesive composition according to any of the preceding claims, wherein the at least one isocyanate functional polyurethane polymer PU has an average isocyanate functionality determined according to ISO 14896-2009 standard method A in the range of 1.2-2.7, preferably 1.5-2.

5.

7. The adhesive composition according to any one of the preceding claims, wherein the at least one diisocyanate P1 and P2 is a monomeric diisocyanate, preferably having a number average molecular weight (M) of not more than 1000 g / mol. n ).

8. The adhesive composition according to any one of the preceding claims, wherein the at least one isocyanate-functional polyurethane polymer PU2 comprises: at least one first isocyanate-functional polyurethane polymer PU21 obtained by reacting at least one polyester polyol PO21 and the at least one diisocyanate P2, and / or at least one second isocyanate-functional polyurethane polymer PU22 obtained by reacting at least one polyester polyol PO22 and the at least one diisocyanate P2, Wherein the at least one polyester polyol PO21 is a polyester polyol which is solid at 23°C, and the at least one polyester polyol PO22 is a polyester polyol which is liquid at 23°C.

9. Adhesive composition according to any of the preceding claims, wherein the at least one diisocyanate P2 comprises at least one diisocyanate P21 and / or at least one diisocyanate P22, wherein the at least one diisocyanate P21 is a monomeric diphenylmethane diisocyanate having a 2,4′-isomer content of at least 25% by weight, preferably at least 35% by weight, based on the total weight of the diisocyanate P21, and wherein the at least one diisocyanate P22 is a monomeric diphenylmethane diisocyanate having a 4,4′-isomer content of at least 75% by weight, preferably at least 95% by weight, based on the total weight of the diisocyanate P22.

10. Adhesive composition according to any of the preceding claims, wherein the at least one polyurethane prepolymer PUP is obtained by reacting at least one polyester polyol PO4 and the at least one diisocyanate P2 in a molar ratio of at least 3, preferably at least 4, and subjecting the reaction mixture thus obtained to a treatment to reduce the amount of residual monomeric diisocyanate, preferably by distillation. 11 . The adhesive composition according to claim 10 , wherein the at least one polyester polyol PO4 comprises or consists of poly(tetramethylene ether) glycol.

12. The adhesive composition according to any one of the preceding claims, wherein the composition further comprises at least one additional thermoplastic polymer TP which does not contain isocyanate groups.

13. A process for producing an adhesive composition according to any of the preceding claims, comprising mixing the at least one isocyanate-functional polymer PU and the other constituents of the adhesive composition with one another.

14. Use of the adhesive composition according to any one of claims 1 to 13 as assembly adhesive, laminating adhesive or as adhesive for building sandwich elements.

15. A method of adhesively bonding a first substrate to a second substrate, the method comprising the steps of: 1) heating the adhesive composition according to any one of claims 1 to 13 to provide a molten adhesive composition, II) applying the molten adhesive composition to the surface of the first substrate to form an adhesive film, III) contacting the adhesive film with a surface of a second substrate, and IV) Chemical curing of the adhesive film with water, in particular with atmospheric moisture.

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