Reactive hot melt adhesive with low content of monomeric diisocyanate

Abstract

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

Description

Technical Field

[0001] The present invention relates to a reactive polyurethane-based hot melt adhesive having a low content of monomeric diisocyanate, and in particular to the use of the adhesive as an assembly adhesive, a laminating adhesive, or a sandwich element construction adhesive in the automotive industry.

Background Art

[0002] A hot melt adhesive is a solvent-free adhesive that is solid at room temperature and is applied in a molten form to the substrates to be joined. After cooling, the adhesive solidifies and forms an adhesive bond with the substrates by physically occurring bonding. Conventional hot melt adhesives are non-reactive adhesives and are not suitable for use at high temperatures because they soften again when heated. Reactive hot melt adhesives contain a polymer having reactive groups that enable chemical curing of the adhesive, for example, by crosslinking of polymer chains. Due to the cured polymer matrix, the reactive hot melt does not soften even when heated, and therefore these adhesives are also suitable for use at high temperatures. Chemical curing of the polymer can be initiated, for example, by heating the adhesive composition or by bringing it into contact with water. Moisture-curing hot melt adhesives typically contain a polymer functionalized with isocyanate groups or silane groups, which enables crosslinking of the polymer chains when in contact with water, especially moisture in the atmosphere.

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

[0004] Since the isocyanate-functional prepolymer is obtained by reacting a polyol with a substantially stoichiometric excess of monomeric diisocyanate, PU-RHM adhesives typically contain large amounts of unreacted monomeric diisocyanate ("residual monomer"). Coating temperatures of hot melt adhesives such as 85 to 200 °C, particularly 120 to 160 °C, increase the vapor pressure of the residual monomers and cause them to volatilize. Since certain diisocyanates are toxic, additional measures are often taken to reduce the concentration in the atmosphere in places where workers are exposed. In some cases, a ventilation structure such as a "down draft booth" is provided to minimize worker exposure to the volatilized monomers. However, the installation of such a ventilation structure can be costly and difficult. According to chemical substance laws and classification criteria, when the content of unreacted monomeric diisocyanate in the adhesive exceeds the limit value of 0.1% by weight, the product is obliged to be labeled as harmful (GHS07 / GHS08). Furthermore, when the concentration of monomeric MDI exceeds 1%, the product must be labeled with an additional danger statement (stamen) (H351). For these reasons, various efforts have been made to reduce the concentration of residual diisocyanate in PU-RHM adhesives.

[0005] One obvious approach to providing a label-free PUR-RHM adhesive is to perform physical unit operations such as distillation or extraction processes on the reaction product obtained from the reaction of a diisocyanate and a polyol to reduce the content of residual monomers. Methods based on this approach are disclosed, for example, in WO 01 / 14443 A1 pamphlet and WO 01 / 40340 A2 pamphlet. However, it has been found that reducing the residual monomer content of a reaction product containing a polyurethane prepolymer obtained from the reaction of a diisocyanate and an amorphous polyol by distillation is almost impossible due to the high viscosity of such polyurethane prepolymers. On the other hand, in order to adjust various adhesive properties of the cured adhesive, particularly open time, green strength, viscosity, and flexibility, amorphous polyols are typically required in PUR-RHM adhesives in addition to other types of polyols.

[0006] Another approach is based on the use of a distilled (stripped) short-chain polyurethane prepolymer with a low content of monomeric diisocyanate, which is commercially available under the trade name Desmodur® such as Desmodur® LS2397 (from Covestro). Such stripped prepolymers can be used to replace a part of the monomeric diisocyanate in the reaction mixture or as a "reactive diluent" to reduce the content of residual monomers in the final adhesive composition. However, it has been found that these types of adhesive compositions have problems such as a decrease in heat resistance, insufficient storage stability, and a decrease in initial (green) adhesive strength.

[0007] The concentration of the residual monomer can also be reduced by using a two-step manufacturing process that includes a first step of reacting a first type of polyol with a diisocyanate monomer to obtain a reaction mixture containing a polyurethane prepolymer and a residual monomer, and a subsequent second step of adding another polyol to the reaction mixture to reduce the content of the residual monomer. An example of this approach is disclosed in European Patent Application Publication No. 3088435A1. Another example is the three-step process disclosed in European Patent Application Publication No. 3116930A1, in which the polyol first reacts with the diisocyanate monomer to produce a reaction product, which is then modified by the addition of mercaptosilane. Subsequently, the amount of monomeric diisocyanate is further reduced by adding a distilled polyurethane prepolymer before, during, and / or after the addition of mercaptosilane. Approaches based on the use of such stepwise manufacturing processes have the inherent drawback of involving multiple reaction steps, which significantly increases the manufacturing cost.

[0008] Therefore, there is a need for a new type of reactive polyurethane hot melt adhesive that has a low content of residual monomers and can be manufactured using a simple and cost-effective manufacturing process.

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a moisture-curing polyurethane hot melt adhesive that overcomes or at least alleviates the drawbacks of the moisture-curing polyurethane adhesives of the prior art described above.

[0010] In particular, an object of the present invention is to provide a moisture-curing polyurethane hot melt adhesive that does not fall within the H351 classification.

[0011] Another object of the present invention is to provide a moisture-curing polyurethane hot melt adhesive not falling under the H351 classification, which is excellent in adhesive bonding properties, particularly in the green (initial) strength, tensile strength, elongation, and heat resistance of the cured adhesive.

Means for Solving the Problems

[0012] The subject of the present invention is the adhesive composition defined in claim 1.

[0013] To achieve the above object, two different approaches based on the same basic principle have been identified. According to the first approach, at least one blocked amorphous polyester polyol as a non-reactive diluent is added to a reaction product containing at least one isocyanate-functional polyurethane polymer with a low residual monomer content in order to obtain an adhesive having the desired properties. A suitable isocyanate-functional polyurethane polymer with a low residual monomer content can be obtained by using a slightly stoichiometric excess of isocyanate groups with respect to the hydroxyl groups in the reaction mixture, or by using a considerably stoichiometric excess of isocyanate groups with respect to the hydroxyl groups and then performing a treatment such as distillation on the reaction product to reduce the residual monomer content.

[0014] The second approach is based on reacting a polyurethane prepolymer with a low residual monomer content with an amorphous polyol to obtain an adhesive composition containing the polyurethane prepolymer with the desired properties and having a low residual monomer content. By both of the above-described approaches, it becomes possible to obtain a moisture-curing polyurethane hot melt composition with very low residual monomer content, having excellent adhesive properties, particularly in the green (initial) strength, tensile strength, elongation, and heat resistance of the cured adhesive. Furthermore, the present invention is not limited to the use of only one of the above-described approaches, and adhesive compositions based on a combination of both approaches are also considered to be within the scope of the present invention.

[0015] Other subjects of the present invention are indicated in other independent claims. Preferred embodiments of the present invention are indicated in the dependent claims.

Mode for Carrying Out the Invention

[0016] The subject of the present invention is an adhesive composition containing at least one isocyanate-functional polyurethane polymer PU, further containing at least one acetylated amorphous polyester polyol APO, wherein at least one isocyanate-functional polyurethane polymer PU is · at least one isocyanate-functional polyurethane polymer PU1 obtained by reacting at least one polyester polyol PO1 and at least one diisocyanate P1 at 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 at a molar ratio of at least 3, preferably at least 5, and performing a treatment to reduce the amount of residual monomeric diisocyanate, preferably distillation, on the resulting reaction mixture is included, or optionally further containing at least one acetylated amorphous polyester polyol APO, wherein at least one isocyanate-functional polyurethane polymer PU is · at least one isocyanate-functional polyurethane polymer PU3 obtained by reacting at least one polyester polyol PO3 and at least one polyurethane prepolymer PUP at a molar ratio of isocyanate groups to hydroxyl groups of 1.9 to 3.5, preferably 2.2 to 2.8 is included, wherein at least one polyester polyol PO3 includes at least one amorphous polyester polyol PO31, is an adhesive composition.

[0017] The prefix "poly" in the names of substances such as "polyol" and "polyisocyanate" formally refers to a substance containing two or more functional groups per molecule. For example, a polyol is a compound having two or more hydroxyl groups, and a polyisocyanate is a compound having two or more isocyanate groups.

[0018] The term "α-olefin" refers to an alkene having the molecular formula C x H 2x (where x corresponds to the number of carbon atoms) and is characterized by a carbon-carbon double bond at the first carbon atom (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 called "α-olefins" in the present disclosure.

[0019] The term "prepolymer" refers to a polymer containing at least one, usually two or more, reactive groups (such as isocyanate groups). Due to the reactive groups, the prepolymer can be chain-extended, crosslinked, or bonded.

[0020] The term "functionalized polymer" refers to a polymer that has been chemically modified such that a functional group is included in the polymer backbone. In contrast, the term "non-functionalized polymer" refers to a polymer that has not been chemically modified to include functional groups such as epoxy, silane, sulfonate, amide, or anhydride groups in the polymer backbone.

[0021] The term "polyurethane polymer" refers to a polymer prepared by a so-called diisocyanate polyaddition process. These include polymers that contain little or no urethane groups. Examples of polyurethane polymers are polyether-polyurethane, polyester-polyurethane, polyether-polyurea, polyurea, polyester-polyurea, polyisocyanurate, and polycarbodiimide.

[0022] The term "polyurethane prepolymer" refers to a polyurethane polymer containing one or more unreacted isocyanate groups. Polyurethane prepolymers can be obtained by reacting an excess of polyisocyanate with a polyol, and they are the polyisocyanate itself. The terms "isocyanate-functional polyurethane polymer" and "polyurethane prepolymer" can be used interchangeably.

[0023] When the isocyanate group is directly bonded to an aliphatic, cycloaliphatic, or arylaliphatic moiety, the isocyanate is called "aliphatic". Accordingly, the corresponding functional group is called an aliphatic isocyanate group. Further, when the isocyanate group is directly bonded to an aromatic moiety, the isocyanate is called "aromatic". Accordingly, the corresponding functional group is called an aromatic isocyanate group.

[0024] 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" may refer to the weight-average molecular weight or the number-average molecular weight (M n , M w ) of an oligomeric or polymeric mixture of molecules or moieties. The molecular weight can be determined by conventional methods, preferably using polystyrene as a standard, styrene-divinylbenzene gels with pore sizes of 100 angstroms, 1000 angstroms, and 10000 angstroms as columns, and using tetrahydrofuran as a solvent at 35 °C or 1,2,4-trichlorobenzene as a solvent at 160 °C depending on the molecule by gel permeation chromatography (GPC).

[0025] The term "average OH functionality" refers to the average number of hydroxyl (OH) groups per molecule. The average OH functionality of a compound is related to the number-average molecular weight (M n) can be calculated based on the hydroxyl value. The hydroxyl value of a compound can be determined by using the method defined in the EN ISO4629-2 standard.

[0026] The term "softening point" or "softening temperature" refers to the temperature at which the compound softens in a rubber-like state or the temperature at which the crystalline portions in the compound melt. The softening point can be measured by the ring and ball method in accordance with the DIN EN1238 standard.

[0027] The term "open time" refers to the length of time during which an adhesive applied to the surface of a substrate can form an adhesive bond after coming into contact with another substrate.

[0028] The "amount or content of at least one component X" in a composition, for example, the "amount of at least one polyisocyanate P", refers to the sum of the individual amounts of all polyisocyanates P contained in the composition. Further, when 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 20% by weight.

[0029] The term "room temperature" refers to a temperature of about 23°C.

[0030] The adhesive composition of the present invention preferably exhibits a low level of monomeric diisocyanate.

[0031] The term "monomeric diisocyanate" in the present disclosure refers to an organic compound having two isocyanate groups separated by a divalent hydrocarbon radical, preferably having an average molecular weight of 1000 g / mol or less, more preferably 500 g / mol or less, and even more preferably 400 g / mol or less. In particular, the monomeric diisocyanate does not contain a urethane group, and oligomeric or polymeric products of diisocyanate monomers such as adducts of monomeric diisocyanates are not regarded as "monomeric diisocyanate" in the context of the present invention.

[0032] 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%, still more preferably less than 0.5 wt%, even more preferably less than 0.35 wt%, particularly 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 with a monomeric diisocyanate content of less than 0.1 wt% can be used safely without special protective measures, and thus can be sold in many countries without being labeled as harmful (Xn).

[0033] Preferably, 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%, still more preferably at least 40 wt%, based on the total weight of the adhesive composition.

[0034] According to one or more embodiments, 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%, still more preferably 40 - 70 wt%, even more preferably 40 - 65 wt%, based on the total weight of the adhesive composition.

[0035] According to one or more embodiments, at least one isocyanate-functional polyurethane polymer PU has an average isocyanate functionality in the range of 1.2 - 2.7, preferably 1.5 - 2.5, determined according to ISO 14896 - 2009 standard method A, and / or has an isocyanate content in the range of 0.5 - 30 wt%, preferably 1.0 - 25 wt%, determined using the method defined in ISO 11909:2007 standard.

[0036] A compound suitable for use as at least one acetylated amorphous polyester polyol APO can be obtained by acetylation of an amorphous polyester polyol.

[0037] According to one or more embodiments, at least one acetylated amorphous polyester polyol APO is obtained by a method 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, and preferably subsequently distilling the reaction product to reduce the amount of residual acetic anhydride. Preferably, the reaction of at least one amorphous polyester polyol with acetic anhydride is carried out in an acetic acid solution.

[0038] Preferably, when used, at least one acetylated amorphous polyester polyol APO 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.

[0039] According to one or more embodiments, at least one acetylated amorphous polyester polyol APO is present in the adhesive composition in an amount of 5 to 65 wt%, preferably 10 to 55 wt%, more preferably 10 to 50 wt%, still more preferably 15 to 45 wt%, even more preferably 20 to 45 wt% based on the total weight of the adhesive composition.

[0040] Suitable polyester polyols for use in the present invention include liquid, amorphous, partially crystalline, and crystalline polyester polyols. These 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 alcohol, neopentyl glycol, glycerol, 1,1,1-trimethylolpropane, or a mixture of the above alcohols and an organic dicarboxylic acid or tricarboxylic acid, preferably a dicarboxylic acid, or its anhydride or ester, 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 acid, isophthalic acid, terephthalic acid, and hexahydrophthalic acid, or a mixture of the above acids, and can be obtained by reacting them, or may be a polyester polyol produced from a lactone such as ε-caprolactone, also known as polycaprolactone for example.

[0041] Preferred polyester polyols include those obtained by reacting adipic acid, sebacic acid or dodecanedicarboxylic acid as a dicarboxylic acid with hexanediol or neopentyl glycol as a dihydric alcohol. Additional examples of suitable polyester polyols include polyester polyols derived from oleochemicals. This type of polyester polyol can be prepared, for example, by fully ring-opening an epoxidized triglyceride 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 partially transesterifying the triglyceride derivative to obtain an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl radical. Particularly suitable crystalline or semi-crystalline polyester polyols include adipic acid / hexanediol polyester and dodecanedicarboxylic acid / hexanediol polyester.

[0042] According to one or more embodiments, 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 polyester polyol PO2 and at least one diisocyanate P2 are reacted in a molar ratio of at least 3, preferably at least 5, and the resulting reaction mixture is subjected to a treatment to reduce the amount of residual monomeric diisocyanate, preferably distillation, to obtain at least one isocyanate-functional polyurethane polymer PU2 is included.

[0043] The reaction of at least one polyester polyol PO1 and at least one diisocyanate P1 can be carried out using conventional techniques used in the preparation of polyurethane prepolymers. This means, in particular, that the hydroxyl groups of the polyester polyol PO1 react with the isocyanate groups of the diisocyanate P1.

[0044] Preferably, by the reaction of at least one polyester polyol PO1 and at least one diisocyanate P1, substantially all of the hydroxyl groups of at least one polyester polyol PO1, for example at least 95%, usually at least 99% of the hydroxyl groups of at least one polyester polyol PO1, are converted.

[0045] The reaction of at least one polyester polyol PO1 and at least one diisocyanate P1 can be carried out, for example, at a temperature in the range of 60 to 160 °C, preferably 80 to 140 °C, optionally in the presence of a catalyst. The reaction time depends on the temperature used as will be understood, 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 and tin catalysts such as Coscat® 83 (from Vertellus Performance Materials Inc.).

[0046] Similar considerations also apply to the reaction of at least one polyester polyol PO2 and at least one diisocyanate P2.

[0047] According to one or more embodiments, 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.

[0048] Generally, the expression "at least one component X comprises at least one component XN", for example, "at least one polyester polyol PO1 comprises at least one solid polyester polyol PO11", is understood in the context of the present disclosure to mean that the composition comprises one or more solid polyester polyols PO11 as representatives of at least one polyester polyol PO1.

[0049] Preferably, at least one polyester polyol PO11 that is solid at 23 °C is a crystalline polyester polyol that is solid at 23 °C and preferably has the following: · A hydroxyl value measured according to EN ISO 4629-2 standard of 10 to 100 mgKOH / g, preferably 15 to 50 mgKOH / g, and / or · A softening point measured by the ring and ball method according to ISO 4625 standard of 50 to 100 °C, preferably 60 to 90 °C, and / or · A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1,500 to 7,500 g / mol.

[0050] Solid polyester polyols suitable for use as polyester polyol PO11 are commercially available under the trade name of the 7300 series (from Evonik Industries).

[0051] Preferably, at least one polyester polyol PO12 that is liquid at 23 °C has the following: · A hydroxyl value measured according to EN ISO 4629-2 standard of 10 to 100 mgKOH / g, preferably 15 to 50 mgKOH / g, and / or · A glass transition temperature measured by DCS of -10 °C or lower, preferably -25 °C or lower, and / or · A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1,500 to 7,500 g / mol.

[0052] Liquid polyester polyols suitable for use as polyester polyol PO12 are commercially available under the trade name of the 7200 series (from Evonik Industries) and under the trade name of Fineplus® HM (from DIC Performance Resins) such as Fineplus® HM2686.

[0053] According to one or more preferred embodiments, at least one polyester polyol PO1 includes at least one polyester polyol PO11 that is solid at 23°C and at least one polyester polyol PO12 that is liquid at 23°C, and 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, still more preferably 2:1 to 1:2, and even more preferably 1.5:1 to 1:1.5.

[0054] Diisocyanates particularly suitable for use as at least one diisocyanate P1 and P2 include, for example, aliphatic, cycloaliphatic, and aromatic monomeric diisocyanates.

[0055] According to one or more preferred embodiments, at least one diisocyanate P1 and P2 is a monomeric diisocyanate, preferably a monomeric diisocyanate having a number average molecular weight (M n ) of 1000 g / mol or less, preferably 500 g / mol or less, and more preferably 400 g / mol or less.

[0056] Examples of suitable monomeric diisocyanates include aliphatic and aromatic monomeric diisocyanates such as 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 - diisocyanato - 2,2,6 - trimethylcyclohexane (TMCDI), 1,3 - and 1,4 - bis(isocyanatomethyl)cyclohexane, m - and p - xylylene diisocyanate (m - and p - XDI) and mixtures of these isomers, m - and p - tetramethyl - 1,3 - and 1,4 - xylylene diisocyanate (m - and p - TMXDI) and mixtures of these isomers, bis(1 - isocyanato - 1 - methylethyl)naphthalene, 2,4 - and 2,6 - tolylene diisocyanate and mixtures of these isomers (TDI), 4,4’ - diphenylmethane diisocyanate (optionally containing a proportion of 2,4’ - and / or 2,2’ - diphenylmethane diisocyanate) (MDI), 1,3 - and 1,4 - phenylene diisocyanate (PDI) and mixtures of these isomers, naphthalene 1,5 - diisocyanate (NDI), 3,3’ - dimethyl - 4,4’ - diisocyanatobiphenyl (TODI), and dianisidine diisocyanate (DADI).

[0057] Suitable aliphatic and aromatic monomeric diisocyanates are commercially available under trade names such as Lupranat® (from BASF), Desmodur® (from Covestro), and Duranate® (from Asahi Kasei Corporation).

[0058] According to one or more embodiments, at least one of the diisocyanates P1 and P2 is selected from the group consisting of 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, tolylene diisocyanate (TDI), particularly 2,4-tolylene diisocyanate (2,4TDI), 2,6-tolylene diisocyanate (2,6TDI), or a mixture of these isomers, 1,6-hexamethylene diisocyanate (HDI), and 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI). Further, those skilled in the art recognize that industrial grade products of diisocyanates may frequently contain isomer mixtures or other isomers as impurities.

[0059] According to one or more embodiments, the isocyanate-functional polyurethane polymer PU2 has a monomeric diisocyanate content of 1.0 wt% or less, preferably 0.5 wt% or less, based on the total weight of the isocyanate-functional polyurethane polymer.

[0060] According to one or more embodiments, at least one of the isocyanate-functional polyurethane polymers PU2 is · at least one first isocyanate-functional polyurethane polymer PU21 obtained by reacting at least one polyester polyol PO21 with 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 with at least one diisocyanate P2, comprising at least one polyester polyol PO21 being a polyester polyol that is solid at 23°C and at least one polyester polyol PO22 being a polyester polyol that is liquid at 23°C.

[0061] According to one or more embodiments, at least one polyester polyol PO21 has the following: ·A hydroxyl value measured according to EN ISO4629-2 standard of 10 to 100 mgKOH / g, preferably 15 to 50 mgKOH / g, and / or ·A softening point measured by the ring and ball method according to ISO4625 standard of 45 to 100°C, preferably 55 to 90°C, and / or ·A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1500 to 7500 g / mol.

[0062] According to one or more embodiments, at least one polyester polyol PO22 has the following: ·A hydroxyl value measured according to EN ISO4629-2 standard of 10 to 100 mgKOH / g, preferably 15 to 50 mgKOH / g, and / or ·A glass transition temperature measured by DSC of -10°C or lower, preferably -25°C or lower, and / or ·A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1500 to 7500 g / mol.

[0063] According to one or more embodiments, at least one isocyanate-functional polyurethane polymer PU2 includes at least one isocyanate-functional polyurethane polymer PU21 and at least one isocyanate-functional polyurethane polymer PU22, and 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, still more preferably 5:1 to 2:1, and even more preferably 5:1 to 3:1.

[0064] According to one or more embodiments, at least one diisocyanate P2 includes at least one diisocyanate P21 and / or at least one diisocyanate P22. At least one diisocyanate P21 is a monomeric diphenylmethane diisocyanate having an 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 at least one second diisocyanate P22 is a monomeric diphenylmethane diisocyanate having an isomer content of at least 75% by weight, preferably at least 95% by weight, based on the total weight of the second diisocyanate P22.

[0065] According to one or more embodiments, at least one diisocyanate P2 includes at least one diisocyanate P21 or is composed of at least one diisocyanate P21. According to one or more embodiments, at least one diisocyanate P2 includes at least one diisocyanate P22 or is composed of at least one diisocyanate P22.

[0066] According to one or more preferred embodiments, at least one diisocyanate P2 is composed of at least one diisocyanate P22.

[0067] According to one or more embodiments, at least one isocyanate-functional polyurethane polymer PU is · 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 comprising, and at least one polyester polyol PO3 comprises at least one amorphous polyester polyol PO31.

[0068] According to one or more embodiments, the isocyanate-functional polyurethane polymer PU3 has a monomeric diisocyanate content of 1.0 wt% or less, preferably 0.5 wt% or less, based on the total weight of the isocyanate-functional polyurethane polymer PU3.

[0069] Preferably, at least one amorphous polyester polyol PO31 has the following: · A hydroxyl value measured according to EN ISO4629-2 standard of 15 to 100 mgKOH / g, preferably 25 to 75 mgKOH / g, and / or · A softening point measured by the ring and ball method according to ISO4625 standard of 55 to 115 °C, preferably 65 to 105 °C, and / or · A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1500 to 7500 g / mol, and / or · A glass transition temperature measured by DCS of at least 0 °C, preferably at least 15 °C, more preferably at least 25 °C.

[0070] Polyester polyols suitable for use as at least one amorphous polyester polyol PO31 are commercially available, for example, under the trade names of Dynacoll® 7100 series (from Evonik Industries) and Fineplus® HM1800 series (from DIC Performance Resins).

[0071] According to one or more preferred embodiments, at least one polyester polyol PO3 comprises at least one amorphous polyester polyol PO31 and at least one crystalline polyester polyol PO32 that is solid at 23°C.

[0072] Preferably, at least one crystalline polyester polyol PO32 that is solid at 23°C has the following: · A hydroxyl value measured according to EN ISO4629-2 standard of 10 to 100 mgKOH / g, preferably 15 to 50 mgKOH / g, and / or · A softening point measured by the ring and ball method according to ISO4625 standard of 45 to 100°C, preferably 55 to 90°C, and / or · A number average molecular weight (M n ) of 500 to 10,000 g / mol, preferably 1,500 to 7,500 g / mol.

[0073] Preferably, 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 performing a treatment to reduce the amount of residual monomeric diisocyanate, preferably distillation, on the resulting reaction mixture.

[0074] According to one or more embodiments, the polyurethane prepolymer PUP has a monomeric diisocyanate content of 1.0 wt% or less, preferably 0.5 wt% or less, based on the total weight of the polyurethane prepolymer PUP.

[0075] Suitable polyester polyols for use as at least one polyester polyol PO4 include liquid polyester polyols and partially crystalline and crystalline polyester polyols that are solid at a temperature of 23°C.

[0076] According to one or more preferred embodiments, at least one polyester polyol PO4 comprises or consists of poly(tetramethylene ether) glycol, preferably having a number average molecular weight (M n ) of 250 to 10,000 g / mol, preferably 500 to 7,500 g / mol.

[0077] According to one or more embodiments, at least one isocyanate-functional polyurethane polymer PU comprises at least one isocyanate-functional polyurethane polymer PU2 and at least one isocyanate-functional polyurethane polymer PU3, and 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.

[0078] According to one or more further embodiments, at least one isocyanate-functional polyurethane polymer PU comprises at least one isocyanate-functional polyurethane polymer PU2 and at least one isocyanate-functional polyurethane polymer PU3, and 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 the adhesive composition further contains at least one acetylated polyester polyol APO.

[0079] According to one or more embodiments, the adhesive composition further contains at least one additional thermoplastic polymer TP that does not contain isocyanate groups.

[0080] Examples of compounds suitable for use as at least one additional thermoplastic polymer TP include, for example, thermoplastic polyurethane (TPU) and thermoplastic polyester resin.

[0081] Thermoplastic polyurethane (TPU) is a polyurethane-based thermoplastic elastomer (TPE), which is a linear segmented block copolymer composed of (or consisting of) alternately arranged hard segments and soft segments (or hard domains and soft domains), formed by (1) the reaction of a diisocyanate with a short-chain diol (so-called chain extender) and (2) the reaction of a diisocyanate with a long-chain diol.

[0082] Suitable thermoplastic polyester resins include, for example, those having a hydroxyl value measured according to EN ISO 4629-2 of 15 mg KOH / g or less, preferably 12 mg KOH / g or less, and / or a number average molecular weight (M n ) of at least 5000 g / mol, preferably at least 7500 g / mol.

[0083] According to one or more embodiments, at least one additional thermoplastic polymer TP includes 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 15 mg KOH / g or less, preferably 12 mg KOH / g or less.

[0084] According to one or more embodiments, at least one additional thermoplastic polymer TP is present in the adhesive composition in an amount of 0.5 to 30% by weight, preferably 2.5 to 25% by weight, more preferably 3.5 to 20% by weight, based on the total weight of the adhesive composition.

[0085] According to one or more embodiments, the adhesive composition further includes at least one crosslinking agent, preferably an oligomeric polyisocyanate.

[0086] According to one or more embodiments, at least one crosslinking agent has the following: · A number average molecular weight (M n ) of 150 to 5000 g / mol, preferably 250 to 3500 g / mol, more preferably 350 to 2500 g / mol, still more preferably 350 to 1500 g / mol, and / or · A viscosity measured at 23 °C according to ISO 3219:1994 of 100 to 5000 MPa·s, preferably 250 to 4000 MPa·s, more preferably 350 to 3500 MPa·s, still more preferably 450 to 2500 MPa·s, even more preferably 500 to 2000 MPa·s, and / or · A free NCO group content measured according to ISO 11909:2007 of 10 to 35% by weight, preferably 15 to 30% by weight, more preferably 20 to 30% by weight.

[0087] According to one or more embodiments, at least one crosslinking agent is an aliphatic or aromatic oligomeric polyisocyanate.

[0088] According to one or more embodiments, at least one crosslinking agent is a trimer of an aliphatic diisocyanate, preferably 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 mixture of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), perhydrodiphenylmethane 2,4'- and 4,4'-diisocyanate (HMDI), 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), xylylene m- and p-diisocyanate (XDI), tetramethylxylylene 1,3- and 1,4-diisocyanate (TMXDI), and 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane.

[0089] The industrial standard form of aliphatic diisocyanate trimers is typically a mixture of substances with different degrees of polymerization and chemical structures. Suitable commercially available aliphatic diisocyanate trimers include oligomeric mixtures of industrial standards with an average NCO functionality of 2.4 to 4.0 and particularly containing isocyanurate groups, iminooxadiazinedione groups, or biuret groups. Further, allophanate groups, carbodiimide groups, uretonimine groups, or oxadiazinetrione groups may be present. A preferred industrial standard form of aliphatic diisocyanate trimers is an oligomeric mixture in which the aliphatic diisocyanate trimers occupy the majority in a mixture with dimers and higher oligomers. Particularly preferred is an oligomeric mixture containing a small amount of monomeric diisocyanate, especially those with a monomeric diisocyanate content of 1.0 wt% or less, preferably 0.5 wt% or less, more preferably 0.25 wt% or less, and even more preferably 0.25 wt% or less.

[0090] Suitable commercially available industrial grade oligomer mixtures of aliphatic diisocyanates are HDI biurets, such as Desmodur® N100 and N3200 (from Covestro), Tolonate® HDB and HDB-LV (from Vencorex), and Duranate® 24A-100 (from Asahi Kasei Corporation); HDI isocyanurates, such as Desmodur® N3300, N3600, and N3790BA (all from Covestro), Tolonate® HDT, HDT-LV, and HDT-LV2 (all from Vencorex), Duranate® TPA-100 and THA-100 (from Asahi Kasei Corporation), and Coronate® HX (from Nippon Polyurethane Industry Co., Ltd.); HDI uretdione, such as Desmodur® N3400 (from Covestro); HDI iminooxadiazinedione, such as Desmodur® XP2410 (from Covestro); HDI allophanate, such as Desmodur® VP LS2102 (from Covestro); and IPDI isocyanurate, such as Desmodur® Z4470 (from Covestro) in solution form or Vestanat® T1890 / 100 (from Evonik Degussa) in solid form.

[0091] According to one or more embodiments, at least one crosslinking agent is present in the adhesive composition in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the total weight of the adhesive composition.

[0092] The adhesive composition can further include substances and additives selected from the group consisting of auxiliary substances and additives, such as fillers, flame retardants, plasticizers, adhesion promoters, UV absorbers, UV stabilizers, heat stabilizers, fluorescent brighteners, pigments, dyes, and desiccants. Examples of suitable UV stabilizers that can be added to the adhesive composition include, for example, hindered phenols.

[0093] Examples of fillers suitable for use in the adhesive composition include inorganic and organic fillers, especially natural, ground, or precipitated calcium carbonate, optionally coated with a fatty acid or fatty acid ester, especially stearic acid, barite, talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica (potassium aluminum silicate), molecular sieve, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica such as fumed silica from a thermal decomposition process, industrially produced carbon black, graphite, metal powders such as aluminum, copper, iron, silver, or steel, PVC powder, or hollow spheres.

[0094] According to one or more embodiments, the adhesive composition preferably further comprises at least one inorganic filler selected from calcium carbonate, barite, talc, quartz powder, quartz sand, dolomite, wollastonite, kaolin, calcined kaolin, mica, molecular sieve, aluminum oxide, aluminum hydroxide, magnesium hydroxide, silica, carbon black, graphite, metal powder, and hollow spheres.

[0095] When used, the at least one inorganic filler is preferably present in the adhesive composition in an amount of 1.5 to 35% by weight, more preferably 2.5 to 30% by weight, even more preferably 5 to 25% by weight, and still more preferably 5 to 20% by weight, based on the total weight of the adhesive composition.

[0096] According to one or more embodiments, the adhesive composition further contains 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.

[0097] 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 to 30% by weight, preferably 5 to 25% by weight, and more preferably 10 to 25% by weight, based on the total weight of the adhesive composition.

[0098] According to one or more embodiments, at least one polyolefin resin that is liquid at 23°C has the following: · A number average molecular weight (M n ) of 500 to 5000 g / mol, preferably 500 to 3500 g / mol, more preferably 1000 to 3000 g / mol, and even more preferably 1500 to 2500 g / mol, and / or · A pour point determined according to ISO 3016 standard in the range of -10 to +15°C, preferably -10 to +10°C.

[0099] According to one or more embodiments, at least one polyolefin resin that is liquid at 23°C is selected from the group consisting of polyisobutylene (PIB) and polybutene, particularly low molecular weight polyisobutylene and low molecular weight polybutene, preferably having a number average molecular weight (M n ) of 500 to 5000 g / mol, more preferably 500 to 3500 g / mol, even more preferably 1000 to 3000 g / mol, and even more preferably 1500 to 2500 g / mol, and / or a pour point determined according to ISO 3016 standard in the range of -10 to +15°C, preferably -10 to +10°C. As used herein, the term "polyisobutylene" refers to polyolefins and olefin oligomers of isobutylene or 2-methyl-1-propene, preferably containing at least 75%, more preferably at least 85% of repeating units derived from isobutylene. As used herein, the term "polybutene" refers 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 only 1-butene, the material is called "poly-n-butene" or "PNB".

[0100] Suitable commercially available polybutenes and polyisobutylenes that are liquid at 23 °C include, for example, Indopol® H-300 and Indopol® H-1200 (from Ineos); Glissopal® V230, Glissopal® V500, and Glissopal® V700 (from BASF); Dynapak® poly230 (from Univar GmbH, Germany); and Daelim® PB950 (from Daelim Industrial).

[0101] The adhesive composition may further comprise one or more catalysts used to promote the reaction of isocyanate groups with moisture. The presence of such catalysts is not essential but may be preferred. Examples of suitable catalysts include metal-based catalysts such as dialkyltin complexes, particularly dibutyltin(IV) or dioctyltin(IV) carboxylates or acetylacetonates, such as dibutyltin dilaurate (DBTDL), dibutyltin diacetylacetonate, dioctyltin dilaurate (DOTDL), further bismuth(III) complexes, such as bismuth octoate or bismuth neodecanoate, zinc(II) complexes, such as zinc octoate or zinc neodecanoate, and zirconium(IV) complexes, such as zirconium octoate or zirconium neodecanoate.

[0102] Further examples of suitable catalysts include amine group-containing compounds such as dimorpholinodialkyl ethers and / or dimorpholino-substituted polyalkylene glycols, such as 2,2'-dimorpholinodiethyl ether and 1,4-diazabicyclo[2.2.2]-octane. Combinations of two or more catalysts can also be used, and preferred are combinations of one or more metal catalysts and one or more morpholine amine compounds.

[0103] When present in the adhesive composition, the total amount of the catalyst that catalyzes the reaction between the isocyanate group and moisture is preferably 0.005 to 2.00% by weight, more preferably 0.05 to 1.00% by weight, based on the total weight of the adhesive composition.

[0104] The adhesive composition is a moisture-curing type adhesive composition. That is, the adhesive composition can be cured by bringing the composition into contact with water, particularly moisture in the air. Preferably, the adhesive composition is a moisture-curing hot melt adhesive composition.

[0105] Furthermore, the adhesive composition of the present invention has excellent workability under typical coating conditions of hot melt adhesives, particularly at temperatures in the range of 100 to 180°C. This means that the adhesive can be applied to the substrate in a molten state because the viscosity of the adhesive is sufficiently low at the coating temperature. Also, the adhesive composition exhibits high initial strength upon cooling immediately after being applied to the substrate, even before the start of the crosslinking reaction with water, particularly moisture in the air.

[0106] According to one or more embodiments, the adhesive composition has a viscosity of 100,000 mPa·s or less, preferably 85,000 mPa·s or less, more preferably 75,000 mPa·s or less, at a temperature of 130°C, and / or a viscosity of at least 10,000 mPa·s, preferably at least 12,500 mPa·s, more preferably at least 15,000 mPa·s, at a temperature of 130°C. The viscosity at a temperature of 130°C can be measured, for example, using a conventional viscometer rotating at 5 revolutions per minute by using a Brookfield DV-2 Thermosel viscometer with spindle No. 27.

[0107] According to one or more embodiments, the adhesive composition has a softening point in the range of 60 to 150°C, preferably 65 to 140°C, more preferably 70 to 130°C, even more preferably 75 to 115°C, measured by the ring and ball method in accordance with the DIN EN1238 standard.

[0108] Furthermore, the adhesive composition can be provided as a one-component composition having storage stability. According to one or more embodiments, the adhesive composition is a one-component moisture-curing hot melt adhesive composition. As used herein, the term "composition having storage stability" refers to a composition that can be stored, for example, for a period of several months to more than one year in a suitable package or facility such as a drum, pouch, or cartridge without causing changes related to use in the coating properties and / or reactivity of the composition, particularly in the absence of moisture.

[0109] The preferred matters shown above for the isocyanate-functional polyurethane polymers PU, PU1, PU2, PU3, the polyester polyols PO1, PO2, PO3, PO4, the diisocyanates P1, P2, and the polyurethane prepolymer PUP are equally applicable to all the subjects of the present invention unless otherwise specified.

[0110] Another subject of the present invention is a method for producing the adhesive composition of the present invention, which includes mixing at least one isocyanate-functional polymer PU with the other components of the adhesive composition.

[0111] Mixing at least one isocyanate-functional polymer PU with the other components of the adhesive composition is preferably carried out at a temperature exceeding 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 to 200 °C, preferably 65 to 180 °C, more preferably 80 to 175 °C, and even more preferably 90 to 160 °C.

[0112] Another subject of the present invention is the use of the adhesive composition of the present invention as an adhesive for assembly, an adhesive for lamination, or an adhesive for constructing sandwich elements.

[0113] Yet another subject of the present invention is a method for adhesively bonding a first substrate to a second substrate, the method comprising I) a step of heating the adhesive composition according to the present invention to obtain a molten adhesive composition II) A step of applying a molten adhesive composition onto the surface of a first substrate to form an adhesive film, III) A step of bringing the adhesive film into contact with the surface of a second substrate, and IV) A step of chemically curing the adhesive film with water, particularly moisture in the air is included.

[0114] The first and second substrates are preferably sheet-like articles or three-dimensional shaped articles defined by a peripheral portion and having first and second main surfaces that define the thickness therebetween.

[0115] 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 onto the surface of the first substrate by using any conventional technique, for example, slot die coating, roller coating, extrusion coating, calendar coating, or spray coating. The adhesive composition can be applied onto the surface of the first substrate at a coating amount of, for example, 50 to 500 g / m 2 , for example, 55 to 350 g / m 2 , particularly 65 to 150 g / m 2 .

[0116] Particularly when the adhesive composition is applied onto the surface of the first substrate as a thin film having a coating amount of, for example, less than 150 g / m 2 , particularly less than 100 g / m 2 , the adhesive film formed in step II) can be reactivated by heating before being brought into contact with the surface of the second substrate. The reactivation temperature depends on the embodiment of the adhesive composition. For example, in some cases, it may be preferable to reactivate the adhesive film by heating it to a temperature of 60 to 200 °C, particularly 70 to 180 °C, preferably 120 to 160 °C. The heating of the adhesive film can be carried out by using any conventional technique such as heating in an oven, heating by an air flow, heating by infrared (IR) irradiation, etc. The reactivated adhesive film preferably comes into contact with the second substrate in a short time within the open time of the adhesive composition after reaching the reactivation temperature.

[0117] After the adhesive film contacts the surface of the second substrate, the adhesive composition exhibits a certain initial adhesion strength by physical curing, i.e., cooling. Depending on the coating temperature and the embodiment of the adhesive composition, particularly the reactivity of the adhesive, the chemical curing reaction may already start while the adhesive composition is being applied to the surface of the first substrate. However, typically, most of the chemical curing occurs after the application of the adhesive, particularly after the applied adhesive film contacts the surface of the second substrate.

[0118] The first and second substrates can be composed of any conventional materials such as polymer-based materials, metals, painted metals, glass, wood, wood-derived materials (such as natural fiber polypropylene (NFPP)), and fiber materials. Suitable polymer-based materials include, for example, polyethylene (PE), particularly high-density polyethylene (HDPE), polypropylene (PP), glass fiber-reinforced polypropylene (GFPP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), acrylonitrile-butadiene-styrene (ABS), polyamide (PA), and combinations thereof. The first and second substrates can be composed of a single layer or multiple layers of different types of materials. The layer composed of a polymer-based material can further contain additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes, and biocides.

[0119] According to one or more embodiments, one of the first and second substrates is composed of a polar material and the other substrate is composed of a non-polar material.

[0120] According to one or more further embodiments, when the first substrate, or when the first substrate is composed of a plurality of layers, the layer constituting the outer outer surface on which the adhesive composition is applied in step II) of the method is composed of a polar material, preferably a polar material selected from the group consisting of PMMA, PA, PC, ABS, glass fiber reinforced plastic (GFRP), glass, and metal. When the second substrate, or when the second substrate is composed of a plurality of layers, the layer constituting the outer outer surface that contacts the adhesive film in step III) of the method is composed of a non-polar material, preferably a non-polar material selected from the group consisting of polypropylene, polyethylene, and polystyrene.

[0121] According to one or more further embodiments, when the first substrate, or when the first substrate is composed of a plurality of layers, the layer constituting the outer outer surface on which the adhesive composition is applied in step II) of the method is composed of a non-polar material, preferably a non-polar material selected from the group consisting of polypropylene, polyethylene, or polystyrene. When the second substrate, or when the second substrate is composed of a plurality of layers, the layer constituting the outer outer surface that contacts the adhesive film in step III) of the method is composed of a polar material, preferably a polar material selected from the group consisting of PMMA, PA, PC, ABS, glass fiber reinforced plastic (GFRP), glass, or metal.

[0122] Yet another subject of the present invention is a composite material element obtained by using a method for adhesively bonding the first substrate of the present invention to a second substrate.

[0123] The composite material element of the present invention can be used, for example, in the manufacture of automotive interior parts. Examples of such interior parts include door panel pieces, switch panels, rear parcel shelves, headliners, sliding roofs, center consoles, glove boxes, sun visors, pillars, door handles, armrests, floor materials, cargo floor materials, trunk area floor materials, as well as truck sleeping cabins and rear panels.

Examples

[0124] In the examples, the following compounds and products shown in Table 1 were used.

[0125] [Table 1]

[0126] Unstripped polyurethane prepolymer PU1 A polyol (PO1X) and a monomeric diisocyanate (P1) were reacted at a temperature of 120 °C using a typical preparation method to obtain a reaction product containing a polyurethane prepolymer and some unreacted monomeric diisocyanate. The composition of the unstripped polyurethane prepolymer used in the preparation of the adhesive compositions Ex-1, Ex-2, and Ref-2 is shown in Table 3.

[0127] Stripped polyurethane prepolymers PU2 and PUP A polyol (PO2X, PO4) and a monomeric diisocyanate (P2X) were reacted at a temperature of 80 °C using a typical preparation method to obtain a reaction mixture containing a polyurethane prepolymer and unreacted monomeric diisocyanate. The reaction mixture was distilled using a short-path evaporator (jacket temperature 170 - 180 °C, pressure 0.05 - 0.002 mbar, condensation temperature 47 °C) to reduce the content of volatile compounds, especially the content of unreacted monomeric diisocyanate.

[0128] Distillation 1: 170 °C, p = 0.03 - 0.05 mbar Distillation 2: 180 °C, p = 0.002 - 0.003 mbar Rotation speed: 400 rpm Flow rate: 8.05 - 8.62 kg / h

[0129] The composition and properties of the stripped polyurethane prepolymer are shown in Table 2.

[0130] Acetylated polyester polyol APO The amorphous polyester polyol (PO31) was first reacted with acetic anhydride in a molar ratio of 1:1 in an acetic acid solution. The resulting reaction product was then distilled to remove the solvent and residual (unreacted) acetic anhydride.

[0131]

Table 2

[0132] Adhesive composition The polyurethane prepolymer (PU1, PU2, or PU3) was mixed with the other components of the adhesive composition and stirred at a temperature of 120 °C for 30 minutes (about 80 rpm). The resulting adhesive composition was filled into tubes and stored at normal room temperature without moisture.

[0133] In the case of the adhesive composition containing the polyurethane prepolymer PU3, the stripped polyurethane prepolymer (PUP) was first reacted with the polyol (PO3X) at a temperature of 80 °C to obtain a reaction product containing the polyurethane prepolymer (PU3). The reaction product was mixed with the other components of the adhesive composition, if applicable, and stirred at a temperature of 120 °C for 30 minutes (about 80 rpm).

[0134] The adhesive composition of Ex-18 was prepared using a two-step process. In the first step, the acetylated polyester polyol (APO) and the thermoplastic polyurethane (TPX) were mixed while continuously stirring at 160 °C until a homogeneous mixture was obtained. In the second step, the temperature of the mixture was lowered to 120 °C, the polyurethane prepolymer (PU2, PU3) was added to the mixture, and it was stirred for 30 minutes (about 80 rpm).

[0135] The components of the adhesive composition and their properties are shown in Tables 3 to 6.

[0136] Open time The sample adhesive composition placed in a sealed tube was first preheated in an oven at a temperature of 110°C for 30 minutes. After heating, 20 g of the molten adhesive sample was applied with a doctor blade onto the surface of a silicone paper piece (B700 white, Laufenberg & Sohn KG) placed on a hot plate. The dimensions of the silicone paper piece were 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 attaching the adhesive film, the silicone paper piece and the doctor blade were heated on the hot plate to a temperature of 110°C.

[0137] Immediately after applying the adhesive, the silicone paper piece was removed from the hot plate and placed (with the adhesive film facing upward) on a plywood sheet at room temperature (23°C), and the time was recorded as the starting point of measurement. Every 10 seconds, a short piece of silicone-coated paper formed in a roll with dimensions of 10 cm × 1 cm was placed (with the non-silicone-treated side facing outward) on the adhesive film, and then slowly peeled off to separate the paper piece from the adhesive film. This procedure was repeated until the paper piece could no longer be peeled off the adhesive film without damaging the paper piece or the adhesive film. The time interval from the start of measurement to the last sampling time point was recorded as the open time (seconds) of the adhesive composition.

[0138] The open time values shown in Tables 3 to 6 were obtained as the average of three measurements performed with the same adhesive composition.

[0139] Green strength (tensile lap shear strength) To ensure that the adhesive was supplied reliably in a molten state, the adhesive was placed in an oven at 130°C for longer than 30 minutes. After heating, a sample of the molten adhesive was applied onto the surface of a wood substrate with dimensions of 9 cm × 2 cm × 5 mm. The adhesive was applied as a coating film with dimensions of 2.5 cm × 1 cm and a thickness of 1 mm.

[0140] 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 material element. The second wood substrate was firmly pressed against the first wood substrate to expel air from the adhesive bond. A 150 g weight was placed on the upper surface of the second wood substrate. The adhesive that protruded from the joint was cut off with a knife. The lap shear strength (LSS) of the test composite material element was measured in accordance with EN1465 standard using a materials testing apparatus (Zwick Z 020) and a test speed of 10 mm / min. The lap shear strength was measured on test composite material elements stored for 6 / 10 / 20 / 30 minutes after joining the first wood substrate and the second substrate in order to examine the green (initial) adhesive bond strength obtained using the tested adhesive composition.

[0141] Curing time A sample of the adhesive composition placed in a sealed tube was preheated in an oven at a temperature of 140 °C for 20 minutes. After heating, 20 g of the melted adhesive sample was applied with a doctor blade onto the surface of a silicone paper piece (B700 white, Laufenberg & Sohn KG) placed on a hot plate. The dimensions of the silicone paper piece were 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 attaching the adhesive film, the silicone paper piece and the doctor blade were heated on the hot plate to a temperature of 150 °C.

[0142] Immediately after applying the adhesive, the silicone paper piece was removed from the hot plate and stored under standard climatic conditions (23 °C, relative humidity 55%). The time point when the adhesive film solidified was recorded as the starting point of the measurement. At the specified sampling times, test pieces with dimensions of 10 cm × 1 cm were cut from the silicone paper piece and placed on a hot plate at a temperature of 150 °C. This procedure was continued until the adhesive film on the test piece no longer melted on the hot plate. The length of the time interval from the starting point to the last sampling time point was recorded as the curing time (hours) of the adhesive composition.

[0143] The values of the curing times shown in Tables 3 to 6 were obtained as the average of three measurements performed with the same adhesive composition.

[0144] Tensile strength and elongation at break The adhesive composition placed in a sealed tube was preheated in an oven at a temperature of 110 °C for 30 minutes. After heating, 40 g of the molten adhesive sample was applied with a doctor blade onto the surface of a silicone paper piece (B700 white, Laufenberg & Sohn KG) placed on a heating plate. The dimensions of the silicone paper were 60 cm × 10 cm, and the adhesive was applied as a film with a thickness of 500 μm and dimensions of 60 cm × 6 cm. Immediately after applying the adhesive, the silicone paper piece was removed from the heating plate and stored under standard climatic conditions (23 °C, relative humidity 55%) for 7 days.

[0145] The measurements were carried out using a method based on the DIN53504 standard. Five rectangular test pieces with dimensions of 2.0 cm × 8.0 cm were cut from the cured adhesive film with a thickness of 500 μm (cured at 23 °C / relative humidity 50% for 14 days). The test pieces were fixed to a tensile testing machine (Zwick Z 020) and pulled apart at a speed of 100 mm / min (test conditions 23 °C, relative humidity 50%). The tensile strength and elongation at the break point were determined based on the measured maximum tensile stress.

[0146] The values of the tensile strength and elongation at break shown in Tables 3 to 6 were obtained as the average of five measurements carried out with the same adhesive composition.

[0147] Viscosity All viscosities were determined 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 )

[0148] The viscosity values in Tables 3 to 6 were obtained as the average of three measurements carried out with the same adhesive composition.

[0149] Heat resistance (thermal stability under static load) The adhesive composition placed in a sealed tube was preheated in an oven at a temperature of 130 °C for 20 minutes. After heating, a sample of the molten adhesive was applied to the surface of a wood test piece (pine) having dimensions of 9 cm × 2 cm × 5 mm and having a 1-mm copper wire as a spacer on the surface. The adhesive was applied as a film with a thickness of 1 mm and dimensions of 2 cm × 2 cm.

[0150] Immediately after applying the adhesive, a second wood test piece (pine) having the same dimensions as the first wood test piece was placed on top of the first wood test piece along the edge of the adhesive film to form a test composite material element. The second wood test piece was firmly pressed against the first wood test piece to remove air from the adhesive joint. A 150-g weight was placed on the upper surface of the second wood test piece. The adhesive that protruded from the joint was cut off with a knife. Thereafter, the test composite material element composed of the joined wood test pieces was stored under standard climatic conditions (23 °C, relative humidity 40 - 60%) for 14 days.

[0151] Thereafter, the test composite material element was vertically suspended with a metal hook from one end of the first wood test piece and placed in an oven. A metal weight equivalent to a static load of 1 kg was attached to the lower end of the second wood test piece of each composite material element. Three composite material elements were placed in the oven at a time for the measurement of thermal stability.

[0152] In the measurement of thermal stability, the oven was first heated to a temperature 40 °C lower than the expected adhesive joint failure temperature. The composite material element was held at this starting temperature for 60 minutes. If joint failure did not occur, the temperature of the oven was raised by 10 °C and the measurement was continued for another 60 minutes. The oven temperature was raised by 10 °C step by step according to the above-described procedure until joint failure occurred. The last measurement temperature before joint failure occurred was recorded as the representative thermal stability temperature.

[0153] The heat resistance values of each adhesive composition shown in Tables 3 to 6 were obtained as the average of three measurements performed on the same test composite material elements prepared using the same adhesive composition.

[0154] Content of residual monomeric diisocyanate The content of residual monomeric diisocyanate was determined using high performance liquid chromatography (HPLC) equipped with a photodiode array and using 0.04 M sodium acetate / acetonitrile as the mobile phase, using N-propyl-4-nitrobenzylamine as the derivatizing agent.

[0155] [Table 3]

[0156] [Table 4]

[0157] [Table 5]

[0158] [Table 6]

Claims

1. An adhesive composition containing at least one isocyanate-functional polyurethane polymer PU, wherein the at least one isocyanate-functional polyurethane polymer PU is, - at least one isocyanate-functional polyurethane polymer PU1 obtained by reacting at least one polyester polyol PO1 and at least one diisocyanate P1 at 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 at a molar ratio of at least 3, preferably at least 5, and then performing a treatment to reduce the amount of residual monomeric diisocyanate in the resulting reaction mixture, preferably by distillation, and includes, the adhesive composition further contains at least one acetylated amorphous polyester polyol APO; or the at least one isocyanate-functional polyurethane polymer PU is, - at least one isocyanate-functional polyurethane polymer PU3 obtained by reacting at least one polyester polyol PO3 and at least one polyurethane prepolymer PUP at a molar ratio of isocyanate groups to hydroxyl groups of 1.9 to 3.5, preferably 2.2 to 2.8, and includes, the at least one polyester polyol PO3 includes at least one amorphous polyester polyol PO31, and the adhesive composition optionally further contains at least one acetylated amorphous polyester polyol APO. An adhesive composition.

2. The adhesive composition according to claim 1, wherein the content of monomeric diisocyanate is 0.85% by weight or less, preferably 0.65% by weight or less, based on the total weight of the adhesive composition.

3. The adhesive composition according to claim 1 or 2, obtained by a method wherein the at least one acetylated polyester polyol APO includes reacting at least one amorphous polyester polyol with acetic anhydride at a molar ratio of 1.3:1 to 1:1.3, preferably followed by distilling the reaction product to reduce the amount of residual acetic anhydride.

4. The at least one acetylated polyester polyol APO is present in the adhesive composition in an amount of at least 5% by weight, preferably at least 10% by weight, based on the total weight of the adhesive composition, the adhesive composition according to any one of claims 1 to 3.

5. The adhesive composition according to any one of claims 1 to 4, containing at least 15% by weight, preferably at least 35% by weight, of the at least one isocyanate-functional polyurethane polymer PU based on the total weight of the adhesive composition.

6. The adhesive composition according to any one of claims 1 to 5, wherein the at least one isocyanate-functional polyurethane polymer PU has an average isocyanate functionality in the range of 1.2 to 2.7, preferably 1.5 to 2.5, determined according to ISO 14896-2009 standard method A.

7. The at least one diisocyanate P1 and P2 is a monomeric diisocyanate, preferably having a number average molecular weight (M ｎ ) of 1000 g / mol or less, the adhesive composition according to any one of claims 1 to 6.

8. The at least one isocyanate-functional polyurethane polymer PU2 is ・ at least one first isocyanate-functional polyurethane polymer PU21 obtained by reacting at least one polyester polyol PO21 with 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 with the at least one diisocyanate P2, and includes, wherein the at least one polyester polyol PO21 is a polyester polyol that is solid at 23°C, and the at least one polyester polyol PO22 is a polyester polyol that is liquid at 23°C, the adhesive composition according to any one of claims 1 to 7.

9. The at least one diisocyanate P2 includes at least one diisocyanate P21 and / or at least one diisocyanate P22, the at least one diisocyanate P21 is a monomeric diphenylmethane diisocyanate having an isomer content of 2,4'-isomer of at least 25% by weight, preferably at least 35% by weight based on the total weight of the diisocyanate P21, and the at least one diisocyanate P22 is a monomeric diphenylmethane diisocyanate having an isomer content of 4,4'-isomer of at least 75% by weight, preferably at least 95% by weight based on the total weight of the diisocyanate P22. The adhesive composition according to any one of claims 1 to 8.

10. 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 performing a treatment to reduce the amount of residual monomeric diisocyanate on the resulting reaction mixture, preferably by distillation. The adhesive composition according to any one of claims 1 to 9.

11. The adhesive composition according to claim 10, wherein the at least one polyester polyol PO4 contains poly(tetramethylene ether) glycol or consists of poly(tetramethylene ether) glycol.

12. The adhesive composition according to any one of claims 1 to 11, further containing at least one additional thermoplastic polymer TP that does not contain isocyanate groups.

13. A method for producing an adhesive composition according to any one of claims 1 to 12, comprising mixing the at least one isocyanate-functional polymer PU and the other components of the adhesive composition with each other.

14. Use of the adhesive composition according to any one of claims 1 to 13 as an adhesive for assembly, an adhesive for lamination, or an adhesive for constructing a sandwich element.

15. A method for adhesively bonding a first substrate to a second substrate, comprising the following steps: (I) 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 onto the surface of the first substrate to form an adhesive film; (III) bringing the adhesive film into contact with the surface of the second substrate; and (IV) chemically curing the adhesive film with water, particularly moisture in the atmosphere. A method comprising the above steps.

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