EP4705366A1

EP4705366A1 - Two-component adhesive composition for primerless substrates

Info

Publication number: EP4705366A1
Application number: EP24761540.4A
Authority: EP
Inventors: Lei KAN; Chao Ma; Yefei ZHANG; Depeng XU; Yingying SONG; Mingxin ZHAO; Liming Song
Original assignee: PPG Coatings Tianjin Co Ltd
Current assignee: PPG Coatings Tianjin Co Ltd
Priority date: 2023-08-02
Filing date: 2024-08-02
Publication date: 2026-03-11
Also published as: WO2025026434A1; MX2025014610A; KR20260005377A; CN117004360A

Abstract

Disclosed is a 2K adhesive composition suitable for primerless substrate comprising a first component and a second component, wherein the first component comprises a polyol and a mono-hydroxyl compound, the second component comprises a PU prepolymer and an isocyanate trimer, and the isocyanate trimer is present in the second component in an amount of less than 8 wt%based on the total weight of the second component. Further disclosed is a coated substrate comprising a substrate and the 2K adhesive composition applied onto at least a part of the substrate.

Description

TWO-COMPONENT ADHESIVE COMPOSITION FOR PRIMERLESS SUBSTRATES

TECHNICAL FIELD

The present invention relates to the field of adhesives, in particular, to a two-component (2K) adhesive composition suitable for primerless substrates.

BACKGROUND

Plastics and composite materials are increasingly used in automobile manufacturing. At present, plastics and composite materials have been used in parts such as car tailgates and spoilers. Common substrates comprise PP (polypropylene) , PP/LGF (long glass figer) , SMC (sheet molding compound) , PC (polycarbonate) /ABS (acrylonitrile-butadiene-styrene) , PMMA (polymethyl methacrylate) /ASA (acrylonitrile-styrene-acrylate) , PC/PET (polyethylene terephthalate) , PVC (polyvinyl chloride) , etc. Often, spoilers and tailgates are directly bonded with adhesives.
The use on plastic and composite substrates proposes a higher demand on the adhesives for bonding. Due to the low surface energy of substrates, it is hard to perform an effective bonding with conventional adhesives, and thus manufacturers often use solvent-based primers to treat the substrates to enhance the adhesion of adhesive to substrate. However, the primers comprise a large amount of volatile solvent, which is not environmentally friendly, involve additional cost, and increase the risk of glue failure between parts such as spoilers and tailgates in the later stage.
The present invention is intended to develop a novel adhesive product that can effectively bond plastic and composite material substrates even in the absence of primer treatment, manifesting as a failure mode of cohesive failure. At the same time, it is also necessary for the adhesive product to have a good bonding strength, high elongation, and good high temperature (e.g., 90-120℃) resistance and water aging resistance, etc.

SUMMARY

The inventors have conducted a lot of research and developed a 2K adhesive composition suitable for primerless substrates, which solves the above technical problems, such as, effective bonding of plastic and composite material substrates in the absence of primer, excellent bonding strength, elongation, high temperature resistance, and water aging resistance.
The present invention provides a 2K adhesive composition, comprising a first component and a second component, wherein the first component comprises a polyol and a mono-hydroxyl compound, the second component comprises a polyurethane (PU) prepolymer and an isocyanate trimer, and the isocyanate trimer is present in the second component in an amount of less than 8 wt%based on the total weight of the second component.
The invention further discloses a coated substrate, comprising a substrate and the 2K adhesive composition applied on at least a part of the substrate.

DETAILED DESCRIPTION

In the present application, unless expressly stated otherwise, the use of a singular comprises a plural and the use of a plural comprises a singular. For example, although “a” polymer is referred to herein, one or more of said substance can be used.
In this application, the terms “include, ” “comprise, ” and “contain” or the like are not intended to limit the invention to exclude any variations or additions. In addition, although the present invention has described the adhesive compositions, preparation methods, or the like with terms such as “comprise” , the adhesive compositions, preparation methods, or the like as detailed herein can further be described as “consist essentially of” or “consist of ... ” In this context, “consist essentially of” means that any additional ingredients would not materially affect the properties of the adhesive layer formed from the adhesive composition.
In the present application, unless expressly stated otherwise, the use of “or” means “and/or” , even though “and/or” can be expressly used in some cases. Additionally, it should be understood that any numerical range described herein is intended to encompass all the sub-ranges contained therein. For example, a range of “1 to 10” is intended to include all the sub-ranges between the listed minimum value of 1 and the listed maximum value of 10 (including the endpoints) , namely, all the sub-ranges having a minimum value equal to or great than 1 and a maximum value equal to or less than 10.
Except those in the examples or otherwise expressly stated, it is to be understood that all numerical values representing amounts of ingredients used in the specification and claims can be varied by the term “about” in all cases. Accordingly, the numerical parameters set forth in the following description and claims are approximations that may vary depending upon desired properties to be obtained by the present invention, unless otherwise indicated to be contrary. At least, it is not intended to limit the application of the doctrine of equivalents to the scope of the claims. Each numerical parameter should at least be construed in terms of its number of significant digits and by applying ordinary rounding.
Although the numerical ranges and parameters describing the broad scope of the present invention are approximations, the numerical values listed in the particular Examples should be reported as precisely as possible. However, any numerical value inherently has a certain error, which is an inevitable result of the standard deviation derived from its corresponding measurement method.
As mentioned above, the present invention provides a 2K adhesive composition, comprising a first component and a second component, wherein the first component comprises a polyol and a mono-hydroxyl compound, the second component comprises a polyurethane (PU) prepolymer and an isocyanate trimer, and the isocyanate trimer is present in the second component in an amount of less than 8 wt%based on the total weight of the second component.
The adhesive composition according to the present invention is a solvent-free system comprising a resin, a curing agent, a pigment/filler, and/or an additive as primary ingredients. As used herein, the term “solvent-free” means that the system does not comprise any organic solvent apart from compounds reacting to form an adhesive layer.
The adhesive composition according to the present invention is a 2K (two-component) system, that is, the ingredients of the adhesive composition are separated into two components, which are packaged separately, and mixed in accurate proportions prior to use.
In the adhesive composition of the present invention, the first component and the second component have appropriate viscosities. Suitably, the first component can have a viscosity of 40, 000-60, 000 cps at room temperature. Suitably, the second component can have a viscosity of 40, 000-60, 000 cps at room temperature. The viscosity can be measured by a Brookfield Viscometer with a RV #7 spindle at a speed of 50 revolutions per second. The room temperature can be 15 to 30℃, such as 23 to 25℃.
The adhesive composition according to the present invention can be cured at room temperature or at an elevated temperature. The room temperature can be 15 to 30℃. For example, the adhesive composition according to the present invention can be cured within 3 to 7 days at room temperature. Alternatively, the adhesive composition according to the present invention can be cured within 3 hours at 80℃. Herein, the term “cured” means that the ingredients in the adhesive composition react chemically after mixing and reaches 80%of the final strength of the adhesive layer, and the curing time is calculated from the mixing of the two components of the adhesive composition. After curing, the adhesive layer formed from the adhesive composition of the present invention can have a thickness of 0.1 to 4 mm.
The adhesive composition according to the present invention can be suitable for use on primerless substrates. The term “primerless” means that the surface of a substrate does not undergo any primer pretreatment, or the surface of substrate is not coated with any primer. As used herein, the term “primer” refers to a coating composition that can be applied onto at least a part of the surface of a substrate to form a coating layer. That is to say, the adhesive layer formed from the adhesive composition of the present invention is in direct contact with the substrate.
The adhesive composition according to the present invention can be suitable for substrates such as plastics and/or composite materials. As used herein, the “composite materials” refer to materials comprising plastic type materials in addition to at least one further, different material, such as metal, glass, etc. The composite materials can comprise fiber reinforced materials. Suitably, the substrate comprises PP, PP/LGF, SMC, PC/ABS, PMMA/ASA, PC/PET, and/or PVC, wherein “/” refers to “and” , e.g., “PP/LGF” refers to a substrate containing PP and LGF.
In the adhesive composition of the present invention, the first component comprises a polyol and a mono-hydroxyl compound. The “polyol” refers to a compound containing at least two hydroxyl groups per molecule. The “mono-hydroxyl compound” refers to a compound containing only one hydroxyl group per molecule. The hydroxyl groups contained in the polyol and the mono-hydroxyl compound can react with the NCO groups in the second component. Moreover, the polyol and the mono-hydroxyl compound can be present in the first component at a specific ratio. Suitably, the weight ratio of the polyol to the mono-hydroxyl compound can be from 2: 1 to 11: 1. For example, the weight ratio of the polyol to the mono-hydroxyl compound can be 3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, or 10: 1. Suitably, the weight ratio of the polyol to the mono-hydroxyl compound can be 2: 1 or higher, 3: 1 or higher, 4: 1 or higher, 5: 1 or higher, or 6: 1 or higher, and/or 11: 1 or lower, 10: 1 or lower, 9: 1 or lower, 8: 1 or lower, or 7: 1 or lower. Suitably, the weight ratio of the polyol to the mono-hydroxyl compound can be 3: 1 to 10: 1, 4: 1 to 9: 1, 5: 1 to 8: 1, or within any other combinational ranges using these end values.
The polyol suitable for the present invention can have an average functionality of 2 to 4, e.g., an average functionality of 2, 3, or 4. The “average functionality” refers to the average number of functional groups in each molecule that can participate in the reaction. Suitably, the polyol can comprise one or more polyols with identical or different functionality. Suitably, the polyol can comprise a polyether polyol, such as aromatic polyether polyol and aliphatic polyether polyol, polyester polyol, such as pendant group-containing dimer acid polyester polyol, polycarbonate polyol, polybutadiene polyol, and/or oleochemical polyol.
For example, the polyol can comprise polybutadiene polyol. The polybutadiene polyol can comprise a terminal hydroxyl group. Suitably, the polyol can comprise 40 to 90 wt%of polybutadiene polyol based on the total weight of the polyol, such as 45 wt%, 50 wt%, 55 wt%, 60 wt%, 70 wt%or 80 wt%of polybutadiene polyol. Suitably, the polyol can comprise 40 wt%or more, 45 wt%or more, 50 wt%or more, 55 wt%or more, or 60 wt%or more, and/or 90 wt%or less, 80 wt%or less, or 70 wt%or less of polybutadiene polyol based on the total weight of the polyol. Suitably, the amount of polybutadiene polyol can be 50 to 80 wt%, 55 to 70 wt%, or within any other combinational ranges using these end values based on the total weight of the polyol. The polyol can further comprise aromatic polyether polyol, aliphatic polyether polyol, pendant group-containing dimer acid polyester polyol, oleochemical polyol, and/or polycarbonate polyol. For example, the polyol can further comprise aromatic polyether polyol, pendant group-containing dimer acid polyester polyol, and/or oleochemical polyol. As used herein, the term “oleochemical polyol” refers to a polyol derived from natural oils via chemical reaction. Suitably, the weight ratio of the polybutadiene polyol, the aromatic polyether polyol, the pendant group-containing dimer acid polyester polyol and the oleochemical polyol can be (4-8) : (0-1) : (0-4) : (0-2) .
The polyol suitable for the present invention can have a number average molecular weight of 400 to 5, 000. For example, the polyol can have a number average molecular weight of 1, 000, 1, 500, 2, 000, 2, 500, 3, 000, 3, 500, 4, 000, or 4, 500. Suitably, the polyol can have a number average molecular weight of 400 or more, 1, 000 or more, 1, 500 or more, 2, 000 or more, or 2, 500 or more, and/or 5, 000 or less, 4, 500 or less, 4, 000 or less, 3, 500 or less, or 3, 000 or less. Suitably, the number average molecular weight of the polyol can be 400 to 4, 500, 400 to 2, 500, or within any other combinational ranges using these end values. The number average molecular weight can be determined by gel permeation chromatography using appropriate standards such as polystyrene standards, and given in Da.
Based on the total weight of the first component, the polyol can be present in an amount of at least about 20 wt%, suitably at least about 25 wt%, suitably at least about 30 wt%, and/or up to about 75 wt%, such as up to about 70 wt%, suitably up to about 65 wt%. Based on the total weight of the first component, the polyol can be present in an amount of about 20-75 wt%, suitably 25-70 wt%, such as 30-65 wt%, or within any other combinational range using these end values.
The mono-hydroxyl compound suitable for the present invention can have a functionality of one. That is to say, only the hydroxyl group in the mono-hydroxyl compound can participate in the reaction. Suitably, the mono-hydroxyl compound can comprise one or more identical or different mono-hydroxyl compounds. Suitably, the mono-hydroxyl compound can comprise lauryl alcohol, ethylene glycol monohexyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monophenyl ether, and/or 2-ethylhexanol, etc. For example, the mono-hydroxyl compound can comprise propylene glycol monophenyl ether.
Based on the total weight of the first component, the mono-hydroxyl compound can be present in an amount of at least about 6 wt%, suitably at least about 7 wt%, suitably at least about 8 wt%, and/or up to about 15 wt%, such as up to about 12 wt%, suitably up to about 10 wt%. Based on the total weight of the first component, the mono-hydroxyl compound can be present in an amount of about 6-15 wt%, suitably 7-12 wt%, such as 8-10 wt%, or within any other combinational range using these end values.
In the adhesive composition of the present invention, the second component comprises a PU prepolymer and an isocyanate trimer. The “PU prepolymer” can further be known as a PU polymer. The PU prepolymer and the isocyanate trimer can provide NCO groups. The PU prepolymer and the isocyanate trimer can be present in the second component at a certain ratio. Suitably, the weight ratio of the PU prepolymer to the isocyanate trimer can be from 3: 1 to 15: 1. For example, the weight ratio of the PU prepolymer to the isocyanate trimer can be 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, 11: 1, 12: 1, 13: 1, or 14: 1. Suitably, the weight ratio of the PU prepolymer to the isocyanate trimer can be 3: 1 or higher, 4: 1 or higher, 5: 1 or higher, 6: 1 or higher, 7: 1 or higher, or 8: 1 or higher, and/or 15: 1 or lower, 14: 1 or lower, 13: 1 or lower, 12: 1 or lower, 11: 1 or lower, 10: 1 or lower, or 9: 1 or lower. Suitably, the weight ratio of the PU prepolymer to the isocyanate trimer can be 4: 1 to 14: 1, 5: 1 to 13: 1, 6: 1 to 9: 1, or within any other combinational ranges using these end values.
The PU prepolymer suitable for the present invention can be obtained by reacting an isocyanate compound with a polyol. Suitably, the isocyanate compound can comprise an aromatic isocyanate-based compound, such as toluene diisocyanate (TDI) and/or diphenylmethane diisocyanate (MDI) . Suitably, the polyol can comprise polybutadiene polyol. The polybutadiene polyol can comprise a terminal hydroxyl group. Suitably, the molar ratio of the NCO group in the isocyanate compound to the OH group in the polyol can be greater than 1, so that an NCO group-terminated PU prepolymer is obtained.
Suitably, the PU prepolymer can have an NCO content of 15-20 wt%. The “NCO content” refers to the weight percentage of the NCO groups based on the weight of the PU prepolymer per molecule, and can be measured according to ISO 14896: 2009.
Based on the total weight of the second component, the PU prepolymer can be present in an amount of at least about 25 wt%, suitably at least about 30 wt%, suitably at least about 35 wt%, and/or up to about 50 wt%, such as up to about 45 wt%, suitably up to about 40 wt%. Based on the total weight of the second component, the PU prepolymer can be present in an amount of about 25-50 wt%, suitably 30-45 wt%, such as 35-40 wt%, or within any other combinational range using these end values.
The isocyanate trimer suitable for the present invention can comprise an aliphatic isocyanate trimer. Suitably, the aliphatic isocyanate can comprise isophorone diisocyanate (IPDI) , hexamethylene diisocyanate (HDI) , and/or 4, 4’-dicyclohexylmethane diisocyanate (HMDI) . For example, the aliphatic isocyanate trimer can comprise an HDI trimer.
Based on the total weight of the second component, the isocyanate trimer can be present in an amount of less than about 8 wt%, such as 3 wt%to less than about 8 wt%. For example, based on the total weight of the second component, the isocyanate trimer can be present in an amount of at least about 3 wt%, suitably at least about 4 wt%, and/or less than about 8 wt%, up to about 7 wt%, such as up to about 6 wt%. Based on the total weight of the second component, the isocyanate trimer can be present in an amount of about 3-7 wt%, suitably 4-6 wt%, within any other combinational range using these end values.
By reacting the groups of the first component with the groups in the second components, e.g. OH group with NCO group, the adhesive composition according to the invention can provide effective bonding to the substrate. Therefore, the ratio of the first component to the second component can be set according to the molar ratio of the two groups. Suitably, the molar ratio of the NCO groups in the second component to the OH groups in the first component can be equal to or greater than 1: 1, such as 1: 1 to 1.15: 1. For example, the molar ratio of the NCO groups in the second component to the OH groups in the first component can be 1.05: 1, 1.1: 1, or 1.15: 1. Suitably, the molar ratio of the NCO groups in the second component to the OH groups in the first component can be 1: 1 or higher, or 1.05: 1 or higher, and/or 1.15: 1 or lower, or 1.1: 1 or lower. Suitably, the molar ratio of the NCO groups in the second component to the OH groups in the first component can be 1.05: 1 to 1.1: 1, or within any other combinational ranges using these end values.
The adhesive composition according to the present invention can further comprise a pigment/filler, and/or an additive. The pigment/filler and/or the additive can be present in the first component of the adhesive composition and/or in the second component of the adhesive composition.
For example, the adhesive composition according to the present invention can comprise the pigment/filler. The pigment/filler can comprise a coloring pigment and/or a filler that provide color, effect and/or functionality to the adhesive. Suitably, the coloring pigment can comprise an inorganic pigment such as carbon black, titanium white, iron red, etc., and/or an organic pigment. Suitably, the filler can comprise fumed silica, calcium carbonate, kaolin, talc powder, and/or aluminum hydroxide, etc. The pigment/filler can be present in an amount of 35 to 55 wt%based on the total weight of the first component; and/or the pigment/filler can be present in an amount of 35 to 55 wt%based on the total weight of the second component.
The adhesive composition according to the present invention can comprise a chain extender. Examples of suitable chain extenders can comprise, but are not limited to, diethylenediamine (DEDA) , monoethanolamine (MEA) , methylenebis (N, N-dibutyldiphenylamine) , isophoronediamine (IPDA) , dodecyl mercaptan, tert-dodecyl mercaptan, 1, 3-butanediol, 1, 4-butanediol, propane-1, 2-diol, 1, 6-hexanediol, polyetheramine or any combinations thereof. For example, the chain extender can comprise 1, 4-butanediol and/or polyetheramine. The polyetheramine can have a number average molecular weight of 200 to 500. The number average molecular weight can be determined by gel permeation chromatography using appropriate standards such as polystyrene standards.
The adhesive composition according to the present invention can comprise a coupling agent. Examples of suitable coupling agents can comprise, but are not limited to, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a bimetallic coupling agent, a phosphate coupling agent, a borate coupling agent, a chromium complex, a coupling agent of other higher aliphatic acids, alcohols, esters, and their combinations. For example, the coupling agent can comprise a silane coupling agent such as an amino silane.
The adhesive composition according to the present invention can comprise a catalyst e.g., for facilitating the reaction between active hydrogen and NCO group. Examples of suitable catalysts can comprise, but are not limited to, stannous (II) octoate, dibutyltin dilaurate, dibutyltin diacetate, dimethylimidazole, diazabicyclo (DBU) type amine catalysts, 2, 2’-dimorpholinyl diethyl ether, and any combination thereof. For example, the catalyst can comprise dimethylimidazole and/or a DBU type amine catalyst.
The adhesive composition according to the present invention can comprise an antioxidant. Examples of suitable antioxidants can comprise, but are not limited to, di (tridecyl) thiodipropionate (DTDTDP) , dilauryl thiodipropionate (DLTDP) , distearyl thiodipropionate (DSTDP) and octadecyl 3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenylpropanate (1076) , 4, 6-di (octylthiomethyl) o-cresol, tris (2, 4-di-tert-butylphenyl) phosphite, and any combination thereof. For example, the antioxidant can comprise 4, 6-di (octylthiomethyl) o-cresol.
The adhesive composition according to the present invention can comprise a moisture scavenger. Examples of suitable moisture scavengers can comprise, but are not limited to, methyldiphenylethoxysilane, vinyltrimethoxysilane (VTMO) , vinyltriethoxysilane, molecular sieves, p-toulenesulfonylisocyanate (PTSI) , anhydride esters (such as diethyl malonate and dimethyl succinate) , and any combination thereof. For example, the moisture scavenger can comprise a molecular sieve, and/or p-toluenesulfonylisocyanate (PTSI) .
The adhesive composition according to the invention can comprise a plasticizer. Examples of suitable plasticizers can comprise, but are not limited to, tris (2-ethylhexyl) trimellitate (TOTM) , trimethylpentanediol biisobutyrate, C1-C20 alkyl sulfonates of phenol, diisononyl phthalate (DINP) , Mesamoll, bio-based plasticizers, and any combination thereof. For example, the plasticizer can comprise diisononyl phthalate (DINP) .
The adhesive composition according to the present invention can comprise a thixotropic agent. Examples of suitable thixotropic agents can comprise, but are not limited to, hydrogenated castor oil, polyamides, and any combination thereof.
The adhesive composition according to the invention can further comprise one or more other additives. The amounts of the above additives and one or more other additives can be adjusted and determined by a person skilled in the art in view of desired performance.
The adhesive composition according to the invention can be prepared as follows:
The first component: the polyol, the mono-hydroxyl compound, and optionally pigment/fillers are added to a reactor, heated to 80℃ and dehydrated under vacuum for 2 h, and then cooled to below 50℃; and, optional additives and optional pigment/fillers are added into the reactor, stirred uniformly under vacuum, packaged and sealed for storage.
The second component: the PU prepolymer and the isocyanate trimer are added to a reactor; and, optional pigment/fillers and optional additives are added, dispersed uniformly under vacuum, packaged and sealed for storage.
Suitably, the preparation of the second component further comprises the preparation of the PU prepolymer: adding the isocyanate compound and the polyol to a reactor, reacting them at 80℃ for 2 h under nitrogen protection, and controlling the NCO content at the end of the reaction to be 15 to 20 wt%based on the weight of the PU prepolymer.
The present invention further relates to a coated substrate, comprising a substrate and the 2K adhesive composition applied on at least a part of the substrate. The substrate comprises a substrate without primer treatment. Therefore, the adhesive layer formed from the 2K adhesive composition is in direct contact with the substrate. Suitably, the substrate can comprise a plastic and/or a composite material. Examples of suitable plastics and/or composite materials can comprise, but are not limited to, PP, PP/LGF, SMC, PC/ABS, PMMA/ASA, PC/PET, and/or PVC. Suitably, the substrate can be part of a vehicle, such as a spoiler, tailgate or the like.
The method of applying the 2K adhesive composition onto the substrate can comprise: mixing the first component with the second component uniformly at a determined ratio, then applying the mixture onto a first substrate, and then contacting the adhesive composition on the first substrate with the second substrate. The “first substrate” and the “second substrate” can be prepared from the same or different materials, such as PP, PP/LGF, SMC, PC/ABS, PMMA/ASA, PC/PET, and/or PVC .
The coated substrate can be cured by exposure to a curing condition for a period of time. For example, the adhesive composition according to the present invention can be cured at room temperature within 3 to 7 days, wherein the room temperature can be 15 to 30℃. Alternatively, the adhesive composition according to the present invention can be cured at an elevated temperature, such as by convective heat or microwave heating. For example, the adhesive composition according to the present invention can be cured at 80℃ within 3 hours. After curing, the adhesive layer formed from the adhesive composition of the present invention can has a thickness of 0.1 to 4 mm.
EXAMPLES
The following examples are provided to further illustrate the invention, but it should not be construed as limiting the invention to the details described in the examples. Unless otherwise stated, all parts and percentages in the following examples are by weight.
Examples:
First Component
The first components A1-A3 of the 2K adhesive composition of the examples were prepared according to the ingredients and weight percentages listed in Table 1. The preparation method comprises:
Polybutadiene polyol, other polyol (s) , mono-hydroxyl compound and a portion of the filler were added to a reactor, heated to 80℃, and dehydrated under vacuum for 2h, and then cooled to 50℃ or lower. The chain extender, coupling agent, catalyst, moisture scavenger, antioxidant, and the rest of the filler were added into the reactor, stirred uniformly under vacuum. The obtained mixture was packaged and sealed for storage.
Table 1. 2K Adhesive Compositions of the Examples: First Components A1-A3

^a one or more selected from the group consisting of aromatic polyether polyol, aliphatic
polyether polyol, dimer acid polyester polyol containing pendant group, oleochemical polyol, and polycarbonate polyol, the polyol hasa number average molecular weight of 400 to 2500;
^b one or more selected from the group consisting of lauryl alcohol, ethylene glycol monohexyl
ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monophenyl ether, and 2-ethylhexanol;
^c 1, 4-butanediol and polyetheramine;
^d dimethylimidazole and DBU amine catalyst (s) ;
^e 4, 6-di (octylthiomethyl) o-cresol;
^f aminosilane;
^g activated powder of molecular sieve; and
^h calcium carbonate.
Second Component
The second components B1-B3 of the 2K adhesive composition of the examples were prepared according to the ingredients and weight percentages listed in Table 2. The preparation method comprises:
The PU prepolymer and isocyanate dimer were added to a reactor, and the filler, plasticizer, anti-oxidant, and moisture scavenger were added to the reactor. The mixture was dispersed uniformly under vacuum, and then packaged and sealed for storage.
Table 2. 2K Adhesive Compositions of the Examples: Second Components B1-B2

^a obtained by reacting toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) with
polybutadiene polyol, with an NCO content of 15 to 20 wt%based on the weight of the PU prepolymer;
^b aliphatic isocyanate trimer, wherein the aliphatic isocyanate is one or more selected from the
group consisting of isophorone diisocyanate (IPDI) , hexamethylene diisocyanate (HDI) and 4, 4'-dicyclohexylmethane diisocyanate (HMDI) ;
^c diisononyl phthalate (DINP) ;
^d 4, 6-di (octylthiomethyl) o-cresol;
^e fumed silica and calcium carbonate; and
^fp-toluenesulfonyl isocyanate.
Comparative Examples 1-3:
First Component
The first components CA1-CA3 of the 2K adhesive composition of the comparative examples were prepared according to the ingredients and weight percentages listed in Table 3. The preparation method comprises:
Polybutadiene polyol, other polyol (s) , mono-hydroxyl compound and a portion of the filler were added to a reactor, heated to 80℃, and dehydrated under vacuum for 2h, and then cooled to 50℃ or lower. The chain extender, coupling agent, catalyst, moisture scavenger, plasticizer, antioxidant, and the rest of the filler were added into the reactor, stirred uniformly under vacuum. The obtained mixture was packaged and sealed for storage.
Table 3. 2K Adhesive Compositions of the Comparative Examples: First Components CA1-CA3

^a one or more selected from the group consisting of aromatic polyether polyol, aliphatic
polyether polyol, dimer acid polyester polyol containing pendant groups, oleochemical polyol, and polycarbonate polyol, the polyol hasa number average molecular weight of 400 to 2500;
^b one or more selected from the group consisting of lauryl alcohol, ethylene glycol monohexyl
ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monophenyl ether, and 2-ethylhexanol;
^c 1, 4-butanediol and polyetheramine;
^d dimethylimidazole and DBU amine catalyst (s) ;
^e 4, 6-di (octylthiomethyl) o-cresol;
^f aminosilane;
^g activated powder of molecular sieve;
^h diisononyl phthalate (DINP) ; and
ⁱ calcium carbonate.
Second Component
The second components CB1-CB3 of the 2K adhesive composition of the comparative examples were prepared according to the ingredients and weight percentages listed in Table 4. The preparation method comprises:
The PU prepolymer and isocyanate trimer were added to a reactor, and the filler, plasticizer, anti-oxidant, moisture scavenger, and filler were added. The mixture was dispersed uniformly under vacuum, and then packaged and sealed for storage.
Table 4. 2K Adhesive Compositions of the Comparative Examples: Second Components CB1-CB3

^a obtained by reacting toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) with
polybutadiene polyol, with an NCO content of 15 to 20 wt%based on the weight of the PU prepolymer;
^b aliphatic isocyanate trimer, wherein the aliphatic isocyanate is one or more selected from the
group consisting of isophorone diisocyanate (IPDI) , hexamethylene diisocyanate (HDI) and 4, 4'-dicyclohexylmethane diisocyanate (HMDI) ;
^c aliphatic isocyanate dimer, wherein the aliphatic isocyanate is one or more selected from the
group consisting of isophorone diisocyanate (IPDI) , hexamethylene diisocyanate (HDI) and 4, 4'-dicyclohexylmethane diisocyanate (HMDI) ;
^d diisononyl phthalate (DINP) ;
^e 4, 6-di (octylthiomethyl) o-cresol;
^f fumed silica and calcium carbonate; and
^g p-toluenesulfonyl isocyanate.
The 2K adhesive compositions of the examples and comparative examples were applied to a substrate and cured as follows.
One of the first components A1-A3 and CA1-CA3 and one of the second components B1-B2 and CB1-CB3 were mixed uniformly at a NCO: OH molar ratio of 1.05: 1, and then applied onto a first substrate. Then, the adhesive composition on the first substrate was put into contact with the second substrate. The first substrate and the second substrate are prepared from the same material, which is PC/ABS or PMMA/ASA.
The 2K adhesive composition applied on the substrates was placed at ambient temperature and humidity (in a standard environment of 23℃/50%RH) for 7 days to obtain a cured adhesive layer. The cured adhesive layer was tested for tensile strength and elongation at break.
Test for Tensile Strength and Elongation at Break:
The test was carried out according to the standard GB/T 528-2009. After placing in a standard environment of 23℃/50%RH for 7 days, the sample (the substrates with a cured adhesive layer) was tested with a tensile machine with a test speed of 200 mm/min.
Test for Shear Strength:
The surface of the substrates was wiped with ethanol to remove dust or stain. The uniformly mixed 2K adhesive composition was applied to the bonding site of the substrates. The substrates were fixed and pressed with clip (s) so that the bonding area was fixed to 25 mm × 12.5 mm and the thickness of the adhesive layer was controlled to 1 mm. The substrates with the 2K adhesive composition was placed in a standard environment (23℃/50%RH) for 7 days, and then tested with a tensile machine in accordance with the standard GB/T7124 at a test speed of 5 mm/min.
Mode of Failure:
According to the shear strength test method, the mode of failure was determined by observing by naked eyes the bonding site of the substrates after break. The mode of failure comprises: Interface failure (AF) means that bare substrate appears on at least one face of the bonding site; and Cohesive failure (CF) means that adhesive layer was found on both faces of the bonding site. The results expressed in percentage mean that the two modes of failure are present.
The test results are shown in the table below:
Table 5. Test Results of Examples and Comparative Examples
Referring to the test results, it can be seen that the comparative examples failed to form effective bonding on the PMMA/ASA substrate, and the bonding failure mode was interface failure. However, the examples according to the present invention can form effective bonding on both the PC/ABS and the PMMA/ASA substrates, and the bonding failure mode is cohesive failure. Among them, the optimized adhesive (e.g., suitable proportion of the mono-hydroxyl compound and the isocyanate trimer, the combination of polyols, etc. ) can achieve 100%of cohesive failure mode (i.e., CF) on the PMMA/ASA substrate.
In addition, the example A1B2 was subjected to high temperature resistance test and water aging resistance test.
High Temperature Resistance test:
The surface of the substrates was wiped with ethanol to remove dust or stain. The uniformly mixed 2K adhesive composition was applied to the bonding site of the substrates. The substrates were fixed and pressed with clip (s) so that the bonding area was fixed to 25 mm × 12.5 mm and the thickness of the adhesive layer was controlled to 1 mm. The substrates with the 2K adhesive composition were placed in a standard environment (23℃/50%RH) for 3 days, and then placed at 90℃ for 7 days. Next, the substrates with the 2K adhesive composition were tested for shear strength according to the standard GB/T7124 using a tensile machine with a test speed of 5 mm/min.
Mode of Failure:
According to the shear strength test method, the mode of failure was determined by observing the bonding site of the substrates after break by naked eyes. The mode of failure comprises: Interface failure (AF) means that bare substrate appears on at least one face of the bonding site; and Cohesive failure (CF) means that adhesive layer was found on both faces of the bonding site. The results expressed in percentage mean that the two modes of failure are present.
Test Results:
The shear strength on the PC/ABS substrate is 2.68 MPa, and the failure mode is 100%cohesive failure; and the shear strength on the PMMA/ASA substrate is 2.38 MPa, and the failure mode is 100%cohesive failure.
Water Resistance Aging Test:
The surface of the substrates was wiped with ethanol to remove the dust or stain. The uniformly mixed 2K adhesive composition was applied to the bonding site of the substrates. The substrates were fixed and pressed with clip (s) so that the bonding area was fixed to 25 mm x 12.5 mm and the thickness of the adhesive layer was controlled to 1 mm. The substrates with the 2K adhesive composition were placed in a standard environment (23℃/50%RH) for 3 days, and then placed in a water bath at 40℃ for 14 days. Next, the substrates with the 2K adhesive composition were tested for the shear strength according to the standard GB/T7124 using a tensile machine with a test speed of 5 mm/min.
Mode of Failure:
According to the shear strength test method, the mode of failure was determined by observing the bonding site of the substrates after break by naked eyes. The mode of failure comprises: Interface failure (AF) means that bare substrate appears on at least one face of the bonding site; and Cohesive failure (CF) means that adhesive layer was found on both faces of the bonding site. The results expressed in percentage mean that the two modes of failure are present.
Test Results:
The shear strength on the PC/ABS substrate is 2.46 MPa, and the failure mode is 100%cohesive failure; and the shear strength on the PMMA/ASA substrate is 2.30 MPa, and the failure mode is 100%cohesive failure.
Therefore, the 2K adhesive according to the present invention also has excellent high temperature resistance and water aging resistance.
Although specific aspects of the invention have been illustrated and described, it will be apparent to a person skilled in the art that various other variations and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended that the appended claims encompass all such variations and modifications falling within the scope of the invention.

Claims

A two-component (2K) adhesive composition, comprising a first component and a second component, wherein the first component comprises a polyol and a mono-hydroxyl compound, the second component comprises a polyurethane (PU) prepolymer and an isocyanate trimer, and the isocyanate trimer is present in the second component in an amount of less than 8 wt%based on the total weight of the second component.
The 2K adhesive composition of claim 1, wherein a weight ratio of the polyol to the mono-hydroxyl compound in the first component is 2: 1 to 11: 1.
The 2K adhesive composition of claim 1, or 2, wherein a weight ratio of the PU prepolymer to the isocyanate trimer in the second component is 3: 1 to 15: 1.
The 2K adhesive composition of any one of claims 1-3, wherein the polyol has an average functionality of 2 to 4.
The 2K adhesive composition of any one of claims 1-4, wherein the polyol has a number average molecular weight of 400 to 5,000.
The 2K adhesive composition of any one of claims 1-5, wherein the polyol comprises 40-90 wt%of a polybutadiene-based polyol, based on the total weight of the polyol in the first component.
The 2K adhesive composition of any one of claims 1-6, wherein the mono-hydroxyl compound has a functionality of 1.
The 2K adhesive composition of any one of claims 1-7, wherein the mono-hydroxyl compound comprises lauryl alcohol, ethylene glycol monohexyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monophenyl ether, and/or 2-ethylhexyl alcohol.
The 2K adhesive composition of any one of claims 1-8, wherein the PU prepolymer has an NCO content of 15-20 wt%based on the total weight of the PU prepolymer.
The 2K adhesive composition of any one of claims 1-9, wherein the PU prepolymer is prepared by reaction of a mixture comprising an aromatic isocyanate compound and a polybutadiene polyol.
The 2K adhesive composition of any one of claims 1-10, wherein the isocyanate trimer comprises an aliphatic isocyanate trimer.
The 2K adhesive composition of any one of claims 1-11, wherein the isocyanate trimer comprises a HDI trimer.
The 2K adhesive composition of any one of claims 1-12, wherein the mono-hydroxyl compound is present in the first component in an amount of 6-15 wt%based on the total weight of the first component.
The 2K adhesive composition of any one of claims 1-13, wherein a molar ratio of NCO group in the second component to OH group in the first component is equal to or greater than 1: 1.
The 2K adhesive composition of any one of claims 1-14, wherein each of the first component and the second component has a viscosity of 40,000-60,000 cps at room temperature.
The 2K adhesive composition of any one of claims 1-15, wherein the 2K adhesive composition is suitable for use on plastics and/or composite materials.
A coated substrate, comprising a substrate and the 2K adhesive composition of any one of claims 1-16 applied on at least a part of the substrate.
The coated substrate of claim 17, wherein the substrate has not been treated with a primer.
The coated substrate of claim 17 or 18, wherein the substrate comprises plastics and/or composite materials.
The coated substrate of claim 19, wherein the substrate comprises PP, PP/LGF, SMC, PC/ABS, PMMA/ASA, PC/PET, and/or PVC.
The coated substrate of any one of claims 17-20, wherein the substrate is part of a vehicle.
The coated substrate of claim 21, wherein the substrate comprises a spoiler and/or a tailgate.
The coated substrate according to claims 17-22, wherein a cured layer formed from the 2K adhesive composition applied on at least a part of the substrate has a thickness of 0.1 to 4 mm.