Siloxane polyisocyanate, waterborne polyurethane adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesive materials, in particular to siloxane polyisocyanate, a waterborne polyurethane adhesive and preparation methods of the siloxane polyisocyanate and the waterborne polyurethane adhesive. The siloxane polyisocyanate has a structure as shown in a formula (I). Wherein R1, R2 and R3 are independently selected from C1-C14 alkyl, C6-C10 alkyl containing a saturated six-membered ring, a benzene ring and C7-C9 alkyl containing the benzene ring; m1 and X1 are independently selected from H and C1-C5 alkyl; y is selected from hydrogen, a C1-C8 alkyl group, a C2-C6 alkenyl group, a C3-C10 acrylate group and a C1-C8 alkoxy group; n is an integer selected from 0-5; and m is a positive integer selected from 1-10. The siloxane polyisocyanate can improve the bonding strength, the thermal stability, the low temperature resistance, the heat and humidity resistance and the water resistance of the adhesive, reduce the surface tension at the same time, and facilitate uniform bonding; the waterborne polyurethane adhesive prepared on the basis of the siloxane polyisocyanate has heat resistance, low temperature resistance, wetting leveling property, damp-heat aging resistance, water resistance and high adhesive property, and can be stably stored without sedimentation and gelling. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive materials, in particular to a siloxane polyisocyanate, a water-based polyurethane adhesive and a preparation method thereof. Background Art

[0002] Polyurethane adhesives are a key component of the rapidly developing polyurethane resin market. With excellent properties, they are widely used in many applications and are one of the eight major synthetic adhesives. Polyurethane adhesives possess excellent shear strength and impact resistance, making them suitable for a variety of structural bonding applications. They also exhibit excellent flexibility. Polyurethane adhesives also feature adjustable toughness, a simple bonding process, excellent low-temperature resistance, and excellent stability. These excellent bonding properties and adaptability to a wide range of substrates have led to a continuous expansion of their application areas, making them the fastest-growing adhesive both domestically and internationally in recent years.

[0003] Waterborne polyurethane adhesives offer excellent wear and chemical resistance, flexibility, adhesion, and high gloss. They are also low in volatile organic solvents, non-toxic, non-flammable, odorless, environmentally friendly, and pose no health risks to operators. These characteristics make them a key development direction for polyurethane adhesives. Waterborne polyurethane adhesives are a key synthetic water-based adhesive product being developed in my country. Due to their excellent bonding properties, polyurethane adhesives are widely used in industries such as footwear, apparel, construction, automotive, food packaging, kitchenware, and laminated films. They are characterized by containing no or minimal organic solvents in their dispersions while maintaining the inherent wear resistance and high strength of conventional polyurethane adhesives. With increasing safety and environmental awareness in China, research into waterborne polyurethane adhesives has rapidly developed. Waterborne polyurethane adhesives are formed by dissolving or dispersing polyurethane in water. Compared to solvent-based adhesives, they offer advantages such as being solvent-free, pollution-free, having excellent film-forming properties, strong adhesion, and easy blending with other polymers, especially emulsion-based polymers, which facilitates modification.

[0004] However, while water-based polyurethane adhesives retain the advantages of polyurethane, they also suffer from issues compared to solvent-based polyurethane adhesives, such as ① poor substrate wettability, ② surface tension mismatch, ③ relatively high surface tension of the solvent water, and difficulty eliminating bubbles caused by stirring. Water-based polyurethane adhesives typically address surface tension issues by introducing wetting agents and leveling agents. However, the addition of additives, especially those specifically designed to address surface tension issues, can deteriorate the adhesive's bonding performance and mechanical properties. Surface tension additives only address the surface tension issues of water-based polyurethane adhesives and cannot improve the high-temperature resistance of the bonded parts, nor can they address the reduced bond strength and insufficient hydrolysis resistance of the adhesive in high-temperature environments.

[0005] At present, waterborne polyurethane is mainly prepared into isocyanate (NCO) end-capped prepolymer S1 by polyester polyol and isocyanate monomer chain extension, then by polyaddition reaction, namely the monomer containing active hydrogen atom and isocyanate end-capped prepolymer S1 chain extension, and according to the viscosity of the system, acetone or butanone is added to regulate the viscosity of the system, while introducing a hydrophilic group, preparing product S2. By diamine monomer post-chain extension, amino alcohol monomer end-capped product is designated as S3, under the condition of room temperature high-speed stirring, deionized water is added dropwise to S3 and emulsified, and then the low-boiling point small molecule solvent is removed under reduced pressure to be prepared into waterborne polyurethane emulsion. In addition, when polyol and isocyanate monomer react, it is necessary to add organic metal or aziridine catalyst, catalyze the reaction of active hydrogen atom and isocyanate group (NCO), can effectively accelerate reaction rate, shorten reaction time, but catalyst cannot be removed and can only be retained in polyurethane adhesive A component. As a two-component polyurethane adhesive, the catalyst can also accelerate the reaction rate between component A and component B (isocyanate curing agent) during the later use of the adhesive, shortening the adhesive's activation period. It should be used as soon as possible after preparation to avoid difficulties in processing or poor bonding performance after curing. However, organotin catalysts may be harmful to organisms and are therefore prohibited by the EU's REACH regulation. The small molecule hydrophilic monomers (also known as internal emulsifiers) used in the relevant patents include dimethylolpropionic acid, dimethylolbutyric acid, sodium 2-(2-aminoethyl)aminoethanesulfonate, sodium 2-(2-aminoethyl)aminopropanesulfonate, sodium 1,4-butanediol-2-sulfonate, sodium 1,2-dihydroxy-3-propanesulfonate, sodium 2,4-diaminobenzenesulfonate, sodium 3,5-diaminobenzenesulfonate, sodium 1-amino-8-naphthol-3,6-disulfonate, sodium N-tris(hydroxymethyl)methyl-3-aminopropanesulfonate, sodium ethylenediamine bis-2-hydroxypropanesulfonate, sodium aminosulfonate, dihydroxy half esters, etc. When dimethylolpropionic acid or dimethylolbutyric acid is a hydrophilic monomer, it is necessary to react with a base to form a carboxylate to achieve hydrophilicity. The commonly used base at present is triethylamine, a weak base. The weak acid and weak base salt emulsion of carboxylic acid and triethylamine has poor stability. When strong bases such as sodium hydroxide or potassium hydroxide are used to neutralize the carboxylate, the emulsion will turn yellow.

[0006] Patents with publication numbers CN105637049B and CN105612234B disclose a hot-press bonding adhesive for bonding metal foil to polymer film layers. The adhesive composition is made from water, a polyurethane compound, a hydrophilically modified isocyanate trimer aqueous dispersion, and an aqueous dispersion / suspension of a silicone compound having epoxy groups, thiol groups, or amino groups with a pH of 1-7. The alkoxy groups of the silicone compound having epoxy groups, thiol groups, or amino groups are hydrolyzed into hydroxyl groups in water with a pH of 1-7, and react with the isocyanate groups in the mixture to form a cross-linked structure, providing strength to the adhesive. However, this technical solution requires controlling the pH of the system in order for the siloxane groups to hydrolyze into silanol structures and react with the hydrophilically modified isocyanate trimer to form a cross-linked structure. However, when the pH of the system changes, the silicone is difficult to hydrolyze into silanols, and thus cannot react completely with component B, resulting in insufficient cross-linking. While the adhesive produced by this technique is resistant to boiling water, its bonding strength and inherent strength are low. Siloxane hydrolysis forms silanol groups, which increase their polarity and impair substrate wettability and spreadability. This can lead to poor coating appearance, such as poor wetting during processing and shrinkage craters, and the adhesive lacks high-temperature creep resistance.

[0007] Patent publication number CN110862409B discloses a method for preparing a diol-containing silane compound and modifying a waterborne polyurethane thereof. The method comprises preparing the diol-containing silane compound from 3-amino-1,2-propylene glycol (APD), a polyester diol, and a silane compound. The diol-containing silane compound is a hydroxyl-terminated silane compound prepared by reacting 3-isocyanatepropyltrimethoxysilane with 3-amino-1,2-propylene glycol (APD). This technical solution is to introduce a higher content of silicone structure through silicone modification to achieve organic-inorganic properties. However, due to the high content of silane introduced and the high proportion of side groups, the waterborne polyurethane chain segments cannot be arranged regularly, and the bonding strength is low when used as an adhesive. In addition, this technical solution uses the unsaturated groups in the capping agent to achieve photocrosslinking to form a three-dimensional crosslinked network structure. However, in carbon-carbon unsaturated photocrosslinking, the higher the proportion of unsaturated groups, the greater the degree of crosslinking, resulting in greater volume shrinkage during the crosslinking process and poorer adhesion to the substrate. In addition, this technical solution cannot improve the high temperature resistance and thermal creep properties of the adhesive.

[0008] Patents with publication numbers CN101974305A, CN105238328A, and CN114032058B all employ the addition of surface wetting agents, leveling agents, and defoaming agents to waterborne polyurethane compositions to reduce surface tension and enhance the wettability and leveling properties of the waterborne polyurethane on the substrate. However, while the addition of additives can improve the wettability and leveling properties of the waterborne polyurethane on the substrate, the additive ratio must be strictly controlled. A too small ratio will not adequately improve wettability and leveling, while a too high ratio can compromise the adhesive properties and mechanical strength of the waterborne polyurethane adhesive.

[0009] Patent publication number CN112210336A discloses a low-temperature-resistant polyurethane adhesive consisting of component A and component B. Component A comprises polyether polyol, butanediol, trimethylolpropane, ethylene glycol, and a metal catalyst, while component B comprises an isocyanate-terminated polydimethylsiloxane prepolymer, a polyisocyanate, and an isocyanate alkyltrialkoxysilane. The isocyanate-terminated polydimethylsiloxane prepolymer is obtained by polymerizing a dihydroxyalkylpolydimethylsiloxane with a diisocyanate in a certain proportion. This technical solution only improves the polyurethane adhesive's low-temperature processing performance and low-temperature bonding properties, but does not improve the adhesive's heat resistance at high temperatures, or its bonding and thermal creep properties under hot conditions. Summary of the Invention

[0010] The present invention aims to at least partially address one of the technical problems in the related art. To this end, the present invention provides a siloxane polyisocyanate, a water-based polyurethane adhesive, and a preparation method thereof. This water-based polyurethane adhesive is a one-component water-based polyurethane adhesive modified with the siloxane polyisocyanate to impart heat resistance, low-temperature resistance, wetting and leveling properties, resistance to wet-heat aging, water resistance, and high adhesion properties. Furthermore, this water-based polyurethane adhesive exhibits stable storage without settling or gelling.

[0011] To this end, the first aspect of the present invention provides a siloxane polyisocyanate having a structure shown in formula (I):

[0012]

[0013] in:

[0014] R1, R2, R3 are independently selected from C1-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0015] M1 and X1 are independently selected from H and C1-C5 alkyl;

[0016] Y is selected from hydrogen, C1-C8 alkyl, C2-C6 alkenyl, C3-C 10 Acrylate group, C1-C8 alkoxy group;

[0017] n is an integer selected from 0 to 5;

[0018] m is a positive integer selected from 1-10.

[0019] This siloxane polyisocyanate has an isocyanate group that reacts with the hydroxyl groups in polyols and small molecule polyols to form a carbamate bond. The carbamate ring structure provides adhesive strength and thermal stability, which means it has advantages in peel strength and creep performance under high temperature conditions. Furthermore, the introduction of the siloxane structure not only achieves low-temperature resistance but also reduces surface tension, solving the problem of poor wetting or non-wetting of low-surface-energy substrates, thereby facilitating uniform bonding. The ordered arrangement of the siloxane segments allows for a dense arrangement, which improves the adhesive's resistance to moisture and heat, as well as its water resistance.

[0020] According to an embodiment of the present invention, R1, R2, and R3 are independently selected from C5-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0021] M1 and X1 are independently selected from H and C1-C5 alkyl;

[0022] Y is selected from hydrogen, C1-C4 alkyl, C2-C4 alkenyl, C3-C5 acrylate, C1-C4 alkoxy;

[0023] n is an integer selected from 0 to 4;

[0024] m is a positive integer selected from 1-9.

[0025] According to an embodiment of the present invention, R1, R2, and R3 are independently selected from C5-C8 alkyl, C8-C8 containing a saturated six-membered ring, 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0026] M1 and X1 are independently selected from H and C1-C3 alkyl;

[0027] Y is selected from C1-C4 alkyl, C1-C4 alkoxy;

[0028] n is an integer selected from 0 to 4;

[0029] m is a positive integer selected from 1-9.

[0030] According to an embodiment of the present invention, R1, R2, and R3 are independently selected from C5-C6 alkyl, C5-C6 alkyl containing a saturated six-membered ring, 10Alkyl, or, R1 is selected from C5-C6 alkyl, R2, R3 are selected from C7 alkyl containing a benzene ring;

[0031] M1 is selected from C1-C3 alkyl;

[0032] X1 is selected from H;

[0033] Y is selected from C1-C4 alkyl, C1-C4 alkoxy;

[0034] n is an integer selected from 0 to 4;

[0035] m is a positive integer selected from 1-9.

[0036] A second aspect of the present invention provides a waterborne polyurethane adhesive, comprising a waterborne polyurethane emulsion and oxazoline, wherein the raw materials for preparing the waterborne polyurethane emulsion include a polymer containing at least two hydroxyl groups, a diisocyanate monomer, and a siloxane polyisocyanate;

[0037] The polymer containing at least two hydroxyl groups includes polyester polyol and / or polyether polyol;

[0038] Wherein, the siloxane polyisocyanate is the siloxane polyisocyanate described in the first aspect.

[0039] The waterborne polyurethane adhesive provided by the present invention utilizes the siloxane polyisocyanate as a chain extender, and generates a carbamate bond through the reaction of the isocyanate group with the hydroxyl group in the polyol. The siloxane structure, the benzene ring, and the saturated ring structure are bonded to the waterborne polyurethane chain through chemical bonds. The carbamate ring structure provides the adhesive with bonding strength and thermal stability, that is, it has advantages in peeling force and creep performance under high temperature conditions; the introduction of the siloxane structure can achieve low-temperature resistance while also reducing surface tension, solving the problem of the adhesive not wetting or having poor wettability on substrates with low surface energy, and is more conducive to uniform bonding; in addition, the orderly arranged siloxane chain segments can be tightly arranged, thereby improving the adhesive's resistance to moisture and heat and water resistance.

[0040] According to an embodiment of the present invention, the water-based polyurethane adhesive further includes a thickener, a leveling agent and a wetting agent.

[0041] According to an embodiment of the present invention, the water-based polyurethane adhesive comprises, by weight, 85-96 parts of water-based polyurethane emulsion, 3-12 parts of oxazoline, 0.05-1 part of thickener, 0.05-1.1 parts of leveling agent, and 0.03-0.9 part of wetting agent.

[0042] According to an embodiment of the present invention, the solid content of the aqueous polyurethane emulsion is 40%-75%.

[0043] According to an embodiment of the present invention, the initial R value of the aqueous polyurethane emulsion is 1.01-2.5.

[0044] The third aspect of the present invention provides a method for preparing the waterborne polyurethane adhesive according to the second aspect, the method comprising the following steps of preparing a waterborne polyurethane emulsion:

[0045] Mixing a polymer containing at least two hydroxyl groups, a diisocyanate monomer, and a first chain extender, and performing a chain extension until the concentration of the isocyanate group in the reaction system is 1% to 7%, thereby obtaining a polymer S1;

[0046] The polymer S1 and the siloxane polyisocyanate are mixed until the concentration of the isocyanate group in the reaction system is 0.3% to 5%, thereby obtaining a polymer S2;

[0047] The polymer S2 and the second chain extender are mixed, subjected to secondary chain extension, and emulsified to obtain the aqueous polyurethane emulsion.

[0048] The waterborne polyurethane adhesive can be prepared by the preparation method provided by the present invention. The waterborne polyurethane adhesive has heat resistance, low temperature resistance, wetting and leveling properties, resistance to moist heat aging, water resistance and high bonding performance, and can be stably stored without sedimentation or gelation.

[0049] According to an embodiment of the present invention, the mass ratio of the polymer containing at least two hydroxyl groups to the siloxane polyisocyanate is 100:(0.5-10).

[0050] According to an embodiment of the present invention, the mass ratio of the polyester polyol to the polyether polyol is (100-0):(0-100).

[0051] According to an embodiment of the present invention, the number average molecular weight of the polyester polyol is 1000-4000, and the polyester polyol includes at least one of polybutylene adipate diol, polyhexamethylene adipate diol, polycaprolactone diol, and polycarbonate diol.

[0052] According to an embodiment of the present invention, the mass average molecular weight of the polyether polyol is 90-2000, and the polyether polyol includes at least one of polytetramethylene glycol, polypropylene glycol, polyethylene glycol, and polybutylene glycol.

[0053] According to an embodiment of the present invention, the molar ratio of the diisocyanate monomer to the isocyanate group in the siloxane polyisocyanate is (0.9:0.01)-(0.7:0.1).

[0054] According to an embodiment of the present invention, the diisocyanate monomer includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, di-cyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and xylylene diisocyanate.

[0055] According to an embodiment of the present invention, the diisocyanate monomer includes hexamethylene diisocyanate and isophorone diisocyanate, and the molar ratio of the hexamethylene diisocyanate to the isophorone diisocyanate is (80-60):(20-40).

[0056] According to an embodiment of the present invention, the first chain extender includes a carboxylic acid containing at least two hydroxyl groups and an optional small molecule polyol.

[0057] According to an embodiment of the present invention, the carboxylic acid containing at least two hydroxyl groups includes at least one of dihydroxymethylpropionic acid, dihydroxymethylbutanoic acid, dihydroxymethylvaleric acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, 4,8-dihydroxynaphthalene-2,6-dicarboxylic acid, 4,5-dihydroxy-pyridine-2-carboxylic acid, 2,5-dihydroxybenzenedicarboxylic acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, and 4,6-dihydroxy-3-quinolinecarboxylic acid.

[0058] According to an embodiment of the present invention, the molar ratio of the oxazoline to the carboxylic acid containing at least two hydroxyl groups is 1:(1-1.25).

[0059] According to an embodiment of the present invention, the molar ratio of the active protons provided by the polymer containing at least two hydroxyl groups to the active protons provided by the small molecule polyol is 1:(0-0.5).

[0060] According to an embodiment of the present invention, the small molecule polyol includes at least one of butanediol, ethylene glycol, isoprene glycol, neodiol, decanediol, diethylene glycol, trimethylolpropane, pentaerythritol, and neopentyl glycol.

[0061] According to an embodiment of the present invention, the temperature of the primary chain extension is 70°C-80°C.

[0062] According to an embodiment of the present invention, the second chain extender includes a diamine salt, an optional fatty diamine, and an optional additive.

[0063] According to an embodiment of the present invention, the diamine salt includes at least one of diamine sulfonate and diamine carboxylate.

[0064] According to an embodiment of the present invention, the aliphatic diamine includes ethylenediamine.

[0065] According to an embodiment of the present invention, the additive includes an amine compound containing a hydroxyl group, preferably ethanolamine.

[0066] According to an embodiment of the present invention, the mass ratio of the second chain extender to the polymer S2 is (0.5-5):(99.5-95).

[0067] According to an embodiment of the present invention, the temperature of the second chain extension is 10°C-45°C.

[0068] According to an embodiment of the present invention, the preparation method further comprises: mixing the aqueous polyurethane emulsion, oxazoline, a thickener, a leveling agent, and a wetting agent to obtain the aqueous polyurethane adhesive.

[0069] The beneficial effects of the present invention compared to the prior art are as follows:

[0070] (1) The water-based polyurethane adhesive provided by the present invention has heat resistance, low temperature resistance, wetting and leveling properties, resistance to moist heat aging, water resistance and high bonding performance, and can be stably stored without sedimentation or gelation;

[0071] (2) The waterborne polyurethane adhesive provided by the present invention uses the siloxane polyisocyanate as a chain extender, and reacts the isocyanate group with the hydroxyl group in the polyol and the small molecule polyol to form a carbamate bond. The siloxane structure, benzene ring, and saturated ring structure are chemically bonded to the waterborne polyurethane chain. The carbamate ring structure provides the adhesive with bonding strength and thermal stability, that is, it has advantages in peel strength and creep performance under high temperature conditions;

[0072] (3) The introduction of siloxane structure can achieve low temperature resistance while reducing surface tension, solving the problem of adhesive not wetting or poor wettability for low surface energy substrates, and is more conducive to uniform bonding. In addition, the orderly arranged siloxane segments can be arranged tightly, thereby improving the adhesive's heat and moisture resistance and water resistance. Siloxane polyisocyanate chemically bonds the siloxane structure to the polyurethane side chain, forming a large bond angle of the siloxane bond, low rotational potential energy of the siloxane bond, and good flexibility. The formed adhesive polymer can be regularly stacked and arranged with a high density. Therefore, it can also slow down the aging and degradation of the polymer by water vapor in a high temperature and high humidity environment. Therefore, it is beneficial to improve the adhesion of the adhesive and its ability to withstand a high temperature and high humidity environment for a long time, which helps to achieve excellent creep resistance under high temperature conditions.

[0073] (4) The siloxane structure introduced by bonding can reduce the surface tension of the waterborne polyurethane adhesive, improve the wettability and leveling properties of the adhesive on different substrates, and will not affect the adhesive's bonding performance even when the introduction ratio is large. When the siloxane is introduced by bonding and the siloxane content is higher than the conventional amount (generally 2%), the adhesive's bonding performance is not reduced;

[0074] (5) Within the polyurethane adhesive layer, the hard segment phase plays a reinforcing role, providing multifunctional physical crosslinking, while the soft segment matrix provides flexibility. The more severe the phase separation, the stronger the crystallinity, and the higher its high temperature and high humidity resistance, mechanical tensile strength, elongation at break, and modulus;

[0075] (6) The addition of an oxazoline crosslinker can achieve the volatilization of the solvent water and the crosslinking of the adhesive during the drying stage after the adhesive is processed and used downstream. The benzene-hydroxyl groups generated by the hydrolysis of the alkoxy groups on the benzene ring of the siloxane isocyanate compound in the water-dispersible polyurethane can react with oxazoline to form a crosslinking structure, thereby improving the cohesion and adhesion of the adhesive, and further achieving water resistance and heat aging resistance. The carboxyl groups in the water-dispersible polyurethane can also react with oxazoline to crosslink and realize the body structure of the adhesive, thereby also achieving the effect of improving the cohesion, adhesion, water resistance and heat aging resistance of the adhesive.

[0076] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0078] Figure 1 A schematic diagram of a high temperature creep test provided by the present invention is shown. DETAILED DESCRIPTION

[0079] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0080] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0081] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0082] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meaning commonly understood by those skilled in the art to which the present invention belongs.

[0083] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention, but not excluding other contents.

[0084] As used herein, the terms "optionally," "optional," or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0085] The term "C1-C 14 “Alkyl” is understood to mean a straight-chain or branched saturated hydrocarbon radical having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 carbon atoms. The alkyl radical is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl, or the like or isomers thereof.

[0086] The term "C1-C8 alkoxy" is to be understood as -O-(C1-C8 alkyl), wherein "C1-C8 alkyl" has the above-mentioned definition.

[0087] The term "C6-C containing a saturated six-membered ring 10 The term "alkyl" is understood to mean a saturated hydrocarbon group having 6 to 10 carbon atoms and containing a cyclohexane structure.

[0088] The term "C7-C9 alkyl group containing a benzene ring" is understood to be a hydrocarbon group having 7 to 9 carbon atoms and containing a benzene ring structure.

[0089] The term "C2-C6 alkenyl" is understood to mean preferably a straight-chain or branched hydrocarbon radical comprising one or more double bonds and having 2, 3, 4, 5 or 6 carbon atoms.

[0090] The term "C3-C 10 "Acrylate group" should be understood as CH2=CH-COO-(C0-C7 alkyl)-, wherein "C0-C7 alkyl" has the above definition, and C0 alkyl is H.

[0091] According to an embodiment of the present invention, a first aspect of the present invention provides a siloxane polyisocyanate having a structure shown in formula (I):

[0092]

[0093] in:

[0094] R1, R2, R3 are independently selected from C1-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0095] M1 and X1 are independently selected from H and C1-C5 alkyl;

[0096] Y is selected from hydrogen, C1-C8 alkyl, C2-C6 alkenyl, C3-C 10 Acrylate group, C1-C8 alkoxy group;

[0097] n is an integer selected from 0 to 5;

[0098] m is a positive integer selected from 1-10.

[0099] According to a specific embodiment of the present invention, said R1, R2, and R3 are independently selected from C5-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0100] M1 and X1 are independently selected from H and C1-C5 alkyl;

[0101] Y is selected from hydrogen, C1-C4 alkyl, C2-C4 alkenyl, C3-C5 acrylate, C1-C4 alkoxy;

[0102] n is an integer selected from 0 to 4;

[0103] m is a positive integer selected from 1-9.

[0104] According to a specific embodiment of the present invention, R1, R2, and R3 are independently selected from C5-C8 alkyl, C8-C8 containing a saturated six-membered ring, 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring;

[0105] M1 and X1 are independently selected from H and C1-C3 alkyl;

[0106] Y is selected from C1-C4 alkyl, C1-C4 alkoxy;

[0107] n is an integer selected from 0 to 4;

[0108] m is a positive integer selected from 1-9.

[0109] According to a specific embodiment of the present invention, R1, R2, and R3 are independently selected from C5-C6 alkyl, C containing a saturated six-membered ring 10 Alkyl, or, R1 is selected from C5-C6 alkyl, R2, R3 are selected from C7 alkyl containing a benzene ring;

[0110] M1 is selected from C1-C3 alkyl;

[0111] X1 is selected from H;

[0112] Y is selected from C1-C4 alkyl, C1-C4 alkoxy;

[0113] n is an integer selected from 0 to 4;

[0114] m is a positive integer selected from 1-9.

[0115] According to an embodiment of the present invention, a second aspect of the present invention provides an aqueous polyurethane adhesive, wherein the aqueous polyurethane adhesive comprises an aqueous polyurethane emulsion and oxazoline, wherein the raw materials for preparing the aqueous polyurethane emulsion comprise a polymer containing at least two hydroxyl groups, a diisocyanate monomer, and a siloxane polyisocyanate;

[0116] The polymer containing at least two hydroxyl groups includes polyester polyol and / or polyether polyol;

[0117] Wherein, the siloxane polyisocyanate is the siloxane polyisocyanate described in the first aspect.

[0118] The waterborne polyurethane adhesive provided by the present invention uses the silicone polyisocyanate as a chain extender, and generates a carbamate bond through the reaction of the isocyanate group with the hydroxyl group in the polyol and the small molecule polyol. The silicone structure, the benzene ring and the saturated ring structure are bonded to the waterborne polyurethane chain through chemical bonds. The carbamate ring structure provides the adhesive with bonding strength and thermal stability, that is, it has advantages in peeling force and creep performance under high temperature conditions; the introduction of the silicone structure can achieve low temperature resistance while reducing surface tension, solving the problem that the adhesive does not wet or has poor wettability for substrates with low surface energy, and is more conducive to uniform bonding. In addition, the orderly arranged silicone segments can be arranged tightly to improve the moisture and heat resistance and water resistance of the adhesive; the silicone polyisocyanate uniformly bonds the silicone structure to the polyurethane side chain through chemical bonds, and the bond angle of the formed silicone oxygen bond is large, and the rotational potential energy of the silicone oxygen bond is low and the flexibility is good, and the formed silicone oxygen bond is large. The adhesive polymers can be regularly stacked and arranged at a high density, thus mitigating the aging and degradation of the polymers by moisture in high-temperature, high-humidity environments. This improves the adhesive's adhesion and long-term tolerance to high-temperature, high-humidity environments, contributing to excellent creep resistance under high-temperature conditions. The siloxane structure introduced through bonding can reduce the surface tension of the waterborne polyurethane adhesive, improving its wettability and leveling properties on various substrates. Even a large proportion of the siloxane structure introduced does not affect the adhesive's bonding performance. Within the polyurethane adhesive layer, the hard segment phase acts as a reinforcement, providing multifunctional physical crosslinking, while the soft segment matrix provides flexibility. The more severe the phase separation and the stronger the crystallinity, the higher the high-temperature, high-humidity resistance, mechanical tensile strength, elongation at break, and modulus. The addition of an oxazoline crosslinker allows for simultaneous volatilization of the solvent and crosslinking of the adhesive during the drying phase after downstream processing and use. The benzene-hydroxyl groups generated after the hydrolysis of the alkoxy groups on the benzene ring of the silicone isocyanate compound in the water-dispersible polyurethane can react with oxazoline to form a cross-linked structure, thereby improving the cohesion and adhesion of the adhesive, and further achieving water resistance and heat aging resistance. The carboxyl groups in the water-dispersible polyurethane can also react with oxazoline to cross-link and realize the body structure of the adhesive, thereby also achieving the effect of improving the cohesion, adhesion, water resistance and heat aging resistance of the adhesive.

[0119] According to a specific embodiment of the present invention, the water-based polyurethane adhesive further includes a thickener, a leveling agent and a wetting agent.

[0120] The wettability and leveling properties of waterborne polyurethane on the substrate can be improved by adding additives, but the proportion of additives must be strictly controlled. Too small a proportion will not be enough to improve the wettability and leveling properties; too high a proportion will affect the bonding properties and mechanical strength of the waterborne polyurethane adhesive itself.

[0121] According to a specific embodiment of the present invention, the water-based polyurethane adhesive comprises, by weight, 85-96 parts of water-based polyurethane emulsion, 3-12 parts of oxazoline, 0.05-1 part of thickener, 0.05-1.1 parts of leveling agent, and 0.03-0.9 part of wetting agent.

[0122] According to a specific embodiment of the present invention, the solid content of the aqueous polyurethane emulsion is 40%-75%. As some specific examples, the solid content of the aqueous polyurethane emulsion can be 40%, 50%, 60%, 70%, 75%, etc.

[0123] According to a specific embodiment of the present invention, the initial R value of the aqueous polyurethane emulsion is 1.01-2.5. As some specific examples, the initial R value of the aqueous polyurethane emulsion can be 1.01, 1.05, 1.1, 1.2, 1.5, 2, 2.5, etc. Specifically, the initial R value is defined as: the ratio of the number of moles of isocyanate groups in the aqueous polyurethane emulsion to the number of moles of active protons before emulsification.

[0124] According to an embodiment of the present invention, a third aspect of the present invention provides a method for preparing the waterborne polyurethane adhesive according to the second aspect, the preparation method comprising the following steps of preparing a waterborne polyurethane emulsion:

[0125] (1) A polymer containing at least two hydroxyl groups, a diisocyanate monomer, and a first chain extender are mixed and chain extended once until the concentration of the isocyanate groups in the reaction system is 1% to 7%, thereby obtaining polymer S1.

[0126] According to a specific embodiment of the present invention, the mass ratio of the polyester polyol to the polyether polyol is (100-0):(0-100). As some specific examples, the mass ratio of the polyester polyol to the polyether polyol can be 100:0, 80:20, 10:90, 0:100, etc.

[0127] According to a specific embodiment of the present invention, the number average molecular weight of the polyester polyol is 1000-4000. As some specific examples, the number average molecular weight of the polyester polyol may be 1000, 2000, 3000, 4000, etc. The type of the polyester polyol is not particularly limited. As some specific examples, the polyester polyol includes at least one of polybutylene adipate diol, polyhexamethylene adipate diol, polycaprolactone diol, and polycarbonate diol.

[0128] According to a specific embodiment of the present invention, the mass average molecular weight of the polyether polyol is 90-2000. As some specific examples, the mass average molecular weight of the polyether polyol may be 90, 100, 200, 500, 1000, 1500, 2000, etc. The type of the polyether polyol is not particularly limited. As some specific examples, the polyether polyol includes at least one of polytetramethylene glycol, polypropylene glycol, polyethylene glycol, and polybutylene glycol.

[0129] The molecular weight of polyether polyol needs to be controlled within an appropriate range, because when the molecular weight of polyether polyol is too small, the molecular weight of the prepared polyurethane prepolymer is too large, and the proportion of rigid groups is too high, the molecular cohesion is large, and it is difficult to dissolve in solvents such as acetone and butanone, resulting in the inability to graft hydrophilic chain extenders and difficulty in emulsification; when the molecular weight of polyether polyol is too large, the proportion of ether bonds is too high, the strength of the adhesive layer is greatly reduced, and the bonding force becomes smaller.

[0130] According to a specific embodiment of the present invention, the type of the diisocyanate monomer is not particularly limited. As some specific examples, the diisocyanate monomer includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, di-cyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and xylylene diisocyanate.

[0131] According to a specific embodiment of the present invention, the diisocyanate monomer includes hexamethylene diisocyanate and isophorone diisocyanate, and the molar ratio of the hexamethylene diisocyanate to the isophorone diisocyanate is (80-60):(20-40). As some specific examples, the molar ratio of the hexamethylene diisocyanate to the isophorone diisocyanate may be 80:20, 80:40, 60:20, 60:40, etc.

[0132] Hexamethylene diisocyanate has a symmetrical and regular structure. A high proportion of hexamethylene diisocyanate facilitates rapid crystallization and enhances adhesive strength in waterborne polyurethanes. Isophorone diisocyanate does not contribute to the crystallization of waterborne polyurethanes. However, due to the significant difference in the reactivity of its two isocyanate groups, only one typically participates in the reaction, making it useful as a capping agent. The remaining isocyanate group can react with highly reactive amino groups during subsequent chain extension.

[0133] According to a specific embodiment of the present invention, the first chain extender includes a carboxylic acid containing at least two hydroxyl groups and an optional small molecule polyol.

[0134] According to a specific embodiment of the present invention, the type of the carboxylic acid containing at least two hydroxyl groups is not particularly limited. As some specific examples, the carboxylic acid containing at least two hydroxyl groups includes at least one of dihydroxymethylpropionic acid, dihydroxymethylbutanoic acid, dihydroxymethylpentanoic acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, 4,8-dihydroxynaphthalene-2,6-dicarboxylic acid, 4,5-dihydroxy-pyridine-2-carboxylic acid, 2,5-dihydroxybenzenedicarboxylic acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, and 4,6-dihydroxy-3-quinolinecarboxylic acid.

[0135] According to a specific embodiment of the present invention, the molar ratio of the oxazoline to the carboxylic acid containing at least two hydroxyl groups is 1:(1-1.25). As some specific examples, the molar ratio of the oxazoline to the carboxylic acid containing at least two hydroxyl groups can be 1:1, 1:1.1, 1:1.2, 1:1.25, etc. Specifically, the hydroxyl group in the carboxylic acid containing at least two hydroxyl groups can react with the isocyanate group to perform a chain extension, and the carboxyl group in its structure can provide a cross-linking site for the oxazoline.

[0136] According to a specific embodiment of the present invention, the molar ratio of the active protons provided by the polymer containing at least two hydroxyl groups to the active protons provided by the small molecule polyol is 1:(0-0.5). As some specific examples, the molar ratio of the active protons provided by the polymer containing at least two hydroxyl groups to the active protons provided by the small molecule polyol may be 1:0, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc.

[0137] According to a specific embodiment of the present invention, the type of the small molecule polyol is not particularly limited. As some specific examples, the small molecule polyol includes at least one of butanediol, ethylene glycol, isoprene glycol, neodiol, decanediol, diethylene glycol, trimethylolpropane, pentaerythritol, and neopentyl glycol.

[0138] According to a specific embodiment of the present invention, the temperature of the first chain extension is 70° C.-80° C. As some specific examples, the temperature of the first chain extension can be 70° C., 75° C., 80° C., etc.

[0139] According to a specific embodiment of the present invention, the preparation method further comprises: adjusting the viscosity of the system. The type of the adjusting agent for adjusting the viscosity of the system is not particularly limited. As some specific examples, the adjusting agent includes but is not limited to acetone.

[0140] According to a specific embodiment of the present invention, the method for detecting the concentration of isocyanate groups in the reaction system is not particularly limited. As some specific examples, the method for detecting the concentration of isocyanate groups in the reaction system includes but is not limited to chemical titration.

[0141] (2) The polymer S1 and siloxane polyisocyanate are mixed until the concentration of isocyanate groups in the reaction system is 0.3% to 5%, thereby obtaining polymer S2.

[0142] The reason why the siloxane polyisocyanate can only be added in step (2) and cannot be added directly in step (1) is that the siloxane contained in the siloxane polyisocyanate has certain inorganic properties, poor compatibility with polyols and small molecule chain extenders, and is difficult to react in a homogeneous phase, resulting in uneven distribution of the siloxane on the formed molecular chain. Adding the siloxane polyisocyanate in step (2) can better graft the siloxane onto the polymer molecular weight chain in sequence, with relatively uniform distribution, and can increase the dispersion uniformity of the inorganic filler added to the subsequent aqueous polyurethane emulsion, and can enhance the wetting and leveling properties of the aqueous polyurethane emulsion; the added siloxane polyisocyanate can enhance the crosslinking degree of the aqueous polyurethane emulsion, thereby improving the mechanical properties and heat resistance.

[0143] Specifically, the reaction temperature in step (2) is the same as the temperature of the primary chain extension.

[0144] According to a specific embodiment of the present invention, the mass ratio of the polymer containing at least two hydroxyl groups to the siloxane polyisocyanate is 100:(0.5-10). As some specific examples, the mass ratio of the polymer containing at least two hydroxyl groups to the siloxane polyisocyanate may be 100:0.5, 100:1, 100:2, 100:5, 100:10, etc.

[0145] According to a specific embodiment of the present invention, the molar ratio of the isocyanate groups in the diisocyanate monomer and the siloxane polyisocyanate is (0.9:0.01)-(0.7:0.1). As some specific examples, the molar ratio of the isocyanate groups in the diisocyanate monomer and the siloxane polyisocyanate may be 0.9:0.01, 0.7:0.01, 0.9:0.1, 0.7:0.1, etc.

[0146] (3) The polymer S2 and the second chain extender are mixed, subjected to secondary chain extension, and emulsified to obtain the aqueous polyurethane emulsion.

[0147] During the secondary chain extension process, the amino group in the second chain extender will react with the isocyanate group, which not only introduces more polar groups such as carbamate or urea, but also further increases the molecular weight, thereby improving the wettability of the adhesive to the substrate. The bonding strength of the adhesive is also improved due to the further increase in molecular weight. In addition, the second chain extender introduces a hydrophilic group. During the shear emulsification stage, the hydrophilic group enables the oil-soluble polymer to successfully achieve phase inversion, exposing the hydrophilic group to the solvent water phase, and finally forming an emulsion. The introduction of hydrophilic groups is a necessary condition for the formation of the emulsion.

[0148] According to a specific embodiment of the present invention, the second chain extender includes a diamine salt, an optional fatty diamine, and an optional additive.

[0149] According to a specific embodiment of the present invention, the type of the diamine salt is not particularly limited. As some specific examples, the diamine salt includes at least one of diamine sulfonate and diamine carboxylate.

[0150] According to a specific embodiment of the present invention, the type of the fatty diamine is not particularly limited. As some specific examples, the fatty diamine includes but is not limited to ethylenediamine.

[0151] According to a specific embodiment of the present invention, the additive includes an amine compound containing a hydroxyl group, preferably ethanolamine.

[0152] According to a specific embodiment of the present invention, the mass ratio of the second chain extender to the polymer S2 is (0.5-5):(99.5-95). As some specific examples, the mass ratio of the second chain extender to the polymer S2 may be 0.5:99.5, 5:99.5, 0.5:95, 5:95, etc.

[0153] According to a specific embodiment of the present invention, the temperature of the second chain extension is 10°C-45°C. As some specific examples, the temperature of the second chain extension can be 10°C, 20°C, 30°C, 40°C, 45°C, etc.

[0154] According to a specific embodiment of the present invention, the preparation method further comprises: removing impurities under reduced pressure after emulsification. The types of impurities are not particularly limited; as some specific examples, such impurities include but are not limited to acetone. The acetone removed under reduced pressure can be recycled as a viscosity modifier for the system.

[0155] According to a specific embodiment of the present invention, the preparation method further comprises: mixing the aqueous polyurethane emulsion, oxazoline, a thickener, a leveling agent, and a wetting agent to obtain the aqueous polyurethane adhesive.

[0156] According to a specific embodiment of the present invention, a bonding method using a water-based polyurethane adhesive includes applying the water-based polyurethane adhesive to a substrate, drying the adhesive, and then hot-pressing the adhesive. This bonding method is applicable to all products requiring hot-press bonding, with applications including, but not limited to, furniture decoration, automotive interiors, apparel, packaging films, and lithium batteries.

[0157] Below, the scheme of the present invention will be explained in conjunction with embodiment.It will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.In the embodiment, if specific technology or conditions are not indicated, the technology or conditions described in the literature in this area or the product instructions are used.The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by commercial purchase.

[0158] Example 1

[0159] 80 g of poly(hexamethylene adipate) diol, 5 g of isophorone diisocyanate, 15 g of hexamethylene diisocyanate, 1.35 g of dimethylolbutyric acid, and 0.8 g of butanediol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 5.43%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0160] The polymer S1 and 3 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in formula (II)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 4.86%, thereby obtaining polymer S2;

[0161] The polymer S2 was mixed with 2 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 2.2 g of ethylenediamine, and 1.8 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0162] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0163]

[0164] in:

[0165] R1, R2, and R3 have the same structure, and are alkanes with 6 carbon atoms, as shown in formula (VIII).

[0166]

[0167] Example 2

[0168] 88 g of poly(hexamethylene adipate) diol, 4.63 g of isophorone diisocyanate, 10.23 g of hexamethylene diisocyanate, 2.5 g of dimethylolbutyric acid, and 1 g of ethylene glycol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 1.65%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0169] The polymer S1 and 5 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in formula (II)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 0.81%, thereby obtaining polymer S2;

[0170] The polymer S2 was mixed with 0.5 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.4 g of ethylenediamine, and 0.2 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0171] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0172] Example 3

[0173] 88 g of polybutylene glycol, 6 g of isophorone diisocyanate, 13 g of hexamethylene diisocyanate, 2 g of dimethylolbutyric acid, and 3 g of neopentyl glycol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 3.67%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0174] The polymer S1 and 1.8 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in formula (III)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 1.48%, thereby obtaining polymer S2;

[0175] The polymer S2 was mixed with 0.5 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.8 g of ethylenediamine, and 0.5 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0176] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0177]

[0178] in:

[0179] R1, R2, and R3 have the same structure and are saturated six-membered cycloalkanes with 10 carbon atoms, and their structures are shown in formula (IV), wherein * indicates the connection position.

[0180]

[0181] Example 4

[0182] 113 g of poly(hexamethylene adipate) diol, 4.63 g of isophorone diisocyanate, 12 g of hexamethylene diisocyanate, 2 g of dimethylolbutyric acid, and 1 g of ethylene glycol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 1.49%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0183] The polymer S1 and 6 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in formula (V)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 0.84%, thereby obtaining polymer S2;

[0184] The polymer S2 was mixed with 0.6 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.4 g of ethylenediamine, and 0.5 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0185] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0186]

[0187] in:

[0188] R1 is an alkane with 6 carbon atoms, and its structure is shown in formula (VIII); R2 and R3 have the same structure, which is a benzene ring-containing structure with 7 carbon atoms, and its structure is shown in formula (VI), where * indicates the connection position.

[0189]

[0190] Example 5

[0191] 92.7 g of poly(hexamethylene adipate) diol, 3.5 g of isophorone diisocyanate, 13.5 g of hexamethylene diisocyanate, 1.5 g of dimethylolbutyric acid, and 2 g of butanediol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 3.06%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0192] The polymer S1 and 2 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in Formula (VII)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 1.61%, thereby obtaining polymer S2;

[0193] The polymer S2 was mixed with 1.3 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.6 g of ethylenediamine, and 0.6 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0194] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0195]

[0196] in:

[0197] R1, R2, and R3 have the same structure, and are alkanes with 5 carbon atoms, as shown in formula (IX).

[0198]

[0199] Comparative Example 1

[0200] 89 g of poly(hexamethylene adipate) diol, 5.8 g of isophorone diisocyanate, 13.4 g of hexamethylene diisocyanate, 2.5 g of dimethylolbutyric acid, and 1 g of ethylene glycol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 2.43%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0201] The polymer S1 and 3.5 g of 3-ureidopropyltriethoxysilane (CAS No.: 116912-64-2) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 2.15%, thereby obtaining a polymer S2.

[0202] The polymer S2 was mixed with 1 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.4 g of ethylenediamine, and 0.5 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0203] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0204] Comparative Example 2

[0205] 86 g of polybutylene glycol, 3.45 g of isophorone diisocyanate, 13.06 g of hexamethylene diisocyanate, 1 g of dimethylolbutyric acid, and 1 g of ethylene glycol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 3.59%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0206] The polymer S1 was mixed with 1 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.4 g of ethylenediamine, and 0.5 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0207] The water-based polyurethane emulsion was mixed with 0.82 g of oxazoline, 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the water-based polyurethane adhesive.

[0208] Comparative Example 3

[0209] 86 g of poly(hexamethylene adipate) diol, 4 g of isophorone diisocyanate, 11.8 g of hexamethylene diisocyanate, 1 g of dimethylolbutyric acid, and 2 g of butanediol were mixed and chain extended once at 75° C. until the concentration of isocyanate groups in the reaction system reached 3.21%. 240 g of acetone was added to adjust the viscosity of the system to obtain polymer S1;

[0210] The polymer S1 and 2 g of siloxane polyisocyanate (the structure of the siloxane polyisocyanate is shown in formula (X)) were mixed and reacted at 75° C. until the concentration of isocyanate groups in the reaction system reached 1.49%, thereby obtaining polymer S2;

[0211] The polymer S2 was mixed with 1.5 g of sodium 2-(2-aminoethyl)aminoethanesulfonate, 0.4 g of ethylenediamine, and 0.5 g of ethanolamine, and subjected to secondary chain extension at 35° C. 172.5 g of deionized water was added for emulsification to obtain the aqueous polyurethane emulsion.

[0212] The aqueous polyurethane emulsion was mixed with 4.32 g of a thickener, 1.44 g of a leveling agent, and 2.3 g of a wetting agent to obtain the aqueous polyurethane adhesive.

[0213]

[0214] Test Case

[0215] The waterborne polyurethane adhesives prepared in the examples and comparative examples were processed (scrape coating, brush coating, or spray coating) onto the surface of the surface-treated polyester substrate, dried to completely evaporate the water, and then hot-pressed bonded at 80°C and 6MPa-7MPa. After standing at room temperature for 24 hours, the bonded samples were cut into 2.5 cm wide test strips at 25±2°C. The peel strength, high-temperature peel strength, high-temperature creep, tensile strength, elongation at break, and surface tension of the test strips were tested. The test results are shown in Table 1. The test method is as follows:

[0216] (1) Peel force test:

[0217] Peel strength is tested according to GB / T 2792-2014 at a constant peeling speed of 100 mm / min. "F" indicates that the adhesive did not peel off during the peeling process, but the substrate broke; "R" indicates that the adhesive layer or the adhesive interface between the adhesive layer and the substrate shifted during the peeling process.

[0218] (2) High temperature peel strength test:

[0219] The test specimens were placed in an 80°C environmental test chamber for 10 minutes. The high-temperature peel strength test was then conducted at a constant peeling speed of 100 mm / min in accordance with GB / T 2792-2014. "F" indicates that the adhesive did not peel off during the peeling process, but the substrate fractured. "R" indicates that the adhesive layer or the interface between the adhesive layer and the substrate shifted during the peeling process.

[0220] (3) High temperature creep test:

[0221] When the test specimen is completely cured, peel off 10 mm from the bonding interface at one end of the specimen manually and make a score line at the end of the peeling. Then, preheat the specimen in a 90°C environmental chamber for 30 minutes, and then load a 100 g weight on the surface of the peeling end and keep it at 90°C for 24 hours. Figure 1 After the test, take out the sample and use a ruler to measure the distance from the scored line to the end point of peeling.

[0222] (4) Tensile strength test:

[0223] Tested according to GB / T 1040.3 method.

[0224] (5) Elongation at break test:

[0225] Tested according to GB / T 1040.3 method.

[0226] (6) Surface tension test:

[0227] Tested according to GB / T 22237-2008.

[0228] Table 1

[0229]

[0230] As can be seen from the data in Table 1, compared with the adhesives prepared in Comparative Examples 1-3, the waterborne polyurethane adhesives prepared in Examples 1-5 of the present invention have excellent tensile strength, elongation at break, peeling performance, high-temperature peeling performance, surface tension and high-temperature creep performance.

[0231] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0232] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A siloxane polyisocyanate, characterized in that The siloxane polyisocyanate has a structure shown in formula (I): in: R1, R2, R3 are independently selected from C1-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring; M1 and X1 are independently selected from H and C1-C5 alkyl; Y is selected from hydrogen, C1-C8 alkyl, C2-C6 alkenyl, C3-C 10 Acrylate group, C1-C8 alkoxy group; n is an integer selected from 0 to 5; m is a positive integer selected from 1-10.

2. The siloxane polyisocyanate according to claim 1, characterized in that Said R1, R2, and R3 are independently selected from C5-C 14 Alkyl, C6-C containing saturated six-membered ring 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring; M1 and X1 are independently selected from H and C1-C5 alkyl; Y is selected from hydrogen, C1-C4 alkyl, C2-C4 alkenyl, C3-C5 acrylate, C1-C4 alkoxy; n is an integer selected from 0 to 4; m is a positive integer selected from 1 to 9; Optionally, the R1, R2, and R3 are independently selected from C5-C8 alkyl, C8-C8 containing a saturated six-membered ring, 10 Alkyl, benzene ring, C7-C9 alkyl containing benzene ring; M1 and X1 are independently selected from H and C1-C3 alkyl; Y is selected from C1-C4 alkyl, C1-C4 alkoxy; n is an integer selected from 0 to 4; m is a positive integer selected from 1 to 9; Optionally, R1, R2, and R3 are independently selected from C5-C6 alkyl, C5-C6 alkyl containing a saturated six-membered ring, 10 Alkyl, or, R1 is selected from C5-C6 alkyl, R2, R3 are selected from C7 alkyl containing a benzene ring; M1 is selected from C1-C3 alkyl; X1 is selected from H; Y is selected from C1-C4 alkyl, C1-C4 alkoxy; n is an integer selected from 0 to 4; m is a positive integer selected from 1-9.

3. A water-based polyurethane adhesive, characterized in that: The waterborne polyurethane adhesive comprises a waterborne polyurethane emulsion and oxazoline, and the raw materials for preparing the waterborne polyurethane emulsion comprise a polymer containing at least two hydroxyl groups, a diisocyanate monomer and a siloxane polyisocyanate; The polymer containing at least two hydroxyl groups includes polyester polyol and / or polyether polyol; Wherein, the siloxane polyisocyanate is the siloxane polyisocyanate according to claim 1 or 2.

4. The water-based polyurethane adhesive according to claim 3, characterized in that The water-based polyurethane adhesive further comprises a thickener, a leveling agent and a wetting agent; Optionally, the waterborne polyurethane adhesive comprises, by weight: 85-96 parts of waterborne polyurethane emulsion, 3-12 parts of oxazoline, 0.05-1 part of thickener, 0.05-1.1 parts of leveling agent, and 0.03-0.9 parts of wetting agent; Optionally, the solid content of the aqueous polyurethane emulsion is 40%-75%; Optionally, the initial R value of the aqueous polyurethane emulsion is 1.01-2.

5.

5. A method for preparing the waterborne polyurethane adhesive according to claim 3 or 4, characterized in that: The preparation method comprises the following steps of preparing an aqueous polyurethane emulsion: Mixing a polymer containing at least two hydroxyl groups, a diisocyanate monomer, and a first chain extender, and performing a chain extension until the concentration of the isocyanate group in the reaction system is 1% to 7%, thereby obtaining a polymer S1; The polymer S1 and the siloxane polyisocyanate are mixed until the concentration of the isocyanate group in the reaction system is 0.3% to 5%, thereby obtaining a polymer S2; The polymer S2 and the second chain extender are mixed, subjected to secondary chain extension, and emulsified to obtain the aqueous polyurethane emulsion.

6. The preparation method according to claim 5, characterized in that The mass ratio of the polymer containing at least two hydroxyl groups to the siloxane polyisocyanate is 100:(0.5-10); Optionally, the mass ratio of the polyester polyol to the polyether polyol is (100-0):(0-100); Optionally, the number average molecular weight of the polyester polyol is 1000-4000, and the polyester polyol includes at least one of polybutylene adipate diol, polyhexamethylene adipate diol, polycaprolactone diol, and polycarbonate diol; Optionally, the mass average molecular weight of the polyether polyol is 90-2000, and the polyether polyol includes at least one of polytetramethylene glycol, polypropylene glycol, polyethylene glycol, and polybutylene glycol.

7. The preparation method according to claim 5, characterized in that The molar ratio of the diisocyanate monomer to the isocyanate group in the siloxane polyisocyanate is (0.9:0.01)-(0.7:0.1); Optionally, the diisocyanate monomer includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, di-cyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and xylylene diisocyanate; Optionally, the diisocyanate monomer comprises hexamethylene diisocyanate and isophorone diisocyanate, and the molar ratio of the hexamethylene diisocyanate to the isophorone diisocyanate is (80-60):(20-40).

8. The preparation method according to claim 5, characterized in that The first chain extender includes a carboxylic acid containing at least two hydroxyl groups and an optional small molecule polyol; Optionally, the carboxylic acid containing at least two hydroxyl groups includes at least one of dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, 4,8-dihydroxynaphthalene-2,6-dicarboxylic acid, 4,5-dihydroxy-pyridine-2-carboxylic acid, 2,5-dihydroxybenzenedicarboxylic acid, 2,3-bis(hydroxymethyl)cyclobutanecarboxylic acid, and 4,6-dihydroxy-3-quinolinecarboxylic acid; Optionally, the molar ratio of the oxazoline to the carboxylic acid containing at least two hydroxyl groups is 1:(1-1.25); Optionally, the molar ratio of the active protons provided by the polymer containing at least two hydroxyl groups to the active protons provided by the small molecule polyol is 1:(0-0.5); Optionally, the small molecule polyol includes at least one of butanediol, ethylene glycol, isoprene glycol, neodiol, decanediol, diethylene glycol, trimethylolpropane, pentaerythritol, and neopentyl glycol; Optionally, the temperature of the primary chain extension is 70°C-80°C.

9. The preparation method according to claim 5, characterized in that The second chain extender includes a diamine salt, an optional fatty diamine, and an optional additive; Optionally, the diamine salt includes at least one of diamine sulfonate and diamine carboxylate; Optionally, the fatty diamine comprises ethylenediamine; Optionally, the additive comprises an amine compound containing a hydroxyl group, preferably ethanolamine; Optionally, the mass ratio of the second chain extender to the polymer S2 is (0.5-5):(99.5-95); Optionally, the temperature of the second chain extension is 10°C-45°C.

10. The preparation method according to claim 5, characterized in that The preparation method further comprises: mixing the water-based polyurethane emulsion, oxazoline, a thickener, a leveling agent, and a wetting agent to obtain the water-based polyurethane adhesive.

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