Bi-component polyurethane heat-conducting adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the field of adhesives, and relates to a two-component polyurethane heat-conducting adhesive as well as a preparation method and application thereof. The bi-component polyurethane heat-conducting glue contains a component A and a component B, the component A contains an isocyanate double-terminated polyurethane prepolymer, polyisocyanate and a modified heat-conducting filler; the component B contains a polyol compound, a free radical initiator and a catalyst; the preparation method of the modified heat-conducting filler comprises the following steps: carrying out free radical polymerization reaction on acrylate monomer and butadiene according to a molar ratio of 1: (0.1-0.3), carrying out click reaction on the obtained prepolymer and mercaptosilane, and coating the heat-conducting filler with the obtained silicon-containing polymer to obtain the modified heat-conducting filler. According to the invention, the double-component polyurethane heat-conducting adhesive is modified by adopting the modified heat-conducting filler, so that the bonding strength and the heat-conducting property of the polyurethane adhesive can be remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of adhesives, and particularly relates to a two-component polyurethane thermal conductive adhesive and its preparation method and application. Background Art

[0002] Polyurethane adhesives refer to adhesives containing urethane groups (-NHCOO-) and isocyanate groups (-NCO) in the molecular chain. Due to the presence of urethane groups (-NHCOO-) and isocyanate groups (-NCO) in polyurethane adhesives, polyurethane adhesives exhibit high activity and polarity, and have excellent chemical adhesion to substrates containing active hydrogen, such as porous materials like foam, plastic, wood, leather, fabric, paper, ceramics, etc., as well as materials with smooth surfaces like metal, glass, rubber, plastic, etc.

[0003] Polyurethane thermal conductive adhesives are a type of polyurethane material with excellent thermal conductivity, and they have a wide range of applications in fields such as new energy vehicles, electronic appliances, and communication equipment. They can not only be used for thermal conductive bonding and sealing of components such as batteries and motor controllers, but also as thermal conductive bonding for electronic components such as CPUs, GPUs, and LEDs to improve the stability and lifespan of electronic devices. At the same time, they can also be used for thermal conductive bonding of equipment such as base stations and routers.

[0004] Currently, polyurethane thermal conductive adhesives are generally obtained by adding thermal conductive fillers to polyurethane adhesives. Two-component polyurethane adhesives have advantages such as a long storage period and adjustable modulus. As is well known, as the amount of thermal conductive filler increases and the resin content decreases, the bonding strength of the adhesive gradually decreases. Traditional polyurethane adhesives generally use polyester polyols, polyether polyols, or polyester polyols as raw materials, and the bonding strength of the resulting polyurethane adhesives still needs to be further improved. Especially when the content of thermal conductive filler is relatively high, the decrease in its bonding strength is more obvious. In order to meet the growing composite requirements of polyurethane thermal conductive adhesives in structural bonding and heat dissipation, how to prepare a two-component polyurethane adhesive with excellent bonding strength and thermal conductivity has become an urgent problem to be solved. Summary of the Invention

[0005] The first object of the present invention is to provide a two-component polyurethane thermal conductive adhesive with good bonding strength and thermal conductivity.

[0006] The second object of the present invention is to provide a preparation method for the above two-component polyurethane thermal conductive adhesive.

[0007] The two-component polyurethane thermal conductive adhesive provided by the present invention contains component A and component B; component A contains an isocyanate double-capped polyurethane prepolymer, a polyisocyanate, and a modified thermal conductive filler; component B contains a polyol compound, a radical initiator, and a catalyst; the ratio of component A to component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate double-capped polyurethane prepolymer and the polyisocyanate to the hydroxyl content in the polyol compound is (1.05 - 1.3):1.

[0008] The modified thermal conductive filler is prepared by the following method:

[0009] S1. The acrylate monomer shown in formula (1) and butadiene are subjected to a radical polymerization reaction in a molar ratio of 1:(0.1 - 0.3) to obtain a prepolymer.

[0010] S2. The prepolymer is subjected to a click reaction with a mercapto silane, and the molar ratio of the amount of the mercapto silane to the amount of the acrylate monomer is (0.5 - 1):1 to obtain a silicon-containing polymer.

[0011] S3. The thermal conductive filler is heat-coated with the silicon-containing polymer and then cooled to obtain the modified thermal conductive filler.

[0012]

[0013] The preparation method of the two-component polyurethane thermal conductive adhesive provided by the present invention includes: uniformly mixing the isocyanate double-capped polyurethane prepolymer, the polyisocyanate, the modified thermal conductive filler, and optionally the thermal conductive whiskers to obtain component A; uniformly mixing the polyol compound, the radical initiator, and the catalyst to obtain component B; the ratio of component A to component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate double-capped polyurethane prepolymer and the polyisocyanate to the hydroxyl content in the polyol compound is (1.05 - 1.3):1.

[0014] The key of the present invention lies in coating the heat-conducting filler with a silicon-containing polymer, which is obtained by free radical polymerization of acrylate monomers and butadiene followed by click reaction. After modifying the polyurethane adhesive with the obtained modified heat-conducting filler, the bonding strength and heat-conducting performance of the polyurethane adhesive can be significantly improved. Presumably, the reasons are as follows: on the one hand, the silicon-containing polymer contains both a six-membered ring, a furan fused ring and silane, and this special structure can significantly improve the bonding strength of the polyurethane adhesive; on the other hand, in the preparation process of the silicon-containing polymer, acrylate monomers and butadiene are first subjected to free radical polymerization reaction. Since both acrylate monomers and butadiene contain two unsaturated double bonds, after the free radical polymerization reaction, many unreacted unsaturated double bonds are uniformly suspended on the entire molecular side chain of the obtained prepolymer. A part of the unsaturated double bonds will participate in the click reaction of mercapto-silane, so that silane is uniformly suspended on the entire polymer molecular chain. The introduction of silane can not only improve the bonding strength of the adhesive, but also enable the heat-conducting filler to be better dispersed in the polyurethane system to fully exert the heat-conducting effect. The remaining unsaturated double bonds will undergo secondary polymerization under the initiation of a free radical initiator to form a micro-crosslinked structure in the polyurethane heat-conducting adhesive. In this way, it is not only more conducive to the improvement of the bonding strength, but also can effectively improve the anti-settling performance of the heat-conducting adhesive, enabling the heat-conducting filler to exert the heat-conducting effect to the greatest extent.

[0015] In a preferred embodiment, the component A further contains heat-conducting whiskers. Since the heat-conducting whiskers have a highly ordered atomic arrangement structure and can approach the theoretical strength of the interatomic valence bond, they can endow the polyurethane heat-conducting adhesive with more excellent bonding performance. Detailed implementation mode

[0016] The two-component polyurethane heat-conducting adhesive provided by the present invention contains component A and component B. Among them, the ratio of component A and component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate double-terminated polyurethane prepolymer and the polyisocyanate to the hydroxyl group content in the polyol compound is (1.05 - 1.3):1, specifically it can be 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, 1.2:1, 1.22:1, 1.25:1, 1.28:1, 1.3:1 or any value between them.

[0017] In the present invention, component A contains an isocyanate double-capped polyurethane prepolymer, a polyisocyanate, a modified thermal conductive filler, and optionally a thermal conductive whisker. Among them, the content of the isocyanate double-capped polyurethane prepolymer is preferably 30 to 70 parts by weight, such as 30, 35, 40, 45, 50, 55, 60, 65, 70 parts by weight or any value therebetween. The content of the polyisocyanate is preferably 40 to 80 parts by weight, such as 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight or any value therebetween. The content of the modified thermal conductive filler is preferably 45 to 85 parts by weight, such as 45, 50, 55, 60, 65, 70, 75, 80, 85 parts by weight or any value therebetween. The content of the thermal conductive whisker is preferably 0 to 10 parts by weight, more preferably 5 to 10 parts by weight, such as 5, 6, 7, 8, 9, 10 parts by weight or any value therebetween.

[0018] In the present invention, component B contains a polyol compound, a radical initiator, and a catalyst. Among them, the content of the polyol compound is preferably 10 to 50 parts by weight, such as 10, 15, 20, 25, 30, 35, 40, 45, 50 parts by weight or any value therebetween. The content of the radical initiator is preferably 0.5 to 5 parts by weight, such as 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 parts by weight or any value therebetween. The content of the catalyst is preferably 0.5 to 5 parts by weight, such as 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 parts by weight or any value therebetween.

[0019] In the present invention, the modified thermal conductive filler is prepared by the following method:

[0020] S1. A radical polymerization reaction is carried out on an acrylate monomer and butadiene in a molar ratio of 1:(0.1 to 0.3) to obtain a prepolymer;

[0021] S2. A click reaction is carried out on the prepolymer and a mercapto silane, and the molar ratio of the amount of the mercapto silane used to the amount of the acrylate monomer used is (0.5 to 1):1 to obtain a silicon-containing polymer;

[0022] S3. The thermal conductive filler is coated with the silicon-containing polymer to obtain the modified thermal conductive filler.

[0023] In the preparation process of the above-mentioned modified thermal conductive filler, in step S1, the acrylate monomer has the structure shown in formula (1). The prepolymer obtained after the radical polymerization reaction has the structure shown in formula (2).

[0024]

[0025] In the preparation process of the above-mentioned modified thermal conductive filler, in step S1, the conditions of the radical polymerization reaction preferably include a temperature of 10 to 160 °C, such as 10 °C, 20 °C, 50 °C, 80 °C, 100 °C, 120 °C, 140 °C, 160 °C or any value therebetween; a pressure of 0.05 to 1 MPa, such as 0.05 MPa, 0.08 MPa, 0.1 MPa, 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa or any value therebetween; and a time of 0.5 to 10 h, such as 0.5 h, 1 h, 2 h, 5 h, 8 h, 10 h or any value therebetween.

[0026] In the present invention, the pressure refers to the gauge pressure.

[0027] In the preparation process of the above-mentioned modified thermal conductive filler, in step S2, the conditions of the click reaction preferably include a temperature of 20 to 150 °C, such as 20 °C, 50 °C, 80 °C, 100 °C, 120 °C, 140 °C, 150 °C or any value therebetween; a pressure of 0.01 to 1 MPa, such as 0.01 MPa, 0.05 MPa, 0.08 MPa, 0.1 MPa, 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa or any value therebetween; and a time of 0.1 to 24 h, such as 0.1 h, 0.5 h, 1 h, 2 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h or any value therebetween.

[0028] In the preparation process of the above-mentioned modified thermal conductive filler, in step S3, the mass ratio of the thermal conductive filler to the silicon-containing polymer is preferably 100:(10 to 20), such as 100:10, 100:12, 100:14, 100:16, 100:18, 100:20 or any value therebetween.

[0029] In the preparation process of the above-mentioned modified thermal conductive filler, in step S3, the method of the coating treatment is to stir and mix the thermal conductive filler and the silicon-containing polymer at 70 to 80 °C for 1 to 5 h and then cool. Among them, the temperature of the stirring and mixing can be 70 °C, 72 °C, 74 °C, 76 °C, 78 °C, 80 °C or any value therebetween; and the time can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value therebetween.

[0030] In the preparation process of the above-mentioned modified thermal conductive filler, the mercapto silane can be exemplified by γ-mercaptopropyltrimethoxysilane and / or γ-mercaptopropyltriethoxysilane.

[0031] In the preparation process of the above-mentioned modified thermal conductive filler, the thermal conductive filler may include at least one of magnesium oxide, zinc oxide, aluminum nitride, boron nitride, silicon carbide, graphene, carbon nanotubes, carbon fiber powder, aluminum hydroxide, and magnesium hydroxide.

[0032] In the present invention, the component A preferably further contains thermal conductive whiskers. Among them, the thermal conductive whiskers are preferably at least one selected from zinc oxide whiskers, calcium sulfate whiskers, and calcium carbonate whiskers.

[0033] In the present invention, the isocyanate double-ended polyurethane prepolymer is obtained by an addition reaction of a polyol compound and a polyisocyanate.

[0034] In the present invention, the polyol compound may be selected from at least one of polyester polyols, polyether polyols, polycarbonate polyols, and polyalkylene polyols. Among them, the polyester polyol can be obtained by an esterification reaction of a polycarboxylic acid and a polyol. Specific examples of the polycarboxylic acid include, but are not limited to, at least one of terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decamethylene dicarboxylic acid, and dodecamethylene dicarboxylic acid. Specific examples of the polyol include, but are not limited to, at least one of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, and cyclohexanediol. In addition, the polyester polyol may also be poly-ε-caprolactone polyol obtained by ring-opening polymerization of ε-caprolactone. The polyether polyol may be an open-ring polymer of a tetrahydrofuran-based compound and / or a bisphenol A-type polyalkylene oxide modified body. Among them, the tetrahydrofuran-based compound may be, for example, tetrahydrofuran, 3-methyltetrahydrofuran, etc. The bisphenol-type polyalkylene oxide modified body refers to a polyether polyol obtained by adding an alkylene oxide (such as ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, etc.) to the active hydrogen part of the bisphenol-type molecular skeleton, and may be a random copolymer or a block copolymer. The polycarbonate polyol may specifically be polycarbonate 1,6-hexanediol ester polyol and / or polyethylene cyclohexane carbonate polyol. The polyalkylene polyol may specifically be selected from at least one of polybutadiene polyol, hydrogenated polybutadiene polyol, and hydrogenated polyisoprene polyol. In addition, the number average molecular weight of the polyol compound is preferably 1000 to 4000.

[0035] In the present invention, examples of the polyisocyanate monomer include at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, hydrogenated diphenylmethane-4,4'-diisocyanate, polymeric diphenylmethane-4,4'-diisocyanate, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl) thiophosphate, tetramethylxylene diisocyanate, and 1,6,10-undecane triisocyanate.

[0036] In the present invention, the type of the catalyst is not particularly limited and may be selected from at least one of azo initiators, peroxide initiators, and redox initiators. Among them, specific examples of the azo initiator include, but are not limited to, at least one of dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylpropionamidine) hydrochloride, azodicarbonamide, 2,2'-azobis(2-isopropylimidazoline) hydrochloride, 2-cyano-2-propylazoformamide, 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2-methylhexanenitrile). Specific examples of the peroxide initiator include, but are not limited to, at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, benzoyl peroxide, and tert-butyl peroxybenzoate. The redox initiator includes an oxidizing agent and a reducing agent, and specific examples thereof include, but are not limited to, at least one of sulfate-sulfite, persulfate-thiourea, persulfate-organic salt, and ammonium persulfate-fatty amine. Among them, the sulfate-sulfite may be selected from at least one of sodium sulfate-sodium sulfite, potassium sulfate-potassium sulfite, and ammonium sulfate-ammonium sulfite. The persulfate-thiourea may be selected from at least one of sodium persulfate-thiourea, potassium persulfate-thiourea, and ammonium persulfate-thiourea. The persulfate-organic salt may be selected from at least one of sodium persulfate-potassium acetate, potassium persulfate-potassium acetate, and ammonium persulfate-ammonium acetate. The ammonium persulfate-fatty amine may be ammonium persulfate-N,N-tetramethylethylenediamine and / or ammonium persulfate-diethylamine. The radical polymerization reaction preferably uses a redox initiator.

[0037] In the present invention, the type of the catalyst is not particularly limited and can be various existing compounds that enable the polycondensation of isocyanate double-terminated polyurethane prepolymers, polyisocyanates and polyol compounds to form polyurethanes. For example, it can be an organotin catalyst and / or an amine catalyst. Among them, the organotin catalyst can specifically be dibutyltin dilaurate and / or stannous octoate. Specific examples of the amine catalyst include but are not limited to at least one of triethylamine, diethylenetriamine, triethylenediamine, N-ethylmorpholine and 2,2-dimorpholinodiethylether.

[0038] In the present invention, components A and B may also selectively contain auxiliaries. Specific examples of the auxiliaries include but are not limited to at least one of color pastes, defoamers, water scavengers, rheology modifiers, leveling agents, wetting agents, coupling agents and stabilizers.

[0039] The preparation method of the two-component polyurethane thermal conductive adhesive provided by the present invention includes: uniformly mixing an isocyanate double-terminated polyurethane prepolymer, a polyisocyanate, a modified thermal conductive filler, and optionally a thermal conductive whisker and an auxiliary to obtain component A; uniformly mixing a polyol compound, a radical initiator and a catalyst to obtain component B; the ratio of component A to component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate double-terminated polyurethane prepolymer and the polyisocyanate to the hydroxyl group content in the polyol compound is (1.05 - 1.3):1.

[0040] The present invention also provides the application of the above two-component polyurethane thermal conductive adhesive in the bonding of electronic products.

[0041] The present invention will be described in detail below through examples.

[0042] In the following examples and comparative examples, the content of NCO was measured using a potentiometric titrator. Specifically, take about m g of the sample in a stoppered conical flask, add 25 mL of anhydrous toluene, cover the flask with a stopper, and heat it on a hot plate for quick dissolution. Pipette 25 mL of a dibutylamine toluene solution (0.1 mol / L), cover with a stopper and shake well to dissolve, add 20 mL of isopropanol, insert the electrode and the titration head, set the titration parameters, and titrate with a 0.5852 mol / L hydrochloric acid standard solution (Vs); repeat the above operation without adding the sample to measure the sample blank (V0). According to W NCO =(V0 - V s ) * 0.5852 * 42 / (1000m) * 100% to calculate the measured content of NCO.

[0043] In the following examples and comparative examples, the parts of the raw materials are all parts by weight.

[0044] In the following examples and comparative examples, the castor oil polyol was selected from Itochu Oil Co., Ltd. of Japan, with the product number URIC AC008; the polyether polyol was purchased from Guodu Chemical Co., Ltd., with the product number GY420; the polybutadiene polyol was purchased from Nippon Soda Co., Ltd. of Japan, with the product number G-2000.

[0045] Preparation Example 1 Preparation of Acrylate Monomer

[0046] This preparation example is used to illustrate the preparation of the acrylate monomer. The specific reaction process and steps are as follows:

[0047]

[0048] 1 mol of isophorone diisocyanate, 0.2 g of dibutyltin dilaurate (DBTDL), and 0.2 g of p-methoxyphenol were added to a reaction kettle. Subsequently, 1 mol of hydroxyethyl acrylate was added dropwise to the reaction kettle, and the reaction was carried out at 70 °C for 3 h under the protection of an inert gas. Then, 0.5 mol of isosorbide was added, and the reaction continued under the protection of nitrogen. When the mass percentage content of isocyanate groups in the system in the reaction kettle ≤ 0.1%, the reaction ended, and the acrylate monomer was obtained.

[0049] Preparation Example 2 Preparation of Modified Thermal Conductivity Filler

[0050] S1. Under the protection of nitrogen, 1 mol of acrylate monomer (obtained from Preparation Example 1), 0.1 mol of butadiene, 2 L of cyclohexane, and 1.1 g of tetrahydrofurfuryl ethyl ether were added to a stainless steel stirring kettle. After heating to 80 °C, 1 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.5 MPa to initiate the reaction, obtaining a prepolymer with a number average molecular weight of 1320;

[0051] S2. Under the protection of nitrogen, 1 mol of γ-mercaptopropyltrimethoxysilane was added to the prepolymer obtained in Step S1. After heating to 80 °C, 1 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.2 MPa to react for 3 h, obtaining a silicon-containing polymer;

[0052] S3. 10 g of the silicon-containing polymer and 100 g of thermal conductivity filler (D 50 Magnesium oxide with a particle size of 5.0 μm) were stirred and mixed at 70 °C for 5 h and then cooled to obtain the modified thermal conductivity filler.

[0053] Preparation Example 3 Preparation of Modified Thermal Conductivity Filler

[0054] S1. Under the protection of nitrogen, 1 mol of acrylate monomer (obtained from Preparation Example 1), 0.2 mol of butadiene, 2 L of cyclohexane, and 1.1 g of tetrahydrofurfuryl ethyl ether were added to a stainless steel stirring kettle. After heating to 80 °C, 0.8 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.5 MPa to initiate the reaction, obtaining a prepolymer with a number average molecular weight of 2160;

[0055] S2. Under nitrogen protection, 0.5 mol of γ-mercaptopropyltriethoxysilane was added to the prepolymer obtained in step S1. After heating to 80 °C, 1 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.2 MPa for reaction for 3 h to obtain a silicon-containing polymer;

[0056] S3. 10 g of the silicon-containing polymer and 100 g of a heat-conducting filler (D 50 is aluminum nitride with a particle size of 8.1 μm) were stirred and mixed at 80 °C for 1 h and then cooled to obtain a modified heat-conducting filler.

[0057] Preparation Example 4 Preparation of a modified heat-conducting filler

[0058] S1. Under nitrogen protection, 1 mol of an acrylate monomer (obtained from Preparation Example 1), 0.3 mol of butadiene, 2 L of cyclohexane, and 1.1 g of tetrahydrofurfuryl ethyl ether were added to a stainless-steel stirring kettle. After heating to 80 °C, 1.2 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.5 MPa to initiate the reaction to obtain a prepolymer with a number-average molecular weight of 1150;

[0059] S2. Under nitrogen protection, 0.8 mol of γ-mercaptopropyltrimethoxysilane was added to the prepolymer obtained in step S1. After heating to 80 °C, 1 mmol of azobisisobutyronitrile was added, and the pressure was controlled at 0.2 MPa for reaction for 3 h to obtain a silicon-containing polymer;

[0060] S3. 10 g of the silicon-containing polymer and 100 g of a heat-conducting filler (D 50 is silicon carbide with a particle size of 6.9 μm) were stirred and mixed at 75 °C for 2 h and then cooled to obtain a modified heat-conducting filler.

[0061] Comparative Preparation Example 1 Preparation of a reference modified heat-conducting filler

[0062] The modified heat-conducting filler was prepared according to the method of Preparation Example 2, except that the acrylate monomer was replaced with the same molar amount of butadiene, and the other conditions were the same as those in Preparation Example 2, to obtain a reference modified heat-conducting filler.

[0063] Comparative Preparation Example 2 Preparation of a reference modified heat-conducting filler

[0064] The modified heat-conducting filler was prepared according to the method of Preparation Example 2, except that the butadiene was replaced with the same weight portion of the acrylate monomer, and the other conditions were the same as those in Preparation Example 2, to obtain a reference modified heat-conducting filler.

[0065] Example 1 Preparation of a two-component polyurethane heat-conducting adhesive

[0066] By weight, 29.48 g of poly(hexamethylene adipate) diol with a number-average molecular weight of 3500, 16.84 g of poly(propylene oxide) ether diol with a number-average molecular weight of 2000, and 16.84 g of neopentyl glycol adipate diol with a number-average molecular weight of 2000 were added to a reaction flask, heated to 110 °C, and vacuum dehydrated for 2 h under stirring at 150 r / min. Then, the temperature was lowered to 80 °C, and 12.63 g of 4,4'-diphenylmethane diisocyanate (MDI) was added. The reaction was carried out under vacuum at a stirring speed of 150 r / min for 2 h to obtain an isocyanate double-capped polyurethane prepolymer.

[0067] The two-component polyurethane thermal conductive adhesive provided in this example includes component A and component B. 30 parts of the isocyanate double-capped polyurethane prepolymer, 40 parts of 4,4'-diphenylmethane diisocyanate (MDI), 45 parts of the modified thermal conductive filler (obtained from Preparation Example 2), and 5 parts of thermal conductive whiskers (tetrapod-shaped zinc oxide whiskers, purchased from Chengdu Tianyou Jingchuang Technology Co., Ltd., brand JC-01) were mixed evenly to obtain component A. 10 parts of castor oil polyol, 0.5 part of azobisisobutyronitrile, and 0.5 part of dibutyltin dilaurate were mixed evenly to obtain component B. The ratio of component A and component B was such that the molar ratio of the total content of isocyanate groups in the isocyanate double-capped polyurethane prepolymer and 4,4'-diphenylmethane diisocyanate to the hydroxyl content in the castor oil polyol was 1.05:1.

[0068] Preparation of the two-component polyurethane thermal conductive adhesive in Example 2

[0069] The isocyanate double-capped polyurethane prepolymer was prepared according to the method of Example 1.

[0070] The two-component polyurethane thermal conductive adhesive provided in this example includes component A and component B. 70 parts of the isocyanate double-capped polyurethane prepolymer, 80 parts of 4,4'-diphenylmethane diisocyanate (MDI), 85 parts of the modified thermal conductive filler (obtained from Preparation Example 3), and 10 parts of thermal conductive whiskers (calcium sulfate whiskers, purchased from Shijiazhuang Zhengyu New Materials Technology Co., brand 110) were mixed evenly to obtain component A. 50 parts of polyether polyol, 5 parts of azobisisobutyronitrile, and 5 parts of dibutyltin dilaurate were mixed evenly to obtain component B. The ratio of component A and component B was such that the molar ratio of the total content of isocyanate groups in the isocyanate double-capped polyurethane prepolymer and 4,4'-diphenylmethane diisocyanate to the hydroxyl content in the polyether polyol was 1.3:1.

[0071] Preparation of the two-component polyurethane thermal conductive adhesive in Example 3

[0072] The isocyanate double-capped polyurethane prepolymer was prepared according to the method of Example 1.

[0073] The two-component polyurethane thermal conductive adhesive provided in this embodiment includes component A and component B. 50 parts of isocyanate double-capped polyurethane prepolymer, 60 parts of 4,4'-diphenylmethane diisocyanate (MDI), 65 parts of modified thermal conductive filler (obtained from Preparation Example 4), and 8 parts of thermal conductive whiskers (calcium carbonate whiskers, purchased from Jinan Quanxin Chemical Co., Ltd., with the brand number 8998) are mixed evenly to obtain component A. 30 parts of polybutadiene polyol, 2 parts of azobisisobutyronitrile, and 2 parts of dibutyltin dilaurate are mixed evenly to obtain component B. The ratio of component A and component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate double-capped polyurethane prepolymer and 4,4'-diphenylmethane diisocyanate to the hydroxyl group content in the polybutadiene polyol is 1.2:1.

[0074] Preparation of Two-Component Polyurethane Thermal Conductive Adhesive in Example 4

[0075] The two-component polyurethane thermal conductive adhesive was prepared according to the method of Example 1, except that the thermal conductive whiskers were not added, and the other conditions were the same as those in Example 1, to obtain the two-component polyurethane thermal conductive adhesive.

[0076] Preparation of Reference Two-Component Polyurethane Thermal Conductive Adhesive in Comparative Example 1

[0077] The two-component polyurethane thermal conductive adhesive was prepared according to the method of Example 1, except that the modified thermal conductive filler was replaced with the same weight of unmodified thermal conductive filler (D 50 for magnesium oxide with a particle size of 5.0 μm), and the other conditions were the same as those in Example 1, to obtain the two-component polyurethane thermal conductive adhesive.

[0078] Preparation of Reference Two-Component Polyurethane Thermal Conductive Adhesive in Comparative Example 2

[0079] The two-component polyurethane thermal conductive adhesive was prepared according to the method of Example 1, except that the modified thermal conductive filler was replaced with the same weight of reference modified thermal conductive filler (obtained from Comparative Preparation Example 1), and the other conditions were the same as those in Example 1, to obtain the two-component polyurethane thermal conductive adhesive.

[0080] Preparation of Reference Two-Component Polyurethane Thermal Conductive Adhesive in Comparative Example 3

[0081] The two-component polyurethane thermal conductive adhesive was prepared according to the method of Example 1, except that the modified thermal conductive filler was replaced with the same weight of reference modified thermal conductive filler (obtained from Comparative Preparation Example 2), and the other conditions were the same as those in Example 1, to obtain the two-component polyurethane thermal conductive adhesive.

[0082] Test Example

[0083] The samples obtained from the above examples and comparative examples were respectively subjected to the following performance tests:

[0084] (1) Adhesion performance: Tested according to the standard GB / T 7124-2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)". Specifically, select aluminum plates with dimensions of 100mm × 25mm × 2mm. Lap two aluminum plates together with the two-component polyurethane thermal conductive adhesives obtained from the above respective examples and comparative examples. The bonding area is 12.5mm × 25mm, and ensure that the thickness of the adhesive layer is 0.15mm. Place the lap spline in a constant temperature and humidity chamber at a temperature of 60°C and a humidity of 60%RH for room temperature curing for 7 days. Use a universal material tensile force testing machine to test the tensile shear strength, and the tensile speed is 5mm / min. The obtained shear strength results are shown in Table 1. The higher the shear strength, the better the adhesion performance, and vice versa, the worse the adhesion performance.

[0085] (2) Thermal conductivity: First, inject the two-component polyurethane thermal conductive adhesive through a static mixer into a standard tetrafluoroethylene mold, scrape it flat, and place it in a constant temperature and humidity chamber at a temperature of 60°C and a humidity of 60%RH for room temperature curing for 7 days; then take out the cured sample piece and test it using the method in ISO 22007-2, and record the thermal conductivity. The obtained results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from the results in Table 1 that the present invention modifies the two-component polyurethane thermal conductive adhesive with modified thermal conductive fillers, which can significantly improve the bonding strength and thermal conductivity of the polyurethane adhesive. From the comparison between Example 1 and Example 4, it can be seen that when the component A further contains thermal conductive whiskers, it can endow the polyurethane thermal conductive adhesive with more excellent adhesion performance.

[0090] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A two-component polyurethane thermally conductive adhesive, characterized in that: The two-component polyurethane thermal conductive adhesive contains component A and component B; component A contains isocyanate diblocked polyurethane prepolymer, polyisocyanate and modified thermal conductive filler; component B contains polyol compound, free radical initiator and catalyst; the ratio of component A to component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate diblocked polyurethane prepolymer and polyisocyanate to the hydroxyl content in the polyol compound is (1.05-1.3):1; The modified thermally conductive filler is prepared according to the following method: S1. The acrylate monomer represented by formula (1) and butadiene are subjected to a free radical polymerization reaction in a molar ratio of 1:(0.1 to 0.3) to obtain a prepolymer; S2. The prepolymer is subjected to a click reaction with mercaptosilane, wherein the molar ratio of the mercaptosilane to the acrylate monomer is (0.5 to 1):1 to obtain a silicon-containing polymer; S3. The thermally conductive filler is coated with a silicon-containing polymer to obtain a modified thermally conductive filler; 2. The two-component polyurethane thermally conductive adhesive according to claim 1, characterized in that: In component A, the content of the isocyanate di-terminated polyurethane prepolymer is 30 to 70 parts by weight, the content of the polyisocyanate is 40 to 80 parts by weight, and the content of the modified thermal conductive filler is 45 to 85 parts by weight; In component B, the content of the polyol compound is 10 to 50 parts by weight, the content of the free radical initiator is 0.5 to 5 parts by weight, and the content of the catalyst is 0.5 to 5 parts by weight.

3. The two-component polyurethane thermally conductive adhesive according to claim 1, characterized in that: In the preparation process of the modified thermally conductive filler, in step S1, the conditions of the free radical polymerization reaction include a temperature of 10 to 160° C., a pressure of 0.05 to 1 MPa, and a time of 0.5 to 10 h; In step S2, the conditions of the click reaction include a temperature of 20 to 150° C., a pressure of 0.01 to 1 MPa, and a time of 0.1 to 24 h; In step S3, the mass ratio of the thermal conductive filler to the silicon-containing polymer is 100:(10-20), and the coating treatment is performed by stirring and mixing the thermal conductive filler and the silicon-containing polymer at 70-80° C. for 1-5 hours and then cooling.

4. The two-component polyurethane thermally conductive adhesive according to claim 1, characterized in that: The mercaptosilane is γ-mercaptopropyltrimethoxysilane and / or γ-mercaptopropyltriethoxysilane.

5. The two-component polyurethane thermally conductive adhesive according to claim 1, characterized in that: The thermally conductive filler is selected from at least one of magnesium oxide, zinc oxide, aluminum nitride, boron nitride, silicon carbide, graphene, carbon nanotubes, carbon fiber powder, aluminum hydroxide and magnesium hydroxide.

6. The two-component polyurethane thermally conductive adhesive according to any one of claims 1 to 5, characterized in that: The component A further contains thermally conductive whiskers; preferably, the thermally conductive whiskers are selected from at least one of zinc oxide whiskers, calcium sulfate whiskers and calcium carbonate whiskers; preferably, the content of the thermally conductive whiskers is 5 to 10 parts by weight.

7. The two-component polyurethane thermally conductive adhesive according to any one of claims 1 to 5, characterized in that: The isocyanate di-terminated polyurethane prepolymer is obtained by an addition reaction between a polyol compound and polyisocyanate.

8. The two-component polyurethane thermally conductive adhesive according to any one of claims 1 to 5, characterized in that: The polyol compound is selected from at least one of polyester polyols, polyether polyols, polycarbonate polyols and polyalkylene polyols; the polyisocyanate is selected from at least one of isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, hydrogenated diphenylmethane-4,4'-diisocyanate, polymerized diphenylmethane-4,4'-diisocyanate, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanate phenyl)thiophosphate, tetramethylxylene diisocyanate and 1,6,10-undecane triisocyanate.

9. The method for preparing the two-component polyurethane thermally conductive adhesive according to any one of claims 1 to 8, characterized in that: The method comprises: uniformly mixing an isocyanate diblocked polyurethane prepolymer, polyisocyanate, a modified thermally conductive filler and an optional thermally conductive whisker to obtain component A; uniformly mixing a polyol compound, a free radical initiator and a catalyst to obtain component B; the ratio of component A to component B is such that the molar ratio of the total content of isocyanate groups in the isocyanate diblocked polyurethane prepolymer and the polyisocyanate to the hydroxyl group content in the polyol compound is (1.05-1.3):

1.

10. Use of the two-component polyurethane thermally conductive adhesive according to any one of claims 1 to 8 in bonding electronic products.

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