Castor oil-based polyol with low viscosity and high hydroxyl value as well as synthesis method and application of castor oil-based polyol

Abstract

The invention is applicable to the field of polyol synthesis, and provides low-viscosity high-hydroxyl-value castor oil-based polyol and a synthesis method and application thereof, and castor oil, small-molecular cyclic carbonate and small-molecular polyol are subjected to cyclic carbonate ring opening and polyol ester exchange under the action of a catalyst to synthesize the low-viscosity high-hydroxyl-value castor oil-based polyol. The low-viscosity and high-hydroxyl-value castor oil-based polyol prepared by the method is suitable for preparing a polyurethane heat-conducting structural adhesive.

Description

Technical Field

[0001] The present invention relates to the field of polyol synthesis, and particularly to a low-viscosity and high-hydroxyl-value castor oil-based polyol, a synthesis method thereof, and an application thereof. Background Art

[0002] Polyurethane thermal conductive structural adhesives are widely used in the bonding between battery monomers and heat dissipation plates of new energy power batteries, and need to have a thermal conductivity of 0.6W / K·M - 2.0W / K·M and a bonding strength greater than 7MPa.

[0003] Polyurethane thermal conductive structural adhesives are prepared by adding a large amount of thermal conductive fillers to low-viscosity polyol substances, in combination with isocyanate substances and other auxiliaries. The main polyol resins that may be used include small-molecule polyether polyols, high-strength modified castor oil polyols, and low-viscosity polyester polyols. For example, polyether polyols such as MN-500, MN-700, MN-1000, DL-400, DL-1000, etc. produced by Shandong Bluestar Dongda Co., Ltd., modified castor oil polyols such as AC-006, AC-009, H-368, H-420, H-870, etc. produced by Ito Oil Co., and modified castor oil polyols such as A4105, AP19-9, AP-13, etc. produced by Shanghai Jingri New Materials Technology Co., Ltd., and small-molecule polycaprolactone polyols such as PCL-3037, PCL-3057, PCl-3087, PCL-2053, etc. produced by Hunan Julong Chemical Industry.

[0004] Small-molecule polyether polyols have strong water absorption, and the polyurethane thermal conductive structural adhesives synthesized therefrom are prone to generate bubbles. Polycaprolactone polyols have strong mechanical properties, high bonding strength, and good high-temperature and high-humidity stability when synthesizing polyurethane thermal conductive structural adhesives, but the supply of polycaprolactone polyols is not very sufficient and the price is high. Modified castor oil polyols are generally synthesized by transesterification of castor oil with small-molecule polyols, or by copolymerization of castor oil and small-molecule alcohols with propylene oxide or ethylene oxide, or by polycondensation of alcoholyzed castor oil with dicarboxylic acids. Their raw material sources are sufficient. By selecting appropriate castor oil-based modified polyols, polyurethane thermal conductive structural adhesives that meet the usage requirements of new energy power battery thermal conductive structural adhesives can be synthesized.

[0005] The main improvement points of traditional modified polyol technologies based on castor oil polyols are the improvement of properties such as hydrolysis resistance stability, tensile strength, compressive strength, and elongation properties of polyurethane materials synthesized from modified castor oil polyols and isocyanate substances.

[0006] For example, Chinese Patent Application Publication No. CN 105585699 A discloses a method for synthesizing castor oil polyester polyol and its application in polyurethane foaming adhesive. The castor oil alcoholysis solution is obtained by reacting castor oil with small molecule diol under the action of a catalyst, and then small molecule dicarboxylic acid is added for polycondensation to obtain a modified castor oil polyester polyol with a number average molecular weight of 2000 - 4000, which is used for the production of polyurethane foaming adhesive. The obtained foaming adhesive overcomes the disadvantages of low strength and poor foam stability of castor oil. However, the polyol prepared by this technology has a relatively high room temperature viscosity, not lower than 1000 cP.

[0007] Chinese Patent Application Publication No. CN 102532513 A discloses a method for synthesizing high molecular weight castor oil polyether polyol, which is prepared by polymerizing castor oil with ethylene oxide or propylene oxide under the action of a double metal catalyst. This high molecular weight castor oil polyether polyol has a low hydroxyl value and is mainly used for synthesizing polyurethane flexible foam materials with low strength.

[0008] Chinese Patent Application Publication No. CN 103534285 A discloses a high molecular weight castor oil-based polyol and its uses. A modified castor oil polyol with a molecular weight of 900 Da - 4000 Da and a hydroxyl value lower than 130 is prepared by reacting castor oil with fatty acid and a catalyst under heating conditions. The characteristics of this technology-improved castor oil-based polyol are that there are branched or straight-chain alkanes with 2 - 6 carbon atoms connecting between hydroxyl groups or ester groups, having the characteristics of low viscosity and excellent hydrolysis resistance stability. The viscosity of its lowest model D1000 polyol at room temperature is 425 cP and the hydroxyl value is 125. If this technology-modified castor oil-based polyol is used as the hydroxyl-containing component in formulating a one-to-one two-component thermal conductive structural adhesive, due to the addition of thermal conductive fillers with a volume ratio greater than 40%, the mechanical properties of the thermal conductive adhesive material will deteriorate sharply, failing to meet the strength requirements of the thermal conductive structural adhesive for new energy power batteries. If this technology-modified castor oil-based polyol is combined with small molecule chain extenders to improve the mechanical properties of the thermal conductive adhesive, other problems such as shortened gel time and easy water absorption of the thermal conductive structural adhesive will occur due to the introduction of relatively small molecule polyols.

[0009] Chinese Patent Application Publication No. CN 110423650 A discloses an alkoxylated castor oil-based polyol. Its process route is to first epoxidize the unsaturated bonds of castor oil and then open the epoxy groups of epoxy castor oil with small molecule alcohols to obtain alkoxylated castor oil polyol. The obtained modified castor oil polyol has a functionality greater than 5 and is made into polyurethane rigid foam with isocyanate substances and has the characteristics of high strength and good dimensional stability. If a large amount of thermal conductive fillers are added for the production of thermal conductive structural adhesive, the originally poor elongation at break will deteriorate even more, and the toughness cannot meet the minimum elongation at break requirements of the thermal conductive structural adhesive for new energy power batteries. Summary of the Invention

[0010] The present invention provides a low-viscosity and high-hydroxyl-value castor oil-based polyol, its synthesis method and application. The synthesized modified castor oil polyol has low viscosity and high hydroxyl value, and is used for formulating a polyurethane thermal conductive structural adhesive with high strength and good toughness. It has a lower viscosity than the commercially available modified castor oil polyol that can be used as a polyurethane thermal conductive structural adhesive, and has an advantage in the viscosity of the thermal conductive structural adhesive when a large amount of thermal conductive filler is filled.

[0011] A low-viscosity and high-hydroxyl-value castor oil-based polyol, the main components of which include the components shown in Structural Formula I, Formula II, and Formula III;

[0012] Formula I: ;

[0013] Formula II: ;

[0014] Formula III: ;

[0015] In the above formula, R1 is one of H and CH3, R is the alkyl group corresponding to the small molecule diol used, or the hydroxyl-containing alkyl chain corresponding to the other polyol used.

[0016] Another object of the present invention is to provide a synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol as described above. The method includes the following steps:

[0017] Mix castor oil, low molecular cyclic carbonate substance, small molecule polyol substance and catalyst, and carry out ring-opening of cyclic carbonate and polyol transesterification at a temperature of 100°C - 160°C to synthesize a modified castor oil-based polyol. Then, evacuate to a gauge pressure of less than -0.09 MPa at 140°C - 150°C for 30 - 60 minutes to remove low molecular volatile substances. Then, cool to a material temperature of 100°C and add cation resin for adsorption and neutralization reaction for 30 - 60 minutes. Cool to below 50°C and filter out the cation resin to obtain a low-viscosity and high-hydroxyl-value castor oil-based polyol;

[0018] Among them, the low molecular cyclic carbonate substance is one of ethylene carbonate and propylene carbonate;

[0019] The small molecule polyol substance is one of di-functional and multi-functional alcohol compounds;

[0020] The catalyst is a composition of an alkali substance and a titanate substance.

[0021] The room temperature viscosity (25°C) of the synthesized low-viscosity and high-hydroxyl-value castor oil-based polyol is 260 - 600 cP, and the hydroxyl value is 240 - 400 mg / g of KOH.

[0022] Preferably, the synthesis conditions of the synthesized modified castor oil-based polyol are a material temperature of 140°C - 160°C and a reaction time of 3 - 6 hours.

[0023] Preferably, the small molecule polyol substance is one of ethylene glycol, glycerol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, and pentaerythritol.

[0024] Preferably, the molar ratio of the small molecule polyol substance to castor oil is 1-2:1.

[0025] Preferably, the molar ratio of the low molecular weight cyclic carbonate to the small molecule polyol substance is 1-2:1.

[0026] Preferably, the catalyst comprises one or more kinds of alkali substances and titanate compounds, wherein the alkali substances include organic tertiary amines, quaternary ammonium salts, and inorganic strong bases; the organic tertiary amines include trimethylamine and triethylamine, the quaternary ammonium salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, the inorganic strong bases include sodium hydroxide and potassium hydroxide, and the titanate substance is a titanate substance with a titanium content of 0.8%-1.5%.

[0027] Preferably, the dosage of the organic tertiary amine in the used catalyst is 0.1%-0.5% of the total mass of the materials, the dosage of the quaternary ammonium salt or inorganic strong base is 0.01%-0.1% of the total mass of the materials, and the dosage of the titanate substance with a titanium content of 0.8%-1.5% is 0.1%-0.5% of the total mass of the materials.

[0028] Preferably, the preparation principle of the titanate substance with a titanium content of 0.8%-1.5% is to heat react one kind of titanate such as tetraisopropyl titanate, tetrabutyl titanate, tetra-tert-butyl titanate, diisopropoxytitanium diacetylacetonate, diethyl acetoacetate diisopropoxytitanium, or Tyzor 726 of Guangzhou Jianyi Chemical Industry Co., Ltd. with one or more small molecule hydroxy-containing compounds, hydroxycarboxylic acids, alkoxysilanes, zinc salts, and phosphoric acid esters to synthesize the titanate substance with a titanium content of 0.8%-1.5%.

[0029] Preferably, the cation exchange resin includes commercially available 001×7 hydrogen-type cation exchange resin, D001 hydrogen-type cation exchange resin, 732 hydrogen-type cation exchange resin, and Suqing brand JY-1 cation exchange resin.

[0030] Another object of the present invention is to provide an application of a low-viscosity and high-hydroxyl-value castor oil-based polyol as described above in a polyurethane thermal conductive structural adhesive.

[0031] The beneficial effects achieved by the present invention:

[0032] The low-viscosity and high-hydroxyl-value modified castor oil-based polyol synthesized by the present invention has the characteristics of low viscosity and high hydroxyl value, and is suitable for making polyurethane thermal conductive structural adhesives. Detailed implementation manners

[0033] The embodiments described in the present invention are some, rather than all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0035] A low-viscosity high-hydroxyl-value castor oil-based polyol, the main components of which include the components shown in Structural Formulas I, II, and III;

[0036] Structural Formula I: ;

[0037] Structural Formula II: ;

[0038] Structural Formula III: ;

[0039] In the above formulas, R1 is one of H and CH3, R is the alkyl group corresponding to the small molecule diol used, or the hydroxyl-containing alkyl chain corresponding to the other polyol used, including but not limited to the groups shown in the following formulas:

[0040] 、 、 、 、 、 、 、 、 、 。

[0041] Another object of the present invention is to provide a synthesis method of a low-viscosity high-hydroxyl-value castor oil-based polyol as described above, the method comprising the following steps:

[0042] Castor oil, a low-molecular cyclic carbonate substance, a small-molecule polyol substance, and a catalyst are mixed and subjected to ring-opening of cyclic carbonate and polyol transesterification at a temperature of 100°C - 160°C to synthesize a modified castor oil-based polyol. Then, it is evacuated to a gauge pressure below -0.09 MPa at 140°C - 150°C for 30 - 60 min to remove low-molecular volatile substances. Subsequently, the temperature is lowered to 100°C of the material temperature, and a cationic resin is added for an adsorption and neutralization reaction for 30 - 60 min. After cooling to below 50°C, the cationic resin is filtered off to obtain a low-viscosity and high-hydroxyl-value castor oil-based polyol;

[0043] Among them, the low-molecular cyclic carbonate substance is one of ethylene carbonate and propylene carbonate;

[0044] The small-molecule polyol substance is one of di-functional and multi-functional alcohol compounds;

[0045] The catalyst is a composition of an alkali substance and a titanate substance.

[0046] The room-temperature viscosity (25°C) of the synthesized low-viscosity and high-hydroxyl-value castor oil-based polyol is 260 - 600 cP, and the hydroxyl value is 240 - 400 mg / g KOH.

[0047] In this example, the synthesis conditions of the synthesized modified castor oil-based polyol are a material temperature of 140°C - 160°C and a reaction time of 3 - 6 hours.

[0048] In this example, the small-molecule polyol substance is one of ethylene glycol, glycerol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, and pentaerythritol.

[0049] In this example, the molar ratio of the small-molecule polyol substance to castor oil is 1 - 2:1.

[0050] In this example, the molar ratio of the low-molecular cyclic carbonate to the small-molecule polyol substance is 1 - 2:1.

[0051] In this example, the catalyst contains one or more alkali substances and titanate compounds. Among them, the alkali substances include organic tertiary amines, quaternary ammonium salts, and inorganic strong bases; the organic tertiary amines include trimethylamine and triethylamine, the quaternary ammonium salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, the inorganic strong bases include sodium hydroxide and potassium hydroxide, and the titanate substance is a titanate substance with a titanium content of 0.8% - 1.5%.

[0052] In this embodiment, the amount of organic tertiary amine in the catalyst used is 0.1%-0.5% of the total mass of the materials, the amount of quaternary ammonium salt or inorganic strong base is 0.01%-0.1% of the total mass of the materials, and the amount of titanate substance with a titanium content of 0.8%-1.5% is 0.1%-0.5% of the total mass of the materials.

[0053] In this embodiment, the preparation principle of the titanate substance with a titanium content of 0.8%-1.5% is to heat react one titanate such as tetra-isopropyl titanate, tetra-butyl titanate, tetra-tert-butyl titanate, diisopropoxytitanium diacetylacetonate, diethylacetoacetate diisopropoxytitanium or Tyzor 726 of Guangzhou Jianyi Chemical Industry Co., Ltd. with one or more small molecule hydroxy-containing compounds, hydroxycarboxylic acids, alkoxysilanes, zinc salts and phosphates to synthesize the titanate substance with a titanium content of 0.8%-1.5%.

[0054] In this embodiment, the hydroxycarboxylic acids include but are not limited to citric acid, malic acid, lactic acid, and the molar ratio of their amount to that of the titanate is 0.1-5:1.

[0055] In this embodiment, the small molecule hydroxy-containing compounds include but are not limited to ethylene glycol, 1,4-butanediol, glycerol, diethylene glycol, dipropylene glycol, 3-methyl-1,5-pentanediol, and the molar ratio of their amount to that of the titanate is 5-40:1.

[0056] In this embodiment, the alkoxysilanes include but are not limited to tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, and the molar ratio of their amount to that of the titanate is 0.05-0.5:1.

[0057] In this embodiment, the phosphates include but are not limited to trimethyl phosphate, triethyl phosphate, and the molar ratio of their amount to that of the titanate is 0-5:1.

[0058] In this embodiment, the zinc salts include but are not limited to zinc isooctanoate, and the molar ratio of their amount to that of the titanate is 0.05-3:1.

[0059] In this embodiment, the conditions for the heating reaction synthesis are to raise the temperature to 80°C-90°C and react for 2 hours, then connect the condensation device and gradually raise the temperature to 150°C for distillation, and end the distillation when no condensed liquid flows out for 20 minutes, and discharge the material after cooling.

[0060] The preparation method of the titanate substance with a titanium content of 1.09% in this embodiment is as follows: Add 75 g of Tyzor 726, 5.07 g of methyl orthosilicate, 96.06 g of anhydrous citric acid, 600 g of 1,4-butanediol, 5.86 g of zinc isooctanoate, and 91.08 g of triethyl phosphate to a 1000 ML four-necked flask. Place it in a 1 L electric heating mantle, insert a stirring paddle, connect a stirring motor, and stir at a speed of 400 - 600 RPM. Heat up to 80℃ - 90℃ and react for 2 hours. Then connect a condensing device and gradually heat up to 150℃ for distillation. Stop distillation when no condensed liquid flows out for 20 minutes. Cool down and pour out the material in the 1000 ml flask to obtain the titanate substance with a titanium content of 1.09%.

[0061] In this embodiment, the cation exchange resin includes commercially available 001×7 hydrogen form cation exchange resin, D001 hydrogen form cation exchange resin, 732 hydrogen form cation exchange resin, and Suqing brand JY-1 cation exchange resin.

[0062] Another object of the present invention is to provide an application of a low-viscosity and high-hydroxyl-value castor oil-based polyol as described above in a polyurethane thermal conductive structural adhesive.

[0063] The raw material castor oil used in the present invention is commercially available refined castor oil. Glycerol, 1,4-butanediol, anhydrous citric acid, and propylene carbonate are all industrial grade and provided by Guangzhou Suixin Chemical Co., Ltd. Trimethylolpropane is industrial grade and provided by Guangzhou Fufei Chemical Co., Ltd. Triethyl phosphate is industrial grade and provided by Shenzhen Dianshifang Technology Co., Ltd. Ethylene carbonate is industrial grade and provided by Aolilong (Jining) Chemical Co., Ltd. 732 hydrogen form cation exchange resin is industrial grade and provided by Langfang Miaoyang Chemical Co., Ltd. Methyl orthosilicate is industrial grade and provided by Hubei Jianghan New Materials Co., Ltd. Tyzor 726 titanate is industrial grade and provided by Guangzhou Jianyi Chemical. Tetramethylammonium hydroxide pentahydrate is industrial grade and provided by Anhui Siyoupiao Chemical Technology Co., Ltd.

[0064] Detection: Detect the viscosity at room temperature (25℃ ± 2) according to GB / T 2794-2022 Determination of Viscosity of Adhesives.

[0065] Detect the hydroxyl value of the low-viscosity and high-hydroxyl-value castor oil-based polyol of the present invention according to the national standard GB / T 12008.3-2009 Determination Method of Hydroxyl Value in Polyether Polyols.

[0066] To facilitate better understanding of the technical solution of the present invention by those skilled in the art, the following are specific embodiments of the present invention:

[0067] Example 1: Add 660 g of refined castor oil, 142.2 g of glycerol, 157.6 g of propylene carbonate, 2 g of triethylamine, and 2 g of a titanate substance with a titanium content of 1.09% into a 1000 ML four-necked flask. Place it in a 1 L electric heating mantle, install a stirring paddle, connect the motor, and start stirring at a speed of 400 - 900 RPM. Set the temperature of the electric heating mantle to 150 °C and start heating. When the temperature rises to 100 °C, add 0.15 g of tetramethylammonium hydroxide pentahydrate. When the temperature rises to about 150 °C, react for 4 h. Connect a vacuum pumping device and vacuum pump at a material temperature of 140 °C - 150 °C until the gauge pressure is below -0.09 MPa for 60 min to remove low-molecular volatile substances. Cool down to about 100 °C, add 10 g of dry 732 hydrogen-type cation exchange resin, and stir at a speed of 300 - 400 RPM for 60 min. Filter out the cation exchange resin with a 100-mesh filter screen to obtain polyol 1.

[0068] Example 2: Add 700 g of refined castor oil, 73.8 g of 1,4-butanediol, 84.3 g of propylene carbonate, 2 g of triethylamine, and 2 g of a titanate substance with a titanium content of 1.09% into a 1000 ML four-necked flask. Place it in a 1 L electric heating mantle, install a stirring paddle, connect the motor, and start stirring at a speed of 400 - 900 RPM. Set the temperature of the electric heating mantle to 150 °C and start heating. When the temperature rises to 100 °C, add 0.15 g of tetramethylammonium hydroxide pentahydrate. When the temperature rises to about 150 °C, react for 4 h. Connect a vacuum pumping device and vacuum pump at a material temperature of 140 °C - 150 °C until the gauge pressure is below -0.09 MPa for 60 min to remove low-molecular volatile substances. Cool down to about 100 °C, add 10 g of dry 732 hydrogen-type cation exchange resin, and stir at a speed of 300 - 400 RPM for 60 min. Filter out the cation exchange resin with a 100-mesh filter screen to obtain polyol 2.

[0069] The performance comparison of polyol 1 synthesized in Example 1 of the present invention and polyol 2 synthesized in Example 2 with commercially available low-viscosity high-hydroxyl value polyols is shown in Table 1:

[0070] Table 1

[0071]

[0072] The hydroxyl value unit is mg / g KOH, and the viscosity is measured in an environment of 25 °C ± 2 °C, with the unit of cP, using an NDJ-8S rotational viscometer.

[0073] PCL-3037 and PCl-3057 are products of Hunan Juren New Materials Co., Ltd., A4105 and AP19-9 are products of Shanghai Jingri New Materials Co., Ltd., H-368 and AC-009 are products of Ito Oil Co., Ltd., and CF-180T is a product of Qingdao Ruinuo Chemical Co., Ltd.

[0074] A two-component polyurethane thermally conductive structural adhesive with a 1:1 ratio was synthesized using polyol 1 synthesized in Example 1 and polyol 2 synthesized in Example 2.

[0075] Using a 5L planetary power mixer, add polyol 1 synthesized in Example 1: 260g, polyol 2 synthesized in Example 2: 200g, refined castor oil: 20g, wetting agent Evonik twin4100: 10g, dispersant BYK-110: 10g, hydrogenated castor oil: 5g, antioxidant 1010: 4g, Cabot M5 fumed silica: 5g, polyurethane blue paste: 4g, aluminum hydroxide FA-06: 1100g, aluminum hydroxide FA-06: 300g. Stir evenly at a frequency of 20 - 45Hz, heat up to 100°C - 120°C, evacuate to a gauge pressure of -0.09MPa for 2H, cool down to a material temperature below 35°C, add molecular sieve activated powder JHL-PU: 30g and stir evenly. Then add coupling agents KH-550: 10g and KH-560: 10g, stir at a frequency of 20 - 45Hz and evacuate to a gauge pressure of -0.09MPa for 30min, and discharge to obtain Component A of the polyurethane thermally conductive structural adhesive.

[0076] Synthesis of the NCO component of the thermally conductive structural adhesive: Using a 5L planetary power mixer, add MDI-50: 210g and polyol BY-3020: 190g. Stir evenly at a frequency of 20 - 45Hz, heat up to 70°C - 80°C, evacuate to a gauge pressure of -0.09MPa and react for 3H. Start cooling down and add Covestro Desmodur 44V20L: 200g and stir evenly. Then add aluminum hydroxide with a medium particle size of 25 microns treated with silane: 950g and aluminum oxide with a medium particle size of 2 microns treated with silane: 150g and stir evenly. Stir and evacuate to a gauge pressure of -0.09MPa at a frequency of 20 - 45Hz for 1H, and discharge when the material temperature is below 35°C to obtain Component B of the polyurethane thermally conductive structural adhesive.

[0077] Aluminum hydroxides FA-06, FA-10, aluminum hydroxide with a medium particle size of 25 microns treated with silane, and aluminum oxide with a medium particle size of 2 microns treated with silane are products of Guangdong Ginge New Materials Co., Ltd. The molecular sieve activated powder JHL-PU is a product of Luoyang Jianlong Micro-Nano New Materials Co., Ltd. The polyurethane blue paste is a product of Yunze Color Paste Co., Ltd. The polyol BY-3020 is a product of Beijing Baiyuan Chemical Co., Ltd. The coupling agents KH-550 and KH-560 are products of Hubei Jianghan New Materials Co., Ltd.

[0078] The performance after curing of Component A and Component B of the polyurethane thermally conductive structural adhesive synthesized by the present invention in a 1:1 ratio is shown in Table 2 below:

[0079] Table 2

[0080]

[0081] The viscosity test was carried out using a BROOKFIELD DV-Ⅱ+PRO viscometer with a No. 7 rotor at a speed of 100 RPM.

[0082] The low-viscosity and high-hydroxyl-value modified castor oil-based polyol synthesized by the present invention has the characteristics of low viscosity and high hydroxyl value, and is suitable for making polyurethane thermal conductive structural adhesives.

[0083] It should be noted that in this text, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including that element.

[0084] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A low-viscosity and high-hydroxyl-value castor oil-based polyol, characterized in that, Its main components include the components shown in Structural Formula I, Formula II, and Formula III; Formula Ⅰ: ; Formula II: ; Formula Ⅲ: ; In the above formula, R1 is one of H and CH3, R is the alkyl group corresponding to the small molecule diol used, or the hydroxyl-containing alkyl chain corresponding to other polyols used.

2. A synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol as described in claim 1, characterized in that, The method includes the following steps: Mix castor oil, low molecular weight cyclic carbonate substance, small molecule polyol substance, and catalyst, and carry out ring-opening of cyclic carbonate and polyol transesterification at a temperature of 100°C - 160°C to synthesize modified castor oil-based polyol. Then, evacuate to a gauge pressure below -0.09 MPa at 140°C - 150°C for 30 - 60 min to remove low molecular weight volatile substances. Then, cool to a material temperature of 100°C and add cationic resin for adsorption and neutralization reaction for 30 - 60 min. Cool to below 50°C and filter out the cationic resin to obtain low-viscosity and high-hydroxyl-value castor oil-based polyol; Among them, the low molecular weight cyclic carbonate substance is one of ethylene carbonate and propylene carbonate; The small molecule polyol substance is one of di-functional and multi-functional alcohol compounds; The catalyst is a composition of an alkali substance and a titanate substance; The room temperature viscosity of the synthesized low-viscosity and high-hydroxyl-value castor oil-based polyol is 260 - 600 cP, and the hydroxyl value is 240 - 400 mg / g of KOH.

3. The synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 2, wherein, The synthesis conditions of the synthesized modified castor oil-based polyol are a material temperature of 140°C - 160°C and a reaction time of 3 - 6 hours.

4. The synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 2, characterized in that, The small molecule polyol substance is one of ethylene glycol, glycerol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, and pentaerythritol.

5. The synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 2, characterized in that The molar ratio of the small molecule polyol substance to castor oil is 1 - 2:

1.

6. The synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 2, characterized in that, The molar ratio of the low molecular weight cyclic carbonate to the small molecule polyol substance is 1 - 2:

1.

7. A method for synthesizing a low-viscosity high-hydroxyl-value castor oil-based polyol according to claim 2, characterized in that, The catalyst contains one or more alkali substances and titanate compounds. Among them, the alkali substances include organic tertiary amines, quaternary ammonium salts, and inorganic strong bases; the organic tertiary amines include trimethylamine and triethylamine, the quaternary ammonium salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, the inorganic strong bases include sodium hydroxide and potassium hydroxide, and the titanate substance is a titanate substance with a titanium content of 0.8% - 1.5%; The dosage of the organic tertiary amine in the catalyst used is 0.1% - 0.5% of the total mass of the materials, the dosage of the quaternary ammonium salt or inorganic strong base is 0.01% - 0.1% of the total mass of the materials, and the dosage of the titanate substance with a titanium content of 0.8% - 1.5% is 0.1% - 0.5% of the total mass of the materials.

8. A method for synthesizing a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 7, characterized in that, The preparation principle of the titanate substance with a titanium content of 0.8% - 1.5% is to heat react a titanate such as tetraisopropyl titanate, tetrabutyl titanate, tetra-tert-butyl titanate, diisopropoxytitanium diacetylacetonate, diethylacetoacetate diisopropoxytitanium, or Tyzor 726 of Guangzhou Jianyi Chemical Industry Co., Ltd. with one or more small molecule hydroxyl-containing compounds, hydroxycarboxylic acids, alkoxysilanes, zinc salts, and phosphate esters to synthesize a titanate substance with a titanium content of 0.8% - 1.5%.

9. The synthesis method of a low-viscosity and high-hydroxyl-value castor oil-based polyol according to claim 2, characterized in that, The cationic resin includes commercially available 001×7 hydrogen-form cationic resin, D001 hydrogen-form cationic resin, 732 hydrogen-form cationic resin, and Suqing brand JY-1 cationic resin.

10. An application of a low-viscosity and high-hydroxyl-value castor oil-based polyol as described in claim 1 in a polyurethane thermally conductive structural adhesive.

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