A low-viscosity, high-hydroxyl-value castor oil-based polyol and its synthesis method and application

Abstract

The present invention is applicable to the field of polyol synthesis and provides a low-viscosity, high-hydroxyl-value castor oil-based polyol and a synthesis method and application thereof. Castor oil, a small-molecule cyclic carbonate, and a small-molecule 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, high-hydroxyl-value castor oil-based polyol prepared by the present invention is suitable for preparing polyurethane thermal conductive structural adhesives.

Description

Technical Field

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

[0002] Polyurethane thermal conductive structural adhesive is widely used in the bonding between new energy power battery cells and components such as heat sinks. It needs to have a thermal conductivity of 0.6W / KM-2.0W / KM and a bonding strength greater than 7MPa.

[0003] Polyurethane thermal conductive structural adhesive is made of low-viscosity polyol material with a large amount of thermal conductive filler added, isocyanate material and other additives. The main polyol resins that may be used include small molecule polyether polyols, high-strength modified castor oil polyols, and low-viscosity polyester polyols, such as MN-500, MN-700, MN-1000, DL-400, DL-1000 and other polyether polyols produced by Shandong Bluestar Dongda Co., Ltd., AC-006, AC-009, H-368, H-420, H-870 and other modified castor oil polyols produced by Ito Oil, and A4105, AP19-9, AP-13 and other modified castor oil polyols produced by Shanghai Jingri New Materials Technology Co., Ltd., and PCL-3037, PCL-3057, PCl-3087, PCL-2053 and other small molecule polycaprolactone polyols produced by Hunan Juren Chemical.

[0004] Small molecule polyether polyols have strong water absorption and are prone to bubbles when used to synthesize polyurethane thermal conductive structural adhesives. Polycaprolactone polyols have strong mechanical properties, high bonding strength, high temperature and humidity resistance, and good stability. However, the supply of polycaprolactone polyols is not sufficient and the price is high. Modified castor oil polyols are generally synthesized by ester exchange between castor oil and small molecule polyols, or by copolymerization of castor oil and small molecule alcohols with propylene oxide or ethylene oxide, or by condensation of alcoholyzed castor oil with dicarboxylic acids. The raw material source is sufficient. The selection of suitable modified polyols based on castor oil can synthesize polyurethane thermal conductive structural adhesives that meet the use requirements of new energy power battery thermal conductive structural adhesives.

[0005] The improvement of traditional modified polyol technology based on castor oil polyol mainly improves the hydrolysis stability, tensile strength, compressive strength, elongation and other properties of polyurethane materials synthesized based on modified castor oil polyol and isocyanate substances.

[0006] For example, Chinese patent application publication number CN 105585699 A discloses a method for synthesizing castor oil polyester polyols and their application in polyurethane foams. Castor oil is reacted with a small molecule diol in the presence of a catalyst to obtain a castor oil alcoholysis solution, which is then added to a small molecule dicarboxylic acid for polycondensation to produce a modified castor oil polyester polyol with a number average molecular weight of 2000-4000 for use in the production of polyurethane foams. The resulting foam overcomes the disadvantages of castor oil, such as low strength and poor foam stability. However, the room temperature viscosity of the polyol produced using this technology is not low, never below 1000 cP.

[0007] Chinese patent application publication number CN 102532513 A discloses a method for synthesizing a high-molecular-weight castor oil polyether polyol. The polyether is prepared by polymerizing castor oil with ethylene oxide or propylene oxide in the presence of a bimetallic catalyst. This high-molecular-weight castor oil polyether polyol has a low hydroxyl value and is primarily used to synthesize polyurethane soft foam materials, but has low strength.

[0008] Chinese patent application publication number CN 103534285 A discloses a high-molecular-weight castor oil-based polyol and its uses. This modified castor oil-based polyol, with a molecular weight of 900-4000 Da and a hydroxyl value below 130, is produced by reacting castor oil with fatty acids and a catalyst under heating. This technologically improved castor oil-based polyol features branched or linear alkanes with two to six carbon atoms connecting the hydroxyl groups or ester groups. It exhibits low viscosity and exceptional hydrolytic stability. The lowest viscosity model, the D1000 polyol, has a room temperature viscosity of 425 cP and a hydroxyl value of 125. If this modified castor oil-based polyol is used in the formulation of a hydroxyl-containing component of a one-to-one two-component thermally conductive structural adhesive, the addition of thermally conductive fillers exceeding 40% by volume can lead to a significant deterioration in the mechanical properties of the adhesive, failing to meet the strength requirements for thermally conductive structural adhesives used in new energy power batteries. If castor oil-based polyols modified by this technology are combined with small molecule chain extenders to improve the mechanical properties of thermal conductive adhesives, the introduction of relatively small molecule polyols will lead to other problems such as shortened gel time of the thermal conductive structural adhesive and easy water absorption.

[0009] Chinese patent application publication number CN 110423650 A discloses an alkoxylated castor oil-based polyol. The process involves epoxidizing the unsaturated bonds of castor oil and then ring-opening the epoxy groups of the epoxidized castor oil with a small molecule alcohol to produce the alkoxylated castor oil polyol. The resulting modified castor oil polyol has a functionality greater than 5 and, when combined with isocyanates and other materials, is made into rigid polyurethane foam, exhibiting high strength and excellent dimensional stability. However, adding a large amount of thermally conductive filler to the thermally conductive structural adhesive further degrades the already poor elongation at break, resulting in a toughness that fails to meet the minimum elongation at break requirement for thermally conductive structural adhesives used in new energy power batteries. Summary of the Invention

[0010] The present invention provides a low-viscosity, high-hydroxyl-value castor oil-based polyol, and a synthesis method and application thereof. The synthesized modified castor oil polyol has low viscosity, high hydroxyl value, high strength and good toughness for preparing polyurethane thermal conductive structural adhesive. The viscosity is lower than that of commercially available modified castor oil polyols for polyurethane thermal conductive structural adhesives, and the viscosity of the thermal conductive structural adhesive is more advantageous when a large amount of thermal conductive fillers are filled.

[0011] A low-viscosity, high-hydroxyl-value castor oil-based polyol, the main components of which include components represented by structural formulas I, II, and III;

[0012] Formula I: ;

[0013] Formula II: ;

[0014] Formula III: ;

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

[0016] Another object of the present invention is to provide a method for synthesizing the low-viscosity, high-hydroxyl value castor oil-based polyol as described above, the method comprising the following steps:

[0017] Castor oil, a low molecular weight cyclic carbonate substance, a small molecular weight polyol substance and a catalyst are mixed at a temperature of 100° C. to 160° C. to perform cyclic carbonate ring opening and polyol transesterification to synthesize a modified castor oil-based polyol, and the mixture is evacuated at 140° C. to a gauge pressure below -0.09 MPa for 30-60 minutes to remove low molecular weight volatiles, and then the mixture is cooled to a material temperature of 100° C., a cationic resin is added to perform an adsorption neutralization reaction for 30-60 minutes, and the mixture is cooled to below 50° C. to filter out the cationic resin to obtain a low-viscosity, high-hydroxyl value castor oil-based polyol;

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

[0019] The small molecule polyol substance is one of difunctional and polyfunctional 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, high-hydroxyl-value castor oil-based polyol is 260-600 cP, and the hydroxyl value is 240-400 mg / g, KOH.

[0022] Preferably, the synthesis conditions of the synthetic modified castor oil-based polyol are a material temperature of 140° C. to 160° C. and a reaction time of 3 to 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 molecular weight polyol is 1-2:1.

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

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

[0028] Preferably, the preparation principle of the titanate material with a titanium content of 0.8%-1.5% is to use one of the titanates such as tetraisopropyl titanate, tetrabutyl titanate, tetra-tert-butyl titanate, diisopropoxy titanium diacetylacetonate, diisopropoxy titanium diacetylacetate or Tyzor 726 produced by Guangzhou Jianyi Chemical Industry Co., Ltd., and one or more small molecule hydroxyl-containing compounds, hydroxycarboxylic acids, alkoxysilanes, zinc salts and phosphates to heat and react to synthesize a titanate material with a titanium content of 0.8%-1.5%.

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

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

[0031] Beneficial effects achieved by the present invention:

[0032] The low-viscosity and high-hydroxyl-value modified castor oil-based polyol synthesized by the invention has the characteristics of low viscosity and high hydroxyl value, and is suitable for preparing polyurethane heat-conducting structural adhesive. DETAILED DESCRIPTION

[0033] The embodiments described in the present invention are some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also 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 understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "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 components represented by structural formulas I, II, and III;

[0036] Formula I: ;

[0037] Formula II: ;

[0038] Formula III: ;

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

[0040] 、 、 、 、 、 、 、 、 、 .

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

[0042] Castor oil, a low molecular weight cyclic carbonate substance, a small molecular weight polyol substance and a catalyst are mixed at a temperature of 100° C. to 160° C. to perform cyclic carbonate ring opening and polyol transesterification to synthesize a modified castor oil-based polyol, and the mixture is evacuated at 140° C. to a gauge pressure below -0.09 MPa for 30-60 minutes to remove low molecular weight volatiles, and then the mixture is cooled to a material temperature of 100° C., a cationic resin is added to perform an adsorption neutralization reaction for 30-60 minutes, and the mixture is cooled to below 50° C. to filter out the cationic resin to obtain a low-viscosity, high-hydroxyl value castor oil-based polyol;

[0043] Wherein, the low molecular weight cyclic carbonate substance is one of ethylene carbonate and propylene carbonate;

[0044] The small molecule polyol substance is one of difunctional and polyfunctional 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, high-hydroxyl-value castor oil-based polyol is 260-600 cP, and the hydroxyl value is 240-400 mg / g, KOH.

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

[0048] In this embodiment, the small molecule polyol substance is one of ethylene glycol, propylene glycol, 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 embodiment, the molar ratio of the small molecule polyol substance to castor oil is 1-2:1.

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

[0051] In this embodiment, the catalyst comprises one or more alkaline substances and titanate compounds, wherein the alkaline substances include organic tertiary amines, quaternary ammonium salts, and inorganic strong bases; organic tertiary amines include trimethylamine and triethylamine, 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 material, the amount of quaternary ammonium salt or inorganic strong base used is 0.01%-0.1% of the total mass of the material, and the amount of titanate material with a titanium content of 0.8%-1.5% is 0.1%-0.5% of the total mass of the material.

[0053] In this embodiment, the preparation principle of the titanate material with a titanium content of 0.8%-1.5% is to use one of the titanates such as tetraisopropyl titanate, tetrabutyl titanate, tetra-tert-butyl titanate, diisopropoxy titanium diacetylacetonate, diisopropoxy titanium diacetylacetate or Tyzor 726 produced by Guangzhou Jianyi Chemical Industry Co., Ltd., and one or more small molecule hydroxyl-containing compounds, hydroxycarboxylic acids, alkoxysilanes, zinc salts and phosphates to heat and react to synthesize a titanate material with a titanium content of 0.8%-1.5%.

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

[0055] In this embodiment, the small molecule hydroxyl-containing compound includes but is not limited to ethylene glycol, 1,4-butanediol, propylene glycol, diethylene glycol, dipropylene glycol, and 3-methyl-1,5-pentanediol, and the molar ratio of the small molecule hydroxyl-containing compound to the titanate is 5-40 to 1.

[0056] In this embodiment, the alkoxysilane includes but is not limited to tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, and phenyltrimethoxysilane, and the molar ratio of the alkoxysilane to the titanate is 0.05-0.5 to 1.

[0057] In this embodiment, the phosphate ester includes but is not limited to trimethyl phosphate and triethyl phosphate, and the molar ratio of the phosphate ester to the titanate ester is 0-5:1.

[0058] In this embodiment, the zinc salt includes but is not limited to zinc isooctanoate, and the molar ratio of zinc isooctanoate to titanate is 0.05-3:1.

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

[0060] In this embodiment, a titanate material having a titanium content of 1.09% was prepared as follows: 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 were added to a 1000 ml four-necked flask, placed in a 1 L electric heating mantle, plugged in a stirring paddle, connected to a stirring motor, and stirred at a speed of 400-600 RPM. The temperature was raised to 80° C.-90° C. for 2 hours, and then a condenser was connected and the temperature was gradually raised to 150° C. for distillation. The distillation was terminated when no condensed liquid flowed out after 20 minutes. The material in the 1000 ml flask was cooled and poured out to obtain a titanate material having a titanium content of 1.09%.

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

[0062] Another object of the present invention is to provide a use of the low-viscosity, high-hydroxyl value castor oil-based polyol as described above in 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 Orilon (Jining) Chemical Co., Ltd.; 732 hydrogen-type cationic 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; and tetramethylammonium hydroxide pentahydrate is industrial-grade and provided by Anhui Siyoupu Chemical Technology Co., Ltd.

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

[0065] The hydroxyl value of the low-viscosity, high-hydroxyl-value castor oil-based polyol of the present invention is tested according to the national standard GB / T 12008.3-2009 method for determining the hydroxyl value of polyether polyols.

[0066] In order to facilitate those skilled in the art to better understand the technical solutions of the present invention, specific embodiments of the present invention are given as follows:

[0067] Embodiment 1: With 1000ML four-necked flask, add refined castor oil 660g, glycerol 142.2g, propylene carbonate 157.6g, triethylamine 2g, titanium content 1.09% titanate material 2g, put into 1L electric heating mantle and install stirring paddle and connect motor to open and stir with the rotating speed of 400-900RPM, electric heating mantle is set 150 ℃ of temperature and opens heating, the temperature rises to 100 ℃ and adds tetramethylammonium hydroxide pentahydrate 0.15g, the temperature rises to about 150 ℃ and reacts 4H, connects vacuum pump and is evacuated to gauge pressure-0.09MPa below 60min under 140 ℃-150 ℃ of material temperatures and removes low-molecular volatile matter, is cooled to about 100 ℃ and adds dry 732 hydrogen type cationic resin 10g with the rotating speed of 300-400RPM and stirs 60min, removes cationic resin with 100 mesh filter screen, obtains polyol 1.

[0068] Embodiment 2: add refined castor oil 700g, 1,4-butanediol 73.8g, propylene carbonate 84.3g, triethylamine 2g, the titanate material 2g of titanium content 1.09% with 1000ML four-necked flask, put into 1L electric heating mantle and install stirring paddle and connect motor with the rotating speed of 400-900RPM and stir, the electric heating mantle is set 150 ℃ of temperature and opens heating, the temperature rises to 100 ℃ and adds tetramethylammonium hydroxide pentahydrate 0.15g, the temperature rises to about 150 ℃ and reacts 4H, connects vacuum pump and is evacuated to gauge pressure-0.09MPa below 60min under 140 ℃-150 ℃ of material temperatures and removes low-molecular volatile matter, be cooled to about 100 ℃ and add dry 732 hydrogen type cationic resin 10g with the rotating speed of 300-400RPM and stir 60min, filter out cationic resin with 100 mesh filter screen, 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 unit of hydroxyl value is mg / g KOH. The viscosity is measured at 25℃±2℃ and the unit is 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 Manufacturing, and CF-180T is a product of Qingdao Ruinuo Chemical Co., Ltd.

[0074] Polyol 1 synthesized in Example 1 and polyol 2 synthesized in Example 2 were used to synthesize a 1:1 two-component polyurethane thermal conductive structural adhesive:

[0075] Use a 5L planetary power mixer to 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 gas silica: 5g, polyurethane blue paste: 4g, aluminum hydroxide FA-06: 1100g, aluminum hydroxide FA-06: 30 0g, stir evenly at a frequency of 20-45Hz, heat to 100℃-120℃, evacuate to the gauge pressure of -0.09MPa and evacuate for 2H, cool to the material temperature below 35℃, add molecular sieve activation powder JHL-PU: 30g, stir evenly, then add coupling agent KH-550: 10g, KH-560: 10g, stir at a frequency of 20-45Hz and evacuate to the gauge pressure of -0.09MPa and evacuate for 30min, and obtain polyurethane thermal conductive structural adhesive agent A.

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

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

[0078] The properties after curing of the polyurethane thermal conductive structural adhesive agent A and the polyurethane thermal conductive structural adhesive agent B synthesized by the present invention in a ratio of 1 to 1 are shown in Table 2 below:

[0079] Table 2

[0080]

[0081] The viscosity test was performed using a Brookfield DV-II+Pro viscometer with a No. 7 rotor and a rotation speed of 100 RPM.

[0082] The low-viscosity and high-hydroxyl-value modified castor oil-based polyol synthesized by the invention has the characteristics of low viscosity and high hydroxyl value, and is suitable for preparing polyurethane heat-conducting structural adhesive.

[0083] It should be noted that, in this document, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for synthesizing low-viscosity, high-hydroxyl-value castor oil-based polyols, characterized in that: The method comprises the following steps: mixing castor oil, a low-molecular cyclic carbonate substance, a small-molecular polyol substance, and a catalyst at a temperature of 100° C.-160° C., performing cyclic carbonate ring-opening and polyol transesterification to synthesize a modified castor oil-based polyol; evacuating the mixture at 140° C.-150° C. to a gauge pressure below -0.09 MPa for 30-60 minutes to remove low-molecular volatiles; then cooling the mixture to a material temperature of 100° C., adding a cationic resin to carry out an adsorption neutralization reaction for 30-60 minutes, cooling the mixture to below 50° C., filtering out the cationic resin, and obtaining a low-viscosity, high-hydroxyl-value castor oil-based polyol; Wherein, the low molecular weight cyclic carbonate substance is one of ethylene carbonate and propylene carbonate; 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; The catalyst is a composition of an alkali substance and a titanate substance; The room temperature viscosity of the synthesized low-viscosity, high-hydroxyl-value castor oil-based polyol is 260-600 cP, and the hydroxyl value is 240-400 mg / g, KOH.

2. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 1, wherein: The synthesis conditions of the synthetic modified castor oil-based polyol are as follows: a material temperature of 140° C. to 160° C. and a reaction time of 3 to 6 hours.

3. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 1, wherein: The molar ratio of the small molecule polyol substance to castor oil is 1-2:

1.

4. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 1, wherein: The molar ratio of the low molecular cyclic carbonate to the small molecular polyol is 1-2:

1.

5. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 1, wherein: The alkaline substance is selected from organic tertiary amines, quaternary ammonium salts, and inorganic strong bases; the organic tertiary amine is selected from trimethylamine and triethylamine, the quaternary ammonium salt is selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, the inorganic strong base is selected from sodium hydroxide and potassium hydroxide, and the titanate substance is a titanate substance having a titanium content of 0.8% to 1.5%; The amount of organic tertiary amine in the catalyst used is 0.1%-0.5% of the total mass of the material, the amount of quaternary ammonium salt or inorganic strong base is 0.01%-0.1% of the total mass of the material, and the amount of titanate material with a titanium content of 0.8%-1.5% is 0.1%-0.5% of the total mass of the material.

6. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 5, characterized in that: The preparation principle of the titanate material with a titanium content of 0.8%-1.5% is to use tetraisopropyl titanate, tetrabutyl titanate, tetra-tert-butyl titanate, diisopropoxytitanium diacetylacetonate, diisopropoxytitanium diacetylacetate, or a titanate with the industrial brand number Tyzor 726 of Guangzhou Jianyi Chemical to heat and react with one or more small molecules containing hydroxycarboxylic acids, alkoxysilanes, zinc salts and phosphates to synthesize a titanate material with a titanium content of 0.8%-1.5%.

7. The method for synthesizing a low-viscosity, high-hydroxyl-value castor oil-based polyol according to claim 1, characterized in that: The cationic resin is selected from commercially available 001×7 hydrogen-type cationic resin, D001 hydrogen-type cationic resin, 732 hydrogen-type cationic resin, and Suqing brand JY-1 cationic resin.

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