Controllable thermal expansion microsphere based on bio-based copolymer and preparation method thereof

Abstract

The invention relates to the technical field of thermal expansion microspheres, in particular to controllable thermal expansion microspheres based on bio-based copolymers and a preparation method thereof.The preparation method comprises the steps that S1, vinyl nitrile-containing monomers, bio-based rigid monomers, bio-based flexible monomers and functional monomers are subjected to condensation polymerization under the action of a catalyst, and prepolymers are obtained; s2, mixing the prepolymer with a foaming agent, adding a bio-based emulsifier, and carrying out emulsification treatment to obtain a uniform emulsion; s3, dispersing the emulsion in a water phase of a natural stabilizer, adding an initiator, and carrying out polymerization reaction at a certain temperature and pressure to form microspheres with core-shell structures; and S4, carrying out solid-liquid separation and drying treatment to obtain the thermal expansion microspheres. The thermal expansion microspheres obtained by the preparation method have higher expansion rate, and the whole preparation process and application are more controllable.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of controllable thermal expansion microspheres based on bio-based copolymer and its preparation method, belong to thermal expansion microspheres technical field. BACKGROUND

[0002] Thermal expansion microspheres as a kind of functional polymer material of core-shell structure, its core is foaming agent, shell is thermoplastic polymer.In the heating process, shell softens and foaming agent gasifies, drive microsphere volume expansion, widely used in lightweight materials, coatings, biological medicine and other fields.However, traditional microspheres are mostly dependent on petroleum-based monomers, there are poor biodegradability, carbon footprint and other problems.In recent years, the development of bio-based alternative materials has become a research hotspot.

[0003] The preparation of traditional thermal expansion microspheres is mainly based on the copolymerization system of vinyl nitrile-containing monomers and petroleum-based monomers, and the patent with publication number CN118221997B discloses a kind of thermal expansion microspheres foaming agent and preparation method, which is prepared by compounding vinyl nitrile-containing monomers, acrylate and vinyl ester monomers, and forming a core-shell structure by emulsion polymerization.Although it has high compressive strength, its biocarbon content is almost zero, and its degradation performance is poor.The patent application with publication number CN116284956A discloses a kind of thermal expansion microspheres and its preparation method and application, which improves the ductility, air tightness and heat resistance of the microspheres by designing and compounding different olefinic unsaturated monomers and different reactive crosslinking agents.However, its raw materials are not renewable, and it produces toxic byproducts and difficult-to-degrade waste.

[0004] In recent years, domestic and foreign research has focused on the synergistic compounding of acrylonitrile and multiple bio-based monomers.The patent application with publication number WO2019043235A1 discloses microspheres based on lactone homopolymer / copolymer, with a bio-based content of 85%, but the expansion ratio is only 3~5 times, and the high-temperature stability problem has not been solved.The patent with publication number CN118909207B discloses a preparation method of micron-sized polymer microspheres, which attempts to copolymerize acrylonitrile and vanillin-based unsaturated monomers, and constructs a crosslinked network through a photo-curing process.This scheme uses the aromatic ring structure of vanillin to enhance the thermal stability of the shell material, but the residual photo-initiator increases the toxicity of the microspheres, and the biodegradation rate is less than 30%, which is difficult to meet the environmental protection requirements.

[0005] Therefore, it is urgent to develop a high-efficiency copolymerization system of acrylonitrile and multiple bio-based monomers, which synchronously realizes high bio-based content, wide temperature range expansion ratio, excellent mechanical properties and controllable degradability by precise compounding of rigid / flexible / crosslinking monomers and combining with water-phase controllable polymerization process. SUMMARY

[0006] This invention addresses the shortcomings of existing technologies by providing a controllable thermal expansion microsphere based on bio-based copolymers and its preparation method. It aims to solve the technical problems of poor biodegradability and high carbon footprint of traditional petroleum-based microspheres, as well as the insufficient mechanical properties and limited functionality of existing bio-based microspheres.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method is as follows: S1, vinyl nitrile monomers, bio-based rigid monomers, bio-based flexible monomers and functional monomers undergo polycondensation reaction under the action of a catalyst to obtain a prepolymer; S2. The prepolymer is mixed with a foaming agent and a bio-based emulsifier is added to emulsify the mixture and obtain a uniform emulsion. S3. Disperse the emulsion in the aqueous phase of a natural stabilizer, add an initiator, and carry out a polymerization reaction under a certain temperature and pressure to form microspheres with a core-shell structure. S4. After solid-liquid separation and drying, thermally expanded microspheres are obtained.

[0008] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, based on parts by weight, the amounts of each monomer added in step S1 are as follows: 40-50 parts of vinyl nitrile monomers; 20-40 parts of bio-based rigid monomers; 10-35 parts of bio-based flexible monomers; and 5-10 parts of functionalized monomers.

[0009] Furthermore, the vinyl nitrile monomer is at least one of acrylonitrile and methacrylonitrile; The bio-based rigid monomer is at least one of furanyl dicarboxylate, vanillin-based unsaturated monomer, lignin derivative, isosorbide derivative, 5-hydroxymethylfurfural ester, and tricitrate. The flexible monomer is at least one of castor oil epoxy ester, linseed oil epoxy ester, soybean oil-based polyol, methyl palmitate, and glyceryl laurate. The functional monomer is at least one of acrylated citrate, methacrylated glyceryl ester, and acrylated itaconic acid ester.

[0010] Furthermore, in step S1, the catalyst is at least one of stannous octoate and tetrabutyl titanate; The amount of catalyst added is 0.1-1% of the total mass of the polymer monomers.

[0011] Furthermore, in step S1, the temperature of the polycondensation reaction is 110-120℃, the acid value is monitored in real time during the polycondensation reaction, and the reaction is stopped when the acid value is ≤5mg KOH / g, to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0012] Furthermore, in step S2, the foaming agent is a low-boiling-point alkane, and the low-boiling-point alkane is at least one of n-butane, isobutane, n-pentane, and isopentane. The bio-based emulsifier is at least one of Span 80 and Tween 60.

[0013] Furthermore, in step S2, the mass ratio of the prepolymer to the foaming agent is 1:(3-10); the amount of the bio-based emulsifier added is 0.5-2% of the mass of the prepolymer.

[0014] Furthermore, in step S3, the natural stabilizer is at least one of sodium alginate and gelatin; the mass concentration of the natural stabilizer in the aqueous phase is 0.5-3%. The initiator is azobisisobutyronitrile; the amount of the initiator added is 0.1-0.5% of the mass of the prepolymer.

[0015] Furthermore, in step S3, the pressure conditions of the polymerization reaction are 0.4-5 MPa, the temperature of the polymerization reaction is 50℃-80℃, and the time of the polymerization reaction is 10-24 h.

[0016] The present invention also discloses a controllable thermal expansion microsphere based on a bio-based copolymer, wherein the thermal expansion microsphere is prepared according to the preparation method described in the present invention.

[0017] The beneficial effects of this invention are: In the method for preparing controllable thermally expandable microspheres based on bio-based copolymers described in this invention, vinyl nitrile monomers, bio-based rigid monomers, and bio-based flexible monomers work together to form an interpenetrating network through transesterification, which is beneficial for increasing the expansion ratio. The double bond distribution density of the functional monomers precisely controls the permeation rate of the foaming agent, preventing premature escape. The resulting thermally expandable microspheres have a higher expansion ratio, and the entire preparation process and application are more controllable.

[0018] The thermal expansion microspheres prepared by the method described in this invention have a high proportion of bio-based monomers, making them suitable for use in environmentally friendly coatings, biodegradable foaming materials, and low-carbon composite materials. Attached Figure Description

[0019] Figure 1 This is an electron microscope image of the thermally expanded microspheres prepared in Example 1. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0022] A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: S1. Synthesis of prepolymer: Vinyl nitrile monomers, bio-based rigid monomers, bio-based flexible monomers, and functional monomers undergo polycondensation reactions under the action of a catalyst to obtain prepolymers; S2, Foaming agent coating and emulsification: The prepolymer is mixed with a foaming agent and a bio-based emulsifier is added to emulsify the mixture and obtain a uniform emulsion. S3, Suspension Polymerization: The emulsion was dispersed in the aqueous phase of a natural stabilizer, and an initiator was added. The polymerization reaction was carried out under certain temperature and pressure to form microspheres with a core-shell structure. S4. Post-processing: Thermally expanded microspheres were obtained through solid-liquid separation and drying.

[0023] Based on the above technical solution, the present invention can be further improved as follows: Specifically, by weight, the amount of each monomer added in step S1 is as follows: 40-50 parts of vinyl nitrile monomer; 20-40 parts of bio-based rigid monomer; 10-35 parts of bio-based flexible monomer; and 5-10 parts of functionalized monomer.

[0024] Specifically, the vinyl nitrile monomer is at least one of acrylonitrile and methacrylonitrile; The bio-based rigid monomer is at least one of furanyl dicarboxylate, vanillin-based unsaturated monomer, lignin derivative, isosorbide derivative, 5-hydroxymethylfurfural (HMF) ester, and tricitrate. The flexible monomer is at least one of castor oil epoxy ester, linseed oil epoxy ester, soybean oil-based polyol, methyl palmitate, and glyceryl laurate. The functional monomer is at least one of acrylated citrate, methacrylated glyceryl ester, and acrylated itaconic acid ester.

[0025] Specifically, in step S1, the catalyst is at least one of stannous octoate and tetrabutyl titanate; The amount of catalyst added is 0.1-1% of the total mass of the polymer monomers.

[0026] Specifically, in step S1, the temperature of the polycondensation reaction is 110-120℃. The acid value is monitored in real time during the polycondensation reaction. When the acid value is ≤5mg KOH / g, the reaction is stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0027] More specifically, the polycondensation reaction time is 10-12 hours.

[0028] Specifically, in step S2, the foaming agent is a low-boiling-point alkane, and the low-boiling-point alkane is at least one of n-butane, isobutane, n-pentane, and isopentane. The bio-based emulsifier is at least one of Span 80 and Tween 60.

[0029] Specifically, in step S2, the mass ratio of the prepolymer to the foaming agent is 1:(3-10); the amount of the bio-based emulsifier added is 0.5-2% of the mass of the prepolymer.

[0030] More specifically, in step S2 of the embodiment of the present invention, high-speed shearing is used during emulsification, with a rotation speed of 4000-5000 rpm and a high-speed shearing emulsification time of 10 min-15 min.

[0031] Specifically, in step S3, the natural stabilizer is at least one of sodium alginate and gelatin; the mass concentration of the natural stabilizer in the aqueous phase is 0.5-3%. The initiator is azobisisobutyronitrile; the amount of the initiator added is 0.1-0.5% of the mass of the prepolymer.

[0032] Specifically, in step S3, the pressure conditions of the polymerization reaction are 0.4-5 MPa, the temperature of the polymerization reaction is 50℃-80℃, and the time of the polymerization reaction is 10-24 h.

[0033] More specifically, in step S4, a centrifuge is used for solid-liquid separation, with a speed of 5000 rpm and centrifugation for 10 min; then the centrifuged microspheres are transferred to an oven and dried at 60°C for 12 h to prepare thermally expanded microspheres.

[0034] The present invention also discloses a controllable thermal expansion microsphere based on a bio-based copolymer, wherein the thermal expansion microsphere is prepared according to the preparation method described in the present invention.

[0035] Example 1 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 50 parts of acrylonitrile, 30 parts of dimethyl furanate, 15 parts of castor oil epoxy ester (Nantong Qianhe Chemical Co., Ltd., EL-12) and 5 parts of acrylated citrate (Kaiping Zicai Chemical Co., Ltd., ZC5601) were mixed, and 0.1% of the total mass of the polymerizing monomers of stannous octoate catalyst was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12 hours. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0036] (2) Mix the prepolymer with isopentane at a mass ratio of 1:3, add 0.5% of the prepolymer mass of bio-based emulsifier Span 80, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0037] (3) The emulsion was dispersed in an aqueous phase containing 0.5% sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500cps) as a natural stabilizer, wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.1% of the prepolymer mass of AIBN was added, and the reaction was carried out for 10 hours under a pressure of 0.4 MPa and a temperature of 50°C to form microspheres with a core-shell structure.

[0038] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0039] Example 2 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 40 parts of methacrylonitrile, 25 parts of isosorbide diacrylate (ROQ-ISDA), 30 parts of methyl laurate and 5 parts of glyceryl methacrylate (Guangzhou Yuanda New Materials Co., Ltd., GMA) were mixed, and 0.2% of the total mass of the polymerizing monomers of tetrabutyl titanate catalyst was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12h. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0040] (2) Mix the prepolymer with n-pentane at a mass ratio of 1:5, add 1% of the bio-based emulsifier Tween 60 by mass of the prepolymer, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0041] (3) The emulsion was dispersed in an aqueous phase containing 1 wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500 cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.2% of the prepolymer mass of AIBN was added, and the reaction was carried out for 18 h under a pressure of 2 MPa and a temperature of 60 °C to form microspheres with a core-shell structure.

[0042] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0043] Example 3 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 40 parts of acrylonitrile, 20 parts of dimethyl furanate, 35 parts of castor oil epoxy ester (Nantong Qianhe Chemical Co., Ltd., EL-20) and 10 parts of acrylated citrate (Kaiping Zicai Chemical Co., Ltd., ZC5601) were mixed, and 1% of the total mass of the polymerizing monomers of tetrabutyl titanate catalyst was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12 hours. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0044] (2) Mix the prepolymer with n-butane at a mass ratio of 1:10, add 2% of the prepolymer mass of bio-based emulsifier Span 80, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0045] (3) The emulsion was dispersed in an aqueous phase containing 3wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.5% of the prepolymer mass of AIBN was added, and the reaction was carried out for 24 hours under a pressure of 5 MPa and a temperature of 80°C to form microspheres with a core-shell structure.

[0046] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0047] Example 4 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 45 parts of acrylonitrile, 40 parts of dimethyl furanate, 10 parts of castor oil epoxy ester (Nantong Qianhe Chemical Co., Ltd., EL-30) and 5 parts of acrylated citrate (Kaiping Zicai Chemical Co., Ltd., ZC5601) were mixed, and 0.2% of the total mass of the polymerizing monomers of stannous octoate catalyst was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12 hours. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0048] (2) Mix the prepolymer and isobutane at a mass ratio of 1:5, add 1% of the prepolymer mass of bio-based emulsifier Tween 60, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0049] (3) The emulsion was dispersed in an aqueous phase containing 1 wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500 cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.2% of the prepolymer mass of AIBN was added, and the reaction was carried out for 18 h under a pressure of 2 MPa and a temperature of 60 °C to form microspheres with a core-shell structure.

[0050] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0051] Example 5 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 50 parts of acrylonitrile, 30 parts of lignin derivative (Luohe Huadong Lignin Co., Ltd., lhhdyq-1 type), 15 parts of soybean oil-based polyol (Cargill Oils & Grains (China) Co., Ltd., Agrol prime™ S-110) and 5 parts of acrylic acid itaconic acid ester (Changzhou Runyang Chemical Co., Ltd., GY-318) were mixed, and 0.1% of the total mass of the polymerization monomers of stannous octoate catalyst was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12h. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0052] (2) Mix the prepolymer with isopentane at a mass ratio of 1:3, add 0.5% of the prepolymer mass of bio-based emulsifier Span 80, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0053] (3) The emulsion was dispersed in an aqueous phase containing 0.5 wt% sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500 cps) as a natural stabilizer, wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.1 wt% of AIBN prepolymer was added, and the reaction was carried out for 10 h under a pressure of 0.4 MPa and a temperature of 50 °C to form microspheres with a core-shell structure.

[0054] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0055] Example 6 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 40 parts of methacrylonitrile, 25 parts of 5-hydroxymethylfurfural ester (Zhongke Guosheng (Hangzhou) Technology Co., Ltd., AR), 30 parts of methyl palmitate (Shanghai Yiyan Biotechnology Co., Ltd., AR) and 5 parts of acrylate itaconic acid ester (Changzhou Runyang Chemical Co., Ltd., GY-318) were mixed, and 0.2% of the total mass of the polymerizing monomers was added as a catalyst tetrabutyl titanate. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12h. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0056] (2) Mix the prepolymer with n-pentane at a mass ratio of 1:5, add 1% of the bio-based emulsifier Tween 60 by mass of the prepolymer, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0057] (3) The emulsion was dispersed in an aqueous phase containing 1 wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500 cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.2% of the prepolymer mass of AIBN was added, and the reaction was carried out for 18 h under a pressure of 2 MPa and a temperature of 60 °C to form microspheres with a core-shell structure.

[0058] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0059] Example 7 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 40 parts of acrylonitrile, 20 parts of tricitrate (Hubei Tuoyuan Fine Chemical Co., Ltd., Citroflex® 2), 35 parts of glyceryl laurate (Hangzhou Fuchun Food Additives Co., Ltd., GML) and 10 parts of acrylated citrate (Kaiping Zicai Chemical Co., Ltd., ZC5601) were mixed, and 1% of the total mass of the polymerizing monomers was added as catalyst tetrabutyl titanate. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12 hours. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0060] (2) Mix the prepolymer with n-butane at a mass ratio of 1:10, add 2% of the prepolymer mass of bio-based emulsifier Span 80, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0061] (3) The emulsion was dispersed in an aqueous phase containing 3wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.5% of the prepolymer mass of AIBN was added, and the reaction was carried out for 24 hours under a pressure of 5 MPa and a temperature of 80°C to form microspheres with a core-shell structure.

[0062] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0063] Example 8 A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, wherein the preparation method comprises: (1) According to the weight parts, 45 parts of acrylonitrile, 40 parts of vanillin-based unsaturated monomer (Specific Polymers, SP-9 S-5-008), 10 parts of flaxseed oil epoxy ester (Zhejiang Xingbang Polymer Materials Co., Ltd., EPOXOL 9-5) and 5 parts of methacrylated glyceryl ester (Guangzhou Yuanda New Materials Co., Ltd., GMA) were mixed, and 0.2% of the total mass of the polymerizing monomers of catalyst stannous octoate was added. Under nitrogen protection, the temperature was set at 120℃ and the polycondensation reaction was carried out for 12h. The acid value was monitored in real time. When the acid value was ≤5m parts KOH / g, the reaction was stopped to obtain a prepolymer with a number average molecular weight of 2000-8000.

[0064] (2) Mix the prepolymer and isobutane at a mass ratio of 1:5, add 1% of the prepolymer mass of bio-based emulsifier Span80, and emulsify at high speed of 5000 rpm for 10 min to form a uniform emulsion.

[0065] (3) The emulsion was dispersed in an aqueous phase containing 1 wt% natural stabilizer sodium alginate (Lianyungang Huanyu Algae Additives Co., Ltd., 50-500 cps), wherein the mass ratio of the emulsion to the aqueous phase was 1:1. Then, 0.2% of the prepolymer mass of AIBN was added, and the reaction was carried out for 18 h under a pressure of 2 MPa and a temperature of 60 °C to form microspheres with a core-shell structure.

[0066] (4) Place the microspheres in a centrifuge, set the speed to 5000 rpm, and centrifuge for 10 min; then place the centrifuged microspheres in an oven at 60℃ for 12 h to prepare bio-based thermal expansion microspheres.

[0067] Comparative Example 1 Thermally expandable microspheres were prepared using the same method as in Example 1, except that no bio-based rigid monomer was added in step (1) of Comparative Example 1, and the other process conditions were the same as in Example 1.

[0068] Comparative Example 2 Thermally expandable microspheres were prepared using the same method as in Example 1, except that no bio-based flexible monomer was added in step (1) of Comparative Example 2, and the other process conditions were the same as in Example 1.

[0069] Comparative Example 3 Thermally expandable microspheres were prepared using the same method as in Example 1, except that no functional monomer was added in step (1) of Comparative Example 3, and the other process conditions were the same as in Example 1.

[0070] Comparative Example 4 Thermally expandable microspheres were prepared using the same method as in Example 1, except that in step (1) of Comparative Example 4, the proportion of bio-based rigid monomers was reduced and the proportion of bio-based flexible monomers was increased.

[0071] The monomer composition used in step (1) of Comparative Example 4, by weight, is as follows: 50 parts acrylonitrile, 5 parts dimethyl furanate, 40 parts castor oil epoxy ester, and 5 parts acrylated citrate.

[0072] Other process conditions are the same as in Example 1.

[0073] Comparative Example 5 Thermally expandable microspheres were prepared using the same method as in Example 1, except that in step (1) of Comparative Example 5, the proportion of bio-based rigid monomers was increased and the proportion of bio-based flexible monomers was decreased.

[0074] The monomer composition used in step (1) of Comparative Example 5, by weight, is as follows: 50 parts acrylonitrile, 42 parts dimethyl furanate, 3 parts castor oil epoxy ester, and 5 parts acrylated citrate.

[0075] Other process conditions are the same as in Example 1.

[0076] Comparative Example 6 Thermally expandable microspheres were prepared using the same method as in Example 1, except that the proportion of functional monomers added was increased in step (1) of Comparative Example 6.

[0077] The monomer composition used in step (1) of Comparative Example 6, by weight, is as follows: 40 parts acrylonitrile, 30 parts dimethyl furanate, 15 parts castor oil epoxy ester, and 15 parts acrylated citrate.

[0078] Comparative Example 7 Thermally expandable microspheres were prepared using the same method as in Example 1, except that the polymerization reaction temperature in step S3 of Comparative Example 7 was 90°C (higher than the temperature conditions specified in this invention).

[0079] Comparative Example 8 Thermally expandable microspheres were prepared using the same method as in Example 1, except that the polymerization reaction pressure in step S3 of Comparative Example 8 was 6 MPa (higher than the pressure conditions specified in this invention).

[0080] The thermal expansion microspheres prepared in the above embodiments and comparative examples were subjected to performance tests. The specific test results are shown in Table 1 below. The test methods involved are as follows: Scanning electron microscope (SEM) was used to observe the gold-plated microspheres for 120 seconds to test their size. Static thermomechanical analysis (TMA) was performed at a heating rate of 5°C / min and a force of 0.06N to test the initial foaming temperature, maximum foaming temperature, and expansion ratio of the microspheres. True density meter, gas displacement method, to test the TMA density of microspheres.

[0081] Table 1 Performance Test Data

[0082] As can be seen from the data in the table above, the thermally expandable microspheres prepared by the method described in this invention in Examples 1-8 have smaller sizes, higher foaming temperatures, a certain foaming temperature range, and larger expansion ratios. Furthermore, from... Figure 1 It can be seen that the microspheres are relatively uniform.

[0083] The comparison between the results of Comparative Example 1 and Example 1 shows that if no bio-based rigid monomer is added, the microsphere particle size increases and foaming is impossible because the structural stability and mechanical strength decrease significantly.

[0084] A comparison of the results from Comparative Example 2 and Example 1 shows that without the addition of bio-based flexible monomers, the microsphere particle size increases, making foaming impossible due to significantly increased brittleness and difficulty in forming microspheres. Therefore, the synergistic combination of bio-based rigid monomers and bio-based flexible monomers is more conducive to obtaining bio-based thermally expandable microspheres with excellent overall performance.

[0085] The comparison between the results of Comparative Example 3 and Example 1 shows that if no functional monomer is added, the microsphere particle size increases, the foaming temperature range decreases, and the foaming ratio decreases because the thermal stability of the microsphere shell cannot be adjusted.

[0086] The comparison between the results of Comparative Example 4 and Example 1 shows that if the proportion of bio-based rigid monomers is reduced and the proportion of bio-based flexible monomers is increased, the foaming temperature range is reduced and the foaming ratio is decreased. This is because the mechanical strength of the microspheres decreases but the flexibility increases, accompanied by a chain reaction such as reduced thermal stability and changes in morphology controllability.

[0087] A comparison of the results from Comparative Example 5 and Example 1 shows that increasing the proportion of bio-based rigid monomers and decreasing the proportion of bio-based flexible monomers reduces the foaming temperature range and foaming ratio. This is because it significantly improves the mechanical strength and thermal stability of the microspheres, but decreases their flexibility and spheroidization tolerance, while also increasing the risk of morphological defects. Therefore, a balanced ratio of bio-based rigid monomers and bio-based flexible monomers is more conducive to obtaining high-performance bio-based thermally expandable microspheres.

[0088] The comparison between the results of Comparative Example 6 and Example 1 shows that if the proportion of functional monomers added is increased, it is impossible to form spheres because the mechanical properties are unbalanced and the difficulty of forming spheres increases.

[0089] The comparison between the results of Comparative Example 7 and Example 1 shows that if the polymerization reaction temperature increases, the microsphere particle size becomes smaller, the thermal stability decreases, and the functional performance is impaired because the polymerization rate increases.

[0090] The comparison between the results of Comparative Example 8 and Example 1 shows that if the polymerization reaction pressure increases, the microsphere particle size becomes smaller and the thermal stability decreases, because the pressure changes the solubility of volatile components, the surface tension of the system, and the probability of molecular collisions.

[0091] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing controllable thermal expansion microspheres based on bio-based copolymers, characterized in that, The preparation method is as follows: S1, vinyl nitrile monomers, bio-based rigid monomers, bio-based flexible monomers and functional monomers undergo polycondensation reaction under the action of a catalyst to obtain a prepolymer; S2. The prepolymer is mixed with a foaming agent and a bio-based emulsifier is added to emulsify the mixture and obtain a uniform emulsion. S3. Disperse the emulsion in the aqueous phase of a natural stabilizer, add an initiator, and carry out a polymerization reaction under a certain temperature and pressure to form microspheres with a core-shell structure. S4. After solid-liquid separation and drying, thermally expanded microspheres are obtained.

2. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, The amounts of each monomer added in step S1, by weight, are as follows: 40-50 parts of vinyl nitrile monomers; 20-40 parts of bio-based rigid monomers; 10-35 parts of bio-based flexible monomers; and 5-10 parts of functionalized monomers.

3. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, The vinyl nitrile monomer is at least one of acrylonitrile and methacrylonitrile; The bio-based rigid monomer is at least one of furanyl dicarboxylate, vanillin-based unsaturated monomer, lignin derivative, isosorbide derivative, 5-hydroxymethylfurfural ester, and tricitrate. The flexible monomer is at least one of castor oil epoxy ester, linseed oil epoxy ester, soybean oil-based polyol, methyl palmitate, and glyceryl laurate. The functional monomer is at least one of acrylated citrate, methacrylated glyceryl ester, and acrylated itaconic acid ester.

4. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S1, the catalyst is at least one of stannous octoate and tetrabutyl titanate; The amount of catalyst added is 0.1-1% of the total mass of the polymer monomers.

5. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S1, the temperature of the polycondensation reaction is 110-120℃. The acid value is monitored in real time during the polycondensation reaction. The reaction is stopped when the acid value is ≤5mg KOH / g, and a prepolymer with a number average molecular weight of 2000-8000 is obtained.

6. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S2, the foaming agent is a low-boiling-point alkane, and the low-boiling-point alkane is at least one of n-butane, isobutane, n-pentane, and isopentane. The bio-based emulsifier is at least one of Span 80 and Tween 60.

7. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S2, the mass ratio of the prepolymer to the foaming agent is 1:(3-10); the amount of the bio-based emulsifier added is 0.5-2% of the mass of the prepolymer.

8. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S3, the natural stabilizer is at least one of sodium alginate and gelatin; the mass concentration of the natural stabilizer in the aqueous phase is 0.5-3%. The initiator is azobisisobutyronitrile; the amount of the initiator added is 0.1-0.5% of the mass of the prepolymer.

9. The method for preparing controllable thermal expansion microspheres based on bio-based copolymers according to claim 1, characterized in that, In step S3, the pressure conditions of the polymerization reaction are 0.4-5 MPa, the temperature of the polymerization reaction is 50℃-80℃, and the time of the polymerization reaction is 10-24 h.

10. A controllable thermal expansion microsphere based on a bio-based copolymer, characterized in that, The thermally expandable microspheres are prepared according to the preparation method described in any one of claims 1-9.

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