Process for the preparation of thermoplastic epoxy acrylate elastomers by low temperature emulsion polymerization

Abstract

The present application relates to a kind of thermoplastic epoxy acrylate elastomer prepared by low temperature emulsion polymerization method, comprising the following steps: (1) preparation of pre-emulsion, (2) preparation of aqueous solution of redox system, (3) emulsion polymerization process;Using the redox system combined by persulfate / organic peroxide, ferrous sulfate heptahydrate and complexing agent, sodium formaldehyde sulfoxylate, high molecular weight epoxy acrylate elastomer without gel is prepared by smooth reaction process, the processing performance and mechanical properties of epoxy acrylate elastomer are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of thermoplastic elastomer preparation, and relates to a method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization. Background Technology

[0002] Acrylic rubber (ACM) is a macromolecular polymer obtained by copolymerization of acrylate as the main monomer, and belongs to special rubber. In the synthetic rubber industry, gel content is a very important indicator. The gel content of general rubber is generally <1%, because once the gel content exceeds this value, it will lead to: (1) the raw rubber is not easy to absorb materials and processing is difficult; (2) the vulcanizing agent, additives and raw rubber are not mixed evenly, and the vulcanization is incomplete. The gel part will cause the internal molecular structure of rubber products to be uneven. For the preparation of acrylic rubber with epoxy groups as crosslinking points (referred to as epoxy ACM), due to the high activity of epoxy groups, they are easily affected by polar reagents and the environment, resulting in ring-opening crosslinking and increased gel content. Therefore, the control of gel content has become the primary problem that must be solved in the preparation of epoxy ACM.

[0003] Existing solution or bulk polymerization methods for preparing acrylamide (ACM) are mostly carried out at low temperatures (<100℃). This results in high system viscosity, difficulty in heat dissipation, unstable reaction, severe gelation, and high gel content in the product. Deng Zhengdong of Zhejiang University (Reaction Characteristics of High-Temperature Solution Polymerization and Bulk Polymerization of Epoxy-Based Acrylic Rubber) studied the reaction characteristics of a copolymerization system of butyl acrylate (BA) and glycidyl methacrylate (GMA) to prepare epoxy-based ACM in high-temperature solution polymerization (105–125℃) and bulk polymerization (140–180℃). While this method is beneficial for synthesizing low-gel ACM, the synthesized ACM has a low molecular weight and a wide molecular weight distribution, affecting the mechanical properties of the rubber.

[0004] Furthermore, while commonly used emulsion polymerization techniques are beneficial for reducing gel content, they cannot completely eliminate it, still posing difficulties for ACM processing. The synthesis of ACM is prone to gel formation, and these methods often involve feeding the system in a "starved" state to the monomers. The polymerization process is complex, not cost-effective, and prolongs the reaction time. Chinese patent CN101914181B mentions low-temperature emulsion polymerization, employing a redox ternary system and a "starved" feeding method to synthesize epoxy ACM with butyl acrylate as the main monomer. This synthesis process is complex, and it still exhibits a gel content of 3-10%, posing difficulties for subsequent rubber vulcanization and processability. Summary of the Invention

[0005] In view of this, in order to solve the problems of complex process, high gel content and difficulties in subsequent rubber vulcanization and processability in the preparation of epoxy ACM by existing low-temperature emulsion polymerization technology, the present invention provides a method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization includes the following steps:

[0008] (1) Preparation of preemulsion

[0009] Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15-45:0.2100-1.5750:0.0075-0.0750:0.10-1.00. The temperature was controlled at 5-40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion.

[0010] The monomer is an acrylate monomer, a sulfurized monomer, and other functional monomers mixed to form a comonomer, in which the sulfurized monomer accounts for 3-15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution;

[0011] (2) Preparation of aqueous solutions for redox systems

[0012] ① First redox complex system:

[0013] The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 1–4.17:1:1–7.5.

[0014] The preparation method of the first redox complex system is as follows: 0.01-5% by mass of a water-soluble oxidant, such as a persulfate oxidant, is prepared into a 5% by mass aqueous solution; ferrous sulfate heptahydrate and a complexing agent are combined in a mass ratio of 1:0.5-5 to form a main reducing agent complex, which is prepared into a 5% by mass aqueous solution, wherein the main reducing agent is 0.005-1.2% by mass of the monomer; and 0.05-4% by mass of a secondary reducing agent, sodium formaldehyde sulfoxylate, is prepared into a 5% by mass aqueous solution. The three solutions are placed separately.

[0015] ② Second redox complex system:

[0016] The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 0.5–5:1:1–10.

[0017] The preparation method of the second redox complex system is as follows: 0.02–6% by mass of an organic peroxide oxidant is prepared into a 5% by mass aqueous solution containing 0.1% emulsifier; a 5% by mass aqueous solution is prepared by combining ferrous sulfate heptahydrate and a complexing agent in a mass ratio of 1:0.5–5 to form a complexing agent complex; the main reducing agent is 0.004–1.5% by mass of the monomer; and a 5% by mass aqueous solution is prepared by combining 0.05–4% by mass of sodium formaldehyde sulfoxylate, a secondary reducing agent; the three solutions are placed separately.

[0018] ③ A mixture of the first and second redox complex systems:

[0019] The preparation of the aqueous solution for the first redox complex system is the same as step ① above, and the preparation of the aqueous solution for the second redox complex system is the same as step ② above. The sum of the proportions of the oxidant aqueous solution, the main reducing agent complex aqueous solution, and the secondary reducing agent aqueous solution prepared for both redox systems is 100%. That is, if 40% of the oxidant aqueous solution prepared for the first redox system is taken, then 60% of the oxidant aqueous solution prepared for the second redox system is taken; if 40% of the main reducing agent complex aqueous solution prepared for the first redox system is taken, then 60% of the main reducing agent complex aqueous solution prepared for the second redox system is taken; if 40% of the secondary reducing agent aqueous solution prepared for the first redox system is taken, then 60% of the secondary reducing agent aqueous solution prepared for the second redox system is taken.

[0020] (3) Emulsion polymerization process

[0021] The redox system is a mixture of the first redox complex system and the second redox complex system.

[0022] Under stirring at 150 rpm and nitrogen purging, the reaction temperature was controlled at 5–40 °C. In the pre-emulsion prepared in step (1), 40% of the main reducing agent ferrous sulfate complex aqueous solution and 40% of the secondary reducing agent sodium formaldehyde bisulfite aqueous solution of the first redox system were simultaneously added to the four-necked flask containing the pre-emulsion. After stirring for 15 min, 40% of the oxidizing agent persulfate aqueous solution of the first redox system was added, and the reaction started immediately. At the 60 min of exothermic reaction, 15% of the emulsifier solution was added. At the same time, 60% of the main reducing agent ferrous sulfate complex aqueous solution and 60% of the secondary reducing agent sodium formaldehyde bisulfite aqueous solution of the second redox system were simultaneously added to the four-necked flask containing the pre-emulsion. After stirring for 15 min, 60% of the oxidizing agent organic peroxide aqueous solution of the second redox system was added. At the 120 min of exothermic reaction, 15% of the emulsifier solution was added. The polymerization reaction was continued for 2–8 hours under nitrogen protection until the polymer emulsion with a conversion rate of over 98% was obtained. The polymer emulsion was then demulsified by freezing, and the resulting polymer solid was washed with water 6–8 times and dried at 120–140°C for 12 hours to obtain a thermoplastic epoxy ACM elastomer.

[0023] Furthermore, a method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization includes the following steps:

[0024] (1) Preparation of preemulsion

[0025] Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15-45:0.2100-1.5750:0.0075-0.0750:0.10-1.00. The temperature was controlled at 5-40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion.

[0026] The monomer is an acrylate monomer, a sulfurized monomer, and other functional monomers mixed to form a comonomer, in which the sulfurized monomer accounts for 3-15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution;

[0027] (2) Preparation of aqueous solutions for redox systems

[0028] First redox complex system:

[0029] The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 1–4.17:1:1–7.5.

[0030] The preparation method of the first redox complex system is as follows: 0.01-5% by mass of a water-soluble oxidant, such as a persulfate oxidant, is prepared into a 5% by mass aqueous solution; ferrous sulfate heptahydrate and a complexing agent are combined in a mass ratio of 1:0.5-5 to form a main reducing agent complex, which is prepared into a 5% by mass aqueous solution, wherein the main reducing agent is 0.005-1.2% by mass of the monomer; and 0.05-4% by mass of a secondary reducing agent, sodium formaldehyde sulfoxylate, is prepared into a 5% by mass aqueous solution. The three solutions are placed separately.

[0031] (3) Emulsion polymerization process

[0032] The redox system is the first redox complex system.

[0033] Under stirring at 150 rpm and nitrogen purging, the reaction temperature was controlled at 5–40 °C. The main reducing agent, ferrous sulfate complex aqueous solution, and the secondary reducing agent, sodium formaldehyde sulfoxylate aqueous solution, were simultaneously added to the four-necked flask containing the pre-emulsion in step (1). The mixture was stirred for 15 min, and then an aqueous solution of persulfate oxidant was added to initiate the reaction. At 60 min and 120 min of exothermic reaction, an average of 15% emulsifier solution was added. The mixture was kept at a constant temperature for 2–8 h under nitrogen protection until the polymerization reaction ended, resulting in a polymer emulsion with a conversion rate of over 98%. The polymer emulsion was demulsified by freezing, and the resulting polymer solid was washed with pure water 6–8 times. The solid was then dried at 120–140 °C for 12 h to obtain a thermoplastic epoxy-type ACM elastomer.

[0034] Furthermore, a method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization includes the following steps:

[0035] (1) Preparation of preemulsion

[0036] Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15-45:0.2100-1.5750:0.0075-0.0750:0.10-1.00. The temperature was controlled at 5-40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion.

[0037] The monomer is an acrylate monomer, a sulfurized monomer, and other functional monomers mixed to form a comonomer, in which the sulfurized monomer accounts for 3-15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution;

[0038] (2) Preparation of aqueous solutions for redox systems

[0039] Second redox complex system:

[0040] The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 0.5–5:1:1–10.

[0041] The preparation method of the second redox complex system is as follows: 0.02–6% by mass of an organic peroxide oxidant is prepared into a 5% by mass aqueous solution containing 0.1% emulsifier; a 5% by mass aqueous solution is prepared by combining ferrous sulfate heptahydrate and a complexing agent in a mass ratio of 1:0.5–5 to form a complexing agent complex; the main reducing agent is 0.004–1.5% by mass of the monomer; and a 5% by mass aqueous solution is prepared by combining 0.05–4% by mass of sodium formaldehyde sulfoxylate, a secondary reducing agent; the three solutions are placed separately.

[0042] (3) Emulsion polymerization process

[0043] The redox system is a second redox complex system.

[0044] Under stirring at 150 rpm and nitrogen purging, the reaction temperature was controlled at 5–40 °C. The main reducing agent, ferrous sulfate complex aqueous solution, and the secondary reducing agent, sodium formaldehyde sulfoxylate aqueous solution, were simultaneously added to the four-necked flask containing the pre-emulsion in step (1). The mixture was stirred for 15 min, and then an organic peroxide oxidant aqueous solution was added to initiate the reaction. At 60 min and 120 min of exothermic reaction, an average of 15% emulsifier solution was added. The mixture was kept at a constant temperature for 2–8 h under nitrogen protection until the polymerization reaction ended, resulting in a polymer emulsion with a conversion rate of over 98%. The polymer emulsion was demulsified by freezing, and the resulting polymer solid was washed with pure water 6–8 times. The solid was then dried at 120–140 °C for 12 h to obtain a thermoplastic epoxy-type ACM elastomer.

[0045] Furthermore, in the first redox complex system, the persulfate oxidant is one or more of sodium persulfate, potassium persulfate, or ammonium persulfate, the main reducing agent is ferrous sulfate heptahydrate, and the complexing agent is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

[0046] Furthermore, in the second redox complex system, the organic peroxide oxidant is a reactive oxygen species. The reagent is one or more of the following: alkyl hydroperoxide, methylcyclohexane hydroperoxide, cumene peroxide, dicumene peroxide, tert-butyl hydroperoxide, or benzoyl peroxide. The main reducing agent is ferrous sulfate heptahydrate, and the complexing agent is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

[0047] Furthermore, the pH buffer is one or both of sodium bicarbonate and sodium dodecahydrate phosphate.

[0048] Furthermore, the molecular weight regulator is one or both of dodecyl mercaptoethanol and mercaptoethanol.

[0049] Furthermore, the emulsifier is one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, nonylphenol polyoxyethylene ether, sodium dodecyl sulfate, or sodium dibutylnaphthalene sulfonate.

[0050] Furthermore, the sulfiding monomer is one or more of glycidyl methacrylate, glycidyl acrylate, and allyl glycidyl ether.

[0051] The beneficial effects of this invention are as follows:

[0052] 1. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization disclosed in this invention adopts a one-pot low-temperature emulsion polymerization (5-40℃). At low temperature, the ring-opening reaction of epoxy groups can be effectively reduced. The synthesis process is simple, low-cost, and has a high yield.

[0053] 2. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization disclosed in this invention employs a composite ternary initiation system of redox reaction (persulfate / organic peroxide, ferrous sulfate heptahydrate and complexing agent, formaldehyde sodium bisulfite), which slowly releases Fe... 2+ Controlling the reaction rate during the synthesis process can effectively control the release of heat during the reaction, greatly weaken the ring-opening reaction of epoxy groups, reduce the occurrence of gelation reaction, and enable the synthesis of gel-free epoxy ACM with high molecular weight and low molecular weight distribution, which can improve the mechanical properties and processing properties of rubber.

[0054] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] Existing solution / bulk polymerization technologies result in high system viscosity at low temperatures (<100℃), hindering heat dissipation and leading to high gel content, which is detrimental to improving rubber processing properties. Conversely, ACM synthesized at high temperatures exhibits low molecular weight and a wide molecular weight distribution, which is also unfavorable for enhancing ACM's mechanical properties. While existing emulsion polymerization technologies are beneficial for reducing gel content, they cannot completely eliminate it, still posing challenges to ACM processing. Alternatively, they may require comonomers to be fed in a "starved" state, resulting in a complex polymerization process that is not conducive to cost savings.

[0057] This invention utilizes a simple synthesis process (one-pot low-temperature emulsion polymerization) and employs a redox complex system composed of persulfates / organic peroxides, ferrous sulfate heptahydrate complexes, and sodium formaldehyde bisulfite to prepare gel-free, high-molecular-weight epoxy ACM through a stable reaction process, which significantly improves the processing and mechanical properties of epoxy ACM.

[0058] Example 1

[0059] A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization includes the following steps:

[0060] (1) Preparation of preemulsion

[0061] A comonomer formed by mixing water, acrylate monomers, sulfur monomers, and other functional monomers, along with 70% emulsifier, molecular weight regulator, and pH buffer, was added to a four-necked flask at a mass ratio of 100:25:0.7:0.0125:0.1. Specifically, 500g ultrapure water, 100g butyl acrylate, 18.75g styrene, 6.25g glycidyl methacrylate, 2.625g sodium dodecylbenzenesulfonate, 0.875g nonylphenol polyoxyethylene ether, 0.0625g dodecyl mercaptan, and 0.5g sodium bicarbonate were added. The temperature was controlled at 5°C, and the mixture was stirred at 500 rpm while nitrogen gas was simultaneously introduced for 30 minutes to obtain a pre-emulsified emulsion.

[0062] The sulfurized monomers in the above monomers account for 5% of the total monomers, and the emulsifiers are prepared as an aqueous solution with a mass fraction of 10%.

[0063] (2) Preparation of aqueous solutions for redox systems

[0064] The redox mixed system is a mixture of the first redox complex system and the second redox complex system;

[0065] The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 3:1:2.

[0066] The preparation method of the first redox complex system is as follows: Potassium persulfate, an oxidant of 0.03% by mass, is prepared into a 5% aqueous solution, wherein the mass of potassium persulfate is 0.0375 g; Ferrous sulfate heptahydrate, a monomer of 0.01% by mass, and disodium ethylenediaminetetraacetate are combined at a mass ratio of 1:0.5 to form a main reducing agent complex, which is then prepared into a 5% aqueous solution, i.e., ferrous sulfate heptahydrate has a mass of 0.0125 g and disodium ethylenediaminetetraacetate has a mass of 0.0063 g; sodium formaldehyde bisulfite, a monomer of 0.02% by mass, is prepared into a 5% aqueous solution, wherein the mass of sodium formaldehyde bisulfite is 0.025 g. The three solutions are placed separately.

[0067] The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 2:1:2.

[0068] The preparation method of the second redox complex system is as follows: 0.02% by mass of cumene hydroperoxide is prepared into a 5% aqueous solution containing 0.1% emulsifier (any of the above emulsifiers is acceptable), wherein the mass of cumene hydroperoxide is 0.025g; 0.01% by mass of ferrous sulfate heptahydrate and disodium ethylenediaminetetraacetate are combined in a mass ratio of 1:1 to form a main reducing agent complex, which is then prepared into a 5% aqueous solution, wherein the mass of ferrous sulfate heptahydrate is 0.0125g and the mass of disodium ethylenediaminetetraacetate is 0.0125g; 0.02% by mass of sodium formaldehyde bisulfite is prepared into a 5% aqueous solution, wherein the mass of sodium formaldehyde bisulfite is 0.025g. The three solutions are placed separately.

[0069] (3) Emulsion polymerization process

[0070] Under nitrogen purging and stirring at 150 rpm, with the reaction temperature controlled at 5°C, 40% of the main reducing agent (ferrous sulfate heptahydrate complex aqueous solution) and 40% of the secondary reducing agent (sodium formaldehyde bisulfite aqueous solution) of the first redox system were simultaneously added to the four-necked flask containing the pre-emulsion. The mixture was stirred for 15 min, and then 40% of the oxidizing agent (potassium persulfate aqueous solution) of the first redox system was added, initiating the reaction immediately. At the 60-minute mark of exothermic reaction, 15% of the emulsifier solution was added. Simultaneously, 60% of the main reducing agent (ferrous sulfate heptahydrate complex aqueous solution) and 60% of the secondary reducing agent (sodium formaldehyde bisulfite aqueous solution) of the second redox system were added to the same four-necked flask containing the pre-emulsion. The mixture was stirred for 15 min, and then 60% of the oxidizing agent (cumene hydroperoxide aqueous solution) of the second redox system was added. At the 120-minute mark of exothermic reaction, 15% of the emulsifier solution was added. The mixture was kept at this temperature for 4 hours under nitrogen protection, at which point the polymerization reaction was complete, yielding a polymer emulsion with a conversion rate of 98.0%. The polymer emulsion was demulsified by freezing, and the resulting polymer solid powder was washed with water 6-8 times and dried at 120°C for 12 hours to obtain a thermoplastic epoxy ACM elastomer.

[0071]

[0072] Example 2

[0073] A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization includes the following steps:

[0074] (1) Preparation of preemulsion

[0075] A comonomer formed by mixing water, acrylate monomers, sulfur monomers, and other functional monomers, along with 70% emulsifier, molecular weight regulator, and pH buffer, was added to a four-necked flask at a mass ratio of 100:40:1.4:0.0125:0.2. Specifically, 500g ultrapure water, 75g butyl acrylate, 75g ethyl acrylate, 30g styrene, 20g allyl glycidyl ether, 5.25g sodium dodecylbenzenesulfonate, 1.75g ​​nonylphenol polyoxyethylene ether, 0.0625g dodecyl mercaptan, and 1.0g sodium bicarbonate were added to the flask. The temperature was controlled at 10℃, and the mixture was stirred at 500 rpm while nitrogen gas was simultaneously introduced for 30 minutes to obtain a pre-emulsified emulsion.

[0076] The sulfurized monomers in the above monomers account for 10% of the total monomers, and the emulsifiers are prepared as an aqueous solution with a mass fraction of 10%.

[0077] (2) Preparation of aqueous solutions for redox systems

[0078] The redox system is a first redox complex system;

[0079] The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 4:1:2.

[0080] The preparation method of the first redox complex system is as follows: Ammonium persulfate, with a monomer mass of 0.04%, is prepared into a 5% aqueous solution, wherein the mass of ammonium persulfate is 0.08 g; Ferrous sulfate heptahydrate, with a monomer mass of 0.01%, and disodium ethylenediaminetetraacetate are combined in a mass ratio of 1:1 to form a main reducing agent complex, which is then prepared into a 5% aqueous solution, i.e., ferrous sulfate heptahydrate has a mass of 0.02 g and disodium ethylenediaminetetraacetate has a mass of 0.02 g; sodium formaldehyde bisulfite, with a monomer mass of 0.02%, is prepared into a 5% aqueous solution, wherein the mass of sodium formaldehyde bisulfite is 0.04 g. The three solutions are placed separately.

[0081] (3) Emulsion polymerization process

[0082] Under nitrogen purging and stirring at 150 rpm, with the reaction temperature controlled at 10°C, the main reducing agent (ferrous sulfate heptahydrate complex aqueous solution) and the secondary reducing agent (sodium formaldehyde bisulfite aqueous solution) of the first redox system were simultaneously added to the four-necked flask containing the pre-emulsion. After stirring for 15 min, the oxidizing agent (ammonium persulfate aqueous solution) of the first redox system was added, initiating the reaction immediately. A 15% emulsifier solution was added at 60 min of exothermic reaction and again at 120 min of exothermic reaction. The reaction was continued at this temperature for 4 h under nitrogen protection until the polymerization reaction was complete, yielding a polymer emulsion with a conversion rate of 99.12%. The polymer emulsion was demulsified by freeze treatment, and the resulting polymer solid was washed with water 6–8 times and dried at 120°C for 12 h to obtain a thermoplastic epoxy-type ACM elastomer.

[0083]

[0084] Example 3

[0085] (1) Preparation of preemulsion

[0086] A comonomer formed by mixing water, acrylate monomers, sulfur monomers, and other functional monomers, along with 70% emulsifier, molecular weight regulator, and pH buffer, was added to a four-necked flask at a mass ratio of 100:20:0.56:0.0125:0.1. Specifically, 500g ultrapure water, 50g butyl acrylate, 25g ethyl acrylate, 17.5g styrene, 7.5g glycidyl methacrylate, 2.1g sodium dodecylbenzenesulfonate, 0.7g nonylphenol polyoxyethylene ether, 0.0625g dodecyl mercaptan, and 0.5g sodium bicarbonate were added. The temperature was controlled at 30℃, and the mixture was stirred at 500 rpm while nitrogen gas was simultaneously introduced for 30 minutes to obtain a pre-emulsified emulsion.

[0087] The sulfurized monomers account for 7.5% of the total monomers, and the emulsifier is prepared as a 10% aqueous solution.

[0088] (2) Preparation of aqueous solutions for redox systems

[0089] The redox system is a second redox complex system;

[0090] The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 2:1:2.

[0091] The preparation method of the second redox complex system is as follows: 0.02% by mass of tert-butyl hydroperoxide is prepared into a 5% by mass aqueous solution containing 0.1% emulsifier (any of the above emulsifiers is acceptable), wherein the mass of tert-butyl hydroperoxide is 0.02g; 0.01% by mass of ferrous sulfate heptahydrate and disodium ethylenediaminetetraacetate are combined in a mass ratio of 1:2 to form a main reducing agent complex, which is then prepared into a 5% by mass aqueous solution, wherein the mass of ferrous sulfate heptahydrate is 0.01g and the mass of disodium ethylenediaminetetraacetate is 0.02g; 0.02% by mass of sodium formaldehyde bisulfite is prepared into a 5% by mass aqueous solution, wherein the mass of sodium formaldehyde bisulfite is 0.02g. The three solutions are placed separately.

[0092] (3) Emulsion polymerization process

[0093] Under nitrogen purging and stirring at 150 rpm, with the reaction temperature controlled at 30°C, the main reducing agent (ferrous sulfate heptahydrate complex aqueous solution) and the secondary reducing agent (formaldehyde sodium bisulfite aqueous solution) of the second redox system were simultaneously added to the four-necked flask containing the pre-emulsion. The mixture was stirred for 15 min, and then the oxidizing agent (tert-butyl hydrogen peroxide aqueous solution) of the second redox system was added. A 15% emulsifier solution was added at 60 min of exothermic reaction and again at 120 min of exothermic reaction. The mixture was kept at this temperature for 4 h under nitrogen protection until the polymerization reaction was complete, yielding a polymer emulsion with a conversion rate of 98.56%. The polymer emulsion was demulsified by freeze treatment, and the resulting polymer solid was washed with water 6–8 times and dried at 120°C for 12 h to obtain a thermoplastic epoxy-type ACM elastomer.

[0094]

[0095] The relevant testing methods include:

[0096] (1) Method for measuring gel content:

[0097] The method for determining the content of epoxy acrylate gel prepared by the present invention is as follows: Take 3g of epoxy acrylate elastomer prepared by the present invention, place it in a Soxhlet extractor (dissolve it in acetone for 24h) for extraction, the extraction time is 24h, the extraction solvent is acetone, take out the insoluble matter and dry it in an oven at 120-140℃ for 6h, take it out, put it in a desiccator, cool it and weigh it, and calculate the gel content.

[0098] Gel content = (Weight of sample after test / Weight of sample before test) * 100%

[0099] (2) Molecular weight measurement method:

[0100] In this invention, the weight-average and number-average molecular weights were determined using gel permeation chromatography and a standard curve based on standard polystyrene. Sample concentration: 0.01 g / mL; solvent: tetrahydrofuran; injection volume: 50 μL; flow rate: 1 mL / min; pressure: 2.94 × 10⁻⁶. 6 Pa.

[0101] (3) Method for measuring epoxy value:

[0102] The method for determining the epoxy value of the epoxy acrylate prepared in this invention is as follows: the epoxy value is determined by using an automatic potentiometric titrator and the hydrochloric acid-acetone method.

[0103] Titration principle:

[0104]

[0105] Epoxy content calculation:

[0106]

[0107] In the formula: epoxy value — unit mol / kg

[0108] C – Concentration of the NaOH standard solution, in mol / L

[0109] V0 — Volume of NaOH solution consumed in blank processing, in mL

[0110] V1 — The volume of NaOH solution consumed by the sample, in mL

[0111] M1 — Mass of the sample, in grams

[0112] (4) Conversion rate measurement method:

[0113] The method for determining the conversion rate of the epoxy acrylate elastomer prepared by this invention is as follows: Take a dry weighing bottle, weigh M1, take a small amount of emulsion into the weighing bottle, weigh M2, add a small amount of aqueous solution of polymerization inhibitor (for synthetic monomers) (e.g., 10% concentration), weigh M3, and put the weighing bottle into a vacuum drying oven at 60℃ until constant weight M4.

[0114] The monomer conversion rate is: [M4-M1-(M3-M2)*0.1-(M2-M1)*R1*R2] / [M2-M1-(M2-M1)*R1*R2]

[0115] Where R1: the percentage of water mass occupied by individual components

[0116] R2: Emulsifier as a percentage of monomer mass

[0117] As can be seen from the above examples, the thermoplastic epoxy acrylate elastomer prepared by this low-temperature emulsion polymerization method has a large molecular weight, a narrow molecular weight distribution (between 1.5 and 2.0), does not contain gel, and has a high conversion rate of over 98%.

[0118] This invention employs a redox ternary system, using trace amounts of ferrous sulfate heptahydrate complexed with disodium ethylenediaminetetraacetate, to slowly release Fe. 2+ By controlling the reaction rate, the heat release during the reaction is effectively reduced, thereby reducing the ring-opening reaction of epoxy groups. This is beneficial for the preparation of thermoplastic epoxy acrylate elastomers. At the same time, it avoids the initiation system from releasing a large number of active free radicals in a short time, prolonging the reaction time and improving the conversion rate (yield).

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization, characterized in that, Includes the following steps: (1) Preparation of pre-emulsion Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15~45:0.2100~1.5750:0.0075~0.0750:0.10~1.

00. The temperature was controlled at 5~40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion. The monomer is an acrylate monomer, a sulfurized monomer and other functional monomers are mixed to form a comonomer, in which the sulfurized monomer accounts for 3 to 15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution; (2) Preparation of aqueous solution of redox complex system ① First redox complex system: The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 1~4.17:1:1~7.5; The preparation method of the first redox complex system is as follows: 0.01-5% by mass of a water-soluble oxidant, persulfate oxidant, is prepared into a 5% by mass aqueous solution; ferrous sulfate heptahydrate and a complexing agent are combined in a mass ratio of 1:0.5-5 to form a main reducing agent complex, which is prepared into a 5% by mass aqueous solution, wherein the main reducing agent is 0.005-1.2% by mass of the monomer; and 0.05-4% by mass of a secondary reducing agent, sodium formaldehyde sulfoxylate, is prepared into a 5% by mass aqueous solution. The three solutions are placed separately. ② Second redox complex system: The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 0.5~5:1:1~10; The preparation method of the second redox complex system is as follows: 0.02-6% by mass of organic peroxide oxidant is prepared into an aqueous solution with a mass fraction of 5% and containing 0.1% emulsifier; ferrous sulfate heptahydrate and complexing agent are combined in a mass ratio of 1:0.5-5 to form a complexing aqueous solution with a mass fraction of 5%; the mass of the main reducing agent is 0.004-1.5% by mass of the monomer; and sodium formaldehyde bisulfite, a secondary reducing agent with a mass fraction of 0.05-4% by mass of the monomer, is prepared into an aqueous solution with a mass fraction of 5%. The three solutions are placed separately. (3) Emulsion polymerization process The redox system is a mixture of the first redox complex system and the second redox complex system in step (2). Under stirring at 150 rpm and nitrogen purging, the reaction temperature was controlled at 5-40℃. In the pre-emulsion prepared in step (1), 40% of the main reducing agent (ferrous sulfate complex aqueous solution) and 40% of the secondary reducing agent (sodium formaldehyde bisulfite aqueous solution) of the first redox system were simultaneously added to the four-necked flask containing the pre-emulsion. After stirring for 15 min, 40% of the oxidizing agent (persulfate aqueous solution) of the first redox system was added, initiating the reaction immediately. At the 60-minute mark of exothermic reaction, 15% of the emulsifier solution was added. Simultaneously, the main reducing agent (ferrous sulfate complex aqueous solution) of the second redox system was added... 60% of the pre-emulsion and 60% of the formaldehyde sodium bisulfite aqueous solution, a secondary reducing agent, were simultaneously added to the four-necked flask containing the pre-emulsion. The mixture was stirred for 15 minutes, and then 60% of the organic peroxide aqueous solution, an oxidant in the second redox system, was added. At the 120-minute mark of exothermic reaction, 15% of the emulsifier solution was added. The mixture was kept at a constant temperature for 2-8 hours under nitrogen protection until the polymerization reaction was complete, yielding a polymer emulsion with a conversion rate of over 98%. The polymer emulsion was demulsified by freezing, and the resulting polymer solid was washed with water 6-8 times and dried at 120-140°C for 12 hours to obtain a thermoplastic epoxy acrylate elastomer.

2. A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization, characterized in that, Includes the following steps: (1) Preparation of pre-emulsion Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15~45:0.2100~1.5750:0.0075~0.0750:0.10~1.

00. The temperature was controlled at 5~40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion. The monomer is an acrylate monomer, a sulfurized monomer and other functional monomers are mixed to form a comonomer, in which the sulfurized monomer accounts for 3 to 15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution; (2) Preparation of aqueous solution of redox system First redox complex system: The first redox complex system consists of a water-soluble oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the water-soluble oxidant, the primary reducing agent, and the secondary reducing agent is 1~4.17:1:1~7.5; The preparation method of the first redox complex system is as follows: 0.01-5% by mass of a water-soluble oxidant, persulfate oxidant, is prepared into a 5% by mass aqueous solution; ferrous sulfate heptahydrate and a complexing agent are combined in a mass ratio of 1:0.5-5 to form a main reducing agent complex, which is prepared into a 5% by mass aqueous solution, wherein the main reducing agent is 0.005-1.2% by mass of the monomer; and 0.05-4% by mass of a secondary reducing agent, sodium formaldehyde sulfoxylate, is prepared into a 5% by mass aqueous solution. The three solutions are placed separately. (3) Emulsion polymerization process The redox system is the first redox complex system in step (2). Under stirring at 150 rpm and nitrogen purging, the reaction temperature is controlled at 5~40℃. The main reducing agent, ferrous sulfate complex aqueous solution, and the secondary reducing agent, sodium formaldehyde bisulfite aqueous solution, are simultaneously added to the four-necked flask containing the pre-emulsion in step (1). The mixture is stirred for 15 min, and then an oxidizing agent, persulfate aqueous solution, is added to initiate the reaction. At 60 min and 120 min of exothermic reaction, an average of 15% emulsifier solution is added. The mixture is kept at a constant temperature for 2-8 h under nitrogen protection until the polymerization reaction ends, resulting in a polymer emulsion with a conversion rate of over 98%. The polymer emulsion is demulsified by freezing, and the obtained polymer solid is washed with pure water 6-8 times. The solid is then dried at 120~140℃ for 12 h to obtain a thermoplastic epoxy acrylate elastomer.

3. A method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization, characterized in that, Includes the following steps: (1) Preparation of pre-emulsion Water, monomer, 70% emulsifier, molecular weight regulator and pH buffer were added to a four-necked flask at a mass ratio of 100:15~45:0.2100~1.5750:0.0075~0.0750:0.10~1.

00. The temperature was controlled at 5~40℃, and nitrogen gas was simultaneously introduced into the flask while stirring at 500 rpm for 30 min to obtain a pre-emulsified emulsion. The monomer is an acrylate monomer, a sulfurized monomer and other functional monomers are mixed to form a comonomer, in which the sulfurized monomer accounts for 3 to 15% of the total monomer content; the emulsifier is prepared as a 10% by mass aqueous solution; (2) Preparation of aqueous solution of redox system Second redox complex system: The second redox complex system consists of an organic peroxide oxidant, a primary reducing agent, and a secondary reducing agent, wherein the mass ratio of the organic peroxide oxidant, the primary reducing agent, and the secondary reducing agent is 0.5~5:1:1~10; The preparation method of the second redox complex system is as follows: 0.02-6% by mass of organic peroxide oxidant is prepared into an aqueous solution with a mass fraction of 5% and containing 0.1% emulsifier; ferrous sulfate heptahydrate and complexing agent are combined in a mass ratio of 1:0.5-5 to form a complexing aqueous solution with a mass fraction of 5%; the mass of the main reducing agent is 0.004-1.5% by mass of the monomer; and sodium formaldehyde bisulfite, a secondary reducing agent with a mass fraction of 0.05-4% by mass of the monomer, is prepared into an aqueous solution with a mass fraction of 5%. The three solutions are placed separately. (3) Emulsion polymerization process The redox system is the second redox complex system in step (2). Under stirring at 150 rpm and nitrogen purging, the reaction temperature is controlled at 5~40℃. The main reducing agent, ferrous sulfate complex aqueous solution, and the secondary reducing agent, sodium formaldehyde bisulfite aqueous solution, are simultaneously added to the four-necked flask containing the pre-emulsion in step (1). The mixture is stirred for 15 min, and then an oxidizing agent, an organic peroxide aqueous solution, is added to initiate the reaction. At 60 min and 120 min of exothermic reaction, an average of 15% emulsifier solution is added. The mixture is kept at a constant temperature for 2~8 h under nitrogen protection until the polymerization reaction ends, resulting in a polymer emulsion with a conversion rate of over 98%. The polymer emulsion is demulsified by freezing, and the obtained polymer solid is washed with pure water 6~8 times. The solid is then dried at 120~140℃ for 12 h to obtain a thermoplastic epoxy acrylate elastomer.

4. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, In the first redox complex system, the persulfate oxidant is one or more of sodium persulfate, potassium persulfate, or ammonium persulfate, the main reducing agent is ferrous sulfate heptahydrate, and the complexing agent is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

5. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, In the second redox complex system, the organic peroxide oxidant is one or more of the following: p-oxane hydrogen peroxide, methylcyclohexane hydrogen peroxide, cumene peroxide, dicumene peroxide, tert-butyl hydrogen peroxide, or benzoyl peroxide; the main reducing agent is ferrous sulfate heptahydrate; and the complexing agent is ethylenediaminetetraacetic acid or disodium ethylenediaminetetraacetic acid.

6. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, The pH buffer is one or both of sodium bicarbonate and sodium dodecahydrate.

7. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, The molecular weight regulator is one or both of dodecyl mercaptoethanol and mercaptoethanol.

8. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, The emulsifier is one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, nonylphenol polyoxyethylene ether, sodium dodecyl sulfate, or sodium dibutylnaphthalene sulfonate.

9. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, The sulfiding monomer is one or more of glycidyl methacrylate, glycidyl acrylate, and allyl glycidyl ether; the other functional monomers are one or more of acrylonitrile, methacrylonitrile, styrene, diphenylethylene, and vinyl acetate.

10. The method for preparing thermoplastic epoxy acrylate elastomers by low-temperature emulsion polymerization according to any one of claims 1 to 3, characterized in that, The acrylate monomer is one or more of methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, and methyl methacrylate.

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