Aqueous phase suspension polymerization method of acrylonitrile, polyacrylonitrile and preparation method of polyacrylonitrile

Abstract

The invention provides a water-phase suspension polymerization method of acrylonitrile, polyacrylonitrile and a preparation method thereof, and relates to the technical field of carbon fiber spinning solution production, and the method comprises the following steps: preparing a suspension: preparing a water-phase composition containing an amphiphilic inorganic material; preparing an oil-phase composition containing acrylonitrile and an initiator, then mixing the water-phase composition and the oil-phase composition to obtain a layered liquid, and homogenizing the layered liquid to obtain a suspension; and polymerization: carrying out polymerization reaction on the suspension to obtain the polyacrylonitrile suspension. By adopting the suspending agent with negative potential on the surface, the initiator free radical with positive electricity dissolved in a water phase can be effectively adsorbed to form a new reaction site, so that a small amount of acrylonitrile mixed with water is subjected to aggregation reaction, and the conversion rate of acrylonitrile polymerization reaction is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon fiber spinning solution production, and specifically relates to an aqueous phase suspension polymerization method of acrylonitrile, polyacrylonitrile and a preparation method thereof. Background Art

[0002] Acrylonitrile is an important chemical raw material with the chemical formula CH2=CH-CN. It has high reactivity. Acrylonitrile suspension polymerization is a free radical polymerization method, in which the monomer is dispersed into small droplets in the water phase and the initiator initiates the reaction to form a polymer.

[0003] At present, the suspension polymerization method of acrylonitrile includes the following steps: (1) dispersion: acrylonitrile monomer is dispersed in water by stirring and emulsifier to form stable suspension droplets; (2) initiation: under the action of initiator (such as potassium persulfate, ammonium persulfate, etc.), the monomer undergoes free radical polymerization reaction; (3) polymerization: the polymerization reaction is carried out inside the droplets, and the generated polymer exists in the aqueous phase in the form of particles; (4) termination: the polymerization reaction is terminated by adding a terminator or lowering the reaction temperature; (5) separation and drying: the generated polymer (polyacrylonitrile) particles are separated by filtration or centrifugation, and then dried. This polymerization method can control the particle size distribution of polymer particles by adjusting the stirring speed, emulsifier dosage, etc., and due to the high specific heat capacity of water, the reaction heat is easy to dissipate, reducing the risk of local overheating of the reaction. At the same time, water as a solvent is more environmentally friendly and reduces the use of organic solvents.

[0004] However, the existing suspension polymerization technology of acrylonitrile has at least the following problems:

[0005] (1) Since acrylonitrile is a low water-soluble substance, the polymerization degree of acrylonitrile dissolved in water is low, resulting in a low conversion rate of acrylonitrile (monomer), thereby affecting the yield of the polymer.

[0006] (2) In suspension polymerization, the choice of emulsifier and stirring speed has a significant effect on the particle size distribution of the polymer, but it is difficult to accurately control these parameters, which can easily lead to uneven polymer particle size distribution.

[0007] (3) The use of organic solvents may result in the generation of by-products or the introduction of impurities during the reaction, which may affect the purity and performance of polyacrylonitrile (polymer). Summary of the invention

[0008] Therefore, the present invention provides an aqueous phase suspension polymerization method for acrylonitrile, polyacrylonitrile and a preparation method thereof, which can solve the technical problem of low acrylonitrile conversion rate in the existing acrylonitrile suspension polymerization technology.

[0009] In order to solve the above problems, the present invention provides an aqueous suspension polymerization method of acrylonitrile, comprising the following steps:

[0010] Preparing a suspension: preparing an aqueous phase composition containing an amphiphilic inorganic material; preparing an oil phase composition containing acrylonitrile and an initiator, then mixing the aqueous phase composition and the oil phase composition to obtain a layered liquid, and homogenizing the layered liquid to obtain a suspension;

[0011] Wherein, the surface of the amphiphilic inorganic material is negatively charged;

[0012] Polymerization: The suspension is polymerized to obtain a polyacrylonitrile suspension.

[0013] Furthermore, the contact angle of the amphiphilic inorganic material is 80-100°; and / or

[0014] The amphiphilic inorganic material is amphiphilic silicon dioxide; and / or

[0015] The amphiphilic inorganic material is prepared from a hydrophilic inorganic material; preferably, the hydrophilic inorganic material is a nanosphere; preferably, the particle size of the hydrophilic inorganic material is 10 to 100 nm.

[0016] Furthermore, in the step of preparing the suspension, the amphiphilic inorganic material is prepared by the following steps:

[0017] Dispersing a hydrophilic inorganic material in a solvent to obtain an inorganic material suspension; adding a mixture containing a silane coupling agent and a catalyst to the inorganic material suspension, then performing a reflux treatment, and then sequentially performing separation, washing, and drying to obtain the amphiphilic inorganic material;

[0018] Preferably, the solvent is toluene;

[0019] Preferably, the temperature of the reflux treatment is 115-125°C;

[0020] Preferably, the reflux treatment time is 3.5 to 4.5 hours;

[0021] Preferably, the silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane;

[0022] Preferably, the catalyst is one or more of sodium hydroxide, ammonia water, potassium hydroxide, and triethylamine;

[0023] Preferably, toluene is used for washing.

[0024] Furthermore, the volume ratio of the aqueous phase composition to the oil phase composition when mixed is 1:0.2-0.4; and / or

[0025] The step of preparing the aqueous phase composition comprises: ultrasonically dispersing the amphiphilic inorganic material into deionized water to obtain the aqueous phase composition; preferably, the mass ratio of the aqueous phase composition to the amphiphilic inorganic material is 1:0.01-0.05.

[0026] Furthermore, the step of preparing the oil phase composition includes: mixing acrylonitrile, an initiator, a comonomer, and a molecular weight regulator to obtain the oil phase composition;

[0027] Preferably, the mass ratio of acrylonitrile to initiator is 1:0.005-0.01; the mass ratio of acrylonitrile to comonomer is 1:0.001-0.005; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0005-0.001;

[0028] Preferably, the initiator is one or more of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile;

[0029] Preferably, the comonomer is one or more of itaconic acid, methyl acrylate, acrylic acid, vinyl acetate, styrene, and maleic anhydride;

[0030] Preferably, the silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane;

[0031] Preferably, the molecular weight regulator is one or more of n-dodecyl mercaptan, thioacetic acid, 2-mercaptoethanol, and n-octyl mercaptan.

[0032] Furthermore, in the step of preparing the suspension: the droplet diameter of the suspension is 80 to 200 μm; and / or

[0033] A homogenizer is used to homogenize the layered liquid; wherein the rotation speed of the homogenizer is 3000-4000 rpm.

[0034] Furthermore, in the polymerization step: a polymerization reaction occurs in the suspension while the suspension is stirred at a constant temperature;

[0035] Preferably, the polymerization reaction temperature is 50 to 90°C;

[0036] Preferably, the polymerization reaction time is 5 to 9 hours;

[0037] Preferably, the constant temperature stirring rate is 60-100 rpm.

[0038] In another aspect, the present invention provides a method for preparing polyacrylonitrile, comprising the following steps:

[0039] Preparation of polyacrylonitrile particles: filtering, washing and drying the polyacrylonitrile suspension in sequence to obtain polyacrylonitrile particles;

[0040] Wherein, the polyacrylonitrile suspension is obtained by the aqueous suspension polymerization method of acrylonitrile described in any one of the above;

[0041] Stirring and filtering: the polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile.

[0042] Furthermore, each of the polyacrylonitrile particles includes a polyacrylonitrile ball located in the inner layer, a polyacrylonitrile layer located in the outer layer, and an amphiphilic inorganic material located between the polyacrylonitrile ball and the polyacrylonitrile layer;

[0043] Preferably, the average diameter of the polyacrylonitrile beads is 80 to 200 μm; the average thickness of the polyacrylonitrile layer is 1 to 2 μm;

[0044] Preferably, the amphiphilic inorganic material is amphiphilic silicon dioxide;

[0045] Preferably, the conversion rate of acrylonitrile is above 96%; and / or

[0046] In the stirring and filtering steps: the stirring rate is 5000-8000 rpm; the stirring time is 2-3 hours; and / or

[0047] The method for preparing polyacrylonitrile further comprises: sequentially centrifuging and drying the filtrate to obtain a recovered amphiphilic inorganic material.

[0048] In another aspect, the present invention provides polyacrylonitrile, which is obtained by any of the preparation methods described above.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] 1. The present invention prepares an aqueous phase composition containing an amphiphilic inorganic material and an oil phase composition containing acrylonitrile and an initiator, mixes the aqueous phase composition and the oil phase composition to obtain a layered liquid, and then homogenizes the layered liquid to obtain a suspension; the obtained suspension is stirred to cause a polymerization reaction to obtain a polyacrylonitrile suspension; the above scheme of the present invention is described as follows: the amphiphilic inorganic material is used as a suspending agent, and its surface is negatively charged, which can effectively adsorb the positively charged initiator free radicals dissolved in the water phase to form new reaction sites, so that the acrylonitrile dissolved in water aggregates and reacts there, thereby improving the conversion rate of the acrylonitrile polymerization reaction.

[0051] 2. Furthermore, the suspending agent of the present invention is an inorganic nanoparticle, and the surface energy of the suspension formed by it is low, which can effectively hinder the fusion of small droplets, so that the size of the suspension (droplets) formed is uniform, thereby improving the problem of uneven particle size distribution of the polymer (polyacrylonitrile).

[0052] 3. Furthermore, the present invention uses amphiphilic silica as a suspending agent, which is an inorganic material and does not participate in the polymerization reaction, so it does not generate by-products or introduce impurities, and has almost no effect on the performance and stability of the product (polyacrylonitrile).

[0053] 4. On the other hand, the present invention provides a method for preparing polyacrylonitrile, which adopts the above-mentioned aqueous suspension polymerization method of acrylonitrile to obtain a polyacrylonitrile suspension, and then the polyacrylonitrile suspension is filtered, washed with water, and dried in sequence to obtain polyacrylonitrile particles; the obtained polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile; the filtrate is centrifuged and dried in sequence to obtain a recovered suspension; based on the above method, the recovery of amphiphilic silica is simple, easy to operate, and environmentally friendly, and can be reused, which can reduce the polymerization cost.

[0054] 5. In another aspect, the present invention provides polyacrylonitrile obtained by the above-mentioned preparation method of polyacrylonitrile; the average diameter of the polyacrylonitrile (microspheres) is 80 to 200 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0056] Figure 1 is an optical micrograph of the suspension in Example 1 of the present invention;

[0057] Figure 2 is a particle size distribution diagram of polyacrylonitrile obtained in Example 1 of the present invention;

[0058] Figure 3 is a particle size distribution diagram of polyacrylonitrile obtained in Comparative Example 2 of the present invention;

[0059] Figure 4 Schematic diagram of the structure of polyacrylonitrile particles in an embodiment of the present invention;

[0060] The reference numerals are: 1-polyacrylonitrile beads, 2-polyacrylonitrile layer, 3-amphiphilic silica. DETAILED DESCRIPTION

[0061] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0062] The present invention provides an aqueous suspension polymerization method for acrylonitrile, wherein the amphiphilic inorganic material is amphiphilic silica, and the amphiphilic silica does not react with reactants for forming polyacrylonitrile (i.e., initiators in an oil phase composition, etc.), and specifically comprises the following steps:

[0063] Preparation of suspension: dispersing hydrophilic silica in toluene to obtain a silica suspension; adding a mixture containing a silane coupling agent and a catalyst to the silica suspension, and then subjecting the mixture to a reflux treatment, and then successively separating solid matter by centrifugation, washing with toluene, and drying to obtain amphiphilic silica (i.e., silica having both lipophilicity and hydrophilicity) with a negatively charged surface and used as a suspending agent;

[0064] The hydrophilic silica is a nanosphere with a particle size of 10 to 100 nm. The surface tension of the nanosphere is low, which ensures that the formed suspension is more stable, is conducive to the smooth progress of the subsequent polymerization reaction, and avoids the demulsification phenomenon. At the same time, it can ensure that the polymer microspheres formed subsequently have a more uniform size and a smoother surface. The temperature of the reflux treatment is 115 to 125°C. The reflux treatment time is 3.5 to 4.5 hours. The contact angle of the obtained amphiphilic silica is 80°-100°. Preferably, the contact angle of the amphiphilic silica is 90°. Exceeding the temperature of the reflux treatment will cause the amphiphilicity of the nanosilica to deviate. For example, if the contact angle of the silica is less than 80°, it is hydrophilic, and if the contact angle is greater than 110°, it is lipophilic, thereby making the stability of the formed suspension worse.

[0065] Ultrasonic dispersion of the amphiphilic silica in deionized water to obtain a water phase composition; mixing acrylonitrile, an initiator, a comonomer, and a molecular weight regulator to obtain an oil phase composition; then adding the oil phase composition to the water phase composition for mixing to form a layered liquid with an oil phase in the upper layer and a water phase in the lower layer, and homogenizing the layered liquid with a homogenizer to obtain a suspension;

[0066] The mass ratio of the aqueous phase composition to the amphiphilic silica is 1:0.01-0.05; the mass ratio of acrylonitrile to the initiator is 1:0.005-0.01; the mass ratio of acrylonitrile to the comonomer is 1:0.001-0.005; the mass ratio of acrylonitrile to the molecular weight regulator is 1:0.0005-0.001; the volume ratio of the aqueous phase composition to the oil phase composition when mixed is 1:0.2-0.4; the speed of the homogenizer is 3000-4000rpm;

[0067] Polymerization: The suspension is stirred at a constant temperature, and a polymerization reaction occurs simultaneously to obtain a polyacrylonitrile suspension; preferably, the polymerization reaction temperature is 50 to 90° C.; the constant temperature stirring rate is 60 to 100 rpm; and the polymerization reaction time is 5 to 9 hours;

[0068] Based on the above method, an amphiphilic silica with a negatively charged surface is obtained and used as a suspending agent. Due to its negatively charged surface, it can effectively adsorb positively charged initiator free radicals dissolved in the water phase to form new reaction sites, thereby allowing a small amount of acrylonitrile dissolved in water to aggregate and react here, thereby improving the conversion rate of the acrylonitrile polymerization reaction.

[0069] In some embodiments, the silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidoxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane;

[0070] The catalyst is one or more of sodium hydroxide, ammonia water, potassium hydroxide and triethylamine;

[0071] The initiator is one or more of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile;

[0072] The comonomer is one or more of itaconic acid, methyl acrylate, acrylic acid, vinyl acetate, styrene and maleic anhydride;

[0073] The silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane;

[0074] The molecular weight regulator is one or more of n-dodecyl mercaptan, thioacetic acid, 2-mercaptoethanol and n-octyl mercaptan.

[0075] In another aspect, the present invention provides a method for preparing polyacrylonitrile, comprising the following steps:

[0076] Preparation of polyacrylonitrile particles: filtering, washing and drying the polyacrylonitrile suspension in sequence to obtain polyacrylonitrile particles;

[0077] Wherein, the polyacrylonitrile suspension is obtained by the aqueous suspension polymerization method of acrylonitrile described in any one of the above; Figure 4 As shown, each of the above-mentioned polyacrylonitrile particles includes a polyacrylonitrile ball 1 located in the inner layer, a polyacrylonitrile layer 2 located in the outer layer, and a plurality of amphiphilic silica (particles) 3 located between the polyacrylonitrile ball 1 and the polyacrylonitrile layer 2;

[0078] Preferably, the average diameter of the polyacrylonitrile beads is 80 to 200 μm; the average thickness of the polyacrylonitrile layer is 1 to 2 μm; preferably, the conversion rate of acrylonitrile is above 96%;

[0079] Stirring and filtering: Mix polyacrylonitrile particles with water, then stir and filter in sequence, and obtain polyacrylonitrile after drying the filter cake; wherein, the stirring rate is 5000-8000rmp; and the stirring time is 2-3h.

[0080] In some embodiments, the method for preparing polyacrylonitrile further comprises: sequentially centrifuging and drying the filtrate to obtain a recovered suspending agent (ie, the amphiphilic inorganic material).

[0081] In another aspect, the present invention provides polyacrylonitrile, which is obtained by any of the above preparation methods.

[0082] The present invention is further described below with reference to specific embodiments and comparative examples.

[0083] Example 1

[0084] This embodiment provides an aqueous suspension polymerization method for acrylonitrile, comprising the following steps:

[0085] Preparation of suspension: 3 g of hydrophilic silica nanospheres with an average particle size of 20 nm are dispersed in 80 ml of toluene to obtain a silica suspension; a mixture of 9 mmol of 3-mercaptopropyltriethoxysilane (silane coupling agent) and 9 mmol of triethylamine (catalyst) is added to the above silica suspension, and then after reflux treatment at 120° C. for 4 h, the solid matter is separated by centrifugation, washed with toluene and dried to obtain amphiphilic silica (particles) as a suspending agent; the contact angle of the amphiphilic silica is 90°;

[0086] 20 g of acrylonitrile, 0.12 g of dicumyl peroxide (initiator), 0.04 g of methyl acrylate (comonomer), and 0.018 g of n-dodecyl mercaptan (molecular weight regulator) were mixed to prepare an oil phase composition;

[0087] 3 g of the above-mentioned amphiphilic silica was ultrasonically dispersed in 100 ml of deionized water to prepare an aqueous phase composition; then the oil phase composition was added to the aqueous phase composition and mixed to form a layered liquid with the oil phase in the upper layer and the aqueous phase in the lower layer; then the layered liquid was homogenized by a homogenizer to obtain a suspension;

[0088] The mass ratio of acrylonitrile to initiator is 1:0.006; the mass ratio of acrylonitrile to comonomer is 1:0.002; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0009; the mass ratio of aqueous phase composition to amphiphilic silica is 1:0.03; the volume ratio of aqueous phase composition to oil phase composition when mixed is 1:0.2; the speed of the homogenizer is 3000rpm;

[0089] Polymerization: The suspension is placed in a reaction vessel to undergo a polymerization reaction while being stirred at a constant temperature to obtain a polyacrylonitrile suspension; wherein the polymerization reaction temperature is 55°C, the stirring rate is 80 rpm, and the stirring time is 7 hours.

[0090] Based on the above polymerization method of this embodiment, polyacrylonitrile is prepared, comprising the following steps:

[0091] Preparation of polyacrylonitrile particles: After the reaction is completed, the polyacrylonitrile suspension is filtered, washed with water, and dried in sequence to obtain polyacrylonitrile particles; the polyacrylonitrile particles include a polyacrylonitrile ball located in an inner layer, a polyacrylonitrile layer located in an outer layer, and a plurality of amphiphilic silicas located between the polyacrylonitrile ball and the polyacrylonitrile layer;

[0092] Stirring and filtering: the polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile; wherein the stirring time is 2 hours and the stirring rate is 5000 rpm.

[0093] from Figure 1 It can be seen that the size distribution of the suspension in this embodiment is uniform; Figure 2 It can be seen that the average diameter of the polyacrylonitrile (ie, the polyacrylonitrile microspheres, including the polyacrylonitrile beads and the polyacrylonitrile layer) obtained in this embodiment is 80 to 200 μm.

[0094] The filtrate is sequentially centrifuged and dried to obtain a recovered suspension.

[0095] The conversion rate of acrylonitrile in this example was measured to be 96%.

[0096] Example 2

[0097] This embodiment provides an aqueous suspension polymerization method for acrylonitrile, comprising the following steps:

[0098] Preparation of suspension: 3 g of hydrophilic silica nanospheres are dispersed in 80 ml of toluene to obtain a silica suspension; a mixture of 9 mmol of 3-mercaptopropyltriethoxysilane (silane coupling agent) and 9 mmol of triethylamine (catalyst) is added to the above silica suspension, and then after reflux treatment at 116° C. for 4.2 h, the solid matter is separated by centrifugation, washed with toluene and dried to obtain amphiphilic silica (particles) as a suspending agent;

[0099] An oil phase composition was prepared by mixing 20 g of acrylonitrile, 0.14 g of azobisisobutyronitrile (initiator), 0.06 g of itaconic acid (comonomer), and 0.012 g of thioacetic acid (molecular weight regulator);

[0100] 4 g of the above-mentioned amphiphilic silica was ultrasonically dispersed in 100 ml of deionized water to prepare an aqueous phase composition; then the oil phase composition was added to the aqueous phase composition and mixed to form a layered liquid with the oil phase in the upper layer and the aqueous phase in the lower layer; then the layered liquid was homogenized by a homogenizer to obtain a suspension;

[0101] The mass ratio of acrylonitrile to initiator is 1:0.007; the mass ratio of acrylonitrile to comonomer is 1:0.003; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0006; the mass ratio of aqueous phase composition to amphiphilic silica is 1:0.04; the volume ratio of aqueous phase composition to oil phase composition when mixed is 1:0.2; the speed of the homogenizer is 3500rpm;

[0102] Polymerization: The suspension is placed in a reaction vessel to undergo a polymerization reaction while being stirred at a constant temperature to obtain a polyacrylonitrile suspension; wherein the polymerization reaction temperature is 60°C, the stirring rate is 80 rpm, and the stirring time is 8 hours.

[0103] Based on the above polymerization method of this embodiment, polyacrylonitrile is prepared, comprising the following steps:

[0104] Preparation of polyacrylonitrile particles: After the reaction is completed, the polyacrylonitrile suspension is filtered, washed with water, and dried in sequence to obtain polyacrylonitrile particles; each of the polyacrylonitrile particles comprises a polyacrylonitrile ball located in an inner layer, a polyacrylonitrile layer located in an outer layer, and a plurality of amphiphilic silicas located between the polyacrylonitrile ball and the polyacrylonitrile layer;

[0105] Stirring and filtering: The polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile; wherein the stirring time is 2 hours and the stirring speed is 5000 rpm. The average diameter of the polyacrylonitrile (i.e., polyacrylonitrile microspheres, including polyacrylonitrile beads and polyacrylonitrile layers) obtained in this embodiment is 100 to 140 μm.

[0106] The filtrate is sequentially centrifuged and dried to obtain a recovered suspension.

[0107] The conversion rate of acrylonitrile in this example was measured to be 98%.

[0108] Example 3

[0109] This embodiment provides an aqueous suspension polymerization method for acrylonitrile, comprising the following steps:

[0110] Preparation of suspension: 3 g of hydrophilic silica nanospheres are dispersed in 80 ml of toluene to obtain a silica suspension; a mixture of 9 mmol of 3-glycidyloxypropyl-trimethoxysilane (silane coupling agent) and 9 mmol of triethylamine (catalyst) is added to the above silica suspension, and then after reflux treatment at 117° C. for 4.5 h, the solid matter is separated by centrifugation, washed with toluene and dried to obtain amphiphilic silica (particles) as a suspending agent;

[0111] 20 g of acrylonitrile, 0.16 g of benzoyl peroxide (initiator), 0.08 g of acrylic acid (comonomer), and 0.01 g of n-octyl mercaptan (molecular weight regulator) were mixed to prepare an oil phase composition;

[0112] 5 g of the above-mentioned amphiphilic silica was ultrasonically dispersed in 100 ml of deionized water to prepare an aqueous phase composition; then the oil phase composition was added to the aqueous phase composition and mixed to form a layered liquid with the oil phase in the upper layer and the aqueous phase in the lower layer; then the layered liquid was homogenized by a homogenizer to obtain a suspension;

[0113] The mass ratio of acrylonitrile to initiator is 1:0.008; the mass ratio of acrylonitrile to comonomer is 1:0.004; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0005; the mass ratio of aqueous phase composition to amphiphilic silica is 1:0.05; the volume ratio of aqueous phase composition to oil phase composition when mixed is 1:0.2; the speed of the homogenizer is 4000rpm;

[0114] Polymerization: The suspension is placed in a reaction vessel to undergo a polymerization reaction while being stirred at a constant temperature to obtain a polyacrylonitrile suspension; wherein the polymerization reaction temperature is 70°C, the stirring rate is 80 rpm, and the stirring time is 9 hours.

[0115] Based on the above polymerization method of this embodiment, polyacrylonitrile is prepared, comprising the following steps:

[0116] Preparation of polyacrylonitrile particles: After the reaction is completed, the polyacrylonitrile suspension is filtered, washed with water, and dried in sequence to obtain polyacrylonitrile particles; each polyacrylonitrile particle includes a polyacrylonitrile ball located in the inner layer, a polyacrylonitrile layer located in the outer layer, and a plurality of amphiphilic silicas located between the polyacrylonitrile ball and the polyacrylonitrile layer;

[0117] Stirring and filtering: The polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile; wherein the stirring time is 2 hours and the stirring speed is 5000 rpm. The average diameter of the polyacrylonitrile (i.e., polyacrylonitrile microspheres, including polyacrylonitrile beads and polyacrylonitrile layers) obtained in this embodiment is 80 to 100 μm.

[0118] The filtrate is sequentially centrifuged and dried to obtain a recovered suspension.

[0119] The conversion rate of acrylonitrile in this example was measured to be 99%.

[0120] Comparative Example

[0121] This comparative example provides an aqueous suspension polymerization method for acrylonitrile, comprising the following steps:

[0122] Preparation of suspension: 20 g acrylonitrile, 0.12 g dicumyl peroxide (initiator), 0.04 g methyl acrylate (comonomer), 0.018 g n-dodecyl mercaptan (molecular weight regulator) were dispersed in 100 ml deionized water, and 1.5 g polyethylene glycol (PEG) was added to stabilize the suspension;

[0123] Then, a homogenizer is used for stirring to make the acrylonitrile uniformly dispersed in the water to form a stable suspension; the speed of the homogenizer is 3000 rpm;

[0124] Polymerization: The suspension is placed in a reaction vessel to undergo a polymerization reaction while being stirred at a constant temperature to obtain a polyacrylonitrile suspension; wherein the polymerization reaction temperature is 55°C, the stirring rate is 80 rpm, and the stirring time is 7 hours.

[0125] Based on the above polymerization method of this comparative example, polyacrylonitrile is prepared, comprising the following steps:

[0126] Post-treatment: After the polymerization is completed, stop heating and stirring, cool the reaction mixture, separate the polyacrylonitrile particles by filtration, and then wash with water to remove unreacted monomers, initiator residues and other impurities; finally, dry the polyacrylonitrile particles to obtain the finished product (polyacrylonitrile).

[0127] The conversion rate of acrylonitrile in this comparative example was measured to be 80%. The conversion rate of acrylonitrile using the above polymerization method of this comparative example is low because acrylonitrile is slightly soluble in water, and part of the acrylonitrile mixed with water cannot undergo polymerization reaction, resulting in a decrease in the conversion rate of acrylonitrile.

[0128] Example 4

[0129] This embodiment provides an aqueous suspension polymerization method for acrylonitrile, comprising the following steps:

[0130] Preparation of suspension: 3 g of hydrophilic silica nanospheres are dispersed in 80 ml of toluene to obtain a silica suspension; a mixture of 9 mmol of 3-mercaptopropyltriethoxysilane (silane coupling agent) and 9 mmol of triethylamine (catalyst) is added to the above silica suspension, and then after reflux treatment at 160° C. for 4 h, the solid matter is separated by centrifugation, washed with toluene and dried to obtain amphiphilic silica (particles) as a suspending agent;

[0131] 20 g of acrylonitrile, 0.12 g of dicumyl peroxide (initiator), 0.04 g of methyl acrylate (comonomer), and 0.018 g of n-dodecyl mercaptan (molecular weight regulator) were mixed to prepare an oil phase composition;

[0132] 3 g of the above-mentioned amphiphilic silica was ultrasonically dispersed in 100 ml of deionized water to prepare an aqueous phase composition; then the oil phase composition was added to the aqueous phase composition and mixed to form a layered liquid with the oil phase in the upper layer and the aqueous phase in the lower layer; then the layered liquid was homogenized by a homogenizer to obtain a suspension;

[0133] The mass ratio of acrylonitrile to initiator is 1:0.006; the mass ratio of acrylonitrile to comonomer is 1:0.002; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0009; the mass ratio of aqueous phase composition to amphiphilic silica is 1:0.03; the volume ratio of aqueous phase composition to oil phase composition when mixed is 1:0.2; the speed of the homogenizer is 1000 rpm;

[0134] Polymerization: The suspension is placed in a reaction vessel to undergo a polymerization reaction while being stirred at a constant temperature to obtain a polyacrylonitrile suspension; wherein the polymerization reaction temperature is 55°C, the stirring rate is 80 rpm, and the stirring time is 7 hours.

[0135] Based on the above polymerization method of this embodiment, polyacrylonitrile is prepared, comprising the following steps:

[0136] Preparation of polyacrylonitrile particles: After the reaction is completed, the polyacrylonitrile suspension is filtered, washed with water, and dried in sequence to obtain polyacrylonitrile particles; each of the polyacrylonitrile particles comprises a polyacrylonitrile ball located in an inner layer, a polyacrylonitrile layer located in an outer layer, and a plurality of amphiphilic silicas located between the polyacrylonitrile ball and the polyacrylonitrile layer;

[0137] Stirring and filtering: The polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence. The filter cake is dried to obtain polyacrylonitrile; wherein the stirring time is 2 hours and the stirring speed is 5000 rpm.

[0138] The filtrate is sequentially centrifuged and dried to obtain a recovered suspension.

[0139] The conversion rate of acrylonitrile in this embodiment was measured to be 89%. Compared with the aqueous suspension polymerization method in the comparative example, the conversion rate of acrylonitrile in this embodiment was improved. Figure 3 It can be seen that the particle size distribution of the polyacrylonitrile (microspheres) obtained in this example is uneven.

[0140] The conversion rate of acrylonitrile is low when the polymerization method of this embodiment is used. This is because the contact angle of the modified silica after reflux treatment at 160°C is 150°C, that is, it is oily, which causes the stability of the suspended droplets to deteriorate. A phenomenon similar to demulsification occurs during the reaction, resulting in irregular shapes of the formed polyacrylonitrile spheres. In addition, the reduction in the homogenization speed will prevent the suspended droplets from being fully broken up, resulting in a larger average particle size of the suspended droplets. Droplets with larger particle sizes are easy to agglomerate due to their higher surface energy, so the polymer spheres are uneven.

[0141] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. A method for aqueous suspension polymerization of acrylonitrile, characterized in that: The following steps are involved: Preparing a suspension: preparing an aqueous phase composition containing an amphiphilic inorganic material; preparing an oil phase composition containing acrylonitrile and an initiator, then mixing the water phase composition and the oil phase composition to obtain a layered liquid, and homogenizing the layered liquid to obtain a suspension; Wherein, the surface of the amphiphilic inorganic material is negatively charged; Polymerization: polymerize the suspension to obtain a polyacrylonitrile suspension.

2. The aqueous suspension polymerization method of acrylonitrile according to claim 1, characterized in that: The contact angle of the amphiphilic inorganic material is 80-100°; and / or The amphiphilic inorganic material is amphiphilic silicon dioxide; and / or The amphiphilic inorganic material is prepared from a hydrophilic inorganic material; preferably, the hydrophilic inorganic material is a nanosphere; preferably, the particle size of the hydrophilic inorganic material is 10 to 100 nm.

3. The aqueous suspension polymerization method of acrylonitrile according to claim 1 or 2, characterized in that: In the step of preparing the suspension, the amphiphilic inorganic material is prepared by the following steps: Dispersing a hydrophilic inorganic material in a solvent to obtain an inorganic material suspension; adding a mixture containing a silane coupling agent and a catalyst to the inorganic material suspension, then performing a reflux treatment, and then sequentially performing separation, washing, and drying to obtain the amphiphilic inorganic material; Preferably, the solvent is toluene; Preferably, the temperature of the reflux treatment is 115-125°C; Preferably, the reflux treatment time is 3.5 to 4.5 hours; Preferably, the silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane; Preferably, the catalyst is one or more of sodium hydroxide, ammonia water, potassium hydroxide, and triethylamine; Preferably, toluene is used for washing.

4. The aqueous suspension polymerization method of acrylonitrile according to claim 1, characterized in that: The volume ratio of the aqueous phase composition to the oil phase composition when mixed is 1:0.2-0.4; and / or The step of preparing the aqueous phase composition comprises: ultrasonically dispersing the amphiphilic inorganic material into deionized water to obtain the aqueous phase composition; preferably, the mass ratio of the aqueous phase composition to the amphiphilic inorganic material is 1:0.01-0.

05.

5. The aqueous suspension polymerization method of acrylonitrile according to claim 4, characterized in that: The step of preparing the oil phase composition comprises: mixing acrylonitrile, an initiator, a comonomer, and a molecular weight regulator to obtain the oil phase composition; Preferably, the mass ratio of acrylonitrile to initiator is 1:0.005-0.01; the mass ratio of acrylonitrile to comonomer is 1:0.001-0.005; the mass ratio of acrylonitrile to molecular weight regulator is 1:0.0005-0.001; Preferably, the initiator is one or more of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile; Preferably, the comonomer is one or more of itaconic acid, methyl acrylate, acrylic acid, vinyl acetate, styrene, and maleic anhydride; Preferably, the silane coupling agent is one or more of methyltrimethoxysilane, 3-glycidyloxypropyl-trimethoxysilane, and 3-mercaptopropyltriethoxysilane; Preferably, the molecular weight regulator is one or more of n-dodecyl mercaptan, thioacetic acid, 2-mercaptoethanol, and n-octyl mercaptan.

6. The aqueous suspension polymerization method of acrylonitrile according to claim 1, characterized in that: In the step of preparing the suspension: the average diameter of the droplets of the suspension is 80 to 200 μm; and / or A homogenizer is used to homogenize the layered liquid; wherein the rotation speed of the homogenizer is 3000-4000 rpm.

7. The aqueous suspension polymerization method of acrylonitrile according to claim 1, characterized in that: In the polymerization step: a polymerization reaction occurs in the suspension while the suspension is stirred at a constant temperature; Preferably, the polymerization reaction temperature is 50 to 90°C; Preferably, the polymerization reaction time is 5 to 9 hours; Preferably, the constant temperature stirring rate is 60-100 rpm.

8. A method for preparing polyacrylonitrile, characterized in that: The following steps are involved: Preparation of polyacrylonitrile particles: filtering, washing and drying the polyacrylonitrile suspension in sequence to obtain polyacrylonitrile particles; Wherein, the polyacrylonitrile suspension is obtained by the aqueous suspension polymerization method of acrylonitrile according to any one of claims 1 to 7; Stirring and filtering: the polyacrylonitrile particles are mixed with water, and then stirred and filtered in sequence, and the filter cake is dried to obtain polyacrylonitrile.

9. The method for preparing polyacrylonitrile according to claim 8, characterized in that: In the step of preparing the polyacrylonitrile particles: each of the polyacrylonitrile particles comprises a polyacrylonitrile ball located in an inner layer, a polyacrylonitrile layer located in an outer layer, and an amphiphilic inorganic material located between the polyacrylonitrile ball and the polyacrylonitrile layer; Preferably, the average diameter of the polyacrylonitrile beads is 80 to 200 μm; the average thickness of the polyacrylonitrile layer is 1 to 2 μm; Preferably, the amphiphilic inorganic material is amphiphilic silicon dioxide; Preferably, the conversion rate of acrylonitrile is above 96%; and / or In the stirring and filtering steps: the stirring rate is 5000-8000 rpm; the stirring time is 2-3 hours; and / or The method for preparing polyacrylonitrile further comprises: sequentially centrifuging and drying the filtrate to obtain a recovered amphiphilic inorganic material.

10. A polyacrylonitrile, characterized in that: The polyacrylonitrile is obtained by the preparation method according to claim 8 or 9.

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