Preparation method of acrylonitrile-maleic anhydride-itaconic acid terpolymer

Abstract

The invention relates to a preparation method of an acrylonitrile-maleic anhydride-itaconic acid terpolymer, which comprises the following steps: under the protection of nitrogen, adding a comonomer acrylonitrile, and maleic anhydride and itaconic acid dissolved in a dimethyl sulfoxide solvent into a three-neck flask, heating to 65 DEG C, reacting for 2-4 hours, and cooling to room temperature to obtain the acrylonitrile-maleic anhydride-itaconic acid terpolymer. Adding an azodiisobutyronitrile initiator dissolved in a dimethyl sulfoxide solvent and the residual dimethyl sulfoxide solvent, reacting for 10 hours, settling the prepared copolymer solution by using methanol, and washing and drying to obtain the terpolymer. A solution polymerization method is used for polymerization, and the method has the advantages of high reaction yield, high absolute molecular weight, small distribution index, stable product quality and the like. The stability and spinnability of the prepared polyacrylonitrile copolymer can be effectively improved, and the polyacrylonitrile copolymer has a certain practical application prospect.

Description

Technical Field

[0001] The invention belongs to the field of preparation of acrylonitrile copolymers for carbon fiber precursors, and particularly relates to a method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer. Background Art

[0002] As a high-tech material, carbon fiber has a series of excellent properties such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, conductivity, shock absorption, heat transfer, radiation resistance and low specific gravity. It is widely used in aerospace, national defense and military industry, automobile high-speed rail, large-scale wind power, sports and leisure, and biomedicine.

[0003] More than 90% of the carbon fibers currently used are made from polyacrylonitrile (PAN)-based precursors, but polyacrylonitrile homopolymer is rarely used as a carbon fiber precursor due to its poor spinnability and stability. A small amount of copolymer is usually introduced into the PAN polymer chain to improve solubility, spinnability, hydrophilicity, and stretchability, especially to promote the stability of PAN, which plays a vital role in the preparation of carbon fibers. Therefore, a certain amount of comonomer should be added to the polymer to cause the cyano cyclization and exothermic peak to move to the low temperature side during pre-oxidation, so that the free radical cyclization reaction of homopolymerized polyacrylonitrile is converted into an ionic cyclization reaction, thereby reducing the exothermic rate of the cyclization reaction and making the reaction easy to control.

[0004] The production of polyacrylonitrile copolymer mainly utilizes the principle of free radical polymerization, and is prepared by solution polymerization or precipitation polymerization. In the industrial production of PAN for carbon fiber, solution polymerization is the most widely used and most thoroughly studied method. The system contains three components: monomer (AN and comonomer), initiator and suitable solvent. During the solution polymerization process, the generated PAN polymer will also dissolve in the solvent at the same time, and the product, solvent and unreacted monomer together form a stable and uniform reaction system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer. The method of the present invention adopts maleic anhydride as the second comonomer and itaconic acid as the third comonomer, and adopts a solution polymerization method to prepare a polyacrylonitrile high molecular copolymer for carbon fiber precursor, thereby improving its thermal stability and spinnability at a high temperature stage.

[0006] The present invention provides a polyacrylonitrile copolymer with higher thermal performance and a preparation method thereof.

[0007] Under nitrogen protection conditions, a comonomer acrylonitrile, maleic anhydride and itaconic acid dissolved in a dimethyl sulfoxide solvent are added into a three-necked flask, and after the temperature is raised to 65° C., an azobisisobutyronitrile initiator dissolved in a dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent are added, and the reaction is carried out for 10 hours. Then, the prepared copolymer solution is precipitated with methanol, and a terpolymer is prepared through washing and drying; wherein the molar ratio of acrylonitrile / maleic anhydride / itaconic acid is 97.5-99:0.5-2.0:0.5.

[0008] The amount of acrylonitrile, maleic anhydride and itaconic acid used is 16-30wt% of the total mass.

[0009] The initiator is azobisisobutyronitrile accounting for 0.1-1.2% of the total weight of the monomer, the reaction temperature is 50-70 DEG C, and the reaction time is 8-12 hours.

[0010] The solvent of the initiator solution is an organic solvent.

[0011] The organic solvent is one of dimethyl sulfoxide, dimethylformamide and dimethylacetamide.

[0012] The solvent for the precipitation is methanol solvent.

[0013] The drying temperature is 50-60° C., and the drying time is 24-48 hours.

[0014] The absolute molecular weight of the terpolymer is 1.01×10 5 -1.30×10 5 , molecular weight distribution is 1.21-1.43.

[0015] The conversion rate of the present invention is greater than 63%.

[0016] The invention discloses a method for preparing a terpolymer with high conversion rate and high absolute molecular weight. The invention uses maleic anhydride as the second comonomer and itaconic acid as the third comonomer, and adopts a solution polymerization method to prepare a polyacrylonitrile high molecular copolymer for carbon fiber precursor, thereby improving its thermal stability and spinnability at high temperature.

[0017] Beneficial Effects

[0018] (1) The azobisisobutyronitrile initiation reaction in the present invention is relatively stable, has a low activation energy, and a moderate decomposition rate that is well controlled, and can achieve the requirement of a high conversion rate in a relatively short reaction time;

[0019] (2) The polymer prepared by the present invention can effectively improve its thermal performance in the high-temperature pre-oxidation stage and has certain application prospects;

[0020] (3) The present invention adopts solution polymerization to obtain a polyacrylonitrile copolymer with a narrow molecular weight distribution (1.21-1.43);

[0021] (4) The present invention adopts a solution polymerization method. The solution obtained after the solution polymerization reaction can be used as a spinning solution to realize one-step spinning. It only needs to undergo single removal and degassing treatment. It has the advantage of a simple production process, and the obtained polyacrylonitrile has few molecular structure defects. It is a polymerization process that is currently widely used;

[0022] (5) The present invention has the advantages of high reaction yield, high absolute molecular weight and narrow distribution, stable product quality, etc. The polyacrylonitrile copolymer prepared by the present invention can effectively improve its thermal properties and spinnability, and has certain practical application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the FTIR spectrum of the polymer in Example 1.

[0024] Figure 2 This is the DSC graph of the polymer in Example 1.

[0025] Figure 3 The rheological diagram of the polymer at different temperatures in Example 1.

[0026] Figure 4 The rheological diagrams of the polymers in Examples 1, 2, 3, and 4 are shown. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0028] Example 1

[0029] Under nitrogen protection, comonomer acrylonitrile and maleic anhydride and itaconic acid dissolved in dimethyl sulfoxide solvent were added into a three-necked flask, the molar ratio of acrylonitrile, maleic anhydride and itaconic acid was

[99] : [0.5]: [0.5], and the total concentration of the mixed monomers was 22%. After heating to 65°C, azobisisobutyronitrile initiator dissolved in dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent were added, and the reaction was carried out at 50-70°C for 8-12 hours, and then the prepared copolymer solution was precipitated with methanol, and the terpolymer was prepared by washing and drying. The molecular weight of the prepared terpolymer was 1.30×10 5g / mol, and the molecular weight distribution is 1.42. Then a certain amount of the copolymer is weighed and added into dimethyl sulfoxide to prepare a spinning solution with a mass percentage of 22wt%.

[0030] Example 2

[0031] Under nitrogen protection, comonomer acrylonitrile and maleic anhydride and itaconic acid dissolved in dimethyl sulfoxide solvent were added to a three-necked flask, the molar ratio of acrylonitrile, maleic anhydride and itaconic acid was [98.5]: [1.0]: [0.5], and the total concentration of the mixed monomers was 22%. After heating to 65°C, azobisisobutyronitrile initiator dissolved in dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent were added, and the reaction was carried out at 50-70°C for 8-12 hours, and then the prepared copolymer solution was precipitated with methanol, and the terpolymer was prepared by washing and drying. The molecular weight of the prepared terpolymer was 1.23×10 5 g / mol, and the molecular weight distribution is 1.25. Then a certain amount of the copolymer is weighed and added into dimethyl sulfoxide to prepare a spinning solution with a mass percentage of 22wt%.

[0032] Example 3

[0033] Under nitrogen protection, comonomer acrylonitrile and maleic anhydride and itaconic acid dissolved in dimethyl sulfoxide solvent were added to a three-necked flask, the molar ratio of acrylonitrile, maleic anhydride and itaconic acid was

[98] : [1.5]: [0.5], and the total concentration of the mixed monomers was 22%. After heating to 65°C, azobisisobutyronitrile initiator dissolved in dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent were added, and the reaction was carried out at 50-70°C for 8-12 hours, and then the prepared copolymer solution was precipitated with methanol, and the terpolymer was prepared by washing and drying. The molecular weight of the prepared terpolymer was 1.20×10 5 g / mol, and the molecular weight distribution is 1.35. Then a certain amount of the copolymer is weighed and added into dimethyl sulfoxide to prepare a spinning solution with a mass percentage of 22wt%.

[0034] Example 4

[0035] Under nitrogen protection, comonomer acrylonitrile and maleic anhydride and itaconic acid dissolved in dimethyl sulfoxide solvent are added to a three-necked flask, the molar ratio of acrylonitrile, maleic anhydride and itaconic acid is [97.5]: [2.0]: [0.5], and the total concentration of the mixed monomer is 22%. After heating to 65°C, azobisisobutyronitrile initiator dissolved in dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent are added, and the reaction is carried out at 50-70°C for 8-12 hours, and then the prepared copolymer solution is precipitated with methanol, and the terpolymer is prepared by washing and drying. The molecular weight of the prepared terpolymer is 1.01×10 5g / mol, and the molecular weight distribution is 1.22. Then a certain amount of the copolymer is weighed and added into dimethyl sulfoxide to prepare a spinning solution with a mass percentage of 22wt%.

[0036] The FTIR spectrum of the polymer is shown in Figure 1 As shown in the figure, it can be seen that 2940cm -1 -CH 2 The characteristic peak of -1 The characteristic peak of -CN in acrylonitrile is 1780cm -1 The characteristic peak of -C=O in maleic anhydride is 1730cm -1 The peak is the characteristic peak of -C=O in itaconic acid.

[0037] The DSC diagram of the polymer is as follows Figure 2 As shown in the figure, it can be seen that the exothermic peak of the terpolymer prepared in Example 1 is broadened and the pre-oxidation starting temperature is 174.76°C, which avoids concentrated heat release and promotes the pre-oxidation of the carbon fiber precursor. In addition, the reduction of the pre-oxidation temperature is beneficial to saving energy consumption.

[0038] The different temperature rheological diagrams of the polymer in Example 1 are as follows Figure 3 As shown in the figure, it can be seen that with the increase of temperature, the apparent viscosity of the solution under the same conditions decreases. The reason is that as the temperature increases, the molecular chain segments are easier to move, thus reducing the apparent viscosity.

[0039] The rheological diagrams of the polymers in Examples 1, 2, 3, and 4 are as follows: Figure 4 As shown in the figure, it can be seen that with the increase of shear rate, the rate of molecular chain disentanglement is faster than the rate of new entanglement points, the number of entanglement points decreases, and the apparent viscosity decreases. The introduction of comonomers can hinder the interaction between cyano groups, reduce the force between molecular chains, and reduce the apparent viscosity.

Claims

1. A method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer, comprising: Under nitrogen protection conditions, a comonomer acrylonitrile, maleic anhydride and itaconic acid dissolved in a dimethyl sulfoxide solvent are added into a three-necked flask, and after the temperature is raised to 65° C., an azobisisobutyronitrile initiator dissolved in a dimethyl sulfoxide solvent and the remaining dimethyl sulfoxide solvent are added, and the reaction is carried out for 10 hours. Then, the prepared copolymer solution is precipitated with methanol, and a terpolymer is prepared through washing and drying; wherein the molar ratio of acrylonitrile / maleic anhydride / itaconic acid is 97.5-99:0.5-2.0:0.

5.

2. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The amount of acrylonitrile, maleic anhydride and itaconic acid used is 16-30wt% of the total mass.

3. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The initiator is azobisisobutyronitrile accounting for 0.1-1.2% of the total weight of the monomer, the reaction temperature is 50-70°C, and the reaction time is 8-12 hours.

4. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The organic solvent is one of dimethyl sulfoxide, dimethylformamide and dimethylacetamide.

5. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The drying temperature is 50-60° C., and the drying time is 24-48 hours.

6. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The absolute molecular weight of the ternary polyacrylonitrile copolymer is 1.01×10 5 -1.30×10 5 g / mol, and the molecular weight distribution is 1.21-1.

43.

7. The method for preparing an acrylonitrile-maleic anhydride-itaconic acid terpolymer according to claim 1, characterized in that: The conversion rate was greater than 63%.

Images