阅读说明：本技术 一种聚丙烯腈共聚物及其制备方法和应用 (Polyacrylonitrile copolymer and preparation method and application thereof ) 是由 周鸿康 王欣 王湘麟 刘玉锇 于 2021-01-20 设计创作，主要内容包括：本发明涉及一种聚丙烯腈共聚物及其制备方法和应用,所述聚丙烯腈共聚物的共聚单体包括丙烯腈和式Ⅰ所示单体的组合。本发明所述聚丙烯腈共聚物具有既能有效的降低环化温度,也能减少预处理过程中的缺陷和降解,利于作为碳纤维前驱体加以应用。(The invention relates to a polyacrylonitrile copolymer and a preparation method and application thereof. The polyacrylonitrile copolymer can effectively reduce cyclization temperature, can reduce defects and degradation in a pretreatment process, and is favorable for being applied as a carbon fiber precursor.)

1. A polyacrylonitrile copolymer, wherein the comonomer of the polyacrylonitrile copolymer comprises the combination of acrylonitrile and a monomer shown as a formula I;

the R is₁Selected from electron withdrawing groups;

the R is₂And R₃Each independently selected from hydrogen, C3-C7 alkyl, phenyl, tolyl, or C3-C7 alkenyl containing one alkenyl group, and R₂And R₃Wherein only one is selected from the group consisting of C3-C7 alkenyl groups having one alkenyl group.

2. The polyacrylonitrile copolymer according to claim 1, wherein the electron withdrawing group includes any one of acyl group, carbonyl group, amido group, sulfonic group, haloform group or quaternary amine group, preferably carbonyl group.

3. The polyacrylonitrile copolymer according to claim 1 or 2, characterized in that the monomer shown in formula i specifically comprises the following structure:

4. the polyacrylonitrile copolymer according to any one of claims 1 to 3, characterized in that the monomer represented by the formula I specifically comprises the following structure:

5. the polyacrylonitrile copolymer according to any one of claims 1 to 4, characterized in that the number average molecular weight of the polyacrylonitrile copolymer is 150000-350000 g/mol.

6. A method for preparing a polyacrylonitrile copolymer according to any one of claims 1 to 5, characterized in that the preparation method comprises the following steps: and (2) polymerizing acrylonitrile and the monomer shown in the formula I under the action of an initiator to form the polyacrylonitrile copolymer.

7. The method of claim 6, wherein the initiator comprises azobisisobutyronitrile;

preferably, the molar ratio of the initiator to the monomer of formula i is from 0.1% to 0.5%, preferably 0.2%;

preferably, the monomer represented by the formula I accounts for 1-10% of the total mole number of the acrylonitrile and the monomer represented by the formula I.

8. The process according to claim 6 or 7, characterized in that the polymerization time is 6 to 20 hours, preferably 8 hours;

preferably, the temperature of the polymerization is 55-70 ℃, preferably 60 ℃;

preferably, the preparation method further comprises: the polymerization is followed by purification, washing and drying in this order.

9. The method according to any one of claims 6 to 8, characterized by comprising the steps of: polymerizing acrylonitrile and a monomer shown in a formula I for 6-20 hours at the temperature of 55-70 ℃ under the action of an initiator, and then sequentially purifying, washing and drying to obtain the polyacrylonitrile copolymer.

10. Use of a polyacrylonitrile copolymer according to any one of claims 1 to 5 in the field of spinning.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a polyacrylonitrile copolymer and a preparation method and application thereof.

Background

Precursors of carbon fibers are generally made of polymers such as Polyacrylonitrile (PAN) fibers, pitch fibers, rayon fibers, cellulose fibers, and the like, wherein PAN fiber precursors have good application values because of great advantages in processing and ultra-high tensile strength and high tensile modulus. During the stabilization process, the linear structure of the PAN will become a trapezoidal structure, which can withstand the high temperature treatment of the carbonization process. However, the PAN precursor is apt to cause degradation and filament breakage due to concentration of heat generation during cyclization, and is not suitable for direct use as a precursor of high-performance carbon fibers. The addition of the comonomer containing the nucleophilic functional group can reduce the cyclization temperature of the polymer, reduce the heat release in the cyclization process and improve the performance of the carbon fiber.

CN101768078A discloses a itaconic acid derivative for acrylonitrile copolymerization, wherein the copolymer adopts itaconic acid derivative with ester group and ammonium group as acrylonitrile comonomer to replace conventional ternary copolymerization, which improves the controllability of the copolymer composition and is used for preparing high-performance PAN precursor. In the disclosed copolymer of acrylonitrile and itaconic acid derivatives, the mass ratio of acrylonitrile is 90-99.99%; the mass ratio of the itaconic acid derivant is 0.01-10%. The number average molecular weight of the copolymer is 1 to 100 ten thousand. The copolymer disclosed therein was studied for cyclization temperature, but the pendant group of the itaconic acid derivative was large and the cyclization temperature of the copolymer would be relatively high.

CN108586658A discloses a novel polyacrylonitrile copolymer and a preparation method of spinning solution thereof, wherein the disclosed polyacrylonitrile copolymer comprises a main monomer unit acrylonitrile and a comonomer unit vinyl derivative, the mass content of the main monomer unit is 90-99.99%, and the mass content of the comonomer unit is 0.001-10%. The novel polyacrylonitrile copolymer has higher hydrophilicity, lower crystallinity and cyclization temperature, milder heat release rate and higher carbon formation rate, but the copolymer formed by the comonomer can be degraded in the processing process, and the performance of the obtained copolymer is influenced.

In view of the above, it is important to develop a polyacrylonitrile copolymer having a lower cyclization temperature and less defects and degradation during pretreatment.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a polyacrylonitrile copolymer, a preparation method and application thereof, wherein the polyacrylonitrile copolymer can effectively reduce the cyclization temperature and defects and degradation in the pretreatment process.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a polyacrylonitrile copolymer, wherein the comonomer of the polyacrylonitrile copolymer comprises a combination of acrylonitrile and a monomer shown in formula I;

the R is₁Selected from electron withdrawing groups;

the R is₂And R₃Each independently selected from hydrogen, C3-C7 (e.g., C4, C5, C6, etc.) alkanyl, phenyl, tolyl, or C3-C7 (e.g., C4, C5, C6, etc.) alkenylene having one alkenyl group, and R₂And R₃One or more of them is selected from C3-C7 (e.g., C4, C5, C6, etc.) alkenyl groups having one alkenyl group.

The comonomer of the polyacrylonitrile copolymer comprises acrylonitrile and a monomer shown as a formula I, wherein in the monomer shown as the formula I, an electron-withdrawing group directly connected with an N atom activates the N atom through electron-withdrawing action. The polyacrylonitrile homopolymer cyclizes by a free radical mechanism, and after a comonomer containing a nucleophilic functional group is added, the preoxidation cyclization process of the copolymer proceeds by an ionic mechanism. The ion mechanism can effectively reduce the cyclization temperature of the formed polyacrylonitrile copolymer; in addition, the side group of the monomer is smaller, the formed copolymer has higher thermal stability, and the thermal degradation in the pre-oxidation process and the formation of small molecules are reduced, so that the defects and the degradation in the pre-treatment process are reduced.

Preferably, the electron withdrawing group includes any one of an acyl group, a carbonyl group, an amido group, a sulfonic group, a haloform group or a quaternary amine group, preferably a carbonyl group.

The electron-withdrawing group is preferably a carbonyl group, the carbonyl group has strong nucleophilicity and small volume, and the steric hindrance effect and the thermal degradation of the copolymer can be reduced while the cyclization of the copolymer is effectively promoted. These features all contribute to the formation of high strength carbon fibers.

Preferably, the monomer shown in the formula I specifically comprises the following structure:

preferably, the monomer shown in the formula I specifically comprises the following structure:

the invention preferably selects the monomer with the structure, and the structure has stronger nucleophilicity and smaller volume. The lone pair of electrons on the nitrogen atom has strong nucleophilicity and can cause the cyclization of the polymer to proceed by an ionic mechanism.

Preferably, the number average molecular weight of the polyacrylonitrile copolymer is 150000-350000g/mol, such as 200000g/mol, 250000g/mol, 300000g/mol, and the like.

In a second aspect, the present invention provides a method for preparing the polyacrylonitrile copolymer, the method comprising the following steps: and (2) polymerizing an acrylonitrile monomer and a monomer shown in the formula I under the action of an initiator to form the polyacrylonitrile copolymer.

Preferably, the initiator comprises Azobisisobutyronitrile (AIBN).

Preferably, the molar ratio of the initiator to the monomer of formula i is 0.1% to 0.5%, such as 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, etc., preferably 0.2%.

Preferably, the monomer of formula i accounts for 1% to 10%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., of the total number of moles of acrylonitrile and the monomer of formula i.

The monomer shown in the formula I accounts for 1% -10% of the total mole number of the acrylonitrile and the monomer (comonomer) shown in the formula I, compared with the condition that the existing carbon fiber precursor can only carry out low-content copolymerization (1% -5%) with the comonomer of the acrylonitrile, the acrylonitrile chain segment in the polyacrylonitrile copolymer formed by the invention is lower in proportion, the obtained polyacrylonitrile copolymer not only has lower cyclization temperature, but also has higher modulus and strength, and the comprehensive performance is further improved.

Preferably, the time of the polymerization is 6 to 20 hours, such as 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, etc., preferably 8 hours.

Preferably, the polymerization temperature is 55-70 ℃, such as 56 ℃, 57 ℃, 58 ℃, 59 ℃, 60 ℃, 61 ℃, 62 ℃, 63 ℃, 64 ℃, 66 ℃, 68 ℃, preferably 60 ℃.

Preferably, the preparation method further comprises: the polymerization is followed by purification, washing and drying in this order.

As a preferred technical scheme, the preparation method comprises the following steps:

polymerizing acrylonitrile and a monomer shown in a formula I for 6-20 hours at the temperature of 55-70 ℃ under the action of an initiator, and then sequentially purifying, washing and drying to obtain the polyacrylonitrile copolymer.

The above preparation process was carried out under a nitrogen atmosphere.

The polyacrylonitrile homopolymer involved in the invention can be a commercially available product or a self-made product, and the preparation method comprises the following steps: under the nitrogen atmosphere, polymerizing an acrylonitrile monomer for 6-20 hours under the action of an initiator, and then sequentially purifying, washing and drying to obtain the polyacrylonitrile homopolymer (PAN).

In a third aspect, the present invention provides a use of the polyacrylonitrile copolymer described in the first aspect in the spinning field.

Compared with the prior art, the invention has the following beneficial effects:

the polyacrylonitrile copolymer can effectively reduce cyclization temperature and defects and degradation in the pretreatment process. The cyclization temperature of the polyacrylonitrile copolymer is lower than 203.81 ℃, the lowest temperature can be 175.09 ℃, and the final hot-weight residue is more than 56.57%.

Drawings

FIG. 1 is a nuclear magnetic spectrum of a polyacrylonitrile copolymer described in example 1;

FIG. 2 is a nuclear magnetic spectrum of a polyacrylonitrile copolymer described in example 2;

FIG. 3 is a nuclear magnetic spectrum of a polyacrylonitrile copolymer described in example 3;

FIG. 4 is a nuclear magnetic spectrum of a polyacrylonitrile copolymer described in example 4;

FIG. 5 is a nuclear magnetic spectrum of the polyacrylonitrile copolymer described in example 5.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

This example provides a polyacrylonitrile copolymer, shown in FIG. 1 as a nuclear magnetic result, in which the comonomers of polyacrylonitrile copolymer (P (AN-co-AM) with a number average molecular weight of 289200g/mol) are acrylonitrile and a monomer represented by formula II:

the preparation method of the polyacrylonitrile copolymer comprises the following steps:

0.893mL of acrylamide solution (VPA solution), 0.665mL of azobisisobutyronitrile AIBN solution (concentration of 0.030g/mL, solvent being dimethyl sulfoxide DMSO), 74.195mL of AN solution, 3.905mL of monomer solution represented by formula II and 8.942mL of DMSO were mixed, and after AN and the monomer represented by formula II were polymerized under nitrogen atmosphere at 60 ℃ for 8 hours, the polymerization product was purified by precipitation in 400mL of high-purity water, followed by filtration, and the filtration product was washed three times with ethanol and finally dried in a vacuum oven at 60 ℃ for 12 hours to obtain the polyacrylonitrile copolymer.

The concentration of the monomer solution shown in the formula II and the AN solution is 5.71mmol/mL, the solvent is DMSO, the molar charge ratio of the monomer solution to the AN solution is 5:95, and the actual copolymerization ratio is 5.32: 94.68.

Example 2

This example provides a polyacrylonitrile copolymer, the nuclear magnetic results of which are shown in fig. 2, wherein the comonomers of the polyacrylonitrile copolymer (P (AN-co-MAM) with a number average molecular weight of 261600g/mol) are acrylonitrile and the monomer shown in formula iii:

the preparation method of the polyacrylonitrile copolymer comprises the following steps:

0.893mL of a methacrylamide solution, 0.665mL of AN AIBN solution (concentration of 0.030g/mL, solvent being DMSO), 35.145mL of AN solution, 3.905mL of a monomer solution represented by formula III and 8.942mL of DMSO are mixed, and after the AN and the monomer represented by formula III are polymerized under the action of AIBN at 55 ℃ for 20 hours under a nitrogen atmosphere, the polymerization product is precipitated in 400mL of high-purity water for purification, and is filtered, and the filtered product is washed three times with ethanol and finally dried in a vacuum oven at 60 ℃ for 12 hours to obtain the polyacrylonitrile copolymer.

The concentration of the monomer solution shown in the formula III and the AN solution is 5.71mmol/mL, the solvent is DMSO, the molar charge ratio of the monomer solution to the AN solution is 10:90, and the actual copolymerization ratio is 9.79: 90.21.

Example 3

This example provides a polyacrylonitrile copolymer, shown in FIG. 3 as a nuclear magnetic result, in which the comonomers of polyacrylonitrile copolymer (P (AN-co-NPA) with a number average molecular weight of 258500g/mol) are acrylonitrile and the monomer shown in formula IV:

the preparation method of the polyacrylonitrile copolymer comprises the following steps:

0.893mL of N-phenylacrylamide solution, 0.665mL of AIBN solution (concentration is 0.030g/mL, solvent is DMSO), 386.595mL of AN solution, 3.905mL of monomer solution shown in formula IV and 8.942mL of DMSO are mixed, after the AN and the monomer shown in formula IV are polymerized under the action of AIBN at 70 ℃ for 6 hours under nitrogen atmosphere, the polymerization product is precipitated in 400mL of high-purity water for purification, then filtered, washed with ethanol three times, and finally dried in a vacuum oven at 60 ℃ for 12 hours, so that the polyacrylonitrile copolymer is obtained.

The concentration of the monomer solution shown in the formula IV and the AN solution is 5.71mmol/mL, the solvent is DMSO, the molar charge ratio of the monomer solution to the AN solution is 1:99, and the actual copolymerization ratio is 1.02: 98.98.

Example 4

This example provides a polyacrylonitrile copolymer, the nuclear magnetic results of which are shown in fig. 4, wherein the comonomers of the polyacrylonitrile copolymer (P (AN-co-NIP) with a number average molecular weight of 249900g/mol) are acrylonitrile and the monomer represented by formula v:

the preparation method of the polyacrylonitrile copolymer comprises the following steps:

0.893mL of N-isopropylacrylamide solution, 0.665mL of AIBN solution (concentration is 0.030g/mL, solvent is DMSO), 74.195mL of AN solution, 3.905mL of monomer solution shown in formula V and 8.942mL of DMSO are mixed, the AN monomer and the monomer shown in formula V are polymerized under the action of AIBN at 60 ℃ for 8 hours under nitrogen atmosphere, the polymerization product is precipitated in 400mL of high-purity water for purification, then filtration is carried out, the filtration product is washed with ethanol three times, and finally the filtration product is dried in a vacuum oven at 60 ℃ for 12 hours, so that the polyacrylonitrile copolymer is obtained.

The concentration of the monomer solution represented by the formula V and the AN solution is 5.71mmol/mL, the solvent is DMSO, the molar ratio of the monomer solution to the AN solution is 5:95, and the actual copolymerization ratio is 5.67: 94.33.

Example 5

This example provides a polyacrylonitrile copolymer with nuclear magnetic resonance as shown in FIG. 5, wherein the comonomers of polyacrylonitrile copolymer (P (AN-co-NVF) with a number average molecular weight of 271800g/mol) are acrylonitrile and the monomer shown in formula VI:

the preparation method of the polyacrylonitrile copolymer comprises the following steps:

0.893mL of N-vinylformamide solution (VPA solution), 0.665mL of AIBN solution (concentration is 0.030g/mL, solvent is DMSO), 74.195mL of AN solution, 3.905mL of monomer solution shown in formula VI and 8.942mL of DMSO are mixed, the AN monomer and the monomer shown in formula VI are polymerized under the action of AIBN at 60 ℃ for 8 hours under nitrogen atmosphere, the polymerization product is precipitated in 400mL of high-purity water for purification, then filtration is carried out, the filtration product is washed with ethanol three times, and finally the filtration product is dried in a vacuum oven at 60 ℃ for 12 hours, so that the polyacrylonitrile copolymer is obtained.

The concentration of the monomer solution shown in the formula VI and the AN solution is 5.71mmol/mL, the solvent is DMSO, the molar ratio of the monomer solution to the AN solution is 5:95, and the actual copolymerization ratio is 4.49: 95.51.

Comparative example 1

This comparative example provides a polyacrylonitrile copolymer that is poly (acrylonitrile-co-itaconic acid) (P (AN-co-IA) with a number average molecular weight of 209800 g/mol).

The preparation method of P (AN-co-IA) is different from that of example 1 in that the monomer solution represented by formula II is replaced by AN equal-concentration equal-volume IA monomer solution, and the rest is the same as that of example 1.

Comparative example 2

This comparative example provides a PAN (number average molecular weight of 200600 g/mol).

The preparation method of the PAN comprises the following steps:

0.893mL of AIBN, 3.905mL of AN, and 8.942mL of DMSO were charged into a 30mL vial through a high throughput feeding device under a nitrogen atmosphere, and after AN monomer was polymerized at 60 ℃ for 8 hours under the action of AN initiator under a nitrogen atmosphere, the polymerization product was purified by precipitation in 400mL of high purity water, followed by filtration, and the filtered product was washed three times with ethanol and finally dried in a vacuum oven at 60 ℃ for 12 hours to obtain the PAN.

Performance testing

Examples 1-5 and comparative examples 1-2 were tested as follows:

(1) basic thermal behavior: the basic thermal behavior of the polymer was studied using a Differential Scanning Calorimeter (DSC). Differential Scanning Calorimetry (DSC) was performed on approximately 3mg (+ -0.1 mg) samples placed in a standard aluminum DSC kettle using a TA Instruments DSC 25 operating at heating rates of 5, 10, 15, 20 ℃/min to determine the activation energy of the cyclization ratio PAN homopolymers and copolymers. The measurement was carried out at a temperature in the range of 30-400 ℃ and with a flow rate of 100mL/min using nitrogen as the protective gas.

(2) Thermogravimetric analysis: the degradation properties of the polymer were studied using a thermogravimetric analyzer (TGA). Thermogravimetric analysis (TGA) was performed using a thermogravimetric analyzer (TGA 55, TA Instruments, USA) under a nitrogen atmosphere, rising from 30 ℃ to 700 ℃ at a rate of 10 ℃/min.

The test results are summarized in table 1.

TABLE 1

	Cyclization temperature (. degree.C.)	Thermogravimetric final residue (%)
			Example 1	187.49	58.20
Example 2	175.86	57.51
			Example 3	203.81	56.57
Example 4	201.82	57.31
			Example 5	175.09	59.43
Comparative example 1	208.74	54.72
			Comparative example 2	236.01	43.57

The data in the table 1 show that the cyclization temperature of the polyacrylonitrile copolymer is lower than 203.81 ℃, the lowest temperature can be 175.09 ℃, and the final hot-gravimetric residue is more than 56.57 percent.

As can be seen from the analysis of comparative example 1 and example 5, the performance of comparative example 1 is inferior to that of example 5, which proves that the overall performance of the polyacrylonitrile copolymer obtained by using the comonomer of the present invention is better.

Analysis of comparative example 2 and example 5 shows that comparative example 2 is inferior to example 5, demonstrating the overall performance of the polyacrylonitrile copolymer obtained with the comonomer of the present invention.

Analysis of examples 1-5 reveals that examples 1-4 are inferior to example 5, demonstrating that the use of the comonomers described in example 5 of the present invention results in polyacrylonitrile copolymers having lower cyclization temperatures, which is more favorable for the preparation of carbon fiber precursors.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.