阅读说明：本技术 一种热塑性聚酰亚胺及其制备方法 (Thermoplastic polyimide and preparation method thereof ) 是由 张鑫 陈海波 刘彪 于 2019-12-11 设计创作，主要内容包括：本发明属于聚酰亚胺合成技术领域,具体涉及一种含卤素封端剂的热塑性聚酰亚胺及其制备方法,包括如下步骤：a)将芳香族二元伯胺、芳香族二元酸酐以及含有卤素的芳香族封端剂与酮、醛类溶剂接触进行混合,加热保温进行缩聚反应,生成聚酰胺酸溶液；b)将所得聚酰胺酸溶液与催化剂和消泡剂混合,在加热回流的条件下发生脱水反应,得到完全亚胺化的聚酰亚胺固体悬浮物；c)将所得聚酰亚胺固体悬浮物进行过滤并干燥,得到含卤素封端剂的热塑性聚酰亚胺。本发明方法能够使所得热塑性聚酰亚胺在同等分子量或聚合度条件下的聚合物结晶度提高,从而实现热塑性聚酰亚胺在高温条件下的流动性好,同时在合成过程中反应时间缩短、回流过程泡沫减少。(The invention belongs to the technical field of polyimide synthesis, and particularly relates to thermoplastic polyimide containing a halogen end-capping reagent and a preparation method thereof, wherein the preparation method comprises the following steps: a) contacting and mixing aromatic binary primary amine, aromatic binary anhydride and an aromatic end-capping reagent containing halogen with a ketone and an aldehyde solvent, heating and preserving heat for polycondensation reaction to generate a polyamic acid solution; b) mixing the obtained polyamic acid solution with a catalyst and a defoaming agent, and carrying out dehydration reaction under the condition of heating reflux to obtain a polyimide solid suspension which is fully imidized; c) and filtering and drying the obtained polyimide solid suspension to obtain the thermoplastic polyimide containing the halogen end-capping reagent. The method can improve the polymer crystallinity of the obtained thermoplastic polyimide under the condition of the same molecular weight or polymerization degree, thereby realizing good fluidity of the thermoplastic polyimide under the condition of high temperature, shortening the reaction time in the synthesis process and reducing the foam in the reflux process.)

1. A method for preparing thermoplastic polyimide is characterized by comprising the following steps:

a) contacting and mixing aromatic binary primary amine, aromatic binary anhydride and an aromatic end-capping reagent containing halogen with a solvent, heating and preserving heat for polycondensation reaction to generate a polyamic acid solution; wherein, the solvent is ketone or aldehyde solvent;

the molar using amount of the aromatic dibasic primary amine is more than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing the halogen is an aromatic end-capping agent containing an anhydride group and the halogen;

or the molar amount of the aromatic dibasic primary amine is less than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing the halogen is an aromatic end-capping agent containing amino and halogen;

b) mixing the obtained polyamic acid solution with a catalyst and a defoaming agent, and carrying out dehydration reaction under the condition of heating reflux to obtain a polyimide solid suspension which is fully imidized;

c) and filtering and drying the obtained polyimide solid suspension to obtain the thermoplastic polyimide containing the halogen end-capping reagent.

2. The process according to claim 1, wherein the ketone or aldehyde solvent has a solubility in water of 0.05g/100g to 2.4g/100 g;

the ketone and aldehyde solvent is one or more selected from aliphatic ketone solvent with boiling point of 126.5-193 ℃, aromatic aldehyde solvent with boiling point of 126.5-193 ℃ and aliphatic aldehyde solvent with boiling point of 126.5-193 ℃; preferably one or more selected from cyclohexanone, 2-octanone, benzaldehyde and n-heptanal.

3. The method of claim 1 or 2, wherein the aromatic primary diamine is a C6-C27 aromatic diamine, preferably one or more selected from the group consisting of diaminodiphenyl ether, diaminodiphenyl sulfone, triphendiether diamine, diaminodiphenylmethane, dimethyldiaminodiphenylmethane, bisphenol a diether diamine, biphenol diether diamine, and phenylenediamine, more preferably one or more selected from the group consisting of diaminodiphenyl ether, diaminodiphenyl sulfone, triphendiether diamine, bisphenol a diether diamine, biphenol diether diamine, and phenylenediamine; and/or

The aromatic binary acid anhydride is C10-C31 aromatic dianhydride, preferably selected from one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, triphenyl diether dianhydride, diphenyl sulfone dianhydride, bisphenol A type diether dianhydride and bisphenol S diether dianhydride, more preferably selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, triphenyl diether dianhydride, bisphenol A type diether dianhydride and bisphenol S diether dianhydride.

4. The production method according to any one of claims 1 to 3,

the aromatic end-capping agent containing anhydride groups and halogens is selected from one or more of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-bromophenthalic anhydride, 4-bromophenthalic anhydride, tetrabromobenzoic anhydride and tetrachlorophthalic anhydride; preferably one or more selected from 3-chlorophthalic anhydride, 4-chlorophthalic anhydride and 4-bromophenylic anhydride;

the aromatic end capping agent containing amino and halogen is selected from one or more of parachloroaniline, m-chloroaniline and chloromethylaniline, and is preferably selected from parachloroaniline and/or m-chloroaniline.

5. The method according to any one of claims 1 to 4, wherein in step a), when the amount of the aromatic diamine primary amine is larger than the amount of the aromatic diamine anhydride, the molar ratio of the aromatic diamine primary amine to the aromatic diamine anhydride is 1:0.96 to 1: 0.995; when the using amount of the aromatic diamine is less than that of the aromatic diamine anhydride, the molar ratio of the aromatic diamine primary amine to the aromatic diamine anhydride is 1:1.005 to 1: 1.04;

in step a), the molar ratio of the aromatic diprimary amine to the aromatic end-capping agent containing halogen is 1:0.01 to 1:0.08, preferably 1:0.04 to 1: 0.06;

in the step a), the mass ratio of the total mass of the aromatic primary diamine, the aromatic dicarboxylic anhydride and the aromatic end-capping agent containing halogen to the ketone and the aldehyde solvent is 10:100 to 25:100, preferably 15:100 to 22: 100.

6. The preparation process according to any one of claims 1 to 5, wherein in step a), the process conditions of the polycondensation reaction comprise: the reaction temperature is 80-120 ℃, and preferably is 100-110 ℃; the reaction time is 1-8h, preferably 3-7 h.

7. The process according to any one of claims 1 to 6, wherein in step b), the catalyst is selected from one or more of benzenesulfonic acid, p-toluenesulfonic acid, thionyl chloride, trifluoroacetic anhydride and benzenesulfonyl chloride;

the mass of the catalyst accounts for 0.5-3 wt%, preferably 1-2 wt% of the total mass of the aromatic dibasic primary amine, the aromatic dibasic acid anhydride and the aromatic end-capping agent containing halogen; and/or

In the step b), the defoaming agent is an alcohol ether defoaming agent, preferably one or more selected from polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxypropylene glycerol ether and polyoxypropylene polyoxyethylene glycerol ether;

the mass of the defoaming agent accounts for 0.5-3.5 wt%, preferably 1.5-2.5 wt% of the total mass of the aromatic dibasic primary amine, the aromatic dibasic acid anhydride and the aromatic end-capping agent containing halogen.

8. The method according to any one of claims 1 to 7, wherein in step b), the process conditions of the dehydration reaction include: the reaction temperature is 126.5-193 ℃, preferably 152-178 ℃; the reaction time is 3 to 24 hours, preferably 4 to 7 hours.

9. The method according to any one of claims 1 to 8, wherein in step c), the drying is vacuum drying;

preferably, the process conditions of the vacuum drying include: the drying temperature is 170-240 ℃, and more preferably 180-220 ℃; the vacuum degree is-0.1 to-0.09 MPa; the drying time is 3 to 8 hours, more preferably 4 to 6 hours.

10. A thermoplastic polyimide obtained by the production method as described in any one of claims 1 to 9, wherein the thermoplastic polyimide has a weight average molecular weight of 46000-68000; the average polymerization degree is 96-98; the crystallinity is 8-30%; the intrinsic viscosity is 0.5-0.54 dL/g.

Technical Field

The invention belongs to the technical field of polyimide synthesis, and particularly relates to thermoplastic polyimide containing a halogen end-capping reagent and a preparation method thereof.

Background

The thermoplastic polyimide is a type of polyimide which can be processed and formed by melt extrusion, injection molding and the like, and can be applied to the aspects of automobile headlight reflectors, flexible copper clad plates, wear-resistant smoke machine materials and the like. The more well-known thermoplastic polyimide resin brands in the world today include: ultem and EXTEM of SABIC, AURUMN and SUPER AURUMN of Mitsui Chemicals, and the like.

Most of the conventional thermoplastic polyimides, except SUPET auruman, are amorphous and have heat resistance. Due to the heat resistance of the imide group contained in the material, the material has better heat resistance, but due to higher viscous flow temperature, the processing conditions required by other resins except Ultem during extrusion and injection molding are harsh, the viscous flow temperature is above 340 ℃, and even the high temperature close to 400 ℃ is required by individual brands during extrusion. Therefore, during extrusion injection molding, the viscous flow temperature needs to be reduced as much as possible under the premise of keeping the glass transition temperature unchanged, so that the processing and forming of extrusion and injection molding are relatively easy.

U.S. Pat. No. 3,79631 discloses a process for the polycondensation to form polyimides in aprotic polar solvents: and performing low-temperature polycondensation on dianhydride and diamine in N, N-dimethylacetamide, N-dimethylformamide or N-methylpyrrolidone to obtain a polyamic acid solution, and adding acetic anhydride and a tertiary amine catalyst to obtain the polyimide. The method mainly uses aprotic polar solvent, such as N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like, and the adding molar ratio of the aprotic polar solvent to dianhydride and diamine is close to 1:1. In addition, when the molecular weight of the polyamic acid solution reaches a certain value, a precipitating agent such as organic alkalis like triethylamine and pyridine and an acid anhydride catalyst such as acetic anhydride are added into the system. The melt-type thermoplastic polyimide is generally soluble in an aprotic polar solvent, and therefore, the solvent needs to be added to water or alcohol to precipitate, and the solid melt-type thermoplastic polyimide can be obtained after high-shear stirring. The polyimide prepared by the method has the obvious defects that substances such as acetic anhydride, pyridine and the like cannot be separated in an aprotic polar solvent, the amount of waste water is large, and the cost is high.

Chinese patent document CN102604093A discloses a method for synthesizing polyimide powder by using aliphatic hydrocarbon, aromatic hydrocarbon and halogenated hydrocarbon as solvents, which comprises the following steps: the dianhydride and the diamine are dehydrated in one step in the heating process to generate polyimide, the generated water is taken out of the system, and the polyimide powder is suspended in the solvent. Although the method uses a nonpolar hydrocarbon solvent, when the meltable thermoplastic polyimide is prepared, the product is not dissolved in the hydrocarbon solvent and is in a suspension state, thereby being beneficial to product separation. However, the method has slow reaction rate and low reaction efficiency.

In conclusion, the existing polyimide synthesis process has some problems, such as poor fluidity at high temperature and increased difficulty of melt processing; in addition, in the reaction process, if an aprotic polar solvent is used for synthesizing polyimide, water generated in the imidization process cannot be completely separated, so that the reaction is not thorough and a reverse reaction is easy to occur; if the polyimide is prepared by the hydrocarbon solvent reflux method, the reaction rate is slow and the reaction time is long because the polyamic acid is not easily soluble in the solvent. Both methods can cause the imidization degree of polyimide molecules to be low, dehydration is not thorough, the thermal expansion coefficient of the material is larger, and the dimensional stability of the material is poor.

The synthesis of aromatic polyimides using ketones and aldehydes as solvents has also been reported, and is similar to the hydrocarbon solvent reflux method. In contrast, although the method of using ketone and aldehyde solvents for reflux to synthesize polyimide is simpler and more convenient than the aprotic solvent method, and has obvious economical efficiency, the method also has some defects: although the reaction rate is faster than that of the hydrocarbon solvent reflux method, the reaction rate is slower than that of the method for synthesizing polyimide by using the aprotic polar solvent. In the process of solvent reflux, as the solvent is azeotropic with water and the surface tension of the high-boiling-point ketone and aldehyde solvents is higher, the solvent can generate more foams during reflux, and the mass transfer and heat transfer are influenced in the reaction process. After the reaction is finished, the imidization degree of the product is not complete, and high-temperature vacuum drying treatment at 250-350 ℃ is further needed, so that certain rigor is brought to the operating conditions.

The crystallinity of crystalline polymers, such as polyolefin, polyetheretherketone and polyphenylene sulfide, is usually above 60%, and the corresponding rheological curve is an abrupt curve, i.e. the high molecular compound becomes a high-fluidity fluid after reaching the abrupt viscous flow temperature, and the processing is easy. However, most of the aromatic polyimides belong to amorphous polyimides, the crystallinity of which is usually below 45%, and the corresponding rheological curve is a gradual change curve, that is, the materials have no obvious melting temperature. That is, if it is intended to facilitate the flowability of the amorphous polyimide during processing, two factors need to be considered: the molecular weight is the first, because the melting temperature of the amorphous polymer is gradually increased along with the increase of the molecular weight, the amorphous polymer is not easy to melt, but the molecular weight is too low to meet the requirement of the polymer on the molecular weight; the second is that the degree of crystallinity, the melting temperature of the high molecular polymer with similar molecular weight and similar polymerization degree is related to the degree of crystallinity, the higher the degree of crystallinity of the molecule is, the more the rheological curve of the molecule has mutation temperature, after the mutation temperature, the fluidity of the molecule is obviously increased, and even if the degree of crystallinity is higher, the fluidity of the molecule is also good.

According to the above analysis of factors affecting processing rheology, for polyimide with low crystallinity, in order to increase its processing fluidity, a capping agent may be used to control the molecular weight, as described in patent document CN101062980A, using a monoamine or a monoanhydride as a capping agent. The method belongs to a conventional method for controlling molecular weight.

If it is desired to obtain polymers of the same degree of polymerization and similar molecular weight by the end-capping agent, and the intention is to change the fluidity of the resin under high temperature conditions, it is necessary to change the crystallinity of the high molecular weight polymer. The crystallinity of the high molecular polymer can be improved by introducing some special groups on the molecular structure, such as halogen side groups, such as fluorine-containing side groups and the like in dianhydride monomers or diamine monomers. However, this causes the halogen content in the material to be too high and the crystallinity to be too high, which deteriorates the material properties.

Therefore, how to balance the influence of the above two factors on the performance of the polyimide material is a topic to be researched.

Disclosure of Invention

The present invention is directed to structurally solve the problems of processability (i.e., difficulty in flowing under high temperature conditions) and the problems of synthesis (e.g., long reaction time, incomplete imidization, and more foams during reflow) of thermoplastic polyimides, and to provide a thermoplastic polyimide and a method for preparing the same, which can improve the crystallinity of a polymer of the obtained thermoplastic polyimide under the same molecular weight or polymerization degree, thereby achieving good flowability of the thermoplastic polyimide under high temperature conditions, and at the same time, shorten the reaction time during synthesis and reduce foams during reflow.

The processability of the thermoplastic polyimide under high temperature conditions includes, for example, a problem of how good the fluidity of the material under high temperature conditions is; when the molecular weight of the thermoplastic polyimide is large and the crystallinity is low, the flowability is poor; when the molecular weight of the thermoplastic polyimide is small and the crystallinity is high, the fluidity is good. However, if the molecular weight of the polymer is too small, the molecular weight requirement of the polymer cannot be met. Therefore, it is required to achieve a good balance of molecular weight and crystallinity of the thermoplastic polyimide.

In order to achieve the purpose, the technical scheme of the invention is as follows:

in one aspect, there is provided a method for preparing a thermoplastic polyimide, comprising the steps of:

a) contacting and mixing aromatic binary primary amine, aromatic binary anhydride and an aromatic end-capping reagent containing halogen with a solvent, heating and preserving heat for polycondensation reaction to generate a polyamic acid solution; wherein, the solvent is ketone or aldehyde solvent;

the molar using amount of the aromatic dibasic primary amine is more than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing the halogen is an aromatic end-capping agent containing an anhydride group and the halogen;

or the molar amount of the aromatic dibasic primary amine is less than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing the halogen is an aromatic end-capping agent containing amino and halogen;

b) mixing the obtained polyamic acid solution with a catalyst and a defoaming agent, and carrying out dehydration reaction under the condition of heating reflux to obtain a polyimide solid suspension which is fully imidized;

c) the resulting polyimide suspension solids are filtered and dried to provide a halogen-containing end-capping agent-containing thermoplastic polyimide (e.g., in powder form).

According to the production method provided by the present invention, in some examples, the ketone and aldehyde solvents have a solubility in water of 0.05g/100g to 2.4g/100g (e.g., 0.1g/100g, 0.5g/100g, 1g/100g, 1.5g/100 g).

In some examples, the ketone and aldehyde solvents are selected from one or more of aliphatic ketone solvents having a boiling point of 126.5 to 193 ℃, aromatic aldehyde solvents having a boiling point of 126.5 to 193 ℃, and aliphatic aldehyde solvents having a boiling point of 126.5 to 193 ℃; preferably one or more selected from cyclohexanone, 2-octanone, benzaldehyde and n-heptanal.

In the present invention, the ketone and aldehyde solvents are used to make the aromatic primary diamine, the aromatic dicarboxylic anhydride and the polyamic acid obtained by the polycondensation reaction as monomers in the system easily dissolved in the solvents, which leads to an increase in the reaction rate. When the ketone and aldehyde solvents are refluxed, the polyamic acid is dehydrated to generate imidization, and the solubility of water in the ketone and aldehyde solvents used in the invention is low, so that the generated water can be quickly discharged out of a reaction system, and a reversible reaction can not be generated, thereby improving the imidization degree and ensuring full and complete imidization.

According to the preparation method provided by the invention, in some examples, the aromatic primary diamine is an aromatic diamine having a carbon number of 6-27, preferably one or more selected from diaminodiphenyl ether, diaminodiphenyl sulfone, diphenylene diether diamine, diaminodiphenyl methane, dimethyldiaminodiphenyl methane, bisphenol a diether diamine, biphenol diether diamine and phenylenediamine, more preferably one or more selected from diaminodiphenyl ether, diaminodiphenyl sulfone, triphenyldiether diamine, bisphenol a diether diamine, biphenol diether diamine and phenylenediamine.

In some examples, the aromatic dibasic acid anhydride is an aromatic dianhydride of C10-C31, preferably selected from one or more of pyromellitic dianhydride, benzophenone dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, triphenyl diether dianhydride, diphenyl sulfone dianhydride, bisphenol a type diether dianhydride, and bisphenol S diether dianhydride, more preferably selected from one or more of pyromellitic dianhydride, biphenyl dianhydride, diphenyl ether dianhydride, triphenyl diether dianhydride, bisphenol a type diether dianhydride, and bisphenol S diether dianhydride.

In the present invention, the halogen-containing aromatic end-capping agent may include an aromatic end-capping agent containing an anhydride group and a halogen, and an aromatic end-capping agent containing an amino group and a halogen. In some examples, when the molar amount of the aromatic dibasic acid anhydride is greater than the molar amount of the aromatic dibasic primary amine, the end-capping is performed using an aromatic end-capping agent containing an amino group and a halogen. For example, capping is performed using one or more of p-chloroaniline, m-chloroaniline, and chloromethylaniline. In some examples, when the molar amount of the aromatic diprimary amine is greater than the molar amount of the aromatic dibasic acid anhydride, the end-capping is performed using an aromatic end-capping agent containing an anhydride group and a halogen. For example, capping is performed using one or more of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-bromophthalic anhydride, 4-bromophthalic anhydride, tetrabromophthalic anhydride, and tetrachlorophthalic anhydride.

In some preferred embodiments, the aromatic capping agent containing anhydride groups and halogens is selected from one or more of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride, 3-bromophthalic anhydride, 4-bromophthalic anhydride, tetrabromobenzoic anhydride, and tetrachlorophthalic anhydride; more preferably one or more selected from the group consisting of 3-chlorophthalic anhydride, 4-chlorophthalic anhydride and 4-bromophenylic anhydride.

In some preferred embodiments, the amino and halogen-containing aromatic end-capping agent is selected from one or more of para-chloroaniline, meta-chloroaniline, and chloromethylaniline, more preferably para-chloroaniline and/or meta-chloroaniline.

In some examples, a method of preparing a thermoplastic polyimide comprises the steps of:

a) contacting and mixing aromatic binary primary amine, aromatic binary anhydride and an aromatic end-capping reagent containing halogen with a solvent, heating and preserving heat for polycondensation reaction to generate a polyamic acid solution; wherein, the solvent is ketone or aldehyde solvent;

the molar using amount of the aromatic dibasic primary amine is more than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing the halogen is an aromatic end-capping agent containing an anhydride group and the halogen;

b) mixing the obtained polyamic acid solution with a catalyst and a defoaming agent, and carrying out dehydration reaction under the condition of heating reflux to obtain a polyimide solid suspension which is fully imidized;

c) the resulting polyimide suspension solids are filtered and dried to provide a halogen-containing end-capping agent-containing thermoplastic polyimide (e.g., in powder form).

In some examples, a method of preparing a thermoplastic polyimide comprises the steps of:

a) contacting and mixing aromatic binary primary amine, aromatic binary anhydride and an aromatic end-capping reagent containing halogen with a solvent, heating and preserving heat for polycondensation reaction to generate a polyamic acid solution; wherein, the solvent is ketone or aldehyde solvent;

the molar amount of the aromatic dibasic primary amine is less than that of the aromatic dibasic acid anhydride, and the aromatic end-capping agent containing halogen is an aromatic end-capping agent containing amino and halogen;

b) mixing the obtained polyamic acid solution with a catalyst and a defoaming agent, and carrying out dehydration reaction under the condition of heating reflux to obtain a polyimide solid suspension which is fully imidized;

c) the resulting polyimide suspension solids are filtered and dried to provide a halogen-containing end-capping agent-containing thermoplastic polyimide (e.g., in powder form).

To control the molecular weight of the resulting thermoplastic polyimide, a common approach is to add a mono-anhydride or mono-amine endblocker. The amount of the end-capping agent used determines the degree of polymerization or molecular weight of the product, and a suitable amount of the end-capping agent can be added to obtain a polymer having a suitable molecular weight. However, even though the polyimide has a suitable molecular weight or polymerization degree and a good fluidity, the polyimide still flows at a high viscous flow temperature, and can be extruded and pelletized. Therefore, if the fluidity of the thermoplastic polyimide can be made better while maintaining the equivalent molecular weight or polymerization degree, it is necessary to lower the viscous flow temperature; increasing the crystallinity of the molecules, results in a decrease in the viscous flow temperature. In the research, the applicant finds that the introduction of a certain amount of halogen into the terminal group of the molecular chain of the thermoplastic polyimide can increase the crystallinity of the molecule. The invention uses the end capping agent containing halogen to change the crystallinity of the product molecule and can ensure a certain range of molecular weight and polymerization degree.

The invention adds the aromatic end capping agent containing halogen, which has the function of improving the crystallinity of the polymer under the condition of the same molecular weight or polymerization degree. The presence of halogens only at the end groups of the product and not in the molecular backbone can alter the crystallinity of the material.

According to the preparation method provided by the present invention, in some examples, in the step a), when the amount of the aromatic diamine primary amine is larger than the amount of the aromatic diamine anhydride, the molar ratio of the aromatic diamine primary amine to the aromatic diamine anhydride is 1:0.96 to 1:0.995 (e.g., 1:0.97, 1:0.98, 1: 0.99); when the amount of the aromatic diamine is less than that of the aromatic diamine anhydride, the molar ratio of the aromatic diamine to the aromatic diamine anhydride is 1:1.005 to 1:1.04 (e.g., 1:1.01, 1:1.02, 1: 1.03).

In the invention, the using amount of the aromatic dibasic primary amine is not equal to the molar using amount of the aromatic dibasic acid anhydride.

In some examples, in step a), the molar ratio of the aromatic diprimary amine to the halogen-containing aromatic capping agent is 1:0.01 to 1:0.08 (e.g., 1:0.02, 1:0.03, 1:0.05, 1:0.07), preferably 1:0.04 to 1: 0.06. In the reaction system, the molecular weight of the product is lowered by using an excessive amount of the aromatic end-capping agent containing halogen.

In some examples, in the step a), the mass ratio of the sum of the mass of the aromatic primary diamine, the aromatic dicarboxylic anhydride, and the aromatic end-capping agent containing halogen to the mass of the ketone and the aldehyde solvent is 10:100 to 25:100 (e.g., 12:100, 14:100, 18:100, 20:100, 24:100), and preferably 15:100 to 22: 100.

In some examples, in step a), the process conditions of the polycondensation reaction include: the reaction temperature is 80-120 deg.C (e.g., 90 deg.C, 95 deg.C, 105 deg.C, 115 deg.C), preferably 100 deg.C and 110 deg.C; the reaction time is from 1 to 8h (e.g., 2h, 4h, 6h, 7.5h), preferably from 3 to 7 h.

According to the preparation method provided by the invention, in some examples, in the step b), the catalyst is selected from one or more of benzenesulfonic acid, p-toluenesulfonic acid, thionyl chloride, trifluoroacetic anhydride and benzenesulfonyl chloride.

In some examples, the catalyst comprises 0.5 to 3 wt% (e.g., 0.6 wt%, 0.8 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2.5 wt%, 2.8 wt%), preferably 1 to 2 wt%, of the total mass of the aromatic primary diamine, the aromatic dicarboxylic anhydride, and the halogen-containing aromatic end-capping agent.

In some examples, in step b), the antifoaming agent is an alcohol ether antifoaming agent, preferably one or more selected from polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxypropylene glycerol ether and polyoxypropylene polyoxyethylene glycerol ether.

The applicant found unexpectedly that when ketone or aldehyde solvents are used in the system, the problem of foaming is high, and the safety problem of water breaking on the surface of the solvents and the impact of foam on equipment is affected. The surface tension of the used ketone and aldehyde solvents is high, and the water generated in the system is difficult to break on the surfaces of the solvents, so that a large amount of bubbles are generated and occupy the volume of a reactor; and the bubbles will entrain solids to impact the reaction equipment. Therefore, in order to overcome the defects caused by the ketone and aldehyde solvents, the invention specifically selects to add the defoaming agent into the system to eliminate the foam generated in the solvent reflux process.

In some examples, the defoaming agent accounts for 0.5 to 3.5 wt% (e.g., 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.8 wt%, 2 wt%, 2.8 wt%, 3 wt%), preferably 1.5 to 2.5 wt%, of the total mass of the aromatic primary diamine, the aromatic dicarboxylic anhydride, and the halogen-containing aromatic end-capping agent.

In some examples, in step b), the process conditions of the dehydration reaction include: the reaction temperature is 126.5-193 deg.C (e.g., 130 deg.C, 140 deg.C, 150 deg.C, 160 deg.C, 170 deg.C, 180 deg.C, 190 deg.C), preferably 152-178 deg.C; the reaction time is 3 to 24 hours (e.g., 5 hours, 8 hours, 10 hours, 15 hours, 20 hours), preferably 4 to 7 hours.

According to the preparation method provided by the invention, in some examples, in the step c), the drying is vacuum drying.

In some preferred embodiments, the process conditions of the vacuum drying include: the drying temperature is 170-; a degree of vacuum of-0.1 to-0.09 MPa (e.g., -0.095 MPa); the drying time is 3 to 8 hours (e.g., 3.5 hours, 4.5 hours, 5.5 hours, 6.5 hours, 7.5 hours), and more preferably 4 to 6 hours.

According to the preparation method of the present invention, in some examples, the chemical structure of the thermoplastic polyimide is represented by formula (I) or formula (II):

(1) when the molar amount of the aromatic dibasic acid anhydride is more than that of the aromatic dibasic primary amine, an aromatic end-capping agent containing amino and halogen is used for end capping, and the thermoplastic polyimide has the structure:

(2) when the molar amount of the aromatic dibasic primary amine is more than that of the aromatic dibasic acid anhydride, the end capping is carried out by using an aromatic end-capping agent containing anhydride groups and halogens, and the thermoplastic polyimide has the structure:

in the formulae (I) and (II), A represents an aromatic group, e.g. selected from

E represents an aromatic group, e.g. selected from

X represents a halogen, for example, selected from F, Cl or Br.

R and R' are the same or different and are each independently selected from the group consisting of: such as, for example,

in the present invention, the chemical structure of the thermoplastic polyimide is not limited to the above-listed structures.

In another aspect, there is also provided a thermoplastic polyimide obtained by the production method as described above, the thermoplastic polyimide having a weight average molecular weight of 46000-68000 (e.g., 48000, 50000, 55000, 60000, 65000); an average degree of polymerization of 96 to 98 (e.g., 97); its crystallinity is 8-30% (e.g., 10%, 15%, 20%, 25%); the intrinsic viscosity is 0.5-0.54dL/g (e.g., 0.51dL/g, 0.52dL/g, 0.53 dL/g).

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

1. the aromatic end capping agent containing halogen is used for end capping polyimide molecules, so that the molecular weight and the polymerization degree of the polyimide molecules can be controlled, and introduced halogen atoms can increase the crystallinity of the whole molecular chain, so that the viscous flow temperature of the obtained polyimide can be reduced under the condition of the same polymer molecular weight and polymerization degree, the processing of the polyimide is easy, and the glass transition temperature and the long-term use temperature are kept unchanged.

2. Ketone and aldehyde solvents are used in the process of synthesizing polyimide, so that the synthesis process can be simplified, and the synthesis period can be shortened; the ketone and aldehyde solvents used can be recovered as they are and reused.

3. In a preferred embodiment, catalysts such as benzenesulfonic acid, p-toluenesulfonic acid, thionyl chloride, trifluoroacetic anhydride, benzenesulfonyl chloride and the like are used to accelerate the rate of the dehydration reaction, thereby improving the imidization degree and ensuring sufficient and complete imidization.

4. In the preferred embodiment, the alcohol ether defoaming agent is used, so that foam generated by water in the reaction process can be eliminated, and the reaction process is safer and smoother.

Detailed Description

In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.

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< test methods >

Glass transition temperature test: reference is made to standard GBT 22232-;

viscous flow temperature test: reference standard GB 3682-83;

and (3) testing the crystallinity: reference to Standard ASTM F2625-2010 (2016);

testing the weight average molecular weight: reference standard GBT 36214.2-2018;

average degree of polymerization test: and (4) calculating the average polymerization degree according to the weight average molecular weight test result and the molecular formula by referring to the standard GBT 36214.2-2018.