阅读说明：本技术 一种低黄色指数无色透明聚酰亚胺薄膜的制备方法 (Preparation method of low-yellow-index colorless transparent polyimide film ) 是由 李祥涛 陈图强 王宏 徐鸿 胡浩亨 于 2020-07-24 设计创作，主要内容包括：本发明了公开一种低黄色指数无色透明聚酰亚胺薄膜的制备方法,包括如下制备步骤：S1：取N,N-二甲基乙酰胺溶剂处理后制得N,N-二甲基乙酰胺溶剂A和N,N-二甲基乙酰胺溶剂B；S2：取处理后的二胺固体与N,N-二甲基乙酰胺溶剂A混合,制得混合溶液A；S3：取单酐类化合物与N,N-二甲基乙酰胺溶剂B制得混合溶液B；S4：取处理后二酐固体与混合溶液A制得预处理树脂液,取混合溶液B继续加入反应容器中,制得聚合物溶液；S5：将聚合物溶液涂覆于玻璃板上,烘干后得到聚酰亚胺薄膜。本发明最终制得的无色透明聚酰亚胺薄膜的黄色指数处于较低的范围,从而能更好的控制产品的质量,满足更高端产业需求。(The invention discloses a preparation method of a low-yellow-index colorless transparent polyimide film, which comprises the following preparation steps: s1: treating an N, N-dimethylacetamide solvent to obtain an N, N-dimethylacetamide solvent A and an N, N-dimethylacetamide solvent B; s2: mixing the processed diamine solid with an N, N-dimethylacetamide solvent A to prepare a mixed solution A; s3: taking a mono-anhydride compound and an N, N-dimethylacetamide solvent B to prepare a mixed solution B; s4: preparing a pretreated resin liquid from the treated dianhydride solid and the mixed solution A, and continuously adding the mixed solution B into a reaction vessel to prepare a polymer solution; s5: and coating the polymer solution on a glass plate, and drying to obtain the polyimide film. The yellow index of the finally prepared colorless transparent polyimide film is in a lower range, so that the quality of the product can be better controlled, and the requirements of higher-end industries are met.)

1. A preparation method of a low-yellow-index colorless transparent polyimide film is characterized by comprising the following steps: the preparation method comprises the following preparation steps:

s1: placing the N, N-dimethylacetamide solvent in a rotary evaporator for dehydration and purification treatment, pouring the N, N-dimethylacetamide solvent A and the N, N-dimethylacetamide solvent B into two dry glass flasks respectively after the dehydration and purification treatment is finished, and standing for later use;

s2: putting the diamine solid into a sublimer for purification treatment, mixing the diamine solid in X weight parts with N, N-dimethylacetamide solvent A in Z weight parts after the purification treatment is finished, and fully stirring for 5-30 minutes until the diamine solid is completely dissolved to prepare a mixed solution A;

s3: mixing a mono-anhydride compound and an N, N-dimethylacetamide solvent B according to a weight ratio of 0.05: 1-0.3: 1 to prepare a mixed solution B;

s4: putting dianhydride solid into a sublimator for purification treatment, after the purification treatment is finished, putting Y parts by weight of dianhydride solid and the mixed solution A into a reaction container, fully stirring for 5-24 hours to prepare a pre-treated resin solution, continuously adding the mixed solution B into the reaction container, and continuously stirring for 1-5 hours to fully perform a polymerization reaction, wherein the weight ratio of the mixed solution B to the pre-treated resin solution is 0.5: 100-5: 100, and a polymer solution with the viscosity coefficient of 5000-70000 mPa & s is prepared;

s5: and uniformly coating the polymer solution on a glass plate, heating to 120 ℃ and keeping the temperature for 30-50 minutes, then gradually heating to 220 ℃ in a gradient of 5-15 ℃, then drying for 30-50 minutes, and finally heating to 310 ℃ and keeping the temperature for 30-45 minutes to finally obtain the colorless transparent polyimide film with the thickness of 50-100 microns.

2. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: in the steps S2, S4, the X parts by weight diamine solids, Y parts by weight dianhydride solids, and Z parts by weight N, N-dimethylacetamide solvent a satisfy the following formula:

3. the method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: the mono-anhydride compound comprises one of ethane residue, propane residue, cyclopropane residue, cyclobutane residue, cyclopentane residue, cyclohexane residue and 1, 2-benzene residue.

4. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: in the step S1, the water content of the N, N-dimethylacetamide solvent is 0 to 0.05% after dehydration and purification.

5. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: in the steps S2 and S4, the molar ratio of the dianhydride solid to the diamine solid is 0.95:1 to 1.05: 1.

6. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: the molecular chain of the colorless transparent polyimide film comprises a repeating unit structure shown in formula 1, wherein the repeating unit structure shown in formula 1 is as follows:

wherein the content of the first and second substances,R_ais cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_bIs one or more of 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4 '-diaminodiphenyl sulfone residue, 3' -diaminodiphenyl sulfone residue, 2 '-bis (trifluoromethyl) benzidine residue and 4, 4' - (hexafluoroisopropylidene) diphenylamine residue.

7. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: in step S4, the molecular chain of the pretreated resin liquid contains a unit structure of formula 2, where the unit structure of formula 2 is as follows:

wherein R is_cIs cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_dIs one or more of 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4 '-diaminodiphenyl sulfone residue, 3' -diaminodiphenyl sulfone residue, 2 '-bis (trifluoromethyl) benzidine residue and 4, 4' - (hexafluoroisopropylidene) diphenylamine residue.

8. The method for preparing a low-yellowness index colorless transparent polyimide film according to claim 7, wherein: in step S4, the molecular chain of the pretreated resin solution further includes a unit structure of formula 3, where the unit structure of formula 3 is as follows:

wherein R is_eIs cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_fIs one or more of 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4 '-diaminodiphenyl sulfone residue, 3' -diaminodiphenyl sulfone residue, 2 '-bis (trifluoromethyl) benzidine residue and 4, 4' - (hexafluoroisopropylidene) diphenylamine residue, R_gIs one or more of ethane residue, propane residue, cyclopropane residue, cyclobutane residue, cyclopentane residue, cyclohexane residue and 1, 2-benzene residue.

9. The method for preparing a low-yellow-index colorless transparent polyimide film according to claim 1, wherein the method comprises the following steps: the colorless transparent polyimide film has a yellowness index < 2.

Technical Field

The invention relates to the field of polyimide films, in particular to a preparation method of a low-yellow-index colorless transparent polyimide film.

Background

At present, the flexible display screen industry is rapidly developed, and a plurality of panel manufacturers develop flexible display screen projects. Polyimide is a key material of a flexible display screen, and the yellow index is an important index of a polyimide film material. Polyimide materials are mostly polymerized from diamines and dianhydrides, but the diamine residues are susceptible to high temperatures, which causes polyimide films to be thermally yellowed. Therefore, the technology for preparing colorless transparent polyimide films with ultra-low yellow index still needs to be further improved.

Disclosure of Invention

Aiming at the defects that diamine residues in polyimide in the prior art are easy to be thermally yellowed and the like, the invention provides a novel preparation method of a low-yellow-index colorless transparent polyimide film.

In order to solve the technical problems, the invention is realized by the following technical scheme:

a preparation method of a low-yellow-index colorless transparent polyimide film comprises the following preparation steps:

s1: placing the N, N-dimethylacetamide solvent in a rotary evaporator for dehydration and purification treatment, pouring the N, N-dimethylacetamide solvent A and the N, N-dimethylacetamide solvent B into two dry glass flasks respectively after the dehydration and purification treatment is finished, and standing for later use;

s2: putting the diamine solid into a sublimer for purification treatment, mixing the diamine solid in X weight parts with N, N-dimethylacetamide solvent A in Z weight parts after the purification treatment is finished, and fully stirring for 5-30 minutes until the diamine solid is completely dissolved to prepare a mixed solution A;

s3: mixing a mono-anhydride compound and an N, N-dimethylacetamide solvent B according to a weight ratio of 0.05: 1-0.3: 1 to prepare a mixed solution B;

s4: putting dianhydride solid into a sublimator for purification treatment, after the purification treatment is finished, putting Y parts by weight of dianhydride solid and the mixed solution A into a reaction container, fully stirring for 5-24 hours to prepare a pre-treated resin solution, continuously adding the mixed solution B into the reaction container, and continuously stirring for 1-5 hours to fully perform a polymerization reaction, wherein the weight ratio of the mixed solution B to the pre-treated resin solution is 0.5: 100-5: 100, and a polymer solution with the viscosity coefficient of 5000-70000 mPa & s is prepared;

s5: and uniformly coating the polymer solution on a glass plate, heating to 120 ℃ and keeping the temperature for 30-50 minutes, then gradually heating to 220 ℃ in a gradient of 5-15 ℃, then drying for 30-50 minutes, and finally heating to 310 ℃ and keeping the temperature for 30-45 minutes to finally obtain the colorless transparent polyimide film with the thickness of 50-100 microns.

In step S1 of the present invention, the N, N-dimethylacetamide solvent contains a part of water, and the reduced pressure distillation is performed by using a rotary evaporator, so as to obtain the N, N-dimethylacetamide solvent a and the N, N-dimethylacetamide solvent B with higher purity, thereby preventing the water from interfering with the subsequent polymerization reaction.

In step S2 of the present invention, the diamine solid is an important monomer for producing polyimide, and has a very high purity, and the diamine solid can be purified by a sublimer to obtain a high purity diamine solid. Adding the diamine solid into the N, N-dimethylacetamide solvent A, and uniformly dispersing the diamine solid in the N, N-dimethylacetamide solvent A after fully stirring, so that the subsequent polymerization reaction is fully and completely facilitated.

In step S3 of the present invention, the monoanhydride compound is completely dissolved in the N, N-dimethylacetamide solvent B, which contributes to sufficient progress of the subsequent reaction.

In step S4 of the present invention, dianhydride solid is another important monomer for producing polyimide, and purification treatment using a sublimer can produce dianhydride solid with high purity. And adding the dianhydride solid into the mixed solution A and fully stirring to promote the dianhydride solid and the diamine solid to fully perform polymerization reaction. Before the polymerization reaction of the dianhydride solid and the diamine solid is finished, the mixed solution B containing the mono-anhydride compound is added, so that other groups are introduced, and redundant amino at the tail end of a molecular chain in the pretreated resin solution is reacted, so that the high-temperature yellowing effect of the amino in the polymer solution is weakened.

In step S5 of the present invention, a gradient thermal curing process is employed to ensure sufficient curing of the colorless transparent polyimide film, thereby improving the uniformity of film formation and reducing the surface defect rate.

According to the invention, the mono-anhydride compound is continuously added before the polymerization reaction is finished, so that other groups are introduced, and residual amino groups in diamine solid are converted into groups which are not affected by heat, thereby fundamentally solving the problem of high yellow index of the colorless transparent polyimide film.

Preferably, in the above method for preparing a low-yellow-index colorless transparent polyimide film, in the steps S2 and S4, the X parts by weight of diamine solids, the Y parts by weight of dianhydride solids, and the Z parts by weight of N, N-dimethylacetamide solvent a satisfy the following formula:

the invention adopts the components in the proportion to prepare the pretreated resin liquid, and can improve the success rate of molecular collision polymerization in the polymerization reaction process, thereby synthesizing a polymer with higher molecular weight and further improving the production efficiency of the later coating process.

Preferably, in the method for producing a low-yellow-index colorless transparent polyimide film, the monoanhydride compound contains one of an ethane residue, a propane residue, a cyclopropane residue, a cyclobutane residue, a cyclopentane residue, a cyclohexane residue, and a 1, 2-benzene residue.

The use of the above-mentioned monoanhydride compound in the present invention enables one of an ethane residue, a propane residue, a cyclopropane residue, a cyclobutane residue, a cyclopentane residue, a cyclohexane residue and a 1, 2-benzene residue to be preferably introduced into the polymerization reaction.

Preferably, in the above method for preparing a low-yellow-index colorless transparent polyimide film, in step S1, the water content of the N, N-dimethylacetamide solvent is 0-0.05% after dehydration and purification treatment.

The N, N-dimethylacetamide solvent is dehydrated and purified to obtain extremely high purity, and the hydrolysis condition in the polymer solution can be avoided.

Preferably, in the method for preparing a colorless and transparent polyimide film with a low yellow index, in the steps S2 and S4, the molar ratio of the dianhydride solid to the diamine solid is 0.95:1 to 1.05: 1.

The dianhydride solid and the diamine solid in the invention are prepared by adopting the molar ratio, so that the dianhydride solid and the diamine solid are equivalent in number during polymerization, the residual amount of the monomer is reduced to the maximum extent, and the polymer can obtain higher molecular weight.

Preferably, in the above method for preparing a colorless transparent polyimide film with a low yellow index, the molecular chain of the colorless transparent polyimide film contains a repeating unit structure of formula 1, and the repeating unit structure of formula 1 is as follows:

wherein R is_aIs cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_bIs one or more of 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4 '-diaminodiphenyl sulfone residue, 3' -diaminodiphenyl sulfone residue, 2 '-bis (trifluoromethyl) benzidine residue and 4, 4' - (hexafluoroisopropylidene) diphenylamine residue.

The molecular chain of the finally prepared colorless transparent polyimide film contains the repeating unit structure shown in the formula 1, so that a conjugated system in the colorless transparent polyimide film is broken, and the problem of a charge transfer complex in the traditional polyimide is solved, so that the polyimide film is colorless and transparent.

Preferably, in the above method for preparing a low-yellow-index colorless transparent polyimide film, in step S4, the molecular chain of the pretreated resin solution contains a unit structure represented by formula 2, where the unit structure represented by formula 2 is as follows:

wherein R is_cIs cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_dIs one or more of 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4 '-diaminodiphenyl sulfone residue, 3' -diaminodiphenyl sulfone residue, 2 '-bis (trifluoromethyl) benzidine residue and 4, 4' - (hexafluoroisopropylidene) diphenylamine residue.

The pretreatment resin liquid prepared by the invention contains the unit structure shown in the formula 2, so that a conjugated system in the pretreatment resin liquid is broken, and the problem that a finally prepared colorless transparent polyimide film has a charge transfer complex is solved.

Preferably, in the above method for preparing a low-yellow-index colorless transparent polyimide film, in step S4, the molecular chain of the pretreated resin solution further includes a unit structure represented by formula 3, where the unit structure represented by formula 3 is as follows:

wherein R is_eIs cyclobutane residue, cyclopentane residue, 4 ' - (hexafluoroisopropylidene) diphenyl residue, diphenyl sulfone residue, norbornane-2-spiro- α -cyclopentanone- α ' -spiro-2 ' -norbornane-5, 5 ', 6,6 ' -tetracarboxylic dianhydride residue, bicyclo [ 2.2.2.2]One or more of octyl-7-ene-2, 3,5, 6-tetracarboxylic dianhydride residues, R_fIs 1, 4-cyclohexanediamine residue, 1, 3-cyclohexanediamine residue, norbornanediamine residue, 1, 4-cyclohexanediamine residue, 4'One or more of-diaminodiphenyl sulfone residue, 3 ' -diaminodiphenyl sulfone residue, 2 ' -bis (trifluoromethyl) benzidine residue, 4 ' - (hexafluoroisopropylidene) diphenylamine residue, R_gIs one or more of ethane residue, propane residue, cyclopropane residue, cyclobutane residue, cyclopentane residue, cyclohexane residue and 1, 2-benzene residue.

The prepared pretreated resin liquid contains a unit structure shown in a formula 3, the content of exposed amino groups in the pretreated resin liquid is reduced by introducing a unit structure system shown in the formula 3, and the yellow index of the finally prepared colorless transparent polyimide film can be greatly reduced by introducing the unit structure system shown in the formula 3 because the exposed amino groups are easily yellow due to the influence of heating high temperature.

Preferably, in the method for preparing the colorless transparent polyimide film with the low yellow index, the yellow index of the colorless transparent polyimide film is less than 2.

The yellow index of the finally prepared colorless transparent polyimide film is in a lower range, so that the quality of the product can be better controlled, and the requirements of higher-end industries are met.

Detailed Description

The invention will now be described in further detail with reference to specific embodiments, but they are not intended to limit the invention: