CN111303416B

CN111303416B - Colorless and transparent polyimide, and preparation method and application thereof

Info

Publication number: CN111303416B
Application number: CN201910352232.6A
Authority: CN
Inventors: 徐勇; 陈坚; 汤学妹
Original assignee: Nanjing Zhonghong Running Advanced Material Technology Co ltd
Current assignee: Nanjing Zhonghong Running Advanced Material Technology Co ltd
Priority date: 2019-04-29
Filing date: 2019-04-29
Publication date: 2022-12-09
Anticipated expiration: 2039-04-29
Also published as: CN111303416A

Abstract

The invention provides colorless and transparent polyimide. The invention also provides a preparation method of the colorless and transparent polyimide. The invention also provides application of the colorless and transparent polyimide in a flexible AMOLED. The polyimide provided by the invention has good light transmission, and has excellent heat-resistant stability, high glass transition temperature, high transparency and excellent flame retardant property on the basis of not changing the transparency of a resin film. The flame-retardant colorless transparent polyimide film prepared by the invention can be used as a flexible material to be applied to the high-tech fields of solar cells, flexible printed circuit boards, microelectronics and the like, and has wide application prospect.

Description

Colorless transparent polyimide and preparation method and application thereof

Technical Field

The invention relates to the field of materials, in particular to colorless transparent polyimide.

Background

Polyimide is a polymer having an imide ring (-CO-NH-CO-) in the main chain, and among them, a polymer having a phthalimide structure is most important. Polyimide is one of organic polymer materials with the best comprehensive performance, has the advantages of high temperature resistance, low dielectric constant, corrosion resistance and the like, has the high temperature resistance of over 400 ℃, has the long-term use temperature range of-200-300 ℃, and has very high insulating property. Polyimide is used as a special engineering material, has been widely applied to the fields of aviation, aerospace, microelectronics, nano-materials, liquid crystals, separation membranes, lasers and the like, and becomes an irreplaceable functional material with excellent comprehensive performance.

Polyimide has high heat resistance and is very suitable as a material for a flexible substrate. Particularly, with the rapid development of flexible display technology, demand for colorless transparent polyimide films is increasing. However, conventional polyimide films generally exhibit color and low light transmittance, mainly due to the presence of intramolecular and intermolecular Charge Transfer Complexes (CTCs) in the polyimide system. In order to reduce the color of the polyimide film and thus improve the light transmittance, the following methods are generally adopted from the viewpoint of reducing CTC: 1) introducing a fluorine-containing group, 2) introducing a substituent group with larger volume, 3) introducing an aliphatic, especially alicyclic structure unit, 4) adopting a monomer capable of bending a main chain, 5) introducing an asymmetric structure, 6) reducing a conjugated double bond structure and the like. Wherein, fluorine atoms are introduced into a polyimide main chain or a branched chain, so that the polyimide has high electronegativity and large free volume; meanwhile, the lower polarizability of the C-F bond can improve the optical transparency of the polyimide, improve the solubility of the polyimide and reduce the dielectric constant. Aliphatic polyimides have excellent transparency, mainly due to the introduction of aliphatic monomers, which effectively inhibit charge transfer interactions based on their low molecular density and low polarity.

However, polyimide has a restrictive relationship between transparency, high thermal stability and high flame retardancy, that is, the transparency of the film is improved while the original excellent flame retardancy and a certain degree of heat resistance of polyimide are lost. The restriction of optical transparency and flame retardant property limits the application of polyimide in the fields of optoelectronics and the like.

Disclosure of Invention

The technical problem is as follows: in order to solve the defects of the prior art, the invention provides colorless and transparent polyimide, and a preparation method and application thereof.

The technical scheme is as follows: the invention provides colorless transparent polyimide, which has a structural formula shown as a formula I:

wherein, R1 to R6 are respectively independent hydrogen, halogen, branched chain or branched chain alkyl.

The invention also provides a preparation method of the colorless and transparent polyimide, which comprises the following steps:

(1) Reacting the compound shown in the formula VI with the compound shown in the formula VII to obtain an intermediate shown in the formula VIII;

(2) VIII, reacting the intermediate to obtain a compound shown in a formula V;

the reaction formula is as follows:

wherein, R1 to R6 are respectively and independently hydrogen, halogen, branched chain or branched chain alkyl.

The invention also provides colorless transparent polyimide, which has a structural formula shown as the formula V:

(2) VIII, reacting the intermediate to obtain a compound shown in a formula V;

the reaction formula is as follows:

preferably, the preparation method of the colorless and transparent polyimide comprises the following steps:

(1) Under the protection of nitrogen and at a certain temperature, stirring the compound shown in the formula VI and the compound shown in the formula VII in an organic solvent for reaction to obtain an intermediate shown in the formula VIII;

(2) Adding a dehydrating agent and a catalyst, continuously stirring the intermediate shown as VIII at a certain temperature for reaction, cleaning, filtering and drying to obtain the compound shown as the formula V.

In the step (1), the organic solvent is one of N-methylpyrrolidone, N-dimethylacetamide and N, N-dimethylformamide; the reaction temperature is 5-25 ℃.

In the step (2), the dehydrating agent is one or a mixture of more of trifluoroacetic anhydride, acetic anhydride, thionyl chloride or an organic silicon compound; the molar ratio of the dehydrating agent to the compound VII is 3.

In the step (2), the catalyst is one or a mixture of triethylamine and pyridine, and the molar ratio of the catalyst to the compound VII is (2).

In the step (2), the reaction temperature is 40-60 ℃.

The invention also provides application of the colorless and transparent polyimide in a flexible AMOLED.

Has the advantages that: the polyimide provided by the invention has good light transmittance, and has excellent heat-resistant stability, high glass transition temperature, high transparency and excellent flame retardant property on the basis of not changing the transparency of a resin film. The flame-retardant colorless transparent polyimide film prepared by the invention can be used as a flexible material to be applied to the high-tech fields of solar cells, flexible printed circuit boards, microelectronics and the like, and has wide application prospect.

Drawings

FIG. 1 is an infrared spectrum of Compound V.

Detailed Description

The present invention is further described below.

In the following examples, the reaction scheme is as follows:

example 1

The preparation method of the colorless and transparent polyimide comprises the following steps:

(1) Under the protection of nitrogen and at a certain temperature, stirring a compound shown in a formula VI and a compound shown in a formula VII in an organic solvent for reaction to obtain an intermediate shown in a formula VIII; the organic solvent is N-methyl pyrrolidone; the reaction temperature is 15 ℃;

(2) Adding a dehydrating agent and a catalyst, continuously stirring the intermediate shown in the formula VIII at a certain temperature for reaction, cleaning, filtering and drying to obtain a compound shown in the formula V; the dehydrating agent is trifluoroacetic anhydride; the molar ratio of the dehydrating agent to the compound VII is 4; the catalyst is triethylamine, and the molar ratio of the catalyst to the compound VII is 3; the reaction temperature was 50 ℃.

Evaluation method of polymer molecular structure: fourier Infrared Spectroscopy (FT-IR): the prepared PI film was subjected to an infrared spectrometer (Bruker sensor-27, germany);

FIG. 1 is a chart showing an infrared spectrum of a polyimide having a polymerization degree of 1 obtained in example 1, from which it can be seen that the wave number is 1776cm ^-1 And 1719cm ^-1 Has asymmetric and symmetric stretching peaks of carbonyl C = O on polyimide ring, 1369cm ^-1 736cm belonging to the C-N extension peak on the imide ring ^-1 Ascribed to C = O flexural vibration absorption peak on imide ring, 1610cm ^-1 Corresponding to the characteristic peaks of the benzene rings.

Example 2

(1) Under the protection of nitrogen and at a certain temperature, stirring the compound shown in the formula VI and the compound shown in the formula VII in an organic solvent for reaction to obtain an intermediate shown in the formula VIII; the organic solvent is N, N-dimethylacetamide; the reaction temperature is 5 ℃;

(2) Adding a dehydrating agent and a catalyst, continuously stirring the intermediate shown in the formula VIII at a certain temperature for reaction, cleaning, filtering and drying to obtain a compound shown in the formula V; the dehydrating agent is acetic anhydride; the molar ratio of the dehydrating agent to the compound VII is 5; the catalyst is pyridine, and the molar ratio of the catalyst to the compound VII is 4; the reaction temperature was 40 ℃.

The infrared spectrum was similar to that of example 1.

Example 3

(1) Under the protection of nitrogen and at a certain temperature, stirring the compound shown in the formula VI and the compound shown in the formula VII in an organic solvent for reaction to obtain an intermediate shown in the formula VIII; the organic solvent is N, N-dimethyl formyl; the reaction temperature is 25 ℃;

(2) Adding a dehydrating agent and a catalyst, continuously stirring the intermediate shown in the formula VIII at a certain temperature for reaction, cleaning, filtering and drying to obtain a compound shown in the formula V; the dehydrating agent is thionyl chloride; the molar ratio of the dehydrating agent to the compound VII is 3; the catalyst is triethylamine, and the molar ratio of the catalyst to the compound VII is 2; the reaction temperature was 60 ℃.

The infrared spectrum was similar to that of example 1.

Example 4

The product properties of examples 1 to 3 were tested.

(1) The method comprises the following steps:

thermal decomposition temperature evaluation method:

the prepared film was tested in a thermogravimetric analyzer (TA of America, Q50 series) at a temperature rise rate of 10 ℃/min

Film transparency evaluation method:

ultraviolet-visible spectrum (UV-Vis):

testing the prepared film in an ultraviolet spectrophotometer (Hitachi U-3210);

the yellowness index and haze of the film were measured with a colorimeter (X-rite color i 7);

the flame retardant evaluation method comprises the following steps:

vertical burning test (UL-94 VTM): carrying out flame retardant grade test on the prepared PI film according to the national standard GB/T2408-2008;

limiting Oxygen Index (LOI) the prepared PI film is subjected to an LOI test according to the national standard GB/T2406-2008.

(2) The results are shown in the following table.

TABLE 1

Claims

1. The preparation method of the colorless and transparent polyimide is characterized by comprising the following steps: the method comprises the following steps:

(2) Adding a dehydrating agent and a catalyst, continuously stirring the intermediate shown in the formula VIII at a certain temperature for reaction, cleaning, filtering and drying to obtain a compound shown in the formula V;

the reaction formula is as follows:

the structural formula of the colorless transparent polyimide is shown as a formula V:

wherein in the step (1), the organic solvent is one of N-methylpyrrolidone, N-dimethylacetamide and N, N-dimethylformamide; the reaction temperature is 5-25 ℃;

in the step (2), the dehydrating agent is one or a mixture of more of trifluoroacetic anhydride, acetic anhydride, thionyl chloride or an organic silicon compound; the molar ratio of the dehydrating agent to the compound VII is 3;

in the step (2), the catalyst is one or a mixture of triethylamine and pyridine, and the molar ratio of the catalyst to the compound VII is 2;

wherein, in the step (2), the reaction temperature is 40-60 ℃.