Polyamic acid composition and modified polyamic acid

Abstract

The present invention provides a polyamic acid composition and a modified polyamic acid, wherein the polyamic acid composition comprises polyamic acid; an additive, wherein the additive comprises at least one of a pH regulator and a stabilizer, wherein the stabilizer is suitable for inhibiting the polyamic acid from being crosslinked or isomerized; and a solvent. Thus, the viscosity of the polyamic acid composition is not easily changed during storage, the film-forming property is good, the polyamic acid can be effectively prevented from being deteriorated, and the storage time is extended.

Description

Technical Field

[0001] The present application relates to the field of organic materials, and in particular, to a polyamic acid composition and a modified polyamic acid. Background Art

[0002] The viscosity of polyamic acid will change during storage because polyamic acid itself undergoes complex chemical reactions in the solvent, including hydrolysis, cross-linking and isomerization. When the temperature is too high or the storage time is too long, the molecular weight and viscosity will change as the reaction continues, causing the polyamic acid to deteriorate.

[0003] Therefore, the current polyamic acid composition still needs to be further improved. Summary of the invention

[0004] The present invention aims to solve, at least to a certain extent, the technical problem that the viscosity of polyamic acid is prone to change during storage.

[0005] In one aspect of the present invention, a polyamic acid composition is proposed, the polyamic acid composition includes polyamic acid; an additive, the additive includes at least one of a pH regulator and a stabilizer, wherein the stabilizer is suitable for inhibiting the polyamic acid from crosslinking or isomerizing; and a solvent. A general polyamic acid solution is composed of a weakly acidic polyamic acid, a weakly alkaline solvent, and an excess of weakly alkaline diamines in the synthesis process, so the solution pH may be weakly acidic or weakly alkaline. However, such a solution is easily hydrolyzed during storage. In addition, a weakly acidic or weakly alkaline environment will cause the polyamic acid to cyclize into polyimide and byproduct water, and the byproduct water further promotes hydrolysis and changes in viscosity. The additive of the present invention can control the pH of the polyamic acid composition and the crosslinking rate of the polyamic acid, thereby, the viscosity of the polyamic acid composition is not easy to change during storage, the film-forming performance is good, and the polyamic acid can be effectively prevented from deteriorating and the shelf life is extended.

[0006] In another aspect of the present invention, a modified polyamic acid is provided, comprising polyimide and an additive, wherein the additive comprises at least one of a pH regulator and a stabilizer. Thus, the viscosity of the modified polymer is not easily changed during storage, the film-forming property is good, the polyamic acid can be effectively prevented from deteriorating, and the storage time is extended. DETAILED DESCRIPTION

[0007] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0008] In one aspect of the present invention, a polyamic acid composition is proposed, comprising polyamic acid, an additive and a solvent, wherein the polyamic acid and the additive can be dissolved in the solvent, and the additive comprises at least one of a pH adjuster and a stabilizer, wherein the stabilizer is suitable for inhibiting the cross-linking or isomerization of the polyamic acid. That is to say, the additive may only comprise a pH adjuster; or the additive only comprises a stabilizer; or the additive comprises both a pH adjuster and a stabilizer. The pH adjuster can adjust the pH of the polyamic acid composition to prevent the polyamic acid from being hydrolyzed, and the stabilizer prevents the viscosity of the polyamic acid composition from changing by preventing the polyimide from being cross-linked or isomerized. As a result, the viscosity of the polyamic acid composition is not easily changed during storage, and the film-forming property is good, which can effectively prevent the polyamic acid from deteriorating and prolong the shelf life.

[0009] According to some embodiments of the present invention, in order to make the polyamic acid composition have good film-forming properties while maintaining the stability of viscosity, the content of the additive is 0.1% to 10% by mass based on the total mass of the polyamic acid composition. Specifically, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, etc. Preferably, the content of the additive is 1% to 3%. As a result, the polyamic acid composition has better film-forming properties. For example, when a film layer structure is made using a spin coating process, the polyamic acid film can be prevented from breaking. If the content of the additive is too little, the ability to prevent polyamic acid from hydrolyzing or cross-linking is weak, and the ability to prevent the viscosity of the polyimide composition from changing is weak; if the content of the additive is too much, the content of small molecules in the polyamic acid composition is too much, which will affect the film-forming properties of the polyamic acid composition to a certain extent.

[0010] According to some embodiments of the present invention, the pH of the polyamic acid composition is 4 to 9. Since polyimide hydrolyzes to generate water, the product water will further hydrolyze the polyimide, resulting in a change in viscosity. When the pH of polyimide is within this range, the hydrolysis ability of polyamic acid is relatively weak, which can prevent the hydrolysis of polyimide from generating water, thereby avoiding a series of hydrolysis reactions, further preventing it from deteriorating, and improving the stability of the polyimide composition.

[0011] According to some specific embodiments of the present invention, polyamic acid needs cold chain transportation during transportation to prevent changes in temperature from affecting the pH of the polyamic acid composition. If the pH changes and causes the polyamic acid to be hydrolyzed, the speed of hydrolysis will be faster and faster, leading to a vicious cycle. In order to further prevent the pH of polyamic acid from changing significantly during storage and transportation, when adjusting the pH of the polyamic acid composition, a pH buffer can be used as a pH adjusting agent. Thus, even if the pH of the polyamic acid composition changes, the pH can be fluctuated within the pH range of the buffer to slow down the rate of hydrolysis of the polyamic acid.

[0012] According to some embodiments of the present invention, the pH of the pH buffer may be 3 to 8.5. Specifically, when 3-morpholinepropanesulfonic acid and sodium 3-morpholinepropanesulfonate are used as the pH buffer, the pH of the pH buffer may be 6.5 to 7.9; when tris(hydroxymethyl)aminomethane and tris(hydroxymethyl)aminomethane hydrochloride are used as the pH buffer, the pH of the pH buffer may be 7.5 to 8.5; when citric acid and sodium citrate are used as the pH buffer, the pH of the pH buffer may be 3.0 to 6.6. After the pH of the polyamic acid composition is adjusted using a buffer having a pH of 6.5 to 7.9, the pH of the polyamic acid composition fluctuates only within the range of 6.5 to 7.9 during storage. Since the hydrolysis rate of polyamic acid is relatively slow under neutral conditions, the hydrolysis of polyimide during storage can be further prevented, thereby making the viscosity of the polyimide composition more stable.

[0013] Specifically, the pH buffer comprises a first component and a second component, and the second component is a conjugate acid or conjugate base of the first component. Wherein, the first component comprises at least one of tris(hydroxymethyl)aminomethane, 3-morpholinepropanesulfonic acid, 2-(N-morpholine)ethanesulfonic acid, 4-hydroxyethylpiperazineethanesulfonic acid, N-tri(hydroxymethyl)methylglycine, phosphoric acid, citric acid, acetic acid, and barbituric acid; the second component is a conjugate acid or conjugate base of the first component, for example, the second component comprises sodium 3-morpholinepropanesulfonate, tris(hydroxymethyl)aminomethane hydrochloride, sodium citrate, sodium 2-(N-morpholine)ethanesulfonic acid sodium, sodium 4-hydroxyethylpiperazineethanesulfonic acid, sodium N-tri(hydroxymethyl)methylglycine, potassium phosphate, sodium acetate, sodium barbiturate, and sodium oxalate. It can be understood by those skilled in the art that the pH buffer comprises a pH buffer pair, that is, the pH buffer comprises at least one compound selected from the first component, and at least one compound in the second component constitutes together, and the two act together to stabilize the pH value of the composition within a certain range. For example, tris(hydroxymethylaminomethane) and its conjugate acid tris(hydroxymethylaminomethane) hydrochloride can be used simultaneously to adjust the pH of the polyamic acid composition, or 3-morpholinepropanesulfonic acid and its conjugate base sodium 3-morpholinepropanesulfonate can be used to adjust the pH of the polyamic acid composition.

[0014] According to some embodiments of the present invention, the structure of the stabilizer is not particularly limited, as long as it can inhibit the cross-linking or isomerization of the polyamic acid. Specifically for the present application, the stabilizer may contain a hydroxyl group, which can form a hydrogen bond with the carboxyl group of the polyamic acid, thereby reducing the possibility of cross-linking of the polyamic acid, thereby preventing a significant change in the viscosity of the polyamic acid composition.

[0015] According to some embodiments of the present invention, the stabilizer may include silanol. First, the hydroxyl group of silanol can form a hydrogen bond with the carboxyl group of polyamic acid to inhibit the cross-linking of polyamic acid; second, the other end of silanol has a hydrophobic group, which can reduce the water absorption capacity of the surface of the polyamic acid composition to a certain extent and reduce the probability of hydrolysis; third, silanol is added to the polyamic acid composition as a stabilizer, and the silicon atom can reduce the dielectric constant of the polyamic acid composition, and when the polyamic acid composition is used as an insulating paint, its insulation performance can be improved.

[0016] According to some specific embodiments of the present invention, silanol may include but is not limited to at least one of tri(trimethylsilyl)silanol, triethylsilanol, triisopropylsilanol, diphenylsilanol, diethyl(isopropyl)silanol, tert-butyldimethylsilanol, tri(tert-butoxy)silanol, furan-2-yldimethylsilanol, and dimethyl(2-thienyl)silanol.

[0017] According to some embodiments of the present invention, when the additive includes a pH adjuster and a stabilizer at the same time, the pH adjuster includes a first component and a second component, and the stabilizer includes a silanol. Based on the total mass of the additive, by mass percentage: the content of the first component is 5% to 40%, specifically, it can be 10%, 15%, 20%, 25%, 30% and 35%, etc.; the content of the second component is 5% to 40%, specifically, it can be 10%, 15%, 20%, 25%, 30% and 35%, etc.; the content of silanol is 20% to 90%, specifically, it can be 30%, 40%, 50%, 60%, 70% and 80%, etc. In the process of adjusting the pH, if the content of the pH adjuster is too much, it will affect the film-forming property of the polyamic acid composition to a certain extent.

[0018] According to some embodiments of the present invention, based on the total mass of the polyamic acid composition, the content of the polyamic acid is 20% to 40%, and the content of the solvent is 50% to 79.9%.

[0019] According to some embodiments of the present invention, the type of solvent in the polyamic acid composition is not particularly limited, for example, the solvent may include at least one of N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide and m-cresol. Thus, the pH regulator and stabilizer are better embedded in the interior of the polyamic acid.

[0020] In another aspect of the present invention, a modified polyimide is provided, comprising polyamic acid and an additive, wherein the additive comprises at least one of a pH regulator and a stabilizer. Thus, the viscosity of the modified polymer is not easily changed during storage, the film-forming property is good, the polyamic acid can be effectively prevented from deteriorating, and the storage time is extended.

[0021] Example 1

[0022] 0.4 g of 3-morpholinepropanesulfonic acid, 0.1 g of sodium 3-morpholinepropanesulfonate and 1.5 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.1.

[0023] Example 2

[0024] 0.4 g of tris(hydroxymethyl)aminomethane, 0.1 g of tris(hydroxymethyl)aminomethane hydrochloride) and 1.5 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.9.

[0025] Example 3

[0026] 0.4 g of citric acid, 0.1 g of sodium citrate and 1.5 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 4.5.

[0027] Example 4

[0028] 0.4 g of 3-morpholinepropanesulfonic acid, 0.1 g of sodium 3-morpholinepropanesulfonate and 1.5 g of tert-butyldimethylsilanol were added to 200 g of N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.1.

[0029] Example 5

[0030] 0.04 g of 3-morpholinepropanesulfonic acid, 0.01 g of sodium 3-morpholinepropanesulfonate and 0.15 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.6.

[0031] Example 6

[0032] 4 g of 3-morpholinepropanesulfonic acid, 1 g of sodium 3-morpholinepropanesulfonate and 15 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 6.3.

[0033] Example 7

[0034] 0.4 g of 3-morpholinepropanesulfonic acid and 0.1 g of sodium 3-morpholinepropanesulfonate were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.1.

[0035] Example 8

[0036] 1.5 g of diphenylsilanol was added to 200 g of N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.5.

[0037] Comparative Example 1

[0038] 200 g of polyamic acid in N-methylpyrrolidone solution was stirred for 1 hour, and the pH was 7.5.

[0039] Comparative Example 2

[0040] 0.5 g of concentrated sulfuric acid and 1.5 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid and stirred for 1 hour. The pH of the obtained polyamic acid composition was 2.3.

[0041] Comparative Example 3

[0042] 0.004 g of 3-morpholinepropanesulfonic acid, 0.001 g of sodium 3-morpholinepropanesulfonate and 0.015 g of diphenylsilanol were added to a 200 g N-methylpyrrolidone solution of polyamic acid with a solid content of 30%, and stirred for 1 hour. The pH of the obtained polyamic acid composition was 7.5.

[0043] Viscosity measuring instrument: GB / T 9751-1998 rotational viscometer

[0044] Specific evaluation criteria for film forming process and film forming performance:

[0045] The process includes the following: preparing a corresponding solution wet film on a clean glass plate by coating and casting; transferring the wet film to an oven, and heating imidization according to the following program: 80°C / 2h, 120°C / 1h, 160°C / 1h, 180°C / 1h, 240°C / 1h, 280°C / 1h, 350°C / 1h, and the heating rate is 2°C / min. After the glass plate reaches room temperature, the glass plate covered with the polyamic acid film is immersed in deionized water to glass it, and finally the corresponding self-supporting PI film is obtained.

[0046] Among them, if the film is in a whole piece on the glass, with no cracks on the film surface and can remain intact after peeling, it is considered to have very good film formation; if the film is in a whole piece on the glass, with no cracks on the film surface and cannot remain intact after peeling, it is considered to have average film formation; if the film is in fragments on the glass, it is considered to have failed to form a film.

[0047] The test results are shown in Tables 1 to 3:

[0048] Table 1

[0049]

[0050] Table 2

[0051]

[0052] Table 3

[0053]

[0054]

[0055] By comparing Example 1 and Example 4, it can be seen that the stabilizer in Example 1 is diphenylsilanol, and the stabilizer in Example 4 is tert-butyldimethylsilanol. In addition to being hydrophobic, the phenyl group in Example 1 can also form a strong force with the rigid structure of polyamic acid, which will not affect the subsequent film formation and improve its film-forming performance.

[0056] It can be seen from Example 1, Example 5, Example 6 and Comparative Example 3 that as the content of the additive in the polyamide acid composition increases, the effect of preventing the viscosity of the polyamic acid from increasing can be improved to a certain extent; when the content of the additive in the polyamic acid composition is 0.1% and 10%, the additive can prevent the viscosity of the polyamic acid composition from increasing to a certain extent; when the content of the additive in the polyamic acid composition is 1%, the viscosity of the polyamic acid composition is easier to control and has good film-forming properties.

[0057] It can be seen from Example 1 and Comparative Example 2 that in Comparative Example 2, the pH value of the polyamic acid composition was adjusted only by concentrated sulfuric acid, and the polyamic acid composition was solidified after stirring at room temperature for thirty days, while the viscosity of the polyamic acid composition in Example 1 was still maintained well after stirring at room temperature for sixty days, indicating that the use of pH buffer solution to adjust the pH value of the polyamic acid composition can further improve the stability of the viscosity of the polyamic acid composition.

[0058] It can be seen from Examples 1 and 3 that the pH of the polyamic acid composition in Example 1 is 7.1, and the pH of the polyamic acid composition in Example 3 is 4.5. The viscosity of the polyamic acid composition in Example 1 can still be maintained at about 30,000 after stirring at room temperature for 60 days, and the viscosity of the polyamic acid composition in Example 3 increases from the initial 29,700 to 69,400 after stirring at room temperature for 60 days, indicating that the pH is close to neutral, which can reduce the degree of hydrolysis of the polyamic acid composition to a certain extent, thereby improving the stability of the viscosity of the polyamic acid composition. It can be seen from Example 3 compared with Comparative Examples 1 to 3 that the addition of a pH adjuster and a stabilizer to the polyimide composition can prevent the viscosity of the polyimide from increasing to a certain extent.

[0059] It can be seen from Examples 1, 2, 3 and 4 and Comparative Example 1 that the polyamic acid compositions in Examples 1, 2, 3 and 4 all contain additives, which can inhibit the rate of increase of the viscosity of the polyimide to a certain extent and better control the viscosity of the polyamic acid composition.

[0060] It can be seen from Examples 1, 2 and 3 that using a pH buffer to adjust the pH of the polyamic acid composition and using a phenyl-containing substance as an additive can not only control the viscosity of the polyamic acid composition but also make the polyamic acid composition have better film-forming properties.

[0061] It can be seen from Example 7 that only adding a pH adjuster to the polyamic acid composition can prevent the hydrolysis of polyimide to a certain extent. It can be seen from Example 8 that only adding a silanol to the polyamic acid composition can prevent the cross-linking of polyimide to a certain extent.

[0062] In the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0063] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A polyamic acid composition, characterized in that include: Polyamic acid; An additive, wherein the additive is a pH adjuster and a stabilizer, wherein the stabilizer is suitable for inhibiting the crosslinking or isomerization of the polyamic acid; as well as Solvents, The pH regulator is a pH buffer, and the pH of the pH buffer is 3 to 8.

5. The pH buffer comprises a first component and a second component, wherein the second component is a conjugate acid or a conjugate base of the first component, and the first component comprises at least one of tris(hydroxymethyl)aminomethane, 3-morpholinepropanesulfonic acid, 2-(N-morpholine)ethanesulfonic acid, 4-hydroxyethylpiperazineethanesulfonic acid, N-tris(hydroxymethyl)methylglycine, phosphoric acid, citric acid, acetic acid, barbituric acid, and oxalic acid; The second component includes at least one of sodium 3-morpholinepropanesulfonate, tris(hydroxymethyl)aminomethane hydrochloride, sodium citrate, sodium 2-(N-morpholine)ethanesulfonate, sodium 4-hydroxyethylpiperazineethanesulfonate, sodium N-tris(hydroxymethyl)methylglycine, potassium phosphate, sodium acetate, sodium barbiturate, and sodium oxalate. Based on the total mass of the polyamic acid composition, by mass percentage, the content of the additive is 0.1% to 3%, the content of the polyamic acid is 20% to 40%, and the content of the solvent is 50% to 79.9%. The stabilizer is diphenylsilanol, Based on the total mass of the additive, in terms of mass percentage, the content of the first component is 5% to 40%, the content of the second component is 5% to 40%, and the content of the diphenylsilanol is 20% to 90%.

2. The polyamic acid composition according to claim 1, characterized in that The pH of the polyamic acid composition is 4-9.

3. The polyamic acid composition according to claim 1, characterized in that Based on the total mass of the polyamic acid composition, the content of the additive is 1% to 3% by mass.

4. The polyamic acid composition according to claim 1, characterized in that The solvent in the polyamic acid composition includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide and m-cresol.

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