JPH0128767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyamideimide.

It is known to obtain a polyamideimide solution by reacting an aromatic polyisocyanate and a polycarboxylic acid having an acid anhydride group in a solvent such as N-methylpyrrolidone. However, since such a polymer solution uses a nitrogen-containing polar solvent, its color is dark and its use is limited to varnishes for heat-resistant enamelled wires. It is also known to obtain a polyamideimide solution using cresol as a solvent. Although such a polymer solution is relatively light in color, since cresol contains active hydrogen, the polymerization reaction is inhibited, making it impossible to obtain a high molecular weight polyamide-imide, and the solution lacks film properties, so its use is limited.

If light-colored, high-molecular-weight polyamide-imide solutions and films can be obtained, their use can be expanded to include electronic materials such as overcoat materials for liquid crystals.

The present inventors have discovered that when γ-butyrolactone is used as a synthesis solvent for polyamide-imide, a high-molecular-weight polyamide-imide that is pale in color, has film properties, and has heat resistance has been completed, and the present invention has been completed.

The present invention uses γ-butyrolactone as a solvent,
The present invention relates to a method for producing polyamideimide, which involves reacting a polycarboxylic acid having an acid anhydride group with an aromatic polyisocyanate at 80 to 190°C.

According to the present invention, a light-colored polyamideimide is obtained.

Examples of the aromatic polyisocyanate used in the present invention include tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, naphthylene-1,5
- diisocyanate, aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate,
Polyisocyanates such as triphenylmethane-4,4',4''-triisocyanate and isocyanurate ring-containing polyisocyanates obtained by trimerization of these polyisocyanates are used. Heat resistance, cost, etc. Considering 4,
Preference is given to using 4'-diphenylmethane diisocyanate, tolylene diisocyanate or xylylene diisocyanate. A suitable method for producing isocyanurate ring-containing polyisocyanates is disclosed in Japanese Patent Application No. 148820/1982. Isocyanurate ring-containing polyisocyanates are used as branching components, and the isocyanurate ring core provides excellent heat resistance. Difunctional polyisocyanates are used in the synthesis of particulate polymers containing imide groups that are substantially linear and thermoplastic. Furthermore, trifunctional or higher-functional polyisocyanates are used to synthesize particulate polymers containing branched thermosetting imide groups and three-dimensionally networked polyamide-imides. These polyisocyanates may be used alone or in combination depending on the purpose. Polyisocyanates contain active hydrogen in methanol, n-butanol, benzyl alcohol, ε-caprolactam, methyl ethyl ketone oxime, phenol, cresol, etc., in order to control the reaction rate during the polycondensation reaction process and obtain stable polyamideimide. It may be stabilized with one suitable blocking agent.

As a polycarboxylic acid having an acid anhydride group,
For example, trimellitic anhydride, 1,2,4-butanetricarboxylic acid-1,2-anhydride, 3,4,
Tricarboxylic acid anhydrides such as 4'-benzophenone tricarboxylic acid-3,4'-anhydride are used,
There is no particular limitation as long as it is a polycarboxylic acid having an acid anhydride group that reacts with an isocyanate group. If necessary, a part of the carboxylic acid having an acid anhydride group can be converted into pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, bicyclo[2,2,2]-oct −
(7)-Ene-2:3,5:6 may be replaced with a carboxylic dianhydride such as tetracarboxylic dianhydride. In consideration of heat resistance, cost, etc., trimellitic acid anhydride is preferred.

If necessary, polycarboxylic acids other than the above-mentioned polycarboxylic acids having an acid anhydride group can also be used in combination. Examples of such polycarboxylic acids include trimellitic acid, trimesic acid, tris(2-carboxyethyl)isocyanurate, terephthalic acid,
Isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, etc. are used. These polycarboxylic acids can be used to modify resin properties such as flexibility, solubility in solvents, and melt flowability (processability) during molding. The amount of polyisocyanate and polycarboxylic acid to be used is such that the equivalent ratio of all carboxyl groups of polycarboxylic acid to all isocyanate groups of polyisocyanate (total carboxyl groups/total isocyanate groups) is 0.5 to 1.
It is preferably within the range of 2.0. Here, 1 equivalent of acid anhydride group of polycarboxylic acid is treated as 1 equivalent of carboxyl group. When a light-colored polyamideimide having a sufficiently high molecular weight and high heat resistance and flexibility is required, the equivalent ratio of carboxyl groups (including acid anhydride groups) to isocyanate groups is preferably 0.85 to 0.85. 1.15, more preferably substantially equivalent. The reaction temperature between polyisocyanate and polycarboxylic acid is 80 to 190°C. The progress of the reaction can be determined by observing the bubbles of carbon dioxide gas generated.

Preferably, the polymerization reaction is carried out in substantially anhydrous conditions. Therefore, it is desirable to carry out the process under an inert atmosphere such as nitrogen gas.

There is no particular limit to the monomer concentration in the polymerization reaction, but when synthesizing a polymer with a high molecular weight, it is desirable to carry out the monomer concentration at 30% by weight or more.

If necessary, after the reaction is complete, add ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as tetrahydrofuran and dioxane, butyl cellosolve acetate, ethyl cellosolve acetate, and methyl cellosolve. Cellosolve solvents such as acetate, aromatic hydrocarbon solvents such as toluene and xylene, N,N
- It can be diluted to an appropriate concentration with a polar solvent such as dimethylformamide or N,N-dimethylacetamide.

The polyamideimide obtained by the production method of the present invention is light in color and has good film properties.
Shows heat resistance, especially alignment control films such as liquid crystal elements,
It is useful for overcoat materials such as protective films for electronic parts, heat-resistant paints, heat-resistant sheets, heat-resistant adhesives, heat-resistant laminated materials, heat-resistant molded products, and heat-resistant composite materials with glass fibers and carbon fibers.

The present invention will be explained below using comparative examples and examples.

Comparative Example 1 274 g of 4,4'-diphenylmethane diisocyanate, 207 g of trimellitic anhydride,
720 g of N-methylpyrrolidone was added, heated to 80°C in a nitrogen stream, and stirred at the same temperature for 1 hour to dissolve. Then, the temperature was raised to 130°C over 2 hours. Subsequently, the reaction was continued at the same temperature for 5 hours to obtain a liquid product.

Next, the resin concentration was adjusted to 30% by weight with N-methylpyrrolidone to obtain a dark brown polyamideimide varnish. In the infrared absorption spectrum of the precipitate produced by pouring this varnish into a large amount of methanol, absorption of imide groups was observed at 1780 cm ^-1 .
Absorption of amide bond was observed at 1650 cm ^-1 and 1540 cm ^-1 . The reduced viscosity of this precipitate was 0.44 (0.5 g/100 cm ³ solution of dimethylformamide). Apply this dark brown polyamide-imide varnish on a glass plate.
The film baked at 250℃ for 30 minutes has a thickness of 62μm.
The color was 5YR/3.8/3.8 (determined using a standard color chart according to JIS Z 8721-1964). The thermogravimetric loss curve of this film is shown in FIG. 1A. The measurement conditions are:
Heating rate: 10℃/min, air atmosphere, sample amount: 10
mg.

Example 1 75 g of 4,4'-diphenylmethane diisocyanate, 57 g of trimellitic anhydride, γ-
Add 132g of butyrolactone and heat to 190℃ in a nitrogen stream.
The temperature was raised in 3 hours. The reaction was continued for 1 hour at the same temperature. The liquid material was lighter in color than the liquid material of Comparative Example 1.

Next, the resin concentration was adjusted to 25% by weight with N,N-dimethylformamide to obtain a light-colored polyamide-imide varnish. In the infrared absorption spectrum of the precipitate produced by pouring this varnish into a large amount of methanol, absorption of imide groups was observed at 1780 cm ^-1 .
Absorption of amide bond was observed at 1650 cm ^-1 and 1540 cm ^-1 . Further, in the ¹ H-NMR spectrum of this precipitate (solvent dimethyl sulfoxide-d ₆ , internal standard tetramethylsilane), no absorption considered to be due to γ-butyrolactone was observed at 1.0 to 3.5 ppm. The reduced viscosity of this precipitate was 0.69 (0.5 g/100 cm ³ solution of dimethylformamide). This light-colored polyamide-imide varnish was heated at 250℃ on a glass plate.
The film baked for 30 minutes has a thickness of 82 μm and a color of 4Y/
It was 8.0/11 (determined using a standard color chart according to JIS Z 8721-1964). The thermogravimetric loss curve of this film shown in FIG. 1B (measurement conditions were the same as in Example 1) was almost equal to that of the polyamide-imide film of Comparative Example 1.

Example 2 In a four-necked flask equipped with a thermometer, stirrer, and bulb condenser, 75 g of 4,4'-diphenylmethane diisocyanate, 57 g of trimellitic anhydride, and γ-
132 g of butyrolactone was added and the temperature was raised to 190°C over 3 hours in a nitrogen stream. The reaction was continued for 1 hour at the same temperature. The liquid material was lighter in color than the liquid material of Comparative Example 1.

Next, the resin concentration was adjusted to 25% by weight with N,N-dimethylacetamide to obtain a light-colored polyamide-imide varnish. In the infrared absorption spectrum of the precipitate produced by pouring this varnish into a large amount of methanol, absorption of imide groups was observed at 1780 cm ^-1 .
Absorption of amide bond was observed at 1650 cm ^-1 and 1540 cm ^-1 . Further, in the ¹ H-NMR spectrum of this precipitate (solvent dimethyl sulfoxide-d ₆ , internal standard tetramethylsilane), no absorption considered to be due to γ-butyrolactone was observed at 1.0 to 3.5 ppm. The reduced viscosity of this precipitate was 0.70 (0.5 g/100 cm ³ solution of dimethylformamide).

The film made by baking this light-colored polyamide-imide varnish on a glass plate at 250℃ for 30 minutes has a thickness of 82μ.
The color was 4Y/8.0/11 (determined using a standard color chart in accordance with JIS Z 8721-1964).

Example 3 In a four-necked flask equipped with a thermometer, stirrer, and bulb condenser, 75 g of 4,4'-diphenylmethane diisocyanate, 57 g of trimellitic anhydride, and γ-
Add 308g of butyrolactone and heat to 190℃ in a nitrogen stream.
The temperature was raised in 3 hours. The reaction was continued for 1 hour at the same temperature. The liquid material was lighter in color than the liquid material of Comparative Example 1.

Next, the resin concentration was adjusted to 10% by weight with N,N-dimethylformamide to obtain a light-colored polyamide-imide varnish. In the infrared absorption spectrum of the precipitate produced by pouring this varnish into a large amount of methanol, absorption of imide groups was observed at 1780 cm ^-1 and absorption of amide bonds was observed at 1650 cm ^-1 and 1540 cm ^-1 . Further, in the ¹ H-NMR spectrum of this precipitate (solvent dimethyl sulfoxide-d ₆ , internal standard tetramethylsilane), no absorption considered to be due to γ-butyrolactone was observed at 1.0 to 3.5 ppm. The reduced viscosity of this precipitate was 0.40 (0.5 g/100 cm ³ solution of dimethylformamide).

This light-colored polyamide-imide varnish is baked on a glass plate at 250℃ for 30 minutes, resulting in a film with a thickness of
At 82 μm, the color was 4Y/8.0/11 (determined using a standard color chart according to JIS Z 8721-1964).

As is clear from the above examples, the polyamide-imide obtained by the production method of the present invention is light in color and exhibits good film properties and heat resistance, and is particularly useful as an alignment control film for liquid crystal elements, and for protection of electronic components. It is industrially very effective as overcoat materials such as membranes, heat-resistant paints, heat-resistant sheets, heat-resistant adhesives, heat-resistant laminated materials, heat-resistant molded products, and heat-resistant composite materials with glass fibers and carbon fibers. be.

[Brief explanation of drawings]

FIG. 1 shows thermogravimetric loss curves of the films obtained in Comparative Example 1 and Example 1. Explanation of symbols A: Comparative example 1, B: Example 1.

Claims (1)

[Scope of Claims] 1. A method for producing polyamideimide, which comprises reacting a polycarboxylic acid having an acid anhydride group with an aromatic polyisocyanate at 80 to 190°C using γ-butyrolactone as a solvent. 2. The method for producing polyamideimide according to claim 1, wherein the polyisocyanate is 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, or xylylene diisocyanate. 3. The method for producing polyamideimide according to claim 1 or 2, wherein the polycarboxylic acid having an acid anhydride group is trimellitic anhydride. 4 Claims 1, 2, or 3 in which the ratio of the isocyanate groups of the aromatic polyisocyanate to the carboxyl groups and acid anhydride groups of the polycarboxylic acid having an acid anhydride group is substantially equivalent. A method for producing the polyamideimide described.