DE2403284C2 - Storage-stable polyamic acids - Google Patents

Description

The invention relates to polyamic acids, which by Reaction of pyromellitic dianhydride and / or benzophenone tetracarboxylic dianhydride with diamines and methylenebisanthranilic acid are produced, which can be converted into temperature-resistant polyamides at higher temperatures.

It is known to produce polyamic acids by that one diamines with aromatic tetracarboxylic dianhydrides in an organic solvent implements (DE-AS 14 20 706). However, the solutions of such polyamic acids have a tendency to develop after a short period of time Zsit to gel, whereby the reactions responsible for this are both inter- and intramolecular in nature could be. This is a major disadvantage for the further processing of such products, e.g. B. on wire enamels, foils, fibers and adhesives.

It was also known that the usual polyimides, for example as wire enamels, have insufficient adhesion Have copper wire and low hardness of the paintwork. The vulnerability of soft foils for example with wire wraps or with slot insulation is much larger. This is the technical use of wires coated in this way, for example on high-speed automatic winding machines severely disabled.

The object of the invention is therefore over a long period of time Produce storage-stable solutions of polyamic acids, which result in coatings with good hardness and adhesive strength as well as with good dielectric properties can be further processed.

The invention relates to storage-stable polyamic acids, preferably in the form of their solutions, based on reaction products Pyromellitic dianhydride and / or 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride and primary aromatic diamines, which are converted into temperature-resistant polyimides at higher temperatures let, which are characterized in that 1 to 25 mol% of the primary aromatic diamines through Methylenbisanthranilsiure are replaced.

Particularly preferred polyamic acids are those in which 1 to 10 mol% of the primary aromatic Diamines are replaced by methylenebisanthranilic acid.

The invention also relates to the use of the polyamic acids according to the invention, preferably in the form of their solutions, for production temperature-resistant wire enamelling, foils, laminates, impregnations and bonds.

Surprisingly, solutions of the polyamic acids according to the invention which, instead of 1 to 25 mol% of the primary aromatic diamines contain methylenebisanthranilic acid condensed in, very good storage stability and result, for example when used for wire enamelling, coatings that compared to the known polyimides have improved dielectric properties and better adhesive strength and hardness. Polyamic acid solutions without

ίο methylenebisanthranilic acid component or those with On the other hand, more than 25 mol% of the methylenebisanthranilic acid components do not give adequate storage stability or coatings with significantly poorer properties mechanical, thermal and dielectric properties stocks.

The copolyamic acids according to the invention are prepared by the customary methods of Polyamic acid production. One works in general with the exclusion of oxygen, for. B. under nitrogen or Argon. The diamine is generally dissolved together with the methyl bisanthranic acid in an organic, polar solvent, such as, for example N-methylpyrrolidone, at room temperature. The tetracarboxylic dianhydride is then metered in so that the temperature remains as constant as possible or changes insignificantly. However, a specific temperature is not important. The reaction can be carried out up to 170 ^° C., preferably in a temperature range between 20 and 80 ^° C. The higher the

the temperature, the shorter the reaction time

The polyamic acids according to the invention generally have molecular weights above 10,000 and inherent viscosities of 0.1 to 3.0, preferably 3 to 3 1.5 dl / g (measured as 0.5% solutions in

j; N-methylpyrrolidone; see Houben-Weyl, Methods of organic chemistry, 4th edition, Volume IH / 1, pages 431 ff, Stuttgart 1955).

The solvents generally used for the reaction should be inert, so should neither the tetracarboxylic dianhydride still react with the diamines or methylenebisanthranilic acid. Suitable polar solvents are e.g. B. amides, such as N-methylpyrrolidone, dimethylformamide, Dimethylacetamide, hexamethylphosphoramide or di methyl sulfoxide.

Pyromellitic anhydride and / or 33 ', 4,4'-benzophenone tetracarboxylic dianhydride are preferably used as tetracarboxylic anhydrides, but other tetracarbic acid dianhydrides can also be used

-λ can also be used, such as B. 3,3 ', 4,4'-Diphenylätherfetracarbonsäuredianhydrid or Diphenylmethante- (racarboxylic acid dianhydride.

Possible primary aromatic diamines are those of the general formula H ₂ NR-NH ₂ , in which R a divalent aromatic or combined aliphatic-aromatic radical in which the carbon structure is optionally replaced by ether, sulfide or -SOrBrücke is interrupted and the NHr groups each sit on separate carbon atoms, such as

ho z. B. 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane or m-phenylenediamine, and mixtures of these diamines. Particularly 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone and 4,4'-diaminodiphenylmethane are preferred. Of the The proportion of diamine in the polyamic acid is either equimolar (1 amino group / 1 anhydride group) or in 1 to 5 mol% excess. 1 to 25, preferably 1 to 10, mol% of these diamines are in accordance with the invention

S3 ν in

replaced by methylenebisanthranilic acid It is advantageous the total amount of diamine, d. H. Methylenebisanthranilic acid and diamine, compared to the anhydrides in use a small excess, up to 5 mol%.

The products according to the invention can be used for the production of wire coatings, films, fibers, molding compounds, Impregnation, bonding, etc. are used, with the production of the polyimides on Temperatures of over 170 ° C is heated. With advantage the polymers according to the invention can be combined with other reinforcing materials, such as glass fibers, metal fibers, Glass fleece, graphite fibers or other temperature-resistant fiber materials can be used. Excellent composite materials are obtained, the polyimide used because of its good properties Adhesion and hardness represent a very good adhesive The parts mentioned in the examples below and percentages are parts by weight and percentages by weight, respectively.

10

example

In 2000 parts of N-methylpyrrolidone 19932 parts of 4,4'-diaminodiphenyl ether, 5.72 parts Methylenbisanthranilsäure (MBAS) were under N 2 at 20 ⁰ C, and dissolved. After 30 minutes, 218.0 parts of pyromellitic dianhydride are added in portions to the solution, the temperature not exceeding 30.degree. To

Local stirring time at room temperature gives a viscous solution. The inherent viscosity of the solution was 0.723 [dl / g] (measured at 30 ° C. with a 0.5% strength by weight solution of the polymer in N-methylpyrrolidone).
Storage stability of the solutions until gelling:

100 C 60 C

Room temperature

Solution according to Example 1 Corresponding polyarridic acid solution, which has been prepared without methylenebisanthranilic acid

16.5 hours 6 hours 55 hours
18 hours

over 2 years
8 weeks

With both solutions (according to Example 1 and with the solution without methylenebisanthranilic acid but otherwise the same Composition), after dilution with dimethylformamide, a 1 mm copper wire was made at a baking temperature of 500 C. coated on a wire enamelling machine (50 μ). The following properties were found with polyimides coated wires (test according to DIN 46 453):

Hardness abrasion resistance
(DH = double strokes)

tg δ (DV \ <P x
Temperature)

250 C

300 C

Wire enamel according to Example 1 Wire enamel without MBAS

6H 5 H 225 DH
35 DH

75
215

120
1675

example

One dissolves in 2200 parts of N-methylpyrrolidone under nitrogen 1993 parts of 4,4'-diaminodiphenyl ether and 5.72 parts methylenebisanthranilic acid at room temperature on. The solution is then at temperatures below 30 ° C with 109 parts of pyromellitic anhydride and then with 161 parts of S.S '^' - Benzopiienontetracarbonskuredianhydrid added in portions. After stirring for 8 hours at room temperature, a highly viscous solution. The inherent viscosity of the solution was 1.05 [dl / g] (measured at 30 ° C at a Concentration of 0.5% by weight in N-methylpyrrolidone). A comparison test was carried out under the same conditions, but carried out without the use of methylenebisanthranilic acid.

Checking the storage stability of the solutions until they gel:

100 C

60 C

Room temperature

Solution according to Example 2 Solution without MBAS

29.5 hours 8 hours 80 hours
22 hours

over 2 years
3 to 4 months

Wires coated with polyimides, which were produced with the solutions according to Example 1 and the comparative experiment without methylenebisanthranilic acid (MBAS) on a horizontal wire enamelling machine at 500 ° C., showed the following properties (according to DIN 46 453):

24 03 284 Abrasion resistance 6th ⁴ X 5 (DII = double tg (5 (D.V. 10 hardness strokes) Temperature) 300 C 92 DH 250 C 85 30DH 70 2450 Wire enamel according to example 2 6 H. 430 Comparative paint without MBAS 5 H.

Glass fiber reinforced laminates were made from the solutions using the prepreg production method. The test of the flexural strength of the laminates showed a flexural strength of 3600 kp · cm " ² for the sample according to Example 2, but only a flexural strength of 2200 kp · cm" ² for the sample without MBAS.

Claims (3)

Patent claims: 1. Storage-stable polyamic acids based on reaction products of pyromellitic dianhydride and / or S ^ '^' - benzophenone tetracarboxylic dianhydride and primary aromatic diamines, characterized in that 1 to 25 mol% of the aromatic diamines are replaced by methylenebisanthranilic acid 2. Use of solutions of the storage-stable polyamic acids according to Claim 1 as wire enamels. 3. Use of the storage-stable polyamic acids according to Claim 1, optionally dissolved in a solvent, for the production of foams, Laminates, impregnations or bonds.