CS247273B1 - Polyimide binder and process for its production - Google Patents

Abstract

The solution relates to a polyimide binder and a method of preparing such a binder for electrotechnical purposes. The binder is used as an impregnator of layered materials usable at temperatures of 160 to 250 °C. The essence of the solution is that a polyimide prepolymer of the bismaleimide type, prepared from a mixed solvent environment, is reacted with a ketone in a further step. The polyimide binder according to this solution has high temperature resistance and, when applied in layered materials, increases their mechanical strength and improves dielectric properties.

Description

247273

The present invention provides a polyimide binder and a process for preparing a polyimide binder for coated materials, in particular electrospray with reinforcement made of inorganic or organic fabrics, fibers or mats. It is an object of the present invention to provide a suitable bonding agent for technically and economically advantageous types of laminates useful at temperatures of 180 to 250 ° C.

The application of polyimide thermosetting resins to composite materials is increasingly expanding due to their excellent mechanical and electro-insulating properties with long-term increased thermal stress. Polyimide-based products such as glass fabric laminates, including metal-clad materials, mats, synthetic papers, molding and potting materials, are used in electrical engineering and electronics, as well as in engineering and aerospace.

Heat-curable polyimide prepolymers, which are used either pure or modified by other additives, form a resinous base of layered insulators with higher temperature resistance. The solvent of these polymers is usually an amide solvent such as N-methyl-2-pyrrolidone, or N, N-dimethylformamide. For the preparation of an imperfect solution of polyimide prepolymer, 1-methoxyethanol (methylcellosolve) or 2-ethoxyethanol (ethylcellosolve) can also be used as a solvent. another glycolether.

A disadvantage of these solvents is that the polyimide prepolymer solution is volatile and has a short shelf life. In the case of the use of N-methyl-2-pyrrolidone or Ν-dimethylformamide as solvent, a high volatile content remains in the impregnated prepreg due to the strong solvent polarity, with the danger of explosion using glycol ethers, mainly methoxyethanol due to low autoignition temperature.

General Electric Patents BP 1374126 and BP 1 374 127 disclose a one-step preparation of polyimide prepolymers in ketone solvents (without separation of the bis-maleimide intermediate) in the presence of a nickel acetate catalyst and acetic anhydride. A disadvantage of this method is that the polyimide oligomer obtained is difficult to wash with water. If the acidic components remain in the product, they prevent the preparation of the laminates, in particular clad sheets.

The invention addresses the drawbacks of the prior art. SUMMARY OF THE INVENTION The present invention relates to a polyimide binder for bismaleinimide-based electrotechnical type laminates suitable for the preparation of high temperature lower laminates, obtainable by reaction of the almimaleimide and diamine at a molar ratio of 2: 1 to 50: 1 in the presence of 1 to 30 weight percent. percent, on the dry weight of the polyimide prepolymer, the ketone of the general formula R-CO-R 1, wherein R is an aromatic or aliphatic hydrocarbon radical of 1 to 6 carbon atoms in the chain, R 1 is an alkyl radical of 1 to 3 carbon atoms, optionally in the presence of 2 to 50 weight percent epoxy or 2 to 40 weight percent phenolic resin or mixtures thereof at a ratio such that their total amount is 2 to 50 percent by weight of the solids of the polyimide prepolymer. bismaleimide is reacted with diamine in molar ratio 2: 1 to 50: 1 in an amide and non-polar mixed solvent, preferably N-methyl-2-pyrrolidone, Ν, Ν-dimethylformamide, dimethylacetamide and benzene, toluene, xylene, or theta solvents or mixtures thereof in proportion to 3: 0.5 to 3: 2, and in the following step, the obtained solution is reacted with 1 to 30% by weight, based on the dry weight of the prepolymer, of the keto of the above formula at a temperature of 15 to 60 ° C, for a period of 3 to 24 hours optionally in the presence of the abovementioned epoxide or phenolic resins.

According to the invention, the ketones are not inert inert solvents but react with the polyimide prepolymer and cooperate in cross-linking them in such a way that the imide content of the polymer is increased by about 10% by comparison with ketone-free polyimides. The prepolymer of the present invention exhibits increased temperature resistance upon curing

Polyimide prepolymer in combination with phenolic resins, respectively. with epoxy resin when applied in laminates it increases fire resistance.

The prepolymers are prepared by known procedures by reacting bisimides with diamines in solvents or in the melt (in a molecular weight of 2: 2.5: 1), respectively. diamines with dianhydridaromatic tetracarbonic acids, preferably pyromellitic in combination with bis-imides in solvents and in the presence of a catalyst (No. AO 174 567 J. The formation of curable compositions is accelerated by the addition of peroxides such as benzoyl peroxide, dicumylper oxides and the like in an amount of 0.5 to 5% per dry of prepolymer.

If the thus prepared prepolymers precipitate in non-solvents, e.g. water, the product dried at 30-50 ° C is suitable as the basis of the polyimide compression and molding materials. To impregnate the reinforcement of the laminate, a pre-polymer prepared in a mixed solvent of amide and non-polar liquids at a ratio of 3: 0.5 to 3: 2 is used. precipitation of the prepolymer, which content in the solvent is 20 to 60 wt. % dry matter. For example, the amide component of the mixed solvent is Ν, β-dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide; the non-polar component is, for example, benzene, toluene or xylene, reisp. thio-solvents such as dioxane, 1,2-dimethoxyethane, dimethylsulfoxide or mixtures thereof. Preferred is the combination of N-methyl-2-pyrrolidone and toluene in a 3: 2 ratio.

The polyimide prepolymer solution containing 20 to 60% by weight of polyimide dry matter is then reacted with ketone hydrocarbon R-CO-R1, v, in an amount of 1 to 30% by weight. %, Preferably 15 to 24 wt. Under these conditions, the imide content of the polyimide prepolymer is increased by about 10%, the gelation time of the polyimide is reduced, and the cure of the laminates is accelerated, increasing the temperature resistance, in particular during long-term thermal stress. The following table shows the bending strength values during the thermal aging of polyimide fiberglass:

Table: Bending strength limits (MPa) after thermal aging

Sample Delivered 25 ° C (MPa) 2,500 hpri 200 ° C 5,000 hpri 200 ° C 2,500 hpri 220 ° C 625 hpri 240 ° C 1 626 389 150 192 408 2 627 551 350 350 500 3 608 450 320 270 517 where: sample 1: fiberglass prepared from polyimide prepolymer in a solution of N-methyl-2-pyrrolidone, sample 2: fiberglass prepared from polyimide-modified epoxide in solution N-methyl-2-pyrrolidone-1-methyl ethyl ketone, sample 3: fiberglass prepared from an epoxide modified polyimide prepolymer in solution N-methyl-2-pyrrolidone-i-acetone. The base impregnating solution can be modified: after reacting with ketones of some thermosetting plastics, e.g. also with epoxy dian resins, gram-equivalent / 100 g 0.17-0.50 in an amount of 2 - 50% by weight on dry matter, b) with epoxy resin coating c) with the bromepoxide resins of dianotype, gram equivalent / 100 g 0.17-0.50 with a bromine content of 15-25 ° / o d) the combinations mentioned in a, b, c can be further crosslinked by the addition of aromatic amine hardeners for epoxides, e.g. 4,4'-diaminodiphenylmethane, 4.4. i) diaminodiphenylsulfone in an amount of 1 to 10 parts by weight on the dry weight of the epoxy resin used; e) with phenolic resin molecules, with a weight of 600 to 2500 in an amount of 2 to 40% on the dry weight of the polyimide resin; mentioned p from points a, b, c, e in any ratio so as to amount to 2 to 50% by weight of the polyimide prepolymer dry matter.

The solution of the polyimide composition is adjusted to the necessary impregnating viscosity, depending on the resin used, from the impregnating device and the impregnation conditions, by addition of a suitable solvent such as N-methyl-2-pyrrolidone and toluene.

The solution of the invention enables the efficient production of an impregnating resin for the preparation of high quality laminates with increased temperature resistance and good electrical and insulating properties.

In order to concretise the solution, examples of the preparation of bituminous binders and their applications for laminates and prepregs are given below. EXAMPLE 1 To 100 g of a 40% solution of polyimide prepolymer prepared by the synthesis of 2.5 moles of 4,4 ' -diaminodiphenylmethane-bismaleimide with 1 mol of 4,4 ' -diaminodiphenylmethane at 105 DEG C. for 4 hours in a solution of N-methyl- 2-pyrrolidone and toluene (3: 2 by weight) are mixed with 15 g of acetone and after 3 hours at 25 to 30 ° C, a 48% solution of polyimide composition impregnates the glass fabric with the dried binder content of 38 to 40 %, and after evaporation of the solvents in the drying tunnel of the impregnating machine at 155-160 ° C, a preperg is obtained. Pressing the prepreg at 170 ° C and a pressure of 7 MPa for 2 hours followed by curing for 48 hours at 200 ° C without pressure yields a glass laminate characterized by high mechanical properties at a working temperature of 180 ° C and 200 ° C . Example 2

100 g of a 45% solution of polyimide resin, which was prepared by synthesizing 12.5 moles of 4,4 ' -diaminodiphenylmethane-bis-maleimide with 1 mol of 4,4 ' -diaminodiphenylmethane at 105 DEG C. 4 hours in a solution of N-methyl-2-pyrrolidone-toluene in a ratio of 3: 2, with 37 g of a 60% acetone solution of di-epoxy resin, equivalent to 100 g, 0.18-0.24, and after 3 hours of stirring at 20 ° C. -25 ° C gives a solution with a solids content of about 57% and a gelation time of 160 ° C for 6 minutes. This is used to pre-form the amine-silane-treated glass fabric to a 33% dry binder content. Dry for 5-10 minutes at 150-180 ° C. Laminated sheets were pressed at 160 ° C, 7 MPa, laminate for 5 hours, and 24 h / 190 ° C and 48 h / 200 ° C. After 2,500 hours of aging at 220 ° C, the laminate has a flexural strength of 300 MPa. The laminate prepared without the addition of epoxide and acetone exhibits a strength of 190-200 MPa after aging. Example 3

100 g of a 50% solution of a resin formed by condensation of 2.5 moles of 4,4 ' -diamodiphenylmethane bis-maleimide and 1 molar of 4,4 ' -diaminodiphenylmethane in N-methyl-2 -pyrrolidone and toluene 2: 1 with 31 g of brominated epoxy resin in the form of a 80% or solution in methyl ethyl ketone. After 24 h, it is used to impregnate the glass tissue as in Example 2 and the impregnated material is pressed and hardened. The laminate obtained after 2500 hours of aging at 220 ° C yields a flexural strength of 350 MPa. Laminate prepared without the addition of epoxide and methyl ethyl ketone achieves a flexural strength of only 200 MPa under the same conditions. Example 4

Mix 100 g of a 45% solution of polyimide prepolymer prepared by Example 2 with 15 g of dianepoxide resin with an epoxy equivalent of 0.17-0.25 / 100 g, 10 g acetone and 0.9 g of 4,4'-diaminodiphenylmethane and after homogenization 2 - 3 hours at room temperature, a solution with a dry matter content of about 56% is obtained and a gelation time at 160 ° C of about 3 minutes, after which a specially prepared glass tissue (aminosilanes, epoxysilanes) is impregnated after the addition of 1.2 g of dicumyl peroxide. in the impregnated material 40-45%, and after removal of the solvents in the drying tunnel of the vertical machine at 150-180 ° C for 5-10 minutes, a pre-preg is obtained, suitable for preparing the copper plated laminate by pressing for 4-6 hours at room temperature. 165-170 ° C and at a pressure of 4-6 MPa. The material optimally has the properties of post-curing without pressure for 48 hours at 180-190 ° C. The prepared material is characterized by a dimensional stability of at least (0.0004 mm) 0.02 - 0.04%, a high temperature resistance at the soldering bath at 270 - 288 ° C for 3 minutes and is suitable for PCB Production Example 5

The impregnating resin is prepared by mixing 100 g of the polyimide prepolymer prepared as in Example 2 with 19 g of bromo-epoxy resin with an epoxy equivalent / 100 g of 0.18-0.24 as an 80% solution of methyl ethyl ketone and 0.6 g of dicumyl peroxide. The solution is diluted with N-methyl-2-pyrrolidone + toluene 3: 2 to such a viscosity that, with impregnation without the use of wiping rolls, the build-up of bituminous binder is 150%, i.e. 60%, of the binder. Upon evaporation of the solvents in the vertical furnace of the impregnating machine at 140-160 ° C, a prepreg suitable as a polishing sheet for self-extinguishing multilayer printed circuit boards is obtained in thermally stressed equipment. Example 6

A solution for impregnating glass cloth or carbon fibers is prepared by mixing 80 g of a 50% strength prepolymer solution, as in Example 1, with 20 g of a cresolaniline formaldehyde resol (50% solution in ethanol or methanol) and after homogenization at the glass fabric is impregnated in the manner described in Example 4 with room temperature. The dry prepreg is pressed at the press pressure of 4-7 MPa, at 160-170 ° C, for 3 hours, after milling and laminating in the number of presses required for the coarse required. The hardening laminate obtained at 200 ° C for 48 hours is characterized by a high bending strength value at 200 ° C (about 70% of the delivered value) and high electrical properties. according to IEC 707/1981 (9), the PV material corresponds to class Vl

To 100 g of a 50% solution of the polyimide prepolymer prepared in Example 3, 12 g of cresol-aniline-formaldehyde resin are added and the mixture is heated at 80 DEG C. for 10 minutes with continuous stirring. Finally, 10 g of methyl ethyl ketone is added to this solution and the glass tissue is impregnated to a dry binder content of 40-45% and prepreg is obtained after evaporation of the solvents with a drying tunnel impregnating machine at t = 150-160 ° C. By pressing 28 layers of pre-preg at 165 ° C and 5 MPa for 3 hours, a fiberglass of about 3 mm with a permanent temperature resistance of 180 ° C and excellent mechanical properties is obtained for groove wedges in high-torque machines.

Claims (2)

10 PREDMET Polyimide binders for bis-maleimide-based electrotechnical type laminates suitable for the production of high temperature resistant laminates, the preparation of a reaction of bismaleimide and diamine in a molar ratio of 2: 1 to 50: 1 in the presence of 1 to 30 weight percent, based on the dry weight of the polyimide prepolymer ketone of the general formula R-CO-R 1, wherein R is an aromatic or aliphatic hydrocarbon radical having from 1 to 6 carbon atoms in the chain, R 1 is an alkyl radical containing from 1 to 3 carbon atoms, optionally also in the presence of 2 to 50 percent by weight epoxy or 2 to 40 percent by weight phenolic resin, respectively. mixtures thereof in any ratio such that the total amount thereof is 2 to 50% by weight on the dry weight of the polyimide prepolymer. 2. A process for preparing a polyimide binder of claim 1, wherein the bismaleimide is reacted with a diamine in a molar ratio of 2: 1 to 50: 1 in an amide and non-polar mixed solvent, preferably N-methyl-2-pyrrolidone. , Β, β-dimethylformamide, abenzene dimethylacetamide, toluene, xylene, or thetar solvents or mixtures thereof in a ratio of 3: 0.5 to 3: 2 and in the next step the obtained solution is reacted with 1 to 30 percent by weight, based on the polyimide prepolymer a ketone of the formula R-CO-R 1, wherein R and R 1 are as defined in point 1, at a temperature of 15 to 60 ° C, for a period of 3 to 24 hours, optionally also in the presence of 2 to 50% by weight of epoxy or 2 to 40% by weight phenolic nutrient -ce, respectively. mixtures thereof in any ratio so that their total amount is 2 to 50% by weight on the dry weight of the polyimide prepolymer.