CS275957B6 - Self-extinguishing prepreg and its production method - Google Patents

Abstract

The solution is useful especially in the electrical engineering industry, advantageous for the production of laminates with a high degree of fire resistance (V-0). A self-extinguishing prepreg has been developed, containing 1 to 35 percent by weight of dry matter of a phenol alcohol or methylol melamine type pre-impregnation resin, modified with low-molecular organic or inorganic flame retardants, soluble and dissociable in water and miscible with aliphatic alcohols. The essence of the solution is that the paper reinforcement is pre-impregnated to 1 to 35 percent by weight of the binder dry matter with a water-alcoholic solution of the pre-impregnation resin, into which 1 to 50 parts by weight per 100 parts by weight of dry matter of a low-molecular organic or inorganic retardant containing some component from the group of balogen, nitrogen, phosphorus, boron, zinc, magnesium is mixed. The retardant is added to the resin in the form of an aqueous solution. Flame retardant prepregs used in the production of laminates improve their fire resistance without increasing material costs.

Description

CS 275957 0 6

BACKGROUND OF THE INVENTION The present invention relates to a flame retardant prepreg of general or electrotechnical type suitable especially for the production of PCB laminates. The purpose of the invention is to obtain a laminate with a high flame retardancy in a simple economically advantageous manner. In the production of flame retardant prepregs, the paper is first impregnated with a water-alcoholic solution of methylolphenol or methylolamine resins prior to impregnation with thermoreactive flame retardant resins. The absorbability of the organic reinforcement is reduced due to the interaction of the hydroxyl groups of the cellulose with the methylol groups of the resins.

In order to obtain laminates with excellent fire resistance, it is necessary to add or modify the thermoreactive resins used in the second stage of impregnation with large amounts of flame retardants, predominantly based on aromatic compounds containing nitrogen, phosphorus, antimony, halogens and the like, which are more expensive than the base resin increasing the final product. In some cases, these additives may impair the mechanical properties of the laminate.

The described disadvantages of the prior art are eliminated by the solution according to the invention, the principle of which is that the flame retardant prepreg is formed from paper impregnated with 1 to 35 wt. binder solids with a pre-impregnating resin of phenolalcohol and / or methylollamine type with a proportion of 1 to 50 wt. flame retardant parts. It is selected from the group of organic and / or inorganic compounds containing one of the elements nitrogen, phosphorus, boron, zinc, magnesium, halogens, water soluble and dissociable and well miscible with alcohols. A practical method of preparing this flame retardant prepreg is that the paper reinforcement is pre-impregnated with a water-alcoholic solution of phenolalkohal resin having a molecular weight of 124 to 233 and / or methyloline amines having a molecular weight of 156 to 306; a flame retardant which consists of organic and / or inorganic compounds of the nitrogen, phosphorus, boron, zinc, magnesium, halogens, water-soluble and dissociable nature and miscible with aliphatic alcohols. Preference is given to the use of low molecular weight compounds in which the addition of 1 to 15 wt% is sufficient to achieve a high flame retardant effect. parts. Said compounds have the ability to diffuse more easily into the fibrous structure of the paper, which reduces flammability. For example, sodium tetraborate, boric acid, ammonium hydrogen phosphate, all salts of hydrogen halide acids with ammonia or alkaline hydroxides, ZnCl 2, MgCl 2, or organic compounds such as tetraethylammonium bromide, bis (beta-chloroethyl) vinylphosphonate, as well as a suitable combination of these compounds. The retarders are dissolved in water and added to the aqueous alcoholic pre-impregnating resin solution. The concentration of the gels is adjusted to the necessary viscosity with alcohols, ketones, water or a mixture thereof. Some etheretarders, such as ammonium sulfate, crystallize in alcohols, so an aqueous solution of this retarder should be used and impregnated with pre-impregnated paper, with methyl-phenol or methylolamine. Preimpregnated paper is adjusted to a dry binder load of 1 to 35 wt. % by passing through a drying channel at a temperature of 80-160 ° C, where the solvents and water are evaporated. This retarded paper is further used to produce highly refractory layered materials and clad laminates. The advantage of the flame retardant prepreg of the present invention is that it exhibits good fire resistance and the laminate made of such prepregs has a V-0 flame resistance. The retarders used are easy to process, available under economically advantageous conditions and low or low consumption. reduce the consumption of other retarders.

The principle of the solution is further illustrated by the five examples of specific embodiments of the invention and the properties of the flame retardant prepreg are shown in three tables. Example 27

Samples, the characteristics of which are given in Table 1, are prepared by the following procedure: 2

Electro-insulating white paper weighing 80 g / m, 50 mm long absorbency, 40 mm / 10 min transverse to Klemma is pre-impregnated with a methylolfenol-type preimpregnation solution, which is prepared by condensation of phenol and formaldehyde, e.g. 1: 1.5, in the presence of 0.02 mole MgO, at 80 ° C to a refractive index at 20 ° C of 1.48, to which 6.25% of the respective inorganic and resp. organic (tetraethylammonium bromide) water-soluble retarder. Dilute the solution with water and ethanol or methanol so that after drying and pre-hardening the resin at 100 to 120 ° C, the paper has a dry and dry pre-impregnation of about 22.5 and 2.5%.

The paper is further impregnated with a resin solution prepared according to No. 216 853 and containing 20.4 diphenyl cresyl phosphate, 13.6% pentabromo-diphenyl ether, and to which a synergistically acting Sb 2 O 3 is added in an amount of 12 to enhance the flame retardant effect. 5% to the added amount of pentabromodiphenyl ether so that after drying and pre-hardening at about 150 ° C it contains about 50-55 µl of dried binder. The time and temperature of the pre-hardening of the resin on the paper is adjusted such that its flow from the press dock during compression at 155 ° C and 5 MPa pressure is about 1 to 3

The cover sheets are prepared as follows: electroinsulating paper 80 g / m 2, 50 mm long, 40 mm / 10 min transverse, according to Klemma, pre-impregnated with a pre-impregnating resin solution prepared by condensation of phenol and formaldehyde, e.g. with a molar ratio of 1: 1.5, in the presence of 0.02 mol of MgO, at 80 ° C, a refractive index at 120 ° C of 1.48. The solution is diluted with water, ethanol or methanol so that the paper, after subsequent drying and pre-hardening of the resin at 100 to 120 ° C, has a resin dryness of about 22.5-2.5%.

The paper is further impregnated with an oil-modified resol solution prepared according to Authorization No. 240 490 and which does not contain any retarder such that after drying and pre-curing at about 150 ° C it contains about 50-52% binder content. The time and temperature of the pre-hardening of the resin on the paper is adjusted so that its leakage from the test bed during compression at 155 ° C. and a pressure of 5 MPa is about 1-3.

10 sheets of paper prepared with a re-entrant and one cover sheet from each side are used to press 1.5 mm thick samples. The samples were pressed for 2 hours.

Some of these laminates, when prepared with a copper foil clad, can be used for the production of printed circuit boards, e.g., those using NH 4 Br, NajB 2 O-y, NH 4 -, PO 3 - for preimpregnation. Unlike the sample where no retarder was used in the prepreg (sample number 0), they have excellent flame retardancy - class V-0 according to method B ČSN 346510 art. UL-94. Example 2

The electrotechnical white paper is pre-impregnated with a methylolfenol-type pre-impregnation solution obtained as in Example 1 to which a retarder (bromoammonium, potassium bromide, ammonium chloride) of 12.5 mg and bis (beta-chloroethyl) vinyl phosphonate in amount of 37.5%.

For the preparation of samples containing KBr, resp. NHC1 was used with a paper weight of 2 - 100 g / m, with a absorbency of 70 mm, seen across 10 min according to Klemma. Paper was used to prepare the next two samples as in Example 1.

The preparation procedure is the same as described in Example 1, except that the original resin according to No. 216 853 contains 13.8 diphenyl cresylphosphate, 24.2 pentabromodiphenyl ether and Sb 2 O 5 in an amount of 25% added pentabromide. diphenylether and 8 sheets of this paper and two cover sheets as in Example 1 are used to prepare 1.5 mm thick samples based on 100 g / m 2 paper. 3 CS 275957 B 6

The flame retardancy of the prepared laminates and some of their other properties are shown in Table 2.

In addition to a laminate that does not contain any retarder in the pre-impregnating resin, all can be included in the V-0 flame retardant class. Example 3 2

Electroinsulating white paper weighing 100 g / m is pre-impregnated with a pre-impregnated resin which is obtained as in Example 1 and to which NH 4 Br is added at 6.25 µm. The sample preparation procedure is the same as in Example 1, except that the impregnating resin of the inventive certificate No. 216 853 contains 26.5 pentabromo-diphenyl ether and 13.3 µs diphenyl cresyl phosphate.

8 sheets of impregnated paper and two-sheet sheets are used to prepare 1.5 mm thick laminate.

For comparison, a laminate was prepared in which NH 4 Br was not used. The flame retardancy of the laminates and some of their other properties are shown in Table 3. Both laminates are flame retardant in accordance with CSN 346510, the laminate which contains NH 4 Brs addition in comparison with the laminate characterized by a better flame retardancy. Example 4 2

An electro-insulating white paper weighing 80 g / m absorbency as in Example 1 is pre-impregnated with a pre-impregnating resin which is obtained as in Example 1 and to which NH 4 Br is added in an amount of 12.5 µm.

The sample preparation procedure is the same as that described in Example 1, except that the impregnating resin according to the Applicant's Certificate No. 216 853 contains 13.3% diphenyl cresyl phosphate and 26.5% mixed flame retardant (pentabromodiphenyl ether, aliphatic phosphate, aromatic phosphate) with a bromine content of 42% and a phosphorus content of 3.6

For comparison, a laminate was prepared in which the NH 4 Br was not used in the prepreg.

Self-extinguishing of laminate with NH ^ Br according to ČSN 346510 art. 2.22, method B is class V-0 (total burning time 30 s) comparative without NH4 Br BO-2BO s.

55 g / m < 2 > high-density dielectric kraft paper was pre-impregnated with a water-alcoholic solution of phenolalcohol with a molecular weight of 200, with the addition of 31 parts by weight of ammonium bromide to the phenol alcohol. The paper is dried at 90 to 100 ° C and deposited at 33%. The dried paper thus pre-impregnated in the flame and extinguished immediately after the flame was removed.

The pre-impregnated flame retardant paper is impregnated in the second stage with cresol formaldehyde resin without flame retardant so that the total deposition of phenol alcohol + resin is dried at 90-115 ° C for 110 ° C.

The laminates were pressed for 90 minutes at 7 MPa and 145 ° C. The ridge hardened paper obtained, 1.5 mm, had a flame retardancy in the vertical V-1 flame test (total burning time of 70 s) and a flame retardant of 3 mm was a flame-retardant V-0 (total burning time of 7 s).

If pre-impregnated paper with phenol alcohol without NH4 Br is used, the material is hot-rolled, but also in a horizontal flammability test.

The absorption of the sample in water at a thickness of 1.5 mm after 24 hours is 85 mg and at a thickness of 3 mm is 105 mg. The flexural strength of the laminate is at least 110 MPa.

Hardened paper has high loss factor and permittivity values, so it is not suitable as an electrical insulating material. CS 275957 8 6

Table 1

Property Retarder in Preimpregnation Resin 0 1 NH4Br - nh4ci - nh4h2po4 - NaH2P02 TEABr Na2B4O7 Flammability according to CSN346510 RE. 2.22, meto-da B Total burning time, s 266 26 86 32 150 120 45 Flammability class V-0 Vl V-0 Vl Vl V-0 Permit at 1 MHz, A 4.61 5.1 5.23 4, 82 4.96 4.70 4.38 Loss factor tg tf at 1 MHz, A 0.042 0.07 0.08 0.054 0.082 0.049 0.06 0 Water absorption after 24 h 'at 23 * 0 water mg 40 39 54 39 72 30 43 Sheariness according to CSN346510 degree I. direction 0,7 0,8 0,7 0,7 0,7 0,7 0,7 II. direction 1.1 i, °. 1,1 1,0 1,1 1,0 1,0 Binder content in laminateX 50,1 48 53 53,2 52 49,4 54 A = after 96 hours storage at 40 ° C and 96% humidity TEABr = tetraethylammonium bromide

Table 2

Property Retarder in Preimpregnation 0 NH4Br KBr nh4ci FBB Flammability According to CSN 346510 C1. 2.22, method BCburn time, s 238 32 31 26 46 Flammability class V V-0 V-0 'V-0 V-0 Permittivity at 1 MHz, A 4,73 5,0' 4,7 4,7 5, 0 Loss factor 'tg' at 1 MHz, A 0,035 0,08 0,07 0,084 0,056 Water absorption after 24 h at 23 * C water mg 35 50 47 40 32 Shearability according to CSN346510 grade I direction 0,7 0,75 0, 6 1,0 1,0 2nd direction 1,0 1,1 0,8 1,0 - Binder content in laminate, 54,8 53,7 52,0% 52 51,1

Claims (2)

PATENT CLAIMS A self-extinguishing prepreg of the general and electrotechnical type, suitable in particular for the production of laminates for printed circuit boards, characterized in that it consists of paper reinforcement impregnated to 1 to 35 wt. Dry matter of the binder with a pre-impregnation resin of the phenol-alcohol type with a molecular weight of 124 to 233 and / or of the methylolmelamine type with a molecular weight of 156 to 306 with a proportion of 1 to 50 wt. % of a flame retardant from the group of organic and / or inorganic compounds of elements from the group of halogens, nitrogen, phosphorus, boron, zinc, water-soluble and water-dissociable magnesium and miscible with aliphatic alcohols. 2. A process for the production of a self-extinguishing prepreg according to item 1, characterized in that inorganic and / or organic compounds containing nitrogen, phosphorus, boron, grain, magnesium, halogens as a flame retardant are dissolved in water and then added to the prepreg. resins based on methylolphenols and / or methylolmelamines, which are pre-impregnated on paper reinforcement and, after pre-impregnation, dried to a coating of 1 to 35% by weight of binder dry matter. .