JPS6231729B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a flame-retardant silicone-modified epoxy resin, which is mainly applied to the production of wiring boards. In order to improve the reliability of through holes in multilayer wiring boards, it is necessary to reduce the occurrence of smear during drilling. Although the best drilling conditions are set by manufacturers of multilayer wiring boards, it is said that the occurrence of smear is still unavoidable in the case of epoxy multilayer wiring boards. For this reason, multilayer wiring board manufacturers carry out smear removal processing, but it is dangerous because it uses concentrated sulfuric acid, hydrofluoric acid, etc., and the processing solution remains due to insufficient water washing, resulting in poor through-hole reliability. may lower the Furthermore, it has been known for some time that resins with a high Tg can be used to reduce the occurrence of smear, but resins with a high Tg are generally hard and can cause wear and tear on drill bits (for drilling small diameter holes (0.8φ or less)).
Problems such as damage to the drill bit occur during the process. The cause of smear is said to be the softening of the resin due to frictional heat during drilling. Although it is possible to prevent softening by using a resin with a high Tg, it also increases hardness and causes various problems. Another way to reduce the occurrence of smear is to reduce the frictional heat generated during drilling. That is, this is a method of reducing frictional heat and preventing softening of the resin by reducing the friction of the resin, which is the intention of the present invention. The present invention relates to a method for producing a flame-retardant silicone-modified epoxy resin that has low friction in order to reduce the occurrence of smear during drilling. Namely, (a) 100 parts by weight of an epoxy resin with a hydroxyl value of 0 to 0.08, (b) tetrabromobisphenol
A40-80 parts by weight, (c) 0.1-20 parts by weight of a silicone intermediate with an alkoxy equivalent of 150-300, and (d) 0.001 parts by weight of catalyst.
It is characterized in that a mixture consisting of ~0.05 parts by weight is heated to 120-200°C and reacted in one step. The present invention will be explained in detail below. The epoxy resin (a) preferably has a small number of hydroxyl groups, and has a hydroxyl value of 0 to 0.08, and the smaller the hydroxyl value, the better. If it is larger than that, the obtained silicone-modified epoxy resin will have a high molecular weight and a non-uniform cured product will be obtained. The hydroxyl value is the reciprocal of the hydroxyl equivalent multiplied by 100, and the hydroxyl equivalent was measured by the acetyl chloride method.
Examples of the epoxy resins used include bisphenol A type epoxy resins, phenol novolak type epoxy resins, cresol novolak type epoxy resins, hydantoin type epoxy resins, tetraglycidyl isocyanurate and their halides. Tetrabromobisphenol A in (b) was selected because it imparts self-extinguishing properties to the epoxy resin, and the hydroxyl group of this compound reacts with the epoxy group of the epoxy resin, but hardly reacts with the alkoxy group of the silicone intermediate. Because of its properties, the reaction of increasing the molecular weight of the epoxy resin and the reaction of modifying the epoxy resin with silicone, which were conventionally carried out in two stages, can be carried out in one step. For 100 parts by weight of epoxy resin, 40 to 80 parts by weight of tetrabromobisphenol A is used, which corresponds to a hydroxyl group/epoxy group ratio of 1/4 to 1/2 in the case of bisphenol A type epoxy resin. If tetrabromobisphenol A is less than 40 parts by weight, sufficient flame retardancy cannot be obtained, and if it is more than 80 parts by weight, the obtained silicone-modified epoxy resin will have a high molecular weight and the cured product will harden unevenly. The silicone intermediate in (c) is

It is an organosiloxane with an alkoxy group such as [Formula] or its condensation product, but the alkoxy group includes methoxy group, ethoxy group, etc., and the alkoxy equivalent is 150 by Zeisel's quantitative method.
~300 are used. If it is larger than that, the silicone intermediate has a high molecular weight, and the obtained silicone-modified epoxy resin also has a high molecular weight, giving a non-uniform cured product. If it is smaller than that, the reaction between the alkoxy group of the silicone intermediate and the hydroxyl group generated by the reaction of the epoxy resin with tetrabromobisphenol A will not take place sufficiently due to steric hindrance, and the unreacted alkoxy group will cause the cured product to Moisture resistance and heat resistance decrease. The silicone intermediate is used in an amount of 0.1 to 20 parts by weight, but if it is less than that, it will have no effect on drillability, and if it is more than that, unreacted alkoxy groups will remain. Examples of the catalyst (d) include tertiary amines, quaternary ammonium salts, imidazole, alkali metal hydroxides, phosphonium halides, sulfonium salts,
Tertiary phosphine and the like are used. Examples of tertiary amines include benzyldimethylamine, triethanolamine, and pyridine. Examples of quaternary ammonium salts include benzyltrimethylammonium hydroxide, benzyltrimethylammonium chloride, tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, and N-cetylpyridinium chloride. Imidazole includes 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,
Examples include 1-cyanoethyl-2-phenylimidazole. Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Examples of the halogenated phosphonium salts include ethyltriphenylphosphonium bromide, tetraphenylphosphonium chloride, tetrabutylphosphonium chloride, and methyltriphenylphosphonium iodide. Examples of sulfonium salts include triphenylsulfonium chloride, benzyldimethylsulfonium chloride, and dimethylpropylsulfonium bromide. Examples of tertiary phosphine include triphenylphosphine and tributylphosphine. These catalysts are used in an amount of 0.001 to 0.05 parts by weight, but if the amount is less than that, the reaction time will be over 10 hours, and if the amount is more than that, they will act as impurities in the resin and affect the electrical properties of the cured product. The synthesis reaction temperature is 120~200℃, preferably 150~
The temperature is 170℃. If the temperature is lower than 120°C, the reaction is slow and takes more than 10 hours. If the temperature is higher than 200°C, the catalytic effect is lost and tetrabromobisphenol A begins to decompose. The synthesis reaction time may be any number of hours, but preferably 2
~5 hours. The end point of the reaction is confirmed by measuring the epoxy equivalent by the cetyltrimethylammonium bromide-perchloric acid method. If the measured epoxy equivalent is between 90 and 110% of the theoretical calculation, it is considered as the end point. Inert gas replacement may or may not be performed. Alcohol, which is a reaction by-product, is removed from the thread by distillation and, if necessary, by vacuum distillation. Mixing and heating (a), (b), and (c) is a common method used to increase the molecular weight and impart flame retardancy to low molecular weight epoxy resins. ) There are no examples of mixing and heating silicone intermediates. The purpose of the present invention is to utilize the selectivity of TBA for OH to perform the synthesis of a flame-retardant silicone-modified epoxy resin in one step, which was conventionally carried out in two steps. As a result, the process can be shortened, the quality can be easily made uniform, and a flame-retardant silicone-modified epoxy resin of constant quality can be obtained in a short time, which improves the drilling workability of wiring boards. used for. The present invention will be explained below based on examples. Example 1 4300 g of bisphenol type A epoxy resin with an epoxy equivalent weight of 175, tetrabromobisphenol
420 g of A2650 g, KR218 (trade name: silicone intermediate with methoxy equivalent weight 210, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.25 g of tetramethylammonium chloride were mixed and stirred, and the mixture was kept at a temperature of 160° C. for 2 hours. During that time, volatile components in the system were removed under reduced pressure. A solid resin with an epoxy equivalent of 584 was obtained. Example 2 4300 g of bisphenol type A epoxy resin with an epoxy equivalent weight of 175, tetrabromobisphenol
A2650g, KR213 (product name: Shin-Etsu Chemical Co., Ltd.)
315 g of a silicone intermediate having a methoxy equivalent of 157 and 0.25 g of tetramethylammonium chloride were mixed and stirred, and the mixture was kept at a temperature of 160° C. for 2 hours. During that time, volatile components in the system were removed under reduced pressure. A solid resin with an epoxy equivalent of 568 was obtained. Comparative example: 4300g of bisphenol A type epoxy resin with epoxy equivalent of 175, tetrabromobisphenol
A2650g, tetramethylammonium chloride
0.25g was mixed and stirred and kept at a temperature of 160°C for 2 hours.
Epoxy equivalent after removing volatile components from the system under reduced pressure
550 solid resin was obtained. Prepreg varnishes were created using the silicone-modified epoxy resins obtained in Example 1, Example 2, and Comparative Example. The formulation is shown in Table 1.

[Table] An epoxy silane-treated glass cloth (thickness: 0.1 tmm) was immersed in this varnish and dried by heating at 165°C for 3 minutes to obtain a prepreg. 15 prepregs and 35
A 6-layer wiring board prototype was created by heating and forming 6 sheets of μ copper foil at 170°C for 1 hour, and drilling was performed. Drill conditions are rotation speed 60000rpm, feed rate 3000mm/
Up to 12,000 holes were drilled with a hole diameter of 1.0φmm and two stacked sheets. Table 2 shows the 6-layer wiring board prototype test results.

[Table] As shown in Table 2, drill workability of #1 and #2 using silicone-modified epoxy resin is considerably improved compared to #3 using normal epoxy resin. Also, although Tg has increased slightly, barcol hardness has hardly changed. Therefore, there is little chance of drill breakage or drill wear when drilling small diameter holes. In addition, the flame retardance of all multilayer wiring boards is UL94V-O.
achieved.

Claims (1)

[Claims] 1 (a) Epoxy resin with a hydroxyl value of 0 to 0.08
(b) 40 to 80 parts by weight of tetrabromobisphenol A, (c) 0.1 to 20 parts by weight of a silicone intermediate having an alkoxy group equivalent of 150 to 300, and (d) 0.001 to 0.05 parts by weight of a catalyst. A method for producing a flame-retardant silicone-modified epoxy resin, which comprises heating the mixture to 120°C to 200°C and reacting in one step. 2. The method for producing a flame-retardant silicone-modified epoxy resin according to claim 1, wherein the catalyst is a quaternary ammonium salt.