JPH0113422B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a flame-resistant epoxy resin laminate having excellent heat resistance, measling resistance, and solvent resistance. Epoxy resin laminates have recently been used in space equipment, large to small computers, microcomputers,
Demand for industrial equipment such as wireless application equipment, industrial measurement equipment, and medical equipment is increasing, and these applications all require high performance. Conventionally, dicyandiamide has been used in large amounts as a curing agent for epoxy resins for laminates because it is inexpensive, has good storage stability for prepregs, and is easy to accelerate curing with a catalyst. However, in systems where dicyandiamide is used as a curing agent for epoxy resins, especially brominated epoxy resins that impart flame retardancy, brown spots tend to occur on copper-clad laminates and the compatibility with the resin is poor, so prepreg production is difficult. Occasionally, precipitation of dicyandiamide may occur. In either case, good results cannot be obtained in terms of laminate properties. As described above, in systems using dicyandiamide, the reaction tends to be uneven, and low molecular weight components are left behind from the reaction, resulting in insufficient solvent resistance.
Particularly, when immersed in methylene chloride, a part of the resin on the surface of the base material is extracted, resulting in a significant decrease in reliability as a substrate. If the reaction is extremely uneven, check the soldering heat resistance and measling resistance (measling is a phenomenon in which the texture of the glass cloth appears white during soldering due to moisture absorption, etc.)
also decreases. In order to eliminate the above-mentioned conventional drawbacks, the present inventors investigated the suitability of various compounds as curing agents, and found that when a specific brominated phenol novolak resin was used in an epoxy resin, it had excellent properties. It has been discovered that a flame-retardant laminate having the following properties can be obtained. The present invention was made based on this knowledge, and the following general formula is added to the epoxy resin. [However, average degree of polymerization (degree of polymerization = n+1) 3 to 15,
A brominated phenol novolac resin with a free monomer content of 1.5% by weight or less] is used, and the equivalent ratio of the phenolic hydroxyl group of the brominated phenol novolac resin to the epoxy group of the epoxy resin is 0.6 to 1.2.
The resulting epoxy resin composition is impregnated into a base material to form a prepreg, and a plurality of the prepregs are laminated or a copper foil is further layered on the surface of the laminated prepreg, and the resultant epoxy resin composition is heated under pressure and molded into one piece. This is a method for producing a flame-retardant laminate, characterized by: As the epoxy resin in the present invention, any epoxy resin having two or more epoxy groups per molecule can be used. Examples of such epoxy resins include glycidyl-based epoxy resins such as glycidyl ether of bisphenol A, glycidyl ether of halogenated bisphenol A, and glycidyl ether of novolac, non-glycidyl-based epoxy resins such as epoxidized polyolefin, and epoxidized soybean oil. Epoxy resins are available and can be used alone or in combination. The brominated phenol novolac resin in the present invention is a resin represented by the above general formula, and is obtained by condensing monobromophenol with formalin using an acidic catalyst or by adding bromine to a phenolic resin intermediate condensate and dehydrating it. You can get it by twisting it. The degree of polymerization, amount of free monomer, and blending amount of the brominated phenol novolak resin in the present invention are limited for the following reasons. First, the average degree of polymerization (degree of polymerization = n+1) is 3 to 15.
The reason for this range is that if it exceeds 15, the impregnation into the base material will be poor, and if it is less than 3, the soldering heat resistance, measling resistance, and solvent resistance of the cured product will deteriorate. In addition, the reason why the amount of free monomer is 1.5% by weight or less is that when the free monomer reacts with the epoxy group, the crosslinking reaction stops there because there is only one functional group, which also improves soldering heat resistance and measling resistance. This is because the solvent resistance decreases. Note that, in order to obtain a laminate particularly excellent in the above-mentioned properties, the amount of free monomer is preferably 0.5% by weight or less. The average degree of polymerization and the amount of free monomer were measured by gel permeation chromatography. Next, the amount of the brominated phenol novolak resin to be blended with the epoxy resin must be such that the phenolic hydroxyl groups of the brominated phenol novolak resin are 0.6 to 1.2 equivalents to the epoxy groups of the epoxy resin. If it exceeds 1.2 equivalents, the brominated phenol novolac resin will remain unreacted, while if it is less than 0.6 equivalents, the epoxy resin will remain unreacted, which will adversely affect soldering heat resistance, measling resistance, and solvent resistance. Deteriorate. The epoxy groups were determined by the hydrochloric acid dioxane method, and the amount of phenolic hydroxyl groups was determined from the above average degree of polymerization. A curing accelerator can be used in combination with the epoxy resin composition used in the present invention, if necessary.
Examples of such curing accelerators include tertiary amines such as benzyldimethylamine and triethylamine, imidazoles such as 2-methylimidazole and 2-ethylimidazole, and their cyanoethylated products, azine adducts, and imidazolines. Additionally, known additives such as diluents, fillers, pigments, flame retardants, and flame retardant aids may be added as appropriate. The laminate or copper-clad laminate in the present invention is a laminate obtained by laminating a required number of prepregs obtained by impregnating and drying a base material such as glass cloth with the above-mentioned epoxy resin composition, or one or both sides of a laminated prepreg. It is obtained by stacking copper foil on top of the copper foil, heating it under pressure, and molding it into one piece. According to the present invention, the brominated phenol novolak resin as a curing agent has good compatibility with the epoxy resin and does not cause precipitation during prepreg processing, and does not produce brown spots when made into a copper-clad laminate. A flame-resistant laminate having excellent heat resistance, measling resistance, and solvent resistance can be obtained by adjusting the average degree of polymerization, amount of free monomer, and blending amount of the brominated phenol novolak resin. Next, an example will be described. Parts and % below mean parts by weight and % by weight, respectively. Example 1 Brominated bisphenol A type epoxy resin DER
-511 (manufactured by Dow Chemical Company: Epoxy equivalent: 490~
530) Brominated phenol novolak resin with an average degree of polymerization of 5.5 and 0.3% free brominated phenol in 100 parts
35 parts so that the equivalent weight of phenolic hydroxyl group to epoxy group is 0.95, and 2-
A varnish was prepared by adding 0.1 part of ethyl-4-methylimidazole and acetone to prepare an epoxy resin composition. This varnish was impregnated and coated on a 0.18 mm thick glass cloth treated with epoxy silane, and dried so that the gelation time of the resin in the prepreg at 155°C was 150 seconds to obtain a prepreg with a resin content of 40.5%. Ta.
Eight sheets of this prepreg were laminated with 35 μm thick copper foil on both sides and molded at 170° C. for 60 minutes under heat and pressure of 40 kg/cm ² to obtain a copper clad laminate with a thickness of 1.6 mm. Example 2 Brominated bisphenol A type epoxy resin DER
-511 (listed above) 80 parts, highly brominated epoxy resin YDB
-400 (manufactured by Toto Kasei Co., Ltd.: epoxy equivalent 390-410) 10
Part, Phenol Novolac Epoxy Resin DEN-
438 (manufactured by Dow Chemical Company: epoxy equivalent: 176-181)
To 10 parts, 40 parts of the same brominated phenol novolak resin as in Example 1 was blended so that the equivalent weight of phenolic hydroxyl group to epoxy group was 0.9,
Add to this 0.15 2-ethyl-4-methylimidazole
A varnish was prepared by adding acetone and acetone to prepare an epoxy resin composition. A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Comparative Example 1 100 parts of DER-511 (mentioned above) and dicyandiamide
A varnish was prepared by blending 3.5 parts of dicyandiamide with 0.1 part of 2-ethyl-4-methylimidazole, 15 parts of dimethylformamide to facilitate dissolution of dicyandiamide, and acetone. A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Comparative example 2 DER-500 (above) 80 copies, YDB-400 (above) 10 copies
3.5 parts of dicyandiamide were mixed with 10 parts of DEN-438 (listed above), and to this were added 0.1 part of 2-ethyl-4-methylimidazole, 15 parts of dimethylformamide to facilitate the dissolution of dicyandiamide, and acetone. A varnish was prepared. A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Comparative Example 3 The same brominated phenolic novolac resin as in Example 1 was added to 100 parts of DER-511 (mentioned above) so that the equivalent weight of phenolic hydroxyl group to epoxy group was 0.5.
A varnish was prepared by adding 0.1 part of 2-ethyl-4-methylimidazole and acetone to the mixture. A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Comparative Example 4 43 parts of brominated phenol novolac resin (average degree of polymerization 5.5) with a free brominated phenol content of 3% was mixed with 80 parts of DER-511 (described above) and YDB-400 (described above).
The equivalent of phenolic hydroxyl group to epoxy group is 0.95.
A varnish was prepared by adding 0.1 part of 2-ethyl-4-methylimidazole and acetone. A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Comparative Example 5 35 parts of brominated phenol novolac resin (0.4 parts of free brominated phenol) having an average degree of polymerization of 20,
A varnish was prepared by blending it with 100 parts of DER-511 (mentioned above) so that the equivalent weight of phenolic hydroxyl group to epoxy group was 0.95, and adding 0.1 part of 2-ethyl-4-methylimidazole and acetone thereto. . A copper-clad laminate was obtained using this varnish in the same manner as in Example 1. Table 1 shows the characteristics of the copper-clad laminates obtained in Examples 1, 2, and Comparative Examples 1 to 5, along with the resin composition.
show.

[Table] As shown in Table 1, the flame-resistant laminate according to the present invention is free from curing agent precipitation and brown spots, and has excellent heat resistance, measling resistance, and solvent resistance. I understand.

Claims (1)

[Claims] 1 The epoxy resin has the following general formula: [However, average degree of polymerization (degree of polymerization = n+1) 3 to 15,
A brominated phenol novolac resin having a free monomer content of 1.5% by weight or less] is blended in such a manner that the equivalent weight of the phenolic hydroxyl group of the brominated phenol novolac resin to the epoxy group of the epoxy resin is 0.6 to 1.2. A flame retardant method characterized by impregnating a base material with an epoxy resin composition to form a prepreg, laminating a plurality of the prepregs, or further layering a copper foil on the surface of the laminated prepreg, and pressurizing and heating to form an integral piece. Method of manufacturing laminates.