JPS6119640A - Preparation of heat-resistant laminate - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant laminate at a low cost, by impregnating a fibrous substance with a composition containing an epoxy resin, bisphenol, a novolak resin, and a curing agent, which is heated to give a semi-cured prepreg, followed by hot-pressing the prepreg. CONSTITUTION:An epoxy resin (A), bisphenol or a dihydric phenol (B) (e.g. bisphenol A), a novolak resin (C) (e.g. a phenol novolak resin), and an epoxy- curing agent of heat-curing type (D) (e.g. dicyandiamide), with components B and C being in amounts to give 0.5-0.95 phenolic hydroxyl group per epoxy group of component A, are mixed. A fibrous substance (e.g. a glass cloth) is impregnated with this composition, which is heated to give a semi-cured prepreg. Then a required number of the prepreg sheets are laid and hot-pressed to give an objective heat-resistant laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an epoxy resin-based laminate, and more particularly, to an economical method for producing an epoxy resin-based heat-resistant laminate that has excellent physical properties.

Laminated boards using epoxy resin have excellent physical properties such as electrical properties and mechanical properties, so they are widely used as printed wiring boards and electronic component mounting boards. With the miniaturization and higher density of electronics, the multilayering of printed wiring, etc., it has become necessary to further improve dimensional accuracy.In other words, during processing such as soldering, drilling, resist processing, etc., and during use, Thermal dimensional stability is primarily required.

In order to meet this requirement, a multifunctional heat-resistant epoxy resin such as a novolac type epoxy resin is used in combination with a relatively high molecular weight epoxy resin that is solid at room temperature (hereinafter referred to as base resin), which is conventionally used for lamination. Efforts have been made to improve dimensional stability by increasing crosslinking density and increasing heat resistance. For example, <77Ay'2.7 and 1 poxy equivalent 400 g/eq to 1000 g/eq
This method uses about 5 to 30% orthocresol type epoxy resin in combination with bisphenol A type or tetrabromobisphenol A type solid resin, but since the two resins have different reactivity with the epoxy resin curing agent, it is difficult to react uniformly. There were disadvantages in that it was difficult to obtain optimal cured physical properties, and expensive multifunctional heat-resistant resins had to be used.

The present inventors conducted extensive research to find a method for manufacturing a laminate that does not have the above-mentioned drawbacks and has excellent physical properties such as heat resistance and economical efficiency. A novolak resin is used instead of a compound and a novolac type epoxy resin, and the epoxy group and phenolic hydroxyl group (including the phenolic hydroxyl group in the novolac resin) are reacted during the laminate manufacturing process, and the remaining epoxy group is removed using an epoxy curing agent. It was discovered that a heat-resistant laminate can be obtained industrially advantageously by curing, and the present invention was completed.

That is, the present invention uses epoxy resin (a), bisphenol or dihydric phenol (b), and novolac resin (c).
A method for producing a heat-resistant laminate, which comprises impregnating a fibrous material with a composition containing a heat-curable epoxy curing agent (d) as an essential component, heating the prepreg to a semi-cured state, and heating-pressing the prepreg. I will provide a.

First of all, the method of the present invention is characterized by the fact that unlike conventional methods, the curing reaction proceeds uniformly, resulting in excellent cured physical properties, instead of using a resin mixture of base resin and multifunctional heat-resistant epoxy resin that have different reactivities. It lies in being able to do things. Second, a cheaper novolak resin can be used instead of an expensive multifunctional heat-resistant epoxy resin.

Furthermore, in a mixture of base resin and the same amount of epoxy resin and a compound having two phenolic hydroxyl groups, if a low molecular weight epoxy resin is used, the former base resin is usually more expensive; There is also the advantage that cheaper latter mixtures can be used instead. Another feature is that because a low molecular weight component can be used in place of a relatively high molecular weight base resin, the viscosity of the composition can be lowered and impregnability can be improved. Alternatively, if the viscosity is the same as that of the conventional method, the amount of solvent used can be greatly reduced, resulting in various advantages such as saving resources, saving energy, and improving the working environment. According to the method of the present invention, in addition to the various industrial advantages mentioned above, a laminate can be obtained which has various physical properties such as heat resistance, water resistance, strength, and adhesion to copper foil etc., which are superior to conventional methods.

In the present invention, as the epoxy resin (a), various conventionally known epoxy resins having two or more epoxy groups in the molecule are used alone or in mixtures. A typical example is bisphenol A, which is shown by the following structural formula.
Examples include molded epoxy resin.

In the present invention, among these epoxy resins, low molecular weight epoxy resins that are liquid at room temperature are preferred (for example, Sumie Epoxy ELA-128 manufactured by Sumitomo Chemical Co., Ltd.).

The bisphenol or dihydric phenol (b) used in the present invention has two phenolic hydroxyl groups in its molecule, and includes bisphenol A1 bisphenol F1 bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl) ) Ether, resorcinol, hydroquinone, catechol, or halogen-substituted, especially bromine-substituted products of these are exemplified, and one or two of these are exemplified.
More than one species is used. It is practical to use tetrabromobisphenol A for laminates that require flame retardancy, and to use bisphenol VIII for laminates that do not.

For example, phenol novolak, orthocresol novolak, meta-cresol novolank, para-cresol novolank, alkylphenol novolak, resorcinol novolank, etc. Among these, phenol novolak and orthocresol novolak are condensates of aldehydes. Novolac is practically preferred. The amount of bisphenol or dihydric phenol (b) and novolac resin (c) added to the epoxy resin (a) is such that the amount of phenolic hydroxyl group per epoxy group is 0.
The number of phenolic hydroxyl groups in the novolac resin (c) is 0.6 to 0.95.
Preferably less than 1. When the number of phenolic hydroxyl groups is less than 0.5, the resulting cured product is hard and brittle, and lacks adhesion.On the other hand, when the number exceeds 0.95, the stability of the epoxy resin composition decreases, Undesirable.

The heat-curable epoxy curing agent used in the present invention is one that hardly reacts with the epoxy resin at a temperature around room temperature, but reacts quickly when heated, and includes, for example, dicyandiamide, diaminodiphenylmethane, phenylene diamine, and diaminodiphenyl sulfone. , imidazoles, etc., and dicyandiamide is preferred from a practical standpoint. A curing accelerator can also be used in combination with these curing agents.

Furthermore, in order to promote the addition reaction between the epoxy group and the phenolic hydroxyl group, amines such as benzyldimethylamine, imidazoles, phosphorus compounds such as triphenylphosphine, lithium compounds such as lithium chloride, and other catalysts may be used. I can do it.

In the present invention, if an epoxy resin that is liquid at room temperature is used as the epoxy resin (a), impregnation is possible even without a solvent, but it is usually preferable to use a solvent, and the solvent is one that uniformly dissolves each component. For example, alcohols such as ethylene glycol monomethyl ether, methanol, and ethanol, dimethylformamide, and these together with ketones such as acetone and methyl ethyl ketone,
A mixed solvent with an aromatic compound such as toluene and xylene is exemplified.

In addition to these components, fillers, reactive diluents, plasticizers, flame retardants, pigments, etc. can be used as necessary.

When mixing the above components, epoxy resin (a),
Although bisphenol or dihydric phenol (b) and novolac resin (c) and other components as necessary may be mixed in advance and heated and aged, the remaining components may be added, but it is more preferable to mix them all at once.

The composition thus obtained is impregnated into a fibrous material such as paper or glass cloth according to a conventional method, heated to obtain a semi-cured prepreg, and this prepreg is heated and pressed according to a conventional method. A laminate can be obtained.

The present invention will be explained below using examples. However, "Example Middle" indicates parts by weight.

Reference example 1 Sumiepoxy ELA-128 (bisphenol A type liquid epoxy resin manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent weight 187 g/e
q) 53.2 parts, tetrabromobisphenol A 3
3.1 parts, 13.7 parts of novolak resin (orthocresol-formaldehyde condensate, softening point 105"C) were dissolved in 7.5 parts of methyl ethyl ketone, 7.5 parts of acetone, and 25 parts of methyl cellosolve, and 1 part of dicyandiamide,
0.3 parts of 2-ethyl-4-methylimidazole was added and uniformly dissolved to form an epoxy resin composition (No.

1) was obtained.

Reference Example 2 The bromine content and novolak skeleton content in the resin are the same as Reference Example 1.
As a composition equivalent to Sumiepoxy ESB-700
(Brominated bisphenol A type solid resin manufactured by Suminen Chemical, epoxy equivalent 690 g/eq, bromine content 25%) 80 parts, Sumiepoxy ESCN-220L (Orthocresol novolac type epoxy resin manufactured by Suminen Chemical, epoxy equivalent 21
．． 8 g/eq, softening point 70°C), 25 parts of methyl ethyl ketone, 20 parts of acetone, 4 parts of methyl cellosolve
0 parts, 3.9 parts of dicyandiamide and 0.3 parts of 2-ethyl-4-methylimidazole were added, and the viscosity was 5 parts.
An epoxy resin composition (No. 2) of 6 cP/20° C. was obtained. Example 1 Glass cloth (KS-1600 plain weave manufactured by Kanebo Glass Fiber ■) was impregnated with the composition (No. 1) obtained in Reference Example 1, and after air-drying, prepreg was prepared by heating in an oven at 13 parts Celsius for 13 minutes. I got it.

100kg/cJ2 by pressing 6 layers of prepreg at 160℃
It was molded in 0 minutes and further post-cured in an oven at 160° C. for 70 minutes to obtain a laminate. Also, copper foil (manufactured by Furukawa Electric, thickness 3
A copper-clad laminate was obtained under the same conditions from 6 layers of prepreg (5 μm) and 6 layers of prepreg. These obtained laminates were tested according to JIS-C-6'48
Table 1 shows the physical properties measured according to 1.

Comparative Example 1 Example 1 was prepared using the prepreg obtained by impregnating glass cloth (KS-1600) with the composition (No. 2) obtained in Reference Example 2, air-drying it, and then heating it in a 130°C oven for 4 minutes. A laminate and a copper-clad laminate were obtained in the same manner as above.Table 1 shows the physical properties of these laminates.

As shown in the table and Reference Example 1.2, the method for producing a laminate obtained by the present invention can reduce the amount of solvent used, and the obtained laminate has better heat resistance, strength, adhesion, and other properties than the conventional method. It can be seen that both have excellent physical properties.

Table 1 Reference Example 3 Sumiepoxy ELA-12866, 1 part, Bisphenol A2'0.3 part, Novolac resin (orthocresol formaldehyde condensate, softening point 105°C) 13.6
20 parts of methyl ethyl ketone, 25 parts of methyl cellosolve
1.3 parts of dicyandiamide and 0.5 parts of 2-phenyl-4-methylimidazole were added and uniformly dissolved to give an epoxy resin composition (N
o, 3) was obtained.

Reference Example 4 As a composition in which the novolac skeleton content in the resin is equivalent to that of Reference Example 3, Sumiepoxy ESA-01) (Bisphenol A type solid resin manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent weight 480 g/e
q) 80 parts, Sumiepoxy ESCN-195X'L (
Sol novolac type epoxy resin manufactured by Sumitomo Chemical, epoxy equivalent 199g/eQ, softening point 73°C)2
0 parts to 33 parts of methyl ethyl ketone, 4 parts of methyl cellosolve
4 parts of dicyandiamide and 0.5 parts of 2-phenyl-4-methylimidazole were added, and the viscosity was 6.
An epoxy resin composition (No. 4) having a temperature of 1 cP/20° C. was obtained.

Example 2 Example 1 using the composition (No. 3) obtained in Reference Example 3
A laminate and a copper-clad laminate were obtained in the same manner as above. Table 2 shows the physical properties of these laminates obtained.

Comparative Example 2 Comparative Example 1 using the composition (NO, 4) obtained in Reference Example 4
A laminate and a copper-clad laminate were obtained in the same manner as above. Table 24 shows the physical properties of these laminates obtained.

As shown in Table 2 and Reference Example 3.4, even in flame-retardant formulations, the amount of solvent used can be reduced and excellent physical properties can be obtained.

Table 2

Claims (8)

[Claims] (1) A fibrous material is impregnated with a composition containing epoxy resin (a), bisphenol or dihydric phenol (b), novolak resin (c), and heat-curable epoxy curing agent (d), and then heated. A method for producing a heat-resistant laminate, characterized by stacking semi-cured prepregs and pressing them under heat. (2) For one epoxy group of epoxy resin (a),
The method for producing a heat-resistant laminate according to claim 1, in which bisphenol or dihydric phenol (b) and novolak resin (c) are used so that the number of phenolic hydroxyl groups is in the range of 0.5 to 0.95. (3) The method for producing a heat-resistant laminate according to claims 1 and 2, in which a bisphenol A epoxy resin is used as the epoxy resin (a). (4) The method for producing a heat-resistant laminate according to claims 1 to 3, in which bisphenol A is used as the bisphenol or dihydric phenol (b). (5) The method for producing a heat-resistant laminate according to claims 1 to 3, in which tetrabromobisphenol A is used as the bisphenol or dihydric phenol (b). (6) The method for producing a heat-resistant laminate according to claims 1 to 5, in which phenol novolac is used as the novolac resin (c). (7) The method for producing a heat-resistant laminate according to claims 1 to 5, using an orthocresol novolac resin as the novolac resin (c). (8) The method for producing a heat-resistant laminate according to claims 1 to 7, using dicyandiamide as the heat-curable epoxy curing agent (d).