JPH03269023A - Production of prepreg - Google Patents

Abstract

PURPOSE:To obtain a prepreg having good varnish-impregnating property, defoaming and forming property by coating and impregnating a substrate with resin varnishes in the order of resin varnish having slower curing rate when resin varnishes having different curing rates are used. CONSTITUTION:When a substrate is coated and impregnated with plural kinds of resin varnishes having different curing rate, a substrate is successively coated and impregnated with a resin vanish in the order of resin varnish having slower curing rate to provide the aimed prepreg. Furthermore, the blend ratio of resin varnish having slow curing rate and resin varnish having quick curing rate is preferably 0.6-0.95.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method for obtaining a prepreg with good moldability during hot-press molding by applying and impregnating a varnish on a base material for a laminate multiple times. It is related to.

(Prior Art) Conventionally, when manufacturing a prepreg, a method of improving varnish impregnation into a base material is to apply varnish multiple times.

In this case, for example, (1) the same varnish is used multiple times, (2) a varnish with a low resin content is applied first, (
There are methods such as 3) applying a low viscosity resin first, and (4) applying in advance an organic solvent that can easily replace the varnish.

These methods improve the impregnating properties of the base material, but the above (
In the cases of 1), (2), and (3), the initial coating or varnish resin hardens or increases in viscosity during drying, making it difficult to remove air from the prepreg during hot-pressure molding. There has not been a sufficient method for manufacturing laminates with good formability. When the organic solvent (4) is applied in advance, the next varnish impregnation is performed without drying, which has the disadvantage that it is difficult to control the resin content in the prepreg.

(Problems to be Solved by the Invention) Therefore, the present invention aims to improve the impregnation of varnish into a base material when obtaining a prepreg, and to produce a laminate with good moldability and easy degassing from the prepreg during molding. The present invention provides a method.

(Means for Solving the Problems) The present invention provides a prepreg characterized in that when applying and impregnating a base material with multiple types of resin varnishes having different curing speeds, the resin varnishes having a slow curing speed are applied and impregnated in order. This is a manufacturing method.

The resin varnish used in the present invention is one normally used for laminated boards, and includes epoxy resin,
These include polyimide resin, phenol resin, polyester resin, etc.

In the case of epoxy resins, curing agents such as amines, acid anhydrides, and novolac resins are used, and a curing catalyst is usually added, and if necessary, flame retardants, fillers, etc. are added.

In the case of other resins, curing catalysts, flame retardants, fillers, etc. are added as necessary. In order to obtain resin varnishes with different curing speeds, for example, in the case of epoxy resins, it is necessary to use a slow-curing resin as the varnish used for the initial impregnation, or to replace part of the usual resin with a slow-curing one. There is also a method using Luna, and the same applies to hardening agents. Furthermore, there are methods such as reducing the amount of curing catalyst.

In the present invention, it is most preferable to reduce the amount of curing catalyst in consideration of ease of implementation and ease of understanding the properties of the obtained laminate.

The ratio of the amount of curing catalyst in a varnish with a slow curing speed (ratio to resin) and the amount of curing catalyst in a varnish with a fast curing speed is 0.
6 to 0.95 is preferred. If this ratio is smaller than 0.6, the curing during molding will be delayed and the heat resistance of the laminate will tend to decrease, while if it is larger than 0.95, the varnish in the primary impregnation of the prepreg will harden too much during drying. , the moldability during molding becomes poor.

In the case of other resins, a slowly curing resin varnish is used as the varnish used for the initial impregnation.

(Function) The resin-impregnated prepreg is dried using a dryer, or an ordinary dryer uses radiant heat and hot air to dry at the same time, which is efficient.

In this case, depending on the radiant heat, the resin of the prepreg is cured from the vicinity of the monofilament of the base material to the surface layer, and depending on the hot air, the resin of the prepreg is cured from the surface layer of the prepreg to the vicinity of the monofilament of the base material. Therefore, compared to the previous dryer that only used hot air drying, it may be more efficient.The prepreg resin has more advanced curing around the base filament, so it is difficult for air bubbles to escape in the prepreg during the forming process. It has the disadvantage of being prone to defects.

In order to solve this problem, a treatment may be performed to slow down the curing around the base filament, but conventionally, such a treatment method is difficult to implement industrially. Therefore, methods such as lowering the degree of curing of the prepreg as a whole or slowing down the temperature rise during molding have been implemented, but there have been problems with the accuracy of the thickness of the laminate and press efficiency.

In the case of the present invention, the base material is impregnated with a resin varnish that has a slow curing speed, is dried (to the extent that the solvent is removed if necessary), and is then impregnated with a resin varnish that has a faster curing speed, so that the resin is not cured very much. It penetrates into the inside of the base material, that is, into the minute gaps between the fibers of the base material. Then, it is efficiently dried by a dryer.

Air bubbles tend to remain in the prepreg near the center layer, especially in the gaps between the monofilaments, among the prepregs that are usually formed and laminated. In the present invention, since the resin is well impregnated in this part and the resin has excellent fluidity, it is possible to prevent bubbles from remaining without excessive resin flowing out from the end of the laminate. Therefore, the thickness accuracy of the laminate is also excellent.

(Example) Hereinafter, an example will be shown in which a glass cloth is impregnated twice with epoxy resin varnish. The formulation of the resin varnish for secondary impregnation is as follows.

100 parts of epoxy resin (
Bisphenol A type, epoxy equivalent: 750) Dianediamide 1.4 parts 2-ethyl 4-methylimidazole (catalyst) 0.1 part Solvent
100 part 1
The formulation of the resin varnish to be subsequently impregnated is such that the amount of 2ethylene 4-methylimidazole, which is a curing catalyst, is changed from the formulation of the secondary impregnated varnish. The amount of catalyst is shown in Table 1.

Got preg. Next, a second impregnation was carried out and drying was carried out in the same manner to obtain a prepreg with a resin content of 42% and a gel time (170° C.) of about 60 seconds. However, in Comparative Example 2, since the primary varnish impregnation was not performed, only the secondary impregnation was performed and the resin content was adjusted to be equal to that of the other examples.

On each side, stack the 8 sheets of prepreg obtained,
A laminate with a thickness of 1.60 was obtained by heating and pressing at 170° C. and 140 kg/a (120 minutes).

In the above manufacturing process, the moldability, glass transition point of the laminate, and plate thickness accuracy were measured, and the results shown in Table 2 were obtained.

A glass cloth was impregnated with the primary varnish and dried in a hot air radiation dryer at 1.70°C for 1.5 minutes to form a yellowtail with a resin content of 25%.
Surface measurement results (measurement method) Formability: The appearance of the laminate was observed.

Glass transition point: Determined from viscoelastic spectrum.

Plate thickness accuracy: The base material thickness was measured at a total of 9 points by dividing the 10111111 point and the center point into 8 equal parts by the lateral base material edge, and the thickness accuracy was determined using the following formula.

(Effects of the Invention) As is clear from the above results, the laminate obtained using the prepreg according to the present invention has good formability, and is therefore superior to the case of ordinary one-time impregnation. It is suitable as a circuit board that requires high performance such as O-7) and -7 Finbatan.

Claims (3)

[Claims] (1) A prepreg manufacturing method characterized in that when applying and impregnating a base material with two or more resin varnishes having different curing speeds, the resin varnishes having a slow curing speed are coated and impregnated in order. (2) The prepreg manufacturing method according to claim 1, wherein the difference in curing speed of the resin varnish is due to a difference in the amount of curing catalyst. (3) The ratio of the curing catalyst compounding ratio (relative to the resin) of the slow curing speed resin varnish and the fast curing speed resin varnish is 0.6 to 0.
95. The method for manufacturing a prepreg according to claim 2.