JPH06158582A - Base paper for resin impregnation and its production - Google Patents

Abstract

PURPOSE:To produce base paper exhibiting a high resin-penetrating speed and a low frequency of occurrence of paper brake in an impregnation process by mixing a specified synthetic resin with cellulose pulp, paper-making the resultant mixture and fusing it. CONSTITUTION:With (A) 100 pts.wt. cellulose pulp, (B) 5 to 50 pts.wt. fibrous or powdery synthetic resin having a chemical structure affinitive to an impregnation resin (a phenol resin, an epoxy resin, a polyester resin, etc.) is mixed and the resultant mixture is subjected to paper making. The component (B) is fused to the component (A) by heating the obtained sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device and a base paper of a resin-impregnated paper used as a base paper of a paper base laminate used for the electronic equipment or a cover of a book.

[0002]

2. Description of the Related Art Conventionally, in a paper base laminate for electronic equipment or electric equipment, a base paper is impregnated with a thermosetting resin such as a phenol resin or an epoxy resin, and the impregnated resin is heated to be semi-cured (prepreg) Then, a plurality of the prepregs are laminated together with a metal foil, and the laminate is heated and pressed to be molded.

The following characteristics are required for the resin impregnated base paper used for such a paper base laminate. 1) To increase the work efficiency of the impregnation process, the penetration speed of the resin solution into the holes in the base paper is fast. 2) A predetermined weight of resin can be retained inside the paper layer, and the problem that the resin remains on the surface of the paper layer and exhibits tackiness (surface adhesion trouble) does not occur. 3) There is little unevenness of resin impregnation. In recent years, high heat resistance and dimensional stability have also been demanded of paper-based laminates. Therefore, the impregnated resin has been subjected to modification treatment to improve its heat resistance, and has been widely used in the past. In addition to the existing phenolic resins, epoxy resins and polyester resins have come to be used. Such a solution of impregnating resin generally tends to have high viscosity. Therefore, there is an increasing need for resin-impregnated base paper that has a high penetration speed of the resin solution and does not cause surface adhesion trouble. In addition, resin-impregnated base paper used for the front cover of documents or other industrial base materials is also required to have various improvements in performance in the same manner as described above.

[0004]

In the conventional base paper for resin impregnation, particularly base paper for paper base laminates, hardwood pulp is often used without beating, but such base paper has a high viscosity. When a prepreg is produced by impregnating a curable resin solution, there arises a problem that the impregnation of the resin into the base paper becomes insufficient. Further, as a means for improving the impregnating property, it is considered that the density of the base paper is reduced and the porosity is increased. However, if the density of the base paper is reduced, the strength of the obtained base paper is lowered, and there is a possibility that troubles such as paper breakage may occur in the impregnation step. Therefore, there is an allowable limit for the decrease in the density of the base paper.

In order to solve such problems, the present invention speeds up the resin permeation rate in the resin impregnation step, increases the resin impregnation amount, and is unlikely to cause a paper breakage trouble in the resin impregnation step. An object of the present invention is to provide a base paper for resin impregnation and a method for producing the same.

[0006]

The present invention has been made as a result of various studies in order to achieve the above-mentioned object, and the outline thereof is as follows.

With respect to 100 parts by weight of cellulose pulp,
A sheet obtained by mixing 5 to 50 parts by weight of a fibrous or granular synthetic resin having a chemical structure compatible with the synthetic resin to be impregnated, the synthetic resin being fused to cellulose pulp. Characteristic resin impregnated base paper.

With respect to 100 parts by weight of cellulose pulp,
An aqueous slurry containing 5 to 50 parts by weight of a fibrous or granular synthetic resin having a chemical structure compatible with the synthetic resin to be impregnated is wet-processed to prepare a mixed sheet, which is then heated. A method for producing a base paper for resin impregnation, wherein the synthetic resin is heat-fused to cellulose pulp.

As the synthetic resin used in the above-mentioned mixed paper of the present invention, those having an affinity with the synthetic resin to be impregnated, for example, those having the same or similar chemical structure are selected and used. The synthetic resin is mixed with the cellulose pulp and then heated to heat-bond to the surface of the cellulose pulp to obtain the base paper of the present invention. As a result, the affinity with the impregnating resin liquid can be improved, the impregnation speed can be increased, the bonds between the celluloses can be strengthened, and the adhesive strength with the impregnated resin can be obtained.

The materials used in the present invention will be described below. Cellulose pulp is appropriately selected from bleached hardwood or softwood, unbleached pulp, bast fibers such as Manila hemp, seed fibers such as cotton linter, and artificial fibers such as viscose rayon. It may be selected according to the purpose of use, and its fiber length, freeness, etc. may be limited from the viewpoint of papermaking properties.
As a fibrous or granular synthetic resin mixed with cellulose pulp, a polyolefin resin, an acrylic resin, a vinyl resin, a polyamide resin, a polyester resin, or the like is used, but is limited to a thermoplastic resin. is not. In addition, the synthetic resin for the mixed paper and the synthetic resin to be impregnated later are chemically selected so that they are compatible with each other such as having the same or similar quality. When the synthetic resin is fibrous, a diameter of 5 to 10 μm and a fiber length of 2 to 5 mm are preferable, and when it is granular, particles or granules having a diameter of 5 to 50 μm are used.

The base paper of the present invention comprises cellulose pulp 10
The requirement is that the content of the fibrous or granular synthetic resin is 0 to 50 parts by weight with respect to 0 parts by weight. The reason is as shown in Table 1 when the amount is less than 5 parts by weight, as is clear from the castor oil permeation rate which is a measure of the impregnation rate of the resin, the permeation rate of the resin decreases and the effect of improving impregnability cannot be obtained. This is because the tensile strength and dimensional stability of the paper are reduced. On the other hand, if the amount exceeds 50 parts by weight, the resin impregnability, the tensile strength of the paper and the dimensional stability cannot be expected to have a great effect. Next, regarding the mixing ratio of the synthetic resin constituting the mixing sheet (however, the mixing ratio indicates the number of mixing parts per 100 parts by weight of cellulose pulp), the permeation rate of castor oil, the tensile strength (vertical length) of paper, and the dimensional stability. The characteristics are summarized in Table 1.

[0012]

[Table 1]

The permeation rate of castor oil was measured by adopting it as a scale for evaluating the permeation rate of the synthetic resin liquid during resin impregnation. The evaluation method cuts out 10 pieces of each 20 mm square test piece from the base paper under test, left the test piece horizontally on the castor oil surface at 20 ° C., and stopped the time until the castor oil uniformly permeated the upper surface of the test piece. Measure with a watch. Five samples were measured for each of the front and back sides of the base paper, and the average value of 10 points was taken as the penetration (second). The smaller the value, the higher the permeation rate. The tensile strength is based on JIS P 8113 and is intended to prevent paper breakage that occurs in the impregnation step. Generally, 4.5 Kg / 15 mm or more is required. For dimensional stability, the Fenchel elongation was used as a measure for determining the expansion and contraction behavior and the curl state of the impregnated paper.
In the evaluation method, a test piece having a width of 15 mm was cut out in the width direction of the base paper, both ends were set to a clamp with a grip gap of 100 mm, immersed in water at 20 ° C. for 60 minutes under a tension of 75 g / 15 mm, and its elongation was measured. did. The indicated value is an average value of 5 test pieces.

In the method for producing a base paper according to the present invention, first, cellulose pulp and fibers or particles of a synthetic resin having a compatibility with the resin to be pre-impregnated are mixed at a predetermined mixing ratio to prepare an aqueous slurry, which is prepared, for example. A mixed sheet is prepared with a multi-cylinder Fourdrinier paper machine and dried with a dryer. The thermal melting of the synthetic resin drawn into the paper layer may be performed in the latter stage of the drying section of the paper machine, or the mixed paper sheet may be wound once and then heated by the following melting means. May be. As the melting means, for example, an oil medium (oil heater) or a roll heater utilizing electromagnetic induction is generally used, but an electric or gas type infrared dryer utilizing radiant heat can also be used. The resin-impregnated base paper that has been subjected to the heat-melting treatment is rapidly cooled and wound up to become a resin-impregnated base paper. At that time, the mixed synthetic resin is melted by heat, deformed and contracted, so that the pore diameter and the void volume inside the paper layer are increased, and the impregnation rate and the impregnated amount of the synthetic resin liquid are improved. Also, the heat-melted synthetic resin plays the role of a hot-melt adhesive,
Combines pulp and cellulose pulp to improve paper strength remarkably. Therefore, the problem of paper breakage at the time of resin impregnation can be solved.

[0015]

【Example】

Example 1 An aqueous slurry obtained by uniformly mixing 20 parts by weight of polyethylene terephthalate fiber (fiber length 4 mm, diameter 8 μm) with 100 parts by weight of unbeaten bleached hardwood kraft pulp (hereinafter referred to as LBKP) was used in a fourdrinier cylinder type. Supply it to the paper machine,
A mixed paper sheet having a basis weight of 150 g / m ² and a density of 0.5 g / cm ³ was made into paper and wound as a roll. The mixed sheet is heat-treated with a hot oil medium in a multi-cylinder dryer having a surface temperature of 280 ° C. to melt the mixed polyethylene terephthalate fiber and fuse it to LBKP to obtain the resin impregnated base paper according to the present invention. Obtained.

Example 2 An aqueous slurry in which 100 parts by weight of unbeaten LBKP and 100 parts by weight of polymethacrylic acid fibers (fiber length 3 mm, diameter 7 μm) were uniformly mixed was obtained in the same manner as in Example 1 to obtain a base paper. However, the surface temperature of the mixed sheet was set to 300 ° C. with a hot oil medium.

COMPARATIVE EXAMPLE 1 The same LBKP 100% (without mixing polyethylene terephthalate fiber) as in Example 1 was used to fabricate a comparative resin impregnated base paper having a basis weight of 150 g / m ² and a density of 0.5 g / cm ³ . When the various properties of the base papers of the above Examples and Comparative Examples were measured and evaluated, the results shown in Table 2 were obtained.

[0018]

[Table 2]

The measuring method is the same as in Table 1 above. As is clear from the results in Table 2, it was confirmed that the resin-impregnated base paper according to the present invention has a high permeation rate of castor oil, which is a measure of the permeation rate of the impregnated resin liquid, and the tensile strength and the dimensional stability are also comparative examples. It was confirmed to be sufficiently superior in practical use as compared with.

[0020]

The base paper for resin impregnation according to the present invention has a high permeation rate of the resin solution for impregnation and retains sufficient tensile strength and dimensional stability necessary for resin impregnation. The working efficiency of can be greatly improved.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7199-3B D21H 3/32 Z

Claims (2)

[Claims] 1. A sheet obtained by mixing 5 to 50 parts by weight of a fibrous or granular synthetic resin having a chemical structure compatible with a synthetic resin to be impregnated with 100 parts by weight of cellulose pulp, A base paper for resin impregnation, wherein the synthetic resin is fused to cellulose pulp. 2. An aqueous slurry in which 5 to 50 parts by weight of a fibrous or granular synthetic resin having a chemical structure having an affinity for the synthetic resin to be impregnated is mixed with 100 parts by weight of cellulose pulp is wet-processed to be mixed and mixed. A method for producing a base paper for resin impregnation, which comprises producing a sheet, and then heating the mixed sheet to heat-seal the synthetic resin to the cellulose pulp.