JPH04163400A - Raw paper for laminated sheet - Google Patents

Abstract

PURPOSE:To efficiently obtain the inexpensive title raw paper having high dimensional stability and useful as a printed circuit board of household electric appliance by making a pulp obtained by subjecting a pulp slurry to compression treatment into paper. CONSTITUTION:A pulp slurry is dehydrated through a wire to form a sheet and the sheet is then subjected to compression treatment by roll press to afford a wet pulp having <=65% water content and as necessary further dried and the obtained pulp is blended with other pulp at a ratio of >=50% and the resultant pulp is made into paper to provide the raw paper. Furthermore, preferably density of sheet of the raw paper is 0.45-0.55 g/cm<2> and pulp having <=3% average rumen hole opening ratio is contained at a ratio of >=50%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a base paper for laminate boards, which has slightly excellent dimensional stability.

[Conventional technology]

Traditionally, laminates have been made by impregnating glass cloth with synthetic resin such as epoxy resin and hardening it by pressing, and by impregnating cotton linter paper with synthetic resin such as epoxy resin or phenolic resin and pressing it. There are hardened ones and paper (usually bleached kraft paper) impregnated with synthetic resin such as phenol resin and hardened by -C pressing. Among these, paper impregnated with phenolic resin and pressed and hardened is relatively inexpensive and has good performance, so it is widely used mainly in household electrical appliances.

When this paper phenol resin laminate is used as a printed wiring board, an electric circuit is formed by etching the copper foil bonded to the surface of the paper phenol resin laminate, and various electric parts such as ICs and condensers are attached to this. Then, mount the resistors, etc., and solder them to form the completed wiring board. BACKGROUND ART In recent years, electrical products have become more sophisticated and smaller, and the mounting density of ICs, connectors, resistors, etc. has increased, and the conductor patterns of wiring have become thinner.

For this reason, in addition to electrical properties such as insulation, the requirements for laminates to improve dimensional stability in the processing of printed wiring boards have become increasingly strict.

In order to improve the dimensional stability, improvements have been made to the resins used, molding conditions, etc., but it is thought that improving the dimensional stability of the laminated board base paper will also make a large contribution.

Various proposals have been made to improve the dimensional stability of this laminated board base paper. For example, a method of adjusting the fiber orientation in the wire part of a paper machine to make the vertical/horizontal tensile strength appropriate (Japanese Patent Laid-Open No. 176788/1988)
, or a method of maintaining the orientation angle within a specific range (Japanese Unexamined Patent Application Publication No. 59/1999)
-49959) is known. In addition, the pulp normally used as raw material for laminated board base paper is bleached kraft pulp, but the type of material also affects dimensional stability, and pulp with thick cell membranes,
It is said that so-called rigid fibers, such as those with a small fiber diameter and high elastic modulus, are good.

However, since pulp is exposed to environmental humidity and absorbs and desorbs moisture, there is a limit to its stability in usage.

In order to compensate for this drawback, a method of mixing paper with glass fiber that does not absorb or desorb moisture (JP-A-59-16653, JP-A-5-RI-12)
01855 Publication, Ina Kaishu No. 60-179244 Publication)
has also been proposed. Other methods include adding thermosetting resins such as melamine resins, epoxy resins, and phenol resins to crosslink or impregnate them (Japanese Patent Laid-Open No. 56-1 [16
No. 055, Japanese Unexamined Patent Publication No. 61-296037, No. 61-296199, 4.7j No. 63-2
11400) etc. have been proposed.

However, the mixing rate of glass fiber cannot be increased very much due to the high cost, and the addition or impregnation of resin has the problem of poor recovery of paper waste and reduced efficiency.

[Problem to be solved by the invention]

Many proposals have been made to improve the dimensional stability of laminated board base paper, but each has its advantages and disadvantages in terms of quality, productivity, and cost, and no satisfactory method has yet been found.

By using compressed pulp, the present invention achieves
The purpose of the present invention is to provide inexpensive, efficient, and highly dimensionally stable paper made from pulp obtained by pressing laminate board base paper.

[Means to solve the problem]

The present invention consists of: 1. Pulp slurry is dehydrated and sweetened to form a sheet through a wire, and then the sheet is compressed with a roll press to reduce the moisture content to 65% or less, or wet pulp, or further dried if necessary. 50% pulp as pulp
A base paper for laminated boards, characterized in that paper is made from the pulp blended above.

2. The density of the base paper sheet is 0.45-0.55g/C
m3 and containing 50% or more of pulp with an average lumen porosity of 3% or less.

It is.

The present invention is characterized in that it uses pulp that has been compressed using a roll press after forming a wet sheet on a wire.

Although the roll press treatment may be performed separately from the formation of the web 1-sheet, it is preferably performed in a paper pulp machine.

The roll-pressed pulp is preferably used in the form of wet pulp. This is because pulp that has been subjected to a drying process has poor bonding properties, which tends to deteriorate the strength and elastic properties of the paper.

The pulp used in the present invention may be obtained from any tree species. Further, the present invention can be applied to both bleached pulp and unbleached pulp.

The mesh of the wire used in the present invention when forming a sheet from the pulp slurry is not limited to the stiffness, but is 20 to 7
0 mesh is preferred. When the number of meshes is less than 20, the fiber content in the dewatered wastewater increases, contaminates the wastewater, and reduces the pulp yield. Also, for 70 meshes or more, wire 1.
Clogging occurs easily and dehydration performance decreases. The wire type may be any cylinder type, twin wire type, Fourdrinier type, etc.

There is no particular restriction on the basis weight of the sheet, but it is between 500 and 1500.
A range of g/m' is preferred.

The linear pressure of the roll press is 70 kg/cm as a normal pressure.
~250 kg/cm, but the higher the linear pressure, the better.
1. 100 kg/cm or more which yields fruits is preferred.

The number of stages of the roll press treatment process may be either one stage processing or multistage processing of two or more stages.

The type of roll may be any group roll (groove ("I roll)", double roll, plain roll, etc.).

Although the blending ratio of the pulp subjected to the roll press treatment is not limited, it is desirable to blend it in an amount of 50% or more.

When laminated board base paper is made using the pulp treated according to the present invention, remarkable characteristics appear in the morphology of the pulp fibers in the paper. The density of the laminated board base paper is 0.0 from the viewpoint of resin impregnation.
It is generally adjusted to 45 g/crn3 to 0.55 g 7 cm3, but when paper is made using normal pulp, within this density range, the lumen (lumen) of pulp fibers in the paper ), that is, the lumen porosity is 3.0% or more, whereas when pulp treated with the present invention is used, the lumen porosity is 3.0%.
It has the following characteristics.

The present inventors examined the relationship between the lumen porosity and the dimensional stability of the laminate base paper and the laminate, and found that the lumen porosity of the pulp fibers in the base paper should be 3.0% or less. It has been found that the dimensional stability of the laminate board base paper and the laminate board is significantly improved by this. This has a lumen porosity of 3
．． When it is less than 0%, the dimensional stability of the single fiber itself improves, and the significant difference in the fiber network structure formed during the papermaking stage causes t[I
It is determined.

Note that the lumen porosity is measured as follows.

First, a photo is taken of the spindle surface of the laminated board base paper that has been made into paper in a direction perpendicular to the flow direction of the paper machine. To create three sets of weight surfaces, the paper is embedded in resin so as not to damage the paper or fiber form during cutting, and then cut with a sharp razor or microtome. A scanning electron microscope is used to take the photographs, which requires a magnification of about 1000 times for measurement accuracy. The ratio of the lumen cross-sectional area to the cross-sectional area of the single fiber (including the lumen) was expressed as a percentage from the photograph of the assembled weight surface, and this was defined as the lumen aperture ratio. Although the lumen porosity varies depending on the fibers to be measured, it is necessary to average the lumen porosity of at least 2,000 fibers M:. In this way, the measured lumen porosity shows an extremely good correlation with the degree of pulp treatment and the dimensional stability of the laminate or laminate base paper.

Example-1 An unbeaten LBK suspension with a concentration of 1.5% was dehydrated using a wire cylinder (1-neem wire mesh; L25 mesh) to obtain LB with a water content of 72%.
KP sheet (1300g absolute dry weight in terms of solid content)
m') was obtained. This sheet is processed in 3 stages using a roll press (grooved rolls): 1 stage linear pressure of each roll is 1180 kg/cm, 2nd stage 160 kg/cm
, 3rd stage 130 kg/cm) and moisture content 5
A sheet of 0% LBKP is manufactured.

A laminate plate was made by a conventional method from the L 13 K P treated in this way, containing 70% and 100%.

The base paper treated in this way containing LB K l) 7 [1% has a pulp with a lumen opening ratio of 2.56%.
%, and the one used at 100% has a pulp content of 100% with a rumen opening [2] rate of 2.56%. 33 Comparative Example-1 Normal L [3] without the roll press treatment of Example 1
A base paper for a laminated board was made by a conventional method using KP. The lumen opening ratio of the pulp contained in this paper is 4.2
It was 8. Table 1 shows the measurement results of the submerged elongation of the base paper and the heat shrinkage rate of the laminate for each of the Hj-ξ papers of Example-1 and Comparative Example-1.

Table 1 (Note) Method for measuring heat shrinkage rate Two stages of phenol resin impregnation into base paper for laminated board, first stage water-based resin Showa Kobunshi Showa Kobunshi Showol BRL-2854 resin content 7%, second stage oil-based resin Showa Shonol BLS-3122 made of polymer (resin content 47%) is dried to create an impregnated paper called Prep 1 Lug. Eight sheets of the prepreg were laminated, heated with a hot press, pressed and cooled naturally at room temperature (temperature 165° C., pressure 100 kg/cm”, time 30 minutes) to produce a laminate.

The laminated plate (20cm x 20cm) formed in this way was heat treated (treated at 80℃ for 30 minutes, then further treated at 1?[]℃ for 15 minutes), and was heated in the vertical (T) direction and horizontal direction (
The length in the Y) direction is measured with a high-precision secondary coordinate measuring device (Digital Reader DI'l-550 manufactured by Dog [21 Screen Manufacturing Co., Ltd.)
) and calculated using the following formula.

QMeasurement method of elongation in liquid J, 'l' Yakumon No. 27 According to method 13 of test for elongation in water of paper and paperboard. (Methyl alcohol was used instead of water) Example-2 In Example-1, roll press treatment was performed at the linear pressure shown in Table 2.
A wet sheet was produced in the same manner as in Example 1 except that it was subjected to step treatment. Four types of pulp were extracted from the four types of wet sheets obtained.
Collect the seeds and use the usual method to obtain a weight of 130 g/m2 and a density of 0.5.
A hand-made paper of g/cm3 was prepared. (1st stage press linear pressure 35 kg/cm.

125kg/cm, 165kg/cm, 205
kg/cm) Comparative Example-2 A handmade paper similar to that of Example-2 was made using LBKP without O-rupress treatment. The elongation in liquid was measured for the handmade paper samples of Example 2 and Comparative Example 2. (Table 2) As shown in the measurement results, Example 2 is better than Comparative Example 2, with a higher pressing linear pressure and a smaller lumen aperture ratio.

Table 2 [Effects of the Invention] According to the present invention, an h'J laminate with high dimensional stability can be provided at a low cost.

Patent applicant: Oji Paper Co., Ltd.

Claims (2)

[Claims] 1. Wet pulp is obtained by dewatering the pulp slurry through a wire to form a sheet, and then compressing the sheet using a roll press to reduce the moisture content to 65% or less, or if necessary, drying the pulp further to form a sheet with a moisture content of 50% or more. A base paper for laminated boards that is made from a blended pulp. 2. The density of the base paper sheet is 0.45-0.55g/cm
A base paper for laminated boards, characterized in that it contains 50% or more of pulp with an average lumen porosity of 3% or less.