JPH03899A - Production of base paper for laminated board - Google Patents

Abstract

PURPOSE:To obtain the subject base paper suitable as base paper for bakelite boards used in printed circuit boards, etc., by specifying beating degree, density of wet sheets and the density after drying and forming sheets using the resultant hardwood bleached kraft pulp as a raw material. CONSTITUTION:Hardwood bleached kraft pulp having >=530cc beating degree is pressed with a wet press to form wet sheets having 0.35-0.45g/cm<3> density, which are then dried by heating in a dryer and calendered to afford the objective base paper having 0.45-0.55g/cm<3> density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to printed wiring boards used in electronic equipment such as computers, home appliances such as televisions and radios, and various measuring instruments, boards in switch boxes such as power supplies, and power distribution boards. The present invention relates to a method for manufacturing laminate base paper, which is a raw material for laminates used for substrates (these substrates are generally called Bakelite plates).

Conventionally, the raw material for laminated board base paper has mainly been hardwood kraft pulp (hereinafter referred to as P in LB), which is prepared by cooking and bleaching hardwood chips. LB and P indicate that the paper is made in an unbeaten or slightly beaten state in order to impregnate the resin in the laminate manufacturing process, prevent warpage of the laminate after processing, and improve dimensional stability. is desirable.

Freeness is Canadian Standard Freeness 530.
It is preferably cc or more, more preferably 560 cc or more.

In the process of making base paper, it is necessary to make a base paper with low density in order to improve impregnation properties.

In order to achieve a low density, the linear pressure of the paper machine's wet paper press is reduced, but if it is reduced too much, it weakens the fiber bonding force in the wet paper, resulting in a decrease in the strength of the base paper, fuzzing of the surface, and breakage. Not only is paper produced, but the amount of steam consumed in the drying process increases.

Appropriately controlling the linear pressure of the wet press is an important operating condition when manufacturing laminated board base paper. control has been in place.

At this time, the linear pressure of the calender normally disposed after the drying process is operated at an extremely low level of about 2 kg/cm 2 , thereby making it possible to set a wide control range of the linear pressure of the wet press.

However, if the density is adjusted only by wet pressing and the calender linear pressure is extremely reduced, the surface smoothness of the laminated base paper will decrease and the difference in density between the surface layer and the inner layer will increase.

In other words, the density of the surface layer is small and the density of the inner layer is high, so when such a base paper is impregnated with resin, the impregnation rate in the inner layer becomes slow, and the impregnation I becomes uneven between the inner and outer layers. The amount of impregnation will also be insufficient.

The present invention improves the above-mentioned drawbacks and provides a method for producing a base paper for laminated board, which has a uniform density distribution in the thickness direction of the paper layer, excellent resin impregnation properties, and improved resin impregnation speed.

The above-mentioned excellent base paper for laminated boards uses bleached hardwood kraft pulp with a freeness (Canadian Standard Freeness) of 530 cc or more, and pressurizes it with a wet press of a paper machine to give a wet sheet density of 0.35 to 0.45 g/ am
', and after drying, the density was reduced to 0.4 by calender pressure.
It can be obtained by a manufacturing method that yields 5 to 0.55 g/cm3.

The main raw material used in the present invention is bleached hardwood kraft pulp, but depending on the quality characteristics of the laminate, various types of raw materials such as bleached softwood kraft pulp, inorganic wam such as glass fiber and carbon fiber, and synthetic fibers such as polyester and nylon can be used. A small amount of fiber can be added. Further, flame retardants, paper strength enhancers, and the like may be added as necessary. In the wet press of a paper machine, wet paper is introduced into the nip where two rolls come into contact, and by pressurizing the rolls, the wet paper is mechanically dehydrated to reduce the water content of the wet paper. density increases and strengthens the fiber bond in the wet paper. These effects are controlled by the magnitude of the linear pressure at the nip portion, as described above.

The press section of a paper machine is usually equipped with two to four nips.

The wet sheet density referred to in the present invention refers to the wet paper that has passed through the final nip of the press part, and the wet paper that has passed through the final nip of the press part is compressed and dried using a normal drying device for making handsheets, and then subjected to a predetermined method. After adjusting the humidity, check the weight and thickness of the sample according to JISP.
This is a value measured and calculated according to -8118.

If the density after the wet sheet is less than 0.35, the fiber bonding in the wet paper web will be reduced and the strength of the base paper will be reduced. Also 0, 4
If it exceeds 5, it is necessary to reduce the nip pressure in the calender, and as mentioned above, the effect of the present invention cannot be obtained. The smoothness of the surface is imparted here.

Calenders stack several metal rolls to form several nips, and introduce paper sheets between the nips. The surface smoothness and density are controlled by adjusting the number of nips and the amount of pressure applied.

The density after calendering is a value measured in accordance with JXS after conditioning the calendered sheet by a predetermined method.

If the density after calendering is less than 0.45, the calender nip pressure cannot be large enough to exhibit the effects of the present invention. If it is larger than 0.55, the amount and rate of impregnation will decrease during resin impregnation, making it unsuitable for use as a base paper for laminate boards.

Next, the present invention will be explained with reference to examples.

Example 1 Unbeaten LB and 100% P (freeness 580 cc) valve were used as raw materials, and two sets of wet breath nips (IP
, 2P) and a two-roll calender with one knob) to produce laminated board base paper. The wet breath nip pressure, calender nip pressure, wet sheet density, and density after calender pressurization are shown in Table 1, and the oil permeability and resin impregnation rate of the obtained laminate base paper are also shown in Table 1. The measurement method is as shown below.

Resin impregnation rate! Humidity control (2
It is impregnated with a water-soluble phenol resin (Schoenol BRL2854, purity 60%, manufactured by Showa Denko) diluted with methanol to a purity of 54.5%.It is determined from the weight before and after impregnation using the following formula.

a; Weight of the sample after humidity conditioning b; Weight of the sample after resin impregnation b - a xO, 545 x 100 = Resin impregnation rate (96)
Oil Penetration Degree: A sample punched into a circular shape with a diameter of 18 m/m is floated in castor oil (class 1 reagent) with the measuring surface in contact with the test surface. )
Measure.

Example 2. and Comparative Example 1 The conditions were the same as in Example 1, except that the distribution of wet press nip pressure and force 1/nib pressure was changed. The results are also shown in Table 1.

Table 1 As explained above, according to the present invention, by adjusting the distribution of the nip pressure between the wet press and the calender to set the density of the wet press sheet and the density after calendering to appropriate values, the impregnation property can be improved. Excellent laminated board base paper can be produced.

Claims (1)

[Claims] Freeness (Canadian Standard Freeness) 53
When making paper from raw materials mainly made of bleached hardwood kraft pulp of 0 cc or more, the wet sheet density is adjusted to 0.35 to 0.45 g/cm by applying pressure with the wet press of the paper machine.
^3, and after drying in the dryer section of a paper machine, the density is adjusted to 0.45 to 0.55 g/cm^3 by calender pressure.