JPH03890A - Paper base for laminate - Google Patents

Abstract

PURPOSE:To provide title paper base having numerous pores, excellent in resin impregnability, capable of giving laminates free from warpage and torsion and good in dimensional stability, consisting mainly of specific pulp fiber. CONSTITUTION:Unbeaten broadleaf pulp fiber >=600ml in Canadian standard freeness is put to papermaking process to obtain the objective paper base having numerous pores with the volume of pores >=15mum in reduced pore size accounting for >=40 (pref. 40-80)% of the total pore volume. The present paper base is impregnated with a thermosetting resin followed by drying to obtain a prepreg. Two or more sheets of the prepreg are mutually laminated and put to hot pressing at the curing temperature of said thermosetting resin, thus obtaining laminates suitable for electrical instruments, electronic ones, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminate paper substrate and a laminate containing this substrate. To explain in more detail, when processing into laminates for electronic and electrical equipment, impregnation with phenolic resin, etc. is fast and does not cause the sticky problem of resin remaining on the surface of the paper layer (hereinafter referred to as surface adhesion problem). The present invention relates to a laminate paper base material with good properties. Furthermore, the present invention relates to a laminate containing this base material, which has good warpage/twisting and dimensional stability.

[Conventional technology]

Ordinary paper-based laminates are made by impregnating the paper base material of the laminate with a thermosetting resin such as phenol resin or epoxy resin, heating and drying this to a semi-cured resin state (prepreg), and making multiple sheets of this prepreg. It is manufactured by laminating the laminate together with metal foil and molding the laminate by heating and pressing.

The laminate paper base material used in such paper base laminates is required to have the following properties.

1) The rate of penetration of the resin liquid into the pores within the paper base material is fast in order to improve the efficiency of the impregnation process.

2) A predetermined weight of resin can be held inside the paper layer, and the problem of resin remaining on the surface of the paper layer and exhibiting stickiness (surface sticking trouble) does not occur.

3) Less uneven resin impregnation.

In recent years, paper-based laminates have also been required to have high heat resistance and dimensional stability. For this reason, the impregnated resin has been modified to improve its heat resistance, and the conventional phenol In addition to resins and epoxy resins, polyester resins are now being used. Solutions of such special impregnating resins tend to be highly viscous. Accordingly, there is an increasing need for a laminated paper base material that allows the resin liquid to penetrate at a high rate and has good impregnation properties that do not cause problems with surface adhesion.

Hardwood pulp or link pulp is usually used as the paper base material for laminated boards.

When using hardwood pulp, depending on the type of wood, there are many fine fibers or the pulp fibers are easily crushed, so the paper layer formed from such pulp has a high content of small pores. If a prepreg is manufactured by impregnating such a paper layer with a highly viscous thermosetting resin liquid, a problem arises in that the impregnation of the resin into the laminated board paper base material is insufficient.

Further, as a means to improve the impregnation property, it is possible to lower the density of the laminated paper base material and increase the porosity. However, when the density is lowered, the strength of the resulting laminated paper base material decreases, and problems such as paper breakage may occur during the impregnation process.

Therefore, there is a permissible limit to the decrease in density, and paper substrates for laminated boards are usually used with a density in the range of 0.48 to 0.52 g/cm<3>.

Link pulp is fine I! Since there are few II fibers and the fibers are rigid, a laminated board paper base material using this material has a high content of large-diameter pores in the paper layer, and has good impregnability with resin liquid. However, if unbeaten link pulp is used, the strength of the paper base material will be low, and problems such as paper breakage may occur during the impregnation process. Therefore, usually csf 400
It is used after being beaten to about ml. This paper base material is impregnated with thermosetting resin and molded under heat to produce a laminate that does not warp or
It may be twisted, have poor dimensional stability, and cause problems in the printed wiring board processing process. In addition, when hardwood pulp is beaten and used, the same warpage and warping as with link pulp occur.
Twisting trouble may occur.

[Problem to be solved by the invention]

In the impregnation process, the present invention provides a laminate paper base material that has a high permeation rate of resin liquid and good resin impregnation properties, and a laminate board containing this base material that is free from warping and twisting and has good dimensional stability. This is what we are trying to provide.

[Means to solve the problem]

The present invention is a laminated paper base material mainly composed of unbeaten hardwood pulp fibers with a Canadian Standard Freeness of 600 or more and having a large number of pores, the paper base material having an equivalent pore diameter of 15 fPIa or more based on the total pore volume. The ratio of the total volume of pores having pores is 40% or more.

The laminate of the present invention is characterized in that it includes two or more prepreg layers that are made of the above-mentioned laminate paper base material and a thermosetting resin impregnated into this base material, and are laminated and pressure-molded together. It is something.

Furthermore, the method for producing a laminate of the present invention includes impregnating the paper base material for the laminate with a thermosetting resin and drying the resulting laminate.
This method is characterized by laminating more than one sheet of prepreg and heating and pressing them to form a mold.

The present inventor has conducted various studies on the relationship between impregnability and paper properties in order to prevent as much as possible the problems caused by poor impregnation of the laminated paper base material in the resin solution impregnation process, and We digested and bleached the pulp material and investigated the relationship between the physical properties of the pulp fiber and the physical properties of paper. As a result, it is unbeaten and Canadian Standard Freeness (C3F).
) is mainly composed of pulp fibers of 600 mg or more and has a large number of pores, the paper base material has a content of 15. The ratio of the total volume of pores having a converted pore diameter of =- or more is 40% or more, preferably 40 to 80%, with respect to a thermosetting resin liquid with high viscosity,
It was discovered that it has excellent impregnation properties, and the present invention was completed.

Below, methods for measuring the total pore volume and pore size distribution of the paper base material for laminated boards, as well as methods for evaluating impregnation properties (castor oil permeability measurement method,
Evaluation of impregnation work using prepreg manufacturing equipment) and methods for measuring warpage of laminates are described in detail.

Total pore volume and pore size distribution measurement method The total pore volume and pore size distribution of laminate paper substrates were measured using a mercury porosimeter (e.g.
sure Porosimater 2000, Ma
cropore Unit 120).

This measurement method takes advantage of the property of mercury not to wet solids such as paper, and measures the surface tension of mercury at 480 dyn/
cm, the contact angle is 141°, and the injection pressure of mercury is P.
(kg/c+n”), the equivalent pore diameter d (μm) of the pores in the paper can be determined by the following equation.

d=15 J/P In addition, a large amount of mercury pressure up to 500 kg/cm' was defined as the total pore volume of the laminate paper base material. The pore size distribution can be calculated from the amount of mercury pressure at each pressure and the above formula. In addition, the equivalent hole diameter is 15μ
The total volume of pores of m or more is Macropore tl
Can be measured using nit 120, press fit pressure 1.0
It is expressed as a mass of mercury pressure at 2 kg/cni”.

Castor oil permeability measurement method The castor oil permeability of the laminate paper substrate can be measured by the method described below.

Ten test pieces of 20rnrn square are cut from the test laminate paper base material. A container containing castor oil was placed in a constant temperature bath kept at a water temperature of 30°C, the temperature of the castor oil was controlled at a constant 30°C, and the test piece was dropped horizontally onto the surface of the castor oil liquid.
The time from the moment the test piece comes into contact with the castor oil until it has uniformly penetrated the upper surface of the test piece is measured with a stopwatch.

Measure five test pieces each on the front and back sides of the paper, and calculate the average value. A low value indicates good impregnating properties.

Evaluation of impregnating workability using a prepreg manufacturing device Using a prepreg manufacturing device (for example, prepreg manufacturing device for composite materials manufactured by Bengami Metal Co., Ltd.), impregnation workability can be evaluated as follows.

Impregnation is carried out twice using different resins. The first time was carried out using a water-soluble resol resin (e.g., Showa Kobunshi BRL-2854), and the second time was carried out using an oil-modified resol resin (e.g., Showa Kobunshi BLS-3122). Evaluate the presence or absence.

How to measure warpage of laminates The warpage of the laminate is measured by the following method.

A thermosetting resin, that is, a water-soluble resol resin (for example, Showa Kobunshi BRL-2854) is applied to the paper base material of the laminate board, and the solid content of the water-soluble resol resin in the prepreg is 10.
% by weight, dried at a temperature of 100°C for 5 minutes, and further added an oil-modified resol resin (for example, Showa Kobunshi BLS-3122) to an oil-modified resol resin solid content of 40% by weight. Impregnated to the weight%,
It is dried at a temperature of 90° C. for 5 minutes to create a prepreg with a base material:resin solid weight ratio of 1=1. 8 sheets of prepreg were laminated at 160℃ and 100 kg/cm.
A laminate is produced by heating and pressurizing for 30 minutes.

After heat-treating this laminate for 15 minutes in a dryer at 120° C., it is placed on a surface plate and the maximum lifting amount of the four corners is measured, and this is taken as the amount of warpage.

The laminated paper base material of the present invention is unbeaten and has a 7-leaness (C3
F) A paper base material made of pulp fibers of 600° C. or more and having a large number of pores, in which the ratio of the total volume of pores having a converted pore diameter of 15° C. or more to the total pore volume is 40° C. % or more, preferably 40 to 80%.

In the beaten pulp, the pulp fibers are fibrillated, making it difficult to obtain large pores in the resulting sheet, impregnating the resin solution, and making it difficult to form laminates using this sheet as the base material. Dimensional stability also deteriorates, and warpage, etc., increases. Also, the freeness of unbeaten pulp is 600rn.
If it is less than 1, it is disadvantageous for the same reason as above.

A laminate paper base material in which the ratio of the total volume of pores with an equivalent pore diameter of 15F@ or more in the paper base material is less than 40% has poor impregnability with a highly viscous thermosetting resin liquid. It will be enough.

In order to produce a laminate using the paper base material for the laminate board of the present invention, the paper base material is impregnated with a thermosetting resin, and a prepreg impregnated with a thermosetting resin obtained by drying or semi-drying is prepared. 2
(The laminated precursor may be laminated with other materials such as metal foil if necessary.) While heating this laminated precursor to the required temperature for thermosetting the thermosetting resin, Pressure is applied in a mold, and this is molded into a mold.

As the thermosetting resin, generally a resol type phenol-formaldehyde resin is used, but it is not limited thereto, and other resins, such as ordinary phenol-formaldehyde resin, are used.
It can be selected from formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, epoxy resin, unsaturated polyester resin, polyimide resin, etc.

The conditions for the heating and pressing operation vary depending on the type of thermosetting resin and the configuration and dimensions of the 11 and laminate, but generally 1
Temperature of 50-180℃, 70-150 kg/cm
2 pressure for 20 to 60 minutes.

When manufacturing a laminate from a laminate paper base material, 1 in the paper base material
The ratio of the total volume of pores having a reduced pore diameter of 5- or more is 4
Even if the paper base material for laminates is less than 0%, if beaten hardwood pulp or beaten link pulp is used, the resulting laminates will have large warps and twists, resulting in problems in the printed wiring board processing process. cause trouble. The content (solid content) of the thermosetting resin in the laminate of the present invention is not particularly limited, but is generally 45 to 55% by weight.

〔Example〕

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 Mangrove wood chips from Porneo (volume weight 700 kg)
/m') obtained from unbeaten (Canadian) raw material.
Standard freeness (csf) 680 rd) LB and P (bleached hardwood kraft pulp), basis weight 135
g/m”: Thickness 270.- (Base paper density 0.5
A laminated paper base material of g/am') was produced, and its total pore volume, pore size distribution, and impregnability were measured.

Furthermore, impregnation workability was evaluated using a prepreg manufacturing device (manufactured by Bengami Metal Co., Ltd., prepreg manufacturing device for composite materials).

In addition, the above laminated board paper base material was impregnated with water-soluble resol resin (Showa Kobunshi BRL-2854) so that the resin solid content in the prepreg was 10% by weight, and the mixture was heated at a temperature of 10°C for 5 minutes. After drying, the prepreg was further impregnated with oil-modified resol resin (BLS-3122 manufactured by Showa Kobunshi Co., Ltd.) so that the resin solid content in the prepreg was 40% by weight, and heated at 90°C.
Dry for 5 minutes at a temperature of
I created a prepreg that looks like this. This prepreg 8
The sheets were laminated and heated and pressed at 160° C. and 100 kg/am'' for 30 minutes to produce a laminate. The amount of warpage of this laminate was measured. The results are shown in Table 1.

Example 2 From unbeaten (csf 670rn1.) LBKP obtained from eucalyptus wood chips (volume weight 670 kg/m') produced in Ew Castle, Australia, basis weight 1.
35g/m", thickness 270/FW+ (base paper density 0,
A laminated paper base material of 5 g/cm 3) was made, and its total pore volume, pore size distribution $, and impregnability were measured. Furthermore, impregnation workability was evaluated using prepreg manufacturing equipment.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and the amount of warpage was measured. The results are shown in Table 1.

Example 3 Kyushu hardwood mixed wood chips (volume weight 560 kg/m')
Unbeaten (csf 630 mi) obtained using as raw material
From L B K P, basis weight 135g/m2, thickness 2
A laminated board paper base material of 70/- (base paper density 0, 58/c+s') was made, and its total pore volume, pore size distribution, and impregnability were measured.

Furthermore, impregnation workability was evaluated using prepreg manufacturing equipment.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and the amount of warpage was measured. The results are shown in Table 1.

Example 4 Hokkaido hardwood mixed material chips (volume weight 530 kg/m
Unbeaten (csf 610 T) obtained using 3) as a raw material
Nf LB to P, basis weight 135g/m2, thickness
270. (base paper density 0, 5 g/cm2) was made into paper, and its total pore volume, pore size distribution, and impregnability were measured.Furthermore, using prepreg manufacturing equipment,
The impregnation workability was evaluated.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and the amount of warpage was measured. The results are shown in Table 1.

Comparative example 1 Soviet poplar wood chips (volume weight 350 kg/m3)
Unbeaten (csf 560 m) LB obtained using P as raw material, basis weight 135 g/m2, thickness 270/-
A laminated board paper base material (base paper density: 0, 5 g/cm 3 ) was made, and its total pore volume, pore size distribution, and impregnability were measured.

Furthermore, impregnation workability was evaluated using prepreg manufacturing equipment.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and warpage was measured. The results are shown in Table 1.

Comparative Example 2 Using unbeaten pulp obtained using the Australian eucalyptus wood chips of Example 2 as a raw material, adding P to B, and beating to csf600-, a pulp with a basis weight of 135 g/1TI2 and a thickness of 270 IcPyn (base paper density 0) was used. , 5g/cm 3)
The total pore volume, pore size distribution, and impregnability were measured. Furthermore, impregnation workability was evaluated using prepreg manufacturing equipment.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and warpage was measured. The results are shown in Table 1.

Comparative Example 3 Linta pulp was beaten to csf 400-, and the basis weight was 13
5g/m', thickness 27Or ([paper density 0, 5g/a
The total pore volume of the laminated paper base material of
Pore size distribution and impregnability were measured. Furthermore, impregnation workability was evaluated using prepreg manufacturing equipment.

In addition, a phenol resin laminate was prepared in the same manner as in Example 1, and the amount of warpage was measured. The results are shown in Table 1.

As is clear from Table 1, the laminated board paper base materials of the present invention obtained in Examples 1 to 3 had high impregnation properties and good impregnation workability. Moreover, the laminate made from the paper base material of the present invention was a good laminate with little warpage.

〔Effect of the invention〕

A paper base material made of unbeaten hardwood pulp fibers and having a large number of pores, the total pore volume of which is 15
The ratio of the total volume of pores having a converted pore diameter of P-m or more is
By using the laminated board paper base material of the present invention having a content of 40% or more, it becomes possible to impregnate a highly viscous resin liquid.

Furthermore, by using this base material, it is possible to manufacture a good laminate with little warpage.

Claims (1)

[Claims] 1) Unbeaten and Canadian Standard Freeness 6
00ml or more of hardwood pulp fibers and has a large number of pores, the ratio of the total volume of pores having an equivalent pore diameter of 15 μm or more to the total pore volume is A laminate paper base material characterized in that the pore volume is 40% or more.