JPH03128244A - Sheetlike pulp-base material for laminate and laminate - Google Patents

Abstract

PURPOSE:To obtain the laminate excellent in the stability of strength, dimension and shape, while the tear or breakage of base material in impregnating process is removed by a method in which unbeated pulp contains the bleached kraft pulp beated into a specified freeness. CONSTITUTION:The sheetlike pulp-base material for laminate making a paper by using the bleached kraft pulp of a broad leaf tree as raw material contains the beated pulp of 10-30wt.% which is heated into Canada Standard freeness of 100-500ml and in which the fine fibers of at most 150 mesh are removed by sieving to the unbeated pulp of 100wt.%. A laminated sheet is formed by laminating under pressurizing at least two prepregs impregnated with thermosetting resin at the weight ratio of 1:1 on the sheet like pulp-base material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sheet-like pulp base material for a laminate and a laminate made of this base material, and more specifically, to an operation in a thermosetting resin impregnation process. The present invention relates to a sheet-like pulp base material with excellent properties and a laminate used for printed wiring boards for electronic and electrical equipment.

[Prior art] Normally, sheet-like base materials for laminates are impregnated with thermosetting resins such as phenolic resins and epoxy resins. There is no tearing or cutting of the sheet-like base material, and the penetration rate of the resin solution is fast.

2) A predetermined weight of resin can be held inside the sheet material.

3) Less unevenness in resin impregnation.

The following characteristics are required.

For this reason, bleached kraft pulp (LBKP) made from domestic hardwood is generally used as a sheet-like pulp base material for laminates without being subjected to beating treatment.

This unbeaten pulp usually has a freeness of 550 to 650 m1, but is made into paper using a known paper machine, and the density of the sheet-like pulp base material obtained is 0.45 to 0.55 g/a.
It is of a low level of s'.

Among the properties required of the base material, increasing the density of the base material and strengthening the bonds between fibers may be considered as a means of improving the strength. However, although increasing the density of the base material improves the strength, It cannot be used because the porosity decreases and the impregnating property of the resin deteriorates.

On the other hand, ordinary laminates, especially laminates for printed wiring boards, are made by impregnating a sheet-like pulp base material with a thermosetting resin such as phenol resin or epoxy resin, heating and drying it to a semi-cured resin state, and then creating a semi-cured resin state. It is manufactured by laminating two or more sheets of prepreg and hot-pressing them together with metal foil, but in recent years, laminates containing sheet-like pulp base materials have also been improved in terms of heat resistance and dimensional stability. As the impregnating resins are now required to have better heat resistance, they are modified to give them heat resistance, and polyester resins are being used in addition to the conventional phenolic resins and epoxy resins. As solution viscosity tends to increase, the impregnating properties of sheet pulp substrates are becoming increasingly important.

That is, the sheet-like pulp base material is required to have properties such that it does not break when impregnated with resin, has a fast penetration rate, and does not leave the resin on the surface of the base material.

Furthermore, with the miniaturization of electrical products in recent years, the mounting density of electrical components such as IC1 capacitors and resistors has increased, and the conductor patterns of printed wiring have become thinner. For this reason, requirements for laminates are becoming increasingly strict, not only in terms of electrical performance, but also in terms of preventing deformation such as dimensional changes, warping, and twisting during the manufacturing process of printed wiring boards, and in order to make them lighter, thinner, and smaller. .

In order to solve these problems, a method of selectively selecting the length of the valve fibers used has been proposed (Japanese Patent Application Laid-Open No. 58-180).
No. 086, Japanese Unexamined Patent Publication No. 184200/1986, and Patent Application No. 1-115783), no satisfactory solution has been achieved.

[Problems to be Solved by the Present Invention] In order to prevent troubles caused by insufficient strength of the sheet-like valve base material during the impregnation process, the present inventors investigated the strength and physical properties of the base material, and further investigated the strength and physical properties of the base material. In order to prevent as much as possible dimensional changes and shape changes such as warping and twisting during the processing process when using the board as a printed wiring board, we have conducted various studies on the relationship between shape and dimensional changes and the physical properties of the base material.
A sheet-like pulp base material that does not tear or cut the base material in the conventional impregnation process and has good impregnation properties with thermosetting resin, and the strength, dimensions, An object of the present invention is to provide a laminate having good shape stability.

[Means for Solving the Problems] The first invention of the present application is a sheet-like pulp base material for a laminate board in which paper is made using bleached hardwood kraft pulp as a raw material,
Per 100% by weight of unbeaten pulp, 10 to 30% of pulp beaten to a Canadian standard freeness of 100 to 500a+1
The second invention is a sheet-like pulp base material for laminates containing 100% by weight of unbeaten pulp, beaten to a Canadian standard freeness of 100 to 500 ml,
The pulp base material for the laminate contains 10 to 30% by weight of beaten pulp from which fine fibers of 150 mesh or less have been removed by sieving. Further, the third invention is characterized in that the sheet-like pulp base material of the first invention or the second invention, which is made from hardwood bleached kraft pulp as a raw material, is impregnated with a thermosetting resin at a weight ratio of 1:l. This is a laminate plate in which two or more sheets of prepreg are laminated and pressure-bonded.

That is, the present invention generally has a freeness of 550 to 650 m1.
For 100% by weight of unbeaten hardwood bleached kraft pulp,
Freeness below 550+sl, preferably 100-5
Most preferably, the pulp is reduced to 300 to 450 ml by beating and contains beaten pulp as it is, or beaten pulp from which fine fibers of 150 mesh or less have been removed (hereinafter referred to as sieved pulp).

In bleached kraft pulp whose freeness has been reduced by beating, some of the fibers are crushed into small pieces, but the entire pulp fiber is not beaten, and the degree of beating can be reduced by incorporating some of the pulp fibers. By appropriately changing or beating the sieved pulp, the permeability of the thermosetting resin solution is not impaired or significantly improved, that is, the strength is improved without almost changing the density of the base material. .

Pulp beating is carried out using a refiner stone or other beating machine used in normal papermaking processes, and the degree of beating is 55%.
Although it depends on the content of beaten pulp below 0 l, it is more convenient for the present invention to lower the freeness level and reduce the content than to increase the overall freeness level and increase the content. It is.

In the present invention, the Canadian standard freeness is 550 m1 or less, preferably 100 to 500 m1 of beaten pulp, or after beating 1
Sieved pulp from which fine fibers of 50 mesh or less have been removed 5~
30% by weight, preferably 10-30% by weight, is contained in the unbeaten pulp. The sieving of the present invention can be easily carried out by filtering the beaten pulp and discharging the generated white water to the outside of the system, or by using a conventional closed screen and changing the gap between the screen plates.

If the content of beaten pulp is less than 5% by weight, the purpose of the present invention cannot be achieved, and if it exceeds 30% by weight, the development of bond strength will be significantly increased, and the density of the base material will be 0.55g/am' or more, making management difficult. It is not desirable because it is accompanied by

That is, the density of the sheet-like pulp base material of the present invention is 0.5±0
．． 05g/am', preferably 0.5±0.03g/c
This is controlled, for example, by changing the press pressure in the paper machine, and when the density of the sheet pulp base material becomes 0.45 g/c+s' or less, impregnation with the resin solution This is not preferable because the speed becomes faster and the amount of impregnation increases.

On the other hand, if the density is set to 0.55 g/a1 or more, the tensile strength and bending strength will increase, but it will take time for the resin to penetrate and the amount of resin impregnated will decrease, which is not preferable.

When the content of beaten pulp exceeds 30% by weight, the development of bond strength increases significantly, and the density of the base material reaches 0.55 g/c.
1 or more, which is difficult to manage, so in the present invention, the content of beaten pulp is set to 30% by weight or less.

In addition, beaten pulp is usually bleached hardwood kraft pulp (L
BKP) is used, but softwood bleached kraft pulp (N
BKP) can also be used.

In the present invention, a sheet-like pulp base material is impregnated with a resin at a weight ratio of 1:1, and it is disadvantageous whether the amount of resin is large or small relative to the base material.

This is because if the amount of resin is small, the adhesion of the laminate will be insufficient, whereas if the amount of resin is large, the flow of the resin will increase during lamination. Conventionally known methods can be applied as they are to manufacture the laminate.

[Examples] The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way.

Examples 1 to 5 Hokkaido hardwood mixed material chips (volume weight 500Kg/l)
The pulp obtained by beating LBKP as the main raw material to 400+ml and the sieved pulp obtained by sieving with a sieving tester according to JISP 8207 and removing fine fibers of 150 mesh or less were mixed in the proportions shown in Table 1. Blend with beaten pulp, and from this blended pulp
A base paper for a laminate was made, and its tensile strength and impregnability were measured.

The weight ratio of this base paper phenolic resin for laminates is paper:resin-
The prepreg was impregnated at a ratio of 1:1 and dried by heating at 135°C for 3 minutes.

Next, 8 sheets of this prepreg were laminated, 165'C, 10
A laminate was prepared by heating and pressing at 0 kg/c+a'' for 60 minutes.

The laminate was conditioned for 24 hours in an environment with a temperature of 20°C and a relative humidity of 65%, marked with a span of 200ea+, then heated at 80°C for 30 minutes, further heated at 120°C for 15 minutes, and then heated again at 20°C. The humidity was controlled for 24 hours in an environment with relative humidity of 65%, the distance between the gauges was measured using a high-precision two-dimensional coordinate measuring device (manufactured by Dainippon Screen Manufacturing Co., Ltd.), and the dimensional change rate was determined. The bending strength of the laminate was also measured.

Comparative example Hokkaido hardwood mixed material Chi Nobu (volume weight 500Kg/m
') is used as raw material to produce LBKP (hardwood bleached kraft pulp), and from this unbeaten pulp, 113 tsubo
A pulp base material for a laminate board having a weight of 5 g/m'' and a thickness of 270 μm was made, and its tensile strength and impregnability were measured.

A laminate was produced from this pulp base material for a laminate in the same manner as in Example 1, and its dimensional change rate and bending strength were determined.

The tensile strength and impregnation properties of the sheet-like base materials, as well as the dimensional change rate and bending strength of the laminates in Examples 1 to 5 and Comparative Examples are as shown in Table 1.

The methods for testing and measuring the pulp freeness, the tensile strength and density of the sheet-like pulp base material, the phenol resin permeation rate, and the dimensional change rate of the laminate according to the present invention are as follows.

Pulp Beating and Freeness Measurement Method Pulp beating and freeness measurement were carried out in accordance with the methods shown in the TAPPI Standard (7200: Laboratory Pulp Processing Method, Beater Method and T227: Pulp Freeness).

Method for Measuring Tensile Strength The tensile strength of a sheet-like base material is measured by the following method. Width: 15 IIllll, length: 1
Cut out six 50mm test pieces and test them with a Tensilon tester (
UTM-]I[-1oo, TOYOBAL DWIN C
The tensile strength was measured using the following method.

Density measurement method: The density of a sheet-like base material can be measured in accordance with JIS P-8118 (
The thickness and density of paper and paperboard are measured in accordance with the following method.

20~25cm long and wide, humidity controlled in the same way as the tensile strength measurement method
The thickness (T) of a square sheet-like base material of m is measured with a micrometer, and the density (D) is calculated using the following formula.

D = W/T Can be done.

Ten test pieces of 2 ha square were cut out from each sample sheet-like base material. A container containing a phenol resin methanol solution was placed in a constant temperature bath maintained at 2°C or lower in ice water, the temperature of the resin liquid was controlled at a constant 2 to 3°C, and the test piece was dropped horizontally onto the surface of the resin solution for testing. The time from the moment the piece comes into contact with the resin liquid until it has uniformly penetrated the upper surface of the test piece is measured with a stopwatch.

The lower this value is, the better the impregnating property is.

Method for measuring dimensional change rate of laminates The dimensional change rate of the laminate is measured by the following method.

A sheet-like base material for a laminate is impregnated with a thermosetting resin, that is, a resol type phenolic resin so that the solid weight of the base material is 12 liters, and dried at a temperature of 135°C for 3 minutes to create a prepreg. . Eight sheets of this prepreg were laminated and heated to 165°C.
, 100 Kg/as'' for 60 minutes to produce a laminate.

This laminate was placed in an environment with a temperature of 20°C and a relative humidity of 65%.
Humidify for 4 hours and mark with a span of 200mm. Next, heat at 80"C for 30 minutes, then heat at 120"C for 15 minutes, and then condition the humidity for 24 hours in an environment of 200"C1 relative humidity of 65%, and measure the distance ML between the gauges with high precision two-dimensional coordinates. Measurement is performed using a device (for example, Digital Reader DR-550-D, manufactured by Dainippon Screen Mfg. Co., Ltd.).

Calculate the dimensional change rate po from the formula below.

g=(200-L)/200 x 100 (%
) The dimensional change rate of the laminate is shown as the average value in the vertical and horizontal directions. The smaller the dimensional change rate, the higher the dimensional stability of the laminate.

Bending strength measurement method of laminate plate The bending strength of a laminate plate is measured by the following method in accordance with JIS C-6481.

Three test pieces with a width of 25 cm and a length of 60 cm are cut from the laminate, and the bending strength is measured using a Tensilon tester at a distance between fulcrums of 30 cm.

As is clear from Table 1 above, in comparison with Comparative Example 1, the pulp base materials for laminates of the present invention obtained in Examples 1 to 5 had significantly lower tensile strength without significantly decreasing impregnability. The dimensional stability and bending strength of the obtained laminate were also good.

On the other hand, it was observed that the pulp base materials of the present invention obtained in Examples 4 and 5 had significantly improved impregnation properties, and also improved dimensional stability and bending strength of the obtained laminates. It will be done.

[Effects of the Invention] As described above, the present invention provides a sheet-like pulp base material used for laminates, which can maintain a constant density of the base material and improve the tensile strength without impairing the resin penetration rate. Work problems such as paper breakage during the resin impregnation of the base material and drying process can be resolved.

Furthermore, the laminate formed from the sheet-like pulp base material has improved bending strength and good dimensional stability.
Since the thickness can be reduced, it is expected to be used in fields that require thinness, precision, and weight reduction, and work efficiency can be improved because thinner products can be manufactured.

Claims (3)

[Claims] (1) In sheet-like pulp base material for laminate boards made from hardwood bleached kraft pulp as raw material, unbeaten pulp 10
A sheet-like pulp base material for a laminate, characterized in that it contains 10 to 30% by weight of bleached kraft pulp beaten to a freeness of 100 to 500ml per 0% by weight. (2) Claim 1, characterized in that the beaten pulp is one from which fine fibers of 150 mesh or less have been removed.
A sheet-like pulp base material for a laminate as described in 1. (3) A sheet pulp base material according to claim 1 or 2, which is made from bleached hardwood kraft pulp as a raw material, is impregnated with a thermosetting resin at a weight ratio of 1:1. A laminate, characterized in that two or more sheets of prepreg are laminated and crimped together.