JPH10102392A - Base paper for laminated plate, and laminated plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminated plate which is excellent in dimensional stability, resistance to heat, and electric properties, by forming prepregs by using a base paper for lamination made of a specific bamboo pulp-containing cellulose fibers, laminating and thermo-compressing the prepregs. SOLUTION: A mixed pulp slurry containing 10-80wt.% of bamboo slurry from which microfine fibers of <=0.2mm length are removed less than 5wt.% content and 20-90wt.% of wood pulp is subjected to sheet making to prepare base paper for lamination. The lamination base paper is impregnated with a thermosetting resin, for example, a phenolic resin or epoxy resin, heated and dried thereby producing prepregs. These prepregs are laminated and thermocompressed to give the objective laminated plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base paper for laminated board and a laminated board using the same, and more particularly, to dimensional stability, electrical characteristics, and the like.
The present invention relates to a laminate base paper and a laminate suitable for producing a laminate having good heat resistance.

[0002]

2. Description of the Related Art A conventional laminate, especially a laminate for a printed wiring board, is prepared by impregnating a laminate base paper with a thermosetting resin such as a phenolic resin or an epoxy resin and heating and drying the same to form a semi-cured resin. (This is referred to as a prepreg), a plurality of the prepregs are laminated, and hot-press molding is performed. Such a printed wiring board is relatively inexpensive and almost satisfies the performance for use in ordinary electric or electronic devices, and thus is widely used mainly for home electric appliances. However, in recent years, since electric products have become lighter, thinner and smaller, the mounting density of electric product parts such as ICs, capacitors, and resistors has increased, and the conductor patterns of printed wiring have become finer. Furthermore, with the entry of home appliances manufacturers into industrial equipment and the trend toward lower prices, the use of paper base materials in fields that were previously impossible with paper base materials is expanding. For this reason, demands for not only dimensional stability but also improvements in electrical characteristics, heat resistance, and the like, of a laminate made of paper as a base material, have become strict.

Conventionally, laminates base paper, bleached kraft pulp from hardwood and (LBKP) be used in non-beaten paper, to paper of low density of the order 0.45~0.55g / cm ³ In general, when electrical characteristics and heat resistance are required, pulp for dissolution or pulp having a high α-cellulose content such as cotton linter is used. However, these pulp fibers are remarkably bent and twisted, and LB
There is a problem that the dimensional stability of the laminated board is significantly inferior to the base paper by KP. To solve this, LBK
In the production process of P, a method of reducing the hemicellulose content of pulp by specific digestion, bleaching conditions or enzymatic treatment (JP-A-6-146193, JP-A-6-287898)
Etc.) had been proposed. However, if these techniques are used, the heat resistance and the electrical properties can be improved while maintaining the dimensional stability of the LBKP, but the heat resistance and electrical properties as excellent as cotton linter and dissolving pulp cannot be obtained. On the other hand, mixing of ordinary LBKP and pulp having a high α-cellulose content such as linter was also studied, but the disadvantages of both were rather large, and the expected effects could not be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a laminate having good dimensional stability, heat resistance and electrical properties, and a laminate base paper suitable for producing the laminate. With the goal. In view of this situation, the present inventors have studied various pulp fibers in order to improve the heat resistance and electrical properties of the laminate.As a result, the laminate made of bamboo pulp using bamboo pulp as a raw material has a dimensional stability. It was found that the balance between heat resistance and electrical properties was extremely excellent, and the present invention was completed.

[0005]

The present invention includes the following aspects. [1] A base paper for a laminate comprising cellulose fibers, wherein the cellulose fibers comprise bamboo pulp. [2] Cellulose fiber is bamboo pulp 10 to 80% by weight
And the laminated stencil paper according to [1], which contains 20 to 90% by weight of wood pulp. [3] The content of fine fibers having a fiber length of 0.2 mm or less in bamboo pulp is 5% by weight or less [1]
Or the laminated board base paper according to [2]. [4] A laminate obtained by laminating a prepreg impregnated with a thermosetting resin on the laminate base paper according to [1], [2] or [3] and molding the laminate.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Bamboo pulp is mainly used for calligraphy paper, art paper, art material paper, speaker cone paper, fancy paper, etc., because bamboo pulp has more rigid fibers and higher oil absorbency than wood pulp. However, it is not used at all in the laminated base paper. However, the present inventors have found that laminated base paper using bamboo pulp is very excellent. The bamboo pulp used in the present invention includes bamboo grown from rhizomes, such as Moso bamboo and bamboo, and chemical pulp obtained from bamboo grown from a strain, and has fiber strength, digestibility, bleaching property, and impurities. If mixing is considered, bamboo pulp from bamboo cooked by alkali cooking, kraft cooking or sulfite cooking is preferred. The bamboo pulp content in the laminated base paper of the present invention is not particularly limited, and is appropriately adjusted according to the material to be combined and the required quality. Although the base paper for a laminate of the present invention mainly contains cellulose fibers, cellulose fibers other than bamboo pulp can be used in combination. Such cellulose fibers are not particularly limited, and chemical pulp obtained from wood chips, mechanical pulp, linter,
Non-wood pulp such as hemp and kenaf, pulp for dissolution and the like can be used, and bleached kraft pulp using hardwood is particularly preferable. Furthermore, as a material other than the cellulose fiber, synthetic fibers, inorganic fibers, fillers, various auxiliaries, and the like can be appropriately blended according to the desired quality.

[0007] It is preferable to use bamboo pulp in combination with wood pulp from broad-leaved trees, since a base paper excellent in formation can be obtained. However, if the bamboo pulp content is low, the effects of the present invention may not be sufficiently obtained. More preferably, the cellulose fiber is 10 to 80% by weight of bamboo pulp and 20 to
Contains 90% by weight. In this case, further pulp may be contained.

Further, bamboo pulp has a content of fine fibers having a fiber length of 0.2 mm or less of about 10 to 20% by weight as compared with wood pulp or the like, but preferably has a fine fiber content of 5% by weight or less. More preferably, the content of fine fibers is 1
By performing the fine fiber removal treatment so as to be not more than the weight%, all of the dimensional stability, heat resistance, and electric characteristics are improved. The method for removing the fine fibers is not particularly limited, and examples thereof include a method by a screen treatment and a method by centrifugal dehydration through a wire.

[0009]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. The percentages in Examples and Comparative Examples all indicate weight%. The bamboo pulp used in the present invention, the method for removing fine fibers of bamboo pulp, the method for measuring the fine fiber content of bamboo pulp, the method for evaluating resin impregnation, the method for manufacturing a laminate, and the method for evaluating the dimensional stability of a laminate are as follows. It is. Bamboo pulp Bamboo pulp used in Examples and Comparative Examples of the present invention is:
The conditions of pulping with Thai bamboo pulp (Thailand: Phoenix cooked product) are as follows. Kraft cooking is performed in the Kamiya continuous digester and the bleaching sequence C-
After bleaching with EHD, a paper-milling treatment was performed to obtain a dry pulp sheet. Fiber length of obtained bamboo pulp 0.2 mm
The following fine fiber content was 14%. This bamboo pulp was bamboo pulp A, and bamboo pulp obtained by the fine fiber removal method described below and having a fiber length of 0.2 mm or less and a fine fiber content of 0.5% by weight was bamboo pulp B, and bamboo pulp A and bamboo pulp B were 7:20. Mixed at a ratio of 0.2mm fiber length
The bamboo pulp prepared to have the following fine fiber content of 4% by weight is referred to as bamboo pulp C.

A method for removing fine fibers from bamboo pulp A method for removing fine fibers from bamboo pulp is described below.
Using a fiber length sieving machine (trade name: Bauer sieving machine / manufactured by Tozai Seiki Co., Ltd.), the water injection amount was 8.3 l / g.
The mixture was stirred under water for 15 minutes to remove fibers passing through 150 mesh. Measurement method of fine fiber content of bamboo pulp The measurement of fine fiber content of bamboo pulp was performed by image analysis of a fiber projection diagram. Fiber length distribution measuring instrument (trade name: FS
-200, manufactured by KAJAANI Co., Ltd.), the fiber length and the fiber width of each fiber are measured, and each fiber is weighed from these values, whereby the content (weight) of the fine fiber having a fiber length of 0.2 mm or less is obtained. %).

Evaluation method of formation The evaluation of formation was evaluated in three stages: (良 い) for those which were good by visual observation, (△) for those which were somewhat bad but had no practical problems, and (×) for those which were not practical for practical use. evaluated.

A method for producing a laminate is performed by impregnating a laminate base paper with a commercially available water-soluble phenol resin (trade name: Shaunol BRL-2854 / manufactured by Showa Polymer Co., Ltd.) By drying at a temperature for 5 minutes, a primary prepreg having a resin to base material ratio of 15:85 was prepared, and a commercially available oil-modified phenol resin (trade name: Shaunol BLS) was added to the primary prepreg.
-3122 / Showa Polymer Co., Ltd.) at 100 ° C.
At a temperature of 5 minutes to prepare a prepreg having a ratio of resin and base material of both water-soluble phenol resin and oil-modified phenol resin of 50:50. Next, eight prepregs were laminated, and 100 kg /
A phenolic resin laminate was obtained by pressure molding at 60 cm ² for 60 minutes. Evaluation method of dimensional stability of laminate The evaluation method of dimensional stability of the laminate was performed by measuring a dimensional change rate by the following method. Span 200 on laminate
mm, and measure the dimension between the gauges before and after heating / cooling with a high-precision two-dimensional coordinate measuring device (trade name: Digital Reader DR)
-550-D / Dainippon Screen Manufacturing Co., Ltd.). The dimensional change rate α is obtained from the following equation. When a hand-made sheet is used, there is no anisotropy in the sheet, and the average value of four points is shown. Fundamentally, the closer the dimensional change rate is to 0%, the better the dimensional stability is. α (%) = [(L ₀ −L ₁ ) / L ₀ ] × 100 L ₀ : length between gauge points before heating and cooling. L ₁ : length between gauge marks after heat treatment at 160 ° C. for 1 hour.

Evaluation method of heat resistance of laminate The heat resistance of the laminate was measured by measuring the solder heat resistance by the following method. A test piece (25 mm × 25 mm) was immersed in a molten solder bath (260 ° C. ± 1 ° C.), and the time until a popping sound was measured. This time (second) was used as an index of heat resistance. The higher the value, the better the heat resistance. Method for Evaluating Electrical Characteristics of Laminated Plate The electrical characteristics of the laminated plate were evaluated by measuring the insulation resistance of the substrate according to JIS-C6481. The measurement was performed under normal conditions and after boiling (100 ° C., 2 hours). The higher the insulation resistance, the better the electrical characteristics.

Example 1 A pulp slurry composed of bamboo pulp A was mixed with a melamine resin (trade name: Sumiretz Resin AC8 / Sumitomo Chemical Co., Ltd.)
1% with respect to pulp and hand-made in a laboratory square hand-making machine to obtain a basis weight of 126 g / m ² and a density of 0.5 g.
/ Cm ³ was obtained. A laminate was prepared using the laminate base paper. Example 2 Except that bamboo pulp C was used instead of bamboo pulp A,
A laminate base paper and a laminate were obtained in the same manner as in Example 1.

Example 3 Except that bamboo pulp B was used in place of bamboo pulp A,
A laminate base paper and a laminate were obtained in the same manner as in Example 1.

Example 4 A pulp formulation was bamboo pulp A 15%, unbeaten bleached kraft pulp from acacia wood from South Africa (hereinafter simply LBK)
A laminate base paper and a laminate were obtained in the same manner as in Example 1 except that 85% was also used. Example 5 A laminate base paper and a laminate were obtained in the same manner as in Example 1 except that the pulp content was 75% bamboo pulp A and 25% unbeaten bleached kraft pulp from acacia wood from South Africa. Example 6 A laminate base paper and a laminate were obtained in the same manner as in Example 1 except that the pulp was blended with bamboo pulp A 85% and unbeaten bleached kraft pulp from South African acacia wood 15%.

Comparative Example 1 Instead of bamboo pulp A, unbeaten bleached kraft pulp (LBKP) from acacia wood from South Africa was used (100%).
Except for using, a laminate base paper and a laminate were obtained in the same manner as in Example 1. Comparative Example 2 Cotton linter pulp was replaced with bamboo pulp A (1
(00%), except that a laminate base paper and a laminate were obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the laminates obtained in the examples and the comparative examples. The fine fiber content of bamboo pulp A is 14%, the fine fiber content of bamboo pulp B is 0.5%, the fine fiber content of bamboo pulp C is 4%, LB
The fine fiber content of KP was 2.5%. As is clear from Table 1, when LBKP is replaced with linter pulp, heat resistance and electrical properties are improved, but dimensional stability is deteriorated (comparison between Comparative Example 1 and Comparative Example 2). Dimensional stability is comparable and heat resistance and electrical properties are improved (Comparative Example 1 and Example 1). Further, by removing the fine fibers of the bamboo pulp, all of the dimensional stability, heat resistance and electrical properties are improved (comparison between Example 1 and Examples 2 and 3). Further, when bamboo pulp and LBKP were used in combination, a laminated base paper having good formation was obtained.

[0018]

[Table 1]

[0019]

As described above, the present invention has an effect of providing a laminate base paper most suitable for producing a laminate having good dimensional stability, heat resistance and electrical characteristics of the laminate. Therefore, its industrial significance is extremely large.

Claims (4)

[Claims] 1. A base paper for a laminate comprising cellulose fibers, wherein the cellulose fibers comprise bamboo pulp. 2. The bamboo pulp having a cellulose fiber content of 10 to 80.
The base paper for laminated board according to claim 1, wherein the base paper contains 20% to 90% by weight of wood pulp. 3. The laminated base paper according to claim 1, wherein the content of the fine fibers having a fiber length of 0.2 mm or less in the bamboo pulp is 5% by weight or less. 4. A laminate obtained by laminating a prepreg impregnated with a thermosetting resin on the laminate base paper according to claim 1, 2 or 3, and molding the laminate.