JPH06146193A - Base paper for laminated electric-insulating sheet - Google Patents

Abstract

PURPOSE:To obtain the subject base paper having excellent affinity to resins and improved heat resistance by specifying a content of hemicellulose in a bleached kraft pulp and a degree of crystallization of cellulose. CONSTITUTION:This base paper for a laminated sheet is produced from a bleached kraft pulp having a hemicellulose content reduced to <=15% and a degree of crystallization increased to >=1.25. It is produced by digesting at about 160 deg.C and at about 25% of an effective alkali addition ratio and adding oxygen- and alkali-bleaching steps in an earlier stage of multistage bleaching process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like paper base material used for an electrically insulating laminated board, and more particularly to a laminated board base paper used for producing a laminated board having good heat resistance. .

[0002]

2. Description of the Related Art Laminated base paper is processed with phenol resin, polyester resin, etc., and is mainly used as a printed wiring board in a wide range of fields such as consumer electronic devices and industrial electronic devices.

In recent years, as the performance of electronic parts has become more sophisticated, the operating conditions of printed wiring boards have become more severe, and the physical properties required for electrical insulating laminated board base paper have become even more severe. In particular, in order to cope with higher density of wiring on the substrate, there is an increasing demand for a laminated plate having good heat resistance, punching workability, dimensional stability and electrical insulation. Further, due to the speeding up and the density increasing of the soldering process and the increase in the amount of heat generated from the electronic components mounted on the substrate, the required level of heat resistance is becoming particularly strict.

Conventionally, bleached kraft pulp produced from wood has been widely used for laminated board base paper, but at present, satisfactory suitability for properties such as heat resistance has not been obtained. For this reason, there is a method using a pulp having a high α-cellulose content, a dissolving pulp having a high degree of refinement, and a cotton linter pulp (JP-A-60-7952 and JP-A-64-14398). Although excellent heat resistance and punching workability can be obtained, the dimensional stability is remarkably inferior because the fiber is significantly bent.

There is also a method (Japanese Unexamined Patent Publication No. 2-175996) in which cooking conditions during production of kraft pulp are changed to keep the 10% KOH-soluble content low and bleached kraft pulp with less fiber bending is used. At present, it cannot be said that the improvement of heat resistance is sufficient despite the high degree. Moreover, no mention is made of the contribution of the crystallinity of cellulose to the heat resistance of the laminate.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides another laminated board by improving the affinity between the laminated board base paper and resin during the production of the laminated board and improving the heat resistance of the laminated board base paper itself. It is intended to provide a laminated board base paper excellent in heat resistance without impairing the characteristics.

[0007]

The laminated board base paper of the present invention is characterized by using bleached kraft pulp (BKP) having a hemicellulose content of 15% or less and a cellulose crystallinity of 1.25 or more.

The laminated board is manufactured by impregnating a laminated board base paper with a phenol resin and thermocompressing it. On this occasion,
The heat-resistant temperature of phenolic resin was 300 ℃ or higher, whereas the heat-resistant temperature of laminated board was as low as 250 ℃. This indicates that it is necessary to improve the heat resistance of the laminated base paper in order to improve the heat resistance of the laminated board.

We have found that the following requirements can be mentioned in order to obtain a laminated board base paper having a high heat resistant temperature.

(A) Of the constituent components of pulp, the decomposition temperature is
It is known to be as low as 200 ° C (Masaki Mangi / other, Nikka 19
75.4.783) Low hemicellulose content.

(B) A large amount of crystalline regions of cellulose, which is a main constituent of pulp.

[0012] Hemicellulose is used in conventional laminated board base paper.
It is contained in 20%, and these pyrolysis gases cause blistering of the laminate during heating. Therefore, the heat resistance of the laminate is improved by reducing the hemicellulose content. When the laminate is further heated, it is presumed that the pyrolysis of cellulose starts in the non-crystalline region. Further, in the crystalline region, the hydroxyl groups are consumed by hydrogen bonds and become entirely hydrophobic, so that the affinity with the resin is improved. Therefore, the heat resistance of the laminate is improved by improving the crystallinity of cellulose. As described above, there are two governing factors of the heat resistance of the laminated base paper, and when both of them are satisfied, the present invention exerts the effect.

Next, the relationship between each factor and the present invention will be described in detail. The conventional laminated board base paper uses bleached kraft pulp (LBKP) which has been subjected to multi-stage bleaching after being cooked by a KP method using Hokkaido hardwood (birch etc.). When the content of hemicellulose in this base paper was measured, it was about 20%. In the present invention, it was attempted to improve the heat resistant temperature of the laminate by reducing the hemicellulose content, as a result 15
It has been found that the heat resistance temperature is greatly improved by controlling the crystallinity to be not more than 0.1% and the crystallinity to be not less than 1.25.

In order to realize the present invention, there is no particular limitation, but it is necessary to select a raw material containing less hemicellulose, or to improve the cooking method and the bleaching method. Regarding the former, various domestic timbers, acacia, mangrove, apiton and eucalyptus lumber were examined as wood raw materials for these pulps. As a result, Eucalyptus grandis (hereinafter referred to as E. grandis ) and Eucalyptus saligna (hereinafter referred to as E. saligna) species are used among eucalyptus materials to improve heat resistance without impairing other laminated plate properties. Was found to be advantageous.

It is considered that this is because the content of hemicellulose and lignin in these materials is small, so that it is extremely easy to set the cooking and bleaching conditions. As a result, it is presumed that a pulp having a low hemicellulose content and a high crystallinity of cellulose could be obtained, and a pulp having a straight fiber form could be obtained.

With regard to the latter, it was found that the hemicellulose content can be effectively reduced by adding bleaching with oxygen and alkali to the preceding stage of multi-stage bleaching with chlorine, alkali, hypochlorous acid and chlorine dioxide.

Further, the crystallinity of cellulose in the conventional laminated board base paper was measured to be about 1.10. In the present invention, an attempt was made to improve the heat resistant temperature of the laminate by reducing hemicellulose and improving the crystallinity of cellulose, and it was found that the heat resistant temperature is greatly improved by setting the crystallinity to 1.25 or more.

In the present invention, hemicellulose is reduced and the crystallinity of cellulose is improved by the following method. Conventional hardwood pulp for laminated board base is cooked, for example, at a cooking temperature of 170 ° C and an effective alkali addition rate of 15%.
It is done by cooking to a value of 12-15. On the other hand, in the present invention, the cooking temperature is about 160 ° C., the effective alkali addition rate is about 25%, and the specific multi-stage bleaching is performed as described above to realize low hemicellulose formation while maintaining high crystallinity. .

[0019]

EXAMPLES The effects of the present invention are shown below by examples.
However, the present invention is not limited to this embodiment.

(Example 1) Using hardwood chips from Hokkaido, kraft cooking was carried out under the conditions shown in Table 1 to obtain an unbleached pulp (UKP) having a K value of 10. This UKP was subjected to multi-stage bleaching with oxygen, alkali, chlorine, alkaline sodium hypochlorite and chlorine dioxide to obtain bleached kraft pulp (BKP). Using this BKP, a laminated base paper having a basis weight of 135 g / m ² and a density of 0.5 g / cm ³ was obtained by handmaking. This base paper was impregnated with a commercially available alcohol-dissolved phenol resin (BLS-3122: Showa Highpolymer Co., Ltd.) and dried to prepare a prepreg. Next, 8 sheets of prepreg and 1 sheet of copper foil with adhesive are laminated and thermocompressed at 155 ° C, 100kg / cm ² for 60 minutes,
After cooling for 30 minutes under pressure, resin content 50%, plate thickness
A 1.6 mm single-sided copper-clad laminate was obtained.

Table 1 shows the laminated plate characteristics such as the heat resistant temperature of the laminated plate obtained by this method. As is clear from Table 1, the heat resistance (heat resistant temperature in air and heat resistance of solder) was greatly improved as compared with Comparative Examples 1 to 3 below while maintaining laminated plate characteristics such as punching workability and dimensional stability. .

Example 2 Eucalyptus (E. gr ) from South Africa
Kraft cooking was carried out using andis and E. saligna ) chips under the conditions shown in Table 1 to obtain UKP having a K value of 10. This UKP was subjected to multi-stage bleaching with oxygen, alkali, chlorine, alkaline sodium hypochlorite and chlorine dioxide to obtain BKP. This B
A laminated base paper having a basis weight of 135 g / m ² and a density of 0.5 g / cm ³ was obtained by hand using KP. Using this laminated board base paper, a laminated board was obtained in the same manner as in Example 1.

Table 1 shows the characteristics of the laminated plate obtained by this method, such as the heat resistant temperature of the laminated plate. As is clear from Table 1, the heat resistance (heat resistant temperature in air and heat resistance of solder) was greatly improved as compared with Comparative Examples 1 to 3 below while maintaining laminated plate characteristics such as punching workability and dimensional stability. .

EXAMPLE 3 Eucalyptus (E. gr ) from South Africa
Andis and E. saligna ) chips were used for kraft cooking under the conditions shown in Table 1 to obtain UKP having a K value of 13. This UKP was subjected to multi-stage bleaching with chlorine, alkaline sodium hypochlorite and chlorine dioxide to obtain BKP. Using this BKP, a laminated base paper having a basis weight of 135 g / m ² and a density of 0.5 g / cm ³ was obtained by handmaking. A laminated board was obtained in the same manner as in Example 1 using this laminated board base paper.

Table 1 shows the laminated plate characteristics such as the heat resistant temperature of the laminated plate obtained by this method. As is clear from Table 1, the heat resistance (heat resistant temperature in air and heat resistance of solder) is greatly improved as compared with Comparative Examples 1 to 3 below while maintaining laminated plate characteristics such as punching workability and dimensional stability. It was

(Comparative Example 1) Hardwood chips from Hokkaido were used for kraft cooking under the conditions shown in Table 1 to obtain UKP having a K value of 13. This UKP is subjected to multi-stage bleaching with oxygen, alkali, chlorine, alkaline sodium hypochlorite and chlorine dioxide, and B
I got KP. Using this BKP, basis weight 135 g / m ² , density
A 0.5 g / cm ³ laminated board base paper was obtained by handmaking. A laminated board was obtained in the same manner as in Example 1 using this laminated board base paper.

Table 1 shows the laminated plate characteristics such as heat resistant temperature of the laminated plate obtained by this method.

Comparative Example 2 Using hardwood chips from Hokkaido, Kraft cooking was carried out under the conditions shown in Table 1 to obtain UKP having a K value of 10. This UKP was subjected to multi-stage bleaching with chlorine, alkaline sodium hypochlorite and chlorine dioxide to obtain BKP. Using this BKP, a laminated base paper having a basis weight of 135 g / m ² and a density of 0.5 g / cm ³ was obtained by handmaking. A laminated board was obtained in the same manner as in Example 1 using this laminated board base paper.

The laminated plate characteristics such as heat resistant temperature of the laminated plate obtained by this method are shown in Table 1.

Comparative Example 3 Using hardwood chips produced in Hokkaido, Kraft cooking was carried out under the conditions shown in Table 1 to obtain UKP having a K value of 13. This UKP was subjected to multi-stage bleaching with chlorine, alkaline sodium hypochlorite and chlorine dioxide to obtain BKP. Using this BKP, a laminated base paper having a basis weight of 135 g / m ² and a density of 0.5 g / cm ³ was obtained by handmaking. A laminated board was obtained in the same manner as in Example 1 using this laminated board base paper.

Table 1 shows the laminated plate characteristics such as heat resistant temperature of the laminated plate obtained by this method.

[0032]

* 1: Effective alkali addition rate (NaOH + 1) / 2NaS

* 2: UKP K value: Based on JIS P8206.

* 3: 10% KOH-soluble component Based on JIS P8101.

* 4: Hemicellulose content The hemicellulose content was measured as follows.
The pulp was hydrolyzed in accordance with Tappi's standard method (T-249hm-85), and pentose and hexose, which are hydrolysates of hemicellulose components, were separated and quantified using a high performance liquid chromatogram.

* 5: Crystallinity of Cellulose The crystallinity of cellulose was measured as follows. When the pulp is subjected to ¹³ C-CP / MS-NMR, it is assigned to each carbon in the glucose skeleton of cellulose. At this time, since the signal at the C4 position was well separated between crystalline cellulose and non-crystalline cellulose, the heights of these signals were measured and calculated by the following formula. Crystallinity = Crystalline C4 signal / Amorphous C4 signal

* 6: Heat-resistant temperature in air Maximum temperature at which blisters do not occur after heating for 5 minutes in a blow dryer.

* 7: Solder heat resistance According to JIS C6481.

* 8: Insulation resistance According to JIS C6481 and JIS K6911.

* 9: Low temperature punching workability The die has hole hole wall intervals of 0.8, 1.0, 1.2 and 1.6 mm, and a pair of square holes of 1 mm x 2 mm and a clearance of 0.05 mm on one side of the punch and the die. Punching is carried out by changing the temperature of the surface of the laminated plate using the test die, and the surface after punching and the state of the hole cut are judged according to ASTM D617 and are classified into excellent, good, good and bad four stages. Evaluated to.

* 10: Coefficient of thermal expansion and contraction Using a push rod type thermal dilatometer, the expansion was 50 to 150 ° C. and the cooling was 150 ° C. under the conditions of a load of 5 g and a heating rate of 5 ° C./min (cooling is allowed to cool). It was carried out in the temperature range from 1 to 50 ° C. From this measurement result, it was evaluated in four grades of excellent, good, good and bad.

[0043]

As is apparent from Table 1, the base papers according to the present invention as shown in Example 1 in which specific cooking and bleaching conditions are set and Examples 2 and 3 using eucalyptus wood from South Africa are used as the base material. Regarding the quality of the single-sided copper-clad laminate, the heat resistance was good, and the overall laminate properties such as electrical characteristics, low temperature punching workability and dimensional stability were good. Therefore, its industrial significance is extremely large.

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[Procedure amendment]

[Submission date] February 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

In order to realize the present invention, there is no particular limitation, but it is necessary to select a raw material containing less hemicellulose, or to improve the cooking method and the bleaching method. Regarding the former, various domestic timbers, acacia, mangrove, apiton and eucalyptus lumber were examined as wood raw materials for these pulps. As a result, in order to improve the heat resistance without deteriorating other laminated plate properties, among the Eucalyptus materials, especially Eucalyptus grandis (hereinafter referred to as E. grandis ) species and Eucalyptus saligna (hereinafter referred to as E. sal).
It has been found to be advantageous to use the species ( designated as igna ).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Inokari 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Sanyo Kokusaku Pulp Co., Ltd. Product Development Laboratory

Claims (2)

[Claims] 1. A base paper for electrically insulating laminated boards using bleached kraft pulp having a hemicellulose content of 15% or less and a cellulose crystallinity of 1.25 or more. 2. The bleached kraft pulp according to claim 1 is used as a tree species in Eucalyptus grandis (Eucalyptus gr).
andis ) species or Eucalyptus saligna (Eucalyptu
The electrical insulating laminated board base paper according to claim 1, which is manufactured by using a Eucalyptus material of Ss saligna type.