JPH10266094A - Laminated plate base paper and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base paper of a laminated plate that is excellent in the penetrability of hydrophilic varnish and coating suitability. SOLUTION: This base paper for a laminated plates is prepared so that it has 30 deg.<= contact angle <70 deg. to the aqueous solution of polyvinyl alcohol having type B viscosity of 15 cPs at 20 deg.C and has an average pore diameter of 12-16 μm, when it is dipped in water, then freeze-dried, by selecting the kinds of materials and the production conditions of the pulp and applying surfactants and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laminate base paper used for a paper base thermosetting resin laminate,
In particular, the present invention relates to a laminated base paper having an improved penetration rate of a hydrophilic aqueous varnish into the base paper.

[0002]

2. Description of the Related Art A laminate base paper is impregnated with a thermosetting resin such as a phenolic resin or a polyester resin, and then laminated and thermally pressed to form a paper base thermosetting resin laminate. It is mainly used as a printed circuit wiring board. In recent years, high reliability has been demanded even for consumer laminates using a paper base material, and a production method based on two-stage impregnation for increasing the affinity between a resin and a paper base material has become mainstream.

[0003] Conventionally, the application of resin to the base paper of a laminated board has been performed by immersing the base paper in a phenol resin and then scraping off excess resin with a squeeze roll. However, as the required quality has advanced in recent years, in order to enhance the adhesion between the resin and the paper base material, a hydrophilic varnish composed of an amino-modified phenol resin has been impregnated (primarily impregnated) and then a lipophilic varnish composed of a phenol resin. (Secondary impregnation) is the mainstream. In addition, price competition for consumer laminates is intense, and the processing speed of these is increasing year by year.

[0004] When the distribution of the resin due to the primary impregnation is not uniform, the distribution of the phenol resin and the flame retardant applied thereafter is also non-uniform, and the quality such as tracking resistance, silver migration resistance and flame retardancy is problematic. Is more likely to cause

[0005] As a method for making the primary impregnation uniform, Japanese Patent Application Laid-Open No. 8-169014 discloses a method of applying a hydrophilic varnish to a laminate base paper with a roll coater, setting a guide roll, and applying the laminate base paper. A method for controlling the area in contact with a roll is disclosed.

[0006] As a method for improving the permeability of a base paper for laminated board,
Short fibers (fiber length) in pulp fiber, which is a raw material of laminated base paper
Methods for removing fractions of pulp fibers having a diameter of 0.1 to 0.2 mm or less are disclosed in JP-A-58-180086, JP-A-62-184200, JP-A-7-26497, and the like. However, it is not practical to use these methods for actual production of laminated base paper because there are many factors that lead to cost increase, such as complicated processes and increased outflow materials.

[0007] The penetration of varnish into the laminated base paper can be regarded as a kind of liquid penetration into the porous body, and the following Lucas-Washburn equation can be applied.

(Equation 1) (Where h = penetration distance, γ = surface tension, r = pore diameter,
(θ = contact angle, t = permeation time, η = viscosity) According to this equation, factors on the base paper side relating to the permeation distance in a fixed time, that is, the permeation speed, are the pore diameter and the contact angle. Therefore, a base paper having a large pore diameter and a small contact angle is desirable for high-speed impregnation, but a laminated base paper that sufficiently satisfies these conditions can be obtained in relation to restrictions on base paper production or other base paper characteristics. Had not been.

Regarding the relationship between the contact angle and the permeability, in the field of ink jet recording paper, a method for improving the printing characteristics by specifying the contact angle between the ink and the paper is disclosed in
63-1578, JP-A-63-87279, JP-A-6-1363
No. 07, JP-A-6-136308. However, these methods correspond to the adjustment of the components of the ink, and in terms of allowing a very small amount of ink to penetrate the recording paper, the large amount of resin-containing liquid required for the impregnated paper as in the present invention. In that the permeability of
It also differs greatly in terms of the use of a resin-impregnated laminate for hot pressing.

[0009] Regarding the pore diameter, attention has hitherto been focused only on the pore diameter of the laminate base paper before the hydrophilic varnish impregnation. However, even if the pore diameter of the base paper is increased by removing short fibers, reducing the density, etc., after contact with the hydrophilic varnish, the pore diameter in the state in which the pulp fibers are swollen does not necessarily become sufficiently large, which is expected. No permeability was obtained.

[0010]

An object of the present invention is to provide a laminated base paper and a method for producing the same, which improve the permeability of the hydrophilic varnish into the laminated base paper and the suitability of applying the hydrophilic varnish by a roll coater. Is to do.

[0011]

Means for Solving the Problems The present inventors have prepared a polyvinyl alcohol (PV) having a B-type viscosity of 15 cps at 20 ° C.
A) The contact angle of the aqueous solution with the laminated base paper is 30 ° or more and 75 °
The average pore diameter measured by immersing the base paper in water and swelling it in water and then freeze-drying it is 12 μm or more and less than 16 μm.
It has been found that the use of a base paper having a thickness of not more than μm effectively improves the permeability of the hydrophilic varnish and the suitability for coating with a roll coater.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The contact angle of the present invention is desirably defined by using a varnish for primary impregnation to be actually applied, but since the resin composition of the varnish differs depending on the laminate manufacturer, the contact angle is integrally evaluated. It is not possible. As the primary impregnating varnish, a water-soluble phenol resin, an amino-modified phenol resin, a melamine resin, etc., water, acetone, a hydrophilic varnish dissolved in a polar solvent such as methanol has a viscosity of 10 to 50.
Many are about cps. Therefore, when the standard solution which can be substituted for these is examined diligently, by using the standard solution as a PVA solution having a B-type viscosity of 15 cps at 20 ° C., it is necessary to define an objective allowable range which is an index of varnish permeability. Became possible.

Conventionally, the contact angle of the laminated base paper used for this standard solution was about 90 ° to 115 °, but by setting this to 30 ° or more and less than 75 °, the coating suitability for primary impregnation was improved. Was greatly improved. A smaller contact angle is advantageous for permeability, but it is difficult to make the contact angle less than 30 °.

[0014] The contact angle of the laminate base paper to the varnish is 30 °
As a method of making the angle less than 75 °, a method of increasing the unevenness of the surface of the laminated base paper and a method of making the surface of the laminated base paper hydrophilic are considered.

As a method for increasing the unevenness of the surface of the laminated base paper, there is a selection of the type of pulp fiber. It is considered that the surface roughness of the laminated base paper depends on the type of the raw pulp, and thin pulp fibers such as beech and oak are formed into a flat ribbon shape by the paper making process and have a smooth surface. On the other hand, since thick-film pulp fibers such as mangrove, acacia, and eucalyptus maintain a tubular shape even after a papermaking process, the base paper surface has fine irregularities. Therefore, it is preferable to use a material which is a pulp fiber having such a thick film in order to reduce the contact angle.

As a method for making the surface of the laminated base paper hydrophilic, a method of hydrating a hydroxyl group of cellulose of pulp fiber and a method of adding a surfactant can be considered. Pulp fibers are composed of cellulose and hemicellulose, each of which has a hydrophilic molecular structure and is considered to be a relatively hydrophilic surface structure. However, while cellulose is mostly crystalline, hemicellulose is mostly amorphous,
In order to further improve the hydrophilicity of the pulp fiber, a method of reducing the content of hemicellulose and increasing the proportion of crystalline cellulose to regularly arrange hydroxyl groups on the pulp surface can be mentioned.

As described above, it is possible to make the contact angle 30 ° or more and less than 75 ° by using a laminated base paper made of thick fibers having a small hemicellulose content. By including a nonionic surfactant in the board base paper, it is possible to make the contact angle of 30 ° or more and less than 75 ° even with a laminated board base paper having properties other than those described above.
As a method of adding a nonionic surfactant, a method of applying a nonionic surfactant solution to a base paper of a laminate using a size press coater, a gate roll coater, a curtain coater, or the like, or a method of applying a laminate base paper to a nonionic surfactant solution The impregnation method may be used.

As the surfactant used in the present invention, when an ionic surfactant is used, there is a possibility that the electrical characteristics of the laminate will be remarkably deteriorated. Therefore, it is essential to use a nonionic surfactant. Nonionic surfactants include polyethylene glycol nonyl phenyl ether,
Examples thereof include polyoxyethylene nonylphenyl ether, polyoxyethylene alkyl ether, octylphenoxypolyethoxyethanol, and the like. The amount of the nonionic surfactant added is preferably 0.05% by weight or more and 0.1% by weight or less based on the base paper of the laminated board. If the addition amount is less than 0.05% by weight, it is difficult to reduce the contact angle to 30 ° or more and less than 75 °, and even if it exceeds 0.1% by weight, the permeability of the hydrophilic varnish is not improved. It reaches a plateau.

Further, in the present invention, noting that the swelling of the laminated base paper is deeply involved in the permeation of the hydrophilic varnish, the laminated base paper is immersed in water and then lyophilized by freeze-drying. The average pore diameter was measured while being fixed, and it was found that the permeability of the hydrophilic varnish was more effectively improved by using a laminate base paper having an average pore diameter of 12 μm or more and 16 μm or less.

The hydrophilic varnish is characterized in that it penetrates while swelling by breaking hydrogen bonds between pulp fibers. Therefore, in order to allow the hydrophilic varnish to penetrate uniformly and quickly, a base paper having a large pore diameter when the base paper of the laminated board swells is more advantageous. Therefore, even with base paper having a relatively large pore diameter before impregnation, sufficient permeability cannot be obtained if the pore diameter after swelling is 12 μm or less due to the effects of pressing conditions, added chemicals, and the like.

The average pore diameter of the conventionally used laminated base paper was about 6 to 8 μm before swelling and about 8 to 10 μm after swelling. However, by increasing the pore diameter after swelling to 12 μm or more, Effectively improved. From the viewpoint of permeability, the larger the pore diameter after swelling is, the more advantageous it is. However, if it exceeds 16 μm, problems such as excessive varnish adhesion and a decrease in wet paper strength are caused.

As a method of increasing the pore diameter after swelling, a method of reducing the bonding strength between fibers is effective.
Examples of this method include a method using pulp having a low hemicellulose content, a method using thick pulp fibers, and a method of reducing the amount of a wet paper strength enhancer to be added. The reduction in wet strength is limited because the risk of paper breakage during the impregnation of the hydrophilic varnish increases. Therefore, from this point of view, it is considered that a method using a thick pulp with a small amount of hemicellulose is effective.

The effect of the present invention is remarkably exhibited when a hydrophilic varnish is actually impregnated with a roll coater or the like.
By measuring the A-permeation time, it is possible to easily evaluate in advance in advance. In general, a castor oil penetration test and a Krem water absorption test are known as methods for evaluating the permeability of base paper for laminated boards. The castor oil permeability is excellent for evaluating the permeability of a lipophilic resin without swelling, but is not suitable for evaluating a hydrophilic varnish. The Klemm water absorption is a method of measuring the penetration distance of water, but the measurement time is as long as 1 and 10 minutes, which is not suitable for evaluation of high-speed coating suitability.

Therefore, in the present invention, the coating time of the hydrophilic varnish was predicted by measuring the time until 10 μl of the PVA standard solution used for measuring the contact angle penetrated. When compared with the evaluation results of an actual coating machine, good coating suitability was obtained when the penetration time of PVA was within 10 seconds.

[0025]

[Action] The contact angle with the PVA standard solution was as large as 90 ° or more in the case of untreated base paper. However, by using thick pulp fiber and adding a nonionic surfactant, the contact angle was reduced to less than 75 °. In addition, the wettability of the hydrophilic aqueous varnish to the base paper was greatly improved, and the uniform coating with a roll coater and the initial permeability were improved.

In addition, the use of pulp of a grade having a thick wall film,
By reducing the hemicellulose content, etc., the pore diameter in the base paper accompanying the penetration of the hydrophilic varnish is increased from a small one of 10 μm or less to a large one of 12 μm or more of the ordinary base paper, whereby the penetration rate of the aqueous varnish is extremely high. became.

[0027]

EXAMPLES The effects of the present invention will be described below with reference to examples. However, the present invention is not limited by this embodiment. The following items were measured and evaluated for the laminated base paper obtained in the examples and comparative examples. Runkel ratio: The value obtained by dividing twice the thickness of the pulp fiber wall membrane by the width of the lumen. Hemicellulose content: The pulp was analyzed by high performance liquid chromatography after acid hydrolysis. Measurement of contact angle: Automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd.):
Using CA-Z type), the standard solution is a sample (laminate base paper)
The contact angle immediately after contact with the sample was measured. The standard solution contains P
Using a VA (Kuraray Co., Ltd .: PVA117) solution,
The mixture was diluted to 3% and adjusted so that the B-type viscosity at 20 ° C became 15 cps. Measurement of average pore diameter: measured using a mercury porosimeter (manufactured by Shimadzu Corp .: Pore Sizer 9300 type),
The pore diameter at which mercury was injected into the pores of 50% of the total pore volume was defined as the average pore diameter. For the measurement of the pore diameter after swelling, a sample obtained by immersing the laminate base paper in water for 30 minutes and then freeze-drying was used. Castor oil permeability: Ten test pieces of 20 mm square are cut out from the base laminate paper. Place the container containing castor oil in a thermostat maintained at a water temperature of 30 ° C, and control the temperature of the castor oil at 30 ° C. The test piece was dropped horizontally on the castor oil liquid level, and the time from when the test piece came into contact with the castor oil until the caster oil uniformly penetrated the upper surface of the test piece was measured. Measure each of the five test pieces on the front and back of the laminated base paper and calculate the average value. Klemm water absorption: Measured according to JIS P8141. PVA penetration time: 10 μl of standard solution used for measurement of contact angle
Was added to the base paper for laminate, and the time until the infiltration was completed was measured. Coating aptitude: A water-based varnish is applied to the base paper of the laminated board with a roll coater and evaluated as ◎ when the varnish has uniformly penetrated and as × when there is unevenness in the penetration, and evaluated in four steps of ◎, ○, △, × did. In the case of Δ and ×, defective impregnation occurs, which adversely affects the suitability of the laminate.

[Example 1] Acacia lumber chips produced in South Africa, which are relatively thick-film grades with a Runkel ratio of 1.2, are kraft cooked, and then oxygen, chlorine, alkali, sodium hypochlorite,
Multi-stage bleaching with chlorine dioxide was performed to obtain bleached kraft pulp (BKP). At this time, the hemicellulose content was reduced to 12 by increasing the amount of alkali added during cooking and strengthening bleaching.
% And less than 20% of Comparative Example 1. Using this BKP, a laminated base paper having a basis weight of 125 g / m ² and a density of 0.5 g / cm ³ was obtained by hand-making. The wet strength agent was added so that the wet strength was 0.5 kg / 1.5 cm. By the above method, a base paper having a low contact angle with the standard solution of 70 ° and a large average pore diameter after swelling of 15 μm was obtained. As is clear from Table 1, the PVA penetration time was short and the hydrophilicity was low. A base paper having good varnish permeability was obtained.

[Example 2] Hokkaido beech chips, which are relatively thin grades with a Runkel ratio of 0.6, are kraft digested and then subjected to multi-stage bleaching with oxygen, chlorine, alkali, sodium hypochlorite, and chlorine dioxide. BKP was obtained. At this time, the content of hemicellulose was reduced to 12%, which was less than 20% of Comparative Example 2, by increasing the amount of alkali added during cooking and strengthening bleaching. Using this BKP, a basis weight of 125
g / m ² , density 0.5 g / cm ³ , wet paper strength 0.5 kg
/1.5 cm of laminated base paper was obtained by hand-making. A 0.1% solution of a nonylphenyl surfactant (Nonipol 60, manufactured by Sanyo Chemical Industries, Ltd.) was applied to the base paper by a size press method. With the above method, the contact angle with the standard solution
A laminated base paper having a low average temperature of 55 ° and a large average pore diameter of 13 μm after swelling can be obtained. As is clear from Table 1, a base paper having a short PVA penetration time and a good permeability to a hydrophilic varnish can be obtained. Was.

Example 3 Acacia wood chips from South Africa, which is a relatively thick-film grade having a Runkel ratio of 1.2, are kraft-cooked, and then oxygen, chlorine, alkali, sodium hypochlorite,
Multi-stage bleaching with chlorine dioxide was performed to obtain bleached kraft pulp (BKP). At this time, the hemicellulose content was reduced to 12 by increasing the amount of alkali added during cooking and strengthening bleaching.
% And less than 20% of Comparative Example 1. Using this BKP, a basis weight of 125 g / m ² and a density of 0.5 g / m
A base paper laminate having a cm ^{3 of} 0.5 kg / 1.5 cm wet paper strength was obtained by hand-making. A 0.1% solution of a nonylphenyl surfactant (Nonipol 60, manufactured by Sanyo Chemical Industries, Ltd.) was applied to the base paper by a size press method. By the method as described above, a base paper having a low contact angle with the standard solution of 40 ° and a large average pore diameter after swelling of 15 μm was obtained. As is clear from Table 1, the PVA penetration time was short and the hydrophilicity was low. A base paper having good varnish permeability was obtained.

[Comparative Example 1] Acacia wood chips from South Africa, which is a relatively thick-film grade having a Runkel ratio of 1.2, are kraft-cooked, and then oxygen, chlorine, alkali, sodium hypochlorite,
Multi-stage bleaching with chlorine dioxide was performed to obtain bleached kraft pulp (BKP). The hemicellulose content of this BKP was 20%. This was comparable to the content of commercially available hardwood BKP. Using this BKP, a laminated base paper having a basis weight of 125 g / m ² , a density of 0.5 g / cm ³ and a wet paper strength of 0.5 kg / 1.5 cm was obtained by hand-making in the same manner as in Example 1. As is clear from Table 1, the contact angle of the laminated base paper with the standard solution was as high as 90 °, the PVA penetration time was long, and it was difficult to uniformly coat the hydrophilic varnish.

[Comparative Example 2] Hokkaido beech wood chips, which are relatively thin grades with a Runkel ratio of 0.6, are kraft digested, and then subjected to multi-stage bleaching with oxygen, chlorine, alkali, sodium hypochlorite, and chlorine dioxide. BKP was obtained. This BKP
Had a hemicellulose content of 20%, which was comparable to the content of commercially available hardwood BKP. Using this BKP, a basis weight of 125 g / m ² and a density of 0.5 g / m
A base paper laminate having a cm ³ and a wet paper strength of 0.5 kg / 1.5 cm was obtained by hand-making. As is clear from Table 1, this base paper had a contact angle of 105 ° with respect to the standard solution of the laminated base paper.
The average pore diameter after swelling was as small as 9 μm, the PVA penetration time of this base paper was long, and uniform coating of the hydrophilic varnish was difficult.

[Comparative Example 3] Beechwood chips produced in Hokkaido, which is a relatively thin grade having a Runkel ratio of 0.6, are kraft cooked, and then subjected to multi-stage bleaching with oxygen, chlorine, alkali, sodium hypochlorite, and chlorine dioxide. BKP was obtained. This BKP
Has a hemicellulose content of commercially available hardwood BK
It was about the same as the P content of 20%. Using this BKP, a basis weight of 125 g / m ² and a density of 0.5 g / m
A base paper laminate having a cm ³ and a wet paper strength of 0.5 kg / 1.5 cm was obtained by hand-making. A 0.1% solution of a nonylphenyl surfactant (Nonipol 60, manufactured by Sanyo Chemical Industries, Ltd.) was applied to the base paper by a size press method. As is clear from Table 1, this base paper has a low contact angle of 65 ° with the standard solution of the laminated base paper, but the average pore diameter after swelling is as small as 9 μm, and the PVA penetration time of this base paper is long, Uniform coating of the hydrophilic varnish was difficult.

(Comparative Example 4) A beech wood chip produced in Hokkaido, which is a relatively thin grade having a Runkel ratio of 0.6, is kraft cooked and then subjected to multi-stage bleaching with oxygen, chlorine, alkali, sodium hypochlorite, and chlorine dioxide. BKP was obtained. At this time,
Increasing the amount of alkali added in the digestion and / or strengthening the bleaching resulted in a hemicellulose content of 12% and 20% of Comparative Example 2.
Less. Using this BKP, a laminate base paper having a basis weight of 125 g / m ² , a density of 0.5 g / cm ³ and a wet paper strength of 0.5 g / cm ³ was obtained by hand-making in the same manner as in Example 1. As is clear from Table 1, this base paper has a high contact angle of 95 ° to the standard solution of the base paper, and the PVA of the base paper
The permeation time was long, and it was difficult to apply the hydrophilic varnish uniformly.

[0035]

[Table 1]

[0036]

As is clear from the results shown in Table 1, the present invention shown in Example 1 in which the selection of raw materials and production conditions were set and Examples 2 and 3 in which chemical treatment was further added, are based on the water-based standard. It was expected that the permeation time to the solution was short and the coating suitability for the hydrophilic varnish was good. Therefore, the industrial significance is extremely large.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazufumi Nagao, 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Inside the Japan Paper Manufacturing Co., Ltd. (72) Inventor Toshifumi Narushima 1-30, Kamiochiai, Shinjuku-ku, Tokyo No. 6 Japan Paper Manufacturing Co., Ltd. Product Development Laboratory

Claims (4)

[Claims] 1. A contact angle with a polyvinyl alcohol aqueous solution having a B-type viscosity of 15 cps at 20 ° C. of 30 ° or more and less than 75 °, and an average pore diameter of 12 μm or more and 16 μm or less when lyophilized after immersion in water. A laminated base paper characterized in that: 2. The laminate base paper according to claim 1, wherein the laminate base paper contains a nonionic surfactant. 3. The laminated base paper according to claim 2, wherein the content of the nonionic surfactant is 0.05% by weight or more and 0.1% by weight or less based on the laminated base paper. 4. The laminated base paper is coated with a nonionic surfactant by a size press.
4. The method for producing a laminated base paper according to any one of claims 1 to 3.