JP2000282397A - Base paper for release paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To a base paper for release paper, capable of directly applying a releasing agent for a solvent-based silicone solution, an aqueous emulsion silicone solution and a solventless silicone solution without requiring polyethylene laminate, having excellent release performance and capable of providing a release paper capable of regenerating as papermaking raw material. SOLUTION: In this base paper for release paper having a pigment coated layer comprising at least pigment and synthetic latex on at least one side of the base paper consisting essentially of a wooden pulp-based fiber, the pigment used in the pigment-coated layer is a flat plate pigment having >=5.0 aspect ratio and classified into <=3.0 wt.% content of particles having >=0.5 and <5.0 μm volume average particle diameter and >=15 μm particle diameter.

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 release paper, and more particularly to a release paper capable of directly coating a solvent-based silicone, an aqueous emulsion silicone or a solvent-free silicone without laminating polyethylene on the base paper. Regarding base paper. The base paper for release paper obtained by the present invention is useful in the fields of general adhesive, tape, casting process paper, molding process paper and the like, and can be recycled as used paper.

[0002]

2. Description of the Related Art Conventionally, release paper has been produced by applying a release agent such as a silicone resin diluted with an organic solvent such as toluene to a polyethylene laminated paper, glassine paper, clay coated paper, clear coated paper or the like. ing. Further, in recent years, demands for water-based emulsion-type release agents and solvent-free silicones have been increasing as release agents against the background of environmental problems.

[0003] The characteristics required for release paper base paper include:
Since the silicone resin is very expensive, a small amount of the silicone coating liquid can be uniformly applied. In order to satisfy this requirement, it is important to minimize the penetration of the silicone coating liquid into the base paper. Therefore, the use of polyethylene laminated paper as a base material has been an effective means.

However, since polyethylene laminated paper has a strong and continuous hydrophobic film formed on the surface of the paper, it is difficult to recover it as waste paper after use as a release paper and to use it as a papermaking raw material. . Also,
Since polyethylene has a small surface energy, when an aqueous emulsion silicone is applied, a repelling phenomenon occurs and a uniform coating film cannot be obtained. In contrast, in the case of release paper using glassine paper, clay-coated paper, or the like as a base material, the barrier properties of the base material are insufficient compared to polyethylene laminated paper, so that sufficient release performance can be obtained. There was a drawback that you could not.

In addition, Japanese Patent Publication No. 1-35959 and Japanese Patent Laid-Open No.
No. 3876 discloses a clay coat type substrate coated with a coating mainly composed of an inorganic pigment and an organic binder as a substrate on which a silicone solution can be directly coated without laminating polyethylene. Have been. Such a base material has an effect of blocking voids on the surface of the base paper, so it can be used to some extent when applying solventless silicone, but it can obtain a high barrier property as required by the present invention. Cannot be used at all and cannot be used for both solvent-based silicone and solvent-free silicone.

JP-A-4-2900, JP-A-4-327300,
And JP 10-1895 A disclose a method of clear coating an aqueous binder such as starch, polyvinyl alcohol (PVA), and a styrene / butadiene copolymer emulsion. However, with these methods,
Although the barrier property is sufficient, a crater-shaped concave portion is formed along the gap in the surface layer of the paper base material, and the adhesive penetrates into the concave portion, so that the peeling performance is reduced, and the release agent (silicone resin) penetrates the concave portion. Therefore, there is a disadvantage that the cost increases.

JP-A-6-264038 discloses that the use of a styrene-butadiene copolymer and starch as a binder for a clay coat provides a barrier property to an organic solvent. However, in this case, the ratio of the pigment and the binder is 100/10 to 100/30, and the ratio of the pigment is high, so that the barrier property is not sufficient, and a styrene-butadiene copolymer for general coated paper is used.
There is a disadvantage that the high solvent resistance aimed at by the present invention cannot be obtained.

Further, Japanese Patent Application Laid-Open No. 7-97797 discloses a method of obtaining a release paper having reduced adhesive strength when processed into an adhesive paper by using an acrylic resin as a binder of a clay coat. It is disclosed that it is possible. However, acrylic resins are generally several times more expensive than polyethylene, and are extremely disadvantageous economically. Further, the pigment is added as a countermeasure against blocking, and there is no mention of specifying the shape of the pigment to improve the peeling performance.

Japanese Patent Application Laid-Open No. 9-21096 discloses that a high water vapor barrier property can be obtained by using a flat pigment having an aspect ratio of 5 or more. Since a very large mica or talc of 5050 μm is used, the high smoothness aimed at by the present invention cannot be expected.

[0010]

As described above, base paper for release paper which has not only the coating suitability for solvent-based silicones as polyethylene-laminated paper but also can be recycled as used paper has not yet been put to practical use. Further, a base paper for release paper which has a coating suitability for a water-based emulsion and a solvent-free silicone and also has a coating suitability for a solvent-based silicone has not yet been put to practical use.

Incidentally, in order to effectively exhibit the release performance, a uniform barrier layer is formed on the surface of the release paper substrate to prevent the penetration of the silicone resin coating solution, that is, the surface of the release paper substrate. It is necessary to suppress the decrease in the peeling force due to the excessive application of the silicone liquid into the void and the penetration of the adhesive into the void by obtaining a smooth surface by noting the void of about 1 to 500 μm. In addition, in order to directly apply solvent-based silicone, which is the mainstream release agent in Japan,
High resistance to solvents such as toluene and hexane is required. Furthermore, in order to reuse the used release paper as a papermaking raw material, it must be defibrated by a general recycled paper manufacturing process.

The inventors of the present invention have conducted intensive studies to solve these problems, and as a result, the gaps between the fibers on the surface of the base paper are sufficiently noticed on the surface of the base paper mainly composed of wood-based pulp fibers. It has been found that by providing a barrier layer composed of a pigment coating layer using a specific synthetic latex that can be used as a binder, a base paper for release paper that can be recycled as waste paper can be obtained, and the present invention has been completed.

Accordingly, an object of the present invention is to provide excellent release performance by directly applying a release agent such as a solvent-based silicone solution, an aqueous emulsion silicone solution or a solvent-free silicone solution without requiring a polyethylene laminate. An object of the present invention is to provide a base paper for a release paper that can be used as a release paper and that can be recycled as a papermaking raw material.

[0014]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
Base paper for release paper having a pigment coating layer comprising at least a pigment and a synthetic latex on at least one surface of a base paper mainly composed of wood pulp fibers, wherein the pigment component satisfies all of the following conditions: And a base paper for release paper. The volume average particle size is 0.5 μm or more and less than 5.0 μm. The content of particles having a particle size of 15 μm or more is 3.0% by weight or less. It is a flat pigment having an aspect ratio of 5.0 or more.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The base paper mainly composed of wood pulp fibers used in the present invention includes softwood kraft pulp, hardwood kraft pulp, chemical pulp such as sulfite pulp, stone pulp, thermomechanical pulp, mechanical pulp such as refiner grind pulp, In addition, recycled pulp obtained from newspaper, coated paper, high-quality paper, or the like can be appropriately blended. If necessary, non-wood pulp such as kenaf, hemp, bamboo and the like, and fiber material other than cellulose fiber such as glass fiber and polyethylene fiber can be blended.

When making the base paper, internal additives such as a sizing agent, a paper strength agent, a fixing agent, a retention aid, a dye, and internal additives such as talc, kaolin, titanium dioxide, aluminum hydroxide, and calcium carbonate are used. Surface treatment is appropriately performed, for example, by adding a filler or applying a paper strength improver such as starch or polyvinyl alcohol, a surface sizing agent, and a dye using a size press, a gate roll, or the like during the papermaking process. It is also possible.

In the present invention, the pigment coating layer is a layer composed of at least a synthetic latex and a pigment, and a base paper for a release paper can be obtained by applying this to a paper substrate. The synthetic latex used in the present invention preferably contains a styrene / butadiene copolymer as a main component. This synthetic latex is copolymerized using a styrene monomer and a butadiene monomer as main raw materials, and appropriately adding monomers such as acrylic acid, acrylic ester, methacrylic acid, methacrylic ester, and acrylonitrile as raw materials. Is also possible. Further, the synthetic latex used in the present invention includes a synthetic latex obtained by modifying the obtained copolymer with a carboxyl group.

The solvent resistance of the barrier layer is effectively controlled by adding an acrylic monomer in an amount of 0.5% by weight or more and less than 5% by weight in addition to styrene and butadiene when producing a synthetic latex. improves. The type of the acrylic monomer is not particularly limited, but acrylonitrile, acrylate, and the like are particularly preferable.

In the pigment coating layer, starch, if necessary,
It is also possible to mix a binder such as polyvinyl alcohol and an acrylic resin until the amount becomes about 20% by weight of the total amount of the binder. If necessary, a dispersant, a water-proofing agent, a lubricant, an antifoaming agent, a preservative, a dye, and the like can be appropriately added to the pigment coating liquid.

The pigment used in the present invention is a tabular pigment having a volume average particle diameter of 0.5 μm or more and less than 5.0 μm, a content of a pigment of 15 μm or more of 3% or less, and an aspect ratio of 5.0 or more. By using such a pigment, the barrier properties of the base paper for release paper of the present invention can be significantly improved. If the volume average particle diameter of the pigment is 0.5 μm or less, the effect of filling the voids between the fibers on the base paper surface is obtained, but the binder required for the adhesion between the pigments is insufficient, so that the fine voids increase and the silicone coating liquid is increased. Can not prevent the penetration.

Whether the volume average particle diameter is 5.0 μm or more,
Alternatively, the content of the pigment having a volume average particle diameter of 15 μm or more is
When the amount exceeds 3% by weight, although the barrier property against the silicone coating liquid is obtained, the particle diameter of the pigment is larger than the thickness of the pigment coating layer, so that the unevenness of the base paper for release paper becomes large, and the Coating cannot be performed uniformly. Further, a flat pigment having an aspect ratio of 5 or more is oriented in a planar direction during coating, so that a surface having excellent barrier properties and smoothness can be easily obtained. Examples of the pigment used in the present invention include kaolin, illite, mica, talc, aluminum hydroxide and the like.

The mixing ratio of the pigment and the synthetic latex is preferably in the range of 55/45 or more and 75/25 or less. In particular, if the compounding ratio is less than 55/45, the ratio of the adhesive synthetic latex is too high, so that the disintegration by the pulper when the used release paper is recycled as used paper is inferior, and is reused as a papermaking raw material. I can't do it. Also, since the base paper surface for release paper is sticky,
Blocking is likely to occur during winding or storage in plain format. Further, if the blending ratio is higher than 75/25 and the pigment ratio is too high, the resin between the pigment and the pigment cannot be sufficiently filled with the resin, so that many fine voids are generated and the coating layer of the silicone coating solution and the base layer are not coated. The penetration into the material cannot be suppressed.

The coating amount of the pigment coating layer is 5 g / m ² or more and 20 g.
/ M ² or less is optimal. If it is less than 5 g / m ² , the voids between the pulp fibers on the surface of the base material cannot be completely clogged, so that the penetration of the silicone liquid into the base material cannot be suppressed. Further, even if the coating amount exceeds 20 g / m ² , improvement in quality with an increase in the coating amount cannot be expected, which is uneconomical.

The method of applying the pigment coating liquid to the substrate is as follows.
Although a method using a blade coater is preferable because of high productivity, various coating apparatuses such as an air knife coater, a rod blade coater, a bar blade coater, and a gravure coater can be appropriately selected and used. When applying a release agent to the base paper for release paper of the present invention, solvent-based silicone,
Either an aqueous emulsion or a solventless silicone resin release agent can be used, and these can be applied directly to the surface of the pigment coating layer of the base paper.

[0025]

EXAMPLES The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, "%" in the examples is all "% by weight",
All “parts” indicate “parts by weight”. The pigment particle size, aspect ratio, solvent barrier property, releasability (solvent-based silicone, water-based emulsion silicone, and solvent-free silicone) and disintegration properties were evaluated by the following methods.

<Pigment Particle Size> The particle size of the pigment was measured by a microtrack laser diffraction method.
(Manufactured by Malvern Instruments).
The volume average particle diameter was calculated according to the standard method of ASTM.

<Aspect ratio> The plane direction and the cross-sectional direction of the pigment are photographed using a scanning electron microscope (SEM), and the particle diameter and thickness are measured. The expression [aspect ratio = particle diameter / thickness]
Was calculated by

<Solvent barrier property> 0.1%
To prepare an oil red toluene solution. The dyeing solution was uniformly applied to the pigment-coated surface of the sample with a cotton ball or the like, wiped off with a gauze after 2 seconds, and the state of penetration of the dyeing solution into the coating layer and the paper substrate was observed.

<Releasability> Heat addition polymerization type silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: KS
-837) 100 parts of catalyst (Shin-Etsu Chemical Co., Ltd .: CAT-
PL-50T) was added to a 5% silicone resin toluene solution, and a coating amount of 1.0 g /
It was coated with a Meyer bar to give a release paper to give m ² . Separately, an adhesive (BPS-5127 manufactured by Toyo Ink Co., Ltd.) was applied to a high-quality paper having a basis weight of 80 g / m ² so as to have a thickness of 125 μm to prepare a surface substrate. After bonding both, the peeling force was measured at a peeling angle of 180 ° and a peeling speed of 1.0 m / min.

Heat addition polymerization type silicone (Shin-Etsu Chemical Co., Ltd .: KM-763) 100 parts catalyst (Shin-Etsu Chemical Co., Ltd.)
A 3% aqueous solution of a silicone resin emulsion containing 2 parts of PM-3) was prepared and applied to the surface of a base paper sample for release paper using a Meyer bar so that the coating amount was 1.0 g / m ^2. To produce a release paper. The same peeling force was measured as in the case of bonding the surface substrate described with this release paper.

A silicone resin obtained by adding 2 parts of a catalyst (PL-56 by Shin-Etsu Chemical Co., Ltd.) to 100 parts of a heat-addition reaction type solvent-free silicone (KNS-320 by Shin-Etsu Chemical Co., Ltd.) is used. It was prepared and coated on a surface of a base paper sample for release paper with a gravure printing machine so that the coating amount was 1.0 g / m ² to prepare release paper. The same peeling force was measured as in the case of bonding the surface substrate described with this release paper.

<Disintegration> The degree of disintegration of the release paper sample using a Tappi standard disintegrator under the conditions of a sample concentration of 1.5%, a capacity of 2.0 l, and a time of 10 minutes was compared. Next, Examples 1-2,
This will be described using Comparative Examples 1 to 3. Tables 1 and 2 collectively show the configurations and quality evaluation results of the base papers for release paper.

Embodiment 1 The volume average particle size is 1.25 μm, the content of particles having a particle size of 15 μm or more is 0.5%, and the aspect ratio is 2
0 kaolin 65 parts, synthetic latex (styrene
35 parts of butadiene latex), dispersant, defoamer,
Lubricants were appropriately blended to prepare a pigment coating liquid having a solid content of 60%. Next, this coating liquid is applied to a high quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for a release paper having a coating amount of 15 g / m ^2. did.
As a result of evaluating this base paper for release paper by the above-mentioned method, a solvent barrier property comparable to that of the polyethylene laminate paper of Comparative Example 1 described later was obtained. In addition, a release paper having good release suitability was obtained when any of the solvent-based, emulsion-based and solvent-free silicone release agents was applied. In addition, the disintegration was good, and it could be recycled as a raw material for papermaking.

Embodiment 2 FIG. The volume average particle size is 0.75 μm, the content of particles having a particle size of 15 μm or more is 1.0%, and the aspect ratio is 1
5 talc 65 parts, synthetic latex (styrene
35 parts of butadiene latex), dispersant, defoamer,
Lubricants were appropriately blended to prepare a pigment coating liquid having a solid content of 60%. This coating solution has a basis weight of 75 g / m ² and a thickness of 100 μm.
Was coated using a test blade coater to produce a base paper for release paper having a coating amount of 15 g / m ² . As a result of evaluating the base paper for release paper by the above-described method, a solvent barrier property comparable to that of the polyethylene laminated paper of Comparative Example 1 was obtained. A release paper having good release suitability was obtained even when any of the solvent-based, emulsion-based and solvent-free silicone release agents were applied. In addition, the disintegration was good, and it could be recycled as a raw material for papermaking.

Comparative Example 1 A low-density polyethylene having a thickness of 20 μm was laminated on the high-quality paper used in Example 1 to produce a polyethylene-laminated paper, which was used as a base paper for release paper. As a result of evaluating the base paper for release paper by the above-described method, a very good solvent barrier property was obtained, and when a solvent-based silicone release agent was applied, good release suitability was obtained. However, when emulsion-based silicone was applied, a repelling phenomenon of the release agent occurred, and a release paper having sufficient release performance could not be obtained. In addition, regarding the disintegration, the polyethylene laminate layer remained in a film shape, and it was difficult to recycle as a papermaking raw material.

Comparative Example 2 A volume average particle size of 0.40 μm, a content of particles having a particle size of 15 μm or more is 1.0%, and an aspect ratio is 1
35 parts of synthetic latex (styrene / butadiene latex), a dispersant, an antifoaming agent, and a lubricant were appropriately blended with 65 parts of kaolin of No. 2 to prepare a pigment coating liquid having a solid content of 60%. This coating solution is applied to a base weight of 75 g / m ² and a thickness of 100 μm.
m high-quality paper was coated using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² . As a result of evaluating the base paper for release paper by the above-described method, the penetration of the silicone coating liquid was larger than that of the examples, and the solvent barrier property equivalent to that of polyethylene laminated paper was not obtained. When any of the solvent-based, emulsion-based, and solvent-free silicone release agents were applied, no release paper having good release suitability was obtained.

Comparative Example 3 Volume average particle size is 33μm, particle size is
35 parts of synthetic latex (styrene-butadiene latex) for 65 parts of mica (A31 made by Mitsuko Yamaguchi Kogyo Co., Ltd.) having a content of particles of 15 μm or more of 80% and an aspect ratio of 30;
Also, the dispersant, defoamer, and lubricant are appropriately blended to increase the solid content.
A 6% pigment coating solution was prepared. When this coating liquid has a basis weight of 75
The thickness in g / m ² by using a test blade coater on a high-quality paper 100μm coated, coating amount to prepare a base paper for release paper of 15 g / m ^2. As a result of evaluating the base paper for release paper by the above-described method, the penetration of the silicone coating liquid was larger than that of the examples,
Solvent barrier properties comparable to polyethylene laminated paper were not obtained. Also, no release paper having good release suitability was obtained when any of the solvent-based, emulsion-based and solvent-free silicone release agents were applied.

Comparative Example 4 A volume average particle size of 2.5 μm, a content of particles having a particle size of 15 μm or more is 1.0%, and an aspect ratio is 1.2.
Light calcium carbonate (Okutama Kogyo Co., Ltd .: Tamapearl)
35 parts of synthetic latex (styrene butadiene latex) and a dispersant, an antifoaming agent, and a lubricant were appropriately blended with 65 parts of TP121) to prepare a pigment coating liquid having a solid content of 60%.
This coating solution was applied to a high-quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater.
A g / m ² base paper for release paper was prepared. The base paper for release paper was evaluated by the above-described method. As a result, the penetration of the silicone coating solution was larger than that of the examples, and the solvent barrier property comparable to that of polyethylene laminated paper was not obtained. No release paper having good release suitability was obtained when any of the solvent-based, emulsion-based, and solvent-free silicone release agents were applied.

[0039]

[Table 1]

[0040]

[Table 2] As is clear from Tables 1 and 2, the release paper base papers of the examples according to the present invention each had satisfactory performance, whereas the release paper base papers of the comparative examples had some properties. The results were unsatisfactory.

[0041]

The base paper for release paper of the present invention has the same solvent barrier properties as polyethylene-laminated paper, provides good release performance even when coated with a solvent-based silicone, and has a higher performance than polyethylene-laminated paper. Since it has good affinity with the aqueous emulsion silicone, good release properties can be obtained even when this release agent is applied. In addition, since a pigment having a high aspect ratio was used, high smoothness was obtained, and good releasability was obtained even when a solventless silicone was applied. Further, it has a disintegration property that cannot be obtained with polyethylene laminated paper, and can be reused as a raw material for papermaking. Therefore, the present invention has great industrial significance.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoki Sekine 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Products Co., Ltd. F-term (reference) 4J004 AB01 CC02 DA04 DB02 4J038 CA041 CC041 GA06 GA10 KA08 MA10 PC06 4L055 AG26 AG27 AG63 AG76 AG97 AH02 AH37 AJ04 BE08 EA16 FA30 GA43

Claims (1)

[Claims] 1. A base paper for release paper having a pigment coating layer comprising at least a pigment and a synthetic latex on at least one surface of a base paper mainly composed of wood pulp fibers, wherein all of the pigment components satisfy the following conditions: A base paper for release paper, characterized by satisfying the following. The volume average particle size is 0.5 μm or more and less than 5.0 μm. The content of particles having a particle size of 15 μm or more is 3.0% by weight or less. It is a flat pigment having an aspect ratio of 5.0 or more.