JPH06108398A - Base material for release paper - Google Patents

Abstract

(57) [Summary] [Object] To provide a release paper substrate which can be directly coated with an organic solvent solution of silicone because it has a sufficient solvent barrier property without a polyethylene laminate and can exhibit excellent releasability. [Structure] A base paper containing wood pulp as a main raw material, and 100 parts by weight of a pigment, which is formed on one surface of the base paper and contains at least one component selected from an alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose. And a barrier layer made of a water-based paint whose main component is a mixture containing 35 to 100 parts by weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release paper substrate. More specifically, the present invention mainly relates to an adhesive label to be attached to the surface of a product or a product container, an adhesive seal, and a base material of a release paper of an adhesive tape used for packaging of a packaging container, and particularly to a base paper. The present invention relates to a release paper substrate which can be directly coated with an organic solvent solution containing a release agent such as silicone without the need of laminating polyethylene thereon.

[0002]

2. Description of the Related Art Conventionally, in order to improve the releasability of a release paper from a base material, that is, a label, a paper for sticker or a tape wound in a cylindrical shape, a release agent or a release agent such as a release agent is used. Polyethylene laminate type, glassine type, clay coat type, super calendered type and other papers are known as base materials for release paper formed by applying a solution of silicone resin dissolved in an organic solvent such as toluene. .

[0003] Among these base materials, the penetration of the above-mentioned silicone coating liquid is suppressed as much as possible on the surface of high-quality paper mainly made of wood pulp, glossy paper, kraft paper, etc. to maximize releasability. The thickness is 10 by the extrusion method for the purpose of exerting it.
Generally, a polyethylene film layer having a thickness of about 25 microns is formed. However, in the base paper for release paper produced by the method of laminating polyethylene described above, this polyethylene forms a strong continuous film, and since it is insoluble in water, this base material is recovered again and used in the papermaking process. It is impossible to recycle, which is a big problem in industrial waste treatment today.

On the other hand, there has been attempted a method in which glassine paper or the like made from extremely beaten pulp is used as a base paper and an organic solvent solution of silicone is directly applied to the base paper without laminating polyethylene. However, such a base paper has a drawback that it is not easily dispersed in water because pulp used as a raw material is beaten to an extreme degree and used, and the interfiber bond is strengthened by calendering or the like. Furthermore, even if it is possible to disperse in water by strengthening mechanical strength and introducing chemical treatment, etc., since fibers are significantly damaged by strengthening beating treatment, it should be reused as a raw material for general paper. It is difficult.

On the other hand, Japanese Patent Publication No. 1-35959 and Japanese Patent Laid-Open No.
No. 23876, a base material for a release paper obtained by directly coating a silicone solution without laminating polyethylene is coated with a paint containing an inorganic pigment and an organic adhesive as main components. Clay coat type substrates for forming an undercoat layer are disclosed. In such a base material, the effect that the microscopic voids (hereinafter referred to as pinholes) in the base paper are covered with the undercoat layer and the pores are stopped is recognized. However, the organic solvent solution of silicone penetrates into the base paper through the infinitesimal continuous pores existing between the pigments of the undercoat layer. Therefore, it is necessary to apply a large amount of expensive silicone as compared with the method of laminating with polyethylene.

Even in a super calendered kraft type base material that is mechanically pressurized and densified, it is still impossible to completely close the minute voids, and further, at the same time when the organic solvent solution of silicone comes into contact with the base material. Swelling of the material occurs, and it is impossible to impart excellent solvent barrier properties comparable to those obtained when laminating polyethylene.

Further, Japanese Patent Laid-Open No. 4-2900 has recently disclosed a method of undercoating starch as a sealing agent, but since the starch solution itself is buried in the pinhole, the pore size is 1 to 200 μm. Since it cannot play the role of stopping the above pinholes, it is impossible to block the permeation of the silicone organic solvent solution (hereinafter referred to as solvent barrier property) only by the undercoat layer of starch.

For the above reasons, there is a strong demand for a base material for release paper which has a solvent barrier property comparable to that of polyethylene laminated and which can be directly coated with an organic solvent solution of silicone. No substrate has been provided that can meet these requirements.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a base material for release paper which does not require a polyethylene laminate, can be directly coated with an organic solvent solution of silicone, and can exhibit excellent releasability. Is what you are trying to do.

[0010]

A release paper base material according to the present invention comprises a base paper containing wood pulp as a main raw material and a mixture of an adhesive and a pigment, which is formed on one surface of the base paper. The barrier layer comprises 35 to 100 parts by weight of an alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose as an adhesive with respect to 100 parts by weight of the pigment.

[0011]

In order to obtain a release paper which has a solvent barrier property comparable to that of polyethylene without laminating polyethylene on the base paper and which can be easily disintegrated in water and can be reused, the base paper is used. As a result of diligent research on the material and coating method of the barrier layer formed thereon, a release paper base material which can satisfy these requirements has finally been obtained.

That is, in the base material laminated with polyethylene, as a result of detailed analysis of the function of the polyethylene, the present inventors have produced wood pulp as a main raw material and have a pore diameter of 0.1 to 1.0 micron. (1) To completely suppress the penetration of the organic solvent solution of silicone into the base paper which has fine voids and is porous and rich in liquid absorbability; and (2) The pore size of 1-200 micron scattered in the base paper. It has been concluded that forming a barrier layer capable of simultaneously achieving pinholes is an effective means of obtaining a substrate having a solvent barrier property comparable to that of a polyethylene laminate substrate. did. As a result of further intensive studies conducted by the present inventors to establish this means, an alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose was selected as a material capable of simultaneously achieving the function of preventing penetration of a silicone organic solvent solution and the function of blocking a pinhole. It was found that forming a barrier layer of a water-based coating material containing a mixture containing 35 to 100 parts by weight of pigment as a main component is a method that exerts an excellent effect satisfying this requirement, and completed the present invention. Let

That is, the inventors of the present invention exhibit a remarkable film-forming property by adhering pigments to each other due to the strong binding force of carboxymethyl cellulose or hydroxyethyl cellulose described above, and have extremely low chemical affinity with organic solvents. It has been found that the feature is that it exhibits an excellent barrier property, and the object of the present invention has been achieved. Here, the pigment has a function of blocking pinholes having a pore size of 1 to 200 μm scattered in the base paper, and the alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose has fine voids having a pore size of 0.1 to 1.0 μm. Then
It has the function of completely suppressing the permeation of the organic solvent solution of silicone into the base paper mainly made of wood pulp which is porous and rich in liquid absorption.

On the other hand, an alkali salt of carboxymethyl cellulose or a pigment of hydroxyethyl cellulose 100
The blending ratio with respect to parts by weight needs to be 35 to 100 parts by weight. When the amount of the alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose is less than 35 parts by weight, the pigment has an excellent effect of preventing pinholes, but because of the fine voids formed by the pigments, the penetration of the silicone in the organic solvent solution becomes extremely remarkable. Also, 10
If the amount exceeds 0 part by weight, penetration of the silicone in an organic solvent solution can be suppressed, but it becomes difficult to prevent pinholes by the pigment, and the above-mentioned Japanese Patent Publication No. 1-35959 and JP-A-4-23.
This method is completely different from the method described in 876 for applying a water-based paint mainly containing a pigment.

The base paper used in the present invention is a broad-leaf bleached kraft pulp, a softwood bleached kraft pulp, or other chemical pulp or mechanical pulp as a main raw material. It includes high-quality paper, medium-quality paper, single-glossy paper, kraft paper, and the like, which have been made by a paper machine or a cylinder paper machine. The base paper may contain organic and inorganic pigments and chemicals.

The alkali salt of carboxymethylcellulose used in the present invention is a substance commonly known as CMC obtained by immersing cellulose in concentrated sodium hydroxide to form alkali cellulose, and then allowing sodium monochloroacetate to act to dechlorinate sodium. It is commercially available not only from chemical companies such as pharmaceuticals but also from industrial chemical companies such as Daiichi Pharmaceutical, Daicel Chemical, and Shikoku Kasei, and is widely used for pharmaceuticals, cosmetics, food additives and the like. In the case of carboxymethyl cellulose, the hydrogen atoms of the six hydroxyl groups of the glucose unit constituting the cellulose molecule are carboxymethyl groups (-CH
₂ COONa). The degree of substitution and the degree of polymerization of glucose unit are not particularly limited, but the condition is that they have a property of dissolving in water under heating.

The hydroxyethyl cellulose used in the present invention is a so-called HE in which six hydroxyl groups of glucose unit are partially substituted with ethylene oxide by reacting alkali cellulose with ethylene oxide.
A substance called C is commercially available from chemical companies such as Wako Pure Chemical Co., Ltd., and industrial chemical companies such as Sumisho Pluschem and Hercules in the United States, and is widely used in water-based paints, adhesives, cosmetics and the like. As in the case of carboxymethyl cellulose, the degree of substitution with ethylene oxide and the degree of polymerization of glucose units are not particularly limited as long as they have a property of dissolving in water under heating.

The pigments used in the present invention include inorganic pigments such as kaolin, talc, calcium carbonate, titanium dioxide and aluminum hydroxide, and organic synthetic pigments such as polystyrene, styrene-acryl copolymer and urea resin. May be used in combination, or further, natural adhesives such as starch and casein, and synthetic adhesives such as styrene-butadiene copolymer latex, acrylic resin emulsion, polyvinyl alcohol, and polyacrylamide are arbitrarily selected and blended. You may. Further, if necessary, a pigment dispersant, a water resistant agent, a lubricant, an antifoaming agent, a colorant, a preservative and the like may be appropriately blended.

These coating facilities can be arbitrarily selected from a size press, gate roll coater, bar coater, roll coater, air knife coater, blade coater and the like. Considering the sealing effect and the price of the coating material, it is desirable that the barrier layer formed on the base paper is prepared so as to be coated in an absolute dry weight of 0.5 to 15 g / m ² .

In the present invention, an aqueous paint prepared by mixing an alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose with a pigment for forming a barrier layer may be applied to the base paper by two or more applying operations.
In addition, after applying the above-mentioned water-based paint, it may be subjected to a smoothing treatment with a finishing equipment such as a super calender, if necessary, so that the surface quality of the barrier layer obtained becomes good and the silicone coating layer becomes It can be formed uniformly. In this case, the smoothness is 20 to 5 depending on the purpose.
000 seconds (JAPAN TAPPI paper pulp test method N
o. It is preferable to control within the range of the Oken type smoothness described in 5).

The silicone release agent is as described above.
It is usually dissolved in an organic solvent such as toluene or hexane to be applied. As the coating liquid, a mixture of silicone and an actinic radiation curable monomer is used, and the barrier layer of the present invention can be applied to the monomer even in a solventless system in which it is cured by irradiation with ultraviolet rays or electron beams. It can exhibit excellent barrier properties.

The base material of the release paper produced by the method of the present invention has a solvent barrier property comparable to that of a base material laminated with polyethylene and is excellent in disaggregation, and the step of laminating polyethylene is unnecessary. It has the advantage that the manufacturing cost is extremely low. Moreover, since the release paper using the base material of the present invention does not have a polyethylene laminate layer, it can be easily subjected to a recycling step after recovery. Since the barrier layer is detached from the base paper when it is put into water in this regenerating step, only the pulp can be easily recovered and reused. Further, since the recycled pulp does not contain silicone having water repellency, the silicone does not mix into the paper making process such as printing paper and cause trouble such as cissing.

[0023]

The present invention will be described in more detail with reference to the following examples, but of course the scope of the present invention is not limited by these. In the examples, "part" means "part by weight of solid content" unless otherwise specified.

Example 1 A base material for release paper was manufactured by the following steps.

(1) Papermaking of base paper First, a paper stock having the following composition was prepared.

[0026] Ingredient wt softwood bleached kraft pulp (freeness: 470 ml) 20 parts of leaf bleached kraft pulp (freeness: 470 ml) 80 parts of a 50% talc dispersion 10 parts 30% fortified rosin sizing agent (trademark: SPE, Arakawa Chemical 0.3 part 30% aluminum sulphate 2 parts Next, from this paper stock, weaving weight 65 with a fourdrinier multi-cylinder paper machine.
A g / m ² base paper was produced. The density of the base paper thus obtained was 0.85 g / cm ³ , and its Oken smoothness was 45 seconds.

(2) Formation of Barrier Layer A coating liquid for barrier layer having the following composition was prepared.

[0028] Ingredient wt 50% kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts of 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao Corporation) 2.5 parts 50% SBR latex (trademark: JSR0610, Japan Synthetic rubber industry) 5 parts 20% oxidatively modified starch (trademark: Oji Ace A, Oji Cornstarch) 2 parts 5% carboxymethyl cellulose (trademark: Serogen 7A, Daiichi Kogyo Seiyaku Co., Ltd.) 50 parts This 10% coating solution , 1 dry weight on one side of the above base paper
It was coated so as to have a concentration of 0.0 g / m ² and dried. Further, a finishing release paper having Oken type smoothness of 860 seconds was produced by a super calendar.

A predetermined piece of paper is prepared from the release paper substrate, and its toluene penetration preventing effect, pinhole preventing effect,
The silicone penetration preventing effect and the disintegration property after silicone coating were evaluated by the following methods.

(1) Toluene prevention effect and pinhole prevention effect: Oil-soluble dye "Olesol Red
Apply toluene colored with "B" (Sumitomo Chemical Co., Ltd.),
After 2 seconds, the surface was wiped with a gauze, and the permeation state of toluene on the surface and the plugging effect of pinholes formed in spots were determined.

(2) Silicon penetration preventing effect A silicone solution having the following composition was prepared.

[0032] Ingredient wt addition reaction type silicone (TM: SD7220, manufactured by Toray Industries) 4.5 part of a platinum catalyst (trademark: SRX212, Toray Industries) by Meyer bar to 0.5 parts 95 parts The above solution onto the test piece of paper toluene, Absolutely dry 3.0
Coating was performed so that the coating amount was g / m ^2, and the surface obtained was observed to evaluate the penetration of silicone.

(3) Disintegration property after coating with silicone The release paper obtained by coating the silicone solution described in (2) above is subjected to disaggregation treatment by a standard disintegrator defined in JIS P8209 to obtain sample components. The dispersibility was evaluated by observing the dispersed state. The results of each test are shown in Table 1.

Example 2 A base material for release paper was prepared in the same manner as in Example 1 and its evaluation test was conducted. However, instead of the base paper of Example 1, a base paper made by the following method was used.

First, a sample having the following composition was prepared.

[0036] Ingredient wt softwood bleached kraft pulp (freeness: 470 ml) 50 parts of leaf bleached kraft pulp (freeness: 470 ml) 50 parts of a 50% talc dispersion 10 parts 30% fortified rosin sizing agent (trademark: SPE, Arakawa Chemical 0.3 part 30% aluminum sulphate 2 parts Next, from this stock material, simple luster paper of beetle 80 g / m ^{2 was made} into paper by a Fourdrin Yankee type paper machine. A barrier layer was formed on the glossy surface of the thus obtained single-glossy paper in the same manner as in Example 1. The test results are shown in Table 1.

Example 3 A release paper substrate was prepared in the same manner as in Example 1 and its evaluation test was conducted. However, instead of 5% carboxymethylcellulose in the coating liquid for barrier layer of Example 1, 5%
Hydroxyethyl cellulose (reagent manufactured by Wako Pure Chemical Industries, Ltd.) was used.

Comparative Example 1 The release paper base material was prepared by laminating "low density polyethylene" (manufactured by Sumitomo Chemical Co., Ltd.) melted on the base paper described in Example 1 with a laboratory melt extruder. As a result of observing the section of this laminated paper with a scanning electron microscope, the thickness of the polyethylene film layer was about 18 microns. The test results are shown in Table 1.

Comparative Example 2 The base paper described in the example was used as a release paper substrate.

The test results are shown in Table 1. Comparative Example 3 5% polyvinyl alcohol "PVA105" (manufactured by Kuraray Co., Ltd.) as a barrier agent was applied on the base paper described in Example 1 by hand coating with a Meyer bar at 10 g / m ² and a super calender to obtain an Oken smoothness of 220 seconds. It was used as a finish release paper base material. The test results are shown in Table 1.

Comparative Example 4 A release paper substrate was prepared in the same manner as in Example 1 and an evaluation test was conducted. However, a coating material having the following composition was used in place of the barrier layer coating solution of Example 1.

[0042] Ingredient wt 50% kaolin (trademark: HT clay, Engel made hard) 100 parts of 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao Corporation) 2.5 parts 50% SBR latex (trademark: JSR0610, 5 Part manufactured by Japan Synthetic Rubber Co., Ltd.) 20% oxidatively modified starch (trademark: Oji Ace A, 2 parts made by Oji Cornstarch) 5% carboxymethylcellulose 20 parts (trademark: serogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) The test results are shown in Table 1. .

Comparative Example 5 A release paper substrate was prepared in the same manner as in Example 1 and its evaluation test was conducted. However, a coating material having the following composition was used in place of the barrier layer coating solution of Example 1.

[0044] Ingredient wt 50% kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts of 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao Corporation) 2.5 parts 50% SBR latex (trademark: JSR0610, Japan Synthetic rubber industry) 5 parts 20% oxidatively modified starch (trademark: Oji ace A, Oji cornstarch) 2 parts 5% carboxymethyl cellulose (trademark: serogen 7A, Daiichi Kogyo Seiyaku Co., Ltd.) 120 parts Table 1 shows the test results. .

[0045]

[Table 1] As is clear from Table 1, the release paper base materials of Examples 1 to 3 according to the present invention obtained satisfactory results, but the release paper base materials of Comparative Examples 1 to 5 have some properties. Was dissatisfied with.

[0046]

The base material for release paper of the present invention has an excellent solvent barrier property comparable to that of a release paper base to which polyethylene is stuck, and can be easily prepared by existing paper machines and coating machines. It can be manufactured according to the present invention and is extremely excellent in practicality.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 7199-3B D21H 1/30

Claims (1)

[Claims] 1. A base paper containing wood pulp as a main raw material, and a barrier layer formed on one surface of the base paper and containing a mixture of an adhesive and a pigment as a main component, the barrier layer being an adhesive layer. As an agent, an alkali salt of carboxymethyl cellulose or hydroxyethyl cellulose is used as a pigment 100.
A base material for release paper comprising 35 to 100 parts by weight with respect to parts by weight.