JPH06123100A - Base material for release paper - Google Patents

Abstract

(57) [Abstract] [Purpose] A base material for release paper which can be directly coated with an organic solvent solution of silicone because it has sufficient solvent barrier properties without a polyethylene laminate and can exhibit excellent release properties. Providing a manufacturing method. It is characterized in that it has a barrier layer formed on one surface of a base paper containing wood pulp as a main component and containing a pigment and an adhesive as a main component, and the barrier layer contains an organic synthetic pigment as a pigment. Base material for release paper.

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. Further, even if it can be dispersed in water by strengthening mechanical force and introducing chemical treatment, it is difficult to reuse it as a raw material for general paper because the fiber is significantly damaged by strengthening the beating treatment. is there.

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. However, since the starch solution itself is buried in the pinhole, a pin having a pore diameter of 1 to 200 μm or more is used. Since it cannot play a role of blocking holes, it is impossible to block the penetration 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 has been 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, but has not yet been demanded. No substrate has been provided that can meet these requirements.

[0008]

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.

[0009]

A base material for release paper according to the present invention is a base paper mainly made of wood pulp, and one of the base papers.
It has a barrier layer formed on the surface and containing a mixture of a pigment and an adhesive as a main component, and the barrier layer contains an organic synthetic pigment as a pigment.

[0010]

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 inventors of the present invention have manufactured the wood pulp as a main raw material and have a pore diameter of 0.1 to 1.0 micron. (1) completely suppress the permeation of an organic solvent solution of silicone into a base paper having fine voids and being porous and rich in liquid absorption; and (2) having a pore size of 1 to 200 microns 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 to establish this means, the present inventors have found that a mixture of a pigment and an adhesive is the main component as a material that can simultaneously achieve the function of preventing penetration of a silicone organic solvent solution and the function of blocking a pinhole. The inventors have found that forming a barrier layer containing an organic synthetic pigment as a pigment is a method of exerting an excellent effect satisfying this requirement, and completed the present invention.

That is, the present inventors not only have the effect that the above-mentioned organic synthetic pigment is effective for sealing the pinholes of the base paper, but also that the hexagonal plate-shaped inorganic pigment such as kaolin tends to have a void-rich orientation. On the other hand, since it is a spherical pigment having a relatively uniform particle size, it is easy to exhibit a hexagonal close-packed structure with the smallest number of voids in the barrier layer, and it is dense and has a high blocking effect, resulting in excellent solvent barrier properties. The present invention has been found, and the object of the present invention has been achieved. Here, the organic synthetic pigment has a function of blocking pinholes having a pore size of 1 to 200 μm scattered in the base paper as described above, and the adhesive mixed with this has a fine pore size of 0.1 to 1.0 μm. It has a function of completely suppressing the permeation of the organic solvent solution of silicone into the base paper mainly made of wood pulp which has various voids and is porous and rich in liquid absorption.

On the other hand, there is no strict limitation on the compounding ratio of the organic synthetic pigment and the adhesive, but in 1987, "Layer str" of Tappi Journal.
Anna Maija Leskine entitled "ucture in model coating"
As described in the paper of Mr. ne, the porosity when the spherical pigment according to the present invention is densely packed is about 26%. From this theory, 100 parts by weight of the organic synthetic pigment is mixed with 2 parts of the adhesive.
It is preferable to contain 5% or more. Further, if the blending ratio is excessively high, the pinhole-preventing effect of the base paper by the organic pigment decreases, so that it is preferable to blend in an amount of 100 parts by weight or less.

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. Alternatively, it includes high-quality paper, medium-quality paper, single-glossy paper, kraft paper, and the like, which have been made by a circular net paper machine. The base paper may contain organic and inorganic pigments and chemicals. The organic synthetic pigment used in the present invention is a spherical pigment containing polystyrene as a component and having a relatively uniform particle size distribution of 0.1 to 10 microns in spherical diameter, which is commercially available from Asahi Kasei Kogyo, for example. "L-8801" corresponds to this, and is also widely commercially available from Japan Synthetic Rubber Industry, Mitsui Toatsu Chemicals, Nippon Zeon, Rohm and Haas in the United States, and the like. The organic synthetic pigment of the present invention is not limited to the above-mentioned polystyrene, but is also insoluble in water such as polyvinyl chloride, polyvinylidene chloride, polymethylmethacrylate, polyamide, polycarbonate, polyfluorinated ethylene, etc. Those made from the above resin can be applied. Further, an organic synthetic pigment having an adhesive force, which is called a binder pigment having a core / shell structure in which butadiene, a styrene / butadiene copolymer or the like is arranged on the surface of polystyrene particles or the like, is also included therein.

On the other hand, the adhesive used in the present invention is an aqueous emulsion or latex of a water-soluble polymer substance or a hydrophobic polymer substance, and adheres the barrier layer containing the organic pigments and the organic synthetic pigments to the base paper. Syntheses such as natural adhesives such as starch, casein and carboxymethyl cellulose, styrene-butadiene copolymer latex, copolymer emulsion of acrylic acid ester and / or methacrylic acid ester, polyvinyl alcohol, polyacrylamide, etc. A resin adhesive can be arbitrarily selected and compounded and used. Further, a dispersant, a waterproofing agent, a lubricant, an antifoaming agent, a coloring agent, a preservative and the like can be optionally added. These coating equipment can be arbitrarily selected from a size press, a gate roll coater, a bar coater, a roll coater, an air knife coater, a blade coater and the like. Also,
Considering the sealing effect and the price of paint, the barrier layer formed on the base paper has an absolute dry weight of 0.5 to 15 g / m 2.
² It is desirable to prepare it so that it can be coated. In the present invention, an aqueous paint containing at least one selected from an organic synthetic pigment, a water-soluble polymer substance and a hydrophobic polymer substance emulsion for forming a barrier layer is used as a base paper.
It may be applied by more than one application operation.

Further, after applying the above water-based paint, if necessary, it may be subjected to a smoothing treatment in a finishing equipment such as a super calender. By doing so, the surface quality of the barrier layer obtained becomes good and the silicone coating is applied. The work layer can be formed uniformly. In this case, it is preferable to control the smoothness within the range of 20 to 5000 seconds (Oken type smoothness described in Japanese TAPPI paper pulp test method No. 5) depending on the purpose. As described above, the silicone release agent is usually dissolved in an organic solvent such as toluene or hexane and 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 release paper substrate produced by the method of the present invention has an excellent solvent barrier property comparable to that of a polyethylene-laminated substrate, an excellent disintegration property of pulp fibers, and a step of laminating polyethylene. Since it is unnecessary, the manufacturing cost is extremely low. Further, the release paper using the base material of the present invention does not have a polyethylene laminate layer and does not penetrate into the inside of the release paper, so that 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. In addition, since this recycled pulp does not contain silicone having water repellency,
Silicone does not become a cause of damage such as cissing due to being mixed in a paper making process such as printing paper.

[0018]

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

Example 1 A release paper substrate was manufactured by the following steps. (1) Papermaking of base paper First, a paper stock having the following composition was prepared. Component weight Softwood bleached kraft pulp (beating degree: 470 ml) 20 parts Hardwood bleaching kraft pulp (beating degree: 470 ml) 80 parts 50% talc dispersion 10 parts 30% fortified rosin sizing agent (trademark: SPE, Arakawa Chemical Industry Co., Ltd. )) 0.3 parts 30% aluminum sulfate 2 parts Next, from this stock material, a rice grammage of 65 by a fourdrinier 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. Ingredient wt 48% Organic Synthesis pigment (trademark: L8801, manufactured by Asahi Kasei) 100 parts of 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao Corporation) 2.5 parts 50% SBR latex (trademark: JSR0610, JSR Industrial) 50 parts 20% oxidatively modified starch (trademark: Oji ace A, Oji cornstarch) 2 parts This 10% coating solution has a dry weight of 1 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 paper supply piece was prepared from the above-mentioned release paper base material, 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: Toluene colored with the oil-soluble dye "Olesol Red B" (manufactured by Sumitomo Chemical Co., Ltd.) was applied on a piece of paper, and after 2 seconds, a glass was applied.
Then, 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. Ingredient weight 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 Toluene 95 parts The above solution onto a test paper, bone 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 silicone coating The release paper obtained by applying the silicone solution described in (2) above is subjected to disaggregation treatment by a standard disintegrator defined in JIS P8209, and the dispersion state of the sample components is measured. It was observed and its disintegration property was evaluated. The results of each test are shown in Table 1.

Example 2 A release paper substrate was prepared in the same manner as in Example 1 and an 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. Component weight Softwood bleached kraft pulp (beating degree: 470 ml) 50 parts Broadleaf bleached kraft pulp (beating degree: 470 ml) 50 parts 50% talc dispersion 10 parts 30% fortified rosin sizing agent (trademark: SPE, Arakawa Chemical Industry Co., Ltd. )) 0.3 parts 30% aluminum sulfate 2 parts Next, a plain glossy paper having a basis weight of 80 g / m ² is made from this paper material 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 was evaluated. However, instead of the organic synthetic pigment L8801 in the coating liquid for barrier layer of Example 1, a 46.5% organic synthetic pigment (trademark: Grosdale 104S, manufactured by Mitsui Toatsu Chemical) was used.

Comparative Example 1 The base paper for release paper 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 base material for release paper. The test results are shown in Table 1.

Comparative Example 3 On the base paper described in Example 1, 5% polyvinyl alcohol "PVA105" (manufactured by Kuraray Co., Ltd.) as a barrier agent was hand-coated with a Mayer bar at 10 g / m ² and super-calendered by Oken. The base material for finish release paper had a smoothness of 220 seconds. 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 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. Component weight 50% Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao) 2.5 parts 50% SBR latex (trademark: JSR0610, Japan Synthetic Rubber Industry) 5 parts 20% oxidatively modified starch (trademark: Oji Ace A, made by Oji Corn Starch) 2 parts The test results are shown in Table 1.

Comparative Example 5 A base material for release paper 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. Component weight 50% Calcium carbonate (Trademark: Softon 2200, Shiraishi Calcium) 100 parts 40% Acrylic dispersion (Trademark: Poise 520, Kao) 2.5 parts 50% SBR latex (Trademark: JSR0610, Japan Synthetic Rubber) Industrial) 5 parts 20% oxidatively modified starch (trademark: Oji Ace A, Oji Corn Starch) 2 parts The test results are shown in Table 1.

[0028]

[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 were: It was unsatisfactory in some way.

[0029]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Tsukada 1-10-6 Shinonome, Koto-ku, Tokyo Oji Paper Co., Ltd. Product Research Laboratory

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 a pigment and an adhesive as a main component, the barrier layer comprising:
A base material for release paper comprising an organic synthetic pigment as a pigment.