JPH06136698A - Substrate for release paper - Google Patents

Abstract

PURPOSE:To obtain a substrate for release paper capable of being directly coated with a solution of a silicone in an organic solvent because of its sufficient solvent barrier properties without polyethylene lamination, exhibiting excellent releasability. CONSTITUTION:This substrate for release paper comprises a base paper composed of wood pulp as a raw material and a barrier layer which is formed on one side of the base paper, consists essentially of a mixture of pigment with an adhesive and contains a polyvinylidene latex as an adhesive.

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 fiber-fiber 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 polyvinylidene chloride latex as an adhesive.

[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. In addition, the present invention has been completed by finding that a method of exerting an excellent effect satisfying this requirement is to include water-dispersible polyvinylidene chloride as an adhesive.

The present inventors have found that the characteristic feature of the above-mentioned polyvinylidene chloride latex, which is capable of adhering pigments to each other due to the strong binding force and exerting remarkable film-forming property, exhibits an excellent solvent barrier property. The object of the invention has been achieved. Here, the pigment has a pore size of 1 to 2 scattered in the base paper.
Polyvinylidene chloride latex has a function of stopping pinholes of 00 microns and has fine voids with a pore size of 0.1 to 1.0 micron. It acts to suppress the permeation of the organic solvent solution entirely.

On the other hand, there is no strict limitation on the blending ratio of the pigment and the polyvinylidene chloride latex, but the 1987 Tappi Jour
nal's "Layer structure in model coating" A
As described in nnaMaija Leskinene's paper, the porosity is about 26% when the spherical pigments are closest packed.
From this theory, it is preferable that the mixing ratio of the polyvinylidene chloride latex is 25 parts by weight or more based on 100 parts by weight of the pigment. On the other hand, when a plate-shaped pigment is used, voids are generally reduced, and thus a lower compounding ratio may be used. If the blending ratio of the polyvinylidene chloride latex is extremely high, the effect of the pigment to prevent pinholes in the base paper decreases, so
It is preferable to add the compound in the range of not more than 00 parts by weight.

Aqueous emulsions and latices of other water-soluble or hydrophobic polymeric substances, for example, natural polymeric compounds such as starch, casein, carboxymethyl cellulose, styrene-butadiene copolymer latex, acrylic ester and / Or a synthetic resin adhesive such as a copolymer emulsion of methacrylic acid ester, polyvinyl alcohol, polyacrylamide copolymer can be arbitrarily selected and used in combination, but in order to obtain a sufficient effect, polyvinylidene chloride It is preferable to mix the latex in an amount not exceeding 100 parts by weight with respect to 100 parts by weight of the latex.

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 polyvinylidene chloride latex used in the present invention is known as a raw material of Saran wrap widely used as a packaging material and is sometimes called Saran latex. The basic composition is a copolymer of polyvinylidene chloride and vinyl chloride, acrylic acid ester or the like, and a small amount of a plasticizer is generally added to the copolymer. Many polyvinylidene chloride latices contain about 90 parts by weight of polyvinylidene chloride, but since polyvinylidene chloride is poor in processability, it is copolymerized with acrylic acid ester or vinyl chloride, but the latter is the barrier. It is disadvantageous to sex. The polyvinylidene chloride latex used in the present invention is an anionic aqueous emulsion having a particle size of about 0.05 to 0.2 micron, such as "L100", "L106" and "L502" commercially available from Asahi Kasei. Corresponds to this.

On the other hand, as the pigment used in the present invention,
There are no particular restrictions, kaolin, talc, calcium carbonate,
Inorganic pigments such as titanium dioxide and aluminum hydroxide can be appropriately selected 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. Further, in consideration of 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 containing a pigment and polyvinylidene chloride latex may be applied to the base paper by a coating operation two or more times in order to form a barrier layer. Further, 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, and the surface quality of the barrier layer obtained in this way 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 Oken type smoothness described in 5).

The silicone is usually applied by dissolving it in an organic solvent such as toluene or hexane as described above. The barrier layer of the present invention can exhibit an excellent barrier property against a monomer even in a solventless system in which a silicone and a monomer are mixed as the coating liquid and the mixture is cured with an ultraviolet ray or an electron beam.

The base material of the release paper produced by the method of the present invention has a solvent barrier property comparable to the base material laminated with polyethylene, is excellent in the disintegration property of pulp fiber, and does not require the step of laminating polyethylene. Therefore, there is an advantage that the manufacturing cost is extremely low. Also,
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. 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.

[0021]

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 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. 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% Reinforced 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. Component weight 50% Kaolin (trademark: HT clay, manufactured by Engelhard) 100 parts 40% acrylic dispersion (trademark: Poise 520, manufactured by Kao) 2.5 parts 49% polyvinylidene chloride latex (trademark: L100, Asahi Kasei Kogyo) 50 parts 20% oxidatively modified starch (trademark: Oji Ace A, made by Oji Corn Starch) 2 parts This 10% coating solution is applied to one side of the above base paper in a dry weight of 1
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 is prepared from the 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 coating the silicone solution described in (2) above was subjected to disaggregation treatment by a standard disintegrator defined in JIS P8209, and sample components The dispersibility was evaluated by observing the dispersed state. 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 Hardwood bleaching kraft pulp (beating degree: 470 ml) 50 parts 50% talc dispersion 10 parts 30% fortified rosin sizing agent (Trademark: SPE, Arakawa Chemical Industries 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 an evaluation test was conducted. However, instead of the organic synthetic pigment L100 in the coating liquid for barrier layer of Example 1, 50% polyvinylidene chloride latex (trademark: L106, manufactured by Asahi Kasei Kogyo)
It 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 an experimental 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 Meyer 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 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% 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 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% 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.

[0033]

[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.

[0034]

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 (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 7199-3B D21H 1/34 G

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, wherein the barrier layer is an adhesive layer. A release paper substrate comprising a polyvinylidene chloride latex as an agent.