JPH08284098A - Base material for release paper - Google Patents

Abstract

PURPOSE: To obtain a base material for releasing paper, capable of being directly coated with the organic solvent solution of a releasing agent, by forming a barrier layer containing gelatinized starch and non-gelatinized particulate starch and excellent in solvent resistance and film formability on raw paper. CONSTITUTION: One side of raw paper containing wood pulp as a main component is coated with a coating solution containing the mixture of gelatinized starch with non-gelatinized particulate starch in an absolute dry weight ratio of 80:20 to 20:80 in a coating amount of 1-7g/m<2> by the use of a gate roll coater disposed at the middle position of the drying machine of a paper-making device to obtain a base material for releasing paper. The base material is coated with a releasing agent coating solution comprising an addition reaction type silicone, a catalyst and toluene to obtain the releasing paper excellent in a toluene penetration-preventing effect, a pin hole-preventing effect, a silicone penetration-preventing effect and a releasing property after coated.

Description

Detailed Description of the Invention

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.

[0001]

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 laminated paper, glassine paper, clay coated paper, super calendered paper and the like are known as base materials for release paper formed by applying a solution of silicone resin dissolved in an organic solvent such as toluene.

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, single-glossy paper and kraft paper to maximize the releasability. For the purpose of exhibiting
A polyethylene film layer having a thickness of about 0 to 25 microns is generally used. However, the base material for release paper manufactured by the method of laminating the above polyethylene forms a strong continuous film of polyethylene, and since it is insoluble in water, the base material is recovered again and the papermaking process is performed. It is impossible to recycle it, which is a big problem in industrial waste treatment today.

On the other hand, a method has been attempted in which glassine paper or the like made from extremely beaten pulp is used as a base paper, and an organic solvent solution of a silicone material is directly applied thereto without laminating polyethylene. There is. However, such a base paper has a drawback that it is not easily dispersed in water when recycled, because the raw material pulp is extremely beaten and used, and the interfiber bond is strengthened by calendering or the like. are doing. 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, in Japanese Patent Publication No. 1-35959 and Japanese Patent Laid-Open No. 23876/1992, a base paper is used as a base material for a release paper obtained by directly coating a silicone solution without laminating polyethylene. Disclosed is a clay coat type base material in which a paint having an inorganic pigment and an organic adhesive as a main component is applied to the surface to form an undercoat layer. In such a base material, it is recognized that an undercoat layer covers minute voids (hereinafter, referred to as pinholes) in the base paper and stops the voids. However, innumerable finer continuous holes are formed between the pigments of the undercoat layer,
There is a problem that the organic solvent solution of the silicone material penetrates into the base paper through the fine continuous holes. Therefore, it is necessary to apply a large amount of expensive silicone as compared with the method of laminating with polyethylene.

Further, even in a super calendered type base material which is mechanically pressed and densified, it is still impossible to completely close the minute inter-fiber voids, and at the same time when the organic solvent solution of silicone is contacted. Since the base material swells, it is impossible to impart excellent solvent barrier properties comparable to polyethylene laminated paper.

Further, in Japanese Patent Laid-Open No. 4-2900,
A method of undercoating a starch solution as a sealing agent has been disclosed. However, since the starch solution itself is buried in the pinhole, it does not play a role of sealing the pinhole having a pore diameter of 1 to 200 microns or more. Therefore, 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 is a strong demand for a base material for release paper which has an excellent solvent barrier property comparable to that of polyethylene laminated paper and which can be directly coated with an organic solvent solution of silicone. No substrate has been provided that can sufficiently meet these requirements.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, a release paper which can be directly coated with an organic solvent solution of a silicone material without using a polyethylene laminate and which has excellent release properties is manufactured by using an inexpensive raw material. The present invention aims to provide a base material for release paper that can be reasonably manufactured.

The present invention also proposes a release paper substrate which can be used in a papermaking process by collecting used substrates.

[0010]

The base material for release paper according to the present invention is as described below. It contains gelatinized starch and non-gelatinized granular starch in a range of 80 to 20:20 to 80 in an absolute dry weight ratio on a base paper mainly made of wood pulp, and is excellent in solvent resistance and film forming property. A base material for release paper, which has a barrier layer and which can be solvent coated with a release agent.

The present inventors have obtained a base material for a release paper which has a solvent barrier property comparable to that of polyethylene without being laminated on a base paper, and can be easily disintegrated in water and can be reused. Therefore, as a result of earnest research on the material and coating method of the barrier layer formed on the base paper substrate, it has finally been possible to obtain a base material for release paper which can satisfy these requirements.

That is, as a result of detailed analysis of the function of this polyethylene in a conventional base material laminated with polyethylene, the present inventors have produced wood pulp as a main raw material and have a pore size of 0.1 to 1.0. (1) Effectively suppressing the permeation of a solution of silicone in an organic solvent into a base paper that has microscopic microscopic voids and is highly absorbent, and (2) Pore diameters 1 to 1 dispersed in the base paper. Forming a barrier layer capable of simultaneously achieving 200 micron pinholes is an effective means of obtaining a substrate having a solvent barrier property comparable to that of a polyethylene laminate substrate. I reached the point of view.

As a result of further intensive studies to establish this means, the present inventors have found that starch which has been heated and gelatinized in a state of being dispersed in water and particles which are not gelatinized by heating in a state of being dispersed in water. 80 g of starch in a dry weight ratio
It is possible to form an organic solvent solution permeation-preventing function by using a gate roll coater installed in the middle of the dryer of a paper machine to form a barrier layer having excellent solvent resistance and film-forming properties, which is contained in the range of 20:20 to 80. The present invention has been completed based on the finding that it is a rational method that can achieve the pinhole sealing function at the same time and exhibits an excellent effect that satisfies this requirement.

In the present invention, the starch used in the barrier layer, which is heated and gelatinized in a state of being dispersed in water, exhibits an excellent film property due to its strong binding force, and as a result, has a pore size of 0.1 to 1 micron. It exerts an effect of effectively suppressing permeation of a silicone organic solvent solution or a solventless silicone liquid into a base paper having fine voids.

On the other hand, the granular starch, which is not gelatinized by heating in a state of being dispersed in water, effectively stops the pinholes having a pore diameter of 1 to 200 microns dispersed in the base paper as its tangible structure. To work. There is a method of containing an inorganic pigment such as kaolin, calcium carbonate, and aluminum hydroxide as a method of stopping the pinhole. In this method, although the pinhole can be stopped in general, a uniform coating surface in a gate roll coater can be obtained. It is difficult to obtain, and even if a uniform coated surface is obtained, adhesion between pigment particles tends to be insufficient, and an effect of effectively suppressing permeation of a silicone organic solvent solution or a solventless silicone liquid is exerted. Becomes very difficult.

The starch which can be used in the present invention to be gelatinized by heating in a state of being dispersed in water is not particularly limited,
Made from corn, potato, rice, etc. as raw materials, and optionally selected from industrially modified oxidatively modified products, enzyme modified products, acetylated modified products, dialdehyde modified products, phosphoric acid ester modified products, etc. , Or a mixture of a plurality of different types of starch can be used. Further, it is possible to use unmodified starch in the form of white particles that has not been modified as described above. In addition, as the starch which is heated and gelatinized in the state of being dispersed in water of the present invention, for example, “Oji Ace A”, “Oji Ace B”, “Oji Ace C” and the like which are commercially available from Oji Corn Starch Co., Ltd. .

On the other hand, the granular starch of the present invention which is not gelatinized by heating in the state of being dispersed in water is selected from the same starches as the starch which is gelatinized by being heated in the state of being dispersed in water. In this case, the same starch as the starch to be heated and gelatinized in a state of being dispersed in water, or a plurality of different starches may be mixed and used.

Since the starches of the present invention use natural raw materials, the price is lower than that of other polyvinyl alcohols.
It is extremely inexpensive as compared with styrene-butadiene copolymer latexes, acrylic acid esters, and styrene-acrylic copolymer emulsions, and is a very preferable material for keeping the production cost low as a component of the barrier layer.

As described above, the starch which is gelatinized by heating in the state of being dispersed in water and the granular starch which is not gelatinized by heating in the state of being dispersed in water are as described above.
Starch heated and gelatinized in a state of being dispersed in water effectively suppresses penetration of a silicone organic solvent solution or a solventless silicone solution into a base paper having fine pores with a pore size of 0.1 to 1 micron. In addition, the granular starch that does not gelatinize due to heating in the state of being dispersed in water exerts the effect of effectively stopping the pinholes having a pore diameter of 1 to 200 microns scattered in the base paper. In order to fully exert each role, starch that has been gelatinized by heating in a state of being dispersed in water and granular starch that is not gelatinized by heating in a state of being dispersed in water are used at a dry weight ratio of 80%. It is necessary to mix and use in the range of 20:20 to 80.

When the proportion of starch that has been gelatinized by heating in a state of being dispersed in water is less than 20 parts by weight with respect to parts by weight of the total solid portion, the starch is gelatinized by heating in a state of being dispersed in this water. It becomes impossible to effectively suppress the permeation of the silicone organic solvent solution or the solvent-free silicone liquid into the base paper having fine pores having a pore size of 0.1 to 1 micron in the starch base paper. On the other hand, when the mixing ratio of the granular starch which is not gelatinized by heating in a state of being dispersed in water is less than 20 parts by weight with respect to the total solid content, the pore size of 1 to 200 micron scattered in the base paper is obtained. It becomes impossible to effectively stop the pinhole.

The barrier layer of the present invention may contain a pigment or other organic component. The pigment is not particularly limited, and inorganic pigments such as kaolin, talc, calcium carbonate, titanium dioxide, and aluminum hydroxide can be appropriately selected and used.The organic component is also not particularly limited, and starch, polyvinyl alcohol, carboxy can be used. Methyl cellulose, polyacrylamide, etc., and derivatives thereof can be used in combination, but in order to obtain a solvent barrier property comparable to polyethylene laminated paper, it is 5 or less dry parts by weight based on the total dry solid content of the resin. There is a need.

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 are made by a cylinder paper machine. The base paper may contain organic and inorganic pigments and chemicals.

However, as the coating equipment for forming the barrier layer of the present invention, it is necessary to use a gate roll coater installed in the middle of the dryer of the paper machine. Since the gate roll coater is installed directly connected to the paper machine, it is possible to form a base paper and form a barrier layer at the same time, and it is a coating method with extremely excellent productivity. Further, since the barrier agent on the applicator roll kneaded between the two nips of the three rolls on one side is transferred to the base paper, the barrier agent does not penetrate into the base paper and the barrier layer is retained on the surface of the base paper. Therefore, it is particularly effective in imparting a solvent barrier property. On the other hand, the size press, which is installed at almost the same position as the gate roll coater for the purpose of imparting sizing property and surface strength to high-quality paper, is widely used. Is formed and the base paper is passed through this nip,
The penetration of the barrier agent into the base paper is large, the barrier layer is not retained on the base paper surface, and sufficient solvent barrier properties cannot be imparted. Further, a method of using a coating machine such as an air knife coater and a blade coater which are widely used in the field of paper coating can be considered, but with such a dedicated coating machine, it costs a lot of money to operate, resulting in high cost Becomes As described above, the release paper substrate coating equipment of the present invention is required to be coated with a simple gate roll coater in order to satisfy both rationality and performance provision.

Although there is no strict limitation on the concentration and coating amount of the barrier agent coating liquid formed on the base paper, the concentration of the coating liquid in the gate roll coater of the present invention is usually 3 to 20.
% By weight, coating amount is usually 1-7 g / m ^{2 on an} absolute dry weight side
Is common.

After forming the barrier layer, it is effective to carry out a smoothing treatment with a finishing equipment such as a super calender, if necessary. In this case, the smoothness is 20 to 5000 seconds (JAPAN). It is preferable to control within the range of TAPPI paper pulp test method No. 5 (Oken type smoothness).

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 that of a polyethylene-laminated base material, is excellent in the disintegration property of pulp fibers, and does not require the step of laminating polyethylene. In addition, since the barrier agent using an inexpensive material is manufactured by a rational coating method, there is an advantage that the manufacturing cost is extremely low. Further, the release paper using the substrate of the present invention does not have a polyethylene laminate layer and the silicone release agent has not penetrated into the release paper, so that it can be easily subjected to a recycling step after recovery. When placed in water in this regeneration process,
Since the barrier layer is detached from the base paper, 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.

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 to these. In the examples, "part" means "part by weight" unless otherwise specified.

[0029]

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. Ingredient Weight 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 Industries ( Co., Ltd.) 0.3 parts 30% aluminum sulphate 2 parts Next, from this paper material, a basis weight of 70 g using a fourdrinier cylinder paper machine.
/ M ² of base paper was produced. A barrier agent having the following composition was applied at a concentration of 5% by a gate roll coater installed in the middle part of the dryer of the above paper machine. Component weight 20% Oxidized modified starch gelatinization liquid 23 parts 20% Oxidized modified starch aqueous dispersion 77 parts * Oxidized modified starch uses "Trademark: Oji Ace A, Oji Corn Starch"

After the papermaking, a finishing treatment was carried out with a super calendar to obtain a release paper base material. The release paper substrate thus obtained had a density of 0.89 g / cm ³ and an Oken smoothness of 120 seconds.

A predetermined paper supply piece was 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: Oil-soluble dye "Olesol Re
Toluene colored with "dB" (Sumitomo Chemical Co., Ltd.) was applied, and after 2 seconds, it was wiped off with gauze, and the permeation state of toluene on the surface and the plugging effect of pinholes formed in spots were determined.

(2) Silicone Penetration Prevention 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 95 parts The above solution onto the test piece of paper toluene, 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 the sample components The dispersibility was evaluated by observing the dispersed state. The results of each test are shown in Table 1.

[0035]

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 barrier agent of Example 1, a barrier agent having the following composition was applied. The results of each test are shown in Table 1. Component weight 20% Oxidized modified starch gelatinization liquid 77 parts 20% Oxidized modified starch aqueous dispersion 23 parts * Oxidized modified starch uses "Trademark: Oji Ace A, Oji Corn Starch"

[0036]

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 the barrier agent of Example 1, a barrier agent having the following composition was applied. The results of each test are shown in Table 1. Component weight 20% phosphate esterified starch gelatinization solution 77 parts 20% phosphate esterified starch aqueous dispersion 23 parts * For phosphate esterified starch, use "Trademark: Neil gum A85, Matsutani Chemical"

[0037]

Example 4 A release paper substrate was prepared in the same manner as in Example 1 and its evaluation test was conducted. However, instead of the barrier agent of Example 1, a barrier agent having the following composition was applied. The results of each test are shown in Table 1. Component weight 20% Oxidized modified starch gelatinization liquid 77 parts 20% Oxidized modified starch aqueous dispersion 23 parts * Oji corn starch "Oji Ace C" is used for the oxidation modified starch

[0038]

[Comparative Example 1] The "low density polyethylene" (manufactured by Sumitomo Chemical Co., Ltd.) melted on the base paper described in Example 1-1 was laminated with a laboratory melt extruder to prepare a release paper substrate.
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 results of each test are shown in Table 1.

[0039]

Comparative Example 2 The evaluation test was performed using the base paper described in Example 1-1, which was not coated with a barrier agent by a gate roll coater, as a base material for release paper. The results of each test are shown in Table 1.

[0040]

Comparative 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 barrier agent of Example 1, a barrier agent having the following composition was applied at a concentration of 18%. The results of each test are shown in Table 1. Component weight 20% Oxidized modified starch gelatinization liquid 83 parts 20% Oxidized modified starch aqueous dispersion 17 parts * Oji corn starch "Oji Ace C" is used for oxidation modified starch

[0041]

Comparative Example 4 A release paper substrate was prepared in the same manner as in Example 1 and the evaluation test was conducted. However, instead of the barrier agent of Example 1, a barrier agent having the following composition was applied at a concentration of 18%. The results of each test are shown in Table 1. Component weight 20% Oxidized modified starch gelatinization solution 17 parts 20% Oxidized modified starch aqueous dispersion 83 parts * Oji corn starch "Oji Ace C" is used for oxidation modified starch

[0042]

[Table 1]

As is clear from Table 1, the release paper bases of Examples 1 to 4 according to the present invention have obtained satisfactory results, but the release paper bases of Comparative Examples 1 to 4 are obtained. The wood was unsatisfactory in some properties.

[0044]

The base material for release paper according to the present invention does not require a step of laminating polyethylene, and a barrier agent using an inexpensive material is manufactured by a rational coating method, so that the manufacturing cost is extremely low. However, it has a solvent barrier property comparable to that of a conventional polyethylene-laminated substrate. Further, since there is no laminated layer of polyethylene, the pulp fibers are excellent in disintegration property, and since the silicone release agent does not penetrate into the inside of the base paper, it can be easily subjected to the recycling step after recovery. Further, in the recycling step, the barrier layer of the release paper substrate of the present invention is composed mainly of gelatinized and non-gelatinized granular starch, so that when it is put into water, it is quickly released from the base paper, and only pulp fibers are left. It can be easily collected and reused. In addition, the recovered recycled pulp does not cause a trouble such as cissing in the coating process and the printing process due to the mixing of the water-repellent silicone.

Claims (1)

[Claims] 1. Gelatinized starch and non-gelatinized granular starch are added on a base paper mainly made of wood pulp in an absolute dry weight ratio of 8%.
0 to 20: 20 to 80 contained in a range, which is characterized by having a barrier layer excellent in solvent resistance and film-forming property,
A base material for release paper that allows solvent coating of release agents. [0001]