JPH06136700A - Substrate for release paper - Google Patents

Abstract

PURPOSE:To obtain a substrate having sufficient solvent barrier properties by itself and excellent releasability, comprising a base paper composed of wood pulp as a main raw material and a barrier layer which is formed on one side of the base paper and consists essentially of a PVA-based resin and a specific boron compound polymer. CONSTITUTION:A paper stock comprising bleached kraft pulp of needle-leaf tree or kraft pulp of broad-leaf tree, 50% talc dispersion, 30% reinforcing rosin sizing agent and 30% aluminum sulfate is made into paper by a long net multi- cylindrical papermaking machine to produce a base paper having 65g/m<2> meter weight. One side of this base paper is coated with a coating solution consisting essentially of a polyvinyl alcohol-based resin and an organic boron compound of the formula ((p) is >=10 integer) so as to give 5.0g/m<2> dry weight, then dried and further finished by a super calender into >=150 seconds smoothness of OKEN type standard to give the objective substrate for release paper which has sufficient solvent barrier properties without polyethylene lamination, capable of being directly coated with a solution of a silicone in an organic solvent and showing excellent releasability.

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. Furthermore, even if this base fiber can be dispersed in water by strengthening mechanical force and introducing chemical treatment, the fiber is significantly damaged by strengthening the beating treatment. It is difficult to reuse.

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.
A base for release paper, which is formed on the surface and provided with a barrier layer containing a polyvinyl alcohol resin and an organoboron compound polymer represented by the following general formula (1) as main components. Material.

[Chemical 2] [However, in the above formula, p represents an integer of 10 or more]

[0010]

In order to obtain a release paper which has excellent solvent barrier properties comparable to polyethylene without laminating polyethylene on the base paper and which can be easily disintegrated in water and reused, As a result of earnest research on the material and coating method of the barrier layer formed on the base paper, finally a base material for release paper which can satisfy these requirements has 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 conducted by the present inventors to establish this means, as a means capable of simultaneously achieving a silicone organic solvent solution permeation-preventing function and a pinhole sealing function, a base material mainly made of wood pulp is used. Forming a barrier layer containing a polyvinyl alcohol-based resin and the organoboron compound polymer represented by the general formula (1) as main components exerts an excellent effect for satisfying this requirement. Therefore, the present invention has been completed.

The polyvinyl alcohol resin used in the barrier layer in the present invention includes polyvinyl alcohol having an arbitrary degree of polymerization and saponification, as well as unsaturated carboxylic acid or its partial or complete ester or acetoacetic acid esterification. "Post-modified" polyvinyl alcohol is also used. The degree of polymerization is preferably in the range of 300 to 1700, and particularly preferably in the range of 500 to 1000 from the viewpoint of coating viscosity and coatability.

The polyvinyl alcohol-based resin having an acetoacetic acid ester group in the molecule is obtained by converting polyvinyl alcohol into an acetoacetic acid ester. The acetoacetic acid esterification is achieved by a method of adding diketene to a polyvinyl alcohol-based resin or transesterifying the acetoacetic acid ester. The degree of polymerization is preferably 700 to 2000, and particularly preferably about 1000 in order to achieve the effects of the present invention and in practicality. The content of the acetoacetic acid ester group may be 0.05 mol% or more with respect to the polyvinyl alcohol-based resin as long as it exhibits water solubility. Usually 0.1 to 20 mol%, especially 0.5 to 10 mol%
Is preferred.

The polymer of the organoboron compound represented by the formula (1), which is one of the polymers constituting the barrier layer of the present invention, is
It has a very good compatibility with a polyvinyl alcohol-based resin, brings about an appropriate thickening effect, and acts to attract the hydrophilic group of polyvinyl alcohol to the boron portion. This allows
It is presumed that the hydroxyl groups of polyvinyl alcohol in the barrier layer are oriented in a certain direction and exhibit excellent barrier properties against organic solvents. The organoboron compound polymer is used in an amount of 1 to 30 parts by weight, preferably 2 to 15 parts by weight, based on 100 parts by weight of the polyvinyl alcohol resin. If the amount used is less than 1 part by weight, the solvent barrier property is insufficient. If the amount used is more than 30 parts by weight, there are problems that the viscosity of the coating liquid increases and the life of the coating liquid is short due to gelation, making it practically difficult to use Become.

The barrier layer of the present invention may contain a pigment and the like in addition to the polyvinyl alcohol resin and the organoboron compound polymer. Such pigments include inorganic pigments such as kaolin, calcium carbonate, talc, aluminum hydroxide and titanium dioxide, and organic synthetic pigments containing polystyrene as a main component. On the other hand, the coating equipment used in the present invention 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, a water-based paint containing a polyvinyl alcohol-based resin and an organoboron compound polymer represented by the above general formula (1) as main components for forming a barrier layer is coated on the base paper twice or more. You may apply by the coating operation of.

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 in the range of 20 to 5000 seconds (Oken type smoothness described in JAPAN TAPPI Paper Pulp Test Method No. 5) depending on the purpose. 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 excellent barrier properties against the monomers 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 a 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.

[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 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 is obtained by a fourdrinier cylinder type 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 10% polyvinylalcohol (trademark: PVA706, manufactured by Kuraray Co.) 100 parts 10% organic boron compound polymer (trademark: Haiho Bu Ron DDGB90, average molecular weight about 10,000, boron content 6.2%) 10 parts The 10% coating The liquid was coated on one surface of the above base paper so that the dry weight was 5.0 g / m ² , and dried. Furthermore, a finishing release paper having a smoothness of 150 seconds was manufactured by using a super calender. A predetermined piece of paper was prepared from the release paper substrate, and its toluene penetration preventing effect, pinhole preventing effect, silicone penetration preventing effect and disintegration 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, wiped with gauze. The state of permeation of toluene on the surface and the plugging effect of pinholes that were spotted 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 is subjected to a disintegration 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 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 part 30% aluminum sulfate 2 parts Next, a plain glossy paper having a rice basis weight of 80 g / m ^{2 was} 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, a coating composition having the following composition was used as the coating liquid for the barrier layer of Example 1. Ingredient wt 50% kaolin dispersion (trademark: HT clay, Enke Bu Ruha Bu preparative Bu made 100 parts of 10% polyvinylalcohol (trademark: PVA706, manufactured by Kuraray Co.) 100 parts 10% organic boron compound polymer (trademark: Haiho Bu Ron DDGB90, average molecular weight about 10,000 , Boron content 6.2%) 10 parts Table 1 shows the test results.

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 "PVA706" (manufactured by Kuraray Co., Ltd.) as a barrier agent was coated with a Meyer bar at 10 g / m ² and a super calender for a smoothness of 220 seconds according to Oken type. Was used as a base material for finish release paper. 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 (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location 7199-3B D21H 1/34 A

Claims (1)

[Claims] 1. A base paper containing wood pulp as a main raw material, a polyvinyl alcohol resin formed on one surface of the base paper, and an organoboron compound polymer represented by the following general formula (1). A base material for release paper, which is provided with a barrier layer contained as a component. [Chemical 1] [However, in the above formula, p represents an integer of 10 or more]