JPH0135959B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a release paper used in the production process of plastics, films, leather, synthetic leather, etc., and relates to a method for producing a release paper obtained by coating a release layer with an aqueous coating liquid. Release paper used in the manufacturing process is generally called process paper (hereinafter referred to as process paper), and is required to have various properties depending on its purpose, but its main properties are appropriate release properties, uniformity of surface condition, and repeatability. It can be summarized in terms of usability, solvent resistance, heat resistance, etc. In general, methods for imparting release properties to engineering paper include (1) applying an aqueous coating solution containing a release agent with water- and oil-repellent properties; and (2) applying water- and oil-repellent materials such as silicone resins and fluororesins. A method of applying an oil-based varnish containing a high-performance release agent (3) A method of laminating chemically inert resins such as polypropylene resin or polymethylpentene resin by heat fusing or laminating. , the present invention corresponds to method (1).
As the release agent, alkyl polysiloxane, mercapto silicone resin emulsion, carboxyl silicone resin emulsion, polycarbonyl silicone resin emulsion, chromium complex, fluorocarbon complex, etc. are generally used. Many of these stripping agents are extremely expensive;
Various types of base paper are used in order to achieve a large peeling effect with a small amount of coating, but in general, paper with a flat surface and a barrier property against the peeling treatment solution is used.(1) Polyethylene laminated paper Method of use (2) Method of using base paper coated with clay (3) Method of using base paper coated with a barrier coating against water and solvents with poval, carboxymethyl cellulose, etc. has a multilayer structure. Among these various manufacturing methods, the method of obtaining a multilayer structure by applying an aqueous coating liquid has higher productivity and can be manufactured at a lower cost than other methods, so this method is currently used. Paper has come to occupy a large portion of the market. However, even with these variously designed engineered papers, they are not always fully satisfactory, and detachment easily occurs between the release agent layer and the barrier coating layer, making it difficult to use repeatedly. There are many things I cannot bear,
Or if you use it with embossing,
Cracks were likely to occur during embossing, resulting in partial peeling defects and problems such as loss of uniformity on the product surface. In addition, there are many applications in which engineering paper is exposed to high temperatures of 180°C to 250°C, and in this case, the sheet-like base material, which is mainly made of pulp, is susceptible to thermal deterioration and mechanical strength deterioration. Therefore, it is often impossible to use it repeatedly. The inventors of the present invention have carried out intensive studies to improve the above-mentioned disadvantages and supply process paper at low cost, and as a result, they have arrived at the present invention, which solves the cause of the above-mentioned disadvantages. (1) Since a release agent layer is provided on top of a water barrier layer with extremely low water absorption, the adhesive strength between the layers is weak, and the release agent layer is likely to separate due to interlayer delamination. (2) The barrier coating layer is When the barrier layer has a layered structure, the vertical pick-up strength of the barrier coating layer itself is a problem, as well as the adhesive strength with the base paper and the release agent layer. If the barrier coating is too weak, this layer breakdown of the barrier coating will result in detachment of the release agent layer. (3) It has a multi-layered structure, and each layer has weak adhesion and is an independent layer structure, so when embossed, cracks are likely to occur due to differences in elongation between layers. (4) Strength deterioration due to heat is due to the strength of the base pulp. It has been found that the deterioration of pulp is greatly affected by the oxidizing substances in the substrate. The present invention was achieved as a result of continued studies to eliminate the above-mentioned drawbacks. That is, the present invention avoids as much as possible the mixing of oxidizing substances into the base material mainly composed of pulp, keeps the pH within the range of 5.5 to 7.0, prevents strength loss due to thermal deterioration that tends to cause problems during repeated use, and further improves interlayer strength. In order to increase the interlayer strength between the release layer and the primary processed sheet, the surface of the primary processed sheet is The purpose is to impart appropriate water absorption to the material and strengthen the interlayer and layer strength. According to the present invention, the primary processing sheet is integrated with the substrate, and the release processing layer is coated in an extremely thin film due to cost considerations. 6 g/m2 or ^less so that the processed layer produced by the primary processing does not constitute a continuous layer that completely covers the substrate, and the water absorption of the surface after the primary processing is reduced to the lump size value 10 seconds after contact with water. 5 to 15 g/ ^m2 , and the coating amount is 6
If it exceeds g/m ² , the primary processed layer becomes continuous, and peeling occurs inside the primary processed layer during embossing or repeated use. If the cob size value is 15 g/m ² or more, the water absorption is large, and the release coating liquid penetrates into the coating so much that the object of the present invention cannot be achieved. When the hump size value is 5 g/m ² or less, the water absorption is small and penetration of the coating liquid for release processing in secondary processing can be suppressed, but the interlayer strength between the primary processed sheet and the release processing layer is reduced. Because the primary processed surface has appropriate water absorption, the binder in the coating liquid containing the release agent penetrates appropriately, and the strong adhesion has high resistance to embossing, making it difficult to crack. It is suitable for embossing. The substrate mainly composed of pulp in the present invention is PH
This refers to so-called neutral paper or something similar to neutral paper with a value within the range of 5.5 to 7.0, and indicates that the addition of commonly used oxidizing substances such as aluminum sulfates or chlorides should be minimized or not used. This is the basic idea. The pulps used are GP, KP,
Any commonly used pulp such as CGP may be used, and pigments and fillers are added to it and the paper is made using an ordinary Fourdrinier paper machine or cylinder paper machine. The primary processing liquid uses pigments used in ordinary coating liquids, such as kaolin, calcium carbonate, aluminum hydroxide, satin white, and titanium dioxide, singly or in combination, and a thermoplastic synthetic resin emulsion is added as a binder. However, the amount added is naturally limited due to the elasticity during embossing and the rigidity of the processing paper, and the solid content is 5 to 30 parts per 100 parts of pigment.
Parts by weight are preferred. If it is more than 30 parts, the processing paper becomes soft and the barrier properties become too strong, which is not compatible with the gist of the present invention. Moreover, if it is less than 5 parts, it will not be flexible and will lack elasticity, which will tend to cause cracks during embossing, which is not good. The thermoplastic synthetic resin emulsion used for the primary processing layer in the present invention may be of any type as long as it has appropriate adhesion and film properties, but the glass transition temperature is lower during embossing. A temperature of 35°C or lower is desirable in order to prevent the occurrence of cracks. The pigment used in the primary processing layer in the present invention may be any pigment normally used in coating liquids. The present invention will be explained below using examples. Example 1 Symmetrical Example 1 Canadian Freeness Beaten to 470ml
50 parts of NBKP and 50 parts of LBKP beaten to 400 ml were mixed, and additives were mixed therewith in the proportions shown in Table 1 to prepare paper stocks of Example 1 and Symmetrical Example 1. This paper stock was made into paper at 130g/ ^m2 using a Fourdrinier paper machine,
As a primary processing treatment, the surface is coated with a size press coater.
Apply the mixed coating solution shown in Table 2 to both sides at a solid content of 6 g/m ² , and after drying, smooth finish using a super calender, and apply the release treatment solution shown in Table 2 to one side using an air knife coater. was coated at 0.5 g/m ² and smoothed using a super calender to create a release paper. The release paper thus produced was embossed through an embossing roll and repeatedly used as a processing paper for PVC leather. Table 1 shows its characteristics during use. From the table, it can be seen that the use of neutral paper for the base material reduces strength deterioration due to heat and increases the number of repeated uses. Examples 2 to 4 Symmetric Examples 2 to 3 Substrates were made in the same manner as in Example 1, and primary processing was performed using the formulations shown in Table 3. Thereafter, a release treatment liquid was applied and embossing was performed in the same manner as in Example 1, and the paper was repeatedly used as a processing paper for PVC leather. In symmetrical example 1, the same coating solution as in example 2 was applied in heavy coating using an air knife coater. The physical properties and mode of use are shown in Table 3. Symmetrical example 2
In the case of , severe cracking of the release layer caused uneven peeling, and it was practically difficult to use it as a process paper after the third use. In Symmetrical Example 3, cracks in the release layer were observed even before use, and the paper had poor characteristics as a processing paper. From this result, the effects of the present invention are clear.

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Claims (1)

[Scope of Claims] 1. Primary processing is performed by impregnating and coating the surface of a base sheet mainly composed of pulp fibers with an aqueous coating liquid mainly containing pigments, and further, after the primary processing, one or both sides are subjected to an aqueous peeling process. A release paper that has been subjected to a secondary process of being coated with a water-based coating liquid, the amount of which is coated with the aqueous coating liquid of the primary process is 6 g/m ² or less, and the water absorption of the surface after the primary process is similar to that of water. A release paper characterized in that the bump size value at 10 seconds after contact is 5 to 15 g/m ² and the substrate mainly composed of pulp has a pH in the range of 5.5 to 7. 2. The release paper according to claim 1, wherein the aqueous coating liquid used in the primary processing mainly contains a pigment and contains a thermoplastic synthetic resin emulsion as a binder. 3. The release paper according to claim 2, wherein the blending ratio of the thermoplastic synthetic resin emulsion is 5 to 30 parts per 100 parts of the pigment.