Release paper base paper, and release paper

Abstract

To provide release paper base paper excellent in pore-filling capability, capable of forming a uniform release-agent layer while including calcium carbonate therein, and release paper comprising a release agent layer formed on the release paper base paper.SOLUTION: The release paper base paper comprises a base paper and a pore-filling layer coated at least on one face of the base paper, with the coating amount (dry mass) on one face of the pore-filling layer being 4 g / m2 or more and 10 g / m2 or less. The pore-filling layer contains an adhesive in an amount of 20 pts.mass or more and 50 pts.mass or less relative to 100 pts.mass of the pigment, the pigment contains calcium carbonate of a volume median particle diameter (D50) of 0.5 μm or more and 5.0 μm or less in an amount of 50 mass% or more and 100 mass% or less, and the adhesive contains a starch-based compound and a synthetic resin latex in an amount of 80 mass% or more relative to the total amount of the adhesive, and in a mass ratio (starch-based compound / synthetic resin latex, based on dry mass) of 5 / 95-50 / 50. The release paper comprises a release agent layer on the pore-filling layer of the release paper base paper.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a base paper for release paper used for release paper used for adhesive labels and the like, and a release paper in which a release agent layer is provided on the base paper for release paper.

Background Art

[0002] Release paper is used by being attached to an adhesive surface in order to protect the adhesive surface and prevent contamination of the adhesive surface, a decrease in adhesive strength, etc. in adhesive labels, adhesive seals, adhesive tapes, etc. Release paper has a release agent layer on the surface in contact with the adhesive surface so that it can be easily peeled off from the adhesive surface. As a release agent for forming the release agent layer, materials having low surface energy and weak adhesive force with the adhesive, such as silicone resins, fluorine resins, polyester resins, and amino alkyd resins, are used, and silicone resins are particularly widely used. Since silicone-based release agents are very expensive, polyethylene laminated paper, which is difficult for the coating liquid to penetrate as a base paper for release paper and has excellent blocking resistance, is used so that the release agent layer can be formed in a small amount. However, polyethylene laminated paper has a problem that it is not suitable for recycling because a tough polyethylene film is formed on the paper surface and it is difficult to dissociate after use.

[0003] The applicant of the present application has proposed in Patent Document 1 a recyclable base paper for release paper having a pigment coating layer composed of a flat pigment and a synthetic resin latex in which the particle size and aspect ratio are within a specific range. In the base paper for release paper described in Patent Document 1, the penetration of the coating liquid for forming the release layer is suppressed by the flat pigments being stacked in the thickness direction in the pigment coating layer. Silicone-based release agents usually contain a silicone resin and a catalyst, and become a release layer by curing. Cations such as sodium ions and calcium ions may inhibit the curing of the silicone resin. Therefore, kaolin, which does not inhibit the curing of the silicone resin, is preferably used for the flat pigment (also referred to as a flat pigment) (paragraph 0017 of Patent Document 2).

[0004] In the field of papermaking, calcium carbonate is widely used as a pigment and filler. Calcium carbonate is inexpensive and has a high whiteness, making it easy to obtain white paper with a good appearance. However, since calcium carbonate is spherical rather than plate-shaped, it has poor plugging properties and is unsuitable as a pigment to be included in the plugging layer. Furthermore, calcium carbonate contains a large amount of cations such as calcium ions and sodium ions derived from impurities, which may inhibit the curing of silicone-based resins.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a base paper for release paper that contains calcium carbonate and has excellent plugging properties and can form a uniform release agent layer, and a release paper having a release agent layer formed on the base paper for release paper.

Means for Solving the Problems

[0007] Means for solving the problems of the present invention are as follows. 1. A base paper and a plugging layer on at least one surface of the base paper, wherein the one-sided coating amount (dry mass) of the plugging layer is 4 g / m 2 or more and 10 g / m 2 or less, the plugging layer contains 20 parts by mass or more and 50 parts by mass or less of an adhesive with respect to 100 parts by mass of a pigment, the pigment contains 50% by mass or more and 100% by mass or less of calcium carbonate having a volume 50% average particle diameter (D50) of 0.5 μm or more and 5.0 μm or less, The base paper for release paper is characterized in that the adhesive contains a starch-based compound and a synthetic resin latex in an amount of 80% by mass or more based on the total amount of the adhesive, and in a mass ratio of 5 / 95 to 50 / 50 (starch-based compound / synthetic resin latex: dry mass). 2. The base paper for release paper according to 1., wherein the pH of the surface of the blocking layer conforms to JAPAN TAPPI No. 49-2 and is 9.5 or less. 3. The base paper for release paper according to 1. or 2., wherein the ISO whiteness of the surface of the blocking layer conforms to JIS P 8148:2018 and is 80% or more. 4. The base paper for release paper according to any one of 1. to 3., wherein the air resistance (Wang Yan type tester method) of the base paper for release paper conforms to JIS P 8117:2009 and is 10,000 seconds or more. 5. The base paper for release paper according to any one of 1. to 4., wherein the calcium carbonate is neutralized calcium carbonate. 6. The basis weight of the base paper for release paper is 25 g / m 2 or more and 80 g / m 2 or less, and is the base paper for release paper according to any one of 1. to 5. 7. The base paper for release paper according to any one of 1. to 6., wherein the ash content of the base paper for release paper conforms to JIS P 8251:2003 and is 20% or more and 40% or less. 8. A release paper characterized by having a release agent layer on the blocking layer of the base paper for release paper according to any one of 1. to 7. 9. The release paper according to 8., wherein the release agent layer is silicone-based.

Advantages of the Invention

[0008] The base paper for release paper of the present invention contains calcium carbonate with a plugging layer being spherical, and can prevent the penetration of the release agent. By providing a release agent layer on this plugging layer, a release paper excellent in adhesion, peelability, and durability can be obtained. The base paper for release paper of the present invention, with the pH of the surface of the plugging layer being 9.5 or less, does not inhibit the curing of the silicone-based resin, so a silicone-based release agent layer can also be formed. The base paper for release paper of the present invention is excellent in disintegration property and recyclable as waste paper.

Embodiments for Carrying Out the Invention

[0009] The base paper for release paper of the present invention has a base paper and a plugging layer on at least one surface of this base paper. The one-sided coating amount (dry mass) of the plugging layer is 4 g / m 2 or more and 10 g / m 2 or less, the plugging layer contains 20 parts by mass or more and 50 parts by mass or less of an adhesive with respect to 100 parts by mass of the pigment, the pigment contains 50% by mass or more and 100% by mass or less of calcium carbonate having a volume 50% average particle diameter (D50) of 0.5 μm or more and 5.0 μm or less, the adhesive contains a starch-based compound and a synthetic resin latex in a mass ratio of 80% by mass or more with respect to the total amount of the adhesive and a mass ratio of 5 / 95 to 50 / 50 (starch-based compound / synthetic resin latex: dry mass). In this specification, the description of "A to B (A and B are numbers)" means a numerical range including the values of A and B, that is, A or more and B or less.

[0010] "Base paper" In the present invention, the base paper is a sheet made of papermaking fibers, fillers, various auxiliaries, etc. It is preferable to use wood pulp as the papermaking fibers. Examples of the wood pulp include chemical pulps such as softwood kraft pulp, hardwood kraft pulp, and sulfite pulp, mechanical pulps such as thermomechanical pulp, stone ground pulp, and refiner ground pulp, and recycled pulp obtained from newsprint, coated paper, fine paper, etc. These wood pulps can be used alone or in combination of two or more. Further, if necessary, one or more non-wood pulps such as kenaf, hemp, and bamboo, and fiber materials other than cellulose fibers such as glass fibers and polyethylene fibers can be blended. Since it becomes difficult for the coating liquid for the blocking layer to penetrate into the obtained base paper and a dense blocking layer can be formed, it is preferable to use softwood kraft pulp. Also, it is preferable to lower the drainage degree of the papermaking fibers. Specifically, the drainage degree (Canadian Standard Freeness: CSF) of the papermaking fibers is preferably 500 ml or less, and more preferably 450 ml or less.

[0011] The base paper of the present invention can contain fillers. As the fillers, known fillers such as white carbon, talc, kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium oxide, zeolite, and synthetic resin fillers can be used. In the present invention, the fillers are optional components, and the base paper can also not contain fillers. By blending fillers, the smoothness, opacity, whiteness, etc. of the base paper are improved, but the coating liquid for the blocking layer easily penetrates into the obtained base paper. Therefore, the blending amount of the fillers is determined in consideration of these characteristics. The content rate of the fillers in the base paper is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0012] As auxiliaries, sizing agents such as sulfuric acid bands and various anionic, cationic, nonionic or amphoteric retention improvers, drainage improvers, paper strength enhancers and internal sizing agents for papermaking can be used as needed. Furthermore, dyes, fluorescent brighteners, pH adjusters, defoamers, pitch control agents, slime control agents, etc. can also be added as needed.

[0013] The method for manufacturing the base paper (papermaking) is not particularly limited, and the base paper can be manufactured by papermaking in an acidic papermaking, neutral papermaking or alkaline papermaking method using a known fourdrinier former, on-top hybrid former, gap former machine, etc. Also, the base paper may be a single layer or may be composed of multiple layers of two or more layers.

[0014] Furthermore, the surface of the base paper can be treated with various chemicals. Examples of the chemicals used include polyacrylamide, polyvinyl alcohol, surface sizing agents, water resistance agents, water retention agents, thickeners, lubricants, etc., and these can be used alone or in a mixture of two or more. The method for surface treatment of the base paper is not particularly limited, but known coating devices such as rod metering size press, pond size press, gate roll coater, spray coater, blade coater, curtain coater, etc. can be used. The basis weight of the base paper is not particularly limited, but it is preferably 25 g / m 2 or more and 80 g / m 2 or less, more preferably 30 g / m 2 or more, even more preferably 35 g / m 2 or more. Also, it is more preferably 75 g / m 2 or less, even more preferably 70 g / m 2 or less.

[0015] "Blocking layer" The caulking layer contains a pigment and an adhesive, and contains 20 parts by mass or more and 50 parts by mass or less of the adhesive with respect to 100 parts by mass of the pigment. Further, the caulking layer can also contain various auxiliaries such as CNF, MFC, dispersant, water resistance agent, lubricant, defoaming agent, thickener, water retention agent, crosslinking agent, surfactant, preservative, dye, fluorescent dye, etc. within a range that does not impair the effects of the present invention.

[0016] · Pigment The pigment contains 50% by mass or more and 100% by mass or less of calcium carbonate having a volume 50% average particle diameter (D50, hereinafter also referred to as the average particle diameter) measured by the laser diffraction / scattering method of 0.5 μm or more and 5.0 μm or less. As a measuring device for the laser diffraction / scattering method, for example, the particle size distribution measuring device "Partica" manufactured by Horiba, Ltd., the particle size distribution measuring device "MASTER SIZER S" manufactured by Malvern, etc. can be exemplified. The average particle diameter of calcium carbonate is preferably 0.7 μm or more, and preferably 4.0 μm or less, and more preferably 3.0 μm or less.

[0017] The calcium carbonate may be either light calcium carbonate or heavy calcium carbonate. Further, as the calcium carbonate, neutralized calcium carbonate obtained by blowing carbon dioxide gas into its slurry for neutralization treatment is preferable because impurities such as Na ions that cause hardening inhibition are removed by the neutralization treatment. The pH after dispersing and stirring the pigment in deionized water so that the pigment concentration becomes 41.5% by mass is about 12 - 13 for non-neutralized calcium carbonate and about 7.5 - 8.5 for neutralized calcium carbonate. Hereinafter, in this specification, the pH of the pigment means the pH measured by the above-described method. As the calcium carbonate, two or more kinds such as light and heavy, neutralized and non-treated, and different particle sizes can also be used. When using two or more kinds with different particle sizes, it is preferable that all have an average particle diameter of 0.5 μm or more and 5.0 μm or less. The ratio of calcium carbonate having a D50 of 0.5 μm or more and 5.0 μm or less with respect to the whole pigment is preferably 55% by mass or more, and more preferably 65% by mass or more from the viewpoints of whiteness, durability, etc.

[0018] As a pigment, it is also possible to contain pigments other than calcium carbonate with an average particle diameter of 0.5 μm or more and 5.0 μm or less. In that case, pigments generally used in papermaking can be used in combination without particular limitation. Specifically, calcium carbonate (heavy / light) with an average particle diameter not within the range of 0.5 μm or more and 5.0 μm or less, kaolin, engineered kaolin, clay, delaminated clay, talc, titanium dioxide, aluminum hydroxide, mica, illite, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white and other inorganic pigments, and pigments such as solid type, hollow type, or core-shell type organic pigments, etc. can be mentioned, and one or more of them can be used. Among these, kaolin is preferred. When other pigments are included, the average particle diameter of the other pigments is also preferably 0.5 μm or more and 5.0 μm or less, more preferably 0.7 μm or more, and further preferably 4.0 μm or less, and still more preferably 3.0 μm or less.

[0019] ·Binder The binder contains at least a starch-based compound and a synthetic resin latex, and the starch-based compound and the synthetic resin latex are contained in an amount of 80% by mass or more based on the total amount of the binder, and in a mass ratio of 5 / 95 to 50 / 50 (starch-based compound / synthetic resin latex: dry mass, total 100). As the starch-based compound, starches such as starch, oxidized starch, hydroxyesterified starch (HES), phosphate ester starch, esterified starch, cationized starch, urea phosphate esterified starch, etc., dextrin obtained by hydrolyzing starch, etc. can be used, and one or more of them can be used.

[0020] The synthetic resin latex is not particularly limited, and latexes of various copolymers such as styrene-butadiene copolymers, styrene-acrylic copolymers, butadiene-methyl methacrylate copolymers, vinyl acetate-butyl acrylate copolymers, maleic anhydride copolymers, and acrylic acid-methyl methacrylate copolymers can be used, and one kind or a combination of two or more kinds can be used. Among these, it is preferable to use a styrene-butadiene copolymer latex having excellent blocking resistance of silicone-based resins. Further, the synthetic resin latex preferably has an average particle diameter of 100 μm or more, more preferably 150 μm or more, measured by the dynamic light scattering method (photon correlation method). Examples of the measuring apparatus by the dynamic light scattering method (photon correlation method) include "FPAR-1000" manufactured by Otsuka Electronics Co., Ltd.

[0021] The glass transition temperature (Tg) of the synthetic resin latex is preferably -20°C or higher and 30°C or lower. If the Tg of the synthetic resin latex is lower than -20°C, the blocking layer becomes too soft and is easily damaged, and the uniformity of the release agent layer provided on the blocking layer may decrease. If Tg exceeds 30°C, the uniformity of the blocking layer decreases, and the uniformity of the release agent layer provided on the blocking layer may also decrease. In this specification, Tg means the midpoint glass transition temperature measured in accordance with JIS K 7121-1987. The mass ratio of the starch-based compound to the synthetic resin latex (starch-based compound / synthetic resin latex: dry mass, total 100) is preferably 8 / 92 to 30 / 70, more preferably 12 / 88 to 20 / 80.

[0022] The adhesive can contain other adhesives as long as the effects of the present invention are not impaired. Examples of other adhesives include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and ethylene copolymerized polyvinyl alcohol; proteins such as casein, soy protein, and synthetic protein; cellulose derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose; water-soluble resins such as polyvinyl pyrrolidone and sodium alginate. One or more of these can be used. However, the total ratio of the starch-based compound and the synthetic resin latex to the total amount of the adhesive is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0023] The method for coating the blocking layer is not particularly limited, and it can be coated with a known coating apparatus and coating system. For example, coating apparatuses include blade coaters, bar coaters, roll coaters, air knife coaters, reverse roll coaters, curtain coaters, gravure coaters, spray coaters, size press coaters, gate roll coaters, and the like. As the coating system, water-based coating mainly using water as a medium is preferred. In the present invention, it is preferable to coat with an on-machine coater in which a paper-making machine and a coating apparatus are integrated. When coating with an off-machine coater in which the paper-making machine and the coating apparatus are separate, after the base paper is made on the paper-making machine, it is once wound up on a winder and then wound up again and applied to the off-machine coater for coating. However, in the case of coating with an on-machine coater, the procedures of winding up the base paper and applying it to the coater can be omitted, so the production efficiency is good. On the other hand, in the case of coating with an on-machine coater, since it is necessary to synchronize the coating speed with the paper-making speed of the paper-making machine, it is more difficult to adjust the coating amount than coating with an off-machine coater that does not require synchronization. Since the blocking layer of the present invention has high uniformity and good blocking properties even when the coating amount is small, it is easy to satisfy the desired performance even in the case of coating with an on-machine coater. As a method for drying the blocking layer, for example, ordinary methods such as steam heaters, gas heaters, infrared heaters, electric heaters, hot air heaters, microwaves, cylinder dryers, etc. are used.

[0024] The coating amount of the blocking layer is 4 g / m in terms of dry mass per side 2 or more and 10 g / m 2 or less. If this coating amount is less than 4 g / m 2 it may be difficult for the resulting blocking layer to prevent the penetration of the coating liquid for the release agent layer. On the other hand, if this coating amount exceeds 10 g / m 2 the releasability decreases and recycling becomes difficult, and also the durability of the release layer decreases. The coating amount of the blocking layer is more preferably 5 g / m 2 or more in terms of dry mass per side, and even more preferably 6 g / m 2 or more. Also, the coating amount of the blocking layer is more preferably 9 g / m 2 or less in terms of dry mass per side.

[0025] "Base paper for release paper" The base paper for release paper of the present invention has a base paper and a blocking layer on at least one surface of this base paper. The blocking layer is provided on at least one surface of the base paper and can also be provided on both surfaces. The base paper for release paper of the present invention preferably has a basis weight of 25 g / m 2 or more and 80 g / m 2 or less. Since release paper is treated as garbage after use, from the viewpoints of garbage reduction and improvement of transportation costs, a low basis weight of 80 g / m 2 or less is desired. On the other hand, if the basis weight is less than 25 g / m 2 paper breakage is likely to occur during adhesive processing, etc. Also, the paper becomes weak and difficult to handle.

[0026] The base paper for release paper of the present invention preferably has an ash content of 20% or more and 40% or less in accordance with JIS P 8251:2003. If the ash content is less than 20%, troubles such as wrinkles on the upper paper may occur due to shrinkage of the paper during adhesive processing or the like. If the ash content exceeds 40%, the strength of the paper becomes weak, and paper breakage is likely to occur during adhesive processing or the like.

[0027] The base paper for release paper of the present invention preferably has a pH of 9.5 or less in accordance with JAPAN TAPPI No.49-2 on the surface of the sizing layer. When this pH on the surface of the sizing layer is 9.5 or less, impurities such as sodium ions in the sizing layer are less, and it is possible to prevent the inhibition of curing of the silicone-based release agent applied on the sizing layer. This pH on the surface of the sizing layer is preferably 9.2 or less, more preferably 9.0 or less, still more preferably 8.8 or less, and even more preferably 8.5 or less.

[0028] The base paper for release paper of the present invention preferably has an ISO whiteness of 80% or more in accordance with JIS P 8148:2018 on the surface of the sizing layer. The base paper for release paper of the present invention contains calcium carbonate and can achieve a high whiteness. This whiteness is more preferably 83% or more, still more preferably 84% or more, even more preferably 85% or more, and even more preferably 86% or more.

[0029] In the base paper for release paper of the present invention, the air permeability resistance (Wang Research type tester method) defined in JIS P 8117:2009 on the surface of the sizing layer is preferably 10,000 seconds or more. When the air permeability resistance (Wang Research type tester method) is 10,000 seconds or more, it becomes easy to uniformly coat the release agent, and the adhesion and peelability when made into release paper are excellent, and further, the dissociation property is excellent. The air permeability resistance (Wang Research type tester method) is more preferably 20,000 seconds or more, still more preferably 24,000 seconds or more, and even more preferably 28,000 seconds or more. The upper limit of the air permeability resistance is not particularly limited.

[0030] "Release paper" By applying a release agent onto the sealing layer of the base paper for release paper to form a release agent layer, release paper can be manufactured. As the release agent, materials with low surface energy and weak adhesive force with adhesives, such as silicone-based resins, fluorine-based compounds, amino alkyd-based compounds, and polyester-based compounds, can be used without particular limitation. However, in the present invention, it is preferable to use a silicone-based resin. Examples of the silicone-based resin used as the release agent include solventless silicone-based resins, solvent-based silicone-based resins, water-based emulsion-type silicone-based resins, and solventless UV-curable silicone-based resins.

[0031] The coating method of the release agent is not particularly limited, and it can be coated with known coating devices and coating systems. For example, as the coating device, there are blade coaters, bar coaters, roll coaters, air knife coaters, reverse roll coaters, curtain coaters, gravure coaters, spray coaters, size press coaters, gate roll coaters, and the like. As a method for drying the release agent layer, for example, ordinary methods such as steam heating heaters, gas heaters, infrared heaters, electric heaters, hot air heating heaters, microwaves, and cylinder dryers are used.

[0032] The coating amount of the release agent layer is preferably 0.2 g / m 2 or more and 3.0 g / m 2 or less in terms of dry mass per side. If this coating amount is less than 0.2 g / m 2 , it becomes difficult to obtain a uniform release agent layer. On the other hand, even if this coating amount exceeds 3.0 g / m 2 , the releasability hardly improves and the effect saturates. The coating amount of the release agent layer is more preferably 0.3 g / m 2 or more and 2.0 g / m 2 or less in terms of dry mass per side. The coating amount of the release agent layer is more preferably 0.4 g / m 2 or more in terms of dry mass per side. Also, the coating amount of the release agent layer is more preferably 1.2 g / m 2 or less in terms of dry mass per side.

[0033] As described above, the base paper for release paper of the present invention has high uniformity of the blocking layer and good blocking properties, and a uniform release agent layer can be formed on this blocking layer.

Example

[0034] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by the description of the examples. In addition, the parts by mass in the examples represent parts by mass on an absolutely dry basis unless otherwise specified.

[0035] 「Example 1」 (Production of base paper) 75 parts by mass of hardwood kraft pulp (LBKP) and 25 parts by mass of hardwood kraft pulp (NBKP) were mixed to obtain a raw material pulp with a Canadian Standard Freeness (CSF) of 400 ml. 0.3 parts by mass of cationized starch was added as a paper strength agent to 100 parts by mass of the raw material pulp, and then 1.5 parts by mass of aluminum sulfate was added. Subsequently, papermaking was carried out using a Fourdrinier multi-cylinder papermaking machine to obtain a base paper with a basis weight of about 44 g / m 2 2.

[0036] (Preparation of coating liquid for blocking layer) As an inorganic pigment, precipitated calcium carbonate (manufactured by Nippon Paper Industries Co., Ltd., D50: 1.04 μm, pH: 12.9) was neutralized by blowing carbon dioxide gas into the slurry to obtain neutralized precipitated calcium carbonate (pH: 8.2) with 100 parts by mass of solids. As an adhesive, 25 parts by mass of styrene-butadiene copolymer latex (manufactured by Japan A&L Co., Ltd., trade name: PA0330, Tg -10°C) on an absolutely dry basis, 5 parts by mass of starch (manufactured by Nippon Shokuhin Kako Co., Ltd.: MS#3800), and 1 part by mass of a lubricant (manufactured by San Nopco Co., Ltd.: Nopcoat C-104) were blended to prepare a coating liquid for the blocking layer. (Coating) On both sides of the base paper, using a blade coater, the coating liquid for the blocking layer was coated on each side so that the one-sided coating amount was 8 g / m in terms of dry mass 2 2, and then dried to obtain a base paper for release paper.

[0037] 「Example 2」 An original paper for release paper was obtained in the same manner as in Example 1, except that the inorganic pigment was 90 parts by mass of neutralized calcium carbonate and 10 parts by mass of kaolin (manufactured by Kamin Co., Ltd., kaiming loss, D50: 1.97 μm, pH: 7.2) in terms of solid content. "Example 3" An original paper for release paper was obtained in the same manner as in Example 1, except that the inorganic pigment was 70 parts by mass of neutralized calcium carbonate and 30 parts by mass of kaolin in terms of solid content. "Example 4" An original paper for release paper was obtained in the same manner as in Example 1, except that the inorganic pigment was 60 parts by mass of neutralized calcium carbonate and 40 parts by mass of kaolin in terms of solid content. "Example 5" An original paper for release paper was obtained in the same manner as in Example 1, except that no neutralization treatment was performed.

[0038] "Comparative Example 1" An original paper for release paper was obtained in the same manner as in Example 1, except that the one-sided coating amount of the blocking layer was 3 g / m² in terms of dry mass. 2 "Comparative Example 2" An original paper for release paper was obtained in the same manner as in Example 1, except that the one-sided coating amount of the blocking layer was 12 g / m² in terms of dry mass. 2

[0039] "Comparative Example 3" An original paper for release paper was obtained in the same manner as in Example 1, except that neutralized calcium carbonate (pH: 8.2) obtained by performing a neutralization treatment by blowing carbon dioxide gas into a slurry of light calcium carbonate (manufactured by Nippon Paper Industries Co., Ltd., D50: 0.30 μm) was used. "Comparative Example 4" An original paper for release paper was obtained in the same manner as in Example 1, except that neutralized calcium carbonate (pH: 8.2) obtained by performing a neutralization treatment by blowing carbon dioxide gas into a slurry of light calcium carbonate (manufactured by Nippon Paper Industries Co., Ltd., D50: 6.0 μm) was used.

[0040] "Comparative Example 5" ​​An undercoating liquid for release paper was obtained in the same manner as in Example 1, except that 10 parts by mass of a styrene-butadiene copolymer latex as an adhesive and 5 parts by mass of starch were blended in a dry basis with respect to 100 parts by mass of the neutralized calcium carbonate solid content. "Comparative Example 6" An undercoating liquid for release paper was obtained in the same manner as in Example 1, except that 60 parts by mass of a styrene-butadiene copolymer latex as an adhesive and 5 parts by mass of starch were blended in a dry basis with respect to 100 parts by mass of the neutralized calcium carbonate solid content. "Comparative Example 7" An undercoating liquid for release paper was obtained in the same manner as in Example 1, except that only 30 parts by mass of a styrene-butadiene copolymer latex as an adhesive was blended in a dry basis with respect to 100 parts by mass of the neutralized calcium carbonate solid content. "Comparative Example 8" An undercoating liquid for release paper was obtained in the same manner as in Example 1, except that the inorganic pigment was calcined clay (Ansilex manufactured by BASF, D50: 2.53 μm, pH: 7.1).

[0041] <Measurement method> <Inorganic pigment> · Volume 50% average particle diameter (D50) Measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Malvern, MASTER SIZER S). <Quality evaluation of base paper for release paper> · Air permeability resistance Measured by a method conforming to JIS P 8117:2009 (Wang Research type tester method). · Paper surface pH The pH of the coated surface was measured in accordance with JAPAN TAPPI No.49-2. · Ash content Conformed to JIS P 8251:2003 · ISO whiteness The undercoating layer coated surface was measured in accordance with JIS P 8148:2018.

[0042] · Dimensional stability Ten samples measuring 15 mm in width and 150 mm in length in the CD direction of the sample were collected. The samples were immersed in water for 1 hour, excess moisture on the samples taken out of the water was wiped off, the length was measured, and the shrinkage rate before and after immersion was evaluated. If the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] 〇: If the shrinkage rate is 2% or less, the dimensional stability is good. △: If the shrinkage rate is 2.5% or less, the dimensional stability is at a level where there are no problems in use. ×: If the shrinkage rate is greater than 2.5%, the dimensional stability is NG.

[0043] ·Dissociability The base paper for release paper was immersed in water so that the concentration became 2.0 mass%, and the degree of dissociation into water when it was dissociated for 60 minutes with a Tappi standard disintegrator was evaluated. If the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] 〇: The pulp fibers are dispersed and the dissociability is good. △: There is a slight bundling of pulp fibers. ×: Lumps of pulp fibers or bundles of pulp fibers remain and it is impossible to dissociate.

[0044] <Manufacture of Release Paper> The necessary amount of catalyst was added to a solventless silicone-based resin (LTC-1053L: manufactured by Toray Dow Corning Silicone Co., Ltd.) to obtain a coating liquid for the release agent layer. Next, using an RI printing machine, the coating liquid for the release agent layer was coated on the blocking layer of each base paper for release paper so that the coating amount was 1.0 g / m 2 After coating, a curing treatment was performed with a dryer (130 °C, 30 sec) to obtain release paper.

[0045] <Quality Evaluation of Release Paper> ·Initial Curing Property of Silicone-Based Resin Immediately after coating the coating liquid for the release agent layer, the surface of the release agent layer of the release paper was rubbed back and forth 5 times by about 5 cm with a finger (approx. 500 g load), and the surface state was visually observed and evaluated according to the following 3 levels. Regarding the use of the silicone-based release agent, if the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] ○: There is no mark on the rubbed area, and the silicone-based resin is cured. △: There is a partial mark on the rubbed area, but the silicone-based resin is generally cured. ×: There is a mark on the rubbed area, and the silicone-based resin is not cured.

[0046] · Durability After treating the sample coated with the coating liquid for the release agent layer at 70 °C and 95% RH for 3 days, the surface of the release agent layer of the release paper was rubbed back and forth 5 times by a finger (with an approximate load of 3 kg) for about 5 cm, and the surface state was visually observed and evaluated according to the following three levels. If the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] ○: There is no mark on the rubbed area. △: There is a mark on the rubbed area, but there is no peeling of the release agent layer. ×: The release agent layer at the rubbed area peels off.

[0047] · Sealing property of silicone-based resin After conditioning the sample coated with the coating liquid for the release agent at 23 °C and 50% RH for 3 days, a line was drawn on the surface of the release agent layer with a red magic pen (manufactured by Teranishi Chemical Industry Co., Ltd., product name: Magic Ink), and after wiping it off with gauze 5 seconds later, the adhesion of the ink was visually observed and evaluated. If the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] ○: The ink is not adhered. △: Slight ink is adhered. ×: The ink is adhered.

[0048] The evaluation results of the base paper for release paper and the release paper obtained in each example and comparative example are shown in Table 1.

Table 1

[0049] The base paper for release paper obtained in the examples of the present invention was excellent in plugging property and durability. In particular, the base paper for release paper obtained in Examples 1 to 4 with a paper surface pH of 9.5 or less did not inhibit the curing of the silicone-based release agent. In addition, the base paper for release paper obtained in Example 5 can also be applied with release agents other than silicone-based ones.

[0050] From Examples 1 to 4 and Comparative Examples 1 and 2, when the one-sided coating amount (dry mass) of the plugging layer was 4 g / m 2 or more and 10 g / m 2 or less, it was confirmed that the plugging property and durability were excellent. From Examples 1 to 4 and Comparative Examples 3 and 4, it was confirmed that by including calcium carbonate with a D50 of 0.5 μm or more and 5.0 μm or less in the plugging layer, a base paper for release paper excellent in plugging property and durability could be obtained. Also, from the comparison with Comparative Example 8, it was confirmed that by including calcium carbonate, a base paper for release paper excellent in whiteness could be obtained. From Examples 1 to 4 and Comparative Examples 5 to 6, when the adhesive contained in the plugging layer contained a starch-based compound and a synthetic resin latex in an amount of 80% by mass or more based on the total amount of the adhesive and in a mass ratio of 5 / 95 to 50 / 50 (starch-based compound / synthetic resin latex: dry mass), it was confirmed that the plugging property and durability were excellent.

Claims

1. A base paper having a blocking layer on at least one surface of the base paper, wherein the one-sided coating amount (dry mass) of the blocking layer is 4 g / m ２ or more and 10 g / m ２ or less, the blocking layer contains 20 to 50 parts by mass of an adhesive with respect to 100 parts by mass of a pigment, the pigment contains 50 to 100% by mass of calcium carbonate having a volume 50% average particle diameter (D50) of 0.5 μm or more and 5.0 μm or less, the adhesive contains a starch-based compound and a synthetic resin latex in a mass ratio (starch-based compound / synthetic resin latex: dry mass) of 80% by mass or more and 5 / 95 to 50 / 50 with respect to the total amount of the adhesive, and the base paper for release paper is characterized by this.

2. The base paper for release paper according to claim 1, wherein the pH conforming to JAPAN TAPPI No. 49-2 on the surface of the blocking layer is 9.5 or less.

3. The base paper for release paper according to claim 1 or 2, wherein the ISO whiteness conforming to JIS P 8148:2018 on the surface of the blocking layer is 80% or more.

4. The base paper for release paper according to claim 1 or 2, wherein the air permeability resistance (Wang Research type tester method) conforming to JIS P 8117:2009 of the base paper for release paper is 10,000 seconds or more.

5. The base paper for release paper according to claim 1 or 2, wherein the calcium carbonate is neutralized calcium carbonate.

6. The basis weight of the base paper for release paper is 25 g / m ２ or more and 80 g / m ２ or less, and the base paper for release paper according to claim 1 or 2 is characterized by this.

7. The base paper for release paper according to claim 1 or 2, characterized in that the ash content conforming to JIS P 8251:2003 of the base paper for release paper is 20% or more and 40% or less.

8. A release paper, characterized in that it has a release agent layer on the blocking layer of the base paper for release paper according to claim 1 or 2.

9. The release paper according to claim 8, characterized in that the release agent layer is a silicone-based one.

Images