JP2012062600A - Cast coated paper for base material of process paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cast coated paper used as a base material of process paper for producing synthetic leather in which the cast coated paper has an excellent gloss developing property and good solvent resistance and is excellent in repetitive use.SOLUTION: There is provided cast coated paper for a base material of process paper in which a cast coated layer including a pigment and a binder as main components is provided on at least one surface of base paper, and an organic pigment is blended in an amount of 1-20 pts.wt. based on 100 pts.wt. pigment. The cast coated layer is preferably formed by a solidification method.

Description

The present invention relates to a cast-coated paper that serves as a base material for process paper that is repeatedly used in synthetic leather production and the like.

Cast coated papers that have a higher glossiness of white paper than ordinary coated paper and a mirror-like surface shape can be broadly classified according to applications: (1) General printing applications such as posters, catalogs, calendars, brochures, etc. (2) Inkjet Ink-jet applications used for printer paper, (3) Bag applications used for luxury shopping bags, book covers, etc., (4) Adhesive label applications used as adhesive paper, (5) Vinyl chloride leather and urethane The process paper is used as a base paper for leather process paper.

Cast coated paper is required to have high white paper glossiness, and the required quality differs depending on the application, and in general printing applications used for offset printing, etc., printability such as surface shape, printing surface strength, ink drying property, etc. Is required. In inkjet applications, various inkjet aptitudes such as ink absorbability and image reproducibility are required. For bag applications, particularly strong paper strength and printing surface strength are required. In adhesive label applications, letterpress printing is the main component, and generally high surface strength is not required, but good surface shape without pinholes and water resistance (blocking resistance) are required. Moreover, since there is a case where the ink on the printing surface adheres to the release paper in the state of being wound up after printing, it is desired that the ink drying property is fast. For process paper applications, good surface feeling and solvent resistance without flicker (pinhole-like minute concave defects) are required.

Process paper is used as a peeling sheet for casting urethane paste, vinyl chloride paste, etc. in the manufacturing process of synthetic leather such as vinyl chloride leather and urethane leather, ceramic sheet, silicon rubber, marking film, etc. A substrate such as paper, coated paper, or plastic film has a release layer such as alkyd resin, silicone resin, or polypropylene resin.

For example, synthetic leather is manufactured by applying a synthetic resin such as urethane resin, vinyl chloride resin, polyamide resin, etc. on process paper, drying and solidifying, and then solidifying with an adhesive as necessary. It is made by pasting the cloth and finally peeling the synthetic leather from the process paper. The process paper must be able to withstand repeated use of these series of processes.

In addition to high-quality paper, coated paper, cast coated paper, plastic film such as polyethylene terephthalate (PET), synthetic paper, or metal foil is also used as the base material for process paper. From the viewpoint of excellent heat resistance, which is important as the processability of synthetic leather, paper base materials using natural pulp are preferred. Among paper base materials, cast coated paper with high white paper gloss and mirror-like surface shape gives high-quality enamel-like synthetic leather by transferring the cast surface. Demand is increasing as a material (see Patent Document 1 and Non-Patent Document 1).

The quality required for cast coated paper as a base material for synthetic leather process paper is included in polyurethane and vinyl chloride paste, with good surface feeling without gloss unevenness and flickering (pinhole-like minute concave defects). Barrier property and fastness (hereinafter sometimes referred to as “solvent resistance”) against solvents such as dimethylformaldehyde (DMF), methyl ethyl ketone (MEK), and toluene. In recent years, with the increase in thickness of synthetic leather, there have been problems such as a decrease in the number of processes due to peeling of the cast layer and poor appearance of the synthetic leather due to transfer of the peeled cast layer. The cause of this is considered to be that the solvent contained in the synthetic resin paste is difficult to escape from the synthetic leather side, and the coating layer on the process paper side is likely to deteriorate, so that the cast layer is peeled off. In order to solve this problem, improvement in solvent resistance has become a major issue for cast coated paper as a base material for process paper.

Thus, in order to improve the solvent resistance, for example, a cast coated paper using a styrene / butadiene copolymer latex having a gel content of 85% by weight or more as an adhesive has been proposed (see Patent Document 2). ). Furthermore, in order to improve solvent resistance, a cast coated paper using a polyacrylic acid-polyvinyl alcohol copolymer as an adhesive has been proposed (see Patent Document 3). However, these conventional coated papers do not satisfy the required solvent resistance and cast surface feeling.

In addition, since the glossiness of the process paper directly affects the glossiness of enamel-like synthetic leather, improve the glossiness expression when a release layer such as an alkyd resin, silicone resin, or polypropylene resin is applied. Has become a major issue. As a cast coated paper excellent in white paper gloss and printability, it has been proposed that the coating composition contains a hollow plastic pigment having a porosity of 45% or more (see Patent Document 4).

JP 2003-55894 A Japanese Patent Application Laid-Open No. 2005-97781 Japanese Patent No. 4210313 JP-A-9-31891 Special Function Paper 2001, p74-78, published by Paper Industries Times

In view of the situation as described above, the present invention is excellent in the glossiness of process paper in process coated paper used as a base material for process paper, in particular, for manufacturing synthetic leather. An object of the present invention is to provide a cast coated paper having good fastness and excellent repeated use.

As a result of intensive studies on the above problems, the present inventors have found that the problems can be solved by using an organic pigment in the cast coating layer, and have completed the present invention. Specifically, the present invention is a cast coated paper in which a cast coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a base paper, and the organic pigment is added in an amount of 1 to 20 per 100 parts by weight of the pigment. It is related with the cast coated paper for process paper base materials characterized by mix | blending a weight part.

According to the present invention, as cast coated paper suitable as a base material for process papers, particularly process papers for the production of synthetic leather, it is excellent in gloss expression, has good barrier properties and fastness to solvents, and can be used repeatedly. A well-balanced cast coated paper with excellent cast surface and operability can be obtained.

In the present invention, a cast coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a base paper, and an organic pigment is used as the pigment. Examples of the organic pigment include plastic pigment, urea-formalin resin, styrene-methacrylic acid copolymer resin, polystyrene resin, and vinylidene chloride. Among these, a plastic pigment is preferable because it is excellent in gloss development and solvent resistance. As the plastic pigment, a solid type having no voids in the pigment, a hollow type having voids in the pigment, or a core-shell type can be used alone or in combination of two or more as required. For melting on a cast drum to form a film and exhibiting solvent resistance and gloss development, it is more preferable that the solid type is excellent in thermal efficiency.

In the present invention, the reason why an excellent effect is obtained by using an organic pigment such as a plastic pigment in the cast coating layer is not clear, but when forming the cast coating layer, it is used as an adhesive described later. Casein, styrene-butadiene copolymer latex, and the like are fine particles of 100 nm or less, and thus are easily affected by migration due to drying, and move to the inside of the base paper, thereby reducing the effect of the adhesive. In contrast, the plastic pigment used in the present invention has relatively large particles as compared with casein and styrene / butadiene copolymer latex, and remains in the coating layer without moving into the base paper. It is thought that the function of the construction layer is maintained.

The organic pigment of the present invention is blended in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the pigment. More preferably, it is 3 to 10 parts by weight. When the amount is less than 1 part by weight, the solvent resistance of the coated paper is inferior. When the amount exceeds 20 parts by weight, the peelability from the cast drum is lowered, drum picking occurs, and the surface feel is deteriorated.

The weight average particle size of the organic pigment is preferably 100 to 2000 nm, more preferably 200 to 1200 nm. If the particle size is too small, it will move to the inside of the base paper due to the effect of migration due to drying. As a result, the solvent resistance of the coated paper will decrease, and conversely if it is too large, the glossiness of the blank paper will decrease. The value of the weight average particle diameter in the present invention is obtained from the weight average (nm) by measuring the particle diameter of 200 organic pigment particles using a transmission electron microscope.

60-120 degreeC is preferable and, as for the glass transition temperature (Tg) of the copolymer which comprises the organic pigment of this invention, More preferably, it is 80-100 degreeC. If the Tg is too low, it will stick to the cast drum and cause operational troubles. If the Tg is too high, the formation of the film will be insufficient and the solvent resistance and fastness will be reduced.

The constituent of the organic pigment of the present invention is a monomer mixture comprising a conjugated diene monomer, an aromatic vinyl monomer, an ethylenically unsaturated carboxylic acid monomer, and other monomers copolymerizable therewith. Is obtained by emulsion copolymerization.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene. it can. These can be used alone or in combination of two or more. Of these, 1,3-butadiene is preferred. The amount of the conjugated diene monomer used is 5 to 25% by weight, preferably 8 to 20% by weight, based on the total monomers. If this amount is too small, the glossiness and surface strength of the coated paper will be poor, and conversely if too large, the peelability of the coated paper from the cast drum will be reduced.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, and hydroxymethylstyrene. These can be used alone or in combination of two or more. Of these, styrene is preferred. The amount of the aromatic vinyl monomer used is 50 to 94.5% by weight, preferably 65 to 85% by weight of the total monomers. If the amount used is small, the peelability of the coated paper from the cast drum decreases, and conversely if it is large, the glossiness and surface strength of the coated paper are poor.

Examples of the ethylenically unsaturated carboxylic acid monomer include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; unsaturated polycarboxylic acids such as fumaric acid, maleic acid, itaconic acid, and butenetricarboxylic acid. A partially esterified product of an ethylenically unsaturated polyvalent carboxylic acid such as monoethyl maleate and monomethyl itaconate; These ethylenically unsaturated carboxylic acid monomers can also be used as alkali metal salts or ammonium salts. These ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. The amount of the ethylenically unsaturated carboxylic acid monomer used is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total monomers. If the amount used is too small, the colloidal stability during the production of the organic pigment is lowered, and a large amount of aggregates are generated, or the surface strength of the coated paper is lowered. On the other hand, if the amount used is too large, the surface strength of the coated paper decreases.

Other monomers that can be copolymerized with the above monomers include: (meth) methyl acrylate, (meth) ethyl acrylate, (meth) propyl acrylate, (meth) butyl acrylate, (meth) acrylic Acid-2-ethylhexyl, (meth) trifluoroethyl acrylate, (meth) tetrafluoropropyl acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, (meth) methoxymethyl acrylate, (meth) ethoxy acrylate Ethyl, (meth) methoxyethoxyethyl acrylate, (meth) cyanomethyl acrylate, (meth) acrylic acid 2-cyanoethyl, hydroxyethyl acrylate, glycidyl methacrylate and other ethylenically unsaturated carboxylic acid esters,

Among these monomers, the content of the aromatic vinyl monomer is 80 to 100% by weight, preferably 85 to 95% by weight of the total monomers. When the content of the aromatic vinyl monomer is too small, the solvent resistance of the coated paper is lowered. On the other hand, when the content is too large, it is difficult to maintain the structure of the organic pigment, and the glossiness is lowered.

In addition to the above organic pigments, the cast coating layer of the present invention includes heavy calcium carbonate, light calcium carbonate, kaolin, talc, titanium oxide, white carbon, satin white, calcium sulfate, barium sulfate, gypsum, water as pigments. One or more inorganic pigments such as aluminum oxide, calcined kaolin, delaminated kaolin, silica, magnesium carbonate, zinc oxide, calcium sulfite, magnesium hydroxide and magnesium oxide can also be used.

In the present invention, styrene / butadiene copolymer latex, casein, soy protein, synthetic protein, polyvinyl alcohol, oxidized starch, esterified starch and other starches, carboxyl methyl cellulose, hydroxy, Cellulose derivatives such as ethyl cellulose, polyvinylpyrrolidone, gelatin, styrene-acrylic resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, urea resin, alkyd resin, urethane resin, polyethylene, etc. One or more kinds may be used in combination. For example, in the case of casein, the blending amount is preferably 1 to 8 parts by weight with respect to 100 parts by weight of the pigment. When the amount of casein is too small, drum picking occurs, and the operability is likely to deteriorate. When the amount of casein is too large, the coating concentration is decreased, so that the coating speed is decreased and the productivity is decreased. In addition, since it peels off in the middle of the drum, the glossiness of the white paper is likely to be lowered, and in addition, yellowing tends to occur, so that the storage stability is lowered.

In this invention, you may make the cast coating layer contain various auxiliary agents normally used, such as a dispersing agent, a mold release agent, a thickener, a water retention agent, an antifoamer, antiseptic | preservative, and a water-resistant agent. As the release agent, fatty acid such as calcium stearate or metal salt of higher fatty acid, fatty acid amide, higher alcohol, wax emulsion, polyethylene emulsion, nonionic surfactant and the like can be used.

The base paper of the cast coated paper used in the present invention is a base paper having a basis weight of 50 to 400 g / m ² used for general printing coated paper and cast coated paper. Select and use. In addition, a coated paper in which a coating layer having a general pigment and an adhesive is provided on one side or both sides of the base paper can also be used as the base paper.

As a method of applying the cast coating solution to the base paper, known coating machines such as blade coater, air knife coater, roll coater, comma coater, brush coater, kiss coater, squeeze coater, curtain coater, bar coater, gravure coater, etc. It can select suitably from the used methods.

The coating amount on the base paper is preferably in the range of 10 to 35 g / m ² in terms of solid content per one side of the base paper. When the coating amount is less than 10 g / m ² , the solvent resistance is lowered, and when it is more than 35 g / m ² , the drying load increases, so that the coating speed is lowered and the productivity is lowered.

For finishing the coating layer formed on the base paper, a casting method is used in which the coating layer is pressed and dried on a mirror drum heated in a wet state. As the casting method, a direct method in which a coating drum is pressure-bonded in an undried state after coating, a coagulation method in which a coating layer is gel-bonded with a coagulating liquid after coating, or a coating once dried after coating. It is possible to use a rewetting method in which the layer is plasticized with a rewetting liquid and pressed.

Since the surface of the cast coating layer produced by the above method affects the quality of the release layer that becomes the surface of the process paper, it is required to have high gloss and no gloss unevenness or pinholes. In the case of the direct method, gloss unevenness and pinholes are likely to occur on the surface of the substrate, and in the case of the rewet method, the coating layer is once dried, so that the glossiness is hardly expressed. Therefore, the method of forming the cast coating layer of the present invention is more preferably a coagulation method that is excellent in gloss expression, hardly causes gloss unevenness and pinholes, and provides a good surface feeling.

In addition, as a method for improving gloss development and solvent resistance, it is important to optimize the film property of the organic pigment in the cast coating layer. As a method for optimizing the film property, the organic pigment is distributed on the surface of the cast coating layer, and can be optimized by sufficiently melting the organic pigment when it is pressed and dried with a mirror drum. In the case of the direct method, the organic pigment tends to be distributed in the deep part of the cast coating layer due to migration during drying. In the case of the rewet method, the organic pigment is distributed on the surface of the cast coating layer, but since the organic pigment does not melt sufficiently, the glossiness and solvent resistance are hardly exhibited. Therefore, a solidification method is more preferable as a method for forming the cast coating layer of the present invention.

In the cast coated paper of the present invention, the coagulation liquid used in the coagulation method is obtained by dissolving a coagulant in an aqueous solution or the like. As the coagulant, formic acid, acetic acid, malic acid, itaconic acid, acrylic acid, citric acid, Acids such as lactic acid, hydrochloric acid, sulfuric acid, carbonic acid, and boric acid, and salts thereof with calcium, zinc, barium, lead, potassium, sodium, cadmium, aluminum, and borax can be used. However, it is preferable to use formate, and among them, formic acid mixed with zinc oxide is preferable from the viewpoint of solvent resistance. Various releasing agents used in the coating solution can also be used as appropriate in the coagulation solution.

The cast coated paper of the present invention is a base material for process paper, and is suitable as a base material for process paper for manufacturing synthetic leather among process papers. It can also be used for substrates.

When using the cast coated paper thus obtained as a base material for the process paper, a release agent is applied to the surface of the cast coated layer of the cast coated paper to provide a release layer. As the release agent, alkyd resins, silicone resins, polyethylene resins, polypropylene resins, acrylic resins, and the like can be used. The coating amount is not particularly limited, but is preferably 0.1 to 2.0 g / m ² . If the coating amount is too small, the peelability is insufficient, and when the process paper is peeled off from the synthetic leather, paper peeling or paper tearing occurs. When the coating amount is too large, the peelability becomes excessive, and the leather coating film floats or peels off during the process.

Moreover, in this invention, the superiority or inferiority at the time of forming peeling layers, such as an alkyd resin, a silicone resin, and a polypropylene resin, can be estimated and evaluated by the method using offset ink. First, in the present invention, it was found that when offset printing is performed on cast coated paper, the ink transfer amount after printing correlates with the barrier property against the solvent. That is, the greater the amount of ink transfer after offset printing, the higher the barrier property of the cast coated paper against the solvent, the higher the film property of the release layer, and the more effective the solvent resistance of the process paper. In the present invention, 0.6 cc of offset printing ink is printed on an RI printer, 100 seconds later, the undried ink is transferred to a blank cast coated paper, and the transferred ink density is measured. Is preferably 0.5 or more. Further, in the present invention, it is found that the print gloss after offset printing correlates with the gloss development, and the print gloss (20 °) measured according to JIS-P8741 is desirably 45 or more.

Furthermore, in the present invention, it was found that repeated use of process paper in the production of synthetic leather and the like can be predicted and evaluated by measuring the fastness of the cast coating layer after impregnating the cast coated paper with an organic solvent. . That is, the number of times the process paper is used can be increased by increasing the fastness of the cast coated paper to the solvent. In the present invention, the cast coated paper is dipped in dimethylformamide (DMF), dried, and then coated with a transparent adhesive tape on the cast coated layer surface, rubbed 20 times with a rubber roll, and peeled off in the direction of 180 degrees. It is desirable that the longest immersion time in which white spots are not removed is 30 minutes or more.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by these. In addition, the part and% in an example show a weight part and weight%, respectively.

[Manufacture of base paper]
100% hardwood bleached kraft pulp was used as a raw material, and the freeness was 370 ml. To 100 parts of absolutely dry pulp, 0.5 parts of cationized starch, 0.2 parts of sizing agent, and light calcium carbonate as a filler were internally added so as to have an ash content of 10%. After paper making and drying with a long paper machine, using a size press, a coating liquid in which 100 parts of oxidized starch and 0.02 part of sizing agent are mixed so that the dry weight per side is 1.0 g / m ^2. Coated. Furthermore, with a blade coater, a coating solution consisting of 50 parts of clay, 50 parts of light calcium carbonate, 5 parts of styrene-based latex, and 3 parts of oxidized starch is applied to 13 g / m ^{2 on} one side and flattened with a super calender (SC). Thus, a coated paper serving as a cast coated paper base paper of the present invention having a basis weight of 150 g / m ² was obtained.

[Example 1]
50 parts of kaolin (trade name: Ultra White 90, manufactured by Engelhard), 45 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.), a solid plastic pigment as an organic pigment (trade name: 5 parts of pigment slurry was prepared. To this, 6 parts of a casein aqueous solution (solid content concentration 17%) dissolved with ammonia as an adhesive and 16 parts of a styrene / butadiene copolymer latex (trade name: PA0330, manufactured by A & L Japan) were added and separated. 2 parts of a mold (SN-3035, manufactured by San Nopco) was blended, and finally water and ammonia were added to adjust the solid concentration to 51% and pH to 10. In addition, an aqueous calcium formate solution having a solid content of 10% was prepared as a coagulation liquid.
Using the coating solution prepared by the above method, the coating solution is applied on one side of the cast coated paper base paper with a roll coater so that the dry coating amount is 20 g / m ^2. After the coating layer is brought into contact with the coagulation liquid, the coating layer is solidified, and then press-bonded to a press roll having a diameter of 750 mm and a cast drum having a surface temperature of 105 ° C. and a diameter of 3000 mm at a press pressure of 150 kg / cm. The cast coated paper was obtained by peeling from the drum.

[Example 2]
Cast coating as in Example 1 except that 40 parts of light calcium carbonate (trade name: Tamapearl TP121-7C manufactured by Okutama Kogyo Co., Ltd.) and 10 parts of organic pigment (trade name: Nipol V1004 manufactured by Zeon Co., Ltd.) were used to prepare a pigment slurry. I got paper.

[Example 3]
Cast coating as in Example 1 except that 35 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 15 parts of organic pigment (trade name: Nipol V1004 manufactured by Zeon Co., Ltd.) were used. A paper was obtained.

[Example 4]
Cast coating as in Example 1 except that 30 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 20 parts of organic pigment (trade name: Nipol V1004 manufactured by Zeon Co., Ltd.) were used. A paper was obtained.

[Example 5]
Example 1 except that a pigment slurry was prepared with 45 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 5 parts of a hollow plastic pigment (trade name: manufactured by AE851 JSR Co.) as an organic pigment. A cast coated paper was obtained in the same manner as above.

[Example 6]
Cast coating as in Example 1 except that 40 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 10 parts of organic pigment (trade name: manufactured by AE851 JSR Co., Ltd.) were used. I got paper.

[Example 7]
Cast coating as in Example 1 except that 35 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 15 parts of organic pigment (trade name: manufactured by AE851 JSR Co., Ltd.) were used. I got paper.

[Example 8]
Cast coating as in Example 1 except that 30 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.) and 20 parts of organic pigment (trade name: manufactured by AE851 JSR Co., Ltd.) were used. I got paper.

[Comparative Example 1]
Implemented except that 50 parts of kaolin (trade name: Ultra White 90, manufactured by Engelhard), 50 parts of light calcium carbonate (trade name: Tama Pearl TP121-7C, manufactured by Okutama Kogyo Co., Ltd.), and a pigment slurry without organic pigments were prepared. A cast coated paper was obtained as in Example 1.

[Comparative Example 2]
A cast coated paper was obtained in the same manner as in Comparative Example 1 except that 21 parts of styrene / butadiene copolymer latex (trade name: PA0330, manufactured by Japan A & L) was prepared.

[Comparative Example 3]
A cast coated paper was obtained in the same manner as in Comparative Example 1 except that 26 parts of styrene / butadiene copolymer latex (trade name: PA0330, manufactured by Japan A & L) was prepared.

[Comparative Example 4]
A cast coated paper was obtained in the same manner as in Comparative Example 1 except that 31 parts of styrene / butadiene copolymer latex (trade name: PA0330, manufactured by Japan A & L) was prepared.

〔Evaluation methods〕
The various coated papers produced as described above were evaluated as follows. The results are shown in Table 1.

1) Fastness test for solvent A sample was immersed in dimethylformamide (DMF) for a predetermined time and then dried with hot air. A transparent adhesive tape (product name cellophane tape) with a width of 18 mm is applied to the cast surface of the obtained sample, rubbed strongly with a rubber roll 20 times, then peeled off in a direction of 180 degrees, and white spots on the coating layer are visually observed. It was evaluated with. The longer the longest immersion time of the solvent in which the white spot of the coating layer is not removed, the better the fastness to solvent and the better the repeated use.
◎ = The longest solvent immersion time in which white spots are not removed from the coating layer is 60 minutes or more. ○ = The longest solvent immersion time in which white spots are not removed from the coating layer is 30 minutes or more and less than 60 minutes. The longest solvent soaking time that does not cause white spot removal of the work layer is 15 minutes or more and less than 30 minutes.

2) Barrier property test with respect to solvent A printing test of 0.6 cc of ink for offset printing (High Unity MZ: manufactured by Toyo Ink Co., Ltd.) was performed with an RI printer. After 100 seconds of printing, the undried ink was transferred to a white coated paper, and the transferred ink density was measured with a densitometer (SpectroEye: manufactured by X-rite). The higher the ink concentration, the better the cast coated paper has a barrier property against the solvent in the ink.
◎ = Ink density transferred in 100 seconds of RI printing is 2.0 or more ○ = Ink density transferred in 100 seconds of RI printing is 0.5 or more and less than 2.0 Δ = Ink density transferred in 100 seconds of RI printing Is less than 0.1 and less than 0.5 × = Ink density transferred in 100 seconds of RI printing is less than 0.1

3) Gloss development test of release layer A printing test of 0.6 cc of ink for offset printing (High Unity MZ: manufactured by Toyo Ink Co., Ltd.) was performed with an RI printer. Printing glossiness was measured at a light incident angle of 20 degrees according to JIS-P8741 using a gloss meter (Gloss Meter VG7000: manufactured by Nippon Denshoku Co., Ltd.). The higher the glossiness, the better the glossiness of the cast coated paper when the release layer is applied.
◎ = Glossiness (20 °) of printed portion is 60 or more ○ = Glossiness (20 °) of printed portion is 45 or more and less than 60 Δ = Glossiness (20 °) of printed portion is 30 or more and less than 45 × = Printed portion Glossiness (20 °) of less than 30

4) Evaluation of texture of cast coated paper The presence or absence of flickering (a pinhole-like minute concave defect) was visually evaluated on the surface of the cast coated paper. When there is a lot of flickering, it causes pinholes when a release layer such as alkyd resin, silicone resin, polypropylene resin, etc. is applied, and quality deterioration such as surface defects and deterioration of solvent resistance when manufacturing synthetic leather cause.
○ = No flickering on the surface of the cast coated paper, and the surface feel is excellent.
Δ = Tickiness is scattered on the surface of the cast coated paper, and the surface feeling is inferior.
X = Many flickers are observed on the surface of the cast coated paper, and a reduction in surface feeling and a reduction in glossiness are observed.

5) Evaluation of operability during production of cast coated paper The coating liquids of the examples and comparative examples of the present invention are coated on a cast coated paper base, dried on the cast drum, and taken off from the cast drum with a take-off roll. The operability when peeled was visually evaluated. Those having poor operability are inferior in peelability, cause drum picking, and at the same time reduce the gloss of cast coated paper.
○ = Excellent peelability, no drum picks, and excellent cast coated paper gloss.
Δ: Poor peelability, drum picking occurs, and cast coated paper has poor gloss.
X = Remarkably inferior in peelability, cast coated paper sticks to the cast drum, and production becomes difficult.

As is clear from Table 1, the cast coated papers of Examples 1 to 8 are excellent in solvent resistance, gloss development, cast surface feeling, and operability, and are excellent as a base material for process paper for synthetic leather production and the like. Yes. On the other hand, Comparative Example 1 containing no organic pigment was inferior in solvent resistance and gloss development. Comparative Examples 2 to 4 in which the styrene / butadiene copolymer latex was increased in place of the organic pigment were inferior in the balance of solvent resistance, gloss development, cast surface feeling, and operability.

Claims (3)

A cast coated paper in which a cast coating layer mainly composed of a pigment and an adhesive is provided on at least one surface of a base paper, wherein 1 to 20 parts by weight of an organic pigment is blended per 100 parts by weight of the pigment Cast coated paper for process paper base. 2. The cast coated paper according to claim 1, wherein the cast coated layer is formed by gelling a wet coated layer with a coagulating liquid, pressing and drying to a mirror drum. Process paper in which a release layer is provided on the cast coating layer surface of the cast coated paper according to claim 1 or 2.