JP5308223B2 - Coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for process paper for a synthetic leather, which exhibits excellent solvent resistance against both of a polar solvent and a nonpolar solvent, and is capable of obtaining the synthetic leather having a good appearance. <P>SOLUTION: The coated paper includes a base paper, and a coated layer formed on the base paper. The coated layer contains a pigment, an adhesive, and a release agent. The coated layer contains casein, a styrene-butadiene latex, and a resin containing a polyacrylic acid resin component and a polyvinyl alcohol resin component, as the adhesive, and further contains a paraffin as the release agent. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a coated paper having excellent resistance to polar solvents and nonpolar solvents. More specifically, the present invention relates to a coated paper suitable for use as a process paper for synthetic leather produced using a polar solvent and a nonpolar solvent.

  The coated paper, especially the cast coated paper in which the coating layer is provided by the casting method, is an industrial substrate (for example, a marking sheet, release paper such as a metal foil), packaging paper (for example, a paper bag, a book cover). Etc.), and process paper (for example, process paper such as synthetic leather and plastic film). When used as process paper, a monomer mixed with a solvent is developed on cast coated paper, and the monomers are reacted with each other by heat or electron beam to form a synthetic leather or a plastic film. In particular, for synthetic leather applications using, for example, vinyl chloride or urethane, after applying a paste such as vinyl chloride to the surface of the process paper, heat it to react with vinyl chloride, and then apply an adhesive. After being bonded to the backing fabric, it is heated and cooled again, and the process paper is peeled off to produce synthetic leather.

  Since such process paper uses vinyl chloride, urethane, etc., it is desirable to have excellent solvent resistance. For example, it contains a styrene / butadiene copolymer latex having a gel content of 85% or more as an adhesive. Cast coated paper (for example, see Patent Document 1), a plate-shaped pigment having a volume distribution average particle diameter of 3 to 20 μm, and a base paper for release paper containing a synthetic resin latex having a gel content of 85% or more (See, for example, cited document 2).

  On the other hand, in recent years, for the purpose of reducing environmental impact, the solvent used is shifting from nonpolar solvents to polar solvents, and process papers are required to have resistance to both polar and nonpolar solvents. Yes. In addition, the requirements regarding solvent resistance are becoming stricter, and it is not said that the coating layer is difficult to peel off even if it is repeatedly used, and high quality such that image clarity and glossiness are not easily lowered is required. It has become. In particular, in the field of synthetic leather processed paper, in order to obtain synthetic leather having a higher quality and a good appearance, processed paper having higher image clarity and less pit defects is required. In addition, it is required to improve the productivity of process paper. As a method for solving these problems, there is a method (see Patent Document 3) in which an adhesive containing a polyacrylic acid component and a polyvinyl alcohol component is contained in the coating layer. To satisfy these requirements sufficiently. Not reached.

Japanese Patent Application Laid-Open No. 2005-97781 JP 2008-88565 A JP 2009-13510 A

  The main problem to be solved by the present invention is a coating for synthetic leather process paper that exhibits excellent solvent resistance against both polar solvents and non-polar solvents, and can obtain a good-looking synthetic leather To provide paper. Furthermore, another object is to provide a technique for producing a coated paper that can be used as a synthetic leather process paper having high image clarity and few pit defects.

The present invention that has solved this problem is a coated paper for synthetic leather process paper comprising a base paper and a coating layer provided on the base paper, the coating layer comprising a pigment, an adhesive, and a mold release Containing at least both polyacrylic acid (PAA) and polyvinyl alcohol (PVA), or polyacrylic acid-polyvinyl alcohol copolymer, and 10 polyacrylic acid resin components and polyvinyl alcohol resin components as the adhesive. : 90 to 90:10 in a mass ratio, and the total of the polyacrylic acid (PAA) and the polyvinyl alcohol (PVA) with respect to 100 parts by mass of the pigment or the polyacrylic acid-polyvinyl alcohol. 1-10 parts by mass of polymer, 10-25 parts by mass of styrene-butadiene latex, 5-30 parts by mass of casein, and 100 parts by mass of the pigment Of the columnar calcium carbonate containing 20 to 60 parts by weight, characterized in that said containing paraffin as a release agent, a coated paper for synthetic leather process paper.

In the present invention, the paraffin is contained in an amount of 0.5 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment, and the mass ratio of the casein and the styrene-butadiene latex is styrene-butadiene with respect to casein 1. The latex is preferably 0.5 to 3.0.

  In the present invention, the melting point of the paraffin is 50 ° C. to 100 ° C., the coating layer is cast, and the temperature of the cast drum when the coating layer is cast is 95 ° C. to 120 ° C. It is preferable that

  According to the present invention, it is a coated paper for synthetic leather process paper that exhibits excellent solvent resistance against both polar and nonpolar solvents. Also, coated paper that can be used as synthetic leather processed paper with high image clarity and fewer pit defects can be produced with higher productivity than before.

  Next, an embodiment of the present invention will be described.

  First, the present inventors have conducted extensive research for the purpose of improving the resistance to polar solvents exhibited by the coated paper. As a result, casein, styrene-butadiene latex, polyacrylic acid resin component, and polyvinyl chloride are applied to the pigment coating layer. It has been found that it is effective to contain an adhesive containing an alcohol resin component and a paraffin release agent.

  That is, the present inventors are a coated paper comprising a base paper and a coating layer provided on the base paper, wherein the coating layer contains a pigment, an adhesive, and a release agent, and the adhesive The agent contains casein, styrene-butadiene latex, polyacrylic acid resin component and polyvinyl alcohol resin component, and by using paraffin as the mold release agent, it has been found that excellent solvent resistance is exhibited. The present invention has been completed.

  That is, it is essential to blend at least both polyacrylic acid (PAA) and polyvinyl alcohol (PVA) or a polyacrylic acid-polyvinyl alcohol copolymer as an adhesive. When one or both of polyacrylic acid and polyvinyl alcohol are not contained, or when polyacrylic acid-polyvinyl alcohol copolymer is not contained, resistance to polar solvents and nonpolar solvents is low, and the coating surface is polar solvent and Easily eroded by nonpolar solvents. In particular, when used as a synthetic leather process paper, it cannot withstand repeated use.

  The ratio of the polyacrylic acid resin component and the polyvinyl alcohol resin component can be defined by mass ratio, preferably PAA resin component: PVA resin component = 10: 90 to 90:10, more preferably. Is PAA resin component: PVA resin component = 15: 85 to 85:15. When the PAA-based resin component is less than 10% by mass, the properties of the PAA-based resin component itself (hard resin, rigid at room temperature, excellent water resistance and adhesive strength) are hardly expressed, and 90% by mass When it exceeds, the PVA-based resin component is reduced, and the properties of the PVA-based resin component (a soft resin that has flexibility at room temperature and excellent water resistance and adhesive strength) are hardly expressed. The reason why the solvent resistance is improved by blending both the PAA resin component and the PVA resin component is unknown, but in both cases, the surface of the coated paper is combined with a water-resistant hard resin and a soft resin at room temperature. By imparting both flexibility and rigidity, it is considered that resistance to polar solvents such as methyl ethyl ketone (MEK) and nonpolar solvents such as toluene is improved. Moreover, it is more preferable to include a polyacrylic acid-polyvinyl alcohol copolymer than to include both polyacrylic acid and polyvinyl alcohol.

  The total blending amount of the PAA-based resin component and the PVA-based resin component essential for the above embodiment is preferably 1 to 10 parts by mass, more preferably 2 to 5 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment. It is. If the amount is less than 1 part by mass, the solvent resistance effect is not sufficiently exhibited and the solvent resistance is inferior. If the amount exceeds 10 parts by mass, the smoothness derived from the pigment is inferior, the image clarity is deteriorated, and the appearance is deteriorated. In addition, the polar solvent tends to accumulate in a portion having low smoothness, erosion tends to proceed locally, and the solvent resistance tends to decrease, which is not preferable.

  It is necessary to use casein and styrene-butadiene latex together with the two components of the PAA resin component and the PVA resin component as an adhesive, which can significantly improve the solvent resistance and image clarity. In particular, in the case of cast coated paper that is subjected to a cast treatment after coating, use of casein that is easy to obtain the effect of improving the image clarity of the coating layer surface provides an effect of improving the image clarity due to the effect of improving the peelability. Casein is particularly preferred for use in synthetic leather process papers where surface properties are particularly important.

  In particular, when a casein is used in combination with a copolymer in which the PAA-based resin component and the PVA-based resin component are copolymerized, uniform peelability is obtained, which is particularly preferable because a coated paper with high image clarity can be obtained. .

  The content of the styrene-butadiene latex (SBR) can be reduced from the cast drum when the release agent is contained, so that the surface strength can be reduced, and 10 to 25 in terms of solid content with respect to 100 parts by mass of the pigment. It is preferable to mix | blend a mass part, and it is more preferable to mix | blend 12-20 mass parts. When the amount is less than 10 parts by mass, sufficient adhesive force is not exhibited, so the image clarity is inferior. On the other hand, when the amount exceeds 25 parts by mass, a film-like surface tends to be formed, and the imageability derived from the pigment is lowered. Since it falls, it is not preferable.

  When an adhesive containing casein and SBR is used together with the polyacrylic acid resin component and the polyvinyl alcohol resin component described above, the adhesive having the polyacrylic acid resin component and the polyvinyl alcohol resin component also has film-forming properties. A coated paper with higher image clarity can be obtained.

  When casein is blended, the resulting coated paper has high image clarity. On the other hand, it is a natural product, has quality fluctuations and price fluctuations, and is commercially expensive.

  The content of casein is preferably 5 to 30 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment in order to produce a synergistic effect with the exfoliation effect by the release agent and further improve the releasability. It is more preferable to set it to ˜25 parts by weight. If it is less than 5 parts by mass, the releasability is lowered, and a trouble that a part of the coated surface adheres to the cast drum is likely to occur. Getting worse. On the other hand, if it exceeds 30 parts by mass, the peeling performance will reach its peak, and there is no meaning to use a large amount of expensive casein and it is inferior in economy, and when the cast treatment is performed, the coating layer does not adhere to the cast drum and is smooth. It is not preferable because the inferior property tends to deteriorate the image clarity.

  In this embodiment, in addition to the above-mentioned adhesives, adhesives generally used in coated paper production can be used in combination as long as solvent resistance is not impaired. Specifically, for example, proteins such as soybean protein; conjugated diene latex such as methyl methacrylate-butadiene copolymer latex and styrene-methyl methacrylate-butadiene copolymer latex; acrylic ester and / or methacrylate ester Acrylic latex such as polymer latex or copolymer latex; Vinyl latex such as ethylene-vinyl acetate polymer latex; Alkaline moiety obtained by modifying these various copolymer latexes with functional group-containing monomers such as carboxyl groups Latexes such as soluble or insoluble latex; synthetic resin adhesives such as olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive starch, esterified starch, dextrin, etc. Starch; Carboxymethyl Loin, cellulose derivatives such as hydroxyethyl cellulose or the like can be cited, and may be used by selecting one or more from among these as appropriate.

  The pigment used in the coating layer is not particularly limited. For example, kaolin clay (including delaminated kaolin, calcined kaolin, structured kaolin, etc.), talc, light calcium carbonate, heavy calcium carbonate, satin white, calcium sulfite , Inorganic pigments such as gypsum, barium sulfate, white carbon, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, silica, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite One or more kinds of organic pigments such as polystyrene resin fine particles, urea formalin resin fine particles, fine hollow particles, and porous fine particles can be appropriately selected and used.

  Among the above pigments, it is preferable to use calcium carbonate or kaolin clay having low oil absorption because a coated paper excellent in solvent resistance can be obtained. Use of a pigment having a large specific surface area such as synthetic amorphous silica or colloidal silica is not preferable because of high oil absorption and poor solvent resistance.

  Examples of calcium carbonate include irregular-shaped heavy calcium carbonate and light calcium carbonates such as spindles, columns, or cubes. Among these, when columnar light calcium carbonate is used, the flatness of the coating layer surface is improved. Since it becomes favorable, it is preferable. The flatness of the coating layer can be improved by containing clay, which will be described later, but there is a problem that air permeability deteriorates when a large amount of clay is used. For this reason, by using in combination with not only clay but also calcium carbonate, especially columnar calcium carbonate, the voids in the coating layer are large and the air permeability is high, and both the air permeability and the flatness of the coating layer surface are achieved. This is preferable because a coated paper having excellent image clarity and solvent resistance can be obtained. In particular, when the cast process is performed to improve the image clarity, the moisture in the coating layer volatilizes as water vapor as the coating layer dries. However, since the coating layer is in close contact with the cast drum, water vapor is not applied. Evaporates from the back of the work layer. When the air permeability of the coated paper is low, it is difficult for water vapor to escape from the back side, and it accumulates between the coating layer and the cast drum, and the cast surface cannot be sufficiently copied to the coating layer, and the coated paper has poor image clarity. Become. For this reason, it is preferable that a coating layer is excellent in air permeability, and it is preferable to use the columnar light calcium carbonate which is a pigment which can provide air permeability as a pigment. Other examples of calcium carbonate that can easily improve air permeability include cubic calcium carbonate, but the cubic shape is inferior in the flatness of the coating layer surface compared to the columnar shape, and it is difficult to improve image clarity and solvent resistance. Therefore, it is not preferable.

  20-60 mass parts is preferable among 100 mass parts of pigments, and, as for the compounding quantity of calcium carbonate, 30-50 mass parts is more preferable. If the blending amount is less than 20 parts by mass, it is difficult to obtain sufficient air permeability, not only inferior in image clarity, but also pit defects, which are fine coating unevenness, are not preferred. On the other hand, when the amount exceeds 60 parts by mass, the fluidity of the coating solution is deteriorated, the profile at the time of coating is deteriorated, and the solvent resistance is easily lowered due to uneven coating, which is not preferable.

  The coated paper has an air permeability measured according to JIS P 8119 of 1,000 to 30,000 seconds, preferably 1,000 to 20,000 seconds by using columnar light calcium carbonate. Preferably, it is 1,000 to 10,000 seconds, so that pit defects are less likely to occur, the image clarity is excellent, and there is little decrease in image clarity after contact with a polar solvent, especially coated paper with excellent solvent resistance, Synthetic leather process paper. Furthermore, by applying a flattening process to the coated paper, the coated paper is further excellent in image clarity. Such flattening is generally performed by a flattening facility that can be used for papermaking. For example, a supercalender, a soft calender, or the like can be used, and can be adjusted by linear pressure, speed, or the like.

  If the air permeability exceeds 30,000 seconds, even if flattening beyond this, the solvent resistance only reaches its peak, which is not economically preferable. Even when the smoothness is adjusted by the super calendar, the linear pressure may be excessive, and the rigidity of the paper may be destroyed. When the air permeability is less than 1,000 seconds, there are many voids on the coated surface, and the solvent easily penetrates, so that the solvent resistance is likely to deteriorate.

  Kaolin clay is a plate-like pigment, and is preferred because it can be easily oriented in a uniform direction on the surface of the coating layer and can improve the smoothness and image clarity of the surface of the coating layer. The amount of kaolin clay is preferably 40 to 80 parts by mass, more preferably 50 to 70 parts by mass, out of 100 parts by mass of the pigment. If the blending amount is less than 40 parts by mass, the image resistance and smoothness are inferior, so that the solvent resistance is liable to decrease. On the other hand, if it exceeds 80 parts by mass, the fluidity of the coating liquid deteriorates and the profile at the time of coating deteriorates. However, it is not preferable because the solvent resistance is likely to deteriorate due to uneven coating. Kaolin clay has poorer fluidity of coating solution than calcium carbonate, and uneven coating tends to occur. However, as described above, the ratio of clay and calcium carbonate is 40:60 to 80:20, preferably 50:50 to 70:30 is preferable because air permeability, solvent resistance and image clarity can be improved.

  As described above, by using columnar light calcium carbonate as a pigment, not only can a coated paper with good image clarity be obtained, but also by using kaolin clay together, a coated paper with better image clarity can be obtained. Since it is obtained, it is preferable.

  In particular, when a casein is used in combination with an adhesive containing a polyacrylic acid resin component and a polyvinyl alcohol resin component, it is more preferable to use kaolin clay as a pigment because both image clarity and solvent resistance can be improved.

  As described above, when columnar light calcium carbonate and kaolin clay are used in combination as a pigment, and a polyacrylic acid resin component, polyvinyl alcohol resin component, casein and SBR are used in combination as an adhesive, a coating having particularly excellent image clarity and solvent resistance. A craft paper can be obtained. In this form, the peelability derived from casein becomes uniform on the surface of the coating layer, so that a coated paper having an image clarity of 85% or more can be obtained.

  In the present invention, it is necessary to contain a release agent in the coating layer composed of the above-described pigment and adhesive in order to improve the solvent resistance. For example, silicone compounds, fluorine compounds, waxes, paraffins, polypropylene resins, acrylic resins, amide resins and the like are known as mold release agents. In the present invention, paraffin type mold release agents are used. By using a paraffinic release agent, a coated paper having a low rate of change in image clarity after solvent contact and excellent solvent resistance can be obtained.

  Among the paraffinic release agents, those having a melting point of 50 to 100 ° C., and further 55 to 80 ° C. are excellent in release properties, and a uniform coated surface is obtained, and image clarity after solvent contact of the coated paper This is preferable because a coated paper excellent in solvent resistance can be obtained. Below 50 ° C, paraffin melts easily due to changes in temperature and the emulsion tends to disintegrate, and the emulsion does not mix uniformly with the coating liquid, resulting in coating unevenness, making it difficult to improve image clarity and solvent resistance. It is not preferable. If the temperature exceeds 100 ° C., the paraffin is not easily melted even when heat is applied by a cast drum, so that coating unevenness is likely to occur, and the effect of improving image clarity and solvent resistance is also difficult to obtain.

  The addition amount of the release agent is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass in terms of solid content with respect to 100 parts by mass of the pigment. If the amount is less than 0.5 parts by mass, the releasability is inferior and the image clarity of the coating layer surface may be deteriorated. If the amount exceeds 10 parts by mass, not only the solvent resistance reaches a peak but also the economy is inferior. It is not preferable.

  When the paraffinic mold release agent is used in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment, the imaging property of the coated paper obtained by the improvement of the peelability is improved. For paper, the rate of change in image clarity after contact with the solvent can be 5% or less, further 1.3% or less, and especially 1% or less. For this purpose, the adhesive content should be as described above. Is preferred.

  That is, it contains 0.5 to 10 parts by mass of a paraffinic mold release agent as a mold release agent with respect to 100 parts by mass of the pigment, and 5 to 30 parts by mass of casein as an adhesive with respect to 100 parts by mass of the pigment. By blending 10 to 25 parts by weight and blending 10 to 25 parts by weight, preferably 12 to 20 parts by weight of styrene-butadiene latex (SBR) with respect to 100 parts by weight of pigment, the rate of change in image clarity after solvent contact can be increased. It can be kept low.

  Further, the mass ratio of casein and SBR is 0.5 to 3.0, preferably 0.6 to 1.5, and most preferably 0.6 to 1.0 with respect to casein 1. The solvent property can be improved, and the rate of change in image clarity after the solvent resistance test can be set to 5% or less, for example. If it is less than 0.5, the SBR is less than that of casein, so that it is difficult to improve the surface strength and it is difficult to obtain sufficient solvent resistance. When 3.0 is exceeded, there are many SBR compared with casein, and image clarity and solvent resistance are easy to fall.

  As described above, the paraffinic mold release agent is included as a mold release agent in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment, and the casein as an adhesive is 5 to 30 parts by mass with respect to 100 parts by mass of the pigment. Preferably 10 to 25 parts by weight, styrene-butadiene latex (SBR) to 10 to 25 parts by weight, preferably 12 to 20 parts by weight with respect to 100 parts by weight of pigment, and the ratio of casein and SBR to casein 1 SBR 0.5 to 3.0, preferably 0.6 to 1.5, and most preferably 0.6 to 1.0, so that the rate of change in image clarity after the solvent resistance test is, for example, 5% or less. , Preferably 1.3% or less, most preferably 1.0% or less.

  In addition, the glass transition temperature (Tg) of the styrene-butadiene latex (SBR) is preferably -20 ° C to 20 ° C, and more preferably -10 ° C to 10 ° C. When the temperature is lower than −20 ° C., the coating layer tends to be soft, and when it exceeds 20 ° C., the coating layer tends to be hard, and any of them is not preferable because the solvent resistance tends to decrease. Particularly when the SBR is as low as 10 to 25 parts by mass, preferably 12 to 20 parts by mass with respect to 100 parts by mass of the pigment as in the present invention, the glass transition temperature is -20 ° C to 20 ° C, preferably -10 ° C to 10 ° C. It is preferable because particularly excellent solvent resistance is obtained. For latex with a non-single glass transition temperature, such as a core-shell type in which the composition is different between the inside and outside of the latex particle, and a gradient type in which the composition changes gradually from the inside to the outside, the outside and inside The simple average value of the upper limit value and the lower limit value of the glass transition temperature may be in the above range. The melting point of paraffin and the glass transition temperature of latex were measured as follows. Paraffin or latex is vacuum-dried at 100 ° C. for 20 hours to prepare a film, and the dry film is measured for a melting point and a glass transition temperature at a heating rate of 20 ° C./min using a differential scanning calorimeter (manufactured by DuPont). did.

  In addition to pigments, adhesives, and release agents, the coating agent of the present embodiment includes, for example, fluorescent whitening agents, dyed substances of fluorescent whitening agents, antifoaming agents, coloring agents, water retention agents, etc. Various auxiliary agents that are usually used can be appropriately blended.

  Application of the coating agent to the surface of the base paper is sufficient if it is performed by general application paper application equipment, for example, blade coater, air knife coater, transfer roll coater, rod metering size press coater, curtain coater, etc. An on-machine coater or an off-machine coater provided with a coating apparatus can be used to coat the coating agent in a single layer or multiple layers on the base paper. Among these, it is preferable to use an air knife coater from the viewpoint that a high-concentration paint can be applied uniformly and high flatness of the coating layer surface is ensured. Moreover, as a drying method in the dryer part, for example, various heating drying methods such as hot air heating, gas heater heating, infrared heater heating and the like can be appropriately employed.

  The surface finish after the coating is preferably performed by a so-called cast coating method for synthetic leather process paper. In general, the cast coating method includes (1) a wet casting method (direct method) in which a coating layer is in a wet state and is dried by pressure bonding (pressure contact) to a mirror-finished heating drum, and (2) a wet coating method. Re-wet casting method (re-wetting method) in which the work layer is once (semi-) dried and then swelled and plasticized (wet) with a re-wetting liquid, and then pressed onto a mirror-finished heating drum (drying method). (3) Wet coating The layer can be divided into three types: gelation cast method (coagulation method), which is made into a gel state by coagulation treatment with a coagulation liquid and then pressed onto a mirror-finished heating drum and dried. However, in this embodiment, the rewet cast method is preferable from the viewpoint of productivity. The gelled casting method is not preferable because the coating layer is difficult to peel off from the cast drum. For example, when high-speed processing is performed at a casting processing speed of 60 m / min, image clarity and solvent resistance tend to decrease.

  The temperature of the cast drum is not a problem as long as it is generally used, but is preferably 95 ° C to 120 ° C, more preferably 100 ° C to 115 ° C. If the temperature is lower than 95 ° C or exceeds 120 ° C, drying is not uniform, and the solvent resistance of the resulting coated paper is lowered, which is not preferable. In addition, when the melting point of paraffin is 50 to 100 ° C., further 55 to 80 ° C., the temperature of the cast drum is 95 to 120 ° C., preferably 100 to 115 ° C. as described above. Although it is unknown, it is preferable because it is easy to prevent a decrease in image clarity after contact with a solvent, and a coated paper excellent in solvent resistance. When the melting point of paraffin is less than 50 ° C or exceeds 100 ° C, and the cast drum temperature is less than 95 ° C or more than 120 ° C, the solvent resistance of the resulting coated paper decreases. Since it is easy to do, it is not preferable. In addition, the temperature of the cast drum is preferably higher than the melting point of paraffin. If the casting drum temperature and the melting point of paraffin are approximately the same, the peelability and image clarity of the coated paper from the casting drum are not a problem, but the solvent resistance may be inferior.

  As described above, in addition to the pigment, in the case of coated paper using a casein, styrene-butadiene latex, and a resin containing a polyacrylic acid resin component and a polyvinyl alcohol resin component as an adhesive, as a release agent It contains 0.5 to 10 parts by mass of a paraffinic release agent having a melting point of 50 to 100 ° C., and further 55 to 80 ° C. with respect to 100 parts by mass of the pigment, and casein as an adhesive with respect to 100 parts by mass of the pigment 5 to 30 parts by mass, preferably 10 to 25 parts by mass, styrene-butadiene latex (SBR) to 10 to 25 parts by mass, preferably 12 to 20 parts by mass with respect to 100 parts by mass of pigment, and the mass of casein and SBR The ratio is SBR 0.5-3.0, preferably 0.6-1.5, most preferably 0.6-1.0 with respect to casein 1, and By performing the cast treatment at a cast drum temperature of 5 ° C. to 120 ° C., more preferably 100 ° C. to 115 ° C., the rate of change in image properties after the solvent resistance test is, for example, 5% or less, preferably 1.3% or less, Most preferably, it can be 1.0% or less, and a coated paper excellent in solvent resistance can be obtained.

The coating amount of the coating layer is preferably ² to 30 g / m ² . If it is less than 2 g / m ² , the covering property of the base paper is lowered, and good image clarity and solvent resistance cannot be obtained. When it exceeds 30 g / m ² , the water vapor generated when the coating layer is dried increases, and the pit defects are likely to occur in the cast coating method, not only the quality is deteriorated but also the economical efficiency is deteriorated.

  When the cast coated paper produced as described above is used as a synthetic leather process paper, if the image clarity is 85% or more, further 87% or more, especially 89% or more, the synthetic leather is excellent in smoothness and gloss. Is preferable because it can be manufactured.

  The coated paper of this embodiment preferably has a reduction rate of image clarity measured based on JIS H 8686-2 of 5% or less, and 1.3% or less when the following processing is performed. Is more preferable, and it is more preferable that the content be 1% or less. In particular, in the synthetic leather processed paper, the smaller the reduction in image clarity, the less the reduction in mirror surface properties of the synthetic leather to be produced, and the better-looking synthetic leather can be obtained. Further, since the deterioration due to the solvent is difficult to occur, the generation of defects such as a tray can be reduced, and the synthetic leather can be efficiently manufactured due to the good releasability. Thus, the process paper can withstand repeated use. In addition, for paper bags and book covers, the coated paper has excellent water resistance with little quality deterioration due to sweat and wind and rain.

(processing)
On the surface of the coating layer, methyl ethyl ketone was No. 2. Coat with wire bar 2 and heat at 130 ° C. for 90 seconds after 30 seconds.

  On the other hand, as the base paper of the coated paper, ordinary raw pulp can be used. For example, unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp ( Chemical pulp such as LBKP; Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Mechanical pulp such as thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), refiner mechanical pulp (RMP), or the like can be used. It is also possible to use waste paper pulp made of waste paper, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, upper white waste paper, Kent waste paper, imitation waste paper, Examples include disaggregated waste paper pulp, disaggregated / deinked waste paper pulp, disaggregated / deinked / bleached waste paper pulp, etc., manufactured from old paper waste paper. In the present invention, one or more of these can be appropriately selected and used.

  In the present embodiment, the above raw material pulp is mixed to prepare a papermaking raw material (stock slurry). The raw material pulp includes, for example, an internal sizing agent, a paper strength enhancer, a paper thickness improver, and a yield. Various additives blended in a normal papermaking process such as an improver can be internally added by appropriately adjusting the kind and blending amount.

  Also, the paper machine for making the base paper is not particularly limited, and for example, various methods such as a long mesh method, a twin wire method, a gap former method, a round mesh method, and a Yankee method can be appropriately used.

  Moreover, before performing the coating of the present invention, for the purpose of flattening the base paper, the coating using the general application paper application equipment and the flattening treatment by the combination of the elastic roll and the metal roll. It is preferable to do this.

  Next, although an example and an example are given and the operation effect by the present invention is clarified, the present invention is not limited to these examples.

[Base paper]
100% hardwood bleached kraft pulp was used as a raw material, and the freeness was 370 ml. 5 kg of cationized starch and 0.2 kg of a sizing agent were internally added to the absolutely dry pulp 1 t on the basis of active ingredients, respectively, and light calcium carbonate as a filler was internally added so as to have an ash content of 10%.

[Formation of coating layer]
First, 40 parts by mass of calcium carbonate and 60 parts by mass of kaolin clay in the form shown in Table 1 as pigments, and 100 parts by mass of pigment, adhesives and release agents in the amounts shown in Table 1 in terms of solid content at room temperature. The mixture was stirred to obtain a coating agent. The pigments, adhesives and release agents used are as follows. Moreover, the compounding quantity of the adhesive agent and release agent of Table 1 is a value with respect to 100 mass parts of pigments.

(Pigment)
・ Calcium carbonate (light, spindle-shaped, product number: TP-121-6S, manufactured by Okutama Kogyo Co., Ltd.)
・ Calcium carbonate (light, cubic, product number: Shiraka Hana PZ, manufactured by Shiraishi Calcium)
・ Calcium carbonate (light, columnar, product number: TP-123, manufactured by Okutama Kogyo Co., Ltd.)
・ Kaolin clay (part number: HYDRASPERSE90, manufactured by HUBER)

(adhesive)
・ Casein (manufactured by Nissei Kyobun Co., Ltd.)
Styrene-butadiene latex (SBR) (Part No .: PA5036, manufactured by Nippon A & L Co., Inc., inclined type, glass transition temperature of -20 to 20 ° C averaged to 0 ° C)
・ Polyacrylic acid-polyvinyl alcohol copolymer (PAA-PVA) (model number: Cogham HW400, Showa Polymer Co., Ltd.)
・ Polyacrylic acid (PAA) (Part No .: Aquaric R HL, manufactured by Nippon Shokubai Co., Ltd.)
・ Polyvinyl alcohol (PVA) (model number: PVA405, manufactured by Kuraray Co., Ltd.)

(Release agent)
Paraffin (paraffin emulsion, product number: Torasol PF60, manufactured by Chukyo Yushi Co., Ltd., melting point 60 ° C.)
・ Silicone (silicone emulsion, product number: KM768, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Polyethylene (polyethylene emulsion, product number: Meitex HP-70, manufactured by Meisei Chemical Co., Ltd.)

The above-mentioned paint is applied to the above-mentioned base paper with an air knife coater so that the dry mass is 12 g / m ² per side, and the re-wetting cast method (re-wetting method) at a speed of 60 m per minute is described in Table 1. Mirror finish was performed at the cast drum temperature. However, Examples 2 to 30 were the same as Example 1 except that the casein content, SBR content and glass transition temperature, the melting point of the release agent, and the temperature of the cast drum were adjusted to the values shown in Table 1. A coated paper was obtained in the same manner. In Examples 12 to 15, SBR was prepared by adjusting the glass transition temperature as described in Table 1, and in Example 16, polyacrylic acid resin and polyvinyl alcohol resin were used in place of the polyacrylic acid-polyvinyl alcohol copolymer. For each of parts by mass, a total of 2 parts by mass was used, and Examples 17 to 20, 29 and 30 used paraffinic mold release agents whose melting points were adjusted as shown in Table 1.

[Comparative example]
The content of the adhesive and the components of the release agent were changed as shown in Table 1, and the production was performed in the same manner as in the examples, which were used as comparative examples.

〔Evaluation method〕
The cast coated surfaces of various coated papers produced as described above were measured and evaluated as follows. The results are shown in Table 1.

1) Air permeability Measured according to JISP 8117: 1998 “Paper and paperboard—Air permeability and air resistance test method (intermediate region) —Gurley method”.

2) Pit defects The state of occurrence of pit defects was visually evaluated according to the following criteria.
A: No occurrence of pit defects, excellent surface feeling, and practical use.
◯: Slight pit defects occurred, but the surface feeling was good, and actual use was possible.
Δ: Although some pit defects occurred, the surface has a feel enough to withstand actual use.
X: A pit defect occurs and it cannot endure actual use.

3) Solvent resistance test Toluene or methyl ethyl ketone (MEK) No. 3 was applied to the surface of the coating layer. The coating was performed with a wire bar No. 2, and after 30 seconds, it was heated at 130 ° C. for 90 seconds. The image clarity before and after this treatment was measured.

3-1) Image clarity Measured according to JIS H 8686-2. The image property before the solvent resistance test was defined as the image property before solvent contact, and the image property after the solvent resistance test was defined as the image property after solvent contact.

3-2) Rate of change The rate of change was calculated from the following equation.
Rate of change (%) = (1− (image clarity after solvent contact / image clarity before solvent contact)) × 100

  As shown in Table 1, in the examples, the rate of change in image clarity by a solvent resistance test using toluene and methyl ethyl ketone is 5% or less, and the resistance to polar solvents and nonpolar solvents is excellent.

  INDUSTRIAL APPLICABILITY The present invention is applicable as a coated paper for a synthetic leather process paper suitable for use as a synthetic leather process paper manufactured using a polar solvent and a nonpolar solvent.

Claims (3)

A coated paper for synthetic leather process paper comprising a base paper and a coating layer provided on the base paper,
The coating layer contains a pigment, an adhesive, and a release agent,
As the adhesive, at least both polyacrylic acid (PAA) and polyvinyl alcohol (PVA), or a polyacrylic acid-polyvinyl alcohol copolymer, and a polyacrylic acid resin component and a polyvinyl alcohol resin component at 10:90 to 90: Containing at a mass ratio of 10,
The total of the polyacrylic acid (PAA) and the polyvinyl alcohol (PVA), or 1-10 parts by mass of the polyacrylic acid-polyvinyl alcohol copolymer, 100% by mass of the pigment, styrene-butadiene latex 10 to 25 parts by mass, 5 to 30 parts by mass of casein ,
Among 100 parts by mass of the pigment, 20 to 60 parts by mass of columnar calcium carbonate is contained,
Coated paper for synthetic leather process paper , characterized by containing paraffin as the release agent. The paraffin contains from 0.5 to 10 parts by mass in terms of solid content with respect to the pigment 100 parts by weight, the casein and the styrene - styrene weight ratio of butadiene latex, relative to casein 1 - butadiene latex 0.5 It is -3.0, The coated paper for synthetic leather process paper of Claim 1 characterized by the above-mentioned. The melting point of the paraffin is 50 ° C to 100 ° C,
The coating layer is cast-treated,
The coated paper for synthetic leather process paper according to claim 1 or 2, wherein a temperature of the cast drum when the coating layer is cast is 95 ° C to 120 ° C.