JP2009209470A - Coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated paper which exhibits excellent solvent resistance to both polar solvents and non-polar solvents. <P>SOLUTION: Provided is the coated paper has base paper and a coating layer consisting mainly of a pigment and an adhesive and disposed on at least one side of the base paper. In the coated paper, the adhesive includes both polyacrylic acid and polyvinyl alcohol or polyacrylic acid-polyvinyl alcohol copolymer, and the coating layer is mirror-treated by a rewet cast method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coated paper excellent in resistance to an organic solvent. More specifically, the present invention relates to a coated paper suitable for use as a process paper for synthetic leather manufactured using an organic solvent.

  This type of coated paper, especially cast coated paper in which a coating layer is provided by a casting method, is an industrial substrate (for example, a marking sheet, a release sheet such as a metal foil), a packaging paper (for example, a paper bag). , Book covers, etc.), process base paper (for example, process base paper such as synthetic leather and plastic film), etc. Specifically, for example, 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, thereby obtaining a plastic film or the like.

  Therefore, this type of coated paper is desired to have excellent solvent resistance. For example, a cast coated paper using a styrene-butadiene copolymer latex having a gel content of 85% or more as an adhesive is proposed. (For example, refer to Patent Document 1).

  On the other hand, in recent years, the organic solvent used has been shifting from a nonpolar solvent to a polar solvent for the purpose of reducing the environmental load, and process base paper and the like are required to have solvent resistance against both the polar solvent and the nonpolar solvent. ing. 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.

However, the conventional coated paper does not satisfy these requirements.
Japanese Patent Application Laid-Open No. 2005-97781

  The main problem to be solved by the present invention is to provide a coated paper exhibiting excellent solvent resistance against both polar and nonpolar solvents. Furthermore, the glossiness is high, there is little degradation in image clarity, and there is little degradation in the specularity of the synthetic leather to be produced. For example, even when high-speed coating is performed at 40 m / min or more, the appearance of micropits is small and the appearance is good. It is to provide a coated paper that can be used as a synthetic leather process paper that can produce a good synthetic leather.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive provided on at least one surface of the base paper,
The adhesive comprises both polyacrylic acid and polyvinyl alcohol;
And the coating layer is mirror-finished by a rewet cast method,
Coated paper characterized by that.

[Invention of Claim 2]
A coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive provided on at least one surface of the base paper,
The adhesive comprises a polyacrylic acid-polyvinyl alcohol copolymer;
And the coating layer is mirror-finished by a rewet cast method,
Coated paper characterized by that.

[Invention of Claim 3]
Polyacrylic acid (total molar amount including both monomers and copolymers) and polyvinyl alcohol (monomers included as copolymers) included in the adhesive The total molar amount including the above) is a molar ratio of 10:90 to 90:10,
The coated paper according to claim 1 or 2.

[Invention of Claim 4]
The total content of polyacrylic acid, polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer contained in the adhesive is 1 to 20 parts by mass with respect to 100 parts by mass of the pigment. The coated paper of any one of -3.

[Invention of Claim 5]
The reduction rate of the image clarity measured based on JIS H 8686-2 when the following processing is performed is 20% or less.
The coated paper of any one of Claims 1-4.
(processing)
The coating layer surface was coated with methyl ethyl ketone (MEK) or toluene so that the coating amount was 1 g / m ² . 2. Coat with 2 wire bars and heat to 130 ° C. for 90 seconds after 30 seconds.

[Invention of Claim 6]
A release layer was provided by applying a release agent on the outermost layer,
The coated paper of any one of Claims 1-5.

  According to the present invention, the coated paper exhibits excellent solvent resistance with respect to both a polar solvent and a nonpolar solvent.

Next, an embodiment of the present invention will be described.
First, the present inventors have conducted extensive research for the purpose of improving resistance to polar solvents in coated paper, and as a result, it is effective to define the type and amount of adhesive in the coating layer. I found out.
That is, the present inventors have made a coating paper having a base paper and a coating layer mainly composed of a pigment and an adhesive provided on at least one surface of the base paper. It is found that excellent solvent resistance is exhibited by including both alcohol, polyacrylic acid-polyvinyl alcohol copolymer, or polyacrylic acid, polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer. Thus, the present invention has been completed.
As an adhesive, it is essential to blend at least both polyacrylic acid (PAA) and polyvinyl alcohol (PVA) or a polyacrylic acid-polyvinyl alcohol copolymer. When only polyacrylic acid or polyvinyl alcohol is blended, resistance to a polar solvent or a nonpolar solvent is low, and the coated surface is easily eroded by the solvent. In particular, when a synthetic leather process paper is used, it cannot withstand repeated use.

  The ratio of polyacrylic acid and polyvinyl alcohol can be defined by the molar ratio of the case of simply mixing (in the case of monomer) and the case of copolymer, preferably PAA: PVA = 10: It is 90-90: 10, More preferably, it is PAA: PVA = 15: 85-85: 15. If the PAA is less than 10 mol%, the properties of the PAA itself (hard resin, rigid at room temperature, and excellent water resistance and adhesive strength) are difficult to be expressed. As a result, the properties of PVA (a soft resin that has flexibility at room temperature and has excellent water resistance and adhesive strength) are hardly exhibited. Copolymerization of PAA and PVA is unclear why the solvent resistance is improved, or both are combined with a hard resin and a soft resin that have water resistance, and both flexibility and rigidity are applied to the coated paper surface at room temperature. It is considered that the 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. This is because the copolymer can be more uniformly mixed at a molecular level than the mixture of polyacrylic acid and polyvinyl alcohol. By mixing at the molecular level, even if a change at the micro level due to solvent contact occurs, the change as a coating surface is not lost while the change is flexibly relaxed.

  Adhesives essential for the present embodiment, that is, the total content of polyacrylic acid, polyvinyl alcohol and polyacrylic acid-polyvinyl alcohol copolymer is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the pigment, More preferably, it is 2-15 mass parts. When the amount is less than 1 part by mass, the solvent resistance effect is not sufficiently exhibited and the solvent resistance is inferior. When the amount exceeds 20 parts by mass, not only the pigment-derived smoothness and gloss are deteriorated, but the appearance is deteriorated. Polar solvent tends to accumulate in a portion with low smoothness, and erosion tends to proceed locally.

  In this embodiment, in addition to the adhesive, an adhesive generally used in coated paper production can be used in combination as long as the solvent resistance is not impaired. Specifically, for example, proteins such as casein and soybean protein; conjugated diene latexes such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex; Acrylic latex such as acrylic acid ester and / or methacrylic acid ester polymer latex or copolymer latex; vinyl latex such as ethylene-vinyl acetate polymer latex; Latexes such as alkali partially soluble or insoluble latex modified with group-containing monomers; synthetic resin adhesives such as olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin; oxidized starch, positive Starch, ester Starches, starches such as dextrin; carboxymethyl cellulose, may be mentioned cellulose derivatives such as hydroxyethyl cellulose, it can be used by selecting one or more from among these as appropriate.

  The types and amounts of these commonly used adhesive components vary depending on the intended use. Specifically, for example, in the case of synthetic leather process paper, in order to provide a high gloss coating layer, cast coating is generally performed, and casein or styrene-butadiene latex is preferably used. Casein is blended in order to improve the peelability from the cast drum, and preferably 1 to 15 parts by mass. If it is less than 1 part by mass, the releasability is lowered, and a trouble that a part of the coated surface adheres to the cast drum tends to occur. On the other hand, if it exceeds 15 parts by mass, the peeling performance reaches its peak, and there is no point in using a large amount of expensive casein, resulting in poor economic efficiency. The styrene-butadiene latex has a function of developing the gloss derived from the pigment in the coated paper, and is preferably 3 parts by mass to 30 parts by mass. If the amount is less than 3 parts by mass, sufficient gloss and adhesive strength are not exhibited. Conversely, if the amount exceeds 30 parts by mass, a film-like surface is formed and the gloss derived from the pigment decreases. The total amount of the adhesive essential to the present invention and these commonly used adhesives is preferably 5 to 60 parts by mass with respect to 100 parts by mass of the pigment. If the amount is less than 5 parts by mass, the solvent resistance, peelability, glossiness, and strength of the coating layer are inferior. On the other hand, if the amount exceeds 60 parts by mass, the glossiness decreases and the economy is inferior. The blending amount of the styrene-butadiene latex is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the pigment. If the amount is less than 3 parts by mass, sufficient gloss and adhesive strength are not exhibited. Conversely, if the amount exceeds 30 parts by mass, a film-like surface is formed and gloss derived from the pigment is lowered.

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

  Among the above pigments, clay is excellent in gloss and smoothness, and therefore it is preferable to blend 20 parts by mass to 80 parts by mass with respect to 100 parts by mass of the pigment. If the blending amount is less than 20 parts by mass, the glossiness and smoothness are inferior, so that the solvent resistance tends to be lowered. On the other hand, if it exceeds 80 parts by mass, the fluidity of the coating liquid is deteriorated and the profile at the time of coating is deteriorated. However, since gloss and smooth unevenness are likely to occur, the solvent resistance decreases.

  As the pigment to be used in combination with clay, heavy calcium carbonate is preferred, which improves whiteness, improves appearance, and is economical. The blending amount is preferably 20 to 80 parts by mass so as to complement the blending amount of clay.

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

  The application of the coating agent to the surface of the base paper is preferably performed by a so-called cast coating method in the use of synthetic leather process paper. In general, the cast coating method includes (1) a wet cast method (direct method) in which a coated layer is in a wet state and is pressed (pressed) on a mirror-finished heating drum (cast drum) and dried (2) Rewet cast method (rewetting method) in which the wet coating layer is once (semi-) dried and then swollen and plasticized (wet) with a rewetting liquid, and then pressed onto a heated mirror drum and dried (3) The wet coating layer is made into a gel state by coagulation treatment with a coagulating liquid, etc., and can be divided into three types: gelling cast method (coagulation method) in which it is pressed against a heated mirror drum and dried. Solvent resistance can be obtained.

  However, when the coating speed is fast, especially when the coating speed is as fast as 40 m / min or more, since a rapid drying is required as compared with the conventional coating speed of about 20 m / min, the coating is performed at the time of drying. Due to water vapor evaporating from the layer, holes are formed in the surface of the coating layer, and defects called micropits are likely to occur. For this reason, it has been difficult to improve the coating speed while sufficiently suppressing the micropits. As a result of intensive studies, the inventors have found that micropits can be sufficiently reduced even when the coating speed is 40 m / min or more according to the method of mirror finishing by the rewet cast method.

Here, in the case of mirror-treating the coating layer mainly composed of an adhesive and a pigment containing both polyacrylic acid and polyvinyl alcohol, and a polyacrylic acid-polyvinyl alcohol copolymer by a rewet cast method. The type of the rewetting liquid is not particularly limited, and a known rewetting liquid can be used. However, it is preferable to use water from the viewpoint of preventing a decrease in solvent resistance. Moreover, the temperature of a cast drum is 70-120 degreeC normally, Preferably it is 80-110 degreeC. When the temperature is lower than 70 ° C., the coating layer of the present embodiment cannot be sufficiently flattened. On the other hand, when the temperature is higher than 120 ° C., the coating layer of the present embodiment may be destroyed. Furthermore, if the coating layer is divided into two or more layers, it is sufficient to rewet only the outermost layer, and the amount of evaporated water during the mirror surface treatment is reduced, so that the coating speed is further improved. Can do. From this viewpoint, the preferable coating amount of the outermost layer is 4 to 10 g / m ² , particularly 5 to 8 g / m ² .

  The coating of the coating agent on the surface of the base paper is sufficient if it is performed using general coating paper 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 processing device can be applied to the base paper in one or more layers. Among these, it is preferable to use a blade coater because 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 coating amount 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 glossiness and solvent resistance cannot be obtained. On the other hand, if it exceeds 30 g / m ² , the water vapor generated when the coating layer dries increases, and pit defects are likely to occur in the rewetting method, which not only lowers the quality but also deteriorates the economy. There is a risk.

  In the present embodiment, a coating layer satisfying the various conditions described above (mirror treatment by the rewetting method, the adhesive includes polyacrylic acid, polyvinyl alcohol, polyacrylic acid-polyvinyl alcohol copolymer), Although it can be provided on both sides of the base paper, it can also be provided on only one side. In the case of providing only on one surface, there is no particular limitation on what kind of processing is performed on the other surface or whether no processing is performed. Of course, a coating layer mainly composed of pigments and adhesives that do not satisfy the above-mentioned various conditions may be provided, and various external additive coating agents for paper such as starch or starch derivatives, sizing agents and synthetic paper strength agents. May be applied. In addition, water coating can be performed from the viewpoint of curling prevention.

The coated paper of this embodiment preferably has a reduction rate of image clarity measured based on JIS H 8686-2 of 20% or less, and 15% or less when the following processing is performed. More preferably, it is preferably 10% or less.
(processing)
No. 1 so that methylethylketone (MEK) or toluene is applied to the surface of the outermost layer at a coating amount of 1 g / m ² . 2. Coat with 2 wire bars and heat to 130 ° C. for 90 seconds after 30 seconds.
According to this embodiment, for example, in the use of synthetic leather process paper, it is preferable that the synthetic leather to be produced is less deteriorated in mirror surface and has good appearance. In particular, if the coating layer is divided into two or more layers, and the coating amount of the outermost layer is 3 to 12 g / m ² , the deterioration due to the solvent hardly occurs and the occurrence of defects such as trays. Therefore, it is a process paper that 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.

  The coated paper of this embodiment thus obtained uses a polyacrylic acid and polyvinyl alcohol or a polyacrylic acid-polyvinyl alcohol copolymer as an adhesive, and has a Beck smoothness of 500 seconds measured based on JIS P 8119. As described above, the air permeability measured based on Tappi T536cm-02 is preferably 500 to 3000 seconds, 1000 seconds or more, and preferably 1000 to 3000 seconds. As a result, the coated paper, in particular, synthetic leather process paper, which has little deterioration in image clarity after contact with the polar solvent and has excellent solvent resistance. This is because when the smoothness is less than 500 seconds, the surface is rough, and therefore, when the solvent is applied, local accumulation of the solvent is likely to occur, and local image clarity is likely to be deteriorated. Further, if it exceeds 3000 seconds, the smoothness is sufficiently high, and even if flattening beyond this, the solvent resistance only reaches its peak, which is economically undesirable. When the air permeability is less than 1000 seconds, there are many voids on the coated surface, and the solvent easily permeates, so that deterioration easily proceeds. Further, if it exceeds 3000 seconds, the air permeability is sufficiently high as in the case of smoothness, and even if the air resistance higher than this is applied, the solvent resistance will reach its peak, which is not economical. Even when the air permeability is adjusted by casting, there is a possibility that the rigidity of the paper is destroyed due to excessive linear pressure.

  The method for adjusting the smoothness and the air permeability is not particularly limited, and can be adjusted by adjusting, for example, cast finish conditions for flattening, particularly linear pressure and speed.

  By applying a release agent to the obtained coated paper, solvent resistance and peelability can be improved. As the release agent, polypropylene resins, polymethylpentene resins, silicone resins, alkyd resins, and the like that are generally used for release paper applications can be used. Polypropylene resins are excellent in repeated use, but have the disadvantages of poor heat resistance and limited use at high temperatures, and the surface is easily damaged. Use of polymethylpentene resins having better heat resistance is preferred. Silicone resins are excellent in releasability, but there are drawbacks in peel strength and gloss control, and uniformity of the coating film, and alkyd resins have excellent heat resistance and gloss control but have poor delamination properties. is there. In the present embodiment, the above four types of release agents can be properly used depending on the use conditions and required quality of the process release paper, but it is particularly preferable to use an alkyd resin having good heat resistance. By applying these resin compositions to base paper, the object of the present invention is a coated paper that is a process release paper that can produce synthetic leather with high glossiness, image clarity, good peelability, and good appearance. Is obtained.

  On the other hand, as the base paper of the coated paper, normal raw pulp can be used. ), Etc .; Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical pulp such as mechanical 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 systems such as a long net system, a twin wire system, a gap former system, a round net system, and a Yankee system can be appropriately used.

  Moreover, before performing the coating of the present invention, for the purpose of flattening the base paper, a coating using the general coated paper application facility or a flattening process by a combination of the elastic roll and the metal roll is performed. Is preferred.

  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%. After making and drying with a long paper machine, a coating solution in which 100 parts by weight of heavy calcium carbonate and 4 parts by weight of latex are mixed using a size press is 5.0 g / m ^{2 in} dry weight per side. It was coated like so. The basis weight of the base paper was 117 to 142 g / m ² , and the coated paper was adjusted so that the basis weight was 157 g / m ² .

[Formation of innermost layer]
A blade coater is used to apply a coating solution comprising 50 parts by mass of clay, 50 parts by mass of heavy calcium carbonate, and 8 parts by mass of latex on the surface of the base paper so that the coating amount shown in Table 1 is calculated in terms of solid content per side. It was coated and flattened with a super calendar (SC).

[Formation of outermost layer]
The coating agent is prepared by mixing and stirring the pigment and adhesive at room temperature according to the types, ratios, and finishing methods shown in Table 1, so that the coating amount in Table 1 in terms of solid content per side is 40 m / Air knife coating was performed on the undercoating layer at a speed of minutes and finished by a cast coating method. The pigments and adhesives used are as follows. Moreover, the compounding quantity of the adhesive agent of Table 1 is a value with respect to 100 mass parts of pigments.
・ Clay (kaolin, product number: HYDRASPERS90, manufactured by HUBER)
・ Heavy calcium carbonate (wet, product number: ESCALON # 90, manufactured by Sankyo Flour Milling Co., Ltd.)
・ Casein (manufactured by Nissei Kyobun Co., Ltd.)
・ Styrene-butadiene latex (SBR) (Part No .: PA5036, manufactured by Nippon A & L Co., Ltd.)
・ Polyacrylic acid (PAA) (Part No .: Aquaric R HL, Nippon Shokubai Co., Ltd.)
・ Polyvinyl alcohol (PVA) (model number: PVA405, Kuraray Co., Ltd.)
・ Polyacrylic acid-polyvinyl alcohol copolymer (PAA-PVA) (model number: Cogham HW400, Showa Polymer Co., Ltd.)

(Formation of release layer)
A release agent solution was prepared by mixing 6 parts by mass of the catalyst and 40 parts by mass of toluene with respect to 100 parts by mass of the synthetic resin. Subsequently, No. 1 was applied so that the release agent had a coating amount of 10 g / m ² per side. After coating with a 2 wire bar, it was cured by heating at 170 ° C. for 1 minute to form a release layer. Table 2 shows the types of coated paper used. The chemicals used are as follows.
Synthetic resin: Alkyd resin (Part No .: Tesfine 303, manufactured by Hitachi Chemical Co., Ltd.)
Catalyst (Product No .: Dryer 900, manufactured by Hitachi Chemical Polymer Co., Ltd.)
Toluene (Product number: Special grade, Wako Pure Chemical Industries, Ltd.)

[Comparative example]
The presence / absence of the coating layer, the coating amount, the adhesive component, the surface finishing method, and the like were changed as shown in Table 1 to obtain Comparative Examples.

〔Evaluation methods〕
The various coated papers produced as described above were measured and evaluated as follows.
1) Beck smoothness Measured according to JIS P 8119.

2) Air permeability Measured according to Tappi T536cm-02.

3) Micropits The outermost layer was observed visually and with a magnifying glass (10 times), and the generated micropits were evaluated according to the following criteria.
(Double-circle): The micropit did not generate | occur | produce but it was favorable.
◯: Some micropits were generated but were good.
Δ: Some micropits were generated, but there was no problem in actual use.
X: Micro pits were generated and were not practically usable.

4) Solvent resistance test No. 1 so that methyl ethyl ketone (MEK) or toluene was applied to the surface of the coating layer of the coated paper (width 100 × length 148 mm) at 1 g / m ² . The coating was performed with a wire bar No. 2, and after 30 seconds, it was heated to 130 ° C. for 90 seconds. The image clarity before and after this treatment was measured. The image clarity was measured according to JIS H 8686-2. The rate of change was calculated by the following formula.
Rate of change (%) = (1− (measured value after test / measured value before test)) × 100

5) Peel resistance Polyvinyl chloride sol obtained by mixing 100 parts by weight of polyvinyl chloride, 50 parts by weight of dioctyl phthalate, 5 parts of foaming agent, and 3 parts of stabilizer on release paper was prepared as It applied so that the coating amount might be 30 g / m < ² > using 2 wire bars. Then, it was heat-cured at 200 ° C. for 3 minutes to form a foamed polyvinyl chloride sheet layer, which was peeled from the release paper. After repeating this operation 10 times, the release paper surface was visually evaluated as follows.
(Double-circle): The coating layer and the peeling layer were not peeled off by the polyvinyl chloride sheet, and were favorable.
A: The coating layer and the release layer are slightly peeled off to the polyvinyl chloride sheet, and the peel resistance is slightly inferior.
X: Many coating layers and peeling layers are peeled off by the polyvinyl chloride sheet, and it is inferior to peeling resistance.
In addition, (double-circle) and (circle) are a level which does not have a problem in actual use. The chemicals used are as follows.
Polyvinyl chloride (Part No .: ZEON 121, manufactured by ZEON CORPORATION)
Dioctyl phthalate (manufactured by CG Esther)
Foaming agent (azodicarbonamide, manufactured by Eiwa Kasei Kogyo Co., Ltd.)
Stabilizer (Product No .: BZ-100CJ, manufactured by Katsuta Chemical Corporation)

  Tables 1 and 2 show the results of the above tests. As shown in Table 1, in Examples 1 to 37, even if the coating speed was as high as 40 m / min, the rate of change in image clarity by a solvent resistance test using methyl ethyl ketone or toluene was 20% or less. Excellent resistance to polar and non-polar solvents and less micropits. On the other hand, Comparative Examples 1 to 5 in which polyacrylic acid and polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer were not blended as adhesives had image clarity by a solvent resistance test using methyl ethyl ketone or toluene. The rate of change exceeds 20%, and the resistance to polar and nonpolar solvents is poor, or micropits are frequently generated.

  As shown in Table 2, in the examples, polyacrylic acid and polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer were blended as adhesives, and the coating layer was mirror-finished by the rewet cast method. Since the release layer was provided, the peel resistance was good. On the other hand, as an adhesive, a comparative example in which a release layer is provided on a coating layer in which polyacrylic acid and polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer are not blended, or a direct method or a gelling method The comparative example in which the release layer was provided on the coating layer that had been mirror-finished by the method had a poor peel resistance and became a coated paper that could not withstand actual use.

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

Claims (6)

A coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive provided on at least one surface of the base paper,
The adhesive comprises both polyacrylic acid and polyvinyl alcohol;
And the coating layer is mirror-finished by a rewet cast method,
Coated paper characterized by that. A coated paper having a base paper and a coating layer mainly composed of a pigment and an adhesive provided on at least one surface of the base paper,
The adhesive comprises a polyacrylic acid-polyvinyl alcohol copolymer;
And the coating layer is mirror-finished by a rewet cast method,
Coated paper characterized by that. Polyacrylic acid (total molar amount including both monomers and copolymers) and polyvinyl alcohol (monomers included as copolymers) included in the adhesive The total molar amount including the above) is a molar ratio of 10:90 to 90:10,
The coated paper according to claim 1 or 2.   The total content of polyacrylic acid, polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer contained in the adhesive is 1 to 20 parts by mass with respect to 100 parts by mass of the pigment. The coated paper of any one of -3. The rate of decrease in image clarity measured based on JIS H 8686-2 when the following processing is performed is 20% or less.
The coated paper of any one of Claims 1-4.
(processing)
The coating layer surface was coated with methyl ethyl ketone (MEK) or toluene so that the coating amount was 1 g / m ² . 2. Coat with 2 wire bars and heat to 130 ° C. for 90 seconds after 30 seconds. A release layer was provided by applying a release agent on the outermost layer,
The coated paper of any one of Claims 1-5.