JP4436418B2 - Process paper - Google Patents

Description

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

The coated paper, especially the cast coated paper in which the coating layer is provided by the cast coating method, is an industrial substrate (for example, a marking sheet, a release sheet such as a metal foil), packaging paper (for example, a paper bag, a book). Cover, etc.), process base paper (for example, process base paper such as synthetic leather and plastic film), etc. In particular, for the process paper , 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.

Therefore, this type of process paper is desired to have excellent solvent resistance. For example, cast coated paper using a styrene / butadiene copolymer latex having a gel content of 85% or more as an adhesive has been 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 process paper does not satisfy these requirements. Moreover, when the cast drum surface temperature is high, the cast coated paper has a rapid boiling of the water in the coating layer when the coating layer is pressed against the cast drum, and the coating layer is destroyed. Innumerable fine pinholes (so-called micropits) are generated. Therefore, the surface temperature of the cast drum cannot be increased, resulting in a decrease in drying speed and a decrease in production speed.
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, it can be used as a synthetic leather process paper that has a high glossiness and is less likely to cause poor visual clarity due to less degradation of the mirror surface of the synthetic leather produced and less micropits. Is to provide a simple process paper .

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
And base paper, a process paper having a least one layer of the coating layer composed mainly pigment and an adhesive provided on at least one surface of the base paper,
The adhesive contains both polyacrylic acid and polyvinyl alcohol so that the total blending amount is 1 to 20 parts by mass with respect to 100 parts by mass of the pigment ,
The pigment contains 20 to 80 parts by mass of clay with respect to 100 parts by mass of the pigment;
The surface layer of the coating layer has a coating amount of 20 to 40 g / m ² and is mirror-finished by a cast coating method.
Process paper characterized by that .

[Invention of Claim 2]
The pigment contains 20 to 80 parts by mass of heavy calcium carbonate with respect to 100 parts by mass of the pigment.
The process paper according to claim 1.
[Invention of Claim 3]
The adhesive contains 1 to 15 parts by mass of casein with respect to 100 parts by mass of the pigment, and 3 to 30 parts by mass of styrene-butadiene latex with respect to 100 parts by mass of the pigment.
The process paper according to claim 1 or 2.
[Invention of Claim 4]
The polyacrylic acid and the polyvinyl alcohol are copolymerized,
The process paper of any one of Claims 1-3.

[Invention of Claim 5 ]
The polyacrylic acid and polyvinyl alcohol contained in the adhesive have a molar ratio of 10:90 to 90:10 (a total molar amount including both a monomer and a copolymer). Ratio) ,
The process paper of any one of Claims 1-4 .

[Invention of Claim 6 ]
The surface layer of the coating layer has a coating amount of 25 to 35 g / m ² ,
The Beck smoothness measured based on JIS P 8119 is 500 to 3000 seconds, and the air permeability measured based on Tappi T536cm-02 is 1000 to 3000 seconds.
The process paper of any one of Claims 1-5 .

[Invention of Claim 7 ]
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 process paper of any one of Claims 1-6 .
(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 8 ]
A release layer was provided by applying a release agent on the coating layer,
Step paper according to any one of claims 1-7.

According to the present invention, the process paper exhibits excellent solvent resistance with respect to both a polar solvent and a nonpolar solvent, and generates less micropits .

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 process paper , and as a result, it is effective to specify 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 nonpolar solvent is low, and the coated surface is easily eroded by the polar 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 blending amount 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, and gloss are inferior. On the other hand, if the amount exceeds 60 parts by mass, the gloss is lowered and the economy is inferior.

  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 Inorganic pigments such as 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 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 coating of the coating agent on the surface of the base paper is performed by a cast coating method when the coating layer is a single layer because the coating layer becomes a surface layer. In addition, when the number of coating layers is two or more, the surface layer (the outermost layer) is formed by a cast coating method. 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) Rewetting cast method (rewetting method) in which the coating layer in a wet state is once (semi-) dried and then swollen and plasticized (wet) with a rewetting liquid, and then pressed onto a mirror-finished heating drum and dried (3) Wetting The coating layer in a state can be divided into three types: gelation cast method (coagulation method) in which the coating layer is made into a gel state by coagulation treatment with a coagulating liquid and then pressed onto a mirror-finished heating drum and dried. Solvent property can be obtained.

  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 of the surface layer is set to 20 to 40 g / m ^2. This coating amount is the same as the coating amount of the coating layer because there is only a surface layer when there is one coating layer. In the synthetic leather process paper, when the surface flatness (image clarity) is low, the liquid pool of the solvent is likely to occur, the coating layer is eroded locally by the solvent, and the image clarity is greatly deteriorated. In order to prevent a decrease in image clarity, the coating amount is 20 g / m ² or more. On the other hand, when the coating amount exceeds 40 g / m ² , holes are formed in the surface of the coating layer due to water vapor evaporated from the coating layer during drying, and many defects called micropits are generated. For this reason, the coating amount is set to 20 to 40 g / m ² from the viewpoint of improving the image clarity while sufficiently suppressing the micropits.

  In this embodiment, the coating layers satisfying the various conditions described above (mirror-treated, and the adhesive contains polyacrylic acid, polyvinyl alcohol, polyacrylic acid-polyvinyl alcohol copolymer) are provided on both sides of the base paper. However, it can also be provided on only one surface. 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 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.

Further, in the process paper of this embodiment, the rate of decrease in image clarity measured based on JIS H 8686-2 when the following processing is performed is preferably 20% or less, and more preferably 15% or less. More preferably, it is 10% or less, particularly 5% or less.
(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.
According to this embodiment, for example, in the use of synthetic leather process paper, it is preferable that the synthetic leather to be manufactured is less deteriorated in mirror surface and has good appearance. Further, since the deterioration due to the solvent is difficult to occur, the occurrence of defects such as trays can be reduced, and the synthetic paper can be efficiently manufactured because of good peelability. Thus, the coated 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.

Thus, the process paper of this form obtained uses polyacrylic acid and polyvinyl alcohol, or a polyacrylic acid-polyvinyl alcohol copolymer as an adhesive agent, and the Beck smoothness measured based on JISP8119 is 500-3000. The air permeability measured based on seconds, preferably 600 to 2000 seconds and Tappi T536 cm-02, is 1000 to 3000 seconds, preferably 1200 to 2000 seconds. As a result, a process paper , particularly a synthetic leather process paper, which has little deterioration in image clarity after contact with a polar solvent and has excellent solvent resistance is obtained. This is because when the smoothness is less than 500 seconds, the surface is rough, and therefore, when the solvent is applied, a local accumulation of solvent is likely to occur, and local image clarity is likely to decrease. On the other hand, 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. On the other hand, 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 economically preferable. In particular, in this embodiment, in order to make the coating amount of the surface layer 20 to 40 g / m ² , when the air permeability exceeds 3000 seconds, moisture in the surface layer escapes as vapor. Is slow and is not preferable. The method for adjusting the smoothness or air permeability is not particularly limited, and can be adjusted by adjusting, for example, cast finish conditions for flattening, particularly linear pressure and speed. However, since the treatment by casting finish also affects the base paper, it is preferable to make the treatment as weak as possible when adjusting the smoothness and air permeability. Therefore, in order to compensate for this, the coating amount of the surface layer is preferably 25 to 35 g / m ² . If the coating amount is 25 g / m ² or more, it is easy to improve the smoothness (image clarity). On the other hand, if the coating amount is 35 g / m ² or less, the air permeability is relatively lowered. Can be a weak process.

Solvent resistance and peelability can be improved by applying a release agent to the obtained process paper . 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, and polymethylpentene resins with better heat resistance are used. 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 paper , but it is particularly preferable to use an alkyd resin having good heat resistance. By coating these resin compositions into the base paper is an object of the present invention, gloss, high clarity, releasability is good, casting paper can be produced good-looking synthetic leather is obtained.

On the other hand, the raw paper for the process paper can use normal raw pulp, for example, unbleached softwood pulp (NUKP), unbleached hardwood pulp (LUKP), bleached softwood pulp (NBKP), bleached hardwood pulp (LBKP) Chemical pulps such as: Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermomechanical Mechanical pulp such as pulp (TMP), chemi-thermomechanical pulp (CTMP), refiner mechanical pulp (RMP), and 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. In this embodiment, one or more of these can be appropriately selected and used.

  In this embodiment, the above raw material pulp is mixed to prepare a papermaking raw material (stock slurry). For the raw material pulp, for example, an internally added sizing agent, a paper strength enhancer, a paper thickness improver, a yield Various additives blended in the 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%. Paper was obtained by paper making and drying with a long paper machine. 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 .

[Coating layer]
The coating agent is prepared by mixing and stirring the adhesives and pigments (clay and heavy calcium carbonate) of the types and proportions shown in Table 1 at room temperature, so that the coating amount shown in Table 1 is calculated in terms of solid content per side. Then, air knife coating was performed at a speed of 20 m / min, 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. Furthermore, since this example has one coating layer, the coating layer and the surface layer are the same.
・ 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.)

[Peeling 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 composition of the adhesive, the coating amount, and the like were changed as shown in Table 1 to make a comparative example.

〔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 surface 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 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 was applied so that methyl ethyl ketone (MEK) or toluene was applied at a coating amount of 1 g / m ^{2 on} the surface of the coating layer of the coated paper (width 100 × length 148 mm). 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 mass of polyvinyl chloride, 50 parts by mass of dioctyl phthalate, 5 parts of foaming agent, and 3 parts of stabilizer on release paper was obtained 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 the examples, the rate of change in image clarity by a solvent resistance test using methyl ethyl ketone or toluene is 20% or less, the resistance to polar solvents is excellent, and the generation of micropits is small. On the other hand, as a comparative example in which polyacrylic acid and polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer are not blended or the coating amount is not within a predetermined range, a resistance value using methyl ethyl ketone or toluene is used. The rate of change in image clarity by the solvent test exceeds 20%, and the resistance to polar solvents is poor or micropits are frequently generated.

  As shown in Table 2, in Examples, on the coated paper, polyacrylic acid and polyvinyl alcohol, and polyacrylic acid-polyvinyl alcohol copolymer were blended as adhesives, and the coating amount was within a predetermined range. Since the release layer was provided on the surface, the peel resistance was good. On the other hand, on the coated paper not blended with polyacrylic acid and polyvinyl alcohol and polyacrylic acid-polyvinyl alcohol copolymer as an adhesive, or on coated paper whose coating amount is not within a predetermined range. The comparative example provided with a release layer was poor in peel resistance and became a coated paper that could not withstand actual use.

The present invention can be applied as a process paper suitable for use as a process paper for synthetic leather produced using an organic solvent.

Claims (8)

And base paper, a process paper having a least one layer of the coating layer composed mainly pigment and an adhesive provided on at least one surface of the base paper,
The adhesive contains both polyacrylic acid and polyvinyl alcohol so that the total blending amount is 1 to 20 parts by mass with respect to 100 parts by mass of the pigment ,
The pigment contains 20 to 80 parts by mass of clay with respect to 100 parts by mass of the pigment;
The surface layer of the coating layer has a coating amount of 20 to 40 g / m ² and is mirror-finished by a cast coating method.
Process paper characterized by that . The pigment contains 20 to 80 parts by mass of heavy calcium carbonate with respect to 100 parts by mass of the pigment.
The process paper according to claim 1. The adhesive contains 1 to 15 parts by mass of casein with respect to 100 parts by mass of the pigment, and 3 to 30 parts by mass of styrene-butadiene latex with respect to 100 parts by mass of the pigment.
The process paper according to claim 1 or 2. The polyacrylic acid and the polyvinyl alcohol are copolymerized,
The process paper of any one of Claims 1-3. The polyacrylic acid and polyvinyl alcohol contained in the adhesive have a molar ratio of 10:90 to 90:10 (a total molar amount including both a monomer and a copolymer). Ratio) ,
The process paper of any one of Claims 1-4 . The surface layer of the coating layer has a coating amount of 25 to 35 g / m ² ,
The Beck smoothness measured based on JIS P 8119 is 500 to 3000 seconds, and the air permeability measured based on Tappi T536cm-02 is 1000 to 3000 seconds.
The process paper of any one of Claims 1-5 . 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 process paper of any one of Claims 1-6 .
(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 coating layer,
Step paper according to any one of claims 1-7.