JP5495073B2 - Clean paper and manufacturing method thereof - Google Patents

Description

The present invention relates to a clean paper and a manufacturing method thereof.

In clean rooms used in the semiconductor industry, paper called clean paper (dust-free paper) with low dust generation is used in order to avoid malfunctions of various devices due to fine dust, product contamination, etc. Yes.

The clean paper needs to have a characteristic that paper dust or other foreign matters are not generated even when it is torn or rubbed, or the amount of generation is small. Therefore, as a clean paper, a paper obtained by impregnating a base paper made of natural fiber or synthetic fiber with a resin in order to suppress dust generation is widely known.

For example, JP-A-60-146099, JP-A-63-105199, JP-A-9-87993, JP-A-2001-293951, JP-A-2003-49392, JP-A-2005-105486, Japanese Patent Application Laid-Open Nos. 2005-281192 and 2008-190065 describe clean paper obtained by impregnating a base paper with a resin emulsion.

JP 60-146099 A JP-A-63-105199 Japanese Patent Laid-Open No. 9-87993 JP 2001-293951 A JP 2003-49392 A JP 2005-105486 A JP 2005-281192 A JP 2008-190065 A

In general, when a clean paper has a large amount of resin impregnation, dust generation is suppressed. However, when the amount of impregnation of the resin increases, the opacity of the clean paper decreases, the stiffness (strain) decreases, blocking occurs when the clean paper is stacked, and the resin is applied to the cutting blade that cuts the clean paper. And the cutting blade is contaminated, and the other clean paper is contaminated by the resin adhering to the surface of the other clean paper.

Incidentally, Japanese Laid-Open Patent Publication No. 9-87993 and Japanese Laid-Open Patent Publication No. 2008-190065 describe clean paper with little blocking. Specifically, JP-A-9-87993 discloses a clean paper provided with a mixture of two kinds of polymer substances having greatly different glass transition temperatures, and JP-A-2008-190065 discloses a glass transition. A clean paper to which a mixture of two kinds of acrylic resin emulsions and polyvinyl alcohols having greatly different temperatures is applied is described. However, in these clean papers, since the resin having a low glass transition temperature is partially present on the surface of the clean paper, it is impossible to completely prevent blocking. Further, since these require a large amount of resin impregnation, there is a problem that dust generation cannot be suppressed if the amount of resin is reduced.

  The present invention has been made in view of such problems, and is compatible with low dust generation and opaqueness, high rigidity, low blocking property, or low contamination such as a cutting blade when cutting. The purpose is to provide clean paper.

The object of the present invention is a base paper,
A (meth) acrylic resin layer comprising at least one (meth) acrylic resin, and
A clean paper comprising a binder layer comprising at least one binder,
The binder layer is located on the (meth) acrylic resin layer,
This is achieved by a clean paper in which one surface of the binder layer constitutes at least a part of the surface of the clean paper.

In the clean paper of the present invention, it is preferable that at least a part of the (meth) acrylic resin is impregnated in the base paper. In this case, the impregnation ratio of the (meth) acrylic resin is preferably 0.8 to less than 5.0%.

The (meth) acrylic resin may have a glass transition temperature of −40 ° C. to less than 0 ° C. The binder may be a (meth) acrylic resin having a glass transition temperature of 0 ° C to 200 ° C.

  The (meth) acrylic resin layer preferably further contains polyvinyl alcohol.

The binder may be a water-soluble binder.

The binder layer is preferably present at a rate of 0.05 to 10 g / m ² in terms of dry weight per unit area of the base paper.

An intermediate layer may exist between the (meth) acrylic resin layer and the binder layer.

In the clean paper of this invention, it is preferable that one surface of the said (meth) acrylic-type resin layer and the other surface of the said binder layer contact. In that case, at least a part of a contact surface between one surface of the (meth) acrylic resin layer and the other surface of the binder layer may be mixed.

The binder layer can include at least one lubricant. The lubricant is preferably a wax.

The clean paper of the present invention comprises a step of applying at least one (meth) acrylic resin on a base paper to form a (meth) acrylic resin layer, and at least on the (meth) acrylic resin layer. It can be manufactured through a step of forming a binder layer by applying one kind of binder.

Before the step of forming the binder layer, a step of forming an intermediate layer on at least a part of the surface of the (meth) acrylic resin layer may be provided.

The clean paper of the present invention is compatible with at least one, preferably all of low dust generation, opacity, high rigidity, low blocking property, and low contamination such as a cutting blade when cutting. .

In the present invention, since the binder layer is present on the surface of the clean paper, dust generation from the surface can be suppressed. Therefore, it is not necessary to use a large amount of (meth) acrylic resin. Therefore, in the present invention, it is possible to realize low dust generation properties while suppressing the amount of resin impregnated into the base paper. As described above, according to the present invention, the amount of resin impregnated into the base paper can be reduced, so that the environmental load is low and the manufacturing cost is advantageous.

Since the clean paper of the present invention can suppress the amount of resin impregnation, it can maintain high opacity. Therefore, it is difficult to see characters and the like written on the clean paper. Moreover, since the clean paper of this invention can suppress the resin impregnation amount, it can maintain high rigidity. Therefore, the clean paper of the present invention is excellent in writing characteristics. And even if it is a case where the clean paper of this invention is piled up, since there is little blocking, it is excellent also in preservability. Further, since the clean paper of the present invention does not contaminate the cutting blade used at the time of cutting, it does not contaminate other clean paper through the cutting blade.

The schematic sectional drawing which shows an example of the clean paper of this invention. The schematic sectional drawing which shows the other example of the clean paper of this invention. The schematic sectional drawing which shows the further another example of the clean paper of this invention.

(1) Base Paper The base paper that is the base material of the clean paper of the present invention is not particularly limited, and those generally used for clean paper can be used. The base paper can be composed of natural fibers, chemical fibers or mixtures thereof. Examples of natural fibers include natural pulps such as wood fibers such as hardwoods and conifers; non-wood fibers such as hemp, bamboo, firewood, kenaf, and Manila hemp. Examples of chemical fibers include synthetic fibers such as polyethylene, polypropylene, polyamide, and polyester; semi-synthetic fibers such as acetate and rayon. In addition, modified pulp such as cationized pulp and mercerized pulp can be used. As the base paper, natural fibers are preferred, and wood fibers such as softwood bleached kraft pulp (NBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached kraft pulp (LBKP), hardwood bleached sulfite pulp (LBSP) and the like are preferred. The base paper can be produced by making one type or two or more types of fibers with a general paper machine. As the paper machine, for example, a long net paper machine, a short net paper machine, a circular net paper machine, or a combination of these can be used.

The fibers constituting the base paper may be beaten in advance as necessary. The beating means is not particularly limited, and for example, a general beating device such as a double disc refiner, a single disc refiner, or a beater can be used. The beating degree is not limited, but 100 to 600 ml C.I. F. S. Is preferred, 300-500 ml C.I. F. S. Is more preferable.

It is preferable to add a wet paper strength enhancer to the base paper in order to improve the strength when wet. One type of wet paper strength enhancer may be used, or two or more types may be used in combination. The wet paper strength enhancer is preferably added when the base paper is made. A general thing can be used as a wet paper strength enhancer, For example, a polyamide epichlorohydrin type resin, a melamine type resin, a urea-type resin etc. can be used. The wet paper strength enhancer can be used, for example, in the range of 0.02 to 3% by mass, preferably 0.05 to 1% by mass of the base paper.

Further, a dry paper strength enhancer may be added to the base paper in order to improve the strength during drying. One type of dry paper strength enhancer may be used, or two or more types may be used in combination. A dry paper strength enhancer is also preferably added during papermaking of the base paper. As the dry paper strength enhancer, a general one can be used. For example, an amphoteric polyacrylamide resin can be used. The dry paper strength enhancer can be used, for example, in the range of 0.1 to 3% by mass, preferably 0.1 to 1% by mass of the base paper.

In the base paper, fillers that are generally used may be added as long as the object of the present invention is not impaired. Examples of the filler include inorganic fillers such as clay, kaolin, talc, titanium dioxide, calcium carbonate, aluminum hydroxide, zinc oxide, aluminum silicate, calcium silicate, synthetic amorphous silica, and zeolite; Examples thereof include organic fillers such as (meth) acrylic resin pigments and polyethylene. One type of filler may be used, or two or more types may be used in combination. The filler is preferably added at the time of making the base paper. A filler can be used in 0.01-5 mass% of a base paper, for example, Preferably it is 0.1-2 mass%.

In addition to the above, various additives can be used for the base paper. For example, dyes, pigments, slime control agents, fixing agents, yield improvers, freeness improvers, antifoaming agents, and the like can be used as appropriate.

Although the basic weight of a base paper is not specifically limited, For example, it can be 30-250 g / m < ² >. 30-100 g / m < ² > is preferable.

(2) (Meth) acrylic resin The (meth) acrylic resin used in the present invention is not particularly limited. For example, (meth) acrylic acid homopolymer or copolymer, (meth) acrylic acid ester Homopolymer or copolymer, copolymer of (meth) acrylic acid and its ester, copolymer of styrene- (meth) acrylic acid and / or (meth) acrylic ester, vinyl acetate- (meth) acrylic acid and / or (meth) acrylic Copolymers of acid esters can be used. Specifically, (meth) acrylic acid monomers such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate are essential, and as required (Meth) acrylic resins can be obtained by polymerizing styrene, styrene derivatives, vinyl acetate, or comonomers such as acrylonitrile, butadiene, maleic acid, acrylamide, and methacrylamide. As the (meth) acrylic resin, one type may be used, or two or more types may be used in combination.

The (meth) acrylic resin preferably has a glass transition temperature of -40 ° C to less than 0 ° C, more preferably -24 ° C to less than 0 ° C. If the glass transition temperature is less than −40 ° C., the clean paper becomes excessively soft and blocking may occur. On the other hand, when the glass transition temperature is 0 ° C. or higher, dust generation from the inside of the clean paper tends to occur.

(3) Binder The binder used in the present invention is not particularly limited, and those generally used in the field of papermaking can be used. The binder may be water-insoluble or water-soluble, but is preferably water-soluble. As the water-insoluble binder, for example, polyethylene resins, polystyrene resins, polybutene resins, chloroprene resins, vinyl chloride resins, vinylidene chloride resins, polyester resins, polyurethane resins, and the like can be used. As the water-insoluble binder, a resin having a glass transition temperature of 0 ° C. to 200 ° C., preferably a (meth) acrylic resin can also be used. It is preferable to use a resin having a glass transition temperature of 0 ° C. to 80 ° C., particularly a (meth) acrylic resin. If the glass transition temperature of the binder is less than 0 ° C., the surface of the clean paper becomes soft, so that blocking is inevitable. On the other hand, when the glass transition temperature exceeds 200 ° C., the stiffness of the clean paper may be excessive. Examples of the water-soluble binder include hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl acetate, oxidized starch, acetylated starch, esterified starch, etherified starch, and cation. Starch such as modified starch, hydroxylethyl etherified starch, modified starch, urea phosphate esterified starch, dextrin, casein, synthetic protein, soybean protein and the like can be used. The binder is preferably a (meth) acrylic resin having a glass transition temperature of 0 ° C. to 200 ° C., polyvinyl alcohol, or polyacrylamide, and a (meth) acrylic resin having a glass transition temperature of 0 ° C. to 200 ° C., or polyvinyl alcohol. Is particularly preferred. Polyvinyl alcohol here includes partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, functional group-modified (carboxyl group, carbonyl group, epoxy group, amino group, amine group, thiol group, sulfonic acid group And various modified polyvinyl alcohols such as polyvinyl alcohol). Polyvinyl alcohol can have a glass transition temperature of 0 ° C to 200 ° C. One type of binder may be used, or two or more types may be used in combination.

(4) Clean Paper The clean paper of the present invention essentially comprises a base paper, a (meth) acrylic resin layer, and a binder layer. The (meth) acrylic resin layer contains at least one kind of the (meth) acrylic resin, and the binder layer contains at least one kind of the binder.

In the clean paper of the present invention, the binder layer is positioned on the (meth) acrylic resin layer, and one surface of the binder layer constitutes at least a part, preferably the entire surface of the clean paper. Here, “up” means the direction from the base paper toward the surface of the clean paper.

1 to 3 show examples of the clean paper of the present invention. 1 to 3 are cross-sectional views showing different examples of the clean paper of the present invention. In any example, the (meth) acrylic resin layer 2 and the binder layer 3 are laminated in this order on both surfaces of the base paper 1. One surface of the binder layer 3 constitutes the surface of the clean paper.

As in the example shown in FIGS. 1 to 3, the (meth) acrylic resin layer 2 is covered with the binder layer 3 in the clean paper of the present invention, so that the amount of (meth) acrylic resin used is reduced. Can exhibit low dust-free properties. Therefore, the clean paper of the present invention can be provided with opacity and high rigidity as well as excellent low dust generation, and has excellent writing characteristics. The presence of the binder layer 3 causes little blocking even when the clean paper of the present invention is stacked, and does not contaminate the cutting blade used at the time of cutting.

In the example shown in FIG. 1, the base paper 1 is impregnated with a part of the (meth) acrylic resin layer 2. On the other hand, in the example shown in FIG. 2, the whole (meth) acrylic resin layer 2 is impregnated in the base paper 1, but a part of the base paper 1 is not impregnated with the (meth) acrylic resin. To do. In the example shown in FIG. 3, the entire (meth) acrylic resin layer 2 is impregnated in the base paper 1.

1 to 3 are schematic cross-sectional views, and the surface of the (meth) acrylic resin layer 2 impregnated in the base paper 1 and / or the binder layer 3 of the (meth) acrylic resin layer 2 are in contact with each other. As shown in the drawing, the surface on the side may not be a straight line, and may be a bent line composed of straight lines or curves having various lengths and directions, for example. In order to suppress dust generation from inside the clean paper, it is preferable that the entire (meth) acrylic resin layer 2 is impregnated in the base paper 1 as shown in FIGS. As shown, the base paper 1 is preferably completely impregnated. This is because there is an effect of suppressing a load applied to the inside of the paper when the surfaces of the clean paper are rubbed together, thereby preventing dust generation from the inside of the paper. The impregnation rate of the (meth) acrylic resin layer 2 is not particularly limited, but is preferably 0.8 to less than 5.0%, more preferably 1.0 to 5.0% of the total mass of the base paper 1. 1.2 to 4.0% is even more preferable. If it is less than 0.8%, there is a risk that the dust generation property may increase. If it exceeds 5.0%, the amount of impregnated resin is too large, and the opacity and stiffness of the paper may be excessively reduced. In addition, a large amount of resin is disadvantageous in terms of manufacturing cost. The impregnation ratio here is calculated by the formula: impregnation ratio (%) = {(mass of solid content of impregnated resin) / (basis weight of base paper before impregnation)} × 100.

The (meth) acrylic resin layer 2 preferably contains polyvinyl alcohol. By blending polyvinyl alcohol in the (meth) acrylic resin layer 2, the dust generation property can be further lowered and the rigidity can be improved. Although the compounding quantity of polyvinyl alcohol is not specifically limited, It can be set as 5-50 mass% of the (meth) acrylic-type resin layer 2, and 20-40 mass% is more preferable.

In the example shown in FIGS. 1 to 3, the binder layer 3 covers the entire surface of the (meth) acrylic resin layer 2. In this way, in the clean paper shown in FIGS. 1 to 3, since the (meth) acrylic resin layer 2 is not exposed on the surface, blocking due to the (meth) acrylic resin 2, cutting blades at the time of cutting, and the like Contamination can be avoided. As long as the object of the present invention is not impaired, a part of the (meth) acrylic resin layer 2 may not be coated, but the amount of (meth) acrylic resin used is suppressed and exposed (meth) In order to prevent blocking of the acrylic resin layer 2 and contamination such as a cutting blade, it is preferable that the binder layer 3 covers the entire surface of the (meth) acrylic resin layer 2. The (meth) acrylic resin layer 2 and the binder layer 3 may be disposed only on one side of the clean paper. For example, when a film or the like is separately attached to one side of the clean paper, the (meth) acrylic resin layer 2 and the binder layer 3 may be disposed only on the side where the film does not exist.

In the example shown in FIGS. 1 to 3, the entire surface of the base paper 1 is covered with the (meth) acrylic resin layer 2 and the binder layer 3, but the entire surface of the base paper 1 is the (meth) acrylic resin layer 2 and It does not need to be covered with the binder layer 3. For example, the (meth) acrylic resin layer 2 or the binder layer 3 may not exist on a part of the surface of the base paper 1. However, in order to suppress the generation of dust due to the base paper 1, it is preferable that the entire surface of the base paper 1 is coated with at least one of the (meth) acrylic resin layer 2 or the binder layer 3, In view of reducing the amount of use of the (meth) acrylic resin, it is more preferable that it is coated with the binder layer 3. 1 to 3 are schematic cross-sectional views, and the contact surface between the (meth) acrylic resin layer 2 and the binder layer 3 is shown as a straight line, but the contact surface may not be a straight line as shown. For example, it may be a bent line composed of straight lines or curves having various lengths and directions.

In the example shown in FIGS. 1 to 3, one surface of the (meth) acrylic resin layer 2 and the other surface of the binder layer 3 are in contact with each other, but they are not necessarily in contact with each other. For example, an intermediate layer may exist between the (meth) acrylic resin layer 2 and the binder layer 3. The intermediate layer may be a layer made of any material. By providing the intermediate layer, mixing of the (meth) acrylic resin and the binder can be avoided. Further, the intermediate layer may exist only on a part of the surface of the (meth) acrylic resin layer 2, and the intermediate layer may not exist on the other surface of the (meth) acrylic resin layer 2. In this case, the other surface of the (meth) acrylic resin layer 2 is in contact with the binder layer 3.

At least part of the contact surfaces of the (meth) acrylic resin layer 2 and the binder layer 3 may be mixed. The miscibility of the contact surface mainly depends on the constituent material of the (meth) acrylic resin layer 2, particularly the constituent material of the (meth) acrylic resin and the binder layer 3, particularly the mutual permeability of the binder. However, the (meth) acrylic resin layer 2 and the binder layer 3 are not mixed and integrated.

The binder layer 3 is preferably present at a rate of 0.05 to 10 g / m ² , more preferably 0.1 to 10 g / m ² in terms of dry weight per unit area of the base paper, -10.0 g / m < ² > is more preferable and 1.0-5.0 g / m < ² > is more preferable. If it is less than 0.05 g / m ² , it is difficult to sufficiently cover the base paper 1, and there is a possibility that the dust generation property is increased. Moreover, when it exceeds 10 g / m < ² >, there exists a possibility that the rigidity of a clean paper may become excess. Moreover, when there is much binder amount, it is disadvantageous also in terms of manufacturing cost. The dry weight here is the total when the binder layer 3 is present on both sides of the base paper 1.

In the clean paper of this invention, when the binder layer 3 consists of (meth) acrylic-type resin, the glass transition temperature of the (meth) acrylic-type resin which comprises the binder layer 3 comprises the (meth) acrylic-type resin layer 2 ( It is higher than the glass transition temperature of the (meth) acrylic resin. Thereby, blocking can be further suppressed.

The binder layer 3 preferably contains at least one lubricant. The lubricant is preferably a wax, and any wax can be used, but olefinic waxes such as polyethylene wax and polypropylene wax are preferred. By including the wax, the dust generation suppressing effect and the blocking preventing effect of the clean paper of the present invention can be enhanced.

In the clean paper of the present invention, the (meth) acrylic resin layer 2 does not need to be impregnated in the base paper 1, and the (meth) acrylic resin layer 2 may exist on the surface of the base paper 1. However, in order to satisfactorily fix the (meth) acrylic resin layer 2 to the base paper 1, it is preferable that the base paper 1 is impregnated with at least a part of the (meth) acrylic resin layer 2. As shown in FIGS. 2 and 3, at least a part of the binder layer 3 is preferably impregnated in the base paper 1. 2 and 3 are schematic cross-sectional views, and the surface of the binder layer 3 on the side impregnated in the base paper 1 does not have to be a straight line as shown, for example, straight lines having various lengths and directions. Alternatively, it may be a bent line composed of a curve.

(5) Manufacturing method The clean paper of the present invention is a (meth) acrylic resin layer forming step in which at least one (meth) acrylic resin is applied to a base paper to form a (meth) acrylic resin layer, and And a production method comprising a binder layer forming step of forming a binder layer by applying at least one binder on the (meth) acrylic resin layer.

In the (meth) acrylic resin layer forming step, at least one (meth) acrylic resin is applied onto the base paper. The base paper is preferably impregnated with (meth) acrylic resin. Therefore, it is preferable that the (meth) acrylic resin is in a liquid form in order to improve the impregnation property. The liquid may be in the form of a solution or emulsion of a (meth) acrylic resin. The solvent of the solution and the medium of the emulsion are arbitrary, and water and various organic solvents can be used, but water is preferable from the viewpoint of environmental burden. Accordingly, the (meth) acrylic resin is more preferably in the form of an aqueous solution or aqueous emulsion in which the (meth) acrylic resin is dispersed in an aqueous medium composed of water or a mixture of water and an aqueous organic solvent. As the aqueous organic medium, any organic solvent miscible with water can be used, but a lower alcohol such as ethanol is preferable. By the application, a (meth) acrylic resin layer that is preferably partially or entirely impregnated is formed on the base paper.

When the (meth) acrylic resin is in the form of a solution or emulsion, the concentration of the (meth) acrylic resin in the solution or emulsion is arbitrary, but is preferably 1 to 50% by mass, and preferably 1 to 30% by mass. Is preferable, 1-10 mass% is more preferable, and 1-5 mass% is still more preferable. In the solution or emulsion, various fillers and additives can be blended as necessary within a range not impairing the object of the present invention. Examples of fillers include inorganic fillers such as titanium dioxide, kaolin, calcium carbonate, clay, talc, aluminum hydroxide, zinc oxide, calcium silicate, and zeolite, styrene or acrylic plastic pigments, polyethylene, microcapsules, and synthetic resins. Organic fillers such as Examples of the additive include a sizing agent, a water resistant agent, a crosslinking agent, a viscosity modifier, a dispersant, an antifoaming agent, a pH adjuster, a surfactant, a dye, and a pigment.

The coating method is not particularly limited, and a general coating apparatus such as a bar coater, an air knife coater, a blade coater, a rod coater, a gravure coater, a size press coater, a gate roll coater, or various impregnation apparatuses is used. The method can be used. In particular, it is preferable to use an on-machine size press coater, a gate roll coater, or other on-machine coater methods because the base paper and the (meth) acrylic resin layer can be formed in one step. Application is preferably performed so that the impregnation amount (solid content) of the (meth) acrylic resin to the base paper is 0.8 to less than 5.0% of the total mass of the base paper, and 1.0 to 5.0%. Is more preferable, and 1.2 to 4.0% is even more preferable.

In the binder layer forming step, at least one binder is applied on the (meth) acrylic resin layer formed in the (meth) acrylic resin layer forming step. In order to improve the coating property, the binder is preferably in a liquid form. The liquid may be in the form of a binder solution or an emulsion. The solvent of the solution and the medium of the emulsion are arbitrary, and water and various organic solvents can be used, but water is preferable from the viewpoint of environmental burden. Accordingly, when the binder is water-insoluble, it is preferably in the form of an emulsion, particularly water or an aqueous emulsion in which the binder is dispersed in an aqueous medium as described above, and when the binder is water-soluble, water or It is preferably in the form of an aqueous solution in which a binder is dissolved in an aqueous medium as described above. The binder preferably contains a lubricant such as polyethylene wax, if necessary. Although the density | concentration of the binder in the said emulsion or aqueous solution is arbitrary, 1-50 mass% is preferable, 1-30 mass% is preferable, 1-10 mass% is more preferable, 1-5 mass% is still more preferable. In the emulsion or the aqueous solution, various additives can be blended as necessary within a range not impairing the object of the present invention. Examples of additives include sizing agents, water resistance agents, thickeners, dispersants, antifoaming agents, antifoaming agents, antistatic agents, antioxidants, ultraviolet absorbers, fluorescent whitening agents, pH adjusting agents, Examples include preservatives, surfactants, dyes, pigments and the like.

The coating method is not particularly limited, and the above-described method using a general apparatus such as a bar coater can be used. In dry weight per unit area of the base paper, it is preferable to perform coating so that the binder layer is present in an amount of 0.05 to 10 g / ^{m 2,} more preferably 0.2 to 10 g / ^{m 2,} 1.0 to 5.0 g / m ² is more preferable. It is preferable to provide a binder layer on both the front and back sides of the base paper. The dry weight here is the total when the binder layer 3 is present on both sides of the base paper 1.

A step of forming an intermediate layer on at least a part of the surface of the (meth) acrylic resin layer, if necessary, after the (meth) acrylic resin layer forming step and before the binder layer forming step. May be further provided. The intermediate layer may be a layer made of any material. The intermediate layer can be formed, for example, by applying a material constituting the intermediate layer onto at least a part of the surface of the (meth) acrylic resin layer. In order to facilitate application, the material is preferably in liquid form.

The clean paper of the present invention has a dust generation amount of 100 pieces / L or less, preferably 30 pieces / L or less, more preferably 15 pieces in a rubbing test measured according to SEMI (SEMICONDUCTOR EQUIIPMENT MATERIALS INTERNALIONAL) standard G67-0996. / L or less.

The clean paper of the present invention can have a stiffness of 70 to 80 (longitudinal) expressed by Clark stiffness based on JIS-P8143 (2009).

The clean paper of the present invention can have an opacity of 75% or more based on JIS-P8149 (2000).

Furthermore, the clean paper of the present invention can have a high blocking performance that hardly adheres to each other when they are stacked at a pressure of 50 kg / cm ² under a temperature condition of 50 ° C.

The clean paper of the present invention can be suitably used in an environment where generation of fine dust should be avoided, such as in a clean room. For example, the clean paper of the present invention can be used as copy paper, memo paper, measurement recording paper, wrapping paper, work paper, process paper, and the like in a clean room.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Manufacture of acrylic resin liquid]
An acrylic resin liquid was prepared by adding water to an acrylic resin (trade name: AM-920, manufactured by Showa Polymer Co., Ltd.) having a glass transition temperature of −20 ° C. so that the solid concentration was 10%.

[Manufacture of binder liquid]
75 parts by mass of polyvinyl alcohol (trade name: Gohsenol P7000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 25 parts by mass of polyacrylamide (trade name: Polymer Set 305, manufactured by Arakawa Chemical Industry Co., Ltd.) were mixed, and the resulting mixture was mixed. 9 parts by mass of a styrene acrylic surface sizing agent (trade name: SE-2012 manufactured by Seiko PMC Co., Ltd.) and 3.5 parts by mass of polyethylene wax (trade name: Polylon L-787 manufactured by Chukyo Yushi Co., Ltd.) are added and stirred. Then, an aqueous binder liquid having a solid content concentration of 10% was prepared.

[Manufacture of base paper]
350 ml C. beating degree of 15 parts by weight of softwood bleached kraft pulp (NBKP) and 85 parts by weight of hardwood bleached kraft pulp (LBKP). S. F. And 0.3 parts by weight of a dry paper strength enhancer (trade name: DS4779, manufactured by Seiko PMC Co., Ltd.), 0.5 parts by weight of a sulfuric acid band, and a wet paper strength enhancer (trade name: TS4070, manufactured by Seiko PMC). 0.05 parts by mass was added to obtain a papermaking raw material. This papermaking raw material was made with a long paper machine to obtain a base paper.

[Example 1]
A base paper was impregnated with the acrylic resin liquid so that the acrylic resin impregnation ratio was 2.5% and dried to obtain an acrylic resin-impregnated base paper having a basis weight of 64 g / m ² . Further, by applying the binder liquid on both sides with a bar coater so that the coating amount per side is 0.65 g / m ² (solid content) (total coating amount 1.30 g / m ² ) and drying. Got clean paper.

[Example 2]
A clean paper was obtained in the same manner as in Example 1 except that the acrylic resin liquid was impregnated so that the acrylic resin impregnation ratio was 0.8%.

[Example 3]
A clean paper was obtained in the same manner as in Example 1 except that the acrylic resin liquid was impregnated so that the acrylic resin impregnation ratio was 1.2%.

[Example 4]
A clean paper was obtained in the same manner as in Example 1 except that the acrylic resin liquid was impregnated so that the acrylic resin impregnation ratio was 4.0%.

[Example 5]
A clean paper was obtained in the same manner as in Example 1 except that the binder liquid was applied on both sides so that the amount of binder applied was 0.12 g / m ² (0.06 g / m ² per side).

[Example 6]
To obtain a clean paper, except that the coating amount of the binder was applied the binder solution on both surfaces so that 0.47 g / ^{m 2} (per side 0.235 g / ^{m 2)} in the same manner as in Example 1.

[Example 7]
A clean paper was obtained in the same manner as in Example 1 except that the binder liquid was applied on both sides so that the amount of the binder applied was 4.7 g / m ² (2.35 g / m ² per side).

[Example 8]
An acrylic resin solution was prepared as follows. 50 parts by mass of polyvinyl alcohol (trade name: Gohsenol P7000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) with respect to 100 parts by mass of acrylic resin (trade name: AM-920, manufactured by Showa Polymer Co., Ltd.) having a glass transition temperature of −20 ° C. It was added and water was added thereto to prepare a solid concentration of 10%. A clean paper was obtained in the same manner as in Example 1 except that this acrylic resin solution was used.

[Example 9]
A binder solution was prepared as follows. Styrene acrylic surface sizing agent (product name: SE-2012) 9 by 100 parts by mass of acrylic resin (product name: AM-2270, manufactured by Showa Polymer Co., Ltd.) having a glass transition temperature of 20 ° C. 9 Mass parts and 3.5 parts by mass of polyethylene wax (trade name: Polylon L-787, manufactured by Chukyo Yushi Co., Ltd.) were added to prepare a binder liquid having a solid content concentration of 3%. A clean paper was obtained in the same manner as in Example 1 except that this binder solution was used.

[Comparative Example 1]
A clean paper was obtained in the same manner as in Example 1 except that the binder liquid was not applied.

[Comparative Example 2]
A clean paper was obtained in the same manner as in Example 1 except that the acrylic resin liquid was not impregnated.

[Comparative Example 3]
Acrylic resin having a glass transition temperature of −20 ° C. (product name: AM-920, manufactured by Showa Polymer Co., Ltd.), 50 parts by mass, polyvinyl alcohol (product name: Gohsenol P7000, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 37.5 parts by mass, And 12.5 parts by mass of polyacrylamide (trade name: Polymer Set 305, manufactured by Arakawa Chemical Industries, Ltd.), and 9 mass of styrene acrylic surface sizing agent (trade name: SE-2012, manufactured by Seiko PMC Co., Ltd.). And 3.5 parts by mass of polyethylene wax (trade name: Polylon L-787, manufactured by Chukyo Yushi Co., Ltd.) were added to prepare a water-based paint having a solid content concentration of 5.0%.

  350 ml C. beating degree of 15 parts by weight of softwood bleached kraft pulp (NBKP) and 85 parts by weight of hardwood bleached kraft pulp (LBKP). S. F. And 0.3 parts by weight of a dry paper strength enhancer (trade name: DS4779, manufactured by Seiko PMC Co., Ltd.), 0.5 parts by weight of a sulfuric acid band, and a wet paper strength enhancer (trade name: TS4070, manufactured by Seiko PMC). 0.05 parts by mass was added to obtain a papermaking raw material. This papermaking raw material was made with a long paper machine to obtain a base paper.

A base paper having a basis weight of 65.0 g / m ² was obtained by impregnating the base paper with the water-based paint so as to have an impregnation ratio of 4.7% and drying.

[Evaluation]
Each of the clean papers of Examples 1 to 9 and Comparative Examples 1 to 3 was evaluated by measuring each characteristic of dust generation, rigidity, opacity, and blocking property. The measuring method of each characteristic is as follows.

[Dust generation-rubbing test]
Two A5 size test pieces are stacked on the front and back in a measuring instrument (trade name: Glove Box, manufactured by Japan Airtech Co., Ltd.), and this is rubbed by hand at a speed of 3 times / 10 seconds for 3 minutes and 20 seconds. While matching, the air in the glove box was sucked and the number of generated dusts of 0.1 μm or more was measured with a particle counter (model: KC-22A, manufactured by Rion Co., Ltd.).

[Stiffness-Clark stiffness]
Based on JIS-P8143 (2009), the longitudinal stiffness of the test piece was measured.

[Opacity]
It measured based on JIS-P8149 (2000).

[Blocking properties]
The front and back surfaces of two test papers having a width of 4 cm and a length of 14 cm were superposed and heated and pressed for 15 minutes at 50 ° C. and 50 kg / cm ^{2 with} a heating press. After pressing, the test paper with adhesion was peeled about 3 cm in the length direction, and the width direction part was grasped with a constant speed extension type tensile tester specified in JIS-8113, and the moving speed was 30 cm per minute. And about 10 cm were peeled off, and the average load was measured.

The evaluation results are shown in Table 1.

As is clear from the results of Examples 1 to 9 and Comparative Example 1, the clean paper of Examples 1 to 9 including the binder layer together with the acrylic resin layer is compared with the clean paper of Comparative Example 1 including only the acrylic resin layer. The dust generation is low, and the rigidity and blocking properties are excellent. Moreover, despite the presence of the binder layer, the opacity of the clean papers of Examples 1 to 9 is comparable to that of Comparative Example 1 in which no binder is present and is not inferior.

Moreover, as is clear from the results of Examples 1 to 9 and Comparative Example 2, the clean paper of Examples 1 to 9 including the binder layer together with the acrylic resin layer is compared with the clean paper of Comparative Example 2 including only the binder layer. And low dust generation. Moreover, despite the presence of the acrylic resin layer, the stiffness and opacity of the clean papers of Examples 1 to 9 are comparable to those of Comparative Example 2 in which no acrylic resin layer is present, and are not inferior.

As is clear from the values of the basis weight and the impregnation rate, in Comparative Example 3, the amount of resin adhered to the base paper is substantially the same as that in Examples 1-9. Therefore, the comparative example 3 respond | corresponds to what mixed and apply | coated the acrylic resin and the binder in Examples 1-9.

However, as is clear from the results of Examples 1 to 9 and Comparative Example 3, the clean paper of Examples 1 to 9 including the acrylic resin layer and the binder layer is the same as that of Comparative Example 3 including the mixed layer of the acrylic resin and the binder. Compared to clean paper, it has excellent dust generation and blocking properties. In addition, the stiffness and opacity of the clean papers of Examples 1 to 9 are the same as those of Comparative Example 3, and are not inferior.

From these results, the clean papers of Examples 1 to 9 including the binder layer together with the acrylic resin layer are Comparative Example 1 in which only the acrylic resin layer is present, Comparative Example 2 in which only the binder resin layer is present, and the acrylic paper and the binder. It turns out that low dusting property and a blocking characteristic are exhibited with respect to all of the comparative example 3 provided with a mixed layer. In addition, the clean papers of Examples 1 to 9 are not significantly inferior to Comparative Examples 1 to 3 in both stiffness and opacity, but rather, some of the characteristics thereof are those of Comparative Examples 1 to 3. Is also excellent.

1: base paper, 2: (meth) acrylic resin layer, 3: binder layer

Claims (20)

Base paper,
A (meth) acrylic resin layer comprising at least one (meth) acrylic resin, and
A clean paper comprising a binder layer comprising at least one binder,
The base paper is impregnated with the (meth) acrylic resin at an impregnation rate of 0.8 to less than 5.0%,
The binder layer is located on the (meth) acrylic resin layer,
The binder is a (meth) acrylic resin having a glass transition temperature of 0 ° C. to 200 ° C .;
A clean paper in which the surface of the binder layer constitutes at least a part of the surface of the clean paper. The clean paper of Claim 1 whose glass transition temperature of the said (meth) acrylic-type resin is -40 degreeC-less than 0 degreeC. The clean paper of Claim 1 or 2 in which the said (meth) acrylic-type resin layer further contains polyvinyl alcohol. The clean paper according to any one of claims 1 to 3 , wherein the binder is a water-soluble binder. The clean paper according to any one of claims 1 to 4 , wherein the binder layer is present at a rate of 0.05 to 10 g / m ² in terms of a dry weight per unit area of the base paper. The clean paper according to any one of claims 1 to 5 , wherein an intermediate layer is present between the (meth) acrylic resin layer and the binder layer. The clean paper according to any one of claims 1 to 6 , wherein the (meth) acrylic resin layer and the binder layer are in contact with each other. The clean paper of Claim 7 in which at least one part of the contact surface of the said (meth) acrylic-type resin layer and the said binder layer is mix | blended. The clean paper according to any one of claims 1 to 8 , wherein the binder layer contains at least one lubricant. The clean paper of Claim 9 whose said lubricant is a wax. A step of impregnating the base paper with at least one (meth) acrylic resin at an impregnation ratio of 0.8 to less than 5.0% to form a (meth) acrylic resin layer impregnated on the base paper, as well as,
A method for producing clean paper comprising a step of applying at least one binder on the (meth) acrylic resin layer to form a binder layer ,
The manufacturing method of the clean paper whose said binder is (meth) acrylic-type resin which has a glass transition temperature of 0 degreeC-200 degreeC. The manufacturing method of the clean paper of Claim 11 whose glass transition temperature of the said (meth) acrylic-type resin is -40 degreeC-less than 0 degreeC. The manufacturing method of the clean paper of Claim 11 or 12 with which the said (meth) acrylic-type resin layer further contains polyvinyl alcohol. The method for producing clean paper according to any one of claims 11 to 13 , wherein the binder is a water-soluble binder. The method for producing clean paper according to any one of claims 11 to 14 , wherein the binder layer is present at a rate of 0.05 to 10 g / m ² in terms of a dry weight per unit area of the base paper. The clean paper according to any one of claims 11 to 15 , further comprising a step of forming an intermediate layer on at least a part of the surface of the (meth) acrylic resin layer before the step of forming the binder layer. Manufacturing method. The method for producing clean paper according to any one of claims 11 to 16 , wherein the (meth) acrylic resin layer and the binder layer are in contact with each other. The manufacturing method of the clean paper of Claim 17 with which at least one part of the contact surface of the said (meth) acrylic-type resin layer and the said binder layer is mix | blended. The method for producing clean paper according to claim 11 , wherein the binder layer contains at least one lubricant. The method for producing clean paper according to claim 19 , wherein the lubricant is a wax.

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