JP2001064895A - Clean paper and method for producing the same - Google Patents

Abstract

(57) [Summary] [Problem] To blend a pigment which is considered to be difficult to use on a paper base, to have remarkably low dusting property, opacity, writability, PPC
Provided is a clean paper excellent in suitability and a method for producing the same. SOLUTION: The composition contains a core-shell type binder pigment latex having an average particle diameter of 0.4 μm or less, and is kneaded,
1000 or less particles having a size of 0.3 μm or more according to a cleanness test for rubbing or breaking, and an opacity of 70%
Clean purper characterized by the above. Preferably, the clean paper has 650 particles of 0.3 μm or more in a cleanness test of rubbing, rubbing, or tearing.
/ ft ³ or less. Further, a base paper containing 20% by weight or more of softwood bleached kraft pulp and a pulp slurry having a freeness of 500 csf or more is formed into a base paper, and the base paper contains a core-shell type binder pigment latex having an average particle diameter of 0.4 μm or less as a main component. A method for producing a clean purper, characterized by impregnating an impregnation liquid with a size press and drying at a temperature of 100 ° C or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a clean paper and a method for producing the same. More specifically, it is a clean paper with extremely low dust generation that can be used inside and outside of a clean room maintained in an environment with very little fine dust floating in the air, and has opacity, writability, PP
The present invention relates to a clean paper excellent in C suitability and a method for producing the same.

In the semiconductor industry, the manufacture of precision parts, and the like, an environment is desired in which minute dust floating in the atmosphere does not affect the quality of products. Such an environment is called a clean room, and when working in this room, clean paper has been used as paper for special applications.

[0003] Currently used clean paper is
As a substitute for the plastic film, a method of impregnating with a binder or the like that suppresses the falling off of the fiber is mainly used. In this case, in order to suppress the dust generation, no filler is used, and the fiber is beaten and manufactured using fine fibers.

[0004] In the case of ordinary paper-based clean paper, in order to suppress dusting properties, the production of fillers that are not mixed into the paper, such as internal additives, is mainly used, but the flexibility and opacity of the paper are high. Inferior in writability, printability and paper gloss.

[0005] In order to suppress the dust generation of the paper itself, the mixing ratio of tree species to be used and the beating level are also important factors.
In addition, taking into account inter-fiber bonding, falling off of fine fibers, etc.,
Adhesion with a binder seems to be essential.
For example, Japanese Patent Publication No. 6-11959 describes a clean paper in which a base paper made of 100% by weight of wood pulp is impregnated with a binder.

There is a demand for clean paper that is used in a clean room without any loss of filler and no loss of fiber, and it is common not to mix such additives into the paper itself.

Furthermore, in order to increase the bonding of each fiber unit, it is common to use a method of using a non-size base paper until the binder is coated so that an adhesive substance such as a binder permeates into the paper. is there.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a clean paper which contains a pigment which can be used as a paper base and which has a remarkably low dusting property and excellent opacity, writability and PPC suitability. And a method for manufacturing the same.

[0009]

Means for Solving the Problems The present inventor has made intensive studies in view of the above, and as a result, has come to invent the clean paper of the present invention and a method for producing the same. That is, the clean paper of the present invention is a clean paper containing a core-shell type binder pigment latex having an average particle size of 0.4 μm or less, and particles having a particle size of 0.3 μm or more obtained by rubbing, rubbing, or breaking cleanliness test of 1000 μm. Pieces / f
It is characterized by being not more than t ³ and having an opacity of not less than 70%.

Further, the clean paper of the present invention has a particle size of 0.3 μm by a cleanness test of rubbing, rubbing or tearing.
It is preferable that the number of particles of m or more is 650 particles / ft ³ or less.

[0011] The method for producing clean paper of the present invention comprises:
An impregnating liquid containing 20% by weight or more of softwood bleached kraft pulp and making a base paper using a pulp slurry having a freeness of 500 csf or more, and the base paper mainly containing a core-shell type binder pigment latex having an average particle diameter of 0.4 μm or less. By a size press and drying at a temperature of 100 ° C. or more.

In the method for producing clean paper of the present invention, it is preferable that the core-shell type binder pigment latex is polystyrene for the core and styrene-butadiene copolymer for the shell.

Furthermore, in the method for producing clean paper of the present invention, the core-shell type binder pigment latex has an impregnation amount (dry solid content) of 1.5 to 3.0 g / m ^2.
It is preferable that

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Papermaking pulp used in the method for producing clean paper of the present invention includes hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) having a freeness (beating degree: JIS-P8121) of 500 mlcsf or more. ) Is used, and preferably, softwood bleached kraft pulp (NBKP) having a freeness of 550 mlcsf or more is used.

[0015] In the present invention, LBK is used as pulp for papermaking.
Although P and NBKP are used, the ratio of NBKP is 20% by weight or more, and preferably 50% by weight or more in consideration of dust generation and the like.

Other pulp used in combination with LBKP and NBKP used in the present invention include, for example, chemical pulp such as hardwood bleached sulphite pulp (LBSP) and softwood bleached sulphite pulp (NBSP), bamboo, abaca, and kenaf. Non-wood pulp such as esparto, esparto and bagasse is used.

In the conventional papermaking technique, in order to form paper, it is usual to beat the raw pulp to some extent,
It is important that the generated pulp fine fibers are chemically and physically fixed to the paper layer.

In the case of clean paper, it is important to select the beatability of pulp and the ratio of pulp to be used in order to suppress the falling off of fine fibers and the generation of fine fibers in the paper layer, and a papermaking technique for suppressing the dust generation in the paper layer. Is required. The freeness of these pulp is preferably 500 mlcsf or more as in LBKP.

In the beating of the pulp, each pulp may be beaten alone or each pulp may be mixed and beaten. When beaten alone, each pulp freeness is 50
It is preferably 0 mlcsf or more. As a beating method, for example, a double disc refiner (DD)
R), a single disc refiner (SDR), a beater, a deluxe finalizer (DF), and the like.

When an aqueous binder or the like is impregnated on-machine, usually, a size press such as an inclined size press, a horizontal size press and a tab size press is used, but the impregnation amount (dry solid content) is large. In case, paper machine after dryer,
It is necessary to pay attention to the occurrence of dirt on the machine calendar.
For impregnation, it is necessary to prepare an impregnating liquid having good permeability to paper and excellent mechanical stability.

The drying temperature after the impregnation is 100 ° C. or higher, preferably 120 ° C. or higher.

The impregnating liquid in the present invention is composed of a composition mainly composed of a core-shell type binder pigment latex and an aqueous binder, but the composition of another composition is not limited.

The most distinctive feature of the clean paper of the present invention is that it contains a core-shell type binder pigment latex having an average particle size of 0.4 μm or less. This core-shell type binder pigment latex is also an organic pigment having a binder function in the shell part, and is a submicron-order fine particle, which has a large effect of diffusing light, and when impregnated into base paper, reduces whiteness and opacity. It can be improved, and it is excellent in prevention of falling off from the base paper by the binder function of the shell part. In particular,
The binder function of the core-shell type binder pigment latex desirably has an adhesive ability of 20% or more.

In the core-shell type binder pigment latex of the present invention, the core polymer may be, for example, polystyrene, p-carbomethoxypolystyrene, p-cyanopolystyrene, p-methylpolystyrene, o-methylpolystyrene, 2,4-dimethyl Polystyrene, 2,5-dimethyl polystyrene, p-ter
Examples thereof include polystyrene derivatives such as t-butyl polystyrene and polymethacrylate. Further, as the polymer of the shell portion, for example, polyethyl acrylate,
Polypropyl acrylate, polybutyl acrylate,
Polyoctyl methacrylate, polydecyl methacrylate, poly-2-ethylhexyl acrylate, poly-n
-Dodecyl methacrylate, styrene-butadiene copolymer and the like. Among them, a core-shell type binder pigment latex in which the core is polystyrene and the shell is a styrene-butadiene copolymer is preferable.

In the clean paper of the present invention, it is essential to contain a core-shell type binder pigment latex. However, ordinary organic pigments such as plastic pigments such as polystyrene latex having an average particle diameter of 0.2 to 0.5 μm are required. A binder pigment having a binder function, hollow polymer particles and the like can be mixed and used with a core-shell type binder pigment latex, and may be appropriately used in consideration of printability, writability, opacity and the like.

The combination of calcium carbonate, talc, kaolin, calcined kaolin, titanium oxide, aluminum hydroxide and the like, which are usually used in coating, is not limited.

In the present invention, the impregnation amount (dry solid content) of the core-shell type binder pigment latex into base paper is preferably 1.5 to 3.0 g / m ² .
Here, when the impregnation amount (dry solid content) of the core-shell type binder pigment latex is less than 1.5 g / m ² , the opacity and the writability tend to decrease.
When it is more than g / m ² , the amount of dust generated in the cleanness test tends to increase.

As described above, the opacity of the clean paper of the present invention can be improved by using a core-shell type binder pigment latex or a combination of the latex and an organic / inorganic pigment. Is 70% or more. Here, if the opacity is less than 70%, it is not practically preferable.

As the aqueous binder used in the present invention, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, polyvinyl alcohol,
Modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, ethylene / Water-soluble adhesives such as alkali salts of maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylate, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, Latexes such as an ethylene / vinyl acetate copolymer are included.

The mixing amount of the aqueous binder is preferably at least 2.5 times the impregnation amount (dry solid content) of the core-shell type binder pigment latex to be used. If the impregnation amount (dry solid content) of the aqueous binder is less than 2.5 times, the target result of the cleanness test may not be satisfied. Further, as the impregnation amount (dry solid content) of the aqueous binder, an impregnation amount that satisfies the target quality is preferable. If the impregnation amount is higher than the drying capacity, workability on site is deteriorated, and it is difficult to perform long-time papermaking. Not only does the opacity decrease, but the target quality is not satisfied.

In addition, starch can be used in combination with the impregnating liquid obtained by the size press.
Oxidized starch, cationic starch, esterified starch, hydroxyethyl starch, enzyme-modified starch and the like. In this case, the mixing ratio of the starch to be used is suitably from 0.3 to 2.0% by weight based on the impregnating liquid, and if it is lower than 0.3% by weight, the water retention of the impregnating liquid is not maintained, On the other hand, if it is higher than 2.0% by weight, the impregnation coating by a size press tends to be unstable due to an increase in viscosity.

The clean paper of the present invention may contain additives usually used in papermaking, such as internal sizing agents (alkenyl succinic anhydride (ASA), neutral rosin, alkyl ketene dimer (AKD), and dry paper strength enhancement. Agents (polyacrylamide starch derivative, polyvinyl alcohol derivative),
An antifoaming agent, a dye, a coloring pigment, a fluorescent agent, a wet paper strength improver, a drainage improver, and a retention improver can be appropriately used.

As an additive used in the clean paper of the present invention, a wet paper strength improver is used in an amount of 0.1% based on the absolute dry weight of pulp.
It is preferable to make paper using 5 to 1.0% by weight. In this case, if the wet paper strength improver is less than 0.5% by weight, it is difficult to pass the paper by liquid impregnation with a size press. Invite.

The viscosity of the impregnating liquid used in the present invention is 10 cps (Tokyo Keiki Seisakusho, Model BL)
Preferably, the viscosity is not higher than 10 cps, which causes a problem in the field operation.

[0035]

The present invention will be described in detail below with reference to examples and comparative examples.

Example 1 A mixed pulp of 50% by weight of LBKP and 50% by weight of NBKP was beaten to a freeness of 500 mlcsf to prepare a pulp slurry. To these pulp slurries was added 0.5% by weight of polyacrylamide (WS-525, Japan PMC Co., Ltd.) based on the absolute dry weight of the pulp, and diluted with water to obtain a 1% slurry. A base paper having a basis weight of 65 g / m ² was made from the slurry using a fourdrinier paper machine, and subjected to size press with the following impregnating liquid to produce clean paper.

The impregnation amount (dry solid content) based on the absolute dry weight of the pulp was 7.5 g / m ² , of which 5.0 g / m ^{2 for} the aqueous binder and 2.0 g / m ^{2 for} the core-shell type binder pigment latex. ^{Was 2} . <Impregnating liquid composition> Aqueous binder 10.0% by weight Core-shell type binder pigment latex 4.0% by weight Starch oxide 1.0% by weight Water 85.0% by weight At this time, the aqueous binder is acrylic latex (Rohm & Haas Japan) Co., Ltd .: Jacril P-22)
And a core-shell type binder pigment latex (Zeon Corporation: LX407BP) and oxidized starch (Nippon Shokuhin Kako Co., Ltd .: MS-3800) were used. The core-shell type binder pigment latex LX407BP has an average particle diameter of 0.38 μm and an adhesive ability of 40%.

Example 2 The composition of the impregnating solution of Example 1 was changed except that the aqueous binder was changed to 8.0% by weight, the core-shell type binder pigment latex was changed to 3.0% by weight, and the water was changed to 88.0% by weight. It carried out like Example 1. The impregnation amount (dry solid content) based on the absolute dry weight of the pulp was 6.0 g / m ² , the aqueous binder was 4.0 g / m ² , and the core-shell type binder pigment latex was 1.5 g / m ² .

Example 3 The composition of the impregnating solution of Example 1 was changed to 15.5 with an aqueous binder.
The same procedure as in Example 1 was carried out except that the weight of the core-shell binder pigment latex was changed to 6.0% by weight, and the amount of water was changed to 77.5% by weight. In impregnation amount (dry solids) of 11.3 g / m ² for the pulp absolute dry weight, aqueous binder is 7.8 g / m ^2, the core-shell binder pigment latex was 3.0 g / m ^2.

Example 4 The composition of the impregnating solution of Example 1 was changed to an aqueous binder containing 10.0%.
%, The core-shell type binder pigment latex was changed to 2.0% by weight, and the water was changed to 87.0% by weight. The impregnation amount (dry solid content) based on the absolute pulp weight was 6.5 g / m ² , the aqueous binder was 5.0 g / m ² , and the core-shell type binder pigment latex was 1.0 g / m ² .

Comparative Example 1 The procedure of Example 1 was repeated, except that heavy calcium carbonate (Bihoku Koka Kogyo Co., Ltd .: Softon 2200) was used instead of the core-shell type binder pigment latex of Example 1.

Comparative Example 2 The procedure of Example 1 was repeated except that a plastic pigment latex (Nippon Zeon Co., Ltd .: V1004) was used instead of the core-shell type binder pigment latex of Example 1. V1004 is a plastic pigment latex having an average particle diameter of 0.31 μm.

Example 5 The procedure of Example 1 was repeated, except that LBKP was changed to 80% by weight and NBKP was changed to 20% by weight.

Comparative Example 3 The procedure of Example 1 was repeated except that LBKP was changed to 85% by weight and NBKP was changed to 15% by weight.

Example 6 The freeness of the mixed pulp of Example 1 was 550 mlcsf.
The procedure was performed in the same manner as in Example 1 except that

Comparative Example 4 The freeness of the mixed pulp of Example 1 was 450 mlcsf.
The procedure was performed in the same manner as in Example 1 except that

Each of the clean papers obtained in Examples and Comparative Examples was tested for opacity and cleanness.
Writability, gloss on white paper, and suitability for PPC were evaluated by the following methods. The results are shown in Table 1 below.

<Opacity> The opacity is measured according to JIS-P81.
It was measured according to the 38 method.

<Cleanness test> The cleanness test is a test for measuring particles generated by rubbing, rubbing and tearing as described below, and is a test for measuring cleanliness, which is a measure of the cleanness of clean paper. is there. The cleanness test was carried out using a cleanness test apparatus shown in FIG. 1 in a clean bench under the following conditions in which dust did not enter from the outside. -Wind speed at the outlet of the blower: 0.6m / sec-Wind speed at the center of the clean bench (test position): 0.3
5m / sec ・ Wind velocity at sample position: 0.55m / sec

(Kneading) In the test apparatus, A4 size (2
A test piece (97 mm x 210 mm) was manually rubbed at a rate of once every 5 seconds for 2 minutes.

(Rubbing) A5 size (210 mm x 148 m
Two test pieces of m) were prepared, and the front and back sides of the test piece were overlapped in the test apparatus, and rubbed by hand once every two seconds for two minutes.

(Tear) Using two pieces of A4 size test pieces, a total of 18 places, 9 places on the short side of each test piece, were torn at a rate of once / 6 seconds for 2 minutes.

The particles having a size of 0.3 μm or less generated in the above-mentioned kneading, rubbing and tearing are subjected to a light scattering particle counter (KC-
01B: manufactured by Rion Mold Co., Ltd.) Dust counter. Cleanliness was expressed by the total number of the particles (in one cubic foot). Therefore, the smaller the value, the better the cleanliness.

<Writing Characteristics> The writing characteristics were determined by drawing a line on paper using a 0.5 mmφ water-based pen (ink: pilot ink), and immediately after drawing, the spread of ink and the ink Bleeding was visually observed. Regarding the spread and bleeding of the line, those having no problem: 、, those having a slight tendency but having no practical problem: Δ, and those having a practical problem: ×.

<Blank gloss> Compared with the base paper before the impregnation, the gloss of the blank was clearly improved after the impregnation: ○, and slightly improved: Δ, almost the same as the base paper Or decrease: x.

<PPC Suitability> The PPC suitability was determined by measuring the toner fixing property and the paper passing property using a PPC copying machine (Canon Inc .: NP6260). Regarding the toner fixability, the one without rubbing the surface after copying:
、: Slightly stained but not problematic in practical use: Δ, Stained with strong stain: X. Regarding paper feedability, A4
Ten plates were passed through a copying machine, and a sample showing occurrence of running failure was evaluated as ○, a sample showing slight running defect but having no practical problem: Δ, and a sample showing practical problem: ×.

[0057]

[Table 1]

As is apparent from the evaluation results of Examples 1 to 4, the core-shell type binder pigment latex was impregnated (dry solid content) with respect to the absolute dry weight of the pulp.
To obtain the target quality by adding 5 to 3.0 g / m ² , the amount of the aqueous binder impregnated (dry solids) is preferably 2.5 times or more the amount of the pigment impregnated (dry solids). In addition, when the amount of the water-based binder impregnated (dry solid content) increases, the opacity decreases and the operation becomes troublesome, such as soiling the apparatus. The amount of the core-shell type binder pigment latex is disadvantageous in terms of opacity when the impregnated amount (dry solid content) is 1.0 g / m ² or less, and when it is 3.0 g / m ² or more, The target quality is not satisfied in terms of blank gloss.

As is clear from the evaluations of Comparative Examples 1 and 2, the dusting property is reduced when a plastic pigment is used instead of a core-shell type binder pigment latex having an average particle diameter of 0.4 μm or less instead of 20% or more. it no longer meets the value of 1000 / ft ³ or less at a point, also in the case of using an inorganic pigment, although there is a point in the superiority of opacity, dustiness, satisfies the target quality in the sheet gloss points Disappears.

As is clear from the evaluations of Example 5 and Comparative Example 3, the pulp used was LBKP and NBKP.
When NBKP is set to 20% by weight or more in the ratio of
A value of 600 / ft ³ or less is shown, but if NBKP is used in an amount of 15% by weight, it will be 1000 / ft ³ or more and the target quality will not be satisfied.

As is clear from the evaluation results of Example 6 and Comparative Example 4, the freeness of the pulp used was 500 mlcsf in order to reduce the dusting property to 1000 pieces / ft ³ or less.
It is necessary to do above.

[0062]

The clean paper according to the present invention is excellent in opacity, writability, glossiness of white paper and PPC suitability, and has a dusting level usable in a clean room.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cleanness test apparatus used for evaluation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Blower 2 Clean bench 3 Dust counter 4 Sampling tube for measurement 5 Dust collection tube

Claims (5)

[Claims] 1. A clean paper containing a core-shell type binder pigment latex having an average particle size of 0.4 μm or less, and 1,000 particles / f or more having a particle size of 0.3 μm or more by a cleanness test of rubbing, rubbing, or breaking.
Clean paper, characterized in that t ³ or less, and is opacity 70%. 2. The clean paper according to claim 1, wherein the number of particles having a particle size of 0.3 μm or more in a cleanness test of rubbing, rubbing, or tearing is 650 particles / ft ³ or less. 3. A base paper containing at least 20% by weight of softwood bleached kraft pulp and a pulp slurry having a freeness of 500 mlcsf or more, and a core-shell type binder pigment latex having an average particle diameter of 0.4 μm or less is mainly added to the base paper. A method for producing clean paper, characterized by impregnating an impregnation liquid as a component with a size press and drying at a temperature of 100 ° C or higher. 4. The method for producing clean paper according to claim 3, wherein the core-shell type binder pigment latex is styrene as a core part and styrene-butadiene as a shell part. 5. The core-shell type binder pigment latex has an impregnation amount (dry solid content) of 1.5 to 3.0 g / m ^2.
5. The method for producing clean paper according to claim 3, wherein: