JPS5928680B2 - Manufacturing method of fiber sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for obtaining a fiber sheet using a known wet papermaking technique or wet nonwoven fabric manufacturing technique, in which anionic polyvinyl chloride latex (hereinafter abbreviated as AVC latex) is the main component. The anionic latex is aggregated in advance to a particle size of 100μ or more and 500μ or less,
This invention relates to a so-called latex internal addition method in which a fiber sheet is produced by adding the aggregate to a separately prepared fiber slurry, forming it into paper, and drying it.

The internal addition method of latex can be roughly divided into (1) the so-called beater addition method, in which latex is aggregated in a fiber slurry and deposited on the fiber surface; (2) latex aggregates are made in advance, and the aggregates are separated from the There is a method of adding the aggregates to the fiber slurry (in this case, the aggregates are retained in the sheet by filtration), which belongs to the technical field of the present invention (2), and which has been difficult until now. We have discovered a new method for controlling the particle size of aggregates whose main component is anionic PVC latex.

Conventionally, in the field of manufacturing paper and paperboard, the above-mentioned method (1) of adding latex using a heater has been used.

However, in this method, adding a large amount of latex, especially in excess of 20% by weight (solid content) based on the weight of the fibers, tends to cause various problems in papermaking.
Therefore, in the field of nonwoven fabrics, where papermaking is often performed with the addition of a large amount of latex, method (2) above is mainly employed. However, in method (2), since the retention of latex in the sheet depends solely on the filtration action, it goes without saying that the most important thing is to control the size of the latex aggregates. Although the optimum particle size varies slightly depending on the thickness, shape, etc. of the fibers used, Akira Honori et al.'s various experiments have revealed that aggregates with a particle size of 100 μm or more and 500 μm or less are optimal.

Large agglomerates with a particle size exceeding 500 microns have a 100% retention in the sheet, but the resulting sheet has unsightly spots and tends to cause problems such as sticking to the dryer surface.

Aggregates with a particle size of less than 100 μm have many drawbacks, such as poor yield and failure to obtain the necessary strength, as well as significant contamination of wastewater.

The present invention is based on the discovery of new agglomeration conditions for anionic latexes, mainly anionic PVC latexes, for which it has been difficult to adjust the size of agglomerates in the past.

The particle size of the aggregate is measured by placing the aggregate under a microscope and defining the maximum diameter passing through the center of each aggregate as the particle size of the aggregate.

When anionic PVC latex is agglomerated with water-soluble cationic polymers or polyvalent metal salts using conventional techniques, even under very slow stirring conditions, fine particles with a diameter of less than 50 μm, most of which are 10 to 20 μm, are produced. You can only get so much.

As a result of various studies to obtain stable aggregates with a size of 100μ to 500μ, it was found that when latex is agglomerated, it goes through the following steps to finally become stable aggregates. . That is, when attempting to obtain an aggregate by adding a water-soluble cationic polymer or a polyvalent metal salt to anionic PVC latex, first, due to the shock of agglomeration caused by the addition, particles of the size of 1 to 10 eyebrows are formed for several seconds. It was found that the particles grew into aggregates, and then redispersed, leaving the shape of a bunch of grapes and becoming aggregates of about 10 to 30 μm, like falling grapes.

Separately, it can be confirmed that anionic acrylic latex etc. undergo a similar process under relatively gentle aggregation conditions using water-soluble cationic polymers, but the difference from anionic PVC latex is that It was found that particles finer than clusters of grapes are difficult to redisperse, and are therefore stabilized as coarse aggregates (200μ to 1w!t).

In addition, in the case of rapid aggregation due to aluminum salt, etc., 1? caused by shock during aggregation due to addition? to 10? It was also found that the aggregates further aggregated and formed into lumps. From the above results, the size of the fusion force inside the latex aggregate has a significant influence on the size of the final aggregate, and therefore, the minimum film forming temperature (hereinafter abbreviated as MFT) of the latex is important. It was discovered that the key was missing, which led to the present invention.

That is, after mixing an anionic PVC latex with an MFT of 10°C or less at least 5% by weight (solid content) based on the solid content of the PVC latex, a water-soluble cationic polymer or a polyvalent metal salt is added. By adding it, aggregates with a particle size of 100μ or more and 500μ or less are obtained, and then the aggregates are added to a separately prepared fiber slurry, and the paper is made and dried by a wet papermaking method. This is a method for manufacturing a fiber sheet. In this method,
Anionic latex with MFT of 10℃ or less is 10℃
Latex is a latex that forms a film even at the following temperatures, and is emulsified with an anionic surfactant and exhibits anionic properties in water.

Typical examples include polyacrylic ester latex, synthetic rubber latex, ethylene/vinyl acetate copolymer latex, acrylic ester/vinyl acetate copolymer latex, etc.
A material with an FT of 10°C or less can be applied.

Of course, mixtures and modified products of the above latexes (e.g.
It also includes carboxyl-modified latex). The amount added must be at least 5% by weight (solid content) based on the solid content of the anionic PVC latex, preferably 10% by weight (solid content).
Solid content) or higher is appropriate.

The effect of mixing anionic latex with MFT of 10°C or less is that anionic PVC latex and MFT
As a result of the co-aggregation of the anionic latex whose temperature is 10°C or less, the internal fusing force of the latex aggregate is increased, and the particle size suitable for paper making is 100μ or more and 500μ, which helps to prevent redispersion of the aggregate due to stirring. This makes it easier to obtain the following aggregates.

The anionic PVC latex referred to herein refers to a latex emulsified with an anionic surfactant, which is aggregated by a water-soluble cationic polymer or a polyvalent metal salt.

Some anionic PVC latexes contain not only vinyl chloride homopolymers but also other vinyl monomers (e.g., vinyl acetate, acrylic esters, vinylidene chloride, etc.) or unsaturated acids (e.g., maleic acid, etc.). Also included are copolymers.

Furthermore, those to which an external plasticizer is added are also included. Anionic latex whose main component is anionic PVC latex means that anionic latex with an MFT of 10°C or less is added to the anionic PVC latex in an amount of at least 5% by weight (solid content) based on the solid content of the PVC latex. This refers to a mixture, which is preferably diluted to 0.5 to 10% by weight (solid content) prior to agglomeration; if the concentration is too high, the collision of agglomerated particles becomes excessive and coarse lumps tend to form. Next, regarding water-soluble cationic polymers, those applicable to the present invention refer to all resins that exhibit cationic properties in water, including polyamides, polyamines, epichlorohydrin resins, and polyethyleneimine resins. ,
Cation-modified melamine-formalin resins, cation-modified urea-formalin resins, and the like are particularly useful.

All of these are useful as retention aids, wetting strength agents, and finished water content regulators for papermaking since they are often used as condensates at the initial stage of the reaction. Cationically modified starch can also be used. As polyvalent metal salts, aluminum salts, calcium salts, and magnesium salts are particularly useful.

The amount of the above-mentioned cationic polymer or polyvalent metal salt to be added cannot be determined unconditionally because the chemical stability of the latex varies, but it is sufficient to add the minimum amount necessary to completely coagulate the latex mixture. be. At most, the minimum amount required is 1.
Should not be added in excess of 5 times. Next, regarding the fibers to be used, any fibers such as natural fibers, regenerated fibers, synthetic fibers, inorganic fibers, metal fibers, and collagen fibers may be used, or a mixture thereof may be used.

It is also possible to blend sizing agents, fillers, furnace water temperature regulators, dispersion regulators, etc. into these fiber slurries. This will be explained below using examples. Example 1 Zeon 576 (manufactured by Nippon Zeon, PVC Radenx) at 9
Kf (solid content) and Nipol L×811 (manufactured by Nippon Zeon Corporation, acrylic latex, MFT approx. 3°C) were mixed with 1K9 (solid content), diluted to 500 t, and while stirring to avoid foaming, polyfix was added. Add 32Kf of a 2% by weight (solid content) aqueous solution of 201 (manufactured by Showa Kobunshi Hanban Co., Ltd., polyamide/polyamine/epichlorohydrin water-soluble cationic polymer) to stably disperse aggregates with a particle size of 100μ or more and 500μ or less. I got the liquid.

This product remained stable even after being left under stirring for several tens of hours.

A predetermined amount of the aggregate was added to a separately prepared fiber slurry, and then paper-formed by a known wet paper-making method and dried to obtain a fiber sheet.

Table 1 shows the physical properties of the obtained product. The sheet had good strength, water resistance, and no hard-to-see resin spots on the sheet surface. Of course, there were no paper-making problems at all. Comparative Example 1 A nonwoven fabric (all blending ratios are the same as the nonwoven fabric of Example 1) made by applying aggregates obtained by agglomerating a 2% by weight (solid content) liquid of Zeon 576 single latex using Polyfix 201 had the following properties: Since the grain size is extremely fine with a particle size of 20 to 30 μm, the yield during paper making is poor, and therefore the strength is low, making it unsuitable for practical use.

Physical properties: weight 46.37/M2, tensile strength 0.5K when dry
P/15W1 width, wet 0.1KV/1577111 width.

Example 2 9Kf (solid content) of Zeon 351 (manufactured by Nippon Zeon, PVC latex) and Polylac ML-520 (
Made by Mitsui Toatsu, methyl methacrylate/butadiene copolymer latex, MFT approx. 5°C) 1Kf (solid content) is mixed with 1001! ．． After diluting the mixture, 8 kg of a 0.5 molar calcium chloride aqueous solution was added while stirring to avoid foaming, to obtain a stable aggregate dispersion having a particle size of 100 μm or more and 500 μm or less.

This product remained stable even after being left under stirring for several tens of hours. Next, the aggregate was added in an amount of 30% by weight (solid content) based on the weight of the fibers into a fiber slurry having the same composition as in the case of the nonwoven fabric of Example 1, and then paper-formed and dried. What was obtained is Example 1
It had almost the same physical properties as the nonwoven fabric, which was satisfactory. No resin spots were observed on the surface of the sheet, and there were no problems during papermaking. Comparative Example 2 When Zeon 351 single latex was aggregated with a calcium chloride aqueous solution, the aggregates were fine particles with a particle size of 20 to 30 μm, and the nonwoven fabric obtained by blending this was extremely poor in physical strength and could not be put into practical use. It was unbearable.

Claims (1)

[Claims] 1 Anionic latex with a minimum film forming temperature of 10°C or less is added to anionic polyvinyl chloride latex in an amount of at least 5% by weight (based on the solid content of the polyvinyl chloride latex).
After mixing (solid content), by adding a water-soluble cationic polymer or polyvalent metal salt, the particle size can be increased from 100μ to 500μ.
A method for producing a fiber sheet, which comprises obtaining the following aggregates, adding the aggregates to a separately prepared fiber slurry, forming the aggregates by a wet papermaking method, and drying the aggregates.