JPH062822B2 - Antistatic treatment method for water absorbent resin powder - Google Patents

Description

The present invention relates to an antistatic treatment method for water-absorbent resin powder.

<Prior Art> Water-absorbent resin powder is a liquid absorbent material that replaces pulpers and water-absorbent paper because of its excellent water-supplying ability and the excellent holding power that it does not separate the liquid that has once absorbed water even if it receives some pressure. It has been put to practical use with a focus on manufacturers of sanitary products such as sanitary products, and in recent years, its applications have been widely spread to agriculture, horticulture, food, medical and the like.

By the way, even though the water-absorbent resin powder is hydrophilic, it is essentially a non-conductive substance, and therefore has a property of easily accumulating due to accumulation of static electricity due to friction between powders.

Therefore, when charged, there is a risk of causing dust explosion due to charging when pneumatically transporting the intermediate product or the final finished product in the manufacturing process of the water absorbent resin.

The water-absorbent resin powder is usually packaged and shipped in 15 to 20 kg units in a paper bag having a moisture-proof plastic film interior, but when the water-absorbent resin powder is charged, a considerable amount of the water-absorbent resin powder is added to the interior. Since the water-absorbent resin powder adheres, it is uneconomical that the water-absorbent resin powder in the package cannot be used completely.

Furthermore, even when diapers, sanitary products, etc. are manufactured using water-absorbent resin powder, static electricity generated by electrification discharges the device and damages the device, and dust or dust adheres to cause a fire. There is a possibility that various equipment troubles may occur.

As an antistatic treatment method for preventing the water absorbent resin powder from accumulating static electricity, a treatment method using a surfactant has been generally used conventionally. The treatment method using this surfactant is to knead a surfactant having an antistatic ability into the water-absorbent resin or to coat it outside.
This is a processing method that prevents the accumulation of static electricity.

<Problems to be Solved by the Invention> However, since the above-mentioned conventional antistatic treatment method is a temporary charge removal method, a permanent antistatic effect cannot be expected, and since the surfactant is generally oily, When the surface-active agent layer is formed by adhering it to the water-absorbent resin powder, there is a problem that the fluidity of the powder is lowered due to stickiness and the workability is deteriorated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to have not only excellent treatment effects but also excellent powder fluidity even after treatment, resulting in reduced workability. Another object of the present invention is to provide an antistatic treatment method for a water-absorbent resin powder that does not have the above.

<Means for Solving the Problems> In the antistatic treatment method for a water-absorbent resin powder according to the present invention for achieving the above object (hereinafter, referred to as “method of the present invention”), a predetermined amount of water-absorbent resin powder is added. The amount of the inorganic compound powder is 0.01% with respect to 100 parts by weight of the water absorbent resin powder.
Add ~ 5 parts by weight.

The inorganic compound powder used in the method of the present invention is an inorganic compound powder having zinc or calcium as a constituent element.

Hereinafter, the method of the present invention will be described in detail.

The powdery water-absorbent resin which can be subjected to antistatic treatment using the method of the present invention does not dissolve in water and has a weight of 50 in water.
It may be a resin that absorbs about twice or more of water and swells to form a hydrogel, for example, a polymer cross-linked product of a partially neutralized acrylic acid with an alkali metal, a hydrolyzate of a starch-acrylonitrile graft polymer. , A starch-acrylic acid graft polymer neutralized product, a crosslinked carboxymethyl cellulose, a hydrolyzed product of a methyl acrylate-vinyl acetate copolymer, a crosslinked polyvinyl alcohol modified product, and the like.

The method of the present invention is applied to the antistatic treatment of powdery water-absorbent resin. The size of the powder to be treated is usually 10 to 20.
It is 0 mesh and is easily charged by friction between these powders. The reason why the particles having the above-mentioned particle size range is used is that the water absorption rate becomes small when the particle size is less than 10 mesh, and the litter phenomenon occurs when the particle size exceeds 200 mesh.

Specific examples of the inorganic compound used in the method of the present invention include zinc oxides and carbonates such as zinc white and zinc carbonate; calcium carbonates such as calcium carbonate, calcium oxide, calcium sulfate and calcium hydroxide; Examples are oxides, sulfates or hydroxides.

The inorganic compound used is not limited to a hydrous substance or an anhydrous substance, and the water content of the hydrous substance is also not limited.

The inorganic compound may be used alone or as a mixture of two or more kinds.

A smaller particle size of the above-mentioned inorganic compound is more suitable for carrying out the method of the present invention, and an average particle size of 50 μm or less is preferable. When the average particle size exceeds 50 μm, the inorganic compound is separated from the water absorbent resin powder, which is not preferable.

In the method of the present invention, it is necessary to use the powdery inorganic compound in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water absorbent resin powder. The reason why the addition amount is limited in this way is that if it is less than 0.01 part by weight, a significant addition effect for antistatic cannot be expected, and if it exceeds 5 parts by weight, the addition effect corresponding to the increase in amount is obtained. Is not only obtained, but also the problem of scattering occurs.

By mixing the water-absorbent resin powder and the inorganic compound, the water-absorbent resin is subjected to antistatic treatment.

As a mixing method, various conventionally known methods can be used. For example, various mixers such as a tumbler, a V blender, a super mixer, a Nauter mixer, a ribbon blender, a conical blender, a Henschel mixer, and a Loedige mixer are used. Can be mixed.

In order to prevent the powder of the inorganic compound from separating from the water-absorbent resin powder, before spreading the two, mix a spreading agent in an amount and kind that does not adversely affect the water-absorbing performance of the water-absorbent resin powder. Then, the surface of the powder may be coated.

Spreading agents that can be used for coating include liquid polybutene, liquid polyethylene glycol, polyhydric alcohols, glycol ether compounds and the like.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.
The method of the present invention is not limited to the processing method shown in the following examples, and it goes without saying that appropriate modifications can be made without departing from the scope of the present invention.

(A) Preparation of Water-Absorbent Resin Powder 75% by weight of 80% acrylic acid, 48.0% by weight of 48.6% sodium hydroxide and 48.6 parts by weight of deionized water are mixed to obtain acrylic acid having a neutralization degree of 70%. An aqueous salt solution was prepared. To 1029 g of this aqueous acrylate solution, 1% N, N
After adding 5 g of a methylenebisacrylamide aqueous solution and performing nitrogen substitution, 36 g of a 2% peroxodisulfate K ₂ S ₂ O ₈ aqueous solution, and 2% of a 2% pyrosulfite K ₂ S ₂ O ₅ aqueous solution 2
50 g of 1.6 g and 40% aqueous glyoxal solution in water
14.4 g of the diluted solution diluted twice was added to obtain a mixed solution.
Then, this mixed solution is poured into a bat (inner Teflon coating) having a length of 48 cm and a width of 37 cm, and the drying temperature is 42
Polymerization was carried out for 20 minutes in a hot air circulation dryer at ℃ to obtain a plate-shaped hydrogel having a length of 48 cm, a width of 37 cm and a thickness of 5 to 6 mm. The obtained water-containing gel was dried with a drum dryer having a surface temperature of 130 ° C. to give a flake-like resin, which was crushed with a pin mill and then classified to obtain a water-absorbent resin powder of 60 to 120 mesh.

The water-absorbent resin powder was dried overnight in a desiccator containing silica gel in a constant temperature / humidity chamber having a temperature of 22 ° C. and a relative humidity of 60%.

(B) Antistatic treatment of water-absorbent resin powder (Example 1) 100 g of the water-absorbent resin powder obtained in (A) above, and 0.5 g of powdered zinc carbonate (manufactured by Shodo Chemical Co., Ltd.) as an inorganic compound
And were uniformly stirred and mixed in the constant temperature and constant humidity chamber with a small stirrer, and antistatic treatment was performed to obtain Sample 1.

(Example 2) A sample 2 was obtained in the same manner as in Example 1 except that Zinc Hua No. 1 (manufactured by Sakai Chemical Industry Co., Ltd.) was used in place of zinc carbonate.

(Example 3) Sample 3 was obtained in the same manner as in Example 1 except that the same amount of light calcium carbonate (manufactured by Takehara Chemical Industry Co., Ltd.) was used instead of zinc carbonate.

(Comparative Example 1) A water absorbent resin powder that was not subjected to antistatic treatment was used as Comparative Sample 1.

Comparative Example 2 Comparative sample 2 was obtained by performing antistatic treatment in the same manner as in Example 1 except that the same amount of talc (manufactured by Takehara Chemical Industry Co., Ltd.) was used instead of zinc carbonate.

(Comparative Example 3) Comparative sample 3 was obtained by performing an antistatic treatment in the same manner as in Example 1 except that the same amount of silica (manufactured by Toyo Soda Co., Ltd., trade name "TOKUSIL") was used instead of zinc carbonate. It was

(C) Antistatic Evaluation Test 10 g of each of the above Samples 1 to 3 and Comparative Samples 1 to 3 was sampled so that the inner surface had a thickness of 0.03 mm, a length of 100 mm and a width of 150.
After putting it in the bag made of polyethylene film of mm, squeezing the opening of the bag by hand, shake the bag strongly up and down, left and right for 30 seconds to check the adhesion state of the water-absorbent resin powder to the film. It was visually observed and the antistatic ability of each sample or comparative sample was evaluated according to the following criteria.

(Evaluation Criteria) Evaluation A: No adherence at all.

Evaluation B: Only a little adhered.

Evaluation C ... Adheres considerably.

Evaluation D: Adhesion almost all over the surface.

The evaluation results are shown in the table below.

As shown in the above table, the water-absorbent resin powder (samples 1 to 3) subjected to antistatic treatment using the method of the present invention does not adhere to the polyethylene film at all, or only slightly adheres to it, whereas The degree of adhesion was high in the case where the antistatic treatment was not performed (Comparative Sample 1) and the case where the antistatic treatment was not performed by the method of the present invention (Comparative Samples 2 and 3).

From the above, it was found that the method of the present invention is an excellent antistatic treatment method as compared with conventionally known antistatic treatment methods.

<Effects of the Invention> As described above, the antistatic treatment method for the water absorbent resin powder according to the present invention enables an excellent antistatic treatment.
The present invention has excellent unique effects.

Claims (1)

[Claims] 1. A water-absorbent resin powder comprising 0.01 to 5 parts by weight of an inorganic compound powder containing zinc or calcium as a constituent element, relative to 100 parts by weight of the water-absorbent resin powder. Antistatic treatment method for water absorbent resin powder.