JPH02178332A - Method for antistatic treatment of water absorbing resin powder - Google Patents

Abstract

PURPOSE:To impart excellent antistatic effects to water absorbing resin powder by adding a specific amount of inorganic compound powder containing zinc, etc., to the water absorbing resin powder. CONSTITUTION:An inorganic compound (e.g. zinc flower or calcium carbonate) in an amount of 0.01-5 pts.wt. based on 100 pts.wt. water absorbing resin powder (a resin capable of absorbing water in an amount of >=50 times based on the own weight thereof in water, swelling and forming a hydrogel without dissolving in water, e.g. a crosslinked polymer of acrylic acid partially neutralized with an alkali metal) containing zinc or calcium as a constituent element is added thereto.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for antistatic treatment of water-absorbing resin powder.

<Prior art> Water-absorbing resin powder has been used as a liquid-absorbing material to replace valves and water-absorbing paper due to its excellent water-absorbing ability and excellent retention horns that prevent liquid from separating once absorbed even when subjected to some pressure.
It has attracted attention and been put into practical use mainly by manufacturers of sanitary products such as diapers and sanitary products, and in recent years, its uses have been expanding widely to agriculture, horticulture, food, medical, etc.

Incidentally, although water-absorbing resin powder is hydrophilic, it is originally a non-conductive substance, so it has a tendency to accumulate static electricity due to friction between the powders and become electrically charged.

For this reason, when charged, there is a risk of causing a dust explosion due to the charging when an intermediate product or a final finished product is air-transported in the manufacturing process of water-absorbent resin.

In addition, water-absorbing resin powder is usually packaged and shipped in small units of 15 to 20 kq in paper bags with inner walls made of moisture-proof plastic film. Since this amount of water-absorbing resin powder adheres to the package, there is an uneconomical situation in that the water-absorbing resin powder in the package cannot be used completely.

Furthermore, even when manufacturing diapers, sanitary products, etc. using water-absorbing resin powder, the static i
There was a risk that various equipment troubles could occur, such as air discharge and damage to the equipment, or dust and dust adhering to it, which could cause a fire or other problems.

Conventionally, a treatment method using a surfactant has been generally used as an antistatic treatment method for preventing the water-absorbing resin powder from accumulating static air. This treatment method using a surfactant is a treatment method in which a surfactant with antistatic ability is kneaded into the interior of the water-absorbing resin or coated on the outside (Ii) to reduce the accumulation of static electricity. It is.

<Problems to be Solved by the Invention> However, the above-mentioned conventional antistatic treatment method is a temporary static elimination method, so permanent antistatic treatment cannot be expected, and the surfactant is generally oily. When a surfactant layer is formed by adhering it to a water-absorbing resin powder, there is a problem that the powder fluidity decreases due to stickiness, resulting in poor workability.

The present invention has been made in view of the above circumstances, and its purpose is to have excellent processing effects, as well as excellent powder flowability even after processing, and to prevent the decrease in workability. To provide a method of treating water-absorbing resin powder to prevent damage.

Means for Solving the Problem> In the method for antistatic treatment of water-absorbing resin powder according to the present invention (hereinafter referred to as the "method of the present invention") to achieve the above-mentioned object, a predetermined amount is added to the water-absorbing resin powder. 0.01 parts by weight of the inorganic compound powder per 100 parts by weight of the water-absorbing resin powder.
Add up to 5 parts by weight.

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

The method of the present invention will be explained in detail below.

The powdered water-absorbing resin treated with antistatic treatment using the method of the present invention does not dissolve in water and has a weight of 50% of its own weight in water.
Any resin that absorbs about 0 times more water, swells, and forms a hydrogel may be used, such as crosslinked polymers of partially neutralized acrylic acid with alkali metals, hydrolysis of starch-acrylonitrile craft polymers, etc. Examples include neutralized products of starch-acrylic acid graft ifi combination, cross-linked carboxyne methyl cellulose, hydrolyzed products of methyl acrylate-vinyl acetate copolymers, and modified products of cross-linked polyvinyl alcohol.

The method of the present invention is applied to antistatic treatment of powdered water absorbent resin. The size of the powder to be treated is usually 10 to 20
0 mesh, and is easily charged due to friction between these powders. The reason for using the particle size within the above range is that if the particle size is less than 10 mesh, the water absorption rate will be low, and if it exceeds 200 mesh, a sticky phenomenon will occur.

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

Furthermore, the inorganic compound used is not limited to whether it is a hydrated compound or an anhydrous compound, and the water content of the hydrated compound is also not limited.

In addition, the above-mentioned mineralized core may be used alone or in combination of two or more powders.

The smaller the particle size of the above-mentioned inorganic compound, the more suitable it is for carrying out the method of the present invention, and the average particle size is preferably 50 μm or less. This is because if the average particle size exceeds 50 μm, the inorganic compound will separate from the water-absorbing resin powder, which is undesirable.

In the method of the present invention, it is necessary to use 0.01 to 5 parts by weight of the above-mentioned powdered inorganic compound based on 100 parts by weight of the water-absorbing resin powder. The reason why the addition port was limited in this way is that if the amount is less than 0.01 parts by weight, no significant effect for preventing static electricity can be expected. This is because not only the effect of addition cannot be obtained, but also the problem of scattering occurs.

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

As a mixing method, various conventionally known methods can be used. For example, mixing can be performed using various mixers such as a tumbler-V blender super mixer, a Nauta mixer-ribbon blender, a conical blender, a Henschel mixer, a Loedige mixer, etc. can.

In order to prevent the inorganic compound powder from separating from the water-absorbing resin powder, two types of spreading agents are mixed before mixing the two to an extent that does not adversely affect the water-absorbing performance of the water-absorbing resin powder. The surface of the powder may be coated.

Examples of spreading agents that can be used for coating include liquid polybutene, liquid polyethylene glycol, polyhydric alcohol, and glycol ether compounds.

<Example> Hereinafter, the present invention will be explained in more detail based on Examples.

It should be noted that the method of the present invention is not limited to the processing method shown in the following examples (it goes without saying that changes may be made as appropriate without changing the gist of the present invention.

(A) Preparation of water absorbent resin powder 75 parts by weight of 80% acrylic acid, 48.0 parts by weight of 48.6% sodium hydroxide and 48.6 parts by weight of ion-exchanged water were mixed to obtain acrylic acid with a degree of neutralization of 70%. An aqueous salt solution was prepared. To 1028 g of this acrylate aqueous solution, add 1% N, N
- After adding 5 g of methylene bisacrylamide aqueous solution and purging with nitrogen, 2 S2 o
A mixed solution was obtained by adding 21.6 g of 2S205 aqueous solution and 14.4 g of a diluted solution of 40% glyoxal aqueous solution diluted 50 times with water to 36 g of S205 aqueous solution and 2% pyrosulfite. Next, spread this mixture into a length of 48 cm.

Width 37 crn butt (inner Teflon coating)
and polymerized for 20 minutes in a hot air circulation dryer at a drying temperature of 42°C to form a product with a length of 48 cm, a width of 37 cm, and a thickness of 5 to 6 m.
A plate-shaped hydrogel of m was obtained. The obtained hydrous gel was dried with a drum dryer at a surface temperature of 130°C to obtain a flaky resin, which was crushed with a pin mill and then classified.
A water absorbent resin powder having a mesh size of 0 to 120 was obtained.

The above water absorbent resin powder was placed in a desiccator containing silica gel in a constant temperature and humidity chamber at a temperature of 22°C and a relative humidity of 60%.
It was left to dry inside for a day and a night.

(B) Antistatic treatment of water-absorbing resin powder (implementation full 1) 100 g of water-absorbing resin powder obtained in (A) above and 0.5 g of powdered zinc carbonate (manufactured by Seido Kagaku Co., Ltd.) as an inorganic compound.
Sample 1 was obtained by uniformly stirring and mixing with a small stirrer in the above-mentioned constant temperature and constant humidity room to perform antistatic treatment.

(Example 2) Sample 2 was obtained by antistatic treatment in the same manner as in Example 1, except that the same amount of Zinc Flower No. 1 (manufactured by Sakai Chemical Industry Co., Ltd.) was used in place of zinc carbonate.

(Example 3) Sample 3 was obtained by antistatic treatment 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 in place of zinc carbonate.

(Comparative Example 1) Comparative Sample 1 was a water-absorbing resin powder that was not subjected to antistatic treatment.

(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 carrying out 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. Ta.

(C) Evaluation test for antistatic ability Take 10 g of each sample from Samples 1 to 3 and Comparative Samples 1 to 3, and measure the inner surface with a thickness of 0.03 mm, a length of 100 mm, and a width of 1 mm.
Place it in a bag made of 50 mm polyethylene film, squeeze the opening of the bag with your hands to close it, and then shake the bag strongly by hand for 30 seconds to see how the water-absorbing resin powder adheres to the film. was visually observed, and the antistatic ability of each sample or comparative sample was evaluated using the following criteria.

(Evaluation basis ■) 1rt' fjlIi A Total flti B - Total FDFI C 1nido 11tli l:) F　　　　　II　Non　ni I, I', I, I.

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table -2.

From the above-1, compared to the conventionally known HF'i (S Vl, l top treatment), the method of the present invention has superior f-i:j:
': It turns out that there is only one principle to prevent 1i.

<Effects of the Invention> As explained above and as mentioned above, the antistatic treatment method for water-absorbing resin powder according to the present invention has excellent results.
The present invention has excellent whitening properties, such as enabling tLQ and processing.
To the 11th self-friend with the effect of ・j
The water-absorbent resin powder (samples 1 to 3) treated with 111 sheets was not attached at all to the film j2 made by -y73; , even though it was only a little I'6, it was 21 and 2 ::) Heavy and double processing was done i)t, - (comparative sample 1)
and Hontaku 1111 Tsuno 7,! , yo・:3 naite:;
``Fun prevention treatment is carried out, -] Dashi (comparison test - 12 and 3) has a strong degree of adhesion.

Claims (1)

[Claims] 1. Add zinc or calcium to water-absorbing resin powder. Inorganic compound containing umium as a constituent element 100 weight of the water-absorbing resin powder 0.01 to 5 parts by weight per part A belt of water-absorbing resin powder characterized by Electrical prevention treatment method.