JPH0680120B2 - Method for producing water-absorbent plastic composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a water-absorbent plastic composite material.

<Prior Art and Problems Thereof> A large number of water-absorbent plastic composite materials in which a fine powdery water-absorbent resin is dispersed in a plastic material to impart water absorbability have been known.

However, since the fine powdery super absorbent resin originally has extremely high humidity and high water absorbability, even if it is mixed in the plastic material as it is, it is possible to sufficiently impart water absorbency as a high-quality composite material. It was difficult.

The cause is that the differentially superabsorbent resin secondary aggregates during kneading with the plastic material to generate coarse particles (so-called lumps), or the foaming phenomenon may occur due to insufficient water dispersion. This is because "pinholes" may occur in the composite material. In addition, a large shearing energy is required at the time of kneading, and the heat generated as a result causes decomposition of the kneaded product, resulting in deterioration of performance.

The inventors of the present invention prevent the occurrence of moisture absorption during handling and storage / storage and scattering during mixing with resin or rubber by using a fine powdery super absorbent resin mixed with mineral oil, a plasticizer, etc. in advance. Method has been proposed (JP-A-60-84).
No. 360 bulletin). Although this method can solve the above problems to some extent, it may not always be possible to obtain a sufficient effect. For example, when a fine powdery super absorbent resin is treated with a mineral oil or a plasticizer by the above method, and when this is mixed with an ethylene-vinyl acetate copolymer to form an agricultural film, agglomeration of the super absorbent resin or Although the scattering can be improved to some extent, blocking with time of the film after film formation becomes large, which is a problem as an agricultural film.

The present inventors, after various studies to eliminate the drawbacks of the conventional method,
The inventors have found that the differential superabsorbent resin can be uniformly dispersed by kneading a fine powdery superabsorbent resin previously treated with a surfactant having a good affinity for plastics into a plastic material, and completed the present invention.

<Means for Solving Problems> The present invention is a method for producing a water-absorbent plastic composite material, which comprises treating a fine powdery super absorbent polymer with a surfactant and then kneading the plastic material.

The fine powdery super absorbent resin (hereinafter referred to as (A)) used in the present invention is a commonly used one, for example, saponified vinyl acetate-acrylic acid ester copolymer, isobutylene-maleic anhydride copolymer Examples thereof include a salt of a crosslinked product of a combined modified product, a polyacrylic acid (salt) having a crosslinked structure, a salt of a starch-acrylic acid copolymer, and a modified product of polyethylene oxide. However, the gel strength after water absorption is strong,
A salt of a crosslinked product of a saponified vinyl acetate-acrylic acid ester copolymer or a modified isobutylene-maleic anhydride copolymer is preferably used because the gel does not decompose and long-term durability is required. As the highly water-absorbent resin, one having a water absorption capacity in the range of 50 to 1000 times its own weight can be used, and more preferably 100 to 500 times the gel strength after water absorption is strong. Further, the particle size of the fine powdery super absorbent polymer is preferably as fine as possible from the viewpoint of properties such as physical properties of the final absorbent plastic composite, and the average particle size is
It is desirable that it is 100 μm or less, particularly preferably 10 μm or less.

The surfactant (hereinafter referred to as (B)) used in the present invention is a commonly used one, and anionic, cationic, nonionic and amphoteric surfactants can be used.
One kind or a combination of two or more kinds can be used. Specifically, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene alkyl esters, sorbitan fatty acid esters, polyoxyethylene sorbitan ether-alkyl esters, glycerin, pentaerythritol, trimethylolpropane Examples thereof include alkyl esters of polyhydric alcohols such as saccharides, polyoxyethylene derivatives thereof, polyoxyethylene alkylamides, fluorosurfactants, silicone surfactants and the like.

In particular, nonionic surfactants are preferable in order to suppress a decrease in the water absorption capacity of the super absorbent polymer, and sorbitan fatty acid esters are particularly preferable because they have a good affinity with (A) and exert an effect in a small amount. In addition, the plastic material as the matrix of the water-absorbent plastic composite is thermosetting,
It may be any of thermoplastic, and may be soft, hard or foamed, and may be an elastomer such as synthetic rubber without any problem, but particularly polyethylene, ethylene-vinyl acetate copolymer, or the Saponified product, chlorinated polyethylene, chlorinated polyprene, sulfonated polyethylene, ethylene-isobutylene copolymer, ethylene-acrylic acid copolymer, polyvinyl chloride or its copolymer, styrene-isoprene-styrene block copolymer, styrene -Butadiene-styrene block copolymer, natural rubber, chloroprene rubber and isoprene rubber are preferable.

The ratio of the amounts of (A) and (B) used varies depending on the respective applications and cannot be limited, but preferably A:
The range of B = 90/10 to 10/90 is good. In addition, in order to obtain a plastic material having high water absorption, it is preferable to increase the mixing ratio of (A).

In the present invention, as a method for treating (A) with (B), a method of mechanically mixing (A) and (B) into a commonly used Reiki vessel, a blender with a heater, a ball mill, a mixer or the like, Alternatively, there may be mentioned a method in which the solvent is removed by heating after mixing in the presence of a suitable solvent such as toluene and ethyl acetate, but it is preferable to carry out under the condition that (A) is sufficiently covered with (B). .

By further mixing this with a plastic material (powder, granule, pellet, etc.) and mechanically kneading, a water-absorbent plastic composite having excellent uniformity can be produced.

In addition, kneading is performed by roll, kneader, Banbury mixer,
A vent type twin screw extruder or the like is used.

Further, in the case of the present invention, carbon black, if necessary,
An inorganic filler, a lubricant, an anti-UV agent, a pigment, an antifungal agent, an antifogging agent and the like can be appropriately mixed.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.
It is not limited to these.

In addition, the dispersibility of the fine powdery super absorbent resin in the plastic material was made into a press sheet of about 200μ, and a microscope (× 100
The observation was made by doubling). The water absorption of the plastic composite was calculated from the following calculation formula.

A: Weight before absorption of water (g) B: Weight after immersion in water for 48 hours (g) Experiment 1 SP-51
0, average particle size = 10 μm, made by Sumitomo Chemical Co., Ltd.) 500 g,
Nonionic surfactant (Sorbone S-60, Toho Chiba
After mixing 300 g of chemical industry) well,
Using a blender, perform mechanical mixing at 80 to 90 ° C for about 20 minutes.
I, Sumika gel Sorbone the surface of SP-510 particles S-6
Coated with 0.

Experiment 2 Sumika gel Instead of SP-510, isobutylene-anhydrous
Cross-linked salt of modified lactic acid copolymer (KI gel 201K,
Kuraray Isoprene Chemical Co., average particle size = 8 μm)
KI gel was the same as in Experiment 1 except that it was used. 201K
Sorbone on the surface of particles Coated with S-60.

Example 1 Ethylene-vinyl acetate copolymer (Evatate H2022, Sumitomo
Obtained in Experiment 1 for 1000 g of pellets (made by Tomo Kagaku)
Sorbon Sumika gel treated with S-60 Mixed SP-510
Add 40g of compound and knead at a roll temperature of 120 ° C.
It is extruded into a strand by an extruder and cut into pieces.
To obtain pellets. Using this pellet,
Making a press sheet, Sumika gel SP-510 dispersibility
When observed under a microscope, Sumika gel SP-510 minutes
The dispersion was uniform.

The water absorption of the press sheet was 5.1%.

Example 2 Low density polyethylene (Dow Poly Made by Asahi Dow)
1000g and sorbon obtained in Experiment 2 KI treated with S-60
gel Add 50g of 201K mixture and knead at a roll temperature of 160 ℃
After that, further extruded into a strand by an extruder,
This was cut to obtain pellets. Use this pellet
And make a pressed sheet of about 200μ, as in Example 1.
KI gel As a result of examining the dispersibility of 201K, KI gel 20
The 1K dispersion was uniform.

The water absorption of the press sheet was 8.2%.

Example 3 Sorbone obtained in Experiment 1 Sumika gel treated with S-60
150 g of a mixture of SP-510, 80 g of dibutyl phthalate, and
Polyvinyl chloride (Smilit FS, Sumitomo Chemical Co., Ltd.) 10
After mixing 00g with a Hensiel mixer, roll temperature 1
After kneading at 50 ℃ for 5 minutes, press sheet of about 2mm is formed.
It was The resulting pressed sheet Sumika gel SP-510 minutes
The dispersion was uniform.

Comparative Example 1 Ethylene-vinyl acetate copolymer (Evatate H2022, Sumitomo
Sumika gel for 1000 g of pellets (made by Tomo Kagaku) S
About 200 μm in the same manner as in Example 1 except that 25 g of P-510 was added.
Make a pressed sheet of, Sumika gel SP-510 dispersion
When the sex was observed with a microscope, Sumika gel SP-510
A large amount of agglomeration was observed, which was extremely dispersed as compared with Example 1.
Was uneven.

The water absorption of the press sheet was 3.5%, which was inferior to that of Example 1.

Comparative Example 2 Low Density Polyethylene (Dow Poly Made by Asahi Dow)
KI gel for 1000g Implemented except that 31g of 201K was added
Create a press sheet of about 200μ in the same manner as in Example 2, and use KI
gel As a result of examining the dispersibility of 201K, KI gel 201K aggregation
Were observed in many cases, and the dispersion was considerably uneven as compared with Example 2.
It was one.

The water absorption of the press sheet was 2.3%, which was slightly inferior.

<Effects of the Invention> By the method of the present invention, a fine powdery super absorbent polymer can be uniformly dispersed in a plastic material. Further, the water is sufficiently dispersed during the kneading, and the occurrence of "pinhole" can be prevented. Furthermore, since the shearing energy at the time of kneading is also small, heat generation is reduced and decomposition of the kneaded product can be prevented.

Therefore, the water-absorbent plastic composite material produced by the method of the present invention is excellent in water absorption and exerts its effect for a long period of time.

Even when the method of the present invention is applied to the production of an agricultural film, the film after film formation does not cause blocking with time.

Claims (1)

[Claims] 1. A method for producing a water-absorbent plastic composite material, which comprises treating a fine powdery super absorbent polymer with a surfactant and then kneading it with a plastic material.