JPH0615639B2 - Water-swellable polyolefin resin composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a polyolefin resin composition having water swelling property and a method for producing the same.

<Prior Art> Water-swellable polyolefin resin compositions have hitherto been widely used in various fields due to their excellent properties, and are being used for, for example, agricultural films, food films, toys and the like.

However, in the conventional production of water-swellable polyolefin-based resin compositions, when the high water-absorbent resin is directly kneaded with the polyolefin-based resin, the dispersibility is poor, resulting in poor processability and poor appearance of the molded article, and eventually in poor water absorption performance. It was difficult to obtain a stable product.

<Problems to be Solved by the Invention> As a result of the above, the present inventors have earnestly studied to solve the above-mentioned problems, and as a result, the dispersibility of the superabsorbent resin is good, and The present inventors have found a manufacturing method for obtaining a composition having stable and high water absorption.

<Means for Solving Problems> That is, the present invention comprises a polyolefin wax (A), a superabsorbent resin (B) and a polyolefin resin, and the weight ratio of (A) and (B) is (A). : (B) = 8-2: 2-8, a water-swellable polyolefin resin composition, and a polyolefin wax (A) and a super absorbent resin (B) in a weight ratio of
(A): (B) = 8-2: Water swelling characterized by being blended in a ratio of 2 to 8 to obtain a highly water-absorbent resin composition, and then adding and blending a polyolefin-based resin A method for producing a heat-fusible polyolefin plastic resin composition.

The polyolefin wax used in the present invention includes polyethylene having a molecular weight of 1,000 to 10,000, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polypropylene, etc. However, two or more kinds may be used in combination.

The super absorbent polymer used in the present invention includes a saponified product of vinyl acetate-acrylic acid ester copolymer, a crosslinked product of isobutylene-maleic anhydride copolymer modified product, polyacrylic acid (salt) having a crosslinked structure, and starch. -Acrylic acid (salt) graft polymers and the like are exemplified, but among these, a polymer compound containing a carboxylate in the molecule (for example, saponified product of vinyl acetate-methyl acrylate copolymer,
A crosslinked product of a modified isobutylene-maleic anhydride copolymer) is excellent in durability and is particularly preferably used.

Such super absorbent polymers may be used alone or in combination of two or more.

These super absorbent resins have a water absorption of 20 g / in terms of water absorption performance.
It is preferably g or more, particularly 100 g / g or more, and the smaller the average particle size of the super absorbent polymer is, the more preferable. Generally, the average particle size is 100 μ or less, preferably 50 μ or less, and particularly 30
It is more preferably μ or less.

The polyolefin resin used in the present invention includes polyethylene, ethylene-vinyl acetate polymer, ethylene-acrylic acid copolymer, polypropylene and the like, and various types are used according to the purpose.

Such polyolefin resins may be used alone or in combination of two or more.

The compounding ratio for obtaining a superabsorbent resin composition (hereinafter referred to as a masterbatch composition) comprising a polyolefin wax (A) and a superabsorbent resin (B) is a weight ratio (A):
It is necessary that (B) = 8-2: 2-8. If the weight ratio of the super absorbent polymer to the polyolefin wax is 2 or less, the effect cannot be expected, and if it is 8 or more, the surface of the super absorbent resin is sufficiently covered with the polyolefin wax. It becomes powdery and has poor dispersion, and is easily removed. A more preferable range is (A) :( B) = 3
-6: 7-4.

In addition, various additives such as a stabilizer, a dispersant, a foaming agent, a filler, and a coloring agent may be blended in the masterbatch composition as required.

The masterbatch composition is kneaded by mechanical kneading such as heating three-roll kneading, biaxial extrusion kneading, Banbury kneading, and pressure kneader kneading. Heating three-roll kneading is preferably used.

When the temperature at which the masterbatch composition is kneaded is higher than the melting point of the polyolefin wax, or at least 100 ° C. or higher, it is possible to obtain a composition having high dispersibility, which is unprecedented and does not have aggregates.

After kneading, it is molded into pellets or coarse powder so that it can be easily kneaded with the polyolefin resin in the next step.

The masterbatch composition thus obtained is blended with a polyolefin resin so as to have a desired high water-absorbent resin content. The ratio is not specified and may be changed depending on the intended use.

Further, at this time, various additives which are usually used at the time of processing or molding the polyolefin-based resin, such as a stabilizer, a dispersant, a foaming agent, a filler, and a coloring agent may be blended as necessary.

Kneading the masterbatch composition and the polyolefin resin, in addition to the kneading method described above, two-roll kneading, single-screw extruder,
It is performed by an injection molding machine or the like, and is molded into pellets, sheets, film molded products, etc. depending on the intended use.

<Effects of the Invention> According to the present invention, a water-swellable polyolefin-based resin composition is produced industrially advantageously rather than directly blending a highly water-absorbent resin with a target polyolefin-based resin.

That is, the obtained composition is excellent in dispersibility and water swellability,
It is used in various fields including agricultural films, food films, toys, etc., and can provide stable effects over a long period of time.

<Example> Hereinafter, the present invention will be described with reference to Examples.

However, in the examples, “part” means “part by weight”.

Example 1. 40 parts of low molecular weight low density polyethylene (average molecular weight 5000) as a polyolefin wax and Sumika Gel SP
60 parts of −510 (vinyl acetate-acrylic acid ester copolymer saponified super absorbent resin, average particle size 10 μm, manufactured by Sumitomo Chemical Co., Ltd.) were mixed with a drum type tumbler for 20 minutes, and then heated to 120 ° C. 3 Knead with this roll.

Then, it was pulverized to obtain a masterbatch composition having a high water-absorbent resin content of 60% by weight. 50 parts of this and an ethylene-vinyl acetate copolymer as a polyolefin resin (vinyl acetate content 15% by weight, melt flow index 3 g / 10 minutes)
After mixing 50 parts in a drum tumbler for 20 minutes,
The mixture was kneaded and granulated with a single-screw extruder to obtain pellets containing 30% by weight of a super absorbent polymer.

The pellets obtained are press-molded at 160 ° C to 1 m /
Table 1 shows the results of examining the swelling coefficient and the dispersibility of the superabsorbent resin as m sheets.

Example 2. As a super absorbent polymer, instead of SUMIKAgel SP-510, SUMIKAgel SP-520 (saponified vinyl acetate-acrylic acid ester copolymer-based super absorbent polymer having an average particle diameter of 20)
A sheet having a thickness of 1 m / m was prepared in exactly the same manner as in Example 1 except that the product (μ Sumitomo Chemical Co., Ltd.) was used, and the swelling ratio and dispersibility of the super absorbent resin were examined.

The results obtained are shown in Table 1.

Example 3. A sheet having a thickness of 1 m / m was prepared in exactly the same manner as in Example 1 except that low density polyethylene (melt flow index 2 g / 10 min) was used as the polyolefin resin instead of the ethylene-vinyl acetate copolymer. The swelling ratio and the dispersibility of the super absorbent polymer were examined.

The results obtained are shown in Table 1.

Comparative Example 1. 30 parts of Sumikagel SP-510 and 70 parts of ethylene-vinyl acetate copolymer (vinyl acetate content 15% by weight, melt flow index 3 g / 10 minutes) are 2 with a drum type tumbler.
After mixing for 0 minutes, the mixture was kneaded and granulated with a single screw extruder to obtain pellets having a high water-absorbent resin content of 30% by weight. 160 ° C
Press molding was carried out in order to make a 1 m / m sheet, and the swelling ratio and the dispersibility of the super absorbent resin were examined.

The results obtained are shown in Table 1.

Claims (2)

[Claims] 1. A polyolefin wax (A), a super absorbent polymer (B) and a polyolefin resin, and (A).
A water-swellable polyolefin resin composition in which the weight ratio of (B) to (A) :( B) = 8-2: 2-8. 2. A highly water-absorbent resin composition obtained by blending a polyolefin wax (A) and a highly water-absorbent resin (B) in a weight ratio of (A) :( B) = 8-2: 2-8. A process for producing a water-swellable thermoplastic resin composition, which comprises obtaining a product, and further adding and blending a polyolefin resin into the product.