JPH0718113A - Production of open cellular material - Google Patents

Abstract

PURPOSE:To provide a method for producing a porous material containing open cells having a uniform size and uniformly dispersed over the whole body and excellent in mechanical strength and ozone resistance. CONSTITUTION:A resin composition containing 100 pts.wt. thermoplastic resin, 20 to 70 pts.wt. water-soluble resin, 20 to 70 pts.wt. water-soluble solid inorganic compound and 0.1 to 5 pts.wt. foaming agent are kneaded. After forming of the resultant kneaded material, the water-soluble resin and the water-soluble inorganic compound are eluted with an aqueous solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing continuous pores of thermoplastic resin.

[0002]

2. Description of the Related Art An air disperser for supplying air into water, which is currently used for aquaculture of fish or for ornamental use, is made of a porous material such as special synthetic rubber and has a large number of small meshes. Materials with holes have been used. In recent years, it has further been found that by feeding ozone together with air, the growth of fish can be improved. However, when a device made of a special synthetic rubber that is currently used is used, there is a problem that it becomes unusable at an early stage due to poor ozone resistance.

Several methods for producing a porous molded article using a resin are known. As a general technique, there is a method of injection molding a resin molding material mixed with a foaming agent. Further, Japanese Patent Laid-Open No. 58-25335 discloses a method of mixing powdery particles of a water-soluble inorganic material with a resin molding material to mold this, and then immersing the molded article in water to dissolve the water-soluble inorganic material. A method of manufacturing a porous molded article is disclosed.
Here, the pore size can be adjusted by adjusting the particle size of the water-soluble inorganic powder. JP-A-2-153945 discloses that a water-soluble thermoplastic organic polymer is eluted by bringing an injection-molded product of a mixture of a water-soluble thermoplastic organic polymer and a water-insoluble thermoplastic organic polymer into contact with water. However, a method for obtaining a porous molded body is disclosed.

However, in any of the above methods,
A porous body having sufficiently satisfactory continuous pores and excellent mechanical strength could not be obtained.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention produces a porous material which has continuous pores uniformly distributed throughout its size and has a uniform size, mechanical strength, and ozone resistance. The purpose is to provide a method.

[0006]

The present invention relates to a method for producing continuous pores of a thermoplastic resin, the thermoplastic resin 1
20 to 70 parts by weight of the water-soluble resin, 20 to 70 parts by weight of the solid water-soluble inorganic compound and 0.
After kneading and molding a resin composition containing 1 to 5 parts by weight,
Provided is a method for eluting a water-soluble resin and a water-soluble inorganic compound with an aqueous solvent.

In the present invention, as the thermoplastic resin,
Any water-insoluble thermoplastic resin can be used. For example, a homopolymer or copolymer of polyvinyl chloride, polyethylene, polypropylene, polyvinyl acetate, polystyrene and the like can be used. Such thermoplastic resins may be used alone or as a mixture of two or more. Preferred is polyvinyl chloride, especially soft polyvinyl chloride.

The water-soluble resin used in the method of the present invention is polyethylene oxide, polyethylene glycol,
It is preferably a homopolymer or copolymer of a resin selected from methylcellulose, carboxymethylcellulose, polyacrylamide, polyvinyl alcohol, polyvinyl ether, polyacrylic acid, polymethacrylic acid, polyitaconic acid and polyvinylpyrrolidone. These water-soluble resins may be used alone or in combination of two or more. Particularly, polyvinyl alcohol having an average polymerization degree of 200 to 2500 and a saponification degree of 65 to 95 mol% is preferable, and more preferably an average polymerization degree of 200 to 1000.
The polyvinyl alcohol has a saponification degree of 85 to 90 mol%. Here, the degree of saponification means the mol% of the saponified vinyl alcohol residue, that is, the mol% of the free hydroxyl group. These water-soluble resins have a particle size of 10 to 5,000.
It is preferable to use those having a thickness of 100 μm, more preferably 100 to 2000 μm.

These water-soluble resins are used in an amount of 20 to 70 parts by weight, preferably 30 to 60 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the amount of the water-soluble resin is too small, it becomes difficult to form high-quality continuous pores, and if it is too large, the physical properties of the molded product may deteriorate.

The water-soluble inorganic compound is readily soluble in water and any solid compound can be used. Preferred examples include calcium chloride, magnesium chloride, calcium hydrogen carbonate, sodium chloride and the like. The water-soluble inorganic compound preferably has a particle size of 10 to 5000 μm, more preferably 100 to 1500 μm. The water-soluble inorganic compound is used in an amount of 20 to 70 parts by weight, preferably 30 to 60 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the amount of the water-soluble inorganic compound is too small, it becomes difficult to form high-quality continuous pores, and if it is too large, the physical properties of the molded product may be deteriorated.

Known foaming agents can be used, and examples thereof include azodicarbonamide type and hydrazine type foaming agents. Preferred is an azodicarbonamide-based foaming agent. The blowing agent is used in an amount of 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the amount of the foaming agent is too small, it becomes difficult to form high-quality continuous pores, and if it is too large, the physical properties of the molded product may be deteriorated.

In the method of the present invention, in addition to the above essential components, a plasticizer, a stabilizer, a processability aid, a foaming aid, a colorant, a flame retardant, an oxidative deterioration inhibitor, a weather resistance improver and a lubricant. A known component such as a release agent can be added. Examples of the plasticizer include phthalic acid diester plasticizers such as di- (2-ethylhexyl) phthalate (sometimes abbreviated as DOP), dioctyl phthalate and dibutyl phthalate; dibasic acid esters such as dioctyl adipate and dioctyl sebacate. Examples of the plasticizer include phosphoric ester plasticizers such as tricresyl phosphate; epoxy plasticizers such as epoxidized fatty acid esters; trimellitic acid ester plasticizers; polyester plasticizers having a molecular weight of 500 or more. Examples of the stabilizer include Ba, Ca, Zn, Sn,
Examples thereof include Pb-based compounds (for example, dibutyl tin maleate). Examples of the processability aid include high molecular weight acrylic resins, butadiene resins such as ABS and MBS, olefin resins such as polyethylene, chlorinated polyethylene and ethylene-vinyl acetate copolymer, and these are vinyl chloride. It is effective for extrusion processability of resin and uniform foaming property. Further, examples of the foaming aid include a foaming agent decomposition accelerator (metal oxide such as ZnO) and a foaming agent decomposition retarder (organic acid anhydride such as phthalic anhydride), and addition of these is uniform. It is effective in forming foam.

In the method of the present invention, the above components are first kneaded. For kneading, known means such as a kneader and a co-kneader can be used. Next, this kneaded product is molded into a desired shape by a known molding method such as injection molding, extrusion molding, compression molding or the like. The obtained molded product is then subjected to elution of water-soluble components using an aqueous solvent. Here, the aqueous solvent is
It means water or an aqueous solution in which at least one kind of acid, alkali and the like is dissolved. As the acid, for example, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as acetic acid and citric acid can be used. Examples of the alkali include hydroxides of alkali metals. The temperature of the aqueous solvent is not particularly limited, but is usually 0 to 100 ° C, preferably 20 to 40 ° C. The method of elution with a solvent is not particularly limited. For example, a method of immersing the molded product in an aqueous solvent, washing the molded product with the aqueous solvent, or the like can be appropriately selected.

The continuous pore body of the present invention can be used in an air dispersing device such as a water tank, a flowerpot, a water dispersing device, wallpaper, a breathable film and the like.

[0015]

Function: The conventional method, that is, a foaming agent, a water-soluble inorganic substance
Even if a water-soluble resin or the like is used alone to produce a porous molded body, continuous pores cannot be obtained. That is, when the foaming agent alone is used, the independent pores are uniformly obtained, and when the water-soluble inorganic substance or the water-soluble resin is used, the independent pores are obtained only on the surface. Even if these two are combined, only partial continuous pores can be obtained when used in a large amount, and continuous pores cannot be obtained when the water-soluble inorganic substance and the water-soluble resin are combined. Only by combining the three in a specific ratio can continuous pores be obtained. The porous molded article obtained by the method of the present invention has pores uniformly distributed throughout and has continuous pores having a uniform pore size. The mechanism of this continuous pore formation is considered to be due to the combination of the closed cells formed by the foaming agent during molding and the pores formed on the surface by the subsequent elution with an aqueous solvent, but not two components. It is not clear why such good quality continuous pores cannot be obtained unless the three components are combined and used in a specific ratio.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

The following compounds were used in the examples: Thermoplastic resin: vinyl chloride resin; TK-1300, manufactured by Shin-Etsu Chemical Co., Ltd., average degree of polymerization 1300, water-soluble resin: average degree of polymerization 500, Ken Polyvinyl alcohol with a degree of conversion of 88 mol%, particle size 1200 μm, water-soluble inorganic compound: sodium chloride, particle size 300 μm, foaming agent: azodicarbonamide-based foaming agent; AZ-H, manufactured by Otsuka Chemical Co., Ltd., plasticizer: di- (2-ethylhexyl) phthalate (DO
P), manufactured by Mitsubishi Kasei Vinyl Co., Ltd. Stabilizer: Ba-Zn stabilizer. Examples 1 to 3 and Comparative Examples 1 to 10 Vinyl chloride resin, polyvinyl alcohol, sodium chloride, a foaming agent, a plasticizer and a stabilizer were mixed in the proportions shown in Table 2, and after kneading and granulating with a co-kneader. Then, it was extrusion molded into a pipe shape (outer diameter 30 mm, inner diameter 20 mm) with an extruder.
Next, this was washed with water (temperature: 25 ° C.) to elute the readily water-soluble material.

The obtained pipe-shaped molded body was cut into a length of 500 mm, both ends thereof were connected with adapters and placed in water, and air having a pressure of 0.5 kg / cm ² was blown inside. Bubbles generated from the surface of the molded product were observed, and the generation and uniformity of continuous pores were evaluated as follows. (1) Generation of continuous pores (uniformity of bubble size) The situation of bubble generation from the pores by blowing air was examined, and bubbles with uniform size were evaluated as ○, bubbles with different sizes. When the occurrence of air bubbles was evaluated as Δ, and when no air bubbles were generated, it was evaluated as x. (2) Uniformity (uniformity of air bubble distribution) Examine the condition of air bubble generation over the entire pipe by blowing air, and check if the air bubble was generated from the entire pipe.
The case where bubbles were generated from a part of the pipe was evaluated as Δ, and the case where no bubbles were generated was evaluated as ×.

Next, the mechanical strength of this porous molded article was examined, and an ozone deterioration test was also conducted. Mechanical strength is J
Tensile strength was measured according to IS 6723. The ozone deterioration test was conducted according to JIS-K6301 as follows:
That is, the elongation test piece was exposed to the air containing artificially generated low concentration of ozone, and its deterioration was accelerated to investigate the ozone resistance. The deterioration state was observed and evaluated. The evaluation criteria are shown in Table 1 below.

[0020]

[Table 1] Table 1 ---------------------------------------------- Number of cracks Crack size ---- −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− A Minority 1 Invisible to the naked eye, but can be confirmed with a 10 × magnifying glass Things 2 Visually visible B Many 3 Deep cracks and relatively large (less than 1 mm) 4 Deep cracks and large (1 mm or more and less than 3 mm) C Innumerable 5 Cracks of 3 mm or more, or those that are likely to cut The results of each test are shown in Table 2. ------------------------------------. Regarding the workability in the above extrusion molding, good results were evaluated as ◯, normal conditions were evaluated as Δ, and defects were evaluated as ×, and the results are shown in Table 2. Comparative Example 11 In this comparative example, a conventional special rubber-made porous body was manufactured, and the same test as that of the above-described example was performed on the porous body to compare its properties.

To 100 parts by weight of tire powder (particle size 500 μm), 50 parts by weight of polyethylene (Mirason 5S, manufactured by Mitsui Petrochemical Co., Ltd.) and 3 parts by weight of sodium hydrogencarbonate (particle size 300 μm) were blended and carried out. The mixture was kneaded in the same manner as in Example 1 and then molded to obtain a porous molded body.

With respect to the obtained molded body, generation of pores, continuity and uniformity were examined in the same manner as in Example 1, and an ozone deterioration test was conducted. The results are shown in Table 2.

[0023]

[Table 2] From the above results, no continuous pores were obtained when the foaming agent, the water-soluble inorganic substance or the water-soluble resin was used alone (Comparative Examples 6, 5 and 2). When these pipes were cut and examined, it was found that in Comparative Examples 2 and 5, pores were formed only on the surface, and in Comparative Example 6, independent pores were formed throughout. With the use of such a single component, continuous pores could not be formed even if the amount was increased (Comparative Examples 7 and 8). It was found that the combination of the foaming agent and the other one component (two-component system) partially formed continuous pores when used in a large amount (Comparative Examples 9 and 10).

[0024]

EFFECTS OF THE INVENTION According to the present invention, it is possible to manufacture a porous body which has continuous pores uniformly distributed over the whole and has a uniform size, has mechanical strength, and has ozone resistance. .

Claims (2)

[Claims] 1. A method for producing a continuous pore body of a thermoplastic resin, wherein the water-soluble resin is 20 to 70 parts by weight, and the solid water-soluble inorganic compound is 20 to 100 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
A method comprising kneading and molding a resin composition containing 70 parts by weight and 0.1 to 5 parts by weight of a foaming agent, and then eluting the water-soluble resin and the water-soluble inorganic compound using an aqueous solvent. 2. The thermoplastic resin is polyvinyl chloride,
Water-soluble resin is polyethylene oxide, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, polyvinyl ether, polyacrylic acid, polymethacrylic acid,
The method according to claim 1, which is a homopolymer or copolymer of a resin selected from polyitaconic acid and polyvinylpyrrolidone.