JP2001078592A - Foamed molded article and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed molded article which scarcely affects surroundings, has excellent water permeability, air permeability, excellent strength and excellent durability, and is suitable for porous pipes and so forth, by forming fine open cells having plural openings on the surface of the article. SOLUTION: This foamed molded article is obtained by foaming and molding a resin composition consisting of (A) a low viscosity polyethylene-based resin having a melt flow rate of 20 to 60 g/10 min preferably in an amount of 60 to 95 pts.wt., (B) a high viscosity polyethylene-based resin having a melt flow rate of 0.1 to 10 g/10 min preferably in an amount of 40 to 5 pts.wt., and (C) a polypropylene-based resin preferably in an amount of 1 to 10 pts.wt. The foamed molded article has fine open cells having two or more openings on its surface. A foaming agent such as a decomposition type foaming agent is preferably compounded in an amount of 1 to 30 pts.wt. per 100 pts.wt. of the total amount of the resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam molded article having excellent water permeability and air permeability, and more particularly to a porous pipe buried in soil or installed in water to supply a liquid or gas. TECHNICAL FIELD The present invention relates to a foam molded article most suitable for performing the method and a method for producing the same.

[0002]

2. Description of the Related Art In order to reduce the amount of water supplied during plant cultivation and to prevent scattering of nutrients, a tube having fine pores in the tube wall is buried in soil, and water, fertilizer, and air are passed through the tube. There is a way to supply. Such a pipe, besides having micropores of an appropriate pore size to supply water by capillary action,
It needs strength, durability, and flexibility to be buried in the soil and used for a long time. In addition, in recent years, it has been required that the disposal process has little adverse effect on the surrounding environment and that the disposal process is easy.

Conventionally, a porous tube made of synthetic resin or rubber has been used as an embedding tube, but none of the above-mentioned conditions has been satisfied in a well-balanced manner.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to foam molding which is excellent in water permeability and air permeability, is inexpensive, has excellent strength and durability, has little adverse effect on the surrounding environment at the time of disposal, and is easy to dispose. The object is to provide a body and a method for its manufacture.

[0005]

The present invention relates to a foamed molded article obtained by subjecting a resin composition mainly composed of a low-viscosity polyethylene resin, a high-viscosity polyethylene resin, and a polypropylene resin to foam molding, The present invention also provides a foam molded article having fine continuous through holes having two or more open ports on the surface of the foam molded article, and a method for producing the same.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The polyethylene resin constituting the low-viscosity polyethylene resin and the high-viscosity polyethylene resin used in the present invention is not particularly limited as long as it is a polyethylene resin having a viscosity as described below.

The polyethylene resin is mainly composed of an ethylene polymer or an ethylene copolymer, and may have one or more monomer components other than ethylene as a monomer component. As monomer components other than ethylene, for example, carboxylic acid vinyl ester,
Unsaturated organic acids, derivatives thereof, and α-olefins. The low-viscosity polyethylene-based resin and the high-viscosity polyethylene-based resin may be used alone or in combination of two or more.

[0008] The molecular weight of the ethylene polymer or ethylene copolymer constituting the polyethylene resin is not particularly limited.

The proportion of monomer components other than ethylene in the above ethylene copolymer is not particularly limited, and can be appropriately set according to desired physical properties such as viscosity. The polymerization state of ethylene and other monomer components in the ethylene-based copolymer is not particularly limited, and may be any of a random copolymer, a block copolymer, and a graft copolymer.

The viscosity of the low-viscosity polyethylene resin and the high-viscosity polyethylene resin used in the present invention is not particularly limited as long as one of the polyethylene resins is larger than the other, and the resin composition containing these resins is foamed. The melt flow rate measured according to JIS K7210 is preferably 20 to 60 g / 10 min for a low-viscosity polyethylene-based resin, although it may be appropriately set according to the desired state and physical properties of the foamed molded article. 0.1 to 10 g / 10 min for viscosity-based polyethylene resin
It is good. In low viscosity polyethylene resin,
If the melt flow rate is less than 20 g / 10 min, the porosity such as the number of fine continuous holes in the foamed molded article will be greatly reduced, and if it exceeds 60 g / 10 min, the mechanical strength of the foamed molded article will be greatly reduced. In a high-viscosity polyethylene resin, the melt flow rate is 0.1 g / 10 mi.
If it is less than n, the porosity, such as the number of fine continuous through-holes in the foamed molded article, is greatly reduced, and if it exceeds 10 g / 10 min,
The mechanical strength of the foam molded article is greatly reduced.

The polypropylene resin used in the present invention is not particularly limited, and is mainly composed of a propylene polymer or a propylene copolymer and has one or more monomer components other than propylene as a monomer component. May be. Examples of the monomer components other than propylene include vinyl esters of carboxylic acids, unsaturated organic acids, derivatives thereof, and α-olefins. Also,
As the polypropylene-based resin, the above-mentioned polypropylene-based resin may be used alone or in combination of two or more.

The molecular weight of the propylene polymer or propylene copolymer constituting the polypropylene resin is not particularly limited.

The proportion of the monomer components other than propylene in the propylene-based copolymer is not particularly limited, and may vary depending on the desired state and physical properties of the foamed molded article obtained by foaming a resin composition containing these. Can be set appropriately. Also,
The polymerization state of propylene and other monomer components in the propylene-based copolymer is not particularly limited, and may be any of a random copolymer, a block copolymer, and a graft copolymer.

In the present invention, the mixing ratio of each of the above components (low-viscosity polyethylene-based resin, high-viscosity polyethylene-based resin, polypropylene-based resin) is not particularly limited, and foaming is performed by foaming a resin composition containing these. What is necessary is just to set suitably according to the desired state, physical properties, etc. of a molded object, Preferably 60-95 weight part of low-viscosity polyethylene resins are used,
It is preferable that the high viscosity polyethylene resin is 40 to 5 parts by weight and the polypropylene resin is 1 to 10 parts by weight.
If the low-viscosity polyethylene resin is less than 60 parts by weight, the porosity such as the number of fine continuous holes in the foamed molded article is greatly reduced, and if it exceeds 95 parts by weight, the mechanical strength of the foamed molded article is greatly reduced. . When the amount of the polypropylene resin is less than 1 part by weight, the porosity such as the number of fine continuous through holes in the foamed molded article is greatly reduced, and when it exceeds 10 parts by weight, the mechanical strength of the foamed molded article is largely decreased.

The resin composition constituting the foamed molded article of the present invention may contain, if necessary, other components such as additives in addition to the above components, as long as the action of the present invention is not impaired. .

The resin composition mainly composed of the above components can be foamed to form a foamed molded article. Since the foamed molded article of the present invention is mainly composed of a polyethylene-based resin and a polyolefin-based resin, it is inexpensive, has excellent durability, has little adverse effect on the surrounding environment at the time of disposal, and is easily disposed of.

The foam molded article of the present invention is a porous body having fine continuous through holes having two or more open ports on the surface of the foam molded article. In the present invention, fine continuous through-holes,
The open cells inside the expanded foam formed by the foam molding are formed by communicating two or more portions of the inner surface of the open cells with the surface of the expanded foam. The foam molded article of the present invention,
Due to the above-mentioned resin composition, fine continuous through-holes are easily formed during foam molding. As described below, when the foamed molded article of the present invention is formed as a tube having water permeability or air permeability, one of the openings of the fine continuous through-holes is present on the inner wall surface of the tube, and the other openings are provided. Is one of the outer walls of the tube,
It is necessary that the inside and outside of the tube be in communication. The foamed molded article of the present invention has excellent water permeability and air permeability by having the above-mentioned fine continuous through-holes, and therefore is particularly buried in soil or installed in water to remove liquids and gases. It is suitable for forming a porous tube for feeding.

The pore size of the fine continuous through-holes and the porosity of the foamed molded article are not particularly limited, and can be appropriately set according to the desired properties of the foamed molded article such as air permeability and water permeability. It can be controlled by a foaming method such as the blending amount.

Further, the foam molded article of the present invention preferably has flexibility. By having the flexibility, the pipe made of the foamed molded article of the present invention can be easily installed when the pipe is buried in the soil.

The density (density of the resin composition excluding air bubbles) and expansion ratio of the foamed molded article of the present invention are not particularly limited, and may be appropriately set according to the desired size and properties of the foamed molded article. Good.

The size and overall shape of the foamed molded article of the present invention are not particularly limited, and the inside diameter, the wall thickness, the cross-sectional shape of the pipe, and the length of the pipe made of the foamed molded article of the present invention are also specified. Is not particularly limited. Further, the tube made of the foamed molded article of the present invention may have another configuration such as a portion having no fine continuous through-hole or a through-hole having a larger diameter than the fine continuous through-hole as necessary.

As the method for producing the foamed molded article of the present invention, a general method for producing a foamed molded article can be used. Preferably, a foaming agent is added to a resin composition mainly composed of the above-mentioned components to form a foamed article. Preferably, it is molded. As a molding method, an extrusion molding method is preferably used.

The foaming agent used for forming the foamed molded article of the present invention is not particularly limited. For example, hydrocarbons such as propane, butane, pentane, hexane and cyclohexane, HFC-134a, HCFC- 142
a, Halogenated hydrocarbons such as HCFC-22, 1,1,1,2-tetrafluoroethane, dichloromethane, etc., ethers such as methyl ether and ethyl ether, ketones such as acetone, volatilization of carbon dioxide gas, nitrogen gas, etc. Foaming agents, ammonium carbonate, alkali metal carbonates such as sodium carbonate, ammonium bicarbonate, alkali metal bicarbonates such as sodium bicarbonate, azo compounds,
Sulfonyl hydrazide compound, semicarbazide compound,
Degradable foaming agents such as nitroso compounds and azide compounds are exemplified. These foaming agents can be used alone or in combination of two or more. The above-mentioned carbonate or hydrocarbon salt is combined with an organic acid (for example, an organic acid having a higher acidity than the above-mentioned carbonate or hydrogen carbonate such as citric acid or oxalic acid) or a salt thereof. May be used.

In the present invention, the foaming agent is mainly composed of one or more decomposable foaming agents selected from ammonium carbonate, alkali metal carbonate, ammonium hydrogen carbonate and alkali metal hydrogen carbonate, and an organic acid. A foaming agent, or a volatile foaming agent having a boiling point of -50 to 70 ° C,
It is preferably used.

In the present invention, the amount of the foaming agent is not particularly limited, and may be appropriately set according to the type of the foaming agent to be used, the desired expansion ratio, and the like. It is preferable to use 1 to 30 parts by weight with respect to 100 parts by weight of the total amount of the resin composition (a resin composition mainly composed of a low-viscosity polyethylene-based resin, a high-viscosity polyethylene-based resin, and a polypropylene-based resin). If the amount of the foaming agent is less than 1 part by weight, the porosity such as the number of fine continuous through holes in the foamed molded article is greatly reduced, and if it exceeds 30 parts by weight, the mechanical strength of the foamed molded article is greatly reduced.

In the foam molded article of the present invention, a nucleating agent can be used. The amount of the core material used is not particularly limited, but the total amount of the resin composition constituting the foam of the present invention is 10%.
It is preferable to add 0.1 to 5 parts by weight of a nucleating agent to 0 parts by weight.

As the nucleating agent, various fine particles,
For example, inorganic fine powders such as calcium carbonate, magnesium carbonate, magnesium hydroxide, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, silica, alumina, talc and the like can be mentioned. These can be used alone,
Two or more kinds may be used as a mixture.

In the molding of the foam molded article of the present invention, molding conditions such as extrusion are not particularly limited. The method of blending the above components is not limited, and the components are blended simultaneously or sequentially at the time of molding, and mixed by heating and melting.
As a mixing method, a commonly used stirrer or the like can be used. Further, after mixing each component, the mixture may be formed into a desired shape such as a pellet, and then foamed.

Hereinafter, the present invention will be described in more detail with reference to Test Examples and Examples, but the present invention is not limited thereto. Test Example Test Method Breathability One end of each of the tubes of Examples 1 to 3 and Comparative Examples 1 to 3 was sealed, and air was sent from the other end to the inside of the tube at a pressure of 0.2 kg / cm ² G, The amount of air leaking from the pipe wall was measured using a float type flow meter, and evaluated based on the following criteria. ：: 20 ml / (mm ² · min) or more ×: less than 20 ml / (mm ² · min)

Water permeability: One end of each of the tubes of Examples 1 to 3 and Comparative Examples 1 to 3 was sealed, and water was fed into the tubes from the other end at a pressure of 1.0 kg / cm ² G. The amount of water leaking from the wall was measured and evaluated based on the following criteria. ○: 5 ml / (mm ² · min) or more ×: less than 5 ml / (mm ² · min)

Test Results Table 1 shows the results of the tests (1) and (2).

[0032]

EXAMPLES Examples 1 to 3 and Comparative Examples 3 to 3 Using the materials shown below, the components shown in Table 1 were blended in the proportions shown below.
And butane as a blowing agent in the proportions shown in Table 1,
Feed to a screw extruder (inner diameter 50mmφ), temperature 2
After melt-kneading at 40 ° C. and a pressure of 200 kg / cm ² , the temperature immediately before being extruded into the atmosphere from a screw extruder is set to 110
C., the mixture was extruded and foamed into a tube to produce a tube made of a foam molded article having an outer diameter of 14 mm and an inner diameter of 10 mm.

[Materials used] Low-viscosity polyethylene resin: (Sumikasen, manufactured by Sumitomo Chemical Co., Ltd.) High-viscosity polyethylene resin: (Yumerit, manufactured by Ube Industries, Ltd.) Polypropylene resin: (Tokuyama Polypro, Tokuyama ( Blowing agent: butane

[0034]

[Table 1]

[0035]

The foam molded article of the present invention is inexpensive, has excellent durability, and has little adverse effect on the surrounding environment during disposal.
Disposal is easy. Further, it has excellent water permeability and air permeability, and is therefore particularly suitable for being buried in soil or installed in water to form a porous tube for supplying a liquid or gas.

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Claims (11)

[Claims] 1. A foam molded article obtained by foam molding a resin composition mainly composed of a low-viscosity polyethylene resin, a high-viscosity polyethylene resin, and a polypropylene resin, and two places on the surface of the foam molded article. A foam molded article having fine continuous through holes having the above-mentioned opening. 2. A low-viscosity polyethylene resin having a melt flow rate (measured according to JIS K7210) of 20 to 20.
The foamed molded article according to claim 1, wherein the molded article is a polyethylene resin of 60 g / 10 min. 3. The high-viscosity polyethylene resin has a melt flow rate (measured according to JIS K7210) of 0.1.
The foam molded article according to claim 1, wherein the foam molded article is a polyethylene resin of 10 to 10 g / 10 min. 4. The mixing ratio of each component is such that the low viscosity polyethylene resin is 60 to 95 parts by weight, the high viscosity polyethylene resin is 40 to 5 parts by weight, and the polypropylene resin is 1 to 10 parts by weight.
The foam molded article according to any one of claims 1 to 3, wherein the proportion is a part by weight. 5. A tube comprising the foamed molded article according to claim 1. 6. The method for producing a foamed molded article according to claim 1, wherein a foaming agent is added to the resin composition and foamed. 7. The method for producing a foamed molded article according to claim 6, wherein the molded article is molded by an extrusion molding method. 8. A method comprising using at least one decomposable foaming agent selected from ammonium carbonate, alkali metal carbonate, ammonium hydrogen carbonate and alkali metal bicarbonate, and a foaming agent mainly comprising an organic acid. A method for producing a foam molded article according to claim 6. 9. The method according to claim 6, wherein a volatile foaming agent having a boiling point of −50 to 70 ° C. is used. 10. The foam according to claim 6, wherein the amount of the foaming agent is 1 to 30 parts by weight based on 100 parts by weight of the total amount of the resin composition. A method for producing a molded article. 11. The resin composition according to claim 6, wherein 0.1 to 5 parts by weight of a nucleating agent is blended with 100 parts by weight of the total amount of the resin composition and foamed. The method for producing a foamed molded article according to the above item.