JP2000319457A - Starch-filled crosslinked polyolefin open-cell foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crosslinked polyolefin open-cell foam desirable for a medium for bacterial proliferation and excellent in water permeability by introducing starch into cell membranes and/or a skeleton. SOLUTION: There is provided a process for producing a starch-filled crosslinked polyolefin open-cell foam, comprising foaming under heating in a non-sealed mold a foamable crosslinkable composition prepared by adding a blowing agent and a crosslinking agent to a polyolefin to form a foam and converting the cells of the foam into open cells by the action of mechanical deformation, which process comprises adding starch to the polyolefin and foaming the mixture under kneading. It is desirable that 10-100 pts.wt. starch is added to 100 pts.wt. polyolefin. The polyolefin is exemplified by a polyethylene or an ethylene/propylene copolymer. The starch used may be one of various starches. The crosslinking agent used is an organic peroxide having a decomposition temperature not lower than the flow initiation temperature of the polyethylene resin. In this case, a chemical blowing agent having a decomposition temperature not lower than the melting temperature of the polyethylene resin is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starch-containing crosslinked polyolefin open cell and a method for producing the same.

[0002]

2. Description of the Related Art Cross-linked polyolefin open-cell foams are excellent in weather resistance, heat insulating properties, sound absorbing properties, etc., and are therefore heat insulating materials in air conditioners, sound absorbing materials in door mirrors of automobiles, bacteria carriers in septic tanks, and coating materials. Widely used for various applications such as. The method for producing a cross-linked polyolefin open cell is as follows: (1) The foaming agent and the cross-linking agent in the foamable cross-linkable composition are partially decomposed in a closed mold, and the foaming agent and the cross-linking agent remaining under normal pressure are mixed. A method has been proposed in which closed cells are obtained by disintegration, and then the obtained closed cells are compressed to break closed cells (Japanese Patent Publication No. 59-23545 and Japanese Patent Application Laid-Open No. 56-14 / 1981).
No. 6732). (2) The present applicant heat-shapes the expandable crosslinkable composition into a desired shape, and then heats it under normal pressure to simultaneously and progressively decompose the crosslinker and the foaming agent to form a foam, Subsequently, a method of making the bubbles open by applying mechanical deformation has been developed (Japanese Patent Publication No. 62-19294, Japanese Patent Publication No. 1-444).
No. 99). (3) As a method for producing a non-crosslinked polyolefin resin open cell, a polyolefin resin is heated by heating a polyolefin resin composition comprising an ethylene-methacrylic acid copolymer, a nucleating agent, a shrinkage inhibitor and the like. A method in which a composition obtained by softening or melt-foaming and then supplying and mixing a volatile foaming agent is opened to a low pressure region (JP-A-10-279).
724) has been proposed. However, the open-cell foam obtained by the methods (2) and (3) has a low open-cell rate, and according to the method (1), the open-cell rate is 100% or close to 100%. Although it was obtained, it was inferior in water permeability inside the foam and was not sufficiently effective as a medium for growing bacteria.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a crosslinked polyolefin open-cell foam which overcomes the above-mentioned drawbacks of the prior art, is suitable as a culture medium for bacterial growth, and has excellent water permeability. Is to do.

[0004]

Means for Solving the Problems In order to achieve the above object, a starch-containing crosslinked polyolefin open cell according to the present invention is characterized in that the cell membrane and / or skeleton contains starch particles. The starch-containing crosslinked polyolefin foam of the present invention preferably contains 10 to 100 parts by weight of starch based on 100 parts by weight of polyolefin. The method for producing a starch-containing crosslinked polyolefin open cell of the present invention comprises producing a foam by heating and foaming a foamable crosslinkable composition obtained by adding a foaming agent and a crosslinking agent to a polyolefin in an airtight mold. A method for producing an open-cell body in which bubbles are communicated by subjecting the polyolefin to continuous deformation, characterized in that starch is added to a polyolefin, kneaded and foamed. In the production method of the present invention, it is preferable to add 10 to 100 parts by weight of starch to 100 parts by weight of polyolefin.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention focuses on the effect of starch on the growth of bacteria, and in the process of producing a crosslinked polyolefin open cell, starch is added to the polyolefin so that the starch is contained in the film and / or skeleton of the cell. This not only promotes the growth of bacteria as a medium, but also promotes the communication of the cell membrane due to the disappearance of starch when used in water.

Hereinafter, a preferred embodiment of the method for producing an open-cell body according to the present invention will be specifically described. First, starch is preferably 10 to 100 parts by weight, particularly preferably 20 to 50 parts by weight, based on 100 parts by weight of polyolefin, a foaming agent, a crosslinking agent, and, if necessary, a foaming aid, a filler, a pigment, and the like. And kneaded with a heated mixing roll, pressure kneader, extruder or the like. In the case where the amount of starch is less than 10 parts by weight, the effect of growing bacteria is insufficient, and the effect of communicating air bubbles is insufficient,
If it exceeds 100 parts by weight, a satisfactory foam cannot be formed.
The polyolefin referred to in the present invention includes, for example, polyethylene, poly-polyethylene produced by high-, medium-, and low-pressure methods which are usually commercially available.
1,2-butadiene, ethylene-propylene copolymer,
Ethylene-butene copolymer, ethylene-vinyl acetate copolymer, copolymer of ethylene with each acrylate or methacrylate of methyl-, ethyl-, propyl-, butyl- up to 45% content, or chlorine (A chlorine content of up to 60% by weight), a mixture of two or more of these, or a mixture of these with a polypropylene having an atactic or isotactic structure.

As the starch used in the present invention, various types can be used. For example, corn starch, potato starch,
Sweet potato starch, wheat starch, kissava starch, sago starch, tabio starch, sorghum starch, rice starch, bean starch, kudzu starch, bracken starch, hasto starch, hisshi starch, etc .; physically modified starch (α-starch, fractionated amylose, etc.) ); Enzyme-modified starch (hydrolyzed dextrin, enzymatically-degraded dextrin, amylose, etc.); Chemically-modified starch (acid-treated starch, hypochlorinated starch, dialdehyde starch, etc.); Chemically-modified starch derivative (esterified starch, etherified) Starch, cationized starch, cross-linked starch, etc.). The cross-linking agent referred to in the present invention has a decomposition temperature in the polyethylene resin at least equal to or higher than the flow start temperature of the polyethylene resin, and is decomposed by heating to generate free radicals to generate intermolecular or intramolecular molecules. Organic peroxides that are radical generators that cause cross-linking to be formed, such as dicumyl peroxide, 1,1-ditert-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2 , 5-Di-tert-butyl peroxyhexane, 2,5-dimethyl-2,5-di-tert-butyl peroxyhexyne, α, α-di-tert-butyl peroxyisopropylbenzene, tert-butyl peroxy ketone, tert-butyl There is peroxybenzoate, etc., but it is used at that time The optimum organic peroxide must be selected depending on the resin used.

The blowing agent which can be used in the present invention is a chemical blowing agent having a decomposition temperature higher than the melting temperature of the polyethylene resin, such as azodicarbonamide, an azo compound,
Barium azodicarboxylate and the like: nitroso compounds such as dinitrosopentamethylenetetramine and trinitrotrimethyltriamine; hydrazide compounds such as p,
p'-oxybisbenzenesulfonyl hydrazide and the like;
There are sulfonyl semicarbazide compounds such as p, p'-oxybisbenzenesulfonyl semicarbazide and toluenesulfonyl semicarbazide.

In the present invention, a foaming aid can be added according to the type of the foaming agent. Examples of the foaming aid include compounds mainly containing urea, metal oxides such as zinc oxide and lead oxide, compounds mainly containing salicylic acid, stearic acid and the like, that is, higher fatty acids and metal compounds of higher fatty acids. In the present invention, for the purpose of improving the physical properties or reducing the price of the composition to be used, a compounding agent (filler) that does not significantly affect cross-linking, for example, zinc oxide, titanium oxide, calcium oxide, magnesium oxide,
Metal oxides such as silicon oxide, carbonates such as magnesium carbonate and calcium carbonate, or fibrous materials such as pulp, or various dyes, pigments and fluorescent materials, and other conventional rubber compounding agents may be added as necessary. it can.

[0010] The foamable crosslinkable composition obtained by kneading as described above is charged into a mold, and is pressurized with a press at 115 to 155 ° C, preferably 1 to 150 ° C, depending on the type of the resin and the crosslinking agent.
Heat shaping at 20-140 ° C. In this heating shaping step, shaping while maintaining the foamable crosslinkable composition preferably in a state where the gel fraction is zero can be achieved by an open cell rate of 10%.
This is a condition for obtaining an open cell close to 0% or 100%.
In this heating shaping step, a very small amount of the foaming agent undergoes initial decomposition, and when the shaped article is taken out of the mold, it can expand to about twice, but this is far from the concept of foaming, and the present invention It doesn't hurt anything.

The foamable crosslinkable composition shaped as described above is then heated under normal pressure to obtain
The decomposition of the crosslinking agent and the blowing agent can be performed simultaneously. This foaming / crosslinking step is performed, for example, by placing the shaped polyolefin composition in a non-hermetic, that is, unsealed mold having a desired cross-sectional shape and dimensions, and heating the metal plate of the mold from outside. The composition is heated indirectly. As a method of indirectly heating,
For example, there is a method in which a heater is brought into close contact with the outer surface of a metal plate and heating is performed, or a flow path of a heat medium is provided in the metal plate and heating is performed by steam, heating oil, or the like in a jacket system.
Alternatively, the shaped polyolefin composition is placed in a mold that is not airtight and can be opened and closed. It is directly heated in a salt bath using a molten salt, in a nitrogen stream, or in a state covered with an extensible (or expandable) iron plate or the like. After heating for a predetermined time, it is cooled to obtain a foam. The heating temperature depends on the type of resin used.
The temperature is set in the range of 0 to 210 ° C, preferably 160 to 190 ° C. The heating time is preferably 30 to 200 minutes, more preferably 50 to 180 minutes. In this way,
A foam having a foam film that can be easily broken by mechanical deformation and having a degree of crosslinking (up to a gel fraction of about 95%) similar to that of a conventional foam can be obtained.

The foam (so-called closed cell) obtained as described above is then subjected to compressive deformation by, for example, a constant-speed double roll or the like, so that the bubble film is broken, and the bubbles are made open to open cells. The body is obtained. Countless small needles are provided on the surface of the constant velocity double roll, or rolls provided with countless small needles are arranged before and / or after the constant velocity double roll, and countless small needles are provided on the surface of the foam. By forming the holes, the communication of bubbles can be promoted. The open cell obtained by this method is ASTM-D2
The open cell ratio measured using an air comparison specific gravity meter 1000 (manufactured by Tokyo Science Co., Ltd.) conforming to 856 is 10
It is close to 0% or 100%. The open-cell body obtained by the method of the present invention can be irradiated with an electron beam to increase the degree of cross-linking on the surface of the open-cell body and improve heat resistance by 5 to 10 ° C. The conditions of the electron beam irradiation are, for example, 800 Kev, 6 m at room temperature by a transformer rectifier type electron beam accelerator.
A, an electron beam of 2.1 × 10 ⁶ rad / sec.
Irradiate.

[0013]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples. Example 1 Ethylene vinyl acetate copolymer (trade name: Novatec EV
A LV540 ", vinyl acetate content 20%, MFR
2.5 g / 10 min, density 0.942 g / cm ³ , manufactured by Nippon Polychem Co., Ltd.) 100 parts by weight, azodicarbonamide 10 parts by weight, flour 30 parts by weight, zinc stearate 0.03 parts by weight, urea foaming aid 0.01 parts by weight, active zinc white 0.03 parts by weight, dicumyl peroxide 1.0
The composition consisting of parts by weight was kneaded with a mixing roll at 85 ° C., and a mold (400
(× 200 × 40 mm), and the mixture was heated under pressure for 80 minutes to form a foamable crosslinkable sheet. The foamable crosslinkable sheet had a gel fraction of 0. Then, the obtained foamable crosslinkable sheet is sealed with a non-hermetic open / close mold (1000 × 500 × 100) already heated to 170 ° C.
mm), heated with steam at 170 ° C. for 180 minutes by a jacket method, taken out after cooling, and obtained a foam. The obtained foam was passed five times between two constant-velocity rolls set at a roll interval of 20 mm to break the cell membrane, thereby allowing the cells to communicate. The obtained open cell had an apparent density of 0.05 g / cm ³ , an open cell ratio of 100%, and a cell diameter of about 1
mm. The obtained open-celled body has excellent water permeability,
After cutting into a rectangle of about 10 mm and using it as a carrier for bacteria in the septic tank, the effect of growing bacterial bacteria as a medium was remarkable.

Comparative Example 1 Example 1 was repeated except that no starch was added.
Under the same composition and under the same conditions as in Example 1, an open-cell foam was obtained. The obtained open-cell foam had an apparent density of 0.05 g / cm ³ and an open-cell ratio of 100%, but had poor water permeability and insufficient bacterial growth. Example 2 In Example 1, except that the starch was changed to 20 parts by weight.
An open cell was obtained under the same composition and under the same conditions as in Example 1.
The obtained open-cell foam has an apparent density of 0.05 g / c.
m ³ , 100% open cell rate and excellent water permeability, and was suitable as a medium for growing bacterial bacteria as in Example 1. Example 3 In Example 1, except that starch was changed to 50 parts by weight.
An open cell was obtained under the same composition and under the same conditions as in Example 1.
The obtained open-cell foam has an apparent density of 0.05 g / c.
m ³ , 100% open cell rate and excellent water permeability, and was suitable as a medium for growing bacterial bacteria as in Example 1. Comparative Example 2 In Example 1, except that the amount of starch was changed to 120 parts, foaming was performed under the same composition and under the same conditions as in Example 1. As a result, the foam shrank and a satisfactory foam could not be obtained. Example 4 In Example 1, 30 parts by weight of flour was replaced with potato starch 30.
An open-cell body was obtained under the same blending and foaming conditions as in Example 1 except that the amount was changed to parts by weight. The obtained open-cell foam was excellent in water permeability with an apparent density of 0.05 g / cm ³ and an open-cell ratio of 100%, and was suitable as a medium for growing bacterial bacteria as in Example 1. Example 5 An open-cell foam was obtained in the same manner as in Example 1 except that 30 parts by weight of wheat flour was changed to 30 parts by weight of sweet potato starch. The obtained open-cell foam was excellent in water permeability with an apparent density of 0.05 g / cm ³ and an open-cell ratio of 100%, and was suitable as a medium for growing bacterial bacteria as in Example 1.

[0015]

[Table 1]

[0016]

As described above, according to the present invention, in the process of producing a crosslinked polyolefin open cell, starch is kneaded into a substrate, foamed, and starch particles are mixed into a cell membrane and / or skeleton. Thereby, bacteria can be propagated as a medium and excellent in water permeability. For example, when used as a carrier for a septic tank, the purification action is promoted, and the medium is suitable as a carrier for bacteria.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 3:00) F-term (Reference) 4D003 EA14 EA19 EA21 EA30 EA38 FA02 4F074 AA03 AA10 AA16 AA17 AA18 AA19 AA20 AA22 AA23 AA25 BA13 BA15 BA16 BA17 BA18 BA19 BB02 CA30 CC06Y CC32X CC32Y CC34X CC42 CD01 CD11 DA13 DA32.

Claims (4)

[Claims] 1. A starch-containing cross-linked polyolefin open cell comprising starch particles in a cell membrane and / or skeleton. 2. The crosslinked polyolefin open cell according to claim 1, which contains 10 to 100 parts by weight of starch based on 100 parts by weight of polyolefin. 3. A foamable crosslinkable composition obtained by adding a foaming agent and a crosslinking agent to polyolefin is heated and foamed in a non-hermetic mold to form a foam, and then mechanically deforms the foam to make it open. A method for producing an open-cell, crosslinked polyolefin containing starch, comprising adding starch to a polyolefin, kneading the mixture, and foaming. 4. Starch per 100 parts by weight of polyolefin
2. The composition according to claim 1, wherein 0 to 100 parts by weight are added.
The manufacturing method as described.