JP2002020532A - Cross-linked foamed material of continuously foaming polyolefin-based resin and carrier material for propagating microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinked foamed material of a continuously foaming polyolefin-based resin, excellent in air-ventilating property and water-absorbing property, and also in fluidityin floating and sinking in water and abrasion resistance, and especially capable of being suitably used as a carrier material for propagating microorganisms. SOLUTION: This crosslinked foamed material of a continuously foaming polyolefin-based resin is characterized by exhibiting <=10 sec time for penetrating 50 cm3 air on applying 5.56 N air pressure through a part having 314 mm2 area and 10 mm thickness in thickness direction, and having 6-50 average number of air bubbles on 25 mm straight line length and also 20-80% ratio of average broken membrane area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked foam of an open-celled polyolefin resin which can be suitably used as a support for propagation of microorganisms, and a support for propagation of microorganisms comprising the crosslinked foam of an open-celled polyolefin resin. .

[0002]

2. Description of the Related Art Conventionally, open-celled polyolefin resin crosslinked foams have been used in many fields as cushioning materials and the like. As a method for producing an open-celled polyolefin-based resin crosslinked foam, for example, Japanese Patent Application Laid-Open No. 56-121739 describes a method in which a polyolefin-based resin is crosslinked and foamed, followed by mechanical deformation to open cells. ing. However, in the manufacturing method, fine communication holes are partially formed in the bubble film, and the bubbles are communicated.
Even if the obtained open-celled crosslinked foam has a high open-cell ratio, it is not suitable for applications requiring air permeability, water absorption, etc., since the air permeability and water absorption are insufficient, and thus are not suitable.

On the other hand, the activated sludge method has been generally used in the treatment of sewage treatment tanks for domestic and industrial effluents, combined septic tanks, garbage disposers, biological deodorizers, and the like, but requires large equipment. In addition, there are problems such as insufficient reduction of nitrogen and phosphorus that cause red tide,
In recent years, treatment methods that effectively utilize microorganisms have been studied in order to make equipment as small as possible and further improve the treatment capacity.

In the above-mentioned treatment method using microorganisms, it is effective to use a carrier for propagation of microorganisms.
Examples of the carrier for propagation of microorganisms include, for example, a particulate gel or fiber made of polyethylene glycol, polyvinyl alcohol, polyurethane, or the like, which is aggregated and fused. However, the granular gel has a problem that the water contact area per volume and the microbial breeding area per volume are small and inefficient, and the fibrous body is easily defibrated when used in flowing rotating water for a long period of time. Due to the small size, there is a problem that the inside is liable to be clogged when the microorganisms adhere, and the effect of propagation of the microorganisms inside is difficult to maintain. As a method of solving the above problem, an open-cell porous body made of a polyurethane resin, cellulose, etc. has been proposed, but durability in water in a treatment tank, abrasion resistance, etc. are insufficient, and There was a problem that it was unbearable for use.

As a method for solving the above problem, there is a method using an open-celled cross-linked foam made of a polyolefin resin having excellent abrasion resistance. The obtained open-celled polyolefin-based resin cross-linked foam has a problem that the air permeability and water absorption are insufficient for use as a carrier for propagation of microorganisms. In addition, for example, Japanese Patent Application Laid-Open No. 5-96288 discloses that a polyethylene communicating foam is used as a carrier for breeding microorganisms in a specific sewage treatment tank,
Japanese Patent Application Laid-Open No. Hei 10-193425 describes a carrier for propagation of microorganisms composed of an extruded foam having penetrating cells, semi-permeating cells and closed cells, but still has insufficient air permeability, water absorption and the like. In many cases, there is a problem that water hardly penetrates into the inside of the carrier for propagation of microorganisms, or water inside the carrier for propagation of microorganisms is hard to move and convert, and the effect of propagation of microorganisms is not efficient.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an open cell which is excellent in air permeability and water absorbency, excellent in floating and sinking fluid in water and abrasion resistance, and particularly suitable for use as a carrier for propagation of microorganisms. It is an object of the present invention to provide a crosslinked polyolefin resin foam. Another object of the present invention is to
An object of the present invention is to provide a carrier for propagation of microorganisms, which is made of the above-mentioned cross-linked foam of open-celled polyolefin resin and in which microorganisms easily adhere and propagate on the surface.

[0007]

The crosslinked foam of the open-celled polyolefin resin of the present invention (hereinafter referred to as "open-celled crosslinked foam") has an area of 314 mm ² and a thickness of 10 mm.
When the air pressure of 5.56 N is applied in the thickness direction, the time for air of 50 cm ³ to permeate is 10 seconds or less,
In addition, the average number of bubbles on a straight line having a length of 25 mm in the cross section is 6 to 50, and the average rupture area ratio in the cross section is 20 to 80%.

The polyolefin resin constituting the open-cell crosslinked foam of the present invention includes, for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-based ethylene. α-olefin copolymer, ethylene-vinyl acetate copolymer containing ethylene as a main component, ethylene-ethyl acrylate copolymer containing ethylene as a main component, polypropylene, propylene-α-olefin copolymer containing propylene as a main component Coalesce, propylene-based ethylene-propylene-butene terpolymer, polybutene, and the like, and these may be used alone or in combination of two or more. As the α-olefin constituting the ethylene-α-olefin copolymer, for example, propylene, 1-
Butene, 1-pentene, 4-methyl-1-pentene, 1
-Hexene, 1-heptene, 1-octene, and the like. Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, and 4-methyl-1. -Pentene, 1-
Hexene, 1-heptene, 1-octene and the like can be mentioned.

In many cases, the specific gravity of the polyolefin resin is smaller than that of water. When the open-celled crosslinked foam obtained from the polyolefin resin is used as a carrier for propagation of microorganisms, water completely penetrates into the inside thereof. However, depending on the aeration conditions, the material may float, and the initial fluidity of floating in water is reduced. Therefore, it is preferable to add an inorganic filler.

Examples of the inorganic filler include calcium carbonate, talc, barium sulfate, aluminum hydroxide, zeolite and the like. These may be used alone or in combination of two or more. When the amount of the inorganic filler is small, the effect cannot be obtained when the amount is small, and when the amount is large, the specific gravity is too large than that of water, the fluidity in water is lowered, and it is difficult to foam at the foaming stage. The amount is preferably from 10 to 80 parts by weight, more preferably from 20 to 60 parts by weight, based on 100 parts by weight, adjusted so that the specific gravity of the polyolefin-based resin after the addition of the inorganic filler is equal to or slightly larger than water. Is preferred.

The open-cell crosslinked foam of the present invention comprises the above-mentioned polyolefin-based resin and the above-mentioned inorganic filler optionally added, and has an area of 314 mm ² and a thickness of 10 mm.
When the time required for 50 cm ³ of air to pass through when the air pressure of 5.56 N is applied in the thickness direction (hereinafter referred to as “air permeability”) becomes longer, the air permeability of the open-cell cross-linked foam increases. And when used as a carrier for propagation of microorganisms, it is difficult for air inside to escape from water, and it is easy to hold air bubbles of aeration inside, and in any case, the fluidity of floating and sinking in water is reduced. In addition, it is difficult to freely move water inside the carrier for propagation of microorganisms, it is difficult to convert water inside the carrier for propagation of microorganisms, and the efficiency of propagation of microorganisms is reduced. 5 seconds or less.

The above air permeability is a value measured using a B-type Gurley type densometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.). Specifically, a thickness of 1 mm from an arbitrary portion of the open-celled crosslinked foam.
A sample of 0 mm is collected, and the sample is sandwiched between two clamping plates having a circular hole of 314 mm ² in such a manner that the thickness direction of the open-cell crosslinked foam is clamped, and set on a B-type Gurley densometer. . One of the samples set in the densometer is open, and the other is a closed airtight space. Next, an air pressure of 5.56 N is applied in the sample thickness direction from the airtight space side so as not to contact the sample,
At this time, the time (air permeability) required for 50 cm ³ of air to pass through the sample is measured. When the thickness of the open-celled crosslinked foam is less than 10 mm, the measurement is performed by laminating.

When the average cell diameter of the above-mentioned open-celled crosslinked foam becomes small, the air permeability and water absorption of the open-celled cross-linked foam decrease, and when the cell is used as a carrier for propagation of microorganisms, the internal air in the water is reduced. It is difficult to remove, and it is easy to hold aerated air bubbles inside, and in both cases, the fluidity of floating in water is reduced, and even if microorganisms adhere and propagate,
Clogging makes it difficult for water to move freely inside the microorganism propagation carrier, and water containing oxygen does not reach the inside of the open-celled cross-linked foam, and the microorganisms are easily killed. When the foamed cross-linked foam is used as a carrier for microbial propagation, the contact area between the open-cell cross-linked foam and water per volume decreases, thereby reducing the area where microorganisms adhere and reducing the microbial propagation efficiency. Therefore, the average number of cells on a straight line having a length of 25 mm in the cross section of the open-cell crosslinked foam is limited to 6 to 50, preferably 12 to 30, and more preferably 15 to 25. .

The average number of cells in the cross section of the open-cell crosslinked foam is a value measured by the following method. First, the open-cell cross-linked foam is cut at an arbitrary portion in the thickness direction, and when the cut surface is an xy surface, the yz surface and the zx surface are cut in a direction in which the cross section is formed. 2
A 5 mm dimensional scale is photographed on the same screen by an electron microscope to obtain a photograph magnified about 10 times. A straight line having the same length as the 25 mm dimensional scale in the photograph was drawn on an arbitrary part of the obtained photograph, the number of bubbles on the straight line was counted, and the number of bubbles on each cross section was averaged to obtain the open cell property. The average number of cells in the cross section of the crosslinked foam. In the present invention, the term “bubble” refers to a portion surrounded by a bubble film in a photographing section (does not consider the bubble film seen in the back of the photographing section), regardless of the presence or absence of communication of the bubble film. Bubble. In the photographing, it is preferable that the photographing is performed after the cross section of the open-celled crosslinked foam is colored with a coloring agent such as Magic Ink (registered trademark) because bubbles can be easily identified.

When the average rupture area ratio of the open-celled crosslinked foam becomes small, the permeability and water absorption of the open-celled crosslinked foam decrease, and when the foam is used as a carrier for propagation of microorganisms, it has an internal It is difficult for air to escape, and it is easy to retain aerated air bubbles inside.In each case, the fluidity of floating in water is reduced. When used as a carrier for propagation of microorganisms, the contact area between the open-celled cross-linked foam and water per volume is reduced, thereby reducing the area where microorganisms adhere and decreasing the efficiency of microorganism reproduction.
It is limited to 0%, preferably 30 to 60%.

The average area ratio of the ruptured membrane is a value measured by the following method. First, the open-cell crosslinked foam is cut at an arbitrary portion in the thickness direction.
In the case of the y-plane, the film is cut in a direction in which the yz-plane and the zx-plane are cross-sections, and photographed with an electron microscope at about 25 times magnification. In the photographs of the obtained cross sections, the area ratio of the portion where the bubble film of the five bubbles is broken to become a black cavity with respect to the total area of the five closely assembled bubbles is calculated. The value obtained by averaging the area ratio is the average rupture area ratio. More specifically, five closely assembled bubbles in the photographing cross section are copied on a transparent graph paper, and the bubble film is broken in the five bubbles to form a black cavity seen in the back of the photographing cross section. Copy the part on the same transparent graph paper. Five bubbles are cut out from the copied graph paper, and the weight W ₁ (mg) is measured. next,
Of the five air bubbles, a portion where the air bubble film was broken and became a black cavity was cut out from the graph paper, and its weight W ₂ (m
g) is measured. From the obtained measured values, the rupture area ratio is calculated by the following equation. Breakage area ratio (%) = (W ₂ / W ₁ ) × 100 After calculating the above-mentioned breakage area ratios at five arbitrary portions for each photograph of the cross section, all values are averaged, and the average breakage area is calculated. Calculate the ratio (%). In the above photographing, photographing after vapor deposition of gold on the cross section of the open-celled cross-linked foamed body makes the image of the bubble film and the portion where the bubble film is broken clear and easy to distinguish. It is preferred.

The gel fraction of the open-celled crosslinked foam is as follows:
When it is smaller, the strength and durability are reduced, and when it is larger, the air permeability and the average rupture area ratio are difficult to be in the above ranges, the air permeability and the water absorption are reduced, and when used as a microorganism propagation support, It is difficult for air inside to escape,
The content is preferably 30 to 70% by weight because air bubbles for aeration are easily retained inside and the floating and sinking fluidity in water is reduced in any case.

The above gel fraction is a value calculated by the following method. First, the open-cell cross-linked foam is about 100 m
g of the sample is taken as a sample, and the dry weight W ₃ (mg) of the sample is measured. Next, the air bubbles of the sample were crushed, placed in 50 ml of xylene at 120 ° C., and allowed to stand for 24 hours, passed through a 200-mesh wire net, and the dry weight W ₄ of the residue on the wire net was removed.
(Mg), and calculate the gel fraction by the following formula. Gel fraction (% by weight) = (W ₄ / W ₃ ) × 100

As the apparent density of the open-cell crosslinked foam becomes smaller, it becomes easier to set, and as it becomes larger, the open cell ratio tends to become lower and the cell membrane becomes thicker. The area ratio is unlikely to be in the above range, the air permeability and water absorption are reduced, and when used as a carrier for propagation of microorganisms, it is difficult for the internal air to escape in water, and
It is easy to hold the air bubbles of aeration inside, and in any case, the fluidity of floating and sinking in water is reduced, so that 0.01 to 0.1 g / cm
³ , more preferably 0.02 to 0.05 g /
cm ³ . The apparent density is a value obtained by measuring the weight W ₅ (g) and the volume D (cm ³ ) of the open-cell crosslinked foam and calculating the value by the following equation. Apparent density = W ₅ / D

In addition, the open-celled crosslinked foam has a skin layer which is not generally communicated at the stage of its production. Therefore, when the foam is used for a carrier for propagation of microorganisms, the skin layer is removed. Is preferred. The method for removing the skin layer is not particularly limited. For example, any conventionally known method such as a method for slicing and removing the surface may be adopted.

As a method for producing the open-celled crosslinked foam, for example, in addition to the above-mentioned polyolefin resin to which the above-mentioned inorganic filler is added, if necessary, in addition to a pyrolytic foaming agent,
If necessary, a crosslinking agent, a foaming aid, etc. are added, and the mixture is melt-kneaded at a temperature at which the thermal decomposition type foaming agent is not substantially decomposed, molded into a predetermined shape, and then heated and crosslinked and foamed. There is a method in which bubbles are communicated by applying mechanical deformation to the foam, and then the communication holes are further enlarged.

The pyrolytic foaming agent is not particularly limited, and any conventionally known one may be used. Examples thereof include azodicarbonamide, azobisisobutyronitrile, p-toluenesulfonylhydrazide, Examples thereof include nitrosopentamethylenetetramine and 4,4′-oxybisbenzenesulfonylhydrazide, which may be used alone or in combination of two or more. Among them, azodicarbonamide is preferable because it is excellent in the amount of generated gas, safety in handling, and the like. The amount of the pyrolytic foaming agent to be added is appropriately adjusted according to the desired apparent density of the obtained open-cell crosslinked foam, but is generally 5 to 30 parts by weight based on 100 parts by weight of the polyolefin resin. Is preferred.

The crosslinking agent is not particularly limited.
Any conventionally known one may be used, for example, dicumyl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, di-t
-Butyl peroxide, 2,5-dimethyl-2,5-
Organic peroxides such as di (t-butylperoxy) hexene-3 may be used, and these may be used alone or in combination of two or more. The amount of the cross-linking agent to be added is appropriately adjusted according to the desired gel fraction, but is generally preferably 0.2 to 1.5 parts by weight based on 100 parts by weight of the polyolefin resin.

Further, a silane compound may be grafted onto the polyolefin resin without adding the crosslinking agent, so that the polyolefin resin is previously crosslinkable.
The silane compound is not particularly limited, and any conventionally known one may be used. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxysilane, vinyldiethoxysilane, 3-methacryloxypropyltrisilane Ethoxysilane and the like can be mentioned.

Further, crosslinking may be performed by irradiation with ionizing radiation. Examples of ionizing radiation include electron beams,
α-rays, β-rays, γ-rays and the like can be mentioned, and the irradiation amount may be appropriately adjusted.

The foaming auxiliary is not particularly limited, and any conventionally known one may be used.
Examples thereof include zinc oxide, urea or a derivative thereof, magnesium stearate, and zinc stearate. These may be used alone or in combination of two or more. The foaming aid adjusts the decomposition temperature, decomposition rate, and the like of the pyrolytic foaming agent. The amount of the foaming aid depends on the production conditions, the amount of the foaming agent, the size of the cells of the obtained open-cell crosslinked foam, and the like. It is adjusted appropriately according to. When the polyolefin-based resin, the cross-linking agent compounding and the like are the same, and the foaming conditions and the like are the same,
It is preferable to adjust the size and the like of the cells of the obtained open-celled crosslinked foam by changing the relative speed of the foaming with respect to the crosslinking reaction with a foaming aid.

In the above-mentioned polyolefin-based resin, conventionally known optional additives such as a lubricant and a pigment may be appropriately added as required.

The method of melt-kneading a polyolefin resin to which the above-mentioned various additives are added (hereinafter referred to as “resin composition”), forming the resin into a predetermined shape, and then heating and cross-linking and foaming the resin, particularly includes: There is no limitation, and any conventionally known method may be employed.For example, after the resin composition is melt-kneaded by a conventionally known method such as a Banbury mixer or a roll, it is poured into a concave or press mold having a predetermined shape, and For example, there is a method in which molding is performed by holding for a period of from one minute to several tens of minutes, and thereafter, further heating is performed to substantially simultaneously perform crosslinking and foaming. In the molding, it is preferable to maintain the temperature at such a level that a part of the crosslinking agent is decomposed.

As a method of applying mechanical deformation to the crosslinked foam to allow the bubbles to communicate, for example, a method of passing between a pair of rolls having a smaller clearance than that of the crosslinked foam may be mentioned. Clearance between rolls, roll speed ratio,
The number of times the crosslinked foam is passed through the roll may be adjusted as appropriate.
In addition, even if the cells of the cross-linked foam are communicated by the mechanical deformation, the communication holes are often fine, and the air permeability and the average rupture area ratio do not fall within the above ranges. Enlarge the communication holes for bubbles.

As a method of expanding the communication holes for the bubbles, a closed container is filled with a cross-linked foam, and the inside of the closed container is sufficiently degassed. There is a method of igniting gas and combustible gas.

The above-mentioned closed container is not particularly limited as long as it can be filled with a cross-linked foam and can make the inside of the container into a vacuum state, and the shape, size and the like may be appropriately determined. If the gap between the cross-linked foam to be filled and the inner wall of the closed container is too large, the cross-linked foam in the vicinity of the gap is easily set when the combustible gas is burned. It is preferable to make them the same shape. Also, in order to make the cross-linked foam the same volume and shape as the closed container,
The crosslinked foam may be cut or laminated.

As a method for degassing the closed container, for example, a method in which a vacuum pump is attached to the closed container and air in the closed container is evacuated by the vacuum pump can be used. If the degassing is insufficient, the expansion of the communication hole will be insufficient,
This is performed sufficiently until the inside of the cells of the crosslinked foam becomes a vacuum.

The method for injecting the oxygen gas and the flammable gas into the closed container is not particularly limited.
From a high-pressure cylinder filled with oxygen gas and flammable gas, adjust the partial pressure to match the desired mixing ratio with a pressure reducing valve and inject it into a closed container through a gas mixing mixer.From a high-pressure cylinder filled with oxygen gas and flammable gas A method in which the pressure is adjusted to a partial pressure suitable for a desired mixing ratio by a pressure reducing valve, and the mixture is injected from different injection ports. Immediately after gas injection, the gas dispersion state in the closed container is not uniform, so it is preferable that the gas is left for several minutes after injection.

The combustible gas is not particularly limited as long as it can burn in the presence of oxygen gas.
Examples include hydrogen gas, methane gas, and propane gas.

The mixing ratio of the above-mentioned oxygen gas and combustible gas is not particularly limited as long as it is in a combustible range when ignited. For example, when hydrogen gas is used as the combustible gas, the ratio of oxygen gas to hydrogen gas is preferably about 1: 2 by volume ratio (pressure ratio).

When the pressures of the oxygen gas and the combustible gas are low, when ignited, the expansion of the communication holes of the bubbles becomes insufficient, and the air permeability and the average rupture area ratio of the obtained open-cell cross-linked foam are reduced. Is easily out of the above range, air permeability and water absorption are reduced, when used as a carrier for propagation of microorganisms, it is difficult for air inside to escape in water, and also easy to hold aerated air bubbles inside, In the case of, the floatability in water also decreases,
When the temperature is increased, the crosslinked foam is easily sagged when ignited. Therefore, the pressure is preferably 0.05 to 0.3 MPa, more preferably 0.08 to 0.15 MPa.

If the pressures of the oxygen gas and the combustible gas are within the above ranges, other inert gases may be mixed. Examples of the inert gas include a nitrogen gas, a helium gas, an argon gas, a carbon dioxide gas and the like, and these may be used alone or in combination of two or more.

As a method of igniting after injecting the oxygen gas and the combustible gas into the closed container, for example, a method in which a spark switch is previously installed in the closed container and sparking is performed.

The open-cell crosslinked foam of the present invention is suitably used as a carrier for propagation of microorganisms. When used as a carrier for propagation of microorganisms, the smaller the size, the easier it is to drain the treated water when discharged, and the larger the size, the more difficult it is for water to move inside the carrier for propagation of microorganisms. Is preferably a substantially cubic shape or a substantially rectangular shape having a side of 0.5 to 2 cm. In the case of a carrier for propagation of microorganisms for deodorization which does not need to flow in water, this is not always the case.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Examples 1 to 6, Comparative Examples 1 to 6) A predetermined amount of low-density polyethylene shown in Table 1 (density 0.921 g /
cm ³ , melt index 2 g / 10 min), ethylene-vinyl acetate copolymer (vinyl acetate content 9% by weight, density 0.940 g / cm ³ ), barium sulfate, azodicarbonamide, dicumyl peroxide and zinc stearate Is melt-kneaded at about 125 ° C. with a Banbury mixer, filled in a concave mold having a recess of 160 mm × 100 mm × 25 mm in depth, held at about 140 ° C. for 30 minutes, and molded into a predetermined shape. A molded article was obtained. During molding, part of dicumyl peroxide was decomposed, but azodicarbonamide was not decomposed. Thereafter, the molded body was heated to about 170 ° C. and was 500 mm long × 500 m wide.
The resultant was transferred to a concave mold having a concave portion having a dimension of mx 80 mm in depth, sealed, and then subjected to crosslinking and foaming to obtain a crosslinked foam having the same shape as the concave portion.

After cooling, the obtained cross-linked foam was passed through two rolls having a clearance of 6 mm several times to be compressed, and after allowing the bubbles to communicate, the skin layer on the surface was removed. After sealing and filling in a cubic closed container, the inside of the closed container was sufficiently degassed using a vacuum pump until the inside of the cells of the crosslinked foam became a vacuum. Thereafter, a mixed gas in which oxygen gas and hydrogen gas were mixed at a volume ratio of 1: 2 was injected until the pressure reached a predetermined pressure shown in Table 1, and the mixture was allowed to stand for 3 minutes. Further, sparks were ignited by using a spark switch in the filling container, and after burning the mixed gas, the closed container was opened to obtain an open-cell crosslinked foam. The air permeability, the average number of cells in the cross section, the average membrane rupture area ratio, and the apparent density of the obtained open-cell crosslinked foam were as shown in Table 1, and the gel fraction was 50 to 56 in all cases.
%Met. In addition, about the comparative example 6, it did not foam at the foaming stage, and the crosslinked foam was not obtained.

About the open-celled crosslinked foams obtained in Examples 1 to 6 and Comparative Examples 1 to 5, and the open-celled polyurethane resin foam (comparative example 7) which is commercially available as a carrier for propagation of microorganisms The following evaluation was performed, and the results are shown in Table 1.
It was shown to.

(Abrasion resistance) Open-cell crosslinked foam and open cell
Cut the open cell polyurethane resin foam, and cut one side
Create 10 1cm cubic specimens and 10 specimens
Dry weight W of ₆(Mg) was measured. Next, vertical 20
cm × 20cm × 30cm depth concrete slab
The water tank made of water is almost completely filled with water at a water temperature of about 20 ° C.
Ten samples were charged. After that, 300 rotations /
Minutes, the sample was taken out after 60 days, and
Total dry weight W₇(Mg) was measured. Obtained measurements
The weight loss rate was calculated from the following equation. Weight loss rate (% by weight) = ｛(W₆-W₇) / W₆｝ × 100

(Floating and sinking and flowing in water) The open-celled crosslinked foam and the open-celled polyurethane resin foam were cut to prepare 400 cubic samples each having a side of about 1 cm. Next, a concrete slab water tank having a length of 20 cm, a width of 20 cm, and a depth of 30 cm is almost completely filled with a glucose aqueous solution (glucose concentration of about 1 mg / cm ³ ) at a water temperature of about 20 ° C.
400 samples and a small amount of microorganisms (activated sludge) were put therein. Thereafter, aeration at 1500 cm ³ / min was continued from the bottom of the water tank, and after 3 days, the water surface was visually observed as an investigation of the state of floating and sinking and flowing of the sample in water, and evaluated as follows. A: There was no sample floating on the water surface (flying rate 0
%) ○: 1 to 40 samples floating on the water surface (floating rate 10% or less) Δ: 41 to 100 samples floating on the water surface (floating rate 10 to 25% or less) ×: There were 101 or more samples floating on the water surface (floating rate was more than 25%)

(Microbial Adhesion) The open-celled cross-linked foam and the open-celled polyurethane resin foam were cut into cubes each having a side of about 1 cm to form 10 samples. Was put in a mesh bag, immersed in a general aeration / aerobic household wastewater treatment tank, and the mesh bag was taken out after 14 days. Next, take out ten samples from the mesh bag,
Put the 10 samples taken out into 80 cm ³ of distilled water,
The sample was squeezed several times with tweezers to remove the microorganisms attached to the sample. Further, the sample was placed in another 80 cm ³ of distilled water, the sample was squeezed in the same manner as described above, and the microorganisms attached to the sample were separated. Thereafter, the sample was further placed in another 80 cm ³ of distilled water, the sample was squeezed in the same manner as described above, and the microorganisms attached to the sample were peeled off. Then, ultrasonic vibration was applied to substantially completely remove the microorganisms from the sample. Distilled water (80
cm ³ × 3) (hereinafter referred to as “dispersion liquid”), the concentration of the dispersion liquid was measured by light transmission, and from the relationship between the previously measured turbidity and the microorganism dispersion concentration, The concentration of microorganisms in the dispersion was determined, and the amount of microorganisms in the dispersion (sample 10
The amount of microorganisms adhering to the individual) was calculated, and the ratio of adhered microorganisms was further calculated by the following equation. Microorganism attachment ratio (mg / cm ³ ) = microorganism amount (mg) in dispersion / volume of 10 samples (cm ³ )

[0047]

[Table 1]

[0048]

The open-celled polyolefin-based resin crosslinked foam of the present invention has excellent abrasion resistance derived from the polyolefin-based resin, and has not only a high open-cell rate but also air permeability and water absorption. It is easy to escape air when put into water, and does not hold air bubbles such as aeration inside for a long time, it is excellent in floating and sinking in water, and it is hard to clog, Since the water inside is easily transferred and converted, and water containing oxygen can always be supplied to the inside, it is easy for microorganisms to adhere and propagate, and it can be suitably used particularly as a carrier for propagation of microorganisms. In addition to the carrier for propagation of microorganisms, it can be suitably used for applications requiring air permeability and water absorption, such as various filters and mats.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4B029 AA21 BB01 CC02 CC10 4D003 AA12 EA01 EA19 EA30 EA38 4F074 AA16 AA17 AA18 AA19 AA20 AA21 AA22 AA23 AA24 AA25 AA26 AC20 AC26 AC30 AC32 AC36 BA18 BA18 BA13 BA18 BB25 CA23 CC04Y CC06Y CD01 DA10 DA13 DA59

Claims (4)

[Claims] 1. A part having an area of 314 mm ² and a thickness of 10 mm is cut by 50 c when an air pressure of 5.56 N is applied in the thickness direction.
m ³ air permeation time is 10 seconds or less, and
The open-cell polyolefin-based resin characterized in that the average number of cells on a straight line having a length of 25 mm in the cross section is 6 to 50, and the average film-breaking area ratio in the cross section is 20 to 80%. Crosslinked foam. 2. The open-celled polyolefin-based resin according to claim 1, wherein the open-celled polyolefin-based resin cross-linked foam comprises 100 parts by weight of a polyolefin-based resin and 10 to 80 parts by weight of an inorganic filler. Crosslinked resin foam. 3. The cross-section of the open-celled polyolefin-based resin cross-linked foam has an average number of cells on a straight line having a length of 25 mm of 15 to 25, and an average film rupture area ratio of 30 to 40 on the cross section. The open-celled crosslinked polyolefin-based resin foam according to claim 1 or 2, wherein the crosslinked foam is 60%. 4. A carrier for propagation of microorganisms, comprising a cross-linked foam of the open-celled polyolefin-based resin according to any one of claims 1 to 3.