JP2017179078A - Polyolefin resin composition porous body and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin composition porous body having excellent antibacterial and freshness retaining properties, and a method of producing the same.SOLUTION: The present invention provides a polyolefin resin composition porous body containing (A) polyolefin resin and (B) powder containing a shell fired product, and a method for producing the same.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a polyolefin resin composition porous body useful for packing and cushioning materials for transportation and / or preservation of fruits and vegetables, marine products, etc., a nursery bed for plant cultivation, a culture medium and the like, and a method for producing the same.

  For the transportation and storage of fruits and vegetables, marine products, etc., plastic foam containers such as polyolefins such as polyethylene and polypropylene, polystyrene and polyurethane are widely used. These containers are required to have better antibacterial properties and freshness retention from the viewpoint of increasing consumer needs for fresher and more delicious vegetables, fruits, seafood, etc., and food safety. . In particular, in recent years, there is a great need from the viewpoint of maintaining freshness during the period of transporting what is harvested in a remote area to a consumption area. In the agricultural and horticultural fields, bacteria are generated during the cultivation of plants such as vegetables and flowers, and the cultivation is contaminated and withered or partly rots to reduce the product value, or after growing until harvest There is a growing demand for prevention of these problems.

  In order to meet such demands, various materials have been developed that impart antibacterial properties and freshness retention to plastic foams. For example, Patent Document 1 proposes a foam in which an antibacterial agent made of a silver-based zeolite compound is added to a mixture containing starch, foaming plastic, and a modifier. Patent Document 2 proposes a foam packaging material carrying silver-containing tobermorite to impart freshness retention.

Japanese Patent Laying-Open No. 2015-124290 JP-A-6-40476

However, against the background as described above, there is an increasing demand for antibacterial properties and freshness retention properties for plastic foams, and it is becoming difficult for the materials of Patent Documents 1 and 2 to sufficiently meet these demands. is there.
This invention is made | formed in view of such a situation, and makes it a subject to provide the polyolefin resin composition porous body excellent in antibacterial property and freshness-keeping property, and its manufacturing method.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a polyolefin resin composition porous body containing a polyolefin resin and a powder containing a fired product of shells having antibacterial properties. And it discovered that it was excellent in the freshness maintenance property, and came to complete this invention.

That is, the present invention relates to the following [1] to [8].
[1] A polyolefin resin composition porous body containing (A) a polyolefin resin and (B) a powder containing a fired product of shells.
[2] The polyolefin according to [1] above, wherein the content of the powder containing the fired product of (B) shell is 0.7 to 15 parts by mass with respect to 100 parts by mass of (A) polyolefin resin. -Based resin composition porous body.
[3] The polyolefin resin composition porous body according to the above [1] or [2], wherein the average particle diameter of the powder containing the fired product of (B) shell is 1 to 15 μm.
[4] The polyolefin-based resin composition porous body according to any one of the above [1] to [3], wherein the powder containing the fired product of (B) shell is a powder made of the fired shell.
[5] The polyolefin resin composition porous body according to any one of the above [1] to [4], wherein the open cell ratio measured by the following method is 60% or more.
[Measurement method of open cell ratio]
A test piece of polyolefin resin composition porous body is immersed in water at 23 ° C., and compression and restoration are repeated until no air bubbles are generated in water. The test piece is allowed to absorb water, and the maximum water absorption is measured. The maximum water absorption (%) was calculated according to
Maximum water absorption rate (%) = (maximum water absorption / mass of test specimen before water absorption) × 100 (1)
Next, the open cell ratio was calculated from the maximum water absorption rate (%) obtained by the above formula (1) according to the following formula (2).
Open cell ratio (%) = (maximum water absorption × apparent density of test piece) / density of water at 23 ° C. (2)
[6] The polyolefin resin composition porous body according to any one of the above [1] to [5], wherein the (A) polyolefin resin is an ethylene vinyl acetate copolymer.
[7] A step of producing a closed-cell polyolefin-based resin composition foam containing (A) a polyolefin-based resin and (B) a powder containing a fired product of shells;
A step of adding mechanical deformation to the obtained closed-cell polyolefin resin composition foam to form continuous cells;
The manufacturing method of the polyolefin resin composition porous body in any one of said [1]-[6] which has.
[8] The closed-cell polyolefin-based resin composition foam is produced using (A) an ethylene vinyl acetate copolymer as the polyolefin-based resin and 4,4′-oxybis (benzenesulfonic acid hydrazide) as the foaming agent. The method for producing a porous polyolefin resin composition according to [7] above.

  ADVANTAGE OF THE INVENTION According to this invention, the polyolefin resin composition porous body excellent in antibacterial property and freshness maintenance property, and its manufacturing method can be provided.

[Polyolefin resin composition porous body]
The polyolefin resin composition porous body of the present invention (hereinafter also simply referred to as “porous body”) comprises (A) a polyolefin resin (hereinafter also referred to as “component (A)”) and (B) a fired product of shells. Containing powder (hereinafter also referred to as “component (B)”).
The baked shellfish has calcium hydroxide as a main component and exhibits strong alkalinity around pH 13, and therefore has the ability to decompose bacteria. Therefore, the fired product of shells has antibacterial, deodorant and antioxidant effects, and also has a food freshness retaining effect. The polyolefin resin composition porous body of the present invention has two functions of antibacterial properties and freshness retention properties that are superior to those of conventional containers, in addition to containing a fired product of shells and a porous body shape. Can be granted.
In the present specification, the “main component” means a component occupying a proportion exceeding 50 mass% of all the constituent components.

<(A) Polyolefin resin>
(A) A polyolefin resin is a polymer containing a structural unit derived from an olefin in one molecule, and is obtained by polymerizing a monomer component containing an olefin.
(A) Polyolefin resin is, for example, a homopolymer of one olefin, a copolymer of two or more olefins, a copolymer of one or more olefins and one or more copolymerization components other than olefins. Etc. In addition, the form of copolymerization of the copolymer is not particularly limited, and may be, for example, a block copolymer or a random copolymer.
Examples of the olefin include olefins having 2 to 20 carbon atoms such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, and decene, and have antibacterial properties, freshness retention, and mechanical strength of the porous body. From the viewpoint of productivity and economy, an olefin having 2 to 10 carbon atoms is preferable, an olefin having 2 to 4 carbon atoms is more preferable, and ethylene or propylene is further preferable. These olefins are preferably α-olefins.
(A) Specific examples of polyolefin resins include polyethylene resins, polypropylene resins, polyethylene propylene copolymers, ethylene vinyl acetate copolymers, etc. Among these, antibacterial properties and freshness retention of porous materials From the viewpoints of mechanical strength, productivity and economy, polyethylene resins, polypropylene resins and ethylene vinyl acetate copolymers are preferred.

(Polyethylene resin)
The polyethylene resin is a polymer containing a structural unit derived from ethylene in one molecule, and is obtained by polymerizing a monomer component containing ethylene.
The polyethylene resin may be a homopolymer of ethylene or a copolymer of ethylene and a copolymer component other than ethylene. However, a copolymer of ethylene and vinyl acetate and a polyethylenepropylene copolymer are not classified as polyethylene resins in this specification.
Examples of the polyethylene resin include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, a copolymer of ethylene and α-olefin, an ethylene-vinyl alcohol copolymer, and an ethylene- (meth) acrylic acid copolymer. And ethylene- (meth) acrylate copolymers such as ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate copolymer. Among these, low density polyethylene is preferable from the viewpoint of the antibacterial property, freshness retention, mechanical strength, productivity, and economy of the porous body.
When the polyethylene resin is a copolymer, the content of the structural unit derived from ethylene in the copolymer is usually relative to the total number of moles of the structural unit derived from ethylene and the structural unit derived from the copolymer component, It is 50 mol% or more, and may be, for example, 70 mol% or more, or 90 mol% or more, depending on the desired performance.
A commercially available product can be used as the polyethylene resin, and examples of the commercially available polyethylene resin include Petrocene (registered trademark) (trade name, manufactured by Tosoh Corporation).
The MFR (melt flow rate) defined in JIS K 7210 of the polyethylene resin is preferably 0.5 to 10 g / 10 min, more preferably 1 to 5 g / 10 min, from the viewpoint of the productivity and mechanical strength of the porous body. 1.5 to 3 g / 10 min is more preferable.
In the present specification, “(meth) acrylic acid” means one or more selected from “acrylic acid” and “methacrylic acid”, and “(meth) acrylate” means “acrylate” and “ It means one or more selected from “methacrylate”.

(Polypropylene resin)
Polypropylene resin is a polymer containing a structural unit derived from propylene in one molecule, and is obtained by polymerizing a monomer component containing propylene.
The polypropylene resin may be a homopolymer of propylene or a copolymer of propylene and a copolymer component other than propylene. However, the polyethylene propylene copolymer is not classified as a polypropylene resin in this specification.
Examples of the polypropylene resin include a homopolymer of propylene, a copolymer of propylene and α-olefin, a copolymer of propylene and alkyl (meth) acrylate, and the like.
When the polypropylene resin is a copolymer, the content of the structural unit derived from propylene in the copolymer is usually relative to the total number of moles of the structural unit derived from propylene and the structural unit derived from the copolymer component, It is 50 mol% or more, and may be, for example, 70 mol% or more, or 90 mol% or more, depending on the desired performance.

(Ethylene vinyl acetate copolymer)
An ethylene vinyl acetate copolymer is a polymer containing a structural unit derived from ethylene and a structural unit derived from vinyl acetate in one molecule, and polymerizes a monomer component containing ethylene and vinyl acetate. It will be.
The ethylene vinyl acetate copolymer may be a copolymer composed of only two components of ethylene and vinyl acetate, or may be a copolymer with a copolymer component other than ethylene and vinyl acetate.
The content of the structural unit derived from vinyl acetate in the ethylene-vinyl acetate copolymer is preferably 5 to 50 mol% with respect to the total number of moles of the structural unit derived from ethylene and the structural unit derived from vinyl acetate. 30 mol% is more preferable and 10-20 mol% is further more preferable.
When the ethylene vinyl acetate copolymer is a copolymer with a copolymer component other than ethylene and vinyl acetate, the total number of moles of the structural unit derived from ethylene and the structural unit derived from vinyl acetate is derived from ethylene. The total number of moles of the structural unit, the structural unit derived from vinyl acetate, and the structural unit derived from a copolymerization component other than ethylene and vinyl acetate is usually 50 mol% or more. It is good also as mol% or more, and good also as 90 mol% or more.
A commercially available product can be used as the ethylene vinyl acetate copolymer. Examples of commercially available ethylene vinyl acetate copolymers include EVAFLEX (registered trademark) (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.), Ultrasen (registered trademark) (trade name, manufactured by Tosoh Corporation) and the like.
The MFR (melt flow rate) specified in JIS K 7210 of the ethylene vinyl acetate copolymer is preferably 0.5 to 10 g / 10 min, and preferably 0.7 to 5 g from the viewpoint of the productivity and mechanical strength of the porous body. / 10 min is more preferable, and 1 to 3 g / 10 min is further preferable.

  The above (A) polyolefin resin may be used alone or in combination of two or more.

<(B) Powder containing Baked Shells>
The porous body of the present invention can have excellent antibacterial properties and freshness-retaining properties by containing, as the component (B), a powder containing a baked shellfish.
When the shell is fired, it is usually changed into a fired product containing calcium oxide as a main component, and the calcium oxide is changed into calcium hydroxide in the air or appropriately added water. That is, it can be said that the porous body of the present invention contains calcium hydroxide derived from shells. In addition, (B) component used for this invention may modify | reform the thing which baked the shell as needed.
Examples of the shell used for the component (B) include scallop shell, sea shell shell, clam shell, etc. From the viewpoint of antibacterial properties and freshness retention of the porous body obtained, and availability, scallop shell Is preferred.

  The component (B) may contain components other than the fired product of the shell, but from the viewpoint of antibacterial properties and freshness retention of the resulting porous body, the content of the fired product of the shell in the component (B) Is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. Further, the content of the fired product of the shell in the component (B) is substantially 100% by mass, that is, the component (B) may be a powder made of the fired product of the shell.

The average particle size of the component (B) is preferably 1 to 15 μm, more preferably 1 to 7 μm, and still more preferably 1 to 5 μm, from the viewpoint of antibacterial properties and freshness retention of the obtained porous body.
In addition, the average particle diameter of (B) component means a volume average particle diameter. Here, the volume average particle diameter is a particle diameter at a point corresponding to a volume of 50% when the cumulative frequency distribution curve by the particle diameter is obtained with the total volume of the particles being 100%, and the laser diffraction scattering method is used. It can be measured with the used particle size distribution measuring device or the like.

(B) A component can be manufactured by baking, for example, after baking a shell. Specifically, first, a shell is fired in the presence of oxygen, for example, to obtain a fired product mainly composed of calcium oxide, and then water is added to the fired product to hydroxylate the calcium oxide. Change to calcium. Next, the obtained fired product mainly composed of calcium hydroxide can be pulverized by a known pulverizer such as a jet mill pulverizer to obtain the component (B). The firing condition of the shell can be set, for example, at 800 to 1200 ° C. for 0.5 to 5 hours. As a more specific manufacturing method, for example, the method described in JP 2014-012752 A can be mentioned.
The component (B) is also available as a commercially available product, and examples of the commercially available product (B) include Scarlow (registered trademark) (trade name, manufactured by Antibacterial Research Institute, Inc.).
(B) A component may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the component (B) in the porous body of the present invention is preferably 0.7 to 15 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the (A) polyolefin resin. 7 parts by mass is more preferable. When the content of the component (B) is 0.7 parts by mass or more, antibacterial properties and freshness retention are sufficiently exhibited, and when it is 15 parts by mass or less, a porous body having homogeneous pores is easily obtained, Excellent productivity of porous material.

<Other ingredients>
The porous body of the present invention contains a heat stabilizer, an ultraviolet stabilizer, a pigment, a flame retardant, various components used in the method for producing a polyolefin resin composition porous body, which will be described later, and components derived therefrom, as necessary. It may be.

<Physical properties and the like of polyolefin resin composition porous body>
The pores of the porous body of the present invention are preferably at least one selected from closed cells and open cells, and are applied to a viewpoint of enhancing antibacterial properties and freshness retention, as well as a nursery for plant cultivation, a medium, and the like. Since water permeability and water retention are required, open cells are preferable.
In the present specification, the “open cell” means a bubble continuous to at least one surface among the bubbles existing in the polyolefin resin composition porous body, and the “closed cell” means a polyolefin-based cell. It means bubbles that are not continuous on either side of the porous resin composition. The open cells in the polyolefin resin composition porous body are preferably pores penetrating from one surface to the other from the viewpoint of water permeability and water retention.
The open cell ratio of the porous body of the present invention is preferably 45% or more, more preferably 60% or more, and further preferably 75% or more, from the viewpoint of water permeability and water retention. The upper limit value of the open cell rate is not particularly limited, and may be 100%. The open cell ratio can be measured by the following method.
[Measurement method of open cell ratio]
A test piece (50 mm x 50 mm x 10 mm) of a porous polyolefin resin composition is immersed in water at 23 ° C and repeatedly compressed and restored until no air bubbles appear in the water. The test piece is allowed to absorb water, and the maximum water absorption is measured. The maximum water absorption (%) was calculated according to the following formula (1).
Maximum water absorption rate (%) = (maximum water absorption / mass of test specimen before water absorption) × 100 (1)
Next, the open cell ratio was calculated from the maximum water absorption rate (%) obtained by the above formula (1) according to the following formula (2).
Open cell ratio (%) = (maximum water absorption × apparent density of test piece) / density of water at 23 ° C. (2)

Apparent density of the porous body of the present invention is preferably 0.02~0.1g / cm ^3, more preferably 0.02~0.06g / cm ^3, more preferably 0.02~0.05g / cm ³ .

[Polyolefin-based resin composition production method]
The porous body of the present invention is produced, for example, by making a polyolefin resin composition containing (A) a polyolefin resin and (B) a powder containing a baked shellfish into a porous material by a known method. Can do.
Examples of the method for making the polyolefin resin composition porous include the following methods (1) to (5) (hereinafter also referred to as “methods (1) to (5)”).
(1) A molded product having a pellet shape, a powder shape, a film shape, a sheet shape, or other shapes by kneading a polyolefin resin composition containing the component (A), the component (B), a foaming agent, a crosslinking agent, and the like (2) The components (A) and (B) are kneaded together with a stabilizer and the like with an extruder, and a foaming agent such as isobutane is injected from the middle part of the extruder and extruded. (3) A method in which a water-soluble filler is previously kneaded and mixed in a mixture of the component (A) and the component (B), and after shaping, is immersed in water, warm water, etc., and the water-soluble filler is extracted. (4) Method of heat welding powder containing a mixture of component (A) and component (B) (5) Main component is a mixture of component (A), component (B), paper powder, starch, etc. Press the molding material with water vapor. How to foam

Moreover, when manufacturing the polyolefin resin composition porous body which has an open cell, as the manufacturing method, after forming the porous body which has a closed cell by the method of said (1)-(5), it is mechanical, for example. A method having a step of making the closed cells into continuous cells by adding deformation is preferable.
That is, the method for producing a porous polyolefin resin composition of the present invention preferably includes the following step 1 and step 2.
Step 1: A step of producing a closed-cell polyolefin-based resin composition porous body containing (A) a polyolefin-based resin and (B) a powder containing a fired product of shells. Step 2: The obtained closed-cells Process of adding a mechanical deformation to the polyolefin-based resin composition porous body to form continuous cells. Each process is described in detail below.

<Step 1>
Step 1 is a closed-cell polyolefin resin composition porous body (hereinafter also simply referred to as “closed-cell body”) containing (A) a polyolefin-based resin and (B) a powder containing a fired product of shells. ).
The closed cell body is preferably produced by any one of the methods (1) to (5), more preferably produced by the method (1) or (2). From the viewpoint of productivity, the method ( More preferably, it is prepared according to 1). In addition, although the closed cell body produced at this process has closed cells as a main body, it may have open cells.
Hereinafter, various conditions of the method (1) will be described.

  As described above, the method (1) comprises kneading a polyolefin resin composition (hereinafter also referred to as “crosslinked foamed composition”) containing the component (A), the component (B), a foaming agent, a crosslinking agent, and the like, and pellets. This is a method of foaming a molded product having a shape, powder, sheet, film or other shape.

As the foaming agent used in the method (1), an organic thermal decomposition type foaming agent that generates a decomposition gas by heating is preferable, and those conventionally used for the production of polyolefin resin foams can be used. . Specifically, for example, azodicarbonamide, hydrazodicarbonamide, barium salt of azodicarboxylic acid, dinitrosopentaethylenetetramine, nitrosoguanidine, 4,4′-oxybis (benzenesulfonic acid hydrazide), trihydrazine symmetric triazine, Examples thereof include barium azodicarboxylate, azobisisobutyronitrile, toluenesulfonyl hydrazide and the like. These foaming agents may be used individually by 1 type, and may be used in combination of 2 or more type. Among these, 4,4′-oxybis (benzenesulfonic acid hydrazide) is preferable from the viewpoint of obtaining a foam having a stable and high open cell ratio, particularly when forming open cells, and ethylene as the component (A) is preferable. More preferably, a vinyl acetate copolymer is used and 4,4′-oxybis (benzenesulfonic acid hydrazide) is used as a foaming agent. A commercially available product can be used as 4,4′-oxybis (benzenesulfonic acid hydrazide), and examples thereof include Neocerbon (registered trademark) (trade name, manufactured by Eiwa Kasei Kogyo Co., Ltd.). When these foaming agents are used, foaming aids such as urea; cell nucleating agents such as sodium bicarbonate and calcium bicarbonate may be used in combination as appropriate.
Depending on the type of foaming agent used, the content of the foaming agent in the cross-linked foaming composition (when foaming aids, cell nucleating agents, etc. are included, the total amount of the foaming agent and these components). What is necessary is just to determine suitably, For example, 1-30 mass parts is preferable with respect to 100 mass parts of (A) polyolefin resin, and 10-25 mass parts is more preferable.
Moreover, content of the foaming adjuvant and cell nucleating agent in a crosslinked foaming composition is 0.01-5 mass%, for example.

As the crosslinking agent used in the method (1), an organic peroxide is preferable. Examples of the organic peroxide include succinic acid peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, p-chlorobenzoyl peroxide, t-butylperoxyisobutyrate, and t-butylperoxide. Oxyisopropyl carbonate, t-butyl peroxyallyl carbonate, t-butyl peroxylaurate, t-butyl peroxyacetate, di-t-butyl diperoxyphthalate, di-t-butyl diperoxyisophthalate, t- Butyl peroxymaleate, cyclohexanone peroxide, t-butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, 2, -Dimethyl-2,5-di (benzoylperoxy) hexane, 1,1-bis (t-butylperoxy) cyclohexane, t-butylperoxy-3,5,5-trimethylhexane, 2,2-bis ( t-butylperoxy) octane, 2,2-bis (t-butylperoxy) butane, and the like. A crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type. The 10 minute half-life temperature of these organic peroxides is preferably in the range of 100 to 170 ° C.
What is necessary is just to determine suitably content of the crosslinking agent in a crosslinked foaming composition according to the kind etc. of crosslinking agent, For example, 0.3-10 mass parts with respect to 100 mass parts of (A) polyolefin resin. Is preferable, and 0.5-3.0 mass parts is more preferable.

  The crosslinked foamed composition may further contain a crosslinking monomer that forms a cross-link with the decomposition of the cross-linking agent, a foam stabilizer having a cell membrane strength adjusting action, and the like.

Next, the crosslinked foamed composition is formed into a molded product having a pellet shape, a powder shape, a sheet shape, a film shape, or other shapes.
The size of the molded article may be appropriately determined in consideration of the use of the porous polyolefin resin composition, the workability of the subsequent foaming process, etc. By setting the thickness within the range of 5.0 to 20.0 mm, excellent foamability can be obtained.
A sheet-shaped or pellet-shaped molded product can be obtained, for example, by kneading the crosslinked foamed composition with a kneader and then molding with a molding machine. Known apparatuses can be used for the kneader and the molding machine. Examples of the kneader include a pressure kneader, a Banbury mixer, an open roll, and the like. Examples of the molding machine include an extruder, a press machine, Examples include pelletizers.
The kneading of the crosslinked foamed composition is preferably melt kneading from the viewpoint of uniform kneading. The melt kneading conditions can be, for example, 40 to 100 ° C. and 1 to 30 minutes. However, the kneading conditions are appropriately determined according to (A) the melting point of the polyolefin resin, the melt viscosity, the decomposition starting temperature of the foaming agent, the half-life temperature of the cross-linking agent, etc. Absent.

Next, the molded product obtained above is foamed. Foaming may be performed by heating the molded product, and for example, an oven with a turntable can be used for heating the molded product.
The heating conditions here are appropriately determined according to (A) the melting point of the polyolefin resin, the melt viscosity, the decomposition initiation temperature of the foaming agent, the half-life temperature of the crosslinking agent, etc. Good foamability can be obtained by heating at a temperature in the range of 130C to 130C for 1 to 30 minutes, preferably 3 to 15 minutes. In general, the pressure during foaming is preferably normal pressure.

<Process 2>
Step 2 is a step in which the closed cells obtained in step 1 are subjected to mechanical deformation to form continuous bubbles.
Examples of the method for forming closed cells into open cells include a method of compressing and deforming closed cells, and a method of deforming closed cells by applying tension.
The compression deformation of the closed cell body can be performed using, for example, a constant speed two roll, a flat plate press or the like. The compression deformation condition may be appropriately adjusted according to the required open cell ratio, etc., for example, the compression deformation to 20 to 50%, preferably 5 to 10% of the thickness of the closed cell before deformation. You can do it.

  Next, the present invention will be described in more detail with reference to the following examples, but these examples are not intended to limit the present invention in any way.

Example 1
Low-density polyethylene (trade name: Petrocene (registered trademark) 226, density: 923 kg / m ³ , MFR: 2 g / 10 min, manufactured by Tosoh Corporation), 100 parts by weight, scallop shell fired powder (trade name: Scarlow (registered) Trademark), average particle diameter: 3 μm, 2 parts by mass, manufactured by Antibacterial Research Laboratories, Inc., azodicarbonamide (trade name: VINYHALL AC # 3, manufactured by Eiwa Kasei Kogyo Co., Ltd.), 15 parts by mass, dicumyl peroxide (trade name) : Park mill (registered trademark) D, manufactured by NOF Corporation) 1 part by mass was melt-kneaded at 120 ° C. for 10 minutes using an extruder, and an unfoamed sheet-like molded product (thickness: 3.0 mm) Was made. This was put into an oven at 220 ° C. for 5 minutes for crosslinking and foaming to produce a porous body (closed cell body) having a thickness of 10 mm, an expansion ratio of 30 times, and an apparent density of 0.035 g / cm ³ .

(Example 2)
In Example 1, a porous body (closed cell body) was produced in the same manner as in Example 1 except that the amount of the scallop shell fired powder added was changed to 0.5 parts by mass.

(Example 3)
To 100 parts by mass of ethylene vinyl acetate copolymer (trade name: Ultrasen (registered trademark) 630, density: 936 kg / m ³ , vinyl acetate content: 15%, MFR: 1.5 g / 10 min, manufactured by Tosoh Corporation) , Scallop shell powder (trade name: Scarlow (registered trademark), average particle size: 3 μm, manufactured by Antibacterial Research Institute), 3 parts by mass, 4,4′-oxybis (benzenesulfonic acid hydrazide) (trade name: 20 parts by mass of Neo Cerbon (registered trademark), manufactured by Eiwa Kasei Kogyo Co., Ltd., 1 part by mass of calcium bicarbonate (trade name: Cellbon FE-507, manufactured by Eiwa Kasei Kogyo Co., Ltd.), urea (trade name: Cell Paste (registered trademark)) ) 1 part by mass of K5, manufactured by Eiwa Kasei Kogyo Co., Ltd., 1 part by mass of dicumyl peroxide (trade name: Park Mill (registered trademark) D, manufactured by NOF Corporation) And 10 minutes melt-kneaded at 100 ° C. and have, unfoamed sheet-like molded article (thickness: 3.0 mm) was prepared. This was put into an oven at 160 ° C. for 10 minutes for crosslinking and foaming to obtain a closed cell having a thickness of 10 mm, a foaming ratio of 20 times, and an apparent density of 0.048 g / cm ³ . The obtained closed cell body was passed through a constant speed two roll with a roll interval of 1 mm five times to form open cells, and a porous body having an open cell ratio of 81% measured by the method described above was obtained.

(Comparative Example 1)
A closed cell was produced in the same manner as in Example 1 except that the scallop shell fired powder was not added.

  Next, the porous bodies obtained in each example were evaluated by the following methods. The results are shown in Table 1.

(Evaluation of water retention and water permeability)
JIS K1913 General nonwoven fabric test method The water retention rate is measured based on the water retention rate test method. If the water retention rate is 500% or more, the water retention and water permeability is "Yes", and the water retention rate is less than 500%. In this case, water retention and water permeability were set to “none”.

(Evaluation of foamability)
First, the apparent density (D1) of the polyolefin resin composition porous body obtained in each example was determined. Next, in each example, a polyolefin resin composition porous body was produced in the same manner as in each example, except that the scallop shell fired powder was not added, and the apparent density (D2). Asked.
The foamability was evaluated as the ratio (%) (D1 × 100 / D2) of the apparent density of the porous body containing the scallop shell fired product to the apparent density of the porous body not containing the scallop shell fired product.
When the ratio was 80% or more, the foamability was “good”, and when it was less than 80%, the foamability was “bad”. In addition, since the polyolefin-type resin composition porous body of the comparative example 1 did not add the powder of the scallop shell baking products, evaluation of foamability was not performed.

(Antimicrobial evaluation method)
Based on JIS Z2801 "Antimicrobial processed product-antibacterial test method / antibacterial effect", an antibacterial test was performed using Staphylococcus aureus as a bacterium, and an antibacterial activity value was calculated according to the following formula (3). The obtained antibacterial activity value is 2.0 or more and is judged to be antibacterial. The higher the antibacterial activity value, the better the antibacterial property.
Antibacterial activity value = log (number of viable cells after culture per 1 cm ^{3 of} unprocessed sample) −log (number of viable cells after 1 cm ^{3 of} processed sample) (3)

(Evaluation method for freshness retention)
A commercially available strawberry or banana is placed one by one on the porous body (length 200 mm × width 200 mm × thickness 10 mm) obtained in each example, and a wrap film for food (trade name: manufactured by Hitachi Chemical Co., Ltd .: A change in the appearance after wrapping in a household Hitachi wrap) and leaving at room temperature (25 ° C.) for 10 days was visually observed and evaluated according to the following criteria.
A: No change B: Slight discoloration due to damage C: Large discoloration due to damage

＊：表中、「−」は未評価を意味する。
＊１：（Ａ）ポリオレフィン系樹脂１００質量部に対する含有量を意味する。

*: In the table, “-” means not evaluated.
* 1: (A) Meaning content with respect to 100 mass parts of polyolefin resin.

  From Table 1, it can be seen that the porous bodies of Examples 1 to 3 which are the porous bodies of the present invention are all excellent in antibacterial properties and freshness retention. On the other hand, the porous body of Comparative Example 1 to which no scallop shell fired powder was added had no antibacterial properties and was inferior in freshness retention.

  The polyolefin resin composition porous body of the present invention has excellent antibacterial properties and freshness retention, and can be applied to packaging materials for transportation and / or storage of fruits, fishery products, plants, and the like. In particular, the polyolefin resin composition porous body of the present invention having open cells also has water retention and water permeability. Therefore, when used as a nursery bed and culture medium for plant cultivation, it is expected to prevent bacterial withering and prevent growth inhibition. it can.

Claims (8)

  A polyolefin resin composition porous body comprising (A) a polyolefin resin and (B) a powder containing a fired product of shells.   (B) Polyolefin resin composition of Claim 1 whose content of the powder containing the baking products of a shell is 0.7-15 mass parts with respect to 100 mass parts of (A) polyolefin resin. Porous body.   (B) The polyolefin-type resin composition porous body of Claim 1 or 2 whose average particle diameter of the powder containing the baked material of a shell is 1-15 micrometers.   (B) The polyolefin resin composition porous body according to any one of claims 1 to 3, wherein the powder containing the fired product of the shell is a powder made of the fired product of the shell. The polyolefin resin composition porous body according to any one of claims 1 to 4, wherein an open cell ratio measured by the following method is 60% or more.
[Measurement method of open cell ratio]
A test piece of polyolefin resin composition porous body is immersed in water at 23 ° C., and compression and restoration are repeated until no air bubbles are generated in water. The test piece is allowed to absorb water, and the maximum water absorption is measured. The maximum water absorption (%) was calculated according to
Maximum water absorption rate (%) = (maximum water absorption / mass of test specimen before water absorption) × 100 (1)
Next, the open cell ratio was calculated from the maximum water absorption rate (%) obtained by the above formula (1) according to the following formula (2).
Open cell ratio (%) = (maximum water absorption × apparent density of test piece) / density of water at 23 ° C. (2)   (A) The polyolefin resin composition porous body according to any one of claims 1 to 5, wherein the polyolefin resin is an ethylene vinyl acetate copolymer. Step 1: Producing a closed-cell polyolefin-based resin composition porous body containing (A) a polyolefin-based resin and (B) a powder containing a fired product of shells;
Step 2: adding a mechanical deformation to the resulting closed-cell polyolefin-based resin composition porous body to form continuous cells;
The manufacturing method of the polyolefin resin composition porous body of any one of Claims 1-6 which have these.   The closed-cell polyolefin-based resin composition foam is prepared using (A) an ethylene-vinyl acetate copolymer as a polyolefin-based resin and 4,4′-oxybis (benzenesulfonic acid hydrazide) as a foaming agent. Item 8. A method for producing a porous polyolefin resin composition according to Item 7.