Foamed object, protective material, and method for producing foamed object

Abstract

Provided is a novel foamed object having excellent ethylene decomposition properties.　This foamed object is obtained from a resin composition comprising inorganic particles and a thermoplastic resin, wherein the inorganic particles have ethylene gas decomposition properties. The foamed object has a structure in which some of the inorganic particles are exposed on the surface of the foamed object.

Description

Foam, protective material, and method for manufacturing foam

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to foams, protective materials, and methods for making foams.

[0002] Fresh foods such as vegetables and fruits produce ethylene gas through their own physiological processes, which accelerates ripening and deterioration. This poses the problem of short shelf life for fresh foods, from production through transportation and sale to consumption.

[0003] Known methods for solving this problem include a method of adsorbing ethylene gas and a method of decomposing ethylene gas.

[0004] For example, Patent Document 1 discloses a sheet-like functional film that is made of plastic and capable of adhering ethylene to its surface, and that contains, or has coated or vapor-deposited on its surface, a substance having a catalytic function that can decompose ethylene into carbon dioxide and water and / or release the ethylene from one side of the functional film to the other side, at least on the order of ppm or ppb.

[0005] International Publication No. 2017 / 135433

[0006] A main object of the present disclosure is to provide a novel foam having excellent ethylene decomposition properties.

[0007] The inventors of the present disclosure have conducted extensive research to solve the above-mentioned problems, and as a result, have found that a foam exhibits excellent ethylene decomposition ability by forming the foam from a resin composition containing inorganic particles and a thermoplastic resin, using inorganic particles having ethylene gas decomposition ability as the inorganic particles, and further by forming the foam into a structure in which some of the inorganic particles are exposed from the surface of the foam.

[0008] The present disclosure has been completed based on these findings and through further investigations. That is, the present disclosure provides the inventions of the following aspects.

[0009] Item 1. A foam of a resin composition containing inorganic particles and a thermoplastic resin, wherein the inorganic particles have ethylene gas decomposition properties, and the foam has a structure in which a portion of the inorganic particles is exposed from the surface of the foam. Item 2. The foam according to Item 1, wherein the inorganic particles protrude from the surface of the foam. Item 3. The foam according to Item 1 or 2, wherein the inorganic particles are at least one selected from the group consisting of zinc oxide, platinum, titanium oxide, magnesium oxide, and calcium oxide. Item 4. The foam according to any one of Items 1 to 3, wherein the inorganic particles have a particle diameter of 50 μm or less. Item 5. The foam according to any one of Items 1 to 4, wherein the thermoplastic resin comprises at least one selected from the group consisting of olefin-based resins, styrene-based resins, vinyl chloride-based resins, vinyl acetate-based resins, polyvinyl alcohol-based resins, acrylic resins, polyacetal-based resins, polyester-based resins, polycarbonate resins, polyamide-based resins, and thermoplastic elastomers. Item 6. Item 7. The foam according to any one of Items 1 to 5, wherein the content of the inorganic particles in the foam is 0.01% by mass or more. Item 8. The foam according to any one of Items 1 to 6, wherein the mass ratio of the inorganic particles to the thermoplastic resin is 0.1 to 10.0 parts by mass per 100 parts by mass of the thermoplastic resin. Item 9. The foam according to any one of Items 1 to 7, wherein the expansion ratio of the foam is 3 times or more. Item 10. The foam according to any one of Items 1 to 8, wherein the foam is in the shape of a rod, a sheet, a mesh, a bag, a cylinder, a box, or a cocoon ball. Item 11. The protective material according to Item 10, wherein the protective material is a protective material for food. Item 12. A method for producing a foam according to any one of Items 1 to 9, comprising foam-molding a resin composition containing the inorganic particles and the thermoplastic resin.

[0010] According to the present disclosure, a novel foam having excellent ethylene decomposition properties can be provided.

[0011] The foam of the present disclosure utilizes the ethylene decomposition action of inorganic particles, and therefore has the advantage that the ethylene decomposition ability is less likely to decrease compared to methods that utilize ethylene adsorbents that physically adsorb ethylene.

[0012] Furthermore, since the packaging body of the present disclosure contains ethylene-decomposing inorganic particles in the foam, for example, by using the foam as a food protective material, the food that has been transported and sold together with the protective material can be stored by the consumer in a refrigerator or the like, whereby the foam will exert its effect of decomposing ethylene gas in the refrigerator, which is expected to lead to a reduction in food waste. In other words, the foam of the present disclosure can be effectively used in all aspects of food production, transportation, sales, and consumption.

[0013] Furthermore, the foam of the present disclosure also exhibits a function of cushioning impacts applied to food, and can therefore exhibit the effect of suppressing deterioration, spoilage, etc. caused by scratches on food. For example, if the foam of the present disclosure is made into a mesh shape, moisture generated during ethylene decomposition can be efficiently evaporated from the foam, thereby exhibiting the effect of suppressing moisture retention.

[0014] Furthermore, by using ethylene-decomposing inorganic particles that have antibacterial properties, it is possible to inhibit food spoilage caused by bacteria.

[0015] 1 is an electron microscope image (magnification: 5000 times) of the foam obtained in Example 1.

[0016] 1. Foam The foam of the present disclosure is a foam of a resin composition containing inorganic particles and a thermoplastic resin, wherein the inorganic particles have ethylene gas decomposition properties and have a structure in which a portion of the inorganic particles is exposed from the surface of the foam. Because of this configuration, the foam of the present disclosure can exhibit excellent ethylene decomposition properties and can be suitably used, for example, as a food protective material. The foam of the present disclosure is described in detail below.

[0017] In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, separately described upper and lower limits, upper and lower limits, or lower and lower limits may be combined to form a numerical range. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0018] Additionally, each feature disclosed herein can be combined with any other feature disclosed herein.

[0019] The foam of the present disclosure is a foam of a resin composition containing inorganic particles and a thermoplastic resin.

[0020] (Thermoplastic Resin) Examples of the thermoplastic resin include olefin resins, styrene resins, vinyl chloride resins, vinyl acetate resins, polyvinyl alcohol resins, acrylic resins, polyacetal resins, polyester resins, polycarbonate resins, polyamide resins, and thermoplastic elastomers containing the constituent components of these resins. These thermoplastic resins may be used alone or in combination of two or more.

[0021] Of these, olefin-based resins, styrene-based resins, and thermoplastic elastomers (e.g., olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, etc.) are preferred, and it is particularly preferred that the resin contains at least an olefin-based resin because of its excellent mechanical properties such as flexibility and elasticity.

[0022] The olefin resin is usually a poly C2-3 olefin resin such as a polyethylene resin or a polypropylene resin, with a polyethylene resin being preferred.

[0023] Examples of polyethylene resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-(4-methylpentene-1) copolymer, ethylene-vinyl acetate copolymer (EVA resin), and ethylene-methyl methacrylate copolymer. These polyethylene resins can be used alone or in combination. Of these polyethylene resins, LDPE, LLDPE, EVA resin, and the like are preferred from the viewpoint of foamability and the like.

[0024] The number average molecular weight of the polyethylene resin may be, for example, about 10,000 to 300,000, preferably about 15,000 to 200,000, and more preferably about 20,000 to 100,000. The molecular weight is measured by gel permeation chromatography (GPC) at a measurement temperature of 140°C using orthodichlorobenzene as a solvent and a column (Shodex GPCAD-806MS) with universal calibration using polystyrene as a standard.

[0025] The melt flow rate (MFR) of the polyethylene resin may be 0.1 g / 10 min or more, for example, 0.1 to 60 g / 10 min, preferably 0.2 to 25 g / 10 min, more preferably 0.25 to 8 g / 10 min, and most preferably 0.3 to 5 g / 10 min, as measured in accordance with JIS K7210 (190°C, load 21.2 N). If the MFR is too high, foamability and strength may be reduced, while if the MFR is too low, foamability may be reduced. It is generally known that as the MFR increases, the melt tension decreases, making cells more likely to break. However, by adjusting the lower limit of the MFR to the above range, foamability can be improved.

[0026] The melting point or softening point of the polyethylene resin is, for example, about 80 to 150°C, preferably about 90 to 140°C, and more preferably about 100 to 130°C.

[0027] The thermoplastic resin containing an olefin-based resin may be an olefin-based resin alone, or may be a combination of an olefin-based resin and another thermoplastic resin (for example, a styrene-based resin such as polystyrene).

[0028] The weight ratio of the olefin resin to the other thermoplastic resin can be selected from the range of about 100 / 0 to 10 / 90 (for example, 100 / 0 to 50 / 50) of olefin resin / other thermoplastic resin, and when both resins are combined, the ratio is about 99 / 1 to 30 / 70, preferably 98 / 2 to 50 / 50, and more preferably 95 / 5 to 70 / 30 (particularly 93 / 7 to 80 / 20). If the ratio of the olefin resin is too low, there is a risk of reduced foamability.

[0029] The content of the thermoplastic resin in the foam of the present disclosure (i.e., in the resin composition constituting the foam of the present disclosure) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and is preferably 99% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less; preferred ranges include about 50 to 99% by mass, about 50 to 80% by mass, about 50 to 70% by mass, about 80 to 99% by mass, and about 90 to 99% by mass.

[0030] (Inorganic Particles) The inorganic particles have ethylene gas decomposition properties. In the present disclosure, the ethylene gas decomposition properties of the inorganic particles specifically mean a property of promoting a reaction that produces water and carbon dioxide when brought into contact with ethylene gas in the presence of oxygen gas (oxidation reaction of ethylene gas by a metal oxide).

[0031] The type of inorganic particles capable of decomposing ethylene gas (hereinafter sometimes referred to as ethylene gas decomposing inorganic particles) is not particularly limited as long as the effects of the present invention are achieved, and examples include zinc oxide, platinum, titanium oxide, magnesium oxide, and calcium oxide. The ethylene gas decomposing inorganic particles contained in the foam of the present disclosure may be of only one type or of two or more types. Among these, from the viewpoint of optimally achieving the effects of the present invention, it is preferable that the ethylene gas decomposing inorganic particles contain zinc oxide. Zinc oxide is an oxide of zinc represented by the chemical formula ZnO.

[0032] From the viewpoint of suitably exerting the effects of the present invention, the particle size of the inorganic particles in the foam is preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 1 μm or less, and is preferably 0.01 μm or more, more preferably 0.02 μm or more, and even more preferably 0.03 μm or more. Preferred ranges include about 0.01 to 50 μm, about 0.01 to 10 μm, about 0.01 to 1 μm, about 0.02 to 50 μm, about 0.02 to 10 μm, about 0.02 to 1 μm, about 0.03 to 50 μm, about 0.03 to 10 μm, and about 0.03 to 1 μm.

[0033] The content of the ethylene gas decomposable inorganic particles in the foam of the present disclosure (i.e., in the resin composition constituting the foam of the present disclosure) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.03% by mass or more, and is preferably 10.0% by mass or less, more preferably 8.0% by mass or less, and even more preferably 7.0% by mass or less. Preferred ranges include about 0.01 to 10.0% by mass, about 0.01 to 8.0% by mass, about 0.01 to 7.0% by mass, about 0.02 to 10.0% by mass, about 0.02 to 8.0% by mass, about 0.02 to 7.0% by mass, about 0.03 to 10.0% by mass, about 0.03 to 8.0% by mass, and about 0.03 to 7.0% by mass.

[0034] The mass ratio of the thermoplastic resin to the ethylene-decomposable inorganic particles in the foam of the present disclosure (i.e., in the resin composition constituting the foam of the present disclosure) is preferably about 0.1 to 10.0 parts by mass, more preferably about 0.2 to 5.0 parts by mass, and even more preferably about 0.3 to 3.0 parts by mass of the ethylene-decomposable inorganic particles per 100 parts by mass of the thermoplastic resin.

[0035] The foam of the present disclosure has a structure in which ethylene-decomposable inorganic particles are partially exposed from the surface of the foam. Since the foam of the present disclosure is a foam of a resin composition, it has a large surface area, and the ethylene-decomposable inorganic particles are exposed on the surface of such a foam. Therefore, the surface area of ​​the ethylene-decomposable inorganic particles on the surface of the foam of the present disclosure is also large, and it is thought that the foam as a whole exhibits excellent ethylene decomposition ability.

[0036] From the viewpoint of more suitably exerting the effects of the present invention, it is preferable that the ethylene decomposable inorganic particles protrude from the surface of the foam. Note that, even in this case, it is not necessary for all of the ethylene decomposable inorganic particles exposed on the surface of the foam to protrude from the surface of the foam, and as long as at least a portion of the ethylene decomposable inorganic particles protrude from the surface of the foam, the effect of enhancing ethylene decomposition can be enhanced. Note that the ethylene decomposable inorganic particles protruding from the surface of the foam are a part of the ethylene decomposable inorganic particles, and the non-protruding parts are buried in the foam.

[0037] (Blowing Agent) The foam of the present disclosure is obtained by foaming a resin composition (expandable resin composition) containing a thermoplastic resin and ethylene-decomposable inorganic particles, and the resin composition may contain a blowing agent. Note that in the process of producing the foam of the present disclosure, the blowing agent is contained in the resin composition, and after the foam is formed, the blowing agent may volatilize and no longer be contained in the foam.

[0038] As the blowing agent, a conventional blowing agent can be used, and a decomposable blowing agent (chemical blowing agent) may also be used, but a volatile blowing agent (physical blowing agent) is preferred because it can improve the expansion ratio in a simple manner. Examples of volatile blowing agents include inorganic blowing agents (nitrogen, carbon dioxide, oxygen, air, water, etc.) and organic blowing agents (aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, fluorinated hydrocarbons, alcohols, ethers, aldehydes, ketones, etc.). Of these, lower aliphatic hydrocarbons such as butane (n-butane, isobutane) and pentane (n-pentane, isopentane, etc.) are commonly used because they are inexpensive and have low toxicity.

[0039] The proportion of the foaming agent in the resin composition is, for example, about 0.01 to 30 parts by mass, preferably about 0.1 to 25 parts by mass, and more preferably about 1 to 20 parts by mass (particularly about 5 to 15 parts by mass) relative to 100 parts by mass of the thermoplastic resin.

[0040] (Foam Nucleating Agent) The foam of the present disclosure may further contain a foam nucleating agent. Examples of foam nucleating agents include silicon compounds (talc, silica, zeolite, etc.), inorganic acid salts (carbonates or bicarbonates such as sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, and ammonium carbonate), organic acids or their salts (citric acid, sodium citrate, calcium stearate, aluminum stearate, zinc stearate, etc.), metal oxides (zinc oxide, titanium oxide, aluminum oxide, etc.), and metal hydroxides (aluminum hydroxide, etc.). These foam nucleating agents may be used alone or in combination.

[0041] The proportion of the foam nucleating agent in the foam of the present disclosure is, for example, about 0.01 to 10 parts by mass, preferably about 0.05 to 5 parts by mass, and more preferably about 0.1 to 3 parts by mass (particularly about 0.5 to 2 parts by mass) relative to 100 parts by mass of the thermoplastic resin.

[0042] (Surfactant) The foam of the present disclosure may further contain a surfactant. Examples of surfactants include fatty acid esters (esters of C8-24 fatty acids with polyhydric alcohols, such as palmitic acid monoglyceride to triglyceride and stearic acid monoglyceride to triglyceride), and fatty acid amides (C8-24 fatty acid amides, such as palmitic acid amide and stearic acid amide). These surfactants can be used alone or in combination of two or more.

[0043] The proportion of the surfactant in the foam of the present disclosure is, for example, about 0.01 to 30 parts by mass, preferably about 0.05 to 20 parts by mass, and more preferably about 0.1 to 10 parts by mass (particularly about 1 to 5 parts by mass) relative to 100 parts by mass of the thermoplastic resin.

[0044] (Other Additives) The foam of the present disclosure may further contain conventional additives as other additives. Examples of conventional additives include colorants (e.g., dyes and pigments), surface smoothing agents, cell regulators, stabilizers (e.g., antioxidants, heat stabilizers, UV absorbers), viscosity modifiers, compatibilizers, dispersants, antistatic agents, antiblocking agents, antifogging agents, fillers (e.g., calcium carbonate and carbon fiber), slip agents, mold release agents, lubricants, impact modifiers, plasticizers, flame retardants, biocides (e.g., disinfectants, bacteriostatic agents, antifungal agents, preservatives, insect repellents), and deodorizers. These conventional additives can be used alone or in combination.

[0045] The proportion of each of the other additives in the foam of the present disclosure is, for example, 50 parts by mass or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

[0046] (Flame Retardant) Examples of flame retardants include phosphate esters and other phosphorus compounds such as ammonium polyphosphate, ethylene bistris(2-cyanoethyl)phosphonium chloride, tris(tribromophenyl)phosphate, tris(tribromophenyl)phosphate, and tris(3-hydroxypropyl)phosphine oxide; chlorine-based flame retardants such as chlorinated paraffin, chlorinated polyolefin, and perchlorocyclopentadecane; bromine-based flame retardants such as hexabromobenzene, ethylene bisdibromonorbornanedicarboximide, ethylene bistetrabromophthalimide, tetrabromobisphenol A derivatives, tetrabromobisphenol S, and tetrabromodipentaerythritol; and mixtures thereof. Flame retardants can be used alone or in combination of two or more.

[0047] (Ultraviolet Absorber) Examples of the ultraviolet absorber include benzotriazole-based, benzophenone-based, salicylic acid-based, acrylate-based, etc. The ultraviolet absorbers may be used alone or in combination of two or more kinds.

[0048] (Colorant) Examples of pigments include inorganic pigments (titanium oxide, iron oxide, chromium oxide, cadmium sulfide, etc.) and organic pigments (azo lakes, thioindigo, phthalocyanine, anthraquinone). Examples of dyes include azos, anthraquinones, triphenylmethanes, etc. Colorants can be used alone or in combination of two or more. The amount of pigment and dye added is not particularly limited and may be the same as the proportion of the other additives described above, but is preferably 5 parts by mass or less, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the resin composition of the present invention.

[0049] (Additional Antistatic Agents) Examples of antistatic agents include the above-mentioned surfactants, fatty acid esters, and polymeric antistatic agents. Examples of fatty acid esters include esters of stearic acid and oleic acid, and examples of polymeric antistatic agents include polyether ester amides. Antistatic agents can be used alone or in combination of two or more.

[0050] (Foam Properties) The expansion ratio of the foam of the present disclosure may be 3 times or more (e.g., 3 to 90 times), for example, 3.1 to 85 times, preferably 3.5 to 80 times, and more preferably 4.0 to 75 times (particularly 20 to 70 times). Despite the inclusion of inorganic particles, the present disclosure also allows for a high expansion ratio, for example, an expansion ratio of 10 times or more (particularly 20 times or more), for example, 10 to 90 times, preferably 20 to 85 times, and more preferably 30 to 75 times (particularly 35 to 70 times). If the expansion ratio is too low, flexibility may be reduced.

[0051] The foam of the present disclosure preferably contains at least a closed-cell structure. The open-cell ratio, which is the ratio of open cells to the total number of cells (open cells and closed cells), may be 90% by volume or less, for example, 0.1 to 90% by volume, preferably 1 to 80% by volume (e.g., 2 to 70% by volume), and more preferably 3 to 50% by volume (particularly 5 to 40% by volume). If the open-cell ratio is too high, the mechanical properties of the foam may be reduced. On the other hand, for applications requiring flexibility, a foam with a high open-cell ratio may be used, for example, a foam with an open-cell ratio of 20% by volume or more, preferably 30% by volume or more, and more preferably more than 50% by volume. The open-cell ratio may be adjusted, for example, by changing the composition of resin components other than the masterbatch.

[0052] The foam of the present disclosure has an average cell diameter of, for example, about 0.3 to 2 mm, preferably about 0.4 to 1.5 mm, and more preferably about 0.5 to 1.3 mm (particularly about 0.6 to 1 mm). If the average cell diameter is too small, it may be difficult to increase the expansion ratio, and if it is too large, mechanical properties may be reduced.

[0053] The foam of the present disclosure preferably has a skin layer on its surface, and the coverage of the skin layer with respect to the entire surface may be 60 area % or more (particularly 80 area % or more), preferably 90 area % or more, or even 100 area % (the entire surface is a skin layer). The skin layer means a non-foamed layer extending with a substantially uniform thickness on the surface of the foam.

[0054] The average thickness of the skin layer can be selected from the range of about 0.001 to 1 mm, for example, about 0.005 to 0.1 mm, preferably about 0.008 to 0.05 mm, and more preferably about 0.01 to 0.03 mm (particularly about 0.012 to 0.025 mm).

[0055] The ethylene decomposition rate of the foam of the present disclosure is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, with the upper limit being, for example, 100% or less.

[0056] Furthermore, in the present disclosure, by using ethylene-decomposable inorganic particles having antibacterial properties, it is possible to suppress bacterial spoilage of food, etc. For example, since zinc oxide has antibacterial properties, by using zinc oxide as the ethylene-decomposable inorganic particles, the foam of the present disclosure can also exhibit antibacterial properties.

[0057] The antibacterial properties of the foam of the present disclosure are evaluated in accordance with the provisions of JIS Z 2801:2012, and are preferably 2.0 or higher, more preferably 2.5 or higher. An antibacterial activity value of 2.0 or higher is considered to have antibacterial performance. A higher antibacterial activity value is preferable because it indicates a higher antibacterial effect, and there is no particular upper limit. The antibacterial activity value preferably satisfies the above conditions against various bacteria, and more preferably satisfies the above conditions against both Staphylococcus aureus and Escherichia coli.

[0058] In this specification and claims, the expansion ratio, open cell ratio, average cell diameter, average skin layer thickness, ethylene decomposition property, and antibacterial property are each measured by the methods described in the examples below.

[0059] The shape of the packaging body of the present disclosure is not particularly limited and can be appropriately selected depending on the application. Specific examples of the shape of the packaging body of the present disclosure include a rod shape, a sheet shape, a mesh shape, a bag shape, a cylinder shape, a box shape, and a cocoon shape.

[0060] The packaging of the present disclosure is useful, for example, as a food protector.

[0061] As described above, the foam of the present disclosure utilizes the ethylene decomposition action of inorganic particles, and therefore has the advantage that the ethylene decomposition ability is less likely to decrease compared to methods that utilize ethylene adsorbents that physically adsorb ethylene.

[0062] Furthermore, since the packaging body of the present disclosure contains ethylene-decomposing inorganic particles in the foam, for example, by using the foam as a food protective material, the food that has been transported and sold together with the protective material can be stored by the consumer in a refrigerator or the like, whereby the foam will exert its effect of decomposing ethylene gas in the refrigerator, which is expected to lead to a reduction in food waste. In other words, the foam of the present disclosure can be effectively used in all aspects of food production, transportation, sales, and consumption.

[0063] Furthermore, the foam of the present disclosure also exhibits a function of cushioning impacts applied to food, and can therefore exhibit the effect of suppressing deterioration, spoilage, etc. caused by scratches on food. For example, if the foam of the present disclosure is made into a mesh shape, moisture generated during ethylene decomposition can be efficiently evaporated from the foam, thereby exhibiting the effect of suppressing moisture retention.

[0064] [Method for producing foam] The method for producing a foam of the present disclosure may be a method for foam-molding a resin composition containing a thermoplastic resin and ethylene-decomposable inorganic particles, and a conventional method can be used as a method for foaming the resin composition. The foam-molding method is usually a method of melt-kneading the resin composition and foam-molding it.

[0065] The melt-kneading may be carried out using a conventional melt-kneader, such as a single-screw or vented twin-screw extruder, etc. Prior to the melt-kneading, the thermoplastic resin, the ethylene-decomposable inorganic particles, and other components (a foaming agent and, if necessary, a foam nucleating agent, additives, etc.) may be premixed using a conventional method, for example, a mixer (a tumbler, a V-blender, a Henschel mixer, a Nauta mixer, a ribbon mixer, a mechanochemical device, an extrusion mixer, etc.).

[0066] As the foam molding method, a conventional method such as extrusion molding (e.g., T-die method, inflation method, etc.), injection molding, etc. Among these, extrusion molding is preferred because it allows the production of foams having strong magnetic force and high expandability with high productivity.

[0067] In the extrusion molding method, for example, a single-screw extruder (e.g., a vented extruder) or a twin-screw extruder (e.g., a co-rotating twin-screw extruder, a counter-rotating twin-screw extruder) can be used as the extruder, and a multi-stage extruder such as a tandem extruder is preferred because it allows easy adjustment of the foaming conditions and can achieve a high foaming ratio.

[0068] In the extrusion molding method, the method for introducing the foaming agent is not particularly limited, and a decomposable foaming agent (chemical foaming agent) may be blended in advance with the foamable resin composition. However, it is preferable to introduce a volatile foaming agent (physical foaming agent) in the extruder, since this is a simple method that can improve the expansion ratio.

[0069] The shape of the nozzle outlet is not particularly limited and can be selected depending on the application of the foam (for example, if the foam is used as a protective material, the shape of the object (or article) to be protected). For example, it may be one-dimensional, such as a rod or a string; two-dimensional, such as a sheet, a film, or a two-dimensional mesh (net); or three-dimensional, such as a block, a plate, a column, a slit, an L-shape, a U-shape, a pipe, or a ring. The sheet foam may have at least one flat or uneven surface, or one surface may be uneven and the other surface may be uneven. This uneven surface is often formed along the longitudinal direction of a long sheet foam. By forming an uneven surface, slippage of the object to be protected can be suppressed, thereby enhancing the cushioning effect. The height of the uneven portion is not particularly limited.

[0070] The extrusion-foamed foam may be cooled by a conventional method, for example, a cooling method using a cooler. In the cooling method using a cooler, cooling media such as compressed air, water (cooling water), and air (blower) may be used. Cooling methods include a method of injecting compressed air, a method of cooling with a blower, a method of cooling by spraying water, and a method of cooling using a cooling jacket. The temperature of the cooling media may be, for example, about 0 to 60°C, preferably about 5 to 55°C, and more preferably about 10 to 50°C.

[0071] In the method of injecting compressed air, the air pressure may be, for example, about 0.1 to 10 MPa, preferably about 0.2 to 5 MPa, and more preferably about 0.3 to 1 MPa. The amount of compressed air injected may be, for example, about 100 to 1000 liters / minute, preferably about 200 to 500 liters / minute, and more preferably about 250 to 400 liters / minute.

[0072] If necessary, the resulting foam (particularly a sheet-like foam) may be subjected to secondary processing [for example, thermoforming (for example, thermoforming using a mold) such as vacuum forming, pressure forming, vacuum pressure forming, or match mold forming].

[0073] The foam molding or post-molding temperature may be, for example, about 70 to 300°C, preferably about 80 to 280°C, and more preferably about 85 to 260°C.

[0074] The shape of the foam can be appropriately selected depending on the application, and may be, for example, a one-dimensional shape such as a rod or string, a two-dimensional shape such as a sheet, film or two-dimensional mesh (net), or a three-dimensional shape such as a mesh, bag, cylinder, box, cocoon, block, plate, column, slit, L-shape, U-shape, pipe or ring.

[0075] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations may be made as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims.

[0076] [Raw materials] LDPE: low-density polyethylene (Novatec, manufactured by Japan Polyethylene Corporation) Ethylene-decomposable inorganic particles: zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.) average particle size 0.28 μm Foaming agent: isobutane (commercially available product) Foam nucleating agent: talc ("Micro Ace K-1", manufactured by Nippon Talc Co., Ltd.) average particle size 7.4 μm Surfactant: stearic acid monoglyceride (commercially available product)

[0077] [Expansion Ratio] The expansion ratio was calculated based on the following formula: Expansion ratio (times) = density of resin composition for foam / apparent density of foam.

[0078] The foam weight was measured in advance, and the foam was placed in water and then left under a reduced pressure of -400 mmHg for 1 minute to allow water to penetrate into the open cell structure. The pressure was returned to atmospheric pressure, and the water adhering to the foam surface was removed. The weight was then calculated using the following formula (1).

[0079] Open cell rate (%) = {(w2 - w1) / d3} / (w1 / d1 - w1 / d2) (1) (wherein w2 is the weight of the foam after water absorption, w1 is the weight of the foam before water absorption, d1 is the apparent density of the foam, d2 is the apparent density of the resin composition used in the foam, and d3 is the density of water at the time of measurement).

[0080] [Average Cell Diameter (Cell Size)] The cross section of the foam was observed with a scanning electron microscope or a digital microscope (Scalar Corporation), and the cell diameters in the TD and MD directions were measured at 10 random locations, and the average value was taken as the cell diameter. Each cell diameter was taken as the average (mm) of the major axis and the minor axis.

[0081] [Average Thickness of Skin Layer] Using a digital microscope (manufactured by Scalar Corporation) and filing & two-dimensional measurement software ("AR-CNVMF" manufactured by Artray Corporation), the thickness of the skin layer in the TD direction was measured at 10 arbitrary points, and the average value was taken as the average thickness (mm) of the skin layer.

[0082] [Ethylene decomposition property] The ethylene decomposition property of the foam was evaluated by the following procedure. The results are shown in Table 1. 10 g of the foam obtained in each of the Examples and Comparative Examples was placed in a 5-liter Tedlar bag, and 3 liters of ethylene gas with an initial concentration of 100 ppm was poured into it. The ethylene gas concentration in the bag was measured over time using a gas detector tube to evaluate the ethylene gas decomposition property of the foam. The evaluation criteria for ethylene decomposition property were as follows: a foam in which a reduction in ethylene concentration of 20% or more was confirmed within 48 hours was given an "A" rating; a foam in which an ethylene concentration reduction rate of 15% or more but less than 20% was given an "B" rating; and a foam in which an ethylene concentration reduction rate of less than 15% was given an "C" rating.

[0083] [Antibacterial Property] The antibacterial property of the foam was evaluated by the following procedure based on the method specified in JIS Z 2801: 2012. The results are shown in Table 1.

[0084] (Preparation of press sheets for measurement) A predetermined amount of each resin composition was filled into an SUS mold. The heating plate was set to 200°C, and using a hydraulic heat press (PEWR-30 manufactured by Kansai Roll Co., Ltd.), the resin was preheated for 7 minutes and pressed at a gauge pressure of 10 MPa for 2 minutes. The resin was then transferred to a cooling plate set to 20°C, compressed at a gauge pressure of 10 MPa, and cooled for 3 minutes to prepare a press sheet for measurement having a thickness of 2 mm.

[0085] (Antibacterial Test) Test specimens were prepared by punching out a 2 mm thick test press sheet prepared according to the method described above in "Preparation of Test Press Sheet" to the specified dimensions (50 mm length, 50 mm width). Next, in accordance with JIS Z2801 (film coating method), test specimens were inoculated with bacterial solutions of Staphylococcus aureus (NBRC 12732) and Escherichia coli (NBRC 3972), respectively, and cultured for 24 hours at a temperature of 35°C and a relative humidity of 90% or higher. The antibacterial evaluation criteria are as follows: A: Antibacterial activity value is 2.0 or higher; C: Antibacterial activity value is less than 2.0.

[0086] [Foam Production] <Masterbatch Production> 80 parts by weight of LDPE and 20 parts by weight of ethylene-decomposable inorganic particles were placed in a ball mill and mixed while rotating for 10 minutes. The resulting mixture was then continuously fed from a hopper into a KRC Kneader (manufactured by Kurimoto, Ltd.) for melt-kneading. The continuously discharged resin composition was cooled with water and then cut with a pelletizer to prepare a masterbatch. <Example 1> 90 parts by weight of LDPE, 2.5 parts by weight of masterbatch, 1.0 part by weight of foaming nucleating agent, and 3.0 parts by weight of surfactant were placed in an extruder. 8.0 parts by weight of isobutane gas was injected midway through the extruder. The mixture was then cooled to an appropriate foaming temperature and extruded through a circular die attached to the tip to obtain a foam. The resulting foam was a cylindrical sheet with an average diameter of approximately 100 mm in a roughly circular cross section. Specifically, it was a cylindrical sheet with an approximately circular cross section having an average diameter (tube width) of 100 mm and a tube wall thickness (thickness) of 2.0 mm, and had a basis weight of 55.7 g / m, an expansion ratio of 33 times, an open cell ratio of 2.2%, an average cell diameter of 0.93 mm, and an average skin layer thickness of 0.028 mm.

[0087] Example 2: 90 parts by weight of LDPE, 5.0 parts by weight of masterbatch, 1.0 part by weight of foaming nucleating agent, and 3.0 parts by weight of surfactant were charged into an extruder. 8.0 parts by weight of isobutane gas was injected midway through the extruder, followed by cooling to an appropriate foaming temperature. The extruder was then extruded through a circular nozzle attached to the tip to obtain a foam. The resulting foam was a cylindrical sheet with a roughly circular cross-section having an average diameter of approximately 100 mm. Specifically, the cylindrical sheet had a roughly circular cross-section having an average diameter (cylinder width) of 104 mm and a cylindrical wall thickness (thickness) of 2.1 mm. The foam had a basis weight of 60.4 g / m², an expansion ratio of 32, an open cell ratio of 2.1%, an average cell diameter of 0.93 mm, and an average skin layer thickness of 0.023 mm.

[0088] Example 3: 90 parts by weight of LDPE, 7.5 parts by weight of masterbatch, 1.0 part by weight of foaming nucleating agent, and 3.0 parts by weight of surfactant were charged into an extruder. 8.0 parts by weight of isobutane gas was injected midway through the extruder, followed by cooling to an appropriate foaming temperature. The extruder was then extruded through a circular nozzle attached to the tip to obtain a foam. The resulting foam was a cylindrical sheet with an average diameter of approximately 100 mm in a roughly circular cross section. Specifically, the cylindrical sheet had an average diameter (cylinder width) of 103 mm in a roughly circular cross section and a cylindrical wall thickness (thickness) of 2.0 mm. The foam had a basis weight of 54.1 g / m², an expansion ratio of 34, an open cell ratio of 2.4%, an average cell diameter of 0.75 mm, and an average skin layer thickness of 0.027 mm.

[0089] Example 4: 90 parts by weight of LDPE, 10.0 parts by weight of masterbatch, 1.0 part by weight of foaming nucleating agent, and 3.0 parts by weight of surfactant were charged into an extruder. 8.0 parts by weight of isobutane gas was injected midway through the extruder, followed by cooling to an appropriate foaming temperature. The extruder was then extruded through a circular nozzle attached to the tip to obtain a foam. The resulting foam was a cylindrical sheet with a roughly circular cross-section having an average diameter of approximately 100 mm. Specifically, the cylindrical sheet had a roughly circular cross-section having an average diameter (cylinder width) of 100 mm and a cylindrical wall thickness (thickness) of 2.1 mm. The foam had a basis weight of 96.6 g / m², an expansion ratio of 20, an open cell ratio of 2.9%, an average cell diameter of 0.69 mm, and an average skin layer thickness of 0.024 mm.

[0090] Example 5: 95 parts by mass of LDPE, 5.0 parts by mass of masterbatch, 1.0 part by mass of foaming nucleating agent, and 3.0 parts by mass of surfactant were charged into an extruder, and 2.0 parts by mass of isobutane gas was injected midway through the extruder. The extruder was then cooled to an appropriate temperature for foaming and extruded through a circular nozzle attached to the tip to obtain a foam. The obtained foam was a cylindrical sheet with an average diameter of approximately 100 mm in a substantially circular cross section. Specifically, the cylindrical sheet had an average diameter of approximately 104 mm in a substantially circular cross section (cylinder width) and a cylindrical wall thickness (thickness) of 1.0 mm, and had a basis weight of 187.7 g / m. 2 The foaming ratio was 4.9 times, the open cell ratio was 3.2%, the average cell diameter was 0.86 mm, and the average thickness of the skin layer was 0.024 mm.

[0091] Example 6: 60 parts by mass of LDPE, 20 parts by mass of PS, 10.0 parts by mass of masterbatch, 1.0 part by mass of foaming nucleating agent, and 3.0 parts by mass of surfactant were charged into an extruder, and 22.0 parts by mass of isobutane gas was injected midway through the extruder. The extruder was then cooled to an appropriate temperature for foaming and extruded through a circular nozzle attached to the tip to obtain a foam. The obtained foam was a cylindrical sheet with an average diameter of approximately 100 mm in a roughly circular cross section. Specifically, the cylindrical sheet had an average diameter of approximately 106 mm in a roughly circular cross section (cylinder width) and a cylindrical wall thickness of 2.6 mm, and had a basis weight of 36.0 g / m. 2 The foam had an expansion ratio of 70 times, an open cell ratio of 1.9%, an average cell diameter of 1.18 mm, and an average skin layer thickness of 0.021 mm.

[0092] Comparative Example 1: 100 parts by mass of the masterbatch, 1.0 part by mass of a foaming nucleating agent, and 3.0 parts by mass of a surfactant were charged into an extruder, and 8.0 parts by mass of isobutane gas was injected midway through the extruder. The extruder was then cooled to an appropriate foaming temperature and extruded through a circular nozzle attached to the tip to obtain a foam. The resulting foam was a cylindrical sheet with a roughly circular cross-section having an average diameter of approximately 100 mm. Specifically, the cylindrical sheet had a roughly circular cross-section having an average diameter (cylinder width) of 100 mm and a wall thickness (thickness) of 2.2 mm, and had a basis weight of 65.3 g / m², an expansion ratio of 31, an open cell ratio of 2.2%, an average cell diameter of 0.95 mm, and an average skin layer thickness of 0.025 mm.

[0093] <Observation of Foam Surface with Electron Microscope> The surface condition of the foam was confirmed by SEM images using a scanning electron microscope (SEM (SU1510: Hitachi)) and an EDX analyzer (EDAX APEX). The SEM images were adjusted to a magnification range of 50x to 10,000x to obtain multiple SEM images (for example, SEM images at 50x, 200x, 1,000x, 2,000x, 5,000x, and 10,000x). Furthermore, as a pretreatment for observation, a cross section of the foam was cut out with a cutter and platinum-coated before SEM observation. The exposed and protruding state of inorganic particles from the foam surface was confirmed from each SEM image, and the particle size of the inorganic particles was measured. The results are shown in Table 1.

[0094] When electron microscope images of the foams obtained in Examples 1 to 6 were examined, zinc oxide was found to be exposed on the surface of the foam, and zinc oxide was found to protrude from the surface of the foam. An electron microscope image (magnification: 5000x) of the foam obtained in Example 2 is shown in Figure 1. It can be seen that zinc oxide was exposed on the surface of the foam, and zinc oxide particles 1, 2, 3, and 4 were found to protrude from the surface of the foam.

[0095]

Claims

1. A foam of a resin composition containing inorganic particles and a thermoplastic resin, wherein the inorganic particles have an ethylene gas decomposition property, and the foam has a structure in which a portion of the inorganic particles is exposed from a surface of the foam.

2. The foam of claim 1, wherein the inorganic particles protrude from a surface of the foam.

3. The foam according to claim 1 or 2, wherein the inorganic particles are at least one type selected from the group consisting of zinc oxide, platinum, titanium oxide, magnesium oxide and calcium oxide.

4. The foam according to claim 1 or 2, wherein the particle diameter of the inorganic particles is 50 μm or less.

5. The foam according to claim 1 or 2, wherein the thermoplastic resin comprises at least one selected from the group consisting of olefin-based resins, styrene-based resins, vinyl chloride-based resins, vinyl acetate-based resins, polyvinyl alcohol-based resins, acrylic-based resins, polyacetal-based resins, polyester-based resins, polycarbonate resins, polyamide-based resins, and thermoplastic elastomers.

6. The foam according to claim 1 or 2, wherein the content of the inorganic particles in the foam is 0.01 mass % or more.

7. A foam according to claim 1 or 2, wherein the mass ratio of the thermoplastic resin to the inorganic particles is 0.1 to 10.0 parts by mass of the inorganic particles per 100 parts by mass of the thermoplastic resin.

8. The foam according to claim 1 or 2, wherein the foam has an expansion ratio of 3 times or more.

9. The foam according to claim 1 or 2, which is in the form of a rod, a sheet, a mesh, a bag, a cylinder, a box, or a cocoon ball.

10. A protective material comprising the foam according to claim 1 or 2.

11. The protective material of claim 10, wherein the protective material is a food protective material.

12. A method for producing a foam according to claim 1 or 2, comprising foaming a resin composition containing the inorganic particles and the thermoplastic resin.

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