Resin foam

Abstract

The present invention improves the cell breakability and realizes cell miniaturization for a resin foam body.　This resin foam body is obtained by foaming a resin composition comprising: a polyolefin resin that contains at least an ethylene-vinyl acetate copolymer; and a petroleum resin and / or a styrene resin.

Description

Technical Field

[0001] The present disclosure relates to a resin foam. This application is based on Japanese Patent Application No. 2021-206942 filed on December 21, 2021, claims the benefit of their priority, and all the contents of those patent applications are incorporated herein by reference.

Background Art

[0002] Patent Document 1 describes a polyolefin resin continuous foam. The polyolefin resin continuous foam is obtained by heating a molded body obtained by adding a resin composition containing 80 parts by weight of an ethylene-vinyl acetate copolymer, 20 parts by weight of low-density polyethylene, 0.6 parts by weight of dicumyl peroxide, 20 parts by weight of an azodicarbonamide-based foaming agent, 0.5 parts by weight of a silicone-based surfactant, and 10 parts by weight of talc as a foam breaker under normal pressure to cause crosslinking and foaming.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, conventional resin foams have poor foamability and insufficient flexibility. In addition, it is required to refine the cells of the resin foam and improve various properties such as sealing properties according to the use of the resin foam.

[0005] The present disclosure has been made in view of the above circumstances, and aims to improve the foamability of the resin foam and achieve refinement of the cells. The present disclosure can be realized in the following forms.

Means for Solving the Problems

[0006] A resin foam obtained by foaming a resin composition containing at least a polyolefin resin containing ethylene vinyl acetate copolymer, a petroleum resin and / or a styrene resin.

Advantages of the Invention

[0007] The resin foam of the present disclosure has good foam-breaking properties and the cells are refined.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] Here, desirable examples of the present disclosure are shown. · The resin foam, wherein the petroleum resin and / or the styrene resin is contained in an amount of 2.0 parts by mass or more and 20 parts by mass or less based on 100 parts by mass in total of the polyolefin resin. · The resin foam, wherein the resin composition contains a silicone resin. · The resin foam, wherein the silicone resin is contained in an amount of more than 0 part by mass and 10 parts by mass or less based on 100 parts by mass in total of the polyolefin resin. · The resin foam having 50 cells / 25 mm or more based on JIS K6767.

[0010] Hereinafter, the present disclosure will be described in detail. In this specification, for a description using "-" for a numerical range, unless otherwise specified, it includes the lower limit value and the upper limit value. For example, in the description of "10 - 20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10 - 20" has the same meaning as "10 or more and 20 or less".

[0011] 1. Resin Foam The resin foam of the present disclosure is formed by foaming a resin composition containing at least a polyolefin resin containing an ethylene vinyl acetate copolymer, and a petroleum resin and / or a styrene resin.

[0012] The resin composition preferably contains a polyolefin resin, a petroleum resin and / or a styrene resin, and a silicone resin. Further, the resin composition may contain a foaming agent and a crosslinking agent (vulcanizing agent). Each component of the composition will be described.

[0013] (1) Polyolefin resin The polyolefin resin is not particularly limited as long as it contains an ethylene vinyl acetate copolymer (EVA). The polyolefin resin may contain only EVA, but preferably contains EVA and a polyolefin resin other than EVA.

[0014] The ethylene vinyl acetate copolymer is a polymer containing a structural unit derived from ethylene and a structural unit derived from vinyl acetate in the molecule. The content of vinyl acetate in EVA is not particularly limited. From the viewpoint of improving flexibility, when the mass of EVA is 100% by mass, the content of vinyl acetate is preferably 5% by mass or more, more preferably 10% by mass or more. From the viewpoint of preventing excessive crosslinking, the content of vinyl acetate is preferably 40% by mass or less, more preferably 30% by mass or less. From these viewpoints, the content of vinyl acetate is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 30% by mass or less. The content of vinyl acetate is based on JIS K 6924-1.

[0015] The melt flow rate (MFR) of EVA is not particularly limited. From the viewpoint of moldability, the MFR of EVA is preferably 0.1 g / 10 min - 20 g / 10 min, more preferably 0.3 g / 10 min - 10 g / 10 min, still more preferably 0.5 g / 10 min - 5.0 g / 10 min, as measured according to JIS K6924-1 at 190°C and a load of 2.16 kg.

[0016] From the perspective of flexibility in the foaming process, when the total amount of the polyolefin resin is 100 parts by mass, the content of EVA exceeds 0 part by mass, preferably 40 parts by mass or more, more preferably 60 parts by mass or more. From the perspective of preventing excessive crosslinking, the content of the above-mentioned EVA is 100 parts by mass or less, preferably 90 parts by mass or less, more preferably 80 parts by mass or less. From these perspectives, the content of the above-mentioned EVA exceeds 0 part by mass and is 100 parts by mass or less, preferably 40 parts by mass or more and 90 parts by mass or less, more preferably 60 parts by mass or more and 80 parts by mass or less.

[0017] Examples of the polyolefin resin other than EVA include polyethylene resins (excluding EVA), polypropylene resins, and mixtures thereof. The polyolefin resin other than EVA may be blended as a diluent resin for the masterbatch. Examples of the masterbatch include a silicone masterbatch containing a silicone resin, a blowing agent masterbatch, and the like.

[0018] Examples of the polyethylene resin (excluding EVA) include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-propylene-1-butene copolymer, ethylene-(4-methyl-1-pentene) copolymer, ethylene-acrylic acid ester copolymer, and the like. These polyethylene resins may be used alone or in combination of two or more.

[0019] Low-density polyethylene is usually formed by randomly branching and bonding repeating units of ethylene. From the perspective of moldability, it is preferably one with a melt flow rate (MFR) measured at 190 °C and 2.16 kgf in accordance with JIS K7210-1 of 0.1 g / 10 min - 20 g / 10 min, more preferably 0.3 g / 10 min - 10 g / 10 min, and even more preferably 0.5 g / 10 min - 5.0 g / 10 min.

[0020] Linear low-density polyethylene is a copolymer of ethylene without long-chain branches and an α-olefin. Examples of the α-olefin include propylene, 1-butene, 1-heptene, 1-hexene, 1-octene, 4-methyl-1-pentene, and the like.

[0021] Polypropylene-based resin is a polymer containing structural units derived from propylene in one molecule and is formed by polymerizing monomer components containing propylene. The polypropylene-based resin may be a homopolymer of propylene or a copolymer of propylene and an olefin other than propylene (excluding ethylene). Also, the polypropylene-based resin may be used alone or in combination of two or more.

[0022] From the perspective of adjusting the degree of crosslinking and melt viscosity for obtaining a good foam and preventing sagging after foam breakage, the polyolefin-based resin preferably contains EVA and a polyethylene-based resin (excluding EVA), and more preferably contains EVA and low-density polyethylene. When the total amount of the polyolefin-based resin is 100 parts by mass, the content of low-density polyethylene is preferably 0 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, and even more preferably 10 parts by mass or more and 35 parts by mass or less.

[0023] (2) Petroleum resin Petroleum resins are obtained by polymerizing fractions containing unsaturated hydrocarbon monomers by-produced by thermal decomposition of petroleum naphtha or the like. Examples of petroleum resins include aliphatic petroleum resins (C5-based petroleum resins), aromatic petroleum resins (C9-based petroleum resins), aliphatic / aromatic petroleum resins (C5 / C9-based petroleum resins), and alicyclic petroleum resins (hydrogenated petroleum resins). The aliphatic petroleum resin (C5-based petroleum resin) is a synthetic resin obtained by polymerizing the purified components of the C5 fraction of petroleum naphtha cracked oil. The aromatic petroleum resin (C9-based petroleum resin) is a synthetic resin obtained by polymerizing the purified components of the C9 fraction of petroleum naphtha cracked oil. The aliphatic / aromatic petroleum resin (C5 / C9-based petroleum resin) is a synthetic resin obtained by copolymerizing a raw material blended with the above C5 fraction and C9 fraction. From the viewpoint of compatibility with polyolefin resins, the petroleum resin is particularly preferably a C9-based hydrogenated petroleum resin.

[0024] From the viewpoints of odor, hue, thermal stability, weather resistance, and compatibility with polyolefin resins, the petroleum resin is preferably a hydrogenated petroleum resin. The hydrogenated petroleum resin is a resin obtained by adding hydrogen atoms to the unsaturated double bonds present in the petroleum resin. As the hydrogenated petroleum resin, both a fully hydrogenated type of hydrogenated petroleum resin with a hydrogenation rate of 90% or more and a partially hydrogenated type of hydrogenated petroleum resin with a hydrogenation rate of less than 90% can be used. The hydrogenation rate (hydrogenation ratio) of the petroleum resin is not particularly limited. From the viewpoint of suitably refining the cells, the hydrogenation rate of the petroleum resin is preferably 5% or more, more preferably 10% or more, still more preferably 25% or more, and may be 40% or more. The upper limit value of the hydrogenation rate of the petroleum resin is not particularly limited and may be 100%, or may be 90% or less, 80% or less, 70% or less.

[0025] Commercially available products of C9 hydrogenated petroleum resins include, for example, Alcon P-90, Alcon P-100, Alcon P-115, Alcon P-125, Alcon P-140, Alcon M-90, Alcon M-100, Alcon M-115, Alcon M-135 (manufactured by Arakawa Chemical Industries, Ltd.), and the like. Commercially available products of C5 hydrogenated petroleum resins include, for example, East Tack C115W (manufactured by Eastman Chemical Company), and the like. Commercially available products of C5 / C9 hydrogenated petroleum resins include those of dicyclopentadiene / aromatic copolymerized hydrogenated petroleum resins, for example, Imarve S-100, Imarve S-110, Imarve P-100, Imarve P-125, Imarve P-140 (manufactured by Idemitsu Kosan Co., Ltd.), and the like. Commercially available products of C5 / C9 non-hydrogenated petroleum resins include, for example, Petro Tack 70 (manufactured by Tosoh Corporation), and the like. Note that the numbers at the end of the above product names are catalog values indicating the softening point (°C) of the petroleum resin. From the viewpoint of handleability, the softening point of the petroleum resin can be, for example, 70°C or higher, 80°C or higher, 90°C or higher, preferably greater than 90°C, more preferably 100°C or higher, 110°C or higher. The upper limit of the softening point is not particularly limited, but from the viewpoint of easy availability, it may be, for example, 140°C or lower. The difference in the softening point does not significantly affect the properties of the resin foam, but a petroleum resin with a low softening point may cause blocking, etc., where a powder becomes a lump during transportation, storage, etc. In that regard, if the softening point is within the above range, the petroleum resin is easy to handle. The petroleum resin may be used alone or in combination of two or more.

[0026] (3) Styrene resin The styrene resin can be obtained by addition polymerization of one or more styrene monomers. The addition polymerization reaction can be carried out according to known methods, for example, by solution polymerization using a living anionic polymerization catalyst, by using a cationic polymerization catalyst, or by addition polymerization using a radical polymerization initiator. Examples of styrene monomers include styrene, α-methylstyrene, β-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-phenylstyrene, and the like. Note that the styrene resin may be used alone or in combination of two or more.

[0027] From the viewpoint of compatibility with polyolefin resins and the like, the styrene resin is preferably a hydrogenated styrene resin. The hydrogenated styrene resin is obtained by hydrogenating a styrene resin to change at least a part of the aromatic ring into an alicyclic ring.

[0028] The hydrogenated styrene resin can be obtained by hydrogenating at least a part of the aromatic ring derived from the styrene monomer in the above styrene resin. The hydrogenation method is a conventionally known method and is not particularly limited. For example, it is carried out by bringing into contact with a solution obtained by dissolving a styrene resin in a solvent in the presence of a known hydrogenation catalyst by blowing hydrogen or the like. Examples of the hydrogenation catalyst include homogeneous catalysts composed of a combination of a transition metal compound / alkyl metal compound such as cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium; heterogeneous metal catalysts such as nickel, palladium, and platinum; and heterogeneous solid-supported catalysts obtained by supporting a metal catalyst such as nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth, palladium / alumina on a carrier.

[0029] The hydrogenation rate (hydrogenation ratio) of the hydrogenated styrene resin is not particularly limited. From the viewpoint of preferably refining the cells, the hydrogenation rate of the hydrogenated styrene resin is preferably 5% or more, more preferably 10% or more, still more preferably 25% or more, and may be 40% or more. The upper limit value of the hydrogenation rate of the hydrogenated styrene resin is not particularly limited and may be 100%, or may be 95% or less, 90% or less, 80% or less, or 70% or less.

[0030] Here, the hydrogenation rate of the hydrogenated styrene resin is a value calculated by the following formula from the peak height of the absorbance derived from the styrene compound using an IR (infrared spectrophotometer). Hydrogenation rate (%) = {(C - D) / C} × 100 C: Peak height of absorbance derived from the aromatic ring before hydrogenation D: Peak height of absorbance derived from the aromatic ring after hydrogenation

[0031] The molecular weight of the styrene resin is not particularly limited. The molecular weight of the styrene resin is preferably 500 - 10,000, more preferably 800 - 5,000, and even more preferably 1,000 - 4,000 as the polystyrene-equivalent weight average molecular weight (Mw) determined by gel permeation chromatography (GPC). Commercially available products of the styrene resin include, as the hydrogenated styrene resin, for example, YS Resin SG-110, YS Resin SM-100, YS Resin SS-115 (manufactured by Yasuhara Chemical Co., Ltd.). Commercially available products of the styrene resin include, as the non-hydrogenated styrene resin, for example, YS Resin SX-100 (manufactured by Yasuhara Chemical Co., Ltd.).

[0032] (4) Content of petroleum resin and / or styrene resin From the viewpoint of improving foamability and cell refinement, the content of the petroleum resin and / or styrene resin is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, and still more preferably 4.0 parts by mass or more with respect to 100 parts by mass in total of the polyolefin resin. From the viewpoint of suppressing deterioration of physical properties such as loss of resilience of the resin foam due to excessive foaming, the content of the above petroleum resin and / or styrene resin is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less. From these viewpoints, the content of the above petroleum resin and / or styrene resin is preferably 2.0 parts by mass or more and 20 parts by mass or less, more preferably 3.0 parts by mass or more and 15 parts by mass or less, and still more preferably 4.0 parts by mass or more and 12 parts by mass or less. Further, even when the content of the above petroleum resin and / or styrene resin is 8 parts by mass or less or 6 parts by mass or less, improvement in foamability and cell refinement can be achieved. In addition, when the resin composition contains only one of the petroleum resin and the styrene resin, the content of the petroleum resin and / or styrene resin means the content of one resin. When the resin composition contains both the petroleum resin and the styrene resin, the content of the petroleum resin and / or styrene resin means the total content of the petroleum resin and the styrene resin.

[0033] (5) Silicone resin The silicone resin is an optional component. As the silicone resin, for example, polyorganosiloxane and the like can be preferably used. Here, polyorganosiloxane has a siloxane bond as the main chain and an organic group in the side chain, and examples of the organic group include a methyl group, a vinyl group, an ethyl group, a propyl group, and a phenyl group.

[0034] Specific examples of polyorganosiloxane include dimethylpolysiloxane, methylethylpolysiloxane, methyloctylpolysiloxane, methylvinylpolysiloxane, methylphenylpolysiloxane, methyl(3,3,3-trifluoropropyl)polysiloxane, and the like.

[0035] The silicone resin can be used in the form of silicone gum, silicone powder, silicone oil, or silicone resin. Among these, from the viewpoint of being less likely to cause blooming, it is preferably used in the form of silicone gum.

[0036] From the viewpoint of improving water stoppage by imparting water repellency, the content of the silicone resin is preferably more than 0 parts by mass, more preferably 1.0 part by mass or more, and still more preferably 1.5 parts by mass or more with respect to 100 parts by mass in total of the polyolefin resin. From the viewpoint of dispersibility in the polyolefin resin, the content of the above silicone resin is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. From these viewpoints, the content of the above silicone resin is preferably more than 0 parts by mass and 10 parts by mass or less, more preferably 1.0 part by mass or more and 7 parts by mass or less, and still more preferably 1.5 parts by mass or more and 5 parts by mass or less.

[0037] (6) Blowing agent The blowing agent is not particularly limited, but a thermal decomposition type blowing agent that decomposes by heat to generate gas is preferred. As the thermal decomposition type blowing agent, an organic blowing agent or an inorganic blowing agent can be used.

[0038] Examples of the organic blowing agent include azodicarbonamide (ADCA), barium azodicarboxylate, azobisisobutyronitrile (AIBN), azocyclohexylnitrile, N,N'-dinitrosopentamethylenetetramine, 4,4'-oxybisbenzenesulfonylhydrazide, toluenesulfonyl semicarbazide, and the like.

[0039] Examples of the inorganic blowing agent include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, sodium nitrite, ammonium nitrite, sodium borohydride, anhydrous sodium citrate, and the like.

[0040] The blowing agent may be used alone or in combination of two or more kinds. Among the above, azo compounds such as azodicarbonamide, barium azodicarboxylate, azobisisobutyronitrile, and nitroso compounds such as N,N'-dinitrosopentamethylenetetramine are preferred because they can form fine bubbles. Particularly preferred is azodicarbonamide (ADCA).

[0041] The blowing agent is preferably 5-35 parts by mass, more preferably 10-30 parts by mass, and still more preferably 15-25 parts by mass with respect to 100 parts by mass in total of the polyolefin resin.

[0042] (7) Crosslinking agent The crosslinking agent is not particularly limited. Examples of the crosslinking agent include organic peroxides such as dicumyl peroxide (DCP), 2,5-dimethyl-2,5-bis-tert-butylperoxyhexane, and 1,3-bis-tert-peroxy-isopropylbenzene.

[0043] (8) Other components The resin composition may contain additives such as a filler (such as calcium carbonate), a foaming aid (such as zinc stearate, urea-based foaming aid), a crosslinking aid, an antioxidant, a pigment, a plasticizer, thermally expandable particles, and a functional agent (for example, a flame retardant) as required. These additives may be used alone or in combination of two or more kinds. Also, the composition may contain a polymer such as a modifier other than the above-mentioned polymers (hereinafter also referred to as other polymers) within a range where the effects of the present disclosure are not significantly inhibited.

[0044] 2. Structure of the resin foam The cell structure of the resin foam is not particularly limited. The resin foam preferably has an open-cell structure. As will be described later, the resin foam having an open-cell structure can be obtained by rupturing the cell membranes to connect the cells of the resin foam. When the resin foam has an open-cell structure, the physical properties of the following resin foam are measured using a sample that has undergone the cell-rupturing process described later. The conditions of the cell-rupturing process can be appropriately changed according to the required physical properties, but the physical properties of the following resin foam are, for example, the measured values obtained using a sample that has passed through 10 rolls in the cell-rupturing process.

[0045] (1) Cell count The resin foam of the present disclosure preferably has a cell count of 50 cells / 25 mm or more, more preferably 60 cells / 25 mm or more, and even more preferably 70 cells / 25 mm or more, as measured based on the procedure described in the cell counting procedure of JIS K6767:1999 Annex A (specified). The upper limit of the above cell count is not particularly limited, but may be, for example, 100 cells / 25 mm or less, 90 cells / 25 mm or less, or 85 cells / 25 mm or less. In the present disclosure, a cell means a pore portion in the foam. The cell count is the number of cells per 25 mm of the sample piece, which is counted based on JIS K6767:1999.

[0046] (2) Density The density of the resin foam is preferably 20 kg / m 3 or more and 100 kg / m 3 or less, more preferably 25 kg / m 3 or more and 50 kg / m 3 or less, and even more preferably 30 kg / m 3 or more and 40 kg / m 3 or less. The above density is the apparent density measured in accordance with JIS K7222:2005. By setting the density within the above range, the resin foam can be lightened. Note that, as shown in the following formula, the expansion ratio can be calculated as the reciprocal of the density. Expansion ratio = 1000 / A A: Density (kg / m 3 ) The expansion ratio of the resin foam is preferably 10 to 50 times, more preferably 20 to 40 times, and even more preferably 25 to 35 times.

[0047] (3) Compressive stress 50% When the compressive stress of the resin foam is measured according to the test method of "compressive stress - strain" in JIS K6767:1999 (when compressed by 50%, corresponding to ISO 3386-1), it is preferably 10 kPa or less, more preferably 8 kPa or less, and even more preferably 5.5 kPa or less. The lower limit of the compressive stress of the resin foam is not particularly limited, but usually it is 0.1 kPa or more. Note that the compressive stress of the above resin foam can be adjusted by changing, for example, the blending ratio of the petroleum resin and / or styrene resin in the resin composition, the degree of cell connection, etc.

[0048] (4) Compressive set When the compressive set of the resin foam is measured according to the test method of "compressive set" in JIS K6767:1999 (measurement of the thickness 24 hours after the end of compression, corresponding to ISO 1856), it is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 2.5% or less. The lower limit of the compressive set of the resin foam is not particularly limited, but usually it is 0.1% or more.

[0049] (5) Gel fraction The gel fraction of the resin foam is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more. The upper limit of the gel fraction is 100% or less, and for example, it may be 95% or less, 90% or less. The gel fraction is measured in accordance with JIS K6796. The higher the numerical value of the gel fraction, the higher the degree of crosslinking of the resin foam. Note that the above gel fraction can be adjusted by changing the type of crosslinking agent, the blending ratio, the presence or absence of electron beam crosslinking, the conditions of electron beam crosslinking, etc.

[0050] (6) Water stoppage property and uses The resin foam is suitable as a water sealing material. When used as a water sealing material, the resin foam is, for example, made into a thickness and shape (e.g., string-like) according to the application by punching or the like and then used. The resin foam preferably has a holding time of 30 minutes or more, more preferably 9 hours or more, and still more preferably 24 hours or more under a water pressure of 100 mmAq as described later. The holding time of 100 mmAq water pressure is determined as follows: A water tightness measurement sample 1 made by punching a 10 mm thick water sealing material into a U shape with the dimensions shown in Fig. 1 is sandwiched between two acrylic resin plates 2, 2 in a compressed state with a predetermined compression ratio (e.g., 50%, 60%, 70%) as shown in Fig. 2, and water W is injected into the U-shaped test sample 1 to a water pressure of 100 mAq in that state, and it is the time during which the 100 mmAq water pressure is maintained. Note that the applications of the resin foam are not limited to water sealing materials, and it can be widely used in various sealing materials, cushioning materials, heat insulating materials, adsorbents, building members, automotive members, daily necessities, etc.

[0051] 3. Manufacturing method of resin foam The manufacturing method of the resin foam is not particularly limited. For example, a method can be adopted in which a foaming agent is added to a polyolefin resin, and if necessary, a crosslinking agent and other additives are arbitrarily added and mixed, and then foaming molding is performed. Preferably, the manufacturing method of the polyolefin resin foam can be any of the following two-stage block foaming method, one-stage block foaming method, long-length foaming method using chemical crosslinking, and long-length foaming method using electron beam crosslinking. Among these, the block foaming method is preferable, and the two-stage block foaming method is more preferable in that a resin foam with a relatively large thickness can be manufactured, and the compression ratio can be increased in the defoaming process described later due to the large thickness.

[0052] <Two-stage block foaming method> The two-stage block foaming method includes, for example, the following steps (1)-(4). (1) Kneading step The above-mentioned polyolefin resin, petroleum resin and / or styrene resin, crosslinking agent, foaming agent, silicone resin (optional component), additive (optional component) and filler and auxiliary agent required as appropriate are melt-kneaded at a temperature below the decomposition temperature of the foaming agent by a kneading device such as an extruder, Banbury mixer, kneader, roll, etc. to obtain a foaming resin composition. (2) Primary foaming process The foaming resin composition obtained in the kneading process is filled into the molding space of the primary mold and heated under pressure. Thereby, a part of the crosslinking agent, or a part of the crosslinking agent and the foaming agent is decomposed. Then, the pressure is released and the foaming resin composition intermediate is taken out. The heating temperature is usually determined in the range of 130-150°C, and the heating time is usually in the range of 25-50 minutes. (3) Secondary foaming process The foaming resin composition intermediate obtained in the primary foaming process is placed in the molding space of the secondary mold, heated under normal pressure for secondary foaming, and then the resin foam is taken out from the secondary mold. (4) Defoaming process The resin foam obtained in the secondary foaming process is subjected to a compression treatment of passing between two rolls rotating in different directions to obtain a continuous cell resin foam. This process is a process of rupturing the cell membrane and connecting the cells of the resin foam by performing a compression treatment of passing the resin foam between two rolls rotating in different directions. Here, the compression conditions (compression ratio, peripheral speed ratio of the rolls) and the number of compression treatments at each compression treatment can be appropriately set according to the degree of cell connection. For example, the compression treatment is preferably performed repeatedly a plurality of times.

[0053] <One-step block foaming method> The one-step block foaming method includes, for example, the following steps (1)-(3). (1) Kneading process The above-mentioned polyolefin resin, petroleum resin and / or styrene resin, crosslinking agent, foaming agent, silicone resin (optional component), additive (optional component) and filler and auxiliary agent required as appropriate are melt-kneaded at a temperature below the decomposition temperature of the foaming agent by a kneading device such as an extruder, Banbury mixer, kneader, roll, etc. to obtain a foaming resin composition. (2) Foaming process The foaming resin composition obtained in the kneading step is filled into a mold, sealed, and heated for a predetermined time under pressure (heated at a temperature equal to or higher than the decomposition temperature of the foaming agent and the crosslinking agent), thereby promoting the crosslinking of the crosslinking agent and the decomposition of the foaming agent. Then, the mold is opened and depressurized to obtain a resin foam. (3) Defoaming step The resin foam obtained in the foaming step is subjected to a compression treatment by passing it between two rolls rotating in opposite directions to obtain a closed-cell resin foam. For details, the description of the defoaming step in the two-stage block foaming method is incorporated by reference.

[0054] <Long-scale foaming method using chemical crosslinking> The long-scale foaming method includes, for example, the following steps (1)-(3). (1) Kneading step The above-mentioned polyolefin resin, petroleum resin and / or styrene resin, crosslinking agent, foaming agent, silicone resin (optional component), additive (optional component) and appropriately required filler and auxiliary agent are kneaded with a single-screw extruder, twin-screw extruder, etc. and extruded into a sheet shape to extrude a foaming resin composition having a predetermined shape such as a sheet (hereinafter referred to as a mother board). (2) Foaming step The mother board obtained in the kneading step is heated and foamed at 120-250 °C (equal to or higher than the decomposition temperature of the foaming agent and the crosslinking agent) for 5-20 minutes while being transported in a heating device such as an oven to obtain a resin foam. It is preferable to use a device in which a heating device such as an oven and a transport device are integrated, so that the mother board can be continuously processed. (3) Defoaming step The resin foam obtained in the foaming step is subjected to a compression treatment by passing it between two rolls rotating in opposite directions to obtain a closed-cell resin foam. For details, the description of the defoaming step in the two-stage block foaming method is incorporated by reference.

[0055] <Long-scale foaming method using electron beam crosslinking> The long-scale foaming method using electron beam crosslinking includes, for example, the following steps (1)-(4). (1) Kneading step The above-mentioned polyolefin resin, petroleum resin and / or styrene resin, foaming agent, silicone resin (optional component), cross-linking agent (optional component), additive (optional component) and filler and auxiliary agent as required are kneaded by a single-screw extruder, twin-screw extruder, etc., and a resin composition in a predetermined shape such as a sheet (hereinafter referred to as a mother board) is extruded. Kneading and extrusion can be carried out collectively by an extruder. In order to perform uniform kneading, it is preferable to perform extrusion after mixing each component in advance. (2) Cross-linking step The mother board obtained in the kneading step is cross-linked. As the cross-linking method, a method of cross-linking with ionizing radiation such as electron beam and γ-ray can be used. As the cross-linking method, cross-linking by electron beam irradiation (electron beam cross-linking) is preferable. This is because electron beam cross-linking can achieve refinement of cells formed in the foam and can control the cell diameter within a predetermined range. Electron beam cross-linking can be carried out using an electron beam irradiator. In addition, if necessary, a cross-linking agent such as the above-mentioned organic peroxide may be blended and chemical cross-linking may be used in combination. The irradiation dose of the electron beam is preferably 4.0 Mrad - 8.0 Mrad (40 kGy - 80 kGy). If the irradiation dose is less than 4.0 Mrad, it may not foam well in the foaming step described later. If the irradiation dose exceeds 8.0 Mrad, the cross-linking is strong and the resin becomes hard, so there is a concern that cracks may occur during foaming. The acceleration voltage of the electron beam may be appropriately adjusted according to the thickness of the mother board, etc., and is not particularly limited. (3) Foaming step The cross-linked mother board obtained in the cross-linking step is heated at 120 - 250 °C (above the decomposition temperature of the foaming agent and cross-linking agent) for 5 - 20 minutes while being transported in a heating device such as an oven to foam, thereby obtaining a resin foam. In addition, it is preferable to use a device in which a heating device such as an oven and a transport device are integrated, because the mother board can be continuously processed. (4) Defoaming step The resin foam obtained in the foaming step is subjected to a compression treatment of passing between two rolls rotating in different directions to obtain an open-cell resin foam. For details, the description of the defoaming step in the two-stage block foaming method is incorporated by reference.

[0056] 4. Effects and advantages of this embodiment The resin foam of this embodiment has good foam breakdown property, and the cells are refined. Generally, when the cells are refined, it becomes difficult to rupture the cell membrane, and the foam breakdown property of the cells tends to deteriorate. In this embodiment, it is presumed that by including a petroleum resin and / or a styrene resin in the resin composition, it was possible to achieve both improvement in foam breakdown property and refinement of the cells. More specifically, since the resin foam of this embodiment has good foam breakdown property, the flexibility of the resin foam can be suitably improved by adopting a closed-cell structure. Therefore, when the resin foam is used as a sealing material, the adhesiveness to the adherend becomes high, and the sealing property can be improved. Furthermore, since the cells of the resin foam of this embodiment are refined, when the resin foam is used as a sealing material, it is difficult to form a gap between the resin foam and the adherend. Therefore, when the resin foam is used as a sealing material, the inflow of water, air, etc. from between the sealing material and the adherend can be suppressed, and the sealing property can be improved.

[0057] Also, when the resin composition contains a silicone resin, the water-stopping property is good. It is presumed that the silicone resin increases the water repellency of the resin foam and improves the water-stopping property.

Examples

[0058] Hereinafter, it will be described in more detail with reference to examples. In Tables 1 and 2, when a "*" is attached as in "Experimental Example 11*", it indicates a comparative example. Experimental Examples 1-10 and 13-20 are examples, and Experimental Examples 11 and 12 are comparative examples.

[0059] 1. Preparation of resin foam The resin foams of the experimental examples were prepared at the compounding ratios shown in Tables 1 and 2. In Tables 1 and 2, the details of the main raw materials are shown below.

[0060] · Polyolefin resin 1: Ethylene vinyl acetate copolymer (EVA) (vinyl acetate content 19% by weight, density 941 kg / m 3 , MFR 2.5 g / 10 min) · Polyolefin resin 2: Low-density polyethylene (LDPE) (density 924 kg / m 3 , MFR 3.0 g / 10 min) · Petroleum resin 1: C5 / C9 hydrogenated petroleum resin (fully hydrogenated type), manufactured by Idemitsu Kosan Co., Ltd., Imarub P-100 (softening point 100 °C) · Petroleum resin 2: C5 / C9 hydrogenated petroleum resin (partially hydrogenated type), manufactured by Idemitsu Kosan Co., Ltd., Imarub S-100 (softening point 100 °C) · Petroleum resin 3: C9 hydrogenated petroleum resin (fully hydrogenated type), manufactured by Arakawa Chemical Industries, Ltd., Alcon P-90 (softening point 90 °C) · Petroleum resin 4: C9 hydrogenated petroleum resin (partially hydrogenated type), manufactured by Arakawa Chemical Industries, Ltd., Alcon M-90 (softening point 90 °C) · Petroleum resin 5: C9 hydrogenated petroleum resin (partially hydrogenated type), manufactured by Arakawa Chemical Industries, Ltd., Alcon M-100 (softening point 100 °C) · Petroleum resin 6: C9 hydrogenated petroleum resin (partially hydrogenated type), manufactured by Arakawa Chemical Industries, Ltd., Alcon M-115 (softening point 115 °C) · Styrene resin 1: Hydrogenated styrene resin (C8) (partially hydrogenated type), manufactured by Yasuhara Chemical Co., Ltd., YS Resin SM-100 (softening point 94.0 °C) · Styrene resin 2: Hydrogenated styrene resin (C8) (partially hydrogenated type), manufactured by Yasuhara Chemical Co., Ltd., YS Resin SG-110 (softening point 106.5 °C) · Styrene resin 3: Styrene resin (C8) (non-hydrogenated type), manufactured by Yasuhara Chemical Co., Ltd., YS Resin SX-100 (softening point 101.0 °C) · Petroleum resin 7: C5 / C9 petroleum resin (non-hydrogenated type), manufactured by Toray Industries, Inc., Petro Tack 70 (softening point 70 °C) · Silicone masterbatch (silicone resin / polyolefin resin 3): A masterbatch made of low-density polyethylene (LDPE) and silicone gum composed of dimethylpolysiloxane at a ratio of 1:1 (mass ratio), manufactured by Shin-Etsu Chemical Co., Ltd., X-22-2125H · Blowing agent masterbatch (ADCA / polyolefin resin 4): A masterbatch made of azodicarbonamide (ADCA) and low-density polyethylene (LDPE) at a ratio of 3:2 (mass ratio) · Filler: Heavy calcium carbonate (average particle diameter (D50) 3.4 μm) · Crosslinking agent: Dicumyl peroxide (DCP) · Foaming aid: Foaming aid containing zinc stearate

[0061] In Tables 1 and 2, the blending ratio represents the blending ratio (parts by mass) when the total amount of the polyolefin resin is 100 parts by mass. For "silicone masterbatch", the blending ratio of "silicone resin (silicone gum)" and "polyolefin resin 3 (LDPE)" is shown in parentheses. For "foaming agent masterbatch", the blending ratio of "ADCA" and "polyolefin resin 4 (LDPE)" is shown in parentheses.

[0062] The raw materials were mixed at the blending ratios described in Tables 1 and 2, and a resin foam was obtained by the two-stage block foaming method described in the embodiment. In the defoaming process, the compression treatment of passing the molded body between two rolls rotating in different directions was performed 10 times. The obtained resin foam was sliced into 10 mm and evaluated by the evaluation method described below.

[0063] 2. Evaluation method (1) Density (apparent density) Density (kg / m 3 ) was measured as the apparent density based on JIS K7222:2005. (2) Compression stress 50% Compression stress 50% (kPa) was measured in accordance with the test method of "compression stress - strain" in JIS K6767:1999 (at 50% compression, corresponding to ISO 3386-1). A low compression stress 50% is one of the indicators of high flexibility of the resin foam. (3) Compression set Compression set (%) was measured in accordance with the test method of "compression set" in JIS K6767:1999 (measurement of the thickness 24 hours after the end of compression, corresponding to ISO 1856). (4) Gel fraction Gel fraction (%) was measured in accordance with JIS K6796. (5) Cell number The number of cells was counted based on JIS K6767:1999 by counting the number of cells per 25 mm of the sample piece. (6) Water resistance Using the evaluation method described in the embodiment, the retention time of a 100 mmAq water pressure in the resin foam was measured. The compression ratio of the resin foam during the measurement was set to 50%. Based on the retention time of the 100 mmAq water pressure, the water resistance of the resin foam was evaluated according to the following criteria. Pass: The retention time of the 100 mmAq water pressure is 24 hours or more. Fail: The retention time of the 100 mmAq water pressure is less than 24 hours.

[0064] [Table 1]

[0065] [Table 2]

[0066] 3. Results The results are shown together in Table 1 and Table 2. Experimental Examples 1-10, 13-20 satisfy the following requirements (a)-(c). In contrast, Experimental Examples 11 and 12 do not satisfy requirement (b). Experimental Examples 1-10, 13-20 had a lower 50% compression stress and a larger number of cells than Experimental Examples 11 and 12. Also, Experimental Examples 1-10, 13-18 showed good physical property values for "density", "50% compression stress", "compression set", and "gel fraction". · Requirement (a): The resin composition contains a polyolefin resin containing at least an ethylene-vinyl acetate copolymer. · Requirement (b): The resin composition contains a petroleum resin and / or a styrene resin. · Requirement (c): The resin composition is foamed.

[0067] Among Experimental Examples 1 - 10, Experimental Examples 1, 2, 9, 10, 14, 15, and 16 satisfy the following requirement (d). In contrast, Experimental Examples 11 and 12 do not satisfy requirement (d). Experimental Examples 1, 2, 9, 10, 14, 15, and 16 had a "qualified" evaluation for water stoppage performance and were excellent in water stoppage. · Requirement (d): The resin composition contains a silicone resin.

[0068] 4. Effects of the Examples According to the above examples, it is possible to provide a resin foam with good foam-breaking properties and refined cells.

[0069] The present disclosure is not limited to the embodiments detailed above, and various modifications or changes are possible.

Claims

1. A resin foam obtained by foaming a resin composition containing at least a polyolefin resin containing an ethylene-vinyl acetate copolymer, a petroleum resin and / or a styrene resin, wherein: The number of cells based on JIS K6767 is 70 cells / 25 mm or more and 100 cells / 25 mm or less, The gel fraction of the resin foam measured based on JIS K6796 is 30% or more.

2. The resin foam according to Claim 1, wherein the resin composition contains an organic peroxide as a crosslinking agent.

3. A resin foam obtained by foaming a resin composition containing at least a polyolefin resin containing an ethylene-vinyl acetate copolymer, a petroleum resin and / or a hydrogenated styrene resin, wherein: The resin foam is a closed-cell resin foam. The density of the resin foam is 20 kg / m ３ or more and 100 kg / m ３ or less. Resin foam.

4. A sealing material comprising the resin foam, wherein: The resin foam is a sealing material obtained by foaming a resin composition containing at least a polyolefin resin containing an ethylene-vinyl acetate copolymer, a petroleum resin and / or a styrene resin.

5. A method for producing a closed-cell resin foam obtained by foaming a resin composition containing at least a polyolefin resin containing an ethylene-vinyl acetate copolymer, a petroleum resin and / or a styrene resin, the method comprising a cell-breaking step. A method for producing a closed-cell resin foam, comprising a cell-breaking step.

6. A sealing material or adsorbent comprising the resin foam, wherein: The resin foam is a sealing material or adsorbent obtained by foaming a resin composition containing at least a polyolefin resin containing an ethylene-vinyl acetate copolymer, a petroleum resin and / or a hydrogenated styrene resin.

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