JP6110213B2 - Thermoplastic resin foam, foam sealing material, and method for producing thermoplastic resin foam - Google Patents

Description

  The present invention relates to a thermoplastic resin foam and a foam sealing material.

Conventionally, resin foam has been used as a gasket material for mobile phones and portable information terminals.
Examples of the resin foam include a low-foam urethane resin foam of fine cells having an open-cell structure, a compression-molded high-foam urethane, and a polyethylene resin foam having closed cells and an expansion ratio of about 30 times, density A polyolefin-based resin foam (see Patent Documents 1 and 2) having a weight of 0.2 g / cm ³ or less has been proposed.

Such a resin foam is usually applied as a gasket material for mobile phones and portable information terminals by being processed into a predetermined shape and fixed to a predetermined part of these devices.
However, in such processing and attachment, a dent may be caused by colliding with a corner of a desk, a roll core or the like, or by gripping with a fingertip, a nail, tweezers or the like.
Such dents in the resin foam generally recover over time. On the other hand, when it takes a long time to recover the dent, or when the dent recovery itself is insufficient, the original function as the gasket material cannot be sufficiently achieved.

  In particular, due to recent demands for small and thin mobile phones and portable information terminals, etc., large-scale or high-functionality image display units (equipment of touch panel functions as information input functions, etc.) Because it is often used in an environment, there is a strong demand for characteristics that can realize sufficient and quick recovery of the dent and prevent the occurrence of defects such as dust intrusion and light leakage due to the dent. Yes. In addition, it is required to have flexibility to follow a small clearance of a small and thin mobile phone and a portable information terminal.

JP 2005-227392 A JP 2007-291337 A

  An object of the present invention is to provide a thermoplastic resin foam and a sealing material that can realize sufficient and rapid recovery of a dent.

  As a result of intensive studies to solve the above problems, the present inventors have made the dent recovery rate to be a predetermined value or more in the thermoplastic resin foam, or in addition to having a good thickness recovery rate. By setting the dent recovery rate to a predetermined value or more, it is possible to obtain a thermoplastic resin foam that can improve the dust-proof performance effectively while being able to follow the minute clearance with flexibility. Heading The present invention has been completed.

The present invention includes the following inventions.
(1) A thermoplastic resin foam characterized by having a dent recovery rate at 23 ° C. defined below of 50% or more.
Depression recovery rate: The thermoplastic resin foam was compressed to the lowest point in the thickness direction of the foam with a jig having a blade angle of 90 degrees and maintained for 15 seconds, then the compressed state was released, and the compressed state was released 60 The ratio of the thickness of the dent after 2 seconds to the initial thickness.
(2) The thermoplastic resin foam according to (1), having an average cell diameter of 10 to 200 μm and an apparent density of 0.01 to 0.20 g / cm ³ .
(3) The thermoplastic resin foam according to (1) or (2), wherein the repulsive stress at 50% compression at 23 ° C. defined below is 0.1 to 3.0 N / cm ² .
Repulsive stress at 50% compression: Repulsive load when a thermoplastic resin foam is compressed to 50% of the initial thickness.
(4) The thermoplastic resin foam according to any one of (1) to (3), which is obtained by decompression treatment of a thermoplastic resin composition impregnated with a high-pressure gas.
(5) The thermoplastic resin foam according to (4), wherein the gas is an inert gas.
(6) The thermoplastic resin foam according to (5), wherein the inert gas is carbon dioxide or nitrogen.
(7) The thermoplastic resin foam according to any one of (4) to (6), wherein the gas is a gas in a supercritical state.
(8) The thickness recovery rate at 23 ° C. defined below is 50% or more, and the repulsion stress at 50% compression at −10 ° C. is less than 10.0 N / cm ² (1) to ( The thermoplastic resin foam according to any one of 7).
Thickness recovery rate: In the thickness direction, after compressing to a thickness of 20% of the initial thickness for 1 minute, the compressed state is released, and the ratio of the thickness 1 second after release of the compressed state to the initial thickness (9) The thermoplastic resin foam according to any one of (1) to (8), wherein the rebound stress at 80% compression is 1.0 to 9.0 N / cm ² .
(10) The thermoplastic resin foam according to any one of (1) to (9), wherein a strain recovery rate at 23 ° C. defined below is 75% or more.
Strain recovery rate: The ratio of the thickness to the initial thickness in the thickness direction after the compression state is released for 24 hours at a thickness of 50% with respect to the initial thickness and then the compressed state is released.
(11) A foamed sealing material comprising the thermoplastic resin foam according to any one of (1) to (10) above.
(12) The foam sealing material according to (11), comprising an adhesive material layer disposed on one or both surfaces of the thermoplastic resin foam.
(13) The foamed sealing material according to (12), wherein the adhesive material layer is disposed on the surface of the thermoplastic resin foam via the film layer.

  ADVANTAGE OF THE INVENTION According to this invention, the thermoplastic resin foam which can improve a dustproof performance effectively can be provided, providing a softness | flexibility and enabling tracking to a micro clearance.

It is the front view and side view of a jig | tool for demonstrating the shape of the jig | tool used for evaluation of the dent recovery rate of the thermoplastic resin foam of this invention. It is a top view which shows the shape of the sample for evaluation used when evaluating dynamic dustproofness. It is the top view and A-A 'line schematic sectional drawing of the evaluation container for dynamic dustproof evaluation which assembled the sample for evaluation. It is the schematic which shows the tumbler which set | placed the evaluation container.

  The thermoplastic resin foam of the present invention (hereinafter sometimes simply referred to as “resin foam”) is a foam containing a thermoplastic resin, and is obtained by foaming and molding a thermoplastic resin composition. The shape of the resin foam of this invention is not specifically limited, For example, any forms, such as a lump shape, a sheet form, and a film form, may be sufficient.

[Physical properties of resin foam]
The resin foam of the present invention has a dent recovery rate at 23 ° C. defined below of 50% or more, preferably 52% or more, 55% or more, more preferably 60% or more, and particularly preferably 65% or more. It is.
The dent recovery rate is determined by compressing the thermoplastic resin foam to the lowest point in the thickness direction of the resin foam with a jig having a blade angle of 90 degrees and maintaining it for 15 seconds, then releasing the compressed state and releasing the compressed state. It is defined as the ratio of the thickness of the recessed portion after 60 seconds to the initial thickness.

  For example, as shown in FIG. 1, the jig having a blade angle of 90 degrees used for the evaluation of the dent recovery rate has a right edge at the tip of the blade that gives a dent to the resin foam, and the length L of one side thereof is 1 to 1. The thickness is about 20 mm, preferably about 5 mm, and the thickness M is about 1 to 20 cm, preferably about 5 cm. As long as the tip of the blade that gives a dent to the resin foam is a right angle when the blade is viewed from the side, variations in the length L and the thickness M on one side have little effect on the dent recovery rate.

  Since the resin foam of the present invention has a dent recovery rate of 50% or more at 23 ° C., it is excellent in strain recovery. Therefore, the resin foam of the present invention can exhibit good dust resistance, in particular, good dynamic dust resistance (dustproof performance in a dynamic environment). As a result, when the resin foam of the present invention is assembled as a foam sealing material in the clearance of a mobile phone, a portable information terminal, etc., the resin foam is compressed by vibration and impact at the time of dropping, and the assembled clearance Even if it is deformed to a state where it is not completely closed, the dent can be recovered quickly and sufficiently, the clearance can be sufficiently closed, and the entry of foreign matter such as dust can be effectively prevented.

  In particular, even if the thickness recovery rate per unit surface (strain recovery rate described later) is good, if the dent recovery rate is not good, partial dent recovery cannot be obtained sufficiently and the clearance is blocked. Since it cannot be performed completely, a sufficient dustproof effect may not be obtained. As in the present invention, dents due to partial stress, that is, a better recovery rate in a short time under more severe conditions compared to compression in units of planes, further dynamic dustproofing It becomes possible to ensure the sex.

In the resin foam of the present invention, for example, the cell structure is a closed cell structure or a semi-continuous semi-closed cell structure (a cell structure in which a closed cell structure and an open cell structure are mixed, and the ratio is not particularly limited). It is preferable that In particular, a cell structure in which the closed cell ratio of the resin foam is 50% or less, preferably 40% or less, more preferably 35% or less can be mentioned. By this range, at the time of compressive deformation when an impact is applied, air can easily escape from the resin, and sufficient shock absorption can be exhibited. Further, there is a cell structure in which the closed cell ratio of the resin foam is 10% or more, preferably 15% or more, more preferably 20% or more. With this range, the ratio of open cells can be adjusted to prevent the passage of fine particles such as dust, thereby improving the dust resistance.
The closed cell ratio can be measured, for example, by the method described in the examples.

The resin foam of the present invention further has an average cell diameter in the cell structure of 10 to 200 μm, preferably 10 to 180 μm, more preferably 10 to 150 μm, still more preferably 10 to 90 μm, and particularly preferably 20 to 80 μm. is there.
The average cell diameter is obtained by, for example, capturing an enlarged image of the bubble portion with a digital microscope (trade name “VH-8000” manufactured by Keyence Corporation), and image analysis software (trade name “Win ROOF” manufactured by Mitani Corporation). It can obtain | require by carrying out image analysis using.

  In the resin foam of the present invention, the upper limit of the average cell diameter of the foam is 200 μm or less, preferably 180 μm or less or 150 μm or less, more preferably 90 μm or less, and particularly preferably 80 μm or less, thereby improving dust resistance, The light shielding property can be improved. On the other hand, when the lower limit of the average cell diameter of the foam is 10 μm or more, preferably 20 μm or more, cushioning properties (impact absorption) can be improved.

The resin foam of the present invention further has an apparent density of preferably 0.01 to 0.20 g / cm ³ , more preferably 0.01 to 0.15 g / cm ³ , and 0.01 to 0.10 g / cm. ³ and more preferably 0.02 to 0.08 g / cm ³ . When the apparent density is within this range, the strength can be sufficiently secured and good workability (particularly punching workability) can be obtained. At the same time, flexibility can be ensured, and followability to minute clearances can be obtained when used as a foamed sealing material.

In the resin foam of the present invention, the repulsion stress at 50% compression at 23 ° C. defined below is preferably 0.1 to 3.0 N / cm ² , preferably 0.1 to 2.0 N. / Cm ² , more preferably 0.1 to 1.7 N / cm ² . The repulsive stress at the time of 50% compression at 23 ° C. is defined as the repulsive load when the resin foam is compressed to a thickness of 50% with respect to the initial thickness at 23 ° C. as described above.

  When the resin foam of the present invention has a repulsive stress at the time of 50% compression in this range, good flexibility can be exhibited. Therefore, in particular, when this resin foam is used as a foam sealing material, it is possible to exhibit followability with respect to a minute clearance. For this reason, when the resin foam of the present invention is assembled into a clearance as a foam seal material, even if the clearance is narrow, a problem due to the repulsion of the foam seal material (for example, deformation of a member or casing around the foam seal material) Occurrence of color unevenness in the image display unit, etc.) can be prevented.

  As described above, the resin foam of the present invention has a specific dent recovery rate and a specific average cell diameter, a specific apparent density, and / or a specific repulsion stress at 50% compression at 23 ° C. As a result, it can be followed by a minute clearance, dust resistance and flexibility can be further improved, and dynamic dust resistance can be significantly improved.

  In the resin foam of the present invention, the thickness recovery rate at 23 ° C. defined below is 50% or more (for example, 50 to 100%), preferably 65% or more (for example, 65 to 100%). More preferably, it is 70% or more (for example, 70 to 100%), and more preferably 75% or more (for example, 75 to 100%).

  As described above, the thickness recovery rate at 23 ° C. is that when the compressed state is released after the resin foam is compressed at 23 ° C. to a thickness of 20% of the initial thickness for 1 minute. It is defined as the ratio of the thickness after 1 second to the initial thickness.

  Since the resin foam of the present invention has a thickness recovery rate of 50% or more, the strain recovery property is quick, and thereby good dust resistance, particularly good dynamic dust resistance (dust protection under dynamic environment). Performance). In the case where this resin foam is assembled in a clearance, for example, as a foam seal material, when the foam seal material is deformed by vibration and impact at the time of dropping, that is, the foam seal material is compressed and below the assembled clearance. When the film is deformed to a thickness of 5 mm, the thickness is recovered very quickly and the clearance can be filled. Thereby, the entrance of foreign matter such as dust can be prevented.

Resin foam of the present invention further, repulsion stress at 50% compression at -10 ° C. is preferably less than 10.0 N / cm ^2, more preferably, 9N / cm ² or less, 8N / cm ² or less further preferably is 7N / cm ² or less or 5N / cm ² or less.
The repulsive stress at 50% compression here is defined as the same repulsive load except that the repulsive stress at 50% compression is different from that at 50 ° C. as described above.
Thus, by making the repulsive stress at the time of 50% compression at a low temperature within this range, it becomes possible to ensure more flexibility.

The resin foam of the present invention further has a repulsion stress at 80% compression at 23 ° C. of preferably 1.0 to 9.0 N / cm ² , more preferably 1.0 to 8 N / cm ² , and still more preferably. Is 1.0 to 7.5 N / cm ² .
The repulsive stress at the time of 80% compression here is defined as the repulsive load when the resin foam is compressed to 80% of the initial thickness at 23 ° C. as described above.

The resin foam of the present invention further preferably has a strain recovery rate at 23 ° C. of 75% or more, more preferably 80% or more, and still more preferably 85% or more.
Here, the strain recovery rate is the ratio of the thickness 24 hours after the release of the compressed state to the initial thickness when the compressed state is released after being compressed to 50% of the initial thickness in the thickness direction for 24 hours. Is defined as

  Since the resin foam of the present invention has a strain recovery rate of 75% or more, even if a load is maintained for a long time, it is excellent in recovering the subsequent strain, good dust resistance, particularly good dynamic Dustproofness (dustproofness in a dynamic environment) can be demonstrated.

  Thus, the resin foam of the present invention has a dent recovery rate at 23 ° C, a rebound stress at 50% compression at -10 ° C, a thickness recovery rate at 23 ° C, and 80% compression at 23 ° C. When two or more, preferably all, of the rebound stress and the strain recovery rate at 23 ° C. are satisfactory, it is sufficient in any temperature range with respect to the deformation of the resin foam that is normally considered. The shape can be quickly recovered, and the dustproof performance under the dynamic environment intended in the present invention can be maximized. In addition, when used in an image display unit such as a mobile phone, sufficient light shielding properties or light leakage can be prevented.

[Material of resin foam]
The resin foam of the present invention is formed by a thermoplastic resin or a resin composition containing a thermoplastic resin.
Examples of the thermoplastic resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, a copolymer of ethylene and propylene, ethylene or propylene and another α-olefin (for example, butene -1, pentene-1, hexene-1, 4-methylpentene-1, etc.), ethylene and other ethylenically unsaturated monomers (for example, vinyl acetate, acrylic acid, acrylic ester, methacrylic) Polyolefin resins such as copolymers with acid, methacrylic acid ester, vinyl alcohol, etc.); styrene resins such as polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin); 6-nylon, 66-nylon, 12 -Polyamide resins such as nylon; polyamideimide Polyurethane; Polyimide; Polyetherimide; Acrylic resin such as polymethyl methacrylate; Polyvinyl chloride; Polyvinyl fluoride; Alkenyl aromatic resin; Polyester resin such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate such as bisphenol A polycarbonate; Polyacetal; polyphenylene sulfide and the like.
A thermoplastic resin can be used individually or in combination of 2 or more types. When the thermoplastic resin is a copolymer, the copolymer may be a random copolymer or a block copolymer.

As the thermoplastic resin, a polyolefin-based resin is preferable from the viewpoints of characteristics such as mechanical strength, heat resistance, and chemical resistance, and molding surfaces such as easy melt thermoforming.
Preferred examples of the polyolefin resin include a resin having a broad molecular weight distribution and having a shoulder on the high molecular weight side, a micro-crosslinking type resin (a slightly cross-linked type resin), a long-chain branched type resin, and the like.

  In particular, as a polyolefin-based resin, melt tension (temperature: 210 ° C., tensile speed: 2.0 m / min, capillary: φ1 mm × 10 mm from the viewpoint of obtaining a resin foam having a high foaming ratio and a uniform cell structure. ) Is preferably 3 to 50 cN (preferably 8 to 50 cN).

The thermoplastic resin includes a rubber component and / or a thermoplastic elastomer component.
Since the rubber component and the thermoplastic elastomer component have, for example, a glass transition temperature of room temperature or lower (for example, 20 ° C. or lower), flexibility and shape followability when a resin foam is obtained are extremely good.

The rubber component and the thermoplastic elastomer component are not particularly limited as long as they have rubber elasticity and can be foamed. For example, natural or natural rubber, polyisobutylene, polyisoprene, chloroprene rubber, butyl rubber, nitrile butyl rubber, or the like Synthetic rubber; Ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, olefinic elastomer such as chlorinated polyethylene; styrene-butadiene-styrene copolymer, styrene-isoprene -Styrene elastomers such as styrene copolymers and hydrogenated products thereof; polyester elastomers; polyamide elastomers; various thermoplastic elastomers such as polyurethane elastomers.
You may use these individually or in combination of 2 or more types.

  Especially, as a rubber component and / or a thermoplastic elastomer component, an olefin type elastomer is preferable. The olefin elastomer has good compatibility with the polyolefin resin exemplified as the thermoplastic resin.

  The olefin-based elastomer may be a type having a structure in which the resin component A (olefin-based resin component A) and the rubber component B are microphase-separated, or the resin component A and the rubber component B are physically dispersed. The resin component A and the rubber component B may be dynamically heat treated in the presence of a cross-linking agent (dynamic cross-linkable thermoplastic elastomer, TPV). Among these, as the olefin elastomer, a dynamically crosslinked thermoplastic olefin elastomer (TPV) is preferable.

  The dynamically crosslinked thermoplastic olefin elastomer has a higher elastic modulus and a smaller compression set than TPO (non-crosslinked thermoplastic olefin elastomer). Thereby, the recoverability is good, and when the resin foam is used, the excellent recoverability is exhibited.

  As described above, the dynamically crosslinked thermoplastic olefin elastomer is a mixture containing the resin component A (olefin resin component A) forming a matrix and the rubber component B forming a domain, in the presence of a crosslinking agent. It is a multiphase polymer having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in the resin component A, which is a matrix (sea phase), obtained by dynamic heat treatment.

  Examples of such a dynamically crosslinked thermoplastic olefin elastomer include, for example, JP 2000-007858 A, JP 2006-052277 A, JP 2012-072306 A, JP 2012-057068 A, No. 2010-241897, JP-A-2009-0697969, RE03 / 002654, etc., “Zeotherm” (manufactured by Nippon Zeon), “Thermorun” (manufactured by Mitsubishi Chemical), “Surlink” 3245D "(manufactured by Toyobo Co., Ltd.) and the like.

  When the resin constituting the resin foam of the present invention includes a rubber component and / or a thermoplastic elastomer component together with the thermoplastic resin, the content is not particularly limited. For example, the ratio of the thermoplastic resin to the rubber component and / or the thermoplastic elastomer component in the resin constituting the resin foam of the present invention is preferably 70/30 to 30/70, more preferably on a weight basis. Is 60/40 to 30/70, even more preferably 50/50 to 30/70, even more preferably 60/40 to 10/90, 58/42 to 10/90, 55/45. 10/90. If the ratio of the rubber component and / or the thermoplastic elastomer component is too small, the cushioning property of the resin foam tends to be lowered or the recoverability after compression may be lowered. On the other hand, the rubber component and / or the thermoplastic elastomer component If the ratio is too large, outgassing tends to occur during foam formation, and it may be difficult to obtain a highly foamable foam.

  The resin foam of the present invention is excellent in so-called rubber elasticity in order to realize flexibility at high compression and shape recovery after compression, that is, to enable large deformation and prevent plastic deformation. Suitable materials are suitable. From this viewpoint, the resin foam of the present invention preferably contains a rubber component and / or a thermoplastic elastomer component together with the above-described thermoplastic resin as the constituent resin composition.

  The resin foam of the present invention preferably further contains a nucleating agent in the constituent resin composition. When the nucleating agent is contained, the cell diameter can be easily adjusted, and a foam having an appropriate flexibility and excellent cutting processability can be obtained.

  Examples of the nucleating agent include oxides and composite oxides such as talc, silica, alumina, zeolite, calcium carbonate, magnesium carbonate, barium sulfate, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, mica, and montmorillonite. Metal carbonates, metal sulfates, metal hydroxides; carbon particles, glass fibers, carbon tubes, and the like. In addition, a nucleating agent is used individually or in combination of 2 or more types.

Although the average particle diameter of a nucleating agent is not specifically limited, Preferably it is 0.3-1.5 micrometers, More preferably, it is 0.4-1.2 micrometers. By setting it as such an average particle diameter, sufficient function as a nucleating agent can be exhibited. In addition, a high expansion ratio can be realized without the nucleating agent breaking through the cell walls.
This average particle diameter can be measured by a laser diffraction particle size distribution measuring method. For example, the measurement can be performed from the sample dispersion dilution (AUTO measurement mode) using “MICROTRAC MT-3000” manufactured by LEEDS & NORTHRUP INSTRUMENTS.

  In the resin foam of the present invention, the content in the case of containing a nucleating agent is not particularly limited, but is preferably 0.5 to 150 parts by weight, more preferably 2 to 140 parts with respect to 100 parts by weight of the constituting resin. Part by weight, still more preferably 3 to 130 parts by weight.

Since the resin foam of this invention is comprised with a thermoplastic resin and is easy to burn, it is preferable to contain a flame retardant.
As the flame retardant, an inorganic flame retardant which is non-halogen-non-antimony type is preferable.
Examples of such inorganic flame retardants include metal hydroxides and hydrates of metal compounds. More specifically, aluminum hydroxide; magnesium hydroxide; hydrates of magnesium oxide and nickel oxide; hydrates of magnesium oxide and zinc oxide, and the like. Among these, magnesium hydroxide is preferable. The hydrated metal compound may be surface-treated. A flame retardant is used individually or in combination of 2 or more types.

  When the flame retardant is contained in the resin foam of the present invention, the content is preferably 5 to 70 parts by weight, and more preferably 25 to 65 parts by weight with respect to 100 parts by weight of the constituent resin.

  The resin foam of the present invention further has a polar functional group, a melting point of 50 to 150 ° C., and contains at least one aliphatic compound selected from fatty acids, fatty acid amides, and fatty acid metal soaps. Also good. Of these, fatty acids and fatty acid amides are preferred.

  When such an aliphatic compound is contained in the resin foam of the present invention, the cell structure is less likely to collapse during processing (particularly punching processing), shape recovery is improved, and workability (particularly, (Punching workability) is further improved. Such an aliphatic compound has high crystallinity, and when added to the thermoplastic resin (especially polyolefin resin), a strong film is formed on the resin surface, and the wall surfaces of the bubbles forming the cell structure block each other. This is presumed to have a function to prevent the above.

  Such aliphatic compounds, particularly those containing a highly polar functional group, are difficult to be compatible with polyolefin resins, so that they easily precipitate on the surface of the resin foam and exhibit the above effects. Cheap.

  The melting point of the aliphatic compound is preferably from 50 to 50 from the viewpoint of lowering the molding temperature when foam-molding the resin composition, suppressing deterioration of the resin (particularly polyolefin resin), imparting sublimation resistance, and the like. 150 ° C, more preferably 70 to 100 ° C.

  The fatty acid preferably has about 18 to 38 carbon atoms, more preferably about 18 to 22 carbon atoms. For example, stearic acid, behenic acid, 12-hydroxystearic acid and the like can be mentioned. Of these, behenic acid is particularly preferable.

  The fatty acid amide is preferably a fatty acid moiety having about 18 to 38 carbon atoms, more preferably 18 to 22 carbon atoms. For example, either monoamide or bisamide may be used. Specific examples include stearic acid amide, oleic acid amide, erucic acid amide, methylene bis stearic acid amide, and ethylene bis stearic acid amide. Of these, erucic acid amide is particularly preferable.

  Examples of the fatty acid metal soap include aluminum, calcium, magnesium, lithium, barium, zinc, and lead salts of the above fatty acids.

  In the resin foam of the present invention, the content when such an aliphatic compound is contained is not particularly limited, but is preferably 1 to 5 parts by weight, more preferably 100 parts by weight of the resin constituting the resin foam. 1.5 to 3.5 parts by weight, still more preferably 2 to 3 parts by weight. As a result, the resin can maintain a sufficient pressure during foam molding, and the content of a foaming agent (for example, an inert gas such as carbon dioxide and nitrogen) can be ensured to obtain a high foaming ratio. .

  The resin foam of the present invention may contain a lubricant. Thereby, while improving the fluidity | liquidity of a resin composition, the thermal deterioration of resin can be suppressed. A lubricant is used individually or in combination of 2 or more types.

  The lubricant is not particularly limited. For example, hydrocarbon lubricants such as liquid paraffin, paraffin wax, microwax and polyethylene wax; butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate And ester lubricants. Moreover, content of a lubricant can be suitably selected in the range which does not impair the effect of this invention.

The resin foam of the present invention may contain other additives as necessary. Examples of such additives include anti-shrinkage agents, anti-aging agents, heat stabilizers, light stabilizers such as HALS, weathering agents, metal deactivators, ultraviolet absorbers, light stabilizers, copper damage inhibitors, and the like. Stabilizers, antibacterial agents, fungicides, dispersants, tackifiers, colorants such as carbon black and organic pigments, fillers, and the like. In particular, when a dynamically crosslinked thermoplastic olefin elastomer is used, a composition containing an additive (for example, a colorant such as carbon black, a softening agent, etc.) may be used. These additives are used alone or in combination of two or more.
The content of these additives can be appropriately selected within a range that does not impair the effects of the present invention.

[Method for producing resin foam]
The resin foam of the present invention is obtained by mixing and kneading a thermoplastic resin (including a rubber component and / or a thermoplastic elastomer component) and optionally an additive such as a nucleating agent, an aliphatic compound, or a lubricant. It can manufacture by foaming and shape | molding a resin composition using the obtained resin composition.

  It does not specifically limit as a foaming method used when foaming and shape | molding a resin composition, For example, methods usually used, such as a physical method and a chemical method, are mentioned. A general physical method is a method of forming bubbles by dispersing a low boiling point liquid (foaming agent) such as chlorofluorocarbons or hydrocarbons in a resin, and then heating to volatilize the foaming agent. Moreover, a general chemical method is a method in which bubbles are formed by a gas generated by thermal decomposition of a compound (foaming agent) added to a resin.

In the present invention, as a foaming method, a method using a high-pressure gas as a foaming agent is preferable because a foam having a small cell diameter and a high cell density can be easily obtained. In particular, a method using a high-pressure inert gas as a foaming agent is preferable.
As a method of using a high-pressure gas as a foaming agent, a method in which a resin composition is impregnated with a high-pressure gas and then subjected to a pressure reduction process is preferable. Specifically, after impregnating a high-pressure gas into an unfoamed molded product made of a resin composition, a method of forming through a step of reducing the pressure, after impregnating a molten resin composition with a gas under a pressurized state And a method of forming by forming together with decompression.

  The inert gas is not particularly limited as long as it is inert and can be impregnated with respect to the resin that is the material of the resin foam, and examples thereof include carbon dioxide, nitrogen, and air. These gases may be mixed and used. Of these, carbon dioxide or nitrogen is preferred, and carbon dioxide is more preferred because the amount of impregnation into the resin is large and the impregnation speed is fast.

  Furthermore, from the viewpoint of increasing the impregnation rate into the resin composition, the high-pressure gas (particularly inert gas, and further carbon dioxide) is preferably a gas in a supercritical state. In the supercritical state, the solubility of the gas in the resin is increased and high concentration can be mixed. In addition, when the pressure drops suddenly after impregnation, since it is possible to impregnate at a high concentration as described above, the generation of bubble nuclei increases, and the density of bubbles formed by the growth of the bubble nuclei has a porosity. Even if they are the same, they become larger, so that fine bubbles can be obtained. For example, carbon dioxide has a critical temperature of 31 ° C. and a critical pressure of 7.4 MPa.

  As a method for foaming and molding a resin composition by a method using a high-pressure gas as a foaming agent, an unfoamed resin molded product (unfoamed resin molded product) is obtained by molding a resin composition into an appropriate shape such as a sheet shape in advance. After that, the unfoamed resin molded body is impregnated with a high-pressure gas and foamed by releasing the pressure, and the resin composition is kneaded with the high-pressure gas under pressure, and simultaneously molded and pressurized. Any of the continuous methods of releasing and simultaneously performing molding and foaming may be used.

  As a method of forming an unfoamed resin molded body to be used for foaming when foaming and molding a resin composition by a batch method, for example, the resin composition is an extruder such as a single screw extruder or a twin screw extruder. Molding method using a kneading machine equipped with blades such as rollers, cams, kneaders, Banbury molds, etc., and then kneading the resin composition to a predetermined thickness using a hot plate press or the like And a method of molding the resin composition using an injection molding machine. In addition, the unfoamed resin molded body can be formed by other molding methods besides extrusion molding, press molding, and injection molding. Furthermore, the shape of the unfoamed resin molded body is not particularly limited, and various shapes can be selected depending on the application, and examples thereof include a sheet shape, a roll shape, a plate shape, and a lump shape. Thus, when foaming or molding the resin composition in a batch mode, the resin composition can be molded by an appropriate method that can obtain an unfoamed resin molded body having a desired shape and thickness.

  When foaming or molding a resin composition by a batch method, the obtained unfoamed resin molded product is placed in a pressure vessel (high pressure vessel) and injected with high pressure gas (especially inert gas or even carbon dioxide) ( Gas) impregnating a non-foamed resin molded body with a high-pressure gas, releasing the pressure when the sufficiently high-pressure gas is impregnated (usually up to atmospheric pressure), and creating bubble nuclei in the resin Bubbles are formed in the resin through a decompression step to be generated, and in some cases (if necessary), a heating step in which bubble nuclei are grown by heating. Bubble nuclei may be grown at room temperature without providing a heating step.

  As the foaming or molding of the resin composition in a continuous system, the resin composition is kneaded using an extruder such as a single screw extruder or a twin screw extruder while a high pressure gas (especially an inert gas, Is injected (introduced) carbon dioxide), and the pressure is released by extruding the resin composition through a kneading impregnation step for impregnating the resin composition with a sufficiently high pressure gas, a die provided at the tip of the extruder ( Usually, up to atmospheric pressure), foaming or molding may be performed by a molding decompression step in which molding and foaming are performed simultaneously. In the kneading impregnation step and the molding decompression step, an injection molding machine or the like may be used in addition to the extruder. In addition, when foaming or molding the resin composition in a continuous manner, a heating step for growing bubbles by heating may be provided as necessary.

  In either the batch method or the continuous method, after the bubbles are grown, if necessary, the shape may be fixed rapidly by cooling with cold water or the like. The high-pressure gas may be introduced continuously or discontinuously. As a heating method for growing bubble nuclei, known methods such as a water bath, an oil bath, a hot roll, a hot air oven, a far infrared ray, a near infrared ray, and a microwave can be employed.

  When manufacturing the resin foam of this invention, in order to produce the stable foam efficiently, it is preferable to extend after passing through the process mentioned above or during the process mentioned above.

The stretching is preferably performed so that the ratio of the resin extrusion speed and the molding speed is 1: 1.2 to 5.
By performing stretching in this range, it is possible to prevent the feeding of the resin sheet from becoming unstable due to the frictional resistance of the roll or the belt, and to avoid crushing in the thickness direction due to excessive stretching. As a result, porosity, cushioning properties and flexibility can be ensured.
Usually, when the resin contains a large amount of a rubber component and / or a thermoplastic elastomer component,
Sliding property against rolls or belt is lowered, but by carrying out the stretching in the range, regardless of the composition of the resin, stability can send a sheet, the shape can be obtained a stable resin foam .
Here, the molding speed means a speed at which the resin sheet is fed by a roll or a belt. A shaping | molding speed | rate is not specifically limited, For example, it is preferable to set it as 2-100 m / min. Thereby, a resin sheet can be shape | molded stably and production efficiency can be ensured.
Further, when the resin sheet is nipped by a roll or a belt, the nip pressure is preferably set so that the foam is not crushed in the thickness direction.

  The mixing amount of the gas when foaming or molding the resin composition is not particularly limited. For example, the amount is preferably 2 to 10% by weight, more preferably 2.5 to the total amount of the resin component in the resin composition. 8% by weight, still more preferably 3-6% by weight. By setting it as this range, a foam with a high foaming rate can be obtained, without gas separating in a molding machine.

  In the resin foam of the present invention, the pressure when impregnating the unfoamed resin molded product or the resin composition with the gas in the gas impregnation step in the batch method or the kneading impregnation step in the continuous method when foaming and molding the resin composition Can be appropriately selected in consideration of the type of gas and operability. For example, when an inert gas, particularly carbon dioxide, is used as the gas, it is preferably 6 MPa or more (for example, 6 to 100 MPa), more preferably 8 MPa or more (for example, 8 to 100 MPa). By setting such a pressure, it is possible to moderately control the bubble growth during foaming, to reduce the cell diameter, and to provide a good dustproof effect. This is because the amount of gas impregnation becomes an appropriate amount, and the number of bubble nuclei formed can be adjusted to an appropriate number by controlling the bubble nucleus formation rate. In addition, the cell diameter and the bubble density can be easily controlled.

  In the gas impregnation step in the batch method or the kneading impregnation step in the continuous method when foaming or molding the resin composition, the temperature when impregnating the non-foamed resin molded product or resin composition with the high-pressure gas is the gas or resin used. It depends on the type. This temperature can be selected within a wide range, and is preferably 10 to 350 ° C. in consideration of operability and the like. For example, in a batch method, the impregnation temperature when impregnating a sheet-like unfoamed resin molded article with a high-pressure gas is preferably 10 to 250 ° C, more preferably 40 to 240 ° C, and even more preferably 60 to 230 ° C. It is. Moreover, in the continuous method, the temperature at which high-pressure gas is injected into the resin composition and kneaded is preferably 60 to 350 ° C, more preferably 100 to 320 ° C, and even more preferably 150 to 300 ° C. When carbon dioxide is used as the high-pressure gas, the temperature during impregnation (impregnation temperature) is preferably 32 ° C. or higher (particularly 40 ° C. or higher) in order to maintain a supercritical state.

  The pressure reduction rate in the pressure reduction step when foaming and molding the resin composition in a batch method or a continuous method is not particularly limited, but is preferably 5 to 300 MPa / second in order to obtain uniform fine bubbles. The heating temperature in a heating process is 40-250 degreeC (preferably 60-250 degreeC), for example.

  When the above method is used when foaming or molding the resin composition, a highly foamed resin foam can be produced, and a thick resin foam can be produced. For example, when the resin composition is foamed or molded in a continuous manner, the gap between the dies attached to the tip of the extruder is as narrow as possible (usually 0.1 to 1 in order to maintain the pressure inside the extruder in the kneading impregnation step. About 0 mm). Therefore, in order to obtain a thick resin foam, it is preferable to foam the resin composition extruded through a narrow gap at a high magnification. However, conventionally, since a high expansion ratio cannot be obtained, the thickness of the formed resin foam is limited to a thin one (for example, 0.5 to 2.0 mm). On the other hand, in the present invention, it is possible to continuously obtain a resin foam having a thickness of 0.50 to 5.00 mm by foaming or molding the resin composition using a high-pressure gas. It is.

  The resin foam of the present invention has a dent recovery rate, a thickness recovery rate, a strain recovery rate, an average cell diameter, a repulsion stress during compression, an apparent density, a relative density, and the like, a gas, a thermoplastic resin, a rubber component, and / or a heat. Depending on the type of plastic elastomer component, etc., for example, operating conditions such as temperature, pressure and time in the gas impregnation process and kneading impregnation process, operating conditions such as the decompression speed, temperature and pressure in the decompression process and molding decompression process, after decompression Or it can also adjust by selecting and setting suitably the heating temperature etc. in the heating process after shaping | molding pressure reduction.

  In particular, the resin foam of the present invention is decompressed after impregnating a resin composition containing at least a nucleating agent and an aliphatic compound in addition to a thermoplastic resin with a high-pressure gas (particularly an inert gas). It is preferably formed through a process. As a result, the cell structure has a small average cell diameter, a low closed cell structure ratio, a high expansion ratio, good flexibility, the bubble structure is difficult to deform or compress, and strain recovery when pressed The resin foam having excellent properties and processability can be easily obtained.

  The resin foam of the present invention is obtained by impregnating a supercritical inert gas with a resin composition containing at least a nucleating agent having a particularly small average particle diameter and an aliphatic compound in addition to a thermoplastic resin. More preferably, it is formed through a pressure reducing step. As a result, the average cell diameter is extremely small, the cell structure ratio is low, the cell structure is high, the foaming ratio is high, the flexibility is good, the cell structure is difficult to deform or compress, and the strain when pressed It has excellent recoverability and can further suppress the nucleating agent from breaking through the bubble wall. Therefore, the resin foam which is more excellent in workability can be obtained easily.

  The resin foam of the present invention is a mixture of a thermoplastic resin and a rubber component and / or a thermoplastic elastomer component, and in addition to the thermoplastic resin whose ratio is 70/30 to 30/70 on a weight basis, A resin composition containing at least 0.5 to 150 parts by weight of a nucleating agent with respect to 100 parts by weight of the thermoplastic resin and 1 to 5 parts by weight of an aliphatic compound with respect to 100 parts by weight of the thermoplastic resin, It is preferably formed through a step of depressurizing after impregnating with a high-pressure gas (particularly an inert gas).

[Foamed sealing material]
The foam sealing material of this invention is a member containing the said resin foam. The shape of the foam sealing material is not particularly limited, and a sheet shape (including a film shape) is preferable. For example, the foamed sealing material may be configured only by a resin foam, or may be configured such that an adhesive layer, a base material layer, and the like are laminated on the resin foam.

  In particular, the foamed sealing material of the present invention preferably has an adhesive layer. For example, when the foamed sealing material of the present invention is a sheet-like foamed sealing material, it may have an adhesive layer on one or both sides. When the foamed sealing material has an adhesive material layer, for example, a processing mount can be provided on the foamed sealing material via the adhesive material layer, and further, fixed to the adherend, temporarily fixed, etc. it can.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive (such as a natural rubber-based pressure-sensitive adhesive, a synthetic rubber-based pressure-sensitive adhesive), a silicone-based pressure-sensitive adhesive, or a polyester-based pressure-sensitive adhesive. Known pressure-sensitive adhesives such as adhesives, urethane-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives can be appropriately selected and used. An adhesive can be used individually or in combination of 2 or more types. The pressure-sensitive adhesive may be any type of pressure-sensitive adhesive such as an emulsion-based pressure-sensitive adhesive, a solvent-based pressure-sensitive adhesive, a hot-melt pressure-sensitive adhesive, an oligomer-based pressure-sensitive adhesive, and a solid-type pressure-sensitive adhesive. Among these, as the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of preventing contamination of the adherend.

The thickness of the pressure-sensitive adhesive layer is preferably 2 to 100 μm, more preferably 10 to 100 μm. The thinner the adhesive material layer, the higher the effect of preventing dust and dirt from adhering to the edge, and thus the thinner the adhesive material layer, the better.
The pressure-sensitive adhesive layer may have any form of a single layer or a laminate, and may be foamable or non-foamable. Of these, a non-foaming pressure-sensitive adhesive layer is preferable.

In the foamed sealing material of the present invention, the pressure-sensitive adhesive layer may be provided via another layer (lower layer). Examples of such a lower layer include other pressure-sensitive adhesive layers, intermediate layers, undercoat layers, base material layers (particularly film layers, nonwoven fabric layers, etc.) and the like. The lower layer may be a foamable layer or a porous layer, but is preferably a non-foamable layer, more preferably a resin layer.
The pressure-sensitive adhesive layer may be protected by a release film (separator) (for example, release paper, release film, etc.).

  Since the foamed sealing material of the present invention includes the resin foam of the present invention, the foamed sealing material has good dust resistance, particularly good dynamic dust resistance, and has flexibility to follow a minute clearance.

  The foamed sealing material of the present invention may be processed so as to have a desired shape and thickness. For example, various shapes may be processed according to the device, equipment, casing, member, and the like used.

  The foamed sealing material of the present invention is suitably used as a member used when attaching (attaching) various members or parts to a predetermined site. In particular, the foamed sealing material of the present invention is suitable as a member used when attaching (attaching) a component constituting an electric or electronic device to a predetermined site in an electric or electronic device.

  Various members or parts that can be attached (mounted) using the foamed member are not particularly limited, and examples thereof include various members or parts in electrical or electronic devices. Examples of such a member or component for electric or electronic equipment include an image display member (display unit) (particularly a small image display member) mounted on an image display device such as a liquid crystal display, an electroluminescence display, or a plasma display. ), Optical members or optical components such as cameras and lenses (particularly small cameras and lenses) mounted on mobile communication devices such as so-called “mobile phones” and “portable information terminals”.

For example, the foamed sealing material of the present invention is preferably used around the display unit such as an LCD (liquid crystal display) and the display unit such as an LCD (liquid crystal display) and a housing for the purpose of dust prevention, light shielding, buffering, and the like. What is inserted and used between a body (window part) is mentioned.
When the foamed sealing material of the present invention is attached to such a member or part, it is preferably attached so as to close the clearance. This clearance is not particularly limited, and examples include about 0.05 to 0.5 mm.
Hereinafter, the thermoplastic resin foam and foamed sealing material of the present invention will be described based on examples.

Example 1
As a resin composition,
35 parts by weight of polypropylene,
60 parts by weight of a thermoplastic elastomer composition,
5 parts by weight of lubricant,
10 parts by weight of the nucleating agent and 2 parts by weight of erucic acid amide (melting point: 80 to 85 ° C.) were kneaded at a temperature of 200 ° C. with a twin-screw kneader.

here,
Polypropylene is a resin having a melt flow rate (MFR) of 0.35 g / 10 min,
The thermoplastic elastomer composition contains 15.0% by weight of carbon black, and is a blend of polypropylene (PP) and ethylene / propylene / 5-ethylidene-2-norbornene terpolymer (EPT) (crosslinked olefin type). Thermoplastic elastomer, TPV), polypropylene: ethylene / propylene / 5-ethylidene-2-norbornene terpolymer = 25: 75 (weight basis),
The lubricant is a master batch in which 1 part by weight of stearic acid monoglyceride is blended with 10 parts by weight of polyethylene,
The nucleating agent is magnesium hydroxide having an average particle size of 0.8 μm.

Thereafter, the resin composition was extruded into strands, cooled with water, cut into pellets, and molded.
This pellet was put into a tandem type single screw extruder manufactured by Nippon Steel Works Co., Ltd., and 3.8% by weight of carbon dioxide gas was injected under an atmosphere of 220 ° C. under a pressure of 14 (18 after injection) MPa. Carbon dioxide gas was sufficiently saturated and cooled to a temperature suitable for foaming. Then, it extrude | pushed out from die | dye and it adjusted so that the ratio of the extrusion speed of resin and a shaping | molding speed might be set to the range of 1: 1.2-2, and the resin foam (sheet shape) was obtained. This resin foam had a semi-continuous semi-closed cell structure with a closed cell rate of 32%.

(Example 2)
A resin foam (sheet-like) was obtained in the same manner as in Example 1 except that 3.7% by weight of carbon dioxide gas was injected into a tandem single screw extruder manufactured by Nippon Steel Works.

(Example 3)
A resin foam (sheet-like) was obtained in the same manner as in Example 1 except that 3.5% by weight of carbon dioxide gas was injected into a tandem single screw extruder manufactured by Nippon Steel Works.

(Comparative Example 1)
As a resin composition,
45 parts by weight of polypropylene,
55 parts by weight of a thermoplastic elastomer composition,
10 parts by weight of a lubricant and 10 parts by weight of a nucleating agent were kneaded at a temperature of 200 ° C. with a biaxial kneader.

here,
The thermoplastic elastomer composition contains 15.0% by weight of carbon black, and a blend (TPO) of polypropylene (PP) and ethylene / propylene / 5-ethylidene-2-norbornene terpolymer (EPT): polypropylene And ethylene / propylene / 5-ethylidene-2-norbornene terpolymer = 30/70 (by weight),
The same polypropylene, lubricant and nucleating agent as in Example 1 were used.

Thereafter, the resin composition was extruded into a strand shape, cooled with water, cut into a pellet shape, and molded.
This pellet was put into a tandem type single screw extruder manufactured by Nippon Steel Works Co., Ltd., and 3.8% by weight of carbon dioxide gas was injected under an atmosphere of 220 ° C. under a pressure of 14 (18 after injection) MPa. Carbon dioxide gas was sufficiently saturated and cooled to a temperature suitable for foaming. Then, it extruded from the die | dye and obtained the resin foam (sheet form). This resin foam had a semi-continuous semi-closed cell structure with a closed cell ratio of 46%.

(Comparative Example 2)
A resin foam (sheet-like) was obtained in the same manner as in Comparative Example 1 except that 3.7% by weight of carbon dioxide gas was injected into a tandem single screw extruder manufactured by Nippon Steel Works.

(Measurement method of closed cell ratio)
The closed cell ratio of the resin foams obtained in Examples and Comparative Examples was measured according to the following method.
From the obtained resin foam, a flat square test piece having a constant thickness and a side of 5 cm is cut out. Subsequently, the weight W ₁ (g) and thickness (cm) of the test piece are measured, and the apparent volume V ₁ (cm ³ ) of the test piece is calculated.
Next, the obtained value is substituted into the equation (1), and the apparent volume V ₂ (cm ³ ) occupied by the bubbles is calculated. The density of the resin constituting the test piece is ρg / cm ₃ .
Apparent volume occupied by bubbles V ₂ = V ₁ −W ₁ / ρ (1)
Subsequently, the test piece is submerged in distilled water at 23 ° C. so that the distance from the upper surface of the test piece to the water surface is 40 mm and left for 24 hours. Then, a test piece is taken out from distilled water and the water | moisture content adhering to the surface of the test piece is removed. The weight W ₂ (g) of the obtained test piece is measured, and the open cell ratio F1 is calculated based on the formula (2). The closed cell rate F ₂ is determined from the open cell rate F ₁ .
Open cell ratio F ₁ = 100 × (W ₂ −W ₁ ) / V ₂ (2)
Closed cell ratio F ₂ = 100−F ₁ (3)

(Evaluation)
With respect to the resin foam sheets obtained in Examples and Comparative Examples, the apparent density, repulsive force at 50% compression, dent recovery rate, average cell diameter, dynamic dust resistance and thickness recovery rate were measured or evaluated. . The results are shown in Table 1.

(Measurement method of dent recovery rate)
A thermoplastic resin foam (width 2 mm × thickness 1 mm × length 5 cm) is compressed at 23 ° C. to a lowest point in the thickness direction of the resin foam with a load of 10 N at a blade angle of 90 degrees, The compression state was maintained for 15 seconds. The thickness of the dent part 60 seconds after decompression was measured. The dent recovery rate was calculated from the following formula.
Depression recovery rate = (thickness of dent 60 seconds after release of compressed state) / (initial thickness) × 100

(Apparent density measurement method)
The density (apparent density) of the foam was calculated as follows.
The foams of each Example and Comparative Example were punched into a size of 30 mm × 30 mm to obtain test pieces, and the dimensions of the test pieces were measured with a caliper. Next, the weight of the test piece was measured with an electronic balance. And it computed by following Formula.
Apparent density (g / cm ³ ) = mass of specimen / volume of specimen

(Measurement method of average cell diameter)
A smooth cross section was created by cutting the resin foam in a direction perpendicular to the main surface of the resin foam (thickness direction) in parallel with the direction perpendicular to the MD direction (flow direction) of the resin foam. These cross-sections are taken with a digital microscope (trade name “VHX-500”, manufactured by Keyence Corporation), and an enlarged image of the bubbles of the resin foam is captured, and analysis software for the measuring instrument (manufactured by Mitani Corporation: Win ROOF) The average cell diameter (μm) was determined by image analysis using The number of bubbles in the captured enlarged image is about 200, and the average of these 200 was used.

(Repulsive load at 50% or 80% compression)
It measured according to the compression hardness measuring method described in JIS K 6767.
The resin foam was cut into a width of 30 mm and a length of 30 mm to obtain a sheet-like test piece. Next, when this test piece was compressed at 23 ° C. or −10 ° C. at a compression rate of 10 mm / min in the thickness direction and the compression rate was reduced to 50% or 80%, the unit area ( The repulsive force (N / cm ² ) was calculated per 1 cm ² ).
These repulsive loads at 50% or 80% compression are also referred to as repulsive stresses at 50% or 80% compression or 50% or 80% compression loads.

(Measurement method of thickness recovery rate)
Using a compression tester (Micro Servo, manufactured by Shimadzu Corporation), compress the sample at 23 ° C for 1 minute in the thickness direction to a thickness of 20% of the initial thickness (1 mm), release the compression, and release the compression. The recovery behavior of the thickness after 1 second was photographed using a high-speed camera. The thickness recovery rate was expressed as the ratio of the thickness after 1 second of decompression to the initial thickness.

(Measurement method of strain recovery rate)
The resin foam was compressed at 23 ° C. to a thickness of 50% of the initial thickness for 24 hours, and after releasing the compressed state, the ratio was set to the initial thickness in the thickness direction for 24 hours.

(Dynamic dustproof evaluation method)
First, the resin foam was punched into a frame shape (window frame shape) (40 mm × 56 mm, width: 2 mm) shown in FIG.
This evaluation sample 22 was attached to the dynamic dustproof evaluation container 2 shown in FIG. The compression rate of the evaluation sample 22 at the time of mounting was set to 50% in the thickness direction with respect to the initial thickness.
As shown in FIG. 3, the evaluation sample 22 is fixed to the base plate 24 with a black acrylic plate 211 attached to the base plate 24 via a foam compression plate 27 by screws 26, and fixed on the aluminum spacer 23. It is provided between the black acrylic board 212 arrange | positioned in this. The compression rate of the evaluation sample 22 can be adjusted by adjusting the thickness of the aluminum spacer 23. The evaluation container 2 to which the evaluation sample 22 is attached has a system in which a certain internal space 29 is closed by the evaluation sample 22.
The evaluation container 2 is configured as a powder supply unit that is positioned adjacent to the outside of the evaluation sample 22 and in which a constant external space 25 is closed between the evaluation sample 22 and the foam compression plate 27. Has been. The external space 25 is filled with 0.1 g of powdered dust (for example, a starch having a particle diameter of 17 μm).
Such an evaluation container 2 was rotated at a speed of 1 rpm by putting the evaluation container shown in FIG. 5 into a dumbler 1 (rotary tank, drum type drop tester). Then, the evaluation container 2 was rotated a predetermined number of times so that 100 collisions (repetitive impact) were obtained. Thereafter, the package was disassembled. And the particle | grains which passed the sample 22 for evaluation from the external space 25 which is a powder supply part, and were made to function as the upper and lower walls of internal space were attached to the digital microscope (device) Name “VHX-600”, manufactured by Keyence Corporation).
Still images are created for the black acrylic plate 211 and the black acrylic plate 212, and binarization processing is performed using image analysis software (software name “Win ROOF”, manufactured by Mitani Corporation), and the number of particles of the starch is counted. did. The observation was performed in a clean bench to reduce the influence of airborne dust.

According to Table 1, since the resin foams of Examples 1 to 3 have a dent recovery rate of 50% or more, good dynamic dustproof properties are obtained with respect to the comparative example having a dent recovery rate of 50% or less. It was confirmed that
In particular, even if the thickness recovery rate is good, if the dent recovery rate is also good, it is possible to expect rapid recovery of the dents of the resin foam, resulting in further dynamic dust resistance It was confirmed.

  The present invention is useful as an internal insulator for electronic devices, cushioning materials, sound insulating materials, dustproof materials, shock absorbing materials, light shielding materials, heat insulating materials, food packaging materials, clothing materials, building materials, etc., cushioning properties and strain recovery Resin foam and foam sealing material with excellent foaming ratio and high foaming ratio, especially around the display part of mobile phones, portable information terminals, LCDs, etc. ) Can be widely used for various members.

DESCRIPTION OF SYMBOLS 1 Tumbler 2 Dynamic dustproof evaluation container 22 Evaluation sample 24 Base plate 26 Screw 27 Foam compression plate 211, 212 Black acrylic plate 23 Aluminum spacer 29 Internal space 25 External space

Claims (10)

An olefin resin,
It consists of a thermoplastic resin containing a dynamically crosslinked thermoplastic elastomer,
The dent recovery rate at 23 ° C. defined below is 50% or more,
A thermoplastic resin foam characterized by having a thickness recovery rate at 23 ° C. of 50% or more and a strain recovery rate at 23 ° C. of 75% or more.
Depression recovery rate: The thermoplastic foam is compressed to the lowest point in the thickness direction of the foam with a load of 10 N with a jig having a blade angle of 90 degrees and maintained for 15 seconds, and then the compressed state is released. , The ratio of the thickness of the recessed portion 60 seconds after the compressed state is released to the initial thickness,
Thickness recovery rate: When the resin foam is compressed to a thickness of 20% with respect to the initial thickness for 1 minute and then released from the compressed state, the ratio of the thickness 1 second after the compressed state is released to the initial thickness,
The strain recovery rate is the ratio of the thickness 24 hours after the release of the compressed state to the initial thickness when the compressed state is released after being compressed to 50% of the initial thickness in the thickness direction for 24 hours. The thermoplastic resin foam according to claim 1, wherein the average cell diameter is 10 to 200 µm and the apparent density is 0.01 to 0.20 g / cm ³ . The repulsion stress at 50% compression at 23 ° C. defined below is 0.1 to 3.0 N / cm ² .
The repulsive stress at 50% compression at −10 ° C. is less than 10.0 N / cm ² , and the repulsive stress at 80% compression at 23 ° C. is 1.0 to 9.0 N / cm ² . The thermoplastic resin foam according to claim 1 or 2, further comprising one or more selected from the group consisting of:
Repulsive stress at 50% compression: Repulsive load when a thermoplastic resin foam is compressed to 50% of the initial thickness,
Repulsive stress at 50% compression: Repulsive load when the resin foam is compressed to 50% of the initial thickness,
Repulsive stress at 80% compression: Repulsive load when the resin foam is compressed to 80% of the initial thickness. A method for producing a thermoplastic resin foam according to claim 1,
A method for producing a thermoplastic resin foam, comprising producing a thermoplastic resin foam by subjecting a thermoplastic resin composition impregnated with a high-pressure gas under reduced pressure.   The method for producing a thermoplastic resin foam according to claim 4, wherein the gas is an inert gas.   The method for producing a thermoplastic resin foam according to claim 5, wherein the inert gas is carbon dioxide or nitrogen.   The method for producing a thermoplastic resin foam according to any one of claims 4 to 6, wherein the gas is a gas in a supercritical state.   A foamed sealing material comprising the thermoplastic resin foam according to any one of claims 1 to 3.   The foaming sealing material of Claim 8 provided with the adhesive material layer arrange | positioned at the single side | surface or both surfaces of a thermoplastic resin foam.   The foaming sealing material of Claim 9 with which the adhesive material layer is arrange | positioned on the thermoplastic resin foam surface through the film layer.

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