WO2013168798A1

WO2013168798A1 - Resin foam and foam sealing material

Info

Publication number: WO2013168798A1
Application number: PCT/JP2013/063164
Authority: WO
Inventors: 齋藤　誠; 逸大畑中; 和通加藤; 清明児玉
Original assignee: 日東電工株式会社
Priority date: 2012-05-11
Filing date: 2013-05-10
Publication date: 2013-11-14
Also published as: CN104284927A; JP2013253241A

Abstract

The purpose of the present invention is to provide a resin foam which exhibits excellent thickness recovery performance (speed) after compressive deformation, is flexible even in low-temperature environments, and balances instantaneous recovery properties with shock absorption properties; and a foam sealing material. The resin foam has a thickness recovery rate of 50% or more at 23°C as defined below, and has a repulsive stress of less than 10.0 N/cm² when at 50% compression at -10°C as defined below. Thickness recovery rate: proportion in relation to initial thickness of resin-foam thickness measured after compressing resin foam for one minute in thickness direction thereof to 20% of initial thickness, releasing state of compression, and allowing one minute to elapse since release of state of compression. Repulsive stress when at 50% compression: opposing repulsive load when compressing resin foam in thickness direction thereof to 50% of initial thickness.

Description

Resin foam and foam sealing material

The present invention relates to a 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, but on the other hand, if it takes a long time to recover the dent, or if the dent recovery itself is insufficient, a gasket material is used. Cannot fully fulfill its original function.

In particular, due to the recent demands for smaller and thinner mobile phones and portable information terminals, and for larger and higher-functionality image display units (equipped with touch panel functions as information input functions, etc.) Often used in environments. Therefore, more than ever, there is a strong demand for characteristics that can prevent the occurrence of problems such as intrusion of dust and light leakage. In addition, there is a demand for flexibility to follow minute clearances such as small and thin mobile phones and portable information terminals. Furthermore, since the thinning of the cellular phone and the portable information terminal also brings the thinning of the display member such as the LCD used, the gasket material used is highly compressed. Even under such high compression, high impact absorbing performance is required to prevent breakage of these components when dropped.

JP 2005-227392 A JP 2007-291337 A

It is an object of the present invention to provide a resin foam and a foam sealing material that are excellent in thickness recovery performance after compression deformation and are flexible even in a low temperature environment, that is, have both instantaneous recovery and shock absorption. To do.

As a result of intensive studies to solve the above problems, the present inventors have made the resin foam a thickness recovery rate of a predetermined value or more and further reduce the repulsive stress during compression in a low temperature environment. As a result, it was found that both instantaneous recovery and shock absorption can be achieved, and both of them can be improved, and the present invention has been completed. And if the recovery speed after compression is high, it will be easy to follow the deformation | transformation of the housing | casing with respect to an impact and a vibration, and will demonstrate high dustproof performance in a dynamic environment. Further, if it is a flexible property even in a low temperature environment, it exhibits a flexible property and exhibits a high impact absorbing performance against high-speed deformation in which the molecular motion of the resin material is restricted.

The present invention includes the following inventions.
(1) Resin foam having a thickness recovery rate at 23 ° C. defined below of 50% or more and a rebound stress at 50% compression of −10 ° C. defined below of less than 10.0 N / cm ² body.
Thickness recovery rate: The ratio of the thickness of the resin foam to the initial thickness after releasing the compressed state after compressing the resin foam in the thickness direction for 1 minute at a thickness of 20% with respect to the initial thickness.
Repulsive stress at 50% compression: Repulsive load when the resin foam is compressed in the thickness direction to a thickness of 50% with respect to the initial thickness.
(2) The resin foam according to (1), wherein the rebound stress at 80% compression at 23 ° C. is 1.0 to 9.0 N / cm ² .
(3) The 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 .
(4) The resin foam according to any one of (1) to (3), which is obtained by decompression treatment of a resin composition impregnated with a high-pressure gas.
(5) The resin foam according to (4), wherein the gas is an inert gas.
(6) The resin foam according to (5), wherein the inert gas is carbon dioxide.
(7) The resin foam according to any one of (4) to (6), wherein the gas is a gas in a supercritical state.
(8) A foamed sealing material comprising the resin foam according to any one of (1) to (7) above.
(9) The foamed sealing material according to (8), comprising a pressure-sensitive adhesive layer disposed on one side or both sides of the resin foam.
(10) The foamed sealing material according to (9), wherein the pressure-sensitive adhesive layer is disposed on the surface of the resin foam via the film layer.

According to the present invention, it is possible to provide a resin foam and a foam sealing material that are excellent in thickness recovery performance (speed) after compression deformation, are flexible even in a low temperature environment, and have both instantaneous recovery and shock absorption. it can.

It is the schematic of the resin foam for demonstrating the measuring method of the thickness recovery rate of the resin foam of this invention. It is a top view which shows the shape of the sample for evaluation used when evaluating dynamic dustproofness. FIG. 4 is a top view of an evaluation container for dynamic dustproof evaluation assembled with an evaluation sample, and a schematic cross-sectional view taken along line A-A ′. It is the schematic which shows the tumbler which set | placed the evaluation container. It is the schematic of the pendulum test apparatus used in order to evaluate the impact absorptivity of the resin foam.

The resin foam of the present invention is a foam containing a resin, and is obtained by foaming and molding a 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.

The resin foam of the present invention has a thickness recovery rate at 23 ° C. defined below of 50% or more (eg, 50 to 100%), preferably 65% or more (eg, 65 to 100%), More preferably, it is 70% or more (for example, 70 to 100%), and further preferably 75% or more (for example, 75 to 100%).
The thickness recovery rate is defined as the ratio of the thickness of the resin foam to the initial thickness after releasing the compressed state after compressing the resin foam in the thickness direction for 1 minute at a thickness of 20% with respect to the initial thickness. Defined.

Since the resin foam of the present invention has a thickness recovery rate of 50% or more (preferably 65% or more), it is excellent in strain recovery. For this reason, the resin foam exhibits good dust resistance, particularly good dynamic dust resistance (dustproof performance in a dynamic environment). In addition, when the foamed sealing material comprising the resin foam of the present invention is assembled to the clearance, when the foamed sealing material is deformed by vibration and impact at the time of dropping, that is, the foamed sealing material is compressed and assembled. Even in a state where the thickness is equal to or less than the clearance, the thickness is recovered quickly and sufficiently. As a result, the clearance can be filled, and entry of foreign matters such as dust can be effectively 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, More preferably, it is 7 N / cm ² or less, 5 N / cm ² or less (usually 0.1 N / cm ² or more).
The repulsive stress at the time of 50% compression at −10 ° C. means the repulsive load (repulsive stress or the rebound stress when the resin foam is compressed in the thickness direction at a thickness of 50% with respect to the initial thickness at −10 ° C. Defined as compression load).
Thus, by setting the repulsive stress at the time of 50% compression at a low temperature within this range, it becomes possible to ensure more flexibility in a wide temperature range. As a result, the followability with respect to the minute clearance can be exhibited, and sufficient recovery can be expected even for high-speed deformation. Therefore, when the resin foam of the present invention is used as a foam seal material and assembled in a clearance, 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.

In particular, as described above, the resin foam of the present invention has a specific thickness recovery rate and has a repulsive stress at the time of 50% compression under a specific low-temperature environment, so that it can follow a minute clearance. It can be improved further. Due to such further dustproofness and flexibility, the dynamic dustproofness can be further improved.

The resin foam of the present invention further has a repulsive 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 is defined as a repulsive load when the resin foam is compressed in the thickness direction at a thickness of 80% with respect to the initial thickness in an atmosphere of 23 ° C.
Thus, by setting the repulsion stress at the time of 80% compression within this range, it is possible to exhibit good flexibility. Therefore, in particular, when this resin foam is used as a foam seal 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 used as a foam sealing material and assembled into a clearance, even if the clearance is narrow, a problem due to the repulsion of the foam sealing material (for example, deformation of a member or casing around the foam sealing material) Occurrence of color unevenness in the image display unit, etc.) can be prevented.

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 preferably 10 to 200 μm or 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.
This 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, 150 μm or less, more preferably 90 μm or less, and particularly preferably 80 μm or less. Accordingly, it is possible to improve the dustproof property and improve the light shielding property. On the other hand, the lower limit of the average cell diameter of the foam is 10 μm or more, preferably 20 μm or more. Thereby, the cushioning property (impact absorbability) 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 . ³ , 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.

Thus, the resin foam of the present invention has a thickness recovery rate at 23 ° C., a repulsive stress at 50% compression at −10 ° C., and a repulsive stress at 80% compression at 23 ° C. of 2 or more, preferably In the case where all are good, the shape can be recovered sufficiently and quickly in any temperature range with respect to the deformation of the resin foam that is normally considered. In addition, since it exhibits good shock absorption, it is possible to maximize the dustproof performance particularly in the dynamic environment intended by the present invention. Furthermore, 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 of a resin. As the resin, a thermoplastic resin is preferable. 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 × from the viewpoint of obtaining a resin foam having a high expansion ratio and a uniform cell structure. A polyolefin resin in which 10 mm) is 3 to 50 cN (preferably 8 to 50 cN) is preferable.

The resin foam of the present invention contains 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 rubbers; Ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutenes, olefinic elastomers such as chlorinated polyethylene; styrene-butadiene-styrene copolymers, 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.

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

The olefin elastomer may be of a type having a structure in which the resin component A (olefin resin component A) and the rubber component B are microphase separated. The resin component A and the rubber component B are physically dispersed, and the resin component A and the rubber component B are dynamically heat treated in the presence of a crosslinking agent (dynamic crosslinking thermoplastic elastomer, TPV).

In particular, 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 2012-056768 A, JP-A-2010-241897, JP-A-2009-0697969, RE-list 03/002654, etc., “Zeotherm” (manufactured by Zeon Corporation), “Thermorun” (manufactured by Mitsubishi Chemical Corporation), “Surlink” 3245D "(manufactured by Toyobo Co., Ltd.) and the like.

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

In the resin foam of the present invention, in order to realize flexibility at high compression and shape recovery after compression, that is, to enable large deformation and prevent plastic deformation, so-called rubber elasticity is used. Good material is suitable. From that viewpoint, it is preferable that the resin foam of the present invention includes a rubber component and / or a thermoplastic elastomer component together with the above-described resin as the constituent resin.

Further, the resin foam of the present invention preferably further contains a nucleating agent. 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.

The average particle size of the nucleating agent is not particularly limited, but is preferably 0.3 to 1.5 μm, more preferably 0.4 to 1.2 μm. 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 when such a nucleating agent is included is not particularly limited, but is preferably 0.5 to 150 parts by weight, more preferably 100 parts by weight of the constituent resin. 2 to 140 parts by weight, still more preferably 3 to 130 parts by weight.

Since the resin foam of this invention is comprised with resin and is easy to burn, it is preferable to contain a flame retardant.
As the flame retardant, a non-halogen-nonantimony inorganic flame retardant 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.

In the resin foam of the present invention, the content when a flame retardant is contained is preferably 5 to 70 parts by weight, 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 / or 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 is further improved. improves. Such an aliphatic compound has high crystallinity, and when added to the resin (especially polyolefin resin), it forms a strong film on the resin surface and prevents the wall surfaces of the bubbles forming the cell structure from blocking each other. It is presumed to have a function.

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 50 to 50 from the viewpoints 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 18 to 22), and specific examples thereof include stearic acid, behenic acid, 12-hydroxystearic acid and the like. Of these, behenic acid is preferable.

The fatty acid amide is preferably a fatty acid amide having a fatty acid moiety having about 18 to 38 carbon atoms (more preferably about 18 to 22), and may be either monoamide or bisamide. 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 preferred.

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 included 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. The amount is 1.5 to 3.5 parts by weight, more preferably 2 to 3 parts by weight. Thereby, sufficient pressure can be maintained when the resin is subjected to foam molding, and the content of a foaming agent (for example, an inert gas such as carbon dioxide and nitrogen) can be ensured, and a high foaming ratio can be obtained.

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 composition forming the resin foam of the present invention is obtained by mixing and kneading an additive such as a resin, a rubber component and / or a thermoplastic elastomer component, and optionally, a nucleating agent, an aliphatic compound, a lubricant and the like. Can be manufactured.

In the resin foam of the present invention, the foaming method used when foaming and molding the resin composition is not particularly limited, and examples thereof include usually used methods such as a physical method and a chemical method. 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. However, general physical methods are concerned about environmental impacts such as flammability, toxicity, and ozone depletion of substances used as blowing agents. Also, in general chemical methods, foaming gas residues remain in the foam, so that contamination by corrosive gas and impurities in the gas is a problem, especially in electronic equipment applications where low pollution requirements are high. Become. Moreover, in any of these physical methods and chemical methods, it is difficult to form a fine bubble structure, and it is particularly difficult to form a fine bubble of 300 μm or less.

For this reason, in the present invention, as the foaming method, a method using a high-pressure gas as the 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 reducing step is preferable. The method of passing through the process of depressurizing after impregnating this gas, the method of impregnating the molten resin composition with the gas under a pressurized state, and then subjecting it to molding with reduced pressure, and the like.

The inert gas is not particularly limited as long as it is inert with respect to the resin constituting the resin foam and can be impregnated, 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 from the viewpoint that the amount of impregnation into the resin is large and the impregnation rate 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.

In the resin foam of the present invention, as a method of foaming and molding the resin composition by a method using a high-pressure gas as a foaming agent, the resin composition is previously molded into an appropriate shape such as a sheet shape, and an unfoamed resin After forming a molded body (unfoamed resin molded product), this unfoamed resin molded body may be impregnated with a high-pressure gas and foamed by releasing the pressure. Alternatively, it may be kneaded with a high-pressure gas, molded and simultaneously released, and the pressure may be released to perform molding and foaming simultaneously.

In the resin foam of the present invention, when the resin composition is foamed and molded in a batch system, as a method of forming an unfoamed resin molded body to be used for foaming, for example, the resin composition is made of a single screw extruder, two A method of molding using an extruder such as a shaft extruder; the resin composition is uniformly kneaded using a kneader equipped with blades such as a roller, a cam, a kneader, a Banbury mold, etc. And a method of press molding to a predetermined thickness using the resin composition; a method of molding the resin composition using an injection molding machine, and the like. 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. For example, a sheet shape, a roll shape, a plate shape, a lump shape, etc. are mentioned. Thus, in the resin foam of the present invention, when the resin composition is foamed and molded in a batch system, the resin composition is obtained by an appropriate method that can obtain an unfoamed resin molded body having a desired shape and thickness. Can be molded.

In the resin foam of the present invention, when the resin composition is foamed and molded in a batch system, the obtained unfoamed resin molded body is put in a pressure vessel (high pressure vessel) and a high pressure gas (especially an inert gas, Furthermore, carbon dioxide) is injected (introduced), and a gas impregnation step in which high-pressure gas is impregnated into the unfoamed resin molded body, and when the sufficiently high-pressure gas is impregnated, the pressure is released (usually up to atmospheric pressure). ), A pressure reducing step for generating bubble nuclei in the resin, and in some cases (if necessary), a bubble is formed in the resin through a heating step for growing the bubble nuclei by heating. Bubble nuclei may be grown at room temperature without providing a heating step.

In the resin foam of the present invention, as the foaming and molding of the resin composition in a continuous mode, the resin composition is mixed with a high pressure while kneading using an extruder such as a single screw extruder or a twin screw extruder. Injecting (introducing) gas (especially inert gas or carbon dioxide) and impregnating the resin composition with a sufficiently high pressure gas, the resin composition is passed through a die provided at the tip of the extruder. The pressure is released by extrusion (usually up to atmospheric pressure), and foaming and molding can be performed by a molding decompression process in which molding and foaming are performed simultaneously. In the kneading impregnation step and the molding pressure reduction step, an injection molding machine or the like can be used in addition to the extruder. Moreover, in the case of foaming and shaping | molding of the resin composition by a continuous system, you may provide the heating process which grows a bubble by heating as needed.

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 introduction of high-pressure gas may be performed 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.

In the resin foam of the present invention, the mixing amount of the gas during foaming and molding of the resin composition is not particularly limited. For example, it is preferably 2 to 10% by weight with respect to the total amount of resin components in the resin composition. More preferably, it is 2.5 to 8% by weight, and still more preferably 3 to 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 resin composition with gas in the gas impregnation step in a batch method or the kneading impregnation step in a 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 is used as the gas, particularly carbon dioxide, the pressure is 6 MPa or more (for example, 6 to 100 MPa), 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 resin foam of the present invention, when an unfoamed resin molded article or resin composition is impregnated with a high-pressure gas in a gas impregnation process in a batch system or a kneading impregnation process in a continuous system when foaming and molding a resin composition The temperature varies depending on the type of gas and resin used, and can be selected within a wide range. However, considering operability and the like, about 10 to 350 ° C. is suitable. For example, in a batch method, the impregnation temperature when impregnating a sheet-like unfoamed resin molded body 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. 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.

In the resin foam of the present invention, 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 preferably 5 to 300 MPa in order to obtain uniform fine bubbles. / Sec. The heating temperature in the heating step is, for example, 40 to 250 ° C., preferably 60 to 250 ° C.

In the resin foam of the present invention, when the above method is used when foaming and 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 and molded in a continuous mode, in order to maintain the pressure inside the extruder in the kneading and impregnation step, the gap of the die attached to the tip of the extruder is as narrow as possible (usually 0.1 to 1). (About 0.0 mm) is effective. 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. 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, by foaming and molding the resin composition using a high-pressure gas, it is possible to finally obtain a resin foam having a thickness of 0.50 to 5.00 mm continuously.

The resin foam of the present invention has a thickness recovery rate, an average cell diameter, a repulsion stress at 50% compression, an apparent density, a relative density, etc., in the type of gas, resin, rubber component and / or thermoplastic elastomer component used. Accordingly, for example, operating conditions such as temperature, pressure and time in the gas impregnation process and kneading impregnation process, operating conditions such as pressure reduction speed, temperature and pressure in the decompression process and molding decompression process, heating process after decompression or after molding decompression The heating temperature can be adjusted by appropriately selecting and setting the heating temperature.

In particular, the resin foam of the present invention comprises a step of reducing the pressure after impregnating a resin composition containing at least a nucleating agent and an aliphatic compound with a high-pressure gas (particularly an inert gas) in addition to the resin. It is preferable that it is formed through. Small cell size, low cell structure ratio, high foaming ratio, good flexibility, bubble structure is difficult to deform or compress, and excellent strain recovery when pressed This is because a resin foam having excellent processability can be easily obtained.

The resin foam of the present invention is obtained by impregnating a resin composition containing at least a nucleating agent having a particularly small average particle diameter and an aliphatic compound with a supercritical inert gas in addition to the resin. More preferably, the resin composition is formed through a step of decompressing the composition, that is, the resin composition is subjected to a decompression treatment. The average cell diameter is extremely small, the cell structure has a low closed cell structure ratio, high expansion ratio, good flexibility, the cell structure is difficult to deform or compress, and the strain recoverability when pressed This is because it is possible to more easily suppress the nucleating agent from breaking through the cell wall, and to easily obtain a resin foam excellent in workability.

The resin foam of the present invention is a mixture of a resin and a rubber component and / or a thermoplastic elastomer component, and in addition to a resin whose ratio is 70/30 to 40/60 on a weight basis, To a resin composition containing at least 0.5 to 150 parts by weight of a nucleating agent and 1 to 5 parts by weight of an aliphatic compound based on 100 parts by weight of the resin, a high pressure gas (particularly an inert gas) ) Is impregnated, and is preferably formed through a step of reducing pressure.

[Foamed sealing material]
The foam sealing material of this invention is a member containing the said resin foam. Although the shape of a foaming sealing material is not specifically limited, A sheet form (a film form is included) 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 foaming sealing material of this invention is a sheet-like foaming sealing material, you may have an adhesive layer on the single side | surface or both surfaces. When the foamed sealing material has an adhesive layer, for example, a processing mount can be provided on the foamed sealing material via the adhesive layer, and further, fixing to the adherend, temporary fixing, etc. it can.

The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, acrylic pressure-sensitive adhesive, rubber-based pressure-sensitive adhesive (natural rubber-based pressure-sensitive adhesive, synthetic rubber-based pressure-sensitive adhesive, etc.), silicone-based pressure-sensitive adhesive, and 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 pressure-sensitive adhesive layer, the higher the effect of preventing the adhesion of dust and dirt at the end, so the thinner the adhesive layer is preferable.
The pressure-sensitive adhesive layer may have any form of a single layer or a laminate, and may be foamable or non-foamable. Especially, a non-foaming 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 contains the resin foam of the present invention, it 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 various members or parts are attached (attached) 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.

The 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”.

As a preferable specific usage mode of the foamed sealing material of the present invention, for example, around a display unit such as an LCD (liquid crystal display) and a display unit such as an LCD (liquid crystal display) The thing used by inserting | pinching between housings | casings (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. The clearance is not particularly limited, but may be about 0.05 to 0.5 mm, for example.
Hereinafter, the resin foam and foamed sealing material of this invention are demonstrated based on an Example.

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,
Ten 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 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 rate of 32%.

(Example 2)
A resin foam (sheet-like) was obtained in the same manner as in Example 1 except that 4.0% by weight of carbon dioxide gas was injected into a tandem single screw extruder manufactured by Nippon Steel Works.

(Example 3)
As a resin composition,
50 parts by weight of polypropylene,
40 parts by weight of a thermoplastic elastomer composition,
5 parts by weight of lubricant,
Ten 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.
Each component used here is the same as in Example 1.

Thereafter, the resin composition was extruded into strands, cooled with water, cut into pellets, and molded.
The pellets were put into a tandem single screw extruder manufactured by Nippon Steel Works, and 3.5% by weight of carbon dioxide gas was injected under a pressure of 14 (18 after injection) MPa in an atmosphere of 220 ° C. 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).

(Comparative Example 1)
As a resin composition,
45 parts by weight of polypropylene,
55 parts by weight of the thermoplastic elastomer composition and 10 parts by weight of the 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 (weight basis),
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)
Resin foam mainly composed of polyurethane (sheet-like, average cell diameter: 70 to 80 μm, repulsive force at 80% compression is 9.6 N / cm ² , resin foam apparent density: 0.15 g / cm ³ ) Got ready.

(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)
For the resin foam sheets obtained in the examples and comparative examples, the apparent density, average cell diameter, thickness recovery rate at 23 ° C., repulsive force at 50% compression at −10 ° C., and at 23 ° C. The repulsive force at 80% compression, the total particle area, and the impact absorption rate were measured or evaluated. The results are shown in Table 1.

(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 40 mm × 40 mm to form test pieces, and the thickness of the test pieces was measured with a caliper and a 1/100 dial gauge having a measurement terminal φ20 mm. Next, the weight of the test piece was measured with an electronic balance having a minimum scale of 0.01 g. And it computed by following Formula.
Apparent density (g / cm ³ ) = mass of test piece / volume of test piece

(Measurement method of average cell diameter)
Using a digital microscope (trade name “VH-8000” manufactured by Keyence Corporation), an enlarged image of the bubble of the resin foam is captured, and analysis software (Mitani Corporation: Win ROOF) of the measuring instrument is used. The average cell diameter (μm) was determined by image analysis. The number of bubbles in the captured enlarged image is about 200, and the average of these 200 was used.

(Measurement method of thickness recovery rate at 23 ° C.)
Using a compression tester (Micro Servo manufactured by Shimadzu Corporation), for example, as shown in FIG. 1, the resin foam 1 is measured at 23 ° C. in the thickness direction with respect to the initial thickness (X, 1 mm). And compressed to a thickness of 20% for 1 minute (M in FIG. 1). Thereafter, the compression was released, and the thickness recovery behavior (Q) one second after the release was photographed using a high-speed camera. The thickness recovery rate (%) was expressed as a ratio (Y / X) of the thickness of the resin foam 1 when recovered to the initial thickness.

(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, the stress (N) when this test piece is compressed at −10 ° C. or 23 ° C. at a compression rate of 10 mm / min in the thickness direction until the compression rate becomes 50% or 80% is a unit. It expressed as an area (1 cm ²⁾ in terms to rebound stress per (N / cm ^2).

(Dynamic dustproof evaluation method)
The dynamic dustproof evaluation method will be described with reference to FIGS.
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 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 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.
Further, 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 powder (for example, silica having a particle diameter of 17 μm) that has been dusted.
Such an evaluation container 2 was rotated at a speed of 1 rpm by placing the evaluation container shown in FIG. 4 in 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. Then, particles attached to the black acrylic plate 211 and the black acrylic plate 212 that have passed through the evaluation sample 22 and functioned as the upper and lower walls of the internal space from the external space 25 that is a powder supply unit are converted into a digital microscope (apparatus Name “VH-8000” (manufactured by Keyence Corporation).
Still images are created for the black acrylic plate 211 and the black acrylic plate 212, binarized using image analysis software (software name “Win ROOF”, manufactured by Mitani Corporation), and the number of silica particles is determined. The total area was measured. The observation was performed in a clean bench to reduce the influence of airborne dust.

The total particle area of the particles adhering to the black acrylic plate 211 and the particles adhering to the black acrylic plate 212 is
Less than 100 mm ² good 100 mm ² or more 200 mm ² or less was judged slightly defective exceeding defect 200 mm ^2. The total area of the particle observation surface was 1872 mm ² .
It should be noted that there is no problem in practical characteristics even if the resin foam is evaluated to be slightly defective.

Further, the total particle area of the particles adhering to the black acrylic plate 211 and the particles adhering to the black acrylic plate 212 is:
Less than 1500 [Pixel × Pixel] Good 1500 to 2000 [Pixel × Pixel] Slightly poor More than 2000 [Pixel × Pixel] The total area of the particle observation surface was 20000 [Pixel × Pixel].
It should be noted that there is no problem in practical characteristics even if the resin foam is evaluated to be slightly defective.

(Measurement method of shock absorption)
As shown in FIG. 5, using a pendulum test apparatus 7 that measures the impact energy (20 mJ) given by the iron ball 74 with the pressure sensor 71, the impact force (F0) when not passing through the resin foam 72, The impact force (F1) when passing through the resin foam 72 was measured, and the impact absorbability was determined from the following formula. The resin foam 72 used for the evaluation is a square of 20 mm × 20 mm, has a thickness of 1.0 mm, and is positioned on the pressure sensor 71 between the acrylic plate 73 and the support plate 76 by the pressing pressure adjusting means 75. The evaluation was performed with the compression ratio adjusted to 50%.
Shock absorption rate (%) = (F0−F1) / F0 × 100

According to Table 1, the resin foams of Examples 1 to 3 are very good in both the thickness recovery rate at 23 ° C. and the rebound stress at 50% compression at −10 ° C. It is excellent in recoverability of the later thickness, and instantaneous deformation of the resin foam can be expected. In addition, since it was possible to ensure flexibility in a low-temperature environment, it was confirmed that the shock absorption was excellent and the dynamic dust resistance could be further improved.

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. ), And can be widely used in various fields.

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 7 Pendulum test device 71 Pressure sensor 72 Resin foam 73 Acrylic plate 74 Iron ball 75 Holding pressure adjusting means 76 Support plate

Claims

A resin foam having a thickness recovery rate at 23 ° C. defined below of 50% or more and a rebound stress at 50% compression of −10 ° C. defined below of less than 10.0 N / cm 2 .
Thickness recovery rate: The ratio of the thickness of the resin foam to the initial thickness after releasing the compressed state after compressing the resin foam in the thickness direction for 1 minute at a thickness of 20% with respect to the initial thickness.
Repulsive stress at 50% compression: Repulsive load when the resin foam is compressed in the thickness direction to a thickness of 50% with respect to the initial thickness.
The resin foam according to claim 1, wherein the rebound stress at 80% compression at 23 ° C is 1.0 to 9.0 N / cm 2 .
2. The 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 resin foam according to any one of claims 1 to 3, obtained by decompression treatment of a resin composition impregnated with a high-pressure gas.
The resin foam according to claim 4, wherein the gas is an inert gas.
The resin foam according to claim 5, wherein the inert gas is carbon dioxide.
The 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 resin foam according to any one of claims 1 to 7.
The foamed sealing material according to claim 8, further comprising an adhesive layer disposed on one or both sides of the resin foam.
The foamed sealing material according to claim 9, wherein the pressure-sensitive adhesive layer is disposed on the surface of the resin foam via the film layer.