JP6425973B2 - Resin foam and foam member - Google Patents

Description

  The present invention relates to a resin foam and a foam member. In particular, the present invention relates to a resin foam which has a small thickness, has excellent shock absorption properties, and can be suitably used as a shock absorber, and a foam member containing the resin foam.

  Conventionally, an image display member fixed to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display, an optical member such as a camera or a lens fixed to a so-called "mobile phone" or "portable information terminal" When fixing to a predetermined part (fixing part etc.), a resin foam or a foam member is used.

  In products to which optical members (image display devices, cameras, lenses, etc.) are attached (set), thinning is progressing, and the clearance (clearance, gap) of the part where resin foam or foam members are used is There is a tendency to become smaller. In order to cope with such a reduction in clearance, a shock absorber with a small thickness has been proposed (see Patent Document 1).

JP, 2010-215805, A

  In recent years, there has been a change in the size of the clearance of the part where the resin foam or the foam member is used, and one that can cope with a smaller clearance has been required. For this reason, resin foams and foam members that can cope with smaller clearances and have higher levels of shock absorption are being sought.

Therefore, an object of the present invention is to provide a resin foam which has a small thickness and is excellent in shock absorption even when applied to a finer clearance.
Furthermore, another object of the present invention is to provide a foam member which has a small thickness and is excellent in shock absorption even when applied to a finer clearance.

  As a result of intensive studies to achieve the above object, the present inventors have found that thin resin foams have a predetermined compressive stress at 50% compression and have a predetermined apparent density to be finer. The present invention has been completed by finding that excellent impact absorption can be obtained even when applied to clearances.

That is, the present invention is a resin foam obtained by foaming a resin composition containing a resin, having a thickness of 0.01 to 0.30 mm, and a compression stress of 6 to 20 N / cm at 50% compression. ^2, to provide a resin foam apparent density, characterized in that a 0.05~0.45g / cm ^3.

  The resin foam preferably further has an average cell diameter of 20 to 130 μm.

  It is preferable that the said resin is polyolefin resin.

  It is preferable that the said resin foam is obtained by making it foam through the process to pressure-reduce, after impregnating the inert gas of a high pressure and impregnating the said resin composition.

  The resin foam is preferably obtained by impregnating a non-foamed molded product made of the resin composition with a high pressure inert gas, and then performing foaming through a pressure reducing step.

  The resin foam is preferably obtained by impregnating the melted resin composition with an inert gas at high pressure and then foaming through a process of reducing pressure.

  It is preferable to heat after the process to decompress, or with decompression, and to obtain the said resin foam.

  The inert gas is preferably carbon dioxide.

  The inert gas is preferably in a supercritical state.

  It is preferable that the said resin foam is obtained by further carrying out heat compression after making the said resin composition foam.

  It is preferable that the temperature in the case of the said heating compression is 50 degreeC or more.

  Furthermore, the present invention provides a foam member comprising the above resin foam.

  The foam member preferably further has a pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive layer.

  The foam member is preferably used as a shock absorber.

  The foam member is preferably used for electrical or electronic devices.

  Furthermore, the present invention provides a foam member laminate characterized in that the foam member is held by a carrier tape.

  Furthermore, the present invention provides an electric or electronic device comprising the above-mentioned foam member.

The resin foam of the present invention has a small thickness and is excellent in shock absorption even when applied to a finer clearance.
The foamed member of the present invention has a small thickness and is excellent in shock absorption even when applied to a finer clearance.

It is a schematic block diagram of an impact test device. It is a figure which shows schematic structure of the holding member of an impact test apparatus. It is a graph which shows the relationship of the compression rate and stress in a resin foam. It is an electron micrograph which shows the cross section of the resin foam. It is an electron micrograph which shows the cross section of the resin foam. It is an electron micrograph which shows the cross section of the resin foam. It is an electron micrograph which shows the cross section of the resin foam.

[Resin foam]
The resin foam of the present invention is a resin foam obtained by foaming a resin composition containing a resin, having a thickness of 0.01 to 0.30 mm, and a compression stress of 6 to 20 N at 50% compression. / Cm ² and the apparent density is 0.05 to 0.45 g / cm ³ . The resin foam of the present invention is made of a resin and has a cell structure (foam structure).

  The shape of the resin foam of the present invention is not particularly limited, but is preferably in the form of a sheet or a tape. Moreover, you may process into a desired shape as needed.

  The thickness of the resin foam of the present invention is 0.01 to 0.30 mm. The thickness of the resin foam of the present invention is preferably 0.05 mm or more, more preferably 0.08 mm or more. Since the resin foam of the present invention has a thickness of 0.01 mm or more, it is possible to ensure good shock absorption, good sealability and good dust resistance. Moreover, the thickness of the resin foam of this invention becomes like this. Preferably it is 0.20 mm or less, More preferably, it is 0.15 mm or less. Since the resin foam of the present invention has a thickness of 0.30 mm or less, it can be applied to follow even smaller clearances (for example, clearances with a size of 0.05 to 0.30 mm).

The compressive stress at 50% compression of the resin foam of the present invention is 6 to 20 N / cm ² (= 0.06 to 0.20 MPa). The compressive stress at 50% compression of the resin foam of the present invention is preferably 8 N / cm ² or more, more preferably 10 N / cm ² or more. Since the resin foam of the present invention has a compressive stress of at least 6 N / cm ² at 50% compression, the required hardness can be secured even if the thickness is small, and the cell structure can be crushed by an impact to absorb the impact. In addition, it is possible to prevent the occurrence of the problem of transmitting an impact, and to obtain excellent shock absorption. In addition, excellent dust resistance can be secured. The compressive stress at 50% compression of the resin foam of the present invention is preferably 18 N / cm ² or less, more preferably 16 N / cm ² or less. Since the resin foam of the present invention has a compression stress of 20 N / cm ² or less at the 50% compression, sufficient softness can be secured, and the occurrence of the problem of being too hard to absorb impact can be prevented. Furthermore, even if it applies to a micro clearance, generation | occurrence | production of the malfunction by repulsion of a resin foam can be prevented.

  The compressive stress at 50% compression (anti-load load when compressed to a thickness of 50%) compresses the resin foam to a thickness of 50% of the initial thickness, that is, the initial thickness The load required for this compression is determined, and the load is expressed in unit area.

The compressive stress at 30% compression of the resin foam of the present invention is not particularly limited, but is preferably 1 N / cm ² (= 0.01 MPa) or more, more preferably 1.5 N / cm ² or more. More preferably, it is 2 N / cm ² or more. If the compressive stress at 30% compression is 1 N / cm ² or more, the required hardness can be secured even if the thickness is small, and the cell structure is crushed by an impact and the impact can not be absorbed, and the impact is transmitted. The occurrence of problems can be prevented, and excellent shock absorption can be obtained. In addition, excellent dust resistance can be secured. Further, the compressive stress at 30% compression of the resin foam of the present invention is not particularly limited, but is preferably 10 N / cm ² (= 0.10 MPa) or less, more preferably 8 N / cm ² or less More preferably, it is 5 N / cm ² or less. When the compressive stress at 30% compression is 10 N / cm ² or less, sufficient softness can be secured, and the occurrence of the problem of being too hard to follow a minute clearance can be easily suppressed. Furthermore, even if it applies to a micro clearance, generation | occurrence | production of the malfunction by repulsion of a resin foam can be prevented.

  The compressive stress at the time of 30% compression (anti-load load when compressed to a thickness of 70%) compresses the resin foam to a thickness of 70% with respect to the initial thickness, that is, the initial thickness The load required for this compression is determined, and the load is expressed in unit area.

The apparent density of the resin foam of the present invention is 0.05 to 0.45 g / cm ³ . The apparent density of the resin foam of the present invention is more preferably 0.06 g / cm ³ or more, still more preferably 0.08 g / cm ³ or more. Since the resin foam of the present invention has an apparent density of 0.05 g / cm ³ or more, it is possible to ensure good shock absorption, good sealability, and good dust resistance. The apparent density of the resin foam of the present invention is more preferably 0.4 g / cm ³ or less, and still more preferably 0.35 g / cm ³ or less. Since the resin foam of the present invention has an apparent density of 0.45 g / cm ³ or less, it is possible to enhance the flexibility and obtain excellent shock absorption and excellent clearance followability.

  As described above, the resin foam of the present invention has a cell structure. The cell structure is not particularly limited, but it may be 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). preferable.

  In particular, the resin foam of the present invention preferably has a cell structure with a closed cell rate of 70% or less. When the above-mentioned independent cell rate in the cell structure is 70% or less, when an impact acts to cause the resin foam to be compressed and deformed, air is easily released, and excellent shock absorption is easily obtained. The above-mentioned closed cell rate in the cell structure is more preferably 60% or less, still more preferably 50% or less. Moreover, it is preferable that the resin foam of this invention has a cell structure whose closed cell rate is 20% or more. When the above-mentioned closed cell rate in the cell structure is 20% or more, the ratio of open cells can be adjusted to effectively block the passage of minute particles such as dust, and it becomes easy to obtain good dust resistance. The above-mentioned closed cell rate in the cell structure is more preferably 25% or more, still more preferably 30% or more.

The closed cell rate of the resin foam is determined as follows. From the resin foam, a flat square test piece of 5 cm on a side is cut out with a constant thickness, the weight W1 (g) and thickness (cm) of this test piece are measured, and the apparent volume V1 (cm ³ ) of the test piece Calculate Next, the obtained value is substituted into equation (1) to calculate the apparent volume V2 (cm ³ ) occupied by the air bubbles. In addition, let the density of resin which comprises a test piece be rho (g / cm < ³ >).
Apparent volume occupied by air bubbles V2 = V1-W1 / ((1)
Subsequently, this test piece is immersed in distilled water at 23 ° C. so that the distance from the top surface of the test piece to the water surface is 40 mm, and left for 24 hours. Thereafter, the test piece is taken out of distilled water to remove moisture adhering to the surface of the test piece. The weight W2 (g) of the obtained test piece is measured, and the open cell ratio F1 is calculated based on Formula (2). From this open cell rate F1, the closed cell rate F2 is determined based on the equation (3).
The open cell ratio F1 = 100 × (W2-W1) / V2 (2)
Closed cell ratio F2 = 100-F1 (3)

  The average cell diameter of the resin foam of the present invention is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. When the average cell diameter is 20 μm or more, excellent impact absorbability can be easily obtained. The average cell diameter of the resin foam of the present invention is not particularly limited, but is preferably 130 μm or less, more preferably 100 μm or less, and still more preferably 80 μm or less. When the average cell diameter is 130 μm or less, excellent sealability and excellent dust resistance can be easily obtained, and furthermore, the light shielding property can be improved.

(Resin composition)
The resin foam of the present invention is a resin foam obtained by foaming a resin composition containing a resin. The said resin composition is a composition used for formation of the resin foam, and contains at least resin which is a raw material of the resin foam. The content of the resin in the resin composition is not particularly limited, but is preferably 30% by weight or more, more preferably 50% by weight or more, based on the total amount (total weight, 100% by weight) of the resin composition. More preferably, it is 80% by weight or more.

  As said resin, a thermoplastic resin is preferable. Such a thermoplastic resin is not particularly limited as long as it is a polymer exhibiting thermoplasticity and can be impregnated with a high pressure gas. As the thermoplastic resin, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, copolymer of ethylene and propylene, copolymer of ethylene or propylene and other α-olefins Olefin polymers such as polymers, copolymers of ethylene and other ethylenically unsaturated monomers (eg, vinyl acetate, acrylic acid, acrylic esters, methacrylic acids, methacrylic esters, vinyl alcohols etc.); Styrene polymers such as polystyrene and acrylonitrile-butadiene-styrene copolymer (ABS resin); polyamides such as 6-nylon, 66-nylon and 12-nylon; polyamide imides; polyurethanes; polyimides; polyether imides; polymethyl methacrylates Such as Le resins, polyvinyl chloride, polyvinyl fluoride; alkenyl aromatic resin; polyacetal; polycarbonate such as bisphenol-A based polycarbonate, polyethylene terephthalate, polyesters such as polybutylene terephthalate and poly (phenylene sulfide) and the like. In addition, the said thermoplastic resin can be used individually or in combination of 2 or more types.

  The thermoplastic resin also includes thermoplastic elastomers which exhibit rubber properties at normal temperature and exhibit thermoplasticity at high temperature. Such thermoplastic elastomers are not particularly limited, and, for example, olefins such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, chlorinated polyethylene and the like Styrene-based elastomers such as styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, and their hydrogenated polymers; Thermoplastic polyester-based elastomers; Thermoplastic polyurethane-based elastomers; thermoplastic acrylic-based elastomers and the like. Since these thermoplastic elastomers have glass transition temperatures below room temperature (eg, 20 ° C. or less), these thermoplastic elastomers provide resin foams that are excellent in impact absorption, flexibility, and shape conformity. Can. In addition, a thermoplastic elastomer can be used individually or in combination of 2 or more types.

  Among them, the thermoplastic resin is preferably a polyolefin-based resin from the viewpoint of easily exhibiting flexibility at room temperature and particularly easily obtaining a resin foam excellent in impact absorption, flexibility and shape conformity. The polyolefin-based resin also includes the olefin-based elastomer.

  The thermoplastic resin may be a mixture. For example, the thermoplastic resin may be only a thermoplastic elastomer, or may be only a thermoplastic resin other than a thermoplastic elastomer, or a mixture of a thermoplastic elastomer and a thermoplastic resin other than a thermoplastic elastomer. It may be

  When the above-mentioned thermoplastic resin is "a mixture of a thermoplastic elastomer and a thermoplastic resin other than a thermoplastic elastomer", the mixing ratio (by weight) is not particularly limited, but in the former / latter, 1/99 to 99 The ratio is preferably 1/1, more preferably 10/90 to 90/10, and still more preferably 20/80 to 80/20.

  Although the resin foam of this invention is obtained by foaming the said resin composition, the said resin composition may contain an additive as needed other than the said resin. The addition amount of the additive can be suitably selected in the range which does not impair formation of a bubble etc. In addition, an additive can be used individually or in combination of 2 or more types.

  Examples of the additives include cell nucleating agents, crystal nucleating agents, plasticizers, lubricants, coloring agents (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, fillers, reinforcing agents, flame retardants And antistatic agents, surfactants, vulcanizing agents, surface treatment agents and the like.

  The above-mentioned lubricant has the effect of suppressing the heat deterioration of the resin as well as improving the fluidity of the resin. Examples of the lubricant include, but are not limited to, hydrocarbon lubricants such as liquid paraffin, paraffin wax, micro wax and polyethylene wax; fatty acid lubricants such as stearic acid, behenic acid and 12-hydroxystearic acid; butyl stearate And ester-based lubricants such as stearic acid monoglyceride, pentaerythritol tetrastearate, hydrogenated castor oil and stearyl stearate. In addition, a lubricant can be used individually or in combination of 2 or more types.

  The addition amount of the above-mentioned lubricant is not particularly limited, but it is based on 100 parts by weight of resin from the viewpoint of suppressing the occurrence of the problem that the fluidity is improved and the stretchability at the time of foaming decreases and the expansion ratio decreases. The content is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more, and still more preferably 1 part by weight or more. Further, the addition amount of the above-mentioned lubricant is preferably 10 parts by weight or less, more preferably 8 parts by weight with respect to 100 parts by weight of the resin, from the viewpoint of suppressing the occurrence of a defect in which the foaming ratio decreases Or less, more preferably 6 parts by weight or less.

  The anti-shrinkage agent has a function of forming a molecular film on the surface of the foam membrane of the foam to effectively suppress the permeation of the foaming agent gas. The anti-shrinkage agent is not particularly limited, and examples thereof include fatty acid metal salts and fatty acid amides. The fatty acid metal salt is not particularly limited, and examples thereof include aluminum, calcium, magnesium, lithium, barium, zinc and lead salts of fatty acids such as stearic acid, behenic acid and 12-hydroxystearic acid. The fatty acid amide may be either monoamide or bisamide, but in order to obtain a fine cell structure, bisamide is preferred. The fatty acid amide is not particularly limited, and examples thereof include stearic acid amide, oleic acid amide, erucic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, lauric acid bisamide and the like. In addition, an anti-shrinkage agent can be used individually or in combination of 2 or more types.

  Although the addition amount of the above-mentioned shrinkage preventing agent is not particularly limited, the resin is insufficient to form a film, gas is generated at the time of foaming, shrinkage occurs, and from the point of suppressing occurrence of a defect that the foaming ratio decreases. It is preferable that it is 0.5 weight part or more with respect to 100 weight part, More preferably, it is 0.7 weight part or more, More preferably, it is 1 weight part or more. In addition, the addition amount of the above-mentioned shrinkage preventing agent causes a decrease in gas efficiency in the cell growth process, suppresses the occurrence of the problem that the expansion ratio decreases, although the non-foamed part is obtained although the cell diameter is small. From the point of view, 10 parts by weight or less is preferable, 100 parts by weight or less is preferable, 8 parts by weight or less is more preferable, and 6 parts by weight or less is more preferable.

  As mentioned above, the additive added as needed to the said resin composition can be used in combination of 2 or more types. For example, the lubricant and the anti-shrinkage agent can be used in combination. For example, a lubricant such as stearic acid monoglyceride and an anti-shrinkage agent such as erucic acid amide and lauric acid bisamide can be used in combination.

  Moreover, the said resin composition can adjust a cell diameter easily, and while having a moderate softness | flexibility, the bubble nucleating agent can be obtained from the point which can obtain easily the resin foam excellent in impact absorption. It is preferable to contain. The above-mentioned cell nucleating agent is not particularly limited, and for example, oxides such as talc, silica, alumina, mica, titania, zinc oxide, zeolite, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, magnesium hydroxide, etc. Complex oxides, metal carbonates, metal sulfates, metal hydroxides and the like can be mentioned. In addition, a cell nucleating agent can be used individually or in combination of 2 or more types.

  The amount of the cell nucleating agent added is not particularly limited, but is preferably 2 parts by weight or more with respect to 100 parts by weight of the resin from the viewpoint of sufficiently obtaining the effect by adding the cell nucleating agent, more preferably Is 3 parts by weight or more, more preferably 5 parts by weight or more. Further, the addition amount of the cell nucleating agent is preferably 150 parts by weight or less, more preferably 140 parts by weight or less, and still more preferably 130 parts by weight with respect to 100 parts by weight of the resin from the viewpoint of suppressing inhibition of foaming. Part or less.

  The said resin composition is obtained by a well-known and usual method. For example, the resin composition can be obtained by adding an additive to a resin as a raw material of a foam, if necessary, and kneading. In addition, at the time of kneading, you may heat.

  An example of a specific embodiment of the above resin composition is, for example, a mixture of a thermoplastic elastomer and a thermoplastic resin other than a thermoplastic elastomer, at least a cell nucleating agent, a lubricant, an anti-shrinkage agent, a thermoplastic elastomer and heat The content of the cell nucleating agent (particularly metal oxide) is 0.5 to 150 parts by weight with respect to 100 parts by weight of a mixture with a thermoplastic resin other than a plasticizable elastomer, and the content of a lubricant (especially ester based lubricant) Is 0.5 to 10 parts by weight, and the content of the anti-shrinkage agent (particularly fatty acid amide) is 0.5 to 10 parts by weight.

(Method for producing resin foam)
The resin foam of this invention is obtained by making the said resin composition foam. The foaming method of the resin composition is not particularly limited, and examples thereof include physical methods, chemical methods, and the like methods commonly used for foam molding. The physical method is to disperse the low boiling point liquid (foaming agent) in the resin and then heat to form bubbles by volatilizing the foaming agent. Moreover, a chemical method is a method of forming a cell with the gas produced by thermal decomposition of the added compound (foaming agent), and obtaining a foam. From the environmental point of view, physical methods are preferred.

  In particular, the above-mentioned foaming method is preferably a physical method using an inert gas at high pressure as a foaming agent from the viewpoint that a cell structure having a small cell diameter and a high cell density can be easily obtained. It is preferable that the resin foam of this invention is obtained by making the said resin composition foam by passing through the process to pressure-reduce, after impregnating the inert gas of a high pressure. In particular, when carbon dioxide is used as the foaming agent, a clean resin foam with few impurities is easily obtained, which is preferable. In the foaming method by the above physical method, there are concerns about the flammability and toxicity of the substance used as a foaming agent, and environmental influences such as ozone layer destruction. Further, in the foaming method according to the above chemical method, since the residue of the foaming gas remains in the foam, it is polluted by corrosive gas or impurities in the gas, particularly in electric or electronic device applications where low contamination is required. Is a problem. It is said that it is difficult to form a fine cell structure by a general physical foaming method or chemical foaming method, and in particular, it is extremely difficult to form a fine cell of 300 μm or less.

  Thus, in the resin foam of the present invention, it is preferable to cause the resin composition to foam by a physical method using an inert gas at high pressure as a foaming agent. That is, it is preferable that the resin foam of this invention is obtained by making it foam through the process to pressure-reduce, after impregnating the inert gas of a high voltage | pressure with the said resin composition. In addition, when impregnating a high pressure inert gas, an inert gas may be impregnated into a non-foamed molded product (a non-foamed molded product of a resin composition) molded in advance, and a molten resin composition may be impregnated. Inert gas may be impregnated under pressure. Therefore, as a method for producing the resin foam of the present invention, a method is preferably mentioned which is formed through a step of reducing pressure after impregnating the above resin composition with a high pressure inert gas, and more specifically, The unfoamed molded product made of the resin composition is impregnated with high pressure inert gas and then subjected to a pressure reducing step, or the molten resin composition is impregnated with the inert gas under pressure. After that, a method of forming by forming with pressure reduction and the like is preferably mentioned.

  Specifically, as a method for producing a resin foam by impregnating the above resin composition with a high pressure inert gas, specifically, a gas impregnation step of impregnating the above resin composition with a high pressure inert gas under high pressure After the step, a pressure reduction step for reducing the pressure to cause foaming and a method for forming the bubbles through a heating step for growing the bubbles by heating as needed can be mentioned. In this case, as described above, the unfoamed molded product previously molded from the resin composition may be impregnated with an inert gas, and the molten resin composition is impregnated with the inert gas under pressure. After that, it may be subjected to molding at the time of depressurization. These steps may be performed by either a batch method or a continuous method.

  The inert gas is not particularly limited as long as it is inert to and can be impregnated into the resin such as the thermoplastic resin. Examples of the inert gas include carbon dioxide, nitrogen gas, air and the like. These gases may be used as a mixture. Among them, carbon dioxide is preferably mentioned from the viewpoint that the amount of the resin such as the thermoplastic resin used as the material of the resin foam is large, and the impregnation rate is large.

  The inert gas is preferably in a liquid state or a supercritical state from the viewpoint of obtaining a cell structure having a high expansion ratio and obtaining a fine cell structure, and particularly preferably in a supercritical state. In the supercritical state, in particular, the solubility of gas in a resin such as a thermoplastic resin is increased, and high concentration mixing is possible. In addition, since the concentration is high at the time of rapid pressure drop after impregnation, the generation of bubble nuclei is increased, and the density of the bubbles formed by the growth of bubble nuclei is increased even if the porosity is the same. Air bubbles can be obtained. The critical temperature of carbon dioxide is 31 ° C., and the critical pressure is 7.4 MPa.

  According to the batch system, for example, a resin foam can be obtained as follows. First, an unfoamed molded product (a sheet-like unfoamed molded product or the like) is formed by extruding the resin composition using an extruder such as a single screw extruder or a twin screw extruder. Alternatively, the resin composition is uniformly kneaded using a kneader provided with rollers, cams, kneaders, and banbury-type blades, and this is press-molded using a hot plate press, unfoamed molding Form an article (such as a sheet-like unfoamed molded article). Then, the obtained unfoamed molded product is placed in a pressure resistant container, a high pressure inert gas is introduced, and the inert gas is impregnated into the unfoamed molded product. In this case, the shape of the unfoamed molded product is not particularly limited, and may be in the form of a roll, a plate or the like. The introduction of the high pressure inert gas may be performed continuously or discontinuously. When impregnated with a sufficiently high pressure inert gas, the pressure is released (usually to atmospheric pressure) to generate bubble nuclei. The cell nucleus may be grown as it is at room temperature, or may be grown by heating if necessary. Examples of the heating method include known or commonly used methods such as a water bath, an oil bath, a heat roll, a hot air oven, far infrared rays, near infrared rays, microwaves and the like. After the bubbles are grown in this manner, they are rapidly cooled with cold water or the like to fix the shape. The heating may be performed after the step of reducing the pressure, or may be performed together with the reduction of pressure.

  Further, according to the continuous method, for example, a resin foam can be obtained as follows. A high pressure inert gas is injected while the resin composition is kneaded using an extruder such as a single screw extruder, a twin screw extruder, etc., and after sufficient gas impregnation, the pressure is released by extrusion (usually At the same time, foaming and forming are carried out simultaneously, and in some cases, the cells are grown by heating. After the bubbles are grown, they are rapidly cooled with cold water or the like to fix the shape. The heating may be performed after the step of reducing the pressure, or may be performed together with the reduction of pressure.

  Although the pressure in the said gas impregnation process is not specifically limited, 6 MPa or more (for example, 6-100 MPa) is preferable, More preferably, it is 8 MPa or more (for example, 8-100 MPa). When the pressure is 6 MPa or more, the occurrence of the problem that the bubble growth at the time of foaming is remarkable and the bubble diameter becomes too large is suppressed, and a fine bubble structure is easily obtained, and good impact absorption and dust resistance are obtained. It becomes easy to obtain the resin foam which it has. This is because when the pressure is small, the amount of gas impregnation is relatively small compared to that at high pressure, and the cell nucleation rate decreases to reduce the number of cell nuclei formed, so the amount of gas per cell increases conversely This is because the bubble diameter becomes extremely large. In addition, when the pressure is small, the cell diameter and the cell density are largely changed only by slightly changing the impregnation pressure, so that the control of the cell diameter and the cell density tends to be difficult.

  The temperature in the gas impregnation step varies depending on the type of inert gas and resin used and can be selected within a wide range, but in consideration of operability and the like, 10 to 350 ° C. is preferable. For example, the impregnation temperature in the case of impregnating an unfoamed molded article such as a sheet or the like with an inert gas is preferably 10 to 200 ° C, and more preferably 40 to 200 ° C. Moreover, when extruding a molten resin composition and performing foaming and molding simultaneously, as for the impregnation temperature at the time of impregnating the molten resin composition with an inert gas, 60-350 degreeC is preferable. In addition, when using a carbon dioxide as an inert gas, in order to maintain a supercritical state, 32 degreeC or more is preferable and, as for the temperature at the time of an impregnation, 40 degreeC or more is more preferable.

  The pressure reducing rate in the pressure reducing step is not particularly limited, but is preferably 5 to 300 MPa / second in order to obtain uniform fine bubbles. Moreover, the heating temperature in the said heating process is although it does not specifically limit, 40-250 degreeC is preferable, More preferably, it is 60-250 degreeC.

  The apparent density, average cell diameter, and cell structure of the resin foam depend on the type of inert gas and resin used, additives used, etc., for example, operating conditions such as temperature, pressure and time in the gas impregnation step, pressure reduction step The pressure reduction rate, the operating conditions such as temperature and pressure, and the heating temperature after pressure reduction can be appropriately selected and set.

  Also, depending on the thickness of the resin foam, the compressive stress at 50% compression, and the compressive stress at 30% compression, depending on the type of inert gas and resin used, additives used, etc. The adjustment can be made by appropriately selecting and setting the operating conditions such as pressure and time, the depressurizing speed in the depressurizing step, the operating conditions such as temperature and pressure, and the heating temperature after depressurization.

  In particular, it is preferable that the resin foam of the present invention be obtained by heating and compressing after the resin composition is foamed. Specifically, it is preferable that the resin foam of the present invention is obtained by expanding the resin composition to obtain a resin foam structure and then heating and compressing the resin foam structure. The resin foam structure is a foam obtained by foaming the resin composition, and is a foam which is heated and compressed. According to the thermal compression, the thickness, the compressive stress at 50% compression, and the compressive stress at 30% compression can be easily adjusted to a desired range. This is because the bubble diameter and the entire thickness can be reduced by heating and compression. According to the thermal compression, in the resin foam, it is possible to easily adjust the desired thickness and the desired hardness.

  The temperature at the time of the heating and compression is not particularly limited, but is preferably 50 ° C. or more, more preferably 80 ° C. or more, still more preferably 90 ° C. or more, and particularly preferably 100 ° C. or more . Further, the temperature at the time of the heating and compression is preferably 140 ° C. or less, more preferably 130 ° C. or less, and still more preferably 120 ° C. or less.

  Although the pressure in the case of the said heating compression is not specifically limited, It is preferable that it is 5 MPa or more, More preferably, it is 10 MPa or more, More preferably, it is 12 MPa or more. Further, the pressure at the time of the heating and compression is preferably 30 MPa or less, more preferably 20 MPa, and still more preferably 18 MPa.

  The heating and compression time is not particularly limited, but is preferably 5 seconds or more, more preferably 10 seconds or more, and still more preferably 15 seconds or more. The heating and compression time is preferably 120 seconds or less, more preferably 90 seconds or less, and still more preferably 60 seconds or less.

  In particular, the thermal compression is preferably performed under the conditions of temperature: 100 to 130 ° C., pressure: 12 to 18 MPa, and time: 15 seconds to 60 seconds.

  The resin foam of the present invention is obtained by foaming the above resin composition, and has a cell structure, and further, the compressive stress at 50% compression is within a predetermined range, and the apparent density is within a predetermined range. Because of this, even if the thickness is small, it is excellent in shock absorption. In addition, it has good flexibility, sealability, dust resistance, sound absorption and the like. And it is excellent in the followability to minute clearance, and excellent in the applicability to minute clearance. Therefore, the resin foam of the present invention is a member (for example, a dustproof material, a sealing material, a shock absorbing material, a soundproofing material, a shock absorbing material, etc.) used when attaching (mounting) various members or parts to a predetermined site. In particular, it is suitably used as a shock absorber. In particular, the resin foam of the present invention is a member (for example, a dustproof material, a sealing material) used when attaching (mounting) a component or optical member constituting an electric or electronic device to a predetermined portion in an electric or electronic device And shock absorbing materials, soundproofing materials, shock absorbing materials, etc. (especially, shock absorbing materials).

  In particular, the resin foam of the present invention contains the thermoplastic elastomer as a resin constituting the resin foam, and when the resin composition is foamed using an inert gas such as carbon dioxide as a foaming agent, flexibility is achieved. Excellent, clean with no harmful substances and no contaminants left. For this reason, it is suitably used as a member (for example, a dustproof material, a sealing material, an impact absorbing material, a soundproofing material, a shock absorbing material, etc., particularly an impact absorbing material) used inside an electric or electronic device.

[Foaming member]
The foam member of the present invention is composed of the resin foam of the present invention having the above-mentioned specific properties. Although the foam member of the present invention can be a foam member exhibiting its function effectively even in the form of the resin foam of the present invention alone, one side or both sides of the resin foam of the present invention The foam | foam member of the form by which the layer or base material (especially adhesive layer etc.) is provided may be sufficient. Further, the shape of the foam member of the present invention is not particularly limited, but is preferably in the form of a sheet or a tape. Moreover, you may process into a desired shape as needed.

  The foam member of the present invention may further have a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) in addition to the resin foam of the present invention. Such a foam member can be effectively fixed to the adherend and temporarily fixed. For example, when a foamed member having an adhesive layer on one side or both sides of the resin foam of the present invention, a member or part such as an optical member can be fixed or temporarily fixed to an adherend. . Therefore, from such a point, it is preferable to have an adhesive layer on at least one surface (one side or both sides) of the resin foam of the present invention constituting the foam member as the foam member of the present invention .

  Although it does not specifically limit as an adhesive which comprises the said adhesion layer, For example, an acrylic adhesive, a rubber adhesive (a natural rubber adhesive, a synthetic rubber adhesive etc.), a silicone adhesive, a polyester adhesive Agents, urethane-based adhesives, polyamide-based adhesives, epoxy-based adhesives, vinyl alkyl ether-based adhesives, fluorine-based adhesives, and the like. The adhesive may be a hot melt adhesive. An adhesive can be used individually or in combination of 2 or more types. In addition, the composition (the composition used for formation of an adhesion layer, an adhesive composition) which forms an adhesion layer may be any forms, such as an emulsion system, a solvent system, an oligomer system, and a solid system.

  As the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of preventing contamination of the adherend, and the like. That is, the pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer can be formed using a known or conventional formation method. For example, after a pressure-sensitive adhesive composition is applied to form a pressure-sensitive adhesive layer on a method (coating method) of applying a pressure-sensitive adhesive composition on a predetermined site or surface (coating method), a pressure-sensitive adhesive layer is formed And a method (transfer method) of transferring to a predetermined site or surface. In addition, in the case of formation of the said adhesion layer, well-known thru | or the usual application method (The casting method, the roll coater method, the reverse coater method, the doctor blade method etc.) can be utilized suitably.

  Although the thickness of the said adhesion layer is not specifically limited, It is preferable that it is 2 micrometers or more, More preferably, it is 10 micrometers or more. Moreover, it is preferable that the thickness of the said adhesion layer is 100 micrometers or less. The thinner the adhesion layer, the higher the effect of preventing adhesion of dust and dirt at the end, so the thickness is preferably smaller. In addition, the said adhesion layer may have any form of a single | mono layer and a laminated body.

  Moreover, the said adhesion layer may be formed on the resin foam via the other layer (lower layer). As such a lower layer, for example, a base layer (in particular, a film layer), other adhesive layers, an intermediate layer, an undercoat layer and the like can be mentioned.

  Furthermore, when the foam member of the present invention is in the form of a sheet or a tape, when the adhesive layer is formed only on one side (one side), another layer is formed on the other side. It is also good. For example, as other layers, other types of adhesive layers, a base material layer, and the like may be formed.

  The shape, thickness, and the like of the foam member of the present invention are not particularly limited, and can be appropriately selected according to the application and the like. The thickness is preferably 0.01 mm to 0.3 mm, more preferably 0.05 mm to 0.15 mm, from the viewpoint of applicability to further minute clearances such as 0.01 mm to 0.30 mm.

  Moreover, the foam member of this invention may be processed into various shapes according to the apparatus used. For example, when the foam member of the present invention is used as a shock absorbing material, such a shock absorbing material may be processed into various shapes according to the apparatus to be used and produced.

  Since the foam member of the present invention has the above-described resin foam of the present invention, it has excellent shock absorption even if the thickness is small. In addition, it has good flexibility, sealability, dust resistance, sound absorption and the like. And it is excellent in the followability to minute clearance, and excellent in the applicability to minute clearance. Therefore, the foamed member of the present invention is used as a member (for example, a dustproof material, a sealing material, a shock absorbing material, a soundproofing material, a shock absorbing material, etc.) used when attaching (mounting) various members or parts to a predetermined site. It is preferably used. In particular, the foam member of the present invention is a member (for example, a dustproof material, a sealing material, a shock absorbing material) used when attaching (mounting) a component constituting an electric or electronic device to a predetermined portion in an electric or electronic device And soundproofing materials, cushioning materials, etc.).

  The foam member of the present invention is suitably used as a shock absorber. That is, the foam member of the present invention is useful as a shock absorber used when attaching (mounting) various members or parts (for example, an optical member etc.) to a predetermined part. In particular, since the foam member of the present invention can fill the minute clearance between the densified parts, a small-sized member or part (for example, a small optical member etc.) can be made into a thin product. It can be suitably used even when attached to

  As an optical member that can be attached (mounted) using the foam member of the present invention, for example, an image display member attached to an image display device such as a liquid crystal display, an electroluminescence display, a plasma display (in particular, small image display Members, cameras and lenses (particularly, small cameras and lenses) mounted on mobile communication devices such as so-called "mobile phones" and "portable information terminals".

  Further, the foam member of the present invention can also be used as a cushioning material when preventing the toner from leaking from the toner cartridge.

  Furthermore, the foam member of the present invention can also be used as a buffer material of the electroluminescent panel of the electroluminescent display.

[Foam member laminate]
The foam member laminate of the present invention is constituted by at least the foam member of the present invention described above and a carrier tape, and the foam member of the present invention described above is held by the carrier tape. According to the foam member laminate of the present invention, processing and transport of the foam member can be easily performed.

  The above-mentioned carrier tape is not particularly limited, but has at least one pressure-sensitive adhesive layer, and exerts an adhesive force (adhesion strength) sufficient for holding the foam member at the time of processing and conveyance of the foam member. On the other hand, at the time of peeling of the foam member, it is important to be able to exert an adhesive force (adhesive force) to such an extent that the film can be easily peeled without breaking the surface.

  The carrier tape is preferably a pressure-sensitive adhesive tape or sheet (hereinafter, may simply be referred to as a "pressure-sensitive adhesive sheet"). It does not specifically limit as an adhesive which comprises the adhesive layer which the said adhesive sheet has. For example, rubber-based adhesives (natural rubber-based adhesives, synthetic rubber-based adhesives, etc.), acrylic-based adhesives, silicone-based adhesives, polyester-based adhesives, urethane-based adhesives, polyamide-based adhesives, epoxy-based adhesives And vinyl alkyl ether pressure-sensitive adhesives and fluorine-based pressure-sensitive adhesives. In addition, these adhesives can be used individually or in combination of 2 or more types. Among them, the above-mentioned pressure-sensitive adhesive is preferably an acrylic pressure-sensitive adhesive from the viewpoint that it is easy to obtain both adhesiveness to a foam member and releasability. That is, the carrier tape is preferably an acrylic pressure-sensitive adhesive sheet.

  The pressure-sensitive adhesive sheet may be a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of the substrate, or may be a substrate-less pressure-sensitive adhesive sheet formed of only the pressure-sensitive adhesive layer. It is preferable that it is an adhesive sheet with a base material from the point of easiness of processing and conveyance.

  The base material of the pressure-sensitive adhesive sheet is not particularly limited. For example, plastic base materials such as plastic films and sheets; paper base materials such as paper; fiber base materials such as cloth, non-woven fabric and net Metal-based substrates such as metal foils and metal plates; rubber-based substrates such as rubber sheets; foams such as foam sheets and laminates thereof (in particular, laminates of plastic-based substrates and other substrates) And a laminate of plastic films (or sheets). Among them, plastic substrates are preferred.

  There are no particular limitations on the thickness and the like of the substrate and the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet as a carrier tape.

[Electric or electronic equipment]
The electric or electronic device of the present invention at least includes the above-described foam member of the present invention. That is, the electric or electronic device of the present invention has a configuration in which the foam member of the present invention described above is used. In the electric or electronic device of the present invention, the foam member of the present invention is used as a dustproof material, a sealing material, a shock absorbing material, a soundproofing material, a shock absorbing material, and the like. Such an electric or electronic device has a configuration in which a member or part for an electric or electronic device or an optical member is attached (mounted) to a predetermined site via the above-mentioned foam member of the present invention There is. Specifically, as the electric or electronic device of the present invention, an image display device such as a liquid crystal display, an electroluminescence display, a plasma display or the like as an optical member or part (in particular, a small image display member is mounted as an optical member) Electrical or electronic equipment (for example, so-called “portable devices”) having a configuration in which a camera or a lens (in particular, a small camera or lens) is mounted via the above-described foam member of the present invention Mobile communication devices such as “telephone” and “portable information terminal”. Such an electric or electronic device may be a thinner product than before, and the thickness, shape, etc. thereof are not particularly limited.

[Shock absorption structure]
The impact absorbing structure (impact absorbing structure when the optical member is attached to a predetermined portion) has a structure in which the optical member is attached via the above-described foam member of the present invention. As the shock absorbing structure, when the foam member of the present invention described above is used when attaching (mounting) the optical member to a predetermined site, the other structure is not particularly limited. Therefore, the optical member, the predetermined portion to which the optical member is attached, and the like are not particularly limited, and can be appropriately selected. For example, as the optical member, the above-described optical members can be mentioned.

  EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited by these examples. The average cell diameter, apparent density, compressive stress at 50% compression, and compressive stress at 30% compression were determined by the following method. Moreover, the closed cell rate was calculated | required by said method.

(Average cell diameter)
An enlarged image of the foam bubble is captured by a digital microscope (trade name "VHX-500" manufactured by KEYENCE CORPORATION), and image analysis is performed using an image analysis software (trade name "Win ROOF" manufactured by Mitani Corporation). By doing this, the average cell diameter (μm) was determined. The number of bubbles in the captured enlarged image is about 100.

(Apparent density)
The resin foam is punched out with a 100 mm by 100 mm punch blade type to obtain a sheet-like test piece, and the dimensions of this test piece are measured. Further, the thickness is measured with a 1/100 dial gauge having a diameter (φ) of 20 mm of the measurement terminal. The volume of the test piece is calculated from these values. Next, the weight of the test piece is measured with a balance with a minimum scale of 0.01 g or more. The density (g / cm ³ ) is calculated from these values.

(Compressive stress at 50% compression (Rebound load when compressed to 50% thickness))
It measures according to the compression hardness measurement method of the foam of the foam described in JIS K 6767.
Specifically, a sheet-like test piece cut into a circular shape having a diameter of 20 mm is compressed to a thickness of 50% with respect to the initial thickness at a compression speed of 2.54 mm / min, and the unit area is stress (N) In terms of contact, the compression stress at 50% compression (anti-load load when compressed to a thickness of 50%) (N / cm ² ) is used.

(Compressive stress at 30% compression (against load when compressed to 30% thickness))
It measures according to the compression hardness measurement method of the foam described in JIS K 6767.
Specifically, the stress (N) when a sheet-like test piece cut out in a circular shape having a diameter of 20 mm is compressed to a thickness of 70% with respect to the initial thickness at a compression speed of 2.54 mm / min is a unit area In terms of contact, the compressive stress at 30% compression (anti-load load when compressed to a thickness of 70%) (N / cm ² ) is used.

Example 1
Polypropylene [melt flow rate (MFR) (230 ° C): 0.35 g / 10 min]: 45 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 55 parts by weight Magnesium hydroxide: 10 parts by weight, carbon (trade name “Asahi # 35” manufactured by Asahi Carbon Co., Ltd.): 10 parts by weight, stearic acid monoglyceride: 1 part by weight, and fatty acid amide (lauric acid bisamide): 2 parts by weight After kneading at a temperature of 200 ° C. with a twin screw kneader manufactured by Japan Steel Works (JSW), the mixture was extruded into strands, water-cooled, and then formed into pellets. The pellets were charged into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 (12 after injection) MPa under an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 6 parts by weight to 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a sheet-like resin foam structure having a thickness of 0.6 mm.
With respect to this resin foam structure, heating and compression were performed by pressurizing for 20 seconds under a pressure of 15 MPa under a temperature condition of 120 ° C. using a press. Then, a sheet-like resin foam having a thickness of 0.12 mm was obtained.

(Example 2)
Polypropylene [melt flow rate (MFR) (230 ° C): 0.35 g / 10 min]: 45 parts by weight, polyolefin elastomer [melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °]: 55 parts by weight Magnesium hydroxide: 120 parts by weight, carbon (trade name “Asahi # 35” manufactured by Asahi Carbon Co., Ltd.): 10 parts by weight, and stearic acid monoglyceride: 1 part by weight by a double screw manufactured by Japan Steel Works (JSW) After kneading at a temperature of 200 ° C. with a kneader, the mixture was extruded in the form of a strand, cooled with water, and formed into a pellet. The pellets were charged into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 (12 after injection) MPa under an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 6 parts by weight to 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and then extruded from a die to obtain a sheet-like resin foam structure having a thickness of 0.8 mm.
With respect to this resin foam structure, heating and compression were performed by pressurizing for 20 seconds under a pressure of 15 MPa under a temperature condition of 120 ° C. using a press. Then, a sheet-like resin foam having a thickness of 0.12 mm was obtained.

(Comparative example 1)
Thickness 0.12 mm, an average cell diameter of 60 [mu] m, the polyolefin apparent density of 0.15g / cm ^3, 30% compressive stress when compressed 1N / cm ^2, 50% -compression of the compressive stress is 5N / cm ² A base resin foam (a foam containing polyolefin as a main component) was used.

(Comparative example 2)
Thickness 0.12 mm, acrylic average cell diameter of 45 [mu] m, an apparent density of 0.48g / cm ^3, 30% compressive stress when compressed 1N / cm ^2, 50% -compression of the compressive stress is 2N / cm ² A system resin foam (foam having acrylic resin as a main component) was used.

(Evaluation)
The impact absorbability of the resin foam was evaluated by the following method.

(Evaluation method of shock absorption)
Impact force (F0) when a steel ball is caused to collide with only the support plate using the impact test apparatus (pendulum tester) shown in FIGS. 1 and 2 and between the fixing jig and the support plate The impact force (F1) when a steel ball was made to collide on a support plate in the state which inserted the resin foam (foam material) was measured, and shock absorption property was calculated | required by Formula (1).
Shock absorption (%) = (F0-F1) / F0 x 100
The resin foam used a 20-mm square thing. In addition, a steel ball with a diameter of 19 mm and a weight of 0.27 N (28 g weight) is attached to the impact test apparatus with a pointer of 350 mm in length. In the impact test device, an aluminum plate was used as a fixing jig.
As a support plate, an acrylic plate (trade name "Akrilite" manufactured by Mitsubishi Rayon, thickness: 3 mm) was used.
In addition, in the case of impact force measurement, the adhesive was used for the fixation of the test piece to a support plate in the range which does not affect impact force measurement.
The impact force is to raise the support rod to which the steel ball is attached by raising it at an angle of 40 degrees, then release the fixation and cause the steel ball to collide with the support plate, and the pressure at the time of the collision is pressured. It was sensed by a sensor and determined by MULTI-Purpose FTT Analyzer (manufactured by Ono Sokki Co., Ltd.).

  When the above-mentioned shock absorption is less than 40%, when it is applied as a shock absorber, the shock can not be absorbed and there is a possibility of breakage.

  The schematic configuration of the shock absorbing device will be described with reference to FIGS. 1 and 2. FIG. As shown in FIGS. 1 and 2, the impact test apparatus 1 (pendulum tester 1) comprises a holding member 3 as a holding means for holding the test piece 2 (impact absorbing material 2) with an arbitrary holding force, and a test piece An impact load member 4 which applies an impact stress to 2 and a pressure sensor 5 as an impact force detection means which detects an impact force on the test piece 2 by the impact load member 4 and the like. Further, the holding member 3 for holding the test piece 2 with an arbitrary holding force comprises a fixing jig 11 and a holding jig 12 which can slide so as to be able to hold the test piece 2 against the fixing jig 11. It is configured. Furthermore, the pressing jig 12 is provided with pressing pressure adjusting means 16. Further, the impact load member 4 which applies an impact force to the test piece 2 held by the holding member 3 is supported so that one end 22 is pivotally supported relative to the support 20 and has the impactor 24 at the other end. It comprises a rod 23 (shaft 23) and an arm 21 for lifting and holding the impactor 24 at a predetermined angle. Here, since a steel ball is used as the impactor 24, by providing the electromagnet 25 at one end of the arm, the impactor 24 can be integrally lifted at a predetermined angle. Furthermore, the pressure sensor 5 for detecting the impact force acting on the test piece 2 by the impact load member 4 is provided on the opposite side of the surface of the fixing jig 11 in contact with the test piece. The impactor 24 is a steel ball. Further, the angle at which the impact element 24 is lifted by the arm 21 (swing-up angle a in FIG. 1) is 40 ° (degrees). As shown in FIG. 2, the test piece 2 (impact absorbing material 2) is a support plate 28 formed of a highly elastic plate material such as a resinous plate material or a metal plate material between the fixing jig 11 and the holding jig 12. It is pinched through. In addition, an impact test apparatus is an apparatus similar to Example 1 of Unexamined-Japanese-Patent No. 2006-47277.

The shock absorber absorbs shock by deformation. That is, the fact that the shock absorber absorbs shock is due to the fact that the shock absorber deforms to absorb power. When the shock absorber is deformed by an impact, the shock absorber deprives the shock of the force necessary to deform. This allows the shock absorber to reduce the impact on other materials. Therefore, it is preferable that the impact absorbing material simultaneously satisfy the following characteristics (i) and (ii).
(I): requiring a certain amount of force for compression from the low compression stage (ii): that the stress does not become too high in the high compression state (not too hard in the high compression state)

  Since Example 1 and Example 2 use a force of 40% or more with respect to predetermined impact for deformation of the foam, they have high impact absorption and are preferable as an impact absorbing material. On the other hand, Comparative Example 1 and Comparative Example 2 use a force of 35% for deformation of the foam for a predetermined impact. That is, in Comparative Example 1 and Comparative Example 2, the impact is deformed by a force of 35%, so that the impact can not be absorbed, and the impact is transmitted. Therefore, Comparative Example 1 and Comparative Example 2 are not preferable as an impact absorbing material.

FIG. 4 is an electron micrograph showing a cross section of the resin foam of Example 1.
FIG. 5 is an electron micrograph showing a cross section of the resin foam of Example 2.
FIG. 6 is an electron micrograph showing a cross section of the resin foam of Comparative Example 1.
FIG. 7 is an electron micrograph showing a cross section of the resin foam of Comparative Example 2.
In each of FIGS. 4 to 7, the magnification is 200 times.

1 Impact test equipment (pendulum test machine)
2 Test piece (shock absorber)
Reference Signs List 3 holding member 4 impact load member 5 pressure sensor 11 fixing jig 12 holding jig 16 pressure adjusting means 20 support column 21 arm 22 end of support rod (shaft) 23 support rod (shaft)
24 impactor 25 electromagnet 28 support plate a swing angle

Claims (16)

It is a resin foam obtained by foaming a resin composition containing a resin, having a thickness of 0.01 to 0.30 mm, a compressive stress at 50% compression of 12 to 20 N / cm ² , and an apparent density resin foam but, wherein Ri 0.12 ~0.45g / cm ³ der, it is shock absorption defined by the following formula is 40% or more.
Shock absorption (%) = (F0-F1) / F0 x 100
(In the above equation, F0 is "impact force when the steel ball collides with only the support plate", and F1 is "support in a state where the resin foam is inserted between the fixing jig and the support plate "Impact force when a steel ball collides on a plate." The impact element is a steel ball of 0.27 N. The impact force is measured using the following impact test device. After swinging up and fixing the supporting rod attached to a 40 degree angle, the fixing is released, the steel ball is caused to collide with the supporting plate, and the force at the time of the collision at this time is measured. )
Impact test apparatus: Impact test apparatus having a support plate and a structure in which steel balls are attached by a support rod having a length of 350 mm, and the steel balls can be swung up to allow the steel balls to collide with the support plate   The resin foam according to claim 1, further having an average cell diameter of 20 to 130 μm. Furthermore, the closed cell rate is 70% or less, The resin foam of Claim 1 or 2. The resin foam according to any one of claims 1 to 3 , wherein the resin is a polyolefin resin. The resin foam according to claim 4, wherein the polyolefin-based resin is a mixture of polypropylene (excluding polyolefin-based elastomers) and a polyolefin-based elastomer. The resin foam according to any one of claims 1 to 5, wherein the resin foam is a foam of a resin composition containing a physical foaming agent. The resin foam according to claim 6, wherein the physical blowing agent is an inert gas. The resin foam according to claim 7, wherein the inert gas is carbon dioxide. The resin foam according to any one of claims 6 to 8, wherein the physical blowing agent is in a supercritical state. A foam member comprising the resin foam according to any one of claims 1 to 9 . The foam member according to claim 10 , further comprising an adhesive layer. The foam member according to claim 11 , wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer. The foam member according to any one of claims 10 to 12 , which is used as a shock absorber. The foam member according to any one of claims 10 to 13 , which is used for electrical or electronic devices. A foam member laminate characterized in that the foam member according to any one of claims 10 to 14 is held by a carrier tape. An electric or electronic device comprising the foam member according to claim 14 .