WO2021106910A1

WO2021106910A1 - Resin foam

Info

Publication number: WO2021106910A1
Application number: PCT/JP2020/043759
Authority: WO
Inventors: 清明児玉; 齋藤　誠
Original assignee: 日東電工株式会社
Priority date: 2019-11-25
Filing date: 2020-11-25
Publication date: 2021-06-03
Also published as: WO2021106911A1; WO2021106912A1; WO2021106914A1; WO2021106913A1; JPWO2021106912A1; JPWO2021106913A1; CN114761473A; CN114616278A; CN114761474A; CN114585670A; KR20220106752A; JPWO2021106914A1; JPWO2021106910A1; CN114641521A; JPWO2021106911A1

Abstract

Provided is a resin foam which is thin and has excellent impact resistance.　A resin foam according to the present invention has an apparent density of 0.02 g/cm³-0.30 g/cm³, a 25% compression load of 90 kPa or less, an elastic strain energy of 10 kPa or more upon compression, and a bubble structure. In one embodiment, the resin foam has an average bubble diameter of 10-200 μm. In one embodiment, the resin foam has a bubble fraction of 30% or more. In one embodiment, the resin foam has a coefficient of variation of bubble diameter of 0.5 or less.

Description

Resin foam

The present invention relates to a resin foam.

Cushion material is often used to protect the screen of electronic devices and the substrate. In recent years, it has been required to narrow the clearance of the portion where the cushion material is arranged in accordance with the tendency of thinning of electronic devices. Furthermore, studies on flexible electronic devices using organic EL panels are also in progress. In such an electronic device, a load of action different from that of the conventional rigid LCD panel is applied.

Examples of the cushioning material include members having a foamed structure, and as a method for obtaining a foam having a fine bubble structure, an inert gas is dissolved in a polymer under high pressure, and then the pressure is rapidly reduced to form a foamed structure. A method of forming has been proposed (Cited Document 1). Attempts have also been made to improve the shock absorption of the foamed member (Cited Documents 2 and 3). However, not only the equipment used in conventional rigid displays, but also the equipment used in flexible displays and the equipment used by bending the flexible display have a high level of impact resistance. A foamed member that has been realized and is thinly constructed has not been obtained.

Japanese Unexamined Patent Publication No. 6-322168 Japanese Unexamined Patent Publication No. 2017-186504 Japanese Unexamined Patent Publication No. 2015-034299

An object of the present invention is to provide a resin foam having excellent shock absorption even if it is thin.

The resin foam of the present invention has an apparent density of 0.02 g / cm ³ to 0.30 g / cm ³ , a 25% compression load of 90 kPa or less, and an elastic strain energy during compression of 10 kPa or more. It has a bubble structure.
In one embodiment, the resin foam has an average cell diameter of 10 μm to 200 μm.
In one embodiment, the resin foam has a bubble ratio of 30% or more.
In one embodiment, the resin foam has a coefficient of variation of bubble diameter of 0.5 or less.
In one embodiment, the resin foam has a non-foam bending stress of 5 MPa or more.
In one embodiment, the resin foam further comprises a filler.
In one embodiment, the filler is an inorganic material.
In one embodiment, the filler is organic.
In one embodiment, the resin foam comprises a polyolefin-based resin.
In one embodiment, the polyolefin-based resin is a mixture of a polyolefin other than the polyolefin-based elastomer and a polyolefin-based elastomer.
In one embodiment, the resin foam has a hot melt layer on one or both sides.
According to another aspect of the present invention, a foamed member is provided. This foamed member has a resin foamed layer and an adhesive layer arranged on at least one side of the resin foamed layer, and the resin foamed layer is the resin foam.

According to the present invention, it is possible to provide a resin foam having excellent shock absorption even if it is thin. The resin foam of the present invention exhibits excellent shock absorption even when combined with a flexible sheet.

It is the schematic sectional drawing of the foaming member according to one Embodiment of this invention.

A. Resin foam The resin foam of the present invention has an apparent density of 0.02 g / cm ³ to 0.30 g / cm ³ , a 25% compression load of 90 kPa or less, and an elastic strain energy during compression of 10 kPa or more. Is. The resin foam of the present invention has a bubble structure (cell structure). Examples of the cell structure (cell structure) include a closed cell structure, an open cell structure, and a semi-continuous semi-closed cell structure (a bubble structure in which a closed cell structure and an open cell structure are mixed). The cell structure of the resin foam is preferably a continuous cell structure or a semi-continuous semi-closed cell structure, and more preferably a semi-continuous semi-closed cell structure. The resin foam of the present invention is obtained by foaming the resin composition. The resin composition is a composition containing at least the resin constituting the resin foam.

As described above, the apparent density of the resin foam of the present invention is 0.02 g / cm ³ to 0.30 g / cm ³ . Within such a range, a resin foam having excellent flexibility and stress dispersibility can be obtained. The apparent density of the resin foam of the present invention is preferably ^{0.03g / cm 3 ~ 0.28g / cm} 3, more preferably from ^{0.04g / cm 3 ~ 0.25g / cm} 3, particularly preferably Is 0.05 ^{g / cm 3} to 0.20 g / cm ³ , and most preferably 0.07 g / cm ³ to 0.15 g / cm ³ . Within such a range, the above effect becomes remarkable. The method for measuring the apparent density will be described later.

As described above, the 25% compressive load of the resin foam of the present invention is 90 kPa or less. If the resin foam has a 25% compressive load in such a range, the load on the applied member can be reduced. More specifically, when the resin foam is applied to a portion having a narrow clearance by compressing it to some extent, the resin foam of the present invention can reduce the stress applied to other members. For example, when the resin foam is applied to the display member, the stress applied to the display member can be relaxed and dispersed, which is useful from the viewpoint of reducing color unevenness and protecting the member. The 25% compressive load of the resin foam of the present invention is preferably 80 kPa or less, more preferably 75 kPa or less, and further preferably 55 kPa or less. Within such a range, the above effect becomes remarkable. The 25% compressive load of the resin foam of the present invention is preferably as small as possible, but the lower limit thereof is, for example, 10 kPa, preferably 5 kPa, more preferably 1 kPa, and particularly preferably 0.1 kPa. is there. The method for measuring the 25% compressive load will be described later.

As described above, the elastic strain energy of the resin foam of the present invention during compression is 10 kPa or more. "Elastic strain energy during compression" means the total amount of compression repulsive force when the resin foam is compressed by 10%. Specifically, the "elastic strain energy during compression" was determined by a compression test (test temperature: 23 ° C., sample size: 10 mm x 10 mm, compression rate: 10 mm / min) according to JIS K 6767. When the compression rate (%) and the compression repulsive force (kPa) are measured, it is obtained from the compression ss curve with the x-axis as the compression rate (%) and the y-axis as the compression repulsive force (kPa), and the compression rate is 0%. It is the area of the region defined by the ss curve and the x-axis in the range of about 10%. If the elastic strain energy during compression of the resin foam is within the above range, a resin foam having excellent shock absorption can be obtained. More specifically, a resin foam having an elastic strain energy in the above range consumes a large amount of energy for deformation of the resin foam when an impact is applied, so that this can be applied even to a strong impact. Can be absorbed well. The elastic strain energy of the resin foam of the present invention during compression is preferably 20 kPa or more, more preferably 28 kPa or more, still more preferably 35 kPa or more, still more preferably 50 kPa or more, still more preferably 80 kPa or more. The above is particularly preferable, 100 kPa or more, and most preferably 150 kPa or more. Within such a range, the above effect becomes remarkable. The upper limit of the elastic strain energy during compression of the resin foam of the present invention is, for example, 500 kPa (preferably 800 kPa).

In the present invention, a resin foam having excellent flexibility, stress dispersibility and impact resistance can be obtained by setting the apparent density, 25% compressive load and elastic strain energy during compression within the above ranges. Further, a resin foam that satisfies all of the above characteristics is a combination with a member (for example, an organic EL panel, a resin base material) that exhibits excellent impact resistance while being a thin layer and has flexibility. Demonstrates excellent impact resistance.

The thickness of the resin foam of the present invention is preferably 30 μm to 5000 μm, more preferably 35 μm to 4000 μm, further preferably 40 μm to 3000 μm, still more preferably 45 μm to 2000 μm, still more preferably 50 μm to 50 μm. It is 1000 μm, and particularly preferably 55 μm to 500 μm. As described above, the resin foam of the present invention exhibits excellent impact resistance even though it is a thin layer. Further, when the thickness of the resin foam is within the above range, a fine and uniform bubble structure can be formed, which is advantageous in that excellent shock absorption can be exhibited.

The elongation at break of the resin foam of the present invention at 25 ° C. is preferably 120% or less, more preferably 110% or less, further preferably 100% or less, and particularly preferably 90% or less. Within such a range, a resin foam having excellent flexibility and stress dispersibility can be obtained. If the elongation at break is small, the deformation of the cell wall of the resin foam becomes small when a load is applied to the resin foam. For example, when a filler is added, the resin foam constitutes the resin foam. Slip is likely to occur at the interface between the resin and the filler, and the load can be further relaxed. On the other hand, if the breaking elongation is too large, the deformation of the cell wall of the resin foam becomes large, and it may be difficult to relax the load. The elongation at break can be measured according to JIS K 6767.

The average cell diameter (average cell diameter) of the resin foam is preferably 10 μm to 200 μm, more preferably 15 μm to 180 μm, further preferably 20 μm to 150 μm, and particularly preferably 23 μm to 120 μm. It is particularly preferably 25 μm to 100 μm, and most preferably 30 μm to 80 μm. Within such a range, a resin foam having more excellent flexibility and stress dispersibility can be obtained. In addition, it is possible to obtain a resin foam having excellent compression recovery and resistance to repeated impacts. The method for measuring the average cell diameter will be described later.

The aspect ratio of bubbles contained in the resin foam is preferably 1.5 or more. Within such a range, a resin foam having excellent thickness recovery can be obtained. The aspect ratio of the bubbles constituting the resin foam is preferably 2.0 or more, and more preferably 2.5 or more. Within such a range, the above effect becomes remarkable. The upper limit of the aspect ratio of the bubbles constituting the resin foam is preferably 8, more preferably 6, and even more preferably 5. Within such a range, a resin foam having excellent shock absorption can be obtained.

In the present specification, the "aspect ratio of bubbles contained in the resin foam" is the aspect ratio of individual bubbles existing ^{in a predetermined area (3 mm 2) in the cross section of the resin foam at randomly selected locations.} Means the average value. The specific method for obtaining the "aspect ratio of bubbles contained in the resin foam" is as follows.
-The resin foam is cut using a razor blade in the TD (direction orthogonal to the flow direction) and in the direction perpendicular to the main surface of the resin foam (thickness direction), and within a predetermined area (3 mm ² ). Is observed at a magnification of 100 times. The length of one bubble in the thickness direction and the length of TD are measured.
-Similar measurement is performed for all bubbles existing in a predetermined area.
-The aspect ratio of bubbles is calculated by dividing the length of TD by the length in the thickness direction, and the same calculation is performed for all bubbles, and the average value is defined as "the aspect ratio of bubbles possessed by the resin foam".

The coefficient of variation of the bubble diameter (cell diameter) of the resin foam of the present invention is preferably 0.5 or less, more preferably 0.48 or less, still more preferably 0.45 or less, and particularly preferably 0.45 or less. It is 0.43 or less, most preferably less than 0.4. Within such a range, it is possible to obtain a resin foam in which deformation due to impact becomes uniform, local stress load is prevented, stress dispersibility is excellent, and impact resistance is particularly excellent. The smaller the coefficient of variation is, the more preferable it is, but the lower limit thereof is, for example, 0.2 (preferably 0.15, more preferably 0.1, still more preferably 0.01). The method for measuring the coefficient of variation of the bubble diameter will be described later.

The bubble ratio (cell ratio) of the resin foam of the present invention is preferably 30% or more, more preferably 50% or more, and further preferably 80% or more. Within such a range, a resin foam having a small repulsive stress during compression can be obtained. Such a resin foam can reduce the stress applied to other members when the resin foam is applied by compressing it to a place having a narrow clearance. For example, when the resin foam is applied to the display member, the stress applied to the display member can be relaxed and dispersed, which is useful from the viewpoint of reducing color unevenness and protecting the member. The upper limit of the bubble ratio is, for example, 99% or less. The method for measuring the bubble ratio will be described later.

The thickness of the bubble wall (cell wall) of the resin foam of the present invention is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 8 μm, still more preferably 0.5 μm to 5 μm, and particularly. It is preferably 0.7 μm to 4 μm, and most preferably 1 μm to 2.8 μm. Within such a range, a resin foam having more excellent flexibility and stress dispersibility can be obtained. If the thickness of the bubble wall is too thin, the resin foam is easily deformed by a load, and a sufficient stress dispersion effect may not be obtained. If the thickness of the bubble wall is too thick, the resin foam is less likely to be deformed by a load, and when used in a gap between devices, the step followability may be deteriorated. The method for measuring the thickness of the bubble wall will be described later.

When the cell structure of the resin foam of the present invention is a semi-continuous semi-closed cell structure, the ratio of the closed cell structure in the cell structure is preferably 40% or less, more preferably 30% or less. In the present specification, the self-foaming ratio of the resin foam is, for example, in an environment of a temperature of 23 ° C. and a humidity of 50%, the object to be measured is submerged in water, the mass thereof is measured thereafter, and then in an oven at 80 ° C. After sufficiently drying, the mass is measured again to obtain the determination. Further, since open cells can retain water, the mass thereof can be measured and obtained as open cells.

The non-foaming bending stress of the resin foam of the present invention is preferably 5 MPa or more, more preferably larger than 5 MPa, more preferably 7 MPa or more, still more preferably 10 MPa or more. Within such a range, a large amount of energy is required to deform the bubble wall (cell wall) of the resin foam, and a resin foam having excellent shock absorption can be obtained. The resin foam of the present invention can improve impact resistance (impact absorption) by appropriately reducing the flexibility, which has been regarded as important in cushioning materials, and balancing it with other characteristics. .. As described above, the resin foam of the present invention that exhibits shock absorption due to an action different from the conventional one is particularly useful in a configuration in which the impact propagates in a narrow range (a configuration in which the impact does not easily spread in the plane direction), for example. , Especially useful when applied to flexible members (eg, members made of resin). The upper limit of the non-foam bending stress is preferably 20 MPa, more preferably 15 MPa. Within such a range, a resin foam having more excellent flexibility and stress dispersibility can be obtained. The “non-foaming bending stress” means the bending stress of the resin molded product a that has been returned to the non-foaming state (bulk) without bubbles by heat-pressing the resin foam. The density of the resin molded body a can be made equal to the density of the resin molded body b before foaming formed by the resin composition described later. The bending stress of the resin molded body a (non-foamed bending stress of the resin foam) can be the same as that of the resin molded body b. The method for measuring the bending stress will be described later.

The thickness recovery rate of the resin foam is preferably 65% or more, more preferably 70% or more, and further preferably 75% or more. The thickness recovery rate of the foamed layer is defined by the following formula. The thickness recovery rate of this foam layer is a recovery rate measured by applying a load to a foam sheet with a certain area and compressing it, and is a so-called dent recovery rate measured by locally applying a load and denting only a part of the foam sheet. Is different.
Thickness recovery rate (%) = {(thickness 0.5 seconds after decompression) / (initial thickness)} x 100
Initial thickness: The thickness of the resin foam before applying a load.
Thickness 0.5 seconds after decompression: Maintained for 120 seconds with a load of ^{1000 g / cm 2 applied to the resin foam, decompressed, 0.5 seconds after decompression} Thickness of resin foam.

As the shape of the resin foam of the present invention, any appropriate shape can be adopted depending on the purpose. Such a shape is typically a sheet shape.

The resin foam of the present invention may have a hot melt layer on one side or both sides thereof. The resin foam having the hot melt layer is, for example, a resin foam (or a precursor of the resin foam) using a pair of heating rolls heated to a temperature equal to or higher than the melting temperature of the resin composition constituting the resin foam. Can be obtained by rolling.

The resin foam of the present invention can be formed by any suitable method as long as the effects of the present invention are not impaired. A typical example of such a method is a method of foaming a resin composition containing a resin material (polymer).

A-1. Resin Composition The resin foam of the present invention can be typically obtained by foaming a resin composition. The resin composition comprises any suitable resin material (polymer).

Examples of the polymer include acrylic resin, silicone resin, urethane resin, polyolefin resin, ester resin, rubber resin and the like. The polymer may be used alone or in combination of two or more.

The content ratio of the polymer is preferably 30 parts by weight to 95 parts by weight, more preferably 35 parts by weight to 90 parts by weight, and further preferably 40 parts by weight to 80 parts by weight with respect to 100 parts by weight of the resin composition. It is a part, particularly preferably 40 parts by weight to 60 parts by weight. Within such a range, a resin foam having more excellent flexibility and stress dispersibility can be obtained.

In one embodiment, a polyolefin resin is used as the polymer.

The content ratio of the polyolefin resin is preferably 50 parts by weight to 100 parts by weight, more preferably 70 parts by weight to 100 parts by weight, and further preferably 90 parts by weight to 100 parts by weight with respect to 100 parts by weight of the polymer. It is a part by weight, particularly preferably 95 parts by weight to 100 parts by weight, and most preferably 100 parts by weight.

The polyolefin-based resin preferably includes at least one selected from the group consisting of polyolefins and polyolefin-based elastomers, and more preferably, polyolefins and polyolefin-based elastomers are used in combination. As for the polyylene and the polyolefin-based elastomer, only one type may be used alone, or two or more types may be used in combination. In this specification, the term "polyolefin" does not include "polyolefin-based elastomer".

When a polyolefin and a polyolefin-based elastomer are used in combination as the polyolefin-based resin, the weight ratio of the polyolefin and the polyolefin-based elastomer (polyolefin / polyolefin-based elastomer) is preferably 1/99 to 99/1, more preferably 10/90 to It is 90/10, more preferably 20/80 to 80/20, and particularly preferably 30/70 to 70/30. Within such a range, the effect of the present invention becomes remarkable.

As the polyolefin, any suitable polyolefin can be adopted as long as the effect of the present invention is not impaired. Examples of such polyolefins include linear polyolefins and branched-chain (branched-chain) polyolefins. In one embodiment, a branched-chain polyolefin is used as the polyolefin-based resin. In this embodiment, as the polyolefin, only the branched polyolefin may be used, or the branched polyolefin and the linear polyolefin may be used in combination. By using the branched polyolefin, it is possible to obtain a resin foam having a small average cell diameter and excellent impact resistance. The content ratio of the branched polyolefin is preferably 30 parts by weight to 100 parts by weight, and more preferably 80 parts by weight to 120 parts by weight with respect to 100 parts by weight of the polyolefin.

Examples of the polyolefin include polymers containing a structural unit derived from α-olefin. The polyolefin may be composed of only a structural unit derived from an α-olefin, or may be composed of a structural unit derived from an α-olefin and a structural unit derived from a monomer other than the α-olefin. When the polyolefin is a copolymer, any suitable copolymerization form can be adopted as the copolymerization form thereof. For example, random copolymers, block copolymers and the like can be mentioned.

Examples of the α-olefin that can constitute the polyolefin include α-olefins having 2 to 8 carbon atoms (preferably 2 to 6, more preferably 2 to 4) (for example, ethylene, propylene, 1-butene, 1-pentene). , 1-Hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc.) are preferred. The α-olefin may be only one kind or two or more kinds.

Examples of the monomer other than the α-olefin constituting the polyolefin include ethylenically unsaturated monomers such as vinyl acetate, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, and vinyl alcohol. The monomer other than the α-olefin may be only one kind or two or more kinds.

Specific examples of the polyolefin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene (propylene homopolymer), a copolymer of ethylene and propylene, and ethylene and other than ethylene. Copolymer with α-olefin, copolymer of propylene and α-olefin other than propylene, copolymer of ethylene and propylene and ethylene and α-olefin other than propylene, propylene and ethylenically unsaturated single amount Examples include a copolymer with a body.

In one embodiment, a polypropylene-based polymer having a propylene-derived structural unit is used as the polyolefin. Examples of the polypropylene-based polymer include polypropylene (propylene homopolymer), a copolymer of ethylene and propylene, a copolymer of propylene and an α-olefin other than propylene, and preferably polypropylene (propylene homopolymer). ). As the polypropylene-based polymer, only one type may be used alone, or two or more types may be used in combination.

The melt flow rate (MFR) of the polyolefin at a temperature of 230 ° C. is preferably 0.2 g / 10 min to 10 g / 10 min, and more preferably 0.25 g / 10 in that the effects of the present invention can be more exhibited. Minutes to 5 g / 10 minutes, more preferably 0.3 g / 10 minutes to 3 g / 10 minutes, and particularly preferably 0.35 g / 10 minutes to 1.5 g / 10 minutes. In the present specification, the melt flow rate (MFR) refers to an MFR measured at a temperature of 230 ° C. and a load of 2.16 kgf based on ISO1133 (JIS-K-7210).

In one embodiment, two or more types of polyolefins having different melt flow rates (MFR) at a temperature of 230 ° C. within the above range are used in combination. In this case, the melt flow rate (MFR) at a temperature of 230 ° C. is preferably 0.2 g / 10 minutes or more and less than 0.7 g / 10 minutes (more preferably 0.2 g / 10 minutes to 0.65 g / 10 minutes). The polyolefin and melt flow rate (MFR) at a temperature of 230 ° C. are preferably 0.7 g / 10 min to 10 g / 10 min (more preferably 0.7 g / 10 min to 5 g / 10 min, and even more preferably 0. 7 g / 10 minutes to 3 g / 10 minutes, particularly preferably 0.7 g / 10 minutes to 1.5 g / 10 minutes, and most preferably 0.7 g / 10 minutes to 1.3 g / 10 minutes). Can be used in combination with the polyolefin of. By doing so, it is possible to obtain a resin foam having a small average cell diameter and excellent impact resistance.

When two or more kinds of polyolefins having different melt flow rates (MFR) at a temperature of 230 ° C. are used in combination as the polyolefin, for example, the melt flow rate (MFR) at a temperature of 230 ° C. is preferably 0. The polyolefin of 2 g / 10 minutes or more and less than 0.7 g / 10 minutes (more preferably 0.2 g / 10 minutes to 0.65 g / 10 minutes) and the melt flow rate (MFR) at a temperature of 230 ° C. are preferably 0.7 g. / 10 min to 10 g / 10 min (more preferably 0.7 g / 10 min to 5 g / 10 min, still more preferably 0.7 g / 10 min to 3 g / 10 min, and particularly preferably 0.7 g / min. The weight ratio of 10 minutes to 1.5 g / 10 minutes, most preferably 0.7 g / 10 minutes to 1.3 g / 10 minutes) with the polyolefin is preferably 1/99 to 99/1. , More preferably 10/90 to 90/10, further preferably 20/80 to 80/20, particularly preferably 30/70 to 70/30, and most preferably 40/60 to 60/40. Is.

As the polyolefin, a commercially available product may be used, for example, "E110G" (manufactured by Prime Polymer Co., Ltd.), "EA9" (manufactured by Japan Polypropylene Corporation), "EA9FT" (manufactured by Japan Polypropylene Corporation), "E-". Examples thereof include "185G" (manufactured by Prime Polymer Co., Ltd.), "WB140HMS" (manufactured by Borealis), and "WB135HMS" (manufactured by Borealis).

As the polyolefin-based elastomer, any suitable polyolefin-based elastomer can be adopted as long as the effects of the present invention are not impaired. Examples of such polyolefin-based elastomers include ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-vinyl acetate copolymers, polybutene, polyisobutylene, chlorinated polyethylene, and polyolefin components and rubber components. So-called non-crosslinked thermoplastic olefin-based elastomer (TPO), such as an elastomer in which is physically dispersed, or an elastomer having a structure in which a polyolefin component and a rubber component are microphase-separated; a resin component A (olefin) forming a matrix. A mixture containing a system resin component A) and a rubber component B forming a domain is dynamically heat-treated in the presence of a cross-linking agent, and cross-linked rubber particles are contained in the resin component A which is a matrix (sea phase). Examples thereof include a dynamically crosslinked thermoplastic olefin-based elastomer (TPV), which is a polyphasic polymer having a sea-island structure finely dispersed as a domain (island phase).

The polyolefin-based elastomer preferably contains a rubber component. Examples of such rubber components include JP-A-08-302111, JP-A-2010-241934, JP-A-2008-024882, JP-A-2000-007858, JP-A-2006-052277, and JP-A. Examples thereof include those described in Japanese Patent Application Laid-Open No. 2012-072306, Japanese Patent Application Laid-Open No. 2012-057068, Japanese Patent Application Laid-Open No. 2010-2418997, Japanese Patent Application Laid-Open No. 2009-067969, and Japanese Patent Application Laid-Open No. 03/002654.

Specific examples of the elastomer having a structure in which the polyolefin component and the olefin rubber component are microphase-separated include polypropylene resin (PP) and an elastomer composed of polypropylene resin (PP) and ethylene-propylene rubber (EPM). Examples thereof include an elastomer composed of ethylene-propylene-diene rubber (EPDM). The weight ratio of the polyolefin component and the olefin rubber component (polyolefin component / olefin rubber) is preferably 90/10 to 10/90, and more preferably 80/20 to 20/80.

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

As described above, the dynamically crosslinked thermoplastic olefin elastomer (TPV) is a cross-linking agent containing a mixture containing a resin component A (olefin resin component A) forming a matrix and a rubber component B forming a domain. 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 dynamically heat-treating in the presence. ..

Examples of the dynamically crosslinked thermoplastic olefin elastomer (TPV) include JP-A-2000-007858, JP-A-2006-052277, JP-A-2012-072306, JP-A-2012-057068, and Japanese Patent Application Laid-Open No. 2012-057068. Examples thereof include those described in Japanese Patent Application Laid-Open No. 2010-2418997, Japanese Patent Application Laid-Open No. 2009-067969, and Re-Table 03/002654.

As the dynamically crosslinked thermoplastic olefin elastomer (TPV), a commercially available product may be used, for example, "Zeotherm" (manufactured by Zeon Corporation), "Thermoran" (manufactured by Mitsubishi Chemical Corporation), "Sarlink 3245D". (Manufactured by Toyobo Corporation) and the like.

The melt flow rate (MFR) of the polyolefin-based elastomer at a temperature of 230 ° C. is preferably 2 g / 10 min to 15 g / 10 min, more preferably 3 g / 10 min to 10 g / 10 min, and even more preferably 3. It is 5 g / 10 minutes to 9 g / 10 minutes, particularly preferably 4 g / 10 minutes to 8 g / 10 minutes, and most preferably 4.5 g / 10 minutes to 7.5 g / 10 minutes.

The melt tension (190 ° C., at break) of the polyolefin-based elastomer is preferably less than 10 cN, and more preferably 5 cN to 9.5 cN.

The JIS A hardness of the polyolefin-based elastomer is preferably 30 ° to 95 °, more preferably 35 ° to 90 °, further preferably 40 ° to 88 °, and particularly preferably 45 ° to 85 °. Yes, most preferably 50 ° to 83 °. The JIS A hardness is measured based on ISO7619 (JIS K6253).

In one embodiment, the resin foam (ie, the resin composition) may further comprise a filler. By containing the filler, it is possible to form a resin foam that requires a large amount of energy to deform the bubble wall (cell wall), and the resin foam exhibits excellent shock absorption. Further, by containing the filler, a fine and uniform bubble structure can be formed, which is also advantageous in that excellent shock absorption can be exhibited. As the filler, only one kind may be used alone, or two or more kinds may be used in combination.

The content ratio of the filler is preferably 10 parts by weight to 150 parts by weight, more preferably 30 parts by weight to 130 parts by weight, still more preferably, with respect to 100 parts by weight of the polymer constituting the resin foam. It is 50 parts by weight to 100 parts by weight. Within such a range, the above effect becomes remarkable.

In one embodiment, the filler is an inorganic substance. Examples of the material constituting the filler which is an inorganic substance include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, and boric acid. Examples thereof include aluminum whisker, silicon nitride, boron nitride, crystalline silica, amorphous silica, metals (for example, gold, silver, copper, aluminum, nickel), carbon, graphite and the like.

In one embodiment, the filler is organic. Examples of the material constituting the filler which is an organic substance include polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetheretherketone, polyetherimide, polyesterimide and the like.

A flame retardant may be used as the filler. Examples of the flame retardant include a bromine-based flame retardant, a chlorine-based flame retardant, a phosphorus-based flame retardant, an antimony-based flame retardant, and the like. Preferably, from the viewpoint of safety, a non-halogen-non-antimony flame retardant is used.

Examples of the non-halogen-non-antimony flame retardant include compounds containing aluminum, magnesium, calcium, nickel, cobalt, tin, zinc, copper, iron, titanium, boron and the like. Examples of such a compound (inorganic compound) include hydrated metal compounds such as aluminum hydroxide, magnesium hydroxide, magnesium oxide / nickel oxide hydrate, and magnesium oxide / zinc oxide hydrate. ..

The above-mentioned filler may be subjected to any appropriate surface treatment. Examples of the surface treatment include a silane coupling treatment and a stearic acid treatment.

The bulk density of the filler is preferably 0.8 g / cm ³ or less, more preferably 0.6 g / cm ³ or less, still more preferably 0.4 g / cm ³ or less, and in particular. It is preferably 0.3 g / cm ³ or less. Within such a range, the filler can be contained with good dispersibility, and the effect of adding the filler can be sufficiently exhibited while reducing the content of the filler. A resin foam having a low filler content is advantageous in that it is highly foamed, flexible, and has excellent stress dispersibility and appearance. The lower limit of the bulk density of the filler is, for example, 0.01 g / cm ^3, preferably 0.05 g / cm ^3, more preferably 0.1 g / cm ^3.

The number average particle size (primary particle size) of the filler is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 1 μm or less. Within such a range, the filler can be contained with good dispersibility and a uniform bubble structure can be formed. As a result, a resin foam having excellent stress dispersibility and appearance can be obtained. The lower limit of the number average particle size of the filler is, for example, 0.1 μm. The number average particle size of the filler can be measured using a particle size distribution meter (MicrotracII, Microtrac Bell Co., Ltd.) using a suspension prepared by mixing 1 g of a filler with 100 g of water as a sample. it can.

The specific surface area of the filler is preferably 2 m ² / g or more, more preferably 4 m ² / g or more, and further preferably 6 m ² / g or more. Within such a range, the filler can be contained with good dispersibility and a uniform bubble structure can be formed. As a result, a resin foam having excellent stress dispersibility and appearance can be obtained. The upper limit of the specific surface area of the filler is, for example, 20 m ² / g. The specific surface area of the filler can be measured by the BET method, that is, by adsorbing a molecule having a known adsorption area to the surface of the filler at a low temperature of liquid nitrogen and measuring the adsorption amount.

The resin composition may contain any suitable other components as long as the effects of the present invention are not impaired. Such other components may be only one kind or two or more kinds. Such other components include, for example, rubber, resins other than polymers blended as resin materials, softeners, aliphatic compounds, antioxidants, antioxidants, light stabilizers, weather resistant agents, and ultraviolet absorption. Agents, dispersants, plastics, carbons, antistatic agents, surfactants, cross-linking agents, thickeners, rust preventives, silicone compounds, tension modifiers, shrinkage inhibitors, fluidity modifiers, gelling Agents, hardeners, reinforcing agents, foaming agents, foaming nucleating agents, coloring agents (pigments, dyes, etc.), pH adjusting agents, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, lubricants, crystal nucleating agents, Examples thereof include crystallization accelerators, solubilizers, surface treatment agents, and dispersion aids.

A-2. Formation of Resin Foam The resin foam of the present invention is typically obtained by foaming a resin composition. As the foaming method (bubble forming method), a method usually used for foam molding, such as a physical method or a chemical method, can be adopted. That is, the resin foam of the present invention may be typically a foam (physical foam) formed by foaming by a physical method, or may be foamed by a chemical method. It may be a body (chemical foam). The physical method is generally one in which a gas component such as air or nitrogen is dispersed in a polymer solution to form bubbles by mechanical mixing (mechanical foam). The chemical method is generally a method of forming a cell by a gas generated by thermal decomposition of a foaming agent added to a polymer base to obtain a foam.

The resin composition to be subjected to foam molding can be, for example, a component of any suitable melt-kneading device, for example, an open mixing roll, a non-open Banbury mixer, a single-screw extruder, a twin-screw extruder, or a continuous type. It may be prepared by mixing using any suitable means such as a kneader and a pressure kneader.

<Embodiment 1 for forming the resin foam of the present invention>
As one embodiment 1 for forming the resin foam of the present invention, for example, a step of mechanically foaming an emulsion resin composition (an emulsion containing a resin material (polymer) or the like) to foam (step A). A form in which a resin foam is formed through the above can be mentioned. Examples of the foaming device include a high-speed shearing device, a vibration device, a pressurized gas discharge device, and the like. Among these foaming devices, a high-speed shearing device is preferable from the viewpoint of reducing the bubble diameter and producing a large capacity. This one embodiment 1 for forming the resin foam of the present invention can be applied to the formation from any resin composition.

The solid content concentration of the emulsion is preferably high from the viewpoint of film forming property. The solid content concentration of the emulsion is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 50% by weight or more.

The bubbles when foamed by mechanical stirring are those in which a gas is incorporated into the emulsion. As the gas, any suitable gas can be adopted as long as it is inert to the emulsion, as long as the effects of the present invention are not impaired. Examples of such a gas include air, nitrogen, carbon dioxide and the like.

The resin foam of the present invention can be obtained by subjecting the emulsion resin composition foamed by the above method (bubble-containing emulsion resin composition) to a substrate and drying it (step B). it can. Examples of the base material include a peel-treated plastic film (peeling-treated polyethylene terephthalate film and the like), a plastic film (polyethylene terephthalate film and the like), and the like.

In step B, any appropriate method can be adopted as the coating method and the drying method as long as the effects of the present invention are not impaired. Step B includes a preliminary drying step B1 in which the bubble-containing emulsion resin composition coated on the substrate is dried at 50 ° C. or higher and lower than 125 ° C., and then a main drying step B2 in which the bubble-containing emulsion resin composition is further dried at 125 ° C. or higher and 200 ° C. or lower. It is preferable to have.

By providing the pre-drying step B1 and the main drying step B2, it is possible to prevent the coalescence of bubbles and the bursting of bubbles due to a rapid temperature rise. In particular, in a foam sheet having a small thickness, bubbles are united and burst due to a rapid rise in temperature, so it is of great significance to provide the pre-drying step B1. The temperature in the pre-drying step B1 is preferably 50 ° C. to 100 ° C. The time of the pre-drying step B1 is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes. The temperature in the main drying step B2 is preferably 130 ° C. to 180 ° C. or lower, and more preferably 130 ° C. to 160 ° C. The time of the main drying step B2 is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes.

<Embodiment 2 for forming the resin foam of the present invention>
As one embodiment 2 for forming the resin foam of the present invention, there is a mode in which the resin composition is foamed with a foaming agent to form a foam. As the foaming agent, those usually used for foam molding can be used, and from the viewpoint of environmental protection and low pollution to the foam to be foamed, it is preferable to use a high-pressure inert gas.

As the inert gas, any suitable inert gas can be adopted as long as it is inert to the resin composition and can be impregnated. Examples of such an inert gas include carbon dioxide, nitrogen gas, and air. These gases may be mixed and used. Of these, carbon dioxide is preferable from the viewpoint of a large amount of impregnation into the resin material (polymer) and a high impregnation rate.

The inert gas is preferably in a supercritical state. That is, it is particularly preferable to use carbon dioxide in a supercritical state. In the supercritical state, the solubility of the inert gas in the resin composition is further increased, a high concentration of the inert gas can be mixed, and the inert gas becomes high concentration at the time of a sudden pressure drop. Since the number of nuclei generated increases and the density of bubbles formed by the growth of the bubble nuclei becomes higher than in other states even if the porosity is the same, fine bubbles can be obtained. The critical temperature of carbon dioxide is 31 ° C., and the critical pressure is 7.4 MPa.

As a method of forming a foam by impregnating a resin composition with a high-pressure inert gas, for example, a gas impregnation step of impregnating a resin composition containing a resin material (polymer) with an inert gas under high pressure, the same. Examples thereof include a decompression step of lowering the pressure after the step to foam the resin material (polymer), and a method of forming the resin material (polymer) through a heating step of growing bubbles by heating if necessary. In this case, a preformed unfoamed molded product may be impregnated with an inert gas, or the molten resin composition is impregnated with an inert gas under a pressurized state and then subjected to molding when the pressure is reduced. You may. These steps may be performed by either a batch method or a continuous method. That is, after the resin composition is previously molded into an appropriate shape such as a sheet to form an unfoamed resin molded product, the unfoamed resin molded product is impregnated with a high-pressure gas to release the pressure for foaming. It may be a batch method in which the resin composition is kneaded together with a high-pressure gas under pressure, and the pressure is released at the same time as molding, and molding and foaming may be performed at the same time.

An example of producing a foam by a batch method is shown below. For example, a resin sheet for foam molding is produced 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 equipped with blades such as a roller, a cam, a kneader, and a bambari type, and pressed to a predetermined thickness using a hot plate press or the like. To prepare an unfoamed resin molded product. The unfoamed resin molded body thus obtained is placed in a high-pressure container, and a high-pressure inert gas (carbon dioxide or the like in a supercritical state) is injected to impregnate the unfoamed resin molded body with the inert gas. When fully impregnated with the inert gas, the pressure is released (usually up to atmospheric pressure) to generate bubble nuclei in the resin. The bubble nuclei may be grown as they are at room temperature, but in some cases, they may be grown by heating. As the heating method, known or conventional methods such as a water bath, an oil bath, a hot roll, a hot air oven, far infrared rays, near infrared rays, and microwaves can be adopted. After growing the bubbles in this way, the foam can be obtained by rapidly cooling with cold water or the like to fix the shape. The non-foamed resin molded product to be foamed is not limited to a sheet-like product, and various shapes can be used depending on the intended use. Further, the non-foamed resin molded product to be used for foaming can be produced by extrusion molding, press molding, or other molding method such as injection molding.

An example of producing a foam by a continuous method is shown below. For example, while kneading the resin composition using an extruder such as a single-screw extruder or a twin-screw extruder, high-pressure gas (particularly inert gas and further carbon dioxide) is injected (introduced) sufficiently. The pressure is released by extruding the resin composition through a kneading impregnation step of impregnating the resin composition with a high-pressure gas, a die provided at the tip of the extruder, etc. (usually up to atmospheric pressure), and molding and foaming are performed at the same time. Foam molding is performed by a reduced pressure step. Further, in the case of foam molding in a continuous method, a heating step of growing bubbles by heating may be provided, if necessary. After the bubbles are grown in this way, the shape may be fixed by rapidly cooling with cold water or the like, if necessary. Further, the high-pressure gas may be introduced continuously or discontinuously. Further, in the kneading impregnation step and the molding depressurization step, for example, an extruder or an injection molding machine can be used. Examples of the heating method for growing the bubble nuclei include any suitable method such as a water bath, an oil bath, a hot roll, a hot air oven, far infrared rays, near infrared rays, and microwaves. Any suitable shape may be adopted as the shape of the foam. Examples of such a shape include a sheet shape, a prismatic shape, a cylindrical shape, and a modified shape.

The amount of the gas mixed when the resin composition is foam-molded is, for example, preferably 2% by weight to 10% by weight, based on the total amount of the resin composition, in that a highly foamed foam can be obtained. It is preferably 2.5% by weight to 8% by weight, more preferably 3% by weight to 6% by weight.

The pressure when the resin composition is impregnated with the inert gas can be appropriately selected in consideration of operability and the like. Such a pressure is, for example, preferably 6 MPa or more (for example, 6 MPa to 100 MPa), more preferably 8 MPa or more (for example, 8 MPa to 50 MPa). The pressure when carbon dioxide in the supercritical state is used is preferably 7.4 MPa or more from the viewpoint of maintaining the supercritical state of carbon dioxide. When the pressure is lower than 6 MPa, the bubble growth during foaming is remarkable, the bubble diameter becomes too large, and a preferable average cell diameter (average cell diameter) may not be obtained. This is because when the pressure is low, the amount of gas impregnated is relatively small compared to when the pressure is high, the bubble nucleation rate decreases, and the number of bubble nuclei formed decreases, so that the amount of gas per bubble increases conversely. This is because the bubble diameter becomes extremely large. Further, in the pressure region lower than 6 MPa, the bubble diameter and the bubble density change greatly even if the impregnation pressure is slightly changed, so that it tends to be difficult to control the bubble diameter and the bubble density.

The temperature in the gas impregnation step varies depending on the inert gas used, the type of component in the resin composition, etc., and can be selected in a wide range. Considering operability and the like, the temperature is preferably 10 ° C to 350 ° C. When the non-foamed molded product is impregnated with the inert gas, the impregnation temperature is preferably 10 ° C. to 250 ° C., more preferably 40 ° C. to 230 ° C. in the batch type. Further, when the molten polymer impregnated with gas is extruded to perform foaming and molding at the same time, the impregnation temperature is preferably 60 ° C. to 350 ° C. in the continuous type. When carbon dioxide is used as the inert gas, the temperature at the time of impregnation is preferably 32 ° C. or higher, more preferably 40 ° C. or higher, in order to maintain the supercritical state.

In the depressurization step, the decompression rate is preferably 5 MPa / sec to 300 MPa / sec in order to obtain uniform fine bubbles.

The heating temperature in the heating step is preferably 40 ° C. to 250 ° C., more preferably 60 ° C. to 250 ° C.

B. Foaming Member FIG. 1 is a schematic cross-sectional view of a foaming member according to one embodiment of the present invention. The foaming member 100 has a resin foaming layer 10 and an adhesive layer 20 arranged on at least one side of the resin foaming layer 10. The resin foam layer 10 is composed of the resin foam.

The thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 300 μm, more preferably 6 μm to 200 μm, further preferably 7 μm to 100 μm, and particularly preferably 8 μm to 50 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, the foamed member of the present invention can exhibit excellent shock absorption.

As the pressure-sensitive adhesive layer, a layer made of any suitable pressure-sensitive adhesive can be adopted. Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include rubber-based pressure-sensitive adhesives (synthetic rubber-based pressure-sensitive adhesives, natural rubber-based pressure-sensitive adhesives, etc.), urethane-based pressure-sensitive adhesives, acrylic urethane-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. Examples thereof include pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is preferably at least one selected from an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive. Such an adhesive may be only one kind or two or more kinds. The pressure-sensitive adhesive layer may be one layer or two or more layers.

When classified by adhesive form, the adhesives are, for example, emulsion type adhesives, solvent type adhesives, ultraviolet crosslinked (UV crosslinked) adhesives, electron beam crosslinked (EB crosslinked) adhesives, and heat melt type adhesives. Agents (hot melt type adhesives) and the like can be mentioned. Such an adhesive may be only one kind or two or more kinds.

Steam moisture permeability of the adhesive layer is preferably not more than ^{50 (g / (m 2 ·} 24 hr)), more preferably ^{30 (g / (m 2 ·} 24 hr)) or less, more preferably 20 ^(g / ^(m 2 · 24 hr)) or less, particularly preferably ^{10 (g / (m 2 ·} 24 hr)) or less. When the water vapor permeability of the pressure-sensitive adhesive layer is within the above range, the foamed sheet of the present invention can stabilize the shock absorption without being affected by moisture. The water vapor permeability can be measured, for example, by a method according to JIS Z 0208 under test conditions of 40 ° C. and a relative humidity of 92%.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer may contain any suitable other component as long as the effect of the present invention is not impaired. Other components include, for example, other polymer components, softeners, antioxidants, hardeners, plasticizers, fillers, antioxidants, thermal polymerization initiators, photopolymerization initiators, UV absorbers, light stabilizers. , Colorants (pigments, dyes, etc.), solvents (organic solvents), surfactants (eg, ionic surfactants, silicone-based surfactants, fluorine-based surfactants, etc.), cross-linking agents (eg, polyisocyanate-based) Cross-linking agents, silicone-based cross-linking agents, epoxy-based cross-linking agents, alkyl etherified melamine-based cross-linking agents, etc.) and the like. The thermal polymerization initiator and the photopolymerization initiator may be included in the material for forming the polymer component.

The foamed member of the present invention can be produced by any suitable method. The foamed member of the present invention is produced, for example, by laminating a resin foam layer and a pressure-sensitive adhesive layer, or by laminating a material for forming a pressure-sensitive adhesive layer and a resin foam layer and then forming a pressure-sensitive adhesive layer by a curing reaction or the like. And the method of manufacturing.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The tests and evaluation methods in the examples and the like are as follows. In addition, when it is described as "part", it means "part by weight" unless there is a special note, and when it is described as "%", it means "% by weight" unless there is a special note.

<Evaluation method>
(1) Apparent density The density (apparent density) of the resin foam was calculated as follows. The resin foam obtained in Examples and Comparative Examples was punched into a size of 20 mm × 20 mm to obtain a test piece, and the dimensions of the test piece were measured with a caliper. Next, the weight of the test piece was measured with an electronic balance. Then, it was calculated by the following formula.
Apparent density (g / cm ³ ) = weight of test piece / volume of test piece

(2) 25% compressive load The measurement was performed according to the method for measuring the compressive hardness of the foam described in JIS K 6767. Specifically, the resin foam obtained in Examples and Comparative Examples was cut into a size of 30 mm × 30 mm to form a test piece, and the stress (N) when compressed to a compression rate of 25% at a compression rate of 10 mm / min. ) Was converted per unit area (1 cm ² ) to obtain a 25% compressive load (N / cm ² ).

(3) Fluctuation coefficient of average cell diameter (average cell diameter) and bubble diameter (cell diameter) Using a razor blade, the resin foam is TD (direction orthogonal to the flow direction) and the main surface of the resin foam. Cut in the vertical direction (thickness direction), and use a digital microscope (trade name "VHX-500", manufactured by Keyence Co., Ltd.) as a measuring instrument to capture an enlarged image of the bubble part of the resin foam and measure it. The number average bubble diameter (average cell diameter) (μm) was obtained by image analysis using the analysis software of the instrument. The number of bubbles in the captured enlarged image was about 400. In addition, the standard deviation was calculated from all the cell diameter data, and the coefficient of variation was calculated using the following formula.
Coefficient of variation = standard deviation / average cell diameter (average cell diameter)

(4) Bubble ratio (cell ratio)
The measurement was carried out in an environment of a temperature of 23 ° C. and a humidity of 50%. Resin foam obtained in Examples and Comparative Examples with a 100 mm x 100 mm punching blade type (two processing blades (trade name "NCA07", thickness 0.5 mm, cutting edge angle 45 °, manufactured by Nakayama Co., Ltd.)) Was punched out, and the dimensions of the punched sample were measured. Further, the thickness was measured with a 1/100 dial gauge having a diameter (φ) of 20 mm of the measurement terminal. From these values, the volumes of the resin foams obtained in Examples and Comparative Examples were calculated. Next, the weight of the resin foams obtained in Examples and Comparative Examples was measured with a precision balance having a minimum scale of 0.01 g or more. From these values, the bubble ratio (cell ratio) of the resin foams obtained in Examples and Comparative Examples was calculated.

(5) Thickness of bubble wall (cell wall) Using a razor blade, the resin foam is TD (direction orthogonal to the flow direction) and perpendicular to the main surface of the resin foam (thickness direction). After cutting, use a digital microscope (trade name "VHX-500", manufactured by Keyence Co., Ltd.) as a measuring instrument to capture an enlarged image of the bubble part of the resin foam, and use the analysis software of the measuring instrument to capture the image. By analysis, the thickness (μm) of the bubble wall (cell wall) was determined. The number of bubbles in the captured enlarged image was about 400.

(6) Non-foam bending stress Non-foaming by pressing the resin foam with a vacuum press molding machine (IVM-70: Iwaki Kogyo Co., Ltd.) at a temperature of (melting point + 70 ° C.) and a pressure of 15 MPa for 5 minutes. A foamed resin molded product a was obtained.
The resin molded body a was cut into a width of 20 mm and a length of 150 mm to prepare a sample, and this sample was placed on a three-point bending tool having a distance between fulcrums of 100 mm, and the pushing speed was 5 mm / in an environment of 23 ° C. × 50% RH. A indentation test (manufactured by Shimadzu Corporation, trade name "AG-Xplus") was performed in min, and the load (g) when the sample was indented by 5 mm was defined as a non-foam bending stress.

(7) Elastic strain energy Based on the section of the compression test of JIS K 6767, the compressibility (%) and compressive repulsive force (kPa) of the resin foam are measured, and the x-axis is the compressibility and the y-axis is the compressive repulsive force. Of the area surrounded by the compression SS curve consisting of the x-axis and the x-axis, the area in the region where the compression ratio was 0% to 10% was calculated as the elastic strain energy.

(8) Shock absorption measurement method Resin foam, double-sided tape (product number: No. 5603W, manufactured by Nitto Denko), and PET film (product number: diamond foil MRF75, manufactured by Mitsubishi resin) are placed in this order on the impact force sensor. To form a test piece. From a height of 50 cm above the PET film, a 66 g iron ball was dropped onto the test piece, and the impact force F1 was measured.
Further, the impact force F0 of the blank was measured by dropping the iron ball directly onto the impact force sensor as described above.
From F1 and F0, the shock absorption (%) was calculated by the formula (F0-F1) / F0 × 100.

(9) Thickness recovery rate The resin foam is ^{maintained for 120 seconds with a load of 1000 g / cm 2} applied to the resin foam, decompressed, and 0.5 seconds after the decompression of the resin foam. The thickness (thickness 0.5 seconds after the compressed state was released) was measured. The thickness recovery rate was calculated from the "thickness 0.5 seconds after the decompressed state" and the thickness (initial thickness) of the resin foam before the load was applied by the following formula.
Thickness recovery rate (%) = {(thickness 0.5 seconds after decompression) / (initial thickness)} x 100

(10) Aspect ratio of bubbles Using a digital microscope (trade name "VHX-2000, manufactured by Keyence Co., Ltd.)" as a measuring instrument, the bubbles contained in the resin foams obtained in Examples and Comparative Examples by the following methods. The aspect ratio was measured.
-The resin foam is cut using a razor blade in the TD (direction orthogonal to the flow direction) and in the direction perpendicular to the main surface of the resin foam (thickness direction), and the cut surface is cut with a microscope (for example, in the thickness direction). , Keyence's "VHX-2000") was used to ^{observe a predetermined area (3 mm 2} ) range at a magnification of 100 times, and the length of one bubble in the thickness direction and the length of TD were measured.
-Similar measurements were made for all bubbles present within a predetermined area.
The aspect ratio of the bubbles was calculated by dividing the length of the TD by the length in the thickness direction, and the same calculation was performed for all the bubbles, and the average value was taken as the "aspect ratio of the bubbles of the resin foam".

[Example 1]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 65 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 35 parts by weight, water 80 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 4.5 parts by weight to 100 parts by weight of the resin. The carbon dioxide gas was sufficiently saturated, cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam a having a thickness of 1.8 mm.
Further, the resin foam a is passed between the rolls (the gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to form the resin foam A having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam A having a thickness of 0.1 mm could be obtained.
The obtained resin foam A was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Example 2]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 65 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 35 parts by weight, water 80 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 3.5 parts by weight to 100 parts by weight of the resin. The carbon dioxide gas was sufficiently saturated, cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam b having a thickness of 1.8 mm.
Further, the resin foam b is passed between the rolls (the gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to obtain the resin foam C having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam B having a thickness of 0.1 mm could be obtained.
The obtained resin foam B was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Example 3]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 65 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 35 parts by weight, water 120 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 3.0 parts by weight with respect to 100 parts by weight of the resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam c having a thickness of 1.8 mm.
Further, the resin foam c is passed between the rolls (the gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to obtain the resin foam C having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam C having a thickness of 0.1 mm could be obtained.
The obtained resin foam C was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Example 4]
A resin foam D containing polyethylene as a main component was prepared, having an apparent density of 0.3 g / cm ³ , a 25% compression load of 50 N / cm ^{2, and an elastic strain energy of 26 kPa.}
This resin foam D was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Example 5]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 60 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 40 parts by weight, water 120 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 3.5 parts by weight to 100 parts by weight of the resin. The carbon dioxide gas was sufficiently saturated, cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam e having a thickness of 0.6 mm.
Further, the resin foam e is passed between the rolls (gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to form a resin foam E having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam E having a thickness of 0.1 mm could be obtained.
The obtained resin foam E was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Example 6]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 60 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 40 parts by weight, water 120 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 4.0 parts by weight with respect to 100 parts by weight of the resin. The carbon dioxide gas was sufficiently saturated, cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam j having a thickness of 0.5 mm.
Further, the resin foam j is passed between the rolls (gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to form a resin foam J having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam J having a thickness of 0.1 mm could be obtained.
The obtained resin foam J was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Comparative Example 1]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 16.5 parts by weight, polypropylene (melt flow rate (MFR) (230 ° C): 1.1 g / 10 min) 16.5 parts by weight, Polypropylene elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 67 parts by weight, magnesium hydroxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.) 40 parts by weight, carbon (trade name "" Asahi # 35 "Asahi Carbon Co., Ltd.) 10 parts by weight and 1 part by weight of stearate monoglyceride are kneaded with a twin-screw kneader manufactured by Japan Steel Works (JSW) at a temperature of 200 ° C. It was extruded into pellets after cooling with water. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 3 parts by weight to 100 parts by weight of the resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam f having a thickness of 1.8 mm.
Further, the resin foam f is passed between the rolls (gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to form a resin foam F having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam F having a thickness of 0.1 mm could be obtained.
The obtained resin foam F was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Comparative Example 2]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 45 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 55 parts by weight, water 10 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 5.5 parts by weight to 100 parts by weight of the resin. After the carbon dioxide gas was sufficiently saturated, it was cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam g having a thickness of 2.2 mm.
Further, the resin foam g is passed between the rolls (the gap between the rolls) in the pair of rolls in which one roll is heated to 200 ° C. to obtain the resin foam G having a thickness of 0.1 mm. Obtained. The gap between the rolls was set so that the resin foam G having a thickness of 0.1 mm could be obtained.
The obtained resin foam G was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Comparative Example 3]
Polypropylene (melt flow rate (MFR) (230 ° C): 0.40 g / 10 min) 65 parts by weight, polyolefin-based elastomer (melt flow rate (MFR): 6 g / 10 min, JIS A hardness: 79 °) 35 parts by weight, water 80 parts by weight of magnesium oxide (trade name "KISUMA 5P" manufactured by Kyowa Chemical Industry Co., Ltd.), 10 parts by weight of carbon (trade name "Asahi # 35" manufactured by Asahi Carbon Co., Ltd.), and 1 part by weight of stearate monoglyceride It was kneaded at a temperature of 200 ° C. with a twin-screw kneader manufactured by JSW), extruded into strands, cooled with water, and molded into pellets. These pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected at a pressure of 13 MPa (12 MPa after injection) in an atmosphere of 220 ° C. Carbon dioxide gas was injected at a ratio of 4.5 parts by weight to 100 parts by weight of the resin. The carbon dioxide gas was sufficiently saturated, cooled to a temperature suitable for foaming, and then extruded from a die to obtain a sheet-shaped resin foam h having a thickness of 1.8 mm. The resin foam h was thinned to a thickness of 0.1 mm using a slicer to obtain a resin foam H. The obtained resin foam H was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

[Comparative Example 4]
Acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylonitrile copolymer (weight ratio 45:48: 7)) 100 parts by weight, fatty acid ammonium surfactant (aqueous dispersion of ammonium stearate, Solid content 33%) 2 parts by weight, carboxybetaine type amphoteric surfactant ("Amogen CB-H", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 2 parts by weight, oxazoline-based cross-linking agent ("Epocross WS-500" manufactured by Nippon Catalyst Co., Ltd.) , Solid content 39%) and 1 part by weight of carbon black (manufactured by "NAF-5091" Dainichi Seika Kogyo Co., Ltd.) were stirred and mixed with a disper (manufactured by "Robomix" Primex Co., Ltd.) to foam. This foam composition was applied onto a peel-treated PET (polyethylene terephthalate) film (thickness: 38 μm, trade name “MRF # 38” manufactured by Mitsubishi Plastics Co., Ltd.) at 70 ° C. for 4.5 minutes at 140 ° C. The mixture was dried for 4.5 minutes to obtain a resin foam I (thickness: 0.1 mm). The obtained resin foam I was subjected to the above evaluations (1) to (10). The results are shown in Table 1.

The resin foam of the present invention can be suitably used, for example, as a cushioning material for electronic devices.

100 Foam member 10 Resin foam layer 20 Adhesive layer

Claims

The apparent density is 0.02 g / cm 3 to 0.30 g / cm 3 .
The 25% compression load is 90 kPa or less,
The elastic strain energy during compression is 10 kPa or more,
Has a bubble structure,
Resin foam.
The resin foam according to claim 1, wherein the average cell diameter is 10 μm to 200 μm.
The resin foam according to claim 1 or 2, wherein the bubble ratio is 30% or more.
The resin foam according to any one of claims 1 to 3, wherein the coefficient of variation of the bubble diameter is 0.5 or less.
The resin foam according to any one of claims 1 to 4, wherein the non-foam bending stress is 5 MPa or more.
The resin foam according to any one of claims 1 to 4, further comprising a filler.
The resin foam according to claim 6, wherein the filler is an inorganic substance.
The resin foam according to claim 6 or 7, wherein the filler is an organic substance.
The resin foam according to any one of claims 1 to 8, which contains a polyolefin-based resin.
The resin foam according to claim 9, wherein the polyolefin-based resin is a mixture of a polyolefin other than the polyolefin-based elastomer and a polyolefin-based elastomer.
The resin foam according to any one of claims 1 to 10, which has a hot melt layer on one side or both sides.
It has a resin foam layer and an adhesive layer arranged on at least one side of the resin foam layer.
The resin foam layer is the resin foam according to any one of claims 1 to 11.
Foam member.