WO2023139878A1

WO2023139878A1 - Foam member

Info

Publication number: WO2023139878A1
Application number: PCT/JP2022/040445
Authority: WO
Inventors: 彰吾佐々木; 亮伊関; 清明児玉; 修平山本; 周澤村
Original assignee: 日東電工株式会社
Priority date: 2022-01-18
Filing date: 2022-10-28
Publication date: 2023-07-27

Abstract

Provided is a foam member comprising a resin foam body and an adhesive layer, said foam member exhibiting superior punch machining properties and cleanliness.　A foam member according to the present invention comprises a resin foam body and an adhesive body positioned on at least one side of the resin foam body, wherein the adhesive body comprises an adhesive layer, the product of the total thickness (µm) of the adhesive layer and the thickness (mm) of the resin foam body is 45 or less, and the total amount of toluene and ethyl acetate outgassed from the adhesive body is 8.0 µg/g or less.

Description

foam material

The present invention relates to foam members.

Foamed materials are often used as cushioning materials to protect electronic device screens, substrates, and electronic components. 2. Description of the Related Art In recent years, there has been a demand for narrowing the clearance of a portion where a cushioning material is arranged in accordance with the trend toward thinner electronic devices. Furthermore, with the miniaturization and multi-functionalization of electronic equipment, there is a tendency for electronic components used to be miniaturized, and thinner cushioning materials (foam members) are sometimes required. In addition, the cushioning material is sometimes required to be dust-proof in order to protect electronic parts and the like.

Usually, when obtaining a foamed member with a desired shape, the raw material is punched. In punching, a foam having a desired shape is obtained by applying high pressure to a foam member using a die. In conventional foam parts, the thickness that is reduced by stamping may not fully recover after the stamping process, resulting in permanent thickness variations. If the thickness is changed by such punching, that is, if the punching workability is poor, there arises a problem that impact absorption, dust resistance, etc. are deteriorated.

On the other hand, in recent years, there has been a high demand for foamed members that are environmentally friendly and have excellent cleanness. From the viewpoint of convenience, etc., the foam member may be configured by integrating a foam and an adhesive layer, but in such a configuration, improvement of cleanness is an important issue.

Japanese Patent Laid-Open No. 2017-186504 Japanese Patent Application Laid-Open No. 2015-034299

An object of the present invention is to provide a foamed member comprising a resin foam and an adhesive layer and having excellent punching workability and cleanness.

The foamed member of the present invention includes a resin foam and an adhesive disposed on at least one side of the resin foam, the adhesive having an adhesive layer, the product of the total thickness (μm) of the adhesive layer and the thickness (mm) of the resin foam being 45 or less, and the adhesive having a total emission amount of toluene outgas and ethyl acetate outgas of 8.0 μg/g or less.
In one embodiment, the adhesive body further comprises a substrate, and the adhesive layer is arranged between the substrate and the resin foam.
In one embodiment, the adhesive is an adhesive sheet.
In one embodiment, the adhesive body includes the adhesive layers arranged on both sides of the substrate.
In one embodiment, the substrate is composed of polyethylene terephthalate.
In one embodiment, the foamed member has a thickness recovery rate of 55% or more after a load of 1000 g/cm ² is maintained for 120 seconds.
In one embodiment, the resin foam has an average cell diameter of 200 μm or less.
In one embodiment, the resin foam has an apparent density of 0.4 g/cm ³ or less.
In one embodiment, the coefficient of variation of cell diameter of the resin foam is 0.5 or less.
In one embodiment, the resin foam has a bubble number density of 30/mm ² or more.
In one embodiment, the resin foam has a void content of 30% or more.
In one embodiment, the resin foam contains a polyolefin resin.
In one embodiment, the polyolefin-based resin is a mixture of a polyolefin other than a polyolefin-based elastomer and a polyolefin-based elastomer.
In one embodiment, the foam member has a heat-melting layer on one side or both sides of the resin foam.
In one embodiment, the pressure-sensitive adhesive layer contains a water-dispersed pressure-sensitive adhesive.
In one embodiment, another pressure-sensitive adhesive layer is formed on the surface of the resin foam opposite to the pressure-sensitive adhesive layer.

According to the present invention, it is possible to provide a foamed member comprising a resin foam and an adhesive layer and having excellent punching workability and cleanliness.

1 is a schematic cross-sectional view of a foam member according to one embodiment of the invention; FIG. FIG. 4 is a schematic cross-sectional view of a foam member according to another embodiment of the invention; It is a schematic block diagram of a dust-proof test apparatus. FIG. 2 is an end view of a cut portion of the dust resistance test device taken along the line A-A';

A. Foam Member FIG. 1 is a schematic cross-sectional view of a foam member according to one embodiment of the present invention. The foam member 100 includes a resin foam 110 and an adhesive 120 arranged on at least one side of the resin foam 110 .

The adhesive body 120 has an adhesive layer 121 . The adhesive body 120 may be composed of only the adhesive layer 121 as shown in FIG. 1, or may be composed of the substrate 122 and the adhesive layer 121 as shown in FIG. By arranging the base material, it is possible to obtain a foamed member having high rigidity and excellent adhesion. In addition, even if each layer is thinned, the sticking property is maintained, so the use of the base material makes it possible to further reduce the thickness of the layer. The pressure-sensitive adhesive layer can be arranged between the substrate and the resin foam. In addition, as shown in FIG. 2 , when the adhesive body 120 includes a base material 122 , the adhesive layers 121 may be arranged on both sides of the base material 122 . The adhesive body provided with a substrate may be an adhesive sheet.

The resin foam has a cellular structure (cell structure). Examples of the cell structure include a closed cell structure, an open cell structure, a semi-open and semi-closed cell structure (a cell structure in which a closed cell structure and an open cell structure are mixed), and the like. Preferably, the cell structure of the resin foam is a semi-open and semi-closed cell structure. Typically, the resin foam of the present invention is obtained by foaming a resin composition. The resin composition is a composition containing at least a resin constituting a resin foam.

In the foamed member, the product of the total thickness (μm) of the adhesive layer and the thickness (mm) of the resin foam is 45 or less. In the present invention, by adjusting the thickness of the pressure-sensitive adhesive layer and the thickness of the resin foam so that the product of the total thickness (μm) of the pressure-sensitive adhesive layer and the thickness (mm) of the resin foam is within the above range, it is possible to obtain a foamed member having excellent punching workability. More specifically, the foamed member prevents the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer from oozing out during punching, and the number of cells in the resin foam is appropriately adjusted, so that crushing due to punching is unlikely to occur and punching workability is excellent. The product of the total thickness (μm) of the adhesive layer and the thickness (mm) of the resin foam is preferably 40 or less, more preferably 35 or less, still more preferably 30 or less, and particularly preferably 25 or less. With such a range, the above effect becomes remarkable. The product of the total thickness (μm) of the adhesive layer and the thickness (mm) of the resin foam is preferably 3.5 or more, more preferably 5 or more. Within such a range, a foamed member having excellent impact resistance and adhesiveness can be obtained. In this specification, the total thickness of the pressure-sensitive adhesive layer is the total thickness of the pressure-sensitive adhesive layer contained in the adherence body. When the pressure-sensitive adhesive layer contained in the adherence body is a single layer, it means the thickness of the pressure-sensitive adhesive layer.

Although not shown, another adhesive layer may be formed on the surface of the resin foam opposite to the adhesive body.

In the sticky substance, the total amount of toluene outgas and ethyl acetate outgas is 8.0 μg/g or less. The foamed member of the present invention is advantageous in that outgassing is small, that is, it is highly clean. As described above, it is one of the great achievements of the present invention that a foamed member which is thin, excellent in punching workability, and excellent in cleanliness can be obtained. The total amount of toluene outgas and ethyl acetate outgas emitted is the amount of outgas generated when the adherent alone was left at 80° C. for 30 minutes. A specific measuring method will be described later. In addition, the weight of the adhesive body, which is the measurement standard for the total amount of toluene outgas and ethyl acetate outgas, is the total weight of the adhesive layer and the base material disposed as necessary. A foamed member with little toluene outgas and ethyl acetate outgas can be obtained, for example, by using a water-dispersible pressure-sensitive adhesive (described later) as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer.

The thickness recovery rate (hereinafter also referred to as instantaneous recovery rate) after a load of 1000 g/cm ² is applied to the foamed member and maintained for 120 seconds is preferably 55% or more, more preferably 60% or more, still more preferably 70% or more, still more preferably 80% or more, still more preferably 85% or more, further preferably 90% or more, and particularly preferably 95% or more. A foamed member having an instantaneous recovery rate in such a range has a small change in shape, such as a change in thickness, even when punched, and exhibits preferable behavior such as recovery in a short time even when the thickness is temporarily reduced by punching, and is excellent in punchability. The higher the instantaneous recovery rate, the better, but the upper limit is, for example, 99% (preferably 100%). A method for measuring the instantaneous recovery rate will be described later.

B. Resin foam The average cell diameter of the resin foam is preferably 900 µm or less, more preferably 200 µm or less, still more preferably 150 µm or less, still more preferably 100 µm or less, and particularly preferably 80 µm or less. The average cell diameter (average cell diameter) of the resin foam is preferably 10 µm or more, more preferably 20 µm or more, and still more preferably 40 µm or more. If the average cell diameter (average cell diameter) is within the above range, the anchoring force of the adhesive (adhesive layer) to the resin foam is high, and the resin foam and the adhesive (adhesive layer) are excellent in integration. A foamed member can be obtained. In addition, a resin foam having excellent flexibility and stress dispersibility can be obtained. In addition, it is possible to obtain a resin foam that is excellent in compression recovery, stamping workability, and resistance to repeated impact. In one embodiment, the resin foam has an average cell diameter of 200 μm or less (preferably 100 μm or less). When the thickness of the pressure-sensitive adhesive layer is thin, if the resin foam has an average cell diameter of 200 μm or less, it is possible to obtain a foamed member having remarkably excellent stamping workability.

The 50% compressive load of the resin foam is preferably 30 N/cm ² or less, more preferably 10 N/cm ² or less, still more preferably 8 N/cm ² or less, particularly preferably 5 N/cm ² or less, and most preferably 3 N/cm ² or less. Within such a range, it is possible to obtain a foamed member that preferably has flexibility and is excellent in stamping workability. The lower limit of the 50% compressive load of the resin foam is, for example, 0.5 N/cm ² . The 50% compressive load of the resin foam is the stress (N) when the resin foam is compressed to a compressibility of 50%, converted per unit area (1 cm ² ).

The cell number density of the resin foam is preferably 30 cells/mm ² or more, more preferably 50 cells/mm ² or more, still more preferably 65 cells/mm 2 or more, still more preferably 80 cells/mm ² or more, still more preferably 90 cells/mm ² or more, still more preferably 100 cells/mm ² or more, particularly preferably 110 cells/mm ² ^or more, and most preferably 120 cells/mm ² or more. . Within such a range, it is possible to obtain a foamed member that preferably has flexibility, is resistant to crushing, and is excellent in punching workability. In addition, the higher the bubble number density, the easier it is to store energy when compressed, and a resin foam having excellent compression recovery can be obtained. A foamed member comprising such a resin foam has excellent stamping workability. The upper limit of the cell number density of the resin foam is preferably 400 cells/mm ² , more preferably 350 cells/mm ² , still more preferably 300 cells/mm ² , particularly preferably 250 cells/mm ² , particularly preferably 200 cells/mm ² . The cell number density of the resin foam is the number density in the cross section of cells observed in a randomly selected cross section of the resin foam, and can be obtained by image analysis of the cross section of the resin foam.

The apparent density of the resin foam is preferably 0.4 g/cm ³ or less, more preferably 0.3 g/cm ³ or less. Moreover, the apparent density of the resin foam is preferably 0.01 g/cm ³ or more, more preferably 0.03 g/cm ³ or more. If the apparent density is within the above range, it is possible to obtain a foamed member having excellent integrity between the resin foam and the adhesive (adhesive layer). In addition, it is possible to obtain a resin foam that is excellent in punching workability, flexibility, and stress dispersion. The foamability can be judged by the apparent density. In one embodiment, the apparent density of the resin foam is preferably 0.1 g/cm ³ or less, more preferably 0.08 g/cm ³ or less, even more preferably 0.06 g/cm ³ or less. In another embodiment, the apparent density of the resin foam is preferably 0.08 g/cm ³ or higher, more preferably 0.1 g/cm ³ or higher, and even more preferably 0.15 g/cm ³ or higher. A method for measuring the apparent density will be described later.

The thickness of the resin foam is preferably 3000 µm or less, more preferably 2000 µm or less, still more preferably 1800 µm or less, still more preferably 1500 µm or less, and still more preferably 1000 µm or less. The thickness of the resin foam is preferably 50 µm or more, more preferably 100 µm or more, still more preferably 150 µm or more, and even more preferably 300 µm or more. If the thickness is within the above range, it is possible to form a fine and uniform cell structure, which is advantageous in that excellent punching workability and impact absorption can be exhibited. In one embodiment, the thickness of the resin foam is less than 2000 μm. Within such a range, the number of cells in the resin foam is particularly preferably adjusted, and collapse due to punching is less likely to occur, so that a foamed member having particularly excellent punching workability can be obtained.

The variation coefficient of the cell diameter (cell diameter) of the resin foam is preferably 0.5 or less, more preferably 0.4 or less, still more preferably 0.35 or less, still more preferably 0.3 or less, particularly preferably 0.25 or less, and most preferably 0.2 or less. Within such a range, a foamed member having excellent integrity between the resin foam and the adhesive (adhesive layer) can be obtained. Also, when a compressive force is applied by punching or the like, variations in cell deformation are reduced. With such a resin foam, for example, a processed product (cut product) having excellent thickness accuracy can be obtained when punched. Further, when the coefficient of variation of cell diameter is within the above range, deformation due to impact becomes uniform, local stress load is prevented, and a foamed member having excellent stress dispersibility and particularly excellent impact resistance can be obtained. Although the coefficient of variation is preferably as small as possible, its lower limit is, for example, 0.15 (preferably 0.1, more preferably 0.01). A method for measuring the coefficient of variation of bubble diameter will be described later.

The foam rate (cell rate) of the resin foam is preferably 97% or less, more preferably 95% or less. In one embodiment, the resin foam has a void content (cell rate) of 90% or less (preferably 85% or less, more preferably 78% or less, still more preferably 75% or less). Within such a range, it is possible to obtain a resin foam having a small thickness change rate when the resin foam and the adherent are pressure-bonded. The foam content (cell ratio) of the resin foam is preferably 30% or more, more preferably 50% or more, and still more preferably 60% or more. Within such a range, a resin foam having moderate flexibility can be obtained. Such a resin foam has excellent punching workability, and prevents the occurrence of uncut parts when punched.

The thickness of the cell wall (cell wall) of the resin foam is preferably 10 µm or less, more preferably 8 µm or less, still more preferably 5 µm or less, particularly preferably 4 µm or less, and most preferably 3 µm or less. The thickness of the cell wall (cell wall) of the resin foam is preferably 0.1 µm or more, more preferably 0.3 µm or more, still more preferably 0.5 µm or more, particularly preferably 0.7 µm or more, and most preferably 1 µm or more. If the thickness of the cell wall (cell wall) is within the above range, a resin foam having appropriate strength can be obtained. Such a resin foam has excellent punching workability, and is prevented from tearing, dusting, and uncut parts during punching. Moreover, when the cell wall thickness is within the above range, a resin foam having excellent flexibility and stress dispersion can be obtained. The thickness of the cell wall can be measured by capturing an enlarged image of the cell portion of the resin foam and analyzing the image using the analysis software of the measuring instrument.

When the cell structure of the resin foam is a semi-open and semi-closed cell structure, the proportion of the closed cell structure therein is preferably 40% or less, more preferably 30% or less. In the present specification, the ratio of the closed-cell structure of the resin foam is obtained, for example, by immersing the object to be measured in water under an environment of a temperature of 23° C. and a humidity of 50%, then measuring the mass, then thoroughly drying it in an oven at 80° C., and then measuring the mass again. In addition, since open cells can hold moisture, the mass of open cells is measured as open cells.

The impact absorption of the resin foam is preferably 20% or more, more preferably 27% or more, still more preferably 30% or more, particularly preferably 35% or more, and most preferably 40% or more. Impact absorption is measured as follows.
- A resin foam, a double-sided tape (product number: No. 5603W, manufactured by Nitto Denko), and a PET film (product number: Diafoil MRF75, manufactured by Mitsubishi Plastics) are placed in this order on the impact force sensor to form a test sample. A 66-g iron ball is dropped onto the specimen from a height of 50 cm above the PET film, and the impact force F1 is measured.
・Furthermore, the impact force F0 of the blank is measured by dropping the iron ball directly onto the impact force sensor as described above.
・From F1 and F0, calculate the impact absorption (%) by the formula (F0-F1)/F0×100.

Any appropriate shape can be adopted as the shape of the resin foam according to the purpose. Such a shape is typically sheet-like.

The resin foam may have a heat-melting layer on one side or both sides. A resin foam having a hot-melt layer can be obtained, for example, by rolling a resin foam (or a resin foam precursor (foam structure)) using a pair of heating rolls heated to a melting temperature of the resin composition constituting the resin foam or higher. By forming a resin foam having a hot-melt layer, the adhesion area between the resin foam and the adhesive (adhesive layer) is increased, the adhesion between the resin foam and the adhesive (adhesive layer) is increased, and a foamed member having excellent integrity between these layers can be obtained.

The foam rate (cell rate) of the hot melt layer is preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, particularly preferably 5% or less, and most preferably 0%. The thickness of the hot melt layer is preferably 0.15 mm or less, more preferably 0.13 mm or less, and even more preferably 0.11 mm or less. Also, the thickness of the hot melt layer is preferably 0.05 mm or more, more preferably 0.07 mm or more, and still more preferably 0.09 mm or more.

(Method for forming resin foam)
The resin foam can be formed by any appropriate method as long as the effects of the present invention are not impaired. Such a method typically includes a method of foaming a resin composition containing a resin material (polymer). The resin composition includes any suitable resin material (polymer).

Examples of the polymer include acrylic resins, silicone resins, urethane resins, polyolefin resins, ester resins, and rubber resins. The above polymers may be used singly or in combination of two or more.

The polymer content is preferably 30 to 95 parts by weight, more preferably 35 to 90 parts by weight, still more preferably 40 to 80 parts by weight, and particularly preferably 40 to 60 parts by weight, relative to 100 parts by weight of the resin composition. Within such a range, it is possible to obtain a resin foam that is more excellent in flexibility and stress dispersibility.

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

The content of the polyolefin resin is preferably 50 to 100 parts by weight, more preferably 70 to 100 parts by weight, still more preferably 90 to 100 parts by weight, particularly preferably 95 to 100 parts by weight, and most preferably 100 parts by weight, relative to 100 parts by weight of the polymer.

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

When polyolefin and polyolefin elastomer are used together as polyolefin resin, the weight ratio of polyolefin and polyolefin elastomer (polyolefin/polyolefin elastomer) is preferably 1/99 to 99/1, more preferably 10/90 to 90/10, still more preferably 20/80 to 80/20, and particularly preferably 30/70 to 70/30. In one embodiment, the weight ratio of polyolefin to polyolefin elastomer (polyolefin/polyolefin elastomer) is preferably 25/75 to 75/25, more preferably 35/65 to 65/35. Within such a range, it is possible to obtain a resin foam that has excellent compression recovery, suppresses shape change (in particular, thickness change) before and after punching, has appropriate strength, and has excellent punching workability.

Any appropriate polyolefin can be adopted as the polyolefin as long as it does not impair the effects of the present invention. Examples of such polyolefins include linear polyolefins and branched (having branched chains) polyolefins. In one embodiment, a branched polyolefin is used as the polyolefin resin. In this embodiment, as the polyolefin, only branched polyolefin may be used, or branched polyolefin and linear polyolefin may be used in combination. By using a branched polyolefin, a resin foam having a small average cell diameter and excellent impact resistance can be obtained. The content of the branched polyolefin is preferably 30 to 100 parts by weight, more preferably 50 to 80 parts by weight, per 100 parts by weight of the polyolefin.

Examples of the above polyolefins include polymers containing structural units derived from α-olefins. The polyolefin may be composed only of structural units derived from α-olefins, or may be composed of structural units derived from α-olefins and structural units derived from monomers other than α-olefins. When the polyolefin is a copolymer, any appropriate copolymerization form can be adopted as its copolymerization form. Examples include random copolymers and block copolymers.

Examples of α-olefins that can constitute polyolefins include α-olefins having 2 to 8 (preferably 2 to 6, more preferably 2 to 4) carbon atoms (eg, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc.). The α-olefin may be of only one type, or may be of two or more types.

Examples of monomers other than α-olefins that constitute polyolefins include ethylenically unsaturated monomers such as vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, and vinyl alcohol. Monomers other than the α-olefin may be of only one type, or may be of two or more types.

Specific examples of polyolefins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene (propylene homopolymer), copolymers of ethylene and propylene, copolymers of ethylene and α-olefins other than ethylene, copolymers of propylene and α-olefins other than propylene, copolymers of ethylene and propylene and α-olefins other than ethylene and propylene, and copolymers of propylene and ethylenically unsaturated monomers.

In one embodiment, a polypropylene-based polymer having structural units derived from propylene is used as the polyolefin. Examples of polypropylene-based polymers include polypropylene (propylene homopolymer), copolymers of ethylene and propylene, and copolymers of propylene and α-olefins other than propylene, and preferably polypropylene (propylene homopolymer). The polypropylene-based polymer may be used alone or in combination of two or more.

The melt flow rate (MFR) of the polyolefin at a temperature of 230°C is preferably 0.25 g/10 min to 10 g/10 min, more preferably 0.3 g/10 min to 6 g/10 min, even more preferably 0.35 g/10 min to 5 g/10 min, particularly preferably 0.35 g/10 min to 1 g/10 min, and most It is preferably 0.35 g/10 minutes to 0.6 g/10 minutes. In this specification, the melt flow rate (MFR) refers to MFR measured at a temperature of 230° C. and a load of 2.16 kgf (21.2 N) based on ISO1133 (JIS-K-7210). In one embodiment, the melt flow rate of the polyolefin that makes up the resin foam controls the die swell ratio and shear viscosity of the resin.

The weight average molecular weight of the polyolefin is preferably 50,000 to 120,000, more preferably 55,000 to 110,000, still more preferably 60,000 to 100,000. Within such a range, the die swell ratio and shear viscosity of the resin can be preferably adjusted. Also, the molecular weight distribution (weight average molecular weight/number average molecular weight) of the polyolefin is preferably 4-10, more preferably 7-10, and more preferably 6-9. Within such a range, the die swell ratio and shear viscosity of the resin can be preferably adjusted. As a result, it is possible to obtain a resin foam that is flexible (highly foamed), has a high bubble number density, and is excellent in punching workability. The weight average molecular weight and number average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene conversion).

Commercially available polyolefins may be used, and examples include "E110G" (manufactured by Prime Polymer Co., Ltd.), "EA9" (manufactured by Japan Polypropylene Corporation), "EA9FT" (manufactured by Japan Polypropylene Corporation), "E-185G" (manufactured by Prime Polymer Co., Ltd.), "WB140HMS" (manufactured by Borealis), and "WB135HMS" (manufactured by Borealis).

Any appropriate polyolefin elastomer can be adopted as the polyolefin elastomer as long as it does not impair the effects of the present invention. Examples of such polyolefin elastomers include so-called non-crosslinked thermoplastic olefin elastomers (TPO), such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, chlorinated polyethylene, elastomer in which polyolefin component and rubber component are physically dispersed, and elastomer having structure in which polyolefin component and rubber component are microphase-separated; resin component A forming matrix (olefin resin component A) and rubber component B forming domain. A dynamically crosslinked thermoplastic olefin elastomer (TPV), which is a multiphase polymer having a sea-island structure in which crosslinked rubber particles are finely dispersed as domains (island phases) in resin component A, which is a matrix (sea phase), obtained by dynamically heat-treating a mixture containing in the presence of a crosslinking agent.

The polyolefin 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, JP-A-2012-072306, JP-A-2012-057068, JP-A-2010-24189. 7, Japanese Patent Application Laid-Open No. 2009-067969, Re-Table 03/002654, and the like.

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

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

A dynamically crosslinked thermoplastic olefin elastomer (TPV) is, as described above, 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 a mixture containing a matrix-forming resin component A (olefinic resin component A) and a domain-forming rubber component B in the presence of a crosslinking agent.

Examples of dynamic cross-linking type thermoplastic olefin elastomers (TPV) include, for example, JP-A-2000-007858, JP-A-2006-052277, JP-A-2012-072306, JP-A-2012-057068, JP-A-2010-241897, JP-A-2009-067969, Retable 03/002654. and the like.

As the dynamically crosslinked thermoplastic olefin elastomer (TPV), commercially available products may be used, such as "Zeotherm" (manufactured by Zeon Corporation), "Thermoran" (manufactured by Mitsubishi Chemical Corporation), and "Sarlink 3245D" (manufactured by Toyobo Co., Ltd.).

The melt flow rate (MFR) of the polyolefin elastomer at a temperature of 230°C is preferably 1.5 g/10 minutes to 25 g/10 minutes, more preferably 2 g/10 minutes to 20 g/10 minutes, and still more preferably 2 g/10 minutes to 15 g/10 minutes.

In one embodiment, two or more polyolefin-based elastomers having different melt flow rates (MFR) at a temperature of 230°C within the above range are used in combination. In this case, a polyolefin elastomer (low MFR polyolefin elastomer) having a melt flow rate (MFR) at a temperature of 230° C. of preferably 1.5 g/10 minutes or more and less than 8 g/10 minutes (more preferably 2 g/10 minutes to 5 g/10 minutes), and a melt flow rate (MFR) at a temperature of 230° C. of preferably 8 g/10 minutes to 25 g/10 minutes (more preferably 9 g/10 minutes to 20 g/10 minutes, more preferably 10 g/10 minutes to 20 g/10 minutes) can be used in combination with a polyolefin elastomer (high MFR polyolefin elastomer). By doing so, the melt tension of the polyolefin elastomer is preferably adjusted, and as a result, the effect of the present invention becomes remarkable.

The compounding ratio of the low MFR polyolefin elastomer to the high MFR polyolefin elastomer (low MFR polyolefin elastomer/high MFR polyolefin elastomer; weight ratio) is preferably 1.5-5, more preferably 1.8-3.5, and particularly preferably 2-3. Within such a range, the melt tension of the polyolefin elastomer is preferably adjusted, and as a result, the effect of the present invention becomes remarkable.

The melt tension (190°C, at break) of the polyolefin elastomer is preferably less than 10 cN, more preferably 5 cN to 9.5 cN. In one embodiment, the die swell ratio and shear viscosity of the resin are controlled by the melt tension of the polyolefin elastomer forming the resin foam.

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

In one embodiment, the resin foam (that is, the resin composition) may further contain a filler. By containing a filler, it is possible to form a resin foam that requires a large amount of energy to deform the cell walls, and the resin foam exhibits excellent impact absorption. In addition, the inclusion of a filler is advantageous in that a fine and uniform cell structure can be formed and excellent impact absorption can be exhibited. Only one filler may be used alone, or two or more fillers may be used in combination.

The content 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, and still more preferably 50 parts by weight to 100 parts by weight with respect to 100 parts by weight of the polymer constituting the resin foam. With such a range, the above effect becomes remarkable.

In one embodiment, the filler is inorganic. Examples of materials constituting inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, silicon nitride, boron nitride, crystalline silica, amorphous silica, metals (e.g., gold, silver, copper, aluminum, nickel), carbon, and graphite.

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

A flame retardant may be used as the filler. Examples of flame retardants include brominated flame retardants, chlorine flame retardants, phosphorus flame retardants, and antimony flame retardants. From the viewpoint of safety, non-halogen-nonantimony flame retardants are preferably used.

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

Any appropriate surface treatment may be applied to the filler. Examples of surface treatment include silane coupling treatment and 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 particularly 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 with a low filler content is advantageous in that it is highly foamed, flexible, stress-dispersible, and has excellent appearance. The lower limit of 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 even more preferably 1 µm or less. Within such a range, the filler can be contained with good dispersibility and a uniform cell 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 analyzer (Microtrac II, Microtrac Bell Co., Ltd.) using a suspension prepared by mixing 1 g of the filler with 100 g of water as a sample.

The specific surface area of the filler is preferably 2 m ² /g or more, more preferably 4 m ² /g or more, still more preferably 6 m ² /g or more. Within such a range, the filler can be contained with good dispersibility and a uniform cell 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, molecules having a known adsorption area are adsorbed on the surface of the filler at a low temperature using liquid nitrogen, and the adsorption amount is measured.

The resin composition may contain any appropriate other component within a range that does not impair the effects of the present invention. Only one such component may be used, or two or more components may be used. Such other components include, for example, rubber, resins other than polymers blended as resin materials, softeners, aliphatic compounds, antioxidants, antioxidants, light stabilizers, weathering agents, UV absorbers, dispersants, plasticizers, carbon, antistatic agents, surfactants, cross-linking agents, thickeners, rust inhibitors, silicone compounds, tension modifiers, shrinkage inhibitors, fluidity modifiers, gelling agents, curing agents, reinforcing agents, foaming agents, foam nucleating agents, colorants (pigments, dyes, etc.), Examples include pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators, lubricants, crystal nucleating agents, crystallization accelerators, vulcanizing agents, surface treatment agents, and dispersing aids.

As described above, resin foams are typically obtained by foaming a resin composition. As the method of foaming (method of forming cells), a method commonly used for foam molding, such as a physical method or a chemical method, can be employed. That is, the resin foam may typically be a foam formed by a physical method (physical foam) or a foam formed by a chemical method (chemical foam). Physical methods generally involve dispersing a gaseous component such as air or nitrogen in a polymer solution and mechanically mixing to form cells (mechanical foam). The chemical method is generally a method in which cells are formed by 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 may be prepared, for example, by mixing the constituent components using any suitable melt-kneading device, such as an open mixing roll, a non-open Banbury mixer, a single-screw extruder, a twin-screw extruder, a continuous kneader, and a pressure kneader.

・Embodiment 1 in which a resin foam is formed
One embodiment 1 for forming a resin foam includes, for example, a step of mechanically foaming an emulsion resin composition (emulsion containing a resin material (polymer)) to foam (step A) to form a resin foam. The foaming device includes, for example, a high-speed shearing device, a vibrating device, and a pressurized gas discharging device. Among these foaming apparatuses, a high-speed shearing apparatus is preferable from the viewpoint of miniaturization of the bubble diameter and production of a large volume. This one embodiment of forming a resin foam is applicable to forming from any resin composition.

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

　Bubbles generated by mechanical stirring are gas trapped in the emulsion. As the gas, any appropriate gas can be adopted as long as it is inert to the emulsion, as long as it does not impair the effects of the present invention. Such gases include, for example, air, nitrogen, carbon dioxide, and the like.

The resin foam of the present invention can be obtained by applying the emulsion resin composition foamed by the above method (cell-containing emulsion resin composition) onto a substrate and drying it (step B). Examples of the substrate include a release-treated plastic film (release-treated polyethylene terephthalate film, etc.), a plastic film (polyethylene terephthalate film, etc.), and the like.

In the process 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 preferably includes a preliminary drying step B1 for drying the bubble-containing emulsion resin composition applied on the substrate at 50°C or higher and lower than 125°C, and a main drying step B2 for further drying at 125°C or higher and 200°C or lower.

By providing the preliminary drying step B1 and the main drying step B2, it is possible to prevent coalescence of air bubbles and bursting of air bubbles due to a rapid temperature rise. In particular, with a foamed sheet having a small thickness, the air bubbles coalesce and burst due to a rapid rise in temperature, so the provision of the pre-drying step B1 is of great significance. The temperature in the preliminary drying step B1 is preferably 50°C to 100°C. The duration of the preliminary drying step B1 is preferably 0.5 to 30 minutes, more preferably 1 to 15 minutes. The temperature in the main drying step B2 is preferably 130°C to 180°C, more preferably 130°C to 160°C. The time of the main drying step B2 is preferably 0.5 to 30 minutes, more preferably 1 to 15 minutes.

・Embodiment 2 in which a resin foam is formed
As one embodiment 2 of forming a resin foam, there is a form in which a foam is formed by foaming a resin composition with a foaming agent. As the foaming agent, those commonly used in foam molding can be used, and from the viewpoint of environmental protection and low contamination of the object to be foamed, it is preferable to use a high-pressure inert gas.

Any appropriate inert gas can be adopted as the inert gas as long as it is inert to the resin composition and can be impregnated. Examples of such inert gas include carbon dioxide, nitrogen gas, and air. These gases may be mixed and used. Among these, carbon dioxide is preferable from the viewpoint of a large impregnation amount to the resin material (polymer) and a high impregnation speed.

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, making it possible to mix the inert gas at a high concentration. At the same time, the concentration of the inert gas becomes high at the time of a sudden pressure drop. Carbon dioxide has a critical temperature of 31° C. and a critical pressure of 7.4 MPa.

Examples of methods for forming a foam by impregnating a resin composition with a high-pressure inert gas include a gas impregnation step in which a resin composition containing a resin material (polymer) is impregnated with an inert gas under high pressure, a decompression step in which the resin material (polymer) is foamed by reducing the pressure after the step, and a heating step in which bubbles are grown by heating as necessary. In this case, a preformed unfoamed molded article may be impregnated with an inert gas, or the molten resin composition may be impregnated with an inert gas under pressure and then molded when the pressure is reduced. These steps may be carried out by either a batch system or a continuous system. That is, after molding the resin composition into an appropriate shape such as a sheet to form an unfoamed resin molded body in advance, the unfoamed resin molded body is impregnated with a high-pressure gas, and the pressure is released to foam it.

Below is an example of producing foam in a batch method. 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, or a Banbury type, and pressed to a predetermined thickness using a hot plate press or the like to produce an unfoamed resin molded body. The unfoamed resin molded article thus obtained is placed in a high-pressure vessel, and a high-pressure inert gas (such as carbon dioxide in a supercritical state) is injected to impregnate the unfoamed resin molded article with the inert gas. When the inert gas is sufficiently impregnated, the pressure is released (usually to atmospheric pressure) to generate bubble nuclei in the resin. The bubble nuclei may be grown at room temperature as they are, or may be grown by heating in some cases. As a heating method, a known or commonly used method such as a water bath, an oil bath, a hot roll, a hot air oven, far infrared rays, near infrared rays, or microwaves can be used. After the cells are grown in this manner, the foam is rapidly cooled with cold water or the like to fix the shape, thereby obtaining a foam. Incidentally, the unfoamed resin molding to be foamed is not limited to a sheet-like article, and various shapes can be used depending on the application. In addition, the unfoamed resin molded article to be foamed can be produced by extrusion molding, press molding, or other molding methods such as injection molding.

An example of continuous production of foam is shown below. For example, while kneading the resin composition using an extruder such as a single-screw extruder or a twin-screw extruder, a high-pressure gas (especially an inert gas, and further carbon dioxide) is injected (introduced), and a sufficiently high-pressure gas is injected (introduced) into the resin composition. A kneading impregnation step in which the resin composition is impregnated, a pressure is released by extruding the resin composition through a die provided at the tip of the extruder (usually to atmospheric pressure), and foam molding is performed in a molding decompression step in which molding and foaming are performed simultaneously. In addition, in the case of continuous foam molding, a heating step may be provided, if necessary, to grow air bubbles by heating. After the bubbles are grown in this way, if necessary, they may be rapidly cooled with cold water or the like to fix the shape. Also, the high-pressure gas may be introduced continuously or discontinuously. Furthermore, for example, an extruder or an injection molding machine can be used in the kneading impregnation step and the molding depressurization step. Any suitable heating method such as water bath, oil bath, hot roll, hot air oven, far infrared rays, near infrared rays, and microwaves can be used as a heating method for growing bubble nuclei. Any appropriate shape can be adopted as the shape of the foam. Such shapes include, for example, a sheet shape, prismatic shape, cylindrical shape, irregular shape, and the like.

The amount of gas mixed when foam-molding the resin composition is, for example, preferably 2% to 10% by weight, more preferably 2.5% to 8% by weight, and even more preferably 3% to 6% by weight, based on the total amount of the resin composition, in order to obtain a highly foamed resin foam.

The pressure when the resin composition is impregnated with the inert gas can be appropriately selected in consideration of operability and the like. Such pressure is, for example, preferably 6 MPa or higher (eg, 6 MPa to 100 MPa), more preferably 8 MPa or higher (eg, 8 MPa to 50 MPa). When using supercritical carbon dioxide, the pressure is preferably 7.4 MPa or more from the viewpoint of maintaining the supercritical state of carbon dioxide. If the pressure is lower than 6 MPa, the cell growth during foaming will be significant, and the cell diameter will become 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, and the bubble nucleus formation speed decreases, resulting in a smaller number of bubble nuclei formed. In addition, in a pressure range lower than 6 MPa, even a slight change in the impregnation pressure significantly changes the bubble diameter and bubble density, making it difficult to control the bubble diameter and bubble density.

The temperature in the gas impregnation process varies depending on the inert gas used and the type of components in the resin composition, and can be selected within a wide range. When operability and the like are considered, the temperature is preferably 10°C to 350°C. The impregnation temperature for impregnating an unfoamed molded article with an inert gas is preferably 10° C. to 250° C., more preferably 40° C. to 230° C. in a batch system. Further, when foaming and molding are simultaneously performed by extruding a molten polymer impregnated with a gas, the impregnation temperature is preferably 60° C. to 350° C. in a continuous system. When carbon dioxide is used as the inert gas, the temperature during impregnation is preferably 32° C. or higher, more preferably 40° C. or higher, in order to maintain a supercritical state.

In the decompression step, the decompression speed is preferably 5 MPa/sec to 300 MPa/sec in order to obtain uniform microbubbles.

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

In one embodiment, after obtaining a foamed structure through a predetermined process (for example, after obtaining a resin foam by the method of <Embodiment 1> or <Embodiment 2>), the foamed structure is thinned and then roll-rolled to obtain a resin foam. Through such steps, a resin foam having an appropriately adjusted aspect ratio can be obtained. Moreover, a resin foam having a small thickness (for example, 0.2 mm or less) can be obtained. The hot melt layer may be formed by the roll rolling.

Thinning of the foam structure can be performed using any appropriate slicer. The thickness of the foam structure after thinning is preferably 0.01 mm or more, more preferably 0.05 mm or more, still more preferably 0.1 mm or more, and particularly preferably 0.15 mm or more. Further, the upper limit of the thickness of the foamed structure after thinning is preferably 3 mm or less, more preferably 2 mm or less, still more preferably 1.5 mm or less, still more preferably 1 mm or less, still more preferably 0.8 mm or less, and particularly preferably 0.5 mm or less. Within such a range, the number of cells in the resin foam is particularly preferably adjusted, and collapse due to punching is less likely to occur, so that a foamed member having particularly excellent punching workability can be obtained.

Preferably, the rolls used for the roll rolling are heating rolls. The temperature of the roll is preferably 150°C to 250°C, more preferably 160°C to 230°C.

The rolling rate of the foamed structure (thickness after rolling/thickness before rolling x 100) is preferably 80% or less, more preferably 10% to 80%, still more preferably 20% to 75%, and particularly preferably 30% to 75%. Within such a range, a resin foam with an appropriately adjusted aspect ratio can be obtained.

C. Adhesive Body As described above, in the adherent body, the total amount of toluene outgas and ethyl acetate outgas is 8.0 μg/g or less. The total emission amount of toluene outgas and ethyl acetate outgas from the sticky substance is preferably 5.0 μg/g or less, more preferably 2.0 μg/g or less. With such a range, the above effect becomes remarkable.

The thickness of the adherent is preferably 5 µm or more, more preferably 10 µm or more, still more preferably 15 µm or more, and particularly preferably 20 µm or more. The upper limit of the thickness of the adherent is preferably 500 µm or less, more preferably 300 µm or less, still more preferably 100 µm or less, and particularly preferably 50 µm or less.

C-1. Adhesive Layer The single-layer thickness of the adhesive layer is preferably 1 µm or more, more preferably 2 µm or more, still more preferably 3 µm or more, and particularly preferably 5 µm or more. The upper limit of the single layer thickness of the adhesive layer is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, still more preferably 20 μm or less, and particularly preferably 18 μm or less. A foamed member having an adhesive layer with such a thickness is suitable for use in areas with narrow clearances. In addition, it is excellent in cleanness and punchability.

The total thickness of the adhesive layer is preferably 100 µm or less, more preferably 80 µm or less, even more preferably 60 µm or less, even more preferably 40 µm or less, and particularly preferably 36 µm or less. The lower limit of the total thickness of the adhesive layer is preferably 2 μm or more, more preferably 4 μm or more, still more preferably 6 μm or more, and particularly preferably 10 μm or more. A foamed member having an adhesive layer with such a thickness is suitable for use in areas with narrow clearances. Also, it is possible to obtain a foamed member that is excellent in cleanliness and punchability. In one embodiment, the total thickness of the adhesive layer is less than 25 μm. Within such a range, extrusion of the adhesive during punching is remarkably prevented, and a foamed member having particularly excellent punching workability can be obtained.

The storage modulus of the adhesive layer at 25°C is preferably 3.0 × 10 ⁴ Pa to 2.0 × 10 ⁵ Pa, preferably 4.5 × 10 ⁴ Pa to 1.2 × 10 ⁵ Pa, more preferably 5.0 × 10 ⁴ Pa to 8.0 × 10 ⁴ Pa, and particularly preferably 5.0 × 10 ⁴ Pa to 6.0 × 10 ⁴ Pa.

As long as the effect of the present invention can be obtained, the adhesive layer contains any appropriate adhesive. Also, the pressure-sensitive adhesive layer is preferably formed from a material that does not contain an organic solvent. Therefore, it is preferable that the adhesive does not contain an organic solvent.

In one embodiment, the pressure-sensitive adhesive layer contains a water-dispersed pressure-sensitive adhesive. In one embodiment, the water-dispersible pressure-sensitive adhesive contains a water-dispersible polymer. By using a water-dispersible pressure-sensitive adhesive, it is possible to obtain a foamed member that generates less outgassing and is excellent in cleanness. In one embodiment, the water-dispersed pressure-sensitive adhesive further contains polyacrylic acid. By adding polyacrylic acid, a foamed member having excellent water resistance and impact resistance can be obtained. The water-dispersible pressure-sensitive adhesive is advantageous in that it has excellent anchoring properties with a base material (described later) made of polyethylene terephthalate and has excellent coatability.

(Water-dispersible polymer)
Examples of the water-dispersible polymer include a water-dispersible acrylic polymer, a water-dispersible urethane-based polymer, a water-dispersible polyaniline-based polymer, and a water-dispersible polyester-based polymer. Preferably, a water-dispersible acrylic polymer is used. A water-dispersible pressure-sensitive adhesive containing a water-dispersible acrylic polymer is advantageous in that it has excellent anchoring properties with a substrate (described later) made of polyethylene terephthalate, and also has excellent coatability.

The water-dispersible acrylic polymer can be a polymer of a monomer composition containing a (meth)acrylic acid alkyl ester. (Meth)acrylic acid is defined as acrylic acid and/or methacrylic acid.

(Meth)acrylic acid alkyl esters include, for example, (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 1 to 20 (preferably 1 to 12) carbon atoms. (Meth)acrylate alkyl esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ) 2-ethylhexyl acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridodecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, (meth)acrylate hexadecyl acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctacyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Among them, methyl acrylate and 2-ethylhexyl acrylate are preferred. (Meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

In one embodiment, methyl acrylate and an acrylate alkyl ester having an alkyl group of 2 to 8 carbon atoms are used in combination. Preferably, methyl acrylate and 2-ethylhexyl acrylate can be used in combination.

In the water-dispersible acrylic polymer, the ratio of structural units derived from (meth)acrylic acid alkyl ester is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more. The (meth)acrylic acid alkyl ester-derived structural unit is, for example, 99.5% by weight or less, preferably 99% by weight or less.

The water-dispersible acrylic polymer may contain structural units derived from monomers copolymerizable with (meth)acrylic acid alkyl esters. Examples of such structural units include structural units derived from one or more functional group-containing vinyl monomers. Functional group-containing vinyl monomers are useful for modifying acrylic polymers, such as securing cohesive strength of acrylic polymers and introducing cross-linking points into acrylic polymers.

Examples of functional group-containing vinyl monomers include carboxy group-containing vinyl monomers (carboxy group-containing monomers), acid anhydride vinyl monomers, hydroxyl group-containing vinyl monomers, sulfo group-containing vinyl monomers, phosphoric acid group-containing vinyl monomers, cyano group-containing vinyl monomers, glycidyl group-containing vinyl monomers, and the like.

Examples of carboxy group-containing vinyl monomers include acrylic acid, methacrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among them, acrylic acid or methacrylic acid is preferable. By using such a monomer, it is possible to obtain a PSA with excellent adhesive properties and mechanical stability of the emulsion particles.

Examples of acid anhydride vinyl monomers include maleic anhydride and itaconic anhydride.

Examples of hydroxyl group-containing vinyl monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl). ) methyl (meth)acrylate and the like.

Examples of sulfo group-containing vinyl monomers include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

Examples of phosphate group-containing vinyl monomers include 2-hydroxyethyl acryloyl phosphate and the like.

Examples of cyano group-containing vinyl monomers include acrylonitrile and methacrylonitrile.

Examples of glycidyl group-containing vinyl monomers include glycidyl (meth)acrylate and 2-ethylglycidyl (meth)acrylate.

The functional group-containing vinyl monomer preferably includes a carboxy group-containing vinyl monomer.

In the water-dispersed acrylic polymer, the proportion of structural units derived from functional group-containing vinyl monomers is, for example, 0.5% by weight or more, preferably 1.0% by weight or more, and more preferably 1.5% by weight or more. The ratio of structural units derived from functional group-containing vinyl monomers is, for example, 30% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less.

The water-dispersible acrylic polymer can be obtained, for example, by emulsion polymerization of the above monomer composition. In emulsion polymerization, for example, first, a mixture containing a monomer, an emulsifier, and water is stirred to prepare a monomer emulsion. Next, a polymerization initiator is added to the monomer emulsion to initiate the polymerization reaction. A chain transfer agent may be used in this polymerization reaction to adjust the molecular weight of the acrylic polymer. Additives such as coupling agents and preservatives may also be used. The polymerization method may be dropping polymerization or batch polymerization. The polymerization time is, for example, 0.5 hours or more and, for example, 10 hours or less. The polymerization temperature is, for example, 50° C. or higher and, for example, 80° C. or lower. By emulsion polymerization, a water-dispersible acrylic polymer is prepared as a water-dispersed liquid, specifically a water-dispersed liquid (emulsion) in which a water-dispersed acrylic polymer is dispersed in water. That is, the aqueous dispersion contains a water-dispersible polymer and water.

Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, and radical polymerizable emulsifiers (reactive emulsifiers).

Examples of anionic emulsifiers include sodium polyoxyethylene lauryl sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate.

Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene polyoxypropylene block polymers, and the like.

Examples of radically polymerizable emulsifiers (reactive emulsifiers) include emulsifiers obtained by introducing radically polymerizable functional groups such as vinyl groups, propenyl groups, isopropenyl groups, vinyl ether groups, and allyl ether groups into the above anionic emulsifiers and nonionic emulsifiers. Specific examples include ammonium-α-sulfonato-ω-1-(allyloxymethyl)alkyloxypolyoxyethylene. When a reactive emulsifier is used, the acrylic polymer, which is a water-dispersible polymer obtained by emulsion polymerization, contains monomer units derived from the reactive emulsifier.

The mixing ratio of the emulsifier is, for example, 0.2 to 10 parts by weight with respect to 100 parts by weight of the total amount of monomers.

Examples of polymerization initiators include azo polymerization initiators and peroxide polymerization initiators.

Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane}n hydrate, 2, 2'-azobis(N,N'-dimethyleneisobutylamidine) and the like.

Examples of peroxide-based polymerization initiators include benzoyl peroxide, t-butyl hydroperoxide, and hydrogen oxide.

The polymerization initiator preferably includes an azo polymerization initiator, more preferably 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane}n hydrate.

The mixing ratio of the polymerization initiator is, for example, 0.01 to 2 parts by weight with respect to 100 parts by weight of the total amount of monomers.

Examples of chain transfer agents include glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, t-lauryl mercaptan, t-dodecanethiol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and preferably t-dodecanethiol.

The blending ratio of the chain transfer agent is, for example, 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the total amount of monomers.

The weight average molecular weight (Mw) of the water-dispersible acrylic polymer is, for example, 100,000 or more, preferably 300,000 or more, and, for example, 5,000,000 or less, preferably 3,000,000 or less. As used herein, the weight average molecular weight is calculated by polystyrene conversion after measurement by gel permeation chromatography (GPC).

(polyacrylic acid)
The blending ratio of the polyacrylic acid is preferably 0.1 parts by weight to 7 parts by weight, more preferably 0.15 parts by weight to 5 parts by weight, more preferably 2.5 parts by weight to 5 parts by weight, and particularly preferably 3.5 parts by weight to 5 parts by weight, with respect to 100 parts by weight of the water-dispersible polymer. Within such a range, the impact resistance of the pressure-sensitive adhesive layer can be improved. Moreover, the adhesive layer which is excellent in adhesiveness can be formed.

The weight average molecular weight of polyacrylic acid is, for example, 50,000 or more, preferably 100,000 or more, and more preferably 150,000 or more. Also, for example, it is 300,000 or less, preferably 250,000 or less.

(Additive)
The water-dispersible pressure-sensitive adhesive may further contain any appropriate additive. Examples of additives include leveling agents, tackifiers, release aids, silane coupling agents, thickeners, cross-linking agents (eg, 3-methacryloxypropyltrimethoxysilane), fillers, antioxidants, surfactants, antistatic agents, and the like.

In one embodiment, the water-dispersed pressure-sensitive adhesive further contains a leveling agent. By adding a leveling agent, it is possible to obtain a water-dispersible pressure-sensitive adhesive that has excellent applicability and can be preferably applied to a substrate (described later) composed of polyethylene terephthalate. Moreover, by using such a water-dispersible pressure-sensitive adhesive, a pressure-sensitive adhesive layer having excellent impact resistance can be formed. Examples of leveling agents include "Surfinol 420" (acetylene glycol ethylene oxide surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), "Pelex OT-P" (sodium dialkyl sulfosuccinate, manufactured by Kao Corporation), "Neocol P" (sodium dialkyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Nopko Wet 50" (sulfonic acid-based anionic surfactant, manufactured by San Nopco Co., Ltd.), "SN Wet 126" (modified silicone/special polyether surfactant, San Nopco Co., Ltd.), "SN Wet FST2" (polyoxyalkyleneamine nonionic wetting agent, San Nopco Co., Ltd.), "SN Wet S" (polyoxyalkyleneamine ether nonionic wetting agent, San Nopco Co., Ltd.), and "SN Wet 125" (modified silicone surfactant, San Nopco Co., Ltd.). A leveling agent can be used individually or in combination of 2 or more types.

In one embodiment, sodium dialkylsulfosuccinate is used as the leveling agent. The carbon number of sodium dialkylsulfosuccinate is, for example, 4 or more, preferably 6 or more, and more preferably 8 or more. The upper limit of the number of carbon atoms is, for example, 20 or less, preferably 13 or less, and more preferably 10 or less.

The blending ratio of the leveling agent is, for example, 1 part by weight or more, preferably 1.5 parts by weight or more, and for example, 3.5 parts by weight or less, preferably 2.5 parts by weight or less with respect to 100 parts by weight of the water-dispersible polymer. Moreover, the mixing ratio of the leveling agent is, for example, 10 parts by weight or more and, for example, 500 parts by weight or less with respect to 100 parts by weight of polyacrylic acid.

Examples of the tackifier include various tackifier resins such as rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenol-based resins, and ketone-based resins, preferably rosin-based resins, terpene-based resins, and more preferably terpene-based resins. The content of the tackifier is, for example, 5 parts by weight or more, preferably 15 parts by weight or more, more preferably 25 parts by weight or more, and still more preferably 33 parts by weight or more, and, for example, 50 parts by weight or less, preferably 45 parts by weight or less, and more preferably 38 parts by weight or less, relative to 100 parts by weight of the water-dispersible polymer.

C-2. Substrate A substrate formed from any appropriate resin can be used as the substrate. Examples of the resin constituting the substrate include polyester-based resins, polyolefin-based resins, polyvinyl chloride, polyimide-based resins, and polyamide-based resins. Among them, polyester-based resins are preferred, and polyethylene terephthalate is more preferred. Using a substrate made of polyethylene terephthalate makes it possible to obtain significantly thinner foamed parts. Moreover, since it has a high breaking strength and is not easily cut, it is also advantageous in that it is easy to process. Moreover, since the melting point is high, the rate of dimensional change at high temperatures is small, and it is also advantageous in that it can be used in various environments. By using the water-dispersible pressure-sensitive adhesive, it is possible to preferably use a base material made of polyethylene terephthalate, and as a result, it is possible to obtain a foamed member that is remarkably thin and excellent in cleanness (e.g., less outgassing).

The breaking strength of the base material at 23°C is preferably 200 MPa to 500 MPa, more preferably 260 MPa to 420 MPa, still more preferably 300 MPa to 380 MPa, and particularly preferably 320 MPa to 360 MPa. Within such a range, it is possible to obtain a substrate having suitable strength. Such a base material has excellent punching workability, and prevents tearing, dust generation, uncut parts, etc. during punching. The breaking strength is measured by preparing a test piece (base material) cut to a size of 10 mm in width and 150 mm in length, and using a tensile tester at a chuck distance of 120 mm and a tensile speed of 50 mm/min in an environment of 23°C and 50% RH. The breaking strength of the base material may be the breaking strength in the processing flow direction when the base material is formed into a film.

When the adherence body includes a base material, the breaking strength of the adherence body at 23°C is preferably 200 MPa to 500 MPa, more preferably 260 MPa to 420 MPa, still more preferably 300 MPa to 380 MPa, and particularly preferably 320 MPa to 360 MPa.

The dimensional change rate when the base material is left at 150° C. for 30 minutes is preferably 1% to 5%, more preferably 1% to 3%, still more preferably 1.2% to 2.8%, and particularly preferably 1.5% to 2.5%. Within such a range, it is possible to obtain a foamed member with little dimensional change even in a high-temperature environment. Such a substrate can maintain its shape even in various environments, and variations in processed dimensions are suppressed. The dimensional change rate is the dimensional change rate in each direction (for example, the width direction, the length direction, the thickness direction, etc.) in a test piece having a width of 100 mm, a length of 100 mm, and a thickness of 1 to 25 μm. For example, the dimensional change rate of 10% or less means that all of the dimensional change rate in the width direction, the dimensional change rate in the length direction, and the dimensional change rate in the thickness direction in the test piece is 10% or less. The dimensional change rate (%) is obtained from the following.
Dimensional change rate (%) = (L0 - L1) / L0 x 100
L0: Initial test piece dimension (blank value)
L1: Dimension of test piece after left at 150°C for 30min

When the adherent has a base material, the dimensional change rate when the adherent is left at 150°C for 30 minutes is preferably 1% to 5%, more preferably 1% to 3%, still more preferably 1.2% to 2.8%, and particularly preferably 1.5% to 2.5%.

The total light transmittance (JIS K 7375-2008) of the substrate is, for example, 80% or more, preferably 85% or more.

The thickness of the substrate is preferably 1 μm or more, more preferably 2 μm or more. The upper limit of the thickness of the substrate is preferably 100 µm or less, more preferably 50 µm or less, still more preferably 10 µm or less, and particularly preferably 7 µm or less. Within such a range, it is possible to obtain a remarkably thin foamed member. It is also advantageous in that it is easy to punch because it has high breaking strength and is not easily cut.

C-3. Easy-Adhesion Layer In one embodiment, the adherence article may further include an easy-adhesion layer between the substrate and the pressure-sensitive adhesive layer. The easy-adhesion layer is formed from an easy-adhesion composition that is an adhesive composition.

In one embodiment, the easy-adhesion composition contains an oxazoline group-containing polyester polymer. In one embodiment, the oxazoline group-containing polyester polymer comprises a polyester-derived structural unit and an oxazoline-derived structural unit.

The above polyester is a polymer in which an ester bond formed by dehydration condensation of a polycarboxylic acid and a polyol connects them. Examples of the polyvalent carboxylic acid include phthalic acid (terephthalic acid, isophthalic acid), naphthalenedicarboxylic acid, and the like. Phthalic acid is preferred. Examples of the polyols include aliphatic glycols having 2 to 8 carbon atoms.

The oxazoline group-containing polyester polymer can be obtained, for example, by reacting a water-soluble copolyester (polyester component) obtained according to the method described in JP-A-06-293838 with an oxazoline-based reactive polymer (oxazoline component).

The water contact angle of the easily adhesive layer is, for example, 60° or more, and for example, 75° or less, preferably 71° or less, more preferably 68° or less, and still more preferably 65° or less.

The thickness of the easy adhesion layer is, for example, 50 nm or less, more preferably 45 nm or less, and for example, 1 nm or more, preferably 10 nm or more.

The foam member can be manufactured by any appropriate method. For example, the foamed member may be manufactured by laminating a resin foam and an adhesive layer (or an adhesive (adhesive sheet)).

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The tests and evaluation methods used in Examples and the like are as follows. "Parts" means "parts by weight" unless otherwise specified, and "%" means "% by weight" unless otherwise specified.

<Evaluation method>
(1) Apparent Density The density (apparent density) of the resin foam was calculated as follows. The resin foams obtained in Examples and Comparative Examples were punched out into 20 mm×20 mm size test pieces, and the dimensions of the test pieces were measured with vernier calipers. 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) 50% Compressive Load Measured according to the method for measuring compression hardness of resin 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 at a compression speed of 10 mm/min until the compression ratio reached 50% was converted to a unit area (1 cm ² ) to obtain a 50% compression load (N/cm ² ).

(3) Average foam diameter (average cell diameter) and foam diameter (cell diameter) The foam emitted in the bubbles (cell diameter) is cut vertically (thickness direction) to the main aspect of the resin foam using a razor blade, and as a measuring instrument, a digital microscope (product name "VHX -500", for Keyence Co., Ltd.) is used. Incorporating the cutting surface image of the resin foam, using the analysis software of the same meter, an average foam diameter (average cell diameter) (μm) was calculated by analyzing the image. 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.
Variation coefficient = standard deviation / average bubble diameter (average cell diameter)

(4) Bubble rate (cell rate)
The measurement was performed in an environment with a temperature of 23°C and a humidity of 50%. The resin foams obtained in Examples and Comparative Examples were punched out with a 100 mm × 100 mm punching blade (two processing blades (trade name “NCA07”, thickness 0.7 mm, cutting edge angle 43°, manufactured by Nakayama Co., Ltd.)), and the dimensions of the punched samples were measured. Also, the thickness was measured with a 1/100 dial gauge having a measuring terminal diameter (φ) of 20 mm. From these values, the volumes of the resin foams obtained in Examples and Comparative Examples were calculated. Next, the weights of the resin foams obtained in Examples and Comparative Examples were measured with a balance with a minimum scale of 0.01 g or more. From these values, the void ratio (cell ratio) of the resin foams obtained in Examples and Comparative Examples was calculated.

(5) Cell Number Density The resin foam was cut with a razor blade in the direction (thickness direction) perpendicular to the main surface of the resin foam. Using a digital microscope (trade name "VHX-500", manufactured by Keyence Corporation) as a measuring instrument, a cut surface image of the resin foam is captured, and image analysis is performed using the analysis software of the same measuring instrument. The number of bubbles per unit area [mm ^] was measured.

(6) Thickness recovery rate (instantaneous recovery rate)
A load of 1000 g/cm ² was applied to the foamed member and maintained for 120 seconds, the compression was released, and the thickness of the foamed member 0.5 seconds after the release (thickness 0.5 seconds after the compression was released) was measured. The thickness recovery rate (instantaneous recovery rate) was obtained from the following formula based on the "thickness 0.5 seconds after releasing the compressed state" and the thickness (initial thickness) of the foamed member before the load was applied.
Thickness recovery rate (%) = {(thickness 0.5 seconds after releasing the compressed state) / (initial thickness)} x 100

(7) Punching workability (10 mm × 10 mm)
Using a mold (two processing blades (product name “NCA07”, thickness 0.7 mm, blade angle 43°, spacing between two processing blades 10 mm, manufactured by Nakayama)), the foam member is punched in the MD direction (flow direction) and TD direction (perpendicular to the flow direction) to a size of 10 mm × 10 mm. X-2000" manufactured by Keyence Corporation). Using the edge thickness measured from the image and the thickness before punching, the thickness recovery rate after processing was measured by the following formula. The larger the thickness recovery rate, the smaller the change in shape due to punching, and the better the punching workability.
Thickness recovery rate after processing (%) = 100 × (1 - (thickness before punching - thickness of edge) / thickness before punching)

(8) Total emission amount of toluene outgas and ethyl acetate outgas The adhesive (adhesive sheet/tape) was cut into a sample of 5 cm ² and sealed in a 20 mL headspace vial. The vial containing the sample was heated at 80°C for 30 minutes with a headspace sampler (HS-20 manufactured by Shimadzu Corporation). The total amount of ethyl acetate outgassed was measured.

(9) Dust Resistance/Dust Resistance Test Apparatus Figs. 3 and 4 show the dust resistance test apparatus used for dust resistance evaluation. FIG. 3 is a schematic configuration diagram of the dustproofness tester, and FIG. 4 is an end view of the dustproofness tester taken along line AA'.
3 and 4, 1 is a dustproof test device, 11 is a ceiling plate, 1121 is a spacer, 1122 is a step forming spacer, 13 is a double-sided adhesive tape, 14 is a test piece (resin foam, the same applies hereinafter), 15 is an evaluation box, 16a is a through hole, 16b is a through hole, 16c is a through hole, 17 is an opening, and 18 is a space. The ceiling plate 11 is in the shape of a substantially rectangular flat plate, and has a rectangular (trapezoidal) notch in plan view that serves as an opening. The spacer 1121 is larger than the opening 17, has a rectangular flat plate shape, and is used to compress the test piece 14 to a desired thickness. The double-sided adhesive tape 13 is a double-sided adhesive sheet forming a foam member, and is used for fixing the spacer 1121 and the test piece 14 together. Through hole 16a is connected to a metering pump via a pipe joint. Through hole 16b is connected to a differential pressure gauge via a pipe joint. Through hole 16c is connected to a needle valve via a pipe joint. In the dust-proof test apparatus 1, by screwing together the ceiling plate 11 and the evaluation box 15, a substantially rectangular parallelepiped sealable space 18 is formed inside. The opening 17 is the opening of the space 18 . In addition, the ceiling plate 11 has a notch that is rectangular (trapezoidal) when viewed open.
·Dust resistance evaluation A test piece 14 was attached to a dust resistance testing device as follows. A rectangular plate-like spacer 1121 larger than the opening 17 was attached to the lower surface of the ceiling plate 11 facing the opening 17 so as to face the entire surface of the opening 17 . Then, a test piece 14 having a window portion having approximately the same size as the opening portion 17 was attached via a double-sided adhesive tape 13 to a position facing the opening portion 17 on the lower surface of the spacer 1121 . Next, the ceiling plate 11 was screwed to the evaluation box 15 after the step forming spacers 1122 were sandwiched under each side of the test piece 14 . In this manner, the test piece 14 was attached to the dust resistance test device. The test piece 14 is compressed in the thickness direction by the spacer 1121 and the peripheral edge of the opening 17 . The compressibility of the test piece 14 was adjusted to 50% compression (state compressed by 50% of the initial thickness) by adjusting the thickness of the spacer 1121 . By screwing the ceiling plate 11 and the evaluation box 15 together, the space 18 in the evaluation box is sealed with the test piece 14 , the spacer 1122 , the double-sided adhesive tape 13 and the spacer 1121 .
After the test piece was attached to the dustproofness tester as described above, the dustproofness tester was placed in the dust box and sealed. The dust box is connected to a dust supply device and a particle counter. Also, the through-hole 16b of the dust resistance testing device is connected to the particle counter via a pipe joint. Next, using a dust supply device and a particle counter connected to the dust box, particles having a predetermined diameter were supplied to the dust box so that the particle count value (number) was approximately constant at around 100,000. Next, with the needle valve connected to the through-hole 16c of the dust resistance test apparatus closed, suction was performed for 30 minutes at a suction rate of 0.5 L/min using a metering pump connected to the through-hole 16a. After the suction, the number of particles in the space 18 of the dust resistance tester was measured with a particle counter, and the particle count value at this time was defined as the foam passing particle number Pf. Then, the dust resistance index (dust penetration rate) was obtained from the following formula.
Dust resistance index (%) = 100 - (P0 - Pf) / P0 x 100
P0: number of particles in the atmosphere Pf: number of particles passing through the foam
(10) Storage modulus of adhesive layer (25°C)
It was obtained by performing dynamic viscoelasticity measurement under the following conditions using a dynamic viscoelasticity measuring device "ARES" manufactured by Rheometric. As a measurement sample, a part of the pressure-sensitive adhesive layer was pressed to a thickness of 2 mm.
- Apparatus: ARES (Advanced Rheometric Expansion System) manufactured by Rheometric Scientific
・Frequency: 1Hz
・Temperature: -60 to 150°C
・Temperature increase rate: 5°C/min ・Deformation mode: twist ・Shape: parallel plate (7.9mmφ)

(11) Impact Absorption A foamed member was produced by punching in the same test method as in (7). After that, a foam member was arranged on the impact force sensor to form a test body. A 66-g iron ball was dropped onto the specimen from a height of 30 cm above the foamed member, and the impact force F1 was measured. In addition, 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 absorbency (%) was calculated by the formula (F0-F1)/F0×100.

[Production Example 1]
<Preparation of adhesive sheet (double-sided adhesive sheet A)>
0.07 parts by weight of an emulsifier and 61.1 parts by weight of distilled water were added to a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, and the mixture was replaced with nitrogen at room temperature (25° C.) for 1 hour while stirring. After that, 0.1 part by weight of a polymerization initiator was further added, and the temperature was raised to 60°C. Furthermore, 2 -ethylhexyl acrylate (2EHA), 85 parts, metal acrylic acid (MA) 13, 1.25 parts, 1.25 parts of acrylic acid (AA), 0.75 metalic acid (MAA), T -dodkanchial (chain mobilization agent) 0.025, 0.025, 0.025 parts. The 02 weight portion and the emulsifier 1.93 heavy part of the weight of a 28 -weight part of the distilled water were polymerized while dropping at 60 ° C. for 4 hours. Then, it was cooled to room temperature, and the pH was adjusted to 6 using 10% aqueous ammonia as a pH adjuster. Thus, a water-dispersible acrylic polymer was synthesized. 30 parts by weight of a tackifier, 3 parts by weight of a thickening agent, and 2 parts by weight of a leveling agent were added to 100 parts by weight of a water-dispersed acrylic polymer solid content, diluted and neutralized with distilled water and 10% aqueous ammonia to prepare a water-dispersed pressure-sensitive adhesive composition A (solid concentration: 25% by mass). The water-dispersible pressure-sensitive adhesive composition A was applied to the surface of the release film to a thickness of 12.5 μm and dried to form (arrange) a pressure-sensitive adhesive layer. Thus, a substrate-less pressure-sensitive adhesive sheet A' was obtained.
Next, on both sides of a polyester film (trade name “K880-4.5W” manufactured by Mitsubishi Chemical Polyester Co., Ltd.; thickness: 5 μm), easy-adhesion layers containing an oxazoline group-containing polyester polymer (intensity ratio of peak intensity derived from oxazoline component to peak intensity derived from polyester component measured by TOFSIMS: 11) were provided.
Furthermore, the pressure-sensitive adhesive sheet A' was transferred to both sides of the easy-adhesion layer-attached polyester film obtained above. Thus, a double-sided pressure-sensitive adhesive sheet A was produced.

[Production Example 2]
<Preparation of adhesive sheet (double-sided adhesive sheet B)>
35 parts by weight of ion-exchanged water was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube, and stirred at 60° C. for 1 hour or more while introducing nitrogen gas. To this was added 0.1 part by weight of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate as a polymerization initiator to prepare a reaction solution.
As monomer raw materials, 90 parts by weight of n-butyl acrylate, 10 parts by weight of 2-ethylhexyl acrylate, 4 parts by weight of acrylic acid, 2 parts by weight of sodium polyoxyethylene lauryl sulfate (emulsifier), and 0.05 parts by weight of dodecanethiol (chain transfer agent) were added to 40 parts by weight of ion-exchanged water and emulsified to obtain a monomer raw material emulsion.
This monomer raw material emulsion was gradually added dropwise over 4 hours to the above reaction liquid kept at 60° C. to effect emulsion polymerization. After the dropping of the monomer raw material was completed, the mixture was further stirred at 60° C. for 2 hours, and the heating was stopped. Then, 0.1 part by weight of ascorbic acid and 0.1 part by weight of 35% hydrogen peroxide solution (additional polymerization initiator) were added to 100 parts by weight of the monomer to carry out redox treatment. After cooling to room temperature, 10% aqueous ammonia was added to adjust the pH to 7 to obtain an acrylic polymer emulsion (water-dispersed acrylic polymer). To the acrylic polymer emulsion, 30 parts by weight of the tackifier resin emulsion was added in terms of solid content per 100 parts by weight of the acrylic polymer contained in the emulsion to obtain a water-dispersed pressure-sensitive adhesive composition. Next, a release liner substrate was prepared by laminating a PE layer having a thickness of 25 μm on one side of fine paper. A mixture of a non-migrating, heat-curable, solvent-free silicone release agent and a curing catalyst was applied onto the PE layer of this substrate. This was dried and cured by holding at 120° C. for 1 minute to obtain a release liner. On the release layer of the release liner thus obtained, the water-dispersible pressure-sensitive adhesive composition was applied to form a pressure-sensitive adhesive layer with a thickness of 55 μm. Two sheets of this were prepared and transferred to each surface of a nonwoven fabric base material (manufactured by Daifuku Paper Co., Ltd., product name "SP base paper-14", pulp nonwoven fabric having a thickness of 50 μm) to obtain a double-sided pressure-sensitive adhesive sheet B.

[Production Example 3]
<Preparation of double-sided adhesive sheet C>
65 parts by weight of n-butyl acrylate, 35 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, 0.05 parts by weight of 4-hydroxybutyl acrylate, and 0.08 parts by weight of AIBN (azobisisobutyronitrile) as a polymerization initiator were added to a toluene solvent. After that, solution polymerization was carried out at 63° C. for 8 hours to obtain an acrylic polymer solution. Also, acrylic acid is 2.9% by weight based on the total monomer components. 30 parts by weight of a polymerized rosin ester (softening point: 128° C., acid value: 12 mgKOH/g) and 2 parts by weight of an isocyanate crosslinking agent were added to the prepared acrylic polymer solution to prepare an acrylic pressure-sensitive adhesive composition c. The pressure-sensitive adhesive composition c was applied to the surface of the release film to a thickness of 12.5 μm and dried to form (arrange) a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was transferred to both sides of a polyester film (trade name “K880-4.5W” manufactured by Mitsubishi Chemical Polyester Co., Ltd.; thickness: 5 μm). Thus, a double-sided pressure-sensitive adhesive sheet C was produced.

[Production Example 4]
<Preparation of adhesive sheet (double-sided adhesive sheet D)>
A water-dispersed pressure-sensitive adhesive composition A was prepared in the same manner as in Production Example 1.
The surface of the release film was coated with the water-dispersed pressure-sensitive adhesive composition A to a thickness of 25 μm and dried to form (arrange) a pressure-sensitive adhesive layer. As a result, a substrate-less pressure-sensitive adhesive sheet D' was obtained.
Next, on both sides of a polyester film (trade name “K880-4.5W” manufactured by Mitsubishi Chemical Polyester Co., Ltd.; thickness: 5 μm), easy-adhesion layers containing an oxazoline group-containing polyester polymer (intensity ratio of peak intensity derived from oxazoline component to peak intensity derived from polyester component measured by TOFSIMS: 11) were provided.
Furthermore, the pressure-sensitive adhesive sheet D' was transferred to both sides of the easy-adhesion layer-attached polyester film obtained above. Thus, a double-sided pressure-sensitive adhesive sheet D was produced.

[Example 1]
Polypropylene resin A (MFR: 0.4 g/10 min, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 108,000, molecular weight distribution: 4.93) 35 parts by weight, polyolefin elastomer A (melt flow rate (MFR): 15 g/10 min) 30 parts by weight, polyolefin elastomer B (melt flow rate (MFR): 2.2 g/10 min) 30 parts by weight, magnesium hydroxide A mixture was obtained by mixing 10 parts by weight, 10 parts by weight of carbon, and 1 part by weight of stearic acid monoglyceride. The mixture was kneaded at a temperature of 200° C. using a twin-screw kneader manufactured by Japan Steel Works (JSW), extruded into strands, cooled with water, and formed into pellets.
The pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected under an atmosphere of 220° C. and a pressure of 13 MPa (12 MPa after injection). Carbon dioxide gas was injected at a rate of 4.5 parts by weight with respect to 100 parts by weight of the resin. After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming, extruded from a die and sliced at a thickness of 0.6 mm to obtain a sheet-like resin foam a. A double-sided pressure-sensitive adhesive sheet A was attached to one side of the resin foam a to obtain a foamed member.
The obtained foamed member was subjected to the above evaluation. Table 1 shows the results.

[Examples 2 to 22]
A foamed member was obtained in the same manner as in Example 1, except that the composition of the mixture for forming pellets (the amount of each component blended) and the thickness of the resin foam were as shown in Tables 1 to 3. The obtained foamed member was subjected to the above evaluation. The results are shown in Tables 1-3.
The contents of "polypropylene resin A2" and "polypropylene resin B" in Table 1 are as follows.
Polypropylene resin A2: MFR: 0.5 g/10 min, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 64500, molecular weight distribution: 8.43
Polypropylene resin B; MFR: 1.1 g/10 min, ethylene content: 0 wt%, propylene content: 100 wt%

[Example 23]
Polypropylene resin A (MFR: 0.4 g/10 min, ethylene content: 0 wt%, propylene content: 100 wt%, weight average molecular weight: 108000, molecular weight distribution: 4.93) 45 parts by weight Polypropylene resin B (MFR: 1.1 g/10 min, ethylene content: 0 wt%, propylene content: 100 wt%) 30 parts by weight Polyolefin elastomer C (melt flow rate (MFR): 6.0 g/1 0 min) 25 parts by weight, 100 parts by weight of magnesium hydroxide, 10 parts by weight of carbon, and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200 ° C. in a twin-screw kneader manufactured by Japan Steel Works (JSW), extruded into strands, and water-cooled to form pellets. The pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected under an atmosphere of 220° C. and a pressure of 13 MPa (12 MPa after injection). Carbon dioxide gas was injected at a rate of 4.5 parts by weight with respect 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 through a die to obtain a sheet-like resin foam. The obtained resin foam was sliced into a thickness of 0.5 mm and rolled to a thickness of 0.15 mm with a hot melt roll at 200° C. to obtain a resin foam in which a hot melt layer was formed. A double-sided pressure-sensitive adhesive sheet A was attached to one side of the resin foam to obtain a foamed member.
The obtained foamed member was subjected to the above evaluation. Table 3 shows the results.

[Example 24]
A foamed member was obtained in the same manner as in Example 23, except that the amount of magnesium hydroxide compounded was 120 parts by weight. The obtained foamed member was subjected to the above evaluation. Table 3 shows the results.

[Example 25]
A foamed member was obtained in the same manner as in Example 23, except that the amount of magnesium hydroxide compounded was 140 parts by weight. The obtained foamed member was subjected to the above evaluation. Table 3 shows the results.

[Comparative Example 1]
Polypropylene (MFR: 0.4 g/10 min. Ethylene content: 0% by weight, propylene content: 100% by weight, weight average molecular weight: 108000, molecular weight distribution: 4.93) 35 parts by weight, thermoplastic elastomer composition a [a blend of polypropylene (PP) and ethylene/propylene/5-ethylidene-2-norbornene three-dimensional copolymer (EPT) (crosslinked olefinic thermoplastic elastomer, TPV), polypropylene and ethylene/propylene/5-ethylene 15.0% by weight of carbon black containing 15.0% by weight of tylidene-2-norbornene three-dimensional copolymer]: 60 parts by weight, 10 parts by weight of magnesium hydroxide, 10 parts by weight of carbon, and 1 part by weight of stearic acid monoglyceride were kneaded at a temperature of 200° C. in a twin-screw kneader manufactured by Japan Steel Works (JSW), extruded into strands, cooled with water, and formed into pellets. The pellets were put into a single-screw extruder manufactured by Japan Steel Works, Ltd., and carbon dioxide gas was injected under an atmosphere of 220° C. and a pressure of 13 MPa (12 MPa after injection). Carbon dioxide gas was injected at a rate of 4.5 parts by weight with respect 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 through a die to obtain a sheet-like resin foam. The skin layer of the obtained resin foam was removed by slicing, and the resin foam was obtained by slicing to a thickness of 0.5 mm. A double-sided pressure-sensitive adhesive sheet B was attached to one side of the resin foam to obtain a foamed member.
The obtained foamed member was subjected to the above evaluation. Table 4 shows the results.

[Comparative Example 2]
A resin foam was obtained in the same manner as in Comparative Example 1, except that the thickness of the resin foam was 1 mm. A double-sided pressure-sensitive adhesive sheet C was attached to one side of the resin foam to obtain a foamed member. The obtained foamed member was subjected to the above evaluation. Table 4 shows the results.

[Comparative Example 3]
A resin foam was obtained in the same manner as in Comparative Example 1, except that the thickness of the resin foam was 2 mm. A double-sided pressure-sensitive adhesive sheet A was attached to one side of the resin foam to obtain a foamed member. The obtained foamed member was subjected to the above evaluation. Table 4 shows the results.

[Comparative Example 4]
A resin foam was obtained in the same manner as in Comparative Example 1, except that the thickness of the resin foam was 1 mm. A double-sided pressure-sensitive adhesive sheet D was attached to one side of the resin foam to obtain a foamed member. The obtained foamed member was subjected to the above evaluation. Table 4 shows the results.

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

100 Foam member 110 Resin foam 120 Adhesive body 121 Adhesive layer

Claims

A resin foam and an adhesive disposed on at least one side of the resin foam,
The adherent comprises an adhesive layer,
The product of the total thickness (μm) of the adhesive layer and the thickness (mm) of the resin foam is 45 or less,
In the adherent, the total emission amount of toluene outgas and ethyl acetate outgas is 8.0 μg/g or less.
foam material.
The adherent further comprises a substrate,
wherein the pressure-sensitive adhesive layer is arranged between the substrate and the resin foam;
The foam member according to claim 1.
The foam member according to claim 2, wherein the adhesive is an adhesive sheet.
The foaming member according to claim 2, wherein the adhesive body comprises the adhesive layers arranged on both sides of the base material.
The foam member according to claim 2, wherein the base material is made of polyethylene terephthalate.
The foamed member according to claim 1, wherein the thickness recovery rate after maintaining for 120 seconds under a load of 1000 g/cm 2 is 55% or more.
The foamed member according to claim 1, wherein the resin foam has an average cell diameter of 200 µm or less.
The foamed member according to claim 1, wherein the resin foam has an apparent density of 0.4 g/ cm3 or less.
The foamed member according to claim 1, wherein the coefficient of variation of cell diameter of the resin foam is 0.5 or less.
The foamed member according to claim 1, wherein the resin foam has a cell number density of 30 cells/mm2 or more.
The foamed member according to claim 1, wherein the resin foam has a void content of 30% or more.
The foamed member according to claim 1, wherein the resin foam contains a polyolefin resin.　
The foamed member according to claim 12, wherein the polyolefin-based resin is a mixture of a polyolefin other than a polyolefin-based elastomer and a polyolefin-based elastomer.
The foamed member according to claim 1, which has a heat-melting layer on one side or both sides of the resin foam.
The foamed member according to claim 1, wherein the adhesive layer contains a water-dispersible adhesive.
The foamed member according to claim 1, wherein another pressure-sensitive adhesive layer is formed on the surface of the resin foam opposite to the pressure-sensitive adhesive layer.