JP2022023200A - Foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam sheet having exceptional low moisture permeability and high impact resistance, a foam sheet endowed with both high-speed impact resistance and low-speed impact resistance, a foam sheet having high handling performance while maintaining high impact resistance, and a foam sheet having high impact resistance and tensile properties suitable for handling.

SOLUTION: A foam sheet has a glass transition temperature (Tg) ranging from -60°C to 0°C and a loss tangent (tanδ) peak value of 0.25 or higher.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a foam sheet, for example, a foam sheet used as a cushioning material for a display.

In portable electronic devices such as notebook personal computers, mobile phones, smartphones, and tablets, cushioning materials may be arranged on the back side of the display device in order to prevent damage or failure. High flexibility is required for the cushion material, and a foam sheet has been widely used conventionally.
In recent years, as electronic devices have become more sophisticated, the housings of devices have become larger. In addition, smartphones and tablets that are used while being carried around, wall-mounted TVs installed in commercial facilities, and other uses other than those used by placing them on a flat surface as in the past are increasing. As a result, the risk of dropping the device is increasing, and the risk of destruction between the panel and the housing is also increasing accordingly. Therefore, a fixing method between the panel and the housing, which is less likely to be broken, is being sought, and a foam sheet having higher impact resistance is required.
In addition, with the increase in screen size of electronic devices such as smartphones, the adhesive area between the screen and the housing is becoming smaller. For example, as shown in FIG. 1, the width (adhesive area) of the foam tape 2 becomes smaller as the screen size increases while the external dimensions of the screen 1 remain the same. Therefore, the foam tape is required to have better impact resistance than before.
Under such circumstances, for example, acrylic foam has been proposed as a material having high impact resistance (see Patent Document 1).

Special table 2012-591750

By the way, as described above, in electronic devices such as smartphones, the adhesive area between the screen and the housing is becoming smaller as the screen size is increased. Therefore, the width of the adhesive tape that separates the outside from the inside is narrowed, and moisture easily penetrates into the inside. Further, in addition to this, even if the material has impact resistance, which has not been a problem until now, the shortage of impact resistance becomes apparent due to the narrow width of the tape.
Although the acrylic foam mentioned above is a material with high impact resistance, it has high water vapor permeability, and the invading moisture causes corrosion (rust generation, etc.) of the metal used for electronic devices, resulting in malfunction or failure. May cause.

In addition, heavy equipment such as wall-mounted TVs installed in the above-mentioned commercial facilities imposes a heavy load on fixing between the panel and the housing, so the foam sheet used for these equipment has excellent low-speed impact resistance. Desired. On the other hand, the impact resistance against dropping and impact from the outside is high-speed impact resistance, and there is a demand for a foam sheet having both low-speed impact resistance and high-speed impact resistance.
The acrylic foam described above is a material having excellent high-speed impact resistance, but has low impact resistance at low speeds, and is not suitable for fixing a wall-mounted television, for example.

Further, although the acrylic foam described above is a material having high impact resistance, it has high flexibility and high tackiness, so that it is complicated to handle, and it is particularly necessary to take measures against blocking. As a blocking measure and a method of reinforcing mechanical strength, a method of bonding with a resin sheet is taken, but when bonding a foam sheet and a resin sheet, a roll-to-roll format is adopted from the viewpoint of productivity. In many cases, transport tension is applied during bonding. Effervescent sheets with high flexibility are deformed and stretched with low stress, so they shrink after bonding, and there are problems such as peeling and wrinkling due to the difference in shrinkage with the resin sheet. ..

Further, although the acrylic foam described above is a material having high impact resistance, it has a high tack property, so that it has difficulty in handling. For example, the acrylic film (acrylic foam) has a problem of adhering to a production machine because of its high tackiness, and there is a problem that the foam sheet is twisted during use and becomes unusable. ..
On the other hand, if a sheet having low flexibility is used in order to suppress tackiness, the followability will be inferior, and when it is used for an electronic device or the like, floating will occur and problems such as deterioration of airtightness will occur. It is possible to make it.

Therefore, an object of the present invention (first invention) is to provide a foam sheet having excellent low moisture permeability and high impact resistance. Another object of the present invention (second invention) is to provide a foam sheet having both high-speed impact resistance and low-speed impact resistance. Further, it is an object of the present invention (third invention) to provide a foam sheet having high impact resistance and tensile properties suitable for handling. Another object of the present invention (fourth invention) is to provide a foam sheet having high handling performance while maintaining high impact resistance.

As a result of diligent studies, the present inventors have found that the above problems can be solved by setting the glass transition temperature (Tg) and the loss tangent (tan δ) within a certain range and keeping the moisture permeability below a certain value. , The present invention (first invention) has been completed. Further, they have found that the above problems can be solved by setting the glass transition temperature (Tg) and the loss tangent (tanδ) within a certain range and setting the interlayer strength to a certain value or more, and the present invention (second invention). Was completed. Further, they have found that the above problems can be solved by setting the glass transition temperature (Tg) and the loss tangent (tanδ) within a certain range and setting the elongation in the tensile direction in the tensile test to a certain value or less, and the present invention (1). The third invention) was completed. Furthermore, they have found that the above problems can be solved by setting the glass transition temperature (Tg) and the loss tangent (tanδ) within a certain range and setting the tackiness of the surface to a certain value or less. Invention) was completed.

That is, the present invention provides the following [1] to [15].
[1] The glass transition temperature (Tg) is -60 to 0 ° C., the peak value of loss tangent (tan δ) is 0.25 or more, and the moisture permeability (WVTR) is 200 g / m ² · day or less. Foam sheet.
[2] The glass transition temperature (Tg) is -60 to 0 ° C., the peak value of loss tangent (tanδ) is 0.25 or more, and the interlayer strength in the tensile test at a speed of 100 mm / min is 2.00 MPa. The foam sheet that is above.
[3] When the glass transition temperature (Tg) is -60 to 0 ° C., the peak value of the loss tangent (tan δ) is 0.25 or more, and the stress in the tensile direction is 0.06 N / 10 mm in the tensile test. A foam sheet having an elongation in the tensile direction of 4% or less.
[4] A foam sheet having a glass transition temperature (Tg) of -60 to 0 ° C., a peak value of tangent loss (tan δ) of 0.25 or more, and a surface tackiness of 5000 gf / cm ² or less. ..
[5] The foam sheet according to any one of the above [1] to [4], which has a 25% compressive strength of 1000 kPa or less.
[6] The foam sheet according to any one of the above [1] to [5], wherein the closed cell ratio is 80% or more.
[7] The foam sheet according to any one of the above [1] to [6], which has a thickness of 0.03 to 2 mm.
[8] The foam sheet according to any one of [1] to [7] above, wherein the storage elastic modulus at 23 ° C. is 2 × 10 ³ Pa or more.
[9] The foam sheet according to any one of [1] to [8] above, wherein the storage elastic modulus at −20 ° C. is 1.0 × 10 ⁵ Pa or more.
[10] The foam sheet according to any one of [1] to [9] above, wherein the breaking point strength at 23 ° C. is 2.0 N / 10 mm or more.
[11] The foam sheet according to any one of the above [1] to [10], which has an average bubble diameter of 20 to 400 μm.
[12] The foam sheet according to any one of the above [1] to [11], which has an apparent density of 0.10 to 0.70 g / cm ³ .
[13] Any of the above [1] to [12] containing the elastomer (A) and the polyolefin resin (B) and having a mass ratio of the component (A) to the component (B) of 90:10 to 40:60. The foam sheet according to item 1.
[14] The foam sheet according to any one of the above [1] to [13], which has a gel fraction of 30 to 80% by mass.
[15] An adhesive tape comprising the foam sheet according to any one of the above [1] to [14] and an adhesive material provided on at least one surface of the foam sheet.

The foam sheet according to the first aspect of the present invention is a foam sheet having excellent low moisture permeability and high impact resistance. Further, the foam sheet according to the second aspect of the present invention is a foam sheet having both high-speed impact resistance and low-speed impact resistance. Further, the foam sheet according to the third aspect of the present invention is a foam sheet having high impact resistance and excellent handleability. Further, the foam sheet according to the fourth aspect of the present invention is a foam sheet having high impact resistance and excellent handleability.

It is a conceptual diagram which shows the screen of a smartphone, a housing, and a foam tape. It is a schematic diagram which shows the measuring apparatus of the interlayer strength.

Hereinafter, the foam sheet of the present invention will be described in more detail.
[Effervescent sheet]
The foam sheet according to the first aspect of the present invention has a glass transition temperature (Tg) of −60 to 0 ° C., a peak value of loss tangent (tan δ) of 0.25 or more, and moisture permeability (WVTR). ) Is 200 g / m ² · day or less.
Further, the foam sheet according to the second aspect of the present invention has a glass transition temperature (Tg) of −60 to 0 ° C., a peak value of loss tangent (tan δ) of 0.25 or more, and a speed of 100 mm. It is characterized in that the interlayer strength in the tensile test at / min is 2.00 MPa or more.
Further, the foam sheet according to the third aspect of the present invention has a glass transition temperature (Tg) of −60 to 0 ° C., a peak value of loss tangent (tan δ) of 0.25 or more, and tensile strength. In the test, when the stress in the tensile direction is 0.06 N / 10 mm, the elongation in the tensile direction is 4% or less.
Further, the foam sheet according to the fourth aspect of the present invention has a glass transition temperature (Tg) of −60 to 0 ° C., a peak value of loss tangent (tan δ) of 0.25 or more, and a surface surface. The tackiness is 5000 gf / cm ² or less.

[Glass-transition temperature]
The foam sheet of the present invention has a glass transition temperature (hereinafter, may be referred to as “Tg”) of −60 to 0 ° C. When Tg is within this range, excellent impact resistance, particularly excellent high-speed impact resistance, can be obtained. From the above viewpoint, Tg is preferably in the range of −30 ° C. to −5 ° C., and more preferably in the range of −25 ° C. to −10 ° C. In the present invention, the temperature at the peak top of the loss tangent (tan δ) obtained by viscoelasticity measurement was defined as Tg. Further, when there are a plurality of peaks of tan δ, if at least one of them is within the above range, excellent impact resistance, particularly excellent high-speed impact resistance is exhibited.

[Loss tangent]
The foam sheet of the present invention has a peak value of tangent loss (hereinafter referred to as "tan δ") measured by dynamic viscoelasticity measurement at a measurement frequency of 10 Hz in the range of -60 to 0 ° C. of 0.25 or more. Is. tan δ is the ratio (G'' / G') of the storage shear modulus (G') and the loss shear modulus (G''), and how much energy the material absorbs when the material is deformed (heat). Will it change to?). When the peak value of tan δ is 0.25 or more, the foam sheet of the present invention can exhibit excellent impact resistance, particularly excellent high-speed impact resistance. From the above viewpoint, the peak value of tan δ is preferably 0.40 or more, and more preferably 0.50 or more.
The Tg and the loss tangent (tan δ) are values measured by the method described in the examples. Here, when two or more points of Tg are observed, it is preferable that at least one point of Tg is within the above temperature range and the peak value of tan δ at that Tg is within the above range. However, typically, it is preferable that one point of Tg is observed, the Tg is within the above temperature range, and the peak value of tan δ at the Tg is within the above range.

[Humidity permeability]
The foam sheet of the present invention (particularly, the foam sheet according to the first invention) preferably has a water vapor transmission rate (WVTR: Water Vapor Transmission Rate) of 200 g / m ² · day or less. When the moisture permeability is 200 g / m ² · day or less, it is possible to prevent the invasion of moisture into the inside of an electronic device or the like. From the above viewpoint, the moisture permeability is preferably 100 g / m ² · day or less, and more preferably 70 g / m ² · day or less.
The lower limit is not particularly limited, but is usually about 5 g / m ² · day.
The moisture permeability is a value measured by the method described in the examples.

[Interlayer strength]
The foam sheet of the present invention (particularly, the foam sheet according to the second invention) preferably has an interlayer strength of 2.00 MPa or more in a tensile test at a speed of 100 mm / min. When the interlayer strength is 2.00 MPa or more, excellent low-speed impact resistance can be exhibited. From the above viewpoint, the interlayer strength is preferably 2.15 MPa or more, more preferably 2.20 MPa or more. The upper limit is not particularly limited, but is usually about 6.00 MPa.
The interlayer strength is a value measured by the method described in Examples.

[Elongation in the tensile direction]
The foam sheet of the present invention (particularly, the foam sheet according to the third invention) preferably has an elongation in the tensile direction of 4% or less when the stress in the tensile direction is 0.06 N / 10 mm in a tensile test. .. By satisfying this condition, peeling and wrinkles do not occur even when the resin sheet is bonded to the resin sheet, and the handleability is extremely good. From the above viewpoint, the elongation is more preferably 3.5% or less, and further preferably 3% or less.
The lower limit is not particularly limited, but is preferably 0.3% or more from the viewpoint of obtaining sufficient impact resistance.
The elongation in the tensile direction is a value measured by the method described in the examples.

[Tackiness]
The foam sheet of the present invention (particularly, the foam sheet according to the fourth invention) preferably has a surface tackiness of 5000 gf / cm ² or less. When the tack property is 5000 gf / cm ² or less, the handleability of the foam sheet is improved in the manufacturing process, and the productivity can be improved. From the viewpoint of improving productivity, the tackiness of the surface is preferably 4500 gf / cm ² or less, more preferably 4000 gf / cm ² or less, and further preferably 3500 gf / cm ² or less.
The tackiness of the surface of the foam sheet is a value measured by the method described in Examples.

[Compressive strength]
The foam sheet of the present invention preferably has a 25% compressive strength of 1000 kPa or less. By setting the compressive strength to 1000 kPa or less, the followability is excellent, and when used as a tape base material or the like, the adhesive strength at the time of adhesion is improved. From the above viewpoint, the 25% compressive strength is more preferably 600 kPa or less, further preferably 500 kPa or less, and particularly preferably 470 kPa or less.
The lower limit is not particularly limited, but is usually about 10 kPa, preferably 20 kPa or more.
The 25% compressive strength is a value measured at a measurement temperature of 23 ° C. by a measurement method based on JIS K6767.

[Breaking point strength]
The breaking point strength of the foam sheet of the present invention at 23 ° C. is preferably 2.0 N / 10 mm or more. When the breaking point strength is 2.0 N / 10 mm or more, good impact resistance can be obtained. From the above viewpoint, the breaking point strength is more preferably 2.5 N / 10 mm or more, and further preferably 4.0 N / 10 mm or more.
The upper limit of the breaking point strength is not particularly limited, but is usually about 50 N / 10 mm, preferably 40 N / 10 mm or less.
The breaking point strength is a value measured by the method described in the examples.

[Storage modulus]
The foam sheet of the present invention preferably has a storage elastic modulus of 2.0 × 10 ³ Pa or more at 23 ° C. When the storage elastic modulus is 2.0 × 10 ³ Pa or more, the impact resistance, particularly the low-speed impact resistance can be improved. From the above viewpoint, the storage elastic modulus is preferably 1.0 × 10 ⁴ Pa or more, and more preferably 1.0 × 10 ⁵ Pa or more.
The upper limit is not particularly limited, but is usually about 1.0 × 10 ¹² Pa, and is preferably 1.0 × 10 ¹⁰ Pa or less from the viewpoint of flexibility.
Further, the foam sheet of the present invention preferably has a storage elastic modulus of 1.0 × ¹⁰⁵ Pa or more at −20 ° C. When the storage elastic modulus at −20 ° C. is 1.0 × ¹⁰⁵ Pa or more, the high-speed impact resistance is particularly good. From the above viewpoint, the storage elastic modulus at −20 ° C. is more preferably 1.0 × 10 ⁶ Pa or more, and further preferably 1.0 × 10 ⁷ Pa or more.
Further, from the viewpoint of improving high-speed impact resistance, the storage elastic modulus at -60 ° C is preferably 1.0 × ¹⁰⁶ Pa or more, and the storage elastic modulus at 0 ° C is 1. It is preferably 0 × 10 ⁴ Pa or more.
The storage elastic modulus is a value measured by the method described in Examples.

(Apparent density)
The apparent density of the foam sheet of the present invention is preferably 0.05 g / cm ³ to 0.70 g / cm ³ , more preferably 0.10 g / cm ³ to 0.70 g / cm ³ . It is more preferably 0.15 g / cm ³ to 0.70 g / cm ³ , and particularly preferably 0.20 g / cm ³ to 0.70 g / cm ³ .
When the apparent density is within the above range, it becomes easy to improve the flexibility and cushioning property of the foam sheet. In addition, a certain level of mechanical strength is imparted to the foam sheet, and it becomes easy to improve impact resistance and the like. Further, when the value is not less than the above lower limit value, the moisture proof property is improved, and the WVTR is easily set to be not more than the above upper limit value. The apparent density is a value measured in accordance with JIS K7222 (2005).

[Crosslinkability (gel fraction)]
The foam sheet of the present invention is preferably crosslinked, and the degree of crosslinking represented by the gel fraction is preferably 30 to 80% by mass. By setting the degree of cross-linking within the above range, the foam sheet tends to have good impact resistance while ensuring a certain degree of flexibility and cushioning property. From the above viewpoint, the gel fraction is more preferably 40 to 70% by mass, further preferably 45 to 65% by mass.
The method for measuring the gel fraction is a value measured by the method described in Examples.

[Closed cell ratio]
The foam sheet of the present invention preferably has a closed cell ratio of 80% or more. When the closed cell ratio is 80% or more, the waterproof property and the moisture proof property are enhanced, and the moisture permeability is easily achieved (particularly, the foam sheet according to the first invention). Further, when the closed cell ratio is 80% or more, impact resistance can be ensured (particularly, the foam sheet according to the second to fourth inventions). From the above viewpoint, the closed cell ratio of the foam sheet is more preferably 90% or more. The higher the closed cell ratio, the better, and it may be 100% or less. In addition, the cushioning property and the impact resistance are improved, and it becomes easy to maintain the original elasticity of the foam sheet even after heating or cooling. There is also an advantage that the rate of change in compressive strength tends to be low.
The closed cell ratio was measured by the method described in Examples.

[Average bubble diameter]
The foam sheet of the present invention preferably has an average cell diameter of 20 to 400 μm. When the average bubble diameter is in the above range, the impact resistance is good. Further, in the first invention, the moisture permeability tends to be good. From the above viewpoint, the average bubble diameter is more preferably 50 to 200 μm, and further preferably 70 to 160 μm.
The average cell diameter in the present invention is the larger of the average value of the bubble diameter in the machine direction (MD: Machine Direction) and the average value of the bubble diameter in the direction perpendicular to the MD (TD: Transverse Direction). Is.
The average bubble diameter was measured by the method described in Examples.

[Thickness]
The thickness of the foam sheet of the present invention is preferably 0.03 to 2.0 mm. In particular, in the third invention, when the thickness is in this range, it is advantageous to suppress deformation and elongation under low stress. When the thickness is 0.03 mm or more, it becomes easy to secure the cushioning property of the foam sheet, and in particular, in the fourth invention, the impact resistance is further improved. Further, when the thickness is 2.0 mm or less, the thickness can be reduced, and it can be suitably used for thin electronic devices such as smartphones and tablets. Furthermore, it becomes easy to secure the flexibility of the foam sheet.
From these viewpoints, the thickness of the foam sheet is more preferably 0.1 to 1.0 mm, further preferably 0.15 to 0.7 mm.
The thickness was measured with a dial gauge.

The foam sheet of the present invention preferably contains an elastomer (A) and a polyolefin resin (B). By using the elastomer and the polyolefin resin, it becomes easy to secure flexibility and impact resistance while improving foamability and the like.

[Elastomer (A)]
Examples of the elastomer (A) include thermoplastic elastomers and ethylene-α-olefin copolymer rubbers. Examples of the thermoplastic elastomer include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and the like. As the elastomer (A), these components may be used alone or in combination of two or more.
Among these, olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, and ethylene-α-olefin-based copolymer rubbers are preferable, styrene-based thermoplastic elastomers, ethylene-α-olefin-based copolymer rubbers are more preferable, and styrene-based rubbers are more preferable. Thermoplastic elastomers are more preferred.

(Olefin-based thermoplastic elastomer)
Olefin-based thermoplastic elastomers (TPOs) generally have polyolefins such as polyethylene and polypropylene as hard segments, and butyl rubber, halobutyl rubber, EPDM (ethylene-propylene-diene rubber), EPM (ethylene-propylene rubber), NBR ( The soft segment is a rubber component such as (acrylonitrile-polyolefin rubber) and natural rubber. As the olefin-based thermoplastic elastomer (TPO), any of a blend type, a dynamic cross-linking type, and a polymerization type can be used.
Preferable specific examples of the rubber component include the above-mentioned EPM and EPDM, and EPDM is particularly preferable. Examples of EPDM include ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber and ethylene-propylene-dicyclopentadiene copolymer rubber. Among these, ethylene-propylene-dicyclopentadiene copolymer rubber is used. preferable.

Further, examples of the olefin-based thermoplastic elastomer include a block copolymer type. Examples of the block copolymer type include those having a crystalline block and a soft segment block, and more specifically, a crystalline olefin block-ethylene / butylene copolymer-crystalline olefin block copolymer (CEBC) is exemplified. Will be done. In CEBC, the crystalline olefin block is preferably a crystalline ethylene block, and examples of such a commercially available product of CEBC include "DYNARON 6200P" manufactured by JSR Corporation.

(Styrene-based thermoplastic elastomer)
Examples of the styrene-based thermoplastic elastomer include a block copolymer having a polymer or copolymer block of styrene and a polymer or copolymer block of a conjugated diene compound. Examples of the conjugated diene compound include isoprene and butadiene.
The styrene-based thermoplastic elastomer used in the present invention may or may not be hydrogenated, but hydrogenation is preferable. When hydrogenating, hydrogenation can be performed by a known method.

The styrene-based thermoplastic elastomer is usually a block copolymer, and is a styrene-isoprene block copolymer (SI), a styrene-isoprene-styrene block copolymer (SIS), or a styrene-butadiene block copolymer (SB). , Steryl-butadiene-styrene block copolymer (SBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / Propropylene-styrene block copolymer (SEEPS), styrene-ethylene / butylene block copolymer (SEB), styrene-ethylene / propylene block copolymer (SEP), styrene-ethylene / butylene-crystalline olefin block copolymer (SEBC) and the like. As the above-mentioned styrene-based thermoplastic elastomer, block copolymers are preferable, among them, SIS, SEBS, SEPS, SEEPS and SEBC are more preferable, and SEEPS and SEBS are even more preferable.

Examples of the SIS include Kuraray Co., Ltd., trade name "Hybler (registered trademark) 5125" (styrene content 20% by mass, Tg = -13 ° C.), and SEPS is a commercially available product of SEPS Co., Ltd. Examples thereof include Kuraray's trade name "Hybuler (registered trademark) 7125F" (styrene content 20% by mass, Tg = -15 ° C.). Examples of the commercially available SEEPS product include Kuraray Co., Ltd., trade name "Hybler (registered trademark) 7311F" (styrene content 12% by mass, Tg = −32 ° C.).
Examples of commercially available SEBS products include the Tough Tech (registered trademark) series manufactured by Asahi Kasei Corporation.

The styrene-based thermoplastic elastomer according to the present invention preferably has a maximum peak temperature of tan δ of −60 to 25 ° C. as measured by dynamic viscoelasticity measurement. When the maximum peak temperature of tan δ is relatively low as described above, the heat loss in the high-speed deformation region such as impact fracture becomes large, and the fracture strength of the foamed sheet tends to be improved. On the other hand, if the maximum peak temperature of tan δ is outside the above range, it may be difficult to improve the breaking strength and flexibility of the foamed sheet. From the above viewpoint, the maximum peak temperature of tan δ of the styrene-based thermoplastic elastomer is more preferably −35 to 10 ° C., and even more preferably −35 to 0 ° C.
In the present specification, the "maximum peak temperature of tan δ" refers to a value measured by a dynamic viscoelasticity measuring device in a tensile mode, a temperature rising rate of 10 ° C./min, and a frequency of 10 Hz. Examples of the dynamic viscoelasticity measuring device that can be used for the measurement include "Leovibron DDV-III" manufactured by Orientec Co., Ltd.

The styrene-based thermoplastic elastomer has a structural unit derived from styrene, which makes it possible to improve the impact resistance of the foamed sheet. The styrene content in the styrene-based thermoplastic elastomer is preferably 5 to 50% by mass. By setting the styrene content in the above range, excellent impact resistance can be obtained. Further, when the value is not more than the above upper limit, the compatibility with the polyolefin resin (B) described in detail later becomes good, and the crosslinkability and foamability tend to be good. From these viewpoints, the styrene content in the styrene-based thermoplastic elastomer is more preferably 7 to 40% by mass, further preferably 7 to 30% by mass.

The number average molecular weight of the styrene-based thermoplastic elastomer is not particularly limited, but is preferably 30,000 to 800,000, more preferably 120,000 to 180,000 from the viewpoint of fracture strength and processability.
The number average molecular weight is a potistyrene-equivalent value measured by gel permeation chromatography (GPC).

[Ethylene-α-olefin copolymer rubber]
The α-olefins used in the ethylene-α-olefin copolymer rubber include propylene, 1-butene, 2-methylpropylene, 3-methyl-1-butene, 1-pentene, 1-hexene and 4-methyl-. Examples thereof include one or more α-olefins having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms such as 1-pentene and 1-octene. Among these, propylene and 1-butene are preferable, and 1-butene is more preferable.
The ethylene-α-olefin-based copolymer rubber used here is an amorphous or low-crystalline rubber-like substance obtained by substantially randomly copolymerizing two or more kinds of olefin-based monomers.

The ethylene-α-olefin copolymer rubber may have other monomer units in addition to the ethylene unit and the α-olefin unit.
Examples of the monomer forming the other monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like. Conjugate diene with 4-8 carbon atoms: dicyclopentadiene, 5-ethylidene-2-norbornene, 1,4-hexadiene, 1,5-dicyclooctadiene, 7-methyl-1,6-octadien, 5-vinyl- Non-conjugated diene having 5 to 15 carbon atoms such as 2-norbornene: Vinyl ester compound such as vinyl acetate: Unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate: Examples thereof include unsaturated carboxylic acids such as acrylic acid and methacrylic acid. These monomers can be used alone or in combination of two or more. Among these, non-conjugated diene having 5 to 15 carbon atoms is preferable, and 5-ethylidene-2-norbornene, 1,4-hexadiene, and dicyclopentadiene (DCPD) are more preferable from the viewpoint of availability.

The ethylene unit content of the ethylene-α-olefin copolymer rubber is usually 30 to 85% by mass, preferably 40 to 80% by mass, more preferably 45 to 75% by mass, and has 3 to 3 carbon atoms of propylene or the like. The content of 15, preferably 3 to 10 α-olefin units is usually 10 to 60% by weight, preferably 15 to 50% by weight, and the content of other monomeric units such as non-conjugated diene is usually. It is 0 to 20% by mass, preferably 1 to 10% by mass.

As the ethylene-α-olefin copolymer rubber, a ternary copolymer such as EPDM (ethylene-propylene-diene rubber) or EBDM (ethylene-butene-1-diene rubber) is preferable. Examples of the ethylene-α-olefin copolymer include "EBT K-9330" manufactured by Mitsui Chemicals, Inc.

[Polyolefin resin (B)]
The polyolefin resin is a thermoplastic resin, and specific examples thereof include polyethylene resin, polypropylene resin, polybutene resin, ethylene-vinyl acetate copolymer, and the like, and polyethylene resin is preferable among them.
Further, as the polyethylene resin, low density polyethylene (LDPE) is preferable, and linear low density polyethylene (LLDPE) is more preferable.
Further, examples of the polyethylene resin include polyethylene resins polymerized with a polymerization catalyst such as a Ziegler-Natta catalyst, a metallocene catalyst, and a chromium oxide compound, and a polyethylene resin polymerized with a metallocene catalyst is preferably used.

(Metallocene catalyst)
Examples of the metallocene catalyst include compounds such as a bis (cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. More specifically, one or more cyclopentadienyl rings or their analogs are present as ligands in tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum. Can be mentioned.
In such a metallocene catalyst, the properties of active sites are uniform, and each active site has the same activity. Since the polymer synthesized using the metallocene catalyst has high uniformity in molecular weight, molecular weight distribution, composition, composition distribution, etc., when a sheet containing the polymer synthesized using the metallocene catalyst is crosslinked, the cross-linking is uniform. Proceed to. Since the uniformly crosslinked sheet is uniformly foamed, it becomes easy to stabilize the physical properties. Moreover, since it can be uniformly stretched, the thickness of the foam can be made uniform.

Examples of the ligand include a cyclopentadienyl ring, an indenyl ring and the like. These cyclic compounds may be substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. Examples of the hydrocarbon group include a methyl group, an ethyl group, various propyl groups, various butyl groups, various amyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups and various decyl groups. , Various cetyl groups, phenyl groups and the like. In addition, "various" means various isomers including n-, sec-, tert-, and iso-.
Further, a cyclic compound polymerized as an oligomer may be used as a ligand.
Furthermore, in addition to π-electron unsaturated compounds, monovalent anion ligands such as chlorine and bromine, divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, phosphides, arylphosphides, etc. May be used.

Examples of metallocene catalysts containing tetravalent transition metals and ligands include cyclopentadienyl titaniumtris (dimethylamide), methylcyclopentadienyl titaniumtris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, and dimethyl. Examples thereof include silyltetramethylcyclopentadienyl-t-butylamide zirconium dichloride.
The metallocene catalyst exerts an action as a catalyst in the polymerization of various olefins by combining with a specific co-catalyst (co-catalyst). Specific examples of the co-catalyst include methylaluminoxane (MAO), boron-based compounds and the like. The ratio of the cocatalyst used to the metallocene catalyst is preferably 100 to 1 million mol times, more preferably 50 to 5,000 mol times.

Further, as the polyethylene resin, linear low-density polyethylene is preferable. The linear low-density polyethylene is obtained by copolymerizing ethylene (for example, 75% by mass or more, preferably 90% by mass or more with respect to the total amount of monomers) and, if necessary, a small amount of α-olefin. Chain low density polyethylene is more preferred. Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Of these, α-olefins having 4 to 10 carbon atoms are preferable.
The density of the polyethylene resin, for example, the above-mentioned linear low-density polyethylene is preferably 0.870 to 0.925 g / cm ³ , more preferably 0.890 to 0.925 g / cm ³ , and 0. .910 to 0.925 g / cm ³ is more preferable. As the polyethylene resin, a plurality of polyethylene resins may be used, or polyethylene resins other than the above-mentioned density range may be added.

Examples of the ethylene-vinyl acetate copolymer used as the polyolefin resin include an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene.
Examples of the polypropylene resin include homopolypropylene and a propylene-α-olefin copolymer containing 50% by mass or more of propylene. These may be used alone or in combination of two or more. Specific examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-hexene, and 1-. Examples thereof include octene, and among these, α-olefins having 6 to 12 carbon atoms are preferable.
Examples of the polybutene resin include a homopolymer of butene-1 and a copolymer with ethylene or propylene.

[Mass ratio of elastomer (A) and polyolefin resin (B)]
The mass ratio of the elastomer (A) to the polyolefin resin (B) is preferably 90:10 to 40:60. Within this range, it is possible to easily manufacture a foam sheet that exhibits the effects of the present invention. From the viewpoint of obtaining a more effective foam sheet, the mass ratio of the component (A) to the component (B) is more preferably in the range of 80:20 to 40:60, and 80:20 to 50. : 50 is more preferable, and a mass ratio of 80:20 to 60:40 is particularly preferable.

[Additive]
The foam sheet of the present invention is preferably obtained by foaming an effervescent composition containing the above resin and a foaming agent. As the foaming agent, a pyrolytic foaming agent is preferable.
As the pyrolytic foaming agent, an organic foaming agent and an inorganic foaming agent can be used. Examples of the organic foaming agent include azodicarbonamides, azodicarboxylic acid metal salts (azodicarboxylic acid barium, etc.), azobisisobutyronitrile and other azo compounds: N, N'-dinitrosopentamethylenetetramine and other nitroso compounds: hydra. Hydrazin derivatives such as zodicarbonamide, 4,4'-oxybis (benzenesulfonyl hydrazide), and toluenesulfonylhydrazide: semicarbazide compounds such as toluenesulfonyl semicarbazide can be mentioned.
Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium boron hydride, anhydrous monosoda citrate and the like.
Among these, azo compounds are preferable, and azodicarbonamides are more preferable, from the viewpoint of obtaining fine bubbles, economy, and safety.
One type of pyrolysis foaming agent may be used alone, or two or more types may be used in combination.

The blending amount of the foaming agent in the effervescent composition is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 1.5 parts by mass or more and 15 parts by mass or less, and 3 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the resin. It is more preferably parts by mass or less. By setting the blending amount of the foaming agent to 1 part by mass or more, the foamable sheet is appropriately foamed, and it becomes possible to impart appropriate flexibility and shock absorption to the foam sheet. Further, by setting the blending amount of the foaming agent to 20 parts by mass or less, it is possible to prevent the foam sheet from foaming more than necessary, and it is possible to improve the mechanical strength of the foam sheet.

The effervescent composition may contain a decomposition temperature adjusting agent. The decomposition temperature adjusting agent is compounded as having a controlling function such as lowering the decomposition temperature of the thermally decomposing foaming agent and accelerating the decomposition rate, and specific compounds include zinc oxide, zinc stearate, and urea. And so on. The decomposition temperature adjusting agent is blended in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin, for example, in order to adjust the surface condition of the foam sheet.

The effervescent composition may contain an antioxidant. Examples of the antioxidant include phenolic antioxidants such as 2,6-di-t-butyl-p-cresol, sulfur-based antioxidants, phosphorus-based antioxidants, amine-based antioxidants and the like. For example, the antioxidant is blended in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin.
In addition to these, the effervescent composition may contain additives generally used for foams such as heat stabilizers, colorants, flame retardants, antistatic agents, and fillers.

In the foam sheet, the elastomer (A) and the polyolefin resin (B) are the main components, and the total content of the components (A) and (B) is, for example, 70% by mass or more based on the total amount of the foam sheet. It is preferably 80% by mass or more, more preferably 90% by mass or more.

[Manufacturing method of foam sheet]
The foam sheet of the present invention is not particularly limited, but can be produced by heating an effervescent sheet made of an effervescent composition containing at least a resin and a pyrolytic foaming agent to foam the pyrolytic foaming agent. Further, preferably, the effervescent sheet is crosslinked, and the crosslinked effervescent sheet is heated to foam.
More specifically, the method for producing the foam sheet preferably includes the following steps (1) to (3).
Step (1): Step of forming an effervescent sheet made of an effervescent composition containing at least a resin and a heat-decomposable foaming agent Step (2): Irradiating the effervescent sheet with ionizing radiation to crosslink the effervescent sheet. Step Step (3): A step of heating a crosslinked foamable sheet to foam a heat-decomposable foaming agent to obtain a foam sheet.

In the step (1), the method for forming the foamable sheet is not particularly limited, but for example, the resin and the additive are supplied to the extruder, melt-kneaded, and the foamable composition is extruded into a sheet from the extruder. It may be molded by this. Further, the effervescent sheet may be formed by pressing an effervescent composition or the like. The molding temperature of the foamable sheet (that is, the temperature at the time of extrusion or the temperature at the time of pressing) is preferably 50 ° C. or higher and 250 ° C. or lower, and more preferably 80 ° C. or higher and 180 ° C. or lower.

As a method for cross-linking the effervescent composition in the step (2), a method of irradiating the effervescent sheet with ionizing radiation such as electron beam, α ray, β ray, and γ ray is used. The irradiation amount of the ionizing radiation may be adjusted so that the degree of cross-linking of the obtained foam sheet is within the above-mentioned desired range, but is preferably 1 to 12 Mrad, and preferably 1.5 to 10 Mrad. More preferred.

In the step (3), the heating temperature at the time of heating the effervescent composition to foam the pyrolyzable foaming agent may be equal to or higher than the foaming temperature of the pyrolyzable foaming agent, but is preferably 200 to 300 ° C. More preferably, it is 220 to 280 ° C. In the step (3), the effervescent composition is foamed to form bubbles to form a foam.

Further, in the present production method, the foam sheet may be thinned by a method such as rolling or stretching.

However, the present production method is not limited to the above, and a foam sheet may be obtained by a method other than the above. For example, instead of irradiating with ionizing radiation, the effervescent composition may be preliminarily blended with an organic peroxide, and the effervescent sheet may be heated to decompose the organic peroxide for cross-linking. ..
Further, if cross-linking is not necessary, the step (2) may be omitted. In that case, in the step (3), the uncrosslinked foamable sheet may be heated and foamed.

[Adhesive tape]
The foam sheet of the present invention may be used for an adhesive tape using the foam sheet as a base material. The adhesive tape includes, for example, a foam sheet and an adhesive material provided on at least one surface of the foam sheet. The adhesive tape can be adhered to another member such as a support member via the adhesive material. The adhesive tape may be a foam sheet provided with an adhesive material on both sides, or may be provided with an adhesive material on one side.
Further, the adhesive material may be at least one having an adhesive layer, may be a single adhesive layer laminated on the surface of the foam sheet, or may be a double-sided adhesive sheet attached to the surface of the foam sheet. However, it is preferable that the pressure-sensitive adhesive layer is a single substance. The double-sided pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer provided on both sides of the base material. The double-sided pressure-sensitive adhesive sheet is used to bond one pressure-sensitive adhesive layer to the foam sheet and the other pressure-sensitive adhesive layer to another member.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, or the like can be used. Further, a release sheet such as a release paper may be further bonded on the adhesive material.
The thickness of the pressure-sensitive adhesive layer is preferably 5 to 200 μm, more preferably 7 to 150 μm, and even more preferably 10 to 100 μm.

[Use of foam sheet]
The use of the foam sheet is not particularly limited, but it is preferably used for electronic devices. Examples of electronic devices include mobile phones such as smartphones, game devices, electronic notebooks, tablet terminals, and portable electronic devices such as notebook personal computers. The foam sheet can be used as a cushioning material inside an electronic device, and is preferably used as a cushioning material for a display device. Further, it may be used as a sealing material for filling gaps between parts inside an electronic device.
Since the foam sheet of the first invention of the present invention has both high impact resistance and low moisture permeability, it is particularly preferably used as a narrow-width adhesive tape. Further, since the foam sheet of the third invention of the present invention has high impact resistance, it is particularly preferably used as a narrow-width adhesive tape. Further, the foam sheet of the fourth invention of the present invention has high impact resistance, low tackiness and is easy to handle, and therefore is particularly preferably used as a narrow-width adhesive tape.

The foam sheet may be used in any shape, but is preferably narrow, and may have an elongated rectangular shape, a frame shape such as a square frame, an L shape, a U shape, or the like. These widths are, for example, 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less, and for example, 0.1 mm or more. In particular, since the foam sheet of the first invention of the present invention has both high impact resistance and low moisture permeability, it has good impact resistance even if it is narrow, and moisture is mixed inside the electronic device. It becomes difficult to make it. Since the foam sheet of the second invention of the present invention is a foam sheet having both high-speed impact resistance and low-speed impact resistance, it has good impact resistance even if it is narrow.

The foam sheet used as a cushioning material for a display device may be arranged on the back side of a display panel provided in various electronic devices, for example, and may be used so as to cushion an impact applied to the display panel. In this case, the foam sheet may be arranged on a support member arranged on the back side of the display panel. The support member constitutes, for example, a part of a housing or the like of various electronic devices.
The foam sheet used in the electronic device may be provided with an adhesive material as described above, and may be attached to a display panel, a support member, or the like by the adhesive material. In particular, since the foam sheet of the second invention of the present invention has excellent low-speed impact resistance in addition to high-speed impact resistance, it is suitably used for bonding and fixing to a heavy device such as a wall-mounted television. obtain.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
The method for measuring each physical property and the method for evaluating the foam sheet are as follows.

Example according to the first invention [Physical characteristics after molding]
(1) Glass transition temperature (Tg), loss tangent (tanδ) and storage elastic modulus Using a tensile storage elastic modulus measuring device manufactured by Aity Measurement Control Co., Ltd. and having a trade name of "DVA-200 / L2", the following measurement conditions Tg, tan δ and storage elastic modulus were determined.
(Measurement condition)
Length between marked lines: 2.5 cm
Sample width: 0.5 cm
Sample thickness: Thickness of foam sheet Deformation mode: Tension static / dynamic stress ratio: 1.5
Setting distortion: 1.0%
Set temperature rise rate: 10 ° C / min
Measurement frequency 10Hz
Temperature range: -100 ° C to 100 ° C

(2) Breaking point strength The foamed sheets produced in each Example and Comparative Example were cut into a dumbbell-shaped No. 1 shape specified in JIS K6251 4.1. Using this as a sample, a tensile tester (product name: Tencilon RTF235, manufactured by A & D Co., Ltd.) was used to carry out tensile measurement at a measurement temperature of 23 ° C. and a speed of 500 mm / min.

(3) Degree of cross-linking (gel fraction)
About 100 mg of the test piece was collected from the foam sheet, and the mass A (mg) of the test piece was precisely weighed. Next, this test piece was immersed in 30 cm ³ of xylene at 120 ° C. and left for 24 hours, then filtered through a 200 mesh wire mesh to collect the insoluble matter on the wire mesh, vacuum dried, and the mass of the insoluble matter. B (mg) was precisely weighed. From the obtained values, the degree of cross-linking (mass%) was calculated by the following formula.
Gel fraction (% by mass) = 100 x (B / A)

(4) Closed cell ratio A planar square-shaped test piece having a side of 5 cm was cut out from the foam sheet. Then, the thickness of the test piece is measured to calculate the apparent volume V1 of the test piece, and the mass W1 of the test piece is measured. Next, the volume V2 occupied by the bubbles was calculated based on the following formula. The density of the test piece is ρ (g / cm ³ ).
Volume occupied by bubbles V2 = V1-W1 / ρ
Subsequently, the test piece was submerged in distilled water at 23 ° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa was applied to the test piece for 3 minutes. After that, the test piece was taken out from the water, the water adhering to the surface of the test piece was removed, the mass W2 of the test piece was measured, and the closed cell ratio F1 was calculated based on the following formula.
Closed cell ratio F1 (%) = 100-100 × (W2-W1) / V2

(5) Average bubble diameter A foam sheet is cut in the thickness direction along each of MD and TD, and a 200-fold magnified photograph is taken using a digital microscope (manufactured by KEYENCE Co., Ltd., product name "VHX-900"). I took a picture. In the magnified photograph taken, the bubble diameter of MD and the bubble diameter of TD were measured for all the bubbles existing on the cut surface having a length of 2 mm in each of MD and TD, and the operation was repeated 5 times. Then, the average value of the bubble diameters of MD and TD of all the bubbles was taken as the average bubble diameter of MD and TD.
In addition, MD means Machine direction, and is the direction which coincides with the extrusion direction and the like. TD means Transverse direction, which is orthogonal to MD and parallel to the foam sheet. Further, ZD is the thickness direction of the foamed sheet, and is the direction perpendicular to both MD and TD.

(6) 25% Compressive Strength The measurement was performed at a measurement temperature of 23 ° C. by a measurement method based on JIS K6767.
(7) Apparent density and foaming ratio The apparent density of the foam was measured in accordance with JIS K7222, and the reciprocal of the measured was taken as the foaming ratio.

(8) WVTR
At a temperature of 40 ° C., the foam sheet produced in each Example and Comparative Example was cut into a size of about 10 cm × 10 cm, installed in the measuring part of a water vapor transmittance measuring device (MOCON, PERMATRAN-W 1/50), and then 40. The water vapor permeability was measured under the conditions of ° C. and 90% RH.
The evaluation criteria are as follows.
〇: Moisture permeability (WVTR) is 200 g / m ² · day or less ×: Moisture permeability (WVTR) is over 200 g / m ² · day

[evaluation]
(9) Impact resistance test (tumbling test)
Two foam sheets produced in each Example and Comparative Example were cut out in a size of 0.15 cm in length × 7 cm in width to prepare test pieces (thickness: shown in Table 1-1). Two of the test pieces are arranged at intervals of 5 cm, two acrylic plates (length: 9.5 cm, width 7 cm) are sandwiched in a shape shifted by 1.5 cm in the vertical direction, fixed with an adhesive, and used for tumbling. It was used as a test piece.
The test piece for tumbling was placed in a commercially available Itto-kan (length of top plate, piece of base plate: about 24 cm, height: about 35 cm) and rotated 500 times to continuously drop 1000 times. .. Then, the test piece was taken out and the breakage between the layers of the foam sheet was visually observed. The evaluation criteria are as follows.
〇: No breakage was observed between the layers of the foam sheet.
X: Destruction was observed between the layers of the foam sheet.

(10) Moisture test (moisture permeability)
The foam sheet produced in each Example and Comparative Example was cut into 5 cm × 7 cm, and a test piece was prepared on a frame (thickness: thickness (mm) shown in the table, width: 1.5 mm). A water-sensitive test paper (Aztool submersion control sheet) was placed inside the test piece, and the two sheets were fixed to an acrylic plate with scissors and an adhesive to prepare a test piece for a humidity test. The test piece was allowed to stand in an oven at 23 ° C. and 70% RH for 24 hours. After 24 hours, changes in the water-sensitive test strip were confirmed.
The evaluation criteria are as follows.
〇: No change in the water sensitive test paper ×: There is a change in the water sensitive test paper

The materials used in the examples and comparative examples are as follows.
Elastomer (a): Hybler (registered trademark) 7311F (manufactured by Kuraray Co., Ltd., hydrogenated styrene / isoprene / butadiene block copolymer, styrene content 12% by mass)
Elastomer (b): K-9330M (Mitsui Chemicals, Inc., ethylene / butene / non-conjugated diene ternary copolymer (EBDM))
Polyolefin resin: Kernel (registered trademark) KF283 (made by Nippon Polyethylene Co., Ltd., ethylene / α-olefin copolymer (LLDPE) polymerized with a metallocene catalyst)
Pyrolytic foaming agent: Azodicarbonamide Decomposition temperature adjuster: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name "OW-212F"
Phenolic Antioxidant: 2,6-di-t-butyl-p-cresol

Example 1-1
Elastomer (a) 80 parts by mass, polyolefin resin 20 parts by mass, pyrolysis foaming agent 9 parts by mass, decomposition temperature adjuster 1 part by mass, and phenolic antioxidant 0.5 parts by mass were prepared as raw materials. .. These materials were melt-kneaded and then pressed to obtain a foamable resin sheet having a thickness of 0.1 mm. Both sides of the obtained foamable resin sheet were irradiated with an electron beam for 6 Mrad at an acceleration voltage of 500 keV to crosslink the foamable resin sheet. Next, the crosslinked foamable resin sheet was foamed by heating to 250 ° C. to obtain a foam sheet having a density of 0.56 g / cm ³ and a thickness of 0.10 mm.
The results of evaluation by the above method are shown in Table 1-1.

Example 1-2
In the same manner as in Example 1-1, except that the thickness of the foamable resin sheet was changed to 0.15 mm in Example 1-1, the apparent density after foaming was 0.56 g / cm ³ , and the thickness was 0.15 mm. Foam sheet was obtained. The evaluation results are shown in Table 1-1.

Example 1-3
In Example 1-1, except that the pyrolysis foaming agent was changed to 8.0 parts by mass, the thickness of the foamable resin sheet was changed to 0.35 mm, and the irradiation dose was set to 5.5 Mrad. In the same manner as in 1-1, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 1-1.

Example 1-4
In Example 1-1, the apparent density after foaming is the same as in Example 1-1, except that the blending amount of the elastomer (a) is 50 parts by mass and the blending amount of the polyolefin resin is 50 parts by mass. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 1-1.

Example 1-5
A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was obtained in the same manner as in Example 1-4 except that the irradiation dose was set to 8 Mrad in Examples 1-4. .. The evaluation results are shown in Table 1-1.

Example 1-6
Foaming in the same manner as in Example 1-4, except that the pyrolyzable foaming agent was changed to 6.0 parts by mass and the thickness of the foamable resin sheet was changed to 0.35 mm in Examples 1-4. A foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm was obtained. The evaluation results are shown in Table 1-1.

Example 1-7
In Example 1-4, a foam sheet was obtained in the same manner as in Example 1-4 except that the elastomer (b) was used instead of the elastomer (a) and the irradiation dose was 7Mrad. The evaluation results are shown in Table 1-1.

Example 1-8
In Example 1-7, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was obtained in the same manner as in Example 1-7 except that the irradiation dose was set to 8 Mrad. .. The evaluation results are shown in Table 1-1.

Example 1-9
In Example 1-7, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the thickness of the foamable resin sheet was changed to 0.35 mm, and the irradiation dose was set to 5Mrad. In the same manner as in No. 7, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 1-1.

Example 1-10
In Example 1-7, the same as in Example 1-7 except that the blending amount of the elastomer (b) was 40 parts by mass, the blending amount of the polyolefin resin was 60 parts by mass, and the irradiation dose was 5 Mrad. A foam sheet was obtained. The evaluation results are shown in Table 1-1.

Example 1-11
In Example 1-10, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was prepared in the same manner as in Example 1-10 except that the irradiation dose was 5.5 Mrad. Obtained. The evaluation results are shown in Table 1-1.

Example 1-12
In Example 1-10, foaming was carried out in the same manner as in Example 1-10, except that the pyrolyzable foaming agent was changed to 6.0 parts by mass and the thickness of the foamable resin sheet was changed to 0.35 mm. A foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm was obtained. The evaluation results are shown in Table 1-1.

Comparative Example 1-1
In Example 1-2, a foam sheet was obtained in the same manner as in Example 1-2 except that 100 parts by mass of the polyolefin resin was used without using an elastomer and the irradiation dose was 4.5 Mrad. Tg was not observed under the measurement conditions of the present application.

Comparative Example 1-2
Foam sheet in the same manner as in Example 1-2, except that the blending amount of the elastomer (a) was 10 parts by mass and the blending amount of the polyolefin resin (b) was 90 parts by mass in Example 1-2. Got The evaluation results are shown in Table 1-1.

As described above, the foam sheet of each example is a foam sheet having both high impact resistance and low moisture permeability, as compared with the foam sheet of the comparative example having high moisture permeability. Recognize.

Examples of the Second Invention [Physical Properties After Molding]
(1) Glass transition temperature (Tg), loss tangent (tan δ) and storage elastic modulus The measurement was carried out under the same method and measurement conditions as the method in the first invention.

(2) Breaking point strength Measured by the same method as the method in the first invention.

(3) Degree of cross-linking (gel fraction)
It was calculated by the same method as the method in the first invention.

(4) Closed cell ratio Compared to the method in the first invention, the test piece was calculated by the same method as in the first invention except that the test piece was submerged in distilled water at 23 ° C. to a depth of 500 mm from the water surface. ..

(5) Average bubble diameter Calculated by the same method as the method in the first invention.

(6) 25% Compressive Strength Measured by the same method as the method in the first invention.
(7) Apparent density and foaming ratio The measurement was carried out by the same method as the method in the first invention.

(8) Interlayer strength FIG. 2 shows a schematic diagram of a test device for evaluating the interlayer strength. After applying a primer (“PPX primer” manufactured by Cemedine Co., Ltd.) to a 25 mm square area of the foam sheet 11, an adhesive 12 (“PPX” manufactured by Cemedine Co., Ltd.) having a diameter of 5 mm was dropped into the center of the coated portion. Immediately after that, a 25 mm square aluminum jig 13 was placed on the adhesive dropping portion, and the foam sheet and the jig 13 were pressure-bonded. Then, the foam sheet was cut according to the size of the jig 13. The primer was applied to the surface of the cut foam sheet to which the jig 13 was not adhered, and the adhesive 12 having a diameter of 5 mm was dropped on the center of the coated portion. Immediately after that, a 10 mm square aluminum jig 14 was placed on the adhesive dropping portion, and the foam sheet and the jig 14 were pressure-bonded. After wiping off the adhesive that had squeezed out around the jig 14, a cut 15 was made in the foam sheet along the size of the jig 14. This was left at room temperature for 30 minutes to cure the adhesive and used as a sample for measuring the interlayer strength.
Subsequently, a 1 kN load cell was installed in a testing machine provided with a constant temperature bath (“Tencilon universal material testing machine” manufactured by A & D Co., Ltd.) so that tests could be performed in the constant temperature bath. Then, a sample for measuring the interlayer strength was attached to the testing machine so that the sheet surface of the foam sheet was perpendicular to the tensile direction. After setting the temperature of the constant temperature bath to 23 ° C., the sample was left to stand until the temperature of the sample for interlayer strength measurement reached 23 ° C. Then, one of the jigs was pulled vertically upward at a speed of 100 mm / min, and only the 1 cm square area of the foam sheet was peeled off. The maximum load at this time was measured and used as the first measurement result. The same operation was repeated three times, and the average value was taken as the interlayer strength at 23 ° C.

[evaluation]
(9) Impact resistance test (tumbling test)
It was measured by the same method as the method in the first invention (thickness of foam sheet: shown in Table 2-1).

The components used in the examples and comparative examples are as follows.
Elastomer (a): Hybler (registered trademark) 7311F (manufactured by Kuraray Co., Ltd., hydrogenated styrene / isoprene / butadiene block copolymer, styrene content 12% by mass)
Elastomer (b): K-9330M (Mitsui Chemicals, Inc., ethylene / butene / non-conjugated diene ternary copolymer (EBDM))
Polyolefin resin: Kernel (registered trademark) KF283 (made by Nippon Polyethylene Co., Ltd., ethylene / α-olefin copolymer (LLDPE) polymerized with a metallocene catalyst)
Pyrolytic foaming agent: Azodicarbonamide Decomposition temperature adjuster: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name "OW-212F"
Phenolic Antioxidant: 2,6-di-t-butyl-p-cresol

Example 2-1
Elastomer (a) 80 parts by mass, polyolefin resin 20 parts by mass, pyrolysis foaming agent 9.0 parts by mass, decomposition temperature adjuster 1 part by mass, and phenolic antioxidant 0.5 parts by mass as raw materials. Prepared as. These materials were melt-kneaded and then pressed to obtain a foamable resin sheet having a thickness of 0.1 mm. Both sides of the obtained foamable resin sheet were irradiated with an electron beam for 6 Mrad at an acceleration voltage of 500 keV to crosslink the foamable resin sheet. Next, the crosslinked foamable resin sheet was foamed by heating to 250 ° C. to obtain a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.10 mm.
The results of evaluation by the above method are shown in Table 2-1.

Example 2-2
In the same manner as in Example 2-1 except that the thickness of the foamable resin sheet was changed to 0.15 mm in Example 2-1 the apparent density after foaming was 0.56 g / cm ³ , and the thickness was 0.15 mm. Foam sheet was obtained. The evaluation results are shown in Table 2-1.

Example 2-3
Except for changing the pyrolysis foaming agent to 8.0 parts by mass, changing the thickness of the foamable resin sheet to 0.35 mm, and changing the electron dose to 5.5 Mrad in Example 2-1. In the same manner as in Example 2-1 to obtain a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming. The evaluation results are shown in Table 2-1.

Example 2-4
In Example 2-1 the apparent density after foaming is the same as in Example 2-1 except that the blending amount of the elastomer (a) is 50 parts by mass and the blending amount of the polyolefin resin is 50 parts by mass. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 2-1.

Example 2-5
In Example 2-1 the elastomer (b) is used instead of the elastomer (a), the blending amount of the elastomer (b) is 40 parts by mass, the blending amount of the polyolefin resin is 60 parts by mass, and the electron dose is 5. A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.1 mm after foaming was obtained in the same manner as in Example 2-1 except that it was changed to 0.0 Mrad. The evaluation results are shown in Table 2-1.

Example 2-6
In Example 2-5, the compounding amount of the elastomer (b) was 50 parts by mass, the compounding amount of the polyolefin resin was 50 parts by mass, and the electron dose was changed to 7.0 Mrad. Similarly, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.1 mm after foaming was obtained. The evaluation results are shown in Table 2-1.

Example 2-7
In Example 2-4, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the thickness of the foamable resin sheet was changed to 0.35 mm, and the electron dose was changed to 5.0 Mrad. In the same manner as in Example 2-4, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 2-1.

Comparative Example 2-1
In Example 2-2, the apparent density after foaming is the same as in Example 2-2, except that the blending amount of the elastomer (a) is 10 parts by mass and the blending amount of the polyolefin resin is 90 parts by mass. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.15 mm was obtained. The evaluation results are shown in Table 2-1.

Comparative Example 2-2
In Example 2-2, the apparent density after foaming was the same as in Example 2-2, except that the elastomer (a) was not blended, only the polyolefin resin was used, and the electron dose was changed to 4.5 Mrad. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.15 mm was obtained. The evaluation results are shown in Table 2-1.

Comparative Example 2-3
In Example 2-7, the apparent density after foaming was 0.14 g / cm ³ , in the same manner as in Example 2-7, except that only the elastomer (a) was used and the electron dose was changed to 4.5 Mrad. A foam sheet having a thickness of 0.5 mm was obtained. The evaluation results are shown in Table 2-1.

As described above, it can be seen that the foam sheet of each example has high impact resistance, has a good storage elastic modulus at low temperature, and is particularly excellent in high-speed impact resistance. In addition, it can be seen that the interlayer strength is high and the low-speed impact resistance is also excellent. That is, the foam sheet of the present invention is a foam sheet excellent in both high-speed impact resistance and low-speed impact resistance.
On the other hand, it can be seen that the foam sheet described in Comparative Example has low impact resistance (Comparative Examples 2-1 and 2-2) or low interlayer strength (Comparative Example 2-3).

Examples of the Third Invention [Physical Properties After Molding]
(1) Glass transition temperature (Tg), loss tangent (tan δ) and storage elastic modulus The measurement was carried out under the same method and measurement conditions as the method in the first invention.

(2) Breaking point strength Measured by the same method as the method in the first invention.

(3) Stretching The foamed sheets produced in each Example and Comparative Example were cut into a dumbbell-shaped No. 1 shape specified in JIS K6251 4.1. Using this as a sample, elongation was performed by a tensile tester (product name: Tencilon RTF235, manufactured by A & D Co., Ltd.) at a measurement temperature of 23 ° C., a tensile speed of 500 m / min, and a stress of 0.06 N / 10 mm. (%) Was measured.

(4) Degree of cross-linking (gel fraction)
It was calculated by the same method as the method in the first invention.

(5) Closed cell ratio Calculated by the same method as the method in the first invention.

(6) Average bubble diameter A foam sheet is cut in the thickness direction along each of MD and TD, and a 200-fold magnified photograph is taken using a digital microscope (manufactured by KEYENCE Co., Ltd., product name "VHX-900"). I took a picture. In the magnified photograph taken, the bubble diameters of MD and ZD and the bubble diameters of TD and ZD were measured for all the bubbles existing on the cut surface having a length of 2 mm in each of MD and TD, and the operation was repeated 5 times. .. Then, the average value of the bubble diameters of MD and TD of all the bubbles is taken as the average bubble diameter of MD and TD, and the average value of the bubble diameters of all ZDs measured by the above operation is used as the average bubble diameter of ZD. And said.
In addition, MD means Machine direction, and is the direction which coincides with the extrusion direction and the like. TD means Transverse direction, which is orthogonal to MD and parallel to the foam sheet. Further, ZD is the thickness direction of the foamed sheet, and is the direction perpendicular to both MD and TD.

(7) 25% compressive strength The measurement was carried out by the same method as the method in the first invention.
(8) Apparent density and foaming ratio The measurement was carried out by the same method as the method in the first invention.

[evaluation]
(9) Impact resistance test (tumbling test)
It was measured by the same method as the method in the first invention (thickness of foam sheet: shown in Table 3-1).

(10) Sheet peeling test after laminating A measurement sample having a width of 100 mm and a length of 200 mm was cut out from the foam sheet produced based on Examples and Comparative Examples. With a tensile tester (product name: Tencilon RTF235, manufactured by A & D Co., Ltd.), the foam sheet was pulled with a load of 0.6 N, and the foam sheet and resin sheet (width 100 mm x length 50 mm) were combined. Was sandwiched between jigs (width 130 mm × length 70 mm × thickness 20 mm), the screws attached to the jig were tightened, and the mixture was allowed to stand for 10 minutes to bond the foam sheet and the resin sheet. Then, the jig was removed and the foam sheet was allowed to stand on a horizontal table for 2 minutes, and then the surface of the foam sheet was visually observed.
〇: No peeling and no wrinkles ×: Peeling or wrinkles occurred

The components used in the examples and comparative examples are as follows.
Elastomer (a): Hybler (registered trademark) 7311F (manufactured by Kuraray Co., Ltd., hydrogenated styrene / isoprene / butadiene block copolymer, styrene content 12% by mass)
Elastomer (b): K-9330M (Mitsui Chemicals, Inc., ethylene / butene / non-conjugated diene ternary copolymer (EBDM))
Polyolefin resin: Kernel (registered trademark) KF283 (made by Nippon Polyethylene Co., Ltd., ethylene / α-olefin copolymer (LLDPE) polymerized with a metallocene catalyst)
Pyrolytic foaming agent: Azodicarbonamide Decomposition temperature adjuster: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name "OW-212F"
Phenolic Antioxidant: 2,6-di-t-butyl-p-cresol

Example 3-1
Elastomer (a) 80 parts by mass, polyolefin resin 20 parts by mass, pyrolysis foaming agent 9.0 parts by mass, decomposition temperature adjuster 1 part by mass, and phenolic antioxidant 0.5 parts by mass as raw materials. I prepared it. These materials were melt-kneaded and then pressed to obtain a foamable resin sheet having a thickness of 0.1 mm. Both sides of the obtained foamable resin sheet were irradiated with an electron beam for 6 Mrad at an acceleration voltage of 500 keV to crosslink the foamable sheet. Next, the crosslinked foamable sheet was heated to 250 ° C. to foam the foamable resin sheet to obtain a foam sheet having a density of 0.56 g / cm ³ and a thickness of 0.10 mm.
The results of evaluation by the above method are shown in Table 3-1.

Example 3-2
In the same manner as in Example 3-1 except that the thickness of the foamable resin sheet was changed to 0.15 mm in Example 3-1 the apparent density after foaming was 0.56 g / cm ³ , and the thickness was 0.15 mm. Foam sheet was obtained. The evaluation results are shown in Table 3-1.

Example 3-3
Except that in Example 3-1 the pyrolysis foaming agent was changed to 8.0 parts by mass, the electron dose was changed to 5.5 Mrad, and the thickness of the foamable resin sheet was changed to 0.35 mm. In the same manner as in Example 3-1 a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 3-1.

Example 3-4
In Example 3-1 the apparent density after foaming is the same as in Example 3-1 except that the blending amount of the elastomer (a) is 50 parts by mass and the blending amount of the polyolefin resin is 50 parts by mass. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 3-1.

Example 3-5
A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming in the same manner as in Example 3-4, except that the electron dose was changed to 8.0 Mrad in Example 3-4. Got The evaluation results are shown in Table 3-1.

Example 3-6
In Example 3-4, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the electron dose was changed to 6.0 Mrad, and the thickness of the foamable resin sheet was changed to 0.35 mm. In the same manner as in Example 3-4, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 3-1.

Example 3-7
In Example 3-4, the apparent density after foaming was 0 in the same manner as in Example 3-4, except that the elastomer (b) was used instead of the elastomer (a) and the electron dose was changed to 7.0 Mrad. A foam sheet having a thickness of .56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 3-1.

Example 3-8
A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming in the same manner as in Example 3-7, except that the electron dose was changed to 8.0 Mrad in Example 3-7. Got The evaluation results are shown in Table 3-1.

Example 3-9
In Example 3-7, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the electron dose was changed to 5.0 Mrad, and the thickness of the foamable resin sheet was changed to 0.35 mm. In the same manner as in Example 3-7, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 3-1.

Example 3-10
In Example 3-7, the compounding amount of the elastomer (b) was 40 parts by mass, the compounding amount of the polyolefin resin was 60 parts by mass, and the electron dose was changed to 5.0 Mrad. Similarly, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.1 mm after foaming was obtained. The evaluation results are shown in Table 3-1.

Example 3-11
A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming in the same manner as in Example 3-10, except that the electron dose was changed to 5.5 Mrad in Example 3-10. Got The evaluation results are shown in Table 3-1.

Example 3-12
In Example 3-10, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the electron dose was changed to 5.0 Mrad, and the thickness of the foamable resin sheet was changed to 0.35 mm. In the same manner as in Example 3-10, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 3-1.

Comparative Example 3-1
A foam sheet was obtained in the same manner as in Example 3-2, except that 100 parts by mass of the elastomer (a) was used without using the polyolefin resin in Example 3-2.

Comparative Example 3-2
A foam sheet was obtained in the same manner as in Example 3-2, except that 100 parts by mass of the elastomer (b) was used without using the polyolefin resin in Example 3-2.

Comparative Example 3-3
In Example 3-2, a foam sheet was obtained in the same manner as in Example 3-2, except that 100 parts by mass of the polyolefin resin was used without using an elastomer and the electron dose was changed to 4.5 Mrad. Tg was not observed under the measurement conditions of the present application.

Comparative Example 3-4
Example 3 except that the compounding amount of the elastomer (a) was 10 parts by mass, the compounding amount of the polyolefin resin (b) was 90 parts by mass, and the electron dose was changed to 6.0 Mrad in Example 3-2. A foam sheet was obtained in the same manner as in -2. The evaluation results are shown in Table 3-1.

As described above, the foam sheets of Comparative Examples 3-1 and 3-2 were peeled or wrinkled in the sheet peeling test after laminating. The foam sheets of Comparative Examples 3-3 and 3-4 had good results in the sheet peeling test after laminating, but did not have sufficient impact resistance.
On the other hand, the foam sheet of each example had high impact resistance, and no peeling or wrinkling occurred in the sheet peeling test after laminating.

Examples of the Fourth Invention [Physical Properties After Molding]
(1) Glass transition temperature (Tg), loss tangent (tan δ) and storage elastic modulus The measurement was carried out under the same method and measurement conditions as the method in the first invention.

(2) Breaking point strength Measured by the same method as the method in the first invention.

(3) Degree of cross-linking (gel fraction)
It was calculated by the same method as the method in the first invention.

(4) Closed cell ratio was calculated by the same method as the method in the first invention.

(5) Average bubble diameter The average bubble diameter was measured by the same method as the method in the third invention.

(6) 25% Compressive Strength Measured by the same method as the method in the first invention.
(7) Apparent density and foaming ratio The measurement was carried out by the same method as the method in the first invention.

(8) Tackability A foam sheet was cut into 10 cm squares and measured at a temperature of 23 ° C. using a tack tester (manufactured by UBM, product name “Tack Tester TA-500”).
When a jig (made of metal) with a cross-sectional area of 0.03 cm ² is pressed against the surface of the foam sheet at a load of 100,000 gf / cm ² for 1 second, and then the jig is pulled up at a speed of 0.8 mm / sec. The load (gf / cm ² ) was measured, and the obtained value was taken as the tackiness of the surface of the resin foam sheet.

[evaluation]
(9) Impact resistance test (tumbling test)
It was measured by the same method as the method in the first invention (thickness of foam sheet: shown in Table 4-1).

(10) Handlingability Using the foam sheets produced in each Example and Comparative Example, a test piece having a size of 5.0 cm in length × 5.0 cm in width was prepared. A weight of 15 kg and 25 cm was placed on the test piece and allowed to stand for 3 seconds. After that, when the weight was lifted, it was evaluated whether the foam sheet would stick to the weight and be lifted.
The evaluation criteria were tested 5 times, and the most common results were used as evaluation results. The evaluation criteria are as follows.
○: The foam sheet does not lift up with the weight (good handling)
×: The foam sheet lifts up with the weight (poor handling)

The components used in the examples and comparative examples are as follows.
Elastomer (a): Hybler (registered trademark) 7311F (manufactured by Kuraray Co., Ltd., hydrogenated styrene / isoprene / butadiene block copolymer, styrene content 12% by mass)
Elastomer (b): K-9330M (Mitsui Chemicals, Inc., ethylene / butene / non-conjugated diene ternary copolymer (EBDM))
Polyolefin resin: Kernel (registered trademark) KF283 (made by Nippon Polyethylene Co., Ltd., ethylene / α-olefin copolymer (LLDPE) polymerized with a metallocene catalyst)
Pyrolytic foaming agent: Azodicarbonamide Decomposition temperature adjuster: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name "OW-212F"
Phenolic Antioxidant: 2,6-di-t-butyl-p-cresol

Example 4-1
Elastomer (a) 80 parts by mass, polyolefin resin 20 parts by mass, pyrolysis foaming agent 9.0 parts by mass, decomposition temperature adjuster 1 part by mass, and phenolic antioxidant 0.5 parts by mass as raw materials. I prepared it. These materials were melt-kneaded and then pressed to obtain a foamable resin sheet having a thickness of 0.1 mm. Both sides of the obtained foamable resin sheet were irradiated with an electron beam for 6 Mrad at an acceleration voltage of 500 keV to crosslink the foamable sheet. Next, the crosslinked foamable sheet was heated to 250 ° C. to foam the foamable resin sheet to obtain a foam sheet having a density of 0.56 g / cm ³ and a thickness of 0.10 mm.
The results of evaluation by the above method are shown in Table 4-1.

Example 4-2
In the same manner as in Example 4-1 except that the thickness of the foamable resin sheet was changed to 0.15 mm in Example 4-1 the apparent density after foaming was 0.56 g / cm ³ , and the thickness was 0.15 mm. Foam sheet was obtained. The evaluation results are shown in Table 4-1.

Example 4-3
Except for changing the pyrolysis type foaming agent to 8.0 parts by mass, changing the thickness of the foamable resin sheet to 0.35 mm, and changing the electron dose to 5.5 Mrad in Example 4-1. In the same manner as in Example 4-1 to obtain a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming. The evaluation results are shown in Table 4-1.

Example 4-4
In Example 4-1 the apparent density after foaming is the same as in Example 4-1 except that the blending amount of the elastomer (a) is 50 parts by mass and the blending amount of the polyolefin resin is 50 parts by mass. A foam sheet having a thickness of 0.56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 4-1.

Example 4-5
In Example 4-4, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was prepared in the same manner as in Example 4-4 except that the irradiation dose was set to 8.0 Mrad. Obtained. The evaluation results are shown in Table 4-1.

Example 4-6
Foaming was carried out in the same manner as in Example 4-4, except that the pyrolysis foaming agent was changed to 6.0 parts by mass and the thickness of the foamable resin sheet was changed to 0.35 mm in Example 4-4. A foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm was obtained. The evaluation results are shown in Table 4-1.

Example 4-7
In Example 4-4, the apparent density after foaming is 0 in the same manner as in Example 4-4, except that the irradiation dose is changed to 7.0 Mrad by using the elastomer (b) instead of the elastomer (a). A foam sheet having a thickness of .56 g / cm ³ and a thickness of 0.1 mm was obtained. The evaluation results are shown in Table 4-1.

Example 4-8
In Example 4-7, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was prepared in the same manner as in Example 4-7 except that the irradiation dose was set to 8.0 Mrad. Obtained. The evaluation results are shown in Table 4-1.

Example 4-9
In Examples 4-7, except that the pyrolysis foaming agent was changed to 6.0 parts by mass, the thickness of the foamable resin sheet was changed to 0.35 mm, and the irradiation dose was set to 5.0 Mrad. In the same manner as in 4-7, a foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm after foaming was obtained. The evaluation results are shown in Table 4-1.

Example 4-10
In Example 4-7, the same as in Example 4-7 except that the blending amount of the elastomer (b) was 40 parts by mass, the blending amount of the polyolefin resin was 60 parts by mass, and the irradiation dose was 5 Mrad. A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.1 mm after foaming was obtained. The evaluation results are shown in Table 4-1.

Example 4-11
A foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming in the same manner as in Example 4-10, except that the irradiation dose was changed to 5.5 Mrad in Example 4-10. Got The evaluation results are shown in Table 4-1.

Example 4-12
After foaming in the same manner as in Example 4-10, except that the pyrolyzable foaming agent was changed to 6.0 parts by mass and the thickness of the foamable resin sheet was changed to 0.35 mm in Example 4-10. A foam sheet having an apparent density of 0.14 g / cm ³ and a thickness of 0.5 mm was obtained. The evaluation results are shown in Table 4-1.

Comparative Example 4-1
In Example 4-2, a foam sheet was obtained in the same manner as in Example 4-2 except that 100 parts by mass of the elastomer (a) was used without using the polyolefin resin and the irradiation dose was 4.5 Mrad. rice field. Tg was not observed under the measurement conditions of the present application.

Comparative Example 4-2
A foam sheet was obtained in the same manner as in Example 4-2 except that 100 parts by mass of the elastomer (b) was used without using the polyolefin resin in Example 4-2.

Comparative Example 4-3
In Example 4-2, a foam sheet was obtained in the same manner as in Example 4-2 except that 100 parts by mass of the polyolefin resin was used without using an elastomer and the irradiation dose was 4.5 Mrad.

Comparative Example 4-4
In Example 4-2, the compounding amount of the elastomer (a) was 10 parts by mass, the compounding amount of the polyolefin resin was 90 parts by mass, and the electron dose was changed to 6.0 Mrad. Similarly, a foam sheet having an apparent density of 0.56 g / cm ³ and a thickness of 0.15 mm after foaming was obtained. The evaluation results are shown in Table 4-1.

As described above, the foam sheets of Comparative Examples 4-1 and 4-2 have high tackiness and inferior handling property. Further, the foam sheets of Comparative Examples 4-3 and 4-4 were inferior in impact resistance. On the other hand, it can be seen that the foam sheet of the present invention exhibits high impact resistance and good tackiness.

1 Screen 2 Foam tape 3 Housing 11 Foam sheet 12 Adhesive 13 Jig 14 Jig 15 Notch

Claims (14)

The glass transition temperature (Tg) is -60 to 0 ° C., the peak value of loss tangent (tanδ) is 0.25 or more, and the interlayer strength in the tensile test at a speed of 100 mm / min is 2.00 MPa or more. Foam sheet. Tensile direction when the glass transition temperature (Tg) is -60 to 0 ° C., the peak value of loss tangent (tanδ) is 0.25 or more, and the stress in the tensile direction is 0.06 N / 10 mm in the tensile test. Foam sheet with an elongation of 4% or less. A foam sheet having a glass transition temperature (Tg) of -60 to 0 ° C., a peak value of tangent loss (tanδ) of 0.25 or more, and a surface tackiness of 5000 gf / cm ² or less. The foam sheet according to any one of claims 1 to 3, wherein the 25% compressive strength is 1000 kPa or less. The foam sheet according to any one of claims 1 to 4, wherein the closed cell ratio is 80% or more. The foam sheet according to any one of claims 1 to 5, which has a thickness of 0.03 to 2 mm. The foam sheet according to any one of claims 1 to 6, wherein the storage elastic modulus at 23 ° C. is 2 × 10 ³ Pa or more. The foam sheet according to any one of claims 1 to 7, wherein the storage elastic modulus at −20 ° C. is 1.0 × 10 ⁵ Pa or more. The foam sheet according to any one of claims 1 to 8, wherein the breaking point strength at 23 ° C. is 2.0 N / 10 mm or more. The foam sheet according to any one of claims 1 to 9, wherein the average cell diameter is 20 to 400 μm. The foam sheet according to any one of claims 1 to 10, wherein the apparent density is 0.10 to 0.70 g / cm ³ . The foaming according to any one of claims 1 to 11, which contains an elastomer (A) and a polyolefin resin (B) and has a mass ratio of the component (A) to the component (B) of 90:10 to 40:60. Body sheet. The foam sheet according to any one of claims 1 to 12, wherein the gel fraction is 30 to 80% by mass. An adhesive tape comprising the foam sheet according to any one of claims 1 to 13 and an adhesive material provided on at least one surface of the foam sheet.

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