CN112074403B

CN112074403B - Foamed composite sheet, adhesive tape, cushioning material for electronic component, and adhesive tape for electronic component

Info

Publication number: CN112074403B
Application number: CN201980021692.9A
Authority: CN
Inventors: 佐藤健人; 滨田哲史; 浜田晶启; 矢野秀明
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2018-03-29
Filing date: 2019-03-27
Publication date: 2022-11-04
Anticipated expiration: 2039-03-27
Also published as: TW201942284A; KR20200138235A; TWI822749B; WO2019189452A1; CN112074403A

Abstract

The foamed composite sheet of the present invention has a foamed sheet containing at least one resin selected from the group consisting of an elastomer resin and a polyolefin resin, and a resin layer laminated on at least one surface of the foamed sheet. The adhesive tape of the present invention comprises the foamed composite sheet of the present invention and an adhesive material provided on at least one side of the foamed composite sheet of the present invention. The cushioning material for electronic components of the present invention uses the foamed composite sheet of the present invention. The adhesive tape for electronic components of the present invention comprises the cushioning material for electronic components of the present invention and an adhesive material provided on at least one surface of the cushioning material for electronic components of the present invention. The invention can provide a foam sheet, an adhesive tape, a cushioning material for electronic components, and an adhesive tape for electronic components, which are excellent in impact absorption and mechanical strength.

Description

Foamed composite sheet, adhesive tape, cushioning material for electronic component, and adhesive tape for electronic component

Technical Field

The present invention relates to a foamed composite sheet having a foamed sheet and a resin layer, an adhesive tape having the foamed composite sheet and an adhesive material, a cushioning material for electronic components, and an adhesive tape for electronic components having the cushioning material for electronic components and the adhesive material.

Background

Porous resin materials having a large number of pores formed in a resin layer have been used for various applications such as packaging materials for articles, members necessary for preventing invasion of gas or liquid, sealing materials for sealing the peripheral portion of a case, cushioning materials for cushioning vibration and impact, and base materials for pressure-sensitive adhesive sheets, because they are excellent in cushioning properties, heat insulating properties, water repellency, and moisture resistance. For example, patent document 1 discloses a crosslinked polyolefin resin foam sheet obtained by foaming and crosslinking a foamable polyolefin resin sheet containing a thermal decomposition type foaming agent (see, for example, patent documents 1 and 2).

In recent years, IT has been desired that resin foam sheets used in IT devices such as mobile phones and notebook personal computers, and various electronic devices such as digital cameras and compact video recorders be made thinner as products are made smaller and thinner.

Documents of the prior art

Patent literature

Patent document 1 International publication No. 2005/007731

Patent document 2 Japanese patent laid-open publication No. 2014-28925

Disclosure of Invention

Problems to be solved by the invention

However, a resin foam sheet having a reduced thickness generally has low impact absorbability and low mechanical strength.

For example, a resin foam sheet having a reduced thickness generally has low impact resistance and impact absorbability, and thus it is difficult to sufficiently exhibit the function of a cushion material when used in an electronic device.

Resin foam sheets containing an elastomer resin are known because of their high impact resistance and impact absorbability. In the case of producing or storing a resin foam sheet, the sheet may be wound on a reel, and particularly, a resin foam sheet containing an elastomer resin is likely to be stuck when wound, and may cause a problem when taken out of the reel and used.

Further, if the foam sheet is thin, the mechanical strength such as tensile strength tends to be low, and therefore, for example, when the foam sheet is used as a tape, the foam sheet is likely to be broken when handled again. On the other hand, if the expansion ratio is decreased in order to improve the mechanical strength of the foamed sheet, the compression strength is increased, and the properties inherent in the foamed sheet such as impact absorbability may be impaired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a foam sheet, an adhesive tape, a cushioning material for electronic components, and an adhesive tape for electronic components, which are excellent in impact absorption and mechanical strength.

Further, another object of the present invention is to provide a foam sheet which is suppressed in blocking and is excellent in impact resistance and impact absorbability.

Further, another further object of the present invention is to provide a cushioning material for electronic components which has high tensile strength, low compressive strength and excellent reworkability, and an electronic component tape using the cushioning material for electronic components.

Means for solving the problems

The present inventors have conducted extensive studies and, as a result, have found that a foamed composite sheet comprising a combination of a foamed sheet having excellent impact absorbability and a resin layer having excellent mechanical strength can solve the above problems, and have completed the present invention.

Namely, the present invention provides the following means [1] to [20].

[1] A foamed composite sheet having a foamed sheet containing at least one resin selected from the group consisting of an elastomer resin and a polyolefin resin and a resin layer laminated on at least one side of the foamed sheet.

[2] The foamed composite sheet according to the above [1], which has a 25% compressive strength of 1.0 to 700kPa.

[3] A foamed composite sheet comprising a foamed sheet and a resin layer laminated on at least one surface of the foamed sheet, wherein the foamed sheet contains an elastomer resin, the foamed sheet has a 25% compressive strength of 30 to 700kPa, and an interlayer strength of 0.3MPa or more.

[4] The foamed composite sheet according to the above [3], wherein the elastomer resin is a thermoplastic elastomer resin.

[5] The foamed composite sheet according to the above [3] or [4], wherein the thermoplastic elastomer resin is at least one selected from the group consisting of olefin elastomer resins, vinyl chloride elastomer resins and styrene elastomer resins.

[6] The foamed composite sheet according to any one of the above [3] to [5], wherein the resin layer is at least one selected from the group consisting of olefin resins, vinyl chloride resins, styrene resins, urethane resins, polyester resins, polyamide resins, and ionomer resins.

[7] The foamed composite sheet according to any one of the above [3] to [6], wherein the foamed sheet has a thickness of 0.05 to 1.5mm, and the resin layer has a thickness of 0.01 to 0.1mm.

[8]As described in [3] above]～[7]The foamed composite sheet according to any one of (1) to (2), wherein the foamed sheet has an apparent density of 0.1 to 0.8g/cm ³ 。

[9] An adhesive tape comprising the foamed composite sheet according to any one of [3] to [8] and an adhesive material provided on at least one surface of the foamed composite sheet.

[10] A cushioning material for electronic parts, having a foamed resin layer containing a polyolefin resin and a skin resin layer containing a polyethylene resin provided on at least one side of the foamed resin layer, the foamed resin layer having a plurality of cells formed by bubbles.

[11] The cushioning material for electronic parts according to the above [10], wherein the thickness of the foamed resin layer is 0.05 to 1.5mm.

[12] The cushioning material for electronic parts according to the above [10] or [11], wherein the thickness of the skin resin layer is 0.005 to 0.5mm.

[13] The cushioning material for electronic parts according to any one of the above [10] to [12], wherein the polyethylene resin is at least one polyethylene resin selected from the group consisting of High Density Polyethylene (HDPE), linear Low Density Polyethylene (LLDPE), high pressure process Low Density Polyethylene (LDPE), and ethylene ionomer.

[14] The cushioning material for electronic components according to any one of the above [10] to [13], wherein a ratio of a thickness of the foamed resin layer to a total thickness of the skin resin layer, i.e., a thickness of the foamed resin layer/the total thickness of the skin resin layer, is 1.5 to 300.

[15] The cushioning material for electronic components described in any one of the above [10] to [14], wherein a ratio of a tensile strength constant of the skin resin layer calculated by the following formula (II) to a tensile strength constant of the foamed resin layer calculated by the following formula (I), that is, a value obtained by multiplying the tensile strength constant of the skin resin layer/the tensile strength constant of the foamed resin layer by a compressive strength constant calculated by the following formula (III), is 1.5 or more,

foamed resin layer tensile strength constant = { (MD direction tensile strength of foamed resin layer) × (TD direction tensile strength of foamed resin layer) } ^1/2 (I)

Skin resin layer tensile strength constant = { (MD direction tensile strength of skin resin layer) × (TD direction tensile strength of skin resin layer) } ^1/2 (II)

Compression strength constant = 200/(200 + 25% compression strength of cushioning material for electronic parts)

(III)

The units of the TD direction tensile strength and the MD direction tensile strength in the formulas (I) and (II) are both MPa, and the unit of the 25% compressive strength in the formula (III) is kPa.

[16]As described above in [10]]～[15]The cushioning material for electronic parts according to any one of (1) to (30) above, wherein the foaming ratio of the foamed resin layer is 1.5 to 30cm ³ /g。

[17] The cushioning material for electronic components according to any one of the above [10] to [16], wherein the polyolefin resin of the foamed resin layer is a vinyl resin.

[18] The buffer material for electronic components according to any one of the above [10] to [17], having a 25% compressive strength of 1.0 to 100kPa.

[19] The cushioning material for electronic parts according to any one of the above [10] to [18], wherein the foamed resin layer is a foam obtained by foaming a foamable composition containing a resin and a thermal decomposition type foaming agent.

[20] An adhesive tape for electronic components, comprising the cushioning material for electronic components according to any one of [10] to [19] above, and an adhesive material provided on at least one surface of the cushioning material for electronic components.

Effects of the invention

The invention can provide a foam sheet, an adhesive tape, a cushioning material for electronic parts, and an adhesive tape for electronic parts, each of which has excellent impact absorbability and mechanical strength.

Further, the present invention can provide a foamed composite sheet which is suppressed in blocking property and is excellent in impact resistance and impact absorbability in the case where the foamed sheet contains an elastomer resin, and has a 25% compressive strength of 30 to 700kPa and an interlayer strength of 0.3MPa or more.

Further, the present invention is a cushioning material for electronic parts using a foamed composite sheet, and when the foamed sheet is a foamed resin layer containing a polyolefin resin having a large number of cells formed of bubbles and the resin layer is a skin resin layer containing a polyethylene resin, the present invention can also exhibit the following effects. That is, in the above-described circumstances, the present invention can also provide a cushioning material for electronic components which has high tensile strength, low compressive strength and excellent reworkability, and an electronic component tape using the cushioning material for electronic components.

Drawings

Fig. 1 is a schematic diagram of a test apparatus for evaluating interlayer strength in examples and comparative examples.

Fig. 2 is a sectional view schematically showing a buffer material for electronic components according to an embodiment of the present invention.

Fig. 3 is a sectional view schematically showing a buffer material for electronic components according to another embodiment of the present invention.

Detailed Description

The present invention will be specifically explained below.

[ foamed composite sheet ]

The foamed composite sheet of the present invention has a foamed sheet containing at least one resin selected from the group consisting of an elastomer resin and a polyolefin resin, and a resin layer laminated on at least one surface of the foamed sheet.

The foamed sheet has excellent impact absorbability because it contains at least one resin selected from the group consisting of an elastomer resin and a polyolefin resin. On the other hand, the mechanical strength of the resin layer is excellent. The foamed composite sheet of the present invention has excellent impact absorbability and mechanical strength by having the foam sheet and the resin layer. In the present specification, the foamed sheet may be referred to as a foamed resin layer.

The 25% compressive strength of the foamed composite sheet of the present invention is preferably 1.0 to 700kPa. When the 25% compressive strength of the foamed composite sheet of the present invention is 1.0 to 700kPa, the balance between the impact absorbability and the mechanical strength of the foamed composite sheet becomes further favorable.

When the foamed sheet contains an elastomer resin, the foamed composite sheet of the present invention can suppress blocking and has more excellent impact resistance and impact absorbability by setting the interlayer strength and 25% compression strength of the foamed composite sheet within predetermined ranges. Further, the foamed composite sheet of the present invention can have high tensile strength, low compressive strength and excellent reworkability by using the foamed composite sheet in which the foamed sheet contains a polyolefin resin and the resin layer contains a polyethylene resin layer as a cushioning material for electronic parts.

Here, a foamed composite sheet of the present invention in which a foamed sheet contains an elastomer resin is described as embodiment 1, and a foamed composite sheet in which a foamed sheet contains a polyolefin resin and a resin layer contains a polyethylene resin layer is used as a cushion material for electronic components is described as embodiment 2.

[1 st embodiment ]

[ foamed composite sheet ]

The foamed composite sheet according to embodiment 1 of the present invention includes a foamed sheet containing an elastomer resin, and a resin layer laminated on at least one surface of the foamed sheet. When foamed sheets containing an elastomer resin are superposed on each other, blocking is generally easy to occur, so that a trouble is easily caused when the sheets are wound on a reel and then unwound from the reel. On the other hand, the foamed composite sheet according to embodiment 1 of the present invention has a resin layer provided on at least one surface of a foamed sheet containing an elastomer resin, and therefore, when wound on a reel, the foamed sheets can be prevented from directly contacting each other, and blocking can be suppressed.

Further, the foamed composite sheet according to embodiment 1 of the present invention has excellent impact resistance and impact absorbability because the interlayer strength and 25% compression strength are within predetermined ranges.

(interlaminar Strength)

The foamed composite sheet according to embodiment 1 of the present invention has an interlayer strength of 0.3MPa or more. When the interlayer strength is less than 0.3MPa, the impact resistance of the foamed composite sheet is deteriorated. The interlayer strength is mainly expressed by the tensile strength in the thickness direction of the foam sheet, that is, the degree of difficulty in breaking the foam sheet when an external force is applied in the stretching direction of the thickness, and by setting the interlayer strength to a certain value or more, the impact resistance can be made excellent.

The interlayer strength of the foamed composite sheet is preferably 0.32MPa or more, more preferably 0.35MPa or more. The upper limit of the interlayer strength is not particularly limited, but is usually 5MPa or less. By setting the interlayer strength of the foamed composite sheet in such a range, the impact resistance can be improved.

The interlayer strength of the foamed composite sheet can be measured by the method described in examples. In this measurement method, the foamed composite sheet is pulled in the thickness direction, and the maximum load at the time of sheet breakage (peeling) is measured. The breakage occurring in the measurement of the interlayer strength of the foamed composite sheet according to embodiment 1 of the present invention does not easily occur at the interface between the foamed sheet and the resin layer, but mainly occurs inside the foamed sheet. Therefore, the interlayer strength is mainly reflected in the tensile strength in the thickness direction of the foamed sheet.

The interlayer strength of the foamed composite sheet can be adjusted by adjusting the type of the elastomer resin constituting the foamed sheet, the apparent density of the foamed sheet, and the thickness of the foamed sheet. Further, the interlayer strength of the foamed composite sheet can be adjusted by the below-described 25% compressive strength.

(25% compressive Strength)

The foamed composite sheet according to embodiment 1 of the present invention has a 25% compressive strength of 30 to 700kPa. Within such a range, the impact absorbability is good and the flexibility is excellent. Further, by setting the 25% compressive strength of the foamed composite sheet to such a range, the interlayer strength can be easily adjusted to the above range. The 25% compressive strength is preferably 35 to 200kPa, more preferably 40 to 100kPa.

Hereinafter, a foamed composite sheet according to embodiment 1 of the present invention will be described in order of a foamed sheet and a resin layer.

< foamed sheet >

In embodiment 1, the foamed sheet contains an elastomer resin. The elastomer resin is not particularly limited, but a thermoplastic elastomer resin is preferable.

Examples of the thermoplastic elastomer resin include olefin elastomer resins, styrene elastomer resins, vinyl chloride elastomer resins, polyurethane elastomer resins, polyester elastomer resins, and polyamide elastomer resins. One kind of them may be used alone, or 2 or more kinds may be used in combination.

Among these, as the thermoplastic elastomer resin, at least one selected from the group consisting of olefin elastomer resins, vinyl chloride elastomer resins, and styrene elastomer resins is preferable, and olefin elastomer resins are more preferable, from the viewpoint of improving the impact resistance and impact absorbability of the foamed composite sheet.

Examples of the olefin-based elastomer resin include ethylene- α -olefin copolymers such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and ethylene-butene rubber (EBM), propylene- α -olefin copolymers, and crystalline olefin-ethylene-butene-crystalline olefin copolymers (CEBC). Among these, from the viewpoint of further improving the impact resistance and impact absorbability of the foamed composite sheet, CEBC is particularly preferable. The crystalline olefin portion of the CEBC is preferably a crystalline ethylene polymer, and the ethylene-butene portion is preferably an amorphous polymer.

Examples of commercially available products of CEBC include DYNARON manufactured by JSR corporation.

Examples of the vinyl chloride elastomer resin include resins obtained by adding a plasticizer to polyvinyl chloride having a high polymerization degree (for example, a polymerization degree of 2000 or more), resins obtained by modifying polyvinyl chloride, and mixtures of the resins with other resins.

Examples of the styrene-based elastomer resin include a styrene-butadiene-styrene (SBS) block copolymer, a styrene-butadiene-butylene-styrene (SBBS) block copolymer, a styrene-ethylene-butylene-styrene (SEBS) block copolymer, a hydrogenated styrene-butylene rubber (HSBR), a styrene-ethylene-propylene-styrene (SEPS) block copolymer, a styrene-isobutylene-styrene (SIBS) block copolymer, and a styrene-isoprene-styrene (SIS) block copolymer.

The foamed sheet may contain other resins than the elastomer resin within a range not to impair the effects of the present invention, and the elastomer resin is preferably 70% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass, relative to the total amount of the resin components in the foamed sheet.

The content of the elastomer resin in the foamed sheet is preferably 70% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and 100% by mass or less.

The apparent density of the foamed sheet is not particularly limited, but is preferably 0.1 to 0.8g/cm from the viewpoint of good impact resistance and impact absorbability ³ More preferably 0.2 to 0.7g/cm ³ More preferably 0.3 to 0.6g/cm ³ 。

The apparent density of the foamed sheet can be measured in accordance with JIS K7222 (2005).

The thickness of the foamed sheet is not particularly limited, but is preferably 0.05 to 1.5mm, more preferably 0.07 to 1.0mm, and still more preferably 0.1 to 0.7mm. When the thickness of the foamed sheet is in such a range and the thickness of the resin layer described later is preferably 0.01 to 0.1mm, more preferably 0.02 to 0.06mm, the foamed composite sheet can be made thin. The foamed composite sheet according to embodiment 1 of the present invention is excellent in impact resistance and impact absorbability even when it is thin, and therefore can be suitably used for miniaturized electronic devices.

The thickness of the foamed sheet is preferably larger than the total thickness of the resin layer, and the total thickness of the resin layer is preferably 0.01 to 0.8, more preferably 0.1 to 0.4, relative to the thickness of the foamed sheet (total thickness of the resin layer/thickness of the foamed sheet). By setting the range, the interlayer strength and the 25% compressive strength can be easily set to the above ranges. The total thickness of the resin layer means the thickness of the resin layer when the resin layer is provided only on one side of the foamed sheet, and means the sum of the thicknesses of the resin layers provided on both sides when the resin layer is provided on both sides.

The foamed sheet is preferably produced by foaming a foamable resin composition containing the elastomer resin and a foaming agent. As the above-mentioned foaming agent, a thermal decomposition type foaming agent is preferable.

As the thermal decomposition type foaming agent, an organic foaming agent or an inorganic foaming agent can be used. Examples of the organic blowing agent include azodicarbonamide, azodicarbonamide metal salts (barium azodicarboxylate, etc.), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N, N '-dinitrosopentamethylenetetramine, hydrazonodicarbonamide, hydrazine derivatives such as 4,4' -oxybis (benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonylsemicarbazide.

Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, and monosodium citrate anhydrous.

Among these, from the viewpoint of obtaining fine bubbles and from the viewpoint of economy and safety, an azo compound is preferable, and azodicarbonamide is more preferable. These may be used singly or in combination of 2 or more.

The amount of the thermal decomposition type foaming agent to be added to the foamable resin composition is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and still more preferably 3 to 10 parts by mass, per 100 parts by mass of the elastomer resin.

The foamable resin composition preferably contains a cell nucleus-adjusting agent in addition to the elastomer resin and the thermal decomposition type foaming agent. Examples of the cell nucleus adjusting agent include phenol compounds, nitrogen-containing compounds, thioether compounds, zinc compounds such as zinc oxide and zinc stearate, and organic compounds such as citric acid and urea, and among these, phenol compounds, nitrogen-containing compounds, thioether compounds, and mixtures thereof are more preferable. The amount of the cell nucleus-adjusting agent is preferably 0.1 to 8 parts by mass, more preferably 0.2 to 5 parts by mass, and still more preferably 0.3 to 2.5 parts by mass, per 100 parts by mass of the elastomer resin.

The foamable resin composition may contain, in addition to the above, additives usually used in foams such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, and fillers, as necessary.

< resin layer >

The foamed composite sheet according to embodiment 1 of the present invention has a resin layer on at least one surface of a foamed sheet. By having the resin layer, blocking at the time of winding the foamed composite sheet can be suppressed. The resin layer may be provided only on one side of the foam sheet, or may be provided on both sides. However, from the viewpoint of more easily suppressing blocking, it is preferably provided on both surfaces.

The kind of the resin layer is not particularly limited, but is preferably at least one selected from the group consisting of olefin-based resins, vinyl chloride-based resins, styrene-based resins, urethane-based resins, polyester-based resins, polyamide-based resins, and ionomer-based resins. Among these, olefin-based resins are preferred from the viewpoint of easy inhibition of blocking.

The olefin-based resin includes polyethylene-based resins, polypropylene-based resins, and the like, and polyethylene-based resins are preferred.

Examples of the polyethylene resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, an ethylene-vinyl acetate copolymer containing ethylene as a main component, and an ethylene-ethyl acrylate copolymer containing ethylene as a main component. Among these, high density polyethylene is preferable because it can have relatively high strength even if it is thin. Preferably of high density polyethyleneThe density was 0.94g/cm ³ More preferably 0.942 to 0.970g/cm ³ 。

Examples of the polypropylene resin include homopolypropylene, maleic acid-modified polypropylene, chlorinated polypropylene, ethylene-propylene copolymer, and butene-propylene copolymer. The polypropylene resin may be used alone, or a plurality of polypropylene resins may be used in combination.

The thickness of the resin layer is preferably 0.01 to 0.1mm, more preferably 0.02 to 0.06mm, as described above. Within this range, the foamed composite sheet can be made thinner, and the 25% compressive strength can be easily adjusted to the above range.

When resin layers are provided on both sides of the foamed sheet, the resin layers may be the same in type and thickness or may be different in thickness.

The resin layer may contain additives such as an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, and a filler.

Method for producing foamed composite sheet

The method for producing the foamed composite sheet according to embodiment 1 of the present invention is not particularly limited. For example, the foam sheet and the resin layer may be prepared separately and then attached to each other, but it is preferably produced by a method including the following steps I to III.

(I) A step of obtaining a multilayer laminate sheet having a layer formed from a foamable resin composition and a resin layer formed on at least one surface of the layer,

(II) a step of crosslinking the multilayer laminate sheet obtained in the step (I),

(III) a step of foaming the layer of the crosslinked multilayer laminate sheet formed of the foamable resin composition to obtain a foamed composite sheet.

The respective steps will be described below.

(Process (I))

In the step (I), a method for obtaining the multilayer laminate sheet is not particularly limited, and it is preferably performed by coextrusion molding.

Specific examples of the coextrusion molding are as follows. The resin for forming the resin layer and other additives blended as necessary are supplied to a 1 st extruder and melt-kneaded, and the foamable resin composition containing the elastomer resin, the foaming agent, and the additives blended as necessary is supplied to a 2 nd extruder and melt-kneaded.

Next, the resin materials supplied from the 1 st and 2 nd extruders are combined and extruded into a sheet shape from a T-die or the like, thereby obtaining a multilayer laminate sheet having a 2-layer structure. In the case of this specific example, a multilayer laminate sheet having a layer formed of the foamable resin composition and a resin layer formed on one surface of the layer can be obtained.

In order to obtain a multilayer laminate sheet having a 3-layer structure in which resin layers are laminated on both sides of a foamable resin composition, for example, the following procedure is performed. The resin for forming the resin layer and other additives added as necessary are supplied to the 1 st and 3 rd extruders for melt-kneading, and the foamable resin composition containing the elastomer resin, the thermal decomposition type foaming agent, and the additives added as necessary is supplied to the 2 nd extruder for melt-kneading.

Next, the resin materials supplied from the 1 st to 3 rd extruders were combined so that the composition of the 2 nd extruder became an intermediate layer, and sheet-like extruded from a T die or the like to obtain a multilayer laminate sheet having a 3-layer structure.

The coextrusion molding may be performed by any of a clamp (feed block) method and a multi-flow (multi-manifold) method, but a clamp method is preferable.

(Process (II))

In the step (II), the multilayer laminate sheet obtained in the step (I) is crosslinked. As a crosslinking method, there are the following methods: the multilayer laminate sheet obtained in step (I) is heated and crosslinked by mixing an organic peroxide in advance. In the present invention, however, the multilayer laminate sheet is preferably crosslinked by irradiation with ionizing radiation. Examples of the ionizing radiation include electron beams and β rays, and electron beams are preferred.

The irradiation dose of the ionizing radiation is preferably 30 to 50kGy, more preferably 35 to 40kGy.

(Process (III))

In the step (III), the multilayer laminate sheet crosslinked in the step (II) is subjected to foaming treatment to foam the layer formed of the foamable resin composition. The treatment may be any treatment as long as it can foam the foaming agent in the layer formed of the foamable resin composition, and in the case where the foaming agent is a thermal decomposition type foaming agent, the multilayer laminate sheet is foamed by heating. The heating temperature may be not lower than the decomposition temperature of the thermal decomposition type foaming agent, and is, for example, about 150 to 320 ℃.

The method of heating the multilayer laminate sheet is not particularly limited, and examples thereof include a method of heating the multilayer laminate sheet with hot air, a method of heating with infrared rays, a method of heating with a salt bath, a method of heating with an oil bath, and the like, and these methods can be used in combination. The foamed composite sheet according to embodiment 1 of the present invention can be obtained by the step (III).

The foamed composite sheet according to embodiment 1 of the present invention is less likely to cause blocking, and therefore, can be manufactured by a process of winding the foamed composite sheet around a reel. The foamed composite sheet according to embodiment 1 of the present invention may be stored in a state of being wound on a reel.

The application of the foamed composite sheet according to embodiment 1 of the present invention is not particularly limited, and is preferably used, for example, in electronic equipment. The foamed composite sheet according to embodiment 1 of the present invention is excellent in impact resistance and impact absorbability even when the foamed composite sheet is thin, and therefore can be suitably used in various portable electronic devices having a small space in which the foamed composite sheet is disposed. Further, the foamed composite sheet can be used in a portable electronic device in a frame shape.

Examples of the portable electronic device include a mobile phone, a camera, a game machine, an electronic notebook, and a notebook computer. The foamed composite sheet according to embodiment 1 of the present invention may be used in an electronic device after being formed into a tape to be described later.

[ adhesive tape ]

Further, the foamed composite sheet may be used for an adhesive tape having the foamed composite sheet as a base material. The adhesive tape may have, for example, a foamed composite sheet, and an adhesive material disposed on at least one side of the foamed composite sheet. The adhesive tape may be adhered to other components by means of an adhesive material. The tape may have an adhesive material on both surfaces of the foamed composite sheet, or may have an adhesive material on only one surface.

The pressure-sensitive adhesive material may be a single pressure-sensitive adhesive layer laminated on the surface of the foamed composite sheet or may be a double-sided pressure-sensitive adhesive sheet attached to the surface of the foamed composite sheet as long as it has at least a pressure-sensitive adhesive layer, but is preferably a single pressure-sensitive adhesive layer. The double-sided adhesive sheet includes a substrate and adhesive layers provided on both surfaces of the substrate. In the double-sided adhesive sheet, one adhesive layer is used for bonding the foamed composite sheet, and the other adhesive layer is used for bonding other members.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, or the like can be used. Further, a release sheet such as release paper may be bonded to the adhesive material.

The thickness of the adhesive is preferably 5 to 200. Mu.m, more preferably 7 to 150. Mu.m, and still more preferably 10 to 100. Mu.m.

[2 nd embodiment ]

[ buffer Material for electronic Components ]

A cushion material for electronic components according to embodiment 2 of the present invention includes a foamed resin layer and a skin resin layer provided on at least one surface of the foamed resin layer. The foamed resin layer is made of a foam and has a large number of cells formed of cells. The skin resin layer is a non-foamed body and is a resin layer having no cell.

As shown in fig. 2, the electronic component cushion material 20 may have a foamed resin layer 21 and a skin resin layer 22 laminated on only one side, or may have a foamed resin layer 21 and skin resin layers 22 and 22 laminated on both sides thereof as shown in fig. 3. However, as shown in fig. 2, the electronic component cushioning material 20 is preferably provided with a skin resin layer 22 only on one surface of a foamed resin layer 21.

The skin resin layer 22 is preferably directly laminated on the foamed resin layer 21 by coextrusion described later, but the foamed resin layer 21 may be laminated through another layer such as an adhesive layer, within a range not to impair the effects of the present invention.

Hereinafter, the cushioning material for electronic components will be described in more detail.

(thickness)

In the cushioning material for electronic parts, the thickness of the foamed resin layer is preferably 0.05 to 1.5mm. When the thickness of the foamed resin layer is within the above range, it is easy to achieve a good balance of mechanical strength, flexibility, and impact absorption. The thickness of the foamed resin layer is more preferably 0.07 to 1.3mm, and still more preferably 0.1 to 1.0mm.

In the cushioning material for electronic parts, the thickness of the skin resin layer is preferably 0.005 to 0.5mm. By setting the thickness of the skin resin layer within the above range, it is possible to easily achieve a good balance between mechanical strength, flexibility, and impact absorbability. The thickness of the skin resin layer is more preferably 0.01 to 0.3mm, and still more preferably 0.02 to 0.1mm.

The thickness of the cushioning material for electronic components according to embodiment 2 of the present invention is preferably 0.055 to 2.5mm. If the thickness of the cushioning material for electronic components is 0.055mm or more, excessive reduction in the thickness of the skin resin layer and the foamed resin layer can be suppressed, and various functions such as mechanical strength and impact absorbability can be improved. Further, if the thickness of the cushioning material for electronic components is 2.5mm or less, the cushioning material for electronic components of embodiment 2 of the present invention can be easily used for various electronic devices that are thinned, and it is possible to suppress the impact absorbability and flexibility of the cushioning material for electronic components from being deteriorated due to the excessively thick skin resin layer.

The thickness of the cushioning material for electronic parts is preferably 0.08 to 1.9mm, more preferably 0.12 to 1.2mm, in order to improve various performances and facilitate use in a thinned electronic device.

The thickness ratio of the thickness of the foamed resin layer to the total thickness of the skin resin layer (thickness of the foamed resin layer/thickness of the skin resin layer) is preferably 1.5 to 300. When the thickness ratio of the thickness of the foamed resin layer to the total thickness of the skin resin layer is 1.5 to 300, the cushioning material for electronic components can satisfy all of the various functions such as mechanical strength and impact absorbability. In the case where only the skin resin layer is provided on one surface of the foamed resin layer, the total thickness of the skin resin layer is 1 layer of the thickness of the skin resin layer. On the other hand, in the case where the skin resin layers are provided on both surfaces of the foamed resin layer, the total thickness of the skin resin layers is the total thickness of the 2 skin resin layers.

The thickness ratio of the thickness of the foamed resin layer to the total thickness of the skin resin layer is more preferably 2 to 100, and still more preferably 2.5 to 50.

(expansion ratio)

The expansion ratio of the foamed resin layer is preferably 1.5 to 30cm ³ (iv) g. The expansion ratio of the foamed resin layer is set to 1.5-30 cm ³ The impact-absorbing material for electronic components can be easily made to have good impact-absorbing properties by optimizing flexibility, mechanical strength, and the like of the impact-absorbing material for electronic components. The expansion ratio of the foamed resin layer is more preferably 2.0 to 20cm ³ A concentration of 2.5 to 15cm ³ /g。

The expansion ratio is the reciprocal of the apparent density measured. The apparent density can be measured in the same manner as the above-mentioned apparent density of the foamed sheet.

(average bubble diameter)

The average cell diameter of the cells in the foamed resin layer in the MD direction is preferably 30 to 350 μm. When the average cell diameter of the cells in the foamed resin layer in the MD direction is 30 to 350 μm, the cushioning material for electronic components is easily improved in flexibility, impact absorbability, and the like. The average cell diameter of the cells in the foamed resin layer in the MD direction is more preferably 60 to 300 μm, and still more preferably 100 to 250 μm.

The foam resin layer preferably has an average cell diameter in the TD direction of cells of 30 to 400 μm. When the average cell diameter of the cells in the foamed resin layer in the MD direction is 30 to 400 μm, the cushioning material for electronic components is easily improved in flexibility, impact absorbability, and the like. The average cell diameter of the cells in the foamed resin layer in the TD direction is more preferably 60 to 350. Mu.m, still more preferably 120 to 300. Mu.m.

The average cell diameter of the cells in the foamed resin layer in the MD direction and TD direction is preferably 30 to 375 μm. When the average cell diameter of the cells in the foamed resin layer in the MD direction is 30 to 375 μm, the cushioning material for electronic components is easily improved in flexibility, impact absorbability, and the like. The average cell diameter of the cells in the foamed resin layer in the TD direction is more preferably 60 to 325 μm, and still more preferably 110 to 275 μm.

The MD direction is a Machine direction (Machine direction) and is a direction corresponding to the extrusion direction, and the TD direction is a Transverse direction (Transverse direction), is a direction perpendicular to the MD direction, and is a direction parallel to the sheet surface of the multilayer foam sheet.

(independent bubble ratio)

The foamed resin layer has independent bubbles, and the independent bubble rate is more than 70%. By making the cells contained in the foamed resin layer substantially independent cells in this way, the impact absorbability and the like are easily improved. The independent bubble rate is preferably 80% or more, more preferably 90 to 100%. The independent bubble ratio was determined in accordance with ASTM D2856 (1998).

The independent bubble ratio can be measured more specifically in the following manner.

First, a test piece having a square planar shape with a side length of 5cm was cut out from a foamed resin layer, and then the thickness of the test piece was measured to calculate the apparent volume V of the test piece ₁ While simultaneously measuring the weight W of the test piece ₁ 。

Next, the volume V occupied by the bubbles is calculated based on the following formula ₂ . The density of the matrix resin constituting the test piece was ρ (g/cm) ³ )。

Volume V occupied by the bubbles ₂ ＝V ₁ -W ₁ /ρ

Next, the test piece was immersed in distilled water at 23 ℃ to a depth of 100mm from the water surface, and a pressure of 15kPa was applied to the test piece for 3 minutes. Then, the test piece was taken out of the water after the pressure was released in the water and left to stand for 1 minute, and the weight W of the test piece was measured by removing the water adhering to the surface of the test piece ₂ The continuous bubble rate F is calculated based on the following formula ₁ And the independent bubble rate F ₂ 。

Ratio of interconnected bubbles F ₁ (％)＝100×(W ₂ -W ₁ )/V ₂

Independent bubble rate F ₂ (％)＝100-F ₁

(degree of crosslinking)

The foamed resin layer and the skin resin layer are preferably crosslinked. Specifically, the crosslinking degrees of the foamed resin layer and the skin resin layer are preferably 15 to 60 mass%, and more preferably 20 to 50 mass%, respectively. When the degree of crosslinking of the foamed resin layer and the skin resin layer is within the above range, the cushioning material for electronic components can be easily made excellent in mechanical strength, flexibility, impact absorbability, and the like. Further, foaming in the foamed resin layer can be appropriately performed. The degree of crosslinking was measured as follows.

About 100mg of each test piece was taken out from the skin resin layer and the foamed resin layer, and the weight a (mg) of each test piece was accurately weighed. The test piece was then immersed in xylene at 120 ℃ for 30cm ³ Then, the mixture was filtered through a 200-mesh wire gauze, and the insoluble matter on the wire gauze was collected, vacuum-dried, and the weight B (mg) of the insoluble matter was accurately measured. The obtained value was substituted into the following formula to calculate the degree of crosslinking (% by mass).

Degree of crosslinking (% by mass) =100 × (B/a)

(25% compressive Strength)

The 25% compressive strength of the cushioning material for electronic parts is preferably 1.0 to 100kPa. The mechanical strength of the cushioning material for electronic components can be improved by setting the 25% compressive strength of the cushioning material for electronic components to 1.0kPa or more. Further, by setting the 25% compressive strength of the electronic component-use cushioning material to 100kPa or less, the electronic component-use cushioning material can be made excellent in flexibility, impact absorbability, and the like. The 25% compressive strength of the cushioning material for electronic parts is more preferably 1.2 to 80kPa. The 25% compressive strength of the cushioning material for electronic parts can be measured according to JIS K6767.

The 25% compressive strength of the foamed resin layer is preferably 1.0 to 100kPa, more preferably 1.2 to 80kPa, from the viewpoint of mechanical strength, flexibility, impact absorbability, and the like.

(compression Strength constant)

The compression strength constant of the cushioning material for electronic components is an index of 25% compression strength indicating how suitable the cushioning material for electronic components is when used as a cushioning material for electronic components. The compression strength constant of the cushioning material for electronic components was calculated by the following formula (III).

Compression strength constant = 200/(200 + 25% compression strength (kPa) of buffer material for electronic parts)

(III)

The cushioning material for electronic components preferably has a compression strength constant of 0.5 to 0.995, more preferably 0.6 to 0.994, from the viewpoint of satisfactory flexibility, impact absorbability, and the like.

(tensile Strength)

The tensile strength of the cushioning material for electronic components is preferably 5 to 30MPa in the MD direction, 5 to 25MPa in the TD direction, more preferably 10 to 25MPa in the MD direction, and more preferably 8 to 20MPa in the TD direction. When the tensile strength is in such a range, the mechanical strength of the cushioning material for electronic components can be easily improved. The tensile strength of the cushioning material for electronic parts was measured according to JIS K6767.

(ratio of tensile Strength constant)

The tensile strength constant ratio of the cushioning material for electronic parts is an index indicating the balance between the tensile strength in the skin resin layer and the tensile strength in the foamed resin layer. The tensile strength constant ratio of the cushioning material for electronic parts is a tensile strength constant ratio of the tensile strength constant of the skin resin layer to the tensile strength constant of the foamed resin layer (skin resin layer tensile strength constant/foamed resin layer tensile strength constant). The tensile strength constant of the foamed resin layer is calculated by the following formula (I). The tensile strength constant of the skin resin layer was calculated by the following formula (II).

Tensile strength constant of the foamed resin layer = { (tensile strength (MPa) in the MD direction of the foamed resin layer)) × (tensile strength (MPa) in the TD direction of the foamed resin layer)) } ^1/2 (I)

The skin resin layer tensile strength constant = { (tensile strength (MPa) in the MD direction of the skin resin layer)) × (tensile strength (MPa) in the TD direction of the skin resin layer)) } ^1/2 (II)

When the cushioning material for electronic components does not have a skin resin layer, the tensile strength constant ratio is set to 1.00.

The cushioning material for electronic components preferably has a tensile strength constant ratio of 1 to 50, more preferably 5 to 40, and even more preferably 10 to 30 from the viewpoints of reworkability, mechanical strength, flexibility, impact absorbability, and the like.

Further, from the viewpoint of improving the flexibility, impact absorbability and the like of the cushioning material for electronic parts, the tensile strength constant of the foamed resin layer is preferably lower than that of the skin resin layer by 0.5 to 10, more preferably 1 to 8, and still more preferably 1 to 3.

In addition, from the viewpoint of mechanical strength of the cushioning material for electronic components, the tensile strength constant of the skin resin layer is preferably 10 to 60, more preferably 20 to 55, and still more preferably 25 to 50.

(tensile Strength constant ratio. Times. Compressive Strength constant)

The value obtained by multiplying the tensile strength constant ratio of the skin resin layer tensile strength constant calculated by the above formula (II) to the foamed resin layer tensile strength constant calculated by the above formula (I) (skin resin layer tensile strength constant/foamed resin layer tensile strength constant) by the compressive strength constant calculated by the above formula (III) is preferably 1.5 or more. By setting this value to 1.5 or more, the cushioning material for electronic components can be easily improved in mechanical strength, flexibility, impact absorbability, and the like, and the reworkability can be improved.

The tensile strength constant ratio is more preferably 3 or more, still more preferably 5 or more, and particularly preferably 10 or more, multiplied by the compressive strength constant.

[ resin ]

In embodiment 2, the foamed resin layer contains a polyolefin resin. Examples of the polyolefin resin contained in the foamed resin layer include polyethylene resin, polypropylene resin, and ethylene-vinyl acetate copolymer, and among these, polyethylene resin is preferred. Further, the skin resin layer contains a polyethylene resin. Examples of the polyethylene resin contained in the foamed resin layer and the skin resin layer include polyethylene resins polymerized by a polymerization catalyst such as a ziegler-natta catalyst, a metallocene catalyst, or a chromium catalyst. The resin used for the foamed resin layer and the skin resin layer may be the same or different. However, from the viewpoint of improving the affinity with the skin resin layer and the laminating property with the skin resin layer, the foamed resin layer preferably contains a polyethylene resin. In addition, from the viewpoint of improving the curved surface conformability and the level difference conformability due to uniform elongation of the foamed resin layer and the skin resin layer during stretching, the catalyst used in the production of the polyethylene resin of the foamed resin layer is preferably the same catalyst as the catalyst used in the production of the polyethylene resin of the skin resin layer.

Examples of the polyethylene resin contained in the foamed resin layer and the skin resin layer include High Density Polyethylene (HDPE), high pressure Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), and ethylene ionomer. These may be used singly or in combination of 2 or more. Examples of the α, β -unsaturated carboxylic acid used in the ethylene ionomer include acrylic acid, methacrylic acid, and maleic acid. Further, examples of the metal ion used in the ethylene ionomer include Na ⁺ 、K ⁺ 、Ag ⁺ 、Cu ⁺ 、Cu ²⁺ 、Ba ²⁺ 、Zn ²⁺ 、Fe ²⁺ And so on.

Among these polyethylene resins, LLDPE is preferable as the polyethylene resin contained in the foamed resin layer. By incorporating LLDPE in the foamed resin layer, high flexibility can be imparted to the cushioning material for electronic components, and the foamed resin layer can be made thinner.

The LLDPE contained in the foamed resin layer is more preferably LLDPE obtained by copolymerizing ethylene (for example, 75 mass% or more, preferably 90 mass% or more based on the total monomer amount) with a small amount of α -olefin contained as necessary.

Specific examples of the α -olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Among them, an α -olefin having 4 to 10 carbon atoms is preferable.

The density of the polyethylene resin, for example, LLDPE is preferably 0.870 to 0.930g/cm ³ More preferably 0.910 to 0.930g/cm ³ . As the polyethylene resin, various polyethylene resins can be used, and further, polyethylene resins outside the above density range can be used.

Among the polyethylene resins, the polyethylene resin contained in the skin resin layer is preferably at least one polyethylene resin selected from HDPE and LLDPE. By incorporating at least one polyethylene resin selected from HDPE and LLDPE in the skin resin layer, the cushioning material for electronic parts can be provided with high tensile strength while maintaining high flexibility due to the foamed resin layer. HDPE is more preferable from these viewpoints.

The HDPE contained in the skin resin layer is more preferably an HDPE obtained by copolymerizing ethylene (for example, 90 mass% or more, preferably 95 mass% or more of the total monomer amount) with a small amount of an α -olefin contained as necessary.

The α -olefin is preferably an α -olefin having 4 to 6 carbon atoms, and specific examples thereof include 1-butene and 1-hexene.

The density of HDPE is preferably 0.942g/cm ³ More preferably 0.942 to 0.959g/cm ³ . Various polyethylene resins may be used as the polyethylene resin, and polyethylene resins outside the above density range may be contained.

As the LLDPE contained in the skin resin layer, the same LLDPE as that contained in the foamed resin layer can be used.

(metallocene catalyst)

HDPE, LLDPE and LDPE contained in the foamed resin layer and the skin resin layer are preferably produced using a metallocene catalyst.

Examples of the metallocene catalyst include compounds such as bis (cyclopentadienyl) metal complexes having a structure in which a transition metal is sandwiched between pi-electron-based unsaturated compounds. More specifically, there may be mentioned compounds in which 1 or 2 or more cyclopentadienyl rings or the like are present as ligands (ligands) on tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, platinum and the like.

The properties of the active sites of such metallocene catalysts are uniform, and each active site has the same degree of activity. Since the polymer synthesized using a metallocene catalyst has high uniformity in molecular weight, molecular weight distribution, composition distribution, and the like, when a sheet including the polymer synthesized using a metallocene catalyst is crosslinked, crosslinking proceeds uniformly. Since the uniformly crosslinked sheet is uniformly foamed, the physical properties are easily stabilized. Further, since uniform stretching is possible, the thickness of the foamed resin layer and the skin resin layer can be formed uniformly.

Examples of the ligand include a cyclopentadienyl ring and an indenyl ring. These cyclic compounds may be substituted with hydrocarbyl, substituted hydrocarbyl or hydrocarbon-substituted metalloid radicals. Examples of the hydrocarbon group include methyl, ethyl, various propyl groups, various butyl groups, various pentyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various cetyl groups, and phenyl groups. The term "various" means that various normal, secondary, tertiary and iso isomers are included.

Further, a compound obtained by polymerizing a cyclic compound in the form of an oligomer can be used as a ligand.

Further, in addition to the pi-electron-based unsaturated compound, monovalent anion ligands such as chlorine and bromine, divalent anion chelate ligands, hydrocarbons, alkoxylates, arylamides, aryl oxides, amides, arylamides, phosphides, arylphosphides, and the like can be used.

Examples of the metallocene catalyst containing a tetravalent transition metal and a ligand include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethylsilyltetramethylcyclopentadienyl-tert-butylamidozirconium dichloride and the like.

Metallocene catalysts function as catalysts in the polymerization of various olefins by combining with a specific cocatalyst (cocatalyst). Specific examples of the cocatalyst include Methylaluminoxane (MAO) and boron compounds. The proportion of the cocatalyst to the metallocene catalyst is preferably 10 to 100 ten thousand mol times, and more preferably 50 to 5,000 mol times.

(Ziegler Natta catalyst and chromium catalyst)

The HDPE contained in the skin resin layer may be manufactured using a ziegler natta catalyst or a chromium catalyst.

As Ziegler-Natta catalysts, preference is given to using, for example, tiCl ₄ The catalyst supported on a magnesium compound, more preferably TiCl ₄ Supported on MgCl ₂ The catalyst of (1).

Examples of the chromium catalyst include phillips catalysts and complex chromium catalysts. The phillips catalyst can be obtained by supporting a chromium compound on a carrier of an inorganic oxide and then calcining the carrier in air to oxidize the chromium compound. Examples of the inorganic oxide include silica, silica-alumina, and silica-titania. Examples of the chromium compound include chromium acetate, chromium tris (acetylacetonate), chromium trioxide, and the like. On the other hand, examples of the complex chromium catalyst include a catalyst in which bis (cyclopentadienyl) chromium is supported on silica.

For example, HDPE can be produced by subjecting the catalyst to a slurry polymerization step, a solution polymerization system or a gas phase polymerization step. Further, HDPE can also be produced by two-stage polymerization in order to broaden the molecular weight distribution.

The resin contained in each of the foamed resin layer and the skin resin layer may be a polyethylene resin alone, or may be used in combination with another polyolefin resin, for example, in combination with another polyolefin resin described below. When used in combination with another polyolefin resin, the proportion of the other polyolefin resin to the polyethylene resin (100 parts by mass) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less.

Examples of the ethylene-vinyl acetate copolymer used as the other polyolefin resin include an ethylene-vinyl acetate copolymer containing 50 mass% or more of ethylene.

Examples of the polypropylene resin used as the other polyolefin resin include polypropylene and a propylene- α -olefin copolymer containing 50 mass% or more of propylene. These may be used singly or in combination of 2 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-heptene, and 1-octene, and among these, α -olefins having 6 to 12 carbon atoms are preferred.

The foamed resin layer and the skin resin layer may contain a resin other than the polyolefin resin. Examples of the resin other than the polyolefin resin include polyamide resins, polycarbonate resins, polyester resins, and elastomer resins such as hydrogenated styrene-based thermoplastic elastomer (SEBS).

In the foamed resin layer, the proportion of the resin other than the polyolefin resin to the total amount of the resin is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less. On the other hand, the proportion of the resin other than the polyolefin resin in the skin resin layer to the total amount of the resin is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.

[ foaming agent ]

The foamed resin layer in the cushioning material for electronic components according to embodiment 2 of the present invention is preferably a foam obtained by foaming a foamable composition containing the resin and a foaming agent. The foamed resin layer obtained by foaming is composed of a foamed body having a resin as a matrix resin, the resin being blended with a resin monomer or an additive added as needed, and having a large number of cells formed of cells inside.

Examples of the foaming agent include a thermal decomposition foaming agent, and examples of the thermal decomposition type foaming agent include an organic foaming agent and an inorganic foaming agent. The thermal decomposition type foaming agent may be used generally as long as it has a decomposition temperature higher than the melting temperature of the resin, for example, 140 to 270 ℃.

Specific examples of the organic foaming agent include those similar to those used for producing the foamed composite sheet according to embodiment 1 of the present invention.

The inorganic foaming agent may be the same as the inorganic foaming agent used for producing the foamed composite sheet according to embodiment 1 of the present invention.

Among these, from the viewpoint of obtaining fine bubbles and from the viewpoint of economy and safety, an azo compound is preferable, and azodicarbonamide is particularly preferable. These thermal decomposition type foaming agents may be used alone or in combination of 2 or more.

The amount of the thermal decomposition type foaming agent to be added to the foamable composition is preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, and still more preferably 1 to 10 parts by mass, per 100 parts by mass of the resin.

[ other additives ]

The resin foam layer, that is, the foamable composition may contain, if necessary, additives generally used in foams, such as an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, a filler, and a decomposition temperature adjusting agent. Among these, antioxidants and decomposition temperature regulators are preferably used.

The skin resin layer may be formed of a resin composition containing no foaming agent, may be formed of only a resin, or may be formed by blending various additives such as an antioxidant, a heat stabilizer, a coloring agent, a flame retardant, an antistatic agent, a filler, and a decomposition temperature adjusting agent with the resin. Of these, antioxidants are preferably used.

Examples of the antioxidant used in the skin resin layer and the foamed resin layer include a phenol-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, and an amine-based antioxidant. The content of the antioxidant in each of the skin resin layer and the foamed resin layer is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the resin.

Specific examples of the decomposition temperature adjusting agent include zinc oxide, zinc stearate, and urea. The content of the decomposition temperature adjusting agent in each of the skin resin layer and the foamed resin layer is preferably 0.01 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the resin.

[ method for producing cushioning Material for electronic Components ]

The cushioning material for electronic components according to embodiment 2 of the present invention is not particularly limited, and may be produced, for example, by a method including the following steps (1) to (2).

Step (1): a step of laminating a resin sheet and a foamable sheet formed from a foamable composition containing a resin and a thermal decomposition type foaming agent to obtain a multilayer sheet;

step (2): and a step of heating the multilayer sheet to foam the foamable sheet.

In the step (1), the multilayer sheet is preferably formed by coextrusion. Specifically, a resin, a foaming agent, and, if necessary, other additives are supplied to the 1 st extruder and melt-kneaded, and a sheet-shaped foamable composition (that is, a foamable sheet) is extruded from the 1 st extruder. At the same time, the resin constituting the skin resin layer and, if necessary, other additives are supplied to the 2 nd extruder and melt-kneaded, and a sheet-like resin composition (i.e., a resin sheet) is extruded from the 2 nd extruder. And then laminating them to obtain a multilayer sheet. In addition, when the skin resin layer is laminated on both surfaces of the foamed resin layer, 2 nd extruders for extruding the resin composition are prepared, and the resin sheet may be laminated on both surfaces of the foamable sheet.

The multilayer sheet may be formed by a method other than coextrusion, and for example, a foamable sheet formed in a sheet shape in advance and a resin sheet may be pressure-bonded between rollers or the like to form a multilayer sheet.

In the step (2), the multilayer sheet is heated by hot air, infrared rays, salt bath, or oil bath, and these methods may be used in combination. The heating temperature may be not lower than the foaming temperature of the thermal decomposition type foaming agent, and is preferably 200 to 300 ℃, more preferably 220 to 280 ℃.

The multilayer sheet may be stretched during the step (2) or in a subsequent step. That is, the stretching may be performed after the foamable sheet is foamed to form a multilayer foamed sheet, or the stretching may be performed while the foamable sheet is foamed. In the present production method, the average cell diameter and the thickness between cells in the above ranges can be easily obtained by stretching the multilayer foamed sheet. When the multilayer foamed sheet is stretched after foaming the foamable sheet, the multilayer foamed sheet may be stretched by continuing to maintain the molten state at the time of foaming without cooling the multilayer foamed sheet, or the multilayer foamed sheet may be stretched in a state in which the multilayer foamed sheet is cooled and then heated again to a molten or softened state.

The multilayer foamed sheet may be stretched in one direction of MD and TD, or may be stretched in two directions, preferably in two directions.

The multilayer foamed sheet is preferably stretched so that the thickness of the multilayer foamed sheet is 0.1 to 0.9 times, more preferably 0.15 to 0.75 times, and still more preferably 0.25 to 0.45 times. By stretching the multilayer foamed sheet within such a range, the compressive strength and tensile strength of the multilayer foamed sheet can be easily made good. Further, by being equal to or more than the lower limit value, it is possible to prevent the foamed sheet from being broken during stretching and the foaming ratio from being significantly reduced by escape of the foaming gas from the foamed resin layer during foaming.

The multilayer foamed sheet may be heated to, for example, 100 to 280 ℃, preferably 150 to 260 ℃ during stretching.

In the present production method, a step of crosslinking the multilayer sheet (crosslinking step) is preferably performed between the steps (1) and (2). In the crosslinking step, as a method for crosslinking the multilayer sheet, a method of irradiating the multilayer sheet with ionizing radiation such as electron beam, α ray, β ray, γ ray, or the like is used. The irradiation amount of the ionizing radiation may be adjusted so that the degree of crosslinking of the resulting multilayer foamed sheet is within the above-mentioned desired range, and is preferably 1 to 15Mrad, more preferably 4 to 13Mrad.

The method for producing the cushioning material for electronic components is not limited to the above method, and may be a method other than the above method. For example, crosslinking may be performed by a method in which an organic peroxide is previously mixed in the foamable composition without irradiating ionizing radiation, and the foamable composition is heated to decompose the organic peroxide.

The cushioning material for electronic parts is preferably used in, for example, electronic devices. The cushioning material for electronic components according to embodiment 2 of the present invention can be suitably used in thin electronic devices, for example, various portable electronic devices. Examples of the portable electronic device include a notebook computer, a mobile phone, a smartphone, a tag, and a portable music instrument. The cushioning material for electronic components is disposed between the electronic component and another component, for example, and absorbs an impact applied to the electronic component. Examples of the other components include other electronic components and components for supporting electronic components such as a housing of an electronic device. The cushioning material for electronic components can be used not only as an impact absorbing material for absorbing impact but also as a sealing material for filling gaps between components in an electronic device.

[ tape for electronic parts ]

The electronic component cushioning material may be used for an electronic component tape having the electronic component cushioning material as a base material. The electronic component tape includes, for example, an electronic component buffer material and an adhesive material provided on at least one surface of the electronic component buffer material. The electronic component tape can be bonded to another component with an adhesive material. The electronic component tape may have an adhesive material on both surfaces of the electronic component cushion material, or may have an adhesive material on one surface. The tape for electronic parts can also be used as an impact absorbing material and a sealing material.

Further, the adhesive material is preferably provided on the surface provided with the skin resin layer in the cushioning material for electronic components. With this configuration, the cushioning material for electronic components is less likely to be damaged during a rework operation.

The pressure-sensitive adhesive material may be a single pressure-sensitive adhesive layer laminated on the surface of the electronic component cushioning material or a double-sided pressure-sensitive adhesive sheet attached to the surface of the electronic component cushioning material, as long as the pressure-sensitive adhesive material has at least a pressure-sensitive adhesive layer. The double-sided adhesive sheet includes a substrate and adhesive layers provided on both surfaces of the substrate. In the double-sided adhesive sheet, one adhesive layer is used for bonding the foamed composite sheet, and the other adhesive layer is used for bonding other members.

Examples

The present invention is more specifically explained by examples, but the present invention is not limited to these examples at all.

[ measurement method ]

The measurement method and evaluation method of each physical property are as follows.

< apparent density and expansion ratio >

The apparent densities of the foam sheet and the multilayer foam sheet were measured in accordance with JIS K7222 (2005), and the reciprocal thereof was taken as the expansion ratio.

< interlayer Strength >

Fig. 1 shows a schematic diagram of a test apparatus for evaluating interlayer strength. A primer (セメダイン, manufactured by "PPX プライマー") was applied to the area of 25mm square of the foamed composite sheet 11, and then an adhesive 12 having a diameter of 5mm was dropped onto the center of the applied portion (セメダイン, manufactured by "PPX"). Immediately thereafter, a 25mm square spacer 13 made of aluminum was placed on the portion to which the adhesive was dropped, and the foamed composite sheet was pressure-bonded to the spacer 13. Then, the foamed composite sheet is cut according to the size of the positioning member 13. A primer was applied to the surface of the cut foamed composite sheet where no spacer 13 was bonded, and an adhesive 12 having a diameter of 5mm was dropped onto the center of the applied portion. Immediately thereafter, a 10mm square spacer 14 made of aluminum was placed on the portion to which the adhesive was dropped, and the foamed composite sheet was pressure-bonded to the spacer 14. The adhesive extruded on the periphery of the positioning member 14 is wiped off, and then the scratches 15 are formed on the foamed composite sheet according to the size of the positioning member 14. The adhesive was cured by leaving it at room temperature for 30 minutes to prepare a sample for interlayer strength measurement.

Next, the sample for interlayer strength measurement was fixed to a tester provided with a 1kN load cell (model エー, アンド, デイ, "テンシロン universal material tester") so that the sheet surface of the foamed composite sheet was perpendicular to the pulling direction. The spacer was pulled vertically upward at a rate of 100 mm/min to peel off only the 1 cm-square area of the foamed composite sheet. The maximum load at this time was measured as the result of the 1 st measurement. The same operation was repeated 3 times, and the average value was defined as the interlayer strength.

(iii) compressive Strength of < 25 >

The 25% compressive strength in the thickness direction of the foamed composite sheet and the multi-layer foamed sheet was measured in accordance with JIS K6767. The multilayer foam sheet may be cut after being immersed in liquid nitrogen for 1 minute to separate the foam sheet from the resin sheet. The 25% compressive strength of the foamed sheet and the resin sheet, respectively, was then measured.

< delamination strength >

The delamination strength of the foamed composite sheet was calculated by superposing 2 foamed composite sheets (280 mm in length and 50mm in width), pressure-bonding the sheets at 23 ℃ for 24 hours under a load of 3Kg, and measuring the delamination strength under conditions of a tensile angle of 180 ℃ and a tensile speed of 300 mm/min.

When 2 foam composite sheets are superposed, the upper and lower directions of the sheets are superposed in the same direction. For example, when the foamed composite sheet has a 3-layer structure, the lower layer of one sheet is brought into contact with the upper layer of the other sheet and superposed thereon.

< comprehensive evaluation >

The case where the interlayer strength was 0.3MPa or more and the peeling strength was 0.1N or less was evaluated as "G (Good)," and the case where the interlayer height was less than 0.3MPa or the peeling strength was more than 0.1N was evaluated as "B (Bad)".

< average bubble diameter >

The multilayer foamed sheet was cut into a 50mm square, immersed in liquid nitrogen for 1 minute, and then cut in the thickness direction in the MD direction and the TD direction, respectively. This operation was repeated 5 times by taking a magnified 200-fold photograph using a digital microscope ("VHX-900" made by キーエンス), measuring the cell diameter in the MD direction and the cell diameter in the TD direction for all the cells present in the cut surface of the foamed resin layer of the taken image, which is 2mm long in the MD direction and the TD direction, respectively. The average value of the cell diameters in the MD direction and the TD direction of all the cells was defined as the average cell diameter in the MD direction and the TD direction.

< tensile Strength >

A dumbbell No. 1 shape prescribed in JIS K6251.4.1 was cut out from the multilayer foamed sheet. Using this as a sample, tensile strengths in the MD direction and the TD direction were measured at a measurement temperature of 23 ℃ in accordance with JIS K6767 by means of a tensile tester (product name: テンシロン RTF235, エー, アンド, デイ Co., ltd.). Further, the multilayer foamed sheet can be separated from the resin sheet by immersing the foamed sheet in liquid nitrogen for 1 minute and then cutting the sheet. The tensile strength of the foamed sheet and the resin sheet can then be measured separately.

< tensile strength constant ratio x compressive strength constant >

The value is calculated by multiplying the ratio of the tensile strength constant to the compressive strength constant by the following formulas (I) to (IV). The tensile strength constant ratio in the case where no resin sheet was laminated was 1.00.

Skin resin layer tensile strength constant = { (tensile strength (MPa) in MD direction of skin resin layer) × (tensile strength (MPa) in TD direction of skin resin layer) } ^1/2 (II)

Compression strength constant = 200/(200 + 25% compression strength (kPa) of buffer material for electronic component)

(III)

Constant ratio of tensile strength = constant of tensile strength of skin resin layer/constant of tensile strength of foamed resin layer

(IV)

[ example 1]

A1 st extruder was charged with high-density polyethylene (HDPE) (product name HJ360, density 0.951g/cm, manufactured by Nippon ポリエチレン K.K.) ³ ) 100 parts by mass were melt-kneaded. 100 parts by mass of a crystalline olefin-ethylene-butene-crystalline olefin copolymer (CEBC) (product name Dynaron6200P, manufactured by JSR) as an elastomer resin, 5.5 parts by mass of azodicarbonamide as a blowing agent, and 1.2 parts by mass of a foaming aid as a cell nucleus adjuster were fed into a 2 nd extruder, and melt-kneaded to prepare a foamable resin composition. Further, the foaming aid was used under the trade name "SB-1018 RG" manufactured by ADEKA, inc. A3 rd extruder was charged with High Density Polyethylene (HDPE) (product name HJ360, manufactured by Nippon ポリエチレン, density 0.951g/cm ³ ) 100 parts by mass were melt-kneaded.

Next, the resin materials supplied from the 1 st to 3 rd extruders were combined and extruded in a sheet form to obtain a multilayer laminate sheet having a layer (middle layer) made of a foamable resin composition and resin layers formed on both surfaces (upper and lower layers) of the middle layer.

Next, both surfaces of the multilayer laminate sheet were irradiated with electron beams 30kGy having an acceleration voltage of 500kV for crosslinking, and then continuously fed into a foaming furnace maintained at 270 ℃ by hot air and an infrared heater for heating for 90 seconds to foam the multilayer laminate sheet, thereby obtaining a foamed composite sheet having a foamed sheet as an intermediate layer and resin layers as upper and lower layers. Table 1 shows the results.

[ example 2]

A1 st extruder was charged with high-density polyethylene (HDPE) (product name HJ360, density 0.951g/cm, manufactured by Nippon ポリエチレン K.K.) ³ ) 100 parts by mass were melt-kneaded. Into a 2 nd extruder, 100 parts by mass of a crystalline olefin-ethylene-butene-crystalline olefin copolymer (CEBC) (product of JSR., trade name Dynaron 6200P) as an elastomer resin, 5.5 parts by mass of azodicarbonamide as a blowing agent, and 1.2 parts by mass of a foaming aid as a cell nucleus adjusting agent were charged, and the materials were mixed, melted and kneaded to form a foamable resin compositionA compound (I) is provided. Further, the foaming aid was prepared under the trade name "SB-1018 RG" from ADEKA, inc.

Next, the resin materials supplied from the 1 st and 2 nd extruders were combined and extruded into a sheet shape, thereby obtaining a multilayer laminate sheet having a layer (intermediate layer) made of a foamable resin composition and a resin composition layer formed on one surface (upper layer) of the intermediate layer.

Next, both surfaces of the multilayer laminate sheet were crosslinked by irradiation with electron beams 30kGy having an acceleration voltage of 500kV, and then the multilayer laminate sheet was foamed by continuously feeding the crosslinked multilayer laminate sheet into a foaming furnace maintained at 270 ℃ by hot air and an infrared heater for 90 seconds to obtain a foamed composite sheet having a foamed sheet as an intermediate layer and a resin layer as an upper layer. Table 1 shows the results.

Comparative example 1

100 parts by mass of a crystalline olefin-ethylene-butene-crystalline olefin copolymer (CEBC) (product name Dynaron6200P, manufactured by JSR) as an elastomer resin, 5.5 parts by mass of azodicarbonamide as a foaming agent, and 1.2 parts by mass of a foaming aid as a bubble nucleus adjuster were fed into a 2 nd extruder and melt-kneaded to form a foamable resin composition. Further, the foaming aid was manufactured by ADEKA, inc., under the trade name "SB-1018 RG".

Next, the foamable resin composition was extruded from the extruder to obtain a sheet made of the foamable resin composition.

Subsequently, both surfaces of the sheet were irradiated with electron beams 30kGy having an acceleration voltage of 500kV to crosslink the sheet, and then continuously fed into a foaming furnace maintained at 270 ℃ by a hot air and infrared heater to be heated for 90 seconds, thereby foaming the sheet to obtain a foamed sheet. Table 1 shows the results.

Comparative example 2

A1 st extruder was charged with high-density polyethylene (HDPE) (product name HJ360, density 0.951g/cm, manufactured by Nippon ポリエチレン K.K.) ³ ) 100 parts by mass were melt-kneaded. 100 parts by mass of an elastomer resin (product name: dynaron6200P, manufactured by JSR) and 0.1 part by mass of an antioxidant were fed to a 2 nd extruder, and melt-kneaded to form a resinA fat composition. A3 rd extruder was charged with High Density Polyethylene (HDPE) (product name HJ360, manufactured by Nippon ポリエチレン, density 0.951g/cm ³ ) 100 parts by mass was melt-kneaded.

Next, the resin materials supplied from the 1 st to 3 rd extruders were combined and extruded in a sheet form, thereby obtaining a multilayer laminate sheet having a layer (middle layer) formed of a resin composition and resin layers formed on both sides (upper layer and lower layer) of the middle layer.

Next, both surfaces of the multilayer laminate sheet were crosslinked by irradiation with electron beams 30kGy having an acceleration voltage of 500kV, and then continuously fed into a foaming furnace maintained at 270 ℃ by hot air and an infrared heater and heated for 90 seconds, thereby obtaining a composite sheet having a resin sheet as an intermediate layer and resin layers as upper and lower layers.

Comparative example 3

Into the 1 st extruder, high Density Polyethylene (HDPE) (product name HJ360, density 0.951g/cm, manufactured by Nippon ポリエチレン, ltd.) ³ ) 100 parts by mass were melt-kneaded. 100 parts by mass of an elastomer resin CEBC (product name Dynaron6200P, manufactured by JSR) and 0.1 part by mass of an antioxidant were fed to the 2 nd extruder, and melt-kneaded to form a resin composition.

Next, the resin materials supplied from the 1 st and 2 nd extruders were combined and extruded into a sheet shape, thereby obtaining a multilayer laminate sheet having a layer (middle layer) formed of a resin composition and a resin layer formed on one surface (upper layer) of the middle layer.

Next, both surfaces of the multilayer laminate sheet were crosslinked by irradiation with electron beams 30kGy having an acceleration voltage of 500kV, and then continuously fed into a furnace maintained at 270 ℃ by hot air and an infrared heater and heated for 90 seconds, thereby obtaining a composite sheet having a resin sheet as an intermediate layer and a resin layer as an upper layer.

Comparative example 4

100 parts by mass of an elastomer resin CEBC (product name Dynaron6200P, manufactured by JSR) was fed to a 2 nd extruder, and melt-kneaded to form a resin composition.

Next, the resin composition was extruded from the extruder to obtain a sheet.

Subsequently, both surfaces of the sheet were irradiated with electron beams 30kGy having an acceleration voltage of 500kV to crosslink the sheet, and then the sheet was continuously fed into a furnace maintained at 270 ℃ by a hot air and infrared heater to be heated for 90 seconds, thereby obtaining a single-layer sheet.

TABLE 1

As is clear from table 1, the foamed composite sheet according to embodiment 1 of the present invention is excellent in impact resistance and impact absorbability because the interlayer strength and 25% compression strength are in predetermined ranges, and is less likely to block because of low delamination strength. On the other hand, in the sheet which does not satisfy the requirements of embodiment 1 of the present invention, the interlayer strength and 25% compression strength are not in the predetermined ranges, and the impact resistance and the like are poor or blocking is liable to occur.

[ example 3]

A 1 st extruder and a 2 nd extruder were prepared.

As the polyolefin resin for the expandable sheet, a linear low-density polyethylene resin obtained by a metallocene catalyst (product name "カーネル KF 283", manufactured by Nippon ポリエチレン Co., ltd.) having a density of 0.921g/cm was used ³ ) Azodicarbonamide is used as a thermal decomposition type foaming agent. Further, zinc oxide (made by Sakai chemical industry Co., ltd., trade name "OW-212F") was used as the decomposition temperature adjuster, and a phenol antioxidant 2,6-di-t-butyl-p-cresol was used as the antioxidant. 100 parts by mass of a polyolefin resin, 8.0 parts by mass of a thermal decomposition type foaming agent, 1 part by mass of a decomposition temperature adjusting agent, and 0.5 part by mass of an antioxidant were supplied to a 1 st extruder, and melt-kneaded at 130 ℃ to prepare a foamable composition.

As the polyethylene resin for the resin sheet, a high-density polyethylene resin (product of タマポリ, trade name "HD" and density: 0.949 g/cm) obtained by using a metallocene catalyst was used ³ ). The polyethylene resin was supplied to the 2 nd extruder and melt-kneaded at 130 ℃.

The foamable composition was extruded from the 1 st extruder, and the polyethylene resin was extruded from the 2 nd extruder, and the resin sheet was laminated on one surface of the foamable sheet by coextrusion, to obtain a multilayer sheet.

Next, the side of the multilayer sheet not having the resin sheet laminated thereon was irradiated with electron beam 4Mrad at an acceleration voltage of 500kV to crosslink the multilayer sheet, and then the crosslinked multilayer sheet was continuously fed into a foaming furnace maintained at 250 ℃ by hot air and an infrared heater to be heated and foamed, thereby obtaining a multilayer foamed sheet of example 3 in which the resin sheet 1 was laminated on one side of the foamed sheet 1.

[ example 4]

As the polyethylene resin for the resin sheet, a linear low-density polyethylene resin obtained by a metallocene catalyst (product name "カーネル KF 283", manufactured by Nippon ポリエチレン Co., ltd.) having a density of 0.921g/cm was used ³ ). Except for this, the resin sheet 2 was laminated on one surface of the foamed sheet 1 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 4.

[ example 5]

As the polyethylene resin for the resin sheet, a high-pressure process low-density polyethylene resin (product of タマポリ, trade name "AJ-1", manufactured by Kabushiki Kaisha, density: 0.924 g/cm) obtained by using a metallocene catalyst was used ³ ). Except for this, the resin sheet 3 was laminated on one surface of the foamed sheet 1 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 5.

[ example 6]

As the polyethylene resin for resin sheets, an ethylene ionomer (product name "NC-5" of タマポリ, manufactured by Kabushiki Kaisha) which is a copolymer of ethylene and methacrylic acid was used. Except for this, the resin sheet 4 was laminated on one surface of the foamed sheet 1 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 6.

[ example 7]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 6.0 parts by mass. Except for this, the resin sheet 1 was laminated on one surface of the foamed sheet 2 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 7.

[ example 8]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 6.0 parts by mass. Except for this, the resin sheet 2 was laminated on one surface of the foamable sheet 2 in the same manner as in example 4 to obtain a multilayer foamed sheet of example 8.

[ example 9]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 6.0 parts by mass. Except for this, the resin sheet 3 was laminated on one surface of the foamed sheet 2 in the same manner as in example 5, to obtain a multilayer foamed sheet of example 9.

[ example 10]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 6.0 parts by mass. Except for this, the resin sheet 4 was laminated on one surface of the foamed sheet 2 in the same manner as in example 6, to obtain a multilayer foamed sheet of example 10.

[ example 11]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 4.0 parts by mass. Except for this, the resin sheet 1 was laminated on one surface of the foamed sheet 3 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 11.

[ example 12]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 4.0 parts by mass. Except for this, the resin sheet 2 was laminated on one surface of the foamed sheet 3 in the same manner as in example 4 to obtain a multilayer foamed sheet of example 12.

[ example 13]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 4.0 parts by mass. Except for this, the resin sheet 3 was laminated on one surface of the foamed sheet 3 in the same manner as in example 5, to obtain a multilayer foamed sheet of example 13.

[ example 14]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 4.0 parts by mass. Except for this, the resin sheet 4 was laminated on one surface of the foamed sheet 3 in the same manner as in example 6, to obtain a multilayer foamed sheet of example 14.

[ example 15]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 2.0 parts by mass. Except for this, the resin sheet 1 was laminated on one surface of the foamed sheet 4 in the same manner as in example 3 to obtain a multilayer foamed sheet of example 15.

[ example 16]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 2.0 parts by mass. Except for this, the resin sheet 2 was laminated on one surface of the foamed sheet 4 in the same manner as in example 4 to obtain a multilayer foamed sheet of example 16.

[ example 17]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 2.0 parts by mass. Except for this, the resin sheet 3 was laminated on one surface of the foamed sheet 4 in the same manner as in example 5, to obtain a multilayer foamed sheet of example 17.

[ example 18]

The amount of the thermal decomposition type foaming agent was changed from 8.0 parts by mass to 2.0 parts by mass. Except for this, the resin sheet 4 was laminated on one surface of the foamed sheet 4 in the same manner as in example 6, to obtain a multilayer foamed sheet of example 18.

Comparative example 5

The resin sheet was not laminated on the foamable sheet, and the thickness of the foamable sheet was adjusted so that the thickness of the foamable sheet was 0.80mm. Except for this, a foamed sheet of comparative example 5 was obtained in the same manner as in example 3.

Comparative example 6

The resin sheet was not laminated on the foamable sheet, and the thickness of the foamable sheet was adjusted so that the thickness of the foamable sheet was 0.80mm. Except for this, a foam sheet of comparative example 6 was obtained in the same manner as in example 7.

Comparative example 7

The resin sheet was not laminated on the foamable sheet, and the thickness of the foamable sheet was adjusted so that the thickness of the foamable sheet was 0.30mm. Except for this, a foam sheet of comparative example 7 was obtained in the same manner as in example 11.

Comparative example 8

The resin sheet was not laminated on the foamable sheet, and the thickness of the foamable sheet was adjusted so that the thickness of the foamable sheet was 0.20mm. Except for this, a foam sheet of comparative example 8 was obtained in the same manner as in example 15.

The foamed sheets 1 to 4 and the resin sheets 1 to 4 were evaluated according to the evaluation methods described above. Table 2 shows the evaluation results of the foamed sheets 1 to 4, and table 3 shows the evaluation results of the resin sheets 1 to 4.

Other than extruding the foamable composition from the 1 st extruder without extruding the polyethylene resin from the 2 nd extruder, the foamed sheets 1 to 4 for evaluation were produced in the same manner as the multilayer foamed sheets of examples 3, 7, 11 and 15. Resin sheets 1 to 4 for evaluation were produced in the same manner as in the multilayer foamed sheets of examples 3 to 6 except that the foamable composition was not extruded from the 1 st extruder, and the polyethylene resin was extruded from the 2 nd extruder.

The multilayer foamed sheets of examples 3 to 18 and the foamed sheets of comparative examples 5 to 8 were evaluated according to the above evaluation methods. The evaluation results are shown in tables 4 to 6.

In tables 4 to 6, the ease of rework evaluation is an index for classifying whether or not the ease of rework after the tape was produced is good into 4 grades. In the case of examples 3 to 6, evaluation was made based on comparative example 5. Specifically, examples 3 to 6 were evaluated as "1" in the case of the same degree as in comparative example 5, as "2" in the case of being superior to comparative example 5 but having a smaller degree than in comparative example 5, as "3" in the case of being superior to comparative example 5 but having a larger degree than in comparative example 5, and as "4" in the case of being superior to comparative example 5 but having a larger degree than in comparative example. The same evaluation was carried out as for examples 7 to 10 with reference to comparative example 6, examples 11 to 14 with reference to comparative example 7, and examples 15 to 18 with reference to comparative example 8. The adhesive tape used in the evaluation was formed by laminating a single layer of an adhesive layer on the surface of the multilayer foamed sheet on which the skin resin layer was provided.

The thickness of the foamed sheets in tables 4 to 6 corresponds to the thickness of the foamed resin layer of the cushioning material for electronic components, and the thickness of the resin sheet corresponds to the thickness of the skin resin layer of the cushioning material for electronic components.

TABLE 2

TABLE 3

TABLE 4

TABLE 5

TABLE 6

In the case of one layer, the tensile strength constant ratio is 1.00.

From the results of tables 4 to 6, it is understood that even when a resin sheet containing a polyethylene resin is laminated on at least one surface of a foamed sheet containing a polyolefin resin, the foamed sheet can maintain a low compressive strength. However, the multilayer foamed sheet has higher tensile strength than the foamed sheet, and the multilayer foamed sheet is also excellent in reworkability.

Description of the figures

11. Foamed composite sheet

12. Adhesive material

13. Locating piece

14. Aluminum positioning piece

15. Scratch mark

20. Multilayer foamed sheet

21. Foamed resin layer

22. Skin resin layer

Claims

1. A foamed composite sheet comprising a foamed sheet and a resin layer laminated on at least one surface of the foamed sheet, wherein the resin constituting the foam of the foamed sheet is composed of an elastomer resin or is composed of an elastomer resin and a polyolefin resin,

the resin layer is at least one selected from the group consisting of olefin-based resins, vinyl chloride-based resins, styrene-based resins, urethane-based resins, polyester-based resins, polyamide-based resins, and ionomer-based resins,

the foamed composite sheet has a 25% compressive strength of 1.0 to 700kPa and an interlayer strength of 0.3MPa or more.

2. The foamed composite sheet according to claim 1, wherein the elastomer resin is a thermoplastic elastomer resin.

3. The foamed composite sheet according to claim 2, wherein the thermoplastic elastomer resin is at least one selected from the group consisting of olefin elastomer resins, vinyl chloride elastomer resins, and styrene elastomer resins.

4. The foamed composite sheet according to any one of claims 1 to 3, wherein the foamed sheet has a thickness of 0.05 to 1.5mm, and the resin layer has a thickness of 0.01 to 0.1mm.

5. The foamed composite sheet according to any one of claims 1 to 3, which has an apparent density of 0.1 to 0.8g/cm ³ 。

6. An adhesive tape comprising the foamed composite sheet according to any one of claims 1 to 5 and an adhesive material provided on at least one side of the foamed composite sheet.

7. A cushion material for electronic parts, which comprises the foamed composite sheet according to claim 1, wherein the foamed sheet is a foamed resin layer containing a polyolefin resin and having a plurality of cells formed by cells, and the resin layer is a skin resin layer containing a polyethylene resin.

8. The cushioning material for electronic parts according to claim 7, wherein the thickness of the foamed resin layer is 0.05 to 1.5mm.

9. The cushioning material for electronic components according to claim 7 or 8, wherein the thickness of the skin resin layer is 0.005 to 0.5mm.

10. The cushioning material for electronic parts according to claim 7 or 8, wherein the polyethylene resin is at least one polyethylene resin selected from the group consisting of High Density Polyethylene (HDPE), linear Low Density Polyethylene (LLDPE), high pressure process Low Density Polyethylene (LDPE), and ethylene ionomer.

11. The cushioning material for electronic parts according to claim 7 or 8, wherein a ratio of a thickness of the foamed resin layer to a total thickness of the skin resin layer, i.e., a thickness of the foamed resin layer/a total thickness of the skin resin layer, is 1.5 to 300.

12. The cushioning material for electronic parts according to claim 7 or 8, wherein the ratio of the tensile strength constant of the skin resin layer calculated by the following formula (II) to the tensile strength constant of the foamed resin layer calculated by the following formula (I), that is, the ratio of the tensile strength constant of the skin resin layer/the tensile strength constant of the foamed resin layer multiplied by the compressive strength constant calculated by the following formula (III), is 1.5 or more,

(III)

13. The cushioning material for electronic parts according to claim 7 or 8, wherein the foaming ratio of the foamed resin layer is 1.5 to 30cm ³ /g。

14. The cushioning material for electronic parts according to claim 7 or 8, wherein the polyolefin resin of the foamed resin layer is a vinyl resin.

15. The cushioning material for electronic parts according to claim 7 or 8, which has a 25% compressive strength of 1.0 to 100kPa.

16. The cushioning material for electronic parts according to claim 7 or 8, wherein the foamed resin layer is a foam obtained by foaming a foamable composition containing a resin and a thermal decomposition type foaming agent.

17. An electronic component tape comprising the electronic component cushioning material according to any one of claims 7 to 16 and an adhesive material provided on at least one surface of the electronic component cushioning material.