JP6955947B2 - Laminate - Google Patents

Description

The present invention relates to a laminate including a resin sheet and a resin foam sheet.

Conventionally, a porous resin material in which a large number of holes are formed inside a resin layer is excellent in cushioning property, heat insulating property, waterproof property, and moisture proofing property, and therefore needs to be protected from packing materials, gases or liquids of articles. It is used in various applications such as a sealing material for sealing parts, a peripheral portion of a housing, a cushioning material for cushioning vibration and impact, and a base material for an adhesive sheet. For example, Patent Document 1 discloses a crosslinked polyolefin-based resin foam sheet obtained by foaming and cross-linking a foamable polyolefin-based resin sheet containing a pyrolysis-type foaming agent (see, for example, Patent Document 1).

In recent years, in various electronic devices such as mobile phones, personal computers and other IT devices, digital cameras and small video cameras, the resin foam sheets used inside these electronic devices have become thinner as the products have become smaller and thinner. It is desired to become.
However, the thinned resin foam sheet has a weak mechanical strength, and there is a problem that elongation, tearing, wrinkles, etc. are likely to occur during processing. In order to prevent this, it is desired that the resin foam sheet be processed in a state of being supported by a support for reinforcing the mechanical strength.

As a method of providing the support on the resin foam sheet, for example, a composition as a raw material of the resin foam sheet is applied on a resin film which is a support, and the composition is foamed on the support. , A method of obtaining a laminate of a support and a resin foam sheet can be mentioned. However, according to this method, since the support and the resin foam sheet are integrated into a laminated body, the support cannot be peeled off from the resin foam sheet, and the compression characteristics of the resin foam sheet are impaired. There was a case.
Further, as another method of providing the support on the resin foam sheet, there is a method of attaching a support having an adhesive layer on the surface facing the resin foam sheet to the resin foam sheet. However, according to this method, after the support is peeled off, a problem may occur in the resin foam sheet such that a component derived from the pressure-sensitive adhesive layer remains on the surface of the resin foam sheet.

International Publication No. 2005/007731

The present invention has been made in view of the above circumstances, and when the resin film as a support functions effectively as a reinforcing material for the resin foam sheet and the resin film is peeled off from the resin foam sheet. Is an object of the present invention to provide a laminate that can be easily peeled off without causing a defect in the resin foam sheet.

As a result of intensive research to achieve the above object, the present inventors have obtained a laminate obtained by laminating a resin sheet as a support and a resin foam sheet, and the resin sheet and the resin foam sheet. The present invention has been completed by finding that a laminate in which the 180 ° peel strength is adjusted to a specific range can solve the above-mentioned problems.
That is, the present invention provides the following [1] to [10].
[1] A laminate formed by laminating a resin sheet (A) and a resin foam sheet (B), and the 180 ° peel strength between the resin sheet (A) and the resin foam sheet (B) is 0. Laminated body of .02 to 0.50 N / 25 mm.
[2] The laminate according to the above [1], wherein the resin sheet (A) contains at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyamide as a main component.
[3] The laminate according to the above [1] or [2], wherein the arithmetic average surface roughness Ra of the surface of the resin sheet (A) facing the resin foam sheet (B) is 0.5 μm or less. body.
[4] The laminate according to any one of the above [1] to [3], which does not have an adhesive coating layer between the resin sheet (A) and the resin foam sheet (B).
[5] The laminate according to any one of the above [1] to [4], wherein the resin foam sheet (B) contains linear polyethylene polymerized using a metallocene catalyst as a main component.
[6] The above-mentioned [1] to [5], wherein the arithmetic average surface roughness Ra of the surface of the resin foam sheet (B) facing the resin sheet (A) is 1.0 to 15.0 μm. The laminate according to any one.
[7] The laminate according to any one of the above [1] to [6], wherein the resin foam sheet (B) has an apparent density of 0.05 to 0.75 g / cm ^3.
[8] The laminate according to any one of the above [1] to [7], wherein the resin foam sheet (B) has a thickness of 0.05 to 3.0 mm.
[9] The laminate according to any one of the above [1] to [8], wherein the resin foam sheet (B) has a tensile elastic modulus of 0.5 to 50.0 MPa.
[10] At least one of the surface of the resin sheet (A) facing the resin foam sheet (B) and the surface of the resin foam sheet (B) facing the resin sheet (A). However, the laminate according to any one of the above [1] to [9], which is obtained by corona treatment.

According to the present invention, the resin film effectively functions as a reinforcing material for the resin foam sheet, and when the resin film is peeled off from the resin foam sheet, the resin foam sheet is not defective. It is possible to provide a laminate that can be easily peeled off.

Hereinafter, the present invention will be described in detail using embodiments.
[Laminate]
The laminate of the present invention is a laminate formed by laminating a resin sheet (A) and a resin foam sheet (B), and the resin sheet (A) and the resin foam sheet (B) are peeled by 180 °. It is a laminated body having a strength of 0.02 to 0.50 N / 25 mm.

<180 ° peel strength>
The 180 ° peel strength (hereinafter, also simply referred to as “peeling strength”) between the resin sheet (A) and the resin foam sheet (B) in the laminate of the present invention is 0.02 to 0.50 N / 25 mm.
In the laminate of the present invention, by setting the peel strength to 0.02 N / 25 mm or more, the resin film (A) can be effectively functioned as a reinforcing material for the resin foam sheet (B), and the resin foam can be effectively used. The handleability and workability of the body sheet (B) can be improved. On the other hand, when the resin film (A) is peeled from the resin foam sheet (B) by setting the peel strength between the resin sheet (A) and the resin foam sheet (B) to 0.50 N / 25 mm or less. , The resin foam sheet (B) can be easily peeled off without causing any trouble.

On the other hand, if the peel strength between the resin sheet (A) and the resin foam sheet (B) is less than 0.02 N / 25 mm, the adhesion strength is too low, and the resin sheet (A) is a resin foam sheet. It becomes difficult to reinforce the mechanical strength of (B). Further, when the peel strength between the resin sheet (A) and the resin foam sheet (B) exceeds 0.50 N / 25 mm, the adhesion strength becomes too high, and the resin sheet (A) is replaced with the resin foam sheet (B). ), It becomes difficult to peel off the resin foam sheet (B) without damaging it.
The 180 ° peel strength between the resin sheet (A) and the resin foam sheet (B) is set to 0. 02 to 0.5 N / 25 mm is preferable, 0.02 to 0.4 N / 25 mm is more preferable, and 0.03 to 0.3 N / 25 mm is further preferable.
The 180 ° peel strength can be adjusted by adjusting the material of the resin sheet (A) and the resin foam sheet (B), which will be described later, the surface treatment method, and the like.
The 180 ° peel strength in the present specification can be obtained by the method described in Examples.
Hereinafter, the resin sheet (A) and the resin foam sheet (B) provided in the laminate of the present invention will be described in order.

<Resin sheet (A)>
The resin sheet (A) is a resin sheet that plays a role as a support for the resin foam sheet (B).
The resin sheet (A) reinforces the mechanical strength of the resin foam sheet (B) as a support during processing, and is peeled off from the resin foam sheet (B) before and after laminating processing such as coating and laminating. NS.

(Arithmetic Mean Surface Roughness Ra of Resin Sheet (A))
The arithmetic mean surface roughness Ra of the surface of the resin sheet (A) facing the resin foam sheet (B) is preferably 0.5 μm or less. By setting the arithmetic average surface roughness Ra to 0.5 μm or less, the adhesion between the resin sheet (A) and the resin foam sheet (B) does not become too large, and the resin sheet (A) is resin-foamed. The body sheet (B) can be peeled off without damaging it. From the same viewpoint, the arithmetic mean surface roughness Ra is more preferably 0.4 μm or less, and further preferably 0.3 μm or less.
The lower limit of the arithmetic mean surface roughness Ra of the resin sheet (A) is not particularly limited, but from the viewpoint of availability and the like, it may be 0.01 μm or more, or 0.05 μm or more. ..
The arithmetic mean surface roughness Ra in the present specification is a value based on JIS B0601 (2001), and can be obtained by the method described in Examples.

(Dimensions of resin sheet (A))
The thickness of the resin sheet (A) is not particularly limited, but is preferably 10 to 500 μm from the viewpoint of effectively functioning as a reinforcing material for the resin foam sheet (B) and improving handleability and workability. ~ 200 μm is more preferable, and 15 to 100 μm is even more preferable.

Examples of the resin constituting the resin sheet (A) include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); high-density polyethylene (HDPE), low-density polyethylene (LDPE), and the like. Polyethylene such as linear low density polyethylene (LLDPE), polyolefin resin such as polypropylene (PP); polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, etc. Vinyl resins; acrylic resins such as methyl poly (meth) acrylate and ethyl poly (meth) acrylate; styrene resins such as polystyrene; polyamide resins such as nylon 6 and nylon 66, and the like. In addition, these resins may be used individually by 1 type and may use 2 or more types together. Further, these polymers may be homopolymers or copolymers into which a plurality of copolymerization units have been introduced.
Among these, from the viewpoint of handleability and versatility, one or more selected from polyester resin, polyolefin resin and polyamide resin is preferable, and one or more selected from polyethylene, polypropylene, polyethylene terephthalate and polyamide is more preferable, and polypropylene is more preferable. More preferred.

Polypropylene may be a propylene homopolymer or a copolymer, but in the case of a copolymer, the copolymerization ratio of propylene units is preferably 50 mol% or more, more preferably 70 mol% or more. 90 mol% or more is further preferable, and 95 mol% or more is even more preferable. Examples of the copolymerizable monomer include α-olefin, acrylic acid ester, vinyl acetate and the like. These monomers may be used alone or in combination of two or more.

The resin sheet (A) preferably contains the above-mentioned resin as a main component, and the content thereof is preferably 60% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The main component in the present specification means the component having the highest content.
In addition to the above-mentioned resin, the resin sheet (A) may contain additives such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, and fillers, if necessary. ..

The resin sheet (A) may be stretched in at least one axial direction in the MD direction and the TD direction, or may be biaxially stretched.
Examples of the biaxially stretched resin sheet (A) include a biaxially stretched polypropylene (OPP) sheet, a biaxially stretched polyethylene terephthalate sheet, and a biaxially stretched polyamide sheet.

<Resin foam sheet (B)>
The resin foam sheet (B) is laminated on the resin sheet (A), and is preferably provided directly on the surface of the resin sheet (A).
(Arithmetic Mean Surface Roughness Ra)
The arithmetic mean surface roughness Ra of the surface of the resin foam sheet (B) facing the resin sheet (A) is preferably 1.0 to 15.0 μm. By setting the above arithmetic average surface roughness Ra to 1.0 μm or more, the area subject to pressure during bonding becomes small, and by concentrating the load, the resin sheet (A) and the resin foam sheet (B) The mechanical strength of the resin foam sheet (B), which has a weak mechanical strength, can be reinforced by the resin sheet (A), and the handleability and workability thereof can be improved. On the other hand, by setting the arithmetic average surface roughness Ra to 15.0 μm or less, the adhesive area between the resin sheet (A) and the resin foam sheet (B) is secured, and appropriate adhesion can be obtained. From these viewpoints, the arithmetic mean surface roughness Ra is more preferably 2.0 to 10.0 μm, further preferably 2.0 to 8.0 μm. The surface roughness Ra of the foamed sheet can be adjusted depending on the degree of foaming, the degree of cross-linking at the time of foaming, the presence / absence and type of surface treatment, and for example, the apparent density and the degree of cross-linking are adjusted to the desired ranges described later. This makes it easier to adjust the surface roughness Ra within the above range.

(Dimensions of resin foam sheet (B))
The thickness of the resin foam sheet (B) is preferably 0.05 to 3.0 mm. By setting the thickness to 0.05 mm or more, it becomes easy to secure the mechanical strength and flexibility of the resin foam sheet (B). On the other hand, when the thickness is 3.0 mm or less, the thin film can be thinned, and it can be suitably used for a miniaturized electronic device. From these viewpoints, the thickness of the resin foam sheet (B) is more preferably 0.05 to 2.0 mm, further preferably 0.05 to 1.5 mm. Further, when the thickness of the resin foam sheet (B) is, for example, 0.2 mm or more, the resin foam sheet (B) is less likely to be stretched when the resin sheet (A) is peeled off.

(Apparent density)
The apparent density of the resin foam sheet (B) is preferably ^{0.05 to 0.75 g / cm 3.} By setting the apparent density to 0.05 g / cm ³ or more, the mechanical strength becomes high and the durability can be easily improved. On the other hand, when the apparent density is 0.75 g / cm ³ or less, the compressive strength and flexibility are improved, and the impact absorption and sealing properties of the resin foam sheet (B) are likely to be improved. From these viewpoints, the apparent density of the resin foam sheet (B) is more preferably 0.07~0.70g / cm ^3, more preferably 0.10~0.60g / cm ^3.
The apparent density of the resin foam sheet (B) can be measured according to JIS K7222 (2005).

(Tensile modulus)
The tensile elastic modulus of the resin foam sheet (B) is preferably 0.5 to 50.0 MPa. By setting the tensile elastic modulus to 0.5 MPa or more, the mechanical strength becomes high and the durability can be easily improved. On the other hand, when the tensile elastic modulus is 50.0 MPa or less, the compressive strength and flexibility are improved, and the impact absorption and sealing property of the resin foam sheet (B) are likely to be improved. From these viewpoints, the tensile elastic modulus is more preferably 1.0 to 45.0 MPa, further preferably 2.0 to 40.0 MPa.
The tensile elastic modulus of the resin foam sheet (B) means the tensile elastic modulus in the MD direction at 23 ° C., and can be obtained in accordance with JIS K7161-1 (2014).

(Crosslink degree)
The resin foam sheet (B) is preferably crosslinked, and the degree of crosslinking is preferably 10 to 80% by mass. By setting the degree of cross-linking to 10% by mass or more, the mechanical strength becomes high and the durability can be easily improved. On the other hand, when the degree of cross-linking is 80% by mass or less, the compressive strength and flexibility are improved, and the impact absorption and sealing property of the resin foam sheet (B) are likely to be improved. From these viewpoints, the degree of cross-linking is more preferably 20 to 70% by mass, further preferably 25 to 65% by mass.
The degree of cross-linking can be measured by the following method.
<Measurement method of degree of cross-linking>
Approximately 100 mg of a test piece is collected from the resin foam sheet (B), and the weight A (mg) of the test piece is precisely weighed. ^{Next, this test piece was immersed in 30 cm 3} of xylene at 120 ° C. and left for 24 hours, filtered through a 200 mesh wire mesh to collect the insoluble matter on the wire mesh, vacuum dried, and the weight of the insoluble matter. Weigh B (mg) precisely. From the obtained value, the degree of cross-linking (mass%) is calculated by the following formula.
Degree of cross-linking (mass%) = 100 x (B / A)

(Material of resin foam sheet (B))
As the resin used for the resin foam sheet (B), various resins may be used, and among them, a polyolefin resin is preferably used. By using the polyolefin resin, it is possible to secure the flexibility of the resin foam sheet (B).

[Polyolefin resin]
Examples of the polyolefin resin include polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer and the like, and among these, polyethylene resin is preferable.
Examples of the polyethylene resin include polyethylene resins polymerized with a polymerization catalyst such as a Cheegler-Natta compound, a metallocene compound, and a chromium oxide compound, and a polyethylene resin polymerized with a polymerization catalyst of a metallocene compound is preferable.

Further, as the polyethylene resin, linear low-density polyethylene is preferable. By using the linear low-density polyethylene, high flexibility can be obtained in the obtained resin foam sheet (B), and the thickness of the resin foam sheet (B) can be thinned. The linear low-density polyethylene is more preferably obtained by using a polymerization catalyst such as a metallocene compound. Further, the linear low-density polyethylene can be obtained by copolymerizing ethylene (for example, 75% by mass or more, preferably 90% by mass or more) with respect to the total amount of monomers and, if necessary, a small amount of α-olefin. The linear low density polyethylene to be obtained is more preferable.
Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Among these, α-olefins having 4 to 10 carbon atoms are preferable.
Polyethylene resin, for example the density of the linear low density polyethylene as described above is preferably 0.870~0.910g / cm ^3, more preferably 0.875~0.907g / cm ^3, 0.880~0.905g / Cm ³ is more preferred. As the polyethylene resin, a plurality of polyethylene resins may be used, or a polyethylene resin other than the above-mentioned density range may be added.

[Metallocene compound]
Examples of the metallocene compound include compounds such as a bis (cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. More specifically, one or more cyclopentadienyl rings or their analogs are present as ligands in tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum. Examples include compounds.
In such a metallocene compound, the properties of active sites are uniform, and each active site has the same activity. A polymer synthesized using a metallocene compound has high uniformity in molecular weight, molecular weight distribution, composition, composition distribution, etc. Therefore, when a sheet containing a polymer synthesized using a metallocene compound is crosslinked, the cross-linking is uniform. Proceed to.

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

Examples of the metallocene compound containing a tetravalent transition metal, a ligand, etc. include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, and dimethylsilyl. Examples thereof include tetramethylcyclopentadienyl-t-butylamide zirconium dichloride.
The metallocene compound exerts an action as a catalyst in the polymerization of various olefins by combining with a specific co-catalyst (co-catalyst). Specific examples of the co-catalyst include methylaluminoxane (MAO) and boron-based compounds. The ratio of the cocatalyst used to the metallocene compound is preferably 10 to 1 million mol times, more preferably 50 to 5,000 mol times.
When the above-mentioned linear low-density polyethylene is used, the above-mentioned linear low-density polyethylene may be used alone as the polyolefin resin contained in the resin foam sheet (B), but it may be used alone with other polyolefin resins. It may be used in combination, for example, it may be used in combination with other polyolefin resins described below. When the other polyolefin resin is contained, the ratio of the other polyolefin resin to the linear low-density polyethylene (100% by mass) is preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less. preferable.

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

When a polyolefin resin is used as the resin, the polyolefin resin may be used alone, or may contain a resin other than the polyolefin resin. In the resin foam sheet (B), the ratio of the polyolefin resin to the total amount of the resin is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more.
Examples of the resin other than the polyolefin resin used for the resin foam sheet (B) include various elastomers such as styrene-based thermoplastic elastomer and EPDM.

(Pyrolytic foaming agent)
The resin foam sheet (B) is preferably formed by foaming a foamable composition containing the above resin and a thermally decomposable foaming agent.
As the pyrolytic foaming agent, an organic foaming agent and an inorganic foaming agent can be used. Examples of the organic foaming agent include azo compounds such as azodicarboxylic amide, azodicarboxylic acid metal salt (azodicarboxylic acid barium, etc.) and azobisisobutyronitrile; nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, and hydrazine. Examples thereof include hydrazine derivatives such as zodicarboxylic amide, 4,4'-oxybis (benzenesulfonyl hydrazide) and toluenesulfonyl hydrazide; and semicarbazide compounds such as toluenesulfonyl semicarbazide.
Examples of the inorganic foaming agent include ammonium acid, sodium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium boron hydride, monosoda anhydrous citrate and the like.
Among these, azo compounds are preferable, and azodicarbonamides are more preferable, from the viewpoint of obtaining fine bubbles, economy, and safety.
One type of pyrolysis foaming agent may be used alone, or two or more types may be used in combination.
The blending amount of the thermally decomposable foaming agent in the effervescent composition is preferably 1 to 10 parts by mass, more preferably 1 to 8 parts by mass, still more preferably 1.5 to 7 parts by mass with respect to 100 parts by mass of the resin. ..

Further, the effervescent composition preferably contains a bubble nucleation adjusting agent in addition to the above resin and a thermally decomposable effervescent agent. Examples of the bubble nucleating agent include zinc compounds such as zinc oxide and zinc stearate, organic compounds of citric acid and urea, and among these, zinc oxide is preferable. By using a bubble nucleating agent in addition to the above-mentioned small particle size foaming agent, it becomes easier to reduce the bubble diameter. The blending amount of the bubble nucleating agent is preferably 0.4 to 8 parts by mass, more preferably 0.5 to 5 parts by mass, still more preferably 0.8 to 2.5 parts by mass with respect to 100 parts by mass of the resin. ..
The effervescent composition contains, if necessary, additives generally used for foams such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, and fillers, in addition to the above. You may be doing it.

(Manufacturing method of resin foam sheet (B))
The method for producing the resin foam sheet (B) is not particularly limited, and for example, it is produced by heating an effervescent composition containing a resin and a pyrolytic foaming agent to foam the pyrolytic foaming agent. More specifically, the manufacturing method includes the following steps (1) to (3).
Step (1): A step of mixing a resin and an additive containing a pyrolytic foaming agent to obtain a foamable composition, and molding the foamable composition into a sheet. Step (2): Sheet-shaped foaming Step of irradiating the sex composition with ionizing radiation to crosslink the effervescent composition (3): A step of heating the crosslinked effervescent composition to foam a pyrolytic foaming agent to form bubbles.

In the step (1), the method for forming the sheet-shaped foamable composition is not particularly limited, but for example, the resin and the additive are supplied to the extruder to be melt-kneaded, and the foamable composition is sheeted from the extruder. It may be molded by extruding into a shape.
As a method for cross-linking the effervescent composition in the step (2), a method of irradiating the effervescent composition with ionizing radiation such as electron beam, α ray, β ray, and γ ray is used. The irradiation amount of the ionizing radiation may be adjusted so that the degree of cross-linking of the obtained foamed sheet is within the above-mentioned desired range, but is preferably 3 to 15 Mrad, more preferably 4 to 13 Mrad.
In the step (3), the heating temperature at which the foamable composition is heated to foam the pyrolysis type foaming agent may be equal to or higher than the foaming temperature of the pyrolysis type foaming agent, but the foaming temperature is preferably +20 to 100 ° C. , Foaming temperature + 30-70 ° C. is more preferable.
Further, after forming the bubbles, the bubbles may be stretched in either one or both of the MD direction and the TD direction.

However, the present production method is not limited to the above, and the resin foam sheet (B) may be obtained by a method other than the above. For example, instead of irradiating with ionizing radiation, the effervescent composition may be preliminarily blended with an organic peroxide, and the effervescent composition may be heated to decompose the organic peroxide for cross-linking. good.

[Structure of laminate]
As described above, the laminate of the present invention can be produced by laminating the resin sheet (A) and the resin foam sheet (B), whereby the resin sheet can be produced without using an adhesive or the like. The (A) and the resin foam sheet (B) have both good adhesion and peelability. Therefore, the laminate of the present invention has an adhesive coating layer between the resin sheet (A) and the resin foam sheet (B) from the viewpoint of maintaining good surface characteristics of the resin foam sheet (B). It is preferable not to use the resin foam sheet (B) directly on the resin sheet (A) as described above.
The pressure-sensitive adhesive coating layer in the present specification is a polymer layer having so-called pressure-sensitive adhesiveness obtained by a coating process such as a gravure coat, and is, for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, or a vinyl alkyl ether type. Includes adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, polyurethane adhesives, fluorine adhesives, epoxy adhesives, polyethylene wax and the like. In general, these may contain low molecular weight components derived from tackifier resins such as main component polymers or rosin derivative resins, polyterpene resins, petroleum resins, and oil-soluble phenol resins, as compared to molded sheets such as the resin sheet (A). In many cases, the low molecular weight component remains at the interface of the adherend after peeling, which may impair the surface property.

The surface of the resin sheet (A) constituting the laminate of the present invention on the side facing the resin foam sheet (B) and the surface of the resin foam sheet (B) facing the resin sheet (A) are surfaces. It may have been processed. Examples of the surface treatment method include corona treatment, plasma discharge treatment, ozone, ultraviolet irradiation treatment, and the like, and among these, corona treatment is preferable.
The conditions for the corona treatment may be appropriately adjusted so that the 180 ° peel strength of the resin sheet (A) from the resin foam sheet (B) is within the above range. For example, the temperature is 23 ° C. and the humidity is 60% RH. Under the atmosphere, the corona treatment density can be set to ^{0.01 to 4.0 kW · min / m 2.}
The laminate of the present invention is at least one of the surface of the resin sheet (A) facing the resin foam sheet (B) and the surface of the resin foam sheet (B) facing the resin sheet (A). It is preferable that one of the surfaces is corona-treated, and it is more preferable that one of the surfaces is corona-treated. As a result, it is possible to achieve a high degree of compatibility between the adhesion for effectively functioning the support as a reinforcing material during processing and the peelability for easily peeling off the support after processing.

[Manufacturing method of laminated body]
The method for producing the laminate of the present invention is not particularly limited, but it is preferable to produce the laminate by laminating the resin sheet (A) and the resin foam sheet (B).
The resin sheet (A) and the resin foam sheet (B) are preferably bonded by applying pressure. Pressurization can be performed using a roll press, a flat plate press, or the like, but from the viewpoint of productivity, it is preferable to bond them by a roll press. The crimping pressure at the time of pressurization may be appropriately determined according to the material of the support and the like, and can be, for example, in the range of 0.5 to 3.0 MPa. Further, it may be heated at the time of pressurization, and the heating temperature can be in the range of, for example, 30 to 70 ° C.

[Use of laminated board, etc.]
In the laminated body of the present invention, the resin sheet (A) is usually peeled off from the resin foam sheet (B) after being processed or the like.
The use of the resin foam sheet (B) included in the laminate of the present invention is not particularly limited, but it is preferably used inside an electronic device, for example. Since the laminate of the present invention is excellent in handleability, it can be suitably used inside various portable electronic devices in which the space for arranging the resin foam sheet (B) is small. Examples of portable electronic devices include mobile phones, cameras, game devices, electronic organizers, personal computers and the like. Further, the resin foam sheet (B) provided in the laminate of the present invention can be used as a shock absorbing material and a sealing material inside an electronic device, and may be used as an adhesive tape.

The present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

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

<180 ° peel strength>
The laminate obtained in each example was cut to a length of 25 mm × 200 mm, and then the foam surface was bonded to a polycarbonate plate using a double-sided adhesive tape using PET as a base material to prepare a measurement sample.
Among the fixed laminates, one end of the resin film (A) was peeled off by 30 mm and fixed to the chuck of a tensile tester (“Tensilon universal material tester” manufactured by A & D Co., Ltd.). Then, the resin sheet (A) was pulled at a peeling angle of 180 ° and a speed of 300 mm / min by 50 mm or more, and the section average value of the load (N) detected by the load cell was recorded and used as the 180 ° peel strength.

<Damage to resin foam sheet (B) during peeling>
After the 180 ° peel strength test, the surface of the resin foam sheet (B) after peeling the resin sheet (A) is visually observed in a range of 25 × 100 mm, and the resin at the time of peeling is based on the following criteria. Damage to the foam sheet (B) was evaluated.
A: No damage was found on the resin foam sheet (B).
B: The surface of the resin foam sheet (B) was roughened.
C: The surface of the resin foam sheet (B) was roughened and stretched.
D: The resin foam sheet (B) was damaged because it could not be peeled off at the interface between the resin sheet (A) and the resin foam sheet (B).

<Apparent density>
The apparent density of the resin foam sheet was measured according to JIS K7222 (2005).

<Tension modulus>
As for the tensile elastic modulus of the resin foam sheet, the tensile elastic modulus in the MD direction at 23 ° C. was determined in accordance with JIS K7222 (2005).

<Surface tension>
The surface tension of the resin film (A) was measured according to JIS K6768 (1999).

<Arithmetic Mean Surface Roughness Ra (μm)>
After photographing the surfaces of the resin sheet (A) and the resin foam sheet (B) at a magnification of 10 times using the laser microscope "VK-X100" manufactured by KEYENCE CORPORATION, use the attached analysis application. The analysis was performed. A measurement line having a length of 1 mm was set at an arbitrary position on the photographed screen, and the line roughness curve of that portion was measured. Next, the obtained curve was analyzed under the conditions shown below to calculate the arithmetic mean surface roughness Ra at any of the above positions. Further, the same measurement was performed at any three points on the resin foam sheet, and the average value was taken as the arithmetic mean surface roughness Ra.
<Analysis conditions>
・ Light intensity smoothing: None ・ Height smoothing: ± 12 simple average ・ Tilt correction: None ・ Cutoff by phase compensation type reduction filter: λs25μm, no λc

[Example 1]
A resin sheet composed of an elongated foaming composition having a composition shown in Table 1 in which a resin, a pyrolysis foaming agent, a bubble nucleating agent and an antioxidant are supplied to an extruder and melt-kneaded at 130 ° C. Extruded to.
Next, both sides of the long resin sheet were irradiated with an electron beam having an acceleration voltage of 500 kV for 5.0 Mrad to crosslink the resin sheet, and then the crosslinked resin sheet was held at 250 ° C. by hot air and an infrared heater for foaming. It was continuously fed into a furnace and heated to foam to obtain a foamed sheet having a thickness of 300 μm. The obtained resin foam sheet was subjected to corona treatment for the purpose of improving the adhesion with the resin sheet as a support. The corona treatment is performed using a high-frequency power supply "AGF-B20" manufactured by Kasuga Electric Works Ltd. and a wire type electrode at a temperature of 23 ° C. and a humidity of 60% in an RH atmosphere, and the corona treatment density is 1.0 kW · min / min /. The condition was m ^2.
Next, the resin foam sheet obtained above and the biaxially stretched polypropylene (OPP) sheet having a thickness of 20 μm shown in Table 1 were subjected to conditions of a temperature of 30 ° C. and a crimping pressure of 1.0 MPa using a roll press. Pressurized underneath and pasted together to obtain a laminate.

[Examples 2 to 13, Comparative Example 3, Comparative Example 4]
In Example 1, a laminate was obtained in the same manner as in Example 1 except that the resin sheet (A) and the resin foam sheet (B) were changed to those shown in Table 1.

[Comparative Example 1]
"PORON SR-S-40P (trade name)" (manufactured by Rogers INOAC Corporation), which is a commercially available laminate having a resin foam sheet and a resin film, was used.

[Comparative Example 2]
A laminate was obtained in the same manner as in Example 2 except that the resin foam sheet was changed to a bulk sheet prepared by the method shown below in Example 2.
<Manufacturing of bulk sheet>
In the method for producing the resin foam sheet of Example 1, the resin foam sheet was produced by the same method as in Example 1 except that the pyrolysis foaming agent and the bubble nucleating agent were not added and the resin foam sheet was not put into the foaming furnace. Was used as a bulk sheet.

Table 1 shows the evaluation results of the laminates obtained in each of the above examples. In addition, "-" in the table means that it has not been measured or is unknown.

(* 1)
-OPP: Biaxially stretched polypropylene sheet (manufactured by Futamura Chemical Co., Ltd., product name: FOA)
-PET-1: Biaxially stretched polyethylene terephthalate sheet (manufactured by Toyobo Co., Ltd., trade name: E3120-12)
-PET-2: Biaxially stretched polyethylene terephthalate sheet (manufactured by Unitika Ltd., trade name: PTFE-25)
-LL: Linear low-density polyethylene sheet (manufactured by Toyobo Co., Ltd., product name: SE620L)
-CPP: Axial-stretched polypropylene sheet (manufactured by Toyobo Co., Ltd., product name: P1128)
(* 2) Linear low-density polyethylene resin (LLDPE) (manufactured by Exxon Chemical Co., Ltd., trade name "EXACT3027", density: 0.900 g / cm ³ )
(* 3) Azodicarbonamide (* 4) Zinc oxide

From Table 1, the laminates of Examples 1 to 13 in which the 180 ° peel strength between the resin sheet (A) and the resin foam sheet (B) is 0.02 to 0.50 N / 25 mm are the resin sheet (A). ) And the resin foam sheet (B) have appropriate adhesion, and it can be seen that the resin foam sheet (B) can be peeled off without damaging it. On the other hand, the laminate of Comparative Example 1 having a 180 ° peel strength of more than 0.50 N / 25 mm could not peel the resin sheet (A) from the resin foam sheet (B). Further, the laminates of Comparative Examples 2 to 4 having a 180 ° peel strength of less than 0.02 N / 25 mm have too low a peel strength and maintain the laminated form of the resin sheet (A) and the resin foam sheet (B). I couldn't.

Claims (8)

It is a laminate formed by laminating a resin sheet (A) and a resin foam sheet (B), and the 180 ° peel strength between the resin sheet (A) and the resin foam sheet (B) is 0.02 to 0.02. 0.50N / 25mm der is,
There is no adhesive coating layer between the resin sheet (A) and the resin foam sheet (B).
The thickness of the resin foam sheet (B) is 0.05 to 3.0 mm.
A laminate in which the laminate is used inside an electronic device. The laminate according to claim 1, wherein the resin sheet (A) contains at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyamide as a main component. The laminate according to claim 1 or 2, wherein the arithmetic average surface roughness Ra of the surface of the resin sheet (A) facing the resin foam sheet (B) is 0.5 μm or less. The laminate according to any one of claims 1 to 3 , wherein the resin foam sheet (B) contains linear polyethylene polymerized using a metallocene catalyst as a main component. The aspect according to any one of claims 1 to 4 , wherein the arithmetic average surface roughness Ra of the surface of the resin foam sheet (B) facing the resin sheet (A) is 1.0 to 15.0 μm. Laminated body. The laminate according to any one of claims 1 to 5 , wherein the resin foam sheet (B) has an apparent density of 0.05 to 0.75 g / cm ^3. The laminate according to any one of claims 1 to 6 , wherein the resin foam sheet (B) has a tensile elastic modulus of 0.5 to 50.0 MPa. The method for producing a laminate according to any one of claims 1 to 7.
At least one of the surface of the resin sheet (A) facing the resin foam sheet (B) and the surface of the resin foam sheet (B) facing the resin sheet (A) is a corona. Ru is processed, method for producing a laminate.