JP2004323842A - Crosslinked polyolefin resin foamed sheet and pressure-sensitive adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crosslinked polyolefin resin foamed sheet which has excellent tensile strength at least in an MD (a sheet extrusion direction) as well as excellent flexibility and compression recovery properties, and can be preferably used for a pressure-sensitive adhesive tape base. <P>SOLUTION: The crosslinked polyolefin resin foamed sheet comprises foaming and orienting a polyolefin resin comprising ≥40 wt.% of a specific polyethylene resin, and has a crosslinking degree of the sheet being 5-60 wt.%, a ratio of an average foam diameter of the sheet extrusion direction to that of a sheet thickness direction being 2.5-7, and a ratio of the average foam diameter of the sheet extrusion direction to that of a sheet width direction being 2-6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a crosslinked polyolefin-based resin foam sheet which is flexible and excellent in mechanical strength and is preferably used as a pressure-sensitive adhesive tape substrate, and a pressure-sensitive adhesive tape using the crosslinked polyolefin-based resin foam sheet as a pressure-sensitive adhesive tape substrate.

Conventionally, pressure-sensitive adhesive tapes have been used for a wide range of applications.In particular, pressure-sensitive adhesive tapes based on foamed sheets are, for example, suitable in the fields of industrial materials and building materials, as non-adjusting materials, sealing materials, and the like. It is used. Further, since the adhesive tape having a foamed sheet as a base material has a good texture, it is often suitably used in vehicles other than fields such as industrial materials and building materials and in the IT field.

The pressure-sensitive adhesive tape is obtained by applying a pressure-sensitive adhesive to at least one surface of a pressure-sensitive adhesive tape base material. Usually, a long-sized pressure-sensitive adhesive tape is wound around a shaft core to form a wound body. Then, when using the adhesive tape, the outer peripheral edge of the adhesive tape is gripped, the adhesive tape is peeled off from the wound body by a desired length from the outer peripheral end side, and the adhesive tape is used at a desired position. The adhesive tape is often pulled in the length direction in order to stick it without wrinkles, and the adhesive tape is often subjected to tensile stress. Therefore, the adhesive tape base material that governs the mechanical properties of the adhesive tape has excellent tensile strength. Strength is required.

Furthermore, when an adhesive tape is used as a non-adjustment material, the adhesive tape substrate must have excellent flexibility in order to exhibit an excellent non-adjustment function, while the adhesive tape is used as a sealing material. When used, the adhesive tape substrate is required to have excellent flexibility and compression recovery in order to maintain the workability and sealability. In applications other than those described above, flexibility and compression recovery are often required in order to improve the feel of the pressure-sensitive adhesive tape.

On the other hand, a crosslinked polyolefin resin foam sheet is extremely excellent in flexibility, and has been conventionally used for a wide range of uses as a cushioning material, a heat insulating material, and the like.

However, when the crosslinked polyolefin-based resin foam sheet is applied to the pressure-sensitive adhesive tape substrate, there is a problem that the tensile strength is insufficient, and in particular, the flexibility and the compression recovery of the crosslinked polyolefin-based resin foam sheet are ensured. Therefore, as shown in Patent Documents 1 and 2, when a flexible resin is used as the polyolefin resin constituting the crosslinked polyolefin resin foam sheet, the tensile strength of the crosslinked polyolefin resin foam sheet is further increased. When the crosslinked polyolefin-based resin foam sheet is used as the base material of the pressure-sensitive adhesive tape, there is a problem that the pressure-sensitive adhesive tape is broken when the pressure-sensitive adhesive tape is used.

Therefore, in order to improve the tensile strength of the crosslinked polyolefin-based resin foam sheet, for example, it is conceivable to make the crosslinked polyolefin-based resin foam sheet to have a low expansion ratio. There is a problem that the compression recovery is reduced.

JP-A-7-173317 (Claims) JP-A-9-157601 (Claims)

An object of the present invention is to provide a crosslinked polyolefin-based resin foam sheet having excellent flexibility and compression recovery properties, and having at least excellent tensile strength at least in the sheet extrusion direction, and which can be suitably used as an adhesive tape base material. Is to provide.

Another object of the present invention is to use the crosslinked polyolefin-based resin foam sheet as a pressure-sensitive adhesive tape substrate, so that it has good texture and excellent tensile strength, does not break during use, and has flexibility and compression recovery. An object of the present invention is to provide a pressure-sensitive adhesive tape which is excellent in ruggedness and can be suitably used as a non-adjustment material or a sealing material.

The crosslinked polyolefin-based resin foam sheet of the present invention comprises a polyolefin-based resin containing 40% by weight or more of a polyethylene-based resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and a pyrolytic foaming agent. A crosslinked polyolefin-based resin foam sheet obtained by supplying a foamable resin composition to an extruder, melt-kneading, extruding from the extruder, crosslinking and then expanding and stretching the foamed resin sheet. And the ratio of the average cell diameter in the sheet extrusion direction to the average cell diameter in the sheet thickness direction (average cell diameter in the sheet extrusion direction / average cell diameter in the sheet thickness direction) is 5 to 60% by weight. 2.5 to 7, and the ratio of the average cell diameter in the sheet extrusion direction to the average cell diameter in the sheet width direction (average cell diameter in the sheet extrusion direction / average cell diameter in the sheet width direction) is 2 to 2. And characterized in that.

The polyolefin resin used in the present invention is not particularly limited as long as it contains at least 40% by weight of a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. What consists only of a polyethylene-based resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, or a polyethylene-based resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst Any one of other polyolefin-based resins may be used, but the resulting cross-linked polyolefin-based resin foam sheet has excellent flexibility, compression recovery properties and mechanical strength. What consists only of the polyethylene resin obtained using the metallocene compound containing this is preferable.

As the polyethylene-based resin obtained using a metallocene compound containing a tetravalent transition metal as the polymerization catalyst, using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst,
Linear low-density polyethylene obtained by copolymerizing ethylene and a small amount of α-olefin is preferred. Examples of the α-olefin include propylene, 1-butene, 1
-Pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like.

The metallocene compound generally refers to a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, and a bis (cyclopentadienyl) metal complex is a typical example. More specifically, as the metallocene compound containing a tetravalent transition metal in the present invention, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, and platinum may be added to one or more cyclopentadienyls. Compounds in which a ring or an analog thereof is present as a ligand (ligand).

Examples of the ligand include a cyclopentadienyl ring; a cyclopentadienyl ring substituted by a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group; a cyclopentadienyl oligomer ring; an indenyl ring; Group, substituted hydrocarbon group or hydrocarbon-
And an indenyl ring substituted with a substituted metalloid group. Besides these π-electron unsaturated compounds, as a ligand, a monovalent anion ligand such as chlorine or bromine or a divalent anion chelate ligand, a hydrocarbon, an alkoxide, an arylamide, an aryloxide, an amide, an arylamide, A phosphide, an aryl phosphide or the like may be coordinated to the transition metal atom.

Examples of the hydrocarbon group substituted on the cyclopentadienyl ring include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, and an octyl group. , Nonyl group, decyl group, cetyl group, phenyl group and the like.

Examples of such metallocene compounds containing a tetravalent transition metal include, for example, cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, Dimethylsilyltetramethylcyclopentadienyl-t-butylamidozirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-t-butylamidohafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamidozirconium chloride , Methylphenylsilyltetramethylcyclopentadienyl-
t-butyl amide hafnium dichloride, indenyl titanium tris (dimethyl amide), indenyl titanium tris (diethyl amide), indenyl titanium tris (di-n-propyl amide), indenyl titanium bis (di-n-butyl amide) (di -N
-Propylamide) and the like.

The metallocene compound exhibits a function as a catalyst at the time of polymerization of various olefins by changing the kind of metal or the structure of the ligand and combining it with a specific cocatalyst (promoter). More specifically, the polymerization is usually carried out in a catalyst system in which methylaluminoxane (MAO), a boron compound or the like is added as a cocatalyst to these metallocene compounds. The usage ratio of the cocatalyst to the metallocene compound is 10 to 1,000,000 times, preferably 50 to 5,000 times.

The polymerization conditions are not particularly limited, and for example, a solution polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, a gas phase polymerization method, and the like can be used. The polymerization temperature is usually from -100 ° C to 300 ° C, and the polymerization pressure is usually from normal pressure to 100 kg / cm ² .

Metallocene compounds have the feature that the properties of active sites are uniform. Since the metallocene compound has the same activity at each active site, the homogeneity of the polymer to be synthesized, such as molecular weight, molecular weight distribution, composition, and composition distribution, is improved. Therefore, the polyolefin-based resin polymerized in the presence of these metallocene compounds has a narrow molecular weight distribution, and in the case of a copolymer, the copolymer component is introduced at almost the same ratio to any molecular weight component. Having.

As the content of the polyethylene-based resin obtained using the metallocene compound containing a tetravalent transition metal as the polymerization catalyst in the polyolefin-based resin decreases, the flexibility and compression recovery of the obtained cross-linked polyolefin-based resin foam sheet decrease. Or, since the mechanical strength is reduced, 4
It is limited to 0% by weight or more, and preferably 60% by weight or more.

Examples of the other polyolefin-based resin include a polyethylene-based resin and a polypropylene-based resin. The polyethylene resin is not particularly limited as long as it is other than a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, for example, linear low-density polyethylene, low-density polyethylene, Polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer containing ethylene as a main component, ethylene-vinyl acetate copolymer containing ethylene as a main component, and the like are used alone. May be used in combination of two or more. The α-olefin constituting the ethylene-α-olefin copolymer includes, for example, propylene, 1-butene, 1-pentene,
-Methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like.

Examples of the polypropylene resin include, for example, polypropylene, ethylene-propylene copolymer containing propylene as a main component, propylene-α-olefin copolymer containing propylene as a main component, and the like. May be used in combination of two or more.
As the α-olefin constituting the propylene-α-olefin copolymer, for example, 1-
Butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-
Octene and the like.

The pyrolytic blowing agent used in the present invention is a compound which is decomposed by heating to generate a decomposed gas, for example, azodicarbonamide, N, N'-dinitrosopentamethylenetetramine, p-toluenesulfonyl semicarbazide These may be used alone or in combination of two or more.

The amount of the pyrolytic foaming agent to be added may be appropriately determined according to the desired apparent density of the crosslinked polyolefin-based resin foam sheet. However, when the amount decreases, the foaming property of the foamable resin composition decreases, and the desired apparent density decreases. A crosslinked polyolefin-based resin foam sheet having the following formulas cannot be obtained, and when the number increases, the tensile strength and compression recovery of the obtained cross-linked polyolefin-based resin foam sheet decrease,
The amount is preferably 1 to 40 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the polyolefin resin.

The crosslinked polyolefin-based resin foam sheet of the present invention is obtained by supplying the foamable resin composition comprising the polyolefin-based resin and the pyrolytic foaming agent to an extruder and melting at a temperature at which the pyrolytic foaming agent does not substantially decompose. The foamable resin sheet obtained by kneading and extruding from an extruder is crosslinked and then expanded in the sheet extrusion direction after foaming or stretched in the sheet extrusion direction during foaming.

When the degree of crosslinking of the crosslinked polyolefin resin foam sheet is reduced, when the crosslinked polyolefin resin foam sheet is stretched in the manufacturing process, the sheet is generally stretched while the foam sheet is heated, but the crosslinked polyolefin resin foam Since the heat resistance of the sheet is insufficient, bubbles on the surface are broken and the surface is roughened, and the appearance of the obtained crosslinked polyolefin resin foam sheet deteriorates, and when it is large, the melt viscosity of the foamable resin composition is large. Therefore, in the process of producing the crosslinked polyolefin-based resin foam sheet, when the foamable resin composition is heated and foamed, the foamable resin composition hardly follows the foaming, and the crosslinked polyolefin-based resin foam sheet having a desired apparent density is obtained. Is limited to 5 to 60% by weight.
% By weight is preferred.

The crosslinking degree of the crosslinked polyolefin resin foam sheet is a value measured by the following method. First, a test piece of about 100 mg is collected from the crosslinked polyolefin resin foam sheet, and the weight A (mg) of the test piece is precisely weighed. Next, this test piece was placed in 120 cm xylene 30 cm.
³ Immerse in and leave for 24 hours. Thereafter, the mixture is filtered through a 200-mesh wire net, the insoluble matter on the wire net is collected, dried in vacuum, and the weight B (mg) of the insoluble matter is precisely weighed. From the obtained value,
The degree of crosslinking (% by weight) is calculated by the following equation.
Degree of crosslinking (% by weight) = (B / A) × 100

When the ratio of the average cell diameter in the sheet extrusion direction (MD) to the average cell diameter in the sheet thickness direction (ZD) in the crosslinked polyolefin-based resin foam sheet (average cell diameter in MD / average cell diameter in ZD) decreases. When the tensile strength, flexibility and compression recovery of the crosslinked polyolefin resin foam sheet in the MD are reduced and increased, the sheet is greatly stretched and cut in the MD in the manufacturing process. It is limited, and 3 to 6 is preferable.

Ratio of the average cell diameter in the sheet extrusion direction (MD) and the average cell diameter in the sheet width direction (CD) of the crosslinked polyolefin resin foam sheet (average cell diameter of MD / average cell diameter of CD).
Is smaller, the tensile strength, flexibility and compression recovery in the MD of the crosslinked polyolefin resin foam sheet are reduced, and when larger, the sheet is greatly stretched to the MD in the manufacturing process and is cut. 6, and preferably 2 to 4.5.

The sheet thickness direction (ZD) in the crosslinked polyolefin resin foam sheet refers to the normal direction to the surface of the crosslinked polyolefin resin foam sheet, and the sheet width direction (CD) in the crosslinked polyolefin resin foam sheet refers to the sheet. The direction perpendicular to the extrusion direction and the sheet thickness direction.

Here, the average cell diameter of MD, CD and ZD in the crosslinked polyolefin-based resin foam sheet is measured in the following manner. First, in order to measure the average cell diameter of the MD in the crosslinked polyolefin resin foam sheet, the crosslinked polyolefin resin foam sheet is placed in the sheet extrusion direction (MD) at the center in the sheet width direction (CD). Insert a cutter blade in the direction (ZD) and cut into two.

Then, the cross section of the crosslinked polyolefin resin foam sheet is scanned with a scanning electron microscope (SEM).
The photograph is taken so that the cross-section of the crosslinked polyolefin resin foam sheet fits in the photograph over the entire length in the sheet thickness direction (ZD).

In the obtained photograph, the length on the photograph is 1 at the center of the cut surface in the sheet thickness direction.
A straight line of 5 cm (actual length 2500 μm before expansion) is drawn so as to be parallel to the surface of the crosslinked polyolefin resin foam sheet. Thereafter, the number of bubbles existing on the straight line is visually counted. Then, based on the following equation, the average cell diameter of MD in the crosslinked polyolefin resin foam sheet is calculated.
Average cell diameter (μm) of MD in foamed sheet = 2500 (μm) / number of cells (pieces)

Further, the average cell diameter in the sheet thickness direction (ZD) of the crosslinked polyolefin resin foam sheet is also calculated using the above photograph. In the above photograph, three straight lines that divide the photographed cut surface into four equal parts in the sheet extrusion direction (MD) are divided into a sheet thickness (ZD) in a direction (ZD) orthogonal to the sheet extrusion direction (MD). Draw over the entire length.

Thereafter, the length of each straight line is measured, the number of bubbles existing on each straight line is visually counted, and the average bubble diameter is calculated for each straight line based on the following formula, and the obtained three averages are calculated. The arithmetic mean value of the cell diameter is defined as the average cell diameter of ZD in the crosslinked polyolefin resin foam sheet.
Average bubble diameter (μm) for each straight line = length of straight line (μm) / [number of bubbles (pieces) × 60]

Next, in order to measure the average cell diameter of CD in the crosslinked polyolefin resin foam sheet, a cutter blade is inserted into the crosslinked polyolefin resin foam sheet in the sheet thickness direction (ZD) toward the sheet width direction (CD). And cut in two.

Then, the cross section of the crosslinked polyolefin resin foam sheet is scanned with a scanning electron microscope (SEM).
The photograph is taken so that the cross-section of the crosslinked polyolefin resin foam sheet fits in the photograph over the entire length in the sheet thickness direction (ZD).

In the obtained photograph, the length on the photograph is 1 at the center of the cut surface in the sheet thickness direction.
A straight line of 5 cm (actual length 2500 μm before expansion) is drawn so as to be parallel to the surface of the crosslinked polyolefin resin foam sheet. Thereafter, the number of bubbles existing on the straight line is visually counted. Then, based on the following equation, the average cell diameter of CD in the crosslinked polyolefin resin foam sheet is calculated.
Average cell diameter (μm) of CD in foam sheet = 2500 (μm) / number of cells (pieces)

Here, irrespective of whether or not the bubbles are communicated in a portion other than on the photograph, one void portion surrounded by a bubble film cross section appearing on the photograph is regarded as one bubble, and a part of the bubble comes out from the straight line. The number of bubbles was 0.5.

In taking a photograph, if the cross section of the bubble film is colored with magic ink or the like, the bubble can be easily distinguished. Furthermore, when taking a photograph, the scale of 2500 μm is enlarged together with the photograph to make it easier to specify the straight line length on the photograph.

In the foamable resin composition, an antioxidant such as 2,6-di-t-butyl-p-cresol and zinc oxide may be used, if necessary, as long as the physical properties of the crosslinked polyolefin resin foam sheet are not impaired. Additives such as a foaming aid such as a foam nucleus adjusting material, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, and a filler may be added.

As a method of crosslinking the foamable resin sheet, a method of irradiating the sheet with an ionizing radiation such as an electron beam, α-ray, β-ray, or γ-ray so as to have the above-described degree of crosslinking, or a method of previously forming an organic resin on the foamable resin composition, There is a method in which a foamable resin sheet is formed after blending a peroxide, and the organic peroxide in the foamable resin sheet is thermally decomposed. These methods may be used in combination.

Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3
5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate , Di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5- Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, benzoyl peroxide, cumylperoxyneodecanate, t-butylperoxybenzoate,
2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butylperoxyallyl carbonate, and the like,
These may be used alone or in combination of two or more.

When the addition amount of the organic peroxide is small, the crosslinking of the foamable resin sheet does not proceed, and the foamable resin sheet cannot be crosslinked to a desired degree of crosslinking, and when it is large, the obtained crosslinked polyolefin resin foam sheet is obtained. Since the decomposition residue of the organic peroxide remains therein, the amount is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the polyolefin resin.

The method for foaming the foamable resin sheet is not particularly limited, and examples thereof include a method of heating with hot air, a method of heating with infrared rays, a method of using a salt bath, a method of using an oil bath, and the like. You may.

The stretching in the sheet extrusion direction (MD) may be performed after foaming the foamable resin sheet, or may be performed while foaming the foamable resin sheet. In the case where the foamed sheet is stretched after the foamable resin sheet is foamed, it is preferable that the foaming sheet is heated again.

As a method of stretching the sheet, for example, by adjusting the speed at which the foamable resin sheet is supplied to the foaming step and the speed at which the foamed sheet is cooled and wound up after the foaming step, the sheet is foamed while the foamable resin sheet is foamed. A method of stretching in the extrusion direction (MD) is preferred.

The apparent density of the crosslinked polyolefin-based resin foam sheet obtained as described above is preferably ^{0.05~0.3g / cm 3, 0.065~0.2g / cm} 3 is more preferable. The apparent density of the crosslinked polyolefin-based resin foam sheet is JIS K676.
7 is measured according to 7.

This is because, when the apparent density of the crosslinked polyolefin-based resin foam sheet decreases, the mechanical strength of the crosslinked polyolefin-based resin foam sheet may decrease, while when it increases, the flexibility of the crosslinked polyolefin-based resin foam sheet decreases, When a cross-linked polyolefin-based resin foam sheet is used as an adhesive tape base material, when the adhesive tape is subjected to shear stress in the direction along the adherend surface or peel stress in the direction away from the adherend, Although the agent deforms and tries to relieve the stress applied to the adhesive tape, the cross-linked polyolefin resin foam sheet cannot follow the deformation of the pressure-sensitive adhesive, and as a result, the cross-linked polyolefin resin foam sheet and the pressure-sensitive adhesive Stress concentration occurs partially at the interface, and the cross-linked polyolefin resin foam sheet and the adhesive cause stress concentration. Adhesive remains on the adherend undergoes surface peeling, there is a possible so-called adhesive residue is generated.

The use of the crosslinked polyolefin resin foam sheet of the present invention is not particularly limited, but it is preferable to use it as a pressure-sensitive adhesive tape base material and apply a pressure-sensitive adhesive on at least one surface thereof to form a long pressure-sensitive adhesive tape. When the crosslinked polyolefin-based resin foam sheet is used as the pressure-sensitive adhesive tape substrate, it is preferable to adjust the sheet extrusion direction (MD) of the crosslinked polyolefin-based resin foam sheet to be the length direction of the pressure-sensitive adhesive tape.

When the cross-linked polyolefin-based resin foam sheet is used as a pressure-sensitive adhesive tape base material, when the thickness of the cross-linked polyolefin-based resin foam sheet is reduced, the mechanical strength such as the tensile strength of the cross-linked polyolefin-based resin foam sheet, flexibility, and adhesion are reduced. When the texture of the tape decreases and becomes thicker, the surface portion of a low expansion ratio formed on both surfaces of the crosslinked polyolefin resin foam sheet, the so-called skin layer becomes thicker, and the flexibility of the crosslinked polyolefin resin foam sheet increases. Because it drops
0.05 to 10 mm is preferable, and 0.1 to 8 mm is more preferable.

The pressure-sensitive adhesive is not particularly limited as long as it is conventionally used for a pressure-sensitive adhesive tape, and examples thereof include an acrylic pressure-sensitive adhesive, an emulsion-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive. .

Examples of the method of applying the adhesive on at least one surface of the crosslinked polyolefin resin foam sheet include, for example, a method of applying with a coating machine such as a coater, a method of spraying with a spray, a method of directly applying with a brush, and the like. Can be

And, when the tensile shear adhesive strength of the pressure-sensitive adhesive tape measured according to JIS Z 1541 becomes small, the crosslinked polyolefin resin foam sheet breaks in its thickness direction,
Since the adherend adhered to the adhesive tape may fall, it is preferably 53 N / 100 m ² or more.

In addition, when the adhesive tape has a 90 ° peel adhesive strength measured according to JIS Z 1541, which is small, when the adhesive tape is peeled off, the cross-linked polyolefin resin foam sheet as the adhesive tape base material is moved in the thickness direction. It is preferable that the thickness be 15 N / 10 mm or more, since the adhesive may remain on the adherend after being destroyed, that is, a so-called adhesive residue may occur.

Further, it is preferable that the pressure-sensitive adhesive tape does not drop in a heat resistance holding force test under conditions of 90 ° C. × 7 days, measured in accordance with JIS Z1541. This is because, for example, when an adhesive tape is used as a joining tape for a structure used in a construction work or the like, the adhesive tape can cope with a temperature change in a use environment.

Since the crosslinked polyolefin resin foam sheet of the present invention is a resin having excellent flexibility, it contains a specific amount or more of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. Since it has excellent flexibility and compression recovery properties and has a specific cell shape, the sheet extrusion direction (MD
) Also has excellent tensile strength.

Therefore, the crosslinked polyolefin-based resin foam sheet of the present invention is suitably used as a pressure-sensitive adhesive tape substrate that requires excellent tensile strength in at least one direction. Furthermore, since the crosslinked polyolefin-based resin foam sheet of the present invention has not only tensile strength but also flexibility and compression recovery properties, the pressure-sensitive adhesive tape base material of the pressure-sensitive adhesive tape used as a non-adjustment material or a sealing material Can also be suitably used.

Furthermore, the pressure-sensitive adhesive tape of the present invention has excellent tensile strength because the crosslinked polyolefin-based resin foam sheet is used as a pressure-sensitive adhesive tape base material. Then, when using the adhesive tape, grip the outer peripheral end of the adhesive tape in the wound state, and peel the adhesive tape from the wound body by a desired length from the outer peripheral end side, or attach the adhesive tape to a desired portion. Even when the pressure-sensitive adhesive tape is pulled in the length direction in order to stick the tape without wrinkles, the pressure-sensitive adhesive tape of the present invention does not break, and is excellent in handleability, workability, and the like. Further, the pressure-sensitive adhesive tape of the present invention is excellent in flexibility and compression recovery, excellent in irregularity adjusting function and sealing property, and is suitably used as an irregularity adjusting material and a sealing material.

(Example 1)
Linear low-density polyethylene obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst (density 0.900 g / cm ³ , weight average molecular weight 2.0: manufactured by Exxon Chemical Company, trade name “EXACT3027” ") 100 parts by weight, azodicarbonamide 5 parts by weight,
A foamable resin composition comprising 0.3 parts by weight of 2,6-di-t-butyl-p-cresol and 1 part by weight of zinc oxide is supplied to an extruder, melt-kneaded at 130 ° C., extruded, and extruded. A 0.8 mm long foamable resin sheet was obtained.

After irradiating 5 Mrad of an electron beam with an acceleration voltage of 800 kV to both sides of the obtained foamable resin sheet, the long foamable resin sheet was continuously placed in a foaming furnace maintained at 250 ° C. by hot air and an infrared heater. This was supplied to obtain a long crosslinked polyolefin resin foam sheet.

The ratio of the speed of feeding the foamable resin sheet to the foaming furnace and the speed of winding the foamed sheet out of the foaming furnace (speed of winding the foamed sheet / speed of feeding the foamable resin sheet to the foaming furnace) To 3.7, the foamed sheet in the process of foaming was stretched in the sheet extrusion direction (MD). In Table 1, "the ratio of the speed at which the foamable resin sheet is supplied to the foaming furnace to the speed at which the foamed sheet coming out of the foaming furnace is wound" is simply referred to as "speed ratio".

(Example 2, Comparative Examples 1 and 2)
Ratio of the speed of feeding the foamable resin sheet to the foaming furnace and the speed of winding the foamed sheet out of the foaming furnace (speed of winding the foamed sheet / speed of feeding the foamable resin sheet to the foaming furnace)
Was as shown in Table 1, and a long cross-linked polyolefin-based resin foam sheet was obtained in the same manner as in Example 1 except that the foaming sheet in the process of foaming was stretched in the sheet extrusion direction (MD). However, in Comparative Example 2, the sheet was cut during stretching, and a crosslinked polyolefin-based resin foam sheet was not obtained.

(Comparative Example 3)
As the foamable resin composition, a linear low-density polyethylene (density 0.900 g / cm ³ , weight average molecular weight 2) obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst
. 0: Polyolefin-based resin 1 composed of 20% by weight of a product name “EXACT3027” manufactured by Exxon Chemical Company and 80% by weight of low-density polyethylene (density 0.923 g / cm ³ )
Example 2 except that a foamable resin composition comprising 00 parts by weight, 5 parts by weight of azodicarbonamide, 0.3 part by weight of 2,6-di-t-butyl-p-cresol and 1 part by weight of zinc oxide was used. In the same manner as in Example 1, a crosslinked polyolefin resin foam sheet was obtained.

The degree of crosslinking, the average cell diameter of MD, the average cell diameter of ZD, the average cell diameter of CD and the apparent density of the obtained crosslinked polyolefin resin foam sheet were measured, and the results are shown in Table 1.

Further, the obtained crosslinked polyolefin-based resin foam sheet was measured for tensile strength, flexibility and compression recovery property in the following manner, and the results are shown in Table 1.

Also, subjected to corona discharge treatment on both sides of the obtained cross-linked polyolefin resin foam sheet,
The wetting index on both sides of the crosslinked polyolefin-based resin foam sheet was 440 μN / cm. Then, on both sides of the crosslinked polyolefin-based resin foam sheet, 100 g of a pressure-sensitive adhesive (trade name “Esdine # 7850” manufactured by Sekisui Chemical Co., Ltd.) is used, the main component of which is an acrylic ester copolymer.
An adhesive tape was prepared by coating at a ratio of m ² . And the tensile shear adhesion of the adhesive tape,
A 90 ° peeling adhesive strength and a heat retention test were measured in accordance with JIS Z1541. The results are shown in Table 1.

(Tensile strength)
The tensile strength of the crosslinked polyolefin-based resin foam sheet was measured in accordance with JIS K 6767 method A, with the sheet extrusion direction (MD) of the crosslinked polyolefin-based resin foam sheet being the longitudinal direction of the test piece.

(Flexibility)
The 25% compression hardness of the crosslinked polyolefin-based resin foam sheet was measured according to JIS K 6767, and used as an index of flexibility.

(Compression recovery)
The compression set of the crosslinked polyolefin-based resin foam sheet was measured in accordance with JIS K 6767, and used as an index of compression recovery.

Claims (3)

A foamable resin composition comprising a polyolefin-based resin containing at least 40% by weight of a polyethylene-based resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst and a pyrolytic foaming agent is supplied to an extruder. A crosslinked polyolefin-based resin foam sheet obtained by subjecting a foamable resin sheet obtained by extruding from an extruder to melt-kneading and then foaming and stretching,
The degree of crosslinking is 5 to 60% by weight, and the ratio of the average cell diameter in the sheet extrusion direction to the average cell diameter in the sheet thickness direction (average cell diameter in the sheet extrusion direction / average cell diameter in the sheet thickness direction). Is 2.
5 to 7, and the ratio of the average cell diameter in the sheet extrusion direction to the average cell diameter in the sheet width direction (
A crosslinked polyolefin resin foam sheet having an average cell diameter in the sheet extrusion direction / average cell diameter in the sheet width direction) of 2 to 6. An adhesive tape, wherein a pressure-sensitive adhesive is applied to at least one surface of the crosslinked polyolefin-based resin foam sheet according to claim 1, and the thickness of the crosslinked polyolefin-based resin foam sheet is 0.05 to 10 mm. A pressure-sensitive adhesive is applied to both sides of the crosslinked polyolefin-based resin foam sheet according to claim 1, and has a tensile shear adhesive strength of at least 53 N / 100 m ² measured according to JIS Z 1541, and a 90 ° peel adhesive strength. 3. The pressure-sensitive adhesive tape according to claim 2, wherein the adhesive tape does not drop in a heat resistance holding force test under a condition of 15 N / 10 mm or more and 90 ° C. × 7 days.