JP2013177630A - Crosslinked polyolefin-based resin foamed sheet and adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinked polyolefin-based resin foamed sheet which has excellent flexibility and compression recovery properties, also has excellent tensile strength at least in MD, and is suitably used as a substrate of an adhesive tape.SOLUTION: A crosslinked polyolefin-based resin foamed sheet is obtained by foaming and extending a polyolefin-based resin containing at least 40 wt.% of a specific polyethylene-based resin, wherein a degree of crosslinking is 5-60 wt.%, a ratio of an average cell diameter in the sheet extrusion direction to an average cell diameter in the sheet thickness direction is 2.5-7, and also a ratio of an average cell diameter in the sheet extrusion direction to an average cell diameter in the sheet width direction is 2-6.

Description

  The present invention relates to a crosslinked polyolefin resin foam sheet that is flexible and excellent in mechanical strength, and is suitably used as an adhesive tape base material, and an adhesive tape using the crosslinked polyolefin resin foam sheet as an adhesive tape base material.

  Conventionally, pressure-sensitive adhesive tapes have been used for a wide range of applications, and in particular, pressure-sensitive adhesive tapes based on foamed sheets are suitable as unevenness adjusting materials, sealing materials, etc. in the fields of industrial materials and building materials, for example. It is used. Moreover, since the adhesive tape based on a foam sheet has a good texture, it is often used suitably in vehicles and IT fields other than industrial materials and building materials.

  The pressure-sensitive adhesive tape is obtained by applying a pressure-sensitive adhesive to at least one surface of a pressure-sensitive adhesive tape substrate. Usually, a long pressure-sensitive adhesive tape is wound around a shaft core to form a wound body. And when using the adhesive tape, the outer peripheral end of the adhesive tape is gripped, and 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 location. The adhesive tape is often pulled in the length direction in order to apply it without crushing, and tensile stress is often applied to the adhesive tape. Therefore, excellent tension is applied to the adhesive tape substrate that governs the mechanical properties of the adhesive tape. Strength is required.

  Furthermore, when an adhesive tape is used as an unevenness adjusting material, an adhesive tape is required as a sealing material, while an excellent flexibility is required for the adhesive tape base material in order to express an excellent unevenness adjusting function. When used, the adhesive tape base material is required to have excellent flexibility and compression recovery properties in order to maintain enforcement performance and sealing performance. Also, in applications other than the above, in order to improve the texture of the adhesive tape, flexibility and compression recovery are often required.

  On the other hand, the cross-linked polyolefin resin foam sheet is very excellent in flexibility, and has been conventionally used in a wide range of applications as a buffer material or a heat insulating material.

  However, when trying to apply the crosslinked polyolefin resin foam sheet to the adhesive tape substrate, there is a problem that the tensile strength is insufficient, and in particular, the flexibility and compression recovery of the crosslinked polyolefin resin foam sheet are ensured. Therefore, as shown in Patent Document 1 and Patent Document 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 cross-linked polyolefin resin foam sheet is used as a pressure-sensitive adhesive tape substrate, there is a problem that the pressure-sensitive adhesive tape breaks when the pressure-sensitive adhesive tape is used.

  Accordingly, in order to improve the tensile strength of the crosslinked polyolefin resin foam sheet, for example, it is conceivable that the crosslinked polyolefin resin foam sheet has a low expansion ratio. There was a problem that the compression recoverability deteriorated.

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

  An object of the present invention is to provide a crosslinked polyolefin resin foam sheet that has excellent flexibility and compression recovery property, and at least excellent tensile strength in the sheet extrusion direction, and can be suitably used as an adhesive tape substrate. Is to provide.

  Another object of the present invention is to use the above-mentioned crosslinked polyolefin resin foam sheet as a pressure-sensitive adhesive tape substrate so that it has a good texture and excellent tensile strength, does not break during use, and is flexible and compressible. The present invention is to provide an adhesive tape that is excellent in use and can be suitably used as an unevenness adjusting material or a sealing material.

  The cross-linked polyolefin resin foam sheet of the present invention comprises a polyolefin resin containing 40% by weight or more of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and a thermally decomposable foaming agent. A cross-linked polyolefin resin foamed sheet obtained by supplying a foamable resin composition to an extruder, melt-kneading and then extruding from the extruder, followed by crosslinking and foaming and stretching. The ratio of the average cell diameter in the sheet extrusion direction and 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. 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 7 And characterized in that.

  The polyolefin resin used in the present invention is not particularly limited as long as it contains 40% by weight or more of a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. A polyethylene resin obtained using only a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, or a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst Although it may be any of those composed of other polyolefin resins, the resulting crosslinked polyolefin resin foam sheet is excellent in flexibility, compression recovery and mechanical strength, so that it is a tetravalent transition metal as a polymerization catalyst. What consists only of the polyethylene-type resin obtained using the metallocene compound containing is preferable.

  As a polyethylene resin obtained by 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, ethylene and a small amount of an α-olefin are obtained. A linear low density polyethylene obtained by copolymerization 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 representative. As the metallocene compound containing a tetravalent transition metal in the present invention, more specifically, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, platinum or the like is added to one or more cyclopentadienyl. Examples thereof include 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 with a hydrocarbon group, a substituted hydrocarbon group, or a hydrocarbon-substituted metalloid group; a cyclopentadienyl oligomer ring; an indenyl ring; And an indenyl ring substituted by a group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. In addition to these π-electron unsaturated compounds, as ligands, monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, 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 tetravalent transition metals include 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-butylamido hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl titanium tri (Diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

  The metallocene compound exhibits the action as a catalyst in the polymerization of various olefins by changing the kind of metal and the structure of the ligand and combining with a specific cocatalyst (co-catalyst). More specifically, the polymerization is usually performed in a catalyst system in which methylaluminoxane (MAO), a boron-based compound or the like is added to these metallocene compounds as a cocatalyst. The use ratio of the cocatalyst with respect to the metallocene compound is 10 to 1,000,000 mole times, preferably 50 to 5,000 mole 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 −100 ° C. to 300 ° C., and the polymerization pressure is usually normal pressure to 100 kg / cm ² .

  The metallocene compound has a feature that the properties of the active sites are uniform. In the metallocene compound, since each active site has the same activity, the uniformity of the molecular weight, molecular weight distribution, composition, composition distribution, etc. of the polymer to be synthesized is increased. Therefore, the polyolefin 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 in almost equal proportion to any molecular weight component. Have

  When the content of the polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as the polymerization catalyst in the polyolefin resin decreases, the flexibility and compression recovery of the resulting crosslinked polyolefin resin foam sheet are reduced. Or since mechanical strength falls, it is limited to 40 weight% or more, and 60 weight% or more is preferable.

  Examples of the other polyolefin resins include polyethylene resins and polypropylene resins. 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 Examples include polyethylene, medium density polyethylene, high density polyethylene, ethylene-α-olefin copolymer based on ethylene, ethylene-vinyl acetate copolymer based on ethylene, and these are used alone. Two or more of them may be used in combination. Examples of the α-olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Etc.

  Examples of the polypropylene resin include polypropylene, an ethylene-propylene copolymer containing propylene as a main component, and a propylene-α-olefin copolymer containing propylene as a main component, and these are used alone. Two or more of them may be used in combination. Examples of the α-olefin constituting the propylene-α-olefin copolymer include 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. .

  The pyrolytic foaming agent used in the present invention is a compound that decomposes by heating to generate a decomposition gas, such as azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, p-toluenesulfonyl semicarbazide. These may be used, and these may be used alone or in combination of two or more.

  The addition amount of the pyrolytic foaming agent may be appropriately determined according to the desired apparent density of the cross-linked polyolefin resin foam sheet. However, if the amount is decreased, the foamability of the foamable resin composition is lowered and the desired apparent density is reduced. When the cross-linked polyolefin resin foamed sheet having a high molecular weight is not obtained and increases, the tensile strength and compression recoverability of the resulting cross-linked polyolefin resin foamed sheet are reduced. Part by weight is preferable, and 1 to 30 parts by weight is more preferable.

  The cross-linked polyolefin resin foam sheet of the present invention is melted at a temperature at which the thermally decomposable foaming agent is not substantially decomposed by supplying the foamable resin composition comprising the polyolefin resin and the thermally decomposable foaming agent to an extruder. The foamable resin sheet obtained by kneading and extruding from an extruder is crosslinked and then stretched in the sheet extrusion direction after foaming or stretched in the sheet extrusion direction during foaming.

  When the degree of cross-linking of the crosslinked polyolefin resin foamed sheet is reduced, the sheet is generally stretched while the foamed sheet is heated in the process of producing the crosslinked polyolefin resin foamed sheet. Since the heat resistance of the sheet is insufficient, bubbles on the surface are broken to cause surface roughening, and the appearance of the resulting crosslinked polyolefin resin foamed sheet is deteriorated and becomes large, and the melt viscosity of the foamable resin composition increases. Therefore, in the process of producing a crosslinked polyolefin resin foamed sheet, when the foamable resin composition is heated and foamed, it becomes difficult for the foamable resin composition to follow the foaming, and the crosslinked polyolefin resin foamed sheet having a desired apparent density. Is not obtained, it is limited to 5 to 60% by weight, and preferably 10 to 40% by weight.

In addition, the crosslinking degree of a crosslinked polyolefin resin foamed sheet is a value measured by the following method. First, about 100 mg of a test piece is taken from the crosslinked polyolefin resin foam sheet, and the weight A (mg) of the test piece is precisely weighed. Next, this test piece is immersed in 30 cm ³ of xylene at 120 ° C. and left for 24 hours. Thereafter, the mixture is filtered through a 200-mesh wire mesh, the insoluble matter on the wire mesh is collected, vacuum dried, 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 formula.
Crosslinking degree (% by weight) = (B / A) × 100

  When the ratio of the average cell diameter in the sheet extrusion direction (MD) and the average cell size in the sheet thickness direction (ZD) (average cell diameter in MD / average cell diameter in ZD) in the cross-linked polyolefin resin foam sheet is small. When the tensile strength, flexibility, and compression recovery property of the cross-linked polyolefin resin foam sheet in MD are lowered and increased, the sheet is greatly stretched and cut in MD in the production process. It is limited and 3-6 are preferable.

  When the ratio of the average cell diameter in the sheet extrusion direction (MD) and the average cell size in the sheet width direction (CD) (average cell diameter in MD / average cell diameter in CD) in the crosslinked polyolefin-based resin foam sheet is small, When the tensile strength, flexibility, and compression recovery property of the cross-linked polyolefin resin foam sheet are lowered and increased, the sheet is greatly stretched and cut in the MD in the production process, and is limited to 2 to 6, 2 to 4.5 are preferred.

  The sheet thickness direction (ZD) in the cross-linked polyolefin resin foamed sheet refers to the normal direction to the surface of the cross-linked polyolefin resin foam sheet, and the sheet width direction (CD) in the cross-linked polyolefin resin foam sheet refers to the sheet. The direction orthogonal to the extrusion direction and the sheet thickness direction.

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

  Then, the cut surface of the crosslinked polyolefin resin foam sheet is enlarged 60 times using a scanning electron microscope (SEM), and the cut surface of the crosslinked polyolefin resin foam sheet extends over the entire length in the sheet thickness direction (ZD). Take a photo so that it fits.

In the obtained photograph, a straight line with a length of 15 cm (actual length of 2500 μm before enlargement) on the photograph is parallel to the cross-linked polyolefin resin foam sheet surface at the center of the cut surface in the sheet thickness direction. Draw like so. Thereafter, the number of bubbles present on the straight line is counted visually. And the average bubble diameter of MD in a crosslinked polyolefin-type resin foam sheet is computed based on a following formula.
Average bubble diameter of MD in foamed sheet (μm) = 2500 (μm) / number of bubbles (pieces)

  The average cell diameter in the sheet thickness direction (ZD) in 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 extruding direction (MD) have a sheet thickness (ZD) in the direction (ZD) orthogonal to the sheet extruding direction (MD). Draw over the entire length.

Thereafter, the length of each straight line is measured, the number of bubbles present on each straight line is visually counted, the average bubble diameter is calculated for each straight line based on the following formula, and the obtained three averages are calculated. The arithmetic average 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 (number) × 60]

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

  Then, the cut surface of the crosslinked polyolefin resin foam sheet is enlarged 60 times using a scanning electron microscope (SEM), and the cut surface of the crosslinked polyolefin resin foam sheet extends over the entire length in the sheet thickness direction (ZD). Take a photo so that it fits.

In the obtained photograph, a straight line with a length of 15 cm (actual length of 2500 μm before enlargement) on the photograph is parallel to the cross-linked polyolefin resin foam sheet surface at the center of the cut surface in the sheet thickness direction. Draw like so. Thereafter, the number of bubbles present on the straight line is counted visually. And based on the following formula, the average cell diameter of CD in the crosslinked polyolefin resin foam sheet is calculated.
Average bubble diameter of CD in foamed sheet (μm) = 2500 (μm) / number of bubbles (pieces)

  Here, regardless of whether or not the bubbles communicate with each other in the portion other than the photograph, one void portion surrounded by the cross section of the bubble film appearing on the photograph is defined as one bubble, and a part of the bubble emerges from the straight line. All the bubbles were 0.5.

  When taking a picture, if the bubble film cross section is colored with magic ink or the like, it becomes easy to distinguish the bubbles. Further, when taking a picture by taking a scale of 2500 μm together and taking a picture at the time of taking a picture, it becomes easy to specify the straight line length on the picture.

  In the foamable resin composition, an antioxidant such as 2,6-di-t-butyl-p-cresol, zinc oxide, and the like, as long as the physical properties of the crosslinked polyolefin resin foamed sheet are not impaired. Additives such as a foaming aid, a cell core modifier, 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 ionizing radiation such as electron beam, α ray, β ray, γ ray or the like so as to have the above degree of crosslinking, an organic material is previously applied to the foamable resin composition. Examples include 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 may be mentioned, and these may be used alone or in combination of two or more.

  If the amount of the organic peroxide added decreases, the foamable resin sheet will not be crosslinked, and the foamable resin sheet cannot be crosslinked to the desired degree of crosslinking. Since decomposition residue of organic peroxide remains therein, 0.01 to 5 parts by weight is preferable with respect to 100 parts by weight of the polyolefin resin.

  The method of 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 using a salt bath, a method using an oil bath, and the like. May be.

  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. Moreover, when extending | stretching a foamed sheet after making a foamable resin sheet foam, it is preferable to carry out after heating again.

  Examples of the method for stretching the sheet include adjusting the speed at which the foamable resin sheet is supplied to the foaming process and the speed at which the foamed sheet is cooled and wound after the foaming process, while foaming the foamable resin sheet. 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. In addition, the apparent density of the crosslinked polyolefin resin foam sheet refers to that measured according to JIS K 6767.

  This is because when the apparent density of the crosslinked polyolefin resin foam sheet decreases, the mechanical strength of the crosslinked polyolefin resin foam sheet may decrease, whereas when it increases, the flexibility of the crosslinked polyolefin resin foam sheet decreases, When a cross-linked polyolefin resin foam sheet is used as the adhesive tape substrate, the adhesive tape is subjected to adhesive stress when it is subjected to displacement stress along the surface of the adherend or peeling stress away from the adherend. The adhesive is deformed and tries to relieve the stress applied to the adhesive tape, but the crosslinked polyolefin resin foam sheet cannot follow the deformation of the adhesive, and as a result, the crosslinked polyolefin resin foam sheet and the adhesive Stress concentration occurs partially at the interface, and the cross-linked polyolefin resin foam sheet and adhesive are caused by 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 preferably used as a pressure-sensitive adhesive tape base material and coated with a pressure-sensitive adhesive on at least one surface thereof to form a long pressure-sensitive adhesive tape. When the crosslinked polyolefin resin foam sheet is used as an adhesive tape substrate, it is preferable to adjust the sheet extrusion direction (MD) of the crosslinked polyolefin resin foam sheet to be the length direction of the adhesive tape.

  When the cross-linked polyolefin resin foam sheet is used as an adhesive tape substrate, the mechanical strength such as the tensile strength of the cross-linked polyolefin resin foam sheet, flexibility, adhesion, etc. when the thickness of the cross-linked polyolefin resin foam sheet is reduced When the texture of the tape decreases and becomes thicker, the thickness of the low expansion ratio surface layer portion, so-called skin layer, formed on both sides of the cross-linked polyolefin resin foam sheet increases, so that the flexibility of the cross-linked polyolefin resin foam sheet increases. Since it falls, 0.05-10 mm is preferable and 0.1-8 mm is more preferable.

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

  Examples of the method of applying the pressure-sensitive adhesive to at least one surface of the crosslinked polyolefin resin foamed sheet include 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, etc. It is done.

And when the tensile shear adhesive force measured based on JIS Z1541 of the said adhesive tape becomes small, the crosslinked polyolefin resin foam sheet will destroy in the thickness direction, and the adherend stuck on the adhesive tape May fall, so 53 N / 100 m ² or more is preferable.

  In addition, when the adhesive strength of the adhesive tape measured in accordance with JIS Z 1541 is reduced, the cross-linked polyolefin resin foam sheet, which is the adhesive tape substrate, is removed in the thickness direction when the adhesive tape is peeled off. In other words, the adhesive remains on the adherend, and so-called adhesive residue may be generated. Therefore, the thickness is preferably 15 N / 10 mm or more.

  Furthermore, it is preferable that there is no drop in a heat resistance holding force test under the condition of 90 ° C. × 7 days, measured according to JIS Z 1541 of the above adhesive tape. This is because, for example, when the adhesive tape is used as a structural joining tape used in construction work or the like, the adhesive tape can cope with the temperature change of the use environment.

  Since the crosslinked polyolefin resin foam sheet of the present invention 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, which is a resin having excellent flexibility. It has excellent flexibility and compression recovery, and has a specific bubble shape, so it has excellent tensile strength in the sheet extrusion direction (MD) without impairing flexibility and compression recovery. ing.

  Therefore, the crosslinked polyolefin resin foam sheet of the present invention is suitably used as an adhesive tape base material that requires excellent tensile strength in at least one direction. Furthermore, since the crosslinked polyolefin 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-land surface adjusting material or a sealing material Can also be used suitably.

  Furthermore, the pressure-sensitive adhesive tape of the present invention has excellent tensile strength because the above-mentioned crosslinked polyolefin resin foam sheet is used as a pressure-sensitive adhesive tape substrate. And when using the adhesive tape, the outer peripheral end of the wound adhesive tape is gripped, and the adhesive tape is peeled from the wound body by the desired length from the outer peripheral end side, or the adhesive tape is removed from the desired location. Even when the pressure-sensitive adhesive tape is pulled in the length direction so that it can be applied without any problem, the pressure-sensitive adhesive tape of the present invention does not break, and is excellent in handling property, effectiveness and the like. Furthermore, the pressure-sensitive adhesive tape of the present invention is excellent in flexibility and compression recovery property, is excellent in unevenness adjusting function and sealing property, and is suitably used as an unevenness 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” ”) A foamable resin composition comprising 100 parts by weight, 5 parts by weight of azodicarbonamide, 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. Were melt-kneaded at 130 ° C. and extruded to obtain a long foamable resin sheet having a thickness of 0.8 mm.

  After irradiating an electron beam with an acceleration voltage of 800 kV for 5 Mrad on both surfaces of the obtained foamable resin sheet, the long foamable resin sheet is continuously put in a foaming furnace held at 250 ° C. by hot air and an infrared heater. This was supplied to obtain a long cross-linked polyolefin resin foam sheet.

  The ratio of the speed at which the foamable resin sheet is supplied to the foaming furnace and the speed at which the foamed sheet coming out of the foaming furnace is wound up (speed at which the foamed sheet is wound up / speed at which the foamable resin sheet is fed into the foaming furnace) By setting the value to 3.7, the foamed sheet in the process of foaming was stretched in the sheet extrusion direction (MD). In Table 1, “the ratio between the speed at which the foamable resin sheet is supplied to the foaming furnace and the speed at which the foamed sheet that has come out of the foaming furnace is wound” is simply expressed as “speed ratio”.

(Example 2, Comparative Examples 1 and 2)
The ratio of the speed at which the foamable resin sheet is supplied to the foaming furnace and the speed at which the foamed sheet coming out of the foaming furnace is wound up (speed at which the foamed sheet is wound up / speed at which the foamable resin sheet is supplied to the foaming furnace) is shown. As shown in 1, a long cross-linked polyolefin resin foam sheet was obtained in the same manner as in Example 1 except that the foam 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 resin foam sheet was not obtained.

(Comparative Example 3)
As a foamable resin composition, a linear low density polyethylene (density 0.900 g / cm ³ , weight average molecular weight 2.0: Exxon Chemical) obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. 100 parts by weight of polyolefin resin consisting of 20% by weight and trade name “EXACT3027”) and 80% by weight of low density polyethylene (density 0.923 g / cm ³ ), 5 parts by weight of azodicarbonamide, 2,6-di- A crosslinked polyolefin resin foamed sheet was obtained in the same manner as in Example 1 except that a foamable resin composition comprising 0.3 parts by weight of t-butyl-p-cresol and 1 part by weight of zinc oxide was used.

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

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

In addition, both sides of the obtained crosslinked polyolefin resin foamed sheet were subjected to corona discharge treatment, and the wettability index on both sides of the crosslinked polyolefin resin foamed sheet was set to 440 μN / cm. Then, a pressure-sensitive adhesive (product name “Sdyne # 7850” manufactured by Sekisui Chemical Co., Ltd.) whose main component is an acrylic ester copolymer is applied to both sides of the crosslinked polyolefin resin foam sheet at a rate of 100 g / m ^2. An adhesive tape was prepared. The tensile shear adhesive strength, 90 ° peel adhesive strength and heat resistance holding strength test of the adhesive tape were measured according to JIS Z 1541. The results are shown in Table 1.

(Tensile strength)
The tensile strength of the cross-linked polyolefin resin foam sheet was measured in accordance with JIS K 6767, Method A so that the sheet extrusion direction (MD) of the cross-linked polyolefin resin foam sheet was the longitudinal direction of the test piece.

(Flexibility)
The 25% compression hardness of the crosslinked polyolefin resin foamed sheet was measured in accordance with JIS K 6767 and used as an index of flexibility.

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

Claims (3)

  A foamable resin composition comprising a polyolefin resin containing 40% by weight or more of a polyethylene resin obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst and a thermally decomposable foaming agent is supplied to an extruder. A cross-linked polyolefin resin foam sheet obtained by cross-linking a foamable resin sheet obtained by melt-kneading and extruding from an extruder, followed by foaming and stretching, and having a cross-linking degree of 5 to 60% by weight, and The ratio of the average cell diameter in the sheet extrusion direction to the average cell size 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 sheet extrusion The ratio between the average cell diameter in the direction and 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 6 Foam sheet.   A pressure-sensitive adhesive tape, wherein a pressure-sensitive adhesive is applied to at least one surface of the cross-linked polyolefin resin foam sheet according to claim 1, and the thickness of the cross-linked polyolefin resin foam sheet is 0.05 to 10 mm. A pressure-sensitive adhesive is applied to both surfaces of the cross-linked polyolefin resin foam sheet according to claim 1, the tensile shear adhesive force measured in accordance with JIS Z 1541 is 53 N / 100 m ² or more, and the 90 ° peel adhesive force The pressure-sensitive adhesive tape according to claim 2, wherein the pressure-sensitive adhesive tape does not fall in a heat resistance holding force test under conditions of 15 N / 10 mm or more and 90 ° C. × 7 days.