JP2008274073A - Expanded sheet and adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expanded sheet and an adhesive tape, low in cost, having good hand cutting properties, without introducing secondary processing or new equipment. <P>SOLUTION: The resin foam is produced by expanding a resin composition containing a polyolefin-based resin (A) and an incompatible resin (B) to the polyolefin-based resin at a ratio of (A):(B)=90:10-60:40, wherein the average major axis of the island part of a sea-island structure formed with the polyolefin-based resin (A) and the incompatible resin (B) of the resin foam is ≥1 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a foamed sheet obtained by foaming a resin composition containing a polyolefin resin and a resin incompatible with the polyolefin resin at a predetermined ratio, and an adhesive tape using the foamed sheet.

  As pressure-sensitive adhesive tapes having a foam sheet as a base material, those that have been punched into a shape for use and those in which tape-like filaments are wound into a roll are on the market.

  The adhesive tape in which the latter tape-shaped linear body is wound in a roll shape is used by an operator by separating it into an arbitrary length, and in particular, in the adhesive tape based on a polyolefin-based foam sheet, the separation is performed. In this case, the cut portion is stretched or the foamed structure of the base material is crushed and thinned, so that a so-called necking phenomenon is likely to occur. That is, there was a problem that the hand cutting property was bad.

  As a solution to this problem, a method of forming a perforated sewing machine hole (Patent Document 1) in a pressure-sensitive adhesive tape in which a release sheet is disposed on a foamed sheet via a pressure-sensitive adhesive layer, or a cloth-like sheet and foaming A method of laminating sheets (Patent Document 2) and the like have been proposed.

Japanese Utility Model Publication No. 7-15750 JP 2004-18571 A

  However, these methods have a problem in that they require secondary processing and introduction of new equipment, which increases the cost.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a foam sheet and an adhesive tape having good hand cutting properties at low cost without introducing secondary processing or new equipment.

  As a result of various studies to achieve the above object, the present inventor has produced a foam sheet having the following characteristics and a pressure-sensitive adhesive tape using the foam sheet at a low cost, and has good hand cutting properties. I found out.

  That is, the foamed sheet according to claim 1 is a resin containing the polyolefin resin (A) and the incompatible resin (B) with respect to the polyolefin resin in a ratio of (A) :( B) = 90: 10 to 60:40. A foamed sheet obtained by foaming the composition, wherein an average major axis of an island portion of a sea-island structure formed by the polyolefin resin (A) and the incompatible resin (B) of the foamed sheet is 1 μm or more. And

  Moreover, the adhesive tape which concerns on Claim 2 uses the foamed sheet of Claim 1 as a base material, It is characterized by the above-mentioned.

  The foam sheet and pressure-sensitive adhesive tape according to the present invention configured as described above are excellent in hand cutting properties, and further, since secondary processing or new production equipment for the foam sheet is not required separately, it is remarkable that it can be manufactured at low cost. It has a great effect.

  The foamed sheet of this embodiment is a resin composition comprising a polyolefin resin (A) and a non-compatible resin (B) for the polyolefin resin in a ratio of (A) :( B) = 90: 10 to 60:40. The average major axis of the island part of the sea-island structure formed by the polyolefin resin (A) and the incompatible resin (B) of the foamed sheet is 1 μm or more.

  The pressure-sensitive adhesive tape of this embodiment is a double-sided pressure-sensitive adhesive tape using the foamed sheet as a base material, and a pressure-sensitive adhesive layer is provided on both surfaces of the foamed sheet, and release paper is laminated on at least one pressure-sensitive adhesive layer surface. ing. Both surfaces of the foam sheet may be subjected to surface oxidation treatment such as corona (discharge) treatment, flame treatment, plasma treatment, glow discharge treatment, ozone treatment, etc. in order to improve the adhesion to the pressure-sensitive adhesive layer.

  As the pressure-sensitive adhesive, commonly used acrylic and rubber-based ones can be used, but an acrylic pressure-sensitive adhesive containing no tackifying resin is preferable in terms of low-temperature adhesiveness.

  Release paper is commonly used with polyethylene resin coated on both sides of kraft paper, fine paper, glassine paper, etc., and the coated surface is release-treated with silicon resin, synthetic resin film such as polyethylene terephthalate film, etc. Is used.

  And in this embodiment, the said adhesive tape is made into the roll body in the roll shape.

  Here, the foamed sheet will be described in more detail.

  Examples of the polyolefin resin (A) constituting the foamed sheet of the present embodiment include polyethylene, polypropylene, ethylene / α-olefin copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid. Acid ester copolymers, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, and the like. Specific examples of polyethylene include very low density polyethylene (VLDPE), linear low density polyethylene ( LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), etc., as polypropylene, specifically, propylene homopolymer (H-PP), ethylene / propylene block copolymer Combined (B-PP), ethylene / propylene Dam copolymer (R-PP) and the like.

  The incompatible resin (B) is not particularly limited, and the resin composition contains the polyolefin resin (A) and the incompatible resin (B) in a ratio of A: B = 90: 10 to 60:40. In the foam sheet obtained by foaming the foamed sheet, the average major axis of the island part of the sea-island structure formed by the polyolefin resin (A) and the incompatible resin (B) is 1 μm or more on the foam wall (non-bubble part) of the foam sheet. Any resin can be used. Examples of such a resin include polystyrene and polyvinyl chloride.

  That is, as an index of the incompatible resin (B), the average major axis of the island portion of the sea-island structure formed by the polyolefin resin and the incompatible resin is 1 μm or more on the foaming wall (non-bubble portion) of the foam sheet. That is. In general, there is a method of using transparency of a film as an index of compatibility (incompatibility) (“Polymer Blend” CMC, P69 (1992, 5th printing) Saburo Akiyama, Takashi Inoue, Nishi Toshio). However, since transparency cannot be confirmed because it is formed as a foamed sheet, the average major axis of the island part of the sea-island structure in the foamed wall is used as a criterion for judgment.

  Further, the resin composition used for the foam sheet includes a mixed resin group obtained by mixing a polyolefin resin (A) and an incompatible resin (B) in a ratio of A: B = 90: 10 to 60:40. Various additives may be added to the material according to the purpose. Specific examples include antioxidants, light stabilizers, ultraviolet absorbers, antistatic agents, bisamides, waxes, dispersants, lubricants, flame retardants, inorganic fillers, organic fillers, pigments, antibacterial agents, and the like. It is done.

  There is no limitation in particular also about the manufacturing method of a foam sheet, A well-known method can be used. For example, a polyolefin resin (A), an incompatible resin (B), and a foaming agent are kneaded with a roll to form a sheet and then foamed, or a polyolefin resin (A), an incompatible resin (B) And a method in which a foaming agent is melt-extruded and foamed.

  In addition, as a foaming agent, you may use any of a chemical foaming agent and a physical foaming agent. Chemical blowing agents include azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, N, N′-dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitroterephthalamide, benzenesulfonyl Examples thereof include hydrazide, p-toluenesulfonyl hydrazide, p 1, p′-oxybisbenzenesulfonyl hydrazide, benzenesulfonyl carbazide, carbonates such as sodium hydrogen carbonate, and organic acid salts such as sodium citrate. Examples of physical foaming agents that are gasified by heating and pressure control include propane, butane, pentane, dichlorodifluoromethane, dichloromonofluoromethane, trichloromonofluoromethane, methanol, ethanol, water, air, nitrogen, carbon dioxide, and the like. .

  A foaming aid can be added to the foaming agent, and examples of the foaming aid include zinc oxide, zinc nitrate, basic zinc carbonate, zinc stearate, lead phthalate, lead carbonate, urea, glycerin and the like. .

  Furthermore, the foamed sheet preferably has a crosslinked structure, and the method for crosslinking is not particularly limited. For example, a method of electron beam cross-linking the resin composition, a method of thermally cross-linking by adding a cross-linking agent such as DCP to the resin composition, and the like.

  Next, examples of specific compositions of the foamed sheets of the present invention and various properties of the foamed sheets are shown in Table 1 together with comparative examples, but the present invention is not limited to the examples.

  In the examples of the present invention and comparative examples thereof, as the polyolefin resin (A), low density polyethylene (LDPE: Sumitomo Chemical Co., Ltd., Sumikasen F200) and ethylene vinyl acetate copolymer (EVA: Tosoh Corporation) Ultra 2 types of Sen 35), 2 types of polystyrene (PS: PS Japan Co., Ltd. GPPS HF77) and polyvinyl chloride (PVC: Shin-Etsu Chemical Co., Ltd. TK-1400E) as non-compatible resin (B). Azodicarbonamide (ADCA: Otsuka) as a foaming agent for 100 parts by weight of the resin base material prepared and mixed in various proportions (weight ratio) of the polyolefin resin (A) and the incompatible resin (B). 10 parts by weight of Chemical Co., Ltd. VI50ST-INP), zinc oxide (ZnO: Naito Shoten Co., Ltd. Zinc Hana) and steel (ZnS) as foaming aids : Nippon Kasei Co., Ltd. Diamond Y) 1.0 parts by weight and Irganox 1010 (Ciba Specialty Chemicals Co., Ltd.) 0.2 parts by weight as an antioxidant were blended to give a resin composition. Obtained.

  In the resin base material of Example 1, LDPE as the polyolefin resin (A) and PS as the incompatible resin (B) were included in a ratio of (A) :( B) = 90: 10. .

  In the resin base material of Example 2, LDPE as the polyolefin resin (A) and PS as the incompatible resin (B) were included in a ratio of (A) :( B) = 70: 30. .

  The resin base material of Example 3 contained LDPE as the polyolefin resin (A) and PS as the incompatible resin (B) in a ratio of (A) :( B) = 60: 40. .

  The resin base material of Example 4 contained EVA as the polyolefin resin (A) and PS as the incompatible resin (B) in a ratio of (A) :( B) = 70: 30.

  The resin base material of Example 5 contained LDPE as the polyolefin resin (A) and PVC as the incompatible resin (B) in a ratio of (A) :( B) = 70: 30.

  The resin base material of Example 6 contained EVA as the polyolefin resin (A) and PVC as the incompatible resin (B) at a ratio of (A) :( B) = 70: 30.

  The resin base material of Comparative Example 1 is composed of only LDPE as the polyolefin resin (A) without containing the incompatible resin (B), and a ratio of (A) :( B) = 100: 0 did.

  The resin base material of Comparative Example 2 does not contain the incompatible resin (B) and is composed only of EVA as the polyolefin resin (A), and the ratio of (A) :( B) = 100: 0 did.

  The resin base material of Comparative Example 3 does not contain the incompatible resin (B), and is mixed with 70 parts by weight and 30 parts by weight of LDPE and EVA as the polyolefin resin (A), respectively (A ) :( B) = 100: 0.

  The resin base material of Comparative Example 4 contained LDPE as the polyolefin resin (A) and PS as the incompatible resin (B) in a ratio of (A) :( B) = 95: 5.

  The resin base material of Comparative Example 5 contained LDPE as the polyolefin resin (A) and PS as the incompatible resin (B) in a ratio of (A) :( B) = 55: 45.

  Each of the 11 resin compositions of Examples 1 to 6 and Comparative Examples 1 to 5 was kneaded using a 135 ° C. two-roll machine and heated to about 0 with a 140 ° C. hot press. After forming into a 5 mm thick sheet, electron beam irradiation (500 kV, 1 Mrad, both sides) was performed for crosslinking, and a foamed sheet was obtained in a 240 ° C. heating furnace.

  A test piece having a size of 5 × 5 cm was cut out from the foamed sheet thus obtained, and the foamability was evaluated by observing the appearance of the foamed sheet. Uniform foaming was rated “good”, foaming was uneven, and foaming was not “bad”.

  In addition, with regard to hand-cutting properties, a 1 x 5 cm specimen was cut out, and the half of the longitudinal direction was held between a desk and the left hand, and the specimen was held with the right hand. Those having a length of 5 mm or less were judged as having good hand-cutting properties and were judged as “good”, and others were designated as “bad”.

  In addition, regarding the cut surface of the foam wall of the foam sheet, SEM (electron microscope) observation is performed at 2000 times, and the major axis (longest diameter) is measured for all islands in the 50 × 50 μm region, and the average value thereof, That is, the average major axis was calculated.

  As a result, as shown in Table 1, Comparative Example 1 and Comparative Example 2 did not contain the incompatible resin (B), so that the foamability was good, but the hand tearability was poor.

  Further, even when a resin having good compatibility was blended as in Comparative Example 3, the hand cutting ability was not improved.

  In Comparative Example 4, the non-compatible resin (B) was 5%. However, hand cutting performance was not improved at this level, and the non-compatible resin (B) was not added in an amount of 10% or more as in Example 1. And hand cutting was not expressed.

  Also, if the polyolefin resin (A) is 55% as in Comparative Example 5, a foamed sheet cannot be formed. However, as in Example 3, if the polyolefin resin (A) is 60%. It was found to foam.

  Further, as in Example 2 and Examples 4 to 6, regardless of the type of polyolefin resin (A) and the type of incompatible resin (B), (A) :( B) = 90: It was found that the foaming property and the hand cutting property can be obtained within the range satisfying the above numerical condition of 10 to 60:40.

  Thus, a foamed sheet obtained by foaming a resin composition containing a polyolefin resin (A) and an incompatible resin (B) with respect to the polyolefin resin at a ratio of A: B = 90: 10 to 60:40, The foam sheet having an average major axis of the island part of the sea-island structure formed by the polyolefin resin (A) and the incompatible resin (B) of the foam sheet has a good hand cutting property. In addition, since the secondary processing and new manufacturing equipment for the foam sheet are not required separately, it has a remarkable effect that it can be manufactured at low cost.

  In addition, the pressure-sensitive adhesive tape of the present embodiment using a foamed sheet having such characteristics as a base material has excellent hand cutting properties and can be manufactured at low cost.

Claims (2)

A resin foam obtained by foaming a resin composition containing a polyolefin resin (A) and an incompatible resin (B) with respect to the polyolefin resin in a ratio of (A) :( B) = 90: 10 to 60:40. The foamed sheet is characterized in that the average major axis of the island part of the sea-island structure formed by the polyolefin resin (A) and the incompatible resin (B) of the resin foam is 1 μm or more. A pressure-sensitive adhesive tape comprising the foamed sheet according to claim 1 as a base material.