Polyolefin resin foam and production method thereof and adhesive tape

Abstract

One object of the present invention is to provide a polyolefin resin foam sheet suitable as a sealing substrate having both flexibility and heat resistance despite its thinness, and an adhesive tape in which the polyolefin resin foam sheet is used. In order to achieve this, the polyolefin resin foam includes a thermoplastic elastomer, wherein the endothermic peaks measured by a differential scanning calorimeter (DSC) occur in the range of at least 110° C. or more and 143° C. or less and at 153° C. or more, and the thermoplastic elastomer resin is contained at a ratio of 30% by mass or more and 60% by mass or less in 100% by mass of the polyolefin resin.

Claims

1. A polyolefin resin foam sheet having front and back surfaces which is made of a polyolefin resin foam comprising a polyolefin resin and a thermoplastic elastomer resin, wherein the polyolefin resin foam sheet endothermic peaks measured by a differential scanning calorimeter (DSC) occur in a range of at least 120° C. or more and 143° C. or less and at 153° C. or more and 170° C. or less, said thermoplastic elastomer resin is contained at a ratio of 40% by mass or more and 60% by mass or less based on 100% by mass of the resins constituting the polyolefin resin foam sheet, said polyolefin resin is contained at a ratio of 60% by mass or less and 40% by mass or more based on 100% by mass of the resins constituting the polyolefin resin foam sheet, together the thermoplastic elastomer resin and the polyolefin resin constitute 100% by mass of the resins constituting the polyolefin resin foam sheet, a surface roughness Sa (arithmetic mean height) of both the front and the back surfaces is 16 μm or more and 80 μm or less, and a difference in surface roughness Sa between the front and the back surfaces is 20 μm or more and less than 50 μm based on the following formula:
(Difference in surface roughness Sa between the front and the back surfaces)=(Surface roughness Sa on the surface B)−(Surface roughness Sa on the surface A), both the surface A and the surface B are sliced and stretched, an average cell size in a machine direction (MD) corresponding to a resin extrusion direction or length direction on both the front and the back surfaces is 134 μm or more and 550 μm or less, and a ratio of the average cell size in the MD direction on the surface B to the average cell size in the MD direction on the surface A is 1.2 or more and 1.35 or less based on the following formula:
(Ratio of the average cell size in the MD direction)=(Average cell size in the MD direction on the surface B)/(Average cell size in the MD direction on the surface A).

2. The polyolefin resin foam sheet according to claim 1, wherein the gel fraction is 20% or more and 60% or less.

3. The polyolefin resin foam sheet according to claim 1, wherein the apparent density is 50 kg/m3 or more and 165 kg/m3 or less, and the thickness is 0.6 mm or more and 1.4 mm or less.

4. A method of producing said polyolefin resin foam sheet according to claim 1, comprising: a foaming step of foaming a resin composition comprising at least said polyolefin resin and said thermoplastic elastomer to produce a first foam sheet product; and a slicing step of slicing said first foam sheet product in parallel to a plane formed by the MD direction and a transverse or width direction perpendicular to the MD direction and parallel to the polyolefin resin foam sheet to produce a second foam sheet product-, a heating step of heating said second foam sheet product to produce a third foam sheet product; and a stretching step of stretching the third foam sheet product in the MD direction to 105% or more and 120% or less to produce a fourth foam sheet product.

5. The method of producing a polyolefin resin foam sheet according to claim 4, further comprising a compression step of compressing said fourth foam sheet product to produce a final foam sheet product.

6. An adhesive tape comprising the polyolefin foam sheet according to claim 1 having an adhesive layer formed on one or both surfaces thereof.

Description

EXAMPLES

(1) The evaluation methods used in the following Examples and Comparative Examples are as follows.

(2) (1) Measurement of Melting Point:

(3) The melting point is the maximum temperature obtained from the endothermic peak of the DSC curve in which the melting heat capacity (J/g) is taken along the vertical axis and the temperature is taken along the horizontal axis after the differential scanning calorimetric analysis. Two milligrams of a sample was prepared and measured in a nitrogen environment using a differential scanning calorimeter (DSC: RDC220-robot DSC manufactured by Seiko Instruments & Electronics Ltd.). The measurement conditions are as follows: the sample was heated to a temperature of 200° C. and melted; the exothermic peak obtained when the sample was then cooled at a rate of 10° C./min to a temperature of −100° C. corresponds to the temperature of crystallization; the sample was further cooled, and the middle point of the step transition points corresponds to the glass transition temperature. Then, the sample was heated at a rate of 10° C./min to measure an endothermic peak per unit mass. The summit of the endothermic peak due to melting obtained at the second temperature rise was taken as the melting point.

(4) (2) MFR:

(5) For the MFR, according to Annex B (reference) “Specified Standards and Test Conditions of Thermoplastic Materials” in JIS K 7210 (1999) “Plastics—Testing Methods of Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) of Thermoplastics,” under the conditions of a temperature of 190° C. with a load of 2.16 kgf for the polyethylene resin (a2) and of a temperature of 230° C. with a load of 2.16 kgf for the polypropylene resin (a1) and the thermoplastic elastomer resin (a3), a melt mass flow rate meter (Melt Indexer F-B01 manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used and a manual cutting method was applied to measure the weight of the resin exited from the die in 10 minutes.

(6) (3) Density of Polyolefin Resin Foam:

(7) The density of a polyolefin resin was measured according to JIS K7112 (1999) “Plastics—Methods of Determining the Density and Relative Density of Non-cellular Plastics”.

(8) (4) Measurement of Endothermic Peaks:

(9) In the present invention, an endothermic peak of a polyolefin resin foam refers to the peak obtained on the endothermic side of the DSC curve in which the melting heat capacity (J/g) is taken along the vertical axis and the temperature is taken along the horizontal axis after the differential scanning calorimetric analysis. Specifically, after the foam cells were crushed in advance with a mixing roll or the like, 2 mg of a test piece was weighed and measured in a nitrogen environment using a differential scanning calorimeter (DSC: RDC220-robot DSC manufactured by Seiko Instruments & Electronics Ltd.). The measurement conditions were as follows: the sample was heated to a temperature of 200° C., melted, then cooled at a rate of 10° C./min to a temperature of −50° C., and then heated again at a rate of 10° C./min to obtain a DSC curve. The peak on the endothermic side determined from the DSC curve obtained at the second temperature rise is referred to as an endothermic peak.

(10) (5) Measurement Method of Surface Roughness Sa (Arithmetic Mean Height):

(11) As for the surface roughness, three random sites of the surface were photographed with a VHX-600 manufactured by Keyence Corporation in accordance with three-dimensional surface property parameters: ISO 25178, and the average value was taken as the arithmetic mean height Sa.

(12) Measurement area: 9 mm.sup.2 or more

(13) Shooting interval (in the height direction): 20 μm

(14) Filter: Gaussian was used.

(15) (6) Measurement Method of Average Cell Size:

(16) The cross section of the prepared polyolefin resin foam sheet was observed at a magnification of 50 times using a scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Corporation, S-3000N), and the obtained images and measurement software were used to measure the cell size (diameter). The cell size was measured in each of the longitudinal direction (MD) and the width direction (TD) within the range of 1.5 mm×1.5 mm of the photographed image, and the average cell size in each direction was calculated. The measurement was performed in ten fields and an arithmetic mean was obtained.

(17) The average cell size on the surface A and the average cell size on the surface B were determined from cells present within the range of 10 μm from each surface.

(18) (7) Gel Fraction of Foam:

(19) The foam is cut into a square of about 0.5 mm, and the approximate amount of 100 mg is weighed with an accuracy to the nearest 0.1 mg. After the immersion in 200 ml of tetralin at a temperature of 140° C. for 3 hours, the solution was naturally filtered with a 100-mesh stainless steel wire mesh, and the insoluble substance on the wire mesh is dried in a hot air oven at 120° C. for 1 hour. Then, the resulting substance is cooled for 30 minutes in a desiccator containing silica gel, and the mass of this insoluble substance is accurately weighed, and the gel fraction of the foam is calculated in percentage according to the following formula.
Gel fraction (%)={Mass of insoluble substance (mg)/Mass of foam weighed (mg)}×100.
(8) Apparent Density of Foam:

(20) The apparent density of the polyolefin resin foam corresponds to a value measured and calculated according to JIS K 6767 (1999) “Cellular plastics—Polyethylene—Methods of test”. The thickness of the foam cut into a 10 cm.sup.2 is measured and the mass of this test piece is also weighed. The apparent density is the value obtained by the following formula, in which the unit is kg/m.sup.3.
Apparent density (kg/m.sup.3)={Mass of the test piece (kg)/Area of the test piece 0.01 (m.sup.2)×Thickness of the test piece (m)}.
(9) Thickness of Foam:

(21) The thickness of the polyolefin resin foam was measured in accordance with ISO 1923 (1981) “Cellular plastics and rubbers—Determination of linear dimensions”. Specifically, using a dial gauge with a circular probe having an area of 10 cm.sup.2, a piece of the foam cut into a certain size is placed still on a flat table, and a constant pressure of 10 g is applied from the top on the surface of the foam for the measurement.

(22) (Evaluation Method)

(23) The evaluation methods used in Examples and Comparative Examples are as follows.

(24) (1) Waterproof Property

(25) A double-sided tape (acrylic double-sided tape, manufactured by EBISU-CHEMICAL CO., LTD.) was attached to a foam, and punched into a U-shape (foam width of 10 mm, and overall length of 300 mm) to prepare a test piece. Then, the test piece was placed so that the open end (opened upper part in the U-shape) of the test piece would face upwards, and the test piece was sandwiched between two acrylic plates having a thickness of 10 mm in the thickness direction so that the adhesive layers of the double-sided tape would contact the acrylic plates. The test piece was then pressed in the thickness direction of the test piece so that the test piece would be compressed to 50% in thickness. Water was poured inside the U-shape of the test piece so that the water level from the inner bottom end of the test piece would be 100 mm. Then, 24 hours and 48 hours later, the presence or absence of water leakage was confirmed and evaluated as follows.

(26) ⊚: Water leakage was not confirmed for 48 hours.

(27) ◯: Water leakage was not confirmed for 24 hours.

(28) x: Water leakage was confirmed in less than 24 hours.

(29) (2) Cushioning Property

(30) The foams were laminated on an iron plate to a thickness of 5 mm. After that, the upper portion of the foams was pressed with a finger and thus the cushioning property was evaluated.

(31) ∘: The finger sinks and sufficient resilience is present.

(32) Δ: The finger sinks insufficiently, or no resilience is present.

(33) x: Hardness is present.

(34) (3) Adhesive Strength Difference

(35) The foam was punched to obtain a test piece having a width of 5 mm and a size of 150 mm in the MD direction×150 mm in the TD direction. A polyester adhesive (trade name: Hi-Bon YA790) manufactured by Hitachi Chemical Co., Ltd. was applied on both surfaces of the foam, and then a SUS flat plate of 3 mm in thickness and 200 mm in length×200 mm in width was attached to both the front and back surfaces of the foam and then peeled off by hand and evaluated.

(36) ⊚: The adhesive strength is strong, and the difference in strength between the surface A and the surface B was firmly observed.

(37) ◯: A difference in strength between the surface A and the surface B was firmly observed.

(38) Δ: A difference in strength was observed between the surface A and the surface B.

(39) x: No difference in strength was observed between the surface A and the surface B.

(40) (4) Adhesive Processability

(41) When the above-described polyester adhesive was applied to the surfaces of the foam, the surfaces were observed.

(42) ∘: An adhesive layer is sufficiently maintained on the surface.

(43) Δ: An adhesive layer is formed on the surface, but the layer is thin. However, if the application amount is increased, the layer is maintained.

(44) x: The formation of an adhesive layer is insufficient.

(45) (5) Heat Resistance

(46) Four sides of a 15 cm square foam were clamped and held for 30 seconds in a molding machine at 200° C., and evaluated for the properties on the surface.

(47) ∘: There is no problem in the properties on the surface and the surface has good appearance.

(48) Δ: Unevenness is slightly observed on the surface.

(49) x: The surface becomes rough and the unevenness gets severe.

(50) (6) Comprehensive Evaluation

(51) The comprehensive evaluation was conducted based on the results of the waterproof property, cushioning property, adhesive strength difference, adhesive processability and heat resistance.

(52) ⊚: The number of ⊚ is one or more, and neither x nor Δ is observed.

(53) ◯: There is no x, and the number of Δ is one.

(54) Δ: There is no x, and the number of Δ is two.

(55) x: The number of Δ is three or more, and the number of x is one or more.

(56) The resins used in Examples and Comparative Examples are as follows.

(57) <Thermoplastic Elastomer Resin>

(58) a-1: “Tafmer” (registered trademark) PN-3560 manufactured by Mitsui Chemicals, Inc.

(59) Density of 866 kg/m.sup.3, MFR (230° C.)=6.0 g/10 min, melting point=160° C.

(60) Crystal melting energy=17 J/g, crystallization temperature=107° C.

(61) a-2: “Prime TPO” (registered trademark) M142E, manufactured by Prime Polymer Co., Ltd.

(62) Density of 900 kg/m.sup.3, MFR (230° C.)=10.0 g/10 min, melting point=153° C.

(63) Crystal melting energy=28 J/g, crystallization temperature=121° C.

(64) a-3: JSR “JSR RB” (registered trademark) RB-840

(65) Density of 914 kg/m.sup.3, MFR (230° C.)=9.0 g/10 min, melting point=126° C.

(66) Crystal melting energy=14 J/g, crystallization temperature=90° C.

(67) a-4: “Tafmer” (registered trademark) PN-2070 manufactured by Mitsui Chemicals, Inc.

(68) Density of 867 kg/m.sup.3, MFR (230° C.)=7.0 g/10 min, melting point=140° C.

(69) Crystal melting energy=14 J/g, crystallization temperature=62° C.

(70) <Polypropylene Resin>

(71) b-1: “Novatec” (registered trademark) PP EG6D manufactured by Japan Polypropylene Corporation

(72) Density of 900 kg/m.sup.3, MFR (230° C.)=0.8 g/10 min, melting point=141° C.

(73) b-2: “Prime Polypro” (registered trademark) J452HAP, Prime Polymer Co., Ltd.

(74) Density of 900 kg/m3, MFR (230° C.)=3.5 g/10 min, melting point=163° C.

(75) <Polyethylene Resin>

(76) “Novatec” (registered trademark) LL UJ960 manufactured by Japan Polyethylene Corporation

(77) Density of 935 kg/m.sup.3, MFR (190° C.)=5 g/10 min, melting point=126° C.

(78) EVA: “Ultrasen” (registered trademark) 636 by Tosoh Corporation <ethylene vinyl acetate copolymer resin>

(79) Density of 941 kg/m.sup.3, MFR (190° C.)=2.5 g/10 min, melting point=82° C.

(80) Blowing agent: azodicarbonamide “Vinyfor AC#R” (registered trademark) manufactured by EIWA CHEMICAL IND. CO., LTD.

(81) Cross-linking auxiliary agent: 55% divinylbenzene manufactured by Wako Pure Chemical Industries, Ltd

(82) Antioxidant: “IRGANOX” (registered trademark) 1010 manufactured by BASF

(83) (Processing Methods)

(84) The processing methods used in Examples and Comparative Examples are as follows:

(85) (1) Slicing Step

(86) The slicing step is a step of cutting the foam into two or more pieces in the thickness direction, which is performed by a slicing machine.

(87) (2) Heating Step

(88) Heating step is a step of heating both surfaces of the foam at a temperature of 150° C. to 180° C. An infrared heater is used.

(89) (3) Stretching Step

(90) Stretching step is a step of stretching the foam by using different speeds between in unwinding and in winding. The foam is stretched by controlling the speed of the driving nip rolls.

(91) (4) Compression Step

(92) Compression step is a step of compressing and rolling the foam in the thickness direction. Compression is achieved by narrowing the gap between the nip rolls so that the gap between the nip rolls will be smaller than the thickness of the original foam.

Examples 1 to 15, Comparative Examples 1 to 13

(93) The foams produced in Examples 1 to 15 and Comparative Examples 1 to 13 are as follows.

(94) The thermoplastic elastomer resin, the polypropylene resin, the polyethylene resin, the blowing agent, the cross-linking auxiliary agent and the antioxidant were mixed in the respective proportions as shown in Tables 1 and 2 (% by mass is a value when the resins constituting the foam is 100% by mass, and part by mass is a value when the total amount of the resins constituting the foam is 100 parts by mass) in a Henschel mixer, and the resulting mixture was melt-extruded at a temperature of 160 to 180° C. using a twin screw extruder. Using a T-die, a polyolefin resin sheet having a thickness of ½ or more of a target foam thickness was prepared. The polyolefin resin sheet thus obtained was irradiated on one surface with an electron beam at an accelerating voltage of 700 kV and in a certain absorption dose to obtain a cross-linked sheet. This cross-linked sheet was floated on a salt-bath at a temperature of 220° C. and heated from the top with an infrared heater for foaming. The foam was cooled with water at a temperature of 50° C., and the foam surface was rinsed with water and dried. Thus, a long roll foam with skins on both surfaces, having a thickness of 1.5 mm to 3.5 mm, an apparent density of 50 to 160 kg/m.sup.3, and a gel fraction of 30 to 60% was obtained. The obtained long roll foam with skins on the both surfaces was sliced in the MD direction from the first surface portion on one side of the foam with skins on the both surfaces, using a slicing machine “NP-120RS” manufactured by NIPPY KIKAI CO., LTD. to produce 3 to 5 slices having a thickness of 0.7 mm to 1.5 m (slicing step). Thus, a sliced long roll foam containing the first surface portion on one side (with a skin surface) and a sliced long roll foam not containing the first surface portion on one side (without a skin surface) were obtained. The top and bottom surfaces of the sliced long roll foams were heated at 150° C. to 180° C. by an infrared heater (heating step), and stretched to 105% to 120% in the MD direction (stretching step), and compressed in the thickness direction in a nip roll gap of 0.1 mm (compression step) to produce a foam having a thickness of 0.6 mm to 1.3 mm in which both top and bottom surfaces were heated, stretched and compressed.

(95) TABLE-US-00001 TABLE 1 Example Example Example Example Example 1 2 3 4 5 Composition Thermoplastic Type a1 a1 a2 a1 a2 elastomer Composition % by 55 60 60 45 40 ratio mass Polypropylene Type b1 b1 b1 b1 b1 resin Composition % by 45 10 20 20 35 ratio mass Polyethylene Composition % by 30 20 35 25 resin ratio mass EVA Composition % by ratio mass Resin subtotal % by 100 100 100 100 100 mass Blowing Composition Parts 9 6 7 6 7 agent ratio by mass Cross-linking Composition Parts 4 3 4 4 3 auxiliary ratio by agent mass Antioxidant Composition Parts 1 1 1 1 1 ratio by mass Properties Thickness mm 1.3 0.9 0.8 0.6 1.3 Density kg/m.sup.3 70 130 110 145 115 Gel fraction % 55 45 50 50 35 Endothermic First ° C. 140 123 122 124 123 peaks Second 160 161 153 155 153 MD average Surface A μm 198 144 189 155 187 cell size Surface B 245 174 253 190 229 Ratio (B/A) 1.24 1.21 1.34 1.23 1.22 Surface Surface A μm 24 29 29 18 33 roughness Sa Surface B 45 55 61 42 54 Sa 21 26 32 24 21 difference Processing Slicing Presence/Absence Present Present Present Present Present method step Heating Presence/Absence Present Present Present Present Present step Stretching Presence/Absence Present Present Present Present Present step Stretching % 110 105 115 105 110 ratio Compression Presence/Absence Present Present Present Present Present step Evaluation Waterproof property ⊚ ◯ ◯ ⊚ ⊚ items Cushioning property ◯ ◯ ◯ ◯ ◯ Adhesive strength difference ◯ ◯ ⊚ ◯ ◯ Adhesive processability ◯ ◯ ◯ ◯ ◯ Heat resistance ◯ ◯ ◯ ◯ ◯ Comprehensive evaluation ⊚ ◯ ⊚ ⊚ ⊚ Example Example Example Example Example 6 7 8 9 10 Composition Thermoplastic Type a2 a1 a1 a2 a2 elastomer Composition % by 35 45 35 55 55 ratio mass Polypropylene Type b1 b1 b1 b2 b1 resin Composition % by 20 40 65 15 35 ratio mass Polyethylene Composition % by 45 15 30 10 resin ratio mass EVA Composition % by ratio mass Resin subtotal % by 100 100 100 100 100 mass Blowing Composition Parts 10 8 6 5 6 agent ratio by mass Cross-linking Composition Parts 4 3 5 4 3 auxiliary ratio by mass agent Antioxidant Composition Parts 1 1 1 1 1 ratio by mass Properties Thickness mm 0.8 1.1 0.6 1.3 0.7 Density kg/m.sup.3 65 80 125 163 145 Gel fraction % 50 35 55 50 40 Endothermic First ° C. 123 125 140 124 124 peaks Second 153 159 160 158 153 MD average Surface A μm 203 248 151 163 134 cell size Surface B 257 323 184 220 165 Ratio (B/A) 1.27 1.30 1.22 1.35 1.23 Surface Surface A μm 36 34 16 19 31 roughness Sa Surface B 67 63 39 44 53 Sa 31 29 23 25 22 difference Processing Slicing Presence/Absence Present Present Present Present Present method step Heating Presence/Absence Present Present Present Present Present step Stretching Presence/Absence Present Present Present Present Present step Stretching % 115 115 110 110 105 ratio Compression Presence/Absence Present Present Present Present Present step Evaluation Waterproof property ⊚ ⊚ ◯ ⊚ ◯ items Cushioning property ◯ ◯ Δ ◯ Δ Adhesive strength difference ⊚ ⊚ ◯ ⊚ ◯ Adhesive processability ◯ ◯ ◯ ◯ ◯ Heat resistance ◯ ◯ ◯ ◯ ◯ Comprehensive evaluation ⊚ ⊚ ◯ ⊚ ◯ Example Example Example Example Example 11 12 13 14 15 Composition Thermoplastic Type a1 a1 a1 a2 a1 elastomer Composition % by 30 40 60 30 60 ratio mass Polypropylene Type b1 b2 b2 b2 b1 resin Composition % by 25 40 30 65 20 ratio mass Polyethylene Composition % by 45 20 10 5 20 resin ratio mass EVA Composition % by ratio mass Resin subtotal % by 100 100 100 100 100 mass Blowing Composition Parts 6 10 6 8 5 agent ratio by mass Cross-linking Composition Parts 3 3 5 4 3 auxiliary ratio by mass agent Antioxidant Composition Parts 1 1 1 1 1 ratio by mass Properties Thickness mm 1.3 1.1 0.8 0.6 1.4 Density kg/m.sup.3 140 53 130 65 155 Gel fraction % 35 25 55 55 30 Endothermic First ° C. 124 125 126 126 126 peaks Second 155 163 162 162 160 MD average Surface A μm 176 408 199 278 225 cell size Surface B 219 549 241 360 271 Ratio (B/A) 1.24 1.35 1.21 1.29 1.20 Surface Surface A μm 33 37 18 28 38 roughness Sa Surface B 71 78 41 48 59 Sa 38 41 23 20 21 difference Processing Slicing Presence/Absence Present Present Present Present Present method step Heating Presence/Absence Present Present Present Present Present step Stretching Presence/Absence Present Present Present Present Present step Stretching % 115 120 110 105 105 ratio Compression Presence/Absence Present Present Present Present Present step Evaluation Waterproof property ◯ ◯ ◯ ◯ ◯ items Cushioning property Δ ◯ ◯ Δ ◯ Adhesive strength difference ◯ ◯ Δ Δ ◯ Adhesive processability ◯ Δ ◯ ◯ Δ Heat resistance ◯ Δ ◯ ◯ ◯ Comprehensive evaluation ◯ Δ ◯ Δ ◯

(96) TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Composition Thermoplastic Type a1 a1 a3 a3 a2 elastomer Composition % by 80 15 60 50 45 ratio mass Polypropylene Type b1 b1 b1 b1 b1 resin Composition % by 20 70 40 30 45 ratio mass Polyethylene Composition % by 20 20 10 resin ratio mass EVA Composition % by ratio mass Resin subtotal % by 100 105 100 100 100 mass Blowing Composition Parts 11 6 8 7 9 agent ratio by mass Cross-linking Composition Parts 4 3 5 4 4 auxiliary ratio by mass agent Antioxidant Composition Parts 1 1 1 1 1 ratio by mass Properties Thickness mm 0.8 1.2 1.3 1.2 1.4 Density kg/m.sup.3 90 130 75 110 70 Gel fraction % 50 35 55 40 45 Endothermic First ° C. 141 124 124 125 125 peaks Second 161 156 140 140 153 MD average Surface A μm 228 167 201 191 223 cell size Surface B 298 190 223 209 251 Ratio (B/A) 1.31 1.14 1.11 1.09 1.13 Surface Surface A μm 39 41 28 48 39 roughness Sa Surface B 52 59 45 51 71 Sa 13 18 17 3 32 difference Processing Slicing Presence/Absence Present Present Present Absent Present method step Heating Presence/Absence Present Present Present Present Absent step Stretching Presence/Absence Present Present Present Present Absent step Stretching % 110 105 110 105 — ratio Compression Presence/Absence Present Absent Present Absent Present step Evaluation Waterproof property ◯ X ◯ X X items Cushioning property ◯ X ◯ Δ Δ Adhesive strength difference Δ X Δ X X Adhesive processability Δ ◯ Δ ◯ Δ Heat resistance ◯ ◯ X ◯ ◯ Comprehensive evaluation Δ X X X X Comparative Comparative Comparative Comparative Example 6 Example7 Example 8 Example 9 Composition Thermoplastic Type — — a3 elastomer Composition % by 45 ratio mass Polypropylene Type b1 b2 b2 resin Composition % by 60 50 70 ratio mass Polyethylene Composition % by 40 5 30 resin ratio mass EVA Composition % by 100 ratio mass Resin subtotal % by 100 100 100 100 mass Blowing Composition Parts 7 6 5 5 agent ratio by mass Cross-linking Composition Parts 3 — 3 5 auxiliary ratio by mass agent Antioxidant Composition Parts 1 1 1 1 ratio by mass Properties Thickness mm 0.8 0.8 1 1.2 Density kg/m.sup.3 115 125 155 180 Gel fraction % 35 40 34 65 Endothermic First ° C. 125 82 127 126 peaks Second 141 — 161 163 MD average Surface A μm 178 155 113 82 cell size Surface B 224 174 170 93 Ratio (B/A) 1.26 1.12 1.50 1.13 Surface Surface A μm 29 25 31 4 roughness Sa Surface B 41 39 45 9 Sa 12 14 14 5 difference Processing Slicing Presence/Absence Present Present Present Present method step Heating Presence/Absence Present Present Present Present step Stretching Presence/Absence Present Present Present Absent step Stretching % 110 120 105 — ratio Compression Presence/Absence Present Present Present Present step Evaluation Waterproof property X ◯ ◯ X items Cushioning property X ◯ Δ X Adhesive strength difference X X X X Adhesive processability ◯ X Δ ◯ Heat resistance ◯ X Δ ◯ Comprehensive evaluation X X X X Comparative Comparative Comparative Comparative Example 10 Example 11 Example 12 Example 13 Composition Thermoplastic Type a1 a3 a4 a4 elastomer Composition % by 25 15 35 60 ratio mass Polypropylene Type b1 b1 b1 b2 resin Composition % by 75 65 65 20 ratio mass Polyethylene Composition % by 20 20 resin ratio mass EVA Composition % by ratio mass Resin subtotal % by 100 100 100 100 mass Blowing Composition Parts 7 10 5 8 agent ratio by mass Cross-linking Composition Parts 5 2 2 3 auxiliary ratio by mass agent Antioxidant Composition Parts 1 1 1 1 ratio by mass Properties Thickness mm 0.7 1.5 0.7 1.3 Density kg/m.sup.3 110 45 185 140 Gel fraction % 62 15 55 45 Endothermic First ° C. 140 125 140 125 peaks Second 160 140 141 162 MD average Surface A μm 198 551 156 241 cell size Surface B 201 573 230 289 Ratio (B/A) 1.02 1.04 1.47 1.20 Surface Surface A μm 31 23 18 34 roughness Sa Surface B 35 81 25 48 Sa 4 58 7 14 difference Processing Slicing Presence/Absence Absent Present Present Present method step Heating Presence/Absence Absent Absent Present Present step Stretching Presence/Absence Absent Present Present Present step Stretching % — 130 105 105 ratio Compression Presence/Absence Present Absent Present Absent step Evaluation Waterproof property X X X ◯ items Cushioning property Δ Δ Δ ◯ Adhesive strength difference X ◯ Δ Δ Adhesive processability ◯ X ◯ Δ Heat resistance Δ Δ Δ Δ Comprehensive evaluation X X X X

INDUSTRIAL APPLICABILITY

(97) The present invention is waterproof and is excellent in flexibility, cushioning, and heat resistance, and thus can be suitably used widely in the fields of architecture, electricity, electronics, vehicles, and the like, particularly as a substrate for a sealing material.