JPS60166436A - Manufacture of porous sheet - Google Patents

Abstract

PURPOSE:To obtain a porous sheet having rubber elasticity by molding a mixture consisting of inorganic powdered bodies and a specific elastomer to a sheet shape and orienting a molded part at a specific temperature. CONSTITUTION:A composition consisting of 40-80wt% inorganic powdered bodies and a 60-20wt% polyolefin group thermoplastic elastomer composition is molded to a sheet shape, and the sheet is oriented at a temperature lower than the softening temperature of an elastomer, thus obtaining a desired porous sheet. The polyolefin group thermoplastic elastomer composition is that the polyolefin group thermoplastic elastomer is included by 50wt% or more, a thermoplastic resin in quantity less than 50wt% may be mixed as required, and it is particularly preferable that the polyolefin group thermoplastic elastomer is brought to the state in which it forms a continuous phase. The force of elastic recovery is increased and heat resistance is improved while cutting-up strength and breaking strength can be augmented by crosslinking the elastomer.

Description

[Detailed description of the invention]

The present invention provides a highly flexible porous sheet. Specifically, it is a sheet having a structure in which inorganic powder is dispersed in a matrix of a polyolefin thermoplastic elastomer, and micropores are formed between the inorganic powder and the matrix. Due to its hydrophobicity and pore size, it does not allow water to pass through it, but it has the unique property of being breathable. Moreover, the sheet has GoJ1 elasticity, and can be used as it is, or with a reinforcing material made of fibrous or cloth material mixed or laminated with it. , and others. The present invention provides a method for obtaining a porous sheet having the characteristics as described in 1-1.
A mixture consisting of 0 to 80% by weight and 60 to 20% by weight of a polyolefin thermoplastic elastomer is formed into a sheet, and then stretched at a temperature below the softening temperature of the polyolefin thermoplastic elastomer in the mixture. This is a method for producing a porous sheet characterized by the following. BACKGROUND ART Conventionally, as a method for manufacturing a porous sheet, a method is known in which a porous sheet is obtained by mixing inorganic powder in a resin such as polypropylene or polyethylene to form a sheet, and then stretching the resulting sheet. At this time, it has also been proposed to add a small amount of rubber to the resin. In these methods, since the resin constitutes the matrix of the sheet, the resin is stretched, oriented, and fixed by the stretching process. on the other hand, they are dispersed within the matrix. Since the inorganic material cannot accommodate the elongation of the resin, holes form at the edges of the inorganic material. On the other hand, similarly, the rubber dispersed in the resin only effectively acts to increase the impact strength of the resin sheet, but does not contribute to the softening of the sheet as a whole. That is, in these known methods, the matrix constituting the sheet is a resin, and by stretching it, the orientation L/crystallization progresses, so the hardness of the sheet increases,
It tends to lose its elasticity. Against this

[9] The present invention is completely different from conventional techniques in that it uses a sheet mainly composed of a polyolefin thermoplastic elastomer. In general, elastomers have a low elastic modulus and a high elastic recovery rate at room temperature, so it was thought that even if an elastomer matrix was stretched with inorganic powder dispersed, it would not become porous due to the elasticity of the matrix. . However, in the case of polyolefin-based thermoplastic nidistomer, although it is an elastic body, it is mixed with inorganic powder in a specific range. It has been found that pores can be formed by doing this. That is, in the present invention, after forming a composition consisting of 40 to 80 weight percent of inorganic powder and 60 to 20 weight percent of a polyolefin thermal RJJ plastic elastomer composition into a sheet shape, This is a method for producing a porous sheet, which is characterized by stretching at a temperature below the softening temperature of a thermal ijJ plastic elastomer. In the present invention, a polyolefin-based thermoplastic nidistomer composition is one in which the polyolefin-based thermoplastic nidistomer is 50% by weight or more, and if necessary, a thermoplastic plastomer (resin) in an amount smaller than 50% by weight is mixed. In particular, it may be in a state in which the polyolefin thermoplastic nidistomer forms a continuous phase. In this case, the thermo-i+J plastic plastomer becomes fine particles and is dispersed in the thermo-f plastic elastomer. Therefore, in order to be incorporated into the thermoplastic elastomer, polyolefin resins are preferred from the viewpoint of compatibility with both. From another point of view, it is preferable that the resin to be dispersed in the thermoplastic elastomer has crystallinity, and polyolefin-based relatively crystalline resins are preferable. That is, when melt-molding a thermoplastic elastomer composition, the elastomer and the resin present in a dispersed state do not crosslink due to the affinity between the two or the action of radicals generated by heating and kneading during molding. As a result, the strength of the obtained sheet further increases (), and the elastic recovery force also increases. Another aspect of effectively practicing the present invention is to crosslink the elastomeric composition. The means for crosslinking between the molecules of the thermoplastic elastomer or between the thermoplastic plastomer and the thermoplastic elastomer is a free radical generating agent such as an aromatic or aliphatic peroxide that decomposes near the melting temperature of the thermoplastic elastomer, such as dicumyl. Peroxide, 2.5bis(t-butylperoxy)2.5-
Peroxide such as dimethylhexyne, 1,4-bis(t-butylperoxyisopropyl)benzene, etc.
It is added in an amount of 1 to 2.0% by weight and kneaded using a general kneading machine such as an open type roll, a closed type Pan Bali mixer, or a kneader 2 extruder. The timing of crosslinking is not particularly limited. For example, after crosslinking a thermoplastic elastomer composition in advance, inorganic powder can be added and molded, or alternatively, crosslinking can be performed after adding inorganic powder to a thermoplastic elastomer silk composition. good. In addition, the degree of crosslinking is judged by whether or not it is partially gelled by extraction with a solvent such as Tung-P-xylene, but in the case of the thermoplastic elastomer composition of the present invention, gelation of about 5 to 60% is obtained. The conversion rate is suitable. Further, the melt flow index at 230°C is 0.1 to 50, more preferably 0.
Those having fluidity of 5 to 20 are preferred. By crosslinking the elastomer in this way, it is possible to increase the elastic recovery force and heat resistance, and also to
The l-split strength and breaking strength can be increased. However, it is natural that if the crosslinking density is increased too much, the elongation properties of the elastomer will decrease and, in some cases, it will tend to become hard, so it should be kept within the range of the gelation rate. The polyolefin thermoplastic elastomer preferably used in the present invention has a tensile stress (100% modulus) of 10 to 300 k at 100% elongation at 25°C.
g/cIII, tensile elongation at break is 00% or more per month, and 1
It is preferable that the permanent strain after 00% elongation is 50% or more and 1.5%, and that the permanent strain can be generated by some method before it breaks. Usually, a permanent strain can be formed by applying strain to the elastomer by stretching beyond the region where the elastomer exhibits hook elasticity. Another method is to heat-set the polyolefin thermoplastic elastomer used in the present invention, that is, heat treat it to a tension F even if the strain is within the range according to Hooke's law. Can be immobilized. This method is often effective, especially for the above-mentioned elastomers that have some degree of crystallinity. The above-mentioned elastomer used in the present invention is preferably one that can leave a permanent strain, particularly one that can leave a permanent strain of 1% or more. 11+1 It is preferable to stretch under conditions where permanent strain remains. Next, the important point of the polyolefin thermoplastic elastomer 1 mer in the present invention is that the elastomer has substantially no plugging group. That is, if the thermoplastic polyolefin elastomer has a polar group, the effects of the present invention will not be exhibited even if its physical properties, ie, tensile stress, elongation at break, and permanent set satisfy the above values. The reason for this is not necessarily clear at present, but it is estimated as follows. That is, the polyolefin thermoplastic nidistomer has a polar group such as -〇COR (R is an alkyl group).
, -9o□CI, -COOR, -COOHl-C1, etc., generally exhibit strong adhesion with the free powder surface mixed in the elastomer, which is the matrix of the present invention. , C is also less likely to produce porosity, which is the object of the present invention, by stretching. Furthermore, the composition itself tends to become hard, which not only reduces the flexibility that is a feature of the present invention, but also tends to cause uneven stretching and stretch breakage. Therefore, the plastic elastomer used in the present invention needs to be substantially free of polar groups. Typical examples of polyolefin-based thermoplastic nidistomers suitably used in the present invention include ethylene-propylene copolymer (EPR), ethylene-propylene-diene copolymer (EP i''), ethylene-butene copolymer,
The propylene-butene copolymer portion is a copolymer of the olefin phase 4 or a copolymer of these and a diene, etc., and satisfies the physical property values defined above. In particular, those having a partially crystalline structure and usually having a degree of crystallinity of 10 to 60% are suitable. Further, in the present invention, as described above, a thermal ijJ plastic synthetic resin can be added and mixed with a polyolefin thermal iiJ elastic elastomer. The thermoplastic synthetic resin is generally selected from polyolefin resins such as ethylene, propylene, etc. in consideration of dispersibility with the polyolefin thermoplastic elastomer.
Homopolymers and copolymers of olefins such as butene are suitable, and the amount added is preferably less than 50% by market weight. In the present invention, the inorganic powder mixed into the polyolefin thermoplastic elastomer composition is not particularly limited, but generally includes calcium carbonate, sodium carbonate, magnesium oxide, magnesia hydroxide, zeolite, aluminum hydroxide, titanium oxide, and silicon oxide. , talc, clay, diatomaceous earth, calcium sulfate. Magnesium sulfate, sodium sulfate, 111 calcium sulfate, magnesium sulfite, etc. are available.
~57z is used. In order to fully exhibit the effects of the present invention, the blending ratio of the inorganic powder and the polyolefin thermoplastic elastomer composition in the present invention is such that the inorganic powder is 40 to 80% by weight and the polyolefin thermoplastic elastomer composition is 40 to 80% by weight. It is preferable to select a plastic elastomer composition with a content of 60 to 20%.If the amount of the aluminous powder is less than the above limit, the pores formed in the resulting sheet will be If the amount is too small, sufficient physical properties cannot be obtained, and conversely, if the amount exceeds the upper limit of 11α, it becomes difficult to restrict the stretching, and the physical properties tend to be insufficient. The method of mixing with the polyolefin thermoplastic elastomer composition is not particularly limited. After mixing the powder and granules together using a general blender, etc., kneading is performed using an extruder, or a melt kneading machine such as a Panbury mixer or the like is used. After pre-mixing by
Form into sheets with or without pelletizing. In this process, for the purpose of improving mechanical properties such as flexibility, elongation, and elastic recovery, or moldability, softeners such as mineral oil-based softeners, liquid polybutadiene, and liquid polybutene, lubricants such as calcium stearate, etc. Various additives such as stabilizers against heat, light, etc., plasticizers, and antistatic agents may also be optionally added. These compositions are formed into sheets by conventional methods. Generally, sheets are formed by commonly used methods such as calendar molding, press molding, or extrusion molding.
In particular, extrusion molding using a circular die or a tie die is preferred. The formed sheet can then be easily made porous by being uniaxially or biaxially stretched at an area magnification of 1.5 to 16 times at a temperature below the softening temperature of the thermal iJ plastic elastomer and above room temperature. . Generally, after the stretching process, it is preferable to cool the film to room temperature below the stretching temperature using a tension knife, and then take it out. By going through each step of the present invention, the sheet obtained generally has an initial tensile modulus of 500 [kg/cm] or more and 1ζ in at least one of the longitudinal and transverse directions at room temperature, and a tensile elongation at break of 50 A porous sheet having continuous pores with a pore size of 10 It or less and a flexible property and a strength property of 10% or more and a permanent strain of 50% or less after 50% elongation is obtained. The air permeability and water resistance of the porous sheet of the present invention vary depending on the number and size of pores in the porous sheet. In the present invention, the air permeability is 10,000 seconds/100cc (
, IIS 1) (according to 1117), preferably 500
0 seconds/100cc and water resistant, 500 m
ml, 0 (according to Federal Standard 191, method 5512), preferably 100 mm [1□0 or less] is obtained. The number and diameter of the pores can be controlled by the particle size of the inorganic filler used, the mixing ratio, and the stretching ratio. That is, the number of pores is determined by the number of particles of the inorganic powder mixed in the polyolefin thermoplastic elastomer composition, that is, the more fine particles are mixed and used, the more the porosity obtained after stretching becomes. The number of holes in the sheet increases. Regarding the pore size, the particle size of the inorganic powder used in the mixing step 1 is larger, and the larger the stretching ratio is, the larger the average pore size becomes (11), and the maximum pore size becomes larger accordingly. As mentioned above, the porous sheet obtained by the present invention has particularly high elongation, elastic recovery power, flexibility, and good air permeability, for example, when kept in contact with the human body for several hours. However, since the contact portion does not cause ventilation obstruction, for example, if the thickness is 0. (Those molded to about 11 to 0.3 mm can be applied to this. (1) Waterproof clothing, various coatings, various waterproof covers, bandages, medical or sports saboteurs, etc. It is a material suitable for wearing on the human body or animals on wet surfaces, such as sanitary products. Examples will be shown below, and the physical property measurements in the present invention were carried out by the method described below. ( 1) Tensile strength (1", s,) and elongation at break (Eb) tensile tester (Tensilon; manufactured by Toyo Baldwin, 2
Measurement was performed at 5° C. and at a speed of 200 mm/min using dumbbell No. 1. (2) Initial tensile modulus - 1 - The slope at the start of tension was calculated from the chart of elongation and tensile stress in a similar test under the same conditions as in (1). 10
The modulus at 0% elongation is the above tensile stress measured when the material is 100% elongated. (:3) Permanent strain: 1 (10 mm/m
The specimen was stretched by 5 ()% or 0% between the gauges at a speed of 100 in. After holding for 10 minutes, the test piece was removed and the recovery length was measured 10 minutes later. (4) Air permeability: In accordance with JIS P8117 (1963), it is expressed as the time (in seconds) it takes for a cylindrical object of fjH 345, 16 mm and weight 11,567 g to pass 100 cc of air through the test piece. (5) Maximum pore diameter (1) Stainless steel tax) By impregnating the sheet with ethanol, AST
It was prepared according to MF-316-70. (6) Gel fraction Determined by refluxing P-xylene in a Waxley extractor at its boiling point for 24 hours. Displayed as gel fraction based on resin component strength. (7) Melt flow index (M[)A S'r
Temperature 230 according to MI) 123B-57
Weight of molten resin extruded by #weight of 2160 g in 10 minutes at C. (Poor () Water Resistance Federal Standard - 1・゛) ≦, Method 5512
I met it according to. In other words, sandwich a 3cmφ diameter zombule and increase the water pressure from one side at a speed of Ikg/cm/m, and the pressure when water leaks from the other side (IIIIIIHρ)
Displayed in To Example 1 3 25°C] Q 0% elongation stress (100% modulus) is 60 kg/r; elongation at break is 7oO% and permanent strain after 100% elongation is 5% ethylene-butene- 1# Polymer (PER-1) [Trademark: Tafmer A/
41) 90, manufactured by Mikata Petrochemical Co., Ltd.] and ribroviren (
PP) (Grade name: Y E -130, M+=4.
0, Toku 111 manufactured by Soda Co., Ltd.), 50 g of a resin mixture whose composition ratio was changed as shown in Table 1, 150 g of heavy calcium carbonate [trade name: Wheaton SR (average particle size 1.77 L) manufactured by Shiraishi Calcium Co., Ltd. Polyester plasticizer (product name;
Polysizer W-2; 300, manufactured by Daih Hon Ink Chemical Co.)
A composition consisting of 2 g was kneaded for 10 minutes using a 3-inch roll heated to 190°C, and then press-molded into a sheet with a thickness of 0°3 mm. The sheet was simultaneously stretched 2×2 times in the longitudinal and transverse directions at 60° C. and a drawing rate of 600%/min using an experimental biaxial stretching machine, then cooled to 25° C. and removed from the stretching machine. Although the stretched sheet was slightly shrunk and the stretching ratio was low, as shown in Table 1, it was a flexible porous sheet with a low tensile modulus, high elongation, and high elastic recovery power. Comparative Example 1 Ethylene-butene-1 co-electrolyte/
As shown in Table 1, the sheet obtained by stretching polypropylene at a weight pressure of 45155 was a porous sheet with a small elongation U and a small elastic recovery force, and could not be said to be a flexible sheet. Comparative Example 2 Polypropylene (grade name: YE-130, M
1=4, manufactured by Tokuyama Soda Co., Ltd.) to 20 g of liquid 1,2-polybutadiene (1,PH) (trade name: N15s.-l) II, l'3-3000, manufactured by Hhon Soda Co., Ltd.);
(Og and Examples) A sheet composition consisting of 50 g of calcium carbonate, the same weight as that used in Example 1, was stretched at 120°C in the same manner as in Example 1. As shown in Table 14, the sheet had little elongation. Comparative example: 50 weight of 3° commercially available ethylene-vinyl acetate copolymer [trade name: Ur!Rasen IJ lzu634 (contains 25% vinyl acetate f#,), manufactured by Toyo Soda Co., Ltd.] When the sheet filled with % charcoal was stretched at 50°C in the same manner as in Example 1, the stretching ratio was 1.
A break occurred at around 1x. This is thought to be because interfacial peeling from calcium carbonate is difficult when an ethylene-vinyl acetate copolymer is used as a matrix. Comparative Example-4 Ethylene-propylene copolymer (trademark: Takuma-P-
0280 Mikata Petrochemical) (Tension at 100% elongation) Q stress 8 kg/cm, elongation at break 600%, permanent strain after 100% elongation 5%) and 50 g of calcium carbonate (trade name: Boyton L) (ilL average particle size 3°; (B Shiraishi Calcium Co., Ltd.) 50g and polyester Ml plasticizer 2g
(Product name: Polycizer W-2: 300 Daih Hon Ink Kagaku Co., Ltd. RA) was heated to 150'C; after melt-kneading with an inch roll for 10 minutes, it was press-molded to a thickness of 0. It was made into a 3 mm sheet. When the sheet was stretched at 40° C. in an experimental biaxial stretching machine in the same manner as in Example 1, it broke at approximately 1.2 times the stretch. The same result was obtained even when the film was stretched at 25°C. In the case of this copolymer, stretching is extremely difficult because the tensile stress is small. Comparative Example-5 Polybutene-1 polymer (PH-1) (trade name: A, A,
Polybutene 1600Shell Chemical c
o,) Pulling I at 100% elongation Iv (stress 180 kg/
cm, elongation at break 600%, permanent strain 30% after 100% elongation, 50 g, the same composition as Comparative Example-4, 50 g of heavy calcium carbonate, and 2 g of polyester plasticizer.
8 (After kneading for 10 minutes with a 3-inch roll heated to 1°C, the sheet was made into a sheet with a thickness of 0.3 mm by press molding, and the sheet was stretched at 80°C using an experimental biaxial stretching machine.)
After stretching to 2% by 2 times in the same manner as in 1, it was cooled to 25°C and removed from the stretching machine. The obtained sheet had large permanent deformation as shown below, and could not be said to be a flexible sheet with large elastic recovery. Actual magnification: (, 7x, thickness: 0.14mm, 1”
S; 9 (month (g/cmF, Eb; 110%
, first n1. Elastic modulus: (30 kg/cm
', Permanent strain: 70%, Air permeability: 1500 seconds/cc1
) max ; 1, 27 in Example 4. 1 (,1(,1% Ethylene I'1 pyrene-diene copolymer (E P l) with a modulus of 15 kg/c, a fracture ratio of 1000% and a permanent set of 10%)
335 g Lipropylene powder (Grade name: YE-130)
To a small bumper mixer, a composition consisting of 15 g of small calcium carbonate (trade name: Whiten S) 3, average particle size 1.7 μ), 1 F1 manufactured by Calcium Carbonate, 41 = 4, 50 g (manufactured by Tokuyama Soda Co., Ltd.) was put into a small bumper mixer. , 1 qoz:
After kneading for 10 minutes, the mixture was press-molded at 200'7 to obtain a sheet-like composition with a thickness of 0.3 mm. Next, the sheet composition was uniaxially stretched at 50° C. in the same manner as in Example 1. When the stretching ratio was set to 2 times and the sheet was cooled and taken out, the obtained sheet shrank slightly. The sheet is shown in Table 2.
As shown in Figure 2, it was a breathable sheet that was flexible and had recovery elasticity. Example 5.6. and 7゜The same composition as in Example 4 was similarly put into a small Banbury mixer 1), 1≦] After kneading for 5 minutes at 0°C, crosslinking agent 2.
0.4 g of 5-dimethyl-2,5<t-butylveroxine-hexyne-3 (trade name: Kayahexa Yl, manufactured by Kayaku Nouri Co., Ltd.) was added and kneaded for an additional 5 minutes. After this,
After adding 1 g of 2,4-ditertiarybutyl cresol and kneading for an additional 3 minutes, the mixture was press-molded at 200 Q: to obtain a sheet-like counterfeit product with a thickness of 0.30 mm. The sheet composition was extracted with P-xylene using a Soxhlet extractor for 24 hours, and the residue had a gel fraction of 10.4% based on the elastomer composition power, and 2 a
The melt flow index at 0° C. was 0.5. Next, the sheet-like composition was sequentially biaxially stretched at 80° C. to the same stretching ratio both vertically and horizontally, and when removed after cooling, a porous structure with flexibility and recovery elasticity was obtained as shown in Table 2. A sex sheet was obtained. In Examples 5 to 7, since the matrix was moderately partially crosslinked, stretching could be carried out smoothly, and the sheets subjected to IH were flexible and elongated, and were porous sheets with excellent elastic recovery power. Example 8.9. and 10 Commercially available polyolefin yarn with 100% modulus of 50 kg/cm, elongation at break of 620% and permanent set of 25% 57) 'uJ plastic elastomer compacted composition trade name; M
i lastmer-85: 0 (PP component; 10%)
Made by Tamai I1 Yukagaku Co., Ltd.] Polypropylene (Grade name: M
The composition ratio of 240 M [=9 Toku 111 Sodasha] is 4
/], and the gravity Cal [trade name: Whiten B (
Particle size 3. 371) (manufactured by Shiraishi Calcium Co., Ltd.) was kneaded and pressed in the same manner as in Example 1 while changing the filling amount to obtain a sheet-like composition. Next, the film was sequentially biaxially stretched vertically, horizontally, and at the same magnification using a small stretching machine at 120 i, cooled to 25° C., and then removed. The obtained sheet was a porous sheet exhibiting good flexibility, elongation, and recovery elasticity within the filling amount range of 40% by weight to 80% by weight. Note that if the filling amount is less than 40%, air permeability is poor and no communicating pores are formed. Further, when the stretching ratio exceeded 80%, stretching became impossible, and breakage occurred at a stretching ratio of 1.5 times or less. Implementation (91111, ~111° S1M Ethyl used in Example 1.) Non-butene-1 copolymer and linear low density poly] -7' l/ :) (It~i
t 1'+;tsu) Lt l'Zex2 (120
' L, - Gai 1 Yukagaku Co., Ltd.) (1゜1, t) P
1id), heavy calcium carbonate used in Example 1, and talc (trade name: Micro Ace ni-1, particle size: 3
．． :3B, manufactured by Nippon Talc Co., Ltd.), magnesium hydroxide (trade name: Kisuma 5A, particle size 2 //, manufactured by Kyowa Chemical Industry Co., Ltd.)
and U Silica Feng + (trade name: Radiolye)-F, particle size 5μ, manufactured by Showa Kagaku Kogyo Co., Ltd.) were blended into the rivers listed in Table 4 () using a 180"C twin-screw extruder. (In addition, the polyester plasticizer used in Example 1 was blended in an amount of 2% by weight based on the total amount of the composition. Using this pellet, a 50+imφ vent type extruder was used to make a pellet. A sheet with a thickness of 0.07 mm was extruded from a circular die at a ladle temperature of ℃, air-cooled (〕) and taken out, then stretched 3 times only in the machine direction (Ml) at a roll temperature of 60 ℃, and then cooled. The width was slightly narrower in the transverse direction (1゛11), and in the column of stretching conditions in Table 4, the actual area magnification was used.
D indicates Ml) and TD(7) multiples, respectively.・

Claims (1)

[Scope of Claims] 1) After forming a composition consisting of 40 to 80% by weight of a non-porous powder and 60 to 2% by weight of a polyolefin thermoplastic elastomer composition into a sheet, the sheet 1. A method for producing a porous sheet, which comprises stretching at a temperature below the softening temperature of a polyolefin thermoplastic elastomer. 2) The polyolefin thermoplastic elastomer composition is a polyolefin thermoplastic elastomer 50 to 00
The method for producing a porous sheet according to claim 1, which is a composition comprising less than 50% to 0% by weight of a thermal afM synthetic resin. 3) The method for producing a porous sheet according to claim 1, wherein the thermoplastic elastomer composition is crosslinked. 4) The method for producing a porous sheet according to claim 2, wherein the thermal '6J plastic synthetic resin is a polyolefin resin. 5) The polyolefin thermal T4J plastic elastomer is made of ethylene-propylene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-butene-1 copolymer, propylene-butene-1 copolymer. 2. A method for producing a porous sheet according to claim 1, wherein at least one elastomer is selected from the following. 6> Polyolefin thermoplastic elastomer at 25℃
Tensile stress (1 (10% modulus)) at 100% elongation at a temperature of 0 to 100 kg/cm per month, elongation at break of 100% or more, and permanent strain after 100% elongation of 50%.
The method according to claim 1, which has the following physical properties. 7) After forming into a sheet, the area ratio is 1.5 x lb.
2. The method for producing a porous sheet according to claim 1, wherein the porous sheet is stretched twice. 1) The composition molded into a sheet has an area ratio of 1.5
Claim 1, characterized in that the composition is stretched within a range of 16 to 16 times and under conditions where permanent strain remains in the composition.
2. Method for producing a porous sheet as described in Section 1.