JPH0518856B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a highly flexible porous sheet. Specifically, it is a sheet with a structure in which inorganic powder is dispersed in a matrix of polyolefin thermoplastic elastomer, and micropores are formed between the inorganic powder and the matrix. Due to its pore size, it does not allow water to pass through it, but it has the unique property of being breathable. Moreover, the sheet has rubber elasticity, and can be used as it is or by mixing or laminating reinforcing materials such as fibrous or cloth materials to waterproof clothing, gloves, various waterproof covers, container materials, medicinal patches, etc. Suitable for other uses. The present invention provides a method for obtaining a porous sheet having the above-mentioned characteristics, and the gist thereof is to obtain a porous sheet having a composition of 40 to 80% by weight of an inorganic powder and 60 to 20% by weight of a polyolefin thermoplastic elastomer composition. This is a sheet in which a polyolefin thermoplastic elastomer forms a continuous phase, and the sheet has an initial tensile modulus in at least one of the longitudinal and transverse directions.
500Kg/cm2 ^or less; Tensile elongation at break is 50% or more; 50%
Permanent strain after stretching is less than 50%; Air permeability is 10000
sec/100 c.c. or less, water resistance is 500 mmH ₂ O or more, and is a porous sheet that is stretched. Traditionally, inorganic powder was mixed into resin such as polypropylene or polyethylene to form a porous sheet.
It is known that the sheet is formed into a sheet and then stretched. At this time, it has also been proposed to add a small amount of rubber to the resin. In these porous sheets, since the resin constitutes the matrix of the sheet, the resin is stretched, oriented, and fixed by the stretching process. On the other hand, since the inorganic material dispersed in the matrix cannot accommodate the elongation of the resin, pores are formed 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. In other words, in the case of these known porous sheets, the matrix constituting the sheet is resin, and as it is stretched, it becomes oriented and crystallized, increasing the hardness of the sheet and causing it to lose its elasticity. There is a tendency to On the other hand, the present invention is completely different from the conventional techniques in that it uses a sheet mainly composed of a polyolefin thermoplastic elastomer. Generally, 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 in it, it would not become porous due to the elasticity of the matrix. However, in the case of polyolefin-based thermoplastic elastomers,
Although it is an elastic material, it has been found that pores can be formed by mixing a specific range of inorganic powder with it, forming a film, and then stretching the material by about 1.5 times or more. That is, the present invention comprises: (1) 40 to 80% by weight of inorganic powder; (2) polyolefin thermoplastic elastomer or
A mixture of 50% by weight or more of the polyolefin thermoplastic elastomer and less than 50% by weight of the polyolefin thermoplastic plastomer from 60 to 20% by weight.
The sheet has a composition of , and a polyolefin thermoplastic elastomer forms a continuous phase, and the sheet has an initial tensile modulus of 500 Kg/cm ² or less in at least one of the longitudinal and transverse directions; a tensile elongation at break of 50 % or more; permanent strain after 50% stretching is 50% or less; air permeability is 10,000 seconds/100 c.c. or less; water resistance is 500 mmH ₂ O or more; and it is a porous sheet that is stretched. . In the present invention, a polyolefin-based thermoplastic elastomer composition is one in which the polyolefin-based thermoplastic elastomer is 50% by weight or more, and if necessary, a thermoplastic plastomer (resin) in an amount smaller than 50% by weight is mixed. Any suitable material may be used, especially one in which the polyolefin thermoplastic elastomer forms a continuous phase. In this case, the thermoplastic plastomer becomes fine particles and is dispersed in the thermoplastic elastomer. Therefore, in order to achieve good dispersion of the thermoplastic plastomer, polyolefin resins are preferred from the viewpoint of compatibility with both. From another point of view, the resin to be dispersed in the thermoplastic elastomer preferably has crystallinity, and polyolefin-based relatively highly crystalline resins are excellent. That is, when a thermoplastic elastomer composition is melt-molded, the elastomer and the resin dispersed therein undergo crosslinking due to the affinity between the two or the action of radicals generated by heating and kneading during molding. , the strength of the obtained sheet is further increased, and the elastic recovery power is also increased. Yet another embodiment of the present invention is to crosslink the elastomeric composition. The means for cross-linking 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 is dispersed near the melting temperature of the thermoplastic elastomer, such as dicumyl. peroxide, 2.5-bis(t-butylperoxy)2.5-dimethylhexyne, 1.4-bis(t-butylperoxyisopropyl)benzene, etc.
Add 0.01 to 2.0% by weight and knead using a general kneading machine such as an open type roll, a closed type Banbury mixer, a kneader, or an extruder. The timing of crosslinking is not particularly limited. For example, after crosslinking a thermoplastic elastomer composition, inorganic powder can be added and molded, or the thermoplastic elastomer composition can be crosslinked after adding inorganic powder. In addition, the degree of crosslinking is usually judged by whether or not it is partially gelled by extraction with a solvent such as P-xylene, but in the case of the thermoplastic elastomer composition of the present invention, the degree of gelation is about 5 to 60%. rate is preferred. Also
It is preferable to have fluidity such that the melt flow index at 230°C is 0.1 to 50, more preferably 0.5 to 20. By crosslinking the elastomer in this manner, it is possible to increase the elastic recovery force and heat resistance, and further increase the tear strength and breaking strength. However, if the crosslinking density is increased too much, the elongation properties of the elastomer tend to decrease, and in some cases, it tends to become hard, so it should be kept within the above range of gelation rate. The polyolefin thermoplastic elastomer suitably used in the present invention has a temperature of 100°C at 25°C.
Tensile stress at % elongation (100% modulus) 10~
100Kg/cm ² , elongation at break is 100% or more and 100
Permanent strain after % elongation is 50% or less,
More preferably, it is capable of producing permanent strain by some method before it breaks. Usually, a permanent strain can be formed by applying a strain to the elastomer by stretching beyond the region where the elastomer exhibits hook elasticity. As another method, the polyolefin thermoplastic elastomer used in the present invention can be heat-set by heat treatment under tension, even if the strain is within the range according to Hook'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.
That is, it is preferable to stretch under conditions where permanent strain remains. Next, the important point of the polyolefin thermoplastic elastomer in the present invention is that the elastomer has substantially no polar groups. That is, if the thermoplastic polyolefin elastomer has a polar group, it will not exhibit the effects of the present invention 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, when the polyolefin thermoplastic elastomer has a polar group such as -OCOR (R is an alkyl group), -SO ₂ Cl, -COOR, -COOH, -Cl, etc., in general, the elastomer which is the matrix of the present invention has It exhibits strong adhesion to the surface of the inorganic powder mixed therein, and porosity, which is one of the objectives of the present invention, is less likely to occur even when stretched. 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. Representative examples of polyolefin thermoplastic elastomers suitably used in the present invention include ethylene-propylene copolymer (EPR),
Ethylene-propylene-diene copolymer (EPT)
Copolymers of olefins such as ethylene-butene copolymers and propylene-butene copolymers, or copolymers of these and dienes, etc., satisfy 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 thermoplastic synthetic resin can be added and mixed with the polyolefin thermoplastic elastomer. Considering the dispersibility with the polyolefin thermoplastic elastomer, the thermoplastic synthetic resin is generally preferably a polyolefin resin, such as a homopolymer or copolymer of olefins such as ethylene, propylene, butene, etc., and the amount added is It is also preferable to use less than 50% by 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, magnesium hydroxide, zeolite, aluminum hydroxide, titanium oxide, and silicon oxide. , talc, clay, diatomaceous earth, calcium sulfate. Magnesium sulfate, sodium sulfate, calcium sulfite, magnesium sulfite, etc. are used, and those with a particle size of 0.01 to 20μ, particularly 0.1 to 5μ, are 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 best to choose one that contains 60 to 20% by weight. When the amount of the inorganic powder blended is less than the above lower limit, the number of pores formed in the obtained sheet is small and sufficient physical properties cannot be obtained; Not only is it becoming more difficult, but the physical properties tend to be insufficient. The method of mixing these inorganic powders and the polyolefin thermoplastic elastomer composition is not particularly limited. Generally, after mixing the granules with a blender or the like, kneading them with an extruder or premixing them with a Banbury mixer or other melt kneading machine, the mixture is formed into a sheet with or without belet formation. In this process, for the purpose of improving mechanical properties such as flexibility, elongation, elastic recovery, or moldability, softeners such as mineral oil-based softeners, liquid polybutadiene, and liquid polybutene, lubricants such as calcium stearate, pigments, heat, light,
Various other additives such as stabilizers, plasticizers, and antistatic agents may also be optionally added. These compositions are formed into sheets by conventional methods. It is generally formed into a sheet by a commonly used method such as calendar molding, press molding, or extrusion molding, but extrusion molding using a circular die or a tie die is particularly preferred. The formed sheet is then heated to an area magnification of 1.5 to 16 times at a temperature below the softening temperature of the thermoplastic elastomer and above room temperature.
It can be easily made porous by axially or biaxially stretching. Generally, after such a stretching step, it is preferable to cool the film under tension to a temperature below the stretching temperature and to room temperature before taking it out. By going through each step of the present invention, the sheet obtained generally has an initial tensile modulus of 500 [Kg/cm ² ] or less in at least one of the longitudinal and transverse directions at room temperature, and a tensile elongation at break of 50% or more. Moreover, a porous sheet having continuous pores with a pore diameter of 10 μm or less and having strength properties with a permanent strain of 50% or less after 50% elongation and a flexible property can be obtained. The air permeability and water resistance of the porous sheet of the present invention vary depending on the number of pores and the size (pore diameter) of the pores in the porous sheet. In the present invention, the air permeability is 10,000 seconds/100 c.c.
(according to JIS P8117), preferably 5000 seconds/100c.c.
and water resistance of 500 mmH ₂ O (according to Federal Standard 191, Method 5512), preferably 1000 mmH ₂ O or more. The number of pores and the pore diameter are determined by the particle size of the inorganic filler used,
It can be controlled by the mixing amount and stretching ratio. In other words, the number of pores increases as the number of particles of the inorganic powder mixed into the polyolefin thermoplastic elastomer composition increases, that is, the more fine particles are mixed and used, the more the porous sheet obtained after stretching increases. The number of holes increases. In addition, as for the pore size, the larger the particle size of the inorganic powder mixed and used is, and the larger the stretching ratio is, the larger the average particle size can be obtained, and the maximum pore size accordingly becomes larger. As mentioned above, the porous sheet of the present invention has particularly high elongation and elastic recovery, is flexible and has good breathability, and even when kept in contact with the human body for several hours, Since the contact area does not cause ventilation problems, for example, if the parts are molded to a thickness of about 0.01 to 0.3 mm, cloth can be attached to them, or they can be used as is for waterproof clothing, protective materials for various liniments, various waterproof covers, bandages, etc. This material is suitable for use on the human body or warm-blooded animals, such as medical or sports supports and sanitary products. Examples will be shown below, and physical property measurements in the present invention were carried out by the method described below. (1) Tensile strength (TS) and elongation at break (Eb) Tensile tester (Tensilon; manufactured by Toyo Baldwin, at 25°C and at a speed of 200 mm/min, dumbbell 1)
Measured with No. (2) Initial tensile modulus 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) above. The modulus at 100% elongation is
This is the above tensile stress measured under a 100% stretched state. (3) Permanent strain: 100 mm/min with dumbbell No. 3 using the same testing machine as above.
Extend the distance between the gauges by 50% or 100% at a speed of 10
After holding for a minute, the test piece was removed and the recovery length was measured 10 minutes later. (4) Air permeability; area according to JIS P8117 (1963)
Time (in seconds) for 100 c.c. of air to pass through a test piece through a cylindrical object measuring 645.16 mm ² and weighing 567 g.
Displayed in (5) Maximum pore diameter (Dmax) It was determined according to ASTM-F-316-70 by impregnating the sheet with ethanol. (6) Gel fraction At the boiling point of P-xylene in a Soxhlet extractor
Determine by refluxing for 24 hours. Expressed as gel fraction per resin component. (7) Melt Flow Index (MI) 10 at 230℃ according to ASTM D1238-57
Weight of molten resin extruded by a load of 2160g per minute. (8) Water pressure resistance Federal Standard 191, Method 5512
It was calculated according to. In other words, a sample with a diameter of 3 cmФ is sandwiched, water pressure is increased from one side at a rate of 1 kg/cm ² /min, and the pressure at which water leaks from the other side (mm
Displayed as _H2O ). Examples 1 to 3 Ethylene-butene-1 copolymer (PEB) has a 100% elongation stress (100% modulus) of 60 Kg/cm ² at 25°C, an elongation at break of 700%, and a permanent set after 100% elongation of 5%. -1) Change the composition ratio of [trademark: Tafmar A4090, manufactured by Mitsui Petrochemical Co., Ltd.] and polypropylene (PP) (grade name: YE-130, MI = 4.0, manufactured by Tokuyama Soda Co., Ltd.) as shown in Table 1. resin mixture
50g, heavy calcium carbonate [Product name: Whiten
A composition consisting of 50 g of SB (average particle size 1.7μ, manufactured by Shiroishi Calcium Co., Ltd.) and 2 g of a polyester plasticizer (trade name: Polysizer W-2300, manufactured by Dainippon Ink Chemical Co., Ltd.) was heated to 190° C. in a roll
After kneading for 10 minutes, it is press-formed to a thickness of 0.3mm.
It was made into a sheet. The sheet was simultaneously stretched 2×2 times in the longitudinal and transverse directions at 60° C. and at 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 obtained stretched sheet slightly shrank and the stretching ratio decreased, 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 A sheet stretched in the same manner as in Example 1 with an ethylene-butene-1 copolymer/polpropylene weight ratio of 45/55 was a porous sheet with low elongation and low elastic recovery as shown in Table 1. Therefore, it could not be said that the sheet was flexible. Comparative example 2 Polypropylene (grade name: YE-130, MI
= 4, manufactured by Tokuyama Soda Co., Ltd.) 20g of liquid 1.2-polybutadiene (LPB) (product name: Nisso-PB, B-
3000, manufactured by Nippon Soda Co., Ltd.) and 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 1, the sheet was was a sheet with low elongation.

【table】

[Table] Comparative Example 3 Commercially available ethylene-vinyl acetate copolymer [trade name: Ultracene UE634 (25% vinyl acetate content), manufactured by Toyo Soda Co., Ltd.]
When a sheet filled with 50% by weight charcoal was stretched at 50°C in the same manner as in Example 1, the stretching ratio was 1.1.
A rupture occurred near the double point. This is thought to be because when an ethylene-vinyl acetate copolymer is used as a matrix, interfacial peeling from calcium carbonate is difficult. Comparative Example 4 50 g of ethylene-propylene copolymer (trademark: Tafmer P-0280 Mitsui Petrochemical) (tensile stress at 100% elongation: 8 Kg/cm ² elongation at break: 600%, permanent strain after 100% elongation: 5%), A composition consisting of 50 g of heavy calcium carbonate (trade name: Whiten B average particle size 3.3μ, manufactured by Shiroishi Calcium Co., Ltd.) and 2 g of a polyester plasticizer (trade name: Polysizer W-2300, manufactured by Dainippon Ink Chemical Co., Ltd.) was heated at 150°C. The mixture was melted and kneaded for 10 minutes using a 3-inch roll heated to 100 mL, and then press-molded into a sheet with a thickness of 0.3 mm. When this sheet was stretched using an experimental biaxial stretching machine at 40°C in the same manner as in Example 1, it broke at around 1.2 times. 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 (PB-1) (trade name;
AA polybutene 1600Shell Chemical co.) 100%
Tensile stress during stretching 180Kg/cm ² , elongation at break 600%,
50g of 30% permanent strain after 100% elongation, Comparative Example 4
A composition consisting of 50 g of the same heavy calcium carbonate and 2 g of polyester plasticizer was kneaded for 10 minutes with a 3-inch roll heated to 180°C, and then press-molded into a sheet with a thickness of 0.3 mm. 2× in the same manner as in Example 1 at 80°C with an experimental biaxial stretching machine.
After stretching to twice the original size, 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 gain magnification: 3.7 times, Thickness: 0.14mm, TS: 90Kg/cm ² , Eb: 110%, Initial tensile modulus: 330Kg/cm ² , Permanent strain: 70%, Air permeability: 1500 seconds/cc Dmax; 1.2μ Example 4 100% modulus is 15Kg/cm ² , elongation at break is 1000
% and permanent set of 10% ethylene-propylene-diene copolymer (abbreviated as EPDM) [trade name;
JSR EP57P (third component ENB) manufactured by Japan Synthetic Rubber Co., Ltd.)] 35g Polypropylene powder (Grade name: YE-130
MI=4 Manufactured by Tokuyama Soda Co., Ltd.) 15g Heavy calcium carbonate [Product name: Whiten SB
(Average particle size 1.7μ) manufactured by Shiraishi Calcium Co., Ltd.] A composition consisting of 50g was put into a small bumper mixer,
After kneading at 190°C for 10 minutes, the mixture was press-molded at 200°C to obtain a sheet 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. The stretching ratio was set to 2 times, and when the sheet was cooled and taken out, the resulting sheet shrank slightly. The sheet is flexible as shown in Table 2,
It was a breathable sheet with recovery elasticity. Examples 5, 6 and 7 The same composition as in Example 4 was similarly put into a small Banbury mixer and kneaded at 190°C for 5 minutes, followed by adding the crosslinking agent 2.5-dimethyl-2.5 (t-butylperoxy).
0.4 g of -Hexine-3 (trade name: Kayahexa YD, manufactured by Kayaku Nouri Co., Ltd.) was added and kneaded for an additional 5 minutes. After that, 1g of 2,4-dithyabutylcresol was added, and after kneading for another 3 minutes, the mixture was heated to 200°C.
A sheet composition with a thickness of 0.30 mm was obtained by press molding. The sheet composition uses P-xylene.
The residue after extraction with a 24 hour Soxhlet extractor had a gel fraction of 10.4% per elastomer composition and a melt flow index of 0.5 at 230°C. Next, the sheet-like composition was sequentially biaxially stretched at 80° C. to the same stretching ratio both vertically and horizontally, and when the composition was cooled and removed, it had a porous structure with flexibility and recovery elasticity as shown in Table 2. A sheet was obtained. In Examples 5 to 7, the matrix was moderately partially crosslinked, so that stretching could be carried out smoothly, and the resulting sheets were flexible, elongated, and porous sheets with excellent elastic recovery power.

【table】

[Table] Examples 8, 9, and 10 100% modulus is 50Kg/cm ² , elongation at break is 620%
and a commercially available polyolefin thermoplastic elastomer composition with a permanent set of 25% [trade name: Milastmer
-8530 (PP component 30%) produced by Mitsui Petrochemicals] The composition ratio of polypropylene (grade name: ME240 MI=9 Tokuyama Soda Co., Ltd.) was kept constant at 4/1, and the heavy charcoal cal [trade name: Whiten B ( A sheet composition was obtained by kneading and pressing in the same manner as in Example 1 while changing the filling amount of Particle size: 3.3μ) (manufactured by Shiroishi Calcium Co., Ltd.).Then, a sheet-like composition was obtained using a small stretching machine at 120°C at the same magnification in length and width. The sheet was sequentially biaxially stretched and removed after cooling to 25°C.The obtained sheet was a porous sheet showing good flexibility, elongation, and recovery elasticity in the filling amount range of 40% to 80% by weight. Note that when the filling amount is less than 40%, air permeability is poor and no communicating holes are formed.When the filling amount is more than 80%, stretching becomes impossible, and breakage occurs at a stretching ratio of 1.5 times or less.

【table】

[Table] Examples 11 to 14 Ethylene-butene-1 copolymer used in Example 1 and linear low-density polyethylene (trade name: Urtozex-2020L, manufactured by Mitsui Petrochemicals) (LLDPE),
In addition to the heavy calcium carbonate used in Example 1, talc (trade name: Micro Ace K-1, particle size
3.3μ, manufactured by Nippon Talc), magnesium hydroxide (trade name: Kisuma 5A, particle size 2μ, manufactured by Kyowa Chemical Industry Co., Ltd.), and diatomaceous earth (trade name: Radiolite-F, particle size 5μ, manufactured by Showa Kagaku Kogyo Co., Ltd.) The mixture shown in Table 4 was made into pellets using a twin-screw extruder at 180°C. (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 mmФ vent type extruder was used, and the resin temperature was 180°C. A sheet with a thickness of 0.07 mm was extruded from a circular die, air-cooled and taken off, and then stretched 3 times only in the machine direction (MD) at a roll temperature of 60°C, and then rolled up while cooling. The width is narrow, and in the stretching condition column of Table 4, the actual area magnification is expressed as MD x TD, which is the multiple of MD and TD, respectively.

【table】

【table】

Claims (1)

[Scope of Claims] 1 (1) 40 to 80% by weight of inorganic powder; (2) polyolefin thermoplastic elastomer or
60 to 20% by weight of a mixture of 50% by weight or more of the thermoplastic polyolefin elastomer and less than 50% by weight of the thermoplastic polyolefin plastomer
This is a sheet in which a polyolefin thermoplastic elastomer forms a continuous phase, and the sheet has an initial tensile modulus of 500 Kg/cm ² or less in at least one of the longitudinal and transverse directions; a tensile elongation at break of 50 % or more; permanent strain after 50% stretching is 50% or less; air permeability is 10,000 seconds/100 c.c. or less; water resistance is 500 mmH ₂ O or more; and is stretched.