JPH0651812B2 - Method for manufacturing porous sheet - Google Patents

Description

The present invention relates to a method for manufacturing a porous sheet. For more information,
The present invention relates to a method for producing a porous sheet from a composition comprising a polyolefin resin, a filler, a polyhydroxy saturated hydrocarbon and an epoxy group-containing organic compound. More specifically, it has excellent extrudability and molding stability in melt extrusion molding, and sometimes has excellent stretchability in uniaxially or biaxially stretching a melt-extruded sheet, resulting in stretch unevenness. The present invention relates to a method for producing a porous sheet having a very small amount of mechanical properties such as tear strength and tensile strength and a good balance of physical properties such as moisture permeability and having a strong surface strength.

Heretofore, many attempts have been made as a means for producing a porous sheet by blending a filler with a polyolefin resin and uniaxially or biaxially stretching a sheet obtained by melt molding.

However, in these sheets, the uniaxially stretched product has a problem in the anisotropy of the physical properties of the sheet, particularly the tear strength in the longitudinal direction (stretching direction), and further the surface strength. Although there is no problem in the anisotropy of physical properties, there are problems in stretchability and surface strength, and in addition, both of them tend to have high rigidity in general, which is a drawback depending on the application.

One of the methods for improving the anisotropy of sheet physical properties and surface strength is to carry out stretching at the lowest possible ratio to realize porosity, and as a method for imparting flexibility to the sheet, a low melting point is used. A method of adding a polymer, a rubber-like substance, a plasticizer, a surfactant, etc. can be considered, but one that satisfies the balance of mechanical properties such as porosity, stretchability, tear resistance and tensile strength, and physical properties such as surface strength. Has not yet been found.

As a method for improving the drawbacks of such conventional porous sheets, JP-A-57-47334 proposes a composition obtained by mixing a filler and liquid polybutadiene or liquid polybutene with a polyolefin resin. The inventors have found that a porous sheet having excellent performance can be obtained from a composition obtained by blending a polyolefin resin, a filler and a polyhydroxy saturated hydrocarbon, and filed an application therefor (Japanese Patent Application No. 56-88734). (JP-A-57-2035
No. 20), Japanese Patent Application No. 56-114865 (see Japanese Patent Laid-Open No. 58-15538)).

When liquid polybutadiene, liquid polybutene, or polyhydroxy saturated hydrocarbon is used, it is possible to realize porosity by low-stretching, but stretching unevenness due to non-uniform stretching still remains, and depending on the application, the commercial value is remarkably high. Spoil. In particular, when colored by adding a pigment, stretch unevenness becomes more remarkable.

The present inventors have good extrudability and moldability in melt molding, and uniaxially stretched sheets obtained by melt molding have mechanical properties such as tear strength and tensile strength and physical properties of moisture permeability. Good balance, both uniaxially stretched products and biaxially stretched products have strong surface strength and excellent stretchability.
The present invention has been achieved as a result of extensive studies in order to provide a porous sheet which is highly flexible and has few stretching irregularities caused by uneven stretching.

That is, the present invention is a porous sheet characterized by stretching a sheet obtained by melt-molding a composition obtained by blending a polyolefin resin with a filler and a polyhydroxy saturated hydrocarbon and an epoxy group-containing organic compound. Manufacturing method.

Hereinafter, the present invention will be described in more detail. The polyolefin resin used in the present invention is polyethylene and crystalline polypropylene, and may be used alone or in combination of two or more kinds. As the polyethylene, an ethylene homopolymer produced by the medium and low pressure method, or a copolymer of crystalline ethylene and other α-olefins, having a melt index of 0.01 to 10 g / 10 min and a density of 0.91 g /
cm ³ or more, and used alone or as a mixture of two or more kinds.

When the melt index is less than 0.01 g / 10 minutes or more than 10 g / 10 minutes, the extrudability at the time of raw fabric molding is deteriorated or the molding stability is lowered. When the density is less than 0.91 g / cm ^3, the flexibility of the product film or sheet is excellent, but problems occur in porosity and dimensional stability.

As the crystalline polypropylene, a homopolymer of propylene or a copolymer of propylene and other α-olefin is used alone or as a mixture of two or more kinds.

These polyolefin resins are pelletized, granular,
It is used in any form such as powder, but it is preferable to use granules or powder.

As the filler, inorganic and organic fillers are used, and as the inorganic filler, calcium carbonate, talc, clay,
Kaolin, silica, diatomaceous earth, magnesium carbonate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, silicate clay, etc. Is used, especially calcium carbonate, talc, clay, silica, diatomaceous earth,
Barium sulfate or the like is suitable.

As the organic filler, cellulosic powder such as wood powder and pulp powder is used. These may be used alone or as a mixture.

The average particle size of the filler is preferably 30 μm or less, more preferably 10 μm or less, most preferably 5 μm or less. If the particle size is too large, the denseness of the pores of the stretched product deteriorates.

The surface treatment of the filler is preferably carried out from the viewpoint of dispersibility in the resin and further stretchability, and treatment with a fatty acid or a metal salt thereof gives preferable results.

The polyhydroxy saturated hydrocarbon is a hydrocarbon polymer having an iodine value of 10 or less in which most or all of the main chains having at least 1.5 hydroxyl groups per molecule are saturated, and is 400 to 48,000, preferably 500. ~ 20,000
Those having a number average molecular weight in the range of (by the vapor pressure method) are preferably used.

If the number average molecular weight is too small, the molding stability at the time of raw material molding will be reduced, and if it is too large, the fluidity will be decreased, which may make handling difficult. The average number of hydroxyl groups per molecule is preferably 1.8 or more, particularly preferably 2.0 to
It is 5.0. The hydroxyl group is preferably at the end of the main chain and the end of the long chain branch.

However, such a polyhydroxy saturated hydrocarbon is obtained by a known method, for example, hydrogenation of a butadiene-based liquid polymer obtained by radical polymerization of butadiene alone or a copolymerizable monomer using hydrogen peroxide or the like as a polymerization initiator. It is obtained by doing.

As the copolymerization monomer, isoprene, chloroprene, styrene, methyl acrylate, methyl methacrylate,
Methyl vinyl ether and the like can be mentioned. For hydrogenation, nickel-based catalysts (eg reducing nickel, Raney nickel),
It is carried out by a conventional method using a cobalt-based catalyst, a platinum catalyst, a palladium catalyst, a rhodium catalyst, a ruthenium catalyst, a mixture thereof, or an alloy-based catalyst.

Examples of the epoxy group-containing organic compound include epoxidized vegetable oil such as epoxidized soybean oil and epoxidized linseed oil, epoxy resin, and preferably liquid epoxy resin containing no curing agent.

The compounding ratio of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is 20 to 90% by weight of the polyhydroxy saturated hydrocarbon and 80 to 10% by weight of the epoxy group containing organic compound with respect to the total amount of both. It is necessary to be.

When the ratio of the epoxy group-containing organic compound is less than 10% by weight, porosity can be obtained by low-magnification stretching, but uneven stretch due to uneven stretching still remains, which is not satisfactory.
If the content exceeds 10% by weight, the moldability is extremely deteriorated in the melt molding of the unstretched raw fabric.

In addition, a heat stabilizer, an ultraviolet stabilizer, an antistatic agent, a pigment, a fluorescent agent and the like may be added to the polyolefin resin according to a conventional method.

When blending the polyolefin resin, the filler, the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound, the blending ratio is 25 to 400 parts by weight of the filler and 1 to 90 parts of the polyhydroxy saturated hydrocarbon to 100 parts by weight of the polyolefin resin. 1 to 80 parts by weight of epoxy group-containing organic compound
The total amount of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is 100 parts by weight or less.
When the blending ratio of the filler is less than 25 parts by weight, the stretched sheet does not sufficiently form pores and the porosity becomes low. On the other hand, if the blending ratio of the filler exceeds 400 parts by weight, the kneadability and dispersibility and the formability of the sheet are deteriorated, and the surface strength of the stretched product is also lowered.

In the present invention, a particularly preferable mixing ratio is 60 to 200 parts by weight of the filler with respect to 100 parts by weight of the polyolefin resin. If the total amount of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound exceeds 100 parts by weight, the properties of the polyelefine resin are weakened, and satisfactory kneading properties, sheet formability and stretchability cannot be secured.

In the present invention, the total amount of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is more preferably 5 to 5
0 parts by weight.

The blending of the polyolefin resin, the filler, the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound in the present invention may be carried out by using an ordinary blender or a mixer.

After mixing, a drum, a tumbler type mixer, a ribbon blender, a Hensiel mixer, a super mixer or the like is used, but a high speed stirring type mixer such as a Henschel mixer is preferable.

Regarding the mixing order, first, the polyolefin resin is put into these mixers, the filler is added thereto, and they are sufficiently stirred and mixed. Then, the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound are added and further stirred to disperse and spread to obtain a final mixed composition.

By using this method, the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound are directly contacted with the filler,
It is possible to prevent the generation of aggregates that occur when dispersing,
The dispersibility of the filler in the resin can be improved during kneading. Furthermore, it is possible to almost completely eliminate the occurrence of spots when the sheet is molded.

On the other hand, first put the resin in the mixer, add polyhydroxy saturated hydrocarbon and epoxy group-containing organic compound to this,
After sufficiently stirring, the filler is added, and the composition obtained by further stirring may be insufficient in preventing the formation of aggregates.
Occasionally, spots may be seen when the sheet is formed.

Next, the kneading of the mixture is appropriately carried out by a conventionally known device, for example, a normal screw extruder, a twin screw extruder, a mixing roll, a Banbury mixer, a twin screw kneader and the like.

By adding the polyhydroxy saturated hydrocarbon and the organic compound containing an epoxy group, the kneading torque can be significantly reduced in any kneading method, and the device can be downsized and resources such as electric power can be saved.

The sheet may be formed according to an ordinary sheet forming apparatus and forming method, and inflation molding with a circular die, extrusion molding with a T die, and the like may be appropriately adopted.

When the formed sheet is stretched, roll stretching is usually adopted in the case of uniaxial stretching, but tubular stretching may be used to emphasize the uniaxial direction (take-up direction).

Further, the stretching may be performed in one stage or in multiple stages of two or more stages.

In the biaxial stretching, a low-magnification stretching is possible in the same or successive stretching as in the uniaxial stretching, and at least one direction is 1.
If it is 1 time, uniform stretching and porosity are possible. Along with this, it is possible to obtain a porous sheet having high mechanical properties such as tensile strength and tensile strength, and further strong surface strength. The stretching ratio capable of achieving porosity and capable of uniform stretching is 1.1 to 3.0 times in at least one direction.

Furthermore, the dimensional accuracy of the sheet can be stabilized by carrying out heat treatment after stretching in both uniaxial stretching and biaxial stretching. or,
Known surface treatments such as corona treatment and frame treatment can also be performed.

In the present invention, the porous sheet is 0.01 to 0.5 mm,
It is preferably formed into a thickness of 0.02 to 0.3 mm, and what is generally called a film is also included in the sheet of the present invention.

In the method of the present invention, (1) porosity is achieved at a low draw ratio.

(2) Stretching stress is low and low temperature stretching is possible.

(3) Uniform stretching is possible with a low stretching ratio.

The porous sheet obtained has the following features: (1) Almost no stretch unevenness is observed.

(2) Excellent moisture and gas permeability, and high water pressure resistance.

(3) It has excellent flexibility.

(4) There is little anisotropy in physical properties.

(5) High tear strength and tensile strength.

(6) Good heat sealability and shrink wrapping is possible.

(7) It is easily incinerated and does not generate harmful gas.

It can be applied to various uses such as clothing, packaging, battery separators, furnace filtering materials, and medical applications.

Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

The polyolefin resins, fillers, polyhydroxy saturated hydrocarbons and epoxy group-containing organic compounds used in the examples and comparative examples are summarized in Table-1.

Reference Example 1 (Production of Polyhydroxy Saturated Hydrocarbon) In an autoclave having a capacity of 10, a commercially available liquid polybutadiene (manufactured by Nippon Soda Co., Ltd .; G-2000, molecular weight 2000) 3 kg,
3 kg of cyclohexane and carbon-supported ruthenium (5
%) 300 g of a catalyst (manufactured by Nippon Engelhardt Co., Ltd.) was charged, the inside of the purified argon gas system was replaced, and then high-purity hydrogen gas was supplied to the autoclave, heating was started at the same time, and steady conditions were taken for about 30 minutes (Internal temperature approx. 100 ° C, internal pressure approx. 50
kg / cm ³ ) was reached.

This condition was maintained for about 15 hours and then the hydrogenation reaction was stopped. The obtained polymer has an iodine value of 5 g / 100 g,
It was a liquid polyhydroxy saturated hydrocarbon having a hydroxyl value of 44 KOHmg / g.

Examples 1 to 25, Comparative Examples 1 to 12 Polyolefin resin and filler were mixed by stirring in a Henschel mixer, and polyhydroxy saturated hydrocarbon and epoxy group-containing organic compound were added thereto, and further mixed by stirring.
0 kg of mixture was obtained. The types and amounts of the raw materials used are shown in Table-2 and Table-3.

50 kg of a mixture obtained by repeating the above operation 5 times was kneaded and granulated by a twin-screw kneader (DSM-65, manufactured by Japan Copper Works Co., Ltd.), and then inflation-molded by a 40 mmφ extruder under the following conditions. Then, a film having a thickness of 60 μm was obtained.

Cylinder temperature: 150-170-180 ° C 170-190-210 ° C (Example 25 only) Head and die temperature: 180-180 ° C 210-210 ° C (Example 25 only) Take-up speed: 12m / min Blow ratio: 2 .5 Folding diameter: 393 mm The obtained film was uniaxially stretched by a roll stretching machine under the following conditions.

Stretching temperature: 60 ° C., but 90 ° C. in Example 4, room temperature in Example 5, and 100 ° C. in Example 25.

Draw ratio: 1.3 to 2.6 Draw speed: 25 m / min Draw ratio and physical properties of the obtained uniaxially drawn film are shown in Table-
4 to 6. The methods for measuring physical property evaluation items are as follows.

1) Stretchability: judged according to the following criteria.

 ⊚: No cutting, uniform stretching, no stretching spots are observed ○: No cutting, stretching spots are hardly seen Δ: No cutting, stretching spots are seen ×: Cutting or stretching spots are noticeable 2) Porosity: It was calculated from the film density.

D _O : Original film density (g / cm ³ ) D: Stretched film density (g / cm ³ ) 3) Tensile strength: Measured in accordance with ASTM 882-64T.

20 mm width × 50 mm length, tensile strength 50 mm / min 4) Tear strength: Measured according to JIS P-8116.

No notch. 14mm width x 110mm length.

5) Water vapor transmission rate: Measured in accordance with ASTM E26-66 (E).

6) Flexibility: Feeling of hand, judged by the following criteria.

◎: Extremely soft ○: Soft Δ: A little hard ×: Hard 7) Surface strength: A cellophane tape was attached to the surface of the film, and the peeling state of the film when it was quickly peeled off was observed and judged according to the following criteria.

◎: No surface peeling ○: Almost no surface peeling △: Little surface peeling ×: Large surface peeling Example 26 When blending the raw materials shown in Table 2, polyhydroxy saturated hydrocarbon and epoxy were added to medium- and low-pressure polyethylene. A uniaxially stretched film was produced in the same manner as in Example 1 except that the modified soybean oil was mixed in a Henschel mixer, spread on polyethylene, and then calcium carbonate was added and mixed.
The physical properties of the film are shown in Table-5.

Examples 27 to 30, Comparative Example 13 A raw film having a thickness of 60 μ was prepared in the same manner as in Example 1 with the composition shown in Table 2 and Table 3, and a long stretcher (manufactured by TM Long Co., USA) was used. Using this, sequential biaxial stretching or simultaneous biaxial stretching (Example 30 only) was performed at 60 ° C. The stretch ratio and the physical properties of the biaxially stretched film are shown in Tables 5 to 6.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C08L 9:00 63:00) (72) Inventor Yu Suzuki 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Kogyo Co., Ltd. (70) Inventor Tsutomu Kobayashi 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Kogyo Co., Ltd.

Claims (7)

[Claims] 1. (a) 100 parts by weight of a polyolefin resin selected from low-pressure polyethylene and crystalline polypropylene, having a density of 0.91 g / cm ³ or more and a melt index of 0.01 to 10 g / 10 min. ) 25 to 400 parts by weight of a filler, (c) 1 to 90 parts by weight of a polyhydroxy saturated hydrocarbon, and (d) 1 to 80 parts by weight of an organic compound containing an epoxy group.
The total amount of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is 100 parts by weight or less, and the weight ratio of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is 20 to 90:80 to 10 parts by weight. A method for producing a porous sheet, which comprises subjecting a sheet obtained by melt-molding the composition to a stretching treatment. 2. The method according to claim 1, wherein the polyhydroxy saturated hydrocarbon contains at least 1.5 hydroxyl groups per molecule and the iodine value is 10 or less. 3. The method according to claim 1 or 2, wherein the polyhydroxy saturated hydrocarbon is obtained by hydrogenating a hydroxyl group-terminated liquid polybutadiene. 4. The method according to any one of claims 1 to 3, wherein the epoxy group-containing organic compound is an epoxidized vegetable oil. 5. The method according to any one of claims 1 to 3, wherein the epoxy group-containing organic compound is a liquid epoxy resin. 6. The method according to any one of claims 1 to 5, wherein the stretching treatment is at least 1.1 times uniaxial stretching. 7. The method according to any one of claims 1 to 5, wherein the stretching treatment is biaxial stretching of at least 1.1 times.