JPH0651813B2 - Method for producing porous sheet - Google Patents

Description

The present invention relates to a method for manufacturing a porous sheet. More specifically, it relates to a method for producing a porous sheet from a composition obtained by mixing linear low-density polyethylene, high-pressure low-density polyethylene, a filler and polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound. More specifically, it has excellent extrudability in melt extrusion molding, good moldability, and exhibits excellent stretchability in uniaxial or biaxial stretching of the sheet subjected to melt extrusion molding, and stretching accompanying uneven stretching. The present invention relates to a method for producing a porous sheet which has few irregularities, has a good balance of mechanical properties such as tear strength and tensile strength, and physical properties such as moisture permeability, and is rich in flexibility and strong in surface strength.

Heretofore, many attempts have been made as a means for producing a porous sheet by blending a polyolefin resin with a filler and subjecting a sheet obtained by melt molding to uniaxial or biaxial stretching. However, in these sheets, problems remain in the anisotropy of the physical properties of the uniaxially stretched product, especially the tear strength in the longitudinal direction (stretching direction), and further the surface strength, and in the biaxially stretched product, the physical properties of the sheet remain. Although there is no problem in anisotropy, there are problems in stretchability and surface strength, and in addition, both 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 or a surfactant can be considered, but one satisfying the balance of physical properties such as porosity, stretchability, tear strength and tensile strength, and further surface strength. Has not yet been found.

As a method for improving the drawbacks of the conventional porous sheet, Japanese Patent Application Laid-Open No. 57-47334 discloses a composition obtained by mixing a filler and liquid polybutadiene or liquid polybutene with a polyolefin resin. The present inventors have also found that a porous film or sheet having excellent performance can be obtained from a composition obtained by mixing a linear low density polyethylene resin, a filler and a polyhydroxy saturated hydrocarbon, and filed a prior application. (JP-A-56-114865 (JP-A-58-1)
(See Japanese Patent No. 5538)).

However, when a linear low-density polyethylene resin is used, the flexibility of the stretched product is excellent, but the stability of the molding during melt extrusion molding of the unstretched raw fabric is not sufficiently satisfactory.

The present inventors have good extrudability in melt molding,
The uniaxially stretched sheet, which exhibits particularly excellent molding stability and is obtained by melt molding, has a good balance of mechanical properties such as tear strength and tensile strength and moisture permeability. Both have strong surface strength and excellent stretchability, and in particular for the purpose of providing a porous sheet that is highly flexible and has very few stretching spots caused by non-uniform stretching especially in low-magnification stretching. As a result, the present invention has been achieved.

That is, the present invention is a sheet obtained by melt-molding a composition obtained by blending a linear low-density polyethylene and a high-pressure low-density polyethylene with a filler and a polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound. The present invention relates to a method for producing a porous sheet, which is characterized by performing treatment.

Hereinafter, the present invention will be described in more detail. As linear low-density polyethylene used in the present invention, ethylene and propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, decene- Α other than ethylene such as 1
-Copolymer with olefin, melt index 0.5-10 g / 10 min, density 0.91-0.94 g
The range is / cm ³ . As a so-called loose high-pressure method low-density polyethylene according to the conventional high-pressure method, one having a melt index of 0.5 to 10 g / 10 min can be mentioned.

The weight ratio of the linear low density polyethylene (a) to the high pressure method low density polyethylene (b) must be within the range of 0.6 ≦ (a) / [(a) + (b)] ≦ 0.97.

If the melt index of the linear low-density polyethylene and the high-pressure low-density polyethylene is less than 0.5 g / 10 min, melt extrusion molding is possible, but the extrudability is poor and the productivity is low. When the melt index is larger than 10 g / 10 minutes, the stability of molding in the raw fabric molding is lowered. On the other hand, if the density of the linear low-density polyethylene is less than 0.91 g / cm ³ , the stretched product will be very excellent, but the porosity will be insufficient and the dimensional stability will be poor. When the density is higher than 0.94 g / cm ³ , the drawn product has poor porosity and dimensional stability but is poor in flexibility.

When the compounding ratio of the high-pressure low-density polyethylene is less than the above range, the stability of the molding is insufficient due to the lack of melt elasticity of the melt during the raw fabric molding, and when it is more than the above range, the molding stability is excellent. However, the porosity of the stretched product is insufficient.

Additives such as a heat stabilizer, an ultraviolet absorber, an antistatic agent, a pigment and a fluorescent agent can be added to these linear low density polyethylene and high pressure method low density polyethylene according to a conventional method.

As the filler, an inorganic filler and an organic filler 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. are used, and particularly calcium carbonate, talc, clay, silica, diatomaceous earth, barium sulfate, etc. are suitable. is there.

As the organic filler, wood powder, cellulosic powder such as pulp, or the like 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 surface treatment amount of the fatty acid or its metal salt is preferably 10 parts by weight or less with respect to 100 parts by weight of the filler. If the amount of surface treatment is large, white smoke may be generated or foaming may occur during kneading, granulation and molding, which is not preferable.

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 400 to 48,000, preferably 500. Those having a number average molecular weight (by vapor pressure method) in the range of up to 20,000 are preferably used. If the number average molecular weight is too small, the molding stability at the time of forming the raw fabric may be difficult, and if it is too large, the fluidity may be lowered and the handling may be difficult. 1
The average number of hydroxyl groups per molecule is preferably 1.8 or more, particularly preferably 20 to 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.

As the epoxy group-containing organic compound, epoxidized soybean oil,
Examples thereof include epoxidized vegetable oils such as epoxidized linseed oil, liquid epoxy resins such as epoxy resins obtained by the reaction of bisphenol A and epichlorohydrin and containing no curing agent.

The mixing ratio of the polyhydroxy saturated hydrocarbon (d) and the epoxy group-containing organic compound (e) is 0.2 ≦ (d) / [(d) +
(e)] ≦ 1.0 is necessary, and particularly 0.2 ≦ (d)
It is preferable that /[(d)+(e)]≦0.9.

When an epoxy group-containing organic compound is blended, it has more excellent stretchability than when it is not blended, uniform stretching is possible even at low stretch ratios, and stretching unevenness due to nonuniform stretching is hardly seen. . Further, if the amount of the epoxy group-containing organic compound exceeds the above range, the moldability is extremely deteriorated in the melt molding of the unstretched raw fabric, which is not preferable.

Linear low density polyethylene (a), high pressure method low density polyethylene (b), filler (e), polyhydroxy saturated hydrocarbon (d) and epoxy group-containing organic compound (e) are mixed in a weight ratio of 0.25 ≤ (c) / [(a) + (b)] ≦ 4.0 0.02 ≦ [(d) + (e)] / [(a) + (b)] ≦ 1.0 It is necessary to satisfy each formula, In particular, it is preferable that 0.6 ≦ (c) / [(a) + (b)] ≦ 2.0 0.05 ≦ [(d) + (e)] / [(a) + (b)] ≦ 0.5.

If the blending amount of the filler is too small, the pores of the stretched sheet are not sufficiently formed and the degree of porosity is reduced, while if the blending amount is too large, the kneadability and dispersibility deteriorate, and And the surface strength is reduced. Further, if the blending amounts of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound are too large, satisfactory kneading properties cannot be obtained, and formability and stretchability of the sheet cannot be secured.

In the method of the present invention, in blending each component, a method of mixing or melt-kneading a linear low-density polyethylene and a high-pressure low-density polyethylene and then adding and mixing other components is adopted. When the polyhydroxy saturated hydrocarbon or the epoxy group-containing organic compound is added and mixed, and then the filler is added and mixed, the formation of agglomerates is observed, and the molded sheet may have lumps. Therefore, it is desirable to add and mix the filler prior to the addition of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound. At this time, the linear low-density polyethylene and the high-pressure low-density polyethylene are used in the form of pellets, granules, powders or the like, but granules or powders are particularly preferable.

A preferred blending method of each component is a drum, a tumbler type mixer, a ribbon blender, a Hensiel mixer, a mixer such as a super mixer, preferably a high speed stirring type mixer such as a Hensiel mixer, and a linear low density polyethylene and High-pressure method Low-density polyethylene is added and mixed, and a filler is added to this and mixed thoroughly, and then polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound is added and stirred to disperse and spread. It is a method of making a mixture.

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

By adding a polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound, 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). The stretching may be performed in one stage or in multiple stages of two or more stages.

In biaxial stretching, low-strength stretching is possible in the same manner as uniaxial stretching in simultaneous and sequential stretching, and at least one direction is 1.
Uniform stretching and porosity can be achieved with 1 time. Porosity is achieved,
In addition, the stretching ratio at which uniform stretching is possible is 1.1 to 3.0 times in at least one direction.

Further, both uniaxial stretching and biaxial stretching can be subjected to heat treatment after stretching to stabilize the dimensional accuracy of the film.
Further, surface treatment such as known corona treatment and frame treatment can be performed.

In the present invention, the porous sheet is formed to have a thickness of 0.01 to 0.5 mm, preferably 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 separator, excess material, and medical use.

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 raw materials used in the following examples and comparative examples are listed in Table-1 and Table-2.

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 it took about 30 minutes to perform steady-state conditions ( 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 was a liquid substance having an iodine value of 4.9 g / 100 g and a hydroxyl value of 53 KOHmg / g.

Examples 1 to 32, Comparative Examples 1 to 17 Linear low density polyethylene (a), high pressure low density polyethylene (b) and filler (c) were mixed by stirring in a Henschel mixer, and polyhydroxy saturated carbonization was carried out. Hydrogen (d) and an epoxy group-containing organic compound (e) were added and further mixed by stirring to obtain 10 kg of a mixture. The types and amounts of the raw material components used are shown in Tables 3 to 4.

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 Steel Works, Ltd.), and then inflation-molded by a 40 mmφ extruder under the following conditions. Thus, a raw film having a thickness of 65 μm was obtained.

Cylinder temperature: 170-190-210 ° C Head, die temperature: 210-210 ° C Take-off speed: 15 m / min Blow ratio: 2.7 Fold diameter: 318 mm The obtained film was uniaxially stretched under the following conditions by a roll stretching machine.

Stretching temperature: 70 ° C. However, 90 ° C. in Example 4 and 50 in Example 5.

Stretching ratio: 1.3 to 2.3 Stretching speed: 25 m / min Tables 5 to 7 show the uneven thickness of the original film, the molding stability at the time of forming the original film, the stretching ratio and the physical properties of the obtained stretched film. Show.

The methods for measuring physical property evaluation items are as follows.

1) Uneven thickness of the original film : Average thickness (μ) σn: Standard deviation (μ) n = 36 (36 equally divided in the circumferential direction) 2) Molding stability In inflation molding, ◎: No bubble fluctuation ○: Bubble fluctuation almost None △: Bubble swaying ×: Difficult to form 3) Stretchability ⊚: No cutting, uniform stretching, stretch unevenness is not observed.

 ◯: No cutting, almost no stretching unevenness was observed.

 Δ: No cutting, uneven stretch is observed.

 X: Remarkably observed in cutting or stretching unevenness.

4) Porosity Calculated from the film density by the following formula D ₀ : Density of original film (g / cm ³ ) D: Density of stretched film (g / cm ³ ) 5) Tensile strength According to ASTM 882-64T.

20mm width x 50mm length, tensile strength 50mm / min 6) Tear strength According to JIS P-8116.

There is a notch. 14mm width x 110mm length.

7) Water vapor transmission rate According to ASTM E26-66 (E).

8) Flexibility Feeling by hand, it was judged according to the following criteria.

◎: Extremely soft ○: Soft Δ: Slightly hard ×: Hard 9) Surface strength A cellophane tape was attached to the surface of the film, and the state of surface peeling when quickly peeled off was observed, and the judgment was made according to the following criteria.

◎: No surface peeling ○: Almost no surface peeling △: Little surface peeling ×: Large surface peeling Example 33 (a), when blending each component described in Table 3
After stirring and mixing (b), (d) and (e) in a Hensiel mixer, and spreading (d) and (e) on (a) and (b),
A stretched film was produced in the same manner as in Example 17 except that (e) was added and mixed. The results are shown in Table-6.

Examples 34 to 37 and Comparative Example 18 A raw film having a thickness of 65 μ was prepared in the same manner as in Example 22 by using the composition shown in Tables 3 to 4 and the long stretching machine (US T.
Sequential biaxial stretching or simultaneous biaxial stretching (Example 37 only) was performed at 70 ° C. using M Long Co. The results are
8 shows.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number in 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 (72) Inventor Tsutomu Kobayashi 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd.

Claims (7)

[Claims] 1. A linear low-density polyethylene (a) having a density of 0.91 to 0.94 g / cm ³ , a melt index of 0.5 to 10 g / 10 min, and (b) a melt index of 0.5 to 10 g / A composition comprising 10 minutes of high-pressure low-density polyethylene, (c) a filler, (d) a polyhydroxy saturated hydrocarbon and (e) an epoxy group-containing organic compound, wherein the composition ratio of each component is by weight. (I) 0.6 ≦ (a) / [(a) + (b)] ≦ 0.97 (ii) 0.2 ≦ (d) / [(d) + (e)] ≦ 1.0 (iii) 0.25 ≦ (c) / [(A) + (b)] ≤ 4.0 (iv) 0.02 ≤ [(d) + (e)] / [(a) + (b)] ≤ 1.0 The composition satisfying each formula is melt-molded. A method for producing a porous sheet, which comprises subjecting the sheet thus obtained 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.