JPS59140235A - Production of porous sheet - Google Patents

Abstract

PURPOSE:To produce a porous sheet excellent in balance among porosity, stretchability, mechanical properties, etc., by stretching a sheet prepared from a composition comprising a specified polyethylene, a filler, a polyhydroxy saturated hydrocarbon and an epoxy group-containing organic compound. CONSTITUTION:The following components are mixed together at a mixing ratio, by weight, satisfying relationships I -IV: (a) linear low-density polyethylene (density; 0.91-0.94g/cm<3>, MI; 0.5-10g/10min), (b) high-pressure process low- density polyethylene (MI; 0.5-10g/10min), (c) filler (e.g., calcium carbonate of an average particle diameter of up to about 30mu), (d) polyhydroxy saturated hydrocarbon (hydroxyl group content >=1.5, iodine value <=10), and (e) epoxy group- containing organic compound (e.g., epoxidized soybean oil). The resulting composition is melt-molded into a sheet, which is stretched at a stretching ratio of above 1.1 to form a porous sheet.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a porous sheet.

Specifically, the present invention relates to a method for producing a porous sheet from a composition comprising linear low-density polyethylene, high-pressure low-density polyethylene, a filler, and a polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound. More specifically, it has excellent extrudability and good formability in melt extrusion molding, and exhibits excellent stretchability and good lance when uniaxially or biaxially stretched the melt extruded sheet. relates to a method for producing a porous sheet that is highly flexible and has strong surface strength.

Conventionally, many attempts have been made to blend a filler into a polyolefin resin and melt-form the resulting sheet and stretch it 'v=s or biaxially, as a means of producing a porous sheet. However, in these sheets,
- In the case of axially oriented products, problems remain in the anisotropy of the sheet physical properties, tear strength in the machine direction (stretching direction), and further surface strength, and in the case of biaxially oriented products, there are no problems in the anisotropy of the sheet physical properties. ,
There are problems with stretchability and surface strength, and both of them generally have high rigidity, which may be a drawback depending on the application.

Anisotropy of physical properties of sheets 4. Methods of imparting flexibility to improve surface strength include low melting point polymers, rubber-like substances, plasticizers, or surface active materials that satisfy the balance of physical properties such as surface strength. has not yet been discovered.

As a method for improving these drawbacks of conventional porous sheets, Japanese Patent Application Laid-Open No. 1983-733 discloses a composition comprising a polyolefin resin mixed with a filler and liquid polybutadiene or liquid polybutene. In addition, the present inventors have discovered that a porous film or sheet with excellent performance can be obtained from a composition formed by blending a linear low-density polyethylene resin, a filler, and a polyhydroxy saturated hydrocarbon, and have previously filed an application. (Special application 1977-ttlIgbs)
.

However, when a linear low-density polyethylene resin is used, although the stretched product has excellent flexibility, it is not fully satisfactory in terms of molding stability during melt extrusion molding of an unstretched original fabric.

In addition to having good extrudability in melt molding, the present inventors have
It shows particularly excellent molding stability, good melting lance, and -
Provides a porous sheet with strong surface strength for both axially oriented and biaxially oriented products, excellent stretchability, very little stretching unevenness caused by non-uniform stretching especially in low ratio stretching, and high flexibility. The present invention has been arrived at as a result of intensive study.

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

Hereinafter, to explain the present invention in detail, the linear low-density polyethylene used in the present invention includes ethylene topropylene, butene-7, hexene-/, Hiro-meterpentene-/, octene-1, and decene-1. α other than ethylene such as / etc.
-Copolymer with olefin, melt index is 0
, S ~ 70% / / 0 min, density 0.97 ~
Examples include those in the range of 0.941y-/crl.

The melt index is θ for conventional high-pressure low density polyethylene! ;-/Of-7
Examples include those in the 10 minute range.

In addition, the weight ratio of linear low density polyethylene (&) and high pressure low density polyethylene (b) is 0.6≦(-)/[:(,
)+(b))≦0.97.

If the melt index of linear low density polyethylene and high pressure low density polyethylene is smaller than o,5Li-770 minutes, melt extrusion molding is possible, but there is a drawback that extrudability is difficult and productivity is low. Moreover, if the melt index is larger than tOf-7io, the stability of molding will decrease in the molding of the original fabric. On the other hand, if the sonicity of the linear low-density polyethylene is smaller than θqiy-7a&, although the stretched product has very good flexibility, it is not sufficiently porous.
Lacks dimensional stability. If the density is higher than a9 hirof/cttl, there will be no problem with the porosity and dimensional stability of the stretched product, but the flexibility will be poor.

If the blending ratio of high-pressure low density polyethylene is less than the above range, the molding stability will be insufficient due to the lack of melt elasticity of the melt during fabric forming, and if it is higher than the above range, the molding stability will be excellent. However, the porosity of the stretched product is insufficient.

Additives such as heat stabilizers, ultraviolet absorbers, antistatic agents, pigments, and fluorescent agents can be added to these linear low-density polyethylenes and high-pressure low-density polyethylenes according to conventional methods.

Inorganic fillers and organic fillers are used as fillers, and inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, calcium sulfate, aluminum hydroxide, zinc oxide, and magnesium hydroxide. , calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder,
Shirasu balloons, zeolite, silicate clay, etc. are used.
Particularly suitable are calcium carbonate, tartar, clay, silica, diatomaceous earth, barium sulfate, and the like.

As the organic filler, cellulose powder such as wood flour and pulp is used. These may be used alone or in combination.

The average particle size of the filler is preferably 30μ or less, more preferably IOμ or less, and most preferably Sμ or less. If the particle size is too large, the density of the pores in the drawn product will deteriorate.

Surface treatment of the filler is preferably carried out in terms of dispersibility in the resin and further stretchability, and treatment with a fatty acid or a metal salt thereof gives preferable results. The amount of surface treatment with the fatty acid or its metal salt is preferably 10 parts by weight or less per 10 parts by weight of the filler. If the amount of surface treatment is too large, it is not preferable because it may cause mixing, granulation, and even white smoke or foaming during molding.

As polyhydroxy saturated hydrocarbons, most or all of the main chain having at least 15 hydroxyl groups per molecule is saturated and has an iodine number i.

The following hydrocarbon polymers, qoo to +goo
o, preferably! ; 00 to 2 (2000) is preferably used. If the number average molecular weight is too small, the molding stability during molding of the original fabric will be difficult; If it is too large, the fluidity may decrease and handling may become difficult.The average number of hydroxyl groups per molecule is preferably 18 or more, preferably 20 to !-0.The hydroxyl groups are located at the end of the main chain. , preferably at the end of a long chain branch.

However, such polyhydroxy saturated hydrocarbons can be obtained by hydrogenating a butadiene-based liquid polymer obtained by radical polymerization of butadiene alone or with a copolymerizable monomer using a known method such as hydrogen peroxide as a polymerization initiator. obtained by doing.

Isoprene, chloroprene, styrene, methyl acrylate, methyl methacrylate, methyl vinyl ether and the like can be mentioned as the 1-4it monomer. Hydrogenation is carried out in a conventional manner using a nickel catalyst (eg reduced nickel, Raney nickel), a cobalt catalyst, a platinum catalyst 1, a palladium catalyst, a rhodium catalyst, a ruthenium catalyst, or a mixture or alloy catalyst thereof.

As the epoxy group-containing organic compound, epoxidized soybean oil,
Examples include epoxidized vegetable oils such as epoxidized linseed oil, liquid epoxy resins, such as hardening agent-free epoxy resins obtained by the reaction of bisphenol and epichlorohydrin.

The weight ratio of the polyhydroxy saturated hydrocarbon (d) and the epoxy group-containing organic compound (,) is 02≦(d)/
It is necessary that [(d)+(-):]≦lθ, especially θko≦(d)/C(d)+(e):)≦09
It is preferable that

When an epoxy group-containing organic compound is blended, the stretchability is even better than when it is not blended, and uniform stretching is possible even at low stretching ratios, and there are almost no stretching irregularities caused by uneven stretching. .

Moreover, if the amount of the epoxy group-containing organic compound exceeds the above range, the moldability will be extremely deteriorated in melt molding of the unstretched original fabric, which is not preferable.

Linear low-density polyethylene (,), high-pressure low-density polyethylene (b), filler (C), polyhydroxy saturated hydrocarbon (d), and epoxy group-containing organic compound (the blending ratio of -1 is 0 by weight, 23≦(c)/[(-)+(b))≦lAOθ
θ2≦[(d)+(-)]/[(-)+(b))
It is necessary to satisfy each formula of ≦10, especially O6≦
(C)/[(-)+(b))≦20o, os≦[(
d)+(e) :) / [(a)+(b))≦a5
It is preferable that

If the amount of filler blended is too small, pores will not be formed sufficiently in the stretched sheet and the degree of porosity will be reduced.On the other hand, if the amount blended is too large, crosstalk and dispersibility will deteriorate, resulting in poor formability of the sheet. This results in a decrease in surface strength. Furthermore, if the blending amount of the polyhydroxy saturated hydrocarbon and the epoxy group-containing organic compound is too large, satisfactory crosstalk properties cannot be obtained, and sheet formability and stretchability cannot be ensured.

In the method of the present invention, when blending each component, a method is adopted in which straight-line low-density polyethylene and high-pressure low-density polyethylene are mixed or melt-kneaded, and then other components are added and mixed. When a polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound is added and mixed after the above polymer is mixed, and then a filler is added and mixed, the formation of agglomerates is observed, and spots appear on the formed sheet. Therefore, it is desirable to add and mix the filler before adding 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, etc., but VC granules or powders are preferred.

A preferred method of blending each component is to mix linear low density Polyethylene and high-pressure low-density polyethylene are added and mixed, a filler is added thereto, and the mixture is stirred thoroughly. Polyhydroxy saturated hydrocarbon or an epoxy group-containing organic compound is then added and stirred to disperse and spread. This is a method to make a mixture.

Mixing of the obtained mixture is suitably carried out using conventionally known equipment such as a conventional screw extruder, twin screw extruder, mixing roll, Banbury mixer 1 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 of the cross-mixing methods, and resources such as electric power can be saved in the compact equipment.

The sheet may be formed using a conventional sheet forming apparatus and forming method, and may appropriately employ inflation forming using a circular die, extrusion forming using a T die, or the like.

When the formed sheet is then stretched, roll stretching is usually used in the case of -axial stretching, but tubular stretching may be used to emphasize the -axial direction (take-up direction). Further, the stretching may be carried out in one stage or in multiple stages of two or more stages.

In biaxial stretching, low-stretching is possible in simultaneous and sequential stretching as well as uniaxial stretching, and at least one direction is 71
Uniform stretching and porosity can be achieved by double the amount. The stretching ratio at which porosity is achieved and uniform stretching is possible is such that at least one direction is i.
t~3.0 times.

Conveniently, heat treatment can be performed after stretching for both -axial stretching and biaxial stretching to stabilize the dimensional accuracy of the film.

Further, known surface treatments such as corona treatment and film V-treatment may also be carried out.

In the present invention, the porous sheet is formed with an angle of θθ/~05-1, preferably θθ2~0.31-, and what is generally called a film is also included in the sheet of the present invention.

The method of the present invention includes (1) Porous formation is achieved at a low stretching ratio.

(2) Low stretching stress and low temperature stretching possible.

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

The resulting porous sheet has the following characteristics: (11
Almost no stretching spots are observed.

(2) Excellent moisture permeability and dirt permeability, and high water pressure resistance (1° (3) Excellent flexibility.

(4) Less anisotropy in physical properties.

(5) High tear strength and tensile strength.

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

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

It exhibits properties such as, and can be applied to a wide range of applications such as clothing, packaging, battery separators, filtration media, and medical applications.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not to be construed as being grounded in the following examples unless the gist of the present invention is exceeded.

Incidentally, a list of raw materials used in the following Examples and Comparative Examples is shown in Table-7 and Table-2.

Table-l (Note) MI (melt index); ASTM
Density measured at 190°C in accordance with D/2.3g-90; Measured at 20C by density gradient tube method in accordance with ASTM D/5θS Table-2 Reference Example 1 (Production of polyhydroxy saturated hydrocarbon) Capacity 1
Commercially available liquid polybutadiene [
Made by Nippon Soda; G-200θ, molecule it 2ooo'
] 3kf, cyclohexane 3yu and carbon-supported ruthenium (5%) catalyst (manufactured by Engelhardt) 3oo
After charging y- and replacing the system with purified arbon gas,
High-purity leaf gas was supplied to the autoclave, and heating was started at the same time, under steady-state conditions (endothermal io) for about 30 minutes.

°C, internal pressure approx! ;Oky/αd). These conditions were maintained for approximately is time and then the hydrogenation reaction was stopped.

The obtained polymer has an iodine value IA9f/100? It was a liquid substance with a hydroxyl value S j KOH■/y-.

Examples/~32, Comparative Examples 1~/7 Linear low-density polyethylene (,), high-pressure low-density polyethylene (b) and filler (c) '& Mixed with stirring in a Behenschel mixer, and added to the polyhydroxy saturated The hydrocarbon (d) and the epoxy group-containing organic compound (,) were added and mixed with further stirring to obtain 10 kff of a mixture. The types and amounts of each raw material component used are listed in Tables 3 to 3.

The mixture obtained by repeating the above operation 5 times was kneaded and granulated using a twin-screw kneader (DSM-43, Japan Copper Works←φ), and then inflation molded using a 1l Onanφ extruder under the following conditions. An original film having a diameter of 65 μm was obtained.

Cylinder temperature: 17θ-/9O-2IOC Head, die temperature: 21θ-2IOC Take-up speed: / J m 7
Blow ratio: Y7 Fold diameter: 3tg The obtained film was uniaxially stretched using a roll stretching machine under the following conditions.

Stretching temperature near θC However, in Example G qoC, in Example S This was done at SOC.

Stretching ratio: 13 to 3 Stretching speed: 2517 minutes The thickness unevenness of the raw film, the molding stability during molding of the raw film, the stretching ratio, and the physical properties of the obtained stretched film are shown in Tables 5 to 7.

Moreover, the measurement method of physical property evaluation items is as follows.

l) Uneven thickness of raw film r: average thickness = 1) - (μ) σn: Standard deviation (μ) n=J4 (divided into 36 equal parts in the circumferential direction) 2) Molding stability In inflation molding, ◎: No bubble fluctuation ○: Almost no bubble fluctuation △: There is some shaking of bubbles. ×: Difficult to mold 3) Stretchability ・: No cutting, uniform stretching, no stretching irregularities No.

○: No cutting, almost no stretching unevenness observed.

Δ: No cutting, stretching spots observed.

×: Significant cutting or stretching spots are observed.

Hiroshi) Porosity Calculated from film density using the following formula D: Density of stretched film (y-/crl) S) Tensile strength Based on ASTM gg2-1,4tT Vc.

20 smg% x 3θ length, tensile speed 5orru
n/min 6) Tear strength According to JIS P-g/14.

Has a notch. /gukannobu x/10 length.

7) Moisture permeability Conforms to ASTM E2A-61, (E) VC.

g) Flexibility Judgment was made by feeling with the hand according to the following criteria.

◎: Extremely soft ○: Soft Δ: Slightly hard ×: Hard 9) Surface strength Sellotape on the film surface? The peeling condition of the surface when pasted and quickly peeled off was observed and judged based on the following criteria.

◎: No surface peeling ○: Almost no surface peeling △: Slight surface peeling x 2 large surface peeling Example 33 When blending each component listed in Table-3, (, ),
(b), (d) and (,) are stirred and mixed in a Henschel mixer, and (d) and (-) are mixed with (a) and (b).
A stretched film was produced in the same manner as in Example 17 except that (C) was added and mixed after spreading. The results are in the table-
6.

Examples 3 to 3 and Comparative Example ig A raw film with a thickness of 65 μm was prepared in the same manner as in Example 22 using the formulation shown in Tables 3 to 3, and a long stretching machine (U.S. T.
Sequential biaxial stretching or simultaneous biaxial stretching (Example 37 only) was carried out at 7θC using a film (manufactured by M Long Co., Ltd.). The results are in the table-
O shown in g Table -3 Table -HiroshiContinued from page 1 0 Inventor: Mitsubishi Chemical Industries, Ltd. General Research Laboratory, 1000 Kamoshida-cho, Midori-ku, Yokohama, Bizenbu-Ren (String Inventor: Minoru Aino, Kamoshida, Midori-ku, Yokohama) 1000 Mitsubishi Chemical Industries, Ltd. General Research Center Inventor: Yu Suzuki Mitsubishi Chemical Industries, Ltd. General Research Laboratory, 1000 Kamoshida-cho, Midori-ku, Yokohama Inventor: Tsutomu Kobayashi Mitsubishi Chemical, 1000 Kamoshida-cho, Midori-ku, Yokohama Inside Kogyo Co., Ltd. Research Institute

Claims (4)

[Claims] (1) (-) Density θ91 ~ θ”I Si'/
crl, melt index 0.3 A-/Of//
0 minute linear low density polyethylene, (b) Melt index 0.3-709-710
high pressure process low density polyethylene, (c) filler, (d) polyhydroxy saturated hydrocarbon and (6)
A composition formed by blending an epoxy group-containing organic compound, in which the composition ratio of each component is <+ on a weight basis.
fi) 0.2≦(a)/((a)+(-)]≦l00
11) θ2S≦eH(a)±(b))≦DaO$y)
o, oko≦[(d)+(-):)/[(&)+(b))
1. A method for producing a porous sheet, which comprises stretching a sheet obtained by melt-molding a composition that satisfies each formula of ≦IO. (2) The polyhydroxy saturated hydrocarbon contains at least is hydroxyl groups per molecule and has an iodine value of 10.
A method according to claim 1, which is: (3) The method according to claim 7 or 2, wherein the polyhydroxy saturated hydrocarbon is obtained by hydrogenating hydroxyl-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. (Stretching process is at least 11 times biaxial stretching.