JPH0715021B2 - Stretched porous film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a stretched porous film having excellent gas and liquid permeability, stable quality, and economical, and a method for producing the same.

(B) Conventional Technology Conventionally, a porous film used for a breathable bag, a membrane for pressure filtration, a support for filtration or the like is manufactured by the following method.

That is, a polyolefin resin is mixed with an inorganic filler that can be eluted with an acid, an alkali, or water and a nonionic surfactant having an HLB of 9 to 15 and formed into a film, followed by stretching, and then the above inorganic filler is added. A porous film is produced by elution with the above-mentioned acid or the like (Japanese Patent Laid-Open No. 50-74667).

In the above, a non-ionic surfactant having an HLB of 9 to 15 is used in place of the ethylene-vinyl acetate copolymer to produce a porous film in the same manner as described above (JP-A-54-54). 43982 publication).

A film obtained by melt-molding a composition obtained by blending a filler and a liquid rubber in a high-density polyolefin resin is stretched to produce a porous film (JP-A-57-47).
334).

In the above, a polyhydroxy saturated hydrocarbon is used in place of the liquid rubber to produce a porous film in the same manner as described above (JP-A-57-203520).

A film obtained by melt-molding a composition obtained by blending a polyolefin resin selected from specific medium / low pressure polyethylene and crystalline polypropylene, a filler, a polyhydroxy saturated hydrocarbon and an epoxy group-containing organic compound is stretched. A porous film is produced (JP-A-59-136334).

(C) Problems to be Solved by the Invention However, in any of the above methods, a porous film is directly obtained by stretching, or in a porous film obtained by stretching, an inorganic material in the porous film is used. It is to obtain a porous film having greater permeability by eluting the filler with an acid or the like, and at the time of stretching, the molecules are oriented to improve the strength of the film, but the formation of through holes As a result, the orientation of the molecules becomes non-uniform, and during this stretching, fine cracks are formed at the through-holes in the film body. This phenomenon becomes more remarkable when the film body (resin) and the filler do not fit well with each other, or when the amount of the filler is increased or the stretching ratio is increased, and as a result, the tearing force in the stretching direction is reduced. However, when a thin porous film is used to form, for example, an air-permeable bag or a filtration membrane for pressurization, the resistance to tearing force is small, so that various problems such as rupture occur during use.

(D) Means for Solving the Problems The inventors of the present invention have earnestly studied to solve the above problems, and have obtained the following findings.

That is, in the case of obtaining a porous film as described above,
The mechanical strength is high, there is little stretching unevenness after stretching, the orientation of the molecules is relatively uniform during stretching, and the resin components with good mechanical strength such as tearing force are repeatedly investigated. However, linear low-density polyethylene resin has high crystallinity and high mechanical strength, and uniaxially or biaxially stretching a film formed using this as a resin component, compared to using other thermoplastic resins. Then, it was found that a stretched porous film with extremely little stretching unevenness can be obtained.

Further, according to the experimental results of the present inventors, in order to improve the compatibility between the filler and the resin composition, the softening agent blended in the resin component becomes a very important factor, and the selection of the softening agent is extremely important. It turned out to be important.

Therefore, the present inventors repeated further studies using various softening agents, the resin composition obtained by mixing the linear low-density polyethylene resin with the olefin terpolymer has the best compatibility with the filler, Moreover, when a film formed using this resin composition is uniaxially or biaxially stretched, as compared with the case of using another thermoplastic resin composition, a stretched porous film with extremely little stretching unevenness is obtained, and at the time of stretching The cracks in the film at the through-holes that occur in the film are uniform and do not have large tears, and the non-uniform orientation of the molecules at the through-holes in the film is extremely small and the mechanical strength is large. Because of this, you don't have to
It was found that the stretched porous film has extremely excellent air permeability and moisture permeability.

Based on these results, the present inventors have used a linear low-density polyethylene resin as a resin component, and formed a film formed of the linear low-density polyethylene resin, a filler, and a resin composition containing an olefin terpolymer as an essential component. When uniaxially or biaxially stretched, a stretched porous film with extremely little stretching unevenness can be obtained, and the stretched porous film thus obtained has high hardness, high bending strength and tensile strength, and high tearing force, and therefore this thin film The stretched porous film was found to be a highly reliable porous film that does not rupture during use even when used as, for example, a breathable bag or a pressure filtration film, and completed the present invention. It is a thing.

That is, the stretched porous film of the first invention of the present application comprises a linear low density polyethylene resin, a resin composition containing a filler and an olefin terpolymer as essential components.

The second invention of the present application relates to a preferred method for producing a stretched porous film of the first invention of the present application, the gist of which is to add a filler and an olefin terpolymer to a linear low-density polyethylene resin. To form a resin composition, and melt-mold the resin composition to stretch a film obtained uniaxially or biaxially.

Hereinafter, first, the first invention of the present application will be described in detail.

As the stretched porous film of the present invention, a stretched porous film formed using a linear low density polyethylene resin (A), a resin composition containing a filler (B) and an olefin terpolymer (C) as essential components It is not particularly limited, and therefore does not matter how the manufacturing method is.

And the mixing ratio of the above (A) and (B) is (A) 10
0 to 100 parts by weight of (B), preferably 150
It is desirable to set it in the range of up to 250 parts by weight, and if (B) is less than 100 parts by weight, the strength of the film may be reduced,
This is because the air permeability and the water vapor transmission rate may decrease, while on the other hand, when the amount (B) exceeds 300 parts by weight, the kneading property and moldability are deteriorated and the film strength is also decreased.

The stretched porous film of the present invention is formed using a linear low density polyethylene resin (A), a resin composition containing a filler (B) and an olefin terpolymer (C) as essential components. However, the addition of the olefin terpolymer further improves the kneadability and dispersibility of the filler, the molding / workability, and the above (A).
This is to improve the conformability of (B) and (B) to obtain a stretched porous film having extremely excellent mechanical strength.

In this case, the mixing ratio of (A) and (C) above is (A)
It is desirable that (C) is in the range of 5 to 95 parts by weight, preferably 30 to 70 parts by weight, relative to 100 parts by weight, and the stretched porous film comprising the resin composition having such a blending ratio is
The mechanical strength is higher and the gas and liquid permeability is even better.

The present invention, as a stretched porous film, by using a resin composition comprising a linear low-density polyethylene resin and a filler and an olefin terpolymer in this manner, a stretched porous film with extremely little stretching unevenness is obtained, and The stretched porous film thus obtained has a high hardness and a high bending strength and tensile strength, and a high tearing force.Therefore, even when this thin stretched porous film is used as, for example, a breathable bag or a pressure-applying filtration membrane, A highly reliable product can be obtained without causing rupture, the stretched porous film is excellent in production and processability and the production cost is low, and the strength of the obtained stretched porous film is large, so that it is a single layer. Therefore, it can be used as a breathable bag or a filtration membrane for pressurization.

The linear low density polyethylene resin used in the present invention is a copolymer of ethylene and α-olefin, and examples of the α-olefin include butene, hexene and octene.

The above-mentioned fillers include calcium carbonate, talc, clay, kaolin, silica, barium sulfate, kaolin sulfate,
Examples thereof include aluminum hydroxide, zinc oxide, calcium oxide, titanium oxide, alumina and mica.

The average particle size of this filler is 30 μm or less,
It is preferably in the range of 0.1 to 10 μm.

If the particle size is too large, the through holes become large, and conversely if it is too small, aggregation occurs and the dispersibility deteriorates, which is not preferable.

The above olefin terpolymer has a number average molecular weight of
It is not particularly limited as long as it is a rubber-like substance of 30,000 to 800,000, and specific representative examples include ethylene,
A cyclic or acyclic copolymer having an α-olefin and a non-conjugated double bond (hereinafter referred to as EPDM) is used.

The EPDM is a terpolymer consisting of ethylene, propylene or butene-1 and polyene monomers listed below, and as the polyene monomer, dicyclopentadiene, 1,5-cyclooctadiene, 1,1-cyclooctadiene, 1,6-Cyclododecadiene, 1,7-Cyclododecadiene, 1,5,9-Cyclododecatriene, 1,4-Cycloheptadiene, 1,4-Cyclohexadiene, 1,6-Heptadiene, Norbornadiene, Methylene Norbornene,
2-methylpentadiene-1,4,1,5-hexadiene, methyl-tetrahydroindene, 1,4-hexadiene and the like. The copolymerization ratio of each monomer is preferably 30 to 80 mol% of ethylene and 0.1 to 20 mol% of polyene.
It is preferable that the terpolymer has a Mooney viscosity of ML _{1 + 4} (100 ° C.) of 1 to 60 such that the rest is α-olefin.

In the present invention, the softening agent (D) may be added to the above resin composition in an amount of 25 parts by weight or less based on 100 parts by weight of the olefin terpolymer (C). Is more than 25 parts by weight, the strength of the stretched porous film deteriorates, which is not preferable.

The softening agent is not particularly limited as long as it has a number average molecular weight of 1,000 to 30,000, and specific representative examples thereof include petroleum-based process oil, liquid paraffin, and aliphatic as a low-viscosity softening agent. There are system oils and low molecular weight plasticizers, and softeners such as polybutene, low molecular weight polyisobutylene, and liquid rubber are preferably used as relatively high viscosity softeners.

The stretched porous film may be added with a commonly used antioxidant, ultraviolet stabilizer, antistatic agent, pigment, lubricant, fluorescent agent and the like.

Next, the second invention of the present application will be described in detail.

In the present invention, first, step A of blending a linear low density polyethylene resin with a filler and an olefin terpolymer is carried out.

The present invention relates to a preferred method for producing the stretched porous film of the first invention of the present application, and therefore, the linear low-density polyethylene resin, the filler and the olefin terpolymer used in the present invention, and the compounding ratio thereof are , Which are the same as those described in the first invention of the present application.

Further, a known mixer is used for mixing the linear low-density polyethylene resin, the filler and the olefin terpolymer, and a known mixer is used. In order to improve the moldability, it is desirable to use a mixer such as a mixing roll, a Banbury mixer, a twin-screw kneader, a Henschel mixer.

In the present invention, next, a step B of forming a stretched porous film by uniaxially or biaxially stretching the film obtained by melt-molding the resin composition obtained in the above step A is carried out.

An ordinary molding apparatus and molding method may be used for molding this film, and an inflation molding machine, a T-die molding machine and the like are preferably used, and the film thus obtained is uniaxially or biaxially stretched and stretched. Although a porous film is formed, this stretching method may be carried out by a conventional method using a normal stretching device, and for example, roll stretching, simultaneous biaxial stretching, sequential biaxial stretching and the like are adopted.

Then, in this stretching treatment, the stretching ratio is 100 to 400% in the case of uniaxial stretching, and the stretching ratio is 10 to 300% in the case of biaxial stretching. It is preferable from the viewpoint of the size of the pores, that is, the permeability of gas or liquid. In particular, in the case of uniaxial stretching, if the stretching ratio is less than 100%, the stretched portion and the unstretched portion are mixed and the stretching becomes uneven, while if it exceeds 400%, it may be broken during stretching, which is not preferable. .

In the present invention, the stretching ratio is a value calculated by the following formula.

In this case, in producing a stretched porous film, a film obtained by melt-molding a resin composition is directly stretched to form a stretched porous film, or stretched to obtain a stretched porous film, which is then Further, it may be formed by eluting the filler with acid, alkali or water.

(E) Action In the present invention, when a resin composition having the above-mentioned constitution and comprising a linear low-density polyethylene resin, a filler and an olefin terpolymer is used, the bending strength, the tensile strength and the tearing force are high and the excellent stretching is achieved. Although the reason why a porous film is obtained is not clear, this linear low-density polyethylene resin has high crystallinity and high mechanical strength, and if a film formed from this resin composition is uniaxially or biaxially stretched, other Compared to using a thermoplastic resin composition, it is possible to obtain a stretched porous film with very little stretching unevenness, and, in addition, during this stretching, the olefin terpolymer has a linear low density polyethylene resin and a filler. It improves the familiarity, and therefore the cracks in the film at the through-holes caused by stretching and the non-uniform orientation of the molecules at the through-holes in the film may cause other thermoplastic resin Very little compared to using fat, therefore
It is considered that the bending strength, the tensile strength, and the tearing force do not increase, so that no rupture occurs during use. For this reason,
Since it is not necessary to form a heat-treated part at all, the stretched porous film has extremely excellent air permeability and moisture permeability, and has a function of being able to be used as a single layer as an air-permeable bag or a pressure filtration film.

Further, since the stretched porous film of the present invention does not need to form a heat-treated part at all, it has excellent production and processability and is inexpensive in production cost, and moreover, the strength of the obtained stretched porous film is large and it is a single layer. Since it can be used, it is highly reliable.

Further, according to the method of the present invention, a stretched porous film having excellent properties can be obtained only by melt-molding the linear low-density polyethylene resin composition, and therefore, it is not necessary to use a special technique or apparatus. It has an action.

(F) Examples Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto.

Examples 1 and 2 As shown in Table 1, linear low density polyethylene resin (MI 2.0, density 0.93), EPDM (trade name, EPT9720, Mitsui Petrochemical Co., Ltd.) as olefin terpolymer, and filler as Calcium carbonate (average particle size 2 μm, treated with fatty acid) and stearic acid as a lubricant were mixed in the mixing ratios shown in Table 1 and mixed thoroughly with stirring, and this mixture was mixed with a twin-screw kneader (TEM-50, Toshiba Machine). The resin composition obtained by sufficiently kneading is manufactured by a company (manufactured by the company).

This linear low-density polyethylene resin composition is melted to obtain 65φ.
The film was formed into a film by an inflation extruder of the above, and the film having the thickness shown in Table 1 was produced.

The film thus obtained was uniaxially stretched by a roll stretching machine (Example 1) or biaxially stretched by a sequential biaxial stretching method (Example 2), whereby a stretched porous material having a stretching ratio shown in Table 1 was obtained. I got a film.

In this case, the stretching conditions are a stretching temperature of 60 ° C and a stretching speed of 6 m.
/ min, stretch ratio, by changing the speed ratio of the roll,
The values were adjusted so that the values shown in Table 1 were obtained.

The obtained stretched porous film had no stretching unevenness and was a porous film.

The characteristics of each of the examples thus obtained are shown in Table 1.

Comparative Example 1 A porous film having the following composition was obtained in the same manner as in Example 1.

Linear low-density polyethylene 100 parts by weight Filler (CaCO ₃ ) 200 parts by weight Liquid polybutadiene (molecular weight 3000) 20 parts by weight Stearic acid 1.6 parts by weight Comparative Example 2 A porous film having the following composition was prepared in the same manner as in Example 1. Obtained.

Linear bottom density polyethylene resin 100 parts by weight Filler (CaCO ₃ ) 200 parts by weight Liquid polybutadiene (molecular weight 3000) 20 parts by weight Stearic acid 1.6 parts by weight Comparative Example 3 A porous film having the following composition was prepared in the same manner as in Example 1. Got

Linear bottom density polyethylene resin 100 parts by weight Filler (CaCO ₃ ) 200 parts by weight Elastomer (ethylene-butene-1 copolymer, trade name: Tuffmer A) 150 parts by weight Stearic acid 1.6 parts by weight Comparative Example 4 of the following composition A porous film was obtained in the same manner as in Example 1.

Linear bottom density polyethylene resin 100 parts by weight Filler (CaCO ₃ ) 200 parts by weight Elastomer (ethylene-butene-1 copolymer, trade name: Tuffmer A) 20 parts by weight Stearic acid 1.6 parts by weight Comparative examples thus obtained The characteristics of are shown in Table 1.

Note 1) The stretching ratio shown in Table 1 is a value obtained by the following formula.

Note 2) The tearing force shown in Table 1 was measured based on JIS K 6772.

Note 3) The moisture permeability shown in Table 1 was measured by the moisture permeable cup method in JIS Z 0208.

From the results shown in Table 1, the examples in which the linear low density polyethylene resin was used as the resin component contained the olefin terpolymer, so the hardness was high and both the tensile strength and the tear strength were high. Is recognized.

Therefore, the stretched porous film is useful as a breathable bag, for pressure filtration, for various packaging materials such as desiccants, hygroscopic agents, pheromone agents, for building materials, and for clothing.

On the other hand, the porous films of Comparative Examples 1 and 2 have low tear strength, and when stored at a high temperature (40 ° C.), the softening agent bleeds onto the surface and contaminates other materials that come into contact with it, or itself. It was recognized that it had a defect that it was easily soiled.

In addition, the porous film of Comparative Example 3 has flexibility but low strength, has a defect that the surface is easily scratched, and has rubber elasticity. Therefore, the effect of porosity was low and the moisture permeability was low.

Further, it is recognized that the material of Comparative Example 4 has good moisture permeability but low tensile strength and tear strength.

(G) Effect of the Invention The stretched porous film of the present invention has the above-mentioned constitution, and uses a linear low-density polyethylene resin as a resin component, in which a filler and particularly an olefin terpolymer are mixed, Since the bending strength, the tensile strength, and the tear strength are high, and the mechanical strength is high, it is not necessary to form a heat-treated part at all, and therefore, the stretched porous film has an extremely high air permeability and moisture permeability. As a result, even if the stretched porous film is used as a single layer, for example, as a breathable bag or a filtration membrane for pressurization, it does not burst at the time of use and has the effect of increasing reliability. .

Further, according to the method of the present invention, it is possible to easily and economically produce a stretched porous film having a uniform and excellent quality without requiring a special technique or a device.

Claims (4)

[Claims] 1. A stretched porous film comprising a linear low density polyethylene resin, a filler and a resin composition containing an olefin terpolymer as essential components. 2. The mixing ratio of the linear low-density polyethylene resin, the filler and the olefin terpolymer is 100 to 300 parts by weight of the filler and 5 to 95 parts by weight of the olefin terpolymer with respect to 100 parts by weight of the linear low-density polyethylene resin. The stretched porous film according to claim 1, which is a part. 3. A linear low density polyethylene resin is blended with a filler and an olefin terpolymer to form a resin composition,
A method for producing a stretched porous film, which comprises uniaxially or biaxially stretching a film obtained by melt-molding the resin composition. 4. A blending ratio of a linear low density polyethylene resin, a filler and an olefin terpolymer to 100 parts by weight of the linear low density polyethylene resin is 100 to 300 parts by weight of the filler and 5 to 95 parts by weight of the olefin terpolymer. The method for producing a stretched porous film according to claim 3, which is a part.