JPS5815538A - Production of porous film or sheet - Google Patents

Abstract

PURPOSE:To form a porous film which is beautiful and highly flexible even at a low draw ratio, by melt-molding a specified polyolefin resin compsn. contg. a filler blended therewith, into a film, and stretching it. CONSTITUTION:100pts.wt. linear low-density polyethylene resin having an MI of 0.1-5 and a density of 0.91-0.94, 25-400pts.wt. filler having as average particle size of 30mu or below, such as calcium carbonate or woodmeal, and 1-100pts.wt. liquid or waxy hydrocarbon polymer such as a substantially satd. hydrocarbon polymer contg. an average of 1.5 or more hydroxyl groups per molecule, are blended together. The resulting resin compsn. is extruded into a film which is then monoaxially or biaxially oriented 1.1-3 times as long to produce a porous film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing porous films or sheets. Specifically, it relates to a method for producing a porous film or sheet from a composition formed by blending a linear low-density polyethylene resin with a filler and a liquid or waxy hydrocarbon agglomerate. Many attempts have been made to uniaxially or biaxially stretch a film or sheet obtained by blending a filler with a resin and melt-molding it as a means of producing a porous film.

However, in these films, anisotropy of film physical properties, especially in the longitudinal direction (stretching direction), is observed in -axially stretched products.
There are still problems with the tear resistance and surface strength of the film, and although there are no problems with the anisotropy of the physical properties of the film in the case of biaxially stretched products,
There are problems with surface strength and stretchability, and both tend to have high overall rigidity, which can be a drawback depending on the application.

One method of improving the film properties such as flatness and surface strength is to achieve porosity by stretching at as low a magnification as possible, but satisfactory results have not yet been obtained.

In addition, adding low-melting point polymers, rubber-like substances, plasticizers, surfactants, etc. may be considered as a method of imparting flexibility to the film; The present inventors have improved the drawbacks of conventional porous films or sheets, and have improved the physical property balance between tear strength and moisture permeability in axial stretching. As a result of extensive research, we have developed this paper with the aim of providing a porous film or sheet that has good surface strength, strong surface strength, excellent surface strength and stretchability when biaxially stretched, and extremely high flexibility in both. This invention has been achieved.

That is, the gist of the present invention is characterized in that a film or sheet obtained by melt-molding a composition obtained by blending a filler and a liquid or waxy hydrocarbon polymer with a linear low-density polyethylene resin is subjected to stretching treatment. The invention consists in a method for producing a porous film or sheet.

The present invention will be explained in more detail below. The linear low-density polyethylene resin used in the present invention is a copolymer of ethylene and α-olefin. Different from density polyethylene resin. The linear low-density polyethylene resin is produced by a low-pressure method, and examples of the α-olefin include butene, hexene, octene, decene, and the like. Describe the difference between high-pressure low-density polyethylene resin and low-pressure low-density polyethylene resin 3- From a structural standpoint, the former has a multi-branched structure with a lot of branching force;
The latter is linear.

There are various manufacturing methods for linear low-density polyethylene resin, and the physical properties are also slightly different, but the linear low-density polyethylene resin used in the present invention has an MI (melt index, f//θm).
in) = θ, /~! , ρ(r/cc)=θ, ri/~
O, it's free.

MI is 0. If it is smaller than /, extrudability will be difficult and productivity will not increase. Also, MI! If it is larger, the molding quality during molding of the original fabric will decrease.

On the other hand, ρ is θ, ? If ρ is larger than 0, the flexibility of the product film straddling sheet will be excellent, but problems will arise in porosity and dimensional stability.If ρ is larger than 0, the flexibility will be impaired.

Among them, MI: θ, j in terms of moldability and physical properties of the product
~2+! , ρ=θ, P/~0. ? Linear low-density polyethylene resin j is 8 preferred.

Inorganic and organic fillers are used as fillers, and inorganic fillers include calcium carbonate, 4-Merck, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, and calcium sulfate. , aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder,
Glass powder, shirasu balloon, zeolite, clay silicate, etc. are used, and calcium carbonate, Merck, clay, silica, diatomaceous earth, barium sulfate, etc. are particularly suitable.

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

The average particle diameter of the filler is preferably 3θμ or less, more preferably 70μ or less, and most preferably /~jμ.

If the particle size is too large, the density of the pores in the drawn product will deteriorate;
Moreover, if the particle size is too small, dispersibility in resin will be poor and moldability will also be poor.

Surface treatment of the filler is preferably not carried out in terms of dispersibility in the resin and further stretchability, and treatment with a fatty acid or a metal salt thereof gives favorable results.

As the liquid or waxy hydrocarbon polymer, liquid polybutadiene, liquid polybutene, and hydrogenated liquid polybutadiene are used. Among them, 4. Polyhydroxy saturated hydrocarbon obtained by hydrogenating hydroxyl group-terminated liquid polybutadiene shows good results.

The polyhydroxy saturated hydrocarbon is a hydrocarbon polymer whose main chain is saturated or mostly saturated and has a molecular weight of at least 5 hydroxyl groups, and has a molecular weight of θ0 to dt, θ
θθ, preferably 500 to 20. Those having a number average molecular weight (by vapor pressure method) in the range of θθθ are used. If the number average molecular weight is too small, the i1 weatherability will not be sufficient, and if it is too large, the fluidity will decrease, making handling difficult. / The average number of hydroxyl groups in the molecular weight is /, preferably more than /
, 7 or more, particularly preferably λ, θ˜S, O. The hydroxyl group is preferably located at the end of the main chain or 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. Then it is obtained by and. Examples of copolymerizable monomers include isoprene, chloroprene, styrene, methyl (meth)acrylate, and methyl vinyl ether.

Hydrogenation is carried out in a conventional manner using a nickel-based catalyst (for example, reduced nickel, Raney nickel), cobalt-based catalyst, platinum catalyst, palladium catalyst, rhodium catalyst, ruthenium catalyst, or a mixture or alloy catalyst thereof.

It is preferable to introduce something with a polar group at the end into the polyolefin resin and filler system in order to improve the compatibility of the two.
It is assumed that this will give results.

Incidentally, heat and ultraviolet stabilizers, pigments, antistatic agents, fluorescent agents, and the like may be added to the linear low-density polyethylene resin according to conventional methods.

When blending the linear low-density polyethylene resin, the filler, and the liquid or waxy hydrocarbon polymer, the blending ratio is 17 parts by weight of the filler θθ to 700 parts by weight of the linear low-density polyethylene resin, and the liquid or 7 to θO parts by weight of the waxy hydrocarbon polymer is preferred.

The ratio of filler is 2! If the amount is less than 1 part by weight, sufficient pores will not be formed in the stretched film, resulting in a low degree of porosity. Furthermore, if the proportion of the filler exceeds 900 parts by weight, crosstalk properties, dispersibility, film or sheet formability will be poor, and the surface strength of the stretched product will be reduced.

In the present invention, a particularly preferable blending ratio is 10 ON linear low density polyethylene resin, 6 filler to 'ik part.
θ˜λθO parts by weight. Regarding the blending ratio of the liquid or waxy hydrocarbon polymer, if it exceeds 1100N, the characteristics of the linear low density polyethylene resin will be weakened, and it will not be possible to achieve satisfactory kneading properties, film or sheet formability, and stretchability. It cannot be guaranteed.

In the present invention, a more preferable blending ratio of the liquid or waxy hydrocarbon polymer is S-tθ parts by weight.

The linear low-density polyethylene resin, filler, and liquid or waxy hydrocarbon polymer may be blended by placing the three in a conventional blender or mixer, but preferably the following method is used to improve mixability and filling. It is good in terms of agent dispersibility and film or sheet formability.

Therefore, the form of the linear low density polyethylene resin is preferably a powder, and one having a mesh size of 10 to /jθ is usually used, but one having a mesh size of 5.20 to 60 is more preferable in terms of uniformity and handling.

As the mixer, a drum, a tumbler type mixer, a ribbon blender, a Henschel mixer, a super mixer, etc. are used, and a high-speed stirring type mixer such as a Henschel mixer is preferable.

Next, mixing of the mixture is carried out as appropriate using conventionally known equipment, such as a conventional screw extruder, twin-screw extruder, mixing roll, Banbury epsilon mixer-1 twin-screw kneader, and the like.

By adding a liquid or waxy hydrocarbon polymer, the crosstalk torque can be significantly reduced in any kneading method, which is useful for downsizing equipment and saving resources such as electric power.

Molding of the film or sheet may be carried out according to a conventional film or sheet molding apparatus and method, and inflation molding using a circular die or T-die molding using a T-die may be appropriately employed. The selection depends on the subsequent stretching method.

That is, in the case of -axial stretching, roll stretching is usually preferred, but tubular stretching may also 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.

The composition according to the present invention has -
It has the following characteristics in axial stretching.

/) When the blending ratios of polyethylene, filler, and liquid or waxy hydrocarbon polymer are the same, uniform whitening occurs at a lower stretching ratio, that is, voids are uniformly formed. Furthermore, since the water vapor permeability is high at the same stretching ratio, it is possible to increase the tear resistance by lowering the stretching ratio. Furthermore, linear low-density polyethylene has a higher moisture permeability, has better releasability at the interface with the filler than oriented phytyrene, and is less prone to so-called necking in tensile tests due to differences in molecular structure. It is related to the difficulty of expression.

, 2) When the blending ratio of polyethylene and filler is the same, the amount of liquid 11-like or wax-like hydrocarbon polymer added to achieve uniform whitening at low stretching ratios, that is, uniform porosity, is greatly increased. It can be lowered into stones.

Due to the effects of 3)/) and 2), the thickness of the stretched film can be reduced and liquid or waxy hydrocarbon purple 1f coalescence can be achieved. This is a big advantage.

- The flexibility of the stretched film is improved. This is to some extent expected since the density of the base polymer is low, but when ordinary high-pressure low-density polyethylene is used as the base polymer, stretching orientation is difficult to occur and, therefore, it is difficult to achieve porosity.

The stretching stress decreases. The effects of reducing the degree of crystallinity, improving the flexibility of the original fabric, and making it possible to create uniform porosity at lower stretching ratios are combined, and the stress during stretching is reduced. , miniaturization and simplification of equipment,
12- It takes advantage of energy saving and becomes more advantageous in terms of production costs.

6) It is possible to lower the stretching temperature. Combined with the lower melting point of the base polymer, it is possible to create uniform porosity at lower temperatures than when high-density polyethylene is used, and it is possible to reduce costs by saving energy.

Normally, the stretching ratio at which porous film or sheet containing filler is achieved is 3.5 to 6 times, but the porous film or sheet made from the composition of the present invention can be made porous at stretching ratio / /～Achieved at low magnification. However, from the viewpoint of increasing the porosity and reducing the anisotropy of the physical properties of the film or sheet, it is preferably 7.3 to 3 times O. Next, the case of biaxial stretching will be described.

Biaxial stretching (both simultaneous and sequential stretching) shows superior stretching properties (compared to when high density polyethylene is used as the base polymer).

Similar to uniaxial stretching, biaxial stretching allows even lower stretching ratios, and uniform stretching and porosity can be achieved at least 7 times in one direction. Accordingly, a porous film with high surface strength can be obtained.

Usually, the stretching ratio at which porosity can be achieved and uniform stretching can be achieved is 7.7 to 3.0 times in both directions. Good luck, /, 7~ko, θ times is good.

Furthermore, by heat-treating after both -axial stretching and biaxial stretching, the dimensional accuracy of the film can be stabilized. Further, known surface treatments such as corona treatment and flame treatment can also be applied.

The film or sheet thus obtained has the following advantages.

1) Porosity: Because it has few stretching irregularities and uniform continuous pores, it has extremely excellent moisture permeability and gas permeability. It also has good water pressure resistance.

l) Film or sheet physical properties In knee-axis stretched products,
By lowering the stretching ratio, the anisotropy can be slightly reduced, improving the vertical and horizontal balance. In particular, the tear resistance in the longitudinal direction (stretching direction) is increased. Also, surface strength can be increased.

Biaxially stretched products have even less anisotropy and can have higher surface strength.

- A stone with significantly improved flexibility in both axially and biaxially stretched products.

(River) Processability: Improves heat sealing strength.

lv) Economic efficiency: By reducing the amount of liquid and waxy hydrocarbon polymer and making it thinner,
Catch 6 figures at a significant cost.

V) Incinurability: Easily incinerated. Does not generate apricot gas.

It is expected that the film sheet obtained according to the present invention will take advantage of the above-mentioned performance and have further expanded applications. □
' For example, for clothing that takes advantage of moisture permeability (waterproof items, rain gear, etc.)
) For battery separators, for F filter materials (for air removal, dust removal, mist removal, industrial wastewater,) for medical purposes, etc.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples.

Reference example/(Production of polyhydroxy saturated hydrocarbon) Capacity/
Commercially available liquid polybutadiene [
Made in Japan: G-1000, molecular weight λθOθ〕3kg
, 300 ml of 9EIU carbon-supported ruthenium (!%) catalyst (manufactured by Engelhard Japan) was added to cyclohexane 3, and heating was started.
An internal temperature of /θO°C and an internal pressure of approximately rOk&la&) were reached.

After maintaining this condition for about 7 hours, the hydrogenation reaction was stopped, and the polymer was purified and dried according to a conventional method.

As a result of analysis by infrared absorption spectrum, the obtained polymer was confirmed to be a saturated carbon-16-hydrogen polymer containing almost no double bonds. Moreover, the -OH group content of the hydrogenated product was θ, (1' meq/f).

Example / Linear low density polyethylene resin (Urto Zexco θ, 2
/ NF, Ultzex is a registered trademark of Mitsui Petroleum & Chemical Industry ■) 2θkgK, reference example / polyhydroxy saturated hydrocarbon obtained from! First, phantom was stirred and mixed in a Henschel mixer, and then calcium carbonate (average particle size/, -2μ, fatty acid treatment) -2! ~ were added and further stirred and mixed.

The mixture thus obtained was mixed in a twin-screw kneader - DB M -
t j (De+ble Screw Mixer,
The mixture was kneaded and granulated at a factory (manufactured by Japan Steel Works, Ltd.).

This was inflation molded using a θmg extruder,
Formed into a 20μ thick film.

The extrusion conditions are as follows.

Cylinder temperature: /70-/ri0-210-430℃
Drilling, die temperature: , 20θ℃ Take-up speed: r m/min, blow ratio≠ko, θ
The film thus obtained with a fold diameter of -3/g was uniaxially stretched using a roll stretching machine.

The stretching conditions are as follows: Stretching temperature: 10°C Stretching ratio: 2. - Double Stretching Speed: //, θm/min The stretched film was porous and sufficiently whitened, had no stretching unevenness, and was a porous film with a beautiful surface.

The performance of this film is shown in Table 7.

The measurement methods for the performance evaluation items in Table 1 are as follows.

Stretchability: ◎: No cutting, uniform stretching, no uneven stretching ○: No cutting,
Stretching unevenness, hardly any △: No cutting, stretching unevenness, slightly present ×: Large cutting or stretching unevenness 2) Porosity Calculated from the density of the film using the quadratic formula Do = Density of the original film (t/Cl1) D : Density of stretched film (y/crd) 3) Strength and elongation: Mu STM
/J', 2-g (according to T) θ width x 0 wing length, tensile speed: jOIII/min Tear strength: conform to J Engineering SF-♂//6. No notch. / l Butt width x /10NN length j) Moisture permeability 2 degrees: According to ASTM E2t-, <4 (K).

6) Flexibility: Judging by the feel of the second hand, it was judged as l- based on the following criteria.

◎: Extremely soft ○: Soft △: Slightly hard ×: Hard 7) Surface strength: Cellotape was applied to the surface of the film, and when it was quickly peeled off, the state of peeling between the surfaces was observed and judged based on the following criteria.

19- ◎: No surface peeling ○: Almost no surface peeling △: Slight surface peeling ×: Large surface peeling The composition symbols in the table are Table-! As shown.

Examples 2 to 7 Porous films were obtained in exactly the same manner as in Example 1, except that the stretching temperature and stretching ratio were changed as shown in Table 1, and their performance was evaluated. The results are shown in Table-7.

Examples t~/θ A porous film was obtained in exactly the same manner as in Example 1, except that the blending ratios of the polymer, filler, and liquid hydrocarbon polymer were changed, and its performance was further evaluated. The results are shown in Table-/.

Comparative Example/~ A porous film was obtained in exactly the same manner as in Example/, except that the stretching temperature and stretching ratio were changed in a system in which no liquid hydrocarbon polymer was blended, and its 20-performance was further evaluated. The results are shown in Table 1, Examples //~/
j Liquid hydrocarbon polymers and liquid polybutadiene (manufactured by Nippon Soda ■, N15sOPBG) and liquid polybutene (manufactured by Nippon Petrochemical ■, Nisseki Polybutene HV-3θO)
), and those using Merck (manufactured by Nippon Talc ■, MS Talc) or diatomaceous earth as a filler were prepared in the same manner as in Example 1 and subjected to -axial stretching. Furthermore, the performance of the film was evaluated in the same manner.

The results are shown in Table-3.

Comparative example 6~? A raw film was formed in the same manner as in Example/, except that rubbery polybutadiene (registered trademark of Tufprene A1 Kagaku Kogyo ■) was added as a liquid hydrocarbon polymer to the formulation in Example/. Stretching was performed. Furthermore, the performance of the film was evaluated in the same manner. The results are shown in Table-3.

Comparative Example 2~/θ A raw film was prepared in the same manner as in Example 2, except that high-density polyethylene resin (Tubatic KR002, Tubatic is a registered trademark of Mitsubishi Chemical Industries, Ltd.) was used instead of the linear low-density polyethylene resin. was prepared and uniaxially stretched.

Furthermore, the performance of the film was evaluated in the same manner. Display the results -
Shown in 3.

Example 76~. 2θ and comparative examples//~7.2 Examples/
In Comparative Example 10, a raw film was prepared using the same formulation and method as in Example 10, and was sequentially and simultaneously biaxially stretched using a Long Stretching Machine K (manufactured by TM Long Co., USA).

In biaxial stretching, uniform stretching was possible at low magnification in all cases. Furthermore, the performance of the obtained film was evaluated in Example/
It was evaluated in the same way. The results are shown in Table D.

Comparative Examples 73 to 4 were prepared in the same manner as Comparative Examples 7 to 7, but in a system in which no liquid hydrocarbon was blended, and Example 4-. The performance of the obtained film was further evaluated in the same manner as in Example. Display the results -
Shown in da.

From Table 1, it can be seen that Examples 1 to 10 of the present invention are superior in various performances, including stretchability, in a well-balanced manner.

On the other hand, as shown in Table 2, the comparative examples of the present invention in which the liquid or waxy hydrocarbon polymer was not used caused breakage or uneven stretching during uniaxial stretching, resulting in L7 and even if stretching was possible, no gains were obtained. The tear strength of the film is extremely low.

According to Table 3, Comparative Examples t~ using a hydrocarbon polymer other than the liquid hydrocarbon bed used in the method of the present invention! It can be seen that the moisture permeability of the film obtained is extremely low even if -axial stretching is not possible, or even if it is possible to be stretched.

Furthermore, as shown in Comparative Examples and /θ, the base polymer using conventional high-density polyethylene has good stretchability, but the moisture permeability is lower than that of linear low-density polyethylene with the same blending ratio. Example using Example y/yet is only about half of that of Example y.

From the table, it can be seen that those using conventional high-density polyethylene as the base polymer, such as Comparative Examples // and /2,
Even if the biaxial stretchability is good, the moisture permeability is low. still,
Comparative Examples /3 and /Da, which did not use the liquid or waxy hydrocarbon 1 coalescence in the present invention, could not be stretched well.〇As is clear from the above results, linear low density polyethylene was filled. Films or sheets obtained from compositions containing a liquid or waxy hydrocarbon polymer exhibit better stretchability than conventional high-density polyethylene, and can be stretched at low stretching ratios. It has the advantage that it can be made porous, and the film or sheet is beautiful and has far superior flexibility.

Furthermore, the physical property balance of tear strength and moisture permeability is improved, and a wide range of applications are expected as films or sheets with continuous pores.

Sender: Mitsubishi Chemical Industries, Ltd.

Claims (5)

[Claims] (1) Porous, characterized by stretching a film or sheet obtained by melt-molding a composition made of a linear low-density polyethylene resin blended with a filler and a liquid wax-like hydrocarbon polymer. method of manufacturing a film or sheet. (2) The blending ratio of the composition is 2j to θOX parts of the filler to 100 parts by weight of the linear low-density polyethylene resin,
Liquid or waxy hydrocarbon polymer/~10θ″M
The manufacturing method according to claim 7, wherein the amount is in parts. (3) A liquid or waxy hydrocarbon polymer is
At least 7 molecules of liquid polybutadiene and liquid polybutene and hydrogenated liquid polybutadiene/
! The method according to claim 1 or 1, wherein the main chain having hydroxyl groups is a saturated or mostly saturated hydrocarbon polymer. (4) The manufacturing method according to any one of claims 1 to 3, wherein the stretching treatment is uniaxial stretching of at least 7.7 times. (5) The manufacturing method according to any one of claims 7 to 3, wherein the stretching process is a biaxial stretching of less than 1/2.