JPH0118091B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a porous film or sheet. Specifically, the present invention relates to a method for producing a porous film or sheet from a composition obtained by blending a filler and a liquid rubber with a polyolefin resin. Conventionally, many attempts have been made to uniaxially or biaxially stretch a film or sheet obtained by blending a filler into a polyolefin resin and melt-molding it as a means of producing a porous film. However, in these films, problems remain in the anisotropy of the film physical properties, especially the ease of tearing in the longitudinal direction (stretching direction) and surface strength, and in the biaxially stretched products, the film physical properties Although there is no problem with anisotropy, there are problems with surface strength and stretchability, and both tend to have high overall rigidity, which may be a drawback depending on the application. One method of improving the anisotropy and surface strength of the physical properties of the film is to stretch it at as low a magnification as possible to make it porous, but satisfactory results have not yet been obtained. Additionally, adding low-melting point polymers, rubber-like substances, plasticizers, surfactants, etc. can be considered as a method of imparting flexibility to the film, but the balance between physical properties such as porosity, stretchability, and surface strength can be considered. Nothing that satisfies this has yet been found. The present inventors have improved the drawbacks of these conventional porous films or sheets, and have achieved a good balance of physical properties and strong surface strength in uniaxial stretching, and excellent surface strength and stretchability in biaxial stretching. The present invention was arrived at as a result of intensive studies aimed at providing a porous film or sheet that both have high flexibility. That is, the gist of the present invention is to provide a method for producing a porous film or sheet, which comprises stretching a film or sheet obtained by melt-molding a composition obtained by blending a filler and liquid rubber with a polyolefin resin. exists in Hereinafter, the present invention will be explained in more detail. The polyolefin resin used in the present invention includes high-density polyethylene, polypropylene, and other α
- copolymers with olefins, etc. alone and
It is also used as a mixture of more than one species. Among them,
High-density polyethylene and polypropylene alone are preferably used, and high-density polyethylene is particularly preferred. Inorganic and organic fillers are used as fillers, and inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, and water. Aluminum oxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, clay silicate, etc. are used, especially calcium carbonate, talc, clay, and silica. , diatomaceous earth, barium sulfate, etc. are suitable. As the organic filler, cellulose powder such as wood flour and pulp powder is used. These may be used alone or in combination. The average particle size of the filler is preferably 30 μ or less, more preferably 10 μ or less, and 1 to 1 μm.
5μ is most preferred. If the particle size is too large, the density of the pores in the drawn product will be poor, and if the particle size is too small, the dispersibility in the resin will be poor and the moldability will be poor. 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. As the liquid rubber, liquid polybutadiene, liquid polybutene, etc. are used. Among them, hydroxyl-terminated liquid polybutadiene shows good results. The hydroxyl group-terminated liquid polybutadiene has a highly reactive hydroxyl group at the end of the polybutadiene. Further, derivatives of hydroxyl-terminated liquid polybutadiene are also used, and examples thereof include liquid products whose terminals are modified with isocyanate, maleic anhydride, or epoxy. However, unmodified products are preferable in terms of color and odor. It is presumed that the introduction of a material having a polar group at the terminal into the polyolefin resin and filler system will give preferable results in improving the compatibility between the two. Note that heat and ultraviolet stabilizers, pigments, antistatic agents, fluorescent agents, and the like may be added to the polyolefin resin according to conventional methods. When blending polyolefin resin, filler, and liquid rubber, the blending ratio is polyolefin resin.
Preferably, 25 to 400 parts by weight of filler and 1 to 100 parts by weight of liquid rubber are used per 100 parts by weight. If the proportion of the filler is less than 25 parts by weight, sufficient pores will not be formed in the stretched film, resulting in a low degree of porosity. If the proportion of the filler exceeds 400 parts by weight, the kneading 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 preferred blending ratio is 60 to 60 parts by weight of filler to 100 parts by weight of polyolefin resin.
It is 150 parts by weight. Regarding the blending ratio of liquid rubber, if it exceeds 100 parts by weight, the properties of the polyolefin resin will be weakened, and satisfactory kneadability, film or sheet moldability, and stretchability cannot be ensured. In the present invention, a more preferable blending ratio is 5 to
The amount is 50 parts by weight, more preferably 10 to 30 parts by weight. The polyolefin resin, filler, and liquid rubber can be blended by placing the three in an ordinary blender or mixer, but preferably the following method is used to improve mixability, filler dispersibility, and film or sheet production. Good in terms of moldability. The polyolefin resin is preferably in the form of a powder, and one with a mesh size of 10 to 150 is usually used, but one with a mesh size of 30 to 80 is more preferable from the viewpoint of uniformity and handling. As the mixer, a drum, a dumbler 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. As for the mixing order, polyolefin resin powder is first put into these mixers, liquid rubber is added thereto, and thoroughly stirred to spread the liquid rubber uniformly on the surface of the polyolefin resin. After reaching this state,
Filler is added and further stirred to obtain the final mixed composition. The advantage of using this method is that it is possible to prevent the formation of agglomerates that occur when liquid rubber and filler are directly brought into contact and dispersed, and it is possible to improve the dispersibility of filler in polyolefin resin during kneading. It is. Next, for kneading the mixture, a conventionally known device is used, such as a conventional screw extruder, a twin screw extruder, a mixing roll, a Banbury mixer,
This is carried out as appropriate using a twin-screw kneader or the like. By adding liquid rubber, the kneading torque can be significantly reduced in any kneading method.
It is useful for downsizing devices 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, T-die molding using a T-die, etc. may be employed as appropriate. The selection depends on the subsequent stretching method. That is, in the case of uniaxial stretching, roll stretching is usually preferred, but tubular stretching with emphasis on the uniaxial direction (take-up direction) may also be used. Further, the stretching may be carried out in one stage or in multiple stages of two or more stages. The characteristics of the uniaxial stretching of this composition are as follows: Porousness is achieved by low-magnification stretching. In other words,
When the stretching ratio is low, the interface between the matrix and the filler peels off, creating voids and forming so-called voids. Therefore, even at a low draw ratio of 1.2 times, porosity and whitening of the film occur.
This can be said to be an extremely unique phenomenon. This low-magnification stretching makes it possible to suppress anisotropy in the physical properties of the film or sheet, and also provides high surface strength. Low stretching stress. Due to the improved flexibility of the original fabric and the ability to make it porous by stretching at a low magnification as described above, it is possible to stretch with low stress during stretching. This leads to miniaturization and simplification of equipment and is very advantageous in terms of production costs. Stretching at low temperatures is possible. ), This is also related to the items above, but the stretching temperature can be lowered. Surprisingly,
The temperature at which porosity can be achieved ranges from the stretching temperature of a single polyolefin resin to room temperature. This is very advantageous in terms of equipment and energy saving. Usually, 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 of the composition of the present invention can be made porous at a stretching ratio of 1.2 to 6 times. This can be achieved even at low magnification. However, from the viewpoint of increasing porosity and reducing the anisotropy of the physical properties of the film or sheet, it is preferably 1.5 to 3 times. Next, the case of biaxial stretching will be described. Biaxial stretching showed extremely good stretching properties in both simultaneous and sequential stretching. Biaxial stretching also allows low stretching ratios, and uniform stretching and porosity can be achieved at least 1.2 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 at least 1.2 to 4.0 times in one direction. Preferably, it is 1.2 to 2.0 times. Further, by performing heat treatment after uniaxial stretching, biaxial stretching, and co-stretching, the precision 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 exhibits the following properties. Porosity: Because it has continuous pores, it has excellent moisture permeability and gas permeability. It also has good water pressure resistance. Physical properties of film or sheet: In uniaxially stretched products, anisotropy can be reduced, so
Good vertical and horizontal balance. Particularly good tear resistance in the longitudinal direction (stretching direction). Moreover, the surface strength can be increased. Biaxially stretched products have even less anisotropy and can have higher surface strength. Both uniaxially and biaxially stretched products have good flexibility. Processability: Heat bonding and shrink coloring are possible. Incinurability: Easily incinerated. Does not generate toxic gas. The film or sheet obtained according to the present invention may be utilized for various purposes by taking advantage of the above-mentioned properties. Examples include applications that utilize moisture permeability for clothing (waterproof products, rain gear, etc.), battery separators, filter materials (air dust removal, mist removal, industrial wastewater, and medical applications). Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples. Example 1 High-density polyethylene resin (Novatec BR002,
Novatec (registered trademark of Mitsubishi Chemical Industries, Ltd.) 20Kg
, hydroxyl group-terminated liquid polybutadiene [Product name:
Poly bd, R-45HT (manufactured by Idemitsu Petrochemical Co., Ltd.) 5Kg
were first stirred and mixed in a Henschel mixer, then 25 kg of calcium carbonate (average particle size 1.2μ, fatty acid treated) was added thereto, and further stirred and mixed. The mixture thus obtained was mixed in a twin-screw kneader.
DSM-65 (Double Screw Mixer, Japan Steel Works, Ltd.)
The mixture was kneaded and granulated in a factory. This was inflation-molded using a 40φ extruder to form a film with a thickness of 130μ. The extrusion conditions are as follows. Cylinder temperature: 150-180-180°C Head and die temperature: 180°C Take-up speed: 4 m/min, blow ratio = 1.3, fold diameter = 300 mm The film thus obtained was uniaxially stretched using a roll stretching machine. The stretching conditions are as follows: Stretching temperature: 100°C Stretching ratio: 2.2x Stretching speed: 4.4 m/min The stretched film is porous and sufficiently whitened, with no stretching unevenness and a porous film with a beautiful surface. It was hot. Table 1 shows the performance of this film. The measurement methods for the performance evaluation items in Table 1 are as follows. 1 Stretchability: ◎: No cutting, uniform stretching, no stretching unevenness 〇: No cutting, stretching unevenness, hardly any △: No cutting, stretching unevenness, slightly present ×: Large cutting or stretching unevenness 2 Porosity: From the following formula , calculated from the density of the film. Porosity (%) = D ₀ - D / D ₀ × 100 (%) D ₀ : Density of raw film (g/cm ² ) D: Density of stretched film (g/cm ² ) 3 Strength and elongation: 20mm width x 50mm length according to ASTM882-64T, tensile speed: 50mm/min 4 Moisture permeability: According to ASTM E96-66(E) 5 Surface strength: Apply sellotape to the film surface and peel it off quickly. The peeling condition of the surface was observed and the judgment was made based on the following criteria. ◎: No surface peeling ○: Almost no surface peeling △: Slight surface peeling ×: Large surface peeling The symbols for the compositions in the table are as shown in Table-5. Examples 2 to 8 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-1. Examples 9 to 13 Porous films were obtained in exactly the same manner as in Example 1, except that the blending ratios of the polymer, filler, and liquid rubber were changed, and their performance was further evaluated. The results are shown in Table-1. Comparative Examples 1 to 5 Porous films were obtained in exactly the same manner as in Example 1, except that the stretching temperature and stretching ratio were changed in a system in which no liquid rubber was blended, and the performance thereof was evaluated.
The results are shown in Table-2. Comparative Examples 6 to 8 Porous films were obtained in exactly the same manner as in Example 1, except that the blending ratios of the polymer, filler, and liquid rubber were changed as shown in Table 2, and their performance was further evaluated. The results are shown in Table-2. Examples 14 to 18 Liquid polybutadiene (Nisso PBG, manufactured by Nippon Soda Co., Ltd.) or liquid polybutene (Nisseki Polybutene LV-150, manufactured by Nippon Petrochemical Co., Ltd.) was used as the liquid rubber.
For those using talc (manufactured by Nippon Talc Co., Ltd., MS Talc) or diatomaceous earth as a filler, original fabrics were prepared in the same manner as in Example 1, and uniaxially stretched. Furthermore, the performance of the film was evaluated in the same manner. The results are shown in Table-3. Comparative Examples 9 to 11 Among the formulations in Example 1, as the liquid rubber, rubbery polybutadiene (Tuffrene A, Tuffrene is a registered trademark of Asahi Kasei Industries, Ltd.) or rubbery EPR (Tuffmer 0480, Tafmer is a registered trademark of Mitsui Petrochemical Industries, Ltd.) A raw film was formed in the same manner as in Example 1, except that the film (registered trademark of Co., Ltd.) was added, and uniaxial stretching was performed. Furthermore, the performance of the film was evaluated in the same manner. Display the results.
Shown in 3. Examples 19-20 A raw film was produced in the same manner as in Example 1, except that polypropylene resin (Novatek P4200Y, Novatek is a registered trademark of Mitsubishi Chemical Industries, Ltd.) was used instead of high-density polyethylene resin. Uniaxial stretching was performed. Furthermore, the performance of the film was evaluated in the same manner. The results are shown in Table-3. Examples 21 to 27 A raw film was produced using the same formulation and method as in Example 1, Examples 19 and 20, and was sequentially and simultaneously biaxially stretched using a Long stretching machine (manufactured by TM Long Co., Ltd. (USA)). did. In biaxial stretching, uniform stretching was possible at low magnification in all cases. Furthermore, the performance of the obtained film was evaluated in the same manner as in Example 1. Table of results-4
Shown below. Comparative Examples 12 to 13 In the same manner as Comparative Examples 1 to 5, a biaxial stretching operation was performed in the same manner as in Examples 21 to 27 in a system without liquid rubber, and the raw film was obtained. The performance of the film was evaluated in the same manner as in Example 1.
The results are shown in Table 4.

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[Table] As is clear from the above results, films or sheets obtained from compositions containing polyolefin resin, filler, and liquid rubber exhibit extremely excellent stretchability, and do not become porous when stretched at low ratios. Furthermore, the film or sheet has advantages such as being beautiful and highly flexible. In addition, it has a high shrinkage property due to heat, and is expected to be used in a wide range of applications as a film or sheet having continuous pores.

Claims (1)

[Scope of Claims] 1. A method for producing a porous film or sheet, which comprises stretching a film or sheet obtained by melt-molding a composition obtained by blending a filler and liquid rubber with a polyolefin resin. 2 The blending ratio of the composition is polyolefin resin
The manufacturing method according to claim 1, wherein the amount of filler is 25 to 400 parts by weight and the liquid rubber is 1 to 100 parts by weight per 100 parts by weight. 3. The manufacturing method according to claim 1 or 2, wherein the polyolefin resin is high-density polyethylene. 4. The manufacturing method according to claim 1 or 2, wherein the polyolefin resin is polypropylene. 5. The manufacturing method according to any one of claims 1 to 4, wherein the liquid rubber is liquid polybutadiene, liquid polybutene, or a derivative thereof. 6. The method according to any one of claims 1 to 5, characterized in that when blending the composition, a filler is mixed after dispersing and spreading the liquid rubber into the polyolefin resin powder. Production method. 7. The manufacturing method according to any one of claims 1 to 6, wherein the stretching treatment is uniaxial stretching of at least 1.2 times. 8. The manufacturing method according to any one of claims 1 to 6, wherein the stretching process is at least 1.2 times biaxial stretching.