JPH0538753A - Stretched polyolefin film - Google Patents

Abstract

PURPOSE:To provide stretched polyolefin film having long-term stable antistatic properties without remarkable lowering of antistatic effect as compared with the antistatic of film before stretching even after stretching when organic antistatic agent is kneaded in polyolefin. CONSTITUTION:The base material of the film concerned is resin composition prepared by compounding 0.5-50 pts.wt. of polyoxyalkyene glycols having the molecular weight of 1,000-6,000 and 2-100 pts.wt. of inorgani.c porous powder having the voids of 0.75-0.95 with 1.00 pts.wt. of polyolefin. The film concerned is obtained by stretching the base material having the above-mentioned resin composition at least in one direction at the temperature lower than the meting point of the polyolefin in the base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched polyolefin film exhibiting an antistatic property equivalent to that of a polyolefin film before stretching. This stretched film is useful as a synthetic paper, a sanitary napkin, a waterproof sheet for disposable diapers, a bag, and a packaging film.

[0002]

2. Description of the Related Art Generally, polyolefin is widely used as a molding material for films, molded products, fibers and the like.
These usually have excellent electric insulation, waterproofness, and chemical resistance, but on the other hand, static electricity is easily charged and accumulated, which causes various obstacles and disasters. Therefore, conventionally, as a method of imparting antistatic properties to polyolefin, sorbitan fatty acid ester, a method of melt-kneading an organic antistatic agent such as glycerin monooleate with polyolefin and polyethyleneimine on the surface of the polyolefin product,
A method of applying an organic antistatic agent such as poly (ethyleneimine-urea) and a water-soluble quaternary cationic polyacrylate has been proposed (Japanese Patent Publication No. 60-34460, Japanese Patent Publication No. 2).
-2910 publication). In addition, inorganic fillers such as calcium carbonate, calcined clay, kaolin clay, vermiculite, and titanium oxide are kneaded with polyolefin together with an antistatic agent, extruded into a film, stretched, and then synthetic paper, sanitary napkins, and disposable diaper waterproofing materials. It is also known to produce (UK 13179911, USP 4318).
950, Japanese Examined Patent Publication No. 3-14057).

[0003]

However, when the polyolefin film is stretched by the former method of kneading the antistatic agent with the polyolefin, the antistatic effect is remarkably lowered as compared with the film before stretching. If a large amount of an organic antistatic agent is added to make up for this, the kneading processability deteriorates, and the physical properties and the like of the obtained stretched product also extremely deteriorate.
On the other hand, the latter method has a drawback that the antistatic agent on the surface of the polyolefin product is easily removed by friction and the antistatic effect is lost. Therefore, in the present invention, when an organic antistatic agent is kneaded into a polyolefin, the antistatic effect is not decreased even when stretched as compared with that of the film before stretching, and has a stable antistatic property for a long period of time. It is intended to provide a stretched polyolefin film.

[0004]

The present invention has a molecular weight of 1,000 to 6,000 relative to 100 parts by weight of polyolefin.
A resin composition prepared by mixing 0.5 to 50 parts by weight of polyoxyalkylene glycol of 0 and 2 to 100 parts by weight of inorganic porous powder having a porosity of 0.75 to 0.95 is used as a base material. A film, which is a stretched polyolefin film obtained by stretching in at least one direction at a temperature lower than the melting point of the polyolefin of the substrate.

The crystalline polyolefin used for this stretched film includes high density polyethylene, medium and low density polyethylene, linear low density polyethylene, polypropylene and the like, and they are used alone or as a mixture of two or more kinds.

The molecular weight used in the present invention is 1,0.
The polyoxyalkylene glycols of 00 to 6,000 include polyoxyalkylene glycol and its derivatives. As the polyoxyalkylene glycol,
Examples thereof include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyoxyethylene / oxypropylene / block polymer and the like.

Examples of the polyoxyalkylene glycol derivative include monofunctional or polyfunctional alcohols such as glycerin, sorbitol, trimethylolpropane and the above polyoxyalkylene glycol adducts of the derivative thereof, stearic acid, oleic acid, 12-hydroxystearic acid, Examples thereof include polyoxyalkylene glycol adducts of monofunctional or polyfunctional fatty acids such as adipic acid and derivatives thereof, nonylphenol, bisphenol A and polyoxyalkylene glycol adducts of derivatives thereof, and the like.

These polyoxyalkylene glycols can be used alone or in admixture of two or more, and it is important that the average molecular weight thereof is 1,000 to 6,000. When it is less than 1,000, the stretched film becomes sticky. On the other hand, if it exceeds 6,000, the antistatic effect is not sufficient.

The inorganic porous powder of the present invention includes diatomaceous earth (porosity about 0.80 to 0.86), perlite (porosity about 0.84 to 0.90), vermiculite (porosity about 0.83). .About.0.90) and the like. In the present invention, the porosity is more than 0.75 and 0.95 or less, preferably 0.1.
The inorganic porous powder in the range of 80 to 0.90 can be used alone or as a mixture of two or more kinds. When the porosity is within this range, the polyalkylene glycols can be favorably held by the apparent bore size (adsorption and collection size due to the interaction between the internal bore size and the surface shape) during kneading. It does not contain, for example, kaolin (about 0.55) having a porosity of less than 0.75 and silica gel (about 0.97) having a porosity of more than 0.95. This is because when the porosity is less than 0.75 and more than 0.95, the retention and effect of the polyalkylene glycol having an antistatic function are not sufficient, the kneading processability of the polyolefin composition is deteriorated, and the antistatic performance of the obtained stretched film is increased. Is not enough. Therefore, even if it is an inorganic powder, kaolin and silica gel which do not fall within the above range of porosity do not exhibit the effects of the present invention.

Here, the porosity means the ratio of voids in the bulk volume of the powder, and the formula is: porosity = (bulk volume of powder-volume of particles) / bulk volume of powder = 1- ( The bulk density of the powder / the true specific gravity of the powder). In addition, the bulk density of the powder is obtained by sufficiently drying the powder in advance,
The weight is precisely weighed, and then the powder is dispersed in a liquid (usually water) and filtered under reduced pressure to form a cake, and the cake volume is measured and calculated by the following formula. Bulk density = dry weight of powder / volume of cake The true specific gravity of the powder is measured according to JIS K-5101.

The blending ratio of the polyalkylene glycols to the polyolefin varies depending on the retention capacity of the inorganic porous powder, but is 0.5 to 50 parts by weight, preferably 2 to 100 parts by weight of the polyolefin depending on the use of the stretched film. It is compounded in a ratio of -40 parts by weight. Further, the inorganic porous powder is 2 to 1 with respect to 100 parts by weight of the above polyolefin.
The amount is 00 parts by weight, preferably 5 to 70 parts by weight. When the blending amount of the polyalkylene glycol is less than the above amount, the desired antistatic performance is not obtained in the stretched film, and when the amount is more than the above amount, the kneading processability of the polyolefin composition is deteriorated, and The physical strength of the drawn product thus obtained is significantly reduced. Further, when the blending amount of the inorganic porous powder is less than the above amount, sufficient holding ability is not exhibited, kneading processability deteriorates, sufficient antistatic performance cannot be obtained, and the obtained stretching The physical strength of the product decreases. When the amount exceeds the above amount, sufficient antistatic performance cannot be obtained, and the physical strength of the stretched product decreases.

The compounding ratio of the inorganic porous powder to the polyalkylene glycols varies depending on the retention capacity of the inorganic porous powder.
It is desirable to be blended in a ratio of 5.

The polyoxyalkylene glycols may be added to the polyolefin by, for example, adding the inorganic porous powder and the polyoxyalkylene glycols to the polyolefin separately and mixing them, or adding them to the polyolefin in a premixed state. Although any method such as a method of mixing can be adopted, it is more excellent in the sustainability of the antistatic performance of the stretched film and the melt-kneading processability of the polyolefin composition, when the both are mixed in advance and added to the polyolefin.

The polyoxyalkylene glycols and the inorganic porous powder can be mixed with the polyolefin by the same means as the known addition of various additives to the polyolefin, for example, a kneader, a mixing roll, an extruder. It may be kneaded under heating with a general kneader such as.

For stretching a stretched film from the kneaded polyolefin composition, a conventional stretching method may be adopted. For example, a method of stretching a blown film by a mandrel stretching method (stretching ratio of 1.35 times or more) by an extruder for 3.5 to 7 times between rolls having different speed ratios (3. 5-12 times stretch) is adopted.

[0016]

In the stretched film of the present invention, the antistatic performance before stretching is maintained even after stretching. In the present invention, since the inorganic porous powder is used even if a large amount of polyalkylene glycols having antistatic performance is blended, the polyalkylene glycols retain the apparent bore size of the inorganic porous powder. Therefore, the separation of the polyalkylene glycols from the polyolefin during the kneading process is hindered, and very good kneadability is obtained. Moreover, the physical strength of the obtained blend is hardly decreased.

When a polyolefin composition containing an organic antistatic agent composition such as an aliphatic amine, sorbitan oleate, or stearic acid glyceride is stretched at a temperature lower than the melting point of the polyolefin, these organic antistatic agents are formed by the orientation of polymer chains. It is generally contained in the blend and compatibilized with the polyolefin, and usually a stretched film does not have a sufficient antistatic effect. However, in the present invention, the polyalkylene glycol may be present in the matrix of the stretched film without being compatibilized with the polyolefin.

When a film is stretched, if inorganic powder or the like is present, microvoids are generated around the powder. The polyalkylene glycol is retained in the inorganic porous powder, and does not become compatible with the polyolefin during stretching, and forms a uniform coating layer of polyalkylene glycol on the inner surface of the microvoid. Furthermore, the polyalkylene glycols unevenly distributed in the surface of the inorganic porous powder and in the stretched film matrix form a conductive layer continuous in the thickness direction together with the polyalkylene glycol layer formed on the inner surface of the micro void, and have a low volume resistivity. It is considered that a stretched film having stable antistatic performance over a long period of time can be obtained.

[0019]

EXAMPLES The present invention will now be described with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 5) As an inorganic porous powder, diatomaceous earth (porosity 0.85) and polyethylene glycol (molecular weight 4000) as an organic antistatic agent were blended in the proportions shown in Table 1 to obtain polypropylene (melt index 10 g /
10 minutes, melting point 165 ° C), and 220 with a kneader
The mixture was melt-kneaded at 10 ° C. for 10 minutes and then pelletized with a pelletizer. Then, the pellets were melt-kneaded at 225 ° C. by an extruder and extruded into a sheet form from a die to obtain a polyolefin sheet having a thickness of 2 mm. It was used as a test piece before stretching.
Next, after heating this sheet to 155 ° C., it is stretched 5 times in the machine direction by utilizing the peripheral speed difference of the rolls, and heated again to stretch the longitudinally stretched sheet at 160 ° C. 6 times using a tenter,
Annealing treatment was performed at 4 ° C., and cooling to 50 ° C. was performed to obtain a biaxially stretched film. This was used as a test piece of a stretched product. Store each test piece at 20 ° C and 60% relative humidity and
After a day, the surface resistivity, the volume resistivity and the stickiness of the sheet were measured according to JIS K-6911. The results are shown in Table 2 together with Examples 1 to 5 and Comparative Examples 1 to 7.

Example 6 A test piece was obtained in the same manner as in Example 1 except that perlite (porosity 0.90) was used instead of diatomaceous earth.

Example 7 A test piece was obtained in the same manner as in Example 1 except that vermiculite (porosity 0.87) was used instead of diatomaceous earth.

Example 8 Example 1 was repeated except that polyoxyethyleneoxypropylene block polymer [Bronone 208 (trade name), molecular weight 2800, manufactured by NOF CORPORATION) was used in place of polyethylene glycol (molecular weight 4000). A test piece was obtained in the same manner.

Example 9 100 parts of polypropylene, 100 parts of diatomaceous earth and polyethylene glycol (molecular weight 4
000) 50 parts, except that the compounding ratio was changed to obtain a test piece in the same manner as in Example 1.

Comparative Example 1 A test piece was obtained in the same manner as in Example 1 except that diatomaceous earth was not used.

Comparative Example 2 A test piece was obtained in the same manner as in Example 1 except that kaolin (porosity 0.55, manufactured by Engelhard Co.) was used instead of diatomaceous earth.

Comparative Example 3 A test piece was obtained in the same manner as in Example 1 except that silica gel (porosity 0.97; manufactured by Mizusawa Chemical Co., Ltd.) was used instead of diatomaceous earth.

Comparative Example 4 A test piece was obtained in the same manner as in Example 1 except that polyethylene glycol (molecular weight 4000) was not used.

Comparative Example 5 A test piece was obtained in the same manner as in Example 6 except that polyethylene glycol (molecular weight 4000) was not used.

Comparative Example 6 A test piece was obtained in the same manner as in Example 7 except that polyethylene glycol (molecular weight 4000) was not used.

Comparative Example 7 A test piece was obtained in the same manner as in Example 1 except that oleic acid diethanolamide was used instead of polyethylene glycol (molecular weight 4000).

[0032]

As is clear from Table 2, the addition of diatomaceous earth, perlite and vermiculite does not improve the antistatic performance, and the organic antistatic agent alone does not provide a sufficient antistatic effect. However, when diatomaceous earth, perlite, and vermiculite are used in combination, the antistatic performance is remarkably improved because the volume resistivity is improved. Further, it can be seen that the volume resistivity hardly changes before and after stretching, and the antistatic function does not deteriorate. On the other hand, when diatomaceous earth, perlite, and vermiculite are not used together, the volume resistivity changes significantly before and after stretching. Also, when an organic antistatic agent other than polyoxyalkylene glycol and its derivative is used, the change in volume resistivity before and after stretching is remarkable.

[0033]

[Table 1]

[0034]

[Table 2]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B29K 23:00 4F B29L 7:00 4F (72) Inventor Masayuki Yamanaka Kamisu-machi, Kashima-gun, Ibaraki Prefecture 23 Towada, Oji Oka Synthetic Paper Kashima Plant Co., Ltd. (72) Inventor Yasuhiko Hara, Kamisu Town, Kashima-gun, Ibaraki Prefecture 23 Towada Oka Petrochemical Synthetic Paper Co., Ltd. Kashima Plant (72) Invention Atsushi Higashizuka, 4 Harima Kasei Co., Ltd., 671 Mizumizu, Noguchi-cho, Kakogawa-shi, Hyogo Prefecture (72) Inventor Ryo Inoue 4 Harima Kasei Co., Ltd., 671, Mizukushi, Noguchi-cho, Kakogawa-shi, Hyogo (72 4) Harima Kasei Co., Ltd. 4 at 671 Mizusui, Noguchi-cho, Kakogawa-shi, Hyogo Prefecture (72) Inventor Satoshi Iwasa 4 Harima-ization, 671 Mizusui, Noguchi-cho, Kakogawa-shi, Hyogo Prefecture Within Cheng Co., Ltd.

Claims (1)

[Claims] 1. 0.5 to 50 parts by weight of polyoxyalkylene glycol having a molecular weight of 1,000 to 6,000 and a porosity of 0.75 with respect to 100 parts by weight of polyolefin.
It is a film which uses as a base material a resin composition which mix | blends 2-100 weight part of inorganic porous powder of -0.95, Comprising: It stretches | stretches at least 1 direction at the temperature lower than the melting | fusing point of polyolefin of a base material. A stretched polyolefin film characterized by the following.