JPH0149302B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyolefin compositions. Specifically, the present invention relates to a polyolefin composition suitable for use in forming a film. Conventionally, polyolefin resins have been widely used for various purposes, and in particular, films have been widely used as packaging materials for various articles. For example, T-die molding, inflation molding, etc. are often used to produce films using polyolefin resin. Inflation molding, in which a cylindrical extrusion is performed, is especially used when trying to obtain a bag-shaped molded product. It is widely used because it is convenient. When forming a film by inflation molding or the like, in order to make the film transparent, the film extruded from a die is rapidly cooled using a coolant such as water. However, when the film is made transparent by this rapid cooling, the surface of the obtained film becomes smooth and the density decreases, making the film weak (reduced rigidity). As a result, even if a small amount of additives such as silica are added, the film surface cannot be made uneven; instead, the additives are incorporated into the film, causing the films to adhere to each other (blocking).
In other words, when cylindrical films are pressed flat and stuck together, or when a single film is wound into a roll, the films stick together and cannot be peeled off. This resulted in poor performance and was very inconvenient in practice. The present inventors have conducted various studies in order to solve the above-mentioned drawbacks of polyolefin resin, and as a result,
By combining two types of specific inorganic fillers with polyolefin resin and further adding a specific lubricant, it is possible to obtain a film that does not cause blocking even when formed by rapid cooling and has excellent transparency. The present invention has been completed based on this discovery. That is, the gist of the present invention is that 0.2 to 0.3% by weight of finely divided silica, 0.05 to 1% by weight of finely divided feldspar, and aliphatic carboxylic acid amide are added to a polyolefin resin.
The polyolefin composition contains 0.01 to 0.5% by weight. The polyolefin resin used in the present invention includes high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-
Vinyl acetate copolymers, etc., especially those with a density of 0.908~
Medium-low density polyethylene of 0.940 g/cm ² and linear low density polyethylene are suitable, and among them linear low density polyethylene is most suitable. Linear low density polyethylene is ethylene and other α
- It is a copolymer with olefin and is different from low-density polyethylene resin produced by conventional high-pressure methods. Linear low-density polyethylene is a copolymer of, for example, ethylene and other α-olefins such as butene, hexene, octene, decene, etc., and is a Ziegler-type catalyst or Phillips-type catalyst used in the production of high-density polyethylene by a medium-low pressure process. It is produced using conventional high-density polyethylene by copolymerizing it into a short branched structure, and the density is appropriately reduced by using this short chain branching to 0.91.
~0.935 g/cm ² , and is a polyethylene with a structure that is more linear than conventional low-density polyethylene and more branched than high-density polyethylene. The inorganic fillers that are combined with such polyolefin resins are finely powdered silica and feldspar. Powdered silica is a roughly spherical fine powder whose main component is silicon dioxide (SiO ₂ ), and there are naturally occurring types and artificially synthesized types. The silica used in the present invention may be natural silica or synthetic silica, but preferably has an average particle size of 1 to 10 microns, preferably 3 to 8 microns. If the average particle size of silica is smaller than this, it will cause agglomeration, resulting in poor dispersibility in the resin, and it will also be more likely to float in the air, causing environmental hygiene problems. It cannot be used because it gels after being molded and the appearance of the film becomes poor. The amount of silica blended in polyolefin resin is 0.2
The amount is ~3.0% by weight; if it is less than this, the anti-blocking effect will not be produced, that is, the opening property of the bag will be poor, and if it is more than this, the transparency of the film will be impaired. Fine powder feldspar is a roughly tabular powder whose main components are aluminosilicates such as calcium (Ca), sodium (Na), and potassium (K). It is divided into types such as anorthite and plagioclase, but it is usually a mixture of these. The feldspar used in the present invention may be in a mixed state as described above, and the proportion of each type of feldspar may be arbitrary, but those with an average particle size of 1 to 10 μm, preferably 3 to 8 μm are preferred. good. When measuring the average grain size of feldspar, the thickness was not taken into account because feldspar is tabular as mentioned above. It was observed with a microscope, and the average value of the long side and short side was determined, and this was taken as the average particle size. If the average grain size of feldspar is outside the above range, it is not preferable because it causes defects similar to those of silica. The amount of feldspar contained in polyolefin resin is 0.05~
The amount is 1% by weight, preferably 0.1 to 0.8% by weight; if it is less than this, the anti-blocking effect will not be produced, and if it is more than this, the transparency of the film will be impaired. Aliphatic carboxylic acid amides are used as specific lubricants used in conjunction with the above-mentioned combination of silica and feldspar. As the aliphatic carboxylic acid amide, a saturated or unsaturated fatty acid amide having a melting point of 50 to 110°C, preferably 70 to 90°C is used, and unsaturated fatty acid amide is particularly suitable. For example, olefinic acid amide {melting point (MP): 75℃}, erucic acid amide (MP: 80℃), ricinoleic acid amide (MP: 98℃), erucic acid amide (MP: 78-81
C), stearic acid amide (MP: 100° C.), oxystearic acid amide (MP: 105° C.), methylolic acid amide (MP: 107° C.), and the like. If the melting point is 110° C. or higher, when formed into a film, the speed at which it bleeds onto the surface of the film becomes too slow, and the film does not have good lubricity, making it difficult to contribute to the opening property when it is made into a bag. melting point
If the temperature is below 50°C, there are problems such as excessive bleeding, for example, adhesion to the surface of a take-up roll during molding and transfer to the film, causing poor transparency and giving a sticky feel. The amount of aliphatic carboxylic acid amide is usually 0.01~
0.5% by weight, preferably 0.05-0.2% by weight,
If the amount is less than this, good lubricity cannot be imparted to the film, and if it is more than this, the same defects as described above will occur due to excessive bleeding. The reason why film blocking can be effectively prevented when film is formed using the composition of the present invention has not been completely elucidated, but it is thought to be due to the following reasons. Silica and feldspar are each used as fillers in resins. However, even if each of these substances is added to the resin, no significant anti-blocking effect can be obtained. This is thought to be because silica has a roughly spherical shape as mentioned above, so the unevenness formed on the film surface is relatively uniform and smooth, and feldspar has a roughly spherical shape. This is thought to be because, since the film has a substantially flat plate shape, when the film is subjected to operations such as melt-stretching during film forming, it lines up substantially parallel to the film surface, and hardly any unevenness is formed on the film surface. However, when silica and feldspar having a predetermined average particle size are combined in a resin, the approximately spherical silica gets between the feldspars, and even when the film is subjected to operations such as melt-stretching, the feldspars do not touch the surface of the film. Since the particles are prevented from being arranged in parallel, an extremely large number of irregularities are formed on the surface of the film due to silica and feldspar, and it is thought that blocking of the film can be effectively prevented. As mentioned above, the composition of the present invention prevents blocking by forming a large number of fine irregularities on the film surface, and can produce a film having a relatively thin thickness, for example, 50 μm or less, preferably 40 μm or less. It is very effective when used to Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In the Examples, regarding transparency, the haze value (Haze) (%) was measured in accordance with JIS-K-6714, and those with a haze value of 4.5% or less were marked [○], and those with a haze value of 4.5 to 4.5% were evaluated.
Those with a haze value of 6.0% were evaluated as [△], and those with a haze value of 6% or more were evaluated as [x]. Regarding openability, the obtained film was made into a bag by heat sealing, and then two 12 cm x 10 cm overlapping test pieces were cut out from any position of the bag, and the test pieces were heated at 20°C. (relative humidity
60%) in a constant temperature room for 12 hours, then peel off both longitudinal ends of this test piece in a 1 cm width, leaving the adhesive surface 10
The test piece should be cm x 10 cm. The ends of the four peeled films were each fixed to a chuck, and the chuck was moved at a speed of 50 mm/min in the direction in which the film was torn off ^. If the value is less than 50g/ ^100cm2 [○], if it is 50 to 100g/ ^cm2 [△], 100
g/100cm ² or more was evaluated as [x]. Examples 1 to 3, Comparative Examples 1 to 4 Linear low density polyethylene (melt index (190°C): 1 g/10 min, density: 0.918 g/cm ² , copolymerization component: butene-1, copolymerization component amount :10% by weight)
Additives as shown in Table 1 were mixed into
450mm with a T-die with a clearance of 1mm), resin temperature 250℃, screw rotation speed.
Extrude downward at 50r.pm, extrusion rate 2Kg/hr., T
A water tank located 10 cm directly below the die (water temperature 20
The film was taken at a speed of 30 m/min while being rapidly cooled at 30°C (°C) to obtain a film with a thickness of 35μ. The transparency and openability of the obtained film were evaluated and shown in Table 1. In addition, in Examples and Comparative Examples, "Silica A"
is silica (manufactured by Fuji Davison Co., Ltd., product name: Thyroid #72) cm ² with an average particle diameter of 4 μ and a surface area of 270 m ² /gr. “Silica B” has an average particle diameter of:
3.3μ, surface area: 300m ² /gr silica (manufactured by Fuji Davison Co., Ltd., product name: Thyroid #244),
"Feldspar" is a feldspar with an average particle size of 4.5μ and a surface area of 1.4 (manufactured by Shiraishi Calcium Co., Ltd., trade name: Minex 7), and erucic acid amide is produced by Nippon Kasei Co., Ltd., trade name: Diamond It is L200. (The same applies to the following examples and comparative examples)

[Table] Note: All compounding amounts are in weight%.
Examples 4 to 5, Comparative Examples 5 to 6 Linear low density polyethylene (melt index) (190°C): 1 g/10 minutes, density: 0.921 g/cm, copolymerization component: butene-1, copolymerization component amount : 10% by weight) with the additives shown in Table 2, and an inflation molding machine (50φ extruder manufactured by Placo Co., Ltd.) having an annular slit with a diameter of 100 mm and a slit gap of 1 mm. (with die attached)
The resin temperature was 200℃ and the screw rotation speed was 560r.p.
m., an extrusion rate of 21 kg/hr., and a blow-up ratio of 1.5. A cooling ring is installed at a position 20 cm directly below the die to allow cooling water (20°C) to flow down along the outside of the cylindrical film, and the film is rapidly cooled. The film was taken at a speed of 30 m/min to obtain a film with a thickness of 40 μm. The transparency and opening properties of the obtained films were evaluated and shown in Table 2.

[Table] Note: All compounding amounts are in weight%.
Comparative Examples 7-8 Instead of linear low-density polyethylene, low-density polyethylene (manufactured by Mitsubishi Chemical Industries, Ltd., Novatek-L) was used.
F131, melt index (190℃): 1.3g/10
Examples 1 to 3 except that minute, density: 0.924) was used.
I got the film as well. The transparency and openness of the obtained film were evaluated and shown in Table 3.

[Table] Note: All compounding amounts are in weight%.

Claims (1)

[Claims] 1. 0.2% fine powder silica in polyolefin resin
-0.3% by weight, 0.05-1% by weight of finely divided feldspar, and 0.01-0.5% by weight of aliphatic carboxylic acid amide. 2. The composition according to claim 1, wherein the polyolefin resin is low density polyethylene. 3. The composition according to claim 1, wherein the polyolefin resin is linear low density polyethylene. 4. The composition according to any one of claims 1 to 3, wherein the silica has an average particle size of 1 to 10 μm. 5. The composition according to any one of claims 1 to 4, wherein the feldspar has an average particle size of 1 to 10 μm.