JPH07119330B2 - Polypropylene composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polypropylene composition having good moldability and stretchability.

(Prior art and problems to be solved by the invention) Conventionally, a sheet or film using polypropylene is used as a matting agent, an anti-blocking agent, etc.
Calcium carbonate having an average particle diameter of 2 to 3 μ is blended in a stretched material such as a band or a yarn to prevent warping and sowing.

By the way, when polypropylene having a narrow molecular weight distribution represented by the ratio of the weight average molecular weight to the number average molecular weight is used as the polypropylene, the transparency and gloss of the sheet or film are improved, and the stretchability of the band or yarn is improved. However, when polypropylene with a narrow molecular weight distribution is mixed with calcium carbonate having an average particle size of 2 μ or more and extrusion molding is performed, calcium carbonate is deposited at the die outlet, and the deposited calcium carbonate adheres to the surface of the polypropylene sheet or film. However, in sheets and films, transparency and gloss are deteriorated, and in stretched products such as yarns, stretch breakage occurs and productivity is significantly impaired. Such a phenomenon is not observed in polypropylene having a wide molecular weight distribution.

(Means for Solving the Problems) As a result of intensive studies to solve the above-mentioned problems with polypropylene having a narrow molecular weight distribution, the present inventors have formulated an inorganic filler having a specific average particle diameter. The inventors have found that the above problems can be solved by the above and have completed the present invention.

That is, the present invention is 100 parts by weight of polypropylene having a ratio of the weight average molecular weight to the number average molecular weight of 7.5 or less, and an inorganic filler having an average particle size of less than 1.5 μm and excluding silicon dioxide. It is a polypropylene composition consisting of about 10 parts by weight.

The polypropylene used in the present invention is a homopolymer of propylene; a block copolymer or a graft copolymer of 50 mol% or more of propylene and an α-olefin other than propylene such as ethylene, butene-1, and pentene-1. Or a random copolymer; a mixture of these polymers; and a mixture of these polymers with a polymer of an α-olefin other than propylene. The polypropylene used in the present invention has a molecular weight distribution represented by the ratio of the weight average molecular weight to the number average molecular weight of 7.5 or less. In the present invention,
Even if the above-mentioned molecular weight distribution is 7.0 or less, precipitation or deposition of the inorganic filler at the die outlet during molding can be effectively prevented by blending an inorganic filler having a specific average particle diameter described later.

The other component of the polypropylene composition of the present invention is an inorganic filler having an average particle size of less than 1.5 μm and excluding silicon dioxide. When an inorganic filler having an average particle size of more than 1.5 μm is used, the inorganic filler is precipitated and deposited at the die outlet during extrusion molding, and the effect of the present invention cannot be obtained. The average particle size of the inorganic filler should be less than 1.5 μm, but in order to completely prevent the precipitation and deposition of the inorganic filler at the die outlet during molding, it should be in the range of 0.1 to 1.2 μm. preferable.

The type of the inorganic filler is not particularly limited, except for silicon dioxide, as long as the average particle size is less than 1.5 μm. The inorganic filler in the present invention is an inorganic filler known to be added to polypropylene such as calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, talc, clay, etc., depending on the purpose. The content of the material is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of polypropylene. If the content is less than the lower limit below, the effect of filling the inorganic filler, that is, the effect of matting or anti-blocking cannot be obtained, while if it is more than the above upper limit, Even if the inorganic filler having a particle diameter of 1 is added, it is not possible to prevent the inorganic filler from precipitating and depositing at the die outlet during molding.

The polypropylene composition of the present invention may be blended with additives usually used within a range that does not impair the effects of the present invention, for example, antioxidants, dispersants, lubricants, colorants and the like.

(Effect) According to the present invention, it is possible to prevent precipitation and deposition of the inorganic filler at the die outlet during extrusion molding. For this reason, the inorganic filler deposited at the die outlet does not deteriorate the transparency and gloss of the polypropylene molded body by adhering to the surface of the polypropylene molded body, and even in the case of a stretched product, stretching breakage may occur. Nothing.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
The present invention is not limited to these examples.

The molecular weight distribution of polypropylene in Examples and Comparative Examples is the ratio of the weight average molecular weight and the number average molecular weight measured by gel permeation chromatography, and the measurement conditions are as follows.

Equipment Waters GPC 150C type column Tosoh GMB6-HT Measurement temperature 135 ° C. Solvent 0-dichlorobenzene The amount of the inorganic filler deposited at the die outlet was visually evaluated according to the following criteria.

1: Not precipitated at all 2: Slightly precipitated 3: Slightly high 4: High 5: Very high Examples 1 to 5 and Comparative Examples 1 to 6 Polypropylene blended with calcium carbonate shown in Table 1 was extruded at 50 mmφ. Using a machine, melt-extrude into a film at 230 ° C with a circular die with a die lip of 0.8 mm, 1
A polypropylene film was obtained by cooling and solidifying while drawing at 5 m / min to obtain a polypropylene film, which was cut into a tape shape and stretched 7 times at 130 ° C. by an oven stretching method to produce a 900 denier polypropylene stretched tape. The compounding amount of calcium carbonate is 2 parts by weight based on 100 parts by weight of polypropylene.

Examples 6 to 8 and Comparative Examples 7 to 11 Polypropylene blended with calcium carbonate shown in Table 2 was used with an extruder having a diameter of 40 mm and a die rive of 0.8 mm.
A sheet having a thickness of 0.5 mm was formed by extruding with a T-die at 240 ° C. and taking it out at 2 m / min. At this time, the state of precipitation of calcium carbonate at the die exit was observed. The compounding amount of calcium carbonate is 5 parts by weight based on 100 parts by weight of polypropylene.

Examples 9 to 10 1 part by weight of the inorganic filler shown in Table 3 was added to 100 parts by weight of polypropylene having a molecular weight distribution of 6.5, and Examples 7 to 10 were added.
A sheet was formed using an extruder in the same manner as in. The results are shown in Table-3.

Claims (1)

[Claims] 1. The ratio of the weight average molecular weight to the number average molecular weight is 7.
100 parts by weight of polypropylene that is 5 or less and the average particle size
A polypropylene composition comprising 0.1 to 10 parts by weight of an inorganic filler less than 1.5 μm and excluding silicon dioxide.