JPH062849B2 - Polypropylene composition - Google Patents

Description

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

[Conventional technology and problems]

Conventionally, as a matting agent, anti-blocking agent, etc. for sheets and films using polypropylene,
Drawouts such as bands and yarns contain calcium carbonate having an average particle diameter of 2 to 3 μm in order 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, transparency and gloss are improved in a sheet or film, and stretchability is improved in a band or yarn. However, when polypropylene having 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 the case of a sheet or film, the transparency and gloss are deteriorated, and in a stretched product such as a yarn, 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]

The present inventors have conducted extensive studies to solve the above-mentioned problems with polypropylene having a narrow molecular weight distribution, and in addition to the above-mentioned inorganic fillers such as calcium carbonate,
It has been found that the above problems can be solved by blending silicon dioxide, and the present invention has been completed.

That is, the present invention is a polypropylene composition comprising 100 parts by weight of polypropylene having a ratio of weight average molecular weight to number average molecular weight of 7.5 or less, 0.01 to 0.5 parts by weight of silicon dioxide and 0.1 to 10 parts by weight of other inorganic filler. is there.

The polypropylene used in the present invention is a homopolymer of propylene; a block copolymer or a graft copolymer of 50 mol% or more propylene and α-olefin other than propylene such as ethylene, butene-1, pentene-1. Or a random copolymer; a mixture of these polymers; and a mixture of these polymers with a polymer of 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 molecular weight distribution is 7.0 or less, the inorganic filler can be effectively prevented from precipitating or accumulating at the die outlet at the time of molding by blending silicon dioxide described later.

Another component of the polypropylene composition of the present invention is an inorganic filler. The average particle size of the inorganic filler is not particularly limited, but even when an inorganic filler having a relatively large average particle size of 2 μm or more is used as described above, the inorganic filler to the die outlet at the time of extrusion molding according to the present invention is also used. Precipitation and deposition of the filler can be effectively prevented.

The type of inorganic filler is not particularly limited as long as it is other than silicon dioxide. For example, known inorganic fillers that can be added to polypropylene, such as calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, talc, and clay, are used according to their respective purposes.

The compounding amount of the inorganic filler is in the range of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of polypropylene. When the compounding amount is less than the above lower limit,
If the filling effect of the inorganic filler, that is, the effects such as matting and anti-blocking, cannot be obtained, on the other hand, when the amount is more than the above upper limit, the inorganic filler is added at the time of molding even if silicon dioxide described below is added. It is not possible to prevent the material from precipitating and depositing at the die outlet.

Another component of the polypropylene composition of the present invention is silicon dioxide. The average particle size of silicon dioxide is 3 μm or less, preferably 0.1 to 1. to prevent precipitation of the inorganic filler.
It is preferably in the range of 5 μm. Silicon dioxide may be either crystalline or amorphous. The blending amount of silicon dioxide is 0.01 to 0.5 with respect to 100 parts by weight of polypropylene.
The range of parts by weight is preferably 0.1 to 0.3. When the blending amount is less than 0.01 parts by weight, the effect of preventing the precipitation of the above-mentioned inorganic filler is small, and when it exceeds 0.5 parts by weight, the surface condition such as the gloss of the polypropylene composition molded article is adversely affected. Not preferred because of

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 or 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.

〔Example〕

The present invention will be described below 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 to the number average molecular weight measured by gel permeation chromatography, and the measurement conditions are as follows.

Equipment Waters GPC 1500 type column Tosoh GMH6-HT Measurement temperature 135 ° C. Solvent O-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: Highly 5: Very high Examples 1 to 5 and Comparative Examples 1 to 4 Polypropylene blended with calcium carbonate and silicon dioxide shown in Table 1 was 50 mmφ. Melt extruded into a film at 230 ° C. with a circular die of 0.8 mm die lip using the extruder of the above, and cooled and solidified while taking it off at 15 m / mm to obtain a polypropylene film, which was cut into a tape and then subjected to an oven stretching method. It was stretched 7 times at 130 ° C. to produce a 900 denier polypropylene stretch 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 5 to 7 Polypropylene blended with calcium carbonate and silicon dioxide shown in Table 2 was extruded at 240 ° C. with a die die 0.8 mm T die using a 40 mmφ extruder.
A sheet having a thickness of 0.5 mm was formed while taking it off at m / mm. 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 12 To 100 parts by weight of polypropylene having a molecular weight distribution of 6.5, 1 part by weight of the inorganic filler shown in Table 3 and 0.1 part of silicon dioxide are used.
Parts by weight were blended, and a sheet was formed using an extruder in the same manner as in Examples 6-8. The results are shown in Table-3.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08K 3:36)

Claims (1)

[Claims] 1. The ratio of the weight average molecular weight to the number average molecular weight is 7.
A polypropylene composition comprising 100 parts by weight of polypropylene of 5 or less, 0.01 to 0.5 parts by weight of silicon dioxide and 0.1 to 10 parts by weight of other inorganic fillers.