JP2654849B2 - Polypropylene composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polypropylene composition having good extrusion properties. More specifically, the present invention relates to a polypropylene composition having a good extrusion property, comprising a specific amount of a hydrotalcite compound and a hydrated silicate mineral of Mg.

[Conventional technology]

Polypropylene, for example, a polypropylene produced using a Ziegler-type catalyst, contains a halogen compound derived from the catalyst used. When the polypropylene containing the halogen compound is molded as it is, hydrogen halide is generated, causing rust in the molding machine. To capture the hydrogen halide, a fatty acid metal salt such as calcium stearate is blended.

On the other hand, it is known that polypropylene is mixed with talc, which is a hydrated silicate mineral of magnesium, for the purpose of improving physical properties such as rigidity.

[Problems to be solved by the invention]

By the way, in an extruder used for pelletizing or film forming, a screen mesh is used for removing foreign substances in a molten resin, increasing the back pressure in a barrel, improving the kneading degree of the resin, and stabilizing the extrusion. Usually, several sheets of 60 to 200 mesh are used by being stacked.

However, in the case where the polypropylene containing the above fatty acid metal salt and talc is molded using an extruder, talc adheres and accumulates on the screen mesh of the extruder, causing the screen mesh to be clogged and extruding over time. It has been found that the formability is significantly deteriorated due to a decrease or fluctuation in the amount, and in the case of a film or the like, fisheye is generated due to talc detached from the screen mesh, and the quality is reduced.

This phenomenon does not depend on the extrusion conditions such as the type of extruder (uniaxial or biaxial), screw shape, temperature, etc., but depends on the molecular weight distribution of the polypropylene used. Therefore, the narrower the distribution, the more clogging occurs. .

In addition, the rigidity and strength of polypropylene used for molding, particularly for obtaining films and fibers, can be improved by stretching orientation. Such stretching,
It may be performed in a state where the polypropylene is melted, or may be performed at a temperature considerably lower than the melting temperature of the polypropylene (so-called cold drawing). If the stretching is performed at a temperature much lower than the melting temperature of polypropylene,
From the viewpoint of stretchability, usually, polypropylene having a wide molecular weight distribution is used.

However, polypropylene having a wide molecular weight distribution has the following problems. That is, in the molding of polypropylene having a wide molecular weight distribution, there is a tendency that a lack of homogeneity occurs during stretching during melting. In addition, there is a problem that the anisotropy of physical properties is large, and particularly in forming a film or the like, the fluctuation width of the thickness is relatively large.

In view of these problems, the present invention is directed to polypropylene having no problem and having a narrow molecular weight distribution. That is, as described in detail below,
The present invention relates to a polypropylene having a weight average molecular weight / number average molecular weight ratio of 7 or less, and a composition in which a hydrous silicate mineral is blended with the polypropylene.

The present inventors have conducted intensive studies on the above-described problem of clogging, particularly on the problem of clogging that is particularly remarkable in the case of a narrow polypropylene having a molecular weight distribution targeted by the present invention. There was found. That is, when the clogging of the screen mesh is analyzed by an X-ray microanalyzer, calcium caused by calcium stearate used as a hydrogen halide scavenger is obtained,
Magnesium and silicon, which are the main components of talc, were mainly detected. From these results, the present inventors considered that the cause of the clogging was caused by the combination of calcium of calcium stearate and magnesium and silicon components of talc, and searched for a compound replacing calcium stearate.

[Means for solving the problem]

As a result, the present inventors have found that a hydrotalcite compound that is not an aliphatic metal salt as a substitute for calcium stearate is very effective, and have reached the present invention.

That is, the present invention is a polypropylene composition containing no metal salt of a fatty acid in the composition component, wherein the weight-average molecular weight / number-average molecular weight ratio is 7 or less, 100 parts by weight of polypropylene, and the hydrotalcite compound is 0.005 to 0.5 part by weight. And a hydrated silicate mineral of magnesium in an amount of 0.05 to 5 parts by weight.

The polypropylene used in the present invention is a homopolymer of propylene or an α-olefin other than propylene, for example, a copolymer of propylene with ethylene, butene-1, pentene-1, and the like, and these polymers or each other. A blend with the polymer is used without any limitation. The copolymer of α-olefin and propylene other than propylene may be a random copolymer or a block copolymer, and the content of the monomer unit based on α-olefin other than propylene is 10 mol% or less. Is preferred. Further, as the polymer used in the blend, low-density or high-density polyethylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-butene-1 copolymer, ethylene-methylpentene-1 copolymer, Styrene-butadiene copolymer and the like can be mentioned. The content of these other polymers is preferably 20% by weight or less.

The polypropylene used in the polypropylene composition of the present invention has a weight average molecular weight (Mw) and a number average molecular weight (Mn).
The molecular weight distribution represented by the ratio (Mw / Mn) is 7 or less. Such a polypropylene has good stretchability at the time of melting as described above, and is suitable for forming a film or the like.However, when hydrated silicate mineral of magnesium is mixed, clogging tends to occur. There is a great practical advantage in solving the problem of clogging.

Next, the hydrotalcite compound referred to in the present invention is:
Formula _{Mg x M y (OH) 2} (x-1) + 3y · CO 3 · nH 2 O ( where, M is Al, a Cr or Fe, x, y and n are positive numbers, x is 1 to 10 and y are preferably 1 to 5.)

Hydrotalcite compounds that can be suitably used in the present invention include, for example, Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O Mg ₅ Al ₂ ( OH) ₁₄ CO ₃ .4H ₂ O Mg ₈ Al ₂ (OH) ₂₀ CO ₃ .5H ₂ O.

The amount of the hydrotalcite compound used in the present invention in the polypropylene is 0.005 to 0.5 part by weight, preferably 0.01 to 2 parts by weight, per 100 parts by weight of the polypropylene. Hydrotalcite compound content
If it is less than 0.005 parts by weight, the rust prevention effect is insufficient, and if it exceeds 0.5 parts by weight, when the molded product is a film, for example, the film surface becomes rough or the transparency decreases, It is not preferable because the appearance of the product is impaired.

Next, the hydrated silicate mineral of magnesium in the present invention is:
Talc and the like, and as the one used in the present invention, talc or the like usually blended as a filler with polypropylene is used without any limitation. The amount is 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight, per 100 parts by weight of polypropylene.

When the amount of the hydrated silicate mineral of magnesium is less than 0.05 part by weight, there is no effect of improving the physical properties such as rigidity. Conversely, when the amount exceeds 5 parts by weight, the extrusion is performed even when the hydrotalcite compound is used in combination. Clogging of the screen mesh of the machine cannot be prevented.

The composition of the present invention may appropriately contain various additives other than the fatty acid metal salt as long as the effects of the present invention are not impaired. Specifically, as an additive, for example,
Examples include an antioxidant, a light stabilizer, an antistatic agent, a lubricant, a pigment, a nucleating agent, a filler, and a twist-resistant agent.

〔The invention's effect〕

Even when the propylene composition of the present invention is molded using an extruder equipped with a screen mesh, it does not cause clogging of the screen mesh, decreases the extrusion amount, deteriorates the moldability, and the quality of the molded product. Prevent drop. Moreover, according to the present invention, rust does not occur in the extruder due to the halogen compound contained in the polypropylene.

〔Example〕

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

Example 1 Polypropylene (MFI = 1.8 g / 10 min, Mw / Mn = 6.5) 100
A required amount of the hydrotalcite compound and talc shown in Table 1 was blended in parts by weight, mixed with a Henschel mixer, and then pelletized at 220 ° C. with an extruder.

Next, the pellets were extruded at 220 ° C. using a 65φ extruder in which three screens of 60 mesh, 100 mesh, and 60 mesh were set in this order, and the extruded amount after 1 hour and 24 hours was measured. As shown in Table 1, there was no change in the extrusion amount. After 24 hours, the screen mesh was removed and observed, and almost no clogging was observed.

Comparative Example The same operation was performed except that calcium stearate and calcium lauryl lactate were used instead of the hydrotalcite compound of Example 1. As shown in Table 2, the throughput decreased significantly after 24 hours. After 24 hours, the screen mesh was removed and observed. As a result, the entire screen mesh was covered with white deposits and clogging occurred.

Example 2 Polypropylene having a molecular weight distribution shown in Table 3 (MFI = 4 g / 10
min) 100 parts by weight of Mg as hydrotalcite compound
_4.5 0.1 parts by weight of Al ₂ (OH) ₁₃ CO ₃ · 3.5H ₂ O and 0.1 parts by weight of talc
After blending 5 parts by weight and mixing with a Henschel mixer, 220
C. and pelletized in an extruder at .degree. Next, the pellets were extruded by an extruder in the same manner as in Example 1, and the extrusion amounts after 1 hour and 24 hours were measured. As shown in Table 3, even when polypropylene having a narrow molecular weight distribution was used, when the hydrotalcite compound was used, there was no reduction in the extrusion amount, and almost no clogging of the screen mesh was observed. In addition, there was no decrease in physical properties due to the use of the hydrotalcite compound.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C08K 3:34) (72) Inventor Saburo Kawahara 2-3-1-1, Kamakura-shi, Kanagawa Toyo Chemical Inside (72) Inventor Takatoshi Suzuki 2-13-1, Dai, Kamakura-shi, Kanagawa Toyo Chemical Co., Ltd. (56) References JP-A-3-239742 (JP, A) JP-A 1-247427 (JP) JP-A-2-163143 (JP, A) JP-A-63-289714 (JP, A)

Claims (1)

(57) [Claims] 1. A composition comprising 100 parts by weight of polypropylene having a weight average molecular weight / number average molecular weight ratio of 7 or less, 0.005 to 0.5 parts by weight of a hydrotalcite compound and 0.05 to 5 parts by weight of a hydrous silicate mineral of magnesium. A polypropylene composition, which does not contain a metal salt of a fatty acid.