JPH0441539A - Polypropylene composition - Google Patents

Abstract

PURPOSE:To prevent the clogging of a screen mesh by compounding a polypropylene with specified amts. of a hydrotalcite compd. and a magnesium hydrosilicate mineral. CONSTITUTION:100 pts.wt. polypropylene having a mol.wt. distribution (expressed by the ratio of the wt.-average to the number-average mol.wt.) of 7 or lower is mixed with 0.005-0.5 pt.wt. hydrotalcite compd. of formula I (wherein M is Al, Cr, or Fe; (x) is 1-10; (y) is 1-5; and (n) is a positive number) (e.g. a compd. of formula II) and 0.05-5 pts.wt. magnesium hydrosilicate mineral (e.g. talc), pelletized, and extrusion molded at 220 deg.C on an extruder equipped with a 60- to 100-mesh screen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polypropylene composition with good extrusion properties. More specifically, the present invention relates to a polypropylene composition with good extrusion properties that contains a specific amount of a hydrotalcite compound and a hydrated Mg silicate mineral.

[Conventional technology]

Polypropylene, for example polypropylene produced using a Ziegler type catalyst, contains halogen compounds resulting from the catalyst used.

If polypropylene containing this halogen compound is molded as is, hydrogen halide is generated, causing rust in the molding machine. To capture this hydrogen halide, fatty acid metal salts such as calcium stearate are included.

On the other hand, it is known that talc, which is a hydrous silicate of magnesium, is added to polypropylene for the purpose of improving physical properties such as rigidity.

[Problem to be solved by the invention]

By the way, screen mesh is used in extruders used for berentization, film molding, etc. in order to remove foreign matter from the molten resin, increase back pressure inside the barrel, improve the degree of kneading of the resin, and stabilize extrusion. Usually, several sheets of 60 to 200 pieces are stacked together and used.

However, when polypropylene blended with fatty acid metal salts and talc is molded using an extruder, talc adheres to and accumulates on the screen mesh of the extruder, causing clogging of the screen mesh and causing problems over time. Along with this, the extrusion rate decreased or fluctuated, resulting in a marked deterioration in formability, and in the case of films, it was found that fins were formed due to sag that separated from the screen mesh, degrading quality. .

This phenomenon is caused by the type of extruder (-shaft, twin-screw, etc.) and screw shape. Although it does not depend on extrusion conditions such as temperature, it depends on the molecular weight distribution of the polypropylene used, and the narrower the distribution, the more clogging occurs.

As a result of intensive study on this problem, the present inventors found that
The following was discovered. That is, when clogging the screen mesh is analyzed using an X-ray microanalyzer,
Calcium derived from calcium stearate, which was used as a hydrogen halide scavenger, and magnesium and silicon, which are the main components of talc, were mainly detected. Based on this result, the present inventors believed that the cause of clogging was the combination of calcium in calcium stearate and the magnesium and silicon components of talc, and searched for a compound to replace calcium stearate.

[Means to solve the problem]

As a result, the present inventors discovered that a hydrotalcite compound is very effective as a substitute for calcium stearate, and have arrived at the present invention.

That is, the present invention is a polypropylene composition comprising 100 parts by weight of polypropylene, 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.

The polypropylene used in the present invention is a homopolymer of propylene, a copolymer of propylene with an α-olefin other than propylene, such as ethylene, butene-1, pentene-1, etc., or a copolymer of propylene with each other or other polymers. Blends with polymers can be used without any restriction.

The copolymer of α-olefin other than propylene and propylene may be either a random copolymer or a block copolymer, and the content of monomer units based on α-olefin other than propylene is 10 mol% or less. It is preferable. Polymers used in blends include low-density or high-density polyethylene, polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-butene-1 copolymer, ethylene-methylhentene-1 copolymer, and styrene. -butadiene copolymers and the like. The content of these other polymers is preferably 20% by weight or less.

The present invention provides a weight average molecular weight (Mw) of the polypropylene.
) and number average molecular weight (Mn) (Mw/Mn) is 7 or less, the effect is particularly remarkable.

Next, the hydrotalcite compound referred to in the present invention is 2MgXMy(Of()z(X-11+37 HCO
:+ ・nLO (However, M is AI, Cr or Fe
, Xy and n are positive numbers, and X is 1 to 10.
V is preferably 1 to 5. ).

Hydrotalcite compounds that can be suitably used in the present invention include, for example, Mg68l 2 (01(), hcO3-4H20Mg
a, SA]2(O)I) 13CO3・3.5820
Mg5A12 (Kano), Co, 4H20”geAlz
Examples include structures such as (OH)zocO3.5H20.

The blending amount of the hydrotalcite compound used in the present invention in polypropylene is as follows: Polypropylene 1003i
0.005 to 0.5 parts by weight, preferably 0
．． The range is 0.01 to 0.2 parts by weight. If the amount of the hydrotalcite compound is less than 0.005 parts by weight, the rust prevention effect will be insufficient, and if it exceeds 0.5 parts by weight, the film surface will be It is not preferable because it causes roughness and decreases transparency, impairing the appearance of the molded product.

Next, in the present invention, the hydrated magnesium silicate mineral is talc or the like, and the talc or the like that is usually blended into polypropylene as a filler can be used without any restriction.

Further, the blending amount thereof is 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight, per 100 parts by weight of polypropylene.

If the amount of hydrated magnesium silicate 112: is less than 0.05 parts by weight, there will be no effect on improving physical properties such as rigidity (on the contrary, if it exceeds 5 parts by weight, hydrotalcite compounds may be used in combination) However, it is not possible to prevent clogging of the screen mesh of the extruder.

Incidentally, various additives may be appropriately added to the composition of the present invention within a range that does not impair the effects of the invention. Specific examples of additives include antioxidants, light stabilizers, antistatic agents, lubricants, pigments, nucleating agents, fillers, flame retardants, and the like.

〔Effect of the invention〕

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, resulting in a decrease in extrusion rate, deterioration of moldability, and molded products. Prevent quality deterioration. Moreover, according to the present invention, rust does not occur in the extruder due to the halogen compound contained in polypropylene.

〔Example〕

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Polypropylene (MFI-1.8g/lomin, M
Required amounts of the hydrotalcite compound and talc shown in Table 1 were added to 100 parts by weight of w/Mn=6.5), mixed in a Henschel mixer, and then pelletized in an extruder at 220°C.

Next, add this beret to 60 mesh, 100 mesh, 6
6. Cented 3 screens with 0 mesh in this order.
It was extruded at 220° C. using a 5φ extruder, and the amount of extrusion was measured after 1 hour and 24 hours. As shown in Table 1, no change in the extrusion rate was observed. When the screen mesh was removed and observed after 24 hours, almost no clogging was observed.

Comparative Example The same operation was carried out as in Example 1, except that carnoum stearate and carnoum lauryl lactate were used instead of the hydrotalcite compound. As shown in Table 2, the extrusion rate decreased significantly after 24 hours.

After 24 hours, the screen mesh was removed and observed, and it was found that the entire screen mesh was covered with white deposits and was clogged.

Below 1, Example 2 Polypropylene (MFI-4g
/10mln) 100 parts by weight of Mg4. s to lz (OH) l 3C03
・3.5) 0.1 part by weight of 120 and 0.5 part by weight of talc were mixed in a Henschel mixer, then 220
Pelletization was performed using an extruder at °C. Next, the pellets were extruded using an extruder in the same manner as in Example 1, and after 1 hour and 2
The extrusion amount after 4 hours was measured. As shown in Table 3, even when polypropylene with a narrow molecular weight distribution was used, when a hydrotalcite compound was used, there was no decrease in the extrusion rate, and almost no clogging of the screen mesh was observed.

Furthermore, there was no deterioration in physical properties due to the use of the hydrotalcite compound.

Margin below, -)

Claims (1)

[Claims] 1. A polypropylene composition containing 100 parts by weight of polypropylene, 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.