JP3174149B2 - Polypropylene composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polypropylene composition having reduced whiteness.

[0002]

2. Description of the Related Art Polypropylene is widely used in various fields because of its excellent mechanical properties and heat resistance. However, since polypropylene has high crystallinity, there is a problem that transparency is inhibited by crystal particles. Among polypropylene, propylene homopolymer or propylene-α-olefin random copolymer has relatively good transparency, but still becomes white and turbid due to its thickness when these resins are molded into sheets. However, there was a problem that transparency was poor. For example, in the case of a propylene-ethylene random copolymer sheet having a thickness of 3 mm, the whiteness is 32.3 and the whiteness is cloudy, and lacks in transparency.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the whiteness of the above-mentioned propylene homopolymer or propylene-α-olefin random copolymer and to expand the uses thereof.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In order to improve the whiteness of propylene homopolymer or propylene-α-olefin random copolymer (hereinafter, these may be simply referred to as polypropylene), research was carried out to achieve the purpose by mixing various additives. .
As a result, surprisingly, the above-mentioned object was successfully achieved by adding a very small amount of carbon black to the above-mentioned polypropylene, and the present invention was proposed. Only
While adding a blue pigment and a red pigment to the thermoplastic resin
Together with a limited amount of black pigments such as carbon black
Improve the UV transmittance of the resin by adding and mixing
An invention to be attempted has been proposed (JP-A-61-26).
No. 8744) to clarify the difference in constitution from the present invention.
Therefore, the present invention is specified as follows.

That is, the present invention relates to a propylene homopolymer and / or a propylene-α-olefin random copolymer containing 1 to 10 ppm of carbon black and
The use of two pigments, a color pigment and a red pigment, in combination
Excluding polypropylene composition.

The polypropylene used in the present invention is a homopolymer of propylene and a random copolymer of propylene other than propylene, for example, ethylene, butene-1, pentene-1 and the like. The content of monomer units based on α-olefin in a random copolymer of α-olefin other than propylene and propylene is preferably 10 mol% or less. Also,
Blends of these polymers with each other or with other polymers can also be used in the present invention. Other polymers used in the blend include low 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 20% by weight
The following is preferred.

The carbon black used in the present invention is:
Known ones can be used without any limitation. For example, carbon black such as furnace black, thermal black, lamp black, acetylene black, and channel black can be exemplified. The average particle size of the carbon black used in the present invention is preferably in the range of 5 to 50 nm.

The amount of the carbon black to be added to the polypropylene must be 1 to 10 ppm in the polypropylene, and is preferably in the range of 2 to 8 ppm.

[0009] When the amount of carbon black is less than 1 ppm, the effect of improving the whiteness of the polypropylene is not observed. Conversely, when the amount exceeds 10 ppm, the polypropylene composition is colored black and the transparency is lowered. Not preferred.

The above-mentioned mixing of the polypropylene and the carbon black is generally carried out at a temperature higher than the melting point of the propylene homopolymer or the propylene-α-olefin random copolymer by using a known kneading apparatus. For example, using a screw extruder, a Banbury mixer, a mixing roll, or the like, 160-330 ° C., preferably 170 ° C.
A method of kneading at ~ 300 ° C can be adopted. In the present invention, since the blending amount of carbon black is extremely small, it is preferable to employ a masterbatch method in order to favorably disperse carbon black in polypropylene.

[0011]

The polypropylene composition of the present invention has improved whiteness of a propylene homopolymer or a propylene-α-olefin random copolymer, and is usually 25 to 25.
It has a whiteness of 30. Further, an effect of improving transparency can be recognized.

[0012]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Examples and Comparative Examples Propylene-ethylene random copolymer (MFI = 1.
8 g / 10 min, ethylene content 2.3 mol%)
Was mixed in a Henschel mixer and then pelletized at 220 ° C. with an extruder.

Using the obtained pellets as a raw material, 50 TON
A whiteness test piece having a thickness of 3 mm was prepared using an injection molding machine, and the whiteness of each test piece was measured using a color computer SM-3.
(Manufactured by Suga Test Instruments Co., Ltd.). Similarly, a sheet having a thickness of 0.6 mm was formed, and the transparency was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.). Table 1 shows the results.

[0015]

[Table 1]

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 23/00-23/36 C08K 3/00-13/08

Claims (1)

(57) [Claims] 1. A propylene homopolymer or propylene-
α-olefin random copolymer with carbon black 1
10 ppm of blue pigment and red pigment
A polypropylene composition excluding the use of two pigments in combination .