JPH0676536B2 - Polypropylene coloring composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polypropylene coloring composition for obtaining a black colored molded product having no color unevenness.

The polypropylene resin to be colored in the present invention is an ethylene / propylene-block copolymer resin containing an inorganic extender, and this resin is characterized by high impact resistance, and is required for automobile parts, home appliances and other strength products. It is widely used as a molded product.

[Prior Art] Generally, in coloring plastics, black is considered to be the most difficult, and various efforts have been made to uniformly obtain a beautiful black tone.

Carbon black, graphite, iron black, phthalocyanine black, aniline black and the like are generally used as coloring pigments for coloring and molding polyolefin resins such as polyethylene and polypropylene in black.

Among these pigments, carbon black is particularly used in large amounts because it has excellent coloring power and is economically inexpensive.

[Problems to be Solved by the Invention] Generally, ethylene containing 0 to 40% by weight of an inorganic extender is used.
To color the propylene-block copolymer black, ordinary carbon black is blended, and this is melt-extruded and pelletized. However, when these pellets are subjected to an extrusion molding machine or an injection molding machine to mold a molded product, there is a defect that uneven coloring such as partial whitening occurs due to anisotropy of the flow direction of the molten resin during molding. It was

In order to prevent the occurrence of color unevenness, for example, ethylene
In the black coloring of propylene-block copolymers, a method of using iron black instead of carbon black has been proposed (Japanese Patent Publication No. 62-14576).

However, iron black does not have a coloring density as compared with carbon black, and therefore, to obtain a coloring density similar to that of carbon black, about 7 to 10 times as much iron black as carbon black is required. As a result, ethylene / propylene-block copolymer composites are characterized by high cost of colorants and high impact resistance when a large amount of iron black is used. There is a drawback that the strength of the resin is impaired.

An object of the present invention is to provide a black pigment which has a large degree of coloring with a small amount of compounding, does not cause deterioration of physical properties of a resin, and can be colored evenly when used with an inorganic filler.

[Means for Solving the Problems] The inventors of the present invention have conducted various studies on a black pigment that has a coloring density higher than that of iron black and does not cause color unevenness even when an inorganic filler is contained. As a result, it was found that if a furnace type carbon black having a very wide PH range, PH2 to 3 and a specific one having a particle size of 10 to 40 μm is used, the color unevenness does not occur,
The present invention has been completed based on this finding.

That is, the present invention, when coloring the ethylene / propylene-block copolymer containing 5 to 40% by weight of the inorganic extender with a black pigment, PH2
(3) A polypropylene coloring composition characterized in that the unevenness of color is prevented by using a furnace type carbon black having an average particle size of 10 to 40 μm.

Hereinafter, the present invention will be described in more detail.

The ethylene / propylene-block copolymer used in the present invention is what is commonly called a block copolymer, but in fact, it is a composition obtained by blending an ethylene / propylene copolymer with polypropylene, Usually, it is produced by multistage polymerization.

Usually, a blend of 1 to 50% by weight of an ethylene / propylene copolymer with 50 to 99% by weight of homopolypropylene is used.

That is, such a resin is obtained by, for example, polymerizing propylene in the first polymerization tank to produce polypropylene, transferring the polymerization liquid containing the polypropylene to the second reaction tank as it is, and adding ethylene gas to the second reaction tank together with propylene gas. It is fed to a reaction tank to produce an ethylene / propylene copolymer, which can be produced as a homogeneous blend with the polypropylene produced in the first reaction tank.

The method for producing the ethylene / propylene-block copolymer used in the present invention is described in JP-B-40-11623 and JP-B-43-112.
30 and Japanese Patent Publication No. 44-16668.

In the above production method, a resin composition produced in the same manner by mixing a small amount of olefin having 4 to 6 carbon atoms with propylene or ethylene as a raw material gas may also be used as the ethylene / propylene-block copolymer of the present invention. it can.

The molecular weight of the ethylene / propylene-block copolymer used in the present invention is not particularly limited, but is usually represented by MI and is 0.1
The thing of about 30 can be used.

Inorganic body material optionally used in the present invention, for example,
Silica, alumina, talc, clay, calcium carbonate,
Examples include barium sulfate and anhydrous gypsum.

These inorganic materials are mixed in an amount of 0 to 40% by weight based on the ethylene / propylene-block copolymer.

Generally, the furnace type carbon black is classified into a gas furnace type and an oil furnace type, but both are manufactured by burning gas or oil in a furnace with a burner and rapidly cooling and collecting the gas or oil.

The properties are very wide, and various properties are obtained by producing an oil-furnace type carbon black, and a wide range of PH from 2 to 9 is commercially available.

The black pigment used in the present invention is a furnace type carbon black having a pH of 2 to 3 and a particle size of 10 to 40 μm.

The furnace type carbon black used in the present invention is
PH2 to PH3 can be preferably used, and if PH3 is exceeded, color unevenness is likely to occur in a molded article having a complicated shape.

As described above, by using the specific furnace type carbon black, color unevenness does not occur even if there is anisotropy in the flow of the molten resin in the molding process.

The furnace type carbon black used in the present invention can be used in a mixing ratio of 0.1 to 7 parts by weight per 100 parts by weight of the ethylene / propylene-block copolymer resin.

In the present invention, if desired, other black pigments, for example,
Cupric oxide-manganese oxide-ferric oxide-based pigments, cupric oxide-chromium oxide-ferric oxide-based pigments or other carbon blacks can be added.

In the present invention, in addition to the black pigments described above, pigments that are generally used for coloring conventional plastics, for example, azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, perylene-based, indigo-based, indanthrene It is possible to use together organic pigments such as those based on cobalt, inorganic pigments such as cobalt blue, yellow lead, red iron oxide, chromium oxide, county blue, and dark blue.

The essential components of the composition of the present invention are the above-mentioned components, but if necessary, various carrier resins, dispersants, ultraviolet absorbers, stabilizers and other additives can be appropriately added.

The resin composition of the present invention can take various forms, but usually after mixing essential components with a mixer (Hensiel mixer), the mixture is melt-kneaded with a kneader such as an extruder,
It can be shaped into pellets and supplied as a molding material.

[Examples] The present invention will be described in more detail with reference to Examples.

Example Using the indicated PH 2.0, 2.5 and 3.0 furnace type carbon blacks, an ethylene / propylene-block copolymer having an ethylene content of 8% by weight and an MFR of 1.8 was used. 80 parts by weight of coalescence, 20 parts by weight of talc, and 1.5 parts by weight of furnace black were uniformly mixed in a mixing machine (Hensiel mixer), and extrusion molding was performed by an extrusion molding machine according to a conventional method to obtain colored pellets.

Use the injection molding machine (Meiki Seisakusho 7 _oz ) to
A plate-shaped molded product of 0 × 100 × 3 mm was molded. (Molding conditions: cylinder temperature 220 ° C., mold temperature 40 ° C.) The state of color unevenness and the degree of coloring of the molded plate were observed. The results are shown in Table 1.

Comparative Example Using the same resin as in Example, the pigments shown in Table 1 were used in the same blending ratio as in Example to uniformly mix them in a mixer (Hensiel mixer), and extrusion molding was performed by an extruder in accordance with a conventional method. Then, colored pellets were obtained.

Using an injection molding machine (Meiki Seisakusho 7 _oz ), the above pellets 1
A plate-shaped molded product of 20 × 100 × 3 mm was molded. (Molding conditions: cylinder temperature 220 ° C., mold temperature 40 ° C.) The state of color unevenness and the degree of coloring of the molded plate were observed. The result is shown in the first display.

Test method PH measurement method PH in the table was taken in a hard Erlenmeyer flask with 5 g of sample and 100 ml of water.
Was added and boiled for 5 minutes. At this time, the evaporated weight loss was supplemented by adding boiling water, then sealed and cooled to room temperature.

This supernatant liquid was transferred to a beaker, and the value was obtained by the PH measurement method using the glass electrode described in JIS Z8802 No. 7.

Volatile content measurement method Volatile content in the table was measured according to JIS 6221 6.4.1.

The particle size of the pigment indicates the average particle size.

From the results in this table, PH1.5-
It can be seen that when colored with the furnace type carbon black of No. 4, no color unevenness occurs and the degree of coloring is large. As compared with iron black, a large degree of coloring can be obtained with such a small addition amount, so that the deterioration of the physical properties of the resin due to coloring does not occur.

[Effects of the Invention] When the resin composition of the present invention thus obtained is molded into various shapes according to a conventional method, even if the molded product has a complicated shape, it is complicated in that case. Since there is no color unevenness due to the flow direction of the molten resin, the coloring of the surface is extremely uniform, and since the use of colorants is small,
There is an advantage that the coloring cost is not lowered and the physical properties of the resin are not lowered.

Claims (1)

[Claims] 1. When coloring an ethylene / propylene-block copolymer containing 5 to 40% by weight of an inorganic substance with a black pigment, the black pigment has a pH of 2 to 3 and an average particle size of 10 to 40 μm. A polypropylene coloring composition comprising a furnace type carbon black to prevent color unevenness.