JP2704968B2 - Polypropylene composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polypropylene composition having improved transparency, which is obtained by blending talc having a very small particle size with polypropylene in a very small amount.

(Problems to be Solved by the Prior Art and the Invention) Polypropylene is widely used as a resin having excellent mechanical properties, transparency, moldability, and chemical stability. However, transparency is generally inferior to other resins such as polystyrene and polyvinyl chloride due to high crystallinity.

Several attempts have been made to improve the transparency of polypropylene. For example, it is known that by adding a nucleating agent such as a sorbitol derivative or a sodium or aluminum salt of an aromatic carboxylic acid to polypropylene, the spherulites of the molded product become smaller and uniform, and the transparency of the molded product is improved. (Eg, JP-A-58-80392 and JP-A-55-12460). However, these organic nucleating agents have a problem in that they bleed from the resin at the time of molding, particularly at the time of forming a sheet or a biaxially stretched film, thereby causing roll contamination, and causing odor during processing. Further, the aromatic carboxylate has a problem of hydrolyzing the aromatic carboxylate or coloring the resin by reacting with other additives.

By the way, it is already well known that the blending of talc with polypropylene improves the dimensional stability, impact resistance and heat-resistant rigidity of molded products, and many proposals have been made. For example, JP-A-57-177038 discloses that the average particle size is
It is described that 1 to 30 parts by weight of talc of about 1.3 to 3.0 μm is blended with respect to 100 parts by weight of polypropylene,
Further, JP-A-57-73033 discloses an average particle size of 0.2 to 1.5.
μm talc to about 5 parts per 100 parts by weight of polypropylene
It is described that 150150 parts by weight is blended.

As described above, conventionally, a large amount of talc having a relatively large average particle diameter is blended with polypropylene to improve the dimensional stability, impact resistance, and heat resistance of a polypropylene molded product. However, there is no example of using talc for improving the transparency of polypropylene.

(Means for Solving the Problems) The present inventors have conducted intensive studies on polypropylene having improved transparency, and as a result, surprisingly, talc having an extremely small particle size was reduced to a very small amount in polypropylene. It was found that the addition of the compound significantly improved the transparency of polypropylene, and it was found that even when a film such as a sheet or a biaxially stretched film was formed, it did not bleed and was excellent in moldability, thereby completing the present invention.

That is, the present invention is a polypropylene composition comprising 100 parts by weight of polypropylene and 0.0001 to 0.1 part by weight of talc having an average particle size of 0.001 to 0.1 μm.

The polypropylene used in the present invention is a homopolymer of propylene; a block copolymer of 50 mol% or more of propylene and an α-olefin other than propylene such as ethylene, butene-1, pentene-1, and 4-methylpentene-1. Coalescing,
Graft copolymers or random copolymers; mixtures of these polymers; and mixtures of these polymers with α-olefin polymers other than propylene.

Talc used in the present invention has an average particle size of 0.001 to 0.1 μ
m, preferably 0.005 to 0.05 μm. Average particle size
If the thickness exceeds 0.1 μm, transparency cannot be improved.
On the other hand, if it is less than 0.001 μm, uniform dispersion becomes difficult due to aggregation of talc particles, and not only transparency is not improved, but also production of such ultrafine talc is difficult.

The average particle diameter of talc in the present invention is obtained by sampling a sample of talc, measuring a major axis (a) and a minor axis (b) of 100 particles observed by a transmission electron microscope, and measuring each particle by the following formula. The particle diameter (D) is calculated, and the particle diameter (D) is represented by an arithmetic mean value of 100 particles.

Particle size (D) = (a + b) / 2 The amount of talc used in the present invention is polypropylene.
0.0001 to 0.1 part by weight, preferably 0.001 part by weight, per 100 parts by weight
1 to 0.05 parts by weight. If the amount is less than 0.0001 parts by weight, transparency is not sufficiently exhibited. If it exceeds 0.1 parts by weight,
It is not preferable because talc particles are aggregated to cause poor dispersion.

Talc having such a fine particle size is marketed by Sumitomo Cement Co., Ltd. as ultrafine talc. Further, it may be produced by a known method. For example, it may be produced by any other method such as a method of sufficiently pulverizing with a micron mill or the like, followed by classification with an air classifier and various filters. The talc used in the present invention may be subjected to a surface treatment with a compound such as various silane coupling agents, various higher fatty acids, and organic titanates.

In the polypropylene composition of the present invention, additives usually used in a range that does not impair the effects of the present invention, for example, an antioxidant, a dispersant, a lubricant, an antistatic agent, an antiblocking agent, a colorant and the like are compounded. Is also good.

The components of the polypropylene composition of the present invention are kneaders usually used, for example, a single-screw kneader, a twin-screw kneader, rolls, mixed using various kneaders such as Brabender plastogram, and then into a pellet. A molding process may be performed. Further, the talc used in the present invention may be blended with the granular polypropylene particles taken out from the polymerization tank and directly molded. Further, talc used in the present invention is previously blended with polypropylene at a high concentration to produce a masterbatch, which is then mixed with polypropylene and diluted so that the amount of talc falls within the range of the blending amount of the present invention.
It can also be used for molding.

(Effects) The transparency of the polypropylene according to the present invention is remarkably improved, and a polypropylene composition having excellent processability can be obtained without forming a stain on a film-forming roll even when forming into a sheet or a biaxially stretched film. it can.

(Examples) Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

In addition, the following methods evaluated the transparency of the molded product of the polypropylene composition obtained in the following Examples and Comparative Examples, and the stain state of the roll.

<Transparency evaluation method> (1) Haze value Measured according to JIS-K6714.

(2) Visual Perspective Evaluation (Film Only) Five obtained 40 μm films were stacked in the same stretching direction, and five layers were visually observed. , 1-bad).

<Observation of Roll Soil Condition> Judgment was made based on the stain condition of the cooling roll for cooling and solidifying the resin extruded from the T-die and the sheet preheating roll of the longitudinal stretching device.

Examples 1 to 5 To 100 parts by weight of a homopolypropylene powder having a melt index of 1.2, 0.1 part by weight of 2,6-di-tert-butylhydroxytoluene as an antioxidant and talc shown in Table 1 were added. After mixing for 5 minutes with a Henschel mixer FM75J manufactured by Mitsui Miike Kakoki Co., Ltd., kneading and granulation were performed at a resin temperature of 230 ° C. using a 50φ extruder (PG50-32 manufactured by Plagiken Co., Ltd., full flight screw). The obtained pellet-shaped polypropylene composition was molded into a plate having a length of 80.0 × 50.0 × 1.0 (mm) under the condition of a resin temperature of 230 ° C. using an injection molding machine (SN150SN manufactured by Niigata Ironworks Co., Ltd.), After time the transparency was measured. The results are shown in Table 1.

Comparative Examples 1 to 5 The same operation as in Example 1 was performed except that the talc particle size and the amount were as shown in Table 1. The results are shown in Table 1.

Example 6 The polypropylene composition obtained in Comparative Example 2 was diluted with a homopolypropylene having a melt index of 1.2.
Was obtained. The results are shown in Table 2.

Examples 7 to 10 To 100 parts by weight of an ethylene-propylene copolymer powder having a melt index of 1.8 and an ethylene content of 0.3% by weight,
Table 3 shows 0.2 parts by weight of the same antioxidant as in Example 1 and talc.
, And granulation was performed in the same manner as in Examples 1 to 5.

The obtained pellet-shaped polypropylene composition was extruded at 280 ° C. by an extruder equipped with a T-die, and immediately cooled and solidified with a cooling roll at 40 ° C. to obtain an unstretched film having a thickness of 2.0 mm.

Next, the obtained unstretched film-like material is stretched 5 times in the longitudinal direction at a stretching temperature of 150 ° C. in a tenter-type sequential biaxial stretching apparatus, and subsequently in a tenter at a furnace temperature of 165 ° C., in the transverse direction. The film was stretched 10 times to obtain a biaxially stretched polypropylene film having a thickness of 40 μm.

Table 3 shows the transparency of the obtained film and the stained state of the roll.

Example 11 Polypropylene resin to be used is melt index 2.
Examples 7-1 except that the homopolypropylene was 0
The operation was performed in the same manner as in Example 0 to obtain a biaxially stretched film. Table 3 shows the results.

Comparative Examples 6 to 10 The particle size and the amount of talc used were changed, and
In the same manner as in 10, a biaxially stretched film was obtained. The results are shown in Table 3.

Claims (1)

(57) [Claims] 1. 100 parts by weight of polypropylene and average particle size
A polypropylene composition comprising 0.0001 to 0.1 part by weight of 0.001 to 0.1 μm talc.