JPH09111065A - Production of molding pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a molding pellet capable of providing a polypropylene resin molding, good in dimensional stability and appearance, having a high mechanical strength such as rigidity and impact resistance and containing a fibrous inorganic filler. SOLUTION: A mixture of 60-99wt.% propylene polymer having >=95% isotactic pentad fraction with 1-40wt.% magnesium-based fibrous inorganic filler having 0.1-2.0μm fiber diameter and 60-200 aspect ratio is melt kneaded and then granulated and molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pellet for molding an inorganic fiber-filled polypropylene resin, which gives a molded article excellent in mechanical strength and dimensional stability, which is used as a material suitable for automobile parts, light electric appliances and the like. is there.

[0002]

2. Description of the Related Art Composite resin compositions prepared by mixing polypropylene with an inorganic filler are widely used in the field of industrial materials due to various advantages such as rigidity and mechanical strength and molding shrinkage. Among them, those reinforced with fibrous fillers are preferably used because of their great improvement in mechanical strength. But,
When a resin having a long fiber length such as glass fiber is filled in the resin, the surface is roughened, so that the appearance is not preferable.
Also, when filled with short fibers such as wollastonite, there is a disadvantage that the effect of improving rigidity is small.
In order to improve the shortcomings of the short fiber filler, Japanese Patent Application Laid-Open No.
No. 09846 has proposed a method of blending fibrous magnesium oxysulfate, but the above-mentioned improvement in mechanical strength is not sufficient.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a molding pellet which provides a polypropylene resin molded product containing a fibrous inorganic filler, which has good dimensional stability and appearance, and high mechanical strength such as rigidity and impact resistance. It is an object of the present invention to provide a manufacturing method of.

[0004]

DISCLOSURE OF THE INVENTION As a result of studies to improve the drawbacks of conventional pellets for molding containing a short fiber filler, the present inventors have found that a mixture of a specific polypropylene and a short fiber filler of a specific shape. It was found that a pellet for molding which gives a polypropylene resin molded product having good surface gloss and dimensional stability and improved rigidity and impact resistance can be obtained by melt-kneading and then granulating, which constitutes the present invention. Came to.

That is, the present invention relates to (A) a propylene polymer 60 having an isotactic pentad fraction of 95% or more.
-99% by weight and (B) 0.1-2.0 μm fiber diameter,
A method for producing pellets for molding polypropylene resin, comprising: kneading a mixture with 1 to 40% by weight of a magnesium-based fibrous inorganic filler having an aspect ratio of 60 to 200; To provide.

[0006] The propylene polymer used in the method of the present invention may be any propylene polymer as long as the isotactic pentad fraction is 95% or more. It can be produced by appropriately selecting the catalyst used at the time of polymerization and the type of monomer used for the pretreatment of the catalyst.

The isotactic pentad fraction is 5
The ratio of the propylene unit at the center of the chain in which two propylene monomer units are successively meso-bonded to the total propylene unit is expressed as a percentage, and is a measure of the stereoregularity of the polypropylene molecule.

As a method for obtaining such a propylene polymer having a high isotactic pentad fraction, for example, a method described in JP-A-61-155404, which has a high Ziegler-type stereoregular polymerization ability, has been proposed. Catalyst 4-
There is a method in which propylene is polymerized using a polymer preliminarily polymerized with a monomer such as methylpentene-1.

As the propylene polymer, a monomer such as α-olefin or ethylene other than propylene is copolymerized in the above polymerization reaction system by one-step polymerization or two-step polymerization, and the other monomers are converted into the entire resin. It is preferable to use a random copolymer or an impact-resistant polypropylene (commonly referred to as a block copolymer) having a content of 7% by weight or less of the amount because the impact resistance can be further improved.

It is necessary that the fibrous inorganic filler used in the method of the present invention has a fiber diameter of 0.1 to 2 μm and an aspect ratio of 60 to 200. The fiber diameter is 0.
If it is 1 μm or less, the bulk specific gravity of the filler becomes too small, making the compounding operation difficult, and if the fiber diameter is 2 μm or more,
The surface appearance of the obtained molded article is poor, and if the aspect ratio is less than 60, the strength of the obtained molded article is not improved, and if the aspect ratio is 200 or more, the dimensional stability and appearance deteriorate.

The magnesium-based fibrous inorganic filler of the component (B) used in the method of the present invention has a fiber diameter of 0.1.
Any shape may be used as long as the conditions of 2 μm and aspect ratio of 60-200 are satisfied. As such,
For example, magnesium sulfate fiber, fibrous magnesium oxysulfate, magnesium hydroxide fiber and the like can be mentioned.

The raw material used in the method of the present invention comprises (A) 60 to 99% by weight of the above-mentioned propylene polymer, preferably 70 to 99% by weight.
A mixture of 〜97% by weight and (B) 1-40% by weight, preferably 3-30% by weight, of a magnesium-based fibrous inorganic filler. If the content of the component (A) in this mixture is 60% by weight or less, the resulting molded article has poor impact resistance, and is 99% by weight.
If it is more than the above, the rigidity of the obtained molded product will be poor.

In the method of the present invention, a pellet giving a molded article with further improved physical properties can be obtained by further using an organic nucleating agent or an inorganic nucleating agent in combination with the components (A) and (B). Examples of the organic nucleating agent used in this case include a metal salt of benzoic acid or a derivative thereof in which an alkyl group is substituted with an aromatic ring, such as an aluminum salt of pt-butyl benzoate, such as dibenzylidene sorbitol and a derivative thereof, for example. 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-di (p-methylbenzylidene) sorbitol, 1,3,2,4-di (p
-Chlorbenzylidene) sorbitol, 1,3,2,4
-Di (p-methoxybenzylidene) sorbitol,
Organic acid salts such as sodium bis (4-t-butylphenyl) phosphate, calcium oxalate, magnesium stearate, zinc salicylate, calcium tartrate and the like can be mentioned.

Examples of the inorganic nucleating agent include clays such as talc, clay, mica, montmorillonite and bentonite, calcium silicate, magnesium silicate, and the like.
Examples thereof include metal oxides such as calcium sulfate, barium sulfate, calcium carbonate, titanium oxide, magnesium carbonate and zinc oxide.

The amount of the nucleating agent may be very small.
By mixing 1 to 1 part by weight, the rigidity, heat resistance, hardness and the like of the molded product can be further improved.
The effect of improving the physical properties does not change even if it is used in an amount larger than 1 part by weight. In the method of the present invention, the mixture 10
By mixing 5 to 25 parts by weight of polyethylene having a density of 0.940 to 0.970 with respect to 0 part by weight, a pellet can be obtained which gives a molded article having further improved impact resistance and the like.

In the method of the present invention, the mixture of the component (A) and the component (B) may contain other additives as long as the object of the present invention is not impaired. Such additives include, for example, antistatic agents, colorants, flame retardants,
Various additives such as an antioxidant, an ultraviolet absorber, a plasticizer, and a heat stabilizer are exemplified.

[0017]

EFFECTS OF THE INVENTION According to the method of the present invention, pellets can be obtained which give molded articles having high mechanical strength such as impact resistance and bending strength and good dimensional stability. Further, since the molded article produced from the pellets has a good appearance, it can be used without the need for overlaying or painting with cloth or the like, which is advantageous.

[0018]

The present invention will be described in more detail with reference to the following examples. In addition, the test method of the raw material used for the Example and the comparative example and the molded article sample is as follows. Propylene polymer 1 (PP-1) homopolymer having an isotactic pentad fraction of 98% Propylene polymer 2 (PP-2) having an isotactic pentad fraction of 98% Ethylene content 4% by weight Propylene copolymer 3 (PP-3) having an isotactic pentad fraction of 98.5% Propylene copolymer having an ethylene content of 3% by weight Propylene polymer 4 (PP-4) 94% Propylene copolymer having an isotactic pentad fraction of 4% by weight of ethylene Propylene polymer 5 (PP-5) Propylene having an isotactic pentad fraction of 9% and an ethylene content of 8% by weight Copolymer

Nucleating agent K: aluminum p- (t-butyl) benzoate L: 1,3,2,4-dibenzylidenesorbitol M: talc polyethylene S: density 0.970, MI20 polyethylene T: density 0.960 , MI6 polyethylene

Test method: (1) Bending strength Measured in accordance with ASTM D 790. (2) Flexural Modulus Measured in accordance with ASTM D790. (3) Izod impact strength It was measured according to ASTM D 256 (with notch). (4) Surface appearance Injection-molded at a molding temperature of 200 ° C. and a mold temperature of 50 ° C. 14
The surface roughness of a flat plate of 0 × 140 × 3 mm was visually observed and evaluated. (5) Warpage ratio After a disc having a thickness of 2 mm, a diameter of 150 mm and a center gate diameter of 5 mm obtained by injection molding was left at room temperature of 23 ° C. for 48 hours, the warpage height H of both ends in the diameter direction of the disc was measured.
(Mm) and h (mm) were measured, and the warpage rate was determined according to the following equation. In this measurement, the position of the largest warp on the circumference of the disk was measured, and the diameter direction at the time of the warp measurement was set on a straight line connecting the point and the center of the disk.

[0021]

(Equation 1)

The relationship between the warp symbol in the table and the warpage ratio is as follows. Warp rate 0-2% ○ 2-5% △ 5% or more ×

(6) Isotactic pentad fraction The isotactic pentad fraction was measured by the method described in Macromolecules, Vol. 8, page 687 (1975). Specifically, the isotactic pentad unit was measured as the intensity fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum of the propylene polymer of the sample.

Examples 1 to 10 and Comparative Examples 1 to 6 A propylene polymer and a fibrous filler were blended in the proportions shown in Table 1 and mixed well with a V-type blender.
The mixture was melted and mixed at ℃ ° C and extruded using a twin-screw extruder to prepare molding pellets. Next, the pellets were added with polyethylene shown in Table 1 and, if necessary, a nucleating agent for each example and injection-molded to obtain a molded product. A physical property test was performed on the molded article. Table 2 shows the results.

[0025]

[Table 1]

[0026]

[Table 2]

Claims (1)

[Claims] 1. A propylene polymer (A) having an isotactic pentad fraction of 95% or more, 60 to 99% by weight, and (B) a fiber diameter of 0.1 to 2.0 μm, and 60 to 20.
After melting and kneading a mixture with 1 to 40% by weight of a magnesium-based fibrous inorganic filler having an aspect ratio of 0,
A method for producing pellets for polypropylene resin molding, which comprises granulating and molding.