JPH06339973A - Method for melt-forming polyolefin resin and melt extruder used therefor - Google Patents

Abstract

(57) [Summary] [Structure] In a method for melt-extruding a polyolefin resin from a molding die, a melt extruder, in which the surface of the molding die that comes into contact with the melt-extruded polyolefin resin is composed of tantalum. A method for melt-molding a polyolefin resin and a melt extruder used therefor, characterized by using. [Effect] The acid resistance, abrasion resistance, and mold release of the die are improved, so when melt extrusion molding of polyolefin resin, rust generation and "meyer" adhesion are suppressed and high quality molded products are obtained. You can

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt molding method for polyolefin resin. More specifically, the present invention relates to a method for melt-molding a polyolefin resin, which suppresses adhesion of a polyolefin resin "meyer" to the extruded surface of a molding die and stably molds a high-quality molded product.

[0002]

2. Description of the Related Art A molding die is used for melt extrusion molding of a polyolefin resin. As a material of this die, S45C or SS41 containing iron as a main component has been used. However, there has been a problem in that the flow path of the polyolefin resin is corroded, which causes streaky surface defects on the surface of the molded product. For this reason, the die is made of SUS316, SUS630, SUS420J2 having an anticorrosive effect.
It has been proposed to use austenitic stainless steel as a material, or to apply a rust-preventive coating by plating the surface of the die with Cr, Ni, or the like.

[0003]

However, in the case of melt extrusion molding of a polyolefin resin using the molding die according to the above-mentioned method, a deterioration product of the polyolefin resin or a part of the additive on the extrusion surface of the die, or Its oxide,
Decomposition products and the like "meyer" adhered, and the "meyer" adhered to the molded product extruded from the die, leading to deterioration of the quality of the molded product.

[0004]

Means for Solving the Problems In view of the above problems associated with melt molding of a polyolefin resin, the present inventors have diligently studied in order to prevent the occurrence of "meyer" in the molding die. It was found that the above object can be achieved by constructing the material with tantalum, and the present invention has been completed.

That is, the gist of the present invention is to use a method in which a polyolefin resin is melt-extruded and molded, and a melt extruder in which the surface of a molding die that comes into contact with the melt-extruded polyolefin resin is made of tantalum is used. And a melt extruder used therefor. Hereinafter, the present invention will be described in detail.

In the present invention, the polyolefin resin is a homopolymer of an α-olefin having 2 to 8 carbon atoms such as ethylene or propylene, a copolymer of two or more kinds of these, or an α-olefin as a main component. Copolymers containing other monomers copolymerizable with and mixtures thereof. Polyethylene, polypropylene and copolymers thereof are particularly preferable.

The melt viscosity (MFR) of polyethylene is 0.5 to 40 g / 10 minutes, and that of polypropylene is 0.5 to 30 g / 10 minutes. Surface defects (thickness unevenness) are significantly prevented. It is preferable because it is possible. In addition, commonly used stabilizers, antioxidants, antistatic agents, plasticizers,
Polyolefin resin compositions containing additives such as dispersants and lubricants, and fillers such as titanium oxide, talc, calcium carbonate and alumina can also be used in the molding die of the present invention.

Examples of the molding die in the present invention include filament dies (for forming monofilaments, multifilaments, ropes, nets, etc.), T dies (for forming sheets or films), inflation dies (for forming film or flat yarn). ), Blow molding dies (for molding containers, industrial parts, etc.), profile extrusion dies (for pipe frame material extrusion molding), laminate dies (for forming laminated films or sheets), and the like. It is not limited to.

The above-mentioned molding die used in the present invention is characterized in that at least the surface which comes into contact with the melt-extruded polyolefin resin is made of tantalum, but a small amount of another metal is combined with tantalum. Alloys may be used. The surface roughness (JIS B 0601 standard) of the molding die made of tantalum is preferably 0.8 S or less, particularly preferably 0.2 S to 0.8 S.
Is the range.

In the present invention, the molding die has the above-mentioned structure, whereby the acid resistance, wear resistance and mold releasability of the die are improved. Therefore, when the polyolefin resin is melt-extruded, the generation of rust is suppressed, and the adhesion of "meyer" is improved. As a specific method of using tantalum for the surface of the molding die in the present invention, the entire molding die may be tantalum, and a surface layer of the molding die, for example, a tantalum layer having a thickness of about 10 μm to 3 mm may be formed of tantalum. It may be configured. As the latter method,
It is carried out by stacking tantalum on the surface of a die base, for example, austenitic stainless steel by plating, sputtering, or the like.

Among the molding dies of the present invention,
It is not necessary that all the portions that come into contact with the polyolefin resin are made of tantalum, and only a part such as the die may be made of tantalum. In the present invention, when extrusion molding is performed using the molding die, the average shear rate of the molten resin at the die outlet is 100 sec ^{−1 to} 6000.
sec ^-1, preferably 400sec ^-1 ~2500sec
A range of ^-1 is preferred. If the shear rate is too low, the residence time in the die becomes long, the deterioration of the resin and the thermal decomposition of the additive are likely to occur, and the occurrence of "meyer" is not preferable. On the other hand, if the shear rate is too high, the swelling effect of the resin may cause the molten resin to be scraped off by the edge of the die outlet, or the contact with the die surface may increase, resulting in increased occurrence of “bulldog”.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples without departing from the gist of the invention.

(Example) Using a die made of tantalum and having a surface roughness of 0.8S, a 30 mmφ extruder was fitted with a pipe die having an outer diameter of 12 mmφ and a die slit of 1 mm. Temperature is 280 ℃
Heated evenly. MFR = 0.8 g / 10 in the extruder
Min., High density polyethylene having a density of 0.958 g / cm ³ was supplied, and the molten resin at 290 ° C. was sheared from the above-mentioned die at a shear rate of 5
It was extruded at 00 sec ^-1 , and the pipe was continuously molded for 30 hours. As shown in Table 1, by using tantalum as the material of the die, the total length of the eyelids generated after 30 hours was 2.8 mm.

(Comparative Examples 1 and 2) As the material of the die, SUS is used.
316, the surface roughness of which is 0.8 S, 0.
In the case of 2S, the total length of the eyelids generated after 30 hours was 20 mm and 47 mm, respectively. The results are shown in Table 1.
Also described in.

[0015]

[Table 1]

[0016]

According to the melt-molding method of the present invention, the acid resistance, wear resistance and mold releasability of the die are improved. Therefore, when the polyolefin resin is melt-extruded, rust is generated or "meyer" is attached. Is suppressed, and a high quality molded product can be obtained.

Claims (2)

[Claims] 1. A method of melt extruding a polyolefin resin for molding, wherein a melt extruder having a molding die surface in contact with the melt-extruded polyolefin resin made of tantalum is used.
Method for melt-forming polyolefin resin. 2. A melt extruder for a polyolefin resin, characterized in that the surface of the molding die that comes into contact with the melt-extruded polyolefin resin is made of tantalum.