JPS5941240A - Method of extrusion - Google Patents

Abstract

PURPOSE:To reduce the amount of die refuse resulting from the extrusion of rubber or plastic compositions, and to continuously removing such die refuse thereby preventing the appearance of an extrudate from becoming defective, by supplying a lubricant to the inner surface of an extruding die. CONSTITUTION:When a rubber or plastic composition (in particular, a composition containing a compound having high adhesion to metals such as Si-O compounds or a composition containing a higher amount of an inorganic filler) is continuously extruded for a longer period, it is liable to allow solids (die refuse) to accumulate at the outlet section of the die. This can be prevented by supplying a lubricant (e.g. mineral oils, polybutenes, silicone oils, etc.) to the die inner wall. It is suitable that the amount of the application is on the order of 10- 100mumin terms of the thickness of the lubricant applied on the die inner wall.

Description

[Detailed description of the invention] Certain types of rubber and plastic compositions.

For example, compositions containing compounds with good adhesion to metals, such as 5i-0 compounds, and those containing large amounts of inorganic fillers are commonly known as "die sludge" at the die exit during long-term continuous extrusion. There is a problem with solids buildup. This die lees is
It causes scratches on the surface of the extrudate, or it irregularly peels off from the die and sticks to the surface of the extrudate, causing poor appearance of the extrudate.

According to the research of the present inventors, this die lees.

When a rubber or plastic composition passes through the die, a large shearing force is generated near the surface layer of the composition due to friction between the composition and the inner wall of the die, and this shearing force causes a part of the plastic composition to break down. becomes granular and separates. Alternatively, it may occur due to detachment of the filler in the composition. Furthermore, according to the research conducted by the present inventors, supplying lubricating oil to the inner wall of the die reduces the above-mentioned frictional force, thereby reducing the amount of lees generated and preventing the separation of even a small amount of solid matter. However, due to the adhesion prevention effect of the lubricating oil that covers the surface of the die outlet, these minute amounts of solid matter adhere to the surface of the extrudate and exit the die, so they do not accumulate as die sludge. In addition, since the amount of individual solids adhering to the surface of the extrudate is very small.

The appearance of the extrudate is not substantially impaired.

The present invention proposes an extrusion molding method as described in the claims, which was completed based on the above new findings.

As a self-lubricating oil, rubber is used for extrusion molding.

A variety of chemical substances may be used, as long as they do not have an adverse effect on the plastic composition from a practical standpoint. Examples include natural oils such as mineral oil and non-drying animal and vegetable oils, and synthetic oils such as polybutene, ethylene oxide-globylen oxide copolymer oil, silicone oil, and heavy alkylbenzene oil.

Regarding the method of supplying lubricating oil to the inner wall of the die.

There are no particular restrictions, such as a method in which the die itself is made of sintered metal and lubricating oil supplied from the outside oozes out from the entire inner wall of the die, or a method in which lubricating oil is applied in a circumferential manner to the land and/or taper portion of the die. This method includes providing a discharge slit and supplying lubricating oil from the outside to the inner wall of the die through the slit.

The amount of lubricating oil to be supplied can be determined by trial and error depending on the presence or absence of die sludge, but generally the thickness of the oil film on the inner wall of the die is approximately 10 μm to 100 μm. When lubricating oil is supplied into the die from the above-mentioned slit, the slit can be provided near the exit of the die to sufficiently prevent the generation of scum, but it is not recommended to provide the slit near the taper part of the die or the land entrance of the die. is preferred.

The remarkable effects of the present invention will be understood from the Examples and Comparative Examples shown below.

Example 1, Comparative Example 1 100 parts of polyethylene (parts by weight, same hereinafter), 2 parts of vinyltrimethoxysilane, 02 parts of dicumyl peroxide,
and 0.05 part of dibutyl-tin-dilaurate at a crosshead temperature of 160°C.
, cylinder-11! L set at 120-150°C
/D 28 cross-sectional area 20 in an extruder with a screen l-
It was extruded at a thickness of 0 and 6.5 mm onto a stranded copper conductor with a conductor shielding layer. 10 minutes after the start of extrusion, the generation of 1 dregs was observed, and after 60 minutes from the right center, 2 to 5 sq. diameter dregs were detached from the die at a rate of approximately 0.05 sq./min and adhered to the surface of the polyethylene layer. did. Extrusion starts 80 minutes right-up die/
Uniloop 50MB-26X (ethylene oxide-propylene oxide block copolymer manufactured by NOF Corporation, viscosity at 230°C: 5.73 c, s, t,)
When the lubricating oil was continued to be supplied, about 1 hour after the start of the supply of the lubricating oil, all of the guinea sludge that had existed up to that time was separated from the guinea fluid, and no new guinea sludge was observed to occur after that.

Example 2, Comparative Example 2 A flame retardant composition prepared by blending 20,810 parts of 5b, 60 parts of calcium carbonate, and 15 parts of zinc white into an ethylene-oxygen vinyl copolymer having a vinyl acetate content of 20% was prepared in Example 1. When the same extruder as in Comparative Example 1 was used and extrusion was carried out under the same conditions, 15 minutes after the start of extrusion, formation of die lees rising to the right was observed, and after another 40 minutes, gui lees with a diameter of 1 to 3 sea bream were observed to appear on the right side. 05 pieces/
It detached from the die and adhered to the polymer surface at a rate of 1.5 min.

Next, a lubricant with a viscosity of 10 at the extrusion temperature was used as a lubricant.
~15 C, S, T, silicone oil 2. When silicone oil was supplied to the inner surface of the die in the same manner as in Example 1 at a flow rate of UccZ, about 1 right from the start of supply of silicone oil, all the scum that had been present until then separated from the die, and after that, No new occurrence of Dairy lees was observed.

patent applicant Dainichi Nippon Electric Cable Co., Ltd. Representative Director Yukio Aoyama

Claims (1)

[Claims] An extrusion molding method characterized by supplying lubricating oil to the inner surface of a molding die in extrusion molding of a rubber or plastic composition that generates die residue.