JPH07329154A - Extrusion molding method of synthetic resin tube - Google Patents

Abstract

PURPOSE:To efficiently form a synthetic resin tube of excellent quality by extrusion molding by extruding a synthetic resin cylindrical body from a mold attached to a tip of an extruder and inserting the cylindrical body into a spiral sizing die for shaping. CONSTITUTION:When a melted synthetic resin is extruded into a cylindrical shape from a mold having an extruder and it is inserted into a sizing die 4 so as to shape by regulating its outer diameter, the sizing die 4 which is spiral is used. As a material of the sizing die 4 to be used, a metal having excellent heat conductivity, for example, aluminum, copper bronze, and brass are desirable. These are machined so as to form a spiral shape. Those elements such as pitch, spiral angle, the number of winds, winding direction (clockwise winding or counterclockwise winding), cross-sectional shape and dimension of line can be set to appropriate values which can smoothly size by considering those element such as dimension of a synthetic resin tube to be molded, kind of resin, molding speed, and others.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding method for a synthetic resin pipe, and more specifically, it is an extrusion molding method of shaping by an outer diameter regulation method, which is of good quality and can be produced for a long time. The present invention relates to an extrusion molding method of a synthetic resin pipe capable of continuous production.

[0002]

2. Description of the Related Art An extruder, a die, a cooling device, a take-up machine and a winding machine or a cutting machine are used as main equipment for molding a synthetic resin pipe by using a thermoplastic resin such as polyethylene, polybutene or polyvinyl chloride. Is used on an extrusion molding device. In this way, by the extrusion molding device in which each device is arranged on one line, through a series of molding processes including an extrusion process, a cooling molding process, a take-up process and a winding or constant-length cutting process, the extruder The raw material resin charged into the hopper finally becomes a synthetic resin tube having a predetermined diameter dimension and is continuously produced.

By the way, from the die attached to the extruder,
The molten resin extruded in a tubular shape enters a cooling molding process. In this case, the molding material being shaped (hereinafter referred to as the tubular body)
Is cooled while controlling its outer diameter or inner diameter by a sizing die to be molded into a predetermined size. Among these, in the case of the outer diameter regulation method, the tip surface of the mold or a cooling device such as a water tank Pass through the sizing die (also called forming tube) attached to the entrance. At this time, by applying gas pressure to the inside of the tubular body, the tubular body is brought into sliding contact with the inner wall surface of the sizing die, and the outer diameter thereof is finished to a predetermined dimension.

There are several methods for controlling the outer diameter, and one of them is a multi-plate sizing die as shown in FIG. 5 (Keiji Sawada, Nikkan Kogyo Shimbun Co., Ltd., “Plastic Profile Extrusion and Composite”). Extrusion ", p. 45, 46). In this method, several annular molding plates a, a ... Each having a cylindrical passage (hereinafter referred to as a through hole) having an inner wall surface for restricting the outer diameter of the synthetic resin pipe are parallel to each other at intervals. The molding plate a is arranged at a predetermined interval by the support rods d, d ... Attached to the side plate of the water tank (not shown) provided at the tip of the mold b. It is used by being fixed so as to hold.

As another method, there is a cylindrical sizing die as shown in FIG. In this method, one cylinder e
A plurality of annular grooves f, f ... Are formed on the inner wall surface of the tank, and vertical holes g, g ... Are formed in the annular groove f so as to communicate with cooling water inside a water tank (not shown). The cylinder e and the mounting plate h are provided so as to be integrated.

[0006]

However, in general, during the operation of the extrusion molding device, the resin and additives (hereinafter referred to as precipitates) which have not been sufficiently kneaded or compatible with the raw material resin are In some cases, these precipitates may adversely affect mainly the appearance quality of the molded body. The case of the above-mentioned outer diameter regulation method in extrusion molding of a synthetic resin pipe is no exception.

When viewed in the extrusion direction, the conventional sizing die has an annular vertical surface around the entrance of the through hole. Therefore, this annular vertical surface serves as a weir plate, and precipitates penetrate the through holes. First adhere to the periphery of the entrance side of, the adhered deposits, because there is no escape, the deposits that deposit one after another deposit on the starting deposit, in the case of a cylindrical sizing die, Adheres and deposits in the annular groove f. Furthermore, this precipitate is cooled and solidifies, grows and grows into large bumps i, i.
・ It becomes.

Then, the bumps i rub against the surface of the continuously extruded cylindrical body p, and the obtained cylindrical body p becomes defective because of streaky scratches. Therefore, the worker needs to frequently perform the work of removing the raised object i during the operation of the apparatus or stopping the operation of the apparatus, resulting in poor workability and reduced manufacturing efficiency.

The present invention provides a method for extruding a synthetic resin pipe which eliminates the above-mentioned troubles when extruding a synthetic resin pipe by the outer diameter regulation method and can efficiently produce a product having excellent quality. It was made for the purpose.

[0010]

The extrusion molding method of a synthetic resin pipe of the present invention is a method in which a molten synthetic resin is extruded in a cylindrical shape from a die equipped with an extruder and is inserted into a sizing die to have an outer diameter thereof. The main point is to use a spiral-shaped sizing die when shaping while controlling the.

As a material for the sizing die used in the molding method of the present invention, a metal having a high heat transfer coefficient, such as aluminum, copper, gun metal or brass, is preferable, and these are processed into a spiral shape. The spiral pitch, spiral angle, number of turns, winding direction (right-handed or left-handed), wire cross-sectional shape, dimensions, etc., take into consideration the dimensions of the synthetic resin pipe to be molded, the type of resin, the molding speed and other factors. Then, it may be set so that smooth sizing can be performed.

As in the case of the conventional multi-plate sizing die, the inner diameter of the through hole is processed so that it gradually becomes smaller in the extrusion direction, and the inner diameter of the last one roll is used for forming. It is preferable to obtain a predetermined outer diameter (including shrinkage allowance) of the synthetic resin pipe to be used. Further, it is preferable that the pitch width of the spiral is wide on the die side and becomes narrower toward the end.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic front view showing an example of an extrusion molding apparatus used in the extrusion molding method of a synthetic resin pipe of the present invention, in which 1 is a metal attached to the tip of an extruder (not shown). The mold 2 is a water tank arranged in front of the mold. A circular opening is provided on the inlet side of the water tank 2, and a circular annular mounting plate 3 is fitted in the opening.

Reference numeral 4 denotes a sanding die, which is formed by spirally winding a square rod body, the winding start end of which is fixed to the mounting plate 3 fitted in the water tank 2, and the winding end end of the holding plate 5. It is also fixed. Further, between the mounting plate 3 and the holding plate 5, a plurality of supporting rods 6, 6 are installed in parallel with the extruding direction, and the outer peripheral surface of the sizing die 4 is fixed to the supporting rods 6 at equal intervals. It is designed to hold the pitch. When the material forming the sizing die has a rectangular rod shape, as shown in FIGS. 2 and 3, the inlet side of the through hole 7, which is the passage of the tubular body formed by the sizing die 4, is a tubular body P. R8 is added to reduce the friction resistance of.

[0016]

Since the sizing die 4 is formed in a spiral shape, it has an opposing surface 9 corresponding to the annular vertical surface of the above-mentioned conventional sizing die when viewed in the extrusion direction. It is not perpendicular to the extrusion direction but is inclined.

Accordingly, the deposit 10 from the outer peripheral surface of the cylindrical body P extruded from the die adheres to the facing surface 9, but when the deposit 10 is pressed by the later-generated deposit, the deposit 10 is attached to the inclined surface thereof. It moves along with it, and comes to be separated from the sizing die 4 successively as shown in FIG. Therefore, the deposit 10 does not adhere to the sizing die 4 and solidify, so that the cylindrical body P is not scratched.

[0018]

EXAMPLES Examples of the present invention will be described in detail below.

Polyethylene is used as a raw material resin, and 2
The inner diameter of the tip of the aluminum rod of × 2mm is 17m
m, a spiral body having a length of 100 mm formed by winding 10 times so that the inner diameter of the root part is slightly larger than 17 mm is used as a sizing die, and the apparatus shown in FIG. 1 is used, the outer diameter is 17 mm and the thickness is 2 mm. Of polyethylene pipe was extruded.

After continuous operation for 48 hours or more, deposition and deposition of deposits were not observed on the sizing die, and appearance defects such as streaks and scratches were not observed on the outer surface of the obtained polyethylene pipe.

On the other hand, when the polyethylene pipe was extruded by the conventional apparatus shown in FIG. 5, after 24 hours, a streak was formed on the outer surface of the pipe, which is considered to have been formed by depositing and depositing deposits.

[0022]

The method of extrusion molding a synthetic resin pipe of the present invention comprises:
Since the spiral sizing die is used, the precipitate deposited on the surface of the tubular body adheres to the inclined facing surface of the sizing die, but is pressed by the later-generated precipitate,
It moves on the inclined facing surface. Therefore, the deposits sequentially move on the sizing die, and finally they leave the water tank and float or settle, so that the deposits can be removed without stopping the operation of the machine, and the production efficiency is improved. Is improved.

[Brief description of drawings]

FIG. 1 is a schematic front view showing an example of an extrusion molding apparatus used in a manufacturing method of the present invention.

FIG. 2 is a partially cutaway enlarged view showing only the sizing die taken out from the same apparatus.

FIG. 3 is a sectional view of only a main part showing a tubular body passing through a through hole of the sizing die of the same.

FIG. 4 is an explanatory view showing a moving direction of deposits attached to the sizing die of the above.

FIG. 5 is a schematic front view showing an example of a manufacturing apparatus used in a conventional molding method.

FIG. 6 is a schematic front view showing another example of the manufacturing apparatus used in the conventional molding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Water tank 3 Mounting plate 4 Sizing die 5 Holding plate 6 Support rod 7 Through hole 8 R 9 Ramped surface 10 Precipitate

Claims (1)

[Claims] 1. A method for producing a synthetic resin pipe by extruding a synthetic resin tubular body from a mold attached to the tip of an extruder and inserting the synthetic resin tubular body into a sizing die to shape the tubular body. A method for extrusion-molding a synthetic resin pipe, which comprises using a spiral sizing die.