JPH069848B2 - Perforated tube manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies gas to each of the holes to be formed independently and by controlling the pressure, and controls the wall thickness of the outer peripheral portion of the molded body by the die. The present invention relates to a method for manufacturing a perforated tube having a plurality of holes in the cross section, which is excellent in the accuracy of the hole diameter and the balance of the wall thickness in each section.

2. Description of the Related Art Perforated tubes having a plurality of holes in their cross section are used in various fields such as multi-lumen catheters and endoscope tubes.

Conventionally, as a method of manufacturing a perforated tube by an extrusion molding method while supplying gas to each of the holes formed through a die, the same pressure gas is supplied even when the plurality of holes to be formed have different diameters. The method was known. However, there is a problem in that the die cannot be formed accurately with the hole diameter ratio set in the die.

Problems and Solution Means As a result of intensive studies to overcome the problems of the above-mentioned conventional techniques, the present inventors achieved the object by changing the pressure of the supply gas according to the diameter of the hole forming the pressure. I found that According to this method, it is possible to obtain a perforated tube having excellent dimensional accuracy of the pore diameter, and it is also possible to change the pore diameter ratio and the cross-sectional outer shape of the perforated tube by using the same die by changing the pressure or pressure difference of the supply gas.

According to the present invention, by changing the wall thickness of the outer peripheral portion of the molded product formed by the die, in addition to the above advantages, it is possible to control the balance of the wall thickness in each cross-sectional portion of the porous tube.

That is, the present invention uses a die capable of independently supplying a gas to each of the holes to be formed when manufacturing a porous tube having a plurality of holes in a cross section by an extrusion molding method, and each of the holes to be formed. The diameter of the hole formed by changing the pressure of the gas supplied to the target, and by changing the wall thickness of the outer peripheral part based on the diameter difference between the bushing inner diameter of the molded body and the mandrel outer diameter by the die, the porous tube of the target The present invention provides a method for producing a perforated tube, which is characterized by controlling the wall thickness between the holes in the.

Action By changing the wall thickness of the outer peripheral part of the molded body by the die, the same mandrel can be used to control the wall thickness between the holes in the cross section of the porous tube of the target object, and thus the wall thickness at each part of the porous tube. It can be adjusted. That is, as the distance d between the inner diameter of the bushing 1 and the outer diameter of the mandrel 2 in the die in FIG. 1 is increased to increase the wall thickness of the outer peripheral portion of the molded body, as shown in FIG.
The wall thickness between the holes in the porous tube formed as shown in FIG. 4 can be reduced.

Exemplary Components of the Invention In the present invention, a die is used that can independently supply gas to each of the plurality of holes to be formed. An example of the die structure is shown in FIG. This die has a bushing 1 and a mandrel 2, and has a structure capable of forming a molded body having three holes in its cross section or a porous tube. The mandrel 2 is provided with three gas passages 3, 4, 5 so that gas can be independently supplied to each of the three holes formed.

In the present invention, when a porous tube having a plurality of holes in its cross section is extruded, the pressure of the gas supplied through a die is changed according to the respective hole diameters of the plurality of holes to be formed, so that the supply gas has a pressure difference. . Thereby, the hole diameter of the formed hole can be controlled with high accuracy. Although gas is not limited, air is usually used. The pressure balance of the gas independently supplied to each of the formed holes is appropriately determined according to the size of the formed hole diameter, the type of molding resin, the extrusion molding conditions, and the like. In terms of the accuracy of the hole diameter, in general, a slight difference in the gas pressure applied is sufficient.

By the way, when molding polyethylene and polyvinyl chloride under the usual extrusion molding conditions, 0.001 to 0.05 kg / c
By giving a pressure difference in the range of m ² , a perforated tube can be obtained with satisfactory accuracy.

In the present invention, by controlling the pressure balance of the supply gas, it is possible to accurately form a perforated tube having a plurality of holes having different hole diameters, and the hole diameter ratio of a plurality of holes formed by using the same die. Can be changed.
Further, the cross-sectional outer shape of the formed porous tube can be changed.

In the present invention, the wall thickness between the holes in the perforated tube of the object is controlled by changing the wall thickness of the outer peripheral portion of the molded body formed by the die. Taking the case of the die shown in FIG. 1 as an example, the inner diameter of the bushing 1 and the mandrel 2 in the die are described.
The thickness b between the holes in the perforated tube of the object is controlled by changing the distance d from the outer shape of the object. The perforated tube 6 in FIG. 2 is the case where the distance d is narrowed, and the perforated tube 8 in FIG. 4 is the case where the distance d is the widest of the three. The perforated tube 7 in FIG. 3 is the case where the distance d is set to an intermediate value between the former two. In this way, as the distance d between the inner diameter of the bushing 1 and the outer diameter of the mandrel 2 is increased to increase the wall thickness of the outer peripheral portion of the molded body (corresponding to a portion of the perforated tube), the perforated tube 6, The wall thickness b between the holes in 7 and 8 can be reduced. The above-mentioned change of the distance d may be performed by using a die having a function for changing the distance d such as a variable orifice die, or by a method of preparing bushings having different inner diameters and replacing them. Good.

The method of the present invention can also be used as a method for forming a film. That is, as shown in FIG. 5, a molded body 9 is formed by a die having an outer shell 91 that is as thick as possible, and its forming holes 92, 92 are formed.
By supplying gas to the holes to expand the holes, the thin film 9 having a small thickness between the holes and excellent in thickness uniformity is obtained.
3 is formed.

The molding resin used in the present invention is not particularly limited, and a resin used for usual extrusion molding can be used. Also, the number of holes to be formed is not particularly limited. Usually,
It is a perforated tube having 2 to 10 holes in its cross section.

EFFECTS OF THE INVENTION According to the present invention, since the pressure of the supply gas is controlled according to the hole diameter, it is possible to accurately manufacture a porous tube having a plurality of holes having different hole diameters in the cross section, and use the same die to measure the hole diameter ratio. Alternatively, it is possible to manufacture porous tubes having different cross-sectional outer shapes.

Furthermore, as a result of being able to control the placement of the holes in the cross-section of the perforated tube by changing the wall thickness between the holes, it is possible to change the hole diameter ratio and cross-sectional outer shape more widely, and the hole occupying area in the cross-section is large or the thickness of each part is large. It is possible to efficiently manufacture a perforated tube having a well-balanced thickness and pore diameter and a small outer diameter.

Example 1 A large diameter hole and a small diameter hole in a mandrel having a hole diameter ratio of 1.90, two large holes and two small holes are alternately provided, and a distance d between the inner diameter of the bushing and the outer diameter of the mandrel is 0.35 mm. 0.009 kg for the hole formed by the large hole using a die
0.0 for a hole formed by small holes at a pressure of / cm ²
Polyethylene (melt index 0.3, density 0.920 g / cm ³ ) was extruded (150 ° C) while supplying air at a pressure of 05 kg / cm ² , and a porous tube with 2 large holes and 2 small holes in total 4 holes in cross section Got The cross-sectional dimensions of the saw are shown in the table (see FIG. 6).

Comparative Example The same pressure (0.
A porous tube was obtained in the same manner as in Example 1 except that air was supplied at 007 kg / cm ² ). The cross-sectional dimensions are shown in the table.

Example 2 The same mandrel as in Example 1 was used, but on the outside of the mandrel, a die provided with a bushing having an inner diameter such that the distance d from the outer diameter of the mandrel was 0.60 mm was used.
At a pressure of 012kg / cm ^2, while supplying air at a pressure of 0.017kg / cm ² for holes formed by small holes, a mixture of polyethylene and ethylene-vinyl acetate copolymer compounded with barium sulfate Extrusion (130 ° C.) was performed to obtain a porous tube having two large holes and two small holes in total, four holes in cross section. The cross-sectional dimensions are shown in the table.

Example 3 The distance d between the inner diameter of the bushing and the outer diameter of the mandrel is 0.85.
mm and supply air pressure to the hole formed by the large hole
0.014 kg / cm ^2, a porous tube having in addition to the supply air pressure was 0.019kg / cm ² is prepared analogously to Example 1 by the large pore small holes in cross-section a two by two four holes for holes formed by small holes Obtained. The cross-sectional dimensions are shown in the table.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a die used in the present invention, FIGS. 2, 3, and 4 are cross-sectional views of a perforated tube,
FIG. 5 is an explanatory diagram of an application example, and FIG. 6 is an explanatory diagram of a cross-sectional dimension of a porous tube. 1: Bushing 2: Mandrel 3,4,5: Gas passage 6,7,8,9: Perforated tube 11, 12, 13, 14, 31, 32, 33, 41, 42, 43, 51, 52, 53, 92: Pores in cross section of perforated tube a, b, d1, d2, d3, d4, d5: wall thickness

Claims (2)

[Claims] 1. When manufacturing a porous tube having a plurality of cross-sections by an extrusion molding method, a die capable of independently supplying a gas to each of the holes to be formed is used, and each of the holes to be formed is formed. By controlling the diameter of the hole formed by changing the pressure of the gas to be supplied, and by changing the wall thickness of the outer peripheral portion based on the diameter difference between the bushing inner diameter of the molded body and the mandrel outer diameter by the die, in the target porous tube A method for producing a perforated tube, which comprises controlling the wall thickness between the holes. 2. The method according to claim 1, wherein the die used is formed so as to form holes having different hole diameters.