JPS608034A - Extrusion molding of deformed and expanded product - Google Patents

Abstract

PURPOSE:To mold deformed and expanded products having spiral projections with a great freedom of shape and dimension at low cost by a method in which an object to be extruded from the die having circularly arranged plural orifices is molded by rotation of a sizer. CONSTITUTION:The compound of a thermoplastic resin (e.g., polystyrene) and a blowing agent (e.g., azodicarbonamide) is charged into the hopper of an extruder 1 and extruded from a die 2 having circularly arranged plural orifices. The molten resin so extruded is molded by a sizer 5 and cooled in a cooling water tank 6, and an aimed product of an expansion ratio of 0.05-5, e.g., a cylinder or round bar whose periphery is provided with a spiral projection, is obtained by a takeout device 7. In the die 2, the land 8 of a comparatively large cross section is throttled into a small land 9 at the tip of the die, and the sizer 5 is turned through a chain 3 by a drive motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a foamed profile extrusion molded product having a spiral protrusion on the outer periphery of a cylinder or round bar and having an expansion ratio of 005 to 5 times.

The purpose of the present invention is to obtain various foamed profile extrusion molded products having a spiral protrusion on the outer periphery of a round bar or cylinder having a circular cross section.Specific uses of the molded product include: Examples include furniture parts, screws for transporting powder, rotating brush stands for vacuum cleaner suction ports, supports for cables, static mixers for transporting liquids, spacers for optical fibers, etc.

The outline of the present invention will be explained below with reference to the drawings. In the side view of FIG.
Push out more. The extruded molten resin is shaped by a sizer 5, then cooled by a cooling water tank 6, and taken by a take-off machine 7.

Dice 2 is the cross-sectional view (left side) and front view (right side) of Figure 2.
It has a structure as shown in FIG. 1, with a land 8 having a relatively large cross-sectional area and a narrow end at the tip of the die. The sizer 5 is driven by a chain 3, and resins such as molene, polypropylene, polystyrene, polyvinyl chloride, ABS, As, polycarbonate, and nylon that can be continuously extruded by an extruder are raised through the drive chain 3. Any foaming agent can be used, and the expansion ratio lio is 0.5 to 5 times, preferably 0.1 to 3 times. If it is less than 0.05 times, shaping is difficult, and if it exceeds 5 times, the strength of the molded product will decrease. This poses a practical problem. The foaming ratio here is 1 (times) from the quotient (times) of the unfoamed density divided by the density after foaming.
is obtained by subtracting .

By rotating the sizer. The pitch of the helix is determined by the sizer's rotational speed and take-up speed.

The effects of the present invention will be described below.

This method uses a round bar or cylinder with a spiral protrusion on its outer periphery. This method requires the use of complexly divided molds, which increases the total mold cost, and the lines of the mold divisions may appear on the molded product. Unfavorable in appearance. Furthermore, in injection molding, it is difficult to increase the expansion ratio. Furthermore, as the cross-sectional area of the molded product becomes larger, it takes longer to cool down, resulting in a longer molding cycle and higher molding costs. Furthermore, when molding a long product with a length exceeding 1 m, injection molding is difficult.

When making a molded product with a spiral protrusion by extrusion molding, it is possible to fix the die and sizer and take the molded product while rotating, but the mechanism of the take-off machine becomes complicated and expensive. . Furthermore, it may be even more expensive to create a take-up machine equipped with a mechanism that independently operates rotation and take-up.

On the other hand, if the sizer is rotated and a normal take-off machine is used as in the present invention, the degree of freedom regarding the shape of the molded product is greater, and the manufacturing cost of the machine is also lower.

In the present invention, the irregularly shaped article having a spiral protrusion is also a foamed article, but a good foamed irregularly shaped article can only be obtained by combining a die having a structure as shown in FIG. 2 and a rotary sizer. If it is desired to make a molded product having a protrusion on the outer periphery of a cylinder, the molding can be performed by blowing air through the hole 10 in the center of the die, as shown in FIG. 2, or by evacuating the sizer.

In order to obtain a good foamed molded product, it is necessary to control the molten resin from the storage tank so that it does not become over-foamed when it is extruded from the die. When a die with a similar structure is used, the pressure gradient in the land direction of the die is large, and it is possible to prevent skin irritation due to foaming inside the die. If the die structure is inappropriate, the blowing agent will decompose within the die and the resin will be extruded with severe skin irritation, making it impossible to obtain a good molded product.

The molten resin that comes out of the die is initially extruded into several strands, but as it expands due to the foaming action, the strands adhere to each other, and are further suppressed from the outside by the sizer, so the foaming action continues inward. forms a rod. Further, the cross-sectional shape of the spiral protrusion may be square, triangular, semicircular, etc., including the width and height, as appropriate. The number of protrusions can also be appropriately selected depending on the required shape.

As described above, according to the present invention, a foamed irregularly shaped article having a spiral protrusion can be formed at low cost with a large degree of freedom in shape and size.

Hereinafter, the present invention will be explained in more detail by showing examples.

Example polystyrene with melt flow rate 49/mjn 1
00 parts by weight of blowing agent ADOA (azodicarbonamide)
1.0 parts by weight of foaming aid talc and 0.15 parts by weight of talc were triblended, and using a single-screw extruder with a barrel diameter of 65 mm, 8 inner diameter 2 pieces centered at equal intervals on a circumference of 35 mm diameter were triblended.
The extrusion speed was 100 mm/mm from the die as shown in FIG.

After melt-extruding at a take-up speed of 250 mm and 1 mm, it was shaped using a rotary sizer.

Pressurized air was blown through a hole with a diameter of 6 mm located at the center of the circumference, and the inside of the rotary sizer had a length of 300 mm, a body diameter of 40 mm without a taper, and a concave groove with a semicircular cross section of 8 mm in diameter. The rotation speed is 1/2 rotation per minute.

The obtained molded product had a body diameter of 40 mm, a semicircular cross section of 8 strips, a protrusion profile with a base of 8 mm, a height of 4 mm, and a pitch of 5.
It was a foamed profile extrusion molded product having a spiral protrusion of 0.001 m and a good appearance and a foaming ratio of 25 times.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an outline of the present invention, and FIG. 2 is a sectional view (left side) and a front view (right side). 1. Extruder, 2. Dice, 3.. Chain, 4. Drive motor, 5. Sizer, 6. Cooling water tank, 7.. Taking machine.
8 Land with relatively large cross-sectional area, 9 Thin land, ]
0...Ko Patent applicant Showa Denko K.K. Patent attorney Sei Kikuchi - Figure 1 Figure 2

Claims (1)

[Claims] When molding a foamed profile extrusion molded product with a foaming ratio of 0.05 to 5 times, which has a spiral protrusion on the outer periphery of a cylinder or round bar, the extrudate from a die with a plurality of orifices arranged in a circular manner is passed through a sizer. A foaming profile extrusion molding method characterized by shaping by rotation.