JPH0324939A - Plastic rod-like body - Google Patents

Abstract

PURPOSE:To prevent large deformation at the time of cutting (cutting into round slices) or halving by providing a void to the almost center part of a plastic rod-like body. CONSTITUTION:Voids 2 are formed to the center part of a plastic rod-like body 1 in a continuous beads state or a continuous hole having a uniform radius is provided to the center part of said rod-like body. Or, beads-like voids 2 having different sizes are continuously formed. When the voids 2 are excessively large, the plastic rod-like body 1 becomes a pipe shape and can not develop its original function and, when the voids 2 are excessively small, the rod-like body becomes poor in the relaxing or removing action of residual stress. Therefore, the size of the voids 2 is preferably set so that the ratio D/d of the diameter D of the plastic rod-like body 1 and the diameter (d) of each void is about 5 - 15, especially, about 6 - 12. When the size of D is 15mm or more, the effect due to the voids 2 is especially large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic rod-shaped body useful as a solid profile, and more particularly to a plastic rod-shaped body having a hole in the center.

[Conventional technology]

Traditionally, Blastinok rods have been widely used in various fields, with feed rolls for photo processing machines being a typical example. The biggest drawback of conventional plastic rod-shaped bodies is that residual stress generated during manufacturing exists in the center of the rod-shaped bodies, so that when the rod-shaped bodies are processed, for example, cut into rings or cut in half, they deform significantly. In addition, such cut workpieces are treated with hot water. Easily deforms. Generally, during the manufacturing process, a blast rod-shaped body is gradually cooled from the outer periphery, so cooling is slowest at the center, and residual stress is generated in the inner layer, especially in the center, due to volumetric contraction during cooling and solidification. This residual stress is difficult to judge from its appearance.For example, it is this residual stress that causes warping to occur when a straight rod-shaped object is cut in half. [Problem to be addressed by the invention] The problem to be solved by the present invention is to solve the above-mentioned difficulties of the conventional plastic rod-shaped body, and more specifically, to significantly reduce the residual stress in the inner layer, especially in the center. Or eliminate it.

[Means to solve the problem]

This problem can be solved by actively creating holes in the inner layer of the plastic rod, especially in the center. [Function and side effects of the invention] In the present invention, holes are actively formed in the center of the blast rod-shaped object, that is, holes are forcibly formed due to contraction at the stage when the center cools and solidifies. This removes the residual stress in the center by tightening it. As described above, conventional rod-shaped bodies of this type are usually manufactured by continuous extrusion or shaping, and the extruded rod-shaped bodies are gradually cooled from the outside. For this reason, the center of the rod-shaped body cools the slowest, and due to the difference in temperature between the outer circumferential surface and the inner center, volumetric contraction of the outer circumferential surface occurs faster than that of the inner center. In such a state, the center part has not yet been sufficiently cooled and solidified, so it is affected by the volumetric contraction of the surface of the outer peripheral part and generates stress, making it easy to be pulled by the outer peripheral part. As a result, the inner center becomes non-uniform, and in extreme cases, the resin filling rate decreases significantly, causing warpage.

On the other hand, in the present invention, in the manufacturing stage of the rod-shaped body, especially during the cooling process, by actively providing small holes in the center of the rod-shaped body, the voids generated in the internal center due to the above-mentioned volumetric contraction can be prevented. This relieves or eliminates residual stress and prevents the internal structure from becoming non-uniform. The shape of the above-mentioned pores does not matter; in short, it is sufficient that the pores are pores that can relieve or remove the residual stress that tends to occur in the center of the plastic rod-shaped material. It is advisable to proactively set this up. A few other preferable examples include one in which holes are formed in the shape of a continuous bead in the center of the plastic rod-shaped body as shown in Figure 1, and one in which holes are formed in the form of a continuous bead in the center as shown in Figure 2. It has continuous holes. Furthermore, as shown in Figure 3, bead-like pores of different sizes are successively formed. If the number of pores is too large, the resulting product will become pipe-shaped and will not function as a plastic rod. On the other hand, if the number of pores is too small, the above-mentioned residual stress relaxation or removal effect will not be achieved. It becomes scarce. Therefore, the size of the pores is 5 to 15, which is the ratio D/d of the diameter D of the plastic rod-shaped body and the diameter d of the pores.
In particular, it is preferably about 6 to 12 liters. Note that the above-mentioned effect due to holes is particularly large in a region where the size of D is 15 mm or more. As a means of positively forming small holes in the center of the rod-shaped body during the rod-shaped body manufacturing stage, especially during the cooling process,
For example, a plastic die whose inner wall is coated with polytetrafluoroethylene or a lubricant is used to extrude and shape the desired plastic, and at this time, gas is supplied to the center of the molten plastic at the entrance of the die. I can give an example of how to do this.
Blastinok materials include various conventionally used plastics, such as nylon, polyolefin, polyvinyl chloride, polyester, polyacetal, polyetheride, borisulfone, polycarbonate, and liquid crystal polymers, among which crystalline polymers are preferred. ．． [Example] The present invention will be explained in detail by showing Examples and Comparative Examples below.

Example 1 Polyacecool (Delrin 100 J, manufactured by DuPont) was continuously fed from an extruder to a molding die whose inner wall was coated with polytetrafluoroethylene and shaped in the molding die. Nitrogen gas was supplied to the center of the molten polyacetal and the core was cooled under pressure.In this way, an outer layer having a continuous hole (hole diameter 2 mm) in the center of the shape shown in Figure 2 was formed. A rod-shaped body with a diameter of 30 mm was manufactured.Example 2 A polyacetal rod-shaped body with an outer diameter of 60 mm and having continuous pores with a diameter of 5 mm in the center was manufactured in the same manner as in Example 1 above.

Example 3 In the above Example 1, polyether ξide (Ultem IOOOJ, manufactured by General Electric Company) was used in place of Boriasecur, and all other treatments were carried out in the same manner as in Example 1.

Comparative Example 1 Commercially available polysecure with an outer diameter of 30 mm (“Delrin 100
J) Rod-shaped body with no continuous pores in the center. Comparative Example 2 Comparative Example 1 with an outer diameter of 60 mm.

Comparative Example 3 Commercially available polyetherimide with an outer diameter of 30 mm (Ultem IO
OOJ rod-shaped body without continuous pores in the center.

The residual stresses of the rod-shaped bodies of Examples 1 to 3 and Comparative Examples 1 to 3 were measured. The results are shown in Table 1 below. However, the measurement method was as follows.

Residual stress -1 = A rod-shaped body with a length of 200 mm was cut in half, and the amount of "warp" was measured.

(See Figure 4) Residual stress-2: Slice into a disk shape with a thickness of 20 mm (However,
For comparative examples, a hole with a diameter of 2 mm was made in the center using a drill and then sliced into rings.The samples were immersed in each of the liquids shown in Table 1 at 23°C and visually observed for the occurrence of cracks. [Margin below] Table 1 The amount of strain generated by ripening of the obtained processed product is extremely small, and it does not break or crack during processing.

]) Dimensions of the rod-shaped body itself of the present invention and its cut products: Changes over time are extremely small.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of the rod-shaped body of the present invention. Figure 4 is an explanatory diagram showing two methods for measuring residual stress. ...Rod-shaped body...Vacancies...Amount of warpage (or more) [Effects of the invention] Since the plastic rod-shaped body of the present invention has holes actively provided in the center, , exhibits the following excellent effects.

Claims (4)

[Claims] (1) A plastic rod-shaped body, characterized in that the plastic rod-shaped body is provided with a hole that can reduce residual stress approximately in the center thereof. (2) The ratio of the diameter of the rod-shaped body to the diameter of the hole is 5 to
15. The rod-shaped body according to claim 1, which is 15. (3) The plastic rod-shaped body according to claim 1, wherein the pores are provided continuously as a whole. (4) The plastic rod-shaped body according to claim 1, wherein the pores are continuous pores having a substantially uniform diameter.