JPS6312776B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a silicone rubber heat-shrinkable tube. In general, heat-shrinkable tubes take advantage of their ability to return to their original shape when heated, and are widely used to tightly coat objects of various shapes and protect them electrically, chemically, and physically. There is.

The typical manufacturing method for conventional heat-shrink tubes is to heat a tube made of heat-recoverable resin or rubber to a temperature above the softening temperature and below the flow temperature, and then introduce it into a molded tube and pressurize the fluid from one end of the tube. A method is used in which the molecules are expanded to the inner diameter of the molded tube, cooled and fixed, and orientational strain remains in the molecules.

The qualities necessary for these heat-shrinkable tubes are that the inner diameter is uniform over the entire length, the shrinkage rate is constant, and the shrinkage in the length direction is small.

To achieve this objective, the heating of the tube before forming must be uniform and isothermal over its entire length;
During the forming process, it is required that the tube is not stretched longer than necessary in the longitudinal direction. However, the hot air method, which is used when heating over 100 degrees is required, such as silicone rubber heat shrink tubes,
Heating by passing through a heating furnace has the following drawbacks.

In the former case, the required temperature can be set arbitrarily, but there is a temperature difference between the part directly in contact with the hot air and the other parts, and when this is expanded under pressure, the cross section will not be uniformly expanded to a circular shape, and variations will occur during contraction.

Therefore, it is necessary to achieve uniformity by heating for a long time, which is uneconomical and disadvantageous in terms of productivity. The latter has the same drawbacks as the former, such as a difference in expansion due to temperature difference between parts near and far from the furnace wall, and variations in shrinkage rate.

Furthermore, in the conventional forming method, the material is expanded to the diameter of the forming tube by the pressure of fluid flowing into the tube in a forming tube having an inner diameter equal to the desired expansion diameter, and then cooling and fixing is carried out. If cooling is insufficient in this step, the tube pulled out from the molded tube may become deformed. Therefore, instead of increasing the cooling time or slowing down the speed in a continuous process, the length of the formed tube is increased.
The former method is not economical, and the latter method tends to trap residual air bubbles between the formed tube and the tube, especially in the center, resulting in defective products.Also, due to the frictional resistance between the formed tube and the tube, the tube is stretched in the longitudinal direction. There is a drawback that a good heat shrinkable tube cannot be obtained because it is stretched. Therefore, attempts have been made to provide gas escape grooves on the inner wall of the molded tube or to coat the molded tube with a fluororesin having a small coefficient of friction, but these methods have problems from an economical and technical standpoint, and are by no means satisfactory.

The present invention solves the above-mentioned drawbacks and provides a highly efficient method for manufacturing a heat-shrinkable tube having a uniform inner diameter and little change in shrinkage in the longitudinal direction. The present invention will be described below with reference to Examples.

Reference numeral 1 denotes a feed drum, which temporarily winds up the raw tube formed by an extruder or the like. Reference numeral 2 denotes a guide roll which functions to take over the original tube being wound up onto the feed drum 1. In addition to 2, there are 4.7.
8 is also a feed roll that also serves as a guide roll, and is driven by a continuously variable speed motor, and the roll interval of each roll can be freely adjusted, and 7 is fed from the rotary joint 11 of the winding drum 9 It works to block the air from flowing. 3 is a liquid bath that heats the raw tube and usually maintains a temperature of 100 to 160 degrees. Each roll in the liquid tank prevents the tube from stretching or sagging. 10 is a molded tube. The formed tube has a plurality of sets of two through holes 13, 13' in the upper and lower parts of the cylinder body 12 parallel to the cylinder axis;
13a, 13'a, 13b, 13'b... are provided radially from the central axis, and U-shaped guides 14, 14a, 14b... are provided in each pair of through holes in the axial direction (arrow direction). It is movable and has a cold air passage 15 and an outlet 16 at the top.

Reference numeral 6 denotes a water tank, which is capable of further completely cooling the tube that has been expanded and cooled and fixed within the molded tube, and at the same time, the lubricant can be washed away with running water. A winding drum 9 winds up the product taken up by the guide roll 8. Reference numeral 11 is a rotary joint, which is a fluid supply port that always supplies an appropriate pressure inside the tube. 2.4.7.
8 to move at a constant speed. During the process, each part is uniformly heated to the optimum molding temperature by passing through glycerin heated to the temperature required for molding. The heated tube is fed into the forming tube with its surface wet with glycerin, and the guides 14, 14 whose position is adjusted in advance so as to be in contact with the enlarged diameter by air pressure sent from the rotary joint 11.
It is enlarged until it touches a, 14b, . . . . The enlarged tube is cooled by the cold air blown from the upper part 16 of the forming tube, and the guides 14, 14a, 1
4b.

At this time, the glycerin that wets the surface acts as a lubricant and improves the slippage between the movement guide and the tube.

The formed tube is led to a water tank, where the glycerin on the surface is washed away with running water, and the tube is completely cooled and fixed, and then rolled up onto a winding drum. The heating medium used in the present invention is not limited to the exemplified glycerin, but may be any one such as ethylene glycol or propylene glycol as long as it has a boiling point higher than the temperature required for molding and can be easily removed by washing with water. Also, although it is preferable to use a round bar as a guide for the molded tube, there is no need to insist on using a round bar.

Since the manufacturing method according to the present invention uses polyhydric alcohols such as glycerin, ethylene glycol, and propylene glycol as the heating medium, it is not only possible to easily obtain the molding temperature required for silicone rubber heat-shrinkable tubes, but also it is difficult to Since the surface of the silicone rubber material is well wetted and no air bubbles are attached to the surface, it can be efficiently and uniformly heated in the heating tank. In addition, it can effectively work as a guide surface lubricant in the molding process to wet the surface well.

Furthermore, since the diameter of the molded tube can be set to any desired diameter using a plurality of guides provided on the cylindrical body, there is no need to prepare a molded tube for each size. Furthermore, since the contact area with the enlarged tube is small, longitudinal elongation due to frictional resistance can be almost eliminated.

Furthermore, since the cooling air passes between the enlarged tube and the inner wall of the cylinder, the cooling efficiency is high and there are no problems caused by trapped air bubbles during the molding process. Furthermore, the molded tube is completely cooled by passing through a water bath in the step of washing away the heating medium adhering to the surface.

Therefore, it is possible to manufacture a silicone rubber heat-shrinkable tube with good dimensional stability at a faster speed than in the conventional method.

As described above, according to the method of the present invention, a heat-shrinkable silicone rubber tube with extremely low shrinkage in the longitudinal direction and good dimensional accuracy can be manufactured easily and economically.

[Brief explanation of the drawing]

Fig. 1 is a process explanatory diagram of the manufacturing method according to the present invention, Figs. 2 to 5 are illustrations of an embodiment of the formed tube of the present invention, Fig. 2 is a top view, Fig. 3 is a side view, and Fig. 4 is 1-1
The sectional view, FIG. 5, is a 11-11 sectional view.

Claims (1)

[Scope of Claims] 1. A long tube made of heat-recoverable silicone rubber, such as glycerin, ethylene glycol, propylene glycol, etc., which has a boiling point above the softening temperature and below the flow temperature of the tube, and which is easily removed by washing with water. A process of heating using a liquid heating medium that can be produced, a process of feeding the heated tube with the heating medium attached to a forming tube equipped with a movable guide so that the inner diameter can be set to an arbitrary diameter, and a process of feeding the tube into a forming tube that is equipped with a movable guide so that the inner diameter can be set to an arbitrary diameter. A method for manufacturing a heat-shrinkable silicone rubber tube, which consists of a molding process in which the tube is expanded to the inner diameter of the molded tube by pressure of a fluid injected from one end and then cooled, and a process in which the molded tube is sent into a water tank and washed with water. 2. A plurality of sets of two through holes are provided in the upper and lower parts of the cylinder parallel to the cylinder axis radially from the central axis, and a U-shaped guide is provided in the through holes so as to be movable in the axial direction. Claim 1 also uses a molded tube with a cold air outlet provided on the inner surface of the upper part of the tube.
A method for producing a heat-shrinkable silicone rubber tube as described in 2.