JPS6013525A - Manufacture of heat shrinkable tube with inner layer - Google Patents

Abstract

PURPOSE:To produce heat shrinkable tube with a rubber or plastic inner layer by a method wherein a diameter expander is inserted inside the inner layer tube being inserted into the inside of an outer layer tube to apply inner pressure and to make a hollow tubular body with a specified outer diameter. CONSTITUTION:In expanding the diameter of tube 20 to be expanded with which inner layer tube 12 is incorporated previously in a unitary body with the inside of outer layer tube 11, the tube 20 to be expanded is heated to a necessary temperature and softened, then taken out of a hot atmosphere to insert diameter expander 10 with one previously sealed end into the inside of the tube 20. Then, when compressed air is introduced from a compressed air inlet mounted at the opening end of the expander 10 to apply inner pressure and expand a fin part, hollow body 10'' with a circular cut-section is while forming the tube 20 expanded to a desired shape to prepare an expanded tube that is composed of outer layer tube 11'' and inner layer tube 12''. This tube is cooled and hardened, the inner pressure is reduced and the expander is removed from the inner part of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-shrinkable tube with an inner layer made of rubber or plastic, suitable for use as a protective cover for joints of cables or metal fittings such as steel pipes.

Here, "heat shrinkability" refers to the property of a member whose diameter has been expanded to contract due to the action of heat and recover almost to its shape before diameter expansion.
When heat-shrinkable tubes are used as protective covers for joints of cables or for entire bodies such as steel pipes, heat-recoverable tubes are used to provide more complete waterproof or corrosion-proof properties. An inner layer that adheres well to the object is placed inside the outer layer tube, which has been given heat shrinkability in advance.

Conventionally, in order to manufacture a heat-shrinkable tube used for the above-mentioned protective cover, first (1) an outer layer tube made of a material capable of imparting heat-shrinkability was heated to a temperature capable of imparting heat-shrinkability. (2) expanding the diameter to a predetermined size using a diameter expanding means of the type, and then cooling and solidifying it to produce a heat-shrinkable outer layer tube; (2) forming a desired shape on the inner surface of this heat-shrinkable outer layer tube A two-step process is used consisting of applying an adhesive inner layer material. but,
This method has the disadvantage that it is difficult to form the inner layer material to a uniform thickness on the inner surface of the heat-shrinkable outer tube. Furthermore, especially for tubes used for cable joints, etc., an inner layer material with a high softening point that will not flow out at the operating temperature (70 to 90°C) is required. To apply the inner layer to the inner surface of the heat-shrinkable outer layer tube, the inner layer is heated in advance to a molten state, and then (a) this is applied to the inner surface of the heat-shrinkable outer layer tube at room temperature, or (b) The method used is to apply it to a heat-shrinkable outer layer tube that has been heated in advance, and then cool and solidify it.

However, these conventional methods have the following serious drawbacks. In other words, it is difficult to uniformly apply the inner layer material to the inner surface of a long preformed outer tube, and (a) it is difficult to apply the inner layer material that has been preheated to a molten state on the inner surface of a heat-shrinkable outer tube at room temperature. In this method, if the temperature of the inner layer material is higher than the thermal contraction start temperature of the outer layer tube,
The outer layer tube is heated by the applied inner layer material and undergoes thermal contraction. Therefore, in order to avoid such thermal shrinkage of the outer layer tube, restrictions arise such as the need to apply the inner layer material extremely thinly or to use an inner layer material whose temperature is lower than the temperature at which the outer layer tube starts to shrink. Also, (b)
In the method of applying a preheated and molten inner layer to the inner surface of a preheated heat-shrinkable outer layer tube, it is necessary to maintain the outer layer tube and inner layer material at a humidity lower than the heat shrinkage start temperature of the outer layer tube. Therefore, it is not possible to use an inner layer material that has a softening point higher than the thermal contraction start temperature of the outer layer tube. Further, when applying such an inner layer material with a high softening point, the outer layer tube undergoes thermal contraction due to such application, and special equipment and operations are required to maintain the original diameter of the outer layer tube. In this way, it is extremely difficult to apply an inner layer with a particularly high softening point to the inner surface of a heat-shrinkable outer layer tube, as there are various constraints in addition to the problem of uniform coating thickness. This is the current situation.

It is an object of the present invention to provide a simple method for manufacturing a wide range of rubber or plastic lined heat-shrinkable tubes that does not have these drawbacks.

In manufacturing a heat-shrinkable tube with an inner layer made of rubber or plastic, which has an inner layer made of a material having a lower heat softening temperature than the outer layer material imparted with heat-shrinkability, the present invention provides: (1) Imparting heat-shrinkability. On the inner surface of the tube for the outer layer made of a possible rubber or plastic material, a rubber or plastic I having a lower thermal softening temperature than the tube for the outer layer is added.
A tube to be expanded in diameter integrally provided with an inner layer consisting of
or an inner layer made of a rubber or plastic material that is preformed in substantially the same shape as the outer layer tube and has a heat softening temperature lower than that of the outer layer tube, inside an outer layer tube made of a rubber or plastic material that can be heat-shrinkable. At least eight fins of the same length projecting in the radial direction (at equal angular intervals in the circumferential direction and extending along the longitudinal axis 1) The fins extend parallel to the line and are sealed directly at one longitudinal end or folded back to form a closed end at one longitudinal end to form a double-walled structure, and by applying internal pressure, the fins are sealed. (2) a step of heating and softening the diameter-expanded tube; (8) this softening; By applying internal pressure into the diameter expanding arm from the open end of the diameter expander inserted into the expanded diameter tube, the fin portion is expanded, and the diameter expander is made into a hollow body having the predetermined thickness. , a step of expanding the diameter of the tube to be expanded into a desired shape in a softened state outside the diameter expander, and (4) inserting the tube to be expanded into the desired shape by the diameter expander. (5) reducing the internal pressure of the diameter expander to return the diameter expander to its pre-expansion shape, and returning the diameter-expanded tube to the desired shape; A method for producing a heat-shrinkable tube with an inner layer made of rubber or plastic, comprising the step of pulling it out from the diameter expander.

In the method of the present invention, the above-mentioned steps may be performed sequentially, or the second step may be performed before the first step. The material is a diameter-expanded tube with an inner layer tube of a predetermined shape placed inside the tube, and this is expanded using a special diameter expander to impart heat shrinkability to the outer layer tube. The diameter of the inner layer H can be expanded at the same time as the inner layer tube is attached to the inner surface of the outer layer tube whose diameter has been expanded. In addition to significantly improving problems such as unevenness of heat shrinkage, heat-shrinkable tubes with an inner layer having a fairly high softening temperature can also be produced.

In the method of the present invention, the outer layer tube may be any commonly used rubber-based or plastic-based material that can be heat-shrinkable, and the inner layer tube may be any material that can be heat-shrinkable to the outer layer tube. Any of the commonly used materials such as polyolefins, modified polyolefins, polyamides, and polyesters that do not flow out within the possible temperature range may be used, and can be appropriately selected depending on the combination with the outer layer tube and the diameter expansion procedure.

The material that makes up the diameter expander used in the method of the present invention must sufficiently withstand the heat and pressure necessary to maintain the predetermined enlarged diameter and shape during diameter expansion, and the material as a whole must have a diameter larger than the predetermined diameter. is a brace that does not expand and has sufficient strength to reduce distortion and distortion in the longitudinal axis direction of the expanded member and provide dimensional stability, and the expandable fin portion can be used repeatedly. It is desirable that the material has strength, bendability, and a certain degree of flexibility to withstand this, and that can be restored to its original shape after being decompressed.

Examples of such materials include sheets of plastic or rubber materials, and reinforcing sheets having at least one reinforcing cross layer on one side, both sides, or an intermediate position between the two sides of such sheets.

The reinforcing cloth layer is a cross layer of fibers selected from the group consisting of natural fibers, inorganic fibers, and synthetic fibers, and the catching cloth layer is arranged in a weave direction parallel to the radial and longitudinal axes of the expander. It is preferable that the The reason for this is that when a diameter expander made of a material reinforced with such a reinforcing cross layer is used, a heat-shrinkable tube can be obtained that expands in the radial direction according to the specified magnification and has no elongation or distortion in the longitudinal axis direction. It is. In addition, plastic material sheets include, for example, polyester resin, zaryamide resin, purple resin,
It is a sheet of heat-resistant plastic resin such as acrylic resin, polyimide resin, etc., and the rubber material sheet is, for example, non-vulcanized or vulcanized natural rubber, SBR, OR,
Engineering R, IIRSBR.

This is a sheet of synthetic rubber such as EPR, silicone rubber, or urethane rubber.

The invention will now be explained by way of example with reference to the drawings.

In a preferred method of the invention, as shown in Figures 1a and b,
At least three, for example eight, radially outwardly projecting fins l of equal length extend parallel to the longitudinal axis at substantially equiangularly spaced positions in the circumferential direction, and The expander is made into a hollow body having a predetermined thickness as shown by lθ″ in FIG. 8C or FIG. A compressed air inlet is provided at the other end, that is, the open end, for use.

Another example of the method of the invention is as shown in Figures 2a and b.
at least eight radially projecting spaces 5, e.g. extending parallel to the longitudinal axis at equiangularly spaced positions;
By applying internal pressure to this space, the fin portion l is expanded to form a double-walled hollow body having a predetermined thickness. A diameter expander 10 is connected to the open end 7, which is the other end, through a compressed air inlet. shall be provided and used.

The process of expanding the diameter using the diameter expander shown in FIGS. IA and B is shown in FIGS. AA, B, and 0, and FIG.

Figures b, c, a, e and 1 will be explained. When expanding the diameter of the tube 20 to be expanded, in which the inner layer tube 12 is preliminarily integrated into the inner surface of the outer layer tube 11 as shown in FIG. The tube for the inner layer is heated to a temperature that allows it to be heat-shrinkable, but the tube for the inner layer is expandable so that it does not flow out. Then, it is removed from the heated atmosphere and immediately placed in an expansion tube with one end sealed in advance. 1'0 is inserted into the inside of the diameter-expanded tube 20 as shown in Fig. 8b, and compressed air is introduced into the diameter expander IO from the compressed air inlet provided at the open end of the diameter expander to increase the internal pressure. In addition, when the fin portion l of this diameter expander is expanded, the diameter expander 10 becomes a hollow body to' having a circular cross section as shown in FIG. The tube 20 is expanded into a desired shape to form an expanded tube 20 consisting of an outer layer tube 11' and an inner layer tube 12.
′ is generated. The tube 20' to be expanded into the desired shape is cooled and solidified with the expander inserted, and then the internal pressure of the expander is reduced to return the expander to the shape before expansion. , the expander is pulled out from inside the diameter-expanded tube 20'. In this way, the inner layered heat-shrinkable tube 20' is easily obtained, in which the outer layer tube and the inner layer tube, which have been integrated in advance, are uniformly expanded in diameter at the same time and integrated. Note that the diameter expander can be inserted as required.
This can be done before heating the diameter-expanded tube 20 to a required temperature range.

In the diameter-expanded tube 20 which has been made into two pieces in advance as shown in FIG. 3a, for example, the outer layer tube 11 needs to be cross-linked in advance by electron beam irradiation, but cross-linking of the inner layer tube 12 is not preferable. If there are constraints on the characteristics such as, the outer layer tube 11 (Fig. 4a) is made in advance by independently cross-linking, and the inner layer having an outer diameter slightly smaller than the inner diameter of the outer layer tube 11 is prepared separately. The inner layer tube 12 is inserted into the outer layer tube 11 as shown in FIG. 4C to form the diameter-expanded tube 20. The expander IO with one end sealed is inserted as shown in Figure 4d, and compressed air is introduced into the expander IO from the compressed air inlet provided at the open end of the expander to apply a slight internal pressure. In a situation where the fin portion l of the diameter expander is slightly expanded and the diameter expander 10 is slightly expanded as shown by to' in Fig. 4e, the required temperature, that is, the outer layer tube can obtain heat shrinkability. When the inner layer tube is softened by heating to a temperature that allows its diameter to expand without flowing out, the inner layer tube 12' is held in close contact with the outer layer tube 11' during the heating process, as shown in FIG. 4e. Next, this is taken out from the heated atmosphere and immediately further compressed air is introduced into the expander io' to apply even higher internal pressure to expand the fin portion 1, so that the expander 10' crosses as shown in Fig. 4f. The outer layer tube tt' and the inner layer tube 12', which are in a softened state on the outside of the diameter expander 1O, are simultaneously expanded to a desired magnification and integrated into a hollow body 10' having a circular surface.
Expanded diameter tube 2 consisting of an outer layer tube 11' and an inner layer tube 12' expanded to a desired magnification.
0' is generated. The diameter-expanded tube 20', which has been expanded to a desired shape, is cooled and solidified in the same manner as described above, and after the internal pressure of the diameter expander is reduced, the diameter expander is pulled out from the tube 20'.

In this way, the inner layered heat-shrinkable tube 20' can be easily obtained, in which the outer layer tube and the inner layer tube, which have been separately molded, are simultaneously and uniformly expanded in diameter and integrated.

When using the diameter expander shown in Figures 2a and 2b, the diameter is expanded in the same manner as described above, except that internal pressure is applied to the space 5 between the outer wall 3 and the inner wall 4 of the fin portion 1. 2′.

I can.

The maximum diameter expansion ratio achieved by the present invention is achieved by using a diameter expander in which the radial length of the fin part l is h and the number of fin parts is X, and the inner diameter is 2h
When expanding the diameter of a slightly larger member, it is expressed by the following equation.

Maximum diameter expansion magnification (x x gh/yr) / 2h For example, in the diameter expanders shown in Figures IA and B and Figures 2A and B, since X = 8, the maximum diameter expansion magnification is approximately 2.6 times. be. As is clear from the above equation, in the present invention, the maximum diameter expansion magnification can be increased or decreased by increasing or decreasing the radial length h and the number X of the fin portion of the diameter expander.

Next, the present invention will be explained with reference to examples. In these examples, an expander made of a material made of a single layer of polyester cloth covered on both sides with silicone rubber and cured by vulcanization was used. The weaving direction of the polyester cloth was made to match the radial and axial directions of the expander. In Examples 1 and 2, first
A diameter expander having eight fins and an expansion diameter of 40 mm as described in FIGS. A compressed air inlet was attached to the end in advance.

Example 1 An outer layer tube made of low-density polyethylene with a thickness of a, 0m and a tube made of dimer acid-based polyamide (R
A tube with an inner layer with an inner layer having a softening point of 165° C. and an inner layer tube having an inner diameter of 20 cm and an enlarged inner layer, as shown in FIG. Then cut it to a length of 39cm,
The whole was heated in a heating atmosphere of 130° C. until the temperature reached a uniform temperature to soften it.

Next, this diameter-expanded tube is removed from the heated atmosphere,
Immediately insert a diameter expander inside this diameter-expanded tube as shown in Figure 8b, introduce compressed air into this diameter expander from the compressed air inlet, and expand the diameter expander at an internal EE of 20ky/c- as shown in Figure 8c. The diameter of the tube to be expanded, which was in a softened state outside the diameter expander, was expanded into a desired shape by expanding it as shown in FIG. Next, the diameter-expanded tube that has been expanded into the desired shape is
Water-cooled and solidified with the expander inserted. Thereafter, the internal pressure of the expander was reduced to return the expander to its pre-inflated shape, and the expanded tube was pulled out from the expander. This tube is a heat-shrinkable tube with a smooth inner layer that has been uniformly expanded to a desired shape, and has a circular cross section as shown in Figure 80, an inner diameter of 49 m+, an outer layer thickness of lJm, and an inner layer thickness of [, It was 99 cm long.

Example 2 A tube made of the same material as the outer layer tube of Example 1, molded separately,
2.0 Megaland electron beam cross-linked inner diameter, wall thickness 8.
A tube for the outer layer as shown in Figure 4a for the 0 fin is separately molded for the inner layer as shown in Figure 14b for the fin with an inner diameter of 19 mm and a wall thickness of 2.0 mm made of EVA (R&B softening point 155°C). Cut the tube together with the tube to a length of 80mm, insert this inner layer tube into the outer layer tube as shown in Figure 40 to create a tube to be expanded in diameter, and then insert a diameter expander inside this tube as shown in Figure 4d. Insert compressed air into this expander from the compressed/air inlet to reduce the internal pressure to 0.3$.
/crn'' to slightly expand the diameter expander as shown in Figure 40, and in that state, heat it in a heated atmosphere of 130°C until the entire body becomes uniform to soften it, thereby converting the tube for the inner layer into the tube for the outer layer. The tube was held in close contact with the tube.Then, the tube was removed from the heated atmosphere, and compressed air was immediately further introduced to create an internal pressure of 2.0~/Cm'', causing the expander to expand as shown in Figure 4f. The diameter of the tube to be expanded, which was in a softened state on the outside, was expanded into a desired shape. Next, this diameter-expanded tube was water-cooled and solidified with the diameter expander inserted. Thereafter, the internal pressure of the expander was reduced to return the expander to its pre-inflated shape, and the expanded tube was pulled out from the expander. This tube is a heat-shrinkable tube with a smooth inner layer whose diameter has been expanded uniformly into a desired shape, and has the same structure and dimensions as those in Example 1,
The inner surface of the diameter-expanded outer layer tube and the outer surface of the diameter-expanded inner layer tube were firmly adhered and integrated.

Since the method for manufacturing a heat-shrinkable tube with an inner layer of the present invention is used, there is no need to uniformly apply the inner layer material to a long pre-formed outer layer tube, and processing can be performed at a temperature higher than the shrinkage start temperature of the outer layer tube. A heat-shrinkable tube with a high softening point inner layer ff can be manufactured very easily since the outer layer tube has a high softening point and no coating is required for the inner layer. In addition, the material of the outer layer tube and the inner layer tube can be selected as appropriate within the temperature range where the outer layer tube can obtain heat shrinkability, but the inner layer tube can be expanded without flowing out. It is also possible to combine the outer layer tube and inner layer tube, which are separately molded, and integrate them at the same time as the diameter expander. , combination of inner layer tube and outer layer tube,
This is an extremely useful method with a wide range of applications, as diameter expansion and procedures can be selected as appropriate.

[Brief explanation of the drawing]

Figures 1a and b are a cross-sectional view and a perspective view, respectively, of an example of a diameter expander used in the method of the present invention; Figures 2a and b are a cross-sectional view and a perspective view, respectively, of another example of a diameter expander used in the method of the present invention; Fig. 8a is a cross-sectional view of an example of a tube to be expanded in diameter in which an outer layer tube and an inner layer tube are integrated in advance, and Figs. A cross-sectional view showing the state before and after diameter expansion in an example of the method of the present invention for expanding the diameter of a tube to be expanded. Figures 4a, e and fl1 are cross-sectional views of an example of a tube to be expanded in diameter in combination with each other, respectively, in an example of the method of the present invention for expanding the diameter of the tube in Figure 86 using the expander in Figure It is an explanatory diagram showing stages. ■...Fin part-2...Closed end 8...Outer wall 4...Inner wall 5...-Space 6...Open end 10, 10'...Expander 10'...Expanded Expander (hollow body) 11111', 11'...outer layer tube 12, 1
2', 12',...Inner layer tube 20.20'.
...Tube to be expanded 20'... Expanded diameter tube (heat-shrinkable tube with inner layer) h...Radial length of the fin portion. Figure 1b Figure 2b

Claims (1)

[Scope of Claims] L In manufacturing a heat-shrinkable tube with an inner layer made of rubber or plastic, the inner layer is made of a material having a lower heat-softening temperature than the outer layer material to which heat-shrinkability is added: An expanded tube in which an inner layer made of a rubber or plastic material having a lower heat softening temperature than the outer layer tube is integrally provided on the inner surface of an outer layer tube made of a rubber or plastic material, or heat shrinkable. An inner layer tube made of a rubber or plastic material, which is preformed in substantially the same shape as the outer layer tube and has a lower heat softening temperature than the outer layer tube, is inserted inside an outer layer tube made of a rubber or plastic material. At least eight radially projecting fins of equal length extend parallel to the longitudinal axis at equal angular intervals in the circumferential direction on the inside of the expanded diameter tube. One end in the direction is directly sealed or one end in the longitudinal direction is folded back to form a closed end to form a double wall structure, and the fin portion is expanded by applying internal pressure to form a hollow body of a predetermined thickness. (2) a step of heating and softening the tube to be expanded, and (8) an open end of the expander inserted into the softened tube to be expanded. The diameter-expanded tube is in a softened state on the outside of the diameter expander by applying internal pressure inside the diameter expander to expand the fin portion and making the diameter expander into a hollow body having the predetermined thickness. (4) cooling and solidifying the diameter-expanded tube into the desired shape with the diameter expander inserted; (5) ) Reducing the internal pressure of the diameter expander to return the diameter expander to its pre-inflated shape, and pulling out the diameter-expanded tube that has been expanded to the desired shape from the diameter expander. A method of manufacturing a heat-shrinkable tube with a rubber or plastic inner layer.