JP6829164B2 - How to manufacture heat shrink tubing - Google Patents

Description

The present invention relates to a method for producing a heat shrinkable tube.

A heat-shrinkable tube is used as an insulating coating material for an electric wire connection portion. Generally, this heat-shrinkable tube is used in a step of extruding a resin composition into a tube shape, a step of irradiating a tube after extrusion with an active energy ray such as an electron beam, a step of heating the tube after irradiation with the active energy ray, and a step after heating. Manufactured by the steps of expanding the diameter of the tube, cooling the expanded tube, and winding the cooled tube. Further, this heat-shrinkable tube is manufactured while being conveyed in the axial direction after being extruded by the extrusion process. The heat-shrinkable tube is shape-memorized by cross-linking by irradiation with the active energy rays, then expanded in diameter, and is cooled and fixed in this expanded state.

The diameter expansion step is performed by passing a tube heated to a temperature higher than the melting point through the sizing tube. More specifically, in the diameter-expanding step, the inside of the sizing tube is depressurized, a tube heated to a melting point or higher is passed through the sizing tube, and a gas is further introduced into the tube from an end opening on the downstream side in the transport direction. It is done by supplying.

However, when gas is supplied into the tube from the end opening on the downstream side in the transport direction, the pressure loss increases as the length of the tube increases. Therefore, in the diameter expansion step, in order to compensate for the pressure loss caused by the increase in the length of the tube, the gas supply pressure is increased at a constant ratio based on the estimated value obtained in advance.

Further, as a method of compensating for the pressure loss, a method of measuring the outer diameter of the tube immediately after heating and adjusting the amount of gas supply pressure into the tube according to the measured value has also been proposed (Japanese Patent Laid-Open No. 7-). 178813 (see).

Japanese Unexamined Patent Publication No. 7-178813

However, if the gas supply pressure into the tube is increased at a constant ratio based on the estimated value as described above, a deviation from the required pressure value tends to occur as the length of the tube increases. ..

Further, as described in the above publication, when the gas supply pressure into the tube is adjusted according to the measured value of the outer diameter of the tube immediately after heating, as the length of the tube becomes longer, the downstream side in the transport direction of the tube The response until the effect of the pressure increased or decreased at the end of the tube is reflected in the enlarged diameter part of the tube becomes poor and the time lag becomes large. As a result, the diameter of the obtained tube tends to be non-uniform in the axial direction.

The present invention has been made based on such circumstances, and an object of the present invention is to provide a method for manufacturing a heat-shrinkable tube capable of making the tube diameter uniform.

The method for producing a heat-shrinkable tube according to one aspect of the present invention, which has been made to solve the above problems, includes a heating step of heating the tube formed of the resin composition to a temperature equal to or higher than the melting point while conveying the tube in the axial direction, and the above-mentioned heating. A gas that includes a diameter-expanding step of expanding the diameter of the tube and a cooling step of cooling the expanded tube, and the diameter-expanding step supplies gas into the tube from the downstream side in the transport direction of the tube. It has a supply step, and in the gas supply step, control is performed so that the flow rate of the gas supplied into the tube under the supply pressure is kept constant.

The method for manufacturing a heat-shrinkable tube according to the present invention can make the tube diameter uniform.

It is a flow chart which shows the manufacturing method of the heat shrink tube which concerns on one Embodiment of this invention. It is a figure which shows the detail of the diameter expansion process of the manufacturing method of the heat shrink tube of FIG. It is a schematic diagram which shows the manufacturing apparatus of the heat-shrinkable tube used in the manufacturing method of the heat-shrinkable tube of FIG. It is a schematic side view for demonstrating the flow rate control method in the gas supply process of the heat shrink tube manufacturing method of FIG. No. It is a graph which shows the relationship between the outer diameter of the heat-shrinkable tube and the winding length obtained by the manufacturing method of the heat-shrinkable tube of 1. No. It is a graph which shows the relationship between the outer diameter of the heat-shrinkable tube and the winding length obtained by the manufacturing method of the heat-shrinkable tube of 2.

[Explanation of Embodiments of the Present Invention]
First, embodiments of the present invention will be listed and described.

The method for producing a heat-shrinkable tube according to one aspect of the present invention includes a heating step of heating the tube formed of the resin composition to a temperature equal to or higher than the melting point while conveying the tube in the axial direction, and expanding the diameter of the heated tube. A step and a cooling step of cooling the expanded tube are provided, and the diameter expanding step includes a gas supply step of supplying gas into the tube from the downstream side in the transport direction of the tube, and the gas supply. In the process, the flow rate of the gas supplied into the tube under the supply pressure is controlled to be kept constant.

According to the findings of the present inventors, in the conventional method for manufacturing a heat-shrinkable tube, the pressure of the gas supplied into the tube is controlled when the diameter of the tube is expanded, so that the pressure loss increases as the length of the tube increases. And the influence of time lag became large, and it was difficult to make the tube diameter uniform. On the other hand, the method for manufacturing the heat-shrinkable tube is based on a new finding that the flow rate of the gas supplied into the tube under the supply pressure is controlled to be constant, thereby making the tube diameter uniform. Can be planned.

In the gas supply step, the flow rate may be determined according to the linear velocity of the tube and the internal cross-sectional area after the diameter is expanded. As described above, in the gas supply step, by determining the flow rate according to the linear velocity of the tube and the inner cross-sectional area after the diameter is expanded, it is possible to easily and surely make the tube diameter uniform. The "inner cross-sectional area" of the tube means the area of the internal space defined by the inner circumference of the tube in the cross section perpendicular to the axis of the tube.

The average inner diameter of the tube after the diameter expansion is preferably 1 mm or more and 5 mm or less. When the average inner diameter of the tube after the diameter expansion is relatively small, the pressure loss of the gas supplied in the gas supply step tends to be large. However, the method for manufacturing the heat-shrinkable tube can make the tube diameter uniform even if the inner diameter of the tube after the diameter expansion is within the above range.

The linear velocity of the tube is preferably 10 m / min or more and 60 m / min or less. When the linear velocity of the tube is relatively high, the pressure loss of the gas supplied in the gas supply step tends to be large. However, the method for manufacturing the heat-shrinkable tube can make the tube diameter uniform even when the linear velocity of the tube is within the above range.

The method for manufacturing the heat-shrinkable tube further includes a winding step of winding the tube after the cooling step, and the winding length of the tube in the winding step is preferably 5000 m or more. In the method for manufacturing the heat-shrinkable tube, the tube diameter can be made uniform even when the winding length of the tube is set to the above lower limit or more.

In the present invention, the "melting point" means the melting point peak temperature measured by a differential scanning calorimeter (DSC) in accordance with JIS-K7121: 2012 "Method for measuring transition temperature of plastics". Further, the "average inner diameter of the tube" means an average value of the inner diameter of the tube along the axial direction measured by a pin gauge.

[Details of Embodiments of the present invention]
A preferred embodiment of the present invention will be described below with reference to the drawings.

[Manufacturing method of heat shrink tube]
As shown in FIG. 1, the method for producing the heat-shrinkable tube includes a heating step of heating the tube formed of the resin composition to a temperature equal to or higher than the melting point while conveying the tube in the axial direction, and expanding the diameter of the heated tube. It includes a diameter step and a cooling step for cooling the expanded tube. In addition, the method for manufacturing the heat-shrinkable tube further includes a winding step of winding the tube after the cooling step. As shown in FIG. 2, the diameter-expanding step includes a gas supply step of supplying gas into the tube from the downstream side in the transport direction of the tube. In the method for manufacturing the heat-shrinkable tube, the flow rate of the gas supplied into the tube under the supply pressure is controlled to be kept constant in the gas supply step.

According to the findings of the present inventors, in the conventional method for manufacturing a heat-shrinkable tube, the pressure supplied into the tube when the diameter of the tube is expanded is controlled, so that the pressure loss and the time lag increase as the length of the tube increases. It was difficult to make the diameter of the tube uniform due to the large influence of. On the other hand, the method for manufacturing the heat-shrinkable tube is a new finding that the flow rate of the gas supplied into the tube under the supply pressure is controlled to be constant, more specifically, the tube transported in the axial direction. It is based on the finding that gas is supplied in response to the increase in volume. As a result, the method for manufacturing the heat-shrinkable tube can make the tube diameter uniform even when the length of the tube is increased.

<Heat shrink tube manufacturing equipment>
First, in explaining the method for manufacturing the heat-shrinkable tube, an example of a heat-shrinkable tube manufacturing apparatus for carrying out the method for manufacturing the heat-shrinkable tube will be described with reference to FIG.

The heat-shrinkable tube manufacturing apparatus includes a heating unit 1 that is formed of a resin composition and heats a tube X that is transported in the axial direction to a melting point or higher, and a diameter-expanded portion that expands the diameter of the tube X heated by the heating unit 1. A portion 2 and a cooling portion 3 for cooling the tube X whose diameter has been expanded by the diameter-expanded portion 2 are provided. Further, the heat-shrinkable tube manufacturing apparatus includes a winding unit 4 that winds up the tube X cooled by the cooling unit 3. Further, the heat-shrinkable tube manufacturing apparatus includes a gas supply unit 5 that supplies gas into the tube X from the downstream side in the transport direction Y of the tube X, and a decompression unit 6 that reduces the pressure inside the diameter-expanding unit 2. In addition, the heat-shrinkable tube manufacturing apparatus is provided between the cooling unit 3 and the winding unit 4, and is provided between a driving unit (not shown) for adjusting the transport speed of the tube X and between the driving unit and the winding unit 4. It is provided with a dancer roll (not shown) that keeps the tension of the tube X constant. The heat-shrinkable tube manufacturing apparatus may further include an outer diameter sensor (not shown) for measuring the outer diameter of the tube X after the diameter has been expanded on the downstream side of the transport direction Y of the cooling unit 3.

Examples of the main component of the resin composition include fluororesin, ionomer resin, polyethylene terephthalate, polyamide, polyolefin such as polyethylene, and the like. The melting point of the resin is, for example, about 70 ° C. or higher and 210 ° C. or lower. The "main component" means the component having the highest content in terms of mass.

A tube X whose shape is memorized by irradiation with an active energy ray such as an electron beam after being extruded into a tube shape by an extruder (not shown) is conveyed to the heating unit 1. The heating unit 1 heats the tube X, which is conveyed in the axial direction, to a melting point or higher. Examples of the heat source used in the heating unit 1 include an infrared heater, hot air, and the like. For example, the shape-memory tube X may be wound on a supply drum (not shown) and then transported from the supply drum to the heating unit 1.

The enlarged diameter portion 2 has a substantially cylindrical sizing tube (not shown) having an internal space through which the tube X passes. This sizing tube has a plurality of through holes that penetrate in the radial direction. A tube X having an outer diameter smaller than the inner diameter of the sizing pipe is conveyed to the enlarged diameter portion 2. The diameter-expanding portion 2 is configured so that the outer diameter of the conveyed tube X can be expanded to the inner diameter of the sizing pipe.

The lower limit of the inner diameter of the sizing tube is preferably 1.5 mm, more preferably 2.5 mm. If the inner diameter is smaller than the lower limit, the use of the obtained heat-shrinkable tube may be limited, or the effect of expanding the diameter may not be sufficiently obtained. On the other hand, the upper limit of the inner diameter of the sizing tube is not particularly limited, but is preferably 6.5 mm, more preferably 5.5 mm. Generally, the smaller the inner diameter of the tube X after the diameter is expanded, the larger the pressure loss of the gas supplied into the tube X. Therefore, according to the conventional heat-shrinkable tube manufacturing apparatus, when the inner diameter of the sizing tube is equal to or less than the above upper limit, the diameter of the tube X after the diameter increase increases as the length of the tube X passing through the diameter expansion portion increases. It tends to be non-uniform in the axial direction. On the other hand, according to the heat-shrinkable tube manufacturing apparatus, even when the inner diameter of the sizing tube is set to be equal to or less than the upper limit, the diameter of the tube X after the diameter expansion can be sufficiently made uniform.

The diameter-expanding mechanism of the tube X by the diameter-expanding portion 2 will be described. As described above, the heat-shrinkable tube manufacturing apparatus has a gas supply unit 5 that supplies gas into the tube X from the downstream side in the transport direction Y of the tube X. The gas supply unit 5 is configured to be able to supply gas, typically air, from the end opening of the tube X after being wound by the winding unit 4. Specifically, the gas supply unit 5 includes a compressor 5a that supplies the gas to the end opening of the tube X, a regulator 5b that adjusts the supply pressure of the gas supplied by the compressor 5a, and an end portion of the tube X. It has a flow meter 5c that measures the flow rate of the gas supplied to the opening.

Further, the heat-shrinkable tube manufacturing apparatus has a decompression unit 6 for reducing the pressure inside the diameter-expanded portion 2 as described above. The decompression unit 6 is configured to be able to decompress the internal space of the sizing tube. The decompression unit 6 is composed of, for example, a vacuum pump. The decompression unit 6 is airtightly connected to the internal space of the sizing pipe via the plurality of through holes.

As a result, the diameter-expanding portion 2 becomes the difference pressure between the internal pressure of the tube X based on the gas supplied into the tube X by the gas supply unit 5 and the pressure in the internal space of the sizing tube decompressed by the decompression unit 6. Based on this, the tube X is configured so that the diameter can be expanded.

The cooling unit 3 cools and fixes the tube X whose diameter has been expanded by the diameter expansion unit 2. The diameter of the tube X after being cooled and fixed by the cooling unit 3 is substantially equal to the diameter of the tube X after being expanded by the diameter-expanded portion 2. Examples of the cooling source of the cooling unit 3 include water, cold air, and a refrigerant. The cooling unit 3 does not have to be provided on the downstream side of the diameter-expanded portion 2 in the transport direction Y, and may be provided, for example, on the outer peripheral side of the sizing pipe. In this case, the cooling unit 4 may be configured to cool the tube X passing through the sizing pipe by, for example, water-cooling the sizing pipe from the outer peripheral surface side.

The winding unit 4 winds up the tube X which has been cooled and fixed by the cooling unit 3. The take-up unit 4 is composed of, for example, a take-up drum.

Subsequently, a method for manufacturing the heat-shrinkable tube will be described.

(Heating process)
In the heating step, the tube X fed in the transport direction Y is heated to a melting point or higher. The heating step is performed by the heating unit 1. The heating temperature in the heating step can be set according to the melting point of the tube X, and can be, for example, 70 ° C. or higher and 230 ° C. or lower.

(Diameter expansion process)
In the diameter expansion step, the diameter of the tube X fed in the transport direction Y is expanded. As shown in FIG. 2, the diameter expanding step includes a gas supply step and a depressurizing step. In the gas supply step, gas is supplied into the tube X from the end opening on the downstream side of the transport direction Y of the tube X. Specifically, in the gas supply step, gas is supplied into the tube from the end opening of the tube X wound by the winding unit 4. Further, in the depressurizing step, the internal space of the sizing pipe is decompressed. In the diameter expansion step, the diameter of the tube X is expanded based on the difference pressure between the internal pressure of the tube X based on the gas supplied in the gas supply step and the pressure in the internal space of the sizing pipe decompressed by the decompression step. To do. The pressure in the internal space of the sizing tube decompressed by the depressurizing step can be, for example, a constant pressure in the range of -100 kPa or more and -80 kPa or less.

The gas supply step is performed by the diameter expansion unit 2 and the gas supply unit 5. Further, the decompression step is performed by the diameter expansion unit 2 and the decompression unit 6.

In the diameter expansion step, by making the flow rate of the gas supplied in the gas supply step correspond to the volume of the tube X after the diameter expansion, the influence of the time lag until the gas supply acts on the diameter expansion of the tube X is suppressed. The diameter of the tube X can be made uniform over the axial direction. Specifically, as shown in FIG. 4, while (Delta] t) from t ₀ to t _1, supplying a gas corresponding to the volume to be newly created during this t ₀ to t ₁ into the tube X By doing so, the diameter of the tube X can be made uniform in the axial direction. Therefore, in the gas supply step, it is preferable to determine the flow rate according to the linear velocity [m / min] of the tube X and the inner cross-sectional area [mm ² ] after the diameter is expanded. More specifically, in the gas supply step, it is preferable to supply the gas into the tube X at a flow rate based on the linear velocity [m / min] × the inner cross-sectional area [mm ² ]. As a result, the method for manufacturing the heat-shrinkable tube can easily and surely make the diameter of the tube X uniform in the axial direction.

In the gas supply step, the pressure of the gas supplied into the tube X may be finely adjusted based on the calculated value of the flow rate under the gas supply pressure. Specifically, the gas supply pressure is increased when the flow rate under the gas supply pressure becomes equal to or lower than the predetermined reference value, and the gas when the flow rate under the gas supply pressure becomes equal to or higher than the predetermined reference value. The supply pressure of the gas may be lowered. In the method for manufacturing the heat-shrinkable tube, the flow rate (flow rate under atmospheric pressure) supplied to the end opening on the downstream side of the transport direction Y of the tube X is measured by the flow meter 5c. The flow rate under the supply pressure of the gas is calculated by the flow rate under the atmospheric pressure / (atmospheric pressure + supply pressure (gauge pressure)) × atmospheric pressure. Therefore, the method for manufacturing the heat-shrinkable tube can control the flow rate of the gas supplied into the tube X with high accuracy.

The flow rate under the gas supply pressure in the gas supply step can be set based on the linear velocity of the tube X, the internal cross-sectional area of the tube X after the diameter is expanded, and the like. For example, 50 ml / min or more and 1500 ml / min. It can be as follows.

The lower limit of the average inner diameter of the tube X after the diameter expansion by the diameter expansion step is preferably 1 mm, more preferably 2 mm. If the average inner diameter is smaller than the lower limit, the use of the obtained heat-shrinkable tube may be limited, or the effect of expanding the diameter may not be sufficiently obtained. On the other hand, the upper limit of the average inner diameter of the tube X after the diameter expansion by the diameter expansion step is preferably 5 mm, more preferably 4 mm. When the average inner diameter is relatively small, the pressure loss of the gas supplied in the gas supply step tends to be large. Therefore, according to the conventional method of controlling the gas supply pressure, the diameter of the tube X after the diameter increase tends to be non-uniform in the axial direction as the length of the tube X after the diameter increase increases. On the other hand, according to the method for manufacturing the heat-shrinkable tube, the diameter of the tube X can be made uniform even when the average inner diameter is set to be equal to or less than the upper limit. The average inner diameter can be adjusted, for example, by adjusting the inner diameter of the sizing pipe described above.

The lower limit of the linear velocity of the tube X in the diameter expanding step is preferably 10 m / min, more preferably 20 m / min. If the linear velocity does not reach the lower limit, the production efficiency of the heat-shrinkable tube may not be sufficiently high. On the other hand, the upper limit of the linear velocity of the tube X in the diameter expanding step is preferably 60 m / min, more preferably 55 m / min. When the linear velocity is relatively high, the pressure loss of the gas supplied in the gas supply step tends to be large. Therefore, according to the conventional method of controlling the gas supply pressure, the diameter of the tube X after the diameter increase tends to be non-uniform in the axial direction as the length of the tube X after the diameter increase increases. On the other hand, according to the method for manufacturing the heat-shrinkable tube, when the linear velocity is equal to or less than the upper limit, the diameter of the tube X can be sufficiently made uniform.

(Cooling process)
The cooling step is performed by the cooling unit 3. In the cooling step, the diameter of the tube X is fixed to the size after the diameter expansion by cooling the tube X whose diameter has been expanded in the diameter expansion step.

(Winding process)
The winding step is performed by the winding unit 4. In the winding step, the diameter is expanded in the diameter expanding step, and the tube X cooled and fixed in the cooling step is wound from the downstream side in the transport direction Y. The winding step is performed in parallel with the heating step, the diameter expanding step, and the cooling step.

The lower limit of the winding length of the tube X in the winding step is preferably 5000 m, more preferably 7000 m. According to the method for manufacturing the heat-shrinkable tube, the outer diameter of the obtained heat-shrinkable tube can be kept substantially uniform even if the winding length of the tube X is at least the above lower limit. The upper limit of the winding length of the tube X in the winding step is not particularly limited, but is preferably 10,000 m, for example, from the viewpoint of sufficiently making the outer diameter of the obtained heat-shrinkable tube uniform in the axial direction. , 9000 m is more preferable.

[Other Embodiments]
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Example]
[No. 1]
Using the heat-shrinkable tube manufacturing apparatus shown in FIG. 3, the heat-shrinkable tube was manufactured by adjusting the flow rate under the gas supply pressure in the gas supply step to 275 ml / min at a linear speed of 50 m / min. A sizing tube having an inner diameter of 3.0 mm was used, and the pressure (vacuum pressure) in the internal space of the sizing tube was adjusted to be −93.2 kPa. As a result, as shown in FIG. 5, a heat-shrinkable tube having an average inner diameter of 2.5 mm (average outer diameter of 3.0 mm) and a winding length of 7430 m was obtained.

[Comparison example]
[No. 2]
Using a heat-shrinkable tube manufacturing device having a heating part, a diameter-expanding part, a cooling part, a decompression part, and a winding part similar to those in FIG. A heat-shrinkable tube was manufactured while increasing at / km). The pressure (vacuum pressure) in the internal space of the sizing tube is No. It was adjusted to -93.2 kPa in the same manner as in 1. As a result, as shown in FIG. 6, when the winding length exceeds 1500 m, the outer diameter of the heat-shrinkable tube gradually decreases.

As described above, the method for manufacturing a heat-shrinkable tube according to the present invention is suitable for increasing the length of the tube and increasing the operating rate of the equipment because the tube diameter can be made uniform.

1 Heating unit 2 Diameter expansion unit 3 Cooling unit 4 Winding unit 5 Gas supply unit 5a Compressor 5b Regulator 5c Flow meter 6 Decompression unit X Tube Y Transport direction

Claims (5)

A heating step of heating the tube formed by the resin composition above the melting point while conveying it in the axial direction.
The diameter expansion process for expanding the diameter of the heated tube and
It is equipped with a cooling process that cools the expanded tube.
The diameter expansion step includes a gas supply step of supplying gas into the tube from the downstream side in the transport direction of the tube by the gas supply unit .
Above gas supplying step, the manufacturing method of the heat shrinkable tube to control to keep the flow rate of the gas supplied in said tube constant at the lower supply pressure of gas supplied the gas supply unit. The method for manufacturing a heat-shrinkable tube according to claim 1, wherein in the gas supply step, the flow rate is determined according to the linear velocity of the tube and the internal cross-sectional area after the diameter is expanded. The method for manufacturing a heat-shrinkable tube according to claim 1 or 2, wherein the average inner diameter of the tube after the diameter expansion is 1 mm or more and 5 mm or less. The method for manufacturing a heat-shrinkable tube according to claim 1, 2, or 3, wherein the linear velocity of the tube is 10 m / min or more and 60 m / min or less. Further provided with a winding step of winding the tube after the cooling step,
The method for manufacturing a heat-shrinkable tube according to any one of claims 1 to 4, wherein the winding length of the tube in the winding step is 5000 m or more.

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