JP2828309B2 - Manufacturing method of heat-shrinkable tube - Google Patents

Description

The present invention relates to a heat-shrinkable tube made of a soft vinyl chloride resin having good dimensional stability, and more particularly to a heat-shrinkable tube made of a soft vinyl chloride resin even when left at room temperature. The present invention relates to a method for producing a heat-shrinkable tube made of a soft vinyl chloride resin, which hardly occurs.

(Prior art) A plastic tube manufactured by extrusion molding
The material plastic is heated to a temperature higher than the softening temperature and lower than the melting point, and a fluid such as air is pressed into the tube, the diameter of the tube is enlarged, and the tube is cooled to produce a heat-shrinkable tube. That is well known.

(Problems to be Solved by the Invention) According to the method as described above, heat-shrinkable tubes manufactured using a soft vinyl chloride resin (hereinafter abbreviated as soft PVC) as a plastic material are widely used for shrink wrapping of various articles. It is used, but the temperature around normal temperature (for example, 25 ~
Even at 40 ° C), shrinkage occurs, so to keep it, keep it at 20 ° C or less in a cold storage warehouse and use a cold-car for transportation. Therefore, if it is possible to prevent the tubes from shrinking even if they are kept at around room temperature, the tubes can be stored in a normal warehouse and transported by a regular freight car, and the cost can be reduced. it can.

(Means for Solving the Problems) The present invention relates to a flexible PVC which suppresses shrinkage at around normal temperature.
It is an object of the present invention to provide a method for producing a heat-shrinkable tube comprising a soft vinyl chloride resin which imparts heat-shrinkability by enlarging its diameter under heating. A method for producing a heat-shrinkable tube, characterized in that a tube is sealed in a tube under an atmosphere of 50 to 80 ° C. and left to mature for 12 hours or more while keeping the diameter of the tube inflated. Exist.

In the method of the present invention, the soft material produced by extrusion molding
The operation of imparting heat shrinkage to the PVC tube and manufacturing the heat shrinkable tube may be performed by any conventionally known method. As an example of the specific conditions, soft PVC (for example, 15 to 70 parts by weight of a plasticizer is blended with 100 parts by weight of PVC, and other commonly added auxiliaries are blended) as a material, and the extruder The extruder is extruded into a tube at a cylinder temperature of 120 to 170 ° C. and a die temperature of 170 to 190 ° C., and cooled (to 80 ° C. or less by water cooling) to obtain an undrawn tube. The diameter of the unstretched tube is expanded under heating by a pressurized fluid (most commonly, air is used) sealed in the tube, and the tube is stretched and oriented in the circumferential direction of the tube. The heating at this time is performed by steam or hot water at 80 to 100 ° C., and the pressure in the tube is 1.5 to 5 kg / cm ² G (G) depending on the diameter, thickness, and degree of expansion of the unstretched tube. Represents gauge pressure). After the diameter of the tube is enlarged, cool the tube.
Cooling is performed, for example, by contacting the inner surface of a water-cooled metal tube.

A heat-shrinkable tube is obtained as described above,
When used, this tube is heated to shrink the diameter, for example, when used for shrink wrapping, 150-200 ° C
What is necessary is just to blow and heat and to heat. In the method of the present invention, in order to suppress spontaneous shrinkage that occurs during storage at room temperature, the heat-shrinkable tube manufactured as described above is placed under a heated atmosphere in a fluid (air is industrially used in the tube). Is sealed), and the tube is left to mature for at least 12 hours in a state in which the tube is inflated. The temperature at this time is in the range of 50 to 80 ° C. If the temperature is lower than 50 ° C, shrinkage at room temperature occurs as in the case where the aging treatment is not performed, while if the temperature exceeds 80 ° C, the tube becomes too soft and partially shrinks. Becomes uneven. The preferred heating temperature range during this aging treatment is 60 to 70 ° C.

The tube is filled with fluid, and the expanded inside diameter is kept in a swollen state so that it does not shrink or expand further, but the internal pressure at that time changes even at a temperature of 50 to 80 ° C Adjust not to. For example, the internal pressure is usually 1 to 7 kg / cm ² G. Then, the swollen tube is wound as it is, placed in a constant temperature chamber at a predetermined temperature, for example, in an atmosphere in the above temperature range, and left for 12 hours or more, preferably 24 hours or more. The upper limit of the leaving time is not particularly limited, but usually may be up to about 100 hours.

(Examples) Examples 1 to 6 and Comparative Example 1 As a flexible PVC material for the tube, polyvinyl chloride 1 was used.
A mixture obtained by mixing 38 parts by weight of DOP and other stabilizers, lubricants, etc. with respect to 00 parts by weight was used. A tube having an inner diameter of 2.0 mm and a thickness of 1.0 mm is manufactured from this material by extrusion, and the tube is immersed in a heated water bath at about 98 ° C. and heated while a 3.5 kg / cm ² G pressure fluid (air )
The diameter is expanded to 5.0 mm in inner diameter to make a heat-shrinkable tube. Due to this expanding process, the tube becomes 4/3 lengthwise.
The tube was stretched 5 times and stretched 5/2 times in the radial direction, and the tube thickness became 0.3 mm.

Using the heat-shrinkable tube having an inner diameter of 5.0 mm obtained as described above, aging was performed under aging conditions (temperature, time, and internal pressure) shown in Table 1 below. Aging, tube inner diameter
While inflated to 5.0 mm, wind it up on a reel and leave it in a constant temperature room. During that time, the pressure inside the tube is kept connected to the constant pressure air supply pipe from the pressure regulating valve.

As described above, a shrinkable tube having a tube inner diameter of 5.0 mm was obtained. With respect to these, the natural shrinkage ratio and the inner diameter stability were examined and are shown in Table 1 below. In Table 1, Examples 1 to
No. 6 changes the conditions at the time of ripening. Comparative Example 1 relates to a shrinkable tube not subjected to the aging treatment in the above example.

In the table, the spontaneous shrinkage ratio indicates the shrinkage ratio after being left at 40 ° C. for 3 days, 7 days, and 14 days, and is calculated by the following equation.

In Table 1, the inner diameter stability is evaluated as follows.

100 per 10cm from each long tube after aging
Take each sample, measure the inner diameter of each sample, and observe the inner diameter variation based on the inner diameter of 5 mm.
Then, according to the degree of variation, the ranking is as follows.

◎ Small variation, within ± 0.2mm for 5mm inner diameter ○ Degree of variation ◎ Slightly larger, ± 0.5 for 5mm inner diameter
Within mm △ The degree of variation Larger than ○, within ± 0.7 mm for an inner diameter of 5 mm × Large degree of variation, ± 1.0 or more for an inner diameter of 5 mm In Table 1, comprehensive judgment was based on the following criteria.

(A) ◎ indicates the natural contraction rate is less than 20% and the inner diameter stability is ◎.

(B) Even if the natural shrinkage ratio is less than 20%, the inner diameter stability is marked with a circle and the triangle is marked with a triangle.

(C) If the natural shrinkage exceeds 20%, it will be 40%
When the value is less than 内径, even if the inner diameter stability is ◎, it is marked with △.

(D) If the natural shrinkage rate exceeds 40%, mark x.

As can be seen from the above results, the temperature during aging is within the range of the present invention, and when the temperature is as low as 50 ° C. and 60 ° C., the inner diameter stability is good, but the natural shrinkage ratio tends to increase, while , 70
When the temperature becomes high, such as 80 ° C. or 80 ° C., the natural shrinkage ratio decreases, but the stability of the inner diameter tends to deteriorate. When the aging temperature is low, it is preferable to take a sufficient aging time.

(Effect of the Invention) The heat-shrinkable tube made of the soft PVC manufactured by the method of the present invention has a reduced natural shrinkage as compared with the conventional heat-shrinkable tube even when it is left near normal temperature,
There is no need to store in a specially cooled cold store, and there is no need to use a cool truck for transportation.

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Claims (1)

(57) [Claims] 1. A tube made of a soft vinyl chloride resin which has been provided with heat shrinkage by enlarging its diameter under heating is filled with a fluid in a tube under an atmosphere of 50 to 80 ° C.,
A method for producing a heat-shrinkable tube, wherein the tube is left and aged for at least 12 hours while keeping the diameter of the tube inflated.