FI72287B - FOERFARANDE FOER FRAMSTAELLNING AV VAERMEKRYMPANDE POLYMERA IHOLIGA ALSTER AV POLYOLEFIN ELLER POLYVINYLKLORIDPLAST - Google Patents

Description

1 72287

The present invention relates to the processing of plastics based on the processing of preformed hollow bodies, and more particularly to methods for making heat shrinkable hollow polymer bodies in electrical engineering, for use in electrotechnical , chemical, petrochemical and other industries as well as compaction. These bodies are made of a solidified (by physicochemical or physical methods) polymeric material to prevent the polymer from flowing during orientation.

Heat-shrinkable hollow polymer bodies have the property of shrinking when subsequently heated.

A method is known in the art for making heat-shrinkable hollow tubes from a thermoplastic polymeric material 20, which comprises heating a thermally conductive type of preformed thermoplastic polymeric material solidified bodies from the inner or outer surface until the heated surface of the bodies reaches a temperature equal to the polymer flow temperature. orientation by mechanical load (by blowing) and cooling of the bodies from the outer surface to solidify the shape of the body (cf. Copper ER Heat Shrinkable Plastics - Electrical Review, Vol. 177, No. 1, 1965, pp. 13-15).

30 In this method, the cooling of the pieces according to the adopted sequence of operations is performed after the pieces have been blown. The resulting stresses in the polymer material and the stresses determining the efficiency of the subsequent heat shrinkage of the final products are greatly facilitated. Therefore, the products made by this method have a relatively low heat shrinkage efficiency.

2 72287

A similar process for the production of heat-shrinkable hollow polymer products is also known, in which tubes made of thermoplastic polymeric materials, such as polyolefin or polyvinyl chloride masses, are used. In this method, cooling of the bodies can be performed both after and during orientation (cf. SU Inventor Certificate No. 325,780, Cl. B 29C 17/02, 1970).

The ability to cool the pieces during orientation 10 increases the level of residual stresses generated in the polymeric material during orientation and increases the subsequent heat shrinkage performance of the final products compared to those made according to the method described above.

However, when using this method (according to the SU inventor certificate cited above in Reference 15), the visible heat shrinkage performance of the final products is theoretically below that achievable based on the temperature-time properties of the thermal orientation of the polymer products.

It is an object of the present invention to overcome the above-mentioned disadvantage.

The present invention is directed to the production of heat-shrinkable hollow polymer products from a polyolefin or polyvinyl chloride mass to provide for a changed temperature distribution in the wall thickness of the body that would allow the final products to heat shrink.

This object is achieved by providing a method for producing heat-shrinkable hollow polymer products from a polyolefin or polyvinyl chloride mass, which comprises heating preformed solidified hollow polyolefin or polyvinyl chloride mass bodies from cooling the sheets from the outer surface to solidify the shape of the body, wherein according to the present invention said heat transfer to the bodies is effected by applying a temperature 15-20% higher than the polymer flow temperature to the heated surface and cooling the outer bodies to a state where the body wall thickness temperature the maximum is located at a distance of 0.1 to 0.8 from the wall thickness of the piece from the outer surface of the piece.

It is not desirable to provide heat conduction to the bodies until a surface (either external or si-10) has been reached below the lower limit of the temperature defined above as a percentage of the polymer flow temperature, as the expected process effect of the present invention is not obtained. in such a case. It is also not permissible to conduct heat to the bodies until a temperature has been reached on their surface (either the inner or outer surface) above the upper limit of the temperature range defined above, in which case there is a possibility of defects in the body.

Cooling the bodies from their outer surfaces to a state where the maximum of the temperature distribution curve of the wall thickness of the body is spaced less than 0.1 or more than 0.8 from the wall thickness of the body does not make it possible to implement the objects of the present invention.

The present invention is further illustrated below by specific examples of its method variants with reference to the accompanying figures, in which:

Figure 1 is a graphical representation of a heat shrinkage ratio of 30 V / VQ (in relative units), where VQ is the initial value of heat shrinkage, V is the fair value of heat shrinkage according to the method prepared according to SU Invented Certificate No. 325,780 (curve 1) and the present invention to the shrinkage temperature t (° C) of the prepared (curve 2) high-density 35-density hollow polyethylene tube; 4 72287

Fig. 2 is a graphical representation of the same ratio for hollow low density polyethylene pipes made according to the method of the SU-inventor certificate referred to above (curve 3) and made according to the method of the present invention (curves 4-8);

Figure 3 is a graphical representation of the same relationship for hollow polyvinyl chloride pulp and ethylene propylene copolymer tubes made according to the method of the SU inventor certificate referred to above (curves 9 and 10) and made according to the method of the present invention (curves 11 and 12, respectively).

The method of the present invention is carried out in the following preferred manner.

A preformed solidified hollow body, for example in the form of a tube, of thermoplastic polymeric material is placed in a heat transfer device where it is heated to temperature by contacting the outer surface of the device or directly contacting a liquid or gaseous heating means 15-20% above the polymer flow temperature. The heated body is then transferred to a cooling device where it is cooled from its outer surface side by touching the inner surface of the cooling means or a coolant (liquid or gas). The length of the cooling device (or cooling zone in the case of coolant) and the flow rate are selected so that the outer surface of the body in contact with the cooling device or coolant cools approximately to the polymer flow temperature, i. to a state where the maximum of the temperature distribution curve of the wall thickness of the body is located on the cooled (outer) -30 surface of the body at a distance of 0.1 to 0.8 from the wall thickness of the body. From the cooling device, the body is fed to a shaping calibrator, in which the polymeric material is oriented by a mechanical load (by blowing) and then the body is cooled from the outer surface to a temperature sufficient to solidify the body shape. This cooling is accomplished by removing heating from the outer surface of the body in contact with the inner surface of the shaping calibrator or the coolant. During orientation, the part expands and acquires the size of a shaping calibrator. The body is blown in a vacuum which is created in the cavity of the body by means of a blowing device. After leaving the shaping-5 librator, the molded product is led to the receiving drum.

The temperature distribution of the body wall thickness (after cooling the body before orientation) is determined by direct temperature measurement on a specially made body model using temperature sensors spaced at different distances along the model wall thickness from its outer surface or by calculating the outer body temperature at the inlet and outlet.

The control of the maximum position of the temperature distribution curve of the wall thickness of the body is performed by selecting the speed of the body through the above heat conducting device and the cooling device, the temperature of these devices or heat transfer agents (liquids or gases) and the length of these devices.

The design calibration device described above consists of two zones arranged in succession in the process stream: the orientation zone and the cooling zone. However, another method alternative is possible, one in which the orientation and the subsequent cooling take place in different devices, namely: the orientation - in the calibration-shaping device, the next cooling - in the cooling device. In the latter case, the process diagram includes two cooling devices: 30 - a first cooling device located immediately after the heat conduction device; - a second cooling device located after the design calibration device.

The preferred embodiment of the method of the present invention described above involves carrying out the process under continuous conditions with the bodies traveling at a constant speed.

6 72287

It is also possible to carry out the method according to the present invention under intermittent conditions in which a preformed solidified product body, for example a mounting glove, is successively transferred from one device to another. In such a method variant, the appropriate temperature of the body is reached and the maximum adjustment of the temperature distribution curve of the wall thickness of the body is performed by selecting the temperatures of the above-mentioned devices and the residence time of the body in each device.

10 The conduction of heat to the body can be performed both on the outer surface side of the body, as already mentioned above, and on the inner surface side of the body. In the latter case, the cooling of the body before orientation is performed in the same manner as described above.

Pre-solidification of the polymeric material of the molded article is carried out by any conventional method: thermochemically - by adding crosslinking agents to the polymeric material, followed by vulcanization; radiochemically -exposing the polymer matrix to ionizing radiation; 20 physically - by adding additives to the polymeric material for certain purposes.

The process of the present invention allows the production of hollow heat shrinkable polymer products of substantially any shape.

The thermoplastic polymeric material used in the process of the present invention is polyolefins, for example high or low density polyethylene, a propylene copolymer of ethylene with a content of propylene units of 3 to 15 mol% as well as polyvinyl-30 chloride masses containing 100 parts by weight of polyvinyl parts by weight of a plasticizer such as dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, trioctyl trimellitate, tetraoctyl pyromellitate, 0.5-5 parts by weight of a stabilizer such as lead trioxy-35 di, triphenyl phosphite, dibutyl phosphite, antimony trioxide antioxidant,

II

7,728,77 such as calcium stearate, diphenylolpropane, 2,6-di-tert-butyl-4-methylphenol.

For a better understanding of the method of the present invention, some specific examples are provided below that illustrate its implementation under continuous production conditions. The results of the use of the method according to the present invention, shown graphically, are given after the examples.

Example 1 10 A tubular solidified body (outer diameter 4 mm, wall thickness 0.7 mm) of high density polyethylene is fed to a heat conductor where the body is heated from the outside until a temperature of 210 ± 5 ° C is reached on this surface, which is 20% higher than 15 polymer flow temperature. The body thus heated is fed to a first cooling device, where it is cooled from the outside until a temperature of 180 ± 5 ° C is reached on that surface. The maximum of the temperature-distribution curve of the wall thickness of the body is located at a distance of 0.5 kappa-20 from the wall thickness of the body from the outer surface of the body. The body is then transferred to a shaping calibrator where it is blown under an excess pressure of 152,0 ± 10,1 kPa. The body is then transferred to another cooling device where it is cooled (to solidify the shape of the product) from the outer surface side 25 to reach a temperature of 60-70 ° C on that surface. The speed of passage of the part through these cooling devices is equal to 6 m / min.

Example 2

A tubular (outer diameter 2 mm, wall thickness 0.6 mm) solidified low density polyethylene body is fed to a heat conductor where the body is heated on its outer surface until a temperature of 185 ± 5 ° C is reached, which is 15% higher than the polymer flow temperature. The heated body is then passed to a first cooling device where it is cooled on its outer surface to a temperature of 160 ± 5 ° C. The maximum of the temperature distribution curve of the wall thickness of the body is located at a distance of 0.1 from the outer surface of the body _ - TT ---- 8 72287. The body is then fed to a shaping calibrator where it is blown under an excess pressure of 121,6 ± 10,1 kPa.

The body is then transferred to another cooling device, where it is cooled (to solidify the shape of the body) from its outer surface side to reach a temperature of 40-50 ° C on this surface. The speed of movement of the body through these cooling devices is equal to 14 m / min.

Example 3 A solidified low density polyethylene body in the form of a tube (outer diameter 2 mm, wall thickness 0.6 mm) is treated by the following method described in Example 2 above. The outer surface temperature of the body after the heat conducting device is 190 + 5 ° C; jo-15 ka is 18% higher than the polymer flow temperature. The temperature of the external surface of the body after the first cooling device is 160 ± 5 ° C (the temperature of the wall thickness of the body, the maximum of the distribution curve is at a distance of 0,8 from the outer wall thickness of the body); the temperature after its cooling device is 40-50 ° C, the travel speed of the body is equal to 10 m / min.

Example 4

A tubular (outer diameter 2 mm, wall thickness 0.6 mm) solidified low density polyethylene cap-25 piece is treated following the procedure described in Example 2. The temperature of the outer surface of the body after the heat transfer device is 185 ± 5 ° C, which is 15% higher than the flow temperature of the polymer. The temperature of the outer surface of the body after the first cooling device is equal to 165 ± 30 5 ° C (the maximum of the temperature distribution curve of the wall thickness of the two bodies is at a distance of 0,2 from the wall thickness of the body); after the second cooling device - 40-50 ° C; the travel speed of the piece is 13 m / min.

Example 5 35 A tubular (outer diameter 2 mm, wall thickness 0.6 mm) solidified low density polyethylene body is treated following the procedure described in Example 2 above 9,72887. The temperature of the outer surface of the body after the heat transfer device is equal to 185 ± 5 ° C, which is 15% higher than the flow temperature of the polymer; the temperature of the outer surface of the body after the first cooling device is equal to 160 ± 5 ° C (the maximum temperature distribution curve of the wall thickness of the body is at a distance of 0.5 wall thickness from the outer surface of the body; after the second cooling device - 40-50 ° C, the travel speed of the body is equal to 12 m / min.

10 Example 6

A tubular (outer diameter 2 mm, wall thickness 0.6 mm) solidified low density polyethylene body is treated following the procedure described in Example 2. The temperature of the outer surface of the body after the heat conductor 15 is equal to 190 i 5 ° C, which is 18% higher than the flow temperature of the polymer; the temperature of the outer surface of the part after the first cooling device is 160 1 5 ° C (the maximum temperature distribution curve of the wall thickness of the part is at a distance of 0.7 wall thickness from the outer wall of the part) - 40-50 ° C after the second cooling device, the travel speed is equal to 11 m / min.

Example 7

A tubular solidified body (outer diameter 2 mm, wall thickness 0.6 mm) of a copolymer of ethylene and propylene (propylene unit content 7 mol%) is treated following the procedure described in Example 2. The temperature on the outside of the body after the heat transfer device is 200 ± 5 ° C; which is 19% higher than the flow temperature of polymer 30; the temperature of the external surface of the body after the first cooling device is 170 ± 5 ° C (the maximum of the temperature distribution curve of the wall thickness of the body is at a distance of 0,6 from the wall thickness of the body); after the second cooling device - 45-55 ° C; The travel speed of the Kap-35 piece is 5 m / min.

10 7228?

Example 8 In this example, a polyvinyl chloride mass having the following composition is used as the polymeric thermoplastic material: 5 polyvinyl chloride 100.0 dioctyl phthalate 45.0 lead trioxide 5.0 calcium stearate 3.0 quartz (SiO 2) 2.5 10 Tubular (outer diameter 2 mm , wall thickness 0.5 mm) a solidified body of the above polyvinyl chloride mass is fed to a heat conducting device where the body is heated on its outer surface until its temperature is equal to 155 + 5 ° C, which is 20% higher than the polymer flow temperature. The heated body is then fed to a first cooling device, where it is cooled from its outer surface until a temperature of 130 + 5 ° C is reached on this surface. The maximum of the temperature distribution curve of the wall thickness of the body is located at a distance of 0.4 from the wall thickness of the body from its outer surface. The body is then transported to a shaping calibrator where it is blown at an excess pressure of 101,3 ± 10,1 kPa. The body is then passed to another cooling device where it is cooled (to solidify the shape of the body) from its outer surface to a temperature of 30-40 ° C on this surface. The transport speed of the part through the above-mentioned device is equal to 10 m / min.

Example 9

The tubular (outer diameter 2 mm, wall thickness 0.6 mm) solidified low density polyethylene body is conveyed to a heat conductor where the body is heated from its outer surface until a temperature of 185 t 5 ° C is obtained on this surface, which is 15% higher than the polymer flow temperature. . The heated body 35 is then passed to a first cooling device where it is cooled from its outer surface until the temperature reaches 160 ± 5 ° C. The maximum of the thermal distribution curve of the wall thickness of the body 11 is located at a distance of 0.1 from the wall thickness of the body from its outer surface. The body is then passed to a shaping calibrator where it is blown in a vacuum (266-667 Pa) formed on the outer surface of the body 5. The body is then transported to another cooling device where it is cooled (to solidify the shape of the body) from its outer surface to a temperature of 40-50 ° C on that surface. The speed of the piece through the above-mentioned devices is equal to 12 m / min.

The heat shrinkage value of the pipe produced by the method of Example 9 is the same as that of the pipe produced according to Example 2 above.

Examples one through nine may be equally applicable to cases of pieces having any different shape (other than a tube) such as an installer's glove, cap, and the like. In these cases, the above-mentioned temperature conditions are maintained, while the residence time of the body in each process device is selected based on the appropriate temperature reached by the body.

The thermal shrinkage of tubes prepared according to the method described in Examples 1-8 and SU Inventor Certificate No. 325,780 is described below by an analysis of the relationship between the degree of thermal shrinkage and the shrinkage temperature (curves in Figures 1-3).

As can be seen in Figure 1, where curve 2 corresponds to Example 1, the present invention makes it possible to produce a heat-shrinkable hollow tube whose heat-shrinkage power exceeds the same property in a tube produced according to method 30 of SU Inventor Certificate No. 325,780 (curve 1): the onset temperature of shrinkage decreases while the degree of shrinkage increases over the entire temperature range.

Fig. 2, in which curves 4-8 show the heat shrinkage of pipes produced according to the coward method of the present invention under the conditions described in Examples 2-6 above, in which the temperature heating and cooling time parameters of the bodies before orientation are selected so that the body wall thickness temperature 12 72287 the maximum displacement of the scattering curve is ensured for a distance equal to the wall thickness of 0.1, 0.8, 0.2, 0.5 and 0.7, respectively, it can be seen that the optimum properties are achieved in the case where the wall thickness of the body 5 the maximum of the temperature distribution curve is shifted from its outer surface to a distance of 0.2 to 0.7 from the wall thickness of the body. At the same time, the pipes produced according to the method of the present invention, regardless of the maximum position 10 of the body wall thickness temperature distribution curve, are superior in heat shrinkage properties compared to similar properties in pipes made according to the method described in SU Inventive Certificate No. 325,780 (curve 3).

It can be seen from Figure 3, where curves 11 and 12 correspond to precursors 8 and 7, that the heat-shrinkage efficiency of hollow tubes made of polyvinyl chloride pulp and a copolymer of ethylene and propylene is higher than that of hollow tubes made of the same polymeric materials in U.S. Pat. according to the method described above (curves 9 and 10).

Therefore, the present invention makes it possible to obtain heat-shrinkable hollow polymer products having better heat-shrinkability properties than similar products made by prior art methods.

Claims (1)

Is 72287 Claim: A process for making heat-shrinkable hollow polymer products from polyolefin or polyvinyl chloride-5 pulp, which process comprises heating preformed solidified hollow polyolefin or polyvinyl chloride pulp bodies using heat from the outer and inner side to solidify the shape of the body from the outer surface, characterized in that the preformed solidified hollow bodies are heated by heat conduction until the heated surface reaches a temperature 15-20% higher than the polymer flow temperature and before the polymeric material of the heated bodies is oriented where the maximum of the temperature distribution curve of the wall thickness of the body is located at a distance equal to k from the outer surface of the body uin 20 0.1-0.8 pieces of wall thickness.