FR2465586A1 - METHOD AND INSTALLATION FOR MANUFACTURING THERMOPLASTIC THERMOPLASTIC MOLDED OBJECTS MADE IN PARTIALLY CRYSTALLIZED CONDITION - Google Patents

Abstract

PROCESS FOR MANUFACTURING MOLDED OBJECTS OF THERMOPLASTIC MATERIALS, IN PARTICULAR POLYETHYLENE TEREPHTHALATE, BY FORMATION, IN PARTICULAR BY EXTRUSION, OF A SEMI-PRODUCT WHICH IS THEN STABILIZED THEN SUBJECTED TO A THERMAL CONDITIONING AND STABILIZED ARTICLES . THE PROCESS IS ESSENTIALLY CHARACTERIZED IN THAT THE DESIRED STATE OF CRYSTALLINITY IN THE WALL OF THE MOLDING IS ACHIEVED BY A FIRST THERMO-PACKAGING CARRIED OUT ON THE SEMI-PRODUCT AND A SECOND THERMO-PACKAGING CARRIED OUT ON THE SAME MOLD, WHICH SECOND PACKAGING MADE WITH A TEMPERATURE LINE ESTABLISHING OR NOWING THE FINAL STATE OF CRYSTALLINITY SEEKED IN THE PLASTIC MATERIAL OF THE WALL.

Description

The invention relates to a method and an installation for the

  production of moldings of a plastic material which can be supplied at will, under the effect of physical influences, in particular by the influence of temperature, in its partially crystallized state, by the formation of a semi-finished product, in particular continuous extrusion of a strip or a hose from the plastified plastic material, stabilization of the semi-product by cooling at least on one surface, - thermal conditioning of the semi-finished product for thermoformability and hot forming to form the final, dimensionally stable moldings from the semi-finished product. No. 2,830,740 and 2,830,788 disclose processes for making thin-walled articles from a crystallized thermoplastic material. The thermoplastic material to be transferred to this process, in particular a polyolefin, is in all cases of purely crystalline structure and thus offers only the possibility of adjusting the more or less strongly crystalline state in the wall of the molding and to influence the crystals contained in the plastic of the wall of the molding by the conduct of the temperature and by physical influences. Accordingly, in these known processes, the crystallinity of the plastics material and the physical influences on the crystals in the plastic material during the manufacture of the moldings are directed to opti- the desired properties of the wall of the molding and at the same time to obtain conditions that can be used for thermoforming. British Patent No. 1,514,277 also discloses the manufacture of molded articles, in particular 2465586 2 of bottles, of polyesters, by injection and blowing combined. According to this patent, an injection preform must first be prepared and stabilized by cooling on the outer surface, then a first enlargement under stretching of the cooled wall regions, and then complete demolding by lorming. blast (Blasformen). This known process is relatively complicated, requires a considerable time and can not be carried out continuously to form semi-finished products. The object of the invention is, on the contrary, to provide a method and a device which enables the user, during the processing of plastics which can be brought as desired to the amorphous or partially crystallized state under the effect of physical influences, particularly under the influence of temperature, to voluntarily bring the plastic of the molding wall to the amorphous state or in a desired state and degree of crystallinity, thereby obtaining the physical properties desired for the molded part, e.g. elasticity, strength and / or dimensional stability at temperature. According to the invention, this problem is solved by a process having the following characteristics - for the manufacture of moldings with such a plastic material whose crystallinity can be supplied at will between the amorphous state and the desired partly crystallized state, The desired state of crystallinity in the wall of the molding is obtained by a first heat-conditioning to be performed on the semi-finished product and by a second heat-conditioning to be performed on the molding; the physical influences to be exerted on the semi-product during the first thermo-conditioning to be made between the stabilization and the thernforming are preset and modified in order to obtain a desired state of prior crystallinity and thermoformability of the plastic material of the semi-finished product, a preliminary temperature profile, determined according to the subsequent thermoforming operation and the desired final crystallinity state of the plastics material of the wall of the molding, being established on the section of the semi-product, and the second thermo-conditioning during the thermoforming operation, and possibly continuing thereafter, is carried out with a temperature line establishing or maintaining the state of final desired crystallinity in the wall of the molding in connection with obtaining the dimensional stability of the molding. The process of the invention has on the one hand a large number of operating parameters which can be modified and adjusted at will, which influence in a reproducible manner and which can be determined in advance in a precise manner on the state. of final crystallinity of the plastic material in the wall of the molding and on the physical properties important for the use of the molding. The efficient use and the mutual combination of the chosen process parameters, in particular the heat treatment during the process, is particularly favorable if two thermo-thermal operations are carried out.

  conditioning. In addition, the process of the invention also offers the possibility of integrating additional stages of physical treatment such as stretching, rolling, calendering, densification, irradiation, electrostatic treatment, electromagnetic treatment, etc. without compromise the stability of the manufacturing process and the desired stability for the adjustment of the crystallinity state in the plastic material of the wall of the molding. For these additional stages of physical processing also, the two thermoconditioning operations have favorable use and combination possibilities. An operating possibility existing within the scope of the invention provides that: - The semi-product, during the stabilization 5 and the first thermo-conditioning, is cooled over its entire section with adjustment of the desired final crystallinity state, to a temperature at which no further change occurs in the plastic material of significant change in crystallinity state, and indeed also in establishing the temperature profile for thermoforming purposes In all regions of the semi-product, temperatures must be maintained at which no significant change in the state of crystallinity occurs; and 15 - During thermoforming, a stamping and a second thermo-conditioning are carried out to fix the state of crystallinity in the plastic material of the wall of the molding, which is thus molded and consolidated. In this basic process, which is possible within the scope of the invention, the crystallinity state of the plastic of the molding wall is to a large extent adjusted early, that is to say at the time of the invention. stabilization and first thermo-conditioning of the semi-finished product, and it is preserved to a very large extent until the completion of the moldings. This fundamental process can be used to bring the plastic into a substantially amorphous state in the semi-finished product upon stabilization and subsequent heat-conditioning thereafter, and to conserve as much as possible this state largely amorphous during the second thermo-conditioning, including thermoforming. The moldings thus produced have the plastics material of their wall in a substantially amorphous state, and are marked by relatively high elasticity and deformability. However, they have only a relatively low heat stability. Another fundamental embodiment, possible within the scope of the invention, consists in: rapidly cooling the semi-finished product during stabilization and first thermo-conditioning over its entire section and bringing it to a temperature profile which allows thermoforming, but which observes in all regions of the semi-product temperatures for which there is no significant change in the crystallinity state of the plastic material, - thermoforming on at least one surface of mold which is heated to a temperature at which crystalline growth occurs in the plastic material, and to harmonize the second heat conditioning which occurs or begins at the point of contact of the wall of the molding with the heated surface of the mold. mold, with respect to temperature and time, with adjustment of the desired partial crystallinity for the plastic of the wall of the molding. With this procedure, a preliminary adjustment of the plastic of the semi-finished product 25 is made in a state of crystallinity, and starting from this state of crystallinity, the final state of crystallinity desired in the wall of the molding is produced during thermoforming. . In this case, the plastic of the semi-product can be stored in a substantially amorphous state during the first heat-conditioning. However, it is also possible to subject the plastic of the semi-finished product, during the first heat-conditioning, to a first crystalline growth of reduced importance. The choice between the two possibilities is based, inter alia, on the desired final crystallinity state for the plastic of the mold wall and on the degree of crystalline growth desired during thermoforming. . To cause the desired degree of crystalline growth during thermoforming, the mold surface can be maintained in a temperature range above or below the temperature corresponding to optimum crystal growth in the plastic considered. . If it is desired to obtain as high a degree of crystalline growth as possible during thermoforming for a sufficiently short thermoforming time, the mold surface will be maintained in the temperature range corresponding to the optimum crystalline growth for the plastic considered. , where appropriate in the upper part of this temperature range

  15 eratures, to bring the plastic as quickly as possible to a temperature allowing optimal crystal growth. In the process of the invention, when the stabilization and the first thermo-conditioning of the semi-product are carried out, such temperature conditions, for which only very slight or no changes in the temperature occur, occur. In the crystallization state, the semi-finished product may be subjected to a drawing at the first heat-conditioning and / or between the first heat-conditioning and the thermoforming, for example a biaxial stretching as a treatment. additional physics, practically preserving the state of crystallinity of the plastic which composes it. This stretching can be carried out on a plastic in a practically amorphous state or in a more or less partially crystallized state. In the process of the invention, this stretching has the astonishing effect that castings made under this additional physical influence exhibit both high strength, elasticity and dimensional stability at high temperature. Another possibility for carrying out the process of the invention consists in bringing the semi-product, during stabilization and first thermo-conditioning, onto its surface regions at temperatures allowing appropriate consolidation. handling the semi-product, and indoors, at temperatures corresponding to optimal crystalline growth in the plastic considered, and thermoforming at least one surface of the mold which is heated to a temperature at which the Crystalline growth occurs in the plastic considered. This variant embodiment of the process of the invention is particularly suitable in the case where it is desired that the plastics in the mold wall be crystallized as far as possible. The castings produced in accordance with this method of the process are distinguished by particularly high dimensional stability at hot temperature. In this embodiment, however, it is desirable that the plastic of the inner part of the semi-product is adjusted, due to the influence of the set temperature and the duration of the first heat-conditioning, to a state of crystallinity such that the plastic considered is still thermoformable. However, it is also possible, if desired, to pass the plastic from the inner part of the semi-finished product, under the influence of the set temperature and the duration of the first heat-conditioning, to a state of crystallinity. beyond the limit of the actual thermoformability of the plastic considered. In this case, the superficial regions of the semi-finished product, which are maintained in a more or less amorphous state, or only partially crystallized, form during the thermoforming sufficiently resistant shells between which the plastic has already been formed. crystallized outside the actual thermoformability can still be deformed safely within the semi-product. In this latter embodiment of the process of the invention, it is particularly advantageous to heat the mold surfaces to a temperature corresponding to optimum crystalline growth in the plastic considered. As a result, the final heating of the entire plastic of the wall of the formed molding takes place, and consequently a regular crystallization. Another possibility of carrying out the present process is to bring the semi-finished product, during the stabilization and the first heat-conditioning, into the surface regions of its section, at temperatures leading to an appropriate reinforcement for the handling of the product. semi-produced, and indoors, leave it practically at the applied plasticizing temperature for the extrusion of the material web, thermoforming on at least one surface of the mold which is heated to a temperature at which crystalline growth takes place in the plastic considered, and - maintain the wall of the molding, the second thermo-conditioning, for a period determined depending on the desired state of final crystallinity, at a temperature at which occurs the Crystalline growth in the plastic of the wall of the molding. In the case of this process run, possible within the scope of the invention, the plastic is maintained within the semi-finished product at a temperature which is higher than the temperature range in which crystalline growth occurs. in the plastic considered. On the other hand, the surface regions of the semi-product are cooled to such a degree that the existing crystalline state, for example the amorphous or weakly crystalline state, is "frozen" therein. Unlike conventional "in-line" thermoforming processes, it now occurs during the thermoforming process

  As such, a complete heart heating of the entire wall of the molding formed, and with this core heating during the thermoforming and the second thermo-conditioning, an adjustment of the more or less strongly crystalline state desired in each case. Since in this type of process the plastic from the interior of the semi-product discharges considerable amounts of heat in the first thermo-conditioning and into the thermoforming and the second thermo-conditioning, it will advantageously be adjusted. The temperature of the molding surfaces a little below the temperature corresponding to optimum crystalline growth, thereby to cause faster cooling of the plastic within the wall of the molding formed in the temperature range in which it is located. 20 produces optimum crystal growth. In all the variants of the process according to the invention, in which crystalline growth is allowed to occur during the actual thermoforming, the wall of the molding can be maintained in contact with the mold surface that the plastic has reached the desired degree of crystallinity. But it can also be limited to initiating crystalline growth on the mold surface and removing the molding from the mold surface when sufficient dimensional stability has been achieved, and performing the second heat-conditioning in a heat treatment device. connected to the output of the thermoforming device. This second thermo-conditioning, which begins at the surface of the mold, can be carried out at a constant temperature. However, it is also possible to modify the temperature during the second heat-conditioning, for example to lower it in time. In the latter type of temperature control, it is possible to start from a temperature on the surface of the mold which is suitable for optimum crystalline growth in the plastic considered, and to cool the wall of the molding with time. In the present process, thermoforming can be effected by exerting a mold pressure on the plastic of the wall of the molding, which pressure may optionally be selected so as to allow some densification of the plastic material. The present process also makes it possible to subject the semi-finished product, between extrusion and thermoforming, to a calendering and / or rolling operation with a reduction in thickness, with a view to exerting a physical influence. additional on the crystallinity state. This calendering and / or rolling may be included in the stabilization of the semi-finished product. The process of the invention is preferably applied for the manufacture of polyethylene terephthalate moldings. However, it can be envisaged both for the manufacture of moldings of modified polyethylene terephthalate, for example a 1,4-cyclohexyldimethylene terephthalate / isophthalate copolymer. One can also think of the manufacture of polybutyleneterephthalate moldings by this method. In the latter case, however, care must be taken that the temperature range within which crystalline growth in polybutylene terephthalate occurs is much lower down to about 30 ° C. For the execution of the process of the invention, it is possible in particular to use an installation comprising an extrusion device for the continuous production of the semi-finished product, a device for stabilizing the semi-finished product, a thermoforming device and a device. thermo-conditioning of the semi-finished product, as well as, where appropriate, a device for separating the moldings of the surrounding parts of the semi-finished product. According to the invention, this type of installation is distinguished by the following features: - between the stabilization device and the thermoforming device, a first packaging station is placed, - the thermoforming device is placed in a second thermo-conditioning station; the stabilization device and the thermoforming device are equipped with a control system for the pre-established and, where appropriate, programmable regulation of physical actions, in particular thermal actions, which are applied to the plastic of the semi-finished product in the stabilization device and in the thermoforming device, and to the thermo-conditioning stations are attached devices intended to exert physical actions, in particular thermal actions, on the plastic of the semi-product or molding, and control systems 20 for pre-established and, where applicable, programmable control of the device. if exercising these actions. Such an installation has the advantage of enabling substantially all the desired variants of the process of the invention to be carried out without substantial adaptation measures. It also has the advantage that it can be easily inserted into the desired location.

  equipment intended to carry out special actions required such as drawing, rolling, irradiation, etc. The installation of the invention can be equipped in its thermo-conditioning stations, mainly in the first thermo-conditioning station. semi-finished product or moldings, a possibility of temperature regulation and heating or cooling time. With this apparatus, the heat-conditioning can be carried out in all conceivable variants, safely and with optimum efficiency. At the first heat-conditioning station, namely that for the semi-finished product, it is also possible to add a drawing device for the semi-product, with the possibility of regulating the drawing temperature. , the draw ratio, and where appropriate the drawing speed. The addition of the drawing device to the first heat-conditioning station has this particular advantage that the drawing operation is carried out at a stage of the semi-finished product in which optimal conditions for stretching are achieved. Also, and also optimal conditions for the effect of stretching on the crystallinity state of the plastic material, can be established and even maintained until thermoforming. If it is desired to provide in the plant according to the invention additional devices for calendering and / or rolling of a semi-produced strip with reduction in thickness, these can be added to the stabilizing device . In the installation according to the invention, the cooling equipment provided in the stabilizing device may be equipped with equipment intended to allow the adjustable temperature to be controlled, acting chronologically on the plastics material. This means that when several cooling devices are available in series, they can operate at different temperatures. In the present installation, the thermoforming device is advantageously equipped with one or more molds with a heatable and coolable surface. The thermoforming device may advantageously comprise one or more molds provided with a control device for producing a temperature variation or temperature control of the thermoforming operation 2465586 13 which can be pre-set and programmable in the process. time, on at least one surface of the mold. The thermoforming device may also comprise one or more molds provided with devices for producing a pressure that can be determined in advance and regulated. These devices for producing the pressure of the mold may be equipped with controllers for varying the pressure over time, in an adjustable and possibly programmable manner, during the thermoforming operation. In the plant of the invention, the second heat-conditioning station may preferably comprise, in its region of entry, the thermoforming device and extend beyond the outlet of the thermoforming device. In this case, the second heat-conditioning station 15 may comprise a device for heat treatment of the moldings, connected to the outlet of the thermoforming device. Exemplary embodiments of the invention will be given hereinafter and explained in more detail with reference to the accompanying drawings in which: Figure 1 shows a flow diagram of the process flow and a principle construction of a installation according to the invention; Figure 2 shows the growth rate of crystals V as a function of temperature T in the case of polyethylene terephthalate; Fig. 3 shows a group of temperature profiles for a first embodiment of the process with polyethylene tere- phthalate; Fig. 4 shows a group of temperature profiles for a second embodiment of the process with polyethylene terephthalate; Figure 5 shows a group of temperature profiles for a third embodiment of the process with polyethylene terephthalate; FIG. 6 shows a group of temperature profiles for a fourth embodiment of the process, again with polyethylene terephthalate; FIG. 7 shows a group of temperature parameters for a fifth embodiment of the process with polyethylene terephthalate; Fig. 8 shows a group of temperature profiles for a sixth embodiment of the process with polyethylene terephthalate; and Figure 9 shows a group of temperature profiles for a seventh embodiment of the process with polyethylene terephthalate. FIG. 1 illustrates the succession of the operating stages in a preferred embodiment of the method of the invention for the manufacture of articles to

  thin wall of a thermoplastic material, which can be supplied at will in an amorphous state or more or less. partially crystallized. In the example shown, there is an extruder 11 which can receive the granulated thermoplastic material, for example polyethylene terephthalate, continuously compress it and heat it to melting and conduct it at a temperature of TE (FIGS. 3 to 8) greater than the melting point of the crystals, to the extrusion member, for example a flat die 12. This flat die 12 provides in the present example a semi-product in strip 10 which, coming from In the stabilizing device 13, the semi-product 10 is first made manipulable for the rest of the process by cooling at least one surface. From the stabilizing device 13, the strip semi-product 10 passes into a first packaging station 14. This packaging station of the semi-product 14 is mainly intended to adjust preparative temperature profiles in the semi-product 10 but also to exert on the semi-product 10 additional physical actions desired, or to set additional physical actions exerted previously on the semi-product 10.- For this purpose, the semi-finished packaging station Product 14 is equipped with heating devices and cooling devices with control systems that can be controlled and optionally programmed as desired. In addition, devices for acting physically on the semi-product 10 can be added to the packaging station of the semi-finished product 14. To these belong stretching, irradiation and possibly rolling devices. de'densification. The latter may, however, already be included in the stabilizing device 13. In the example shown, the packaging station for the semi-finished product 14 has two stages, that is to say that it comprises a first stage 14a. , for treatment, that is to say the thermo-conditioning of the semi-product 10 which passes through it continuously, and a second stage 14b, which is intended for the treatment and the thermoconditioning of the semi-product 10 which is introduced in stages. Between the two steps 14a and 14b of the semi-product-14 conditioning station, and included in this station, is a system 15 for controlling and modifying the motion of the semifinished product 10 of the continuous feedstock. 'advance in stages. With this system 15, the advancing movement of the semi-product 10 is set to the work rate of the conditioning station 17 of the finished moldings with the thermoforming station 16 receiving in stages the semi-finished product. In the first part, the finished thermo-forming device 16, which in the example shown is equipped with stamping tools whose mold surfaces are heatable or heatable at will, and may also be designed to change the temperature during each operation. According to FIG. 1, a section of the packaging station 17 of the finished parts is again connected to the thermoforming device 16, which, in the example shown, is traversed in stages by the semi-produced strip carrying the moldings coming from the thermoforming device.16. In this second section 17 of the finished parts conditioning station are housed heating and cooling devices. Devices for the physical treatment of the moldings 18 may also be installed, for example for irradiation, exposure to ultrasound, etc. At the outlet of the second thermo-conditioning station 17, the semi-finished product The strip carrying the moldings 18 passes into a cutting device 19, which cuts the moldings 18, and the remains of the semi-product 20 are removed for the recovery of the material and, if appropriate, for the return of the milled material directly. The semi-finished product 10, identified by way of example as a strip of plastic material, can have a thickness of about 2 mm in the case of polyethylene terephthalate. Instead of the semi-product in the form of a strip, it is also possible to envisage any other semi-product imaginable and which can be manufactured continuously, for example sheaths, profiled cords, etc. The semi-product can It should also be a laminate made of various plastics, of which however a large part must be made of plastics which can be supplied at will, by physical influences, in particular by temperature control, in the amorphous state or at the same time. state of partial crystallinity desired. A compression treatment of the plastic material can be carried out on the semi-finished product,

  2465586 17 for example by rolling or calendering, in the stabilization station 13 or in the first part 14a of the conditioning station 14 of the semi-finished product. However, it is also conceivable to perform a compression treatment of the plastic by stepwise flat pressing upon stepwise introduction through the second portion 14b of the semi-finished conditioner station 14. The invention also makes it possible to carry out the compression treatment on the molded part or on the finished part, that is to say inside the second heat-conditioning station 17. compression treatment on the finished part, exerting a predetermined mold pressure in the thermoforming device 16. In place of the compression treatment, whether on the semi-finished product or on the finished part, or in addition to that it is also possible to perform an ultrasound treatment. In addition to their influence on the crystallinity state, ultrasonic compression or ultrasound treatments lead to a significant increase in rigidity and consequently to better cold-dimensional stability of the moldings produced. The curve in FIG. 2 represents the variation of the growth rate of crystals V in polyethylene terephthalate as a function of temperature T in degrees Celsius. As shown in FIG. 2, the polyethylene terephthalate has a crystal growth temperature range between 1000.degree. C. and the melting point of the crystals (250.degree. To 2600.degree. C.) within which optimum growth occurs around 170C to 1750C. Above the melting point of crystalline state, the terephthalate passes to the plasticized state, whereas below 600C it is in the solid state, without the crystals continuing to grow. a notable degree. This means that by cooling the terephthalate below 600C, the crystallinity state of the material is "frozen". To simplify the comment that follows, we will consider in this memory the amorphous state as being also a state of crystallinity, namely a state of "zero crystallinity". The process of the invention offers economically favorable possibilities for the manufacture of plastic moldings having the properties described above, and offers a possibility of choice as to the state of final crystallinity in the process. wall of the molding. This is essentially achieved by the invention by manufacturing a semi-finished product, according to the above-explained detailed line of practice with respect to FIG. 2 and with the plastics considered in this specification, by extrusion It continues at a temperature TE (see FIGS. 3 to 8) greater than the melting point of the crystals, in a temperature range in which the material is in the plasticized state. From this plasticized state, the material must be cooled and thermally conditioned, in accordance with the particular requirements and requirements for molding, across the crystalline growth temperature range shown in FIG. 2, so that when When it reaches the temperature range in which it is in the solid state (below 600 ° C. in the case of polyethylene terephthalate), it has the desired crystallinity state associated with the desired physical properties. Some examples of the possibilities offered by the thermo-packaging according to the invention emerge from the explanation below of FIGS. 3 to 8. In the example of FIG. 3, in the case of the manufacture of terephthalate moldings. of polyethylene, the by-product 10 is strongly cooled, and is thermoformed to a temperature profile of 55-100 ° C, where it does not occur. virtually no crystal growth or crystal formation. The outer regions or the surface regions of the semi-product can then be cooled below this temperature range, while the temperature of the plastic material in the interior of the semi-finished product can reach at about 1000 ° C, or at least should not significantly exceed this temperature. In the stabilization, it is possible, as shown in the upper part of FIG. 3, starting from a temperature profile existing at the time of extrusion, situated in the vicinity of the extrusion temperature TE by rapidly cooling to the temperature indicated at the top left of FIG. 3, substantially keeping or "freezing" the amorphous state in the plastics material. In subsequent heat-conditioning (middle part of Fig. 3) and thermoforming including a second heat-conditioning (Fig. 3, bottom), temperature conditions can be maintained at the surface and inside the semifinished product 10 and molding 18, such that even

  then, there is no significant growth of crystals, nor significant formation of crystals. When made of unpigmented plastic, the molding thus made is clear, which means that the plastics material of the molding wall is in a substantially amorphous state. The dimensional stability at the molding temperature is about 700C. With this procedure, if it is desired to admit or reveal a certain degree of partial crystallinity in the plastic material of the wall of the molding, this can be done at the stabilization and the first thermo-conditioning, by performing more slowly the cooling of the semi-finished product 10 and then already giving rise to a certain degree of partial crystallinity. This partial crystallinity can then be substantially maintained during thermoforming and second heat-conditioning by appropriate temperature control (see bottom of FIG. 3) in the plastics material of the present invention. molding or the finished part. FIG. 4 illustrates a possibility for carrying out the process of the invention, in which the semi-product 10 is rapidly cooled in order to consolidate it in its external or superficial zones and make it manageable, but the plastics material of the interior of the semi-product remaining at a temperature well above 100 ° C. The change in the temperature profile in the vicinity of the extrusion temperature TE to the temperature profile adjusted by the stabilization results from the examination of the upper part of FIG. 4. In the thermo-conditioning of the semi-finished product. Following stabilization, a temperature profile can be adjusted in which the external areas of the semi-product are at temperatures just above 500 ° C and the core at temperatures above 100 ° C. With this temperature control during the stabilization and the first heat-conditioning, in the terephthalate within the semi-product 10 there is a noticeable formation of crystals and a notable growth thereof. which results in a disorder in the matter. Since the time interval between the conditioning of the semi-finished product (middle part of FIG. 4) and the thermoforming with conditioning of the finished part (the lower part of FIG. 4) is fixed in the present method, it is possible to determine in advance, by the temperature profile shown on the middle part of FIG. 4, and by the extent to which the temperature in the semi-product 10 is greater than 1000 ° C., how important is the degree of crystallization of the semi-finished product at the beginning of the conditioning of the finished part. In this example, the thermoforming is carried out by forming the material on a hot mold surface, the temperature of which must be 120.degree. To 180.degree. In the example shown, a temperature at the mold surface of 180 ° C. is allowed. During the conditioning of the finished parts which starts during the thermoforming and which still occurs, if necessary, beyond the thermoforming, it has therefore produced a high crystallization of the polyethylene terephthalate. The molding has an opaque wall if starting from an unpigmented material, and its dimensional stability at temperature is above 2000C. A similar procedure of the process could be achieved in accordance with FIG. 5, by establishing, during the stabilization and / or conditioning of the semi-finished product, a temperature profile such as that represented in the upper and middle parts. FIGS. 3 and 5. In such a case, if it is desired to provoke in the plastic material, during the conditioning of the finished pieces, a thorough crystallization, it is necessary, starting from a terephthalate in the almost amorphous state, to leave more crystallisation time to complete, otherwise a degree of crystallinity as high as in the initial conditions of Figure 4 would not be obtained. As indicated in the lower temperature profile of FIG. 5, one can also, in such a case, possibly work at a slightly higher temperature on the surface of the mold, for example until 2000C. However, the conditioning of the finished part after thermoforming can also be prolonged in time, as is indicated in FIG. 1, with the second heat-conditioning station 17. The moldings thus produced exhibit (when starting from an unpigmented material) a transparent wall, and their dimensional stability under heat is about 1500C to 2000C. FIG. 6 shows a possibility for carrying out the process of the invention, which is different from that of FIG. 3 or that of FIG. 5, in that during the conditioning of the semi-finished product (see middle part of Figure 6), that is, between the

  stabilization and thermoforming, the semi-finished product 10 is drawn, during which, as indicated by the temperature profile of the medium of FIG. 6, additional cooling of the semi-finished product 10 is produced.

The stretched semi-product, preferably biaxially, is then pressed by thermoforming on the hot surface of the mold, which may be at a temperature for example between 150 and 2000C. In the example of FIG. 6, a temperature of approximately 2000 ° C. is started on the surface of the thermoforming mold. The moldings produced by conducting the process according to FIG. 6 also have a transparent wall (when starting from an unpigmented wall), but their dimensional stability under hot conditions is still greatly improved, namely up to Temperatures from 200 to 2500C. They are also distinguished by improved strength and elasticity. In the example corresponding to FIG. 7, on the semi-finished product 10, during stabilization and then during heat-conditioning, a temperature profile 25 is set in which relatively thick surface regions 10a are cooled to a temperature below 100 ° C. 1000C and its maintained in the substantially amorphous state of polyethylene terephthalate. Inside the semiproduct 10, the temperature is adjusted to a maximum of 1500C.

Starting from this temperature profile shown in the middle part of FIG. 7, thermoforming and conditioning of the finished parts takes place on molding surfaces which are heated to about 150 to 1800 ° C. In the example shown, the temperature of the two molding surfaces between which is formed the wall of the part 18 is 1800C, and the plastic 2465586 23 of the wall of the molding is to a large extent crystallized between the two surfaces maintained at 1800C. The molding thus produced has a dimensional stability at about 200 ° C.

In the example of FIG. 8, a rapid cooling of both sides of the semi-finished product 10 is carried out during the stabilization, and in the packaging of the semi-finished products, their surfaces are then adjusted to an inclined temperature. between about 50 and 1000 ° C., while the terephthalate of the core or the interior of the semi-product still retains much of the extrusion temperature, and is therefore around 2700 ° C. The semi-finished product, with this temperature profile (shown in the middle part of Figure 8), is thermoformed between two hot molding surfaces, which can be here a temperature of 150 to 1600 ° C. Between the molding surfaces, as shown in the lower part of Figure 8, a significant equalization of the temperature profile occurs. As a result, the terephthalate has a high degree of crystallization in the surface regions of the formed part wall 18, at about 160.degree. C., and in the internal region of the wall, at about 190.degree. the outer regions a little below and in the inner region a little above the optimum crystallization temperature of about 170 ° C. The casts so manufactured have opaque walls when starting from an unpigmented material, and their dimensional stability under heat is about 200 ° C. Fig. 9 shows a modified operating technique in which the semi-product is made manageable upon stabilization by abrupt cooling of both surfaces thereof. In the conditioning of the semi-product, a temperature profile is restored which, as shown in the middle part of the figure, is between the extrusion temperature (260 to 290 ° C) and about 170 ° C, and the thermoforming and conditioning 2465586 24 finished parts, is established on the wall of the molding a temperature profile of 120 to 1700C. Molds made in this modified manner also have opaque walls when starting from an unpigmented material, and a thermal heat stability of about 200 to 2200C. In addition to the above considerations, it is also possible to carry out, in addition to the drawing mentioned above, other mechanical and physical treatments when conditioning the semi-finished product; likewise, during the conditioning of the finished part, it is possible, for example, to perform a densification and a reduction in thickness by rolling or compression in a mold, and by irradiation with very different kinds of scrapings; treatment with ultrasound etc ... The embodiments described above of the process of the invention can be applied to the most diverse semi-products, such as flexible pipes, rods or profiled rods etc ... 2465586 25

Claims (44)

R E V E N D I C A T I 0 N S   1. A process for manufacturing molded articles made of a thermoplastic material that can be brought to a partially crystallized state by means of physical actions, in particular thermal actions, by forming a semi-finished product, in particular continuous extrusion of a strip or hose of the plastified plastic, - stabilization of the semi-product by cooling at least on one surface, - thermal conditioning of the stabilized semi-finished product for thermoformability, and hot forming to form from of the semi-finished product of the dimensionally stable final moldings, characterized in that: - for the production of moldings from such a plastic material, whose state of crystallinity can be brought at will between the state In the case of the amorphous state and a desired partially crystallized state, the desired crystallinity state in the wall of the molding is obtained by a first heat-conditioning to be carried out on the semi-crystalline surface. produced and by a second thermo-conditioning to be performed on the molding itself, the physical actions to be exerted on the semi-finished product, during the first thermo-conditioning to take place between the stabilization and the thermoforming, are preset and modified in order to of obtaining a desired prior crystallinity state and the thermoformability of the plastic material of the semi-finished product, a prior temperature profile, determined as a function of the subsequent heat-sealing and the desired final crystallinity state of the plastic material of the wall of the molding, being established on the section of the semi-product, and 2465586 26 - the second thermo-conditioning during the thermoforming, and possibly continued thereafter, is carried out with a temperature line establishing or now the state of final crystallinity 5 sought in the plastic material of the wall of the molding, in connection with obtaining the dimensional stability of This one.   2. A process according to claim 1, characterized in that: during the stabilization and first thermo-conditioning, the semi-product is cooled over its entire section, with establishment of the final state of crystallinity desired, until at a temperature at which no further change in the crystallinity state of the plastic material occurs, and even when establishing the temperature profile to the thermoforming requirements in all parts of the semi-finished product, Temperatures are maintained at which no significant change in the crystallinity state occurs, and - during thermoforming, a stuffing and a second heat conditioning are carried out to set the crystallinity state of the plastics material. the mold wall formed and consolidated.   3. A process according to claim 2, characterized in that during the stabilization and the first thermo-conditioning, while maintaining to a high degree the amorphous state of the plastic material, the semi-finished product is rapidly cooled. at a temperature at which no significant change in the crystallinity state occurs.   4. A process according to claim 2 or 3, characterized in that the moldings are made of polyethylene terephthalate and the temperature in the material web is set between 50 and 1000 ° C during stabilization and first heat-conditioning. 2465586 27   5. A process according to claim 1, characterized in that - the semi-product is rapidly cooled over its entire section during stabilization and first thermo-conditioning, and brought to a temperature profile which allows thermoforming but which in all areas of the semi-product, temperatures are observed at which no significant change in the crystallinity state of the plastic material occurs, thermoforming takes place on at least one molding surface which is heated to a temperature at which crystalline growth takes place in the plastic material, and the second thermo-conditioning occurring or initiated at the contacts between the wall of the molding and the heated surface of the mold is controlled in temperature and in duration to obtain the desired partial crystallinity of the plastic material. 20   6. A process according to claim 5, characterized in that the plastic material of the semi-product is maintained in a high degree in the amorphous state at stabilization and first heat-conditioning.   7. A process according to claim 5, characterized in that the plastic material of the semi-product is already the seat, during the stabilization and the first heat-conditioning, of a first light crystalline growth.   8. A process as claimed in any one of claims 5 to 7 characterized in that the mold surface is maintained at a temperature in areas below or above the optimum growth temperature of the crystals. of the plastic material.   9. A process according to claim 8, characterized in that the mold surface is maintained at a temperature in the optimum crystalline growth temperature range of the plastics material.   10. Process according to any one. Claims 1 to 9, characterized in that the semi-product is subjected during the first thermo-conditioning and / or between the first thermo-conditioning and the thermoforming, essentially maintaining the state of crystallinity plastic, stretching, preferably biaxial stretching, as an additional physical action.   11. A process according to any one of claims 5 to 10, characterized in that, in the manufacture of moldings of polyethylene terephthalate - during the stabilization and the first thermo-conditioning of the semi-finished product, the temperature is adjusted. - between 50 and 1000C, and - is maintained on the surface of the mold a temperature of 120 to 180 C.   12. A process according to claim 1, characterized in that the semi-product is maintained during stabilization and first thermoforming, in its surface areas at temperatures suitable to consolidate it for handling, and the interior at temperatures corresponding to optimum ceistalline growth of the plastic material, and thermoforming is effected on at least one mold surface which is heated to a temperature at which crystal growth of the plastic material occurs. .   13. A process according to claim 12, characterized in that the plastic material of the interior of the semi-finished product is brought, under the effect of the set temperature and the duration of the first heat-conditioning, 2465586 29 to a state of crystallinity in which it is still thermoformable.   14. A process according to claim 12, characterized in that the plastic material of the interior of the semi-finished product is fed, under the effect of the set temperature and the duration of the first heat-conditioning, to a state of crystallinity beyond its thermoformability limit proper.   15. A process according to any one of claims 12 to 14, characterized in that the surface of the mold is heated to a temperature corresponding to the optimum growth of the crystals of the plastics material.   16. A process according to any one of claims 12 to 15, characterized in that in the manufacture of moldings of polyethylene terephthalate: - during the stabilization and the first thermo-conditioning of the strip of material, the The temperature of the surface areas is set at about 50.degree. to 1000.degree. C. and that of the internal region at about 140.degree. to 160.degree. C., and the mold surface is heated at thermoforming and at the second temperature-conditioning stage. from about 120 to 180 ° C. 25   17. A process according to claim 1, characterized in that during the stabilization and the first thermo-conditioning, the semi-product is brought into the surface areas of its section at temperatures allowing a clean consolidation to its handling, and it is left inside practically at the plasticizing temperature chosen for the extrusion of the material web. Thermoforming is carried out on at least one surface of the mold which is heated to a temperature at which growth of the crystals of the plastic material occurs, and the wall of the furrow is maintained for the second heat-conditioning. for a period of time depending on the desired final crystallinity state for that wall, at a temperature at which crystal growth of the plastic material of the wall occurs. 10   18. A process according to claim 17, characterized in that the temperature at the surface of the mold is set a little below the optimum crystalline growth temperature, and in that the molding is maintained during the second heat. conditioning at a temperature in the range of optimum crystalline growth temperatures.   19. A process according to claim 17 or 18, characterized in that the plastic material of the superficial areas of the semi-product is maintained, during the stabilization and the first thermo-conditioning, in a largely amorphous state.   20. A process according to claim 17 or 18, characterized in that the plastic material of the superficial regions of the semi-product is fed, during the stabilization and first thermo-conditioning, to a predetermined low crystallinity state.   21. A process according to any one of claims 17 to 20, characterized in that, during the manufacture of polyethylene terephthalate moldings: - at the stabilization and at the first heat-conditioning of the strip of material, the temperature of the zones superficial is set between about 800 and 1000C and the temperature inside the band is left between about 250 and 3000C, and 2465586 31 - the mold surface, during thermoforming and the second heat-conditioning, is maintained between about 140 and 1600C.   22. A process according to any one of claims 5 to 21, characterized in that the wall of the molding, for the second heat-conditioning, is kept in contact with the surface of the mold.   23. A process according to any one of claims 5 to 21, characterized in that the molding, during the second heat-conditioning, is removed from the surface of the mold and subjected to heat treatment.   24. A process according to claim 22 or 23, characterized in that during the second heat-conditioning, the plastics material of the wall of the molding is substantially crystallized.   25. A process according to any one of claims 22 to 24, characterized in that the wall of the molding, during the second conditioning, is maintained at a substantially constant temperature. 20   26.- Process according to any one of claims 22 to 24, characterized in that during the second thermo-conditioning, the wall of the molding is subjected to a temperature decreasing with time.   27. The process according to claim 26, characterized in that the temperature line during the second heat-co-packing is effected essentially by cooling from the optimum crystalline growth temperature of the plastic material.   28. A process according to any one of claims 1 to 27, characterized in that the thermoforming is effected by a pressure of the mold on the plastic material of the wall of the molding.   29. The process as claimed in any one of claims 1 to 28, characterized in that the semi-finished product is subjected between extrusion and thermoforming to a calendering and / or cleaning operation with reduction of the temperature. thickness to exert an additional physical effect on the crystallinity state.   30.- Process according to claim 29, characterized in that the calendering and / or rolling operation is included in the stabilization of the semi-finished product.   31. A process according to any one of claims 1 to 30, characterized in that glycol-modified polyethylene terephthalate is used as the thermoplastic material.   32. A process according to any one of claims 1 to 30, characterized in that polybutylene terephthalate is used as thermoplastic material. 15   33.- Installation for carrying out a process according to any one of claims 1 to 32, comprising an extrusiofi device for the continuous manufacture of the semi-finished product, a device for stabilizing the semi-finished product and a device for thermoforming and, if appropriate, a device for separating the moldings from the surrounding parts of the semi-finished product, characterized in that: - a first heat-conditioning station (14) is arranged between the stabilizing device 25 (13) and the thermoforming device (16), - the thermoforming device (16) is located in a second heat-conditioning station (17), - the stabilizing device (13) and the thermoforming device (] 16) are equipped with a control system 30 for a predetermined and, if appropriate, programmable control of the physical, in particular thermal, actions which are exerted on the plastic material of the semi-finished product (10). ns the stabilizing device (13) and in the thermoforming device (16), and 2465586 33 - devices for exerting physical actions, particularly thermal, on the plastic material of the semi-product (10) or molding (18), and a control system for a predetermined and optionally programmable control of the device carrying out these actions, are associated with the thermo-conditioning stations (14, 17).   Apparatus according to claim 33, characterized in that the heat-conditioning stations (14, 17) comprise heating and cooling devices for the semi-finished product (10) or moldings (13), with possibility of setting the temperature and duration of heating or cooling.   35.- Installation according to claim 33 or 34, characterized in that at the first heat-conditioning station (14) is attached a device for drawing the semi-product (10) with the possibility of adjusting the temperature of the stretching, the amount of stretching and, if appropriate, the speed of stretching. 20   36.- Installation according to claim 35, characterized in that the drawing device is designed for the biaxial stretching of a semifinished product (10) shaped strip or hose.   37. Installation according to any one of claims 33 to 36, characterized in that the stabilizing device (13) is provided with means for calendering or rolling a semi-finished product in the form of a strip. reduction of the thickness.   38.- Installation according to any one of claims 33 to 37, characterized in that the cooling devices provided in the stabilization device (13) are equipped with temperature control systems, adjustable in time.   39.- Plant according to any one of claims 33 to 38, characterized in that the 2465586 34 thermoforming device (16) comprises one or more molds heated surface and adjustable cooling   40.- Plant according to any one of claims 33 to 39, characterized in that the thermoforming device (16) comprises one or more molds at least one surface is provided with a control system for modifying or driving the temperature over time in a predeterminable and, where appropriate, programmable manner, during the thermoforming operation.   41. Installation according to any one of claims 33 to 40, characterized in that the thermoforming device (16) comprises one or more molds equipped with systems for producing a predetermined and adjustable pressure.   42. An installation according to claim 41, characterized in that the pressure generating systems are provided with a control device for varying the pressure over time in an adjustable and programmable manner during operation. thermoforming operation.   43.- Installation according to any one of claims 33 to 42, characterized in that the second thermo-conditioning station (17) comprises at its inlet the thermoforming device (16) and extends over the output of this device (16).   44. Installation according to claim 43, characterized in that the second thermo-conditioning station (17) comprises a device for heat treatment of the moldings following the output of the thermoforming device (16).