FR2500788A1 - METHOD AND INSTALLATION FOR MANUFACTURING THERMOPLASTIC MOLDED PIECES WHICH CAN GIVE A FOAM PRODUCT - Google Patents

Abstract

THE INVENTION PROVIDES A PROCESS AND A PLANT FOR THE MANUFACTURING OF MOLDED PARTS FROM THERMOPLASTIC MATERIAL CAPABLE OF GIVING A FOAM PRODUCT. ACCORDING TO THE INVENTION, THE MOLDED PART 20, AFTER THE DELIVERY OF THE PLASTIC MATERIAL IN A FOAMING MOLD AND AFTER VAPORIZATION OF THE PART IN A VAPORIZATION CHAMBER, IS STABILIZED EXCLUSIVELY THANKS TO THE FACT THAT IMMEDIATELY AFTER THE FOAMING, WITHOUT SPRAYING, FROM A STABILIZING AGENT SUCH AS WATER, AIR OR THE LIKE, THE VACUUM IS APPLIED AND THE FOAMING AGENT IS IN THE FOAM MOLD 3 IS EXTRACTED.

Description

Method and apparatus for manufacturing molded articles

thermoplastic that can give a

foam product.

  The invention relates to a process for manufacturing molded parts made of thermoplastic material that can give

  a foam product, in which the molded part is stabilized

  after the plastic material has been introduced into a foaming mold and after vaporization of the molded part in a vaporization chamber, a vacuum is applied to the molded part prior to demolding of the molded part out of the foaming mold. The invention also provides an installation for carrying out this method and which comprises a vaporization chamber provided with a foaming mold which is housed inside the vaporization chamber, which

  divides the steam chamber into two heating chambers

  fage and which presents the entrance openings for the agent of

  vaporization and the plastic material.

  German Patent Application No. 15 04 360 discloses a method of

  in which cold water is supplied for cooling

  during the stabilization phase, the vacuum being then applied. After cooling the molded part with cold water, the molded part is ejected by means of vacuum. In a process of the same type (German Patent Application NI 29 11120), pressurized air is introduced as a stabilizing agent after the foaming of the piece.

  molded, to make the cell structure of the room -

  molded permeable to blowing and foaming agents included.

  However, the molded part acquires a rougher outer surface than when stabilized with water. For the smoothing of the external surface, a vacuum is applied at the end of the stabilization phase, thanks to which

  is the structure of the molded part.

  The stabilizing agent used for the cooling (cold water or compressed air) entails not only the need to provide labor consuming and time consuming process steps, but also requires a special material structure of the plant used to implement the method. In addition, the application of vacuum is necessary as an additional measure of the process, to avoid the disadvantages caused by the stabilizing agent. Despite these complicated measures, it is not possible to prevent further foaming of the molded part, because the foaming agent present in the room

  molded can not be cooled fast enough, or

  core the molded part has such a cellular structure that

  the foaming agent can only be released slowly.

  The object of the invention is to provide a method of this type by which any subsequent foaming can be avoided by

  Sudden withdrawal of the foaming agent.

  This object is achieved according to the invention by virtue of the fact that the molded part is exclusively stabilized by virtue of the fact that immediately after the foaming without the addition of a stabilizing agent such as water, air or the like , the vacuum is applied and the foaming agent is in the

Foaming mold is extracted.

  In the process according to the invention, the use of

  a particular stabilizing agent, such as water or air, for cooling the molded article after foaming, and instead applying the

  empty immediately after spraying. When applying

  vacuum is formed, a sudden strong suction is formed which abruptly causes all the foaming agent and the vapor present, so that the molded part is rapidly

  cooled and therefore subsequent foaming is effi-

  prevented hiding. Thanks to the process according to the invention, the molded part acquires a smooth outer surface, such as that which has only been presented until now by water-cooled castings, without any

  additional measures are needed. The external surface

  the molded part can be further smoothed

  by injecting water into the water vapor during the vaporization. Thus, there is a cooling which leads to a higher humidity and therefore to a better

  welding granular corpuscles of plastics material.

  In the process according to the invention, it is not necessary to provide stabilizing agents or special measures for bringing and removing them, so that the process according to the invention can be carried out in a much simpler and better way. account by saving material, work and time. Since no water is used for cooling, the mold and the molded part,

  when the latter is removed, are almost

  moisture, so that subsequent drying can be largely saved. Finally, the profitability is further improved by the fact that the service temperature during the evacuation is substantially maintained, so that the mold does not have to be reheated for the process.

foaming next.

  An embodiment of the invention will now be disclosed.

  by way of example, in conjunction with the single figure of

  appended drawing which shows a cross-section of a foam installation

  wise to implement the method according to the invention.

  The foaming plant 1 comprises a steam chamber

  tion 2 in the middle part of which is located a

  foaming mold 3 with upper mold walls 32 and lower

  32 ', so that the vaporization chamber is divisible

  It is divided into an upper heating chamber 2 'and a lower heating chamber 2' 'A filling injector 5 passes through the upper heating chamber 2' and opens into a supply opening 31 of the upper wall 32

  of the foaming mold 3. In the upper and lower walls

  32 and 32 'of the foaming mold are arranged two or more nozzle openings 4 regularly distributed on either side of the filling injector 5. In the side walls 6 and 7 and in the bottom 8 of the chamber 2 , there are respectively two openings 9, 10 and

  11. The openings 9 of the right side wall of the chamber

  bre are access openings in which open conduits 12 for supplying steam. Two piston valves 13 and 14 open are placed one behind the other in the supply duct 19, in the direction Z of the steam supply, valves through which the supply of steam can be controlled from a container (not shown) of saturated steam outside the plant; the rear valve 14 is for this purpose connected to a control valve 15. In the left side wall 7 are provided two exhaust openings 10 which open, similarly to the access openings 9, respectively in one of the chambers The exhaust openings 10 are connected to open piston valves 16 for draining the chamber, through which the condensate can be discharged into unrepresented water discharge ducts. Other openings 11 in the bottom chamber 8 are connected to control valves 17 open for degassing the chamber, the ducts 12 are connected to a vacuum installation via a valve duct 21, this installation comprising a vacuum pump. vacuum 22, a piston valve 29 open, arranged

  behind the pump in the direction A of the suction, a separa-

  cyclone 27 having a drain valve 28 for the condensate, a valve 25 or a vacuum valve

  for the adjustment of the vacuum, a pressure gauge 26 and a sight 23

  as a control element.

  The process according to the invention can also be carried out with a vaporization chamber to which is supplied not steam but water. In this case, respectively

  disposed near the inner face of the chamber walls

  upper and lower parts, heating elements

  the shape of an electric heating plate, and between

  that heating plate and the chamber wall vis-à-vis

  is arranged a water vaporization duct whose openings

  tures are directed to the heating plate.

  The necessary amount of plastic material is brought into

  the foaming mold 3 heated prior to a temperature of

  approximately 85 to 1000 ° C., by the filling injector 5.

  The foaming mold, in the installation 1 shown, is preheated and maintained in temperature by introduction of

  water vapor through the openings 9. In a room with

  heating elements and water spray pipes, the pre-

  heating and maintaining the temperature are done by introducing

  water ducting in the vaporization ducts and then vaporization and maintenance temperature through the hot plates. For the introduction of steam into the heating chambers 2 'and 2 ", the valves 13 and 14 of the steam supply duct 19 are open, while the control valve 29 of the vacuum installation is closed. A compressed air valve 18 of a compressed air conduit 30 is

  same time closed, this duct being also connected to the con-

  12 for the ejection of the molded part. After the steam thus fed has been introduced into the foaming mold 3 through the nozzle openings 4, the plastic material, such as polystyrene, is inside the foaming mold. Water can be injected into the saturated steam for cooling and for better welding of the granular plastic material, the

  molded part thus obtaining a smooth surface structure.

  At the end of this foaming process, a vacuum is applied in the vaporization chamber 2 to the molded part 20

thanks to the nozzle openings 4.

  The vacuum is produced immediately after the vaporization phase; it may in this case be useful to open the valve 16 on the left side wall 7 of the chamber, for a few seconds, preferably about 2 seconds, so that the overpressure disappears. Condensed water escapes

  thus from the chamber 2 to the discharge ducts.

  The vacuum is produced by the fact that the pressure valve 18 and the valve 13 of the steam duct 19 are closed and that the control valve 29 of the setting up installation

  empty is open. When evacuating, it is possible to reach

  tagously a depression of 0.5 to 0.8 bar. At the moment o

  the vacuum is applied, the foaming agent, for example

  tane, pentane or the like, contained in the molded part, is evacuated suddenly and completely from the chamber 2

  through the nozzle openings 4, thanks to the suction occurs

  Then, the molded part 20 can not further foam subsequently, which achieves in manufacturing high dimensional accuracy. The water vapor present is sucked by the vacuum pump 22 at the same time as the foaming agent. The molded part 20 is thus cooled, as when using a stabilizing agent during the stabilization phase of the known process. In order to prevent water from reaching the pump during evacuation and that it is damaged, the condensate present is

  eliminated by the cyclone separator 27 and the evaluation valve

  cuation 28, the rear control valve 24 and the valve 29 being closed. With the indicator 23, we check if all the

  The condensate was trapped by the cyclone separator 27. The

  The quality of the molded part is even better than the

  in the vaporization chamber 2 is elevated.

  At the end of this process step, the valve 29 is closed again and the pressure valve 18 is opened, so that compressed air is introduced into the chamber 2 through the compressed air duct 30 and the ducts. 12. One of the mold halves is thus moved away from the molded part 20. Compressed air is blown onto the molded part 20 through the nozzle openings 4, the molded part being all

  first extracted from the other mold half and ejected.

  Demolding and removal of the molded part can

  also be achieved by the fact that air ducts

  the first outlet directly into the foaming mold, these ducts being insulated from the heating chambers of the vaporization chamber and being connected to the corresponding inlet opening by a valve opening towards the foaming mold, opening which is in turn isolated from the heating chamber. In such an embodiment (not shown) of the chamber,

  only residual moisture, possibly

  it is not entrained by compressed air, so that

  the foaming mold and the molded part remain dry.

Claims (8)

Claims.   A method of manufacturing molded thermoplastic moldings, wherein the molded part is stabilized after feeding the plastic material into a foaming mold and after   vaporization of the molded part in a steam chamber   tion, a vacuum being applied to the molded part beforehand.   demoulding of the molded part out of the foam mold.   characterized in that the molded part (20) is stable   exclusively because, immediately after foaming, without the addition of a stabilizing agent such as water, air or the like, the vacuum is applied and the foaming agent is in the foaming mold (3) is extracted.   2. Method according to claim 1, characterized in that   water is injected into the steam during the steam   authorization. 3. Method according to claim 1 or claim 2, characterized in that the overpressure in the chamber of   vaporization (2) is deleted briefly before application vacuum.   4. Foaming plant for the implementation of the process   according to any one of claims 1 to 3, comprising   a vaporization chamber inside which is   a foaming mold which divides the vapor chamber   two chambers of heating, the mold having access openings for the spraying agent and the   plastic material, characterized in that in the openings   access ducts (9) for the spraying agent, open conduits (12) which are connected to a steam duct (19),   a duct (30) of compressed air for demolding and ejecting   tion of the molded parts and -an empty conduit (21) arranged between them.   5. Installation according to claim 4, characterized in that a control valve (15) connected to a pressure regulator (14) is provided in the conduit (19) supply of steam.   6. Installation according to claim 4 or claim, characterized in that, in the vacuum conduit (21) of a vacuum pump (22) of a vacuum system are connected one behind the other, in the suction direction A, the following installation components: an anterior control valve (29), a cyclone separator (27) with a drain valve (28) for the condensate, a valve (25) for adjusting the vacuum, a control rear valve (24) or a vacuum control valve and a control element (23) disposed   upstream of the vacuum pump, preferably a light.   7. Installation according to any one of the claims   4 to 6, characterized in that the vaporization chamber (2) has on its side wall (7) facing the side wall (6) having the access openings (9) for the at least two steam exhaust openings (10) opening into each heating chamber, and that the steam exhaust openings (10) can   be opened or closed by means of control valves (16).   8. Installation according to any one of claims 4   at 7, characterized in that the duct (30) for supplying air   tablet comprises a control valve (18) for   the ejection and ejection of the molded part.