DE3011519A1 - METHOD FOR PRE-FOAMING PEARLS FROM THERMOPLASTIC RESIN MATERIALS, AND METHOD AND DEVICE FOR MOLDING FOAMED OBJECTS FROM THERMOPLASTIC RESIN MATERIALS - Google Patents

Description

thermoplastic synthetic resin materials and methods and apparatus for molding foamed articles made of thermoplastic

Synthetic resin materials 20

The invention relates to a method for prefoaming beads from thermoplastic synthetic resin materials, especially for use in a subsequent molding process, as well as a method and an apparatus for molding foamed articles from thermoplastic synthetic resin materials, especially made of polystyrene.

An initial pre-expansion of thermoplastic beads to form so-called "pre-puffs" (hereinafter simply (referred to as "prefoamed beads") is a common process. The prefoamed beads are up to foamed to a volume amounting to at least 50% of the volume of the finished molded article. By the Preforming or prefoaming of the beads can substantially fill a shape, thereby creating a more uniform Expansion or foaming of the pearls, an elimination

XI / rs

0300-64 / 0.574

ORIGINAL INSFECfED

3011513

- 14 - DE 0206

of cavities, application of lower molding pressures, higher production cycles and formation of Low density foaming can be enabled. The basic process is described by G. R. Franson in Plastics Technology, July 1956, pages 452 to 455.

When forming pre-expanded beads, it is important to have uniform, dimensionally stable products Manufacture at high production speed, the type of polymer, the content of the pearls of volatile Substances before and after prefoaming and the moisture content of the environment are taken into account have to. Finally, the device used for prefoaming and shaping the foam must be quick and easy be able to work trouble-free.

The invention relates to a method and a device for prefoaming thermoplastics Materials that contain a blowing agent, in particular on a device for prefoaming, through the dimensionally stable, Pre-expanded beads are formed, which directly form their final shape without further post-processing Dimensions can be shaped. By the method according to the invention and the device according to the invention a finished product is produced in a considerably shorter time than was previously possible was. In addition, this is achieved by the method according to the invention and the device according to the invention in terms of its density and its integrity Structure much more uniform than products that are manufactured by known methods and devices, and the product of the present invention can be manufactured at a lower cost and with a lower capital outlay.

03 084/0 57

- 15 - DE 0206

] In brief, thermoplastic beads, e.g. B. polystyrene beads containing a blowing agent, e.g. B. pentane, contain, prefoamed by first heating a measured amount of stirred beads in a container maintained at substantially atmospheric pressure to their softening point by conduction. The heating is continued and regulated until the beads have expanded or foamed to a predetermined extent. A gaseous medium, e.g. B. air can be passed through the container or chamber for rinsing in order to remove any propellant that has been released from the beads and thereby avoid any safety risks that may be present. The container is then closed and evacuated in order to reduce the propellant content of the beads considerably. When the propellant level has been reduced to the appropriate level, the container is returned to atmospheric pressure.

The beads can then be conveyed directly to a mold cavity. As an alternative, the pearls can be in a reservoir that maintains the partially foamed beads at an elevated temperature, to atmospheric pressure be returned. It was determined, that the subsequent molding process is carried out much faster and with a lower overall energy consumption can be achieved if the pre-expanded beads are kept at an elevated temperature.

The pre-expanded beads are removed from the chamber used for the pre-expansion or, if appropriate, from the heated storage container by means of conventional, air-operated filling guns into a preheated mold cavity or blown into preheated mold cavities. So that the mold cavity is filled as quickly as possible, a Number of filling guns used. To a quick one

• $ • 014/0574

3011513

- 16 - DE 0206

ι To facilitate filling of the mold cavities, can be attached to the A vacuum can also be applied to the mold cavities in a constant manner by means of a suction pump.

c When filling is complete, a suction vacuum is applied through a molding surface of the mold cavity, while a heating fluid such as superheated through the other molding surface of the mold cavity for a certain period of time Steam or hot air is passed through. Then it will be

IQ the direction in which the heating fluid or heating medium flows through the mold cavity flows through, conversely, to ensure uniform heating and foaming or expansion of the pre-expanded beads for the purpose of fusing the product. That in the pre-expanded beads contained, residual blowing agent allows during the application of the higher temperatures during molding (further) foaming or (further) expansion and is necessary for complete fusion.

When the foaming and fusing of the pre-expanded beads are complete, the flow of the Heating fluids interrupted. A vacuum is maintained for a short period of time to substantially reduce the to remove all of the moisture and all of the propellant, thereby also causing the formation of a skin on the shaped object is promoted, which can also be achieved by cooling the mold surfaces. Thereafter the interior of the mold cavities is returned to atmospheric pressure, and the mold cavities become automatic ejection of the finished article opened.

In a preferred embodiment of the invention the pre-expanded beads .during the pre-expansion step further foamed by blowing steam into the container after the initial heating.

030064/0574

- 17 - DE 0206

This procedure is used to further soften the pre-expanded beads and to add the blowing agent To make it easier to migrate out of the pre-expanded beads. This embodiment increases the evacuation period, which is necessary to remove substantially all of the propellant shortens, and enables it the formation of stable pre-expanded beads with an extremely low density.

The method according to the invention not only eliminates dwell times and the occurrence of hardening between the pre-expansion step and the molding step, but also the need for conditioning the finished object removed after molding, so that the product can be packaged directly and shipped to buyers once it reaches the molding facility has left.

It is believed that the unique advantages of the invention can best be explained by considering the effect that each individual step of the method according to the invention has on the thermoplastic Particle exercises. In the beginning, during the preheating stage, the pearls are in a dry place The atmosphere is thrown against the hot walls of the device used for prefoaming while stirring. the Beads are heated uniformly throughout and are allowed to expand freely as they expand the propellant evaporates. The expansion or expansion

foaming is not delayed because the device used for prefoaming is neither closed nor later is exposed to a pressure above atmospheric pressure. During this stage, the density of the pre-expanded Pearls have been regulated by varying the temperature of the pearls. While the pearls in all cases are softened to a certain extent,

030064/0574

- 18 '- DE 0206

they become more fluid at higher temperatures,
and there is greater expansion. Because the
The temperature of the beads (and therefore the density of the pre-expanded beads) for each batch that has been introduced into the pre-expanding device.,
can be easily adjusted by merely regulating the temperature of the heating mantle and the heating period, a wide range of products can be manufactured.

In the preheating step of the present invention
two other advantages are achieved. First, since the beads are heated by conduction through the walls of the prefoaming device, the surface of the beads softens to a greater extent

than the interior of the pearls, which is why a dense skin or crust forms around the particles or pearls when they cool down. This will make the pre-expanded beads
Dimensional stability bestowed. Steam does not have this effect as it penetrates through the pre-expanded beads. Second, the softening of the volatilized blowing agent is not delayed because the preheating is carried out under atmospheric pressure.

After the expansion in the pre-heating stage has been completed, this is used for the pre-expanded beads applied vacuum to reduce the concentration of the propellant to a minimum. For this step

less time is required, of course, because during the on
^ου Preheating a significant amount of the propellant has been eliminated. The elimination of the propellant is a major reason for achieving a dimensionally stable product. However, the pre-expanded beads must still contain a minimum amount of the blowing agent, as this is required to further expand the product during the final molding carried out.

030064/0574

- 19 - DE 02O6

In the preferred embodiment of the invention, a small amount is added at the end of the preheat period blown by high temperature steam to reduce the concentration of propellant and the To facilitate molding process. As a result, the pre-expanded beads are quickly heated and expanded further. This not only leads to a reduction in the density of the pre-expanded beads, but also to one Increasing the permeability of the surface skin, thereby.

the time and energy required to remove the propellant from the pre-expanded one during the evacuation stage Peel off pearls are diminished. Also the heating and evacuation of volatile substances during the molding step are facilitated.

In the method according to the invention, the mold is completely filled with the pre-expanded beads, which is why the volume of the beads used for molding changes little during the molding step. Indeed however, the individual pre-expanded beads expand further, thereby reducing the interparticle size located cavities are filled. For this reason, a small amount of the propellant must remain. Without the blowing agent, there would be no further expansion or foaming under the conditions prevailing during molding enter and it would only merge at the contact points of the spherical particles. on the other hand essentially all of the blowing agent must be removed once molding is complete. To this end

^ou and the particles for fusion is alternatively introduced steam from one side in shape, while a vacuum is applied to the mold from the other side. The final evacuation step also becomes essentially complete

Removal of the propellant and the moisture

Q30 0 64 / Q574

- 20 - DE 0206

perform. If both of these were not removed, the cooling time that had to be waited for would be the molded object can be removed from the mold because of the high specific heat of water and due to of the pressure developed by the blowing agent would be prolonged, and the dimensional stability would be get lost.

In summary, it can be concluded that the method according to the invention is effective because its unique combination of steps serves to remove the propellant and moisture quickly, as soon as these have served their purpose, and because it is used to produce an excellent product leads, as it could not previously be obtained, with the method according to the invention in particular a high production speed is also achieved.

The attached figure is a schematic representation of the device for prefoaming according to the invention and forms and the method of the invention.

The figure shows a device 10 which is used for prefoaming and which has a cylindrical container 12 a generally horizontal axis. The container 12 has in its end wall 14 a for holding non-foamed, thermoplastic synthetic resin material in the form of pearls 16 serving opening. The most common type of this material is Polystyrene containing n-pentane as a blowing agent. This material has a density of about 0.64 kg / 1, and the following conditions apply when using such a material. The pearls 16 are first placed in a hopper 18. The desired amount of pearls 16 is then with-

0300G4 / 0574

- 21 - DE 0206

by means of a loading piston 20 which is actuated by air can be supplied to the interior of the container 12.

The inner wall of the container 12 is heated by a heating to a temperature of about 107 ⁰ C to 121 ⁰ C. The heating fluid is circulated through a heating jacket 22 which surrounds a major portion of the outer surface of the container 12. The heating fluid is introduced through the inlet 24 which is adjacent the upper edge 23 of the heating jacket on one side of the container 12 and the heating fluid is discharged through the outlet 26 located at the bottom of the heating jacket.

The stirring devices used for stirring the pearls located in the Eehälters 12 are in the form of a A plurality of agitating arms 28 mounted on a rotating motor driven by a motor (not shown) Rod are attached. Stirring prevents the pearls from sticking together or agglomerating and facilitates the process even heating.

While the feed piston 20 adjacent inlet is above the central axis of the container 12, the outlet 30 is perpendicularly below the Center axis arranged so that the pre-expanded beads under the influence of gravity to a storage container 34 flow when the discharge piston 32 to open

tion of the outlet 30 is actuated. This promotion The pre-expanded beads can be speeded up by moving the pre-expanded beads with the help of air from the blower 36 out of the container 12

bites.
35

030064/0574

- 22 .- DE 0206

T If the charging piston 20 with the appropriate

Amount of beads 16 is loaded, the walls of the container 12 are brought to the appropriate foaming temperature. heated. This is a temperature sufficient to soften the surface of the beads and volatilize the propellant, but not high enough to cause the beads to fuse together during agitation. The degree of softening of the beads and the preheating period depend on the density of the pre-expanded beads desired and the finished product. It is known that the expansion is greater and the density of the pre-expanded pearls is lower, the more the pearls are softened. For example, the temperature of the incoming steam into the heating jacket · 107 ⁰ C and the Vorerhitzungsperiode to 70 s should be set when a loading of 20 kg of polystyrene beads with a content of the seventh % Pentane as blowing agent, and the production of a finished product having a density of 0.096 kg / 1 is desired, the other hand, the temperature should be supplied to said heating mantle vapor are s set to 121 ⁰ C at a preheat of 70 when a product having-a Density of 0.026 kg / 1 is desired. By doubling the preheating period to 140 s at a steam temperature of

121 ⁰ C, the density can be reduced to 0.020 kg / l. The appropriate combination of temperature and time for the preheating step can be easily made considering the type of thermoplastic beads, batch weight, equipment and density desired

to be established. The loading piston 20 is used to fill the pearls into the interior of the container 12 actuated while the agitator arms 28 are set in Dr.ehung_ be heated to the beads continuously with the.

To bring surface of the container 12 into contact. 35

030084/0574

ίΑϊί'5, * "- -i

- 23 - DE 0206

Hot air, preferably at a temperature above the softening point of the pearls, can can be introduced into the interior of the container 12 from a source 36 through the conduit 38 and the wall 14. In the container 12 a strong flow of hot air is maintained by the in the container Sucks the atmosphere through a line 40 connected to a vacuum pump. That way it becomes Inside of the container at atmospheric pressure or at a pressure very close to atmospheric pressure held, and any vapors or gases evolving during the foaming of the pearls will quickly become removed. The rapid removal of these vapors or gases is important because it aids in the removal of the pentane from the pearls and serves as a safety precaution because the gaseous pentane that evolves and released into the atmosphere of the container is highly explosive when it is exposed to oxygen mixed. Know the incoming pearls from long-term storage or from before processing If the cleaning steps carried out carry moisture with them, it is also important that the moisture is removed so that the foaming of all the pearls takes place at a reasonably constant rate goes.

If a foam with a particularly low density or higher production speeds is desired after the initial foaming of the beads with the dry air, a measured amount of steam can be used at high temperature through a plurality of inlet ducts (not shown) into the bottom of the container 12 were introduced. This steam has a higher temperature than the pre-expanded beads, e.g. Legs

Temperature from 100 ⁰ C to 177 ⁰ C, and relies on the

Q30084 / O574

BADORfGfNAL

- 24 - DE 0206

Poiystyroi-Teiichen free latent heat of condensation, which serves to rapidly increase the temperature of the particles and leads to additional foaming. This step is also carried out at atmospheric pressure or in the vicinity of atmospheric pressure. While During this step, only a limited amount of condensate is formed because of the bulk of the pearls provided heat is added during the preheating step by convection. This During the evacuation step described below, condensate is drained through a number of (not shown) outlet openings, which are at the top and on the side of the container 12 are completely removed. The use of a variety of inlet ports and outlet openings for the steam ensure uniformity throughout the stirred beads Distribution of the steam.

When the pre-expanded beads have reached the desired density, that prevailing in the chamber 12 becomes Pressure by actuating the vacuum pump via line 40 to a value below de.Pi atmospheric pressure (to a vacuum of 60 to 853 mbar, preferably 333 to 680 mbar). By diminishing the pressure in this stage can be the content of the residual gas present in the pre-expanded beads can be reduced, thereby giving the pre-expanded beads excellent stability. By this vacuum step becomes the bulk of the propellant

(and the condensate if steam is added) removed while leaving an amount that will go straight, to allow further foaming of the beads during the molding step. When the polystyrene beads originally about 5 to 7% by weight propellant

held, the concentration of the remaining gas is preferably set to 0.75 to 2 wt .-% by the vacuum step,

03006A / 0574

3011513

- 25 - DE 0206

'in particular to about 1% by weight. Through the Applying the preferred embodiment of the invention, i. H. in the event of adding steam after preheating, the evacuation of the propellant is made easier. It is believed that this is due to the fact that the skin for the gases become more permeable.

After the vacuum step, the emptying piston is actuated so that the pre-expanded beads are quickly transferred to the

kept at atmospheric pressure and at a temperature of 49 ⁰ C to 77 ⁰ C, insulated storage container 34 are poured. From the storage container 34, the partially foamed or pre-foamed beads are pneumatically through lines 46 and 48 of a molding device.

'^ device 50 supplied.

Alternatively, the outlet 42 can be connected directly to a conduit for rapid evacuation of the container 12 and an immediate loading of a

Cavity as described below cause. In such a case, the pre-expanded pearles must be brought to atmospheric pressure before the cavity is charged be returned.

As explained in more detail below, with

Compressed air operated filling pistons are used to form the pre-expanded peria into a pair of identical mold heights 52 and 54 that are shown in the figure

are shown schematically.
30th

The molding device 50 includes molding plates 56 and 58 which are attached to a frame device 60 are. In addition, a mold plate 62 is movable with respect to the mold plate 56 on the frame device 60 attached, while an identical mold plate 64 relative to the mold plate 58 movable on the frame device

030064/0574

- 26 - DE 0206

device 60 is attached. As will be discussed in more detail below, the mold plates 56, 58, 62 and 64 contain all of them a number of holes extending through the mold plates. Some of these holes are used for Letting in pre-expanded beads supplied from the filling gun 66 while others have holes for letting in a fluid for heating and for evacuating the interior of each mold cavity are provided.

The mold plates 62 and 64 can be moved to and from their opposing counterparts will. With this arrangement, by simply varying the size of the mold cavities 52 and 54 as well the design of the shaping surfaces even shaped objects such as insulating panels or panels with a wide range of thicknesses and shapes can be manufactured.

The fluid handling system of the molding facility 50 is explained in more detail below with reference to the figure.

In the preferred method, a heated fluid such as hot air is supplied to two separate fluid storage spaces 68 and 70, suitably located in proximity to the forming device 50. Although hot air can be used as the heated fluid, superheated steam with a temperature of 93 ^° C. to 135 ^° C. is preferred. The heated fluid is supplied from the fluid storage space 68 through one or more conduits 72 to a fluid distribution chamber (not shown) located behind the molding surface of the mold plate 62. A solenoid valve 74, which can be moved between an open and a closed position, regulates the flow through line 72

occurring flow of the fluid. Similarly, the fluid is passed through one or more conduits 76 passing through

030064/0574

- 27 - DE 0206

a similar valve 78 regulates grounding a fluid distribution chamber located behind the forming surface of the mold plate 64 fed. Since the mold plates 62 and 64 are movable on the frame assembly 60, it is It is desirable that lines 72 and 76 be flexible so that this movement can be compensated for.

The ueni I'iuid storage space 70 is used for heating serving fluid is supplied through one or more lines 80 and 84 to the mold plates 56 and 58, respectively. the Flow through lines 80 and 84 is similarly regulated by solenoid valves 82 and 86, respectively. As follows is described is a through conduit 90 via valve 92 to the rear of the forming surface the mold plate 62 located fluid distribution channel connected Discharge pipe 88 is preferably arranged vertically below the shaping device 50. In a similar way Way is conduit 94 via valve 96 at a number of locations with de r behind the forming surface of the

Form plate 56 located fluid distribution chamber and with the drain pipe 88 connected. Lines 98 and 100 connect the behind the molding surfaces of the mold plates 58 and 64 located fluid distribution chambers via valves 102 and 104 with the discharge pipe 88. The discharge pipe 88 is via a

Valve 106 K ₁ It connected to a vacuum pump 108, which has a high capacity. The drain pipe 88 communicates via a valve 110 with a drain leading to the atmosphere. All valves that are used in the fluid transport system are preferably solenoid valves so that remote actuation of the valves, preferably using a program, is made possible. In addition, all valves show a two-point behavior so that they operate either in the fully open or in the fully closed state.

030064/0574

- 28 - DE 0206

After the shaping device described above, the method steps according to the invention are now carried out explained in more detail.

When the molding plates have been moved 62 and 64 in its closed position relative to their respective counterparts 56 and 58, the temperature of the mold cavities is maintained at 93 ⁰ C to 135 ⁰ C 52 and 54 by, if one is necessary, the Introduces fluid from one or the other of the fluid storage spaces 68 and 70 into the mold cavities. When the mold plates are properly clamped and locked, valves 74, 82, 86, 78 and 110 are closed while valves 92, 96, 102, 104 and 106 are open and vacuum pump 108 is turned on is to reduce the pressure in the mold cavities 52 and 54 below atmospheric pressure, preferably to a vacuum of 267 to 307 rabar. Shortly thereafter, the filling pistols 66 are actuated to blow the partially foamed or pre-expanded hot beads into the mold cavities 52 and 54 and to fill the mold cavities. When the mold cavities have been filled, the fill guns 66 are disabled and the valves 82, 86, 92, 104 and 106 are disabled

^ are in their open position while valves 96, 102, 74, 78 and 110 are closed. Accordingly, in this stage, the fluid flows from the fluid storage space 70 through the lines 80 and 84 and through the molding surfaces of the respective mold plates 56 and

58 through, across the respective mold cavities 52 and 54, through the molding surfaces of the mold plates 62 and 64 out and through lines 90 and 100 to vacuum pump 108. After a period of time the direction of flow of the heated fluid can be reversed will.

030064/0574

BATH ORIGINAL

- 29 - DE 0206

In the event that a reversal of the flow direction is used, this is effected by the valves 82 and 86 are closed while valves 74 and 78 are opened and valves 92 and 104 are closed while the valves 96 and 102 are opened, which results in the fluid from the fluid storage space 68 transversely through the molding surfaces of the mold plates 62 and 64 in the de-energizing direction by the form elevations and by those in the molding surfaces of the mold plates 56 and 58 located openings out and through the lines 94 and 98 to the vacuum pump 108 flows. This arrangement makes it possible to generate a spread across the thickness direction of the molded article extending density gradient

'5 considerably reduced, so that a much more uniform and better salable product is obtained. As is known, the partially foamed ones work or pre-expanded beads are also very effective insulating materials, so that a considerably longer

™ Forming time would have to be applied to achieve a complete Ensure fusing of the beads in the entire mold height, if that is used for heating Fluid in the case of making a very thick one Plate is only attached to a cavity from one side

leads would be. By the method according to the invention and the device according to the invention, however, considerably reduces the molding time since the pre-expanded ones Pearls are soaked or flushed through the fluid from opposite sides,

whereby an intimate and thorough heating of all pearls is ensured.

030064/0574

- 30 - DE 0206

The product located in the mold cavities is then cooled by opening all the valves that come with the Fluid storage spaces 68 and 70 are in communication, closes and the valves 92, 96, 102, 104 and 106 opens, while the vacuum pump is actuated and the valve 110 still remains closed to reduce the pressure to one below atmospheric pressure, preferably to a vacuum of about 333 mbar. the Moisture and any gases contained in the mold cavities 52 and 54 are then evacuated, and as the pressure decreases, the temperature in the mold cavities also decreases. With this one Step is the concentration of the propellant to less than 0.5 wt .-%, preferably to less than 0.3% by weight, reduced. Then the valve 106 is closed and the valve 110 is opened to the To bring cavities back to atmospheric pressure, whereupon the mold plates are unlocked and opened and the finished molded article is automatically removed from each the mold cavities is ejected.

The device according to the invention, as described above, enables a faster process the molding process achieved, which is mainly due to the fact that the Foriahöblungen quickly with the pre-expanded Pearls can be filled and that the pearls then uniformly to their melting temperature or melting temperature can be heated to solidify the peries in the form of the finished article.

The molded product is then ejected from the mold cavities and is immediately available for packaging and for available for carriage to a buyer.

030064/0574

- 31 - DE 0206

The invention has been described above on the basis of a special embodiment in which polystyrene beads containing n-pentane were used as blowing agent, but these are only preferred materials. Examples of other foamable, particulate polymeric materials that can be used are other homopolymers and copolymers derived from vinyl monomers, e.g. As vinyl chloride, Divinyibenzol, oil -methyl! Styrene, Nuclear-or with germ

^ O forming dimethyl styrene and vinyl naphthalene. In addition to the polystyrene homopolymers, copolymers of styrene with ^Λ -methyl styrene, divinyibenzene, butadiene, isobutylene and acrylonitrile with a styrene content of about 50% or more are particularly suitable. At-

'~ * Games of suitable blowing agents are other volatile aliphatic or cycloaliphatic hydrocarbons having aligemeinen 1 to 7 carbon atoms per molecule. Examples of such hydrocarbons are methane, methane, propane, butane, hexane, petroleum ether,

Cyciopentane, cyclohexane, cyclopentadiene and halogenated Derivatives whose boiling points are below the softening point of the polymers. Other examples of propellants are dichloromethane, dichlorodifluoromethane, acetone, methanol, methyl acetate, ethyl acetate, methyl formate,

Ethyiformate, propionaldehyde and dipropyl ether. That Propellant is generally in an amount of 3 to 15% by weight, preferably 5 to 8% by weight, based on the weight of the polymers.

The invention is completed by the following

Examples explained in more detail.

030064/0574

- 32 - DE 0206

example 1

The device described above was used. 16 kg of polystyrene beads containing 7% n-pentane as a blowing agent were filled into the container 12. The temperature of the heating mantle was set at 107 ⁰ C, and the beads were preheated 100 s long, while air flowed at a rate of 2,832 l / min through the container. During the preheat period, the container was at approximately atmospheric pressure and the beads expanded. The container was then closed and a vacuum of 773 mbar was applied for 3 minutes, as a result of which the concentration of the n-pentane was reduced to about 1% by weight. The pre-expanded beads obtained had a density of 0.026 kg / l. The pre-expanded beads were then shaped to form a plate, for which purpose a double-forming plate device was used for forming plates or plates, the size of which was 1.2 m × 2.4 m and a thickness of 51 mm mm had. The molding was carried out using steam at a pressure of 0.686 bar. Excellent fusing of the particles was achieved. The product was cooled under vacuum for 3 minutes; it had good dimensional stability and a blowing agent concentration of about 0.25%.

Example 2
30th

The procedure of Example 1 was repeated, but after the preheating period was over one Period of 6 s steam is introduced into the container at a pressure of 6.86 bar, while the container is at-

atmospheric pressure was maintained. Then it was attached to the container

030064/0574

- 33 - DE 0206

a vacuum was applied, the container was evacuated for 30 seconds and the vacuum was maintained for 1.5 minutes, which was sufficient to reduce the pentane content to about 1% by weight. The product obtained had an extremely low density (0.012 kg / l) and was dry. This product was also made as in Example 1 described, but steam was included to penetrate through the pre-expanded beads a pressure of only 0.549 bar required. The cooling time was reduced to 20 s. Excellent fusing of the pearls and the product was achieved had excellent dimensional stability. The reduction in the cooling time shows that the molded product was completely free of moisture and blowing agent.

030064/0574

ι ³ ■ Blank page

Claims (1)

TlEDTKE - ÜÜHLING "KlNNE rupe - P ellmann 3011519 Dipl.-Ing. R. Kinne - * Dipl.-Ing. R group Dipl.-Ing. B. Pellmann Bavariaring 4, Postfach 20 2403 8000 Munich 2 Tel .: 089-539653 Telex: 5-24 845 tipat cable: Germaniapatent Munich March 25, 1930 DE 0206 / case ADK 853-11-F Claims ■ 1. Process for prefoaming beads from a a thermoplastic synthetic resin material containing a blowing agent, characterized in that one (a) Place the pearls in a chamber, the one at about the melting temperature of the pearls and above the inner surface is heated to the boiling point of the propellant, (b) the beads at substantially atmospheric pressure to their softening point and Stirred continuously until its volume expanded to prevent the beads from agglomerating caking while absorbing heat applied from the inside surface of the chamber, (c) The pressure in the chamber is reduced to give the foamed beads a significant proportion of the gas to withdraw shaped propellant, and (d) allowing the foamed beads to return to substantially atmospheric pressure. XI / rs 030064/0574 Deutsche Bank (Munich! KIo. 51/61070 Dresdner Bank (Munich) Account. 3939844 Postscheck (Munich) Account. 670-43-804 ORIGINAL INSPECTED - 2 '- DE 0206 3011513 2. The method according to claim 1, characterized in that that at the end of step (b) steam with a temperature above the temperature of the foamed beads Introduces temperature and brings into direct contact with the foamed beads to form the foamed beads continue to heat and froth. 3. The method according to claim 1 or 2, characterized characterized in that polystyrene is used as the thermoplastic synthetic resin material and n-pentane as the blowing agent and that the foamed beads after step (c) contain between about 0.7% and 2% by weight of blowing agent. 4. The method according to claim 1, characterized in that during step (b) a non- flammable gas is passed through the chamber in order to drive off the volatilized propellant which has escaped from the beads. 5. The method according to any one of claims 1 to 3, characterized in that the pre-expanded beads after they have returned to substantially atmospheric pressure are conveyed to a mold cavity, with a heated fluid introduced from one side of the mold cavity while a vacuum is maintained on the opposite side of the mold cavity, to continue to foam the pearls until they have fused, so that after the fusing is complete, the The supply of the heated fluid is terminated and a negative pressure is maintained at the mold cavity in order to remove the remaining To remove the propellant and residual moisture, and that the mold cavity after the removal of the brings the remaining moisture and the remaining propellant back to atmospheric pressure and the on this ^OJ way shaped object removed. 030064/0574 ^{DE 02} St) 11519 6. The method according to claim 5, characterized / that the direction in which the fluid used for heating flows through the mold cavity is reversed, by supplying the heated fluid from the other side of the cavity, while on one side Side of the mold cavity maintains a negative pressure. 7. A method of forming a polystyrene foamed article from a blowing agent in the form of polystyrene beads containing n-pentane, characterized in that that he (a) brings the pearls into a chamber which is heated inside to a temperature of 82 ⁰ C to 121 ⁰ C, (b) the beads are kept at substantially atmospheric pressure to prevent caking. Agglomeration is continuously stirred, the beads being fed from the inner surface of the chamber Absorb heat, soften it and expand its volume, (c) the pressure in the chamber is reduced to a value of 333 to 680 mbar by the amount of the Polystyrene contained n-pentane to a value of about 0.75 to 2 wt .-% reduce, and (d) allowing the foamed beads to return to substantially atmospheric pressure. 8 . Process according to Claim 7, characterized in that steam at a temperature higher than the temperature of the pearls is introduced and brought into direct contact with the pearls in order to further expand the pearls after the pearls have been expanded in step (b). 30 064/0574 - ⁴ - ^{CE 02} §!) 11519 9. Device for forming a foamed, thermoplastic article made from beads formed from a thermoplastic synthetic resin material containing a blowing agent exist, indicated by 5 Heating devices (12, 22, 24, 26, 36) that serve to to raise the temperature of the beads to substantially atmospheric pressure prior to their formation foam up to a desired extent, 10 Forming devices (50) and Conveying devices (46, 48, 66) used for conveying the pre-expanded beads from the heating devices to the forming devices are used, wherein the shaping means a first (62) and a second (5 6) mold plate facing each other, a frame device (60) to which the mold plates are attached so that a mutually directed, leading to a closed position, and one facing away from each other, to an open position allows leading, relative movement of the mold plates the mold plates, when they are in the determined position, by a device (60) so that between the Mold plates a mold cavity (52) is defined, with one side of the mold cavity through the first mold plate and the opposite side of the mold cavity is formed by the second mold plate, a .Fluid heating source and 030064/0574 - 5 - DE 03 $ -Y 1 5 -Y Fluid conveying devices, which serve to supply a heated fluid to the mold cavity from one side of the mold cavity, while the fluid conveying devices discharge fluid from the mold cavity through the other side of the mold cavity, and then serve to discharge the fluid that is present in the mold cavity Reduce the pressure below atmospheric pressure and bring the mold cavity back to atmospheric pressure,
10 contain. 10. Apparatus according to claim 9, characterized in that the heating devices are cylindrical Chamber (12), one for heating the inner surface of the chamber serving heating jacket (22), one for loading Serving inlet and an outlet serving for emptying, which are located at spaced apart locations of the Chamber are located, circulation devices (36) which serve to circulate heated air at substantially atmospheric pressure to circulate through the interior of the chamber, and feed devices (28) for stirring of the pearls in the chamber. 11. Device according to claim 10, characterized in that that the heating jacket contains circulating devices which serve to pass hot oil through the heating jacket to lead in the cycle. 12. The device according to claim 9, characterized in that for the storage of pre-expanded pearls which have been emptied from the heating devices, _t a storage container (34) for pre-expanded pearls is provided.
35 030064/0574 ORlGtNAL INSPECTED ^DE 13. Device according to / mspruch 12, characterized in that that the conveying devices serving for the conveyance of pre-expanded beads have a large number of pipelines (46, 48), each end of the pipelines being connected to the reservoir (34) and another end of the conduits is connected to an air operated manifold, each Dispensing means comprises a bead distribution nozzle (66) and wherein the bead distribution nozzles are at locations which are arranged along one of the mold plates at a distance from one another, in communication with the mold cavity stand. 14. The device according to claim 9, characterized '5 indicates that heating devices are used to heat all of the mold plates are provided. 15. Apparatus according to claim 9, characterized in that that each mold plate contains a molding surface., over which a plurality of passing through the forming surface Vent holes is distributed, wherein the frame means (60) includes a wall that the The side of the mold plate that is opposite the side facing the other molding surface surrounds or closes and defines a fluid distribution chamber. 16. The device according to claim 15, characterized in that that the fluid heating source is an air heating device contains, which via the fluid loading conveyors with each fluid distribution chamber connected is. , 17th Device according to claim 15, characterized in that that the fluid heating source includes a source of pressurized steam. 030064/0574 - 7 - DE 0206 13. Apparatus according to claim 16 or 17, characterized in that the fluid conveying devices aside from that a first conduit (72) connecting the fluid distribution chamber connects the first mold plate to the fluid heating source, a second line (80), which the fluid distribution TO treatment chamber of the second mold plate with the fluid heating source connects, a first valve device (74) in the first conduit,
15th a second valve device (82) in the second line, a vacuum pump (108),
20th a drain pipe (88) which is connected to the vacuum pump (108) via a valve (106), a third conduit (90) connecting the fluid distribution chamber connects the first mold plate to the drain pipe, a third valve means (92) in the third Management,
30th a fourth conduit (94) connecting the fluid distribution chamber the second mold plate connects to the drain pipe, and ^OJ a fourth valve device (96) in the fourth management 030064/0574 - 8 - DE 0206 contain. 19. Apparatus for forming a foamed, thermoplastic article from beads, which consist of a thermoplastic synthetic resin material · consist, at least partially, but incompletely, foamed by heat have been and contain a blowing agent, characterized by molding devices that a first (62) and a second (56) mold plate facing each other, a frame device (60) to which the mold plates are attached so that a mutually directed, leading to a closed position, and one facing away from each other, to an open position leading / relative movement of the mold plates is enabled, the first and second mold plates if they are in the closed position are closed by a device (60) so that a first mold cavity (5 2) is fixed between the mold plates, one side of the first mold height through the first mold plate and the opposite side of the first mold cavity through the second mold plate is formed a fluid heating source and. Fluid conveying devices (68, 70) which ^ou serve to first supply a heated fluid to the first mold cavity (5 2) from one side of the mold cavity, while the fluid conveying devices discharge fluid through the other side of the first mold cavity, which then serve the first form heightening from the opposite side of the first cavity to supply the heated fluid, while the fluid 030064/0574 - 9 - DE 02O6 ] Conveying devices discharge fluid through one side of the first mold cavity and which then serve to reduce the pressure prevailing in the first mold cavity below atmospheric pressure and to bring the first mold cavity back to atmospheric pressure, contain. ] 0 20. Device according to claim 19, characterized in that that the shaping devices have a third (58) and a fourth (64) mold plate for forming a foamed thermoplastic article, wherein the third and fourth mold plates face one another ] 5 and so attached to the frame device are that one towards each other, leading to a closed position, and one from each other directed away, leading to an open position, allows relative movement of the mold plates (58) and (64) the third and fourth mold plates when in the closed position through. means (60) are closed off so that a second mold cavity between the mold plates (58) and (64) (54) is set, with one side of the second mold cavity through the third mold plate and the opposite side of the second mold cavity is formed by the fourth mold plate, the third and fourth mold plates so connected to the fluid handling devices are that they come from the fluid heating source first from the one Side eier second mold cavity ago a heated fluid is supplied while fluid is discharged through the other side of the second mold cavity, that a heated fluid is then supplied to them from the other side of the second mold cavity, 030064/0574 3011513 - 1.0 - - DE 0206 while through one side of the second cavity Fluid is discharged »and that then the pressure" in "the The second mold cavity is reduced to below atmospheric pressure and the second mold cavity is reduced to atmospheric pressure is brought back. 21. The device according to claim 19 or 20 / characterized 'by ejectors,' the to serve when moving the mold plates from a closed one ejecting articles molded to the open position from a mold cavity. 22. The device according to claim 21, characterized in that that the ejector means comprise a plurality of rod members which are carried on the frame means are slidably arranged, one end of each rod member through an opening in a of the mold plates protrudes and wherein each rod element with the other mold plate, the one mold plate opposite, is coupled so that the rod elements in the relative movement of the mold plates in the Space between the mold plates are stretched. 23. Device according to one of claims 19 to 22, characterized in that one of the mold plates, which forms one side of a mold cavity, is an auxiliary heating device that surrounds its perimeter. that the auxiliary heating means includes ^ου 24. An apparatus according to claim 23, characterized in that a plurality of tube means, which serve individually to receive a heating fluid, wherein said tube devices side by side from the surface of a Mold plate that forms one side of a mold cavity / extend away. 030064/0674 -11- DE Q2O6 ] 25. Device according to one of claims 19 to 24, characterized by movable clamping devices for clamping or locking the mold plates serve, which face each other in the closed position. 26. Device according to one of claims 19 to 25, characterized in that a mold plate, which forms one side of a mold cavity, on the frame device is attached and contains side wall elements that enclose the mold plate which is the opposite side which forms a cavity. 27. Apparatus for forming a pair of foamed thermoplastic articles from beads; which consist of a thermoplastic synthetic resin material, at least in part, but incompletely, by heat have been foamed and contain a blowing agent, characterized by molding devices which 20th a first pair (62, 56) and a second pair (58, 64) of mold plates, the mold plates of each Couple facing each other, frame means (60) to which each pair of mold plates is attached so that one is on top of one another too directed, leading up to a closed position, and one directed away from each other, up to one relative movement of the form leading to the open position ° 0 plates in each pair is made possible, Means for closing the mold plate pairs, when they are in the closed position, to between the mold plates of each pair ^OJ a first (52) or. defining a second (54) mold cavity, one of the mold plates of each pair being one 030064/0574 - 12 - DE O2O6 Side and the other mold plate of each pair the opposite Side of the corresponding mold cavity, a fluid heating source and 5 Fluid handling devices (68, 70), the serve to first supply a heated fluid to each of the mold cavities from one side of this mold cavity, while the fluid conveying devices discharge fluid from the other side of this mold cavity, which then serve to heat each of the mold cavities from the opposite side of this mold cavity Supplying fluid while the fluid conveying means is through one side of this mold cavity discharge fluid through it, and which then serve to reduce the pressure in each mold cavity below atmospheric pressure reduce and bring the mold cavities back to atmospheric pressure contain, each pair of mold plates having a mold plate attached to the frame means while the other mold plates are attached to guide rods connected to motor means so that the other mold plates move simultaneously from their corresponding ones when the motor devices are operated open position to their corresponding closed position on the frame assembly move and that the other mold plates move from the closed position substantially simultaneously ^o move to their corresponding open position when the direction of rotation of the motor assemblies is reversed.