WO2011086120A1

WO2011086120A1 - Device and method for producing large-volume hollow bodies made of synthetic material, comprising a vacuum chamber

Info

Publication number: WO2011086120A1
Application number: PCT/EP2011/050387
Authority: WO
Inventors: Günter Richter
Original assignee: Richter, Bodo
Priority date: 2010-01-14
Filing date: 2011-01-13
Publication date: 2011-07-21
Also published as: TW201130636A

Abstract

The invention relates to a device (10) and method for producing large-volume hollow bodies made of synthetic material using a vacuum chamber (14), which completely surrounds a blowing mold (16) and a preform (28) and seals said blowing mold and preform in an air-tight manner. The preform (28) contains a synthetic material foam layer. The vacuum chamber (14) is arranged on the die head (30) or underneath said die head. Said design prevents a vacuum leak, improves the quality of the production method and decreases the expenditure for synthetic material.

Description

Apparatus and method for producing large-volume hollow body made of plastic, comprising a vacuum chamber

The invention relates to a device for producing large-volume hollow body made of plastic, with a multi-part blow mold, which receives in an open state issued from a nozzle head coextrusion a tubular, multilayer preform made of plastic, wherein at least one layer of the preform one Foam layer is.

Furthermore, the invention relates to a method for producing large-volume hollow body.

When using a blow molding process for producing large-volume hollow bodies, which comprise a plastic foam layer, it is advantageous if the blown air has a low pressure in the blowing process, so as not to obstruct or prevent the formation of the foam structure. If, after the ejection of the preform from the coextrusion device, a pressure is applied to the still thermoplastic melt, the foam structure collapses. Therefore, efforts are made to produce only a small pressure in the blow molding inside the hollow body. If a vacuum is generated between the inner wall of the multi-part blow mold and the hollow body, only a small blow pressure for forming the hollow body in the blow mold is required in the interior of the hollow body. However, in the case of large-volume hollow bodies, it is technically problematic to maintain the vacuum because it is difficult for a multi-part blow mold to remove the separating level of the blow mold along a relatively long parting line sufficient to seal.

From EP 1 112 164 Bl of the same applicant, a method and an apparatus for producing a large-volume container is known in which vacuum is used to form the hollow body. The blowing device is designed so that the hollow body around its entire circumference around a circumferential crushing edge and the squeezing closes airtight. Such a circumferential Abquetschbereich is disadvantageous because it creates a nonuniform wall thickness distribution, with the result that the weight of the hollow body increases and the desired effect of weight reduction by using a

Foam structure is at least partially canceled.

WO 2005/097462 A1 of the same Applicant discloses an apparatus and a method for producing tubular preforms having a multilayered structure. A preform made of thermoplastic material is ejected through an annular nozzle. The nozzle is opened and closed by means of a reciprocating sleeve.

It is an object of the invention to provide an apparatus and a method for producing large-volume hollow body made of thermoplastic, multilayer plastic with at least one foam layer, wherein the material used for producing a high-quality hollow body is reduced.

This object is achieved for a device by the combination of the features of claim 1. According to another aspect of the invention A manufacturing process is specified. Advantageous developments are specified in the dependent claims and in the description.

According to the invention, the device includes a vacuum chamber which surrounds the multi-part blow mold and the closed multi-part blow mold airtight seals against the outside atmosphere. The blow mold contains at least one connection opening which connects the interior of the blow mold with the interior of the vacuum chamber. If vacuum is applied to the vacuum chamber, the preform is pressed against the inner surface of the multi-part blow mold, with air being injected into the interior of the sealed preform via the hollow blow pin. The vacuum chamber is located at the nozzle head which ejects the tubular preform or below it. Accordingly, the vacuum chamber has an internal space which is only slightly larger than the volume of the blow mold. The vacuum to be applied to the vacuum chamber is therefore limited in volume, which gives economic advantages. With the help of the upper hose closing device and the lower hose closing device, the preform is clamped and provisionally hermetically sealed, without making high demands on airtightness. In this way, the preform is held securely in the open blow mold until it takes over the further formation of the hollow body at a later time. A long circumferential pinch edge is avoided, which reduces plastic material. The subsequent blowing process takes place in the interior of the closed vacuum chamber, the blow mold and the closed preform completely surrounds, so that vacuum leakage can be avoided. This will be the training of a uniform wall thickness, even the foam layer, favors, resulting in the production of a high quality hollow body.

According to an exemplary embodiment, the upper side of the vacuum chamber is completely closed in its closed state and has such a distance from the upper side of the blow mold that parts of the upper hose closing device projecting upwards are completely accommodated in a space above the blow mold and upper side of the vacuum chamber. The Butzenteile are after separating the expelled from the nozzle head preform on the upper hose-closing device, so that the vacuum chamber in the upper part can be completely closed and Butzenteile not hinder the closing process. In this way, a vacuum leak is avoided and a vacuum with high constancy can be formed.

In another embodiment, the top of the vacuum chamber includes an opening whose edge in the closed state of the vacuum chamber sealingly abuts the jacket of the nozzle head of the coextrusion device. The preform ejected at the nozzle head is separated by closing the nozzle gap. Its Butzenteile fall due to gravity on the upper hose-closing device and do not hinder the manufacturing process. In this embodiment, can be dispensed with an upper tube-separating device which separates the tubular preform. In this way, the device is structurally further simplified.

Another development, which relates to both the device and the manufacturing method, provides that the bottom of the vacuum chamber is arranged at such a distance from the bottom of the blow mold, in that a part of the block protruding below the lower hose closing device can be completely raised in a space between the blow mold and the bottom of the vacuum chamber. In this way it is prevented that when closing the vacuum chamber hanging parts of parts protrude into the separation region of the divided bottom of the vacuum chamber and thus can cause a vacuum leak.

Another embodiment of the device and the manufacturing method is characterized in that the multi-part blow mold and the multi-part vacuum chamber are rigidly connected together and are moved together in the open state and the closed state. In this way, the structure of the device and the manufacturing process is further simplified.

Embodiments of the invention are explained below with reference to the drawings. Show:

Figure 1 shows a schematic cross section through the blow mold and the

Vacuum chamber, in which a tubular Vorform- ling is received;

FIG. 2 shows the device according to FIG. 1 with closed vacuum chamber and closed blow mold;

FIG. 3 shows another embodiment of the vacuum chamber, which seals against a jacket surface of the nozzle head; and

Figure 4 shows the embodiment of Figure 3 with closed vacuum chamber and closed blow mold. Figure 1 shows a first embodiment of the apparatus for producing large-volume hollow body made of plastic. The device 10 is arranged below a coextrusion device 12 when viewed in the vertical direction and comprises a clam-shell vacuum chamber 14, within which a two-shell blow mold 16 is arranged. The vacuum chamber 14 and / or the blow mold 16 may also consist of more than two parts.

The vacuum chamber 14 and the blow mold 16 are shown in Figure 1 in the open state. Each half of the blow mold 16 is rigidly connected to the associated side wall of the vacuum chamber 14, for example screwed. In this way they are together transversely to the central axis 18 by means of a right machine clamping plate 20 and a left machine clamping plate 22 in the closed state and from there again in the open state movable. Above the upper side 24 of the vacuum chamber 14, a hose separator 26 is arranged, which is adapted to separate a preform 28 made of thermoplastic material.

Of the coextrusion device 12, only one nozzle head 30 is shown in the interior with the aid of a vertically reciprocable sleeve 32, a nozzle gap 34 is opened and closed, via which the tubular, multilayer preform 28 is ejected. This preform 28 contains at least one plastic foam layer.

At the upper side 24 of the blow mold 16, an upper hose closing device 36 is arranged, which is movable in the transverse direction and in the opened state allows the preform 28 to enter the blow mold 16 (see dashed preform 28). In the figure shown in FIG. In the closed state, the upper tube closing device 36 squeezes the tubular preform 28 so that the upper portion of the preform 28 is largely closed. A separated by the hose-separating device 26 Butzenteil 38 comes due to its gravity on the hose closing device 36 to rest. A gap 40 above the blow mold 16 and the top 24 of the vacuum chamber 14 is so large that the slug portions 38 are completely absorbed in it.

Below the blow mold 16, a lower hose closing device 42 is arranged, which presses in the closed state shown in Figure 1, the lower portion of the preform 28 against the circumference of a hollow mandrel 44 and the airtight seal the preform 28 in the lower portion. Blast air 46 can be blown in through the blow pin 44, so that the sealed preform 28 inflates like a balloon in a preform phase, as shown in FIG. The clamping of the preform 28 in the lower region results in a lower slug 48. A gap 50 between the bottom 52 of the vacuum chamber 14 and the underside of the blow mold 16 is dimensioned such that the slug 48 is completely received by the intermediate space 50.

The two-shell vacuum chamber 14 contains sealing means 54 in its respective peripheral edge. When the two shells of the vacuum chamber 14 move together, the latter is also completely closed at the top 24 in the center. In the lower region of the vacuum chamber 14, the bottom 52 includes an opening 56 and sealing means 54, by means of which a seal against the mandrel 44 in the closed state of the vacuum chamber 14 takes place. By means of the circulating sealing means 54, for example a rubber seal, the closed vacuum chamber 14 is airtight. sealed the outside atmosphere. A vacuum line 58 is inserted airtight in the bottom 52. Via this vacuum line 58, a vacuum can be applied to the interior of the vacuum chamber 14 by means of a vacuum device (not shown). The two-part blow mold 16 contains connection openings 60, so that the vacuum in the vacuum chamber 14 is also present in the interior of the blow mold 16. The upper tube closing device 36 and the lower tube closing device 42 can be moved by means of mechanical slides or hydraulic devices. The moving elements may also be hermetically sealed between the interior of the vacuum chamber 14 and the external atmosphere.

Figure 2 shows the embodiment of Figure 1 in the closed state of blow mold 16 and vacuum chamber 14. The same parts are designated the same. When closed, the vacuum chamber 14 is closed completely airtight over the sealing means 54. The upper gap 40 and the lower gap 50 take the slugs 38, 48 completely in such a way that the closing operation of the vacuum chamber 14 is not hindered. The blow mold 16 has on each shell a circumferential Abquetschkante 62, which cooperate in the closed state of the blow mold 16 and squeeze the preform 28. The lower hose closing device 42 has moved apart again, since the holding of the preform 28 and the squeezing of the Butzens 48 is no longer necessary.

The production process for a large-volume hollow body will now be explained with reference to FIGS. 1 and 2. The coextrusion device 12 projects over the opened nozzle gap 34 from a multilayer preform 28, wherein the sleeve 32 in Figure 1 in the axial direction is moved down to open the nozzle gap 34. At least one layer of the preform 28 is a plastic foam layer. The rigidly connected two-part vacuum chamber 14 and the two-part blow mold 16 have moved apart, so that the tubular preform 28 moves according to the dashed lines when ejecting down. The hose separating device 26, the upper hose closing device 36 and the lower hose closing device 42 are also open in the insertion phase of the preform 28. When a predetermined amount of plastic material is ejected, which corresponds to a predetermined length of the preform 28, the ejecting operation is stopped and the upper tube closing device 36 and the lower tube closing device 42 close. In the upper area of the preform 28, the still warm Thermoplastic plastic material squeezed airtight. In the lower region of the preform 28, the squeezing along the circumference of the mandrel 44 takes place. Thereafter, with the aid of the hose disconnecting device 26 of the preform 28 is separated and the Butzenteile 38 fall due to its own weight on the upper hose-closing device 36. About the mandrel 44 is the preform 28 is inflated balloon-like to give it a certain initial stability. Thereafter, the blow mold 16 and with it the vacuum chamber 14 is closed, wherein the pinch edges 62 squeeze the preform and the slug portions 38 and 48 are received in recesses 64 (Figure 2). When the two-part blow mold 16 moves together, the preform 28 welds along the squeezing edge 62, wherein the opening for the blow mandrel 44 remains free at the center in the lower region.

When the blow mold 16 moves together, the two parts of the vacuum chamber 14 are brought together and an airtight discharge takes place. seal along the parting plane of the vacuum chamber 14 by means of the circumferential seal 54. When moving together the vacuum chamber 14, the slugs 38, 48 hinder the seal, since these slugs 38, 48 are completely received in the intermediate spaces 40, 50. Accordingly, the length of the ejected preform 28 is sized so that the drooping plug material 48 is not too long to protrude into the space between the two-piece bottom 52 of the vacuum chamber 14.

After the vacuum chamber 14 is closed airtight and also the blow mold 16 is closed, vacuum is applied to the interior via the vacuum line 58 and at the same time the pressure of the blown air, which flows out via the blow mandrel 44, is reduced to a minimum. As a result of the connection openings 60 in the blow mold 16, the preform 28 is sucked by the vacuum to the inner surface of the blow mold 16 and pressed on the differential pressure between the vacuum in the blow mold 16 and the blowing pressure inside the preform 28. In this case, the preform 28 is cooled due to the close contact with the walls of the blow mold 16. At the same time, cooled cooling air is blown into the interior of the preform 28, which is now in the form of a hollow body, via the mandrel 44. Due to the low air pressure inside the preform 28, the foam structure in the plastic foam layer of the preform 28 can form completely. Due to the high tightness of the vacuum chamber 14 there is no vacuum loss, so that a high quality and a uniform formation of the wall of the hollow body is achieved. After the end of the cooling process, the hollow body is removed after opening the blow mold 16 and the vacuum chamber 14. FIG. 3 shows a variant of the device according to FIG. 1. Identical parts are again denoted the same. The vacuum chamber 14 has on its upper side an opening 70 with a frontal seal 54. In the closed state of the vacuum chamber 14, the seal 54 is located on a jacket 72 of the nozzle head 30 at. After closing the vacuum chamber 14 results in a hermetic seal against the outside atmosphere and in the interior of the vacuum chamber 14, a stable vacuum can be generated without leakage occurring at the parting plane. The gap 40 is in turn to be sized so that the Butzenteil 38 is completely absorbed. A hose-separating device (as in Figure 1) can be omitted here. By controlling with the help of the sleeve 32, the nozzle gap is opened and closed. When closing the nozzle gap 34, the multilayer preform is also separated.

The manufacturing process for plastic hollow body is analogous to the manufacturing process described above.

The hollow bodies may have a volume of 50 liters to 40 m ³ , preferably 200 liters to 10 m ³ . The plastic material used may preferably be polyethylene (PE), polypropylene (PP) and as a plastic foam layer PE or PP with blowing agent.

The blowing pressure in the interior of the preform for forming the foam structure of the plastic foam layer is in the range from 1 bar to 5 bar, preferably from 1 bar to 2 bar.

In the embodiments shown, the blow mold and the vacuum chamber are rigidly connected to each other and become one another moved simultaneously. Alternatively, blow mold and vacuum chamber can also be moved independently of each other.

LIST OF REFERENCE NUMBERS

10 Apparatus according to the invention

12 coextrusion device

14 vacuum chamber

16 blow mold

18 central axis

20 right machine clamping plate

22 left machine clamping plate

24 top of the vacuum chamber

26 Hose separator

28 preform

30 nozzle head

32 quill

34 nozzle gap

36 Upper hose closing device

38 block part

40 space

42 Lower hose closing device

44 Blowing pin

46 blowing air

48 slugs

50 space

52 bottom of the vacuum chamber

54 sealant

56 opening

58 vacuum line

60 V e r i n d u n g s o f in g

62 recess

70 opening

72 jacket of the nozzle head

Claims

claims

1. A device (10) for producing large-volume hollow plastic body, with a multi-part blow mold (16) in an open state of a nozzle head (30) of a coextrusion device (12) issued tubular, multilayer preform (28) made of thermoplastic Plastic, wherein at least one layer of the preform (28) is a foam layer, with an upper tube closure device (36) closing the preform (28) in the upper region, with a lower tube closure device (42) forming the preform (28) closes in the lower area against a hollow mandrel (44), with a on the nozzle head (30) or below arranged multipart vacuum chamber (14) surrounding the multi-part blow mold (16) and the closed multi-part blow mold (16) airtight against the outer atmosphere seals, and with a vacuum device, which applies a vacuum to the interior of the vacuum chamber (14), wherein the blow mold (16) includes at least one connection opening (60) connecting the interior of the blow mold (16) with the interior of the vacuum chamber (14).

2. Apparatus according to claim 1, characterized in that the upper side (24) of the vacuum chamber (14) is completely closed in its closed state and from the top of the blow mold (16) has a distance such that from the upper hose closing device ( 36) upwardly projecting Butzenteile (38) in a space (40) above the blow mold (16) and top (24) of the vacuum chamber (14) is completely removable.

3. Apparatus according to claim 1, characterized in that the upper side (24) of the vacuum chamber (14) includes an opening (70) whose edge in the closed state of the vacuum chamber (14) on the jacket (72) of the nozzle head (30) of the coextrusion - Device (12) sealingly.

4. Device according to one of the preceding claims, characterized in that the bottom (52) of the vacuum chamber (14) is arranged at such a distance from the bottom of the blow mold (16) that a below the lower hose closing device (42) protruding Butzenteil (48) in a gap (50) between the blow mold (16) and the bottom (52) of the vacuum chamber (14) is fully absorbable.

5. A method for producing large-volume hollow plastic body in which a coextrusion device (12) via a nozzle head (30) a tubular, multilayer preform (28) made of plastic, wherein at least one layer of the preform (28) is a foam layer, the Preform (28) is received by a multi-part blow mold (16) in its opened state, the preform (28) in its upper part of an upper

Hose closure device (36) is closed, the preform (28) in its lower portion of a lower

Hose closure device (42) is closed against a hollow mandrel (44), the preform (28) is partially inflated by supplying air through the mandrel (44) and the blow mold (16) is closed, the closed blow mold (16) by an am Düsenkopf (30) or below it arranged multipart vacuum chamber (14) is sealed airtight against the outside atmosphere, by means of a vacuum device, a vacuum to the interior of the vacuum chamber (14) is applied, the blow mold (16) via at least one connection opening (60) is connected to the interior of the vacuum chamber (14), wherein a below the lower hose closing device (42) projecting Butzenteil (48) in a space (50) between the blow mold (16) and bottom (52) of the vacuum chamber (14) completely absorbed becomes.

6. The method according to claim 5, characterized in that the tubular preform (28) above the upper hose closing device (36) by means of a hose-separating device (26). is separated and the protruding Butzenteile (38) in a space (40) above the blow mold (16) and top (24) of the vacuum chamber (14) is received.

7. The method according to claim 5, characterized in that the upper side (24) of the vacuum chamber (14) in its closed state on a jacket (72) of the nozzle head (30) of the coextrusion device (12) sealingly abuts, the tubular, multi-layered Preform (28) by closing the nozzle (34) in the nozzle head (30) is separated and the Butzenteil (38) in a space (40) above the blow mold (16) and top (24) of the vacuum chamber (14) is received.

8. The method according to any one of the preceding claims, characterized in that the pressure with which air via the mandrel (44) is blown into the preform (28), is reduced to form the foam structure to a predetermined minimum.