DE2239265A1 - METHOD OF MANUFACTURING MULTI-LAYERED OBJECTS - Google Patents

Description

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65-19.232P (19.-233H) 9 8th 1972

Ilikon Corporation, NATICK (Massachusetts), V.St.A.

Method of making multilayer

Objects

The invention relates to a method of molding multilayer thermoplastic articles Materials. ■

Currently there is the use of thermoplastic materials for forming containers for food, especially beverages, very limited. A main reason for this is that the thermoplastic materials that allow a reliable seal between the food and the atmosphere can be relatively expensive, to the extent that their economic Use in known container manufacturing processes a thickness sufficient for container strength

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is necessary, does not allow. Therefore, there is currently an economic incentive to report a procedure

"Stable, _, ..,. . _J "for forming / multi-layer containers where a sufficient seal can be achieved.

The invention shows an injection-blow molding process for Forming of multi-layer, structurally stable containers. The procedure consists of four or more stages. In the In the first stage, a thermoplastic material is injected around a mandrel and the molding then goes to the second stage Transferred, in which a second thermoplastic material is sprayed onto the first thermoplastic, ^ oll der If the object has more than two layers, the two-layer molding becomes a third! Injection mold transferred and injected a third thermoplastic material onto the two-layer molding. The spray stages can be as often be repeated as necessary to achieve the desired number of layers. The last injection mold is then opened and the resulting multi-layer molding transported to a blowing stage on the mandrel, in which it is expanded under fluid pressure. In the last stage the multilayer article is removed from the mandrel under fluid pressure and then to form the finished article chilled. During the transfer between the first and the following injection stages and the blow molding stage, the thermoplastic materials heated, with the temperature is kept in an area in which the plastic materials are workable.

The thermoplastic materials must be in the same Temperature ranges can be processed, so that the temperature to which the multi-layer parison (molding) is heated

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is enough to put all plastic materials in one keep editable state, d. h, which is a plastic (non-elastic) deformation during the transfer between the injection stages and the last injection molding and the blowing stages. However, this temperature should not be so high that the thermoplastic materials are brought to a pour point where they at the Overpass flow away.

The invention is explained in more detail below with reference to the drawing. Show it:

Fig. 1 is a plan view of an apparatus for injection molding two thermoplastic materials with subsequent blow molding

Fig. 2 is a vertical section through a mandrel closed shape along the line 2-2 in Fig »

As is apparent from Fig. 1, the molding apparatus includes a turntable 1 with a number of for forming a Molding> and a multi-layer molding 4 executed Thorns 2 on each of its outer sides. Obwoxil in this version a plurality of mandrels is provided, only a single mandrel can of course be used.

In the first stage of the process, the thermoplastic Material in a heater 6 to its working temperature heated and injected into the heater nozzles 7 and the spray nozzles 8. The plastic penetrates into the gap between the Forms 9 and 2 in the thorns and forms the molding ^. each of the molds 9 is made up of two mating mold parts

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formed, each of which with lines IO and 11 to A fluid flows through and is provided to maintain the desired molding temperature. After Forming the molding 5, the moldings are except brought mutual contact. The turntable 1 is then at an appropriate angle, which in the execution according to Fig. 1 is 90 °, rotated so that the molding 3 is connected to the injection nozzles 15. The injection nozzles are heater nozzles 16 and a heater 17 and lines and 19 assigned in the manner described for the first injection stage.

In the second injection stage, a second plastic material is injected over the molding 3. The multi-layer molding 4 consists of two thermoplastic materials which do not need to be glued together, but which have the same working temperatures and should not react chemically with one another. After the multilayer molding has been formed the turntable 1 is welter rotated by an appropriate angle, so that the multi-layer molding 4 to the corresponding Blow molding 20 arrives. As soon as the moldings 4 have reached the blow molding stage, a fluid is under Pressure is pressed in through the center of the mandrel via the line 22 in order to expand the molding 4 to the desired final shape 23. After the expansion is completed, the blow molds 20 are separated into two parts in the same manner as the injection molds and thereby exposing the formed multilayer product to the atmosphere.

The turntable 1 then moves again through a corresponding angle to the discharge station 25. At this discharge station 25 the finished articles are solidified so that

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they are not expanded further under fluid pressure. A fluid is then passed through the central part via the line 22 the mandrel is introduced into the article 26 in order to blow it from the mandrel into a collecting station (not shown). The turntable 1 is then rotated further so that the mandrels 2 are again at the injection nozzles 8 in order to repeat the cycle in the manner described. Although at 1, the article is blown from the mandrel 2, it is obvious that other Äus.tragsmethods can be used.

According to Fig. 2, the molds used in the injection stages have the same internal design, whereas the shape of the blow molding stage has the shape of the desired finished article. The shape of each step includes a top mold part 30 and a bottom mold part 31 attached to plates 32 and 33, respectively. In either the blowing or injection stages, the mandrel 2 is brought into position when the mold parts 30 and 3I are separated. After the mandrel has been aligned, the mold parts 14 and 31 are brought together by pressure acting on the plates 32 and 35, so that the mandrel is enclosed by the mold. If the mold parts 30 and 31 are closed, the lines 10, 11 and 35 are also aligned with a hot or cooling fluid generator (not shown), so that fluid flows through these lines and the molding either during blow molding or during injection molding of the finished article either heated or cooled. In the blow molding stage, once the article has been expanded, it is cooled sufficiently so that it remains intact when it is transferred to the discharge station. -'- ■■ . .

If an article with more than two layers is required, then

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the number of spray stages increases. A five-sided turntable is used to form a three-layer article used which order between each procedural stage Can be rotated 72 °. If a four-layer article is required, then the turntable has seohs sides and is rotated by 60 ° between each process step. For the production Articles with more than four layers are handled in a correspondingly similar manner.

The method of the invention is suitable for various thermoplastic compositions as long as the thermoplastic materials used in a multilayer article have similar processing temperatures and mold shrinkage exhibit. In particular, useful materials include polyethylene with polyvinylidene chloride (Saran), acrylic acids with acrylonitrile-ethyl acrylate copolymer (ζ. B. Barex 210) Polystyrene with Barex 210 or a Cellulose, like ζ. B. ethyl cellulose, cellulose acetate, cellulose acetate butylrate, cellulose propionate or the like with Barex 210.

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Claims (7)

■ - 7 - claims Iy device for molding multilayer plastic articles from at least two thermoplastic materials, characterized by injecting a first hot-plasticized thermoplastic material around a mandrel (2) in an injection mold to form a first molding (3), transferring molding 0) to at least one other Injection mold, injection of a hot-plasticized thermoplastic material onto the molding in each further injection stage to form a multi-layer molding (4), transfer this multi-layer molding on the mandrel to a blow mold (20), blow molding the multi-layer molding (4) in the blow mold for the finished article and ejection of the article from the mandrel (2), the thermoplastic materials having similar processing temperatures and form shrinkage. 2. The method according to claim 1, characterized in that the multi-layer molding made of two thermoplastic materials is formed. J>. Method according to Claim 2, characterized in that the first plastic is polyethylene and the second plastic is polyvinylidene chloride. 4. The method according to claim 2, characterized in that the first plastic is an acrylic acid and the second plastic is an acrylonitrile-ethyl acrylate copolymer. 309807/126 4 5. The method according to claim 2, characterized in that the first plastic is a polystyrene and the second Plastic is an acrylonitrile-ethyl acrylate copolymer. 6. The method according to claim 2, characterized in that the first plastic is a cellulose and the second thermoplastic Material an acrylonitrile-ethyl acrylate copolymer is. 7. Device for performing the method according to one of the preceding claims, characterized in that at least one mandrel (2) is arranged on at least one side of a turntable (1) and at certain angles offset against each other at least two injection stations, a blow molding station and a discharge station around the table (1) are arranged and that ^ ede spray station has divisible molds (9) with spray nozzles (8), which in this Station swiveled mandrel (2) enclose that the blowing station has a device for introducing a pressure medium has in the interior of the formed multi-layer molding (4), that each mold contains channels for the passage of a hot or coolant and that the discharge station with Pressure medium connections for blowing out the finished molding from the mandrel (2) is provided. 3 Π 9 R 0 7/1? β /