DE2807949A1 - Transparent polyester returnable bottle for carbonated drinks - produced by multistep, biaxially drawing and blow-moulding a sectionally heated parison - Google Patents

Abstract

Mfr. of plastics bottles, esp. for beverages comprises biaxially blow-moulding a parison at elevated temp., in several stages. Both the walls are oriented and moulded from an initial thickness of >=4mm in a draw ratio of longitudinal stretch to tranverse stretch of 1:1.15-1:3, and also the unitary bottom in functionally increasing stretch ratios up to 1:6, at temps. between 80-110 degrees C. The result is a transparent repeatedly usable bottle which resists, when empty, buckling by exterior stresses of up to 500 N at 0-30 degrees C. Capacity is >=2 litres. It is break-resistant when dropped from 4m height whilst subjected to inner pressure up to 10 bar. IT is made of polyethylene terephthalate-based polyester, intrinsic viscosity 0.85-1.5, having high creep resistance and low crystallinity. The bottles are physiologically acceptable, easy to clean, highly transparent, mechanically strong suitable for repeated use.

Description

Process for making bottles from plastic

The invention relates to a method for producing bottles from Plastic, especially for drinks, made from a macromolecular polymer Blowing a preform made by pressing, casting and / or injection molding at an elevated temperature, the preform being biaxially deformed. Also concerns the invention a returnable bottle produced according to the method in a method of this type, according to DE-AS 1 604 660, the macromolecular polymer is polyvinyl chloride used and this material by blowing in the temperature range of 90 to 14000 at a strain rate of over 100 i / s biaxially oriented. Because such bottles As a substitute for glass bottles, the aim is to use plastic bottles with transparent, especially crystal clear, Willden. That is so far only possible with extremely low thicknesses of less than about 0.5 mm.

Such thin-walled bottles can - in contrast to glass bottles - only once, d. H. as disposable bottles. At best, can feed this plastic hollow body to a so-called recycling process, in which the Bottle material is crushed and processed again to form a hollow body. This Procedure is energy and costly as well as physiological The harmlessness of bottles made from it is problematic on the other hand Processing or reshaping of thick-walled preforms (injection molded parts) made of PVC so far not at all, since the thermoelastic stretching required for this material Heat profile cannot be applied. If the stabilization is insufficient, Finally, monomeric vinyl chloride from the polyvinyl chloride as a decomposition product regress, which is why this plastic is not physiologically harmless.

The invention is based on the object of a method for the former 1 of plastic bottles with glass-like transparent, in particular to create crystal clear walls that result from a physiologically unproblematic Consist of plastic and should nevertheless be able to be designed so as to be stable - in other words, in particular should have such a large wall thickness - that they are suitable as non-returnable bottles. The bottle according to the invention should therefore meet all previous stability requirements - i.a. Concerning the breaking height and the bursting strength - suffice and additionally at least 15 to 20 final physiologically and microbiologically perfectly reconditioning, that means being cleanable and refillable. The inventive solution to this The task is described in the characterizing part of claim 1.

According to the invention can be made of polyethylene terephthalate (PE? P) with iv values (Civ = intrinsic viscosity) from 0.85 to 1.5, preferably> 1, im thermoelastic range at temperatures between 80 to 110 0c stretch-deformed Manufacture bottles with crystal clear walls that have sufficiently stable and strong walls, Have bottoms, etc. for use as a returnable bottle. The bottles can have filling volumes from 0.5 1 upwards and preferably the filling volume should be between 1 and 2 1 lie.

The bottles according to the invention should chen compared to conventional Disposable plastic bottles disproportionately higher wall thicknesses up to about 5 mm made of saturated polyesters based on PETP. Important with the The method according to the invention is therefore glass-like transparency despite the great wall thickness to achieve the wall material so that the plastic bottles outwardly Look similar to bottles made of glass. Previously used polymers for the production of plastic hollow bodies tend to form crystals and with it and so on to become opaque if the wall is thicker than about 0.5 mm can be produced. According to the invention, it has unexpectedly also been found that for the larger ones required for returnable bottles - especially in terms of size 10 times the wall thickness, the transparency and drop resistance of the wall material are retained if the bottle is made of PETP with an IV value>. 1 manufactures This material is relatively highly viscous and is less prone to crystallinity so far known containers made of thermoplastics such as polyvinyl chloride or polyacrylonitrile (cf. DE-AS 1 604 660 and DE-OS 2 406 335), which with minimal use of material due to high Molecular stretching are produced, are pressure-stable, drop-break resistant and sufficiently gas-tight, but because of the small wall thickness, they are only for the suitable for single use Even when they are partially emptied, these bottles are especially bottles with a filling volume of more than 0.7 l, because of the denting unwieldy These disadvantages result from the fact that too thick-walled finished parts have hitherto been used could not be stretched, it was also the firm opinion that thick-walled Plastic containers have significantly reduced transparency and drop resistance.

According to the invention it is possible to essentially overcome these difficulties to be overcome by the fact that the starting material for the manufacture of plastic existing bottles of polyethylene terephthalate (PETP) with a relatively high IV value selects between 0.85 and 1.5, which is preferably at least 1. A such highly viscous material is less likely to crystallize when in production of the preform with appropriate temperature control worked out of it The bottle produced is therefore both transparent and resistant to dropping. It can therefore according to the invention bottles made of PETP with wall thicknesses of up to to about 5 mm or - if necessary - also more, the transparent one can be produced Have walls and are at least as drop-resistant as previous thin-walled containers of this type. It should be added that the bottle made of plastic, in spite of the high wall thickness only has a fraction of the tare weight as a comparable one Glass bottle.

The method according to the invention is suitable, for example, for economic Manufacture of internal and external pressure-resistant as well as gas-tight hollow bodies of 0.5 1 up to about 3 l capacity with wall thicknesses of preferably 0.5 to 1.0 or even up to 5 mm or more.

Starting from a preform body with wall thicknesses between the order of magnitude 4 and 8 mm are all critical, taking advantage of its molecular stretchability Zones stretched. The preform, preferably by means of radiant heating, is axially divided into zones, to temperatures above the respective glass melting point warmed up.

In the meantime, the thermoelastic stretching takes place in a combined mechanical / pneumatic manner in two axes with selectable time phase shift, whereby in Hegel a mechanical A lead time is provided, which is within 1/5 to 1/50 partial cycle time. Further the bottom of the bottle can be achieved by combining material accumulation with partial Reverse stretching in the bottom part of the container with sufficient strength are produced (see, for example, DE-OS 2 406 335).

According to the invention, therefore, relatively thick-walled, pressure-stable Plastic hollow bodies with unexpectedly high mechanical strength produce the are superior to the printing behavior and the transparency of glass bottles and the latter also in the drop resistance and thus in the transport resistance surpass it many times over but weigh only 1/10 as much as corresponding glass bottles0 With regard to gas permeability, in particular against Carbon dioxide9, oxygen and water vapor, as well as special flavors, are the new ones Bottles equivalent to glass bottles.

In general, plastic bottles have a drop resistance Aimed at more than 295 m at 5 to 10 bar internal pressure, even those with large volumes According to the invention, bottles can be made with glass-like transparency despite their high wall thickness In combination with physiologically harmless light protection paints Transparency coloring is also possible. The outer surfaces of the new bottles can also be used Be structured like a flat relief0 The plastic hollow body according to the invention differs from known, extremely light containers with, for example, about 60 g weight per 195 1 filling volume and correspondingly small wall thicknesses of less than 0.4 mm by an unusually high weight of, for example, about 150 g weight per 1.5 1 filling volume and correspondingly high wall thicknesses, with the help of the invention Process, despite the high wall thickness, is an optimal stretching of all pressure-stressed Layering of the container by 1: 495 possible, this is the one for empty returnable bottles Required buckling and denting compressive strength against external forces achieved.

Partly based on the schematic drawing of an exemplary embodiment further details of a bottle produced according to the invention are explained, The reusable bottle denoted as a whole by 1 according to the exemplary embodiment consists from a pressure-resistant floor 2, a cylindrical outer surface 3 with or without indentation 109 a conical shoulder 4 and a neck part 5, on which a thread for screwing on a gas-tight screw cap 6 is provided is. The bottle 1 is shown partly in elevation and partly in longitudinal section.

The lateral surface 3 and the conical shoulder 4 can have surface structures 7 to 9.

It is a stretch-formed in the thermoelastic range, thick-walled PETP bottle of higher molecular weight corresponding to IV values # 1. The iv value is selected so that the PETP material has a reduced crystallinity and has high creep resistance. Preferably the bottle is made of im Commercially available saturated polyesters based on polyethylene terephthalate (PETP) with so-called "lower crystallinity". However, this plastic itself is not the subject of the invention.

The volume range of bottles that can be produced according to the invention is of the order of magnitude approximately between 0.5 and 2.5 liters, preferably in the range from 1 to 2 liters. The mouth diameter can for example be chosen between 28 and 38 mm.

The new bottle is also open depending on the nominal volume 0.5 to 5 mm increasing, possibly proportionally excessive wall thicknesses transparent. In the case of a bottle produced according to the invention with a wall thickness / mouth diameter ratio from 0.02 to 0.03 and a tare / net ratio of 0.085 to 0.09 results an internal pressure resistance of up to about 10 bar without any loss of other functional features, whereby the bottle against partially acting external forces up to about 500 N and more also when unfilled, it is dent-resistant and with a fill content of, for example, 2 l in the temperature range between 0 and + 300C, simultaneous internal pressure load of up to 10 bar, a drop resistance of 4 m.

The bottle is also carbonized with repeated filling Drinks so stable in volume and shape that they meet the requirements of the proportions according to the calibration regulations applicable in the Federal Republic of Germany, The The bottle can also be reclosed in a gas-tight manner, for example with roll-on closures made of aluminum or screw caps made of plastic0 The new bottle can come with Purified with the help of ecologically harmless chemicals at temperatures up to 5500 are0 Common raw materials are therefore suitable as cleaning agents, e.g. sodium or # aliumhydroxide9 sodium and / or potassium ortho- and / or polymer phosphates as well as complexing agents9 # silicates and surface-active substances9 such as ethoxylated and / or propoxylated addition products, optionally in aqueous solution9 hypochlorite abapaltende organic substances In one embodiment of the invention Method is made from a transparent9 thick-walled 9 biaxially stretched bottle PETP based on a transparent preform, for example a pipe section or a closed container with a wall thickness of more than 4 mm9 preferably 5 to 6 mm, manufactured in several stages, preferably an injection-molded9 becomes more transparent Parcels used as the starting material for forming the bottles according to the invention. The parison should have a stretching range with a ratio of longitudinal stretchability to cross stretchability of 1: 1.15 to 1 e 3. While making the bottle In the process, all wall thickness zones are created from the parison (or the pipe section) of the transparent parison or pipe section in the thermoelastic area of the PETP stretch-deformed between 80 and 110 ° C The thermoelastic stretching deformation of a for example, an internal pressure of 20 bar resisting i with the bottle According to the invention, the standing floor is functionally increasing Stretching ratios from 1.0 to about 6.1 also between 80 and 110 ° a. The stretching of the ground does not take place linearly but in the aforementioned proportions, so that the finished Bottom # - as desired - in concentric zones from the outer edge or ring to the center towards, preferably steadily, increases in thickness.

Since, according to the invention, it is a non-returnable bottle, the at least Can be reused 15 times5 energy-intensive intermediate recycling stages are eliminated, where old bottles are used as raw material for the production of new bottles. It is however, it is easily possible to discard bottles, for example after 15 to 20 times Use as a raw material for the manufacture of new, usually other plastic items, z. B. transport boxes, DUbelmassen, etc. to use. Under certain conditions The last-mentioned raw material is also used as an additive for new, according to the invention Process producing bottles can be used.

Claims (4)

Method for producing bottles from plastic Claims 1. Process for the production of bottles made of plastic, especially for beverages, from a macromolecular polymer by blowing one by pressing, casting and / or injection molded preform at elevated temperature, wherein the Preform is biaxially deformed, characterized in that a transparent, Unfilled, it is indentable up to at least 500 N against partially acting external forces and up to a volume of at least 2 liters in the temperature range of 0 up to 3000 with simultaneous internal pressure load of approx. 10 bar up to 4 m height resistant to falling as well as with repeated filling with carbonated beverages calibratable volumetric and dimensionally stable, below 5500 cleanable and gastight reclosable Reusable bottle (1) with a volume of 0.5 1 and up and wall thicknesses up to approx 5 mm made of saturated polyesters based on polyethylene terephthalate (PETP) with corresponding iv values of 0.85 to 1.5 high viscosity and creep resistance and accordingly low crystallinity is produced, with multi-stage both all wall thickness zones from a transparent preform with an original sland thickness of at least 4 mm and a stretching ratio from longitudinal to transverse stretching from 1: 1.15 to 1: 3 as well as functionally increasing The one-piece standing base (2) in the thermoelastic one-piece stretching ratio up to about 1: 6 Range at temperatures between 80 and 1100 C are stretch-deformed. 2. The method according to claim 1, characterized in that polyethylene terephthalate with an iv value of> 1 is used. 3. The method according to claim 1 or 2, characterized in that the Preform during stretching, in particular with the aid of radiant heating, axially Subdivided into zones, heated to temperatures above the respective glass point will. 4. Reusable bottle manufactured according to the method according to one or more of claims 1 to 3, characterized in that they have a filling volume of on the order of 1 to 2 1 crystal clear and sufficient for multiple use has stable and strong walls (3, 4).