WO2012095285A1

WO2012095285A1 - Plastic container produced in a two-stage stretch blow-molding process and preform for the production thereof

Info

Publication number: WO2012095285A1
Application number: PCT/EP2012/000052
Authority: WO
Inventors: Robert Siegl
Original assignee: Alpla Werke Alwin Lehner Gmbh & Co. Kg
Priority date: 2011-01-11
Filing date: 2012-01-09
Publication date: 2012-07-19
Also published as: CH704325A2

Abstract

Disclosed are plastic containers, in particular plastic bottles, which are produced in a two-stage stretch blow-molding process and consist of a plastic mixture comprising 20% to 80% of an unpolar plastic and 80% to 20% of a polar plastic. The invention also relates to a preform for producing the plastic container and to an associated method.

Description

The invention relates to a plastic container produced in a two-stage stretch blow molding process according to the preamble of patent claim 1. Furthermore, the invention also relates to a preform which is suitable for the production of the plastic container. A large number of plastic bottles and plastic containers used today are manufactured in a stretch blow molding process. In this method, a so-called preform, which usually has an elongated tube-like shape, at its one longitudinal end a bottom and at the other longitudinal end has a neck portion with molded threaded portions or the like, inserted into a mold cavity of a blow mold and inflated by a medium blown with overpressure. In this case, the preform is additionally stretched in the axial direction with a retracting mandrel inserted through the neck opening. After the stretching / blowing process, the finished plastic bottle is removed from the blow mold.

The preform is produced before the stretch blow molding process in a separate injection molding or in a plastic fleece press process. In the so-called single-stage stretch blow molding process, the preform is inflated and stretched to a plastic container immediately after its production. In many cases, however, the plastic containers are produced in a two-stage process spatially and / or temporally separate from the stretch blow molding process and temporarily stored for later use. In the later stretch blow molding process, the preforms are reheated to produce plastic bottles. In this way, both processes, injection molding and stretch blow molding, can be operated separately and optimally. In the stretch blow molding process, the preform is brought to the required temperature by infrared radiation, for example, and stretched in the axial direction with a stretching rod during the forming process and formed radially in the mold by means of overpressure.

CONFIRMATION COPY The plastic containers known from the prior art and produced in the two-stage stretch blow molding process are usually made from the low-cost mass-produced polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS), polypropylene (PP), polyethylene (PE), polylactide (PLA ), Polyamide (PA), as well as copolymers of this material. The two-dimensional stretching gives these materials very special mechanical properties. Each of the materials mentioned has very specific barrier properties.

Polyethylene terephthalate-made plastic containers, in particular PET bottles, have, for example, oxygen barrier properties which are 20 to 40 times higher than the barrier properties of comparable plastic bottles made of oriented polyethylene (OPE) or oriented polypropylene (OPP).

Plastic bottles made of OPP, in turn, have a barrier property to water vapor which is 5 to 15 times higher than the barrier property of comparable PET bottles or oriented polyamide (OPA) bottles.

The barrier properties of the plastics used are related to the solubility of polar and non-polar molecules in polar and non-polar plastics, which is crucial for the permeation of the molecules. The same applies, the same dissolves in the same, or similar attacks similar. For example, polar PA is more resistant to non-polar fuels, especially gasoline and diesel, than non-polar PE. Polar polymers are therefore poor barrier materials for polar molecules, except their size and shape influence the migration or permeation. Nonpolar plastics in turn are poor barrier plastics for nonpolar molecules, unless their size and shape already influence their migration and permeation. Since polar and non-polar plastics are difficult to mix, multilayer structures with and without adhesion promoters are offered to achieve the desired barrier properties of the plastic bottles produced in the two-stage stretch blow molding process. An example of this is multilayer bottles made of a polypropylene layer and an EVOH layer with adhesion promoters between the two layers or mixed with one of the two plastics. For the production of multilayer plastic containers, in particular plastic bottles, in the two-stage stretch blow molding process, multilayer preforms must first be produced. For this purpose either complex and expensive multi-component injection molding facilities must be used or the preforms must be provided in a complex multi-step process with the desired layers.

Unstretched compositions of polar and nonpolar plastics are also known from the prior art, which enable the preparation of a homogeneous plastics material by the addition of a so-called compatibilizer consisting of copolymers or terpolymers or anhydrites. Above all, these mixtures have the task of improving the physical parameters, such as the impact strength, the notched impact strength or the cold break strength.

The object of the present invention is to provide a plastic container which can be produced in a two-stage stretch blow molding process and which has the desired barrier properties without requiring a multilayer structure which is complicated to produce.

The solution to this problem consists in a plastic container with the features listed in claim 1. Advantageous embodiments and / or developments of the invention are the subject of the dependent claims.

The invention proposes plastic containers, in particular plastic bottles, which are produced in a two-stage stretch blow molding process and are made of a synthetic material. consist of 20% to 80% of a non-polar plastic and 20% to 80% of a polar plastic.

Through the use of a plastic mixture with different compositions of non-polar and polar plastics, the barrier properties can be varied within wide ranges and adapted to the requirements of the filling material. For example, some coffee products require a good barrier against oxygen and water vapor that can not be met by either PE or PET alone at the usual low wall thicknesses. On the other hand, by using a plastic composition consisting of a mixture of PE and PET, at comparable wall thicknesses, an oxygen barrier better than that of the PE alone and, in addition, a water vapor barrier better than that of PET alone can be obtained.

In order to improve the strain hardening of the plastic mixture, it may be admixed with at least one passive compatibilizer which does not react with the plastics used, or at least one active compatibilizer which reacts, for example, with the hydroxyl group of the PET used, or a combination of passive and active compatibilizers. For example, 0.5% to 10% Fussabond or 0.5% to 10% Evaloy are used as compatibilizers.

A further embodiment variant of the invention proposes that the plastic containers, in particular plastic bottles, produced in the two-stage stretch blow molding process consist of a plastic mixture which comprises about 75% PET and about 25% HDPE. Plastic bottles made of this plastic mixture have more than twice as good a water vapor barrier as pure PET bottles, with their barrier properties to oxygen being reduced by only about 10%.

Depending on the nature of the combination of non-polar and polar plastics, it is also possible to produce opaque plastic mixtures that do not require any metallic pigments. This allows the production of opaque plastic containers that can be incinerated without residue and environmentally friendly. In a further variant of the invention, the plastic containers produced in the two-stage stretch blow molding process, in particular plastic bottles, consist of a plastic mixture of pure vegetable-based plastics and plastics based on petroleum. With such plastic mixtures, the life cycle assessment can be significantly improved. In the case of plastics, which are based on plant-based products, the very poor barrier properties, for example to oxygen or water vapor, are improved by the addition of petroleum-based plastics.

A further variant of the invention provides that the plastic mixture used consists entirely of non-polar and polar plastics which are based on plants. The selection of plastics takes place according to the barrier criteria which the plastic containers produced in the two-stage stretch blow molding process should have with respect to the contents.

The plastic mixture of nonpolar and polar plastics and optionally of compatibilizers is chosen such that the plastic containers produced in the two-stage stretch blow molding process have a global draw ratio of 4 to 18, the longitudinal draw being 1.5 to 4.5 and the diameter drawing being 2 to 6. The global draw ratio is defined as the product of the longitudinal draw and the diameter draw.

The preforms used for the production of the plastic containers in the two-stage stretch blow molding process consist of the above-described plastic mixtures comprising 20% to 80% of a non-polar plastic and 20% to 80% of a polar plastic. They are produced in a plastic injection molding or in a flow molding process. However, they can also be produced in an extrusion blown process.

Claims

claims:

1. Plastic container, in particular plastic bottle, which is produced in a two-stage stretch blow molding process, characterized in that the plastic container consists of a plastic mixture comprising 20% to 80% of a non-polar plastic and 80% to 20% of a polar plastic.

2. Plastic container according to claim 1, characterized in that the plastic mixture at least one passive compatibilizer which does not react with the plastics used, or at least one active compatibilizer, which reacts for example with the hydroxyl group of the PET used, or a combination of passive and active Compatibilizers has.

3. Plastic container according to claim 2, characterized in that the plastic mixture has 0.5% to 10% of compatibilizer (s).

4. Plastic container according to claim 2 or 3, characterized in that is used as Kompatibilizer Fussabond or Evaloy.

5. Plastic container according to one of the preceding claims, characterized in that the plastic container produced in the two-stage stretch blow molding process have a global stretching of 4 to 18, wherein the Längsverstreckung 1.5 to 4.5 and the Durchmesserverstreckung 2 to 6.

6. Plastic container according to one of the preceding claims, characterized in that it has a white color or an opaque appearance, but it is free of coloring pigments, in particular metal oxide pigments or zinc sulfide pigments in micro or nano-structure.

7. Plastic container according to one of the preceding claims, characterized in that at least one of the plastics of the plastic mixture is a plastic which is at least 80% of vegetable origin.

8. preform for producing a plastic container in a two-stage stretch blow molding process, characterized in that it consists of a plastic mixture comprising 20% to 80% of a non-polar plastic and 80% to 20% of a polar plastic.

9. preform according to claim 8, characterized in that it in one

Plastic injection process, produced in a flow molding process or by extrusion bubbles.

10. A method for producing a plastic container according to one of the claims 1 to 7 from a preform according to one of the claims 8 to 9.