DE102005018245A1 - Multilayer preform, multilayer hollow body and process for their preparation - Google Patents

Abstract

The present invention relates to a preform or preform for blow molding, wherein the wall of the preform at least partially consists of at least three layers, namely two cover layers and a barrier layer arranged between the cover layers. DOLLAR A To provide a preform available, with the aid of a hollow body with corresponding barrier properties can be produced, wherein the preform is easy to manufacture and compared to known preforms improved properties, the invention proposes that the outer layers and the barrier layer essentially from the the same thermoplastic material are formed, wherein the thermoplastic material of the barrier layer is mixed with a barrier material.

Description

The The present invention relates to a multilayer preform or preform for the blow molding. Furthermore, the present invention relates to a multilayer hollow body, e.g. a bottle and a method for the production of preform or hollow body.

Of the Term blow molding refers to various manufacturing processes, at first a thermoplastically deformable preform is produced, which in a further manufacturing step in a hollow tool in general is inflated by means of compressed air to a hollow body.

So For example, extrusion blow molding is known in which a tubular preform is extruded and then from a blow mold squeezed and trapped and finally with compressed air from 3 to 10 bar is inflated. By contact with the general cooled, forming tool solidifies the blower.

One Another method is injection blow molding. Here is by injection molding Preform produced, which inflated in the further processing step and after cooling is ejected.

Farther Stretch blow molding is known in which a by extrusion or by injection molding produced preform before the actual blowing mechanically is stretched. This creates a stretching that leads to a Solidification of the molding wall leads. this leads to generally an increase of tensile strength and impact resistance as well as transparency and shine.

For example become standard PET bottles produced by first using a PET preform injection molding is made, which then before filling with the male Good, e.g. a liquid, inflated by stretch blow molding in the actual bottle shape becomes.

The The present invention is within the scope of manufacturing optimization of PET bottles, but can also be used in preforms for others Form or Blasteile be used.

The finished hollow body, e.g. PET bottles, however, generally show some permeation or permeability across from individual substances or opposite electromagnetic radiation, e.g. visible light or UV light. For example, oxygen molecules on the bottle surface adsorb absorbed by this, diffuse through the bottle wall and can be attached to the Inside the bottle of desorption subject. Especially in food technology, however, there is a requirement that quality of the bottled Product as possible long unchanged to obtain. Especially for carbonated beverages this means that as possible no oxygen should penetrate through the bottle or its closure and no carbon dioxide should escape from the bottle. packagings with improved "barrier properties" lead beyond that to an extension the best before date of the bottled product, which is highly desirable for bottlers is.

It is therefore an important goal in packaging technology and in particular in the development of PET bottles, the barrier properties to improve in a simple way with little cost.

It is already common to add barrier materials to the thermoplastic material for the Barrier effect. The barrier material is distributed even within of the preform and the individual barrier particles or barrier molecules for example Oxygen is a barrier. The most effective barrier possible to achieve that Proportion of the barrier material are relatively high, resulting in a Preform significantly more expensive and secondly mostly negative Effects on the other physical-mechanical properties Has. So leads the use of a PET Compund, i. PET mixed with barrier materials, for the preform, often to cause the preform and thus also the hollow body to be produced therefrom no longer transparent is, but not always desired is.

Farther it is already known, in an additional process step while or after blow molding on the inside or outside of the blown out hollow body to apply a corresponding barrier layer. Some barrier materials have to be included activated after the layer application under vacuum (plasma-processed) become. With this method, however, additional costs associated with another manufacturing step is needed. In addition, at least not all barrier materials used in food technology as they may be directly with the to be filled Product in contact can come.

Furthermore, preforms have already been proposed in which, at least in sections, a gas barrier layer by means of co-injection is introduced. Such a preform is described for example in US Pat EP 1 498 355 , However, such preforms have the disadvantage that they sometimes delaminate, that is, that the individual layers separate from one another, which leads to an increased reject rate. In addition, these preforms are recyclable only at great expense.

outgoing from the described prior art, it is an object of the invention a preform available to provide, with the help of a hollow body with appropriate barrier properties can be prepared, the preform easy to manufacture is and opposite known preforms has improved properties.

According to the invention this Task solved by a preform for blow molding, at the wall of the preform at least partially from at least There are three layers, two Cover layers and one arranged between the cover layers Barrier layer, wherein the cover layers and the barrier layer essentially of the same thermoplastic material are formed, wherein the thermoplastic material of the plastic Barrier layer is mixed with a barrier material.

Of the For example, preform can be produced by co-injection or sandwich injection molding become. The barrier layer is thereby of the two outer layers essentially included. It is not necessary that the barrier layer in whole preform is present. For example, the section of the preform, the later the thread of the blow molding, e.g. the bottle, forms, without barrier layer be educated. Due to the fact that according to the invention both Cover layer as well as barrier layer essentially the same thermoplastic plastic material is formed, is an improved compatibility achieved between the individual layers, so that the probability of a Delamination is reduced. In addition, the preform or the the preform blow-molded container be recycled more easily after its use. Due to the use the same plastic material for both the cover layers as well as the barrier layer will also be a more homogeneous behavior achieved the preform in the stretch blown. Furthermore, can The preform can be made easier because both the topcoat as well as the barrier layer processed at the same temperature can be. If the preform is produced by injection molding, then both can Materials in the same hot runner manifold are processed. Furthermore, the blow molding properties are also very good, because the heat transport is largely comparable in cover and barrier layer.

Around To realize the barrier layer becomes merely a barrier material introduced into the thermoplastic material of the barrier layer.

It has been surprising exposed that it for the Barrier effect primarily less on the amount of barrier material rather, it depends on its concentration. By the realization a barrier layer and the associated limitation of the Barrier material on the inner layer can there concentration be comparatively high, although the total amount of barrier material in the preform is very low.

When Plastic material is in principle any thermoplastic material usable. Especially considering PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), PVC (polyvinyl chloride), PS (polystyrene), PSB (styrene-butadiene rubber), PC (polycarbonate), COC (cyclopolyolefin copolymers) and PAN (polyacrylonitrile), the present invention being developed especially for PET preforms has been.

The Barrier layer is characterized by the fact that they are for certain substances or energy is less permeable than the topcoat in any form. Barrier material can be any material that when added to the barrier layer ensures that their permeability for certain Fabrics or energy in any form compared to the topcoat is reduced.

So is it possible, for example, that the barrier layer a barrier for Represents water vapor. It then provides protection against dehydration and weight loss, but also for protection against moisture absorption for dry products.

Farther It is beneficial if the barrier layer provides a barrier to oxygen represents what can provide protection against oxidation of the product.

Of course it is it also possible a barrier for to provide different substances. This can either different Barrier materials are introduced into the barrier layer or - which is preferred is it can several barrier layers, all arranged between the cover layers are to be provided.

Furthermore, it is advantageous if the barrier layer is a barrier to carbon dioxide. This may be particularly advantageous if the contents are stored in a protective gas atmosphere or CO ₂ -containing products. Furthermore, it may be advantageous if the barrier layer is a barrier represents electromagnetic waves of at least a certain frequency range. For example, the barrier layer could be a barrier to visible light and / or UV light. As a result, the durability of the medium can be improved if necessary.

The barrier material particularly preferably consists of PE (polyethylene), EVOH (ethylene vinyl alcohol), PA (polyamide), PA 6, PA 66, PA 6.66, partially aromatic PA, nanocomposites, PA 6 nanocomposites, PA 6 clay nanocomposites, sheet silicates, bentonites, benzites , calcium carbonate, montmorillonite (such as aluminum silicates), modified montmorillonites (such as Cloisite ^®), nanoparticles, TiO _2, AlO _x or PVDC (polyvinylidene chloride) or a combination thereof.

Especially the use of nanoparticles, the most preferred at least in the barrier layer in chopsticks or platelet shape present, has proved to be particularly advantageous. Thereby, that this Barrier material limited to the barrier layer may be the same Proportion of barrier materials has achieved a better barrier effect be as if the barrier material over the entire preform distributed. The barrier particles are thereby restricted to a limited space, which improves the barrier properties. It is thus a highly concentrated Barrier layer formed, although the total amount of barrier material in the preform is very low.

In a particularly preferred embodiment is the proportion of barrier material in the barrier layer less as 50% by weight, preferably less than 15% by weight, and especially preferably less than 10% by weight. Furthermore, it is advantageous that the proportion of the barrier material in the barrier layer is greater than 1% by weight, preferably greater than 3 wt .-% and particularly preferably greater than 5 wt .-% is.

With Advantage is the thickness of the barrier layer is smaller than the thickness the cover layers chosen, wherein both outer layers are preferably at least twice each as thick as the barrier layer. Advantageously, the barrier layer much thinner be as the topcoats. For example, the cover layer less than a fifth make the thickness of the preform wall and particularly preferred less than a tenth. This will ensure that the barrier materials on a very thin Layer limited which in turn, due to the labyrinth effect, improves the Barrier effect leads, while using relatively little barrier material in the preform becomes.

Farther is it possible, for example, in the barrier layer to introduce a material, for example in a post-activation CVD coating process is used. In the CVD coating process, the applied Layer deposited by decomposition of a gaseous compound. The CVD processes are usually plasma-assisted or plasma-enhanced triggered. The plasma treatment is generally carried out under vacuum, which is very expensive. Since the barrier layer according to the invention of the Cover layer is included in the preform according to the invention be dispensed with the treatment in a vacuum. It could therefore for example titanium nitrite, titanium carbide or silicon nitrite layers be formed without a Plasma processing must be done in a vacuum. The same applies mutatis mutandis to those in PVD or materials used in PCD processes.

ever after used barrier material and in particular the concentration of the barrier material in the barrier layer may be beneficial be when a separation between the outer layer and the barrier layer and / or connecting layer is provided. The separation layer can intended for it be a mixing of topcoat and barrier layer in the Prevent production. The connection layer is intended to a better connection of the molecules between the cover layer and the barrier layer to achieve a delamination of the individual Prevent layers.

In a preferred embodiment the thickness of the release and / or bonding layer is less than half as thick as the thickness of the barrier layer.

Further Advantages, features and applications become clear with reference to the following description of a preferred embodiment and the associated Characters.

1 shows schematically the structure of a preform wall and

2 shows a cross-sectional view of a preform according to the invention.

To recognize the two cover layers 1 and 3 , as well as between the two cover layers 1 . 3 arranged barrier layer 2 , The two cover layers 1 and 3 here are made of PET, while the barrier layer 2 consists of PET, in which between 5 and 10% nanoparticles, such as TiO ₂ or AlO _{x have been} introduced. Some nanoparticles are schematically in the barrier layer under the reference number 4 located. Because the nanoparticles 4 only in the barrier layer 2 are present, they are on this barrier layer limited and form closely adjacent barriers, so that due to the Labyrintheffekts the barrier properties of the barrier layer 2 are very good.

Basically it is possible the barrier layer 2 very thin to choose. For example, the cover layers 1 . 3 each be at least ten times thicker than the barrier layer 2 ,

It can be seen that in the embodiment shown, the barrier layer 2 not in the center of the preform wall, passing through the layers 1 . 2 and 3 is formed, but closer to the outer wall, which here through the top layer 1 is formed. As a result, a high barrier effect of the barrier layer can be maintained especially when using the preform for producing bottles filled with fluid products. If the finished bottle is filled with water, for example, individual water molecules will diffuse through the cover layer. If these reach the barrier layer, this can - depending on the barrier material used - lead to a reduction of the barrier effect of the barrier layer. For this reason, it is advantageous to lay the barrier layer further outwards in the preform wall, since then the water molecules which diffuse to a slight extent into the inner cover layer have to cover a further path to the barrier layer and therefore the number of water molecules reaching the barrier layer is reduced ,

In 2 is a cross-sectional view of an embodiment of a preform according to the invention 5 shown. The preform has a threaded section 6 on. It can be clearly seen that the preform 5 sections of three layers, namely an outer cover layer 1 a barrier layer 2 and an inner cover layer 3 consists. In the embodiment shown, the barrier layer is not in the region of the thread 6 and not provided in the floor area. It is understood, however, that the barrier layer could also be provided substantially in all wall sections, ie also in the bottom section.

One Inventive PET preform can be prepared by a co-injection process. there the outer layers consist of PET and a PET compound made of PET and the barrier material is using a second injection unit injected. Injection can be done either with a pre-made PET compound (e.g., PET and nanocomposites, e.g., alumina or so-called nanoclays, to improve the barrier properties) or while injection are mixed directly. It may be the barrier material for example, be mixed in powder form. The latter has the Advantage that inexpensive PET can be used and only bought the barrier material must become.

Claims (19)

Preform or preform for blow molding, wherein the wall of the preform at least partially consists of at least three layers, namely two outer layers and arranged between the outer layers barrier layer, characterized in that the outer layers and the barrier layer formed substantially from the same thermoplastic material are, wherein the thermoplastic material of the barrier layer is mixed with a barrier material. Preform according to claim 1, characterized that this Plastic material PET, PP, PE, PVC, PS, SB, PC, COC or PAN and preferably is PET. Preform according to claim 1 or 2, characterized that the Barrier layer a barrier for Represents water vapor. Preform according to one of claims 1 to 3, characterized that the Barrier layer a barrier for Represents oxygen. Preform according to one of claims 1 to 4, characterized that the Barrier layer a barrier for Represents carbon dioxide. Preform according to one of claims 1 to 5, characterized that the Barrier layer a barrier for Represents nitrogen. Preform according to one of claims 1 to 6, characterized that the Barrier layer a barrier for electromagnetic waves at least a certain frequency range represents. Preform according to claim 7, characterized that the Barrier layer a barrier to visible Light and / or UV light represents. Preform according to one of Claims 1 to 8, characterized in that the barrier material consists of EVOH, PE, PA, PA 6, PA 66, PA 6.66, partially aromatic PA, nanocomposites, PA 6 nanocomposites, PA 6 clay nanocomposites, nanoparticles, TiO ₂ , AlO _x , or PVDC or a combination thereof. Preform according to one of claims 1 to 9, characterized that the Proportion of barrier material in the barrier layer less than 50% by weight, preferably less than 15% by weight, and more preferably less than 10 wt .-% is. Preform according to one of claims 1 to 10, characterized that the Proportion of barrier material in the barrier layer greater than 1 wt .-%, preferably greater than 3 wt .-% and particularly preferably greater than 5 wt .-% is. Preform according to one of claims 1 to 11, characterized that the Thickness of the barrier layer less than the thickness of the cover layers is, wherein both outer layers preferably at least twice as thick as the barrier layer. Preform according to one of claims 1 to 12, characterized that between Cover layer and barrier layer a release and / or bonding layer is. Preform according to claim 13, characterized that the Thickness of the release and / or bonding layer less than half as thick is like the thickness of the barrier layer. Preform according to one of claims 1 to 14, characterized that the both thick layers have a different thickness, preferably the outside one Cover layer of the preform thinner is considered the inner cover layer of the preform. hollow body for receiving a filling product, characterized in that the Hollow body out a preform according to any one of claims 1 to 15 has been prepared is. hollow body according to claim 16, characterized in that the hollow body of the preform by Blow molding, preferably by stretch blow molding is. hollow body according to claim 16 or 17, characterized in that the hollow body a Bottle, preferably consisting essentially of PET material Bottle is. Process for producing a preform according to one of the claims 1 to 18, characterized in that cover layers and barrier layer produced by the co-injection process or in the sandwich injection process become.