DE2537491C3 - Multi-layer container - Google Patents

Description

The invention relates to a packaging container according to the preamble of the applicable main claim.

Containers such as those used for food, beverages and medicines are intended have a low gas permeability with regard to oxygen, carbon dioxide and water vapor and on the other hand, good mechanical properties for the purpose of processing and protecting the contents of the container own. A synthetic resin or plastic material which at the same time meets the above requirements fulfilled, but can hardly be found and manufactured.

It is therefore already known to use various plastic layers to combine in a laminate, resulting in a combination of the good properties of the respective plastic component results, by which the above-mentioned problem can be solved can. In order to put the different materials together in a layered structure, however, larger ones are needed To overcome difficulties, in particular, both layers need to be connected to each other.

H) Polyethylene can be used as a moisture barrier widely used in the food and beverage industry for containers will. This plastic has excellent flexibility and transparency. It is health-wise

'·' Completely harmless, food in polyethylene containers to store. However, polyethylene has the serious disadvantage that it is safe for oxygen and Carbon dioxide is extremely permeable, so that food for long periods of time not in such Containers can be stored.

As a plastic with low gas permeability, there is polyvinyl chloride, which is used for various purposes is used in single-layer containers. However, poly-vinyl chloride is not entirely healthy

2> harmless, as monomers remaining in the plastic, the z. B. can be solved by food, are extremely toxic. Poly vinyl chloride leads continues to cause problems in waste incineration plants, as it contains chlorine and hydrochloric acid during its incineration

in what environmental problems developed as well as a faster Can cause corrosion of waste incineration plants.

To improve the gas permeability of the polyethylene various procedures have already been

Ji winds, taking the ethylene with various types of Vinyl polymer was copolymerized. So is z. B. known that saponification or esterification products of ethylene vinyl acetate copolymers, compared to polyethylene only very low oxygen permeability

Ή> th own. Saponification products of the copolymer however, have an prohibitively high permeability due to the hydrophilic groups, in addition to is the material is not good due to its mechanical strength, particularly its poor impact resistance

• i ^r ) suitable for the manufacture of containers.

It is therefore advisable to use laminated layers to solve the problem already mentioned, how it z. B. from DE-OS 19 65 856 is known. In this known method, a liquid

■) () barrier layer made of polyolefin with a gas barrier layer from ethylene-vinyl alcohol glued together with the help of an adhesive and from this satisfactory Container manufactured.

DE-OS 17 86 278 also discloses laminates

Y> known, which lead to liquid- and gas-tight walls. For this purpose, a mixture of 90-98% by weight propylene and 10 to 2% by weight ethylene was used as the liquid-blocking layer, while the gas barrier is ensured by means of ethylene-vinyl acetate copolymers.

hü was presented.

Unfortunately, there is nothing in this laid-open specification about the processing of such a laminate Suggestion. From chemical considerations, however, it can be deduced that the adhesion between propylene /

fa ¹ ; Ethylene on the one hand and ethylene vinyl acetate copolymers are extremely weak, since they can only be based on hydrophobic interactions - if no adhesive is used.

25 3? 491

The use of layers glued together in this way, however, is extraordinary in terms of processing troublesome and incurs high costs. The step of gluing together and the cost of using it Adhesives are not acceptable for mass-produced items.

The foregoing shows that the manufacture of multilayer containers in which the The gas or liquid barrier properties of each material component are used in an optimal way have caused considerable difficulties so far. The invention is therefore the object based on creating a multilayered container 7u, which is easier and more economical to manufacture and which has improved properties, namely very low gas permeability to oxygen, carbon dioxide and water vapor and good mechanical Properties, especially impact resistance, flexibility and toughness, as well as transparency.

According to this task, a packaging container according to the characteristics of the applicable main claim solved.

A preferred embodiment of the invention is characterized in that on each side of the gas barrier layer a pair of layers of modified Polyolefin or the polyolefin mixture and unmodified polyolefin are arranged.

Another embodiment of the invention can provide that it has a polyolefin layer, wherein the polyolefin layer and the gas barrier layer are disposed on either side of the modified polyolefin layer are.

Further embodiments of the invention emerge from the subclaims.

The multi-layer packaging containers according to the invention which achieve the above object and have the desired properties are produced by coextrusion. There are two or more kinds of thermoplastics or resins separated in the corresponding number of Melted extruders. The melted plastics are then put into a multiple extrusion head given, in which plastic tubes are formed from the respective plastics. The ones from melted Existing plastic tubing is then placed inside the plastic under the application of pressure and heat The spray head assembled. Then the layered plastic product comes out of the molding opening of the extrusion head, resulting in a multilayered blank or parison. This blank will then processed by blow molding, which creates a multilayer container after cooling down Invention results. The extruder and blow molding machine described in the above method are of a conventional type. The person skilled in the art is therefore also without a detailed explanation of such a thing Apparatus able to manufacture multilayered containers according to the invention by referring to the following Description of the container itself refers.

Are special plastics for the individual layers of the container in the type according to the invention is used, the adhesion between the individual plastic layers is without the use of an adhesive or an adhesive layer excellent when the coextrusion process in the manner described above is performed.

According to the invention, the adhesion between the various layers of thermoplastics can be determined still improve by adding suitable polymers to one or both of the plastics Plastics are entered.

The composition of each individual layer which together make up the multilayer container according to the invention are described below. The gas barrier layer according to the invention has mainly a polyamide, a saponification product of an ethylene-vinyl acetate copolymer or a copolymer one by a C5-Cao-α-olefin or a C5 -C20 long chain alkyl group modified polyvinyl alcohol on. These plastics have very low gas permeabilities. On the other hand, they have named ethylene-vinyl acetate copolymers as well as those with the C5-C2o-a-01efin or with the long-chain

i ¹ "C5 -C2o-alkyl group modified polyvinyl alcohol high permeability for water vapor and are very brittle. In order to compensate for the above disadvantageous properties of these polymers according to the invention, a layer or layers of an ethylene-vinyl acetate copolymer or of a polyolefin graft-modified with unsaturated carboxylic acid is used applied to the inner and / or outer surface of the aforementioned gas-barrier layer. These layers of ethylene-vinyl acetate copoly-

2 ^r > mer and modified polyolefins protect the gas-barrier layer and have excellent adhesion properties with respect to the ethylene-vinyl copolymer mentioned as well as to the C5-C2o-olefin or the long-chain C5-C2o-alkyl group

ίο modified polyvinyl alcohol because it is covalent Ester bonds between the carboxylic acid groups of the graft modified polyolefin and the hydroxyl groups the polyalcohols are formed.

To have better adhesion between the said

to obtain i ^r> copolymers according to the invention can also be used a special ionomers 50 to 0.5 parts. The 50-0.5 parts of the ionomer, the ethylene vinyl acetate copolymer or the polyolefin are then added to 100 parts of the ethylene vinyl alcohol copolymer or the polyvinyl alcohol modified with the C5-C2o-a-olefin or with the long-chain C5-C2o-alkyl group for the gas-barrier layer . If the special ionomer, the ethylene vinyl acetate copolymer or the polyolefin in one

Ί5 used larger than specified above the adhesive properties are improved, but ■ the advantage of low gas permeability of the ethylene vinyl alcohol copolymer or the one with the C5-C2o - «- 01efin or with the long-chain C5-C2o-alkyl group modified polyvinyl alcohol impaired. It therefore becomes as stated above Additive is preferably used only to a small extent, as long as the adhesive properties are only satisfactory stay. There can also be other additives or a

v> polyamide can be added to the material for the gas barrier layer.

In the multi-layer structure according to the invention, it is not always necessary that on the inner and applied outer surface of the gas barrier layer

M) layers have the same composition. However, if the inner and outer layers are made of the same Material can exist, so can the three-layer structure, in which the gas-barrier layer between coincident inner and lower

i> ^r > layers is embedded by a sandwich extrusion process, whereby two extruders are used. The influence of moisture on the gas-barrier layer made of the ethylene vinyl alcohol

polymeric or with the Cs-C2o-a-olefin or with of the long-chain C5 - C2o-alkyl group Polyvinyl alcohol can be reduced by covering the inner and outer surfaces with layers of the Ethylene vinyl acetate copolymers or a modified one Polyolefin coated. The multilayer container according to the invention is thus made by water and moisture on the inside or outside of the container is not affected. In addition, the Brittleness of the ethylene vinyl alcohol copolymer or that with the C5-C2o- <x-01efin or with the long-chain C5 -C20 -alkyl group of modified polyvinyl alcohol absorbed and balanced by the outer layers, bearing in mind that the brittleness could become a problem if the gas barrier layer is placed on the outside were.

As stated above, when an ethylene _{-vinyl alcohol copolymer or a polyvinyl alcohol is modified with a C5-C 2} oa-01efin or with a long-chain Cs-C20-alkyl group, as the material for the gas barrier layer and an ethylene-vinyl acetate copolymer or a modified Polyolefin can be used as the material for the inner and outer layers to produce multilayer containers according to the invention with good adhesion between the individual layers.

It is also possible to use the ethylene vinyl alcohol copolymer, the one with Cs-C2o - «- 01efin or with a long-chain Cs-Qio-alkyl group modified polyvinyl alcohol, the ethylene vinyl acetate copolymer, the ionomer and the modified polyolefin by fire to destroy, with only water vapor and carbon dioxide in gaseous form, so that the elimination of such Container can be made very easily and without damaging the environment.

The gas permeability of the polyamide synthetic resin is also slightly higher than that of the modified one Polyvinyl alcohol and ethylene vinyl alcohol copolymer. Accordingly, the polyamide resin can can be used as a gas barrier layer because it has excellent mechanical properties. If this gas barrier layer is combined with moisture barrier layers, it could separation of the layers can easily occur. This problem can be solved by using the unsaturated Carboxylic acid modified polyolefin is used as the material for the moisture-proof layer. Farther let si: h, if modified polypropylene, which contains 1-15% by weight of the modified polyethylene, used as the material for the moisture-proof layer, multi-layer container with excellent mechanical strength properties obtained.

When the above polyamide synthetic resin is used as the material for the gas barrier layer, not only three-layer containers but also acceptable two-layer containers can be produced, since the material has relatively good mechanical properties and a sufficient reduction in moisture permeability compared with the mentioned ethylene vinyl alcohol copolymers and the modified polyvinyl alcohol.

The invention is explained in detail below on the basis of exemplary embodiments.

example 1

With maleic acid (melt index: 2, density: 0.920) graft-modified polyethylene of low density was melted and kneaded in an extruder. Then the melted polyethylene was put into the for that inner and outer layers defined sections of the extrusion head of a blow molding machine at 200 ° C

■ entered y. A saponification product of an ethyl / vinyl acetate copolymer (Ethylene content: 30 mol%, degree of saponification: 99.5%) was treated in the same way and fed to the spray head as material for the intermediate layer at 200 ° C. The spray head has concentric

H) look at synthetic resin diameter. In this order Inner layer, outer layer and intermediate layer became the modified high pressure polyethylene and the Ethylene vinyl acetate copolymers extruded through the spray head, resulting in containers, the layer thickness

r> ken of 0.4 mm, 0.05 mm and 0.02 in the order given. These containers had an adhesive strength of 800 g / l 5 mm, an oxygen gas permeability of 3.8 ml / m ² day χ atm, and a moisture ^{permeability of 0.92 g / m 2} χ day.

Example 2

Polyvinyl alcohol modified by alkyl groups (dodecyl ether: 10 mol%, degree of saponification: 99.2%), with a Content of 10 wt .-% high pressure polyethylene

2ί (melt index: 2, density: 0.920) was melted and kneaded in an extruder. The melt was then transferred to the injection head of a blow molding machine 200 ° C supplied. The internal structure of the spray head was similar to that in Example 1. The high-pressure polyethy-

Ji) len for the inner and outer layers and the alkyl group-modified polyvinyl alcohol with 10% by weight of high-pressure polyethylene for the intermediate layer were extruded from the die head, becoming hollow Containers with a thickness of the inner and outer

Vi gave a layer of 0.2 mm and an intermediate layer thickness of 0.05 mm.

These containers had an adhesive strength of 120 g / 15 mm and an oxygen permeability of 4.8 ml / m ² day χ atm.

Example 3

A composition consisting of 90% by weight of high pressure polyethylene (melt index: 2.0, density: 0.920) and 10% by weight of 6-nylon was made in an extruder

4 ¹ S melted and kneaded. The composition was fed to the die head at 200 ° C., producing blanks or parisons. The blanks were then fed to a blow molding machine and processed there, as a result of which multilayer containers according to the invention could be obtained.

An ethylene vinyl alcohol copolymer was made in the same way (Ethylene content: 29 mol%, degree of saponification: 99.5%) melted in an extruder and dtm Spray head supplied at 200 ° C. The extrusion was carried out in the same way as in Example 1. It resulted three-layer hollow containers, in which the inner and outer layers of the mixed composition existed and had a thickness of 0.2 mm, while the intermediate layer of the ethylene vinylal

fao alcohol copolymers and was 0.03 mm thick. The containers had an adhesive strength of 350 g / 15 mm, the oxygen permeability was 1.2 inl / m ² day χ atm, and the moisture ^{permeability was 0.40 g / m 2} χ day.

Example 4

In the same way as in Example 3, 45% by weight of high-pressure polyethylene and 55% by weight of 6-nylon were produced

10

mixes and used as the material for the inner and outer layers. Ethylene vinyl alcohol copolymer, similar to that of Example 3 was used for the intermediate layer. The blow molding took place in the same way as in example 3.

The containers thus obtained had an adhesive strength of 625 g / 15 mm, an oxygen permeability of 1.2 ml / m ² day χ atm and a moisture ^{permeability of 0.4 g / m 2} χ day.

Example 5

A mixture of 100 parts of an ethylene vinyl alcohol copolymer (Ethylene content: 30 mol%, degree of saponification: 99.2%) and 10 parts of "Surlyn A" was and used as the material for the intermediate layer. An ethylene vinyl acetate copolymer was made used as the material for the inner and outer layers. A blank die head with two extruders was used for blow molding and produced hollow containers. The containers thus obtained had a Thickness of the outer layer of 0.14 mm, a thickness of the intermediate layer of 0.03 mm and a thickness of Inner layer of 0.16 mm.

These containers had an adhesive strength of 600 g / 15 mm and an oxygen permeability of 11 ml / m ² day χ atm.

Example 6

Purified xylene, maleic anhydride and polypropylene powder were introduced into a reaction vessel and heated to 120 ⁰ C. Thereafter, benzoyl peroxide was dissolved in purified acetone, whereupon the solution was added dropwise to the above mixture. The reaction then takes place. After the reaction was carried out, the unreacted maleic anhydride was eliminated from the polymer by acetone extraction.

The polyvinylpropylene thus obtained was mixed with 10% by weight of a modified polyethylene, which was made in a similar manner.

This modified polypropylene as well as nylon were fed to respective extruders and at 250 ° C applied to a spray head. The two layers were connected to one another in the spray head, whereupon blow molded containers were made in a blow molding machine.

The containers thus obtained had an adhesive strength of 1500 g / 15 mm or more. The containers could be dropped 10 times or more at room temperature. The impact resistance was 3.2 m at 0 ° C. The containers had an oxygen permeability of 15 ml / m ² day χ atm, that is, lower than in the last example, but the mechanical strength was better.

Example 7

1% by weight of nylon was added to polypropylene, whereupon the mixture was kneaded by an extruder and pelletized. The mixture was then used as polypropylene and nylon in appropriate extruders melted and fed to a spray head which was kept at 250 ° C.

In a manner similar to Example 6, blow molded containers having an outer layer of Nylon and an inner layer made of the mixed polypropylene.

These containers had an adhesive strength of 1500 g / 15 mm and an oxygen permeability of 15 ml / m ² day χ atm.

After the above example it is clear that the invention excellent containers with excellent Properties are gained. The exemplary embodiments are of course only intended to make it easier to understand of the invention, but do not limit the inventive concept.

Claims (6)

1 claims: 1. Packaging container with at least two-layer plastic wall, wherein a gas-barrier layer consists of a substantially gas-impermeable first thermoplastic material and a moisture-barrier layer consists of a substantially moisture-impermeable, second thermoplastic material, characterized in that the packaging container is made by means of adhesive-free coextrusion of the plastics as a hollow container wherein the gas barrier layer consists of a plastic composition made from a member of the group: polyamide, a saponification product of an ethylene-vinyl acetate copolymer and a copolymer of a _{polyvinyl alcohol modified by a C 5} -Cjo-α-olefin or a Cs-C20 long-chain alkyl group, and that the moisture barrier layer by unsaturated carboxylic acids to about ⁴ ΙΟ- -3 wt .-% graft-modified polyolefin or a mixture of the modified polyolefin to unmodified polyo lefin exists. 2. Packaging container according to claim 1, characterized in that the saponification product of the Ethylene-vinyl acetate copolymers have an ethylene content of 20-60 mol% and a degree of saponification of at least about 95%. 3. Packaging container according to claim 1 or 2, characterized in that the polyolefin of layer containing graft-modified polypropylene and graft-modified polypropylene has between 1 to 15 wt .-% graft modified polyethylene. 4 packaging container according to one of the preceding claims, characterized in that on on each side of the gas barrier layer a pair of layers of modified polyolefin or the Polyolefin mixture and unmodified polyolefin are arranged. 5. Packaging container according to one of claims 1 to 3, characterized in that it has a Polyolefin layer, with the polyolefin layer and the gas barrier layer on each side the modified polyolefin layer are arranged. 6. Packaging container according to claim 5, characterized in that the polyolefin layer consists of a member of the group consisting of: polyethylene, polypropylene, ethylene-vinyl acetate copolymer, Ethylene-ethyl acrylate copolymer or ionomer, is selected.