DE19703901A1 - Sterilisable polyethylene@ film containing talc filler - Google Patents

Abstract

A sterilisable polyethylene film (I) containing a talc filler is claimed.Also claimed is a process for the production of (I) by extrusion of a mixture of polyethylene and talc. Preferably the polyethylene film (I) is a metal-polymer composite. (I) contains 10-25, preferably 12-18 wt.% talc with a particle size of 0.5-20 microns. (I) is prepared from polypropylene with a density of 0.939-0.962 g/cm<3>, m.pt. of 110-130, preferably 115-125 deg C. The metal-polymer composite contains an intermediate adhesive layer that contains 10-25 wt.% talc.

Description

The present invention relates to fillers Plastic films and fillers Metal-plastic composites and processes for their Manufacturing.

To make a can or a closure for the Use as packaging material, especially for the Food packaging, the tear-off closure of beverage bottles, yoghurt cups and. a. are made of sheets Tinplate, chromated steel like ECCS (electrolytic chromium-coated steel) and aluminum in table or Band shape coated. The lacquer layer acts as a protective layer, around the metal before the attack of the filling material and from it protect resulting corrosion on the one hand and around on the other hand, by influencing the filling material To prevent corrosion products of the metal. Of course, it can also be through the paint layer itself, for example due to detached paint components, none Influence or impairment of the filling material,  neither with the one after the bottling Sterilization of the filling material during the subsequent one Storage of packaged goods, especially food.

Furthermore, the leaks must be constructed so that they in the further processing of the coated sheets into cans or closures occurring mechanical Stresses such as deforming, punching, flanging, Beads and the like, withstand. In addition, when used as Closure for food containers a defined Opening behavior must be guaranteed.

As an advantageous method for coating sheet metal, which in particular for making life medium packaging are used, Fo proven coating of metal sheets. So is for example in DE-OS 31 28 641 a method for Manufacture of laminates for food packaging described in which the metal sheet and a ther plastic resin film together with one between them Layers of adhesive based on a layer carboxyl group-containing polyolefin at temperatures heated above the melting point of the adhesive and then cooled together using pressure are produced, whereby the metal-plastic composite becomes.  

Furthermore, from DE-OS 29 12 023, the GB-A-2027391 and EP-B-31701 laminates and from them Laminated food packaging containers, especially bags known.

EP-A-4633 discloses opaque films made of thermoplastic, known organic plastic by bi-axial stretching are oriented and 1 to 25 wt .-%, based on the weight of the polymer plastic, inorganic particles, such as. B. Titanium dioxide, calcium carbonate and silicon dioxide. The inorganic particles lead to the opaque appearance of plastic films.

Finally, EP-A-199 228 relates to composite films, the two contain plastic films connected with adhesive, whereby at least one of the two films on its inner surface is provided with a metal layer and one of the two Plastic films has an opaque appearance due to Micro voids in the film caused by inorganic fillers, such as sulfates, carbonates, silicates, oxides are formed. The Laminated film is recommended for packaging Oxidation-sensitive foods and stimulants. Of the opaque plastic film, which is essentially made of plastic The main component and filler is biaxial stretched. The transparent plastic film is also preferably stretched.  

These plastic films have non-biaxially stretched Condition poor barrier properties, d. H. the Plastic films are water vapor, acid and general gas permeable. As a result, during sterilization unwanted signs of corrosion.

All previously described plastics and plastic composites exhibit when used as tearable closures of Packaging containers for food none satisfactory results. This applies in particular to the tear-off behavior is usually not defined Direction.

The object underlying the present invention consisted of developing plastic films that Suitable for closing food packaging containers and are characterized by a defined opening behavior when Label tearing off the packaging container. Out these plastic films should Have metal-plastic composites made, too should have excellent barrier properties all with regard to UV permeability, water vapor permeability and gas permeability and in particular Sulfide permeability.

The object is surprisingly achieved in that the fillers consist of talc.  

The plastics used according to the invention include Polyolefins each in the form of a film or a film.

Such polyolefin films are made by known methods (Blowing process, chill-roll process etc.) from granules of Homopolymers of ethylene and propylene as well Copolymers. Polyethylene is lower Density (PE-LD), medium density (PE-MD), high density (PE-HD), linear low and linear very low density polyethylene (PE-LLD, PE-VLD), polypropylene, whose copolymers with Ethylene and the copolymers of ethylene with one or several comonomers from the groups of vinyl esters, Vinyl alkyl ethers, unsaturated mono- and dicarboxylic acids, their salts, anhydrides and esters.

Polyethylene of medium density in the range from 0.939 to 0.961 g / cm ^{3 is} particularly preferred.

The melting point of the polyethylene is preferably between 110 and 130 ° C, especially 115 to 125 ° C. It is Surprisingly, that in the mixture according to the invention with Talc the polyethylene films despite the low Melting point can be sterilized.

The polyolefins mentioned are commercially available, for example, under the following brand names:
Escorene®, Lupolen®, Lotader®, Lacqtene®, Orevac®, Lucalen®, Dowlex®, Primacor®, Surlyn®, Admer®, Novatec®, Sclair®, Stamylan® and others

According to the application, the plastic films contain at least 10 wt .-% talc, based on the Total weight of the mixture of plastic and filler. A content of 10 to 25% by weight of talc is preferred, based on the total weight of the mixture of Plastic and filler. 12 to are very particularly preferred 18% by weight talc. Depending on the application, you can also Contents of approx. 15% by weight, based on the total weight the mixture of plastic and filler. in the however, contents of up to 15% by weight are generally sufficient.

The average particle size of the talc is preferably as well as the other metal powders in the range from 5 to 20 µm, however, deviations are also possible.

The plastic films can also be useful additives, such as Lubricants, stabilizers, dyes, pigments, antistatic agents, Antiblocking agents and the like in an effective each Amount included.

The invention also relates to the method for producing the the plastic films containing talc. The Plastic mixed with the talc and into one  Extruded plastic film. The extrusion of plastics is a well known process. It is beneficial to use the talc by feeding the extruder into the side Introduce plastic melt. Preferably be Twin screw extruder used. It is preferred to use one multi-stage extrusion for the production of plastic films carry out, in the first extrusion stage Talc together with part of the plastic underneath Production of a film with a high proportion of talc is extruded and in the second stage that from the film granules obtained is extruded with additional plastic. In this way, a better homogenization of the Mixture of plastic and talc reached.

The thickness of the plastic films containing talc is in generally 10 to 1000 microns, preferably 20 to 500 microns.

The present invention also relates to fillers containing metal-plastic composites, thereby are characterized in that connected with a metal sheet Plastic films at least 10 wt .-%, preferably 10 to 25% by weight talc, based on the total weight of the Mixture of plastic and filler. Especially 12 to 18% by weight are preferred.

The talc can also be in the adhesion promoter layer or in the between the plastic film and the metal sheet arranged adhesive layer may be included. So that affects  present invention also metal-plastic composites that are characterized in that a plastic film with a bonding agent layer connecting a metal sheet at least 10% by weight, preferably 10 to 25% by weight, particularly preferably 12 to 18% by weight of talc, based on the total weight of the mixture of coupling agent and Filler. The present invention further relates to Metal-plastic composites, which are characterized by that one between a metal sheet and a plastic film arranged adhesive layer at least 10 wt .-%, preferred 10 to 25 wt .-% talc, based on the total weight of the Mixture of filler and the solid weight of the Adhesive layer, contains. 12 to 18 are particularly preferred % By weight talc.

The average particle size of the talcum is preferably Range from 0.5 to 20 µm, 1 to 10 µm.

Are suitable for producing the coated metal sheets Sheets of 0.1 to 5 mm thickness made of black sheet, Tinplate, aluminum and various iron alloys, with a passivation layer based on nickel, Chromium and zinc compounds are provided. Depending on Intended use are also thicknesses of more than 5 mm suitable.

The resin sheets or films used in the present invention include the above Polyolefins.  

All those on the market today come as adhesion promoters materials insensitive to sterilization.

In contrast to adhesives, adhesion promoters are said to solid adhesion-promoting plastics are understood that be co-extruded with the plastic and on the inside of the coextruded plastic film into one Adhesion promoter layer are formed.

Copolymers, terpolymers, Be graft copolymers and ionomers, with the proviso that they carboxyl or anhydride groups or groups belonging to Carboxyl groups are hydrolyzable, and that Melt index of the polymers measured at 190 ° C and one Load of 2.16 kg between 0.1 and 30 g / 10 min, preferred between 0.2 and 25 g / 10 min and particularly preferred is between 0.5 and 20 g / 10 min.

Suitable copolymers or terpolymers can be produced by Copolymerization of ethylene with α, β-unsaturated Carboxylic acids such as B. acrylic acid, methacrylic acid, Ita cons acid, crotonic acid, isocrotonic acid, maleic acid and fumaric acid, the corresponding anhydrides or the corresponding esters or half-esters with 1 to 8 C atoms in the alcohol residue such as B. the methyl, ethyl, propyl, Butyl, pentyl, hexyl, cyclohexyl, hep-tyl, octyl and  2-ethylhexyl ester of the acids listed. Likewise the corresponding salts of listed carboxylic acids, such as the sodium, potassium, Lithium, magnesium, calcium, zinc and ammonium salts. The carboxylic acids and their are preferably used Anhydrides.

Furthermore, in the copolymerization, other, with Ethylene and the unsaturated carbonyl compounds copolymerizable monomers are used. Suitable Examples are alpha olefins with 3 to 10 carbon atoms, Vinyl acetate and vinyl propionate.

The amounts of the monomers used are so chosen that the corresponding polymer is a carboxyl group content of 0.1 to 30 wt .-%, preferably 2 to 20 Wt .-%, and that the content of ethylene units in Polymer up to 99.9% by weight, preferably between 75 and 95% by weight.

Suitable graft copolymers can be produced by grafting of at least one polymer from the group of Polyolefins with up to 10% by weight, preferably up to 5% by weight, based on the total weight of the monomers, at least of a monomer from the group of the α, β-unsaturated Carboxylic acids, their anhydrides, their esters or salts in Presence or absence of peroxides. Examples of  suitable polyolefins are those already described of the cover layers listed in this description Polyolefins. Examples of suitable carbonyl compounds are those above in the description of the adhesion promoter Copolymer based carbonyl compounds.

The ionomers used as an adhesion promoter layer are can be produced by the one already described above Copolymerization of ethylene and possibly other monomers with salts α, β-unsaturated carboxylic acids or by partial neutralization of those already described above carboxylic acid-containing co-, ter- and graft polymers with Salts, oxides and hydroxides of sodium, potassium, Lithium, magnesium, calcium, zinc and ammonium. The Neutralization can be in the melt or in solution be performed. The amount of basic compound is chosen so that the degree of neutralization of the Polymers between 0.1 and 99%, preferably between 0.1 and 75% and very particularly preferably between 0.1 and 40% lies.

Adhesion promoters based on polyurethane also come in Question.

Both the adhesion promoter layer and the plastic layer can also use conventional additives such. B. inner and outer Lubricants, antiblocking agents, stabilizers, antioxidants,  Contain pigments, crystallization aids and the like. These additives are used in manufacturing, Processing, packaging and application necessary Amounts in the form of powder, powder, pearls or one directly concentrate incorporated in the corresponding polymer used. Details of the commonly used Quantities and examples of suitable additives are for example the Gächter-Müller, plastic additive, Carl-Hanser Verlag. These are preferred Additives incorporated into the plastic layer.

The adhesives which may be used are preferably applied by application from solutions or dispersions in water or organic solvents. The solutions or the dispersions generally have an adhesive content of about 5 to 60% by weight. The amount of adhesive applied is usually about 1 to 10 g / m ² area. Particularly suitable adhesives are the synthetic adhesives, consisting of thermoplastic resins such as cellulose esters, cellulose ethers, alkyl or acrylic esters, polyamides, polyurethanes and polyesters, of thermosetting resins such as epoxy resins, urea / formaldehyde resins, phenol / formaldehyde resins and melamine-formaldehyde resins or of synthetic rubbers.

The present invention also relates to several methods for the production of the Me tall plastic composites.

A manufacturing process is characterized in that the mixture of plastic and talc is extruded and the resulting plastic film using an adhesive layer the metal sheet is laminated on. But also can the mixture of plastic and talc together with a Adhesion promoters are coextruded. In this process on the inside of the plastic film containing talc an adhesion promoter layer is formed. Then the plastic film obtained laminated onto a metal sheet.

In addition, there is also a manufacturing process the metal-plastic composites possible, in which the Plastic together with a mixture of adhesion promoters and talc is coextruded, a metal sheet is heated and the plastic film is laminated onto the metal sheet.

Finally, the present invention relates to a Manufacturing process of metal-plastic composites, at which the plastic film obtained by extrusion by means of a Adhesive layer, which contains the talc, on the metal sheet is laminated on.

The process of making with a plastic film coated metal sheets are generally known, so that at this point does not need to be discussed in more detail.  

With regard to suitable adhesives and adhesion promoters, reference is made to the previously described adhesives and adhesion promoters referred.

The plastic films and metal Plastic composites are therefore ideally suited for the Packaging of food and luxury food, being preferred for packaging oxidation-sensitive food and stimulants can be used. You instruct Orientation-accurate tear-off behavior and excellent Sterilization properties.

Claims (12)

1. filler-containing, sterilizable plastic film made of polyethylene, characterized in that the fillers consist of talc. 2. Filler-containing, sterilizable metal Plastic composite, characterized in that the Contains plastic layer as filler talc. 3. Plastic film or metal-plastic composite after one of claims 1 or 2, characterized in that the Plastic film 10 to 25, preferably 12 to 18% by weight Contains talc. 4. plastic film or metal-plastic composite according to one of claims 1 to 3, characterized in that the plastic film made of polypropylene medium density, preferably in the range of 0.939 to 0.962 g / cm ³ with a melting point of 110 to 130 ° C, preferably 115 to 125 ° C exists. 5. Plastic film or metal-plastic composite after one of claims 1 to 4, characterized in that the Particle size of the talc is 0.5 to 20 microns. 6. metal-plastic composite containing fillers, characterized in that one between a sheet of metal and one Plastic layer arranged adhesive layer at least 10 % By weight, preferably 10 to 25% by weight, of talc on the total weight of the mixture of filler and contains the solid weight of the adhesive layer. 7. Process for the production of the plastic film Claim 1 or 5, characterized in that the mixture is extruded from the plastic and the talc. 8. Process for producing the metal-plastic composite according to claim 2 or 5, characterized in that either the Mixture of plastic and talc is extruded and the plastic film obtained by means of a Adhesive layer is laminated onto the metal sheet or the mixture of plastic and talc together with an adhesion promoter is co-extruded, the metal sheet heated up  and the plastic film on the metal sheet is laminated on. 9. Process for producing the metal-plastic composite according to claim 3 or 5, characterized in that a plastic together with a mixture of adhesion promoter and Talc is co-extruded, the metal sheet is heated and the plastic film on the metal sheet is laminated on. 10. Process for producing the metal-plastic composite according to claim 4 or 5, characterized in that the by Extrusion plastic film obtained using a Talc-containing adhesive layer on the metal sheet is laminated on. 11. Use of the plastic film still claim 1 or 3 to 5 for the manufacture of vascular occlusions or Composite packaging. 12. Use of the metal-plastic composites after Claim 2, 3, 4 or 5 for the production of Vascular closures or composite packaging.