Method of providing a package with a barrier and the package thus obtained

Abstract

A method of providing a package for pourable food products with an oxygen barrier, which method comprises the step of post-applying a liquid oxygen barrier composition comprising a polymer dispersion or solution, as a coating, onto the entire or a selected part of an outside surface of the package. The invention also relates to the package thus produced.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of providing a package for pourable food products with an oxygen barrier. The invention also relates to the package thus obtained. BACKGROUND OF THE INVENTION [0002] Packages for pourable food products need to have oxygen barrier proper-ties in order for the filled and unopened packages to be able to be stored. The required shelf-life and the degree of oxygen barrier needed depends on the type of food product, the type of packaging material, the type of package, the type of opening on the package etc., and also on aspects such as if the package is aseptic and intended for ambient storage or if is not aseptic and thus intended for chilled storage, e.g. In all cases, some degree of oxygen barrier is needed. [0003] Hitherto, it has been common to provide the packaging material, having a polymeric or fibre based core material e.g., with a barrier layer, already before the package is formed from the packaging material. For ...

AI Technical Summary

Benefits of technology

[0013] It has now been found that surprisingly good oxygen barrier properties can be achieved in a package by post-applying a liquid oxygen barrier composition comprising a polymer dispersion or solution, as a coating, onto the entire or a selected part of an outside surface of the package. By “post-applying” is meant that the coating is applied onto the finished package, preferably even after filling and sealing of the same.

[0038] It has also been found in connection with the development of the invention, that surprisingly good oxygen barrier properties are achieved when there is made use of colloidal silica particles, exhibiting a particle size of 3-150 nm, preferably 4-100 nm and even more preferred 5-70 nm, which particles are preferably amorphous and / or spherical. The use of colloidal silica particles moreover has the advantage that the liquid barrier composition may be applied at a dry content of 15-40 weight %, preferably 20-35 weight % and even more preferred 24-31 weight %, whereby the demand on forcible drying is decreased.

[0039] Optionally, the composition may also comprise an additive for increasing the resistance to scratching of the coating. Alternatively, or in combination, the coating may be treated to exhibit increased resistance to scratching.

[0042] According to another preferred embodiment of the invention, it has been found that the wetting and adhesion is surprisingly improved if a first part coating, in direct contact with the object to be provided with an oxygen barrier, is composed of a coating polymer dispersion or solution, that is essentially free from any nano-scale particles. The second part coating should then preferably be composed of a coating polymer dispersion or solution, but including nano-scale particles, to provide for the oxygen barrier effect. Finally, a third part coating is applied, that again is preferably composed of a coating polymer dispersion or solution, that is essentially free from any nano-scale particles. This final and outermost part coating layer serves as a protection against moist and scratching etc. The first, second and third part coatings are preferably based on the same type of polymer dispersion or solution, of the same or different qualities. Between each coating step, the resulting coating is dried or cured, preferably by a treatment in the group that consists of hot air treatment, IR treatment, UV treatment or electron beam treatment of the coating or any combination of such treatments. Optionally, the coating is forcibly dried between the different coating steps and cured at the end, when all part coatings have been applied. It is also conceivable that the first, second and / or third part coatings, preferably the second part coating comprising nano-scale particles, are applied in two or more steps, with intermediate drying or curing.

Problems solved by technology

One problem of providing the packaging material with an oxygen barrier layer before forming the package is that it is hard or even impossible to control the barrier effect on different parts of the package.

For example, an increased need for an oxygen barrier at the seals of the package is difficult to achieve without affecting the rest of the package.

Also, due to the overlapping nature of conventional seals in a fibre based packaging laminate, a barrier layer in the laminate may not give the desired barrier properties at the overlap of the same.

Moreover, any functional details, such as plastic details or opening devices, pre-applied onto the packaging material or even applied onto the final package, will not exhibit the same oxygen barrier properties as the rest of the material.

This is a problem especially in connection with opening devices on aseptic, i.e. sterilised, D packages for oxygen sensitive food products such as fruit or vegetable juices e.g. Some package types may also be built up from different parts of different materials, one example being a package that has side walls and a bottom of a fibre based packaging laminate but a top which is made of plastics (Tetra Top®).

In this case, it may be difficult to achieve the same or essentially the same oxygen barrier properties on all parts of the package.

One type of opening device that poses a special problem in connection with oxygen barrier properties is a pre-applied, direct injection moulded, plastic cap, especially on an aseptic package.

The aim of achieving such oxygen barrier properties is rendered extra difficult by the fact that any barrier layer created on the cap at its moulding or in connection therewith, must be able to withstand the sterilisation treatment.

Though it might be possible to provide a plastic cap with barrier properties by producing it from a polymer blend, this has a severe impact on mechanical and sealing properties.

To our knowledge, no known technique exist which is able to give barrier and at the same time acceptable sealing and mechanical properties in the cap.

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