Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1993-04-06
1994-12-27
Nold, Charles R.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
2065246, 270200, 270361, 270364, 156 69, 1562753, B65D 5300
Patent
active
053764161
DESCRIPTION:
BRIEF SUMMARY
The subject of the present invention is a process for the production of closures for tight sealing of packaging containers, with which process a sealing composition is applied and baked on the inside of the closures.
The invention also relates to closures for packaging containers with which a sealing composition has been applied and baked on the inside, and also packaging containers having said closures.
The purpose of the various packaging materials is the hermetic sealing of the packaged material against environmental influences, specifically also under extreme conditions, such as prevail, for example, during heat sterilization of foodstuffs. In order to ensure this insulation of the packaged materials from the environment, suitable sealing compositions are introduced into lids and closures with which the packaging containers are closed. Commercially, that is to say economically, satisfactory sealing compositions for closures must have a number of critical properties, as a result of which they are highly specialized materials and compositions.
Furthermore, the required properties of the sealing compositions are also determined by the intended use of the packaging.
Thus in the case of foodstuffs packaging it is in particular the stability of the sealing compositions towards the packaged materials during the sterilization or pasteurization and also the storage, which can often extend over a period of several years, of the packaged foodstuffs which is of importance. In the case of industrial packaging, the packaged materials are often chemically highly reactive or aggressive and the sealing compositions must also be able to withstand these. Usually the sealing compositions used for closures and lids of packaging made of glass and metal are sealing compositions consisting of plasticizer-containing PVC plastisols, such as are described, for example, in DE-AS 20 03 693 in the case of closures for glassware.
The PVC plastisols used as sealing composition as a rule consist of a polyvinyl chloride, which can be mixed to a paste and which is distinguished in particular by a defined swelling capacity in the plasticizer, one or more plasticizers and optionally fillers, stabilizers, pigments and polyvinyl chloride processing auxiliaries.
The formulation of plasticizer-containing PVC plastisols, their production and processing is described extensively in K. Weinmann, Beschichten mit Lacken und Kunststoffen, (Coating with varnishes and plastics), 1967, Verlag W.A. Colomb, Stuttgart.
It is known that under the influence of the packaged materials, in particular as a result of fatty and oily substances, and under thermal stress (pasteurization, sterilization) it is, in principle, not possible in the case of such PVC sealing compositions to prevent plasticizer migration from the sealing composition and also incipient dissolution and swelling of the sealing composition in the case of solvent-containing packaged materials.
The degree of plasticizer migration can exceed regulations in foodstuffs legislation which are currently valid and under discussion. Furthermore, under certain circumstances the plasticizer migration causes a loss of vacuum in the case of pasteurized and sterilized packaging and also a loss of solvents as a result of an increased gas permeability in the case of industrial packaging. In the case of industrial packaging, in principle the problem also exists of the contamination of the packaged materials as a result of the plasticizer migration and incipient swelling or dissolution of the polyvinyl chloride. A further disadvantage of these sealing compositions is that the disposal of PVC-containing waste is becoming increasingly problematical and cost-intensive.
In addition to the PVC sealing compositions customarily employed, sealing compositions based on polyurethane are, however, also known. Thus, for example, in U.S. Pat. No. 3,971,785 and in GB Patent 1,374,745 sealing compositions for packaging containers are described which contain--optionally blocked--polyisocyanate prepolymers and carbon dioxide-bloc
Krause Siegfried
Nussen Peter
BASF Lacke & Farben Aktiengesellschaft
Nold Charles R.
Sabourin Anne Gerry
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