Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-02-12
1998-03-10
Morgan, Kriellion S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524357, 524399, 524400, 524425, 524432, 524433, 524436, C08K 318, C08K 504, C08K 509
Patent
active
057262349
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a stabilised PVDC-containing PVC, preferably a PVC recyclate, as well as to a process for stabilising such polymers.
Copolymers based on vinylidene chloride (PVDC), typically comprising vinyl chloride, acrylonitrile, acrylates or ethylene as comonomers, are important coating materials as barrier layers for films (PVC films) for packaging food, pharmaceuticals and other substances. This barrier layer is intended to reduce file permeability of the packaging film e.g. for water, oxygen, fats, gases and aromatic substances. Further details concerning PVDC may be found in H. Domininghaus, Die Kunststoffe und ihre Eigenschaften, VDI-Verlag, D sseldorf, 4th ed., 1992, pages 219ff and in M. C. Patterson and D. L. Dunkelberger, Additives for Processing Rigid PVDC Copolymers, J. of Vinyl Technology, March 1994, Vol. 16, pages 46-51.
The recycling of the multilayer films, which may also be combined with other films, e.g. aluminium foils, and their reuse for processing to new products, typically by extrusion and injection moulding (in particular at a processing temperature above 170 C.), give rise to problems resulting from degradation and discoloration (HCl evolution, corrosion problems), even at very low concentrations of PVDC. The standard PVC stabilisers based, for example, on Ca/Zn, do not effect sufficient stabilisation.
U.S. Pat. No. 5,075,355 discloses a process for the stabilisation of recycled PVDC-containing films. In addition to the use of a carrier polymer and a pyrophosphate, said process requires the use of a metal hydroxide complex of the hydrotalcite type.
Accordingly, it is the object of this invention to meet the continuing need for the provision of stabilised PVDC-containing PVC, preferably a PVC recyclate, which may be used for recycling without marked discoloration and/or while preserving the mechanical properties in an economic and technically feasable manner.
It has now been found that it is possible to stabilise PVDC-containing PVC, preferably a PVC recyclate, in simple and economic manner with an inorganic compound of the metal oxide, metal hydroxide or metal carbonate series against thermal-oxidative degradation during processing and subsequent use.
The invention relates to stabilised PVDC-containing PVC, preferably a PVC recyclate, comprising as polymer at least 50% by weight of polyvinyl chloride (PVC) and 0.05-50% by weight of PVDC and additionally comprising at least one inorganic compound of the series of the metal oxides, metal hydroxides or metal carbonates.
Preferred stabilised PVDC-containing PVC, in particular a PVC recyclate, is that comprising as polymer at least 80% by weight of polyvinyl chloride (PVC) and 0.05-20% by weight of PVDC and particularly preferred stabilised PVDC-containing PVC, in particular a PVC recyclate, is that comprising as polymer at least 90% by weight of polyvinyl chloride (PVC) and 0.1-10% by weight of PVDC.
The polymers stabilised according to the practice of this invention are distinguished by excellent colour stability and exhibit only minor tendency to striation when injection moulded.
The PVDC-containing PVC recyclate consists, for example, of film waste from the production of multilayer films, or also of film blends from useful material collections.
The recyclate may also contain minor amounts of foreign material such as paper, pigments, adhesives, adhesion promoters (e.g. EVA), foreign polymers (e.g. polyolefins), which are often difficult to remove. These foreign materials may also originate from contact with diverse materials during use or working up, typically paint components, traces of metal or also of water.
Within the scope of this invention PVC will also be taken to mean copolymers or graft polymers of PVC with polymerisable compounds such as acrylonitrile, vinyl acetate or ABS, which polymers may be suspension, mass or emulsion polymers. However, PVC does not embrace copolymers with vinylidene chloride. PVC is preferably in the form of a suspension polymer, a mass polymer and an emulsion polymer.
Preferred
REFERENCES:
patent: 3481912 (1969-12-01), Vanderbilt et al.
patent: 4877821 (1989-10-01), Hall et al.
patent: 5075355 (1991-12-01), Hall et al.
Patterson, et al., Journal of Vinyl Technology, Mar. 1994, vol. 16, No. 1, pp. 46-51.
Herbst Heinz
Hoffmann Kurt
Pfaendner Rudolf
Ciba Specialty Chemicals Corporation
Hall Luther A. R.
Malia Victoria M.
Morgan Kriellion S.
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