Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-06-20
1999-01-12
Morgan, Kriellion S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524118, 524119, 524120, 524126, 524153, 523 46, 25240021, 25240024, 25240052, 25240061, C08K 549, C08K 553, C08K 1532
Patent
active
058591028
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the stabilization of PVDC-containing polyolefin mixtures, in particular recyclates, and to the stabilizer mixtures which can be used for this purpose.
Copolymers based on vinylidene chloride (PVDC), for example with vinyl chloride, acrylonitrile, acrylates or ethylene as comonomers, are used as coating materials and films as a barrier layer in the packaging of foods, pharmaceuticals and other products in order to achieve impermeability, for example to water and oxygen, fats, gases and flavours. Further information on PVDC is given in H. Domininghaus "Die Kunststoffe und ihre Eigenschaften", VDI-Verlag, Dusseldorf, 4th Edn., 1992, pages 219ff.
The recycling of such materials, which are generally in the form of laminates (multilayer films), usually in combination with polyolefins, such as LDPE (high-pressure polyethylene), HDPE and PP (polypropylene), and their conversion into new products, for example by extrusion and injection moulding, causes problems, even at very low PVDC concentrations, due to decomposition and discoloration and thus unsatisfactory mechanical properties. A corresponding situation applies to the processing of film mixtures from collected valuable materials, which can contain PVDC, for example as a coating on a film, which in general cannot be separated out by physical methods.
U.S. Pat. No. 5,075,355 describes a process for the stabilization of recycled PVDC-containing films. In addition to the use of a supported polymer and a pyrophosphate, the process requires a metal hydroxide complex of the hydrotalcite type.
Other ways of stabilizing PVDC-containing polymers are described in EP-A 0 510 800, U.S. Pat. No. 5,286,424 and EP-A 0 604 136.
Thus, there continues to be a demand, and this is the object of the present invention, for the provision of a process which enables the processing of PVDC-containing plastic mixtures, predominantly comprising polyolefins, without significant discoloration and/or with retention of the mechanical properties in an economical and technically feasible manner.
It has now been found that PVDC-containing plastic mixtures, in particular recyclates, can be stabilized in a simple and economical manner against thermo-oxidative degradation during processing and subsequent use by a mixture of an organic phosphite or phosphonite and a metal salt of a fatty acid.
The invention relates to a process for the stabilization of a plastic mixture predominantly comprising polyolefins and 0.05-20% by weight PVDC, which comprises adding (a) at least one organic phosphite or phosphonite and (b) at least one metal salt of a fatty acid to this mixture.
The plastic mixtures to be stabilized are, for example, film offcuts generated in the production of multilayer films, films coated with an aqueous PVDC dispersion or film mixtures from collected valuable materials. However, fresh plastic mixtures can also be employed in the process.
These plastic mixtures comprise predominantly polyolefins. Preferred plastic mixtures comprise 80-99.95% by weight, in particular 95-99.9% by weight, of polyolefins and 0.05-20% by weight, in particular 0.1-5% by weight, of PVDC, it also being possible for the polyolefins to be in the form of mixtures. Small amounts of polymers such as polystyrene, PET, PVC or polyamide can also be present. Furthermore, the term polyolefins also includes copolymers such as EVA. It may furthermore be expedient, in particular in the case of polyolefin mixtures, to add compatibility improvers (compatibilizers).
In particular, the invention relates to the stabilization of recycled plastic mixtures of said composition. Recycled plastic mixtures may also contain small amounts of foreign materials, for example paper, pigments and adhesives, which are frequently difficult to remove. These foreign materials can also originate from contact with diverse substances during use or treatment, for example fuel residues, paint residues, traces of metal, initiator residues or traces of water.
In the plastic mixtures, the dominant polyolefins are usua
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Herbst Heinz
Hoffmann Kurt
Pfaendner Rudolf
Ciba Speciality Chemicals Corporation
Crichton David R.
Hall Luther A. R.
Malia Victoria M.
Morgan Kriellion S.
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