Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-03-20
1998-08-04
Morgan, Kriellion S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 94, 524 98, 524102, 524424, 524430, 2524002, 252403, C08K 534, C08K 318, C08K 322
Patent
active
057894701
DESCRIPTION:
BRIEF SUMMARY
The invention relates to stabilized recycled plastics, as predominantly produced in the household, in commerce and also in industry and in valuable material collections, and to a stabilization process and to the use of a stabilizer.
The recycling of waste is a task of increasing importance for ecological reasons. The recycling of paper, textiles, glass or metals is already carried out on a large scale, whether by separate collection or by sorting of the refuse. The recycling of plastic waste and used plastics is also an increasing aim. Thermoplastics are generally processed by re-melting.
The plastic waste produced in the household, in commerce or in industry or the valuable plastic materials or used plastics obtained from collections or a return obligation, for example in specific sectors of industry, such as the automobile industry, electrical industry, agriculture or the packaging industry, predominantly comprises thermoplastics based on polyolefins, styrene polymers, polyvinyl chloride or polyesters.
These used plastics, which may constitute valuable raw materials, can be obtained either as a single type or as a mixture. Single-type plastic waste can be generated directly during production of plastic parts or obtained by separate collections or sorting.
On the other hand, the recycling of used plastic frequently means the use of a mixture of different types of plastic. Known industrial separation methods, for example hydrocyclone separation, mostly give only moderately clean fractions of various plastic mixtures, for example a polyolefin mixture.
The post-stabilization of recycled plastics is disclosed, for example, in WO 94/07946, WO 94/07950 and WO 94/07951. The main proposal here is to use compounds from the group consisting of the phosphites and/or sterically hindered phenols.
For the stabilization of recycled high-density polyethylene, P. Vink, R. T. Rotteveel and J. D. M. Wisse in Polymer Degr. and Stability, Issue 9, p.133 (1984) studied various stabilizers from the classes of the phosphites, hindered phenols, benzotriazoles, hindered amines and phosphonites.
These authors also indicated that the recyclates must be re-stabilized. Although the plastics have mostly been treated originally with stabilizers against thermooxidative and in some cases also against photooxidative degradation, these stabilizers are lost during use of the plastics, during storage of the waste and during processing of the recyclates, in some cases due to migration, extraction or by degradation. In addition, a recycled plastic generally differs structurally and also chemically from a new plastic as a consequence of the prior use or due to storage and processing; for example, initiator points (hydroperoxides, carbonyl groups etc.) for oxidative attack may already have formed due to oxidation. An additional adverse effect on the ageing behaviour can be due to foreign substances, for example paper or adhesives. These foreign substances can also originate from contact with diverse substances during use or processing, for example paint components, printing inks, wood, traces of metal, initiator residues or traces of water. A recycled plastic therefore requires, for example, a relatively large amount of stabilizers or alternatively stabilizers which take into account these particular circumstances. The difficulty of finding suitable stabilizers is due to the specific type of previous damage/impurities, which may have taken place over an extended period.
The stabilization of a plastic mixture is also a difficult task, since each type of plastic makes specific requirements of the stabilizers. Thus, for example, completely different stabilizers are used for vinyl chloride polymers than for polyolefins or styrene polymers.
Owing to previous damage and impurities, recyclates also have a modified solution behaviour vis-a-vis additives. For example, an increase in the concentration of polar additives through dissolution in polar components can be expected, which adversely affects the ageing stability as a whole and means that a complex
REFERENCES:
patent: 4442250 (1984-04-01), Cantatore
patent: 5004759 (1991-04-01), Muttterer et al.
patent: 5198546 (1993-03-01), Borzatta et al.
patent: 5298540 (1994-03-01), Pauquet et al.
Derw. Abst. 91-269006.
Herbst Heinz
Hoffmann Kurt
Masina Franca
Pfaendner Rudolf
Sitek Franciszek
Ciba Specialty Chemicals Corporation
Hall Luther A. R.
Malia Victoria M.
Morgan Kriellion S.
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