Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-02-17
2001-05-01
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S180000, C524S387000, C524S424000, C524S436000
Reexamination Certificate
active
06225387
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a stabilizer blend used to protect organic polymer compositions from the deleterious effects of heat during processing and from the effects of thermal degradation, and to the articles produced therefrom.
BACKGROUND OF THE INVENTION AND PRIOR ART
Halogenated flame-retardants are widely used in polymer compositions to impart flame-retardant properties. However, halogenated flame-retardants, and particularly those containing aliphatic halogen, are susceptible to deterioration or degradation during processing in an organic polymer or upon subsequent thermal aging of the polymer composition. Hydrohalide acids such as HCl or HBr, that are generated during the processing or aging history, can both autocatalytically degrade the halogen-containing flame retardant and catalytically degrade the organic polymer. The ensuing chain scission typically results in undesirable lowered melt viscosity and discoloration of the composition.
Many compounds and compositions have been used to stabilize halogen-containing organic polymers during processing, during subsequent aging, and during recycling. Examples include organotin mercaptides, sulfides, and carboxylates, mixed metal stabilizer systems such as barium/cadmium, barium/zinc, and calcium/zinc, lead-based stabilizers such as sulfates, stearates, carbonates, phthalates, and phosphites, and metal-free systems based on aminocrotonic acid esters. These are discussed in Plastics Additives Handbook edited by R. Gachter and H. Muller, Hanser Publishers, 3rd Edition, pp. 281-300, hereby incorporated by reference.
Costabilizers are also used. They do not possess a thermo-stabilizing effect, but improve the effectiveness of one or more primary stabilizers. Examples include organic phosphites, epoxy compounds, polyols, phenolic antioxidants, 1,3-diketones, dihydropyridine, and betaketocarboxylic acid esters. These are discussed at pages 300-308 of the Plastics Additives Handbook referenced above, hereby incorporated by reference.
The prior art discloses the use of these stabilizers and costabilizers in single-stabilizer and multi-stabilizer systems. For example, U.S. Pat. Nos. 4,089,912, 4,183,846, 4,217,258, 4,219,605, 4,532,287, 4,558,083, 4,593,059, and 4,963,606, hereby incorporated by reference, disclose various systems containing dibutyltin maleate or other organotin compounds. U.S. Pat. Nos. 4,154,718, 4,299,759, 4,427,816, 5,106,898, 5,141,980, 5,216,058, and 5,234,981, hereby incorporated by reference, disclose systems incorporating hydrotalcite and similar stabilizer compounds.
Although these stabilizers have been known for many years, an improved solution to stabilizing flame-retarded polyolefin and polystyrene compositions is needed. Compounders prefer working at higher temperatures in order to increase their throughput, and the increased emphasis on recycling requires working with feed streams containing a variety of additives. Both scenarios require a robust stabilizer system to protect the polymer composition.
SUMMARY OF THE INVENTION
One aspect of the present invention is to provide an improved thermal, process, and recycle-enhancing stabilizer blend that resists process instability, thermal degradation of the stabilizer, and resists thermal degradation of the organic polymer being thermally stabilized during processing and aging, and provides a polymer composition that is recyclable.
It is another aspect of the present invention to provide a thermal stabilizer and flame-retardant blend for organic polymers such that the organic polymer containing the thermal stabilizer and flame retardant has improved process stability, recyclability, and heat-age stability.
It is an additional aspect of the present invention to provide a stabilized organic polymer that has improved process stability, recyclability, and heat-age stability.
It is still a further aspect of the present invention to provide a stabilized halogenated flame-retarded organic polymer that has improved process stability, recyclability, and heat-age stability.
It is yet another aspect of the present invention to provide a finished article containing a stabilizer blend that provides new and unexpected stability to the article.
Accordingly, the present invention is a stabilizer blend comprising:
a) an acid scavenger, for example a hydrotalcite or an amorphous basic aluminum magnesium carbonate;
b) a heat stabilizer comprising an organotin compound; and
c) a polyhydroxyaliphatic costabilizer.
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Plastics Additives Handbook, edited by R. Gächter and H. Müller, Hanser Publishers, 3rd Edition, pp. 281-308.
Doumen Cindy Nancy
Hallenbeck Donald Robert
Prins Anne-Marie
Great Lakes Chemical Corporation
Hoke Veronica P.
Marshall O'Toole Gerstein Murray & Borun
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