Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
2002-03-15
2004-08-10
Anthony, Joseph D. (Department: 1714)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C252S400610, C252S407000, C252S182290, C554S156000, C554S157000
Reexamination Certificate
active
06773631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid overbased mixed metal stabilizer composition of calcium, barium and zinc (Ca/Ba/Zn) for stabilizing halogen-containing polymers. Shelf stable haze free liquids of overbased calcium carboxylates are used to provide a mixed metal ternary stabilizer of calcium, barium and zinc. The liquid overbased ternary system of Ca/Ba/Zn provides polymers such as polyvinyl chloride (PVC) with improvements in thermal stability, early color, plate-out resistance and clarity.
BACKGROUND OF THE INVENTION
The preparation of overbased calcium or barium salts of carboxylic acids, alkyl phenols, and sulfonic acids are disclosed in the following U.S. Pat. Nos. 2,616,904; 2,760,970; 2,767,164; 2,798,852; 2,802,816; 3,027,325; 3,031,284; 3,342,733; 3,533,975; 3,773,664; and 3,779,922. The use of these overbased metal salts in the halogen-containing organic polymer is described in the following U.S. Pat. Nos. 4,159,973; 4,252,698; and 3,194,823. The use of overbased barium salt in stabilizer formulations has increased during recent years. This is due, in the main, to the fact that overbased barium salts possess performance advantages over the neutral barium salts. The performance advantages associated with overbased barium salts are low plate-out, excellent color hold, good long-term heat stability performance, good compatibility with the stabilizer components, etc. Unfortunately, most of the overbased barium salts are dark in color and, while these dark colored overbased barium salts are effective stabilizers for halogen-containing organic polymer, their dark color results in the discoloration of the end product. This feature essentially prohibits the use of dark colored overbased barium salts in applications where a light colored polymer product is desired.
According to the teachings of U.S. Pat. No. 4,665,117, light colored alkali or alkaline earth metal salts are prepared where alkyl phenol is used as a promoter. However, alkyl phenol is also a major cause for the development of color in the final product. This problem is overcome by the use of propylene oxide which displaces the hydrogen of the phenolic hydroxyl group and thereby restricts the formation of colored species. However, there are disadvantages associated with this approach, principally due to the toxic nature of propylene oxide. Propylene oxide is classified as a possible carcinogen and laboratory animal inhalation studies have shown evidence of a link to cancer. Propylene oxide is also listed as a severe eye irritant, and prolonged exposure to propylene oxide vapors may result in permanent damage to the eye. Furthermore, propylene oxide is extremely flammable and explosive in nature under certain conditions. Propylene oxide boils at 94° F. and flashes at −20° F. As a result, extreme precautions are required to handle propylene oxide at the plant site. Special storage equipment is required for propylene oxide and other safety features are necessary. U.S. Pat. No. 4,665,117 describes the use of propylene oxide at 150° C. At this temperature, propylene oxide will be in the gaseous phase. Under these operating conditions, more than stoichiometric amounts of propylene oxide are required to carry the reaction to completion because propylene oxide will escape from the reaction mixture and this requires additional handling of the excess propylene oxide.
With the movement in the plastics industry to remove heavy metals, liquid calcium-zinc stabilizers are desirous, but not practical, as replacements for barium-cadmium or barium-zinc. Low metal concentrations, poor compatibility, haziness in clear products and plate out during processing in PVC have severely limited the universal acceptance of calcium based liquid stabilizer compositions. Problems are encountered in the stability of these compositions upon standing or storage. Storage stability is due to the incompatibility among the metal salts employed in the composition and is exhibited by increased turbidity, viscosity, or insoluble solids over time. As a result, the liquid calcium compositions are no longer homogeneous or readily pourable and must be specially treated in order to be used. U.S. Pat. No. 5,322,872 is directed to stabilized compositions of mixed metal carboxylates having improved storage stability. According to this patent, a complexing agent is added to the mixed metal carboxylate in order to improve shelf stability. Complexing agents disclosed in this patent include phosphines, phosphites, aromatic cyanides, aromatic hydroxy compounds, oximes and other compounds. U.S. Pat. Nos. 5,830,935 and 5,859,267 have also issued as directed to processes for improving basic metal salts and stabilizing halogen-containing polymers therewith.
Notwithstanding the state of the art as exemplified by the above patents, there is a need for further improvements in making compositions of overbased alkaline earth metal carboxylates and in methods for their use in stabilizing halogen-containing polymers.
SUMMARY
The present invention relates to liquid overbased mixed metal stabilizer compositions of calcium, barium and zinc (Ca/Ba/Zn) for a halogen-containing polymer. The invention described in application Ser. No. 09/861,393, filed May 18, 2001, relates to a shelf stable haze free liquid of an overbased alkaline earth metal carboxylate. The shelf stable liquids that were described in that application have now been found to provide a mixed metal stabilizer composition with barium and zinc having improved properties in the stabilization of halogen-containing polymers.
A number of benefits are obtained by the liquid overbased Ca/Ba/Zn stabilizer products of this invention. In particular, shelf stabilities are achieved with the overbased Ca/Ba/Zn liquids with the reduction of phenol and phenolic derivatives such as phenolic reaction products. This is an especially desirable advantage in view of the efforts of the trade to reduce or eliminate such phenolic products because of environmental concerns. In addition, enhanced shelf stabilities for the liquid overbased calcium fatty acid carboxylates and barium/zinc mixed metal stabilizer compositions of this invention have been demonstrated over presently commercially available products. In particular, presently available liquid mixed metal systems exhibit the development of turbidity or haze, whereas the liquid compositions of this invention remain stable over extended periods of time. Therefore, the shelf stable and preferably haze free liquids of this invention allow easy handling, storage and filtration. Furthermore, when the liquid overbased Ca/Ba/Zn ternary stabilizer systems are employed in vinyl halide polymers, they exhibit better compatibilities with improvements in thermal stability, early color, clarity and plate-out resistance.
The Ca/Ba/Zn ternary stabilizer systems are employed in polyvinyl chloride (PVC) compositions in amounts of from about 1 to about 5 parts of stabilizer, preferably about 2-3 parts, per 100 parts PVC.
The metal ratio of Ca/Ba/Zn in such systems is on the order of about 3:14:2, within a general range of about 0.5% to 3% Ca, about 4% to 8% Ba, and about 0.5% to 3% Zn to achieve the benefits of this invention.
The above advantages, benefits and further understanding of this invention will be apparent with reference to the following detailed description and preferred embodiments.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS
A. Shelf Stable Haze Free Liquids of Overbased Calcium Salts for Use In the Ca/Ba/Zn System
In one preferred form of the invention, a shelf stable haze free liquid of a calcium salt of a fatty acid is used to make the Ca/Ba/Zn ternary system. The liquid comprises
a calcium carbonate,
a calcium carboxylate of a fatty acid,
a liquid hydrocarbon, and
an aliphatic alcohol having at least 8 carbon atoms, with the liquid being preferably free of a phenol or a phenolic derivative such as a phenolic reaction product.
In another form of the invention, the calcium sulfate, sulfide or sulfite may be formed instead of the carbonate where the acid
Hackett Jeremy A.
Reddy James E.
Anthony Joseph D.
Hammond Group, Inc.
Wood Herron & Evans L.L.P.
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