Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
1999-05-11
2002-02-19
Wu, Shean C. (Department: 1756)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C252S400240, C252S400520, C252S400530, C252S400620, C524S327000, C524S368000, C524S377000, C524S436000, C524S450000
Reexamination Certificate
active
06348164
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing shelf stable liquid overbased calcium carboxylates and mixed metal stabilizers containing the overbased calcium carboxylate and a metal carboxylate of zinc, cadmium or tin. The shelf stable mixed metal stabilizer compositions are used as stabilizers for halogen-containing polymers such as polyvinyl chloride (PVC).
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.
Notwithstanding the state of the art as exemplified by the above patents, there is a need for further improvements in making shelf stable compositions of calcium carboxylates and in methods for their use in stabilizing halogen-containing polymers.
SUMMARY OF THE INVENTION
The present invention relates to a process for making a shelf stable liquid overbased calcium carboxylate and a mixed metal stabilizer composition of (a) an overbased calcium carboxylate/carbonate and (b) a metal carboxylate. The metal carboxylate is preferably selected from the group of zinc, cadmium and tin fatty acid salts. The process involves preparing a reaction mixture containing a basic calcium carboxylate/carbonate under controlled temperature conditions with a mixture of alcohol and phenolic promoters to make a stable liquid. The stable liquid is then added to the metal carboxylate to provide the shelf stable mixed metal stabilizer composition.
The overbased calcium carboxylate/carbonate is made by reacting a basic calcium compound, a carboxylic acid, a phenol/alcohol promoter mixture and carbon dioxide to produce a stable liquid. The temperature conditions of the reaction mixture must be controlled up to a temperature of about 80° C., preferably in the range of about 15° C. to about 80° C., to produce a stable liquid. Above about 80° C., the reaction stalls and the desired stable liquid product is not obtained. Thereafter, the stable liquid is added to a metal soap stabilizer selected from the group of zinc, cadmium and tin carboxylates to provide a shelf stable mixed metal stabilizer composition.
The liquid overbased calcium carboxylate/carbonate may be first treated with an organic phosphite to react with any phenolic color-producing component to improve its color as disclosed in U.S. Pat. No. 5,859,267, and this application in its entirety is incorporated herein by reference. As disclosed in that patent application, organic phosphites suitable for use include various diorganic phosphites and triorganic phosphites to react with color species which may be produced by or in conjunction with the phenol.
A number of benefits are obtained by the inventive process over the prior art methods. Improvements in shelf stability of liquid overbased calcium carboxylates are achieved. Also, shelf stable mixed metal stabilizer systems of an overbased calcium carboxylate/carbonate and metal soap stabilizers are obtained. For example, enhanced shelf stability for the liquid overbased calcium carboxylates and mixed metal stabilizer compositions of this invention have been demonstrated over presently commercially available products. Whereas, in contrast, presently available liquid overbased calcium carboxylates exhibit an early development of turbidity, the liquid compositions of this invention remain stable over extended periods of time. Therefore, they allow easy handling, storage and filtration. When the mixed metal stabilizer systems containing the liquid calcium carboxylates are employed in vinyl halide polymers, they exhibit better compatibilities with improvements in thermal stability, clarity and plate out.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. Shelf Stable Liquid Overbased Calcium Carboxylate
Highly overbased calcium carboxylate is prepared by reacting calcium hydroxide with oleic acid in the presence of a mixture of alcohols and alkyl phenol followed by bubbling carbon dioxide through the reaction mixture. The product contains about 13-14% calcium. This product, when combined with other stabilizer additives, for example zinc carboxylate, phosphite, anti-oxidant, &bgr;-diketones, etc., produced a s
Baker Paulette
Khattar Rajesh
Labovitz Benjamin Paul
OMG Americas, Inc.
Wood Herron & Evans L.L.P.
Wu Shean C.
LandOfFree
Process for improving shelf stability of liquid overbased... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for improving shelf stability of liquid overbased..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for improving shelf stability of liquid overbased... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971682