Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Reexamination Certificate
2001-02-23
2004-11-23
Anthony, Joseph D. (Department: 1714)
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
C252S400240, C252S182290, C252S407000, C264S109000, C264S115000, C264S117000, C264S118000
Reexamination Certificate
active
06821456
ABSTRACT:
TECHNICAL FIELD
This invention relates to the provision of improved polymer additives—i.e., additives which are for use in polymers—where the additives are in granular form such as pellets.
BACKGROUND
A wide variety of particulate additives are used in thermoplastic polymers in order to improve the properties of the polymer and/or the utility of products formed from such polymers. Included among the types of particulate polymer additives used are, for example, such substances as antioxidants, flame retardants, flame retardant synergists, thermal stabilizers, UV stabilizers, nucleating agents, acid neutralizers, polymer clarifiers, and the like. In order to facilitate blending operations it is desirable to provide additives in a granular form because many additives can cake up or form rat-holes in feed hoppers, and/or feed unevenly through metering equipment. Moreover, certain additives, especially finely-divided additives, often used in the manufacture of polymers, such as high melting nucleating agents and inorganic acid neutralizers can create hazardous airborne dusts during handling and blending operations.
Various methods for converting polymer additives into granular forms have been described heretofore. Such methods include melting at least one component of a dry blend of additives to thereby bond the particles of the blend together, or including in a blend of the additives a special component such as a wax, fatty acid, a compound containing a fatty acid chain or fatty alcohol chain, or metal salt of a fatty acid, and then converting the dry blend into granules or pellets by compacting or milling the blend. All such methods require use of extraneous components to serve as binders, which components are not necessarily desired as components in the finished polymer composition, and which may actually interfere with product specifications of the polymer producer. Moreover, use of some previously used binders can detract from performance properties of the host polymer. And, in some cases the scope of the additives that can be converted into granules or pellets is quite specific and thus not of widespread utility.
Some of these prior developments are described, for example, in U.S. Pat. Nos. 4,957,956; 5,240,642; 5,597,857; 5,844,042, 5,846,656; and 6,033,600.
It would be of considerable advantage if a way could be found of converting a blend of two or more particulate polymer additives into granular form such as pellets without depending upon melting a component of the blend or the binding action of a special binder component included in the powder blend such as a wax, a fatty acid, a compound containing a fatty acid chain or fatty alcohol chain, or metal salt of a fatty acid. It would be of even greater advantage if the scope of the blends of particulate additives converted into granules such as pellets could be broadened so that it is unnecessary to rely on only certain specific combinations of additives that produce granules.
This invention is deemed to accomplish these objectives in an efficient and effective manner.
BRIEF SUMMARY OF THE INVENTION
This invention makes it possible to provide granules of particulate polymer additives without use of conventional binder components and without relying on substantial melting of one or more components of the additive blend. In addition the invention is deemed to possess widespread utility in that a very large number of particulate polymer additives can be used in forming the granular additive compositions of this invention. Thus not only is it unnecessary to be restricted to use of specific combinations of additives but in addition, all of the components can be selected from components which are widely-used in thermoplastic polymers. This in turn makes it possible to avoid use of particular components which would be undesired or undesirable in the finished polymer product in which the granular additive composition is employed.
Thus, in one of its embodiments this invention provides a polymer additive composition consisting essentially of granules of dry compacted particles from the following components:
(a) at least one particulate sterically-hindered phenolic compound, and
(b) one or more particulate polymer additives other than a sterically-hindered phenolic compound,
wherein the particles in said granules are held interbonded one to another in compacted dry granular form exclusively or substantially exclusively by interbonding with in situ desolvated surfaces of particles of one or more components of (a), and optionally by interbonding with in situ desolvated surfaces of particles of one or more components of (b). In other words, particles in these compositions are held together in compacted dry granular form exclusively or substantially exclusively by desolvated, dried, formerly at least partially-solvated particles of one or more components of (a), and optionally by desolvated, dried, formerly at least partially-solvated particles of one or more components of (b).
In another of its embodiments this invention provides a process of producing a compacted particulate polymer additive composition in a dry granular form, which process comprises:
1) forming a paste from (a) at least one particulate sterically-hindered phenolic compound, (b) one or more particulate polymer additives other than a sterically-hindered phenolic compound, and (c) an inert organic processing solvent that can be temperature of (a) and (b);
2) compressing and shaping the paste while preventing or substantially preventing melting of solids used in forming the paste, to produce a wet compacted composition in granular form; and
3) drying said wet compacted composition in granular form by vaporizing said processing solvent therefrom to form the dried compacted particulate polymer additive composition in a granular form.
Typically a compression apparatus operated so as to prevent or substantially prevent melting of solids is used in conducting step 2) of the process.
An optional further step that may be used is to screen or otherwise classify the dried granular product mixture to separate from the granular product fine particles, if any, that may be present. Such fine particles may be recycled as a feed to the process.
Still another of the embodiments of this invention is a compacted particulate polymer additive composition in a dry granular form, formed by a process which comprises:
1) forming a paste from a substantially uniform mixture of (a) at least one particulate sterically-hindered phenolic compound, (b) one or more particulate polymer additives other than a sterically-hindered phenolic compound, and (c) an inert organic processing solvent that can be vaporized at a temperature below the lowest melting point or initial melting temperature of (a) and (b);
2) compressing and shaping the paste while preventing or substantially preventing melting of solids used in forming the paste, to produce a wet compacted composition in granular form; and
3) drying said wet compacted composition in granular form by vaporizing said processing solvent therefrom to form said additive composition in a dry granular form;
said additive composition having compressive hardness and physical integrity resulting from the particles in said granules being held interbonded one to another in compacted dry granular form exclusively or substantially exclusively by interbonding with in situ desolvated surfaces of particles of one or more components of (a), and optionally by interbonding with in situ desolvated surfaces of particles of one or more components of (b). In other words, the resultant composition has compressive hardness and physical integrity resulting exclusively or substantially exclusively from desolvated, dried, formerly at least partially solvated particles of (a), and optionally from desolvated, dried, formerly at least partially solvated particles of (b).
Other embodiments and features of this invention will be still further apparent from the ensuing description and appended claims.
FURTHER DETAILED DESCRIPTION OF THE INVENTION
As used herein, including the claims, the
Albemarle Corporation
Anthony Joseph D.
Spielman, Jr. Edgar E.
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