Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-03-03
2002-06-25
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S497000
Reexamination Certificate
active
06410614
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of thermoplastic polymeric materials containing titanium dioxide (TiO
2
). In preferred exemplary embodiments, the present invention relates to synthetic filament containing TiO
2
and to methods for incorporating TiO
2
in melt flows of filament-forming thermoplastic polymeric materials prior to melt-spinning to form synthetic filaments therefrom.
BACKGROUND OF THE INVENTION
The incorporation of additives, including TiO
2
, into thermoplastic polymeric host materials is known. TiO
2
is commonly added to fibers and other thermoplastic materials as a delusterant. Thus, the art has conventionally incorporated colorants, stabilizers, delusterants (such as TiO
2
), flame retardants, fillers, antimicrobial agents, antistatic agents, optical brighteners, extenders, processing aids and other functional additives into polymeric host materials in an effort to “engineer” desired properties of the resulting additive-containing polymeric host material. Such additives are typically added any time prior to shaping of the polymeric material, for example, by spinning or molding (e.g., extrusion, injection, or blow-molding) operations.
The incorporation of TiO
2
in filaments formed by melt-spinning a polymeric material has presented unique challenges. For example, the amount of TiO
2
is typically dispersed in a concentrate in the form of a solid chip which is added to the polymeric material. The concentrate usually is composed of the TiO
2
in a carrier. It is important for optimal performance that the carrier is compatible with the host thermoplastic material. It is also important that the concentration of the TiO
2
is sufficiently high to impart the intended result (such as white color, delustering, etc.) but not so high as to interrupt the spinning process, especially when the carrier is not compatible with the thermoplastic host.
Liquid (i.e., paste) TiO
2
concentrates are known. Commercial white pastes are typically prepared with mineral oil as the carrier. Mineral oil does not disperse well into polar polymers like nylons during extrusion. (As used herein, the term “paste” refers to a concentrate which has a smooth, viscous, but flowable or pumpable, nature at room temperature.)
U.S. Pat. No. 3,846,360 to Needham describes color concentrates, including TiO
2
concentrates, that comprise a least a minor amount of certain solution-polymerized hydrocarbons and which allegedly exhibit compatibility in a wide range plastic materials. Exemplary concentrates contain TiO
2
, a carrier (elastomeric), an extender oil (petroleum oil), and an optional binder, such as homopolymers or copolymers of monoolefins.
U.S. Pat. No. 4,168,180 to Peabody describes pigment concentrates which contain by weight about 35 to about 60% of organic pigments and about 5 to about 55% of certain low molecular weight, friable polymers of styrene and/or alkyl substituted styrenes; or about 45 to about 90% of inorganic pigments (such as TiO
2
) and about 5 to about 55% of the friable polymer. A dispersing agent is optional and, if present, the weight ratio of polymer to dispersing agent is at least 1. Suitable dispersing agents include caprolactone.
U.S. Pat. No. 4,388,425 to Strehler describes TiO
2
concentrates that are formulated for incorporation into caprolactam or polycaprolactam melt. The concentrate contains TiO
2
and caprolactam, and is described as omitting water. However, up to 10% by weight of water is disclosed as being present.
U.S. Pat. No. 4,474,681 to Belde et al. describes an aqueous suspension of TiO
2
and caprolactam which is useful for delustering polycaprolactam.
U.S. Pat. No. 4,710,535 to Perrot et al. describes concentrates (“masterbatches”) for delustering polyamides which contain a copolyamide of hexamethylene adipamide and caproamide units. Anatase TiO
2
coated with silica and alumina and treated with polydimethylsiloxane is present in the masterbatch as the delustering agent.
U.S. Pat. No. 5,393,510 to Blumel et al. describes a thixotropic TiO
2
suspension. The suspension contains TiO
2
at a 75% by weight or greater. A dispersing agent is also present as about 0.1 to 5% by weight of the aqueous suspension. The suspension is taught to have particular application to the paper making industry.
U.S. Pat. No. 5,837,049 to Watson et al. describes a masterbatch of an inorganic solid (such as TiO
2
). The inorganic solid is coated with certain alkylphosphonic acids or esters of alkylphosphonic acid. The Treated inorganic solids may be used in a masterbatch where the carrier is one of several listed polymers but, preferably, polyethylene or polypropylene.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high solids TiO
2
concentrate that is compatible with nylon.
Another object of the present invention is a TiO
2
concentrate that is suitable for use in thermoplastic fibers.
Yet another object is a to provide a TiO
2
concentrate which is economical to make compared to existing concentrates.
Still another object of the present invention is to provide a TiO
2
concentrate which dispersed readily into the host polymer.
A further object of the present invention is process for making a TiO
2
concentrate which concentrate has a good particle size distribution without requiring milling.
The present invention achieves these and other objectives in a composition consisting essentially of up to about 70 wt. % titanium dioxide, a carrier that is a liquid below about 25° C. and which has ester functionality, from 0 to about 5 wt % water, and optionally, one or more dispersants.
The present invention is embodied also in a method of making a titanium dioxide concentrate by TiO
2
having a mean particle size not exceeding 6 microns with carrier that is a liquid below about 25° C. and which has ester functionality and optionally, one or more dispersants. In this method milling is not necessary, and it is preferred to not mill the concentrate as doing so is unnecessary and would merely complicate the production process.
In another embodiment, the invention involves a method of making filaments containing titanium dioxide by supplying a melt flow of a melt-spinnable polymeric host material to spinneret orifices; incorporating within at least a portion of the melt flow of polymeric host material upstream of the spinneret orifices, a concentrate consisting essentially of titanium dioxide dispersed in a polymeric carrier that is a liquid at about 25° C. and which contains less than 5% by weight water and, optionally, a dispersant, to form a mixture of the polymeric host material and the titanium dioxide; and then extruding a melt of the mixture through the spinneret orifices to form filaments containing titanium dioxide. Again, it is not necessary, or desirable to mill the concentrate before adding it to the polymeric host material.
The invention also involves a method of making titanium dioxide containing polymer compositions in general. This method involves introducing a concentrate consisting essentially of up to 60% by weight titanium dioxide; a polymeric carrier that is a liquid at about 25° C.; from 0 to about 5% water; and, optionally, a dispersant, into a polymeric host material; and dispersing the concentrate into the polymeric host material to form a titanium dioxide-containing polymer composition.
These and other aspects and advantages of this invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
To promote an understanding of the principles of the present invention, descriptions of specific embodiments of the invention follow and specific language describes the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and that such alterations and further modifications, and such further applications of the principles of the invention as discussed are contemplated as would normally occur to one
Denney Raymond L.
Jones Frank R.
McIntosh Stanley A.
BASF Corpotation
Michl Paul R.
Nixon & Vanderhye P.C.
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