Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-08-28
2003-07-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S297000, C524S447000, C106S487000, C264S177200, C264S211000, C264S211210, C264S328180
Reexamination Certificate
active
06596802
ABSTRACT:
FIELD OF THE INVENTION
This invention belongs to the field of thermoplastic resins. In particular, it relates to nanocomposite compositions comprising plasticizers and their use in polymer processing.
BACKGROUND OF THE INVENTION
The most common means of producing a finished article, such as a film or injection molded part, from a plasticized thermoplastic resin consists of the following steps: (1) mixing the molten thermoplastic with the plasticizer or plasticizers (2) isolating this mixture as a solid, usually in the form of pellets and (3) supplying this solid mixture to a second thermal process, such as extrusion or injection molding, in order to convert the plasticized thermoplastic material into the finished article. Such a process is described in U.S. Pat. No. 4,889,673, U.S. Pat. No. 5,362,778, and in European Patent Application Publication No. 0413972A2.
U.S. Pat. No. 3,667,733 describes a device that can be placed immediately before the thermal conversion process to produce the finished article; the purpose of this device is to circumvent the need for a separate compounding step. This patent recognized the expense associated with the compounding step but the device claimed in this patent would require considerable capital to build and install. This patent does state, “that it is, in effect, impossible to plasticate in single screw machines”.
The use of organoclays as thixotropic agents for liquids is also known. Organoclays are used in solvent-borne and water-borne coatings for this reason. They are also used in combination with hydrocarbons to make “inorganic gel” greases. The use of organoclays to deliver active ingredients to plastics has been described in European Patent Application Publication No. EP0846660A2 and U.S. Pat. No. 5,721,306. EP 0846660A2 describes the use of clay platelets that have been “intercalated with long chain monomers” and “combined with a polar organic solvent” to plasticize thermoplastic or thermosetting polymers. No part of this patent application suggests that the inventors recognized the ability to use plasticizers that had been modified with organoclays to eliminate the need for a separate compounding step as provided by the present invention as described below. This patent application also teaches that “the exfoliated platelets are free to move throughout the polymer matrix” and when mixed with a carrier or solvent, “maintain viscosity and thixotropy of the carrier material”. Such a consideration does not hold for solids at room temperature such as the plasticizers that are the subject of this invention. Finally, the intercalates taught in EP 0846660 are designed to contain at least about 4% water, by weight.
SUMMARY OF THE INVENTION
One of the issues faced in the commercialization of highly plasticized thermoplastic formulations is the need to compound the plasticizer with the thermoplastic resin prior to processing the formulation into a finished film, sheet or molded part. This invention describes the use of organoclays as additives to plasticizers to provide a plasticizer composition, to allow the mixing of the plasticizers with the thermoplastic resins in the same process used to convert the resin formulation to finished product. The practice of this invention eliminates the need for a preliminary compounding step prior to extrusion or molding. The preferred plasticizers in this invention are those that are solids at room temperature. Benzoate esters are one class of these solid plasticizers and employed below in the examples. The preferred organoclays in this invention are those based on sodium montmorillonite modified by the exchange of the sodium ion with an organic ammonium ion. In a preferred embodiment, when the plasticizer has sufficient organoclay to have an inorganic content of about 10 wt %, the plasticizer composite can be formed into pellets. These plasticizer pellets can then be blended with thermoplastic resin pellets and the physical blend may then be directly extruded into film or sheet, or can be injection molded into parts.
This invention also provides the use of solid ester plasticizers that have been modified with quaternary ammonium layered smectite clays thereby circumventing the need for a separate compounding step to obtain plasticized thermoplastic products. Thus, the plasticizer that is modified with organoclay and the thermoplastic can be added to the film/sheet extruder or injection-molding machine to make the final product in one step.
As used herein, the terms set forth below will have the following meanings:
“Layered Material” shall mean an inorganic material such as a smectite clay mineral, that is in the form of a plurality of adjacent, bound layers and has a thickness, for each layer of about 3 angstroms to about 50 angstroms, preferably about 10 angstroms.
“Platelets” shall mean individual layers of the Layered Material.
“Gallery” shall mean the space between two adjacent Platelets.
A “clay” is defined here as a swellable layered clay material, such as the smectite clay mineral montmorillonite. An “organoclay” is defined here as a clay that has been ion exchanged with an onium ion.
DETAILED DESCRIPTION OF THE INVENTION
Thus, in a first embodiment of the present invention, there is provided a plasticizer composition comprising a plasticizer and an organically-modified clay, wherein said composition contains less than 4%, preferably less than 1% water by weight. Moreover, virtually any water which is present will be “bound” water. That is, it will exist as part of the crystal structure of the clay and requires temperatures in excess of 250° C. to be driven off. The plasticizer compositions of the present invention are useful as processing aids for thermoplastic resins and can be added directly to the thermoplastic resin during the thermal extrusion or molding process to provide plasticized finished articles.
In a second embodiment, the present invention provides a method for blending a plasticizer with a thermoplastic polymer to form a plasticized polymer composition, comprised of about 3 to about 80 weight percent of plasticizer, preferably about 7 to 60 weight percent plasticizer, and most preferably about 10 to about 40 weight percent plasticizer, which comprises
(a) blending at least one plasticizer at or above the melt or softening point temperature of said plasticizer with at least one organically-modified clay to form a plasticizer composition; followed by
(b) melt blending said composition with a thermoplastic polymer.
In the practice of this invention, solid plasticizers are combined with organically modified, layered smectite clays to form plasticizer/clay composites that may be combined with a thermoplastic resin in a film/sheet extruder or injection-molding machine. The modification with the organically modified clay allows the plasticizer to be combined with the thermoplastic resin without having to go through a separate compounding step. There is considerable cost savings from eliminating the capital equipment to perform the compounding step and avoiding the energy requirement for melting the thermoplastic resin in order to combine it with the plasticizer, only to resolidify the plasticized thermoplastic resin and then melt it a second time to extrude the film or mold the product. There is also an increase in product quality because the degradation caused by going through a compounding process at high temperatures is avoided. Thus, in large measure, the molecular weight of the polymer will be preserved and the color formation due to polymer degradation will be avoided. Furthermore, any difficulty in drying a plasticized resin, such as blocking or loss of plasticizer, is avoided when the formulation is converted to the finished product without an intermediate compounding step.
Preferred swellable layered clay materials include natural, synthetic, and modified phyllosilicates. Illustrative of such clays are smectite clays, such as montmorillonite, bentonite, saponite, and hectorite, synthetic clays, such as synthetic hectorite, and modified clays, such as fluoronated montmorillonite. P
Gilmer John Walker
Owens Jeffrey Todd
Piner Rodney Layne
Sand Irving Daniel
Eastman Chemical Company
Graves, Jr. Bernard J.
Middlemas Eric D.
Szekely Peter
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