| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 09.99 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 28.09.99 |
| PATENT TITLE |
Processibility and lacing resistance when silanized pigments are incorporated in polymers |
| PATENT ABSTRACT | White-pigmented polymers (particularly polyolefins such as polyethylene) containing white pigments treated with at least one silane or a mixture of at least one silane and at least one polysiloxane are disclosed to improve processibility in compounding and improve performance properties such as lacing resistance in a polymeric matrix |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 03.03.97 |
| PATENT REFERENCES CITED |
Modern Plastics--Special Buyers' Guide & Encyclopedia Issue for 1993. Debal Gupta, Prediction of Dispersion of Pigments in Thermoplastic Resins with the Help of an Extruder, Soc. Plast. Eng., Tech. Paper 25, pp. 311-318 (1979). David Williams, The Effect of Siloxane-additioned Titanium Dioxide Pigments on the Heat Sealing and Printing Properties of Low Density Polyethylene Film, Soc. Plast. Eng. Tech. Paper, 25, pp. 307-310 (1979). White Concentrates, Modern Plastics, vol. 68, No. 2, p. 90 (Feb. 1991). Stable TiO2 Pigment, Modern Plastics, vol. 68, No. 4, p. 96 (Apr. 1991). The Biggest Antec Ever Covers All the Bases, Modern Plastics, vol. 68, No. 6, pp. 54, 231 (Jun. 1991). Modified Heavy Metals Prosper, Despite Reformulation Trend, Modern Plastics, vol. 69, No. 9, p. 46 (Sep. 1991). Heavy-Metal Restrictions Promote Organic Replacements, Modern Plastics, vol. 69, No. 9, p. 58 (Sep. 1992). Handbook of Fillers for Plastics, edited by Harry S. Katz and John V. Milewski, Van Nostrand Reinhold, excerpted portions (1987). TiO2 in Plastics: A Balancing Act, Plastics Compounding, p. 44 (Nov./Dec. 1992). Dialog Alert DA001, Dialog File 319: Chem Bus. Newsbase (Aug. 1991). Ampacet in Concentrates, CMR (Oct. 1991). H. P. Schreiber, Pigment Dispersion in Thermally Modified Polyethylenes, Journal of Applied Polymer Science, vol. 39, pp. 465-470 (1990). J. Winkler, Influence of Surface Treatment on the Strength of TiO2 Agglomerates, Farbe & Lack 94, No. 4, p. 263 (1988). Meyer R. Rosen, Technological Review, From Treating Solution to Filler Surface and Beyong--The Life History of a Silane Coupling Agent, Journal of Coatings Technology, vol. 50. No. 644, pp. 70-82 (Sep. 1978). Edwin P. Plueddemann, Silane Coupling Agents, Additives for Plastics, vol. 1, pp. 123-167. Hans G. Volz, Gunther Kampf and Hans G. Fitzky, Surface Reactions on Titanium Dioxide Pigments in Paint Films During Weathering, Process in Organic Coatings, 2, pp. 223-235 (1973-1974). R. B. McKay, Pigment Dispersion in Apolar Media, Ciba-Geigy Pigments, Paisley, Scotland, pp. 361-403. D. H. Solomon and D. G. Hawthorne, Chemistry of Pigments and Fillers, Krieger Publishing Co., pp. 143-153 (1991). Film Extrusion Manual-Process, Materials, Properties, editors Thomas I. Butler and Earl W. Veazey, Tappi Press (1992). Juergen H. Braun, Andrejs Baidins and Robert E. Marganski, TiO2 Pigment Technology: A Review, Progress in Organic Coatings, 20, pp. 105-138 (1992). Union Carbide's Product Information brochure on A-137 (1991). Witucki, Gerald L., A Silane Primer: Chemistry and Applications of Alkoxy Silanes, Journal of Coating Technology, 65, No. 822, 57-60, Jul. 1993. Union Carbide Corporation, Filler Treatment, 1968. Castor, W.S., et al., Optical and Other Effects of White Pigments in Plastics, Additives For Plastics, vol. 1, 233-244, 1978. Pawlenko, S., et al., Organosilicon Compounds, 1980. Union Carbide Corporation, Organofunctional Silanes, 1991. "The Pigment Handbook", vol. 1, 2.sup.nd Edition, John Wiley & Sons, NY, 1988. Plueddeman, et al, The Society of the Plastics Industry, Inc., "Evaluation of New Silane Coupling Agents for Glass Fiber Reinforced Plastics", Section 14--The Glass Resin Interface Seminar, p. 11, Chicago, Feb. 6-8, 1962. Chemical Abstracts, vol. 112, 57383n, 1990. World Surface Coatings Abstracts, Chemical Surface Treatment of Alumina, Titanium Dioxide and Talc, and Their Surface Nature, J. Jap. Soc. Col. Mat, 65, No. 2, 59-67, 1992. Patent Abstracts of Japan, vol. 8, No. 153, p. 287, (Jul. 17, 1984). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A highly loaded polymer concentrate comprising: (a) polymer resin, and (b) about 50 to about 87% by weight silanized TiO.sub.2 pigment, based on the weight of polymer concentrate, wherein the silanized TiO.sub.2 pigment is obtained by treating TiO.sub.2 pigment with reaction products of water and a silane compound having the formula: R.sub.x Si(R').sub.4-x wherein, R is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic group having 8-20 carbon atoms; R' is a hydrolyzable group selected from alkoxy, halogen, acetoxy or hydroxy or mixtures thereof, and x=1 to 3. 2. The polymer concentrate of claim 1, wherein reaction products of the water and silane compound react and bond with the surface of the TiO.sub.2 pigment. 3. The polymer concentrate of claim 1, comprising about 70 to about 87% by weight silanized TiO.sub.2 pigment. 4. The polymer concentrate of claim 1, wherein the silane compound is octyltriethoxysilane. 5. The polymer concentrate of claim 1, wherein the silane compound is octyltrichlorosilane. 6. The polymer concentrate of claim 1, wherein R is an aliphatic having 8-18 carbons, R' is methoxy, ethoxy, chloro, hydroxy, or mixtures thereof and x=1 to 3. 7. The polymer concentrate of claim 6, wherein R is an aliphatic having 8 carbons, R' is ethoxy, hydroxy, or mixtures thereof and x=1 to 3. 8. The polymer concentrate of claim 6, wherein R is an aliphatic having 8 carbons, R' is chloro, hydroxy, or mixtures thereof and x=1 to 3. 9. The polymer concentrate of claim 1, wherein the polymer resin is selected from the group consisting of polyolefins, polyesters, polyvinyl chlorides and polystyrenes. 10. The polymer concentrate of claim 9, wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, and polybutylene. 11. The polymer concentrate of claim 10, wherein the polyolefin is polyethylene. 12. The polymer concentrate of claim 1, wherein the TiO.sub.2 pigment is silanized with about 0.1 to about 5.0% by weight of the silane compound based on the weight of silanized TiO.sub.2 pigment. 13. A composition comprising the polymer concentrate of claim 1, wherein the concentration of the silanized TiO.sub.2 pigment is about 0.2 to about 20% by weight, based on the weight of the composition. 14. The composition of claim 13, wherein the composition is a film. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
BACKGROUND OF THE INVENTION The present invention relates to white-pigmented polymers (particularly, polyolefins such as polyethylene) containing white pigments treated with an organosilicon compound to improve processibility in compounding and improve performance properties such as lacing resistance in a polyolefin matrix. Treatment of TiO.sub.2 pigment with organosilicon compounds to improve dispersibility in a polymer matrix is well known in the art. For example, U.S. Pat. Nos. 4,061,503 and 4,151,154 disclose enhanced dispersibility of TiO.sub.2 in paints and plastics. Therein, the TiO.sub.2 is surface treated with a silane possessing at least two hydrolyzable groups bonded to silicon and an organic group containing a polyalkylene oxide group. In addition, U.S. Pat. No. 4,810,305 discloses a modified hydrophobic pigment or filler containing 0.05 to 10 weight % of an organopolysiloxane, with improved dispersibility in synthetic resins. However, deficiencies in the prior art include, but are not limited to, (1) unacceptable processibility, i.e., dispersibility of TiO.sub.2 pigment in a polymeric matrix at slow rates; and (2) lacing, i.e., development of imperfections in a polyolefin matrix. Lacing occurs as a result of volatiles released from the pigment during high temperature polyolefin fabrication processes. Lacing may also be attributable to TiO.sub.2 concentrates picking up moisture. A further disadvantage is that higher loadings of TiO.sub.2 pigment in a polymer concentrate result in slower processing rates. It has been found that the above combined disadvantages of the prior art can be overcome by the present invention. SUMMARY OF THE INVENTION In accordance with this invention there is provided a polymeric matrix comprising polymer and about 0.01 to about 87% by weight silanized TiO.sub.2 pigment, based on the weight of the polymeric matrix, wherein the silanized TiO.sub.2 pigment has a coating of about 0.1 to about 5% by weight, based on the weight of silanized TiO.sub.2 pigment, of an organosilicon compound selected from at least one silane, or a mixture of at least one silane and at least one polysiloxane. It has been found that the silanized pigmentary TiO.sub.2 provides a unique combination of enhanced processibility in a polymeric matrix having higher TiO.sub.2 loadings, and improved end use performance properties such as lacing resistance in a polyolefin matrix at TiO.sub.2 concentrations ranging from about 0.2 to about 20% by weight, based on the weight of the polyolefin matrix. DETAILED DESCRIPTION The TiO.sub.2 pigments useful in the present invention generally are in the rutile or anatase crystalline form. It is commonly made by either a chloride process or a sulfate process. TiCl.sub.4 is oxidized to TiO.sub.2 particles in the chloride process. Sulfuric acid and ore containing titanium are dissolved, and the resulting solution goes through a series of steps to yield TiO.sub.2, in the sulfate process. Both the sulfate and chloride processes are described in greater detail in "The Pigment Handbook", Vol. 1, 2nd Ed., John Wiley & Sons, NY (1988), the teachings of which are incorporated herein by reference. The optimum average particle size can range from about 0.005 to about 1 micron. The TiO.sub.2 pigments may also contain ingredients added thereto to further improve dispersibility characteristics or other properties such as durability. Thus, by way of example, but not limited thereto, the pigment may contain additives and/or inorganic oxides, such as aluminum, silicon or tin as well as triethanolamine, trimethylolpropane, phosphates, etc. "Silanized" TiO.sub.2 is defined herein to refer to TiO.sub.2 treated with either at least one silane, or a mixture of at least one silane and at least one polysiloxane (collectively referred to herein as organosilicon compounds). Suitable silanes have the formula: R.sub.x Si(R').sub.4-x wherein R is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic group having at least 1 to about 20 carbon atoms; R' is a hydrolyzable group such as an alkoxy, halogen, acetoxy or hydroxy or mixtures thereof; and x=1 to 3. For example, silanes useful in carrying out the invention include octyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, tridecyltriethoxysilane, tetradecyltriethoxysilane, pentadecyltriethoxysilane, hexadecyltriethoxysilane, heptadecyltriethoxysilane and octadecyltriethoxysilane. Additional examples of silanes include, R=8-18 carbon atoms; R'=chloro, methoxy, hydroxy or mixtures thereof; and x=1 to 3. Preferred silanes are R=8-18 carbon atoms; R'=ethoxy; and x=1 to 3. The R=8-18 carbon atoms is preferred for enhanced processibility. R'=ethoxy is preferred for ease of handling. Surprisingly, lower chain alkyl silanes resulted in longer processing times. Mixtures of silanes are contemplated equivalents. Weight content of the silane, based on total silanized pigmentary TiO.sub.2 is typically about 0.1 to about 5 weight %, preferably about 0.5 to about 1.5 weight %. In excess of 5 weight % may be used but no particular advantage is observed. In an alternative embodiment, a mixture of at least one silane with at least one polysiloxane is useful in carrying out the invention. Suitable polysiloxanes have the formula: ##EQU1## wherein R is organic or inorganic groups; n=0-3; and m.gtoreq.2. For example, polydimethylsiloxane (PDMS), vinyl phenylmethyl terminated dimethyl siloxanes, divinylmethyl terminated polydimethyl siloxane and the like are suitable polysiloxanes. PDMS is a preferred polysiloxane. The silane useful in the mixture may be the silane described above with R=1-8 carbon atoms, R'=alkoxy and x=1 preferred. Weight content of the silane and polysiloxane, based on total silanized pigmentary TiO.sub.2, is about 0.1 to about 5.0 weight %, preferably from about 1 to 3 weight %. Especially preferred is about 0.5 to 1 weight % silane with R=4 or 8 carbon atoms, R'=alkoxy, and x=1; and 1 weight % PDMS. The ratio of silane to polysiloxane can be 1 silane:2 polysiloxane up to 2 silane:1 polysiloxane. An especially preferred ratio is 1 silane:1 polysiloxane. The silane and polysiloxane are commercially available or can be prepared by processes known in the art such as those described in "Organosilicon Compounds", S. Pawlenko, et al., New York (1980), the teachings of which are incorporated herein by reference. The method of addition is not especially critical and the TiO.sub.2 pigment may be treated with the silane in a number of ways. For example, the silane addition can be made neat or prehydrolyzed to a dry pigmentary base, from a slurry, a filtration step, during drying or at a size operation such as a fluid energy mill, e.g., micronizer, or media mill as described in greater detail in copending application entitled "IMPROVED SLURRY PROCESS FOR PREPARING SILANIZED TiO.sub.2 PIGMENTS, USING A MEDIA MILL", the teachings of which are incorporated herein by reference, or post blending after micronizing. For example, U.S. Pat. No. 3,834,924 describes organosilane and pigment dispersion mixed or blended directly in a suitable solids mixing apparatus. An example of post blending is described in greater detail in U.S. Pat. Nos. 3,915,735 and 4,141,751. The polysiloxane addition can be made in conjunction with the silane or post addition to the silanized pigment. The silane addition and polysiloxane addition is described in greater detail below. If water, either a liquid or vapor (steam), is present as a component of the process stream, hydrolysis of the hydrolyzable groups of the silane will occur and the silane coating will bond to the TiO.sub.2 base. Prehydrolyzing the silane is a preferred step in treating the TiO.sub.2 pigment with the silane. If the silane is added neat to the TiO.sub.2 base, then moisture adsorbed on the TiO.sub.2 will effect the hydrolysis, but at a lower rate than if excess moisture is present. Hydrolysis of silanes is described in greater detail in "Organofunctional Silanes" by Union Carbide (1991), the teachings of which are incorporated herein by reference. Polymers which are suitable for use in the present invention include, by way of example but not limited thereto, polymers of ethylenically unsaturated monomers including olefins such as polyethylene, polypropylene, polybutylene, and copolymers of ethylene with higher olefins such as alpha olefins containing 4 to 10 carbon atoms or vinyl acetate, etc,; vinyls such as polyvinyl chloride, polyvinyl esters such as polyvinyl acetate, polystyrene, acrylic homopolymers and copolymers; phenolics; alkyds; amino resins; epoxy resins, polyamides, polyurethanes; phenoxy resins, polysulfones; polycarbonates; polyether and chlorinated polyesters; polyethers; acetal resins; polyimides; and polyoxyethylenes. The polymers according to the present invention also include various rubbers and/or elastomers either natural or synthetic polymers based on copolymerization, grafting, or physical blending of various diene monomers with the above-mentioned polymers, all as generally known in the art. Thus generally, the present invention is useful for any such white-pigmented plastic or elastomeric compositions (collectively referred to herein as a white-pigmented polymers). For example, but not by way of limitation, the invention is felt to be particularly useful for polyolefins such as polyethylene, polypropylene, polyvinyl chloride, polyamides and polyesters. As used herein, "high loaded" TiO.sub.2 may vary widely for each polymeric matrix but will be in a well known range for those skilled in the art. For example, in a polyolefin matrix, a high loaded TiO.sub.2 would be 50 or above % by weight TiO.sub.2 pigment, based on the weight of the polyolefin matrix. A wide variety of conventional additives may be included in the polymers as is necessary, desirable or conventional for the intended end use. Such additives include, but are not limited to, antioxidants, light stabilizers, lubricants, thermal processing additives and the like. TiO.sub.2 coated with organosilicon compounds can be incorporated into a melt-fabricable polymer to form the polymer composition of this invention by any melt compounding technique known in the art. Generally, TiO.sub.2 and polymer resin are brought together and then mixed in a blending operation that applies shear to the polymer melt. The polymer resin is usually available in the form of powder, granules, pellets, or cubes. Commonly, TiO.sub.2 and resin are first combined while the resin is in the solid state (not melted) and dry-blended in some way. This can be done in simple ways, such as by shaking in a bag or tumbling in a closed container, or in more sophisticated ways such as by using blenders having agitators or paddles. TiO.sub.2 and polymer resin can be brought together by co-feeding the materials to internal mixers and allowing a screw to mix them together before the resin reaches the molten state. The melt blending of TiO.sub.2 and polymer resin can be done using known equipment, such as single-screw extruders, twin-screw extruders, internal mixers, and the like. Internal mixers are commonly used. The melt blending can be done as part of the process of forming a finished article of the composition, as by melt extrusion. Alternatively, the melt blending can be done in a preliminary step, optionally isolating the polymer composition, e.g., as cubes, followed by forming a finished article in a subsequent process. As one skilled in the art will recognize, there are many possible variations of the technique for preparing polymer compositions of the invention. One may, for example, first prepare a concentrate having high TiO.sub.2 concentration, i.e., one composition of the invention, and then combine the concentrate with polymer resin containing no TiO.sub.2 to obtain another composition of the invention. The highly loaded polymer concentrates are made as described above with the desirable weight % for the intended end use. For example, in polyolefin concentrates, about 50-87% by weight concentrate may be used to opacify. The concentrate is "let down" into the polyolefin. Used herein, "let down" refers to a ratio or percent of resin mixed with concentrate. Let down may be accomplished in a number of ways and is described in great detail in "Film Extrusion Manual" (1992), the teachings of which are incorporated herein by reference. For example, in lacing evaluation, a 50 wt. % to 87 wt. % concentrate may be let down to about 0.2 to about 20 weight % by dry mixing polyolefin and extruding at a specific processing temperature and casting it into a film. Pigment performance is then evaluated in an end use application. The highly loaded silanized pigmentary TiO.sub.2 exhibits outstanding processibility in a polymeric matrix and lacing resistance when incorporated into a polyolefin matrix. Additional advantages observed are increased bulk density, lower viscosity, excellent dispersibility, moisture resistance, and excellent optical properties such as high tint strength. The following examples are construed as illustrative and not limitative of the remainder of the disclosure in any way whatsoever. Farrel BR Banbury.backslash.-type mixers (available from Farrel Corp., Ansonia, Conn., USA) have been used in the Examples. Broad range internal mixers as known in the art are contemplated equivalents. For example, Farrel Continuous Mixers (FCM) (available from Farrel Corp., Ansonia, Conn., USA) and twin screw extruders are equally applicable. Bulk density is given as grams per cubic centimeter of uncompacted pigment. A pigment bulk density below about 0.6 will result in difficult solids handling in polymer compounding. For rapid compounding of TiO.sub.2 and a polymer in a Banbury.backslash.-type mixer, a bulk density above about 0.6 is desirable. Total flux time is a measure of processing time, or time to disperse, in a Banbury.backslash.-type mixer. Viscosity, at 180 degrees Celsius, of product from the Banbury.backslash.-type mixer, was measured at a shear rate of 550 1/sec. Viscosity was measured with a Kayeness capillary rheometer (available from Kayeness Corp., Honey Brook, Pa., USA). |
| PATENT EXAMPLES | This data is not available for free |
| PATENT PHOTOCOPY | Available on request |
|
Want more information ? Interested in the hidden information ? Click here and do your request. |