Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carbohydrate or derivative as a reactant
Reexamination Certificate
2002-10-07
2004-10-05
Seidleck, James L. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carbohydrate or derivative as a reactant
C527S103000, C106S031710
Reexamination Certificate
active
06800712
ABSTRACT:
BACKGROUND OF THE INVENTION
The U.S. Pat. Nos. 3,935,099, 3,981,100, 3,985,616 and 3,997,484 all issued in 1976 have been given credit for the materials referred to as super absorbent polymers. Since 1976, many inventors have been issued patents for super absorbent polymers (SAP). Most all of these patents claim compositions made by copolymerizing acrylic acid and acrylamide in the presence of a coupling agent. A few of these patents also include a natural polymer such as starch as claimed in U.S. Pat. Nos. 3,935,099, 3,981,100, 3,985,616 and 3,997,484. The patents made without starch refer to their SAP as totally synthetic copolymers. Today the market for the totally synthetic copolymers, SAP, is estimated to be about 2 billion pounds per year worldwide. These SAPs are used almost totally in baby diapers, adult diapers, catamenials, hospital bed pads, cable coating and the like.
Starch graft copolymer compositions with the ability to absorb up to 1000 times their weight in aqueous fluids are known in the prior art. The prior art disclosed cross-linked starch-graft copolymers which absorb large quantities of aqueous fluids for use in absorbent softgoods, in increasing the water holding capacity of soils, and as coatings onto seeds, fibers, clays, paper and the like. The prior art also disclosed methods for drying the compositions to give films by drying in trays, or by heating on drum dryers. These films can then be ground or milled to give flakes or powders. An alternative method for drying was disclosed in the prior art where a viscous mixture of alkali starch-graft copolymer was diluted with a waster miscible organic solvent such as alcohol or acetone. The precipitated alkali starch graft copolymer was then isolated in a fine powder form by filtration and drying.
Surprisingly, agricultural companies that market seed, fertilizer, herbicides, insecticides and other agricultural materials, have found little use for the totally synthetic copolymers (SAPs) in agriculture. In evaluations of SAPs, the SAPs performed poorly and were of no interest to agricultural companies.
It is surprising that the application of starch-containing graft copolymers, made by the methods disclosed herein, directly to the soil resulted in earlier seed germination and/or blooming, decreased irrigation requirements, increased propagation, increased crop growth, increased crop production, and decreased soil crusting. Thus, starch graft copolymers made by the methods disclosed herein have great advantages to assist in agriculture practices and production.
Also surprising was that the prior art dried films or dried powders are not useful in broad scale agricultural applications since these powders are smaller, finer than 80 mesh, in particle size, and are limited to this particle size due to the ways in which these powders are produced. One inherent limitation with finer mesh particles is that they cannot be used in typical granule applicators. The films and powders would not be useful to apply with granule fertilizers, granule pesticides or other granule agricultural additives. In granule applicators, the particle size needs to be somewhat larger, at least about 25 mesh. The starch graft copolymer of this invention provides a commercially viable product for use in broadscale agricultural applications.
SUMMARY OF THE INVENTION
In one aspect of the invention, a first method of producing a starch graft copolymer for use in agricultural applications is disclosed. It includes the following steps: (a) providing grafting reactants and a starch; (b) graft polymerizing the grafting reactants onto the starch to form a starch graft copolymer; (c) saponifying the starch graft copolymer; (d) precipitating the starch graft copolymer; and (e) granularizing the starch graft copolymer to form particles.
A second method of producing a starch graft copolymer for use in agricultural applications is also disclosed. It includes the following steps: (a) providing grafting reactants and a starch; (b) graft polymerizing the grafting reactants onto the starch to form a starch graft copolymer; (c) saponifying the starch graft copolymer; (d) adding an acid to lower a pH of the starch graft copolymer to about between 2.0 and 3.5 to precipitate the starch graft copolymer to form a starch graft copolymer precipitant; (e) separating the starch graft copolymer precipitant; (f) neutralizing the pH of the starch graft copolymer precipitant to about between 6.0 and 8.0 to form a starch graft copolymer; and (g) granularizing the starch graft copolymer to form particles.
In another aspect of the invention, methods of using a starch graft copolymer produced by the two methods above, are disclosed to increase crop production. These methods of using include applying the granulated starch graft copolymer directly to the furrow, as well as coating a root or seed with the starch graft copolymer.
In another aspect of the invention, a starch graft copolymer for use in agricultural applications made in accordance with the two methods above is disclosed.
DETAILED DESCRIPTION OF THE INVENTION
The alkali starch graft copolymers of this invention are produced by graft polymerizing grafting reactants onto a starch. The grafting reactants of this invention include an acrylonitrile and an initiator. The starch may be selected from the group consisting of starches, flours, and meals. The preferred embodiment includes gelatinized cornstarch. The acrylonitrile may be used alone or in conjunction with other monomers commonly used in the industry. The preferred weight ratio of the starch to the acrylonitrile is in the range of about between 1:2 and 1:5. The acrylonitrile is graft polymerized onto starch in the presence of an initiator, preferably a cerium (+4) salt. The preferred initiator is cerium ammonium nitrate. However, other suitable initiator systems are known to those skilled in the art. The polymerization is accomplished in several minutes producing long grafted chains of polyacrylonitrile, or polyacrylonitrile with other monomers attached to the starch. This starch graft copolymer is then saponified with an alkali metal, preferably potassium hydroxide or sodium hydroxide, to change the nitrile groups into a mixture of carboxamides and alkali carboxylates.
The saponification step provides a highly viscous mass that must be isolated in a dry form for usage in agriculture. The resulting saponificate is then precipitated into a solid form and formed into the desired size particles. Formation of the starch-containing graft copolymers into particles of the desired size for direct use in agricultural equipment is achieved by converting the viscous mass of alkali starch-graft copolymers into rod-shaped forms and drying the forms to the desired particle size. Selecting an appropriate die can vary the rod-shaped forms. A plate is used that has been drilled or formed to contain holes of selected size and shape. Rod-shaped forms may be lightly coated, after the die, to reduce the tackiness of the rod-shaped forms. Clays, starches, flours and cellulose can be used to dust the rods.
There are two methods of making the starch-containing graft copolymers of this invention. In the first method, the starch-containing graft copolymer is prepared and rod shapes of the copolymer are formed from the viscous alkali starch graft copolymer. The isolated product is recovered from the viscous polymerization dough with the use of water miscible solvents such as alcohols. These include methanol, ethanol, propanol and isopropanol. Since methanol is generally the least expensive of the alcohols, it is often chosen and it is the preferred alcohol in this method. The resulting dough is then immersed into the alcohol, and the alkali starch graft copolymer is precipitated into particles that are then screened after drying to the desired size. The diameter of the rods is controlled by drilling holes in the end plate of {fraction (1/16)} inch to ¼ inch diameters. This first method of precipitation by the use of alcohols is very different from the second method of precipitatio
Doane Steven William
Doane William McKee
Seidleck James L.
Stoel Rives LLP
Tran Thoa
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