Chemistry: fertilizers – Processes and products – Organic material-containing
Reexamination Certificate
1999-10-15
2001-08-14
Langel, Wayne (Department: 1754)
Chemistry: fertilizers
Processes and products
Organic material-containing
C071S031000, C071S061000, C423S277000, C423S279000, C516S079000
Reexamination Certificate
active
06273928
ABSTRACT:
This invention relates to pourable aqueous boron-containing compositions, particularly pourable aqueous borate-containing compositions having a high boron content, and to their preparation.
BACKGROUND OF THE INVENTION
It is known to prepare borate solutions with a high boron content using organic solvents. Thus U.S. Pat. No. 4,332,609 describes a method of fertilising plants in which the reaction product of a boric acid compound with an alkanolamine or aliphatic polyamine, in particular monoethanolamine, is applied to plants. The reaction products are water-soluble and thus can be dissolved in water for application to crops. The production of the monoethanolamine reaction products for example, adds to the cost of the boron to be applied to the crops.
Using an alternative organic solvent, U.S. Pat. No. 4,572,733 describes a so-called storage-stable concentrate formed by making a solution of a first boron compound in a water-miscible glycol solvent and then dispersing fine particles of a second boron compound in the solution. For use, the storage-stable concentrate is diluted with water and applied to crops.
Aqueous borate suspension formulations have been proposed for the treatment of timber. Thus AU-A-574389 proposes the use of a preservative composition comprising a colloidal micro-crystalline suspension of boron salts and a thickening agent, which serves to maintain the stability of the suspension. Similarly EP-A-0289317 describes timber preservative compositions comprising a boron-containing preservative, which may be a micro-crystalline suspension, e.g. 10 to 30 microns, and a thickening agent such as the polysaccharide xanthan gum in a preferred amount of 0.25 to 3.0% by weight. These compositions are obtained by forming, with heating, a borate solution, cooling rapidly to obtain crystals and adding thickening agent to maintain the crystals in suspension. Such compositions are stiff and pasty.
The combination of borates and xanthan gum has also been described in connection with other applications. For example, UK Patent No. 1,395,502 discloses herbicidal compositions containing gelling agent compounds such as a combination of xanthan gum and a borate salt. U.S. Pat. No. 3,326,733 discloses a gelled explosive containing water, Xanthamonous hydrophilic colloid, borax and a monovalent water-soluble explosive salt. Japanese Patent Application No. S61-158907 describes compositions for a mold and mildew removing agent that contains an organic polymer, such as xanthan gum, guar gum, locust bean gum, casein or other similar materials, in combination with a peroxide compound, such as hydrogen peroxide or a hydrogen peroxide producing compound such as sodium perborate monohydrate or sodium perborate tetrahydrate.
SUMMARY OF THE INVENTION
According to this invention, there are provided highly stable yet readily pourable aqueous borate-containing formulations having a high boron content. They can be prepared using an anti-settling system comprising a swellable clay and a polysaccharide. The compositions of this invention comprise a pourable aqueous borate-containing suspension which suspension in water contains 8 to 13% by weight boron as sodium pentaborate, 0.1 to 3% by weight, based on the total weight of the composition, of a swellable clay, and 0.05 to 0.2% by weight, based on the total weight of the composition, of a polysaccharide.
DETAILED DESCRIPTION OF THE INVENTION
It has surprisingly been found that the presence of the specified amounts of clay and polysaccharide in the aqueous suspension compositions of this invention have a significant viscosity-reducing effect. This means that there may readily be obtained according to the invention aqueous borate-containing suspensions which on the one hand have a high boron content and on the other hand are pourable making them capable of being easily handleable by users. Thus the compositions according to the present invention may be sprayed directly or, alternatively poured for dilution by water or aqueous systems for application, e.g. onto crops, or for other applications where there is a need for aqueous soluble borate suspensions.
The compositions according to the invention are pourable and, at the same time, physically stable, that is the compositions have:
(a) a sufficiently high viscosity at low stresses (shear rates) e.g. under stable storage and transport conditions so as to prevent particle sedimentation or significant separation; and
(b) a sufficiently rapid decrease in viscosity at a particular stress (depending on the application) e.g. under pouring, pumping or spraying conditions that ensures the pourability of the product on application.
Thus the suspensions according to the invention do not separate when stored or when subjected to minor vibration e.g. when transported. Typically under such conditions the suspensions are subjected to shear rates below 1 sec
−1
, e.g. 0.001 to 0.1 sec
−1
for storage. At higher shear rates, the compositions are capable of being poured, pumped or sprayed.
The pourable aqueous borate-contaning compositions according to the present invention may contain from 8 to 13% by weight boron as sodium pentaborate, generally 9.5 to 12.5% by weight boron as sodium pentaborate, preferably 10 to 12% by weight boron as sodium pentaborate.
Suitable swellable clays which may be used in the suspensions according to the present invention include the montmorillonite group of clays, particularly sodium enriched montmorillonite clays and sodium montmorillonite clays, some of which are known commercially as bentonite, minerals analogous to montmorillonite such as hectorite, and sepiolite.
The amount of swellable clay employed in the suspensions according to the present invention is 0.1 to 3% by weight, preferably 0.5 to 1.5% (e.g. approximately 1%) by weight, based on the total weight of the composition. Generally the composition would contain between 1 and 1.5% by weight of montmorillonite clays such as IGB clay minerals available from IMV Nevada. When other clays are used, such as sodium enriched bentonite, e.g. Bentonite MB 300S from Fordamin Company Limited, the amount of clay required may be up to 3% by weight, preferably approximately 2.5% by weight.
A particularly preferred polysaccharide in the compositions according to the invention is xanthan gum. The amount of polysaccharide, e.g. xanthan gum, used may be 0.05 to about 0.2%, preferably 0.05 to 0.16%, more preferably 0.08 to 0.15% or 0.08 to 0.14%, most preferably about 0.1% or 0.12%, based on the total weight of the composition.
Optionally a dispersant, for example an acrylic polymer, or water soluble polymeric dispersants such as polyethylene oxide, hydrolysed polyvinal acetates, polyvinyl pyrrolidone, polyacrylamide and polyvinyl alcohol, may be added prior to the polysaccharide during the manufacture of the suspension according to the invention. This aids the dispersion of the polysaccharide in water. The amount of dispersat may be small. For example 0.05 to 1%, generally about 0.1% by weight, of a polyacrylate dispersant may be used.
Preferred suspensions according to the present invention contain, based on the total weight of the composition:
10 to 12% by weight boron as sodium pentaborate;
0.5 to 1.5% by weight of IGB;
0.05 to 0.16, e.g. to 0.15% by weight xanthan gum;
0.00 to 0.5% by weight polyacrylate dispersant;
the remainder being water.
The amount of the anti-settling system incorporated obviously depends on the size and concentration of the resulting suspended particles. Generally speaking the suspension comprises particles less than 10 microns in size, e.g. in the range 0.1 to 10 microns, and more preferably below 5 microns (e.g. 0.1 to 5 microns) in size.
The nature of the interaction between the sodium pentaborate and clay and polysaccharide, leading to reduced viscosity, is not fully understood. The reduced viscosity observed with the addition of ingredients which would normally be expected to result in a thickening effect is regarded as most surprising.
The suspensions according to the present invention may suitably be
Campbell Colin William
Hayati Igan
Ganderup Kurt R.
Langel Wayne
U.S. Borax Inc.
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