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
2000-10-30
2003-03-04
Yoon, Tae H. (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...
C524S035000, C524S047000, C524S444000, C524S448000, C524S449000, C071S013000, C071S027000, C071S064010
Reexamination Certificate
active
06528569
ABSTRACT:
This invention relates to a solid composition and to a process for preparing a solid composition and in particular to a process for preparing a solid, water-soluble or water-dispersible composition containing a water-soluble material which is not film-forming and a film-forming water soluble material.
Film-forming polymers are used in a number of industries to provide a solid polymer medium within which a second non film-forming component may be supported. Typical of such applications is the casting of an aqueous solution of the film-forming polymer to form polymer sheets (tapes) or flakes.
Thus for example in WO 93/23999 there is disclosed a packaging for storing and releasing incompatible crop protection materials in which a chemical is “encapsulated” or supported in a water-soluble polymer film.
Such processes typically involve as a first step dissolving a film-forming polymer in water to form an aqueous film-forming medium in which a material to be supported is dissolved or suspended. The film-forming medium is then for example cast onto a suitable substrate and dried to form a solid tape containing the material to be supported. Under certain conditions the tape may loose coherence during drying to form flakes. Alternatively, the film-forming medium can be dried to produce granules, agglomerates or powders.
We have found however that problems may arise when the non film-forming material to be supported is itself water-soluble, particularly if it is a strong electrolyte. Specifically, we have found that the presence of a water-soluble electrolyte in an aqueous solution of a film-forming polymer tends to interact adversely with the polymer at the relatively high polymer concentration required to provide adequate film-forming properties. As a result the film-forming polymer may be thrown out of solution as a rubbery deposit, and even quite small concentrations of water-soluble electrolyte may have a deleterious effect on the film-forming properties and homogeneity of the medium. The problem is exacerbated if the water-soluble electrolyte is hygroscopic such that even if a solid composition can be formed, it tends to pick up water causing the film-forming polymer component to become sticky.
According to the present invention there is provided a process for producing a solid, water-soluble or water-dispersible composition comprising a non film-forming material supported by a film-forming polymer wherein the supported material is a water-soluble material, which process comprises (i) preparing a film-forming aqueous medium containing (a) a film-forming polymer (b) a water soluble material which is non film-forming and (c) a water-miscible solvent in which the film-forming polymer is soluble and thereafter (ii) drying the film-forming aqueous medium to form the solid composition.
Whilst the process of the present invention may be applied to any water-soluble material which is not film-forming and which is suitable for being supported in a solid composition of a film-forming polymer, it is of particular relevance when the water-soluble supported material is a strong electrolyte and even more particularly when the water-soluble supported material, in its dry form, is hygroscopic. Typical strong electrolytes are salts, for example inorganic salts or salts of an organic acid or base. The scope of the present invention is not restricted to a water-soluble supported material having a specific utility, although it is illustrated herein with reference to a water-soluble supported material having utility in the agrochemical field, either as an active agrochemical or as an agrochemical adjuvant. Typical examples of water-soluble active agrochemicals which are strong electrolytes are salts of glyphosate, including without limitation the trimethylsulphonium salt, the isopropylamine salt, the sodium salt, the potassium salt and the ammonium salt and bipyridylium salts such as paraquat dichloride, glufosinate and fomesafen.
Typical examples of agrochemical adjuvants which are strong electrolytes are organic or inorganic salts such as ammonium sulphate. The process of the present invention provides a convenient method of obtaining a solid formulation of an agrochemical or an agrochemical adjuvant or an agrochemical formulation containing both active agrochemical and adjuvant having advantages in respect of handling, storage, transportation and reduced container contamination. Typical solid formulations of the present invention such as tapes or flakes provide a convenient delivery vehicle for the agrochemical or agrochemical formulation and may be arranged for example such that a single unit dose of agrochemical is contained in a unit dose package, for example in a conventional unit dose package or in water-soluble sachet packaging. If the process of the present invention is used to form a cast tape, the tape may be cut to provide a length corresponding to a desired dose. Furthermore we have found that the process of the present invention may be used to provide solid compositions containing a higher loading of agrochemical or agrochemical adjuvant than would be possible in the absence of water-miscible solvent. In certain circumstances the process of the present invention may be used to provide a solid composition containing an agrochemical formulation whose individual components are incompatible if used in the form of an aqueous liquid concentrate. Thus for example it may be possible to use a higher content of an adjuvant such as ammonium sulphate than would be compatible as an aqueous liquid concentrate formulation of an agrochemical.
In a preferred embodiment of the present invention, the solid composition additionally contains a solid filler.
According to a further aspect of the present invention there is provided a process for producing a solid, water-soluble or water-dispersible composition comprising a non film-forming material supported by a film-forming polymer wherein the supported material is a water-soluble material, which process comprises (i) preparing a film-forming aqueous medium containing (a) a film-forming polymer, (b) a water soluble material which is non film-forming, (c) a water-miscible solvent in which the film-forming polymer is soluble and (d) a solid filler and thereafter (ii) drying the film-forming aqueous medium to form the solid composition.
The solid filler is preferably a water-dispersible solid inorganic or organic filler such as calcium silicate, magnesium silicate (talc), sodium aluminium silicate, silica, mica, cellulosic fibre such as wood fibre, starch and diatomaceous earth. It is especially preferred that a highly adsorptive filler is used, for example a filler having a high surface area for example a surface area greater than 5 m
2
/g and preferably greater than 80 m
2
/g. As a specific example of a suitable filler there may be mentioned CALFLO E (CALFLO is a trade mark World Minerals), a calcium silicate filler having a surface area of about 100 m
2
/g.
The term “film-forming” polymer includes any polymer which is capable of providing film-forming properties in the presence of water. The film-forming polymer will generally be water-soluble but could also provide a film-forming aqueous medium in which the film-forming polymer is present in the form of a dispersion, and in particular a colloidal dispersion or in the form of a sol or in the form of a solution containing some dispersed material.
Suitable film-forming polymers include both synthetic and natural polymers such as polyvinylpyrrolidone, polyvinyl alcohol, partially hydrolysed polyvinyl acetate, modified polyvinylpyrrolidone such as a polyvinylpyrrolidone/vinyl acetate copolymer, polyethylene oxides, ethylene/maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, water-soluble cellulose such as carboxymethylcellulose, water-soluble polyamides or polyesters, copolymers and homopolymers of acrylic acids, starches, natural gums such as alginates, dextrins and proteins such as gelatins and caseins. Mixtures of such film-forming polymers may also be used. Polyvinylpyrrolidone is an
Landham Rowena Roshanthi
Oza Mrinalini Sachin
Syngenta Limited
Yoon Tae H.
LandOfFree
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