Title of Invention	A DISPERSIBLE FAST-HYDRATING POLYSACCHARIDE
Abstract	This invention relates to a dispersible and fast-hydrating polysaccharide having a molecular weight of greater than lxl06 gimol, in dry fonn, characterized in that at least 75% by weight of the particles of the said polysaccharide have a diameter of between 60 and 250 microns and a mean diameter (dso) of between 100 and 250 microns.

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DISPERSIBLE KND FAST-HYDRATING BIOPOLYMER The present- invention relates to dispersible and fast-hydrating biopolymers in dry form and to their use as thickeners, emulsifiers and/or stabilizers for the preparation of industrial formulations (such as, for example, the construction, paints, paper, textiles, plant-protection, water-treatment and petroleum industries), food, cosmetic, agrochemical and pharmaceutical formulations, Biopolymers of high molecular weight, which are polysaccharides in the context of the present invention, are increasingly used in many industrial applications for their thickening, viscosity-modifying, emulsifying and/or stabilizing properties in media, especially aqueous media. Thus, xanthan gum, on account of its exceptional rheological properties, is used in fields as varied as construction, paints, paper, textiles, cosmetics, food, agriculture, water treatment and oil drilling and recovery. For many applications, when the biopolymer is in dry form, it is necessary to place it in aqueous solution. However, the major drawback of these powders is their difficulty in dispersing and hydrating quickly in a given aqueous medium. Often, the dispersion and/or hydration of these biopolymers results in the formation of lumps, which are harmful to the functionality of the medium. In the case of a thickening biopolymer such as xanthan, the improvement in terms of dispersion and hydration without the formation of lumps allows in particular better control of the viscosity of the reaction medium. For this reason, it would be advantageous to develop a biopolymer, in dry form, in particular of xanthan gum type, which can be easily dispersed and quickly hydrated in aqueous media while at the same time reducing or even eliminating the fozrmation of lumps. In practice, one of the solutions recommended to avoid the formation of lumps while at the same time maintaining good dispersibility and hydratability of the powders consists in modifying the polymer powder by the so-called "granulation" method. This method consists in aggregating the biopolymer powder in slightly humid medium ("fluid bed" technique) in order to obtain granules with an average size of between 300 and 1000 microns. The major drawback of this method lies in its high implementation cost. Toother solution consists in supplementing the biopolymer with a compound of surfactant type. However, the addition of such compounds does not correspond with the current trend which is to reduce the number of additives added to a given formulation, in particular in the food sector. The aim of the present invention is to propose a biopolymer powder which, in aqueous media, without the need to add an additive and/or vigorous stirring means, gives an improved dispersion and fast hydration while at the same time reducing or even eliminating the formation of lumps. To this end, a subject of the invention is a dispersible and fast-hydrating biopolymer, in dry form, at least 75% by weight of the particles of which have a diameter of between 60 and 250 microns and a mean diameter (dso) of between 100 and 250 microns. Preferably, at least 75% by weight of the biopolymer particles have a diameter of between 100 and 200 microns and a mean diameter (dgo) of between 100 and 200 microns. The judicious selection of the particle size distribution of the biopolymers according to the invention makes it possible both to control the dispersion of the powder and to promote its hydration while at the same time substantially reducing and usually entirely eliminating the formation of lumps. The biopolymers of the invention also have the advantage of being dust-free and easy to pour. other advantag-^s and characteristics of the present invention wil I emerge more clearly on reading the description, the -examples and the figures which follow. In the -prer.i-r^*- description, the notation dso represents the particle r;ize distribution such that 50' by volume of the partLcI-'-S are less th'ah or equal to the said size. For ex'^rrp^e, a dso of 100 microns means that 5 0% by volume of '■'.': particles are less than or equal to 100 microns .--"- -i^e. The partici': .';:2e is determined by laser spectroscopy with a n.-^c'.ine such as a "Coulter LS 23 0" machine in dry-route '.-or. .* igyration . In the contf--x' of the present invention, the term "biopolymer" mor'-- >^..rticularly denotes polysaccharides of hi';-' .-nolecular weight, usually greater than 1 x 10^ :;/'"-! (measured by gel permeation) and which consists of gl-^cose, mannose, galactose, rhamnose, glucuronic ^.cid, mannuronic acid and guluronic acid units, -..'-ionally with acetate and pyruvate derivatives. Tr.eir particular structure and their properties are ';._3closed, for example, in the book Industrial Gums -.'r-istler - 2nd edition -chapters XXI-XXIII (i:-"^ - These biopolymers are advantageously produced by aerobic culturing of microorganisms in an aqueous nutrient medium. Many microorganisms such as bacteria, yeasts, fungi and algae are capable of producing these biopolymers. Mention may be made, inter alia, of: • bacteria belonging to the genus Xanthomonas and more particularly to the species described in Bergey's Manual of Determinative Bacteriology (8th edition -1974 - Williams N. Wilkins Co. Baltimore) such as Xanthomonas begoniae, Xanthomonas campestris, Xanthomonas caxotae, Xanthomonas hederae, Xanthomonas incanae, Xanthomonas malvacearum, Xanthomonas papayericola, Xanthomonas phaseoli, Xanthomonas pisi, Xanthomonas vasculorum, Xanthomonas vesicatoria, Xanthomonas vitians and Xanthomonas pelargonii; • bacteria belonging to the genus Arthrobacter and more particularly the species ArthroJbacter stabilis and ArthroJbacter viscosus; • bacteria belonging to the genus Erwinina; • bacteria belonging to the genus AzotOjbacter and more particularly the species Azotobacter indicus; • bacteria belonging to the genus Agrojbacteriuin and more particularly the species Agrobacterium radiobacter, Agrobacterium rhizogenes and Agrobacterium tumefaciens; • bacteria belonging to the genus Alcalxgenes and more particularly Alcaligenes faecalis; • bacteria belonging to the genus Pseudomonas and more particularly Pseudomonas methanica; • bacteria belonging to the genus CoryneJbacteriujn; • bacteria belonging to the genus Bacillus and more particularly Bacillus polymyxa; • fungi belonging to the genus 5cIerotiuin and more particularly to the species Sclerotium glucanicum, Sclerotium rolfsil or Plectania occidentalis; • fungi belonging to the genus Aspergillus and more particularly to the species Aspergillus itaconicus and Aspergillus terreus; • yeasts belonging to the genus Hansenula, such as the species Hansenula capsulata, In one preferred embodiment of the invention, the microorganism is a bacterium of the genus Xanthomonas, more particularly the species Xanthomonas campestris, and the biopolymer is xanthan gum. The biopolymers according to the invention may be obtained by any process for controlling the particle size distribution of a powder. By way of example, mention may be made of screening, As indicated above, the biopolymers according to the present invention disperse easily in aqueous media and do not require high-shear means. The dispersibility of the biopolymer powder is evaluated by counting the lumps formed when the biopolymer is placed in aqueous solution. The greater the number of lumps formed, the poorer the dispersibility- The hydration speed may be determined, for example, by measuring the viscosity developed over time under gentle stirring conditions. As a guide, gentle stirring may correspond to stirring with a deflocculating paddle at a speed which may be between 400 and 600 rpm. These characteristics make it possible to incorporate the biopolymers according to the invention into many formulations, as thickeners, viscosity modifiers, emulsifiers and/or stabilizers. The invention also covers the use of a biopolymer as defined above as a thickener, viscosity modifier, emulsifier and/or stabilizer in: formulations for the drilling for and assisted recovery of petroleum and for water treatment; formulations for paper, construction and textiles; food, cosmetics, agrochemical and pharmaceutical formulations; formulations for industrial and household cleaning; as well as the said formulations containing such a biopolymer. The examples given below are given by way of non-limiting illustration of the present invention. Key to the figures: Figure 1^represents the particle size distribution of the samples; products A, B and C, obtained using a Coulter LS230 granulometer in dry-route configuration. Figure 2 represents the hydration speed of samples A, B and C, in distilled water. This speed is determined by measuring the viscosity developed over time under the conditions of Example 1 - moisturization test in distilled water. Figure 3 represents the hydration speed of samples A, B and C, in a medium containing 40% sucrose. This speed is determined by measuring the viscosity developed over time under the conditions of Example 2. EXAMPLES Example 1 • Preparation of the samples Product A: Product A is a standard commercial xanthan gum powder sold under the name Rhodige.l by the company Rhodia. Product B: Product B is according to the invention. It is a xanthan gum with a particle size of between 180 ^.m and greater than 125 ^.m, This product is obtained by two simultaneous screenings: one screening through a screen with a mesh size of 180 ^,m and one screening through a 125 M^I screen. Product C; Product C is a xanthan guiu powder which has undergone 'a granulation by so-called 'fluid bed" technique according to Example 1 of patent FR-A-2 600 267. Table 1 Sample Product A Product B Product C % of particles between 60 and 250 microns 58 98 38 % of particles between 100 and 200 microns 48 79 18 • dso microns 149.6 180.8 177 .1 Figure 1 represents the particle size distribution of samples A, B and C. • Dispersibility test The dispersion properties of a hydrocolloid may be evaluated by a test for counting the number of lumps present in a solution after dispersion. Solutions of xanthan gum at 0.3% in distilled water are prepared. This dissolution is carried out on an amount of 500 ml of distilled water, in a low-line 1000 ml beaker, with a deflocculating paddle 65 mm in diameter, at a speed of 400 rpm for 15 min. The said solution is filtered through a screen with a 1 mm mesh size and the number of lumps present on the screen after filtration is recorded. ' The results are summarized in Table 2. Table 2 Product Number of lumps Product A 55 Product B 0 Product C 0 A product is considered as - "VERY GOOD" if the number of lumps is less than 5; - 'GOOD" if the number of lumps is less than 10; - "POOR" if the number of lumps is greater than 10. • Hydration test This test makes it possible to evaluate the hydration speed of a biopolymer powder in aqueous media. 0.3% of xanthan gum powder (products A, B and C) is dissolved in distilled water. This dissolution is carried out on an amount of 500 ml of distilled water, in a 1000 ml low-line beaker, with a deflocculating paddle 65 mm in diameter, at a speed of 4 00 rpm for 15 min. The viscosity of the said solution is measured at four different moments, using a Brookfield LVT viscometer, spindle No. 2, set at 12 rpm. These four moments are at 1, 2, 5 "and 15 minutes. The viscosity values are given in Table 3 below: Table 3 Product Viscosity at 1 min viscosity at 2 min Viscosity at 5 min Viscosity at 15 min Product A 2 0 mPa.s 100 mPa.s 3 3 2 mPa.s 605 mPa.s Product B 23 8 mPa.s 692 mPa.s 7 47 mPa.s 742 mPa.s Product C 13 7 mPa.s 712 mPa.s 6 87 mPa.s 67 5 mPa.s Figure 2 represents the hydration speed of samples A, B and C. in distilled waner. This speed is determined by measuring the viscosity developed over time. Example 2 Hydration test in a 40^ sucrose solution This test makes it possible to evaluate the hydration speed of a biopolymer powder in sugar-containing aqueous media, 0.3% of xanthan gum powder (products A, B and C) is dissolved in a solution containing 40% sucrose. This dissolution is carried out on an amount of 500 g CLAIMS 1. Dispersible and fast-hydrating biopolymef in dry form, characterized in that at least 75% by weight of the particles of the said biopolymer have a diameter of between 60 and 250 microns and a mean diameter (dso) of between 100 and 250 microns." 2. Biopolymer according to claim 1, characterized in that at least 75% by weight of the particles of the said biopolymer have a diameter of between 100 and 2 00 microns and a mean diameter (d5c) of between 100 and 2 00 microns. 3. Biopolymer according to either of claims 1 and 2, characterized in that the said biopolymer is a xanthan gum. 4. Use of a biopolymer according to any one of claims 1 to 3 as a thickener, viscosity modifier, emulsifier and/or stabilizer. 5. Use of a biopolymer according to any one of claims 1 to 3 as a thickener, viscosity modifier, emulsifier and/or stabilizer in formulations for the drilling for and the assisted recovery Of petroleum and for water treatment. 6. Use of a biopolymer according to any one of claims 1 to 3 as a thickener, viscosity modifier, emulsifier and/or stabilizer in food, cosmetics, pharmaceutical and agrochemical formulations, 7. Use of a biopolymer according to any one of claims 1 to 3 as a thickener, viscosity modifier, emulsifier and/or stabilizer, in formulations for industrial-and household cleaning. 8. Use of a biopolymer according to any one of claims 1 to 3 as a thickener, viscosity modifier, emulsifier and/or stabilizer in formulations for paper, construction and textiles. 9. Formulation for drilling for and assisted recovery of petroleum, for water treatment, food, cosmetics, pharmaceuticals or agrochemicals, for industrial and household cleaning or for paper, construction or textiles, using a biopolymer according to any one of claims 1 to ,3, as a thickener, viscosity modifier, emulsifier and/or stabilizer. Dispersible and fest-hydrating biopolymer in dry fonn sobsftaotially as herein described with reference to the acc

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