Sugar – starch – and carbohydrates – Products – Modified starches
Reexamination Certificate
2000-10-20
2002-11-19
Brunsman, David (Department: 1755)
Sugar, starch, and carbohydrates
Products
Modified starches
C127S038000
Reexamination Certificate
active
06482267
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for the conversion of starchy substances including stages of chemical liquification and stabilization carried out in the dry phase. It is also designed for the converted starchy substances obtained by this process, some of these substances also constituting new industrial products. Finally it relates to the industrial uses for these converted starchy substances.
By “chemical liquification”, we understand here all operations which consist of subjecting a starchy substance to the hydrolyzing action of a chemical agent, for example an acid or (per)oxidant; said agent may be used in the form of a liquid, solid and/or gas.
By “chemical liquification in the dry phase” we understand here a chemical liquification such as that defined above, performed within a reaction mix (including the starchy substance) the humidity of which is in practice below approximately 25%, preferentially in the approximate range 6% to 22%.
Techniques in the dry phase differ from the methods in an aqueous medium which involve a much more dilute reaction medium, with formation of a starch milk, presenting a dry matter, which usually does not exceed 35% to 40%.
These methods of liquification in an aqueous medium, however, involve the use of an additional filtration stage which has the disadvantage of causing substantial losses in soluble materials, principally in damaged starch granules, solubilized molecules of starch and salts produced during the preliminary neutralization of the fluidified starch. This in turn results in a reduction of the output in fluidified starchy substances and an increase in the polluting capacity of effluents.
These disadvantages have contributed to the search for and introduction of processes of chemical liquification in the dry phase. Thus, U.S. Pat. Nos. 3,479,220 and 3,692,581 describe a process for chemical liquification of starchy substances (starches, flours) by bringing these substances into contact, at ambient temperature (≈25° C.), with a concentrated mineral acid placed on a dry inert support and finely divided.
Patent EP 710.670 describes a process of continuous chemical modification by which a starch powder and a modifying agent, for example a hydrolyzing agent such as hydrochloric acid, are simultaneously introduced into a particular reactor (a “turboreactor”), the blade of which permits the almost instantaneous creation by centrifuge of a fine, dynamic and highly turbulent fluid layer of an intimate mix between the starch particles and the chemical agent.
The application for patent WO 97/13788 describes, in general terms, a process of chemical liquification of starches, performed in the dry phase and in a continuous fashion, involving the obligatory use, among other things, of a piston-type reactor (“plug flow reactor”) and of reaction temperatures of at most 77° C. (170° F.). According to this patent, a very wide range of chemical agents with hydrolyzing action are recommended, the preferred agents being hydrochloric acid, particularly in its gaseous form, and sulfuric acid. However, no exact example of the preparation of a fluidified starch is actually detailed in this document.
The application for patent EP 902.037 in the name of the Applicant, for its part, gives an example of liquification in the dry phase, under typical residence time and temperature conditions, of native starches or cationic starches.
In any case, whether they are used in an aqueous medium or in the dry phase, the processes of chemical liquification permit the preparation of converted products with commonly researched physical and chemical properties such as, in particular, reduced intrinsic viscosity and viscosity on heating, the viscosity on heating being evaluable by the classic measurement of water fluidity (WF), which may be measured according to the method described in patents EP 373.313 and U.S. Pat. No. 4,499,116 using a STORMER® viscosimeter as recommended in “Modified Starches: Properties and Uses”, O. B. WURZBURG, M. S., CRC Press, Inc, 1986, page 20, it being understood that the measurement of WF values above 90 is refined by an extrapolation of the WF curve as a function of the time taken for 100 revolutions according to a regression of type in (WF)=a+b×1n(t) (henceforward “equation (1)”) and taking the details from the table in column 9 of U.S. Pat. No. 4,499,116 for a mass of dry starch of 13.20 g. The value of the equation coefficients (1) is 5.384 for a and −0.4080 for b with a correlation coefficient R
2
of 0.997. By way of an example, applying equation (1), when the time for 100 revolutions is 7.0 seconds, the water flow (WF) thus calculated is 98.5.
Among the other properties researched, we may name:
increased solubility on heating, and
increased gel strength and film strength.
One of the main technical and economical advantages of chemically-fluidified starchy substances is their ability to be used and processed, especially to be cooked, to very highly dry matter; this is due to their viscosity, which is much lower than that of native products.
This ability results in energy gains (smaller volumes of water to eliminate) and technological advantages which are turned to good account in industry. However, whatever their preparation process, chemically fluidified starchy substances usually involve the disadvantage of producing unstable glues, particularly glues which very significantly increase viscosity on cooling and/or during prolonged storage. This instability often shows as irreversible gelation or downgrading.
This is why we usually associate chemical liquification processes with stabilization reactions, and particularly with reactions of esterification, etherification or oxidation, with a view to rendering fluidified starchy substances useful industrially. They may in particular involve reactions of acetylation, hydroxypropylation or oxidation by bleach. Although effective, these processes have the disadvantage of causing considerable organic and/or saline pollution. Other methods aim to combine chemical liquification processes with cross-linking reactions.
Thus U.S. Pat. No. 3,705,046 describes the cross linking, in the aqueous phase, of a starch, either native or cationic, by the use of paraformaldehyde, and this, either at the time of its liquification or before, also in the aqueous phase, by hydrochloric acid. Taking into account the intended application (the finishing of textile fibers), the cross-linked/fluidified starch obtained should therefore be relatively little depolymerized and should still have a relatively high viscosity, i.e. a Brabender viscosity, measured at a rather weak dry matter (“MS”) (10%), always above 200 Brabender units (“UB”) and usually in the range of approximately 230 to 930 UB. Such viscosities correspond to limited WF values, i.e. below approximately 45, although the authors envisage the use of relatively large quantities of hydrochloric acid. The contents of this patent show in fact that to obtain the desired products the normality of the filtered reaction medium (“filtrate acidity”) should be below 2 N and, in practice, should be in the range 0.05 to 0.30 N, corresponding overall to reaction pH of 1.3 at most.
In addition, it seems that the duration of the reaction must be long (usually in the range of 10 to 15 hours, even 24 hours according to example 1) to obtain the desired levels of cross-linking and depolymerization.
U.S. Pat. Nos. 3,778,431 and 3,884,909 describe the cross linking, in the aqueous phase, of a native or cationic maize starch using a cross-linking agent such as 1,3-dichloro-2-propanol, 1,4-dichlorobutene-2 or epichlorhydrin, prior to its liquification by hydrochloric acid, also in an aqueous medium.
However, such processes present, and even accentuate, the above mentioned disadvantages inherent in processes in the aqueous phase (reduction of output, increase in pollution load).
For their part, the above mentioned patents EP 710 670, WO 97/13788 and EP 902 037, which are much more recent, are not specifically concerned with comb
Dreux Jean-Louis
Fuertes Patrick
Lambin Anne
Brunsman David
Henderson & Sturm LLP
Roquette Freres
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