SE439313B - PROCEDURE FOR PRODUCING MODIFIED STARCHES - Google Patents

Description

10 15 20 25 30 35 731192? -S 2 all commonly used starches or flours, such as maize, wheat or rice starch and potatoes, manioc or other powders.

According to the present invention, one begins with a starch slurry, performs at least one initial drying phase before the reaction chamber, which phase is accompanied by dilution drying phase, and a second drying phase after the chamber and man uses the filtrate from the second drying phase such as process water, which is returned at least once more the dilution phase.

This water was used for the preparation of starch. the slurry during dilution of the starch cake, obtained from the first drying phase, current circuit for the production of the modified the starch has a real barrier against water, which has turned in the production of the starch slurry, which used as starting material.

Discharges of contaminated water are avoided by it waste water laden with solutes is recycled as process water. As a result, some of the solved substances to be included in the dried end product and a another part remains in the recirculation water. During the The successive reactions tend to have a residual content soluble substances in the modified starch obtained to reach a limit, which in practice is reached after a few cycles such as will be explained in more detail in it following.

According to the invention, the degree of dilution of substances contained in the recirculation water after by adding fresh water, preferably when filtering the tract leaves the second drying phase. The reactants, required to obtain the modified starch addition, is further added by mixing and evenly heat these with the filtrate from the second dryer. phase upstream of the reaction chamber.

A device according to the invention for carrying out the method involves a first drying centrifuge connected to a body which feeds starch slurry, lO 15 20 25 30 781192743 3 at the centrifuge, means for the outgoing cake are connected to a dilution tank in series with a mixer, which has suitable means for feeding reactants, and with a any device for reheating, which results in the reaction chamber, which has suitable supply lines and the outlet end is connected to a second drying center modified starch fugue, wherein the filtrate feeder the centrifuge is connected to the dilution tank supply line for dilution water.

According to the invention it is preferred that: - the means for outgoing filtrates from the second the bird drying device is equipped with a concentration device for insoluble substances in the filtrate, which concentration device is intended to return these substances to the second centrifugal drying device, a safety filter is provided in the circuit for the filtrate the return from the second centrifugal dryer downstream of the concentrator when it is connected, the mixer is preferably of static type and fresh water supply means are provided at the inlet end of the safety filter.

Additional features and advantages of the invention is clearer from the description that accompanies it reference to the accompanying non-limiting drawing, which in the form of a block diagram shows the conversion at a device according to the invention and shows the success of the method. siva phases. ' The conversion circuit shown in the drawing includes grips an inlet 1 for starch slurry, which inlet in a known manner starts from a station A for manufacturing (not shown) for a first centrifugal dryer 2. The filtrate from dryer 2 is passed through a line 3 to the starch production station A, which the starch slurry. The dried cake, which contains about 35% moisture, is brought to 4 by means of exemplary a worm screw and a conveyor belt for a diluent tank 5, which is equipped with a suitable stirrer lO 15 20 25 30 35 7811927-8 4 order, where the cake is redispersed in water from the inlet pet 6 for regenerating a starch slurry.

All the elements in the conversion circuit are arranged in series. The outlet from the dilution tank 5 is therefore the end of a mixer 7 of, for example, static type, which mixer is connected to a possible device for reheating, which results in a reaction chamber or tank 9, which in turn is connected to a second centrifugal dryer 10, whose filtrate outlet 11 constitutes the starting point of a line 12 for returning process water to the dilution tank 5 and the mixer 7, optionally via a concentrator 13 and a safety filter 14, and a fresh water inlet is provided nat at the inlet end of the l5i.filter.

The mixer 7 usually includes an inlet 16 for a suitable reactant, an inlet 17 for an alkaline one agent, a catalyst or other agent and an aqueous inlet 18. The reaction tank 9 includes an inlet 19 for an acidic or neutralizing agent. The the second dryer 10 includes an outlet 20 for the central trifugated cake, which is the modified starch, which outlet, for example, is connected to a suitable one dryer S. The filtrate outlet 11 can feed concentrator 13, the outgoing quantity 21 of which is returned to the inlet pet 22 in the second centrifugal dryer 10. Of practical For this reason, a relay tank 23 may be provided in series between the outlet from the dilution tank 5 and the 7. The water used for redispersion » the centrifuged cake from the centrifugal dryer 2 i dilution tank 5, consists essentially of the filtrate from the second dryer 10 arranged in the starch conversion circuit sens end. The density of the starch slurry can be adjusted at will but is suitably selected within the range dâš = 1,184 to 1,188. It is perfectly dispersed and density controlled the starch slurry is transferred to the holding tank 23 with corresponding capacity, the first tank 5 emptied and the supply of the circuit is ensured.

This supply of the reaction tank circuit 9 10 l5 20 25 30 35 7811927-8 5 achieved at a speed which depends on the capacity of the circuit. citation and reaction time; preferably the speed so that the final dryer S works continuously with looking at these parameters. During the pumping for food reaction tank 9, starch slurry is circulated. through one or more static mixers 7, which allows an even insertion through the inlets 16 and 17 of products capable of modifying the starch in an appropriate manner, such as means for transfer to the form, compounds, which can be combined with starch by the addition of catalysts or products, which improves the resistance of starches to swelling, especially at high pH values and temperatures. Starch- the slurry then flows through the heater 8, which is usually a plate-type heat exchanger with sufficient capacity to produce starch the slurry with the highest planned outlet velocity at a temperature which is usually between 40-55 ° C.

The reaction begins at the heater 8 outlet. The neutralizing agent, which terminates the reaction, may be an acid or base, and this agent is fed directly into the reaction tank 9 through the inlet 19.

The time to empty the reaction chamber 9 with a capacity density identical to the capacity of tanks 5 and 23, depends on the capacity of the downstream part of the circuit, which includes the centrifugal dryer 10 and the dryer S, the latter is of the pneumatic type.

The filtrate from the centrifugal dryer 10 is fed to insoluble starch by mixing with overflow the flow from the centrifuge 10. This starch can be separated by taking advantage of its different densities. passing through at least one concentration ring device 13, which may be of the hydrocyclone type. The concentrated insoluble starch fraction is then returned at 21 to material fed to the centrifuge] L) and the the clarified fraction from the outlet 24 was used as the described more as water for diluting starch then in tank 5 (at 6) and as water for dilution of Pooa Quarter 10 15 20 25 30 35 7811927-8 6 s the chemical reactants and additives (at 18).

The safety filter 14 eliminates the risk present non-soluble starch, which has a tendency to not be desirable in the latter case.

In practice, it is enough to have a conversion circuit comprising two reaction tanks in succession for to ensure continuous production. All thoughts in the circuit preferably has the same capacity and is equipped with stirring means.

It has been found according to the present invention that the content of residual soluble substances in the modified starch during the course of the successful siva reactions focus on a limit, as in practice is achieved after 5 or 6 cycles and.correspondingly the sum of the solubilized starch and the chemical compounds or reactants which are introduced or formed during a single reaction.

For greater clarity, reference is now made to a simple system, defined by the following weight data: total amount of loose material formed or introduced underneath a reaction = x, - dry starting material = 100, water from initially centrifuged starch = 59, - recirculation water = V = 91, Vo = 150, modified starch = 100, modified starch water = 59.

Since the distribution of soluble substances in aqueous phase is constant, it is possible to calculate the increase the concentration of soluble substances during the total water = seven cycles: The importance of soluble substances in the circulating water net: Reaction 1 I »X lO 15 20 25 30 35 7811927-8 Reaction2 (znx L + J-) Y ... -LXY_ (1 + V) Vo o Vo o . V V V 2 Reaction 3 IX WH + v-O-) + 1J% = LX lxšalß1 + šíro + V V V Reaction n: IX% [1 + V6 + (va) + ... + (V n-1 V0 For ga <1, as is the case in the present method, and for an infinite number of reactions n, the limit of the soluble substances in circulation of the ratio I x Vo multiplied by the sum of a geometric series of holding åš as under: limit mass of circulatory loose material = JC x x ï -; - = Y. vo The content of dissolved material in the circulating water 1'x 1009 = .d x x 100 V0 _ V 0 water, varvi = 1.69 xça / Vätten present example.

The content of dissolved material in starch _r __> <__ 1_92 x ï V0 - V lOO 1% / dry material.

The calculation thus gives a logical result because with such an isolated system in equilibrium going quantities must compensate for the quantities included.

The chemical additives used for a reaction is in some cases not found in the liquid phase because those at the end of production are in a form which is insoluble or sparingly soluble in water (such as calcium sulphate, which is obtained when sulfuric acid is neutralized with quicklime or calcium carbonate). The content of foreign sub- punches in the finished starch then reach their limit value faster, but the limit remains the same and the Poor QUALITYJ _, ___ _ ___... ___.___.... ï _ .. ~ ......-.._...-- lO 15 20 25 30 35 7811927-'8 8 the cooling liquids become less loaded with soluble material. _ In cases where the circulating fluids have to be race during a rather long production stoppage it is appropriate to protect them against the risk of fermentation during the ring. Certain preservatives, such as sodium hypoclonal rit, has proved effective for this purpose then it -used in small quantities.

The following non-limiting examples, given in purpose of illustrating the invention, makes it possible to realize both the scope and usefulness of the the finding.

EXAMPLE 1 Preparation of liquid starch by the acid method This procedure is performed in a circuit similar to the one previously described and comprising four tanks with the same capacity, namely: a tank for dispersing centrifuged starch, - a holding tank, - two reaction tanks.

Hydrochloric acid (d = 16,6) was used for transfer to in the proportions 40 liters per tonne dry materials per starch.

The hydrochloric acid is fed continuously into the starch slurry. during the filling of the reaction tank, which takes 3kn through an intermediate static mixer. A heating plate-type device located immediately downstream raises erärkeleene temperature to 52 - s3 ° c.

At the end of the reaction, neutralization is effected with a sodium carbonate powder and the pH is adjusted to 6.0.

Since the capacity of the circuit is such that the reaction the tank must be emptied at ll h becomes the time available for the reaction for transfer to liquid form (ll h - 3 h) = 8 h plus half of the tank filling time, because the starch begins its conversion immediately on departure from the heater, which does 1 h 30 min or a total of 9 h 30 min. This time period has proved to be more than sufficient to lO l5 20 25 30 7811927-8 9 achieve the desired viscosity reduction and final the product has a Scott viscosity (60 g starch - pourable 100 ml) of 45 to 60 for 13 reactions.

Continuous operation with two reaction tanks programmed according to Table 1 below, in which the figures are expressed in hours: TABLE 1 Reaction thoughts 'Nr l Nr 2 Nr l Nr 2 The starch dispersion begins O h ll h 22 h 9 h The starch dispersion ends h 15 h 2 h 13 h Stay tank full h 16 h 3 h 14 h Reaction tank full h 19 h 6 h 17 h The reaction is terminated 16 h 3 h 14 h l h Reaction tank up to 3 h l4 h l h 12 h There is no interruption in the circuit of the circuit. downstream of the reaction tanks.

For practical reasons and to allow a certain delay in the recovery of the filtered water for dispersing the starch, which is fed into the an additional amount of 400 liters of water is added per tonne of dry matter / starch during the first the dispersion step.

The first two steps are performed with starch sludge (dââ = 1,184), which comes directly from starch set production without centrifugation.

From the third step, the cycles become normal.

How residual loose material in the liquefied starch The development is summarized in Table 2 below: -1 --_ - ._.._.-____.._.._..__ ..-_ lO 15 20 25 30 35 7811927-8 'lo TABLE 2 Soluble material in end product (% / dry material) Inorganic Organic Total l = a cycle 0.95 0.40 1.35 2nd cycle 1.50 0.65 2.15 3rd cycle 1.85 0.80 2.65 4th cycle 2, l0 0.90 3.00 s = e cycle á, 2o- 0.95 3.15 6th cycle 2.30 0.95 3.25 7th cycle 2.35 1.00 3.35 Limit 2.40 1, oo 3,400 As shown, the limit levels of soluble matter are reached. material for all practical purposes at about the 6th cycle keln. The average content after mixing the different reactions ions is about 2.70% / dry matter for the total amount. the soluble material. ' EXAMPLE 2 Preparation of cationic starch This method is performed with the same device as in preparation of the liquefied starch, which is is written in example l.

The reactant used is a block when ammonium compound, which comprises an epoxy group reaction (2,3-epoxypropyltrimethylammonium chloride) - The additive is added to the starch slurry in the amount of 20 parts per 1000 parts dry material / starch proportionally against the feeding of starch to the reaction tank below pumping and for this purpose a first was used static mixer.

A reaction catalyst is then added, which catalyst consists of sodium hydroxide in an amount of 12 parts per 1000 parts of dry starch. The sodium hydroxide is dissolved first and then diluted in 120 liters of water of the same type as the water used to disperse the starch 10 15 20 30 35 7811927-8 ll after which it is introduced into the starch slurry tinuous and proportional to the feed rate via an intermediate second static mixer. Since the soda water must be insoluble starch, a safety filter with a retention was used. capability corresponding to a size of 3 nm to complement the impact of the concentration and clarification bodies of the liquids from the centrifuge arranged in the circuit final.

The starch slurry is heated to a reaction temperature. temperature of 49 ° C by passing it through a plate-type heat exchanger.

The filling of the reaction tank takes 3 hours and with this two-tank systems will therefore be the time available for the reaction and its interruption 9 h 30 min, and the The required reaction time is of the order of 8 hours.

When the conversion is complete, the starch is neutralized with hydrochloric acid (d = 16, 16) with a pH close to 5.0.

With this procedure, it has not been necessary to perform the first two steps with non-centrifuged starch slurry or to use a certain excess ~ amount of water for the first dispersion of the fugue starch as residual filtered water (stored after the manufacture of liquefied starch as in Example 1) was recycled for the dispersion of starch. with 35% moisture from starch production.

The modified starch, which was finally formed after 14 reactions, had the following properties: Humidity: 12% pH value: u 5 Degree of substitution: 0.017 Total amount of loose material: less than 2.5% Inorganic material: less than 1.75%.

The distribution of residual loose material in it cationic starch formed in this way is taken in Table 3 below (it should be noted that a cycle corresponds to two reactions).

* Poor Qtfamïr 7811927-8 10 15 20 25 30 35 12 TABLE 3 Soluble material in end product (% / dry material) Inorganic Organic Total 1st cycle 1.49 0.83 2.32 2nd cycle 1.60 0.79 2.39 3rd cycle 1.66 0.78 2.44 4th cycle 1.69 0.77 2.46 5th cycle 1.71 0.76 2.47 6th cycle '1.73 0.75 2.48 7th cycle 1.73 0.75 2.48 Limit 1.75 0.75 2.50 This example shows that it is possible to re-use turn the liquids, which: remain after production of a certain type of converted starch to produce another type of converted starch provided that these liquids have been stored so that they are prevented from fermentation (in this example, 1 liter of hypochlorite was added at a concentration of 155 g of active chlorine per liter to per cubic meter of water) and provided that production processes for various modified starches varieties are so programmed as to exclude incompatibilities called.

The soluble compounds are derived from the liquid made starch, and is present in the circulatory system. the water decreases from one cycle to the next cycle in one geometric series with a ratio less than 1 and finally reaches the limit value 0. The limit for soluble materials, which are finally obtained in the manufacture of the cationic starch thus does not differ the limit that would be achieved when using pure water.

EXAMPLE 3 Preparation of an oxidized starch The procedure carried out in the previous written circuit and which included the four thoughts for lO 15 20 25 781192? -A 13 starch dispersion, pause and reaction and equipment for introducing reactant during pumping to the reaction thoughts.

The reactant used was a solution of sodium hypochlorite titrated to 150 g C12 per liter and containing 48 g per liter of sodium.

With a static mixer was introduced into the reactant in the starch slurry during the time taken for the reaction the idea of being filled. A plate-type heating device arranged immediately downstream raises the temperature to about 42 ° C if necessary.

The amount of hypochlorite solution injected was such that the chlorine content introduced had a ratio of about 1.2 to the dry starch material.

The reaction time was about 3 hours.

The oxidized starch formed had the following properties. creates: Humidity: l2% pH value 8 to 9 Carboxyl: 0.1 Total amount of material 3.8% Inorganic solution material 2.8% The content of soluble material remaining in the oxidized the starch was developed såsonxvisasi.table 4 below.

Pocm ouimmg 7811927-8 10 15 20 25 30 35 l4 TABLE 4 Soluble material in end product (% / dry material) Inorganic Organic Total 1st cycle 1.07 0.39 1.46 2nd cycle 1.72 0.62 2.34 3rd cycle 2.12 0.77 2.89 4th cycle 2.37 0.86 3.23 5th cycle 2.50 0.91 3.41 6th cycle '2.60 0.94 3.54 7th cycle 2.65 0.96 3.61 Limit 2.70 l 3.70 EXAMPLE 4 Preparation of an acetylated starch The process was carried out in a circuit of a similar kind as the circuit previously described and already used in Example 1. This circuit includes four tanks identical capacity, namely: a tank for dispersing the centrifuged starch, - a holding tank, - two reaction tanks.

The reactant used consists of acetic anhydride and the catalyst is a soda solution, as previously developed set by diluting soda in flake form in a appropriate volume of water drained from the recirculation.

These two solutions are injected into the starch slurry portionwise against their feed rate during the entire pumping against the reaction tank until amounts of 30 per 1000 and 19 per 1000.

Because the soda water must be free from insoluble starch was used a safety filter with a retention size of 3 μm as in Example 2 above.

The acetylated starch formed has the following properties creates: 10 15 20 25 30 7811927-8 '15 Humidity: 12% pH: 5 to 6 % acetyl: close to 1 Total amount of soluble material less than 4.2% Inorganic soluble substances less than 3.7% The content of residual soluble material in the converted the starch develops as shown in Table 5 below: TABLE 5 Soluble material in end product (% / dry material) Inorganic Organic Total 1st cycle 1.33 0.20 1.53 2nd cycle 2.18 0.30 2.48 3rd cycle 2.74 0.35 3.09 4th cycle 3.07 0.40 3.47 5th cycle 3.30 0.45 3.75 6th cycle 3.45 0.45 3.85 7th cycle 3.53 0.48 4.01 Limit 3.70 0.50 4.20 A similar procedure can be performed for of an acetylated starch and this time one can use water, obtained during the production of a oxidized starch (see previous example) to bring the starch into suspension. ' Under these operating conditions, the previously obtained but with greater homogeneity in the results obtained by analyzing the strength varieties, which resulted from the different reactions.

The content of residual soluble material in the starch has developed as shown in Table 6 below: 10 15 20 25 30 35 7811927-8 16 TABLE 6 Soluble material in end product (% / dry material) Inorganic Organic Total 1st cycle 3.69 1.04 4.73 2nd cycle 3.69 0.84 4.53 - 3rd cycle 3.71 0.65 4.36 4th cycle 3.69 0.62 4.31 5th cycle 3.69 0.59 4.28 6th cycle 3.70 0.54 4.24 7th cycle 3.69 0.54 4.23 Limit 3.70 0.55 4.25 According to a variant of the invention, it is possible start with powdered starch with a moisture content of about 12% and return it in suspension directly to the diluent the first centrifugation phase carried out before the drying of the starch.

The method according to the invention can be applied to all types of starch, which do not the estate is destroyed. The soluble substances, which are included in the final product, may possibly contain a small portion degraded starch, an inactive part of reactants, saline from a neutralization or other chemical additives.

The modified starch types obtained according to the finding, includes in particular: - liquefied starches in acidic medium or in oxi- medium, starches, crosslinked by multifunctional groups, - cationic starches, acetylated starches, - carboxymethyl starches, hydroxyalkyl starches, starches treated in an alkaline environment, - phosphated starches. 7811927-8 17 The modified starch obtained according to invention, can be used in particular for preparation of starch pastes.

The present invention has, of course, been described and damaged with the help of examples and modifications and modifications can be made without deviating from the scope of the invention as set forth herein requirement.

Claims (8)

7811927-8 10 15 20 25 30 35 PATENT CLAIMS 1. Methods of preparing modified starches, starting from a starch slurry which is centrifuged, subjected to a dilution phase and reacted by chemical reactants in a reaction chamber, characterized in that a first centrifugation is carried out upstream of the reaction chamber and a second centrifugation downstream of the chamber and using the filtrate originating from the second centrifugation phase as process water, which is returned at least once to the dilution phase, eliminating waste water discharges. 2. A method according to claim 1, wherein the degree of dilution of the substances in the recirculation water is adjusted at will by adding fresh water, preferably to the filtrate resulting from the second centrifugation. 3. A method according to any one of the preceding claims, characterized in that the centrifuged cake obtained from the second centrifugation and constituting the modified starch is subjected to drying. Device for carrying out the method according to any one of the preceding claims, characterized in that it comprises a first centrifugal dryer connected to feed means for feeding starch slurry and with means for outgoing cake connected to a dilution tank, which is placed in series with a mixer , which has means for incoming reactant and with an optional heating device, which opens into a reaction chamber, which has suitable supply lines and which has its outlet means connected to a second centrifugal dryer for modified starch, the filtrate outlet means from the latter being connected to the circuit for supply of dilution water to the dilution tank. Device according to claim 4, characterized in that the outlet means for the filtrate from the second centrifugal dryer comprise a concentration device 10 fa, _ C: _ | q 78119 -8 for insoluble substances contained in the filtrate, which concentration device is intended to return the substances to the second centrifugal dryer. Device according to one of Claims 4 or 5, characterized in that a safety filter is arranged in the line for returning filtrate from the second centrifugal dryer downstream of the concentrating device. Device according to one of Claims 4 to 6, characterized in that means for fresh water supply are arranged at the inlet of the safety filter. Device according to any one of claims 4 to 7, characterized in that the outlet means for the cake centrifuged in the second centrifugal dryer are connected to a dryer for drying the obtained modified starch.