RU2190623C2 - Method of synthesis of hydroxyalkylcarboxymethyl-starch - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: method of synthesis of hydroxyalkylcarboxymethyl-starch involves the preparing a homogenized reactive mixture from starch, monochloroacetic acid sodium salt, sodium hydroxide an aqueous solution into high-effective mixers of blade of anger type and esterification. In the process of preparing the reactive mixture monochloroacetic acid sodium salt is added in the amount 0.1-0.2 mole per 1 anhydroglucose starch link. Then the prepared reactive mixture is fed into autoclave where a mixture is treated with a hydroxyalkylating agent taken in the amount 0.1-0.3 mole per 1 an anhydroglucose starch link at temperature from 35 to 82 C for 0.5-3.0 h. Then the obtained product is dried at temperature 60-90 C for 0.5-2.0 h. Method provides preparing water-swelling hydroxyalkylcarboxymethyl-starch with the substitution degree by carboxymethyl groups = 0.07-0.15 and the mole substitution by hydroxyalkyl groups = 0.05-0.10 that provides the required properties in their using as a water-retaining agent in drilling solutions, namely, high swelling rate, enhanced salt resistance, water loss and an uniform fine-grained structure and friability. EFFECT: improved method of preparing, valuable properties. 5 cl, 3 tbl

Description

 The invention relates to the field of production of mixed starch ethers, namely, hydroxyethyl and hydroxypropyl carboxymethyl starch.

 The field of use of hydroxyalkyl carboxymethyl starch (hereinafter - GACMC) is due to their ability to swell in cold water with the formation of aqueous gels - these are various industries where GACMC can be used as thickeners, emulsifiers, stabilizers for aqueous solutions, suspensions, emulsions, in particular in oil and the gas industry as reagents that reduce the loss of water-based drilling fluids in the textile industry as compositions as thickeners for printing or concentrate dyeing agent in the paper industry for sizing paper in various adhesive compositions.

 Compared to simple starch monoesters: carboxymethyl starch (hereinafter referred to as KMK) and hydroxyalkyl starch (hydroxyethyl and hydroxypropyl starch), GACMK have advantages due to the combination of the properties of ionic and nonionic polymers, which extends the range of their properties due to the presence of carboxymethyl (ionic) groups drilling fluids and at the same time the presence of hydroxyalkyl groups that increase the stability of the resulting product under conditions of polymineral aggression.

 A known method for producing hydroxyalkyl starch described in "Starch: Chemistry and Tecnology" (volume 1, p. 439). According to the described process, the concentrated starch paste is hydroxyalkylated in the presence of sodium hydroxide (hereinafter NaOH) used as a catalyst, sodium chloride and sodium sulfate, respectively used as a cocatalyst and a reagent that inhibits the gelatinization of starch and the resulting hydroxyalkyl starch.

 The disadvantages of this method are, firstly, the low efficiency of the starch hydroxyalkylation reaction carried out in an aqueous medium, and secondly, the high energy costs associated with the need for glycol regeneration - by-products of the reaction, and thirdly, the need for continuous drying of the finished product containing up to 50 % water.

A known method of producing KMK [US patent 4716186] by the esterification of starch with monochloracetic acid (hereinafter MCCA) or its sodium salt (NaMXYK) in the presence of an aqueous solution of NaOH in an aqueous solution of aliphatic alcohols with C _1-4 , which ensure its isolation in dry granular form. The disadvantage of the claimed method is the use of a large number of organic solvents - alcohols with the need for their subsequent regeneration.

 The closest technical solution to the claimed method is a method for producing technical sodium salt KMK [RF patent 2107693]. According to this method, the CMC production process is carried out in two stages: mixing starch, carboxymethylating agent (MCAA or NaMCAC), NaOH and water in special highly efficient mixers and heating in a drying reactor, where carboxymethylation and drying are combined.

 This method allows to obtain CMC with a degree of substitution from 0.1 to 0.5, swelling in cold water with a swelling volume of 35 to 200 ml / g, with a high viscosity of aqueous gel (4%) - up to 6500 MPa • s.

 However, the obtained product cannot have sufficient and necessary water loss under conditions of polymineral aggression and salt resistance (water loss in a solution containing ions, in particular, Ca and Mg) when using CMC as constituent drilling fluids. In addition, in the process of obtaining CMC, gelatinization and agglomeration of the resulting product is possible, as a result of which the resulting CMC must be subjected to additional grinding.

 The technical task of the proposed method is to refine the sequence of stages for obtaining GACMC, esterification modes (temperature, time), special conditions (introduction of special reagents) that prevent gelatinization of starch and its derivatives in the process of esterification at the stages of carboxymethylation and hydroxyalkylation and, as a result, agglomeration of the target product.

 The technical result of the proposed method is to obtain water-swelling hydroxyalkylcarboxymethyl starch with a degree of substitution on carboxymethyl groups of 0.07-0.15 and molar substitution on hydroxyalkyl groups of 0.05-0.10, which provides the desired properties when used, in particular, as a water-holding reagent in drilling fluids, namely: high quality of the product as a whole, high swelling rate, increased salt resistance, water loss and, in addition, a uniform fine-grained structure and flowability.

 This problem is solved by preparing a homogenized reactive mixture of starch, NaMXYK - carboxymethylating agent and an aqueous solution of NaOH 20-50% wt. concentration in special high-performance mixers (a reactor-mixing twin-screw machine, an intensive paddle mixer), transferring it to an autoclave used as an oxyalkylator, treating it with a hydroxyalkylating agent at a given elevated temperature for a certain time, and drying at elevated temperature.

When using ethylene oxide as a hydroxyalkylating agent, the treatment is carried out at a temperature of from 35 to 70 ^{° C.} , when using propylene oxide, the treatment is carried out at a temperature of from 60 to 82 ^° C.

A feature of the proposed method is that the esterifying agent NaMXУK is both a carboxymethylating agent and an agent that prevents gelatinization, i.e. sticking together of swollen grains of the resulting product, leading to agglomeration. This is achieved by conducting two processes in parallel: carboxymethylation and hydroxyalkylation. The presence of NaMXУK in the reactive medium, as well as the stated synthesis synthesis temperature, allow hydroxyalkylation without the introduction of special agents that require the introduction of a separate washing step at the end of the process and, as a result, obtain a fine-grained bulk product with desired properties. In this case, the amount of NaMHUK necessary to achieve the result is determined by a quantitative interval equal to 0.10-0.20 mol per one anhydroglucose unit (hereinafter - AGZ) of starch, and provides the necessary degree of substitution of 0.07-0.15. The boundaries of the temperature regime are determined by the following factors: the lower boundary of the hydroxyethylation and hydroxypropylation processes (35 ^° C and 60 ^° C, respectively) - the duration of the reactions, the upper boundary of the hydroxyethylation and hydroxypropylation processes (70 ^° C and 82 ^° C, respectively) - a sharp increase in the proportion of non-target products reactions, in particular glycols.

 An attempt to carry out hydroxyalkylation after the completion of carboxymethylation in accordance with the method described in the prototype leads to a product in the form of a pasty mass, the use of which is extremely difficult and requires the introduction of additional technological stages for its processing.

It is known that the introduction of salts of Na (NaCl, Na ₂ SO ₄ , Na ₃ PO ₄ ) in the synthesis of polysaccharide ethers reduces the solubility of the resulting water-soluble and water-swellable products and / or prevents their agglomeration [US patent 2588463].

 However, known agglomeration inhibiting agents are usually introduced in large quantities and, in addition, upon completion of the process, they must be removed from the target product by introducing a separate washing step, since their presence in the target product degrades the quality.

 As a result of this, the advantage when using NaMXYK as an agent preventing the agglomeration of the starch system is obvious over known agents of similar use.

 A special case of the implementation of the proposed method is the introduction of a non-volatile organic solvent in an amount of 1.0-10 wt.% By weight of starch at the stage of preparation of a homogenized reactive mixture. As non-volatile organic solvent can be used low molecular weight liquid mono-, di-, triethylene glycols, polypropylene glycols and low molecular weight polyethers based on ethylene oxide: their introduction into a reactive mixture contributes to better homogenization of the mixture, improving the overall processability, preventing agglomeration of starch systems, improving operational properties of the resulting product.

 Another particular case of the proposed method is the introduction of a crosslinking agent at the rate of 0.0001-0.0100 mol per 1.0 AGZ of starch at the stage of preparation of a homogenized reactive mixture. Epichlorohydrin can be used as a cross-linking agent, the introduction of which regulates the swelling process, preventing gelatinization and agglomeration of the resulting product, and, in addition, allows changing the operational properties (see table 3).

The inventive method is as follows. In a highly efficient screw or paddle type mixer, a reactive mixture is prepared consisting of starch, an aqueous NaOH solution of 20-50 wt.% And NaMHUK at a temperature of 10-50 ^o C for 0.5-3.0 minutes, which is a homogenized mass. The resulting reactive mixture is loaded into an autoclave equipped with a thermostatic device, where a hydroxyalkylating agent is also supplied, stirred and kept at a given elevated temperature for 0.5-3.0 hours. The resulting intermediate is discharged from the autoclave and transferred to a drying reactor equipped with a jacket for heating and removal of evaporating water, keeping the product at a temperature of 60-90 ^o C for 0.5-2.0 hours, and thus complete the carboxymethylation process, combining it with drying of the finished product.

 The introduction of a non-volatile organic solvent in the reactive mixture in the particular case of the method is carried out before feeding an aqueous solution of NaOH.

 The introduction of a crosslinking agent in a reactive mixture in the particular case of the method is carried out by dissolving the crosslinking agent in the applicable organic solvent.

 As the main feedstock, various types of starch are used, for example, potato, corn, etc.

 The possibility of implementing the method is illustrated by the following examples.

 Examples 1-9. Preparation of hydroxyethyl carboxymethyl starch (HECMC).

1500 g / min of starch is fed into the continuous twin reactor twin mixing machine (water mass fraction in the case of corn starch - 12%, in the case of potato starch - 20 wt.%), Carboxymethylating reagent (NaMHUK) and an aqueous solution of NaOH. In the case of using a non-volatile organic solvent, it is supplied before the aqueous NaOH solution is supplied, and in the case of using a cross-linking agent, it is fed in the solution of the used organic solvent. The components of the mixture undergo intensive mixing. The reactive mixture after leaving the reactor-mixing machine weighing 160 kg is loaded into an autoclave with a capacity of 350 l, in which, after feeding ethylene oxide into it, the processes of hydroxyethylation and carboxymethylation are carried out at a temperature of from 35 to 70 ^o C. After completion of the reactions, the product is fed to a dryer, where drying the product at a temperature of 60-90 ^o C.

 The non-volatile organic solvent Laprol used in the synthesis is a polyether based on ethylene oxide of the corresponding molecular weight.

 The data of specific technological parameters are given in table 1.

 Example 10 (prototype).

 1500 g / min, starch, NaMHUK, an aqueous solution of NaOH are fed into a continuous reactor twin-mixing machine. The components of the mixture undergo intensive mixing.

 The reactive mixture is transferred to a continuous dryer, in which the processes of carboxymethylation of starch and drying of the product take place. The resulting carboxymethylated starch weighing 150 kg with a mass fraction of water of 10% is loaded into an autoclave with a capacity of 350 l, into which 114 ml of NaOH solution with a mass fraction of 24% and 3700 g of ethylene oxide are fed. After the hydroxyethylation process, the product obtained in the reactor has the consistency of a dough. Processing a product of this consistency into a finished powdery product is extremely difficult and requires the introduction of additional process steps.

 Examples 11-15. Obtaining hydroxypropylcarboxymethyl starch (HPMC).

 1500 g of starch, NaMXУK, an aqueous solution of NaOH are fed into an intensive batch mixer of periodic action, and in the particular case of the method before the introduction of an aqueous solution of NaOH, a non-volatile organic solvent. The components of the mixture are vigorously mixed. The resulting reactive mixture is loaded into an autoclave with a capacity of 4 l, in which, after supplying propylene oxide to it, hydroxypropylation and carboxymethylation are carried out. Next, the process is carried out similarly to examples 1-9 (table 1).

 The data of specific technological parameters are given in table.2.

 Example 16 (prototype).

 1,500 g of starch, an aqueous solution of NaOH, NaMXUK and Laprol 402 are fed into an intensive batch mixer of periodic action as a non-volatile organic solvent. The components of the mixture are intensively mixed. The resulting reactive mixture is fed to a batch dryer. The resulting carboxymethylated starch is loaded into an autoclave with a capacity of 4 l, in which, after supplying propylene oxide to it, the process of hydroxypropylation of carboxymethyl starch is carried out. In the course of the reaction, particles of the obtained product agglomerate, which, similarly to Example 10, makes it difficult to process it into a finished powder product.

 The properties of GACMC obtained by the specific technological modes described in examples 1-16 are shown in table 3.

Claims (5)

1. The method of obtaining hydroxyalkylcarboxymethyl starch by preparing a homogenized reactive mixture of starch, sodium salt of monochloracetic acid, an aqueous solution of sodium hydroxide in high-performance mixers of paddle or screw type and esterification, characterized in that in the preparation of the reactive mixture the sodium salt is monochlorate 0.1 -0.2 mol per 1 anhydroglucose starch unit, after which the prepared homogenized reactive mixture transfer to an autoclave, where it is treated with a hydroxyalkylating agent in an amount of 0.1-0.3 mol per 1 anhydroglucose starch unit at a temperature of from 35 to 82 ^o C for 0.5-3.0 hours, after which the resulting product is dried at a temperature of 60 -90 ^o C for 0.5-2.0 hours 2. The method according to claim 1, characterized in that ethylene oxide is used as the hydroxyalkylating agent, while the treatment with ethylene oxide is carried out at a temperature of from 35 to 70 ^o C. 3. The method according to claim 1, characterized in that propylene oxide is used as the hydroxyalkylating agent, while the treatment with propylene oxide is carried out at a temperature of from 60 to 82 ^o C.  4. The method according to claim 1, characterized in that when preparing a homogenized reactive mixture, before feeding an aqueous solution of sodium hydroxide, a non-volatile organic solvent selected from the group of glycols (mono-, di-, triethylene- and propylene glycols, low molecular weight polyethylene glycols, polypropylene glycols) and low molecular weight polyethers based on ethylene oxide in an amount of 1.0-10.0% by weight of the input starch.  5. The method according to claim 4, characterized in that in the preparation of a homogenized reactive mixture, a crosslinking agent, epichlorohydrin, is added in an amount of 0.0001-0.01 mole per 1 starch anhydroglucose unit to a non-volatile organic solvent.

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