DD213227A1 - METHOD FOR PRODUCING NETWORKED CARBOXYMETHYL CELLULOSE WITH HIGH WATER RESET HOLDING COMPOSITES - Google Patents

Abstract

The invention relates to a process for the preparation of crosslinked carboxymethylcellulose with high water retention capacity. The products obtained by the process can be widely used in the field of pharmacy and medicine. Furthermore, there are many applications in the chemical, paper, textile and other fields. The aim of the invention is a technically and economically favorable process which avoids the use of additional crosslinking agents or an annealing process at high temperatures and leads to physiologically harmless products with readily reproducible properties. According to the inventive behavior of a carboxymethylcellulose having a DS of preferably 0.5 to 1.5, a portion of the carboxymethyl, namely 1 to 4 meq / g of carboxymethylcellulose, by addition of an equivalent amount of a strong acid i. Presence of a limited swelling, hydrous organic medium released and partially intermolecularly and crosslinked at temperatures in the range of 50 to 100 degrees Celsius with hydroxyl groups of carboxymethyl cellulose and cross-linked.

Description

Bodo Bornneister Teltow, 15.12.1982

Dr, Horst Dautzenberg

Title of the invention

Process for the preparation of crosslinked carboxymethylcellulose with high water retention capacity

Field of application of the invention

The invention relates to a process for the preparation of substantially water-insoluble, crosslinked carboxymethylcellulose (CMC) with high. Absorption and retention of water and aqueous liquids including physiological solutions »The products obtained by the process can be used in many different ways in the field of pharmacy and medicine · In addition, there are many possible applications in the chemical, paper, textile and other fields.

3 α DE1 1982 * 058385

Characteristic of the known technical solutions

In the prior art, high water retention products (WHY) are prepared in a variety of forms based on polysaccharides and derivatives thereof (see: Paper 32 (1978) 4, 10A, pp. 77-713). Numerous patents describe the preparation of such products from cellulose ethers, in particular carboxymethylcellulose (CMC). The procedure is preferably such that cellulose is etherified with monochloroacetate to an average degree of substitution (DS) which would give water solubility and additionally crosslinked with a polyfunctional reagent to a water-insoluble content of more than 50 % . Such crosslinking can be carried out before, during or after the etherification. Such more or less insoluble products are thus obtained, for example, by covalent crosslinking of CMC with spichlorohydrin (DB-OS 1 912 740) or with acrylamido, chloroazomethine, Allyloxy-azomethine, activated chlorine compounds (DE-OS 2,357,013 ) and.a number of other reactive compounds (see: Angew. Makromol · Chemie 76/77, 1979, p 177-190). A disadvantage of these known methods that one relies on the additional use of crosslinking agents, which are usually expensive, more or less toxic or difficult to handle · Furthermore, in any case crosslinker bridges of foreign substances are introduced into the material, which the use of Exclude products for certain applications or at least require extensive toxicological testing. DE-OS 2,151,973 describes a slurry process for the preparation of CMC in a water-miscible organic diluent, in which a further cross-linking is effected by the etherification agent itself. In this special process, a large excess of sodium monochloroacetate, based on sodium hydroxide and anhydroglucose, is used. cose units in the system, and formed a weakly acidic product towards the end of the reaction.

The products have high WRV values between 1000 and 7000 and a high degree of whiteness. However, the process requires a disproportionately high use of expensive monochloroacetic acid at comparatively low yields and yields a product of particularly high salt content. "Another solution is described in some processes which do not require any additional crosslinking agent. Eggs are in principle triggered by intermolecular reactions and crosslinking between the functional groups of the CMC by a heat treatment at elevated temperature. For example, the crosslinking of CMC into high-yielding products in U.S. Patent 3,723,413 is in the presence of some of the by-product salts described by the etherification or in DE-OS 2 290 019 after treatment with dried hydrochloric acid gas under a nitrogen atmosphere · These methods have in common that the CMC must first dried v / earth and then a tempering at temperatures greater than 100 ⁰ C, preferably at 130 to 210 ^° C., which is necessary for crosslinking · The difficult process control hardly gives sufficiently reproducible product properties, and lower WRV values are achieved than when using additional crosslinking agents. · In addition, coloring of the products is usually unavoidable · The Dl -OS 1 518 171 describes egg n A process for the intermolecular crosslinking of CMC, after which mim this dissolves in water or Hydrous organic liquid or dispersed "is acidified to a pH of 0-2, and z" B. after one hour of reaction at room temperature neutralized and worked up "to give crosslinked products, the highly viscous gels of creamy or acidic consistency with very low cohesion in water form highly insoluble products with high water retention capacity can not be prepared by this process.

Aim of the invention

The aim of the present invention is a technically and economically favorable. A process for the preparation of CMC products with high water retention capacity, which overcomes the ITachteile mentioned and deficiency of the known methods, the use of an additional Yemetzungsmittels or Temperprozessea at high temperatures superfluous and with good reproducibility to physiologically harmless products with good performance properties, such as high water retention © high power, high whiteness and low solubility leads.

Explanation of the essence of the invention;

- Task

The object of the invention is to develop a process for crosslinking of carboxymethylcellulose to largely water-insoluble products with high water retention capacity, which is based on an intermolecular crosslinking between the functional groups of the CMC and allows a wide variation of the product properties.

Features of the invention

It has surprisingly been found that water-soluble carboxymethylcellulose can be converted by a controlled esterification reaction between free carboxyl and hydroxyl groups to largely water-insoluble products with high water retention and partially crosslinked by 1 to 4 mVal of carboxymethyl groups per gram of CMC by addition of the equivalent amount- a strong acid converted into the free acid form and in the presence of a limited swelling medium under relatively mild reaction conditions at temperatures below 100 ⁰ C implemented. According to the method, water-soluble CMC in the fumed form with an average degree of substitution (BS) greater than 0.4 *, preferably from 0.5 to 1.5 »is used.

The necessary conversion of carboxyl groups from the Hatriumsalz-. The free acid form is carried out in the presence of a limited swelling medium by introducing defined amounts of a strong acid, preferably hydrochloric acid in the system. Thus, of the carboxymethyl groups 1 to 4 meq / g CMC, but at most all carboxymethyl groups, but preferably 1 to 2 meq / g are converted into the free acid form. The amount of acid added should not exceed the equivalent of the carboxymethyl groups present in the CMC. Outside the range indicated, the products obtained do not show the desired properties. The required amount of acid is the CMC, advantageously dissolved in the limited swelling medium as a diluent, f dosed in one piece.

Bs is used in systems of water-miscible liquids, and lower alcohols, such as ethanol, isopropanol and tertiary-butanol are preferably used for this purpose. In the limited-swelling medium, taking into account the amount of water introduced with the other components, a water content of between 5 and 50 %, preferably from 5 to 20 % _r . After.The process more than 0.5 parts, preferably 2 to 10 parts, of the limited swelling medium per part of CMC used by • temperature increase above room temperature to preferably 50 to 100 ⁰ C in 15 to 180 minutes, but usually in 30 90 minutes, achieves degrees of crosslinking which give the product the desired properties.

A particular advantage of the method according to the invention is that it can be controlled easily and relatively clearly, which makes it possible to obtain products with readily reproducible properties. The achieved WRV values (see Jayme, G, Büttel, H.: Wochenblatt für Papierfabr., 96 (1968), p 180) of the products can be determined both over time and temperature as well as in the Acid form released proportion of Carboxymethy! Groups and the water content, can be adjusted and regulated in the system within wide limits.

Under comparable conditions, a higher proportion of released carboxymethyl groups results in faster crosslinking, while at low water levels in the system particularly high WV values can be achieved. The process according to the invention can be used to prepare crosslinked products with high eve retention from commercial water-soluble carboxymethylcelluloses * Ss can also be combined directly with a manufacturing process for CMC, especially if it is a production process in organic diluents.

I _n this case, is set following the etherification in consideration of the resulting water of reaction, if necessary by Erhöhung.des proportion of the organic component in the diluent, the water content in the whole system to the required level "of the excess alkali is neutralized by addition of acid and, in addition to crosslinking The required proportion of carboxymethyl groups is converted into the free acid form, whereupon preferably 50 to 100 ^° C. are converted to water solubility of less than 50 % or to the desired degree of crosslinking in the hydrous organic diluent. After the esterification reaction, the residual Proportion of present in the acid form carboxymethyl be wholly or partially reconverted to the salt form, preferably in the Hatriumform. Since the intermolecular ester groups formed during crosslinking are not very resistant to strong alkalis, a weakly alkaline agent, preferably sodium bicarbonate, is advantageously used for this purpose and adjusted to a pH of preferably from 6 to 7. The resulting crosslinking products with high water retention can be worked up by conventional methods, for. B. washed with aqueous methanol, separated and dried ·

embodiments

1. 35.3 l / liter Tl. purified, fibrous carboxymethyl cellulose having a DS of 0.95 and a moisture content τοπ 15.0 % were mixed in a mixture of 160 mass Tl · isopropanol and 20 mass Tl · water at a temperature of.

70 ⁰ C registered and with stirring a mixture of 13.1 mass Tl. 5 η hydrochloric acid and 20 mass Tl · isopropanol finely divided added · The converted into the free acid form proportion of carboxymethyl was about 50 %, corresponding to 2, meq / g.

The CMC was 120 min at 70 ⁰ C under stirring, then separated from the liquid phase, and repeatedly washed with aqueous methanol, 80% Yol- "Here, the first wash was much Hatriumbicarbonat added such that the aqueous solution CMC-Produkt.in neutral reacted. Hach drying at 105 ⁰ C showed the product einen.WRV value of 2,230 at a content of solubles of 14.7% ·

2. To 37.6% by mass of purified carboxymethylcellulose with a DS of 1.0, a moisture content of 20.2% and a reduced viscosity jg spec / c (2.0% in cuoxa) 0.717 was a mixture of 150 mass Tl · isopropanol, 20 mass Tl. Water and 8.1 mass parts 5 η hydrochloric acid at a temperature of the mixture of 70 ⁰ C added with circulation · About 30 % ₉ corresponding to 1.24 meq / g, the carboxymethylgruppen.in the free acid form was transferred by the acid portion. The CMC was treated for up to 180 min at 70 ⁰ C with mixing. At certain times, samples were taken, neutralized, washed mit.wäßrigem methanol and dried at 105 ⁰ C.

WRV value soluble 7950 34 % 6700 30 % 4810 21 % 2570 11 % 1650 10 %

The samples taken after different reaction times gave the characteristics listed in the following table:

reaction time

15 minutes

30 min

.60 min

120 min

180 min

3 · To 37.6 mass-Tl. Carboxymethylcellulose from Example 2 was a mixture of 150 Hasse-Tl. Isopropanol with 6.8 mass Tl..5 η hydrochloric acid was added, so that about 25 %, corresponding to 1 m7al / g, the carboxymethyl groups were converted into the free acid form. With circulation, the mixture was mixed at room temperature for 30 minutes, heated to 60 ^° C. and crosslinked at this temperature for a further 90 minutes. After cooling to 30 ⁰ C was made neutral with sodium bicarbonate, then the product was separated from the liquid phase, washed with aqueous methanol, 80 Tol-%, and dried at 105 ⁰ C.

The crosslinked CMC had a WRV of 3500 with a soluble content of 17 %.

4. To 37.6 mass Tl. Carboxymethylcellulose from Example 2, a mixture of 450 mass Tl .. Isopropanol with 10.8 mass Tl, 5 η hydrochloric acid was added so that about 40 %, corresponding to 1.6 mVal / g, the carboxymethyl groups were released. It was heated to 60 ⁰ C within 30 min, then taken after different reaction times samples. These were worked up as above and showed the following values:

WRY value soluble Q Time 5000 7140 4960 25.3% 22.1 % 17.5 % Whiteness. 60 min 90 min 120 min 77.5 % 75.0-96

The untreated GMC had a brightness of 73.0 %,

37.6 mass-Il. Carboxymethylcellulose from Example 2 were as described there, but in an increased volume of liquid. From 325% by weight of Cl. Isopropanol and 69 mass ¹ · Il. Water, treated · Samples taken from increasing reaction times gave the following values after neutralization, washing and drying at 105 ° C:

reaction time

WRV value

soluble

60 min. 90 min 120 min

5560 2610 1630

25.6 % 16.6 % 10.9 %

6 · 37.6 mass-Tl. Carboxymethyl cellulose of Example 2 were as described there, however, treated at 50 ⁰ C for 240 min * At the end of reaction, still present free carboxymethyl! Groups were left in the acid form and washed with aqueous methanol, the Produkt.lediglich ,, then at 105 ⁰ C dried * / Das. Product had a WRY value of 2300 at 17.8 % soluble content »

7. 36.3 mass Tl. of purified wood pulp carboxymethylcellulose having a DS of 0.71, a solids content of 82.7 %, and a fyspeic / c of 0.385 was added to a mixture of .325 by weight of isopropanol, 69% by weight of water, and 8 , 1 mass-Tl 5n hydrochloric acid, corresponding to 1.23 mVal Carboxymethylgruppen per gram of CMC, introduced at 60 ⁰ C and 180 min implemented therein. "The partially still obtained in the acid form reaction product after washing and drying had a? / RV value of 1150 at 21.1 % soluble fraction.

8, To 40.5 mass Tl. of purified wood pulp carboxymethylcellulose with a DS wn 0.73, a solids content of 86.4 %, and a value of ^ spec / c of 0.338, was a mixture of 91 % by mass ethanol 96 % ± ß and 7.7 mass % Tl 37% hydrochloric acid added within 30 min, mixed for a further 30 min and heated to 70 ^° C. in about 30 min. The amount of carboxymethyl groups transferred to the free acid form by the hydrochloric acid was 2.3 mVal / g CMC · extracted at various reaction times samples were neutralized, washed with aqueous methanol and dried at 105 ⁰ C. The repetition of the experiment showed a good reproducibility of the WRV values:

Reaction time: 30 min 60 min 90 min WRV value {%) Trial 1: 3220 2740 1960 Soluble (%) 36.0 30.6 26.5 WRV value {%) Trial 2: 2800 2410 2280 Soluble {%) 32.7 33.7 26.7 WRV value {%) Try 3 s 3280 2770 1930 Soluble (%) 39.0 35.0 27.5 WRV value (%) Trial 4 :. 3280 2890 2270 Soluble ^) 39.0 35.9 30.9

Claims (4)

ErfindungsansOruch 1 · A process for the preparation of crosslinked carboxymethylcellulose having high water retention capacity by internal esterification between hydroxyl groups and Carbosymethylgruppenj located in the acid form characterized in that 1 to 4 mVal Carboxymethylgruppen per gram of carboxymethylcellulose, wherein the carboxymethylcellulose has a degree of substitution between C> 4 and 1.5, in Presence of more than 0.5, preferably 2 to 10 parts of a limited swelling medium having a water content of 5 to 50 %, consisting of a water-miscible organic liquid and water, are converted by addition of acid in the acid form and the mixture at Temperatures between 50 and 100 ⁰ C within a reaction time of 15 to 180 min is treated · 2. The method according to item 1, characterized in that.The water-miscible organic liquid is an alcohol, in particular ethanol, isopropanol or tertiary butanol. 3 · Method according to items 1 and 2, characterized in that the conversion of the carboxymethyl groups into the acid form takes place by addition of equivalent amounts of a strong acid, preferably hydrochloric acid, 4 · Method according to point 1 and 2 _t, characterized in that after the esterification reaction unreacted free carboxymethyl groups are completely or partially converted back into the salt form, preferably a sodium form.