WO1993022362A1

WO1993022362A1 - Process for producing polyesters from citric acid and polyhydroxy compounds and use thereof

Info

Publication number: WO1993022362A1
Application number: PCT/EP1993/000904
Authority: WO
Inventors: Dieter Boeckh; Heinrich Hartmann; Elisabeth Kappes; Alfred Oftring; Richard Baur; Alexander Kud; Volker Schwendemann
Original assignee: Basf Aktiengesellschaft
Priority date: 1992-04-23
Filing date: 1993-04-14
Publication date: 1993-11-11
Also published as: DE4213282A1; EP0637325A1

Abstract

Process for the production of polyesters from (a) citric acid or isocitric acid which may be replaced to the extent of up to 29 mol.% by mono or dibasic hydroxy carboxylic acids or by up to 60 mol.% of other di to tetrabasic aliphatic carboxylic acids, and (b) polyhydroxy compounds of the polysaccharide and modified polysaccharide or polyvinyl alcohol group or their mixtures in such a molar ratio (a):(b) that 1.25 to 12 mol of component (a) is used per quantity of component (b) containing 1 mol hydroxy groups, to form condensation products with a K of 8 to 120, and the use of the polyesters as additives in low-phosphate or phosphate-free washing and cleaning agents in quantities of 0.1 to 30 wt % related to the formulation employed.

Description

Process for the preparation of polyesters from citric acids and poly ydroxy compounds and their use

* 5 Description

The invention relates to a process for the preparation of polyesters from citric acid or isocitric acid with polyhydroxy compounds based on saccharides and / or poly-

10 vinyl alcohols and the use of the polyester as detergent additive

From US-A-2 868 780 a process for the preparation of polysaccharide esters is known, in which for example

15 Starch condensed with ammonium citrate at temperatures from 85 to 140 ° C. while removing the ammonia from the reaction mixture. According to the information in the examples, 0.1 to 0.2 mol of ammonium citrate are used per mole of starch.

From US-A-3 661 955 polyesters of citric acid and sorbitol are known which are produced by condensing citric acid and sorbitol in a molar ratio of 1: 2 to 2: 3. These condensation products are used as emulsifiers in the food industry.

25

From DE-B-27 13 673 a process for the production of starch esters is known in which, among other things. Starch and / or modified starch are mixed with citric acid in a form partially neutralized with alkali bases and the mixture is mixed in

30 dry conditions heated to 80 to 180 ° C. The weight ratio of dry starch substance to citric acid is 1: 0.05 to 1: 0.4. The starch esters thus obtainable are used in the food industry.

35 EP-A-0 433 010 discloses esterification products of polyhydroxy compounds, such as polyvinyl alcohol, polyallyl alcohol and polysaccharides with citric acid. According to the information in the examples, the direct esterification of polyvinyl alcohol with acetylcitric anhydride or by

• 40 direct reaction with citric acid in a molar ratio of 1: 1. As has been established on the basis of our own experiments, the direct esterification of polyvinyl alcohol with citric acid described in EP-A-0 433 010 leads to polyesters with a nem degree of esterification of the hydroxyl groups in the polyvinyl alcohol of only a few percent and is very problematic because usually crosslinked and thus water-insoluble polyesters are formed. The reworking of example 2 of this literature passage resulted in an almost completely insoluble product.

However, the reaction of polyvinyl alcohol with acetylcitric acid anhydride is technically extremely problematic for two reasons: firstly, citric acid anhydride is practically inaccessible. According to the method described in Example 1 of EP-A-0 433 010, not citric acid anhydride is obtained, but rather O-acetylcitric acid anhydride. The use of this compound thus leads to acetylated citric acid esterification products. On the other hand, reactions with O-acetylcitric acid anhydride are only sensibly possible in water-free aprotic organic solvents. From the esterification products obtainable in this way, the O-acetyl groups derived from the O-acetylcitric anhydride cannot be selectively hydrolyzed to a hydroxyl group without cleaving the other ester groups. In addition, the separation and recovery of the organic solvents is technically complex.

The object of the present invention is to provide a more suitable process for the preparation of water-soluble polycondensates from citric acid or isocitric acid and polyhydroxy compounds. The invention is also based on the object of providing detergent additives.

The first-mentioned object is achieved with a process for the production of polyesters from citric acid or isocitric acid by condensing

a) citric acid or isocitric acid, which can optionally be replaced by up to 70 mol% of mono- or dibasic hydroxycarboxylic acids or by up to 50 mol% of other dibasic to four-basic aliphatic carboxylic acids b) oligosaccharides, polysaccharides, modified oligosaccharides, modified polysaccharides, polyvinyl alcohols or mixtures thereof

to condensation products with a K value of 8 to 120 (determined according to H. Fikentscher in a 2% strength by weight aqueous solution at 25 ° C. and pH 7 on the Na salt of the condensation products) if components a ) and b) is used in the condensation in a molar ratio such that 1.25 to 12 mol of component a) are present in an amount of component b) containing 1 mol of hydroxyl groups. The products obtainable in this way can be used as additives to low-phosphate or phosphate-free washing and cleaning agents.

Through the use of superstoichiometric amounts of citric acid or isocitric acid, the multiple esterification of citric acid is suppressed to such an extent that polycondensates with a high degree of esterification are formed which have no macroscopic crosslinking.

In the procedure described above

a) citric acid or isocitric acid, each of which can optionally be replaced by up to 70 mol% of mono- or dibasic hydroxycarboxylic acids or by up to 50 mol% of other two- to four-basic aliphatic carboxylic acids,

With

b) oligosaccharides or polysaccharides and / or polyvinyl alcohols

implemented in such a molar ratio a): b) that 1.25 to 12 moles of component a) are present per 1 mole of hydroxyl group-containing component b). This gives rise to condensation products with a K value of 8 to 120 (determined according to H. Fikentscher in a 2% strength by weight aqueous solution at 25 ° C. and pH 7 on the Na salt of the condensation products), the Condensates contain residual portions of unreacted component a). This reaction mixture can be fed in without further separation of the stated use or the polycondensation products can be largely separated from residues of components a). separate form come into use. The polycondensates prepared by this process are used in the form of their partially or completely neutralized water-soluble salts as additives to detergents and cleaning agents in amounts of 0.1 to 30% by weight, based on the formulation.

Citric acid or isocitric acid are suitable as component (a). Both carboxylic acids can optionally be replaced by up to 70, preferably up to 40 mol% of mono- or dibasic hydroxycarboxylic acids. Suitable hydroxycarboxylic acids are e.g. Glycolic acid, lactic acid, tartaric acid, malic acid and tartronic acid. Also suitable as component (a) are mixtures in which citric acid or isocitric acid is replaced by up to 50 mol% of other two- to four-basic aliphatic carboxylic acids, e.g. by succinic acid, adipic acid, butane-1,2,3,4-tetracarboxylic acid, propane-1,2,3-tricarboxylic acid, cyclopentane tetracarboxylic acid, oxalic acid or aconitic acid.

Mixtures of the mono- or dibasic aliphatic hydroxycarboxylic acids can optionally also be used, e.g. Mixtures of lactic acid and tartaric acid or mixtures of tartaric acid and malic acid.

As component (b), polyhydroxy compounds from the group of the oligosaccharides, the polysaccharides, the modified oligosaccharides, the modified polysaccharides and / or the polyvinyl alcohols are used. The polysaccharides can be of plant or animal origin or can be derived from the metabolism of microorganisms. These products can be used as component (b) in native form or in modified form. Polysaccharides suitable as component (b) are, for example, starch, cellulose, pectin, algin, chitin, chitosan, dextrin, cyclodextrin, alginic acids, heparin, carrageenan, agar, gum arabic, tragacanth, carraja gum, ghatti gum, locust beans nmehl, gua-gum, tara-gum, inulin, xanthan, dextran, Nigeran and Pentosaπe such as xylan and araban. From an economic point of view, native starch or a modified starch is preferably used as component (b). Modified starches can be used, for example thermally and / or mechanically treated starch, oxidatively, hydrolytically or enzymatically degraded starches, oxidized hydrolytically or oxidized enzymatically degraded starches and chemically modified starches. The starches are preferably only broken down to such an extent that at least 20% by weight of starch derivatives which have at least five monosaccharide units in the molecule are still present; the starches are particularly preferably only broken down to such an extent that 50% of poly saccharide with at least five monosaccharide units in the molecule.

All strengths occurring in nature are suitable. However, starches from corn, wheat, rice, tapioca and from potatoes are preferred. The starches are practically insoluble in water, but can be converted into a water-soluble or water-dispersible form in a known manner by thermal and / or mechanical treatment or by enzymatic or acid-catalyzed partial degradation. Starch breakdown products which are obtainable by oxidative, hydrolytic or enzymatic partial breakdown of native starch are, for example

Dextrins such as white and yellow dextrins as well as maltodextrins and cyclodextrins. Also suitable as component (b) are oxidized starches, such as dialdehyde starch and oxidized starch degradation products, preferably with a content of at least 20% of polysaccharides with at least five monosaccharide units in the molecule. Such compounds can be obtained, for example, by oxidizing starch with periodate, chromic acid, hydrogen peroxide, nitrogen dioxide, nitrogen tetroxide, nitric acid or hypochlorite.

Also suitable as component (b) are chemically modified polysaccharides, in particular chemically modified starches, for example starches and starch degradation products partially converted with acids to esters and with alcohols to ethers. The esterification of these substances is possible both with inorganic and with monobasic organic acids, their anhydrides or chlorides. In the case of direct esterification, the water released causes an acid-catalyzed cleavage of glycosidic bonds. Phosphated and acetylated starches and starch breakdown products are of particular technical interest. The most common method of etherifying starch is to treat the starch and starch degradation products with organic halogen compounds, Epoxides or alkyl sulfates in aqueous alkaline solution. Starch, for example, mono- and dialkyl ethers, hydroxyalkyl _r carboxyalkyl and allyl ethers of starch.

Chemically modified polysaccharides also include, for example, acetyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, carboxymethyl hydroxyethyl cellulose, sulfethyl cellulose, carboxymethyl sulfoethyl cellulose, hydroxypropyl sulfoethyl cellulose, hydroxyethyl sulfoethyl cellulose, methyl sulfoethyl cellulose and ethyl cellulose.

Polyvinyl alcohols are also suitable as component (b), all water-soluble or water-dispersible polyvinyl alcohols being suitable. They generally have viscosities of 3 to 10,000, preferably 10 to 5,000 mPas (determined in 10% solution at 20 ° C. using a Höppler falling-ball viscometer in accordance with DIN 53 015). The polyvinyl alcohols are usually produced by hydrolysis of polyvinyl acetate. They can be in partially or completely hydrolyzed form. For example, the degree of hydrolysis is generally 70 to 100%, preferably 85 to 99%. It is also possible to use oxidatively degraded polyvinyl alcohols as component b), which are obtained by oxidation of the polyvinyl alcohols with oxidizing agents such as e.g.

Hydrogen peroxide, peroxodisulfates or sodium hypochlorite or by reaction with 1,2-diol-splitting oxidizing agents such as e.g. Periodates, permanganates or lead tetraacetate are available. The polyvinyl alcohols have average molecular weights (weight average) of 1000 to 250,000, preferably 1500 to 90,000. The oxidatively degraded polyvinyl alcohols have average molecular weights of 350 to 50,000, preferably 500 to 10,000.

Starch, dextrins, cellulose or polyvinyl alcohol and mixtures of the components mentioned are preferred as component (b).

The polyesters are produced by condensing components (a) and (b), component a) being used in a clearly overstoichiometric amount, based on the hydroxyl groups of component b). The condensation is carried out so far that condensation products with a K-Werc of 8 to 120, preferably 15 to 100 (determined according to H. Fikentscher in 2% by weight aqueous solution at 25 ° C. and pH 7 on the sodium salt of the condensation products). The condensation can be carried out in inert organic solvents or in a melt of the reactants. Which method is the most suitable depends on the nature of component (b). Insoluble polysaccharides (b) are preferably used in the finest possible form. When condensing in the absence of inert organic solvents, it is advantageous to dissolve the polyhydroxy compound in a sufficient amount of water or to convert it into a finely divided aqueous dispersion. In order to dissolve or stably disperse component (b), it is often necessary to heat the water-containing solution to temperatures of up to 100 ° C. In the case of condensation, it can also be advantageous to neutralize the three- or polybasic carboxylic acids to be used as component (a) up to a proportion of 30%.

If citric acid in a mixture with mono- or dibasic hydroxycarboxylic acids is used in an amount of up to 70 mol% in the production of the polyester as component (a), oligomeric condensation products are formed which are associated with the polyhydroxy compounds the component (b) condense with elimination of water.

For example, an aqueous solution of the components

partially neutralize (a) and (b) by adding sodium hydroxide solution or another base such as potassium hydroxide solution, ammonia, ethanolamine, triethanolamine, diethanolamine, morpholine or ammonia or substituted amines. To produce the polyesters, the water is then largely distilled off at temperatures from 50 to 120 ° C. and the temperature of the reaction mixture is then increased to above 100 to 220, preferably 110 to 170 ° C. The condensation of components (a) and

(b) is then preferably carried out at an elevated temperature. This gives viscous melts, some of which become solid as the conversion progresses or when they cool to room temperature. The condensation is preferably carried out in an inert gas stream or under reduced pressure. If the condensation of components (a) and (b) is carried out in an inert organic solvent, it is preferably carried out in suspension. For example, the compounds which are suitable as component (a) can be introduced into the reactor together with an aqueous solution (suspension of components b), the inert solvent and, if appropriate, a protective coloid, and by boiling under reflux and distilling off the reaction arising water from the reaction mixture are condensed. Suitable organic solvents are, for example, toluene, o-, m- and p-xylene, mesitylene, cumene, higher-boiling aliphatic hydrocarbons (boiling range from 120 to 160 ° C.) and mixtures of the solvents. In some cases it may be advantageous to carry out the condensation in the presence of protective colloids, which then the formed

Disperse the condensate and prevent the formation of a viscous mass that solidifies after cooling. The protective colloids can be ionic or nonionic in nature and generally contain hydrophilic and hydrophobic structural elements. Suitable protective colloids are, for example, alkoxylated polyhydric C ₂ - to C _ß alcohols such as the reaction products of 3 to 25 moles of ethylene oxide and / or propylene oxide with glycerol, oligoglycerol or pentaerythritol. The protective colloids can additionally contain C ₆ -C ₂ -alkyl groups bonded via ether, ester or amide bonds. Other suitable protective colloids are, for example, polyvinylpyrrolidone, block copolymers of ethylene oxide and propylene oxide or butylene oxide, mono- or polyvalent C ₆ -C ₂₂ -Al} carboxylic acids or sulfonic acids or hydrophobically modified phyllosilicates. The amount of protective colloid is 0.05 to 5% by weight, based on the polyester. If an inert organic solvent is used in the condensation, the concentration of the solids, ie the polyester formed in the inert diluent, is 10 to 70, preferably 20 to 65% by weight.

The control of the progress of the reaction in the esterification can be determined in all processes by determining the amount of water distilled off from the reaction mixture. Since the acid number and the viscosity of the reaction mixture also change during the esterification, by determining these measured variables on samples which be taken mixed, the course of the esterification are checked.

The esterification of components (a) with (b) is preferably carried out in the melt in the absence of catalysts. However, the use of conventional acidic catalysts, which are usually used in esterification reactions, is possible. The condensation in the melt can be carried out in the usual flasks or kettles, each of which is equipped with a stirrer. In many cases, however, it is more advantageous to carry out the condensation reaction in a reactor which has a more powerful mechanical mixing device than a kettle provided with a conventional stirrer. For example, an evacuable kneading reactor with a vertical or horizontal shaft, inert gas supply and distillation device is particularly suitable. Other suitable reactors are e.g. Condensation extrusion reactors which allow melt condensation in a first reaction zone while distilling off the reaction water and in which the melt is then extruded in a shaping zone. The extruded strands are then broken up or pulverized into a lumpy reaction product.

In the case of condensation in batch reactors, the viscosity of the water-containing melt rises to such an extent that it can no longer be mixed in stirred tanks and can no longer be discharged. In order to lower the viscosity during the condensation, a diluent is added to the highly viscous melt and the condensation reaction is continued. Suitable diluents are, for example, monobasic aliphatic carboxylic acids, such as formic acid, acetic acid, propionic acid, lauric acid, palmitic acid, stearic acid, coconut fatty acid, tallow fatty acid, oleic acid and mixtures thereof. If the boiling point of the fatty acids used as diluents is below the condensation temperature, the condensation is carried out under elevated pressure. This is especially the case when using formic acid, acetic acid and propionic acid. The volatile monobasic aliphatic carboxylic acids serve both as diluents and as entraining agents for the water formed during the condensation. The low volatility carboxylic acids that reduce viscosity tion can remain in the condensation product.

A particularly advantageous variant for the production of the polyester consists in firstly a largely water-free melt composed of a mixture of citric acid or isocitronic acid with up to 70, preferably 40 mol% of mono- or dibasic hydroxycarboxylic acids or up to 50 mol. % to produce their aliphatic carboxylic acids and to meter the polyhydroxy compound into this melt. The temperature of the melt can be in the range from 100 to 160 ° C. The polyhydroxy compound can be added in pure form or as a solution in water. It may be advantageous to use a different e.g. to choose a lower temperature in order to minimize thermal damage to the condensation product. When component (b) is metered in in the form of an aqueous solution, the amount of water introduced with component (b) is preferably distilled off together with the water formed during the condensation at the rate at which the addition of the component (b ) follows.

The superstoichiometric components of components a) favor the process of condensation in the

In addition, melt by first ensuring the meltability of the reaction mass with advanced conversion and reducing the viscosity. They can remain in the product as monomers or oligomers or can be separated off from the condensation product. The separation ge lingt for example, by ultrafiltration, dialysis, extractant tion ^"or precipitation using aqueous or wasser¬ miscible solvents. The separation may be complete or only partial.

To produce the polyesters, components a) and b) are used in such an amount that on each hydroxyl group of components b) at least 1.25 molecules of components a), preferably at least 1.45 molecules of the components a) particularly preferably at least 1.65 molecules of components a) come. The molar ratios given correspond to a weight ratio of a): b) from 50: 1 to 3.65: 1, preferably 30: 1 to 4.0: 1 and particularly preferably 10: 1 to 4.5: 1 in the case of the polysaccharides and 50: 1 to 5: 1, preferably 30: 1 to 6.5: 1 and particularly preferably 15: 1 to 8: 1 in the case of the polyvinyl alcohols.

The condensation is carried out to such an extent that soluble polyesters with K values of 8-120 (determined according to H. Fikentscher in a 2% strength by weight aqueous solution at 25 ° C. and pH 7 on the sodium salt of the condensation products) are formed . The degree of esterification of the hydroxyl groups of the polyhydroxy compounds of component b) is at least 10, preferably 20 to 80, particularly preferably 25 to 60%.

The polyesters are preferably prepared in such a way that a water-containing melt (water content 10 to 40% by weight) of a mixture

and

b) polyhydroxy compounds from the group of the polysaccharides, the modified polysaccharides, the polyvinyl alcohols or mixtures thereof

which contain components a) and b) in a molar ratio such that 1.25 to 12 mol of components a) are present per 1 mol of hydroxyl group-containing component b), with water being distilled off soluble condensates with a K value of 8-120 (determined according to H. Fikentscher in 2% by weight aqueous solution at 25 ° C. and pH 7 on the Na salt of the condensation products) esterified. The citric acid or isocitronic acid used as component a) can be neutralized with up to 1 molar equivalent of a base. If polysaccharides are used as component b), the polysaccharides are gelatinized, preferably before the esterification, by heating in an aqueous medium, where they dissolve, and the citric acid is partially neutralized to 5 to 20%; provided that as component b) polyvinyl If alcohols are used, they are preferably dissolved in an aqueous medium before the esterification.

The polyesters obtainable in the condensation reactions described above can be used in the acid form or in the partially neutralized form if component (a) has been partially neutralized in the preparation of the products. However, they can also be completely neutralized. The salts of the polyesters are obtained, for example, by neutralization with bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, sodium, potassium, lithium, calcium, ammonium carbonate or hydrogen carbonate, ammonium hydroxide, ethanolamine, diethanolamine or triethanolamine . These bases are preferably used as aqueous solutions. The neutralization is preferably carried out with sodium hydroxide solution, soda or sodium hydrogen carbonate, the pH being controlled, e.g. it is kept constant in the range from 4.5 to 8, preferably at about 7, so that the polyester is hydrolysed as little as possible. In order to store the polyesters obtained in the condensation without modification by hydrolysis, they can be isolated from the neutralized aqueous solution, preferably in the form of the neutral sodium salt. Freeze drying, spray drying or spray fluidized bed drying are suitable for this. The aqueous solution can be dried without further additives or with a mixture with washing-active substances.

The polyesters described above are used as an additive to powdery and liquid detergents and cleaning agents, preferably in phosphate-free or low-phosphate detergents which contain no more than 25% by weight of sodium tri-phosphate. The amounts of polyester used are 0.1 to 30, preferably 0.5 to 15% by weight, based on the detergent or cleaning agent formulation. The polycondensation products can be used without removing the superstoichiometric proportions of components a). In this case, these low molecular weight carboxylic acids act as builders in the detergent formulation. The low molecular weight fraction can of course also be separated off and only the high molecular weight fraction of the polycondensates can be used. The polyesters have a good dispersibility for particle dirt in the detergent liquor, especially for clay minerals. This property is important because loam-like soiling of textiles is widespread. The polyesters also act as builders in detergents and reduce the incrustation and graying on the washed textile during the washing process. They are therefore also suitable as incrustation inhibitors and graying inhibitors. The polyesters are biodegradable to a high degree, for example the degradation rates are more than 90%. The polyesters are used in detergents which contain up to 45% by weight of phosphate, the use of the polyesters in detergents with a reduced phosphate content (which is to be understood as meaning a phosphate content of less than 25% by weight sodium tri-phosphate) or in phosphate-free detergents - as well as in phosphate-free cleaning agents is preferred. The polyesters can be added to the detergent formulation in the form of granules, a paste, a highly viscous mass, as a dispersion or as a solution in a solvent. They can also be adsorbed on the surface of leveling agents, eg sodium sulfate or builders (zeolites or bentonites) as well as other solid additives in the detergent formulation.

The composition of the detergent and cleaning agent formulations can be very different. Washing and cleaning formulations usually contain 2 to 50% by weight of surfactants and optionally builders. This information applies to both liquid and powder detergent formulations. Examples of the composition of detergent formulations which are common in Europe, the USA and Japan can be found, for example, in Chemical and Engn. News, Vol. 67, 35 (1989) is shown in a table. Further information on the composition of detergents and cleaning agents can be found in WO-A-90/13581 and Ulimann's Encyclopedia of Industrial Chemistry, Verlag Chemie, Weinhein 1983, 4th edition, pages 63-160. Also of interest are detergent formulations which contain up to 60% by weight of an alkali silicate and up to 10% by weight of a polycondensate prepared according to the invention. Examples of suitable alkali silicates are the amorphous sodium disilicates, which are described in EP-A-0 444 415, and crystalline layered silicates, which according to EP-A-0 337 219 in Detergent formulations are included as builders and are used according to EP-B-0 164 514 for softening water, and sodium silicates, which are obtained by dewatering sodium silicate solutions and drying to water contents of 15 to 23, preferably 18 to 20,% by weight. -% are available.

Detergents can optionally also contain a bleaching agent, e.g. Sodium perborate, which, if used, can be present in the detergent formulation in amounts of up to 30% by weight. The detergents and cleaning agents can optionally contain other conventional additives, e.g. Complexing agents, opacifiers, optical brighteners, enzymes, perfume oils, color transfer inhibitors, graying inhibitors and / or bleach activators.

The K values of the polyesters were determined according to H. Fikentscher, Cellulosechemie, Vol. 13, 58 to 64 and 71 to 74 (1932) in aqueous solution at a temperature of 25 ° C. and a concentration of 2% by weight at pH 7 am Sodium salt of the polyester determined. The percentages in the examples mean% by weight.

Examples

Examples 1 to 3

Condensation of (a) citric acid with (b) starch or (a) mixtures of citric acid and tartaric acid with (b) starch

The amounts of components (a) and (b) given in table 1 are introduced with the addition of the amounts of sodium hydroxide solution and water likewise listed therein in a 2 liter glass reactor which is equipped with a stirrer, gas inlet device, internal thermometer and distillation bridge see is. The substances presented therein are stirred and flushed with nitrogen for 30 min. The contents of the flask are then heated to 120 ° C. As soon as the internal temperature has reached 100 ° C, water distills off. After 30 minutes, the pressure is reduced to approximately 30 mbar and the condensation reaction is continued until the water introduced with the reaction components and the water formed during the condensation has distilled off. Very viscous melts are obtained, which solidify after cooling. To get the sodium To produce salts of the polyester, the condensates are crushed, dispersed in water at room temperature and neutralized by adding aqueous sodium carbonate solution (pH = 7). The condensation products had the K values given in Table 1.

Table 1

l ⁾ Starch type I = hydroxypropylated potato starch with a viscosity of 95 mPas

(measured at 85 ° C in 10% aqueous solution with a Brookfield viscometer type RVF, spindle 1, 20 Up) Type II - soluble acid partially degraded starch with a K value of 15.3 in 22% aqueous solution

² > Before the determination of the K value, the Na salt solution was ultrafiltered on a membrane with a 10,000 D exclusion limit in order to separate off unconverted citric acid.

The degree of esterification was determined by enzymatic determination of the bound citric acid and is given in mol% of esterified OH groups of components b).

Example 4

315 g of citric acid monohydrate, 120 g of 50% sodium hydroxide solution and 225 g of tartaric acid were placed in a 2 l glass reactor with stirrer, gas inlet device, internal thermometer and distillation bridge, heated to 150 ° C. bath temperature and water was distilled off. After 1 h, a pressure of 300 mbar was set and an inlet of 20.3 g of hydroxypropylated potato starch with a viscosity of 95 mPas (measured in 10% aqueous solution at 85 ° C. with a Brookfield viscometer type RVF, spindle 1, 20 rpm ) and 182.7 g of water were added. The inflowing water is continuously distilled off. After the feed had ended, the pressure was reduced to 50 mbar and condensation continued for 1 h. A total of 336 g of distillate were obtained. The product was dissolved in water with the addition of 10% sodium hydroxide solution at 10 ° C. and freeze-dried. The product showed a K value of 12.2 (2% in water).

Example 5

Example 4 was repeated, 16.2 g of hydroxypropylated potato starch having a viscosity of 95 mPas (measured in 10% aqueous solution at 85 ° C. using a Brookfield viscometer type RVF, spindle 1, 20 rpm) in 145.8 g of water ¬ were dosed. 299 g of distillate were obtained. The product had a K value of 11.3 (2% solution in water).

Example 6

In a single-shaft 2 l kneading reactor with a horizontal stirrer shaft, 3.0 mol of citric acid monohydrate were partially neutralized with 60 g of 50% sodium hydroxide solution and 97.2 g of hydroxypropylene potato starch with a viscosity of 95 mPas (measured in 10% aqueous solution at 85 °) C with a Brookfield viscometer type RVF, spindle 1, 20 rpm). Within 4.75 h, 117.3 g of water were distilled off at 120 ° C. in vacuo (350-450 mbar). The product was dissolved in water with the addition of 10% sodium hydroxide solution at 10 ° C., filtered on an ultrafiltration membrane with an exclusion limit of 10,000 D and the retentate was freeze-dried. The product showed one K value of 16.3 (2% in water) and a degree of esterification of the OH groups of 22%.

Example 7

The approach from Example 6 was repeated, using wheat starch. 133.2 g of water were distilled off at 120 ° C./350 mbar within 2 hours. The product had a K value of 23.5 (2% in water) and a degree of esterification of the OH groups of 34%.

Example 8

The approach from Example 7 was repeated, with 181 g of water being distilled off at 120 ° C./200 mbar within 3 h. The product has a K value of 26.8 (2% in water) and a degree of esterification of the OH groups of 46%.

Example 9

35 g of dextrin (white dextrin, Merck, 10% water) and 157.5 g of citric acid monohydrate are heated to boiling in a 2 l three-necked flask with 225 ml of xylene while stirring. With the help of a water separator, 30.5 g of water are distilled off azeotropically. Then the xylene is decanted off and the xylene still adhering to the reaction product is distillatively removed under reduced pressure. The sodium salt prepared from the remaining reaction product by neutralization with aqueous sodium carbonate solution has a K value of 8.7 (2% strength in water) and a degree of esterification of the OH groups of 57%.

Examples 10 to 15

Condensation of (a) citric acid or citric acid / tartaric acid mixtures with (b) polyvinyl alcohol

22 g of polyvinyl alcohol (containing 0.5 mol of hydroxyl groups at 100% degree of saponification of the polyvinyl alcohol) with the specification given in Table 2 are dissolved in water, so that a 10% aqueous solution of polyvinyl alcohol is formed. The amounts of acids given in Table 2 are in a 2 1 glass reactor equipped with a stirrer, gas inlet. line device and distillation bridge is provided, melted and condensed at 160 ° C. The water present as hydrate or the water formed during the condensation is distilled off within 3 hours at a pressure of 300 mbar, then the polyvinyl alcohol solution is metered in within 3 hours at a temperature of 140 ° C., the metered in Water is continuously distilled off and the viscosity of the melt rises sharply. After the addition of polyvinyl alcohol has ended, the reaction mixture is condensed for a further hour at the temperature given in Table 2. After the melt has cooled, a brittle, water-soluble product is obtained. In order to produce the sodium salts from this, the condensate is crushed, dispersed in water at room temperature and little by little an aqueous sodium carbonate solution is added until the pH is 7. The polyesters thus obtained had the K values given in Table 2.

Table 2

¹ 'Before the determination of the K value, the Na salt solution was ultrafiltered on a membrane with a 10,000 D exclusion limit in order to separate off unconverted citric acid.

Application engineering examples

Clay dispersion

The removal of particle dirt from tissue surfaces is supported by the addition of polyelectrolytes. The stabilization of the dispersion formed after the particles are detached from the tissue surface is an important task of these polyelectrolytes. The stabilizing influence of the anionic dispersants results from the fact that, due to the adsorption of dispersant molecules on the solid surface, their surface charge is increased and the repulsive energy is increased. Other factors influencing the stability of a dispersion include steric effects, temperature, pH value and the electrolyte concentration.

The dispersibility of various polyelectrolytes can be assessed in a simple manner using the clay dispersion test (CD test) described below.

CD test

As a model for particulate dirt, it becomes finer ground

China clay SPS 151 used. 1 g of clay is intensively dispersed in a standing cylinder (100 ml) for 10 minutes with the addition of 1 ml of a 0.1% sodium salt solution of the polyelectrolyte in 98 ml of water. Immediately after stirring, a 2.5 ml sample is taken from the center of the standing cylinder and, after dilution to 25 ml, the turbidity of the dispersion is determined using a turbidimeter. After the dispersion has stood for 30 or 60 minutes, samples are taken again and the turbidity is determined as above. The turbidity of the dispersion is given in NTU (nephelometric turbidity units). The less the dispersion settles during storage, the higher the measured turbidity values and the more stable the dispersion. The dispersion constant t, which describes the temporal behavior of the sedimentation process, is determined as the second physical measurement variable. Since the sedimentation process can be approximately described by a mono-exponential law of time, τ gives the time in which the turbidity drops to 1 / eth of the initial state at the time t = 0.

The higher a value for τ, the slower the dispersion settles.

Calcium carbonate dispersion

The calcium carbonate dispersing capacity was determined by dissolving 1 g of the copolymer in 100 ml of distilled water, neutralizing it if necessary by adding sodium hydroxide solution and adding 10 ml of 10% sodium carbonate solution. The solution was then titrated with a constant pH and temperature with 0.25 M calcium acetate solution until it became cloudy. The pH was adjusted either by adding dilute sodium hydroxide solution or hydrochloric acid solution. The dispersing capacity was determined at 20 ° C. and pH 11. The results are shown in Table 4.

Table 3

Clay dispersion

Comparative Example No.

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D K value measured as a 1% aqueous solution at 25 ° C

Table 4

20 Calcium carbonate dispersing capacity

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Comparative Example No.

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Claims

1. Process for the preparation of polyesters from citric acid or isocitric acid by coding

a) citric acid or isocitric acid, each optionally by up to 70 mol% mono- or dibasic hydroxycarboxylic acids or by up to 50 mol% other two- to four-basic aliphatic

Carboxylic acids can be replaced with

b) oligosaccharides, polysaccharides, modified oligosaccharides, modified polysaccharides, polyvinyl alcohols or mixtures thereof

to condensation products with a K value of 8 to 120 (determined according to H. Fikentscher in 2% by weight aqueous solution at 25 ° C. and pH 7 on the Na salt of the condensation products), characterized in that the components ¬ ten a) and b) are used in the condensation in such a molar ratio that 1.25 to 12 mol of component a) are present in an amount of component b) containing 1 mol of hydroxyl groups.

Process according to Claim 1, characterized in that a water-containing melt of a mixture of components a) and b) is condensed with water being distilled off.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that the citric acid or isocitric acid used as component a) is neutralized with up to 1 molar equivalent of a base.

4. The method according to any one of claims 1 to 3, characterized ge indicates that component b) is dissolved prior to the esterification by heating in an aqueous medium. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the condensation of components a) and b) in a single- or multi-shaft continuously or discontinuously operated kneading reactor

5 leads.

6. The method according to any one of claims 1 to 4, characterized ge indicates that the condensation of components a) and b) in a single or multi-wave continuously

10 operated extruder.

7. The method according to claim 1, characterized in that one carries out the condensation in an inert organic solvent in the presence of a protective colloid.

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8. The method according to any one of claims 1 to 7, characterized ge indicates that the non-condensed portion of component a) partially or completely from the reaction mixture by extraction or ultrafiltration.

20 is separated.

9. Use of the polyesters prepared according to one of claims 1 to 8 with a degree of esterification of the hydroxyl groups of at least 10% as an additive

25 low-phosphate or phosphate-free washing and cleaning agents in amounts of 0.1 to 30% by weight, based on the formulations.

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