NL1002527C2 - Process for oxidizing polysaccharides using ozone in the presence of a halide-containing catalyst. - Google Patents

Description

Title: Process for oxidizing polysaccharides using ozone in the presence of a halide-containing catalyst.

The invention relates to a process for oxidizing polysaccharides using ozone and in the presence of a halide-containing catalyst.

The oxidation of polysaccharides has been described in various variants. Known oxidizing agents for this purpose are periodic acid, peracetic acid, perborate, persulfate, potassium permanganate, lead (IV) salts, hydrogen peroxide, chlorite and hypochlorite.

The most common method for the oxidation of polysaccharides uses hypochlorites. This method has the drawback that large quantities of salts are formed in the process, which causes problems in the processing of the waste water. In addition, the yield of oxidized polysaccharides is often insufficient and long reaction times are required.

Dutch patent 43493, European patent application 0 427 349 and international patent application 91/17189 describe the oxidation of 20 polysaccharides with a catalytic amount of bromide to form oxidized polysaccharides. The bromide is converted into hypobromite by hypochlorite or electrochemically. Using hypochlorite, relatively many salts are introduced, while the electrochemical regeneration is complicated, among other things because of the use of different compartments and because of contamination of the electrodes.

It is also known that ozone can be used as an oxidizing agent for polysaccharides.

1002527 - 2 -

For example, Angibeaud et al. In "Cellulose, lts Derivatives" ed. J.F. Kennedy, Horwood Chichester U.K. (1985) entitled "Cellulose and Starch Reactivity with Ozone" describes the use of ozone as an oxidizing agent for 5 polysaccharides.

In the introduction to this article, it is concluded that the use of ozone as an oxidizing agent for polysaccharides, citing starch as an example, is prevented by the absence of selectivity. Both carbonyl and carboxyl groups are formed, while glycosidic bonds are broken. No details are given on any effect of catalysts on the oxidation with ozone.

Furthermore, in the Journal of Applied 15 Polymer Science (1964), 1597-1606, Szymanski describes a method of oxidizing corn starch using ozone. Oxidation with ozone is carried out under dry conditions as well as in aqueous suspension and in an organic solvent.

The purpose of the study described in this article by Szymanski was to introduce a large amount of aldehyde groups into the starch. Since, in addition to the intended aldehyde groups, a considerable amount of ketone groups also arose, the objective was not achieved according to the author.

Part of this study describes the effect of the iron sulfate and manganese sulfate salts on the ozone oxidation of corn starch. The manganese salt led to a 38% increase in the degree of carbonyl substitution, while the iron salt showed an inhibitory effect.

In addition, it is known from U.S. Patent 3,361,741 that starch in an aqueous suspension can be oxidized by tetravalent lead ions, these lead ions being obtained by oxidation of divalent or trivalent lead ions with ozone.

1002527 - 3 -

German Offenlegungsschrift 22 33 977 describes the oxidation of polysaccharides using an aqueous basic solution of a silver oxide system. In the presence of this silver oxide system, the polysaccharides can be oxidized by a large number of agents, including ozone.

International patent application 93/01905 describes the oxidation of polysaccharides with periodate, wherein the periodate is electrochemically regenerated in a separate reaction space. Such a method requires complicated equipment and complicated process management.

It has now been found a process for the oxidation of polysaccharides using only small amounts of salt and leading to a yield of more than 90% of desired products within short reaction times.

In addition, in this polysaccharide oxidation process, the halide-containing catalyst is regenerated in the same space as where the oxidation reaction takes place.

The present invention provides processes in which polysaccharides such as starch can be selectively oxidized using ozone and in the presence of a catalyst. More particularly, the invention relates to a method in which polysaccharides are treated with ozone in the presence of a halide-containing catalyst, whereby, depending on the choice of the catalyst and the reaction conditions, it is possible to set which oxidation product can be obtained or within product formation limits. 30 can optimize.

This object is achieved by the process of the invention, which is characterized in that polysaccharides are oxidized in the presence of a catalyst selected from the group consisting of bromine and iodine compounds, ozone being passed through an aqueous suspension or solution of these polymers .

1002527 - 4 -

Preferably the bromine compounds are bromides or oxybromides such as hypobromite, while the iodine compounds are iodides, oxyiodides and iodic acid compounds.

Without wishing to be bound by certain theories, it is believed that the bromine and iodine compounds are converted in the presence of ozone to reactive oxidizing oxidants, such as hypobromite and periodic acid, which compounds oxidize the polysaccharides. In principle, only a small amount of these reactive bromine and iodine compounds need to be present in the reaction medium, since the compounds are continuously regenerated into the active oxidants by ozone.

The bromine and iodine compounds already show effect in small amounts. These catalysts are already active in concentrations from 0.05% by weight, as dry matter based on the starch.

Bromine compounds such as NaBr form C2 - C3 and C6 carboxyls and carbonyls. With increasing amount of NaBr, 20 C2 - C3 carboxyl groups are increasingly formed relative to C6.

In the case of iodine compounds such as HIO3, mainly the C2 - C3 and C6 groups are oxidized to aldehydes. This has been demonstrated with a gas chromatography / mass spectrometry technique (Hewlett 25 Packard, gas chromatograph GC 5890 series II and mass spectrometer MS 5989A).

The Dutch patent application of the same rank with filing number (VO 8313) describes the oxidation of starch with ozone in the absence of catalysts. The present inventors have found that when chlorine compounds such as hypochlorite are added to this ozone system, hardly any benefits or other effects are found. In fact, only a small increase in the content of carboxyl and carbonyl groups was found. In this connection, reference is also made to Example 1 below. Without wishing to be bound by any particular theory, it is believed that chlorine ions are rapidly formed from 1002527-5 chlorine compounds in the presence of ozone. Chlorine ions have little or no oxidizing power.

When instead of the chlorine compounds the bromine-5 or iodine compounds according to the present invention are used, it appears that very much less halogen ions will suffice. For bromine compounds, it has been found that only about one-tenth the weight amount of chlorine compounds with which any effect is found are required to obtain the desired results.

Depending on the pH and the catalyst, an oxidized polysaccharide with any desired carbonyl / carboxyl ratio between 1: 1000 and 20: 1 can be obtained. At increasing pH, 15 carboxyl groups are increasingly formed. The invention therefore makes it possible, by adjusting the pH in the same reaction system, in the case of starch to form an aldehyde starch or a carboxyl starch or an intermediate form thereof, depending on the final application of the product. The products obtained according to the method of the invention can be used in many different technical fields of application. For example, carbonyl-containing starches are well applicable in adhesives, in paper (for example in coating layers and surface adhesion), and in textiles (for example as a strength agent).

Starting products in which the sugar ring is openly oxidized, which takes place, for example, in C2-C3 starch oxidation, can be used as co-builders in detergents.

Carbonyl groups formed according to the invention are interesting reaction centers and can be converted according to the usual methods to e.g. amines, imines, acetals, and the like.

The pH is kept constant by adding a base or a solution thereof during the reaction, for example a solution of sodium hydroxide or potassium hydroxide. Buffer systems are less preferred, because they are based on salts, and thus bring salts into the product. In addition, buffers are more expensive.

The invention can be applied to polysaccharides such as starch, cellulose, inulin and derivatives thereof. The starches to be oxidized according to the invention can be of all types. Preferably carrot starches (e.g. tapioca), tuber starches (e.g. potato) and sticky corn starches (e.g. waxy maize, waxy rice) are used because of their low impurities content. Physically and chemically modified polysaccharides, such as roll-dried polysaccharides, and etherified and esterified polymers, can also be oxidized according to the invention.

According to the above-mentioned method, the polysaccharide is oxidized in aqueous suspension and after reaction the aqueous phase with catalyst can be easily separated from the reaction product in a known manner and recycled. Bromine and / or jew compounds can optionally be removed using ion exchangers.

In a preferred embodiment, a surface tension reducing agent is present in the aqueous reaction medium which allows the ozone-containing gas bubbles to become smaller. Thus, the starch molecules are more intimately contacted with the oxidizing agent.

Suitable surface tension reducing agents are acetic acid, tertiary butanol and surfactants such as octanols, known anti-foaming agents such as block polymers of ethylene oxide and propylene oxide (eg Pluronic L61). The acetic acid can be used in concentrations from 0.1 to 10%, preferably from about 0.2 to 2%; tertiary butanol in concentrations of 0.1 to 15%; anti-foaming agents in concentrations from 0.01 to 5%, preferably from about 0.05 to 2.5%. These percentages refer to the amount of dry starch processed for a reaction.

The pH during the reaction should not exceed 10.5 because ozone decomposes at higher pH's; and not less than 1 in 1002527-7 in connection with hydrolysis of the polysaccharides. Preferably the pH is between 4 and 10.5 when using bromine compounds as a catalyst and preferably between 2.5 and 7.0 when using iodine compounds as a catalyst.

The polysaccharide concentration of the reaction mixture can vary from 1 to 45% (on dry matter) and is preferably from 10 to 40%.

Oxygen, air or any other oxygen-containing gas can be used as a source and carrier gas for the ozone.

10 In addition, ozone can be generated directly from water. When using a gas, oxygen is preferably used.

The reaction can be carried out at temperatures from 0 to 60 ° C and preferably between 5 and 40 ° C. The reaction time is between 10 minutes and 20 hours and depends on the desired degree of oxidation.

By using the above method, the intrinsic viscosity of polysaccharides can be reduced. This makes the polysaccharides suitable for various applications, for which polysaccharides with a reduced viscosity are important. The intrinsic viscosity can be adjusted with, inter alia, the reaction pH, the amount of catalyst, reaction temperature, reaction time, addition of surface tension reducing agents. The intrinsic viscosity of a substance is understood to be the degree to which one molecule of that substance in solution can increase the viscosity and is determined by measuring the hydrodynamic volume of that substance. The intrinsic viscosity is given in dl / g.

In the preferred embodiment of the above process, wherein polysaccharide in aqueous suspension is oxidized with ozone under the influence of a catalyst, after reaction the aqueous phase with catalyst can be easily separated from the reaction product and the reaction medium can be reused. If desired, the bromine and iodine compounds can be recovered from the reaction mixture.

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The invention will be further illustrated by the following non-limiting examples.

The oxidation products are analyzed in the following manner.

5

The content of carboxyl groups (DScooh) is expressed in the number of moles of carboxyl per mole. anhydroglucose unit (DScooh) and is determined titrimetrically. To this end, the sample material is brought into H + form 10 with 1NHC1; and titrated to pH 8.6 with 0.1 M NaOH. The titration is performed in 0.5 M NaCl.

The content of carbonyl groups (DSc-o) is expressed in the number of moles of carbonyl per mole of anhydroglucose unit (DSC = 0) and is determined by determining the dextrose equivalent (in mg / g) of the sample material using the Luff-Schoorl method and then convert as follows: (DSc = o) = DE / (1000-DE).

The intrinsic viscosity (IV) is determined in known manner with a Viscotek Y501B with 1 M NaOH as solvent and is expressed in g / dl.

1 0 0 2 5 2 7 - 9 -

Examples

Oxydatle conditions and standard work-up procedure

Unless otherwise noted, the experiments were conducted in a 1 L glass batch reactor equipped with a stirrer, a gas inlet and a pH meter with an attached automatic titrator containing 4.4 weight percent NaOH solution. The partial overpressure was 0.1 bar.

Ozone was generated by passing approximately 10 250 L oxygen gas per hour through an ozone generator (Fischer, type 502), unless otherwise noted. The ozone production at this flow was 8 g / hour. The ozone-containing gas was passed through the reaction mixture.

At the end of the reaction, the product was worked up by adjusting to pH 5.5 in aqueous suspension with 6 M sulfuric acid or 4.4% by weight NaOH solution. The product was then filtered off and washed with a 10-fold amount of water based on starch. Product loss and physical data were determined after the products were dried.

The amount of an addition is expressed in wt% of the amount of starch, calculated on a dry matter basis.

Demineralized water was used in all experiments.

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Example 1

Oxidation of potato starch with. ozone under the influence of various catalysts (NaBr, NaCl, Nal, HI03) at constant temperature and pH.

5 la Blank reaction with 5% NaBr without ozone 250 g (200 g of dry matter) potato starch was suspended in a solution of 10 g of NaBr in 750 ml of water. Subsequently, oxygen was passed through a line in a porous stone at 35 ° C for 7.5 hours and thus into the reaction system.

During the reaction, the pH was adjusted using 4.4% NaOH and an automatic titration combination kept at 9.0.

After reaction, the product was filtered off, washed and dried.

15 lb Oxidation with ozone without catalyst 250 g (200 g dry matter) of potato starch were suspended in 750 ml of water. Subsequently, ozone-containing oxygen was passed through a porous stone for 7.5 hours at 35 ° C.

During the reaction, the pH was adjusted by means of 4.4% NaOH and an automatic titration combination kept at 9.0.

After reaction, the product was filtered off, washed and dried.

Oxidation with ozone with 5% NaBr as catalyst 250 g (200 g dry matter) potato starch was suspended in a solution of 10 g NaBr in 750 ml water.

Also executed as lb.

30 ld Oxidation with ozone with 5% NaCl as catalyst 250 g (200 g dry matter) potato starch was suspended in a solution of 10 g NaCl in 750 ml water.

Also executed as lb.

Oxidation with ozone with 12.5% Nal as a catalyst 250 g (200 g dry matter) potato starch was suspended in a solution of 25 g Nal in 750 ml water.

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Also executed as lb.

Oxidation with ozone with 12.5% HIO3 as catalyst 250 g (200 g dry matter) potato starch was suspended in a solution of 25 g HIO3 in 750 ml water.

Also executed as lb.

Table 1

Ozone oxidation with different catalysts 10 "I ..................................

catalyst ° 3 DScooh DSc = o IV

NaBr (1a) - <0.001 <0.003 2.57

Do not take (lb) __ + 0.004 __ <0.003__1.24

NaBr (1c) + 0.060 0.010-0.15

NaCl (ld) + 0.005 0.003 1.35 _Ver_____

Nal __ + 0.042 0.004__0.27 HI03 + 0.009 0.004 0.91

The addition of chlorine ions does not show a catalytic effect.

15 Example 2

Oxidation of potato starch with ozone with increasing amounts of NaBr as a catalyst; 0% - 0.05% - 0.5% - 5% - 50% NaBr

In five tests, 250 g (200 g dry matter) of potato starch were suspended in 750 ml of water, in the presence of increasing amounts of NaBr and 0; 0.05; 0.5, 5 and 50%. Subsequently, ozone-containing oxygen was passed through a porous stone for 7.5 hours at 35 ° C. The pH was adjusted during the reaction

1002527 - 12 - using 4.4% NaOH and an automatic titration combination kept at 10.5.

After reaction, the product was filtered off, washed and dried.

5

Table 2

Oxidation of potato starch with ozone in the presence of increasing amounts of NaBr

NaBr DScooh DSc = o IV

0% __ 0.001 __ <0.003__2.13 0.05% __ 0.001 <0.003__2.02 0.5% __ 0.010 __ <0.003__0.46 5% __ 0.010__0.003__0.46 50% 0.014 0.003 0.41 10 after = below the detection limit of the determination method Example 3a

Oxidation of potato starch with ozone at different pH's: 6.6 - 7.5 - 9.0 - 10.5 with 5% NaBr as a catalyst 250 g (200 g dry matter) potato starch was suspended in a solution of 10 g NaBr in 750 ml of water. Subsequently, ozone-containing oxygen was passed through a porous stone for 7.5 hours at 35 ° C.

During the reaction, the pH was adjusted using 4.4% NaOH and an automatic titration combination kept constant.

After reaction, the product was filtered off, washed and dried.

The reaction at pH 6.6 was started at pH 6.0. After a short time, the pH stabilized at 6.6 without addition of NaOH.

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Table 3a

Oxidation with ozone at different pH's

| pH DScooh DSc ~ oIV

6.6__0.038__0.057__0.09 7.5 0.056 0.047__0.10 9.0 __0.060 0.010__0.15 10.5 0.010 0.003 0.46 5 Example 3b

Oxidation of potato starch with ozone at different pH values 3.0-4.5 with 1% HCO3 as a catalyst 470 g (400 g dry matter) potato starch was suspended in 1530 g water. 4.0 g of HIO3 were added to this suspension, after which the pH was adjusted using a 4.4% NaOH solution was adjusted to 3.0 and 4.5, respectively. Subsequently, ozone-containing oxygen was passed through a porous stone for 8 hours at 30 ° C (± 3% ozone; flow rate 100 l / h).

During the reaction, the pH was adjusted using 4.4% NaOH and an automatic titration combination kept at 3.0 and 4.5, respectively. After reaction, the product was filtered off and washed with 2 L of water.

20

Table 3b

Oxidation with ozone at different pH's

pH DScooh DSc-o TV

3.0 __0.013 0.045__0.15 4.5 0.002 0.015 0.39 1002 527 - 14 -

Example 4

Oxidation of potato starch with ozone under the influence of a surfactant, Pluronic L61 with NaBr as a catalyst 590 g (400 g dry matter) potato starch was suspended in 1510 g water. 2.0 g NaBr was added to this suspension, after which the pH was adjusted using a 4.4% NaOH solution was adjusted to 7.5. Subsequently, ozone-containing oxygen was passed through a porous stone (± 3% ozone; flow rate 100 1 / h) for 5 hours at 10 ° C. During the reaction, the pH was adjusted using 4.4% NaOH and an automatic titration combination kept at 7.5. After reaction, the product was filtered off and washed with 2 L of water.

15

The above reaction was repeated again with the addition of 1.0 g Pluronic L61 (0.25%).

Table 4 20 Oxidation of potato starch under the influence of Pluronic L61

Pluronic DScooh DSc = o IV

not present__0.012__0.042__0.15 0.25% 0.015 0.060 0.12

Example 5 Oxidation with ozone of different starches under equal conditions (pH = 7.5; 25 ° C, 0.5% NaBr) 5a Potato starch (AM) 490 g (400 g dry matter) potato starch was suspended in 1510 g water . The pH was adjusted to 7.5 with 4.4% NaOH. Subsequently, ozone-containing oxygen was passed through a porous stone for 5 hours (± 3% ozone; flow rate 100 l / h).

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During the reaction, the pH was adjusted using 4.4% NaOH and an automatic titration combination kept at 7.5.

5b Amylopectin potato starch (AAZM) 5 488 g (400 g of dry matter) amylopectin potato starch was suspended in 1510 g of water. Also executed as 5a.

Waxy maize starch (WM) 449 g (400 g dry matter) of waxy maize starch was suspended in 1550 g water, to which 4 g Pluronic L61 was added to prevent foaming. Also executed as 5a.

Tapioca starch (TZ) 459 g (400 g dry matter) tapioca starch was suspended in 1550 g water, to which 4 g Pluronic L61 was added to prevent foaming. Also executed as 5a.

Table 5

Oxidation with ozone of various starches 20% starch DScooh DSc = o - AM__0.015 0.050 AAZM 0.008 0.027 WM__0.011 0.023

TZ 0.021 0.076 I.

Example 6

Ozone oxidation of other polysaccharides; inulin and cellulose

Reaction with inulin with 6% NaBr as a catalyst 82 g (75 g dry matter, 0.46 mol) Inulin (from chicory root) was suspended in a solution of 5 g NaBr in 669 ml water. The suspension was heated to 35 ° C then with NaOH

1002527-16 - the pH was adjusted to 9.0. Then 8 g / hour ozone was passed through for 6.5 hours. After reaction, the pH was adjusted to pH 3.0 with 6 M hydrochloric acid, after which the product was flocculated in ethanol. The flocculated material was air dried.

Reaction with cellulose with 8% NaBr as catalyst 138 g (129 g dry matter, 0.80 mol) Avicel PH102 was suspended in a solution of 10 g NaBr in 750 ml AD.

The suspension was heated to 35 ° C, after which the pH was adjusted to 9.0 with NaOH. Then 8 g / hour ozone was passed through for 7.5 hours. After reaction, the pH was adjusted to 5.5 with 6 M HCl. The product was then taken up in 1 L AD and isolated by centrifugation. This washing procedure was repeated two more times.

Oxidation with ozone of inulin and cellulose substrate DScooh DSc = o inulin__0.036__0.022 cellulose 0.027 0.004 1002527

Claims (8)

1. A method of oxidizing polysaccharides in the presence of a catalyst selected from the group consisting of bromine and iodine compounds, wherein ozone is passed through an aqueous suspension or solution of these polysaccharides. The method of claim 1, wherein the polysaccharide is starch or a derivative thereof. The method of claim 1, wherein the polysaccharide is cellulose or a derivative thereof. The method of claim 1, wherein the polysaccharide is inulin or a derivative thereof. A method according to any one of claims 2-4, wherein the polysaccharide is present in aqueous suspension. A method according to any one of claims 1 to 5, wherein the pH 15 is maintained at a constant value. A method according to claims 1-6, wherein surface tension-reducing substances are added. The method of claim 7, wherein the surface tension reducing agents are selected from acetic acid, 20 t. butanol, octanol and anti-foaming agents. 1002527 bAMfcNWbHMNüoV fenunMo vrv- / REPORT ON NEWNESS RESEARCH OF INTERNATIONAL TYPE IDENTIFICATION OF OE NATIONAL APPLICATION Kentmrk of applicant, among others, o (of the gamacnugoe Nw 8314 Neoenanose application nr InawnoeBEan p. wet sweetened for to onoerzoe * of mtemaienate type By ao Maanie for ntamasonaai OnoarzoeR (ISA) to wet νβτζοβκ for an undergrowth of mernaDonal typa bogeieano nr. SN 27273 NL I. CLASSIFICATION OF THE SUBJECT (at eepessmg van veracncaoesano ct daacnülloct. ) Voigans among others inamaoonaie cussiftcaee (IPC) Int.Cl.6: C 08 B 31/18, C 08 B 15/02, C 08 B 37/18 ______________________________I II. RESEARCHED FIELDS OF TECHNIQUE Onoarrocffia mtnrmum documentation | Classification system I Classification tools ~ [Int.Cl.6: C 08 B Onoarzocrta anoara oocumenaoe to ae minimum oocumenatM insofar as primordial ooeumana n n and others gabases sentence included III .: NO EXAMINATION FOR CERTAIN CONCLUSIONS (comments on supplement pay) | IV .: LACK OF UNITY OF INVENTION (oomenangen oo complemento totao) | | i Sorm PCT.ISATOUaiCS: Sfc