Reversibly crosslinked cellulose ethers and process for the production thereof by selective oxidation of vicinal OH groups

Abstract

Reversibly crosslinked, water-soluble cellulose ethers having at least two different ether components is disclosed. At least one ether component is an alkyl, hydroxyalkyl or carboxymethyl group and at least one is an alkyl group having an aldehyde function which forms hydrolyzable hemiacetals with free OH groups of the cellulose ether. The cellulose ethers are obtainable by selective oxidation of cellulose ethers containing alkyl groups having vicinal OH groups (glycol cleavage). Preferably, water-soluble cellulose ethers are co-etherified simultaneously or subsequently with 2,3-epoxypropanol (glycidol) or 3-chloro-1,2-propanediol and the 2,3-dihydroxypropyl ether groups converted entirely or partly into 2-oxoethyl ether groups by oxidation. Suitable oxidants include periodate, periodic acid or lead tetraacetate. After washing and drying, cellulose ethers reversibly crosslinked via hemiacetals can be dispersed in water or aqueous solutions, going into solution homogeneously with a time delay. No low molecular weight dialdehydes or other problematical crosslinking reagents are liberated on dissolution.

Claims

1. A reversibly crosslinked, water-soluble dried cellulose ether comprising hydrolysable hemiacetals, said cellulose ether having at least two different ether components, a) a first ether component that is at least one of an alkyl, hydroxyalkyl or carboxymethyl group and b) a second ether component consisting of 2-oxo-ethyl moieties and optional 2,3-dihydroxypropyl moieties, the degree of substitution DS (2-oxo-ethyl) moiety and its hydrolysable hemiacetals is in the range of from 0.0001 to 0.1, wherein the 2-oxo-ethyl moieties may or may not be present as hydrolysable hemiacetals, and no low molecular weight aldehydes are liberated upon dissolution of the cellulose ether in water.

2. The cellulose ether as claimed in claim 1, wherein the ether component a) is a methyl, ethyl, propyl, butyl, sec-butyl, isobutyl, 2-hydroxyethyl, hydroxypropyl and/or carboxymethyl group.

3. The cellulose ether as claimed in claim 1, wherein the degree of substitution DS(2-oxoethyl) is in the range from 0.001 to 0.05.

4. The cellulose ether as claimed in claim 1, wherein the degree of substitution DS(alkyl) is in the range from 1.2 to 2.2.

5. The cellulose ether as claimed in claim 1, wherein the degree of substitution MS(hydroxyalkyl) is in the range from 0.8 to 3.0 and the degree of substitution DS(carboxymethyl) is in the range from 0.1 to 1.0.

6. The cellulose ether as claimed in claim 5, wherein the degree of substitution MS(hydroxyalkyl) is in the range from 1.0 to 2.4 and the degree of substitution DS(carboxymethyl) is in the range from 0.2 to 0.7.

7. The cellulose ether as claimed in claim 1, wherein the degree of substitution DS(carboxymethyl) is in the range from 0.3 to 1.2.

8. The cellulose ether as claimed in claim 1, wherein, after breaking the cellulose ether crosslinking by adding alkali, the cellulose ether has a viscosity in 1% strength aqueous solution in the range from 1 to 15 000 mPa.Math.s.

9. The cellulose ether as claimed in claim 8, wherein, after breaking the cellulose ether crosslinking by adding alkali, the cellulose ether has a viscosity in 1% strength aqueous solution in the range from 100 to 10 000 mPa.Math.s.

10. The cellulose ether as claimed in claim 1, wherein the cellulose ether is periodate-oxidized.

11. The cellulose ether as claimed in claim 1, wherein the cellulose ether is not ethyl cellulose.

12. The cellulose ether as claimed in claim 1, wherein the incipient dissolution time ranges from 7 to 27 minutes.

13. The cellulose ether as claimed in claim 1, wherein the cellulose ether is periodate-oxidized cellulose without polymer degradation.

14. The cellulose ether as claimed in claim 1, wherein the cellulose ether further comprises OH groups.

15. The cellulose ether as claimed in claim 1, wherein the aldehyde function of said 2-oxo-ethyl moieties is essentially present as hydrolysable hemiacetal bonded with free OH groups of the cellulose ether.

16. The cellulose ether as claimed in claim 1, wherein said cellulose ether exhibits a delayed dissolution whose dissolution can be accelerated by increasing the pH.

17. A reversibly crosslinked, water-soluble dried cellulose ether comprising hydrolysable hemiacetals, said cellulose ether having at least two different ether components, a) a first ether component that is at least one of an alkyl, hydroxyalkyl or carboxymethyl group and b) a second ether component consisting of 2-oxo-ethyl moieties and optional 2,3-dihydroxypropyl moieties, the dried aldehyde function of said 2-oxo-ethyl moieties consisting of hydrolysable hemiacetal bonded with free OH groups of the cellulose ether, the degree of substitution DS (2-oxo-ethyl) moiety is in the range of from 0.0001 to 0.1, and no low molecular weight aldehydes are liberated upon dissolution of the cellulose ether in water, wherein the degree of substitution DS(alkyl) is in the range from 1.2 to 2.2 and the degree of substitution MS(hydroxyalkyl) is in the range from 0.02 to 1.0.

18. A reversibly crosslinked, water-soluble dried cellulose ether comprising hydrolysable hemiacetals, said cellulose ether having at least two different ether components, a) a first ether component that is at least one of an alkyl, hydroxyalkyl or carboxymethyl group and b) a second ether component consisting of 2-oxo-ethyl moieties and optional 2,3-dihydroxypropyl moieties, the degree of substitution DS (2-oxo-ethyl) moiety is in the range of from 0.0001 to 0.1, the 2-oxo-ethyl moieties may or may not be present as hydrolysable hemiacetals, and no low molecular weight aldehydes are liberated upon dissolution of the cellulose ether in water wherein (i) the degree of substitution MS(hydroxyalkyl) is in the range from 1.0 to 4.0; (ii) the degree of substitution MS(hydroxyalkyl) is in the range from 0.8 to 3.0 and the degree of substitution DS(carboxymethyl) is in the range from 0.1 to 1.0; (iii) the degree of substitution MS(hydroxyalkyl) is in the range from 1.0 to 2.4 and the degree of substitution DS(carboxymethyl) is in the range from 0.2 to 0.7 or (iv) the degree of substitution DS(carboxymethyl) is in the range from 0.3 to 1.2.

19. A reversibly crosslinked, water-soluble dried cellulose ether having two different ether components consisting of a) a first dried ether component selected from a methyl, ethyl, propyl, butyl, sec-butyl, isobutyl, 2-hydroxyethyl, hydroxypropyl and/or carboxymethyl group and b) a second dried ether component consisting of hydrolysable hemiacetal bonds and optional 2,3-dihydroxypropyl groups, no low molecular weight aldehydes are liberated upon dissolution of the cellulose ether in water and the incipient dissolution time ranges from 7 to 27 minutes, unless accelerated by alkali.

20. A reversibly crosslinked, water-soluble dried cellulose ether comprising hydrolysable hemiacetals, said cellulose ether having at least two different ether components, a) a first ether component that is at least one of an alkyl, hydroxyalkyl or carboxymethyl group and b) a second ether component consisting of 2-oxo-ethyl moieties and optional 2,3-dihydroxypropyl moieties, the degree of substitution DS (2-oxo-ethyl) moiety is in the range of from 0.0001 to 0.1, with the dried 2-oxo-ethyl moieties consisting of hydrolysable hemiacetals, no low molecular weight aldehydes are liberated upon dissolution of the cellulose ether in water, and the final dissolution time ranges from 21 to 70 minutes unless accelerated by alkali.

21. A process for preparing the reversibly crosslinked, water-soluble cellulose ether having at least two different ether components as claimed in claim 1, which comprises the steps a) treating a cellulose or a cellulose ether with aqueous alkali metal hydroxide, b) reacting the alkalized cellulose with i) ethylene oxide, propylene oxide and/or an alkyl halide and/or 2-chloroacetic acid or the sodium salt of 2-chloroacetic acid and ii) with 2,3-epoxypropanol or 3-chloropropane-1,2-diol, or reacting the alkalized cellulose ethers with 2,3-epoxypropanol or 3-chloropropane-1,2-diol, thereby forming 2,3-dihydroxypropyl ether groups, c) optionally washing the product obtained in step b), d) oxidative cleaving of the vicinal hydroxy groups in the 2,3-dihydroxypropyl ether groups by treatment with periodate, periodic acid or lead tetraacetate, thereby forming 2-oxoethyl ether groups to form 2-oxoethyl cellulose ether having a DS (2-oxo-ethyl) in the range of from 0.0001 to 0.1, e) washing the product obtained in step d), and f) drying of the washed cellulose ether to form hemiacetal bonds between the 2-oxoethyl ether groups and hydroxy groups on the cellulose ether, wherein, the alkalization and the etherification of the celluloses or the cellulose ether are carried out in a slurry process.

22. The process as claimed in claim 21, wherein the reaction of the alkalized cellulose with ethylene oxide, propylene oxide and/or an alkyl halide occurs simultaneously with the reaction with the 2,3-epoxypropanol or the 3-chloropropane-1,2-diol.

23. The process as claimed in claim 21, wherein the reaction of the alkalized cellulose with the 2,3-epoxypropanol or the 3-chloropropane-1,2-diol is carried out immediately after the reaction with the ethylene oxide, propylene oxide and/or alkyl halide.

24. The process as claimed in claim 23, wherein the reaction of the alkalized cellulose with the 2,3-epoxypropanol or the 3-chloropropane-1,2-diol is carried out immediately after the reaction with the ethylene oxide, propylene oxide and/or alkyl halide in the same reaction vessel.

25. The process as claimed in claim 21, wherein the oxidative cleaving is carried out at a temperature of from 10 to 60° C. for a period of time of from 30 minutes to 10 hours.

26. The process as claimed in claim 21, wherein the oxidative cleaving is carried out at a pH of from 5 to 7 without polymer degradation.

27. The process as claimed in claim 21, wherein the cellulose ether in step a) is methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxyethyl carboxymethyl cellulose, carboxymethyl cellulose or hydroxypropyl cellulose.

Description

DETAILED DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS OF THE INVENTION

(1) This object is achieved by a reversibly crosslinked, water-soluble cellulose ether having at least two different ether components, wherein a) at least one of the ether components is an alkyl, hydroxyalkyl or carboxymethyl group and b) at least one of the ether components is an alkyl group having an aldehyde function which can form hydrolyzable hemiacetals with free hydroxy groups of the cellulose ether, wherein the ether component b) is a 2-oxo-ethyl group and the degree of substitution DS (2-oxo-ethyl) is in the range of from 0.0001 to 0.1.

(2) The ether component a) is preferably a methyl, ethyl, propyl, butyl, sec-butyl, isobutyl, 2-hydroxyethyl, hydroxypropyl and/or carboxymethyl group. The degree of substitution DS(alkyl) is advantageously in the range from 1.2 to 2.2, preferably in the range from 1.4 to 2.0. The degree of substitution MS(hydroxyalkyl) is advantageously in the range from 1.0 to 4.0, preferably in the range from 1.5 to 3.5. The degree of substitution DS(carboxymethyl) is advantageously in the range from 0.2 to 1.2, preferably in the range from 0.4 to 1.0. In the case of a plurality of ether components, the additional components can also have a significantly lower degree of substitution. It is critical that the total etherification is sufficiently high to ensure good solubility of the products in water. In principle, all customary ether combinations and degrees of substitution of commercially available water-soluble cellulose ethers are preferably possible. The ether component b) is a 2-oxoethyl group (—CH.sub.2—CH═O). The degree of substitution DS.sub.aldehyde (2-oxoethyl) is advantageously in the range from about 0.0001 to 0.1, preferably in the range from about 0.001 to 0.05. This is preferably formed from a 2,3-dihydroxypropyl ether group by means of selective oxidation by reaction with preferably sodium periodate. Here, the MS.sub.HPO before oxidation should advantageously be somewhat higher than the desired DS.sub.aldehyde. In principle, the MS.sub.HPO can also be set to a higher value, i.e. in the range of the degree of substitution MS(hydroxyalkyl) mentioned under a), but this is of rather minor interest because of the significantly greater raw materials cost for 2,3-epoxypropanol (glycidol) or 3-chloro-1,2-propanediol compared to, for example, ethylene oxide or propylene oxide in an industrial preparation of the reversibly crosslinked, water-soluble cellulose ethers claimed according to the invention.

(3) As starting cellulose, it is possible to use all pulp materials which can be used for preparing cellulose. Preference is given to using pulp from conifers and broad-leaved trees and also cotton linters. The limiting viscosity number of the pulps is usually in the range from about 200 to 2200 ml/g.

(4) The viscosities of the cellulose ethers of the invention which can be set in this way correspond to those which are known to a person skilled in the art from the literature concerning conventional cellulose ethers or are commercially available. When low-viscosity cellulose ethers are being prepared, the degradation processes known to those skilled in the art, e.g. molecular weight reduction by treatment with hydrogen peroxide, can be employed. The Brookfield viscosity of a 1.0% strength aqueous solution of the cellulose ethers can thus be in the range from 1 to about 15,000 mPa.Math.s, preferably in the range from 100 to 10,000 mPa.Math.s (after a sufficiently long dissolution time or breaking of the crosslinking by addition of alkali).

(5) The cellulose ether of the invention is water-soluble. For the purposes of the present invention, this means that at least 10 g thereof are soluble in 1 liter of distilled water having a temperature of 20° C.

(6) The cellulose ethers of the invention can be prepared by a process comprising the steps: a) treatment of cellulose or cellulose ether with aqueous alkali metal hydroxide, b) reaction of the alkalized cellulose with (i) ethylene oxide, propylene oxide and/or an alkyl halide and/or 2-chloroacetic acid or the sodium salt of 2-chloroacetic acid and (ii) with 2,3-epoxypropanol (glycidol) or 3-chloropropane-1,2-diol, or reaction of the alkalized cellulose ether with 2,3-epoxypropanol or 3-chloropropane-1,2-diol, forming 2,3-dihydroxypropyl ether groups in each case, c) optionally washing of the product obtained in step b), d) oxidative cleavage of the vicinal hydroxy groups in the 2,3-dihydroxypropyl ether groups, forming 2-oxoethyl ether groups, e) washing of the cellulose ether obtained in step d), and f) drying of the washed cellulose ether.

(7) The cellulose ether used in step a) is preferably methyl cellulose, methyl carboxymethyl cellulose, methyl hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxyethyl carboxymethyl cellulose, carboxymethyl cellulose or hydroxypropyl cellulose. It is thus possible to use either ionic or nonionic cellulose ethers.

(8) Both the alkalization and the etherification of the celluloses or the cellulose ether are preferably carried out in a slurry process. The reaction of the alkalized cellulose with the ethylene oxide, propylene oxide and/or alkyl halide in step b) can be carried out simultaneously with the reaction with 2,3-epoxypropanol or 3-chloropropane-1,2-diol. As an alternative, the reaction with the 2,3-epoxypropanol or the 3-chloropropane-1,2-diol can be carried out immediately after the reaction with the ethylene oxide, propylene oxide and/or alkyl halide, preferably in the same reaction vessel.

(9) The oxidative cleavage in step c) is preferably effected by treatment with periodate, periodic acid or lead tetraacetate. Suitable oxidants are in principle all reagents which oxidize the vicinal hydroxy groups very selectively to the aldehyde stage with cleavage of the C—C bond. The cleavage is preferably carried out at a temperature of from 10 to 60° C., in particular from 30 to 50° C., for a period of time from 30 minutes to 10 hours, in particular from 3 to 5 hours. The pH of the mixture during the oxidative cleavage is advantageously in the range from 4 to 7, preferably from 5 to 6. The oxidative cleavage forms formaldehyde which is removed during the subsequent washing of the cellulose ether. The oxidative cleavage is optionally carried out in such a way that only part of the 2,3-dihydroxypropyl groups is cleaved.

(10) The washing and drying of the cellulose ethers is carried out in a routine manner. Here, the carbaldehyde groups react with hydroxy groups of the cellulose ethers with elimination of water and formation of hemiacetals. If hemiacetal formation occurs between two adjacent cellulose ether chains, branched and, in the case of a sufficiently large number of hemiacetal bridges, completely crosslinked cellulose ethers are initially obtained. Crosslinking thus occurs via the same chemical reaction as in the case of crosslinking with glyoxal. Unlike crosslinking with glyoxal, however, only one hemiacetal bond is formed per crosslinking point here, so that no low molecular weight compound is liberated on hydrolysis of the hemiacetal groups, i.e. the aldehyde group used for crosslinking is monofunctional and is firmly bound to in each case one of the participating cellulose ether chains by means of a covalent bond which is hydrolysis-resistant in water or water-containing solvents.

(11) The particular advantage of the present invention compared to crosslinking with low molecular weight bifunctional or multifunctional compounds is that no further low molecular weight substance is eliminated from the cellulose ethers which have been crosslinked according to the invention when the crosslinked cellulose ethers are dissolved in water and that problems connected with toxicological concerns about the elimination products therefore can no longer occur.

(12) Analytical Methods:

(13) Determination of the Limiting Viscosity Number (LVN):

(14) The limiting viscosity numbers cited for characterizing the pulps used were determined on copper-ethylene diamine solution (Cuen solution) at 25.0° C. using a VISCOMAT® II from Lagge in accordance with the method ISO 5352:2010 which is known to those skilled in the art.

(15) Determination of the Dry Matter Content (DMC):

(16) The dry matter contents cited for characterizing the pulps used were determined at a drying temperature of 105° C. on an infrared rapid-drier Moisture Analyzer MA 30 from Sartorius. Here, about 3 g of pulp were dried to constant weight.

(17) Determination of the Viscosity (visc):

(18) The viscosity values cited for characterizing the cellulose ethers prepared were determined on an aqueous solution after a dissolution time of two days at 20.0° C. on a rotational viscometer from Brookfield (model RVDV-III) using deionized water and a rotational speed of 20 rpm. The concentration of the cellulose ether solution of 1.0 or 1.9% by weight is based on the absolutely dry cellulose ether (adr). The number of the spindle used is shown in parentheses after the viscosity value.

(19) Determination of the Degrees of Etherification or the Molar Degrees of Substitution (MS.sub.EO and MS.sub.HPO):

(20) The molar degrees of substitution cited for characterizing the cellulose ethers prepared were determined by means of Zeisel digestion with hydroiodic acid and GC analysis. For this purpose, the cellulose ether was treated with hydroiodic acid at about 143-150° C. in the presence of adipic acid, toluene (internal standard) and xylene (solvent) in a closed vessel, with the alkyl iodide formed by elimination of the ether groups dissolving in the xylene phase. To determine the content, an aliquot of the xylene phase was injected into a gas chromatograph (e.g. TRACE™ GC ultra, Thermo Electron Corporation). The components were separated in the separation column of the gas chromatograph (e.g. 30 m DB-624×0.53 mm I. D.×3.0 μm film or comparable column; preliminary column, e.g. 2.5 m deactivated capillary tube, 0.53 mm I. D.). The peak areas were evaluated by means of a laboratory data system. The content determination was carried out by the method of internal standards (ISTD), by means of multipoint calibration. The MS.sub.EO is the molar degree of substitution resulting from the etherification using ethylene oxide. The MS.sub.HPO is the molar degree of substitution resulting from the etherification with 2,3-epoxypropanol (glycidol or hydroxypropylene oxide). Here, a blank value of 0.005 (examples 1-8 and comparative example 1) or 0.003 (examples 9-14 and comparative example 2) was taken into account, i.e. subtracted from the MS.sub.HPO value calculated from the OC.sub.3H.sub.6 content determined by means of GC. In addition, the determination was carried out on the end product and thus after treatment with periodate. Assuming selective cleavage of the 2,3-dihydroxypropyl ether groups and 100 percent reaction (periodate no longer detectable), the MS.sub.HPO value before treatment with periodate can be calculated therefrom by adding the amount of periodate used per anhydroglucose unit (mol of periodate per mol of AHG).

(21) Calculation of the Alkyl Groups Having an Aldehyde Function (DS.sub.aldehyde) Produced by Means of Glycol Cleavage:

(22) The DS.sub.aldehyde is the average degree of substitution by 2-oxoethyl groups resulting from reaction of the 2,3-dihydroxypropyl ether groups with periodate. Assuming selective cleavage of the 2,3-dihydroxypropyl ether groups and 100 percent reaction (periodate no longer detectable), the DS.sub.aldehyde is identical to the amount of periodate used per anhydroglucose unit (MR PI; mol of periodate per mol of AHG). Here, the MS.sub.HPO before treatment with periodate has to be sufficiently high. This is the case only when the DHPHEC has been washed sufficiently before treatment with periodate, since otherwise ethylene glycol (by-product of the etherification with ethylene oxide) likewise reacts with the periodate. Without prior washing, the amount of periodate required for setting a desired dissolution delay is therefore greater than in the case of previously washed DHPHEC.

(23) Determination of the pH Value (pH):

(24) The pH values cited for characterizing the cellulose ethers prepared were determined on 1.0% strength by weight solutions (adr) in deionized water at 25° C. by means of a pH meter having a combination pH electrode.

(25) Determination of the Centrifuge Residue (CR):

(26) The centrifuge residues cited for assessing the dissolution quality of the cellulose ethers prepared were determined by gravimetric determination of the water-insoluble material (based on dry matter of the cellulose ethers). For this purpose, the cellulose ethers were dissolved in deionized water and the insoluble suspended particles present in the solution were centrifuged down in a centrifuge. The supernatent liquid was drawn off and the soluble cellulose ether remaining in the precipitate was washed out by means of a plurality of washing and centrifugation operations. The insoluble residue which remained was dried and weighed. Both water-insoluble fibers and swelled bodies are determined by the method.

(27) Determination of the Incipient Dissolution Time (IDT) and Final Dissolution Time (FDT):

(28) The incipient dissolution times and final dissolution times cited for the assessment of the dissolution delay of the cellulose ethers prepared were determined in water by means of a continuous viscosity measurement and recording via an xt plotter during the dissolution process in a Brabender VISCOGRAPH® at 20.0° C. using mains water, a weight of cellulose ether of 1.5% by weight and a stirring speed of 75 rpm. The swelling time is the time in minutes between introduction of the product and achievement of a viscosity of 100 Brabender units (BE)=65 mPa.Math.s. The final dissolution time is the time in minutes after which no further viscosity increase occurs.

(29) Molar Ratios (MR):

(30) The molar ratios shown in the tables are always based on the number of moles of anhydroglucose units (AHG) of the pulp used. MR EO=mole of ethylene oxide per mole of AHG; MR HPO=mole of 2,3-epoxypropanol (glycidol or hydroxypropylene oxide) per mole of AHG; MR PI=mole of sodium metaperiodate per mole of AHG.

(31) With the aid of the examples, it will be shown how the cellulose ethers according to the invention which have been modified so as to exhibit delayed dissolution can be prepared by coetherification of conventional cellulose ethers and mixed ethers with a further ether component having one or optionally more vicinal hydroxy groups and subsequent oxidative cleavage of the C—C bond bearing the hydroxy groups without a particular outlay. The degree of dissolution delay can be easy set in a targeted way via the degree of coetherification and/or the degree of oxidation. Owing to the high selectivity and the mild reaction conditions required in the oxidation, modified cellulose ethers which still have a high viscosity can be prepared. However, it is also possible to reduce the viscosity of the modified cellulose ether in a targeted manner by means of the oxidation reaction. The coetherification of the cellulose ether can here be carried out by the conventional methods known to those skilled in the art. In particular, the coetherification can be carried out either in one or two stages or else subsequently. Furthermore, the etherification can be carried out both without and with partial neutralization during the etherification, with the latter usually being employed in the preparation of cellulose ethers having increased biostability. The oxidation of the vicinal hydroxy groups of the ether component can be carried out before, during or after washing of the cellulose ether. The examples describe, by way of example, the preparation of delayed-dissolution modified hydroxyethyl cellulose, which has been carried out by etherification in the slurry process using tert.-butanol or isopropanol as suspension medium. 2,3-epoxypropanol was always used as coetherification component and sodium metaperiodate was always used as oxidant.

(32) Percentages in the following examples are percentages by weight, unless indicated otherwise or apparent from the context.

EXAMPLE 1

(33) 83.2 g (0.50 mol) of milled pulp (DMC=97.4%; LVN=1 350 ml/g) were admixed with 537.6 g of 95% strength tert.-butanol and 73.0 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 83.9 g of 31.0% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 20 minutes. After addition of 66.1 g (1.50 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 85° C. over a period of 120 minutes and subsequently partially neutralized with 60.9 g of 59.0% strength nitric acid (0.57 mol) via a dropping funnel which had also been made inert, 18.5 g (0.25 mol) of 2,3-epoxypropanol were added and the mixture was stirred at 85° C. for 120 minutes. After cooling to 30° C., the mixture was neutralized with about 4.8 g (0.08 mol) of acetic acid and the product was washed free of salts by multiple treatments with 80% strength acetone. The moist filter cake which had been filtered off with suction via a glass frit was returned to the reactor and suspended in 1000 g of 85% strength acetone. A pH of 5.0 was set by addition of acetic acid. A solution of 0.86 g (0.004 mol) of sodium metaperiodate in 50 g of water was subsequently added and the mixture was stirred at 50° C. for 3 hours. After cooling to 30° C., the product was washed free of salts by treatment with 80% strength acetone and dewatered by treatment with 100% strength acetone and filtered off with suction on a glass frit. The filter cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the atmosphere of the room, milled and sieved to less than 1000 μm. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated here (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.18; MS.sub.HPO=0.347; visc 1.0%=2 495 mPa.Math.s (sp. 3); visc 1.9%=20 300 mPa.Math.s (sp. 6); pH 1.0%=5.6; CR=0.1%; IDT=27 min; FDT=70 min.

COMPARATIVE EXAMPLE 1

(34) 83.2 g (0.50 mol) of milled pulp (DMC=97.4%; LVN=1 315 ml/g) were admixed with 537.6 g of 95% strength tert.-butanol and 73.0 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 83.9 g of 31.0% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 20 minutes. After addition of 66.1 g (1.50 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 85° C. over a period of 120 minutes and subsequently partially neutralized with 60.9 g of 59.0% strength nitric acid (0.57 mol) via a dropping funnel which had also been made inert. 18.5 g (0.25 mol) of 2,3-epoxypropanol were added and the mixture was stirred at 85° C. for 120 minutes. After cooling to 30° C., the mixture was neutralized with about 4.8 g (0.08 mol) of acetic acid and the product was washed free of salts by multiple treatments with 80% strength acetone and dewatered by treatment with 100% strength acetone and filtered off on a glass frit. The filter cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the air of the room, milled and sieved to less than 1 000 μm. The pulverulent DHPHEC obtained displayed no dissolution delay and formed lumps on stirring into water; although the solution immediately became viscous, the lumps went completely into solution only after some days. The following product data were determined: MS.sub.EO=2.22; MS.sub.HPO=0.368; visc 1.0%=2 730 mPa.Math.s (sp. 4); visc 1.9%=19 550 mPa.Math.s (sp. 6); pH 1.0%=6.8; CR=0.1%; IDT and FDT not determined since the product could not be stirred in without lumps.

EXAMPLE 2

(35) The experiment was carried out in a manner analogous to Example 1, but only 0.43 g (0.002 mol) of sodium metaperiodate instead of 0.86 g (0.004 mol) were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which when completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.19; MS.sub.HPO=0.380; visc 1.0%=2 970 mPa.Math.s (sp. 4); visc 1.9%=22 100 mPa.Math.s (sp. 6); pH 1.0%=5.9; CR=0.4%; IDT=13 min; FDT=42 min.

EXAMPLE 3

(36) The experiment was carried out in a manner analogous to Example 1, but only 0.11 g (0.0005 mol) of sodium metaperiodate instead of 0.86 g (0.004 mol) were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.23; MS.sub.HPO=0.378; visc 1.0%=2 770 mPa.Math.s (sp. 4); visc 1.9%=19 200 mPa.Math.s (sp. 6); pH 1.0%=5.8; CR=0.6%; IDT=7 min; FDT=33 min.

EXAMPLE 4

(37) The experiment was carried out in a manner analogous to Example 2, but only 1.85 g (0.025 mol) of 2,3-epoxypropanol dissolved in 20 g of 95% strength tert.-butanol were added instead of 18.5 g (0.25 mol). The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.16; MS.sub.HPO=0.031; visc 1.0%=1 875 mPa.Math.s (sp. 3); visc 1.9%=16 060 mPa.Math.s (sp. 5); pH 1.0%=6.7; CR=0.7%; IDT=9 min; FDT=29 min.

EXAMPLE 5

(38) The experiment was carried out in a manner analogous to Example 2, but only 0.37 g (0.005 mol) of 2,3-epoxypropanol dissolved in 20 g of 95% strength tert.-butanol were added instead of 18.5 g (0.25 mol). The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.27; MS.sub.HPO=0.004; visc 1.0%=1 185 mPa.Math.s (sp. 3); visc 1.9%=11 500 mPa.Math.s (sp. 5); pH 1.0%=6.5; CR=0.6%; IDT=8 min; FDT=21 min.

EXAMPLE 6

(39) The experiment was carried out in a manner analogous to Example 4, but 79.3 g (1.80 mol) instead of 66.1 g (1.50 mol) of ethylene oxide and 1.28 g (0.006 mol) instead of 0.43 g (0.002 mol) of sodium metaperiodate were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated here (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.64; MS.sub.HPO=0.024; visc 1.0%=1 500 mPa.Math.s (sp. 3); visc 1.9%=16 200 mPa.Math.s (sp. 6); pH 1.0%=6.0; CR=0.6%; IDT=13 min; FDT=51 min.

EXAMPLE 7

(40) The experiment was carried out in a manner analogous to Example 6, but the oxidation by means of sodium metaperiodate was carried out at 40° C. instead of 50° C. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.64; MS.sub.HPO=0.027; visc 1.0%=2 745 mPa.Math.s (sp. 3); visc 1.9%=22 100 mPa.Math.s (sp. 6); pH 1.0%=5.6; CR=0.3%; IDT=15 min; FDT=58 min.

EXAMPLE 8

(41) 83.2 g (0.50 mol) of milled pulp (DMC=97.4%; LVN=1 350 ml/g) were admixed with 537.6 g of 95% strength tert.-butanol and 73.0 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 83.9 g of 31.0% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 20 minutes. After addition of 66.1 g (1.50 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 85° C. over a period of 120 minutes and subsequently partially neutralized with 60.9 g of 59.0% strength nitric acid (0.57 mol) via a dropping funnel which had also been made inert. 18.5 g (0.25 mol) of 2,3-epoxypropanol were added and the mixture was stirred at 85° C. for 120 minutes. After cooling to 30° C., a pH of 5.0 was set by addition of acetic acid. A solution of 1.28 g (0.006 mol) of sodium metaperiodate in 25 g of water was subsequently added and the mixture was stirred at 50° C. for 3 hours. After cooling to 30° C., the product was washed free of salts by repeated treatment with 80% strength acetone and dewatered by treatment with 100% strength acetone and filtered off with suction on a glass frit. The filter cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the air of the room, milled and sieved to less than 1000 μm. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.22; MS.sub.HPO=0.036; visc 1.0%=3 510 mPa.Math.s (sp. 4); visc 1.9%=26 950 mPa.Math.s (sp. 6); pH 1.0%=6.3; CR=0.7%; IDT=6 min; FDT=36 min.

EXAMPLE 9

(42) 83.5 g (0.50 mol) of milled pulp (DMC=97.1%; LVN=1.569 ml/g) were admixed with 584.3 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 157.1 g of 16.5% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 15 minutes. After addition of 110.1 g (2.50 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 40° C. over a period of 30 minutes, stirred at 40° C. for 60 minutes and heated to 85° C. over a period of 60 minutes. 2.6 g (0.035 mol) of 2,3-epoxypropanol dissolved in 20 g of 100% strength isopropanol were added and the mixture was stirred at 85° C. for 60 minutes. After cooling to 30° C., the mixture was neutralized with 59.6 g of 37.0% strength hydrochloric acid (0.605 mol) and 2.7 g of acetic acid (0.046 mol) and the product was washed free of salts by multiple treatments with 80% strength isopropanol. The moist filter cake which had been filtered off with suction via a glass frit was returned to the reactor and suspended in 1000 g of 85% strength isopropanol. A pH of 5.0 was set by addition of acetic acid. A solution of 2.57 g (0.012 mol) of sodium metaperiodate in 50 g of water was subsequently added and the mixture was stirred at 30° C. for 3 hours. The product was subsequently washed free of salts by treatment with 80% strength isopropanol and dewatered by treatment with 100% strength acetone and filtered off with suction on a glass frit. The filter cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the air of the room, milled and sieved to less than 1000 μm. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.55; MS.sub.HPO=0.007; visc 1.0%=4 430 mPa.Math.s (sp. 4); visc 1.9%=33 050 mPa.Math.s (sp. 6); pH 1.0%=5.8; CR=0.4%; IDT=37 min; FDT=74 min.

COMPARATIVE EXAMPLE 2

(43) 83.5 g (0.50 mol) of milled pulp (DMC=97.1%; LVN=1 569 ml/g) were admixed with 584.3 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 157.1 g of 16.5% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 15 minutes. After addition of 110.1 g (2.50 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 40° C. over a period of 30 minutes, stirred at 40° C. for 60 minutes and heated to 85° C. over a period of 60 minutes. 2.6 g (0.035 mol) of 2,3-epoxypropanol dissolved in 20 g of 100% strength isopropanol were added and the mixture was stirred at 85° C. for 60 minutes. After cooling to 30° C., the mixture was neutralized with 59.6 g of 37.0% strength hydrochloric acid (0.605 mol) and 2.7 g of acetic acid (0.046 mol). The product was washed free of salts by multiple treatments with 80% strength isopropanol dewatered by treatment with 100% strength acetone and filtered off by suction on a glass frit. The filter cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the air of the room, milled and sieved to less than 1 000 μm. The pulverulent DHPHEC obtained displayed no dissolution delay and formed lumps on stirring into water; although the solution immediately became viscous, the lumps went completely into solution only after some days. The following product data were determined: MS.sub.EO=2.68; MS.sub.HPO=0.030; visc 1.0%=4 370 mPa.Math.s (sp. 4); visc 1.9%=29 000 mPa.Math.s (sp. 6); pH 1.0%=7.0; CR=0.6%; IDT and FDT not determined since the product could not be stirred in without lumps.

EXAMPLE 10

(44) The experiment was carried out in a manner analogous to Example 9, but only 0.86 g (0.004 mol) of sodium metaperiodate instead of 2.57 g (0.012 mol) were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.61; MS.sub.HPO=0.019; visc 1.0%=4 580 mPa.Math.s (sp. 4); visc 1.9%=30 950 mPa.Math.s (sp. 6); pH 1.0%=5.9; CR=0.1%; IDT=9 min; FDT=27 min.

EXAMPLE 11

(45) The experiment was carried out in a manner analogous to Example 9, but 5.6 g (0.75 mol) instead of 2.6 g (0.035 mol) of 2,3-epoxypropanol and 0.86 g (0.004 mol) instead of 2.57 g (0.012 mol) of sodium metaperiodate were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.63; MS.sub.HPO=0.052; visc 1.0%=4 710 mPa.Math.s (sp. 4): visc 1.9%=30 500 mPa.Math.s (sp. 6); pH 1.0%=5.8; CR=0.1%; IDT=16 min; FDT=43 min.

EXAMPLE 12

(46) The experiment was carried out in a manner analogous to Example 9, but 1.9 g (0.025 mol) instead of 2.6 g (0.035 mol) of 2,3-epoxypropanol and 0.86 g (0.004 mol) instead of 2.57 g (0.012 mol) of sodium metaperiodate were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.57; MS.sub.HPO=0.011; visc 1.0%=4 720 mPa.Math.s (sp. 4); visc 1.9%=30 900 mPa.Math.s (sp. 6); pH 1.0%=5.8; CR=0.1%; IDT=19 min; FDT=42 min.

EXAMPLE 13

(47) 83.5 g (0.50 mol) of milled pulp (DMC=97.1%; LVN=1 569 ml/g) were admixed with 584.3 g of 100% strength isopropanol and suspended with stirring in a 2 l pressure reactor. The suspension was freed of oxygen by means of a plurality of vacuum/nitrogen cycles (evacuation to 0.1 bar three times with introduction of nitrogen to 2.1 bar in between). 157.1 g of 16.5% strength sodium hydroxide solution (0.65 mol) were then introduced via a dropping funnel which had also been made inert, the suspension was once again freed of oxygen in a manner analogous to before and stirred at 25° C. for 15 minutes. After addition of 99.1 g (2.25 mol) of ethylene oxide via a dead-space-free connected pressurized gas bottle, the suspension was heated to 40° C. over a period of 30 minutes, stirred at 40° C. for 60 minutes and heated to 85° C. over a period of 60 minutes. 2.6 g (0.035 mol) of 2,3-epoxypropanol dissolved in 20 g of 100% strength isopropanol were added and the mixture was stirred at 85° C. for 60 minutes. After cooling to 30° C., the mixture was neutralized with 59.6 g of 37.0% strength hydrochloric acid (0.605 mol) and 2.7 g of acetic acid (0.046 mol) and a pH of 5.0 was set by addition of acetic acid. A solution of 2.14 g (0.010 mol) of sodium metaperiodate in 50 g of water was subsequently added and the mixture was stirred at 40° C. for 3 hours. The product was then washed free of salts by multiple treatments with 80% strength isopropanol and dewatered by treatment with 100% strength acetone and filtered off with suction on a glass frit. The filler cake was broken up, dried overnight at 70° C., moisture-conditioned relative to the air of the room, milled and sieved to less than 1000 μm. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.41: MS.sub.HPO=0.027; visc 1.0%=4 800 mPa.Math.s (sp. 4); visc 1.9%=30 750 mPa.Math.s (sp. 6); pH 1.0%=6.5; CR=0.6%; IDT=9 min; FDT=18 min.

EXAMPLE 14

(48) The experiment was carried out in a manner analogous to Example 13, but only 1.07 g (0.005 mol) of sodium metaperiodate instead of 2.14 g (0.010 mol) were added. The pulverulent, modified DHPHEC obtained could be stirred into water without formation of lumps, giving firstly a fluid turbid dispersion which went completely homogeneously into solution with an increase in viscosity only after a significant dissolution delay until finally a transparent, virtually colorless, viscous solution was obtained. The dissolution behavior corresponded to that of glyoxal-crosslinked cellulose ethers, but without glyoxal being liberated (negative test for glyoxal). The dissolution delay could be spontaneously ended by addition of alkali, as in the case of glyoxal-crosslinked cellulose ethers. The following product data were determined: MS.sub.EO=2.25; MS.sub.HPO=0.027; visc 1.0%=5 090 mPa.Math.s (sp. 4); visc 1.9%=32 950 mPa.Math.s (sp. 6); pH 1.0%=6.4; CR=0.2%; IDT=5 min; FDT=12 min.

(49) TABLE-US-00001 TABLE 1 Product data for DHPHEC after-treated with sodium metaperiodate (tert.-butanol process). MR EO MR HPO MS.sub.HPO MR PI Periodate Visc 1.0% Visc 1.9% CR IDT/FDT LVN [ml/g] [mol/mol] MS.sub.EO [mol/mol] (after PI) [mol/mol] oxidation [mPa s] [mPa .Math. s] pH [%] [min] Example 1 1 315 3.00 2.18 0.50 0.347 0.008 3 h/50° C. 2 495 20 300 5.6 0.1 27/70 Example 2 1 315 3.00 2.19 0.50 0.380 0.004 3 h/50° C. 2 970 22 100 5.9 0.3 13/42 Example 3 1 315 3.00 2.23 0.50 0.378 0.001 3 h/50° C. 2 770 19 200 5.8 0.6  7/33 Example 4 1 315 3.00 2.16 0.05 0.031 0.004 3 h/50° C. 1 875 16 060 6.7 0.7  9/29 Example 5 1 315 3.00 2.27 0.01 0.004 0.004 3 h/50° C. 1 185 11 500 6.5 0.6  8/21 Example 6 1 315 3.60 2.64 0.05 0.024 0.012 3 h/50° C. 1 500 16 200 6.0 0.6 13/51 Example 7 1 315 3.60 2.64 0.05 0.027 0.012 3 h/40° C. 2 745 22 100 5.6 0.3 15/58 Example 8 1 315 3.00 2.22 0.05 0.036 0.012 3 h/50° C. 3 510 26 950 6.3 0.7  6/36 Comparative 1 315 3.00 2.22 0.50 0.368 — — 2 730 19 550 6.8 0.1 n.m. example 1 (formed lumps)

(50) TABLE-US-00002 TABLE 2 Product data for DHPHEC after-treated with sodium metaperiodate (isopropanol process). MR EO MR HPO MS.sub.HPO MR PI Periodate Visc 1.0% Visc 1.9% CR IDT/FDT LVN [ml/g] [mol/mol] MS.sub.EO [mol/mol] (after PI) [mol/mol] oxidation [mPa .Math. s] [mPa .Math. s] pH [%] [min] Example 9 1 569 5.00 2.55 0.07 0.007 0.024 3 h/30° C. 4 430 33 050 5.8 0.4 37/74 Example 10 1 569 5.00 2.61 0.07 0.019 0.008 3 h/30° C. 4 580 30 950 5.9 0.1  9/27 Example 11 1 569 5.00 2.63 0.15 0.052 0.008 3 h/30° C. 4 710 30 500 5.8 0.1 16/43 Example 12 1 569 5.00 2.57 0.05 0.011 0.008 3 h/30° C. 4 720 30 900 5.8 0.0 19/42 Example 13 1 569 4.50 2.41 0.07 0.027 0.020 3 h/40° C. 4 800 30 750 6.5 0.6  9/18 Example 14 1 569 4.50 2.41 0.07 0.027 0.010 3 h/40° C. 5 090 32 950 6.4 0.2  5/12 Comparative 1 569 5.00 2.68 0.07 0.030 — — 4 370 29 000 7.0 0.6 n.m. example 2 (formed lumps)