Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/20—Post-etherification treatments of chemical or physical type, e.g. mixed etherification in two steps, including purification
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/02—Alkyl or cycloalkyl ethers
  • C08B11/04—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals
  • C08B11/08—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals with hydroxylated hydrocarbon radicals; Esters, ethers, or acetals thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B11/00—Preparation of cellulose ethers
  • C08B11/193—Mixed ethers, i.e. ethers with two or more different etherifying groups

Definitions

• cellulose ethers strongly depend on the viscosity of their solutions. While mainly medium viscosity cellulose ethers, i.e. those with a medium molecular weight are processed, but high and low viscosity cellulose ethers have also become important.
• Low-viscosity cellulose ethers which also have a low molecular weight compared to medium- and high-viscosity cellulose ethers, can basically be produced in two different ways. Either one starts from a low molecular weight alkahcellulose and etherifies it, or one degrades a finished cellulose ether up to the desired molecular weight.
• the degradation of high molecular weight cellulose ethers to low molecular weight, low viscosity cellulose ethers mentioned as the second possible method can be caused by the action of oxidizing agents, e.g. Hypochlorite or hydrogen peroxide.
• oxidizing agents e.g. Hypochlorite or hydrogen peroxide.
• the oxidative degradation of higher-viscosity cellulose ethers can be carried out after the cleaning process. Losing losses and difficulties during washing are thus avoided.
• DE 1 543 116 from Kalle AG claims a process for producing low-viscosity cellulose ethers by oxidative degradation of higher-viscosity cellulose ethers with hydrogen peroxide.
• This process is characterized in that a higher-viscosity cellulose ether is mixed with an aqueous solution of hydrogen peroxide, the water content of the mixture not exceeding 75% by weight, based on the total amount.
• the mixture is then dried at temperatures from 100 ° C. to 250 ° C. until the hydrogen peroxide is consumed. The loss of moisture and hydrogen peroxide run almost parallel to the decrease in viscosity.
• the object was to provide a process which allows the viscosity to be adjusted directly after washing the cellulose ether in such a way that the subsequent drying, shaping (grinding, granulation) and mixing are not influenced, and that the degradation reaction is not affected by the subsequent process steps of drying , Shaping (grinding, granulation) and mixing is influenced.
• the mixture is then kept in motion at temperatures of 65-125 ° C., preferably 75-100 ° C. until the hydrogen peroxide is consumed and then dried.
• a low-viscosity, water-soluble cellulose ether is obtained by these processes.
• the subsequent process steps for the production of the ready-to-sell cellulose ether such as drying, shaping (grinding, granulation) and mixing, are not influenced by the degradation reaction.
• the degree of moisture and grinding can be set independently of the reduction in viscosity.
• Low-viscosity cellulose ethers are to be understood here as cellulose ethers whose 2% strength aqueous solutions at 20 ° C. and a shear rate of 2.55 s _ 1 have viscosities of 2 to 400, in particular 2 to 100 mPa * s (Haake Rotovisko).
• a higher-viscosity cellulose ether is to be understood here to mean a cellulose ether whose 2% aqueous solutions at 20 ° C.
• a shear rate of 2.55 s -1 have a viscosity of 100 to 100,000, preferably 400 to 20,000 mPa * s the viscosity reduction in the end product caused by the process according to the invention compared to the starting material is preferably at least 50%, in particular at least 70% and very particularly preferably at least 98%.
• Ionic or nonionic cellulose ethers can be used as the starting material, such as preferably carboxymethyl cellulose, hydrophobically modified carboxymethyl cellulose, hydroxyethyl carboxymethyl cellulose, sulfoethyl cellulose, hydrophobically modified sulfoethyl cellulose, hydroxyethyl sulfoethyl cellulose, hydrophobically modified hydroxyethylsulfoethyl cellulose, hydroxyethyl cellulose, methyl methyl cellulose, methyl methyl cellulose, hydrophobethyl cellulose, - se, methyl hydroxypropyl cellulose, hydroxypropyl cellulose and mixtures or
• Methylhydroxy- are particularly preferred as starting material.
• Water-moist filter cakes of these cellulose ethers, as are present after washing and separation, are advantageously used.
• the process can be conveniently integrated into the usual production flow of a manufacturing process
• Cellulose ether are inserted. After washing, the higher-viscosity starting material is spun off to a dry content of 25 to 80% by weight, based on the total weight.
• An aqueous solution of hydrogen peroxide is then mixed in intensively at temperatures of 65-125 ° C., if appropriate in stages, the mixing ratio being chosen so that the hydrogen peroxide content, based on the dry substance, is 0J-10% by weight , the dry content of the mixture does not fall below 25% by weight, based on the total amount.
• the mixture is then kept at temperatures of 65-125 ° C., preferably temperatures of 75-
• a higher molecular weight cellulose ether with a dry content of 35-80% by weight, particularly preferably 40-55% by weight, based on the total amount, is preferably used in the process.
• 0J to 10% by weight of hydrogen peroxide, based on the dry cellulose ether, are used to degrade the higher-viscosity cellulose ether; preference is given to 0J to 2.5% by weight, particularly preferably 0.5 to 1.8% by weight.
• Hydrogen peroxide, based on the dry cellulose ether work.
• the degradation reaction results in products whose 2% by weight aqueous solutions have acidic pH values of 3 to 5. It has proven to be useful here to adjust the pH of the products before, during or after the degradation reaction, but in any case before each further processing step such as drying or shaping. Particularly good results are achieved if the pH is adjusted after the degradation reaction.
• the pH is adjusted using aqueous solutions of salts which have a pH of 5 to 12 and which may contain all or part of the hydrogen peroxide required. These solutions are added to the reaction mixture in such quantities that the pH
• the value of the mixture after the addition is set to greater than 4.5, preferably to 6 to 7.
• Aqueous solutions of sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, disodium carbonate and sodium bicarbonate or aqueous solutions of mixtures of these salts are advantageously used.
• alkali salts of weak acids such as those of
• Citric acid or succinic acid can be used in the form of aqueous buffer solutions.
• An advantage of the claimed method is that the actual molecular weight reduction is completely decoupled from subsequent drying.
• any drying units with different residence time behavior of the cellulose ether particles to be dried can be used without having an influence on the degradation reaction.
• only one unit, the mixer in which the degradation reaction is carried out is affected by the corrosive properties of the hydrogen peroxide introduced.
• additives and modifiers after the degradation reaction, but before drying in the solvent-moist (eg water-moist) cellulose ether.
• the group of dialdehydes should be mentioned here in particular. These compounds are used for the production of solution-delayed cellulose ethers. Their use together with the hydrogen peroxide required for the degradation reaction is prohibited due to their oxidation possibility. It is also possible to mix in oligomeric or polymeric substances sensitive to oxidation (eg polysaccharides, polysaccharide ethers, polyvinyl alcohol, polyesters, polyamides) after the degradation reaction and before drying.
• the amount of hydrogen peroxide used, the initial viscosity and the final viscosity can be found in the table.
• the amounts given relate to the dry methylhydroxyethyl cellulose.
• Amounts of disodium hydrogen phosphate and disodium carbonate, as well as the pH values of 2% by weight solutions of the products and the hydrogen peroxide used quantity can be found in the table.
• the amounts given relate to the dry methylhydroxyethyl cellulose.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 1998
  • 1998-11-27 DE DE19854770A patent/DE19854770A1/de not_active Withdrawn
• 1999
  • 1999-11-15 CN CNB998137154A patent/CN1269841C/zh not_active Expired - Fee Related
  • 1999-11-15 CA CA002352186A patent/CA2352186C/en not_active Expired - Fee Related
  • 1999-11-15 HK HK02105446.7A patent/HK1044005B/zh not_active IP Right Cessation
  • 1999-11-15 EP EP99957311A patent/EP1153040B1/de not_active Revoked
  • 1999-11-15 BR BR9915690-3A patent/BR9915690A/pt not_active Application Discontinuation
  • 1999-11-15 AT AT99957311T patent/ATE297411T1/de not_active IP Right Cessation
  • 1999-11-15 UA UA2001064446A patent/UA73294C2/uk unknown
  • 1999-11-15 WO PCT/EP1999/008779 patent/WO2000032636A1/de not_active Ceased
  • 1999-11-15 DE DE59912164T patent/DE59912164D1/de not_active Revoked
  • 1999-11-15 ES ES99957311T patent/ES2242432T3/es not_active Expired - Lifetime
  • 1999-11-15 KR KR1020017006602A patent/KR20010080592A/ko not_active Ceased
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  • 1999-11-15 AU AU15061/00A patent/AU1506100A/en not_active Abandoned
  • 1999-11-15 US US09/856,545 patent/US6939961B1/en not_active Expired - Fee Related
  • 1999-11-15 PL PL99349790A patent/PL349790A1/xx not_active Application Discontinuation
  • 1999-11-15 JP JP2000585276A patent/JP2002531593A/ja active Pending
• 2001
  • 2001-05-25 NO NO20012577A patent/NO20012577L/no not_active Application Discontinuation

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