US2007246177A1PendingUtilityA1

Activator for Pulp Bleaching

44
Individually held — no corporate assignee on recordPriority: Jun 14, 2004Filed: Jun 10, 2005Published: Oct 25, 2007
Est. expiryJun 14, 2024(expired)· nominal 20-yr term from priority
Inventors:Alan MarlandAlison MathewsGary D. Miller
D21C 9/166
44
PatentIndex Score
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Claims

Abstract

A process for the bleaching of cellulosic fibres comprising the steps of (a) providing a water supply; (b) adding hydrogen peroxide to the stabilised water supply to form a hydrogen peroxide solution; (c) adjusting the pH of the hydrogen peroxide solution by adding alkali; mixing the pH adjusted solution resulting from step (c) to allow complete formation of perhydroxyl ion; (e) adding a carboxylic acid anhydride compound to the solution resulting from step (d); (f) mixing the solution resulting from step (e) to allow complete formation of percarboxylic acid to give a dilute solution of percarboxylic acid; and (g) contacting the solution with a suspension of cellulosic fibres.

Claims

exact text as granted — not AI-modified
1 . A process for the bleaching of cellulosic fibres comprising the steps of: 
 (a) treating a fresh water supply with chelating agent to give a stabilised water supply;    (b) adding hydrogen peroxide to the stabilised water supply to form a hydrogen peroxide solution;    (c) adjusting the pH of the hydrogen peroxide solution by adding alkali;    (d) mixing the pH adjusted solution resulting from step (C) to allow complete formation of perhydroxyl ion;    (e) adding a carboxylic acid anhydride compound to the solution resulting from step (d);    (i) mixing the solution resulting from step (e) to allow complete formation of percarboxylic acid to give a dilute solution of percarboxylic acid; and    (g) contacting the solution of peracid with a suspension of cellulosic fibres.    
   
   
       2 . The process according to  claim 1  in which the fresh water supply is at a temperature in the range 15-30° C.  
   
   
       3 . The process according to  claim 1 , wherein the chelating agent is an aqueous phosphonic acid based.  
   
   
       4 . The process according to  claim 3 , wherein the phosphonic acid based chelating agent is Dequest SPE9505 and/or Dequest 2066.  
   
   
       5 . The process according to  claim 1 , wherein the amount of chelating agent added is in the range 0.1-0.4 wt %.  
   
   
       6 . The process according to  claim 1 , wherein the amount of chelating agent added is in the range from 0.125-0.3 wt %.  
   
   
       7 . The process according to  claim 1 , wherein the amount of chelating agent added is in the range 0.15-0.25 wt %  
   
   
       8 . A process according to  claim 1  wherein the amount of hydrogen peroxide added based on a 50% solution is in the range 0.5-6 wt %, more preferably in the range 1.5-4.0 wt % and most preferably in the range 1.75-2.5 wt %.  
   
   
       9 . The process according to  claim 1  wherein the alkali is sodium hydroxide.  
   
   
       10 . A process according to  claim 1  wherein the amount of alkali added is in the range 0.2-3 wt %, preferably in the range 0.4-1.5 wt % and more preferably in the range 0.5-1.0 wt %.  
   
   
       11 . A process according to  claim 1  wherein the pH is adjusted to a value in the range 10.5-11.5.  
   
   
       12 . A process according to  claim 1  in which the duration of the mixing step (d) is at least 1 minute.  
   
   
       13 . A process according to  claim 1  in which the amount of carboxylic acid anhydride compound added is in the range 0.02-0.6 mol %, preferably in the range 0.05-0.3 mol % and more preferably in the range 0.075-0.15 mol %.  
   
   
       14 . A process according to  claim 1  in which the duration of the mixing step (f) is up to 10 minutes.  
   
   
       15 . The process according to  claim 1  which further comprises an additional pH adjusting step prior to the solution being contacted with the fibrous cellulosic solution.  
   
   
       16 . The process according to  claim 1  wherein the carboxylic acid anhydride is selected from one or more of the group consisting of acetic anhydride, maleic anhydride, succinic anhydride, malonic anhydride, benzoic anhydride and propanoic anhydride.  
   
   
       17 . The process according to  claim 16 , wherein the carboxylic acid anhydride compound comprises acetic anhydride.  
   
   
       18 . The process of  claim 17 , wherein the carboxylic anhydride compound additionally comprises a further carboxylic acid anhydride with a higher flashpoint and the acetic anhydride has been premixed with the further carboxylic acid anhydride with a higher flashpoint to form an acetic anhydride/carboxylic acid anhydride mixture with a modified flash point of 55.1° C. or above.  
   
   
       19 . The process of  claim 18  wherein the ratio of acetic anhydride to maleic anhydride in the acetic anhydride/carboxylic acid anhydride mixture with a modified flashpoint is greater than 50:50.  
   
   
       20 . The process of  claim 18  wherein the ratio of acetic to maleic anhydride with a higher flashpoint in the acetic anhydride/carboxylic acid anhydride mixture with a modified flashpoint is 80:20.  
   
   
       21 . The process according to  claim 19 , wherein the carboxylic acid anhydride with a higher flashpoint is maleic anhydride.  
   
   
       22 . A method for increasing the flash point of acetic anhydride to at least 55.1° C. comprising forming a mixture of acetic anhydride and a further carboxylic acid anhydride with a higher flashpoint in order to form a acetic anhydride/carboxylic acid anhydride mixture with a modified flashpoint.  
   
   
       23 . The method of  claim 22 , wherein the acetic anhydride/carboxylic acid anhydride mixture with a modified flashpoint has a ratio of acetic anhydride to carboxylic acid anhydride with a higher flashpoint greater than 50:50.  
   
   
       24 . The method according to  claim 22 , wherein the acetic/carboxylic acid anhydride mixture with a modified flashpoint has a ratio of acetic anhydride to carboxylic acid anhydride with a higher flashpoint of 80:20.  
   
   
       25 . The method according to  claim 22 , wherein the carboxylic acid anhydride with a higher flashpoint is maleic anhydride.  
   
   
       26 . A composition comprising acetic anhydride and a further carboxylic acid anhydride with a higher flashpoint, which has a flashpoint of at least 55.1° C. and wherein the ratio of acetic anhydride to carboxylic acid anhydride with a higher flashpoint is greater than 50:50 but less than or equal to 80:20.  
   
   
       27 . The composition according to  claim 26  which consists of acetic anhydride and a further carboxylic acid anhydride only.

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