Method of treating cellulose fibers and products obtained thereby

Abstract

A method for reducing the level of or removing wood extractives from cellulose fibers and products having cellulose fibers, by the use of a supercritical or near supercritical fluid in order to increase the absorption rate of such cellulose fibers and products having cellulose fibers. Also disclosed are cellulose fibers and products having cellulose fibers, such as cellulose tissue paper, sanitary napkin or towel, nonwoven industrial wipes, baby diaper, incontinence garments, or pulp having improved qualities, such as improved absorption rate.

What is claimed is:  
     
         1 . A method for reducing the level of or substantially removing wood extractives from fibers, the method comprising the steps of: 
 contacting the fibers with a supercritical or near supercritical fluid to create an extract of the wood extractives; and    removing the extract from the fibers so as to obtain improved cellulose fibers with a reduced content of extractives.    
     
     
         2 . The method according to  claim 1 , wherein the supercritical or near supercritical fluid is selected from the group consisting of carbon dioxide, ethane, ethylene, propane, propylene, cyclohexane, isopropanol and chlorotrifluoromethane.  
     
     
         3 . The method according to  claim 1 , wherein the supercritical or near supercritical fluid is carbon dioxide.  
     
     
         4 . The method according to  claim 1 , wherein the contacting of the cellulose fibers with the supercritical or near supercritical fluid is made under conditions where the temperature is at least T C  for said supercritical or near supercritical fluid and the pressure is at least P C  for said supercritical or near supercritical fluid.  
     
     
         5 . The method according to  claim 1 , wherein the contacting of the cellulose fibers with the supercritical or near supercritical fluid is made under conditions where the temperature is at least T C  for said supercritical or near supercritical fluid.  
     
     
         6 . The method according to  claim 1 , wherein the contacting of the cellulose fibers with the supercritical or near supercritical fluid is made under conditions where the pressure is at least P C  for said supercritical or near supercritical fluid.  
     
     
         7 . The method according to  claim 4 , wherein the temperature is at least 1.5 times T C .  
     
     
         8 . The method according to  claim 4 , wherein the temperature is at least 2 times T C .  
     
     
         9 . The method according to  claim 4 , wherein the pressure is at least 2 times P C .  
     
     
         10 . The method according to  claim 4 , wherein the pressure is at least 3 times P C .  
     
     
         11 . The method according to  claim 4 , wherein the pressure is at least 4 times P C .  
     
     
         12 . The method according to  claim 4 , wherein the pressure is at least 5 times P C .  
     
     
         13 . The method according to  claim 4 , wherein the pressure is at least 6 times P C .  
     
     
         14 . The method according to  claim 1 , wherein the wood extractives in the extract are substantially hydrophobic substances.  
     
     
         15 . The method according to  claim 14 , wherein the wood extractives in the extract comprise hydrophobic substances selected from the group consisting of fatty acids, resin acids, sterylesters and triglycerides.  
     
     
         16 . The method according to  claim 1 , wherein the wood extractives in the extract comprise substances selected from the group consisting of lignin or sterols.  
     
     
         17 . The method according to  claim 1 , wherein the extracted wood extractives are collected in an organic solvent.  
     
     
         18 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.5.  
     
     
         19 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.55.  
     
     
         20 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.6.  
     
     
         21 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.65.  
     
     
         22 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.7.  
     
     
         23 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.75.  
     
     
         24 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.8.  
     
     
         25 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.85.  
     
     
         26 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.9.  
     
     
         27 . The method according to  claim 1 , wherein the ratio calculated between the total extract content and the extract content obtained by a standard method SCAN C 7:62 is at least about 0.95.  
     
     
         28 . Cellulose fibers obtainable by the method claimed in  claim 1 .  
     
     
         29 . Cellulose fibers having a reduced level of or being substantially free from wood extractives, which impart—due to ageing—decreased absorption rate to the cellulose fibers.  
     
     
         30 . A method of producing a fibrous web, said method comprising the step of using cellulose fibers according to  claim 28  for the production of the fibrous web.  
     
     
         31 . A method of producing a fibrous web, said method comprising the step of using cellulose fibers according to  claim 29  for the production of the fibrous web.  
     
     
         32 . A method of producing an absorbent product, said method comprising the step of using cellulose fibers according to  claim 28  for the production of the absorbent product.  
     
     
         33 . A method of producing an absorbent product, said method comprising the step of using cellulose fibers according to  claim 29  for the production of the absorbent product.  
     
     
         34 . An improved fibrous web comprising cellulose fibers according to  claim 28 .  
     
     
         35 . An improved fibrous web comprising cellulose fibers according to  claim 29 .  
     
     
         36 . The fibrous web according to  claim 34 , wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 5% higher liquid absorption rate than the parent cellulose fibers.  
     
     
         37 . The fibrous web according to  claim 34 , wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 12% higher liquid absorption rate than the parent cellulose fibers.  
     
     
         38 . The fibrous web according to  claim 34 , wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 20% higher liquid absorption rate than the parent cellulose fibers.  
     
     
         39 . The fibrous web according to  claim 34 , wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 30% higher liquid absorption rate than the parent cellulose fibers.  
     
     
         40 . The fibrous web according to  claim 34 , wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 50% higher liquid absorption rate than the parent cellulose fibers.  
     
     
         41 . A fibrous web comprising cellulose fibers, which have a reduced level of or is substantially free from wood extractives, which impart—due to ageing—decreased absorption rate to the cellulose fibers.  
     
     
         42 . A method of producing an absorbent product, said method comprising the step of using the fibrous web according to  claim 34  for the production of the absorbent product.  
     
     
         43 . A method for reducing the level of or substantially removing wood extractives from cellulose fibers, the method comprising the steps of: 
 contacting the cellulose fibers with a supercritical or near supercritical fluid to create an extract with the wood extractives; and    removing the extract from the cellulose fibers so as to obtain improved cellulose fibers with a reduced content of extractives;    wherein an improved fibrous web of said cellulose fibers is prepared and wherein the improved fibrous web at least after an initial period of time of at least about two days, has a 5% higher liquid absorption rate than the parent cellulose fibers.    
     
     
         44 . The method of  claim 43 , wherein the improved fibrous web has a 12% higher liquid absorption rate.  
     
     
         45 . The method of  claim 43 , wherein the improved fibrous web has a 20%higher liquid absorption rate.  
     
     
         46 . The method of  claim 43 , wherein the improved fibrous web has a 30% higher liquid absorption rate.  
     
     
         47 . The method of  claim 43 , wherein the improved fibrous web has a 50% higher liquid absorption rate.  
     
     
         48 . An absorbent product comprising cellulose fibers according to  claim 28 .  
     
     
         49 . An absorbent product comprising cellulose fibers, which have a reduced level of or is substantially free from wood extractives, which impart—due to ageing—decreased absorption rate of the absorbent product.  
     
     
         50 . Absorbent product according to  claim 48 , wherein the product is a cellulose tissue paper, sanitary napkin or towel, nonwoven industrial wipe, baby diaper, or incontinence garment.  
     
     
         51 . Absorbent product according to  claim 49 , wherein the product is a cellulose tissue paper, sanitary napkin or towel, nonwoven industrial wipe, baby diaper, or incontinence garment.  
     
     
         52 . Stratified absorbent product comprising cellulose fibers according to  claim 28 , comprising at least one outer layer and possibly at least one middle layer, the outer layers having a high amount of improved cellulose fibers.  
     
     
         53 . A fibrous web according to  claim 34 , comprising at least one outer layer and possibly at least one middle layer, the outer layers having a high amount of improved cellulose fibers.