Method of deinking

Abstract

A method of deinking printed paper comprises pulping the paper to form an aqueous slurry, adding a deinking additive to the paper, and removing detached ink by flotation, wherein the additive comprises an organo-modified siloxane comprising units of the formula: [R 1 a Z b SiO (4-a-b)/2 ] n in which each R 1 is independently selected from a hydrogen atom, an alkyl, aryl, alkenyl, aralkyl, alkaryl, alkoxy, alkanoyloxy, hydroxyl, ester or ether group; each Z is independently selected from an alkyl group substituted with an amine, amide, carboxyl, ester, or epoxy group, or a group —R 2 —(OC P H 2P ) q (OC r H 2r ) s —R 3 ; n is an integer greater than 1; a and b are independently 0, 1, 2 or 3; R 2 is an alkylene group or a direct bond; R 3 is a group as defined for R 1 or Z above; p and r are independently an integer from 1 to 6; q and s are independently 0 or an integer such that 1≦q+s≧400; and wherein each molecule of the organo-modified siloxane contains at least one group Z.

1 . A method of deinking printed paper, the method comprising pulping the paper to form an aqueous slurry, adding a deinking additive to the paper, and removing detached ink by flotation, wherein the additive comprises an organo-modified siloxane comprising units of the formula:  
       [R 1   a Z b SiO (4-a-b)/2 ] n    in which each R 1  is independently selected from the group consisting of a hydrogen atom, an alkyl, aryl, alkenyl, aralkyl, alkaryl, alkoxy, alkanoyloxy, hydroxyl, ester and ether group;    each Z is independently selected from the group consisting of (i) an alkyl group substituted with a substituent selected from the group consisting of an amine, amide, carboxyl, ester, or epoxy group, and (ii) a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 ;    n is an integer greater than 1;    a and b are independently selected from the group consisting of 0, 1, 2 and 3;    R 2  is selected from the group consisting of an alkylene group and a direct bond;    R 3  is selected from the group consisting of R 1  and Z as defined above;    p and r are each independently an integer from 1 to 6;    q and s are independently selected from the group consisting of 0 and an integer such that 1 ≦q+s≧ 400;    and wherein each molecule of the organo-modified siloxane contains at least one group Z.    
   
   
       2 . A method according to  claim 1  wherein Z is a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 2 .  
   
   
       3 . A method according to  claim 2  wherein p is an integer from 2 to 4 inclusive.  
   
   
       4 . A method according to  claim 2  wherein q and s are each independently integers from 10 to 30.  
   
   
       5 . A method according to  claim 4  wherein q and s are each independently integers from 15 to 25.  
   
   
       6 . A method according to  claim 2  wherein p is 2, r is 3, and q and s are both 18.  
   
   
       7 . A method according to  claim 1  wherein R 2  is selected from the group consisting of a methylene, ethylene, propylene, butylene, pentylene and hexylene group.  
   
   
       8 . A method according to  claim 1  wherein R 3  is selected from the group consisting of a hydrogen atom and a hydroxyl group.  
   
   
       9 . A method according to  claim 1  wherein the siloxane is linear.  
   
   
       10 . A method according to  claim 1  wherein the siloxane contains branching.  
   
   
       11 . A method according to  claim 1  wherein Z is a group —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 , and R 3  is selected from the group consisting of a hydroxyl and an alkanoyloxy group.  
   
   
       12 . A method according to  claim 1  wherein 2 to 20 mole percent of silicon atoms in the siloxane molecule are substituted by a group Z.  
   
   
       13 . A method according to  claim 12  wherein 5 to 16 mole percent of silicon atoms in the siloxane molecule are substituted by a group Z.  
   
   
       14 . A method according to  claim 1  wherein the siloxane has a hydrophilic/lipophilic balance (HLB) in the range of about 5.0 to about 7.3.  
   
   
       15 . A method according to  claim 1  wherein the siloxane has a molecular weight in the range of about 1,000 to about 500,000.  
   
   
       16 . A method according to  claim 15  wherein the siloxane has a molecular weight in the range of about 10,000 to about 100,000.  
   
   
       17 . A method according to  claim 1  wherein the siloxane is a hydroxy-endcapped linear polydimethylsiloxane having an HLB of about 5.9 to about 6.3, in which 10 to 12 mole percent of silicon atoms are substituted by Z groups of the formula  
     —R 2 —(OC p H 2p ) q (OC r H 2r ) s —R 3 , in which p is 2, r is 3 and q and s are both 18, R 2  is selected from the group consisting of an alkylene group having from 1 to 6 carbon atoms and a direct bond, and R 3  is selected from the group consisting a hydrogen atom, a hydroxyl, ester and ether group.  
   
   
       18 . A method according to  claim 1  wherein the additive further comprises one or more components selected from the group consisting of a polydimethylsiloxane, an organic polyether, and a fatty acid.  
   
   
       19 . A method according to  claim 18  wherein the additive further comprises an organic polyether of the formula  
     R 4 —(OC p H 2p ) q (OC r H 2r ) s —R 5  in which R 4  and R 5  are selected from the group consisting of a hydrogen atom, hydroxyl, alkyl and alkoxy groups, p and r are independently an integer from 1 to 6, and q and s are independently selected from the group consisting of 0 and an integer such that 1≦q+s≧400.  
   
   
       20 . A method according to  claim 18  wherein the additive further comprises a fatty acid selected from the group consisting of a saturated and unsaturated monobasic aliphatic carboxylic acid.  
   
   
       21 . A method according to  claim 20  wherein the carboxylic acid is selected from the group consisting of lauric, myristic, palmitic, stearic, arachidic, behenic, lignoceric, palmitolic, oleic, linoleic, linolenic, and arachidonic acids.  
   
   
       22 . A method according to  claim 1  wherein the additive is an emulsion.  
   
   
       23 . A method according to  claim 22  wherein the additive is a gum based self-emulsifying siloxane.  
   
   
       24 . A method according to  claim 1  wherein the additive is added to the paper in an amount within the range 0.1 to 1 wt % of the paper.  
   
   
       25 . A method according to  claim 24  wherein the additive is added to the paper in an amount within the range 0.1 to 0.5 wt % of the paper.  
   
   
       26 . A method according to  claim 1  which is performed at substantially neutral pH.  
   
   
       27 . A method according to  claim 1  wherein the additive is added to the paper at a stage selected from the group consisting of before, during and after pulping.  
   
   
       28 . A method according to  claim 2  wherein r is an integer from 2 to 4 inclusive.  
   
   
       29 . A method according to  claim 2  wherein both p and r are each independently an integer from 2 to 4 inclusive.