Sizing of paper

Abstract

The present invention relates to a process for the production of paper which comprises: (a) providing an aqueous cellulosic suspension; (b) separately adding to the suspension: (i) a nitrogen-containing organic compound having a molecular weight less than 1,000; and (ii) a cellulose-reactive sizing agent; and (c) dewatering the obtained suspension to form paper. The invention further relates to a process in which a nitrogen-containing organic compound having a molecular weight less than 1,000 is mixed with an aqueous dispersion of a cellulose-reactive sizing agent to form a pre-mix and which premix is added to the suspension.

1 . Process for the production of paper which comprises:
 (a) providing an aqueous cellulosic suspension;   (b) separately adding to the suspension:
 (i) a nitrogen-containing organic compound having a molecular weight less than 1,000; and 
 (ii) a cellulose-reactive sizing agent; and 
   (c) dewatering the obtained suspension to form paper.   
   
   
       2 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is a quaternary ammonium compound. 
   
   
       4 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is added to the cellulosic suspension prior to adding the cellulose-reactive sizing agent. 
   
   
       5 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is added to the cellulosic suspension simultaneously with the cellulose-reactive sizing agent. 
   
   
       6 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is added to the cellulosic suspension after the cellulose-reactive sizing agent. 
   
   
       7 . Process according to  claim 1 , wherein the nitrogen-containing organic compound comprises any one of methyl bis[ethyl (tallowate)]-2-hydroxyethyl ammonium methyl sulphate, di(hydrogenated tallow)dimethylammonium chloride, di(hydrogenated tallow fatty acids-2-hydroxyethyl ester) dimethyl ammonium chloride, didecyldimethylammonium chloride, (vegetableoil)benzyl-dimethylammonium chloride, (dodecyl)benzyl-dimethylammonium chloride or quaternary imidazolinium compound. 
   
   
       8 . Process according to  claim 1 , wherein the cellulose-reactive sizing agent is a ketene dimer. 
   
   
       9 . Process according to  claim 1 , wherein the sizing agent is added as an aqueous dispersion. 
   
   
       10 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is added in an amount of greater than 20% by weight based on the weight of the cellulose-reactive sizing agent. 
   
   
       11 . Process according to  claim 1 , wherein the nitrogen-containing organic compound is added in an amount of 0.005 to 0.5% by weight, based on the dry weight of the aqueous cellulosic suspension. 
   
   
       12 . Process according to  claim 1 , wherein the sizing agent is added in an amount of 0.01 to 1.0% by weight, based on the dry weight of the aqueous cellulosic suspension. 
   
   
       13 . Process for the production of paper which comprises:
 (a) providing an aqueous cellulosic suspension;   (b) separately adding to the suspension:
 (i) a nitrogen-containing organic compound which is a quaternary ammonium compound having a molecular weight less than 1,000; and 
 (ii) an aqueous dispersion of a cellulose-reactive sizing agent which is a ketene dimer; and 
   (c) dewatering the obtained suspension to form paper.   
   
   
       14 . Process according to  claim 13 , wherein the nitrogen-containing organic compound comprises any one of methyl bis[ethyl (tallowate)]-2-hydroxyethyl ammonium methyl sulphate, di(hydrogenated tallow)dimethylammonium chloride, di(hydrogenated tallow fatty acids-2-hydroxyethyl ester) dimethyl ammonium chloride, didecyldimethylammonium chloride, (vegetableoil)benzyl-dimethylammoniumchloride, or (dodecyl)benzyl-dimethylammonium chloride. 
   
   
       15 . Process according to  claim 13 , wherein the nitrogen-containing organic compound comprises quaternary imidazolinium. 
   
   
       16 . Process for the production of paper which comprises:
 (a) providing a cellulosic suspension;   (b) mixing a nitrogen-containing organic compound having a molecular weight less than 1,000 with an aqueous dispersion of a cellulose-reactive sizing agent to form a pre-mix, wherein the mixing is carried out by bringing an aqueous stream of the nitrogen-containing organic compound into a contact with an aqueous stream of the sizing agent and introducing the resulting stream into the cellulosic suspension;   (c) adding the pre-mix to the suspension; and   (d) dewatering the obtained suspension to form paper.   
   
   
       17 . Process according to  claim 16 , wherein a contact time of the nitrogen-containing organic compound and the aqueous dispersion of the sizing agent in the pre-mixture is less than 20 minutes before the addition. 
   
   
       18 . Process according to  claim 16 , wherein the nitrogen-containing organic compound comprises any one of methyl bis(ethyl (tallowate)]-2-hydroxyethyl ammonium methyl sulphate, di(hydrogenated tallow)dimethylammonium chloride, di(hydrogenated tallow fatty acids-2-hydroxyethyl ester) dimethyl ammonium chloride, didecyldimethylammonium chloride, (vegetableoil)benzyl-dimethylammoniumchloride, (dodecyl)benzyl-dimethylammonium chloride or quaternary imidazolinium compound. 
   
   
       19 . Process according to  claim 16 , wherein the cellulose-reactive sizing agent is a ketene dimer. 
   
   
       20 . Process according to  claim 16 , wherein the nitrogen-containing organic compound is added in an amount of greater than 20% by weight, based on the weight of the cellulose-reactive sizing agent.