Translucent paper products

Abstract

A translucent paper comprising a base paper layer, and optionally a coating layer adjacent to the base paper layer, wherein the base paper layer comprises a mixture of wood pulp fiber and microfibrillated cellulose, characterized in that the pulp fiber has a degree of Schopper-Riegler (SR) of more than or equal to 50 SR and that the microfibrillated cellulose is comprised in the mixture of pulp fiber and microfibrillated cellulose in an amount of 10 weight percent to about 50 weight percent, based on the weight of the mixture of pulp fiber and microfibrillated cellulose and wherein the mixture of pulp fiber and microfibrillated cellulose has a degree of Schopper-Riegler (SR) of between 65 SR and 95 SR, preferably of between 70 SR and 90 SR, as measured under ISO 5267-1.

1 . A translucent paper comprising:
 a base paper layer, wherein the base paper layer comprises a mixture of wood pulp fiber and microfibrillated cellulose,   wherein the wood pulp fiber has a degree of Schopper-Riegler (SR) of more than or equal to 50 SR,   the microfibrillated cellulose is comprised in the mixture of pulp fiber and microfibrillated cellulose in an amount of 10 weight percent to about 50 weight percent, based on the weight of the mixture of wood pulp fiber and microfibrillated cellulose,   the mixture of wood pulp fiber and microfibrillated cellulose has a degree of Schopper-Riegler (SR) of between 65 SR and 95 SR, measured according ISO 5267-1,   the translucent paper has a transmittance of 60% or more according to DIN 53147, and   the wood pulp fiber comprises a mixture of a hardwood pulp fiber and softwood pulp fiber, wherein the mixture of hardwood pulp fiber and softwood pulp fiber contains at least 50 weight percent of the hardwood pulp fiber and 50 weight percent or less of the softwood pulp fiber.   
     
     
         2 . The translucent paper according to  claim 1 , wherein the translucent paper has a transmittance of 65% or more, according to DIN 53147. 
     
     
         3 . The translucent paper according to  claim 1 , wherein the microfibrillated cellulose is comprised in the mixture of pulp fiber and microfibrillated cellulose in an amount of 10 weight percent to about 30 weight percent. 
     
     
         4 . The translucent paper according to  claim 1 , wherein the mixture of hardwood pulp fiber and softwood pulp fiber contains 75 weight percent or more of the hardwood pulp fiber, and/or 25 weight percent or less of the softwood pulp fiber. 
     
     
         5 . The translucent paper according to  claim 1 , wherein the average fiber length of pulp fibers is between 900 to 1400 micrometers, according to ISO 16065. 
     
     
         6 . The translucent paper according to  claim 1 , wherein the mixture of wood pulp and microfibrillated cellulose comprises at least 40 weight percent of fines. 
     
     
         7 . The translucent paper according to  claim 1 , wherein the base paper layer comprises a coating layer adjacent to the base paper layer, the coating layer comprising a polymeric coating. 
     
     
         8 . The translucent paper according to  claim 7 , wherein the base paper layer has a grammage between 25 and 100 gsm and/or wherein the coating layer is between 0.5 and 20 gsm. 
     
     
         9 . The translucent paper according to  claim 1 , wherein the pulp fiber has a degree of Schopper-Riegler (SR) of between 50 to 90 SR. 
     
     
         10 . The translucent paper according to  claim 1 , wherein the translucent paper has a density of more than 1.1 g cm−3, as measured according to ISO 534. 
     
     
         11 . The translucent paper according to  claim 1 , wherein the pulp fiber is chemical wood pulp fiber, such as kraft or sulphite wood pulp fiber. 
     
     
         12 . A packaging item comprising
 a packaging body; and   a window element in the body, the window being formed of a translucent paper that comprises   a base paper layer, wherein the base paper layer comprises a mixture of wood pulp fiber and microfibrillated cellulose, characterized in that   wherein the wood pulp fiber has a degree of Schopper-Riegler (SR) of more than or equal to 50 SR,   the microfibrillated cellulose is comprised in the mixture of pulp fiber and microfibrillated cellulose in an amount of 10 weight percent to about 50 weight percent, based on the weight of the mixture of wood pulp fiber and microfibrillated cellulose,   the mixture of wood pulp fiber and microfibrillated cellulose has a degree of Schopper-Riegler (SR) of between 65 SR and 95 SR, measured according ISO 5267-1,   the translucent paper has a transmittance of 60% or more according to DIN 53147, and   the wood pulp fiber comprises a mixture of a hardwood pulp fiber and softwood pulp fiber, wherein the mixture of hardwood pulp fiber and softwood pulp fiber contains at least 50 weight percent of the hardwood pulp fiber and 50 weight percent or less of the softwood pulp fiber.   
     
     
         13 . A process for making a translucent paper on a paper machine, where the translucent paper has a transmittance of 60% or more according to DIN 53147, said process comprising
 (a) in the wet end of the paper machine, forming a wet base paper layer from a furnish comprising a wood pulp fiber comprising a mixture of a hardwood pulp fiber and softwood pulp fiber and microfibrillated cellulose,   wherein the pulp fiber of the furnish has a degree of Schopper-Riegler (SR) of more than 50 SR,   the microfibrillated cellulose of the furnish is comprised in an amount of about 10 weight percent to about 50 weight percent, based on the weight of pulp fiber and microfibrillated cellulose in the mixture of pulp fiber and microfibrillated cellulose, and   the mixture of a hardwood pulp fiber and a softwood pulp fiber and microfibrillated cellulose of the furnish has a degree of Schopper-Riegler (SR) of between 65 SR and 95 SR, as measured under ISO 5267-1, and   the wood pulp fiber comprises a mixture of a hardwood pulp fiber and softwood pulp fiber, wherein the mixture of hardwood pulp fiber and softwood pulp fiber contains at least 50 weight percent of the hardwood pulp fiber and 50 weight percent or less of the softwood pulp fiber, and   (b) drying the wet base paper layer to form a dry base paper layer.   
     
     
         14 . The process for making a translucent paper on a paper machine according to  claim 13 , further comprising the rewetting the dry base paper layer to form a rewetted base paper layer, and keeping the rewetted base paper layer wet. 
     
     
         15 . The process for making a translucent paper on a paper machine according to  claim 14 , further comprising (super) calendaring the rewetted base paper layer. 
     
     
         16 . The process for making a translucent paper on a paper machine according to  claim 14 , further comprising redrying the rewetted base paper layer 
     
     
         17 . The translucent paper according to  claim 5 , wherein the average fiber length of pulp fibers is between 900 and 1100 micrometers. 
     
     
         18 . The translucent paper according to  claim 9 , wherein the pulp fiber has a degree of Schopper-Riegler (SR) of 73 to 83 SR. 
     
     
         19 . The translucent paper according to  claim 1 , wherein the mixture of wood pulp fiber and microfibrillated cellulose has a degree of Schopper-Riegler (SR) of 70 to 90 SR. 
     
     
         20 . The translucent paper according to  claim 7 , wherein the polymeric coating comprises a polymer or copolymer of vinyl alcohol