Process for making refiner mechanical pulp

A process for making an improved refiner mechanical pulp from wood chips, said improved refiner mechanical pulp being capable of being used in competitive quality newsprint without the addition of chemical pulp, having a lower debris and shive content, a lower bulk and a higher brightness, without the use of bleaching chemicals, than refiner mechanical pulp made by a conventional refiner mechanical pulping process, comprising:

• (a) comminuting said wood chips by splitting them along the wood grain to make smaller particles;
• (b) wetting the surfaces of said particles by dipping them into or spraying onto said surfaces a solution of a sulphite salt of an alkali metal to add an amount of said alkali metal salt within the range of 1% to 10% of the oven dry weight of said particles, said solution having a pH within the range of 7 to 12.5;
• then
• (c) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing particles, after draining any excess solution therefrom, to a temperature within the range between 80.degree. C. and 165.degree. C. and holding the particles for a time varying from 0.5 to 80 minutes, said particles not being immersed in liquid subsequent to said draining and prior to completion of steam heating and holding;
• and
• (d) passing the particles, after the period of steam heating, through a disc refiner to produce refiner mechanical pulp.

The process for making an improved refiner mechanical pulp from wood particles, said improved refiner mechanical pulp being capable of being used in competitive quality newsprint without the addition of chemical pulp, having a lower debris and shive content, a lower bulk and a higher brightness, without the use of bleaching chemicals, then refiner mechanical pulp made by a conventional refiner mechanical pulping process, comprising:

• (a) spraying a solution of a sulphite salt of an alkali metal onto the surfaces of said particles to wet them and to add said sulphite salt in an amount of about 1% to about 10% of the oven dry weight of said particles, said solution having a pH of about 7 to about 12.5;
• then
• (b) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing particles, after draining any excess solution therefrom, to a temperature range between about 80.degree. C. and about 165.degree. C. and holding the particles for a time varying from 0.5 to 80 minutes, said particles not being immersed in liquid subsequent to said draining and prior to completion of steam heating and holding;
• and
• (c) thereafter passing said particles through a disc refiner to produce refiner mechanical pulp.

A process for making an improved refiner mechanical pulp from wood chips, said improved refiner mechanical pulp being capable of being used in competitive quality newsprint without the addition of chemical pulp, having a lower debris and shive content, a lower bulk and a higher brightness, without the use of bleaching chemicals, than refiner mechanical pulp made by a conventional refiner mechanical pulping process, comprising:

• (a) comminuting the wood chips by splitting them along the wood grain thereof to make smaller particles;
• (b) spraying a solution of a sulphite salt of an alkali metal onto the surfaces of said particles to wet them and to add said sulphite salt in an amount of about 1% to about 10% of the oven dry weight of said particles, said solution having a pH of about 7 to 12.5;
• then
• (c) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing particles, after draining any excess solution therefrom, to a temperature ranging between about 80.degree. C. and about 165.degree. C. and holding the particles for a time varying from 0.5 to 80 minutes, said particles not being immersed in liquid subsequent to said draining and prior to completion of steam heating and holding;
• and
• (d) thereafter passing said particles through a disc refiner to produce refiner mechanical pulp.

A process for making an improved refiner mechanical pulp from wood chips, said improved refiner mechanical pulp being capable of being used in competitive quality newsprint without the addition of chemical pulp, having a lower debris and shive content, a lower bulk and a higher brightness, without the use of bleaching chemicals, than refiner mechanical pulp made by a conventional refiner mechanical pulping process, comprising:

• (a) comminuting the wood chips predominantly by splitting them along the wood grain thereof to make particles having dimensions in the cross grain direction of not over four millimeters;
• (b) wetting said particles by spraying them with a solution of a sulphite salt of an alkali metal to add said sulphite salt in an amount of about 1% to about 10% of the oven dry weight of said particles, said solution having a pH of about 7 to about 12.5;
• then
• (c) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing particles, after draining any excess solution therefrom, to a temperature ranging between about 85.degree. C. and about 100.degree. C. and holding the particles within that temperature range for about 30 minutes, said particles not being immersed in liquid subsequent to said draining and prior to completion of steam heating and holding;
• and
• (d) thereafter passing said particles through a disc refiner to produce refiner mechanical pulp.

A process for making an improved refiner mechanical pulp from sawdust or shavings, said improved refiner mechanical pulp having lower debris and shive contents, lower bulk and higher brightness, without the use of bleaching chemicals, than refiner mechanical pulps made from sawdust or shavings by a conventional refiner mechanical pulping process, comprising:

• (a) wetting said sawdust or shavings by spraying them with a solution of a sulphite salt of an alkali metal to add said sulphite salt in an amount of about 1% to about 10% of the oven dry weight of said sawdust or shavings, said solution having a pH of about 7 to about 12.5;
• then
• (b) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing sawdust or shavings, after draining any excess solution therefrom, to a temperature ranging between about 85.degree. C. and 100.degree. C. and holding the sawdust or shavings within that temperature range for about 2 to about 80 minutes, said particles not being immersed in liquid subsequent to said draining and prior to completion of steam heating an holding;
• and
• (c) thereafter passing said sawdust or shavings through a disc refiner to produce refiner mechanical pulp.

A process for making an improved refiner mechanical pulp from sawdust or shavings, said improved refiner mechanical pulp having lower debris and shive contents, lower bulk and higher brightness, without the use of bleaching chemicals, than refiner mechanical pulps made from sawdust or shavings by a conventional refiner mechanical pulping process, comprising:

• (a) wetting said sawdust or shavings by dipping the into or spraying onto them a solution of a sulphite salt of an alkali metal to add said sulphite salt in an amount of about 1% to about 10% of the oven dry weight of said sawdust or shavings, said solution having a pH of about 7 to 12.5;
• then
• (b) steam heating, by adding steam directly thereto, the sulphite salt solution-bearing sawdust or shavings, after draining any excess solution therefrom, to a temperature ranging between about 80.degree. C. and 165.degree. C. and holding the sawdust or shavings within that temperature range for about 0.5 to about 80 minutes, said sawdust or shavings not being immersed in liquid subsequent to said draining and prior to completion of steam heating and holding;
• and
• (c) thereafter passing said sawdust or shavings through a disc refiner to produce refiner mechanical pulp.