Treatment of wood chips with an alkali metal borohydride solution followed by mechanical defibration

• US 3,981,765 A
• Filed: 12/17/1974
• Issued: 09/21/1976
• Est. Priority Date: 07/30/1969
• Status: Expired due to Term

• Current Assignee: Vita Mayer & C
• Original Assignee: Vita Mayer & C
• Inventors: Ruffini, Guglielmo, Gandini, Giovanni, Kruger, Emilio, Ghislandi, Franco
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Corbin, Arthur L.
• Application Number:
  US05/533,638
• Time in Patent Office: 644 Days
• Field of Search: 162/19, 162/25, 162/26, 162/28, 162/71, 162/80, 162/85, 162/86, 162/89, 162/84, 162/83, 162/82, 162/88, 162/87, 162/90
• US Class Current: 162/80
• CPC Class Codes: D21C 3/02 with inorganic bases or alkaline reacting compounds, e.g. sulfate processes

Abstract

A chemi-mechanical process for producing unbleached pulp with improved yields at high brightness including impregnating a lignocellulosic material in the form of wood chips with an alkaline solution containing an alkali metal borohydride in an amount over 0.1% by weight at a pH greater than 13, heating the impregnated chips at a temperature less than 150° C to provide semi-cooked chips having a brightness in excess of 60 GE, and then defiberizing the semi-cooked chips to mechanically separate the fibers into an unbleached pulp having said brightness and a yield of at least 85%.

Claims

1. A chemi-mechanical process for making an unbleached pulp with yield of at least 85% and brightness in excess of 60 G.E. with good color stability and high strength characteristics for papermaking purposes, the steps comprising in sequence:

a. providing a lignocellulosic material in the form of wood chips having a thickness in the range between 1/16 and 1/8 inch, and a dryness between 50 to 90%,

b. impregnating the chips at a temperature from room temperature to 50°

C with an alkaline solution comprised of an aqueous solution of sodium hydroxide and an alkali metal borohydride in an amount from 0.1 to 2.0% by weight of the chips and with a ratio of solution to chips of 2;

1 to 20;

1, said alkaline solution having an alkalinity, based on the Na2₂ O content of the alkaline material, from 3.5% to not in excess of 16%, by weight, and having a pH in excess of 13,

c. heating the alkaline borohydride-impregenated chips at a temperature not greater than 150°

C for at time between 15 minutes to 30 minutes to provide semi-cooked chips,

d. separating said semi-cooked chips from the solution, and

e. defiberizing the separated semi-cooked chips to mechanically separate the fibers of the chips into an unbleached pulp having said brightness, yield, and strength characteristics.

2. A process according to claim 1 , wherein

the impregnation is carried out for a time of at least 10 minutes at room temperature.

3. A process according to claim 1, wherein

the chips are impregnated with an aqueous acid solution prior to said impregnating to give a brightness of at least 80% GE.

4. A process according to claim 3, wherein

said aqueous acid solution comprises a solution selected from the group consisting of an aqueous solution of sulfur dioxide and an aqueous solution of sodium bisulphite.

5. A process according to claim 3, wherein the acid solution has a pH from 2 to 5.