IL33277A - Method of producing paper making pulp in a high yield and with a high degree of brightness - Google Patents

Description

nivna Method of producing paper making pulp in a high yield and with a high degree of brightness VITA MAYER VITA The present invention relates to methods producing ulps in high yields and with high degree of for use in the paper making and related The increasing demand for and related products from lignocellulose requires a more utilization of wood and an ampler of the pulping process must be inexpensive and provide high yields of pulp having good mechanical properties and a high degree of It is known that it is possible to obtain high of pulp by treating wood particularly with an aqueous sodium hydroxide solution whose cooking action on the wood is more than other The wood swells rapidly when treated with caustic soda The structure of lignin limits the swelling of the whole Because the differential creates stresses within the much of the highly outer layers is shed by the fiber when the treated wood is fiberized in a disc The exposed surface provides a good The caustic soda solution saponifies the groups associated the the esters and lactone groups which probably bond the hemicelluloses to the and all this increases the swellin of the cell walls and facilitates the separatio of the fibers and the Work at a temperature above room temperature increases the rate of penetration of the alkaline solution into the speeds the abovermentioned reactions of the alkali the wood and produces a pulp with improved The alkaline treatment of the wood produces coloured their colours varying pale yellow to The brightening of these pulps is difficult and increases the capital and operating By another known described in the US Patent for producing Specification pulp having a high degree of the lignocellulosic raw material is impregnated with an bisulfite solution either at the same time or with sodium The borohydride has the function of increasing the brightness of the but does not make for improved mechanical properties of The ob of this invention is to provide a method for producing pulps in yields and with a high degree of brightness and having good mechanical and this in a simple manner and with relatively low capital and operating The invention consists in a process for preparation o pulp in a high yield and with a high degree of brightness and good mechanical soaking a lignocellulosic material with an aqueous alkaline solution having a pH of 9 or above and containing from about to about of alkali metal calculated on the dry weight of the lignocellulosic soaking effected at a temperature between room temperature and about lowering the pH of the soaked mass to within the range between about 9 and about 3 by means of an aqueous solution of sulfur dioxide an alkali metal cooking the mass at a temperature from about to about and mechanically refining the The aqueous alkaline solution may a solution of sodium possibly in admixture with sodium sulfite or a solution of sodium sulfite and sodium a buffered solution of The treatment with the alkaline solution should be for at least 15 The treatment of material with the acidic aqueous solution may be done immediately after the removal of the alkaline solution and material can be then The cooking may be for by steaming at a temperature within the range of from about to about or by heating the fibrous material i an aqueous sodium for about of sodium at a temperature from about to about By a modification of the process the treatment of the fibrous material with the acidic aqueous at a temperature from about to about may be effected before the material is treated with the alkaline By the process of the a yield of pulp is obtained and the pulp possesses a high degree of brightness and does not require further The use of sodium borohydrlde has a twofold it prevents colour formation and it increases the yield of the pulp by as much as 10 to This increase of the is presumably due to a reduction of the terminal aldehyde groups of the polysaccharides by the following 4 2 The invention is illustrated by the following Examples to which it is not u EXAMPLE 1 100 g of poplar veneer were heated with 500 ml of an aqueous solution of 20 of sodium hydroxide and 4 of sodium borohydride at for 30 Then the wood mass was separated from the liquor and in a laboratory disc The pulp was then neutralized with an aqueous solution of sulfur dioxide and The amounts of sodium hydroxide of sodium borohydride taken up from the solution and calculated on The yield of pulp was its brightness its freeness 600 p Handsheets of 60 of basis weight exhibited a breaking length of 6700 bursting factor of 28 and a tear facto of Handsheets of made from birch pulp prepared by the same process had a breaking length of 6000 a tear of 6o and a brightness of 78 EXAMPLE 2 100 g of poplar veneer waste were heated at over a period of 60 minutes with an aqueous solution of 10 of sodium 10 of sodium sulfite and o sodium The ratio was The process was then continued as described in Example p Handsheets of 60 basis weight had a breaking length of 5100 a burst factor of a tear of 32 and a brightness of 70 EXAMPLE 3 g of red spruce chips were heated at for 2 hours with an aqueous solution of 20 of sodium 20 of sodium sulfite and 4 of sodium The process was Handsheets of 60 basis weight exhibited a breaking length of 5000 a tear factor of 55 and a brightness of 68 100 g of poplar veneer chips were heated at for 1 hour with an solution of 20 of sodium hydroxide and 2 of sodium The process was then continued as described in The sodium borohydride up the solution was calculated on dry Handsheets made from this pulp exhibited a brightness 75 breaking length of 6700 a tear factor of 47 and a burst factor of EXAMPLE 5 100 of poplar chips were soaked for 2 hours at room temperature with 1000 ml of an aqueous solution of 20 of sodium hydroxide and of sodium of the liquor was then separated and the drained were steamed at for 30 then The fiberlzed pulp was acidified with an solution of sulfur The sodium borohydride consumed was calculated on dry The yield of pulp was Handsheets of 60 basis weight exhibited a brightness of 65 a breaking of a tear factor 35 a burst factor of 6 as The process was Example 5 but in the aqueous alkaline 20 of sodium hydroxide was replaced 5 of sodium with the same amount of sodium hydride as specified in Example and the treatment the dips alkaline solution was performed at The ield of ul Handsheets made from pulp at 450 ml exhibited a breaking length a burst factor of a factor of 40 and a brightness of 73 7 100 of poplar chips wore heated at for 90 minutes with a solution containing 10 sodium Wood and liquor separated and the treated chips were then cooked with an aqueous solution containing of sodium hydroxide and 2 of sodium borohydride at for 30 of 60 basis weight exhibited a breaking length of 8600 a burst actor of a tear factor of and a brightness of 78 8 100 g of tropical locally named were treated by the process described in 2 The yield of pulp was Handsheets of 60 basis weight exhibited a breaking length of 6600 burst of a tear factor of 33 and a brightness of 9 100 g of poplar chips were soaked at room temperature in an aqueous solution of 40 of sodium hydroxide and 2 of sodium of the alkaline solution was drained and 200 an aqueous solution containing 25 of sulfur dioxide was to the soaked The mixture was then heated at for 90 minutes and thereafter The yield of pulp was the sodium borohydride sumption was calculated on dry Handsheets made from this at 530 ml exhibited a brightness of 73 a breaking length of 8500 burst factor of 34 and a tear factor of The properties of the pulps prepared in accordance with the present invention were compared with pulps made by known and the data are compiled in Tables 1 and In each the first three lines of figures refer to pulp made b known the last four lines to pulps made in accordance with the TABLE 1 KIND PULP YIELD BREAKING LENGTH POPLAR 90 143 1700 OOD SPRUCE 165 3300 92 180 3000 EXAMPLE 1 94 600 6700 EXAMPLE 4 95 640 6700 EXAMPLE 6 92 450 8750 EXAMPLE 9 94 530 8500 TABLE 2 KIND OF PULP BURST TEAR BRIGHTNESS consumed wood POPLAR 6 22 70 SPRUCE 14 49 12 33 51 EXAMPLE 23 40 83 EXAMPLE 30 47 75 EXAMPLE 6 32 40 73 EXAMPLE 9 34 37 78 It is evident from the data shown in Tables 1 and 2 that the properties of the pulps made in accordance with the present invention are better than those by known The pulp thus produced can be used in a general manner as substitutes of or additions to groundwood and hardwood chemical pulps for the manufacture of printing and writing papers towelling and tissue cardboard or paper board for food containers and other bleached In mixture with small of synthetic fibers the pulp can be as substitute for bleached coniferous chemical insufficientOCRQuality

Claims (3)

-10 33277/2 OfrAIMS

1. A process for the preparation of pulp in a high yield and with a high degree of brightness and good mechanical strength, comprising. (a) soaking a lignocelluloslc material with an aqueous alkaline solution having a pH of 9 or above and containing from about 0.1 to about 2o of alkali metal borohydride, calculated on the dry weight of the lignocelluloslc material, the soaking being effected at a temperature between room temperature and about 100°C.} (b) lowering the pH of the soaked mass to within the range between about 9 and about 3 by means of an aqueous solution of sulfur dioxide and/or an alkali metal bisulfite; (c) cooking the mass at a temperature from about 110° to about 180°C} and (d) mechanioally refining the mass.

2. A process according to Claim 1, wherein the alkaline solution is separated from the soaked mass and the latter is heated at about 80°0 to about 100°C before being contacted with the acidic aqueous solution.

3. A modification of the process according to Claims 1 or 2, wherein the lignocelluloslc material is first treated with the acidic aqueous solution, then this solution is separated from the mass and the latter is cooked with the alkaline solution containing sodium borohydride. For the Applicants RC;ed