US2789902A

US2789902A - Refining of wood pulp

Info

Publication number: US2789902A
Application number: US405043A
Authority: US
Inventors: George W Seymour; Wayman Morris; Helge P Holkestad
Original assignee: Celanese Corp; Columbia Cellulose Co Ltd
Current assignee: Celanese Corp; Columbia Cellulose Co Ltd
Priority date: 1954-01-19
Filing date: 1954-01-19
Publication date: 1957-04-23
Anticipated expiration: 1974-04-23
Also published as: GB764045A

Description

U d States Patent 1 2,789,902 REFINING F woon PULP 5' to the refining of wood pulp and ,Xelates more particularly to an improved process for the refill fllg df- W0 o d pulp which will reduce the resin content of said wood pulp to an extremely low value.

In the production of chemical wood pulp suitable for small proportion of the non-cellulosic materials present .therein. During such treatment,- it is important to minimize the degradation of the cellulosic material since such degradation would reduce the alpha cellulose 'content and p the viscosity of the final product to undesirably low values.

'To avoid 'an excessive degree of degradation of the pulp,

the treatments to which said pulp is subjected must be relatively mild. However, mild treatments make it difficult to obtain a satisfactory degree of refining of the wood pulp. This represents an especially difiicult problem in the production of acetylation grade wood pulp that is employed for the manufacture of cellulose acetate and other organic acid esters of cellulose since such pulp must have a high alpha cellulose content and a high viscosity, together with an extremely low content of non-cellulosic impurities.

It is an important object of this invention to provide an improved process for the refining of wood pulp which will overcome at least in part the foregoing and other difiiculties.

A further object of this invention is to provide an improved process for the refining of wood pulp which will reduce the resin content of said pulp to an extremely low value.

Other objects of this invention will be apparent from the following detailed description and claims.

According to the present invention, a digested wood pulp is subjected as one stage in its refining to a hot alkali boil in the presence of a non-ionic detergent, comprising a polyglycol ether of an alkyl phenol, and tall oil. It has been found that the treatment of the wood pulp in this manner reduces its resin content to an extremely low value without, however, causing an excessive reduction in the alpha cellulose content of the wood pulp or in the viscosity thereof. The product obtained is well suited for use as an acetylation grade wood pulp. The efiectiveness of the non-ionic detergent mixed with the tall oil is quite surprising since it reduces the resin content of the wood pulp to values of from one-fifth to one-half of that obtained when the detergent is used alone, yet tall oil itself has little or no effect on the resin content of the wood pulp.

In carrying out this process, the digested wood pulp, which'may advantageously be a sulfite wood pulp, may be treated first with chlorine and also with a bleaching agent such as a hyp-ochlorite, in a manner well known in the art. Following these initial treatments, the wood pulp is subjected to an alkali boil. For the alkali boil the consistency of the wood pulp is adjusted to between about 2. and 20% by weight and the concentration of sodium hydroxide to between 3 and 25% by weight on the weight .tion further.

of the bone dry pulp. There are present in the wood pulp slurry during the alkali boil from about 0.1 to 1% by weight on the Weight of the bone dry pulp of the nonionic detergent and from about 0.1 to 5% by weight on the weight of the bone dry pulp of tall oil. The alkali boil is carried out at a temperature of between about and 170 C. and for a period of between about 10 and 240 minutes. Following the alkali boil the wood pulp is drained and washed and may be treated with bleaching agents such as hypochlorite, chlorine dioxide and the like further to improve its properties.

The non-ionic detergent used in carrying out this invention comprises a polyglycol ether of an alkyl phenol in which the alkyl group contains from about 4 to 20 or preferably from about 6 to 15 carbon atoms. The polyglycol with which the alkyl phenol is etherified contains from about 6 to 20 or preferably from about 8 to 15 recurring units in its chain, which units may be derived from ethylene oxide, propylene oxide, butylene oxide and the like. The preparation of these non-ionic detergents is fully described in U. 5. Patent No. 2,213,477. The tall oil which is present during the alkali boil is a by-product derived from the digestion of wood pulp by the sulfate process and is a mixture of rosin acids and fatty acids with minor quantities of sterols and the like.

The following example is given to illustrate this inven- Example A sulfite wood pulp which has been chlorinated and washed is diluted with an aqueous sodium hydroxide solution to a consistency of 8% by weight, the sodium hydroxide content of the diluting solution being selected to bring the sodium hydroxide concentration of the slurry to 12% by weight on the weight of the bone dry pulp. There is incorporated into the wood pulp slurry 0.3% by weight on the weight of the bone dry pulp of the mixed ether made by condensing monyl phenol with about 10 moles of ethylene oxide for each mole of the phenol and about 1% by weight on the weight of the bone dry pulp of a tall oil having an acid number of 186 to 191, and including from 66 to 71% by weight of fatty acids, 25 to 30% by weight of rosin acids and 2 to 4% by Weight of sterols and the like. The slurry is charged into a pressure vessel and heated over a period of 25 minutes to a temperature of C. and is held at this temperature for an additional 20 minutes. The wood pulp is then washed and soured to a pH of 5.5 with sulfur dioxide water.

The alcohol-benzene solubles in the wood pulp, which is a measure of the resin remaining in the pulp, are only 0.030% by weight on the weight of the bone dry pulp. The alpha cellulose content of the purified wood pulp and the viscosity thereof are high, so that after bleaching with hypochlorite the product obtained is suitable for use as an acetylation grade pulp.

In the appended claims the weight of the wood pulp is on a bone dry basis.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. In a process for the purification of wood pulp, the step which comprises subjecting the pulp to a hot caustic boil in the presence of tall oil and a polyglycol ether of an alkyl phenol.

2. In a process for the purification of wood pulp, the step which comprises subjecting the pulp to a hot caustic boil at a temperature of between about 80 and C. for a period of between about 10 and 240 minutes in the presence of tall oil and a polyglycol ether of an alkyl phenol.

boil at a consistency of between about 2 and 20% by weight and a caustic concentration of between about 3 and 25% by weight on the weight of the pulp in the presence of tall oil and a polygiycol ether or an alkyl phenol.

4. In a process for the purification of wood pulp, the step which comprises subjecting the pulp to a hot caustic ,boil in the presence of from about 0.1 to 1% by weight on'the weight of the pulp of a polyglycol ether of an alkyl phenol and from about 0.1 to by weight on the weight of the pulp of tall oil.

5.- In a process for the purification of wood pulp, the step which comprises subjecting the pulp to a hot caustic boil at a temperature of between about 80 and 170 C. for a period of between about and 240 hours at a consistency of between about 2 and 20% by weight and a caustic concentration of between about 3 and 25% by weight on the weight of the pulp in the presence of from about 0.1 to 1% on the weight of the pulp of a polyglycol ether of an alkyl phenol and from about 0.1 to 5% by weight on the weight of the pulp of tall oil.

6. In a process for the purification of wood pulp, the steps which comprise forming a wood pulp slurry containing sodium hydroxide, adding tall oil and a poly- IgIyool ether of an alkyl phenol to said wood pulp slurry, and subjecting said Wood pulp slurry to elevated temperature.

7. In a process for the purification of wood pulp, the steps which comprise forming a wood pulp slurry containing sodium hydroxide, adding to said wood pulp slurry from 0.1 to 5% by weight on the weight of the pulp of 4 tall oil and from 0.1 to 1% by weight on the weight of the pulp of a polyglycol ether of an alkyl phenol, and subjecting said wood pulp slurry to elevated temperature.

8. In a process for the purification of wood pulp, the steps which comprise forming a wood pulp slurry containing sodium hydroxide in a concentration of between about 3 and 25% by weight on the weight of the pulp, adding to said wood pulp slurry from 0.1 to 5% by weight on the weight of the pulp of tall oil and from 0.1 to 1% by weight on the weight of the pulp of a polyglycol ether of an alkyl phenol, and subjecting said wood pulp slurry to a temperature of between about to C. for a period of between about 10 and 240 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 1,833,976 Richter et a1 Dec. 1, 1931 1,847,311 Schur et a1 Mar. 1, 1932 2,128,928 Estes Sept. 6, 1938 2,213,477 Steindorff et al Sept. 3, 1940 2,596,092 Bonneville May 13, 1952 FOREIGN PATENTS 740,664 Germany Mar. 31, 1944 OTHER REFERENCES Printing Inks, by Ellis, p. 482, published by Reinhold Pub. Corp., New York (1940).

Deinking of Waste Paper, by West, pp. 8 and 9, published by Institute of Paper Chemistry, Appleton, Wis. (1943).