FI79358C - MASSAFRAMSTAELLNINGSFOERFARANDE. - Google Patents

Description

1 79358

The present invention relates to a process for the production of wood pulp which can be used in papermaking and for other purposes.

In the production of wood chips, the chips are first boiled under alkaline, acidic or neutral conditions.

In the sulphate process, wood chips are treated (boiled) at high temperature in an alkaline solution containing a mixture of sodium hydroxide, sodium sulphide and sodium carbonate to sulphide the lignins and thus dissolve them. In the sulphite process, lignin is dissolved in an acidic or neutral solution containing sulphites and bisulphites. The methods are generally carried out in such a way that the chemical treatment of the chips begins at a temperature below 100 ° C and continues as the temperature gradually rises to a range of 150 to 180 ° C.

A known problem is that chemicals penetrate the chips slowly and incompletely. This may result in some of the lignin having time to polymerize before "" dissolving, resulting in a high lignin content (kappa number) in the pulp and the formation of a considerable amount of uncooked fiber (screen reject). For example, in the sulfate process, penetration is optimized by allowing the temperature to gradually rise for 1.5-3 hours. The problem of such operations still remains, and in order to obtain an acceptable low number of pieces and a small number of sieve objects, it is necessary to compensate by increasing the cooking time at maximum temperature by a few hours, which means a decomposition of carbohydrates and a reduction in pulp yield.

In the past, the use of a surfactant has been proposed to improve the penetration of soil chemicals into the wood structure. But so far it has not been possible to improve pulping methods with the addition of a surfactant and no such substances are used in current methods.

It is an object of the present invention to provide additives which can be shown to improve the penetration of chemicals and the dissolution of lignin so that carbohydrates are not degraded more than normal and cooking takes place in a considerably shorter time. It has surprisingly been found that the desired benefits are achieved to a substantial and economically very important extent by adding small amounts of amphoteric surfactant to the broth.

Thus, the invention relates generally to a process for the preparation of pulp-10 in which one or more amphoteric surfactants are included in the broth.

The broth may be any broth conventional in pulping and may be basic, acidic or neutral. Thus, the broth may be a basic broth, such as a sulphate or soda broth or an acidic or neutral sulphite or bisulphite broth. The chemical composition of these broths, as described e.g. in S.A., is well known to pulp manufacturers. Rydholm, Pulping Processes (Interscience Publishers, 1965).

The method of the invention is most preferably applied; alkaline cooking broths, and in particular those normally used in the sulphate process.

The surfactant used must, of course, be stable and soluble in the broth.

Preferably, the surfactant is of the type of general formula (I) or (II), in particular the preceding formula: R- (CO) - (OCH.CH.CH_) - (N- (CHR1)) -NQ (I) z 2. I λ n, xy,

B B

30 ® R- (CO) 2 - (OCH 2 CH 2 CH 2) n - (N- (CHR 1) x) γ-N-Q (II)

B B

wherein R is a C 8 -C 20 hydrocarbon radical, optionally substituted, R "* - is H or C 1 -C 4 alkyl, B is H, alkyl, substituted alkyl or a group as defined below, Q, Q is an anionic moiety, x is 2-6, y is 0-5, z is 0-1 and n is 0 or 1 (z is 0 when n is 1).

3 79358 In these compounds, R may be, for example, a straight or branched alkyl or alkenyl group or a cycloalkylalkyl group (e.g. cyclohexylalkyl), an aralkyl or aralkenyl group (e.g. phenalkyl or phenalkenyl) in which the alkyl-5- or alkenyl moiety contains at least six carbon atoms; or as a hydrocarbon radical moiety in a rosin acid having at least two fused rings, e.g. in tricyclic pine rosin acids such as abietic acid. R is preferably a C 1 -C 4 alkyl group, e.g. a C 1-4 group. For example, R may be as a hydrocarbon radical moiety in a lauric or coconut fatty wax moiety, both of which are rich in C12 components. An example of an unsaturated group R is oleyl and an example of a branched group C The aliphatic moiety of R may be e.g. substituted with hydroxy, such as in hydroxystearyl, or -COOH (e.g. in the 2-position).

R 1 is usually a hydrogen atom, but may be an alkyl group such as methyl.

When B is an alkyl group, it may contain 1 to 6, preferably 2 to 4 carbon atoms, and most preferably is a straight-chain group. Examples of such groups are methyl and ethyl. The alkyl group may be substituted with e.g. hydroxy, such as 2-hydroxyethyl, or amino.

2 2

The group Q may be, for example, of the formula -R COOM, wherein R is a C 1 -C 6 alkylene group (e.g. methylene or ethylene) and 25 M is hydrogen or an alkali metal, alkaline earth metal, ammonium or substituted ammonium ion (e.g. mono -, di- or trihydroxyethylammonium). M is preferably sodium and R is preferably methylene.

x is preferably 2 and y is preferably 0 or 1.

In surfactants of formula (II), the associated anion may be, for example, a halide (e.g. chlorine or bromine).

Thus, the surfactant preferably has one of the following formulas: 4 79358

RCO-NH-CH2CH2NCH2COOM CE ^ CH OH

RN (CH2CH2COOM) 5 RNH-CH2CH2COOM (e.g. RaCH (CH3) NH-CH2CH2COOM, where

RaCH (CH3) is a group R)

RNH-CH (CH3) CH2COOM

10 rn + (ch3) 2 rn + (ch2ch2oh) rco-nh- (ch2) 3n + (ch3) 2

CH2COOM CH2COOM CH2COOM

In my method, one or more amphoteric surfactants can be used as a broth additive. Amphoteric surfactants can also be used in combination with one or more other types of surfactants, e.g. non-ionized or fluorinated surfactants. According to this latter aspect, the amphoteric surfactant may act as a solubilizing surfactant for other general types of surfactants that are stable in broth but not normally soluble therein.

The amount of surfactant or surfactants used can generally be, for example, up to 2% (e.g. 0.01 to 2.0%) of the broth, and the recommended amount is 0.1 to ^ 0.6% by weight.

It should be noted that, with the exception of the addition of a surfactant, the cooking process is generally carried out in a conventional manner, e.g. as in "Pulping" cited above.

Processes "is described. However, the cooking time can be shortened as described below, especially under alkaline conditions.

- - Experiments have shown that, for example, the addition of 0.5% of this type of surfactant, based on the broth, considerably reduces the cooking time required and the percentage of sieve reject in the sulphate process and also in the sulphate process. It is not clear why the surfactants of the invention are better than previously tested. Attempts to correlate the effect of surface tension reduction have not been successful and it can be assumed that this.

5 mechanisms are complex.

The following examples illustrate the invention.

Example 1

A series of sulfate cooking experiments were performed in autoclaves with and without the additives of the invention. The additives used were amphoteric surfactants of general formula I, manufactured by Rexolin Chemicals, Helsingborg, Sweden, under the tradenames Rexoteric XCE and XJO. The amount used was 0.5% based on the broth (white liquor). In order to demonstrate the beneficial effect of the additives on the penetration of the chemicals into the chips, the time required to gradually raise the temperature to the maximum temperature, which was normally 2.5 hours, was only 45 minutes in all experiments. After cooking was continued for the time required to achieve the desired kappa number, it was found that when said additive was used, the kappa number 60 had a residue (sieve effect) of uncooked fibers of 0.9%. At the same kappa number without additive, the residue was 4%. At 70 and when additives were used in the broth, the uncooked fibers were 1.1% and this value was 6% when no additives were used in the broth. With a piece number of 35 and with additives, the sieve residue was 0.5% and without additives 1.5%.

Example 2

A series of sulfite cooking experiments were performed using 0.5% of the Rexoteric XJO mentioned in Example 1, calculated from the acidic broth, as an additive. For comparison, experiments were performed without additive. The temperature was raised from 20 ° C to 105 ° C in 1.5 hours and, to demonstrate the effect of the additive, the residence time at 105 ° C normally used to achieve good penetration was omitted.

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Instead, heating was continued and a final cooking temperature of 132 ° C was reached in one hour.

After the cooking was continued for the time required to reach the desired kappa number, it was found that when said additive 5 was used, the residual number of uncooked fibers at the kappa number 50 was 2.8%. The same residue was 5.5% without additive.

Claims (2)

7 79358 A process for preparing a chemical pulp, characterized in that one or more surfactants of the formula R- (CO) 2 - (OCH 2 CH 2 CH 2) n - (N- (CHR 1))) yNQ are added to the alkaline cooking broth. I) BB 10 wherein R is a C 8-20 hydrocarbon group which may be substituted, R 1 is H or a C 1-8 alkyl group, B is H or a substituted or unsubstituted alkyl group or a group Q, Q is an anionic group, x is 2-6 , y is 0-5, z is 0 or 1 and n is 0 or 1, provided that when z is 0, then n is 1. Process according to Claim 1, characterized in that the amount of surfactant in the cooking broth is at most 2% by weight.