SE463463B - PREPARATION OF TRAEMASSA BY ALKALIC COOKING IN THE PRESENCE OF AMPHOTIC SURFACTURING AGENTS - Google Patents

Description

463 463 2 the temperature. Even with this, the problem still exists and in order to obtain an acceptably low Kappa number and low sieve rejection, it must be compensated by extending the cooking at maximum temperature for a few hours with the resulting decomposition of carbohydrates and loss of mass yield.

It has previously been suggested that the penetration of chemicals into the wood structure would be facilitated by a surfactant.

Attempts to improve the cooking processes by the addition of surfactants have so far not been successful and such agents have not been used in current processes.

An object of the present invention is to provide additives which show obvious advantages in ensuring penetration of the chemicals and release of the lignin with no more than normal hydrocarbon decomposition in a considerably shorter boiling cycle. It has surprisingly been found that the desired benefits are obtained to a significant and economically very significant degree by the addition to the cooking liquid of small amounts of an amphoteric surfactant.

The invention relates to a process for the production of wood pulp using an alkaline cooking liquor which comprises one or more amphoteric surfactants.

The lye is thus an alkaline lye, such as a Kraft or soda lye. The chemical constitution of these liquors is very well known to pulp manufacturers and is described, for example, in "Pulping Processes", S.A. Rydholm (Interscience Publishers, 1965).

The process according to the invention has its greatest advantage in connection with liquors normally used in the Kraft process.

The surfactant used should, of course, be an MV 465 463 which is stable in and soluble in the cooking liquor.

The surfactant is of the type having the general formula (I): R- (cmz- (oc fl zcuzc fl zjn- (N - (CHR1) x) y - N - Q (ï) BB wherein R is a C8_2Û hydrocarbon group, optionally substituted with hydroxy or carboxyl, R 1 is H or C 1-6 alkyl, B is H, C 1-6 alkyl, C 1-6 alkyl substituted with hydroxy or amino, or a group Q as defined below; Q is R 2 COOM, wherein R 2 is 1-6 or an alkali metal, alkaline earth metal or ammonium ion or an ammonium ion substituted with up to 3 is a C 1-4 alkylene group and M is -H hydroxyethyl substituents, x is 2 to 6, y is 0 to 5, z is 0 to 1, and n is 0 or 1 (wherein z is 0 when n is 1).

In these compounds, R may be, for example, a straight or branched chain alkyl or alkenyl group or cycloalkylalkyl (for example cyclohexylalkyl) group, an aralkyl or aralkenyl group (for example phenalkyl or phenalkenyl) wherein the alkyl or alkenyl moiety contains at least 6 carbon atoms; or the hydrocarbon moiety of a resinic acid containing at least two fused rings, for example as in the tricyclic pine resin acids such as abietic acid. R is preferably a C 1-6 alkyl group, for example a C 12 group. R may be, for example, the hydrocarbon moiety of lauric or coconut fatty acid which both contain a high proportion of C12 components. An example of an unsaturated R group is oleyl and an example of a branched chain group is C 16 H 33 CH (CH 3) -. The aliphatic portion of R may be, for example, substituted with hydroxy, such as in hydroxystearyl, or with -COOH (for example at 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 contains 1-6, preferably 2-4 carbon atoms and is preferably a straight chain group. Examples of such groups are methyl and ethyl. The alkyl group may be substituted, for example, by hydroxy, such as in 2-hydroxyethyl, or by amino.

ZCOOM wherein R 2 is a C 1-64 alkylene group (such as Group Q is -R methylene or ethylene) and M is hydrogen or an alkali metal, alkaline earth metal, ammonium or an ammonium ion substituted with up to three hydroxyethyl substituents. M is preferably sodium, and R 2 is preferably methylene. x is preferably 2 and y is preferably 0 or 1.

Thus, the surfactant preferably has one of the following structures: RCO.NH.CH2CH2NCH2COOM CHZCHZOH RN (ca2cH2cooM) 2 mm. cnccoom (e.g. Ra cH (C143) NH. cnzcnzcoon wherein RaCH (CH3) is the R group) RNH-CH (CH3) cH2cooM 5 465 463 One or more amphoteric surfactants can be used as a coke additive in the present process. The amphoteric surfactants can also be used in combination with one or more surfactants of other types, for example nonionic or fluorinated surfactants. In this latter respect, the amphoteric surfactant may have the effect of solubilizing surfactants of other general types which are stable in the cooking liquor but not normally soluble therein.

The surfactant (s) can usually be used in an amount of, for example, up to 2% (for example 0.01% -2.0%) of the cooking liquor, and preferably in amounts of 0.1 to 0.6% by weight. percent.

It is to be understood that with the exception of the addition of the surfactant, the cooking process is generally carried out in the same manner as in conventional practice, again as described, for example, in "Pulping Processes" referred to above.

However, the cooking time can be reduced as shown below, especially under alkaline conditions.

Tests have shown that the addition of, for example, 0.5% based on the cooking liquor, of a surfactant of this type will reduce the required cooking time and the percentage of strainer rejects considerably in the Kraft process and also in the sulphite process. The reasons why the surfactants according to the invention are superior to those previously tested are not clear. Attempts to correlate the effect with the reduction of the surface tension have not been successful and the mechanisms involved are probably complex.

The invention is further illustrated by the following examples.

Example 1 A series of Kraft cooking experiments in autoclaves were performed with and without the additives of the invention. The additives used were amphoteric surfactants having the general structure shown in formula I and were obtained from Rexolin Chemicals in Helsingborg, Sweden, under the tradenames Rexoteric XCE and XJO. The amounts used were 0.5% of the cooking liquor (white liquor). To demonstrate the beneficial effect of the additives on the penetration of the chips, the time allowed for the gradual heating to the maximum temperature, normally 2.5 hours, was only 45 minutes in all experiments. After the cooking was continued for the time required to obtain the desired Kappa numbers, it was found that when using said additive at Kappa number 60, the residue of undigested fibers (sieve reject) was 0.9%, the same residue amounting to to 4% when the additive was not used in the same Kappa number. At Kappa number 70, the undigested fibers were 1.1% when using the additives in the cooking liquor and were 6% when using the cooking liquor without the additives. At Kappa number 35, the residue on the screen was 0.5% with the additives and 1.5% without the additives.

Example 2 A series of sulfite cooking experiments were performed using as an additive 0.5%, based on the acidic cooking liquor, of Rexoteric XJO mentioned in Example 1. Experiments without the additive were performed for comparison. The temperature was raised from 20 to 105 ° C in 1.5 hours and to show the effect of the additive, the pause at 105 ° C was omitted which was normally used to obtain good penetration. Instead, heating was continued and the final boiling temperature of 32 ° C was reached in 1 hour.

After the cooking was continued for the time required to obtain the desired Kappa numbers, it was found that when using said additive at a Kappa number 50, the residue of undigested fibers was 2.8%. The same residue amounted to 5.5% without the additive.

Claims (3)

1. A process for the production of wood pulp - characterized in that an alkaline cooking liquor is used in which fat or several amphoteric surfactants are included, which surfactants correspond to the formula R- (CO) 2 - (OCH 2 CH 2 CH 2) n - (N - (CHR 1) x) y - N - Q (I) BB wherein R is a C hydrocarbon group, optionally substituted with 8-20 hydroxy or carboxyl, R 1 is H or C 1-6 alkyl, B is H, C 1-6 alkyl , C 1-6 amino, or a group Q as defined below, Q is R 2 COOM, wherein R 2 is a C 1-6 alkylene group and M is -H or an alkali metal, alkaline earth metal or alkyl substituted with hydroxy or ammonium ion or an ammonium ion substituted with up to 3 hydroxyethyl substituents, x is 2 to 6, y is 0 to 5, z is 0 or 1, and n is 0 or 1 (wherein z is 0 when n is 1). 2. A method according to claim 1 characterized in that the surfactant is present in the cooking liquor in an amount of up to 2% by weight. 3. A method according to claim 1 characterized in that one or more non-amphoteric surfactants are also included in the cooking liquor.