Chapter IV — Classification of Soaps (part 4 of 4)

TEXTILE SOAPS.

Soap is a very important product to every branch of the textile industry. For woolen fabrics it is used for scouring, fulling and throwing the wool; in the silk industry it is necessary for degumming the raw silk, as well as for dyeing; in the cotton mills it is used to finish cotton cloth and to some extent in bleaching; it is, furthermore, employed in a number of ways in the manufacture of linen. Large quantities of soap are thus consumed in an industry of so great an extent and the requirements necessitate different soaps for the different operations. We will, therefore, consider these in detail.

SCOURING AND FULLING SOAPS FOR WOOL.

The soaps used to scour wool and for fulling the woven cloth are usually made as cheaply as possible. They are, however, generally pure soaps, as filling material such as sodium silicate does not readily rinse out of the wool and if used at all must be added very sparingly. Both cold made and boiled settled soaps are made for this purpose. The soap is generally sold in barrels, hence is run directly to these from the crutcher or soap kettle. As cold made soaps the following serve for wool scouring or fulling.

I.
Palm Oil	200 lbs.
Bone Grease	460 "
Soda Lye, 36° B.	357 "
Water	113 "
Soda Ash	50 "
Citronella	2 "
II.
Palm Oil (Calabar, unbleached)	155 "
House Grease	360 "
Soda Lye, 36° B.	324 "
Water	268 "
Sodium Silicate	83 "
III.
House Grease	185 "
Palm Oil (unbleached)	309 "
Soda Lye, 36° B.	309 "
Water	391 "
Soda Ash	70 "
Sodium Silicate	60 "
Corn Starch	10 "

These soaps are made in a crutcher by the usual process for cold-made soaps, crutched until smooth, dropped into a barrel and crutched by hand the next day or just before cooling.

As a settled soap for these operations the following charge is typical:

Palm Oil	34	parts
Cottonseed foots or its equivalent in fatty acids	33	"
Rosin	10	"
House Grease	23	"

The method of boiling such a soap is the same as for any settled soap up to the strengthening change. When this stage is reached, sufficient lye is added to strengthen the kettle strongly. It is then boiled down with closed steam on salt brine or “pickle” until a sample of the lye taken from the bottom stands at 16°-22° B. The soap is then run into barrels and after standing therein for a day is hand crutched until cool to prevent streaking of the soap.

Besides a soap of this type a settled tallow chip soap is used.

WOOL THROWER’S SOAP.

Soaps for wool throwing are sometimes made from olive oil foots but these are often objected to because of the sulphur-like odor conveyed to the cloth due to the method by which this oil is extracted with carbon disulphide. A potash soap hardened somewhat with soda is also used. As a formula for a suitable soap of this type this may be given.

Olive Oil Foots	12 parts
Corn Oil	46 "
House Grease	20 "
Soda Lye, 36° B.	3 "
Potassium Carbonate (dry)	5-3/4 "
Potassium Hydrate (solid)	23 "

This soap is made as a “run” soap by the general directions already given for a soap thus made. The kettle is boiled with open and closed steam, adding water very slowly and aiming to obtain a 220-225 per cent. yield or fatty acid content of the finished soap of 46 per cent. When the soap is finished a sample cooled on a plate of glass should be neither slippery or short, but should string slightly. The finished soap is run directly into barrels.

A soap for wool throwing by the semi-boiled process may be made from olive oil foots in a crutcher thus:

Olive Oil Foots	600 lbs.
Potash Lye, 20° B.	660 "

The oil is heated to 180° F., the lye added and the mass stirred until it bunches, when it is dropped into barrels.

WORSTED FINISHING SOAPS.

For the finishing of worsted cloth soaps high in cocoanut oil or palm kernel oil are preferred. These soaps are finished very neutral, being made as settled soaps, but given an extra wash change after strengthening strongly. They are then finished as usual and run into barrels. If framed too hot, the high percentage of cocoanut oil causes mottling, which is prevented by crutching by hand until the temperature of the soap is 140°-145° F. Some typical charges, all of which are saponified with soda lye, follow:

I.
Palm Kernel Oil	60 parts
Corn Oil	40 "
II.
Palm Kernel Oil	30 "
Red Oil (single pressed)	70 "
III.
Red Oil	33-1/3 "
Corn Oil	33-1/3 "
Cocoanut Oil or Palm Kernel Oil	33-1/3 "

SOAPS USED IN THE SILK INDUSTRY.

Soap is used to a very large extent in silk mills, both for degumming the raw silk and in silk dyeing. Raw silk consists of the true silk fibre known as fibroin and a gummy coating, sericin, which dulls the lustre of the silk unless removed. For this purpose a slightly alkaline olive oil foots soap is best adapted, although palm oil and peanut oil soaps are sometimes used, as well as soaps made from a combination of house grease to the extent of 30 per cent., together with red oil or straight olein soaps, both of which are artificially colored green. In using house grease, if 30 per cent. is exceeded in combination with red oil, the titer is raised to such an extent that the soap does not readily rinse from the silk nor dissolve readily. They are also not advisable because they impart a disagreeable odor to the silk.

To make a soap for this purpose from olive oil foots it is made as a settled soap, care being taken to thoroughly boil the mass on the saponification change in the closed state to assure proper saponification. The kettle is usually grained with lye and given a good wash change to remove the excess strength. The change previous to the finish should not be too heavy or too large a nigre results. The lighter the grain is, the better the finished kettle is. A yield of 150 per cent. is usually obtained. This soap is generally run to a frame, slabbed upon cooling and packed directly into wooden cases.

For silk dyeing the above soap is suitable, although any well-made soap of good odor and not rancid is useable. While soap alone is often used in the bath for silk dyeing, certain dyestuffs require the addition of acetic or sulphuric acid, which sets free the fatty acids. If these be of bad odor it is taken up by the silk and is difficult to remove. The most generally used soaps are the just mentioned olive foots soap or a soap made from a good grade red oil.

Both kinds are extensively used.

SOAPS USED FOR COTTON GOODS.

In the manufacture of cotton goods, as compared to the wool and silk industries, very much less soap is used and it is only applied to the finished fabric either to clean the cloth preparatory to dyeing or to aid in dyeing with certain colors. It is also used in calico printing. For cleansing the cloth ordinary chip soap is suitable although a more alkaline soap finished as a curd soap is an advantage in that the free alkali contained therein aids in removing the dirt and has no harmful effect on the cotton. For dyeing cotton goods or to brighten certain colors after dyeing an olive oil foots soap is most generally employed. In calico printing soap is used to wash and clear the cloth after printing. A soap for this purpose should be easily soluble in water and contain no free alkali, rosin or filler. The best soaps for use in calico printing are either an olive oil foots soap or an olein soap.

SULPHONATED OILS.

While sulphonated oils are not used to any great extent in the manufacture of soap, they are used very largely in the dyeing and printing of turkey and alizarine reds on cotton as well as other colors. Just what action these oils have is not known. Turkey red oil or sulphonated castor oil is the best known sulphonated oil.

The process of making these oils is simple. The equipment necessary is a wooden tank or barrel of suitable capacity, approximately two and a half times the amount of oil to be treated. There are furthermore required other tanks or vessels to hold the solutions used such as caustic soda, ammonia and acid. The tank to be used for the preparation of sulphonated oil should be provided with a valve at the bottom of the tank and a gauge to measure the quantity of liquid therein.

The process is carried out as follows:

Three hundred pounds of castor oil are placed in the tank and 80 pounds at 66 deg. B. sulphuric acid are weighed out in another vessel. The acid is run into the tank containing the oil in a very thin stream while the oil is well stirred. At no time should the temperature exceed 40 deg. C. This operation should consume at least an hour and stirring should be continued half an hour longer to insure the thorough mixing of the oil with the acid. The mass is then allowed to settle for 24 hours, after which 40 gallons of water are added and the mixture stirred until it has a uniform creamy color indicating no dark streaks. This mixing process should be carefully carried out and when completed allowed to settle 36 hours. At this point the mass will have separated into two layers, the lower layer consisting of a water solution of acid and the upper layer of oil. The former is run out through the valve located at the bottom of the tank. Another wash may now be given or dispensed with as desired. In this wash the addition of salt or sodium sulphate at the rate of 1-1/2 pounds per gallon of water is advisable. A 24 deg. B. caustic soda solution is prepared and added slowly to the acidified oil with constant stirring. The mass first turns creamy, then becomes streaked, increasing in streaks as the caustic solution is poured in, and finally becomes clear and transparent. Water is now added to bring the volume to 75 gallons. The oil is now milky in appearance, but the addition of a little more soda solution restores the transparency.

In some cases ammonia is used in addition to caustic soda in neutralizing the oil. Three-fourths of the amount of caustic soda required to complete the neutralization is first added and then the neutralization is completed with a one to one liquid ammonia and water solution.

FOOTNOTES:

[9] Seifensieder Ztg., 40, 47, 1266 (1913).

[10] Seifensieder Ztg. (1913), p. 334 and 338.
“           “   (1912), p. 1229 and 1257.

[11] Seifensieder Ztg. (1912), p. 954.

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