US2647114A - Method for making readily filterable viscose - Google Patents

Description

Patented July 28, 1953 METHOD FOR MAKING READILY FILTERABLE VISCOSE Erich 'Iorke,. Hamburg, and Werner Matthaes,v Krefeld (Rhine), Germany; assignors to Phrix- Werke, A. G., Hamburg, Germany, a corpora tion of Germany No Drawing. Application December 2, 1950-, Serial No. 198,906. In Germany May 7, 1949 8 Claims. It;

This invention relates to method for making readily filterable viscose.

It more particularly relates to the manufacture of. readily filterable viscoses, which can be spun into threads and films.

In the methods generally used for this purpose in the industry, cellulose or linters are impregnated with about 10 times by weight of a 1:6 26-% sodium hydroxide solution, squeezed 01f to approximately 3v times the weight of the pulp used, and the fibers. disassociated. The alkali cellulose are then air-aged and placed in rotary drums or kneadingdevices for sulfiding. Sulfidin (xanthating) is carried out for about 90 minutes at 1'6-28 C., whereupon solvent lye or solvent water is added in portions during 3 hours in order to avoid the formation of lumps.

The drum method, as heretofore carried. out, has the disadvantage that: the dissolving of the xanthogenate must be eifected in a separate apparatus. This disadvantage can, be avoided by sulfi'din in the churn, but considerable power must be used for the churning of the mass which is initially crumbly and becomes rubberlike in the last stage of the sulfi'ding.

The disadvantages of the two methods are avoided by the method: described in the following. In the method according to the invention, there is added to the alkali cellulose prior to or during the sulr'iding, at least to and preferably or more of the solvent lye and the solvent water, i. e., of the total diluent liquid. The alkali cellulose may be obtained in known manner by impregnating the pulp or lin-ters with 16-26% sodium hydroxide solution. The formation of rubberlike tough masses during the sulfiding is avoided in this way and at the same time the Xanthogenate obtained is entirely or partially dissolved in the course of the sulfiding reaction. In this connection, it is essential that the sulliding temperature beabove 20 C. However, it must also not be too high and should not be more than 40 C. As a rule, the sulfiding is carried out at 26-30 C. For example, the sulfiding is commenced at 20-23 C. and. the temperature at the end of the reaction is permitted to rise to 26-29 C. However, it is also advantageous, particularly in order to obtain the shortest possible sulfiding and dissolving times, to carry out an isothermal sulfiding in the temperature range between 20-40 C. and preferably between 26-30 C.

Methods have already been describedv in connection with which a pasty alkali cellulose, is sulfided but in this case. the sulfiding, is effected at 5-12" 0., In this way viscoses having the customary cellulose and alkali concentration were not obtained. Furthermore, mercerizing lyes of low alkali concentration were used, which renders the production of a readily sulfided alkali cellulose dii-ficult.

In the method according to the present invention, the alkali cellulose can be diluted prior to the commencing of the sulfiding by the addition of the corresponding quantity of solvent lye and solvent Water. The shortest manufacturing times are however had if the solvent lye and sol-vent water are continuously added at the very' start of the sulfiding. However, it is also possible to first sulfide the alkali cellulose in dry conditionv for ashort period of time, for instance, 5-15- minutes, and, then effect the dilution.

In the method according to the invention, the alkalizing can also be effectedin such manner that only enough 16-26% mercerizing lye, is caused to act on the cellulose as to render a squeezing off of excess lye unnecessary. In order to obtain good alkalizing and rapid sulfiding, it may be advisablein. this connection to add to the alkalizing lye a wetting agent, as for instance, sulfonated castor oil, or else to add an organic liquid which is soluble in the lye and in carbon disulfide, such as, for example, methanol, glycol, orglycerine, in small quantities, for example, 1-10 cc. per kg. cellulose. The addition of the wetting agent and of the organic liquid can also be made to the carbon disulfide during the sulfiding.

These wetting agents, and in particular abietic acid, also act to improve the degree of disassociation of the fibers. They can therefore also be added: during the disassociation process. A good disassociation of the alkali cellulose fibers is essential for the wet sulfidingmethod, particularly if the alkalizing is effected without excess lye. When using low polymer pulp having a polymerization degree of about 250-400, and alkalizingwithout excess lye, there can be directly obtained by dilution, without ageing,v a spinnable viscose of ordinary concentration. If pulps of higher degrees of polymerization are used, for example 600-1000, the alkali cellulose must be subjected to an ageing, which is preferably carried out at elevated temperatures, for example 35-80" C. In order to shorten the ageing, it is advantageous to cause suitable oxidizing or reducing agents to act on the alkali cellulose at elevated temperatures, for example, 3050 C., in.

which connection the oxidizing or reducing agents can be added to the alkalizing caustic or be permitted to trickle down in aqueous solution onto the alkali cellulose. Suitable oxidizing agents are persulfate, percarbonate and hydrogen peroxide. Examples of suitable reducing agents in accodance with the invention are sodium sulfide, sodium sulfite, sodium nitrite, hydroquinone or phenylhydrazine.

The method can be carried out suitably in a conventional churn, or in simple agitator provided with a temperature jacket, although a temperature jacket is not necessary in all cases. The method can also be carried out in a rotating drum. A horizontal agitator is found to function particularly advantageously. The introduction of the pulp sheets, if the alkalizing is efiected without lye excess, can take place therein directly or after they have been subjected to a lye-trickling treatment. The lye-trickling treatment in this connection suitably takes place on a chute provided on the agitator, through which chute the pulp sheets are fed to the receptacle. However, the pulp can also be introduced dry and the agitator be filled with the lye. The disassociation of the fibers of the cellulose is effected by the agitator blades or the agitator arms which pass close to the wall of the vessel. An oxidizing or reducing ageing can be simultaneously connected with the alkalizing, the oxidizing or reducing agents being added to the trickling lye or the prior lye, or being permitted to trickle in aqueous solution down onto the alkali cellulose.

An exact maintaining of the sulfiding temperature is necessary in connection with wet sulfiding. At temperatures below 28 C., the carbon disulfide is emulsified in the pasty alkali cellulose. If the temperature increases substantially above 28, the vapor pressure of the carbon disulfide, which has a boiling point of 46 C., increases too rapidly and the carbon disulfide passes to a considerable extent out of the emulsion. At a lower sulfiding temperature of less than the sulfiding velocity of the alkali cellulose is too low and the carbon disulfide passes mainly into the side reactions. However, with the high reaction velocity of the pasty alkali cellulose, the sulfiding temperature can be increased to 3540 C. without the carbon disulfide concentration in the alkali cellulose paste becoming too low to effect the uniform impregnation and emulsifying of the carbon disulfide. The carbon disulfide may be added to the alkali cellulose when the cellulose temperature is 16 to 20 C. and the temperature may then be increased to about 24 C. for the rapid initiation of the sulfiding reaction.

In the method according to the invention, the

sulfiding temperature can be controlled by suitably controlling the temperature of the solvent lye and solvent water added, as is also true of the temperature of the alkali cellulose subjected to the sulfiding. The shortest sulfiding and dissolving times are obtained if the sulfiding temperature does not drop below 26 C. during the course of the sulfiding. Preferably, the temperature of the alkali cellulose, the speed of addition and temperatures of the solvent water and solvent lye are so regulated that the sulfiding reaction takes place at a temperature between 26 and 30 C. With this manner of operation, sulfiding and dissolving times of 20 to minutes can be obtained.

The addition of the solvent lye water may take place during the first 20 to 60 minutes after the commencement of the sulfiding. As already mentioned, the addition of the solvent lye water may also be commenced before the beginning of iii the sulfiding. The alkali cellulose used according to the invention may be obtained in the customary manner by alkalizing with excess lye and squeezing off the excess lye, alkali cellulose so obtained must of course be subjected to an air ageing. If the ageing of the alkali cellulose takes place in an accelerated process at elevated temperatures, as for example, at 30 to 45 C., the sulfiding can be commenced directly after the degradation has taken place without cooling the alkali cellulose, the temperature of the solvent lye and of the solvent water being chosen accordingly. With an alkali cellulose temperature of 35 C., the temperature of the solvent lye is, for instance, adjusted to 35 C., as is the temperature of the solvent water. Inasmuch as it is necessary to cool the cellulose after the sulfiding is completed in order to avoid a strong ripening of the viscose, it is also possible to add cold solvent lye toward the middle or end of the sulfiding, in order to reduce the final temperature of the viscose obtained. In the carrying out of the sulfiding, the heat capacity of the sulfiding vessel and the quantities of heat generated by the churning or agitating mechanism must be taken into consideration in connection with the adjustment with the desired sulfiding temperature. This quantity of heat is naturally considerably less in connection with the pasty mass than in connection with the previous methods of dry sulfiding.

The method of the invention is further explained by the following examples:

Example 1 4000 grams of an alkali cellulose which were obtained from a spruce sulfite pulp by alkalizing with 18% NaOH in excess with a liquor ratio of 1/ 10, the excess lye being pressed off, are sulfided in an agitating vessel after 17 hours ageing at 34 C. The alkali cellulose has an alpha content of 25.1% and 17.2% NaOH. Prior to the sulfiding, the alkali cellulose is diluted by the addition of 2260 cc. water and 1950 cc. solvent lye grams NaOI-I per liter) to 10.5% NaOH, and sulfided after prior cooling to minus 3 C. for 50 minutes at 20 to 28 C. By the addition of 3500 cc. water during the course of 180 minutes, there is obtained at 10 to 15 C. a viscose containing 8.4% cellulose in addition to 7.2% NaOI-I and 33.5% CS2. The viscose has a viscosity of 39 seconds and a filtration constant of 174. The filtration capacity is 460 liters per minute. The viscose is spun at an ammonium chloride number of 11 and gives a fiber having a breaking load of grams per denier and 23% elongation. The degree of polymerization of the fiber is 280.

Example 2 75 kilos of a rayon-sulfite-spruce-pulp (alpha content 88.5%, polymerization degree 800) are churned at 20 C. with 260 liters of a sodium hydroxide solution to which 400 cc. of Monopol Brillant Oil (sulfonated castor oil or some other suitable wetting agent in the required amount) have been added and which contains 240 grams per liter NaOH, for two hours and then aged for 1'7 hours at 34 C. mixed in a churn or agitating vessel with 248 liters of water with the simultaneous addition of 16 liters CS2 and thereupon sulfided for 70 minutes at 20 to 28 C'. By the addition of 113 liters of water, there is then obtained a viscose having a viscosity of 36 seconds and a cellulose content of 8.3% in addition to 6.8% NaOH. The viscose is easily filtered (filtration constant in accordance with the Convention Method of 89) and gives threads of normal strength when spun in a Muller bath.

Example 3 700 grams of a synthetic fiber-spruce-sulfitepulp of a polymerization degree of 750 are coarsely comminuted in a xanthogenate churn. Over this there is poured a mixture of 2300 cc. lye (240 r ms NaOH per liter) and 2000 cc. water, heated to 80 C. in which 5 cc. of the wetting agent known under the trade name of Monopol Brillant Oil or some other wetting agent has been poured, and churning is efiected for one hour. After cooling to C. sulfiding is effected for 90 minutes with 260 grams of carbon disulfide. Thereupon a further 3000 cc. of water are added in the course of 3 hours and a viscose is obtained containing 8% cellulose, 7% NaOH and carbon disulfide (referred to alpha cellulose). The viscose does not have any swollen fibers. The viscosity is 89 seconds, the filtration constant 127 (KW) and the filter capacity 260 liters per minute.

Example 4 The manner of operation is the same as the one indicated in Example 3, with the only difference that 75 grams NazS (referred to anhydrous sodium sulfide) are added to the 80 lye. In this way, a strong decrease in the viscosity is obtained. The viscosity of of the viscose obtained is 39 seconds with a cellulose content of 8% in addition to 7% NaOH; KW 198, filtration capacity 304 liters per minute. The viscose is spun in the customary manner in a Muller bath and gives a fiber of a dry strength of 160 grams per denier and 20% dry elongation. The polymerization degree of the fiber is 350. The alkali solubility corresponds to that of a viscose synthetic fiber spun in accordance with convention method.

Ewamnle 5 1000 grams of a spruce-sulfite-pulp (alpha content 886%, degree of polymerization 600) are alkalized with 3.5 liters NaOI-I (240 grams NaOH per liter) containing 2 cc. Monopol Brillant Oil per liter, at 20 C. for 2 hours in an agitating vessel and thereupon diluted to a NaOI-I content of about 11% by the addition of 3 liters of water. Thereupon sulfiding is effected for 70 minutes at 20 to 28 C". with 350 cc. of CS2 and by the addition of the corresponding quantity of solvent water, there is obtained a viscose containing 7.5% alpha and 7.5% NaOI-I. The viscosity of the viscose is 940 seconds (measured at 18 according to the convention method with a steel ball of 3 mm. diameter and a distance of fall of 20 cm). The viscose is ripened to a salt point of 0.1% and after setting aside for three days at 20 C'., is spun under a pressure of 8.5 atmospheres guage according to the funnel spinning process through nozzles of a width of 0.8 mm., into water of a temperature of 20 C. The drawing-01f velocity is 80 meters. After leaving the precipitating funnel, the thread which passes over a guide bar, passes through a setting bath containing 3% H2804 and 5% N azSOe. During the spinning process, the viscose feed is adjusted in such a manner that a fiber thickness of 3.6 denier is obtained. The strength of the spun fiber is 1.6 to 2 grams per denier and the elongation is between 12 and 18%.

Eazample 6 kilos of alkali cellulose of an alpha cellulose content 01 25 to 29%, for example 25.6%,. and a caustic soda content of 16.5 to 17.5 for example 17.1%, produced from a rayonspruce-sulfitepulp of a polymerization degree of 750 (alpha cellulose content 88.5%) by steeping in a sodium hydroxide solution containing 240 grams caustic soda per liter in a liquor ratio of 1 to 10- with the squeezing 01f of the excess lye are introduced after 17 hours ageing at 34 C. into an xanthate churn. To the alkali cellulose cooled to 28, there are added 4.5 liters carbon disulfide. With the churning and agitating mechanism operating, 29 liters of solvent lye (9% caustic soda) of 29 C., are permitted to flow in over a period of 10 minutes and thereupon 75 liters of water of 29 C. are introduced over a period of 20 minutes. After the addition of all the solvent lye and all the solvent water, the dissolving is continued for a further 5 minutes, During the entire sulfiding and dissolving, the temperature of the reaction mixture stays at 29 C. The viscose obtained has a filtration value of 63, and after a further 25 minute of dissolving, it has a filtration value of 47. The viscose does not contain any swollen fiber, has a cellulose content of 8.3%, a caustic soda content of 6.4% and a viscosity of 20. The polymerization degree of the film precipitated from the viscose is 299. The total sulphur in the viscose corresponds to 32% carbon disulfide referred to alpha cellulose.

Example 7 40 kilos of alkali cellulose of 29 C. produced in the same manner as indicated in Example 6, are mixed in the churn with 25 liters 9% solvent lye and 5 liters water, both of 29 0., and thereupon 3.5 liters of carbon disulfide are added. Sulfiding is effected for 20 minutes, the temperature rising to 31 C. Thereupon, the remaining50 liters of 15 C. solvent water are added over the course of 12 minutes, due to which any decrease in the temperature of the viscose obtained is obtained simultaneously with the dissolving. Dissolving is continued for 20 minutes after the addition of the rest of the solvent water. The viscose obtained has the same composition as the one according to Example 6 and has a filtration value KW of 83.

Example 8 50 kilos of cellulose (alpha cellulose content 88.5%. polymerization degree 750) are brought by a chute into an agitating vessel in which there are contained liters of 19.5% sodium hydroxide solution in which 1.5 kilos of sodium sulfide (anhydrous NazS) are dissolved. The pulp sheets fill up with lye and are converted into a fiber paste by the passing of the agitator blades close by the vessel wall. Alkalizing is efiected for one hour at 40 C. Thereupon, 15 liters of carbon disulfide are added andat the same time or immediately after the. addition of. 270 liters of water of 20 C. are permitted to run into the sulfiding vessel over the course of 20 minutes, the rate of admission being so. regulated that the temperature of the reaction mixture is maintained at. 27 C. There is obtained a viscose of a viscosity of i5 seconds and an alpha cellulose. con.- tent of 8.5% caustic soda. Thev viscose can readily be filtered and has a filtration value of 90.

tent of 25 to 29%. for example, 25.5%, and an NaQI-E content of 16.5 to 17.5%, for example,

17.1%, made from a rayon-spruce-sulfite-pulp of a polymerization degree of 750 (alpha content 88.5%) by steeping in a sodium hydroxide solution containing 240 grams NaOH per liter in a liquor ratio of 1 to 10 with the squeezing off of the excess lye, are diluted after 17 hours ageing at 34 C. in a xanthate churn by the addition of 4550 cc. of water to 8% NaOI-I. The alkali cellulose paste of a temperature of 23 to 24 C. is sulfided for 50 minutes with 360 grams carbon disulfide, the temperature rising to 28 C. By the addition of 2200 cc. solvent lye (100 grams NaOI-I per liter) and 1550 cc, Water during the course of 90 minutes, there is obtained a viscose containing 6.6% NaOH and 8% cellulose. The viscose has a viscosity measured according to the convention method of 22 seconds, a filtration constant of 40, and a filtration capacity of 908 liters.

The viscose can be readily filtered and spun and gives a thread of a dry strength of 145 grams per denier and elongation.

Example 10 An alkali cellulose produced and aged as indicated in Example 9 is diluted in a quantity of similarly 4000 grams by the addition of 2260 cc. Water and 1950 cc. solvent lye (100 grams NaOl-I per liter) to 10.5% NaOI-I and sulfided in an agitating vessel for 30 minutes at 20 to 28 C. By the addition of 3500 cc. water, there is obtained a viscose containing 8.4% cellulose in addition to 7.2% NaOH and 33.5% CS2, The addition of the water is effected within 5 minutes. After 30 minutes pumping in order to obtain more rapid dissolving and homogenizing, there is obtained a viscose having a viscosity of 30 seconds and a filtration constant measured by the convention method of 90. The polymerization degree 01 the fiber obtained from a viscose by spinning in a conventional Muller bath is 280.

Example 11 17, kilos of alkali cellulose prepared and aged in the manner indicated in Example 9, are

churned in an agitator vessel provided with a pumping line for a few minutes with 6 liters of viscose is easily filterable and has a filtration value of 50.

Example 12 kilos of alkali cellulose prepared in the manner indicated in Example '7 are introduced into a rotating drum (alpha content of the alkali cellulose 24.8%, NaOH content 17.1%, temperature 27). After the closing and evacuation of the drum, 31.5 liters CS2 are permitted to fiow in during rotation and thereupon 200 liters of solvent lye containing 100 grams NaOH per liter and 100 liters of water, both of 30 C., are added over the course of 10 minutes. sulfiding is continued for an additional 30 minutes without any addition, and thereupon a further amount of 250 liters of water are added over the course of 20 minutes. By the addition of a further 250 liters of water of 30 0., there is obtained within 10 minutes, a viscose containing 8% cellulose and 7% NaOH and having a viscosity of 30 seconds. If necessary, the viscose can be further dissolved for a After the addition of 23.1 liters short period of time, for instance, one hour in a dissolver or high speed mixer, or can be worked on by a crushing pump for further homogenizing. The viscose is easily filterable and has a KW value of 115. It is advantageous to subject the alkali cellulose to a good shredding prior to the sulfiding.

The above examples are given by way of illustration only, the invention being limited by the claims.

For the purpose of the above description, the viscosity of a spinning solution is defined in Goetze Kunstseide und Zellwolle, pages 262-263. The viscosity is equal to the time needed by a ball to fall through the spinning solution. For example a viscosity of 30 means that the time which the ball needs to fall through the solution is 30 seconds. A special ball of a diameter of 3.160 millimeters and a weight of 129-131 milligrams is used for this purpose. The ball has to fall through a height of 200 millimeters of solution at a temperature of 20 C.

Liquor ratio means the quantity of liquid in liters which is used for solving one kilogram of solid matter. For example a liquor ratio of 3 means that one kilogram of cellulose pulp is alkalized with 3 liters of caustic soda solution.

The polymerization degree is defined in Goetze (see above) pages 31-36. The polymerization degree is measured by means of a diluted ammonia solution of copper hydroxide. The polymerization degree will be arrived at by dividing the time which such a solution containing cellulose needs to pass a viscosity meter by the respective time needed by the pure copper hydroxide ammonia solution.

The filter capacity KW is defined in the publication of Hermans and H. L. Bredes Rec. Trav. chim. 547-548, 680, 1935. The KW value is equal to the number of cubic centimeters of a spinning solution passing a standard filter in a fixed time.

The salt point is a measure for the degree of ripeness of a spinning solution. It is defined in Goetze (see above) page 289. The method is based on the fact that the coagulation speed of a viscose increases with the degree of ripeness. To determine the salt point it is necessary to drop a solution of sodium chloride of decreasing concentrations into the spinning solution. The salt point is reached at that concentration of the sodium chloride solution at which the viscose no longer coagulates.

We claim:

1. In the method for making readily filterable viscose by the sulfiding at a temperature of 20 to 40 C. with carbon disulfide of an alkali cellulose produced by the impregnation of cellulose with a 16-26% caustic solution, and having a degree of polymerization corresponding to an alkali cellulose produced from cellulose with a polymerization degree of about 250 to 400, and the addition of a solvent selected from the group consisting of lye and Water to the resulting xanthagenate for the formation of viscose, the improvement which comprises adding at least one fifth of said solvent after the completion of the carbon disulfide addition for said sulfiding and efiecting said sulfiding in the presence of said solvent.

2. Improvement according to claim 1 in which at least one fifth of said solvent is added immediately after the completion of the addition of carbon disulfide for said sulfiding.

3. Improvement according to claim 1 in which at least one fifth of said solvent is added about 5 9 to 15 minutes after the beginning of said sulfiding.

4. Improvement according to claim 1 in which at least one fifth of said solvent is added continuously over a period of about 10 to 30 minutes.

5. Improvement according to claim 1 in which said sulfiding is effected in the presence of a wetting agent at a temperature of about 26 to 30 C.

6. Improvement according to claim 5 in which said alkali cellulose is a pre-ripened alkali cellulose of a degree of polymerization corresponding to the degree of polymerization of an alkali cellulose prepared without pre-ripening from cellulose with a degree of polymerization of about 250 to 400.

7. Improvement according to claim 1 in which at least one fifth of said solvent is added within 5 to minutes after the beginning of said sulfiding and in which said sulfiding is effected at a temperature of 26 t 30 C., the viscose formed by the addition of the remainder of said solvent after the xanthagenate formation having a cellulose content higher than its alkali content.

8. Improvement according to claim 1 in which said alkali cellulose is a pre-ripened alkali cellulose having a polymerization degree corresponding to the polymerization degree of an alkali cellulose produced from a cellulose having a polymerization degree of about 250 to 400 without pro-ripening.

ERICH 'I ORKE. WERNER MATTHAES.

References Cited in the file of this patent UNITED STATES PATENTS Number Re. 22,459 1,279,329 1,435,650 1,857,948 1,862,592 10 1,955,299 2,064,356 2,068,631 2,076,594 r 2,076,595 2,106,812 2,114,605 2,126,976 2,139,302 2,222,050 2,513,652 2,542,285

Name Date Schlosser et a1. May 30,1944 Glover et a1 Sept. 17, 1918 Mitscherling Nov. 14, 1922 Dosne May 10, 1932 Goth June 14, 1932 Kampf et al. Apr. 7, 1934 Picard et al. Dec. 15, 1936 Richter Jan. 19, 1937 Richter Apr. 13, 1937 Ritcher Apr. 13, 1937 Richter et al Feb. 1, 1938 Nicoll Apr. 19, 1938 Richter et a1 Aug. 16. 1938 Booys Dec. 6, 1938 Stoeckly et a1 Nov. 19, 1940 Kline July 4, 1950 Mitchell Feb. 20, 1951 OTHER REFERENCES Heuser, Cellulose Chemistry, 1944, pages 319, 320, 325 to 327.

Claims (1)

1. IN THE METHOD FOR MAKING READILY FILTERABLE VISCOSE BY THE SULFIDING AT A TEMPERATURE OF 20* TO 40* C. WITH CARBON DISULFIDE OF AN ALKALI CELLULOSE PRODUCED BY THE IMPREGNATION OF CELLULOSE WITH A 16-26% CAUSTIC SOLUTION, AND HAVING A DEGREE OF POLYMERIZATION CORRESPONDING TO AN ALKALI CELLULOSE PRODUCED FROM CELLULOSE WITH A POLYMERIZATION DEGREE OF ABOUT 250 TO J00, AND THE ADDITION OF A SOLVENT SELECTED FROM THE GROUP CONSISTING OF LYE AND WATER TO THE RESULTING XANTHAGENATE FOR THE FORMATION OF VISCOSE, THE IMPROVEMENT WHICH COMPRISES ADDING AT LEAST ONE FIFTH OF SAID SOLVENT AFTER THE COMPLETION OF THE CARBON DISULFIDE ADDITION FOR SAID SULFIDING AND EFFECTING SAID SULFIDING IN THE PRESENCE OF SAID SOLVENT.