Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
  • D01F2/06—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from viscose
  • D01F2/08—Composition of the spinning solution or the bath

Definitions

• the invention relates to a process for the manufacture of viscose from raw material containing cellulose. It is well known that the preparation of the spinning or casting solution-viscose-in the manufacture of viscose fibers and films is conventionally effected as follows:
• pulp utilized as raw material is steeped either as sheets or slurry with 17-22 percent NaOH solution.
• the alkali cellulose is shredded and aged at 20-60 C. until the molecular size of the cellulose is reduced to the desired level.
• the reaction can be acclerated by using oxidizers or catalysts, such as peroxides, ions of cobalt, manganese, and so on.
• the aged alkali cellulose is xanthated with an amount of carbon disulphide which is dependent upon the product to be manufactured.
• the proportions most frequently used are: for staple fibers and film 28-35 percent of the amount of cellulose in the alkali cellulose, for high wet modulus type staple fiber considerably more, for polynosic fiber as much as 50-60 percent; for filament yarn 32-40 percent, for rayon cord more than 36 percent.
• the xanthate is dissolved in NaOH solution, of which the amount and concentration is chosen in such a way that the prepared solution, the viscose, acquires the desired composition: cellulose 4-10 percent and NaOH 2.5-8 percent, dependent upon the product to be manufactured.
• the viscose is ripened and filtered once or several times either during or after ripening, and is spun into fibers or cast into film.
• One condition of good spinnability is that the filterability of the viscose to be spun is good.
• the properties of the final viscose product depend upon a number of different factors.
• the strength characteristics of the fibers and films are perhaps most influenced by the spinning and casting procedure.
• a notable factor is also the amount of low-molecular weight carbohydrates in the alkali cellulose to be xanthated, as material of this kind exercises a disturbing effect upon the preparation and spinning of viscose, and also upon many properties of the final product.
• the manufacturer of viscose products would prefer to utilise as raw material pulp which contains a minimum of low-molecular weight material, i.e. pulp of a very high alpha cellulose content.
• the costs of production of pulp of this kind are considerable, and this in turn renders less profitable the manufacture of the viscose product.
• the degree of refinement of the pulp used as raw material has no decisive eifect upon the amount of low-molecular weight material in the aged alkali cellulose.
• at least one half of the low-molecular weight material of the pulp is removed during the first stages of the viscose process, steeping and pressing.
• the molecules of alpha cellulose, the main component of the pulp are split to a suitable level for the spinning and the end product, and at the same time new low-molecular weight material is formed to a marked extent.
• the original pulp was sulphite pulp from conifer, with an alpha cellulose content of 90.8 percent, viscosity l9 cp., S 11.1 percent, and steeping loss 6.1 percent.
• Alkali cellulose S (.perce'nt) Immediately after steeping and pressing 2.8 Aged 24 hours at 25 C. 5.4 Aged 48 hours at 25 C. 6.6 Aged 72 hours at 25 C 9.1
• the low-molecular weight material of the alkali cellulose is detrimental not only to the properties of the final viscose product, but also interferes with the xanthation of the long-chain alkali cellulose.
• short-chain carbohydrate material of this kind reacts at a considerably higher rate with carbon disulphide than does long-chain alkali cellulose, and consequently correspondingly less carbon disulphide remains available for the latter material.
• carbon disulphide is also consumed by side reactions, i.e. by reactions with free NaOH present in the alkali cellulose. It is calculated that under ordinary conditions of xanthation these side reactions generally consume 25-35 percent of the amount of CS added.
• the largest raw material costs involved in the manufacture of viscose products are those arising from pulp, carbon disulphide, and sodium hydroxide.
• Manufacturers of viscose products consider that the ratio between NaOH and cellulose in viscose is one of the most important factors which influence the production cost of viscose products. This partly results from the fact that, in addition to the cost arising from the consumption of NaOH, the consumption of sulphuric acid in spinning is directly proportional to the NaOH content of the viscose. If, in a conventional viscose process, 19 percent steeping liquor is used in the manufacture of viscose which contains 9 percent cellulose, a NaOH content of less than 4.8 percent is unattainable, even if the xanthate is dissolved in pure water. The ratio NaOH/ cellulose will then be about 0.53- 0.54.
• the invention to be presented here is aimed at elimination of the disadvantages mentioned above and is chiefly characterized in that the aged alkali cellulose manufactured by known procedures, before xanthation, is steeped at least once with steeping liquor of a concentration below percent, pressed after each steeping, and, after possible shredding subsequent to these steepings and pressings, is xanthated with an amount of carbon disulphide equal to that normally used in the conventional viscose process for the manufacture of the corresponding product, or less than this, the said xanthation being possibly carried out at a considerably higher temperature, and during a shorter period of time than is normal, and that, on dissolving the said xanthate into viscose by known procedures, the NaOH content of the viscose is adjusted to a level lower than normal when xanthation is effected with a normal amount of carbon disulphide, and to a level normal or less than normal when xanthation is effected with an amount of carbon disulphide which is less than normal,
• the procedure may be as follows. After aging, the alkali cellulose is re-steeped.
• concentration of the steeping liquor used may be chosen arbitrarily, but with the final result in view about 10 percent NaOH solution is the most advantageous, as at this concentration the NaOH solution has a maximum dissolving and swelling power.
• there is the advantage gained from the content of free NaOH in the alkali cellulose to be xanthated being lower than that in the conventional viscose process, for which reason also the consumption of carbon disulphide by the side reactions with NaOH is reduced in the xanthation.
• the alkali cellulose is shredded, and can be xanthated with an amount of carbon disulphide which is less than normal. This is practicable because alkali cellulose contains much less low-molecular material and NaOH than is usual, and consequently considerably less carbon disulphide is consumed by the reactions with these compounds than in the ordinary process.
• the NaOH content of the alkali cellulose to be xanthated is about 11 percent. It has proved that the solubility of the xanthate in this case is extremely good, so that, by using a very dilute dissolving lye a viscose of good filterability may be manufactured, with a NaOH content only silghtly exceeding 3 percent when the cellulose content is 9 percent.
• the ratio of NaOH/ cellulose achieved is 0.340.35.
• the xanthation temperature may be increased above that curcently applied, for instance to 50 0., without increasing to an unreasonable extent the proportion of carbon disulphide consumed by the side reactions.
• the xanthation time may thus be reduced, say to 2040 minutes, which facilitates making the entire viscose process continuous.
• the viscose process is convertible into a continuous process in such a way that the pulp from which the viscose is made is fed as a continous flow or web into a series of successive reaction vessels and devices, in each of which one or more of the treatments in the preparation of viscose occurs, and that the material after continuously passing through the equipment will have passed in the correct order through either all or some of the stages of the viscose manufacture.
• EXAMPLE 1 Eight similar samples of sulphite pulp from conifer, with an alpha cellulose content of 90.8%, and viscosity of 19 cp., were steeped as sheets at 25 C. in exactly the same way, with 19% NaOH solution, and pressed in such a way that the alkali cellulose contained 30.5% cellulose and 15.7% NaOH. All the samples were aged without shredding of the sheets, 4 samples for 60 hours, and 2 samples for 72 hours at 25 C., and the remaining two samples at 60 C. for 3 hours and 3% hours, respectively. The first-mentioned 4 samples were xanthated without re-steeping, using 29, 26, 23, and 20% carbon disulphide calculated on the amount of cellulose in the alkali cellulose.
• the viscosity of the viscoses was determined by the falling ball method familiar in viscose technology, and the filterability was evaluated on the basis of the clogging value, K With the filtering device and the filter material applied in the test, and with a viscose composition of 9% cellulose and 5% NaOH and a viscosity of 40-60 seconds, the filterability can be appraised by means of the following scale:
• Samples 1, 2, and 3 were Xanthated without re-steeping, by the use of 28, 24, and 22% CS calculated on the amount of cellulose in the alkali cellulose. All the other samples were re-steeped before xanthation, using 10% NaOH solution. After pressing, the alkali cellulose contained 32.9% cellulose and 11.4% NaOH.
• carbon disulphide was used as follows: sample 4, 22%, sample 5, 20%, sample 6, 22%, and sample 7, 20%. In all cases, the Xanthation was effected at 25 C. for 150 minutes. The xanthate was in each case dissolved at 20 C.
• EXAMPLE 4 Four similar samples of the sulphite pulp from conifer mentioned in Example 1 were steeped as sheets at 25 C., with 19% NaOH solution, upon which the sheets were pressed as in Example 1, aged at 25 C. for 72 hours,
• EXAMPLE 3 steeped with 10% NaOH solution, and pressed as in Ex- Four similar samples of the sulphite pulp from conifer mentioned in Example 1 were steeped as sheets at 25 C. with 19% NaOH solution, samples 1 and 2 for 60 minutes without addition of catalyst, samples 3 and 4 for 15 minutes with lye containing 0.5 mg./l. cobalt as CoCl All the samples were pressed as in Example 1. Samples 1 and 2 were aged at 60 C. for 3 hours, samples 3 and 4 at 50 C. for minutes, samples 2, 3, and 4 were then steeped with 10% NaOH solution, sample ample 1. All the samples were xanthated with 24% carbon disulphide at 25 C. for 150 .minutes.
• the xanthates were dissolved in such an amount of NaOH solution or water to give a cellulose content of 8.7-8.8% in the viscose.
• the concentrations of the NaOH solutions were so chosen that the NaOH content of the viscose in sample 1 was 5.0%, in sample 2, 4.0%, and in sample 3 3.5%.
• the xanthate in sample 4 was dissolved in water. The results have been compiled in Table 4.
• Example 7 EXAMPLE Eight similar samples of the sulphite pulp from conifer mentioned in Example 1 were steeped as sheets at 25 C., with 19% NaOH solution, and pressed as in Example 1. Samples l-4 were aged at 60 C. for 3 hours, and samples 5-8 for 3 /2 hours. All the samples were then steeped with NaOH solution, and pressed as in Example 1. 0n xanthation, 28% carbon disulphide was used in runs 1, 4, and 7, 24% carbon disulphide in runs 2, 5, and 8, and carbon disulphide in runs 3 and 6. The xanthates were dissolved in NaOH solution of such concentrations that the NaOH content of the viscoses was 5.0% in runs 1-3, 4.0% in runs 4-6, and 3.5% in runs 7-8. The amount of dissolving lye was such that the cellulose content of all viscoses was 8.7-8.8%.
• a continuous process for the manufacture of viscose comprising the steps of:
• the alkali cellulose can be re-steeped twice or several times in accordance with the object in view, without deviating from the main principle of the invention.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Baking, Grill, Roasting (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (14)

Cited By (12)

Families Citing this family (3)

• 1969
  • 1969-05-14 AT AT461169A patent/AT293438B/de not_active IP Right Cessation
  • 1969-05-14 DE DE19691924804 patent/DE1924804A1/de not_active Withdrawn
  • 1969-05-15 GB GB1256790D patent/GB1256790A/en not_active Expired
  • 1969-05-16 US US825390A patent/US3600379A/en not_active Expired - Lifetime
  • 1969-05-20 SE SE6907092A patent/SE397533B/xx unknown
  • 1969-05-21 CH CH770469A patent/CH518319A/de not_active IP Right Cessation
  • 1969-05-22 YU YU1273/69A patent/YU34538B/xx unknown
  • 1969-05-23 NO NO2116/69A patent/NO131389C/no unknown
  • 1969-05-23 NL NL6907993A patent/NL6907993A/xx unknown
  • 1969-05-23 JP JP4053769A patent/JPS4729448B1/ja active Pending
  • 1969-05-23 FR FR6917019A patent/FR2009286A1/fr not_active Withdrawn
  • 1969-05-23 CS CS6900003703A patent/CS182757B2/cs unknown
  • 1969-05-23 PL PL1969133772A patent/PL80034B1/pl unknown
• 1973
  • 1973-06-08 BE BE132055A patent/BE800670Q/xx active

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