Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
  • D06L4/10—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which develop oxygen
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
  • D06L4/20—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen
  • D06L4/22—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents
  • D06L4/23—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents using hypohalogenites
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
  • D06L4/70—Multi-step processes

Definitions

• This invention relates to improvements in the bleaching of bast fibers such as linen, jute, hemp and the like.
• solubility number furnishes a measure of the amount of the material soluble in caustic soda solutions under closely specified conditions, and since it is mainly the chemically degraded cellulose that dissolves under these conditions, high solublility numbers are associated with severe degradation and low numbers with but slight attack.
• the conditions and method of determining solubility numbers are set out in a paper by C. R. Nodder in The Journal of the Textile Institute 1931, 22, T416.
• bast fibers such as linen
• solubility number it is one of the objects of the present invention to provide a rapid and convenient process whereby bast fibers such as linen, can be bleached to any degree of white without undue attack on the cellulose as evidenced by the solubility number.
• a still further object is to produce bast fibers of any desired degree of whiteness and a low solubility number. Further objects will appear hereinafter.
• bast fiber materials are bleached by a Process comprising at least two stages in one of which the materials are treated with a hypochlorite.
• the preliminary treatment of the goods prior to the hypochlorite treatment may be merely a thorough wetting out by means of a solution of a wetting agent.
• the goods are subjected to an alkaline scour which may be mild or severe, provided only that it renders the fibers readily wettable by the hypochlorite.
• alkaline scour which may be mild or severe, provided only that it renders the fibers readily wettable by the hypochlorite.
• hypochlorite solution within the controlled pH range are conveniently effected by the addition to a suitable hypochlorite solution, e. g. sodium or calcium hypochlorite, of a salt having the required buffer characteristics. More particularly, we have found that excellent results can be achieved by the addition of sodium bicarbonate in suflicient quantity to a hypochlorite solution.
• a suitable liquor of wide range of applicability contains before use between 2.5 and 3.5 grams per litre available chlorine and about 8 grams per litre of the bicarbonate.
• Such a liquor is substantially neutral, the precise pH value depending on a number of factors including the alkalinity of the stock bleaching powder liquor and the quality of the water which is used for its preparation.
• amount of buffer salt necessary to keep the liquor in the required substantially neutral pH range we have found it advisable when making a liquor of a strength 1.5 grams per litre available chlorine that there should be added at least 3 grams per litre sodium bicarbonate; for a liquor of 3, grams per litre available C12 at least 5 grams per litre sodium bicarbonate; and for a liquor of 5 grams per litre available C12 at least 8 grams per litre sodium bicarbonate.
• the concentration of the neutral hypochlorite liquor should not be higher than 4.5 to 5.0 grams of available chlorine per litre when treating material scoured in a normal manner.
• the time and temperature at which the hypochlorite bath can be used are not unduly critical, and we do not find it necessary to pay any marked attention to the color which is achieved solely by treatment with the neutral hypochlorite, as the subsequent steps of the process can be operated to furnish the desired whiteness.
• One of these conditions is the presence of light during the treatment of the goods with the neutral hypochlorite solution. It is one of the features of the present invention that this treatment is carried out with the substantial exclusion of actinic rays. For most purposes this can be achieved by the screening of the vessels in which the hypochlorite treatment is carried out, in such a manner as to prevent the access of bright light, such as direct sunlight, to the goods undergoing treatment.
• the permissible light in the treatment of linen we may instance the use of a normal electric light bulb of c. p. placed not less than about 6 feet from the material undergoing treatment.
• an essential condition of the material is that it shall be capable of'being rapidly impregnated by the hypochlorite solution in a thorough and uniform manner.
• This condition may be achieved by a mild treatment, e. g. with an aqueous solution of a wetting agent, or by a severe one, such for example as a boil in an alkaline solution.
• Goods treated by either of these extremes or by any treatment of intermediate severity can be efiectively treated with the neutral hypochlorite in such a manner as to avoid a marked increase in solubility number. This is most conveniently illustrated with reference to linen.
• hanks of yarn are suspended on rotating arms of wood or other material, so that the lowest portion of the hank dips into a volume of liquor While the hank constantly rotates.
• the speed of rotation and the depth of immersion have a considerable influence on WEN?"- CtiEitilCeL FfQDIFL the amount of liquor carried out by the yarn, and with rapid rotation the reeling treatment approximates to an immersion of the hank.
• This fact must be borne in mind when adjusting the severity of the hypochlorite treatment when working in this manner.
• the more rapid the rotation the more should the severity of the treatment be reduced to approach that used with complete immersion of the yarn.
• hypochlorite liquors which, when tested by means of the glass electrode, have shown pH values of 6.1, 6.4, 6.9, 7.4, and 7.8. More particularly have we obtained excellent results in the region of pH 6.5.
• sour should preferably be applied cold and may be of any strength normally applied to cellulose fibers.
• Sulphuric acid may be used but it is better to use a hydrochloric acid sour when the hypochlorite bath has been made up from bleaching powder. The risk of calcium sulphate remaining on the fibre due to its relatively low solubility is thereby avoided.
• the goods are thoroughly washed in cold water and then treated in an alkaline solution and with an oxidising bleaching agent.
• This treatment may comprise two stages such as a plain treatment at an elevated temperature with an alkaline solution, followed by hydrogen peroxide solution.
• we combine the alkali and oxidising bleaching treatment by using an alkaline solution. containing hydrogen peroxide.
• the hydrogen peroxide bath may be made up in the normal manner from any source which wll give hydrogen peroxide in solution. This may be done by dissolving sodium peroxide in water, or in an amount of diluteacid which is sufficient to give complete or partial neutralization, depending on the degree of alkalinity desired in the peroxide .bath. In the event of the peroxide being completely neutralized, a suitable alkaline material is then added to put the liquor into bleaching condition.
• the peroxide bath may be prepared by diluting a strong hydrogen. peroxide solution with water and adding a suitable alkali. Other additions as have been mentioned in connection with the bath made from sodium peroxide may also be made.
• the concentrations of the alkali and peroxide in the liquor are capable of being varied within very Wide limits, while still enabling very good whites to be attained. It will be evident, however, that there are minimum values below, which results of commercial value are not obtained, and for this reason we find it desirable to use liquors having an alkalinity equal to or greater than 0.15 per cent NazO and a peroxide content equalto or greater than 0.05 per cent H202.
• the upper limits of the concentrations are influenced by the desirability of avoiding undue attack on the ma terial and in the case of the peroxide economic considerations are also of importance.
• the peroxide may be used in a concentration up to about 1 per cent H202.
• the figure is, however, very much more than is normally permissible by economic considerations, and for these reasons it is best not to exceed a concentration of about 0.2 per cent H20
• the other factors which it is necessary to consider in this treatment are temperature and time.
• textile materials are capable of being bleached to different shades of white.
• shades In the case of linen there are generally recognised the shades known as half-white, three-quarter White, and full white.
• a half white stage can be attained with the following series of operations carried out in accordance with the general principles laid down above:(a) scour and wash, (b) treat with neutral hypochlorite solution, rinse, sour and wash, (0) treat with alkaline peroxide. If the half white is the shade required the material will now be washed, finished as desired, and dried. If, however, higher shades of white are desired it is only necessary to apply one or more treatments with hypochlorite liquors and alkaline liquors alternately as required.
• Example I 570 lbs. of linen yarn were scoured for three hours at about 65 C. in 800 gallons (imperial gallons) of liquor containing 45 pounds soda ash, and then washed. The hanks of yarn were then transferred to a reeling machine and treated for thirty minutes in a neutral hypochlorite solution at 14 C. in subdued light. For this operation 900 gallons of liquor were used containing initially 3.5 grams per litre available chlorine and having a pH value 6.5. The liquor was prepared from a batch which had been previously used several times in similar operations, by adding a stock solution of bleaching powder to give the desired content of 3.5 grams per litre available chlorine, and a stock solution of sodium bicarbonate.
• the ratio of these stock solutions was such that about equal weights of available chlorine and sodium bicarbonate were added.
• the direction of rotation was reversed several times, and throughout the operation approximately 15 inches of each hank were immersed in the liquor and the linear speed at which the hanks were moving through the liquor was six feet per minute.
• the hypochlorite liquor was run off rapidly and the yarn was immediately rinsed in three changes of cold water in the same machine. It was then removed from the machine and soured for half an hour in cold 0.5 per cent hydrochloric acid and washed.
• An alkaline peroxide bath was prepared by dissolving 18 pounds of sodium peroxide in 700 gallons of water containing 20 pounds 168 Tw. sulphuric acid, and then adding 4 gallons of 84 Tw. sodium silicate solution. The yarn was heated in this bath for 3 hours at 65 C. and was then washed off and dried.
• the dried yarn was a good half white and Weighed 510 lbs. Tests were made on the solubility number and strength of the yarn before and after bleaching, and the following results were obtained:
• Example II The hypochlorite liquor for this example was prepared by adding to 720 gallons of water 60 gallons of a stock bleaching powder solution containing 4.5 per cent available chlorine and 100 gallons of a solution containing pounds of Na2HPO4. After mixing thoroughly the pH value was adjusted to 6.8 by the addition of a small amount of caustic soda solution.
• the peroxide liquor was made up as in Example I.
• the bleaching was carried out in a very similar manner to that described in Example I.
• a batch of linen yarn was scoured in a liquor containing 10 per cent soda ash on the weight of the yarn for 2 hours at 65 C. and thoroughly washed.
• the scoured yarn was then reeled in the hypochlorite liquor for 30 minutes at 15 C., rinsed in cold water, soured in 0.5 per cent HCl for 15 minutes and washed. It was then bleached in the peroxide liquor for 2 hours at 65 (2., washed off and dried.
• the yarn was somewhat better than a half white and had a solubility number 3.7.
• Example III This example is illustrative of the bleaching of linen yarn to the full white stage.
• a batch of yarn was treated precisely as in Example I but was not dried at the finish. Instead it was immersed for 30 minutes in a neutral hypochlorite liquor containing 0.5 gram per litre of available chlorine and 1.5 grams per litre of sodium bicarbonate. The temperature was 15 C. The yarn was then washed and again bleached for 3 hours at 65 C. in a peroxide liquor made up in a similar manner to the previous one but using only half the quantities of peroxide and acid. After washing, another immersion in neutral hypochlorite was given for the same time and at the same temperature, but using a liquor containing only 0.35 gram per litre of available chlorine. Finally the goods are washed, given an antichlor in 0.1 per cent sodium thiosulphate, washed 011 and dried. The full white yarn had a solubility number of 4.
• Example 1V For this example showing the bleaching of hemp, a neutral hypochlorite liquor was made up precisely as in Example I, and of the same strength.
• the peroxide liquor was prepared by diluting strong hydrogen peroxide solution with e. mum-m le a UYUNG; FLUID TREATF:
• Hemp yarn was scoured in a 0.5 per cent solution of caustic soda at 70 C. for three hours and washed. It was then reeled as in the previous examples in the neutral hypochlorite for 30 minutes at 15 C., rinsed, soured and washed in cold water. The bleaching in the peroxide bath was carried out for 3 hours at 65 C. and the yarn washed off and dried. The color was threequarter white and no sprit was observed.
• Example V This example is illustrative of the bleaching of a 50 per cent flax-jute mixture yarn.
• the peroxide solution was made up precisely as in Example IV, and of the same strength.
• the yarn was first scoured in a 1 per cent solution of caustic soda at 60 C. for three hours and washed. It was then reeled in the neutral hypochlorite for thirty minutes at normal temperature, washed, bleached in the peroxide liquor for 2 hours at 65 C., washed ofi and dried.
• Example VI For this example which is illustrative of the bleaching of cloth, the same general methods of preparing the hypochlorite liquors were used as are described in Examples I, III, IV, and V, While the peroxide baths were prepared similarly to those in Examples IV and V.
• the series of operations used were as follows: scoured twice in soda ash solution for 5 hours at 75 C. For the first scour the liquor contained 4.5 per cent soda ash on the weight of the goods, and for the second 3.5 per cent. Washed, treated in a neutral hypochlorite liquor containing 1.5 grams per litre of available chlorine for 4 hours at normal temperature, rinsed, soured in 0.5 per cent HCl and washed. Bleached for 5 hours at 75-80 C. in a peroxide liquor containing 0.1 per cent H202, rinsed, soured and. washed. Treated in neutral hypochlorite containing 0.5 gram per litre of available chlorine for three hours cold, washed, soured and washed. Bleached in peroxide liquor as before, rinsed, soured and washed. Treated in neutral hypochlorite containing 0.3 gram per litre of available chlorine, washed, antichlored, and washed ofi.
• hypochlorite liquors we have used only bleaching powder as the material from which to prepare the hypochlorite liquors. We could have prepared the liquors from other hypochlorites which are commercially available, e. g. high strength calcium hypochlorite, basic calcium hypochlorite and sodium hypochlorite. We could also have used potassium hypochlorite.
• hypochlorite solution we could have used instead of the sodium bicarbonate and phosphate which are illustrated, other salts which have a bufiering action in the range desired, e. g. the corresponding potassium salts.
• salts which have a bufiering action in the range desired, e. g. the corresponding potassium salts.
• the improved process which comprises scouring the linen yarn with dilute aqueous soda ash solution containing 5 to 10 per cent sodium carbonate on the weight of the yarn at about 65 C. for 3 hours, washing the so-scoured yarn, reeling the yarn in a neutral hypochlorite solution having a pH of 6.5 and initially containing 3.5 grams per liter of available chlorine and 3.5 grams of sodium bicarbonate, at 14 C.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Detergent Compositions (AREA)
• Paper (AREA)
• Coloring (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=60016067

Family Applications (2)

Family Applications After (1)

Country Status (4)

Cited By (2)

Families Citing this family (1)

• 1937
  • 1937-01-23 GB GB2088/37A patent/GB489496A/en not_active Expired
  • 1937-06-28 GB GB18007/37A patent/GB499873A/en not_active Expired
• 1938
  • 1938-01-04 US US183396A patent/US2202333A/en not_active Expired - Lifetime
  • 1938-01-21 BE BE425908D patent/BE425908A/fr unknown
  • 1938-01-22 FR FR832397D patent/FR832397A/fr not_active Expired
  • 1938-06-21 US US215062A patent/US2202331A/en not_active Expired - Lifetime
  • 1938-06-28 BE BE428871A patent/BE428871A/fr unknown
  • 1938-06-28 FR FR839914D patent/FR839914A/fr not_active Expired

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