Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01C—CHEMICAL OR BIOLOGICAL TREATMENT OF NATURAL FILAMENTARY OR FIBROUS MATERIAL TO OBTAIN FILAMENTS OR FIBRES FOR SPINNING; CARBONISING RAGS TO RECOVER ANIMAL FIBRES
  • D01C1/00—Treatment of vegetable material
  • D01C1/04—Bacteriological retting

Definitions

• the invention comprises a method for batchwise enzymatic retting of flax or other rettable plants in regard to fibre release.
• flax usually the above group of plants will be referred to in the following as flax, even if it also comprises all other rettable plants, e.g. jute, sisal, hemp and ramie.
• the flax After the cutting of the flax, it is usually dried and then subjected to the retting process, which is actually a rotting of the flax or the first step in the normal decomposition or degumming of flax stalks, whereby the pectic material binding the flax fibres together is dissolved to separate the fibres.
• Retting is usually carried out in the following ways : - "field retting” or “dew retting” - “pool retting” - “tank retting” or “warm water retting” - “enzymatic retting”
• the cut flax is spread in the fields and exposed to dew, rain, etc.
• the time required for complete retting is around 4 to 7 weeks, and also microbiological attack on the flax will impair the strength and colour of the flax fibres. Subsequent bleaching for improving the colour will further impair the strength of the flax fibres.
• the method according to the invention for batchwise enzymatic retting of flax or other rettable plants in regard to fibre release is characterized by the fact that the cut flax or other rettable plant is treated with an SPS-ase preparation producible by means of a strain belonging to the genus Aspergillus, preferably to Aspergillus japonicus or Aspergillus aculeatus, in an aqueous medium until the retting is completed or substantially completed, whereafter, if desired, the retted flax or other rettable plant is decolourized by being exposed to a moderate bleaching procedure only.
• SPS-ase preparation is understood to mean a preparation of SPS-ase, as described and defined in UK patent application No. 2 115 820 A, provided that the SPS-ase preparation is producible by means of a strain belonging to the genus Aspergillus. It has been found that a similar retting time reducing effect does not appear if a similar treatment is carried out with PECTINEX pectinase or CELLUCLAST cellulase and thus, it is assumed that the active principle pertaining to the treatment of the flax fibres with an SPS-ase preparation is the SPS-ase enzyme itself. However, the applicant does not want to be bound to this hypothesis.
• a moderate bleaching procedure we mean a bleaching procedure with a maximum bleaching capability corresponding to sodium perborate in a concentration of 0.3 % weight/volume, at 45°C and pH 9 for 1.5 hours.
• the treatment is carried out in a suitable container or tank, and usually without any significant movement of the flax or the aqueous medium ; however, agitation in the container could be carried out, if wanted.
• US patent No. 1 842 024 describes the retting of fibres of flax and similar plants by means of enzymes capable of degrading ligneous material. However, the use of the SPS-ase in this prior art retting process is not described.
• the method according to the invention offers the following unobvious combination of advantages in comparison to the prior art methods :
• the cut flax is dried before the treatment. In this way a stock of dry flax is provided, thereby facilitating a smooth subsequent batchwise retting procedure.
• the SPS-ase activity in the aqueous medium is between 25 to 350 SPS-ase units/1, preferably between 90 and 250 SPS-ase units/litre.
• the SPS-ase unit (SPSU) is as defined in UK patent application GB 2 115 820 A, page 14, lines 12-14. With an activity below 25 SPS-ase units/l the retting time is not reduced satisfactorily, and with an activity above 350 SPS-ase units/l the retting is uneconomic at the present time.
• the SPS-ase preparation is a liquid preparation with an SPS-ase activity of between 10 and 100 SPS-ase units/g, preferably between 25 and 50 SPS-ase units/g.
• a liquid preparation is easily distributed in the aqueous medium, and thus the retting process starts immediately after addition of the liquid SPS-ase preparation.
• the activity interval indicated is convenient for application on an industrial scale, as a volume of the SPS-ase preparation has to be added which is small enough for easy handling and large enough for accurate dosage.
• a biocide is added to the aqueous medium in a bacteriocidal amount. In this way the reproducibility of the process is improved.
• an antifoam agent is added in an amount sufficient for foam prevention. In this way a smooth retting process is secured.
• the pH value is not adjusted artificially. This embodiment is simple and yet effective.
• the initial pH value is adjusted to a value between 3.5 and 6.5, preferably between 4.5 and 5.5 In this way an initial pH is secured, at which the SPS-ase exhibits its maximum activity.
• the temperature is not adjusted artificially. This embodiment is simple and yet efficient.
• the initial temperature is adjusted to a value between 15 and 45°C, preferably to around 40°C. In this way an initial temperature is secured, at which the SPS-ase exhibits both a satisfactory activity and a good stability.
• the container in which the retting is carried out is preferably closed in order to keep the temperature from dropping.
• the aqueous medium contains a pectolytic enzyme besides the SPS-ase preparation.
• a pectolytic enzyme besides the SPS-ase preparation.
• the combination of SPS-ase and a pectolytic enzyme gives rise to an improved retting efficiency.
• the weight proportion between flax (dry matter) and aqueous medium is between 1:5 and 1:15, preferably around 1:10. With a proportion of more than 1:5 it has been found that it is difficult to provide a sufficient soaking of the flax, and with a proportion of less than 1:15 it has been found that the process is too costly due to an enzyme consumption which is too large.
• the aqueous medium is separated and used for retting of another batch of unretted flax after completion or substantial completion of the retting.
• the economy of the process is improved tremendously, and it has been found that the stability of the SPS-ase is sufficient for satisfactory reuse at least around 10-15 times under normal conditions.
• a certain amount of SPS-ase solution is removed with the batch of retted flax, a minor amount of SPS-ase solution has to be added each time another batch of unretted flax is to be treated for replenishing purposes.
• a docolourisation is carried out by exposing the retted flax fibre or other rettable plant fibre to a moderate bleaching procedure only. In this manner a fibre with an especially good combination of satisfactory appearance and fibre strength is obtained.
• the decolourisation is carried out by immersing the fibre in a solution of 0.5-2.5 % by weight of citric acid or acetic acid and 1-5 % by weight of sodium carbonate or sodium hydroxide at 40-60°C for 0.5-2 hours, whereafter the fibre is washed 1-3 times in hot water at 50-60°C.
• a cheap and yet effective decolourisation is obtained.
• the decolourisation is carried out by immersing the fibre in a solution containing 0.3-1.5 % by weight of sodium perborate, 0.1-0.5 % by weight of sodium tripolyphosphate and 0.05-0.25 % by weight of an anionic surfactant, preferably sodium alkyl ether sulphate, 3EO for 20-60 minutes at 40-50°C, whereafter the fibre is washed 1-3 times in hot water at 50-60°C.
• an anionic surfactant preferably sodium alkyl ether sulphate, 3EO
• Retting was performed at 40°C for 24 hours using 50 g flax and a flax to enzyme solution ratio of 1:10.
• This example illustrates a most simple enzymatic flax retting method on pilot plant scale.
• the restored volume of 2800 litres is pumped over a new batch of flax (placed for retting in a neighbouring tank), and again the retting process is continued at 40°C for another 24 hours. This is repeated six times.
• the example illustrates the combination of enzymatic stepping of the flax followed by a decolourisation of the extracted fibre.
• the retting procedure is carried out exactly the same as in example 1, except that the enzyme dose used was 5 g/l of SP 249, no biocide was added and the treatment period used was 16-19 hours.
• 10 g of fibre is added to 200 ml of a solution containing 0.6 % by weight sodium perborate, 0.2 % by weight sodium tripolyphosphate and 0.1 % sodium alkyl ether sulphate, 3EO at 45°C for 30 minutes.
• the fibre is then washed twice with hot water at 50-60°C.
• the fibre is then immersed in 200 ml of a solution of sodium perborate, sodium tripolyphosphate and sodium alkyl ether sulphate, 3EO as described in procedure B.
• the decolourised fibre is washed twice with hot water (50-60°C) and then dried.
• This example illustrates the combination of enzymatic steeping of the flax followed by after-retting in a moist tank or chamber, on a laboratory scale. It is intended that the term "after-retting” is referring to the retting effect produced by the enzyme absorbed by the plant tissues. The process is performed without any further water supply in a moist tank or chamber at 40° to 45°C.
• the flax straw in the second tank is then allowed to ret for 16 hours and then the enzyme solution is transferred back to the first tank which has been filled with fresh flax straw.
• the retted flax from the second tank is then dried and extracted in the normal manner. This double cycle is repeated 10 times.
• this example illustrates the combination of enzymatic steeping of flax followed by squeezing of the retted flax between rollers, on a laboratory scale.
• the recovered enzyme solution may be added back to the enzyme solution remaining in the retting apparatus and the above procedure may be repeated 10 times, under normal laboratory conditions.
• evacuation of the retting tank e.g. at 1/5 of the atmospheric pressure can be carried out, thus providing maximal exploitation of the enzymatic activity combined with after-retting in a special moist tank or chamber at 40°C.
• a suitable vacuum pump for example a good Leybold pump
• the preheated (40°C) retting tank is first filled with flax. Thereafter, the preheated (42°C) enzyme solution prepared in a heated (45°C) neighbouring container is pumped into the retting tank until all flax is submerged by the enzyme solution. Subsequently, the latter tank is covered with a hood, whereafter a vacuum is applied by means of the vacuum pump.

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• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
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• Coloring Foods And Improving Nutritive Qualities (AREA)

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Cited By (5)

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• 1985
  • 1985-10-21 DK DK481385A patent/DK481385D0/da not_active Application Discontinuation
• 1986
  • 1986-10-16 PH PH34374A patent/PH24092A/en unknown
  • 1986-10-20 EP EP86308136A patent/EP0220913A3/fr not_active Withdrawn
  • 1986-10-20 CN CN 86106605 patent/CN1007361B/zh not_active Expired

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