Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P5/00—Other features in dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form
  • D06P5/02—After-treatment
  • D06P5/04—After-treatment with organic compounds
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P1/00—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed
  • D06P1/44—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed using insoluble pigments or auxiliary substances, e.g. binders
  • D06P1/653—Nitrogen-free carboxylic acids or their salts
  • D06P1/6533—Aliphatic, araliphatic or cycloaliphatic
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P3/00—Special processes of dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form, classified according to the material treated
  • D06P3/34—Material containing ester groups
  • D06P3/52—Polyesters
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P3/00—Special processes of dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form, classified according to the material treated
  • D06P3/34—Material containing ester groups
  • D06P3/52—Polyesters
  • D06P3/54—Polyesters using dispersed dyestuffs

Definitions

• the present invention relates to a process to remove excess dye from dyed polyester fabric.
• a weak organic acid such as ascorbic acid or citric acid, to remove the excess dye.
• Polyester fabric is typically dyed using disperse dyes.
• Disperse dyes are ready made dyes that do not have any ionic character and as such they are insoluble or only poorly soluble in water under ambient conditions. Such dyes are utilised in the dyeing process by dispersing them in acidified water at elevated temperatures, e.g. 80°C to 100°C, or at both elevated temperature and pressure, e.g. 105°C to 140°C and 1.1 to 3.6 bar. Such conditions result in the dye diffusing into the plasticized polyester fibres to form a molecular dispersion in the polymer matrix.
• Dispersing agents and carrier chemicals are commonly used in the dyeing of polyester fabric. Dispersing agents are needed to keep the bulk of the poorly soluble disperse dye in an homogeneous state throughout the dyebath liquor. Such dispersing agents are typically strong surfactants such as alkylsulphonates and alkylarylsulphonates. Carrier chemicals are substances that are designed to swell the fibres and help facilitate the diffusion of the disperse dye into the fabric. Typical carrier chemicals that may be used are based on glycol ethers. [0006] Once sufficient colour strength has been achieved on the fabric it is necessary to remove excess dye.
• Reduction clearing usually uses a strong reducing agent at a high temperature and pH to remove excess dye.
• the most commonly used reagent in reduction clearing is sodium dithionite in the presence of sodium hydroxide. This reagent has several disadvantages, not least its reactivity which leads to complications in handling. It is unstable in non-alkaline conditions where decomposition will occur, even resulting in spontaneous combustion.
• Another disadvantage of using sodium dithionite is that it acts as a sulphonating agent that can act on any residual surfactants remaining in the fabric. This can result in any residual surfactants becoming persistent.
• Use of such sulphur containing compounds also suffers from the disadvantage that as the compounds are not readily biodegradable the waste water from the process needs to be extensively treated before it can be returned to
• US patent No. 6 730 132 discloses a process for reduction clearing of polyester textiles that comprises adding to the acidic dyeing liquor or wash bath an after-treatment composition comprising dithionite/acid acceptor sulphinate optionally mixed with sulphonate.
• a process to remove excess dye from dyed polyester fabric comprising adding a solution of a weak organic acid or a salt thereof to the fabric in a dyeing vessel, raising the temperature and allowing the acid or salt thereof to remain in contact with the fabric for a period of time, followed by removal of all liquid.
• the weak organic acid is a Bronsted acid that contains at least 4 carbon atoms, and which has a pK a or pK a i value of at least 1, and preferably a pK a or pK a i value of less than 5.
• a preferred pK a or pK a i range is from 3 to 4.5.
• the pK a i value refers to the first dissociated proton for multiprotonic acids. Examples of such acids include ascorbic acid, citric acid, caprylic acid, adipic acid, succinic acid, maleic acid and butyric acid. Preferred examples are ascorbic acid and citric acid.
• Salts of the weak organic acid can also be used. Examples of salts include those having monovalent cations, such as alkali metal salts. Preferred salts are sodium or potassium salts. Ascorbic acid or a salt thereof is most preferred.
• One or more weak organic acids and/or salts thereof can be used.
• the temperature in the vessel is preferably raised to a value in the range of from 60 °C to 100 °C, most preferably from 75 °C to 80 °C or at least 80°C.
• the weak organic acid is preferably maintained in contact with the fabric for at least 6 minutes to allow it to react with the dyed fabric. Preferably, the contact time is up to 60 minutes.
• the dyeing liquor is removed from the dyeing vessel prior to adding the weak organic acid.
• the dry dyed fabric may be loaded into a dye bath or suitable vessel to which may be added water and an appropriate amount of the weak organic acid.
• the organic acid is added at a rate of 80g to 120g per litre, if for example the dyeing liquor is not removed before the organic acid is added. Alternatively, if the dyeing liquor is removed before adding the organic acid 2g to 50g per litre, preferably 2g to lOg, most preferably 5g per litre of the acid are used.
• the polyester fabric is preferably rinsed with water at ambient temperature, after which it is spun and dried.
• a weak organic acid, or a salt thereof that is still acidic is utilised as the reduction clearing agent.
• this has the advantage that it is not necessary to change the pH between the dyeing stage, which is typically carried out at a low pH, and the reduction clearing stage.
• the dyed polyester fabric is to be subsequently treated, for example to render it water-repellent, then, following the reduction clearing treatment using a weak organic acid, the pH is raised to between pH 9 and pH 12.
• an alkaline hydroxide such as sodium hydroxide potassium hydroxide or ammonium hydroxide at a rate of from 1.4 g to 1.7 g per litre.
• One advantage of the process of the present invention is that it avoids the need to use sulphur containing compounds, such as sodium dithionite, that act as sulphonating agents which can act on residual surfactants remaining in the fabric making the surfactants more persistent. This persistence causes problems in later textile finishing processes such as the application of water-repellent treatments to the polyester fabric.
• sulphur containing compounds such as sodium dithionite
• Other advantages of using a weak organic acid in the reduction clearing process are that the process is safer to operate, less polluting of the environment as well as being cheaper to operate.
• a dye bath was prepared to the following composition by subsequently adding, whilst under continual mixing, the components below:-
• the temperature of the bath was slowly raised at a rate of approximately 1 °C/minute to 95 °C.
• the pH of the dye bath was adjusted to between 4.0 and 5.0 with the addition of acetic acid (80% Technical grade) - 25 g (5 g/litre).
• a 500 g sample of un-dyed polyester microfibre fabric with a weight of 215 g/m 2 was added to the dye bath. With continual mixing, the dye bath was heated to the boil and maintained at a steady temperature for a period of 90 minutes. During this time, the pH of the dye bath was maintained by the addition of further doses of acetic acid at the rate of 5g every 15 minutes, if necessary.
• the dye bath was allowed to cool to a temperature of 60 °C before the liquid contents of the dyeing vessel were drained.
• the fabric was then washed in the dyeing vessel with three separate washes of Tergitol 15-S-7 (10 g in 5 litres of deionised water at 60 °C for two minutes).
• the dyeing vessel was then refilled with water (5 litres of deionised water at 60 °C) and sodium hydroxide was added (20 g, 4 g/litre). The temperature of the dyeing vessel contents was then raised to 80 °C and the following was added in the prescribed order:-
• the temperature of the dyeing vessel contents were maintained at 80 °C for a further 25 minutes.
• the dyeing vessel was then drained of the liquid contents.
• the fabric was then rinsed using five separate charges of water (5 litres of deionised water at 20°C for two minutes). In the final rinse, the pH of the dye was lowered to between 6.0 and 7.0 with the addition of acetic acid (80% Technical grade).
• the dyeing vessel was then drained of the liquid contents and the dyed fabric was recovered and air dried.
• the fabric was loaded into a Fong's Minitec3-1T high temperature dyeing machine.
• the service tank of the machine was charged with the following components in the prescribed order :- water (20 °C, deionised) - 150 litres sodium hydroxide - 400 g ascorbic acid - 750 g

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Coloring (AREA)
• Cleaning By Liquid Or Steam (AREA)

Priority Applications (10)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (16)

Cited By (1)

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Citations (3)

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• 2016
  • 2016-01-04 GB GBGB1600098.6A patent/GB201600098D0/en not_active Ceased
  • 2016-12-28 TW TW105143602A patent/TWI738699B/zh not_active IP Right Cessation
• 2017
  • 2017-01-03 AR ARP170100009A patent/AR107286A1/es active IP Right Grant
  • 2017-01-04 PL PL17700613T patent/PL3390711T3/pl unknown
  • 2017-01-04 EP EP17700613.7A patent/EP3390711B1/en active Active
  • 2017-01-04 WO PCT/EP2017/050163 patent/WO2017118671A1/en not_active Ceased
  • 2017-01-04 JP JP2018553315A patent/JP6773805B2/ja not_active Expired - Fee Related
  • 2017-01-04 CN CN201780014202.3A patent/CN108779602B/zh active Active
  • 2017-01-04 KR KR1020187021098A patent/KR20180098595A/ko not_active Abandoned
  • 2017-01-04 CA CA3010538A patent/CA3010538C/en active Active
  • 2017-01-04 PT PT17700613T patent/PT3390711T/pt unknown
  • 2017-01-04 US US16/068,126 patent/US10533279B2/en active Active
  • 2017-01-04 ES ES17700613T patent/ES2742131T3/es active Active
  • 2017-01-04 BR BR112018013726-0A patent/BR112018013726B1/pt not_active IP Right Cessation
• 2018
  • 2018-07-04 CL CL2018001831A patent/CL2018001831A1/es unknown
  • 2018-07-04 CO CONC2018/0006994A patent/CO2018006994A2/es unknown

Patent Citations (3)

Non-Patent Citations (1)

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