Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1994-05-09
1995-08-15
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
210670, 210681, 210683, 210687, 210688, 264187, 521 26, B01D 1504, D01F 200, D01F 1302
Patent
active
054416892
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improved methods of purifying aqueous solutions of tertiary amine N-oxides, particularly spinning baths used in the manufacture of regenerated cellulose fibres and films.
Cellulose can be dissolved in certain tertiary amine N-oxides (hereinafter also referred to as amine oxides) to form a solution. Examples of such amine oxides include dimethylbenzylamine N-oxide, dimethylethanolamine N-oxide, dimethylcyclohexylamine N-oxide, and particularly N-methylmorpholine N-oxide (NMMO). The solutions so formed can be extruded through a die into an aqueous spinning bath to form regenerated cellulose articles in the form of fibres or films, depending on the shape of the die. Such processes are described in U.S. Pat. Nos. 3,447,939, 3,508,941 and 4,246,221, the contents of which are incorporated herein by way of reference.
The used or spent spinning bath must be purified and concentrated in order to recover and re-use the amine oxide it contains. If purification is not carried out, the recovered amine oxide and hence cellulose solutions made using it become progressively more discoloured as soluble coloured impurities accumulate in the system. Consequently, regenerated cellulose articles will be produced which are discoloured and thus of poor quality. Woodpulp used as a commercial source of cellulose contains a low level of non-cellulosic coloured impurities. Coloured impurities are also formed by degradation of organic compounds during the handling of solutions of cellulose in amine oxides at elevated temperatures.
The use of ion-exchange resins for colour removal from aqueous sugar juices is known, and is described for example in an article entitled "Ion Exchangers" in Ullmann's Encyclopaedia of Industrial Chemistry, fifth edition, Volume A14 (VCH Publishers, 1989) at page 393. The preferred resins are strongly basic resins used in the chloride form, which contain quaternary ammonium groups --CH.sub.2 N(CH.sub.3).sub.3.sup.+ Cl.sup.-, preferably the highly porous types of resin referred to as macroporous resins.
U.S. Pat No. 4,193,817 describes a process for the production of bottler's liquid brown sugar which involves passing remelted brown sugar over a strongly basic anion-exchange resin in the chloride form. The resin may be regenerated by treatment with an aqueous solution of hydrochloric acid, containing for example 3.5% w/w HCl, followed by treatment with an aqueous solution of sodium chloride and sodium hydroxide, containing for example 10% NaCl and 1% NaOH.
DD-A-254199 describes the purification of aqueous solutions of N-methylmorpholine N-oxide, especially those produced during the regeneration of polymers in the synthetic fibre and plastics industry. The solutions are passed through a column containing two separate styrene-divinylbenzene copolymer anion-exchange resins in successive stages. The resin used in the first stage is a weak anion-exchange resin carrying amino groups --CH.sub.2 N(CH.sub.3).sub.3 and that used in the second stage is a strong anion-exchange resin carrying quaternary ammonium groups --CH.sub.2 [N(CH.sub.3).sub.3 ].sup.+ OH.sup.-. The solution being purified, initially dark brown, is reported to be light brown or yellow after the first stage of treatment and to be light yellow or colourless after the second stage of treatment. The resins are activated by treatment with 3% w/w aqueous sodium hydroxide and are regenerated by treatment with an aqueous solution containing 3% w/w sodium hydroxide and 10% w/w sodium chloride.
EP-A-427701 describes the purification of aqueous solutions of N-methylmorpholine N-oxide, especially spinning bath solutions obtained during the manufacture of cellulosic products, by passage over an anion-exchange resin. The resin contains exclusively --CH.sub.2 N.sup.+ (CH.sub.3).sub.3 X.sup.- or --CH.sub.2 N.sup.+ [(CH.sub.3).sub.2 (CH.sub.2 OH)]X.sup.- groups, where X.sup.- is the anion of an inorganic or organic acid. The solution to be purified contains coloured degradation products of polyhydric phenols and their complexes with i
REFERENCES:
English Translation of Japan 2-298,358 (Published Dec. 10, 1990).
Abstract of Japan 61-42,336 (Published Feb. 28, 1986).
Abstract of Japan 62-121,650 (Published Jun. 2, 1987).
Courtaulds PLC
Tentoni Leo B.
LandOfFree
Process of making regenerated cellulose articles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process of making regenerated cellulose articles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of making regenerated cellulose articles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2179844