Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1993-11-16
1996-12-31
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
26421113, 26421114, 26421116, 26421119, 264237, 425 722, 4253782, 4253822, 425464, D01F 224
Patent
active
055891250
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for the preparation of cellulose mouldings in which a solution of cellulose in a tertiary amine-oxide is moulded in a hot state and the moulded solution is introduced into a precipitation bath in order to precipitate the contained cellulose, as well as a device for carrying out the process.
It is known from U.S. Pat. No. 2,179,181 that tertiary amine-oxides are capable of dissolving cellulose and that cellulose mouldings can be obtained from these solutions by precipitation. A process for the preparation of such solutions is known for example from EP-A 0 356 419. According to this publication, a suspension of cellulose is firstly prepared in aqueous tertiary amine-oxide. The amine-oxide contains up to 40 weight% water. The aqueous cellulose suspension is heated and water is removed under reduced pressure until the cellulose goes into solution. The process is carried out in a specially-developed stirring device which can be evacuated.
A process of the type described at the start is known from DE-A 2 844 163 and from DD-A 218 121. In order to prepare cellulose fibres or cellulose films, an air space or an air gap is arranged between the spinneret and the precipitation bath in order to achieve drawing at the die. This drawing is necessary because drawing the fibre becomes very difficult after the moulded spinning solution makes contact with the aqueous precipitation bath. The fibre structure produced in the air gap is fixed in the precipitation bath.
In the air gap however the danger exists that the individual fibres which are not yet coagulated will stick to one another or will fuse together because of their extremely high stickiness, thus making the spinning of fibres impossible. In the nature of things, this danger of sticking together is all the greater, the longer is the gap between the die plate and the surface of the precipitation bath (the air space). On the other hand, a long gap would be advantageous because a certain time is necessary for orientation of the cellulose molecules. In order to minimise this danger of sticking together when using large air gaps, the hole density in the spinneret must be reduced which in turn has an adverse effect on the economics of the spinning process.
Whilst the use of a short air gap does allow spinning using a high hole density, it also impairs the reliability of the spinning process since due to the capillary action of the filaments, liquid from the precipitation bath gets onto the exit side of the spinning bores or spinning holes. The result is that the fibre material, which is moulded but still fluid, does not undergo drawing, ie, the desired fibre thickness is not achieved. At the same time it can be shown that the textile values relating to the strength and to the elongation of the fibres are scarcely affected by the shortened dwell time in the air gap.
It is stipulated in DD-A 218 121 that shortening the length of the drawing gap at the die, with its associated reduction in the danger of individual fibres sticking together, can be achieved without any effect on the reliability of spinning or on the fibre strength by the addition to the spinning solution of a polyalkylene ether, especially polyethylene glycol. Reference is also made in DE-A 2 844 163 to the extreme stickiness of the spun fibres and to overcoming this problem, wherein among other things spraying the fibres in the air gap with a liquid which does not dissolve cellulose is proposed.
Tests have shown that not all the proposed solutions are satisfactory in respect of either the achievable spinning-fibre density or the effect on the textile properties of the cellulose fibres. According to DE-A 2 844 163, the distance between the spinneret and the surface of the precipitation bath amounted to 270 mm, but this apparently only allowed a spinning-fibre density of about 0.0046 fibres/mm.sup.2 (corresponding to a spinning-hole density in the spinneret of 0.0046 holes/mm.sup.2). Spinning on a large scale using such a small hole density is unthinkable. To do this, spinnerets
REFERENCES:
patent: 2179181 (1939-11-01), Graenacher
patent: 2284028 (1942-05-01), Ubbelohde
patent: 3118012 (1964-01-01), Kilian
patent: 3299469 (1967-01-01), Charlton
patent: 3824050 (1974-07-01), Balk
patent: 3858386 (1975-01-01), Stofan
patent: 3969462 (1976-07-01), Stofan
patent: 3996321 (1976-12-01), Weinberger
patent: 4038357 (1977-07-01), Boyes et al.
patent: 4078034 (1978-03-01), Lewis
patent: 4144080 (1979-03-01), McCorsley, III
patent: 4261943 (1981-04-01), McCorsley, III
patent: 4285646 (1981-08-01), Waite
patent: 4340559 (1982-07-01), Yang
patent: 4440711 (1984-04-01), Kwon et al.
patent: 4713290 (1987-12-01), Kwon et al.
patent: 4836507 (1989-06-01), Yang
patent: 5252284 (1993-10-01), Jurkovic et al.
English language abstract of EP 40 482.
English language abstract of EP 50 483.
English language abstract of EP 105 169.
English language abstract of EP 442 405.
English language abstract of JP 57-16113 (Published Mar. 1981).
English language abstract of DE 28 30 685 (Published Dec. 1980).
English language abstract of DE 37 08 168 (Published Sep. 1988).
English language abstract of DD 218 121 (Published Jan. 1985).
Zachara, A., "How To Estimate The Flow Characteristics In Multifilament Spinning", Part II, Fiber World, Jul. 1987, pp. 52-60.
English language abstract of Austrian application AT 2724/89 (Published Nov. 29, 1989).
Ecker Friedrich
Jurkovic Raimund
Koberger Hermann
Rauch Ernst
Ruf Hartmut
Lenzing Aktiengesellschaft
Tentoni Leo B.
LandOfFree
Process of and apparatus for making cellulose mouldings 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 and apparatus for making cellulose mouldings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of and apparatus for making cellulose mouldings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1139769