Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1997-06-03
1999-05-11
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
2642091, 2642101, 2642108, 26421113, 26421114, 264237, B29C47/88
Patent
active
059025328
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for manufacturing cellulose formed objects, whereby a solution of cellulose is formed in the warm state in a tertiary amine N-oxide and, if necessary, water and the formed solution is cooled with air before introducing it into a coagulation bath, as well as a yarn of cellulose filaments.
2. Description of the Related Art
Such a process is described in WO 93/19230, whereby the cooling is to take place immediately after the forming. The object of this process is to reduce the stickiness of the freshly extruded formed objects so that a spinneret with a high hole density can be employed for manufacturing cellulose filaments. For cooling, the formed solution is preferably exposed to a gas stream.
A cooling of the warm formed solution already takes place as the formed solution leaves the forming tool, for instance a spinneret, in which temperatures are typically above 90.degree. C., and reaches into the so-called air gap. The area between the forming tool and the coagulation bath in which the cellulose is precipitated is referred to as the air gap. The temperature in the air gap is lower than in the spinneret, but it is significantly higher than the room temperature due to the heat radiation from the spinneret and the warm-up of the air due to the enthalpy flow of the formed objects. Due to the continuous evaporation of water which is usually used as a coagulation bath, humid warm conditions prevail in the air gap. The measure proposed in WO 93/19230, that is to cool the formed solution immediately after the forming, results in a more rapid cooling so that the stickiness of the formed solution decreases more rapidly as a result.
SUMMARY OF THE INVENTION
The present invention is based on the objective to improve such a process, and in particular to improve the properties of the formed objects produced herewith, preferably filaments or a filament yarn.
This objective is met by a process for manufacturing cellulose formed objects whereby a solution of cellulose is formed in the warm state in a tertiary amine N-oxide and, if necessary, water and the formed solution is cooled with air before introducing it into a coagulation bath, whereby conditioned air is employed for cooling which exhibits a water content of 0.1 to 7 g water vapor per kg dry air and whose relative humidity amounts to less than 85%.
The water content of the conditioned air is preferably 0.7 to 4 g water vapor per kg dry air, and more particularly 0.7 to 2 g. The cooling can be carried out by streaming air, whereby this air is blown against the formed solution or drawn away from it. The drawing away can be carried out in such way that conditioned air is provided and is drawn through e.g. a bundle of freshly spun fibers or filaments. A combination of blowing and drawing away is especially advantageous.
The formed solution can be exposed to the conditioned air throughout the entire pathway up to the point of introduction into the coagulation bath, or only over a portion of this pathway, whereby it is advantageous to carry out the application of air in the first part, i.e. in the area of the air gap which is immediately adjacent to the forming tool. The conditioned air should flow at an angle of 0 to 120.degree., preferably 90.degree., in relation to the direction of movement of the formed solution, whereby the angle of 0.degree. corresponds to a flow opposite to the running direction of the formed solution.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With the process of the invention, fibers, in particular filaments, films, hollow filaments, membranes, e.g. for applications in dialysis, oxygenation or filtration, can be manufactured in an advantageous fashion. The forming of the solution to a desired cellulose formed object can be carried out by known spinnerets for manufacturing fibers, slit nozzles or hollow filament nozzles. Subsequent to the forming, i.e. prior to the introduction of the formed solution into the coagulation bath, the formed solution c
REFERENCES:
patent: 4144080 (1979-03-01), McCorsely, III
patent: 4416698 (1983-11-01), McCorsely, III
patent: 5252284 (1993-10-01), Jurkovic et al.
patent: 5543101 (1996-08-01), Ruf et al.
patent: 5589125 (1996-12-01), Zikeli et al.
German Search Report, P 44 42 890.1-44, Jan. 9, 1995.
Derwent--Abstract 94-290987/36 of Japanese Patent Application 06220213 (Published Aug. 9, 1994).
Derwent--Abstract 89-266892/37 of Japanese Patent Application 01193338 (Published Aug. 3, 1989).
Akzo Nobel nv
Tentoni Leo B.
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