Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-04-01
2002-02-12
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C428S395000
Reexamination Certificate
active
06345654
ABSTRACT:
BACKGROUND OF THE INVENTION
European patent application EP 80 906 describes a process for the production of polyester filament yarn for technical applications by melt-spinning a polyester-containing polymer in which all process elements are covered in a single process pass. Such a process is also known as a one-step process. It is indicated in this publication that in such a process it is preferred to select a winding speed of less than 5500 m/min, since higher winding speeds will give rise to filamentation and difficulty in operation.
However, an increase in the winding speed is desired. When manufacturing polyester filament yarn for technical applications on an industrial scale, it is advantageous to produce the largest possible quantity of yarn per unit of time on an appropriate apparatus. One of the ways of increasing the quantity of yarn produced per unit of time lies in a higher winding speed.
U.S. Pat. No. 4,491,657 also discloses the process mentioned in the opening paragraph. This patent specification states that the winding speed of the yarn in such a one-step process is not less than 6.5 km/min. However, there are no examples in this patent specification of polyester filament yarns for technical applications made by such a one-step process at such a winding speed, nor is there any teaching on how to solve the problems which were found to occur when making polyester filament yarns for technical applications at such winding speeds.
Patent application WO 90/00638 indicates that in a one-step spinning process an increase in the spinning speed goes hand in hand with increased crystallinity of the as yet undrawn filaments. Yarn wound at a speed of about 4800 m/min can be obtained from undrawn filaments having a crystallinity in the range of 13 to 18%.
SUMMARY OF THE INVENTION
The invention pertains to a process which makes it possible to manufacture polyester filament yarn for technical applications at high winding speeds without the aforementioned problems occurring. The term winding speed in this context is defined as the peripheral velocity of the package being wound.
DETAILED DESCRIPTION OF THE INVENTION
The invention pertains to a process for manufacturing polyester filament yarn for technical applications by spinning a polymer over 90% of the chains of which are composed of ethylene terephthalate units, with the spinning process having the following elements:
extruding the polymer in the molten state through a spinneret plate,
passing the thus formed filaments through a heated zone and a cooling zone in that order,
fixing the filament speed,
drawing the filaments to a length of 1.5 to 3.5 times their original length, and
winding the resulting filament yarn,
with all elements being covered in a single process pass.
The invention consists in that when manufacturing polyester filament yarn for technical applications in the manner described in the above paragraph,
the filaments prior to being drawn have a crystallinity smaller than 16% and
the winding speed of the yarn is larger than 6000 m/min.
Surprisingly, it has proved possible to make polyester yarn for technical applications using a higher winding speed than the one commonly used so far when manufacturing such a yarn. The process conditions selected should be such that at a yarn winding speed above 6000 m/min, the crystallinity of the undrawn filaments is smaller than 16%.
It was found that if at such winding speeds the undrawn filaments have a crystallinity in excess of 16%, the result will be an unstable spinning process with a great deal of filamentation in the drawn yarn or a process which does not result in a yarn with advantageous use properties. The crystallinity of the undrawn filaments can, e.g., be affected by: the polymer viscosity, the spinning temperature, the length of the heated zone, the temperature in the heated zone, the degree of cooling in the cooling zone, and the mass per unit length (linear density) of the filaments.
It is preferred, when making polyester filament yarn for technical applications according to the invention, to employ polyester polymer at least 90% of the polymer chains of which are composed of ethylene terephthalate units and which has a relative viscosity (&eegr;
rel
) of 2.04 to 2.60, preferably of 2.04 to 2.42, more in particular of 2.15 to 2.35. All other process conditions remaining unchanged, a lower relative viscosity of the polymer will generally lead to a lower crystallinity of the undrawn filaments.
It is preferred, when making polyester filament yarn with advantageous use properties according to the invention, to employ polyester polymer with a DEG (diethylene glycol) content of less than 2.5 wt. %, especially of less than 1 wt. %, more particularly of less than 0.8 wt. %. This can be achieved, e.g., by using dimethyl terephthalate as one of the constituents in the polymerisation reaction. All other process conditions remaining unchanged, a reduction of the DEG content in the polymer will generally lead to an increase in the crystallinity of the undrawn filaments. Further, the polymerisation reaction is preferably carried out such that the polymer obtained will have a low carboxyl end groups content. In the polymer to be spun this content preferably is less than 15, more particularly less than 10, milli-equivalents/kg. Such can be achieved, e.g., by performing the polymerisation reaction under mild conditions. For the stability of the spinning process it is preferred that the polymer contain as few impurities, such as dust and other minute particles, as possible. Alternatively, adjuvants such as titanium dioxide may be added to the polymer to improve the spinning behaviour. Furthermore, it is preferred for the polymer to be as completely anhydrous as possible. The polymer preferably contains less than 40 ppm, more particularly less than 20 ppm, of water.
The polymer is fed to a spinneret plate in the molten state, e.g., by means of an extruder. To this end small pieces of polymer (so-called polymer chips) can be charged to an extruder, the temperature in the extruder causing the chips to melt. The extruder feeds a spinning pump, which conveys the most constant polymer stream possible to a spinneret plate. The spinneret plate is heated to a temperature in the range of T
m
to T
m
+100° C., with T
m
representing the melting temperature of the polymer, preferably to a temperature in the range of T
m
+20° C. to T
m
+70° C. All other process conditions remaining unchanged, an increase in the spinning temperature will generally lead to a reduction of the crystallinity of the undrawn filaments.
Preferably, a single spinneret plate is employed to spin the total number of filaments of one bundle. The spinneret plate preferably has 100 to 1000 spinning orifices, more particularly 200 to 400 spinning orifices. All other process conditions (such as the total polymer throughput through all the spinning orifices) remaining unchanged, reducing the number of spinning orifices will generally lead to a reduction of the crystallinity of the undrawn filaments.
If so desired, additional members can be placed between the extruder, the spinning pump, and the spinneret plate, such as filters to clear the polymer stream of minute particles, static or dynamic mixers to homogenise the polymer stream, or heat exchangers to adjust the temperature of the polymer stream.
To minimise the differences among the filaments in the bundle as much as possible, it is preferred that the spinning orifices be distributed over the spinneret plate in a regular pattern. The capillary inlet opening may be variously shaped, e.g., conically, like a trumpet, or in some other shape known to the skilled person, to facilitate the polymer inflow. The capillary outlet opening preferably is cylindrical, the length/diameter ratio (L/D ratio) being 0.5 to 5, more particularly 1 to 3. Alternatively, the capillary's shape may be such as will exert a positive, constant elongation of flow on the polymer stream. The throughput per spinning orifice is dependent on the desired filament count of the drawn fi
Feijen Henricus Hubertus Wilhelmus
Hofs Hendrikus Wilhelmus Jacobus
Kiefer Heinrich Johannes Gustav
van den Heuvel Christiaan Jurriaan Maria
van den Tweel Michael Henricus Jacobus
Akzo Nobel NV
Johnstone Adrienne C.
Oliff & Berridg,e PLC
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