Process of making a yarn

Details Process of making a yarn Process of making a yarn

2001-05-22

2003-06-24

Tentoni, Leo B. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

With twining, plying, braiding, or textile fabric formation

C264S17800F, C264S210600, C264S210700, C264S210800, C264S211120, C264S211140, C264S211170

Reexamination Certificate

active

06582634

ABSTRACT:

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
The present invention concerns an improved method for making a plastics material yarn, particularly, but not exclusively, a dental floss.
Methods and materials used for the manufacture of dental floss are known to give reasonable results. However, there is a desire to improve the methods for manufacturing the floss and to find materials that will provide the desired properties in the floss.
SUMMARY OF THE INVENTION
According to one aspect of this invention there is provided a method of converting a plastics material into a yarn, comprising heating the plastics material to melt it, passing melted material through an extrusion die to form an extruded filament, and thereafter cooling the filament, wherein the plastics material is selected from the group comprising nylon, polyesters, polyethylene, polyvinyl chloride, polyphenylene sulphite, polystyrene.
The method may further include the step of passing the extruded filament through a draw roller assembly while elevating the temperature of the filament. The filament may be heated after exiting from the draw roller assembly.
The method may further include the step of passing the extruded filament through a plurality of draw roller assemblies whereby the temperature of the filament is elevated at least one of the assemblies. The filament may be heated after exiting from at least one of the draw roller assemblies.
According to another aspect of the present invention there is provided a method of converting a plastics material into a yarn the plastics material being selected from the group comprising nylon, polyesters, polyethylene, polyvinyl chloride, polyphenylene sulphide, polystyrene, the method comprising heating the material to melt it, pumping melted material through an extrusion die to form an extruded filament, cooling the extruded filament, passing the extruded filament through a first draw roller assembly while elevating the temperature of the filament, heating the filament in a heating zone as it exits from the first draw roller assembly and, thereafter, passing the filament through a second draw roller assembly operating at a different linear speed than the first draw roller assembly and spooling the filament exiting the second draw roller assembly.
Means may be included for pumping the material through the extrusion die. The pumping means may be a metering pump which may operate in the region of substantially 3 to substantially 18 rpm. preferably substantially 3 to substantially 5 rpm. In one embodiment, the metering pump may operate at substantial 7 to substantially 6 rpm. In another embodiment, the pump may operate at substantially 7 rpm. In a third embodiment the pump may operate at substantially 5 to substantially 4 rpm.
The plastics material may include Silica. Preferably, the silica is added in the form of particles. Preferably, silica is added to the material in an amount of 0 to substantially 25% wt/wt, suitably substantially 1 to substantially 5%. The silica may be added to the material prior to or during heating thereof. The silica may be a coloured silica.
The plastics material may include a silicone. The silicone may be linear polydimethyl silicone, suitably one sold by Dow Corning under the designation MB50-001 SILICONE MASTERBATCH. The silicone may be added in an amount 0 to substantially 50% wt/wt, preferably 0 to substantially 25% wt/wt, more preferably substantially 10 to substantially 15% wt/wt.
The material may further include polytetrafluroethylene (PTFE), for example, in an amount of substantially 5 to substantially 10% wt/wt.
The material may include a rubberising agent. The agent may be, for example a product sold under the trade mark ADFLEX. Alternatively, the agent may be any other similar product. The rubberising agent may be added to the material in an amount 0 to substantially 70% wt/wt, preferably 0 to substantially 40% wt/wt. The use of the rubberising agent has the effect of rendering to the gain a more rubbery texture, which can be advantageous when the yarn is to be used as a dental floss.
In the first embodiment, the rollers in the first heated draw roller assembly are rotating such as to impart to the filament a speed which may lie within the range 0 to substantially 200 m per minute, preferably within the range substantially 10 to substantially 50 m per minute. More preferably it is substantially 20 m per minute.
The temperature of the rollers in the first heated draw roller assembly of the first embodiment may lie within the range 0 to substantially 200° C., preferably within the range substantially 80 to substantially 160° C. More preferably it is substantially 105° C. The temperature in the heating zone at the exit from the first draw roller assembly may lie within the range 0 to substantially 200° C., preferably within the range substantially 80 to substantially 140° C. More preferably it is substantially 120° C.
Preferably the second draw roller assembly operates at a higher speed than the first draw roller assembly. In a first embodiment of the invention the second draw roller assembly is heated.
The temperature of the rollers in the second heated draw roller assembly of the first embodiment may lie within the range 0 to substantially 200° C., preferably within the range substantially 60 to substantially 90° C. More preferably it is substantially 70° C.
The rollers of the second heated draw roller assembly of the first embodiment are rotating such as to impart to the filament a speed which may lie within the range 0 to 1000 m per minute, preferably with the range substantially 50 to substantially 250 m per minute. More preferably it is substantially 95 to substantially 100 m per minute.
In a second embodiment, the filament may be passed through an intermediate draw roller assembly arranged downstream of the first draw roller assembly and upstream of the second draw roller assembly.
In the second embodiment, the extruded filament may, be further heated in a second heating zone as the filament exits the intermediate draw roller assembly.
In the second embodiment, the rollers in the first draw roller assembly are rotating such as to impart to the filament a speed which may lie within the range of substantially 5 to substantially 50 m per minute, conveniently substantially 20 m per minute.
Preferably, the first draw roller assembly of the second embodiment comprises a plurality of rollers, conveniently five. The temperature of at least one of the rollers in the fire draw roller assembly of the second embodiment may lie in the range of substantially 50 to substantially 130° C., conveniently 95 to substantially 110° C., preferably substantially 105° C. Conveniently the roller of the first draw roller assembly arranged furthest downstream thereof is heated. Preferably, the roller immediately upstream of said furthest downstream roller is also heated.
The temperature of the first mentioned heating zone at the exit from the first draw roller assembly of the second embodiment may lie in the range of substantially 50 to substantially 180° C., conveniently substantially 115 to substantially 175° C., preferably substantially 120° C.
The temperature of the second heating zone at the exit from the intermediate draw roller assembly may lie in the range of substantially 50 to substantially 180° C., suitably, substantially 100 to substantially 150° C. conveniently substantially 140° C.
The intermediate draw roller assembly may comprise a plurality of rollers, conveniently five. The rollers in the intermediate draw roller assembly are rotating such as to impart to the filament a speed which may lie in the range substantially 5 to substantially 250 m per minute, conveniently substantially 70 to substantially 175 m per minute, preferably substantially 70 or substantially 75 m per minute. Preferably, the temperature of at least one of the rollers of the intermediate draw roller assembly lies in the range of substantially 50 to substantially 150° C., conveniently substantially 75 to substantially 125° C., preferably substantially 100° C.
The second draw

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