Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1994-08-04
2001-03-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S244000, C524S245000
Reexamination Certificate
active
06204317
ABSTRACT:
BACKGROUND OF THE INVENTION
The propensity of synthetic fibers to develop a static charge is a well known phenomenon. Static electricity is generated when two relatively non-conducting surfaces, such as those of synthetic fibers, come into close contact and are rubbed together. This leads to a continuous flow of electrons in both directions across the two surfaces. On separation the electron distribution on the surfaces is disturbed; one surface retaining more electrons than in its normal state acquires a negative charge and the other an equivalent positive charge.
Static can be controlled by eliminating the charge generation or by increasing the rate of charge dissipation. Due to the hydrophobicity of synthetic fibers, the synthetic fibers are not able to dissipate the generated electricity. Most anti-static treatments attempt to increase the hygroscopicity, (i.e. the ability of fibers to adsorb moisture from the air), to increase the rate of charge dissipation.
Anti-static treatments for synthetic fibers and fabrics generally include spray-on treatments applied to fibers after the fiber is extruded or to fabrics, after the fabric is woven or knitted.
For synthetics or polymeric materials, such as polyamide, anti-static treatment may also be achieved by mixing large quantities (20%-50%) of an anti-static agent with caprolactam in a polymerization vessel during the polymerization reaction of polyamide to produce a “master batch” of polyamide containing anti-static agent. The anti-static polyamide fiber is then produced by blending the “master batch” with virgin polyamide chips in a blender or tumbler.
However, this method has serious drawbacks as the concentration of anti-static agent is batch dependent and varies according to the requirements of the specific batch. The anti-static containing polyamide chips of the “master batch” do not blend uniformly with the virgin polyamide and the anti-static properties of the extruded fiber are not uniform. Also, this anti-static treatment to polyamide requires elaborate and expensive spinning equipment to control or regulate the rate of addition of anti-static agent. Examples of such equipment include side arm extruders and colortronics.
The present invention provides a method for addition of an anti-static agent to molten polymeric material contained in a spinning extruder without the use of equipment such as a side arm extruder. According to the method of the present invention, an anti-static agent that is solid at room temperature, is melted and added to the molten polymeric material. The method is an improvement over the prior art, as it provides an accurate and efficient method for addition of an anti-static agent to a spinning extruder, without the use of expensive equipment.
Unexpected results are achieved when fibers or fabrics are treated with the anti-static agent according to the present invention. These unexpected advantages include improved stability of the fabric to ultraviolet light, significantly improved dye lightfastness and improved dye uptake, resulting in deeper dyeing, in comparison to untreated control samples.
SUMMARY OF THE INVENTION
The present invention is directed to a method for addition of an anti-static agent to a polymeric material in a spinning extruder, wherein the method improves the anti-static properties and deep dyeability of the treated polymeric materials. The method is particularly useful for polyamide polymers, but may be used with any suitable polymeric material to be extruded such as polyester, polyethylene and polypropylene. The method employs anti-static agents that are solid, waxy substances at room temperature. The anti-static agent is fed into a standard spinning extruder. In the preferred embodiment, the solid anti-static agent is dispersed in powdered or pulverized form in a liquid carrier and injected into a spinning extruder. The carrier acts as a liquid transporting vehicle for the dispersed anti-static agent. The injection is performed with the aid of a mechanical pump. Particularly useful for the method of the present invention is a peristaltic pump. Other mechanical pumps such as metering pumps and positive displacement pumps may also be used. Polymeric material is fed into the spinning extruder from a reservoir. The anti-static agent and polymeric material are melted in the extruder at temperatures ranging from 250° C. to 285° C. Preferably the temperature is about 270° C.
In an alternative embodiment the anti-static agent is first melted in a heated vessel and fed through heated feed lines by a pump to the spinning extruder. Polymeric material is also fed into the extruder, preferably in solid chip form. The anti-static agent and polymeric material are heated to a molten state in the spinning extruder at temperatures ranging from 250° C. to 285° C. and preferably about 270° C.
REFERENCES:
patent: 4065532 (1977-12-01), Wild et al.
patent: 5116897 (1992-05-01), Burton
patent: 5157067 (1992-10-01), Burditt et al.
patent: 5236645 (1993-08-01), Jones
BASF Corporation
Rajguru U. K.
Seidleck James J.
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