US3422180A - Solvent tipping of polyethylene terephthalate filaments - Google Patents

Description

United States Patent Office 3,422,180 Patented Jan. 14, 1969 3,422,180 SOLVENT TIPPING OF POLYETHYLENE TEREPHTHALATE FILAMENTS Doyce B. Hanson, John E. Hansen, and Nolan D. Boyer,

Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 21, 1965, Ser. No. 500,211 US. Cl. 264-341 1 Claim Int. Cl. D011? 7 /06; A46d 1/04 ABSTRACT OF THE DISCLOSURE Preparation of tipped bristles of polyethylene terephthalate, by repeatedly dipping and withdrawing a bundle of the bristles from a solvent for polyethylene terephthalate. The preferred solvent is 40% tetrachloroethane and 60% phenol. The preferred temperature for this solvent is 50 to 70 C.

This invention relates to the modifying of synthetic filaments for use as bristles, and more particularly, to a process for tipping of filaments of polyethylene terephthalate for use as bristles.

The preparation of filaments from polyethylene terephthalate has been described in Whinfield et al., US. Patent 2,465,319. The production of monofils thereof for use as bristles by a drawing and heat-setting process has been described in McClellan, US. Patent 2,615,784. A method of producing improved bristles consists of forming tapered filaments according to Fields, US. Patent 2,423,182, and then mechanically tipping the filaments to a slender point. However, mechanical tipping of filaments of polyethylene terephthalate with commercial abrasive tipping machines is not practical, since the filaments are readily damaged therein. Therefore, alternative tipping techniques are desirable.

This invention provides a solvent-dipping method for tipping tapered or untapered filaments of polyethylene terephthalate fiber for use as bristles. The tipping is accomplished in accordance with this invention by repeated dipping of a bundle of polyethylene terephthalate filaments in a solution. It would generally be expected that such treatment of a bundle of filaments with a solvent would result in fusion of the filaments to a solid mass. However, after the dipping operation as described herein, the surprising result is that the filaments are readily separable and each filament appears to have a pencil-point tip, as shown by photomicrographs.

A bundle of filaments is tipped according to this invention by repeated lowering into and raising from a solvent bath. The filaments used may be either level (untapered) or tapered at the start. The degree of tapering of the filaments may vary widely; the invention lies in the tipping of the filaments.

Any of the known solvents for polyethylene terephthalate can be used within the scope of this invention, for example, phenol, m-cresol, or variations proportions of mixed solvent systems, for example tetrachloroethanephenol. The tetrachloroethane-phenol solvent system is preferred, and, for best results, a mixture of 40% tetrachloroethane and 60% phenol is employed for the tipping bath.

The temperature of the tipping bath should be below the softening temperature of the filaments and can be varied from room temperature to the boiling point of the solvent or solvent mixture employed within the limits of the above proviso. Better results are obtained with warm solvent systems (40100 C.). With the preferred solvent of this invention, 40% tetrachloroethane60% phenol, a temperature in the 5070 C. range is preferred.

With a fresh tipping solution, a bath temperature of 60 C. gives the best results.

The duration of the dipping operation can be varied depending, among other things, upon the rate of dipping, the solvent employed, and the bath temperature. With 40% tetrachloroethane-60% phenol held at about 50-70" C., a dipping time of 10 to 30 minutes is preferred. With a fresh solution of the latter, best results are obtained with dipping period of about 20 minutes. After the dipping treatment, the filamentsare washed with any solvent in which polyethylene terephthalate is insoluble and in which the tipping solution is soluble. Preferably, the solvent for the tipping solution is water-soluble, so that, after the tipping solution has been washed off, the bundle of filaments can then be rinsed with water and dried. For example, methanol, ethanol, acetone, or methyl ethyl ketone can be used to remove the tipping solution. However, water-insoluble solvents for the tipping solutioncan also be used, such as benzene, toluene, dichloromethane, chloroform, and carbon tetrachloride, after which the filaments are dried. The preferred washing operation consists of first rinsing the filaments with methanol to remove the tipping solution, followed by rinsing with water to remove the methanol.

In order that the invention may be better understood, the following detailed examples are given in addition to the examples already given above.

Example 1 Filaments of polyethylene terephthalate with taper ratios (diameter of butt end to that of tapered end) of either 7/4 or 9/5 and of a uniform length (varying between 3% and 4 /2 inches from run to run) were gathered into pound bundles approximately 2 inches in diameter at the butt end.

The bundle was clamped at the butt end to an oifset mounted on the shaft of a clock motor which revolved at 2 rpm, thereby raising and lowering the bundle. A vessel containing a solution composed of 40% tetrachloroethane and 60% phenol (by weight) was arranged so that the tips of the filaments were submerged to a depth of /2 inch at the .bottom of the stroke, and were completely removed from, the solution at the top of the stroke. With the tetrachloroethane-phenol solution held at 60 the bundle was subjected to the cyclic dipping and withdrawing treatment for 20 minutes, then flushed with methanol from the butt end to the tip end so as to wash solution out of the bundle without exposing the butt end to the dipping solution. After repeated washing with fresh methanol the bundle was thoroughly rinsed with water, then placed in a vacuum oven at room temperature for 16 hours with a nitrogen sweep. The filaments were easily separable, and each appeared to have a pencil-point tip.

Example 2 A 4-inch paint brush constructed from untipped, but tapered polyethylene terephthalate bristles was treated by the method of Example 1, with the result that the bristles were likewise tipped.

While the invention has been described with particular reference to specific embodiments, it will be appreciated that no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, since obvious modifications will occur to those skilled in the art.

We claim:

1. A process of tipping polyethylene terephthalate filaments for use as bristles which comprises dipping only the tip of a bundle of polyethylene terephthalate filaments into a solvent mixture of 40% tetrachloroethane and the remainder phenol, the temperature of the solvent being about 5070 C., withdrawing the tip from the solvent,

about 20 minutes.

References Cited UNITED FOREIGN PATENTS 1,107,637 5/1961 Germany.

STATES PATENTS JULIUS FROME, Primary Examiner. whi fi ld et 1 2 0.45 5 A. H. KOECKERT, Assistant Examiner.

Watson 2 75 Rieber 260 75 US. Cl. X.R. MacAllister. 156-7, 2