US2745770A - Organic shaped structures coated with werner-type chromium compounds and method of making the same - Google Patents

Description

United States Patent O M ORGANIC SHAPED STRUCTURES COATED WITH WERNER-TYPE CHROMIUM COMPOUNDS AND METHOD OF MAKXNG THE SAME No Drawing. Application April 9, 1952, Serial No. 281,481

4 Claims. (Cl. 117139.5)

This invention relates to shaped structures having improved anti-static properties and to processes for producing the same. More particularly, it relates to films, filaments, fibers, monofils, coatings, fabrics and like structures, having a moisture regain of no greater than five percent and a resistivity of at least 400,000X10 ohms, the surfaces of which have uniformly distributed thereon as an anti-static agent a complex compound of the Werner type in which trivalent nuclear chromium atoms are coordinated with a monocarboxylic acid selected from the clas consisting of p-nitrophenlacetic acid, p-nitrobenzoic acid, phenylacetic acid, trichloroacetic acid, thioglycollic acid, cyanoacetic acid and gluconic acid.

Films, filaments, fibers, monofils, coatings fabrics and like structures having low moisture regain and high resistivity have a propensity to ready develop strong electrostatic charges which make them difficult to manipulate during manufacture, subsequent processing and use, such as, for instance, in the steps of spinning, knitting, weaving, slitting, printing, perforating, winding, sealing, packaging and other finishing operations. By reason of their highly charged surfaces, these articles also accumulate heavy dust deposits which, of course, are very undesirable.

Then, too, in the manufacture of film for photographic uses having low moisture regain and high resistivity, the discharge of positive and negative charges during processing exposes the light-sensitive silver halides leaving characteristic static marks after development.

Various agents, methods and apparatus have heretofore been proposed to eliminate or at least minimize the accumulation of electrostatic charges on shaped structures without detracting from their physical properties, but they are not entirely satisfactory.

Now I have found that the surface characteristics of films, filaments, fibers, monofils, sheets, coating and like structures having a moisture regain of no greater than 5% and a resistivity in ohms of at least 400,000 1.0 can be improved by applying to the surfaces of these structures a Werner type chromium complex in which a trivalent chromium atom is coordinated with a monocarboxylic acido group of the class consisting of p-nitrophenylacetato, p-nitrobenzoato, phenylacetato, trichloroacetato, thioglycollato, cyanoacetato and gluconato; from solutions of such complexes, and thereafter drying said structures by any suitable expedient. These complex compounds are outstanding in that they Wet the surface of the shaped structure, resulting in a substantially uniform, adherent coating application.

Chromium coordination complex compounds of the Werner type suitable for use in accordance with my invention can be coordinated with any of the aforenamed monocarboxylic acids. A compound of the acid such as an ester or salt which can liberate the free acid under the condition of the coordination reaction is, of course, equivalent to the free acid.

General methods for preparing suitable Werner type chromium acid complexes are described in ller Patents Nos. 2,273,040, 2,356,161 and 2,524,803. The processes 2,745,770 Patented May 15, 1956 described in 2,273,040 and 2,356,161 effect the reaction between a carboxylic acido group and a basic trivalent chromium salt of a monobasic acid in the substantial absence of free water. U. S. 2,524,803 teaches a method whereby contact between the basic chromium chloride and the carboxylic acido group .is effected in the presence of alcohol.

The nature of the Werner-type complex chromium compounds and the nomenclature applied to them is described fully in U. 5. Patents 2,273,040, 2,356,161 and 2,524,803. By deleting the suffix -ic from the name of the carboxylic acid and adding the sufiix -ato a system of naming the acido groups coordinated with the chromium, and hence for naming the chromium complexes, is provided. Thus, p-nitrophenylacetic acid gives p-nitrophenylacetato groups and the complex is called p-nitrophenylacetato chromic chloride.

The Werner complexes are admixed with a suitable volatile solvent which does not affect the complex, such as, for example, water, methanol, ethanol, isopropanol, t-butanol, aqueous solutions of these alcohols, and butyl acetate.

These solutions should contain from about 0.1% to about 1.0% by weight of the Werner type chromium complex.

Application of the solution of the Werner-type chromium complex to the surface of the structure having a moisture regain of 5% or less and resistivity of at least 400,0O0X10 ohms can be accomplished by any convenient expedient which insures intimate contact of the complex with the substrate. For instance, dipping, spraying, brushing, roll coating, paddling, and the like operations may be employed.

The temperature of the application bath is not critical but it should be such that the chromium complex is dissolved or thoroughly dispersed. In general, the temperature should be maintained preferably below F.

Aqueous solutions of the Werner type chromium complexes are particularly well suited for purposes of this invention. Should, however, the type of fabric or fiber under treatment he very difficult to wet because of the presence of sizing agents or other contaminates on the surface, it may be necessary to add some isopropanol to the aqueous solution of the complex compound to improve the wetting characteristics, but in most instances this will not be necessary.

The shaped structure treated with an aqueous solution of a chromium complex can be cured on a tenter frame, drum dryers or other suitable apparatus at a temperature of from to 250 F. for a period of from about 1 to 5 minutes. Air drying will suffice.

The thickness of the anti-static layer is variable from that just sufiicient to form a uniform coherent coating to a maximum thickness determined by the characteristics of the layer. Thus too thick a coating may lead to tackiness or flaking. While the optimum coating weight may vary depending upon coating conditions, a practical range for film is from about 2 to 50 milligrams of complex per square yard of film surface. The preferred coating weight for photographic film is from about 0.15 mg. to 0.35 mg. total solids per square decimeter.

The shaped structures whose surfaces have uniformly distributed thereon a Werner-type chromium complex may be in the form of films, filaments, fibers, monofils, coatings, fabric and the like but they are all characterized by having a moisture regain no greater than 5 per cent and a resistivity of at least 400,000X10 ohms.

By the term moisture regain is meant the per cent moisture in the shaped structure based on a bone-dry basis. This definition is in accord with that used in the art and is fully described by Bruce E. Hartsuch inhis the circuit is measured with a microametcr.

" book lntroduction'to Textile Chemistry, John Wiley &

Sons, Inc., New York, 1950, at pages 118-122.

The American Society for Testing Materials has established a set of standard moisture regains, shown in Table 1 7- of the aforementioned Hartsuch reference. The per cent moisture regain approximates the per cent of water that each structure would absorb if exposed to an average or normal atmosphere, which is assumed to have a relative humidity of 65% at a temperature of 70 F. In other words, a percentage of moisture regain of 5 means that 5 per cent of water on a bone-dry basis is absorbed by the shaped structure when exposed to an atmosphere having a relative humidity of 65% at a temperature of 70 F.

The term resistivity is used in its conventional sense to mean the electrical resistivity of the shaped structures. The apparatus used to determine the electrical resistance of the various structures is fully described by Mason Hayek and F. C. Chromey in volume 40 of American Dyestufi Reporter, at pages 225-227.

The principle involved in the Hayek-Chromey instrument is the measurement of the IR drop in a known resistance, where I is the current leaking thru the sample. The voltage across the standard resistance is amplified with an electrometer tube, and the extent of the unbalance of From a graph of the logarithm of the meter deflection against the logarithm of the test resistance in standard resistor units, the unknown resistance can be determined.

Included among the shaped structures which have moisture regains of 5% or less and electrical resistivities of at least 400,000X ohms are polyamides, polyesters, such as for instance polyethylene terephthalate, acrylic polymers, such as for instance polyacrylonitrile, vinyl polymers other than polyvinyl alcohol, vinylidene chloride polymers, vinyl-acrylic copolymers, polystyrene, polyethylene and the like.

The electrostatic voltages of the various shaped structures against synthetic rubber are measured by the method first described by D. I. Lehmicke, American Dyestuif Reporter 38, 853 (1949) and more recently by L. B. Chandler, Textile World 101, 116 (1951). In brief, the method comprises charging the shaped structure such as nylon fabric by rubbing it ten times with a neoprenegloved hand. The charged structure is then dropped into an aluminum beaker insulated from the ground and connected to a voltmeter. The voltage generated is measured by reading the voltmeter.

The nature of this invention and its method of application will be better understood by reference to the following illustrative examples:

Example 1 Example 2 A film strip composed of polyethylene terephthalate as described in Example 1 is coated on one side with an aqueous solution heaving the following composition by weight:

7 Parts p-Nitrobenzoatolchromic chloride 0.156 Wetting agent (alkyl aryl polyether alcohol) 1.00 Water 4 100.00

The coating is dried at 160 F. for a period of three minutes. The surface resistivity of the treated film is 5000 10 ohms. The control untreated film has a surface resistivity of l0,000,000 X 10 ohms.

Example 3 against synthetic rubber was determined by the aforementioned method of Lehmicke and Chandler. A voltmeter reading of 76 volts (78 F., 72% R. H.) was obtained for the treated fabric. The electrostatic voltage of the nylon control (untreated) generated against syn thetic rubber was 760 volts.

The treated nylon taffeta retained 6 mg./sq. ft. of the complex chromium compound.

Example 4 A 7 x 9 inch piece of polyethylene terephthalate tafleta having a moisture regain of about 0.4% R. H.) and a resistivity of greater than 1,000,000 X 10 ohms was coated with. an aqueous solution containing 0.6% by Weight of stock p-nitrophenylacetato chromic chloride.

The treated fabric was dried and its electrostatic voltage generated against synthetic rubber was then determined. The treated fabric generated 140 volts against neoprene while the polyethylene terephthalate control fabric generated 960 volts.

. The polyester taffeta treated with the p-nitrophenylacetato chromic chloride retained about 4 ing/sq. ft. of the chromium complex.

I claim:

1. A method which comprises applying to an organic shaped structure having a moisture regain of no greater than 5% and a surface resistivity of at least 400,000 X 10 ohms a solution containing a complex chromium compound of the Werner type selected from the group consisting of p-nitrophenylacetato chromic chloride, p-nitrobenzoato chromic chloride, phenylacetato chromic chloride, trichloroacetato chromic chloride, thioglycollato chromic chloride, cyanoacetato chromic chloride and gluconato chromic chloride, and subsequently drying said 2. A method which comprises coating an aqueous solution of a complex compound of the Werner type in which a trivalent nuclear chromium atom is coordinated with a monocarboxylic acido group of the class consisting of p-nitrophenylacetato, p-nitrobenzoato, phenylacetato, trichloroacetato,.thioglycollato, cyanoacetato and gluconato groups onto a surface of an organic shaped structure having a moisture regain of no greater than 5% and a surface resistivity of at least 400,000 X10 omhs and subsequentlydrying said coated structure.

3. A method which comprises coating a solution containing a volatile solvent and a complex compound of the Werner type said complex chromium compound being selected from the group consisting of p-nitrophenylacetato chromic chloride, p-nitrobenzoato chromic chloride, phenylacetato chromic chloride, trichloroacetato chromic chloride, thioglycollato chromic chloride, cyanoacetato chromic chloride, and gluconato chromic chloride, in which a trivalent nuclear chromium atom is coordinated with a monocarboxylic acido group of the class consisting of pface resistivity of at least 400,000 X 10 ohms and dry- References Cited in the file of this patent ing the layer- UNITED STATES PATENTS 4. Organic shaped stmctures the surfaces of which have uniformly distributed thereon as an anti-static agent a Her 1 1942 complex hromium compound of the Werner-type, said 5 2,356,161 r Aug. 22, 194 pl x hromium compound being selected from the 2,532,691 e y Dec.5,1950 group consisting of p-nitrophenylacetato chromic hlo- 2,628,176 Simon et a1 1953 ride, p-nitrobenzoato chromic chloride, phenylacetato 2,647,336 'f 4, 1953 chromic chloride, trichloroacetato chromic chloride, thio- 10 2,673,824 mefeld et a1 1954 glycollato chromic chloride, cyanoacetato chromic chlo- 2673825 Blefeld et a1 1954 ride, and gluconato chromic chloride, said structures hav- OTHER REFERENCES mg Prior to surface application of Said chromium Knowlton: Standard Handbook for Electrical Engipound a moisture regain no greater than 5% and a surface nears 7th edition 1941 4 595 e resistivity of at least 400,000 X 10 ohms. 15 S Pag

Claims (1)

1. A METHOD WHICH COMPRISES APPLYING TO AN ORGANIC SHAPED STRUCTURE HAVING A MOISTURE REGAIN OF NO GREATER THAN 5% AND A SURFACE RESISTIVITY OF AT LEAST 400,000 X 10**8 OHMS A SOLUTION CONTAINING A COMPLEX CHROMIUM COMPOUND OF THE WERNER TYPE SELECTED FROM THE GROUP CONSISTING OF P-NITROPHENYLACETATO CHROMIC CHLORIDE, P-NITRO BENZOATO CHROMIC CHLORIDE, PHENYLACETATO CHROMIC CHLORIDE, TRICHLOROACETATO CHROMIC CHLORIDE, THIOGLYCOLLATO CHROMIC CHLORIDE, CYANOACETATO CHROMIC CHLORIDE AND GLUCONATO CHROMIC CHLORIDE, AND SUBSEQUENTLY DRYING SAID STRUCTURE.