US3490938A - Electroconductive flock - Google Patents

Description

United States Patent O "ice 3,490,938 ELECTROCONDUCTIVE FLOCK Merwin Frederick Hoover, Bethel Park, and Robert O.

Carothers, Coraopolis, Pa., assignors, by mesne assignments, to Calgon Corporation, a corporation of Delaware No Drawing. Filed Dec. 20, 1966, Ser. No. 603,158 Int. Cl. B44d 1/18; C03c 25/02 US. Cl. 117-100 6 Claims ABSTRACT OF THE DISCLOSURE New electroconductive flocking fibers are disclosed, employing polymers of diallyl quaternary ammonium compounds to form an electroconductive coating.

BACKGROUND OF THE INVENTION This invention relates to flocked fabrics and methods of making them; in particular it relates to rendering textile flocking materials more suited for electrostatic flocking by increasing their surface conductivity through the use of certain polymers.

Plush fabrics or similar materials are made by passing an adhesive-coated backing through an electrostatic field into which is introduced a quantity of short fibers, known as flock, having an electrostatic charge. Under the influence of the electrostatic field, the flock (i.e. fibers on the order of inch) are directed onto the adhesive in an orientation perpendicular to the backing. Under proper control, this process can produce a uniform coating of perfectly aligned, closely set fibers even on rounded contours. See the reference to this process in Chemical Engineering, Jan. 17, 1966, page 87. See also U.S. Patents 3,203,821 and 2,715,585 and Flocking, Special Edition No. 2 of Bayer Farben Review, a publication of the Dye stuffs Sales Division of Farbenfabriken Bayer AG, Leverkusen, Germany.

The ability of the flock to achieve maximum polarity is critical to its alignment with the lines of force of the field, and therefore to its orientation with respect to the backing. At maximum polarity, the charges at the ends of the fibers are as strong as possible and as far apart as possible under the circumstances. A fiber having a charge of given strength may respond to the electrostatic field by aligning itself in the field with varying resolution depending on the distribution of the charge throughout its length. The distribution of the charge or the polarity, i.e. the relative concentrations of the charge at the ends of a given flock unit, is strongly influenced by the conductivity of the flock, particularly on its surface. The surface of the flock should be uniform with respect to conductivity; otherwise there will be minor poles of relatively positive and negative areas at points other than on the ends of the flock. The minor poles and consequently irregular field around the individual flock are likely to cause a poor response or misalignment of the fiber with respect to the flocking field.

In addition to polarization or alignment, conductivity is also important to the acceptance of a charge. When the flock is initially introduced to the field, it must be able to accept a full charge immediately, and a relatively high conductivity is beneficial in this respect. This is an important factor because the introduction of large quantities of flock fibers to the field is a difiicult process to control, and the maximum charge must be accepted by the fibers under even relatively adverse conditions.

It also may be observed that there are great variations in conductivities, and hence the various responses outlined above, from one kind of fiber to another and even from lot to lot of a given type of fiber. The response of the 3,490,938 Patented Jan. 20, 1970 flock also fluctuates with the relative humidity of the atmosphere in which the flocking operation is performed. Variable responses due to humidity are caused by the relative difficulty of placing a charge on the flock and the dissipation of it from the flock into the atmosphere under more humid conditions.

It is also a known disadvantage of fibers having relatively poor conductivity that the charge is only slowly dissipated after impingement into the adhesive-coated substrate. As a result, fibers approaching the newly impinged fibers are repelled or deflected so that they have a tendency to strike the adhesive at an angle depending on the intensity of the repelling force. Fibers of high conductivity are immediately drained of their charge and, other factors being optimum, will form a very even, upright, parallel product.

There are some important fibers which are limited in their use because of their lack of any significant conductive properties. Perhaps most notable of these is polypropylene, a fiber which otherwise has many properties desirable for flocking, such as strength and ready availability. Attempts have been made to coat such fibers with various salts to render them conductive. However, due partly to the fact that inoganic salts generally tend to particulate and separate into crystals upon drying, a continuous conductor is not formed on the surface by such materials.

SUMMARY OF THE INVENTION We'have found that certain polymeric materials, to be described further herein, are capable of forming a continuous electroconductive surface on flocking fibers, overcoming all of the problems due to insufficient or uneven conductivity described above, and providing many benefits. The use of flock of our invention in conventional electrostatic flocking processes and machines results in a uniform, well-aligned product. Our invention is useful for any kind of fiber on which a film may be formed, including polypropylene and glass as well as the more conventional textile fibers.

The polymers we employ in our invention are of the general type disclosed by Butler in US. Patent 3,288,770, although several of the specific polymers we may employ are not contemplated in that disclosure. The polymers We employ have repeating units of the general formula:

2 f A l I CH HC-CH2 where A is lower alkyl (up to 4 carbon atoms) and B is selected from the group consisting of lower alkyl, ,8- propionamido, carboxymethyl, and fatty alkyl groups of up to 18 carbon atoms. Where fatty alkyl groups are used, those having 818 carbon atoms are preferred.

For convenience, the polymers of Butler will be referred to herein as the diallyl quaternary ammonium polymers. They are made in accordance with the methods described by Butler in the above US. patent, from diallyl quaternary ammonium monomers of the formula (CH1=CHCH2)2N by a suitable polymerization method such as with a redox system or thermal peroxide initiators. The anion associated with the diallyl monomers used to prepare the polymers of our invention is chloride.

We do not intend to be limited to homopolymers how- :ver. Copolymers of diallyl quaternary ammonium salts :an be made with each other and with copolymerizable nonomers, especially monoethylenically unsaturated monomers, such as acrylamide and other acrylic mon- )mers, for example. See Schuller & Thomas U.S. Patent 1,923,701. The diallyl quaternary moiety of the co- Jolymers should constitute at least 90% of the copolymer Jy weight for best results. Other copolymerizable mononers which are useful in addition to acrylamide fall into ieveral groups, (a) through (c):

(a) Monomers such as N-substituted acryl amides dis- :losed in British Patent 788,079 as being useful in making mtistatic agents for synthetic fibers. Examples are N-(B- liethylarnino ethyl) methacrylamide, N ('y dimethvlamino propyl) methacrylamide, N ('y diethylimino propyl) methacrylamide, N ([3 piperidinoethyl) methacrylamide, N (,6 dimethylamino ethyl)- icrylamide, N (,8 diethylamino ethyl) acrylamide, and -N ('y dimethylamino propyl) acrylamide, N- (B dimethylamino ethyl) methacrylamide, N (B- norpholinethyl) methacrylamide, N ('y piperidinopropyl)-methacrylamide and N-('y-hexamethylene-aminopropyl -methacrylamide;

(b) Vinyl benzyl monomers of the general formula wherein R, R and R" each represents individually at monovalent radical selected from the group consisting of OH OHCH CH CHOHCH CH OHCHOHCH and alkyl, aryl, cycloalkyl, and arylalkyl hydrocarbon radicals, and R, R and R collectively represent the trivalent radical of the formula:

CHCH= wherein, the three valences are attached to the nitrogen atom, the said R groups containing a total of not more than 12 carbon atoms in the sum of the constituent radicals, such as are discussed in Silvernail & Zembal US. Patent 3,011,918.

(c) Monomers such as are disclosed and discussed in Hayek US. Patent 2,741,568, of the general formula Il a CH2=CH where R is a member of the class consisting of hydrogen, methyl and ethyl radicals, R R and R are alkyl radicals of from 1 to 4 carbon atoms, and B is a saturated bivalent hydrocarbon radical of from 1 to 4 carbon atoms.

Any polymerizable (monoethylenically unsaturated) quaternary ammonium compounds, such as trialkyl ammonium salts of amino ethyl acrylates and methacrylates, N-(trialkyl amino alkyl) acrylamides, polyvinyl pyridine quaternaries, etc., are also useful as monomers in our invention. See, for example, the disclosure of US. Patent 3,264,137.

The preferred polymer is a homopolymer of dimethyl diallyl ammonium chloride, which is linear and water soluble. It may be cross linked if a permanently insoluble conductive surface is desired, by incorporating a crosslinkable comonomers such as acrylamide, N-methylolacrylamide, diacetoneacrylamide, etc. into the copolymer polymerization mixture in amounts up to about or less by weight. Very small amounts of N,N-methylene bisacrylamide may be used in the monomer mix to create a branched or cross-linked product.

A film of any of the above polymers may be deposit'e on the fiber by spraying, dipping, or any other method of depositing from a solution to be followed preferably by drying. A very thin film of the polymer is sufficient to achieve significant improvements in the various factors affected by conductivity. The treatment may take place in the tow or after the flock is cut. 9

A preferred method of placing the film on the flock is to pass the tow through a solution of the polymer, dry the tow, and cut or chop the tow into small segments.

A two percent solution of the homopolymer of dimethyl diallyl ammonium chloride has a viscosity which is handy to work with if dipping is to be the method of application. Generally the thickness of the applied film is immaterial, and great variations in thickness are tolerable. Concentrations greater than 10% will be operable but inconvenient to use.

Our polymers are compatible with commercial conductive treatments such as Catanac SN and Leomine KP, and other so-called antistatic additives. Catanac SN, a product of American Cyanamid Co. is stearamidopropyldimethyl fi-hydroxyethyl ammonium nitrate.

We have tested the conductivity of our treated fiber under standardized conditions as follows: The fiber tow sample is washed or scrubbed to remove any extraneous sizing or like materials, dried and weighed. It is then dipped in the subject polymer solution, wrung, and dried by hanging in a room under ambient conditions. The tow is then cut into approximate flock size inch- A inch) and left to stand for conditioning in a constant known humidity. Still under the same humidity and temperature conditions, a weighed quantity, usually one gram, is placed in a pressure cylinder equipped with electrodes similar to the Textometer described in FIG. 18 of the publication Flocking previously referred to. Resistivity readings are taken of the treated flock compressed between the electrodes at a pressure of 200 pounds.

Tables I and II show the results of such tests on nylon (27 denier) and polypropylene fibers. In each test,'after treatment with the respective concentration of a homopolymer of dimethyl diallyl ammonium chloride and drying as outlined above, the flock was conditioned at the noted relative humidity and F. before being compressed at 200 pounds per square inch and measured for conductivity.

TABLE I.NYLON FIBE RS Grams Resistance Pol iner c0110., percent:

We do not intend to be limited to the above specific examples and illustrations.

We claim:

1. A synthetic flocking fiber having a coating comprising an electroconductive polymer of 3,5 methylene N,N dimethyl piperidinium units.

2. A synthetic flocking fiber comprising a fiber having thereon a film of electroconductive polymer comprising at least 90% by weight repeating units of the formula 4. Fiber of claim 2 in which the fiber is polypropylene. 20

5. Fiber of claim 2 in which the fiber is nylon.

6 6. Flocking fiber of claim 2 in which the polymer is substantially a homopolymer of dimethyl diallyl ammonium chloride.

References Cited UNITED STATES PATENTS 2,848,451 8/1958 Schuller 117--139.5 X 2,897,201 7/1959 Albrecht l17139.5 X 2,992,126 7/1961 Roberts et al 117-27 X 3,203,821 8/1965 Domin 11717 3,248,279 4/1966 Geyer 117201 X 3,264,137 8/1966 Gess 117201 3,288,770 11/1966 Butler 26088.3 3,322,554 5/1967 Wyss et al 117-100 X 3,335,100 8/1967 Geyer 117201 X 3,356,521 12/1967 Boltniew 117-17 WILLIAM D. MARTIN, Primary Examiner US Cl. X.R.

UNITED STATES PATENT OFFICE L CERTIFICATE OF CORRECTION Patent No. 3,490,938 January 20, 1970 Merwin Frederick Hoover et a1 It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, Table I last column, line 1 thereof, "2 8x10 should read 2 .8x10 same column 4 Table II in the heading "Resistance 51% Tel; hum. in ohms" cancel "1S" and insert at (SEAL) Attest:

WILLIAM E. SCHUYLER, 1

Commissioner of Paten Edward M. Fletcher, Ir.

Attesting Officer