US 3071856 A
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. than.steelorstain'less steel'.
United States Patent Orifice 3,07L855 Patented Jan. 8, 1963 3,071,856 RAZOR BLADE AND METHOD OF MAKING SAME Irwin W. Fischbein, 18 Joyce Road, Hyde Park, Mass. No Drawing. Filed Dec. 31, 1959, Ser. ,No..863,10,9 15 Claims. (Cl. 30-346) This invention relates tosafety razor blades, either single edged or double edged, andpertains more specifically to an improved safety razor. blade'with a cutting edge on which is an adherent-coating comprising afiuorocarbon which improves theshaving effectiveness. of the blade edge and to-the method of making suchblades.
Conventional steel safety razor blades to which the. present invention may be appliedto produce improved blades are from 0.003 to 0.015 inch-thick and havewedgeshaped cutting edges, the included-solid angle of which is greater than 14 and less than 35; The faces or sides of some such cutting edges extend back from the edge for a distance upto as muchv astOJl inch or even more. Each face need notlbe .asingle planaruninterrupted continuous blade edgeuis composed may be either carbon steel or hardenable stainless steel. In either case it is hardened by asuitable'heat treatingprocess. There is ali'mit'to the extent to which the blade subsequently may be heated sinceexcessive reheating will lead to loss of hardness; As a general rule the hardenedmetal blade edges cannot be subjected to a temperature above about 400 F. for more than 'five minutes without risk that some objectionable temperingxor softeningof the steel will occur. However, the coating. may also beappliedl to blades having-cutting edges of (or coated with) metals or metal alloys "other --Conventional.razor blades despite-their sharpness cannot :be. employed :for shaving adry beard without excessive discomforttand. pain, and it is as apractical matter necesthrough the unsoftened beard 'hairs, which force is trans- 1 mitted to :the nerves in the skin adjacent the'hair follicles from which the beard hairs extend, and, as is :well known, the irritation "produced by excessive pulling of .these hairs may continue for a considerable period of time after the pulling has ceased. Although aivariety of materials have been applied both -to the cutting edgesof blades and to the beard hair in an effort to reduce the pull, the only materials which have been found commercially useful prior to the present invention are those which soften the beard. hair itself.
Applicant has discovered that by providingon the cutting edgc of a safety razor blade athin integumentof a fluorocarbon which isadherent'to the substrate, the blade exhibits a remarkable increase in shaving effectiveness. This improvement-is characterized by'a decrease in pull; that is, a. decrease in the force. required to cut the beard hairs, which manifests itselfin markedly increased ease and. smoothness-of-shavi-ng, making it possible, if desired, to abbreviate the customary beard softening stepwhichprecedes shaving, sinceasoftenin'g of the beard isnot so blades of the present invention when tested under carefully controlled conditions off the face require much less force to cut water-softened hair than do similar blades without the integument. This reduction in pull may persist during several successive shaves with the same blade putting edge, although it does not persist indefinitely.
The fluorocarbon integument or coating may extend over the entire wedge faces back from the ultimate edge or even farther, or it. may cover only the portion of the final facet immediately adjacent to the ultimate edge. The precise thickness of the integument does not appear to be critical, athin continuous adherent coating having a thickness of the order of an oriented monolayer of molecules having been found effective for the purpose of the present invention. The thickness of the integument need not be uniform throughout its extent.
The fluorocarbon materials which may be used in practicing the present invention are solid materials and include a variety ofysolidv polymers of tetraliuoroethylene containing a chain at carbon atoms including. a. plurality of (-C'F -CF groups. These polymers may vary widely in molecularweight in the form in which they are used for applying to the cutting. edge, ranging from a. molecular weight of the order of 2000 or even lower to a molecular weight above 2,000,000. The terminal groups at the ends'of the carbon chains may also vary, depending, as is well known, upon the method of making the polymer. Polymers made in aqueous media are reported to have terminal carboxyl groups, while others may have hydrogen and/or chlorine atoms attached to the terminal carbon atoms .of the chain.
In the case of high molecular weight fluorocarbons, the material may be applied to the blade cutting edge by placing the edgev in close proximity toa supply of the fluorocarbon while the latter is heated, to deposit a fluorocarbon coating on the cutting edge. Electrophoresismay also be employed to deposit the material from charged liquid dispersions thereof, or the cutting edge may be sprayed with or simply dipped in the dispersion and allowed to dry. Solid fluorocarbons having a molecular weight in the lower part of the above range may also be applied to the cutting edge by dipping the edge in a dispersion of the important as in thecaseof. conventional blades. The
particulate fluorocarbon in a volatile liquid mediumor by spraying or brushing such a dispersion onto the edge, then evaporating the liquid medium. Among the volatile liquid media which may be used are water, and such .Freons as dichlorodifiuoromethane, dichlorotetrafluoroethane, .trichlorotrifluoroethane, and mixtures thereof.
No matter how the solid fluorocarbon is deposited on the cutting edge, it is essential that the blade carrying the deposited solid fluorocarbon be baked at an elevated temperature of the orderiiof 200: to 750 F. for a period of time suflicient .for the fluorocarbon to become firmly adhered to the substrate. The time, may vary'from lessthan two minutes up to 48 hours or more depending on the particular fluorocarbon employed, the nature of the substrate, the rapidity with which the coated blade is brought up to temperature, and the temperature achieved.
In the case of steel blades, of course, as pointed out.
above, the blade cannot be heated to temperatures higher than about 400 F. for more than five minutes without some tempering or softening of the blade. In some cases, however, particularly with stainless steel blades, some softening or tempering of the blades can be tolerated since its disadvantages are more than offset by the improvement'in shavingeifectiveness brought about by the present invention. 'In general, steel blades when heated to 300 to 320 F. must be baked for at least thirty minutes toachieve optimum results, although longer heating does noharm -to the coating. In some cases it is -possible to-heat the blade before or during the deposition of the solid fluorocarbon, thus carrying out the baking step simultaneously with the deposition step.
Although the integument on the cutting edge of the blade when the blade is ready for use may be extremely thin, as pointed out above, it is desirable, in order to produce such an integument, that the coating be substantially thicker at the time the baking step begins. Any excess material remaining on the cutting edge which does not bond to the substrate during the baking step is in the form of a loose film which can be readily removed by brushing or rubbing. It is not essential that this excess material be removed before the blade is used.
While the manner of formation of the integument may not be fully understood and applicant does not wish to be bound by the following explanation, it is believed that coalescence of at least some of the solid fluorocarbon particles occurs and that some interaction between the fluorocarbon and the underlying surface such as steel occurs to form a strong bond between the fluorocarbon and the substrate. The resultant thin adherent coating, which is given mechanical support throughout its extent by the underlying blade, reduces the pull during the shaving operation and increases the ease and smoothness of shaving.
The following specific examples are illustrative of the nature of the present invention. Each of the treated blades was found by actual shave tests to have remarkably improved shaving characteristics as compared with a like blade untreated.
Example 1 Five hundred milligrams of solid tetrafluoroethylene polymer (pieces cut from Teflon commercial sheet) were placed into a stainless steel lined (stainless steel thickness=0.03 inch) ceramic tube (2" long, in diameter, wall thickness A The ceramic tube was heated by passing an electric current through a helical tungsten coil made of 40 mil wire with 30 turns in 2 inches of length wound tightly about the outside of the ceramic tube. A Gillette razor blade, previously thoroughly cleaned by washing with trichloroethylene and then dried, was placed with its cutting edge facing the open end of the tube at a distance of four centimeters. This combination was placed in a vacuum chamber evacuated to a pressure of mm. of mercury. The mag sten coil was heated electrically until the crucible temperature reached 700-750 F. The current was then controlled so that a pressure of 3 10 mm. of mercury was maintained during the heating which was continued for four hours. The blade was removed and showed a deposited layer on its cutting edge which exhibited interference colors in the light microscope. The blade was then placed in an air oven at 320 F. for 40 minutes.
Example 2 A hardened stainless steel razor blade purchased on the open market was thoroughly cleaned by washing with trichloroethylene and dried; then its cutting edge was dipped into an aqueous colloidal dispersion containing 25% by weight of finely divided solid tetrafluoroethylene polymer (Du Ponts Teflon Clear Finish). Upon removal from the dispersion, the cutting edge of the blade carried with it a coating of the aqueous dispersion which was then dried for one hour at 120 F. in the atmosphere, after which the deposited coating was baked at 750 F. for 7 minutes.
Example 3 A finely divided solid fluorocarbon polymer containing a chain of carbon atoms including a plurality of (-CF --CF groups and also containing a minor proportion (about 1% by weight) of chlorine atoms and a similar proportion of hydrogen atoms with a melting range of 265293 C. (Du Ponts Fluorowax TLT-17 Lot No. 2) was dispersed in a 40:60 mixture by weight of Freon l2 (dichlorodifluoromethane) and Freon ll4 (dichlorotetrafluoroethane) to from a dispersion containing 1% by weight of solids. This dispersion was sprayed from a pressure container onto the cutting edge of a Gillette razor blade, cleaned as described in the preceding examples; and the blade was baked at 330 F. in an air oven for 7 hours.
Example 4 The fluorocarbon solid described in Example 3 was dispersed in Freon 113 (trichlorotrifluoroethane) to form a dispersion containing 1% by weight of solids. The cutting edge of a Gillette razor blade, cleaned as described above, was dipped into this dispersion and allowed to dry in the atmosphere. The blade was then baked at 320 F. for 16 hours. Similar results were also obtained using similar dispersions containing up to 11% by weight of fluorocarbon polymer.
Example 5 The fluorocarbon solid described in Example 3 was deposited onto a Gillette razor blade edge as described in Example 1 except that the temperature of the crucible was maintained at 335 F. and the heating continued for 10 minutes. The blades were removed from the vacuum chamber and showed interference colors on the cutting edge. Similar results can be obtained by heating at a temperature as low as 250 F. for a longer time. The blades were placed in an air oven at 320 F. for 15 minutes. Similar results were also obtained using times up to 16 hours at the same temperature.
Example 6 The fluorocarbon solid described in Example 1 was heated in air at atmospheric pressure in a silica crucible to a temperature of 450 C. until a thick white smoke continuously emanated from the crucible. A Gillette razor blade cleaned as described above was held with its edge in the white smoke at a distance of three inches from the crucible for 10 minutes. By reason of its proximity to the crucible, the blade attained a temperature of the order of 300 F. during the deposition of the fluorocarbon on its cutting edge and required no further baking.
Although specific embodiments of the invention have been described herein, it is not intended to limit the invention solely thereto, but to include all of the variations and modifications which suggest themselves to persons skilled in the art.
What is claimed is:
l. A safety razor blade having on its cutting edge an adherent coating comprising a solid fluorocarbon polymer.
2. A safety razor blade having on its cutting edge an adherent coating comprising a solid polymer of tetrafluoroethylene.
3. A safety razor blade as claimed in claim 2 in which said blade is composed of stainless steel.
4. A steel safety razor blade having on its cutting edge an adherent coating comprising a solid polymer of tetrafluoroethylene.
5. A safety razor blade having on its cutting edge an adherent coating compirsing a solid polymer containing a chain of carbon atoms including a plurality of (--CF CF groups.
6. A safety razor blade as claimed in claim 5 in which heating said deposited polymer to form a coating adherent to said edge.
9. The method of treating a steel safety razor blade which comprises depositing on its cutting edge a composition comprising a solid polymer containing a chain of carbon atoms including a plurality of (CF -CF groups and also including terminal groups selected from the class consisting of carboxyl groups, hydrogen atoms and chlorine atoms, and heating said deposited polymer to form a coating adherent to said edge.
10. The method of treating a steel safety razor blade which comprises depositing on its cutting edge a dispersion in a volatile liquid containing discrete particles of solid polymer containing a chain of carbon atoms including a plurality of (CF CF groups, evaporating said volatile liquid, and heating the resulting deposit at an elevated temperature to form a coating adherent to said edge.
11. The method as defined in claim in which said volatile liquid comprises water.
12. The method as defined in claim 10 in which said heating is carried out for at least 30 minutes at 300 to 330 F.
13. The method as defined in claim 10 in which said volatile liquid is selected from the class consisting of dichlorodifiuoromethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, and mixtures thereof.
14. The method of treating a steel safety razor blade which comprises heating a solid polymer containing a chain of carbon atoms including a plurality of groups to a temperature sufiicient to vaporize a portion thereof, maintaining a cutting edge of said blade in said vapors to deposit a coating thereon, and heating the resulting deposit to form a coating adherent to said edge.
15. The method as defined in claim 14 in which said heating step is carried out simultaneously with said deposition step.
References Cited in the file of this patent UNITED STATES PATENTS Gasket Co.; Bulletin B-4A; page 1, received in Patent Olfice June 10, 1952.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,071,856 January 8, 1963 Irwin W. Fi'schbein It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
In the grant, lines 1 to 3, for :"Irwin W Fischbein, of Hyde Park, Massachusetts," read Irwin W. Fischbein, of Hyde Park, Massachusetts, assignor to The Gillette Company, of Boston, Massachusetts, a corporation of De1aware,3 line 12, for --""Irwin W. Fischbein, his heirs"- read The Gillette Company, its successors in the heading to the printed specification, line 3, for "rlrwin W. Fischbein, 18 Joyce Road, Hyde Park, Mass, read Irwin Wo Fischbein, Hyde Park, Mass, assignor to The Gillette Company, Boston, Mass, a corporation of Delaware column 2, line 20, for 'af" read of column 3, lines 61 and 74, for Du Ponte'"", each occurrence, read duPonts column 4, line 2, for "from" read form Signed and sealed this 23rd day of July 1963,,
ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents