US 3605163 A
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United States Patent 01 :"fiee Patented Sept. 20, 1971 ABSTRACT OF THE DISCLOSURE Toothbrushes having bacteriostatic nylon bristles are produced by immersing the bristles in an aqueous-alcoholic solution containing a bacteriostat selected from the group consisting of 2,2'-methylene bis[3,4,6-trichlorophenyl] and 2,4,4 trichloro-2 hydroxydiphenyl ether. Boric acid in small amounts may also be added to the solution to assist in the conditioning of the bristles.
BACKGROUND OF THE INVENTION This invention relates to the production of toothbrushes having bacteriostatic properties which are retained for a substantial period of time, at least during the normal life of the brushes.
Nylon bristles have, to a large extent, replaced animal bristles in the manufacture of toothbrushes. While the strength and cleanability of the nylon bristles are excellent, such bristles have a disadvantage in that they may support bacterial growth.
Attempts in the past to render nylon bristles self-sterilizing, have not always proven successful. A substantial amount of development work in this connection has made use of various phenyl mercury compounds, particularly phenyl mercury salts, as agents for rendering the bristles bacteriostatic. In many cases, the phenyl mercury compound, because of its extremely limited solubility in water, had to be applied as a suspension. This method of application was not particularly successful because of the difficulty in securing a uniform deposit of the agent upon the surfaces of the bristles which would be retained for a reasonable length of time.
In order to overcome this difficulty, it was suggested that the phenyl mercury salt be dissolved in a relatively strong acid prior to application to the nylon bristles. This procedure, too, had its disadvantages. Hydrochloric acid was found to be substantially useless for this purpose because the addition of the acid to the phenyl mercury salt precipitated the very insoluble chloride. Some use was made of concentrated nitric acid, but this procedure had the disadvantage of discoloring and softening the bristles to the extent that they became limp and substantially useless for the intended purpose.
SUMMARY OF THE INVENTION It has now been discovered that nylon bristles may be rendered bacteriostatic for extended periods of time by immersing them in a solvent solution containing selected bacteriostatic agents.
Accordingly, it is an object of the present invention to provide a method for treating nylon toothbrush bristles so as to render them bacteriostatic for a substantial period of time.
It is a further object of the invention to provide an improved toothbrush having a bacteriostatic agent absorbed thereon.
The means for accomplishing these and other objects of the present invention will be apparent from the following disclosure.
In accordance with the present invention bacteriostatic toothbrushes are provided by immersing the nylon bristles of said brushes in a clear aqueous solution comprising between about 45 to 55 percent by weight of an organic solvent having between 1 to 4 carbon atoms per molecule and between about 0.5 to 2.5 percent by weight, based on the total weight, of a bacteroostat selected from the group consisting of 2,2-mthylene bis [3,4,6-trichl-orophenol] and 2,4,4'-trichloro-2-hydroxy diphenyl ether.
In a preferred embodiment of the invention the aqueous solution further comprises between about 0.5 to 2.5% by weight of boric acid.
DETAILED DESCRIPTION OF THE INVENTION As previously mentioned, the toothbrushes treated according to this invention are comprised of nylon bristles. The type of nylon which may be treated is not particularly critical since successful results have been demonstrated with most of the conventional forms used in toothbrushes such as Tynex 66 nylon which is a polymerized hexamethylene diamine adipate and Tynex 6-10 nylon which is hexamethylene diamine sebacate.
Such bristles may be immersed in the above-mentioned aqueous solution for a period of at least 3 minutes, but preferably between about 3 to 10 minutes. The entire head of the brush, including the stern if desired, may be immersed in the solution which is maintained at a temperature of between about 50 to 60 C. at atmospheric pressure.
The solution comprises between about 45 to 55% by weight, based on the total weight, of an organic solvent having between about 1 to 4 carbon atoms per molecule. Any of the conventional solvents such as lower alkyl alcohols and ketones may be utilized in the invention although isopropyl alcohol and/or acetone are preferred. Such solvents may be employed singly or in combination. in the case of an isopropyl alcohol/acetone combination, the acetone will be employed in a relatively smaller amount, that is between about 5 to 15% by weight, based on the weight of the solvent mixture.
In a preferred embodiment, boric acid in an amount between about 0.5 to 2.5 by weight, based on the total weight, will also be added to the aqueous solution. In such a case, the bacteriostat will generally be dissolved in the organic solvent and the boric acid dissolved in water. The aqueous and the alcoholic solutions are then mixed and heated to the desired temperature followed by the immersion of the toothbrush heads for the required period of time. The treated toothbrushes are then removed from the solution and dried.
The bacteriostat used in the invention may be selected from the group comprised of 2,2'-me-thylenebis [3,4,6-trichllorophenol] and 2,4,4 trichloro 2-hydroxydiphenyl et er.
2,2 methylenebis [3,4,6 trichlorophenol] is a well known germicidal agent and insoluble in water but when used in accordance with this invention, it is rendered soluble so as to thoroughly impregnate or coat the nylon bristles.
2,4,4'-trichloro-2'-hydroxydiphenyl ether is also a known bacteriostat which displays satisfactory bacteriostatic activity against gram-positive and gram-negative bacteria. It is only slightly soluble in water but is readily dissolved in the solution of this invention to provide an effective treatment for the nylon bristles.
While the manner in which the bacteriostats act to improve the durable characteristics of the coating on the nylon bristles is not clear, it appears that conditioning either by surface reaction, or some other mechanism such as hydrogen bonding, causes a tenacious bond between the bacteriostat and the nylon filament without impairing the physical property of the filaments or discoloring them. Whatever the mechanism, it has been established that the bacteriostats used in this invention provide improved re sults which are not achieved by the use of various other bacteriostats suggested in the prior art.
In testing the bacteriostatic properties of the treated bristles, a nutrient agar is seeded with Staphylococcus aureus. The bristle or bristles to be tested is placed within the agar and incubated for a period of about 48 hours. The zone of inhibition, in which there is no growth of the bacteria is measured with a ruler at various points about the bristle. Any zone of inhibition whatever is considered satisfactory, and an inhibited zone of two millimeters or more is considered excellent.
In the absence of indications to the contrary, all pro portions and concentrations of materials are expressed herein on a weight basis.
The invention is additionally illustrated by the following examples.
EXAMPLE 1 A clear solution having the following formulation was prepared:
Percent by wt.
2,4,4'-trichloro-2-hydroxydiphenyl ether 0.75 Isopropyl alcohol 50.00 Water 49.25
2,4,4'-trichloro-2-hydroxydiphenyl ether was dissolved in the isopropyl alcohol and water slowly added thereto. The resulting solution was heated to 60 C. at atmos pheric pressure and the nylon bristles of a toothbrush immersed therein for minutes. The brush was then removed from solution and let dry for 24 hours. The bristles were then leached in running water for 48 hours and tested by the agar-cup plate method using Staphylococcus aureus as the test organism. The zones of inhibition observed were 9 millimeters at each portion of the bristles tested.
In order to test the ability of the bristles to retain their bacteriostatic activity over an extended period of use, the brush to be tested was fastened by means of a clamp to a rotary brushing machine, having a counter, so that the bristles pass over a series of glass rods which are A in. in diameter and placed side by side in groups of eight. The motion of the glass rods over the bristles simulates conditions as though the brush were used to scrub the teeth. The brush is wetted when the machine is started with a one inch length of tooth paste. Additional amounts of tooth paste are added every minutes. During the brushing or scrubbing operation, the brush is always immersed in a slurry of tooth paste. Normally, the brush is operated in the machine for approximately an 8-hour period. The position of the brush is reversed from time to time.
After 40,000 strokes in such an abrasion test the bristles were tested for bacteriostatic activity at various portions thereof. At the tip of the bristles, there was a zone of 3 millimeters in which the growth of the bacteria was static. Along the sides of the bristle the zone extended to about 7 millimeters and at the bight, it extended to about 7 millimeters. When the entire head was tested in the same manner, the bristles evidenced a bacteriostatic inhibition extending for 8 millimeters beyond the head.
EXAMPLE 2 The same procedure was followed as in Example 1 except the formulation contained 1.5% by weight of boric acid, and 47.25% by weight of water. The other components were present in the same amount. Inhibition zones after brushing measured 3.8 and 8 millimeters.
EXAMPLE 3 A clear solution having the following formulation was prepared:
Water 4 2,2'-methylenebis[3,4,6-trichlorophenol] was dissolved in the mixture of acetone and isopropyl alcohol. The boric acid was dissolved in water and slowly added to the organic solvent solution. The entire solution Was then heated to 60 C. and tested as in Example 1. The following zones of inhibition were observed:
Bristles Before brushing: Mm. Tip 3 Sides 5 Bight 5 After brushing:
Tip 1 Sides 5 Bight 5 The entire head of the brush exhibited an inhibition zone of 7.0 mm. before brushing and 4.0 mm. after brushing.
EXAMPLE 4 The same procedure was following as in Example 3 except various formulations were prepared in which 2,2- methylenebis[3,4,6-trichlorophenol] was replaced with the following known bacteriostats: 2.0% chlorphenesin, 2.0% phenylsalicilate, 1.75% 2-methylbenzoic acid, 0.75% o-phenylphenol, 0.8% tert-butyl-o-cresol (ethyl), 3.0% benzylparaben and 0.75% thiobischlorophenol. Nylon bristle specimens were then treated with each of the formulations.
Following leaching in water for 48 hours, each of the specimens were tested according to the aforementioned method. However, no zones of inhibition were observed.
The principles preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. It should be understood, however, that the invention which is intended to be protected herein may be practiced otherwise than as described without departing from appended claims.
1. A method for producing toothbrushes having bacteriostatic nylon bristles, which remain bacteriostatic for an extended usage period, which comprises providing an aqueous solution comprising between about to by weight of an organic solvent having between 1 to 4 carbon atoms per molecule and between about 0.5 to 2.5% by weight of a bacteriostat selected from the group consisting of 2,2- methylene bis[3,4,6-trichlorophenol] and 2,4,4-trichloro-2'-hydroxy diphenyl ether,
immersing nylon bristles in said aqueous solution for a period of time of at least 3 minutes,
removing said bristles from said solution and,
drying said bristles.
2. A method as defined in claim 1 wherein said organic solvent is isopropyl alcohol.
3. A method as defined in claim 1 wherein said organic solvent is a mixture of isopropyl alcohol and acetone in an amount between 5 to 15% by weight based on the total weight of the solvent.
4. A method as defined in claim 2 wherein said aqueous solution further comprises 0.5% to about 2.5% by weight of boric acid.
5. A toothbrush having bacteriostatic nylon bristles, said bristles having absorbed thereon a bacteriostat selected from the group consisting of 2,2-methylenebis- [3,4,6-trichlorophenol] and 2,4,4-trichloro-2'-hydroxy diphenyl ether, said bristles being characterized by a retention of said bacteriostatic activity over an extended usage period.
6. A toothbrush as defined in claim 5 wherein said bacteriostat is absorbed on said bristles in an amount between about 0.5 to 2.5 wt. percent based on the total weight of the bristle.
(References on following page) 6 References Cited 2,939,164 6/1960 Rosenthal 15-159 3,076,218 2/1963 Cook et a1 15-4159 UNITED SITATES PATENTS 3,294,099 12/1966 Warthen et a1. 15159X 11/1937 H111 et a1. 15-159X 9/1940 Austin 15-159UX 5 PETER FELDMAN, Primary Examiner 10/1940 Carothers 15-159UX 12/1942 Rosenzweig 15159X US. Cl. X.R.
2/ 1943 Macht et a1. 15-159X 5/1950 DAlelio et a1 1s 1s9 424-31 347