THERMOPLASTIC MATERIALS HAVING BENEFICIAL PROPERTIES AND PROCESSES FOR PROVIDING THE SAME

Abstract

Methods of providing sustained sterilization of thermoplastics; providing thermoplastics that have the capacity to dispense sodium fluoride, and, a method of providing sustained sterilization of thermoplastics and providing thermoplastics that have the capacity to dispense sodium fluoride, both from the same thermoplastic article.

Claims

1. A method of providing sustained sterilization of thermoplastics said method comprising: a. providing a hydrolyzate of a silane having the general formula:
(RO).sub.3Si(CH.sub.2)nN.sup.+(R).sub.2(R)Cl.sup. wherein R is an alkoxy group having 1 to 4 carbon atoms, n has a value of 3 to 8, each R is selected from alkyl groups having 1 to 4 carbon atoms, and R is the radical (CH.sub.2)mCH.sub.3Cl.sup. wherein m has a value of 12 to 20; B. coating particulates of said thermoplastic with said hydrolyzate; C. heating and drying said coated particulates to yield dry coated particulates; D. providing said coated particulates as feedstock for providing thermoplastic products by a process selected from the group consisting of: i. melt-spinning and, ii. injection molding.

2. A method as claimed in claim 1 wherein the feedstock for providing thermoplastic products is coated particulate thermoplastic.

3. A method as claimed in claim 1 wherein the feedstock for providing thermoplastic products is a mixture of coated particulate thermoplastic and uncoated particulate thermoplastic.

4. A method as claimed in claim 1 wherein said coated particulate thermoplastic is mixed with an additional thermoplastic that is not the same as the coated thermoplastic.

5. The method as claimed in claim 1 wherein said coating is provided by spraying said hydrolyzate onto said particulate thermoplastic while agitating said particulate thermoplastic.

6. The method as claimed in claim 1 wherein said coating is provided by adding said hydrolyzate to said particulate thermoplastic while agitating said particulates.

7. A method of providing thermoplastics that have the capacity to dispense sodium fluoride said method comprising: a. adding a desired amount of sodium fluoride to water to form a solution; b. coating particulate thermoplastics with said solution c. thereafter heating and drying said particulate thermoplastics. d. provide said coated particulates as feedstock for a p process selected from: i. melt-spinning and, ii. injection molding.

8. A method as claimed in claim 7 wherein the feedstock for providing thermoplastic products is coated particulate thermoplastic.

9. A method as claimed in claim 7 wherein the feedstock for providing thermoplastic products is a mixture of coated particulate thermoplastic and uncoated particulate thermoplastic.

10. A method as claimed in claim 7 wherein said coated particulate thermoplastic is mixed with an additional thermoplastic that is not the same as the coated thermoplastic.

11. The method as claimed in claim 7 wherein said coating is provided by spraying said solution onto said particulate thermoplastic while agitating said particulate thermoplastic.

12. The method as claimed in claim 7 wherein said coating is provided by adding said solution to said particulate thermoplastic while agitating said particulates.

13. A method of providing sustained sterilization of thermoplastics and dispensing sodium fluoride from thermoplastics said method comprising: A. providing a hydrolyzate of a silane having the general formula:
(RO).sub.3Si(CH.sub.2)nN.sup.+(R).sub.2(R)Cl.sup. wherein R is an alkoxy group having 1 to 4 carbon atoms, n has a value of 3 to 8, each R is selected from alkyl groups having 1 to 4 carbon atoms, and R is the radical (CH.sub.2)mCH.sub.3Cl.sup. wherein m has a value of 12 to 20; B. adding a desired amount of sodium fluoride solution to said hydrolyzate; C. coating particulates of said thermoplastic with said hydrolyzate containing said sodium fluoride; D. heating and drying said coated particulates to yield dry coated particulates; D. providing said coated particulates as feedstock for providing thermoplastic products by a process selected from the group consisting of: i. melt-spinning and, ii. injection molding.

14. A method as claimed in claim 13 wherein the feedstock for providing thermoplastic products is coated particulate thermoplastic.

15. A method as claimed in claim 13 wherein the feedstock for providing thermoplastic products is a mixture of coated particulate thermoplastic and uncoated particulate thermoplastic.

16. A method as claimed in claim 13 wherein said coated particulate thermoplastic is mixed with an additional thermoplastic that is not the same as the coated thermoplastic.

17. The method as claimed in claim 13 wherein said coating is provided by spraying said solution onto said particulate thermoplastic while agitating said particulate thermoplastic.

18. The method as claimed in claim 13 wherein said coating is provided by adding said solution to said particulate thermoplastic while agitating said particulates.

19. The method as claimed in claim 1 wherein the thermoplastic particulate is nylon.

20. The method as claimed in claim 7 wherein the thermoplastic particulate is nylon.

21. The method as claimed in claim 13 wherein the thermoplastic particulate is nylon.

22. A composition of matter provided by the process of claim 1.

23. A composition of matter provided by the process as claimed in claim 7.

24. A composition of matter provided by the process as claimed in claim 13.

25. A composition of matter as claimed in claim 22 that is a fiber.

26. A composition of matter as claimed in claim 25 that is a bristle for a brush.

27. A composition of matter as claimed in claim 23 that is a fiber.

28. A composition of matter as claimed in claim 27 that is a bristle for a brush.

29. A composition of matter as claimed in claim 24 that is a fiber.

30. A composition of matter as claimed in claim 29 that is a bristle for a brush.

31. An article manufactured from the composition of claim 22.

32. An article as claimed in claim 31 that is a toothbrush.

33. An article as claimed in claim 31 that is a woven mesh.

34. An article manufactured from the composition of claim 23.

35. An article as claimed in claim 34 that is a toothbrush.

36. An article as claimed in claim 34 that is a woven mesh.

37. An article manufactured from the composition of claim 24.

38. An article as claimed in claim 37 that is a toothbrush.

39. An article as claimed in claim 37 that is a woven mesh.

40. The method as claimed in claim 1 wherein the thermoplastic polymer is selected from the groups consisting of: i. nylon, ii. acrylic, iii. polyurethanes, and, iv. ethylene vinyl acetate.

41. The method as claimed in claim 40 wherein the thermoplastic polymer is polyurethane polyester.

42. The method as claimed in claim 1 wherein the thermoplastic product is selected from the group consisting of: i. dental retainers, ii. teeth aligners, iii. boil-and-bite mouth guards, iv. mouth guards, and, v. elastomeric orthodontic ligatures.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 shows release of fluoride from nylon coupon.

THE INVENTION

[0013] Thus, what is described herein in one embodiment is a method of providing sustained sterilization of thermoplastics said method comprising providing a hydrolyzate of a silane having the general formula: (RO).sub.3Si(CH.sub.2)nN.sup.+(R).sub.2(R)Cl.sup. wherein R is an alkoxy group having 1 to 4 carbon atoms, n has a value of 3 to 8, each R is selected from alkyl groups having 1 to 4 carbon atoms, and R is the radical (CH.sub.2)mCH.sub.3Cl.sup. wherein m has a value of 12 to 20; coating particulates of said thermoplastic with said hydrolyzate; heating and drying said coated particulates to yield dry coated particulates; providing said coated particulates as feedstock for providing thermoplastic products by a process selected from the group consisting of: melt-spinning and injection molding.

[0014] Contemplated within the scope of this invention are compositions provided by this process and articles provided from the compositions of this process.

[0015] In a second embodiment, there is a method of providing thermoplastics that have the capacity to dispense sodium fluoride, said method comprising: adding a desired amount of sodium fluoride to water to form a solution; coating particulate thermoplastics with said solution thereafter heating and drying said particulate thermoplastics; providing said coated particulates as feedstock for a process selected from melt-spinning and injection molding.

[0016] Contemplated within the scope of this invention are compositions provided by this process and articles provided from the compositions of this process.

[0017] In yet a third embodiment there is a method of providing sustained sterilization of thermoplastics and providing thermoplastics that have the capacity to dispense sodium fluoride, both from the same thermoplastic, said method comprising providing a hydrolyzate of a silane having the general formula:

(RO).sub.3Si(CH.sub.2)nN.sup.+(R).sub.2(R)Cl.sup.

wherein R is an alkoxy group having 1 to 4 carbon atoms, n has a value of 3 to 8, each R is selected from alkyl groups having 1 to 4 carbon atoms, and R is the radical (CH.sub.2)mCH.sub.3Cl.sup. wherein m has a value of 12 to 20; adding a desired amount of sodium fluoride solution to said hydrolyzate; coating particulates of said thermoplastic with said hydrolyzate containing said sodium fluoride; heating and drying said coated particulates to yield dry coated particulates; providing said coated particulates as feedstock for providing thermoplastic products by a process selected from the group consisting of melt-spinning and injection molding.

[0018] Contemplated within the scope of this invention are compositions provided by this process and articles provided from the compositions of this process.

DETAILED DESCRIPTION OF THE INVENTION

[0019] What has been discovered is a method that allows for solventless incorporation of silanes into thermoplastics during the melting of the thermoplastic without scorching of the thermoplastic part. Furthermore, this method also results in thermoplastic parts that demonstrate substantial antimicrobial activity for incorporation of silanes that are also proven to demonstrate antimicrobial activity.

[0020] An aqueous solution of a silane is prepared and allowed sufficient time with appropriate pH adjustment and dilution to achieve a solution or dispersion of completely hydrolyzed silane (hydrolyzate).

[0021] The silanes can be purchased from Dow Corning Corporation, Midland, Mich. and consist of silanes such as (RO).sub.3Si(CH.sub.2)n-N.sup.+(R).sub.2(R)Cl.sup. wherein R is an alkoxy group having 1 to 4 carbon atoms, n has a value of 3 to 8, each R is selected from alkyl groups having 1 to 4 carbon atoms, and R is the radical (CH.sub.2)mCH.sub.3Cl.sup. wherein m has a value of 12 to 20. Preferred silanes are those having methoxy groups or ethoxy groups and an alkyl radical wherein m is 14 to 20, most preferred are methoxy groups and m equal to 18.

[0022] Such a molecule is (CH.sub.3 0).sub.3Si(CH.sub.2).sub.3N.sup.+(CH.sub.3).sub.2(C.sub.18H.sub.37)Cl.sup..

[0023] The hydrolyzate is then applied to a particulate thermoplastic such as pellets, or chips, and this can be accomplished in at least two ways. One method is to spray coat the particulates while agitating them in a container and the other way is to simply immerse the particulate thermoplastics into the hydrolyzate, both at room temperature.

[0024] The coated beads and then subjected to mild heat and drying to yield dry coated particulates. The dried coated particulates can then be used as is in a melt spinning operation or in injection molding. The heat and drying can be accomplished by forced hot air with the aid of an oven, a vacuum oven, a forced hot air dryer, or a coating machine capable of forced hot air drying, with drying occurring until further drying causes no significant loss of mass, insuring removal of the water.

[0025] It is believed that the unexpected success of this method (incorporation of the silane without scorching and survival of antimicrobial activity of the extruded or molded part despite the high temperatures involved in melting the thermoplastic) is due to the use of aqueous solutions of application of the silane to the particulate thermoplastics and the use of low heat when drying.

[0026] Additionally, we have discovered that soaking the final thermoplastic part in ambient water allows for a release of sodium fluoride into aqueous solution.

[0027] The compositions are useful for providing articles that are antimicrobial in nature. The compositions are also useful for delivering sodium fluoride, such as, for example, from toothbrush bristles while brushing teeth. It is also contemplated that the compositions would be useful for other brush configurations and as a woven mesh, for example in the application of clarifying and sterilizing water for drinking.

[0028] Examples of thermoset plastics that are useful in this invention include, for example, nylon, acrylic, polyurethanes, ethylene vinyl acetate. Especially useful are polyurethane polyesters and nylon.

[0029] Dental retainers are manufactured from acrylic resin thermoplastics, aligners used for movement of teeth are manufactured from polyurethane thermoplastics, boil-and-bite mouth guards are manufactured from ethylene vinyl acetate thermoplastics, mouth guards are injection molded from thermoplastics, and elastomeric orthodontic ligatures are manufactured from polyester polyurethanes.

[0030] Antimicrobial active Mouth guards used by children, especially children with braces, is a huge need as mouth guards get dirty pretty easily and children with braces more commonly have exposed cuts which presents a greater risk of infection.

EXAMPLES

[0031] The following examples illustrate the inventive method and are not meant to be limiting in any way to the general method outlined Supra, nor are the percentages of components indicated meant to be limiting, but are only illustrative.

[0032] The source of the silane was Dow Corning 5772, a 72% solution of 3-(trimethoxysilyl)propyldimethyl-octadecyl ammonium chloride in methanol. From this, a stable pH 9-10 3.6% solution of 3-(trihydoxysilyl) propyldimethyloctadecyl ammonium chloride (hydrolyzate) was prepared via 24 hour hydrolysis via aqueous dilution and addition of NaOH, with methanol removed via vacuum stripping. This was a clear pale orange solution upon formation (marketed by QuadSil Inc., Midland, Mich. as QS72-5), but became a stable milky dispersion upon standing for many weeks. Either form was successfully employed for proof of concept. Addition of sodium fluoride from 0.8-2.0% by mass rapidly converted both the solution and the dispersion to a stable gel.

Example 1

[0033] QuadSil QS72-5 (124.15 g) was combined and stirred with 1.035 g NaF to yield a stable gel.

Example 2

[0034] BASF Ultramid 8202 Polyamide 6 (Nylon 6) (10.0 g of approx. 3 mm diameter pellets) were coated with a total of 4.488 g of gel from Example 1 in a Pyrex beaker and then stirred and dried while heating on a hot plate (>300 C.) and with the aid of a hot air gun. The result was a dry whitish coating on the pellets. Note that such heating and drying could also be accomplished using an oven or a coating machine typically used to coat tablets and candies. The dried coating represented 1.79% of the total mass of the coated pellets (1.45% 3-(trihydoxysilyl)propyldimethyloctadecyl ammonium chloride (hydrolyzate); 0.34% NaF). Approximately 20 pellets were placed in an aluminum weigh boat and heated on a hot plate (cycling between 324-353 C.) to melting while being stirred with a stainless steel spatula, which was subsequently used to press a flat coupon. The coupon, upon cooling, demonstrated no visible scorching. Coupons were also prepared in a similar manner using uncoated pellets.

Example 3

[0035] Bayer Texin 285 aromatic (20.4 g of approx. 3 mm diameter pellets) were coated with a total of 10.105 g of gel from Example 1 in a Pyrex beaker and then stirred and dried while heating on a hot plate (>300 C.) and with the aid of a hot air gun. The result was a dry whitish coating on the pellets. Note that such heating and drying could also be accomplished using an oven or a coating machine typically used to coat tablets and candies. The dried coating represented 1.23% of the total mass of the coated pellets (1.05% 3-(trihydoxysilyl) propyldimethyloctadecyl ammonium chloride (hydrolyzate); 0.18% NaF). Approximately 20 pellets were placed in an aluminum weigh boat and heated on a hot plate (cycling between 324-353 C.) to melting while being stirred with a stainless steel spatula, which was subsequently used to press a flat coupon. The coupon, upon cooling, demonstrated no visible scorching. Coupons were also prepared in a similar manner using uncoated pellets.

Example 4: Antimicrobial Activity Evaluation of Treated Nylon and Polyurethane Thermoplastics

[0036] Antimicrobial activity employing Staphylococcus aureus was performed using Shake Test ASTM Method E2149-10 and samples Example 2 and 3. The results are presented in Table I.

TABLE-US-00001 Material Avg. CFU/ml % Reduction Two Hour Bacteria Control 3.32 10.sup.5 Not applicable Untreated Ultramid 8202 1.32 10.sup.5 60 Nylon 6 Untreated Texin 286 1.76 10.sup.5 47 Polyurethane Example 2 coupon 1.2 10.sup.4 96 Example 3 coupon 1.32 10.sup.5 60 Four Hour Bacteria Control 3.08 10.sup.5 Not applicable Untreated Ultramid 8202 2.8 10.sup.5 9 Nylon 6 Untreated Texin 286 2.64 10.sup.5 14 Polyurethane Example 2 coupon 8.0 10.sup.3 97 Example 3 coupon 2.4 10.sup.4 92

Example 5

[0037] QuadSil QS72-5 (49.04 g) of was combined and stirred with 1.00 g NaF to yield a stable gel.

Example 6

[0038] BASF Ultramid 8202 Polyamide 6 (Nylon 6) (20.30 g of approx. 3 mm diameter pellets) were coated with a total of 8.56 g of gel from Example 5 in a Pyrex beaker and then stirred and dried while heating on a hot plate (>300 C.) and with the aid of a hot air gun. The result was a dry whitish coating on the pellets. Note that such heating and drying could also be accomplished using an oven or a coating machine typically used to coat tablets and candies. The dried coating represented 1.65% of the total mass of the coated pellets.

[0039] Additional uncoated BASF Ultramid 8202 Polyamide pellets (14.78 g) were added to the coated pellets. This yielded a batch of pellets that were 99.04% Nylon, 0.61% 3-(trihydoxysilyl)propyldimethyloctadecyl ammonium chloride (hydrolyzate), and 0.35% NaF. Approximately 2 g of pellets were placed in a circular aluminum weigh boat (50 mm diameter) and heated on a hot plate (approx. 380 C.) to melting while pressing down on the pellets with the flat end of a Pyrex beaker (while rotating the beaker to simulate stirring of the melt) for 2.5 minutes, to yield a 0.8 mm thick flat coupon. The coupon, upon cooling, demonstrated no visible scorching. Coupons were also prepared in a similar manner using uncoated pellets.

Example 7

[0040] A 1.024 g circular coupon (0.8 mm thick, 43 mm diameter; 99.04% Nylon, 0.61% 3-(trihydoxysilyl)propyldimethyloctadecyl ammonium chloride (hydrolyzate), and 0.35% NaF) trimmed from an Example 6 coupon, was placed into a 300 mL beaker along with a magnetic stir bar and 200.0 g of RO water. The beaker was covered to prevent evaporation and the contents were stirred. Fluoride concentration was measured with a fluoride selective electrode as a function of time. The results are plotted in FIG. 1.

Example 8: Antimicrobial Activity Evaluation of Treated Nylon

[0041] Antimicrobial activity employing Staphylococcus aureus and Escherichia coli was performed using Test JIS Z 2801 Antimicrobial ProductsTest for antimicrobial activity and efficacy and samples from Example 6. The bacteria were in direct contact with the test material and covered with a coverslip in a humidity chamber for specified time points, then neutralized, dilutions made and plated out. The results are presented in Tables II and III.

TABLE-US-00002 TABLE II (Staphylococcus aureus) - Sixty Minute Time Point Material Average CFU/ml % Reduction Log Reduction Control 3.23 10.sup.4 Not applicable Not applicable Treated 3.3 10.sup.1 99.9 3

TABLE-US-00003 TABLE III (Escherichia coli) - Sixty Minute Time Point Material Average CFU/ml % Reduction Log Reduction Control 2.56 10.sup.4 Not applicable Not applicable Treated 5.67 10.sup.3 77.9 0.6