WO2010048436A2

WO2010048436A2 - Antimicrobial polymer with anti-yellowing property

Info

Publication number: WO2010048436A2
Application number: PCT/US2009/061722
Authority: WO
Inventors: Jonathan Robert Clapp
Original assignee: Microban Products Company
Priority date: 2008-10-22
Filing date: 2009-10-22
Publication date: 2010-04-29
Also published as: WO2010048436A3

Abstract

A polymer possessed of antimicrobial efficacy resist yellowing upon prolonged exposure to ultraviolet radiation. A combination of stabilizing additives protect the polymer and organic antimicrobial agent from degradation which commonly leads to such discoloration.

Description

ANTIMICROBIAL POLYMER WITH ANTI-YELLOWING PROPERTY

[0001] FIELD OF THE INVENTION

[0002] This invention relates generally to an antimicrobial polymer concentrate and, more particularly, to an antimicrobial composition containing non-yellowing additives.

[0003] BACKGROUND OF THE INVENTION

[0004] In the past, polyolefin articles exhibiting antimicrobial characteristics have been manufactured by combining a plurality of pellets of a polyolefin antimicrobial composition (composition or masterbatch) with a resin to form a polyolefin antimicrobial mixture (mixture) that is subsequently molded or extruded during manufacture of an polyolefin antimicrobial article (article). [0005] The composition/masterbatch is manufactured by compounding an antimicrobial agent into a polyolefin material (material) having a polyolefin substrate (substrate), including without limitation such materials as polyethylene (PE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ultra high density polyethylene (UHDPE), and polypropylene (PP).

[0006] The resultant masterbatch conventionally is combined with an unadulterated resin (with respect to antimicrobial agents) to produce the mixture. The material of the masterbatch composition must be compatible with the resin utilized in the process of making the mixture. [0007] A major disadvantage is that the antimicrobial agent may, in some instances, be sensitive to radiation (i.e., fluorescent light). As a result, the antimicrobial agent may degrade and cause subsequent yellowing of the substrate of the article upon extended exposure to fluorescent light or ultraviolet irradiation. Yellowing of the article is aesthetically unpleasing. [0008] DETAILED DESCRIPTION

[0009] As used herein, the terms "microbe" or "microbial" should be interpreted to refer to any of the microscopic organisms studied by microbiologists or found in the use environment of a ceramic article or ceramic-glazed article. Such organisms include, but are not limited to, bacteria and fungi as well as other single-celled organisms such as mold, mildew and algae. Viral particles and other infectious agents are also included in the term microbe.

[0010] As well, "antimicrobial" and like terms should be interpreted as encompassing both microbe-killing as well as microbistatic activities.

That is, it herein is considered efficacious if an antimicrobial composition reduces the number of microbes on a substrate or it the composition retards the normal rate of microbial growth.

[0011] For ease of discussion, this description uses the terms microbes and antimicrobial to denote a broad spectrum activity (e.g. against bacteria and fungi). When speaking of efficacy against a particular microorganism or taxonomic rank, the more focused term will be used

(e.g. antifungal to denote efficacy against fungal growth in particular).

[0012] Using the above example, however, it should further be understood that efficacy against fungi does not in any way preclude the possibility that the same antimicrobial composition demonstrates efficacy against another class.

[0013] For example, discussion of the strong bacterial efficacy demonstrated by a disclosed embodiment should not be read to exclude the embodiment from also demonstrating antifungal activity. This method of presentation should not be interpreted as limiting the scope of the invention in any way.

[0014] "PHR" is used in abbreviation for parts per hundred parts of resin. For example, as used in composites formulations, 5 PHR means that 5 pounds of an ingredient would be added to 100 pounds of resin.

Note that it differs slightly from other expressions of addition rate. For example, 1 % addition rate means if batch size is 100kg, then 1 kg is additive and 99kg is base resin. Here, 1 PHR means add 1 kg additive to 100kg base resin.

[0015] COMPOSITION

[0016] In a first embodiment, the present antimicrobial composition is a combination of an antimicrobial agent, two ultraviolet irradiation stabilizers and/or anti-oxidants, and optionally, a color/molecular weight stabilizer. One exemplary composition comprises: [0017] (a) 1 1.0% 5-chloro-2-(2,4-dichlorophenoxy)phenol (CAS No.

3380-34-5);

[0018] (b) 0.5% O,O'-dioctadecylpentaerythritol bis(phosphite) (CAS

No. 3806-34-6) (a color/molecular weight/UV stabilizer; available as Weston 618 from Crompton Corp., Middlebury CT); [0019] (C) 2.0% 1 ,3,5-triazine-2,4,6-triamine,N,N""-[1 ,2-ethane-diyl- bis[[[4,6-bis-[butyl(1 ,2,2,6,6-pentamethyl-4-piperidinyl)amino-1 ,3,5- triazine-2-yl]imino]-3,1 -propanediyl]]bis[N'N'"-dibutyl-N',N'"-bis(1 ,2,2,6,6- pentamethyl-4-piperidinyl)]-1 (CAS No. 106990-43-6) (available as Chimassorb 1 19 FL from Ciba Specialty Chemicals Co., Ltd., Tarrytown NY);

[0020] (d) 4.0% 2-(2'-hydroxy -3' -tert-butyl-5'-methylphenyl)-5- chloro benzotriazole (CAS No. 3896-1 1 -5) (available as Tinuvin 326 from Ciba Specialty Chemicals); and [0021] (e) 82.5% (balance) polypropylene.

[0022] INCORPORATION INTO POLYMER

[0023] Manufacture of a polymeric article having an additive incorporated therein can be accomplished in several ways. The manufacturer can incorporate the additive directly into the polymeric resin and form the article therefrom. Exemplary processes include, without limitation, extrusion of filaments, films sheets, casting of sheets and slabs, injection molding and spin molding.

[0024] A suitable resin may be selected from cellulose plastics, epoxy resins, ethyl cellulose, nylons, polybutylenes, polybutyleneterephthalate, polyethylenes, polyimides, polyphenylene oxide, polypropylenes, styrene butadienes, styrene polymers and copolymers, urethane elastomers, and vinyl polymers and copolymers, or a combination of two or more of these.

[0025] The composition is also suitable for use in thermoplastic resins, and particularly in polyvinyl chloride.

[0026] The mixture may subsequently be molded or extruded during manufacture of the article.

[0027] In processes such as extrusion, for example, the resin typically is fed into the extruder in a pelletized form. In some cases, a manufacturer can use a form of resinous pellet having incorporated therein the additive at the desired final concentration.

[0028] Alternatively, two resinous pellets can be used: an unadulterated resin, and a masterbatch resin containing the additive at an elevated concentration. In this second method, discussed generically herein, the two types of pellets are mixed in a ratio calculated to produce a finished polymeric article having the target concentration of additive therein.

[0029] The present antimicrobial composition can be incorporated in a masterbatch composition for subsequent incorporation in a polymeric material. Alternatively, the present antimicrobial composition can be incorporated at elevated concentration in a masterbatch, which then can be blended with another resin to form the finished polymeric article.

[0030] The ratio of stabilizer package (i.e., UV stabilizers) to triclosan is scalable, and there also is variation permissible from both sides. While the ratio of antimicrobial composition to resin in the exemplary masterbatch is 82.5:4:2, variations are permissible in the total UV stabilizer presence. For example, although 82.5:6 currently, variations can be from about 82.5:2 to about 82.5:10, inclusive. [0031] As to the ratio between triclosan and the stabilizer package, it is generally believed that >0 PHR to 2 PHR of triclosan and >0 PHR to 5 PHR of stabilizer package are acceptable without loss of the benefits and advantages discussed herein. As well, ratios between the two UV stabilizers (2:1 in the exemplary composition) may be from about 4:1 to about 1 :4, inclusive. [0032] A masterbatch containing the present antimicrobial composition can be manufactured by combining the antimicrobial concentrate with a resin. In one exemplary method, a polypropylene resin can be fed into an extruder, and the components of the antimicrobial composition introduced into the extruder at a desired point. The polypropylene extrudate will have the present antimicrobial composition incorporated therein. This technique is known in the extrusion art, and selection of parameters (e.g. temperature, screw dimensions, point of introduction of the antimicrobial composition) likewise is within the reach of the person having ordinary skill in this art. [0033] Further disclosed is a method of forming an antimicrobial product containing the present antimicrobial composition having an non- yellowing property, e.g. by molding or extruding. [0034] Because the present antimicrobial composition has a high affinity for remaining in solution within the amorphous zones and interstitial regions of polymers and in particular polypropylene, gross migration of the antimicrobial agent or other components of the composition to the surface of the antimicrobial concentrate at high concentrations is not observed. That is, no evidence is seen of chalking, oiliness or other indication of separation of the antimicrobial composition from the polymer. [0035] As a result, clumping of the masterbatch is reduced or substantially eliminated, even where the pellet size is greatly reduced. This property is generally advantageous and holds special promise for powder coating, wherein minute polymeric particles are employed and aggregation is strongly disfavored.

[0036] PROPERTIES OF FINISHED ARTICLE [0037] Products, manufactured from polymeric material containing the present antimicrobial composition as herein described, may include without limitation formed non-linear geometric shapes, slabs, sheets, films and fibers. Such products made for particular applications involving contact with food or liquids meant for human consumption may include, without limitation, cutting boards, countertop material, table covers, placemats, interior and exterior appliance components (e.g. refrigerator, dishwasher, microwave), plates and bowls, utensils, straws, carry-out or storage containers for food, food wrappers, sealable containers, sealable bags, bottles and bottle caps for beverage containers, water filter components, water softener components, water piping, and spouts intimately associated with beverages such as coffee, soda, and the like. [0038] A significant feature of the present antimicrobial composition is that an antimicrobial product made therefrom displays greater resistance to antimicrobial degradation and subsequent yellowing upon extended exposure to fluorescent or ultraviolet light. Therefore, the aesthetically unpleasing results of the yellowing of the antimicrobial product upon extended exposure to fluorescent light are mitigated. [0039] From the foregoing, the present non-yellowing antimicrobial composition has an antimicrobial agent and stabilizing components that do not exhibit gross migration through the amorphous zones and interstitial regions of the antimicrobial concentrate and subsequently to the surface of the concentrate at high concentrations. The present composition also does not exhibit chalking and clumping of its components on the surface of the polymer in which it is incorporated. [0040] Prevention of leaching of the antimicrobial agent from the surface of the antimicrobial product by chemical or mechanical means also alleviates a number of other problems otherwise pertaining to an antimicrobial polymeric product. For example, taste and odor issues can be associated with food and liquids meant for human consumption if antimicrobial composition components separate from the polymer and can be absorbed into the food. Phase separation further results in loss of the desired antimicrobial efficacy on the surface of the finished article.

[0041] EXAMPLES

[0042] Sample discs were made for evaluation using the exemplary composition disclosed above. A letdown rate of was chosen to achieve a final concentration of 2000 ppm antimicrobial agent in the samples.

[0043] Polypropylene was selected as the polymer substrate, owing to the yellowing issues conventionally observed when organic antimicrobial agents are incorporated therein. Similarly, triclosan was chosen as the organic antimicrobial agent because it displays particularly aggressive yellowing in polymers exposed to ultraviolet or fluorescent light.

[0044] Samples were placed in the test chamber of a Xenon-Arc

Weatherometer and exposed to light for 28 days (672 hours) without water spray. The wavelength of the lamps using the "Daylight Filter" option mimics the spectral output and intensity profile of sunlight, including spectral output from ultraviolet-B, ultraviolet-A and extending into the visual wavelengths.

[0045] The discs then were assessed for evidence of yellowing, clouding, chalking, or other visual defects.

[0046] Of the three sample discs, the untreated (negative) control was observed to have a typical cloudy or milky appearance, although still translucent.

[0047] The sample containing 3000 ppm triclosan displayed a noticeable yellow discoloring and darkening, of the type and degree typical for triclosan in plastics exposed to prolonged ultraviolet irradiation. [0048] The sample disc made with the present stabilized antimicrobial composition appeared clearer — that is, less milky/cloudy — than the negative control sample disc.

[0049] By experience, ultraviolet light-mediated discoloration of polymer samples containing organic antimicrobial additives (especially triclosan) has been observed to occur fairly immediately, and always within one week of xenon-arc exposure. Because samples having the present composition incorporated therein show superior color fastness after 28 days, it is postulated that the protection from discoloration will extend to far beyond the test timeline.

[0050] From the foregoing, it should be apparent that the present stabilized antimicrobial composition can be employed in the manufacture of polymeric articles intended for use in areas where exposure to ultraviolet or fluorescent light is expected, and that such articles will be protected from undue discoloration and/or yellowing suffered by conventional polymeric items having organic antimicrobial agents incorporated therein.

[0051] It will therefore be readily understood by those persons skilled in the art that the present composition and methods are susceptible of broad utility and application. Many embodiments and adaptations other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested to one of ordinary skill by the present disclosure and the foregoing description thereof, without departing from the substance or scope thereof. [0052] Accordingly, while the present composition and methods have been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary and is made merely for purposes of providing a full and enabling disclosure. The foregoing disclosure is not intended or to be construed to limit or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements.

Claims

1. An antimicrobial polymer, comprising: a polymer resin; and an antimicrobial composition including: an organic antimicrobial agent, and an ultraviolet radiation stabilization package that includes: a hindered amine ultraviolet radiation stabilizer, and a benzophenone-based ultraviolet radiation stabilizer; wherein the antimicrobial polymer is resistant to yellowing when exposed to ultraviolet radiation.

2. The antimicrobial polymer of claim 1 wherein the concentration ratio of organic antimicrobial agent to ultraviolet radiation stabilization package is from 0.1 :5 to 2:0.1 , respectively.

3. The antimicrobial polymer of claim 2 wherein the concentration ratio of organic antimicrobial agent to ultraviolet radiation stabilization package is 1.7:1.

4. The antimicrobial polymer of claim 1 wherein the hindered amine ultraviolet radiation stabilizer and benzophenone-based ultraviolet radiation stabilizer are present in a ratio of from about 4:1 to about 1 :4, inclusive.

5. The antimicrobial polymer of claim 1 wherein the hindered amine ultraviolet radiation stabilizer and benzophenone-based ultraviolet radiation stabilizer are present in a ratio of 1 :2.

6. The antimicrobial polymer of claim 1 wherein: the hindered amine ultraviolet radiation stabilizer is 1 ,3,5-triazine- 2,4,6-triamine,N,N""-[1 ,2-ethane-diyl-bis[[[4,6-bis-[butyl(1 , 2,2,6,6- pentamethyl-4-piperidinyl)amino-1 ,3,5-triazine-2-yl]imino]-3,1 - propanediyl]]bis[N'N'"-dibutyl-N',N'"-bis(1 ,2,2,6,6-pentamethyl-4- piperidinyl)]; and the benzophenone-based ultraviolet radiation ultraviolet radiation stabilizer is 2-(2'-hydroxy -3' -tert-butyl-5'-methylphenyl)-5-chloro benzotriazole.

7. The antimicrobial polymer of claim 1 wherein the ultraviolet radiation stabilization package comprises from about 2 percent to about 10 percent.

8. The antimicrobial polymer of claim 1 wherein the ultraviolet radiation stabilization package comprises about 6 percent.

9. The antimicrobial polymer of claim 1 wherein the ultraviolet radiation stabilization package comprises from about 364 ppm to about 1818 ppm.

10. The antimicrobial polymer of claim 1 wherein the ultraviolet radiation stabilization package comprises about 1090 ppm.

1 1. The antimicrobial polymer of claim 1 , further comprising a color/light stabilizing compound.

12. The antimicrobial polymer of claim 1 1 wherein the color/light stabilizing compound is O,O'-dioctadecylpentaerythritol bis(phosphite).

13. The antimicrobial polymer of claim 10 wherein O,O'- dioctadecylpentaerythritol bis(phosphite) comprises about 0.5 percent of the polymer.

14. The antimicrobial polymer of claim 1 wherein the organic antimicrobial agent is selected from the group consisting of 5-chloro-2- (2,4-dichlorophenoxy)phenol; diiodomethyl-p-tolylsulfone; and azole-based fungicides.

15. The antimicrobial polymer of claim 1 wherein the organic antimicrobial agent is 5-chloro-2-(2,4-dichlorophenoxy)phenol.

16. The antimicrobial polymer of claim 1 wherein the resin is selected from the group consisting of cellulose plastics; epoxy resins; ethyl cellulose; nylons; polybutylenes; polybutyleneterephthalate; polyethylenes; polyimides; polyphenylene oxide; polypropylenes; styrene butadienes; styrene polymers and copolymers; urethane elastomers; vinyl polymers and copolymers; and a combination of two or more of these.

17. The antimicrobial polymer of claim 16 wherein the polyolefin material is a polyethylene or a polypropylene.