LUBRICANT COMBINATIONS OF ERUCAMIDE AND A SATURATED CO-LUBRICANT IN COMPOSITIONS USED FOR MAKING CLOSURES

Abstract: Compositions for making closures which contain polyolefin resins and at least two lubricants; compositions for making linerless closures containing tocopherol anti-oxidant and closures made from the foregoing compositions are disclosed. Preferably, the lubricants are erucamide and at least one saturated co-lubricant

Description: LUBRICANT COMBINATIONS OF ERUCAMIDE AND A SATURATED CO-LUBRICANT IN COMPOSITIONS USED FOR MAKING CLOSURES This invention is directed generally to compositions for making closures which contain polyolefin resins and at least two lubricants; compositions for making linerless closures containing tocopherol anti-oxidant and closures made from the foregoing compositions. Preferably, the lubricants are erucamide and at least one saturated co-lubricant. Closures for containers are effective when they can both adequately seal a container after the container is filled, and subsequently readily opened for emptying of the contents of the container by the end-user. The composition of the closure will dictate each of these properties. Determination of whether or not a particular composition will be useful involves evaluation of both the application torque and removal torque of the closure. Application torque is a measure of the force required to seal the container when the closure is initially applied, and removal torque is a measure of the force required to remove the closure. The contents of the container and the container material are also relevant to the selection of the proper closure. Normally, a closure which is more tightly applied is also more difficult to remove. In order to improve the ease of removal of a closure, lubricants are often added to the closure composition. However, these lubricants have the potential for interacting with and leaching into the contents of the container. Fatty acid amides such as erucamide are typically used as lubricants in closures. However, these oleamides have double bonds which are susceptible to attack by oxygen. The result of this attack is that compounds such as aldehydes and ketones may be produced from the lubricants. These aldehydes may give an off- flavor or an off-odor to the contents of the container, which may be more or a less pronounced, depending upon the contents. Notably, mineral waters have such delicate bouquets that they cannot tolerate even relatively slight off-flavors. Moreover, bottled drinking water may be disinfected with ozone to remove micro-organisms. Typically, ozone is present in bottled water in trace amounts, from 0.1 to about 0.4 mg/1. The ozone may also react with double-bond containing compounds (such as erucamide) to yield aldehydes. These aldehydes are thought to be responsible for fruity to musty off-flavors in bottled water, depending upon the concentration of the contaminant. Since drinking water standards specify that drinking water should not have a smell or a taste, use of erucamides in closures can present a problem. Anti-oxidants are frequently added in an attempt to retard undesirable interactions of the lubricant or other closure composition additives. However, these must also be carefully selected to avoid unfavorable interactions. It is therefore an object of the invention to provide closure compositions containing lubricants which reduce off-flavor and/or off-odor problems. It is a further object of the invention to provide an anti-oxidant which reduces off-flavor and/or off-odor problems by protecting against oxidation of polypropylene or lubricants. The invention is directed to a closure composition comprising: a) from about 98.5 to about 99.9 weight percent of at least one polyolefin resin; and b) from about 1.5 to about 0.01 weight percent of a combination of erucamide and at least one saturated co-lubricant, wherein the ratio of erucamide to co-lubricant is 1 :10 to 10:1. The composition may further comprise from about 0.1 to about 3 weight percent of at least one anti-oxidant. The anti-oxidant may be tocopherol or a homologue thereof. The composition may also contain an additional anti-oxidant, wherein the ratio of said anti-oxidant to said additional anti-oxidant is from about 1 :5 to about 5:1. The invention is also directed to a closure composition for a linerless closure comprising: a) from about 97 to about 99.9 weight percent of at least one polyolefin resin; and b) from about 3 to about 0.1 weight percent of anti-oxidant tocopherol or homologues thereof. The composition may further comprise a lubricant, or an additional anti-oxidant, wherein the ratio of said tocopherol to said additional anti-oxidant is from about 1 :5 to about 5:1. More particularly, the lubricant may be about 1.5 to about 0.01 weight percent of the total composition, and the lubricant may be a combination of erucamide and at least one saturated co-lubricant. The ratio of erucamide to co-lubricant may be 1:10 to 10:1. The invention is also directed to a closure comprising: a circular top wall having a depending annular skirt; said skirt having internal threads and a depending pilfer band; wherein said closure is molded from the composition described above. For any aspect of this invention, the polyolefin may be polypropylene; additives such as pigments and emulsifiers may also be included; or the closure may be a linerless closure. More particularly, an additive pigment which may be utilized is ultramarine blue. The saturated co-lubricant may be stearamide, behenamide, ethylene bis-stearamide or zinc stearate. The invention is also directed to a method for reducing off-odors and off- flavors of contents stored in sealed containers comprising the step of: sealing said container with a linerless closure, wherein said linerless closure is of the composition described above. The container's contents may be water or other potable beverages, and the off-odors and off-flavors may be derived from aldehydes or ketones which may be formed by undesirable reactions with certain additives to a closure composition. Figure 1 is a cross-sectional view of a plastic closure embodying the principles of the present invention; and Figure 2 is an enlarged, fragmentary view of the closure shown in Figure 1 illustrated with an associated container. This invention is directed generally to compositions for making closures which contain polyolefin resins and at least two lubricants; compositions for making linerless closures containing tocopherol anti-oxidant and closures made from the foregoing compositions. Preferably, the lubricants are erucamide and at least one saturated co-lubricant. Definitions of Terms: As used herein, the term "composition" is intended to encompass a product comprising the specified ingredients in the specified amounts, as well as any product which results, directly or indirectly, from a combination of the specified ingredients in the specified amounts The Lubricants Lubricants have been utilized externally to treat the sliding surfaces of caps for reducing opening torque as disclosed in U S Patent No 4,710,409 Alternatively, lubricants may be constituents of the closure composition, as taught for example by U S Patent No 4,209,102 Those skilled m the art understand that erucamide is a useful lubricant for incorporating into the closure composition However, the possibility for unfavorable interactions of erucamide which produce off-flavors or off-odors exists, as was previously described We have found that when the amount of erucamide is reduced, and a suitable co-lubπcant is utilized, the resultant lubricant combination allows for retention of desirable torque properties and minimization of the potential for undesirable interactions of the closure and the associated product Combinations of lubricants for use in closure liners are disclosed m U S Patent Nos 5,306,542 and 5,925,430 However, closure liners are based on different resins than the present linerless closures Moreover, there is no recognition m these patents that a saturated co-lubπcant will be particularly useful for the prevention of off-odors and off-flavors At least one co-lubπcant is utilized in combination with erucamide in the closure composition In the present compositions, the co-lubπcant is a compound which is saturated, meaning it does not have double bonds The use of a co-lubπcant decreases the amount of erucamide which must be utilized Furthermore, if the co-lubπcant is unsaturated, there is a lesser likelihood of unfavorable interactions Consequently, the potential for production of off-flavors or off-odors from the lubricant combinations will be minimized The ratio of erucamide to the co-lubπcant is from 1 10 to 10 1, preferably from 1 5 to 5 1 and most preferably from 1 2 to 2 1 The co-lubπcants to be used in conjunction with erucamide may be aliphatic hydrocarbon lubricants such as liquid paraffin, white mineral oils of industrial grade, synthetic paraffin, petroleum wax, petrolatum and odorless light hydrocarbons, sihcones such as organopolysiloxanes, higher saturated fatty acids obtained from vegetable and animal oils and fats and hydrogenation products thereof, having 8 to 22 carbon atoms, hydroxysteaπc acid, linear aliphatic monohydπc alcohols having at least 4 carbon atoms, obtained by reducing animal and vegetable oils and saturated fats or by cracking distillation of natural waxes, dodecyl alcohol, polyglycols such as polyethylene glycols having a molecular weight of 200 to 9500, polypropylene glycols having a molecular weight of at least 1000, and polyoxypropylene-polyoxyethylene block copolymers having a molecular weight of 1900 to 9000, alkali metal, alkaline earth metal, zmc or aluminum salts of higher saturated- fatty acids, various metal soaps, low molecular weight olefin resms such as low molecular weight polyethylene, low molecular weight polypropylene and oxidized polyethylene, fluorine resms such as polytetrafluoroethylene, tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotπfluoroethylene and polyvinyl fluoride, propylene glycol alginate, dialkyl ketone and acrylic copolymers among others The co-lubπcant may be an amide or an amme such as higher fatt\ acid amides, 2-steroamιdoethyl stearate, ethylene-bis- saturated fatty acid amides, N,N'-bιs-(2-hydroxyethyl)-alkyl amides having 12 to 18 carbon atoms in the alkyl group, N,N'-bιs(hydroxyethyl)-lauroamιde, fatty acid diefhanolamines and disteaπc acid esters of dι(hydroxyethyl)-dιethylene tπamme monoacetate The co-lubπcants may also be fatty acid esters of monohydπc or polyhydπc alcohols such as n-butyl stearate, methyl ester of hydrogenated rosin, di-n-butyl sebacate, 2-ethylhexyl sebacate, octyl sebacate, glycerin fatty acid ester, steaπc acid ester of pentaerythritol, pentaerythritol tetrastearate, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyethylene glycol monostearate, polyethylene glycol dilaurate, polyethylene glycol monooleate, polyethylene glycol dioleate, polyethylene glycol coconut fatty acid ester, polyethylene glycol tall oil fatty acid ester, 1,3-butanediol diethylene glycol stearate and propylene glycol fatty acid ester among others The co-lubπcants may also be tπglyceπdes and waxes such as hydrogenated edible oils and fats, cotton seed oil and other edible oils, linseed oil, palm oil, glycerin ester of 12-hydroxysteaπc acid, hydrogenated fish oils, beef tallow, spermaceti wax, montan wax, carnauba wax, bees' wax, haze wax, esters of monohydπc aliphatic alcohols with aliphatic saturated acids such as hardened whale oil, lauryl stearate and stearyl stearate and lanolme among others Those skilled in the art understand that some of the natural products described in this paragraph may be partially unsaturated. Such products would be hydrogenated prior to use as saturated co-lubricants in the compositions described herein. Presently preferred co-lubricants are behenamide (CRODAMIDE BR, available from Croda Oleochemicals of England); ethylene bis-stearamide, stearamide and zinc stearate. The lubricant combination is incorporated in an amount of 0.01 to 1.5% by weight, preferably 0.2 to 1% by weight, and especially preferably 0.2 to 0.5% by weight in the closure composition, based on the base resin. When the amount of the lubricant is too small and below this range, the opening torque becomes too high and the opening operation is difficult. When the amount of lubricant is too large and exceeds the above range, the application torque is too low, causing insufficient sealing. The Anti-Oxidants: Useful anti-oxidants include ascorbic acid; iso- ascorbic acid; gallic acid; tocopherol; hydroquinone; catechol; resorcine; dibutylhydroxytoluene; dibutylhydroxyanisole; pyrogallol; hydroxyphenylpropionates such as tetrakismethylene(3,5-di-t-butyl-4'-hydroxyphenyl propionate; alkyl phenols such as 2,6-di-tert-butyl-4-rnethylphenol; hydroxybenzyl compounds such as tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate; alkylidene bisphenols such as 2,2'-methylene-bis(4-methyl-6-t-butylphenol); phosphites and phosphonites such as bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite; sorbose; glucose; lignin; iron based anti-oxidants such as iron powder, activated iron, ferrous oxide and iron salt; inorganic anti-oxidants such as sulfite, thiosulfite, dithionite and hydrogen sulfite; polymers such as redox resins and polymer-metal complexes; zeolites; activated carbon or salts thereof among others. Combinations of the above-mentioned anti-oxidants will also have utility in the present closure compositions. Tocopherol is a preferred anti-oxidant; however, a wide variety of tocopherol compounds may be used. The compound dl-alpha-tocopherol (2,5,7,8-tetramethyl-2-(4',8',12'-trimethyltridecyl)-6-chromanol) also known as Vitamin E is quite useful. However, homologues such as the stereospecific isomers of alpha or beta tocopherol; gamma tocopherol and 6-tocopherol may also be used in accordance with the present invention. Vitamin E has been described as a useful anti-oxidant in HDPE polymers by Ho et al. in the Journal of Vinyl & Additive Technology, June 1998, Vol. 4, No. 2, pp 139-150. Tocopherol has also been disclosed as a flavor protecting in conjunction with another compound for closure liners in U.S. Patent Nos. 5,863,964 and 5,663,223. Moreover, tocopherol has also been disclosed as a useful oxygen scavenger in a cover for a container in U.S. Patent No. 5,143,763. However, tocopherol has not been disclosed for use as an anti-oxidant in compositions for making linerless closures. Closure liners normally contain ethylene vinyl acetate, through which the tocopherol readily disperses. However, the polyolefin resins such as polypropylene utilized in compositions for making linerless closures, would not be assumed to allow facile, tocopherol dispersion. Furthermore, useful anti-oxidants may contain catalysts, water-retentive agents or hydrates. Preferably, the anti-oxidants are present in the closure composition in an amount of from about 0.1 to about 3%> weight percent, more preferably in an amount of from about 0.2% to 2% weight percent, and most preferably in an amount of from about 0.5 to 1.5 weight percent. When two anti-oxidants are used together in the closure compositions, the ratio of the first anti-oxidant to the second anti-oxidant is from about 1 :5 to about 5:1, preferably from about 1 :3 to about 3:1 and most preferably from about 1 :2 to about 2: 1. The Resins: Polyolefms such as polyethylene, polypropylene or copolymers formed from propylene or ethylene with at least a second monomer may be utilized in the closure compositions. Polypropylene is a particularly preferred resin. Combinations of any of the above-mentioned polyolefin may also be utilized. Other Constituents: Pigments may be added to the closure compositions. In order to color the closure, or render it opaque, white pigments such titanium dioxide may be added; color pigments such as carbon black, red iron oxide, tartrazine lake or ultramarine blue (ULTRAMARINE BLUE NUBIX E-25, available from Clariant) may be added. Microencapsuled pigments may be particularly advantageous. Pigment is usually from about 0.2%o to about 0.8%> of the total composition. Emulsifiers may be added to the co-lubricants, or separately to the closure compositions. Appropriate emulsifiers include non-toxic, non-ionic surfactants which are virtually tasteless at the concentrations employed, or at least devoid of any unpleasant or undesired taste. Examples are sorbitan polyoxyethylene fatty acid esters such as sorbitan polyethylene (20) mono-oleate (TWEEN 80). The ratio of the lubricating composition to the emulsifier and the concentration of the emulsifier in the lubricating formulation may vary within wide limits, depending upon circumstances. The Closures: The compositions described above may be utilized to form closures. A presently preferred closure is described as follows. While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. With reference to FIGURES 1 and 2, therein is shown a container closure 10 which is used in conjunction with an associated container C. The closure includes a circular top wall portion 12, and a depending annular skirt portion 14. The closure includes an internal thread formation 16 on the skirt portion 14 for threaded cooperation with a thread formation on the associated container C. In order to facilitate venting of gas pressure from within an associated container, the skirt portion 14 of the closure 10 defines a plurality of axially extending vent grooves 18. In the illustrated embodiment, the closure 10 is configured for tamper-indication, and accordingly, includes an annular pilfer band 20 which depends from, and is at least partially frangibly connected to skirt portion 14. The pilfer band includes an annular band portion 22 which is distinguished from the skirt portion 14 by a circumferentially extending score 24 which separates the pilfer band from the skirt portion. A plurality of circumferentially spaced frangible bridges 26 extend between the inside surfaces of the skirt portion and pilfer band to provide the desired frangible connection therebetween. In the illustrated embodiment, the pilfer band 20 of the closure 10 is configured in accordance with the teachings of U.S. Patent No. 4,938,370, to McBride, hereby incorporated by reference. Accordingly, the illustrated pilfer band includes a plurality of circumferentially space, inwardly extending flexible projections 28 which are configured for cooperative engagement with the annular locking ring of the associated container C. The pilfer band of the closure 10 may be otherwise configured, such as in accordance with the teachings of U.S. Patent No. 4,418,828, to Wilde et al., hereby incorporated by reference. The illustrated closure 10 is of a linerless construction, that is, the closure does not include a sealing liner component or like element positioned near or adjacent to the top wall portion 12 for sealing engagement with an associated container. Rather, the closure includes an integral and unitary annular sealing lip 30 which projects inwardly generally from the juncture of top wall portion 12 and skirt portion 14. Annular sealing lip 30 is configured for resiliently flexible engagement with the associated container C, as shown in FIGURE 2. The desired sealing cooperation between the sealing lip and the container is enhanced by the provision of an annular stop element 32 which depends from top wall portion 12 of the closure 10. As illustrated in FIGURE 2, flexible sealing lip 30 is urged upwardly against the stop element 32 as the closure 10 is applied to the associated container C, with the stop element thus cooperating with the sealing lip to urge the sealing lip into sealing cooperation with the container C. The following examples are presented to describe preferred embodiments and utilities of the invention and are not meant to limit the invention unless otherwise stated in the claims appended hereto. EXAMPLE 1 To illustrate the utility of the compositions of the present invention, the combinations of erucamide and saturated co-lubricant were formulated into compositions typically utilized for linerless closures, and then injection molded into closures. These closures were subjected to conditions which would enhance any potential undesirable interactions, and then informally odor tested to determine whether or not any off-odors could be detected. The experiments were performed as follows. Polypropylene resin samples were prepared using a 2" single screw extruder to compound fluff containing lubricants as specified in Table 1 below. Erucamide was from Witco as KEMAMIDE E, having as the major constituent 13-czs-docosanamide. The co-lubricants were behenamide (available from Croda Oleochemicals of England as CROD AMIDE BR, major constituent: docosanamide); ethylene bis-stearamide, stearamide (octadecanamide, available from Witco as KEMAMEDE S) and zinc stearate (available from Akzo Nobel). Each formulation was then rotary compression molded to form a closure for evaluation. To determine the oxidative stability of the resultant closures, a piece of each closure was placed in a jar containing hydrogen peroxide. The jars were sealed, and the pressure was reduced within the jar. Subsequently, the jars were placed in an oven and the temperature was maintained at 120°F for three days. After this time period, a 10 ml sample of the headspace was analyzed via GC/MS to identify any volatile compounds present. The solution was also analyzed by GC/MS. The analytical tests indicated that amines were not present in the closure materials containing the lubricant combinations, though amines could be detected when compositions containing erucamide as the sole lubricant were tested. The formulations which were further informally tested by a panel to determine whether or not there were disagreeable odors. Formulations 1 through 3 represent the combinations described herein, and formulations 2 and 3 clearly show that contaminants were not detected either analytically or by an informal panel, and none of the three formulations contained amines according to GC analysis. Since the odor tests were informal, reliance upon the GC analysis results was given greatest weight in the determination of acceptability. TABLE 1 0.2% o composition EXAMPLE 2 The procedure for making test samples described in Example 1 was utilized to test other formulations by a panel, using the conventional triangle test or multiple comparison test. The composition of the formulations is detailed in Table 2. Formulations 4 and 5 represent the conventional lubricant, erucamide alone. Formulations 6 and 7 represent the combinations disclosed herein. Test samples were evaluated after one week, after two weeks, after two months and after four months after the sample was placed in the jar. In each case, formulations 6 and 7 were judged by the panel to be within the requirements met by currently acceptable closures. The currently acceptable closure is made of polyethylene, a resin which requires much less lubrication than polypropylene. TABLE 2 All references cited are hereby incorporated by reference. The present invention is illustrated by way of the foregoing description and examples. The foregoing description is intended as a non-limiting illustration, since many variations will become apparent to those skilled in the art in view thereof. It is intended that all such variations within the scope and spirit of the appended claims be embraced thereby. Changes can be made in the composition, operation and arrangement of the method of the present invention described herein without departing from the concept and scope of the invention as described in the following claims.

Claims: C L A I M S 1. A closure composition comprising: a) from about 98.5 to about 99.9 weight percent of at least one polyolefin resin; and, b) from about 1.5 to about 0.01 weight percent of a combination of erucamide and at least one saturated co-lubricant, wherein the ratio of erucamide to co-lubricant is 1 :10 to 10:1. 2. The composition of claim 1, wherein said polyolefin is polypropylene. 3. The composition of claim 1, for a linerless closure. 4. The composition of claim 1, further comprising from about 0.1 to about 3 weight percent of at least one anti-oxidant. 5. The composition of claim 4, wherein said anti-oxidant is tocopherol or a homologue thereof. 6. The composition of claim 4, further comprising an additional anti- oxidant, wherein the ratio of said anti-oxidant to said additional anti-oxidant is from about 1 :5 to about 5:1. 7. The composition of claim 1, further comprising an additive selected from the group consisting of pigments and emulsifiers. 8. The composition of claim 7, wherein said additive is ultramarine blue. 9. The composition of claim 1, wherein said saturated co-lubricant is selected from the group consisting of stearamide, behenamide, ethylene bis- stearamide and zinc stearate. 10. A closure composition for a linerless closure comprising: a) from about 97 to about 99.9 weight percent of at least one polyolefin resin; and, b) from about 3 to about 0.1 weight percent of anti-oxidant tocopherol or homologues thereof. 11. The composition of claim 10, further comprising an additive selected from the group consisting of pigments and emulsifiers. 12. The composition of claim 11, wherein said additive is ultramarine blue. 13. The composition of claim 10, wherein said polyolefin is polypropylene. 14. The composition of claim 10, further comprising a lubricant. 15. The composition of claim 10, further comprising an additional anti-oxidant, wherein the ratio of said tocopherol to said additional anti-oxidant is from about 1 :5 to about 5:1. 16. The composition of claim 10, further comprising from about 1.5 to about 0.01 weight percent of a combination of erucamide and at least one saturated co-lubricant. 17. The composition of claim 15, wherein said co-lubricant is selected from the group consisting of stearamide, behenamide, ethylene bis-stearamide and zinc stearate. 18. A closure comprising: a circular top wall having a depending annular skirt; said skirt having internal threads and a depending pilfer band; wherein said closure is molded from the composition of claim 1. 19. A method for reducing off-odors and off- flavors of contents stored in sealed containers comprising the step of: sealing a container with a linerless closure, wherein said linerless closure is of the composition of claim 1.

Inventors: DOUN STEPHEN KUNSHEN, GAIKWAD SANJEEV M, LELAND MARK E, DOUN, STEPHEN, KUNSHEN, GAIKWAD, SANJEEV, M., LELAND, MARK, E.
Applicants: ALCOA INC, DOUN STEPHEN KUNSHEN, GAIKWAD SANJEEV M, LELAND MARK E, ALCOA INC., DOUN, STEPHEN, KUNSHEN, GAIKWAD, SANJEEV, M., LELAND, MARK, E.
Application year: 2001
Main classification: C08K5
IPC codes: B65D41, B65D51, C08J5, C08K5, C08L23