Field of Invention

This invention relates to novel amides having utility as antioxidants.

Background Many organic materials, such as polymers, fuels, and lubricants, are normally susceptible to oxidative deterioration and tend to suffer severe degradation and/or discoloration during processing and/or later use unless they are stabilized.

The compounds which have previously been proposed for use in stabilizing these materials have frequently been phenolic compounds, and some such compounds have been very successfully employed as antioxidants for some of the normally oxidizable materials. However, no single compound could be the best possible antioxidant for each of the variety of organic materials which are normally susceptible to oxidative deterioration, since:

( 1 ) the compounds which have the lowest volatility and highest thermal stability are not necessarily those which have the most suitable melting points, the least tendency to degrade to highly-colored compounds, and the greatest ability to stabilize organic materials during processing,

(2) some of the orgamc materials (e.g., the polymers) are less capable than others (e.g., fuels and lubricants) of tolerating the substantial discoloration that occurs when many phenolic compounds are subjected to processing conditions,

(3) some antioxidant compounds are so volatile and have such poor thermal stability that they are unsuitable for use in organic materials for which high processing temperatures and/or long-term stabilization are required, and

(4) some antioxidant compounds have melting points so high as to present a drawback to their use in materials which must be processed at low or moderate temperatures.

Thus, it is necessary to have different antioxidants to serve the different needs of the various organic materials which require stabilization.

Because of the need for these different antioxidants for different organic materials, it would be desirable to be able to find a class of antioxidants which could be derived from a common intermediate or a common genus of intermediates that could be easily modified so as to provide the different antioxidant properties required in the variety of specific market needs.

As disclosed in U.S. Patents 3,780,103 (Knell), 3,808-273 (Burdet et aL), 3,927,091 (Huber-Emden et al.), 3,996,194 (Gencarelli et aL), 4,098,760 (Cornell), 4,100,191 (Fischer et al.), and 4,132,702 (Schmidt et al.) and Netherlands Patent Application 7905000 (Cincinnati Milacron Chemicals), it is known that some amides containing substituted hydroxyphenyl groups have been found to be useful as stabilizers for some orgamc materials which are normally susceptible to oxidative deterioration.

N,N-bis(3 -di-t-butyl-4-hydro)q.benzyl)acetamide is disclosed by G. A. Nikiforov et al. in Izvesάya Akad mii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2765-2770, 1989.

Summary of Invention The invention resides in (1) tertiary amides corresponding to the formula:

wherein R is a mono-, di-, or trivalent aromatic or saturated aliphatic hydrocarbon group containing 1-20 carbons; n is an integer of 1-3 which is equal to the valence of R; R' is phenyl, benzyl, or - alkyl; m is an integer of 1-3; R" is a -C-, alkylene group; Z and Z' are independently selected from hydrogen and alkyl; and Q is carbonvl or sulfonyl and (2) the use of the tertiary amides is antioxidants for organic materials which are normally susceptible to oxidative deterioration.

Detailed Description

The novel tertiary amides of the invention are amides containing alkyl-substituted hydroxyphenyl groups which are separated from the amido nitrogens by a linking chain of at least two carbons. This type of linkage is an important feature of the compounds, since it provides lower volatility and higher thermal stability than a linkage constituted by a single carbon and thus makes the compounds superior to the corresponding compounds containing the shorter linkage, e.g., the compounds of Nikiforov et al. As indicated by the formula, the p-alkyl substitutent represented by CZZ'R" may have a branched chain when R" is a branched alkylene group and/or at least one of Z and Z' is alkyl (usually an alkyl of only 1-4 carbons). However, it is generally preferred for that substituent to be unbranched except for the branching provided with Z is methyl; and it is apt to be most preferred for the R" alkylene group to be unbranched and for Z and Z' to be hydrogen so that the CZZ'R" of the formula is a -(CH ₂ ) _p group in which p is an integer of 2-5. As also indicated by the formula, (1) the novel tertiary amides may be derivatives of aliphatic or aromatic carboxamides, diamides, triamides, or the corresponding sulfonamides which provide an R hydrocarbon group of up to 20 carbons, and (2) the R' substituents on the p-hydroxyphenylalkyl groups may be 1-3 in number; may be phenyl, benzyl, or - alkyl; and, when there is more than one, may be the same or different. However, it is usually preferred that there be two such substituents, which are most commonly alkyl groups containing 1-4 carbons, in the positions ortho to the hydroxy group.

Exemplary of the novel tertiary amides of the invention are the (1) acetamides, propionamides, isopropionamides, butyramides, palmitamides, stearamides, and benzamides, (2) diamides of malonic, succinic, glutaric, adipic, dodecanoic, tetradecan- dioic, hexadecandioic, dicarboxycyclohexane, phthalic, isophthalic, and terephthalic acids, (3) triamides of and 1,2,4- and 1,3,5-benzenetricarboxylic acids, and (4) corresponding sulfonamides, such as the methanesulfonamides, propanesulfonamides, and benzenesulfonamides in which the N-substituents are 9-(3,5-di-t-butyl-4-hydroxypheπyl)ethyl, 0-(3-methyl-5-t- butyl-4-hydroxyphenyl)ethyl, 0-(3,5-diphenyl-4-hydroxypbenyl)ethyl, 0-(3-benzyl-5-

methyl-4-hydroxyphenyl)ethyl, ø-(3-t-butyl-4-hydroxyphenyl)ethyl, 0-(2-methyl-3,5-di-t- butyl-4-hydroxyphenyl)ethyl, 3-(3,5-diisopropyl-4-hydroxyphenyl)ethyl, γ-(3,5-di-t-butyl- 4-hydroxyphenyl)propyl, 7-(3-methyl-5-t-butyl-4-hydroxyphenyl)propyl, α.-methyl-γ-(3,5- di-t-butyl-4-hydroxyphenyl)propyl, or e -(3-t-butyl-4-hydroxyphenyl)pentyl. Among the more preferred tertiary amides of the invention are (1) the N,N- bis[S-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]acetamide, N,N-bis[£-(3,5-di-t-butyl-4- hydroxyphenyl)ethyl]stearamide, N,N-bis[^-(3^-dii-_opropyl-4-hydro3-ypheιιyl)ethyl]acet- amide, and N,N-bist^-(3-metl^l-5-t-butyl-4-hydro)Q henyl)ethyl]acetamide monoamides, (2) the N,N,N',N'-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]- and N,N,N',N'- tetrakis[3-(3-methyl-5-t-butyl-4-hydroxyphenyl)ethyl]glutara mide, terephthalamide, succinamide, and adipamide bisamides, (3) the N,N,N',N ^, ,N ^, ',N"-hexakis[i9-(3^-di-t-butyl-

4-hydτoxyphenyl)ethyl]-andN,N,>F,N\>W nyl)ethyl]-1 ,5-beπzenetricarboxamides, and (4) the N,N-bis[ 3-(3,5-di-t-butyl-4- hydro heι_yl)etbyl]-,N,N-bis[3-(3,5-dusop (3-methyl-5-t-butyl-4-hydroj_yphenyI)ethyl]methanesulfonamid es.

The most preferred of the tertiary amides are apt to be N,N-bis[.β-(3,5-di-t-butyl- 4-hydroxyphenyl)ethyl]acetamide, N,N-bis[ S-(3-5-di-t-butyl-4-ltydro)0'pheπyl)ethyl]meth- anesulfonamide, N,N,N',N'-tetrakis[jS-(3-5-di-t-butyl-4-hydroxyphenyl)ethyl] gluta_ram N,N,N',N'-tetrakis[jS-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl] terephthalamide, and N,N,N\ r,^N"-hexakis[ H3-5-di-t-buty^ boxamide — the particular tertiary amide preferred in any specific instance depending on the needs of the particular organic material being stabilized.

The tertiary amides may be prepared by reacting the appropriate acyl or sulfonyl halide corresponding to the formula R(QX) _n with the appropriate secondary amine corresponding to the formula:

R--C22 — I — OH

H N

X representing halo, preferably chloro or bromo; and R, R\ R", Q, Z, Z\ m, and n being as previously defined. Thus, for example, (1) an acyl halide such as acetyl chloride, propionyl chloride, butyryl bromide, isobutyryl chloride, stearoyl chloride, or benzoyl chloride, (2) a dicarboxylic acid dihalide such as glutaryl dichloride, malonyl dichloride, adipyl dibromide, succinyl dichloride, terephthaloyl dichloride, isophthaloyl dichloride, cyclopentane-l,3-dicarboxylicaciddibromide,cyclohexane-l,4-d icarboxylic acid dichloride, 1,12-dodecanedicarboxylic acid dichloride, or 1,14-tetradecanedicar- boxylic acid dichloride, (3) a tricarbonyl trihalide such as a 1,2,4- or 1,3,5-benzenetricar- bonyl trichloride, 1,23-propanetricarbonyl tribromide, bonyl trichloride, or (4) a sulfonyl halide such as methanesulfonyl chloride, 1- butanesulfonyl bromide, 1-pentanesulfonyl chloride, 1-decanesulfoπyl chloride, or benzenesulfonyl chloride is reacted with a secondary amine such as bis[/3-(3-5-di-t-butyl- 4-hydroxyphenyl)ethyl]amine, bis[γ-(3-methyl-5-t-butyl-4-hydrθ3^phenyl)propyl]amine, or other such amine. In the synthesis of the tertiary amides, the amines and acid halides are reacted in substantially stoichiometric amounts in a solvent which is inert to the reaction and which is capable of solubilizing both the reactahts and the product and optionally in the presence of an acid scavenger which can neutralize acid produced by the reaction without adversely affecting the process. Solvents suitable for use in the reaction include, e.g., toluene, benzene, xylene, mesitylene, pentane, hexane, heptane, octane, chlorobenzene, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,2-trichloroethane, diethyl ether, and petroleum ether, the preferred solvents usually being toluene and methylene chloride. Examples of acid scavengers which may be used in the process are trimethyl- amine, triethylamine, tripropylamine, tributylamine, pyridine, 4-dimethylaminopyridine. and 2.6-lutidine, with the preferred acid scavenger being triethylamine. When employed, the acid scavenger is used in an amount such as to provide about one mol of acid scavenger per mol of acid generated by the reaction. In the preparation of the tertiary amides, the components of the reaction mixture are combined in any suitable way, conveniently by slowly adding a solution of the amine

(and optionally also an acid scavenger) in a portion of the solvent to a solution of the acid halide in the remainder of the solvent while maintaining the reaction mixture at a temperature of 0-25 * C. Then, when combination of the reactants is at least substantially complete, the temperature is raised, if necessary, to be in the range of 10-45 ' C, preferably 25-35 * C, and kept in that range for a suitable time, e.g., 2-10 hours. It is ordinarily most convenient in this reaction to use ambient temperature.

After completion of the reaction, the product can be recovered in any appropriate way. For example, the reaction mixture may be diluted with solvent, preferably the same solvent as was used in the reaction; the diluted reaction mixture may then be washed with an inorganic acid, such as HQ; the organic phase resulting from this wash may be recovered and washed with a base, such as NaOH; the organic phase resulting from this wash may be recovered and washed with a salt solution, e.g., aqueous NaCl; and the organic phase resulting from this wash may be recovered and dried to yield the desired tertiary amide. In an embodiment of the invention, the tertiary amides are used as antioxidants for organic materials which are normally susceptible to oxidative deterioration, such as the organic materials taught in Knell, Huber-Emden et al., Gencarelli et al., and Schmidt et al.

Although the organic materials that can be stabilized in the practice of the invention include various materials such as fuels, hydrocarbon and ester lubricants, plasticizers, epoxy resins, polycarbonates, polyurethanes, polyureas, polyamides, polyesters, polyethers, phenol-formaldehyde resins, urea-formaldehyde resins, melamine- formaldehyde resins, and natural polymers (e.g., cellulose, rubber, proteins, and their derivatives), those which are apt to be most beneficially stabilized are synthetic polymers such as:

(1) polymers and interpolymers of etirylenicaUy-unsaturated hydrocarbons, such as ethylene, propylene, butylene, isobutylene, styrene, butadiene, and piperylene. including the homopolymers, copolymers, and other interpolymers thereof with one another, and copolymers and interpolymers of at '.east one of them with one or more copolvmerizable non-hydrocarbons, such as vinyl acetate, aσylonitrile, methacrylonitrile, methvl acrvlate, and methvl methacrvlate.

(2) halogen-containing polymers, such as polyvinyl chloride and fluoride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymers, polychloroprene, and chlorinated rubbers,

(3) other vinyl and allyl polymers, such as polyvinyl alcohol, acetate, stearate, benzoate, maleate, and butyral, polyallylmelamine, and polyallyl phthalate, and

(4) acrylic polymers, such as polyacrylates, polymethacrylates, polyacrylamides, polyacrylonitrile, and polymethacrylonitrile.

In a particularly preferred embodiment of the invention, the tertiary amides are used to stabilize thermoplastic polymers, such as polyethylenes, polypropylenes, and polycarbonates, during processing, e.g., extrusion or injection molding.

The tertiary amides are combined with the normally oxidable materials in antioxidant amounts, usually an amount in the range of 0.005-5%, preferably 0.01-2%, based on the weight of the organic material.

When used as antioxidants, the tertiary amides may be employed as the sole stabilizers for the normally-oxidizable organic materials, or they may be used in conjunction with other stabilizers, such as conventional phenolic antioxidants or thioester synergists. Moreover, their activity as antioxidants does not appear to be inhibited by the presence in the organic materials of additives such as those convention¬ ally employed in such materials, e.g., light stabilizers, ultraviolet light absorbers, metal deactivators, pigments, dyes, lubricants, nucleating agents, and fillers.

In general, all of the tertiary amides of the invention are good processing stabilizers. However, those having the higher molecular weights — typically also having lower volatility and greater thermal stability — are superior when high processing temperatures and/or long-term stabilization are required, while those having the lower molecular weights — typically also having lower melting points — are more suitable for use when low-to-moderate processing temperatures are required.

The following examples are given to illustrate the invention and are not intended as a limitation thereof. Unless otherwise specified, quantities mentioned in the examples are quantities by weight. Code names are sometimes used in these examples to identify compounds as shown in Table I.

TABLE I Compound Code Name l,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6-trimethylbe n- E-330 zene — a commercially-available antioxidant sold by Ethyl

Corporation as Ethanox ^β 330

N,N-bis(3,5-di-t-butyl-4-hydroxybenzyl)acetamide — a com- N-1190 pound taught by Nikiforov et al.

N,N-bis[^-(3^-di-t-butyl-4-hydroxypheπyl)ethyl]-2A2-tric hlo- C-l 176 roacetamide — a compound taught by Cornell

Bis[β-(3^-di-t-butyl-4-bydroxypheπyl)ethyl]amine — a reactant S-1161 used in preparing products of the Examples

N,N-bis[ S-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]acetamide AN-1162

N,N,N',N'-tetrakis[S-(3^-di-t-butyl-4-hydroxyphenyl)ethyl ]glu- AN-1163 taramide

N-N, ,N etrakis[ø-(3,5-di-t-b^^ AN-1164 phthalamide

NJJ-bis[^-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]methanesu l- AN-1168 fonamide N,N,N',N',N ^M ,N ^M -hexakis[^-(3,5-di-t-butyl-4-hydroxyphenyl)- AN-1178 ethyl]-1 ,5-benzenetricarboxamide

EXAMPLE ! Preparation of AN-1162 Charge a suitable reaction vessel with 1.6g of acetyl chloride and 10 mL of dry toluene. While stirring the reaction mixture and maintaining the temperature at 0-8 ^• C, slowly add a solution of 9g of S-l 161, 2.1g of triethylamine, and 30 mL of dry toluene. Then allow the reaαion mixture to reach ambient temperature and maintain that temperature for four hours.

After completion of the four-hour period, wash the reaction mixture consecutive- ly with 50 mL of 3N HCl, 50 mL of IN NaOH, and 50 mL of a saturated aqueous

NaCl solution, the organic phase being recovered after each wash and then subjected to the next wash. Recover the final washed organic phase, dry. and concentrate in

vacuo to provide a 98% yield of N,N-bis[/3-(3,5-di-t-butyl-4-hydroxyphenyl)ethyljacetarn- ide.

Recrystallize the crude product from 100 mL of heptane and wash the precipitated product with 75 mL of heptane. GC analysis shows the recrystallized

5 product to contain 99% of the tertiary amide, which has a melting point of 153-155 ^• C.

Spectral analyses (H-NMR, ¹³ C-NMR, IR, GC-MS) confirm the identity of the solid as N,N-bis[^-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]acetamide.

EXAMPLE 2 Preparation of AN-1168

10 Repeat Example 1 except for replacing the acetyl chloride with 2.9g of methanesulfonyl chloride and using 2.7g of the triethylamine. Prior to the recrystalliza- tion of the crude product from heptane, it contains 97.6 area % of N,N-bis[ 5-(3,5-di-t- butyl-4-hydroxyphenyl)ethyl]meώanesulfonan_ύde.Afterrecrys tallization,GC analysis shows the product to contain >99% of the tertiary sulfonamide, which has a melting

15 point of 132- 134 ^• C. Spectral analyses (H-NMR, ^ϊ3 C-NMR, IR, GC-MS) confirm the identity of the solid as N,N-bis[9-(3^-di-t-butyl-4-ltydroxypheityl)ethyl]methanesulf onam- ide.

EXAMPLE 3 Preparation of AN- 1163 20 Charge a suitable reaction vessel with 1.78g of glutaryl dichloride and 10 mL of dry toluene. While stirring the reaction mixture and maintaining the temperature at 0-8 ^• C, slowly add a solution of lO.lg of S-1161, 231g of triethylamine, and 30 mL of dry toluene. Then allow the reaαion mixture to reach ambient temperature and maintain that temperature for four hours.

"- «. After completion of the four-hour period, dilute the reaction mixture with 50 mL of toluene and wash it consecutively with 50 mL of 3N HCl. 50 mL of IN NaOH. and 50 mL of a saturated aqueous NaCl solution, the organic phase being recovered after each wash and then subjected to the next wash. Recover the final washed organic phase, dry it. and concentrate it on a rotary evaporator to provide 11.4g of product.

Dissolve the product in 350 mL of heptane at 100 ' C and recrystallize it at 0 ^β C to provide 9.9g of recrystallized product. TLC analysis shows the recrystallized product to contain 98.1 area % of N,N,N\N'-tetrakis[0-(3,5-di-t-butyl-4-hydroxyphenyl)ethyl]- glutaramide, which has a melting point of 167-169 ° C. The yield is 92%, and spectral analyses (H-NMR, IR, HRMS, and ¹³ C-NMR) confirm the structure of the product.

EXAMPLE 4 Preparation of AN- 1164 Repeat the reaction of Example 3 except for replacing the glutaryl dichloride with 2.09g of terephthaloyl dichloride to provide 11.4g of product. Stir the product in 100 mL of refluxing heptane for one hour, cool to room temperature, and isolate the precipitated produα by filtration. Recrystallize the produα from a mixture of 200 mL of heptane and 160 mL of toluene to provide 9.2g of recrystallized product. TLC analysis shows this produα to contain 99.0 area % of N,N,N',N'-tetrakis[ø-(3,5-di-t- butyl-4-l droxyphenyl)ethyl3terephthalamide, which has amelting point of 208-210 * C. The yield is 83%, and spectral analyses (H-NMR, IR, HRMS, and ¹³ C-NMR) confirm the structure of the product.

EXAMPLE Preparation of AN-1178 Slowly add a solution of lO.lg of S-1161 and 23g of triethylamine in 50 mL of dry toluene to a stirred solution of 1.8g of 1,3,5-benzenetricarbonyl trichloride in 15 mL of dry toluene maintained at 0-8 * C. Then warm the reaαion mixture to room temperature and stir overnight to provide 11.7g of product.

After completing the overnight stir, dilute the reaction mixture with 50 mL of toluene and wash it consecutively with 50 mL of 3N HCl, 50 mL of IN NaOH, and 50 mL of a saturated aqueous NaCl solution, the organic phase being recovered after each wash and then subjeαed to the next wash. Recover the final washed organic phase, dry it, and concentrate it on a rotary evaporator to provide 11.7g of product. Stir the crude produα in refluxing heptane for 15 minutes, cool, and isolate the precipitated solids by filtration. Recrystallize the resulting 10.3g of solids in 100

mL of ethanol and then from a mixture of 100 mL of heptane and 70 mL of toluene. TLC analysis shows this product to contain 97.5 area % of N,N,N',N',N",N"-hexakis[ 3- (3^-di-t-butyl-4-hydroxyphenyl)ethyl]-1 ,5-benzenetricarboxamide, which has a melting point of 193-195 *C. The yield is 58%, and spectral analyses (H-NMR, IR, HRMS, and ¹³ C-NMR) confirm the structure of the product.

EXAMPLE 6 Determination of Volatility and Thermal Stability Subjeα the products of Examples 1-5 to thermogravimetric analysis by heating different samples of the products at 10 * C/minute from 25 ^• C under nitrogen and air, respectively, to determine the temperatures at which there is a 10% weight loss. The results of the analyses are shown in Table II.

When N-l 190, a compound which has a chain of less than two carbons between the alkyl-substituted hydroxyphenyl groups and the amido nitrogen, is subjeαed to the same analysis, the analytical results show the temperatures at which a 10% weight loss is found in nitrogen and air are 245 ^• C and 249 ^• C, respectively. This demonstrates the lower volatility and the superior thermal stability of the amides of the invention.

EXAMPLE 7 Evaluation of Antioxidants in Polypropylene

Pan A

Prepare two series of polypropylene compositions by (1) blending two different samples of Profax* 6501, a product of Himont Incorporated, with 0.05% of calcium

stearate as an acid neutralizer and lubricant, (2) dividing each of these blends into aliquots, and (3) blending each of the aliquots to be stabilized with 0.1% of an antioxidant. The antioxidants used in the blends are: An i xi nt

Test the compositions of Part A for melt flow index and yellowness index by extruding them in a Brabender twin screw extruder at 150-245-245 ^• C and 30 rpm under nitrogen and then making five passes through a Brabender single sαew extruder at 260-260-260-260 ^• C and 30 rpm with ambient air. The test results are shown in Table m.

IAELE-ffl

TABLE III (CONTINUED .

Blend MFI @ 230' C/2160g Load Yellowness Index

Extrusion Passes Extrusion Passes

ss5

B-l

Test the compositions of Part A for resistance to failure on oven aging by (1) molding pellets of the compositions retained from the twin sαew pass of Part B into plaques having a thickness of -0.06 cm, using a hydraulic press set at 245 *C for the molding, (2) cutting each of the plaques into five -2.5 cm squares, (3) placing each of the squares into glass Petri dishes, (4) placing the Petri dishes into an air-curculating oven set at 150 ^* C, and (5) checking the samples every 24 hours for failure — failure being determined when at least three of the five squares of a paπicular composition are visually decomposed. The test results are shown below. '

As demonstrated in the preceding examples, the tertiary amides of the invention include a variety of compounds which (1) have utility in stabilizing organic materials against deterioration during processing and oven aging, (2) have melting points sufficiently lower than the 240-245 ° C melting point of E-330 to make them preferable to that commercial antioxidant for use in low-to-moderate temperature processing, (3) have greater thermal stability than amides such as N-1190, and (4) in general, compare favorably with known antioxidants as stabilizers for organic materials which are normally susceptible to oxidative deterioration. Those which have the least tendency toward developing color bodies are particularly valuable for stabilizing organic materials, such as some of the organic polymers, that are to be used in applications wherein the impartation of color would be undesirable. Those which show greater tendencies to form color are more apt to be useful in stabilizing organic materials in which color is not a disadvantage, e.g., fuels, lubricants, and some organic polymers.