MXPA96003197A - Hule and met composition formulation - Google Patents

Abstract

The present invention relates to a formulation comprising insoluble sulfur, an elastomeric material and an effective amount of a reaction product produced by combination: A) a first reactive ingredient, itself produced by the reactive combination of an aliphatic ketone with an amine primary aromatic, and A) a second reactive ingredient, which is a dehydrated anhydride, wherein the reaction product is present in the formulation in an amount from 0.25 to 6 parts by weight per 100 parts by weight of elastomeric material. A method for reducing the rate at which the insoluble sulfur is converted to a migratory form of sulfur, in an article produced from a curable formulation including insoluble sulfur and an elastomeric material comprising: incorporating in the formulation 0.25 to 6 parts by weight of a reaction product, produced by the reactive combination of (A) a first reactive ingredient, itself produced by the reactive combination of an aliphatic ketone and a primary aromatic amine, with (B) a second reactive ingredient, which is an acid anhydride, per 100 parts by weight elastomeric material

Description

r FORMULATION OF RUBBER COMPOSITION AND METHOD TECHNICAL FIELD 5 Our present invention relates to a formulation for producing a cured elastomeric article. This formulation includes insoluble sulfur. Our invention prevents the conversion of insoluble sulfur to soluble sulfur, the soluble sulfur being able to migrate towards the surface of the elastomeric article before vulcanization.

TECHNICAL BACKGROUND In general it is well known that an atmosphere that contains oxygen can cause a surface cracking of conventional unsaturated rubber vulcanizates when subjected to repeated flexing in an environment that - * ~ contains oxygen. It has been observed that deterioration occurs when small "superficial" cracks grow rapidly to deep fissures. Fissures of this kind can significantly shorten the service life of an elastomeric article made from a rubber vulcanizate. The continuing desire to extend the life of the 25 elastomeric items made of rubber - either natural or synthetic - is also well known.

The Patent of the United States of North America No. 4,158,000 to Nagasaki et al., For example, describes antidegradants for rubber, saying that they are useful for preventing aging by heat and flex cracking. In the Nagasaki patent it is mentioned that a mixture consisting essentially of the specified percentages of 2,2,4-trimethyl-l-2-dihydroquinoline monomer, the dimer thereof and the more highly polymerized products provide the rubber with an antidegradant ingredient . Moreover, the United States Patent of North America Issue 2,400,500 by Gibbs describes different condensation products of 1,2-dihydroquinolines with diaryl amines, saying that they are useful in preventing flex cracking of rubber. Gibbs mentions in this patent that the reaction of an aliphatic ketone with a primary aromatic amine to produce a 1,2-dihydroquinoline is known. 2,2,4-Trimethyl-1,2-dihydroquinoline, a major product resulting from the reaction of acetone and aniline, is a known useful antioxidant. In fact, many chemical antidegradants have been developed, mainly based on amine chemistry, to stop or otherwise delay the physical deterioration of articles made from cured elastomeric materials. Current formulations for producing cured elastomeric articles typically include an insoluble form of sulfur, which prevents the migration of the sulfur prior to vulcanization. The conversion of the insoluble form of sulfur to its soluble form, which is currently known to result in the migration of soluble sulfur to the surface of an uncured rubber article, appears to be caused by the presence of amine-based antidegradants. Although mixtures are known to include 2,2,4-trimethyl-1,2-dihydroquinoline to prolong the useful life of the elastomeric articles, which is desirable, the presence of 2,2,4-trimethyl-1 is known, 2-dihydroquinoline and its different forms causes the insoluble sulfur to become a soluble form of sulfur, which is undesirable. For example, it is known that soluble sulfur migrates to the surface of uncured rubber articles. Emigration of this kind, called "flowering" of sulfur, is known to cause loss of "consolidation viscosity". The term "consolidation viscosity" refers to certain adhesion properties of uncured elastomeric materials, such as rubber, particularly when these materials are produced as relatively thin sheets, and these sheets are subsequently layered and used in the manufacture of a tire. Accordingly, obtaining undesirable "viscosity consolidation" properties, using these kinds of elastomeric materials, can become a matter of concern.

OBJECTS OF THE INVENTION 5 An object of our present invention, therefore, is to markedly reduce the rate at which an insoluble form of sulfur is converted to its soluble form. A related object is to prevent the "flowering" of sulfur. Still another object is to prolong, during periods of long time, many of the desirable physical properties of cured elastomeric articles. The additional features and advantages of our present invention will become more clear to those skilled in the art upon reading the following specification. SUMMARY OF THE INVENTION - One aspect of our invention relates to a novel formulation for producing a cured elastomeric article. Another aspect of our invention relates to methods for producing our formulation. Our formulation includes a non-migrating form of sulfur, known as insoluble sulfur. With reference to the preparation of our As a novel formulation, we have discovered that selected relative amounts of: (A) a first reactive ingredient can be used, and (B) a second reactive ingredient, when combined in a chemically reactive environment, to produce (C) a reaction product which is effective in reducing the rate at which the insoluble sulfur becomes a migrating form of sulfur (soluble sulfur). The first reactive ingredient (A) is itself a reaction product, resulting from the reactive combination of an aliphatic ketone with a primary aromatic amine. The second reactive ingredient (B) is an acid anhydride. The two reactive ingredients (A and B) are combined reactively and consequently, become our novel product (C). We have discovered that our product (C), because it results from the use of an amine-based reagent, can provide our novel formulation with certain desirable physical properties, such as those typically provided otherwise by an amine-based antidegradant.

INDUSTRIAL APPLICABILITY Our present invention can be used to manufacture different articles from unsaturated rubber vulcanizates. This rubber can be natural, synthetic or a mixture of both.

Some representative examples of the unsaturated elastomers commonly used in the composite articles of our present invention include natural rubber, synthetic polyisoprene, polychloroprene, so-called "cyclone" rubbers, norbornene rubbers, polysulfide rubbers, styrene-butadiene rubbers, polybutadiene, nitrile rubbers, carboxylated nitrile rubbers, butyl rubbers, rubbers based on ethylene-propylene-diene monomer ("EPDM"), homopolymers and copolymers of epichlorohydrin, ethylene-propylene rubbers ("EPR"), and rubbers of polyisobutylene. We would currently expect that the greatest short-term commercial use would be in the areas of tires, conveyor belts and elastomeric hoses. In particular, the antidegradative composition of the present invention can be used more conveniently as any component or portion of a tire. These uses include portions of the wire or carcass band of a tire. This tire may be a truck tire, a passenger tire, or a vehicle tire for riding. Moreover, any tire may contain many different reinforcing elastomer layers therein, incorporating any of those different layers characteristic of our invention. For example, tire components of these classes typically contain more than one thermosetting rubber polymer in a mixture that must be protected from oxidative attack. Our data presented below demonstrate that the antidegradant compositions of our present invention prevent the conversion of insoluble sulfur to its soluble forms. The antidegradant compositions of our present invention also improve the oxygen resistance and heat aging properties of the elastomeric materials in which our novel compositions are incorporated. However, our novel compositions do not cause a noticeable reduction in the flexural properties of the elastomeric materials in which they are incorporated. Also, the novel antidegradant compositions of our present invention are typically solid, which promote ease of use.

BEST MODE FOR CARRYING OUT THE INVENTION Typically, the ingredient "A" (ie, the reaction product of an aliphatic ketone and a primary aromatic amine), and the ingredient "B" (an acid anhydride) are combined in an environment chemically reactive, and subsequently used to produce "C", the novel antidegradant ingredient of our invention. Also, 85 to 99 percent by weight of A, preferably 90 to 98 percent of A, and more preferably 93 to 96 percent by weight of A are typically combined with sufficient B so that the sum of the weight of ingredients A and B count for 100 percent of the total weight of the novel antidegradant ingredient C which is incorporated in a formulation to produce a cured elastomeric article. The term "elastomeric" is understood to include rubber-like polymers and copolymers, as well as different compositions that have been characterized as "rubber" by those skilled in the art, such as natural rubber, synthetic rubber, and various mixtures thereof. Accordingly, the term "elastomeric" includes natural rubber, "EPDM", cis-polyisoprene, polybutadiene, styrene-butadiene copolymers, polychloroprene, and acrylonitrile-butadiene copolymers, both by themselves and in different rubber mixtures. The term "EPDM" is understood to mean an elastomeric terpolymer of ethylene, propylene and diene monomers. (See, for example, pages 400-401 of The Textbook of Polymer Science, second edition, by F.W. Billmeyer Jr., published in 1971 by John Iley &Son, Inc.). The novel antidegradant ingredient of our invention is preferably used in combination with formulations that include natural rubber. The additional terms used throughout our specification include the following. The term "composition", when used in combination with an elastomer, such as rubber, will mean the mixing of the different ingredients, possibly including heating, but without the application of pressure. The term "curing" of a formulation of an elastomeric compound (usually rubber) includes the application of heat and pressure over time. The term "vulcanizing" will mean modifying the properties of an elastomer, such as rubber, by treating it with sulfur and other additives in the presence of heat and pressure. Prior to the application of heat and pressure, this vulcanizable elastomeric material would need to include double bonds, to make vulcanization of the elastomeric material possible. In general, between about 0.2 and about 8, and preferably between about 2 and 7 parts of sulfur, per hundred (100) parts by weight of rubber are used. The elastomeric articles to be protected can be formulated in any conventional manner, the ingredients of the composition being normally also present. For example, vulcanizing agents, accelerators, activators, retarders, antiozonants, plasticizing or softening oils, and fillers, as well as reinforcing pigments or carbon black may be included in the formulations described herein.

The novel antidegradant ingredient of our present invention can be added to the classes of unsaturated polymers or rubbers mentioned above, at a level of 0. 25 to 6 parts by weight per hundred (100) parts of elastomeric material. A more preferred level is from 0.3 to 5 parts by weight of antidegradant ingredient per one hundred (100) parts of elastomeric material. Still more preferably, the level is 0.5 to 2 parts by weight of antidegradant ingredient per one hundred (100) parts by weight of elastomeric material. The aliphatic ketones that can be used in our present invention are those wherein the separated alkyl groups may each contain from 1 to 4 carbon atoms. Suitable examples include acetone, methyl ethyl ketone, methylpropyl ketone, diethyl ketone and methylbutyl ketone. The primary aromatic amines used in our invention include anilines, such as para-ethoxyaniline, as well as toluidines and xylidenes, any of which may be substituted or unsubstituted, including mixtures thereof, wherein the toluidines may also be, either, of ortho or meta structure. The preferred aliphatic ketone is acetone, and the preferred primary aromatic amine is aniline. A preferred reaction product of an aliphatic ketone and a primary aromatic amine is a mixture of 2,2,4-trimethyl-1,2-dihydroquinoline monomer, dimer, trimer and higher molecular weight components thereof. For the purposes of our present invention, the term "acid anhydride" will mean the composition that may be represented structurally by having an oxygen atom bonded with two carbonyl carbon atoms. In this regard, an acid anhydride composition suitable for the purposes of our present invention can be illustrated, either as structurally acyclic or cyclic. For example, suitable symmetrical acid anhydride compositions which are illustrative, and which possess an acyclic structure, include acetic anhydride, propionic anhydride, normal butyric anhydride, isobutyric anhydride, normal valeric anhydride, normal caproic anhydride, cyclohexanecarboxylic anhydride, and anhydride bis - (3-bromopropanoic). (See, for example, pages 226 and 233 of Organic Chemistryf 3 »edition, by R.Q. Brewster and W.E. McEwen, published in 1964 by Prentice-Hall Inc. of Englewood Cliffs, New Jersey, and page 137 of the Nomenclature of Organic Compounds, by J.H. Fletcher, O.C. Dermer and R.B. Fox, published in 1974 in Washington, D.C., by the American Chemical Society). The acid anhydride compositions derived from two molecules of the same monocarboxylic acid are designated as "symmetrical", while the "asymmetric" acid anhydride compositions are derived from two different monocarboxylic acids. (Nomenclature of Organic Compounds, on pages 137-138). Asymmetric acid anhydride compositions illustrative of the acyclic structure and suitable for the purposes of our present invention include acetyl butyrate (also known as acetylbutyryl oxide) and propanoic cyclohexanecarboxylic anhydride. (See, for example, page 233 of Organic Chemistry by Brewster and McEwen, and page 138 of the Nomenclature of Organic Compounds, respectively). Acid anhydride compositions having a cyclic structure are prepared from compositions possessing at least two carboxylic acid moieties (See, for example, page 667 of Organic Chemistry, 3rd edition, by RT Morrison and RN Boyd, published in 1976 by Allyn and Bacon Inc. of Boston, Mass.). In this regard, the acid anhydride compositions illustrative of the cyclic structure and suitable for the purposes of our present invention include succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride and pyromellitic anhydride. (See, for example, pages 340, 341, 354, 665 and 667, respectively, from Organic Chemistry, by Brewster and McEwen). Preferred acid anhydrides include maleic anhydride, phthalic anhydride, acetic anhydride and succinic anhydride. In the preferred methods for the preparation of the novel antidegradant ingredients of our present invention, "Naugard Q" (registered trademark or "brand") dihydroquinoline is added to a preferred acid anhydride. ("Naugard Q") is a registered trademark of Uniroyal Chemical Company, Inc., of Middlebury, Connecticut, for polymerized 2,2,4-trimethyl-1,2-dihydroquinoline). Furthermore, in this regard, our preferred acid anhydride is added to the "Naugard Q" dihydroquinoline, where there may still be some 1,2-dihydroquinoline monomer present, in an amount of 3 to 9 weight percent ("% by weight "), based on the polymer" Naugard Q "(brand). The amount of monomer present can be adjusted by vacuum or vapor separation of the polymer, as is well known, if desired. The amount of acid anhydride added to the 1,2-dihydroquinoline may be from about 3 to 20 weight percent, based on the weight of 1,2-dihydroquinoline and acid anhydride. Also, a more preferred scale may be from 4 to 10 weight percent, and an even more preferred scale may be from 4 to 7 weight percent, both of which are present on the aforementioned bases. A method for "custom manufacturing" a unique antidegradant ingredient, in accordance with the different principles of our present invention, contemplates reacting with each other reactive ingredients previously selected from aliphatic ketone and primary aromatic amine, to produce an antidegradant possessing the properties desired physical, and then add an acid anhydride to the antidegradant, to produce a mixture. The mixture can be "finished" in the usual manner, such as flake formation.

DETAILED DESCRIPTION OF THE EXAMPLES The following examples are stipulated to more clearly illustrate, to those skilled in the art, the different principles and practice of the present invention. However, as such, they are not intended to limit our invention, but rather are merely illustrative of the general principles, as well as of the different characteristics and advantages of the different preferred embodiments of our present invention.

Example 1: Polymer of maleic anhydride and 1,2-dihydroquinoline 40 grams of commercially available dihydroquinoline polymer "Naugard Q" (brand) (2,2,4-trimethyl-1,2-dihydroquinoline polymer with less than 3 percent by weight) monomer weight present), and 1.6 grams of maleic anhydride (commercially available from Aldrich Chemical Company of Milwaukee, Wisconsin) were combined in a 50 milliliter 3-necked round bottom flask, to produce a mixture. The flask was equipped with a thermometer, a mechanical stirrer, and a nitrogen purge line. The mixture was heated to 140 ° C (284 ° F), and stirred to effect the reaction of the ingredients of the mixture. The reaction mixture was maintained at 140 ° C (284 ° F) for two hours. Subsequently, the reaction product was removed from the flask, and formed into flakes. After the formation of flakes, the reaction product was milled, bottled and stored at room temperature, ie at 25 ° C (77 ° F) until needed. The material was subsequently used in the composition of a rubber article. Following the composition, the test of certain physical properties of the articles took place, the results being presented in Tables V-VII and X-XII below.

Example 2: Polymer of phthalic anhydride and 1,2-dihydrocruinoline 40 grams of dihydroquinoline polymer "Naugard Q "and 2 grams of phthalic anhydride (from Aldrich Chemical Co.) were combined in accordance with the procedures stipulated in Example 1, the results also being presented in Tables V-VII and X-XII below.

Example 3: Polymer of acetic anhydride and 1,2-dihydroquinoline 40 grams of dihydroquinoline polymer "Naugard Q" and 2 grams of acetic anhydride (from JT Baker Company of Phillipsburg, New Jersey) were combined in accordance with the procedures stipulated in Example 1 , the results also being presented in Tables V-VII and X-XII below.

Example 4: Maleic anhydride polymer v 1.2-dihydroquinoline 20 grams of 2,2,4-trimethyl-1,2-dihydroquinoline polymer with a monomer content of 4 to 9 weight percent, based on the polymer (commercially available in Uniroyal Chemical Company Inc. of Middlebury, Connecticut), were combined with 1 gram of maleic anhydride (Aldrich) according to the procedures stipulated in Example 1, except that the reaction time was three hours, the results also being presented in the Tables V-VII and X-XII below.

Example 5: Phthalic anhydride polymer and 1,2-dihydroquinoline 40 grams of the dihydroquinoline polymer of the Example 4 were combined with 3 grams of phthalic anhydride (Aldrich) in accordance with the procedures stipulated in Example 1, also presenting the results in the Tables V-VII and X-XII below.

Example 6: Polymer of succinic anhydride and 1,2-dihydroquinoline 40 grams of the dihydroquinoline polymer of Example 4 were combined with 2 grams of succinic anhydride (commercially available from Aldrich) in accordance with the procedures stipulated in Example 1, and the results are presented in Tables V-VII and X-XII below.

Antideqradant Evaluation Procedure In each of Examples 1 to 6, confirmation that the amine and the anhydride reacted to form an imide was determined by high performance liquid chromatography. The reaction products of Examples 1 to 6 * .. were tested on a rubber compound, to determine the extent to which they are capable of reducing the conversion of insoluble sulfur to a form that can migrate (soluble) from sulfur, the which would otherwise migrate to the surface of an unvulcanized elastomeric article (eg, rubber). To make our evaluations, we use the following recipe.

Table i: Evaluation Recipe Ingredients Parts in weight elastomer 200.00 sulfur 7.50 antidegradant 2.00 The elastomer was rubber of cis-4-polybutadiene (commercially available from American Synthetic Rubber of Louisville, Kentucky), which has a number average molecular weight of about 139,000, and a weight average molecular weight of about 315,000. Sulfur was poly bristle sulfur "Crystex HS 90 OT "(trademark) commercially available from Akzo Chemicals of Chicago, Ill. The antidegradant was the reaction product of Examples 1 to 6. For each of Examples 1 to 6, the ingredients listed above in Table 1 were mixed with each other. Yes in a "Brabender" (brand) mixer, at an internal internal mixer temperature of 80 ° C (176 ° F) .5 The mixer included a cavity portion to hold the mixing ingredients, a mixing element disposed inside the mixer. the cavity for mixing the ingredients, and a movable roller in the cavity to bring the ingredients into contact with the element or mixer, mixing the ingredients continued for five (5) minutes, or until the internal temperature the mixer reached 99 ° C (210 ° F), whichever came first.For the reaction product of each of the 5 Examples 1 to 6, an 80 gauge plate of 8.9 centimeters by 7.6 centimeter was compressed. os (3 1/2 inches x 3 inches) "" "between two sheets of polyester film" Mylar "(brand) (of the same approximate dimensions) for fifteen (15) minutes at a pressure of 2,812 kilograms per square centimeter (40,000 pounds of pressure per square inch), a the elevated temperatures of 99 ° C (210 ° F), 110 ° C (230 ° F), and 121 ° C (250 ° F) .The samples subsequently remained at room temperature, ie at 25 ° C (77 ° C). ° F) for two (2) 5 days.

On the third day, each of the three plate samples at different temperatures for each of Examples 1 through 6 was compressed for seven (7) minutes at 2,812 kg / cm2 (40,000 psi), at 132 ° C (270 ° F) ). Subsequently, the plaque samples were returned to room temperature still covered with the polyester film "Mylar". The surfaces of the plates were visually monitored subsequently for fourteen (14) days, on a daily basis, by the appearance of sulfur crystals. If no sulfur crystals have formed on the surfaces of the plates within the two week period, the general consensus throughout the industry is that any subsequent surface sulfur crystal formation will be negligible. No surface crystal formation was observed on the plate samples at the 14 day point, after the reaction products of Examples 1 to 6 were tested as described above.

In the Absence of a Previous Reaction To investigate another aspect of our invention, we add 1.90 parts by weight of Naugard Q (low monomer content) and 0.10 parts by weight of maleic anhydride as individual components of the mixture, following the procedures stipulated above, for the purposes of evaluating the sulfur conversion test. (Discussed above). We observe the appearance of sulfur crystals at forty-eight (48) hours.

No Acid Anhydride The composition procedures stipulated in Examples 1 to 6 were substantially repeated, except that the "Naugard Q" antidegradant was the antidegradant used in the composition of a rubber article. We observed the plate samples by the sulfur crystal formation, using dihydroquinoline polymer at the levels of less than 3 and from 4 to 9 weight percent of monomer, described above, the results being presented immediately in Table II.

Table II; Sulfur Crystal Formation Dihydroquinoline Polymer Crystals Observed at With less than 3% by weight of the monomer. 24 Hours With 4 to 9% by weight of the monomer. 22 Hours Other Physical Properties of the Reaction Products of Examples 1 to 5 In addition to suppressing the formation of sulfur crystal, other desirable characteristics and advantages of the reaction products of Examples 1 to 5 were investigated. To ensure that the reaction products of each of Examples 1 to 5 functioned satisfactorily as antioxidants, the reaction product of each was used. of Examples 1 to 5 for preparing a master batch using the recipe stipulated in Table III. The masterbatch was prepared by mixing twice in the Brabender mixer mentioned above. For the first mix (see Table III, below, for the ingredients), the natural rubber and the carbon black were mixed in the mixer for 1.5 minutes. Subsequently, zinc oxide, stearic acid and naphthalene oil were added and mixed, either until the mixture reached 132 ° C (270 ° F) or for an additional 3.5 minutes, whichever came first. The mixer was swept at 2.5 and 3.5 minutes, and the batch was subsequently discharged after 5 minutes, or when the internal temperature of the mixer reached 132 ° C (270 ° F), whichever came first. (The term "swept", as used in this paragraph, means lifting the roller above the mixer cavity, sweeping the mixing ingredients from the back of the roller into the mixer cavity, to ensure that the mixture contains the desired amount of each ingredient). Table III; Recipe of Rubber Composition Ingredient Parts in Weight Natural rubber 100.00 Black Smoke 58.00 Zinc Oxide 7.00 Naphthenic Oil 6.00 Resin 2.50 Stearic Acid 2.00 Cobalt Naphthenate 1.00 The natural rubber presented in Table III, known throughout the industry as "SMR 5CV" (branded rubber), is commercially available from Herman Weber Co., Inc. of Chatham, Massachusetts. Cobalt naphthenate is 10 percent cobalt, based on total weight. The resin is a commercially available resorcionol-formaldehyde resin, Schenectady Chemicals of Schenectady, New York. The second mixture was prepared starting with the mixture of the previous batch for one (1) minute, and then adding the cobalt naphthenate and the resorcionol-formaldehyde resin.

The second mix was then discharged, either after 5 minutes, or when the internal temperature of the mixer reached 121 ° C (250 ° F), whichever came first. Typically, the internal temperature limitation was not reached and, consequently, the mixture was discharged after 5 minutes, often at 104 ° C (220 ° F). The master batch was mixed in a mill immediately for use in the third mix. The resulting product or material was further compounded by mixing according to the recipe in Table IV, which appears below.

Table IV; Recipe Material Ingredient Parts Master lot 176.50 Sulfur (80% oiled) 6.25 Hexametoxymethyl melamine 2.50 Reaction product of Examples 1 to 5 1.00 N, N-dicyclohexyl-2-benzothiazole sulfonamide. 0.70 Total weight of material 186.95 The mixture of the ingredients of Table IV was presented as follows. First, half of the ingredients of the masterbatch were added individually to the mixer together with the reaction product of each of Examples 1 to 5, each addition followed by the addition of the remaining ingredients of the masterbatch. After mixing for one minute, the hexametoxymethyl melamine ingredient (available in American Cyanamid from Akron, Ohio), the sulfenamide ingredient of N, N-dicyclohexyl-2-benzothiazole, and the sulfur to the mixture. Each sample of material was mixed subsequently for three additional minutes, and the internal temperature of 116 ° C (241 ° F) was typically reached before being discharged from the mixer. The samples of material were subsequently ground, each sample of material in five passes through the mill.

(A "pass" is defined as once through the mill rolls). Each sample of material was then cured in a 75 gauge mold of 15 centimeters by 15 centimeters (6 inches by 6 inches) at 160 ° C (320 ° F), at a pressure of 2,812 kg / cm2 (40,000 psi). The curing time was defined as "the amount of time required to achieve a cure of 90 percent, more 2 minutes. "Subsequently, the" Shore A "hardness, the tensile strength, the modulus of 100 to 300 percent, and the percentage of elongation of each of the material samples thus cured were evaluated in three levels of aging. : not aged, 2 days at 100 ° C (212 ° F) in a hot air circulation oven, and 4 days at 100 ° C (212 ° F) in a hot air circulation oven. Tables V to VII below for the novel antidegradant ingredients of Examples 1 to 5, and these results are compared with the unreacted Naugard Q antidegradant (only), the otherwise "standard" antidegradant.

Table V: Physical Properties Without Aging Table VI: Physical Properties, Aged 2 Days to Approximately 100 ° c Table VII: Physical Properties, Aged 4 Days T 100 ° C Notes for Tables V-VII TMQ is commercially available poly (1,2-dihydro-2,2,4-trimethylquinoline) having from about 4 to 9 weight percent of monomer present.

The values of tensile strength and elongation of Tables VI and VII, both expressed as percentage values (%), are each without dimension, because each is formed in a proportion, with each proportion being the final value of the tensile strength or elongation divided by the original value, this proportion multiplying immediately by one hundred (100), to arrive at the percentage value without dimension presented previously in Tables VI and VII. The value "Delta" presented above is determined by subtracting the value of hardness without aging (presented previously in Table V) from the value of aged hardness that we determine. The reaction product of Example 6 was not included in these evaluations.

Second Evaluation To further verify the antidegradative performance qualities of the reaction products of our present invention, a second group of evaluations was carried out. In this second group of evaluations, the level of sulfur used was more moderate (that is, less quantity), and the aging conditions were less severe than in the first group of evaluations.

In the master batch recipe (from the second set of evaluations), cobalt naphthenate, hexametoxymethyl melamine, and resorcinol-formaldehyde resin were removed, and the sulfur level was reduced to 2.50 parts by weight, compared to 6.25 parts by weight as stipulated in Table IV, and the maturations were twenty-four (24) hours at 100 ° C (212 ° F), and 2 weeks at 70 ° C (158 ° F), rather than two ( 2) and four (4) days at 100 ° C (212 ° F). For the second evaluation, the recipe used is stipulated immediately in Table VIII.

Table VIII: Recipe of Rubber Composition Ingredient Parts Natural rubber 100.. 00 Black Smoke 58. . 00 Zinc oxide 7. . 00 Naphthenic oil 6., 00 Stearic acid 2. . 00 The rubber identified in Table VIII is described above in relation to Table III. Half of the rubber, all the carbon black, all the zinc oxide, all the stearic acid, and all the naphthenic oil were combined in sequence, with the rest of the rubber being incorporated in the mixture.

The resulting mixture was then mixed using the same equipment mentioned with respect to Table I. The mixer was swept twice, that is, once at 2.5 minutes and once again at 3.5 minutes. The batch was discharged, either after 5 minutes, or when the mixer reached an internal temperature of 149 ° C (300 ° F), whichever came first. Normally the temperature limitation was satisfied first. The batch was mixed with mill immediately, and subsequently cut to be used in the recipe of material stipulated in the following Table IX.

Table IX: Second Recipe of Material Ingredient Parts Master lot 173.00 Sulfur (80% oiled) 2.50 Reaction product of Examples 1 to 5 1.00 Sulfenamide of N, N-dicyclohexyl-2-benzothiazole 0.70 Total weight of the material sample 177.20 The material samples from the second evaluation were mixed in a manner similar to the mixing procedures described above for the material samples from the first evaluation, and subsequently cured in a similar manner.

The same physical properties were measured, and are presented in Tables X to XII, below, along with the "aged" ones, which were as follows: not aged, twenty-four (24) hours at 100 ° C (212 ° F) and two (2) weeks at 70 ° C (158 ° F). The results presented in Tables X to XII clearly show that the antidegradative properties of the compounds of our present invention are comparable to the antidegradant properties of a well-known and widely used commercial rubber antidegradant.

Table X: Non-aged Physical Properties Table XI: Physical Properties, Aged 24 Hours at 100 ° C Table XII: Physical Properties, Aged 2 Weeks at 70 ° C Notes to Tables XI and XII; (a) The percentage values of tensile strength and elongation, as well as the "Delta" hardness values were determined as described above in relation to Tables V and VII. (2) The percentage value of the 300 percent module presented in Tables XI and XII is determined by forming a proportion, this proportion being the final 300 percent module value divided by the original value, multiplying this proportion by one hundred (100) to arrive at the 300 percent non-dimension percent module values presented above in Tables XI and XII.

An invention related to the rubber composition is described above. Although our invention has been described with reference to preferred embodiments and examplesIt will be clear to experts in the field of rubber composition technology that our invention should not be limited to either the preferred embodiments or the particular examples presented above. For example, one skilled in the art of organic chemistry and having the benefit of this description, would know that not only benzoic anhydride, but also sis-cyclopentan-1,2-dicarboxylic acid anhydride are examples of anhydrides of acid having such classes of symmetrical and cyclic acyclic structures that would be suitable for the purposes of our present invention. (See, for example, page 659 of Morrison and Boyd, Organic Chemistry, and page 355 of Brewster and McEwen, Organic Chemistry, respectively). In accordance with the above, the experts in the relevant prior art will be able to see different changes, modifications, alternatives, and functional equivalents when reading our patent specification. Therefore, it should be understood that those changes, modifications, alternatives, and functional equivalents should be considered as forming a part of our invention as far as they fall within the spirit and scope of the following claims.

Claims (6)

1. In a formulation including insoluble sulfur, the improvement comprising an effective amount of a reaction product in the formulation, wherein the reaction product is produced by the combination of: (A) a first reactive ingredient, itself produced by the reactive combination of an aliphatic ketone with a primary aromatic amine, and (B) a second reactive ingredient, which is an acid anhydride, wherein the reaction product is present in the formulation in an amount that is effective in reducing the rate of which the insoluble sulfur becomes a form that can migrate from sulfur.

2. The improved formulation of claim 1, wherein the aliphatic ketone is acetone, and the primary aromatic amine is aniline.

3. The improved formulation of claim 1, wherein the first reactive ingredient is a monomer mixture of 2,2,4-trimethyl-1,2-dihydroquinoline, dimer, trimer and higher molecular weight components thereof.

4. The improved formulation of claim 1, wherein the acid anhydride is either maleic anhydride, phthalic anhydride, acetic anhydride or succinic anhydride.

5. A method to reduce the rate at which insoluble sulfur becomes a form that can migrate from sulfur, in an article produced from a 5 a curable formulation including insoluble sulfur, which comprises: incorporating into the formulation an effective amount of a reaction product, produced by the reactive combination of (A) a first reactive ingredient, itself produced by the reactive combination of a aliphatic ketone and a primary aromatic amine, with (B) a second reactive ingredient, to reduce the rate at which the insoluble sulfur becomes a form that can migrate from sulfur.

6. The method of claim 5, which further includes the step of curing the formulation