CA1076339A - Oxidation stabilized organic compositions - Google Patents

Abstract

OXIDATION STABILIZED ORGANIC COMPOSITIONS

Abstract of the Disclosure The use of a condensation reaction product of (1) meta-cresol, para-cresol or a mixture of meta and para cresols, and (2) an aldehyde defined by R-CHO wherein R is hydrogen or an alkyl group having at least 1 carbon atom as an antioxidant in organic compositions.

Description

33~3 ~his invent;ion relat~s to organic composltions having improved oxidative stabili~y. More particularly, the invention relates to the use o~ certain condensation reaction products as antioxidants for organic compositions such as lubricating oils, rubber, polymers; e.g., poly-propylene~ and the like.
Oxidative deterioration of various organic com-positions has long been recognized as a problem and, as a result~ a great deal of effort has been expended in the art in developing suitable antioxidants to inhibit such deterioration. Among the many antioxidants which have been developed are the bis phenols and it has generally been understood that, to be most effective~ these bls phenols should be hindered. Examples of such hindered phenols are 2,2'-methylene bis (4-methyl-6-t butyl phenol) and 4,4'methylene bis (2-methyl-6-t-butyl phenol). Such hindered bis phenols have been produced by condensing a hindered phenol with an aliphatic aldehyde, U.S. 2,515,907 and U.S. 2,647,102.
In accordance with the inventlon, it has been found that condensation reaction ~roducts of certain non-hlndered phenols with aliphatic aldehydes are ef~ec-tlve antioxidants for various organic compositions. Not only are these reaction products effectlve antioxidants but they also are non-staining. ~riefly descrlbed, the antioxidant condensation reaction products are derived from a non-hindered cresol and an aliphatic aldehyde.

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The cresol reactants use~ in preparing the antioxidant condensation reaction products are m-cresol, p-cresol or a mixture of m- and p- cresols. Compared to each other, m-cresol provides higher antioxidant effectiveness than p-cresol in the reaction products.
The above cresol reactants may also contain minor amounts Or o-cresol, various xylenol isomers and phenol. By minor amount is meant that amount which does not unduly interfere with obtaining the antioxidant benefits of the invention, usually not more than about 20-25 percent by weight.
The aliphatic aldehydes suitable for use may be defined as R-CHO wherein R is hydrogen or an alkyl group having at least 1 carbon atom. The number of carbon atoms ls not believed important from an anti-oxidant standpoint. However, the physical character- -istics of the reaction product will vary from a solid or semi-solid form with a lower aldehydes to a liquid or seml-liquid form with the higher aldehydes. Solu-bility in organic compositions will also vary with the aldehyde; generally, increasing solubility ls obtained with increaslng carbon content of the aldehyde. ~rom a pracitlcal view, the aldehyde will generally vary from 1 to àbout 44 carbon atoms for most purposes. Most preferably, the aldehyde will generally vary from 1 to 9 carbon atoms when the reactlon products are used as antioxidants in polymers; e.g., polyoleflns and rubber, and aldehyde will vary fro~ 5 to 9 carbon atoms when the reaction products are used as an~ioxidants in organic oils such as lubrlcatlng oils.

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Illustrative of the pre~erred aldehydes are butyraldehyde, heptanol, propionaldehyde, isobutyralde-hyde, 2-ethylhexanol, acetaldehyde, formaldehyde and the lilce.
The condensation reaction is carried out in accordance with procedures known in the art such as generally shown in U.S. 2,647,102 and ~.S. 2,5159907.
For example, the cresol and aldehyde reactants may be condensed using conventional acid or strong basic cata-lysis. It is generally desirable to use a mol ratio of aldehyde to cresol of at least 1/1, preferably in the ran~e of 1/2 to 1/4. For a given aldehyde, ratios above about 1/2 seem to provide a reaction product having better solubility in organic compositions such as olls. This may be of concern depending upon intended use. Mol ratios higher than 1/4 may be employed; e.g. 5 as high as 1/10 or higher, but the excess cresol reactant then essentially serves as a diiuent for the reaction system.
While not required, suitable inert diluents may be employed. Examples of such diluents include benzene, toluene, xylenes, paraffins, and the like.
ailuents may be advantageous in aiding to maintain reaction temperatures and aiding in removal o~ water of reaction.
Pressure ls not critical and can be atmospheric or below to 1000 psi or higher. Atmospheric pressure is preferred for convenience. The pressure should be sufficient to maintain the cresol and aldehyde reactants in the liquid phase.

1~7G339 Temperatures are suitably in the range of about 50C to about 150C, preferably in the range of about 75C to 125~. Temperatures below 50C are undesirable as the rate of reaction is unduly slow. Temperatures can be used above 200C, the only concern being degra-dation of the materials.
The acid catalysts which may be employed include hydrogen, halide; e.g., HCl, sul~uric acid, phosphoric acid, aluminum ehloride, ferrie chloride, oxalic acid;
1~ acetie acid. Suitable strong basic catalysts include alkali metal bases such as sodium hydroxide and potassium hydroxide. The reactants together with the catalyst and any diluent which may be employed may be charged to a reactor and reacted under conditions outlined above.
Water of reaction, together with any that may have been introduced with the initial charge, is removed during the course of reaction to drive the condensation to completion.
Most eonveniently, this may be done by distillation over-head although other techniques known in the art could also be used. The condensation is essentially complete when no further water of reaction oceurs. The crude reaction produet mixture may then be cooled, neutralized, and water washed to remove the catalyst, dried, followed by stripping to remove excess cresol reactant, any un racted materials, and any diluent that may have been used.
The resulting condensation reaction product may be in a solid, semi-solid, semi-liquid or liquid 1~7~339 ~orm, depending on the particular aldehyde or aldehydes employed. These reaction products may be employed as such in stabilizing organic compositions against oxida-ti~e deterioration. Additionally, they may be employed in solvent solution. I~ it is desirable to employ the liquid or semi-liquid reaction products in a solid form, it is possible to blend them with an inert absorbent granular or powdery material such as diatomaceous earth or one may add formaldehyde to the reactlon product and sub~ect the mixture to post condensation conditions whereby a hard, solid resinous product is obtained having similar antioxidant properties to the initial reaction product.
For stabilizing organic compounds against oxidative degradation, a stabilizing amount of the reac-tion product or its equivalent is used. Usually an amount in the range of about 0.05 to 5 percent by weight will suffice.
The ~olowing examples illustrate the prepara tion of the antioxidant condensation reaction products:

Example 1 A 500 ml, 3-necked ~lask equipped with a magnetic stirrer, a thermometer, and a Dean-Stark trap was charged with 216 g of a mixture of meta and para-cresols (60~/40%), 72 g of distilled butyraldehyde and 0.15 g of sulfuric acid (conc). The reaction was then heated by a heat lamp to a temperature of about 115C
whereat water began to collect in the trap. Stirring and heating are continued until no further water is ~7`~339 collected ror a pe3':10d Or 2bout l5 millut~s. The tempera-tur~ had risen to 219C and a tol;al of about 16.2 ml collected water was noted.
After cooling to 125C, the crude reaction product was passed through a bed of 10 g o~ 8-mesh alumina to remove the catalyst. The temperature of the reaction product was maintained sufficiently high to keep the product in a fluid state. The neutralized reaction product was then transferred to a round-bottom flask and vacuum stripped at 0.01 mm and 125C to remove excess cresol. The resulting warm viscous rliquid was cooled to ~orm a hard, glossy product which was dark red in color~

Rxample 2 The general procedure outlined in Example 1 was followed using 2.3 mols of butyraldehyde and 4.6 mols of a 60/40 mixture of meta and para- cresol as the reactants, about 460 ml benzene as a diluent and about 0.03 weight percent conc H2SO4 catalyst. The mixture was refluxed until no further water was collected and the reaction product was recovered in the manner des-cribed in Example 1 except that the benzene dlluent was stripped prior to vacuum stripping.

F.xample 3 A one-liter, 3-necked flask equipped as des cribed in Example 1 was charged with 3 mols (324 g) of a commercially available meta-para cresol, 1 mol (72 g) of ~076339 butyraldehyde and 120 ~1 o~ conc ~l2S04. Tlle commercial cresol analyzed about 84.7 percent meta-para cresol ~42.8 percent meta, 57.2 percent para), 0.3 percent phenol, 0.5 percent o-cresol, 11.2 percent xylenols,

2.4 percent trimethyl phenols and 0.9 percent o-ethyl phenol. The mixture was heated to about 116C at which point water began to collect in the top. Heating was continued for about 2 hours during which about 15 ml of water was collected with no water collected during the last 15 minutes. The temperature at thls point had risen to 200 C.
The crude reaction mixture was cooled to 100C and passed through a bed of 30 g of 8-mesh alumina to remove the sulfuric acid. The resulting mixture was vacuum stripped to remove unreacted cresol. Further cooling gave a reaction product which hardened to a glassy solid.

Example 4 The procedure of Example 3 was followed in preparing antioxidant condensation reaction products using the following materials:
(a) 1 mol 60/40 mixture of meta and para- cresols 0.5 mol heptanal 100 ml benzene 0.4 weight percent 112S04 (conc) (b) 1 mol 60/40 mixture of meta and para- cresols 0.425 mol butyraldehyde 0.075 mol heptanal 100 ml benzene 0.03 welght percent ll2S04 (conc) , .. ~, . . ..

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(c) 1 mol 60/40 mixture of meta and para- cresols O . 5 ~ol 2-ethyl-hexanal 100 ml benzene 0.4 weight percent H2S04 (conc) (d) 4.6 mol 60/40 mixture of metal and para- cresols ? . 3 mol isobutyraldehyde 460 ml benzene 0.03 weight percent H2S04 (conc) (e) 1 mol meta- cresol 0.5 mol butyraldehyde 100 ml benzene 0.4 weight percent H2S04 (conc) (f) 1 mol para- cresol 0.5 mol butyraldehyde 100 ml benzene 0.4 weight percent H2S04 (conc) (g) 1 mol mixed cresols (54 percent meta, 29 percent para, 17 percent other phenols -Eastman Tech ~rade) 0.5 mol butyraldehyde 100 ml benzene 0.03 weight percent H2S04 (conc) (h) 1 mol 60/40 mixture o~ meta and para- cresols 0.5 mol butyraldehyde 100 ml benzene 0.03 weight percent H2S04 (conc) (i) 1 mol 60/40 mixture of meta and para-cresols 0.5 mol butyraldehyde 0.03 weight percent H2S04 (conc) ~7~33~

F.xample ~
The procedure of Example 3 was followed using 1 mol 60/40 mixture of meta and para~ cresols, 0.5 mol butyraldehyde, 100 ml b-enzene and 0.03 weight percent H25O4 (conc). After the condensation reaction was com-pleted and cooling to 50C (a liquid solution in benzene), 0.1 of formaldehyde (paraformaldehyde) was added and, with heating, further reaction proceeded until no water was collected. The product was recovered ln the same manner as Example 3 and was a hard, glossy material which could be ground to a fine, free-flowing powder.
The condensation reaction products were evalu-ated for their antioxidant properties as illustrated in the following examples.

Example 6 A series of tests were conducted on the oxida-tion stability of 170 pale oil using the rotating bomb test designated AS~M D-2272-67. In this series of tests, a control sample of pale oll without any anti-oxidant along with several pale oil samples containing 0.5 weight percent antioxidant. The following table outlines the samples tested and the test results.

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TABLE A
Pale Oil with 0.5 Percent Antloxidant Samp le Antio~ldant Bomb Lif (Min) Control (None) 18 Commercial Antioxidants Di-t-butyl-p-cresol 170-200 4,4 ~ -Methylene-bis( 2, 6-di-t-butyl phenol) 75 125 Condensation Reaction Products NO a Cresolb Aldehyde 1 m,p butyraldehyde ~285 2 m,p butyraldehyde 335

3 m,p butyraldehyde 225

4 m,p butyraldehyde 325

5 m,p butyraldehyde 320

6 m,p butyraldehyde 340

7 m,p butyraldehyde 2 75

8 m,p heptanal 265

9 m,p heptanol 95 10m,p heptanol 235 11m,p isobutyraldehyde 335 12m,p 2-ethyl hexanal . 235 13 m butyraldehyde 395 14 p butyraldehyde 335 o butyraldehyde 275 16m,p butyraldehyde and heptanal 330 ~ .

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TABLE_A
(continued) NO.a Cresolb Aldehyde 17 m,p butyraldehyde and heptanal (mol ratio .475/.025) 535 18 m,p butyraldehyde and heptanal (mol ratio .45/.05) 425 19 m,p butyraldehyde and heptanal (mol ratio .4/.1) 375 m,p butyraldehyde and heptanal (mol ratio .375/.125) ' 295 21 m,p butyraldehyde and heptanal (mol ratio .35/.15) 360 22 m,p butyraldehyde and heptanal (mol ratio .3~.2 375 23 m,p butyraldehyde and - heptanal (mol ratio 3/.2) 325 24 m,p butyraldehyde 3gO
m,p butyraldehyde 385 26 m,p butyraldehyde 395 27 m,p butyraldehyde and heptanal (mol ratio .45/.05) 310 28 m,p butyraldehyde and 2-ethyl hexanal (mol ratio .45/.05) l145 29 m,p butyraldehyde and 2-ethyl hexanal (mol ratlo .45/.05) 460 m,p butyraldehyde and 2-ethyl hexanal (mol ratio .4/.1) 425 ~7633~

TABLE A
(continued) ~O aCresolb Aldehyde 31 m,p-l butyraldehyde 555 32commercial butyraldehyde 480 a - Runs 1-9 and 16-22 prepared by procedure in Example 4(b) Runs 10-14 prepared by procedure in Example 4(c) Run 15 prepared by procedure in Example 4(b) Runs 23-30 prepared by procedure in Example 4(1) b - m,p is a 60/40 mlxture of meta and para- cresols m is meta- cresol p is para- cresol o is ortho- cresol m,p-l is a 43/57 mixture of meta and para- cresols c - cresol is same as used in Example 3 Note - the above data are representative of numerous tests carried out.

Example 7 A series of tests were conducted on the oxi-dation stability of rubber (50/50 SBR and natural rubber) as reflected by percent retention of physical properties after aging. The rubber masterbatch tested comprised 50 parts natural rubber, 50 parts SBR, 2 parts stearic acid, 4 parts zinc oxide, 50 parts carbon black, 1 part accelerator and 2 parts sulfur. Samples containing various antioxidants including a control without any - ]3 -~7~33~

antioxidant were prepared and tested in accordance with ASTM D-412 and D-572~67:

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Example 8 Another series of tests were conducted on the oxidative stability Or rubber in the same manner des-cribed in Example 7. The ~ollowing table sets forth the antioxidants evaluated and the test results:

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Example 9 A series of tests were carried out on the oxidative stabllity of a conventionally refined parafflnlc petroleum based oil having typical properties of flash point - 400F, pour point - 0 to 10F, and SUS viscosity at 210F of 43-45 and at 100F of 145-170, Two commercial antioxidants and a reaction product of m,p-cresols and butyraldehyde were evaluated in accordance wlth ASTM
D-943. The results are indicated in the following table.

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TAI~I.,T. D
Parafflnlc Oil Contalning 0.5 Percent Antioxidant Stability Li~e Antioxidant (hrs) Di-t-butyl-p-cresol .800-1000 4,4'~methylene-bis(2,6-di-t-butylphenol) 500- 800 Reaction Product El 2200-~

1 - Reaction product o~ 2 mols 60/40 mixture of meta and para- cresols and 1 mol of butyraldehyde using 1 weight percent H2S04 (conc) and,200 ml benzene dil~ent Example 10 Following the procedure of Example 1, 108 g (1 mol) of a mixture of meta and para- cresols (60 percent/40 percent), 15 g (0.5 mol) of paraformaldehyde, 0.075 g conc sulfuric acid and 100 ml benzene were charged to the reaction flask. The condensation reac-tion was carried out at reflux of about 60C until no further water was collected. The reaction product was worked by passing through an alumin.a b.ed followed by hot and vacuum stripplng to remove the benzene and excess cresols. The resulting recovered reaction prod-uct was a hardg glassy solid.
Since the reaction product was a solid and essentially insoluble in hydrocarbon oils, lt has no practical use 1n inhibiting oxidation of oils. How-ever, it was ground and tested in an SBR rubber formu-lation and found to be an effective antioxldant.

L~ _ F.xam~le ~ 1 ~ rurther scl~ies Or t;ests were conducted on the oxidation stability of a commercial motor oll in accordance with the Sequence III-C test of ASTM STP
315F. The motor oil employed was essentially an SAE 30 grade without a supplemental antioxidant. Tests were run on this oil which served as the control and also on the same motor oil to which had been added 1.14 percent of a 50 percent xylene solution of a reaction product of mixture of meta and para- cresols and butyraldehyde and desi~nated as 968-L. The reaction product was prepared from 50 mols of 60/40 mixture of meta and para-cresols and 0.25 mol of butyraldehyde using 0.05 percent H2S04 (conc) and 5 1 benzene as diluent. The percent vlscosity increase results of the tests are shown in the following table.

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mABLE E

Elapsed PERCE~T VISCOSITY INCREASE
TimeControl 968-L
8 19.9 25 16 3~7 38.1 24 41.9 49.9 32 192.7 61.2 2193 105.3 48(terminated) 294.6 56 ~ 585.4 ~'7~3~
Example 12 Oxidative stability was evaluated on a poly-proplylene sample (A) containing n-octadecyl-3,5-di-t-butyl-4-hydroxy-phenyl acetate (Irganox 1076*, a known commercial antioxidant and a polypropylene sample (B) containing DSTDP (distearylthiodipropionate) and a reaction product of 0175 mol of a 60/40 mixture of meta and para-cresols and 0.75 mol of heptanol using 0.03 weight percent ~2SO4 (conc) and 75 ml benzene as diluent. Each sample contained the same level of DSTDP and 0.03 percent of either the reaction product or Irganox 1076. The samples (A) and (B), were ov~.n aged at 150C for 24 hours. Visual inspection indicated about the same degree of crazing and discoloration.
Thus, having described the invention in detail it will be understood by those skilled in the art that certain variations and modifications may be made without departing from the spirit and scope of the invention disclosed herein and defined in the appended claims.

* Registered Trade Mark of Ciba-Geigy Corporation ~.~

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition comprising an oxidation-prone organic material and an oxidation inhibiting amount up to 5% by weight of the composition of a condensation reaction product of (1) meta-cresol or a mixture of meta- and para-cresols, optionally containing up to 25% by weight of ortho-cresol, xylenols, phenol, or mixtures of any of these but substantially free of other alkylphenols, and (2) an aldehyde defined by R--CHO wherein R
is hydrogen or an alkyl group, said reaction product having at least predominantly, the general formula wherein R is hydrogen or an alkyl group containing from 1 to 9 carbon atoms and the methyl substituents are in the 3 or 4-positions of the pheonolic rings.

2. The composition of claim 1 wherein (1) is a mixture of meta- and para- cresols.

3. The composition of claim 2 wherein R is an alkyl group having 5 to 9 carbon atoms.

4. The composition of claim 2 wherein the condensation reaction product is used in an amount 0.05 to 5 percent by weight.

5. The composition of claims 1, 2 or 3 wherein said oxidation prone organic material is a lubricating oil, rubber or resinous polymer.

6. The composition of claim 1 wherein said oxidation-prone organic material is natural rubber, SBR or polypropylene.