US3497531A - Stabilization of oxirane containing fatty derivatives - Google Patents

Description

United States Patent U.S. Cl. 260348 3 Claims ABSTRACT OF THE DISCLOSURE Fatty, oxirane-containing compounds stabilized against loss of oxirane oxygen by the presence of phenolic fat antioxidants such as propyl gallate.

This application is a continuation of application Ser. No. 166,420, filed Jan. 15, 1962 and now abandoned.

This invention relates to the stabilization of oxygencontaining fatty derivatives and, more panicularly, to stabilized oxirane-containing higher fatty derivatives protected against loss of oxirane oxygen and increases in acidity.

oxirane-substituted higher fatty acids, higher fatty alcohols, higher fatty acid amides, and higher fatty acid esters are valuable compositions, particularly the esters of oxirane-substituted higher fatty acids and esters of oxirane-substituted higher fatty alcohols and the value of these compositions is attributable in many cases to the oxirane oxygen content of the composition. Oxiranecontaining higher fatty acid esters, for example, have been found of significant value as plasticizer-stabilizers for halogen-containing compositions such as the vinyl halide resins.

Oxirane-containing glyceride oils and epoxidized fatty acid esters of mono-, di-, and polyhydric alcohols generally are employed Widely as plasticizer-stabilizers in synthetic resins. These epoxy esters inhibit degradation of the vinyl resin and this inhibition has been attributed to the presence of the oxirane group. Also, the presence of the oxirane group in the ester appears to promote compatibility of the ester with resins.

These oxirane-substituted higher fatty derivatives undergo certain changes upon long periods of storage and when the materials are subjected to elevated temperature and/or pressure as is encountered in the processing of resins with which they are formulated. These changes include an increase in acidity of the oxirane-containing material and a development of an objectionable odor and loss of epoxy oxygen accompanied by lessening of stabilizing properties and poorer compatibility with resins.

It is accordingly an object of this invention to stabilize oxirane-containing higher fatty derivatives against loss of oxirane oxygen and odor development and also preserve the stabilizing properties and compatibility of such derivatives with resins.

A further object of the invention is the provision of oxirane-containing higher fatty derivatives stabilized against decreases in oxirane oxygen content.

Another object of the invention is the provision of synthetic plastics containing stabilized oxirane-substituted fatty materials which oxirane-substituted fatty materials retain plasticizer and stabilizing efficiency as well as compatibility substantially undiminished after long periods of storage.

Still another object of the invention is the provision of a method for protecting oxirane-substituted higher fatty materials against loss of oxirane oxygen.

3,497,531 Patented Feb. 24, 1970 ice.

Additional objects, if not specifically set forth herein, will be readily apparent to those skilled in the art from the detailed description of the invention which follows.

Generally, the invention comprises oxirane-containing higher fatty derivatives having embodied therein protective agents for the group and synthetic plastic compositions containing oxirane-substituted higher fatty materials which plastics can be stored for long periods and/or processed and formulated at elevated temperatures without substantial decrease in oxirane content of the fatty material. Also within the contemplation of-the invention are methods for inhibiting and preventing the oxidative degradation of the oxirane-substituted fatty materials and the development of objectionable odors in such materials. The method of the invention involves the embodiment in such oxirane-substituted fatty materials of a protective amount of an organic phenolic composition.

More specifically, the invention provides epoxidized higher fatty acids, aromatic and lower aliphatic alcohol esters of such fatty acids, amides and hydrazides of such fatty acids, as well as esters of oxirane-containing higher fatty alcohols, stabilized against degradation and loss of oxirane oxygen by a small amount of a phenolic fat antioxidant.

While directed to oxirane-containing fatty materials generally, the stabilization is directed particularly to epoxy esters which are employed extensively in plasticizing vinyl halide resins. The oxirane-containing fatty acid derivatives to which the invention is particularly directed are the mono-, di-, tri-, tetra-, and pentahydric alcohol esters of oxirane-containing fatty acids of 730 and preferably 1030 carbons. Esters of such acids with monohydric aliphatic alcohols having 118 carbons and esters with dihydric aliphatic alcohols of 26 carbons, as Well as with aliphatic polyhydric alcohols generally, are contemplated. Suitable monohydric alkyyl and alkenyl alcohols providing the alcohol moiety of such esters include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, and octyl alcohols. Dihydric alcohols include the lower glycols as ethylene glycol, 1,2-propanediol, 1,3-propanediol, dimethylene glycol, trimethylene glycol, tetramethylene glycol up to and including hexamethylene glycol.

Benzenoid alcohols which may be employed in preparing the oxirane-containing fatty acid esters which can be advantageously treated in accordance with the invention are those benzenoid alcohols having less than 10 carbons and including benzyl, phenyl, 2-phenylethyl, lphenylethyl, and nuclear methylated phenyl alcohols.

The polyhydric alcohol esters of oxirane-containing fatty acids include the tri-, tetra-, penta-, and hexahydric alcohol esters of the fatty acid moiety. Included within this group are those aliphatic alcohols having 3-6 carbons and three or more alcohol groups. These include glycerol, erythritol, pentaerythritol, and hexitols such as mannitol and sorbiol. Mixed oxirane-containing esters such as those disclosed and claimed in U.S. Patent No. 2,978,463, issued Apr. 4, 1961, to F. E. Kuester et a1. may also be used.

Highly epoxidized low lay-product esters such as those disclosed in co-pending application Ser. No. 807,985, filed Apr. 22, 1959, now U.S. Patent No. 3,117,754, are particularly well suited to treatment in accordance with the invention. These materials because of their high oxirane content and low hydroxyl and low polymer content are more compatible with vinyl resins than epoxy esters having a lower oxirane content and greater amount of byproducts. Because of the low by-product and low polymer content of these materials a higher level of compatibility with the resin is obtained and larger amounts of such esters can be employed in plasticizing a vinyl halide polymer.

The invention has particular application as applied to aliphatic monoand polyhydric lower alcohol esters of high oxirane higher fatty acids which contain a minimum of by-products such as polymers and hydroxylated esters. Those epoxidized fatty acid esters made from fatty acids having an oxirane content in the range of about 8.8 12.3% oxirane oxygen should have an infrared absorptivity at 2.9 microns (corrected for background) of .020 maximum. Other epoxy esters of fatty acids having an oxirane content of about 5.87% oxirane oxygen should have an infrared absorptivity at 2.9 microns (corrected for background) of .01 maximum. High oxirane linseed or perilla oil are examples of glyceride esters characterized by an absorptivity of .02 maximum at 2.9 microns while high oxirane soybean oil and Z-ethylhexyl esters of tall oil fatty acids, among others, have an obsorptivity of .01 maximum at 2.9 microns.

The phenolic antioxidants which are known in the art as fat antioxidants provide stabilization of the oxiranesubstituted compositions. Antioxidants such as butylated hydroxy anisole, butylated hydroxy toluene, and propyl gallate are representative of the group generally known as fat antioxidants. Commercial butylated hydroxy anisole is a mixture of B-tertiary butyl-4-hydroxy anisole and Z-tertiary butyl-4-hydroxy anisole. Butylated hydroxy toluene (2,6-ditertiary butyl-p-cresol) is also an article of commerce. It is generally desirable to dissolve the additive or mixture of additives in a mutual solvent such as propylene glycol, ethanol, monoglycerides or like solvent in order to insure distribution of the stabilizer throughout the oxirane-containing composition.

The edible or nontoxic phenolic antioxidants are preferred for use in oxirane-containing esters which are to be used with vinyl halide resins designed for use around foods. The production of food packaging films from polyvinyl chloride requires that the film not contain inedible or toxic ingredients and thus epoxidized oils used in such formulations should contain stabilizers approved for food use. Further when the epoxidized oil is utilized in vinyl halide resins the stabilizer should be a composition which does not adversely affect the vinyl halide. For this reason stabilizers having amino groups are not favored in such formulations. Other suitable antioxidants useful in some applications are beta-naphthol, hydroquinone and compounds such as Z-tertiary -butyl-4-decyloxyphenol, 2-tertiary butyl-4-dodecyloxyphenol, Z-tertiary butyl-4-tetradecyloxyphenol and 2-tertiary butyl-4-octadecyloxyphe- 1101. A preferred stabilizer mixture for use in oxirane substituted compositions to be used with polyvinyl chloride resins is as follows:

Percent by weight Propyl gallate 20 Citric acid 1O Propylene glycol 70 Substitution of gentisic acid for propyl gallate in the above formulation results in an almost equally effective degree of stabilization.

Because the stabilizing efficiency of individual compositions and mixtures of such compositions vary, the amount of stabilizer required depends upon the particular composition employed. Also, the conditions to which the oxirane-containing material is subjected affect the amount of stabilizer required. Usually about .01-0.5% of the stabilizing material based en the Weight of the oxiranecontaining composition serves to satisfactorily stabilize aga s n ea e n ac y of the oxi an -substit ted o position. Smaller amounts down to around .0025% appear to provide a beneficial result although amounts in the range around .02.04% appear to be optimum. While larger amounts can be used, up to around 5% without adversely affecting the oxirane compositions, the use of such large amounts may not be desirable inasmuch as the increased protection is not commensurate with the increase in the amount used. In some cases the use of larger amounts is advantageous as where the epoxidized fatty material is employed as a plasticizer-stabilizer for vinyl halide resins. Amounts in the range of 13 parts of antioxidant per hundred parts of resin in a vinyl chloride formulation improve processability of the resin and inhibit viscosity build-up.

The method for incorporating the stabilizers in the oxirane-containing derivative or in plastic formulations containing such oxirane derivative is not critical so long as the stabilizer is distributed throughout the mixture and maintained in contact with the oxirane-containing material. The stabilizer can be incorporated in the resinoxirane-containing composition mixture or the stabilizer can be incorporated in the oxirane-containing material as part of the manufacturing operation producing such material.

Best results in realizing the benefits of the invention are obtained, if the oxirane-containing composition is refined as by caustic refining. If an epoxidized glyceride, for example, is treated with sodium hydroxide, potassium hydroxide or other alkali to remove any acidic materials and/or peroxides, the effect of the stabilizer will be substantially increased. A convenient method for incorporating butylated hydroxy toluene and/or butylated hydroxy anisole in an epoxidized glyceride involves first dissolving the additives in a solvent such as propylene glycol, incorporating the solvent containing the additives in the glyceride oil and subsequently subjecting the oil to a steam deodorization step to remove volatiles which volatiles also include the glycol solvent. Alkali refining prior to addition of the stabilizer insures that no residual inorganic acid possibly employed in the production of the epoxidized composition will be present therein to accelerate degradation on storing.

Accelerated aging tests have been employed to demonstrate the stabilizing effect of the additives of the invention. This accelerated aging test involves placing the sample containing the stabilizer, as well as a control sample with no stabilizer, in 50 gram amounts in open 100 ml. beakers in a laboratory electrically heated oven. The temperature of the oven is adjusted to a given temperature and observations are made after varying lengths of time. Other methods for testing stability of the epoxide can also be used and this method has been selected for simplicity and convenience.

The following examples which are intended to be illustrative and which should not be considered to place any limitation upon the invention, show the stabilizing effect of the phenolic antioxidants.

Example I The oxirane-containing material is epoxidized soybean oil having an oxirane content of 7.02%, an iodine value of 2, a Gardner color of less than 1, and an infrared absorptivity at 2.9 microns (corrected for background) of .01 maximum. This epoxidized soybean oil contains an average of over 4 reactive epoxy groups per molecule. A 50 gram sample of this epoxidized oil containing no stabilizer was compared with 50 gram samples of same oil containing 01% propyl gallate and a sample containing .01% butylated hydroxy anisole and a sample containing .01% butylated hydroxy toluene. The samples were heated in the oven at C. for varying lengths of time up to 28 days and peroxide values, as well as free fatty acid (as actic acid) and oxirane analyses, were conducted. Table I shows the increase in acidity of the unstabilized sample and the in; hibition of this acidity increase by the additives.

TABLE I Percent Free Fatty Acid (as Acetic) After Number of Days Indicated as 85 0.

Sample days 7 days 14 days 21 days 28 day Sample I, epoxidized soybean oil (control) 013 027 040 095 160s Samplelcontain %propylgalla .009 .009 .016 .030 Sample I containing .01% butylated hydroxy anisole 009 009 016 035 Sample I containing .01% butylated hydroxy toluene 009 008 016 052 Oxirane determinations were made after 14 and 28 EXAMPLE II days and the results are as follows:

TABLE II Percent Oxirane After Number of days Indicated 15 Indicated Sample 0 14 28 Sample I epoxidized soybean oil (control) Sample I containing .01% propyl gallate Sample I containing .0l% butylated hydroxy amsole Sample I containing .01% butylated hydroxy toluene TABLE III Percent Free Fatty Acid (as Acetic) After Number of Days Indicated as 85 0.

Sample 0 days 7 days 14 days 21 days 28 days Sample I, epoxidized soybean oil (control) 0125 0338 074 084 129 Sample I contining .0025% butylated hydroxy toluene: 0303 054 075 103 Sample I containing 005% butylated hydroxy toluene .I 0267 050 065 104 Sample I containing .01% butylated hydroxy toluene 0171 036 037 084 Sample I contining .02% butylated hydroxy toluene 0155 036 025 025 Sample I containing .04% butylated hydroxy toluene- 0161 034 026 018 The stabilized epoxidized soybean oil samples also exhabited far greater compatibility in vinyl chloride formulations than the unstabilized control. While films prepared from polyvinyl chloride resin formulations plasti- Oxirane determinations were made after 14, 21, and 28 days. The increasing elfectiveness of the stabilizer in inhibiting loss of oxirane oxygen as increasing amounts are added can be seen.

TABLE IV Percent Oxirane After Number of Days Indicated at C.

Sample 0 days 14 days 21 days 28 days Sample I, epoxidiaed soybean oil (control) 7.02 7.03 6.87 6. 77 Sample I containing .0025% butylated hydroxy toluene 7. 03 6. 93 6. 89 Sample I containing .005% butylated hydroxy toluene 7. 03 6. 91 6. 87 Sample I containing .01% butylated hydroxy toluene 7. 05 6. 98 6. 91 Sample I contalmng .02% butylated hydroxy toluene 7. 07 7. 00 7. 00 Sample I containing 04% butylated hydroxy toluene 7. 07 7. 00 7. 00

cized with the control sample showed considerable exudation of the plasticizer films prepared from similar polyvinyl chloride resin formulations plasticizcd with the stabllized epoxidized oils were substantially free of exuded plasticizer.

Example III TABLE V Percent Free Fatty Acid (as Acetic) After Number of Days Indicated as 85 C.

Sample 0 days 7 days 14 days 21 days 28 days Epoxidized Z-ethylhexyl tallate (control)- 036 169 246 38 56 Sample I containing .01% butylated hydroxy toluene 036 35 232 30 38 Sample I containing .1% butylated hydroxy toluene 036 .082 071 096 172 Sample I refined with aqueous sodium hydroxide and containing .02% butylated hydroxy toluene .036 016 034 7 8 Oxirane determinations for these samples were con- The two batches were worked on a 2-roll mill for 5 ducted and the results are as follows: minutes at 330 F. with the roll speeds being adjusted to TABLE VI Percent Oxirane After Number of Days Indicated at 85 0.

It can be seen that alkali refining of the epoxidized 50% and 60%. Small pieces, 6" x 6" were cut from the ester aids considerably in stabilizing effectiveness. films obtained and these small pieces were placed in a preheated (345 F.) chrome mold. The mold was placed Example IV in a Carver Press so that the heating plates of the press The oxirane-containing material employed in this test Were in Contact With the mold- The Contact Pressure was is high-oxirane linseed oil having an oxirane oxygen value maintained for 5 minutes, while the temperature was held of 9.22%, an iodine value of 4, a Gardner color less than at and t the Pressure as increased to 20, 1, and infrared ahsorptivity at 2.9 microns (corrected for psi. The mold was held under this pressure for 5 minbackground) of .020 maximum. The epoxidized linseed utes. After cooling, the pieces were removed from the oil has a low polymer content and a low hydroxyl content, mold and placed in a Fadeometer for 100 hours. Examias illustrated by the infrared absorption. In addition, the nation of the films after 100 hours showed that the film low viscosity (8.8 poises) is further evidence of the low prepared from the epoxidized oil containing no stabilizer polymer content. exhibited some loss of gloss and some exudation, while Varying amounts of butylated hydroxy toluene were the film prepared from the formulation having stabilized added to this oil and the stabilizing effect as compared epoxidized oil was substantially free of exudation and to a control sample having no stabilizer added was deterwas characterized by good gloss. mined by free fatty acid content and oxirane oxygen 3 The stabilizers employed herein are compatible with values. other materials employed in vinyl halide resin formula- TABLE VII Percent Free Fatty Acid (as Acetic) After Number of Days Indicated as 85 0.

Percent Oxirane After Number of Days Indicated at 85 0.

Sample 0 days 7 days 14 days 21 days 28 days Epoxidized linseed oil (control) 9. 22 9. 16 9. 10 8. 92 Sample I containing .02% butylated hydroxy toluene 9. 22 9- 18 9- 23 9. 20

yp of the Vinyl halide p y With Which the tions such as lubricants, heat stabilizers (such as the stabilized epoxidized fats are most useful are those polymetal salts) and antistatic agents. The alkyl phenols can mers in which at least of the monomer units prior 50 b l d alone or i combination to Obtain the to polymerization are vinyl halide units. This includes perior stabilization. In addition, stability enhancing mapolyvinyl Ch r p lyvinyl hrOmide, P y y fluoride, terials can be employed with the phenolic stabilizers. These polyvinylidene ChlOIldC, vinyl chloride-vinylidene, ChlO- enhancing agents include citric acids, phosphoric acid, ride copolymers, vinyl chloride, vinyl acetate copolymers as well as homopolymers and interpolymers of vinyl halides. Other monomer which may be copolymerized with vinyl halides include vinyl ketones such as vinyl butyl ketone, the acrylates and lower alkyl acrylates and alkacrylates as well as lower alkyl esters of maleic and The stabilizers impart improved color stability to polyvinyl chloride resin compositions containing the stabilized oxirane-containing fatty materials. The improvement in color stability in the polyvinyl chloride compositions after formulation on extruders and after exposure to elefumanc aclds' Exam 1e V vated temperatures is substantial. This improvement has p been noted at low levels of the stabilizer around .0l1% A formulation Containing the following ingredients: and also at much higher levels in the range of up to 5%. parts Obviously, many modifications and variations of the P 1 i 1 chlorid 100 invention as hereinbefore set forth may be made without Epoxidized soybean oil (oxirane oxygen 7%) 40 departing from the spirit and scope thereof and, accord- Zinc stearate 0.25 ingly, only such limitations should be imposed as are in- Mineral oil 1 dicated in the appended claim. wa prepared and a similar formulation was prepared We claim! containing the same ingredients in the same amounts, 1. Esters of oxirane substituted higher fatty acids of with the exception that stabilized epoxidized soybean oil 7-30 carbon atoms containing from about .0025% to was substituted for the unstabilized plasticizer. This staabout 5% of propyl gallate based on the weight of said bilized oil contained .05 based on the weight of the oil esters. of a stabilizer mixture made up of 20 parts propyl gallate, 2. The product of claim 1, wherein said ester is epoxi- 10 parts citric acid, and 7 0 parts propylene glycol. dized soybean oil.

3. The product of claim 1, wherein said propyl gallate is in admixture with citric acid Which together are present in an amount of about .0025 to about 5% based on the weight of said esters.

References Cited UNITED STATES PATENTS Mattil et a1. 260398.5

Hall 260398.5 Bell et al. 99163 Hall 260--398.5 Orloff et a1. 252-48.2 Hudson 12737 Havens et al. 260348 XR Fetscher et a1. 26023 XR 10 3,075,940 1/1963 Pazinski 26045.85 XR 3,091,597 5/1963 Henriques 260-23 XR 3,125,592 3/1964 Nevin 260-4585 FOREIGN PATENTS 841,890 7/ 1960 Great Britain.

OTHER REFERENCES Jundberg, W. G.: Autoxidation and Antioxidants, vol. 10 -II, chapter 12, pp. 477-542, Interscience Publisher, 1962.

NORMA S. MILESTONE, Primary Examiner US. Cl. X.R.