Lubricant additives derived from catalytically polymerized reaction products of succinimides and unsaturated monocarboxylic acids or anhydrides

BACKGROUND OF THE INVENTION

Field of the invention \ . ²⁵

The present invention relates to a process for producing novel lubricant, additives and the. additives produced. More particularly, it relates, to additives derived from succinimide detergents. 30

Description of the prior art

It is known to prepare lubricant additives by reaction of a substituted succinic acid or anhydride with an amine. See, for example, U.S. Pat. 3,361,673. The substituent ih ,.the succinic acid or anhydride is a substantially saturated aliphatic group having about 30 to 200 carbon atoms. The acid or anhydride reacts with the amine to give a product or mixture of products which includes a succinimide structure. These compounds are used as^- detergents in lubricant compositions. Compounds which may be obtained in this manner and have detergency properties are hereafter referred to as succinimide detergents.

In many cases the amine used in the preparation of the succinimide detergent contains more than one amino ni- 45 trogen atom, and the product of reaction of the substituted succinic acid or anhydride with the amine may, therefore, contain a free primary amino group.

SUMMARY

The present invention is a process for producing a ⁵θ lubricant additive having detergency and viscosity indeximproving properties by reacting a succinimide detergent having a free primary amino group with a polymerizable acid or acid additive and polymerizing the product to Ob- _Rrtain the lubricant additive. ^J

DETAILED DESCRIPTION OF THE INVENTION

In its broadest form, this invention is a process for producing a lubricant additive having detergency and viscosity index-improving properties by reacting a succinim- ⁰⁰ide detergent having a free amino group with a polym erizable acid or acid derivative and polymerizing the product to obtain the lubricant additive.

One of the two principal.reactants is a succinimide detergent having a free amino group. As used herein, “succinimide detergent” refers to compounds having the formula: 0

R“—CH—O ,

I . . ^N—(R^bNH)y—R^bNH2

- ... CH;-/ wherein R^a is a long-chairi polyolefin radical having a number average molecular weight of about 300 to 3,000, R^b is an alkylene radical containing 2 to 8 carbon atoms, and y is an integer from 0 to 10. These compounds are described in more detail in numerous references in the art. See, for instance,.the aforesaid U.S. Pat. 3,219,666 as well as U.S. Pats. 3,018,250, 3,087,936, 3,172,892, and 3,202,678. Usually they are prepared by reacting polyolefin, succinic anhydride, and ammonia, alkylene monoamines, · or. alkylene polyamines. Such reactions are also described in the art. See,, for instance, the patents cited immediately above.

The preferred succinimide detergents are polyisobuten,yl succinimides prepared by reaction of a substituted succinic acid or anhydride derived from a polybutene of (number average) molecular weight about 950 to 2,800 and tetraethylene pentamine. Polyolefins having number average molecular weights of 950 or greater are preferred as solubility problems may be encountered with the lower molecular weight materials, particularly where .the succinimide is derived from a high polyamine. Other typical succinimides are those derived from polybutenes of 350 and 3,000¹ molecular weight, respectively. Particularly preferred are succinimides derived from polybutenes having 950, 1,400, or 2,700 molecular weight and which are commercially available from Chevron Chemical Company under the trade names of, respectively, “Polybutene 24,” “Polybutene 32,” and “Polybutene 128.” The succinic acid or anhydride and the amine are preferably reacted in approximately equimolar ratio to obtain the succinimide dispersant.

Typical polyolefins which can be used to prepare the succinimide detergents include polyethylene, polypropylene, and polyisobutylene. Typical monoamine reactants may be methylamine, ethylamine, propylamine, and higher alkyl monoamines. Typical polyamine reactants include ethylene diamine, propylene diamine, pentylene diamine, octylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, tetrapropylene pentamine, tetrabutylene pentamine, and nonaethylene decamine.

Suitable polymerizable acids are those which have unsaturation in the molecule, as, for example, acrylic methacrylic, or crotonic acids. Acrylic and methacrylic acids are preferred. While this explanation is in no way to be considered limiting, it is believed that the acid or derivative reacts with a free amino group to form an amide.

Accordingly, the acid derivative which may be used is

3,630,902 any which will form an amide on reaction with an amino group, as, for example, an anhydride, acid chloride, or ester. The reaction between the succinimide detergent and polymerizable acid is usually carried out in an inert solvent, such as toluene, and if solubility problems are encountered, the product of reaction may be dissolved in lubricating oil by solvent extraction with the oil from the inert solvent. It is preferred to react the succinimide detergent and polymerizable acid in equimolar proportions.

The product may be polymerized with or without a catalyst, although use of a catalyst is preferred. If a catalyst is used, it is preferred that it be a free radical catalyst such as azo-bis(isobutyronitrile) or a peroxide such as benzoyl peroxide, t-butylhydroperoxide or di-t-butylhydroperoxide. Although it is not known with certainty, it is believed that with acrylic acid the final product of reaction in the presence of a free radical catalyst has the structure

--CH-CIL- \h

I _ A -Jx when x is an integer and A is the residue of the succinimide detergent having a free amino group. The catalyst may also be a base, in which case the product may contain the structure

--N-C O-CH-CH-I

La Jx

Suitable basic catalysts include alkali metal alkoxides, Grignard reagents, zinc alkyls, lithium alkyls and the like.

Reactions to give both structures may occur simultaneously.

The product of reaction of the succinimide detergent and the polymerizable acid may be further copolymerized with a copolymerizable monomer in the presence of a free radical polymerization catalyst. The copolymerizable monomer may be a further quantity of the polymerizable acid, although this is not preferred as the product will be acidic, which is undesirable in a lubricant additive. It is, therefore, preferred that the copolymerizable monomer be a neutral compound having an olefinic double bond which is activated by another group in the molecule to make it polymerize under mild conditions, for example, alkyl ester of acrylic or methacrylic acid such as methyl, n-butyl, 2-ethylhexyl or laurylacrylate, or methacrylate, acrylamide, vinyl esters such as vinyl acetate or vinyl propionate, styrene, α-methyl styrene, allyl acetate and acrylonitrile.

When producing a copolymer, it is preferred to react 2 to 3 moles of the copolymerizable monomer with 1 mole of the product of reaction between the succinimide detergent and polymerizable acid.

The amount of polymerization in the final product can vary greatly depending on the ease of polymerization of the constituent monomer, and the value of the integer x may range from 2 to 200. A typical lubricant which can be improved by the additives described herein comprises a mixture of a lubricating oil and the additive produced by the process of this invention. The additives are generally present as 0.1 to 10 weight percent of the whole lubricant composition. The preferred concentration is about 2 weight percent. It is also possible to use these additives in “concentrates,” in which the concentration of additive in the mixture of oil and additive is 10 to 80 weight percent. Preferably the concentration is about 40 weight percent.

The invention is further illustrated in the examples.

Example 1

An oil solution of a polyisobutenyl succinimide (1,000 g.), containing 36% active succinimide and prepared from tetraethylene pentamine and a substituted succinic anhydride derived from polybutene of 1,000 M.W. at a molar ratio of 0.9:1.0, was charged to a glass reactor. The succinimide was further diluted with toluene and the mixture stirred. The temperature of the contents was raised to 40° C. and acrylic acid (29 g.) added dropwise. When addition of acrylic acid was complete, the temperature of the reactants was raised until the mixture boiled. Water of reaction was then removed continuously as a tolueneiwater azeotrope with the aid of a Dean and Stark receiver. When the water of reaction had ceased to be evolved, the reaction mixture was cooled to 30° C. and 4 g. of azo-bis (isobutyronitrile) was added. The temperature was raised and the mixture stirred at 70° C. for 5 hours. The temperature was further raised to 100° C. and stirring continued for a further hour. The toluene was then removed by distillation under reduced pressure. The final product was a viscous dark amber liquid having a characteristic odor. Infrared examination of the product revealed the presence of both imide and amide groups. The nitrogen content was found to be 2 weight percent.

The product was evaluated for viscosity index-improving tendencies by blending at various concentrations into a base oil having a viscosity index of 68. The results of these tests are tabulated below in Table I. The viscosity index was calculated according to ASTM method D-567.

TABLE I

Material of example (wt. percent) Viscosity index (base oil) 68

170.1

277.4

583.2

1090.2

The product of the example was evaluated for detergency in the Petter AV-1 120-hour Engine Test operated to Ministry of Defense Specification DEF 2101D. It was evaluated in a formulation containing an overbased calcium sulfurized alkyl phenate as a basic additive and a zine dialkyldithiophosphate in which the alkyl groups were derived from C₄ and C₆ primary alcohols as an antioxidant. It is compared with a similar nitrogen-containing succinimide commercially available at the equivalent concentration (based on nitrogen content). The results from the test are listed below in Table II. In the test, results are reported on a scale of 0 to 10, with 10 representing a clean engine.

TABLE II

Grooves and lands, average

Lubricant A (Material of Example 1)------------8.2

Lubricant B (Commercial Succinimide)__________5.2

As may be seen from the tests, the material of this invention has both viscosity index-improving properties and shows excellent detergency when tested in a diesel engine.

Examples Al through II

In each of the examples tabulated in Table III, below, a succinimide detergent with an alkenyl side chain and derived from tetraethylenepentamine was reacted on a mole-to-mole basis with a polymerizable acid. The reactants plus toluene and, in some cases, a catalyst, were heated to toluene reflux temperature and the water of reaction removed via a Dean and Stark receiver, leaving an intermediate product. The polymerization catalyst was then added and the intermediate product polymerized under the conditions noted. Heating was continued until no more water was evolved. In some examples, the polymeric material was then further polymerized with the same acid or another monomer. The data in Table III illustrate the wide variety of conditions under which the viscosity indeximproving polymers of this invention may be produced.

3,630,902

TABLE III

Number of carbon atoms in Polymerization conditions Reactants and mole ratio (MR) alkenyl portion--------------------------------- -----------------------------------------------of polyiso- Reaction Tempera- Catalyst, Pollso- Acid Other butenyl time, ture, wt. butenyl------------------ -----------------Run no. succinimide hrs. °C. percent > succinimide MR Compound MR Compound

Viscosity index of noted wt. percent polymeric product in oil solution

Al.

A2.

A3. Bl. B2. B3. Cl. C2. 03. C4. C5. C6. 07. DI. El. E2. E3. Fl. Gl. G2.

300.13

800.13

1100.26

1000.13

1000.66

1001.3

600.13

600.13

600.13

600.13

600.13

600.13

600.13

600.1

762 0.2

75 ^{* 8}0.2

75‘ 0.2

600.1

600.1

600.1

600.1

1 Acrylic_____________________________________

1_____do______________________________

1.....do....................................

1_____do......................................

1_____do______________________________________

1.....do______________________________________

1_____do______ 0.5 Acrylic (excess)_________

1_____do______ 1.0_____do__________________

1_____do______ 2.0_____do..._______________

1_____do______ 3.0_____do__________________

1_____do______ 2.0 Methylacrylate_________

1_____do______ 1.0 n-butyl methacrylate___

1_____do______ 1.0 Acrylamide_____________

1 Crotonic____ 2.0 Methyl acrylate_________

1 Acrylic_____ 1.0 .....do..._______________

1_____do______ 1.0.....do__________________

1_____do______ 1.0_____do..................

1_____do______ 2.0_____do__________________

1_____do______________________________________

1_____do______ 2.0 Methylacrylate.........

, f 1_____do______12.0 Acrylic (excess)__________ ¹ (1-0 Diluent oil..)

108

108

108

109

107

104

108

109

111

107

115

112

108

108

110 .

106

109

107 ’107”

118

114

112

113

110

106

106

118

118

111

115

116

114

115

103

110

105

118

110

114 ϊϊΐ

The catalyst was azo-bis(isobutyronitrile) unless otherwise noted.

⁸ The catalyst was benzoyl peroxide.

⁸ The catalyst was t-butylhydroperoxide.

• The catalyst was dl-t-butylhydroperoxide.

of an aliphatic substituted succinic acid or anhydride, the aliphatic substituent being substantially saturated and having a molecular weight of about 300 to 3000, and an alkylene polyamine having 2-12 amino groups and 1-11 alkylene groups each containing 2-8 carbon atoms; and wherein said polymerizable compound is selected from the group consisting of acrylic, methacrylic, and crotonic acids and their anhydrides.

2. The process described in claim 1, wherein polymerization of the product of reaction between the succinimide and the polymerizable compound is carried out in the presence of a free radical polymerization catalyst.

3. The process described in claim 2, wherein said free radical polymerization catalyst is azo-bis(isobutyronitrile), benzoyl peroxide, t-butylhydroperoxide, or di-tbutylhydroperoxide.

4. The process described in claim 1, wherein polym50 erization of the product of reaction between the succinimide and the polymerizable compound is carried out in the presence of a basic catalyst.

5. The process described in claim 4, wherein said basic catalyst is an alkali metal alkoxide, Grignard Reagent, 55 zinc alkyl, or lithium alkyl.

6. The process described in claim 1, wherein the aliphatic substituent of said succinimide is derived from a polyolefin having a number average molecular weight of at least 950.

7. The process described in claim 6, wherein said polyolefin is polybutene.

8. The process described in claim 1, wherein following the polymerization of said succinimide and polymerizable compound to form a polymerized reaction product, 65 said reaction product is further catalytically polymerized with a copolymerizable monomer selected from the group consisting of alkyl esters of acrylic or methacrylic acid, vinyl acetate, vinyl propionate, styrene, α-methyl styrene, allyl acetate, acrylamide, and acrylonitrile, the mole ratio 70 of said copolymerizable monomer to said reaction product being in the range 2-3:1.

9. The process described in claim 8, wherein said copolymerizable monomer is methyl-, η-butyl-, 2-ethylhexyl-, or lauryl-acrylate or methacrylate, vinyl acetate or vinyl propionate.

It is apparent from the data that a wide variety of reaction conditions and reactants may be used to produce the polymeric viscosity index improvers of this ₃₅invention. Runs Al through A3 illustrate the effect of varying polymerization reaction time and temperature. It is seen that high viscosity index products a,re obtained under all conditions. Runs Bl through B3 llustrate the effect of increasing the amount of catalyst present. Runs 40 Cl through C7 illustrate the effectof further polymerization following removal of the water with additional acid or other monomers. Run DI illustrates the effectiveness of polymerizable acids other than acrylic. Runs El through E3 illustrate the effects of polymerization catalysts other than azo-bis(isobutyronitrile). Run Fl illustrates a lower molecular weight polyisobutenyl succinimide as a reactant.

In Runs Gl and G2, the polymerization reactants were heated at the listed temperature to form a salt. The salt was then contacted with the polymerization catalyst to form an intermediate polymer. The intermediate polymer was then heated to the reflux temperature of the solvent to form the final polymeric product. Water of reaction was removed via a Dean and Stark receiver. Run II was conducted under substantially the same conditions as Runs Gl and G2, with the exception that excess acrylic acid was used and the succinimide detergent was diluted 50% with oil.

It will be seen from these data that a wide variety of polymeric materials may be made by the process of this invention, and that these polymers find considerable utility as viscosity index improvers for lubricating oils.