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(11) | EP 0 084 910 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | High dropping-point lithium-complex grease having improved anti-noise properties |
| (57) High dropping-point lithium-complex grease composition naving improved anti-noise
properties, comprising a lubricating oil and the following components:
(a) at least one lithium soap selected from the group consisting of the lithium salts of C10 to C34 fatty acids and C12 to C24 hydroxy fatty acids, (b) at least one lithium salt selected from the group consisting of the dilithium salts of C4 to C12 aliphatic dicarboxylic acids, the lithium salts of boric acids, and the lithium salts of aromatic hydroxy carboxylic acids, and (c) a high-molecular viscosity-index improver, and/or succinimide-type dispersant and/or metal salt detergent. |
[0001] The present invention relates to a high-quality lithium-complex grease composition having improved anti-noise properties, a high dropping point, a long lubrication life and an excellent oxidation stability also at high temperatures.
[0002] High dropping-point lithium-soap greases are generally referred to as lithium-complex greases, and several of them are proposed so far (see e.g. US patent specifications 2,940,930, 3,223,624, 3,758,407 and 3,929,651). However, these lithium-complex greases were inferior in their anti-noise properties because of the low dispersancy in the base oils of the metal salts used for the formation of complexes with lithium soaps.
[0003] The purpose of the present invention is to provide a lithium-complex grease composition having a long lubrication life, markedly improved anti-noise properties, a high dropping point, and an excellent oxidation stability also at high temperatures, by uniformly admixing and dispersing in a base lubricating oil a gelling agent (a), a complexing metal salt (b) and a dispersing component (c).
[0004] This invention therefore relates to a high dropping-point lithium-complex grease composition having improved anti-noise properties, comprising a lubricating oil and the following components:
(a) at least one lithium soap selected from the group consisting of the lithium salts of C10 to C34 fatty acids and CI2 to C24 hydroxy fatty acids,
(b) at least one lithium salt selected from the group consisting of the dilithium salts of C4 to C12 aliphatic dicarboxylic acids, the lithium salts of boric acids, and the lithium salts of aromatic hydroxy carboxylic acids, and
(c) a high-molecular viscosity-index improver, and/or succinimide-type dispersant and/or metal salt detergent.
[0005] The use of component (c) results into unexpectedly superior grease properties compared with the known greases which do not contain this component (c).
Lubricating oil
[0006] Any conventional lubricating oil can be used. While a typical one is a mineral oil, use can also be made, singly or in combination with the mineral oil, of a synthetic oil including ester oils, such as a diester oil, e.g. dioctyl azelate, and a tetra-ester oil, e.g. the pentaerythritol ester of an aliphatic monocarboxylic acid, or poly-alpha-olefin oligomers, such as octene-l/decene-1 copolymers, having a viscosity of 41.0 cSt at 37.8°C, a viscosity index (V.I.) of 130 and a flash point of 223°C.
[0007] The lubricating oil may have a viscosity ranging from about 2 to 500 cSt, preferably from 20 to 200 cSt, at 40°C.
Component (a)
[0008] The C10 to C34 fatty acids include the saturated or unsaturated higher aliphatic monocarboxylic acids, especially those acids containing 16 to 22 carbon atoms, such as stearic acid and oleic acid.
[0009] The C12 to C24 hydroxy fatty acids include saturated or unsaturated monocarboxylic fatty acids containing a hydroxyl radical, especially those acids containing I8 carbon atoms and a hydroxyl radical in the 9-, 10- or 12-position, such as 12-hydroxy stearic acid and ricinolic acid.
[0010] The lithium salts of the above fatty acids and hydroxy fatty acids can be singly used or combinedly with one or more of others. In addition, when said lithium salts are prepared, said carboxylic acids can be reacted with lithium hydroxide not only in the form of free acids but also as glycerides.
Component (b)
[0011] Suitable C4 to C12 dicarboxylic acids used in the formation of the dilithium salt, are e.g. succinic acid, glutaric acid, adipic acid, suberic acid, pimelic acid, azelaic acid, dodecane dionic acid and sebacic acid. Acids containing 6 to 10 carbon atoms, especially adipic acid, sebacic acid and azelaic acid, are preferred.
[0012] The lithium salts of boric acids can be used in place ot or in combination with said dilithium salt or the other lithium salt. Suitable boric acid salts are lithium metaborate, lithium tetraborate lithium pentaborate, lithium perborate and the monolithium salt of ortho boric acid (H3B03).
[0013] The lithium salt of an aromatic hydroxy carboxylic acid can be used in place of or in combination with the above components (b). Suitable acids have the formula:
wherein R is a hydrogen atom or a hydroxyl, lower alkyl or lower alkoxy radical.
[0014] Such acids include p-hydroxy benzoic acid, salicyclic acid (o-hydroxy benzoic acid), 2-hydroxy-4-hexyl benzoic acid, m-hydroxy benzoic acid,'2,5-dihydroxyl benzoic acid (gentisic acid), 2,6-dihydroxyl benzoic acid (y-resorcylic acid) and 4-hydroxy-3-methoxy benzoic acid. Salicylic acid is preferred. Incidentally, the hydroxyl radical (OH) in said lithium salt can he present in its free state as well as in the form of -OLi.
Component (c)
[0015] This component is used for the acceleration of the fine dispersion of the components (a) and (b) in the base oil, and the high-molecular VI-improver, succinic-imide type dispersant and metal salt detergent can be employed singly or combinedly with one or more of other ones.
[0016] Suitable high-molecular VI-improvers are oil-soluble high-molecular compounds having a mean molecular weight of about 1,000 to 1,500,000 in general, preferably about 2,000 to 300,000, and they reduce the temperature-dependency of the oil viscosity. Any of the conventional VI-improvers can be used, such as:
(1) polyisobutylenes, especially, those of the mean molecular weights in the range from 1,000 to 300,000;
(2) homopolymers and copolymers of C1 to C18 alkyl methacrylates, especially those of the mean molecular weights in the range from 20,000 to 1,500,000;
(3) copolymers of C4 to C18 alkyl methacrylates with acryl or methacryl monomers represented by the general formula,
wherein R is a hydrogen atom or methyl radical and X means a polar radical, such as;
or
wherein R' represents a C1 to C10 alkyl radical and n is an integer from 1 to 8, especially those of the mean molecular
weights ranging from 20,000 to 1,500,000;
(4) polymers or copolymers of one or more C1 to C18 alkyl acrylates, especially those of the mean molecular weights ranging from 20,000 to 1,500,000;
(5) hydrogenated styrene-butadiene copolymers, especially those of the mean molecular weights ranging from 20,000 to 250,000 and styrene contents ranging from 25 to 70 weight %;
(6) hydrogenated styrene-isoprene copolymers, especially those of the mean molecular weights ranging from 20,000 to 250,000 and styrene contents ranging from 20 to 65 weight%;
(7) ethylene-propylene copolyaers, especially those of the mean molecular weights ranging from 20,000 to 250,000 and ethylene contents ranging from 10 to 50 weight %;
(8) esters or amides of styrene-maleic acid copolymers; and
(9) polyethylenes, especially those of the mean molecular weights ranging from 5,000 to 300,000.
[0017] Among these oil-soluble high-molecular compounds, particularly preferred are those methyl-methacrylate polymers of the mean molecular weights fanging from 100,000 to 200,000, hydrogenated styrene-butadiene copolymers of the mean molecular weights ranging from 80,000 to 160,000 hydrogenated styrene-isoprene copolymers of the mean molecular weights ranging from 80,000 to 160,000, ethylene-propylene copolymers of the mean molecular weights ranging from 80,000 to 160,000 and mixtures of theem.
[0018] Suitable succinimide type dispersants are synthezised by reaction of polyamines with the polybutenyl succinic anhydrides obtained by the reaction of polybutenes and maleic anhydride. They include those dispersants represented respectively by the following formulae:
and
wherein A1 denotes a C30 to C200 polyisobutenyl radical, p means an integer from 2 to 8 and q represents an integer from 1 to 8.
[0019] Suitable metal salt detergents include sulphonates, phenates, phosphonates and salicylates represented respectively by the following formulae:
(i) Sulphonates
wherein A2 and A2' are respectively a hydrogen atom or C8 to C30 alkyl radical, Ar means a benzene ring or naphthalene ring, M1 represents an alkaline earth metal, such as Ca, Ba or Mg, and M means an alkali metal,
such as Na, K or Li
(ii) Phenates
wherein A3 is a C4 to C16 alkyl radical, M means an alkaline earth metal, such as Ca, Ba or Mg, and x represents
an integer, 1 or 2.
(iii) Phosphonates
wherein A4 means a C30 to C200 polyisobutenyl radical and M1 denotes an alkaline earth metal, such as Ca, Ba or Mg.
(iv) Salicylates
[0020] Among these metal salt detergents, calcium sulphonate, calcium phenate, calcium salicylate and magnesium salicylate are preferred.
[0022] The above metal salts may be neutral, basic or super-basic. Combinations of the metal salts may also be suitable.
Preparation of greases composition
[0023] The grease composition according to the present invention can be prepared by uniformly admixing and finely dispersing the three components (a), (b) and (c) in the base oil mentioned above. While the amounts of these three components compounded in the base oil above are not necessarily critical but can be variable for individual components, it is generally advantageous to use them in the following proportions per 100 weight parts (pbw) of the base oil;
Component (a): 2 to 40 weight parts, preferably.5 to 30 weight parts
Component (b): 0.05 to 20 weight parts, preferably 0.5 to 10 weight parts
Component (c): 0.01 to 10 weight parts, preferably 0.1 to 5 weight parts
[0024] Also, it is particularly preferable to use the components (a) and (b) in the following mol ratio within the above ranges of the proportions;
[0026] In the grease composition according to the present invention, use can be made, in addition to the three components (a), (b) and (c) above, of other ordinary lubricant-additives, such as neutral or basic metallic detergents, such as basic Ca salicylate, or ashless dispersants, rust inhibitors (e.g., paraffin oxide, amino imidazoline or barium dinonylnaphthalene-sulphonate), oxidation inhibitors (e.g. 2,6-ditertiary butyl-4-methylphenol, N-phenyl-a-naphthylamine or diphenylamine octylate) and extreme-pressure additives (e.g. zinc naphthenate, or other zinc compounds such as zinc dithiophosphates or zinc-oxide, lead naphthenate, sulphurized oils and fats, or tricresyl phosphate), in the proportions ordinarily employed.
[0027] The grease composition of the present invention can e.g. be prepared in the following manner.
[0028] A component (c) is first admixed and dissolved in a base oil, and the fatty acid or hydroxy fatty acid for the preparation of the lithium soap, as a component (a), is admixed and dissolved in the mixture thus obtained, at 70 to 80°C. Then, the lithium hydroxide roughly in an equivalent amount to the fatty acid or hydroxy fatty acid above is admixed in the resulting mixture at 80 to 90°C to form a soap, and the mixture is further heated to 140 to 150°C under pressure for dehydration. After the dicarboxylic acid or boric acid for the formation of a component (b) is admixed in the dehydrated mixture, the resulting mixture is cooled to 80 to 100°C and further admixed with the lithium hydroxide roughly in an equivalent amount to said dicarboxylic acid or boric acid, and the final mixture is again dehydrated by heating to 140 to 150°C under pressure. The last dehydrated mixture is further heated to 195 to 215°C, then cooled to 175 to 193°C, maintained at this temperature for about 10 to 40 min. and finally cooled to the room temperature.
[0029] It is also possible to add an aqueous slurry ot the reaction product of LIOH.H20 and boric acid, if this is used, to an autoclave containing lubricating oil, fatty acid and detergents, e.g. Ca salicylate and Ca naphthenate.
[0030] The lithium-complex grease composition according to the present invention and thus prepared has a very high dropping point, satisfactory anti-noise properties and very long lubricating life and exhibits exceedingly high performance as a lubricating grease. Moreover, the present composition possesses a very high extreme-pressure property, in addition to the excellent properties above, due to the lithium borate contained as the component (b). Therefore, the present grease composition can be suitably used, for example, for the lubrication of the bearings fitted in electric motors as well as of the wheel bearings in automotive bearing/axle integrated structures. Furhtermore, these greases make little noise even if used in the bearings of air-conditioners and others, giving no environmental injury.
[0031] In the following, the present invention is further concretely illustrated by means of examples.
Example 1
[0032] 2,233.5 g of a refined mineral oil (paraffinic, VI : 102, pour pt.: -15°C, viscosity: 44.9 cSt at 37.8°C and 6.4 cSt at 98.9°C), 300 g of the 10% solution of a hydrogenated styrene-butadiene copolymer (mean mol. wt.: about 130,000, styrene content: 59 weight %) in the mineral oil above and 270 g of 12-hydroxy stearic acid were charged into a 8 litre autoclave, and the contents were heated to 80°C under stirring in 30 to 40 min to completely dissolve the 12-hydroxy stearic acid.
[0033] Then, 300 g of a hot aqueous solution (95°C) containing 38.5 g of lithium hydroxide were admixed in the autoclave, the contents were stirred for about 10 min under stirring and normal pressure at about 90°C and, then, slowly heated under pressure to about 145°C. At this temperature, the contents of the autoclave were further stirred for about 15 min under pressure (about 2.5 to 2.8 kg/cm2) and, subsequently, the pressure was released with the moisture being removed.
[0034] After dehydration, the contents were admixed with 67.8 g of azelaic acid, the mixture was slowly cooled to about 90°C under stirring, and 250 g of a hot aqueous solution (95°C) containing 30.2 g of lithium hydroxide were admixed in the mixture. The resulting mixture was slowly heated to 145 to 155°C under stirring and pressure in 1 to 1.5 hrs, and, at this temperature, the autoclave was released of the pressure and removed of the moisture.
[0035] After the dehydration, the contents of the autoclave were again heated to I95 to 215°C and, then, left cooling under stirring to 188 to 192°C. The contents were kept at this temperature for 20 to 30 min, then left cooling to about 160°C. At this temperature, 60 g of the oxidation inhibitor, diphenylamine octylate, were admixed in the contents, the mixture was cooled to about 80 to 85°C under stirring in 30 to 60 min and treated in a homogenizer at this temperature.
Comparison example 1
[0037] A grease composition was prepared in a similar manner to that in Example 1 except that 2,533.5 g of the refined mineral oil were used without employing the hydrogenated styrene-butadiene copolymer mentioned in Example 1. The properties of the product were as follows;
Examples 2 to 8
[0038] Grease compositions were prepared by employing the various components shown in Table 1 below in a similar manner to that in Example 1, and the properties of these compositions are collectively tabularized in Table 1.
Examples 9 to 21
[0039] Grease compositions were prepared by treating the various components shown in following Tables 2A and 2B in similar manners to that in Example 1. The properties of these compositions are shown collectively in Tables 2A and 2B.
Examples 22 to 25 and Comparison Examples 2 and 3
[0040] Grease compositions were prepared by treating the various components shown in following Table 3 in similar manners to that in Example 1. The properties of these compositions are collectively tabularized in Table 3.
Example 26
[0041] 2,521.2 g of a refined mineral oil (paraffinic, VI: 102, pour point : -15°C, kin. viscosity : 44.9 cSt at 37.8°C, 6.4 cSt at 98.9°C), 30 g of a succinimide (A) (ref. Note 1) and 270 g of 12-hydroxy stearic acid were introduced into a 5 liter autoclave and the contents were heated to 80°C under stirring in 30 to 40 min to completely dissolve the hydroxystearic acid. (Note 1) Succinimide (A)
A1 : C52 to C76 polyisobutenyl radical, mean molecular weight : 2,302 (as containing boron), 110 wt. parts of the compound above dissolved in 100 wt. parts of the base oil.
[0042] Subsequently, 300 g of a hot aqueous solution (95°C) containing 38.5 g of lithium hydroxide were admixed in the autoclave contents, which were then kept at 90°C under stirring for 5 to 15 min. After the contents were cooled to 75°C, 300 g of a hot aqueous solution (93°C) containing 49.8 g of salicylic acid were admixed in the contents and dissolved by stirring for 10 to 15 min. Then, 250 g of a hot aqueous solution (95°C) containing 31.0 of lithium hydroxide were admixed in the resulting mixture, which was then gradually heated under stirring and pressure. When this mixture arrived at 145 to 150°C after 1 to 1.5 hrs, the autoclave was released of the pressure and the contents were dehydrated at this temperature in 15 to 25 min. After the dehydration, the contents of the autoclave were further heated to 195 to 205°C, then cooled to 188 to 192°C under stirring and, after being kept at this temperature for 20 to 30 min, further cooled to about 160°C. At this temperature, 60 g of an oxidation inhibitor were admixed in the contents, the mixture thus obtained was cooled by stirring to about 80 to 85°C in 30 to 60 min and then treated in a homogenizer at this temperature.
Comparison Example 4
[0044] A grease composition was prepared in a similar manner to that in Example 1 except that 2,531.2 g of the refined mineral oil were employed without the succinimide(A) being admixed. The properties of the resulting composition were as follows;
Examples 27 to 33, Comparison Examples 5 and 6
[0045] Seven grease compositions were prepared by treating the various components shown in Table 4 below in similar ways to that in Example 26 and the properties thereof are collectively tabularized in Table 4. Also, the properties of a market grease comprising the lithium soap of 12-hydroxystearic acid are shown as * Comparison Example 5 in the table as well. In addition, Comparison Example 6 in the Table is a grease prepared in a similar manner to that in Example 26 but by employing in a similar manner to that in Example 26 but by employing an increase amount of the refined mineral oil without the components (b) and (c) being admixed.
(a) at least one lithium soap selected from the group consisting of the lithium salts of CI0 to C34 fatty acids and C12 to C24. hydroxy fatty acids,
(b) at least one lithium salt selected from the group consisting of the dilithium salts of C4 to C12 aliphatic dicarboxylic acids, the lithium salts of boric acids, and the lithium salts of aromatic hydroxy carboxylic acids, and
(c) a high-molecular viscosity-index improver, and/or succinimide-type dispersant and/or metal salt detergent.
component (a) : 2-40 pbw
component (b) : 0.05-20 pbw
component (c) : 0.01-10 pbw