CA1068672A

CA1068672A - Solid lubricant combinations

Info

Publication number: CA1068672A
Application number: CA244,772A
Authority: CA
Inventors: Dietmar W. Grosse
Original assignee: Dow Corning GmbH
Current assignee: Dow Silicones Deutschland GmbH
Priority date: 1975-04-03
Filing date: 1976-02-02
Publication date: 1979-12-25
Also published as: ATA124676A; FR2306256A1; DE2514575A1; JPS51126473A; IT1061014B; AT356231B; AU1087276A; DE2514575B2; DE2514575C3; BR7602034A; JPS614873B2; GB1543592A; JPS5932516B2; FR2306256B1; JPS56127693A

Abstract

Abstract of the Disclosure This invention relates to solid lubricants, in specific combinations, which give unique properties for specific lubrication applications. For example, solid lubricant combinations such as graphite, zinc sulfide, calcium fluoride and molybdenum disulfide when incorporated in an epoxy binder, give good bonded lubricant coatings.

Description

~ 8672 The present invention relates to the field of solid lubricants.
Solid lubricants are being used more and more `
in modern lubricating technology in order to overcome the increasing demands for improved properties, for example, to avoid or minimize specific conditions at friction points. Such solid lubricants are not only being used in the common method of applying them in powder form to a surface, but they are also being used in oil-based lubricants and greases and as bonded coatings.
There have beeff instances when such solid lubricants have been incorporated in plastics or metals in order to maXe self-lubricating surfaces.
In addition to the now amiliar solid -lubricants, molybdenum disulfide and graphite, a whole ;
series of wideIy varying chemical compounds consisting of hydroxides, oxides, sulfides, fluorides and phosphates ' has been studied and utilized in the solid lubricant technology.
Such known lubricants can be found, for instance, ;~
in U.S. Patent No. 3,377,279. Such solid lubricants are described as graphite, sulfides of metals from Group II
of the periodic system of elements~ particularly zinc sulfide and cadmium sulfide and inorganic fluorides such as calcium fluoride and cryolite. Those solid lubricants are then treated with lnorganic anions, the whole purpose `
of the treatment being to give enhanced adhesion of the .
lubricant to the surface.
Essentially the same solid lubricants are ` 30 referred to again in U.S. Patent No. 3,453,209 as being '.

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useful lubricating materials for use with metal-forming dies such as presses, forges and drop hammers. It is noted that the composition consists of a solid lubricant and a material which evolves gas under those operating ~`
conditions.
Finally, in U.S. Patent No. 3,808,130, essentially the same solid lubricants are again set forth as part of compositions including perfluoroalkylene polymers and -~
epoxy resins, which are useful in preparing self-lubricating bearings and other machine elements. The object of that , invention is to produce large numbers of self-lubricating parts with` excellent precision and low dimensional change. - -In order to accomplisll this object, the U.S.
Patent No. 3,808,130 speaks of using compositions which contain "... inorganic solid materials... of at ~
least one and preferably two solid lubricants." Thus, ~' `
it is known from such patent that solid lubricants !'~':"' ' ' ` ` ;'' can be used in conjunction with the perfluoroalkylene polymer and epoxy resin in preparing self-lubricating materials.
l~hat the 3,808,130 patent does not teach or ~ ~`
make obvious, however, is that certain combinations of ` -solid lubricants in specific ratios, without the aid of the perfluoroalkylene polymers, have synergistic ; :
lubricating effects which give high load carrying ~ -capacities and reduced wear and friction.
It is, therefore, an object of this invention to provide lubricant compositions which consist of certain ~ -solid lubricants in specific ratios to give enhanced -~
lubricating properties which allow high load carrying

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capacities and reduced wear and friction on metal-to-metal interfaces, In connection with achieving such an object, it has now been found that a combination of graphite, zinc sulfides, calcium fluoride and optionally molybdenum sulfide in specific weight ratios results in a surprising .
synergism in lubrication properties whereby exceptional properties are obtained.
The solid lubricant composition of the instant : -invention consists therefore of 20 to 70 percent by weight of graphite, lS to 50 percent by weight of zinc sulfide, 3 to 30 percent by weight of calcium fluoride and 0 to S0 percent by weight of MoS2. Preferably, :~
the composition consists of 35 to 50 percent by weight ~-of graphite, 20 to 40 percent by weight of zinc sulfide, 7 to 25 percent by weight of calcium fluoride and 10 to 30 percent by weight of molybdenum disulfide :: -and, the components graphite, zinc sulfide and calcium :
fluoride, are present primarily in a weight ratio of 5 to 4 to 1. :~
: All of the materials employed in this composition . .
are standard articles of commerce and their methods of .
preparation are not considered material to this invention.
The compositions of this invention can be :~
prepared by any conventional means such as simply blending the materials in a mixer or milling on a roll mill.
The compositions can be further treated to render them useful for specific applications such as ~ ;
embedding the solid lubricants in curable binders such as epoxy resins, silicone resins or phenolic resins :~

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in order to prepare bonded coatings and composites such :~
as brake linings and the like. Further, such combinations can be carried in solvents and used as lacquers which can be used as dips or sprays or can be brushed in place which upon curing give lubricating films.
Greases can also be formulated from the basic ;~
solid lubricant combinations. Ordinary oil-based greases such as lithium soap greases are an example~ -It is within the scope of this invention to include as optional ingredients those materials commonly known and used in the lubricating industry such as ~;
viscosity regulators, corrosion inhibitors~ detergents, emulsifiers and the like.
The invention will be described in greater detail by way of the following examples which are not to be considered as limiting the scope of the invention. ~;
Example 1 `~; -'.. - :. .
An epoxy resin (prepared from bis(para-hydroxyphenyl)-dimethylmethane and epichlorohydrin, epoxy equivalent weight ca. 500) is filled with 80 percent by weight of . . .
a solid lubricant combination of 50 percent by weight graphite and 50 percent by weight of a varying mixture -of zinc sulfide and calcium fluoride and is made into cylindrical cans with an inside diameter of 25 mm., an outside diameter of 30 mm. and a length of 25 mm. in a known manner. The cans thus obtained are then subjected to a wear test, the A. A. ~artel Lubrimeter (Schmiertechnik ~;
3, 184 ~1956)). The solid materials and solid lubricant `-combinations used here and the test data obtained therefrom are given in Table I. It can be seen that the .~" ,::

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1~6~3672 three-component system of 50 percent graphite with the :~
remainder of varying quantities of zinc sulfide and .`
calcium fluoride acts synergistically, whereby the best wear is obtained from a solid lubricant combination of 50 percent by weight graphite, 40 percent by weight zinc sulfide and 10 percent by weight calcium fluoride.
TABLE I .
% Graphite % ZnS % CaF2 % MoS2 Wear 0 0 11 .

~0 30 0 10 0Greater than 18 .:
0 50 0Greater than 18 Example 2 . .
The solid lubricant combinations were prepared as shown in Table II
The above combinations and their pure individual components are made into pastes each con~aining 60 percent by weight solid lubricant combinations or individual solid lubricant and 40 percent by weight oil having lubricating oil viscosity, the pastes being given a uniform viscosity ;~ :
by adding 1 percent by weight of a thickener ~based on ~::
the silicon dioxide). The friction values of these pastes are then determined on the LFW-4 testing machine ~see .
U.S. Patent No. 3,028,746) and the frictional force an Almen-Wieland machine (Schmiertechnik 7, page 284 ~1970)) under a final load of 2000 kp. The solid lubricants used for this example and the results obtained are noted on ~ Teble III which follows:

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TABLE III
~lid Lubricant Friction Friction Force in kp Molybdenum `.`
Disulfide 0.05 243 Graphite 0.14 > 350 Zinc Sulfide 0.20 > 350 :. .
,.. .
Calcium Fluoride 0.18 > 350 : : :
Combination A ~ :~
(Example 2) 0.13 242 `
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Combination B i~
t~xample 2)0.13 262 ~ `~
Combination C
(Example 2)0,04 228 Combination D .`:
Example 2) 0.05 180 ~
. ~: . ' , , Example 3 . ~
Lithium soap greases (lithium-12-hydroxy stearate) .- : . :
are prepared using the solid lubricants and solid lubricant ..
combinations designated in Table IV in the percentages : :
given. The lubricity of these greases is then established - .
by evaluating the so-called load allowance in a four-ball apparatus (DIN 51350) (ASTM D-2596-67T). The load .
allowance values can be seen in Table IV. ::~
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TABLE IV
Loads in the 4-Ball Apparatus in kp at the Given Percentages o Solid Lubricants in the Grease :'' ' ~.' : , Solid Lubricant 3 Wt. % 5 Wt. % 7 Wt, % `
Molybdenum ,~
Disulfide 210 220 190 Graphite 200 260 300 Zinc Sulfide 200 240 280 Calcium Fluoride 190 240 240 '.," ~'` '.
Combination A
tExample 2) 260 360 420 Combination B
~Example 2) 260 340 440 Combination C
(Example 2) 280 360 420 Combination D
(Example 2) 260 320 340 ample 4 , `
Lubricant lacquers were prepared with the use :.. ~ . . .
of the solid lubricants and solid lubricant combinations -specifled ln Table V in a solvent dispersion which also ;
contained some curable organic resin. 20 percent solld lubricant or solid lubricant combination was used.
The data obtained while determining the friction values "
by the Press Fit Method on the LFW-4 tes~ing machine as i `
:. -described in Example 2 and the evaluation of the life of the gliding lacquer film on the LFW-l testing machine (ASTM D-2714) may be taken rom Table V.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A solid lubricant composition consisting essentially of 20 to 70 percent by weight of graphite;
15 to 50 percent by weight of zinc sulfide;
3 to 30 percent by weight of calcium fluoride; and 0 to 50 percent by weight of molybdenum disulfide, wherein the components graphite, zinc sulfide and calcium fluoride are present in a weight ratio of about 5:4:1.

2. A solid lubricant composition according to claim 1 wherein it consists essentially of 35 to 50 percent by weight graphite;
20 to 40 percent by weight zinc sulfide;
7 to 25 percent by weight calcium fluoride; and 10 to 30 percent by weight molybdenum disulfide.

3. A solid lubricant composition of claim 1 or claim 2 wherein there is also present a solvent or solvents.

4. A solid lubricant composition of claim 1 or claim 2 wherein there is also present a curable binder material.

5. A solid lubricant composition of claim 1 or claim 2 wherein there is also present an oil-based paste and the total composition is a grease.