Technical Field
[0001] This invention relates generally to a composition of matter suitable for use in lapping
and a method of lapping and more particularly to such a composition and method when
used in conjunction with an abrasive material.
Background Art
[0002] Lapping or polishing processes conventionally utilize an abrasive grain carried in
a liquid vehicle to provide lubrication and abrasion between two rubbing surfaces.
In some systems the abrasive is kept suspended by constant agitation. In other systems,
the abrasive is kept suspended in the liquid by utilizing an appropriate thickening
agent. During the lapping operation the two rubbing surfaces become quite hot and
are cooled by evaporation of the carrier liquid. In some instances, the supports for
the.surfaces are conductively cooled as by a liquid coolant to further cool the surfaces.
In the systems which utilize a suspending agent, as the liquid is evaporated the suspending
agent becomes more concentrated and can present a real problem in being difficult
to clean off of the surfaces following the lapping operation.
[0003] Since the liquid evaporates as it is used to cool the surfaces being rubbed together,
it is desirable that it be relatively low in cost. Water is particularly advantageous
because of its low cost and very high heat of vaporization, whereby it provides especially
effective cooling. However, water has very poor lubricating properties. Oil alone
can be used, but it has a relatively low heat of vaporization, thus requiring large
quantities of oil for adequate cooling, and is more expensive than water. To provide
good lubricating properties, it is desirable to combine an organic or other liquid
having good bulk and polar lubricity with water. It is particularly desirable to form
a water-in-oil emulsion so as to have oil-like lubricity and to adequately suspend
the abrasive. This can be accomplished by use of an appropriate emulsifying agent.
The same emulsifying agent can also provide suspending of the abrasive. A discussion
of such an emulsion can be found in U.S. Patent 4,059,929, issued November 29, 1977
to David C. Bishop.
[0004] Higher amounts of heat are generated in the rough lapping operation than are generated
in the later fine lapping operation. As a result, the lapping compounds utilized for
rough lapping should generally have a much higher percentage of water in them or the
compound should be supplied at a higher flow rate. When water-in-oil emulsified type
systems are utilized, the oil to water ratio must usually fall in a relatively-small
range of concentrations or the emulsion will not be sufficiently stable or maintain
a useful viscosity. As a result, it is not generally possible to first utilize a water-in-oil
emulsion system for fine lapping and then to later dilute that system with water,
and add larger abrasive to it, for the rough lapping operation. If this is attempted,
the solution will generally deemulsify to its separate liquids or change to an oil-in-water
emulsion with reduced abrasive-supporting capacity.
[0005] Further, many of the chemicals presently used to provide lapping systems are relatively
expensive. That is, the emulsifiers are generally expensive and the organic liquid
is generally expensive. Thus, a system wherein the organic liquid can be diluted after
a fine lapping operation with addition of water and then reused for rough lapping
would be highly desirable. Yet further, if a relatively inexpensive emulsifying agent
could be utilized, this too would be desirable.
[0006] According to one aspect of the present invention we provide a composition of matter
suitable for use in lapping comprising: at least one amide of formula

(wherein R
1 represents a optionally substituted alkyl, alkenyl, aryl, alkynyl, alkaryl,aralkyl,
alkenaryl, aralkenyl or alkynaryl radical having at least eight carbon atoms; and
[0007] R
2 and R
3, which may be the same or different, each represent an optionally substituted alkylene,
alkenylene or arylene diradical having less than eight carbon atoms) said amide being
present in an amount which falls within a range from 4 to 20%,by weight, of said composition;
and an oil, in an amount which falls within a range from 65 to 96%, by weight, of
said composition.
[0008] According to a further aspect of the present invention we provide a water-in-oil
emulsion wherein the oil phase of the said emulsion comprises a composition of matter
according to the present invention, the said oil phase constituting from 5 to 75%
by volume and the water phase constituting from 25 to 95% by volume of the said emulsion.
[0009] According to a yet further aspect of the present invention we provide a method of
lapping a surface by rubbing the surface against a further surface whilst maintaining
a lubricating abrasive film between the said surfaces wherein the said film comprises
a water-in-oil emulsion according to the invention and a suspended abrasive agent.
[0010] The above described composition of matter provides both better polar and bulk lubricity
than water systems during lapping operations, thereby allowing reduction of cycle
times for lapping. The resulting lapped parts are easily cleanable. Very reliable
suspension of abrasives is obtained in the water-in-oil emulsion. Chemical costs are
relatively low. The lapping medium can be diluted with additional water and reused
in rough lapping operations since the amide provides the capability for maintaining
the water-in-oil emulsion and suspension of abrasive over a wide range of ratios of
water to oil. The surface temperatures during lapping operations of the pieces being
lapped are kept lower than when conventional oil only lapping systems are utilized.
[0011] In accordance with one aspect of the present invention, a composition of matter has
been developed which is useful in lapping. An essential ingredient of the composition
of matter is an amide respresentable by the formula R
1CON(R
2OH)(R
3OH). In this formula the radical R
1 may itself be substituted by groups, for example halide or hydroxy groups, which
do not deleteriously effect the properties of the amide which are desirable in the
present invention. R
1 will generally have at least 8 carbon atoms, more preferably at least about 12 carbon
atoms, and generally no more than about 40 carbon atoms
[0012] R
2 and R
3 are each organic diradicals having less than 8 carbon atoms, and preferably no more
than about 4 carbon atoms. The diradicals may be saturated, unsaturated or aromatic.
The diradicals may also include substituent groups such as halides, hydroxides, or
the like, so long as these groups do not interfere with the overall usefulness of
the amide as a lapping composition constituent. For example, R
2 and R
3 may be substituted or unsubstituted alkylene, alkenylene or arylene diradicals.
[0013] The amide will generally form from about 4% to about 20%, by weight, of the overall
composition. The amount of the amide is generally selected to provide the desired
emulsifying and suspending properties in the water-in-oil emulsion which is utilized
as a lapping composition.
[0014] Also part of the composition of matter is an oil in an amount which falls within
a range from about 65% to about 96%, by weight, of the composition. Any of a number
of suitable oils may be utilized, although it is preferred that a hydrocarbon oil,
such as a petroleum oil, be utilized. It is somewhat more preferred that a petroleum
oil having a relatively high naphthene content be utilized. Such oils are generally
referred to as naphthenic oils. Naphthenic oils tend to provide particularly good
bulk lubrication. A particularly preferred naphthenic oil is one having a viscosity
of about 40 to 45 Saybolt Seconds Universal at 37°C.
[0015] A triglyceride ester (oil or fat) is preferably present as a part of the composition,
suitably in an amount which falls in a range from about 2% to about 10%, by weight
thereof. The triglyceride ester, a polar oil or fat, tends to provide improved polar
lubricity, i.e., improved lubricity under high temperature and high pressure conditions.
Any of a number of triglyceride esters can be utilized, for example, any of the naturally
occuring vegetable or nut oils such as coconut oil, corn oil, cottonseed oil, safflower
oil, babassu oil, castor oil, cocoa butter, linseed oil, mustard oil, neem oil, niger-
seed oil, oiticica oil, olive oil, palm oil, palm- kernel oil, peanut oil, perilla
oil, poppy-seed oil, rapeseed oil, sesame oil, soybean oil, sunflowerseed oil, tung
oil, wheat-germ oil, or the like. Naturally occuring triglyceride esters obtained
from animals, such as lard, oil, butterfat, depot fat, neatis-foot oil, beef tallow
or mutton tallow, are also quite suitable. Sulfurized lard is a particularly preferred
triglyceride oil because it provides particularly desirable lubricity under high temperatures
and extreme high pressure conditions.
[0016] While the amide discussed above is a surfactant, and provides desired surfactant
and emulsifying properties as well as thickening properties, it is preferred that
an additional surfactant be present, generally in an amount which falls in the range
from about 1% to about 10%, by weight, of the composition. The additional surfactant
has some use as a coemulsifying agent along with the amide, but its main use is to
assure that the emulsifying agent, the oil, and the triglyceride ester, if present,
can be easily washed off of pieces which are being lapped. Any of a number of conventional
surfactants can be utilized, although it is preferred that a nonionic surfactant be
utilized. A particularly useful nonionic surfactant is an octylphenoxypolyethoxy ethanol
having an hydrophylic lipophylic balance of about 10.4 and sold under the tradename
"Triton X'45" by Rohm and Haas Company, Philadelphia, Pennsylvania.
[0017] The amide can be formed by reacting an appropriate mono-hydroxylamine or preferably
di-hydroxylamine, or mixture of such hydroxylamines, with an appropriate acid, generally
a fatty acid. For example, diethanol amine has been reacted with oleic acid under
reaction conditions which assure that the amide is formed in preference to the ester;
that is, under conditions wherein the hydrogen which is attached to the nitrogen reacted
with the acid group of the oleic acid, rather than with the hydrogen of one of the
hydroxide groups. This has been accomplished by running the reaction at a temperature
which is sufficiently high, generally a temperature of at least about 180°C. Water
is produced by this reaction and the reaction must be run for a sufficient time to
drive off at least most of the water and to allow the reaction to go sufficiently
towards completion. It is not necessary to separate the amide from the reaction product
obtained as just set out above. Instead, it can simply be combined with the hydrocarbon
oil, and in appropriate cases also with the triglyceride ester and the surfactant.
Alternatively, pure amide can be conventionally separated from the reaction mixture,
or produced in any other manner, and later used to form a lapping oil concentrate.
[0018] A lapping oil concentrate includes the amide and the oil and generally also includes
both the triglyceride ester and the additional surfactant. A particularly advantageous
composition which has been prepared includes 7 to 9% of the amide formed by reaction
of diethanol amine with oleic acid, 3 to 4% of Triton X-45, about 2.5% of sulfurized
lard and the remainder of a naphthenic oil. These ingredients are thoroughly mixed
to form a homogeneous solution.
[0019] When it is desired to prepare an emulsion for lapping purposes, a lapping oil concentrate
as just described is mixed by slowly adding sufficient water to provide the desired
emulsion. Vigorous mixing is normally necessary to create the emulsion.
[0020] A conventional abrasive agent, for example, aluminum oxide, silicon carbide, boron
carbide, diamond, garnet, corundum, emery, silica, tripoli, or any pf various metallic
Oxides or mixtures thereof, may be utilized. The grain particle size of the abrasive
agent may vary but will generally fall in the range from about 0.25 micron to about
200 microns. The particle size chosen will depend upon the particular use of the lapping
composition.
[0021] An emulsion can be prepared utilizing the lapping oil concentrate and a relatively
small amount of water, for example 1 part of lapping oil concentrate to 1 part of
water, and a relatively fine abrasive agent can be suspended therein. This composition
can then be used for fine lapping operations. Thereafter, additional water and additional
(and coarser) abrasive can be added to prepare a composition which is useful for rough
lapping operations. Further it is possible to have an oil phase which comprises the
just discussed lapping oil concentrate in an amount of 5% to 75%, by volume, and a
water phase in an amount of 25% to 95% of the emulsion, by volume. Such a water-in-oil
emulsion will remain stable over the above set out very wide range of water and oil
concentrations, due to the presence of the aforedescribed amide. When the oil concentration
is relatively high and the water concentration is relatively low, the emulsion flows
more or less like syrup. When the water concentration is relatively high and the oil
concentration is relatively low, the consistency of the emulsion is such that it sets
up and resembles mayonnaise in consistency and appearance.
[0022] The preparation of the amide is preferably carried out with non-stoichiometric proportions
of the amine and acid. In particular, the amount.of the amine utilized is generally
above that which would be required to stoichiometrically react with the acid. Generally,
about a 30.to 60% excess of amine is utilized over that necessary for stoichiometric
reaction with the acid. For example, if the amine is diethanol amine and the acid
is oleic acid, about 5 volumetric units of the amine would be reacted with about 9
volumetric units of the acid, whereas the stoichiometric mixture would be 3 volumetric
units of the amine to 9 volumetric units of the acid.
[0023] The amount of the abrasive agent suspended can vary over a wide range but will usually
fall in a range from about 10% to about 50%, by weight, of the overall lapping composition,
that is of the total weight of the water-in-oil emulsion plus the abrasive agent.
[0024] The amide above described generally the reaction product of a fatty acid having 12
to 20 carbon atoms with diethanolamine. While oleic acid is particularly preferred,
this is really only one example of a large number of acids which may be reacted with
diethanol amine, or with a similar amine, to form the amide useful in the present
invention. It would be voluminous if not impossible to list all of the acids which
may be utilized to form amides useful with the composition of the present invention,
but a brief and incomplete list would include: lauric acid, myristic acid, caproic
acid, caprylic acid, decenoic acid, palmitic acid, stearic acid, arachidic acid, margaric
acid, erucic acid, gadoleic acid, ricinoleic acid, eleostearic acid, oleic acid, linoleic
acid, palmitoleic acid and linolenic acid. Basically, the acids which are most useful
are'those which are naturally occurring as parts of triglyceride esters, such as the
various naturally occuring oils and fats. It is preferred that the acid utilized be
a liquid, at least at 180°C, so that reaction with diethanol amine can proceed most
efficiently.
Industrial Applicability
[0025] The composition, emulsion and method previously described are useful in lapping to
provide smooth surfaces, generally on metallic
[0026] parts, but also on mineral specimens. In particular, this lapping composition is
useful to provide smooth surfaces for seals.
[0027] A lapping composition as set out herein provides good polar and bulk lubricity and
resulting relatively short cycle times for lapping, is easily cleaned off of pieces
which have been lapped, very reliably suspends abrasive agents, provides relatively
low surface temperatures during lapping operations and utilizes relatively low cost
chemicals.
[0028] Further, the emulsion can be, in essence, reused, since it can first be used for
fine lapping, and then diluted with more water and through the addition of more and
larger abrasive particles, for use in rough lapping operations. This latter property
flows from the fact that the emulsion is stable and thick over wide ranges of relative
oil and water contents.
1. A composition of matter suitable for use in lapping comprising:
at least one amide of formula: R1CON(R2OH)(R3OH) (wherein
R1 represents an optionally substituted alkyl, alkenyl, aryl, alkynyl, alkaryl, aralkyl,
alkenaryl, aralkenyl or alkynaryl radical having at least 8 carbon atoms; and
R2 and R3,which may be the same or different, each represent an optionally substituted alkylene,
alkenylene or arylene diradical having less than 8 carbon atoms) said amide being
present in an amount which falls within a range from 4% to 20%, by weight, of said
composition; and
an oil, in an amount which falls within a range from 65% to 96%, by weight, of said
composition.
2. A composition as claimed in claim 1, further including
a triglyceride ester in an amount which falls within a range from 2% to 10%, by weight,
of said composition.
3. A composition as claimed in either of claims 1 and 2 further including
a surfactant in an amount which falls in a range from 1% to 10%, by weight, of said
composition.
4. A composition as claimed in any one of claims 1 to 3 wherein in said amide substituent
group R1 represents a substantially straight chain alkyl or alkenyl group having at least
12 carbon atoms and substituent groups R2 and R3, which may be the same or different, each represent an alkylene or alkenylene diradical
having no more that 4 cabron atoms, and wherein said oil is a hydrocarbon oil.
5. A composition as claimed in any one of claims 1 to 4 wherein said amide is of formula
6. A composition as claimed in any one of claims 1 to 5 wherein said oil has a high
naphthene content.
7. A composition as claimed in any one of claims 1 to 6 wherein said amide is the
reaction product withdiethanolamine of a fatty acid which occurs in nature as part
of a triglyceride ester
8. A water-in-oil emulsion wherein the oil phase of the said emulsion comprises a
composition of matter as claimed in any one of claims 1 to 7, the said oil phase constituting
from 5 to 75% by volume and the water phase constituting from 25 to 95% by volume
of the said emulsion.
9. An emulsion as claimed in claim 8, further including a suspended abrasive agent.
10. A method of lapping a surface by rubbing the surface against another surface by
whilst maintaining a lubricating abrasive film between the said surfaces, wherein
the said film comprises a water-in-oil emulsion as claimed in claim 8 and a suspended
abrasive agent.