Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02106036 1999-07-07
HAC1CGROOND OF THE INVENTION
This invention relates to the field of
metalworking lubricants in general and, in one
particular respect, to forging lubricants. More
l0 particularly, it relates in one aspect to a new
forging lubricant composition and a method of using
that composition in the hot forging of metal
workpieces. Metal parts of a multitude of sizes and
shapes are manufactured by various types of forging
operations, and these parts are formed from stock
composed of a great many metals and metal alloys. A
great many parts are forged from such metals and
metal alloys as, for example, steel, aluminum,
titanium, and high nickel alloys, to name but a few.
The conditions under which metal parts are
forged, of course, are widely variable, depending
upon not only the nature of the metal, but upon the
size and complexity of configuration of the desired
part. Small, thin, simply shaped parts may
obviously be forged from a relatively flowable metal
such as aluminum under much less rigorous conditions
than are required to forge large more complex shaped
parts from a metal such as steel.
Each set of forging conditions requires a
specialized lubricant, and there is therefore a
multitude of aqueous-based, oil-based and organic
solvent-based lubricants currently in use in various
forging operations. Many such lubricant systems,
particularly those used under the most demanding
forging conditions, by their nature require the user
to make compromises in order to achieve the desired
functional characteristics while avoiding as much as
possible any safety, occupational health or
environmental hazards involved in their use.
2
Mareover, in some instances, more restrictive health
and environmental guidelines are now in force which
may make the use of certain lubricant systems either
extremely expensive or simply unworkable. It is to
these and related concerns which the present
invention is directed.
Tn a typical high performance forging
operation, such as one which might be devoted to the
manufacture of large, complex parts from aluminum
alloy stock; an effective lubricant is one which
ordinarily contains a variety of lubricity agents in
a carrier comprising mineral oil andjor volatile
organic solvents. The dies used in such forging
operations are maintained at high temperatures,~in
the range of 350°F to 825°F, in order to permit
proper metal flow during the forging operation.
The forging lubricant is typically applied to
the die and the workpiece by spraying, and, on
account of the temperatures involved, the mineral
oil and volatile arganic compounds immediately flash
off, leaving only a relatively small amount of
residue which actually fun~ations as the lubricant.
As anyone who has observedt such a forge operation
well knows, the flashing of~'f of the mineral oil and
volatile organic compounds creates a significant
amount of open flames, and the spray wand by which
the lubricant is applied takes on the appearance of
a flame thrower. Moreover, a large amount of smoke
is typically generated when the mineral oil and
volatile organic compounds flash off, since, at the
same time, a rather significant portion of the
lubricity agents may burn off as well. an this
context, it is well known that any improvements in
the performance of the forge lubricant which are
achieved by reformulation frequently come at the
cost of significantly higher smoke generation.
Similar difficulties are inherent when
oil-based paste type lubricants are utilized. While
a
the paste lubricants contain little or no volatile
arganic compounds, their oil carriers partially or
completely burn at typical forging temperatures,
resulting in significant heavy smoke generation.
The hazards, expense and envir~remental problems
associated with such forging operations are of great
proportion and are quickly becoming even more s~.
In a state such as California, where
environmental protection statues and regulations
impose rigid standards on industrial operations, and
in other states which have similar environmental
protection schemes, the smoke generated by a large
forge operation creates tremendous difficulties.
Since environmental agencies frequently monitor
smoke emissions by aerial surveillance, there is
close attention paid to reducing the smoke generated
in the forging operation. Unfortunately, this often
limits the efforts made to vent the smoke from the
buildings in which the forge operati~n is housed.
The result of this is a significant degradation of
the air quality within the buildings.
An important economic consideration is that in
California, for example, a tax may be levied upon
each gallon of volatile organic compounds emitted
into the air. More importantly, as air quality
standards are progressively raised, there will soon
came a time when a forge operation will simply be
prohibited from emfttins~ large amounts of smol~e.
The choice then will be to find an alternative
lubricant which produces significantly reduced
amounts of smoke or t~ cease operations entirely.
Similar problems exist with respect to the use
of oil or solvent-based lubricants in smaller scale
forge and other metalworking operations, since waste
~5 lubricant materials of this type are considered an
environmental hazard. Dispasal is therefore tightly
controlled and increasingly expensive.
Other related concerns create a strong demand
for aiterna~ive metalworking lubricants.
As described above, open flame is generated
when conventional mineral oil and volatile organic
compound-based lubricants are applied to a heated
die. One must therefore have available fire
prevention and fire control equipment, such as fire
extinguishers and sprinkler systems, in the
immediate area of the forge operation. Indeed, fire
extinguishers see regular use in many forge
operations, and the cost of their maintenance is
significant. In general, fire prevention, fire
control and fire detection systems of all types are
regular and significant capital and maintenance cost
items for hot forge operations.
A related problem associated with the use of
conventional volatile organic compound-based
lubricants is the need for special storage
facilities on account of their high flammability.
This too imposes a significant cost associated with
the use of conventional lubricants.
Transportation of these flammable lubricants in
special containers and special vehicles is yet
another source of additional cost, hazard, and
inconvenience associated wa.th their use.
A still further disadvantage of conventional
lubricant systems which results from the flashing
off of oil and solvent carriers is that the sr<eoke
generated forms tar-like deposits on machinery,
finished parts, floors, windows, and nearly
everything else housed in the same building with the
forge operation. Quite apart from the aesthetic
undesirability of such deposits, there are economic
and health concerns as well. Many large forge
operations maintain permanent steam-cleaning
facilities at a significant cost.
Various types of dry lubricants and methods for .
applying them to metal surfaces have been proposed
5
for use in diverse environments, but none has been
widely adopted on account of certain inherent
disadvantages in either tine lubricant itself or the
method of its application.
for example, in titanium forging ~perations, it
has been proposed to utilize a powdered lubricant
composed of glass and ceramic components, with the
optional use of steel shot, in a process in which
the lubricant is imbedded in the forge tool surface
by a high pressure spray. This pr~cess is described
in terms of sandblasting the lubricant ont~ the tool
surface, and is intended to effect a cold working
and smoothing of the tool surface. Of course, such
a high pressure spray pracess inv~lves the use of
rather expensive spray equipment, and it also
presents the risk of worker injury due tp
misdirected spray.
Others have proposed to spray dry reactant
materials onto hot metal surfaces in order to form a
reaction product lubricant in situ. Still others
have proposed various combinations of dry lubricant
components for use in a wide range of applications.
Many of these lubricant compositions, h~wever, have
drawbacks, as well.
After forging, whether with a conventional or
dry lubricant, aluminum parts are subjected to a
caustic etch for the purpose of removing lubricant
residues. In a preferred procedure which is well
known in the art, the caustic etch may be used in
combination with an acid wash. In many aluminum
forge operations, the acid wash advantageously ~ '.
precedes the caustic etch.
As is well known in the art, the conditions of
these wash and etch procedures are quite harsh.
Typically, the caustic etch bath is 5% to 15% by
weight alkali metal hydr~xide in water. Typical
acid baths are similarly strong, ~ften containing a
high concentration of nitric acid. In forge
~1~~~3
a
operations using conventional solvent or ail based
lubricants,~the wash and etch procedure works quite
well to remove essentially all lubricant residues
from the forged parts.
Notwithstanding the harsh conditions of the
wash and etch, however, it has been found that
residues of powdered lubricants may still adhere to
the parts with such tenacity that even subjecting
the parts to physical removal procedures, such as
brushing and scraping, after the etch will not
adequately clean them.
zt has also been found, in working with
mufti-component powdered lubricants, that obtaining
a consistent spray pattern using conventional powder
coating equipment is extremely difficult.
Ovex~spray, underspray, puffing, and sputtering have
been found to be serious drawbacks, both from the
standpoint of obtaining a functional lubricant
coating on the workpiece and from the standpoint of
z0 efficient use of powder lubricant material.
Overall, the spray process has heretofore been found
too erratic to be acceptable commercially.
Moreover, it has been unexpectedly found that the
spray was particularly unpredictable when utilizing
powder coating equipment which, as is quite common,
utilizes a fluidized bed as a reservoir from which
the powder was sprayed. Even utilizing powder
coating equipment which has a gravity-fed reservoir
has typically provided only a marginal improvement
in consistency.
While the particular problems encountered in an
aluminum forge operation have been described in
detail, many of the same and other related concerns
exist in other metal working environments. These
include not only other hot forge operations, such as
the manufacture of forged steel and titanium parts,
but also a wide variety of other metalworking and
metal forming operations. Examples include
CA 02106036 1999-07-07
7
extrusion, drawing, stamping, and other hot and cold forming
operations, many of which employ lubricants in aqueous or solvent
based carriers. Thus, many of the same technical and economic
benefits could be realized in such operations by adopting an
improved dry lubricant composition.
It is an object of the invention to provide an improved
method of forming a metal working lubricant composition.
SUMMARY OF THE INVENTION
According to the present invention there is provided a
method of forming a carrier-free pulverulent metalworking
lubricant composition from particulate lubricant components, the
method using an agglomeration process comprising the steps of:
a) forming in an agglomerator a dry admixture of said
particulate lubricant components; and
b) agitating said dry admixture to form agglomerated
particles which consist essentially of particulate lubricant
components which have become fused together in a heterogeneous
mass in the absence of a melted matrix.
A carrier-free pulverulent metalworking lubricant is one
CA 02106036 1999-07-07
8
which is entirely free of the oils and volatile organic compounds
commonly employed as carriers for forge lubricant compositions. A
method of forming a workpiece in a metal-forming apparatus may
include the steps of applying to at least one of the metal-forming
apparatus and the workpiece a coating of an effective amount of a
carrier-free pulverulent lubricant composition, and forming the
workpiece in the apparatus.
The carrier-free pulverulent metalworking lubricant may, in
general, include any material which will provide lubricating
properties at the temperatures typically encountered in a forging
process and which can be put into a physical form which permits it
to be applied to the die and/or the workpiece by conventional
powder-coating equipment.
The need to incorporate a mineral oil and/or a volatile
organic compound-based carrier is completely eliminated, with the
result that the smoke generated by conventional lubricants is
significantly reduced.
A carrier-free pulverulent metalworking lubricant
composition may include at least one resin having a highly polar
functional group, which may be solubilized under strong acid or
CA 02106036 1999-07-07
9
basic conditions, and which is a solid at room temperature.
A method of forming a carrier-free pulverulent
metalworking lubricant may comprise the steps of forming a dry
admixture of the particulate components, and agitating the
admixture whereby agglomerated particles of a carrier-free
pulverulent metalworking lubricant are formed. Preferably, the
method further includes the step of adding a binder to facilitate the
adherence of the particles to one another. More preferably, the
binder is an aqueous based solution; most preferably the binder is an
aqueous solution that includes a thickener and/or a surfactant.
A method of forging a workpiece in a die may include the
steps of applying to at least one of said die and said workpiece a
coating of an effective amount of a carrier-free pulverulent
lubricant composition having at least one resin having a highly
polar functional group, which may be solubilized under strong acid
or basic conditions, and which is a solid at room temperature, and
forging the workpiece in the die.
The advantages inherent in the composition and methods
disclosed herein are numerous. In particular, the elimination of
much of the smoke previously generated by the flashing off of a
CA 02106036 1999-07-07
mineral oil and volatile organic compound carrier permits a forging
operation to continue in business in full compliance with
environmental statutes and regulations. Moreover, the business
may continue without the economic burden of tax payments based
5 on the emission of volatile organic compounds. In many instances,
the use of the composition and method will permit a forge
operation to continue in existence under a stringently regulated
environmental scheme which would otherwise cause it to be shut
down entirely.
10 Other economic advantages of the composition and method
are of equally great importance. The reduction in weight and
volume which occurs when the carriers of conventional lubricants
are eliminated leads to savings in the cost of shipment and storage.
Even further savings are realized in transportation and storage costs
because the carrier-free composition of the invention is neither
flammable nor hazardous, and it can be shipped and stored in the
same manner as any other nonhazardous material. Moreover,
packaging costs are significantly reduced, since a five-gallon plastic
pail of the carrier-free pulverulent metalworking lubricant will be
the functional replacement for a fifty-five gallon steel drum of a
CA 02106036 1999-07-07
11
conventional lubricant.
In the forge operation itself, the composition and method
result in significant reductions in the cost of installing and
maintaining fire prevention and fire control systems, and in
general permit the maintenance of a much safer environment for
personnel at a much lower cost.
Still further savings resulting from the use of the
composition and method may be realized in reduced premiums for
fire, workmen's compensation, and liability insurance.
The elimination of the carrier material significantly reduces
raw material cost, since, on a weight and volume basis, the carrier
in conventional lubricants accounts for well over 80% of the
composition.
The need to maintain expensive and space-consuming
cleaning facilities for plant and finished parts is also reduced by the
use of the composition and method, since significantly less
combustion residues will be produced in the absence of the flashing
off of mineral oil and volatile organic compound carriers.
The incorporation of a resin which is solubilized in an alkali
and/or acid bath provides the advantage of a cleanable forged part,
CA 02106036 1999-07-07
12
even with the use of a dry powder lubricant.
Further, maintaining the particle size of the lubricant powder
within a narrow range permits a uniform coating of lubricant
powder to be applied with conventional powder coating equipment,
even when utilizing equipment which employs a fluidized bed as a
powder reservoir. And, controlling the particle size of the lubricant
powder by its novel method of manufacture not only provides
spray consistency, but improves lubricant properties and cleanability
as well.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graphical representation of the change in particle
size distribution over time during the process of Example 23.
~~ ~~
13
Fig. 2 is a graphical representation the
of
change in particle size distribution over time
during the process of Example 24.
Fig. 3 is a graphical representation the
of
change in particle size distribution over time
during the process of Example 25.
Fig. ~ is a graphical representation the
of
change in particle size distribution over time
during the process of Example 26.
Fig. 5 is a graphical representation the
of
change in particle size distribution over time
during the process of Example 27.
Fig. 6 is a graphical representation the
of
change in particle size distribution over time
during the process of Example 29.
Fig. 7 is a graphical representation the
of
change in particle size distribution over time
during the process of Example 29.
Fig. ~ is a graphical representation the
of
change in particle size distribution over time
during the process of Example 30.
Fig. 9 is a graphical representation the
of
change :in particle size distribution over time
during the process of Example 31.
Fig. 10 is a graphical representationthe
of
change in particle size distribution over time
during the process of Example 32.
14
DIETAI%.~D D~sCRIPT~o33
As stated above, the composition of the present
invention, in its most basic form, is a carrier-free
pulverulent metalworking lubricant. It may include
any material which will provide lubricating
properties at the temperatures typically encountered
in a metal-forming process and which can be put into
a physical form which permits it to be applied to
the die and/or the workpiece by conventional
l0 powder-coating equipment.
Many materials which will perform the function
of lubricating the die and maintaining a physical
separation between the die and the workpiece are
well known, and, of these materials, many are in the
physical form necessary to the practice of the
present invention; namely, a solid at room
temperature. It is not necessary that the materials
employed in the composition of the invention remain
either solid or pulverulg:nt at the temperatures
typically encountered during a hot forging
operation, e.g., about 600°F up to 7.000°F for
aluminum, and about 1500°F up to 2500°F for steel or
titanium. It is enough that they may be made to
exist in a particulate form at ambient temperatures.
In that form, they can be applied by conventional v
powder-coating equipment, even though they may
partially or completely melt or burn when in contact
with the heated die or workpiece. Indeed, it is
preferred that at least one component of the
carrier-free pulverulent metalworking lubricant
becomes sticky upon being heat~:d so as to assist in
adhering the dry metalworking lubricant composition
to the workpiece and die surfaces.
Typical materials which are capable of
maintaining a physical barrier between the die and
the workpiece and which function as solid lubricants
are contemplated for use in the composition of the
invention. They include, by way of example only,
2~ ~'~~~~:~~~
metal soaps, fatty acids, graphite, ceramics, high
melting polymer resins, natural and synthetic waxes,
gilsonite, glasses, and mixtures of these materials.
Useful metal soaps are those which are solids
5 at room temperature, including many sulfonates,
naphthenates, and carboxylates. of these, fatty
acid soaps such as zinc stearate and sodium stearate
are preferred on account of their known properties,
their ready availability and low cost. However,
l0 other metal soaps known for their lubricant
properties, including, by way of example only, tin,
copper, titanium, lithium, calcium, and other alkali
and alkaline earth metal soaps of fatty acids, gaay
be advantageously included.
15 Fatty acids themselves which are solids at room
temperature may also be included, and their
relatively low cost, ready availability, and their
contribution to the overall lubricity of the
composition makes them attractive for such use. One
example is stearic acid, which is advantageously
used since it has good lubricating properties, is
nontoxic, inexpensive, and readily available.
Materials such as graphite and certain ceramic
materials such as boron nitride are useful for
maintaining a physical sex>aration between the die
and the workpiece. While the precise mechanism of
the physical separation is not known, this
characteristic is believed to be attributable to the
relatively planar crystalline structure of these
materials.
Useful high melting polymer resins include, by
way of example, poly(tetrafluoroethylene) (PTFE),
high density polyethylene (HDPE),
poly(vinylchloride) (PVC), polyesters, polyethylene
glycols, polyacrylates, polymethacrylates, and
polyamides. Indeed, almost any thermoplastic
material may be used.
lb
It is believed that the thermoplastic resins of
the invention provide a plastic matrix on the heated
metal surfaces within which the individual lubricant
components may be supported during metal forming.
As is well known, thermosetting resins, such as
phenolic resole resins typically lose the ability to
flow following heating. The ability of
thermoplastic resins to remain plastic throughout
the metal forming process is believed to be an
l0 important 'characteristic of the polymer resin
components of the lubricant of the invention.
Of the natural and synthetic waxes which may be
advantageously employed, polyethylene waxes of
relatively high molecular weights are in general
preferred on account of the lubricity which they
impart.
Glass materials useful in the present invention
are preferably the low melting glasses, including
alumina, alumina/silica, , silica, and borax.
Optionally, these glass materials may be used in
chopped fiber form.
In one basic form of the method of the
invention, a coating of an effective amount of a
carrier-free pulverulent lubricant composition is
applied to at least one of the die and the
workpiece, and the workpiece is then formed into the
desired finished part. In general, the application
of the lubricant in accordance with the invention
may be accomplished by any convents~nal
powder-coating equipment.
In one alternative method falling within the
scope of the present invention, the carrier-free
pulverulent metalworking lubricant is applied by
means of an electrostatic spray apparatus, inasmuch
~5 as there is little loss of material on account of
the electrostatic attraction of the particles to the
die and/or workpiece, and, since electrostatic spray
2~.~~~~
is known to produce a uniform coating on even
complex-shaped parts.
In high temperature environments, such as
aluminum, steel, and titanium forging operations,
maintaining sufficient charge on the lubricant
particles is quite difficult when the powder spray
is directed to the die or workpiece in the vicinity
of the press, and the electrostatic powder coating
apparatus provides little advantage over
l0 non-electrostatic equipment. However, an
electrostatic apparatus provides a significant
benefit for pre-coating aluminum, steel, or titanium
workpieces at ambient temperature, after which the '
workpiece is heated in an oven prior to insertion
into the press. Similarly, in cold forming
operations, such as stamping and the like, which are
carried out at much lower temperatures, the
advantages of electrostatic spray are maintained.
The lubricant of the invention may be applied
to a heated or heating die in a manner analogous to '
the application of conventional lubricants.
Alternatively, the lubricant composition may be
sprayed onto a cold unforg:ad workpiece, after which
the workpiece is heated to achieve a partial melt of
~5 the composition and subsequently placed into a
heated die for forging. In cold-forming operations,
the workpiece may be spray-coated, and the
conventional step of heating the workpiece to flash
off or evaporate an aqueous solvent or oil carrier
may be eliminated.
It has been found that on account of their very
powdery, even dust-like, nature, such materials as
graphite and amorphous boron nitride are, unless
they have an electrostatic charge, less easily
retained on the surfaces of the die and workpiece
than are some of the other materials enumerated
above. Drafts or currents of air may therefore
undesirably remove the pulverulent forging lubricant
~~~~3
18
from the die and/or the workpiece prior to the
forging operation. Thus, when including one or more
of these materials in a lubricant of the invention
formed as a dry admixture which is to be delivered
by a non°electrostatic powder coating apparatus, it
is preferred to also include at least one component
having adhesive properties at 'typical forging
temperatures, such as a glass, gilsonite, or high
melting polymer resin for the purpose of retaining
l0 the lubricant on the die and the workpiece.
Some examples of the lubricant composition and
metalworking method of the inventi~n are set forth
below.
samples 1 ~Bt~ Z
The following compositions were used to forge a
box channel with high walls, approximately 0.125
inches thick, in a wrap die fro~a aluminum alloy
stock. The press was of the hydraulic type, with
the workpiece temperature being 700°F and the die
temperature 375°Fe
Euample i
component i~eig~at%
gilsonite 5
zinc stearate 34
sodium stearate 10
graphite 17
polyethylene 34
' 100
Example 2
Camp~nent Weig~at%
gilsonite 5
zinc stearate 34
sodium stearate 10
graphite 17
amide wax 34
100
Only seven parts were forgedp thus,
optimization of spray techniques could not be
achieved. However, examination of the forged parts
~~.~~
19
showed excellent metal movement, with a complete die
fill of the walls of the channel. There was
excellent downsize of the critical part dimension,
and the parts released easily from the die, with no
sticking. The dies had some tendency to stick
togetherp however, this is normally experienced with
this configuration of parts. Smoke levels were
noticeably lower than those produced when a
conventional solvent, oil and graphite lubricant was
used. Based on this rather limited trial, the
composition of Example 1 outperformed the
composition of Example 2 in each of the observed
respects, though both were effective as forging
lubricants.
Example 3
~n a comparative trial, the composition of
Example 1 was evaluated using a conventional
solvent-based zinc stearate forging lubricant as a
standard. The press was of the mechanical type,
with the workpiece temperature being 700°F and the
die temperature 400°F.
Forty parts were forged from each composition.
Examination of the forged parts showed excellent
metal movement with no drag. There was excellent
downsize of the critical part dimension. The parts
released easily from the die, with no sticking, and
there was no buildup of lubricant residue on the
parts. Smoke levels when using the composition of
Example 1 ware significantly lower than those
produced during the trials reported in Examples 1
and 2.
Examples 4 aad S
Each of the following compositions was
evaluated under the same conditions as those of
Example 3, and each was found to perform
satisfactorily with significantly lower smoke
generation than conventional solvent-based
lubricants.
~~ ~~.~ ~'~
' 20
Example 4
4:~I~pOneli$ ~ W~1g39$%
graphite 33.0
zinc stearate 34.5
gilsonite 10.9
polyethylene wax 21.1
99.5
. Exple 5
. C~x~ponen$ ~eig3~$~
graphite 23.8
;' sodium stearate 33.4
' gilsonite 23.8
polyethylene wax 9.5
zinc stearate _9.5
100.0 .
The composition of Example 5 was also evaluated
in the high-temperature environments of steel and
titanium forging, and it was found to perform
satisfactorily in the forging of bo$h metals.
Examples 6-8
The following carrier-free pulverulent
lubricant compositions have 'also been found useful ...
for the forging of alum9.num and aluminum alloy
worlepieces
E~mmple tr
'c~mpon~n1c Weic~h$~
graphi$e ~ 23.8
sodium stearate 33.4
gilsonite 23.0
3o polyamide 9.5
zinc stearate 9.5
100.0
Example 7
Coa~poaant We ig~a$~
graphite 23.8
sodium stearate 33.4
gilsonite 23.8
polyacrylate 9.5
dibutyl tin carbonate 9.5
100.0
,_ ~~~~Q~~
21
Exaznpl~ 8
C~mpOn~nt ~ Weight
graphite a5
gilsonite 25
100.0
Example 9
C:oHtp~nent Waight~
graphite 50
sodium stearate 15
gilsonite 25
poly
(tetrafluoroethylene)10
100.0
Examples i~-1~
Other carrier-free pulverulent lubricant
compositions have been found useful for high
temperature forging of
titanium and steel, and
they
include the following:
E~~npl~ 1~
Cpmpon~nt 'd~~ight~
graphite 20.0
gilsonite 20.0
sodium stearate 30.0
stearic acid 20.0
polyethylene wax 10.0
100.0
Examp~.a ~.1
C~~np~aent Weight
graphite 15.0
gilsonite 20.0
sodium stearate 30.0
stearic acid 20.0
polyethylene wax 10.0
boron nitride 5.0
100.0
22
Expl~ 12
1
Componemmt Weight%
graphite 40.0
gilsonite 20.0
sodium stearate 20.0
stearic acid 20.0
100.0
Exempla 13
Compone~i't '~gight%
alumina/silica 40.0
glass
graphite 60.0
100.0
Z5 Example 2.9-1...
Co~pon~nt Waight%
boron nitride25.0
borax 75x0
100.0
EBampl~ ~.~i-2
Compon~n~ We$ght%
graphite 35.0
borax ' 65.0
100.0
Tn one particular applicationp naanely, the
forging of steel engine valves, a number of .
advantages
were realized
by employing
a lubricant
of
the followingcomposition:
E$ampl~ 35
Colapogl~nt ~e1ght%
graphite 20.0
gilsonite 5.0
polyethylene wax 70.0
23
powdered sulfur 5.0
100.0
In this particular application, the composition
of Example 15 outperformed the composition of
Example 5 in a number of respects. In particular,
better metal flow was achieved, resulting in the
elimination of crack formation; improved part
configuration was observed; and, better die life was
achieved. ~ Though the precise mechanism which
resulted in these improvements is not known, it is
believed that the sulfur particles become molten on
the die and workplace surfaces, and that the molten
sulfur provides added lubricity and enhances the
extreme pressure properties of the dry lubricant
composition. It is further believed that the sulfur
promotes the formation of cartoon sulfides and other
lubricant residues which function as parting media,
enabling tree forged part and the die to separate
cleanly.
Addition of sulfur to the composition in an
amount of from about 2~ to about 30% by weight
provides the benefits described above, while an
amount in the range of from about 5~ to about 20~ is
preferred for functional and economic reasons.
It is possible to achieve a limited improvement
in cleanability of aluminum and aluminum alloy parts
by reducing or eliminating gilsonite from the
composition, since it tends to contribute to the
formation of tar-like residues on the forged parts.
But eliminating this component improves cleanability
only marginally, and at the price of reduced
performance, since the gilsonite provides good
lubricity, while at the same time its tacky
character at forging temperatures tends to help a
lubricant formed as a dry admixture to adhere to the
workplace and the die.
2~
What has been discovered to be extremely
effective, however, is to replace the gilsonite with
a component which unexpectedly provides the
combination of the same desirable performance
attributes contributed by gilsonite and other
similar tacky substances, together with a level of
cleanability which is the equal of a conventional
solvent and/or oil based forging lubricant.
Specifically, the use of a resin component
l0 having certain physical and chemical attributes can
provide the combination of good performance and far
superior cleanability required for successful
industrial use.
In general, any resin which has good lubricity
properties at forging temperatures, is a solid at
ambient temperatures, and contains a highly polar
functional group which enables the resin to be
solubilized in the caustic etch and/or acid bath
will provide this combination of properties. In
general, halogenated resins are preferably avoided
in hot forging operations on account of their
tendency to form hazardous combustion products.
Particular resins which have been found useful
in the practice of the invention include the
~5 polyethylene glycol resins, polyester resins having
terminal hydroxyl or carboxyl functional groups,
polyacrylate, polymethacrylate, and polyamide resins
and mixtures of these resins.
It is further believed that the thermoplastic
resin components of the invention contribute to the
ease with which these lubricants can be cleaned fr~m
the parts, following metal forming. As is well
known, thermoplastic resins which have oxygen
linkages in the polymer backbone provide reactive
sites for acid or base attack which, in turn,
provides a ready mode by which the resin may be
broken down and solubilized. Breakdown of the long '
chain polymer during post-formation cleaning ~f the
CA 02106036 1999-07-07
workpiece in acidic or basic solvents may assist the
removal of the other lubricant components as well,
since the resin ordinarily tends to adhere the other
components to the workpiece.
5 Presently preferred are the polyester and
polyethylene glycol resins on account of their good
lubricity properties, superior cleanability, and
lack of objectionable burn characteristics. Some
examples of such resins are the polyethyleneglycol
10 resins sold under the tradename PluracolTM by BASF,
such as E4000 and E8000, the hydroxyl functional
polyester resins sold by Cargill, such as 30-3016,
and the carboxyl functional polyester resins sold by
Cargill, such as 30-3065. These materials are
15 generally dry solids at room or ambient temperature,
so that they are readily applied to the workpiece
and die by conventional powder coating equipment.
These resins provide the desired combination of
lubricity and cleanability characteristics when
20 utilized in the carrier-free lubricant composition
of the invention in amounts of from about 5% to
about 50% by weight of the composition, with a
preferred range of from about 10% to about 30% by
weight of the composition. Most preferably, the
25 amount of resin is maintained as low as possible
while still providing the desired performance
characteristics, since these resins tend to be more
expensive on a weight unit basis than many of the
other components of the composition. While, in
general, an observable improvement in cleanability
is achieved when at least about 5% by weight of the
composition is a high-melting resin having a highly
polar functional group, the upper concentration
limit is more an economic than a functional one.
It is important to note in this regard (and
with respect to the determination of the optimum
concentration of any of the other components of the
composition) that small variations in the amount of
26
resin used do not manifest themselves in readily
observable ~ variations in performance or
cleanability. Tndeed, the evaluation of perforanance
and cleanability is highly subjective and not
susceptible to quantification to any meaningful
degree. Thus, the weight percentage of resin or any
other component in the lubricant composition is not
narrowly critical to the practice of the present
invention and may vary considerably without an
adverse effect on performance.
Example if>
A lubricant powder composition was formulated
in accordance with the invention as follows:
~~mp~nent ~eight% .
graphite 15
stearic acid 15
zinc stearate 30
sodium stearate 10
polyethylene glycol 20
carboxyl functional
polyester
100
The lubricant so formulated was successfully
utilized in a high performance aluminum forge
operation for the purpose of forging a number of
aircraft parts. The lubricant of Example 16 was
further found to perform successfully in typical
steel (engine valves) and titanium (turbine blades)
forging operations.
Ex~6pln 17
The forging of a first group of aluminum parts
using the composition of Example 16 was carried out
together with the forging of a second group of
aluminum parts using the composition of Example 5,
and a series of three comparative cleaning tests was
conducted. The cleaning procedures and the results
obtained are summarized below:
Meaning Rests D~tail
Test A - process (Standard Etch)
27
Step 1 - Caustic soda, 8 oz/gal, 175-180° F,
120 sec.
Step 2 - Rinse, cold.
Step 3 - Rinse, cold.
Step 4 - Desmut, nitric acid 25%, 60 sec.
Step 5 - Rinse, Cold.
Step 6 - Rinse, cold.
Step 7 - Rinse, hot.
Results:
Removimg Example 5 lubricant: poor cleaning.
Removing Example 16 lubricant: marginally
acceptable cleaning.
Test B - Process:
Step 1 - 24% sulfuric acid, 6% nitric acid,
180°:F, 10 min.
Step 2 - Rinse, cold.
Step 3 - Rinse, cold.
Step 4 - Caustic socla, 8 oz/gal, 175-180°F,
120 sec.
Step 5 - Rinse, cold.
Step 6 - Rinse, cold.
Step 7 - Desmut, nitric acid 25%, 60 sec.
Step 8 - Rinse, cold.
Step 9 - Rinse, cold.
Step 10 - Rinse, hot.
Results:
Removing Example 16 lubricant: essentially
clean; equivalent to cleaning liquid lubricant with
standard etch process.
Test C - Process:
Step 1 - Nitric acid 50%, 120 sec.
Step 2 - Rinse, cold.
Step 3 - Caustic soda, 8 oz/gal, 140°F, 30-180 .
sec.
Step 4 - Rinse, cold.
Step 5 - Desmut, nitric acid 50%, 120 sea.
2~~~~~
28
Step 6 - Rinse, cold.
Step 7~- Rinse, hot.
Results:
Removing Example 16 lubricant: essentially
clean; equivalent to cleaning liquid lubricant with
the same etch process.
Following a number of such comparative cleaning
tests, a still further advantage of the lubricant of
Example 16 over a conventional zinc-containing
lubricant was discovered; namely, a 95% reduction in
the amount of zinc present in the etch solutions.
Reduction of the metal content of industrial wastes
is, of course, a valuable environmental and economic
benefit.
Exampl~ 1~-21
Lubricant powder compositions also formulated in
accordance with the present invention are:
Example a8
component ~a~3ght%
2o graphite 15
stearic acid 20
dibutyl tin
carboxylate 20
sodium stearate 25
polyamide 10
hydroxyl functional
polyester l0
:100
~~v~~~
2'~
Exa~aple
~ompo3le~t ~~lght~
graphite 15
carboxyl functional
polyester 20
sodium stearate 20
SteariC acid 20
polyethylene glycol 10
boron nitride _5
100
E~a~aple 20
~oaaponent ~eight%
graphite 40
hydroxyl functional
polyester 20
zinc stearate 20
stearic acid _20
100
Example 21
Co~ipoae~lt W~~.g~lt%
alumina/silica
glass 40
graphite 55
polyethylene glycol 5
100
It was determined that maintaining a narrow
particle size range for the carrier-free pulverulent
lubricant of the present invention would provide
greatly improved spray efficiency and consistency,
such that a substantially uniform coating of powder
lubricant was capable of losing applied to the '
workpiece. thus, in anather aspect, the present
invention is directed to a carrier free pulverulent
lubricant composition wherein the particles are of
substantially uniform size.
By the phrase "substantially uniform size" as
used herein is meant that there be relatively few or
no particles having a size, as measured by
"diameter," more than 50% larger nor 50% smaller
i~~~~~3~
than the mean particle size. Most preferably,
relatively few or no particles of the lubricant
powder have a particle size that is more than 10%
larger or more than 10~ smaller than the mean
5 particle diameter.
Substantially uniform sized lubricant
particles, having a mean particle size (i.e.,
diameter) within the range of 10 microns to 420
microns produced acceptable results. However, a
10 mean partic~.e diameter of 40 microns or greater is
preferred. This lower size limit was selected to
minimize the extent to which lubricant particles
remain airborne in the form of dust. There are two
objectives in minimizing dusting; namely, to provide
15 an environmentally safer environment for the worker,
and to reduce lubricant material loss by increasing
the efficiency and accuracy of the powder spray.
The upper limit on particle size is essentially a
function of the capability of the spray equipment
20 and of the ability of the particles to adhere to the
surface of the workpiece in a substantially uniform
coating. The commercially available powder coating
equipment that was used herein seemed to function
best with particles ranginc; in size from 50 microns
25 to 100 microns.
One manner of controlling both mean particle
size and the range of part:<cle sizes is to utilize,
as starting materials, lubricant components that
have been ground and/or sieved to a substantially
30 uniform size. The sieved components may then be
readily admixed by conventional dry mixing
techniques, such as by use of a ribbon blender, a
tumbling blender, or a twin shell blender, such as
manufactured by lPattersondKelly Co., East
Stroudsburg, PA. An obvious drawback of the dry
mixing procedure is the time, effort, and expense
involved in either purchasing or processing each of
the components to the desired size and size range.
3g 2~~~~~
A second drawback is that the dry blending process
itself causes the particles to abrade one another,
thereby creating a multitude of sma~.l particles
which once again broadens the particle size range.
further difficulties also arise in lubricants
manufactured by this method; namely, segregation of
the lubricant particles on account of differences in
particle size and weight of the various components,
unacceptable levels of dusting on account of the
presence of very fine particles, and, poor
flowability.
A second method for preparing a carrier-free
pulverulent lubricant composition, having particles'
of a substantially uniform size, involves hammer
milling a solidified melt phase of the lubricant
composition. Specifically, it has been discovered
that a high performance powdered lubricant having
particles of a substantially uniform size may be
formed by the following methods First, the
lubricant components, which may be in any
conveniently available comminuted form, such as
powders, flakes, small pellets, and the like,
essentially regardless of their particle size, are
admixed in the desired proportions to form a dry
lubricant premix. The dry lubricant premix is then
heated with agitation to form an essentially
homogenous melt. A temperature of from about 100°C
to about 200°C is usually sufficient to provide a
consistency which permits melt mixing. The
homogenous melt is then cooled to form a solid mass.
The solid mass is then ground at low temperature to
the desired particle size by conventional
cold-grinding techniques. Equipment capable of
performing this operation is commercially available.
In one such process, the homogenous lubricant melt
is discharged onto a rotating metal plate which is
chilled to about 40°F X10°C) to solidify the mass in
sheet foran. The sheets are then broken into shards
21'~~~
32
which are in the range of 1 to 3 centimeters across.
The shards are then, in turn, hammer-milled to the
desired particle size in an air-conditioned room.
Other similar processes solidify the melt into
ribbon form, after which it is broken into chips and
milled to the desired particle size under suitable
conditions. Hammer milling the melt phase overcomes
a shortcoming of the drymixing method, i.e.,
controlling the particle size, and may also achieve
other significant improvements, by forming the
lubricant powder in an entirely different manner
Typically, the hammer milling equipment is
rather massive, and is constructed of steel or
another metal. If the equipment is conditioned~to
the ambient room temperature, i.e., about 60°F' to
70°F', it provides a highly efficient heat sink for
the lubricant composition as it is milled. If
necessary, the apparatus can be further chilled by,
for example, circulating liquid nitrogen through a
network of internal channels provided for that
purpose. Even simply pouring liquid nitrogen into
the intake hopper of a conventional grinder along
with the lubricant material is an effective, albeit
rudimentary, cooling method. This temperature
control permits optimization of the process in terms
of controlling particle size, since many of the
lubricant components would become tacky or
semi-solid upon being subjected to the heat
generated in conventional grinding or milling
processes, but remain dry solids at lower
temperatures.
Manufacturing the lubricant composition in this
manner avoids the undesirable results of the dry mix
method in that it produces a lubricant powder which
has a much more narrow particle size distribution, w
which has better flowability on account of the more
uniform particle size, and which produces little or
no dust.
33
The lubricant powder produced by the melt
mixing process is physically different, as well,
since the individual particles are of heterogenous
composition. Visual examination of the lubricant
particles produced by the melt mixing process shows
that the meltable components fuse to form a solid
matrix in which the non-melting components (e. g.,
graphite) are fixed. This matrix structure, in
which discrete particles of non-melting components
are fixed iri a matrix of the meltable components, is
clearly visible under 20:1 to 100:1 magnification on
account of the color differences among the lubricant
components.
While the melt-mixing and grinding process is
effective in overcoming many of the deficiencies of
the dry mix process, that effectiveness comes at the
cost of a significantly more complicated and
expensive mufti-step process. Moreover, the process .
has functional drawbacks as well. On the one hand,
2o the typical equipment used to melt mix 'the lubricant
components; namely, a vessel heated by an oil-filled
jacket, cannot produce temperatures high enough to
melt certain metal soaps (e:.g., tin soaps) which are
quite desirable components of the lubricant
composition. On the other hand, typical grinding or
milling equipment (unlesss operated in a cooled
environment, or unless supplied with an integrated
chilling system) heats the lubricant composition to
the point at which some low-melting components
(e.g., waxes) become tacky and can no longer be
processed as powders.
Alternatively, the lubricant of the invention
may be produced by forming a homogenous melt of the
components as described above, and then spray-drying
the melt in a conventional manner to the desired
particle size to produce heterogeneous particles
having a matrix structure much Like that of the
34
particles produced by the melt mix and grind process
described above.
Plot only do these processes of producing the
lubricant of the invention greatly facilitate
controlling the particle size of the composition,
which optimizes the process of applying it to the
die and workpiece, but they produce improvements in
the performance of the lubricant composition. Since
the lubricant particles are ground or spray-dried
from an essentially homogenous mass, the lubricant
components are far more evenly distributed in the
composition than could be accomplished using
conventional dry mixing techniques.
A third method for preparing a carrier-free
pulverulent lubricant composition wherein the
particles are of a substantially uniform size is wet
granulation. In the wet granulation method, the
lubricant components are premixed, such as in a
Patterson-Kelly granulatox°~or V mixer, until a
homogeneous mixture is obtained. Thereafter a
sufficient amount of an aqueous binder is added to
the homogeneous mixture to produce a slurry. The
binder may contain thickening agents, such as
polyvinylpyrrolidone (ISP Technologies/GAF, Wayne,
New Jersey, PVP K-Series, e.g., K30 (MW=40,000), K60
(MW~160,000), K90 (MW~360,000) or hydr~xy~lethyl
cellulose (e. g., QP 300 cellosize, Union Carbide
Corp., Danbury, CT), which upon drying forms a
bridge between adjacent particles. 9ptionally, the
binder may also contain one or more non-ionic
surfactants, preferably from 0.1% to 0.3% by weight,
such as diisopropyl adipate (Van Dyke Ceraphyl 230)p
octyldodecylstearoyl stearate (Ceraphyl 847); or a
polyoxyethylene ether e.g., Triton N-101 (Triton~ is
a registered trademark of Rohm and Haas Co.) A
variety of polyoxyethylene ethers are commercially
available under the Triton mark from Sigma Chemical
Co., St. Louis, Mo. The slurry is poured onto
CA 02106036 1999-07-07
cookie sheets and allowed to dry in an oven
preferably set at about 210°-220°F. The dried
slurry is broken up into chips, ground into
lubricant particles of heterogeneous composition and
5 segregated according to particle size. Segregation
is accomplished sequentially be passing the ground
particles through 40 mesh and 80 mesh filters and
retaining the lubricant particles that pass through
the 40 mesh filter but that are retained by the 80
10 mesh filter. The retained particles provide a
carrier-free pulverulent composition wherein the
lubricant particles are of a substantially uniform
size.
A fourth method for preparing a carrier-free
15 pulverulent lubricant composition having particles
of substantially uniform size is agglomeration.
Agglomerating the particulate lubricant components
to form agglomerated particles of heterogeneous
composition has proven advantageous in that the
20 previously mentioned melt step and slurry step, and
their accompanying shortcomings, may be eliminated
altogether. Various techniques for agglomerating
particles are known to the art. See for example,
Ulmann's Encyclopedia of Industrial Chemistry, VCH
25 Publishers, NY, NY 1988 at Vol. B-2 DD. 7-1 to 7-37.
The process for forming the agglomerated
lubricant particles may be carried out in either the
presence or absence of a binder; preferably in the
30 presence of a binder; more preferably, an aqueous
binder; most preferably, an aqueous binder
containing a polymeric binding agent (i.e.,
"thickener") and/or a non-ionic detergent. For
purposes of this invention, the phrase "aqueous
35 binder" is meant to include any binder solution
wherein more than 50% of the solvent is water,
preferably more than 75%, and more preferably
greater than 90%. The balance of solvent in the
36
aqueous based solution is a non-interfering water
miscible organic solvent. Typical water miscible
organic solvents include alcohols having from 1 to 3
carbon atoms, polyols, such as ethylene or propylene
glycol, or glycerine, polyethylene glycols having a
molecular weight (°~MW~~) from 200 ~ 500, acetone,
tetrahydrofuran (THF), dimethylsulfoxide (DMSt~) and
the like. ether water miscible organic solvents are
well known to those of ordinary skill in the art.
For many such solvents, however, care must be taken
to avoid buildup of static electricity in the
equipment which could provide a source of ignition.
Binder components that may effectively be used
to adhere the component lubricant particles in the
agglomeration process of the present invention
include natural gums or products including algin,
starch, and xanthan gum; cellulose derivatives,
including methyl cellulose, hydroxylpropylmethyl
cellulose and glyoxal hydroxymethyl cellulose;
polymers, including polyvinylpyrrolidone (PVP), and
sodium carboxymethyl starch; compressibility
enhancers including microcrystalline cellulose and
bentonite; and matrix binders, such as care syrup,
waxes, sorbitol, paraffin, shellac alcohol, and .
polymethacrylate. Many other chemical binders are
also available. Binder components may be chosen
based upon a number of factors, including the type
of agglomeration, viscosity, concentration, bond
strength and drying characteristics.
Agglomerating in the presence of a binder
permits many individual particles of differing
composition, size, and surface characteristics to
coalesce and adhere to one another to form larger
particles comprised of the various component
particles. The strength and size of the resulting
agglomerated particles is dependent upon the binding
characteristics of each individual component
~1~603~
37
particle, the binder characteristics, and the method
of agitation.
In the present invention, the various
particulate components are selected based upon their
performance in a heterogeneous pulverulent metal
working lubricant composition. From an economic .
standpoint, it is desirable to utilize the
agglomeration process of the present invention to
form the (heterogeneous) carrier~free pulverulent
metalworking lubricant composition. The various
component particles may be purchased in the
appropriate particle size ranges to facilitate
controlling the particle size range of the carrier
free pulverulent lubricant composition.
Depending upon the relative size of the
component particles, agglomeration may be described
as a coalescence between equal size particles, a
layering of a larger granule with smaller particles
or an absorption of still smaller particles by a
partially filled binder droplet.
While it is possible to calculate rough
relationships between the amount of binder, the
agitation intensity and the process duration,
selecting the optimum parameters requires routine
experimentation with each particular piece of
agglomerating equipment. Agglomerating equipment
that may be useful in forming the agglomerated
particles of the invention include drum and disk
blenders, pinmixers, spray~dryers, compactors, and
fluidized bed or spouted bed granulators.
Tn a typical drum blender agglomeration
process, the agglomeration can be expressed as a
function of the dimensionless Stokes number (Stv),
which is given by the equation:
Stv = 2mu.. - ~uu"a - ~.6 a
3Ua i 9U 9U
Where m = mass of the particle (mg)
U = Fluid binder viscosity (cps)
2~.~~~-
3~
a = particle radius (microns)
p'= particle material density (g/m3)
w = drum rotational speed (rpm)
uo = relative particle velocity = taw (for
drum granulation) (m/s)
Normally, a distribution of particle sizes is
encountered in a one component system. In a
multiple component particle system, wherein the
various component particles may have a variety of
configurations, surface contours, radii, masses and
densities, some experimentation is required to
achieve an effective agglomeration. The two
variables that are most readily adjusted are the
fluid binder viscosity (U) and the relative particle
velocity (uo) attributable to the rate of agitation.
In Examples 22 - 32 which follow, a carrier
free pulverulent metalwor3cing lubricant having a
substantially uniform size was prepared by
agglomeration using either a laboratory scale or a
commercial scale °°V'° or twin~°shell liquid-
solids
blender/granulator (Patte:rson-Kelly Co., East
Stroudsburg, PA) hereafter °°the granulator.°°
This
granulator performs batch process agglomeration.
However, continuous proces:a agglomeration equipment
may also be used. In the agglomeration process, the
particulate components of the lubricant composition
were added ~o the chambers of the granulator and dry
blended for sufficient time to assure a homogeneous
mixture. Thereafter, while the granulator was still
drymixing, the binder solution was added all at one
time. The commercial scale twin-shell blender
utilized in certain of the examples was modified to
permit excess moisture to escape during processing.
The modification consisted of drilling small holes
of about 1/4°' diameter into the tops of the cover
plates, covering the holes with filter paper of
sufficient pore size to allow air to escape while
retaining substantially all of the fines, and
3 S~
pumping relatively dry air through the liquid
dispersion bar to reduce the moisture content of the
agglomerated particles therein.
It is desirable to keep the moisture of the
product as low as possible both during
agglomeration, to prevent caking, and afterwards to
both avoid conditions conducive to microbial growth
and, more importantly, maintain the lubricant in a
free-flowing state which permits effective
application by powder-coating ee~uipment. In
accordance with the present invention, the moisture
content of the agglomerated metalworking lubricant
is preferably below 15% by weight following
processing; more preferably, below 2%; most
preferably, below 0.5%. Optionally, anti-caking
agewts, such as silica, tricalcium phosphate,
calcium aluminum silicate, and microcrystalline
cellulose may loe added in an amount of up to about
l0% by weight to improve the flow characteristics of
the agglomerated particles.
For the examples which follow, the following
were used: graphite 3731, .average particle size 50
microns, available from Superior Graphite as SF33;
sodium stearate, average particle size less than 325
mesh, available from Witco Chemical; zinc stearate,
average particle size less than 325 mesh, available
from Witco Chemical.
40
Raw Material ~ by Weight
Particulate Components
1 Graphite 3731 14.50
2 Sodium Stearate 24.00
3 Cargill 30-3065 9.60
4 Pluracol E-4000 19.23
5 Zinc Stearate 28.80
Finder Components
l0 1 ~ Water 3.67
2 QP300 Cellosize 0.16
(hydroxymethyl cellulose)
3 Triton N-101
(a non-ionic
surfactant) 004
100.00
The above-listed binder components were
premixed in the recited proportions until they
became clear and thick. The premix was then set
aside. The particulate components were added to the
agglomerator in a dry state in the order in which
they are listed, and were dry blended for one half
hour. The binder was then poured into the
agglomerator, taking care that it did not hit the
walls or the sweep bar. The agglomerator contents
were then agitated at a drum rotational speed ~f 15 ~ .,
rpm for four hours. Thereafter, the resulting '
agglomerated particles were separated according to
size by being passed through a 40 mesh screen and
then through an 80 mesh screen. The substantially
uniform particles of the carrier-free pulverulent
metalworking lubricant of the present inventi~n
passed through the 40 mesh screen, but were retained
by the 80 mesh screen. In terms of relative
particle size, this means that the substantially
unifarm particles have diameters in the range of
about 17o microns to about 420 microns.
Agglomerated carrier-free lubricant particles in
41
this size range carried well to the surface of the
metal with a minimum of dusting.
Ex~lples 23-32
Examples 23 - 32 set forth the particle size
distribution of the lubricant composition as a
function of time for 3 lb. batches (Examples 23
29), Or 200 lb. batches (Examples 30 - 32).
Examples 23 - 32 use the same particulate components
1 - 5 listed in Example 22 but vary the quantity and
composition~of the binder solution. Figures 1 - 10,
which correspond to Examples 23 - 32, graphically
compare the particle size distribution as a function y
of agglomeration time. The particle distribution at
time zero reflects the particle size distribution
after mixing but prior to the addition of the
binder. As Example 24 reflects, there is~a higher
distribution of oversized particles at time zero if
the raw particles are not grounGl prior to
agglomeration. The lxighe:~t yield of ideal sized
particles was obtained as dtescribed in Example 32.
Fxemp3e 23 (see F~gare 1)
Ido Binder
Size: 3 lbs.
Distribution 0 1S min. 30 min. 60 min. 120 min.
Overs'izc 12% 14% 12% 22% 33%
(+40 mesh)
Ideal ~4% 6S% 72% 4S% 44%
(+80 ~l0 mesh)
Undcraiu 18.5% 1396 6.896 20% 13%
3 0 (-xo mesh)
Fxa~ple Z4 (see Figure Z)
Binder: S 96 by weight; Binder composition: FI=O.
Raw paeticiea, i.c., unground.
Size: 3 lba.
3 5 Distribution 0 1S min. 30 min. 60 min. 120 min.°
Oversize 32 % 42 % 33 % 51 %
(+40 mesh)
Ideal 35% 38% 42% 37%
(+80 - 40 mesh)
42
Undersize 23% 14% 20% 7%
(-80 mash)
'No data; Experiment
interrupted.
Example 25 (Fgure
3)
The raw particles
were first
ground with
5% Hs0 by wt.
Size: 3 lba.
Distribution 15 min. 30 min 2 90 120 min.
0 60 min. min.
Oversize 6% 14% 15% 34% 72% 82%
(+40 mesh)
Ideal 34'% 40% 35% 39% 16% 9%
(-40 +80 mesh)
Undersize 55% 40% 45% 25% 4% 2%
(-80 mesh)
'Added 2% H=O H30
for a total
of 7%
Example zb (15gare
~)
Binder: 5 %
by weight;
Binder composition:
5 % polyvinylpyreolidone
("PVP'~
IviW - ? , 95
% H10 (v/v).
Size: 3 Ibs.
Disuibution 15 min. 30 min. 60 90 120 min.
0 min. mia.
Overe'tze 8% 20% 28% 56% 42% 26%
(+40 mesh)
Ideal 34% 51% 43% 32% 42% 48%
(-40 +80 mesh)
Undetv'~zo 52% 26% 22% 6% 10% 20%
2 5 (-80 mash)
Example z7 (Figure
S)
Binder: 5 % 0.1 %
by weight;
Binder composition:
3 % QP300 glyoxal
hydroxymethylcalluloae
solution,
Triton N101,
95.9% Hs0 (v/v).
S'tze: 3 lba.
3 0 Distribution 15 min. 30 min. 60 90 120 min.
0 min. min.
Oversize 9% 2896 20% 26'.6 28% 34%
(+40 mash)
Ideal 38% 57% 46% 53% 52% 53%
(-~0 +80 mash)
35 Undersize 48% 20% 24% 14% 12% 7%
(-80 mesh)
Fxatmple z8 (F'~gure
~
Binder: 5% by
weight; Binder
composition:
5% diisopropyladipete
(i.e., Van
Dyka Ceraphy1230),
!6
H=O (v/v).
4 0 S'~ze: 3 Ibs.
Distribution 15 min. 30 min. 60 90 120 min.
0 min. rttin.
Oversize 10% 16% 10% 16% 16% 20%
(+ 40 mesh)
4~
0
Ideal 33% 63% 52% 63% 60% 48%
(-40 +80 mesh)
Undersize 56% 22% 26% 16% 20% 20%
(-80 mesh)
Example Z9 (ESgatre
7)
Binder: 5 % composition: e., ~6
by weight; 5 Cerephyl
Binder % 847)
octyldodecyl
stcroyl
stearate
(.
Hr0 (v/v).
Size: 3 lba.
Distribution 15 90 120
0 mia. min. min.
30
min.
60
min.
t?vereize 8% 40% 46% 52% 40% 50%
(+40 mesh) '
Ideal 34% 52% 44% 44% 48% 37%
(-40 +80 mesh)
Underaizs 54% 6.0%2.6% 3% 3% 10%
(-80 mesh)
Example 30 (F>8arre
~
Scale up agglomerationBinderweight
with 5% by
Binder Composition:
H=O.
2 Particles: Raw.
0
Size: 20016x.
Duration in Minutes
Distribution 30 60 90 120 150 180 210 240
0
Oversize 20% 42% 39% 37% 37% 39% 40% 42% 39%
2 (+40 mesh)
5
Ideal 20% 35% 35% 46% 42% 40% 34% 35% 35%
(-40 +80 mesh)
Undersize 56% 20% 24% 14% 15% 18% 20% 19% 20%
(-80 mesh)
3 ' Example 31 p~rgare
0 9)
Scale up agglomerationBindeeweight.
with 5 % by
Binder Composition: + 0.1 Triton
3% QP300 celloaiu N101 + 96.9%
H=O (vlv).
Panictea: Rew.
Size: 200 lba.
3 Dueation is Minutia
5
Distribution 30 60 90 120 150 180 210 240
0
Overstza 20% 30% 40% 46% 49% 52% 68% 80% 76%
(+AO mash)
Ideal 34% 35% 36% 36% 32% 28% 20% 15% 22% ..
4 (-40 +80 mesh)
0
Undersize 42% 20% 12% 6% 5% 6% 2% 0% 0%
(-80 mesh)
~.~.~~~_~
44
>:tta>aple 32 (~g,tr~ lo)
Scale up agglomeration with 3 'X~ Bindet
by weight
Binder Composition: 35L QP300 cellos'iae96.996
+ 0.196 Trieon N101 + F1,0
(v/v).
Particles: Ground
Siae: 200 lba. Duration in Minutes
Distribution 0 30 60 90 120 150 180 210 240
Oversize 8~ 129'0 18'~ 22~ 189610~ 20961696 1896
(+40 mesh)
Ideal 22Yu 2696 369b SSSb' 55965096 579b609'062~
( 10 +80 mesh)
Undets'tze 6096 52~Xr 3896 lti9b 20~ 24% 205618~r 1696
(-80 mesh)
The process of Example 32 produced a 62% yield
of a carrier-free pulverulent lubricant composition
having a substantially uniform size. Example 32,
relative to Example 31, produced a 40% increase in
ideal sized particles when the amourlt of binder
solution was reduced from 5% by weight (Example 31)
to 3% by weight (Example 32).
As is apparent from the above, the individual
particles of the lubricant compositian produced by
the agglomeration process are essentially
heterogenous in composition, and they are therefore
physically different from the particles produced by
the dry mix process. They are, moreover, physically
different from those produced in both the'melt-mix
and grind process and the melt-mix arid spray dry
processes, . since agglomerated particles are
aggregates of the individual lubricant components
which have become fused together into a
heterogeneous mass in the absence of a melted
matrix. While physically quite different, the
lubricant compositions produced by the melt-mix and
grind process, and by the agglomeration process,
respectively, display no readily observable
functional differences; i.e., their performance
appears to be equivalent.
Each of the processes of the present invention
(whether melt-phase, dried slurry, or agglomerating)
~1~~~~-
is capable of producing individual particles of
heterogeneous composition, that have more uniform
dielectric properties than a strictly dry-mixed
composition.
5 One advantage of manufacturing the carrier-free
pulverulent lubricant composition in a substantially
uniform size range is that, when the lubricant
particles are sprayed onto the die and workpiece at
elevated temperatures, the particles melt and fuse
10 to form a 'lubricant film which is substantially
uniform. Not only are the lubricant components
more evenly distributed on the die and workpiece
surfaces when the particles are manufactured in this
fashion, thus providing improved resistance to
15 sticking and more uniform metal flow along surfaces,
but the cleanability of the composition is improved
on account of the more uniform distribution of the
resins which are included for that purpose.
Further, flashing has been eliminated or minimized
20 due to the absence of a carrier.
The process of applying the carrier-free
pulverulent lubricant composition of the present
invention is carried out at essentially ambient
pressure by the use of conventional powder coating
25 equipment. For example, it is well known that, in a
conventional electrostatic powder coating apparatus,
a fluidized.bed of powder feeds a spray wand having
an electrode at its tip. ~laile the apparatus
injects air into the powder at rather low pressure
30 to form the fluidized bed, by the time the powder
reaches the applicator wand tip (typically a
distance of about 20 feet), the air carrying the
powder (and therefore the powder stream) is at quite
low, essentially ambient pressure. The charge
35 imparted to the powder by the electrode provides the
acceleration necessary to carry the powder to the
die (maintained at ground). Once on the die
surface, the lubricant powder may be retained there
by the adhesive properties of at least one component
included for that purpose.
Alternatively, a conventional powder coating
apparatus, whether electrostatic or
non-electrostatic, may utilize a gravity-fed conical
hopper as a powder source, rather than a fluidized v
bed. Such an apparatus has been found particularly
useful when utilizing lubricant powders of widely
varying particle size or relatively heavy lubricant
blends, which do not readily form fluidized beds.
Then such a gravity-fed apparatus is utilized, it
has been further found that optimal results in
feeding the powder to the spray wand are obtained
when the lubricant particles are either
substantially spherical in shape or have
substantially smooth surfaces, or, most preferably,
both. These characteristics permit the lubricant
particles to flow more easily, since they will have
less tendency to fuse on account of impact or to
2o wedge against one another, thereby blocking flow of
material. From the standpoint of optimizing both
shape and surface characteristics, the method of
manufacture described above which employs spray-
drying is the preferred one, since spray-drying
~5 inherently produces substantially spherical,
substantially smooth particles.
From the standpoint of obtaining substantially
uniform particles of heterogeneous composition
without the necessity of a melt step, the
30 agglomeration method of the invention is preferred.
In the process of the invention, a coating of
the lubricant powder is applied to the workpiece and
the die in a fashion much like painting. The
lubricant is not worked onto or into the die or
35 workpiece surface. Rather, the process is more akin
to painting the lubricant onto the die than to
hammering it into the surface.
r~
5. ~J ~.3 ~ c~
From the foregoing description and examples, it
is apparent that the objects of the present
invention have been achieved. While only certain
embodiments have been set forth, alternative
embodiments and various modifications will be
apparent to those skilled in the art. These and
other alternatives and modifications are considered
ecquivalents and within the spirit and scope of the
present invention.
