Technical Field
[0001] The present invention relates to aqueous lubricants that are coated onto either the
surface of a metal material or the molding surface of a metal mold, or both, to form
a lubricating film on the metal surface, so that friction between the material and
the mold is reduced, thereby enabling satisfactory plastic working of the metal. The
present invention further relates to methods of using the aqueous lubricant and to
chemical substances that are particularly suited for production of the aqueous lubricant.
Background Art
[0002] When a metal material is subjected to plastic working, such as forging, extrusion,
drawing, rolling or pressing, a lubricant film must be disposed on the surface of
the metal material and/or the molding surface of the metal mold to reduce friction
between the material and the mold and the prevent the generation of drag, seizures
and the like.
[0003] In most cases, the metal is immersed in a zinc phosphate solution to produce a zinc
phosphate or iron phosphate chemical film (hereafter referred to as "phosphate film")
on the surface, and then further immersed in a sodium soap or the like to produce
a metallic soap layer on the surface, This process creates a surface protective layer
of satisfactory quality, and allows heavy working (meaning working of material surfaces
with large elongation rates). However, this process requires washing treatments with
cold water, hot water or acid, as well as different types of equipment. Such treatments
also require long periods of time, thus lengthening the lead time. Usually, 30 minutes
or longer is necessary to complete a series of treatments. It is also necessary to
accomplish a single surface treatment of the entire portion of the metal that is subjected
to plastic working in a subsequent step during the treatment time, and therefore this
process is not suitable for production of small, sundry products.
[0004] In order to overcome these problems, the use of working oils has been proposed. For
example, Japanese Laid-Open Patent Publication No. 7-118682 teaches a working oil
prepared by dispersing in a mineral oil a zinc or molybdenum salt, such as zinc dithiophosphate,
molybdenum dithiocarbamate or the like, which has been rendered lipophilic by the
introduction of a higher alkyl group. This working oil solves most of the aforementioned
problems, but because the main component is oil, it creates problems, such as contamination
due to adhesion of the oil to surrounding machines and generation of oil mist. In
other words, contamination of the working environment is unavoidable. A number of
other problems also remain, such as the need to degrease the material surface after
plastic working.
Disclosure of the Invention
[0005] The present invention overcomes the problems mentioned above, and allows formation
of lubricating films on surfaces by application of aqueous lubricants containing no
oil. Because no oil is used, the problems of working environment contamination and
the need for subsequent degreasing treatment are solved. Because a simple application
is sufficient, a solution is also provided to the problems of large equipment requirements
and the need to accomplish simultaneous treatment of large volumes of materials.
[0006] The invention according to claim 1 relates to the aqueous lubricant itself, in which
the aqueous lubricant comprises a metal chelate compound suspended or dispersed in
water. The metal chelate compound described herein comprises a polydentate or multidentate
chelate ligand in which at least one of the coordinating atoms is sulfur, coordinated
to a coordination site of at least one metal species selected from among zinc, manganese,
iron, molybdenum, tin and antimony. For the purposes of this explanation, the term
"suspension" is intended to mean a metal chelate compound distributed in water, for
example, by continuous stirring. The term "dispersion" is intended to mean a metal
chelate compound distributed in water without precipitation, by use of a surfactant
or the like. Anionic and non-ionic surfactants are suitable for dispersion of the
metal chelate compounds in water.
[0007] The metal may have multiple coordination sites and the chelate ligand may be coordinated
to all the multiple coordination sites. Alternatively, the chelate ligand may be coordinated
to only some of the multiple coordination sites, thereby allowing coordination of
a species other than the chelate ligand to the remaining coordination sites. The lubricant
can be produced by dispersing the prepared metal chelate compound in water, or it
may be produced by adding the chelate ligand to an aqueous solution containing a metal
salt. The metal species may be any of one or more desired species and a greater number
of species will expand the range of workable conditions and workable metals.
[0008] The aqueous lubricant is applied onto the surface of a metal material and/or the
molding surface of a metal mold to form an effective lubricating film on the metal
surface. Because the lubricating film has sulfur as a coordinating atom, extreme pressure
produces sulfur radicals through decomposition by friction or tribo-chemical reactions.
The sulfur radicals are highly reactive, and react rapidly with the metal surface
to produce metal sulfides, which have a lubricating effect. The sulfur radicals also
react with the metal ions (one or more selected from among zinc, manganese, iron,
molybdenum, tin and antimony) produced by decomposition of the metal chelate compound,
also producing metal sulfides having a lubricating effect. The aqueous lubricant thus
exhibits a satisfactory lubricating effect.
[0009] The invention according to claim 2 relates to chemical substances particularly suited
for production of the aqueous lubricant. The chemical substances are multi-ligand
metal chelate compounds, in which a polydentate or multidentate chelate ligand having
sulfur as at least one of the coordinating atoms coordinates by partially filling
the multiple coordination sites of the one or more metal species selected from among
zinc, manganese, iron, molybdenum, tin and antimony, whereas ligands that do not have
sulfur as a coordinating atom coordinate to the remaining coordination sites. That
is, the chelate ligand is characterized as having sulfur as a coordinating atom that
does not fill all the coordination sites of the metals, so that it is not coordinated
to some of the coordination sites. When the multi-ligand metal chelate compound is
used as an aqueous lubricant suspended or dispersed in water, a very satisfactory
lubricating film is produced.
[0010] The invention according to claim 3 also relates to a chemical substance particularly
suited for production of the aqueous lubricant. The chemical substance is characterized
in that a chelate ligand having sulfur as a coordinating atom is coordinated to some
of the multiple coordination sites of the metal, whereas a hydroxide ion, condensed
phosphate, polycarboxylic high molecular activator and/or polyoxycarboxylic acid are
coordinated to the remaining coordination sites.
[0011] In the multi-ligand metal chelate compound, a chelate ligand having sulfur as a coordinating
atom is strongly coordinated with the metal, and a hydroxide ion, condensed phosphate,
polycarboxylic high molecular activator and/or polyoxycarboxylic acid are weakly coordinated
with the metal via oxygen anions. When the multi-ligand metal chelate compound is
used as an aqueous lubricant suspended or dispersed in water, a very satisfactory
lubricating film is produced.
[0012] The aqueous lubricant according to claim 5 has a soluble condensed phosphate salt,
a soluble polycarboxylic high molecular activator and/or a soluble polyoxycarboxylic
acid salt added to the aforementioned aqueous lubricant. Addition of these adjuvants
improves the performance of the lubricating film. A soluble condensed phosphate salt
will associate with the surfactant present in the system, thus increasing the dispersability
of the metal chelate compound that forms hydrophobic fine particles. A soluble polycarboxylic
high molecular activator or soluble polyoxycarboxylic acid salt will increase the
adhesion of the lubricating film to the metal surface. Using an aqueous lubricant
containing such adjuvants will allow more intense heavy working.
[0013] The invention according to claim 6 relates to a process of forming a lubricating
film on a phosphate film using an aqueous solution, if the phosphate film had already
been formed on a metal surface. In this process, a metal material on which the phosphate
film has already been formed is immersed in an aqueous solution of a multidentate
or polydentate chelate ligand having sulfur as at least one of the coordinating atoms,
so that the chelate ligand reacts with the zinc ion and/or iron ion in the phosphate
film to produce a crystalline multi-ligand metal chelate compound on the phosphate
film. This process takes advantage of both the lubricating effect of the phosphate
film and the lubricating action of the metal chelate compound, in which sulfur is
a coordinating atom chelated to the zinc ion and/or iron ion.
[0014] The invention according to claim 7 also relates to a process of forming a lubricating
film on a phosphate film. In this process, the phosphate film is formed on a metal
material and the metal material is then immersed in an aqueous lubricant according
to claim 4 or 5. A ligand, which is not a ligand having sulfur as a coordinating atom,
reacts with the zinc ion and/or iron ion in the phosphate film to produce a crystalline
polynuclear metal chelate compound on the phosphate film. This process takes advantage
of both the lubricating effect of the phosphate film and the lubricating action of
the metal chelate compound, in which sulfur is a coordinating atom chelated to a metal.
[0015] The invention according to claim 8 relates to a method of using the aqueous lubricant,
in which prior to plastic working of the metal material, an aqueous lubricant according
to claim 1, 4 or 5 is applied onto either or both surfaces of the metal material and
the molding surface of the metal mold to form lubricating films on those surfaces,
thus allowing plastic working of the metal material with a lubricating film formed
on the surface.
[0016] The invention will be more fully appreciated in light of the explanation that follows.
Best Mode for Practicing the Invention
[0017] First, an embodiment of a metal chelate compound will be explained in which at least
one metal species selected from among zinc, manganese, iron, molybdenum, tin and antimony
is chelated and at least one of the coordinating atoms is sulfur. Chemical structures
1-28 below are examples of such metal chelate compounds, and the chelate ligands in
chemical structures 1-28 (the compounds adjacent to M in the structures) react with
the above-mentioned metal ions in aqueous solution or in water or organic solvents
(alcohols, ketones and dioxane) to produce crystalline precipitates that are insoluble
in water. The coordinated structures of the crystalline precipitates are shown in
chemical structures 1 through 28. The crystalline precipitates produced thereby are
metal chelate compounds. The crystalline precipitated metal chelate compounds are
made minute and one, two or more different metal chelate compounds are suspended or
dispersed in water to generate aqueous lubricants.
[0018] In the structures, M represents divalent zinc, divalent or trivalent manganese, divalent
or trivalent iron, trivalent, tetravalent or pentavalent molybdenum, divalent [(MoOS)
2]
2+, divalent [Mo
2S
4]
2+, divalent or tetravalent tin, trivalent or pentavalent antimony, divalent MoO or
monovalent MoOS.
[0019] In chemical structures 1-12, 15, 16, 18, 19 and 28, n varies depending on the M species.
For example, when M is zinc, tin or antimony, n-1 or 2; when M is manganese or iron,
n=1, 2 or 3; and when M is molybdenum, n=1 or 2. In the case of zinc, for example,
if n=1, the chelate ligand having sulfur as a coordinating atom only coordinates with
two of the four coordination sites of zinc. In this case, the two remaining coordination
sites coordinate with a chelate ligand that does not have sulfur as a coordinating
atom, such as a hydroxide ion, condensed phosphate, polycarboxylic high molecular
activator and/or polyoxycarboxylic acid. Generally, this means that when the number
of coordination sites of the metal M in the following chemical structures cannot be
filled by a chelate ligand having sulfur as a coordinating atom, a chelate ligand
containing no sulfur, such as hydroxide ion, condensed phosphate, polycarboxylic high
molecular activator and/or polyoxycarboxylic acid, coordinates to the coordination
sites of the metal that are not coordinated with the chelate ligand having sulfur
as a coordinating atom.
[Chemical formula 1]
[0020]

wherein R
1 and R
2 may be the same group, in which case R
1 (=R
2) is H, -CH
3, -C
2H
5, -C
3H
7 (straight chain), iso-C
3H
7, -C
4H
9 (straight chain), iso-C
4H
9, tert-C
4H
9 or -C
6H
5. R
1 and R
2 also may be different, and when R
1 is H, R
2 is -CH
3, -C
2H
5, -C
3H
7 (straight chain), iso-C
3H
7, -C
4H
9 (straight chain), iso-C
4H
9, tert-C
4H
9 or -C
4H
9 (straight chain). When R
1 is -CH
3 or -C
2H
5, R
2 is -C
6H
5.
[Chemical formula 2]
[0021]

wherein R is H, -CH
3 or -C
2H
5.
[Chemical formula 3]
[0022]

[Chemical formula 4]
[0023]

[Chemical formula 5]
[0024]

wherein R is ortho-NO
2, para-NO
2, meta-OCH
3, meta-CH
3 or meta-C
2H
5.
[Chemical formula 6]
[0025]

wherein R is -CH
3, -C
2H
5, -C
3H
7 (straight chain) or iso-C
3H
7.
[Chemical formula 7]
[0026]

wherein R is a hydrogen atom or an alkyl group of 1-12 carbon atoms.
[Chemical formula 8]
[0027]

When m=1 and l=0:
R1-R3, and R6-R8 are H,
R1 is -CH3 and R2-R3, R6-R8 are H,
R1 is -C2H5 and R2-R3, R6-R8 are H,
R1 is -C3H5 (straight chain) or iso-C3H5 and R2-R3, R6-R8 are H,
R1 is -C4H9 (straight chain), iso-C4H9 or tert-C4H9, and R2-R3, R6-R8 are H,
R2 and R3 are -CH3 and R1, R6-R8 are H,
R2 and R6 are -CH3 and R1, R3, R7-R8 are H,
R2, R3, R6 and R7 are -CH3 and R1 and R8 are H,
R1 and R8 are -CH3 and R2-R3, R6-R7 are H,
R1 and R8 are -C2H5 and R2-R3, R6-R7 are H,
R1 and R6 are -C3H5 (straight chain) or iso-C3H5 and R2-R3, R6, R7 are H,
R1 and R8 are -C4H9 (straight chain), iso-C4H9 or tert-C4H9 and R2-R3, R6-R7 are H, or
R2 and R6 are -C6H5 and R1, R3, R7-R8 are H.
When m=1 and l=1,
R1-R6 are H, or
R4 and R5 are -CH3 and R1-R3, R6-R7 are H.
When m=1 and l=2-7,
R1-R8 are H.
When m=2-9 and l=0,
R1-R8 are H, or
R2 is -CH3 and R1, R3, R6-R8 are H.
When m=2-9 and l=1,
R1-R8 are H.
[Chemical formula 9]
[0028]

[Chemical formula 10]
[0029]

[Chemical formula 11]
[0030]

[Chemical formula 12]
[0031]

wherein R is a linear or branched alkyl group of 1-12 carbon atoms.
[Chemical formula 13]
[0032]
wherein R is H, l=2-3 and m=1, or
R is an alkyl group of 1-12 carbon atoms, l=2-3 and m=2-3.
[Chemical formula 14]
[0033]

wherein R
1-R
3 are H and m=1,
R1 is an alkyl group of 1-12 carbon atoms R2-R3 are H and m=2,
or
R1-R2 are H, R3 is -NH2 and m=2.
[Chemical formula 15]
[0034]

[Chemical formula 16]
[0035]
wherein R is H, l=1-6 and n=2-3, or
R is -COOH, l=1-6 and n=2-3.
[Chemical formula 17]
[0036]

wherein R
1 and R
2 are H and l=2-12,
R1 is H, R2 is -CH3 and 1=2-12,
R1 is -C2H4S-, R2 is H and l=2-12, or
R1 is -C2H4S-, R2 is CH3 and l=2-12.
[Chemical formula 18]
[0037]
wherein R1 and R2 are H, l=1-2, m=1-6 and n=2-3, or
R1 is -C2H4S-, R2 is H, m=1-6 and n=1.
[Chemical formula 19]
[0038]

[Chemical formula 20]
[0039]
wherein l is 0, 1, 2 or 3,
R1 and R2 are H, -CH3, -C2H5, -C3H7 (straight chain) or iso-C3H7,
R1 is H and R2 is CH3, -C2H5, -C3H7 (straight chain) or iso-C3H7,
or
R1 is -C2H5 and R2 is -C6H5,
X is an anionic monodentate ligand and n=2-3.
[Chemical formula 21]
[0040]
wherein l is 0, 1, 2 or 3,
X is an anionic monodentate ligand and n=2-3.
[Chemical formula 22]
[0041]
wherein R is H and l=1-4, or
R is an alkyl group of 1-3 carbon atoms and l=1-4,
X is an anionic monodentate ligand and n=2-3.
[Chemical formula 23]
[0042]

wherein X is an anionic monodentate ligand and n=2-3.
[Chemical formula 24]
[0043]
wherein R is H, -CH3, -OCH3, -ON or -C6H5,
X is an anionic monodentate ligand and n=2-3.
[Chemical formula 25]
[0044]
wherein R is H, -CH3, -OCH3 and -OH,
X is an anionic monodentate ligand and n=2-3.
[Chemical formula 26]
[0045]

[Chemical formula 27]
[0046]

wherein m=1-12, X is an anionic monodentate ligand and n=2-3.
[Chemical formula 28]
[0047]

wherein R is an alkyl group (C=1-12).
[0048] As clearly seen in chemical structures 1-28, in these metal chelate compounds, at
least one coordinating atom is sulfur, which is chelated to at least one metal species
selected from among zinc, manganese, iron, molybdenum, tin and antimony. The metal
chelate compounds are hydrophobic fine particles, but at pH 8.0-13.0, they disperse
in water with anionic or non-ionic surfactants and are maintained as stable dispersions
in water. If the metal chelate compounds are instead made minute, they can be suspended
for relatively long periods without precipitation, even if a surfactant or the like
is not used, and a physical suspension also can be created by stirring or agitation.
Thus, an aqueous lubricant can be realized that does not require any oil or organic
solvent.
[0049] When the suspension or dispersion is coated onto either or both a metal material
surface and the molding side of a metal mold, a lubricating film is formed on the
coated surface. The lubricating film adheres well to the surface and does not easily
peel from the surface during plastic working of the metal material. It also has satisfactory
lubricating properties and effectively prevents seizing of the material and the mold.
This lubricant has the advantage of adhering well to the coated metal surface as long
as no oil is present on that surface, and also has the feature of not requiring preparatory
steps, such as degreasing and washing. In addition, the lubricant requires no special
management and can be recycled, so that the only management necessary is re-supply
of the consumed portion. Stringent washing is not required, even when electron beam
welding is performed after plastic working.
[0050] A number of methods can be used for the application, and for example, application
onto the surface of the material can be accomplished by any desired method, such as
immersion of the material in the lubricant, painting with a brush or spraying. For
application to the molding side of the mold, the method employed may be painting with
a brush, spraying or the like.
[0051] The lubricant-coated material or mold may be permitted to stand so that the lubricant
may naturally dry, but if necessary, it may be forcibly dried. The method employed
for forcibly drying the lubricant may be any desired method, such as exposure to hot
air, preheating the material or mold or drying by high-frequency heating. The extent
of drying can be adjusted, if necessary, to achieve total dryness or partial dryness.
The extent of drying can be adjusted, as desired, by varying the drying temperature
and drying time.
[0052] The metal chelate compound may be produced in solution instead of preparing the metal
chelate compound beforehand and adding it to water. That is, the lubricant used can
have one or more chelating agents in which at least one of the coordinating atoms
is sulfur, and adding thereto a salt, oxide or hydroxide of one or more metals selected
from among zinc, manganese, iron, molybdenum, tin and antimony and an anionic or non-ionic
surfactant. This type of lubricant can be used in exactly the same manner.
[0053] In the case of the metal chelate compounds represented by chemical structures 1-28,
chelate ligands, in which sulfur is a coordinating atom, may be coordinated to all
the coordination sites of the metals. Alternatively, chelate ligands, in which sulfur
is a coordinating atom, may be coordinated to only some of the coordination sites
of the metals, and other ligands, in which sulfur is not a coordinating atom, are
coordinated to the remaining coordination sites. Suitable examples of ligands in which
sulfur is not a coordinating atom are hydroxide ions, condensed phosphate, polycarboxylic
high molecular activators and/or polyoxycarboxylic acid. Chemical structures 1-28
also show compounds in which chelate ligands having sulfur as a coordinating atom,
as represented in the structures, are coordinated to only some of the coordination
sites of the metals.
[0054] When a phosphate film has been formed on the metal surface, and the metal is immersed
in an aqueous solution of any of the chelate ligands (the compounds adjacent to M
in the structures) represented in chemical structures 1-28, the chelate ligand having
sulfur as a coordinating atom coordinates with the zinc ion or iron ion present in
the phosphate film to produce a crystalline multi-ligand metal chelate compound on
the phosphate film, which results in a lubricating effect.
[0055] When a phosphate film has been formed on the metal surface, and the metal is immersed
in an aqueous solution of a metal chelate compound in which a chelate ligand having
sulfur as a coordinating atom is coordinated to only some of the coordination sites
of the metal, while other chelate ligands are coordinated to the remaining coordination
sites, a crystalline polynuclear chelate compound is produced on the phosphate film,
resulting in a lubricating effect.
[0056] When the lubricating film includes two or more different types of metal chelate compounds,
their lubricating effects are synergistic, so that a highly satisfactory effect is
achieved.
[0057] The lubricant described above forms a lubricating film by strong adhesion to surfaces
of primarily iron, especially steel and iron alloys, but it can also be used for non-ferrous
metals, such as aluminum.
[0058] Various additives, such as pH adjusters, viscosity controllers, preservatives, antifoaming
agents and the like may also be added to the lubricant. It is particularly preferred
to add soluble condensed phosphate salts, fatty acid sodium salts, fatty acid potassium
salts, soluble polycarboxylic high molecular activators and/or soluble polyoxycarboxylic
acid salts. These compounds increase the dispersability of the metal chelate compound
in water, and improve the adhesive strength of the lubricating film to the metal surface.
[0059] Experimental examples will now be explained.
[Experimental Example 1]
[0060] 150 g of zinc bis-(N,N-diethyldithiocarbamate) was added to a prepared solution of
20 g of sodium stearate in 100 ml of warm water and the mixture was gently stirred
to produce an aqueous lubricant.
[0061] The following examples are analogous as aqueous lubricants to this Experimental Example
1. The metal chelate compound is not limited to zinc bis-(N,N-diethyldithiocarbamate),
and it may be replaced with any of the species represented by chemical structures
1-28, such as N,N-dibutyldithiocarbamate oxymolybdenumsulfate.
[0062] Sodium stearate was used as the anionic or non-ionic surfactant in this experimental
example, but adjustment to pH 8.0-13.0 with any other well-known anionic or non-ionic
surfactants, such as sodium salts of fatty acids and/or potassium salts of fatty acids,
can effect adequate dispersion of the metal chelate compound in water. A similar aqueous
lubricant can be obtained by making the metal chelate compound fine, adding water
and stirring it to create a suspension.
[Experimental Example 2]
[0063] A 50 g/200 ml aqueous solution of zinc sulfate heptahydrate was added to a 78 g/300
ml aqueous solution of sodium N,N-diethyldithiocarbamate trihydrate, while stirring,
to prepare a suspension of zinc bis-(N,N-diethyldithiocarbamate). Separately, a suspension
was created by dispersing 100 g of N,N-dibutyldithiocarbamate oxymolybdenumsulfate
in a warm solution (500 ml) containing 20 g of sodium stearate, 20 g of sodium tripolyphosphate
and 20 g of a polycarboxylic high molecular activator. Both suspensions were mixed
together by stirring to obtain an aqueous lubricant.
[0064] The following examples are analogous as aqueous lubricants to this Experimental Example
2. In addition to the aqueous solution of sodium N,N-diethyldithiocarbamate trihydrate,
the aqueous solution of zinc sulfate hydrate that produces a metal chelate compound
may be replaced with another water-soluble zinc salt or zinc hydroxide compound. It
may also be replaced with a water-soluble salt of manganese, iron, molybdenum, tin
or antimony. Experimental Example 2 differs from Experimental Example 1 primarily
in using a metal chelate compound of two or more different metals and zinc and molybdenum
are used here. Any combination of two or more metals from among zinc, manganese, iron,
molybdenum, tin and antimony may be used. The chelate ligand used can be any of those
represented in chemical structures 1-28.
[0065] Sodium tripolyphosphate need not be included, but its addition will improve the dispersability
of the metal chelate compound. The polycarboxylic activator also need not be included,
but its addition will improve adhesion of the lubricating film to the metal. A soluble
polyoxycarboxylic acid salt may be added instead of a polycarboxylic high molecular
activator.
[Experimental Example 3]
[0066] A solution of 45.3 g of sodium N,N-diethyldithiocarbamate trihydrate and 8.5 g of
sodium hydroxide dissolved in 200 ml of water was slowly poured into a 57.8 g/300
ml aqueous solution of zinc sulfate heptahydrate while stirring to prepare a suspension
of zinc mono-(N,N-diethyldithiocarbamate)-hydroxoaqua.
[0067] Zinc mono-(N,N-diethyldithiocarbamate)-hydroxoaqua has a chelate ligand with sulfur
as a coordinating atom strongly coordinated to some of the coordination sites of zinc,
and sodium hydroxide ion weakly coordinated to the remaining coordination sites. Zinc
mono-(N,N-diethyldithiocarbamate)-hydroxoaqua can be dispersed in water with a sodium
fatty acid salt and/or potassium fatty acid salt, such as sodium stearate.
[0068] The following examples are analogous as aqueous lubricants to this Experimental Example
3. The chelate ligand having sulfur as a coordinating atom that chelates to some of
the coordination sites of the metal can be replaced with any desired ligand represented
in chemical structures 1-28. The sodium hydroxide ion that coordinates to the remaining
coordination sites can be replaced with any other desired hydroxide ion, except for
sulfur.
[0069] As in the above experimental examples, soluble condensed phosphate salts, soluble
polycarboxylic high molecular activators and/or soluble polyoxycarboxylic acid salts
may be added when necessary.
[Experimental Example 4]
[0070] 18 g/100 ml of sodium tripolyphosphate was slowly poured into a 57.8 g/300 ml aqueous
solution of zinc sulfate heptahydrate while stirring to prepare a suspension of a
zinc tripolyphosphate crystalline precipitate. 45.3 g/200 ml of sodium N,N-diethyldithiocarbamate
trihydrate was then slowly poured into the suspension, while stirring, to give a crystalline
precipitate of zinc mono-(N,N-diethyldithiocarbamate)-triphosphate (hereunder, "G").
[0071] Separately, a suspension was prepared by dispersing 100 g of N,N-dibutyldithiocarbamate
oxymolybdenumsulfate in a solution of 20 g of sodium stearate, 10 g of sodium tripolyphosphate
and 12 g of a polycarboxylic activator dissolved in 500 ml of hot water (hereunder,
"H"). G and H were mixed together by stirring to obtain a yellow dispersion that was
used as a lubricant.
[0072] The zinc mono-(N,N-diethyldithiocarbamate)-triphosphate has a chelate ligand, with
sulfur as a coordinating atom, strongly coordinated to some of the coordination sites
of zinc, and sodium tripolyphosphate weakly coordinated to the remaining coordination
sites via an oxygen anion. The species weakly coordinated to the remaining coordination
sites via the oxygen anion is not limited to a condensed phosphate, such as sodium
tripolyphosphate, and it may be replaced with a polycarboxylic high molecular activator
and/or polyoxycarboxylic acid.
[0073] Experimental Example 4 differs from Experimental Example 3 primarily in using a metal
chelate compound of two or more different metals, and zinc and molybdenum are used
here. Alternatively, any combination of two or more metals selected from among zinc,
manganese, iron, molybdenum, tin and antimony may be used. For two or more different
metal chelate compounds, they may both have chelate ligands, in which sulfur is a
coordinating atom, coordinated to some of the coordination sites of the metal, but
as explained above, either of the metal chelate compounds may also have a chelate
ligand with sulfur as a coordinating atom that coordinates to all the coordination
sites of the metal. The chelate ligand used can be any of those represented in chemical
structures 1-28.
[Experimental Example 5]
[0074] A metal material on which a phosphate film had already been formed was immersed in
a warm solution of 5% sodium N,N-diethyldithiocarbamate (pH 10), and the crystalline
multi-ligand zinc chelate compound produced on the phosphate film was used as a lubricant.
[0075] By adjusting the pH to a range of 6.5-13.5, the sodium N,N-diethyldithiocarbamate
(ligand with sulfur as a coordinating atom) coordinates with the zinc ion or iron
ion in the phosphate film to produce a crystalline multi-ligand zinc or iron chelate
compound on the phosphate film, thus forming a lubricating film. The chelate ligands
may be any desired ones represented by chemical structures 1-28.
[Experimental Example 6]
[0076] A mixed aqueous solution (150 ml) of 31 g of sodium N,N-diethyldithiocarbamate trihydrate
and 5.9 g of sodium hydroxide was slowly poured into 40 g/200 ml of zinc sulfate heptahydrate,
while stirring, to prepare a suspension of zinc mono-(N,N-diethyldithiocarbamate)-hydroxoaqua
(hereunder, "I") (pH 11.5-12.0). A metal material, on which a phosphate film had already
been formed, was immersed in I at 40-50°C and stirred for 30-60 seconds to produce
a crystalline polynuclear zinc chelate on the phosphate film, which was used as the
lubricating film.
[0077] A crystalline polynuclear zinc chelate can also be disposed on the phosphate film
by immersing the metal material with a phosphate film already formed thereon in any
of the lubricants obtained in Experimental Examples 1 to 4. The chelate ligand can
be any one represented in chemical structures 1-28, and it is particularly preferred
for a chelate ligand with sulfur as a coordinating atom to be coordinated to some
of the coordination sites of the metal and chelate ligands without sulfur coordinated
to the remaining coordination sites. In such cases, the sulfur-containing chelate
ligand coordinates with the metal while the non-sulfur-containing chelate ligand reacts
with the zinc ions or iron ions in the phosphate film to produce a crystalline polynuclear
metal chelate compound.
[0078] Each of the lubricants prepared in Examples 1-6 was coated onto the perforated side
of a perforated testing billet (for area reduction of 12%: a cylindrical member was
used and having an inner diameter of 15 mm, an outer diameter of 29.9 mm and a length
of 50 mm), and dried by exposure to 150°C hot air for 60 seconds. The time required
for this treatment was about 2 minutes.
[0079] For comparison, a phosphate film was formed on the same type of billet and a metallic
soap film was disposed on top of the phosphate film (Comparative Example 1). The time
required for this treatment was over 30 minutes.
[0080] For further comparison, a working oil (with lubricating adjuvant added) was coated
onto the same type of billet (Comparative Example 2). The time required for this treatment
was about 30 seconds.
[0081] Each of the billets was subjected to a ball-push test. This test measured the load
required for plastic deformation of a billet when an iron ball with a larger diameter
than the diameter of the perforation in the billet was forcibly pushed through the
billet perforation. The lubricating performance was evaluated based upon the surface
condition of the inner diameter of the billet. A smaller load indicates more satisfactory
lubrication, allowing smoother plastic deformation. The results (maximum loads) are
listed in the following table. In the table, the area reductions are the rates of
change in the billet perforations before and after deformation, with larger values
indicating a higher degree of deformation, i.e. heavy working. It will be appreciated
that better lubrication is achieved when the surface condition has no seizing or,
where seizing occurs, the length is shorter.
Values in table indicate loads (units: t) |
Area Reduction |
6% |
8% |
10% |
12% |
Treatment Time |
Exp. Example 1 |
19.625 |
NG |
NG |
NG |
2 min. |
Exp. Example 2 |
11.676 |
15.858 |
20.721 |
NG |
2 min. |
Exp. Example 3 |
13.930 |
16.710 |
NG |
NG |
2 min. |
Exp. Example 4 |
9.265 |
9.876 |
11.934 |
15.992 |
2 min. |
Exp. Example 5 |
10.176 |
13.945 |
17.116 |
20.174 |
2 min. |
Exp. Example 6 |
8.096 |
9.371 |
10.767 |
15.130 |
2 min. |
Comp. Example 1 |
8.383 |
10.128 |
14.068 |
18.060 |
30 min. |
Comp. Example 2 |
21.391 |
NG |
NG |
NG |
30 sec. |
[0082] In the table, NG indicates seizing between the iron ball and the billet, showing
that a satisfactory surface condition was not obtained. Not all of the experimental
examples of the invention were suitable for heavy working, but light working was possible
in all of the experimental examples, and satisfactory lubricating performance was
confirmed in all of the experimental examples, as compared with using oil. Heavy working
is also possible by appropriate selection among the lubricants of the invention.
[0083] These examples confirm that results comparable to Comparative Example 1 can be obtained
with adequate functionality by simple coating and formation of a lubricating film.
Because the treatment times were only about 2 minutes, treatment is possible within
a very short time. The performance difference was particularly notable in comparison
with Comparative Example 2, thus confirming that working is possible by these examples
even in cases in which working was not possible by Comparative Example 2.
Effect of the Invention
[0084] With the lubricating solution of the invention, effective lubricating films can be
formed by a simple application process, which films exhibit performance comparable
to that achieved by the troublesome and difficult procedure of forming phosphate films
and disposing metallic soap films on the metal object. Because the present invention
does not use oil, the problems of working environment contamination and the need for
subsequent degreasing treatment do not occur. Because a simple application is sufficient,
a solution is also provided to the problems of large equipment requirements and the
need to perform simultaneous treatment of large volumes of materials. Apparatus can
therefore be installed for formation of lubricating films in the narrow spaces adjacent
to the apparatus for plastic working of materials, forming the lubricating films in
sequence with the plastic working apparatus cycles without requiring extra storage
between the two treatments, so that it becomes possible to shorten lead times.