Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to an emulsion
with lubricating and cooling abilities, intended
for use at deforming metal working, mainly
machining by detachment of cuttings, but also
suitable for deepdrawing an~ rolling.
In machining by detachment of cuttings
like drilling, turning, milling, tapping and
grinding, cutting fluids based on mineral oil
products are usually used, mainly because of the
relative cheapness of the mineral oils. In most
cases, they consist of water emulsions, and to meet
the requirements of the metal working industryl a
long list of additives are used, e.g. EP-additives
to improve lubrication (EP = Extreme Pressure).
In recent years increased attention to
working environments and industrial safety has
created the need for a new type of metal working
fluid. Unsatisfactory working environments and
accompanying medical complaints are common problems
with the products used in the metal working
industry today. The mineral oil-based products
produce oil smoke and oil mist at the working
premises, as well as fouling in and around the
machines. The mineral oil and the additives used
can cause irritation of the skin, eczema and
allergic reactions. Risk of cancer is present on
prolonged skin exposure, and risk of lung damage is
present on inhalation of the oil smoke and the oil
mist. Lately there have been several reports on
the presence of carcinogenic substances in cutting
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fluids. Mineral oils contain polyaromatic
hydrocarbons, e.g. benzopyrenes. Because of the
high temperatures in the cutting zone, it is also
probable that polyaromatic compounds are formed
when the products are used.
Environmental control legislation imposes
heavy requirements on the metal working industry's
handling of waste water. The technology of
purifying spent emulsions and degreasing baths has
grown complicated, because product development has
resulted in the use of more and more additives and
more stable emulsifier systems. Consequently the
treatment of spent cutting fluids, mainly
emulsions, has become very troublesome and
expensive.
Smaller companies have to use specialized
waste disposal services and only the largest
companies have their own emulsion breaking plants,
which however don't always function satisfactorily.
The breaking of the emulsions results in a water
phase, which has to be treated further in
conventional sewage treatment plants, and an oil
containing sludge, which has to be disposed of, or
at the best is usable as a fuel. A reuse of the
oil is not an alternative. Consequently the
industry is very much in need of a new type of
cutting fluid, and the requirements on such a fluid
are extensive:
- to have minimal detrimental
effect on man and the
environment,
- to form very little oil smoke
and oil mist,
- facilitate an easy waste
treatment without disposal
problems,
- to be uncomplicated in
composition and with few
additives, and
- to be resistant to attack by
micro-organisms.
Fatty oils, i.e., vegetable oils and
animal oils and fats, are by function suitable raw
materials for lubricants, and have earlier been
used extensively before the cheaper mineral oils
came to completely dominate the market. Contrary
to mineral Gils, fatty oils are renewable,
proenvironmental and can be completely broken down
biologically.
For metal cutting or grinding, it is
generally advantageous to use a cutting fluid in
the form of a water-containing emulsion of the
oil-in-water type, through which an improved
cooling effect is achieved at the same time as the
lubricating effect of the oil part is retained.
Also, from an economic point of view, a water
emulsion is considerably more favorable.
These emulsions can be prepared in
ready-to-use concentrations, but from
transportation and handling aspects it is more
suitable to first prepare a concentrate, which
later can be diluted with water by the user - the
metal working industry.
The requirements for such a concentrated
emulsion are that the stability should be very
good, that it should be easily and unlimitedly
dilutable with water, and that it should be stable
as an emulsion even when diluted. To be able to
manufacture such an emulsion, one has to use
special emulsifiers (surface active agents).
Strong synthetic surfactants may be used, but
because of the health and environmental problems,
referred to above, these should be avoided.
The object of this invention is to
prepare a metal working emulsion, of the
oil-in-water type, based on triglyceride oils,
which is adequately stable, which can be
unlimitedly diluted, and which at the same time has
sufficiently good and lubricating properties,
compared to those products used today, without
having their undesirable environmental and health
aspects.
We have found that, surprisingly,
starting from triglyceride oils, one can prepare an
emulsion which fulfills the requirements of
stability and dilutability with aid of an
emulsifying system comprising fatty acid
monoglycerides and alkali soaps of fatty acids. By
using only "natural" and completely harmless
components the requirements of the product from
environmental aspects are fulfilled.
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To bring the lubricating and cooling
properties of the emulsion to the level of the
mineral oil based products, however, additional
components are required.
We have found that the use of an organic
amine, such as an alkanolamine, e.g.
triethanolamine, or a fatty amine, considerably
increases the wetting properties of the emulsion
and, thereby, its cooling effect. It has further
been shown, that the addition of free fatty acid to
the glyceride oil increases its lubricating
properties. In fact, the amine and the fatty acid
are believed to be present in the emulsion mainly
as their salts, i.e. as soaps.
The present invention is thus a metal
working emulsion consisting essentially of an oil
phase dispersed in a continuous water phase wherein
the oil phase comprises:
0.5 - 50 parts by weight of triglyceride
oil,
0.1 - 10 parts by weight of fatty acid
monoglyceride,
0.05 - 10 parts by weight of a fatty
acid, and
0.05 - 10 parts by weight of an
alkanolamine or a fatty amine;
and the water phase comprises:
0.05 - 3 parts by weight of an alkali
soap of fatty acids, and
45 - 98 parts by weight of water.
The larger amounts of fatty components
are used when preparing the emulsion concentrates,
which, as mentioned earlier are usually prepared at
the manufacturer's plant, and the lower amounts are
used when preparing the ready-to-use emulsions.
When preparing the oil phase the fatty
acid monoglyceride the fatty acid and the amine
are dissolved in the triglyceride oil at a
temperature of 40 - 70C. The wa~er phase is
prepared by dissolving the alkali soap at a
temperature of 20 - 70C, preferably at 20 - 40C.
The oil phase is slowly mixed into the
water phase, while stirring, at a temperature of 20
_ 50C.
For the preparation of the ready-to-use
emulsions it is thereafter enough with just
powerful agitation to obtain a stable emulsion,
while for the preparation of the emulsion
concentrate, homogenization of the product is
usually required. The homogenization is preferably
carried out at a temperature of 40 - 60C in a
conventional homogenizer.
The triglyceride oil may be animal or
vegetable oil, or oil mixture, which has a
solidifying point low enough to allow a convenient
handling of the emulsion in the concentrated as
well as the ready-to-use form, but which at the
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same time is mainly free from fatty acids like
linolenic acid to avoid oxidation and
polymerization difficulties. The oil should
therefore be preferably liquid at room temperature,
and have an oleic acid content of at least 40%.
Especially suitable oils, from a functional point
of view, are olive oil, peanut oil and lobra oil
(rapeseed oil with a low content of erucic acid).
Also the lowest melting fractions of fractionated
fats, like e.g. "palm olein", have been found
excellent for this purpose.
The fatty acid monoglyceride should be of
the so called "soft product" type, i.e. have a
melting point below 60C. The best product is pure
oleic acid monoglYceride, (mono-oleoglycerol), but
also other commercial products can be used, a~
1~ ~r~Je/n~(r~
Dimodan ~, a molecular distilled monoglyceride
manufactured by Grindstedvaerket, Denmark, from
edible, refined lard, with an approximate fatty
acid composition of 30% palmitic acid, 18% stearic
acid and 40% oleic acid.
It is also possible to use the so called
technical monoglYcerides, manufactured through
glycerolysis (glycerolesterification) of e.g. lobra
oil. Such products, with a content of 40-60%
monoglycerides, are easy to manufacture without
complicated equipment. and therefore of interest.
Of course, if such products are used, the ratio
between triglyceride oil to glycerolysis product
must be adjusted so that the content of
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monoglyceride in the emulsion is correct. The oil
soluble monoglyceride is used, primarily because of
its surface active properties, as the lipophilic
component of the emulsion system.
The surface activity also imparts a
wetting effect, through which the lubricating
effect of the oil increases.
The fatty acid is preferably oleic acid.
The requirements on this component are the same as
on the oil and the monoglyceride: to be liquid at
room temperature, that is to have a titer lower
than 25C, and not to contain substantial
quantities of more unsaturated homologues.
The fatty acid has shown to increase the
lubricating effect substantially. The presence of
fatty acid prevents the formation of odor at more
severe machining operations, which is believed
partly to result from the fatty acid's improvement
of the lubricating effect and partly to be
connected with the formation of soaps of amine and
fatty acid.
As alkanolamine, an amine with 2-4 carbon
atoms in the alkanol-part is preferred. Especially
suitable is triethanolamine, which as well as
having good wetting and rust-preventing properties,
also has the advantage of being dermatologically
harmless, which is also evident in its wide use in
cosmetic preparations.
The amine can also be based on fatty raw
materials, whereby the same good wetting and
rust-preventing properties can be achieved. Suitably a fatty
amine with 8 to 18 carbon atoms in the carbon chain can be
used; especially suitable is dodecylamine.
The fatty acid soap is suitably a sodium- or
potassium salt of a fatty acid with 12-22 carbon atoms, usually
16 or 18 carbon atoms (palmitic- or steraic acid). Potassium
stearate gives slightly better results than does sodium
stearate, but if stearic soaps are to be used, de-ionized
water must be used to prevent flocculation of calcium and
magnesium soaps. When using oleic acid soaps (sodium or
potassium) this problem is fully avoided, although when
manufacturing the concentrate it is advisable to use de-ionized
water.
In metal working operations with very heavy contact
pressure, the lubricating properties of the metal working
emulsion can, if needed, be further increased by adding a
slightly chlorinated and/or sulfurized triglyceride oil. These
components are well compatible with the metal working emulsion
according to the invention. Preferably 20-40% of the
triglyceride oil is replaced by such components at extremely
heavy operations.
To prevent problems with oxidation and polymerization
an antioxidant can possibly be added. Suitable antioxidants
are butyl hydroxyanisole, BHA, and butyl hydroxytoluene, BHT.
C, _g_
Advantageously e.g. Eastman Kokak's products Tenox (a trade mark)
2 or Tenox 6 (a trade mark) can be used. These agents are
suitably added in an amount o~ 0.1-1.0 percent by weight to the
concentrated emulsion.
Under the unfavorable conditions encountered in the
workshop environment, attack by micro-organisms can easily take
place. If these micro-organisms are allowed to develop
uncontrolled for a sufficiently long time, an unpleasant odor
may develop. Also, the corrosion inhibiting properties of
the emulsion may decrease through the formation of acid
degradiation products in the same way as takes place when using
traditional mineral oil based products. This is avoided by
adding a bacteria controlling agent to the metal working
emulsion. A formaldehyde releasing agent can be used e.g.
~rotan BK, (a trade mark) which is manufactured by Schulke
Mayr GmbH.
Thus, the product manufactured according to the
invention offered from the user's point of view a long list of
advantages:
The product is completely based on fatty oils or
components of these. These oils are renewable, proenvironmental
and bio-degradable.
The occurrance of skin irritation, eczema and allergic
reactions can considerably be reduced, and the risk of cancer
can be removed.
Because of the higher molecular weight of the
triglyceride oils, and the considerably lower vapor pressure
in connection therewith, no
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troublesome oil smoke will be formed. Generally
this means a considerably cleaner working
environment.
Products based on fatty oils present no
difficulty from the standpoint of waste treatment.
By using known proper separation techniques the
fatty phase can easily be separated, and the
remaining water doesn't require any special
cleaning before discharge. The fatty phase can
10easily be separated by hydrolysis with known
techniques, and the recovered fatty acids can be
reused.
The invention is further illustrated by
the following examples:
Example 1. Preparation of a metal
working emulsion in concentrated form.
Oil phase: 34.7 parts by weight of palm olein
4.9 parts by weight of
monoglyceride Dimodan S
202.7 parts by weight of
rapeseed fatty acids
2.7 parts by weight of
triethanolamine
Water phase: 1.1 parts by weight of sodium
oleate
5~0 parts by weight of de-ionized
water
The palm olein was a low melting fraction
of palm oil. The content of oleic acid in the palm
30 olein was 50%.
The components of the oil phase were
mixed at 60-70C. The soap was dissolved in water
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8~
at 25C, after which the oil phase was added slowly
and while stirring to the water phase. The
dispersion so obtained was thereafter homogenized
at 50C in a homogenizer of conventional type.
The emulsion concentrate could be diluted
easily and unlimitedly with water of various
hardness (0-12dH). Both the emulsion concentrate
and the diluted emulsions were stable during
storage, i.e., the oil not having a tendency to
separate.
The product was tested in a dilution 1:10
in a multiple-spindle drilling machine in
production, where the working operation was tapping
in aluminum. After 1 month of working the function
of the emulsion was unchanged, and completely
comparable with the function of a conventional
mineral oil based emulsion.
Example 2. A metal working emulsion
was prepared for testing in a heavy loaded
numerically controlled automatic lathe. Many
iron-metals, e.g. cast iron and hardened tool-steel
were worked by tools with a cutting edge of hard
metal. The metal working emulsion was prepared as
follows:
Oil phase: 27.9 parts by weight of rapeseed oil
11.7 parts by weight of technical
monoglyceride from rapeseed oil
2.7 parts by weight of rapeseed
fatty acids
2.7 parts by weight of
triethanolamine
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0.4 parts by weight of an
antioxidant, Tenox 6
Water phase: 1.1 parts by weight of sodium
oleate
55.0 parts by weight of de-ionized
water
The rapeseed oil was of the low erucic
acid type with an oleic acid content of 52%. The
technical monoglyceride had a content of 40~ actual
monoglyceride. The components in the oil phase
were mixed at a temperature of 40-50C. Thereafter
the oil phase was added slowly, while stirring, to
the water phase. The dispersion obtained was
homogenized at 50C in a conventional homogenizer
equipment.
The emulsion concentrate obtained in this
way was diluted 1:15 in tap water and tested in an
automatic lathe. After 3 months of running the
function of the metal working emulsion was
unchanged. The worked parts showed no tendencies
of corrosion. The metal working emulsion caused no
drying coatings; on the contrary, the machine
surfaces were very easy to keep clean.
Example 3. This example is intended
to illustrate the improved lubricating effect
imparted to the emulsion by the fatty acid.
Two metal working emulsions in
ready-to-use concentration were prepared for
testing in a cylinder-grinding machine. The metal
working emulsions were prepared from the following
components:
1~5684
Sample A Parts by Weight
Oil Phase:
rapeseed oil 2.00
technical monoglyceride
from rapeseed oil0.78
triethanolamine 0.18
Water Phase:
sodium stearate 0.10
de-ionized water 97
Sample B Parts by Weight
Oil Phase:
rapeseed oil 1.80
technical monoglyceride
from rapeseed oil0.78
rapeseed fatty acid0.20
triethanolamine 0.18
Water Phase:
sodium stearate 0.10
de-ionized water 97
The rapeseed oil was of the low erucic
acid type with an oleic acid content of 60%. The
technical monoglyceride had a content of 40% actual
monoglyceride.
The components in the oil phase were
mixed at 40-50C, and the sodium stearate was
dissolved in the water phase at 60-70C.
Thereafter the oil phase was added slowly to the
water phase while stirring intensively, whereby a
stable emulsion was obtained.
The metal working emulsions prepared in
this way were tested in a cylinder-grinding machine
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by working hardened tool-steel. It was found that
regarding the surface fineness of the material, as
well as the relative wear of the abrasive wheel,
sample B (with fatty acid addition) gave better
results than sample A (without fatty acid
addition). On the average, the surface fineness
was 10% better and the relative wear of the
abrasive wheel 30~ lower with sample B than with
sample A. The results were completely comparable
with those obtained when using conventional mineral
oil based emulsions without EP-additives.
Example 4. This example is intended
to illustrate the improved wetting function
obtained by adding triethanolamine to the emulsion.
Two emulsion samples were prepared
according to the same process as in Example 3:
Sample A Parts by Weight
Oil Phase:
rapeseed oil 3.50
monoglyceride of oleic acid 1.00
triethanolamine 0.50
Water Phase:
sodium stearate 0.10
de-ionized water 95
Sample B Parts by Weight
Oil Phase:
rapeseed oil 4.00
monoglyceride of oleic acid 1.00
Water Phase:
sodium stearate 0.10
de-ionized water 95
The rapeseed oil was of the low erucic
acid type with an oleic acid content of 60%.
Measurements were made of the wetting
capacity of these emulsions on steel surfaces. It
was hereby found that emulsion sample B (without
triethanolamine) gave a wetting angle of 40-45,
and emulsion sample A (with triethanolamine) gave a
wetting angle of 15-20. This latter result was
even somewhat better than what is obtained with
10conventional mineral oil based emulsions.
Example 5. A metal working emulsion
was prepared according to Example 1 with the
following ingredients.:
Oil phase:34.3 parts by weight of palm olein
4.8 parts by weight of
monoglyceride Dimodan S
2.7 parts of weight of rapeseed
fatty acids
5.4 parts by weight of
triethanolamine
Water phase: 1.1 parts by weight of sodium
oleate
55.0 parts by weight of de-ionized
water
The metal working emulsion was tested for
a longer period of time in a numerically controlled
machine tool for drilling and tapping. In the
machine toughened steel was worked with high speed
tools.
3~The machining results were compared to
those obtained when a conventional cutting fluid of
-16-
s~
the emulsion type with EP-additives was used. The
conventional cutting fluid was especially intended
for heavy machining like drilling, tapping, thread
cutting and deep drawing in different iron
materials. Both cutting fluids were used in the
same dilution, about 15 times, with ordinary tap
water.
The surface smoothness of the worked
parts was equal for the conventional cutting fluid
and for the cutting fluid according to this
invention. The lifetime of the tools for the
drilling operation was equally good. For the
tapping operation the lifetime with the cutting
fluid according to this invention was even somewhat
better than with the conventional cutting fluid.
