Note: Descriptions are shown in the official language in which they were submitted.
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I~HERENTLY BACTERICIDAL M~TAL WORKING FLUID
Background of the Invention
This invention relates to metal working fluids.
More particularly, this invention relates to aqueous metal
working fluids having inherent anti-bacterial properties.
A number of materials have been utilized to
stabilize aqueous metal working fluids from bacterial
attack. The combination of substituted nitroperilines and
organic acids is disclosed in U.S. Patent 3,826,746.
~ U.S. Patent 3,265,620 describes an aqu~ous
cutting fluid utilizing sodium benzoate, triethanolamine,
EDTA, henzotriazole and watern Pelargonic acid is
described as an additive which can be used to reduce pH
and improve lubricity.
~ U.S. Patent 2,621,159 describes metal working
lubricants which can include naturally occurring fatty
acids.
; U.S. Patent 3,719,598 describes a metal working
fluid based on boric acid optionally containing amine
fatty acid salts, the fatty acid having from 18 to 22
carbon atoms. ~i
U.S. Patent 3,969,236 describes various
compositions containing monoalkanola~ide borates. These
matsrials are disclosed for a variety of reasons,
including use as a mold growth inhibitor for paints and
varnishes.
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U.S. Patent 4,039,462 describes a synthetic
aqueous lubricant prepared by condensing alcoxylated
primary amines, monobasic acids and dibasic acids.
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Brief Description of the Invention
It has been found that the synthetic aqueous
metal working fluids of the present invention have
inherent antibacterial properties, high lubricity, low
foaming, rapid dropping of fines, oil rejection, and
excellent corrosion inhibition for ferrous metals. These
compositions include boric acid, an alkali tetraborate,
pelargonic acid, a nonionic surfactant and water.
Objects and Advantages
It is the primary object of the present invention
to provide an aqueous synthetic metal working fluid having
excellent lubricating properties suitable for use in
central systems.
It is a further object of the present invention
to provide an aqueous synthetic metal working fluid which
is inherently antibacterial.
It is a still further object of the present
invention to provide a synthetic metal working fluid
having good corrosion inhibition properties.
It is a still further object of the present
invention to provide a synthetic metal working fluid
having high lubricity.
It is a still further object of the present
invention to provide a synthetic metal working fluid which
is low foaming and does not emulsify oil.
It is a still further object of the present
invention to provide a synthetic metal working fluid which
quickly drops fines.
Still further objects and advantages o~ the
compositions of the invention will become apparent from
the following more detailed description.
Detailed Description of the Invention
The present invention relates to a synthetic
metal working fluid composition co~tprising from about 1-5%
by weight of pelargonic acid, from about 5-~0% by weight
of a lower alkanolamine, from about 1-5% by weight of a
borate selected om sodium tetraborate, potassium
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tetraborate and mlxtures thereof, ~rom about 1-20~ by
weight of boric acid, from about 1-5% by weight of a
nonionic surfactant, and the balance of the composition
comprising water.
As used in the instant specification and the
following claims, the term "lower alkanolamine" means an
alkanolamine having from 1 to 4 carbon atoms.
The above composition i5 designed to be utilized
as a synthetic metal working 1uid. Metal working fluids
have a variety of uses including grinding, cutting and
other metal forming operations. In order to be useful in
large metal working establishments utilizing a central
system, i.e. a central sump or tank which supplies metal
working fluid to a variety of metal working machines, the
composition must be stable to all foxms of bacterial
contamination, must have excellent lubricity, low foaming
and good corrosion inhibition for all types of metals.
Especially for central systems, compatability for
a variety of metals is important as a variety of metals
may be worked. Likewise, good separation of oil, i.e.
poor emulsification of oil, is important so that tramp oil
can be removed from the system and disposed of properly.
Bacterial contamination is a problem for aqueous
metal working fluids because the bacteria destroys the
lubricity of the composition and changes the pH rendering
the fluids useless after a short period of time.
Typically, metal working fluids are stabilizing against
bacterial attac~ by including a biocidal agent. Although
these agents are quite e~fective, it is an advantage if no
such agent need be added to the system for a variety of
reasons, such as cost. Therefore, it i5 desirable to
prepare metal working and other compositions which are
inherently biocidal and resist attack by bacterial
contamination.
The compositions of the present invention
inherently resist bacterial contamination when combined as
described below. Both the pelargonic acid, as the
potassium salt and borate lubricants have some bacterial
properties. Neither of these materials by themselves are
sufficiently bacteriacidal to be used without added
biocides~ In fact, if the aqueous composition does not
inclade the pelargonic acid, the borax, the nonionic
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surfactant and the boric acid, the composition will nat
resist bacterial contamination. Furthexmore, the
lubricating properties of these compositions alone are
inferior to the lubricatiny property of the combined
composition.
The metal working fluids are formed by mixing the
pelargonic acid, boric acid and the lower alkanolamine.
These materials react in situ to form pelargonic saltæ of
the alkanolamine and borate salts of the alkanolamine.
The salts formed are simple and complex salts of these
materials. As it is difficult to determine the exact
composition of these salts, the compositions of the
present invention will bè described in terms of the
starting materials~
As indicated above, the compositions of the
present invention should include from about 1-5~ of
pelargonic acid. At amounts of less than about 1% the
effects of the pelargonic acid are not evident~ while
beyond about 5%, no increase in effect is noticed. The
pelargonic acid functions as a lubricating agent and in
combination with the other components provides biocidal
activity.
The compositions also include from about 5-20~ by
weight of a lower alkanolamine, such as monoethanolamine,
diethanolamine, triethanolamine, isopropanolamine~ etc.
The amine acts as a base to form the pelargonic acid amine
salt and the boric acid amine salt. The amine provides
corrosion inhibition, neutralizes the two acids present in
the composition to provide the amine salts and gives the
composition a basic pH.
The composition also includes from about 1-5% of
a tetraborate. The tetrahorate can be sodium tetraborate,
also known as borax, potassium tetraborate and mixtures
thereof. The sodium tetraborate can be used in the for~
of sodium tetraborate decahydrate or sodium tetraborate
pentahydrateO A preferred source of sodium tetraborate is
native borax. The preferred borate is sodium
tetraborate~ Th~ borax is present in the composition as a
buffer, as a corrosion inhibiter and as an antimicrobial
agent.
The composition of the present invention also
lnclude~ from a t 1-20~ hy weight of boric acid The
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boric acid provides corrosion inhibition lubricity and
antimicrobial effects.
- The composition of the present invention also
includes from about 1-5~ by weight of a nonionic
surfactant. This surfactant should have an HLB of from
about 5 to 11 and a cloud point greater than 50 C. The
HLB is important as the surfactant should not form an
emulsion of oil in the composition. It is important that
oil be easily separable from the metal working fluid for
easy oil reclamation. Further, the cloud point is
important so that the composition is stable during
storage. Preferred materials àre high molecular weight
block polyethers of propylene oxide and ethylene oxide,
and propylene oxide, ethylene oxide and pentaerythritol.
The surfactants act to defoam the composition and certain
nonionic surfactants provide additional lubricity.
The compositions of the present invention are
aqueous compositions and include a substantial percentage
of water. Also, the compositions are designed to be
diluted with water on site and are sold as a concentrate
to be diluted. The compositions of the present invention
- maintain their corrosion inhibition and lubricating
- properties when diluted at ratios of up to 70:1 parts
water per part metal working fluid. The composition has
biocidal properties at dilutions of from 15:1 to 40:1.
The operable dilution of the composition is within the
range of 15:1 to 100:1 parts water per part metal working
fluid. The preferred dilution is within the range of from
15:1 to 50:1.
The composition of the present invention also can
include small amounts, i.e., from about 0.1-0.5~ of
various nonferrous corrosion inhibitors such as 2-methyl
benzotriazol, benzotriazol, etc. These materials can be
included to help reduce corrosion for the nonferrous
portions of the metal working equipment and promote
compatability of the composition with a wide variety of
metals. Also, the composition can include from 0 to 0.5
by weight of a chelating agent such as tetrasodium EDTA,
~TA, tripotassium EDTA and the like and preferably from
0.1 to 0.5~ ~y weight. These chelating agents maintain
the solubility of the compositions in hard water which may
be used r di1ution to the workirlg concentration. Tbe
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composition can also contain up to 10~ of a glycol solvent
such as ethylene glycol, hexylene glycol, propylene
glycol, glycerine, the polyols such as carbowax~ These
glycols help resolublize the formula and prevent excessive
film formation on the tool.
The composition of the present invention will no~
be illustrated by the following examples wherein all parts
and percentages are by weight and 211 temperatures in
degrees celsius.
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EXAMPLE 1
A metal working fluid was prepared by dissolving
11 parts by weight boric acidl 3 parts by weight sodium
borax, 3.5 parts by weight pelargonic acid in 63~29 parts
deionized water. To this aqueous system 16 parts by
weight of monoethanolamine is added followed by 3 parts by
weight of HOE 2328, a nonionic surfactant available from
American Hoechst ~a block polymer based on ethylene oxide,
propylene oxide and pentaerythritol). At this point 0.01%
dye and 0.2% of 2-methylbenzotriazol is added. The
composition has a pH of 10.51.
This composition, when challenged hy bacteria
samples, did not sustain bacterial growth. Furthermore,
this composition performed suitably in a variety of single
point turning operations. This composition, in dilutions
of 50:1, had 0% corrosion and 70:1 had 10~ corrosion
utilizing the Herbst corrosion test. The composition had
bactericidal properties at dilutions of from 20:1 to 40:1
when tested according to ASTM, New Standard for the
Evaluation of Anti-Microbial Agents in Aqueous Metal
Working Fluids, as published by Subcommittee E-35.15.
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EXAMPLE 2
A metal working composition was prepared by
reacting 11 parts boric acid, 16 parts monoethanolamine, 3
parts sodium borax and 3.5 parts pelargonic acid at 110
C. This mixture was cooled to 90 C. and 63.3% part per
weight water, 0.2 parts 2-methylbenzotriazol and 3 parts
HOE 2328 are added. This composition has a pH of 10.39
and when diluted at 50:1 had 0% corrosion, while 70:1 had
20-30% corrosion. This composition had lubricating and
bactericidal properties as in Example 1.
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EXAMPLE 3
Using the procedure of Example 1, the following
formulation was prepared:
Boric Acid 11.0
Potassium Tetraborate3~0
Pelargonic Acid 3.5
: Monoethanolamine 16.0
2-Methylbenzotriazol 0.2
Genopol PN-30 3.0
Dye 0.01
Water 63.29
This composition was essentially similar in
performance to that of Example 1.
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: EXAMPLE 4
The following formulation was prepared using the
procedure of Example 1:
Boric Acid 11.0%
Sodium Borax 3.0
: Pelargonic Acid : 3.5
Monoethanolamine 16.0
2-Methylbenzotriazol 0.2
HOE 2823 3.0
Ethylene Glycol 6.0
Dye 0.01
Water 57.29
This composition had a pH of 1~.4 and performed
in a manner similar to Example 1 and left a softer film
: residue.
