Compositions – Heat-exchange – low-freezing or pour point – or high boiling... – Organic components
Reexamination Certificate
2001-07-18
2003-07-15
Kopec, Mark (Department: 1751)
Compositions
Heat-exchange, low-freezing or pour point, or high boiling...
Organic components
C252S071000, C252S079000, C508S110000, C508S431000
Reexamination Certificate
active
06592775
ABSTRACT:
Present invention relates to an aqueous metalworking liquid containing a non-ionic polypropylene glycol compound and an anionic compound, which is selected from the group consisting of a phosphate ester and an ether carboxylate, and contains alkyleneoxy groups. The metal working liquid has excellent lubricating properties and it can also easily be worked up and reused without leaving troublesome coatings on the metal surfaces.
Metal working operations are often performed in the presence of aqueous cooling lubricants containing ethanolamines, such as monoethanolamine, diethanolamine and triethanolamine, as a corrosion inhibitor. However, ethanolamines have a limited lubricating ability and cause in addition dissolution and/or discoloration of many metals, such as cobalt, copper and aluminium. The dissolved metals also constitute a troublesome environmental problem.
In order to diminish the negative effects of ethanolamines, anionic surfactants having long aliphatic groups, such as groups containing 14-44 carbon atoms, have been added. Example of such surfactants are phosphate esters, fatty acids and dimeric acids. Their protective effect depends on the formation of water-insoluble, organic layers on the metal surfaces. However, if dissolved di- or trivalent metal ions are present in the cooling lubricant, then the anionic surfactants and these metal ions will form water-insoluble salts. In some cases this could further increase the corrosion inhibiting effect, but it can also in other cases result in the formation of sticky precipitates, which for example make it more difficult to work up the cooling lubricant. Another disadvantage is the fact that the hydrophobic layers formed on the metal surfaces are difficult to remove. Unless they are removed they will cause problems in the subsequent operations, for example pickling, phosphatizing, galvanizing or other metal depositing processes. The presence of the long chain anionic components may also cause undesirable foaming and scum.
U.S. Pat. No. 4,315,889 discloses a method of reducing the release of cobalt by performing the metal working in the presence of a cooling lubricant containing, as an active component, a specific triazole or thiadiazole compound. However, since these active compounds are consumed in the presence of ethanolamines, the aqueous cooling lubricant has to be regularly upgraded.
EP-A-0180561 describes the use of a tertiary alkanol amine compound for reducing the release of cobalt. According to the application the tertiary alkanol amine compound can advantageously be combined with carboxylic acids for further protection against the release of cobalt and the corrosion of iron. Although this combination improves the properties of the cooling lubricant it is not a fully satisfactory solution on the earlier mentioned problems.
The aim of the present invention is to provide an aqueous metalworking liquid, which does not form precipitates that are sticky or difficult to remove from the metal working liquid. At the same time the metal working liquid must be easy to upgrade and to reuse, exhibit excellent lubricating and have good anti-corrosion ability.
Surprisingly, it has now been found that these aims can be met by an aqueous metalworking liquid, which has the form of a clear solution at 20° C., is in the form of a precipitate at a temperature higher than 20° C. and contains
a) a non-ionic polypropylene glycol compound containing 6-100, preferably 10-50 propyleneoxy groups, and lacking the presence of hydrocarbon groups having more than 12 carbon atoms, and
b) at least an aqueous anionic compound selected from the group consisting of a phosphate ester or an ether carboxylate, both of which containing 1-40 alkyleneoxy groups, preferably 4-20 alkyleneoxy groups, having 24 carbon atoms, and lacking hydrocarbon groups having more than 12 carbon atoms.
According to the invention it has been found that the polypropylene glycol compound and the anionic compounds co-operate in the metal working process, if the temperature of the metal working liquid exceeds the cloud point. Under this condition the compounds are precipitated together and a synergistically improved lubrication is obtained. Normally the cloud point is not over 60° C., preferably not over 40° C., since it is valuable to be able to perform the metal working processes at a low temperature and secure both excellent lubrication and effective cooling. Suitably, the contents of the polypropylene glycol compound and the anionic compounds are 0.2-5% by weight. The metalworking liquid can suitably be used in metal removing operations, such as drilling, milling, turning, grinding and thread forming, and in metal forming operations, such as rolling, deep drawing, press turning and thread forming.
The metalworking liquid according to the invention has a relatively high critical micelle concentration (CMC), which means that the contents of the lubricating components can be kept on a relatively high level without exceeding CMC. Contents below the CMC of the lubricating components also result in a low emulsification of leak oils from the working machine. The oils can easily be removed together with other water-insoluble impurities in a manner known per se at a temperature below the cloud point of the metal working liquid. Therefore, the metal working liquid preferably contains the lubricating components in a content of 50-100% by weight of CMC of the mixture at the working temperature of the liquid.
The working up of the metal working fluid can be done, for example by filtration or centrifugation. One suitable method is to filtrate the liquid through a hydrophilic regenerated cellulose membrane having a pore size letting through linear polymer compounds with molecular weights of below 100 000. The leak oil can usually be completely removed, if the pore size of the filter does not exceed 0.1 micrometer. Other suitable membranes are hydrophobic membranes made of organic fluoro polymers and hydrophilic membranes made of polysulphones or ceramic materials.
It is also possible to clean the liquid from water-soluble impurities, such as salts, by performing the cleaning process at a temperature above the cloud point of the liquid and remove at least a part of the water and the impurities dissolved therein from the precipitated lubricating compounds. Since the metalworking fluid can be effectively cleaned, the demand for biocides, corrosion inhibitors and complementary additions of lubricating compounds is reduced. At the same time the life time of the metal working fluid is prolonged and the environmental problems reduced.
Suitable polypropylene glycol compounds to be used in the metal working liquid are compounds of the formula
RO(AO)
n
H (I),
in which R is hydrogen or a hydrocarbon group having 1-12 carbon atoms, preferably 1-8 carbon atoms, AO is an alkyleneoxy group having 2-3 carbon atoms, at least 50% of all the alkyleneoxy groups being propyleneoxy groups, and n is a number from 6-100, preferably from 10 to 50. Preferred polypropylene glycol compounds are polypropylene glycol having a molecular weight of 700-3 000 and glycol compounds having a molecular weight of 750-4 000, containing both ethyleneoxy groups and propyleneoxy groups, and in which R in formula I is hydrogen.
The phosphate ester, which also has anti-corrosion properties, suitably consists of compounds of the formula
R
1
(oxyalkylene)
p
OP(O)(X)(OH) (II), or
(HO)
2
(O)P-(oxyalkylene)
q
—OP(O)(OH)
2
(III),
in which R
1
is an alkyl group having 1-12 carbon atoms, oxyalkylene is a group having 2-4 carbon atoms, p is a number from 1-20, preferably 4-15, X is hydroxyl, R
1
O or R
1
(oxyalkylene)
n
O, where R
1
, oxyalkylene and n have the meanings mentioned above, and q is a number from 4-40, preferably 5-20; or a preferably monovalent salt thereof. The (oxyalkylene)
p
group and the (oxyalkylene)
q
group in the phosphate esters of formula II and formula III, respectively, are suitably chosen in such a manner that the phosphate esters become water-soluble in water of 20° C. T
AB Chem Dimension
Hamlin D G
Kopec Mark
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