Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-10-26
2002-05-21
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S045000, C528S059000, C528S074500, C525S453000, C428S375000
Reexamination Certificate
active
06392000
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a binder for a coating composition for enamel-insulated electrical conductors which is suitable for use as a lubricant.
In the manufacture of magnetic windings in electrical equipment, such as motors and transformers, electrical conductors coated with an insulating enamel are used. In order to improve processing of the enamelled wires on fast winding machines, the surface of the enamelled wire is coated with a lubricant. The lubricant is generally applied to the enamelled wire directly after it leaves the enamelling stove, and once the solvent has evaporated it forms a coating with good sliding capacity.
Known lubricants are paraffins and waxes applied to the enamelled wire with felts, for example as a 0.5 to 2% solution in an aromatic solvent.
U.S. Pat. No. 5,254,408 mentions, for example, the following organic lubricants: polyolefin hydrocarbons, such as polyethylene, polypropylene or polymethylene pentene. However, when used in motors running in coolants based on fluorocarbons, they can cause the nozzles to clog.
DE-A 195 17 199 and WO 93/0379 describe lubricants based on fatty acid esters or fatty acid amides which are readily soluble but not suitable for certain applications. For example, in enclosed relays they may shorten the service life of the contacts.
Furthermore, so-called internal lubricants are known. Lubricants of this type are incorporated into the composition of the wire enamel and migrate to a greater or lesser extent towards the enamel surface during curing. Examples of internal lubricants are the compounds mentioned above, such as polyethylene, polypropylene and polypropylene glycol and polytetrafluoroethylene and silicone oils, corresponding to EP-A 103307, EP-A 104986 and DE-A 195 15 263. The limited compatibility of these modifications usually results in phase separation, agglomeration or precipitation during storage.
EP-A 72178 describes modifications of wire enamel binders having hydrocarbon chains longer than 21 carbon atoms. The resulting enamel compositions are applied to the wire as the topcoat and cured. The disadvantages here are that the condensation into a wire enamel binder means that only small amounts of active substance are possible and it becomes difficult to align the hydrocarbon chains with the enamel surface. In particular with modern high-capacity enamelling plants, in which curing takes place extremely rapidly, the alignment of the active substance component with the surface of the enamel cannot be achieved to a satisfactory level.
SUMMARY OF THE INVENTION
The present invention provides a binder for a coating composition for enamelled wires which is suitable for use as a lubricant, is generally readily soluble, is highly efficient and does not have any disadvantageous effect on the technical parts connected to the magnetic windings, such as contacts and the like, so that it can be used for coating enamelled wires without any limitations and independently of the intended use thereof.
This binder is based on a structural block polymer of aliphatic monocarboxylic acids, polyisocyanates, polycarboxylic acids and/or polyalcohols, in which the individual components of the block polymer are in the form of structural blocks comprising A and B, C and D and E and F and the block polymer comprises any of the following structures: structural blocks A and B and at least one of the structural blocks C and D or E and F or structural blocks A and B and both structural blocks C and D and E and F and where the block polymer has free and/or blocked isocyanate groups; the structural blocks of the block polymer are prepared from:
A aliphatic, saturated or unsaturated, linear or branched monocarboxylic acids having 15 to 50 carbon atoms,
B aromatic and/or aliphatic polyisocyanates having at least 2 isocyanate groups,
C aromatic and/or aliphatic polycarboxylic acids having at least 2 carboxyl and/or anhydride groups,
D aromatic and/or aliphatic polyisocyanates having at least 2 isocyanate groups which may be the same as or different from B,
E polyalcohols having at least 2 hydroxyl groups, and
F aromatic and/or aliphatic polyisocyanates having at least 2 isocyanate groups which may be the same as or different from B and D, and
in which the composition of the block polymer corresponds to the following definition:
(
f+g
)/
h
=0.5 to 1.0
i
/(
h−f−g
)=2.0 to 25.0
a
/(
c+e
)=0.1 to 1.0
where a=total moles of A, c=total moles of C, e=total moles of E, f=total equivalents of hydroxyl groups, g=total equivalents of carboxyl and anhydride groups, h=total equivalents of isocyanate groups, i=total moles of A to F.
DETAILED DESCRIPTION OF THE INVENTION
In the structural block polymer used in this invention, blocks comprising A and B are called AB below, and analogously the structural blocks comprising C and D are called CD and E and F are called EF. The block polymer comprises polymers of the structure AB—CD, AB—EF and AB—CD—EF.
Preferably, the ratios (f+g)/h should be 0.6 to 0.9 and i/(h−f−g) should be 2.5 to 10.
To manufacture the block polymer according to the invention, preferably first the reaction of at least one monocarboxylic acid A with at least one polyisocyanate B is carried out to give the structural block AB.
The structural block CD can be manufactured at the same time as or after formation of the structural block AB. For this, at least one polycarboxylic acid C is reacted with at least one polyisocyanate D, with the release of carbon dioxide and the formation of amide or imide groups.
In a subsequent reaction stage, the structural block EF can be incorporated by reacting at least one polyalcohol E with at least one polyisocyanate F and the still free isocyanate groups of AB and where appropriate CD.
The conversion reactions between the polyalcohols and polyisocyanates can be accelerated by using conventional catalysts for urethane formation. Suitable catalysts are for example tin or zinc compounds.
The reactions described can be carried out at temperatures in a range between 50 and 150° C.; for example, the reaction between A and B can be carried out in a range from 80 to 150° C.
The end of the reaction can be established for example by IR spectroscopy, or by the amount of carbon dioxide evolved, or by determining the isocyanate groups, or by the subsiding of the exothermic action when reacting polyisocyanates and polyols.
The result is a block polymer having free isocyanate groups, in which the remaining free isocyanate groups can where appropriate be blocked by the addition of conventional capping agents for isocyanates.
The resulting block polymer can be diluted to processing consistency using conventional solvents. Preferably, inert solvents are used for this, or solvents which are used as blocking agents, such as technical cresols, are used.
Further examples of solvents used for diluting include conventional solvents used for wire enamels such as N-methyl pyrrolidone, dimethyl formamide, dimethylacetamide, technical cresol s and the known glycol ether diluting agents, such as methyl glycol-tert.-butyl ether, ethyl glycol-tert.-butyl ether, methyl diglycol-tert.-butyl ether, and esters such as methoxypropyl acetate and ethoxypropyl acetate, ketones such as cyclohexanone and methyl isobutyl ketone and aromatic and aliphatic hydrocarbons such as toluene, xylene and Solvesso 100®.
The resulting block polymer can also be mixed with a conventional wire enamel composition.
Examples of A the aliphatic, saturated or unsaturated, linear or branched monocarboxylic acids having 15 to 50 carbon atoms are stearic acid, arachidic acid, oleic acid, erucic acid or the montanic acids (waxy acids having 24 to 36 carbon atoms).
Those monocarboxylic acids having more than 20 carbon atoms, such as erucic acid or the montanic acids, are preferred.
Examples of the polyisocyanates B, D and F are hexamethylene diisocyanate, isophorone diisocyanate, 1,12-dodecane diisocyanate, 2,4- and 2,6-toluylene diisocyanate (TDI
Krause Rainer
Schuelke Wolfgang
Winkler Diethard
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Gorr Rachel
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