Coating processes – Electrical product produced – Coil or winding
Reexamination Certificate
1997-05-20
2003-06-17
Barr, Michael (Department: 1762)
Coating processes
Electrical product produced
Coil or winding
C427S386000, C427S430100, C427S435000, C427S434600
Reexamination Certificate
active
06579566
ABSTRACT:
The present invention relates to a process for fixing wire coils (windings) by trickling an impregnating resin on to the heated rotating coil or by dipping the heated rotating coil in a bath filled with an impregnating resin, which process comprises using as impregnating resin a composition comprising an epoxy resin and a blocked polymerisation initiator.
Wire coils of rotors or stators are frequently impregnated with suitable insulating resins to afford protection against harmful environomental influences and to enhance their mechanical strength. Thus, for example, in the manufacture of electromotors the windings are fixed on a support by means of an insulating varnish.
A conventional method of impregnating wire coils is dip impregnation using solvent-based impregnating varnishes. The dip impregnation method, however, cannot be satisfactorily integrated into continuous in-line production, as the dripping and the evaporation of the solvent are very time-consuming. Good impregnation can only be achieved by repeated dipping and applying a vacuum. Moreover, the use of solvent-based varnishes is ecologically undesirable.
For these reasons, methods like trickle impregnation and hot dip rolling using solventless impregnating resins are being increasingly used at the present time.
In trickle impregnation, the resin is dripped on to the heated winding that rotates at a moderate speed until complete impregnation is achieved. The subsequent cure can be effected cold or at elevated temperature, depending on the trickle resin employed.
In the hot dip rolling method too the rotor or stator is preheated in an oven (oven temperature c. 200° C.). The heated rotor or stator is then fixed on an apparatus and dipped, while rotating, into an impregnating bath filled with the insulating resin. After complete impregnation of the windings, the rotor or stator is removed from the impregnating bath while continuing to rotate until the insulating resin has gelled. It may be necessary to effect a postbake in an oven.
Unsaturated polyester resins and epoxy resins are often used in trickle impregnation and hot dip rolling (q.v. inter alia H. Batzer: “Polymere Werkstoffe”, Georg Thieme Verlag 1984, Volume III, pp. 307-309). These resins, however, are two-component systems, i.e. resin and hardener have to be stored separately and are not mixed until shortly before application. This means that a fairly complicated metering and mixing process is necessary before impregnation when using these systems. Moreover, the processing time after mixing the individual components, the so-called pot life, is often too short when using two-component resins.
There is therefore a need to provide one-component impregnating systems which are storage-stable at room temperature and can be used, without prior mixing, direct for trickle impregnation and hot dip rolling.
Suitable one-component systems are the polyester imides disclosed in DE-A 1 445 263. The mechanical properties, especially flexibility, of the cured polyester imide resins are, however, substantially poorer than those of corresponding epoxy resins. Moreover, the use of polyester imides is toxicologically undesirable because of the high concentration of volatile products.
Unexpectedly, it has now been found that epoxy resins can be used in combination with specific blocked polymerisation initiators as storage-stable one-component impregnating resins which, after deblocking, have a long pot life and afford products that have excellent mechanical properties. The use of such resins for trickle impregnation or hot dip rolling is also advantageous for toxicological and environmental reasons, as virtually no volatile cleavage products occur.
Accordingly, the invention relates to a process for fixing wire windings by trickling an impregnating resin on to the heated rotating winding or by dipping the heated rotating winding in a bath filled with an impregnating resin, which process comprises using as impregnating resin a composition comprising
(A) an epoxy resin and
(B) an initiator for the polymerisation of the epoxy resin, said initiator (B) being one of the following components (B1) or (B2) or a mixture of (B1) and (B2), and
(B1) a compound which is activatable by UV irradiation of formula I, IIa, IIb or IIc
[R
1
(Fe
II
R
2
)
a
]
(a·b)⊕
(
a·b
)·[X]
⊖
(I),
wherein a and b are each independently of the other 1 or 2, R
1
is a &pgr;-arene, R
2
is a &pgr;-arene or the anion of a &pgr;-arene, R
3
, R
4
and R
5
are each independently of one another C
1
-C
18
allyl, C
2
-C
18
alkenyl or C
5
-C
18
aryl, each unsubstituted or substituted by one or more than one member selected from the group consisting of alkyl, alkoxy, phenyl, amino, alkylamino, dialkylamino and halogen, q is an integer from 1 to 10, [X]
⊖
is an anion [LQ
m
]
⊖
or an anion of a partially fluorinated or perfluorinated aliphatic or aromatic sulfonic acid, L is B, P, As or Sb, Q is fluoro, and some of the substituents Q may also be hydroxyl groups, and m corresponds to the valency of L increased by one, and
(B2) is a heat-activatible initiator consisting of a mixture comprising
(a) at least one quarternary ammonium salt of an aromatic-heterocyclic compound which contains 1 or 2 nitrogen atoms, and of a complex halide anion selected from the group consisting of BF
4
⊖
, PF
6
⊖
, SbF
6
⊖
, SbF
5
(OH)
⊖
and AsF
6
⊖
, and
(b) at least one thermal radical former (b1), (b2), (b3) or (b4), wherein
(b1) is a diarylethane derivative of formula III
wherein Ar is phenyl, naphthyl, or C
1
-C
4
alkyl- or chloro-substituted phenyl, R
6
is hydroxy, C
1
-C
4
alkoxy, —O—CO—R
8
or —OSiR
9
R
10
R
11
, wherein R
8
is C
1
-C
8
alkyl or phenyl, and R
9
, R
10
and R
11
are each independently of one another C
1
-C
4
alkyl or phenyl, and R
7
is C
1
-C
4
alkyl or cyclohexyl or has the same meaning as Ar,
(b2) is an oligomer of formula IV
wherein Ar, R
7
, R
9
and R
10
have the same meaning as in formula II and n is 2-20,
(b3) is an organic peroxy compound, and
(b4) is a quinone.
Component (A) in the process of this invention may in principle be any compound commonly employed in the art of epoxy resins. Illustrative examples of suitable epoxy resins are:
I) Polyglycidyl and poly(&bgr;-methylglycidyl) esters which are obtainable by reacting a compound containing at least two carboxyl groups in the molecule with epichlorohydrin or &bgr;-methylepichlorohydrin. The reaction is conveniently carried out in the presence of a base.
Compounds containing at least two carboxyl groups in the molecule may suitably be aliphatic polycarboxylic acids. Examples of such polycarboxylic acids are oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, sebacic acid, suberic acid, azelaic acid or dimerised or trimerised linoleic acid. It is, however, also possible to use cycloaliphatic polycarboxylic acids such as tetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, hexahydrophthalic acid or 4-methylhexahydrophthalic acid. Aromatic polycarboxylic acids can also be used, typically phthalic acid, isophthalic acid and terephthalic acid.
II) Polyglycidyl or poly(&bgr;-methylglycidyl) ethers which are obtainable by reacting a compound containing at least two free alcoholic hydroxyl groups and/or phenolic hydroxyl groups and epichlorohydrin or &bgr;-methylepichlorohydrin, under alkaline conditions or in the presence of an acid catalyst and subsequent treatment with an alkali.
Ethers of this type may be derived from acyclic alcohols, typically from ethylene glycol, diethylene glycol and higher poly(oxyethylene) glycols, 1,2-propanediol or poly(oxypropylene) glycols, 1,3-propanediol, 1,4-butanediol, poly(oxytetramethylene) glycols, 1,5-pentanediol, 1,6-hexanediol, 2,4,6-hexanetriol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol, sorbitol, as well as from polyepichlorohydrins. They may also be derived from cycloaliphatic alcohols such as 1,3- or 1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol, bis
Bär Daniel
Mayer Carl W.
Moser Roland
Barr Michael
Proskauer Rose LLP
Vantico Inc.
LandOfFree
One-component epoxy resin system for trickle impregnation... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with One-component epoxy resin system for trickle impregnation..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and One-component epoxy resin system for trickle impregnation... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3129439