Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a novel method of producing winding
wire havillg two insulating layers made of different materials, i.e. so-called
double-layer enamel-insulated wire.
Enamel-insulated winding wires are defined precisely in German Standard
DIN 46 435 of April 1977 and are widely used in electrical machines, trans-
formers and electronics.
The metal of the conductor, preferably copper or aluminum, is insulated
with a layer of synthetic resin lacquer which is thin but extremely resistant
to mechanical and thermal stress. Enamelled wires of this kind are made on wire-
enamelling machines by continuous and repeated application of a wire enamel to
the metal wire.
In addition to wire-enamels containing solvents, use is made of wire-
coating resin melts or dispersions and aqueous solutions of wire-coating resins.
Mowever, because of the relatively low take-off speeds o~tainable, all of these
known methods are highly time-consuming and labour-intensive.
The extrusion of thermoplastic material$ for thick coatings on
bundles of eleetrical conductors, and for the production of conductor wire, has
long been known in the cable indu$try.
United States Patent 4,1~5,474 describes a met~od of producing enamel-
insulated winding wires by extruding partly crystalline thermoplastic poly-
condensates with crystallite melting points of above 170C, preferably above
250C.
This earlier invention was a major factor in overcoming the conviction
that it was impossible to produce by extrusion the thin insulating layers
required according to DIN 46 435.
The method according to United States Patent 4,145,474, and all subse-
quent applications, has the great advantage of requiring no after-treatment such
as stretching or reaction-hardaning, and this saves a considerable amount of time
and energy.
Now for special applications in electrical engineering, for example in
building electrical machines and in entertainment electronics, there is a need to
apply to existing insulation another layer of a different polymer, in order to
meet increased requirements covering the processing safety of such winding wires,
or to achieve special effects, among them increasing surface hardness and abras-
ion resistance, or for causing insulated wires -to adhere together, after winding,
by treating them with heat or solvents.
Thls is generally achieved by using, for the basic insulation, a harden-
able heat-resistant resin, for example -tereph-thalic-acid polyester or polyes-ter-
imide-resin, which in conventional inskallations is applied repeatedly to the
wire and is then baked.
Suosequently, or even in the same operation, a second layer in the form
of a lacquer made of another, preferably linear, polymer, for example polyamide,
polyvinyl-acetal, polyester or polyamide--imide, is applied to the conductor by
the same method.
The disadvantage of this method is the often poor solubility of the
preferably linear polycondensates, as a result of which these lacquers have a
very low solids content and require aggressive solvents which may be detrimental
to the basic insulation of the conductor.
A novel and advantageous method has now been found for producing double
layer lacquer-insulated wires. Accordingly, the invention provides in a method
of manufacturing insulated electric wire of the enamelled wire type in which a
solvent-free thermoplastic material containing at least one partially crystalline
thermoplastic polycondensate having crystallites with a melting point above 170C
is introduced into an extruder and extruded at or ahove the crystalline melting
-- 2 --
point of the thermoplastic polycondensate onto and around a metal wire so as to
form on said wire a thin layer, the improvement comprising extruding a second
layer onto and around the first layer using said solvent-free thermoplastic ma-ter-
ial containing at least one partially crystalline thermoplastic polycondensate
with a melting point at a temperature lower than those of the polycondensates of
said first layer.
Suitable for the basic insulation of the electrical conductor are all
usual, known wire-enamels or wire-coating resins used in producing heat-stable
winding wires of types M, W 155 and W l~0 according to German Standard DIN 46 416,
parts l, 4 and 5. More particularly, these are wire-enamels and wire-coating res-
ins based upon terephthalic-acid-polyes-ter, polyester-imide, polyamide-imide and
polyamide. The said wire-coating resins may be dissolved in organic solvents or
in water, or they may be dispersed. However, they may also be applied from the
melt.
Suitable for basic insulation of the electrical conductor by extrusion-
coating are the partly crystalline thermoplastic polycondensates according to
United States Patent 4,145,474, e.g. linear polyesters and polyamides, and the
amorphous polyether-sulphones and partly crystalline polyether-ketones of subse
quent applications. These polycondensates may be used if, necessary, in admix-
ture with dyestuEfs, pigments, fillers and other additives.
In this case, a specially preferred embodiment of the method residesin using, for the second layer, thermoplastic synthetic materials having soften-
ing points lower than those of the polycondensates in the first layer.
As regards the second insulating layer to be applied, according to the
invention, by extrusion, all extrudable thermoplastic synthe-tic materials are
suitable for this purpose in principle and, in order to improve the adhesion
between the two layers, either an adhesive may be applied to the basic layer, or
-- 3 --
the insulated wire may be heated intermediately. In practice, however, the onlypolymers to be used are those which aan be baked-on by heating or applied with
solvents that are easily volatili~ed, or those which improve the mechanical prop-
erties, such as surface hardness, resistance to abrasion, or resiliency, of
- 3a -
the al.ready insulated, heat-resistant enamelled wi.re. Special preference is
given to partly crystalline or amorphous polyamides.
Suitable partly crystalline polyamides are, among others, 6,6-poly-
amides and 6J10-polyamides produced by polycondensation frorn aliphatic di-
carboxylic-acids and aliphatic diamines, also 6-polyamides, ll-polyamides, 12-
polyamides, among others, made from lactams or ~amino-carboxylic-acids.
Suitable amorphous polyamides are, for example, a transparent poly-
amide made from terephthalic-acid or dimethyl-terephthalate and trimethylhexa-
methylenediamine ~a mixture of 2,2,4- and 2,4,4-isomers); also a three-componentpolyamide based UpOII caprolactam, hexamethylenediamine/adipic-acid and p,p'-
~_ diaminodicyclohexylmethane/adipic-acid; and other glass-clear mixed polyamides
t r c~ r~ s ~
based upon a plurality o:E components havlng glass~temperatures of between 100
and 200C.
As may be gathered from a few e.xamples, certain polyamides second
layers ha.ve, above all, ~he advantage of flowing at moderately high temperatures
and of firmly baking any windings or coils used in electrical machines and
entertainment electronics, thus rendering unnecessar-y the use of the otherwise
usual immersion varnishes or resins.
Polyvinyl-acetals, or example~ may also be used to form the second
ZO layer. Special preference is given, within this group, to polyvinyl-butyrals
because of their solubility in easily volatilized sol~ents, e.g~ alcohols, which,
as an alternative to the above-mentioned haking by heat~ allow coils to be
solidified by solvent action.
Particularly suitable in this field are polyvinyl-butyrals having
degrees of butyralization of from 70 to 80% and average molecular weights of
from 309000 to 200,0QO.
One decisiYe adyantage of the method is that it also makes possible
~ 4 -
the use of polymers which are insoluble, or hardly soluble, in conventional sol-
vents. A preerred apparatus Eor -the execution of the method is described in
United States Patent 4,165,957.
rn producing the ~asic and second layers by extrusion, it is possible
to use one and the same extruder to apply the second layer to a wire carrying
basic insulation of the type described above, or to use two extruders in tandem
to apply the two layers in a single operation.
The following Examples indicate the processing conditions for indivi-
dual polymer systems and some of the properties of winding wires produced with
the apparatus described in the above-mentioned Swiss patent app:Lication. In
Examples 1 to 4, use was made of soft-annealed circular copper wire 0.6 mm in
diameter, passing from an unwinding unit to a preheat-section, through the coat-
ing zone in the ex-truder head, and then through a scraper nozzle controlling the
thickness of the layer. After passing through a cooling section, the coated wire
was reeled. The second layer was then applied.
The extruder-temperatures given relate to the section between the in-
let and the nozzle. The final three values apply to the nozzle system.
Example 1
Coating material:
1st layer: polyethylene terephthalate pigmented with 8~ of -titanium dioxide;
2nd layer: 12~polyamide (lauric-lactam polymer, melting point about 180C).
Processing conditions;
Extrusion temperature:
1st layer: 240/250/260/270/270/280C
2nd layer: 165/180/180/190/200/220C
~P~
~..
Take-off velocity:
1st layer: 200 m/min.
2nd layer: "
Layer thi,ckness ~increase in diameter)
1st layer: 34 ~m
2nd layer: 3Q "
Properties of winding ~ire~:
hardness: B
softening temperature: 245~C
The great resiliency and good ad~esion of the coating is demonstratcd
by the fact that after the ~ire w,as stretched to the brea~ing point ~23%), a
loop of wire ~ound around its own diameter ~0~6 mm~ was still crack-free.
Tinning abil~ty: at 375QC ~n 6Q/4Q tin-~ase solder; 3.5 s
at 42QC " " " " " : 2.0 s
Breakdown voltage (DIN 46 453, Part 1, Sec. 13.2.2.): 5.0 lcV
Baking temperature ~DIN 46 453, Part 1, Sec. 18.2.1): 200C
Resoftening temperature ~DIN 46 453, Part 1, Sec. 18.2.2): 130C.
Example 2
Coating material:
1st layer: polyether-sulphone of the formula
L (~ So2 -~3 - ca . Iaa
2nd layer: 12-polyamide ~as in Example 1~.
Processing conditions:
Extrusion temperature:
1st layer: 315/34Q/35Q/34Q/35Q/37QQC
2nd layer: 165/180,/18Q/l~Q~2QQ/220C
Take-o~f velocity:
1st layer: 2Q0 m/min
2nd layer: " "
-- 6 --
Layer thickness (increase in diameter):
1st layer: 42 ~m
2nd layer: 38 "
i.e. a total increase in diameter o 8~ ~m.
Properties of winding wires:
llardness: B
Softening temperature: 255C
Wireloop around its own diameter (a.G ~m~
as in Example 1 still crack-free
Breakdown ~oltage (DIN 46 453, Part 1, Sec. 1~.2.2); 8~0 k~
Baking temperature ~DIN 46 453, Sec. 18~2.1~: 20ac
Resoftening temperature (DIN 46 453~ Part 1, Sec. 18.2.2): 125C
Example 3
Coating material:
1st layer: polyether-ketone of the ormula
~ o -.~ a ~ co -~
2nd layer: 12-pol~amide (laur~c-lacta~ polym,er, Dlelting point about 180C).
Processing conditions:
Extrusion temperatures:
1st layer: 39Q/410/420/420/420/44QC
2nd layer: 165/180/18a/15a~2Qa~220QC
Take-off velocity:
1st layer: 200 m/min.
2nd layer: 2QQ m/min.
Layer thickness: (increase in diameter2
1st layer: 42 ~m
2nd layer: 36 "
i.e. a total increase in diameter of 78
Properties of winding ~ires:
Hardness: B
Softening temperature: 38QC
~ 7 -
Wlre loop around its own diameter ~0.6 mm~
as in Example l still crack-free
Breakdo~m ~oltage (DIN 46 453, Part l, Sec. 13.2.2): 5.5 k~
Baking temperature (DIN 46 453, Part 1, Sec. 18.2.1): 2Q0C
Resoftening temperature (DIN 46 453, Part 1, Sec. 18.2.2): 125C
Example 4
Coating material:
1st layer: polyethy~leneterephthala-te pigmented wi~th 8% of titanium dioxide.
2nd layer: polyvinylbutyral, average molecular weight about 100,000.
Processing conditions:
Extrusion temperatures:
1st layer: 240/250/260/270/270/280C
2nd layer: 120/160/18Q/170/170/190C
Take-off velocity;
1st layer: 200 m/min
2nd layer: lQ0 m/min
Layer thickness (increase in diameter~
1st layer: 44 ~m
2nd layer: 22 "
i.e. a total increase in diameter of 66 ~m
Properties of winding ~ires:
Hardness H
Wire loop around its own diameter
after prestretching of the wire -~ crack-free;
Baking test:
Two ends of wire, not in contact ~ith each other, ~Ycre immersed for 5
seconds in solvent and then pressed together. ~dhes~on ~as assessed after
pulling apart. When ethanol or methanol were used, adhesion was excellent.
Example 5
Use was made of a lu~ricant-free copper ~ire, insulated ~y conven-
tional methods with a polyester-imide-based wire enamel of the W 155/W180 ~ype,
having a nominal diameter of Q.95 mm. The oyerall d-iameter of the insulated
wire was 1005 mm. The layer thickness ~increase in diameter~ of the first layer
_. ~ _.
of insulation was thus 55 ym.
The properties of this wire were as follows:
Pencil hardness 4 H
Wire loop around its o~n diameter (0.95 mm)
after 25% prestretching of the wire: several cracks
after 20% prestretching of the ~ire; crack-free
Peel test: 170 revolutions
Softening temperature CDIN 46 453): 340C
Thermal shock (D~N 46 453): 200C
Coating material or the 2nd la~er:
Amorphous low-viscosity polyamide
Density (dry) 1.14
Melting temperature (DIN 53736) 196C
Processing conditions:
Extrusion temperature: 210/240/265/280/275/270/280/300C
Take-offvelocity: 5Q m/min
Nozzle diameter: 1.09 mm
Layer thickness (increase in diameter - 2nd layer) 64 ~m
Properties of winding wires:
Pencil hardness, upper la~er: HB
lower layer: 4 H
Wire loop around its own diameter (0.95 mm)
after 25% prestretching of the wire: crack-free
Peel test: 250 revolutions
Softening temperature (DIN 46 453) 340C
Thermal shock (DIN 46 453, Part 1, Sec. 18.2.2) 136C
le 6
Use was made of a lubricant-free copper wire, insulated by conven-
tional methods with a pol~ester-imide-based wire enamel and having a rated
diameter of 0.40 mm. The overall diameter of the insulated wire was 0.430 mm.
The increase in diameter produced by the basic insulation was thus 30 ~m. The
properties of this wire were as follo~s:
_ g _
Surface hardness ~pencil hardness) 4 H - 5 H
Wire loop around its own diameter
after 25% prestretching: crack-free
Softening temperature (DIN 46 453~ 285C
Thermal shock (DIN 46 453): 250C
Coating material for the second layer:
Extrusion temperature: 310/300/290/280/280/300C
Take-off velocity: 200`m/min
Nozzle diameter: 0.445 mm
Increase in diameter of 2nd layer: 16 ~m
Increase in diameter of total insulation: 46 "
Properties of winding wire:
Surface hardness (pencil hardness) 3 H
Wire loop around its own diameter
after 25% prestretching: crack-~ree
SoEtening temperature (DIN 46 453); 280C
Thermal shock ~DIN 46 453~ 250C
Baking temperature ~DTN 46 453, Part l, Sec. 18.2.1~: 17ac
Resoftening temperature (DIN 46 453, Part 1,
Sec. 18.2.2): 136C
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