U.S. patent number 3,906,139 [Application Number 05/394,611] was granted by the patent office on 1975-09-16 for insulated wire.
This patent grant is currently assigned to Dainichi-Nippon Cables, Ltd.. Invention is credited to Yukio Hiraoka, Sadao Nakao, Yoshinobu Noda.
United States Patent |
3,906,139 |
Hiraoka , et al. |
September 16, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Insulated wire
Abstract
An insulated wire suitable as a magnet wire having a baked layer
of a specific polyacryl resin as an under-layer and a baked layer
of a specific polyester resin as an upper-layer on the conductor as
well as a process for producing the insulated wire are disclosed.
The insulated wire according to the present invention exhibits
well-balanced overall properties necessary for use as a magnet wire
and has an excellent heat resistance.
Inventors: |
Hiraoka; Yukio (Osaka,
JA), Nakao; Sadao (Itami, JA), Noda;
Yoshinobu (Itami, JA) |
Assignee: |
Dainichi-Nippon Cables, Ltd.
(Amagasahi, JA)
|
Family
ID: |
14351403 |
Appl.
No.: |
05/394,611 |
Filed: |
September 5, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Sep 5, 1972 [JA] |
|
|
47-103340 |
|
Current U.S.
Class: |
428/383; 204/477;
204/488; 427/118 |
Current CPC
Class: |
H01B
7/292 (20130101); C25D 13/16 (20130101); H01B
3/308 (20130101); H01B 3/447 (20130101); H01B
13/065 (20130101); H01B 13/16 (20130101); H01B
7/0208 (20130101); C09D 5/4411 (20130101); Y10T
428/2947 (20150115) |
Current International
Class: |
C09D
5/44 (20060101); C25D 13/16 (20060101); H01B
13/06 (20060101); H01B 7/02 (20060101); C25D
13/12 (20060101); H01B 13/16 (20060101); H01B
3/30 (20060101); H01B 7/29 (20060101); H01B
3/44 (20060101); H01B 7/17 (20060101); H01B
003/44 () |
Field of
Search: |
;117/218,232,128.4
;174/12C,12SR ;428/383 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Husack; Ralph
Attorney, Agent or Firm: Sughrue, Rothwell, Mion, Zinn &
Macpeak
Claims
What is claimed is:
1. An insulated wire comprising a conductor having thereon a
coating of a baked insulating layer of a polyacryl resin and a
baked layer of a polyester resin overcoated on said polyacryl resin
layer,
said polyacryl resin comprising a copolymer of (a) at least one
compound represented by the formula (I): ##EQU3## (b) at least one
compound represented by the formula (II) ##EQU4## and (c) at least
one unsaturated organic acid, said acid having from 3 to about 30
carbon atoms and at least one double bond which is reactable with
the double bond of said compound of the formula (I) or (II),
wherein R.sub.1, represents a hydrogen atom or an alkyl group
having 1 to about 30 carbon atoms, R.sub.2 represents a cyano
group, an aldehyde group or a carboxyalkyl ester group having from
2 to about 30 carbon atoms, and R.sub.3 and R.sub.4 each represents
a hydrogen atom, an organic group having 1 to about 30 carbon atoms
selected from the group consisting of an alkyl group, an amide
group, an N-alkylamide group, an alkylol group, a glycidylether
group and a glycidylester group, except that both R.sub.3 and
R.sub.4 are not simultaneously a hydrogen atom or an alkyl group
and said polyester resin comprising a copolymer of (d) at least one
compound selected from the group consisting of terephthalic acid
and a derivative thereof, and (e) a mixture of polyols comprising
at least one diol and at least one of a triol, a tetraol, or a
mixture of a triol and a tetraol, and said polyol mixture
containing about 40 to about 97% equivalents of said diol.
2. The insultated wire of claim 1, wherein said groups for R.sub.1,
R.sub.2, R.sub.3 and R.sub.4 contain no more than about 20 carbon
atoms.
3. The insulated wire of claim 1, wherein the total number of
carbon atoms in each of said compound of the formula (I), said
compound of the formula (II) and said unsaturated organic acid is
less than about 15 carbon atoms.
4. The insulated wire of claim 1, wherein said polyacryl resin
comprises from 1 to about 20 moles of said compound of the formula
(I) per mole of said compound of the forumula (II) and from about
0.01 to about 0.2 mole of said unsaturated organic acid per mole of
the total moles said compound of the formula (I) and said compound
of the formula (II).
5. The insulated wire of claim 1, wherein said compound of the
formula (I) is acrylonitrile, methacrylonitrile, methylacrylate,
ethylacrylate, propylacrylate, butylacrylate, methylmethacrylate,
ethylmethacrylate, propylmethacrylate, or acrolein, wherein said
compound of the formula (II) is glycidylacrylate,
glycidylmethacrylate, allylglycidylether, acrylamide,
methlolacrylamide, or ethylacrylamide and wherein said unsaturated
organic acid is acrylic acid, methacrylic acid,
.alpha.-ethylacrylic acid, crotonic acid, maleic acid, or fumaric
acid.
6. The insulated wire of claim 1, wherein said polyacryl resin is a
copolymer of said components (a), (b), (c) and additionally styrene
or a derivative thereof, said styrene or a derivative thereof being
present at a level of no more than about 2 mole per mole of said
component (a).
7. The insulated wire of claim 6, wherein said styrene derivative
is styrene in which the phenyl group is substituted with at least
one substituent, said substituent being an organic group having 1
to about 20 carbon atoms or a halogen atoms.
8. The insulated wire of claim 7, wherein said phenyl group is
substituted with 1 to about 3 said substituents.
9. The insulated wire of claim 8, wherein said styrene derivative
is methylstyrene, ethylstyrene, dimethylstyrene, benzylstyrene,
dibenzylstyrene, divinylbenzene, chlorostyrene, or
dichlorostyrene.
10. The insulated wire of claim 1, wherein said unsaturated organic
acid is a monobasic unsaturated acid, a dibasic unsaturated acid, a
tribasic unsaturated acid or a mixture thereof.
11. The insultated wire of claim 9, wherein said unsaturated
organic acid is acrylic acid, crotonic acid, vinylacetic acid,
methacrylic acid, tiglic acid, .alpha.-ethylacrylic acid,
.beta.-methylcrotonic acid, 2-pentenoic acid, 2-hexenoic acid,
2-heptenoic acid, 2-octenoic acid, 10-undecenoic acid,
9-octadecenoic acid, cinnamic acid, atropic acid,
.alpha.-benzylacrylic acid, methyl atropic acid, 2,4-pentadienoic
acid, 9,12-octadecadienoic acid, maleic acid, fumaric acid,
itaconic acid, citraconic acid, mesaconic acid, glutaconic acid,
dihydromuconic acid, muconic acid, or 1,2,4-tricarboxybutene.
12. The insulated wire of claim 1, wherein said polyacryl resin is
a copolymer of said components (a), (b), (c) and additionally a
diolefin, said diolefin being present at a level of no more than
about 1 mole per mole of said component (a).
13. The insulated wire of claim 12, wherein said diolefin has 3 to
about 20 carbon atoms.
14. The insulated wire of claim 12, wherein said diolefin has about
4 to 10 carbon atoms.
15. The insulated wire of claim 14, wherein said diolefin is
butadiene, pentadiene, or methyl-butadiene.
16. The insulated wire of claim 1, wherein said derivative of
terephthalic acid is represented by the formula (III) ##SPC2##
wherein R.sub.5 and R.sub.6 each represents a halogen atom, or an
organic group having 1 to about 5 carbon atoms selected from the
group consisting of an amino group, an alkoxy group, an
N-alkylamino group, or an aryloxy group.
17. The insulated wire of claim 1, wherein said polyol mixture
comprises a mixture of polyols represented by the formula (IV)
R.sub.7 -- (OH).sub.n (IV)
wherein R.sub.7 represents a hydrocarbon group having 1 to about 10
carbon atoms and n is a positive integer of 2 to 4.
18. The insulated wire of claim 17, wherein said hydrocarbon group
is selected from the group consisting of a saturated hydrocarbon
group and an unsaturated hydrocarbon group.
19. The insulated wire of claim 17, wherein said saturated
hydrocarbon group contains at least one ring selected from the
group consisting of a four to eight membered heterocyclic ring and
a benzene type ring in the carbon chain thereof.
20. The insulated wire of claim 17, wherein said saturated
hydrocarbon group is substituted with at least one group selected
from the group consisting of a phenyl group and an aralkyl group
having about 7 to about 10 carbon atoms.
21. The insulated wire of claim 17, wherein when n is 2 said polyol
is an aliphatic diol, or an aromatic diol.
22. The insulated wire of claim 17, wherein when n is 2 said diol
is ethylene glycol, propylene glycol, butane diol, or 2,2
-bis(p-hydroxyethoxyphenyl)-propane, and wherein said polyol
mixture is a mixture with glycerin, 1,1,1-trimethylolethane,
1,1,1-trimethylolpropane, tris-2-hydroxyalkyl isocyanurate or
pentaerythritol.
23. The insulated wire of claim 1, wherein a portion of said
terephthalic acid is replaced by isophthalic acid or a derivative
thereof in an amount up to less than 60 moles of said isophthalic
acid per 100 moles of said terephthalic acid.
24. The insulated wire of claim 1, wherein said polyester resin
comprises the polymerization product of said terephthalic acid,
said polyol mixture and additionally an imide- or
amide-imide-containing substance comprising the reaction product of
a tribasic or higher polybasic acid and a diamide, a diisocyanate
or a mixtue of said diamine and said diisocyanate.
25. The insulated wire of claim 1, wherein the thickness of said
polyacryl resin layer ranges from about 1 to 300 .mu. and the
thickness of said polyester resin layer ranges from about 0.3 to
100 .mu., and wherein the thickness ratio of said polyacryl resin
layer to said polyester resin layer ranges from about 0.1 to
30.
26. The insulated wire of claim 1, wherein said resin layers are
simultaneously baked.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an insulated wire useful as a magnet wire
for use in electric equipment such as motors, transformers and the
like, and to a process for producing the insulated wire.
2. Description of the Prior Art
Most of the conventional magnet wires insulated with an insulating
varnish heretofore in use generally do not satisfy all the critical
properties recently required, except for magnet wires coated with
recently developed heat resistant resins, such as the
polyamideimides, and techniques for multiple coating of the
conductor with two or more different insulating materials have been
proposed as disclosed in U.S. Pat. No. 3,022,200 and U.S. Pat. No.
3,702,813, etc.
Generally speaking, the multiple coating insulating layer exhibits
some advantages, i.e., the excellent properties possessed by
specific layers included in the layers of multiple coatings
compensate for the defects of the other layers. On the other hand,
the excellent properties possessed by the layers sometimes can be
masked by the presence of other layers and, in some cases, the
presence of other layers adversely affects the properties. For
example, the difficulty of operations for uncovering the tip of the
wire coated with a polyamide-imide resin due to an excessively
strong chemical resistance of the resin to a remover can be solved
by providing a polyester layer under the polyamide-imide layer,
but, due to the presence of the polyester layer the abrasion
resistance, the heat resistance, etc., of the
polyester-polyamide-imide dual coated wire are inferior to those of
a wire coated with the polyamide-imide alone. The thermoplastic
polyester layer of the insulated wire wherein the thermoplastic
polyester layer is coated on a baked thermosetting polyester layer
functions to improve the heat-shock resistance and the abrasion
resistance properties of the baked polyester layer, but it lowers
the cut through temperature of the insulated wire.
As a result of extensive studies, it was surprisingly found that a
dual insulating coating comprising a specific polyacryl resin layer
having coated thereon a specific polyester resin layer exhibits
excellent heat resistance properties over a coating of each of the
above described resins and further it possesses well-balanced
overall properties required for a coating of magnet wires. The
present invention has been completed by a further investigation of
the above unexpected finding.
SUMMARY OF THE INVENTION
A primary object of this invention is to provide an insulated wire
having excellent heat resistance and well-balanced overall
properties required for magnet wires.
Another object of this invention is to provide a process for
improving the heat resistance of the magnet wires.
A further object of this invention is to provide a process for
producing a magnet wire having excellent heat resistance and
well-balanced overall properties for magnet wires.
More specifically, the present invention comprises an insulated
wire having a baked layer of a specific polyacryl resin on a
conductor and a baked layer of a specific thermosetting polyester
resin on the above polyacryl resin layer and to a process for
producing such an insulated wire.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 is an enlarged schematic sectional view of the dual coated
wire prepared according to an embodiment of this invention.
FIG. 2 illustrates an example of the processing line for producing
the dual coated wire according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, the dual coated wire having an excellent
heat resistance and well-balanced overall properties can be
obtained by providing a baked insulating layer 2 of the polyacryl
resin as hereinafter specified on a conductor 1, and further by
providing a baked insulating layer 3 of the polyester resin as
hereinafter specified on the layer 2.
The polyacryl resin which can be used in the present invention is a
copolymer of (a) at least one compound (hereinafter, designated the
a-component for brevity) represented by the formula (I): ##EQU1##
and (b) at least one compound (hereinafter, the b-component) of the
formula (II): ##EQU2## and (c) an unsaturated organic acid
(hereinafter, the c-component) having 3 to about 30 carbon atoms
and at least one double bond which is reactable with the double
bond of the a-component or b-component.
In the formula (I) or (II), R.sub.1 represents hydrogen atom and an
alkyl group having 1 to about 30 carbon atoms, such as methyl,
ethyl, propyl, butyl and the like, R.sub.2 represents a cyano
group, an aldehyde group and a carboxyalkyl ester group having 2 to
about 30 carbon atoms, such as carboxymethyl ester, carboxyethyl
ester, carboxypropyl ester, carboxybutyl ester and the like,
R.sub.3 and R.sub.4 each represents a hydrogen atom, an amide
group, a glycidyl ester group, glycidyl ether group and an organic
group having 1 to about 30 carbon atoms selected from the group
consisting of an alkyl group, such as methyl, ethyl, propyl, butyl
and the like, an N-alkylamide group, such as N-methylamide,
N-ethylamide, N-propylamide and the like, and an alkylol group,
such as methylol, ethylol, propylol and the like, except that both
R.sub.3 and R.sub.4 are not simultaneously a hydrogen atom or an
alkyl group. When the number of carbon atoms of the above
c-component and the R.sub.1, R.sub.2, R.sub.3, or R.sub.4 organic
groups exceed about 30, the heat resistance of the resulting
polyacryl resin tends to decrease and, therefore, the maximum
number of carbon atoms of the c-component and the above R.sub.1,
R.sub.2, R.sub.3, or R.sub.4 organic groups preferably does not
exceed about 20.
Examples of the c-component are monobasic unsaturated acids, such
as acrylic, crotonic, vinylacetic acid, methacrylic, tiglic,
.alpha.-ethylacrylic, .beta.-methylcrotonic, 2-pentenoic,
2-hexenoic, 2-heptenoic, 2-octenoic, 10-undecenoic, 9-octadecenoic,
cinnamic, atropic, .alpha.-benzylacrylic, methyl atropic,
2,4-pentadienoic, 2,4-hexadienoic, 2,4-dodecadienoic acid,
9,12-octadecadienoic acid; dibasic unsaturated acids, such as
maleic, fumaric, itaconic, citraconic, mesaconic, glutaconic,
dihydromuconic, muconic; and tribasic unsaturated acids, such as
1,2,4-tricarboxylic butene and the like.
The polyacryl resin used in the present invention can be prepared
by the well-known polymerization procedures such as an emulsion
polymerization, a solution polymerization, a suspension
polymerization and the like as described, for example, in U.S. Pat.
Nos. 2,787,561 and 3,509,033, and in "Acryl Resin" by Kou Asami,
published by Nikkan Kogyo Shinbun, Tokyo, 1970, p. 25 to p. 27,
using about 1 to 20 moles, preferably about 2 to 10 moles, or most
preferably about 4 to 6 moles, of the a-component per one mole of
the b-component and about 0.01 to 0.2 mole, preferably about 0.03
to 0.1 mole of the c-component per one mole of the a- and b-
components, i.e., per mole of the sum of the moles of the
a-component and the b-component.
Among the above described a-, b-, c-components, more preferred
examples are those components in which the total number of carbon
atoms is less than 15 from the standpoint of the heat resistance of
the polyacryl resin obtained. More preferred examples of the
a-component are acrylonitrile, methacrylonitrile, methylacrylate,
ethylacrylate, propylacrylate, butylacrylate, methylmethacrylate,
ethylmethacrylate, propylmethacrylate, and acrolein. More preferred
examples of the b-component are glycidylacrylate,
glycidylmethacrylate, allylglycidylether, acrylamide,
methylolacrylamide, and ethylolacrylamide. More preferred examples
of the c-component are acrylic acid, methacrylic acid,
.alpha.-ethylacrylic acid, crotonic acid, maleic acid, and fumaric
acid.
The polyacryl resin employed in the present invention may also be
those modified with one or more of styrene and its derivatives or
diolefins. As the derivatives of styrene, there are employed those
compounds in which the phenyl group of styrene is substituted with
at least one group selected from the group consisting of a cyano
group, a nitro group, a hydroxy group, an amine group, a vinyl
group, a phenyl group, a halogen atom such as chlorine, bromine,
etc., an organic group having 1 to 20 carbon atoms, such as an
alkyl group, an aralkyl group, an N-alkylamine group. Examples of
the above alkyl groups are methyl, ethyl, propyl, butyl, etc., and
examples of the above aralkyl groups are benzyl, .alpha.- or
.beta.-phenylethyl, etc., and examples of the above N-alkylamine
groups are N-methylamine, N-ethylamine, N-propylamine, etc. Among
the styrene derivatives, those which have 1 to 3 substituent groups
are preferable because of their ready reactivity with the a- to
c-components. Preferable examples are methyl styrenes, ethyl
styrenes, divinyl benzenes, chlorostyrenes. As the diolefins used
as a modifying agent, those compounds are used whose total number
of carbon atoms is 3 to about 20, preferably 4 to about 10.
Examples of the above diolefins are the butadienes, pentadienes,
methyl-butadienes and the like.
Polyacryl resins modified with those modifying agents can be
prepared using well-known polymerization methods previously
described using a starting material mixture containing one or more
of the above modifying materials in addition to a-, b-, and
c-components. However, the amount of styrene and its derivatives or
diolefins should be restricted to about 2 moles or one mole or
less, respectively, per one mole of the a-component, since use of
the modifying materials in an amount greater than that described
above results in the formation of a polyacryl resin poor in
flexibility in the case of styrenes, and in the formation of
polyacryl resin poor in the cut through temperature in the case of
the diolefins.
In the present invention, a polyacryl resin (including the modified
resin) having a degree of polymerization of approximately about
10,000 to about 1,000,000 is used, since a polyacryl resin having
too low a degree of polymerization is lacking in toughness, and, in
turn a polyacryl resin having too high a degree of polymerization
tends to result in a somewhat uneven coating surface due to a poor
fluidity of the resin in the uncured state. Therefore, more
preferable polyacryl resins are those having a degree of
polymerization of about 100,000 to about 500,000.
The polyacryl resin employable in this invention prepared by any
one of the prior art processes can be coated on a conductor in the
form of a dispersion or a solution in water or in an appropriate
organic solvent such as N-methyl-2-pyrrolidone,
N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide and
the like using a polymer concentration of about 5 to about 50,
preferably about 10 to about 30% by weight and subsequently the
coating can be baked at a temperature ranging from about
100.degree.C to about 600.degree.C, preferably about 200.degree.C
to 500.degree.C, whereby a tough insulating film can be formed on
the conductor by cross-linking.
The polyester resin used in the present invention is a copolymer of
(d) at least one terephthalic acid compound and its derivatives,
generally represented by the Formula (III); ##SPC1##
and (e) a mixture of polyols represented by the Formula (IV);
the mixture comprising at least one diol (that is, n in the Formula
(IV) is 2) and at least one compound of tri- and/or tetraol (that
is, n in the Formula (IV) is 3 or 4), and containing the diol(s) in
an amount of about 40 to 97% equivalents in this polyol
mixture.
In the polymerization between a compound represented by Formula
(III) and a mixture of polyols represented by Formula (IV), the
same polyester resin is obtained whether terephthalic acid or a
derivative thereof is used as the compound of Formula (III), in
other words, in spite of wide variation in R.sub.5 and/or R.sub.6
of the same formula. As a result, a broad range of R.sub.5 and
R.sub.6 components can be used in that R.sub.5 and R.sub.6 are
removed as condensation by-products in the course of the
polymerization. Therefore, in the present invention, as R.sub.5 and
R.sub.6 of Formula (III), various kinds of groups well-known to
those in the art can be employed and are suitable. Examples of
R.sub.5 and R.sub.6 groups are hydroxyl groups, amino groups,
halogen atoms, such as chlorine, bromine, etc., alkoxy groups, such
as methoxy, ethoxy, propoxy, butoxy, etc., N-alkylamino groups,
such as N-methylamino, N-ethylamino, etc., aryloxy groups such as
phenoxy groups. However, from the standpoint of reactivity of the
terephthalic acid derivatives with the polyol mixture, R.sub.5 and
R.sub.6 groups having a total number of carbon atoms less than
about 10, especially less than about 5, are preferred.
In the Formula (IV), n is a positive integer of 2 to 4, and R.sub.7
represents saturated or unsaturated hydrocarbon group having 1 to
10 carbon atoms. When the above n in the Formula (IV) is 2, 3, or
4, the valency of R.sub.7 becomes divalent, trivalent, or
tetravalent, respectively.
Examples of divalent R.sub.7 groups are alkylene, alkenylene,
alkylidene or alkenylidene groups alkylene or alkenylene groups of
which one or two hydrogen atoms on one or both end carbon atoms can
be replaced by one or two alkyl groups or alkenyl groups,
alkylidene or alkenylidene groups of which one hydrogen atom of the
end carbon atom having two free valencies can be substituted with
one alkyl group or alkenyl group, and the like.
Examples of trivalent R.sub.7 groups are alkane-yl-ylidene groups
or alkane-yl-ylidene groups, the above groups of which one hydrogen
atom of the end carbon atom having two free valencies can be
replaced by one alkyl group or alkenyl group, or of which one or
two hydrogen atoms of another end carbon atom can be replaced by
one or two alkyl or alkenyl groups, alkylene or alkenylene groups
of which a hydrogen atom of one end carbon atom is replaced by one
alkylene, alkenylene, alkylidene, or alkenylidene group, or of
which a hydrogen atom of both end carbon atoms are replaced by one
alkyl or alkenyl group and one alkylidene or alkenylidene group,
alkylene or alkenylene group of which an inner carbon atom between
both end carbon atoms is substituted with one alkylene or
alkenylene group and one alkyl or alkenyl group and the like.
Examples of tetravalent R.sub.7 groups are alkene-diylidene groups
or alkene-diylidene groups, the above groups of which one hydrogen
atom of one or both end carbon atoms is replaced by one alkyl group
or alkenyl group, alkane-yl-ylidene or alkene-yl-ylidene groups of
which a hydrogen atom of one end carbon atom are replaced by one
alkylene, alkenylene, alkylidene or alkenylidene group, alkylene or
alkenylene groups of which a hydrogen atom of an end carbon atom
and another end carbon atom, are substituted with one alkylene,
alkenylene, alkylidene or alkenylidene group, or of which an inner
carbon atom between the both end carbon atom is substituted with
two alkylene or alkenylene groups, and the like. The above
hydrocarbon group may contain in its carbon chain a hetero atom
such as oxygen, nitrogen and the like or at least one, preferably 1
to 5, four to eight membered heterocyclic ring, such as a pyrazine
ring, a pyrazole ring, a triazine ring, etc., or 1 to 5 benzene
type rings, such as phenylene, phenylene ether, and may also be
substituted with at least 1, preferably 1 to 5, phenyl groups
and/or aralkyl groups having about 7 to 10 carbon atoms such as
benzyl groups.
Examples of the above polyols which can be used in the preparation
of the polyesters are aliphatic diols such as ethylene glycol,
propylene glycol, butane diol and the like, aromatic
ring-containing diols such as 2,2-bis(p-hydroxyethoxyphenyl)propane
and the like, triols such as glycerine, 1,1,1-trimethylolethane,
1,1,1-trimethylolpropane, tris-2-hydroxyalkyl isocyanurate and the
like, and tetraols such as pentaerythritol and the like. When the
amount of the diol in the polyol mixture is greater than about 97%
equivalents, the cut through temperature of the resulting polyester
resin tends to decrease, and, on the other hand, when the amount of
the diol is lower than about 40%, a reduction in flexibility of the
polyester resin tends to result. Thus, the polyol mixture
preferably contains about 45 to 90% equivalents of the diols. The
polyester resins can be prepared using well-known polymerization
techniques, e.g., a solution polymerization as described in U.S.
Pat. No. 3,296,024. In the polymerization of terephthalic acid or
its derivatives with the polyol mixture, isophthalic acid or its
derivatives in an amount less than about 60 moles per 100 moles of
terephthalic acid of the Formula (III) may be added in the
polymerization reaction. As derivatives of isophthalic acid, those
corresponding to the derivatives of terephthalic acid described
above can be employed. Particularly preferred polyester resins are
those obtained by reacting about 25 to 56 % equivalents of
terephthalic acid or a derivative thereof with about 15 to 46%
equivalents of ethylene glycol and about 7 to 22% equivalents of
glycerine and about 7 to 22% equivalents of tris-2-hydroxyethyl
isocyanurate. In the above reaction, the proportion of glycerine
and tris-2-hydroxyethyl isocyanurate can be varied as long as the
sum of equivalents of glycerine plus tris-2-hydroxyethyl
isocyanurate is about 14 to 44%.
The polyester resins which can be used in the present invention can
be a modified polyester resin containing not greater than 70 imide
groups or the sum of the amide groups plus the imide groups per 100
ester linkages in the resin. Modified polyester resins can be
prepared by using an imide- or amide-imide-containing substance in
the reaction between terephthalic acid or a derivative thereof and
a polyol mixture. Alternatively, the modified polyester resins can
also be prepared by reacting an imide- or amide-imide-containing
substance with a polymerization product having a low degree of
polymerization of about 1 to about 10 between terephthalic acid or
a derivative thereof and the polyol mixture. Such an imide- or
amide-imide-containing substance can be obtained, for example, by
reacting a polybasic acid or its anhydride higher than tribasic
acid as disclosed in U.S. Pat. Nos. 3,489,696, 3,471,444 and
3,485,796 such as trimellitic anhydride, pyromellitic dianhydride,
butane tetracarboxylic dianhydride, with a diamine as disclosed in
U.S. Pat. No. 3,480,588 such as 4,4'-diaminodiphenyl methane,
4,4'-diaminodiphenyl ether, hexamethylenediamine, and/or a
diisocyanate as disclosed in U.S. Pat. No. 3,489,696 such as
4,4'-diisocyanate-diphenyl methane, 4,4'-diisocyanate-diphenyl
ether, hexamethylene diisocyanate. Preferred imide- or
amide-imide-containing substances are those having a low degree of
polymerization, containing imide groups or the sum of amide and
imide groups of 1 to 2, to a degree of polymerization about 10.
Substances having such a degree of polymerization can easily be
prepared by adjusting the molar ratio of starting materials and
polymerization conditions such as temperature and period of
polymerization. An alternative procedure of introducing the imide
groups or amide and imide groups into the polyester resin comprises
dissolving the above described imide- or amide-imide-containing
substance, a polyamide-imide resin, or a polyamic acid resin which
is a precursor of the polyimide together with the polyester resin
in a suitable solvent, such as phenol, cresol, xylenol,
N-methyl-2-pyrollidone, N,N-dimethylacetamide and the like,
applying the resulting varnish on a conductor, and baking the
varnish. In this case, the polyester resin reacts with the above
additive upon baking whereby the imide groups or amide-imide groups
are introduced into the polyester resin.
In the present invention, a polyester resin (including the modified
resins) having a degree of polymerization of approximately about 2
to 200 is used, since a polyester resin having too low a degree of
polymerization lacks toughness, and a polyester resin having too
high a degree of polymerization tends to gel in the preparation of
a varnish thereof. Therefore, more preferable polyester resins are
those having a degree of polymerization ranging from about 10 to
50.
The polyester resin used in the present invention forms a tough
insulating layer by crosslinking when a dispersion or solution
thereof in a solvent such as water, phenol, cresol, xylenol,
N-methyl-2-pyrollidone, N,N-dimethylacetamide and the like in a
polymer concentration of about 5 to about 50%, preferably about 15
to about 45% by weight is applied to a conductor and baked at a
temperature ranging from about 100.degree.C to about 600.degree.C,
preferably about 200.degree.C to about 500.degree.C.
In the present invention, the layer thickness of both the
under-layer and the upper-layer can be varied freely, but the layer
thickness of the under-layer is preferably from about 1 to 300
.mu., particularly, from about 5 to 100 .mu. and the thickness of
upper-layer is preferably from about 0.3 to 100 .mu., particularly,
from about 2 to 50 .mu.. The particularly preferred heat resistance
and the well-balanced overall properties as an insulated wire for
coils can be obtained when the thickness ratio of the under-layer
to the upper-layer is within the range of from about 0.1 to 30,
preferably from about 7 to 15.
In producing an insulated wire according to the present invention,
the layer of the polyacryl resin and the layer of the polyester
resin can be formed on a conductor using any conventional procedure
such as, for example, by a well-known coating method such as
dip-coating, spray-coating, brush-coating or using
electrodeposition coating as described in Wire World, vol. 13,
May/June, page 69, 1971, and Wire, vol. 40, No. 6, page 832, 1965,
followed by baking according to a conventional baking procedures.
The polyester resin varnish can be applied onto an uncured or cured
polyacryl resin layer, and baked together with the uncured or
already cured polyacryl resin layer. In using either a separate or
a simultaneous baking of the polyacryl resin layer and polyester
resin layer, the baking can generally be carried out at a
temperature ranging from about 200.degree.C to 600.degree.C. It is
preferred to dry the coated wire at a temperature below about
200.degree.C prior to the baking since the tendency of blistering
of the coating layers which is frequently observed in baking
without previous drying, can effectively be prevented. The above
described drying prior to the baking is desirable when the
insulated wire is produced at a rate higher than about 50 m per
minute.
However, in a preferred embodiment for advantageously, especially
economically, producing an insulated wire of high quality, the
polyacryl resin is first electrodeposited on a conductor, and then
the polyester resin film is formed thereon using electrodeposition
coating or the dip-coating of a polyester resin varnish.
The process for producing the insulated wire according to the
present invention is hereinafter described in greater detail by
reference to FIG. 2 in a preferred embodiment comprising coating a
conductor with a polyacryl resin by electrodeposition coating and
then applying a polyester varnish by dip-coating to the polyacryl
resin film.
Referring to FIG. 2, a conductor W such as copper, aluminum and the
like which is connected to the positive terminal of a D.C. power
supply (not shown) is passed through an electrodeposition bath 6
filled with a polyacryl resin varnish 4 in the form of an aqueous
solution or an aqueous dispersion. A cylindrical cathode 8 is
mounted in the electro-deposition bath 6, and the polyacryl resin
particles from the varnish are deposited uniformly on the conductor
W by electro-phoresis due to the potential difference between the
conductor, as the anode, and the cathode while the conductor passes
through the cathode. As a polyacryl resin varnish used in the
electrodeposition coating, suitable varnishes may be used, such as
the emulsified product per se of a polyacryl resin prepared by the
emulsion polymerization process described in U.S. Pat. Nos.
2,787,561 and 3,509,033, an aqueous solution of a polyacryl resin
together with, if necessary, an amine disclosed in U.S. Pat. No.
3,230,162, and a water dispersion of a polyacryl resin having
particle size of about 0.01 .mu. to about 1.0 .mu. in diameter with
a well-known surface active agent.
The electrodeposition coating using the above described polyacryl
resin in the present invention can be carried out under the
conditions well-established in the art as described in U.S. Pat.
No. 3,378,477. That is, the polyacryl resin varnish containing from
about 5 to 50% by weight of a polyacryl resin can be used with a
load voltage of from about 10 to 200 V for the aqueous solution
varnish and from about 1 to 50 V for the aqueous dispersion
varnish. In the electrodeposition coating, an A.C. current can be
superposed on the D.C. current. The conductor W having coated
thereon the electrodeposited coating of the polyacryl resin can
then be dried and baked, or can be directly subjected to the
over-coating of the polyester resin varnish. However, it is
preferred, in particular, when the polyacryl resin varnish is in
the form of an aqueous dispersion, that the polyacryl resin coated
conductor be passed through an organic solvent bath 12 filled with
an organic solvent 10 which is capable of dissolving water to an
extent of at least about 1% by weight, preferably at least about
10% by weight and which is capable of at least swelling,
preferably, dissolving the polyacryl resin deposited on the
conductor prior to the heat-drying or the crosslinking of the
resin. In this manner, the water contained in the polyacryl resin
deposited on the conductor is eluted into the organic solvent and,
at the same time, a portion of the organic solvent penetrates into
the deposited polyacryl resin layer during the passage of the
conductor through the organic solvent bath, whereby the penetrated
solvent retained in the resin layer serves to render the film more
uniform with less pinholes by swelling or dissolving the resin
until it is removed in a subsequent evaporation step. The treatment
with the organic solvent should preferably be accomplished while
the polyacryl resin deposited on the conductor remains wet by a
medium for the polyacryl resin varnish (in this embodiment, water),
or a poor result will be obtained if the treatment is carried out
after the deposited polyacryl resin is dried.
Also, since the treatment with the organic solvent is not effective
on the semi-cured or completely cured polyacryl resin, it is
necessary that the organic solvent used be capable of at least
swelling the polyacryl resin before the semi-cured stage. Examples
of such organic solvents both dissolving water and swelling and/or
dissolving the resin are monohydride or polyhydric alcohols such as
methanol, ethanol, propanol, ethylene glycol, glycerine and the
like, cellosolves such as ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether, ethylene glycol isopropyl ether,
ethylene glycol monobutyl ether, ethylene glycol diethyl ether,
ethylene glycol dibutyl ether, ethylene glycol monophenyl ether and
the like, nitrogen-containing organic solvents such as
N,N-dimethylformamide, N,N-dimethylacetamide, N-2-methylpyrrolidone
and the like, sulfur-containing organic solvents such as
dimethylsulfoxide, etc. In particular, N,N-dimethylformamide,
N,N-dimethylacetamide, N-2-methylpyrrolidone and dimethylsulfoxide
are preferred.
In a preferred and particularly, advantageous embodiment of this
invention, a D.C. voltage of from about 30 to 500 V with or without
an A.C. voltage superposed thereupon lower than the D.C. voltage is
applied between a cathode (not shown) mounted in the bath 12 and
the conductor W passing through the cathode. In this manner, the
water in the deposited layer can be removed uniformly and
effectively so as to give an insulated wire having more stable
qualities.
As an alternative procedure for treatment of the deposited resin
layer with an organic solvent, the deposited resin layer can be
exposed to an organic solvent vapor or the organic solvent can be
sprayed on the deposited resin layer, etc. as described in British
Pat. No. 1,169,447.
It is preferred to continuously remove any excess of the bath
liquid 4 and the bath liquid 10 adhering to the resin layer by
providing a wiping means such as an air-wiper, roll-wiper and the
like at the outlet of the electrodeposition bath 4 and the organic
solvent bath 12. The adhering liquid sometimes prevents a high
speed operation of the electrodeposition coating of the polyacryl
resin, because of blistering of the adhering liquid in the baking
process and such a wiping means eliminates the liquid so as to
permit a conductor line speed of greater than about 50 m per
minute.
The conductor from the organic solvent bath 12 is then introduced
into a drying means 14 where the conductor is heated and the
organic solvent from the bath 12 and water remaining in the resin
layer in those methods retaining water are removed by evaporation.
The drying temperature in the drying means 14 varies somewhat
depending upon the type of the organic solvent, but generally
ranges from about 60.degree. to 200.degree.C, preferably from about
100.degree. to 200.degree.C. In the drying means 14, an elevated
temperature (for example, about 200.degree.C to 600.degree.C) can
be used for promoting the removal of liquids and at the same time
for curing or semi-curing the polyacryl resin deposited on the
conductor. Alternatively, the last portion of the drying means 14
can be maintained at the temperature required for curing the
polyacryl resin or a baking means can be provided separately at the
end of the drying means, whereby the polyacryl resin layer is first
dried at a relatively low temperature, i.e., about 100.degree.C and
then cured or semi-cured at a high temperature. The above-described
procedure where the drying and baking are conducted separately is
particularly preferred for prevention of blistering due to the
rapid evaporation of the liquid from the polyacryl resin layer. The
conductor from the drying means 14 is then passed on the bath 18
filled with a polyester resin varnish 16 while contacting a roll 20
which is mounted in the bath 18 and rotates freely. While passing
on the roll 20, the polyacryl resin layer on the conductor is
over-coated with a polyester resin varnish 16 by the roll 20, and
an excess of the varnish 16 is wiped by a metering device 22 such
as a metal die which is fixedly mounted downstream of the roll 20.
The conductor W which has been dual coated with the polyacryl resin
and the polyester resin is sent to a baking oven 24 and both layers
(or the polyester layer alone when the polyacryl resin layer has
already been baked) are baked and cured. The baking temperature of
the baking oven 24 can be approximately the same whether both
polyacryl and polyester layers are baked simultaneously or only the
polyester resin layer is baked and generally is in the range of
from about 200.degree. to 600.degree.C. The conductor from the
baking oven can be immediately wound on a reel 26 or, if necessary,
the conductor may be repeatedly passed several times through the
polyester resin bath 18 and the baking oven 24 in order to obtain a
desired layer thickness of the polyester resin layer.
In place of the application of the polyester resin as described
above, the polyester resin can be coated on the polyacryl resin
layer using electrodeposition coating under conditions and
procedures similar to those described for the electrodeposition of
the polyacryl resin layer using an electrodeposition varnish of the
polyester resin in the form of an aqueous dispersion or an aqueous
solution containing about 5 to 50% by weight of the polyester
resin.
The following examples illustrate in greater detail the insulated
wires of the present invention and their excellent properties as
well as the process for the production of the insulated wires, but
they are not to be construed as limiting the scope of this
invention.
The coating materials containing polyacryl resins or polyester
resins were prepared according to the following procedures. Of
these coating materials, "Acryl-A" to "Acryl-L" and "Polyester-A"
to "Polyester-I" are polyacryl resins and polyester resin coating
materials, respectively, suitable for the present invention, and
"Acryl-M" and "Polyester-J" were prepared for the purpose of
comparison.
[Polyacryl-A]
A monomer mixture consisting of 5 moles of acrylonitrile, 1 mole of
acrylic acid, 0.3 mole of glycidylmethacrylate, 760 g of deionized
water, 7.5 g of sodium lauryl sulfate, and 0.13 g of sodium
persulfate were charged into a flask, and stirred under a nitrogen
stream at room temperature for 15 to 30 minutes. Thereafter the
mixture was reacted at a temperature of 50.degree. to 60.degree.C
for a period of 4 hours to obtain an acryl varnish as an aqueous
dispersion.
[Polyacryl-B]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using a monomer mixture
consisting of 5 moles of acrolein, 1 mole of methacrylic acid and
0.3 mole of acrylic amide in place of the monomer mixture of
Polyacryl-A.
[Polyacryl-C]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using a monomer mixture
consisting of 5 moles of ethylacrylate, 1 mole of acrylic acid, 0.3
mole of methylol acrylamide, 1200 g of deionized water, 12 g of
sodium lauryl sulfate and 0.2 g of sodium persulfate.
[Polyacryl-D]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of acrylonitrile,
1 mole of maleic acid, 0.3 mole of glycidyl methacrylate, 840 g of
deionized water, 8 g of sodium lauryl sulfate and 0.15 g of sodium
persulfate.
[Polyacryl-E]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of ethylacrylate,
1 mole of maleic acid, 0.3 mole of glycidyl acrylate, 1300 g of
deionized water, 13 g of sodium lauryl sulfate and 0.2 g of sodium
persulfate.
[Polyacryl-F]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using a monomer mixture
consisting of 5 moles of methacrylonitrile, 1 mole of methacrylic
acid, 0.3 mole of methylol acrylamide, 900 g of deionized water, 9
g of sodium lauryl sulfate and 0.2 g of sodium persulfate.
[Polyacryl-G]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of
methacrylonitrile, 1 mole of maleic acid, 0.3 mole of allyl
glycidyl ether, 970 g of deionized water, 10 g of sodium lauryl
sulfate and 0.15 g of sodium persulfate.
[Polyacryl-H]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 3 moles of acrylonitrile,
2 moles of ethylacrylate, 0.5 mole of acrylic acid, 0.5 mole of
methacrylic acid, 0.2 mole of glycidyl methacrylate, 0.1 mole of
acrylamide, 950 g of deionized water, 9.5 g of sodium lauryl
sulfate and 0.16 g of sodium persulfate.
[Polyacryl-I]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of
methylmethacrylate, 0.5 mole of acrylic acid, 0.5 mole of
methacrylic acid, 0.2 mole of glycidyl methacrylate, 0.1 mole of
acrylamide, 1200 g of deionized water, 12 g of sodium lauryl
sulfate and 0.2 g of sodium persulfate.
[Polyacryl-J]
the acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of butyl acrylate,
0.5 mole of acrylic acid, 0.5 mole of methacrylic acid, 0.2 mole of
glycidyl methacrylate, 0.1 mole of acrylamide, 1500 g of deionized
water, 15 g of sodium lauryl sulfate and 0.25 g of sodium
persulfate.
[Polyacryl-K]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 5 moles of acrylonitrile,
1 mole of acrylic acid, 0.3 mole of glycidyl methacrylate, 2 moles
of styrene, 1200 g of deionized water, 12 g of sodium lauryl
sulfate and 0.2 g of sodium persulfate.
[Polyacryl-L]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 3 moles of acrylonitrile,
2 moles of ethyl acrylate, 0.5 mole of acrylic acid, 0.5 mole of
methacrylic acid, 0.2 mole of glycidyl methacrylate, 0.1 mole of
acrylamide, 1 mole of 1,3-butadiene, 1100 g of deionized water, 11
g of sodium lauryl sulfate and 0.18 g of sodium persulfate.
[Polyacryl-M]
The acryl varnish was prepared in the same manner as described in
the preparation of Polyacryl-A but using 2 moles of styrene, 5
moles of ethyl acrylate, 1400 g of deionized water, 14 g of sodium
lauryl sulfate and 0.2 g of sodium persulfate.
The concentration of a polyacryl resin in each of the above
Polyacryl-A to Polyacryl-M varnishes was about 30% by weight.
[Polyester-A]
The polyester resin was prepared from the following
composition:
Dimethyl Terephthalate 223.1 g (46% equivalents) Ethylene Glycol
48.1 g (31% equivalents) Glycerin 35.2 g (23% equivalents)
A mixture of the above composition and 50 g of xylol was charged
into a four-necked flask equipped with a thermometer, a stirrer and
a Liebig condenser. The flask was then heated to a temperature of
about 130.degree.C over 30 minutes while introducing nitrogen gas
through an additional inlet, with the methyl alcohol formed in the
course of the reaction being removed continuously from the flask as
an azeotropic mixture with the xylol. At this point, lead acetate
was added to the reaction mixture in an amount equivalent to about
0.03% by weight based on the weight of dimethyl terephthalate, and
the heating was continued for additional 3.5 hours at the end of
which time the temperature of reaction mixture reached
240.degree.C. To the resulting hot resin was then added cresol in
an amount sufficient to obtain a resin solution having a solids
content of 44.8% by weight.
[Polyester-B]
52.4 g of 4,4'-diisocyanate-dicyclohexylmethane, 57.6 g of
trimellitic anhydride and 250 g of cresol were heated in a flask at
a temperature of 70.degree. to 75.degree.C for a period of 5 hours
while stirring. To the resulting solution was then added an excess
of acetone to precipitate a resin.
388 g (39.8% equivalents) of dimethyl terephthalate, 137 g (35.8%
equivalents) of propylene glycol, 75 g (24.4% equivalents) of
glycerin, 337 g of the above resin precipitate and xylene were then
charged into a flask, and lead acetate was added to the mixture in
an amount of 0.05% by weight based on the amount of dimethyl
terephthalate. The mixture was then heated at a temperature of
150.degree.C under a nitrogen stream for 10 hours to obtain a
polyesteramide-imide resin. The resin was diluted with cresol to a
solids content of 40% and zinc octoate was added in an amount
sufficient to adjust to a zince content of 0.2% by weight to obtain
the desired varnish.
[Polyester-C]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-A but using 43.5 g (10%
equivalents) of tris-2-hydroxyethyl isocyanurate and 19.9 g (13%
equivalents) of glycerin in place of 35.2 g (23% equivalents) of
glycerin to obtain a varnish having a solids content of 40% by
weight.
[Polyester-D]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-B but using 33.6 g of hexamethylene
diisocyanate in place of 52.4 g of
4,4'-di-isocyanate-dicyclohexylmethane and 51.6 g of butane
tricarboxylic anhydride in place of 57.6 g of trimellitic
anhydride.
[Polyester-E]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-A but using 223.1 g (46%
equivalents) of dimethyl terephthalate, 31.0 g (20% equivalents) of
ethylene glycol, 20.9 g (11% equivalents) of propylene glycol, 19.9
g (13% equivalents) of glycerin and 22.3 g (10% equivalents) of
1,1,1-trimethylolpropane to obtain a varnish having a solids
content of 30% by weight.
[Polyester-F]
150 g of trimellitic anhydride was dissolved in 500 g of cresol at
a temperature of 150.degree.C and, after the anhydride was
completely dissolved, 60 g of 4,4'-diaminediphenylmethane was added
to the resulting solution. The mixture was then stirred for 6 hours
at a temperature of 140.degree.C and allowed to cool to obtain a
pale yellow precipitate. The precipitate was filtered and washed
several times with ethanol and ether to obtain an imide-group
containing substance.
Separately, 388 g (39.8% equivalents) of dimethyl terephthalate,
163 g (36.0% equivalents) of 1,4-butanediol and 75 g (24.2%
equivalents) of glycerin were reacted in the same manner as
described in the preparation of Polyester-A to obtain a polyester
resin.
137 g of the above imide-group containing substance was then added
to the polyester resin, and the mixture was heated at a temperature
in the range of from 180.degree. to 215.degree.C until a
homogeneous mixture where the imide-group containing substance was
completely integrated with the polyester resin was obtained. Then,
1.8 g of cadmium acetate was added to the mixture and the resulting
mixture was heated at a temperature of 215.degree.C for 3 hours in
vacuo. 450 g of cresol and 27 g of a cresol solution containing 9 g
of butyl titanate were added followed by cresol to obtain a varnish
having a solids content of 37% by weight.
[Polyester-G]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-F but using 70 g (22.5%
equivalents) of ethylene glycol and 51 g (13.3% equivalents) of
propylene glycol in place of 163 g (36.0% equivalents) of
1,4-butanediol and 45 g (14.6% equivalents) of glycerin and 85 g
(9.8% equivalents) of tris-2-hydroxyethylisocyanurate in place of
75 g (24.2% equivalents) of glycerin to obtain a varnish having a
solids content of 37% by weight.
[Polyester-H]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-A but using 195.0 g (40.2%
equivalents) of dimethyl terephthalate, 28.1 g (5.8% equivalents)
of dimethyl isophthalate, 31.0 g (20.0% equivalents) of ethylene
glycol, 13.5 g (6.0% equivalents) of 1,4-butanediol and 42.9 g (28%
equivalents) of glycerin to obtain a varnish having a solids
content of 43% by weight.
[Polyester-I]
The polyester varnish was prepared in the same manner as described
in the preparation of Polyester-A but using 223.1 g (46.0%
equivalents) of dimethyl terephthalate, 38.8 g (25.0% equivalents)
of ethylene glycol, 13.5 g (6.0% equivalents) of 1,4-butanediol,
30.7 g (20.0% equivalents) of glycerin, 5.1 g (3.0% equivalents) of
pentaerythritol to obtain a varnish having a solids content of 30%
by weight.
[Polyester-J]
98 g (23.8% equivalents) of maleic anhydride, 148 g (23.8%
equivalents) of phthalic anhydride and 233 g (52.4% equivalents) of
diethylene glycol were reacted in a manner similar to that
described in the preparation of Polyester-A but using about 0.02 g
of hydroquinone as a polymerization inhibitor and a sufficient
amount of styrene to obtain a polyester resin solution having a
solids content of 50% by weight.
EXAMPLE 1
A copper conductor having a diameter of 0.3 mm was coated with
Polyacryl-A by the conventional dip-coating procedure using a
horizontal coating machine and a metal die, and the coated
conductor was then baked at a line speed of 40 m/minute at a
temperature of 400.degree.C. The above procedure was repeated five
times to form an insulating under-layer having a layer thickness of
22 .mu. on the copper conductor. Polyester-A was then coated on the
insulating under-layer at a lined speed of 40 m/minute and the
coated conductor was baked one time at a temperature of
450.degree.C to form an insulating upper-layer having a layer
thickness of 3 .mu. to obtain a dual coated wire having a total
insulating coating thickness of 25 .mu..
EXAMPLE 2
A copper conductor having a diameter of 0.3 mm as an anode was
coated with Polyacryl-B by employing conventional electrodeposition
coating using a horizontal coating machine at a line speed of 40
m/minute under the following conditions:
Cathode: A copper cylindrical tube of 6 cm in diameter and 30 cm in
length
Distance between Electrodes: 3 cm
Electrodeposition Voltage: 5V D.C.
Varnish Temperature: 30 .+-. 1.degree.C
The coated conductor was then passed through a chamber having a
length of 1 m filled with a saturated vapor of
N,N-dimethylformamide at 155.degree.C to provide a vapor of
N,N-dimethylformamide on the acryl varnish resin layer deposited on
the copper conductor, and the deposited layer thus treated with the
vapor was dried at 200.degree.C to from a smooth insulating
under-layer having a layer thickness of 22 .mu.. Polyester-B was
then coated one time on the above insulating under-layer at a line
speed of 40 m/minute and a simultaneous baking of the insulating
under-layer and the upper-layer was carried out at a temperature of
450.degree.C to form an insulating upper-layer having a layer
thickness of 3 .mu. whereby a dual coated wire having a total
coating thickness of 25 .mu. was obtained.
EXAMPLE 3
A copper conductor having a diameter of 0.3 mm as an anode was
coated with Polyacryl-C by employing conventional electrodeposition
coating using a horizontal coating machine at a line speed of 60
m/minute under the following conditions:
Cathode: A copper cylindrical tube of 6 cm in diameter and 30 cm in
length
Distance between Electrodes: 3 cm
Electrodeposition Voltage: 7V D.C.
Varnish Temperature: 30 .+-. 1.degree.C
Any excess of the electrodeposition varnish remaining on the
resulting deposited acryl resin layer was then removed using an
air-wiper with a blowing nozzle angle and a slit width of the
blowing nozzle of 45.degree. and 0.1 mm, respectively, under an air
supply pressure of 0.3 Kg/cm.sup.2. And the thus coated conductor
was passed through a cylindrical cathode tube described below which
was set in a liquid bath filled with N,N-dimethylformamide, while a
voltage was applied between the conductor as an anode and the
cathode under the following conditions:
Cathode: A copper cylindrical tube of 6 cm in diameter and 30 cm in
length
Distance between Electrodes: 3 cm
Voltage Applied: 200V D.C.
Bath Temperature: 30 .+-. 1.degree.C
Any excess of N,N-dimethylformamide remaining on the acryl resin
layer leaving the bath was then removed by air-wipering as
described above but using an air-supply pressure of 0.5
Kg/cm.sup.2, and the resin layer was dried at a temperature of
200.degree.C to form a smooth insulating under-layer having a layer
thickness of 22 .mu.. Polyester-C was then coated one time on the
above insulating under-layer at a line speed of 60 m/minute, and a
simultaneous baking of the insulating under-layer and the
upper-layer was carried out at a temperature of 550.degree.C to
form an insulating upper-layer having a layer thickness of 3 .mu.
whereby a dual coated wire having a total coating thickness of 25
.mu. was obtained.
EXAMPLES 4 TO 12 AND COMPARATIVE EXAMPLES 1 TO 5
Similar preparation methods for producing a dual coated wire as
described in Example 3 were repeated in Examples 4 to 12, and in
Comparative Examples 3 and 4, whereas similar preparation of
Example 1 in Comparative Examples 1, 2 and 5, were conducted but
using the varnishes shown in Table 1 in place of the Polyacryl-B
and Polyester-B, or Polyacryl-A and Polyester-A, respectively,
employed in these examples.
The polyvinyl formal (PVF) varnish used in Comparative Examples 4
and 5 is composed of 100 parts (by weight) of a polyvinyl formal
resin (trade name: "BINIREKKU-FL", manufactured by Chisso Co.), 70
parts of trimer of toluene diisocyanate stabilized with glycerin
and phenol, 15 parts of a resole type phenolformaldehyde resin
(trade name: "Plyophen 5030", manufactured by Japan Reichhold
Chemicals Inc.), 5 parts of butylated melamine, 200 parts of
m-cresol, and 300 parts of solvent naphtha.
Each insulated wire prepared in Examples 1 to 12, and Comparative
Examples 1 to 5 was subjected to several tests including heat
resistance as well as general test evaluations for determining the
characteristics and properties of the insulated magnet wire.
The test results obtained are shown in Table 1, wherein heat
resistance of each wire is shown as thermal life which corresponds
to the period of time at the end of which wire, tested in
accordance with IEEE No. 57, failed.
In order to compare the heat resistance of each dual coated wire of
the above Examples and Comparative Examples with those of
corresponding single coated wires which are insulated only with the
varnish used in the under or upper layer of corresponding dual
coated wire, single coated wires prepared by the methods described
hereinafter and were subjected to heat resistance test at
220.degree.C and 260.degree.C in accordance with IEEE No. 57.
The test result of each of single coated wire insulated with the
under layer varnish of tfhe corresponding dual coated wire is shown
with thermal life in the row of Table 1 designated as "Single
Coated Wires-a", whereas the test result of each wire insulated
with the upper layer varnish of the corresponding dual coated wire
in the row indicated as "Single Coated Wire-b", respectively.
Preparation of single coated wires
Using the above described polyacryl varnishes Polyacryl-A to
Polyacryl-L, twelve kinds of polyacryl single coated wires were
prepared by the method used in applying Polyacryl-C on a conductor
as described in Example 3 except that the electrodeposition
voltages was 8V instead of 7V, whereby a coating thickness after
baking at 550.degree.C became 25 .mu.. Insulated wires coated with
Polyacryl-M or the PVF varnish were prepared using the method for
applying Polyacryl-A on the conductor as described in Example 1
except that the coating and baking procedure was repeated six times
instead of five times so that the film thickness became 25 .mu.
after baking at 400.degree.C. Also, using the above polyester
varnishes, Polyester-A to Polyester-J, 10 kinds of polyester single
coated wires were prepared, wherein a copper conductor, 0.3 mm in
diameter, was coated with a polyester varnish aforementioned by the
conventional dip-coating using a horizontal coating machine and a
metal die, thenafter the coated conductor was introduced into an
oven maintained at a temperature of 400.degree.C in a line speed of
40 m/minute to bake the coating layer at that temperature. The
above procedure was repeated six times to form a baked coating
layer having a coating thickness of 25 .mu..
As seen in Table 1, all of the dual coated insulating wire of
Examples 1 to 12 not only has a surpisingly superior thermal life
(heat resistance) at both of the temperatures examined in
comparison with the thermal life of the corresponding single coated
wires as well as that of any of the dual coated insulating wires of
the Comparative Examples, but also has well-balanced
properties.
Table 1
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Example 1 Example 2 Example 3 Example 4 Example Example
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6 Under Layer Polyacryl Polyacryl Polyacryl Polyacryl Polyacryl
Polyacryl Wire B C D E F Structure Polyester Polyester Polyester
Polyester Polyester Polyester Upper Layer A B C D E F Continuity*
(number of 0 0 0 0 0 0 pinholes/5m) Mandrel Diameter* good for good
for good for good for good for good for 1X 1X 1X 1X 1X 1X Breakdown
Voltage* (KV) 9.0 8.8 9.0 9.5 9.0 8.5 Abrasion Resistance* 35 55 30
43 38 51 (strokes) Cut Through Tempera- 180 178 178 172 163 183
ture** (.degree.C) Heat Shock, good for good for good for good for
good for good for at 200.degree.C .times. 1 hr 2X 1X 3X 1X 2X 1X
Sulfuric Chemical and Acid (S.G. pass pass pass pass pass pass
Solvent = 1.2) Resistance*, Sodium 30.degree.C .times. 24 Hydroxide
pass pass pass pass pass pass hrs (1%) Benzene pass pass pass pass
pass pass Thermal Life***, 2520 11840 5830 6510 1730 1820
220.degree.C (hrs) Compared Single coated 278 270 273 280 278 303
Thermal wire - a Life***, 220.degree.C Single coated 1380 4030 3420
2632 1221 1050 (hrs) wire - b Thermal Life***, 230 643 465 583 184
139 260.degree.C (hrs) Compared Single coated 45 42 42 40 39 39
Thermal wire - a Life***, 260.degree.C Single coated 153 344 338
268 154 81 (hrs) wire - b
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Example 7 Example 8 Example 9 Example 10 Example Example
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12 Under Layer Polyacryl Polyacryl Polyacryl Polyacryl Polyacryl
Polyacryl Wire H I J K L Structure Polyester Polyester Polyester
Polyester Polyester Polyester Upper Layer G H I A C G Continuity*
(number of 0 0 0 0 0 0 pinholes/5 m) Mandrel Diameter* good for
good for good for good for good for good for 1X 1X 1X 1X 1X 1X
Breakdown Voltage* (KV) 9.0 9.0 8.8 9.4 9.2 9.0 Abrasion
Resistance* 52 34 40 36 40 49 (strokes) Cut Through Tempera- 185
170 169 163 180 177 ture** (.degree.C) Heat Shock, good for good
for good for good for good for good for at 200.degree.C .times. 1
hr 1X 2X 3X 2X 3X 1X Sulfuric Chemical and Acid (S.G. pass pass
pass pass pass pass Solvent = 1.2) Resistance*, Sodium 30.degree.C
.times. 24 Hydroxide pass pass pass pass pass pass hrs (1%) Benzene
pass pass pass pass pass pass Thermal Life***, 11400 1710 2030 1982
6321 11310 220.degree.C (hrs) Compared Single coated 298 308 273
270 295 284 Thermal wire - a Life***, 220.degree.C Single coated
5110 998 1032 1380 3420 5110 (hrs) wire - b Thermal Life***, 680
183 210 178 525 598 260.degree.C (hrs) Compared Single coated 43 40
41 42 41 44 Thermal wire - a Life***, 260.degree.C Single coated
473 126 137 153 338 473 (hrs) wire - b
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Comparative Comparative Comparative Comparative Comparative Example
1 Example 2 Example 3 Example 4 Example
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5 Under Layer Polyacryl Polyacryl Polyacryl Polyacryl PVF Wire M A
A Structure Polyester Polyester Polyester PVF Polyester Upper Layer
J A J A Continuity* (number of O 0 0 0 0 pinholes/ 5 m) Mandrel
Diameter* good for good for good for good for good for 1X 1X 1X 1X
1X Breakdown Voltage* (KV) 8.1 8.4 9.1 9.4 9.9 Abrasion Resistance*
3 5 17 44 65 (strokes) Cut Through Tempera- 83 90 140 170 201
ture** (.degree.C) Heat Shock, good for good for good for good for
good for at 200.degree.C .times. 1 hr 5X 4X 3X 1X 1X Sulfuric Acid
(S.G. pass pass pass pass pass Chemical and = 1.2) Solvent
Resistance*, Sodium 30.degree.C .times. 24 Hydroxide pass pass pass
pass pass hrs (1%) Benzene fail fail pass pass pass Thermal
Life***, 100 295 195 185 290 220.degree.C (hrs) Compared Single
coated 101 101 278 278 96 Thermal wire - a Life***, 220.degree.C
Single coated 89 1380 89 96 1380 (hrs) wire - b Thermal Life***, 19
49 29 33 43 260.degree.C (hrs) Compared Single coated 23 23 45 45
22
Thermal wire - a Life***, 260.degree.C Single coated 13 153 13 22
153 (hrs) wire - b
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*tested in accordance with JIS C 3210 **tested in accordance with
MIL-W-583C 4,7,11,1. ***tested in accordance with IEEE No.57
While the invention has been described in detail and with reference
to specific embodiments thereof, it will be apparent to one skilled
in the art that various changes and modifications can be made
therein without departing from the spirit and scope thereof.
* * * * *