TITLE: Electrically insulating material
European Patent EP0262472
 B1

ABSTRACT:
Abstract of EP0262472
The present invention is an electrically insulating material,
comprising a cured product of a liquid polymer composition comprising a
hydrogenated product of a liquid polyisoprene containing hydroxyl
groups and a polyisocyanate compound, which is useful for electronic
and electrical circuit boards; the molding materials for current
transformers or transformers; molding materials for connecting portions
such as cables, impregnation or casting materials for transformers or
coils, etc.

INVENTORS:
Okamoto, Kohei (6-37, Wakakusa-cho Tokuyama-shi, Yamaguchi-ken, JP)
Tsurushita, Kenji (6-37, Wakakusa-cho Tokuyama-shi, Yamaguchi-ken, JP)
Fujii, Isao (2777-5, Tondahamada Shinnanyo-shi, Yamaguchi-ken, JP)

APPLICATION NUMBER: EP19870113114
PUBLICATION DATE: 12/22/1993
FILING DATE: 09/08/1987

ASSIGNEE: IDEMITSU PETROCHEMICAL CO. LTD. (1-1, Marunouchi 3-chome Chiyoda-ku,
Tokyo, 100, JP)
INTERNATIONAL CLASSES: C08G18/62; H01B3/30; C08G18/00; H01B3/30; (IPC1-7): H01B3/30;
C08G18/62; C08G18/69
EUROPEAN CLASSES: C08G18/62B6; H01B3/30B

OTHER REFERENCES:
CHEMICAL PATENTS INDEX BASIC ABSTRACTS JOURNAL, section A, PLASDOC, 4th
May 1988, no. 88-067035/10, Derwent Publications Ltd, London, GB; &
JP-A-63 020 315 (IDEMITSU PETROCHEM K.K.) 28-01-1988
CHEMICAL PATENTS INDEX, BASIC ABSTRACTS JOURNAL, section A, PLASDOC,
15th October 1986, no. 86-223178/34, Derwent Publications Ltd, London,
GB; & JP-A-61 155 419 (SANYO CHEM. IND. LTD) 15-07-1986
WPI, FILE SUPPLIER, no. 80-75830C, Derwent Publications Ltd, London,
GB; & JP-A-55 116 720 (MITSUBISHI CHEM. IND. K.K.) 09-09-1980
WPI, FILE SUPPLIER, no. 80-75829C, Derwent Publications Ltd, London,
GB; & JP-A-55 116 719 (MITSUBISHI CHEM. IND. K.K.) 09-09-1980
DIE ANGEWANDTE MAKROMOLEKULARE CHEMIE, vol. 95, April 1981, pages
67-81, Hüthig & Wepf Verlag, Heidelberg, DE; Y. CAMBERLIN et al.:
"Synthèse et propriétés de poly(uréthannes-b-diènes hydrogénés)"
Attorney, Agent or Firm:
Kraus, Dr. Walter (Patentanwälte Kraus, Weisert & Partner
Thomas-Wimmer-Ring 15, München, D-80539, DE)

CLAIMS:
1. Use of a cured product of a liquid polymer composition comprising a
hydrogenated product of a liquid polyisoprene containing a hydroxyl
group and a compound selected from the group consisting of toluylene
diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate
(MDI), xylylene diisocyanate, cyclohexyl diisocyanate, phenylene
diisocyanate, naphthalene-1,5-diisocyanate,
isopropylbenzene-2,4-diisocyanate, isophorone diisocyanate, an adduct
of polypropylene qlycol and toluylene diisocyanate, and optionally a
polyol compound or a polyamine compound as an electrically insulating
material for a circuit board.
2. Use according to claim 1 wherein a liquid polyisoprene having a
hydroxyl group which has a number average molecular weight of 300 to
25,000 is used.
3. Use according to claim 2 wherein a liquid polyisoprene having a
hydroxyl group which has a number average molecular weight of 500 to
10,000 is used.
4. Use according to claim 1 wherein a liquid polyisoprene having a
hydroxyl group content in the range of 0.1 to 10 meq/g is used.
5. Use according to claim 4 wherein a liquid polyisoprene having a
hydroxyl group content in the range of 0.3 to 7 meq/g is used.
6. Use according to claim 1 wherein a polyisocyanate compound selected
from the group consisting of
      diphenylmethane diisocyanate and toluylene diisocyanate is used.
7. Use according to claim 1 wherein the ratio of the isocyanate groups
relative to the hydroxyl groups is in the range of 0.2 to 25.
8. Use according to claim 7 wherein the ratio of the isocyanate groups
relative to the hydroxyl groups is in the range of 0.5 to 15.

DESCRIPTION:
This invention relates to an electrically insulating material.
In the prior art, as an insulating material for a circuit board, for
example, compositions comprising a liquid polybutadiene and a
polyisocyanate compound have been known. Since these are liquid
compositions, they have been used, for example, as the so called
potting material which is casted on a print board, or as the so called
dipping material in which a print board is dipped, and, in general,
after completion of these treatments, curing is effected to form an
insulating material. Whereas, the electrical insulating material
comprising the above composition suffered from inconveniences such as
inferior weathering resistance and thermal aging resistance.
Synthèse et propriétés de poly(uréthannes-b-diènes hydrogénés); Die
angew. Makromolekulare Chemie 95, (1981); p. 67-81, describes on page
67 the reaction of hydroxyterminated, hydrogenated isoprene oligomers
with diphenylmethane diisocyanate (MDI) and 1,4-butanediol.
JP-61 155 419 describes a composition consisting of hydrogenated,
hydroxyterminated polyisoprene, certain triisocyanates and an inert
oleophilic compound.
Accordingly, in place of the above liquid polybutadiene, it has been
proposed to use a hyrogenated product thereof. When such a hydrogenated
product of the liquid polybutadiene is used, although weathering
resistance of the insulating material obtained can be improved to some
extent, the following problems ensue as the result of influence from
the skeleton of the polybutadiene which is the starting material of the
hydrogenated product. That is, when the polybutadiene has much
1,4-addition type skeleton, the hydrogenated product becomes solid to
give no fluidity necessary as the potting material or the dipping
material, while when it contains much 1,2-addition type skelton, the
average functionality number becomes smaller due to its polymerization
process, and therefore there has been involved the problem that the
cured product will flow when heated.
An object of the present invention is to provide an electrically
insulating material having good fluidity as the potting material and
the dipping material before curing, and yet having excellent thermal
aging characteristic after curing.
A further object of the present invention is to provide an insulating
material useful for an electronic and electric circuit boards; the
molding materials for current transformers or voltage transformers; the
molding materials for connecting portions such as cables, impregnation
or casting materials for voltage transformers or coils, etc.
The present invention relates to the use of a cured product of a liquid
polymer composition comprising a hydrogenated product of a liquid
polyisoprene containing a hydroxyl group and a compound selected from
the group consisting of toluylene diisocyanate, hexamethylene
diisocyanate, diphenylmethane diisocyanate (MDI), xylylene
diisocyanate, cyclohexyl diisocyanate, phenylene diisocyanate,
naphthalene-1,5-diisocyanate, isopropylbenzene-2,4-diisocyanate,
isophorone diisocyanate, an adduct of polypropylene qlycol and
toluylene diisocyanate, and optionally a polyol compound or a polyamine
compound as an electrically insulating material for a circuit board.
As the liquid polyisoprene having hydroxyl group which is one essential
component in the above liquid polymer composition, there may be
employed a liquid polyisoprene having hydroxyl group in the molecule or
at the terminal end of the molecule, having a number average molecular
weight of 300 to 25,000, preferably 500 to 10,000. Here, the content of
hydroxyl groups may be generally 0.1 to 10 meq/g, preferably 0.3 to 7
meq/g.
Such a liquid polyisoprene can be produced by, for example, subjecting
isoprene to heating reaction in a liquid reaction medium in the
presence of hydrogen peroxide.
Further, by hydrogenating the liquid polyisoprene thus obtained in the
presence of a conventionally employed hydrogenation catalyst such as
Ni, Co, Ru, Pt and Rh, the liquid polyisoprene having hydroxyl groups
according to the present invention can be obtained.
Next, the polyisocyanate compound which is the second essential
component is an organic compound having two or more isocyanate groups
in one molecule, having isocyanate groups reactive with the hydroxyl
group of the above hydrogenated product of a liquid polyisoprene
containing hydroxyl groups, and is selected from the group consisting
of toluylene diisocyanate, hexamethylene diisocyanate, diphenylmethane
diisocyanate (MDI), xylylene diisocyanate, cyclohexyl diisocyanate,
phenylene diisocyanate, naphthalene-1,5-diisocyanate,
isopropylbenzene-2,4-diisocyanate, isophorone diisocyanate, an adduct
of polypropylene glycol and toluylene diisocyanate. Above all, MDI,
diphenylmethane diisocyanate and toluylene diisocyanate are preferred.
The formulation ratio of the above-mentioned two components may
generally be such that the ratio of the isocyanate groups (NCO) in the
polyisocyanate compound relative to the hydroxyl groups (OH) in the
hydrogenated product of the polyisoprene containing hydroxyl groups may
be 0.2 to 25, preferably 0.5 to 15, particularly preferably 0.7 to 5,
in terms of molar ratio.
Further, if necessary, a polyol compound or a polyamine compound may be
added as a reinforcing agent. As the procedure for adding a polyol
compound or a polyamine compound, it may be added simulaneously with
formulation of the hydrogenated product of the polyisoprene containing
hydroxyl groups and the polyisocyanate compound, or it may be also
added after the hydrogenated product of the polyisoprene containing
hydroxyl group and the polyisocyanate compound are formulated at a
NCO/OH molar ratio of 1.5 or more to form a hydrogenated product of
polyisoprene containing isocyanate group at the terminal end.
In any case, as useful polyol compounds, any of primary polyols,
secondary polyols and tertiary polyols may be employed. Specific
examples may be low molecular weight polyols containing at least one
hydroxyl group bonded to a secondary carbon atom such as 1,2-propylene
glycol, dipropylene glycol, 1,2-butane diol, 1,3-butane diol,
2,3-butane diol, 1,2-pentane diol, 2,3-pentane diol, 2,5-hexane diol,
2,4-hexane diol, 2-ethyl-1,3-hexane diol, cyclohexane diol, glycerine,
N,N-bis(2-hydroxypropyl)aniline,
N,N'-bishydroxyisopropyl-2-methylpiperazine, a propylene oxide adduct
of bisphenol A, etc.
Further, as the polyol, there may also be used ethylene glycol,
1,3-propylene glycol, 1,4-butane diol, 1,5-pentane diol, 1,6-hexane
diol, etc. containing no hydroxyl group bonded to a secondary carbon
atom. As the polyol, a diol is usually used, but a triol such as
trimethylol propane, etc. or tetraol may be also used, and its
molecular weight is within the range of from 50 to 500.
On the other hand, as the polyamine compound, any of a diamine, a
triamine or a tetramine may be used. Further, any of primary
polyamines, secondary polyamines and tertiary polyamines can be used.
As examples for the polyamine compounds, there may be mentioned
aliphatic amines such as hexamethylene diamine; alicyclic amines such
as 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane; aromatic amines such
as 4,4'-diaminodiphenyl; tetramines such as
2,4,6-tri(dimethylaminomethyl)phenol; and so on.
When these polyol compounds or polyamine compounds are to be
formulated, their formulation ratios are not particularly limited, but
usually 1 to 1000 parts by weight, preferably 3 to 200 parts by weight,
particularly preferably 4 to 100 parts by weight, of a polyol compound
or a polyamine compound are formulated per 100 parts by weight of the
liquid hydrogenated polyisoprene containing hydroxyl group as described
above.
Further, as other additives to be added if desired, there may be
included fillers such as mica, graphite, vermiculite, calcium
carbonate, hydrated alumina, barium sulfate, synthetic zeolite, slate
powder, etc.
Further, it is possible to add plasticizers such as dioctyl phthalate
as the viscosity controller, to add softening agents such as aromatic,
naphthenic and paraffinic oils or to add tackiness imparting agents
such as a alkyl phenol resin, a terpene resin, a terpene phenol resin,
a xylene formaldehyde resin, rosin, a hydrogenated rosin, a coumarone
resin, aliphatic and aromatic petroleum resins for controlling tacky
force or adhesive force. Also, a curing promotor such as dibutyl tin
dilaurate, stannous octoate, polyethylene diamine, etc. can be added.
For imparting flame retardancy, flame retardants such as phosphorus
compounds, halide compounds can be added, or a silicon compound can be
added as the defoaming agent.
Preparation example 1 (preparation of a liquid polyisoprene having a
hydroxyl group at the terminal end of the molecular chain).
A pressure reactor made of stainless steel having an inner volume of 1
litre was charged with 200 g of isoprene, 16 g of an aqueous 50 wt.%
hydrogen peroxide and 100 g of sec-butyl alcohol as the solvent, and
the reaction was carried out for 2 hours at a temperature of 120 °C and
under the maximum pressure of 8.10^5 Pa (8 kg/cm² G). After completion
of the reaction, the reaction mixture was withdrawn and shaken in a
separation funnel with addition of 600 g of water, and then the mixture
was left to stand for 3 hours. After separation of the organic layer,
distillation was conducted for 2 hours under a pressure of 266 Pa (2
mmHg) and at a temperature of 100 °C to remove the solvent, the monomer
and low boiling comonents to obtain a liquid polyisoprene having a
hydroxyl group at the terminal end. The yield was 68%. The liquid
polyisoprene had a number average molecular weight of 2150, a hydroxyl
group content of 0.96 meq/g and a viscosity of 56 ·10̅^5 Pa·s (56
poise) at 30°C.
Next, 100 g of the so obtained liquid polyisoprene having a hydroxyl
group at the terminal end was placed in the reaction vessel as
described above, and 100 g of cyclohexane as the solvent and 10 g of a
catalyst of 5 wt.% Ru-C were charged therein, and hydrogen was
introduced under a pressure of 5·10^6 Pa (50 kg/cm²G) into the vessel.
The temperature was 140 °C and the reaction time was made 5 hours.
After completion of the reaction, the reaction mixture was withdrawn
and filtered through a membrane filter (0.45 µ) to remove the catalyst,
followed by evaporation of the solvent for two hours under a pressure
of 2 mmHg and at a temperature of 110 °C to obtain the desired
hydrogenated product of the liquid polybutadiene having a hydroxyl
group at the terminal end of the molecular chain. The hydrogenated
product obtained had a number average molecular weight of 2210, a
hydroxyl group content of 0.94 meq/g, an iodine value of 1 or less and
a viscosity of 3.83·10̅^3 Pa·s (383 poise) at 30°C.
Preparation example 2 (preparation of a hydrogenated product of a
liquid polyisoprene having a hydroxyl group at the terminal end of the
molecular chain).
A liquid polyisoprene having a hydroxyl group at the terminal end of
the molecular chain was obtained in the same manner as in the above
Preparation example 1 except for changing the amount of the 50 wt.%
aqueous hydrogen peroxide used to 50 g, the amount of sec-butyl alcohol
used to 300 g, the reaction temperature to 115 °C and the reaction time
to 2.5 hours. This product had a number average molecular weight of
1380, a hydroxyl group content of 1.39 meq/g and a viscosity of
23·10̅^5 Pa·s (23 poise) at 30°C.
Subsequently, under the same conditions as in the above Preparation
example 1, hydrogenation was conducted to obtain a hydrogenated
product. This product had a number average molecular weight of 1450, a
hydroxyl group content of 1.36 meq/g, an iodine value of 1 or less and
a viscosity of 2.48·10̅^3 Pa·s (248 poise) at 30°C.
Preparation example 3 (preparation of a hydrogenated product of a
1,4-addition type liquid polybutadiene having a hydroxyl group at the
terminal end of the molecular chain).
As the 1,4-addition type liquid polybutadiene having a hydroxyl group
at the terminal end of the molecular chain, R-45HT produced by Idemitsu
Arco K.K. (average molecular weight: 2800, OH content: 0.82 meq/g,
viscosity at 30°C: 50·10̅^5 Pa·s (50 poise), 1,4-addition type skelton:
80 mol%, 1,2-addition type skelton: 20 mol%) was used and hydrogenated
to obtain a hydrogenated product. The hydrogenation conditions were set
in the same manner as in the above Preparation example 1 except that
the reaction time was made 4.5 hours and 500 ml of toluene was added
after completion of the reaction. The hyrogenated product obtained had
a number average molecular weight of 2920, an OH content of 0.80 meq/g,
and it was a waxy solid.
Preparation example 4 (preparation of a hydroqenated product of a
1,2-addition type liquid polybutadiene having a hydroxyl group
internally in the molecular chain).
As the 1,2-addition type liquid polybutadiene having a hydroxyl group
internally in the molecular chain, NISSO PB G-2000, produced by Nippon
Soda K.K. (number average molecular weight: 2,000, OH content: 0.85
meq/g, viscosity at 30°C: 19.3·10̅^3 Pa·s (1930 poise) was used and
hydrogenated under entirely the same conditions as in the Preparation
example 1 to obtain a hydrogenated product. The hydrogenated product
had a number average molecular weight of 2,080, an OH content of 0.84
meq/g, and it was a highly viscous liquid with its viscosity at 30 °C
being unmeasurable by use of a B type viscometer.
Preparation example 5 (preparation of a hydrogenated product of a
liquid polyisoprene having an isocyanate group at the terminal end of
the molecular chain)
An amount of 50 g of the hyrogenated product obtained in the above
Preparation example 1 was charged into a separable flask having an
inner volume of 300 ml, and 15.8 g of toluylene diisocyanate was added
thereto to carry out the reaction at 25 °C for 2 hours, followed by the
reaction at 70 °C for 4 hours, to give a hydrogenated product of a
liquid polyisoprene having an isocyanate group at the terminal end of
the molecular chain. This product contained 8.93 wt.% of isocyanate
groups (NCO groups) and had a viscosity of 5.73·10̅^3 Pa·s (573 poise)
at 30°C.
Examples 1 - 6, Comparative examples 1 - 3
The components indicated in the Table were sampled in a vessel in the
indicated amounts, and stirred at 25 °C for 2 minutes to prepare a
liquid polymer composition. Subsequently, this composition was casted
into a mold and press cured at 120 °C for 1 hour to obtain an
electrically insulating material of the present invention.
For each electrically insulating material obtained, volume resistivity
and elongation at 25 °C were measured. Also, physical properties after
a thermal aging test were measured for examination of the thermal aging
resistance, and the results are shown in the following Table.