Note: Descriptions are shown in the official language in which they were submitted.
11~65VO
1. Title of the Inventio~
C~L~ULO~ A~ED ELECTRIC I~SUI~TIO~ MATERIAL AND
P~OCESS FOR ~RODUCI~G '~`~R~O~
2. Field of Applicatio~ of the Inve~tion
rl'he prese~t i~ve~tion relates to electric i~sulation
materials ~nd ~rocesses ~or produci~g thereof, and more
particularly to a collulose-b~sed electric insalation
material and to a process of produci~g thereo~.
There is a~ ever gI'OWi~g demand for usuch mater1als
(electric insul~tion paper and cardboard) i~ spite of
-~he fact that more and more electric insulation materials
based o~ ~y~the~ic polymers, ceramics, etc find wide
application .
I~evertheless, as ~ar as the mai~ dielectric properties
and prolon~ed stability i~ a wide ran~e o~ operating tem-
peratures are co~cerned, cellulose-based electric insula-
tion materials do not meet growing requireme~ts imposed
on their quality by the electrical and radio engi~eeri~g
i~dustries.
One o~ the main dielectric properties are dielectric
power los~e~ i~ insulators op~rating in alter~ati~g curre~t
curcuits a3, ~or e~ample, intermediate layer i~ paper
c~pacitors or cable wi~di~s. Qualitatively these losses
are evaluated by dielec~ric lo~s ta~gent de~oted further
as ta~ ~ . The smaller this parameter, the lesser part
,,,. ~ , ~
- 2 - ~
65~0
of electric ~nergy is co~sumed for heat losses ar~d the
more reliable and long-lived is an article in which an
electric insulation material is used.
Another important property of electric insulation ma-
terials is their resistiYit~ measured usually in Ohm.cm.
'~he above-mentioned dielectric properties affect the
third importarlt parameter, ~amely, electric stre~gth.
This ef~ect is the stror~er, the less stable are tan
and resistivity within the operating temperature range
and the more pronounced i8 their change during operation.
Thus, for example, it has been shown that an ancre~se
in tan ~ due to cellulose ageing leads to a temperature
rise i~side the condenser which, in its tur~, accelerates
cellulose ageing and causes a further increase of tan
a~d temperature u~til a therm~lbreak-dow~ takes place
and the condenser or cable fail to operate. A decrease of
resistivity due to a rise irl operating temperature because
o~ some other reasons. -
3. Background of the Inve~tio~
~ ow~ i~ the art are some electric insulation materials
based o~ cellulose a~d processes for producing thereof
aimed at impro~in~ stabilization of tan ~ a~d resistivit~
Enown processe~ comprise the ~tages of paper pulp prepara-
tio~, ~heet-maki~g, pressiDg, and dryiDg, A decrease in
, .. . . . . . . .
.
- .
. , :
- . .
~651)0
io~ic dielectric los~es is attained by introducing of
chemlcal reagents in~o a paper pulp, (for instance, zinc
salts (InYentor'~ Certificate of the USS~ ~o.540,003)
and magnesium salts (I~ven~or's Certificate of the USSl~
I~o.~00562).
~ owever, a decrease i~ tan ~ o~ electric in~ulation
material is observed o~ly at elevated temperatures
(80-140~C) and is very small at lowered temperatu~e
(30-80C).
Also knoYJn in the art is electric insulation material
based on a ~odified cellulo~e and process for preparing
thereof.
As ~ modified cellulose use is made of boryla~ed
cellulose obtained by .treating cellulo~e with a melt of
a boric acid mixture with urea.or borax at 180-260C
with subsequent water - washing o~ an unreacted boric
acid (Inve~tor's Certificate~ of the USSR Nos ~03390
and 536275)~ The eleccric insulation material obbained by
know~ method has decreased dipole dielectric los~es,
~hereas ionic dielectric lo~es remal~ unchanged. In addi-
tion, thi~ method is tech~ologically complicated and does
not ~ind practical application.
4. Brief Description of the I~vention
It i~ an object of the invention to eliminate the above-
-cited disadva~tages.
,, ' ' - ' . . .
. _ 4 _
~;26500
~ 'he principal object of the inventio~ is, by selecting
a new chemical reagent for treating paper pulp or paper
sheet, to provide a cellulose-ba~ed electric i~sulation
material which will improve the value~ of tan ~ and
electric resistivity.
I~he principal ob~ect of the iL~ention is to decrease
tan ~ , increase electric resistivity of cel}ulose-ba-
sed electric insulation materials and to stabilizea said
parameters during operation.
Said principal ob3ect i8 aocomplished by the provision
of a cellulose-based electric~insulation material contai- -
ni~g ~rom 0.02 to ~.1 weight ~ of boron with respect to
absolutely dry material. ~ ~'
'l'he process ~or preparlng a cellulose-based electric
insulation mat~rial comprises bhe~staees o~ cellulose-
based p~aper pulp prepara~ion, sheet-making,; pressing, ~ ~'",','', '-"~,~reating with~a,chemical reagent, drying, and prepara~
tion of the final material;~ according to the i~ve~tion,
as a chemical reagent use ie made or boric acid or a bo- ~ '
ron compound~forming boric acid when reacting with water,
aid reagents being used either se~arately or in combi-
nation and taken in amounts ensuraug the boron content
in the fi~al product of ~rom 0.0~ to ~.1 w~ight % with
~, ~
re~ect to ~b~olu~iy dry material.
,~. , ~ ,
, ~ . ,~, . . . . .
~: ' ,: .: . ........... .
.
, : - ,
. ,
- - . - .
': ; ': . .. .': : ~
.. . .
. -,
.. ~, -. , . ~, . .
.
:: : - - : -
.
; ~ ~ Z 6 S~ 0
~ o simplify the treatment of paper pulp or paper
sheet with a chemical reage~t, it is expedient to use
boric acid in the form of its aqueous or water-alcohol
solution. '~he us~ of boric acid i3 the ~orm of water-al-
cohol solution makes it possible to obtain paper with
practically constant den~ity without co~siderable deforma-
~ion, which excludes subse~uent shrinkage of the paper
sheets on special eguipme~t,
It is pre~erable to use ~s the boron compound formi~g
boric acid w~en reacti~g with water, boric a~hydride, meta-
boric acid, or trie~hylborate; it iB expedient to use the
boron compouna in the form of its alcohol solution for a
better treatment o~ paper pulp or paper sheets.
The compounds used as the chemical reagent, namely,
boric acid or boron compou~ds forming boric acid when
reac~ing with water, said reage~ts bei~g used either se-
parately or in combinatio~, can be introduced both at the
stage of paper pulp preparation and ~efore the pressing
or drying Rtage.
5. Detailed Description of the Invention
The propo~ed process i~ accomplished in the ~ollowi~g
way.
Paper pulp containing wood or cotton cellulo~e as the
mai~ ingredient is prepared by one o~ the method~ ~own
i~ the alt.
: . - 6 _
, .,~.. .
.. .
''', ., ''~
~L~;Z6500
Alreaoy at the stage o~ paper pulp preparation, boric
acid or such boron compounds as boric anhydride~ metaboric
acid, triethylborate, or mixtures thereo~, can be introduced
into the pulp. Boric ~cid dissolves in water enteri~g the
pap~r pulp composition, whereas boric anhydride, metaboric
acid, or triethylborate react with water yielding boric
acid solu~ion. The amount OI` boric acid or one of the
boron compound~, or the mix~ure thereof lS calculated so
~s to ensure the boro~ co~tent in the final product from
0.02 to 1.~ weight % with respect to absolutely dry
material. ` ~
Boric acid and boron compou~s can be used both in :~ -
their crystalline state and in the ~orm of solutions.
It is expedient to use boric acid ~8 an aqueous or
water-alcohol solution and the boro~ compound as an
alcohol solution.
The paper pulp obtained is cast for sheet making by one
of co~ventional processes; the sheet prepared is pressed
and dried with the use o~ e~uipment commonly employed in
paper-making plant~. When electric insulatio~ material
with a~ i~creased de~sity is required, the paper sheet is
~ub~ected to calendering.
~; - The introductio~ of borio acid, the boron compound,
- or a mixture thereof i~ po~8ible at other Atages of the
, ' .
,': . .
-- 7 --
- . ~ ~ .
.:
~', . ' ~ '
. -
6500
process which follow after ~aper ~ulp prep~ration andsheet making, nam~ly, before pressing or drying.
The introduction of boric acid or boron compounds
into paper pulp or sheet~ decreases not only ionic
dielectric losses in electric i~sulation material but
dipole dielectric losses as well and stabilize tan S
value of absolutely dry electric i~sulation material
within a wide temperature range. Thus, for example, at
60-120C, when the boron content in electric insulation
can ~
paper i8 0.27-0.45 weight %, ~ i8 practically constant.
7Jith i~creasing boron content in absolutely dry
electric insulation material up to 1.1 weight ~o, tan
at different temperatures changes only slightly.
Cellulose-b~sed electric insulation materials obtai-
ned by the described proce~s has the followiDg technical
parameters:
thickness, mm 5-500
volume mass, g/cm 0.6-1.35
boron content in weight %
with respect to absolu~ely
dry material 0.02-1.~
~a~ S of dry electric insulatio~ papér made ~rom electric
insulation wood cellulose and having a density of
.7 g/cm3:
,
,
,
- ~ ,
. .
~ J
. .. ~` ~
~Z65~
-- _ _ _ . . . A . _ _ _
l`empera- For paper prep~red For paper prepared with
ture C with the use of the u~e of inaustrial
deionized water water with conductivity
about 250~ ~/cm and
containing about
0.5 mg-equiv/l of
sodium salts
~:
0.00040 0.00040
0.00035 o.ooo~5
100 o.ooQ30 0.00040
120 0.000~5 0-00050
. __
tan ~ of dry paper prepared from electric insulation
cellulose and havi~g a den~ity of 1.2 g/cm3:
~empera- For papex prepared P~or paper prepared with
tuxe & with the use of the u~e of industrial
deio~ized Y~ater . water with co~ductivity
. about 250 ~ S/cm a~d
containing about
0.5 mg-eguiv/l of
~odium ~alts
0.0008 ~.0008
100 0.0008 . 0.0010
1Z0 0.0008 0,0013
9 _
,..... ......
,
.
,
: ., ': . '
~. .; : ,
/~
llZ~ O
.
~ or a better u~derstanding of the present invention
specific examples of realizi~ thereo~` are give~ herein-
below by way of illustratio~ which i~ no way limit the
scope of the i~vention as it i8 to be u~derstood by ~hose
skillad i~ the art.
Example
Electric i~sulatio~ paper is prepared u~der labora~o~
co~ditions on the basis of pure electric i~sulation cellu-
lose obtained ~rom tissue of cunifers with the use of
desalted water.
Paper pulp is prepared by breaking i~ a laboratory stir-
rer 10 g of electric insulation cellulose poured over ~ith
0.~ % o~ aqueous solution of boric acid àuring half of a~
hou at 1000 rpm, a~d by grinding the obtai~ed suspensio~
in a la~oratory beater ~or 12 hours to 95Schotter-i~iegler.
~ 'he paper pulp i~ the~ diluted with 1000 ml o~ desal-
ted ~iater a~ter which paper is ma~ufactures o~ a laboratory
i~sballation by easti~g, pressi~g, a~d dr~i~g of the paper
sheets. ~he paper prepared has a density of 0.7 g/cm3,
thickness 50 ~ , and co~tai~ 0.02 weight % o~ boron
with respect to absolutely dry material.
The same material i8 used ~or prepari~g b~ the same
proces~ a~d o~ the same equipment but with the use o~
desalted water control ~amples o~ electric insulation
paper, the density and thick~e~s o~ which equal those of
the paper conbai~ing boric acid.
::
... .
'10 _
.,,,........... ,. -, ,
. ........... . .
., . , .: . ,
,
, : -
.
1~;265(~0
The value o~ ta~ ~ is determined ~or the samples
of paper o~ both types in the ~ollowing way.
Paper samples are collected into a pack 280-3~0~(
thick. The pack is pressed between flat electrodes 46 mm
in diameter u~der a pressure o~ 0.2 kg~/cm2 an~ dxied in
vacuum under a residual pressure of 5.10-4 mm Hg at
125C for 2 hours. Then the packs are cooled i~ v~uum
under the same residual pressure down to experimental tem-
perature ~7hich is 30,~,100, or 120C and thermostat~ea
at o~e of the~e temperature value. After the electrodes
are co~nected to the measuri~g arm of the Schering
bridge, the tests are conducted with ~he use o~ i~dustri-
al alt~rnating current with a frequency of 50 Hz at a
volta~e of 5 V~ . ~he ta~ ~ values are bei~g read directly
off the Scheri~g bridge aYter bhe latter has be~ bala~ced.
Table 1 presents the values oY ta~ ~ determi~ed ~or
the paper samples obtained accordi~g to the described
process.
Table 1
'i'empera- ta~ S of the samples
o
ture, C co~tai~i~g co~trol
boro~
0.00105 0.00105
0.00085 0.00085
100 0 .00085 o .00085
120 0.0010 0.0012
,............ .
,
_ 11 --
, .. . .. . .
.
''
.
11265~0
~xample 2
~ lectric i~sulatio~ paper is prep~red under laboratory
condi~ions o~ the basis of pure electric insulation cellu-
lose obtai~d from fissu~ of coni~ers with the use of
deionized water.
Paper pulp is prepared b~ breaki~g ~0 g of electric
insulation cellulose poured over with 1000 ml of 1,Z~o
aqueous solution of boric acid in a la~oratory stirrer
for half an hour at 1000 rpm and by grinding the obtained
suspe~sion i~ a laborabory beater for 16 hour~ to 96
Schotter-Riegler.
The paper pulp i~ then diluted with 3000 ml of desalted
water after which paper is manuYactured on a laboratory
i~stallation by c~sti~g, pressi~g, a~d drying of the paper
sheets. l'he paper prepared has a density of 0.7 g/cm3t
thickness 50~ , and contai~s 0.11 weight % of boron
with respect to absolutely dry material.
The co~trol samples o~ electric i~sulatio~ paper are
obtained from the same material by the same process and o~
the same equipme~t but with the use of deionized water. The
density and thickness of control paper equal those of the
paper containin~ boric acid.
The value of tan ~ i~ determined for the samples
of paper of both t~pes by following the proceaure
described ,~ ~xample 1.
The determi~ed values of tan S are give~ in ~able 2.
, ,
_ 12 -
~Z65~0
Table 2
.
Tempera- ta~ S o~ the samPles __
ture, C co~taini~g control
boron
_. ... . _ . . . .
0~0009 0.00105
0 .0007 0 .00085
100 0 . 000 7 0 . 00090
120 0.0007 0.0012
Example 3
Electric insulation paper is prepared under laboratory
co~ditio~s on the basis o~ pure electric insulation cellu-
lose obtained from fissue o~ conifers with the use of
deionized water.
Paper pulp is obtai~ed by breaking 10 g of electric
insulation cellulose, poured over Yiith 100 ml of Z~
aqueous solutio~ of boric acid a~d 900 ml of deionized
water, in a laboratory stirrer ~or half an hour at
1000 rpm.
Dilution and preparatio~ of paper samples as ~ell as
preparation of control samples of electric insulation
paper not contai~i~g boro~ is performed by following
the ljrocedure described in Example 2. The thickness of
the salllples is 50 ~ , de~sity 0.7 g/cm3, and boro~
co~te~t 0,2~ weight % with respect to absolutely dry ma-
terial.
- 13 -
~'1265VO
'l`he sa~ples o~ the paper of both types are tested by
~ollowing the procedure described in ~xa~lple 1.
The determi~ed values of tan ~ are given i~ ~able 3
~able 3
.
~empera-
ture, C co~tai~ing co~trol
boro~
.
0.0006 0.00105
0.000~ 0.00085
~00 0.0005 0,00090
120 0.0005 0.00~2
.
Example 4
31ectric i~sulation paper i~ prepared u~der l~boratory
co~ditions on the basis o~ pure ele ctric i~sulation cellulo-
se obtained from tissue o~ co~i~ers with the use of ::
deionozed water~
~ or preparatio~ of the laboratory paper samples use ismade of ~he paper pulp co~taini~g 2~o cellulose and manu~ac-
~ured u~der industrial conditions. ~00 g o~ said paper
pulp are ground i~ a laboratory breaker to ~6,5
Schovter-Riegler. Th~ ~0 g of boric aci~ are lntroduced
into the pulp a~d the volume o~ the mixture i8 brought
ul~ to 'lO00 by adding deio~ized water. After stirri~g
the diluted paper pulp for three mi~utes, the s~mples
_ 14 -
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1126500
of electric insulation paper are prepared by casting,
pressing, and drying paper shee~s on a laboratory
paper-maki~ installation. qlhe samples are 50 ~ thick,
have a density o~ 0.7 g/cm3 and contain 1.1 weight ~o
of boron with respect to absolutely dry material.
Control samples of electrla insulation paper not con-
taining boron are obtained in a similar way but with the
use of deio~ized water onl~. Tan ~ iR measured by follo-
wi~g t~e pLocedure described in Example 1.
~ T'he Yalu~s of tan S determined for the paper samples
.
are given in T~able 4.
Table 4
,
~empe- tan g of the-:samples
~: :: rature, ~-
~- & ~ ; obntaining ~ control
, ~ .. . - . ~.. ..
:: ~ ~ 0.00050 ~ 0.00105
~ ~ 0.00040~ 0.00085
100 ~ -35 ~ -9
120 0,00040 : 0,00120
E~ample 5
hé~capacitor paper manufaotured under industrial condi-
tio~s with the use of deionized waber at all stages of the
proae~s~ ~aid paper having a maBs of 13 g per ~ , humidity
8~, dénsiity 0.8 g/cm3, i~ wetted;with 8% aqueous solution
,~"",,, ~, , ,, , , :
~ ol bario acid~up eO~ a moi8ture~aonte~t o~ 26~o~
~ , . ,
: .
, . .. ~ , -.
.. -. . . . ..
, . . ..
-~ ~ -. ~, - : .
~,. . ~ , , , . -, .
~, -.,. . ~ .. , ~ . -. :
i~26500
The wetted paper is calendered up to a density of
1.2 g/cm3 and dried. Co~trol samples are prepared from
th~ ~ame paper wetted with deio~ized water o~ly.
~ lhe ~amples obtained are subjected to complex testing.
Tan ~ values are determi~ed by ~ollowing the procedure
described in ¢xample 1. Other technical palameters show~
below are ~ound by k~ow~ procedures~
The parameters o~ experimental a~d &ontrol samples o~
electric insulation paper aré give~ i~ Table 5.
~able 5
.
~OB Parameter ~ a m p 1 e
co~taini~g co~trol
boron
1 2 ~ 4
1. ~hick~es~, ~ 10.6 10.4
2. Density, g/cm3 1.20 1.19
~. ~ength o~ fracture, km 9.6 9~7
4, ~peci~ic conductivity of
water extract ~ S/cm at a
~odulu~ o~ 1;50 11 10
5, p~ of water extract 6.8 7.
6. Breakaow~ voltage ~or one
paper layer, V 490 490
7. Dielectric los~ tange~t for
dry paper at temp~ratu~e, C
30 Q,0012 0.0020
~0 0.00095 0.00165
~ 16 -
'
.... ..
: .
,~
1~26S0(~
.. .. _ .
~ 2 ~ 4
100 0.00095 0.018
120 0.0010 0.0023
8. ReqistiYity of dry paper,
Ohm,cm, at 120C 3.9.1016 2.8.~o15
9. Dielectric constant 2.9 ~1
10. Dielectric loss tanæent of the
paper impreg~ated with trich-
lorophenyl (in small-size capa-
citors at tempera~ure, C
0.0021 o.oo35
0.0018 0.0030
100 0.0017 0.00~2
120 0.0020 0.0040
11. ~oron conte~t with respect toabsolutely dry material, weight
% 0.27 : :
Ex~mple ~
Ca~acitor paper manufactured under industrial
conditio~s with the use at all stages of water with
conductivity about ~50 ~ s/cm, containing 0.5 mg-equiY/l
o~ ~odium s~lts a~d havi~g a density of 0.76 g/cm3,
i~ wetted with 8% aqu~ou~ ~olution of boric acid up to a
~ moisture co~te~ 2~%~ cale~dered to a de~sity o~ 1.2 g/cm3,
:~ a~d dried.
_ 17 _
- , , .
.
. ~
.. ..
.
112 ~
The same paper wetted o~ly with i~u~trial water is
treated i~ a similar way a~d used f'or preparin~ control
samples.
The samples obtained are sub3ected to complex
testing th~ results of which are given in Table 6.
Table 6
.
~os Parameter S a m ~ l e s
co~tai~ing co~trol
boron
.. . .. ~
1 2 . 3 4
, . , , , ~ , , ,
1. Thicknes~, ~ 8.2 8.2
2. Density, g/cm3 1.20 . 1,Z0
3. Length of fracture, km 9.7 9.5
4. Specific conductivity
of water extract,~ S/cm,
at a modulu~ of 1.50 33 26
5. pH o~ water extract 7.3 7.6
6. .Breakdow~ voltage of
one paper layer, V 400 400
7. Dielectric lo~s tange~t
of dry paper at tempera-
ture, C
30 0.0010 0.0023
60 0.0008 0.0019
100 0.0010 0.0032
120 0.00135 0.0068
; - 18 -
65()0
.. _ . ........... . .... ..U . . . ~ . ~
1 2 3 4
. , . ................. _ . . . . . . . _ .. . . .
8. ~esistivity o~ dry paper at
120, Ohm.cm 6.1.10~5 2.8.1014
9. Diel~ctric consta~t of dry
paper 2.7 3.1
10. Dielectric loss tangent of
the paper impre~nated with
trichlorodiphenyl (i~ small-.
-size capacitors) at tempe-
rature,C
0.0021 0.0035
0.0018 0.00~2
100 0.0018 0.0046
120 0.0025 0.0081
11. Boron content, weig~t %
with respect to absolutely
dr~ material 0.45 0
.. . ...................... .
Exam~le 7
El0ctric i~sulation paper on the basis of pure electric
insulatio~ cellulose obtai~ed ~rom tissue o~ coni~ers with
the use of deio~iæed water i~ prepared in the followi~g
vJay .
,; ,
- 19 _ `
~ r~-` llZ6S~O
Paper pulp manufactured under industrial co~ditions
with 0.23 weight ~o o~ cel~ulose and ground to 96 Schotter-
-~iegler i~ taken from a pre6sure box of a paper-making
machine. 14 g o~ boric an~ydride are added to 1000 ml
of said ~aper pulp and the mixture i~ stirred ~or
3 mi~utes.
Boric an~ydride introduced into the paper pulp reacts
~itn water co~taining i~ the pulp accordi~ to the
reaction:
B20~ + 3X20 ~ 2 H3B0~
~ rom the paper pulp treated i~ the described way the
sample~ of electric insulation paper are prepared on a
labora~ory paper-making machine by casting, pressing, and
dL~in~r 0~ paper sheets.
l'he paper obtained a thick~ess of 50 ~ , density
0.7 g/cm3, and boron content 0.9 weight % with respect
to absolutely dr7 msterial.
~ Control samples o~ eIectric insulation paper not co~-
taining boron are prepared by the same proces~ but
without i~troduction o~ boro~ a~hydride a~d on the same
equipment.
'g S is determi~ed ~or the prepared samples by fol-
lowing the procedure de~cribed i~ example ~; its value are
listed i~ r~able 7.
:
_ 20 -
:, : . . . .
.
,, , ~, , ~
! :, . : : - ~ ~
'~ '" '`~`' ' ' ' " ' ' ' '. , " ' ,
, .
~z~ss~o
Table 7
'i~empera- tan (~ __ o~ the samples
ture, C con~aining control
boron
~0 0.0005 0.00~05
0.0004 0.0085
100 0.0004 0.00090
~20 0,0004 0.0012
~xample 8
Samples of electric insulation paper containi~g 0.9
wei~ht % o~ boron with respect to absolu~ely dry ~aterial
and control samples without boron are prepared by follo-
~ing the procedure described in ~xàmple 7, as the boron
compound use being made o~ metaboric acid.
~ etaboric acid reacts with water cortai~ed i~ the
paper pulp with the ~ormation of boric acid according
to the scheme:
~2 + ~2 ~~~ ~I3B03
~ he tan ~ values given i~ Table 8 are de~ermined
for the ~amples b~ ~ollowing the procedure described in
~xample 1.
l~able 8
'~empera- tan c~ o~ the samples
ture,oa containing boron control
.
~0 0~0005 0.00105
0.0004 0.00085
100 0.0004 0.0009
120 0.000~ 0.0012
~ r,~ ~ _
.
. . . .
11265~0
~xal~ple 9
~ lectric insulation pap~r is prepared u~der labora-co~J
conditions o~ the basis of pure electric insulation cellulose
obtained from tissue of conifers with the use of deionized
water.
~ a~r pulp is prepared b~ breaking 20 g o~ electric
insulation cellulose poured over with 1000 ml of deionized
water in a laboratory stirrer for half an hour at 1000 rpm
and by grinding the obtained suspension in a laboratory
breaker ~or 12 hours to 95 Schotter-Riegler.
The paper pulp thus prepared is diluted with 1000 ml
o~ deionized water after which paper sheet is obtai~ed on
a laboratory installat~on by cas~ing a~d pressing.
Half amou~t of the paper ~heet is treated with the
aid of a pulverized by 10 ml of 0.1% a~ueous solution
of boric acid, said boric acid being applied evenly to the
whole surface area of the paper sheet. After repeated
pressing and dr~ing, electric insulation paper is pre-
pared with a thickness of 50 mkm, density 0.7 g/cm3, and
0.04 weight % of boron with respect to absolutely dry
material.
The remaining half of the paper sheet is dried and
u~ed for prepar mg control samples of electric i~sulation
paper which doeA not co~tain boron and has the ~ame
thick~e~s a~d density.
,; .
, .
~, .
~ 2 -
, . . . . . . .
.
.' ,.' ',, ' ''' , .; - . . .~ ~ ': '" '
... . .. . . . .
' . ' ~': ' '''- ' ., ,, ' ' .,
': ' ' , . . . ~ ,
~ 12 6~
The values o~ ta~ ~ ~ive~ in 'l'able ~ are dQter-
mi~ed for the samples of paper of both types by followi~g
the ~rocedure de~cribed in Example 1.
Table 9
. . , , _ _
Temper~- ta~ ~ of samples
ture, ~C containing co~trol
boro~
- 30 0.0010 0.0011
0.0008 0~00085
~00 0.0008 0.0009
120 0.0010 0.0012
Example 10
The samples of electric insulatio~ paper traated ~vith
boric acid a~d co~trol samples of electric insulation paper
~ot containi~g boro~ are prepared by following the procedure
described in ~ample 9. The samples are 50 mkm thick and
have a density o~ 0.7 g/cm3
~ he paper sheet i8 treated with 6~o aqueous solutio~
of boric acid to produce the samples of electric insula-
tio~ paper. The sarnples obtained co~tai~ 0.91 weight %
o~ poro~ with respect to absolutely dry material.
The values o~ ta~ ~ given i~ 'l'able 10 are determi~ed
for the ~amples o~ paper ot` both types.
1126S/~0
Table 10
__ ,_ . . , . . . . __ .. ,. . _ _ . . _ _ ~
'i`emperature, tan ~o~ the sam~les
.. _ _ ~
C contai~i~g control
boro~
~0 0.0004 0.00085
100 o . 00035 o . ooog
120 0.0004 0.0012
.
Example 11
The samples of cable electric insulatio~ paper are
prepared under industxial co~ditio~s ~rom pure electric
i~sulation cellulose obtained from tissue of conifers
with the use of deionized wa~er. In the process o~
sample pxeparatio~ the paper pulp is used also obtained
with deio~ized water. The samples are 120 mkm thick and
have a density of 0,80 g/cm~.
'l'he obtained samples are im~ersed ~or 5 s~cond6 i~to
~0 aqueous solution of boric acid and aried. The density
of dried samples i8 0.7 g/cm3, boron content 1~1 weight %
with respect to absolutely dry material.
The values o~ tan S give~ i~ Table 11 have been
determined for the samples of cable paper treated with
boric acid accol~ding to t~é invention a~d ~or the samples
of the initial cabel paper not containing boro~. ~an S
is determined by follo~Jing the procedure described in
~xample 1.
- 24 -
.
,
1126S~30
Table 11
. . ~ . . _ .. _ . _
Tempera- tan ~ o~ the samples
-ture~C containing co~trol
boron
.
0.0008 0~0018
100 0,0009 0.0025
120 0.0011 0.0049
.
Example 12
Suspension containing 2.0 weight % oX electric insula-
~ion cellulose is prepared under industrial conditions
with the use of deionized ~ater from pure electric insu-
lation cellulose, said cellulose being obtained fro~ the
tissue of coni~ers also with the use of deionized ~ater.
After grinding the above-cited suspension to 96Schotter-
-Xiegler, two portions are withdrawn 150 g each. 100 ml
of 0.08% aqueous suspe~sion of active aluminium
\6-oxide a~d 50 ml of 28% boric acid solution are succes-
sive~r added to one portion whereas to the other portio:~
only 100 ml of 0.08~o aqueous suspe~sion of active alumi-
nium y -oxide are added.
rl'he volume of each portion a~ter a~ding the above-ci-
ted in~redients is brought to 1000 ml with deionized
water, ~tirred for 5 minutes at 1000 rpm and the paper
,..
-- 25 --
1126S~O
pulp thus obtained is used for prepari~ the sa~ples of
electric insulation paper with 0.55 weight % of boron
by casting~ pressing, and dryi~g of paper sheets o~ a
laboratory installatio~ as well as for preparin6r co~trol
~amples ~rom paper ~ot containin~ boro~. The thickness
of all the samples is 50~ , density 0.7 g/cm3.
~ l'he values of tan S given i~ Table 12 are deter~ined
~or all samples by ~ollowi~g the procedure described
in Example 1.
Table 12
'i'empera- tan ~ of the samPles
ture,C containi~g control
boron
.
0.00045 0.0009
100 0.00040 0.0010
120 0.00045 0,00115 :
Example 13
Electric insulatio~ paper is prepared under laboratory
conditions from pure electric insulatio~ cellulose ob~ai~ed
~rom ti~sue of conifers with ~he use of deio~ized water.
Paper pulp is prepared by breaki~g 10 6~ of electric
i~sulatio~ cellulos~ poured over with 1000 ml of desaltled
water i~ a laboratory ~irrer for half an hour at 1000 :rpm
a~d by grinding the obtai~ed suspension in a laborator~
.
26 -
.. .............. .
.' , . . .
- . -
', ~
'
l~Z65~0
braaker for 16 hours to 96 ~chotter-Riegler. The paper
pulp thus prepared is diluted with 3000 ml of desalteà
water then 75 g o~ triethylborate are ad~ed into the
pulp alld the mixture is stirred for 5 mi~utes.
Triet~ylborate reacts with water contai~ed in the
pape ~ ulp giving boric aci~ accor~in~ to the reaction:
(C2~5o)3B~ ~ H20 3 C2M50H + ~3B03.
After this the paper pulp i6 used for prepari~g
the ~amples of electric insulatio~ paper ~vibh a density
of 0.7 g/cm3, thick~ess 50~ , and a boron co~tant of
0.~7 weight % with respect to absolutely dry material.
The control samples of electric insulation paper are
prepared from the same material, on the same equipme~t r
and by the same process. The co~trol samples are of th~
same thick~ess and density as those containing boric acid.
The values of tan S were determined for the samples
of both ~ypes of the paper by ~ollowing the ~rocedure
described in Example 1. The values obtained are prese~ted
in Table 13.
$~able 13
. . .
TempeOra- , tan ~ o~ the samples
ture, C containing control
_boron _ _
0.00050 0.00105
0.00040 0.00085
100 0.00035 0.00090
- 27 -
.
li265~)0
~xample 1
Electric insul~tion paper ba~ed on pure electric
insulation cellulose obtained from tissues of coni~ars
with the use of deionized water is prepared in the
following way.
Paper pulp prepared under industrial conditions, con-
taining 0.2~ weight % of cellulose, and grinding to 96 ~ -
Schotter-Riegler is withdrawn from a pressure box of a
paper-making machine. A~mixture of boric aci~ and boric
anhydrice in amounts 5 and ~.4 g~ respectively is aaded ;
upon stirrin~ to ~OOO ml of Raid paper pulp and stirring --
i8 continued for 3 minutes.
he above-clted boric anbydride, being introduced -~ -
into the paper pulp, intoracts with water conGainad in it
with the formation of boric acid~according to the scheme: ;
The samples of electric insulation paper~are prepared
from the~paper pulp treated in the above way on a labora-
tory paper-making machine by casting, pressing~and drying
paper shoet. ~he ~amples are 50 ~ /thick, has a density
o~ 0.7 g~cm3 and boron content 0.27 weight % with respect
~;r~ m" ~: to absolutely~dry~material.
he co~trol 8amples 0f electric insulation paper of
he~ame ~hiGkness and densit~ but not containing boron
. , , ~ . ~ , . ,
~ 28 -
~'' ~ , ', .
,. ~ , , .
, ' . . ' ' . . l :'
''.~ '', ' ' ,' ~ "' . . '
,': ', ,: ' '. ' ' ' '' '' '
'' , ' ' ' ' ' . ' ' ' :
', . : ' ' ' " . ' : ' '.
; :~' ' . .. .
. ' " -~ :
, ' :-:` : '
.. ..
11265~0
are obtained o~ the same equipment by the sam~ process
with the exception o~ the stage o~ boric acid and boron
anhydride introductlon.
The ~alues of ta~ ~ given in Table 14 are determined
for the samples of said papers.
Table ~.4
'l~emper~- tan S of the samples
ure, C contaiLing control
boron
.
0.00070 0.00105
0.00060 0.00085
100 0.00055 - 0.00090
120 0.00055 0.00~20
.
~xample ~5
The samples of electric insulation paper co~taini~g
0.45 weight % of boron with respect to absolu~ely dry
material and control samples without boron are prepared
b~ followi~g the procedure described in ~xample 14 but
with the u~e as the boro~ compound o~ a mixtuxe o~
boric and metaboric acids in amou~ts 7.5 and 3.5 g,
res~ectivelY.
Metaboric acid interact~ with water contained in
the pa~er pulp with the ~ormation o~ boric acid according
~o the scheme:
. HB02 + H20 ~ H3B03.
' fS.. '
~ , - Z~ _
: .. ~ - .
' ~ :
.
.
.
~lZ65~0
ll~he values of ta~ ~ presented in rl`able ~5 are
determined for all the ~apers by following the procedure
described in Example 1.
Table 15
.
Tempe~a- tan_c~ of the samples
ture,C containi~g co~trol
boron
,
0.00050 0.00'105 ~ -
0.00040 0.00085
100 0.00040 0.00090
120 0.00040 0.0012
.
Example 16
'l'he samples of electric insulation paper containing
0.35 weight % of boron with respect to absolutely dry
material and control sample~ not contai~in~ boro~ have
been prepared by followi~g ~he procedure de~cribed i~ ~
~xample 1~ with the use as the boxon compound of a mixture
of boric acid and triethylborate in amou~ts 5 and 12 g,
respectively.
l'rie~bylborate react~ with water co~tai~ed i~ the
paper ~ulp with the ~ormatio~ of boric acid according
to the ~cheme:
~C2H50)~B ~ 3 ~2 3 C2H50H ~ H3B03
0 --
,
,,,, . ~ , .. .... .. .
,
.
' -
l~Z6~0
'l'he values o~ pre~sented in '~able 1~ are deter-
mined ~or the samples of the paper of both types by
followi~g the procedure deæcribea in ~xample 1.
'l'able 16
~em~era- ton ~ o~ the sarnples
ture,C --
containing co~trol
boron
0~00055 0.00105
0.00045 0.00085
'100 0.00045 0.00090
120 o . 00045 o .00120
_ : .
Example 17
Electric i~sulation p~per is prepared under laboratory
co~ditions~y ~ollowi~g the procedure described in
~ample 1 on the basis of pure electric insulation
cellulose obtained from tissues of coni~ers with the
use of desalted water.
Then the part o~ the samples is u~iformly pulverized
with 4% water-alcohol solution of boric acid (weight
ratio water: alcohol is 6:4) in amou~t 0.5 g o~ solutio~
per g o~ absolutely dry paper. Then the samples are
dried. 'l'he boro~ content is 0.~6 wt.% with re~pect to
~b~olutely dry paper; dcnsity o~ the paper is 0.7 g/cm3,
thickness 50~ .
_ 31 _
, .
:` , . , ~
.
~Z65~;)0
~he value~ o~ ta,~ 0 prese~ted in Table 17 are de-
termined for treated and untreated samples by following -:
the procedure described in Example 1.
Table 17
-- ,
~empe~a- _ tan ~ of the samPles
ture, C co~taining co~trol
boron
.
0.0006 0.00105
0.0005 0.00085
100 0.0005 0.0009
120 0.0005~ 0.0012
~xample 18
Electric i~sulation paper is prepared u~der labora-
tor7 conditions by following the procedure deacribed in
~xample 1 on the ba~ie of pure electric insulation
: cellulo~e obtained from tissue of coni~ers.
. '1'he~:the part o~ the samples is treated with 3%
: ~ ~water-alcohol ~olution of boric acid (weight ratio
,
alcohol:water is 14:1) in amount 1 ml of the solution
per g of absolutely dry paper. The boron conte~t i~
t~ paper i~ 0.54 weight Yo with respect to absolutely
dry paper.
~ ` ~ The ~alues o~ tan ~ listed i~ table 18 are determi-
: ned ~or the samples of treated and untreated paper by
~ollowi~g the procedure described in Example 1. The den-
siby of ~he paper is 0.7 g/cm3, thickness 50 ~ .
~ .,
~ ~r ; ~: ~
.
' '' ' ' ' ' ' ' ' I
' ' ' ~' ' '
.
''. '''' ' '' ' ' ~ ~ , .
,
1~65~0
Table 1 ~
.
Tempera- tan ~,g OI the samples
ture, C -- -
containing co:~trol
boron
~0 0.0005 0 .00'105
~0 0.0004 0.00085
100 0.0004 0.0039
120 0.0004 0~0012
.
-- 33 --
