DE1931252A1 - Process for the production of fibrous, electrically insulating material - Google Patents

Description

Process for the production of fibrous, electrically insulating material

The invention relates to a method for the production of Faöer-like, electrically insulating material with low dielectric losses, which is particularly advantageously _{suitable as a dielectric in capacitors 9,} transformers, electrical cables and the like _{or the like}

Must _"o, in the form of paper or cardboard at using cellulose to produce Isolierinaterialien, see also the dielectric losses affecting Paktoren be · = be taken into account, d" h _0, it does not only the chemical composition of the cellulose used, but also whose chemical and mechanical purity is a problem. At the operating temperature of a capacitor, for example, part of the dielectric losses consists of what are known as ion losses, which are caused by the relative movement of the cations that are more or less firmly bound to the cellulose.

S09881 / U81

To remove cations of various types from cellulose as far as possible (so-called ash removal), the cellulose in the sail is treated electrolytically or with an acid and then washed with completely desalinated water. The carboxyl groups present in the cellulose are in the form of hydrogen Ions bound, which leads to a fairly low pH value ₉ which, if the gelatinous product is stored for a long time, causes hydrolysis and thus leads to a lower heat stability, a shorter service life and a poorer dielectric strength of the insulating material formed

It is known that monovalent ions, ZoB. Lithium, sodium "and potassium ions ₉ have a particularly adverse effect on the dielectric losses of cellulose ₉ whereas bivä = · lente or polyvalent lietallionen, z _o B" calcium ", magnesium, zinc barium * = *, strontium, aluminum - and titanium ions, behave quite neutrally in this respect, and it is further known that the adverse influence of the monovalent ions can be reduced by treating the cellulose in aqueous solution with such toi- or polyvalent metal ions to effect such a treatment a higher pH value of the cellulose »which had a favorable effect on the heat resistance and service life of the finished insulating material

Bs ,, has now been found that under certain conditions, a cellulosic material can be produced having unusually low Dielektrikumsverliaste and therefore in a particularly advantageous manner as a dielectric of a wide variety of type ₉ ZOB ₉ as condensate or _a cable paper of paper board _a transformer

and the like _{9 can} be used.

The surprising finding lies in the process of the invention underlying that a considerable reduction in dielectric Losses caused by Xon movement in a fibrous insulating material exposed to an electrical field

909881 / U61

a, can be achieved in that the are esterified in the cellulose in Hydrogenioaenfprm carboxyl groups with the help of Bpoxdenο

To carry out the process of the invention, a considerable amount of the metal ions present, preferably at least 50 $> _{9, is} removed from the cellulose in the customary known manner by electrolysis or ion exchange, after which the cellulose obtained is treated in aqueous suspension with one or more oxides in this way that the carboxyl groups present in hydrogen ion form are esterified to at least 50 $>. ·

In addition to reducing the dielectric losses, the method of the invention also achieves other advantages, ZoBo has a lower ash content, good heat stability as well as improved aging properties of the insulating material obtained,

Chemical wood cellulose is primarily used in practicing the method of the invention, although it is also calibrated Cotton and other cellulosic textile materials are suitable have proven. Epoxides of all types are suitable for esterification, ZoBe ethylene oxide, propylene oxide, butylene oxide, vinylcyclohexane dioxide and the like «, Particularly good results have been obtained when using a mixture of vinylcyelohexanedioxide and propylene oxide or ethylene oxide obtained "

The dielectric properties of cellulose are with Stoning degree of esterification improved, which is why the esterification should be carried out as completely as possible in a particularly advantageous manner. Even with incomplete esterification however, good results are achieved if the any remaining carboxyl groups present in hydrogen ion form are bound in a known manner by daaa the esterified cellulose finally with bi- or polyvalent ...

90 9 881/146 1.

BAD ORIQiNAL

th metal ions in the form of oxides, hydroxides, salts or suitable metals are treated »

The invention is further illustrated by the examples given below explained.

The starting material used was an unbleached sulfate pulp with an ash content of $ 0.85> which is designated in Table ¹¹ A "below with SQG-haltigera treated water for 1 hour, so that the pH "value of the aqueous solution was lowered to 2.8. Then, the pulp was in a rotating wash filter with water whose specific conductivity by complete desalination at 18 ⁰ C to 0 2 juS / em (Micro-Sieraens / cra) had been lowered, washed, for desalination, the water was first separated in a cation exchanger in fiber ion form and an anion exchanger in hydroxyl ion form and then in a mixed filter that contained both types of the specified ion exchangers, treated

You on this partially ashed, washed cellulose, hereinafter referred to as "B", was too acidic (pH 3.5) for use in capacitors.

For comparison purposes, a portion of the pulp was diluted B by addition of fully desalinated water at a concentration of 1.0 i * to a concentration of 5 i *, after which the pulp was treated in ^ known manner with a Aufsehläramung of MgO in water in the manner that the pH rose to 6.8. The comparison sample obtained in this way is hereinafter referred to as "C"

9 0 9881 IA 46 BAD

example 1

Another portion of the indicated pulp B was diluted from a concentration of 10 $ to a concentration of 5 $ 6 with a mixture of equal parts by volume of completely demineralized water and ethylene oxide. The esterification was carried out by heating to 35 ⁰ O for 48 hours to a degree of esterification of more than 95 i * , after which the pulp obtained was washed with completely deionized water to remove the liquid used for the esterification «,

Example 2

A further portion of the indicated pulp B was diluted from a concentration of 10 # to a concentration of 5 ^e A with a mixture of equal parts of completely demineralized water and propylene oxide. After 48 hours of heating at 35 ^° C., the esterification was practically 100%. The P _u received lpe was then sur removal see the used for the esterification ver ~ liquid with vollkommsn desalinated water gewä · = *,

Example. ^,

Another portion of the specified pulp B was diluted from a concentration of 10 9 ^ to a concentration of 5 # with a mixture of 1 part by volume of propylene oxide, 1 part by volume of vinyl eyelohexanedioxide and 2 parts by volume of completely demineralized water »after 48 hours longer treatment which led to an almost complete esterification at 35 ⁰ C _9, the pulp obtained to remove the treatment liquid was washed with completely desalinated water

A further portion of the indicated pulp B was increased from a concentration of 10 # to a concentration of 5 $> with a mixture of 1 part by volume of propylene oxide <, 1 volume of vinyl =

909881 / U61 BAD

cyclohexane dioxide and 2 parts by volume completely desalinated Diluted water * Haeh treatment for 16 hours at 25 ° ö, which resulted in about 50% esterification became the one obtained Pulp for removing the loading liquid with completely desalinated water washed »the remaining, in Carboxyl groups present in the form of hydrogen ions were neutralized with the aid of a slurry of MgO in water in the manner that the pH was 6.8.

The starting _{pulp A 9,} the pretreated pulp B _9, the pulp G obtained by known methods and the pulps yeasted according to the invention according to the methods described in Examples 1 to 4 were analyzed. _{eem produced 9} whereupon, as is usually the case with condensate or papers, the paper samples obtained were impregnated with trichlorodiphenyl and a measurement voltage of 5 kV / mia. The measurement temperature was 120 ° 0 »J) The analysis results obtained are listed in the following table, in which the ^{response for w} tg S ^{n is shown} in the last line»

909881/1461
SAD QRK5INAI

lab el 1 β

sample

PH value

sp © z “Conductivity

Carboxyl group content Wages

Hatrium
potassium

Magnesiura

iron

manganese

Silicon

mg / kg

mg / kg mg / kg mg / kg mg / kg mg / kg

DIN 6741 8.7 3.5

SOAH-P 15 120

ASTM D 1926 0.34 0.33

, SCAN-C 6 0.85 0.05

Flame 1700 photometer

75

SOAN-O 10 1650

SGAN-C 10 310

SCAIi-G 13 35

SCAIi-G 14 95

mg / kg ASTM D 2438 540

Dielectric losses in tg S determined according to ASOT D 15Ö / D202 for a paper impregnated with SriohXord 6.8 15

0.33 0.28 5

100 95Ö

15th

450

6.0 10

0.08 0.05 5

15th

450

6.4 8

0.05 0.05 5

1 "

5 5

15 5

450

6.6

10

0.06 0.05 • 5

15th

450

B9P.4

6.8

0.18 0.14 5

50

450

450

> 0.0200 0.0040 0.0037 0.0028 0.0028 0.0020 0.0025

The starting pulp A is only of interest in order to be able to compare the results obtained in the chemical analysis. According to the requirements previously regarded as normal , the paper made from pulp B shows only moderate dielectric losses, but is unusable due to its acidity. Sample C represents a normal condenser paper with good quality is "Aue the results shown it can be seen that the capacitor papers produced according to the method of the invention according to Examples 1 to 4 be = siderably improved properties ,, Particularly noteworthy is the low value of 0 , 0020 for tg £ _v that the sample prepared according to Example 3 _{has o}

909881 / U61 BAD ORIGINAL

Claims (3)

Claims 1. Process jsur production of fibrous, electrically insulating material from cellulose containing metal ions, in which at least 50 # of the metal ions present are removed from the cellulose by electrolysis or by ion exchange »characterized» that the cellulose treated for the removal of the metal ions is removed in aqueous suspension with a or several epoxies treated in the way that at least 50 fa of the carboxyl groups present in hydrogen ion form are esterified. 2. The method according to claim 1 »characterized in that one the In the esterified © !! Cellulose still in hydrogen ion form existing carboxyl groups by subsequent treatment of the cellulose with bi- or polyvalent metal ions sets 3. The method according to claims 1 or 2, characterized in that that you can carry out the esterification with the help of a mixture of Vinyleyolohexandioxyd and propylene oxide or ethylene oxide carries out. 909881/1461