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Патент USA US2562141

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Patented July 24, 1951
" UNITD
‘2,562,138
rice:
STATES
2,562,138
DESTATICIZIN G PROCESS
Charles Kilbourne Bump, Hampden, and Harold
F. Park, East Longmeadow, Mass., assignors to
Monsanto Chemical Company, St. Louis, Mo., a
corporation of Delaware
No Drawing. Application April 4, v1950,v
Serial No. 154,002
7 Claims. (Cl. 250-106)
.
.
.
‘1
2
‘This invention relates to processes for render
ing non-conductive materials resistant to the
scope of this invention. Where parts are men-lv
tioned they are parts by weight.
development of electrical charges by static ex
Example I
citation and to ‘the’ materials so treated.
More
particularly, the invention relates to destaticized
Anv aqueous solution of radium bromide con
non-conductive materials and to a process for
taining 10 parts of combined radium is slurried‘
acquire‘fa static charge. The charge may be
come strong enough to give a disconcerting jolt
with 300 parts of powdered beryllium. The‘
slurry is then dried by heating at about 180° ,C;
and the dried mixture is densi?ed in pellet
form. The pellet is then placed in a brass cap_-'
sule and the capsule is imbedded in a block of:
para?in. The dimensions ‘of the paraflin are'
such that a layer of about 4 inches of paraf?n
toan individual who discharges it by bodily con
surround the entire capsule; This para?in ‘en-1
and lint to accumulate on the surface of thenon
conductive materials by placing it in close jux-v
taposition thereto. Flat discs ‘of polystyrene
containing about 0.1% of zinc stearate, poly
destaticizing non-conductive materials by radio
active ‘means;
Noneconductive materials such as glass, por
celain,'cellulose ?lms and webs, cellulose deriva
tive articles, vsynthetic resin articles, etc. easily
tact. ' Moreover, the static charge causes dust 15 closed capsule‘is then used for destaticizing non
conductive
material.
' Many ' means
for
'
rendering
'
‘
non-conductive
vinyl chloride containing about 0.2% of tri
materials resistant to static excitation have
been proposed most of which depend either .on 20 phenyl stibine become destaticized after about
1 ‘hour in contact with the para?‘ln' block con
operating under condtions of controlled humid
taining the radioactive capsule. When tested.
ity, or on the incorporation of hygroscopic ma
by-the cigarette‘ ash test, no amount of rubbing
terial'into the electrically non-conductive ma-_
caused the development of electrostatic charges
terials. It has also been observed that expo‘
sure to radioactive materials will destaticize 25 thereon. The antistatic properties remain un
non-‘conductive materials for short periods of
time.
diminished for more than a year. '
‘
In contrast to the, treated discs of the ex
ample, untreated discs of the same materials‘
picked‘ up a strong electrostatic charge With but
' One object of this invention is to provide elec
trically non-conductive materials which are re-r
sistant to the development of electrical charges
slight rubbing. ‘ A} polystyrene disc, for example,‘
picks up a strong enough charge‘ to attract dry
cigarette ashes from a distance of more than 1/2".
Another object‘is to provide a process for
rendering electrically non-conductive materials
Example II
resistant to the development of electrical
Example-I
is
repeated
except that powdered
charges by static excitation. '
M 35
boronlis used instead of beryllium, The results
‘A particular object is to provide a process for
are substantially the same and the resistance to
destaticizing organic plastic materials.
the development of‘ an electrostatic charge re
‘ "These and other objects are accomplished by
mains effective over long periods of time.
subjecting electrically non-conductive materials
If a disc of polystyrene is subjected to'the di
40
to the'radiation of a mixture of a radioactive
rect action of the radiation from radium bro-'
material‘with boron or beryllium._~ mide, it quickly becomes destaticized but the
A simple and e?ective test for static elec
eiTect of the radiation fades rapidly and disap
tricity charges on the non-conductive materials
pears almost entirely within -2 or 3 hours.
by static excitation.
_
_
is as follows:
Place dry cigarette ashes on a smooth insulated 45
wooden surface in an atmosphere having a con
Example III
Ten‘ pieces of platinum foil coated with
polonium are superimposed and’placed between
trolled relative humidity of about 20%, rub the
plates of boron carbide. .The laminar structure
non-conductive material vigorously with a piece
of soft cloth and then bring the rubbed surface 50 thus made is inserted into a thin-walled brass
box and the box placed in a graphite container
to about 1/8" from the cigarette ashes.
Even
a slight charge will cause the ashes to fly to the
non-conductive material and adhere thereto.
The following examples are given in illustra-‘
tion and are not intended as limitations of the
~
‘ having walls about 3 inches thick. The ratio of
polonium to combined boron is about 100:400 on
a weight basis. A sheet of polyvinyl chloride
containing a small amount of a phospho
5,5 tungstate dye‘ becomes completely destaticized
2,562,138
3
4
after exposure to the radiation from the graphite
container. The effective resistance to the de
velopment of electrostatic charges remains un
‘perature and should be substantially pure. Thus,
changed for more than a year.
providing these material are substantially pure
materials such as graphite, para?'in, polymers of
ethylene, isobutylene, styrene, etc. may be used
and free from metallic elements.
}
Example I V
In order for the radiation from the. radioactive
An aqueous’ solution containing thorium
compositions to accomplish the destaticizing
tetrachloride and boron bromide in proportions
action, there must be present in 100 parts of the
equivalent to 100 parts of combined thorium
non-conductive materials’ at least 0.05 part of
and 300 parts of combined boron is, dried by 10 certain metals either in the elemental form or
gentle heating. The dried material is then
chemically combined. Among the most effective
pelletized and enclosed in a brass capsule which
metals are‘ antimony, zinc and silver. Less ef
is in turn enclosed in a substantially pure poly
fective metals are tin, calcium, scandium, ti
styrene container having walls four inches
tanium, selenium, strontium, zirconium, indium,
thick. Non-conductive materials including pa 15 cerium, tellurium, gadolinium, terbium, thulium,
per, polystyrene and polymerized methyl. meth
tantalum, tungsten, osmium, iridium, mercury
acrylate, each of which contain small amounts
and lead. Since many dyestu?s, especially
~of a zinc salt, are rendered impervious to the
mordant dyes, lubricants, stabilizers and pig
vdevelopment of electrostatic charges by short ex
ments contain su?icient amounts of one or more
posure to the polystyrene enclosed radioactive 20 of. the effective metals, it frequently isnot neces
material.
sary to modify the non-conductive materialsltov
The destaticizing'agents of'this invention are
insure incorporation of an activating . metal.‘
combinations of radioactive materials with boron
The incorporation of small amounts of. the. acti-,
or beryllium or a mixture of boron and beryl
vating metals or their derivatives in 11011-76011.
lium. Among the radioactive materials which 25 ductive materials which do not contain them is
may be used are ionium, radium, radon, poloni
generally accomplished with ease.
I
um, protactinium, thorium, actinium, and mix
The radioactive compositions of thisinvention
turesthereof. The radioactive materials may
retain their effectiveness for many years.. The
be used in their elemental form or in the form.
amount of the compositions used determines; the
of their organic or inorganic derivatives. The 30 exposure time necessary to render the non-cone
destaticizing agent may be in the form of. an
ductive material impervious to electrostaticex
intimate mixture of the radioactive material with
citation. A large amount of the radioactive
the boron or beryllium or the latter may be inter
composition spread thinly over a large area may.
posed between the radioactive material and the
be used to destaticize sheets and continuous;
non-conductive object so that the radiations
lengths of non-conductive materials. If the.
must pass through the boron or berylliumbefore
radioactive composition is concentrated’ in a
reaching
the
non-conductive
material- As
small area, the radiations therefrom will quickly
penetrate relatively thick objects.‘ These thick
objects may then be molded, carved, machined,
shown in the examples, the intimate mixture may
be obtained by dissolving water-soluble salts of
each of the components in water and then evap
etc. and yet the new surfaces thus exposed will,
crating the water or by dissolving a water
still be‘ destaticized.
‘
V
soluble salt of the radioactive element in water
The process of this invention is applicable: to.
and, forming a slurry with pulverulent boron,
all electrically non-conductive materials which.
beryllium or insoluble derivatives thereof. The
contain the minimum amounts of the. activating.
ratio of radioactive material to boron orberyl
metals. Among. the materials which. may, be
lium should be regulated on the basis of the 45 treated are glass, wood, paper, natural and syn-*5
radioactive element and elemental boron or.
thetic organic materials such as regenerated
beryllium. For every 100 parts of radioactive
cellulose, cellulose ethers and esters, naturalor
element, either alone or chemically combined,
synthetic. rubber, organic plastics such as phen
there should be from 100 to 1000.parts vof eleolic resins, urea resins, melamine.resins-,..poly-'
mental boron or berylliumeither alone or chemi
ically combined.
Other elements than boron'and beryllium are
either inoperative or so dii?cult to employ that
they are useless in-the process of this invention.
Boron or beryllium may be used per se or they
may be used. in the form of their organic or in
organic derivatives.
The insoluble derivatives
may be used in pulverulent form or in the formof
thin‘films or sheets.
The combination of the radioactive material
with-the boron or beryllium is convenientlyen
50
styrene, polyethylene, vinyl chloride. polymers‘
and copolymers, polymers and copolymers of
other vinylidenecompounds, etc. The non-cone,
ductive materials may be in the shapeoffsheeta,
rods, tubes, ?bers, molded.andextruded-designs,
etc.
The process of this invention is advantageous‘
in that it provides a quick method forrendering,
electrically non-conductive materials resistant‘
60 to electrostatic excitation over a relatively‘lon‘g
period of time.
-
What is claimed is:
closed. ina thin-walled-metal container such as"
1. A process which comprises placing radio-'
a brass or platinum container which is trans
active material in substantial contact with a
parent to the radiations of'the radioactive com
substance from the group‘ consisting- oflelemental
bination and which does not alter the proper 65 and chemically combined boron and. beryllium‘,
ties of said radiation. However, such‘ a con
thereafter embedding the" radioactive material
tainer is’ not any absolute necessity since“ the
and said substance-in a casing having’walls‘ from
radioactive composition may be placed directly
2 to 6 inches thick, saidcasing comprising a
in the hydrocarbon casing.
70 solidi'material taken from. the group‘consisting
The radioactive composition must be enclosed
of carbon and hydrocarbons, and subjecting" a~
in a casing having walls from 2 to 6 inches ‘thick,
non-conductive material to the‘ radiations‘ ema:-»
said casing being made of carbon or a hydro
nating from the'casing, said non-conductive‘ma
carbon material. The hydrocarbon may be alie
terial containing-at least 0.05% by weight~of:a*
phatic' or‘ aromatic, should be solid at room tem 75 substance from the group consisting of elemental
2,562,138
5
6
and chemically combined zinc, silver, antimony,
1 tin, tellurium, cerium, gadolinium, terbium, thu~
calcium, scandium, titanium, selenium, stron
tium, zirconium, indium, tin, tellurium, cerium,
gadolinium, terbium, thulium, tantalum, tung
lium, tantalum, tungsten, osmium, iridium,
sten, osmium, iridium, mercury and lead.
2. A process as in claim 1 wherein the radio
active material is radium bromide.
3. A process as in claim 1 wherein the radio
active material is polonium.
4. A process as in claim 1 wherein the sub
stance associated with the radioactive material is
mercury and lead, said non-conductive material
having been subjected to the radiation of a radio
active material associated with a substance taken
from the group consisting of elemental and chem
ically combined boron and beryllium, said radio
active material being embedded in a casing having
walls from 2 to 6 inches thick and said casing
comprising a solid material taken from the group
consisting of carbon and solid hydrocarbons.
beryllium.
CHARLES KILBO-URNE BUMP.
HAROLD F. PARK.
5. A process as in claim 1 wherein the sub
stance associated with the radioactive material
15
is boron.
6. A process as in claim 1 wherein the non
conductive material is an organic polymer.
7. A substantially permanently destaticized
non-conductive
material comprising
a
non
conductive material containing at least 0.05% by
weight of a substance taken from the group con
sisting of elemental and chemically combined
zinc, silver, antimony, calcium, scandium, ti
tanium, selenium, strontium, zirconium, indium,
REFERENCES CITED
The following references are of record in the
?le of this patent:
UNITED STATES PATENTS
Number
Name
Date
2,048,490
2,264,683
Bilstein _________ __ July 21, 1936
Smith ____________ __ Dec. 2, 1941
2,479,882
Wallhausen et a1. __ Aug. 23, 1949
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