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Патент USA US2406837

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Patented Sept. 3, 1946
2,406,837
UNITED ‘STATES. PATENT OFFICE,
STABILIZED POLYVIINYL FLUORIDE
‘Frederick L. Johnston, Claymont, Del., assig‘nor V
to E. I. du Pont ‘de Nemours & Company, Wil- ’ .
mington, Del., a corporation of ‘Delaware
No Drawing.
Application ‘November 19, 1943,
Serial No. 510,962
2Claims.
.
V
'
1
(01. 260-88) '
_
softening temperature of polyvinyl ?uoride. Best
This invention relates to compositions compris
ing polyvinyl ?uoride of improved heat stability,
results are obtained by using dicyclohexylamine
as the stabilizing compound. Polyvinyl ?uoride‘
containing the stabilizers of this invention can
and more particularly to new and valuable mold
ing compositions comprising polyvinyl ?uoride.
The polymeric vinyl halides and their copoly
be heated in a molding press for 5 minutes at 250°
mers are subject to discoloration and decomposi
tion under the‘ influence of heat. For'example,
polyvinyl chloride shows marked evidence of de
composition at temperatures as low as 135° C.
C. without any discoloration or decomposition,
whereas in the absence of stabilizer polyvinyl
?uoride darkens at 225°C. in 5 minutes and de-.
composes explosively ‘at 235° C. after 5 minutes
The ‘minimum decomposition temperatures. of 10
in a moldingpress.
‘
,
" The invention in the examples givenpherein has
been illustrated in connection with orientable
polyvinylv ?uoride from which the most valuable
agents which areeffective for polyvinyl chloride
products are obtained for the reasons previously
are not effective in the‘case of polyvinyl ?uoride.
A successful method forinjection molding of the 15 given. This invention, however, by reason of the
vinyl chloride polymers can be raised to some de
gree by the addition of stabilizers. Many of these
orientable; high molecular weight polyvinyl ?uo
markedly greater heat stability conferred, is also
ride wouldin particular be desirable because of
the high tensile strength and ?exibility of this
polymer. In spite of the fact‘that polyvinyl fluo
ride is a high softening polymer, it cannot, with
ride as ordinarily prepared. The orientable poly
vinyl ?uoride can .beprepared by heating vinyl
out modi?cation as described herein, be suitably
injection molded withoutevidences of decomposi
pheres and at a temperature above thes‘decom
useful in enhancing ‘the utility of polyvinyl ?uo
?uoride in the presence of an organic peroxy
compound. under‘ a pressure above 150 atmos-.
position point of the peroxycompound and below
that of the vinyl ?uoride. In contrast with the
ing press after 5 minutes‘ heating; ~Gradual de 25 non-orientable polymer which breaks after a
stretching of a few per cent, a fused sample of
composition also occurs even at 200° C. after 15
tion. For example, even at235° C.‘ polyvinyl'?uo
ride decomposes explosivelyiin an injection mold
or ‘20 minutes heating.
-
.
l
the orientable‘ polymer in the form ‘of a ?lm or
l
?lament ‘when subjected toilongitudinal stress in
the solid state will permanently elongate at least
. This invention has as anobject theprepara
tion of polyvinyl‘ ?uoride compositions of im
proved heat stability.” A further object is the
production of polyvinyl ?uoride molding‘ compo
sitions comprising polyvinyl ?uoride which are of
especial-‘value in the manufacture of polyvinyl
?uoride articles by; injection molding. Other ob-_
jects will appear hereinafter. V
.
\
-
s The above objects ‘are accomplished by incor
porating with- a“ polyvinyl ?uoride a stabilizing
agent comprising a small amount-of a formalde
hyde-reactive compound of the/kind described
hereinafter, and in the case of compositions par
ticularly adaptedfor molding, by preparing an
intimate mixturev of the ?nely divided polymer
and the stabilizing agent.
‘
_ The formaldehyde-reactive compounds most
advantageously usedsin the practice of this in
vention are nitrogen-containing compounds hav
ing a replaceable hydrogen attached to the nitro
gen, e. _g., primary and secondary amines and
amides,~ and in particular ‘the primary and sec
ondary aliphatic amines and amides.
1n the preferredl'practiceof this invention poly
vinyl ?uoride is powdered and uniformly mixed
by grinding with from 0.5% to 2% by weight
100% and up to 400% or more. Before orienta
tion it shows an X-ray diffraction pattern charac
teristic of a crystalline powder, and after orienta
tion it shows the pattern characteristic of an
oriented ?ber.
35
'
The invention is further illustrated by the fol
lowing examples in which the parts are by weight.
Example 1
One hundred parts of orientable polyvinyl
?uoride are ground with 2 parts of urea‘ until a
uniformly’ mixed powder is obtained. A sample
of this composition is tested ,for heat stability
by pressing between aluminum foils in a Carver
laboratory press (supplied by Fred S. Carver, New
York city), at 250° C. for 5 minutes under 10,000
lbs;/sq_ in. pressure.“ When the vsample is re;
moved from‘ the press and cooled, there is ob
tamed a water-white ?lm 0.025” thick which is
completely fused by the molding ‘process. ‘ There
50 is no evidence of decomposition or discoloration.
.A sample of the same polyvinyl fluoride con
taining no stabilizer heated in the molding press
based on the polyvinyl ?uoride of a primary‘or
under the same conditions as above decomposes
violently after 2 minutes leaving a charred black _
secondary. amine or amide which boils above ‘the
friable residue.
2,406,837
4
3
Example II
One hundred parts of orientable polyvinyl
pheres. After 15 hours the reaction is complete,
80% of the polymerization having occurred dur
aluminum foils in a Carver laboratory press at
orientable polyvinyl ?uoride after washing and
ing the ?rst '7 hours. The reactor is cooled, pres
?uoride is ground with 1/2 part of dicyclohexyl
sure
is released, and the product is discharged.
amine until a uniform powder is obtained. A
sample of this powder is then pressed between O1 It is a friable white cake consisting of 62 parts of
drying.
250° C. ‘for 5' minutes under 10,000 lbs/sq. in.
In addition to the stabilizing agents mentioned
pletely fused by the molding process is obtained. 10 in the examples formaldehyde-reactive com
pounds containing phenol groups can be em
The product shows no decomposition or discolora
ployed, e. g., para-aminophenol. Other phenols
tion.
can be used although those which do not contain
Similarly, when 2 parts of the following com
a nitrogen having a replaceable hydrogen are not
pounds were uniformly mixed with 100 parts of
as effective as are nitrogen containing compounds.
polyvinyl ?uoride, no decomposition or discolora
The stabilizers are used in amounts from 0.25%
tion of the product occurred when molded for 5 15
to 2% by weight for best results. The proportions
minutes at 250° C. under 10,000 lbs/sq. in.‘pres-,
are usually within 0.1% to 5% since lower pro
sure: Hexamethylene-bis-urea, biuret, mono
portions give insu?icient stabilizing effect for most
acetylurea, monobenzylurea, cyanamide, dicyan
purposes and with higher proportions compat
diamide, diethylenetriamine, melamine, and
pressure. A water-white ?lm of the product com
20
furylamine.
Example III
ibility with polyvinyl ?uoride decreases and the
molded products become weaker. The stabilizers
can be incorporated in the polyvinyl ?uoride by
dissolving both the polyvinyl ?uoride and the sta
.One hundred parts of orientable polyvinyl ?uoe
ride is ground with 2 parts of urea until a uniform
bilizer in a mutual solvent and evaporating off the
then chopped to pass a %" screen. The product
is injection molded in a De Mattia, one ounce
corporation into polyvinyl ?uoride and to avoid
powder is obtained. .This powder is pelleted by 25 solvent. The stabilizer may also be incorporated
by grinding it and the polyvinyl ?uoride together,
cold pressing at 15,000 lbs/sq. in. pressure and
capacity vertical injection molding machine (sup
plied by the De Mattia Machine and Tool Com
or they may be mixed on a mill. For ready in
volatilization during'the molding process, the sta
30 bilizers should have a boiling point above the
pany, Clifton, New Jersey). The injection mold
softening point of the polyvinyl ?uoride.
ing machine is ?tted with a die capable of mold
ing test pieces 5" x 1/2" x 1/8”. With an injection
cylinder wall temperature of 250° C. and at a pres
The stabilizers which are effective fOr polyvinyl
?uoride are unsatisfactory when applied to poly
vinyl chloride. For example, polyvinyl chloride
sure of 23,500 lbs/sq. in. on the injection piston,
35 pressed between aluminum foils for 5 minutes at
tough molded objects are obtained which are
faithful reproductions of the die cavity and which
showno discoloration or decomposition in com
shows a medium brown discoloration indicating a
certain amount of decomposition. In this same
parison with the original molding powder.
Orientable poly-vinyl ?uoride containing no sta
bilizer and subjected to the same molding condi
tions decomposes violently when it comes in con
tact with the heating zone at 250° C.
Example IV
One hundred parts of orientable polyvinyl ?uo
ride is ground with 1/2 part of dicyclohexylamine.
175° C. under 10,000 lbs/sq. in. yields a ?lm which
test polyvinyl chloride containing 2 parts per
hundred of magnesium stearate, a known stabil
izer for polyvinyl chloride, remains light colored.
When heated at 175° C. polyvinyl chloride con
taining 2 parts per hundred of hexamethylene
bis-urea gives a dark maroon, opaque ?lm and
polyvinyl chloride containing 2 parts per hundred
The polyvinyl ?uoride containing the dicyclo
of dicyclohexylamine heated in a press at this
temperature gives a dark reddish-brown ?lm
?ecked with black areas of complete decomposi
hexylamine stabilizer is injection molded in a De
Mattia machine as in Example III under a pres
sure of 25,300 lbs/sq. in. on the injection piston
tion illustrating that even at the lower tempera
tures these compounds, which are excellent heat
stabilizers for polyvinyl ?uoride, do not satis
and with an injection cylinder Wall temperature
factorily stabilize polyvinyl chloride against the
of 210° C. By this procedure tough molded ob
in?uence of heat. Conversely, many compounds
which are effective heat stabilizers for polyvinyl
chloride, e. g., magnesium stearate, sodium carbo
J'ects of excellent appearance are obtained.
A_ method for obtaining the polyvinyl ?uoride :
used in the foregoing examples is as follows:
A silver-lined reactor is swept with oxygen-free
nitrogen and charged with 120 parts of deoxy
nate and maleic anhydride are of no value in
raising the temperature at which polyvinyl ?uo
ride is subject to decomposition.
Stabilized polyvinyl ?uorides of this invention
genated water, 80 parts of pure methanol, and 0.2
part of benzoyl peroxide. It is then closed, nitro 60 ?nd particular use in molded products since their
gen is removed by evacuation, and 100 parts of
decomposition temperature is sufficiently raised to
vinyl ?uoride containing 20 P. P. M. of oxygen and
enable them to be successfully injection and com
a trace of acetylene (less than 50 P. P. M.) is ad
mitted. The reactor is placed in a reciprocating
pression molded without discoloration or decom
position. These Products are also useful in melt
agitator, ?tted with temperature and pressure re
cording and controlling instruments, and connect
spinning of polyvinyl ?uoride and in calendering
operations where temperatures above 200° C. are
ed through a valve to a source of additional mono
used.
meric vinyl ?uoride of the same purity. Heating
and agitation are begun, and when the tempera
ments of this invention may be made without
ture within the reactor reaches 78° C. additional
vinyl ?uoride is injected to raisethe pressure in
the system to 250 atmospheres. Reaction sets in
and the temperature is maintained at 80° C.
Monomeric vinyl ?uoride is injected as rapidly as
necessary to maintain the pressure at 250 atmos
As many apparently widely different embodi~
departing from the spirit and scope thereof, it is
to be understood that I do not limit myself to the
speci?c embodiments thereof except as de?ned in
the appended claims.
'
I claim;
1. A composition of matter comprising poly
2,406,837
‘
vinyl ?uoride which is stable against discoloration
and decomposition when heated 5 minutes at 225°
C., said composition comprising polyvinyl ?uoride
having dieyclohexylamine intimately dispersed
therethrough in amount of 0.1% to 5% by weight
of the polyvinyl ?uoride.
2. A molding powder comprising ?nely divided
6
orientable polyvinyl ?uoride having dicyclohexyl
amine ‘intimately dispersed therethrough in
amount of 0.1% to 5% by weight of the polyvinyl
?uoride, said polyvinyl ?uoride being character
ized in that it is capable of being permanently
elongated at least 100% under longitudinal stress.
FREDERICK L. JOHNSTON.
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