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Патент USA US3080345

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United States PatentO 7 1C6
cadmium primrose yellow, cadmium lemon yellow and
cadmium red. However, mixtures of the latter-mentioned
pigments may, if desired, be similarly incorporated to
treat the polyethylene resin.
Itis an advantage of the present invention that small
amounts of pigment can be incorporated into the resin
Stanley Klosowski, East Orange, N.J., assiguor to Cela
nese Corporation of America, New York, N.Y., a cor
poration of Delaware
No Drawing. Filed Feb. 29, 1960, Ser. No. 11,410
19 Claims.
. Patented Mar. ,5, 1963
(Cl. 260—41)
The present invention relates to a novel process for
' pigmenting thermoplastic resins. More particularly, it is
concerned with a process for uniformly distributing 1a..
to obtain uniform dispersion therein. Usually not more
than about ?ve percent and preferably between one and
three percent, based on the weight of the resin is a good
practice, though higher or lower percentages may be used
without detrimental effect. With carbon black and high
density polyethylene, acceptable results are obtained where
a range of between one and three percent is employed.
' - Uniform dispersion of the pigment in'the polyethylene
.pigment in polyethylene resins.’ Still ,more’particularly,
resin is advantageously accomplished by the'use of minor
"it relates to the uniform distribution of a pigment in a 15 amounts of an ammonia-yielding compound capable of
high density polyethylene resin with the aid of an ant
yielding ammonia at the temperature at whichthe resin
is in the plastic state. In most cases it is preferred that
'the decomposition products other than ammonia be vola
tile'or at least non-deleterious in the resin composition.
Some of the more typically illustrative ammonia-yield
ing compounds are: ammonium hydroxide; ammonium
,salts of carbonic acid including ammonium bicarbonate
and ammonium carbonate; and ammonium salts of car
' monia-yielding compound.
Pigments are conveniently dispersed in a thermoplastic
resin by admixture of the pigment, generally in a dry
state, with theresin in a particulate state, followed by
heating the admixture to a thermoplastic state 'while
mechanically working the admixture to obtain uniform
blending. It is often advantageous to achieve pigmenta
tion while heating ‘and working the resin for another
boxylic acids including-ammonium oxalate, ammonium
purpose, as for example, during the formation of mold 25. succinate, ammonium tartrate and ammonium citrate.
The particular ammonia-yielding compound best suited
ling pellets or during the formation of shaped consumer
articles. It has been found that the uniformity of pig
for a particular application will depend upon the tempera
ment dispersion in such cases, for a given amount of ' ; ture range for the softening and working of the particular
working, is often not as good as required for commercial
resin. Compounds requiring relatively high temperatures
for ammonia‘release are best suited for resins requiring
‘It is a principal object of the present invention to pro
relatively high temperatures for softening and thermo
vide a process for obtaining uniformly pigmented thermo
plastic working. For high density polyethylene a suitable
plastic resin and particularly high density polyethylene
temperature range is between about 130° and 250° C. and
‘resin of high grade. It is a further object to provide a
preferably between about 150° and 200° C.
shaped'polyethylene resin product intimately and uni 35 The amount of ammonia yielding compound used in
“formly admixed‘ with a pigment.
the admixture may suitably vary from about 0.02 to 3
‘These and other objects are attained in a convenient
percent, based on the weight of 'the resin. Lesser propor
and straightforward manner. It has been unexpectedly
tions will assist in achieving uniformity but will not be
found that uniform dispersion of pigment in a‘ thermo
fully effective; Greater proportions are uneconomical. A
plastic. resin can be accomplished by. utilizing
preferred range of proportions is from about 0.05 to 2.5
amount of an ammonia-yielding compound in either liq
Auid or solid form in the pigmentation. of the resins in the
Any suitable apparatus may be used in admixingthe
thermoplastic state.
pigment and ammonia-yielding compound with the par
According to the present invention, the overall process
ticulate resin to obtain a uniform blend. Tumbling end
contemplates the intimate admixing of a major amount of
a thermoplastic resin, a minor amount of an ammonia-M
yielding compound and a minor amount of a pigment at.
an elevated temperature sufficient to maintain the resin in
thermoplastic state and to release ammonia in si-tu, and if
desired, the pigmented resin may be further treated to 50
shape the same to obtain, for instance, an extruded or
injection molded product.
Prior to treatment, the resin which may be treated ac
cording to the process of the invention can exist in various
physical forms. For instance, high density polyethylene
resin in the form of ?akes or pellets may be treated. It.
is a convenient practice to employ ?akes of resin, since
this permits pigmentation to be accomplished during a
over vend in a drum blender is generally a suitable method
of blending. »A ribbon blender may be used to handle
larger quantities of material. The blending process is
suitably continued until gross uniformity of the admixture
is obtained, that is until a sample of about 1% taken from
one portion of the admixture would have the same com
position as a sample of about 1% taken from another
The heating of the admixture to plastic state and the
working‘thereof may also take place on any suitable ap
paratus. For example, it may take place on the rolls of a
rubber mill. Most conveniently however, the heating and
working take place in an apparatus wherein the plastic
admixture'is forced through a small ori?ce as ‘in an extru
'_ _
. A large variety of pigments can be employed for pur 60 sion operation or an injection molding operation. The
poses of this invention. Some such pigments are carbon
operation of the screw in the barrel 'of an extruder fol
black, titanium dioxide, ultramarine blue, copper phthalo- I ' 1lowedbythe turbulence created in forcing the vplastic
cyanine blue, burnt sienna iron oxide, raw umber iron
mixture through the extruder ori?ce usually provides suf?
pelletizing operation. 7
oxide, alizarin maroon, copper phthalocyanine green,
cient working for obtaining uniform admixture in accord
densities between about 0.94 and about 0.96 g./cm.3, but
also including conventional polyethylene resins. The in
vention is also applicable to other polyole?n resins, such
as polypropylene and to copolymers of ethylene and
propylene with other ole?nic monomers.
It is to be understood that the foregoing detailed de
ance with this invention.
In the extrusion of high density polyethylene, barrel
temperatures are between about 150° and 200° C.
Uniformity of pigment dispersion is ‘determined by the
' Universal Rating System (URS) of the overall treated
resin. This test can be characterized as follows:
scription is given merely by way of illustration and that
Each specimen consists of 24 round ?lms, approxi
many variations may be made therein without departing
mately 0.070" in diameter, sandwiched between two mi
from the spirit of my invention.
croscope slides. Each ?lm is made by pressing a single 10
Having described my invention What I desire to secure
pellet of the sample and punching a circle from the
by Letters Patent is:
resultant ?lm.
II. In a process for intimately admixing and uniformly
. Eighteen of the 24 circles are examined by two dif
dispersing pigment in a thermoplastic polyole?n resin in
ferent observers and‘ rated by comparison (at 100x magni
which an ‘admixture of pigment and resin particles is
l?ca'tion) with a set of standard photomicrographs. The 15 heated to thermoplastic state and worked in said thermo~
standard photomicrographs, are numbered to No. 15 with
plastic state, the improvement which comprises incorpo
the higher number representing photomicrogra'phs show
ing large numbers of large agglomerated particles. The
rating into said resin and pigment a‘ minor amount of an
ammonia-yielding compound which decomposes to release
individualcircles are rated to the nearest whole number
‘ammonia in situ at the temperature of said resin in ther
by each observer and the 18 values for each observer are 20 moplastic state.
averaged and reported to the nearest tenth of a dispersion
2. A process according to claim 1 wherein the pig
unit.‘ Then the averaged values for both observers are
ment is carbon black.
averaged andre'ported to the nearest tenth of a dispersion
3. A process according to claim 1 wherein the‘ so
unit on the URS rating. The lower the URS reading, the
pigmented resin is shaped simultaneously with the work
more uniform the dispersion of pigment in the product
ing thereof.
. _
will be. Advantageously, subs'tantialimprovement is ob
tained herein when utilizing the aforementioned princi
4. A process according to claim 1 wherein the am
monia-yielding compound is present in an amount of from
about 0.05 to about 2.5 percent, based on the weight of
The following examples are illustrative of the best
said resin.
practice .of the invention and should not be taken ,as
5. A process according to claim 1 wherein the am
monia-yielding compound is ammonium hydroxide. .
6. A process according to claim 1 wherein the am
limitive thereof. Unless otherwise stated, the parts are
by weight.
Example '1
monia-yielding compound, is ammonium bicarbonate.
7. A process according to claim 1 wherein the am
, 97 parts of polyethylene resin in ?ake form having a 35
monia—yielding compound is ‘ammonium carbonate.
density of 0.96 g./cm.3 and a melt index of 0.7 are inti
8. A process according to claim 1' wherein the am
'mately admixed with 0.5 part of aqueous ammonium hy
monia-yielding compound is ammonium oxalate.
droxide (28%) in a stainless steel vessel which is ‘tum
bled end-over-end at about 30 rpm. for about 30 min
utes. Two and one-half (2.5) parts of channel black
:(M‘on'arch'74) are next added and tumbled for an addi
tion'al 30 minutes. The resin so treated is placed in a two
9. Aprocess according to claim 1 wherein the am
monia-yielding compound is ammonium succinate.
10. A process according to claim 1 wherein the resin
is in ?ake form prior to treatment.
11. A process according to claim 1 wherein said resin
inch, vented, twin-barreled extruder With a 34-inch long
is a high density polyethylene resin.
main screw and a 17% inch long secondary‘screw. The
extruder had a screen pack having screens of 20, 50, 80, 45
ment in a high density polyethylene resin which ‘com
1‘00 and 20 mesh respectively in the direction of resin
prises: incorporating into said resin a pigment and a
?ow. I The screw speed, temperature at the ori?ce, output
minor amount of an ammonia-yielding compound, heating
vand ‘Universal Rating of the pigment dispersion are
shown in Table I, below.
the mixture at an elevated temperature su?icient to con
50 vert the mixture to a thermoplastic state and to release
Exampies II to VIII
ammonia in situ, forcing saidvthermoplastic. mixture to
. ,Example I was repeated, using ammonia-yielding ma
pass through ‘a constricted ‘ori?ce wherebysaid resinis
terials‘ of the “nature and amount ‘shown in Table I and
-shaped while’ uniform ‘dispersion of pigment is obtained.
using screw speeds and ori?ce temperatures also shown in
. 13'. A' process. according to claim 12 wherein the pig
Table I. The results were as follows:
NHa-Yielding Comp’d
Parts by Screw
Weight Speed
NH4OH(28%)“__ ........ ._
O. 5
NH4OH(28%) 8-.
ment is carbon black.
> _
Output b
6. 9
8. 4
6. 6
NH4OH(24%) “Q.
7. 2
NHJHO O3 ____________ -_
(NH4)2(OOO)2.H2O.. --_
NHlOH(28%) R __________ __
2. 3
2. 4
170 ’
6. 9
6. 2
8- 1
b-Lbs. per hr.
, While the invention has been described Wm. speci?c
reference‘ to a particular polyethylene resin,‘ it is to be
understood that it is applicable toloth'er polyethylene
resins,pespecially high density polyethylene resins having 75
_ 14. A process according to claim 13, wherein the-am
m-onia-yielding compound is present in an amount of from
about 0.05 to about 2.5 percent, based on the weight‘ of
said resin.
\15. A process according to claim 12 wherein the con
stricted ori?ce is an extrusion ori?ce.
16. A process according to claim 15 wherein said ex
trusion is carried out at a barrel temperature between
150° and 200° C.
17. A composition comprising an admixture of [a ther
moplastic polyole?n resin in particulate form, a pigment
and an ammonia-yielding compound.
18. The composition of claim 17 wherein said resin is
high density polyethylene and said pigment is carbon
19. The composition of claim 17 wherein said am
monia-yielding compound is present in an amount of
about 0.05 to 2.5 percent, based on the weight of the
References Cited in the ?le of this patent
Carson _______________ .. Nov. 3, 1925
Stober ________________ __ Feb. 6, 1951
Jordan _______________ __ Apr. 14, 1953
Great Britain ___________ __ July 8, 1948
Great Britain __________ ___ Apr. 10, 11957
Canada _______________ __ Jan. 12, 1954
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