Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ n3 1477
ANTITACKIN~ C~POSITION
~ackground of the Invention
This invention relates to a composition of fatty
amides and more particularly to such compositions as anti-
tacking agents for storage of rubber sheets when stacked one
on top of the other.
In many standard rubber manufacturing operations,
unvulcanized rubber is rolled out as sheets, stacked one on
top the other, and stored for a period of weeks or months
until needed. The uncured stock is tacky and tends to fuse
to itself during storage, making it impossible to separate
the sheets when it is time to use them. To prevent this
from happening, manufacturers use sheets of plastic or
antitack agents to keep the stock sepsrated. Use of sheets
of plastic is expensive and labor intensive.
The standard antitsck agents are carboxylic acid
amides of sliphatic diamines, particularly ethylene bis-
stearamide wax powder. It has the desirable property of
preventing the layers from adhering before vulcanization but
contributing to adhesion during vulcanization of layers of
stock in such uses as V-belt manufacture. It is believed
the amide groups of the bisstearamide chemically bond to the
rubber during vulcanization, accounting for its adhesive
property. In order for the bis-stearamide to be used
efficiently, it must be applied as a fine powder. The
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powder is an inhalation nuisance for the workers and a
housekeeping problem because it accumulates throughout the
workplace.
Attempts to eliminate the dusting problem by
preparing aqueous emulsions have failed because dispersants
which kept bisstearamide dispersed before application also
prevented adhesion during vulcanization.
Accordingly, it is a purpose of the instant
invention to provide a method of preventing or substantially
reducing adhesion between elastomer sheets when stacked one
on top of the other during storage without preventing
adhesion during vulcanization and to provide a liquid
dispersion of an antitack composition therefor.
U.S. Patents 4,129,543 and 4,225,554 (the latter
being a division of the former) disclose a mold lubrication
and parting compound for a liquid thermosetting polyester
resin composition comprising an alkylphosphate ester parting
agent in combination with an alkylene bis-alkamide material
such as ethylene bis(stearamide). However, there is no
disclosure of an oxyalkylene fatty amide type compound and
the reference requires an alkylphosphate ester. Further-
more, the mechanism by which unsaturated polyester resins
crosslink (cure) is quite different from vulcanization of
rubber. The former involves free radical coupling of
carbon-carbon double bonds, the latter involves addition of
sulfur across double bonds to form sulfide crosslinks.
-- 2 --
)3
U.S. Patent 3,935,143 relates to dispersing on the
surface of an ABS resin an organic compound. The organic
compound msy be ethylene bis(stearamide). However, there is
no disclosure of a composition including a polyoxyalkylene
fatty amide.
U.S. Patents 3,862,066 and 3,340,219 describe
methods for making molded plastic articles, i.e., in the
first patent vinyl chloride polymer compounds, in the second
patent polyacetal compositions which involve uniformly
dispersing as a lubricant in the resin or plastic composi-
tion, a lubricant which may be an ethylene stearamide. This
composition also does not include an oxyalkylene fatty
amide.
Summary of the Invention
The instant invention relates to a process and
composition for preventing or substantially reducing
adhesion between elastomer sheets when stacked one on top of
the other during storage wherein an aqueous dispersion
composition is applied to the sheets which composition
comprises:
a) carboxylic acid amides of aliphatic diamines
having the structure
R ~N~-R~ I
n
-- 3 --
1~ti 7503
wherein Ry is an aliphatic moiety derived from a
higher fatty carboxylic acid having at least 10
carbon atoms up to about 33 carbon atoms, Rx is an
aliphatic moiety having from 1 to about 33 carbon
atoms and n is an integer from 1 to 2.
b) an'oxyalkylated fatty amide having the structure
R~N ~A)n~ II
5
wherein R is an aliphatic group having from about
9 to 18 carbon atoms, A is -C2H4O-; -C3H6O- or a
heteric or block mixture thereof and n is 1 to 15.
The composition contains about 5 to 75 percent by
weight of the two amides (a) plus (b) and the ratio of the
carboxylic acid amide of an aliphatic diamine (a) to the
oxyalkylated fatty amide (b) is from about 95:5 to 5:95.
Description of the Preferred Embodiments
Preferably, in formula I above, Rx is an aliphatic
moiety derived from saturated and unsaturated (non-
benzenoid) hydrocarbons and their substituted derivatives
(wherein the substituents are inert) having an open chain or
cyclic structure which may include a minor proportion of
-- 4
~2~'7S03
heteroatoms selected from the group consisting of oxygen,
sulfur, and nitrogen in the skeletal structure. The
preferred aliphatic moieties have an open chain (linear or
branched) carbon skeleton of at least one up to about 33
carbon atoms and n is an integer from 1 to 2.
It is to be understood that the carboxylic acid
moieties may be ~he same or different in the bis-aliphatic
amides, and that the aliphatic moiety msy contain additional
amide groups of the structure
-N-J-Ry
Suitable such fatty acid amides of aliphatic diamines
include, for example, ethylene distearamide, propylene
distearamide, butylene distearamide, propylidene dioleamide,
N-(ethylideneoleamide) stearamide, methylene-bis-lauramide,
N-(ethylenestearamide) lauramide, N-(methylene palmitamide)
capramide, etc.
The preferred carboxylic scid amide is N,N'-
ethylene-bis-stearamide.
The preferred oxyalkylated fatty amide is one
wherein A is all or substantially all -C2H4O-; n equals 5
and R is a mixture of C12 - C18 aliphatic groups.
-- 5 --
The ra-tio of carboxylic acid amide of aliphatic
diamine (a) to oxyalkylated fatty amide (b) is from about
95:5 to 5:95, preferably about 70:30 to 30:70. The
dispersion contains from about 5 to 75 percent by weight
total carboxylic acid amide of aliphatic diamine (a) plus
oxyalkylated fatty amide (b) and preferably 15 to 40 percent
by weight of (a) plus (b), balance water.
The dispersion may contain standard fungicides and
bactericides in an amount of about 0.05 to 1.0 percent by
weight to prevent spoilage of the dispersion during storage.
Any conventional fungicide may be employed such as those
sold by R.T. Vanderbilt Company, Inc. under the trade mark
Vancide, for example, Vancide 51Z-zinc dimethyldithiocarba-
mate and zinc 2-mercaptobenzothiazole and Vancide TH
hexahydro-1,3,5-triethyl-s-triazine. Suitable bactericides
include those sold by the Dow Chemical Company under the
trade marks Dowicil 75, Dowicil 200, and Nuodex PNA the
latter of which is a mercury compound.
The dispersion may also contain standard
accelerators in amount of about 0.1 to 0.5 percent by
weight. Any standard rubber compound accelerators may be
employed such as bismutate-bismuthdimethyldithiocarbamate,
cadmate-cadmium diethyldithiocarbamate, cumate-copper
dimethyldithiocarbamate. Others include tetramethylthiuram5 monosulfide dipentamethylene thiuram hexasulfide, and zinc
/
-
-- 6
5~
2-mercaptobenzothiazole. Other accelerators are disclosed
on pages 338-348, vol. 20, 3rd Edition of the Encyclopedia
of Chemical Technolo~y by Kirk and Othmer.
Inorganic accelerators may also be employed such
as lead carbonate, lead oxide, litharge, hydrated lime, zinc
oxide and magnesium oxide. Mixtures of organic accelerators
and metal accelerators may be employed. The term "acceler-
ator" as used herein includes both the inorganic
accelerators as well as the organic accelerators. The total
amount of accelerators is from about 0.1 to 0.5 percent by
weight of the composition. The total amount of such
additives, i.e., bactericides, fungicides and accelerators
is about 0.05 to 1.5 percent by weight. It has been found
that the dispersion of this invention solves the problems
presented by antitacking powders while retaining good anti-
tacking properties without interfering with the
vulcanization of elastomers employing free radical
mechanisms. The dispersion of the invention has been found
to be effective with Neoprene, SBR, EPDM, Nitrile, Isoprene
and Butadiene rubbers.
The term "SBR" refers to the widely used styrene-
butadiene copolymer rubber well known to those skilled in
the art. This rubber is commonly made with a charge ratio
of 25 percent styrene and 75 percent butadiene.
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The term "EPDM" is used in the sense of its
definition as found in ASTM-D-1418-64 and is intended to
mean a terpolymer of ethylene, propylene and a diene
monomer. Illustrative methods for preparing such
terpolymers are found in U.S. Patent No. 3,280,082 and
British Patent No. 1,030,289. The preferred terpolymers
contain from about 40 to about 80 weight percent ethylene
and from about 1 to about 10 weight percent of the diene
with the balance of the terpolymer being propylene. This is
an elastomer which can be vulcanized; used for automotive
parts, cable coating, hose, footwear, and other products.
The following examples illustrate the excellent
antitacking properties of the composition of the instant
invention as well as demonstrating that the instant
dispersion composition accomplishes this result with good
adhesion whereas prior art dispersions had poor adhesion.
The antitacking and adhesion tests procedures are as
fo~lows.
Procedure for Antitacking Test
Rubber stock (5" x 4" x .09") is coated with a
dispersion using a wet film thickness applicator. The
thickness of the film is 3 mils (0.003"). The stock is air
dried for 30 minutes and the appearance of the coated rubber
observed. After 30 minutes an identical piece of rubber is
placed over the coated rubber. Both sides of the sample are
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. .
, '`': '
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covered with Mylar*film and placed under a lO lb. weight and
allowed to stand undisturbed for 24 hours. After 24 hours
the weight is removed and the sample is checked for sticking
and rated from l to 5, respectively. The lowest number
being the best.
Adhesion Test Procedure
The same sample, which was used for the anti-
tacking test, is cured in a small laboratory press at 150 C
for 30 minutes at a pressure of 80 psig.
A strip 4" x 1" is cut from the center of the
sample and tested for adhesion on a Scott-Instron tester in
accordance with ASTM D413-82.
Unless otherwise indicated throughout the instant
specification and claims, all temperatures are in degrees
centigrade and all parts and percentages are by weight.
* (trade mark of Dupont)
,...
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Examples 1 snd 2
Two samples of Neoprene rubber stock were coated
with a dispersion comprising 20 percent N,N'-ethylene-bis-
stearamide; 10 percent of a mixture of fatty amides having
the formula II set forth above wherein R vsries from
C12- C18 aliphatic group, A is -C2H40-, and n is 5, balance
water. As 8 control, rubber stock, as described in the
tests above, was coated with conventional N,N'-ethylene-bis-
stearamide powder and subjected to the above adhesion test
procedure. The results of these tests are shown in Table I
below.
TABLE I
Example No. Antitacking Adhesion
Appearance Test Sample Control
Wet Dry Rating lbs. lbs.
1 Smooth White 1 7 7
2 Smooth White 1 7.5 8
Examples 3 and 4
Samples of SBR rubber stock were coated with a
dispersion comprising 20 percent N,N'-ethylene-bis-stear-
amide; 10 percent of a mixture of fatty amides having the
formula II set forth above wherein R varies from
-- 10 --
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C12- C18 aliphatic group, A is -C2H4O- and n is 5, balance
water. As a control, rubber stock, as described in the
tests above, was coated with conventional N,N'-ethylene-bis-
stearamide powder and subjected to the above adhesion test
procedure. The results of these tests are shown in Table II
below,
TABLE II
Example No. Antitacking Adhesion
Appearance Test Sample Control
Wet Dry Rating lbs. lbs.
3 Smooth White 1 16.5 18
4 Smooth White 1 16.5 16.7
_xample 5
Example 1 is repeated with the exception that EPDM
rubber is employed in lieu of Neoprene rubber. Excellent
antitacking is achieved and the adhesion of the dispersion
is comparable to the conventional stearamide powder.
Example 6
Example 1 is repeated with the exception that the
dispersion composition consists of 10 percent of the N,N'-
ethylene-bis-stearamide, 1 percent of the oxyalkylated fatty
amide and the balance water. Excellent antitacking is
achieved and the adhesion is comparable to that achieved
~2~;7~:i03
with the N,N'-ethylene-bis-stearamide powder. This disposi-
tion is stable for more than one week at room temperature
and is stable after two freeze and thaw cycles.
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