Note: Descriptions are shown in the official language in which they were submitted.
sackground of the Invention
Crude natural rubber is generally quite high in
viscosity and therefore does not mix easily and quickly with
the many additives used during processing. To facilitate the
addition of these additives, the rubber usually is softened by
undergoing a preliminary step called mastication.
The rubber is placed into a usual mixer, such as the
Banbury*, and is subjected to heat and a plasticizer (peptizer),
while being mixed for several minutes. The resulting mixture
is then dumped, sheeted on a roll mill and cooled. The softened
rubber then undergoes the mixing step.
The processing aids of United States Patent No.
3,787,341 were developed to eliminate the need for the mastica-
tion step. These compositions are added directly to the crude
rubber in the mixing cycle along with the other additives. In
addition to facilitating the breaking of the polymer and the
elimination of the need for both the mastication step and the
peptizer, these compositions have other beneficial effects in
rubber compounding. They reduce the mixing time required for
rubber compounding and provide for better dispersal of additives
than traditional methods. In addition, they enable'"~he use of
; lower mixing temperatures and provide for improved flow,
improved physical properties, improved mixing and extruding
characteristics, and improved physical characteristics of the
rubber. Hence, even the compounding of synthetic rubber
*Denotes Trade Mark
., - . ; :. .- : . -
~ ~ . .. .. . . . .
1045804
requiring no pre~astication will be enhanced by the use of these
formulations.
The compositions of the prior invention are homogeneous
mixtures of:
1) alkali salts of aromatic sulfonic acids having the
general formula: ~
Xn ~ ~ OH
wherein X can be either hydrogen or a branched or straight chain
alkyl group having from 4 to 14 carbon atoms, and preferably
about 8 to 12 carbon atoms; and n has a value of from 1 to 5,
and preferably l; and
2) long chain fatty acids having a maximum of about 2Z
carbon atoms in the chain, such as, but not limited to, stearic
acid, palmitic acid, oleic acid, neodecanolc acid and mixtures
o~ such aci`ds. The ~atty acids should be present in amounts at
least about equal to the amount o~ sulfonates but may be present
in substantial excess if desired.
It has been found in accordance with the present
invention that thioethers catalyze the action of the prior com-
positions. In particular, they promote further reduction in
the viscosity of the rubber compound. This results in a reduced
energy input to effect compounding. In addition, it enables
mixing of the rubber compound at lower temperatures, thereby
minimizing the danger of scorching the rubber compound.
Thus according to this invention there is provided an -
improved rubber processing aid comprising:
a) an alkali or amine salt of an aromatic sulfonic `~
ac1d h i g the
: . ' '' ' '. ' ' . . ~ . : :.
.
1045804
wherein c~n be either hydrogen or ~ br~nched or str~ght chain
alkyl group having from 4 to 14 carbon atoms, and n has a value
of from 1 to 5; and
b) a long chain fatty acid having a maximum of
about 22 carbon atoms in the chain, wherein the amount by weight
of said fatty acid present is at least equal to the amount by
weight of said sulfonic acid salt, the improvement wherein said
processing aid includes a thioether in an amount sufficient to
catalyze the peptizing action of said salt.
This invention also provides improved rubber composi-
tions containing the improved rubber processing aids of this
invention.
Finally this invention provides an improved method
for compounding rubber.
The thioethers which are employed in accordance with
this invention are those of the formula:
`. ~ Rl _y_R2
wherein Y is sulfur or dithioalkylene, i.e. -SCXH2xS - wherein x
has a value of from 1 to about 5, and preferably is 1; and each
l and R2 is alkyl, aryl, alkaryl, aralkyl as well as sub-
stituted alkyl, aryl, alkaryl and aralkyl. The precise nature
of Rl and R is not highly critical, provided the thioether is
sufficiently non-volatile to remain in the rubber compound for
¦a sufficient period of time to provide effective catalyzing
¦action. In general, thioethers having boiling points in excess
; of about 130C. are sufficiently non-volatile to be useful in
accordance with the invention. In addition, the size of the
compound should be such that sufficient catalytic activity can
be imparted with relatively small amounts of thioether.
Accordingly, each of ~1 and R2 preferably contains no more than ~ ;
,
.:
lOqS804
about 12 carbon atom3. Lastly, substituents, if any, should be
inert and compatible with the compounds of this invention as
well as with the ultimate rubber compound into which they will
be incorporated. Suitable substituents include ether oxygen,
carbonyl oxygen (i.e. keto, ester and carboxyl groups), cyano,
amine nitrogen (primary, secondary or tertiary), amide groups
and the like.
A preferred class of thioethers comprises
thiodicarboxylic acids and their lower alkyl ethers of the
formula:
Y~CzH2z_a (Co2R3)l~a~2
wherein Y is as defined above; z is a number having a value of
from 1 to about 2; a is a number having a value of from about O
to about l; and R3 is hydrogen or lower alkyl of up to about 3
carbons. Typical thioethers include thio-diglycolic acid,
thiodipropionic acid, methylene bis(thioacetic acid), dimethyl
thiodipropionate, thiodisuccinic acid, thiodipropionitrile, and
dibenzyl sulfide.
The thioether is believed to act as a catalyst. In
particular, it is believed that the alkali metal sulfonate
component of the prior composition is converted in part into the
corresponding sulfonic acid which acts as a peptizer during the
compounding process, and that the thioether catalyzes the
peptizing action of the sulfonic acid. This theory is offered
solely by way of explanation, however, and it is not intended to
limit the invention to this theory.
Regardless of theory~ the amount of thioether suffi-
cient to achieve a reduction in compound viscosity and mixing
temperature is small. In general it will be from about 5 to
about 10 per cent, based upon the weight of the sulfonate salt,
"' . ., ' ~ .
1!)4~8~)4
or from about 1 to about 3 per cent based upon the combined
weight of sulfonate salt and fatty acid.
The resulting composition is blended with the rubber
at the beginning of the mixing cycle. The amount of the
composition necessary to achieve improved compounding ordinarily
is from about 0.5 to about 2 per cent, and preferably about 0.9
- to about 1.5 per cent, based upon the weight of the rubber in
the compound. As a result, the thioether is present in the
compound at levels of only 0.005 to about 0.06 per cent, based
upon the rubber. Nonetheless, the incorporation of such small
amounts of the thioether has a material effect on reducing com-
pound viscosity and compounding temperatures.
The composition of this invention preferably is mixed
with suitable materials to facilitate its introduction into the
rubber. Such materials include esters and ethers of aromatic
alcohols, acids, etc. These additional materials are preferably
similar to the materials comprising the composition of the inven-
tion of United States Patent No. 3,855,165, issued December 17,
1974. These generally are aromatic esters, compounds with
alcoholic and glycolic hydroxyl groups, potassium or sodium soaps
~; of fats or fatty acids, metal soaps of zinc, magnesium, calcium or
barium, and a paraffin. Specifically, these additional materials
may comprise:
(a) From about 5% to about 15% aromatic esters
selected from groups consisting of (1) di-
aryl- and di-arylalkyl phthalates, (2) di-
aryl- and arylalkyl mono-glycolether
phthalates, (3) phthalates from polyglycol
mono-ethers of aryl, aralkyl and alkaryl com-
pounds wherein the polyglycol chain contains
:
l 104S804
from 2 to 6 ethylene oxide groups in the chain,
(1l) di-benzoates of glycol and propyleneglycol,
and their di- and tri-mers; and (5) mixtures
of the above.
From about 5% to about 30% of eompounds with
alcoholie or glyeolie hydroxyl groups selected
from ~1) straight or branehed chain aliphatie
aleohols having -from about 8 to about 20 ear-
bons in the ehain, (2) alkyl-phenoxy ethers
of glyeols or polyglycols wherein the alkyl :.
group is limited to about 12 earbons in the :
ehain, and the polyglyeol grouping does not
eontain more than about 6 (CH2-CH2-0-) groups,
~' ~ , '
.
.
-`` 1045804
(3) polypropylene glycol of about three pro-
pylene oxide groups in the molecule, and
(4) mixtures of the above.
(c) From about 5~ to about 15% of potassium or
sodium soaps made from commercial mixtures of
fats or fatty acids containing from about 12
to about 18 carbon atoms in the chain, said ~ -
chains having only a small degree of unsatura-
tion, with more than 50% of them having 18
carbon atoms in the chain.
(d) From about 10% to about 30% of fatty acids
having from about 12 to about 18 carbon atoms
in the chain, said chains having only a small
degree of unsaturation, with more than 50% of
them having 18 carbon atoms in the chain.
(e) From about 5% to about 10% of a metal soap
where the metal is selected from the group
consisting of zinc, magnesium, calcium, or
barium; and the fatty acid part of the soap
has from about 12 to about 18 carbon atoms
in the chain and contains a high percentage
of chains with a single double bond in the
; chain.
(f) From about 15% to about 60~ of hydrocarbons
selected from the group consisting of mineral
oil, mineral waxes, and petrolatum, or mix-
tures of them.
Preferably the potassium or sodium soaps of (c) above
or the fatty acids of (d) above are compounds which have iodine
values in the range of from about 5 to about 15. The metal soaps
of (e) above are more unsaturated and have iodine values in the
:
-7-
: `
` 16)45804
range of about 80 to about 95.
Typical aromatic esters of (a) above which may be used
in the compositions of this invention are dibenzyl phthalate;
diphenyl phthalate; bis(2-phenoxyethyl) phthalate; bis(nonyl-
phenoxyethyl) phthalate; bis(nonylphenoxytetraethyleneglycol)
phthalate; benzyl dodecylphenoxyhexaethyleneglycol phthalate;
bis(octylphenoxy) hexaethyleneglycol phthalate; diethyleneglycol
dibenzoate; dipropyleneglycol dibenzoate; and triethyleneglycol
dibenzoate.
Illustrative of the compounds with alcoholic or glycolic
hydroxyl groups referred to in (b) above which may be employed
are 2-ethylhexanol, cetyl alcohol, stearyl alcohol, nonyl-
phenoxyglycol, nonylphenoxydiglycol, nonylphenoxytetraethylene-
glycol, dodecylhexaethyleneglycol, dipropyleneglycol,
tripropyleneglycol.
Among the potassium or sodium soaps referred to in (c)
above are sodium and potassium soaps of hydrogenated tallow,
hydrogenated oils of vegetable or marine origin, and soaps of
potassium or sodium made with fractions prepared from oils and
fats, such fractions having iodine values from about 5 to about :~
15. ~:
Typical fatty acids which may be employed are those
derived from hydrogenated tallow and hydrogenated oils of
vegetable or marine origin.
Illustrative of the fatty acids part of the metal soaps
referred to in te) above are oils of vegetable origin or fractions ` :
of animal fatty acids such as red oil.
Among the petroleum jellies, mineral oils, and mineral
waxes, which may be employed in the compositions of this inven- :- :
tion, are waxes having melting points of about 120 to 170F.
- : - . , . - " , .
1~458~4
However, compositions of this invention are not limited
to use in combination with the above additional materials and
any similar chemicals will suffice. All ingredients may be of
technical grade and may contain varying amounts of related
materials, by-products, etc. The novel rubber processing aids
of this invention can be made by melting the ingredients together,
mixing and cooling, forming a waxy solid. The additionalmaterials
may be added together with the sulfonic acid salt, fatty acid and
thioether and all components heated until a clear melt is
obtained. The alkali soaps and soaps of the bivalent metals
can also be made in situ as is well known in the art, from the
oxide, hydroxide or carbonate of the metal and the desired acids
or acid anhydrides, followed by the evaporation or boiling off of
the resulting water.
A preferred formulation for balanced processing aids
of this invention contains the following approximate percentages
by weight of compounds which are typical of their class: -
3% to 15% alkali salt of aromatic sulfonic acid
5% to 25% fatty acid
0.5% to 1.5% thioether
7% to 15% diphenylphthalate
10% to 20% tetraethyleneglycol mono-nonylphenol ether
5% to 10% tripropyleneglycol
5% to 20~ potassium stearate
4% to 10% zinc oleate
0% to 5% cetyl alcohol
15% to 40% petrolatum
In general, the above-described compositions are solids.
It is desirable that they be in liquid form to facilitate mixing ;
of the composition with the rubber compound. Such liquid com-
_g_
~C~45804
positions can be achieved by the use of amine salts of the
aromatic sulfonic acids disclosed above. The salts are those of
amines of the formula:
R R R N
and
H tNHCH2CH2t NH2
Wherein R4 is alkyl or hydroxyalkyl, each of R5 or R6 is
hydrogen, alkyl or hydroxyalkyl, and n is a number having a
value of from 2 to 5. Preferred amines are those having a
molecular weight of at least 149 which are themselves liquid
and react with the aromatie sulfonic acid to form a liquid salt. ~
Preferred amines are tertiary amines, with triethanolamine being ~ -
especially preferred.
The aromatic sulfonie aeid amine salt can be pre~
formed or it ean be formed in situ by adding the acid and the
amine separately. In the latter case, the aromatic sulfonic acid ~-
and the amine are added in approximately equivalent amounts.
The amine salt of the sulfonie acid, the carboxylie -
aeid and the thioether ean be mixed with certain of the
ingredients (a)-(f) discussed above and still afford a liquid
formulation. In particular, the aromatic esters (a), the
aleoholie eompounds (b), and the hydroearbon (f) can be employed.
However, the metal soaps (c) and (e) are to be avoided if a liquid
formulation is desired. As a result, the proportions of the
additional materials are appropriately ad~usted to refleet the
omission of these eomponents as follows:
5.5% to 20% of ester (a)
5.5% to 38% of alcoholie eompound (b) - -
5.5% to 38% of acid (d), and
16% to 75% of hydrocarbon (f)
-10- " "
. . .
- , . , - .. : ~ ' '
,. , - ., . -: . . :
1045804
Prefcrre~ liqui~ formulatlons contain:
20~ to 25~o amine salt of aroma~ic sulfonic acid
15% to 25% fatty acid
0.5~ to 1. 5~ thioether
5~ to 15~ dipropylene glycol dibenzoate
20% to 25~ tetraethyleneglycol mono-nonylphenol ether
5~ to 15% tripropyleneglycol
10% to 20% mineral oil
As noted above, the compos~ions of this invention
generally are added to the rubber at the beginning of the mixing
cycle. The usual additives, such as pigments, fillers, vul- ~ -
canizing agents, etc., can then be added and the entire com-
pounding performed in one operation. They may be added to any
type rubber, whether it is of a natural, synthetic or reclaimed
type.
The following Examples are illustrative of the present
invention. The processing aids employed in the Examples are as
follows:
COMPOUND A
(illustrative of the composition of
U.S. Patent No. 3,787,341 issued January 22, 1974)
10.0 Parts potassium n-dodecylbenzenesulfonate,
techn. (mixed isomers)
22.0 " stearic acid, techn. rubber grade
10.0 " diphenylphthalate, techn.
15.0 " tetraethyleneglycol mono-nonylphenol ether,
techn.
5.0 " tripropyleneglycol, techn.
18.0 " potassium stearate, techn.
4.0 " zinc oleate, techn.
2.0 " cetyl alcohol, techn.
14.0 " petrolatum, N.~.
11-
. . ~' ' , ~ . ~,
1~)45~04
COMPOUND B
(Illustrative of this Invention)
10.0 Parts potassium n-dodecylbenzenesulfonate,
tech. (mixed isomers)
22.0 " stearic acid, techn. rubber grade
10.0 " diphenylphthalate, techn.
15.0 " tetraethyleneglycol mono-nonylphenolether,
techn. ;~-
5.0 " tripropyleneglycol, techn.
18.0 " potassium stearate, techn.
4.0 " zinc oleate, techn.
2.0 " cetyl alcohol, techn.
14.0 " petrolatum, N. F.
0.6 " thiodiglycolic acid
COMPOUND C
- (Illustrative of this Invention)
10.0 Parts potassium n-dodecylbenzenesulfonate,
techn. (mixed isomers)
; 22.0 " stearic acid, techn. rubber grade
10.0 " diphenylphthalate, techn.
15.0 " tetraethyleneglycol mono-nonylphenolether, -
techn.
5.0 " tripropyleneglycol, techn.
18.0 " potassium stearate, techn.
4.0 " zinc oleate, techn.
2.0 " cetyl alcohol, techn.
14.0 " petrolatum, N. F.
0.7 " thiodipropionic acid -
Ah ...... ..
-12-
. '
. ., , :,. . .. .. : :.
1(~458U4
COMPOUND D
(Liquid formula of this Invention)
1.0 Parts thiodiglycolic acid
10.0 " tripropylene glycol
23.0 " tetraethyleneglycol mono-nonylphenoxyether
10.0 " dipropyleneglycol di-benzoate
14.0 " paraffinic mineral oil 100/100
20.0 " neodecanoic acid
15.0 " dodecylphenylsulfonic acid
7.0 " triethanolamine 99%
COMPOUND E
(Liquid formula of this Invention)
1.2 Parts thiodipropionic acid
9.8 " tripropylene glycol
23.0 " tetraethyleneglycol mono-nonylphenoxyether
10.0 " dipropyleneglycol di-benzoate
14.0 " paraffinic mineral oil 100/100
20.0 " neodecanoic acid
15.0 " dodecylphenylsulfonic acid
7.0 " triethanolamine 99%
COMPOUND F
1.3 Parts methylene bis(thioacetic acid)
~- 7 " tripropylene glycol
22 " tetraethyleneglycol mono-nonylphenol ether
13.4 " dipropyleneglycol dibenzoate
12 " paraffinic mineral oil 100/100
18 " neodecanoic acid
18 " dodecylphenylsulfonic acid
8.4 " triethanolamine 99
-13-
1~4S8~4
COMPOUND G
1.5 Parts dimethyl thiodipropionate
9 " tripropylene glycol
24 " tetraethyleneglycol mono-nonylphenol ether
14 " dipropyleneglycol dibenzoate
13.5 " paraffinic mineral oil 100/100
18 " neodecanoic acid
14 " dodecylphenylsulfonic acid
6 " triethanolamine 99%
COMPOUND H
2.0 Parts thiodisuccinic acid
9 " tripropylene glycol
24 " tetraethyleneglycol mono-nonylphenol ether
14 " dipropyleneglycol dibenzoate ;~
13. " paraffinic mineral oil 100/100
18 " neodecanoic acid
: 14 " dodecylphenylsulfonic acid
6.6 " triethanolamine 99%
COMPOUND I
1.0 Parts thiodipropionitrile -
9 " tripropylene glycol
25 " tetraethyleneglycol mono-nonylphenol ether
14.5 " dipropyleneglycol dibenzoate
14 " paraffinic mineral oil 100/100
18 " neodecanoic acid
14 " dodecylphenylsulfonic acid
6.5 " triethanolamine 99%
. , .
-14-
.
~04580~
COMPOUND J :
1.5 Parts d.ibenzyl sulfide
9 " tripropylene glycol
" tetraethyleneglycol mono-nonylphenol ether
14 " dipropyleneglycol dibenzoate
14 " paraffinic mineral oil 100/100
18 " neodecanoic acid
14 " dodecylphenylsulfonic acid
6.5 " triethanolamine 99%
Example I
Three rubber compounds were prepared in a Banbury* mixer
as follows. Crude natural rubber was added and subjected to
mixing. After 1 minute Compound A, B or C was added with finely
divided silica (Hi-Sil*). After continuing mixing for an addi-
tional 5 minutes, carbon black (F T Black), mineral oil (Circo
Light* Oil), poly(tetrafluoroethylene) plasticizer (Flexone 3C*)
microcrystalline wax, zinc oxide and stearic acid were added.
After mixing for an additional 3 minutes, the ram was cleaned and
after 2 more minutes the batch was dumped. Benzothiazyl disul-
fide (MBTS) and sulfur accelerators were then added on the millin 3-1/2 minute's mixing.
Each of the resulting mixtures was inspected visually
and was found to be a good dispersion without apparent difference.
However, the dump temperatures and the Mooney Viscosities for the
two compositions made with the processing aids of this invention,
Compounds B and C, were lower than those of the composition
employing the processing aid of my prior application (Compound A).
The data for this Example is summarized as follows:
*Denotes Trade Mark
-15- .:
. .: .
.
. - , .- ,, . . , , . :.
~0458~4 .
Compound No.
Compound Component _ 2 3_
Crude Natural Rubber 100 100 100
Compound A 3.10 - -
Compound B - 3.10
Compound C - - 3.10
Hi-Sil* 10.00 10.00 10.00
F. T. Black 65.00 65.00 65.00
Circo Light* Oil15.00 15.00 15.00 :~
Flexone 3C* 2.00 2.00 2.00
Microcrystalline wax 2.00 2.00 2.00 ;-
Zinc oxide 5.00 5.00 5.00
Stearic acid 2.00 2.00 2.00
MBTS 0.60 0.60 0.60
Sulfur 2.50 2.50 2.50
Dump Temperature, F. 270 260 260
Mooney Viscosity~4.0-44.~ ~41.~~1.5-42.
Example II
Employing procedures similar to those described in
Example I, three crude rubber compounds were prepared employing
Compounds B, D or E. The formulations were as follows: .
*Denotes Trade Mark .
, '
-16- -~
: '. ..... . ..... . . ' ... '' : ' ~ ': : . '
. ,.. , : . :
`` 15~45804
Compound No.
Compound Component 1 2 3
_
Natural Rubber (crude, #3
Rib Smoked Sheet) 100 100 100
Compound B 2.0 - -
Compound D - 2.0
Compound E - - 2.0
Activated zinc salt of
pentachlorothiophenol
(ENDOR*) 0.80 0.80 0.80
Mercaptobenzothiazole
(CAPTAX*) 1.46 1.46 1.46
Benzothiazyl-disulfide
(ALTAX*) .66 .66 .66
Zinc dimethyldithiocarbamate
(METHYL ZYMATE*) .025 .025 .025
Tetraethylthiuram disulfide `
(ETHYL TUADS*) .150 .150 .150
zinc oxide 5.00 5.00 5.00
Stearic acid 1.00 1.00 1.00
Petrolatum 2.00 2.00 2.00
Whiting 82.50 82.50 a2.50
Sulphur 2.00 2.00 2.00
For each formulation three measurements of Mooney
viscosity were made after 10 minutes of mixing and the values
were averaged. The average viscosity achieved with Compound B
was 26, while average viscosities of 8.5 and 9.5 were achieved
employing Compounds D and E, respectively.
It has been found that the thiodicarboxylic acid also
has an effect upon the accelerators employed in the rubber
compound, causing increased curing. Accordingly, the amount
of accelerator can be reduced by from about 10 to about 20 to : -
avoid the risk of over-curing.
*Denotes Trade Mark
-17-
,
4s8Q4
Example III
Employing procedures similar to those described in
Example I, eight crepe rubber compounds were prepared
employing Compounds B, D, E, E, G, H, I and J. The mixing
time and dump temperatures were recorded and the Mooney
viscosity and the radiograph dispersion rating for each of
the resulting rubber compounds were determined. The data
for these experiments are summarized as follows:
-18-
:~Q45804
o Lr U~ o U~ ~ ~ CO CO ~ ~, ~
~ ~ ~ er
o u~ Lf) o ~ ~ ~ oo 1- o
I~ ~
o U~ U~ o U~ ~ ~ CO o U~ U~
~D O
I o U~ o
Z
o In U~ O In a~ ~ a~
er O
o Ln Lr~ o U~
~1 1
. ~o ~ L~ o n ~ ~ oo CO o
~ o ~1 ~I LO N I I I I I ~ ~
O 1/~ 1~') 0 1)~ ~ ~ 00 ~ O Ot~ CO
~1 O
' ~'
z
~ ` ~ o ~ :
O ~ Ul N ` ` ` ` ` ` ` ` a) h t~
c~ ~ m ~ E~ C H 1~
U rl O O ~ ~ N ~ ~
O ~ Q ~ ~ ~ ~ O
'
-19- ~:~
-:
