CA1043927A - Low temperature plasticizer composition for natural and synthetic butadiene-styrene rubber - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A low temperature natural and butadiene-styrene rubber plasticizing composition is provided which is effect-ive at 60° to 100°C. and comprises 0,0'-dibenzamidodi-phenyldisulfide and not less than 0.6 parts of iron phthalo-cyanine per 100 parts of the 0,0'-dibenzamidodiphenyldisul-fide. In addition, a method for plasticizing natural and butadiene rubber is provided which comprises intimately in-corporating into said rubber, at a temperature of from about 60° to 100°C., an effective plasticizing amount of said plasticizing composition.

Description

~O'i3~'~7 Generally stated, the subject matter of the present invention relates to the process of peptizing (plasticizing) natural rubber and synthetic butadiene-styrene rubber and to a composition for the low temperature catalytic plasticiza`
tion thereof.
BACKGROUND OF THE INVENTION
Natural rubber and elastomers derived from conju-gated dienes, e.g., butadiene, can be plasticized by mechani-cal working in air or oxygen. The extent of plasticization depends on the temperature, length of time and extent of mechanical effort. This "working" of the elastomer, either on a standard rubber mill or Banbury mixer, can lead to deterioration of the elastomer, and in order to reduce the time, temperature and power required, a wide variety of chemi-cal peptizing agents (catalytic plasticizers) have become available to the rubber industry over the years. These in-clude aryl mercaptans and their divalent metal salts, and certain diaryl disulfides. Exemplary of both types of com-pounds are penta-chlorothiopheno1 and its zinc salt, O,O'--dibenzamidodiphenyldisulfide and zinc o-benzamidothiophenol, represented by the following structures designated I, IIand III: Cl ` Cl ~ Cl i ¦ 1 Cl ~ ~S~1(2 ) Cl , 3~

NH-C- ~
/ III

~S(2 ) - 5 The compounds represented by structures I and II
are effective at high temperatures, that is above about 100C., for example, 120 to 150C., while the compound repre- `; sented by structure III is effective at low temperatures, thatis 60 to 100C. However, one of the disadvantages of the ùse `~
of this compound is its high cost. Pikl in U.S. Patent

2,860,116 discloses the use of iron phthalocyanine, either as the sole peptizing agent or in combination with another known peptizing agent, such as those descri~ed above. The combina-tion described by Pikl are shown to be more effective at high temperatures, that is, at 135C., than similar compositions without iron phthalocyanine. Pentachlorothiophenol, Examples 6 and 7 of Pi~l, is not effective at temperatures of about 60 to 100C., nor is O,O'-dibenzamidodiphenyldisulfide. See Example 16 of Pikl. On the other hand, only a few compounds are available to effect low temperature, 60 to 100C., pepti-zing of natural rubber or butadiene-styrene rubber. One of the most effective of these is zinc O-benzamidothiophenol.
It is a primary object of this invention to provide a composition which is effective as a low temperature catalytic plasticizer for natural rubber and butadiene-styrene rubber.
It is another object of the invention to provide a method for the plasticization of natural rubber and butadiene--styrene rubber at low temperatures.
Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention, the objects and advantages being realized and attained by means of the c~ompositions, processes, and im-provements particularly pointe~d out in the appended claims.
THE INVENTION
To achieve the foregoing objects and in accordance with its purpose, this invention as embodied and broadly des-cribed, provides a low temperature natural and butadiene--styrene rubber plasticizing composition which is effective at 60 to 100C. and comprises O,O~-dibenzamidodiphenyldisulfide and not less than 0.6 parts of iron phthalocyanine per 100 parts of the O,O'-dibenzamidodiphenyl disulfide. In addition, a method for plasticizing natural and butadiene rubber is pro-vided which comprises inti:mately incorporating into said rub-ber, at a temperature of from about 60 to 100C., an effective plasticizing amount of said plasticizing composition.
Natural rubber as normally used is a very tough, "nervy" composition. It ordinarily has a Mooney viscosity at 100C. of about 110 to 120. Thus, before compounding the rub-ber with the various ingredients which comprise the vulcani-zate, the rubber must be "broken down" or plasticized to a Mooney viscosity in the range of about 40 to 50. This is ordinarily accomplished on a standard rubber mill or Banbury mixer at a temperature of about 120 to 150C. with the aid of a peptizing agent. This can be accomplished also with certain compounds, such as zlnc O-benzamidothiophenol, at 60 to 100C.
One of the major advantages of the present invention is that by using the composition of the present invention, the rubber may be plasticized wlth O,O'-dibenzamidodiphenyl-disulfide at a temperature from about 60C. to about 100C.
Up to now, this has not been feasible.
In preferred embodiments of the invention, the plas-.. . . .
.

llO~3~Z7 ticizing agents comprise mixtures of 0,0'-dibenzamidd~iphenyl-disulfide and iron phthalocyanine. Because of the high ac-tivity of the mixture, and to insure uniform distribution in the rubber, it is advantageous, and therefore preferable, to incorporate on inert diluent into the blend. The blends con-taining diluents are easily handled, free-flowing powders.
The preferred mixtures contain about 50 percent by weight of 0,0'-dibenzamidodiphenyldisulfide. The exact amount is not critical and may be 40 to 60 percent by weight.
In addition, about 48 t~ 49.9 percent by weight of an inert diluent is used, although this may also vary, so long as the composition contains an amount of iron phthalocyanine not less than about 0.6 part nor greater than about 2 parts per 100 parts of 0,0'-dibenzamidodiphenyldisulfide. The ratio is im-portant and applied equally to mixtures without clay.
If less than about 0.6 part of iron phthalocyanine per 100 parts 0,0'-dibenzamidodiphenyldisulfide are used, plasticization at 60 to 70C. is not effected. If greater than about 2 parts of iron phthalocyanine per 100 parts of the disulfide is used, the rubber becomes too soft or even approaching liquid properties at 60 to 70C. Of course, this effect becomes worse the higher the amount of iron phthalo-cyanine per 100 parts disu3fide over 2 parts.
In general, it should be pointed out that when de-fining the method of the present invention in terms of plasti-cization with O,0'-dibenzamidodiphenyldisulfide and from about 0.6 to 2 parts per 100 parts thereof of iron phthalocyanine, it is desirable in plasticizing rubber to use the least amount of plasticizer consistent with reducing the viscosity in the shortest time. Thus, ordinarily the plasticizer is used in an amount of from about 0.1 to 0.5 parts per hundred parts of rubber, preferably 0.2 to 0.5 part per hundred of rubber.

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~0~ 3'~7 Thus, it is seen that the desirable low tempera-ture properties of the compositions of the invention are obtained over a rather narrow ran~e of mixtures oE 0,0'-di-benzamidodiphenyldisulfide with from about 0.6 to 2 parts iron phthalocyanine per 100 parts of the disulfide.
0,0'-dibenzamidodiphenyldisulfide is a well-known, widely used chemical peptizing agent. See Compounding Ingredients for Rubber, 3rd Edition, 1961, published by Rubber World, N.Y., N.Y., page 239.
Iron phthalocyanine is another well-known sub-stance, prepared by any of the methods disclosed in the Pikl patentO Ibid.
As indicated, in the preferred embodiments the acti~e components, i.e., the iron phthalocyanine and the 0,0'-dibenzamidodiphenyldisulide, because o~
their very active peptizing effects, are blended with some inert material. Suitable inert materials include the various clays, diatomaceous earth, calcium carbonate, silicas or waxes. It is preferred to use a clay, such as a hydrated aluminum silicate, although other similar inert clays may also be used. Mixtures of inert solid diluents may also be used.
The following examples are provided for illustra-tive purposes and may include particular features of the invention. However, the examples should not be construed as limiting the invention, many variations of which are possible without departing from the spirit or scope thereof.
EXAMPLE I
PREPARATION OF PLASTICIZER MIXTURE
To a ribbon blender was charged:
0,0'-Dibenzamidodiphenyldisulfide1,100 lb Iron PhthalocyaninQ 11 lb Paragon Clay (hydrated aluminum silicate J.M. Huber Co.) 1,060 lb -' ` ' . ' 1". ' ' . .

The mixture was blended for one hour and analyzed:
O,O'-DibenzamidodiphenyLdisulfide 51.8~
Iron phthalocyanine 0.5%
Clay 47.8 EXAMPLE II
PLASTICIZING ACTIVI'rY OF CATALYST BLENDS
Following the procedure of Example I, plasticizer blends were prepared containing 50% by weight of O,O'-di-benzamidodiphenyldisulfide iron phthalocyanine in the amounts stated in the following table, the remainder being inert clay.
Natural rubber was plasticized on an open mill at both 70C.
and 100C. for 10 minutes, using two levels o~ concentration, 0.25 and 0.5 part per 100 parts of rubber. Mooney viscosity was measured at 212F after 4 minutes using the large rotor (ML-4), according to ASTM-D-1646. Mooney viscosity data are shown in the following table.
Mooney Viscosity(ML~`4), at 212F
FePcy., pts. per ` 100 parts of 70C. 100C.
Sample Plasticizer Blend _.25% 0.5% 0.25% 0 5%
20Zn o-benzamidothio-phenol - 35 35 37 34.5 o,o'-dibenzamidodiphenyl-; disulfide - 47.5 (47.5) 66 Plasticizer Blend* 0.1 40 37.5 51.5 36 1 .. 0.2 39.5 35.5 45.5 34 1l " 0.3 36.5 33.5 40 31 " " 0.4 37 31.5 37 29.5 " " 0.45 36.5 33 38.5 29.5 " " 0.5 36.5 30 35 26 * Contain 50% by weight of o,o'-dibenzamidodiphenyl-disulfide, 0.1 to 0.5% by weight of iron phthalo-cyanine and 49.9% to 49.5~ by weight of inert clay.
The data show that at low temperatures O,O'~-dibenz-amidodiphenyldisulfide containing from 0.6 to 1 part per 100 .

.. - - ~ , ~0 4 3~ $
parts thereof is as effective in plasticizin~ natural rubber as zinc o-benzamidoth.iophenol, a well Icnown and widely used low temperature plzsticizer.

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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for plasticizing natural and butadiene-styrene rubber which comprises intimately in-corporating into said rubber, at a temperature of from about 60° to below about 100°C., an effective plasticizing amount of a low temperature natural and butadiene-styrene rubber plasticizer composition which comprises 0,0'-di-benzamidodiphenyldisulfide and from 0.6 to 2 parts of iron phthalocyanine per 100 parts of the 0,0'-dibenzamidodiphenyl-disulfide.

2. The method according to Claim 1 wherein the plasticizing agent employed has an iron phthalocyanine concentration from 0.8 to 1.2 parts per 100 parts of 0,0'-dibenzamidodisulfide and said plasticizing agent is diluted with a solid, inert diluent.

3. The method according to Claim 2 wherein said solid, inert diluent is hydrated aluminum silicate.