GB2087898A

GB2087898A - Peptisers for rubber

Info

Publication number: GB2087898A
Application number: GB8131915A
Authority: GB
Original assignee: Technical Processing Inc
Current assignee: Technical Processing Inc
Priority date: 1980-11-21
Filing date: 1981-10-22
Publication date: 1982-06-03
Also published as: FR2494705A1

Abstract

Novel rubber processing compositions contain an effective amount of one or more poly(polysulfide) compounds of the formula A-(-Sn-R-)-mB wherein: n is from 1.5 to 4; m is from 3 to 200; R is a divalent aliphatic radical having from about 2 to 10 carbon atoms, wherein said radical may optionally include one or more ether linkages; and A and B are individually mercapto, mercaptoalkyl, mercaptoalkoxyalkyl, hydroxyalkyl, hydroxy or hydroxyalkoxyalkyl. Optionally a small proportion of the R radicals may be trivalent. The processing compositions may also contain sulfonamides, compounds with hydroxyether groups, waxes and hydrocarbons.

Description

SPECIFICATION Polymeric (polysulfide) rubber processing compositions 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 subjecting it to a preliminary step called mastication.

During mastication, the rubber is placed into a mixer, such as the Banbury, and is subjected to heat and optionally a peptizer, as for example, dixylyl disulfide, pentachlorophenyl disulfide or dibenzamido-diphenyldisulfide while being mixed for several minutes. The resulting mixture is then dumped, sheeted on a roll mill and cooled. The softened rubber is then mixed with the necessary ingredients.

Although somewhat effective in processing rubber, these conventional processes suffer from a number of inherent disadvantages. For example, the conventional peptizers cannot be mixed with the compounding ingredients during the mastication step, which results in a multi-step process. The need for a separate mastication step greatly increases the energy input, time and expense of the process, and also the complexity of the equipment required to carry out the process.

In addition, because of their relatively low disulfide content, the prior art peptizers are also often very inefficient. One result of the inefficiency is an increase in mixing times and mixing temperatures which in turn, results in inconsistent mixing results, a decrease in the capacity of the mixing equipment, and an increase in the danger of scorching the rubber during compounding. Another result is that the physical properties of the rubber, such as its flow, mixing and extruding characteristics are adversely affected.

When conventional peptizers react with the rubber, a resulting by-product is often a molecular weight mercaptan. This by-product adversely affects the physical properties of the rubber.

There is, therefore, a need for a processing composition, and a process for using such a composition which obviate the disadvantages associated with conventional rubber processing.

It is, accordingly, an object of this invention to provide a rubber processing composition and a process for using such a composition in processing rubber compositions which eliminate the need for a separate mastication step, thus allowing the mastication and mixing steps to be combined into one continuous operation.

It is yet another object of this invention to provide a composition and process for use in compounding natural and synthetic rubbers, which allow shorter mixing times, use less energy, lower mixing and dump temperatures, and provide for improved flow, improved physical properties, improved mixing and extruding characteristics and improved physical characteristics of the rubber.

It is also a further object of this invention to provide novel rubber processing compositions which facilitate the mixing of rubber compounds with natural and synthetic rubbers in relation to time requirements, arrangement of schedule for the addition of various compounding ingredients, and the possibility of uninterrupted working with the mixed compound because of lower, safer dump temperatures without adversely affecting physical properties of said rubber compounds. Other objects and advantages will be apparent from the following disclosure.

In accordance with this invention it has now been found that these and other objects are achieved through the use of a blending agent comprised of an aliphatic poly(disulfide) or poly(polysulfide) compound in an amount sufficient to break down natural or synthetic rubber.

Such compounds are often referred to as "polymeric aliphatic di-or polysulfides." An essential component of the processing composition of this invention is an aliphatic poly(disulfide) or poly(polysulfide) compound which provides a polymeric residue on reaction with the rubber, and in which the weight ratio of carbon to sulfur is in the range of from about 1.9 to 1 to about .19 to 1. Such compounds may be represented by the formula: A~(~Sn~R~)~mB wherein: n is from 1.5 to 4; m is from 3 to 200; R is divalent aliphatic radical having from about 2 to 10 carbon atoms and, optionally, one or more ether linkages, or a small proportion of R groups may be trivalent; A and B are individually mercapto, mercaptoalkyl, mercaptoalkoxyalkyl, hydroxy, hydroxyalkyl or hydroxyalkoxyalkyl.In a preferred embodiment of this invention, n is from 1.9 to 2.1 m is from 3 to 30 R is an alkylene moiety having from about 2 to 6 carbon atoms, as for example, ethylene, propylene, hexamethylene, 1, 1-dimethylethylene, and the like; or such an alkylene moiety having up to about 2 ether linkages, such as, ethyleneoxyethylene, ethyleneoxymethyleneoxyethylene, and the like; and A and B are individually mercapto or mercaptoalkoxyalkyl.

Illustrative of compounds within the scope of the aforementioned formula are poly(dithioethylene), poly(tetrathioethylene), poly(trithiohexamethylene), poly(oxyethylenedithioethylene), poly(oxymethyleneoxyethylenedithioethylene), and the like. Poly(polysulfide) compounds useful in the conduct of this invention can be obtained from commercial sources, or prepared in accordance with known preparative methods. For example, such compounds can be prepared in accordance with the preparative methods described in "Vanderbilt Rubber Handbook", R. T.

Vanderbilt Company, 1978 Edition at pages 201-8.

In addition to the essential component, the processing composition of this invention includes other optional ingredients to convert the polysulfide into a more convenient form such as a powder or paste, or to facilitate the introduction of the composition into the natural or synthetic rubber. One such ingredient may be finely divided absorbent mineral. The expression "absorbent mineral" as used in this disclosure, refers to any particulate inorganic mineral substance, to the outer surface of which the poly(polysulfide) composition can be absorbed. Illustrative of such substances are the natural and synthetic clays.

As is known, clay minerals are hydrous silicates of aluminum, iron or magnesium, and may contain other mineral particles. Typical natural clays which may be employed in accordance with this invention are the kaolinite, the montmorillonite, the illite, the clorite and attapulgite clays, including china clay, kaolin, ball clay, fire clay, flint clay, diaspore clay, mullute, bentonite, and the like. Synthetic silica and silicate clay materials, as well as diatomaceous earth may also be employed. For example, synthetic molecular sieves, such as 1 3A molecular sieves, may be employed if desired. The mesh size of the particulate absorbent mineral for use in accordance with this invention is not critical. Mesh size is generally in the range of 80 to 400 + mesh with a preferred size of 100 mesh or finer.

Other such materials include hydrocarbons, hydroxy ethers compounds with alcoholic and glycolic hydroxyl groups, sulfonamides, waxes and paraffins. Specifically, these additional materials may comprise: (a) From 0% to about 20% of sulfonamides selected from the group of N-alkyl derivatives of arylsulfonic acids; (b) From about 0% to about 20% of compounds selected from the group of alkylphenoxy ethers of ethylene glycols or polyglycols whrein the alkyl group contains from about 6 to about 1 2 carbon atoms, and the polyglycol grouping contains from about 2 to about 6 oxyethylene groups; (c) From about 0% to about 20% of waxes of animal or vegetable origin; and (d) From about 0% to about 20% of hydrocarbons selected from the group consisting of mineral oil and mineral waxes.

Illustrative of the sulfonamides referred to in (a) are N-ethyl-p-toluenesulfonamide, N methylbenzenesulfonamide, and N-butyl-2,4-xylenesulfonamide.

Typical hydroxyethers of (b) above which may be used in the compositions of this invention are octylphenoxyhexaethylene glycol, dodecylphenoxytriethylene glycol, nonylphenoxytetraethylene glycol, and nonylphenoxydiethylene glycol.

Among the waxes referred to in (c) above are carnauba wax, lanolin, and jojoba oil.

Illustrative of the hydrocarbons referred to in (d) are petrolatum, mineral oil, and paraffin wax.

It would be noted that compositions of this invention are not limited to 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 weight ratios of optional additives are not critical, and are dependent on such factors as, compatibility of individual additives, the desires of the formulator, the availability of individual additives, and other factors which are apparent to those of skill in the elastomer blending art.

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: (a) 100 percent to 25 percent of a poly(polysulfide) compound of the formula A~(~Sn~R~)~mSn~A; wherein A, R, n and m are as defined hereinabove; (b) 0 percent to 1 5 percent lanolin; (c) 0 percent to 1 5 percent tetraethyleneglycol monononylphenolether; (d) 0 percent to 1 5 percent petrolatum; (e) 0 percent to 65 percent of absorbent mineral.

The compositions of this invention are generally added to the rubber at the beginning of the mixing cycle. The usual additives, such a pigments, fillers, vulcanizing agents, etc., can then be added and the entire compounding performed in one operation.

The processing aid of this invention is employed in small, but effective amounts. It is generally added such that the amount of the poly(polysulfide) is in the range of about 0.2 percent to about 5 percent and preferably in the range of about 0.5 percent to about 1.5 percent, and the total weight of the composition (all components), is in the range of about 0.2 to about 10, preferably from about 0.5 to 3, all weight percents based on the total weight of the rubber material.

The processing aids of this invention can be employed in the compounding of any type of natural or synthetic rubber or mixtures thereof. Rubbers which can be used in conjunction with the breakdown agent of this invention include naturally occurring rubbers, styrene butadiene rubber, ethylene propylene rubber, butadiene rubber, butadiene-acrylonitrile rubber, epichlorohydrin rubber, acrylic rubber, neoprene rubber, chloroprene rubber, butyl rubber, block polymers of styrene and butadiene, and like synthetic and natural rubbers. The rubber may be virgin or reclaimed.

The following Examples are presented to more particularly describe the present invention and the advantages thereof.

EXAMPLE I The rubber compositions of Table I were prepared by mixing the various ingredients in an internal mixer in the conventional manner. The sulfur and accelerator of composition 2 could not be added in the mixer because of the high temperatures and were therefore added on a two-roll mill in a second step. After dumping, the compositions were cured in a 1 150 X 150 X 2.5 mm mold and various physical characteristics were evaluated.

TABLE I Ingredients Comp. #1 Comp. #2 #4 Ribbed Smoked Sheet 100.0 pts. 100.0 pts.

N- 1 1 0 Carbon Black 45.0 45.0 Pine Tar 4.5 4.5 Stearic Acid 4.5 4.5 Zinc Oxide 4.5 4.5 Disulfide Polymer" 1.62 N-Cyclohexyl2-benzothiozolesulfonamide 0.5 0.5 Sulfur 2.6 2.6 * The disulfide polymer has the approximate structure HS(C2H4OCH2OC2H4SS)5C2H4OCH2OC2H4SH in which a fractional number of units within the parenthesis are trivalent.

The data from these experiments are summarized in Table II as follows: TABLE II Composition and Results Property 1 2 Mixing time (minutes) 9 14 Stock Temperature at dump ("F) 255 315 Final amperage draw 43 68 Scorch at 320"F (minutes) 10 6 100% Cure at 320"F (minutes) 14 9 Viscosity (ML4 at 212 F) 54 70 Dispersion quality very good fair Single pass capability yes no Tensile strength (psi) 4300 4200 300% Modulus (psi) 2000 1980 Elongation (%) 580 530 Hardness (Shore A) 67 64 Tear Strength, Die C (psi) 215 210 As is apparent from the data set forth in Table II, the use of the composition of this invention permits faster mixing, requires less power, and breaks down the rubber to a much lower Mooney viscosity.The data also show that the physical properties of the cured stock are as good or better than those of the control in which the novel composition was not used.

EXAMPLE II The synthetic rubber compositions shown in Table Ill were prepared in an internal mixer. For composition 4, the sulfur and accelerator could not be added in the mixer because of the high temperature, and were therefore added on a two-roll mill in a second step. The compositions were cured and evaluated as in Example I.

TABLE 111 Ingredient Comp. #3 Comp. #4 Type 1500 SBR 100.0 100.0 N-100 Carbon Black 50.0 50.0 Zinc Oxide 2.5 2.5 Naphthenic Oil 10.0 10.0 Zine Laurate 1.5 1.5 Disulfide Polymer" 1.67 N-tert-Butyl2-benzothiozolesulfonamide 1 .25 1.25 Sulfur 1.75 1.75 same as in Example I The data from these experiments are summarized in Table IV as follows:: TABLE IV Composition and Results Property 3 4 Mixing time (minutes) 8 1 3 Stock temperature at dump ("F) 250 305 Final amperage draw 57 70 Scorch at 320"F (minutes) 6 5 100% Cure at 320"F (minutes) 11 12 Viscosity(ML4at212'F) 55 69 Dispersion quality very good fair Single pass capability yes no Tensile strength (psi) 3380 3390 300% Modulus (psi) 1 580 1600 Elongation (%) 540 550 Hardness (Shore A) 55 58 Tear strength, Die C (psi) 1 85 200 As is apparent from Table IV use of the composition of this invention provides for significant decreases in mixing times, and dump temperatures and provides other beneficial effects in compounding synthetic rubber.As is also apparent, these beneficial results are achieved without adversely affecting the physical characteristics of the rubber.

EXAMPLE 111 Various embodiments of this invention which included an absorbent mineral were prepared.

These compositions were employed for use in processing synthetic and natural rubbers. The resulting composition and the weight percent of the various ingredients are set forth in Table V.

TABLE V Compositions Ingredient A B C D E Non-reinforcing ground clay 37 53 53 53 53 Reinforcing ground clay 24.7 - - - - Disulfide polymer 23.3 42 42 42 42 Lanolin 5 5 - - Petrolatum - - 5 - N-Ethyltoluenesulfonamide 10 5 - 5 - Nonylphenoxytetraethylene glycol - - - - 5 * Same as in Example #l Five natural rubber compositions, 5, 6, 7, 8 and 9 were prepared using 1.62 parts of products A, B, C, D 8 E respectively, in the formulation of Example I, composition 1. Control composition 10 was also prepared as in Example I, composition 2. The mixing characteristics of these compositions are set forth in Table VI.

TABLE VI Natural Rubber Compositions and Results and Results Property 5 6 7 8 9 10 Mixing time (minutes) 9 8 11 11 10 14 Stock temperature at dump ("F) 245 235 250 255 250 315 Final Amperage draw 57 30 52 52 49 68 Viscosity(ML4at212'F) 50 48 63 60 60 70 Dispersion quality vg exc. vg vg vg fair Single pass capability yes yes yes yes yes no vg = very good; exc. = excellent EXAMPLE VI Employing procedures and formulations similar to those described in Example II five synthetic rubber compositions 11, 12, 13, 1 4 and 15, were prepared employing products A, B, C, D and E. One additional composition, control composition 16, was prepared employing the procedure of Example II, composition 4. The mixing characteristics of these compositions are summarized in Table VII.

TABLE VII Synthetic Rubber Compositions and Results Property 11 12 13 14 15 16 Mixing time (minutes) 9 8 11 9 8 1 3 Stock temperature at dump ("F) 245 238 250 250 250 305 Final Amperage draw 57 42 51 52 52 70 Viscosity (ML4 at 212 "F) 49 48 61 60 55 69 Dispersion quality vg exc. vg vg vg fair Single pass capability yes yes yes yes yes no vg = very good; exc. = excellent As is apparent from the foregoing, the novel compositions of this invention eliminate the need for a separate mastication operation, and require less energy to breakdown rubber and to intermix all ingredients. This invention also provides for improved mixing times, improved dispersion of additives and lower mixing temperatures when compounding rubber. In addition, the novel compositions of this invention allow the mastication and mixing steps to be combined into one continuous operation because mixing times are shorter and mixing temperatures are lower.

This invention has been described in terms of specific embodiments set forth in detail.

Alternative embodiments will be apparent to those skilled in the art in view of this disclosure, and accordingly, such modifications are within the spirit of the invention as disclosed and

Claims

claimed herein. CLAIMS

1. A poly(polysulfide) rubber processing composition comprising a polymeric compound of the formula: A-(-S,-R-)-,B wherein: n is from 1.5 to 4; m is from 3 to 200; R is a divalent aliphatic radical having from about 2 to 10 carbon atoms, wherein said radical may optionally include one or more ether linkages; and A and B are individually mercapto, mercaptoalkyl, mercaptoalkoxyalkyl, hydroxyalkyl, hydroxy, or hydroxyalkoxyalkyl.

2. A composition according to Claim 1 wherein a small proportion of said R radicals are trivalent.

3. A composition according to Claim 1 or 2 wherein: n is from about 1.9 to about 2.1; m is from about 3 to about 30; R is alkylene having from about 2 to about 6 carbon atoms, or said alkylene having up to 2 ether linkages; and A and B are individually mercaptoalkoxyalkyl.

4. A composition according to Claim 3 wherein R is selected from the group consisting of ethylene, propylene, hexamethylene, 1,1 -dimethylethylene, ethyleneoxyethylene, and ethyleneoxymethyleneoxyethylene.

5. A composition according to Claim 1 wherein said polymeric compound is selected from the group consisting of poly(dithioethylene), poly(tetrathioethylene), poly(trithiohexamethylene), poly(oxyethylened ith ioethylene) and poly(oxymethyleneoxyethylenedithioethylene).

6. A composition according to any one of Claims 1 to 5 to which is added additional materials including sulfonamides, compounds with hydroxyether groups, waxes and hydrocarbons.

7. A composition according to Claim 6 wherein these additional materials comprise: (a) From 0% to about 15% of one or more sulfonamides selected from the group consisting of N-alkyl derivatives of arylsulfonic acids; (b) From about 0% to about 15% of one or more hydroxyethers compound selected from the group consisting of alkylphenoxy ethers of ethylene glycols or polyglycols wherein the alkyl group contains from about 6 to about 1 2 carbon atoms, and the polyglycol grouping contains from about 2 to about 6 oxyethylene groups; (c) From about 0% to about 15% of one or more waxes selected from the group consisting of waxes of animal or vegetable origin; and (d) From about 0% to about 15% of one or more hydrocarbons selected from the group consisting of mineral oil and mineral waxes.

8. A composition according to Claim 7 wherein said sulfonamide is selected from the group consisting of Nethyl-p-toluenesulfonamide, N-methylbenzenesulfonamide, and N-butyl-2,4-xylenesulfonamide.

9. A composition according to Claim 7 or 8 wherein said hydroxyether is selected from the group consisting of octylphenoxyhexaethylene glycol, dodecylphenoxytriethylene glycol, nonylphenoxytetraethylene glycol and nonyephenoxydiethylene glycol.

10. A composition according to Claim 7, 8 or 9 wherein said waxes are selected from the group consisting of carnauba wax, lanolin and jojoba oil.

11. A composition according to Claim 7, 8, 9 or 10 wherein said hydrocarbons are selected from the group consisting of petrolatum, mineral oil and paraffin wax.

1 2. An improved rubber processing composition comprising a particulate absorbent mineral, and absorbed on the surface thereof, a rubber processing composition according to any one of Claims 1 to 11.

1 3. An improved rubber composition comprising a natural or synthetic rubber base and rubber additives, and a small but effective amount of a composition according to any one of Claims 1 to 12.

1 4. A Composition according to Claim 1 3 wherein the amount of polymeric compound present is from about 0.2 percent to about 5 percent, preferably from about 0.5 percent to about

1.5 percent, of the total weight of the composition.

1 5. A composition according to Claim 1 3 or 14 wherein the amount of said rubber processing composition is from about 0.2 to 3 weight percent based on the total weight of the composition.

16. An improved method for compounding rubber comprising admixing rubber with additives of the class consisting of pigments, fillers and vulcanizing agents, wherein the improvement comprises admixing a small but effective amount of a composition according to any one of Claims 1 to 1 2 with rubber at the beginning of the mixing cycle prior to mastication of the rubber.

1 7. A method according to Claim 1 6 wherein the amount of polymeric compound added is from about 0.2 percent to about 5 percent, preferably from about 0.5 percent to about 1.5 percent, of the total weight of the rubber mix.

1 8. A method according to Claim 1 6 or 1 7 wherein the amount of said rubber processing composition is from about 0.2 percent to about 3 percent of the total weight of the rubber mix.