POLYMERS BACKGROUND OF THE TNVENTTON This invention relates to novel chlorosulfonated ethylene alpha-olefϊn graft copolymers.

Chlorosulfonated ethylene alpha-olefm copolymers (chlorosulfonated linear low density polyethylenes) are elastomeric compositions which exhibit an outstanding combination of chemical resistance and outdoor weatherability. Such compositions are disclosed in U.S. Patents 2,879,261; 3,206,444; and 4,786,665. Physical properties are similar to those of chlorosulfonated polyethylene and, in certain respects, exceed those of the non-branched chlorosulfonated polyethylene homopolymer. Although the chlorosulfonated copolymers are useful in many applications, particularly those in which low temperature performance is necessary, it would be desirable to further improve the physical properties of these compositions to overcome certain deficiencies. For example, the oil resistance of polymers having chlorine contents in the range of 22-32 weight percent is inadequate for many automotive applications.

By chemically modifying chlorosulfonated ethylene/C4-Cjo alpha-olefϊn copolymer base resins by reaction with highly polar grafting agents, a new class of chlorosulfonated ethylene alpha-olefm copolymer compositions has been developed having properties useful in a broad range of applications, for example as general purpose elastomers, in adhesives, and in coatings. In addition, a class of particularly oil resistant compositions, having chlorine contents of 22-32 weight percent, has been identified which exhibit excellent dynamic properties and heat resistance. SUMMARY OF THE INVENTION More specifically, the present invention is directed to a novel class of chlorosulfonated ethylene alpha-olefin graft copolymers which comprises chlorosulfonated copolymers of ethylene and C4-C \ Q alpha-olefins having grafted thereon units selected from the group consisting of ethvlenicallv unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid anhydrides, copolymers of ethylene and

Cl-Cio alkyl esters of acrylic acid, and copolymers of ethylene and Cj-Cio alkyl esters of methacrylic acid, said chlorosulfonated copolymers having 0.5 to 6 weight percent sulfur, 20 to 55 weight percent chlorine, and from 0.2 to 25 weight percent of said grafted units. The invention is further directed to compositions of this class having chlorine contents of 22-32 weight percent. Such compositions have been found to exhibit an optimum combination of oil resistance and low temperature properties.

DETAILED DESCRIPTION OF THE INVENTION The chlorosulfonated ethylene alpha-olefm graft copolymer compositions of the present invention may be prepared by one of two methods. That is, an ethylene C4-C10 alpha-olefm base resin may be chlorosulfonated and subsequently grafted, or, alternatively, a graft- modified ethylene C4-C10 alpha-olefin base resin may be chlorosulfonated.

The ethylene alpha-olefm copolymer base resins are copolymers of ethylene and C4-C10 monoethylenically unsaturated alpha- olefins which have been prepared in the presence of transition metal catalysts. The expression ethylene alpha-olefin copolymer as used herein is understood to mean ethylene alpha-olefm dipolymers, terpolymers, and higher order copolymers. Examples of such copolymers include ethylene/ 1-butene copolymers, ethylene/4-methyl-l-pentene copolymers, ethylene/ 1-hexene copolymers, ethylene/ 1-octene copolymers, ethylene/ 1-decene copolymers, ethylene/ 1-butene/l-octene copolymers, ethylene/4-ethyl- 1 -hexene copolymers, ethylene/4-ethyl- 1 -octene copolymers, and ethylene/ 1-butene/l -hexene copolymers. Copolymers of ethylene with 1-butene, 1 -hexene, or 1 -octene are preferred because they are available on a commercial scale. The polymers generally contain about 3-12 weight percent of the C4-C10 alpha-olefin. Preferably the compositions contain 4-8 weight percent alpha-olefm.

Graft-modification of the ethylene alpha-olefm copolymer base resins is accomplished by free radical-initiated addition of ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid anhydrides, copolymers of ethylene and C J-C JO alkyl esters of acrylic acid, or copolymers of ethylene and C 1 -C \ 0 alkyl esters

of methacrylic acid. Bulk, solution, or suspension processes may be utilized. Bulk processes are characterized by reaction of the polymer and grafting agent in the presence of a free radical-generating compound at elevated temperatures, generally 150-180°C, in an extruder or mixer. In 5 solution processes, the polymer, grafting agent, and free radical generator are dissolved, generally in an organic solvent, and reaction takes place at temperatures around 100°C. An aqueous suspension process has also been disclosed for use under conditions wherein the grafting agents are not subject to hydrolysis. In that method the polymer, grafting agent, and l o free radical generator are contacted at temperatures of 60- 100°C, sometimes in the presence of a surfactant. The bulk process is most generally used on a commercial scale.

Examples of ethylenically unsaturated carboxylic acids and ethylenically unsaturated carboxylic acid anhydrides which may be used

15 as grafting agents include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, itaconic anhydride, maleic anhydride, and substituted maleic anhydrides, such as dimethylmaleic anhydride, 4-methylcyclohex-4-ene- 1 ,2-dicarboxylic anhydride, 2,3-dichloromaleic anhydride, and 2-carbomethoxymaleic

20 anhydride. Preferred acids and anhydrides each contain 4-6 carbon atoms. The most preferred carboxylic acids are maleic acid and fumaric acid, while maleic anhydride is the most preferred anhydride grafting agent.

Copolymers of ethylene and CJ-CJO alkyl esters of acrylic acid, and copolymers of ethylene and Cj-Ci o alkyl esters of methacrylic

25 acid are also effective grafting agents. Examples of such compositions include ethylene/methyl acrylate copolymers, ethylene/methyl methacrylate copolymers, ethylene/butyl acrylate/carbon monoxide copolymers, ethylene/methyl acrylate/carbon monoxide copolymers, ethylene/2-ethylhexyl acrylate copolymers, and ethylene/ethyl

30 methacrylate copolymers. Particularly preferred are ethylene/methyl acrylate/carbon monoxide copolymers, and ethyl ene/n-butyl acrylate/carbon monoxide copolymers.

The graft copolymer may contain from about 0.2 to 25 weight percent units of the grafting agent. Monomeric grafting agents,

35 such as maleic anhydride, maleic acid, or methacrylic acid, are preferably

used in quantities at the lower end of this range, generally in amounts below about 10 weight percent, preferably in amounts no greater than 4 weight percent, and, most preferably, in amounts of about 0.5 to 2 weight percent. If less than 0.2% is present, there is no appreciable modification of the properties of the base resin. It has been found that if greater than 2% is present certain of the graft polymers are scorchy because the grafted moieties interact with metal oxide curing agents. In contrast, when polymeric grafting agents are used, a greater weight percent grafting agent is generally used. Preferably at least 10 weight percent of a polymeric grafting agent is used. If greater than about 25 weight percent is used, an undesirable amount of chain branching occurs which adversely affects polymer hysteresis. Most preferably, 10-20 weight percent of the polymeric grafting agents are used because this provides optimum viscosity improvement. The graft-modified ethylene alpha-olefin copolymers are converted to the chlorosulfonated compositions of the present invention by reaction with a chlorosulfonating agent at temperatures of about 50-150°C, preferably 80-110°C, in a solvent substantially inert to chlorination. Examples of suitable solvents include carbon tetrachloride, chloroform, methylene chloride, trichlorofluoromethane, dibromofluoromethane, difluorotrichloroethane, tetrafluorotrichloropropane, 1 , 1 ,2-trichloroethane, pentafluorodichloropropane, monochlorobenzene, dichlorobenzene, fluorobenzene, and monochloromonofluorobenzene. In addition, the reaction is preferably run at pressures of 0.10-0.35 MPa. Typical chlorosulfonating agents include sulfuryl chloride, a mixture of chlorine and sulfuryl chloride, and a mixture of chlorine and sulfur dioxide. Sufficient chlorosulfonating agent is introduced to provide a chlorine level of 20-55 weight percent, preferably 22-32 weight percent, and a sulfur content of 0.5 to 6 weight percent, preferably 0.5-2 weight percent, in the product. Chlorosulfonation of base resins having a wide range of molecular weights is possible, for example from 10,000-200,000 weight average molecular weight. Those products which are of low molecular weight, i.e. those having molecular weights less than 20,000, are particularly suited for use in adhesive and coating applications, while

those of higher molecular weight, particularly those above 50,000, are more useful as general purpose elastomers.

The chlorosulfonation reaction is promoted by means of a free radical initiator such as an organic peroxide, an organic hydroperoxide, or an aliphatic azo compound. Typical initiators include 2, 2'-azobis(2-methylpropane nitrile), benzoyl peroxide, diisopropylbenzene hydroperoxide, and α, α'-azobis(α, γ- dimethylvaleronitrile). Generally the initiator is present in amounts of 0.1-3% by weight of polymer present. The chlorosulfonation reaction may be carried out as a batch or continuous operation.

The chlorosulfonated graft-modified polymers may also be prepared by the alternative method of chlorosulfonation of the ethylene alpha-olefin base resin with subsequent grafting of the chlorosulfonated product. In such cases, the chlorosulfonation proceeds as described above. Free radical initiated addition of grafting agent may occur following completion of the chlorosulfonation reaction in the same reactor or the grafting reaction may be a separate process performed subsequent to isolation of the chlorosulfonated product. A particularly useful class of polymers which falls within the scope of the present invention is that comprising chlorosulfonated ethylene alpha-olefin graft copolymers wherein the chlorine level is 20-35 percent by weight, preferably 22-32 percent by weight. These compositions exhibit unusually enhanced oil resistance in combination with excellent low temperature properties, particularly low temperature fracture resistance and resiliency. This combination of properties is a result of the presence of the pendant alkyl groups introduced by copolymerization of ethylene and higher alpha-olefins and a balance in the level of chlorine and highly polar graft units. The polymers are rubbery at low chlorine content due to the modification of crystallinity brought about by copolymerization. Preferred compositions contain 22-32 weight percent chlorine and 0.8-2.0 weight percent sulfur. In a further preferred embodiment, unsaturated anhydride and ethylene copolymers are both used as grafting agents to produce an especially oil resistant composition. These preferred compositions are particularly suited for use in automotive

power transmission belts wherein it is desirable to have a combination of good high and low temperature properties, as well as excellent oil resistance.

The broad class of chlorosulfonated graft-modified ethylene alpha-olefin compositions of the present invention are useful in applications such as automotive belts, hoses, and gaskets.

The following examples, wherein all parts are by weight unless otherwise indicated, illustrate certain embodiments of the present invention. EXAMPLES

TEST METHODS The following procedures were used to evaluate the compositions described in the examples:

Stress/Strain Properties ASTM D-412

Tensile Strength at Break, Tβ Elongation at Break, Eg Hardness, Shore A ASTM D-2240

Volume Swell ASTM D-471 Brittle Point @ -65°C ASTM D-746

Tan Delta was measured on molded cylindrical pellets 1/4 inch (0.64 cm) in diameter and 1/2 inches (1.27 cm) in height using an MTS 830 Elastomer Testar System test apparatus in the compression mode at a strain of 5.0%, amplitude ± of 2.5%, and a frequency of 20 hertz at ambient temperature (approximately 76± 3°F; 24±2°C).

Example 1

Four lbs. (1818g) of a maleic anhydride-grafted copolymer of ethylene and butene (melt flow index 1.98g/10 minutes, density 0.918g/cc, butene content 6.2 wt.% prior to grafting, and maleic anhydride content 0.8-1.0 wt.%) was dissolved in 70 lbs. (31.78kg) of carbon tetrachloride at 110°C and 0.27MPa in a 10 gallon (37.9 liter) reactor kettle fitted with an agitator and condenser. A 1% solution of an azo initiator, 2, 2'-azobis(isobutyronitrile) in chloroform was added continuously throughout the reaction cycle at a rate of 20cc/minute.

Chlorine gas was added at rate of 1 lb/hour (0.45kg/hr) for 12 minutes, followed by the addition of a mixture of chlorine and sulfuryl chloride. The rate of addition of the chlorine was 1 lb/hour (0.45kg/hour) and the rate of addition of sulfuryl chloride was 70cc/minute. Addition continued 5 until a total of 1.25 lbs. (0.57kg) chlorine and 1224cc of sulfuryl chloride had been added. The reaction temperature was reduced from 110°C to 84 °C during the addition of sulfuryl chloride through use of a combination of external cooling and evaporation and condensation of the solvent. The contents of the reaction vessel were then heated to 98°C and the pressure o was reduced to 0.10 MPa to remove residual gases. The product contained 30.0% Cl and 1.56% S. After stabilization with 1% epoxy resin, having an epoxy equivalent weight of 180, the product was isolated from the solvent by drum drying. The Mooney viscosity (ML 1+4 @ 100°C) of the isolated product was 94.3. A portion of the product was 5 compounded with the additives shown in Table I and cured at 150°C. Physical properties of the cured product are also shown in Table I.

Comparative Example 1

Example 1 was repeated in substantially the same manner, 0 using the same ratio of reactants, and the same reaction conditions except that in place of the maleic anhydride-grafted ethylene butene copolymer, an ungrafted copolymer of ethylene and butene having a density of 0.918g/cc was used. The product contained 29.7% Cl and 1.07% S. Mooney viscosity (ML 1+4 @ 100°C) was 63. The product was 5 compounded, cured, and tested under the same conditions as the composition of Example 1. Results are shown in Table I.

TABLE I

Formulation Example 1 Comparative Example 1

Polymer 100 100

N762 Carbon Black 35 35

Paraffin 2 2

PE617 A® Polyethylene 3 3

Magnesium Oxide 4 4

Pentaerythritol, 200 mesh 3 3

Sulfur 1 1

Dipentamethlyenethiuram 1 1 Hexasulfide

Mercaptobenzothiazole 1 1 Disulfide

M-Phenylene Bis Maleimide 1 1

Nickel Dibutyldithiocarbamate 3 3 Poly-Dispersion T(HRL)D 90® 12 12 Lead Oxide 1

Phvsical Properties of Samples ( Cured (a)153°C

Tensile Strength, MPa 22.3 17.6 Elongation at Break, % 142 241 Hardness, Shore A 76 73 Tan Delta (2) 20 Hertz 0.16 0.14

Volume Swell, 70 hours @ 121°C, ASTM #1 Oil

7.9 20 Brittle Point (2. -65°C Pass Pass

1. Blend of sublimed lead oxide (90%) in a binder of EPDM rubber and aromatic oil.

Example 2

Example 1 was repeated in substantially the same manner, using the same ratio of reactants, the same reaction conditions, and the same starting materials. The product had a chlorine content of 31.8% and

a sulfur content of 1.63%. After completion of the reaction, 20 percent (based on the weight of the final chlorosulfonated grafted product) of a copolymer of ethylene, methyl acrylate, and carbon monoxide (weight ratio 53/38/9) was added. The reaction mass was heated to 80°C and 26g of benzoyl peroxide dissolved in carbon tetrachloride was added over a period of 3 hours while maintaining a reaction temperature of 80°C. The product was isolated by drum drying. The Mooney viscosity (ML 1+4 @ 100°C) of the product was 114.6. Chlorine content was 25.4% and sulfur content was 1.3%. The product was compounded, cured, and tested under the same conditions as the Example 1 composition. Results are shown in Table II.

Example 3

Three pounds (1362g) of a copolymer of ethylene and octene-1 (melt index 5.95g/10 minutes; density 0.920; 10 wt.% octene-1) was dissolved in 40 lbs. (18.2kg) carbon tetrachloride at 105°C and 0.27MPa in the reaction vessel described in Example 1. A l% solution of an azo initiator, 2, 2'-azobis(isobutyronitrile) in chloroform, was added continuously at a rate of 20cc/minute. Chlorine gas was added at a rate of 1 pound/hour (0.45kg/hour) and sulfuryl chloride was added at a rate of 70cc/minute until a total of 1.28 lbs. (0.58kg) of chlorine and 615cc of sulfuryl chloride had been added. The reactor pressure was reduced to atmospheric pressure and stabilized. The chlorine content of the chlorosulfonated ethylene/octene copolymer product was 28.6% and the sulfur content was 1.22%. An amount of a copolymer of ethylene, methyl acrylate, and carbon monoxide (weight ratio 53/38/9) equivalent to 10% by weight of the chlorosulfonated grafted polymer produced was added to the reaction mass. The temperature of the reactor was set at 86°C and the reactor pressure was set at 0.27MPa. A solution of 20g benzoyl peroxide in carbon tetrachloride was added at a rate of 4cc/minute over the next two hours. During that time the reactor temperature was raised to 93 °C. After 3.5 hours, the grafted product was isolated by drum drying. The product had a chlorine content of 25.7%, a sulfur content of 1.1%, and a Mooney viscosity (ML1+4 @ 100°C) of 37.3. The product was compounded, cured, and tested under the conditions described in

Example 1. Results are shown in Table II.

Example 4

The reactor system described in Example 1 was charged with 4 lbs. (1.82kg) of a maleic anhydride- grafted ethylene/octene/butene copolymer (melt flow index 5.2g/10 minutes, density 0.918g/cc, maleic anhydride content 0.91%, weight ratio 90.6/4.7/4.7 before grafting) and 70 lbs. (31.8kg) of carbon tetrachloride. The reaction mixture was heated to 110°C and a reactor pressure of 0.3 IMPa. A 1% solution of 2, 2'- azobis(isobutyronitrile) in chloroform was added continuously at a rate of 2.3g/minute throughout the reaction. Chlorine gas was added at a rate of 1 lb ./hour (0.45kg/hour) and sulfuryl chloride was added at a rate of 70cc/minute until a total of 1.25 lbs. (0.57kg) of chlorine and 1224cc of sulfuryl chloride had been added. The reactor pressure was reduced to atmospheric pressure and the product was stabilized with 1% epoxy resin having an epoxy equivalent weight of 180. The product, isolated from the solvent by drum drying, had a chlorine content of 32.1 %, a sulfur content of 1.1 % and a Mooney viscosity (ML1 +4 @ 100 °C) of 97.1.

TABLE TT

Formulation Example 2 Example 3 Example 4

Polymer 100 100 100

N762 Carbon Black 35 35 35

Paraffin 2 2 2

PE 617A® Polyethylene 3 3 3

Magnesium Oxide 4 4 4

Pentaerythritol, 200 mesh 3 3 3

Sulfur 1 1 1

Dipentamethlyenethiuram 1 1 1 Hexasulfide

Mercaptobenzothiazole 1 1 1 Disulfide

Meta-Phenylene Bis 1 1 1 Maleimide

Nickel Dibutyldithio- 3 3 3 carbamate

Poly-Dispersion 12 12 12 T(HRL)D 90® Lead Oxide 1

Phvsical Properties of Samples Cured 30 Minutes (α).153°C

Tensile Strength, MPa 19.4 19.8 22.3

Elongation at Break, % 140 258 140

Hardness, Shore A 68 72 81

Tan Delta @ 20 Hertz 0.19 0.15 0.22

Volume Swell, 70 hrs. @ 4.2 14.4 5.8

121°C, ASTM #1 0il

Brittle Point (2> -65 °C Pass Pass Pass

1. Blend of sublimed lead oxide (90%) in a binder of EPDM rubber and aromatic oil.