ENHANCED TOUGHENING AND IMPROVED PROCESSABILITY OF POLYOLEFINS AND POLYOLEFIN COPOLYMERS WITH LOW MOLECULAR WEIGHT ADDITIVES

Abstract: In one embodiment of the present invention, there is provided a composition comprising a major amount of the polyolefin or polyolefin copolymer and a minor amount of a low molecular weight ionomeric polymer and anionic surfactant.

Description: ENHANCED TOUGHENING AND IMPROVED PROCESSABILITY OF POLYOLEFINS AND POLYOLEFIN COPOLYMERS WITH LOW MOLECULAR WEIGHT ADDITIVES FIELD OF THE INVENTION The present invention relates to polyolefin and polyolefin copolymer compositions. More particularly, the present invention is concemed with enhancing the toughness and processability of polyolefin polymers and copolymers that have been prepared using single-site catalysts. BACKGROUND OF THE INVENTION In recent years, a new class of polyolefin and polyolefin copolymers has been developed based on use ofthe so-called single site catalysts. These catalysts, which are organo-metallic coordination compounds of cyclopentadienyl derivatives of Group IVB metals ofthe Periodic Table of the Elements (56th Ed. ofthe Handbook of Chemistry and Physics, CRC Press (1975)), produce polyolefins that possess a more narrow molecular weight distribution than can be achieved with conventional Ziegler-Natta type catalysts. This narrow molecular weight distribution results in polymer materials that have better physical properties than that achieved with typical Ziegler-Natta type catalysts. Notwithstanding these improved physical properties, however, there still remains a need to further toughen polymers prepared from single site catalysts. Additionally, because ofthe narrow molecular weight distribution of these materials, they tend to be more difficult to process. Consequently, there also is a need to provide a method for enhancing the processability of polyolefins and polyolefin copolymers prepared with single site catalysts. SUMMARY OF THE INVENTION The present invention is based on the discovery that copolymers that are prepared in the presence of a single site catalyst have their toughness and processability enhanced by including in the polymer or copolymer an effective amount of a low molecular weight ionomeric copolymer and anionic sufactant. Thus, in one embodiment ofthe present invention, there is provided a composition comprising a major amount of the polyolefin copolymer and a minor amount of a low molecular weight ionomeric polymer and anionic surfactant. These and other embodiments of the present invention will become apparent upon reading of the Detail Description of the Invention which follows. DETAILED DESCRIPTION OF THE INVENTION The polymers useful in the present invention include polyolefins and polyolefin copolymers such as ethylene alpha olefin copolymers that have been prepared using single site catalysts, especially those catalysts described in U.S. Patent 5,391,629 which is incorporated herein by reference. Typically, the polymers and copolymers useful in the present invention will have weight average molecular weights of between about 30,000 to about 1 million and preferably between about 50,000 to about 200,000. The compositions of the present invention will also include a minor amount of a low molecular weight ionomeric polymer or copolymer, that is, one having a weight average molecular weight of between about 1,000 to 20,000 and most preferably between 2,000 to 10,000. In general the ionomeric polymer will have from about 0.1 to about 200 milli-equivalents of pendant ionomeric groups per 100 grams of polymer and preferably from about 1.0 to 100 milli-equivalents of pendant ionomeric groups. Examples of useful ionomeric groups are carboxylate, phosphate, and sulfonate. Preferably the ionomeric groups will also be about 50% neutralized with Group IA, IIA, IB or IIB metal (see the previously cited Table of Elements), an amine or ammonia. The amount of ionomeric polymer or copolymer will be used in amounts ranging below about 20 weight % based on the total weight ofthe composition and typically in the range of about 0.5 to about 10.0 wt%. Ionomeric polymers and copolymers especially suitable in the practice ofthe present invention include ethylene-methacrylic acid copolymers, sulfonated polystyrene, sulfonated t-butyl styrene, sulfonated ethylene copolymers, sulfonated propylene copolymers, sulfonated styrene-acrylonitrile copolymers, sulfonated styrene-methyl methacrylate copolymers, sulfonated polyisobutylene, sulfonated ethylene-propylene terpolymers, sulfonated polyisoprene, and sulfonated elastomers and their copolymers. The anionic surfactant used in the compositions ofthe present invention include alkali metal salts of alkyl sulfonates and carboxylates having from about 6 to 20 carbon atoms and alkaline metal salts of alkenyl sulfates having from about 6 to about 20 carbon atoms in the alkenyl group. The anionic surfactant will be used in a minor amount in the composition ofthe present invention. Typically it will constitute about 1 wt. % based on the total weight ofthe composition and preferably in the range of about 0.1 to about 10.0 wt.%. The compositions ofthe present invention can be prepared by any convenient method. For example, the compositions can be prepared by mixing in a suitable blender such as a Brabender mixer. EXAMPLES The following examples will demonstrate the improved toughness and enhanced processability of polyolefin compositions ofthe present invention. In all ofthe examples which follow the base polymer or copolymer was prepared using a single site catalyst. The compositions were melt processed in a Brabender mixer heated at 193°C. The materials were mixed for five minutes at 100 RPM. After mixing the material was cooled to room temperature, cut into pieces and compression molded at 193°C into tensile specimens. The specimens were compression molded into approximately 2" x 2" x 0.02" pads at 29 tons pressure. The appropriate size sample for the tensile testing measurements were cut from these pads. The mechanical properties were obtained from an Instron® Tensile Tester with a clamp speed of 0.2 crn/min. The ionomers used in the examples were metal neutralized, ethylene methacrylic acid polymers having a weight average molecular weight of2,000g/mole. The surfactant used was a sodium neutralized alpha olefin sulfonate having a carbon number of about 12 with a head group composed of a sodium neutralized sulfonate group. The torque reduction is measured directly on the Brabender melt mixer. The reduction in torque is based on comparing the torque value ofthe additive-containing melt with one containing no additives. Example 1 An ethylene-butene copolymer prepared using a single site catalyst and having a density of 0.873g/cc and a melt index of 4.5 was melt blended with varying amounts ofthe ionic surfactant and the low molecular weight ionomeric material in which the metal was zinc. Tensile properties ofthe various blends and the reduction in torque were obtained and are listed in Table I which follows. Also included in Table I are results obtained without the addition of surfactant and ionomer. The data confirms that the addition of the combination of surfactant and lower molecular copolymer ionomer to the elastomeric ethylene copolymer product reduces the torque, i.e., improves processability. In addition, the solid state properties show an overall enhancement in the mechanical properties. Example 2 Table 2 lists the mechanical properties of an ethylene-butene copolymer (See Example 1) that was melt blended, as detailed in Example 1, with a 0.5 wt.%of the alpha olefin sulfonate surfactant and varying amounts of a low molecular weight ionomer which was sodium neutralized. The tensile strength ofthe mixtures are included in the tables as well as the energy to break and the torque reduction (100 RPM). The results are compared to a run without the addition ofthe surfactant. The results again confirm the utility ofthe mixture ofthe low molecular ionomer copolymer and surfactant to markedly improve the mechanical properties and the processability. Example 3 In this Example, various runs were conducted using a linear low density polyethylene possessing a crystallinity in the range of 40 to 50% and the zinc neutralized ionomer. The procedure used is described in Example 1 and the results are given in Table 3 which follows. Example 4 Again a series of runs were conducted using a linear low density polyethylene of Example 3 and following the procedure outlined in Example 1; however in this instance the sodium salt of the ionomeric copolymer was employed. Results are set forth in Table 4 which follows. TABLE 1 MECHANICAL PROPERTIES AND TORQUE REDUCTION MEASUREMENTS Surfactant, (%) Ionomer, (%) Modulus (psi) Tensile Strength Elongation at Energy to Break Torque (psi) Break(%) (In.Lbs.) Reduction(%) 0.0 0.0 301.0 1905.0 1059.0 12.7 0.0 0.5 0.25 419.0 1932.0 1 196.0 23.0 12.0 0.5 0.5 434.0 1962.0 1208.0 23.8 17.0 0.5 1.0 500.0 2015.0 1224.0 24.1 15.0 0.5 3.0 542.0 2037.0 1257.0 28.6 13.0 0.0 0.0 301.0 1905.0 1059.0 12.7 0.0 0.0 1.0 701.0 1776.0 1099.0 18.0 14.0 0.0 3.0 918.0 1728.0 1099.0 17.9 17.0 0.0 5.0 1078.0 1677.0 1069.0 15.8 1 16.0 TABLE 2 MECHANICAL PROPERTIES AND TORQUE REDUCTION MEASUREMENTS TABLE 3 MECHANICAL PROPERTIES AND TORQUE REDUCTION PERFORMANCE Surfactant, (%) Ionomer (%) Modulus (psi) Tensile Strength Elongation at Energy to Break Torque (psi) Break(%) (In.Lbs.) Reduction(%) 0.0 0.0 35108.0 3834.0 693.0 25.3 0.0 0.5 0.25 34421.0 4177.0 784.0 39.8 20.0 0.5 0.5 35427.0 5182.0 887.0 47.9 20.0 0.5 1.0 32438.0 4842.0 862.0 42.7 20.0 0.5 3.0 33701.0 7443.0 849.0 40.9 21.0 0.0 0.0 35108.0 3834.0 693.0 25.3 0.0 0.0 1.0 32594.0 4478.0 783.0 38.4 10.0 0.0 3.0 34046.0 3943.0 721.0 33.3 14.0 0.0 5.0 33366.0 4497.0 821.0 38.7 14.0 TABLE 4 MECHANICAL PROPERTIES AND TORQUE REDUCTION PERFORMANCE Surfactant ,(%) Ionomer,(%) Modulus (psi) Tensile Strength Elongation at Energy to Break Torque (psi) Break(%) (In.Lbs.) Reduction(%) 0.0 0.0 35108.0 3834.0 693.0 25.3 0.0 0.5 0.25 33461.0 4567.0 824.0 41.8 19.0 0.5 0.5 33521.0 4898.0 892.0 48.8 19.0 0.5 1.0 34304.0 4994.0 897.0 46.4 15.0 0.5 3.0 33934.0 4718.0 869.0 46.0 19.0 0.0 0.0 35108.0 3834.0 693.0 25.3 0.0 0.0 1.0 33947.0 4599.0 816.0 39.8 17.0 0.0 3.0 33069.0 4540.0 838.0 42.2 14.0 0.0 5.0 33351.0 4564.0 838.0 41.8 15.0

Claims: CLA S: 1. A composition comprising: (a) a major amount of a first polyolefin or polyolefin copolymer prepared using a single site catalyst of a cyclopentadienyl derivative of a Group IVB metal and having a weight average molecular weight of between about 30,000 to about 1 million; and (b) a minor amount of (i) a second polymer having a weight average molecular weight in the range of about 1,000 to about 20,000, and from about 0.1 to about 200 multi-equivalents of pendant ionomeric groups per 100 grams of polymer, the ionomeric groups being selected from the group consisting of carboxylate, phosphate and sulfonate groups wliich are about 50% metal, amine or ammonia neutralized and, (ii) an anionic surfactant. 2 The composition of claim 1 wherein the second polymer is present in an amount t rraannggiinngg from about 0.5 to about 20 wt.%, based on the total weight ofthe composition 3. The composition of claim 2 wherein the anionic surfactant is selected from alkali metal salts of alkyl sulfonates and carboxylates of from about 6 to about 20 carbon atoms, alkali metal salts of alkenyl sulfates of from about 6 to about 20 carbon atoms and mixtures thereof. 4. The composition of claim 3 wherein the surfactant is present in an amount ranging from about 0.1 to about 10 wt.% based on the total weight of the composition. 5. The composition of claim 4 wherein the second polymer is about 50% neutralized with a metal. 6. The composition of claim 5 wherein the metal is zinc. 7. The composition of claim 5 wherein the metal is sodium.

Inventors: CHLUDZINSKI JAMES JOSEPH, ERDERLY THOMAS CRAIG, LUE CHING-TAI, PEIFFER DENNIS GEORGE, CHLUDZINSKI, JAMES, JOSEPH, ERDERLY, THOMAS, CRAIG, LUE, CHING-TAI, PEIFFER, DENNIS, GEORGE
Applicants: EXXON RESEARCH ENGINEERING CO, EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1996
Main classification: C08L23
IPC codes: C08L23