Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
  • C08L23/14—Copolymers of propene
  • C08L23/142—Copolymers of propene at least partially crystalline copolymers of propene with other olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/06—Polyethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
  • C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/16—Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend

Definitions

• thermoplastic olefins which display quasi-single phase behavior.
• this invention relates to thermoplastic olefins comprising a blend of propylene based random copolymer, ethylene propylene rubber and polyethylene.
• Polypropylene exhibits several advantageous properties, for example, relatively low density excellent resistance to higher temperatures and aqueous and non-aqueous liquids. Polypropylene also has the less favorable characteristic of inadequate impact strength at temperatures below room temperature especially below O ⁇ C. Adequate impact strength, however, is required and is of importance in many uses such as for example freight containers, suitcases, automobile parts and similar parts. Articles made of high density polyethylene possess this satisfactorily high impact strength but show a lower resistance to deformation at high temperatures. Ethylene propylene elastomers, saturated as well as unsaturated, exhibit good mechanical properties such as high heat ageing resistance, high ozone resistance and impact resistance at low temperatures, such that the copolymers are also excellently suited for use where the product is exposed to weathering.
• Blends of polyethylene with EPDM terpolymers of ethylene, propylene and nonconjugated diene are known from US Patent No. 3,919,358 and exhibit high tear strengths. The blends do not show sufficient heat resistance due to the low melting temperature polyethylene.
• Ternary molding compositions are also described in British patent No. 1,154,447. These crystalline polypropylene, polyethylene and ethylene propylene block copolymer ternary blends exhibit a tensile strength of only 10 N/mm 2 and are not flexible at temperatures below 30°C.
• Various polyolefin ternary blends have still been used in many industrial applications because of the balance achieved among several properties, for example, between rigidity and impact resistance.
• thermoplastic elastomers TPE's
• TPE thermoplastic elastomers
• a thermoplastic olefin (TPO) is a subset of TPE's.
• a TPO is a blended product of a hard segment of semi-crystalline polypropylene or semi-crystalline polyethylene and a soft segment of an olefin elastomer such as ethylene propylene rubber (EPR) , ethylene/propylene/diene terpolymer (EPDM) , polyisobutylene or pclybutadiene.
• EPR ethylene propylene rubber
• EPDM ethylene/propylene/diene terpolymer
• the TPO may also be subject to partial cross-linking in order to improve physical properties.
• this invention further relates to a blend of propylene based random copolymer (RCP) containing up to 20 weight percent ⁇ -olefin, particularly ethylene , high density polyethylene (HDPE) and ethylene/ ⁇ -olefin rubber (ER) .
• RCP propylene based random copolymer
• the random copolymer is present in the blend from 25 to 45 weight percent
• the ER is present from 20 to 40 weight percent
• the HDPE is present from 25 to 35 weight percent.
• the high density polyethylene used in this invention has a density in the range of 0.94 g/cnr and above.
• An hdpe with an MFR of around 5 can also be used in this invention.
• compositions of this invention can be formed into molded articles.
• examples include, but are not limited to: automobile bodyparts, bumpers, facia, interior trim, exterior trim, weather trim, hoses, exterior parts, wheel arches, air dams, trash cans, bottles, storage containers and the like.
• Figure 1 is the notched Izod strength at -29°C vs 2° Secant modulus.
• Figure 2 is the Gardner impact strength at -29°C vs 2° Secant modulus.
• This invention relates to a composition of propylene based random copolymer (RCP) , polyethylene (PE) and ethylene/ ⁇ -olefin rubber (ER) .
• RCP propylene based random copolymer
• PE polyethylene
• ER ethylene/ ⁇ -olefin rubber
• composition of this invention is 25 to 45 weight percent random copolymer,preferably 25 to 35; 20 to 40 weight percent ethylene/ ⁇ -olefin copolymer, preferably 30 to 40; and 25 to 45 weight percent high density polyethylene, preferably 25 to 35, based upon the total weight of the RCP, ER and PE.
• the random copolymer useful in this invention is a propylene based copolymer produced by methods well known in the art that can contain up to 20 mole percent of a C2 to C2 0 ⁇ -olefin.
• the ⁇ -olefin include but are not limited to, ethylene, propylene, butene, hexene, pentene, octene-1 and 4-methylpentene- 1.
• the preferred ⁇ -olefin is ethylene.
• These ⁇ -olefin comonomers are present preferably at 0.1 to 10 mole percent, more preferably 3 to 7.5 mole percent.
• the polyethylene useful in this invention is a high density polyethylene with a density of 0.940 g/cm 3 or above measured according to ASTM D1505 with an ethylene content of 95 to 100%.
• Such HDPE is available commercially from Exxon Chemical Company under the trade name ESCORENE.
• polyethylene of greater than 0.940 -> , . . . g/cm is regarded as being high density polyethylene
• HDPE high density polyethylene
• LDPE low density polyethylene
• VLDPE Very low density polyethylene
• Ultra low density polyethylene typically has a density from 0.865 to about 0.900 g/cm 3
• the ethylene rubber useful in the invention is a substantially non-crystalline ethylene/
• C3 to CIO ⁇ -olefin copolymer or non-crystalline ethylene/C3 to C10 ⁇ -olefin/ nonconjugated diene terpolymer examples of the ⁇ -olefin include propylene butene-1, pentene-1, 4-methylpentene-l, hexene-1, octene-1, with propylene being particularly preferred.
• the ethylene propylene rubber useful in this invention is avaiable from Exxon Chemical under trade name Vistalon 719 and is characterized by having an MFR of less than 1 and ethylene content of approximately 77 wt.%.
• Non-elastomeric ethylene/ ⁇ -olefin copolymer is distinguished from an ethylene/ ⁇ -olefin rubbers in that even if both are at the same point of the constituent monomers and density, the maximum peak temperature melting (TM) is much higher in the ethylene/alpha- olefin rubber. If the ethylene ⁇ -olefin rubber has a maximum peak melting temperature, it is typically in the range of 30 to 50°C at most.
• ethylene ⁇ - olefin rubbers typically contain very small amounts of hexane insolubles or do not contain hexane insolubles at all.
• the two copolymers also greatly different in preparation.
• the ethylene/ ⁇ -olefin copolymer is typically prepared using a catalyst which contains magnesium and titanium while an ethylene ⁇ -olefin rubber is usually prepared using vanadium catalyst.
• the compositions of the present invention are excellent in low temperature impact resistance and appearance, among other properties. When inorganic filler is added to the composition the properties obtained, especially when vehicle exterior members are produced, are much improved not only as scratch resistance, but also in thermal resistance, paintability and rigidity.
• the blends of this invention may also have fillers and additives blended into the composition to enhance their properties for their ultimate use.
• Inorganic fillers which may be blended in applicant's invention are exemplified by powdery or granular fillers such as calcium carbonate, calcium hydroxide, calcium sulfate.
• preferable ones are calcium carbonate, calcium silicate, magnesium hydroxide, clay, talc, silica, carbon black, mica, glass flakes, glass fiber, carbon fiber, graphite fiber and whisker and more preferable ones are calcium carbonate, talc and mica.
• the addition quantities of these fillers is up to 100 parts by weight to 100 parts of the composition of the present invention. When the addition quantity of filler exceeds 100 parts by weight it not desirable because the impact resistance of the formed product can be lowered.
• the fillers are surface treated with a fatty acid such as steric acid, oleic acid, palmitic acid, metal salts, paraffin wax, polyethylene wax or modified products or organic silane, organic borane or organic titanate.
• a fatty acid such as steric acid, oleic acid, palmitic acid, metal salts, paraffin wax, polyethylene wax or modified products or organic silane, organic borane or organic titanate.
• composition of the present invention can also include other components such as, but not limited to, thermoplastic resins; antioxidants; thermal stabilizers, (hindered phenols, phosphites, hydroquinones and thioethers) ; UV absorbers,
• the blends of this invention can be produced in a two step process. Master batches of the random copolymer and the ethylene alpha-olefin rubber are prepared under high shear to produce an intimate blend of small ER particles in a matrix of random copolymer.
• the dry blend is then extruded and pelletized.
• a Werner and Pfleiderer 50 mm twin screw extruder under conditions of minimum breakdown is adequate for this purpose.
• the RCP/ER master batch pellets are then barrel tumbled with the PE pellets to produce a dry blend that is then extruded and pelletized.
• a 60 mm Reifenhauser single screw extruder is adequate for this purpose.
• the pellets produced in the second step comprise the thermoplastic olefins of this invention.
• thermoplastic olefins All the components of thermoplastic olefins embodied in the examples are commercial materials available from Exxon Chemical Company. The key characteristic of these materials are listed below in the following table I.
• Sample morphology was determined by scanning electron microscopy (SEM) .
• Small blocks of the thermoplastic olefin of the invention measuring 2 mm by 2 mm by 1 mm were cut from Izod test pieces, 25 mm from end, 3 mm from the edge and 1 mm from the surface.
• One face of the block, parallel with the machine direction was cryomicrotomed with a fresh glass knife at -130°C to give a microscopically smooth surface.
• the microtomed surface was etched with xylene at room temperature for 20 minutes in an ultrasonic bath to dissolve the exposed EPR regions. Samples were degassed under vacuum for 2 hours then vacuum coated with gold for 1 minute, to lay down a coating " 100 angstroms thick. Scanning electron micrographs were recorded on an Amray 1200 SEM.
• the regions that previously contained ethylene alpha-olefin rubber can be seen as holes.
• the high density polyethylene particles are encapsulated by a skin of ER to form a "core/shell" (CS) structure surrounded by a matrix of random copolymer
• CS core/shell
• one of two things can happen when the ethylene propylene rubber is dissolved, the HDPE core can fall out of the hole upon removal of the ER, or the HDPE can remain trapped either by an opening too small to allow its egress or by connections to RCP matrix.
• the morphology can take on a fibrous (F) appearance.
• thermoplastic olefins for use in the automotive industry, it is important to understand the relationship between their morphology and properties, the key variables that control morphology should be identified.
• Thermoplastic polyolefins exhibit physical properties in a range that makes them useful in a wide variety of applications where toughness resiliency and moderate flexural modulus are desirable.
• the scanning electron microscope reveals a spectrum of morphologies of TPO blends. At one extreme the blend with the highest concentration of random copolymer has a particulate morphology. 80% random copolymer has particulate morphology with elongated core/shell domains of HDPE and EPR surrounded by a matrix of random copolymer, the other extreme is exemplified by the blends containing higher levels of EPR, such as 40% EPR, where quasi-single phase is oserved. Quasi-single phase is defined to mean no distinct boundaries are observed. Texturing of the samples indicates that an insoluble matrix of ER and HDPE surrounds poorly defined highly elongated domains of RCP. Between the two extremes various levels of texturing and elongation of domains are displayed. Quasi-phase morphology has been found to convey an excellent balance of impact resistance combined with flexural modulus.
• thermoplastic olefin Two important properties of the thermoplastic olefin relevant to their use as external automotive parts are impact resistance, especially at low temperatures, and elastic modulus. Obviously parts such as bumpers and bumper covers must be reasonably elastic to recover from blows and must not shatter even at sub zero temperatures. In general, there is an inverse relationship between flexural modulus and low temperature impact resistance, one falls as the other rises. Conventionally a greater concentration of EPR dispersed in a matrix of polypropylene, will show better impact resistance, but will also show a lower modulus.
• Modulus is readily measured by a number of techniques, one of the most reliable being the 2 secant modulus measurement of flexural modulus. In this test a standard sample is deformed 2° from linearity, the force required being proportional to the modulus. Low temperature impact resistance is more difficult to evaluate. Two methods are commonly used the notched Izod test wherein a bar with a notch cut is struck with a pendulum, the energy absorbed when the sample breaks gives a measure of the impact resistance. In this test specimens that are highly impact resistant often do not break and no numerical value is available. In the accompanying figures specimens that did not break are arbitrarily assigned a value of 3 ft lb/in. The other test is the Gardner test wherein a falling weight strikes a disk supported on an annulus. Here there is a maximum value of approximately 250 to 300 in/lb which many samples reach.
• the two figures show impact resistance measured by the two methods as a function of flexural modulus. Samples have been keyed to the morphology. In both figures it can be seen that for a given impact strength, the samples with quasi single phase morphology have higher modulus. Similarly at a given modulus level, samples with quasi-single phase morphology show superior low temperature impact resistance to the other morphologies.
• Tables 1 and 2 report the testing data for the above samples.
• VLDPE low density polyethylene
• example 16 using high density polyethylene is of a fibrous morphology.
• PS1 (g/IOinin) (PS1) (%) (PSI) (PS1) (FTLB/IN)(FTLB/IN) (IN/LB) (g/cm 3 ) (°C) (°)
• Injection molded model TPOs exhibit three main morphologies which are directly rated to their mechanical properties. Fibrous morphology generally have good low temperature impact resistance, but poor modulus. Particulate morphologies exhibit good modulus, but poor impact resistance. The quasi- single phase morphology exhibits good low temperature impact resistance and respectable modulus values. The morphology is controlled by the composition and molding conditions of the samples.
• the fibrous morphology has a brittleness temperature of less than -57°C, a Gardner impact strength of greater than 250 ft/lb/in and 2"Secant modulus of less than 27,000 psi.
• Samples with a particulate morphology have brittleness temperatures of -42 to -46°C, a Gardner impact strength of 180 to 230 ft lb/in and 2"Secant modulus of 45,000 to 56,000 psi.
• quasi-single phase exhibits desirable qualities of both fibrous and particulate morphology types with a brittleness temperature of less than -57"C, a Gardner strength of about 280 ft lb/in and greater, and a 2"Secant modulus above about 40,000 psi (particularly those above 45,000 psi).
• the impact strength and modulus which are two of the key attributes identified above may be optimized by obtaining quasi-single phase morphology.

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• 1993
  • 1993-07-21 CA CA 2141296 patent/CA2141296A1/en not_active Abandoned
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  • 1993-07-21 WO PCT/US1993/007065 patent/WO1994003538A1/en not_active Application Discontinuation
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