US20060079642A1

US20060079642A1 - Method for the preparation of a poly (arylene ether)-polyolefin composition, and composition prepared thereby

Info

Publication number: US20060079642A1
Application number: US11/291,466
Authority: US
Inventors: Adeyinka Adedeji; Thomas Hartle
Original assignee: Individual
Current assignee: SABIC Global Technologies BV
Priority date: 2004-01-09
Filing date: 2005-11-30
Publication date: 2006-04-13
Also published as: US7022765B2; US20050154130A1

Abstract

A poly(arylene ether)-polyolefin composition is prepared by melt-blending a poly(arylene ether) and a compatibilizer to form a first blend, and melt-blending the first blend and a polyolefin to form a second blend. The composition lacks an unhydrogenated block copolymer, a poly(alkenyl aromatic) resin, or both. Multiple mixing elements, low throughput, and high extruder rotations per minute may be used to achieve high energy mixing of the first and second blends. Compositions prepared by the method exhibit an improved balance of impact strength, stiffness, and heat resistance, as well as reduced variability of physical properties.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. Nonprovisional application Ser. No. 10/754,126 filed 9 Jan. 2004.

BACKGROUND

Poly(arylene ether)-polyolefin compositions are well known. Many references teach the desirability of preparing these compositions by combining all components in a single mixing step. See, for example, U.S. Pat. No. 4,764,559 to Yamauchi et al.; U.S. Pat. No. 4,772,657 to Akiyama et al.; U.S. Pat. No. 4,863,997 to Shibuya et al.; U.S. Pat. No. 4,985,495 to Nishio et al.; U.S. Pat. No. 4,990,558 to DeNicola, Jr. et al.; U.S. Pat. Nos. 5,071,912, 5,075,376, 5,132,363, 5,159,004, 5,182,151, and 5,206,281 to Furuta et al.; U.S. Pat. No. 5,418,287 to Tanaka et al., and European Patent Application No. 412,787 A2 to Furuta et al.
Alternatively, some references teach the desirability of adding components in order of higher to lower viscosities. See, for example, U.S. Pat. No. 4,764,559 to Yamauchi et al., 4,985,495 to Nishio et al., and U.S. Pat. No. 5,418,287 to Tanaka et al.
In yet another proposed blending method, a polyphenylene ether and a polypropylene-graft-polystyrene copolymer, with or without unmodified polypropylene, are pre-mixed before one or more rubbery substances are added with additional mixing. See, for example, U.S. Pat. Nos. 5,071,912, 5,075,376, 5,132,363, 5,159,004, 5,182,151, and 5,206,281 to Furuta et al.; European Patent Application No. 412,787 A2 to Furuta et al.; and Japanese Unexamined Patent Application 63[1988]-113049 to Shibuya et al.
The above-described methods produce compositions that are inadequate for many commercial uses because they exhibit excessive variability in key properties, including stiffness and impact strength. There remains a need for a method of producing poly(arylene ether)-polyolefin compositions having improved property balances. In particular, there remains a need for a method of producing poly(arylene ether)-polyolefin compositions exhibiting reduced property variability and improved tradeoffs between stiffness, impact strength, and heat resistance.

BRIEF SUMMARY

The above described and other drawbacks and disadvantages of the prior art are alleviated by a method of preparing a thermoplastic composition, comprising: melt-blending a poly(arylene ether) and a compatibilizer to form a first intimate blend; and melt-blending the first intimate blend and a polyolefin to form a second intimate blend; wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin.
Additional embodiments are described in detail below.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagrammatic view of kneading blocks used in high and low intensity upstream and downstream kneading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment is a method comprising: melt-blending a poly(arylene ether) and a compatibilizer to form a first intimate blend; and melt-blending the first intimate blend and a polyolefin to form a second intimate blend; wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin.
Extensive experiments by the present inventors have led to the surprising observation that the properties of the composition prepared according to this method are substantially and unexpectedly improved compared to compositions prepared by known methods, especially those methods in which all components are blended simultaneously.
In a preferred embodiment, melt-blending to form the first intimate blend comprises high-energy mixing. The energy of mixing may be expressed in various ways. One factor contributing to the energy of mixing is the extruder addition point. For example, when the composition is compounded on an eleven barrel twin-screw extruder, high-energy mixing of the first-intimate blend may be expressed as addition of first intimate blend components to one of the first four barrels.
Another factor contributing to the energy of mixing is the number of mixing sections, with greater numbers of mixing sections corresponding to higher energy mixing. Each mixing section may comprise at least one mixing element. The first intimate blend and the second intimate blend are each preferably formed using at least one mixing section. Mixing sections and mixing elements are generally well known in the art as components of twin-screw extruders. Each mixing element is disposed non-rotatably on a screw shaft and is used to disperse and distribute components of a thermoplastic composition throughout the blend. The mixing element may or may not advance the composition toward the outlet of the extruder. The present inventors have found that the properties of the composition are improved if the processes of mixing to form the first intimate blend and the second intimate blend each employ at least one mixing section. In a preferred embodiment, mixing to form the first intimate blend and the second intimate blend each employ at least two mixing elements on each screw shaft.
There is no particular limitation on the design of the individual mixing elements. Suitable mixing elements include, for example, mixing elements on each of said shafts which are in radial interwiping relation within the extruder barrel and configured to wipe one another and the cylinder walls, as described in U.S. Pat. No. 4,752,135; mixing element disks having mixing wings as described in U.S. Pat. No. 3,195,868 to Loomans et al. and U.S. Pat. No. 5,593,227 to Scheuring et al.; mixing elements having two opposing lobes wherein one lobe is tapered, as described in U.S. Pat. No. 6,116,770 to Kiani et al.; and the various mixing elements, including those characterized as prior art mixing elements, described in U.S. Pat. No. 5,932,159 to Rauwendaal.
In one embodiment, melt-blending to form a first intimate blend and melt-blending to form a second intimate blend collectively comprise mixing with a mixing energy input of at least about 0.20 kilowatt-hour/kilogram (kW-hr/kg). A mixing energy input of at least about 0.22 kW-hr/kg may be preferred, and an energy input of at least about 0.24 kW-hr/kg may be more preferred. Such quantitative mixing energy input may be determined by measuring the rotation rate of the extruder motor and the extruder motor's current draw. Since a direct current (DC) motor speed is directly proportional to the voltage applied, a previously measured proportionality constant may be used to convert the measured motor speed, in rpm, to a voltage in volts. The energy input may then be calculated as the product of the extruder motor current and voltage, divided by the extruder throughput rate. For example, an extruder operating at 120 volts, 2 amps, and a throughput of 1 kg/hr has an energy input of
(120 V)(2 A)/(1 kg/hr)=240 W-hr/kg
or 0.240 kW-hr/kg.
In one embodiment, the first intimate blend may be formed and pelletized in one step, then mixed with the polyolefin to form the second intimate blend in another step.
Suitable temperatures for forming the composition are generally about 180° C. to about 400° C. Within this range it may be preferred to form the first intimate blend by exposing the first intimate blend components to a temperature of at least about 200° C., more preferably at least about 250° C., yet more preferably at least about 280° C. Also within the above range, it may be preferred to form the first intimate blend by exposing the first intimate blend components to a temperature of up to about 320° C., more preferably up to about 300° C., yet more preferably up to about 290° C. The same temperatures are also suitable for formation of the second intimate blend.
The method is suitable for preparing the poly(arylene ether)-polyolefin compositions on any scale, from grams to tons. For economical production of commercially significant amounts of the composition, it may preferred that the method have a throughput rate of at least about 10 kilograms per hour (kg/h), more preferably at least about 5,000 kg/h, based on the total weight of the composition. Throughput rates of 100,000 kg/h and higher may be used.
Any known apparatus may be used to carry out the method. Utilization of the method on a laboratory scale may employ a lab-scale mixer such as, for example, a Labo Plastomill available from Toyo Seiki Company, Hyogo, Japan. Preferred apparatuses for conducting the method on a larger scale include single-screw and twin-screw extruders, with twin-screw extruders being more preferred. Extruders for melt blending of thermoplastics are commercially available from, for example, Coperion, Ramsey, N.J. The method may also be carried out using apparatus designed to compound the composition and mold it directly, without an intermediate pelletizing step. Such apparatus is described, for example, in U.S. Pat. No. 6,109,910 to Sekido, and 6,464,910 B1 to Smorgon et al; U.S. Patent Application No. 2003/0021860 A1 to Clock et al; and International Publication No. WO 02/43943 A1 to Adedeji et al.
FIG. 1 illustrates non-limiting examples of extruder configurations useful for conducting the method. The upper half of the figure is a full extruder configuration using high intensity (“+1”) upstream kneading (“kneading 1”) and low intensity (“−1”) downstream kneading (“kneading 2”). High intensity upstream and downstream kneading correspond to use of assemblies of multiple right-handed, left-handed, and neutral kneading elements as depicted in FIG. 1 as Kneading 1 (+1) and Kneading 2 (+1), respectively. Likewise, low intensity upstream and downstream kneading corresponded to the use of assemblies depicted in FIG. 1 as Kneading 1 (−1) and Kneading 2 (−1), respectively. In the screw elements labeled in FIG. 1, RSE stands for right-handed screw element, SFE stands for single flighted element, RKB stands for right-handed kneading block, NKB stands for neutral kneading block, and LKB stands for left-handed kneading block. Each labeled element includes a two-number or three-number designation following the three letter acronyms described above. For conveying elements (i.e., those elements for which the third letter of the three letter acronym is “E”), the first number is the pitch (i.e., the axial length in millimeters required for a flight to make a full revolution). For kneading blocks (i.e., those elements for which the third letter of the three letter acronym is “B”), the first number is the offset angle of each individual disk to its neighbor, and the second number is the total number of disks that make up the screw element. For all screw elements, the last number is the total length of the screw element in millimeters. The numbered sections above the screw elements are known as barrel numbers. Each kneading section is bounded by the first and last kneading blocks within that section. For example, “Kneading 1 +1” is bounded on the left by RKB 45/5/28 and on the right by LKB 45/5/14. It will be understood that the lower half of the figure is meant to show the “opposite” versions of Kneading 1 and Kneading 2 that may be inserted into the corresponding kneading sections in the upper half of the figure.
The first intimate blend may comprise any conventional poly(arylene ether). The term poly(arylene ether) includes polyphenylene ether (PPE) and poly(arylene ether) copolymers; graft copolymers; poly(arylene ether) ether ionomers; and block copolymers of alkenyl aromatic compounds, vinyl aromatic compounds, and poly(arylene ether), and the like; and combinations comprising at least one of the foregoing; and the like. Poly(arylene ether)s are known polymers comprising a plurality of structural units of the formula:

wherein for each structural unit, each Q¹is independently halogen, primary or secondary C₁-C₈alkyl, phenyl, C₁-C₈haloalkyl, C₁-C₈aminoalkyl, C₁-C₈hydrocarbonoxy, or C₂-C₈halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q²is independently hydrogen, halogen, primary or secondary C₁-C₈alkyl, phenyl, C₁-C₈haloalkyl, C₁-C₈aminoalkyl, C₁-C₈hydrocarbonoxy, or C₂-C₈halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms. Preferably, each Q¹is alkyl or phenyl, especially C₁-C₄alkyl, and each Q²is independently hydrogen or methyl.
Both homopolymer and copolymer poly(arylene ether)s are included. The preferred homopolymers are those comprising 2,6-dimethylphenylene ether units. Suitable copolymers include random copolymers comprising, for example, such units in combination with 2,3,6-trimethyl-1,4-phenylene ether units or copolymers derived from copolymerization of 2,6-dimethylphenol with 2,3,6-trimethylphenol. Also included are poly(arylene ether)s containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes, as well as coupled poly(arylene ether) in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo reaction in known manner with the hydroxy groups of two poly(arylene ether) chains to produce a higher molecular weight polymer. Poly(arylene ether)s of the present invention further include combinations of any of the above.
The poly(arylene ether) generally has a number average molecular weight of about 3,000 to about 40,000 atomic mass units (AMU) and a weight average molecular weight of about 6,000 to about 80,000 AMU, as determined by gel permeation chromatography. The poly(arylene ether) generally may have an intrinsic viscosity of about 0.1 to about 0.6 deciliters per gram (dL/g) as measured in chloroform at 25° C. Within this range, the intrinsic viscosity may preferably be at least about 0.2 dL/g, more preferably at least about 0.3 dL/g. Also within this range, the intrinsic viscosity may preferably be up to about 0.5 dL/g, more preferably up to about 0.47 dL/g. It is also possible to utilize a high intrinsic viscosity poly(arylene ether) and a low intrinsic viscosity poly(arylene ether) in combination. Determining an exact ratio, when two intrinsic viscosities are used, will depend on the exact intrinsic viscosities of the poly(arylene ether)s used and the ultimate physical properties desired.
The poly(arylene ether)s are typically prepared by the oxidative coupling of at least one monohydroxyaromatic compound such as 2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are generally employed for such coupling; they typically contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.
Particularly useful poly(arylene ether)s for many purposes include those that comprise molecules having at least one aminoalkyl-containing end group. The aminoalkyl radical is typically located in an ortho position relative to the hydroxy group. Products containing such end groups may be obtained by incorporating an appropriate primary or secondary monoamine such as di-n-butylamine or dimethylamine as one of the constituents of the oxidative coupling reaction mixture. Also frequently present are 4-hydroxybiphenyl end groups, typically obtained from reaction mixtures in which a by-product diphenoquinone is present, especially in a copper-halide-secondary or tertiary amine system. A substantial proportion of the polymer molecules, typically constituting as much as about 90% by weight of the polymer, may contain at least one of the aminoalkyl-containing and 4-hydroxybiphenyl end groups.
The first intimate blend may comprise poly(arylene ether) in an amount of about 10 to about 70 weight percent, based on the total weight of the composition. Within this range, it may be preferred to use at least about 15 weight percent, more preferably at least about 20 weight percent, of the poly(arylene ether). Also within this range, it may be preferred to use up to about 60 weight percent, more preferably up to about 50 weight percent, still more preferably up to about 40 weight percent, of the poly(arylene ether).
The first intimate blend further comprises a compatibilizer. While not wishing to be bound by any particular hypothesis, the present inventors believe that the compatibilizer acts to stabilize the interface between the poly(arylene ether) phase and the polyolefin phase. Suitable compatibilizers include, for example, hydrogenated block copolymers of an alkenyl aromatic compound and a conjugated diene compound, partially hydrogenated block copolymers of an alkenyl aromatic compound and a conjugated diene compound, polyolefin-poly(alkenyl aromatic) copolymers, polyolefin-poly(arylene ether) graft copolymers, polyolefin-poly(arylene ether) block copolymers, and the like, and mixtures thereof.
The compatibilizer may be a hydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene. The hydrogenated block copolymer is a copolymer comprising (A) at least one block derived from an alkenyl aromatic compound and (B) at least one block derived from a conjugated diene, in which the aliphatic unsaturated group content in the block (B) is reduced by hydrogenation. The arrangement of blocks (A) and (B) includes a linear structure and a so-called radial teleblock structure having branched chains.
Preferred of these structures are linear structures embracing diblock (A-B block), triblock (A-B-A block or B-A-B block), tetrablock (A-B-A-B block), and pentablock (A-B-A-B-A block or B-A-B-A-B block) structures as well as linear structures containing 6 or more blocks in total of A and B. More preferred are diblock, triblock, and tetrablock structures, with the A-B diblock and A-B-A triblock structures being particularly preferred.
The alkenyl aromatic compound providing the block (A) is represented by formula:

wherein R²and R³each independently represent a hydrogen atom, a C₁-C₈alkyl group, a C₂-C₈alkenyl group, or the like; R⁴and R⁸each independently represent a hydrogen atom, a C₁-C₈alkyl group, a chlorine atom, a bromine atom, or the like; and R⁵-R⁷each independently represent a hydrogen atom, a C₁-C₈alkyl group, a C₂-C₈alkenyl group, or the like, or R⁴and R⁵are taken together with the central aromatic ring to form a naphthyl group, or R⁵and R⁶are taken together with the central aromatic ring to form a naphthyl group.
Specific examples, of the alkenyl aromatic compounds include styrene, p-methylstyrene, alpha-methylstyrene, vinylxylenes, vinyltoluenes, vinylnaphthalenes, divinylbenzenes, bromostyrenes, chlorostyrenes, and the like, and combinations comprising at least one of the foregoing alkenyl aromatic compounds. Of these, styrene, alpha-methylstyrene, p-methylstyrene, vinyltoluenes, and vinylxylenes are preferred, with styrene being more preferred.
Specific examples of the conjugated diene include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and the like. Preferred among them are 1,3-butadiene and 2-methyl-1,3-butadiene, with 1,3-butadiene being more preferred.
In addition to the conjugated diene, the hydrogenated block copolymer may contain a small proportion of a lower olefinic hydrocarbon such as, for example, ethylene, propylene, 1-butene, dicyclopentadiene, a non-conjugated diene, or the like.
There is no particular restriction on the content of the repeating unit derived from the alkenyl aromatic compound in the hydrogenated block copolymer. Suitable alkenyl aromatic content may be about 10 to about 90 weight percent based on the total weight of the hydrogenated block copolymer. Within this range, it may be preferred to have an alkenyl aromatic content of at least about 40 weight percent, more preferably at least about 50 weight percent, yet more preferably at least about 55 weight percent. Also within this range, it may be preferred to have an alkenyl aromatic content of up to about 85 weight percent, more preferably up to about 75 weight percent.
There is no particular limitation on the mode of incorporation of the conjugated diene in the hydrogenated block copolymer backbone. For example, when the conjugated diene is 1,3-butadiene, it may be incorporated with about 1% to about 99% 1,2-incorporation with the remainder being 1,4-incorporation.
The hydrogenated block copolymer is preferably hydrogenated to such a degree that less than 20%, yet more preferably less than 10%, of the aliphatic unsaturation in the aliphatic chain moiety derived from the conjugated diene remains unreduced. The aromatic unsaturated bonds derived from the alkenyl aromatic compound may be hydrogenated to a degree of up to about 25%.
The hydrogenated block copolymer preferably has a number average molecular weight of about 5,000 to about 500,000 AMU, as determined by gel permeation chromatography (GPC) using polystyrene standards. Within this range, the number average molecular weight may preferably be at least about 10,000 AMU, more preferably at least about 30,000 AMU, yet more preferably at least about 45,000 AMU. Also within this range, the number average molecular weight may preferably be up to about 300,000 AMU, more preferably up to about 200,000 AMU, yet more preferably up to about 150,000 AMU.
The molecular weight distribution of the hydrogenated block copolymer as measured by GPC is not particularly limited. The copolymer may have any ratio of weight average molecular weight to number average molecular weight.
Some of these hydrogenated block copolymers have a hydrogenated conjugated diene polymer chain to which crystallinity is ascribed. Crystallinity of the hydrogenated block copolymer can be determined by the use of a differential scanning calorimeter (DSC), for example, DSC-II Model manufactured by Perkin-Elmer Co. Heat of fusion can be measured by a heating rate of, for example, 10° C./min in an inert gas atmosphere such as nitrogen. For example, a sample may be heated to a temperature above an estimated melting point, cooled by decreasing the temperature at a rate of 10° C./min, allowed to stand for about 1 minute, and then heated again at a rate of 10° C./min.
The hydrogenated block copolymer may have any degree of crystallinity. In view of a balance of mechanical strength of the resulting resin composition, those hydrogenated block copolymers having a melting point of about −40° C. to about 200° C. or having no definite melting point (i.e., having non-crystallinity), as measured according to the above-described technique, are preferred. More preferably, the hydrogenated block copolymers have a melting point of at least about 0° C., yet more preferably at least about 20° C., still more preferably at least about 50° C.
The hydrogenated block copolymer may have any glass transition temperature (T_g) ascribed to the hydrogenated conjugated diene polymer chain. From the standpoint of low-temperature impact strength of the resulting resin composition, it preferably has a T_gof up to about 0° C., more preferably up to about −120° C. The glass transition temperature of the copolymer can be measured by the aforesaid DSC method or from the visco-elastic behavior toward temperature change as observed with a mechanical spectrometer.
Particularly preferred hydrogenated block copolymers are the styrene-(ethylene-butylene) diblock and styrene-(ethylene-butylene)-styrene triblock copolymers obtained by hydrogenation of styrene-butadiene and styrene-butadiene-styrene triblock copolymers, respectively.
Suitable hydrogenated block copolymers include those commercially available as, for example, KRATON® G1650, G1651, and G1652 available from Kraton Polymers, and TUFTECO® H1041, H1043, H1052, H1062, H1141, and H1272 available from Asahi Chemical. Preferred hydrogenated block copolymers include the highly hydrogenated styrene-(ethylene-butylene)-styrene triblock copolymers commercially available as, for example, TUFTEC® H1043 from Asahi Chemical.
The compatibilizer may be a partially hydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene compound (“partially hydrogenated block copolymer”). The partially hydrogenated block copolymer is similar to the hydrogenated block copolymer described above, but varies in its degree of hydrogenation. The partially hydrogenated block copolymer is preferably hydrogenated to such a degree that 20% to about 80% of the unsaturated bonds in the aliphatic chain moiety derived from the conjugated diene remain unreduced. Within this range, the percentage of unreduced unsaturated bonds is preferably at least 30%, more preferably at least 35%. Also within this range, the percentage of unreduced unsaturated bonds is preferably up to about 70%, more preferably up to about 65%.
Preferred partially hydrogenated block copolymers include the selectively hydrogenated block copolymers in which the hydrogenation selectively reduces pendant aliphatic unsaturation resulting from 1,2- and 3,4-incorporation of the diene while effecting less reduction of the in-chain aliphatic unsaturation resulting from 1,4-incorporation of the diene. For example, in-chain aliphatic unsaturation may remain at least about 30 percent unhydrogenated, preferably at least about 40 percent unhydrogenated, more preferably at least about 50 percent unhydrogenated; and pendant aliphatic unsaturation remains up to about 20 percent unhydrogenated, preferably up about 10 percent unhydrogenated, more preferably up to about 5 percent unhydrogenated. In one embodiment, the ratio of the percentage of unhydrogenated in-chain aliphatic unsaturation to the percentage of unhydrogenated pendant aliphatic unsaturation is at least about 2, preferably at least about 5, more preferably at least about 10.
The partially hydrogenated block copolymer may be synthesized by block polymerization followed by hydrogenation as described, for example, in U.S. Pat. No. 4,994,508 to Shiraki et al. Suitable partially hydrogenated block copolymers include the styrene-(butadiene-butylene)-styrene triblock copolymers commercially available from Asahi Chemical as, for example, TUFTEC® P-series copolymers. Additional description of partially hydrogenated block copolymers may be found in U.S. Patent Application Publication No. 2003-0036602 A1 to Adedeji et al.
The compatibilizer may be a polyolefin-poly(alkenyl aromatic) copolymer. This copolymer may be, for example, a random copolymer, a block copolymer (including, for example, diblock copolymers, multiblock copolymers, and radial teleblock copolymer), a graft copolymer, or a combination thereof. The polyolefin-poly(alkenyl aromatic) copolymer may be added during formation of the first intimate blend, the second intimate blend, or both. It is preferably added during formation of the first intimate blend. When the polyolefin-poly(alkenyl aromatic) copolymer is added during formation of both the first intimate blend and the second intimate blend, about 1% to about 99% of the total polyolefin-poly(alkenyl aromatic) copolymer may be added as a component of the first intimate blend, with the remainder added as a component of the second intimate blend.
In a preferred embodiment, the polyolefin-poly(alkenyl aromatic) copolymer comprises a polypropylene-polystyrene graft copolymer. The polypropylene-polystyrene graft copolymer is herein defined as a graft copolymer having a propylene polymer backbone and one or more styrene polymer grafts.
The propylene polymer material that forms the backbone or substrate of the polypropylene-polystyrene graft copolymer is (a) a homopolymer of propylene; (b) a random copolymer of propylene and an olefin selected from the group consisting of ethylene and C₄-C₁₀olefins, provided that, when the olefin is ethylene, the polymerized ethylene content is up to about 10 weight percent, preferably up to about 4 weight percent, and when the olefin is a C₄-C₁₀olefin, the polymerized content of the C₄-C₁₀olefin is up to about 20 weight percent, preferably up to about 16 weight percent; (c) a random terpolymer of propylene and at least two olefins selected from the group consisting of ethylene and C₄-C₁₀alpha-olefins, provided that the polymerized C₄-C₁₀alpha-olefin content is up to about 20 weight percent, preferably up to about 16 weight percent, and, when ethylene is one of the olefins, the polymerized ethylene content is up to about 5 weight percent, preferably up to about 4 weight percent; or (d) a homopolymer or random copolymer of propylene which is impact-modified with an ethylene-propylene monomer rubber in the reactor as well as by physical blending, the ethylene-propylene monomer rubber content of the modified polymer being about 5 to about 30 weight percent, and the ethylene content of the rubber being about 7 to about 70 weight percent, and preferably about 10 to about 40 weight percent. The C₄-C₁₀olefins include the linear and branched C₄-C₁₀alpha-olefins such as, for example, 1-butene, 1-pentene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 1-octene, 3-methyl-hexene, and the like. Propylene homopolymers and impact-modified propylene homopolymers are preferred propylene polymer materials. Although not preferred, propylene homopolymers and random copolymers impact modified with an ethylene-propylene-diene monomer rubber having a diene content of about 2 to about 8 weight percent also can be used as the propylene polymer material. Suitable dienes include dicyclopentadiene, 1,6-hexadiene, ethylidene norbornene, and the like.
The term “styrene polymer”, used in reference to the grafted polymer present on the backbone of propylene polymer material in the polypropylene-polystyrene graft copolymer, denotes (a) homopolymers of styrene or of an alkyl styrene having at least one C₁-C₄linear or branched alkyl ring substituent, especially a p-alkyl styrene; (b) copolymers of the (a) monomers with one another in all proportions; and (c) copolymers of at least one (a) monomer with alpha-methyl derivatives thereof, e.g., alpha-methylstyrene, wherein the alpha-methyl derivative constitutes about 1 to about 40% of the weight of the copolymer.
The polypropylene-polystyrene graft copolymer will typically comprise about 10 to about 90 weight percent of the propylene polymer backbone and about 90 to about 10 weight percent of the styrene polymer graft. Within these ranges, the propylene polymer backbone may preferably account for at least about 20 weight percent, of the total graft copolymer; and the propylene polymer backbone may preferably account for up to about 40 weight percent of the total graft copolymer. Also within these ranges, the styrene polymer graft may preferably account for at least about 50 weight percent, more preferably at least about 60 weight percent, of the total graft copolymer.
The preparation of polypropylene-polystyrene graft copolymers is described, for example, in U.S. Pat. No. 4,990,558 to DeNicola, Jr. et al. Suitable polypropylene-polystyrene graft copolymers are also commercially available as, for example, P1045H1 and P1085H1 from Basell.
The compatibilizer may be a polyolefin-poly(arylene ether) graft copolymer. In one embodiment, the polyolefin forms the backbone and the poly(arylene ether) the grafts of the graft copolymer. In another embodiment, the poly(arylene ether) forms the backbone and the polyolefin the grafts of the graft copolymer. Included are copolymers in which a divalent linking group is used to join the polyolefin and poly(arylene ether) chains. Suitable polyolefin-poly(arylene ether) graft copolymers include, for example, the polyphenylene ether-graft-polyethylene copolymers described in U.S. Pat. No. 3,522,326 of Bostick et al., the polyolefin-graft/link-poly(arylene ether) copolymer described in U.S. Pat. No. 5,124,410 to Campbell, and the polyolefin-graft-polyphenylene ether copolymers described in U.S. Pat. No. 4,876,310 to Bartmann.
The compatibilizer may be a polyolefin-poly(arylene ether) block copolymer. The polyolefin-poly(arylene ether) block copolymer comprises at least one polyolefin block and at least one poly(arylene ether) block. In one embodiment, two blocks may be covalently joined by a divalent link. Suitable polyolefin-poly(arylene ether) block copolymers include those having divalent imide or amide links as described in U.S. Pat. No. 5,262,477 to Kasai et al., and the polyolefin-link-polyphenylene ether copolymers in which the linking group is derived from a polyolefin-terminal carboxylic acid, acid anhydride, epoxy, amine, alkoxysilyl, or sulfonic acid group as described in JP 06-287367 A to Tomita et al.
The compatibilizer may be present in an amount of about 0.5 to about 30 weight percent, based on the total weight of the composition. Within this range, the compatibilizer amount may preferably be at least about 1 weight percent, more preferably at least about 2 weight percent. Also within this range, the compatibilizer amount may preferably be up to about 25 weight percent, more preferably up to about 20 weight percent, even more preferably up to about 15 weight percent. In one embodiment, all of the compatibilizer is added during formation of the first intimate blend. In another embodiment, a portion, preferably more than half, of the compatibilizer is added during formation of the first intimate blend, and the remainder, preferably less than half, is added during formation of the second intimate blend.
The method comprises melt blending the first intimate blend and a polyolefin to form a second intimate blend. The polyolefin may be a homopolymer or copolymer having at least about 80 weight percent of units derived from polymerization of ethylene, propylene, butylene, or a mixture thereof. Examples of polyolefin homopolymers include polyethylene, polypropylene, and polybutylene. Examples of polyolefin copolymers include random, graft, and block copolymers of ethylene, propylene, and butylene with each other, and further comprising up to 20 weight percent of units derived from C₅-C₁₀alpha olefins (excluding aromatic alpha-olefins). Polyolefins further include blends of the above homopolymers and copolymers. Preferred polyolefins may have a flexural modulus of at least about 100,000 pounds per square inch (psi) at 23° C. as measured according to ASTM D790. Suitable polyolefins are may comprise, for example, the linear low density polyethylene available from ExxonMobil as LL-6201, the low density polyethylene available from ExxonMobil as LMA-027, the high density polyethylene available from ExxonMobil as HD-6605, the ultra-high molecular weight polyethylene available as Type 1900 from Montell Polyolefins, and the polybutylene (polybutene-1) available as PB0110 from Montell Polyolefins.
Presently preferred polyolefins include propylene polymers. The propylene polymer may be a homopolymer of polypropylene. Alternatively, the propylene polymer may be a random, graft, or block copolymer of propylene and at least one olefin selected from ethylene and C₄-C₁₀alpha-olefins (excluding aromatic alpha-olefins), with the proviso that the copolymer comprises at least about 80 weight percent, preferably at least about 90 weight percent, of repeating units derived from propylene. Blends of such propylene polymers with a minor amount of another polymer such as polyethylene are also included within the scope of propylene polymers. The propylene polymer may have a melt flow index of about 0.1 to about 50 g/10 min, preferably about 1 to about 30 g/10 min when measured according to ASTM D1238 at 2.16 kg and 200° C. The above-described propylene polymers can be produced by various known processes. Commercially available propylene polymers may also be employed.
Preferred propylene polymers include homopolypropylenes. Highly preferred propylene polymers include homopolypropylenes having a crystalline content of at least about 20%, preferably at least about 30%. Suitable isotactic polypropylenes are commercially available as, for example, PD403 pellets from Basell (formerly Montell Polyolefins of North America).
The composition may comprise polyolefin in an amount of about 10 to about 80 weight percent, preferably about 10 to about 70 weight percent, more preferably about 10 to about 60 weight percent, based on the total weight of the composition. In one embodiment, all of the polyolefin is added during formation of the second intimate blend. In another embodiment, a portion of the polyolefin, preferably less than half, is added during formation of the first intimate blend, and the remainder, preferably more than half, is added during formation of the second intimate blend.
The thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin. The term “substantially free” is herein defined as constituting less than 0.5 weight percent, preferably less than 0.1 weight percent, more preferably 0 weight percent, of the total composition. While the composition is substantially free of at least one of these components, it may contain one but not the other. Thus, in one embodiment, the composition comprises an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene (referred to hereinafter as an “unhydrogenated block copolymer”), and it is substantially free of a poly(alkenyl aromatic) resin. In another embodiment, the composition comprises a poly(alkenyl aromatic) resin, and it is substantially free of an unhydrogenated block copolymer.
When the method comprises adding a poly(alkenyl aromatic) resin, it may be added during formation of the first intimate blend, or the second intimate blend, or both. Preferably, the poly(alkenyl aromatic) resin is added during formation of the first intimate blend. The term “poly(alkenyl aromatic) resin” as used herein includes polymers prepared by methods known in the art including bulk, suspension, and emulsion polymerization, which contain at least 25% by weight of structural units derived from an alkenyl aromatic monomer of the formula

wherein R¹is hydrogen, C₁-C₈alkyl, halogen, or the like; Z is vinyl, halogen, C₁-C₈alkyl, or the like; and p is 0 to 5. Preferred alkenyl aromatic monomers include styrene, chlorostyrenes such as p-chlorostyrene, vinyltoluenes such as p-vinyltoluene, and the like. The poly(alkenyl aromatic) resins include homopolymers of an alkenyl aromatic monomer; random copolymers of an alkenyl aromatic monomer, such as styrene, with one or more different monomers such as acrylonitrile, butadiene, alpha-methylstyrene, ethylvinylbenzene, divinylbenzene and maleic anhydride; and rubber-modified poly(alkenyl aromatic) resins comprising blends and/or grafts of a rubber modifier and a homopolymer of an alkenyl aromatic monomer (as described above), wherein the rubber modifier may be a polymerization product of at least one C₄-C₁₀nonaromatic diene monomer, such as butadiene or isoprene, and wherein the rubber-modified poly(alkenyl aromatic) resin comprises about 98 to about 70 weight percent of the homopolymer of an alkenyl aromatic monomer and about 2 to about 30 weight percent of the rubber modifier. Within these ranges it may be preferred to use at least about 88 weight percent of the homopolymer of an alkenyl aromatic monomer. It may also be preferred to use up to about 94 weight percent of the homopolymer of an alkenyl aromatic monomer. It may also be preferred to use at least about 6 weight percent of the rubber modifier. It may also be preferred to use up to about 12 weight percent of the rubber modifier.
The stereoregularity of the poly(alkenyl aromatic) resin may be atactic or syndiotactic. Highly preferred poly(alkenyl aromatic) resins include atactic and syndiotactic homopolystyrenes. Suitable atactic homopolystyrenes are commercially available as, for example, EB3300 from Chevron, and P1800 from BASF. Suitable syndiotactic homopolystyrenes are commercially available, for example, under the tradename QUESTRA® (e.g., QUESTRA® WA550) from Dow Chemical Company. Highly preferred poly(alkenyl aromatic) resins further include the rubber-modified polystyrenes, also known as high-impact polystyrenes or HIPS, comprising about 88 to about 94 weight percent polystyrene and about 6 to about 12 weight percent polybutadiene, with an effective gel content of about 10% to about 35%. These rubber-modified polystyrenes are commercially available as, for example, GEH 1897 from General Electric Plastics, and BA 5350 from Chevron.
When the composition comprises the poly(alkenyl aromatic) resin, it may be present in an amount of about 1 to about 46 weight percent, preferably about 3 to about 46 weight percent, based on the total weight of the composition.
Alternatively, the amount of poly(alkenyl aromatic) resin, when present, may be expressed as a fraction of the total of poly(arylene ether) and poly(alkenyl aromatic) resin based on the combined weight of poly(arylene ether) and poly(alkenyl aromatic) resin. The first intimate blend may comprise preferably comprise poly(alkenyl aromatic) resin in an amount of about 10 to about 80 weight percent, based on the combined weight of poly(arylene ether) and poly(alkenyl aromatic) resin. Within this range, it may be preferred to use at least about 20 weight percent, more preferably at least about 40 weight percent, of the poly(alkenyl aromatic) resin based on the total of the poly(arylene ether) and the poly(alkenyl aromatic) resin. Also within this range, it may be preferred to use up to about 70 weight percent, more preferably up to about 65 weight percent of the poly(alkenyl aromatic) resin based on the total of the poly(arylene ether) and the poly(alkenyl aromatic) resin. The proportions of poly(alkenyl aromatic) resin and poly(arylene ether) may be manipulated to control the glass transition temperature (T_g) of the single phase comprising these two components relative to the T_gof the poly(arylene ether) alone, or relative to the melting temperature (T_m) of the polyolefin alone. For example, the relative amounts of poly(alkenyl aromatic) resin and poly(arylene ether) may be chosen so that the poly(arylene ether) and the poly(alkenyl aromatic) resin form a single phase having a glass transition temperature at least about 20° C. greater, preferably at least about 30° C. greater, than the glass transition temperature of the poly(alkenyl aromatic) resin alone, which may be, for example, about 100° C. to about 110° C. Also, the relative amounts of poly(alkenyl aromatic) resin and poly(arylene ether) may be chosen so that the poly(arylene ether) and the poly(alkenyl aromatic) resin form a single phase having a glass transition temperature up to about 15° C. greater, preferably up to about 10° C. greater, more preferably up to about 1° C. greater, than the T_mof the polyolefin alone. The relative amounts of poly(alkenyl aromatic) resin and poly(arylene ether) may be chosen so that the poly(arylene ether) and the poly(alkenyl aromatic) resin form a single phase having a glass transition temperature of about 130° C. to about 180° C.
In one embodiment, the composition comprises an unhydrogenated block copolymer. When the composition comprises an unhydrogenated block copolymer, it may be added during formation of the first intimate blend, or the second intimate blend, or both. Preferably, the unhydrogenated block copolymer is added during formation of the first intimate blend. The unhydrogenated block copolymer is a copolymer comprising (A) at least one block derived from an alkenyl aromatic compound and (B) at least one block derived from a conjugated diene, in which the aliphatic unsaturated group content in the block (B) has not been reduced by hydrogenation. The alkenyl aromatic compound (A) and the conjugated diene (B) are defined in detail above in the description of the hydrogenated block copolymer. The arrangement of blocks (A) and (B) includes a linear structure and a so-called radial teleblock structure having a branched chain.
Preferred of these structures are linear structures embracing diblock (A-B block), triblock (A-B-A block or B-A-B block), tetrablock (A-B-A-B block), and pentablock (A-B-A-B-A block or B-A-B-A-B block) structures as well as linear structures containing 6 or more blocks in total of A and B. More preferred are diblock, triblock, and tetrablock structures, with the A-B-A triblock structure being particularly preferred.
The unhydrogenated block copolymer may comprise about 10 to about 90 weight percent of the (A) blocks. Within this range, it may be preferred to use at least about 20 weight percent (A) blocks. Also within this range, it may be preferred to use up to about 80 weight percent (A) blocks.
Particularly preferred unhydrogenated block copolymers included styrene-butadiene-styrene triblock copolymers.
Suitable unhydrogenated block copolymers may be prepared by known methods or obtained commercially as, for example, KRATON® D series polymers, including KRATON® D 1101 and D1102, from Kraton Polymers.
When present, the unhydrogenated block copolymer may be used at about 1 to about 20 weight percent, preferably about 1 to about 15 weight percent, more preferably about 1 to about 10 weight percent, based on the total weight of the composition.
The method may, optionally, further comprise the addition of an ethylene/alpha-olefin elastomeric copolymer. The alpha-olefin component of the copolymer may be at least one C₃-C₁₀alpha-olefin. Preferred alpha-olefins include propylene, 1-butene, and 1-octene. The elastomeric copolymer may be a random copolymer having about 25 to about 75 weight percent, preferably about 40 to about 60 weight percent, ethylene and about 75 to about 25 weight percent, preferably about 60 to about 40 weight percent, alpha-olefin. Within these ranges, it may be preferred to use at least about 40 weight percent ethylene; and it may be preferred to use up to about 60 weight percent ethylene. Also within these ranges, it may be preferred to use at least about 40 weight percent alpha-olefin; and it may be preferred to use up to about 60 weight percent alpha-olefin. The ethylene/alpha-olefin elastomeric copolymer may typically have a melt flow index of about 0.1 to about 20 g/10 min at 2.16 kg and 200° C., and a density of about 0.8 to about 0.9 g/ml.
Particularly preferred ethylene/alpha-olefin elastomeric copolymer rubbers include ethylene-propylene rubbers, ethylene-butene rubbers, ethylene-octene rubbers, and the like, and mixtures thereof.
The ethylene/alpha-olefin elastomeric copolymer may be prepared according to known methods or obtained commercially as, for example, the neat ethylene-propylene rubber sold as VISTALON® 878 by ExxonMobil Chemical and the ethylene-butylene rubber sold as EXACT® 4033 by ExxonMobil Chemical. Ethylene/alpha-olefin elastomeric copolymers may also be obtained commercially as blends in polypropylene as, for example, the ethylene-propylene rubber pre-dispersed in polypropylene sold as product numbers Profax 7624 and Profax 8023 from Basell, and the ethylene-butene rubber pre-dispersed in polypropylene sold as Catalloy K021P from Basell.
In one embodiment, the ethylene/alpha-olefin elastomeric copolymer may be added during formation of the first intimate blend. In another embodiment, the ethylene/alpha-olefin elastomeric copolymer may be added during formation of the second intimate blend. In yet another embodiment, about 1 to about 99% of the ethylene/alpha-olefin elastomeric copolymer may be added during formation of the first intimate blend, with the remainder added during formation of the second intimate blend. In still another embodiment, the ethylene/alpha-olefin elastomeric copolymer may be prepared as a heterophasic copolymer with the polyolefin, and the resulting heterophasic copolymer comprising ethylene/alpha-olefin elastomeric copolymer and polyolefin may be added during formation of the first intimate blend, or, preferably, during formation of the second intimate blend.
When present, the ethylene/alpha-olefin elastomeric copolymer may be used in an amount of about 1 to about 20 weight percent, based on the total of the composition. Within this range, the ethylene/alpha-olefin elastomeric copolymer may preferably be used in an amount of at least about 3 weight percent. Also within this range, ethylene/alpha-olefin elastomeric copolymer may preferably be used in an amount up to about 15 weight percent.
In one embodiment, the amount of ethylene/alpha-olefin elastomeric copolymer may be expressed as a fraction of the total of polyolefin and ethylene/alpha-olefin elastomeric copolymer. Thus, when the ethylene/alpha-olefin elastomeric copolymer is present, its amount may be expressed as about 1 to about 60 weight percent, preferably about 10 to about 40 weight percent, based on the combined weight of polyolefin and ethylene/alpha-olefin elastomeric copolymer.
The method may, optionally, comprise the addition of one or more reinforcing fillers. Reinforcing fillers may include, for example, inorganic and organic materials, such as fibers, woven fabrics and non-woven fabrics of the E-, NE-, S-, T- and D-type glasses and quartz; carbon fibers, including poly(acrylonitrile) (PAN) fibers, vapor-grown carbon fibers, and especially graphitic vapor-grown carbon fibers having average diameters of about 3 to about 500 nanometers (see, for example, U.S. Pat. Nos. 4,565,684 and 5,024,818 to Tibbetts et al., U.S. Pat. No. 4,572,813 to Arakawa; U.S. Pat. Nos. 4,663,230 and 5,165,909 to Tennent, 4,816,289 to Komatsu et al., U.S. Pat. No. 4,876,078 to Arakawa et al., U.S. Pat. No. 5,589,152 to Tennent et al., and U.S. Pat. No. 5,591,382 to Nahass et al.); potassium titanate single-crystal fibers, silicon carbide fibers, boron carbide fibers, gypsum fibers, aluminum oxide fibers, asbestos, iron fibers, nickel fibers, copper fibers, wollastonite fibers; and the like. The reinforcing fillers may be in the form of glass roving cloth, glass cloth, chopped glass, hollow glass fibers, glass mat, glass surfacing mat, and non-woven glass fabric, ceramic fiber fabrics, and metallic fiber fabrics. In addition, synthetic organic reinforcing fillers may also be used including organic polymers capable of forming fibers. Illustrative examples of such reinforcing organic fibers are poly(ether ketone), polyimide benzoxazole, poly(phenylene sulfide), polyesters, aromatic polyamides, aromatic polyimides or polyetherimides, acrylic resins, and poly(vinyl alcohol). Fluoropolymers such as polytetrafluoroethylene, may be used. Also included are natural organic fibers known to one skilled in the art, including cotton cloth, hemp cloth, and felt, carbon fiber fabrics, and natural cellulosic fabrics such as Kraft paper, cotton paper, and glass fiber containing paper. Such reinforcing fillers could be in the form of monofilament or multifilament fibers and could be used either alone or in combination with another type of fiber, through, for example, coweaving or core-sheath, side-by-side, orange-type or matrix and fibril constructions or by other methods known to one skilled in the art of fiber manufacture. They may be in the form of, for example, woven fibrous reinforcements, non-woven fibrous reinforcements, or papers.
Preferred reinforcing fillers include glass fibers. Preferred glass fibers may have diameters of about 2 to about 25 micrometers, more preferably about 10 to about 20 micrometers, yet more preferably about 13 to about 18 micrometers. The length of the glass fibers may be about 0.1 to about 20 millimeters, more preferably about 1 to about 10 millimeters, yet more preferably about 2 to about 8 millimeters. Glass fibers comprising a sizing to increase their compatibility with the polyolefin are particularly preferred. Suitable sizings are described, for example, in U.S. Pat. No. 5,998,029 to Adzima et al. Suitable glass fibers are commercially available as, for example, product numbers 147A-14P (14 micrometer diameter) and 147A-17P (17 micrometer diameter) from Owens Corning.
Preferred reinforcing fillers further include talc. There are no particular limitations on the physical characteristics of the talc. Preferred talcs may have an average particle size of about 0.5 to about 25 micrometers. Within this range, it may be preferred to use a talc having an average particle size up to about 10 micrometers, more preferably up to about 5 micrometers. For some uses of the composition, it may be preferred to employ a talc that is F.D.A. compliant (i.e., compliant with U.S. Food and Drug Administration regulations). Suitable talcs include, for example, the F.D.A. compliant talc having an average particle size of about 3.2 micrometers sold as CIMPACT® 610(C) from Luzenac. Preferred reinforcing fillers further include mica.
Preferred reinforcing fillers further include organoclays. As used herein, an organoclay is a layered silicate clay, derived from layered minerals, in which organic structures have been chemically incorporated. Illustrative examples of organic structures are trimethyldodecylammonium ion and N,N′-didodecylimidazolium ion. Since the surfaces of clay layers, which have a lattice-like arrangement, are electrically charged, they are capable of binding organic ions. There is no limitation with respect to the layered minerals employed in this invention other than that they are capable of undergoing an ion exchange with the organic ions. Preferred organoclays include layered minerals that have undergone cation exchange with organocations and/or onium compounds. Illustrative of such layered minerals are the kaolinite group, the montmorillonite group, and the illite group which can include hydromicas, phengite, brammallite, glaucomite, celadonite and the like. Preferred layered minerals include those often referred to as 2:1 layered silicate minerals like muscovite, vermiculite, saponite, hectorite and montmorillonite, wherein montmorillonite is often preferred. The layered minerals described above may be synthetically produced. However, most often they are naturally occurring and commercially available. Organoclays and their preparation are described, for example, in U.S. Pat. Nos. 4,569,923, 4,664,842, 5,110,501, and 5,160,454 to Knudson, Jr. et al.; U.S. Pat. Nos. 5,530,052 and 5,773,502 to Takekoshi et al.; U.S. Pat. No. 5,780,376 to Gonzales et al.; U.S. Pat. No. 6,036,765 to Farrow et al.; U.S. Pat. No. 6,228,903 B1 to Beall et al.; and U.S. Pat. No. 6,262,162 B1 to Lan et al.
Combinations of any of the foregoing reinforcing fillers are contemplated. When present, the reinforcing filler may used in an amount of about 1 to about 70 weight percent, based on the total weight of the composition. Within this range, the reinforcing filler amount may preferably be at least about 5 weight percent. Also within this range, the reinforcing filler amount may preferably be up to about 60 weight percent, more preferably up to about 50 weight percent.
The compatibility of the reinforcing filler and the polyolefin may be improved not just with sizings on the surface of the reinforcing fillers, but also by adding to the composition a graft copolymer comprising a polyolefin backbone and polar grafts formed from one or more cyclic anhydrides. The graft copolymer comprising a polyolefin backbone and polar grafts formed from one or more cyclic anhydrides may also be useful in the absence of a reinforcing filler. It may be added during formation of the first intimate blend, the second intimate blend, or both. Such materials include graft copolymers of polyolefins and C₄-C₁₂cyclic anhydrides, such as, for example, those available from ExxonMobil under the tradename EXXELOR® and from DuPont under the tradename FUSABOND®. Examples of suitable polyolefin-graft-cyclic anhydride copolymers are the polypropylene-graft-maleic anhydride materials supplied by ExxonMobil as EXXELOR® PO1020 and by DuPont as FUSABOND® M613-05. Suitable amounts of such materials, when present, may be readily determined and are generally about 0.1 to about 10 weight percent, based on the total weight of the composition. Within this range, a polyolefin-graft-cyclic anhydride copolymer amount of at least about 0.5 weight percent may be preferred. Also within this range, a polyolefin-graft-cyclic anhydride copolymer amount of up to about 5 weight percent may be preferred.
The one or more reinforcing fillers may be melt blended with the first intimate blend and the polyolefin during formation of the second intimate blend. Alternatively, the method may comprise an additional blending step in which the one or more reinforcing fillers are blended with the second intimate blend. In another alternative, it may be advantageous to add the reinforcing fillers, especially particulate fillers (i.e., those having an aspect ratio less than about 3), during formation of the first intimate blend.
The method may, optionally, comprise the addition of additives to the composition. Such additives may include, for example, stabilizers, mold release agents, processing aids, flame retardants, drip retardants, nucleating agents, UV blockers, dyes, pigments, particulate fillers (i.e., fillers having an aspect ratio less than about 3), antioxidants, anti-static agents, blowing agents, and the like. Such additives are well known in the art and appropriate amounts may be readily determined. There is no particular limitation on how or when the additives are added. For example, the additives may be added during formation of the first intimate blend. Alternatively, the additives may be added during formation of the second intimate blend. In another alternative, the additives may be added in a separate step following formation of the second intimate blend.
As the composition is defined as comprising multiple components, it will be understood that each component is chemically distinct, particularly in the instance that a single chemical compound may satisfy the definition of more than one component.
One embodiment is a method of preparing a thermoplastic composition, comprising: melt-blending about 10 to about 70 weight percent of a poly(arylene ether) and about 0.5 to about 30 weight percent of a compatibilizer to form a first intimate blend; and melt-blending the first intimate blend and about 10 to about 80 weight percent of a polyolefin to form a second intimate blend; wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin; and wherein all weight percents are based on the total weight of the composition.
Another embodiment is a method of preparing a thermoplastic composition, comprising: melt-blending about 10 to about 70 weight percent of a poly(2,6-dimethyl-1,4-phenylene ether), a poly(2,6-dimethyl-1,4-phenylene ether-co-2,3,6-trimethyl-1,4-phenylene ether), or a mixture thereof, and about 0.5 to about 30 weight percent of a styrene-(ethylene-butylene)-styrene triblock copolymer to form a first intimate blend; and melt-blending the first intimate blend and about 10 to about 80 weight percent of a homopolypropylene to form a second intimate blend; wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin; and wherein all weight percents are based on the total weight of the composition.
Another embodiment is a method of preparing a thermoplastic composition, comprising: melt blending a poly(arylene ether) and a compatibilizer to form a first intimate blend; and melt blending the first intimate blend and a polyolefin to form a thermoplastic composition consisting essentially of the poly(arylene ether), the compatibilizer, and the polyolefin. In this embodiment, the phrase “consisting essentially of” will be understood as excluding an amount of an additional component that substantially degrades a physical property of the composition. For example, it would exclude an amount of an additional component that reduces by more than 5% an objective measure of the composition's stiffness (e.g., flexural modulus measured at 25° C. according to ASTM D79), impact strength (e.g., notched or unnotched Izod impact strength measured at 25° C. according to ASTM D256), heat resistance (e.g., heat distortion temperature in ° C. measured according to ASTM D658), or blow moldability (e.g., hang time measured using 2.5 inch diameter low work screw with 24:1 ratio of parison length to outer diameter, a single cardioid head design, a step mold, a screw speed of 25 rotations per minute (rpm), a die gap of 35%, a blow air pressure of 80 psi, and a mold temperature of 80° C.). The percent change in an objective property value is measured in comparison to a corresponding composition without the additional component. In particular, the addition of an amount of block copolymer of an alkenyl aromatic compound and a conjugated diene to this composition would be expected to substantially decrease the composition's flexural modulus and tensile modulus. The addition of an amount of homopolystyrene would be expected to substantially decrease the heat distortion temperature and dispersed phase softening temperature.
Another embodiment is a method of preparing a thermoplastic composition, comprising: melt blending a poly(arylene ether), a poly(alkenyl aromatic) resin, and a compatibilizer to form a first intimate blend; and melt blending the first intimate blend, and a polyolefin to form a thermoplastic composition consisting essentially of the poly(arylene ether), the poly(alkenyl aromatic) resin, the compatibilizer, and the polyolefin. As above, the phrase “consisting essentially of” will be understood as excluding an amount of an additional component that substantially degrades a physical property of the composition.
Another embodiment is a method of preparing a thermoplastic composition, comprising: melt blending a poly(arylene ether), an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and a compatibilizer to form a first intimate blend; and melt blending the first intimate blend, and a polyolefin to form a thermoplastic composition consisting essentially of the poly(arylene ether), the unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, the compatibilizer, and the polyolefin. As above, the phrase “consisting essentially of” will be understood as excluding an amount of an additional component that substantially degrades a physical property of the composition.
Another embodiment is a thermoplastic composition prepared according to any of the above-described methods.
While the method has been described in terms of poly(arylene ether)-polyolefin blends, it is generally applicable to a wide variety of thermoplastic blends in which a stiffer (e.g., higher flexural modulus) polymer is to be dispersed in the matrix of a less stiff (e.g., lower flexural modulus) polymer to produce blends having consistently reproducible properties. Furthermore, while the method has been described in terms of upstream and downstream addition of components during a single extruder pass, the first and second intimate blends may be formed in separate passes. For example, the poly(arylene ether), the compatibilizer, and optional components may be added to an extruder to form a first intimate blend that is extruded into strands and pelletized. This pelletized first intimate blend may then be added to an extruder in a second pass, with downstream addition of the polyolefin and additional optional components to form the second intimate blend.
The method is particularly useful for thermoplastic blends comprising at least three components, where the first component is intended to form the matrix phase of the final blend, the second component is intended to be a dispersed phase, and the third component is intended to reside at least partially at the interface of the matrix phase and the dispersed phase. Thus, the method may comprise: melt-blending to form a first intimate blend comprising a dispersed phase component and an interfacial component; and melt-blending to form a second intimate blend comprising the first intimate blend and a matrix component.
The invention is further illustrated by the following non-limiting examples.

EXAMPLES 1-4, COMPARATIVE EXAMPLES 1, 2

Five formulations were compounded by various methods in a twin screw extruder. The components of the formulation are summarized in Table 1. The formulations and compounding methods are summarized in Table 2.
General Blending/Compounding Procedure: Using quantities specified in Table 1, components to be added upstream were hand mixed in a bag. The resulting mixture was subsequently mixed aggressively with a mechanical blender for uniformity. The uniform mixture was subsequently fed through a feeder and entered into an extruder at the extruder initial entry point. Downstream components were added at barrel 6 of a 10-barrel extruder.
General Extrusion: a 30 millimeter co-rotating twin-screw extruder was used. Blends were melt extruded at 520° F., 450-500 rpm, and a throughput rate of 30-50 pounds per hour. Melt from the extruder was forced through a three-hole die to produce melt strands. These strands were rapidly cooled by passing them through a cold-water bath. The cooled strands were chopped into pellets. Pellets were dried in an oven at 200° F. for 2-4 hours.
General Molding: ASTM parts were molded on a 120 tonne molding machine (manufacturer Van Dorn) at 450-550° F. barrel temperature and 100-120° F. mold temperature.
Parts were tested according to ASTM methods. Izod notched impact was measured at 23° C. according to ASTM D256. Heat distortion temperature (HDT) was measured at 66 psi and 264 psi on ⅛ inch samples according to ASTM D648. Flexural modulus and flexural strength were measured at 23° C. on ⅛ inch samples according to ASTM D790. Tensile strength at yield, tensile strength at break, and tensile elongation at break were measured at 23° C. according to ASTM D638. Where presented, standard deviations reflect measurements on three samples for heat distortion temperature measurements, and for five samples for other tests.

Results of property measurements are presented in Table 2. The results show that the Example 1 composition, consisting of poly(arylene ether), polypropylene, and styrene-(ethylene-butylene)-styrene copolymer, exhibits higher flexural modulus, higher flexural strength, higher heat distortion temperatures, and higher tensile strengths than the Comparative Example 1 composition that additionally comprises homopolystyrene and a styrene-butadiene-styrene block copolymer. The Example 1 composition, which was blended using downstream addition of polypropylene, also exhibits higher flexural modulus, higher flexural strength, and higher tensile strength at break than Comparative Example 2, which used upstream addition of polypropylene. The Example 2 composition, consisting of poly(arylene ether), polypropylene, styrene-(ethylene-butylene)-styrene copolymer, and homopolystyrene, exhibits higher flexural modulus, higher flexural strength, higher heat distortion temperatures, and higher tensile strengths than the Comparative Example 1 composition that additionally comprises a styrene-butadiene-styrene block copolymer. The Example 3 composition, consisting of poly(arylene ether), polypropylene, styrene-(ethylene-butylene)-styrene copolymer, and styrene-butadiene-styrene triblock copolymer exhibits higher heat distortion temperatures and higher tensile strengths than the Comparative Example 1 composition that additionally comprises homopolystyrene. The Example 4 composition, in which polypropylene addition was split upstream and downstream, exhibits higher notched and unnotched Izod impact strengths, and higher tensile strength at yield than Comparative Example 2, which used upstream addition of polypropylene.

TABLE 1


material
abbreviation	Description

PP	homopolypropylene, obtained as D-015-C2 from Sunoco
	Chemicals
SEBS	styrene-(ethylene-butadiene)-styrene copolymer, 66
	weight percent polystyrene, and obtained as TUFTEC ®
	H1043 from Asahi
PPE	poly(2,6-dimethyl-1,4-phenylene ether), IV = 0.46 dl/g,
	obtained from General Electric Company
SBS	styrene-butadiene-styrene block copolymer, obtained as
	KRATON ® D1101 from Kraton Polymers
xPS	homopolystyrene, obtained as PP-738 from Huntsman
	Chemical, MFI = 10.5 g/10 min at 200° C., 5 kg

TABLE 2


Ex. 1	Ex. 2	Ex. 3	C. Ex. 1	Ex. 4	C. Ex. 2

upstream components
PPE	50	20	40	15	50	50
xPS	—	30	—	25	—	—
SEBS	10	10	10	10	10	10
SBS	—	—	10	10	—	—
PP	—	—	—	—	20	40
downstream components
PP	40	40	40	40	20	—
properties
flex. mod., 23° C.,	243729 ± 432	274872 ± 1138	203940 ± 2844	215292 ± 511	241143 ± 1464	240795 ± 793
⅛ in. (psi)
flex. strength at yield	8569 ± 23	9754 ± 52	7205 ± 69	7161 ± 59	8429 ± 69	8424 ± 108
(psi)
HDT at 66 psi (° C.)	291.9 ± 1.2	236.0 ± 1.8	270.6 ± 4.3	211.04 ± 1.5	288.3 ± 2.2	294.0 ± 5.8
HDT at 264 psi (° C.)	201.9 ± 4.4	195.7 ± 1.4	172.1 ± 0.6	169.3 ± 0.5	196.6 ± 3.6	197.8 ± 2.7
notched Izod, 23° C.	1.4 ± 0.1	0.4 ± 0.0	1.7 ± 0.1	1.9 ± 0.1	1.9 ± 0.1	1.3 ± 0.1
(ft-lb/in)
unnotched Izod, 23° C.	36.6 ± 4.8	20.3 ± 3.7	no break	no break	no break	39.9 ± 2.6
(ft-lb/in)
tensile strength at yield,	6108 ± 67	7006 ± 37	5202 ± 10	5114 ± 14	6150 ± 23	6065 ± 45
23° C. (psi)
tensile strength at break,	5972 ± 85	4950 ± 63	4928 ± 85	4064 ± 41	5574 ± 253	5770 ± 57
23° C. (psi)
tensile elongation at break,	25.7 ± 2.6	58.2 ± 12.1	37.4 ± 4.4	93.7 ± 6.7	46.5 ± 14.9	31.7 ± 2.0
23° C. (%)

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
All cited patents, patent applications, and other references are incorporated herein by reference in their entirety.

Claims

1. A method of preparing a thermoplastic composition, comprising:

melt-blending

about 10 to about 70 weight percent of a poly(arylene ether), and

about 0.5 to about 30 weight percent of a compatibilizer

to form a first intimate blend; and

melt-blending

the first intimate blend, and

about 10 to about 80 weight percent of a polyolefin

to form a second intimate blend;

wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin; and

wherein all weight percents are based on the total weight of the composition.

2. The method of claim 1, wherein the melt-blending to form a first intimate blend comprises heating to a temperature of about 180° C. to about 400° C.

3. The method of claim 1, wherein the melt-blending to form a first intimate blend comprises mixing with at least two mixing elements.

4. The method of claim 1, wherein the melt-blending to form a first intimate blend and the melt-blending to form a second intimate blend collectively comprise mixing with a mixing energy input of at least about 0.20 kW-hr/kg.

5. The method of claim 1, wherein the first intimate blend further comprises a polyolefin in an amount not greater than that of the polyolefin added during formation of the second intimate blend.

6. The method of claim 1, wherein the poly(arylene ether) comprises a plurality of structural units of the formula:

wherein for each structural unit, each Q¹is independently halogen, primary or secondary C₁-C₈alkyl, phenyl, C₁-C₈haloalkyl, C₁-C₈aminoalkyl, C₁-C₈hydrocarbonoxy, or C₂-C₈halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q²is independently hydrogen, halogen, primary or secondary C₁-C₈alkyl, phenyl, C₁-C₈haloalkyl, C₁-C₈aminoalkyl, C₁-C₈hydrocarbonoxy, or C₂-C₈halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms.

7. The method of claim 6, wherein each Q¹is independently C₁-C₄alkyl or phenyl, and each Q²is independently hydrogen or methyl.

8. The method of claim 1, wherein the poly(arylene ether) has an intrinsic viscosity of about 0.2 to about 0.6 dL/g as measured in chloroform at 25° C.

9. The method of claim 1, wherein the poly(arylene ether) comprises a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol.

10. The method of claim 1, wherein the compatibilizer comprises a hydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene compound.

11. The method of claim 10, wherein the hydrogenated block copolymer comprises:

(A) at least one block derived from an alkenyl aromatic compound having the formula

wherein R²and R³each represent a hydrogen atom, a C₁-C₈alkyl group, or a C₂-C₈alkenyl group; R⁴and R⁸each represent a hydrogen atom, a C₁-C₈alkyl group, a chlorine atom, or a bromine atom; and R⁵-R⁷each independently represent a hydrogen atom, a C₁-C₈alkyl group, or a C₂-C₈alkenyl group, or R⁴and R⁵are taken together with the central aromatic ring to form a naphthyl group, or R⁵and R⁶are taken together with the central aromatic ring to form a naphthyl group; and

(B) at least one block derived from a conjugated diene, in which the aliphatic unsaturated group content in the block (B) is reduced by hydrogenation.

12. The method of claim 10, wherein the hydrogenated block copolymer is hydrogenated to such a degree that less than 20% of the aliphatic unsaturation derived from the conjugated diene remains unreduced.

13. The method of claim 10, wherein the hydrogenated block copolymer has an alkenyl aromatic content of about 10 to about 90 weight percent.

14. The method of claim 10, wherein the hydrogenated block copolymer has an alkenyl aromatic content of about 50 to about 90 weight percent.

15. The thermoplastic composition of claim 10, wherein the hydrogenated block copolymer comprises a styrene-(ethylene-butylene)-styrene triblock copolymer.

16. The thermoplastic composition of claim 10, wherein the hydrogenated block copolymer comprises a styrene-(ethylene-butylene) diblock copolymer.

17. The method of claim 1, wherein the compatibilizer comprises a polyolefin-poly(alkenyl aromatic) copolymer selected from polyolefin-poly(alkenyl aromatic) graft copolymers, polyolefin-poly(alkenyl aromatic) diblock copolymers, polyolefin-poly(alkenyl aromatic) multiblock copolymers, polyolefin-poly(alkenyl aromatic) radial block copolymers, and mixtures thereof.

18. The method of claim 17, wherein the polyolefin-poly(alkenyl aromatic) copolymer comprises a polypropylene-polystyrene graft copolymer comprising about 50 to about 85 weight percent of a propylene polymer backbone and about 15 to about 50 weight percent of one or more styrene polymer grafts.

19. The method of claim 1, wherein the polyolefin comprises a homopolymer or copolymer having at least about 80 weight percent of units derived from polymerization of ethylene, propylene, butylene, or a mixture thereof.

20. The method of claim 1, wherein the polyolefin is a propylene polymer comprising a homopolymer of polypropylene; or a random, graft, or block copolymer of propylene and at least one olefin selected from ethylene and C₄-C₁₀alpha-olefins; with the proviso that the copolymer comprises at least about 80 weight percent of repeating units derived from propylene.

21. The method of claim 1, wherein the polyolefin comprises a homopolypropylene.

22. The method of claim 1, wherein the first intimate blend further comprises about 1 to about 20 weight percent of an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene compound; wherein the unhydrogenated block copolymer comprises a styrene-butadiene diblock copolymer or a styrene-butadiene-styrene triblock copolymer.

23. The method of claim 1, wherein the first intimate blend further comprises about 1 to about 20 weight percent of an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene compound.

24. The method of claim 23, wherein the wherein the unhydrogenated block copolymer comprises a styrene-butadiene diblock copolymer or a styrene-butadiene-styrene triblock copolymer.

25. The method of claim 1, wherein the first intimate blend and/or the second intimate blend further comprises a reinforcing filler.

26. The method of claim 1, wherein the first intimate blend and/or the second intimate blend further comprises an additive selected from stabilizers, mold release agents, processing aids, flame retardants, drip retardants, nucleating agents, UV blockers, dyes, pigments, antioxidants, antistatic agents, and combinations comprising at least one of the foregoing additives.

27. The method of claim 1, wherein

wherein the poly(arylene ether) comprises a poly(2,6-dimethyl-1,4-phenylene ether), a poly(2,6-dimethyl-1,4-phenylene ether-co-2,3,6-trimethyl-1,4-phenylene ether), or a mixture thereof;

wherein the compatibilizer comprises a styrene-(ethylene-butylene)-styrene triblock copolymer;

wherein the polyolefin comprises a homopolypropylene; and

wherein the thermoplastic composition is substantially free of at least one component selected from (a) an unhydrogenated block copolymer of an alkenyl aromatic compound and a conjugated diene, and (b) a poly(alkenyl aromatic) resin.

28. A method of preparing a thermoplastic composition, comprising:

melt blending

a poly(arylene ether) and

a compatibilizer

to form a first intimate blend; and

melt blending

the first intimate blend and

a polyolefin

to form a thermoplastic composition consisting essentially of the poly(arylene ether), the compatibilizer, and the polyolefin.