MXPA97001925A - High impa polyphenylene ether compositions - Google Patents

Abstract

Thermoplastic compositions of poly (phenylene ether) (PPE) having improved impact strength and reduced modulus loss are disclosed. These compositions are based on a mixture of PPE and an elastomeric interpolymer of a C1 to C4 isomonoolefin, for example isobutylene, and a para-alkylstyrene co-monomer, for example para-methylstyrene, the interpolymer may also contain benzylic functional groups such as halogen

Description

COMPOSITIONS OF HIGH IMPACT POLYPHENYLENE ETHER BACKGROUND OF THE INVENTION The invention relates to more tenacious polymeric compositions based on a poly (phenylene ether) physically mixed with an isomonoolefin / para-alkylstyrene copolymer. Poly (phenylene ether) (PPE) resins are well-known engineering thermoplastics having melt viscosities and relatively high softening points, for example of more than about 275 ° C. These polymers are useful in many applications where good mechanical properties and heat resistance are required. On the negative side, PPEs generally suffer from poor impact resistance and poor processing capacity. For example, the Izod impact resistance with notch at room temperature of PPEs is generally less than 1 ft.-lb / in. The intrinsic viscosity of a typical PPE is around 0.50, which is not suitable for processing by the usual injection molding techniques. U.S. Patent No. 3,383,435 teaches that the processing characteristics of PPE resins can be improved by forming physical blends of PPE and compatible styrene polymers, for example polystyrene or copolymers of styrene with acrylonitrile. Impact properties are also improved using high impact polystyrene as a physical blend component. The high impact polystyrene is a product that can be prepared by polymerization in styrene solution in the presence of a dissolved elastomer, for example cis-polybutadiene, such that the final product consists of a polystyrene matrix having from about 1 to 20% by weight of a discrete phase of polybutadiene particles dispersed therein. Other polymeric additives used to improve the impact and processing properties of PPE include block copolymers of hydrogenated styrene / butadiene / styrene, as described, for example, by J.P. Kirkpatrick et al., Elastomerics, October 30, 1988, p. 30-32. A disadvantage of using an impact modifier containing polybutadiene is that the polybutadiene segment tends to partially degrade at the high temperature required to process PPE, for example 290 ° C or more. The use of hydrogenated styrene / butadiene / styrene block copolymers as an impact modifier generally results in a composition having a substantially reduced modulus which is undesirable in many applications. SUMMARY OF THE INVENTION The present invention provides thermoplastic polymer compositions having improved impact strength and reduced modulus loss, comprising a physical mixture of: a) a poly (phenylene ether) polymer; and b) an interpolymer of a C4 to C7 isomonoolefin containing from about 0.5 to 20 mol% para-alkylstyrene-non-copolymerized. Preferred physical mixtures contain from about 1 to 100 parts by weight of isomonoolefin interpolymer per 100 parts by weight of PPE. The isomonoolefin interpolymer also includes functionalized interpolymers prepared by replacing a portion of benzyl hydrogen with functional groups such as halogen or other functional groups such as acrylics. The composition may also contain one or more additional modifying polymers such as an olefin polymer and / or a styrene-based polymer. The compositions can be physically mixed in the molten state and molded or extruded to form molded articles exhibiting improved impact, modulus and stiffness properties. Detailed Description of the Invention The C4-C7 / para-alkylstyrene isoolefin interpolymers used in the invention are random copolymers of a C4 to C7 isomonoolefin, such as isobutylene and a para-alkylstyrene co-monomer, preferably para-methylstyrene. containing at least about 80%, more preferably at least about 90% by weight of the para-isomer, and also include functionalized interpolymers wherein at least some of the alkyl substituent groups present in the monomeric styrene units contain halogen or some other functional group. Preferred materials can be characterized as isobutylene interpolymers containing the following monomer units spaced randomly along the polymer chain: 1. where R and R 'are independently hydrogen, lower alkyl, preferably C: to C7 alkyl and X is a functional group such as halogen. Preferably, R and R 'are each hydrogen. Up to about 60 mol% of the para-alkylstyrene present in the interpolymer structure may be the above functionalized structure (2). Where monomer units 2 are absent in the above formula, then the isomonoolefin interpolymer is non-functionalized, ie it is a random copolymer of isomonoolefin and para-alkylstyrene. Most preferred of such interpolymers are copolymers of isobutylene and para-methylstyrene containing from about 0.5 to about 20 mol% para-methylstyrene randomly copolymerized along the polymer chain. Where monomer units 2 in the above formula are present, the isomonoolefin interpolymer is at least one terpolymer containing from about 0.5 to 60 mol% of monomeric units 2 functionalized based on the content of the aromatic monomer units 1 and 2. The functional group X can be halogen or some other functional group incorporated by a nucleophilic substitution of benzyl halogen with other groups such as alkoxide, phenoxide, carboxylate, thioether, thioether, thiocarbamate, dithiocarbamate, thiourea, xanthate, cyanide, malonate, amine, amide , carbazole, phthalamide, maleimide, cyanate and their mixtures. These functionalized isomonoolefin interpolymers and their method of preparation are more particularly disclosed in U.S. Patent No. 5,162,445, the full disclosure of which is incorporated herein by reference. Most useful of such functionalized materials are random elastomeric interpolymers of isobutylene and para-methylstyrene containing from about 0.5 to about 20 mol% para-methylstyrene, where up to about 60 mol% of the methyl substituent groups present in the benzyl ring they contain a bromine or chlorine atom, preferably a bromine atom. These polymers have a substantially homogeneous composition distribution such that at least 95% by weight of the polymer has a para-alkylstyrene content within 10% of the average para-alkylstyrene content of the polymer. More preferred polymers are also characterized by a narrow molecular weight distribution (M / Mn) of less than about 5, more preferably less than about 2.5, a preferred viscosity average molecular weight in the range of about 200,000 to about of 2,000,000, and a preferred number average molecular weight in the range of about 25,000 to about 750,000, as determined by gel permeation chromatography. The interpolymers can be prepared by slurry polymerization of the monomer mixture using a Lewis acid catalyst, followed by halogenation, preferably bromination, in solution in the presence of halogen and a radical initiator such as heat and / or light and / or a chemical initiator. Preferred interpolymers are brominated interpolymers generally containing from about 0.1 to about 5 mol% bromomethyl groups, most of which are monobromomethyl, with less than 0.05 mol% of dibromomethyl substituents present in the copolymer. The most preferred interpolymers contain from about 0.05 to about 2.5% by weight of bromine based on the weight of the interpolymer, most preferably from about 0.05 to 0.75% by weight of bromine, and are substantially free of ring halogen or halogen in the chain of the polymeric backbone. These interpolymers, their method of preparation, their method of curing and grafting, or functionalized polymers derived therefrom, are disclosed more particularly in U.S. Patent No. 5,162,445 referred to above. Poly (phenylene ether) (PPE) thermoplastic engineering resins that are modified in accordance with this invention are well known, commercially available materials produced by oxidative coupling polymerization of substituted alkyl phenols. They are generally linear, amorphous polymers, having a glass transition temperature in the range of about 190 to 235 ° C. Preferred PPE materials comprise the structure: where Q is a monovalent substituent group selected from halogen, hydrocarbon having less than 8 carbon atoms, hydrocarbonoxy and halohydrocarbonoxy. More preferably, Q is an equal or different alkyl group having from 1 to 4 carbon atoms and n is an integer of at least 100, preferably from 150 to about 1,200. Examples of preferred polymers are poly (2,6-dialkyl-1, 4-phenylene ether) such as poly (2,6-dimethyl-1, 4-phenylene ether), poly (2-methyl-6-methyl ether) ethyl-1, 4-phenylene), poly (2-methyl-6-propyl-1, 4-phenylene ether), poly (2,6-dipropyl-1, 4-phenylene ether) and poly (2-phenyl ether). -ethyl-6-propyl-1, 4-phenylene). In order to achieve improved properties of impact resistance and processing, the PPE and the isomonoole-fine interpolymer (I-PMS) are physically mixed in the melted state in a ratio in the range of about 1 to about 100 parts by weight of I-PMS per 100 parts by weight of PPE, more preferably from about 5 to about 50 parts by weight of I-PMS, and most preferably from about 15 to 50 parts by weight of I-PMS per 100 parts by weight of PPE. As mentioned before, physical mixtures that contain PPE and the isomonoolefin interpolymer additive exhibit improved physical properties compared to PPE without the added interpolymer. It has been found that these properties are even more improved where the interpolymer contains a benzyl functional group such as halogen, for example bromine, which is capable of interacting with PPE under mixing conditions. It is believed that these improved properties are achieved as a result of a chemical interaction between benzyl halogen, for example bromine, present in the halogenated interpolymer and displaceable hydrogen present in the PPE, preferably an electrophilic substitution reaction, which occurs when the polymers are mixed physically in a melted state at a temperature in the range of about 280 to about 310 ° C. This reaction can be further promoted by the inclusion of a catalyst in the formulation, which will promote the electrophilic substitution reaction, such as zinc oxide, magnesium oxide, zinc bromide, ferric chloride, and the like. These promoters can be added at a level in the range of about 0.01 to about 1.5% by weight, more preferably from about 0.05 to about 0.5% by weight, based on the content of the halogenated interpolymer present in the composition . The I-PMS interpolymer has a saturated structure of the spine, which makes it very stable during physical mixing in the melted state, unlike impact modifiers of the prior art, which contain unsaturated diolefin polymers, for example polybutadiene. Accordingly, the components of the physical mixture can be combined using any mixing device in a suitable melted state, such as a Banbury mixer, or most preferably a mixer / extruder. Preferred mixing temperatures in the melted state are in the range of about 270 to about 320 ° C, more preferably from about 280 to about 310 ° C, for a sufficient mixing time to achieve uniform dispersion of the interpolymer I-PMS within the PPE matrix, usually around 0.5 to about 4 minutes. The melt-state processing capacity of the composition can be further controlled by including an aromatic vinyl polymer or copolymer in the composition.

Examples of such polymers are polystyrene and styrene copolymers with less than 50% by weight of acrylonitrile. A good balance between impact resistance and processability can be achieved by varying the content of the aromatic vinyl polymer in the PPE / I-PMS physical mixtures. The level of addition of the aromatic vinyl polymer may also vary from about 1 to about 100 parts by weight per 100 parts by weight of PPE, more preferably from about 5 to about 60 parts by weight per 100 parts by weight of PPE. Since the I-PMS interpolymer is quite sticky even at room temperature, it may be desirable to first form a master-charge composition of I-PMS mixed with another polymer such as an olefin polymer, physically mix in the melted state and extrude the mixture to form pearls not sticky. The formation of pearls facilitates the combination. These beads can then be physically mixed in the melted state with PPE to form the compositions of this invention. Suitable olefin polymers include one or a mixture of crystallizable polymers such as polypropylene, high density polyethylene, and ethylene / propylene copolymers as well as amorphous polymers such as low density polyethylene and ethylene / propylene copolymers and up to 10% by weight of a non-conjugated diene such as norbornadiene, 1,4-hexadiene, dicyclopentadiene, and the like. Generally speaking, these physical pre-mixes of master filler may contain from about 20 to 95% by weight of the I-PMS copolymer and the remainder one or a mixture of the olefin polymers. The tackiness can also be reduced by prepolishing the I-PMS copolymer, for example a brominated I-PMS copolymer, with zinc oxide or another of the above-described pulverized reaction promoters. The compositions of this invention may also include effective amounts of other ingredients normally included in the PPE compositions including anti-oxidants, pigments, colorants, fillers, plasticizers and the like. The following examples are illustrative of the invention. The material identified in the following description as Exxpro (brand) elastomer is a brominated interpolymer of isobutylene and para-methylstyrene (PMS) containing 4.7% by weight of PMS, 0.15% by mole of benzylated brominated PMS (measured by NMR), 0.35% by weight. bromine weight based on the weight of the polymer (measured by X-ray fluorescence), and the interpolymer has a viscosity average molecular weight of 350,000, measured as a solution diluted in diisobutylene at 20 ° C. The material identified as XP-50 is a non-functionalized isobutylene copolymer containing 5% by weight of PMS having a viscosity average molecular weight of 300,000, measured as a solution diluted in diisobutylene at 20 ° C. Other materials referred to below are commercially available, as follows: The compositions of the examples were prepared by physically blending all the components (including 0.5% by weight of an anti-oxidant) in a melted state into a 0.8 in (20 mm) counter-rotating twin screw extruder Welding Engineers, equipped with two zones of feeding and a filament die at the exit of the extruder. With respect to the compositions containing zinc oxide, ground particles of the Exxpro (brand) polymer were pre-powdered with zinc oxide powder before adding the material to the mixer / extruder. The compositions were mixed and extruded on a product temperature profile of 250 to 320 ° C. The extruded filaments were cooled in a water bath before being formed into 5 x 5 mm beads. The resulting beads were dried to remove any surface moisture present. Mechanical tests were obtained by molding the beads into mechanical molding bars using a 15-ton injection molding machine Boy (registered trademark). The tests were carried out according to the following procedures.

Composition A shows the properties of the PPE control (PPO (R) N640), which has an Izod impact resistance at room temperature of 0.6 ft-lb / in. PPE compositions modified with both XP-50 and Exxpro exhibited 5 improved Izod impact properties when compared to control composition A. Exxpro elastomer-modified PPE (composition C) has an Izod impact resistance with 9.2 ft notch. -lb / in, which is a further improvement over PPE modified with XP-50 elastomer (composition B, 5.6 ft-lb / in), demonstrating the importance of the functional group of benzyl bromide. The physical mixture of PPE / Exxpro is also more tenacious than the physical mixture of PPE / Kraton (R) G-1650 (composition D, 8.5 ft-lb / in). Furthermore, the physical mixture of PPE / Exxpro has a higher flexural modulus and higher tensile strength than both physical mixtures of PPE / XP-500 and PPE / Kraton (R) G-1650. Likewise, since the latter contains 33% by weight of polystyrene (PS) in the form r- 'of block, while the elastomer Exxpro does not contain plastic segment, if the elastomers Kraton (R) G-1650 and Exxpro were compared with base in net rubber content, the use of the first would possibly lead to even less stiffness and impact resistance. Example 2 Four additional physical mixtures were prepared as in Example 1 above, except that the PPE material used was a physical pre-mix of PPE and polystyrene (PS). As in the case of Example 1 A series of four different physical mixtures (A-D) having the composition shown in Table 1 was prepared, as described above. Physical mixture C (containing the Exxpro polymer) also contains 0.1% by weight of zinc oxide powder based on the weight of the Exxpro polymer. Sample A is a control that does not contain added polymeric modifiers and samples B-D contain 20% by weight of the modifying polymers indicated in Table 1. Table 1 - Physical Mixtures with PPE as Matrix At the same time, the physical mixture C also contains 0.1% by weight of zinc oxide, based on the weight of the Exxpro polymer, the formulations and the test data are shown in Table 2. Table 2 - Physical Mixtures with PPE / PS 70/30 Mixture as Matrix * Temperature ta ta n, samples e 1"Due to the added polystyrene, the resultant physical mixtures EH all have a lower resistance to Izod impact.PPE compositions modified with both Exxpro and XP-50 exhibited improved impact properties compared to the control PPE modified with the Exxpro elastomer (composition G) has an Izod impact resistance with notch of 2.7 ft-lb / in, which is a further improvement over PPE modified with the XP-50 elastomer (composition F, 1.4 ft- lb / in), demonstrating again the importance of the functional group of benzyl bromide The physical mixture of PPE / Exxpro has a Izod impact with slightly less notch than the physical mixture of PPE / Kraton (R) G-1650 (composition H, 3.0 ft-lb / in). Again, the physical mixture of PPE / Exxpro has a higher flexural modulus and a higher tensile strength than both physical mixtures of PPE / XP-50 and PPE / Kraton (R) G-1650. Example 3 Four additional physical mixtures (I-L) were prepared, containing varying amounts of the Exxpro elastomer. The composition and the mechanical property data for these physical mixtures are compared with the mixtures C and G as prepared above in Table 3. As in the case of the above physical mixtures based on Exxpro, the compositions contain all 0.1% in weight of zinc oxide, based on the weight of the Exxpro polymer. The results show an improvement in the impact properties when the Exxpro elastomer level is increased in the range of 10 to 20%.

Table 3 - Physical Mixtures Containing Different Amounts of the Exxpro Elastomer * Temperature at tac, samples e 1

Claims (21)

1. CLAIMS 1. A thermoplastic polymer composition, comprising a physical mixture of: a) a poly (phenylene ether) polymer; and b) an interpolymer of a C4-C7 isomonoolefin containing from about 0.5 to about 20 mol% of copolymerized para-alkylstyrene. The composition of claim 1, wherein said composition contains from about 1 to about 100 parts by weight of said interpolymer per 100 parts by weight of said poly (phenylene ether). 3. The composition of claim 1, wherein said isomonoolefin is an isobutylene and said para-alkylstyrene is para-methylstyrene. The composition of claim 1, wherein said interpolymer is an isobutylene polymer containing the following aromatic monomer units spaced randomly along the chain where R and R 'are independently hydrogen or Cx to C4 alkyl, and X is a functional group. The composition of claim 4, wherein the monomeric units containing X comprise from about 0.5 to 60 mol% of the total content of said aromatic monomer units present in said interpolymer. 6. The composition of claim 4, wherein X is halogen. The composition of claim 6, wherein R and R 'are each hydrogen and X is bromine present in said interpolymer at a level of less than about 2.5% by weight. The composition of claim 7, wherein bromine is present in said interpolymer at a level of from about 0.05 to about 0.75% by weight. The composition of claim 2 or 7, wherein said composition contains from about 5 to about 60 parts by weight of said interpolymer per 100 parts by weight of said poly (phenylene ether). The composition of claim 1, wherein said polyphenylene ether comprises the structure: where Q is an equal or different alkyl group having from 1 to 4 carbon atoms and n is an integer of at least 100. The composition of claim 10, wherein said poly (phenylene ether) is poly (ether of 2, 6-dimethyl-1, 4-phenylene). The composition of claim 1 or 7, further containing from about 1 to about 100 parts by weight of an aromatic vinyl polymer per 100 parts by weight of said poly (phenylene ether). The composition of claim 12, wherein said aromatic vinyl polymer is polystyrene. The composition of claim 6, further containing from about 0.01 to about 1.5% by weight of an electrophilic reaction promoter, based on the weight of said interpolymer present in the composition. 15. The composition of claim 14, wherein said reaction promoter is zinc oxide. 16. A process for improving the physical properties of a poly (phenylene ether), comprising forming a mixture of poly (phenylene ether) and an interpolymer of a C4-C7 isomonoolefin containing from about 0.5 to about 20% by weight of copolymerized para-alkylstyrene and mixing said mixture in the melted state at a temperature in the range of about 270 to 320 ° C until a uniform physical mixture is obtained. The process of claim 16, wherein said mixture contains from about 1 to about 100 parts by weight of said interpolymer per 100 parts by weight of said poly (phenylene ether). The process of claim 17, wherein said interpolymer is a brominated polymer of isobutylene and para-methylstyrene. The process of claim 18, wherein said mixture further contains from about 0.01 to about 1.5% by weight of zinc oxide, based on the weight of said brominated interpolymer present in the composition. 20. A shaped article, prepared from the composition of claim 1 or 6. The composition of claim 12, wherein the vinyl aromatic polymer is in the range of 1 to 60 parts by weight of the poly (phenylene ether) ).