COMPATIBILIZED BLENDS OF SYNDIOTACTIC POLYSTYRENE WITH FURTHER THERMOPLASTIC POLYMERS

Abstract: Polymeric compositions exhibiting improved physical properties are provided from blends of polystyrene having a syndiotactic configuration and thermoplastic polymers which are compatibilized using acid functional polymers which are fully or partially neutralized with a metal counter ion.

Description: TITLE COMPATIBILIZED BLENDS OF SYNDIOTACTIC POLYSTYRENE WITH FURTHER THERMOPLASTIC POLYMERS This application claims the benefit of Preliminary Application 5 Number 60/030,412, filed November 4, 1996. BACKGROUND OF THE INVENTION This invention relates to blends of polystyrene with thermoplastic polymers which are compatibilized to provide improved properties. More particularly, the invention relates to syndiotactic polystyrene, hereinafter referred 10 to as SPS, with polyamides or polyesters compatibilized by compatibilizers as described in detail below which are suitable for preparing articles by melt processing. It is well known in the art to prepare molded articles from blends of SPS and thermoplastic polymers. Various compatibilizers have been disclosed. 15 Compatibilization of polymer blends usually means preparing a stable, fine dispersion or co-continuous network of one polymer in another and may be defined by a variety of techniques. Improving the compatibilization between the blend components determines, in part, the desirable physical properties of the blend. The utility of polymer blends is often defined by their physical properties, 20 e.g. toughness, stiffness, strength, heat resistance, etc. The toughness of the polymer blends is often limited by the presence of large domains of the dispersed polymer which act as flaws within the molded article. Indicators of improved compatibilization include, for example, increased tensile elongation, reduced delamination tendency, increased ductility and/or improved phase morphology 25 stabilization. The test area of a tensile specimen comprises a large portion of the volume of a molded part in which a few large particles may be present so tensile testing is an often used technique to determine improved compatibility by comparing percent elongation at break. SUMMARY OF THE INVENTION 30 The present invention resides in the discovery that flaws resulting from poorly dispersed particles in blends of SPS and thermoplastic polymers can be significantly reduced or eliminated by fully or partially neutralizing acid functional polymers which are used as compatibilizers with zinc, magnesium, lithium, or other metal counter ions or combinations of metal counter ions. 35 Alternatively, previously neutralized acidic monomers such as zinc acrylate and the like may be used in the polymerization or functionalization of previously prepared polymers. Alternatively, acid functional polymers may be partially reacted with polyether alcohols and amine terminated polyethers. A composition of this invention comprises (a) a syndiotactic polystyrene,(b) a thermoplastic resin, and (c) a compatibilizer for components (a) and (b). Further, the composition comprises from 1 to 99% by weight of component (a), from 1 to 99% by weight of component (b), and an amount of component (c) sufficient to increase the percent elongation over the elongation of a blend of (a) and (b) alone by at least about 15% relative to the elongation of a blend of components (a) and (b) wherein the compatibilizer has an acid functionality which is partially or fully neutralized by a metal counter ion. DETAILED DESCRIPTION The polystyrene of component (a) is a styrene-based resin with a syndiotactic configuration. The styrene based resin includes polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(alkoxystyrene), poly(vinyl benzoic ester), and their mixtures or copolymers containing the above polymers as the main components. Polyamides and polyesters useful in this invention may be prepared from a cyclic ring opening polymerization, a condensation polymerization or a combination thereof. The polyamides or polyesters may be homopolymers, copolymers, terpolymers, or blends of homo and/or copolymers. The polyamides or polyesters may be liquid crystalline in nature. Furthermore, they may be previously compounded with other additives such as tougheners, plasticizers, fillers, reinforcing agents, antioxidants, stabilizers and the like. The blends of the invention include from 1 to 99% by weight polystyrene, from 1 to 99% by weight thermoplastic resin, and from 1 to 30% by weight compatibilizer, based upon the total weight of polystyrene, polyamide, polyester and compatibilizer only, wherein the sum of weight percentages of polystyrene, polyamide, polyester and compatibilizer polymer level equal 100%). Preferred compositions contain from 20 to 80% by weight polystyrene, 20-80% by weight thermoplastic resin and 2 to 25% by weight compatibilizer. Particularly preferred compositions contain 30 to 70% by weight of polystyrene, 30 to 70% by weight thermoplastic resin and 3 to 20% by weight compatibilizer. The compatibilizer may be selected from the following compatibilizers A through D which follow in which the acid functionality has been partially or fully neutralized by a metal counter ion. Compatibilizers described in E through L do not require neutralization. They function to compatibilize, or reduce interfacial energy between the two components, by use of (a) a polymer having intermediate polarity, or (b) block copolymers whose block segments are compatibile with either the thermoplastic resin or SPS, or (c) polymers being almost miscible in one component (usually SPS) with structures capable of complexing with the other (usually hydrogen bonding by nylon). A. Polymers of styrene and/or cyclohexylmethacrylate or other methacrylate or acrylate esters with aliphatic or aromatic esters with four or a greater number of carbon atoms such as phenyl or benzyl, and an acid functional monomer such as methacrylic acid, acrylic acid, a sulfonic acid, or the like or an epoxide functional monomer such as glycidyl methacrylate. Although not strictly speaking acid or anhydride functionality, epoxy groups are capable of reacting with the end groups of the thermoplastic polymers as well as the neutralizing inorganic compounds such as lithium hydroxide, magnesium hydroxide and the like. Acid functionality is meant to include 1,2-diacids and anhydrides formed from them such as maleic anhydride, fumaric acid, and the like. The acid functionality may be from 0.1 to 25% of the weight of the polymer. Different levels are useful for different purposes. For example, a low level of anhydride may be adequate for a moderately dispersed blend of at a low level and a high level of a weak acid desired when both dispersion and melt viscosity needs to be extreme. The polymer may be prepared by commonly used techniques such as free radical initiation, group transfer polymerization or other known in the art. Optionally, ethyl acrylate may be present in the polymer to enhance thermal stability. B. The acid, anhydride, or epoxide functionality may be added to the compatibilizer after it is polymerized by a variety of techniques including free radical grafting, nitrene addition (e.g., reaction with a functionalized sulfonyl azide) various oxidation processes, shear induced cleavage generating reactive moieties that subsequently graft the functionalizing monomers, and the like. C. Blends of a styrenic polymer or polymers with one or more polyamides where the compatibilizing agent is a polyamide grafted with polystyrene, polycyclohexyl methacrylate, or polyphenylene oxide. Combinations of these unsaturated monomers with moderate levels of other monomers such as ethyl acrylate are also effective. D. Blends of a styrenic polymer or polymers with one or more polyamides where the compatibilizing agent is prepared in situ by grafting an unsaturated acid or epoxy moiety onto the styrenic polymer, with or without a free radical initiator, and dispersing in the polyamide without isolating the compatibilizer. E. Blends of a styrenic polymer or polymers with one or more polyamides where the compatibilizing agent contains blocks of poly ethers compatible with the styrenic polymer such as polyethylene oxide, polypropylene oxide, and the like and blocks of a polyamide. F. Blends of a styrenic polymer or polymers with one or more polyamides where the compatibilizing agent is a highly aliphatic polyamide homopolymer or copolymer containing, but not limited to, nylon 612, 11, 12, dimer acid and/or aromatic nylon components. G. Blends of a styrenic polymer or polymers with one or more polyamides where the compatibilizing agent is a styrene or cyclohexyl methacrylate containing polymer with 1% or greater phenol functionality. H. Blends of a styrenic polymer or polymers with one or more polyesters where the compatibilizing agent is a polyester grafted with polystyrene, polycyclohexyl methacrylate, or polyphenylene oxide. Combinations of these unsaturated monomers with moderate levels of other monomers such as ethyl acrylate is also claimed. I. Blends of a styrenic polymer or polymers with one or more polyesters where the compatibilizing agent is prepared in situ by grafting an unsaturated acid or epoxy moiety onto the styrenic polymer, with or without a free radical initiator, and dispersing in the polyester without isolating the compatibilizer. J. Blends of a styrenic polymer or polymers with one or more polyesters where the compatibilizing agent contains blocks of polyethers compatible with the styrenic polymer such as polyethylene oxide, polypropylene oxide, and the like and blocks of a polyester. K. The blends disclosed above may also include a polymer or copolymer containing imidized groups or hydroxyl groups as an additive or compatibilizer. L. Another class of related compatibilizers are reaction products of a styrene/anhydride copolymer with other functional oligomers or polymers such as amine or hydroxy terminated polyethers. The above described compatibilizing components which have acid functionality are either fully or partially neutralized by metal counter ions such as zinc, magnesium, manganese, and lithium. Alternatively, previously neutralized monomers such as zinc acrylate and the like may be used in the polymerization. The acid functional polymers may be reacted with polyether alcohols and amine terminated polyethers. Included in this invention are blends as set forth above where the morphology is that of one phase dispersed within the other. Also included are blends as set forth above where the morphology is that of a co-continous network. The blends of this invention may include additives such as lubricants, mold release agents, antioxidants, UV stabilizers, fire retardants, glass fibers and flake, minerals, particulate solids, carbon black, rubber tougheners, nucleants, pigments, antistatic additives, fibers of fluoropolymers, fibers of aramides, and the like commonly used in polymers to enhance properties or processing may be present in either or both phases. Fillers which may be added to the blends of this invention include: conductive fillers such as polyaniline and polypyrrole, metal fibers, organic and/or inorganic powders coated with metals, or nanoparticles. Depending on the particular filler selected, up to 50% by weight, based on the total weight of the composition, of filler may be added Generally, an amount from 5 to 40% will be used. The blends may be fabricated by extrusion or injection molding or structural foam molding, or gas assisted molding to make hollow injection molded parts. These blends may be extruded into sheets/films which then could be thermoformed to make large and small parts, or the blends may be blowmolded. The blends may also be made into fibers by extrusion processes or melt blown processes. These fibers, optionally combined with reinforcing fillers such as carbon or glass fibers, may be made into paper like sheets, and formed into composite articles. The blends may be used to coat optical fibers via a melt process or a powder coating process. The blends are also useful in encapsulating electrical components, chips, or other microelectronics. The powders from these blends may be processed by rotational molding. These blends may be melt fabricated into useful articles. Examples of articles which may be made from the blends of this invention include automotive parts, electronics, electrical and industrial parts. These may also include radiator headers, end tanks, intake manifolds, parts for electronics/electrical applications, overmolded electrical parts, paintable parts such as automotive body parts, electrostatically paintable parts (without additional pretreatment), panels and tubings and parts for plastic heat exchangers, plastic water heaters, insulation, thermoformed parts such as automotive/industrial panels and body parts, encapsulated electrical transformers, light weight panels for electric/hybrid vehicles, and rigid, foamed/thermoformed parts for floating devices such as boats. EXAMPLES The invention is further illustrated by the following examples in which parts and percentages are by weight unless otherwise indicated. Preparation of samples: Blends were prepared by either mixing and tumbling together pellets or other forms of the ingredients in a plastic bag prior to feeding into the intensive melt mixing device or by co-feeding several of the ingredients independently. Glass is usually co-fed since it usually is incorporated into the compounds part way down the extruder rather than at the rear to minimize fiber attrition. Melt mixing can be accomplished on any device capable of developing high shear such as an extruder, co-kneaders, continuous Banburys, multiple barrel devices, etc., that possess sufficient length and adequate geometry required for the specific blends. Blends described below were prepared on either a Werner and Pfleiderer 28mm trilobal, corotating twin screw extruder or a Werner and Pfleiderer 30mm bilobal, corotating twin screw extruder. Both used a severe screw design with several sets of neutral kneading blocks followed by a reverse in the rear and a lighter working section including a reverse just prior to the vacuum port. Compounds containing glass were made on the 30mm extruder using a glass side stuffer prior to the vacuum port to incorporate glass. The 28mm extruder was run at 200 rpm and about 20 pounds per hour. The 30mm extruder was run either at 200 rpm and about 20 pounds per hour or 300 rpm and about 30 pounds per hour. All percentages listed are weight per cent of the total composition unless otherwise noted. Articles may be formed from blends of this invention by the normal methods of thermoplastic forming. Unless otherwise noted, the following blends were molded in a Van Dorn 6 oz. reciprocating screw injection molding machine with 150 tons clamping pressure and a gear driven screw. A general purpose molding screw was used in the machine, with a 1/8 inch (32 mm) thick tensile bar cavity, a 1/8 inch (32mm) flex bar and a 1/16 inch (16 mm) flex bar cavities in the mold. The results in the following examples are the per cent elongation at break of 1/8 inch (32 mm) specimens tested by ASTM D 638. Table 1 Example I Non-hydrogenated SBS block copolymer thermoplastic elastomer (Stereon 857, available from Firestone Rubber Co.) was extruded in a 28mm twin screw extruder at 19 pounds per hour, 200 rpm, and with a melt temperature of 230°C. It contained 3% fumaric acid and 0.1% dicumyl peroxide. When compared at the 6% level to prior art compatibilizer A in a formulation of 50% nylon A, 44% SPS C, and 6% compatibilizer, as shown in Table 2 which follows, improved elongation was demonstrated: Table 2 Example 2 In the following experiments, use of other functionalizing monomers are demonstrated. PPO is sometimes referred to as PPE, both are poly-2,6 dimethyl phenylene oxide. They were prepared by passing a mixture of 95% PPO (Mn = 28,000) 5% monomer through a 28mm extruder at 10 pounds per hour with a barrel setting of 330°C. These were then mixed with nylon and SPS as indicated in Table 3. Table 3 Example 3 Block copolymers of polyamide and polyether can compatibilize SPS with nylon. Table 4 Example 4 The utility of using a higher polyamide to compatibilize nylon 66 and SPS is demonstrated by the following experiment.. A larger portion of nylon A was removed from the formulation than SPS as the compatibilizer was also a nylon. (Nylon copolymers containing longer aliphatic chains than nylon 6 or nylon 66 can compatibilize SPS with nylon 66) Table 5 Additional compatibilizers are described in Table 6. Table 6 Example 5 Polyethylene glycol is used as a compatibilizer. Table 7 Example 6 Carbon monoxide containing ethylene interpolymers is used to compatibilize SPS with nylon. Table 8 Example 7 Polyethylene interpolymers functionalized with either partially zinc neutralized carboxylic acid or glycidyl methacrylate can compatibilize SPS with nylon. They even function better than a compatibilizer claimed in the prior art. Table 9 Example 8 The function of certain types of compatibilizers is improved by neutralization with metal salts such as zinc, lithium, magnesium as demonstrated in the following series of experiments. Other salts such as, but not limited to, manganese, sodium, aluminum, and the like, may also function in this manner. Due to kinetic limitation in the working zones of the extruder, greater than 100% of the stoichiometric amount of the neutralizing metal salt may be added. The following series were prepared by blending all ingredients in the rear of the extruder simultaneously. Thus the compatibilizer was being neutralized at the same time it was being dispersed and acting as a dispersing agent. Table 10 Example 9 The table below demonstrates not only the superiority of claimed compatibilizer C over a similar level of equally soft and rubbery prior art compatibilizer A and hard but efficient prior art compatibilizer B, but how compatibilizers can be used in combination with each other. Table 11 Example 10 The examples below demonstrate the improvement made by neutralization of a rubbery prior art compatibilizer. Table 12 Example 11 The examples below again demonstrate the superiority of compositions of this invention over an equal amount of equally soft and rubbery prior art compatibilizer and that a further increase in elongation is possible in combination with other types of compatibilizers. Table 13 Example 12 The function of Prior Art Compatibilizer B is improved by neutralization with metal salts such as zinc, lithium, magnesium as demonstrated in the following experiment. Other salts such as, but not limited to, manganese, sodium, aluminum, and the like, may function in the same manner. Due to kinetic limitations in the working zones of the extruder, greater than 100% of the stoichiometric amount of the neutralizing metal salt may be added. Table 14 Example 13 In addition to the use of Prior Art Compatibilizer B, the elongation of nylon blends with SPS is improved by using plasticizers. In the following experiments plasticizer A is Uniplex 214 available from Unites Cml Co. and plasticizer B is Plasthall 809 available from C.P. Hall Corp. Table 15 Example 14 Glass is one of the most commonly used additives in injection molded crystalline thermoplastic resins. The presence of short glass fibers increases the modulus yet allows sufficient melt fluidity for injection molding. The increased modulus above their T g and below their T m greatly increases the ability of semicrystalline resins to support a load at elevated temperatures However the presence of glass reinforcement also greatly decreases ductility. The adhesion to the glass which generates true reinforcement in a tensile strength measurement, reduces the mobility of the molecules to respond to stress by movement, thus the part breaks at lower strain, or elongation. This is particularly true of the more brittle thermoplastics, such as SPS. In addition, blends which embrittle by reason of containing large domains on one resin poorly dispersed in the other, become very brittle when reinforced with glass. Thus finding "good" compatibilizers which allow relatively large portions of brittle and non-polar SPS to be dispersed in ductile, polar nylon or polyesters becomes particularly valuable because all of these resins have high melting points so are capable of being reinforced to give compositions capable of withstanding stress at elevated temperatures. The following experiments were carried out in a 30mm twin screw extruder with all polymeric components added in the rear unless otherwise noted. Short glass fiber, PPG 3540, was added by means of a side stuffer feeding the glass directly into the melt about two thirds of the length down the barrel. A gentle mixing section just past that point ensured adequate break-up of the glass bundles and dispersion of the individual glass fibers in the molten blend. An amount of 15 weight percent of the entire mass was glass that was added, thus the totals in the following table add up to 85%, not 100%. The results of the experiments recorded below demonstrate a further improvement can be made with greater than the calculated theoretical amount necessary for 100% neutralization. Table 16 Example 15 The experiments below demonstrate that a variety of metal counter ions may be used to neutralize the experimental compatibilizer. Table 17 Example 16 In preparing blends of several polymers, whether for toughening or other purposes, sequence of addition may have an effect. The following examples illustrate several processing variations. A blend of 13% nylon A, 27% SPS D, and 17% compatibilizer C with sufficient ZnO present to enable 100 % neutralization were blended in the rear of a 30mm twin screw extruder. The glass (15%) and remaining nylon, 28 %, was added as a concentrate where the glass had previously been dispersed. The elongation was 5.3 %. When all of the nylon was added in the rear of the extruder, the elongation was 4.3%. The SPS and thermoplastic resin may be previously rubber toughened, glass reinforced, contain a filler, and the like, prior to being blended. Preferred thermoplastic resins included nylon 6, nylon 66, polybutylene terephthalate, and polyethylene terephthalate.

Claims: CLAIMS What is claimed is: 1. A composition comprising: (a) from 1 to 99% by weight of a syndiotactic polystyrene, (b) from 1 to 99% by weight of a thermoplastic resin; and (c) from 1 to 30% by weight of a compatibilizer having an acid functionality which is partially or fully neutralized by a metal counter ion. 2. A composition of claim 1 wherein said thermoplastic resin is selected from the group consisting of polyamides and polyesters. 3. A composition of claim 1 wherein said metal counter ion is selected from the group consisting of zinc, magnesium, manganese, and lithium. 4. A styrene-based resin composition which comprises (a) 20 to 80% by weight of a styrene-based polymer having a syndiotactic configuration, (b) 20 to 80% by weight of a thermoplastic resin, (c) 2 to 25% by weight of a compatibilizer having an acid functionality which is partially or fully neutralized by a metal counter ion, and (d) 0 to 50% by weight of an organic or inorganic filler based on the total weight of the composition 5. The composition of claim 4 wherein said filler is glass. 6. A styrene-based resin composition which comprises (a) 20 to 80%) by weight of a styrene-based polymer having a syndiotactic configuration, (b) 20 to 80% by weight of a thermoplastic resin, and (c) 2 to 25 % by weight of a compatibilizer selected from the group consisting of a polymer having intermediate polarity, block copolymers whose block segments are compatibile with either component (a) or (b), and polymers close to miscible with either component (a) or (b) with structures capable of complexing with the other component. 7. The composition of claim 6 wherein said thermoplastic resin is selected from the group consisting of nylon and polyester. 8. A shaped article prepared from the composition of claim 1. 9. A shaped article prepared from the composition of claim 6.

Inventors: FLEXMAN EDMUND ARTHUR, KIRCHNER OLAF N, SUBRAMANIAN PALLATHERI MANACKA, FLEXMAN, EDMUND, ARTHUR, KIRCHNER, OLAF, N., SUBRAMANIAN, PALLATHERI, MANACKAL
Applicants: DU PONT, FLEXMAN EDMUND ARTHUR, KIRCHNER OLAF N, SUBRAMANIAN PALLATHERI MANACKA, E.I. DU PONT DE NEMOURS AND COMPANY, FLEXMAN, EDMUND, ARTHUR, KIRCHNER, OLAF, N., SUBRAMANIAN, PALLATHERI, MANACKAL
Application year: 1997
Main classification: C08L25
IPC codes: C08K7, C08L25, C08L67, C08L77, C08L101