MXPA00008693A - Compositions containing a polyarylene ether and a dispersible reactive solvent and articles prepared therefrom - Google Patents

Abstract

A blend of a polyarylene ether and a dispersible reactive solvent such as a thermoplastic polyurethane or a cyclopentadiene can be processed at temperatures below the oxidative degradation temperature of the polyarylene ether, yet form an article upon cooling that substantially retains the properties of the polyarylene ether.

Description

COMPOSITIONS CONTAINING POLYARYLENE ON ETHER AND A REACTIVE SOLVENT DISPERSAB E AND ITEMS PREPARED FROM THEMSELVES The present invention relates to a composition comprising a polyarylene ether and a dispersible reactive solvent. Polyarylene ethers (PAE) are a class of thermoplastic resins with excellent mechanical and electrical properties, heat resistance, flame retardants, low moisture absorption, and dimensional stability. These resins are widely used in automotive interiors, particularly in dashboards, as well as in electrical and electronic applications. Polyarylene ethers are very difficult to process (for example, by injection molding) as a result of the high melt viscosities and their high processing temperature relative to their oxidative degradation temperature. Accordingly, polyarylene ethers are commonly mixed with compatible polymers such as polystyrene (WO 97/21771 and U.S. Patent Number: 4,804,712); polyamides (U.S. Patent Number: 3,379,792); polyolefins (U.S. Patent Number: 3, 351, 851); rubber modified styrene resins (U.S. Patent Nos. 3,383,435 and 3,959,211, and Ger. Offen, No. 2,047,613); and blends of polystyrene and polycarbonate (U.S. Patent Nos. 3,933,941 and 4,446,278). Unfortunately, improvements in processing have generally been obtained at the expense of the flexural modulus, the flexural strength, or the heat distortion temperature. Epoxy resins have also been investigated as a reactive solvent for polyarylene ether. (See Venderbosch, RW, "Processing of Intractable Polymers using Reactive Solvents," Ph.D. Thesis, Eindhoven (1995), Vanderbosch et al., Polymer, vol 35, p.4,449 (1994); Vol 36, p.2903 ( 1995b)). In this case, the polyarylene ether is first dissolved in an epoxy resin to form a solution that is preferably homogeneous. An article is then formed from the solution, and the solution is cured at elevated temperatures, resulting in a phase separation that can give a continuous polyarylene ether phase with inter-dispersed epoxy domains therein. The properties of the finished article are determined mainly by the polyarylene ether; however, the use of an epoxy resin as a reactive solvent for the polyarylene ether is not practical in a continuous melt process such as injection molding because the epoxy needs a curing agent to bind. The curing agent will accumulate over time in the barrel of injection molding by embedding the machine. In addition, curing and subsequent phase separation have to be carried out at least at 150 ° C, which is impractical in a molding environment. In view of the deficiencies in the art, it would be desirable to find a reactive solvent that solves the processing problems inherent in some reactive solvents for the polyarylene ether, without detrimentally affecting the physical properties of the polyarylene ether. The present invention is directed to a need in the art, by providing in one aspect, a composition comprising a molten substance of polyarylene ether and a reactive solvent which is a thermoplastic polyurethane or a cyclopentadiene, wherein the polyarylene ether is represented by the formula: - (Ar-0) n-wherein Ar is a substituted or unsubstituted aromatic nucleus and n is an integer of at least 10, with the proviso that when the reactive solvent is a thermoplastic polyurethane having a temperature of transition to glass (Tg) less than 50 ° C, the polyarylene ether and the reactive solvent comprise at least 60 weight percent of the composition. In a second aspect, the present invention is an article comprising a dispersion of: (a) a dispersible reactive solvent which is a thermoplastic polyurethane or a cyclopentadiene; and (b) a polyarylene ether represented by the formula: - (Ar-0) n -where Ar is a substituted or unsubstituted aromatic nucleus and n is an integer of at least 10, with the proviso that when the reactive solvent is a thermoplastic polyurethane having a glass transition temperature (Tg) of less than 50 ° C, the polyarylene ether and the reactive solvent comprise at least 60 weight percent of the composition. In another aspect the present invention is a composition comprising a melting of a polyarylene ether and a thermoplastic polyurethane having a glass transition temperature of not less than 50 ° C, wherein the polyarylene ether is represented by the formula: (Ar-0) n-wherein Ar is a substituted or unsubstituted aromatic nucleus and n is an integer of at least 10. Thermoplastic polyurethanes (TPU) are depolymerizable at advanced temperatures, resulting in an impressive decrease in melt viscosity , and repolymerizable at reduced temperatures. Similarly, the cyclopentadienes undergo retro-Diels-Alder reactions at advanced temperatures and, after cooling in the presence of a suitable catalyst, construct the molecular weight to re-form a polycyclopentadiene. In this way, the thermoplastic polyurethanes and the cyclopentadienes are advantageously fixed without the addition of heat. Moreover, the mixtures of molten substances of polyarylene ether / thermoplastic polyurethane or polyarylene / cyclopentadiene ether are advantageously homogeneous, while the cooled articles have separate phases. This feature allows the melt to be processable at temperatures below the degradation temperature of the polyarylene ether, and still retain the properties of the unadulterated polyarylene ether. In one aspect, the present invention is a molten substance comprising a polyarylene ether and a thermoplastic polyurethane or a cyclopentadiene, preferably a thermoplastic polyurethane. The polyarylene ether is represented by the following formula: - (Ar-0) Q- wherein Ar is a substituted or unsubstituted aromatic nucleus and n is an integer of at least 10. The aromatic nucleus may be, for example, phenylene, alkylated phenylene, chlorophenylene, bromophenylene, and naphthalene. Ar is preferably 2,6-dimethyl-1,4-phenylene, 2-methyl-6-ethyl-1,4-phenylene, 2,6-diethyl-1,4-phenylene, and 2,3,6-trimethyl- 1, 4-phenylene; Ar is more preferably 2,6-dimethyl-1,4-phenylene. The preferred polyarylene ethers are poly (2,6-dimethyl-1,4-phenylene) ether and the copolymer obtained by the polymerization of 2,6-dimethylphenol and 2,3,6-trimethylphenol, with ether being most preferred. poly (2,6-dimethyl-1,4-phenylene). As used herein the term "dispersible reactive solvent" refers to a substance which forms a solution with the polyarylene ether at an advanced temperature, and which forms a heterogeneous dispersion with the polyarylene ether after cooling. The solution is preferably a homogeneous solution, and the dispersible reactive solvent is preferably the dispersed phase. Examples of these dispersible reactive solvents include thermoplastic polyurethanes and cyclopentadienes, with thermoplastic polyurethanes being preferred. The thermoplastic polyurethanes contain structural units formed from the reaction of a polyisocyanate, a polyfunctional chain extender, and optionally, a high molecular weight polyol. The polyisocyanate that is used to form the thermoplastic polyurethane preferably is a diisocyanate, which may be aromatic, aliphatic, or cycloaliphatic. Representative examples of these preferred diisocyanates can be found in the Patents of the United States of North America Numbers: 4,385,133; 4,522,975; and 5,167,899. Preferred diisocyanates include 4,4'-diisocyanatodiphenyl methane, p-phenylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-diisocyanatocyclohexane, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3 '-dimethyl-4,4' -biphenyl diisocyanate, 4,4'-diisocyanatodicyclohexylmethane, and 2,4-toluene diisocyanate, or mixtures thereof. More preferred are 4,4'-diisocyanatodicyclohexylmethane and 4,4'-diisocyanatodiphenylmethane. As used herein, the term "polyfunctional chain extender" refers to a low molecular weight polyol, preferably a diol having a molecular weight of not more than 200. Preferred chain extenders include ethylene glycol, 1,3- propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, neopentalglycol, 1,4-cyclohexanedimethanol, and 1,4-bis-hydroxyethylhydroquinone, and combinations thereof . Particularly preferred dysfunctional chain extenders include 1, 6-hexanediol and mixtures of 1,4-butanediol and diethylene glycol, 1,4-butanediol and triethylene glycol, and 1,4-butanediol and tetraethylene glycol. The thermoplastic polyurethane can also include units formed from the reaction of an aromatic diol, preferably at a concentration sufficient to lower the temperature at which the rigid thermoplastic polyurethane can be processed melted. These thermoplastic polyurethanes are described in U.S. Patent Number: 5,574,092. Examples of suitable aromatic diols include resorcinol, catechol, hydroquinone, dihydroxynaphthalenes, dihydroxyanthracenes, bis (hydroxyaryl) fluorenes, dihydroxyphenanthrenes, dihydroxybiphenyls, and bis (hydroxyphenyl) propanes. Preferred aromatic diols include hydroquinone, 4,4'-dihydroxybiphenyl 9,9-bis (4-hydroxyphenyl) -fluorene, and bisphenol A. When the aromatic diol is used, the amount of the aromatic diol preferably does not exceed an amount that causes The tensile elongation at break of the thermoplastic polyurethane is less than 5 percent, as determined by ASTM D-638. Preferably, the concentration of the aromatic diol is not less than 0.1, more preferably not less than 0.5, and more preferably not less than 1 mole percent, and preferably not more than 20, more preferably not more than 10, and more preferably no more of 5 mole percent, based on the total moles of the diol used to prepare the thermoplastic polyurethane. The term "high molecular weight polyol" is used herein to refer to a polyol, preferably a diol having a molecular weight of not less than about 500 au, preferably not less than about 600 amu, more preferably not less than about 1000 amu, and preferably not greater than about 6000 amu, more preferably not greater than about 3000 amu, and more preferably not greater than about 2000 amu. Examples of optional high molecular weight diols include polyether glycols such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol; and glycol polyesters such as polycaprolactone glycol, as well as compounds that can be prepared from the condensation reaction of an aliphatic diacid, diester, or di (acid chloride) with a linear, branched, or cyclic diol with from 2 to 8 carbon atoms , or a diol containing ether, or mixtures thereof. The most preferred high molecular weight polyester glycols include polycaprolactone glycol, polyethylene glycol adipate and polybutylene glycol adipate. Thermoplastic polyurethanes are advantageously prepared in the presence of a convenient catalyst such as those described in U.S. Patent Number: 5,068,306, column 5, line 46 to column 6, line 5. Preferred catalysts include stannous octoate, oleate stannous, dibutyl tin dioctoate, and dibutyltin dilaurate. The amount of catalyst used is sufficient to increase the reactivity of an isocyanate group with an OH group without undesirably affecting the properties of the final product, and is preferably in the range of about 0.02 to about 2.0 percent by weight based on the total weight of the reagents. The isocyanate to OH ratio of the reagents is preferably not less than 0.95: 1, more preferably not less than 0.975: 1, and more preferably not less than 0.985: 1, and preferably not greater than 1.05: 1, preferably not greater than 1025: 1, and most preferably not greater than 1015: 1. The thermoplastic polyurethanes can be conveniently prepared by batch or continuous processes such as those known in the art. A preferred continuous mixing process is the extrusion of reagents, such as the double screw extrusion process described in U.S. Patent Number: 3,642,964. The thermoplastic polyurethanes suitable for use as a reactive solvent for the polyarylene ether can be rigid thermoplastic polyurethanes or soft thermoplastic polyurethanes. The rigid thermoplastic polyurethanes have a glass transition temperature of not less than 50 ° C, and are also characterized by having a hard segment (that is, structural units formed from the polymerization of the polyisocyanate and the dysfunctional chain extender) or preferably not less than about 75, and more preferably not less than about 90 weight percent, based on the weight of the thermoplastic polyurethane, and as much as about 100 weight percent. A commercially available class of rigid thermoplastic polyurethanes includes thermoplastic polyurethane resins technically designed ISOPLAST® (a Trademark of The Dow Chemical Company). The soft thermoplastic polyurethanes have a glass transition temperature of less than 50 ° C, preferably less than 25 ° C, and are further characterized by having a hard segment of no more than 75 weight percent, based on the weight of the thermoplastic polyurethane . Examples of preferred soft thermoplastic polyurethanes are PELLETHANO® thermoplastic polyurethanes (a Trademark of The Dow Chemical Company). An unusual feature of a polyarylene ether / thermoplastic polyurethane mixture is that the mixture is homogeneous as a molten substance, but becomes heterogeneous as the molten substance cools. The homogeneity of the molten substance allows the mixture to be processable at a temperature below the oxidative degradation of the polyarylene ether; as the molten substance cools, the thermoplastic polyurethane phase segregates and the thermoplastic polyurethane forms a dispersion in a continuous phase of polyarylene ether so that the physical properties of the final article (e.g., the heat distortion temperature, the flexural modulus and flexural strength) are more similar to unadulterated polyarylene ether. The weight to weight ratio of the polyarylene ether against the thermoplastic polyurethane in the melt mixture (as well as in the final article) is generally greater than 1: 1. It is also possible to include other thermoplastic polymers in the thermoplastic polyarylene / polyurethane ether mixture, such as polystyrene (PS), syndiotactic polystyrene, or polyvinylcyclohexane. The polyarylene ether / thermoplastic polyurethane blends are particularly useful in injection molding applications that require the maintenance of high heat properties of the polyarylene ether. The following examples are for illustrative purposes only and are not intended to limit the scope of this invention. Examples 1-6 Various mixtures of poly (2,6-dimethyl-1,4-phenylene) ether (PPO 803, obtained from General Electric Plastics, Bergen op Zoom, The Netherlands) were prepared with a rigid thermoplastic polyurethane (polyurethane resin) thermoplastic, technically engineered ISOPLAST® 2530, a registered trademark of The Dow Chemical Company) or a soft thermoplastic polyurethane (PELLETHANO® thermoplastic polyurethane resin, a registered trademark of The Dow Chemical Company) and optionally N5000 polystyrene resin (obtained from Shell, weight average molecular weight is 305,000, Mw / Mn is 2.37). Samples of the PPO resin and the polystyrene were prepared in a single screw extruder at 245 ° C for the 50/50 weight / weight ratio, and at 250 ° C for the 75/25 weight / weight ratio. These samples were granulated and combined with rigid thermoplastic polyurethane or soft thermoplastic polyurethane and then mixed in an Arburg 270M single-screw injection molding machine at different temperature, pressure and molding temperature profiles as illustrated in Table 1. Samples of the PPO resin and the thermoplastic polyurethanes were prepared in the injection molding machine. The PPO / soft thermoplastic polyurethane blend was first mixed in a double roller mixer at 245 ° C, due to the difficulty in spraying the soft thermoplastic polyurethane. Table I - Molding Conditions to Produce Plates The glass transition temperatures of the different samples were analyzed using dynamic mechanical thermal analysis. Two glass transition temperatures were observed in each case. The samples were polished at thicknesses of 1 mm and 3 mm and at lengths of 13 mm and 25 mm, and were analyzed in traction mode (1Hz) using a heating regime of 2 ° C / minute. Table II illustrates the glass transition temperature, the flexural modulus, and the flexural strength of the various samples. Table 2. Physical Properties of PPE TPU Mixtures

Claims (8)

1. A composition comprising a molten substance of polyarylene ether and a rigid thermoplastic polyurethane, wherein the polyarylene ether is represented by the formula: - (Ar-0) n-wherein Ar is a substituted or unsubstituted aromatic nucleus and n is an integer of at least 10. The composition of claim 1, which is homogeneous as a molten substance and becomes a dispersion of the reactive solvent dispersible in the polyarylene ether after the molten substance is cooled. The composition of claim 1, wherein Ar is 2,6-dimethyl-1,4-phenylene, 2-methyl-6-ethyl-1,4-phenylene, 2, 6-diethyl-l, 4-phenylene, or 2, 3, 6-trimethyl-1,4-phenylene, or a combination thereof. The composition of claim 1 wherein the polyarylene ether is an ether of poly (2,6-dimethyl-1,4-phenylene) or the copolymer obtained by the polymerization of 2,6-dimethylphenol and 2,3, 6-trimethylphenol. The composition of claim 4 wherein the composition further includes a soft thermoplastic polyurethane. 6. The composition of claim 1 which further includes an additional thermoplastic polymer or an impact modifier or both. The composition of claim 5 which includes polystyrene, or a rubber with polystyrene-butadiene graft. The composition of claim 4 wherein the thermoplastic polyurethane includes structural units formed of an aromatic diol which is hydroquinone, 4,4'-dihydroxybiphenyl, 9, 9-bis (4-hydroxyphenyl) fluorene, or bisphenol A, or a combination thereof, and the concentration of structural units formed of the aromatic diol is not less than 1 mole percent and not more than 10 mole percent, based on the total moles of diol used to prepare the rigid thermoplastic polyurethane.