Moldable styrene-maleic anhydride/polybutylene terephthalate composition

Abstract: Moldable blends of styrene/maleic anhydride copolymer, poly­ butylene terephthalate ester, and styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups are provided. In one embodiment, the incorporation of the styrene-maleimide copolymer results in a composition having co-continuous phases. The compositions of this invention facilitate the production of blow molded articles.

Description: This invention relates to improved molding compositions. In one of its more specific aspects, this invention relates to molding compositions containing a styrene-maleic anhydride copolymer, a polybutylene terephthalate ester, and a minor amount of a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. Polymer blends of styrene-maleic anhydride copolymers (S/MA) and polybutylene terephthalate esters (PBT) are known from U.S. Pat. No. 3,644,574. Also known is a polymer mixture of PBT and a rubber modified styrene-maleic anhydride copolymer. This polymer mixture is described in EPA Publication No. 0 257 693. Molding compounds and films made from the polymer mixture are further described in EPA Publication Nos. 0 257 691 and 0 257 692, respectively. U.S. Pat. No. 4,080,354 describes compositions of PBT with a second resinous component containing 1 to 40% vinyl aromatic units with the balance being non-aromatic units. U.S. Pat. No. 4,217,427 describes PBT having incorporated thereinto pendant side chains of polystyrene to enhance its melt flow characteristics. Notwithstanding the general knowledge that blends of S/MA and PBT are useful compositions, it is well known that their combination, using melt mixing in an extruder, results in molded products which delaminate due to the gross immiscibility of the polymers. This tendency to delaminate has led the molding industry to continue to seek ways to combine these polymers attempting to obtain a composition which exhibits the high heat distortion temperature of the S/MA, the excellent solvent resistance of the PBT, and resistance to delamination. The present invention provides compositions of S/MA and PBT in which the S/MA and PBT phases are co-continuous. Scanning electron microscopy has shown the compositions of this invention to be near interpenetrating-type morphology. As used herein, the term "co-continuous" in relation to polymer blends means a distribution of two polymers in a blend such that both polymers are present as continuous phases, i.e., neither polymer is identifiable as a dispersed phase in a continuous phase of the other polymer. The term is intended to include the transition area between separate dispersed phases and co-continuous phases. The present invention also provides improved molding compositions in which the S/MA and PBT are present as separate dispersed phases or which fall within the transition area between two separate and co-continuous phases. The compositions of this invention are achieved by the incorporation of a minor amount of a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups into a blend of S/MA and PBT. Molded products prepared from the compositions of this invention exhibit excellent deflection temperature under load, flexural modulus, unnotched impact strength, solvent resistance, and resistance to delamination. According to this invention, there is provided a composition comprising: (a) a styrene-maleic anhydride copolymer; (b) a polybutylene terephthalate ester; and (c) a styrene-maleimide copolymer having pendant carboxyl and hydroxyl groups, wherein the weight ratio of copolymer (a) to polyester (b) is from 10:90 to 90:10, and the amount of copolymer (c) in parts by weight is from 1 to 20 per each 100 total parts by weight of (a) + (b) + (c). Also according to this invention, there is provided a method of producing the moldable composition defined in the preceding paragraph which comprises blending a styrene-maleic anhydride copolymer, a polybutylene terephthalate ester, and a minor amount of a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. Molded products prepared from the above-described moldable compositions are also provided by this invention. One particularly unique feature of the moldable compositions of this invention is that they can be blow molded. In a preferred embodiment of the invention, the weight ratio of S/MA copolymer to PBT is within the range of from 60:40 to 40:60, and the composition exhibits co-continuous S/MA and PBT phases. Any suitable styrene-maleic anhydride copolymer can be used. The S/MA copolymer may be impact modified typically by the incorporation thereinto of a rubber. Preferably, the S/MA copolymer will contain from 1 to 25 weight percent maleic anhydride with the balance being styrene. If a rubber modified S/MA is employed, the rubber content will be 2 to 20 weight percent (add on) based on the total weight of the copolymer. If an impact modified S/MA copolymer is employed in a composition according to this invention, the rubber remains finely dispersed in the S/MA phase of the composition. The number average molecular weight of the S/MA copolymer will be within the range of from 50,000 to 300,000. Suitable S/MA copolymers are available from ARCO Chemical Company under the trademark DYLARK. The compositions of this invention will contain S/MA copolymer or impact modified S/MA copolymer or their mixtures in an amount within the range of from 90 to 10 weight percent, preferably, and in order to achieve co-continuous phases, from 60 to 40 weight percent, based on the total weight of the S/MA and PBT. Any suitable PBT resin can be used. They are typically prepared by the condensation reaction of 1,4-butanediol and terephthalic acid. The compositions of this invention will contain PBT in an amount within the range of from 10 to 90 weight percent, preferably, and in order to achieve co-continuous phases, from 40 to 60 weight percent, based on the total weight of the S/MA and the PBT. The styrene-maleimide copolymer containing pendant carboxyl or hydroxyl groups is not known to be commercially available. Accordingly, Examples 1-5 describe the preparation of styrene-maleimide copolymers suitable for use in this invention. Generally, the procedure for producing the styrene-maleimide copolymer with pendant groups involves the modification of a styrene-maleic anhydride copolymer (DYLARK® resin) with an amino acid or ester (e.g., p-aminobenzoic acid, ethyl p-aminobenzoate, methyl p-aminobenzoate, dimethyl aminoisophthalate, dimethyl aminoterephthalate, p-aminophenol, or glycine) by refluxing with azeotropic removal of water in a solvent. The styrene-maleimide copolymer containing pendant carboxyl or hydroxyl groups will be employed in an amount of from 1 to 20 parts by weight, preferably from 8 to 12 parts by weight, for each 100 parts by weight of total S/MA, PBT, and styrene-maleimide copolymer. The styrene-maleimide copolymer functions as an interfacial modifier between the S/MA and PBT phases. Thus, according to the present invention there is also provided a molded composition comprising a first continuous phase, a second continuous phase, and an interface, wherein the first continuous phase comprises styrene-maleic anhydride copolymer, the second continuous phase comprises polybutylene terephthalate, and the interface comprises a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. The following examples will serve to further demonstrate the invention. Examples 1-5 demonstrate the preparation of styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. Examples 6-18 demonstrate the preparation of moldable compositions of this invention and their properties in molded form. Example 19 describes the preparation of a blow molded article. EXAMPLE 1 About 600 g. of a styrene-maleic anhydride copolymer containing 14% maleic anhydride (DYLARK® 332 resin) and about 62 g of glycine were mixed and then refluxed in about 1400 g of a 70:30 (by weight) solvent mixture of xylene and dimethylformamide. After azeotropic removal of about 15 ml. of water, the solution was poured into a pan, and the solvent mixture was evaporated in a vacuum oven at 60°C. The resultant polymer--a styrene-maleimide copolymer with pendant carboxyl groups--was finely ground and placed in a vacuum oven to remove residual solvent. The total product recovered weight 590 g. (91.5% yield) and had a Tg of 152°C. EXAMPLE 2 About 500 g. of a styrene-maleic anhydride copolymer containing 14% maleic anhydride (DYLARK® 332 resin) and about 47.8 g of hydroxylamine - HC1 were mixed and then refluxed in about 1400 g of a 70:30 (by weight) solvent mixture of xylene and dimethylformamide. After azeotropic removal of about 12 ml. of water, the solution was poured into a pan, and the solvent mixture was evaporated in a vacuum oven at 60°C. The resultant polymer--a styrene-maleimide copolymer with pendant hydroxyl groups--was finely ground and placed in a vacuum oven to remove residual solvent. The total product recovered weight 514 g. (96.0% yield) and had a Tg of 114°C. EXAMPLE 3 About 500 g. of a styrene-maleic anhydride copolymer containing 14% maleic anhydride (DYLARK® 332 resin) and about 113.7 g of ethyl p-aminobenzoate were mixed and then refluxed in about 1400 g of a 70:30 (by weight) solvent mixture of xylene and dimethylformamide. After azeotropic removal of about 12 ml. of water, the solution was poured into a pan, and the solvent mixture was evaporated in a vacuum oven at 60°C. The resultant polymer--a styrene-maleimide copolymer with pendant carboxyl groups--was finely ground and placed in a vacuum oven to remove residual solvent. The total product recovered weight 569 g. (94.5% yield) and had a Tg of 136°C. EXAMPLE 4 About 500 g. of a styrene-maleic anhydride copolymer containing 14% maleic anhydride (DYLARK® 332 resin) and about 75 g of p-aminophenol were mixed and then refluxed in about 1400 g of a 70:30 (by weight) solvent mixture of xylene and dimethylformamide. After azeotropic removal of about 12 ml. of water, the solution was poured into a pan, and the solvent mixture was evaporated in a vacuum oven at 60°C. The resultant polymer--a styrene-maleimide copolymer with pendant hydroxyl (phenolic) groups--was finely ground and placed in a vacuum oven to remove residual solvent. The total product recovered weight 546 g. (97% yield) and had a Tg of 159°C. EXAMPLE 5 About 500 g. of a styrene-maleic anhydride copolymer containing 14% maleic anhydride (DYLARK® 332 resin) and about 94.4 g of p-aminobenzoic acid were mixed and then refluxed in about 1400 g of a 70:30 (by weight) solvent mixture of xylene and dimethylformamide. After azeotropic removal of about 12.2 ml. of water, the solution was poured into a pan, and the solvent mixture was evaporated in a vacuum oven at 60°C. The resultant polymer--a styrene-maleimide copolymer with pendant carboxyl groups--was finely ground and placed in a vacuum oven to remove residual solvent. The total product recovered weight 546 g. (93.8% yield) and had a Tg of 167°C. EXAMPLES 6-10 The physical properties obtained from a series of five molded compositions of the invention are shown in following Table I. Each composition contained 10 parts by weight of the styrene-maleimide copolymer containing pendant carboxyl groups prepared in Example 5. Each of the five molding compositions was prepared by blending the designated amounts of materials in a 25.4 mm (1 in) Sterling extruder (36:1 L/D) at a 249°C (480°F) profile (melt temperature 246°C (475°F)). After extrusion, each composition was pellitized and dried at about 93°C (200°F). The pellets were molded into ASTM test samples on a Battenfeld injection molding machine at 241°C (465°F) profile and 60°C (140°F) mold temperature. PHYSICAL PROPERTIES OF MOLDED COMPOSITIONS OF THE INVENTION (EXAMPLES 6-10) Example No. 6 7 8 9 10 Materials (Parts by Weight) S/MA (DYLARK 332) 81 72 63 45 9 PBT 9 18 27 45 81 S/MI Copolymer of Ex. 5 10 10 10 10 10 Physical Property Flex. Modulus MPa (x10³, psi) 3544(514) 3509(509) 3385(491) 3158(458) 2723(395) Tensile Strength MPa (psi) 42.7(6200) 45.5(6600) 52.4(7600) 53.8(7800) 53.1(7700) Tensile Elongation (%) 2.4 2.5 2.8 3.1 15.0 Unnotched Izod J/m (ft-lbs/in) 107(2.0) 139(2.6) 149(2.8) 229(4.3) 895(16.8) Deflection Temp. under Load °C (°F.) 104(219) 103(218) 103(217) 104(220) 67(152) The physical property data in Table I demonstrate that molded compositions of this invention achieve the beneficial combination of component physical properties, i.e., the heat distortion of the styrene-maleic anhydride copolymer and the impact strength of the polybutylene terephthalate ester. Moreover, all molded samples were visually inspected and showed no delamination. The composition of Example 9 exhibited co-continuous phases of S/MA and PBT. EXAMPLES 11-18 Using substantially the procedure set forth in Examples 6-10, a second series of eight molding compositions of the invention was prepared, molded, and tested to determine physical properties and solvent resistance. The styrene-maleimide copolymer employed in all eight compositions was the styrene-maleimide copolymer containing pendant carboxyl groups prepared in Example 1. The physical properties of Examples 10-18 are shown in following Table II. Also shown in Table II are the solvent resistance data obtained on Examples Nos. 11, 12, 14, 17, and 18 (Examples 13, 15, and 16 were not subjected to solvent testing). The solvent resistance data were obtained by submersing ASTM D-368 type V tensile bars molded from each of the five compositions and the control samples in the designated solvents for three days at room temperature (25°C.). Before tensile strength testing, all submersed bars were allowed to set for one day. The compositions of Examples 11, 12, 17, and 18 exhibited separate dispersed phases of S/MA and PBT. The compositions of Examples 13, 14, 15, and 16 all exhibited co-continuous morphology. Examples 14 and 15 were co-continuous, whereas Examples 13 and 16 containing 60:40 and 40:60 weight ratios of S/MA to PBT respectively exhibited substantially co-continuous phases, i.e., they fall within the transition area between separate dispersed phases and co-continuous phases. The solvent resistance data in Table II show that the incorporation of minor amounts of a styrene-maleimide copolymer bearing pendant carboxyl groups into a blend of S/MA and PBT serves to significantly enhance the ability of the blend to retain its tensile strength property value after being immersed in solvent. The excellent resistance to solvents possessed by the compositions of this invention is observed even with methylene chloride. No delamination of the molded compositions was observed. EXAMPLE 19 The moldable composition of Example 15 is blow molded on an Impco B13 blow molding machine into a 10-inch long hourglass-shaped article having a major diameter of about 4 inches. The following approximate blow molding conditions are used: Rear Zone Temp. °C (°F.) 216-227 (420 - 440) Front Zone Temp. °C (°F.) 210-221 (410 - 430) Die Head Temp. °C (°F.) 216-227 (420 - 460) Blow Time (sec.) 20 - 60 Exhaust (sec.) 1 - 5 Parison Drop Time (sec.) 1 - 3 Blow Pressure kPa (psi) 276-552 (40 - 80) It will be evident from the foregoing that various modifications can be made to this invention. Such, however, are considered as being within the scope of the invention.

Claims: Claims for the following Contracting States : BE, FR, GB, IT, NE, DE A moldable composition comprising: (a) a styrene-maleic anhydride copolymer; (b) a polybutylene terephthalate ester; and (c) a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups, wherein the weight ratio of copolymer (a) to polyester (b) is from 90:10 to 10:90, and the amount of copolymer (c) in parts by weight is from 1 to 20 parts per each 100 parts by weight of total (a) + (b) + (c). The composition of claim 1 in which said styrene-maleic anhydride copolymer contains from 1 to 25 weight percent maleic anhydride. The composition of claim 1 or claim 2 in which said weight ratio of copolymer (a) to polyester (b) is from 60:40 to 40:60. The composition of claim 1, claim 2 or claim 3 in which said amount of copolymer (c) in parts by weight is from 8 to 12 per each 100 parts by weight of total (a) + (b) + (c). The composition of any one of claims 1 to 4 in which said styrene-maleic anhydride copolymer has number average molecular weight within the range of from 50,000 to 300,000. A moldable composition comprising: (a) a styrene-maleic anhydride copolymer having a number average molecular weight within the range of from 50,000 to 300,000; (b) a polybutylene terephthalate ester; and (c) a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups, wherein the weight ratio of copolymer (a) to polyester (b) is from 60:40 to 40:60, and the amount of copolymer (c) in parts by weight is from 8 to 12 parts per each 100 parts by weight of total (a) + (b) + (c), and wherein copolymer (a) and polyester (b) are present in the composition as co-continuous phases. The composition of any one of claims 1 to 6 in which said styrene-maleic anhydride copolymer is an impact modified styrene-maleic anhydride copolymer. The composition of claim 7 in which said styrene-maleic anhydride copolymer is impact modified by the incorporation of a rubber. A method of producing a moldable composition which comprises blending: (a) a styrene-maleic anhydride copolymer; (b) a polybutylene terephthalate ester; and a minor amount of (c) a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups, wherein the weight ratio or copolymer (a) to polyester (b) is from 90:10 to 10:90, and the amount of copolymer (c) in parts by weight is from 1 to 20 parts per each 100 parts of total (a) + (b) + (c). The method of claim 9 in which said styrene-maleic anhydride is an impact modified styrene-maleic anhydride copolymer. A molded article produced by molding a composition as claimed in any one of claims 1 to 8. The molded article of claim 11 being a blow molded article produced by blow molding said composition. A molded composition comprising a first continuous phase, a second continuous phase, and an interface, wherein the first continuous phase comprises styrene-maleic anhydride copolymer, the second continuous phase comprises polybutylene terephthalate, and the interface comprises a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. The molded composition of claim 12 in which said styrene-maleic anhydride is impact modified. The molded composition of claim 13 or claim 14 in which the weight ratio of styrene-maleic anhydride copolymer to polybutylene terephthalate is from 60:40 to 40:60. The molded composition of claim 13, claim 14 or claim 15 in which said interface copolymer is present in an amount of from 1 to 20 parts by weight per each 100 parts by weight of the total composition, including the interface copolymer. The molded composition of any one of claims 13 to 17 in which said styrene-maleic anhydride copolymer has a number average molecular weight within the range of from 50,000 to 300,000 and contains from 1 to 25 weight percent maleic anhydride. Claims for the following Contracting State : ES A method of producing a moldable composition which comprises blending: (a) a styrene-maleic anhydride copolymer; (b) a polybutylene terephthalate ester; and a minor amount of (c) a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups, wherein the weight ratio of copolymer (a) to polyester (b) is from 90:10 to 10:90, and the amount of copolymer (c) in parts by weight is from 1 to 20 parts per each 100 parts of the total of (a) + (b) + (c). A method as claimed in claim 1 wherein the weight ratio of copolymer (a) to polyester (b) is from 90:10 to 10:90, and the amount of copolymer (c) in parts by weight is from 1 to 20 parts per each 100 parts of total (a) + (b) + (c). A method as claimed in claim 1 or claim 2 in which said styrene-maleic anhydride copolymer contains from 1 to 25 weight percent maleic anhydride. A method as claimed in any one of claims 1 to 3 in which said weight ratio of copolymer (a) to polyester (b) is from 60:40 to 40:60. A method as claimed in any one of claims 1 to 4 in which said amount of copolymer (c) in parts by weight is from 8 to 12 per each 100 parts by weight of total (a) + (b) + (c). A method as claimed in any one of claims 1 to 5 in which said styrene-maleic anhydride copolymer has a number average molecular weight within the range of from 50,000 to 300,000. A method as claimed in claim 1 which comprises blending: (a) a styrene-maleic anhydride copolymer having a number average molecular weight within the range of from 50,000 to 300,000; (b) a polybutylene terephthalate ester; and (c) a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups, wherein the weight ratio of copolymer (a) to polyester (b) is from 60:40 to 40:60, and the amount of copolymer (c) in parts by weight is from 8 to 12 parts per each 100 parts by weight of total (a) + (b) + (c), and wherein copolymer (a) and polyester (b) are present in the composition as co-continuous phases. A method as claimed in any one of claims 1 to 7 in which said styrene-maleic anhydride copolymer is an impact modified styrene-maleic anhydride copolymer. A method as claimed in claim 8 in which said styrene-maleic anhydride copolymer is impact modified by the incorporation of a rubber. A method of forming a molded article said method comprising molding a composition obtained by the method claimed in any one of claims 1 to 9. A method as claimed in claim 10, comprising blow molding said composition. A molded composition comprising a first continuous phase, a second continuous phase, and an interface, wherein the first continuous phase comprises styrene-maleic anhydride copolymer, the second continuous phase comprises polybutylene terephthalate, and the interface comprises a styrene-maleimide copolymer having pendant carboxyl or hydroxyl groups. The molded composition of claim 12 in which said styrene-maleic anhydride is impact modified. The molded composition of claim 12 or claim 13 in which the weight ratio of styrene-maleic anhydride copolymer to polybutylene terephthalate is from 60:40 to 40:60. The molded composition of claim 12, claim 13 or claim 14 in which said interface copolymer is present in an amount of from 1 to 20 parts by weight per each 100 parts by weight of the total composition, including the interface copolymer. The molded composition of any one of claims 12 to 15 in which said styrene-maleic anhydride copolymer has a number average molecular weight within the range of from 50,000 to 300,000 and contains from 1 to 25 weight percent maleic anhydride.

Inventors: MCCREADY RUSSELL J, MCCREADY, RUSSELL J.
Applicants: ARCO CHEM TECH, ARCO CHEMICAL TECHNOLOGY, L.P.
Application year: 1989
Main classification: C08L35
IPC codes: C08L67, C08L35, C08L25