A PROCESS FOR PREPARING HIGH IMPACT STRENGTH POLY(1,4-CYCLOHEXYLENEDIMETHYLENE TEREPHTHALATE)/IONOMER BLENDS

Abstract: This invention relates to a process for preparing poly(1,4-cyclohexylenedimethylene terephthalate)/ionomer compositions which exhibit high impact strength and to articles made therefrom. The process involves melt blending poly(1,4-cyclohexylenedimethylene terephthalate) with an ionomer of ethylene, an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid wherein the carboxylic acid groups are neutralized with zinc or sodium ions, and an alkyl acrylate, at a shear rate of 3500 to 7000 reciprocal seconds; and thermoforming the blend into an article.

Description: A PROCESS FOR PREPARING HIGH IMPACT STRENGTH POLY(1,4-CYCLOHEXYLENEDIMETHYLENE TEREPHTHALATE)/IONOMER BLENDS FIELD OF THE INVENTION This invention relates to a process for preparing poly(1,4—cyclohexylenedimethylene terephthalate)/ionomer compositions which exhibit high impact strength and to articles made therefrom. The process involves melt blending poly(1,4—cyclohexylenedimethylene terephthalate) (PCT) with an ionomer of ethylene, an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid wherein the carboxylic acid groups are neutralized with zinc or sodium ions, and an alkyl acrylate, at a shear rate of 3500 to 7000 reciprocal seconds; and thermoforming the blend into an article. BACKGROUND OF THE INVENTION Thermoplastic polyesters based on terephthalic acid and diols such as ethylene glycol and 1,4—cyclohexanedimethanol have proven to be very desirable for injection molding articles for high strength applications. Because many of such articles must withstand considerable temperature changes and/or physical abuse, it is customary to blend poly(1,4—cyclohexylenedimethylene terephthalate) with other polymers to improve its impact resistance as shown by notched Izod impact values. There are advantages, however, in keeping PCT as the matrix material in PCT/polymer blends and those are to retain tensile strength, flexural modulus, elongation percent, weather resistance and heat deflection temperature. Thermoplastic compositions exhibiting high impact strength are found in U.S. Pat. Nos. 3,435,093, 4,680,344, 4,172,859 and 4,753,980, and in PCT Application No. WO 92/03505. U.S. Pat. No. 3,435,093 discloses blends of polyethylene terephthalate and alpha—olefin/alpha—beta unsaturated carboxylic acid copolymers wherein the carboxylic acid groups are 0—100% neutralized by metal cations such as sodium, potassium, calcium, magnesium, zinc and lead. Moreover, the polyethylene terephthalate is present in an amount of between 55 to 95 weight percent of the blend. Izod impact values of blends indicated in the Examples of U.S. Pat. No. 3,435,093 range from 27.8 J/m to 59.8 J/m at 23°C. U.S. Pat. No. 4,680,344 discloses blends containing a linear polyester and at least 60 weight percent of alpha—olefin/alpha—beta—ethylenically unsaturated carboxylic acid ionomer neutralized with zinc, calcium, or magnesium. No third comonomer is present. Izod impact values of blends indicated in the Examples of U.S. Pat. No. 4,680,344 range from 26.7 J/ϊn to 1308 J m at 23°C. U.S. Pat. No. 4,172,859 discloses multiphase thermoplastic molding compositions containing 60—99 weight percent of polyester matrix resin, and 1—40 weight percent of ionomer having a particle size in the range of 0.1—3.0 microns. The compositions are prepared using a multi—screw extruder to generate high shear. U.S. Pat. No. 4,172,859, however, gives no indication of which shearing parameters are critical and no direction as to which of many shearing block designs are likely to be successful to accomplish a shear rate of at least 3500 reciprocal seconds which the present inventors have determined to be critical. U.S. Pat. No. 4,753,980 discloses toughened thermoplastic polyester compositions comprising 60—97 weight percent of a polyester and 3—40 weight percent of an ethylene copoly er such as ethylene/methacrylate/ glycidyl methacrylate. PCT Application No. WO 92/03505 discloses a semi-crystalline thermoplastic molding composition containing 60 to 90 weight percent of a polyester resin and 10 to 40 weight percent of an ionomer consisting of ethylene, an alkyl acrylate and an unsaturated carboxylic acid. The ionomer has from 20% to 80% of the carboxylic acid groups neutralized with zinc, cobalt, nickel, aluminum or copper (II) . In contrast, the present inventors have unexpectedly discovered a process for preparing superior impact resistant thermoplastic polyester molding compositions as determined by notched Izod impact values which are double the impact values found in the previously mentioned patents. The process involves melt blending poly(1,4—cyclohexylenedimethylene terephthalate) with an ionomer of ethylene, an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid wherein the carboxylic acid groups are neutralized with zinc or sodium ions, and an alkyl acrylate, at a critical shear rate of 3500 to 7000 reciprocal seconds; and forming the blend into an article. High impact strength is obtained even though the inherent viscosity of the poly(1,4—cyclohexylenedimethylene terephthalate) polyester component is significantly reduced due to the high shearing action. The high shearing process of this invention which is used to improve the impact strength of a polyester thermoplastic composition is contrary to the teachings of U.S. Pat. No. 4,780,506. Such patent teaches, in column 2, lines 6 to 13 that high shear blending of polyester/polycarbonate blends with impact modifiers leads to unpredictable results and transesterification which can be minimized by the use of inhibitors and/or by lowering the shear level. SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the impact properties of poly(1,4-cyclohexylenedimethylene terephthalate)/ionomer blends. Another object of the invention is to provide a process for preparing poly(l,4-cyclohexylenedimethylene terephthalate)/ionomer blends under conditions of high shear. A further object of the invention is to provide poly(1,4—cyclohexylenedimethylene terephthalate)/ionomer blends which exhibit excellent mechanical properties such as impact resistance, stress crack resistance and heat resistance, and which display excellent melt flowability at the time of molding thereof. These and other objects are accomplished herein by a process for preparing a poly(1,4-cyclohexylenedimethylene terephthalate)/ionomer blend which exhibits high impact strength comprising: (I) melt blending (A) 70 to 90 weight percent of a polyester which comprises (1) a dicarboxylic acid component consisting essentially of repeat units from terephthalic acid, and (2) a diol component consisting essentially of repeat units from 15 to 100 mole percent l,4—cyclohexanedimethanol and from 0 to 85 mole percent ethylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol, said polyester having an inherent viscosity of 0.4 to 1.5 dl/g; and (B) 30.0 to 10.0 weight percent of an ionomer comprising repeat units from 80 to 95 weight percent of ethylene and 5 to 20 weight percent of an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid, and the carboxylic acid groups being neutralized to the extent of 40 to 95 percent with zinc or sodium ions; wherein the combined weights of (A) and (B) total 100 percent and the blending is conducted in an extruder capable of providing a shear rate of 3500 sec -1 to 6000 sec -1 ; and (II) forming the blend into an article. DESCRIPTION OF THE INVENTION Component (A) of the present invention is a polyester which contains repeat units from mixtures of terephthalic acid, 1,4—cyclohexanedimethanol and ethylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol. The dicarboxylic acid component of the polyester (A) consists essentially of repeat units from terephthalic acid. The diol component of the polyester consists essentially of 15 to 100 weight percent 1,4—cyclohexanedimethanol and 0 to 85 weight percent ethylene glycol. Preferably, the diol portion consists of 20 to 70 weight percent ethylene glycol and 80 to 30 weight percent 1,4—cyclohexanedimethanol. The term "consists essentially of" means that in addition to the terephthalic acid, 1,4-cyclohexanedimethanol and ethylene glycol, other dicarboxylic acids and diols may be present in the polyester provided that the basic and essential characteristics of the polyester are not materially affected thereby. For example, the polyester, component (A) , may optionally be modified with up to 3 mole percent, based on 100 mole percent dicarboxylic acid, of one or more different dicarboxylic acids other than terephthalic acid or suitable synthetic equivalents. Such additional dicarboxylic acids include aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12 carbon atoms. Examples of dicarboxylic acids to be included with terephthalic acid are: phthalic acid, isophthalic acid, naphthalene-2,6—dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, dipheny1-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. In addition, the polyester may optionally be modified with up to 3 mole percent, based on 100 mole percent diol, of one or more different diols other than 1,4-cyclohexanedimethanol and ethylene glycol. Such additional diols include cycloaliphatic diols preferably having 6 to 15 carbon atoms or aliphatic diols preferably having 3 to 8 carbon atoms. Examples of such diols to be included with 1,4-cyclohexanedimethanol and ethylene glycol are: propane-l,3-diol, butane—1 ,4—diol, pentane—1,5—diol, hexane—1,6—diol, 3—methylpentanediol— (2,4), 2—methylpentanediol—(1,4), 2,2,4—trimethylpentane—diol—(1,3) , 2-ethylhexanediol—(1,3) , 2,2-diethylpropane-diol—(1,3) , hexanediol-(1,3), 1,4—di—(hydroxyethoxy)—benzene, 2,2—bis-(4-hydroxycyclohexyl)—propane, 2,4-dihydroxy—1,1,3,3—tetra ethyl—cyclobutane, 2,2—bis-(3-hydroxyethoxypheny1)—propane, 2,2-bis-(4-hydroxypropoxyphenyl)-propane, and the like. Polyesters useful as component (A) have an inherent viscosity of 0.4 to 1.5 dl/g. Preferably, the polyesters have an inherent viscosity of 0.5 to l.l dl/g. Polyesters comprising substantially only 1,4—cyclohexanedimethanol, ethylene glycol and I - 7 - terephthalic acid are preferred for use in the present invention. Examples of commercially available polyesters useful as component A include Ektar PCT—3879, PCTG—5445 and PETG—6763 which are available from Eastman Chemical Company, Kingsport, TN. Ektar PCT—3839 is a homopolymer of crystallized poly(1,4—cyclohexylene¬ dimethylene terephthalate) having an I.V. of 0.75. Kodar PCTG-5445 and PETG-6763 are polyesters consisting of terephthalic acid, ethylene glycol and 1,4—cyclohexanedimethanol with an I.V. of 0.75. The polyesters can be prepared by conventional polycondensation procedures well-known in the art. Such processes include direct condensation of the acid with the glycol or by ester interchange using lower alkyl esters. The essential components of the polyesters; e.g., terephthalic acid or dimethyl terephthalate, 1,4—cyclohexanedimethanol and ethylene glycol are commercially available. Component (B) of the present invention is an ionomer. Ionomers suitable for use in the present invention consist of copolymers and terpolymers of ethylene, an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid and, optionally, an alkyl acrylate having from 1 to 8 carbon atoms in the alkyl group. The carboxyl group—containing copolymers and terpolymers usually are converted at least in part to the salt form or, are neutralized to a certain degree. Such neutralization is obtained by adding to the carboxyl group-containing polymeric material a calculated amount of a zinc or sodium salt, for example, zinc acetate or sodium methoxide, and heating the mixture to a temperature below 140°C, while thoroughly mixing the materials together. The resulting partly or completely neutralized carboxylic group—containing polymeric material is known generically as an ionomer. The present inventors have determined through experimentation that cations other than zinc and sodium such as aluminum, potassium and magnesium do not result in improved impact strength for articles incorporating such carboxyl group-containing copolymers and terpolymers. The ionomer has from 40 to 80 percent of the carboxylic acid groups neutralized with zinc or sodium. Preferably, the ionomer has from 50 to 75 percent of the carboxylic acid groups neutralized with zinc or sodium and most preferably 70 percent. Some of such ionomeric materials are available commercially, for example "SURLYN" (trademark) ionomer resins of the E.I. DuPont de Nemours Company. Particularly preferred ionomers are SURLYN 9020 which is a random terpolymer of ethylene/methacrylic acid/isobutyl acrylate neutralized with zinc, SURLYN 9721 which is a ethylene methacrylic acid copolymer neutralized with zinc, SURLYN 8020 which is a random terpolymer of ethylene/methacrylic acid/isobutyl acrylate neutralized with sodium, and SURLYN 8527 which is a ethylene/methacrylic acid copolymer neutralized with sodium. The ethylene content of the copolymer or terpolymer is at least 50 weight percent, based on the ethylene/acid copolymer or terpolymer. The unsaturated carboxylic acid content of the ionomer should fall in the range of from 2 to 20 weight percent, the preferred range being from 5 to 15 weight percent and the most preferred range being from 8 to 12 weight percent, based on the ionomer to give the best combination of low temperature impact resistance and high temperature resistance. The alkyl acrylate content of the terpolymer is from 2 to 15 weight percent. Preferably the alkyl acrylate is n-butyl acrylate or isobutyl acrylate. Most preferably, the alkyl acrylate is isobutyl acrylate. Ionomer copolymers of this invention preferably contain repeat units from 80 to 95 weight percent of ethylene and 5 to 20 weight percent of acrylic acid or methacrylic acid. Ionomer terpolymers of this invention preferably contain repeat units from 70 to 90 weight percent of ethylene, 5 to 15 weight percent of acrylic acid or methacrylic acid, and 5 to 15 weight percent of an alkyl acrylate or methacrylate having 1 to 8 carbon atoms in the alkyl group. Ethylene/methacrylic acid copolymers partially neutralized with zinc or sodium but which do not contain an alkyl acrylate, for example, isobutyl acrylate, are not as effective as ethylene/methacrylic acid copolymers partially neutralized with zinc or sodium which contain isobutyl acrylate. The present inventors have determined that the presence of an alkyl acrylate tends to reduce the modulus of the ionomer. Isobutyl acrylate, for example, reduces the modulus of the ionomer which in turn gives a more favorable ratio of PCT modulus to ionomer modulus. The ratio of PCT modulus to ionomer modulus should be greater than 10:1, and preferably greater than 20:1. Thus, the absence of an alkyl acrylate necessarily requires higher concentrations of the ionomer in the polyester/ionomer blend in order to obtain high impact strength. The ionomer generally is present in the blends of the present invention in an amount of from 10 to 30 weight percent. Consequently, at least 70 weight percent of the blends is PCT. Such critical amounts take into consideration the advantages which exist in keeping PCT as the matrix material. The advantages include retention of tensile strength, flexural modulus, elongation percentage, and heat deflection temperature. Preferably the concentration of ionomer should be from 15 to 25 weight percent and most preferably from 18 to 22 weight percent. The compositions of the present invention may be made from a single polyester resin and a single ionomer or from a polyester and a mixture of ionomers. The process for preparing the polyester/ionomer blends of the present invention involve preparing the polyester and zinc ionomer, respectively, by processes as mentioned previously. The polyester and zinc ionomer are dried in an atmosphere of dried air or dried nitrogen, or under reduced pressure. The polyester and ionomer are blended and subsequently melt blended or compounded in an extruder operated in a manner to provide a shear rate of 3500 sec -1 to 7000 sec -1 in the melt phase. Such shear rate is essential to provide the blends of this invention with high impact strength. Preferred extruders are twin screw extruders set up to provide a shear rate of 3500 sec -1 to 7000 sec -1 . The ionomer(s) are dispersed throughout the polyester as discrete particles, which particles have a number average particle size of less than or equal to l micron. The ionomer dispersed phase in PCT obtained by this type of blending has particle diameters of 0.1 to 0.3 microns. Torque can be used as a measurement of the amount of shear being applied to a blend. Higher torque values result in more shear being applied to a sample. The highest impact properties are achieved with the blends of the present invention at the maximum torque attainable. The maximum torque attainable by the present inventors is 102 Joules which translates into 6000 sec -1 . The present invention, however, is not limited by a torque value of 102 Joules. In fact, the highest impact properties are achieved with the blends at the maximum torque. Higher torque values are expected to result in even greater notched and unnotched impact strength. The necessary shearing force can be obtained, for example, in an extruder such as a Werner and Pfleiderer ZSK-28mm or ZSK-30mm corotating, intermeshing twin screw extruder, at a melt temperature of 260 β C. It is important to note that the Werner and Pfleiderer ZSK-28mm corotating, intermeshing twin screw extruder has at least two different screw designs, a "hard" screw design and a "medium" screw design. The "hard" screw design is a screw configuration which has 215 mm of kneading block length, eight elements which slide on, near the center and end of the screw for mixing and homogenizing the material. Two of the elements are left—handed elements capable of providing a higher shear field. A left—handed screw bushing element is included to back up the flow in the machine to create higher shear. The total length of the "hard" screw is 800 mm. Within the "hard" screw design, there are infinite settings that would provide the necessary shear. The maximum shear rate obtainable with the "hard" screw design on the Werner and Pfleiderer ZSK—28mm extruder is 5500 sec -1 . Thus, the "hard" screw is appropriately named since it is "hard" on the polymer. The "medium" screw design has a mixing screw which is the same length as the "hard" screw. The "medium" screw has 45 mm of kneading block length, four elements which slide on, near the center and end of the screw for mixing and homogenizing the material. The maximum shear rate obtainable with the "medium" screw design is less than 3500 sec -1 . The present inventors have determined that the impact strength of blends prepared with the "medium" screw design on the Werner and Pfleiderer ZSK-28mm extruder have significantly lower Izod impact values than blends prepared with the "hard" screw design. Moreover, the present inventors have determined that blends prepared on single screw extruders have even lower Izod impact values than blends prepared with a Werner and Pfleiderer ZSK—28mm extruder having a "medium" screw design. Single screw extruders do not provide the necessary shear to prepare blends with high notched impact strength as compared to twin screw extruders. It is important to note that while the "medium" screw design gives less shearing action than the "hard" screw design, the "medium" screw design gives more shearing action than a single screw extruder. Moreover, twin screw extruders do not necessarily provide the proper amount of shear unless the "hard" screw design is employed. The twin screw configuration required to attain the high impact compositions of the present invention requires that 25 percent of the screw length contain kneading blocks. These kneading blocks are distributed in groups of 2 to 4, for example, and each group is generally ended with a left—handed kneading block to insure that the kneading block groups are being maintained at full capacity to maximize their mixing capability. However, other configurations that have at least the minimum length of kneading blocks and left—handed kneading blocks will provide the desired results. Such configurations provide maximum shear rates, good extensional flow and backmixing. Melt temperatures must be at least as high as the melting point of the polyester component or sufficiently above the glass transition temperature for an amorphous polyester, which typically is in the range of 260-310°C. Preferably, the melt blending or compounding temperature is maintained as low as possible within said range. The composition is molded preferably at 260°C. to 280°C. under low temperature mold conditions such as 23°C. to provide an amorphous molded specimen. High impact strength is obtained even though the I.V. of the poly(1,4—cyclohexylenedimethylene terephthalate) polyester component has been significantly reduced due to the high shearing action. After completion of the melt compounding, the extrudate is withdrawn in strand form, and recovered according to the usual way such as cutting. Under melt processing conditions the PCT undergoes molecular weight degradation in the presence of contaminants such as water, thus, it is preferable that the polyester be incorporated in anhydrous form into the blends of the present invention. The blends should also be protected from moisture prior to melt processing. Many other ingredients can be added to the compositions of the present invention to enhance the performance properties of the blends. For example, surface lubricants, denesting agents, stabilizers, antioxidants, ultraviolet light absorbing agents, mold release agents, metal deactivators, colorants such as titanium dioxide and carbon black, nucleating agents such as polyethylene and polypropylene, phosphate stabilizers, fillers, and the like, can be included herein. All of these additives and the use thereof are well known in the art and do not require extensive discussions. Therefore, only a limited number will be referred to, it being understood that any of these compounds can be used so long as they do not hinder the present invention from accomplishing its objects. The blends of the present invention serve as excellent starting materials for the production of moldings of all types. Specific applications include medical parts, appliance parts, automotive parts, tool housings, recreational and utility parts. The molding compositions of the present invention are especially useful in applications that require toughness in hard to fill injection molded parts. Additionally, the blends can be used to prepare extruded sheets for thermoforming applications. The materials and testing procedures used for the results shown herein are as follows: Break Elongation: ASTM-D638 Density (gradient tube method) : ASTM—D1505 Flexural Modulus and Flexural Strength: ASTM-790 Heat Deflection Temperature: ASTM-D648 Melt Flow Index: ASTM-D1238 Tensile Strength and Yield Strength: ASTM-T638 Izod Impact Strength: ASTM-D256. The Izod Impact Strength Test was repeated three to five times for each material. The letters CB, PB and NB listed under impact strength have the following meanings: CB — complete break, brittle failure PB — partial break NB — no break, ductile failure. Inherent viscosity (I.V.) was measured at 23°C. using 0.50 grams of polymer per 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane. Ionomer A is a 80/10/10 weight percent terpolymer consisting of ethylene, isobutyl acrylate and methacrylic acid, respectively, containing 2.63 weight percent zinc. The degree of neutralization of the acid is 69%. Flexural Modulus at 23°C. is 14,000 psi (lOO MPa) . Melt Index at 190°C. (grams per 10 minutes) is 1.0. Polyester/ionomer ratio is 10:1. Ionomer A is commercially available under the trademark SURLYN 9020 from E.I. DuPont de Nemours and Company. Ionomer B is a 80/10/10 weight percent terpolymer consisting of ethylene, isobutyl acrylate and methacrylic acid, respectively, with 70% of the carboxyl groups neutralized with sodium. Melt Index at 190°C. (grams per 10 minutes) is 1.0. Polyester/ionomer ratio is 10:1. Ionomer B is commercially available under the tradename SURLYN 8020 from E.I. DuPont de Nemours and Company. The invention will be further illustrated by a consideration of the following examples, which are intended to be exemplary of the invention. All parts and percentages in the examples are on a weight basis unless otherwise stated. EXAMPLE 1 A homopolymer of crystallized poly(1,4—cyclohexylenedimethylene terephthalate) having an I.V. of 0.75 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. The PCT was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK—28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The PCT was melt processed at 295°C. under high shear conditions, stranded and pelletized. The I.V. of the PCT was 0.61. The pelletized PCT was dried at 100°C. for 8 hours in desiccant air with a dew point <—29°C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 295°C. and a mold temperature of 23°C. to provide an amorphous test specimen. The I.V. of the PCT after molding was 0.55. The impact properties of the PCT are summarized in Table I. EXAMPLE 2 The PCT of Example 1 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer A was dried at 60°C. for 16 hours in desiccant air with a dew point <—29°C. The PCT and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 20 weight percent. The PCT/Ionomer A blend was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK—28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The blend was melt processed at 295°C. under high shear conditions, stranded and pelletized. The pelletized blend was dried at 100°C. for 8 hours in desiccant air with a dew point <—29°C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 295 β C. and a mold temperature of 23 β C. to provide amorphous test specimens. The impact properties of the blend are summarized in Table I. EXAMPLE 3 The PCT of Example 1 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer B was dried at 60°C. for 16 hours in desiccant air with a dew point <—29°C. The PCT and Ionomer B were pellet blended in a polyethylene bag such that the concentration of Ionomer B was 20 weight percent. The PCT/Ionomer B blend was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK—28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The blend was melt processed at 295°C. under high shear conditions, stranded and pelletized. The pelletized blend was dried at 100°C. for 8 hours in desiccant air with a dew point <-29°C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 295°C. and a mold temperature of 23°C. to provide amorphous test specimens. The impact properties of the blend are summarized in Table I. EXAMPLE 4 The PCT of Example 1 was dried at 150 β C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer B was dried at 60°C. for 16 hours in desiccant air with a dew point <—29°C. The PCT and Ionomer B were pellet blended in a polyethylene bag such that the concentration of Ionomer B was 30 weight percent. The PCT/Ionomer B blend was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK—28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The blend was melt processed at 295°C. under high shear conditions, stranded and pelletized. The pelletized blend was dried at 100°C. for 8 hours in desiccant air with a dew point <—29°C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 295°C. and a mold temperature of 23°C. to provide amorphous test specimens. The impact properties of the blend are summarized in Table I. TABLE I IONOMER IONOMER IZOD IMPACT STRENGTH (J^m) A B Notched Unnotched Notched Unnotched EXAMPLE (wt%) (wt%) (23°C.) (23°C.) (-40°C.) (-40°C.) Ex. 1 0 0 EX. 20 EX. 3 20 Ex. 4 0 30 The results in Table I indicate that PCT/Ionomer A and PCT/Ionomer B blends wherein the acid component is neutralized with zinc or sodium exhibit significant increases in impact strength at 23°C. and —40°C. over the PCT control sample. The data also indicates that PCT/Ionomer A blends are more effective at lower ionomer concentrations of increasing the impact strength than PCT/Ionomer B blends. Thus, ionomers neutralized with zinc are preferred. The mode of impact failure for the blends was ductile as opposed to brittle for the PCT control. EXAMPLE 5 A polyester consisting of 100 mole percent terephthalic acid, 34 mole percent ethylene glycol and 66 mole percent l,4—cyclohexanedimethanol with an I.V. of 0.75 was dried at 150°C. for 16 hours in desiccant air with a dew point <-29 e C. The PCTG was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK- 28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The PCTG was melt processed at 275°C. under high shear conditions, stranded and pelletized. The I.V. of the PCTG was 0.61. The pelletized PCTG was dried at 100°C. for 8 hours in desiccant air with a dew point <—29°C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 275°C. and a mold temperature of 23°C. to provide an amorphous test specimen. The I.V. of the PCTG after molding was 0.55. The impact properties of the PCTG is summarized in Table II. EXAMPLES 6-8 The PCTG of Example 5 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer A was dried at 60°C. for 16 hours in desiccant air with a dew point <—29°C. The PCTG and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 10 to 30 weight percent. The PCTG/Ionomer A blend was melt blended and molded as in Example 5. The weight percents of Ionomer A used in each example and impact properties of the PCTG/Ionomer A blends are summarized in Table II. EXAMPLES 9-11 The PCTG of Example 5 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer B was dried at 60°C. for 16 hours in desiccant air with a dew point <-29 β C. The PCTG and Ionomer B were pellet blended in a polyethylene bag such that the concentration of Ionomer B was 10 to 30 weight percent. The PCTG/Ionomer B blend was melt blended and molded as in Example 5. The weight percents of Ionomer B used in each example and impact properties of the PCTG/Ionomer B blends are summarized in Table II. TABLE II IONOMER IZOD IMPACT STRENGTH (J/m) A B Notched Unnotched Notched Unnotched EXAMPLE (Wt%) (wt%. (23°C.) (23°C. (-40°C.) (-40°C. EX. 5 Ex. 6 10 EX. 7 20 Ex. 8 30 Ex. 9 10 EX. 10 20 EX. 11 30 The results in Table II indicate that a polyester consisting of 100 mole percent terephthalic acid, 34 mole percent ethylene glycol and 66 mole percent 1,4—cyclohexanedimethanol blended with Ionomer A and Ionomer B, wherein the ionomer is present in as little as 10 weight percent, exhibit significant increases in notched impact strength at —40°C. over the PCTG control sample. The data also indicates that PCTG/Ionomer A blends are more effective at lower ionomer concentrations of increasing the impact strength than PCTG/Ionomer B blends. Thus, ionomers neutralized with zinc are preferred. The mode of impact failure at —40°C. for the blends was ductile as opposed to brittle for the PCTG control. EXAMPLE 12 A polyester consisting of 100 mole percent terephthalic acid, 69 mole percent ethylene glycol and 31 mole percent 1,4—cyclohexanedimethanol with an I.V. of 0.75 was dried at 150°C. for 16 hours in desiccant air with a dew point <-29°C. The PETG was placed in the hopper, under dry N 2 , of a Werner and Pfleiderer ZSK— 28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The PETG was melt processed at 260°C. under high shear conditions, stranded and pelletized. The I.V. of the PETG was 0.61. The pelletized PETG was dried at 100°C. for 8 hours in desiccant air with a dew point <—29°C. and injection ; molded on a Boy 22S injection molding machine using a melt temperature of 260°C. and a mold temperature of 23°C. to provide an amorphous test specimen. The I.V. of the PETG after molding was 0.55. The impact properties of the PETG are summarized in Table III. EXAMPLES 13-14 The PETG of Example 12 was dried at 150°C. for 16 hours in desiccant air with a dew point <—29°C. Ionomer A was dried at 60°C. for 16 hours in desiccant air with a dew point <-29°C. The PETG and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 10 and 20 weight percent. The PETG/Ionomer A blend was melt blended and molded as in Example 12. The weight percents of Ionomer A used in each example and impact properties of the PETG/Ionomer A blends are summarized in Table III. EXAMPLES 15-16 The PETG of Example 12 was dried at 150°C. for 16 hours in desiccant air with a dew point <-29°C. Ionomer B was dried at 60°C. for 16 hours in desiccant air with a dew point <-29°C. The PETG and Ionomer B were pellet blended in a polyethylene bag such that the concentration of Ionomer B was 10 and 20 weight percent. The PETG/Ionomer B blend was melt blended and molded as in Example 12. The weight percents of Ionomer B used in each example and impact properties of the PETG/Ionomer B blends are summarized in Table III. The results in Table III indicate that the addition of 10 weight percent zinc ionomer, Ionomer A, to the PETG polyester consisting of 100 mole percent terephthalic acid, 69 mole percent ethylene glycol and 31 mole percent 1,4—cyclohexanedimethanol results in a significant increase in notched Izod impact strength at 23 β C. from 53 J/m with complete break to 1244 J^m with no break. The addition of 20 weight percent sodium ionomer, Ionomer B, results in a similar increase in notched Izod impact strength at 23°C. Low temperature impact values are also increased with the blends, especially with the PETG/Ionomer A blend at 20 weight percent, as compared to the PETG control. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious modifications are within the full intended scope of the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A process for preparing a poly(1,4-cyclohexylenedimethylene terephthalate)/ionomer blend which exhibits high impact strength comprising: (I) melt blending (A) 70 to 90 weight percent of a polyester which comprises (1) a dicarboxylic acid component consisting essentially of repeat units from terephthalic acid, and (2) a diol component consisting essentially of repeat units from 15 to 100 mole percent 1,4—cyclohexanedimethanol and from 0 to 85 mole percent ethylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol, said polyester having an inherent viscosity of 0.4 to 1.5 dl/g; and (B) 30.0 to 10.0 weight percent of an ionomer comprising repeat units from 80 to 95 weight percent of ethylene and 5 to 20 weight percent of an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid, and the carboxylic acid groups being neutralized to the extent of 40 to 95 percent with zinc or sodium ions; wherein the combined weights of (A) and (B) total 100 percent and the blending is conducted in an extruder capable of providing a shear rate of 3500 sec -1 to 6000 sec -1 ; and (II) forming the blend into an article. 2. A process for preparing a poly(1,4—cyclohexylenedimethylene terephthalate)/ionomer blend which exhibits high impact strength comprising: (I) melt blending (A) 70 to 90 weight percent of a polyester which comprises (1) a dicarboxylic acid component consisting essentially of repeat units from terephthalic acid, and (2) a diol component consisting essentially of repeat units from 15 to 100 mole percent 1,4-cyclohexanedimethanol and from 0 to 85 mole percent ethylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol, said polyester having an inherent viscosity of 0.4 to 1.5 dl/g; and (B) 30.0 to 10.0 weight percent of an ionomer comprising repeat units from 80 to 95 weight percent of ethylene, 5 to 15 weight percent of an unsaturated carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid, the carboxylic acid groups are neutralized to the extent of 40 to 95 percent with zinc ions, and 5 to 15 weight percent of an alkyl acrylate or methacrylate having 1 to 8 carbon atoms in the alkyl group, wherein the combined weights of (A) and (B) total 100 percent and the blending is conducted in an extruder capable of providing a shear rate of 3500 sec -1 to 7000 sec -1 ; and (II) forming the blend into an article. 3. The product of the process of Claim 1. 4. The product of the process of Claim 2. 5. The process according to Claim 1 wherein the polyester, component (A) , is poly(l,4-cyclohexylenedimethylene terephthalate). 6. The process according to Claim 2 wherein the polyester, component (A) , is poly(l,4-cyclohexylenedimethylene terephthalate) . 7. The process according to Claim 1 wherein the poly(1,4—cyclohexylenedimethylene terephthalate) has an inherent viscosity of 0.5 to 0.9. 8. The process according to Claim 2 wherein the poly(l,4-cyclohexylenedimethylene terephthalate) has an inherent viscosity of 0.5 to 0.9. 9. The process according to Claim 1 wherein the ionomer, component (B) , has a melt index at 190°C. of 0.5 to 5.0 grams. 10. The process according to Claim 2 wherein the ionomer, component (B) , has a melt index at 190°C. of 0.5 to 5.0 grams. 11. The process according to Claim 9 wherein the ionomer, component (B) , has a melt index at 190°C. of 1.0 to 2.0 grams. 12. The process according to Claim 10 wherein the ionomer, component (B) , has a melt index at 190°C. of 1.0 to 2.0 grams. 13. The process according to Claim 1 wherein the ionomer, component (B) , comprises discrete particles, the major portion of which have diameters of 0.1 to 0.3 microns. 14. The process according to Claim 2 wherein the ionomer, component (B) , comprises discrete particles, the major portion of which have diameters of 0.1 to 0.3 microns. 15. The process according to Claim 1 wherein the blending is conducted in an extruder capable of providing a shear rate of 3500 sec -1 to 6000 sec -1 . 16. The process according to Claim 2 wherein the blending is conducted in an extruder capable of providing a shear rate of 3500 sec -1 to 6000 sec -1 . 17. The process according to Claim 1 further comprising an additive selected from the group consisting of crystallization aids, surface lubricants, denesting agents, stabilizers, antioxidants, ultraviolet light absorbing agents, metal deactivators, colorants, nucleating agents, phosphate stabilizers, processing aids and fillers. 18. The process according to Claim 2 further comprising an additive selected from the group consisting of crystallization aids, surface lubricants, denesting agents, stabilizers, antioxidants, ultraviolet light absorbing agents, metal deactivators, colorants, nucleating agents, phosphate stabilizers, processing aids and fillers.

Inventors: BREEDING KENNETH EZRA, DOMBROSKI JOHN RICHARD, MEYER MAX FREDERICK JR, TANT MARTIN RAY, BREEDING, KENNETH, EZRA, DOMBROSKI, JOHN, RICHARD, MEYER, MAX, FREDERICK, JR., TANT, MARTIN, RAY
Applicants: EASTMAN CHEM CO, EASTMAN CHEMICAL COMPANY
Application year: 1993
Main classification: C08L67
IPC codes: B29C47, C08J3, C08L67