CA2142720A1 - A process for preparing high impact strength polyethylene terephthalate/ionomer blends - Google Patents

Abstract

ABSTRACT
This invention relates to a process for preparing polyethylene terephthalate/ionomer compositions which exhibit high impact strength. The process involves melt blending polyethylene 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 ions, and an alkyl acrylate, at a shear rate of about 3500 to about 7000 reciprocal seconds; and thermoforming the blend into an article.

Description

W O 94/06864 PC~r/US93/08132 :2 1 ~ 2 0 .
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A PROCESS ~OR PREPARING ~IG~ IMPACT STR~NGT~
POLYET~YLENE TE~EP~T~ALATE/IONOMER BLBNDS ;~

EIELD OF THE INVENTION
This invention relates to a process for preparing polyethylene terephthalate~ionomer compositions which exhibit high impact strength and to articles made therefrom. The process involves melt blending polyethylene terephthalate with an ionomer of ethylene, an unsaturated carboxylic acid selected from the group con~isting of acrylic acid and methacrylic acid wherein the carboxylic acid groups are neutralized with zinc ions, and an alkyl acrylate, at a shear rate of 3500 to 7000 reciprocal seconds; and thermoforming the blend into an article.
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BACKGROUND OF THE INVENTION
Polyethylene terephthalate (PET) is widely used as an extrusion and injection-molding resin for the fabrication of various articles for household or industrial use, including appliance parts, containers, ~-~
and auto parts. Because many of such articles must withstand considerable temperature changes and~or physical abuse, it is customary to blend polyethylene terephthalate with other polymers to improve its impact resistance as shown by notched Izod impact values.
There are advantages, however, in keeping PET as the matrix material in PET~polymer blends and those are to ~ -~
retain tensile strength, flexural modulus, elongation percent, weather resistance and heat deflection temperature.
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 me~al W O 94/06864 PC~r/US93/08132 ~
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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. 3,435,0g3 range from 27.8 J~m to 59.8 J~m at 23C.
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~m to 1308 J~m at 23C.
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.
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).

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U.S. Pat. No. 4,753,980 discloses toughened thermoplastic polyester compositions containing 60 to 97 weight percent of a polyester and 3 to 40 weight percent of an ethylene copolymer such as S ethylene~methacrylate~glycidyl methacrylate.
U.S. Pat. No. 4,303,573 discloses high velocity impact thermoplastic polyester compositions containing ~ -polyethylene terephthalate, 2 to 20 weight percent of an ~ -ionomeric terpolymer which is the zinc salt of a terpolymer of ethylene, methacrylic acid, and ;~
isobutylacrylate, and 2 to 20 weight percent of a second terpolymer of ethylene, propylene, and 1,4-hexadiene `~
which has succinate groups pendant from the copolymer -chain.
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 polyethylene ter-phthalate with an ionomer of ~ i 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 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 polyethylene terephthalate polyester component is ~ ''",'~''~,'"1'' "
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 , ~ ,"

W094/06864 PCT/~'S93/08t32 ~4'~ 4 - ~ ~ ~

PET~polycarbonate blends with impact modifiers leads to unpredictable results and transesterification which can be minimized by the use of inhibitors andXor by lowering the shear level. ~ -SUMMARY OF THE INVENTION
It is therefore an object of the present invention to improve the impact properties of polyethylene terephthalate~ionomer blends.
Another object of the invention is to provide a process for preparing polyethylene terephthalate~ionomer blends under conditions of high shear. -A further object of the invention is to provide polyethylene terephthalatexionomer 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 polyethylene terephthalate~ionomer blend which exhibits high impact strength comprising~
(I) melt blending (A) 70.0 to 90.0 weight percent of a polyester which comprises (1) a dicarboxylic acid component comprising repeat ~-~
units from at least 95 mole percent terephthalic acid; and (2) a diol component comprising repeat units from at least 95 mole percent ethylene glycol based ~
on lOO mole percent dicarboxylic acid and 100 ~ -mole percent diol said polyester having an inherent viscosity of 0.4 to 1.2 dl~g; and (B) 30.0 to lO.O weight percent of an ionomer comprising repeat units from 80 to 95 weight percent-of - . ..... ...
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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 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~l to 7000 sec~l; and (II) forming the-blend into an article.
DESCRIPTION OF THE INVENTION
The polyester, component (A), of the present invention is a polyethylene terephthalate (PET) resin.
The polyethylene terephthalate resin contains repeat units from at least 95 mole percent terephthalic acid and at least 95 mole percent ethylene glycol, based on 100 mole percent dicarboxylic acid and lOo mole percent diol.
The dicarboxylic acid component of the polyester may optionally be modified with up to 5 mole percent of one or more differont dicarboxylic acids other than ~-terephthalic acid or suitable synthetic equivalents such as dimethyl terephthalate. 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, ; 30 isophthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Polyesters may be prepared from two or more of the above dicarboxylic acids.

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It should be understood that use of the corresponding acid anhydrides, esters, and acid chlorides of these acids is included in the term "dicarboxylic acid". ~ ;
In addition, the polyester, component (A), may -optionally be modified with up to 5 mole percent, of one or more different diols other than ethylene glycol.
Such additional diols include cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms. Examples ~ -~
of such diols to be included with ethylene glycol are~
diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, propane-1,3-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-tetramethyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, and 2,2-bis-(4-hydroxypropoxyphenyl)-propane. Polyesters may be prepared from two or more of the above diols.
The polyethylene terephthalate resin may also contain small amounts of trifunctional or ~`
tetrafunctional comonomers such as trimellitic anhydride, trimethylolpropane, pyromellitic dianhydride, -pentaerythritol, and other polyester forming polyacids - ~
or polyols generally known in the art. -Polyesters comprising substantially only dimethyl --terephthalate and ethylene glycol are preferred in the `- i case where the blends of the present invention are used ;
in making thermoformed crystallized PET articles.
Polyethylene terephthalate based polyesters of the ~ :;
present invention can be prepared by conventional "'' ;'~ '.''` '' W 0 94/06864 PC~r/US93/08132 ; ~
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polycondensation procedures well-known in the art. Such processes include direct condensation of the dicarboxvlic acid(s) with the diol(s) or by ester interchange using a dialkyl dicarboxylate. For example, a dialkyl terephthalate such as dimethyl terephthalate is ester interchanged with the diol(s) at elevated temperatures in the presence of a catalyst. The polyesters may also be subjected to solid state polymerization methods.
The polyester, component (A), useful in the practice of this invention is the condensation product -~
of terephthalic acid, usually employed as the dimethyl ester, and ethylene glycol, hereinafter referred to as polyethylene terephthalate or PET. The PET has a melting point (Tm) of 255C. +5C. and a glass -~
transition temperature (Tg) of 80C. l5C. The PET may exhibit a relatively broad molecular weight range as determined by inherent viscosities of from 0.4 to 1.2.
However, inherent viscosities of from 0.5 to 0.9 are preferred.
A preferred polyester Sor use in this invention is ~ -~
a crystallized polyethylene terephthalate having an ~ `
inherent viscosity of 0.70 which is commercially~--available as XODAPAX PET 7352 (trademark) from Eastman Kodak Company.
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 -~
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obtained by adding to the carboxyl group-containing polymeric material a calculated amount of a zinc salt, for example, zinc acetate, and heating the mixture to a temperature below 140C., 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 such as aluminum, potassium, sodium 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.
Preferably, the ionomer has from 50 to 75 percent of the carboxylic acid groups neutralized with zinc 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 i~
and Company. Particularly preferred ionomers are SURLYN ` ;
9020 which is a r~ndom terpolymer o~
ethylene~methacrylic acid~isobutyl acrylate 70%
neutralized with zinc, and SURLYN 9721 which is a ethylene~methacrylic acid copolymer 70% neutralized with -`
zinc. - ~-The ethylene content of the copolymer or terpolymer is at least 50 weight percent, based on the i 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 i `
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 ~

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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.
S 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 but which do not contain an alkyl acrylate, for example, isobutyl acrylate, are not as ~ ;- 3 effective as ethylene~methacrylic acid copolymers partially neutralized with zinc 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 PET modulus to ionomer modulus.
The ratio of PET 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 PET. Such critical amounts take into consideration the advantages which exist in keeping PET as the matrix material. The-advantages , .:

W O 94/06864 PC~r/US93/08132 10~

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 subseguently 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 1 micron. ' The zinc ionomer dispersed phase in PET obtained by this `,.
type of blending h~s 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. 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 J~m ; ~ ~ -which translates into 6000 sec~l. The present invention, however, is not limited by a torque value of 102 J~m. In fact, higher torque values are expected to ; ~
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W O 94/06864 PC~r/US93/08t32 2 ~ ~ 2 72 0 result in even greater notched ~nd unnotched impact strength.
The necessary shearing force can be obtained, for example, in an extruder such as a Werner and Pfleiderer ~`
ZSX-28mm or ZSK-30mm corotating, intermeshing twin screw extruder, at a melt temperature of 260C. It is ~- -important to note that the Werner and Pfleiderer ZSR-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 neces6ary shear. The `~ `
maximum shear rate obtainable with the "hard" screw design on the Werner and Pfleiderer ZSK-28mm extruder is 5500 sec~l. Thus, the "hard" screw i8 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~l. The present inventors have determined that thè impact strength of blends prepared with the "medium" screw design on the Werner and Pfleiderer ;
ZSR-28mm extruder have significantly lower Izod impact values than blends prepared with the "hard" screw - 12 ~

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 i-"medium" screw design. i ~i 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-ii -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 . ~ . ' r.
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 glas~ transition temperature for an amorphous polyethylene terephthalate polyester, which typically is in the range of 260-310C. Preferably, the melt -blending or compounding temperature is maintained as low as possible within said range. The composition is ;~
molded preferably at 260C. to 280C. under low temperature mold conditions such as 23C. to provide an amorphous molded specimen. High impact strength is obtained even though the I.V. of the polyethylene 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.

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Under melt processing conditions the PET 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 ~ a~
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 .;.s.

W O 94/06864 PC~r/US93/08132 . ~ .~ , .

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 23C.
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 23C. is 14,000 psi (100 ~ `
MPa). Melt Index at 190C. (grams per 10 minutes) is 1Ø 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 8 is a 80~10~10 weight percent terpolymer consisting of ethylene, isobutyl acrylate and methacrylic acid, respectively, with 70% of the carboxyl i~
groups neutralized with sodium. Melt Index at 190C.
(grams per 10 minutes) is 1Ø Polyester~Ionomer ratio is 10:1. Ionomer B is commercially available under the trade name SURLYN 8020 from E.I. DuPont de Nemours and Company.
Ionomer C is a 90~10 weight percent copolymer consisting of ethylene and methacrylic acid, respectively, with 70% of the carboxyl groups . . ~, ....

neutralized with zinc. Melt Index at 190C. (grams per 10 minutes) is 1Ø Polyester/Ionomer ratio is 10:1.Ionomer C is commercially available under the trade name SURLYN 9721 from E.I. DuPont de Nemours and Company.
Ionomer D is a 90~10 weight percent copolymer consisting of ethylene and methacrylic acid, respectively, containing 0.93 weight percent sodium.
The degree of neutralization of the acid is 70%, flexural modulus at 23C. is 14,000 psi (100 MPa), and melt index is 1.0 g~10 min @ 190C. Melt Index at 190C. (grams per 10 minutes) is 1Ø Polyester~Ionomer ratio is 10:1. Ionomer D is commercially available under the trade name SURLYN 8527 from E.I. DuPont de Nemours and Company.
In the following examples, all the blends of ;~
neutralized acid copolymer and terpolymer with polyethylene terephthalate that were prepared on a Werner and Pfleiderer ZSK-28mm twin-screw extruder with "hard" screw design utilized the following conditions:
SET TEMPERATURE ~C.) Zone Zone Zone Zone Zone ::: :: :~: ::
MELT TEMPERATURE (C#3) 52 288 ~ 273 DIE TEMPERATURE (C.) TOROUE RPM
825 232 ~4~ '' .''. .' ` 1 ~ . ~: ' .' ' The resulting pelletized materials were injection molded on a BOY-22S Injection Molding Machine or on a Toyo T9OG
injection molding machine using the following condition: `

Open Cycle Time 4 seconds Injection and Hold Time14 seconds -~
Cooling Time 12 seconds . - -.-~
Injection Time 4 seconds - ~ I
Total Cycle Time34 seconds Zone 1 240C. ~ -~
Zone 2 260C i--Mold Temperature 23C
Nozzle temperature 260C.
Screw Speed 125 rpm Injection Pressure600 psig (4238 RPa) Hold Pressure600 psig (4238 KPa) . ::: . ::
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.
E~ MPLE
A homopolymer of crystallized polyethylene terephthalate having an I.V. of 0.70 was dried at 150C.
for 16 hours in desiccant air with a dew point S-29C.
The PET was placed in the hopper, under dry N2, of a Werner and PSleiderer ZSK-28mm corotating, intermeshing twin screw extruder having the "hardN screw design. The PET was melt processed at 260C. under high shear ;
conditions, stranded and pelletized. The I.V. of the PET was 0.61.
The pelletized PET was dried at 100C. for 8 hours in desiccant air with a dew point S-29oc- and injection molded on a Boy 22S injection molding machine using a melt temperature of 260C. and a mold temperature of ~ ~
23C. to provide an amorphous test specimen. The I.V. ~ ~ -of the PET after molding was 0. 55 . The impact ~ -~
propertiés of the PET is summarized in Table I. ;`

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W O 94/06864 PC~r/US93/08132 21~20 The PET of Example 1 was dried at 150C. for 16 hours in desiccant air with a dew point <-29C. -~
Ionomer A was dried at 60OC. for 16 hours in desiccant air with a dew point S-29C. The PET and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was lO weight percent. The PET~Ionomer A blend was placed in the hopper, under dry N2, of a Werner and Pfleiderer ZSK-28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The blend was melt processed at 260C. under high shear conditions, stranded and pelletized.
The pelletized blend was dried at 100C. for 8 hours in desiccant air with a dew point S-29C. and injection molded on a Boy 22S injection moldinq machine ~-using a melt temperature of 260C. and a mold temperature of 23C. to provide amorphous test specimens. The impact properties of the blend are summarized in Table I.
EXAMP~ES 3-5 ~ he procedure of Ex~mple 2 was followed except that the concentration of Ionomer A in the PET blend was changed to provide Ionomer A concentrations of 15, 20 and 30 weight percent, respectively. The effect of the zinc ionomer concentrations in PET are summarized in ; ;
T~ble T

WO 94/06864 PCT/US93/08t32 The procedure of Example 2 was followed except that Ionomer A was substituted with Ionomer B. The ~ ~ ;
concentration of Ionomer B in the PET blends was lo, 15, 20 and 30 weight percent, respectively. The results are summarized in Table III.

EXAMPLE 10 ; ;~
A blend containing 80 weight percent of the PET of Example 1 and 20 weight percent of Ionomer A was prepared as in Example 2 except that a Werner Pfleiderer ZSX-30mm corotating, intermeshing, twin-screw extruder was used. The extruder has a screw length of 1061 mm and 266 mm of this length is comprised of kneading blocks and left-handed blocks to provide high shear.
The pelletized blend was injection molded on a Toyo T9OG ~ z molding machine at 265C. The test results are summarized in Table I.
The results in Table I indicate that essentially identical high impact strength was obtained with this blend as was obtained by the same blend in Example 2 which was prepared on the Werner Pfleiderer ZSK-28mm extruder and molded on the Boy 22S injection molding ~-machine.

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wos4/o6864 PCT/US93/08132 21 ~ 2 72 o - 19 - ' TABLE I
Impact Strength of Zinc and Sodium Terpolymer Ionomers IONOMER IONOMER IZOD IMPACT STRENGT~ (J~m) A 8 Notched Unnotched Notched Unnotched EXAMPLE (wt%) ~wt%) (23C.) ~23C.) (-40C.) ~-40OC.) Ex. 1 0 0 32 2362 30 1949 (5CB) (5NB) (5CB) (3NB,2CB) Ex. 210 0 70 1754 42 1362 (5CB) (5NB) (5CB) (5NB) Ex. 315 0 1039 1627 56 1293 (lPB,3NB) (5NB) (5CB) (3NB,2CB) Ex. 420 01145 1850 75 2200 (5NB) (5NB) (5CB) (5NB) Ex. 530 01049 1362 236 1606 (5NB) (5NB) (5CB) (5NB) Ex. 6 0 0 28 2523 24 2215 ~ 5 (5CB) (5NB) (5CB) (3NB,lCB) ~4 Ex. 7 0 10 45 1961 34 2306 (5CB) (5NB) (5CB) (2NB,3CB) Ex. 8 0 lS S9 1924 34 2809 (5CB) (SNB) (SCB) (2NB,3CB) ;
Ex. 9 0 20 S9 1781 37 2814 ~,;` `,~
(SCB) (SNB) (SCB) (SNB) Ex. 100 30 101 1754 59 1675 `
(SCB) (SNB) (SCB) (3NB,lCB) ~ "-~
''.' ,:' .''`''~'`";
The data in Table I indicates that significant increases in notched impact strength are achieved with the PET~Ionomer A blends in spite of the drastic ;~
reduction in inherent viscosity experienced by the PET ;~
portion of such blends. The decrease in inherent `~
viscosi~y would have been expected to have resulted in a - severe loss of impact strength rather than an increase.
For example, the notched Izod impact strength at 23C.
of the PET~Ionomer A blend of Example 4 is 1145 J~m and ~ .

~ . ~ ' ' ':' W O 94/06864 PC~r/US93/08132 ~ - 20 ~

no break failure mode compared to 32 J~m and complete break failure mode for the PET control of Example 1.
The notched Izod impact strength at -40C. of the PET
blend of Example 4 is 75 J~m compared to 30 J~m for the PET control. ~. `~
The data also indicates that PET~Ionomer A blends wherein the acid component is neutralized with zinc exhibit significant increases in notched impact strength at 23C. and -40C. as compared to PET~Ionomer B blends wherein the acid component is neutralized with some other ion such as sodium. Moreover, the mode of impact failure for the blends utilizing zinc was ductile as opposed to brittle for the blends utilizing sodium.
The data in Table I further indicates that a preferred combination of low temperature impact resistance and high temperature impact resistance was achieved where the PET~Ionomer A blends contained from 5 to 15 weight --~
percent ionomer. In contrast, Ionomer B which is the sodium neutralized ionomer, even at the 30 weight percent level only slightly increased notched Izod impact strength from the PET control. For example, at 23C. notched Izod impact strength for the PET control ;
is 28 J~m with complete break failure mode, and for the PET~Ionomer B blend at 30 weight percent ionomer level is lO1 J~m with complete break failure mode.
: -The procedure set forth in Example 2 was followed except that the pellet blend composition fed into the Werner and Pfleiderer ZSK-28mm corotating, intermeshing twin screw extruder having the "hard" screw design ~ ~`
consisted of 40 weight percent PET and 60 weight percent ~ p Ionomer A. The 40~60 PET~Ionomer A concentrate blend in pellet form was blended with s~fficient PET pellets to provide a final concentration of 20 weight percent 21~272~ . ~

Ionomer A in the PET. The test results are summarized in Table II. Test results from Example l and Example 4 '~
are included for comparison purposes. - ~, TABLE II
Effect of PETxIonomer Concentrate IONOMER IZOD IMPACT STRENGTH (Jxm) A Notched Unnotched Notched Unnotched EXAMPLE (wt~ (23C.) (23OC.) (-40C.) (-40OC.) Ex. 1 0 322362 30 1949 (5CB)(5NB) (5CB) (3NB,2CB) ~
Ex. 4 20 1145 1850 75 2200 "'''''!.''""'"''' (SNB) (5NB) (5CB) (5NB) , ~ ,,,,",~"
Ex. 11 20 1240 2147 93 2131 '~
(5NB) (5NB) (5CB) (SNB) The results in Table II clearly show that essentially identical improvements in impact strength ''''''''~I'''.,~;''A.~'',``, are obtained by preparing a concentrate of the zinc , ' ionomer in PET and then adding the additional PET needed ~,''', to provide the desired ionomer conoentration prior to molding. , EXAMPL~ 12 The PET of Example 1 was dried at 150C. for 16 'i," ~",~",,,~'' hours in desiccant air with a dew point S-29C. '-~
Ionomer A was dried at 60C. for 16 hours in desiccant '~
air with a dew point S-29C. The PET and Ionomer A were ' pellet blended in a polyethylene bag such that the ; concentration of Ionomer A was 15 weight percent. The PET~Ionomer A blend was placed in the hopper, under dry ,~
N2, of a,'MPM single screw extruder equipped with a mixing screw. The blend was meltiprocessed at 260C., ,~
stranded and pelletized. ;' ,, :~ ' '.;
:. ~

W O 94/06864 PC~r/US93/08132 -: .
, :
22 - ' '~
, ~', '::''-The pelletized blend was dried at 100C. 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 260C. and a mold ',~
temperature of 23C. to provide amorphous test specimens. The impact properties of the blend are ;~
summarized in Table III. ; -' The PET of Example 1 was dried at 150C. for 16 ''~
hours in desiccant air with a dew point S-29C.
Ionomer A was dried at 60C. for 16 hours in desiccant ~ ' air with a dew point S-29C. The PET and Ionomer A were ' pellet blended in a polyethylene bag such that the concentration of Ionomer A was 15 weight percent. The PET~Ionomer A blend was placed in the hopper, under dry N2, of a Brabender single screw extruder equipped with a '~
mixing screw. The blend was melt processed at 260C., , i~
stranded and pelletized.
The pelletized blend was dried at 100C. for 8 hours in desiccant air with a dew po,int S-29C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 260C. and a mold ~a ~ ,`'' temperature of 23C. to provide amorphous test specimens. The impact properties of the blend are ~ '' ',,', summarized in Table III. ; , ,,,~

The PET of Example 1 was dried at 150C. for 16 hours in desiccant air with a dew point S-29C.
Ionomer A was dried at 60C. for 16 hours in desiccant air with'a dew point S-29C. The PET and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 15 weight percent. The ~ ~' PET~Ionomer A blend was placed in the hopper, under dry ~'' ~':

~:

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N2, of a Sterling single screw extruder equipped with a mixing screw. The blend was melt processed at 260OC., stranded and pelletized.
The pelletized blend was dried at 100C. for 8 `
hours in desiccant air with a dew point <-29C. and injection molded on a Boy 22S injection molding machine - - ~
using a melt temperature of 260C. and a mold -, :
temperature of 23C. to provide amorphous test specimens. The impact properties of the blend are ~ ~ ~;
summarized in Table III.

The PET of Example 1 was dried at 150C. for 16 ~- -hours in desiccant air with a dew point S-29C. ;~
Ionomer A was dried at 60C. for 16 hours in desiccant air with a dew point S-29C. The PET and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 15 weight percent. The PET~Ionomer A blend was placed in the hopper, under dry N2, of a Werner and Pfleiderer ZSK-28mm corotating, intermeshing twin screw extruder having the "medium"
screw design. The blend was melt processed at 260C., stranded and pelletized.
The pelletized blend was dried at 100C. for 8 ;~
hours in desiccant air with a dew point S-29C. and in~ection molded on a ~oy 22S injection molding machine using a melt temperature of 260C. and a mold temperature of 23C. to provide amorphous test -specimens. The impact properties of the blend are summarized in Table III.

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W O 94/06864 PC~r/US93/08132 -.

TABLE III
Effect of Different Extruders ~-IZOD IMPACT STRENGTH (J~m) -EXTRUDER Notched Unnotched Notched Unnotched EXAMPLE TYPE (23C.) (23C.) (-400C.) (-40C.
Ex. 12 MPM
Control 39 2321 31 2687 ~ -~
(5CB) (5NB)(5CB) (5NB) ~ ~-Blend 80 1871 51 2300 ~ -(5CB) (5NB)(5CB) (5NB) Ex. 13 Brabender Control 39 1776 30 2645 (5CB) (3NB,lPB) (5CB) (5NB) Blend 87 1839 50 2184 - ~- -(5CB) (5NB)(5CB) (5NB) ;~
Ex. 14 Sterling Control 40 2401 28 2565 (5CB) (5NB)(5CB) (5NB) Blend 98 2030 56 2162 (5CB) (5NB)(5CB) (4NB) Ex. 15 WP-Med. Screw Control 33 2374 30 2470 (5CB) (5NB) (5CB) (3NB,lCB) Blend 528 206253 2253 30(2NB,3CB) (5NB)(5CB) (5NB) -Ex. 3 WP-Hard Screw Control 32 241724 1712 ~ -~
(5CB) (5NB)(5CB) (2NB,3CB) 3581end 1198 191954 2200 (5NB) (5NB)(5CB) (5NB) The results in Table III clearly show that single screw extruders do not provide the necessary shear to prepare blends with high notched impact strength as compared to twin screw extruders. (The data from Example 3 is included for comparison purposes.) 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 ~-"

W O 94/06864 PC~r/US93/08132 2~ 720 - 25 ~

single screw extruder. However, the results also indicate that twin screw extruders do not necessarily ~ `~
provide the proper amount of shear unless the "hard"
screw design is employed.

The PET of Example 1 was dried at 150C. for 16 hours in desiccant air with a dew point S-29C. -~
Ionomer A was dried at 60C. for 16 hours in desiccant air with a dew point S-29C. The PET and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 20 weight percent.
Samples containing only PET were used as control examples. The blend and control sample were run on the same extruder and injection molded on the Boy 22-S ~ ~p ~-injection molding machine. The blend and control sample were annealed and crystallized at 150C. in a forced air oven for a period of zero, two, four, six, and eight ~ ~ -minutes, respectively. The test results are summarized ;~
in Table IV. Unannealed bars of the PET control and the blend are included in Table IV for comparison purposes.

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TABLE IV . . ~ :
ANNEALING -~
TINE AT IZOD IMPACT STRENGTH (J~m) 150C. Notched Unnotched Notched Unnotched S EXAMPLE (min.)(23C.) (230C.l(-40C.l (-40C.l Ex. 16 '~
Control 0 28 2475 30 3355 (5CB) (5NB)(5CB) (4NB) Blend 0 1203 2226 56 2783 ' '~
(5N8) (5NB)(5CB) (5NB) '~'~''''''"
Ex. 17 , -8~
Control 2 31 287g 29 1685 ~~''~''''' ' (5CB) (5NB)(SCB) (lNB,4CB) `~
Blend 2 109 2131 66 1866 (lPB,4CB) (5NB) (5CB) (3NB,lCB) Ex. 18 ' -~
Control 4 30 2995 28 2300 (5CB) (5NB)(SCB) (2NB,3CB) '~
Blend 4 93 2465 90 2592 (5CB) (5NB) (5CB) (5NB) Ex. 19 '~
Control 6 28 3254 36 2602 ~'~'"'""-'';'~' (5CB) (5NB)(5CB) (lNB,4CB) Blend 6 92 2560 73 1908 (5CB) (5NB)(5CB) (3NB,lCB) ~ ' Ex. 20 Control 8 23 2889 33 1373 (5CB) (3NB,lCB) (5CB) (lNB,4CB) '' Blend 891 2518 82 2374 (5CB) (5NB) (5CB) (SNB)"~ ' The results in Table IV clearly show that the ';~
blends Or the present invention, even in a highly crystalline form, have better impact strength than "' '~
crystalline PET. As the annealing time at 150C. is increased from-2 to 8 minutes the crystallinity of the polymers increases as determined by density gradient `~;-';' ' tube measurements. After the maximum crystallization time of 8 minutes is obtained, the PET~ionomer blend still retains a notched Izod impact strength at 23C. of 91 J~m compared to 23 J~m for the similarly treated PET

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W 0 94/06864 PC~r/US93/08132 ~ ~
2~i~272~

control. This is a 300% increase in impact strength.
Low temperature notched Izod impact strength determined -at -40C. also shows improvement over the annealed control. For example, the PET~ionomer blend still 5 retains a notched Izod impact strength at 23c. of 82 J~m compared to 33 J~m for the similarly treated PET
control. It is important to note that even after 8 minutes of annealing, the notched Izod impact strength is higher than the uncrystallized PET control which is 30 J~m at -40C.
In addition, the unnotched Izod impact strength of the blend at -40C. after annealing for 8 minutes also shows significantly improved ductile strength, 5NB, as compared to the PET control which had a value of 4CB,lNB -indicating mostly brittle failure. ~-,~

The PET of Example 1 was dried at 150C. for 16 hours in desiccant air with a dew point 5-29C.
Ionomer A was dried at 60C. for 16 hours in desiccant air with a dew point S-29C. The PET and Ionomer A were pellet blended in a polyethylene bag such that the concentration of Ionomer A was 20 weight percent. The PET~Ionomer A blend was placed in the hopper, under dry N2, of a Werner and Pfleiderer ZSK-30mm corotating, intermeshing twin screw extruder having a screw length of 1061 mm wherein 266 mm of the screw length contains kneading blocks and left-handed blocks to provide high shear. The blend was melt processed at 260C. under high shear conditions, stranded and pelletized. ~ -The pelletized blend was dried at 100C. for 8 hours in desiccant air with a dew point S-29C. and injection molded on a Toyo T9OG injection molding machine using a melt temperature of 265C. and a mold ' ' ' ~ ' ' " ' ~4~ 28 -temperature of 230c. to provide amorphous test specimens.
The same high impact strength was obtained with this blend as was obtained from the identical blend of Example 4 which was made on the Werner and Pfleiderer ZSK-28mm corotating, intermeshing twin screw extruder ;
and molded on the Boy 22S injection molding machine. ~-The Werner and Pfleiderer ZSK-28mm twin screw extruder has a torque meter. The effect of torque over ~ ~-a range of 67.8 Joules to 101.7 Joules (600in-lb to -~
900in-lb) was evaluated. The torque was adjusted by changing the throughput rate of the polymer. A higher throughput rate of polymer resulted in higher torque.
Torque was also adjusted by changing the extruder RPM.
Example 22 contained the PET of Example 1.
Example 22 was not passed through an extruder but was ~ -injection molded, thus no torque was applied. Examples 23 to 30 were passed through an extruder and injection molded. Example 23 contained the PET of Example 1 and 101.7 Joules of torque wa8 applied. Example 24 was a PET~Ionomer A blend such that the concentration of Ionomer A was 15 weight percent, and 101.7 Joules of torque was applied. Example 25 contained the PET of Example 1 and 90.4 Joules of torque was applied.
Example 26 was a PE?~Ionomer A blend such that the concentration of Ionomer A was 15 weight percent, and 90.4 Joules of torque was applied. Example 27 contained -the PET of Example 1 and 79.1 Joules of torque was applied. Example 28 was a PET~Ionomer A blend such that the concentration of Ionomer A was 15 weight percent, ;;
and 79.1 Joules of torque was applied. Example 29 contained the PET of Example 1 and 67.8 Joules of torque 3S was applied. Example 30 was a PET~Ionomer A blend such ; ~ `

.,~',... `: :', .~

2~272`0 .

,. - ~ ~;

that the concentration of Ionomer A was 15 weight percent, and 67.8 Joules of torque was applied.

TABLE V
Effect of Torque on Izod Impact Strength TEST Ex. 22 Ex. 23 Ex. 24 Ex. 2S Ex. 26 -~
TORQUE (J) 0 101.7 101.7 90.4 90.4 DENSITY
Before Nolding 1.399 1.378 1.280 1.377 1.296 After Nolding 1.337 1.335 1.267 1.338 1.268 HEAT DEFLECTION TEMP.(C.) 0 0.45 MPa 70 69 66 71 67 ` `-~ 1.82 MPa 61 63 60 63 S9 I.V. (dl~g) Before Molding 0.692 0.643 0.654 0.642 0.664 After Molding 0.629 0.641 0.573 0.621 0.544 FLEXURAL STRENGTH
(NPa) 74.62 74.96 52.16 74.62 52.92 -~
FLEXVRAL MODULUS
(MPa) 2432 2391 17502439 1771 BREAX ELONGATION
(%) 450 313 376 422 344 TENSILÉ STRENGTH .;.~.. --.. -./
(MPa)81.564.0 65.9 79.3 60.8 ~-- -, " .'.!,`
YIELD STRENGTH `~
(MPa) 56.2 56.9 43.8 56.4 44.6 `
BREAX STRENGTH
(MPa) 81.5 64.0 65.9 79.3 60.8 MOLD SHR.(%) 0.270 0.250 0.480 0.280 0.460 ;, ~-23C NOTCHED42.238.4 1127 28.8 584.7 ~ ` :
(J~m) SCB 5CB SNB 5CB 3CB,2NB

(J~m) 5NB 5NB 5NB 5NB 5NB ~ ;
-40C NOTCHED27.826.2 44.3 26.7 46.5 (J~m) 5CB 5CB 5CB 5CB 5CB ; ~`

(J~m) 5NB3CB,2NB 5NB 2CB,3NB 5NB
ZINC (%) 0 0 0.42 0 0.42 .--. - :...

W094/06864 PCT/VS93/08132 ~

~4~ 30 - ;~
TABLE V (continued) Effect of ~orque on Izod Impact Strength i Ex. 27 Ex. 28 Ex. 29 Ex. 30 TORQUE (J) 79.1 79.1 67.8 67.8 DENSITY - -Before Molding 1.3751.292 1.373 1.288 ~ ;
After Molding 1.337 1.268 1.337 1.268 HDT (C.) 0 0.45 MPa 66 64 66 64 Q 1.82 MPa 66 60 60 57 ~ -I.V. (dl~g) Before Molding 0.6500.648 0.616 0.626 After Molding 0.6210.553 0.558 0.549 FLEXURAL STRENGTH
(MPa) 74.8 52.6 74.0 52.7 FLEXURAL MODULUS
(MPa) 2418 1785 2363 1791 ~-BREAK ELONGATION
(%) 405 365 523 381 TENSILE STRENGTH ;-(MPa) 76.5 63.4 78.865.8 YIELD STRENGTH
(MPa) 56.2 43.9 56.343 9 BREAK STRENGTH
(MPa) 60.8 76.5 63.765.8 MOLD SHR.(%) 0.280 0.500 0.200 0.480 23C NOTCHED 30.4 940.9 36.8552.7 (J~m) 5CB lCB,3NB 5CB3CB,2NB
23C UNNOTCHED 2740.5 2308.5 2390.7 2176.1 (J~m) SNB 5NB 5NB5NB
-40C NOTCHED 24.0 40.6 25.6 41.7 -~ ~
(J~m) SCB 5CB 5CB 5CB - i -(J~m) 5NB 5NB lCB,3NB 5NB
ZINC (t) O 0.43 0 0.43 ~ -i The results in Table V indicate that higher torque results in more shear being applied to the sample. The -data also indicates that the blends of PET~Ionomer A
display significantly more impact resistance than the control ~amples of PET. Moreover, the highest impact properties are achieved with the blends at the maximum ~ ".!,,~
torque. Notched and unnotched impact strength continued ... ~ ~ ......

W O 94/06864 PC~r/U593/08132 21~2 ;72~
~:

to increase for the blends as the torque was increased from 67.8 Joules to 101.7 Joules.

The PET of Example 1 was dried at 150C. for 16 hours in desiccant air with a dew point S-29C.
Ionomer C was dried at 60C. for 16 hours in desiccant air with a dew point s-29C. The PET and Ionomer C were pellet blended in a polyethylene bag such that the concentration of Ionomer C was 5 weight percent. The PET~Ionomer C blend was placed in the hopper, under dry ~2, of a Werner and Pfleiderer ZSK--28mm corotating, intermeshing twin screw extruder having the "hard" screw design. The blend was melt processed at 260C. under high shear conditions, stranded and pelletized.
The pelletized blend was dried at 100C. for 8 hours in desiccant air with a dew point S-29C. and injection molded on a Boy 22S injection molding machine using a melt temperature of 260C. and a mold temperature of 23C. to provide amorphous test specimens. The impact properties of the blend are summarized in Table VI. The impact properties of Example 1 which is the PET control is provided for comparison purposes.

$~5 32-34 The procedure of Example 31 was followed except : :-that the concentration of Ionomer C in the PET blend was changed to provide Ionomer C concentrations of 10, 15 and 20 weight percent, respectively. The effect of the zinc ionomer concentrations in PET are summarized in ; Table VI.

W O 94/06864 PC~r/US93/D8132 ~ ~ ~

~4~ 32 ~

The procedure of Example 2 was followed except that Ionomer C was substituted with Ionomer D. The concentration of Ionomer D in the PET blends was 5, 10, 15 and 20 weight percent, respectively. The results are summarized in Table VI.
-' '~"~, ' TABLE VI
Impact Strength of Zinc and Sodium Copolymer Ionomers IONOMER IONOMER IZOD IMPACT STRENGTH (J~m) C D Notched Unnotched Notched Unnotched EXAMPLE (wt%~ (wt~) r23C.) (23C.) (-40C.) (-40C.
Ex. 10 0 32 2362 30 1949 lS (5CB) (5NB) (5CB) (3NB,2CB) ;~
Ex. 31 5 0 44 1720 37 2076 ~ -(5CB) (5NB) (5CB) (5NB) Ex. 32 10 0 56 1837 41 2173 (5CB) (5NB) (5CB) (5NB) ~ -Ex. 33 15 0 119 2050 52 2452 (5CB) (5NB) (5CB) (5NB) Ex. 34 20 0 1050 2046 61 2102 (4NB) (5NB) (SCB) (5NB) Ex. 35 0 S 30 2590 28 2811 ~- `
(SCB) (SNB) (SCB) (5NB) Ex. 36 0 10 38 2562 34 2728 (5CB) (SNB) (SCB) (SNB) Ex. 37 0 lS 47 2232 41 2419 - '-(SCB) (SNB) (5CB) (5NB) ! I Ex. 38 0 20 43 2443 39 2303 ,~
(5CB) (5NB) (5CB) (5NB) The data in Table VI indicates that significant increases in impact strength at 23~C. and -40C. are ;
achieved with the PET~Ionomer C blends wherein the acid component is neutralized with zinc exhibit as compared ~

:

- .

W O 94/06864 PC~r/US93/08132 2~ ~27~

- 33 ~

to PET~Ionomer D blends wherein the acid component is neutralized with some other ion such as sodium.
Moreover, the mode of impact failure for the blends utilizing zinc was ductile as opposed to brittle for the blends utilizing sodium. ~ - ;
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.

,'~: i

Claims (6)

WHAT IS CLAIMED IS:

1. A process for preparing a polyethylene terephthalate/ionomer blend which exhibits high impact strength comprising:
(I) melt blending (A) 70.0 to 90.0 weight percent of a polyester which comprises (1) a dicarboxylic acid component comprising repeat units from at least 95 mole percent terephthalic acid; and (2) a diol component comprising repeat units from at least 95 mole percent ethylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent diol, said polyester having an inherent viscosity of about 0.4 to about 1.2 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 about 40 to about 95 percent with zinc ions;
wherein the combined weights of (A) and (B) total 100 percent and the blending is conducted in an extruder containing at least eight kneading blocks wherein at least two of the kneading blocks are left-handed, at a shear rate of 3500 sec-1 to 7000 sec-1; and (II) forming the blend into an article.

2. The process according to Claim 1 wherein the polyester, component (A), is polyethylene terephthalate.

3. 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.

4. The process according to Claim 3 wherein the ionomer, component (B), has a melt index at 190°C. of 1.0 to 2.0 grams.

5. The process according to Claim 1 wherein the ionomer, component (B), comprises discrete particles, the major portion of which have diameters of about 0.1 to about 0.3 microns.

6. The process according to Claim 1 wherein the blending is conducted in an extruder at a shear rate of 3500 sec-1 to 6000 sec-1.