CA1315934C - Multilayered articles formed by coextrusion of polycarbonate and polyester - Google Patents

Multilayered articles formed by coextrusion of polycarbonate and polyester

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Publication number
CA1315934C
CA1315934C CA000599436A CA599436A CA1315934C CA 1315934 C CA1315934 C CA 1315934C CA 000599436 A CA000599436 A CA 000599436A CA 599436 A CA599436 A CA 599436A CA 1315934 C CA1315934 C CA 1315934C
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Prior art keywords
multilayer article
polyester
polycarbonate
article
carbonate
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CA000599436A
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French (fr)
Inventor
James M. Mihalich
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General Electric Co
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General Electric Co
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  • Polyesters Or Polycarbonates (AREA)

Abstract

MULTILAYERED ARTICLES FORMED BY COEXTRUSION
OF POLYCARBONATE AND POLYESTER

ABSTRACT OF THE DISCLOSURE

The present invention relates to a multilayer article formed by the coextrusion of a polyester and polycarbonate. The polyester and polycarbonate are extruded into a film wherein the polyester forms the top and bottom layers of the film and the polycarbonate becomes the inner layer. The films may be thermoformed into articles which exhibit excellent strength and impact values.

Description

13~.3934 ~ RTICLES FORMED BY COEXTRUSION
~

~b--~ -The present invention relates to a multilayer arti~le comprising the coextrusion product of a polyester and polycarbonate.
Currently, there is a large commercial interest in 10 the packa~ing indus~ry for container8 which are able to be heated in both conventional hot air ovens and microwave ovens. Polyesters and particularly polyethylene terephShalates are being employed in an increasing nu~ber of such applications. Unfortunately, to obtain the desired impact strengths~ these contain~rs have generally been constru~ted from relatively thick materials (e.g., 40 mils or more~. The use of such thick materials adds substantially to the cost of the container. It therefore i5 desirable to provide articles 20 for conven~ional and microwave u~e that provide improvsd strength~ over the p~lyester article~ which utilize l~ss pl~stic.
3~b~
The presen~ inven~ion relates to multilayer articles which are formed by the coextrusion of a polyester and polycarbonate. Advan~ageously, multilayer film~ o~ the present invention can be used i~ both cold and high temperature applicationsO are able to be mass produ~ed with little wa~te~ an~ have i~proved i~pac~ s~reng~hs over prior art polyester articles.

: The present invention relates to mul~ilayer ar~icles . that are formed by the coextrusion of a polyester and : polycarbonate. Tbe polyester and polycarbona~e are first coextruded into a mul~ilayer fllm which may be later u-~d ;

.

.

in packaqing or ~hermoformed into containers such a~
trays. The multilayer articles have the advantage o~
ease of processing since the polycarbonate assumes its shape at a temperature above the crystallization temperatures of the polyester. This allows for crystallization of the ~rticle in a subsequent step to thermoforming which provides faster production rates.
~ he articles of the present invention have excellent low temperature impact strengths avoiding the typical brittleness of polyethylene terephthalate articles ~t freezing tempera~ures. Polycarbonate is not embrittled at these temperatures and imparts excellent impact properties to the articles.
The multilayer articles have improved high temperature dimensional stability by freeing the polyester from the low temperature impact requirements ~i.e., thickness) and allows for higher crystallinity.
The polycarbonate provides dimensional stability and offsets the brittleness commonly associated with crystalline polyesters.
The polyester that can be used in the present invention can be of the formula:

11 ~

0-R-0-C_ ~ ~

b : ' where b represent~ a whole number in excess of 1, e.g., 10 to lO,OOG or more, R i5 a divalent alkylene radical containing from 1 to 10 or more carbon atoms, and the two carbonyl gropus are located on the aromatic ring in a para- or meta- position relative to each other.

' ~ 3 ~ 08CS-04351 The polyesters can be obtained by any of the method~
well-known to those skilled in the art including reaction sf any aromatic dicarboxylic acid of the formula:

~- OR1 o where independently R1 and R2 is an alkyl radical having from 1-10 or more carbon atoms, with an aliphatic diol of the formula:
.
HO - R - OH

where R is as previously defined~
As used herein, and in the appended claims, the term polyesters include esters of the above formula prepared by esterifying or transesterifying terephthalic acid, isophthalic acid, or their low molecular weight esters of the above formula, or mixtures thereof, plus other polyesters derived from aromati~ dicarboxylic acids on ; their al~yl es~ers and other aliphatic diols or polyols other than the above formuias, respectively.
: ~ : Examp1es~of polyesters that can be used 1n the : : invention include polyethylene terephthalate, polybutylene t~rephth~late resins and pol~cyclohexylene terephth~alate, here~fter sometimes referred to as PET, PBT~and~PCT, respectively. ~PET is preferred for use in ~ thla lnvention. In general, the:P~T, PBT and PCT resins :::: ::

,., , :
~: , , ' -~ 3 1 5 ~ 3 '1 OZCS-04351 comprise high molecular weight poly~1,4-ethylene terephthalate) resins, poly(l,4-butylene terephthalate) resins and poly(1,4-cyclohexylene terephthalate) having repeating units of the gener~l formulas, respectively:
s ~O ~ CHz ;~ O -- C ~-- C

~ O O
- O ~ CH2 ~ O - C ~ C - b O O ---- O ~ O ~ _ b and mixtures thereof, b being as previously defined.
The polyesters which may be used in this inventiQn also include PET copolyes~ers t PBT copolyesters and PCT
:~ copolyesters, i.e., esters that contain a minor amount, e.g., from about 0.5:to:about 2% by weight, of repeating : units derived from an aliphatic or another aromatic dicarboxylic acid and/or another aliphatic diol and ~15 polyol. ~mong the units which can be presene in the : copolyesters are those derived from aliphati~
dicarboxylic acids, e.g., acids having up to about 50 ~ 3 ~ 08CS-04351 earbon atoms, including cycloaliphatic, straight and branched chain acids, such as adipic ~cid, cyclo-hexanediacetic acid, dimerized C16_1g unsaturated acids (which have 32 to 36 carbon atoms), tri~erized such acids, and the like. Among the units in the copolyesters can also be minor amounts derived from aromatic dicarboxylic acids, e.g., acids having up to about 36 carbon a~oms, such as isophthalic acid and the lik~. In addition to the PET and PBT units derived from ethylene glycol and 1,4-butylene glycol, respeotively, there can also be minor amounts of units derived from other aliphatic glycols and polyols, e~g., d$- and polyols having up to about 50 carbon atoms, including ethylen~
glycol, propylene glycol, butylene glycol, cyclo-hexanediol, and the like.
The polyesters useful in forming the multilayered articles are known as "high molecular weight. n ~igh molecular weight" means a polyecter having an intrinsic viscosity (I.V.) ranging from about 0.5 to about 1.10 and 20 preferably from about 0.70 to about 1.0 as measured in a 60/40 by volume mixed sol~ent of phenol/tetraehloroethane at 30UC. The polyesters useful in the pre~ent invention will also be characterized by densities of about 1.361 grams per cubic centime~er or less.
Polycarbonates for use in the produotion of the multilayered articles of the invention are high molecular weight, thermoplastic, aromatic polymers and include homopolycarbonates, coopolycarbonates and copolyestercarbona~es and mix~ure~ thereof which have 30 average molecular weigh~s of abou~ 8,000 to more than 200,000r preferably of about 20,000 to 80~000 and an I~V.
of 0.40 ~o 1.0 dl/g as measured in ~ethylene chloride at 25-C. In one embodimen~, ~he polycarbonates are d~rived ~31 ~3~ 08CS-0435l from dihydric phenols and carbonate precursors and generally contain recurring structural units of the formula:

_ O ---Y. O - C _ where Y is a divalent aromatic radieal of the dihydric ~phenol employed in the polyc~rbonate producting reaction.
Suitable dihydric phenols for producing polycar~onates include the dihydric phenols such as, for : 10 example, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxy-phenyl~methane, 202-bis(4-hydroxy-3-methylphenyl)-propane, 4,4-bis(4-hydroxyphenyl)heptane, 2,2-(3,5,3l,5'-: tetrachloro-4,4'-dihydroxyphenyl)propane, 2,2-(3,593',5'-tetrabromo~4,4'-dihydroxyphenyl)propane, and 3,3'-di-15 chloro-4,4'-dihydroxydiphenyl)methaner O~her dihydric phenols which are also suitable for use in the ~preparation of the a~ove polyc~arbonates are disclosed in U.S. Patent Nos. 2,999,835t 3,0389365, 3,334,154~ and : ::: 4,131,575.
: 20~ ~ It is of course possible to employ two or more different dihydric phenols or a copolymer o~ a dihydric phenol with a glycol or wi~h a hydroxy- or acid-terminated polyester, or with a dibasic a~i~ in the event a:carbonate copolymer or interpolymer raSher than a ~:

O~CS-04351 1 3 1 ~ 9 3 4 homopolymer is desired for use in the preparation of th~
articles of the invention. Blends of any of the above materials can also be employed to provide thP aromatic polycarbonate. In addition, br~nched polycarbon~tes such S as are described in U.S. Patent ~o. 4,001,184, can also be utilized in the prac~ice of this invention, as can blends of a linear polycarbonate and a br~nched polycarbon~te.
The carbonate precursor employed can bs either a 10 ~arbonyl halide, a carbona~e ester or a haloformate. Ths carbonyl halide which can be employed are carbonyl bromide, carbonyl chloride and mixtures thereof. Typical of the carbon~te esters which can be.employed ar~
diphenyl carbonate, a di(halopherayl~carbonate such a~
1 5 d i ( ch lorophenyl 3 c arbonate, d i ( bromophenyl ) carbonate, di (trichlorophenyl )carbonate, di (tribromophenyl )-carbonate, etc., di(alkylphenylicarbonate such as di ( tolyl ) carbonate, etc., di ~ nap'chyl ) carbon~te, di ( chloronaphthyl ) carborlate, etc ., or mixt:ures thereof .
20 The suitable haloforma~es includ~ bis-haloformates of dihydric phenols (bischloroformates of hydroquinone, etc.) or glycols (~ishaloformate of ethylene glycol, neopentyl qlycol, polyethylene gly.,ol, etc. ) . Whil~
other carbonate precursors will occur to those skil~ed in 25 the art, carbonyl chloride, also known as phosgene, i~
pre f e r red.
The polycarbonate may also be a copolyestercarbonate as described in Clayton B. Quinn in United States Patent Number 4j430,484 and the references cited therein.: Preferred polyestercarbonates are those derived from the dihydric phenols and carbonate precursors described above and aromatic dicarboxyli~ a~id~ or their relative derivatives, such as the id dihalides, e.~., dichlorides. A quite useful class of aromati~

-- ~ 3 1 ~ 9 ~ ~ 08C~-04351 polyestercarbonates ar~ those derived from bisphenol A;
terephthalic acid, isophthali~ acid or a mixture thereof or their respective acid chlorides; and phosgene. If a mixture of terephthalic acid and isophthalic acid i~
employed, the weight ratio of terephthalic acid to isophthalio acid may be from about 5:95 to about 95:5~
Another polycarbonate wbich may b~ used has from ~bout 70 to about 95 weight percent ester con~cent and a range o~
terephthalate groups o fro~ 2 to about 15 weiyht percent of the total ester content. The remaining ester units are isophthalate units. These polycarbonates are more commonly known as polyphthalate carbonates and arP
described, for example, by Miller et al., United States Patent Number 4,465, 820 issued, August 14, 1984.
The polycarbonates used to for~ the present invention can be manufactured by known processe~, such as, for example, by reacting a dihydric phenol with a carbonate precursor su~h as diphenyl c~rbonate or phosgene in ccordance with the methods set forth in the abov2-cited literature and U.S. Patent Ncs. 4,018,750 and 4,123,436, or by transesterification processes such as are disclosed in U.S. Patent No. 3,153,008 as well as other processes known to those skilled in the art.
The aromatic polycarbonates are typi~ally prep~red by employing a molecular weight regulator~ an acid acceptor and a catalyst. The mole~ular weight regulators which can be employed include phenol, cyclohexanol, methanol, al~ylated phenols, such as octrylphenol, parater~iary-butyl-phenol, etc.
Preferablyt phenol or an alkylated phenol is employed as . the molecular weight regulator.
: The acid acceptor can be either an org~nic or an iQOrganic acid acceptor. A sui~able organic acid acceptor is a tertiary amine and includes such materials 3 ~
g : as pyridine, triethylamine, dimethylaniline, tributylamine, etc. The inorganic acid acceptor can be one which can be either a hydroxide, a carbonate, a bicarbonate, or a phosphate or an alkali or alkaline earth metal.
The catalyst which can be employed are those that typically aid the polymeriza~ion of the monomer with phosgene. Sui~able catalysts include tertiary amines such ~s triethylamine, tripropylamine, N,~-dimethyl-aniline, quaternary ammonium bro~ide, cetyl trie~hylammonium bromidet tetra-n-heptyl æmmonium iodide, tetra n-propyl ammonium bromide, tetramethyl ammonium chloride, tetra-methyl ammonium hydroxide, tetra-n-butyl ammonium iodide, benzyltrimethyl ammonium chloride and quaternary phosphoniu~ compounds such a~, for example, n-butyltriphenyl phosphonium bromide and methyltriphenyl phosphonium bromideO
Also included are branched polycarbonates wherein a polyfunctional aromatic compound is r~acted with the monomer ~nd c~rbonate precursor to provide a thermoplastic randomly branched polycarbonate. The polyfunctional aromatic compounds contain at least three functional groups which are carboxyl, carboxylic anhydride, haloformyl, or mixtures thereof. Illustrativ~
polyfunctional aromatic compounds which can be employed include trimellitic anhydride, trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalic, ~nhydride, pyromellitio acidO pyromellitic dianhydride, : : mellitic a~id, melli~ic anhydride, benzophenon-30 ~ tetracarboxylic anhydride~ and ~he like. The preferredpolyfunctional aromatic compounds are trimelliti~
anhydride and trimelliti~ acid or their acid halide derivatives.

~ 13~5~3~ 08CS-04351 As used throughout this specification and the appended claims the term "crystallization temperature"
means that temperature or temperature range in ~hich a regularly r~peating msrphology, brought about by a combination of molecular mobility and secondary bonding forces, is induced in a polymer over a molecular distance of at least seYeral hundred angstroms.
The multilayered film is formed by the coextrusion of the polyester and polycarbonate at a temperature at or above the melt temperature of the polycarbonate. The polyester is a relatively low viscosity material in the melt and has a tendancy to flow to the outer surfaces o~ the film. The polycarbonate is a relatively high viscosity material in the melt and forms the middle layer of the multilayered film. The method of coextrusion is a method common to those skilled in the art.
After the polycarbonate and polyester have been coextruded to form a multilayered sheet, one can then process the film to form a number of packaging products. One may elect to utilize the film as is or thermoform the film to make trays, dishes, bowls, etc.
If the film is thermoformed, the thermoformed article is heated to a sufficiently high temperature to crystallize the polyester. Upon crystallization, the article is die cut and is now suitable for use.
Alternatively, the article can be die cut and then crystallized by heating. Surprisingly, the disadvantages of brittleness o crystallized polyester articles are avoided by the addition of amorphous polycarbonate which is particularly important in avoiding cracking during die cutting the crystallized articles.
The multilayered films can be extruded in a variety of thicknesses. Generally, such films range from a total thickness of about 1 to about 60 mils.

~ ~5~ 08CS-04351 Generally, the outer layer, i.e., top and bottom, of the film polyester having each layer having a thickness of from about 0.4 to about 30 mils. The middle layer is generally polycarbonate having a thickness of from about 0.1 to about 30 mils. Preferably, the outer layers of polyester each have a thickness of from 5 to 20 mils with the inner layer of polycarbonate ranging from about 3 to about 10 mils.
Various colorants may b~ used in the multiiayer 10 ar~icles of the present invention. Preferably, the colorants are Fl:~A-approved colorants since the articles may be used wi'ch foods~uffs. The colorants can be added at any stage during the preparation of the polyester m~terial as during esterification or transesterification 15 stage, ~he polycondensation stage, during re~in drying, during extruding, and the llke. Generally, any ~olorant~
that is dyes which are soluble~ or inoryanic or org~nie pigments can be utilized. Examples of dyes include ~he various azo dyes, anthraquinone dyes, ~zine dyes, ~d tha 20 lilse. Examples of inorganic pigments which are added to the polyester to impart a color or hue thereto in lude titanium dioxide, carborl black, iron oxide, chrs~mium oxide greens, iron blue, chrome gr~en, viole~ pigments, ultramarine pigments, titanate pigments, pearlescent pigments, metallic pigments such as aluminum, browns~
powders, e~c., and the like. Organic pigmen~ include monazo pigments, disazo pigment~, and the like9 Naturally, various a~ounts utilized to impart a d~sired color or hue and such amounts can change over a wide range~
;The following exampl~ illustra~es a specific multilayer article of the pr~snt invention~ It should b~ underskood that tAe exampl~ is given for the purpose of illustration and dces not li~it the invention.

- ~ 3 1 .~ 3 3 ~ 08CS 04351 ~xample A multilayer film of polyc~rbonate-polyester w~8 formed by ~he coextrusion of the two polymers. The polycarbona~e was known as Lexan~ 104 which is S commercially available from the General ~lectric Compsny.
The polyester was polyethylene terephthalate and is commercially available from the Goodyear Tire and Rubber Company of Akron, Ohio as Cleartuff0 7207. The PET
eactruder had a heating profile of 540'F, 530-F, 520'P and 10 520~F. The polycarbonate extruder had a heating pro~ile of 535'F, 530F, 530qF and 520'F. The bloc3c was heated at 520~F. The temperature of the rolls was maintained at 205~F (top~, 155~F (center) and 130"F (bottomj. The resulting multilayer film had a total thickness o~ 40 15 mi~s wherein the top layer of PET was 14 mil, the middls layer of polycarbonate was 8 mil and the bottom layer of PE~r was 18 mi l .
While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the spirit and scope of the in~ention as defined in the appended claims.

Claims (18)

1. A multilayer article comprising two outer layers and a middle layer, said outer layers comprising a polyester resin of the formula:

where b represents a whole number in excess of 1, R is a divalent alkylene radical containing from 1 to 10 or more carbon atoms, and the two carbonyl groups are located on the aromatic ring in a para- or meta- position relative to each other, said middle layer comprising a polycarbonate resin.
2. The multilayer article of claim 1, wherein said article is in the form of a film or container.
3. The multilayer article of claim 2, wherein said article is a film.
4. The multilayer article of claim 3, wherein said article consists essentially of three layers.
5. The multilayer article of claim 3, wherein the film is thermoformed.
6. The multilayer article of claim 5, wherein the polyester in the thermoformed film is crystallized by heating.
7. The multilayer article of claim 1 wherein the polycarbonate is derived from a dihydric phenol and a car-bonate precursor.
8. The multilayer article of claim 7, wherein said dihydric phenol is 2,2-bis(4-hydroxyphenyl) propane and the carbonate precursor is carbonyl chloride.
9. The multilayer article of claim 7, wherein said dihydric phenol is 2,2-bis(4-hydroxyphenol)propane and the carbonate precursors is diphenyl carbonate.
10. The multilayer article of claim 2, wherein the polycarbonate contains recurring structural units of the formula:

where Y is a divalent aromatic radical of the dihydric phenol employed in the polycarbonate procarbonate producing reaction.
11. The multilayer article of claim 1, wherein said polycarbonate is a polyphthalate carbonate prepared from a dihydric phenol, a carbonate precursor, a terephthalic acid or ester-forming derivative thereof, an isophthalic acid or ester-forming derivative thereof, said polyphthalate carbonate having from about 70 to 95 weight percent ester content and a range of terephthalate groups ranging from about 2 to about 15 percent of the ester content.
12. The multilayer article of claim 11, wherein the weight percent ester content is from 75 to 90.
13. The multilayer article of claim 12, wherein the range of terephthalate groups range about 5 to about 10 percent of the ester content.
14. The multilayer article of claim 1, wherein the polyester is polyethylene terephthalate.
15. The multilayer article of claim 1, wherein the polyester is polybutylene terephthalate.
16. The multilayer article of claim 1, wherein the polyester is polycyclohexylene terephthalate.
17. The multilayer article of claim 1, wherein the outer two layers are from about 0.4 to about 30 mils thick and the middle layer is from about 0. l to about 30 mils thick.
18. The multilayer article of claim 1, wherein the outer two layers are from about 5 to about 20 mils thick and the middle layer is from about 3 to about 10 mils thick.
CA000599436A 1989-05-11 1989-05-11 Multilayered articles formed by coextrusion of polycarbonate and polyester Expired - Fee Related CA1315934C (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000599436A CA1315934C (en) 1989-05-11 1989-05-11 Multilayered articles formed by coextrusion of polycarbonate and polyester

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000599436A CA1315934C (en) 1989-05-11 1989-05-11 Multilayered articles formed by coextrusion of polycarbonate and polyester

Publications (1)

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CA1315934C true CA1315934C (en) 1993-04-13

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