Field of Invention

The present invention is directed to blends of poly(ethylene terephthalate) and polyester from 4,4' -biphenyldicarboxylic acid and at least one aliphatic glycol. The blends have improved gas barrier and chemical resistance properties .

Background of the Invention

Polyesters of 4,4 ' -biphenyldicarboxylic acid (BDA) and certain aliphatic glycols have been known in the art for decades . The homopolymers based on BDA are described as very crystalline (see U.S.

Patent 2,976,266, column 2, line 72, through column 3, line 1) and often are modified with other glycols to lower the polymer melting point. The glycols most often used are branched, aliphatic glycols such as 2, 2-dimethyl-1,3-propanediol or polyether glycols such as polyethylene glycols or polytetra ethylene glycols (U.S. Patent 3,261,812) or aliphatic-aromatic glycols such as p-xylene glycol (U.S. Patent 3,008,932). One other method for lowering the melting point of the copolyesters is to reduce the biphenyldicarboxylic acid modifier content of the polymers by the addition of another aromatic dicarboxylic acid modifier such as terephthalic acid (U.S. Patent 4,082,731). Specifically, homopolyesters of 4,4 ' -biphenyldicarboxylic acid and certain aliphatic glycols are disclosed in journal literature. Homopolyesters of 4,4' -biphenyldicarboxylic acid and ethylene glycol, 1,4-butanediol, and 1, 6-hexanediol are

disclosed by Meurisse et al., in the British Polymer Journal, Volume 13, page 57 (1981) (Table 1). Jackson and Morris include a review of homopolyesters from 4,4' -biphenyldicarboxylic acid and various aliphatic glycols in the Journal of Applied Polymer Science,

Applied Polymer Symposia, 41, 307-326 (1985). Krigbaum et al. , disclose relatively low molecular weight homopolyesters from 4,4' -biphenyldicarboxylic acid and various aliphatic glycols in the Journal of Applied Polymer Science, Polymer Letters Edition, 20, 109-115 (1982). Low molecular weight homopolyesters of 4,4' -biphenyldicarboxylic acid are also disclosed by Wanatabe et al. , Macromolecules, 21(1), p. 278-280 (1988), and Krigbaum et al. , Polymer, 24(10), p. 1299-1307 (1983). Jp . Kokai Tokkyo Koho JP

61,236,821 [86,236,821] (1986) also discloses ^" low molecular weight polyesters from

4,4' -biphenyldicarboxylic acid and 1,4-butanediol prepared below their melting temperatures in a nonvolatile liquid. Polyesters of 1,6-hexanediol and 4,4' -biphenyldicarboxylic acid are disclosed in Kobunshi Ronbunshu, Vol. 44(12), 983-986 (December 1987) having limiting viscosity number of about 0.31.

U.S. 3,842 _r 040 and U.S. 3,842,041 disclose the homopolyester of 4,4' -biphenyldicarboxylic acid and ethylene glycol.

Copolyesters of 4,4'-biphenyldicarboxylic acid (BDA) and certain aliphatic glycols are disclosed and ethylene glycol (EG), 1,4-butanediol (BD) , 1,6-hexanediol (HD) are specifically disclosed in column 2, line 70 of U.S. 2,976,266 in a general listing along with other aliphatic glycols useful in this disclosed invention. However, copolyesters of BDA

and linear, non-branched glycols are not specifically disclosed.

U.S. 4,742,151 discloses ultra-high-molecular weight polyesters prepared from aromatic dicarboxylic acids and alkylene glycols containing from 2 to 6 carbons having an intrinsic viscosity greater than 1.5.

4,4' -Biphenyldicarboxylic acid is disclosed in a list of dicarboxylic acids useful in the disclosed invention.

Blends of these polymers with other polyesters are not disclosed.

German Offenlegungsschrift, DE 1935252, discloses polyesters of two aromatic dicarboxylic acids which include 10 to 50 mol % 4,4-biphenyldicarboxylic acid, 50 to 90 mol % of terephthalic acid and the two glycols ethylene glycol and 1,4-cyclohexanedimethanol.

Japanese patent, Kokai Tokkyo Koho JP 57/198726 discloses copolyesters containing 25 to 80 mol %

4,4' -biphenyldicarboxylic acid with various aliphatic glycols and aromatic dicarboxylic acids . Heretofore, blends of PET and polyesters from

4,4' -biphenyldicarboxylic acid and at least one non-branched, aliphatic glycol having 2 to 6 carbon atoms have been unknown.

Summary of the Invention

The present invention is directed to a polymer blend comprising

(A) about 99 to about 10 weight % of poly(ethylene terephthalate) having an inherent viscosity of greater than or equal to about 0.4 determined at 25°C in 25/35/40 (wt./wt./wt. ) phenol/tetrachloroethane/p-chlorophenol at a

concentration of 0.1 gram (g)/100 milliliters (mL) , and (B) about 1 to about 90 weight % of a polyester comprising repeating units of 4,4'-biphenyldicarboxylic acid and at least one non-branched, aliphatic glycol having 2 to 6 carbon atoms wherein said polyester has an inherent viscosity of greater than or equal to about 0.2 determined at 25°C in 25/35/40 (wt./wt./wt. ) phenol/tetrachlorό- ethane/p-chlorophenol at a concentration of 0.1 g/100 L. A preferred polymer blend of the present invention comprises a polymer blend comprising (A) about 99 to about 10 weight % of pol (ethylene terephthalate) having an inherent viscosity of greater than or equal to about 0.4 determined at 25°C in 25/35/40 (wt./wt./wt.) phenol/tetrachloroethane/p-chlorophenol at a concentration of 0.1 g/100 mL, and

(B) about 1 to about 90 weight % of a homopolyester comprising of repeating units of 4,4'-biphenyldicarboxylic acid and diethylene glycol or 1,6-hexanediol, wherein said homopolyester has an inherent viscosity of greater than or equal to about 0.6 determined at 25°C in 25/35/40 (wt./wt./wt.) phenol/tetrachloroethane/p-chlorophenol at a concentration of 0.1 g/100 mL.

Detailed Description of the Invention

The prior art discloses molding, spinning, and extrusion into film as viable processes for shaping the

individual polyesters in the blend of this invention. Oriented or shaped objects from blends of poly(ethylene terephthalate) (PET) and BDA homopolyesters and copolyesters are not disclosed. The blends of this invention provide a way of reducing the gas barrier properties of poly(ethylene terephthalate) which has begun to find wide commercial acceptance in food packaging and other miscellaneous applications. We have found, for example, that it is very difficult or not even possible to biaxially orient on a T.M. Long film stretcher homopolyesters or copolyesters prepared from BDA and one or more aliphatic, non-branched glycols of the art. Generally, this is because the polymers are highly anisotropic and/or highly crystalline. Film extruded from a die is often strong only in the direction of film extrusion. Anisotropy present in the extruded films can cause the films to crack or tear along the film extrusion direction as the film exits the die. The brittle character of the extruded films can be caused by the highly crystalline nature of many of the BDA polyester films . It is usually not possible to prepare completely amorphous films by quenching films of many of the BDA homopolyesters of the art as is typical for polyesters such as poly(ethylene terephthalate) . Hence, when attempts are made to reheat extruded film of the neat BDA polyester prior to biaxial orientation, the films typically crystallize even more, preventing further extension of the polymer chains during biaxial orientation. The films often tear when stretched 200% to 300% in a manner similar to PET and will not orient. We have found that by blending these BDA polymers with PET, we are able to extrude tough films that are

biaxially orientable. The presence of as little as 1 weight % of the BDA polyesters in PET acts to reduce the carbon dioxide transmission rate by about 15%. Generally, raising the BDA polyester content to 50 weight % reduces the carbon dioxide transmission rate of PET about one half. The ability to biaxially orient the blends will allow one to use commercial stretch blow techniques for the manufacture of containers with superior gas barrier properties. For example, a 70/30 PET/(BDA) (DEG) blend (that is a blend of 30 weight % PET and 70 weight % of a (BDA) (DEG) homopolyester) would have about one half the carbon dioxide gas transmission rate of unmodified PET. One might be expected to prepare a carbonated beverage container from the blend which would have about twice the shelf life of the unmodified stretch blow molded carbonated beverage container prepared from unmodified PET.

In the polymer blend of the present invention it is preferred that the weight % of component (A) is about 10 to 90, and the weight % of component (B) is about 90 to about 10.

It is also preferred that component (B) is a homopolyester of 4,4' -biphenyldicarboxylic acid and a glycol having 2 to 6 carbon atoms, or a copolyester of 4, '-biphenyldicarboxylic acid and two glycols having 2 to 6 carbon atoms.

It is preferred that the aliphatic glycol of component (B) is 1,6-hexanediol, 1,4-butanediol, 1,3-propanediol, or 1,5-pentanediol. The PET portion of the blends (i.e., component (A)) suitable for blending with the BDA polyester (i.e., component (B) ) should have inherent viscosity (I.V.) of at least about 0.4, but preferably about 0.6 or more.

- 7 -

The PET portion of the blend may also be modified with up to about 30 mol % of other glycols containing 2 to 16 carbon atoms or other aromatic acids having up to 16 carbon atoms . Examples of suitable dicarboxylic acid modifiers include aliphatic dicarboxylic acids such as malonic, succinic, glutaric, adipic, pimelic, azelaic, suberic, sebacic, and dodecanedicarboxyliσ acids and aromatic dicarboxylic acids such as isophthalic acid, 4,4' -biphenyldicarboxylic acid, trans-4,4' -stilbene- dicarboxylic acid, 2,6-naphthalenedicarboxylic acid,

2-chloroterephthalic acid, and 2,5-diσhloroterephthalic acid.

The glycol portion of the PET may be modified with various glycols which include 1, 3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol,

1,5-pentanediol, 1,6-hexanediol, p-xylenediol, ^' and 1,3- or 1,4-cyclohexanedimethanol (trans and/or cis) . The BDA homopolyester and copolyester portion of the blends (i.e., component (B)) may be modified with up to about 30 mol % of other aromatic dicarboxylic acids having up to 20 carbon atoms such as terephthalic acid, 2-chloroterephthalic acid, trans-4,4' -stilbenedicarboxylic acid, 2,6-naphthalene¬ dicarboxylic acid, and isophthalic acid so long as the blends substantially retain their improved gas barrier properties. The BDA polyesters should have inherent viscosities of at least about 0.2, but preferably, at least about 0.6 or even about 1.0 or more.

It is preferred that component (B) is modified with about 0 to about 20 mol % of said second modifier.

When the polymer blend of the present invention is in the form of an extruded film, it is preferred that

said extruded film has a carbon dioxide permeability of

2 less than or equal to 55 cc-mil/100 in -24 hours-atm.

Other more specific polymer blends of the present invention include: (1) wherein the glycol component of component (B) comprises about 30 to 95 mol % 1,6-hexanediol, and about 5 to 70 mol % ethylene glycol, and (2) wherein the glycol component of component (B) comprises about 5 to 95 mol % 1,4-butanediol and 5 to 95 mol % 1,6-hexanediol.

The following examples are to illustrate the invention but should not be interpreted as a limitation thereo .

The inherent viscosities of the polyesters are determined in 25/35/40 phenol/tetrachloro- ethane/p-chlorophenol at 25°C at concentration of 0.1 g/100 mL. The polyesters are ground, dry-blended, dried at 100°C, and extruded and pelletized on a Werner- fleiderer extruder or on a 3/4-in. Brabender extruder at 240° to 300°C. The blends are redried at 100°C and extruded into film that is 20-mil thick and about 6 inches (in. ) wide. The films are biaxially oriented on a T.M. Long film stretcher and submitted for gas permeability testing. The oxygen permeability is determined on a Mocon Model 1000 or Model 10/50 oxygen permeability tester at 30°C and 68% relative humidity and the carbon dioxide permeability is determined on a Mocon Permatran C IV permeability tester at 0% relative humidit .

EXAMPLE 1

This example illustrates the preparation of the homopolyester consisting of 100 mol % 4,4'-biphenyl-

dicarboxylic acid units and 100 mol % 1,6-hexanediol units.

A mixture of 162.0 g (0.60 mol) dimethyl 4,4' -biphenyldicarboxylate, 85.0 g (0.72 mol) 1, 6-hexanediol, and 0.14 g titanium tetraisopropoxide is placed in a 1-L flask equipped with an inlet for nitrogen, a metal stirrer, and a short distillation column. The flask is heated at 240°C for about 1 hour, at 260°C for about 1/2 hour, and a vacuum of 0.5 millimeters (mm) is gradually applied over the next

5 minutes. Full vacuum is maintained for about 1 hour. A high melt viscosity, white crystalline polymer is obtained with an I.V. of 1.30 and a melting endotherm measured by Differential Scanning Calorimetry (DSC) at 217°C.

EXAMPLE 2

A polyester is prepared to an I.V. of 1.25 similar to that of Example 1, ground, and solid-state polymerized by heating 1 hour at 110°C and then for

4 hours at 210°C to give a polymer with an I.V. of 2.26.

EXAMPLE 3

This example illustrates the extrusion and film stretching of PET 7352 (I.V. = 0.85) obtained from

Eastman Chemicals Products, Inc.

PET 7352 is extruded into film at 280°C and stretched 4X by 4X or 300% on the T.M. Long film stretcher. The biaxially oriented film has an oxygen permeability of 6.1 cc-mil/100 in -24 hr-atm and a carbon dioxide permeability of 31.5 cc-mil/100 in -

24 hr-atm.

EXAMPLE 4

This example illustrates the extrusion and film stretching of a 70/30 wt./wt. blend of PET 7352 and (BDA) (DEG) polyester. A polymer of BDA and diethylene glycol is prepared according to the procedure of Example 1, ground to pass a 3-mm screen, and dry blended with 70 weight % PET 7352 (I.V. = 0.85, Eastman Chemicals Products, Inc. ) . The blend is extruded and pelletized, and then extruded into film, and subsequently biaxially oriented 3X by 3X or 200% on a T.M. Long film stretcher at 100°C. The oriented film has an oxygen permeability of 3.2 cc-mil/100 i 24 hr-atm and a carbon dioxide permeability of 16.2 cc-mil/100 in ² 24 hr-atm. The other polyesters and blends shown in Tables 1 and 2 are prepared according to procedures similar to those described in Examples 1 and 2 above.

Table 1

Gas Barrier Properties of Films of PET/(BDA) (HD) Polyester/Polyester Blends

Gas Permeability,

^a These films were biaxially oriented 300% on a T.M. Long Film Stretcher at 100°C.

These films were biaxially oriented 200% on a T.M. Long Film Stretcher at 100°C.

° This film could not be biaxially oriented at 100°C and was too brittle.

Codes: P02 = oxygen permeability,

PC02 = carbon dioxide permeability,

BDA = 4,4' -biphenyldicarboxylic acid, and

HD = 1,6-hexanediol.

Table 2

Gas Barrier Properties of Films of PET/(BDA) (DEG) Polyester/Polyester Blends

Gas Permeability,

PET 7352 (BDA) (DEG) cc-mil/100 in ² 24 hr-atm Content, Content, P02 PC02 wt. % t. % Ext. Oriented Ext. Oriented

100 12.4 6.1 65.3 31.4

(control)'

₉₉ a

95 5

90 ^a 10

80 20

70 ^b 30 ₇₀ a,c 30

50 ^b 50

30 ^c 70

These films were biaxially oriented 300% on a T.M. Long Film Stretcher at 100°C.

These films were biaxially oriented 200% on a T.M. Long Film Stretcher at 100°C. ^c The PET used in this blend is PET 10388 (I.V. = 1.12) obtained from Eastman Chemicals Products, Inc. Kingsport, Tennessee.

This film could not be biaxially oriented at 100°C.

Codes: P02 = oxygen permeability,

PC02 = carbon dioxide permeability,

BDA = 4,4' -biphenyldicarboxylic acid, and

DEG = diethylene glycol.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.