IE42820B1 - Copolyester blends - Google Patents

Description

This invention relates to blends of copolyester elastomers and ethylene/carboxylic acid copolymers. More particularly it relates to such copolyesters that have a melt strength sufficiently great that the blend can be more readily processed by blow molding and film blowing than the copolyesters without the ethylene/carboxylic acid copolymer.

The copolyester elastomers used in the blends of this invention are well known and are described, among other places, in U.S. Patent 3,763,109, 3,766,146 and 3,651,014. These patents point out that the copolyesters can be used to form articles by blow molding and extruded to form film (blown and unblown).

In particular, the copolyesters used in this invention consist essentially of recurring intra-linear long chain ester units and short chain ester units randomly joined head-to-tail through ester linkages, the long chain ester units being represented by the formula ,5 fi fi {_o_g—0 —C — R— C-4 and the short chain ester units being represented by the formula 0 II II {— 0 — D — 0 — C —R — C-l where G is a divalent radical remaining after the removal of terminal hydroxyl groups from at least one long chain glycol having a molecular weight of from 400-6000; R is a divalent radical remaining after removal of carboxyl groups from at least one dicarboxylic acid having a molecular weight less than 300; and D is a divalent radical remaining after removal - 2 42830 of hydroxyl group from at least one low molecular weight diol having a molecular weight of less than 250. The short chain ester units are present in the copolyest^r to the extent of between 15 to 95% by weight of the copolyester, and often between 25 and 85% by weight.

The copolymers are produced by techniques described in the abovementioned U.S. patents. It is preferred that the copolyesters are of such molecular weight that the inherent viscosity (0.1 gm./dl. in meta cresol at 30°C.) is between 0.75-1.7.

The preferred copolyesters are those prepared from (1) poly(tetramethylene oxide)glycol or poly(propylene oxide) glycol, (2) 1,4-butanediol, and (3) terephthalic acid or an ester equivalent of terephthalic acid such as dimethyl terephthalate. Optionally up to about 30 mole percent of the terephthalic acid (or ester thereof) may be replaced with phthalic acid or isophthalic acid or the ester equivalents thereof such as dimethyl phthalate or dimethyl isophthalate.

It has now been found that the addition of between about 0.2% and 20% by weight based on the resulting copolymer blend of a copolymer containing polymerized ethylene units and polymerized carboxylic acid to the copolyesters of the above-mentioned U.S. patents make compositions that are easier to process by blow molding techniques and by extrusion film blowing techniques. The carboxylic acid units may be 0 to 100% neutralized with metal ions. When the carboxylic acid units are 0 to 10% neutralized a linear polycarbodiimide must also be present in the blend.

The copolymer containing polymerized ethylene units and polymerized carboxylic acid units should contain between 25 and 98.5% by weight ethylene 128 2Ό units, and from 1.5 to 30% by weight carboxylic acid containing units, and usually from 2 to 16% by weight carboxylic acid containing units.

Other polymerized units can be present in major or minor amounts. Copolymers of this type are known in the art and are described, among other places, in U.S. Patent 2,599,123 to Pinkney, U.S.Patent 3,264,272 to Rees, and Belgian Patent 818,609 to Greene. It is generally preferred that the carboxylic acid containing units be randomly distributed along the copolymer molecules. The Rees patent and the Greene patent teach how to obtain random copolymers. It is also possible to employ as the ethylene/ carboxylic acid copolymer, copolymers obtained by copolymerizing ethylene and other alkylenes, such as propylene and/or a diene such as hexadiene, and then grafting a*carboxylic acid monomer to the polymeric substrate.

Such grafting processes are described in published German Patent Applications 2,401,149 and 2,448,598. When copolymers of this latter type are to be employed it is generally desirable that the other alkylenes of the copolymer be present in an amount such that the copolymer prior to grafting is elastomeric. Elastomeric copolymers of this type are well known and are taught, for example, in U.S. Patent 2,933,480 to Gresham and Hunt. Particularly desirable ethylene/carboxylic acid copolymers are the copolymers of ethylene and acrylic acid, methacrylic acid, maleic acid, fumaric acid, ethyl hydrogen maleate, or methyl hydrogen maleate. The above copolymers can be made more elastomeric by the inclusion of such polymeric units as methyl acrylate, and ethyl acrylate in amounts up to about 60% by weight of the total polymer composition. Such copolymers containing between about 50 and 60 weight percent methyl acrylate form desirable blends with - 4 43830 the copolyester. The other polymerized units listed in the Rees patent can also be included as desired. The ethylene containing copolymers useful in this invention are of high molecular weight and have a melt index (unneutralized) in the range of about 0 to 400 gm. per 10 minutes when measured under ASTM Test D 1238-52T at 190°C.

The acid groups on the ethylene copolymer may be neutralized with metallic ions. The preferred ions for neutralizing the acid groups are alkali metal ions, alkaline earth ions, and zinc ions, but the other ions shown in the Rees patent may also be employed. The amount of metallic ion in the polymer may be chemically equivalent to the number of acid groups, or substantially less. Polycarbodiimide can be used to increase the melt strength of such blends. Polycarbodiimide is required in blends in which 0 to 10% of the acid groups of the ethylene copolymers are neutralized, but polycarbodiimide can be used in blends in which the acid groups are neutralized to an extent of greater than 10%. The polycarbodimide also serves as a hydrolytic stabilizer for the blend.

The addition of substantially linear polycarbodiimide to copolyesters is known and taught, among other places, in U.S. Patent 3,835,098 to Brown et al. The substantially linear polycarbodiimides contemplated for use in this invention are disclosed in the Brown et al patent, i.e., polycarbodiimides having the formula XrRj-tN = C = N —R2-4n N = C = N-R3-X2, where R1( R2 and R3 which may be the same or different, are Cj-C^ aliphatic, C6-Ci5 cycloaliphatic, or C6-C15 aromatic divalent hydrocarbon radicals, Xj and X2 may be the same or different and are selected from —N—C—N—Rt,, II or H 0 R5 II —N—C—ORg - 5 2820 where Ri,, R5 and Rs which may be the same or different are C1-C12 aliphatic, C5-CX5 aromatic monovalent hydrocarbon radicals and additionally Ri, and R5 can be hydrogen, and n is at least 2 and not more than 30 and preferably between 3 and 10.

The amount of polycarbodiimide that may be added to the blend can vary with the particular ethylene/acid copolymer employed, and the amount of neutralization of the acid groups, and with the particular polycarbodiimide added, but in general the polycarbodiimide can be present in an amount of about 0.2 to 30 percent by weight of the copolyester, preferably about 2 to 8% by weight.

The production of hollow objects from thermoplastics by blow molding is a known commercial method of manufacturing. See for example U.S.

Patent 3,745,150 to Corsover. The production of film from thermoplastics by extrusion and blowing is also a known comnerica] method of manufacturing.

Both of these techniques have been previously disclosed as useful techniques for the processing of copolyesters; however, on a commercial scale such techniques have not been widely employed on these copolyesters because, it is believed, the copolyesters in the molten state have very little melt strength and when it is attempted to process the copolyesters by blow molding the extrudate (also called a parison) instead of hanging from the nozzle, often drops off. When attempts are made to blow such copolyesters into film, the resin tends to fold back onto the surface of the extrusion die.

The blends of the present invention provide compositions having the desirable properties of the copolyesters when formed into molded objects - 6 42820 or film and improved processing characteristics, that is, the blends have increased melt strength. One method of measuring melt strength is to find the force necessary to draw the extrudate of a predried polymer at a constant rate of 10 ft,/min. from an Instron capillary rheometer (Instran is a trade mark) operated at a temperature 30°C above the melting point of the copolyester and using a die having an inside diameter of 0.04 inch, length-to-diameter ratio of 4 and 90° entrance angle with Instron cross head speed of 0.2 in./min. (The polymer is predried for 1 hour at 100°C, in a vacuum oven before testing). This force is referred to herein as melt tension. In order for a copolymer compound to be blow moldable and extrudable into blown film at commercially desirable rates the copolyester compound should have a melt strength such that the product will have a melt tension of at least 0.4 gm.

In the following examples all parts and percentages are by weight and all melt tension measurements are at 230°C unless otherwise specified.

General Procedure for the Preparation of Blown Film The copolyester thermoplastic elastomer, the ethylene/acid copolymer and other additives such as stabilizer and carbon black are thoroughly mixed in conventional equipment such as: (1) electrically heated rubber mill at 205-210°C. for 7 min. (2) single screw extruder with a mixing die or mixing torpedo at 210°C. for 30-40 sec. (3) twin screw continuous mixer-extruder at 230-275°C. for 5-10 sec. in the mixer before extrusion.

The blends are granulated or pelletized and dried at 70-100°C. for to 3 hours.

Film is blown on a film blowing machine by the following procedure.

The dried blend pellets are fed into an extruder where they are melted and forced, under pressure, through an adaptor and into a tubing die.

The melt flows around the mandrel of the die into a channel leading to the die lips. The melt leaving the die is in the form of a circular sleeve which is blown up by internal nitrogen or air to the desired final tube size and correspondingly thinner gauge. The tube travels vertically at full diameter until it reaches a pair of pinch rollers. The flattened tube is led away from the pinch rollers and wound on a roll. Sheets of film can be obtained by slitting the tube lengthwise.

Two important characteristics of the extruded film, the thickness and the width, are controlled by the through-put of the extruder, the blow up ratio (ratio of diameter of the tube to that of the die) and the up take rate of the pinch rollers.

The equipment used for the following examples is a Million 1 extruder (Million is a Trade Mark) and a conventional blow film device as just described. The molten copolyester flows through a diameter ring die with a gap of -50 mil. Usually the temperature inside the ex20 truder is set at 5-10°C. above the melting point of the particular copolyester thermoplastic elastomer being used. The temperature of the die is set at about the same temperature as the melting point of the thermoplastic elastomer.

Control 1 Polyether polyester thermoplastic elastomer A (see Table 1) pellets - 8 42830 were fed into the film blowing apparatus. The temperature settings for the extruder unit were: 150°C. rear, 210-220°C, center and front, 205-210°C. die. When the molten polymer blend exited from the die, it flowed sideways and folded backward.

Although the molten extrudate was very fluid it could be led manually to the up-take rollers. Attempts to blow up the extruded tube into an inflated cylinder were difficult and generally failed due to the folding back of the extrudate which caused leakage of the bubble. With extreme care films of less than 5 mil thick could be obtained at a blow up ratio of less than 1. Attempts to increase the blow up ratio resulted in the j formation of 1 to 2 mil films. The melt tension of the thermoplastic elastomer A was <0.1 gm.

Table I and Table II list the various copolyester and ethylene/acid copolymers used in the examples.

TABLE I The copolyester thermoplastic elastomers may be prepared by the procedures described in U.S. Patents 3,651,014, 3,766,146 and 3,763,109.

The polymers have the following compositions and melt index as measured by tentative ASTM method D-1238-52T.

The thermoplastic elastomers also contain -1 weight percent antioxidant and catalyst residues. - 9 2820 co Ο ο ο CM Ο Ο Ο CM ι -σ ω • * c -Pr- <Ο fd fe5C3O • Ld Ο •PE Ο «ρ· ο* ο r- (Λ <0 Η4 •Ρ χ: Ου •r* Ρ Sω ω rd Ε γ— Ο CL-P Ο Μ Ξ (0 £- γ— Φ LU σι «φ <3· co Γ*.

CM <3* Ο ΓΟ «5Τ «t σ» CM Γ*· Ο υ >» ε rd S•Ρ φ -Ρ =5 - 10 42820 Example 1 Control 1 was repeated except that a mixture of 5 parts of a 4 wt. percent ethyl hydrogen maleate/ 54% methyl acrylate/ 42% ethylene copolymer having a Melt Index of - 3.5 and 10 parts of the mixture of copolyester C containing 20% of a mixture of hindered aromatic polycarbodiimides having an average molecular weight of about 1000 was used. The polycarbodiimide contains units of the following structure: --{CH(CH3)2}n wherein n has an average value of about 3 and is sold as Stabaxol PCD 10 by Naftone, Inc., New York, N.Y. (Stabaxol is a Trade Mark).

The melt tension of the mixture was 0.4 gm. Blown films more than 10 mils thick and with a blow up ratio of greater than 2 were readily produced from this blend.

Example 2 The blend was made by mixing in a Farrel 2 cm. (Farrel Co., Ansonia, Conn.) twin screw continuous mixer extruder at -475°C. for a total cycle time of about 50 sec. (5-10 sec. in the mixer and 30-40 sec. in the extruder) the following four ingredients: - 11 12 8 2 0 1. Copolyester A 2. A copolymer of 78 wt.% ethylene 16% methyl acrylate, 6% methacrylic acid 3. 20% polycarbodiimide in copolyester C 4. 40% SAP black in Copolyester D (SAF is a Trade Hark) Parts M.I. 100 7.5 35 The blend had a melt tension of 0.6 gm. Blown film of more than 10 mil thick with a blow up ratio of more than two was produced from this blend.

Examples 3-5 Blends were made using 100 parts by weight copolyester A and the other ingredients shown in the following Table. The blends had the melt tension shown in the Table.

Polycarbo- Ex- Acid Copolymer Parts ample di imide, Parts Melt Tension Melt*** Index 3 16 wt.% isobutylacrylate/6% methacrylic acid/78% ethylene 5 4* 1.5 35 4 84% ethylene/16% methacrylic acid 5 84% ethylene/16% methacrylic 8 4 0.65 60 acid 4 2 0.6 gm. - * As a 20% concentrate in copolyester C.

** The same polymer as 4., except that 5% of the acid was neutralized by NaOH.

*** Melt index of the acid copolymer. - 12 4283ο TABLE II Ethylene/Acid Copolymer Compositions Co- polymer Composition % Neutralization Metal Ions M.I.C) 5 A 16% methacrylic acid 60 Na+ 0.9 B 16% methacrylic acid b) Na+ < 0.1 C 11% methacrylic acid 54 Zn++ 5.0 D 11% methacrylic acid 75-100 Zn^ a, 0.7 10 E 16% isobutyl acrylate, 60% methacrylic acid n,100a) b) c) Na+ - F 54% methyl acrylate, 4% ethyl hydrogen maleate 100 Na+ < 0.1 G 34% methyl acrylate 2.8% methacrylic acid 100 Ca++ < 0.1 15 H 25.4% propylene, 4.5% hexadiene,!.5% grafted fumaric acid 35 Zn++ I 10% methacrylic acid a, 100 Zn++ A. 1.0 J 11% methacrylic acid a, 75 Na+ a» 0.7 20 K 15% methacrylic acid a- 40 Na+ 1.2 L * 54% methyl acrylate, 4% ethyl hydrogen maleate -v ioob) Zn+ < 0.1 a) All polymers contain complemental amounts of ethylene. b) 100% Neutralization indicates equivalent amount of metal ions are present to convert all the carboxylic acids to their salts. The reaction may not be 100% complete. c) Melt Index was measured according to ASTM I238-52T at 190°C. on the neutralized product. - 13 2830 Example 6 One hundred parts of thermoplastic elastomer A were blended with 13 parts of copolymer A (see Table II) on a 3 electrically heated roll mill at 205-210°C. for 10-15 minutes. The blend was sheeted out on a cold mill to a sheet about J thick. The sheet was granulated into 1 chips.

The chips after drying by sweeping with a stream of nitrogen for about 12 hours and further drying at 100°C. in a vacuum oven for 1 hour, were fed into the extruder of the film blowing apparatus. The blend could be blown into films 10 mils or more thick using a blow up ratio of more than 3. The melt tension of the blend was >5.0 gms.

Example 7.

The procedure of Example 6 was repeated using 4 parts of copolymer A.

The blend was blown into film at least 10 mils thick, using a blow up ratio of more than 2. The melt tension of the blend was 0.9 gm.

Example 8 The procedure of Example 6 was repeated except that 10 parts of copolymer A were used and the blending was carried out by a Farrel 2 CM (Farrel Co., Ansonia, Conn.) twin screw continuous mixer extruder at *475°F.

This blend was blown into film as in Example 1. The melt tension of 20 the blend was 2.4 gms.

Example 9 The procedure of Example 8 was followed using the following thermoplastic elastomer-ethylene/acid copolymer blend: thermoplastic elastomer A (100 parts); copolymer A (2 parts); copolyester C containing 20% of a mixture of hindered aromatic polycarbodiimides having an average molecular weight of about 1.000 the polycarbodi imide contains units of the following structure: - 14 4s820 N=C=N{CH(CH3)2} wherein n has an average value of about 3 and is sold as Stabaxol PCD by Naftone, Inc., New York, N.Y. (15 parts); copolyester D containing 40% SAF carbon black (10 parts).

The blend could be blown into films more than 10 mils thick using a blow up ratio of greater than 2. The melt tension of the thermoplastic elastomer-ionomer blend was 0.8 gm.

Examples 10-20 These examples were conducted as those described above using thermo- plastic elastomer A and the other ingredients shown in Table III. Example Ethylene/ Acid Copolymer TABLE III Parts Stabilizer Mixture Parts Melt Tension gm 15 10 B 2 - 0.5 11 0 10 - 1.7 12 K 1 10a) 1.2 13°) c 8.3 2ob) 0.5 14c) D 8.3 2ob) 0.6 20 15 E 5 - 0.6 16 F 5 - 0.4 - 15 42830 TABLE III (contd.) Example Ethylene/ Acid Copolymer Parts Stabilizer Mixture Parts Melt Tension gm 17 G 10 - 0.95 18 H 9.5 - 0.95 19c) I D 0.5 5 20b) 0.5 20c) J 5.8 15a> -υ 0.9 a) A mixture containing 20% of the polycarbodiimide of example 4 and 80% thermoplastic elastomer C. b) A mixture containing 20% of the polycarbodiimide of example 4 and 80% thermoplastic elastomer B. c) These samples cilso contain 10 parts of a mixture containing 40% SAF carbon black and 60% thermoplastic elastomer C.

Example 21 One hundred parts of thermoplastic elastomer C and 10 parts of ethylene/acid copolymer A were mixed and blown into film using the procedure of Example 6, except that the temperature settings of the extruder unit were: Rear 150°C Center 185°C Front 185°C Die 180°C The blend was blown into a film at least 10 mils thick using a blow up ratio of more than 2. The melt tension of the blend was 0.5 gm. - 16 42830 Control 2 General Procedure for Blow Molding An Impco screw extrusion blow molding machine (Impco is a Trade Mark) Model No. B-13S-R17 was used under the following conditions: Rear screw section temperature = 205°C.

Front screw section temperature = 215°C.

Die temperature = 215°C.

Nozzle temperature = 220°C Blow cycle = 6 sec.

Exhaust cycle = 8 sec.

Air pressure = 60 lbs.

Mold temperature (regulated by water) = 80°C.

Polymer pellets were fed into the extruder, melted and extruded as a molten hollow slug (parison) of predetermined weight and wall thickness. The two halves of the mold were then closed around the hollow slug. Compressed air is introduced into the interior of the slug forcing the slug to expand and conform to the shape of the mold. The molded article was kept in the mold for a short time to cool, thus attaining form stability, before the mold halves were separated and the article removed.

In order to successfully blow mold, the extruded slug must be able to maintain its shape without distortion before the mold halves are closed and the compressed air is introduced. A mold for the shaping of a 5J x 2J bottle was used.

A blow molding experiment as described above was carried out using thermoplastic polymer B. The molten extruded slug continued to elongate - 17 2830 before the mold could be closed. The distortion of the slug was so rapid that when the mold was closed and before the blowing up process could be completed, only a portion of the slug remained within the confine of the mold. This rendered the blow up process impossible most of the time because the air leaked through the wall of the slug. When the slug was blown up, the molded articles were so badly distorted in dimension and thickness that they were useless. The melt tension of the thermoplastic elastomer was 0.2 gm.

Example 22 The procedure of Control 2 was repeated using thermoplastic elastomer B containing 10 parts of ethylene/acid copolymer A. The blend was mixed in a single screw extruder with a mixing die and extruded in the form of pellets. The extruded slug from this sample was dimensionally stable long enough for the mold to close and the blowing up process to be com15 pleted. Uniform molded articles were obtained. The melt tension of the blend was 2.5 gms.

Example 23 The blend of Example 8 was used in the procedure of Example 21. The extruded slug had very good dimensional stability and was readily blown into the desired article with no distortion.

Example 24 The following blend was prepared and may be used for film blowing and blow molding: Copolyester C Ethylene/Acid Copolymer A Melt Tension 90 10 7.2 Copolyester C, unblended, had a melt tension of about 0.2 gm. - 18 42830 Example 25 The following blend was prepared and may be used for film blowing and blow molding: Copolyester C Ethylene/Acid Copolymer L Melt Tension 5 80 20 10.0 Copolyester C, unblended, had a melt tension of about 0.2 gm. Example 26 The following blends were prepared and may be used for film blowing and blow molding: Copolyester B Ethylene/Acid Copolymer K Melt Tension 0.9 gm. 1.8 gms.

Copolyester B, unblended, has a melt tension of about 0.2 gm.

Example 27 The following blend was prepared and may be used for film blowing.

Copolyester D Ethylene/Acid Melt Tension Copolymer A 185°C. 2.9 gms.

Copolyester D, unblended, had a melt tension of 0.35 gm. at 185°C.

Claims (5)

1. WHAT WE CLAIM IS:1. A polymer blend which comprises a) 80 to 99.8% by weight of a copolyester comprising recurring intralinear long chain ester units and short chain ester units randomly joined head-to-tail through ester linkages, the long chain ester units being represented by the formula 0 II {_ 0 — G —0 — C — R — C — and the short chain ester units being represented by the formula 0 0 II II { —0 — D — 0 — C —- R — C —} where G is a divalent radical remaining after the removal of terminal hydroxyl groups from at least one long chain glycol HO-G-OH having a molecular weight of from 400-6000; R is a divalent radical remaining after removal of carboxyl groups from at least one dicarboxylic acid HOOC-R-COOH having a molecuTar weight less than 300; and D is a divalent radical remaining after removal of hydroxyl groups from at least one low molecular weight diol HO-D-OH having a molecular weight of less than 250, said short chain units being present in the polyester to the extent of between 15 and 95% by weight of the polyester, and b) 0.2 to 20% by weight of a copolymer containing ethylene units and carboxylic acid containing units, said copolymer containing between 25 and 98.5% by weight ethylene units, and 1.5 and 30% by weight carboxylic acid containing units, said carboxylic acid units being from 0 to 100% neutralized with metallic.ions, said blend also containing at least one linear polycarbodiimide when said carboxylic acid units are 0 to 10% neutralized, and having a melt tension of at least 0.4 gm.

2. A blend as claimed in claim 1 wherein the carboxylic acid units are 0-10% neutralised and the blend contains at least one linear polycarbodiimide.

3. A blend as claimed in claim 1 wherein the carboxylic acid units are 10-100% neutralised.

4. A blend as claimed in any of claims 1-3 in which the ethylene copolymer is a terpolymer which contains units derived from methyl acrylate, 5. A blend as claimed in claim 4 in which the methyl acrylate units are present to the extent of 50-60 weight percent of the ethylene copolymer. 6. A blend as claimed in any of the preceding claims in which the ethylene copolymer contains 2 to 16% by weight carboxylic acid containing units. 7. A blend as claimed in claim 6 in which the carboxylic acid containing units are derived from methyl hydrogen maleate or ethyl hydrogen maleate. 8. A blend as claimed in any of the preceding claims in which the short chain ester units of the copolyester component amount to from 25 to 85% by weight of the copolyester. 9. A blend as claimed in any of the preceding claims in which a portion of the acid groups on the ethylene copolymer are neutralized with alkali metal ions, alkaline earth metal ions, or zinc ions. 10. A blend as claimed in any of the preceding claims in which the ethylene containing copolymer contains units derived from methacrylic acid. - 21 42820 Π. A blend as claimed in any of the preceding claims in which the ethylene containing copolymer contains units derived from isobutyl acrylate and methacrylic acid. 12. A blend as claimed in any of the preceding claims wherein the 5 copolyester has an inherent viscosity at a concentration of 0.1 g/dl in m-cresol at 3O°C. of from 0.75 to 1.7. 13. A blend as claimed in any of the preceding claims containing a polycarbodiimide having the formula Xi-R 1 -{N=C=N-R 2 4 n N=C=N-R 3 -X 2 where R ls R 2 and R 3 which may be the same or different, each represent a C x —C X2 ali10 phatic, C 6 —C I5 cycloaliphatic, or C 6 —C 15 aromatic divalent hydrocarbon group, X x and X 2 may be the same or different and are selected from H, - N - C - N - Ru, or H I 11 I I H 0 R 5 - N - C—0R 6 where Rij, Rj and R 6 which may be the same or different, each represent C x —C 12 aliphatic, C 5 —C 15 cycloaliphatic or C 6 —C3.5 aromatic monovalent 15 hydrocarbon group and additionally R u and R s can be hydrogen, and n is from 2 to 30. 14. A blend as claimed in claim 13 wherein n is from 3 - 10. 15. A blend as claimed in claim 13 or claim 14 in which the polycarbodiimide is present in the amount of about 0.2 to 30 percent by weight 20 of the copolyester. 16. A blend as claimed in claim 15 wherein the polycarbodiimide is present in the amount of from 2 to 8% by weight of the copolyester. 17. A blend as claimed in claim 1 substantially as hereinbefore described. - 22 • «·’ 43830 18. A blend as claimed in claim 2 substantially as hereinbefore described with reference to examples 1 - 5. 19. A blend as claimed in claim 3 substantially as hereinbefore described with reference to Examples 6-22.

5. 20. Moulded articles and films wherever prepared from a blend as claimed in any of claims 1-19.