POLYESTER BLENDS

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional

Application Serial No. 61/164,050, filed March 27, 2009, the disclosure of

which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention generally relates to polymer blends comprising polyesters made from terephthalic acid; 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol; and 1 ,4-cyclohexanedimethanol; and polyalkylene terephthalate. The blends are characterized by a unique combination of properties such as thermal stability and toughness. The blends can be formed into, for example, molded articles, films, and fibers.

BACKGROUND OF THE INVENTION

[0003] Polymer blends are mixtures of structurally different polymers or copolymers. Commercially important polymer blends are generally mechanical mixtures, which are made by melt blending the various polymers in an extruder or other suitable intensive mixer. Most polymer-blend pairs form immiscible two-phase structures. For miscible systems, properties close to additive, relative to the properties of the neat polymers, are typically obtained. For immiscible systems, however, the two-phase structure can result in toughness properties somewhat lower than would be predicted from simple additivity.

[0004] Multi-component polyester blends (e.g., polycarbonate/PET blends) tend to have poor thermal stability in the molten state. Part of this instability is due to the tendency of the blend components to undergo transesterification in the melt. This reaction can result in gas evolution, changes in melt viscosity, and if one of the polyesters is crystalline, a reduction in both the degree of crystallinity and the crystalline melting point. [0005] Thus, there is a need in the art for polyester blends with improved toughness and thermal stability, and a higher degree of crystallinity and melting point. The present invention addresses this need as well as others that will become apparent from the following description and claims.

SUMMARY OF THE INVENTION

[0006] In one embodiment, the invention provides a polyester blend comprising:

(a) 5 to 95 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 100 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 0 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 5 to 95 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent. [0007] For the purposes of this invention, polyester (A) refers to the polyester containing TMCD and polyester (B) refers to polyalkylene terephthalate (PAT).

[0008] In another embodiment, the invention provides a polyester blend comprising:

(a) 15 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 95 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 5 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0009] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 100 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 0 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0010] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 100 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 0 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0011] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 100 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 0 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0012] In one embodiment, the invention provides a polyester blend comprising:

(a) 5 to 95 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 5 to 95 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent. [0013] In another embodiment, the invention provides a polyester blend comprising:

(a) 15 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0014] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyM ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0015] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0016] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0017] In one embodiment, the invention provides a polyester blend comprising:

(a) 5 to 95 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 50 mole percent of

2,2,4,4-tetramethyl-1,3-cyclobutanediol residues and 50 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 5 to 95 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent. [0018] In another embodiment, the invention provides a polyester blend comprising:

(a) 15 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 50 mole percent of

2,2,4 ,4-tetramethyl-i ,3-cyclobutanediol residues and 50 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0019] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 50 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0020] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 15 to 50 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0021] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0022] In another embodiment, the invention provides a polyester blend comprising: (a) 15 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0023] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 15 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0024] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 15 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0025] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 15 to 40 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 85 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0026] In another embodiment, the invention provides a polyester blend comprising: (a) 15 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 20 to 40 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0027] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 20 to 40 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0028] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 20 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0029] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 20 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0030] In another embodiment, the invention provides a polyester blend comprising: (a) 15 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 20 to 30 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 70 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer.

[0031] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 20 to 30 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 70 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0032] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 20 to 30 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 70 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0033] In one embodiment, the invention provides a polyester blend comprising:

(a) 50 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 20 to 30 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 70 to 80 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0034] In another embodiment, the invention provides a polyester blend comprising: (a) 15 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 30 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 70 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 85 weight percent of polyester (B) comprising a polyethylene terephthalate;

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer. [0001] In one embodiment, the invention provides a polyester blend comprising:

(a) 20 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 30 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 70 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 80 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0035] In one embodiment, the invention provides a polyester blend comprising:

(a) 30 to 85 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 30 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 70 mole percent of 1 ,4-cyclohexanedimethanol residues; and (b) 15 to 70 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0036] In one embodiment, the invention provides a polyester blend comprising:

(a) 45 to 80 weight percent of a polyester (A) comprising: (i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 30 to 40 mole percent of

2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 70 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 20 to 55 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0037] In one embodiment, the invention provides a polyester blend comprising: (a) 50 to 85 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 30 to 40 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 60 to 70 mole percent of 1 ,4-cyclohexanedimethanol residues; and

(b) 15 to 50 weight percent of a polyester (B) comprising a polyalkylene terephthalate; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0038] In one embodiment, the polymer blend according to the invention comprises:

(a) 20 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 80 weight percent of polyalkylene terephthalate (polyester

B);

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0039] In one embodiment, the polymer blend according to the invention comprises:

(a) 45 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyM ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 55 weight percent of a polyakylene terephthalate (polyester B);

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer; wherein the total weight percentage of the blend equals 100 weight percent; and wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %.

[0040] In one embodiment, the polymer blend according to the invention comprises:

(a) 20 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 50 mole percent of

2, 2,4 ,4-tetramethyl-i ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues; (b) 20 to 80 weight percent of polyethylene terephthalate (PET);

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer; wherein the total weight percentage of the blend equals 100 weight percent; and wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %.

[0041] In one embodiment, the polymer blend according to the invention comprises:

(a) 45 to 80 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising 90 to 100 mole percent of residues of terephthalic acid, isophthalic acid, or both; and

(ii) a glycol portion comprising 5 to 50 mole percent of

2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues and 50 to 95 mole percent of 1 ,4-cyclohexanedimethanol residues;

(b) 20 to 55 weight percent of a polyethylene terephthalate (PET);

(c) 2 to 10 weight percent of an impact modifier; and

(d) 0 to 1 weight percent of a phosphorus stabilizer; wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentage of the blend equals 100 weight percent.

[0042] It has been surprisingly discovered that the immiscible blends of the present invention can have a toughness, as measured by notched Izod impact strength, that is significantly higher than additivity would predict. In addition, when polyester (B) (which is the polyalkylene terephthalate (PAT) component), of the present invention is crystalline, it has been surprisingly found that the PAT can retain a significant amount of its crystallinity and melting point. The blends of the present invention can also have very good melt stability based on low gas evolution and good retention of melt viscosity. Thus, the blend compositions of the present invention can have a surprising combination of toughness and good melt stability.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a graph of small-amplitude oscillatory shear (SAOS) rheology as a function of time of the blends from Example 1 (E1 ), Comparative Example 1 (C1 ), and Example 5 (E5) at 300 ⁰ C. [0044] Figure 2 is a graph of SAOS rheology as a function of time of the blends from Example 2 (E2) and Comparative Example 2 (C2) at 300 ⁰ C. [0045] Figure 3 is a graph of SAOS rheology as a function of time of the blends from Example 4 (E4), Comparative Example 4 (C4), and Example 6 (E6) at 300 ⁰ C.

DETAILED DESCRIPTION OF THE INVENTION

[0046] According to the present invention, there is provided a polyester blend comprising:

(a) 5 to 95 weight percent of a polyester (A) comprising:

(i) a dicarboxylic acid portion comprising residues of terephthalic acid, isophthalic acid, or both; and (ii) a glycol portion comprising 5 to 100 mole percent of 2,2,4 ,4-tetramethyl-1 ,3-cyclobutanediol (TMCD) residues and 0 to 95 mole percent of 1 ,4-cyclohexanedimethanol (CHDM) residues; and

(b) 5 to 95 weight percent of polyester (B), a polyalkylene terephthalate (PAT); wherein for each of polyester (A) and polyester (B), the total mole % of the dicarboxylic acid portion is 100 mole %, and the total mole % of the glycol portion is 100 mole %; and wherein the total weight percentages of the blend equal 100 weight percent.

[0047] The polyesters (a) used in the present invention typically can be prepared from dicarboxylic acids and diols, which react in substantially equal proportions and are incorporated into the polyester polymer as their corresponding residues. The polyesters of the present invention, therefore, can contain substantially equal molar proportions of acid residues (100 mole%) and diol residues (100 mole%) such that the total moles of repeating units is equal to 100 mole%. The mole percentages provided herein, therefore, may be based on the total moles of acid residues, the total moles of diol residues, or the total moles of repeating units. For example, a polyester containing 20 mole% of isophthalic acid residues, based on the total acid residues, means that there are 20 moles of isophthalic acid residues for every 100 moles of acid residues. In another example, a polyester containing 30 mole% of 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol residues, based on the total diol residues, means that there are 30 moles of 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol residues for every 100 moles of diol residues. [0048] The dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, or mixtures thereof. As used herein, therefore, the term dicarboxylic acid is intended to include dicarboxylic acids and any derivative of a dicarboxylic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, or mixtures thereof, useful in a reaction process with a diol to make polyester. Furthermore, as used in this application, the term "diacid" includes multifunctional acids, for example, branching agents. As used herein, the term "terephthalic acid" is intended to include terephthalic acid itself and residues thereof as well as any derivative of terephthalic acid, including its associated acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, or mixtures thereof or residues thereof useful in a reaction process with a diol to make polyester. [0049] In one embodiment, terephthalic acid may be used as the starting material. In another embodiment, dimethyl terephthalate may be used as the starting material. In yet another embodiment, mixtures of terephthalic acid and dimethyl terephthalate may be used as the starting material and/or as an intermediate material.

[0050] The term "polyester," as used herein, is intended to include

"copolyesters."

[0051] The term "residue," as used herein, means any organic structure incorporated into a polymer through a polycondensation and/or an esterification reaction from the corresponding monomer. Thus, for example, the dicarboxylic acid residues may be derived from a dicarboxylic acid monomer or its associated acid halides, esters, salts, anhydrides, or mixtures thereof. Therefore, reference to a dicarboxylic acid is intended to include the dicarboxylic acid itself and any derivative of the dicarboxylic acid, including its associated isomers, acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, and mixtures thereof, useful in a reaction with a diol to make a polyester. Examples of esters of the dicarboxylic acids useful in this invention include the dimethyl, diproplyl, diisopropyl, dibutyl, diphenyl, etc.

[0052] For example, the term "terephthalic acid" is intended to include terephthalic acid itself as well as any derivative of terephthalic acid, including its associated isomers, acid halides, esters, half-esters, salts, half-salts, anhydrides, mixed anhydrides, and mixtures thereof, useful in a reaction with a diol to make a polyester.

[0053] In one embodiment, terephthalic acid may be used as the diacid starting material for the polyester component. In another embodiment, isophthalic acid may be used as the diacid starting material. In another embodiment, mixtures of terephthalic acid and isophthalic acid may be used as the diacid starting material.

[0054] The dicarboxylic acid portion of polyester (A) may be substituted with up to 20 mole%, or up to 10 mole %, or up to 5 mole%, of other aromatic dicarboxylic acids. Examples of suitable other aromatic dicarboxylic acids include 4,4'-biphenyldicarboxylic acid; 1 ,5-, 2,6-, and 2,7- naphthalenedicarboxylic acid; 4,4'-oxydibenzoic acid; and trans-4,4 ¹ - stilbenedicarboxylic acid. In addition, the dicarboxylic acid portion of the polyester may be substituted with aliphatic or cycloaliphatic dicarboxylic acids containing 6 to 12 carbon atoms such as succinic, glutaric, adipic, sebacic, suberic, azelaic, decanedicarboxylic, and dodecanedicarboxylic acids. [0055] The TMCD may be cis, trans, or a mixture of the two. The

CHDM may be cis, trans, or a mixture of the two.

[0056] The glycol portion of the polyester (A) may contain up to 20 mol% or up to 10 mole % or up to 5 mol%, of another glycol containing 2 to 16 carbon atoms. Examples of suitable other glycols include ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, neopentyl glycol, 1 ,4-butanediol, 1 ,5- pentanediol, 1 ,6-hexanediol, and p-xylene glycol. The polyester may also be modified with polyethylene glycols or polytetramethylene glycols. [0057] The term "glycol" as used in this application includes, but is not limited to, diols, glycols, and/or multifunctional hydroxyl compounds, for example, branching agents.

[0058] The polyesters (A) and/or (B) useful in the invention can comprise from 0 to 10 mole percent, for example, from 0.01 to 5 mole percent, from 0.01 to 1 mole percent, from 0.05 to 5 mole percent, from 0.05 to 1 mole percent, or from 0.1 to 0.7 mole percent, or 0.1 to 0.5 mole percent, based the total mole percentages of either the diol or diacid residues; respectively, of one or more residues of a branching monomer, also referred to herein as a branching agent, having 3 or more carboxyl substituents, hydroxyl substituents, or a combination thereof. In certain embodiments, the branching monomer or agent may be added prior to and/or during and/or after the polymerization of the polyester. The polyesters (A) and/or (B) useful in the invention can thus be linear or branched. The polycarbonate can also be linear or branched. In certain embodiments, the branching monomer or agent may be added prior to and/or during and/or after the polymerization of the polycarbonate.

[0059] Examples of branching monomers include, but are not limited to, multifunctional acids or multifunctional alcohols such as trimellitic acid, trimellitic anhydride, pyromellitic dianhydride, trimethylolpropane, glycerol, pentaerylhritol, citric acid, tartaric acid, 3-hydroxyglutaric acid and the like. In one embodiment, the branching monomer residues can comprise 0.1 to 0.7 mole percent of one or more residues chosen from at least one of the following: trimellitic anhydride, pyromellitic dianhydride, glycerol, sorbitol, 1 ,2,6-hexanetriol, pentaerythritol, trimethylolethane, and/or trimesic acid. The branching monomer may be added to the polyester reaction mixture or blended with the polyester in the form of a concentrate as described, for example, in U.S. Patent Nos. 5,654,347 and 5,696,176, whose disclosure regarding branching monomers is incorporated herein by reference. [0060] In one embodiment, the dicarboxylic acid portion of the polyester

(A) comprises 100 mole percent of terephthalic acid residues, and the glycol portion of the polyester comprises 5 to 70 mole percent of TMCD residues and 30 to 95 mole percent of CHDM residues. In another embodiment, the dicarboxylic acid portion of the polyester (a) comprises 100 mole percent of terephthalic acid residues, and the glycol portion of the polyester comprises 5 to 50 mole percent of TMCD residues and 50 to 95 mole percent of CHDM residues.

[0061] In other aspects of the invention, the glycol component for the polyesters useful in the invention include but are not limited to at least one of the following combinations of ranges: 15 to 50 mole % 2,2,4,4-tetramethyl- 1 ,3-cyclobutanediol and 50 to 85 mole % 1 ,4-cyclohexanedimethanol; 15 to 45 mole % 2,2,4,4-tetramethyM ,3-cyclobutanediol and 55 to 85 mole % 1 ,4- cyclohexanedimethanol; 15 to 40 mole % 2,2,4,4-tetramethyl-i ,3- cyclobutanediol and 60 to 85 mole % 1 ,4-cyclohexanedimethanol; 15 to 35 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 65 to 85 mole % 1 ,4- cyclohexanedimethanol; 15 to 30 mole % 2,2,4,4-tetramethyM ,3- cyclobutanediol and 70 to 85 mole % 1 ,4-cyclohexanedimethanol; 15 to 25 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 75 to 85 mole % 1 ,4- cyclohexanedimethanol.

[0062] In other aspects of the invention, the glycol component for the polyesters useful in the invention include but are not limited to at least one of the following combinations of ranges: 20 to 50 mole % 2,2,4,4-tetramethyl- 1 ,3-cyclobutanediol and 50 to 80 mole % 1 ,4-cyclohexanedimethanol; 20 to 45 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 55 to 80 mole % 1 ,4- cyclohexanedimethanol; 20 to 40 mole % 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol and 60 to 80 mole % 1 ,4-cyclohexanedimethanol; 20 to 35 mole % 2,2,4,4-tetramethyl-i ,3-cyclobutanediol and 65 to 80 mole % 1 ,4- cyclohexanedimethanol; 20 to 30 mole % 2,2,4,4-tetramethyM ,3- cyclobutanediol and 70 to 80 mole % 1 ,4-cyclohexanedimethanol; and 20 to 25 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 75 to 80 mole % 1 ,4- cyclohexanedimethanol.

[0063] In other aspects of the invention, the glycol component for the polyesters useful in the invention include but are not limited to at least one of the following combinations of ranges: 25 to 50 mole % 2,2,4,4-tetramethyl- 1 ,3-cyclobutanediol and 50 to 75 mole % 1 ,4-cyclohexanedimethanol; 25 to 45 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 55 to 75 mole % 1 ,4- cyclohexanedimethanol; 25 to 40 mole % 2,2,4,4-tetramethyM ,3- cyclobutanediol and 60 to 75 mole % 1 ,4-cyclohexanedimethanol; 25 to 35 mole % 2,2,4,4-tetramethyM ,3-cyclobutanediol and 65 to 75 mole % 1 ,4- cyclohexanedimethanol.

[0064] In other aspects of the invention, the glycol component for the polyesters useful in the invention include but are not limited to at least one of the following combinations of ranges: 30 to 50 mole % 2,2,4 ,4-tetramethyl- 1 ,3-cyclobutanediol and 50 to 70 mole % 1 ,4-cyclohexanedimethanol; 30 to 45 mole % 2,2,4,4-tetramethyl-1 ,3-cyclobutanediol and 55 to 70 mole % 1 ,4- cyclohexanedimethanol; 30 to 40 mole % 2,2,4,4-tetramethyM ,3- cyclobutanediol and 60 to 70 mole % 1 ,4-cyclohexanedimethanol; 30 to 35 mole % 2,2,4,4-tetramethyM ,3-cyclobutanediol and 65 to 70 mole % 1 ,4- cyclohexanedimethanol.

[0065] The polyester (A) of the polymer blend may be prepared by methods known in the art.

[0066] The PAT component of this invention may be selected from polyethylene terephthalate (PET), polypropylene terephthalate (PPT) , and polybutylene terephthalate (PBT). [0067] The PAT contains repeat units from at least 90 mole percent of terephthalic acid and at least 65 mole percent of alkylene glycol, based on 100 mole percent dicarboxylic acid and 100 mole percent glycol. PAT resins are available commercially and methods for their preparation are described, for example, in U.S. Patent No. 2,465,319 and U.S. Patent No. 3,0477,539. In one embodiment, the alkylene glycol may be one or more of ethylene glycol, propylene glycol, and butylene glycol. In one embodiment, the alkylene glycol is ethylene glycol.

[0068] The dicarboxylic acid portion of the PAT may be substituted with up to 20 mole%, or up to 10 mole% or up to 5 mol% of one or more dicarboxylic acids other than terephthalic acid or suitable equivalents thereof such as dimethyl terephthalate. Such additional dicarboxylic acids include but are not limited to aromatic dicarboxylic acids having 8 to 14 carbon atoms, aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms. Examples of suitable additional dicarboxylic acids include isophthalic acid, naphthalene-2,6- dicarboxylic acid, cyclohexande dicarboxylic acid, cyclohexane diacetic acid, diphenyl-4,4'-dicarboxylic acid, succinic, glutaric, adipic, sebacic, suberic, azelaic, decanedicarboxylic, and dodecanedicarboxylic acids. The PAT may include two or more of the above additional dicarboxylic acids. [0069] In addition, the PAT may be modified with up to about 35 mol% of another aliphatic glycol containing 2 to 16 carbon atoms. Examples of suitable other glycols include 1,2-ethanediol, 1 ,2-propanediol, 1 ,3- propanediol, neopentyl glycol, 1 ,4-butandediol, 1 ,5-pentanediol, 1 ,6 hexanediol, and 1 ,4-cyclohexandimethanol. The PAT may also be modified with polyethylene glycols or polytetramethylene glycols. [0070] In one embodiment, the PAT is a polyethylene terephthalate

(PET) comprising at least 90 mole percent of terephthalic acid residues based on 100 mole percent of dicarboxylic acid residues in the PET, and 65 to 100 mole percent of ethylene glycol residues and 0 to 35 mole percent of 1 ,4- cyclohexanedimethanol residues based on 100 mole percent of glycol residues in the PET. [0071] In another embodiment, the PAT is a polyethylene terephthalate

(PET) comprising at least 90 mole percent of terephthalic acid residues based on 100 mole percent of dicarboxylic acid residues in the PET, and at least 90 mole percent of ethylene glycol residues based on 100 mole percent of glycol residues in the PET.

[0072] For certain embodiments of the invention, the polyesters (A) or

(B) may exhibit at least one of the following inherent viscosities as determined in 60/40 (wt/wt) phenol/ tetrachloroethane at a concentration of 0.5 g/100 ml at 25 ⁰ C: 0.10 to 1.2 dL/g; 0.35 to 1.2 dL/g; 0.50 to 1.2 dL/g; 0.50 to 1.1 dL/g; 0.50 to 1 dl_/g; 0.50 to less than 1 dL/g; 0.50 to 0.98 dL/g; 0.50 to 0.95 dL/g; 0.50 to 0.90 dL/g; 0.50 to 0.85 dL/g; 0.50 to 0.80 dL/g; 0.50 to 0.75 dL/g; 0.50 to less than 0.75 dL/g; 0.50 to 0.72 dL/g; 0.50 to 0.70 dL/g; 0.50 to less than 0.70 dL/g; 0.50 to 0.68 dL/g; 0.50 to less than 0.68 dL/g; 0.50 to 0.65 dL/g; 0.55 to 1.2 dL/g; 0.55 to 1.1 dL/g; 0.55 to 1 dL/g; 0.55 to less than 1 dL/g; 0.55 to 0.98 dL/g; 0.55 to 0.95 dL/g; 0.55 to 0.90 dL/g; 0.55 to 0.85 dL/g; 0.55 to 0.80 dL/g; 0.55 to 0.75 dL/g; 0.55 to less than 0.75 dL/g; 0.55 to 0.72 dl_/g; 0.55 to 0.70 dL/g; 0.55 to less than 0.70 dL/g; 0.55 to 0.68 dL/g; 0.55 to less than 0.68 dL/g; 0.55 to 0.65 dL/g; 0.60 to 1.2 dL/g; 00.60 to 0.85 dL/g; 0.60 to 0.80 dL/g; 0.60 to 0.75 dl_/g; 0.60 to 0.70 dL/g; or 0.60 to 0.68 dL/g. [0073] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 15 to 99 weight % polyester (A) and 1 to 85 weight % polyester (B); 15 to 95 weight % polyester (A) and 5 to 85 weight % polyester (B); 15 to 90 weight % polyester (A) and 10 to .85 weight % polyester (B); 15 to 85 weight % polyester (A) and 15 to 85 weight % polyester (B); 15 to 75 weight % polyester (A) and 25 to 85 weight % polyester (B); 15 to 70 weight % polyester (A) and 30 to 85 weight % polyester (B); 15 to 65 weight % polyester (A) and 35 to 85 weight % polyester (B); 15 to 60 weight % polyester (A) and 40 to 85 weight % polyester (B); 15 to 55 weight % polyester (A) and 45 to 85 weight % polyester (B); 15 to 50 weight % polyester (A) and 50 to 85 weight % polyester (B); 15 to 40 weight % polyester (A) and 60 to 85 weight% polyester (B); 15 to 35 weight % polyester (A) and 65 to 85 weight % polyester (B); 15 to 30 weight % polyester (A) and 70 to 85 weight % polyester (B); and 15 to 25 weight % polyester (A) and 75 to 85 weight % polyester (B).

[0074] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 20 to 99 weight % polyester (A) and 1 to 80 weight % polyester (B); 20 to 95 weight % polyester (A) and 5 to 80 weight % polyester (B); 20 to 90 weight % polyester (A) and 10 to 80 weight % polyester (B); 20 to 85 weight % polyester (A) and 15 to 80 weight % polyester (B); 20 to 80 weight % polyester (A) and 20 to 80 weight % polyester (B), 20 to 75 weight % polyester (A) and 25 to 80 weight % polyester (B); 20 to 70 weight % polyester (A) and 30 to 80 weight % polyester (B); 20 to 65 weight % polyester (A) and 35 to 80 weight % 1 polyester (B); 20 to 60 weight % polyester (A) and 40 to 80 weight % polyester (B); 20 to 55 weight % polyester (A) and 45 to 80 weight % polyester (B); 20 to 50 weight % polyester (A) and 50 to 80 weight % polyester (B); 20 to 45 weight % polyester (A) and 55 to 80 weight % polyester (B); 20 to 40 weight % polyester (A) and 60 to 80 weight % polyester (B); 20 to 35 weight % polyester (A) and 65 to 80 weight % polyester (B); and 20 to 30 weight % polyester (A) and 70 to 80 weight % polyester (B).

[0075] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 25 to 99 weight % polyester (A) and 1 to 75 weight % polyester (B); 25 to 95 weight % polyester (A) and 5 to 75 weight % polyester (B); 25 to 90 weight % polyester (A) and 10 to 75 weight % polyester (B); 25 to 85 weight % polyester (A) and 15 to 75 weight % polyester (B); 25 to 80 weight % polyester (A) and 20 to 75 weight % polyester (B), 25 to 75 weight % polyester (A) and 25 to 75 weight % polyester (B); 25 to 70 weight % polyester (A) and 30 to 75 weight % polyester (B); 25 to 65 weight % polyester (A) and 35 to 75 weight % polyester (B); 25 to 60 weight % polyester (A) and 40 to 75 weight % polyester (B); 25 to 55 weight polyester (A) and 45 to 75 weight % polyester (B); 25 to 50 weight % polyester (A) and 50 to 75 weight % polyester (B); 25 to 40 weight % polyester (A) and 60 to 75 weight % polyester (B); and 25 to 35 weight % polyester (A) and 65 to 75 weight % polyester (B).

[0076] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 30 to 99 weight % polyester (A) and 1 to 70 weight % polyester (B); 30 to 95 weight % polyester (A) and 5 to 70 weight % polyester (B) ; 30 to 90 weight % polyester (A)and 10 to 70 mole % weight % polyester (B); 30 to 85 weight % polyester (A) and 15 to 70 weight % polyester (B); 30 to 80 weight % polyester (A) and 20 to 70 weight % polyester (B), 30 to 75 weight % polyester (A) and 25 to 70 weight % polyester (B); 30 to 70 weight % polyester (A) and 30 to 70 weight % polyester (B); 30 to 65 weight % polyester (A) and 35 to 70 weight % polyester (B); 30 to 60 weight % polyester (A) and 40 to 70 weight % polyester (B); 30 to 55 weight % polyester (A) and 45 to 70 weight % polyester (B); 30 to 50 weight % polyester (A) and 50 to 70 weight % polyester (B); 30 to 40 weight % polyester (A) and 60 to 70 weight % polyester (B); 30 to 35 weight % polyester (A) and 65 to 70 weight % polyester (B).

[0077] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 35 to 99 weight % polyester (A) and 1 to 65 weight % polyester (B); 35 to 95 weight % polyester (A) and 5 to 65 weight % polyester (B); 35 to 90 weight % polyester (A) and 10 to 65 weight % polyester (B); 35 to 85 weight % polyester (A) and 15 to 65 weight % polyester (B); 35 to 80 weight % polyester (A) and 20 to 65 weight % polyester (B), 35 to 75 weight % polyester (A) and 25 to 65 weight % polyester (B); 35 to 70 weight % polyester (A) and 30 to 65 weight % polyester (B); 35 to 65 weight % polyester (A) and 35 to 65 weight % polyester (B); 35 to 60 weight % polyester (A) and 40 to 65 weight % polyester (B); 35 to 55 weight % polyester (A) and 45 to 65 weight % polyester (B); 35 to 50 weight % polyester (A) and 50 to 65 weight % polyester (B).

[0078] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 40 to 99 weight % polyester (A) and 1 to 60 weight % polyester (B); 40 to 95 weight % polyester (A) and 5 to 60 mole % weight % polyester (B); 40 to 90 weight % polyester (A) and 10 to 60 weight % polyester (B); 40 to 85 weight % polyester (A) and 15 to 60 weight % polyester (B); 40 to 80 weight % polyester (A) and 20 to 60 weight % polyester (B), 40 to 75 weight % polyester (A) and 25 to 60 weight % polyester (B); 40 to 70 weight % polyester (A) and 30 to 60 weight % polyester (B); 40 to 65 weight % polyester (A) and 35 to 60 weight % polyester (B); 40 to 60 weight % polyester (A) and 40 to 60 weight % polyester (B); 40 to 55 weight % polyester (A) and 45 to 60 weight % polyester (B); and 40 to 50 weight % polyester (A) and 50 to 60 weight % polyester (B).

[0079] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 45 to 99 weight % polyester (A) and 1 to 55 weight % polyester (B); 45 to 95 weight % polyester (A) and 5 to 55 weight % polyester (B); 45 to 90 weight % polyester (A) and 10 to 55 weight % polyester (B); 45 to 85 weight % polyester (A) and 15 to 55 weight % polyester (B); 45 to 80 weight % polyester (A) and 20 to 55 weight % polyester (B), 45 to 75 weight % polyester (A) and 25 to 55 weight % polyester (B); 45 to 70 weight % polyester (A) and 30 to 55 weight % polyester (B); 45 to 65 weight % polyester (A) and 35 to 55 weight % polyester (B); 45 to 60 weight % polyester (A) and 40 to 55 weight % polyester (B); and 45 to 55 weight % polyester (A) and 45 to 55 weight % polyester (B). [0080] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 50 to 99 weight % polyester (A) and 1 to 50 weight % polyester (B); 50 to 90 weight % polyester (A) and 10 to 50 weight % polyester (B); 50 to 85 weight % polyester (A) and 15 to 50 weight % polyester (B); 50 to 80 weight % polyester (A) and 20 to 50 weight % polyester (B), 50 to 75 weight % polyester (A) and 25 to 50 weight % polyester (B); 50 to 70 weight % polyester (A) and 30 to 50 weight % polyester (B); 50 to 65 weight % polyester (A) and 35 to 50 weight % polyester (B); 50 to 60 weight % polyester (A) and 40 to 50 weight % polyester (B).

[0081] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 55 to 99 weight % polyester (A) and 1 to 45 mole % weight % polyester (B); 55 to 95 weight % polyester (A) and 5 to 45 weight % polyester (B); 55 to 90 weight % polyester (A) and 10 to 45 weight % polyester (B); 55 to 85 weight % polyester (A) and 15 to 45 weight % polyester (B); 55 to 80 weight % polyester (A) and 20 to 45 weight % polyester (B), 55 to 75 weight % polyester (A) and 25 to 45 weight % polyester (B); 55 to 70 weight % polyester (A) and 30 to 45 weight % polyester (B); and 55 to 65 weight % polyester (A) and 35 to 45 mole % weight % polyester (B). [0082] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 60 to 99 weight % polyester (A) and 1 to 40 weight % polyester (B); 60 to 95 weight % polyester (A) and 5 to 40 weight % polyester (B); 60 to 90 weight % polyester (A) and 10 to 40 weight % polyester (B); 60 to 85 weight % polyester (A) and 15 to 40 weight % polyester (B); 60 to 80 weight % polyester (A) and 20 to 40 weight % polyester (B), 60 to 75 weight % polyester (A) and 25 to 40 weight % polyester (B); and 60 to 70 weight % polyester (A) and 30 to 40 weight % polyester (B). [0083] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 65 to 99 weight % polyester (A) and 1 to 35 weight % polyester (B); 65 to 95 weight % polyester (A) and 5 to 35 weight % polyester (B); 65 to 90 weight % polyester (A)and 10 to 35 weight % polyester (B); 65 to 85 weight % polyester (A) and 15 to 35 weight % polyester (B); 65 to 80 weight % polyester (A) and 20 to 35 weight % polyester (B) ₁ and 65 to 75 weight % polyester (A) and 25 to 35 weight % polyester (B).

[0084] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 70 to 99 weight % polyester (A) and 1 to 30 weight % polyester (B); 70 to 95 and 5 to 30 weight % polyester (A); 70 to 90 weight % polyester (A) and 10 to 30 weight % polyester (B); 70 to 85 weight % polyester (A) and 15 to 30 weight % polyester (B); 70 to 80 weight % polyester (A) and 20 to 30 weight % polyester (B).

[0085] In certain embodiments of the invention, the weight percentages of polyester (A) and polyester (B) useful in the blends of the invention include but are not limited to at least one of the following combinations of ranges: 75 to 99 weight % polyester (A) and 1 to 25 weight % polyester (B); 75 to 95 weight % polyester (A) and 5 to 25 weight % polyester (B); 75 to 90 weight % polyester (A) and 10 to 25 weight % polyester (B); and 75 to 85 weight % polyester (A) and 15 to 25 weight % polyester (B).

[0086] The polyalkylene terephthalates useful in the invention may be recycled prior to their use in the blends of the invention. In one embodiment, the polyalkylene terephthalates useful in the invention may be post-consumer recycled PAT. In another embodiment, polyester (B) may be post-consumer recycled PET.

[0087] The polymer blends of the invention may contain up to 20 weight percent of an impact modifier and up to 5 weight percent of a phosphorus stabilizer based on the total weight of the blend. The polymer blends of the invention may contain up to 20 weight percent of an impact modifier and up to 1 weight percent of a phosphorus stabilizer based on the total weight of the blend. In one embodiment, the blend comprises 1 to 15 weight percent of the impact modifier based on the total weight of the blend. In another embodiment, the blend comprises 2 to 10 weight percent of the impact modifier based on the total weight of the blend.

[0088] The impact modifier may be selected from the broad classes of acrylic core-shell polymers, ABS copolymer, butyl rubber, functional epoxy olefins, and modified polyethylenes such as ethylene/propylene rubbers (EPR) and their modifications.

[0089] The acrylic core-shell impact modifiers have a rubbery core, which may be either an acrylic rubber or butadiene or styrene-butadiene rubber. In each modifier, the Tg of the rubber phase should be below 25°C as measured by Differential Scanning Calorimetery (DSC). The shell of these impact modifiers is a hard acrylic-based polymer, for example, poly(methylmethacrylate). Representatively, acrylic core-shell polymers and their use are described in U.S. Patent Nos. 4,096,202; 3,864,428; and 4,200,567.

[0090] In one embodiment, the ethylene/propylene rubbers may be copolymers of ethylene and propylene with a ratio of about 1 :1. They may also contain a small amount of diene monomer such as ethylidene norbomene, dicyclopentadiene, and hexadiene (EPDM rubbers). Any of these systems may be further grafted with other monomers such as an alkenoic nitrile, ester, amide, or acid, or a vinyl aromatic monomer such as styrene, or mixtures of an alkenoic monomer and vinyl aromatic monomer. These systems are described, for example, in U.S. Patent Nos. 4,550,138; 4,485,212; and 4,493,921.

[0091] The phosphorus stabilizer has at least one or a combination of two or more of the following advantages: catalyst deactivation, melt stability and color stability. Melt stability can be important in melt processing. Examples of phosphorus stabilizers include but are not limited to organic phosphite stabilizers such as tris(2,4-di-butylphenyl) phosphite (Irgafos 168), distearyl pentaerythritol diphosphite (Weston 619), trisnonylphenyl phosphate (TNPP), trilauryl phosphite, triphenyl phosphate, triphenyl phosphine and diisooctyl phosphite. Other phosphorus compounds useful in the invention can include other phosphates, aryl phosphonites and acidic phosphorous compounds. The phosphorus stabilizer can be replaced by other compounds known to be effective as catalyst deactivators, melt stabilizers and/or color stabilizers.

[0092] The blends of this invention may be prepared by any conventional mixing methods. In one embodiment, one method comprises mixing the polyesters, impact modifiers, and stabilizers in powder or granular form in an extruder and extruding the mixture into strands, chopping the strands into pellets, and molding the pellets into the desired article. [0093] The polymer blend may comprise 0.01 to 25 weight percent of at least one other additive such as colorants, dyes, mold release agents, flame retardants, plasticizers, nucleating agents, UV light stabilizers, fillers, processing aids, and reinforcing materials such as glass fibers. [0094] Another aspect of the present invention relates to articles of manufacture comprising the polyester blends of the invention. Such articles of manufacture can be chosen from films, sheets, fibers, and molded articles. [0095] The following abbreviations apply throughout the specification, working examples and figures:

[0096] This invention can be further illustrated by the following working examples, although it should be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.

EXAMPLES Measurement Methods

[0097] The inherent viscosity (IV) of the polyesters was determined in

60/40 (wt/wt) phenol/tetrachloroethane at a concentration of 0.5 g/100ml at 25°C, and is reported throughout this section in units of dl/g. [0098] The composition of the neat resins was determined by proton nuclear magnetic resonance spectroscopy (NMR).

[0099] The glass transition temperatures, melting points, and heat of fusion were determined using a TA Instruments differential scanning calorimeter (DSC) at a scan rate of 20 ⁰ C. All reported values are of the second cycle. Because the blends in the following examples were mostly immiscible, two glass transition temperatures were observed - one for the PET phase and one for the second polyester component. These Tg's are reported in Tables 1-4 for all of the polyester blends. The occurrence of only one Tg may indicate increasing miscibility of the two phases. But it cannot preclude the possibility that the transition was simply too weak for the DSC instrumentation to detect.

[00100] The degree of crystallinity of the PET in each blend was determined by dividing the measured heat of fusion by the known heat of fusion for 100% crystalline PET (29 cal/g).

[00101] Mechanical properties of all blends were characterized using the following methods:

-Heat deflection temperature, at 264 psi, was determined according to ASTM D648.

-Flexural modulus and flexural strength were determined according to ASTM D790.

-Tensile properties (break strength, break elongation) were determined according to ASTM D638. -Notched Izod impact strengths were determined according to ASTM D 256, at 23°C for both 0.125" and 0.250" thick bars. [00102] Polyester blends tend to have poor thermal stability in the molten state, due to reaction between the components. Consequently, the melt stability of each prepared blend was evaluated using both small- amplitude oscillatory shear (SAOS) rheology and gas evolution analysis. The former allows quantification of changes in the melt viscosity as a function of time, while the latter allows for the detection of degradation byproducts. Both provide useful assessment of blend stability.

[00103] SAOS rheological analysis was performed at 300 ⁰ C for 20 min, using a frequency of 100s ^'1 . For the offgas measurements, two grams (+/- 0.01 g) of the dried polymer sample were weighed into a 20-ml screw top headspace glass vial. The vial was fitted with a screw top containing a silicone septum. The container was purged with nitrogen for two minutes, prior to experimentation. The blends were heated to 300 ⁰ C by an aluminum heater block, controlled by a Eurotherm controller which kept the temperature within 1°C of the set point.

[00104] The gas evolution during heating was monitored by gas chromatography (GC) using an Agilent 3000A, two-channel Micro GC, which automatically sampled the headspace every 3.5 min. Because carbon dioxide (CO ₂ ) is a common degradation byproduct in polyester blends, analysis software was used to quantify the CO2 evolution over a 60-minute period. This, in turn, allowed calculation of an offgas rate.

Blend Preparation Procedure

[00105] All blends were prepared using a 30-mm Werner Pflieder twin- screw extruder. The polyester components were first dried at 90 ⁰ C and the PET polyester was dried at 100 ⁰ C, both for 6 hours. The polyesters and other additives were premixed by tumble blending polyester pellets with the other components. The mixture was fed into the extruder and run at 350 rpm and at a feed rate to give a machine torque between 80-100%. The final extrudate was pelletized and subsequently injection molded into test specimens on a

Toyo 90 injection molding machine. Melt temperatures for both compounding and injection molding were maintained in the range of 260 ⁰ C to 300 ⁰ C for all blends.

[00106] All blends contain 0.2 wt% of the phosphorus stabilizer identified below.

[00107] All blends contain 8 wt% of the impact modifier identified below, except for those in Examples 3, 4, and 6, and Comparative Examples 3 and 4, which contain only 6 wt% of the impact modifier.

Polyester Components

[00108] Copolyester 1 (AAC 1 ) - This copolyester contained 100 mol% of terephthalic acid residues, 23 mol% of 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol (60 mol% cis isomer) residues, and 77 mole% of 1 ,4- cyclohexanedimethanol residues. The inherent viscosity was measured to be 0.72 (± 0.03) dl/g. Blends using Copolyester 1 (AAC 1 ) are considered examples of this invention.

[00109] Copolyester 2 (AAC 2) - This copolyester contained 100 mol% of terephthalic acid residues, 35 mol% of 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol (60 mol% cis isomer) residues, and 65 mol% of 1 ,4- cyclohexanedimethanol residues. The inherent viscosity was measured to be 0.64 (± 0.03) dl/g. Blends using Copolyester 2 (AAC 2) are considered examples of this invention.

[00110] Polycarbonate polyester (PC) - This polyester is the polycarbonate of 4,4'-isopropylidenediphenol (bisphenol A), a commercially available resin sold under the name Makrolon 2608. Blends using polycarbonate polyester with PET are considered comparative examples.

Polyethylene Terephthalate (PET) Components

[00111] PET 1 - In addition to terephthalic acid and ethylene glycol residues, this PET contained 3.5 mole% of 1 ,4-cyclohexanedimethanol residues and 1.5 mole% of diethylene glycol residues. PET 1 had an inherent viscosity of about 0.76 dl/g.

[00112] PET 2 - In addition to terephthalic acid and ethylene glycol residues, this PET contains 3.5 mole% of 1 ,4-cyclohexanedimethanol residues and 1.5 mole% of diethylene glycol residues. PET 2 had an inherent viscosity of about 0.56 dl/g.

[00113] PET 3 - In addition to terephthalic acid and ethylene glycol residues, this PET contained 2.5 mole% of isophthalic acid residues and 1.5 mole% of diethylene glycol residues. PET 3 had an inherent viscosity of about 0.71 dl/g.

[00114] PET 4 - In addition to terephthalic acid and ethylene glycol residues, this PET contained 2.5 mole% of isophthalic acid residues and 1.5 mole% of diethylene glycol residues. PET 4 had an inherent viscosity of about 0.80 dl/g.

Additive Components

[00115] Methyl methacrylate-butadiene-styrene (MBS) Copolymer - This is an impact modifier commercially sold under the name Clearstrength E920. [00116] Tris-(2,4-di-t-butylphenyl) phosphite - This is a phosphorus stabilizer commercially sold under the name lrgafos 168.

Example 1

[00117] AAC 1 and PET 1 were blended together according to the Blend Preparation Procedure described above. The amounts of AAC 1 and PET 1 in each blend are set forth in Table 1. The properties of each blend are also reported in Table 1. The measured off-gas rate of CO ₂ during annealing of Blend E at 300 ⁰ C is reported in Table 5. Example 2

[00118] AAC 1 and PET 2 were blended together according to the

Blend Preparation Procedure described above. The amounts of AAC 1 and PET 2 in each blend are set forth in Table 2. The properties of each blend are also reported in Table 2. The measured off-gas rate of CO ₂ during annealing of Blend E at 300 ⁰ C is reported in Table 5.

Example 3

[00119] AAC 1 and PET 3 were blended together according to the Blend Preparation Procedure described above. The amounts of AAC 1 and PET 3 in each blend are set forth in Table 3. The properties of each blend are also reported in Table 3. The measured off-gas rate of CO ₂ during annealing of Blend E at 300 ⁰ C is reported in Table 5.

Example 4

[00120] AAC 1 and PET 4 were blended together according to the Blend Preparation Procedure described above. The amounts of AAC 1 and PET 4 in each blend are set forth in Table 4. The properties of each blend are also reported in Table 4. The measured off-gas rate of CO ₂ during annealing of Blend E at 300°C is reported in Table 5.

Example 5

[00121] AAC 2 and PET 1 were blended together according to the Blend Preparation Procedure described above. The amounts of AAC 2 and PET 1 in each blend are set forth in Table 1. The properties of each blend are also reported in Table 1. The measured off-gas rate of CO ₂ during annealing of Blend E at 300°C is reported in Table 5. Example 6

[00122] AAC 2 and PET 4 were blended together according to the Blend Preparation Procedure described above. The amounts of AAC 2 and PET 4 in each blend are set forth in Table 4. The properties of each blend are also reported in Table 4. The measured off-gas rate of CO ₂ during annealing of Blend E at 300 ⁰ C is reported in Table 5.

Comparative Example 1

[00123] PC and PET 1 were blended together according to the Blend Preparation Procedure described above. The amounts of PC and PET 1 in each blend are set forth in Table 1. The properties of each blend are also reported in Table 1. The measured off-gas rate of CO ₂ during annealing of Blend E at 300 ⁰ C is reported in Table 5.

Comparative Example 2

[00124] PC and PET 2 were blended together according to the Blend Preparation Procedure described above. The amounts of PC and PET 2 in each blend are set forth in Table 2. The properties of each blend are also reported in Table 2. The measured off-gas rate of CO ₂ during annealing of Blend E at 300°C is reported in Table 5.

Comparative Example 3

[00125] PC and PET 3 were blended together according to the Blend Preparation Procedure described above. The amounts of PC and PET 3 in each blend are set forth in Table 3. The properties of each blend are also reported in Table 3. The measured off-gas rate of CO ₂ during annealing of Blend E at 300°C is reported in Table 5. Comparative Example 4

[00126] PC and PET 4 were blended together according to the Blend Preparation Procedure described above. The amounts of PC and PET 4 in each blend are set forth in Table 4. The properties of each blend are also reported in Table 4. The measured off-gas rate of CO ₂ during annealing of Blend E at 300°C is reported in Table 5.

Table 1 - Blends of Examples 1 (ED and 5 (E5), and Comparative Example 1

(CD [00127] Table 1 shows the composition and physical properties of the blends of this invention (E1 and E5) - the copolyesters AAC 1 and AAC 2 compounded with PET 1. Relative to the comparative example (C1), the blends of this invention consistently showed higher tensile elongation at break, notched Izod impact toughness at room temperature (23°C), melting temperatures, and levels of crystallinity for the PET phase of the immiscible blend. These improvements were consistent across the compositional space examined. Furthermore, both of the copolyesters showed this unique behavior, despite having differences in composition (23/77 compared to 35/65 mol% TMCD / mol% CHDM for AAC 1 and AAC 2, respectively) and inherent viscosity (0.72 compared to 0.64).

[00128] In particular, the toughness enhancement for the example blends compared favorably with the comparative example. For example, the YΛ" notched Izod (23°C) energy at break values in Table 1 for E1 were higher than those of the comparative example (C1 ). In addition, the blends of this invention generally increased in toughness with higher amounts of PET, until at least 68.9 wt%. In contrast, the polycarbonate comparative example showed only limited improvement before exhibiting a dramatic drop in toughness with addition of the PET beyond only 45.9 wt%. The higher Izod values strongly indicate improved toughness of the blends of this invention. [00129] The example blends in Table 1 also exhibited higher melting temperatures and levels of PET crystallinity, compared to the comparative example blends. (In the table, "absent" indicates that no melting point was detected in the DSC experiment, whereas V denotes the test was not performed.) The higher melting points signify that the crystal structure of PET may be more perfectly formed when blended with the copolyesters, rather than other polyesters like polycarbonate. Increased levels of crystallinity suggest that the PET is more phase separated in blends with AAC 1 or AAC 2, consequently allowing it to crystallize more readily and to a higher degree than in the polycarbonate blends. Table 2 - Blends of Example 2 (E2) and Comparative Example 2 (C2)

[00130] Table 2 shows the composition and physical properties of the blends of this invention (E2) - the copolyester AAC 1 compounded with PET 2. These examples show that the higher tensile elongation at break, improvements in notched Izod toughness, increased melting temperature, and higher levels of crystallinity shown in Table 1 , were also observed when a lower IV PET (0.56) was used. Blends of AAC 1 with PET 2 essentially showed similar mechanical property enhancements relative to the comparative example (C2), as were seen in the examples prepared with the higher IV PET (0.76). The E2 blends showed a general increase in notched Izod toughness with increased PET loading, up to 68.9 wt%. On the contrary, the comparative example (C2) blends showed little to no toughness enhancement as a result of the PET addition.

Table 3 - Blends of Example 3 (E3) and Comparative Example 3 (C3)

[00131] Table 3 shows the composition and physical properties of the blends of this invention (E3) - the copolyester AAC 1 compounded with PET 3. E3 demonstrates that the higher tensile elongation at break, improvements in notched Izod toughness, increased melting temperature, and higher levels of crystallinity shown in Tables 1-2, are not unique to a specific PET resin. Additionally, these blends contain only 6 wt% of the MBS impact modifier compared to 8 wt% for E1 , E2, and E5. Comparing E3 to the comparative example (C3), which contains polycarbonate blends with PET 3, further confirms the superior properties exhibited by the blends of this invention.

Table 4 - Blends of Examples 4 (E4) and 6 (E6), and Comparative Example 4

(C4) [00132] Finally, Table 4 shows the composition and physical properties of the blends of this invention (E4 and E6) - the copolyesters AAC 1 and AAC 2 compounded with PET 4, which has a higher IV of 0.80. Once more, both E4 and E6 generally showed the improvements in notched Izod toughness, increased melting temperature, and higher levels of crystallinity, relative to their polycarbonate counterparts (C4) prepared at the same concentration. This example demonstrates that the advantages of this invention extend to higher IV and different grade PET resins. [00133] In addition to the mechanical and thermal property improvements exhibited by the blends of this invention in Tables 1-4, significant improvements were also observed regarding melt phase stability. Figures 1-3 show the viscosity of the molten blend at 300 ⁰ C as a function of time, for several examples and comparative examples at a 50/50 (PET/copolyester) ratio. As expected, all samples showed viscous decay, which is indicative of thermo-oxidative degradation and molecular weight breakdown of typical polyester materials at elevated temperatures. But while the examples (E1 , E2, and E4-E6) of this invention showed a common monotonic decay in the rheological signature, the comparative examples (C1 , C2, and C4) showed very irregular character for the viscosity versus time curve. While not intending to be bound by any particular theory, it appears that this erratic behavior indicates that a chemical reaction, like transesterification, may be occurring in the polycarbonate blends, creating significant melt instabilities and viscosity reduction that are not present in the blends of this invention.

Table 5 - Measured Offqas Rates of CO? During Annealing of Blends at

300 ⁰ C

[00134] Gas evolution experiments were conducted to analyze the presence or absence of a reaction within each blend. Carbon dioxide (CO ₂ ) is a common offgas generated in polyester blends, due to the breakdown of unstable end-groups produced during reaction between the PET and polyester phases. Table 5 shows the rate of CO ₂ generation for several systems. All of the polycarbonate comparative example blends (C1-C4) showed significant generation of carbon dioxide (96-119 μg/g _Sa mpi _e /min). Conversely, the examples of this invention (E1-E6) showed very little CO ₂ release (3-5 μg/g _S am _P i _e /min).

[00135] This result is reliable across the variety of PET types examined. For the examples of this invention, the offgas data suggests that very little reaction between blend components occurred. Less reaction would likely permit easier formation of the PET crystalline structure (higher melting temperatures and degree of crystallization). In contrast, the comparative example offgas data suggests that significant chemical reaction occured. This would probably reduce the opportunity for PET to be crystallizable. [00136] In summary, the rheological data presented in Figures 1-3, combined with the offgas data, confirm that blends of the copolyesters of this invention (AAC 1 and AAC 2) with PET possess much higher levels of melt- phase stability than other polyesters (PC) blended with PET. Not only does this promote higher levels of crystallinity and elevated melting temperatures, the improved melt stability offers advantages for industrial polymer processing

(e.g., injection molding, extrusion, etc).

[00137] 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.