Modified Polyester Compositions This invention relates to modified thermoplastic poly¬ ester compositions which make moldable articles of improved impact 5 strength and thermal resistance. More particularly, the invention pertains to compositions of (a) a polyd,4-butylene terephthalate) in combination with a poly(ethylene terephthalate) resin and/or a polyester copolymer resin, which are modified with (b) an effective amount of a resinous combination comprising a selective¬

10 ly hydrogenated monoalkenyl arene-diene block copolymer and an aro¬ matic polycarbonate. Also provided are such compositions further including (c) fibrous glass reinforcement and/or (d) a flame re- tardant.

High molecular weight

^- ^> linear polyesters and copolyesters of glycols and terephthalic or isophthalic acid have been available for a number of years. These are described inter alia in Whinfield et al, U.S. 2,465,319 and in Pengilly, U.S. 3,047,539, incorporated herein by refer¬ ence. These patents 'disclose that the polyesters are particularly 0 advantageous as film and fiber formers.

With the development of molecular weight control, the use of nucleating agents and two-step molding cycles, poly¬ ethylene terephthalate) has become an important constituent of injection moldable compositions. Poly(l,4-butylene terephtha- 5 late), because of its very rapid crystallization from the melt, .is uniquely useful as a component in such compositions. Work- pieces molded from such polyester resins, alone or combined with reinforcements, in comparison with other thermoplastics, offer a high degree of surface hardness and abrasion resistance, high 0 gloss, and lower surface friction.

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Stable polyblends of poly(l,4-butylene terephthalate) and poly(ethylene terephthalate) can be molded into useful un- reinforced and reinforced articles. See Fox and Wambach, U.S. 3,953,394, incorporated herein by reference.

5 Block copolyesters containing units derived from poly(l,4-butylene terephthalate) and from an aromatic/aliphatic or aliphatic polyesters are also known. See, copending applica¬ tion U.S. Serial No. 752,325, filed December 20, 1976, incorpor¬ ated herein by reference. Such block copolyesters are useful 10 per se as molding resins and also in intimate combination with poly(l,4-butylene terephthalate) and/or poly(ethylene tere¬ phthalate) .

.: It has been proposed to increase the impact strengths of polyesters by adding various modifiers. For example,

15 Brinkmann et al in U.S. 3,591,659.disclose that a useful family of modifiers comprises polyalkyl acrylates, methacrylates and/or ethacrylates. Baron et al in U.S. 4,044,073 disclose that a useful impact modifier for such polyesters is an aromatic poly¬ carbonate. Schlichting et al in U.S. 4,022,748 disclose that

20 a rubber-elastic graft copolymer having a glass temperature below -20 ^β C. is a useful modifier. Lane, U.S. 4,034,013, and Farnham et al, U.S. 4,096,202 disclose that useful impact modifiers comprise multiple stage polymers having a rubbery first stage and a hard final stage, preferably including units

25 derived from alkyl acrylates, especially butyl acrylates.

Baron et al in U.S. 4,034,016 (corres. German 2,650,870) disclose an impact modifier combination comprising a blend of a poly- urethane and an aromatic polycarbonate. Copending application Serial No. 870,679, filed January 19, 1978, discloses an impact

30 modifier combination comprising a segmented block copolyester

and an aromatic polycarbonate. Copending application Serial No. , filed November 6, 1978 under attorney's docket No. GE-809 (8CH-2752/2843/2855+) discloses an impact modifier combin¬ ation comprising a blend of a polyalkylacrylate and an aromatic polycarbonate. Gergen et al, U.S. 4,090,996 disclose an impact - modifier combination for poly(l,4-butylene terephthalate) and other polyester resins comprising a selectively hydrogenated monoalkenyl arene-diene block copolymer, and an engineering thermoplastic, e.g., poly(aryl ether), poly(aryl εulfone) , poly¬ carbonate, acetal, etc. Gergen does not disclose alloyed poly- blends of poly(l,4-butylene terephthalate) and poly(ethylene terephthalate) or block copolyesters. Applicants' herein co- pending application Serial No. , filed , 1978 under attorney's Docket No. GE-970 (8CV-2897/2942/3012) describes combinations of polyesters, block copolymers, aromatic poly¬ carbonates and reinforcing mineral fillers with unique impact properties. All of the foregoing patents and the applications are incorporated herein by reference.

Although filled and/or reinforced and/or flame retardant modifications of the foregoing are described in the above- mentioned references, they lack one or more desirable attributes, when molded.

It has now been discovered that alloyed poly(l,4- butylene terephthalate) and poly(ethylene terephthalate) or block copolyesters of poly(l,4-butylene terephthalate) and combinations thereof be greatly improved in impact strength as molded as well as after annealing and at -20 ^β F., by intimately admixing therewith an impact improving modifier combination comprising a selectively hydrogenated monoalkenyl arene-diene block copolymer resin and an aromatic polycarbonate resin. As will also be shown, the new compositions of this invention can be reinforced with glass, and/or rendered flame-retardant.

According to this invention, there are provided thermoplastic compositions which are useful for molding, e.g., injection molding, compression molding, transfer molding, and the like, the compositions comprising:

(a) a polyester comprising:

(i) a blend of a poly(l,4-butylene terephthalate) resin and a poly- (ethylene terephthalate) resin; (ϋ) _a block copolyester of poly(l,4- butylene terephthalate) and an aromatic/aliphatic or aliphatic polyester; (iii) a blend of ^' (ii) and a poly(ethylene terephthalate) resin; or (iv) a blend of (ii) and a poly(1,4- butylene terephthalate) resin; and

(b) an impact modifier therefor comprising a combination of:

(i) a selectively hydrogenated monoalkenyl arene-diene block copolymer resin; and (ii) an aromatic polycarbonate resin, in an amount of up to 60 parts per 100 parts by weight of (a) and (b) together;

The polyester resin components used in (a) of the compositions of this invention are available commercially or can be prepared by known techniques such as by the alcoholysis of esters of terephthalic acid with ethylene glycols with the free acids or with halide derivatives thereof, and similar pro¬ cesses. These are described in U.S. 2,465,319, and U.S. 3,047,539, and elsewhere. As has been mentioned, preparation

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of the block copolyesters is described in Borman, Dolce and Kramer, U.S. Serial No. 752,325, filed December 20, 1976, and incorporated herein by reference.

Illustratively, the high molecular weight polyesters will have an intrinsic viscosity of at least about 0.4 deci¬ liters/gram and preferably, at least 0.6 deciliters/gram as measured in a 60:40 phenol/tetrachloroethane mixture at 30 ^β C.

Especially useful when high melt strength is important are branched high melt viscosity poly(l,4-butylene terephthalate) resins, which include a small amount of e.g., up to 5 mole per¬ cent based on the terephthalate units, of a branching component containing at least three ester forming groups. The branching component can be one which provides branching in the acid unit portion of the polyester, or in the glycol unit portion, or it _ca n be a hybrid. Illustrative of such branching components are tri- or tetracarboxylic acids, such as tri esic acid, pyromelli- tic acid, and lower alkyl esters thereof, and the like, or prefer¬ ably, polyols, and especially preferably, tetrols, such as penta- erythritol, triols, such as tri ethylolpropane; or dihydroxy carboxylic acids and hydroxydicarboxylic acids and derivatives , such as dimethyl hydroxyterephthalate, and the like.

The branched poly(l,4-butylene terephthalate) resins and their preparation are described in Borman, U.S. 3,953,404, incorporated herein by reference.

Impact modifier (b) comprises a combination of (i) a selectively hydrogenated monoalkenyl arene-diene block copolymer resin and (ii) an aromatic polycarbonate. The block copolymer resin (b) (i) can be made in known ways and they are available commercially from Shell Oil Company, under the trade designation Kraton, and from Phillips Chemical Co., tinder the trade designa¬ tion Solprene. Resins in U.S. ^" 4,090,996 can be used,

especially those containing units in the linear ABA struc¬ ture or in the radial ABA teleblock structure derived from styrene and butadiene or isoprene. Especially preferably, the block copolymer will comprise a selectively hydrogenated block copolymer of styrene and butadiene, the butadiene having a 1,2 content of between about 35% and 55 . The polycarbonate resins (b) (ii) can be made in known ways and they are available commercially from sources, e.g., General Electric Company, Pittsfield, Mass., U.S.A., under the trademark LEXAN. In general, any of the aromatic polycarbonates described in Baron et al, U.S. 4,034,016 can be used, especially those including units derived from bisphenol-A.

The reinforcing fibrous (filamentous) glass can be untreated, but preferably, it will be treated with silane or titanate coupling agents, etc. The filamentous glass to be employed as reinforcement in such embodiments of the present compositions is well known to those skilled in the art and is widely available from a number of manufacturers. For composi¬ tions ultimately to be employed for electrical uses, it is preferred to use fibrous glass filaments comprised of lime- aluminum borosilicate glass that is relatively εode free. This is known as "E" glass. However, other glasses are useful where electrical properties are not so important, e.g. , the low soda glass known as "C" glass. The filaments are made by standard processes, e.g., by steam or air blowing, flame blowing and mechanical pulling. The preferred filaments for plastic rein¬ forcement are made by mechanical pulling. The filament diameters range from about 0.00012 to 0.00075 inch,but this is not critical to the present invention.

The length of the glass filaments and whether or not they are bundled into fibers and the fibers bundled in turn to yarns, ropes or rovings, or woven into mats, and the like, are also not critical to the invention. However, in preparing the molding compositions, it is convenient to use the filamentous glass in the form of chopped strands of from about one-eighth to about 2 inches long. In articles molded from the compositions, on the other hand, even shorter lengths will be encountered be¬ cause, during compounding, considerable fragmentation will occur.

10 This is desirable, however, because the best properties are exhibited by thermoplastic injection molded articles in which the filament lengths lie between about 0.0005 to 0.250 inch.

The amount of the filler can vary widely depending on the formulation and needs of the particular composition, it

^A - ^> being essential only that an amount is selected which is at least sufficient to provide reinforcement. Preferably, however, the reinforcing filler will comprise from about 1 to about 60% by weight of filler (c) and (a) and (b) , combined. Especially preferably the filler will comprise less than about 40% by

20 weight of the combination.

It has further been found that even relatively minor amounts of the modifier (b) are effective in providing signifi¬ cant improvements in impact strength, and the like. In general, however, the modifier (b) will be present in amount of at least " about 17. by weight, preferably from about 2.5 to about 507. by weight of (a) and (b) . The ratio of block copolymer to aro¬ matic polycarbonate can vary widely, i.e., within the range of 1 to 99 parts of the former to; correspondingly, 99 to 1 parts

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of the latter, but in general, from 60 to 40 parts of the block copolymer will be present for each 40 to 60 parts of the aro¬ matic polycarbonate per 100 parts by weight of (b) .

The impact modified polyesters alone, or in combina¬ tion with glass reinforcement can be rendered flame retardant with an effective amount of a conventional flame retardant agent (d). As is well known, flame retardants can be based on elemen¬ tary red phosphorus, phosphorus compounds, halogen and nitrogen compounds alone or preferably in further combination with εyner- gists, such as antimony compounds. Especially useful are poly¬ meric and oligomeric flame retardant agents comprising tetra- bromobisphenol-A carbonate units, see, for example, Wambach, U.S. 3,833,685, which is incorporated herein by reference.

Other ingredients, such as dyes, pigments, drip retard¬ ants, and the like can be added for their conventionally employ¬ ed purposes.

The compositions of this invention can be prepared by a number of procedures. In one way, the modifier and, optionally, reinforcing glass and/or fire retardants is put into an extru¬ sion co pounder with resinous components to produce molding pellets. The modifier and other ingredients are dispersed in a matrix of the resin in the process. In another procedure, the modifier and any reinforcing glass and/or flame retardants is mixed with the resins by dry blending, then either fluxed on a mill and comminuted, or then are extruded and chopped. The modifying agent and any other ingredients can also be mixed with the resins and directly molded, e.g., by injection or transfer molding techniques.

It is always important to thoroughly free all of the ingredients; resin, modifier, reinforcing filler, flame retard¬ ants and any optional, conventional additives from as much as water as possible.

In addition, compounding should be carried out to ensure that the residence time in the machine is short; the temperature is carefully controlled; the friction heat is utilized; and an intimate blend between the resin and the modi¬ fier and any other ingredients is obtained.

Although it is not essential, best results are obtained if the ingredients are pre-compounded, pelletized and then molded Pre-compounding can be carried out in conventional equipment. For example, after carefully pre-drying the polyester and modi¬ fier e.g., four hours at 250 ^e F, a single screw vacuum vented extruder is ed with a dry blend of the ingredients, the screw employed having a long transition section to ensure proper melt¬ ing. On the other hand, a twin screw extrusion machine, e.g., a 53 mm Werner Pfleiderer machine can be fed with resin and additives at the feed port and reinforcement down stream. In either case, a generally suitable machine temperature -will be about 450 to 560 ^β F.

The pre-compounded composition can be extruded and cut up into molding compounds such as conventional granules, pellets, etc., by standard techniques.

The composition can be molded in any equipment con¬ ventionally used for glass-filled thermoplastic -compositions,

e.g., a Newbury type injection molding machine with conventional cylinder temperatures, e.g., 450-535 ^β F. and conventional mold temperatures, e.g., 130-200 ^β F.

Description of the Preferred Embodiments. - The following example ^' s illustrate the invention. They are set forth as a further description but are not to be construed as limiting the invention thereto. In the data tables, the abbreviation "N.D." means not determined. All parts are by weight.

EXAMPLES 1-2 A dry blend of poly(l,4-butylene terephthalate) resin (PBT) , poly(ethylene terephthalate) resin,hydrogenated block copolymer of styrene of butadiene and aromatic polycarbonate of bisphenol-A and phosgene and mold release/stabilizer is compounded and extruded at 520 ^β F. in an extruder. The extrudate is pelletized and injection molded at 520 ^β F. (mold temperature 130 ^β F) . The formulations and physical properties are shown in Table 1.

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Table 1. - Composition Comprising Polyesters,

Block Copolymer and Aromatic Poly- carbonate

Example Composition (parts by weight) 1 _^

Poly(l ,4-butylene tere- phthalate ) 54.8 39.8

Poly(ethylene ,tζ _< φ=rre-

S-B-S Block copolymer ^ ^ 15.0 15.0

Aromatic polycarbonate'&) ("' 15.0 15.0

Mold/release stabilizers (to make 100%)

Properties

Notched Izod impact,ft.lbs./ in. 1/8" 20.7 21.0

Unnotched Izod impact,ft.lbs, 1/8" No break No break

Flexural strength, psi 9100 8700 Flexural modulus , psi 250,000 247,000 Tensile strength, psi 5700 5500 Elongation, % 257 254

(a) (i) Valox 315; General Electric Co., melt viscosity

7250 - 9000 (a)(ii) VF-738-A7C; Goodyear, i.v. 0.62

(b)(i) Kraton G 1651, Shell Chemical Co., A-B-A linear selectively hydrogenated styrene- butadiene-styrene block copolymer

(b) (ii) Lexan, General Electric Co.

The composition according to this invention exhibits excellent impact strength and other properties.

EXAMPLES 3-4 The general procedure of Example 1 is used to make a composition of poly(l,4-butylene terephthalate) aromatic- aliphatic copolyester, S-B-S block copolymer and aromatic poly¬ carbonate formulation used and the properties obtained is set forth in Table 2.

Table 2. - Compositions Comprising Block Copolyester, Block Copolymer and Polycarbonate

Exam le Composition(parts by weight)

Poly(1,4-butylene, terephthalate) copolyester^' ⁽ - ¹¹ ' 69.8 54.8

S-B-S Block copolymer (b)(i) 15.0 15.0

Aromatic Polycarbonate (b)(ii) 15.0 15.0 PET __ 15.0

Mold release/stabilizer (to give 100%)

Properties

Distortion Temp.,Under Load, °F. at 264 psi 128 126

Notched Izod,ft. lbs./in. (1/8") 19.6 16.3 Notched Izod,ft.lbs./in. (1/4") 17.6 N.D. Unnotched Izod.ft. lbs. /in. N.D. No break Flexural strength.psi 7600 8400 Flexural modulus, psi 200,000 230,000 Tensile strength, psi 4600 5100 % Elongation 259 144

(a) (ii) Valox 330, General Electric Co., PBT/aromatic- aliphatic polyester

(b)(i) See Table 1

(b) (ii) Lexan 135, General Electric Co.

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The compositions of this invention are seen to exhibit excellent impact strength, independent of thickness.

EXAMPLES 5-7

The general procedure of Example 1 is used to make compositions of poly(l,4-butylene terephthalate), poly(ethylene terephthalate), S-B-S block copolymer, aromatic polycarbonate and reinforcing fibrous glass. The formulation used and the properties obtained are set forth in Table 3.

Table 3. Compositions Comprising Polyesters,

S-B-S Block Copolymers, Polycarbonates And Glass Reinforcement

Example

Composition (parts by weight)

Poly(l,4-butylene tere¬ phthalate) )(i ⁾ 38.3 24.8 14.8

Poly(ethylene terephthalate) 15. 0 30.0 25.0

S-B-S block copolymer X ¹ ) 15.0 15.0 15..0

Aromatic polycarbonate^ ^^ ' 15.0 15.0 15.0

Fibrous gJLass 15. 0 15.0 30.0

Stabilizer/mold release (to give 100%) ^■

Properties

Distortion Temp., Under Load °F. at 264 psi 230 240 220

Notched Izod, ft.lbs./in. d/8") 4.0 2.4 4.0

Unnotched Izod, ft.lbs./in. 16.9 13.8 18.0 ^' Flexural strength, psi 13,700 14,400 18,600 Flexural modulus, psi 440,000 470,000 800,000 Tensile strength, psi 9,000 9,500 11,500 Gardner dislodge, in-lbs. 134 90 122

(a) (i) Valox 315 resin (b) (i) ; (b) (ii) See Table 1

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The composition has especially excellent impact strength.

EXAMPLES 8-10 Impact modified, fire retarded, unreinforced and reinforced compositions are prepared by the general procedure of Example 1. The formulations and results are set forth in

Table 4.

Table 4. Compositions Comprising Polyesters

Block Copolymer, Polycarbonate, Flame Retardant and Optional Glass

Example 8 10 Composition(parts by weight)

Poly(l,4-butylene terephthalate) ( ^a K ) 3 311..88 21. 8 13.8 Poly(ethylene terephthalate) ( ^a ) ( ^i:L ) 15.0 15.0 15.0 Block copolymer

S-B-S Linear (b)(i) 10. -0 15. 0 15.0 b)(ii)

Aromatic polycarbonate 10.0 15.0 15.0

Fibrous glass -- — 15.0

Brominated aromatic polycarbonate (d) 28.0 28.0 20.0

Antimony oxide 5. 0 5.0 6.0

Stabilizer/mold release (to give 100%)

Properties

Distortion Temp., Under Load °F. , 264 psi 215 212 286

Notched Izod ft.lbs./in. 8.3 11.6 2.7 Unnotched Izod ft.lbs./in. No break No break No break Flexural strength, psi 12,300 10,900 15,700 Flexural modulus, psi 320,000 280,000 505,000 Tensile strength, psi 7,100 6,400 9,900 % elongation 92 112 8.2

(a)(i) Valox 315 resin, General Electric Co. (a)(ϋ) See Footnote to Table 1 (b)(i) Kraton G-1651

(b) (ii) Lexan

(d) 50-50 wt.% tetrabromobisphenol-A, bisphenol-A poly¬ carbonate, Wambach, U.S. 3,833,685

Obviously, other modifications and variations of the present invention are possible in the light of the above teach¬ ings. For example, the poly(l,4-butylene terephthalate) and/or poly(ethylene terephthalate) can be replaced in part with a copolyester, and vice versa. It is therefore, to be understood that changes may be made in the particular embodiments described , above which are within the scope of the invention as defined in the appended claims.