CA2065366A1 - Poly(1,4-cyclohexylene dimethylene terephthalate) molding compositions - Google Patents

Abstract

2065366 9106603 PCTABScor01 Disclosed is reinforced poly(1,4-cyclohexylene dimethylene terephthalate) containing 5-30 weight % of polyphenylene sulfide as a thermo-oxidative stabilizer.

Description

WO91/06603 Z~3~ PCT/US90/~583~

POLY(1,4-CYCLOHEXYLENE DIMETHYLENE
TEREPHTHALATE) MOLDING COMPOSITIONS

Technical Field This invention relates to reinforced poly(l,4-cyclohexylene dimethylene terephthalate) (PCT) molding compositions having improved thermo-oxidative stability.
Backqround of the Invention .

Polyesters have been used as engineering plastics for mechanical parts of various machines, electrical equipment and parts of motor cars. Preferably, ~;
engineering plastics are provided with fire-proof properties, i.e., flame retardancy, in addition to well-balanced ordinary physical and chemical properties.
Such properties are indispensable in thermoplastic polyesters in order to enlarge their use as engineering plastics, because they are normally used at temperatures higher than 100C.
This invention concerns the discovery of reinforced molding compositions based on PCT or high melting crystalline copolymers of PCT with improved thermo-oxidative stability. Surprisingly, the addition ofpolyphenylene sulfide (PPS) to reinforced (GFR) PCT by-conventional melt blending will cause improvement in the thermo-oxidative stability of GFR PCT while maintaining excellent mechanical properties in the resulting formulations. These materials have high strength, stiffness, and heat re.~i stance properties. These materials find application as a molding plastic in the electronics industry as printed circùit boards, connectors, etc. These are applications that require WO91/ ~ 03 PCT/US90/05831 _ ~

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the material to have high strength, stiffness, heat resistance, and continuous use temperature rating.
U.S. ~atent 4,140,671 discloses mi~tures of linear polyesters, polyphenylene sulfide powder, flame retardants, fiber glass and talc to reduce the warpage of the polyester. No indication of improved long-term ;~
oven stability is made. Further, the PPS is present in the form~of a filler, rather than as a melt blend, as~in .
the present invention.
U.S. Patent 4,689,365 discloses blends of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) with polyphenylene sulfide of a specifled melt flow, which provide materials with an improvgd~heat deflection~temperature. No disclosure of -~
~ po~lyesters~other than~PBT and~PET is made. There is no indioation of improved long-term oven stability in the . ~`~
blends.~Accard~ing to the~examples, molding conditions were~such~that the PPS~wa~s`also not melted (molding done :~
below tho~melting point of PPS).
20~ Other U.S.~;patents of interest include 4,251,429 :
and 4~,284,549 ~blends of PPS with polyarylates) and 4,267,3~9~7 ~bl-nd of PPS with~a wholly aromatic liquid crystalline polyester~). Blends of polysulfones with polyesters~a~re disclosed i~n U.S. Patent 3,742,087.
25~ Polysulfones are~not useful in the present invention because the heat deflection temperataure is lowered.

DescriPtion of the Invention According to the present invention, there are provided polyeste~r molding compositions containing a reinforcing material and polyphenylene sulfide as a thermo-oxidative stabilizer, the polyester containinq - repeat units from terephthalic acid and 1,4-cyclohexane-dimethanol.
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More particularly, the present invention provides reinforced polyester molding compositions having improved physical properties comprising (a) a polyester having repeat units from terephthalic acid and 1,4-cyclohexane-dimethanol and having an I.V. of 0.5-l.0, and (b) 5 to 30%, based on the weight of polyester, of polyphenylene sulfide, the repeat units of -~
which consist essentially of 1 0 .
r.~

n and having a degree of polymerization of at least 50.
The polyester portion of the molding compositions of the present invention is prepared by conventional polycondensation procedures well known in the art. The polyester, poly(l,4-cyclohexylene dimethylene terephthaIate), contains repeat units from a dicarboxylic acid component and a glycol component. The dicarboxylic acid component, a total of lO0 mol ~, is at least 90 mol % terephthalic acid and the glycol component, a total of lO0 mol %, is at least 90 mol %
l,4-cyclohexanedimethanol. ~
The dicar~dxylic acid component may contain up to lO mol % of other conventional aromatic, aliphatic or alicyclic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, cyclohexane-dicarboxylic acid, succinic acid, sebacic acid, adipic acid, glutaric acid, azelaic acid and the like.
The glycol component may contain up to lO mol % of other conventional aliphatic or alicyclic glycols such as diethylene glycol, triethylene glycol, ethylene WO91/~603 z~S3~ PCT/US90/05831 _ '~

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glycol, propanediol, butanediol, pentanediol, hexanediol, and the like.
The polyesters can be prepared by direct condensation of terephthalic acid with 1,4-cyclohexane-dimethanol or ester interchange using dimethylterephthalate. The essential components of the polyester, e.g., terephthalic acid or dimethyl terephthalate and 1,4-cyclohexanedimethanol are ~
- commercially available.
The polyesters and copolyesters described above should have an I.V. (inherent viscosity) of from 0.5 to 1Ø
It is important in the present invention that the polyester and the PPS have melting temperatures close to each other s~o that the two can be melt blended without degradation of either. The melting temperature of the polyester is 295C and the melting temperature of PPS is 285C. In the prior art, PPS is used mostly as a ;~
filler and is not melt blended with the polyester.
Thus, in applicants' invention, the blend of polyester and PPS is homogeneous.
- The improved polyester resin composition of this - invention includes a reinforcing material. A preferred reinforcing filler is glass fibers which may be ~- 25 introduced into the composition as chopped glass fibers or continuous glass fiber rovings in amounts of 10-50%
by weigh~ of the composition.~ Other reinf~rcing materials such as metal fibers, graphite fibers, aramid fibers, glass beads, aluminum silicate, asbestos, mica, talc and the like may be used in combination with, or in place of the glass fibers.
Substantially any of the types of glass fibers generally known and/or used in the art are useful in the present invention. Typical types are those described in 35 British Patent No. 1,111,012, U.S. Patent No. 3,368,995 WO91/G6603 ~ ~ ~ ~ PCT/US90/05831 and German Auslegeschrift No. 2,042,447. Thus, the average length of useful fibers covers a wide range, for example, l/16 to 2 inches (0.159 cm to 5 cm~. The presently preferred glass fibers have an average length of l/16 to l/4 inch (0.159 cm to 0.64 cm).
Glass filaments made of calcium-aluminum-boron silicate glass, which is relatively free from sodium carbonate, are preferably used. Glass of this type is known as "E" glass; however, where the electrical properties of the reinforced polyesters are not importar.t, other glasses can also be used, for example the glass with a low sodium carbonate content which is known as "C" glass. The diameters of the filaments can be in the range ~rom 0.003 to 0.018 mm, but this is not critical for the present invention.
In addition to the components discussed above, the blends of this invention may contain additives commonly employed with polyester resins, such as colorants, mold release agents, tougheners, nucleating agents~
crystallization aids, plasticizers, ultraviolet light and héat stabilizers and the like. Materials such as Irganox lOlO stabilizer and/or Weston 619 stabilizer in ~-amounts of up to 2%, preferably O.l-05% by weight of the composition, are preferred.
2~ Preferably, the molding compositions according to this invention include at least one conventional flame retardant such as a halogenated organic compound, an~
antimony compound, or the like.
The blends of this invention are prepared by blending the components together by any convenient means to obtain an intimate blend. Compounding temperatures `~
must be at least the melting point of the PCT. For example, the polyester can be mixed dry in any suitable blender or tumbler with the other components and the 3~ mixture melt-extruded. The extrudate can ~e chopped.

WO91/~03 PCT/US90/05831 3~

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If desired, the reinforcing material can be omitted ;-initially and added after the first melt extrusion, and the resulting mixture can then be melt extruded. The product is especially suitable as an injection molding materlal for producing molded articles.
These blends will find application in injection molded parts that require a good combination of strength, stiffness, heat resistance, and continuous use - temperature such as required in the electronics industry.
The following examples are submitted for a better understanding of the invention.
A series of blends of PCT with 30~ glass fiber (GFR ~-PCT) are prepared containing 0, 5, 10, 20, and 30% PPS
based on the weight of the polyester. These formulations are then melt blended by extrusion compounding using the 1.5 inch single screw extruder at 300C. The resulting formulations are then molded into --1/8 inch tensile and flexural test bars using an injection molding machine. Mechanical properties are determined~on these test bars (see Table 1). Generally, the;GFR PCT formulations containing PPS maintain excellent heat deflection temperature with only minimal loss~of strength properties (tensile, flexural, Izod 2$ impact)~ The flammability properties of these formulations are improved as shown by the increasing oxygen index with increasinlg PPS concentration. Thermo-oxidative stability is determined on these formulations by heating the tensile bars in a forced air oven at 180C for 0-2352 hours and measuring the retained .~ .
tensile strength (see Table 2). Generally, the retained tensile strength increases as the PPS concentration increases in the GFR PCT blends, which represents impro~ed thermo-oxidative stability. The blends contain conventional amounts of Benzoflex S312 crystallization ~, :

W O 91/06603 . PC~r/US90/05831 enhancer and Weston 619 and I~ganox 1010 stabilizers Ryton P4 polyphenylene sulfide is used.

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' W O 91/06603 2~5~d~S PCT/US90/05831 TA8L~ 1 Effect of PPS on the Mechanical and Flammability Properties of PCT/30% Glass Fiber Reinforced Example No. .
1 2 3 4 5 :.
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PPS, % - 5 10 20 30 Benzoflex S312 crystallization -~
enhancer, % 5 4.64 4.29 3.57 2.86 Weston 619 stabilizer, % 0.25 0.23 0.22 0.18 0.14 Irganox 1010 stabilizer, ~ 0.25 0.23 0.22 0.18 0.14 ~old temperature, C 120 120 120 120 120 ~ Ash 29.8 29.9 30.1 30.6 31.2 IV ~before molding)/ dl/g* - 0.63 0.57 0.48 0.37 I~ (after molding)~ dl/g* 0.68 0.63 0.57 0.47 0.31 Density 1.445 1.452 1.464 1.460 1.502 % Xold shrinkage 0.09 0.08 0.10 0.11 0.10 Rockwell Hardness R 122 121 120 122 122 .

10 Mil notched Izod ft-lb/in. (Joules/meter) @-40C 1.6c 1.5c 1.4c 1.4c 1.6c (85.4) (80) (74.7) t74.7 (a5-4) @ 23~C 1.6c 1.4c 1.3c 1.3c 1.6c 185.4) (74.7) (69.4) ~69.4) (85.4) ~nnotched Izod ft-lb/in. (Joules/meter) @-40C lO.Bc 8.2c 6.4c 5.1c 4.9c @ 23C lO.9c 8.4c 6.0c 4.4c 4.8c Flexural strength 103 psi (kPa) 30.07 25.43 23.76 20.62 22.14 (207.~3) (175) (163.8) (142) (152.6 Flexural modulus 105 psi (kPa) 12.47 12.69 12.86 13~.54 14.39 (~5.98~ (87.5) (88.6) (93.3) (99.216) ~eat deflection temperature C
@ 264 psi 259 259 261 252 260 (1820 kPa) WO 91/06603 PCr/lJS90/05831 2~

g TABLE 1 (Cont'd.) Effect of PPS on the Mechanical and Flammability Properties of PCT/30~ Glass Fiber Reinforced Example No.

_ Tensile strength 3 @ Break 10 psi 19.69 18.47 17.86 16.S8 15.39 (kPa) 5 (135.7) (127) (123) (114) (104) @ Yield 10 psi (kP~
Elongatisn @ ~reak 4 4 3 3 3 @ Yield - - - - -Oxygen index 20.0 20.2 20.7 21.6 25.2 *IV determinations corrected for ~ Ash cComplete breaks (Izod impact strength) S

-- 10 -- ,, Effect of PPS on the Thermo-Oxidative Stability of PCT/30~ Glass Fiber Example No.

~old temperature C 120 120 120 120 120 PPS, % - 5 10 20 30 Benzoflex S312 crystallization enhancer, ~ 5 4.64 4.29 3.57 2.86 Weston 619 stabilizer, ~ 0.25 0.23 0.22 0.1& 0.14 Irganox 1010 stabilizer, ~ 0.25 0.23 0.22 0.18 0.:L4 Tensile strength @ break 103 psi SkPa) after exposure to 180C air 0 hrs 19.69 18.47 17.86 16.58 15.09 (135.7) (127) (123) (114.3) (104) 187 hrs 16.39 15.61 15.09 14.27 14.19 (113) (107.6) (104) (98.3) (978) 336 hrs 15.47 15.04 14.71 14.05 13.11 (106.6) (103.6) (101) (g6.8) (90.4) 672 hrs 14.20 14.11 13.S7 12.36 12.92 (97.9) (97~ (93.5) (85.2) (89) 1027 hrs 12.61 13.53 13.02 12.45 12.85 (86.9) (93.2) (89.7) (85.6) (88.6) 1344 hrs 11.76 12.33 11.66 11.01 11.01 (81) (85) (80.3) ~75.9) (75.9) 1680 hrs 11.43 11.44 10.88 10.61 10.86 (78.8) (78.8) (75) (73.1) (74.8) 2016 hrs 10.99 11.00 11.57 11.68 12.30 (75.7~ (75.8) (79.7) (80.5) ~84.8) 2352 hrs 9.86 10.43 10.42 10.20 10.44 ~67.9) ~71.9) ~71.8) ~70.3) ~71.9) % Retained tensile strength after exposure to 180C Air 0 hrs 187 hrs 83 85 84 86 94 336 hrs 79 81 82 85 87 672 hrs 72 76 76 76 86 1027 hrs 64 73 73 75 85 1344 hrs 60 67 65 66 73 1680 hrs 58 62 61 64 72 2016 hrs 56 60 65 70 82 2352 hrs 50 56 58 62 69 WO91/06603 2~ 5~ PCTI~S90/05831 The data on percent retained tensile streng~h show that, surprisingly, as the amount of PPS in the composition is increased, the percent retained tensile strength after extended exposure to 180C air increases.
With no PPS, only 50% of the tensile strength is retained after 2352 hours at 180C. This steadily increases with increasing levels of PPS, indicating the impro~ed thermo-oxidative stability of the compositions of this invention.
As used herein, the inherent viscosity tI.V.) is measured at 25C using 0.50 g of polymer per 100 mL of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane. , The tests used herein for determination of mechanical properties are described as follows~
Tensile Strength ASTM D638-80 ,~

Elongation ASTM D638-80 Flexural,Modulus ASTM D790-80 Flexural Strength ASTM D790-80 Rockwell Hardness ~ Izod Impa,c,f , ~ ASTM D256-81 ~eat Deflection ASTM D648-72 Temperature, C
Oxygen Index is defined as the minimum ~
concentration of oxygen in an oxygen and nitrogen ' mixture that will support combustion of a material in a ' candle-like configuration (ASTM designation D2863-77).

WO91/0~03 PCT/US90/05831 ~

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Unless otherwise specified, all parts, percentages, ratios, etc., are by weight. Weight of reinforcing glass fibers and nucleating agents(s) are based on total composition weight.
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 inventr~n.

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' WO 91/06603 PCI /USgO/05831 , _ 2~3s~

the weight of polyester of a reinforcing material, and 5-30% based on the weight of polyester of a polypropylene sulfide having repeat units consisting essentially of r o L 1~ ,b--and having a degree of polymerization of at least 50.

Claims (3)

1. l. A reinforced polyester molding composition characterized as a melt blend of (a) a polyester having repeat units from at least 90 mol % terephthalic acid and at least 90 mol % 1,4-cyclohexanedimethanol, said polyester having a I.V. of 0.5-1.0, (b) 10-50% based on the weight of polyester of a reinforcing material, and said composition further comprising 5 to 30% based on the weight of polyester, of a polyphenylene sulfide, the repeat units of which consist essentially of and having a degree of polymerization of at least 50.
2. 2. A molding composition according to Claim l wherein said polyester consists essentially of repeat units from terephthalic acid and 1,4-cyclohexane-dimethanol.
3. 3. The method of preparing a reinforced polyester molding composition characterized by melt blending a polyester having repeat units from at least 90 mol %
   terephthalic acid and at least 90 mol %
   1,4-cyclohexanedimethanol, 10-50% based on