DE2541351A1 - POLYBUTYLENE TEREPHTHALATE MOLDING COMPOUNDS WITH A WIDE TEMPERATURE RANGE DURING PROCESSING - Google Patents

Description

Our sign; OZ 31 5 ^ 6 Ka / DK 6700 Ludwigshafen, 9/11/1975
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Polybutylene terephthalate molding compounds with a wider temperature range during processing

Polybutylene terephthalate is used as a construction material in many areas. The thermoplastic polyester can be processed using a variety of techniques, especially extrusion and injection molding. Above all, because of its high crystallization rate, polybutylene terephthalate is used with advantage in injection molding applications, with very short cycle times being possible. Parts made of polybutylene terephthalate are characterized by high impact strength and heat resistance. To increase the rigidity, the
Reinforcing fillers such as glass fibers, glass spheres or mineral substances such as chalk or talc are added to the material in the usual way.

Experience has shown that polybutylene terephthalate can only be used in injection molding
are processed at temperatures above 2 ¹ IO C. At processing temperatures between 230 and 240 ° C the flowability is the
Too little melt and moldings with lower impact strengths are obtained. If polybutylene terephthalate molding compositions containing reinforcing fillers are processed, molded parts with maximum impact strength can only be obtained at processing temperatures above 250 ° C.

However, because of the thermal degradation of the polyester, the processing temperature, especially with longer residence times
The melt in the processing machine is limited upwards, around 285 ° C, and the processor only has a relatively small amount
Temperature range open for processing.

It was the object of the invention to expand this processing range, without adversely affecting the mechanical properties.

709813/0963

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The invention relates to a polybutylene terephthalate which, in addition to 1,4-butanediol, also contains 0.5 to 5 mol, preferably 1 to 3 mol? Contains neopentyl glycol as an additional diol component. The invention also relates to molding compositions made from such a material, still 0.5 to 5 moles? Containing neopentyl glycol as a further diol component Polybutylene terephthalate and 10 to 60 wt / S, based on the entire molding compound, of reinforcing fillers.

The polybutylene terephthalate according to the invention preferably has a relative solution viscosity of 1.4 to 1.75, measured a 0.5% solution in phenol / o-dichlorobenzene (weight ratio 3: 2, 25 ° C).

Glass fibers and glass spheres are preferably used as reinforcing fillers or talc may be used, but other reinforcing fillers may also be considered if desired. Of course The compositions can also contain other additives such as stabilizers, lubricants, pigments and the like.

The polybutylene terephthalate according to the invention can be in unreinforced form already at a temperature of 230 C and reinforcing fillers in a form containing at temperatures 235-2 ^{1 0} JO C by injection molding to give moldings with high impact resistance process.

The expansion of the processing temperature range is special in the case of polybutylene terephthalate molding compositions containing reinforcing fillers This is an advantage because this area is narrower than in the case of unreinforced material.

It is generally observed that the incorporation of a comonomer into a partially crystalline polymer lowers its degree of crystallization will. As a result of the reduced crystalline content, there is a lowering of the surface hardness, a decrease of Young's modulus, tensile strength, tear strength and flexural strength and a deterioration in heat resistance and Long-term heat resistance.

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It was therefore all the more surprising that these extremely negative effects of the incorporation of a comonomer in the inventive Polymers or reinforced molding compounds were not observed.

In comparison to the homopolymeric polybutylene terephthalate, the values for surface hardness, heat resistance, long-term heat resistance, modulus of elasticity, tensile strength, and tensile strength remained the same and flexural strength constant.

The impact strength level of reinforced polybutylene terephthalate molding compounds is much lower than that of unreinforced. Therefore, especially in the case of reinforced polybutylene terephthalate Molding compositions, an increase in impact strength, especially at lower processing temperatures, is of considerable importance.

example 1

The polyesters used in the example are characterized by their neopentyl glycol content in mol? and their relative Solution viscosity, measured on a 0.5% solution in phenol / o-dichloro * »benzene in a weight ratio of 3: 2 at 25 ° C.

Polyester A is a homopolymeric polybutylene terephthalate with a relative viscosity of 1.67, polyester B contains 2.5 mol? Neopentyl glycol with a relative viscosity of 1.66 and polyester C contains 5 mol? Neopentyl glycol with a relative viscosity of 1.65. The polyesters A to C were treated in exactly the same way in all tests. Using an extruder, 30 wt.? mixed in on glass fibers, the mixture is pressed through nozzles, the strands obtained are passed through a water bath, granulated and the granules are carefully dried. The dried granulate was injected with an injection molding machine at various temperatures and cycle times at a mold temperature of 60 ° C. to give rods with the dimensions ¹ × 6 × 50 mm. The melt temperatures were 2 ^ 0, 255, 270 and 285 ° C. The cycle times were 45 and 90 seconds, corresponding to the residence times of the melt in the cylinder of the injection molding machine.

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casting machine of 10 min and 20 min. The following tables show

the values obtained for the impact strength oo _n in kilojoules / m, tested in accordance with DIN 53 453 at 23 ° C

Cycle time 45 sec

iopentyl glycol <

240 255 270 285

Polyester mole? Neopentyl glycol A, at melt ^{temperature (0} C)

A. 0 35 43 43 44 B. 2.5 43 44 44 45 C. 5 42 43 44 44

Cycle time 90 sec

Polyester mole? Neopentyl glycol ou at melt ^{temperature (0} C)

240 255 270 285

A. 0 36 42 44 44 B. 2.5 42 43 41 42 η 5 43 43 43 43

The example shows that the impact strength in the case of polybutylene terephthalate is 2.5 and 5 mol? Neopentyl glycol at the melt temperature of 240 ⁰ C is about 35 % greater than with homopolymers.

Example 2

In this example it is shown with the molding compositions used in Example 1 that the long-term heat resistance is not adversely affected by the comonomer neopentyl glycol. At a melt temperature of 255 ° C, test specimens with the dimensions 4 × 6 × 50 mm were injected and ^{stored in air at HO 0} C and 140 ° C. After a storage time of 30 and 60 days, the impact strength was ^{measured in kilojoules / m 2 in} accordance with DIN 53 453 at 23 ° C.

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Polyester mole? Neopentyl

glycol impact strength
hot air

HO ⁰ C

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when stored in

IiIO ⁰ C

0 days 30 days 60 days 30 days 60 days,

A. 0 13th HO 40 40 34 B. 2.5 44 41 40 40 34 ■ C. 5 43 41 40 40 33

709813/0963

Claims (2)

Claims ο.ζ. 51 Z 0 4 I O 0 I. Copolyester from terephthalic acid, butanediol-1, ¹ ! and neopentyl glycol, where the neopentyl glycol content is 0.5 to 5 mol $ and the relative solution viscosity, measured on a 0.5 $ solution in phenol / o-dichlorobenzene in a weight ratio of 3: at 25 ° C, I ₉ H to 1, 75 is. 2. Thermoplastic molding composition consisting of a copolyester according to claim 1 and 10 to 60 Gew.JS, based on the total Molding compound, a reinforcing filler. BASF Aktiengesellschaft ¹ V. - C ^ © 671 / 11-16 709813/0963