Continuous manufacture of poly(trimethylene terephthalate)
A technology of polytrimethylene terephthalate and polytrimethylene phthalate, which is applied in the field of continuous method for producing polytrimethylene terephthalate
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Embodiment 1 and 2 and comparative Embodiment 1
[0083] In Comparative Example 2, the mixture of 1,3-propanediol and trimethylene terephthalate cyclic dimer was circulated through the inner glass tube at an inlet temperature of 55.2°C, while in Examples 1 and 2 , and the temperatures were 45.3°C and 39.7°C, respectively. The results are shown in Table 1.
[0084] Table 1
[0085] Comparative Example 1
[0086] In comparative example 1 where the cycle temperature into the heat exchanger was higher than 50°C, precipitation and fouling occurred at the restricted flow point, as evidenced by prolonged cooling after 24h, ie lower outlet temperature. In contrast, in Examples 1 and 2, where the cycle temperature was below about 50°C, there was little drop in outlet temperature, indicating little or no fouling. This demonstrates that maintaining the recycled coagulation by-product 1,3-propanediol at a temperature no higher than about 50°C minimizes the amount of fouling due to precipitation of the cyclic dimer of trimet...
Embodiment 3～6
[0088] These examples were performed with a 5 / 32 inch outlet tube instead of the 0.25" outlet tube used in Examples 1 and 2. Therefore, it is expected that fouling should have a greater effect on flow restriction in these examples than in the previous examples The results are shown in Table 2.
[0089] Table 2
[0090] Example 3
[0091] As expected, the effect of the smaller diameter tube in these examples was to slightly increase the observed outlet temperature drop. However, comparing the results of Examples 4, 5 and 6 with Example 3 shows that when the cycle temperature is below about 50°C, the amount of precipitation / fouling is less than at about 50°C, as evidenced by the temperature drop. It can be seen that, in addition to illustrating the advantage of using lower temperatures, it was unexpectedly revealed that by increasing the content of the trimethylene terephthalate cyclic dimer, fouling was reduced.
Embodiment 7 and 8 and comparative Embodiment 2
[0093] These examples illustrate the effect of increasing the solids content of trimethylene terephthalate cyclic dimer and poly(trimethylene terephthalate) on precipitation and fouling, as demonstrated in preferred embodiments of the invention Show. These examples were carried out using the same equipment used in Examples 3, 4, 5 and 6 above.
[0094] In all of these examples, a small amount of terephthalic acid was included in the 1,3-propanediol mixture in order to simulate the use of dimethyl terephthalate as the starting material for the manufacture of poly(trimethylene terephthalate). Dimethyl ester (DMT). The poly(trimethylene terephthalate) used in these examples has an intrinsic viscosity of 1.02 dl / g and has been cryogenically ground and sieved to above 80 mesh in Example 8, while in Example 7 , and sieve to 60-80 mesh.
[0095] The results are in Table 3.
[0096] table 3
[0097] Comparative Example 2
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Abstract
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