Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2007-03-27
2007-03-27
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C524S745000, C528S275000, C528S293000, C528S302000, C528S308000, C528S308500
Reexamination Certificate
active
11239858
ABSTRACT:
A process for the production of polytrimethylene terephthalate (PTT), wherein the process comprises:(i) one or more esterification steps, wherein terephthalic acid (TPA) or an alkyl diester of terephthalic acid is reacted with 1,3-propanediol (PDO); and(ii) one or more subsequent polycondensation steps,wherein the process further comprises the addition of a protic acid, other than terephthalic or isophthalic acid, before and/or during the one or more esterification steps, wherein the protic acid has a dissociation constant of at most 4 (pKameasured in water at 25° C.), and wherein the total amount of protic acid added before and/or during the one or more esterification steps is in the range of from 0.001 to 10 millimole of acid per kilogram of polytrimethylene terephthalate produced.
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Johnson Emery Don
Kelsey Donald Ross
Tse Cecilia Zuqi
Boykin Terressa
Shell Oil Company
Taylor Richard B.
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