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Why Use A Concentration Of 88 Wt% As Lactic Acid Commercially?

fermentation lactic acid polymer pla cargill natureworks purification

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#1 Wondor


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Posted 22 June 2020 - 07:15 PM

I'm studying Lactic acid and PLA manufacturing process.
It seemed that 88 wt% of lactic acid is used for polymer and pharmaceutical grades as standard, commercially.
Looking at typical lactic acid purification process at the lactic acid production plant, at the end of the process, there is a step to add deionized water to 99wt% of LA to set it to 88wt%.
Anyway, it should be concentrated at >99wt% again in the polymer manufacturing plant, so I'm wondering why adding water to lower the concentration to 88wt%?
Maybe is that material problems when transporting? (the higher concentration, the higher acidity?)
Or to purify the impurities in LA once more while removing water at the polymer production plant?
If Lactic acid plant and Polymer plant are connected to each other, do you use 99 wt% of Lactic acid right away?

Edited by Wondor, 22 June 2020 - 07:20 PM.

#2 MrShorty


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Posted 24 June 2020 - 10:29 AM

Maybe is that material problems when transporting?
I don't really know, but that could be a good guess. I notice that the melting point of lactic acid is 18 C (according to Wikipedia). Adding water may be about lowering the melting point to avoid freezing the lactic acid during transport/distribution. I would be curious what the melting curves look like for water-lactic acid and where the eutectic is.


That looks like one good reason one may add water to lactic acid.

#3 abhi_agrawa


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Posted 24 June 2020 - 11:31 PM



Also consider the impact of viscosity. A quick internet search showed that for 88.6wt% solution, at 25 degrees C, the viscosity is 36.9 mPas. For higher concentrations, viscosity would be higher.


Further, in concentrated solutions, Lactic Acid would have significant amount of dimers, trimers and tetramers. Not sure if this is good for the downstream polymerization plant.



#4 breizh


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Posted 25 June 2020 - 04:18 AM


Consider this link with references :



Good luck


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