Polyester Production

[rodrigotoledo11]

Hi,

I need your help: I would like to know how to improve vacuum distillation process regarding polyester production. The reaction is carried out at 220 degrees Celsius and bottom of the column at 110-120 degrees C and at these conditions much of the DEG and MEG is distilled off when removing the water produced by polycondensation mainly when working under vacuum distillation

If someone here has experience on this kind of process, please, help me with tips/tricks to improve my process decreasing the amount of glycol that is distilled off.

The reactor is charged with Adipic Acid, MEG and DEG.

Sorry any mistakes with my written english: I´m brazillian.

Best regards,

Rodrigo Toledo

 

[DocMax]

Hello Rodrigo

I had worked for a polyester production plant for three years in the past and I was involved in a R&D. I did a lot of synthesis in pilot plants to produce new types of polyesters and I tried a lot of glycols and catalyst.
I know what you whant to produce, a ployester with low crystallization beaviour.
The problem is DEG because during the esterification process it degradate to dioxane.
In the esterification process do you work in pressure? In this phase it's better to work in pressure 2.5 barg, and work with a temperature rate.
What kind of catalyst do you use? Titanium base catalyst? After the end of esterification what is the acidity of monomer? If this acidity is to high you don't esterificated the acid with glycols.
For this reason it's necessary to work with catalyst, the most active are titanium base; but this catalyst has the disavanteges to get some yellow in the polymer.
I don't understand if your problem is the esterification or the polycondensation step.
Please explain better your problem.
Mybe I could help you.
Good luck
DocMAx.

 

[rodrigotoledo11]

Hi DocMax, Thank you very much for the comments.

The polyester I want to produced will be used to produce polyurethane adhesive (Will react with Isocynate)

I´ll to explain my process in details Excuse any mistakes with my english, ok ? )

DEG+MEG is added to the reactor and heated to 70C/1atm and stirred at 60RPM. At this point, Adipic Acid is added and the temperature is raised to +/- 200C/1atm. Water is continuously removed. As soon as the acidity reach 15-20mgKOH/g, tetra butyl titanate is added and the process is carried at vacuum´s conditions (500 mmHg). I need an acidity value of <2mgKOH/g and OH value of 55.

The problem is that great amount of glycols is removed with water and I´ve to make corrections adding more glycols to reach the OH=55.

I know I could reflux the distillated to the column´s top to keep temperature rounded to 100-110C but I don´t have how to make this right now.

I would like to know what I can do to improve my process, I mean, how to design the column and the distillation condition to reduce the amount of glycols distilled off.

What kind of column fit´s better in this case ?

The company I´m now working for has experience in Nylon production but none in polyester production but how both are produced by means of step-polymerization I think the reactor they´ve would be used to produced polyester, isn´t it ?

Thank you vey much,

Regards,

 

[DocMax]

Hi Rodrigo

Probabily my plant was different about your, but I remembre that we did this syinthesis and we had not some problems.
The plant was a pilot plant 150 L. We putted the glycols and after the acid, it's also importatnt the molar excess of glycols to acid.
Our column was a packet type with pall rings. The pressure was 2.5 barg with a reflux. The set point of temperature was 190°C. I remember the colum worked ok. Probabily you will use a reflux with a temperature controll.When the esterification was at he end I depressurized the reactor till 0 barg.
For the vacum phase I isolated the reactor and made a gentile vacum step. In this phase I removed all the glycols add in molar ecxess.
After this the polymer was ready. Also I used the tetrabutyl titanate, but I remember the TNBT was not active during the esterification because with water precipiate titanium dioxide, so I added the TNBT at the end of edterification, just befor the vacum phase.

That's all, but i didn't remember the feagures.

ciao

 

[rodrigotoledo11]

Hi DocMax,

Thank you very much for all your help !
Still remain the problem to improve the distillation process but your advices helped a lot !

Regards,

Rodrigo Toledo

 

[DocMax]

Ciao Rodrigo

Let me know if you solve the problems and how the synthesis go.

you're welcome

Best regards
DocMax

 

[Rocco8]

What is your reflux ratio?

How many theoretical stages do you have in your column?

Have you considered increasing the reflux ratio? You must be able to get additional heat into the unit to maintain the same production rate. Also you don't want to flood the column.

 

[elguero]

DuPont has a bunch of patents in this area -- all expired. I would commission a patent searcher to make copies of US patents and send them to you.

Also contact the corporate legal department at DuPont, they probably have now-how (in addition to patent information) for sale. As you may know, a patent is often the tip of the iceberg, so to speak.

 

[rodrigotoledo11]

Hi,

I´ve a basic question now: How calculate the amount of glicol (MEG for example) to be added to correct the acidity index of a polyeser resin ? I mean, i´ve a PET with 3,45 mgKoH/g of acidity and I want a resin with acidty value below 0,5 mg KOH. How to make this calculation ?

Thanks in advance,

Rodrigo Toledo