Process for recovering an esterified cellulose ether from a reaction product mixture
A technology for esterifying cellulose ethers and reaction products, which is applied in the field of recycling cellulose ether esters, and can solve problems such as difficult to effectively remove impurities
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example
[0053] All parts and percentages are by weight unless otherwise indicated. The following test program was used in the examples.
[0054] Ether and ester group content in hydroxypropylmethylcellulose acetate succinate (HPMCAS)
[0055] Ether groups in esterified cellulose ethers are determined in the same manner as described for "Hypromellose", United States Pharmacopeia and National Formulary, USP 35, pp. 3467-3469 group content.
[0056] Acetyl group (-CO-CH 3 ) of the ester substitution and the succinyl group (-CO-CH 2 -CH 2 -COOH) ester substitution. Reported values for ester substitution were corrected for volatiles (determined as described in the section "Loss on Drying" in the HPMCAS monograph above).
[0057] Properties of Hydroxypropyl Methyl Cellulose (HPMC)
[0058]Methoxy groups and hydroxypropoxy groups in HPMC were determined as described for "Hypromellose", United States Pharmacopeia and National Formulary, USP 35, pp. 3467-3469 group content.
[00...
example 1
[0061] I. Generation of reaction product mixture comprising HPMCAS
[0062] 514.07 g of glacial acetic acid, 202.49 g (dry content 98.77%) of hydroxypropyl methylcellulose (HPMC) and 43.54 g of sodium acetate (without water) were introduced into a glass reactor with an inner diameter of 147 mm, and were diameter, MIG running at 300rpm TM Stirrer (two-blade axial flow impeller, EKATO, Schopfheim, Germany) mixed vigorously. HPMC has a viscosity of 5 mPa·s measured as a 2% aqueous solution at 20° C., a methoxyl degree of substitution DS (methoxy) of 2.0 and a hydroxypropoxyl degree of substitution MS (hydroxypropoxyl) of 0.86.
[0063] The glass reactor was placed in a heating bath, and the mixture was heated to 85°C. 33.84 g of succinic anhydride and 147.69 g of acetic anhydride were added. Mixing was continued for 30 minutes, then 130.61 g of sodium acetate (no water) was added. Vigorous mixing was continued for 3 hours to achieve esterification while maintaining the bath...
example 2
[0087] I. Generation of reaction product mixture comprising HPMCAS
[0088] A reaction product mixture comprising HPMCAS was generated as in Example 1.
[0089] II: HPMCAS is reclaimed according to the method of the present invention
[0090] The hot reaction product mixture as obtained in Procedure I was quenched by adding 318.46 g of water. Water has room temperature. 100 g of HPMC of the same type as in Example 1 were added as a solid to the diluted reaction product mixture. After 10 min, HPMCAS was precipitated from the diluted reaction product mixture by adding 2 L of water at 21 °C.
[0091] HPMCAS was separated from the resulting suspension by filtration. The filter cake was even less viscous than in Example 1.
[0092] The filter cake was then resuspended in 3 L of boiling water using an Ultra-Turrax mixer S50-G45, and again separated from the resulting suspension by filtration (as described in Example 1). Again, the resulting filter cake was even less viscou...
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