Polytrimethylene ether glycol and preparation method thereof

Abstract

Provided are a polytrimethylene ether glycol and a preparation method thereof, wherein various by-products and oligomers may be effectively removed from a polytrimethylene ether glycol product without exposing to a high temperature for a long period of time, and therefore, a molecular weight variation may be reduced due to the removal of various by-products and low molecular weight oligomers.

Claims

1. A polytrimethylene ether glycol having a molecular weight distribution (Mw/Mn), measured by gel permeation chromatography using polyethylene glycol as a standard material, of 1.8 to 2.1, wherein a content of oligomers having a number average molecular weight of 400 or less is 0.5 wt % or less.

2. The polytrimethylene ether glycol of claim 1, wherein a content of 1,3-propanediol is 100 ppmw or less.

3. The polytrimethylene ether glycol of claim 1, wherein a content of aldehyde is 300 ppmw or less.

4. The polytrimethylene ether glycol of claim 1, wherein an end-group number average molecular weight of the polytrimethylene ether glycol, measured by end-group analysis, is 400 to 4,000.

5. A method of preparing a polytrimethylene ether glycol, the method comprising the steps of: preparing a product comprising polytrimethylene ether glycol by polymerizing 1,3-propanediol (Step 1); and preparing purified polytrimethylene ether glycol by distilling the product under conditions of a temperature of 150° C. to 250° C. and a pressure of 0.001 torr to 2.0 torr (Step 2).

6. The method of preparing the polytrimethylene ether glycol of claim 5, wherein the temperature of Step 2 is 160° C. or higher and 220° C. or lower.

7. The method of preparing the polytrimethylene ether glycol of claim 5, wherein the pressure of Step 2 is 0.005 torr or higher and 0.1 torr or lower.

8. The method of preparing the polytrimethylene ether glycol of claim 5, wherein the distillation of Step 2 is thin film evaporation, falling film evaporation, or short path evaporation.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, preferred Examples will be provided for better understanding of the present invention. However, the following Examples are for illustrative purposes only, and the scope of the present invention is not intended to be limited by the following Examples.

Example

(2) (Step 1)

(3) A 20 L double jacketed reactor was packed with 1,3-propanediol (15 kg) and sulfuric acid (150 g), and heated at 166±1° C. under nitrogen for 35 hours to prepare a polymer, and by-products were removed through an upper condenser.

(4) Viscosity of the prepared polymer was measured as 2300 cps (at 25° C.). Thereafter, deionized water (5 kg) was added, and a produced mixture was maintained under nitrogen at 95° C. for 4 hours to hydrolyze acid ester formed during polymerization. After hydrolysis, 124 g of Ca(OH).sub.2 in 1000 mL of deionized water was added, and the mixture was heated at 80° C. while stirring under a nitrogen stream. Neutralization was continued for 3 hours, and subsequently, the product was dried at 110° C. under reduced pressure for 2 hours, and filtered using a Nutche filter to obtain a total of 8.7 kg of polytrimethylene ether glycol product.

(5) Each 1 kg of nine samples (#1˜9) was prepared by aliqouting the above product, and the following physical properties were measured for the samples, respectively.

(6) (1) OHV and End-Group Average Molecular Weight (Mn)

(7) 6 g of the polytrimethylene ether glycol prepared in Example and 15 mL of an acetylation reagent (acetic anhydride/pyridine=10/40 vol %) were introduced into a 100 mL flask, and reacted at 100° C. for 30 minutes under reflux. After reaction, the mixture was cooled at room temperature, and 50 mL of pure water was introduced thereto. The prepared reactant was subjected to titration reaction with KOH having a normal concentration of 0.5 using an automatic titrator (manufacturer: metronome, Titrino 716). OHV was calculated according to the following Mathematical Equation 1.
OHV=56.11×0.5×(A−B)/feed amount of sample  [Mathematical Equation 1]

(8) wherein

(9) 56.11 represents a molecular weight of KOH,

(10) 0.5 represents a normal concentration of KOH,

(11) A represents a dispensed amount of a NaOH solution used in a blank test, and

(12) B represents a dispensed amount of a NaOH solution used in sample titration.

(13) The measured OHV was converted into an end-group average molecular weight (Mn) according to the following Mathematical Equation 2.
Mn=(56.11×2/OHV)×1000  [Mathematical Equation 2]

(14) wherein

(15) 56.11 represents a molecular weight of KOH, and

(16) 2 Represents the Number of Functional Groups of PO3G.

(17) (2) Molecular weight distribution (Mw/Mn) and Oligomer content (wt %)

(18) The polytrimethylene ether glycol prepared in Example was dissolved at a concentration of 1% by weight in THF (tetrahydrofuran), and a weight average molecular weight (Mw) and a number average molecular weight (Mn) were calculated by gel permeation chromatography (manufacturer: WATERS, model: Alliance, Detector: 2414 RI Detector, Column: Strygel HR 0.5/1/4) using polyethylene glycol as a standard material. From the measured Mw and Mn, a molecular weight distribution value and a content of low molecular weight oligomers having Mn of 400 or less were calculated.

(19) (3) Carbonyl Content (Carbonyl Value; ppmw)

(20) The polytrimethylene ether glycol prepared in Example was dissolved at a concentration of 1% by weight in methanol, and measured by UV spectrometry (manufacturer: Varian, model: Cary300). A carbonyl content was determined according to a calibration data obtained by converting the measured carbonyl absorbance into 2,4-dinitrophenyl hydrazine derivatives according to a concentration of a standard reference (butyl aldehyde).

(21) (4) PDO (1,3-propanediol) Content (wt %)

(22) About 0.5 g of the polytrimethylene ether glycol prepared in Example was dissolved in 10 mL of methanol, and measured by gas chromatography (model: agilent 7890, column: DB-WAX). About 1 g of 1,3-PDO was dissolved in 10 mL of methanol, and additionally diluted according to concentrations, and measured using a standard reference to calculate the 1,3-PDO content in the polytrimethylene ether glycol.

(23) The results are shown in Table 1 below.

(24) TABLE-US-00001 TABLE 1 #1 #2 #3 #4 #5 #6 #7 #8 #9 OHV 52.56 52.07 54.11 56.00 54.96 52.41 56.62 55.89 56.19 End-group 2135 2155 2074 2004 2042 2141 1982 2008 1997 average molecular weight (Mn) Dispersity 2.1 2.0 2.1 2.2 2.1 2.1 2.3 2.2 2.2 Carbonyl value 340 320 380 400 380 360 430 380 390 (ppmw) PDO content 0.05 0.04 0.055 0.07 0.065 0.05 0.09 0.08 0.09 (wt %) Oligomer 0.8 0.7 0.9 1.8 1.6 2.4 3.5 2.9 3.2 content (wt %)

(25) As shown in Table 1, it was confirmed that although the polytrimethylene ether glycols were prepared in the same manner, distribution of each component was localized due to a polarity difference between polytrimethylene ether glycol, and 1,3-propanediol and oligomer. In particular, the number average molecular weight showed a variation up to 175 Dalton, and the molecular weight distribution was also different for each sample.

(26) (Step 2)

(27) Purification of each sample prepared in Step 1 was performed using a lab-scale thin film evaporation equipment. In detail, the thin film evaporation equipment was VKL-70-4 model manufactured by VTA, which is a kind of short path distillation, in which a condenser was installed inside a distillation column and an evaporation diameter and a surface area were 70 mm and 0.04 m.sup.2, respectively. When a distillation column jacket was set at an appropriate temperature by a hot oil system and a vacuum level of about 0.001 torr˜0.1 torr was formed inside the column by a vacuum pump, each of the previously prepared samples was introduced into the upper portion of distillation at an appropriate feed rate. At this time, the polytrimethylene ether glycol formed a thin film having a uniform thickness inside the column by a mechanical stirrer equipped with a wiper. Evaporated low molecular weight materials were condensed in the internal condenser and discharged toward a distillate, and purified polytrimethylene ether glycol was discharged as a residue.

(28) Thin film evaporation conditions applied to each sample were as in the following Table 2, and physical properties of the purified polytrimethylene ether glycol thus discharged were measured in the same manner as in Step 1, and results are shown in the following Table 2.

(29) TABLE-US-00002 TABLE 2 Feed sample #1 #2 #3 #4 #5 #6 #7 #8 Feed rate 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 (kg/hr) Evap. Temp 150 160 170 180 190 200 210 220 (° C.) Condenser 35 35 35 35 40 40 40 40 Temp. (° C.) Vacuum level 0.01 0.02 0.03 0.05 0.05 0.07 0.08 0.1 (torr) Distillate 0.8 0.9 1.4 1.6 1.5 1.3 1.7 1.7 (wt %) Residue (wt %) 99.2 99.1 98.6 98.4 98.5 98.7 98.3 98.3 OHV 52.05 51.67 51.71 51.29 51.52 51.20 50.89 51.13 End-group 2156 2172 2170 2188 2178 2192 2205 2195 average molecular weight (Mn) Dispersity 2.0 1.95 1.95 1.9 1.9 1.9 1.85 1.8 Carbonyl value 110 90 62 70 55 65 38 36 (ppmw) PDO content 52 37 32 34 20 N.D. N.D. N.D. (ppmw) Oligomer 0.48 0.43 0.18 0.14 0.15 0.12 0.09 0.1 content (wt %)

(30) As shown in Table 2, it was confirmed that when the thin film evaporation process was applied, oligomer and PDO contents were decreased, and the variation of the number average molecular weight of polytrimethylene ether glycol was decreased to 50 dalton or less. Further, the carbonyl values representing the aldehyde contents were also greatly decreased, indicating that residual amounts of the reaction by-products were also significantly reduced.