CN102432860A - A kind of preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether - Google Patents

Abstract

The invention discloses a preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether, which comprises the steps of dissolving dried polytetrahydrofuran diol in a solvent, adding an alkali metal hydride, generating polytetrahydrofuran diol alkoxide at the temperature of between room temperature and 150 ℃ for more than 1 hour, placing the polytetrahydrofuran diol alkoxide in a high-pressure kettle, adding ethylene oxide, initiating the ethylene oxide to carry out anion ring-opening polymerization, and polymerizing for 1 to 120 hours at the temperature of between room temperature and 150 ℃ by taking nitrogen or argon as a protective atmosphere to prepare the hydroxyl-terminated polyethylene glycol-polytetrahydrofuran diol-polyethylene glycol ABA type block copolyether. The method is stable and controllable, and the prepared hydroxyl-terminated triblock copolyether has high purity, definite structure and narrow molecular weight distribution.

Description

A kind of preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether

technical field

The invention belongs to the field of polymer material synthesis and relates to a preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether.

Background technique

Polytetrahydrofuran glycol (PTMEG), also known as polytetrahydrofuran (PTHF), is a polyether material with excellent low-temperature performance. Its molecular chains are flexible, tightly arranged, and there are no side chains in the structure. The density is higher than other polyethers. And has a lower glass transition temperature. Usually, PTMEG is used as a soft segment component in block copolymers, endowing materials with excellent physical and mechanical properties and low-temperature performance. Polyethylene glycol (PEG) is a non-toxic, non-irritating polyether product, which is water-soluble and compatible with many organic substances. Due to its excellent moisture retention, lubricity and dispersibility, polyethylene glycol can be used as adhesives, antistatic agents and softeners, etc., in cosmetics, chemical fibers, pharmaceuticals, papermaking, electroplating, plastics, rubber, paints, pesticides, metals, etc. And food processing and other industries are widely used.

PEG-PTHF block copolyether can retain the excellent properties of PEG and PTHF to a certain extent, and has more excellent mechanical properties and wider application prospects than traditional polyether products. In addition, the hydrophobicity of polytetrahydrofuran and the hydrophilicity of polyethylene glycol make the copolyether amphiphilic and can be self-assembled in solution. Due to the good biocompatibility of polyethylene glycol and polytetrahydrofuran, the block copolyether has good biocompatibility. Drug carrier and controlled release have potential application value.

In the field of solid propellant design, the HTPE binder used in a new generation of high-performance propellants is a block copolymer obtained by living polymerization of ethylene oxide (EO) and tetrahydrofuran (THF) (Yan Daqing, Xu Dandan, Shi Jingguo . Solid Propellant Binder HTPE Research and Overview of Molecular Design Ideas. Solid Rocket Technology. 2009, 32: 644-649.). This hydroxyl-terminated polyether adhesive has the characteristics of low glass transition temperature, good flexibility, and good compatibility with nitrate plasticizers. As an adhesive for solid propellants, it can not only improve the mechanical properties of propellants and The sensory performance has been significantly improved, and the energy of the propellant has also been greatly increased due to the introduction of the nitrate plasticizer. The preparation of hydroxyl-terminated block copolyether binder is a key technology in the development of HTPE propellants, but there are few research reports on this aspect.

At present, block copolyether is prepared by coupling PEG and PTHF mainly through terminal group reaction. In this method, the terminal hydroxyl groups of PTHF and PEG react with -NCO, -COOH and other groups in the coupling agent molecule to realize the polymerization. The bonding between objects is used to prepare block copolymers. Niua et al. used novozyme-435 lipase to catalyze the reaction between PTHF and diethyl malonate to prepare PTHF with ethyl ester groups at both ends, and then transesterified it with PEG of different molecular weights to prepare PEG-PTHF- PEG block copolyether. The block copolyether has amphiphilicity and can aggregate to form micelles in aqueous solution, and its critical micelle concentration (CMC) and micelle size can be changed by adjusting the size of PEG segment on the molecular chain. Gerfried et al. used acid as a catalyst to prepare block copolymers of polytetrahydrofuran and polyethylene glycol. Neumer et al. used acidic montmorillonite as a catalyst to condense PTHF and formaldehyde in cyclohexylamine solution to obtain a block copolymer of PTHF and formaldehyde. With this idea, block copolymers of PTHF and polymers such as PEG or polybutylene oxide can be prepared. The copolymer has more excellent properties than the original two polymers: at the same temperature, the viscosity of the copolyether is only one-half of that of PTMEG, and the obtained polyurethane is better than that of PTMEG with the same relative molecular mass. Polyurethane has better mechanical properties.

Literature (Barcock Richard A, Hobson Rachel J. Photographic emulsion. [P]. USP 5773207, 1998.) introduces another method for synthesizing PTHF and PEG block copolymers. First, one of the polymers is reacted with methylsulfonyl chloride to obtain a methylsulfonyl-terminated polymer, and then reacted with another polymer to finally obtain an ABA or BAB type block polymer.

Using the terminal group reaction method, the hydroxyl-terminated PEG-PTHF block copolyether can be prepared simply and cheaply under the action of the coupling agent, but the molecular weight distribution of the block copolyether prepared by this method is wide, and the structure is difficult to control. Meet the needs of high-performance material preparation.

In addition, PEG-PTHF block copolyether can also be prepared by using macromolecular PEG to terminate the cationic ring-opening polymerization of THF. In 1999, Inge C. De Witte and others used polyethylene glycol monomethyl ether mPEG750, mPEG2000, mPEG5000 to terminate the cationic ring-opening polymerization of THF initiated by trifluoromethanesulfonic anhydride, and successfully prepared narrow molecular weight PEG-PTHF- PEG tri-block copolyether. Subsequently, Catherine Pomel et al. repeated the above method to prepare PEO-PTHF-PEO triblock copolyether and applied it to the study of gene transmission in muscle tissue.

The preparation of tetrahydrofuran-ethylene oxide block copolyether by the PEG termination method of Tf ₂ O system is an efficient preparation method. The reaction is rapid and the prepared copolymer has a clear structure and narrow distribution. However, strict isometry is required in the preparation process. Adding materials, and the obtained copolyether molecules have no hydroxyl groups at both ends, and the application value is limited.

Recently, Luo Yunjun et al. (Wang Cundong, Luo Yunjun, Wang Cundong et al. Synthesis and characterization of hydroxyl-terminated PTHF-PEO-PTHF block copolyether. Solid Rocket Technology. 2011, 34: 202-206.) used macromolecular PEG as the initiator ( Initiator), boron trifluoride ether complex as a catalyst, under the condition of a small amount of propylene oxide ring-opening aid, THF undergoes cationic ring-opening polymerization, and PTHF chain segments are connected to both ends of polyethylene glycol, Thus, a hydroxyl-terminated PTHF-PEO-PTHF tri-block copolyether was prepared. However, in this method, the initiator cannot fully participate in the initiation reaction, resulting in a large amount of PEG homopolyether and diblock copolyether in the product, requiring complicated separation and purification procedures.

Contents of the invention

In order to overcome the disadvantages of the prior art that the structure is difficult to control, the application value is limited, or the separation and purification are complicated, the present invention provides a method for preparing hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether. The method is stable and controllable. The hydroxyl-terminated triblock copolyether has high purity, definite structure and narrow molecular weight distribution.

The technical solution adopted by the present invention to solve its technical problems comprises the following steps:

In the first step, the dried PTMEG is dissolved in a certain amount of solvent in the reactor, and an appropriate amount of alkali metal hydride is added to the reactor, and the molar ratio of PTMEG and alkali metal hydride addition is 1:2-1 : 4, after vacuuming to 0.01-0.1MPa, react at room temperature to 150°C, and the reaction time is more than 1 hour. It is also possible to fill the kettle with nitrogen or argon to form a protective atmosphere after vacuuming, and then carry out the reaction. Control the amount of protective gas to keep the pressure in the kettle at 0.01-6MPa, and then react at room temperature to 150°C for more than 1 hour, and finally PTMEG The terminal hydroxyl group reacts to generate PTMEG alkoxide, and PTMEG alkoxide has the following structure:

其中，M为钾(K)或钠(Na)，n＝9～100，O代表氧元素。

Wherein, M is potassium (K) or sodium (Na), n=9-100, and O represents oxygen element.

The molecular weight Mn of the PTMEG used in the above method is 650-6000 g/mol, preferably a narrow distribution PTMEG with a molecular weight distribution (Mw/Mn) less than 1.30.

The alkali metal hydride used in the above method is sodium hydride (NaH) or potassium hydride (KH).

The solvent used in the above method is tetrahydrofuran (THF) or toluene (Toluene).

The solvent used in the above method is refluxed with sodium, calcium hydride or sodium hydride to remove water, and the mass ratio of the solvent to the amount of PTMEG added is preferably 1:1 to 2:1.

In the above method, the molar ratio of the added amount of PTMEG and the alkali metal hydride is preferably 1:2.1˜1:2.4.

The reaction temperature of the above method is preferably 50-70°C.

The reaction time of the above method is preferably 4 hours.

In the second step, PTMEG alkoxide is placed in the autoclave, and ethylene oxide is added, and the molar ratio of ethylene oxide and PTMEG alkoxide is 2: 1 to 200: 1, which triggers ethylene oxide to carry out anion opening. Ring polymerization, using nitrogen or argon as the protective atmosphere, controlling the filling amount of protective gas so that the pressure in the kettle is 0.2-6MPa, and the polymerization reaction temperature is from room temperature to 150°C. High temperature is beneficial to increase the reaction rate, and low temperature is beneficial to reduce the product chroma, improve product quality, after polymerization for 1 to 120 hours, terminate the reaction, and prepare an ABA-type block copolyether of hydroxyl-terminated PEG-PTHF-PEG, whose structure is as follows:

其中n、m、m′为整数，n＝9～100，m+m′＝2～200，O表示氧，H表示氢。

Where n, m, and m' are integers, n=9-100, m+m'=2-200, O represents oxygen, and H represents hydrogen.

In the above method, the anionic ring-opening polymerization of ethylene oxide is solution polymerization or bulk polymerization. During solution polymerization, the solvent used is a stable solvent under tetrahydrofuran and toluene under alkaline conditions, and the molar ratio of the amount added to the amount of PTMEG alkoxide added is 1:10 to 10:1, preferably 1:1. For the preparation of small batches of samples, bulk polymerization can be used, that is, without adding any solvent.

In the above method, the polymerization temperature is preferably 70 to 110°C.

For the scheme of high conversion rate of ethylene oxide, the polymerization reaction can be stopped when the pressure in the reactor drops to the same level. When the molecular weight of the prepared target block copolyether is less than 10000, the conversion rate of ethylene oxide can reach more than 90% when the polymerization temperature is higher than 70° C. and the reaction time is 8 hours.

The beneficial effects of the present invention are:

1. The present invention adopts highly active metal hydrides and PTMEG to react to prepare macromolecular alkoxides. The reaction is rapid and efficient, and almost all terminal hydroxyl groups of PTMEG react to form alkoxides.

2. The method provided by the present invention can flexibly design the molecular weight and block ratio of the block copolymer by selecting polyPTMEG with different molecular weights and adjusting the feed ratio, and then can prepare a large class of block copolymers that meet the needs of different occasions. ether products.

3. In the method provided by the present invention, the two-step reaction can be completed successively in the same reactor, and the continuous high efficiency of the reaction process and the airtightness of the system are guaranteed in the experimental process, so that the prepared block copolyether product has high purity and high chromaticity. Low, narrow molecular weight distribution.

Below in conjunction with embodiment the present invention is further described.

Detailed ways

Example 1

Add 50mL of dry THF, 40.97g of PTMEG-2000 (Mn=2092, Mw=2815, Mw/Mn=1.35) and 1.11g of NaH into a 300mL autoclave, vacuum the autoclave to 0.01MPa at room temperature, and then seal the autoclave , the temperature was set at 60° C., and the reaction was stirred at 200 rpm for 3 hours.

Cool the reaction kettle to a temperature below 25°C, and then vacuum again to 0.01MPa to stop. Add 48g ethylene oxide to the feed tank in an environment where _the temperature is lower than 5°C, then by means of high-pressure N ethylene oxide is charged into the autoclave, while controlling the amount of _N charged so that the pressure in the still is at 25°C 2MPa. The temperature of the autoclave was raised to 80° C., and the reaction was stirred at 200 rpm for 8 hours.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let stand overnight, filter to remove salt and evaporate the filtrate to obtain white to light yellow block copolyether The product (characterized by gel permeation chromatography-laser light scattering: Mn=3642, Mw=4163, Mw/Mn=1.14).

Example 2

Add 25mL of dry tetrahydrofuran, 25.2g of PTMEG-4000 (Mn=4021, Mw=5037, Mw/Mn=1.23) and 0.37g of NaH into a 300mL autoclave, and vacuumize the autoclave to 0.01MPa at room temperature, then seal the autoclave , the temperature was set at 65° C., and the reaction was stirred at 200 rpm for 2 hours.

Cool the reaction kettle to a temperature below 25°C, and then vacuum again to 0.01MPa to stop. Add 27.2g of ethylene oxide to the feeding tank in an environment with a temperature lower than 5°C, then fill the ethylene oxide into the autoclave with high-pressure N ₂ , and control the amount of N ₂ charged so that the pressure in the autoclave is at 25°C is 2MPa. The temperature of the autoclave was raised to 75° C., and the reaction was stirred at 200 rpm for 6 hours.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let stand overnight, filter to remove salt and evaporate the filtrate to obtain white to light yellow block copolyether The product (characterized by gel permeation chromatography-laser light scattering, Mn=7006, Mw=7763, Mw/Mn=1.11).

Example 3

Add 50mL dry THF and 40.97g PTMEG-2000 (purchased from Sigma-alderich company) and 1.72g KH in the 300mL autoclave, seal the autoclave immediately after vacuumizing the autoclave to 0.01MPa at room temperature, and set the temperature at 60 ° C, 200 rpm stirring reaction for 1 hour.

Cool the reactor to a temperature below 25°C, and then evacuate to 0.01MPa again. Add 48g ethylene oxide to the feed tank in an environment where _the temperature is lower than 5°C, then by means of high-pressure N ethylene oxide is charged into the autoclave, while controlling the amount of _N charged so that the pressure in the still is at 25°C 0.2MPa. The temperature of the autoclave was raised to 90° C., and the reaction was stirred at 200 rpm for 8 hours.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let it stand overnight, filter the desalination and evaporate the filtrate to dryness to obtain the block copolyether product (gel Characterized by permeation chromatography-laser light scattering, Mn=3752, Mw=4199, Mw/Mn=1.12).

Example 4

Add 20mL of dry THF and 11.65g of PTMEG-2000 (purchased from Sigma-alderich company) and NaH 0.35g in a 300mL autoclave, seal the autoclave immediately after vacuumizing the autoclave to 0.01MPa at room temperature, and then inject Feed helium, control the amount of helium feed so that the pressure in the kettle is 0.05Mpa, the temperature is set at 70°C, and the reaction is stirred at 200 rpm for 4 hours.

Cool the reaction kettle to a temperature below 25°C, vacuum again to 0.01Mpa and continue vacuuming for 1 hour, then slowly raise the temperature under vacuum conditions, and raise the temperature to 75°C within 45 to 60 minutes. At this time, the THF in the kettle has been eliminated. Add 9.9g of ethylene oxide to the feeding tank in an environment with a temperature lower than 5°C, then fill the ethylene oxide into the autoclave with high-pressure helium, and control the amount of helium charged so that the pressure in the autoclave is at 25°C is 3MPa. The temperature of the autoclave was raised to 80° C., and the reaction was stirred at 200 rpm for 1 hour.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let it stand overnight, filter the desalination and evaporate the filtrate to dryness to obtain the block copolyether product (gel Characterized by permeation chromatography-laser light scattering, Mn=3156, Mw=3600, Mw/Mn=1.14).

Example 5

Add 20mL dry toluene and 9.98g PTMEG-2000 (purchased from Sigma-alderich company) and 0.28g NaH in the 300mL autoclave, seal the autoclave immediately after vacuumizing the autoclave to 0.01MPa at room temperature, and set the temperature at 50°C, 200 rpm stirring reaction for 4 hours.

Cool the reactor to a temperature below 25°C, and then evacuate to 0.01MPa again. Add 11.9g of ethylene oxide to the feeding tank in an environment with a temperature lower than 5°C, then fill the ethylene oxide into the autoclave with high-pressure N ₂ , and control the amount of N ₂ charged so that the pressure in the autoclave is at 25°C is 2.5MPa. The temperature of the autoclave was raised to 110° C., and the reaction was stirred at 200 rpm for 12 hours.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let it stand overnight, filter the desalination and evaporate the filtrate to dryness to obtain the block copolyether product (gel Characterized by permeation chromatography-laser light scattering, Mn=3612, Mw=3821, Mw/Mn=1.06).

Example 6

Add 15mL dry THF and 9.65g PTMEG-650 (purchased from Sigma-alderich company) and 1.43g KH in a 300mL autoclave, and seal the autoclave immediately after vacuumizing the autoclave to 0.01MPa at room temperature, 200 rpm The reaction was stirred for 12 hours.

Cool the reactor to a temperature below 25°C, and then evacuate to 0.01MPa again. 70g of ethylene oxide is added to the feed tank in an environment where the temperature is lower than 5°C, then ethylene oxide is charged into the autoclave by means of high-pressure _N , while controlling the amount _of N charged so that the pressure in the still is at 25°C 6MPa. Turn off the heating and cooling system of the reactor, and stir and react at room temperature for 120 hours at 200 rpm.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let it stand overnight, filter the desalination and evaporate the filtrate to dryness to obtain the block copolyether product (gel Characterized by permeation chromatography-laser light scattering, Mn=5089, Mw=6521, Mw/Mn=1.28).

Example 7

Add 40mL dry toluene, 20.6g PTMEG-6000 (Mn=6027, Mw=6944, Mw/Mn=1.15) and 0.19g NaH into a 300mL autoclave, vacuum the autoclave to 0.01MPa at room temperature and seal it immediately Reactor, heated up to 150°C, stirred and reacted at 200 rpm for 3 hours.

Cool the reactor to a temperature below 25°C, and then evacuate to 0.01MPa again. Add 7.6g of ethylene oxide into the feeding tank in an environment with a temperature lower than 5°C, then fill the ethylene oxide into the autoclave with high-pressure N ₂ , and control the amount of N ₂ charged so that the pressure in the autoclave is at 25°C is 2MPa. The temperature was raised to 150° C., and the mixture was stirred and reacted at room temperature at 200 rpm for 6 hours.

Remove the pressure in the autoclave, take out the materials in the autoclave, dissolve and dilute with 50mL of absolute ethanol, add phosphoric acid to terminate the reaction, stir for 0.5h and let it stand overnight, filter the desalination and evaporate the filtrate to dryness to obtain the block copolyether product (gel Characterized by permeation chromatography-laser light scattering, Mn=7889, Mw=8621, Mw/Mn=1.09).

Claims (9)

1. a preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether, is characterized in that comprising the steps: In the first step, dry polytetrahydrofuran diol is dissolved in a solvent in a reaction kettle, and alkali metal hydride is added, and the molar ratio of polytetrahydrofuran diol and alkali metal hydride addition is 1:2～1:4, at room temperature To react at a reaction temperature of 150°C, the reaction time is more than 1 hour, and finally the terminal hydroxyl groups of polytetrahydrofuran diol react to form polytetrahydrofuran diol alkoxide, and polytetrahydrofuran diol alkoxide has the following structure: Wherein, M is potassium or sodium, n=9～100, O represents oxygen element; Described alkali metal hydride is sodium hydride or potassium hydride; Described solvent is THF or toluene; In the second step, polytetrahydrofuran glycolate is placed in an autoclave, and ethylene oxide is added, and the molar ratio of ethylene oxide and polytetrahydrofuran glycolate is 2:1 to 200:1 to initiate epoxy Carry out anionic ring-opening polymerization of ethane, use nitrogen or argon as the protective atmosphere, control the filling amount of nitrogen or argon so that the pressure in the kettle is 0.2-6MPa, the polymerization reaction temperature is from room temperature to 150°C, after polymerization for 1-120 hours , terminate the reaction, prepare the ABA type block copolyether of hydroxyl-terminated polyethylene glycol polytetraoxyfuran diol-polyethylene glycol, and its structure is as follows:

Where n, m, and m' are integers, n=9-100, m+m'=2-200, O represents oxygen, and H represents hydrogen. 2. The preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that: the polytetrahydrofuran diol molecular weight Mn is 650～6000g/mol, preferably molecular weight distribution Narrow distribution polytetrahydrofuran diol less than 1.30. 3. The preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that: after the first step of feeding, the reaction is carried out by vacuuming to 0.01-0.1 MPa, or After evacuating, fill the kettle with nitrogen or argon to form a protective atmosphere and then carry out the reaction. Control the amount of nitrogen or argon charged so that the pressure in the kettle is 0.01-6MPa. 4. the preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, is characterized in that: after described solvent and sodium, calcium hydride or sodium hydride reflux, distill and remove water, solvent The mass ratio of the added amount of polytetrahydrofuran diol to polytetrahydrofuran diol is preferably 1:1˜2:1. 5. the preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1 is characterized in that: the mol ratio of described polytetrahydrofuran diol and alkali metal hydride add-on is preferably 1 : 2.1～1: 2.4. 6. The preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that the reaction temperature in the first step is preferably 50-70°C. 7. The preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that: the reaction time in the first step is preferably 4 hours. 8. The preparation method of hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that: the anionic ring-opening polymerization of ethylene oxide is solution polymerization or bulk polymerization , During solution polymerization, the solvent used is tetrahydrofuran or toluene, and the molar ratio of solvent and polytetrahydrofuryl alkoxide is 1:10 to 10:1, preferably 1:1; bulk polymerization does not add any solvent. 9. The method for preparing the hydroxyl-terminated polyethylene glycol-polytetrahydrofuran triblock copolyether according to claim 1, characterized in that the polymerization reaction temperature is preferably 70-110°C.