CN1277852C - Process for preparing high molecular weight, narrow molecular weight distribution polystyrene and its copolymer - Google Patents

Abstract

The invention discloses a preparation method of polystyrene with high molecular weight and narrow molecular weight distribution and its copolymer. It is to mix the required amount of RAFT chain transfer reagent, co-stabilizer and a certain amount of styrene monomer to form a uniform solution (monomer flow 1), then add emulsifier aqueous solution, stir for 10 minutes, and ultrasonically pulverize for 15 minutes. A fine emulsion is produced. The mini-emulsion was transferred into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, and the water bath heating was maintained at the reaction temperature. After passing through _N2 to remove oxygen, add an initiator to initiate polymerization. After the polymerization is completed, slowly cool to room temperature, discharge, demulsify, wash, and dry. When the present invention prepares high-molecular-weight polymers, the molecular weight distribution is narrower, and the content of emulsifiers and co-stabilizers in the polymers is lower, which greatly improves the purity of the polymerization products and effectively reduces the complex synthetic process in the RAFT mini-emulsion polymerization process. The nuclear period accounts for the time fraction of the entire aggregation process.

Description

High molecular weight, narrow molecular weight distribution polystyrene and its copolymer preparation method

technical field

The invention relates to a preparation method of polystyrene with high molecular weight and narrow molecular weight distribution and its copolymer.

Background technique

Free radical polymerization has been widely used due to its wide range of applicable monomers and mild polymerization conditions. The free polymerization process has the following characteristics: slow initiation, fast growth, and fast termination. Therefore, conventional radical polymerization cannot synthesize polymers with fine features such as narrow molecular weight distribution (molecular weight distribution index less than 1.5), high-purity blocks, and the like. However, since the 1990s, breakthroughs have been made in the research of active free radical technology. Formed Nitroxide-Mediated Living Radical Polymerizations (NMP), Atom Transfer Radical Polymerization (ATRP) and Reversible addition-fragmentation chain transfer radical polymerization (Reversible addition-fragmentation chain transfer polymerization) , RAFT) and other three efficient living radical polymerization systems. Living radical polymerization can prepare narrow molecular weight distribution polymers, block copolymers, etc. RAFT living polymerization is applicable to a wide range of functional monomers and solvents (such as: -OH, -COOH, -CONR ₂ , -NR ₂ , -SO ₃ Na, etc.). RAFT living free radical polymerization was first proposed by Chiefari, J. et al. (Macromolecules 31, 5559 (1998)), which propagates the reversible addition-chain transfer-fragmentation between free radicals and RAFT (dithioester) chain transfer agents. And the control of the polymerization process is realized, so that the polymerization product with fine structure can be obtained. The synthesis of RAFT reagents therein has been disclosed in Chem.Commun.1044 (2001) and WO.98/01478.

From the point of view of industrial application, it is highly desirable to implement RAFT living polymerization in emulsion polymerization. There have been many research reports on RAFT emulsion polymerization and miniemulsion polymerization. The polymerization processes used in these reports are all batch polymerizations.

Contents of the invention

The purpose of this invention is to provide a kind of high molecular weight, the preparation method of narrow molecular weight distribution polystyrene and its copolymer.

The steps of the method are as follows:

1) Mix 0.1-10 parts of RAFT chain transfer agent and 1-20 parts of co-stabilizer with 50-200 parts of vinyl monomer to form monomer stream 1 oil solution; dissolve 1-20 parts of emulsifier in 300- 500 parts of water to form an aqueous solution; after mixing the monomer flow 1 oil solution with the aqueous solution, under mechanical stirring, after being subjected to a high shear field, it was pulverized to obtain a fine emulsion;

2) Move the miniemulsion into the reactor, feed nitrogen gas for 30-60 minutes, then add an aqueous solution of a water-soluble initiator to initiate polymerization, the temperature of the polymerization reaction is 40-90°C, and the polymerization reaction is carried out under anaerobic conditions;

3) When the conversion rate of the monomer stream 1 reaches 40% to 100%, based on the reaction system of step 2) per liter, the pre-deoxygenated monomer stream 2 is continuously added dropwise at a rate of 0.03 to 0.15 liters/hour, and the monomer stream 2 After the dropwise addition, continue the reaction for 30 to 90 minutes until the reaction is complete.

Compared with batch miniemulsion polymerization, the present invention has narrower molecular weight distribution when preparing high-molecular-weight polymers, lower content of emulsifiers and co-stabilizers in polymers, greatly improves the purity of polymerization products, and effectively reduces RAFT The complex nucleation period in the miniemulsion polymerization process accounts for the time fraction of the entire polymerization process, providing a one-step synthesis of block polymers with active characteristics using the miniemulsion polymerization process, thereby simplifying the production process of block polymers .

Detailed ways

The present invention mixes the required amount of RAFT chain transfer reagent, co-stabilizer and a certain amount of styrene monomer to form a homogeneous solution (monomer flow 1), then adds emulsifier aqueous solution, stirs for 10 minutes, and ultrasonically pulverizes for 15 minutes , to produce a fine emulsion. The mini-emulsion was transferred into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, and the water bath heating was maintained at the reaction temperature. After passing _N2 to remove oxygen, add an initiator to initiate polymerization, and continuously add the remaining monomer (monomer stream 2) at a predetermined conversion rate of monomer stream 1. After the dropwise addition was completed, the polymerization was continued until the monomer was completely converted, and the polymerization was stopped. After the polymerization is completed, slowly cool to room temperature, discharge, demulsify, wash, and dry to obtain the desired polymer.

The structural general formula of RAFT chain transfer agent of the present invention is as follows:

Wherein: the Z group is a benzylidene group, and R is from an optionally substituted alkyl or aryl group.

Costabilizers are: long-chain alkanes such as cetadecane, octadecane, eicosane, paraffin or long-chain fatty alcohols such as cetyl alcohol and octadecyl alcohol, and hydrophobic polymers. Monomer stream 1 is one or more vinyl comonomers based on styrene. Comonomers are: vinyl acetate, methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl acrylate, Any one or a mixture of hydroxypropyl acrylate, hydroxyethyl methacrylate, lauryl acrylate, α-methylstyrene, isobornyl acrylate, vinyl toluene, tert-butylstyrene . The emulsifier is: anionic emulsifier, cationic emulsifier, nonionic emulsifier or compound of ionic emulsifier and nonionic emulsifier. Monomer stream 2 is: styrene or styrene with vinyl acetate, methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate Any of esters, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, lauryl acrylate, α-methylstyrene, isobornyl acrylate, vinyltoluene, tert-butylstyrene One or a mixture of several.

The high-shear field is provided by an ultrasonic pulverizer, a high-pressure homogenizer, and a supergravity field generator.

Example 1

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 20.0 g of styrene and 0.3 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent), and mix evenly under magnetic stirring. Form an oil solution; dissolve 1.0 g of sodium dodecyl sulfate (SDS) in 75 g of water to form an aqueous solution; mix the oil solution with the aqueous solution, stir for 10 minutes, and ultrasonically pulverize with a Ningbo Kesheng KS-600 ultrasonic cell pulverizer For 15 minutes (70% output power), a miniemulsion was produced. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 75 °C. After 0.5 hour deoxygenation by passing through N ₂ , an aqueous solution of potassium persulfate (0.08 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. When the conversion rate of this stage reaches 45%, 42 grams of styrene deoxygenated for 30 minutes are dropped into the reactor at a rate of 6.0 ml/hour (0.06 liters/hour, based on the reaction system), and the monomer dropwise addition is completed, continue React for 60 minutes, slowly cool to room temperature and discharge.

Example 2

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 20.0 g of styrene and 0.3 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent), and mix evenly under magnetic stirring. Form an oil solution; dissolve 1.0 g of sodium dodecyl sulfate (SDS) in 75 g of water to form an aqueous solution; mix the oil solution with the aqueous solution, stir for 10 minutes, and ultrasonically pulverize with a Ningbo Kesheng KS-600 ultrasonic cell pulverizer For 15 minutes (70% output power), a miniemulsion was produced. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 75 °C. After 0.5 hour deoxygenation by passing through N ₂ , an aqueous solution of potassium persulfate (0.08 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. When the conversion rate of this stage reaches 62%, 42 grams of styrene deoxygenated for 30 minutes are dropped into the reactor at a rate of 7.0 ml/hour (0.07 liters/hour, based on the reaction system). React for 60 minutes, slowly cool to room temperature and discharge.

Example 3

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 20.0 g of styrene and 0.3 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent), and mix evenly under magnetic stirring. Form an oil solution; dissolve 1.0 g of sodium dodecyl sulfate (SDS) in 75 g of water to form an aqueous solution; mix the oil solution with the aqueous solution, stir for 10 minutes, and ultrasonically pulverize with a Ningbo Kesheng KS-600 ultrasonic cell pulverizer For 15 minutes (70% output power), a miniemulsion was produced. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 75 °C. After 0.5 hour deoxygenation by passing through N ₂ , an aqueous solution of potassium persulfate (0.08 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. When the conversion rate at this stage reaches 80%, 72.3 grams of styrene deoxygenated for 30 minutes are added dropwise into the reactor at a rate of 11.0 ml/hour (0.11 liters/hour, based on the reaction system). React for 60 minutes, slowly cool to room temperature and discharge.

Example 4

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 20.0 g of styrene and 0.3 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent), and mix evenly under magnetic stirring. Form an oil solution; dissolve 1.0 g of sodium dodecyl sulfate (SDS) in 75 g of water to form an aqueous solution; mix the oil solution with the aqueous solution, stir for 10 minutes, and ultrasonically pulverize with a Ningbo Kesheng KS-600 ultrasonic cell pulverizer 15 minutes (70% output power), ⊙ made a fine emulsion. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 50 °C. After 0.5 hour deoxygenation by passing through N ₂ , an aqueous solution of potassium persulfate (0.08 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. When the conversion rate of this stage reaches 80%, 38.0 grams of styrene deoxygenated for 30 minutes are added dropwise into the reactor at a rate of 4.0 ml/hour (0.04 liters/hour, based on the reaction system). React for 60 minutes, slowly cool to room temperature and discharge.

Example 5

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 7.0 g of styrene, 13.0 g of methyl methacrylate, and 0.3 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent) , mixed evenly under magnetic stirring to form an oil solution; 1.0 g of sodium dodecyl sulfate (SDS) was dissolved in 75 g of water to form an aqueous solution; the oil solution was mixed with the aqueous solution, and after stirring for 10 minutes, use Ningbo Kesheng KS -600 Ultrasonic Cell Pulverizer Ultrasonic pulverization for 15 minutes (70% output power) to obtain a fine emulsion. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 60 °C. After 0.5 hour deoxygenation by passing through N ₂ , an aqueous solution of potassium persulfate (0.08 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. When the conversion rate of this stage reaches 100%, 41.3 grams of styrene deoxygenated for 30 minutes are added dropwise into the reactor at a rate of 6.0 ml/hour (0.06 liters/hour, based on the reaction system). React for 60 minutes, slowly cool to room temperature and discharge.

Embodiment 6 (comparative example)

Add 1.0 g of hexadecane (co-stabilizer, HD) to a mixture of 20.0 g of styrene and 0.09 g of phenylacetic acid-1-phenylethanol dithioester (PEPDTA, RAFT reagent), and mix evenly under magnetic stirring. Form an oil solution; dissolve 1.0 g of sodium dodecyl sulfate (SDS) in 75 g of water to form an aqueous solution; mix the oil solution with the aqueous solution, stir for 10 minutes, and ultrasonically pulverize with a Ningbo Kesheng KS-600 ultrasonic cell pulverizer For 15 minutes (70% output power), a miniemulsion was produced. Move the miniemulsion into a reactor equipped with mechanical stirring, condenser, _N2 inlet device and feeding port, place the reactor in a water bath, and keep the temperature of the water bath at about 75 °C. After deoxygenation by passing _N2 for 0.5 hours, an aqueous solution of potassium persulfate (0.03 g of potassium persulfate dissolved in 5 g of water) was added to initiate polymerization. After the polymerization is completed, slowly cool to room temperature and discharge.

polymer properties Example Product number average molecular weight (*10 ⁴ g/mol) Product Molecular Weight Distribution Coefficient SDS/HD residual % in the product 1 4.2 1.33 1.7/1.7 2 6.0 1.28 1.8/1.8 3 8.0 1.33 1.5/1.5 4 4.9 1.28 1.5/1.5 5 5.0 1.31 1.8/1.8 6 5.10 2.05 5/5

Wherein: molecular weight and molecular weight distribution are measured by gel chromatography polystyrene as a standard sample.

Claims (6)

1. a kind of high molecular weight, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, the steps of method are as follows: 1) Mix 0.1-10 parts of RAFT chain transfer agent and 1-20 parts of co-stabilizer with 50-200 parts of styrene monomer to form monomer flow 1 oil solution; dissolve 1-20 parts of emulsifier in 300- 500 parts of water to form an aqueous solution; after mixing the monomer flow 1 oil solution with the aqueous solution, under mechanical stirring, and after being subjected to a high shear field, pulverize to obtain a fine emulsion; 2) Move the miniemulsion into the reactor, feed nitrogen gas for 30-60 minutes, then add an aqueous solution of a water-soluble initiator to initiate polymerization, the temperature of the polymerization reaction is 40-90°C, and the polymerization reaction is carried out under anaerobic conditions; 3) When the conversion rate of the monomer stream 1 reaches 40% to 100%, based on the reaction system of step 2) per liter, the pre-deoxygenated monomer stream 2 is continuously added dropwise at a rate of 0.03 to 0.15 liters/hour, and the monomer stream 2 After the dropwise addition, continue the reaction for 30 to 90 minutes until the reaction is complete. 2. a kind of high molecular weight according to claim 1, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, the general structural formula of said RAFT chain transfer agent is as follows:

Wherein: the Z group is a benzylidene group, and R is from an optionally substituted alkyl or aryl group. 3. a kind of high molecular weight according to claim 1, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, said co-stabilizer is: hexadecane, octadecane, eicosane alkanes, paraffins, cetyl or stearyl alcohols. 4. a kind of high molecular weight according to claim 1, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, said emulsifier is: anionic emulsifier, cationic emulsifier, nonionic emulsifier Emulsifier or compound of ionic emulsifier and nonionic emulsifier. 5. a kind of high molecular weight according to claim 1, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, said monomer flow 2 is: styrene or styrene and vinyl acetate , methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methacrylic acid Any one of hydroxyethyl ester, lauryl acrylate, α-methyl styrene, isobornyl acrylate, vinyl toluene, tert-butyl styrene or a mixture of several. 6. a kind of high molecular weight according to claim 1, the preparation method of narrow molecular weight distribution polystyrene and copolymer thereof is characterized in that, said high shear field is ultrasonic pulverizer, high-pressure homogenizer or supersonic The gravity field generating device is provided.