CN102250273B - A kind of preparation method of styrene-maleic anhydride random copolymer - Google Patents

Abstract

The invention discloses a preparation method of a styrene-maleic anhydride random copolymer, belonging to the field of macromolecule polymerization. The method comprises the following steps: adding a monomer maleic anhydride and an initiator into a solvent for dissolution under the protection of nitrogen protection, and then adding a monomer styrene in a system for dissolution; then heating the reaction system with an oil bath so that the reaction is carried out for 1.5-24 hours at the temperature of 90-130 DEG C so as to obtain a metastable state dispersion system of a copolymer; and after the reaction is finished, centrifuging and filtering, and finally drying so as to obtain the styrene-maleic anhydride random copolymer. In the preparation method, the solvent is organic acid alkyl ester, the molar ratio of styrene to maleic anhydride is (9.7:0.3)-(5:5), the mass concentration sum of the monomers namely styrene and maleic anhydride is 15%-55%, and the mass of the initiator is 0.5-5%of total monomer mass; and stirring and a dispersing agent are not needed, the reaction system is extremely simple, and the process is simple and is easy to control.

Description

A kind of preparation method of styrene-maleic anhydride random copolymer

technical field

The invention belongs to the field of macromolecular polymerization, and in particular relates to a method for preparing styrene-maleic anhydride random copolymers by precipitation polymerization.

Background technique

Styrene-maleic anhydride copolymer (SMA) is a polymer with excellent heat resistance, rigidity and dimensional stability, widely used in latex coatings, water treatment agents, modifiers for adhesives, pesticides Emulsifiers, textile auxiliaries, printing inks, composite materials and curing agents for epoxy resins, etc.

Styrene-maleic anhydride copolymers can be divided into two types according to the composition and sequence structure of the copolymers: one is an alternating copolymer (A-SMA) with a molar ratio of styrene and maleic anhydride close to 1:1, The other is a random copolymer (R-SMA) with low maleic anhydride content. Alternating copolymer (A-SMA) was first produced by Sinclair Petrochemicals and named it SMA resin. SMA alternating copolymers for industrial applications can also be divided into two categories, one is low molecular weight alternating copolymers, such as SMA resins with a molecular weight of 1600-2000 produced by Arco Chemical Company and MonsantoScriptest Company, and sulfonated SMA (S- SMA1000 and S-SMA3000). The other is high molecular weight SMA resin.

In 1974, Arco Chemical Company of the United States first developed a random SMA copolymer named Dylark as an engineering plastic. At present, a series of products have been formed, and the content of MA is 5-20%. In addition, on the basis of SMA, a third monomer is introduced to obtain engineering materials with better performance. In 1976, Dow Chemical Company of the United States synthesized a SMA-based terpolymer (styrene-maleic anhydride-butadiene), with a trade name of XP5272. In 1981, the American Monsanto Company announced a series of products named Cadon. It is a plastic alloy of random SMA and ABS (Herman F.Mark, Encyclopedia of PolymerScience and Technology [M], Wiley-Interscience, Third Edition, 2004, Vol 9, pp.225-294).

Due to the characteristics of molecular structure, styrene monomer as an electron donor is easy to form a charge transfer complex with maleic anhydride as an electron acceptor. Therefore, there is a strong tendency to alternate during the copolymerization process, and the copolymerization tendency of the two is much greater than their homopolymerization tendency. Alternating copolymers of maleic anhydride and styrene can be easily obtained by traditional bulk, solution, emulsion and suspension polymerization methods. In the early 1970s, Zhang Juxian and others synthesized SMA alternating copolymers by segmented heating method in "Research on KS-1 Syntans"("Leather Science and Technology", 1983, 1:1-7, 15). US Pat. No. 3404135 and the patent publication number CN1069035 all disclose the methods for synthesizing styrene-maleic acid alternating copolymers respectively. Tang Bingtao, Zhao Jie et al., in "Synthesis of Styrene-Maleic Anhydride Alternating Copolymer by Solution Polymerization"("Fine Chemical Industry", 2010, 27(3), pp.217-221), by using methyl ethyl ketone as solvent, Styrene-maleic anhydride alternating copolymers were synthesized by solution polymerization. Li Chunsheng, Zhang Shuxiang, etc. in the "polymerization of maleic anhydride and styrene in supercritical CO ₂ "("Polymer Materials Science and Engineering", 2006, 22 (5), pp.95-97), introduced the When the reaction pressure is greater than 16 MPa, the styrene-maleic anhydride alternating copolymer with higher conversion rate and higher molecular weight can be obtained, and the product is a fine powder solid.

However, styrene-maleic anhydride alternating copolymers cannot be used as thermoplastic materials due to their easy water absorption and difficulty in molding. Styrene-maleic anhydride random copolymer is a new type of material developed in the late 1970s. High molecular weight styrene-maleic acid random copolymer has good heat resistance, low melt viscosity, and easy processing Excellent performance, can be blended and modified with various polymer materials, and has good chemical stability, foaming performance, transparency and high hardness. In addition, its adhesion, electroplating and coloring properties are also good. During the free radical copolymerization of styrene-maleic anhydride, the tendency of alternating structure is relatively strong, which increases the difficulty of obtaining random copolymers of styrene-maleic anhydride. To obtain random copolymerized SMA, it is necessary to destroy the charge transfer complex of styrene and maleic anhydride. There are usually two methods, one is to increase the temperature of the polymerization reaction, and the other is to use a polar solvent.

At present, the preparation methods of random copolymers of styrene and maleic anhydride mainly include bulk polymerization, solution polymerization, bulk-suspension polymerization, precipitation polymerization and solution phase inversion emulsion polymerization.

Jiang Zhongmin, Li Huaming, etc., in the article "Synthesis of Styrene-Maleic Anhydride Random Copolymer" ("Elastomer", 1998, 8(1), pp.6-8), took dicumyl peroxide as the trigger agent, a styrene-maleic anhydride random copolymer was synthesized by bulk polymerization. Because there is no dispersion medium in bulk polymerization, the viscosity of the polymerization system changes rapidly, so it is difficult to achieve a high monomer conversion rate. It is difficult for the system to release heat, and the reaction is not very stable. During the polymerization reaction, implosion is often caused by slight fluctuations in polymerization conditions. Publication number is that CN1103408A patent discloses a kind of process method of synthetic styrene-maleic anhydride random copolymer with bulk method, and publication number is the patent of CN1247876A on the basis of Chinese patent CN1103408A, has carried out to its disclosed technology again Partially improved. Chinese patent CN1295085A discloses a process for synthesizing styrene-maleic anhydride random copolymers with relatively high maleic anhydride content by bulk method.

U.S. Pat. No. 4772671 uses butanone as a solvent to prepare a copolymer with a maleic anhydride content ranging from 5% to 54% by solution method. Although this process can prepare SMA resins with high maleic anhydride content, the solvent methyl ethyl ketone introduced by this method not only reduces the rate and efficiency of the styrene-maleic anhydride reaction, but also participates in the chain transfer reaction, resulting in a decrease in the molecular weight of SMA and resin machinery. Performance degradation. Li Huaming, Zhou Disheng, etc., in the article "Synthesis of Styrene-Maleic Anhydride Random Copolymer by Solution Polymerization" ("Synthetic Rubber and Plastics", 1998, 15(3), pp.64-65), through acetone solvent A random styrene-maleic anhydride copolymer has been prepared by adding the polar solvent dimethyl sulfoxide and increasing the reaction temperature, but the solution polymerization preparation process is complicated, the solvent recovery is difficult, and it causes environmental pollution and high production costs. .

Zhou Wen and Pan Enli, in the article "Synthesis and Characterization of SMA Resin by Bulk-Suspension Method" ("Modern Plastics Processing Application", 1999, No. 4, pp.5-9), through the method of continuous dropwise addition of monomers, The random styrene-maleic anhydride copolymer is prepared by carrying out bulk polymerization first, and then carrying out suspension polymerization when the conversion rate reaches half. In the bulk-suspension method, maleic anhydride is easily hydrolyzed into maleic acid in water medium, which affects the copolymerization rate, composition and distribution. At the same time, the acid must be re-dehydrated into acid anhydride during post-treatment, and the process is complicated.

Zhang Guoyun used benzoyl peroxide (BPO) as the initiator in the article "Preparation and Application of SMA Surface Sizing Agent" ("Paper Chemicals", 2005, 17(3), pp.30-32), Random copolymer of styrene and maleic anhydride was synthesized by precipitation polymerization using toluene as solvent. The precipitation polymerization process is characterized by low viscosity and high heat transfer efficiency during the reaction process. Moreover, after the polymerization reaction is completed, the separation and post-treatment process of the product is simple. However, toluene is highly toxic, and toluene is used as a reaction medium, which pollutes the environment.

Shen Yiding and Li Xiaorui, in the article "Preparation and Properties of Styrene Maleic Anhydride Random Copolymer" ("Polymer Materials Science and Engineering", 2000, 13(3), pp.32-35), through solution transfer emulsion polymerization According to the method, a styrene-maleic anhydride copolymer with a random structure is prepared at a temperature of 90-130° C. and using a polar solvent.

Although there are a variety of techniques for preparing styrene-maleic anhydride random copolymers mentioned above, the bulk polymerization process is still the main method used in industrial production. Therefore, the development of a new and easy-to-control green polymerization production process has practical application value.

Contents of the invention

The object of the present invention is to provide a low-cost preparation method of a simple, environment-friendly styrene-maleic anhydride random copolymer.

A kind of preparation method of styrene-maleic anhydride random copolymer provided by the present invention is characterized in that, monomer maleic anhydride, styrene and initiator are added in the solvent and fully dissolved, then reaction mixture is heated to React at 90-130°C for 1.5-24 hours to obtain a metastable dispersion system of the copolymer. After the reaction is completed, it is centrifuged, filtered, and finally dried to obtain a styrene-maleic anhydride random copolymer.

Wherein, the described initiator is an organic peroxide; the described solvent is an organic acid alkyl ester; the amount relationship between styrene (St) and maleic anhydride (Man), the molar ratio is 9.7:0.3～5: 5. The sum of the mass concentrations of the monomers styrene and maleic anhydride in the reaction system is 15% to 55%; the mass of the initiator in the reaction system is 0.5 to 5% of the total mass of the monomers.

The mass concentration of the monomer in the reaction system is preferably 20-35%.

Wherein, the initiator is a conventional thermal decomposition initiator, and organic peroxides well known to those skilled in the art include dibenzoyl peroxide, dicumyl peroxide, ditert-butyl peroxide , lauryl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxydicarbonate or dicyclohexyl peroxydicarbonate, etc. The polymerization reaction temperature is related to the decomposition rate of the initiator used. Generally, the temperature with a half-life of 0.5-10 hours is selected as the polymerization temperature. The time of the polymerization reaction is 1-10 times of the half-life of the initiator at this temperature. The preferred temperature is 0.5-5 hours for the half-life, and the polymerization time is 2-5 times the half-life.

For the copolymerization reaction of styrene and maleic anhydride, the selection of temperature should also fully consider that maleic anhydride and styrene can generate charge transfer complexes, and the existence of charge transfer complexes is easy to generate styrene and maleic anhydride. alternating copolymers. The formation of charge transfer complexes is related to the reaction temperature, and lower temperature is beneficial to the formation of charge transfer complexes. Generally, to obtain random copolymers, the reaction temperature should be higher than 80°C. However, for free radical polymerization, the increase in temperature will reduce the molecular weight of the product. Therefore, the choice of temperature must consider the source of the initiator, the structure of the copolymer and the molecular weight requirements of the target product. For the preparation of the random copolymer of styrene and maleic anhydride proposed in the present invention, the suitable polymerization reaction temperature is 90-130°C, more preferably 100-130°C.

式中，R₁为H、C原子数为1～8的烷基，R₂为C原子数为1～5的烷基，考虑到介质需要具有适度的极性、溶解度参数和沸点，R₁优选C原子数为2～5的烷基。此类介质在工业操作及环保方面的优点是其毒性较低，并大都无刺激性气味。具体包括乙酸乙酯、乙酸丁酯、乙酸异丁酯、乙酸仲丁酯、乙酸戊酯、乙酸异戊酯、丙酸甲酯、丙酸乙酯、丙酸丁酯、丁酸甲酯、丁酸乙酯、丁酸丁酯、丁酸异戊酯、异戊酸乙酯、异戊酸异戊酯等。其中，优选的有机酸烷基酯为丁酸乙酯、乙酸异戊酯、丙酸乙酯。The selection of reaction medium is particularly critical for realizing precipitation polymerization in the present invention, and its basic principle is: (1) medium has good dissolving action for two kinds of monomers and initiator of maleic anhydride and styrene, to ensure that the reaction of the system is Homogeneous system; (2) the medium is insoluble for the generated random copolymer of styrene and maleic anhydride, and when the macromolecular chain of the copolymer reaches a certain critical length, it precipitates out from the medium; (3) the solvent Sources, cost and safety. Aromatic hydrocarbons (such as benzene, toluene and xylene, etc.) and alkyl esters of organic acids and mixed solvents can meet the requirements (1) and (2). However, aromatic solvents are harmful to the environment, and the recovery process of mixed solvents is complicated. Therefore, in the present invention, the medium of the polymerization system is an organic acid alkyl ester. Wherein, the structural general formula of described organic acid alkyl ester is:

In the formula, _R1 is H and an alkyl group with 1 to 8 C atoms, and _R2 is an alkyl group with 1 to 5 C atoms. Considering that the medium needs to have moderate polarity, solubility parameter and boiling point, _R1 An alkyl group having 2 to 5 C atoms is preferred. The advantages of such media in terms of industrial operation and environmental protection are their low toxicity and most of them have no irritating odor. Specifically include ethyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, butyl Ethyl butyrate, butyl butyrate, isopentyl butyrate, ethyl isovalerate, isopentyl isovalerate, etc. Among them, preferred organic acid alkyl esters are ethyl butyrate, isopentyl acetate, and ethyl propionate.

The maleic anhydride content of the styrene-maleic anhydride random copolymer frequently used in industry is between 5% and 20%. The present invention can obtain the maleic anhydride content at 5% by adjusting the feed ratio of styrene and maleic anhydride. ~40% random copolymer. Obviously, the obtained styrene-maleic anhydride copolymer in the present invention has a random structure and can be used to generate the desired styrene-maleic anhydride random copolymer for industrial applications.

The present invention has the following beneficial effects:

1) The present invention does not need to stir and add dispersant, the reaction system is very simple, the process is simple and easy to control.

2) The reaction medium used in the present invention is a low-toxic chemical, and the post-polymerization treatment is simple, reducing environmental pollution.

3) The styrene and maleic acid copolymer prepared by the inventive method can be known to have random structure by nuclear magnetic analysis.

Description of drawings

Fig. 1, carbon nuclear magnetic resonance ( ¹³ C-NMR) spectrum of the copolymer prepared in Example 2.

Detailed ways

In order to better illustrate the implementation method of the present invention, some examples are listed below. Obviously, the present invention is not limited to these Examples.

The relative molecular weights and distributions of the copolymers in the following examples were determined by using a gel permeation chromatograph and using the universal calibration method for polystyrene.

Example 1

St and MAn molar ratio 8: 2, wherein MAn 0.23g, St 1.0g; Initiator is dicumyl peroxide (DCP) 0.006g; Medium is ethyl butyrate, 7.5mL (monomer mass concentration 15% ). Heat in an oil bath, react at a temperature of 130°C under the protection of nitrogen, and take samples after the reaction for 10min, 20min, 30min, 60min, 120min, and 150min respectively to obtain the dispersion system of random copolymer of styrene and maleic anhydride , the dispersion system was centrifuged and dried to obtain a white powder of styrene-maleic acid drunk random copolymer. The polymerization yields under different reaction times were 14%, 31%, 38%, 50%, 56%, and 62%, respectively, and the MAn content in the copolymer was measured to be 35%, 32%, and 30% by acid-base titration. , 27%, 25%, 24%. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Example 2

St and MAn molar ratio 8: 2, wherein MAn 1.37g, St 5.80g; initiator is dicumyl peroxide (DCP) 0.357g; medium is ethyl butyrate, 30mL (monomer mass concentration 20%) . Heated in an oil bath and reacted at 120°C for 24 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride. The dispersion system was centrifuged and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield was 82%, and the content of MAn in the copolymer measured by acid-base titration was 21%. The number average molecular weight of the copolymer was 14000 g/mol, and the molecular weight distribution coefficient was 1.7. The carbon nuclear magnetic resonance ( ¹³ C-NMR) spectrogram of the prepared copolymer is shown in Fig. 1, which shows that the copolymer of styrene and maleic anhydride prepared by the present invention is a random copolymer.

Example 3

St and MAn molar ratio 9.7: 0.3, wherein MAn 0.21g, St 7.03g; Initiator is dicumyl peroxide (DCP) 0.179g; Medium is ethyl butyrate, 30mL (monomer mass concentration 20% ). Heated in an oil bath and reacted at 110°C for 24 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride. The dispersion system was separated by filtration and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield is 50%, and the content of MAn in the copolymer measured by acid-base titration is 5%. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Example 4

St and MAn molar ratio 9.5:0.5, wherein MAn 0.34g, St 6.89g; initiator is dibenzoyl peroxide (BPO) 0.357g; medium is ethyl propionate, 25mL (monomer mass concentration 25%) . Heated in an oil bath and reacted at 100°C for 2 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride. The dispersion system was separated by filtration and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield was 52%, and the content of MAn in the copolymer measured by acid-base titration was 11%. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Example 5

St and MAn molar ratio 9: 1, wherein MAn 0.11g, St 1.09g; Initiator is dicumyl peroxide (DCP) 0.024g; Medium is ethyl propionate, 3.1mL (monomer mass concentration 30% ). Heated in an oil bath and reacted at 120°C for 24 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride. The dispersion system was separated by filtration and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield was 56%, and the MAn content in the copolymer was 18% as measured by acid-base titration. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Example 6

The molar ratio of St and MAn is 5:5, wherein MAn is 0.57g, St is 0.61g; the initiator is dibenzoyl peroxide (BPO) 0.024g; the medium is butyl acetate, 5mL (monomer mass concentration 20%). Heated in an oil bath and reacted at 100°C for 1.5 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride, which was centrifuged and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield was 88%, and the content of MAn in the copolymer was 40% as measured by acid-base titration. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Example 7

St and MAn molar ratio 8: 2, wherein MAn 1.37g, St 5.80g; Initiator is dibenzoyl peroxide (BPO) 0.143g; Medium is isoamyl acetate, 6.7mL (monomer mass concentration 55% ). Heated in an oil bath and reacted at 90°C for 5 hours under the protection of nitrogen to obtain a dispersion system of random copolymer of styrene and maleic anhydride, which was separated by filtration and dried to obtain styrene-maleic anhydride White powder of random copolymer. The polymerization yield is 70%, and the MAn content in the copolymer is 20% as measured by acid-base titration. The prepared copolymer of styrene and maleic anhydride is a random copolymer.

Claims (5)

1. the preparation method of an atactic styrene-maleic anhydride copolymer is characterized in that, may further comprise the steps: monomer maleic anhydride, vinylbenzene and initiator are joined fully dissolving in the solvent; Then above-mentioned reaction mixture is heated to 100 ~ 130 ℃ of reaction 1.5 ~ 24h; Obtain the metastable state dispersion system of multipolymer, after reaction is accomplished, through spinning and filtration; Final drying obtains atactic styrene-maleic anhydride copolymer;

Wherein, described initiator is an organo-peroxide; Described solvent is the organic acid alkyl ester; Vinylbenzene and maleic anhydride use magnitude relation, be 9.7:0.3 ~ 5:5 in molar ratio, the mass concentration sum of monomer styrene and maleic anhydride is 15% ~ 55% in the reaction system; The quality of initiator is 0.5 ~ 5% of a monomer total mass in the reaction system.

2. according to the method for claim 1, it is characterized in that the mass concentration of monomer in reaction system is 20 ~ 35%.

3. according to the method for claim 1, it is characterized in that the general structure of organic acid alkyl ester does

In the formula, R ₁For H, C atomicity are 1 ~ 8 alkyl, R ₂It for the C atomicity 1 ~ 5 alkyl.

4. according to the method for claim 3, it is characterized in that R ₁Preferred C atomicity is 2 ~ 5 alkyl.

5. according to the method for claim 1, it is characterized in that the organic acid alkyl ester is ethyl n-butyrate, Isoamyl Acetate FCC, ethyl propionate.

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