A low molecular weight styrene-maleic anhydride copolymer and its preparation method

Abstract

This invention discloses a low molecular weight styrene-maleic anhydride copolymer. The raw materials for preparation include at least styrene and maleic anhydride, wherein the molar ratio of styrene to maleic anhydride is 1:(1-9). This invention uses 2,3-dimethyl-2,3-diphenylbutane as a capping accelerator, which works in conjunction with a di-tert-butyl peroxide initiator to prepare a styrene-maleic anhydride copolymer with low molecular weight, low yellowness, and stable acid value. The process of this invention is simple, can be continuously produced, has high production efficiency, and does not use molecular weight regulators. The product has low odor, low residue, and is transparent.

Description

Technical Field

[0001] This invention relates to a low molecular weight styrene-maleic anhydride copolymer and its preparation method, specifically to C08F, and more particularly to the field of styrene and its polymer synthesis. Background Technology

[0002] Modifying styrene polymers with maleic anhydride can improve their properties, making them widely applicable in coating dispersions, leather tanning agents, and other fields. Styrene-maleic anhydride copolymers exist in high and low molecular weight forms. High molecular weight styrene-maleic anhydride copolymers are mostly used in engineering plastics, while low molecular weight styrene-maleic anhydride copolymers contain highly reactive anhydride groups and have a wide range of applications. Currently, there are many methods for preparing low molecular weight styrene-maleic anhydride copolymers, such as solution polymerization, bulk polymerization, and precipitation polymerization. Styrene-maleic anhydride copolymers prepared by traditional methods have a wide molecular weight distribution, limiting their applications. Furthermore, traditional processes reduce molecular weight by adding chain transfer agents; the addition of 3-mercaptopropionic acid as a chain transfer agent results in products with strong odors, long reaction times, and low efficiency.

[0003] Chinese invention patent CN202010151001.1 discloses a low molecular weight, narrow-distribution styrene-maleic anhydride copolymer and its preparation method. This method uses a tubular reactor with temperature-controlled reaction, enabling continuous production. The prepared low molecular weight styrene-maleic anhydride copolymer has high conversion rate and a narrow molecular weight distribution. However, at the beginning of the feed, most of the maleic anhydride has already reacted, leaving a large amount of residual styrene that later self-polymerizes into polystyrene. This results in inconsistent anhydride content between the initial and later stages, showing a gradually decreasing trend. The prepared copolymer exhibits large fluctuations in anhydride content and acid value, is opaque, has a high styrene self-polymer content, contains many insoluble substances, and has poor dispersion. Chinese invention patent CN99119956.1 discloses a method for preparing a styrene-maleic anhydride random copolymer. By introducing the styrene-maleic anhydride random copolymer into the polymerization reaction of styrene and maleic anhydride, low-temperature polymerization is achieved, reducing subsequent processing steps and resulting in a pure product. However, the formed styrene-maleic anhydride copolymer has a high molecular weight. Summary of the Invention

[0004] In order to prepare a low molecular weight styrene-maleic anhydride copolymer with low odor, low residue, and high purity, the first aspect of the present invention provides a low molecular weight styrene-maleic anhydride copolymer, wherein the raw materials for preparation include at least styrene and maleic anhydride, and the molar ratio of styrene to maleic anhydride is 1:(1-9).

[0005] In a preferred embodiment, the raw materials for preparation further include an initiator, a capping accelerator, and a solvent. The amount of initiator added is 0.1-1% of the total mass of styrene and maleic anhydride, the amount of capping accelerator added is 0.5-2% of the total mass of styrene and maleic anhydride, and the amount of solvent added is 5-15% of the total mass of styrene and maleic anhydride.

[0006] In a preferred embodiment, the low molecular weight styrene-maleic anhydride copolymer has a weight-average molecular weight of 4000-9500 Da.

[0007] In a preferred embodiment, the end-capping accelerator is a phenylalkane, which is selected from one or a combination of several of 2,3-dimethyl-2,3-diphenylbutane, diphenylmethane, 3,4-dimethyl-3,4-diphenylhexane, 1,3-diphenylbutane, 1,4-diphenylbutane, diphenylethane, and diphenylpropane.

[0008] In a preferred embodiment, the end-capping accelerator is 2,3-dimethyl-2,3-diphenylbutane.

[0009] In a preferred embodiment, the initiator is a free radical initiator, selected from one or a combination of several peroxide initiators, azo initiators, and redox initiators.

[0010] In a preferred embodiment, the peroxide initiator is selected from one or a combination of several of hydroperoxides, dialkyl peroxides, and ester peroxides.

[0011] In a preferred embodiment, the peroxide initiator is a high-temperature initiator, with an activation energy of 138-183 KJ / mol at an environment >100°C.

[0012] In a preferred embodiment, the high-temperature initiator is selected from one or a combination of several of cumene hydroperoxide, tert-butyl hydroperoxide, and di-tert-butyl peroxide.

[0013] During the experiment, the applicant discovered that using 2,3-dimethyl-2,3-diphenylbutane as a capping accelerator, in conjunction with di-tert-butyl peroxide initiator, resulted in a styrene-maleic anhydride copolymer with low molecular weight, low yellowness, and stable acid value. The applicant speculates that the possible reasons are as follows: by controlling the weight ratio of styrene to maleic anhydride, the raw materials are fed into a continuous reactor for polymerization. Under the combined action of 2,3-dimethyl-2,3-diphenylbutane and di-tert-butyl peroxide initiator, the di-tert-butyl peroxide initiator can rapidly decompose into free radicals at high temperatures, initiating the polymerization reaction. 2,3-dimethyl-2,3-diphenylbutane not only generates free radicals to initiate polymerization but also regulates molecular weight. Simultaneously, the reactor is continuously stirred, and the action of 2,3-dimethyl-2,3-diphenylbutane promotes rapid capping of the polymerization reaction, preventing explosive polymerization and improving the thermal stability of the product, resulting in a styrene-maleic anhydride copolymer with a low molecular weight.

[0014] Furthermore, the reaction in this application occurs in a fully mixed reactor, ensuring a consistent reaction temperature throughout. This avoids the problem of uneven polymerization of styrene and maleic anhydride caused by the high polymerization efficiency of maleic anhydride in the early stages and the concentrated polymerization of styrene in the later stages, which is common in tubular reactors. The styrene-maleic anhydride copolymer prepared by the method of this application exhibits alternating polymerization of styrene and maleic anhydride, resulting in a uniform polymerization reaction, minimal fluctuations in the anhydride content and acid value of the copolymer, and high product transparency.

[0015] In a preferred embodiment, the solvent is selected from one or a combination of toluene, ethylbenzene, xylene, and cumene.

[0016] In a preferred embodiment, the maleic anhydride is in a liquid state and maintained at a temperature of 60-65°C.

[0017] A second aspect of the present invention provides a method for preparing a low molecular weight styrene-maleic anhydride copolymer, comprising the following steps:

[0018] (1) A solvent is introduced into the reactor and the temperature is increased;

[0019] (2) The initiator, end-capping accelerator and remaining solvent are mixed to obtain a mixture. Styrene, maleic anhydride and the mixture are added to the solvent in step 1 in proportion by metering pump.

[0020] (3) After the polymerization reaction, the material is discharged;

[0021] (4) The material is fed into a devolatilizer for devolatilization to obtain a low molecular weight styrene-maleic anhydride copolymer. The material removed is then processed and recycled.

[0022] In a preferred embodiment, the reactor is a continuously stirred fully mixed reactor.

[0023] In a preferred embodiment, the polymerization reaction is carried out at a temperature of 150-300°C and for a reaction time of 1-60 min.

[0024] In a preferred embodiment, the polymerization reaction is carried out at a temperature of 180-260°C for a reaction time of 5-20 minutes.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The low molecular weight styrene-maleic anhydride copolymer of the present invention is prepared by using a high temperature initiator with an activation energy of 138-183 KJ / mol at an environment of >100℃, which can make the polymerization reaction occur rapidly, thus obtaining a low molecular weight styrene-maleic anhydride copolymer and improving the thermal stability of the product.

[0027] (2) The low molecular weight styrene-maleic anhydride copolymer of the present invention uses 2,3-dimethyl-2,3-diphenylbutane as a capping promoter and works together with di-tert-butyl peroxide initiator to prepare a styrene-maleic anhydride copolymer with low molecular weight, low yellowness and stable acid value.

[0028] (3) The low molecular weight styrene-maleic anhydride copolymer of the present invention has a simple process, can be produced continuously, has high production efficiency, does not use molecular weight regulators, and has low odor, little residue, and is pure. Detailed Implementation

[0029] Example 1

[0030] A low molecular weight styrene-maleic anhydride copolymer, wherein the raw materials for preparation include: 23.5 kg of styrene, 22.0 kg of maleic anhydride, 3 kg of solvent, 0.45 kg of initiator, and 0.50 kg of end-capping accelerator.

[0031] The molar ratio of styrene to maleic anhydride is 1:1.

[0032] The solvent is toluene; the initiator is di-tert-butyl peroxide, with an activation energy of 138-183 KJ / mol at temperatures above 100°C.

[0033] The end-capping accelerator is 2,3-dimethyl-2,3-diphenylbutane.

[0034] The maleic anhydride is in a liquid state and is maintained at a temperature of 60°C.

[0035] A method for preparing a low molecular weight styrene-maleic anhydride copolymer includes the following steps:

[0036] (1) Pass 2 kg of solvent into the reactor and raise the temperature;

[0037] (2) The initiator, end-capping accelerator and 1 kg of solvent are mixed to obtain a mixture. Styrene, 60℃ liquid maleic anhydride and the mixture are added to the solvent in proportion by metering pumps. The total feed rate of the three materials is 240 kg / h.

[0038] (3) After a period of time, the material in the reactor reaches 20 kg and is discharged at a rate of 240 kg / h.

[0039] (4) The material is fed into a devolatilizer for devolatilization to obtain a low molecular weight styrene-maleic anhydride copolymer. The material removed is then processed and recycled.

[0040] The reactor is a continuously stirred fully mixed reactor.

[0041] The polymerization reaction was carried out at a temperature of 225°C for 5 minutes.

[0042] Example 2

[0043] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are described. The specific steps are the same as in Example 1, except that the reaction time is 12 min.

[0044] Example 3

[0045] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are described. The specific steps are the same as in Example 1, except that the reaction time is 18 min.

[0046] Example 4

[0047] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are disclosed. The specific steps are the same as in Example 2, except that the molar ratio of maleic anhydride to styrene is 2:1.

[0048] Example 5

[0049] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are disclosed. The specific steps are the same as in Example 2, except that the molar ratio of maleic anhydride to styrene is 3:1.

[0050] Example 6

[0051] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are disclosed. The specific steps are the same as in Example 2, except that the molar ratio of maleic anhydride to styrene is 9:1.

[0052] Comparative Example 1

[0053] Toluene, styrene, and 22 kg of maleic anhydride were added to a three-necked flask equipped with an electric stirrer and a condenser. The mixture was stirred until dissolved and heated to 50 °C. After stirring for 15 min, azobisisobutyronitrile was added dropwise from a dropping funnel while the temperature was slowly increased to 86 °C. The mixture was reacted at a constant temperature for 3 h. The flask was then removed, cooled to 25 °C, filtered under reduced pressure, and the filter cake was washed three times with petroleum ether. The final product was then dried under vacuum at 60 °C.

[0054] The molar ratio of styrene to maleic anhydride is 1:1; the amount of toluene added is 9 times the total mass of styrene and maleic anhydride, and the amount of azobisisobutyronitrile added is 0.65% of the mass of toluene.

[0055] Comparative Example 2

[0056] The solvent cyclohexanone is 30 kg, accounting for 30% of the total mass of all materials; the molar ratio of maleic anhydride to styrene is 3:1, with maleic anhydride 6.6 kg and styrene 63.4 kg; the initiator azobisisobutyronitrile (AIBN) is 0.21 kg, and the mass of the initiator accounts for 0.3% of the total mass of maleic anhydride and styrene.

[0057] Preparation of copolymer: Styrene, maleic anhydride, initiator and solvent are added to monomer mixing reactor. After purging with nitrogen, the mixture is stirred until the maleic anhydride is dissolved. Then, the resulting mixture is fed into a tubular reactor at 200°C using a feed pump. The residence time of the mixture is 10 min. The resulting reactants are then fed into a devolatilizer for devolatilization to obtain a low molecular weight narrow distribution styrene-maleic anhydride copolymer.

[0058] Comparative Example 3

[0059] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are disclosed. The specific steps are the same as those in Comparative Example 2, except that the residence time of the mixture is 15 min.

[0060] Comparative Example 4

[0061] A low molecular weight styrene-maleic anhydride copolymer and its preparation method are disclosed. The specific steps are the same as those in Comparative Example 2, except that the residence time of the mixture is 20 min.

[0062] Performance testing

[0063] 1. Polymer solid content: After drying the glass dish, weigh it, take 10g of the polymer liquid and place it in the glass dish, place it in a vacuum oven at 200℃ for 30min, take it out and cool it, weigh it, subtract the weight of the glass dish from the obtained weight and divide it by 10g to get the polymer solid content.

[0064] 2. Weight-average molecular weight: The weight-average molecular weight was determined by GPC gel chromatography.

[0065] 3. Acid value: Acidity is tested according to ASTM D3644 standard.

[0066] 4. Transparency: Visually.

[0067] 5. Insoluble matter content: 10g of the prepared styrene-maleic anhydride copolymer was wrapped in a filter screen and placed in 90g of acetone. After 24 hours, the 1000-mesh filter screen was dried and weighed. The weight of the insoluble matter was obtained by subtracting the dry weight of the filter screen from the obtained weight. Insoluble matter content = insoluble matter mass / 10g × 100%.

[0068] 6. Odor: Refer to the odor test PV3900 standard test examples 1-6 and comparative examples 1-3. Level 1 is the lowest odor and level 6 is the highest odor.

[0069] 7. YI value: The yellowness value is measured using a colorimeter.

[0070] The test results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

Claims

1. A low molecular weight styrene maleic anhydride copolymer characterized in that, The preparation raw materials at least include: styrene and maleic anhydride, and the molar ratio of the styrene and the maleic anhydride is 1: (1-9) ; The preparation raw materials further include an initiator, a capping accelerator and a solvent, the adding amount of the initiator is 0.1-1% of the total mass of the styrene and the maleic anhydride, the adding amount of the capping accelerator is 0.5-2% of the total mass of the styrene and the maleic anhydride, and the adding amount of the solvent is 5-15% of the total mass of the styrene and the maleic anhydride; The capping accelerator is 2, 3-dimethyl-2, 3-diphenylbutane; The initiator is di-t-butyl peroxide; The solvent is selected from one or a combination of several of toluene, ethylbenzene, xylene and cumene; The reactor for preparing the styrene maleic anhydride copolymer is a continuous stirring full-mixing reactor.

2. The low molecular weight styrene maleic anhydride copolymer according to claim 1, characterized in that, The weight average molecular weight of the low-molecular-weight styrene maleic anhydride copolymer is 4000-9500 Da.

3. The low molecular weight styrene maleic anhydride copolymer according to claim 1, characterized in that, The maleic anhydride is in a liquid state, and the holding temperature is 60-65 ℃.

4. A process for the preparation of a low molecular weight styrene maleic anhydride copolymer according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) introducing part of the solvent into the reactor and heating; (2) mixing the initiator, the capping accelerator and the remaining solvent to obtain a mixed liquid, and adding the styrene, the maleic anhydride and the mixed liquid into the solvent in step (1) through metering pumps in proportion; (3) discharging after the polymerization reaction; (4) discharging into a devolatilizer to remove volatiles and obtain the low-molecular-weight styrene maleic anhydride copolymer.

5. The method for preparing the low molecular weight styrene-maleic anhydride copolymer according to claim 4, characterized in that, The temperature of the polymerization reaction is 150-300 ℃, and the reaction time is 1-60 min.

Images