1. A method for preparing a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer, said method comprising the steps of:

the preparation method comprises the following steps: in an inert atmosphere, adding maleic anhydride, styrene, alpha-methyl styrene, vinyl acetate and a photoinitiator into an organic solvent for dissolving to form a homogeneous solution;

and (3) photo-initiated polymerization: irradiating the homogeneous solution prepared in the preparation step with light under the protection of inert gas to perform photoinitiated polymerization reaction to generate maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer and obtain emulsion suspension containing maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer;

a separation step: and after the step of photopolymerization is finished, separating the obtained copolymer emulsion suspension to obtain a maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer precipitate.

2. The method of claim 1, further comprising the steps of:

and (3) raw material supplement step: supplementing maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate and a photoinitiator to the reaction liquid remaining after the separation of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer after the separation step;

after the raw material replenishing step, the photoinitiated polymerization step and the separation step are continued.

3. The production method according to claim 1 or 2, wherein in the step of photo-initiated polymerization, the reaction temperature is controlled to be 20 to 40 ℃.

4. The production method according to claim 1, wherein the maleic anhydride, the styrene, the alpha-methylstyrene, and the vinyl acetate are contained in an amount of 40 to 50% by mass, 10 to 20% by mass, and 20 to 30% by mass, respectively, based on the total weight of the maleic anhydride, the styrene, the alpha-methylstyrene, and the vinyl acetate.

5. The production method according to claim 1 or 2, wherein the light irradiated in the photo-initiation polymerization step is an LED light having a wavelength of 365nm to 405nm, an irradiation time of 10 minutes to 3 hours, and an illumination intensity of 10 mw/cm to 1000 mw/cm.

6. The production method according to claim 1 or 2, wherein the photoinitiator is a photolysis-type initiator and/or a hydrogen abstraction-type photoinitiator.

7. The method according to claim 6, wherein the photolytic initiator is at least one selected from the group consisting of α -hydroxyketone photoinitiators 1173, α -hydroxyketone photoinitiators 184, α -hydroxyketone photoinitiators 2959, photoinitiators 651, oxalate photoinitiators MBF, α -aminoketone photoinitiators 907, α -aminoketone photoinitiators 369, acylphosphino photoinitiators TPO, acylphosphino photoinitiators 819, represented by the following structural formula,

8. the production method according to claim 6, wherein the hydrogen abstraction type photoinitiator is at least one selected from the group consisting of benzophenone type photoinitiators BP, benzophenone type photoinitiators EMK, and thioxanthone type photoinitiators ITX represented by the following structural formula, and at least one selected from the group consisting of MDEA and EDB as co-initiators,

9. the production method according to claim 1 or 2, wherein the organic solvent is at least one selected from the group consisting of butyl acetate, isobutyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, benzyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, isoamyl butyrate, ethyl isovalerate, isoamyl isovalerate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, isoamyl benzoate, methyl phenylacetate, and ethyl phenylacetate.

10. The production method according to claim 9, wherein the organic solvent is butyl acetate or isoamyl acetate.

Background

Maleic anhydride is a commonly used free radical polymerizable monomer, but maleic anhydride by itself cannot undergo homopolymerization. Therefore, the maleic anhydride-containing copolymer can be obtained only in a form copolymerized with other monomers. For example, styrene can form a complex with maleic anhydride at low temperature, alternating polymerization can occur under the action of a thermal initiator, and random copolymerization can occur at higher temperature.

These classical polymerization reactions are all prepared by solution polymerization or precipitation polymerization. In order to control the composition of the polymer, whether it is solution polymerization or precipitation polymerization, it is generally necessary to add the raw materials by dropping or the like, and to control the reaction time, dropping speed, and the like by controlling the reaction temperature under heating, depending on the half-life of the thermal initiator at various temperatures, and the like. In addition, the energy consumption is high, and a precipitator or toxic toluene and the like are required to be used as a solvent, so that the environmental pollution, the carbon emission and the like are unfavorable.

CN101235117A discloses a method for preparing styrene/maleic anhydride copolymer by self-stabilization precipitation polymerization, which solves the defect of using stabilizer in the traditional dispersion polymerization system, and prepares styrene/maleic anhydride copolymer microspheres by thermal initiation polymerization under nitrogen condition. Such a polymerization method is also used to prepare a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer. However, such a production method still has problems of low production efficiency and high reaction cost, such as the need for heating and a long reaction time.

How to further save energy consumption and carry out preparation more efficiently in the preparation of maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer is a problem to be solved in the field.

Disclosure of Invention

The present inventors have conducted extensive studies and found that a maleic anhydride-styrene- α -methylstyrene-vinyl acetate system can be directly copolymerized by irradiating light at room temperature without using a high-temperature reaction condition required for thermal polymerization by using a photoinitiator to generate radicals by photo-initiated polymerization. The inventor introduces the photo-initiated polymerization preparation method into the copolymerization system of maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate system for the first time, compared with the traditional thermal initiated polymerization, because no additional heating condition is needed and the reaction time is reduced, the cost can be saved and the production efficiency can be improved.

The invention provides a preparation method of maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer, which comprises the following steps:

the preparation method comprises the following steps: in an inert atmosphere, adding maleic anhydride, styrene, alpha-methyl styrene, vinyl acetate and a photoinitiator into an organic solvent for dissolving to form a homogeneous solution;

and (3) photo-initiated polymerization: irradiating the homogeneous solution prepared in the preparation step with light under the protection of inert gas to perform photoinitiated polymerization reaction to generate maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer and obtain emulsion suspension containing maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer;

a separation step: and after the step of photopolymerization is finished, separating the obtained copolymer emulsion suspension to obtain a maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer precipitate.

In the method for preparing the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer of the present invention, preferably, the following steps are further included:

and (3) raw material supplement step: supplementing maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate and a photoinitiator to the reaction solution remaining after the separation of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer;

then, the photo-initiated polymerization step and the separation step are continued.

In the preparation method of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer, the reaction temperature is preferably controlled to be 20 to 40 ℃ in the photo-initiated polymerization step.

In the preparation method of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer, preferably, the weight percentage of the maleic anhydride, the styrene, the alpha-methylstyrene and the vinyl acetate is 40-50%, 10-20% and 20-30% respectively.

In the method for preparing the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer of the present invention, preferably, the light irradiated in the photo-initiated polymerization step is LED light having a wavelength of 365nm to 405nm, an irradiation time of 10 minutes to 3 hours, and an illumination intensity of 10 mw/cm to 1000 mw/cm.

In the method for producing a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer of the present invention, the photoinitiator is preferably a photolysis-type initiator and/or a hydrogen abstraction-type photoinitiator.

Preferably, the photolytic initiator is at least one selected from the group consisting of α -hydroxyketone photoinitiators 1173, α -hydroxyketone photoinitiators 184, α -hydroxyketone photoinitiators 2959, photoinitiators 651, oxalate photoinitiators MBF, α -aminoketone photoinitiators 907, α -aminoketone photoinitiators 369, acylphosphine oxide photoinitiators TPO, and acylphosphine oxide photoinitiators 819, which are represented by the following structural formula.

Preferably, the hydrogen abstraction photoinitiator is at least one selected from the group consisting of benzophenone-based photoinitiators BP, benzophenone-based photoinitiators EMK, and thioxanthone-based photoinitiators ITX represented by the following structural formulae, and at least one selected from the group consisting of MDEA and EDB as co-initiators.

In the method for producing a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer of the present invention, the organic solvent is preferably at least one selected from the group consisting of butyl acetate, isobutyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, benzyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, isoamyl butyrate, ethyl isovalerate, isoamyl isovalerate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, isoamyl benzoate, methyl phenylacetate, and ethyl phenylacetate.

Further preferably, the organic solvent is butyl acetate or isoamyl acetate.

The preparation method of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer of the invention utilizes photo-initiated polymerization reaction, and the photo-initiator is excited to generate free radicals, so as to initiate the copolymerization of maleic anhydride, styrene, alpha-methylstyrene and vinyl acetate systems, and prepare the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer. The novel method for preparing the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer by photo-initiated polymerization can be carried out under the condition of illumination at normal temperature without heating required by thermal initiation, does not need additional heating conditions and reduces reaction time compared with the traditional preparation method of thermal initiated polymerization, thereby saving cost, improving production efficiency and improving production safety because heating is not required.

Drawings

FIG. 1 is a FT-IR spectrum of a product obtained by the method for producing a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer of example 1.

Detailed Description

The preparation method of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer comprises the following steps:

the preparation method comprises the following steps: in an inert atmosphere, adding maleic anhydride, styrene, alpha-methyl styrene, vinyl acetate and a photoinitiator into an organic solvent for dissolving to form a homogeneous solution;

and (3) photo-initiated polymerization: and irradiating the homogeneous solution prepared in the preparation step with light under the protection of inert gas to perform photoinitiated polymerization reaction to generate maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer, thereby obtaining a milky suspension containing the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer.

A separation step: and after the step of photopolymerization is finished, separating the obtained copolymer emulsion suspension to obtain a maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer precipitate.

Thermally initiated polymerization, as used in the prior art, is a conventional method for preparing polymers by initiating polymerization of comonomers by thermal initiator decomposition by heating to generate free radicals. For the preparation of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer, the thermal initiators usually used are mainly azobisisobutyronitrile, dibenzoyl peroxide and the like, the thermal decomposition temperature of the thermal initiators is 70-90 ℃, and the half-life of the thermal decomposition of the two initiators is 5-12 hours in the temperature range. For example, azobisisobutyronitrile and dibenzoyl peroxide have half-lives of 5.08 hours and 13.25 hours, respectively, at 69 ℃. Therefore, when maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer is prepared by thermal initiation polymerization, the whole polymerization system must be heated and kept for a long enough time to ensure the generation of sufficient free radicals and the yield of polymer preparation, and the energy consumption and time consumption in the reaction process are high, so that the reaction efficiency is difficult to improve. In addition, high temperature reaction has certain potential safety hazard and has the danger of implosion and kettle flushing.

The present inventors have innovatively contemplated incorporating photoinitiated polymerization into the preparation of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymers. For a preparation system of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer, the reaction time required by photopolymerization is greatly shortened compared with that of a thermal polymerization process, so that the reaction efficiency can be greatly improved. The photo-initiated polymerization is a reaction in which a photo-initiator molecule is photolyzed by light irradiation to generate a radical, thereby initiating polymerization of a monomer. The efficiency of photolysis is improved by many times compared with the efficiency of thermal decomposition, so that the energy consumption is greatly reduced, the cost can be saved, and the environment is protected.

The efficiency improvement and energy saving effects of photopolymerization over thermally initiated polymerization are illustrated below by taking photons emitted from a 365nm LED as an example.

Assuming that the quantum yield of photolysis is 0.5 (i.e. two photons can decompose one photoinitiator, in practice the efficiency may be higher), 2mol photons are required to decompose 1mol photoinitiator. The energy per photon is the product of the planck constant and the photon fluctuation frequency, so the energy E for 2mol photons is:

E＝2*NA*h*c/λ

where NA is the Avogastrol constant, h is Planck's production, c is the speed of light, and λ is the wavelength, here taken to be 365 nm.

Thus, E ═ 2 × 6.02 × 10²³×6.626×10^-34×3×10⁸/(365×10^-9)＝6.5×10⁵Joule 650 kilojoules. That is, only 650 kj of energy is required to decompose 2mol of photoinitiator. Assuming that the power of the light source is 1kW, all the photoinitiators can be photolyzed only by light for 650 seconds and less than 11 minutes, corresponding to the electric energy consumption of about 0.18 degrees, the photoelectric conversion efficiency of the LED light source is about 30% at 365nm and reaches more than 60% at 385nm, and therefore, the power consumption in the whole process is calculated to be less than 1 degree. In the actual polymerization process, the process can be appropriately slowed down to control the progress of the reaction, for example, by light for 30 minutes. Weaker light may also be usedThe same effect is achieved with intensity, since the optical excitation is dependent only on the wavelength of the photons and not on the intensity of the light.

In the same case, the molecular weight of azobisisobutyronitrile, for example, was 164.21, and 2mol was 328.4 g, based on 1% by weight of the thermal initiator based on the total monomer mass and 20% by weight of the total monomer based on the polymerization system, 32.8 kg of the monomer system and 164 kg of the total system were required. Calculated by the specific heat of isoamyl acetate of 1.92 KJ/(kg. K), the required energy for heating from room temperature of 20 ℃ to 70 ℃ is as follows:

e ═ c × m × Δ T ═ 1.92 × 164 × 50 ═ 15744 kilojoules. The energy is only the energy required by temperature rise, and the energy consumed by heat preservation for 5-12 hours is not included.

From the above analysis, it can be shown that by introducing photoinitiated polymerization in the preparation of maleic anhydride-vinyl acetate- α -methylstyrene-styrene copolymer, both the reaction time and the energy required for the reaction are greatly reduced. Therefore, compared with the preparation method of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer by thermal initiation polymerization in the prior art, the preparation method of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer can greatly improve the reaction efficiency, is more environment-friendly and energy-saving, can greatly reduce the cost, and is more suitable for industrial application.

Hereinafter, each step will be described in detail.

[ preparation procedure ]

In the preparation step, maleic anhydride, styrene, alpha-methyl styrene, vinyl acetate and a photoinitiator are added into an organic solvent to be dissolved in an inert atmosphere, and a homogeneous solution is formed.

The inert gas atmosphere may be, for example, a helium gas atmosphere or a nitrogen gas atmosphere, and a nitrogen gas atmosphere is preferred from the viewpoint of cost saving. Before maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate and photoinitiator are added to the organic solvent, inert gas such as nitrogen can be introduced to form an inert gas atmosphere in the system.

The dissolution may be performed by stirring or the like, and the stirring may be mechanical stirring or magnetic stirring, and is not particularly limited. The added maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate and photoinitiator are dissolved in an organic solvent by stirring to form a homogeneous solution.

In the homogeneous solution, the total mass of the maleic anhydride, styrene, alpha-methylstyrene and vinyl acetate as monomers is 5 to 30 wt%, preferably 10 to 20 wt%, based on the total weight of the homogeneous solution.

In the preparation step, maleic anhydride, styrene, α -methylstyrene, vinyl acetate added are monomers forming a maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer. The ratio of these components is not particularly limited, and may be determined according to the properties of the desired copolymer. Preferably, the weight percentage of the total weight of the maleic anhydride, the styrene, the alpha-methyl styrene and the vinyl acetate is 40-50%, 10-20% of the styrene, 10-20% of the alpha-methyl styrene and 20-30% of the vinyl acetate.

The content of the initiator in the homogeneous solution is preferably 0.2 to 4.0 wt%, more preferably 0.5 to 2.0 wt%, and still more preferably 0.8 to 1.5 wt%, based on the total mass of the monomers.

Preferably, the aforementioned photoinitiator is selected from photolytic initiators and/or hydrogen abstraction initiators. That is, only one of the photolysis-type initiator and the hydrogen abstraction-type initiator may be used, or both types of initiators may be used in combination. Among the above photoinitiators, a photolytic initiator is preferably used.

Examples of the photolytic initiator include an α -hydroxyketone photoinitiator 1173, an α -hydroxyketone photoinitiator 184, an α -hydroxyketone photoinitiator 2959, a photoinitiator 651, an oxalate photoinitiator MBF, an α -aminoketone photoinitiator 907, an α -aminoketone photoinitiator 369, an acylphosphine oxide photoinitiator TPO, and an acylphosphine oxide photoinitiator 819, which are represented by the following structural formulae.

In the case where only the photolytic initiator is used, one or two or more initiators may be selected from the above-listed photolytic initiators. Among the above photolytic initiators, the following α -hydroxyketone photoinitiator 1173 or α -hydroxyketone photoinitiator 184 is preferably used.

Examples of the hydrogen abstraction photoinitiator include benzophenone type photoinitiators BP, benzophenone type photoinitiators EMK, thioxanthone type photoinitiators ITX, and the like. When a hydrogen abstraction photoinitiator is used, a co-initiator such as MDEA or EDB represented by the following structural formula may be used in combination. When the co-initiator is used, the co-initiator is regarded as a photoinitiator and the proportion is calculated.

In the production method of the present invention, the organic solvent is preferably at least one selected from the group consisting of ethyl formate, propyl formate, isobutyl formate, pentyl formate, ethyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, benzyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, isoamyl butyrate, ethyl isovalerate, isoamyl isovalerate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, isoamyl benzoate, methyl phenylacetate and ethyl phenylacetate. Butyl acetate or isoamyl acetate is more preferable.

[ photo-initiated polymerization step ]

In the photo-initiation polymerization step, under the protection of inert gas, the homogeneous solution obtained in the preparation step is irradiated with light to perform photo-initiation polymerization reaction, so that the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer is generated.

In the aforementioned photo-initiated polymerization step, the polymerization reaction is initiated by irradiating light. By irradiating light to the reaction system, the photoinitiator in the system generates active species such as free radicals or cations after being irradiated by the light, the maleic anhydride, styrene, alpha-methylstyrene and vinyl acetate in the reaction system are initiated to generate chain polymerization reaction, and the copolymer generated by the reaction is precipitated from the reaction system, belonging to precipitation polymerization, also called heterogeneous polymerization.

The principle of photoinitiated polymerization will be described below by taking α -hydroxyketone photoinitiator 1173, which uses a photolytic photoinitiator, as an example of the photoinitiator. The homogeneous solution containing maleic anhydride, styrene, α -methylstyrene, vinyl acetate, α -hydroxyketone photoinitiator 1173 obtained through the preparation step and an organic solvent was irradiated with light using 365nm or 385nm LED as a light source. The molecule of the alpha-hydroxy ketone photoinitiator 1173 serving as the photoinitiator is irradiated by light to generate homolytic reaction shown in the following reaction formula (1) to generate two high-activity free radicals, and the generated free radicals attack double bonds of maleic anhydride, styrene, alpha-methylstyrene and vinyl acetate to initiate chain reaction to generate the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer. The aforementioned chain reaction process is well known to those skilled in the art, and the description thereof is omitted here.

Reaction formula (1): mechanism for generating free radicals by homolytic cleavage reaction of photoinitiator 1173

In the case of using a hydrogen abstraction type photoinitiator, first, ITX as a main initiator, for example, obtains one proton from MDEA as a co-initiator by a hydrogen abstraction reaction under irradiation of light, and MDEA as a co-initiator forms a corresponding radical, and has a very high initiating activity to initiate polymerization of a monomer. Specifically, the reaction is represented by the following reaction formula (2).

Reaction formula (2): mechanism for generating free radicals under ITX (internal transcribed X) illumination of hydrogen abstraction type photoinitiator

The light source used in the aforementioned photo-initiated polymerization step is not particularly limited, and light in the ultraviolet or visible wavelength range may be used. Preferably, LED lamps are used.

The conditions of light irradiation, such as the area of the light source, the light intensity, and the light irradiation time, can be appropriately set depending on the scale of the system at the time of production, as long as the photoinitiator can be excited to cleave. Since the chain reaction proceeds spontaneously after the start, the light irradiation may be performed intermittently, not necessarily continuously.

The wavelength of the light source used may be, for example, 365nm to 405 nm. For example, light having a wavelength of 365nm, 385nm, 395nm, or 405nm may be used. More preferably, 365nm or 385nm light is used.

The light source may be a surface light source or a point light source, and is preferably a surface light source. The light irradiation time may be, for example, 10 minutes to 3 hours, and the light irradiation intensity may be, for example, 10 milliwatts per square centimeter to 1000 milliwatts per square centimeter.

The photo-initiated polymerization reaction is carried out in an inert gas atmosphere, preferably a nitrogen gas atmosphere.

As the polymerization reaction is exothermic, the exothermic heat of reaction is accumulated in the reaction system along with the reaction, so that the temperature of the system is increased continuously. According to the scale of the reaction system, the temperature of the reaction system is preferably controlled to be 20 to 40 ℃, more preferably 25 to 30 ℃ in the photoinitiated polymerization step. By controlling the temperature of the reaction system to be in the range, the phenomenon that the complexation of the monomers is damaged due to the increase of the reaction temperature is avoided, and the structure and the performance of the prepared copolymer are further influenced; on the other hand, by controlling the temperature of the reaction system within the above range, the produced polymer precipitates after reaching a certain molecular weight, and the increase in the solubility of the produced copolymer due to the increase in the reaction temperature is avoided, so that the polymer is not easily precipitated from the reaction system. Further, by controlling the temperature of the reaction system in the above range, the broadening of the molecular weight distribution of the copolymer due to the large temperature fluctuation is avoided.

The temperature control of the reaction system may be performed by a low-temperature cycle such as a cycle of condensed water, and is not particularly limited.

In the photo-initiated polymerization step, the reaction may be carried out by irradiating with light while stirring in order to make the temperature of the reaction system uniform. The stirring may be mechanical stirring or magnetic stirring, and is not particularly limited. By stirring, the reaction solution shielded by the maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer precipitate can be exposed to a place where light can be irradiated, thereby allowing the unreacted monomer to continue to react. As the reaction proceeds, the reaction system gradually becomes a white suspension system, and after a certain amount of the maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer is produced, the amount of the maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer increases, so that the system is difficult to continue to absorb light to be photopolymerized, and at this time, the reaction is terminated.

The maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer is reacted by the aforementioned photo-initiated polymerization step to produce a milky suspension containing the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer.

[ separation step ]

After the photopolymerization step is finished, separating the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer in the obtained emulsion suspension to obtain the precipitate of the maleic anhydride-styrene-alpha-methylstyrene-vinyl acetate copolymer.

The separation may be performed by a solid-liquid separation method such as precipitation, filtration, or centrifugation, which is conventionally used in the art, and centrifugation is preferably used. When centrifugal separation is adopted, the centrifugal rotation speed can be set to be 1000-3000 rad/min, and the centrifugal time can be 10-30 min.

Further, the preparation method of the present invention may further comprise the steps of:

and (3) raw material supplement step: after the separation step, maleic anhydride, styrene, α -methylstyrene, vinyl acetate, and a photoinitiator are supplemented to the reaction liquid remaining after the separation of the maleic anhydride-styrene- α -methylstyrene-vinyl acetate copolymer. The amounts of the maleic anhydride, styrene, α -methylstyrene, vinyl acetate and photoinitiator to be replenished were calculated from the concentrations of the monomers and photoinitiators in the remaining reaction solution recovered by gas chromatography, and the amounts of the monomers and photoinitiators consumed in the reaction, that is, the amounts of the monomers and photoinitiators to be replenished were calculated.

After the raw material replenishing step, the photo-initiated polymerization step and the separation step are continued.

After the separation step, the residual reaction solution is supplemented with maleic anhydride, styrene, α -methylstyrene, vinyl acetate and a photoinitiator as monomers, so that the photo-initiated polymerization reaction can be continued under the condition of light irradiation. The separation step may then be continued.

By recycling the aforementioned raw material replenishment step, photo-initiation step and separation step, the organic solvent can be reused many times, thereby avoiding the generation of a large amount of organic waste liquid during the reaction and also causing little solid waste.

In the photo-initiated polymerization, small amounts of oligomers having a relatively low molecular weight are also produced, and these oligomers are dissolved in an organic solvent such as isoamyl acetate, butyl acetate, etc. Therefore, after the aforementioned raw material replenishing step, photo-initiation step, and separation step are repeatedly circulated a plurality of times, the concentrations of these oligomers increase, thereby affecting the photopolymerization of maleic anhydride, styrene, α -methylstyrene, and vinyl acetate, and in this case, the aforementioned circulation is ended. The number of cycles may be, for example, 2 to 10 cycles, preferably 2 to 5 cycles.

Further, the preparation method of the present invention may further include the steps of:

washing and drying: washing and drying the maleic anhydride/vinyl acetate/styrene/alpha-methylstyrene/vinyl acetate copolymer separated in the previous separation step with an organic solvent. The organic solvent may be, for example, butyl acetate or the like.

The washing may be performed once or more, and the drying may be performed by, for example, drying in an oven or the like, spray drying, or the like.

The maleic anhydride/vinyl acetate/styrene/alpha-methylstyrene/vinyl acetate copolymer prepared by the preparation method has good heat resistance, and can be used as a heat-resistant modifier applied to polymers, for example, as a heat-resistant modifier of polypropylene.

Examples

The present invention will be described in detail below by way of examples.

In the following examples, the polymerization yield (Cp) was calculated as follows

Cp＝Mp×100％/Mm

Wherein Mp is the mass of the polymer formed by the reaction; mm is the total mass of monomers added to the reaction system.

The content of each structural unit in the copolymer is adopted¹H NMR is used for testing, and the testing method is to pass¹Measuring the content of each structural unit according to the ratio of the peak areas corresponding to the characteristic hydrogen in the corresponding structural unit in H NMR;

the heat resistance of the polypropylene is measured by a GB/T1634.2-2004 method;

maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate were purchased from Annaiji technologies, Inc.

Polypropylene K8009, available from china and korea petrochemical company.

Examples and comparative examples all other materials were commercially available.

Example 1

(1) In a 250 ml quartz flask with a thermometer, electromagnetic stirring and nitrogen gas introduction device, 9.8 g of maleic anhydride (maleic anhydride, 0.1mol), 2.08 g of styrene (0.02mol), 2.36 g of alpha-methylstyrene (0.02mol), 5.2 g of vinyl acetate (0.06mol) and 0.2 g of photoinitiator 184(1 wt%) were added, 80 g of butyl acetate was added, stirred and dissolved, and nitrogen gas was blown in for 15 minutes;

(2) LED surface light source with 5 lamp beads multiplied by 5 lamp beads and 385nm as central wavelength is close to quartz flaskSurface, directly irradiating the solution in the bottle with light intensity of about 50mW/cm²Irradiating for 15 minutes to generate photo-initiated polymerization reaction, wherein the temperature of the system is raised to 50 ℃ at most in the reaction process;

(3) separating the obtained precipitate by a centrifugal machine, washing the precipitate by new butyl acetate once, and drying the precipitate after centrifugation to obtain 9.2 g of white solid powder A1, wherein the yield of the corresponding polymer is 45.7%;

(4) the concentration of the photoinitiator in the mixture of the centrifugate and the washing solution was calibrated by gas chromatography, and the residual amount of the initiator 184 was found to be 23%.

(5) The polymer powder was subjected to 1H NMR analysis to determine the molar content of maleic anhydride structural units was about 48%, the molar content of styrene structural units was about 10.5%, and the molar content of α -methylstyrene structural units was about 10.5%, based on the total molar amount of the structural units in the polymer; the molar content of vinyl acetate structural units is about 31%. In addition, FT-IR measurement was performed, and the obtained spectrum is shown in FIG. 1. In FIG. 1, 1786cm^-1、1890cm^-1Characteristic absorption peak of anhydride group, 1250cm^-1Is an absorption peak of a C-O bond of 709cm^-1Is the absorption peak of the phenyl function of C-O, on the basis of which the product was determined to be a maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer.

Example 2

(1) A 250 ml quartz flask with a thermometer, electromagnetic stirring and nitrogen gas introducing device is added with 75 g of the centrifugate and the washing liquid in the embodiment 1, 5 g of maleic anhydride (maleic anhydride), 1 g of styrene, 1.2 g of alpha-methyl styrene, 2.6 g of vinyl acetate and 0.15 g of photoinitiator 184, 15 g of butyl acetate are added, stirred and dissolved, and nitrogen gas is blown for 15 minutes;

(2) an LED surface light source with the wavelength of 385nm of 5 lamp beads multiplied by 5 lamp beads as a central wavelength is close to the surface of the quartz flask to directly irradiate the solution in the flask, and the light intensity is about 50mW/cm²Irradiating for 20 minutes to generate a photo-initiated polymerization reaction, wherein the temperature of the system is raised to 52 ℃ at most in the reaction process;

(3) separating the obtained precipitate by a centrifugal machine, washing the precipitate once by using new butyl acetate, and drying the precipitate after centrifugation to obtain 11.0 g of white solid powder A2;

(4) the concentration of the photoinitiator in the mixture of the centrifugate and the washing solution was calibrated by gas chromatography, and the residual amount of the initiator 184 was found to be 20%.

Example 3

(1) In a 2.5 liter quartz flask equipped with a thermometer, mechanical stirring, nitrogen gas introduction device, 98 g of maleic anhydride, 15.6 g of styrene, 17.7 g of alpha-methylstyrene, 60.2 g of vinyl acetate and 2 g of photoinitiator 1173 were added, 800 g of isoamyl acetate was added, stirred and dissolved, and after 15 minutes of nitrogen gas was bubbled;

(2) an LED surface light source with the wavelength of 385nm of 5 lamp beads multiplied by 5 lamp beads as a central wavelength is close to the surface of the quartz flask to directly irradiate the solution in the flask, and the light intensity is about 50mW/cm²Irradiating for 30 minutes to generate a photo-initiated polymerization reaction, wherein the temperature of the system is raised to 58 ℃ at most in the reaction process;

(3) separating the obtained precipitate by a centrifugal machine, washing the precipitate once by using new isoamyl acetate, and drying the precipitate after centrifugation to obtain 124 g of white solid powder A3; the polymer yield was about 68.3%.

(4) The concentration of photoinitiator in the mixture of centrate and wash was calibrated by gas chromatography and the residual amount of initiator 1173 was found to be 17%.

Example 4

(1) In a 2.5 liter quartz flask equipped with a thermometer, electromagnetic stirring or mechanical stirring, nitrogen gas was introduced into the apparatus, 98 g of maleic anhydride, 20.8 g of styrene, 23.6 g of α -methylstyrene, 51.6 g of vinyl acetate and 2 g of photoinitiator 184 were added, 800 g of isoamyl acetate was added, dissolved by stirring, and after 15 minutes of nitrogen gas was bubbled;

(2) an LED surface light source with the wavelength of 385nm of 5 lamp beads multiplied by 5 lamp beads as a central wavelength is close to the surface of the quartz flask to directly irradiate the solution in the flask, and the light intensity is about 50mW/cm²Irradiating for 25 minutes to generate photo-initiated polymerization reaction, wherein the temperature of the system is raised to 57 ℃ at most in the reaction process;

(3) separating the obtained precipitate by a centrifugal machine, washing the precipitate once by using new isoamyl acetate, and drying the precipitate after centrifugation to obtain 128 g of white solid powder A4;

(4) the concentration of the photoinitiator in the mixture of the centrifugate and the washing solution was calibrated by gas chromatography, and the residual amount of the initiator 184 was found to be 19%.

Example 5

(1) In a 2.5 liter quartz flask equipped with a thermometer, electromagnetic stirring or mechanical stirring, nitrogen gas was introduced into the apparatus, 98 g of maleic anhydride, 20.8 g of styrene, 23.6 g of α -methylstyrene, 51.6 g of vinyl acetate and 2 g of photoinitiator 907 were added, 800 g of isoamyl acetate was added, dissolved by stirring, and after 15 minutes of nitrogen gas was bubbled;

(2) an LED surface light source with the wavelength of 385nm of 5 lamp beads multiplied by 5 lamp beads as a central wavelength is close to the surface of the quartz flask to directly irradiate the solution in the flask, and the light intensity is about 50mW/cm²Irradiating for 15 minutes to generate photo-initiated polymerization reaction, wherein the temperature of the system is raised to 50 ℃ at most in the reaction process;

(3) separating the obtained precipitate by a centrifugal machine, washing the precipitate once by using new isoamyl acetate, and drying the precipitate after centrifugation to obtain 126 g of white solid powder A5;

(4) the concentration of the photoinitiator in the mixture of the centrifugate and the washing solution was calibrated by gas chromatography, and the residual amount of the initiator 907 was found to be 18%.

Example 6

The same procedures as in example 1 were repeated except that a jacketed reactor was used in the photopolymerization initiation reaction, the temperature of the reaction system was lowered by circulating a cooling liquid through a low-temperature bath, and the system temperature was kept at 25 to 30 ℃ to obtain 10.9 g in total of white solid powder A6, which corresponds to a polymer yield of 53.8%.

Comparative example 1

(1) In a 250 ml three-neck flask with a thermometer, electromagnetic stirring, nitrogen gas introduction device and reflux condenser, 9.8 g of maleic anhydride (maleic anhydride, 0.1mol), 2.08 g of styrene (0.02mol), 2.36 g of alpha-methyl styrene (0.02mol), 5.2 g of vinyl acetate (0.06mol) and 1.0 g of thermal initiator azobisisobutyronitrile (5 wt%), 80 g of butyl acetate is added, stirred and dissolved, and nitrogen gas is blown for 15 minutes;

(2) transferring the flask to a water bath at 70 ℃, heating for 5 hours for reaction, centrifugally separating the obtained polymer milky suspension by a centrifuge at the rotating speed of 2000rad/min after the reaction is finished, and drying to obtain 9.57g of polymer microspheres A7, wherein the corresponding polymer yield is 47.2%;

test example

The copolymer powders obtained in examples and comparative examples were mixed with polypropylene in the amounts shown in table 1, and then subjected to extrusion granulation to obtain polypropylene pellets. The screw rotating speed of the extruder is 110r/min, the barrel temperature of the extruder is set to be 175-.

The polypropylene and the polypropylene pellets were subjected to a heat resistance test in accordance with GB/T1634.2-2004, and the results are shown in Table 1.

TABLE 1 formulation and related Properties of maleic anhydride-vinyl acetate-alpha-methylstyrene-styrene copolymer precipitation blended Polypropylene

From the above-mentioned test examples, it is understood that the material obtained by mixing the maleic anhydride-vinyl acetate- α -methylstyrene-styrene copolymer obtained by the production process of the present invention in polypropylene has improved heat resistance as compared with the case of using polypropylene alone, and the properties thereof are comparable to those of the comparative example obtained by using heat-initiated polymerization.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.