阅读说明：本技术 一种银纹改善的苯乙烯-丙烯腈共聚物及其制备方法、装置 (Styrene-acrylonitrile copolymer with improved silver streaks and preparation method and device thereof ) 是由 刘波 刘铭 孟磊 孙一峰 麻宁 韩强 赵以兵 乔义涛 黎源 于 2020-07-16 设计创作，主要内容包括：一种银纹改善的苯乙烯-丙烯腈共聚物及其制备方法、装置,该共聚物的制备方法为：将苯乙烯类单体、丙烯腈类单体、任选的链转移剂及任选的溶剂混合液加入到反应器中,在一定条件下进行聚合反应；反应器内部分单体和溶剂气相挥发经冷凝后形成反应器气相冷凝液,反应器气相冷凝液再次进入反应器循环反应,反应后的浆料进入脱挥单元脱除挥发性组分,脱挥单元脱除的挥发性组分冷凝后再次进入反应器参与反应,反应器气相冷凝液中聚合物浓度不高于100ppm,优选不高于50ppm。本发明的制备方法制得的苯乙烯-丙烯腈共聚物具有极佳的光学性能,特别是注塑后具有极低的银纹。(A styrene-acrylonitrile copolymer with improved silver streaks and a preparation method and a device thereof are provided, wherein the preparation method of the copolymer comprises the following steps: adding a styrene monomer, an acrylonitrile monomer, an optional chain transfer agent and an optional solvent mixed solution into a reactor, and carrying out polymerization reaction under certain conditions; and volatilizing partial monomer and solvent gas phase in the reactor, condensing to form reactor gas phase condensate, feeding the reactor gas phase condensate into the reactor again for cyclic reaction, feeding the reacted slurry into a devolatilization unit to remove volatile components, condensing the volatile components removed by the devolatilization unit, and feeding the condensed volatile components into the reactor again for reaction, wherein the concentration of the polymer in the reactor gas phase condensate is not higher than 100ppm, preferably not higher than 50 ppm. The styrene-acrylonitrile copolymer prepared by the preparation method has excellent optical performance, and particularly has extremely low silver streaks after injection molding.)

1. A preparation method of a styrene-acrylonitrile copolymer with improved silver streaks is characterized in that a styrene monomer, an acrylonitrile monomer, an optional chain transfer agent and an optional solvent mixed solution are added into a reactor, and polymerization reaction is carried out under certain conditions; and volatilizing partial monomer and solvent gas phase in the reactor, condensing to form reactor gas phase condensate, feeding the reactor gas phase condensate into the reactor again for cyclic reaction, feeding the reacted slurry into a devolatilization unit to remove volatile components, condensing the volatile components removed by the devolatilization unit, and feeding the condensed volatile components into the reactor again for reaction, wherein the concentration of the polymer in the reactor gas phase condensate is not higher than 100ppm, preferably not higher than 50 ppm.

2. The process according to claim 1, wherein the polymerization inhibitor is added to the reactor gas phase volatiles and the total acid content of the reactor gas phase condensate recycled to the reactor is not higher than 100ppm, preferably not higher than 50 ppm.

3. The production method according to claim 1 or 2, characterized in that the polymerization inhibitor is a hydroxylamine compound, preferably one or more of hydroxyalkyl hydroxylamine, alkyl hydroxylamine, aryl hydroxylamine, more preferably diethyl hydroxylamine; the amount of the polymerization inhibitor added is such that the concentration of the polymerization inhibitor is from 0.1 to 20ppm, preferably from 1 to 10ppm, based on the total amount of the monomer and the solvent in the gas phase;

preferably, the polymerization inhibitor is added in gaseous form, and the two are mixed in gaseous form before the reactor gas phase condensate is not condensed;

preferably, the boiling point of the inhibitor is less than 150 ℃, more preferably less than 135 ℃;

the polymerization inhibitor injection pressure is 0.1-1.0MPa, preferably 0.2-0.5 MPa.

4. The production method according to any one of claims 1 to 3, wherein the volatile component condensate of the devolatilization unit and/or the reactor vapor phase condensate is subjected to acid removal by an acid treatment unit and then enters the reactor;

preferably, the temperature of the acid treatment unit is 0-50 ℃, preferably 10-30 ℃;

preferably, the acid treatment unit is a packed tower filled with basic ion exchange resin.

5. The production method according to any one of claims 1 to 4, wherein the mass parts of the components added to the reactor are as follows:

60 to 90 parts by mass, preferably 70 to 80 parts by mass of a styrene monomer,

10 to 40 parts by mass, preferably 20 to 30 parts by mass of a vinylcyanide monomer,

0 to 30 parts by mass, preferably 5 to 20 parts by mass of a solvent,

0 to 0.5 parts by mass, preferably 0.05 to 0.25 parts by mass, of a chain transfer agent;

preferably, the styrenic monomer is styrene or alpha-methylstyrene, preferably styrene; the acrylonitrile-based monomer is acrylonitrile or methacrylonitrile, and acrylonitrile is preferred.

6. The preparation method according to claim 5, wherein the solvent is one or more of toluene, ethylbenzene, cyclohexane, acetonitrile, tetrahydrofuran, N-dimethylformamide, preferably toluene or ethylbenzene; preferably, the content of the solvent is 5 to 20 wt% based on the total amount of the mixed liquid and the recovery liquid added to the reactor.

7. The method according to any one of claims 4 to 6, wherein the chain transfer agent is tert-dodecyl mercaptan and is added in an amount of 0.05 to 0.2 wt% based on the total monomers.

8. The method as claimed in claim 1, wherein the temperature in the reactor is 130-170 ℃, preferably 150-160 ℃; controlling the temperature of the melt of the devolatilization unit at 180-240 ℃, preferably at 200-220 ℃; the devolatilization absolute pressure is within 5KPa, preferably within 2 KPa.

9. A styrene-acrylonitrile copolymer produced by the production method according to any one of claims 1 to 8.

10. The device for preparing the styrene-acrylonitrile copolymer is characterized by comprising a reactor, a devolatilization device, a reactor gas phase condenser, a devolatilization system gas phase condenser and an acid treatment unit, wherein a reactor gas phase outlet is connected with the reactor gas phase condenser, a reactor discharge port is connected with the devolatilization device, the devolatilization device gas phase outlet is connected with the devolatilization system gas phase condenser, and an outlet pipeline of the devolatilization system gas phase condenser and/or the reactor gas phase condenser is also connected with the acid treatment unit;

preferably, the acid treatment unit is a packed tower filled with basic ion exchange resin;

preferably, the outlet of the reactor gas-phase condenser is connected with a reactor gas-phase condensate buffer tank, and the reactor gas-phase condensate can return to the reactor to continuously participate in the reaction;

preferably, a devolatilization system gas phase condensate buffer tank is connected between the devolatilization system gas phase condenser and the acid treatment unit;

preferably, a polymerization inhibitor injection port is arranged on an inlet pipeline of the reactor gas phase condenser;

preferably, the devolatilization temperature of the devolatilizer is 180-240 ℃, and preferably is 200-220 ℃; the devolatilizer absolute pressure is less than 5KPa, preferably less than 2 KPa;

preferably, the temperature of the acid treatment unit is 0-50 ℃, preferably 10-30 ℃; the residence time in the acid treatment unit is 0.1 to 2h, preferably 0.2 to 1 h.

Technical Field

The invention relates to the field of styrene-acrylonitrile copolymers, in particular to a styrene-acrylonitrile copolymer with improved silver streaks and a preparation method and a device thereof.

Background

An acrylonitrile-styrene copolymer (also referred to AS SAN resin or AS resin) is a high molecular polymer formed from styrene and acrylonitrile AS raw materials. The SAN resin copolymer has the advantages of uniform composition, good molecular weight distribution, good transparency, oil resistance, aging resistance and chemical stability, easy dyeing processing and stable size of a finished product. SAN products are widely used in industries such as household appliances, automobile manufacturing, instrument accessories, building materials, daily necessities and the like; can be used for manufacturing various transparent or dyed products, such as high-grade lamps, tape cassettes, instrument covers, decorative plates, automobile tail lamps, refrigerator storage boxes and the like, and can also be used as a composite material for modifying ABS resin. SAN resins have excellent processability and can be molded by injection molding, extrusion, blow molding, and the like.

The SAN resin is produced by continuous bulk polymerization, the reactor is mostly a complete mixed flow reaction kettle, styrene and acrylonitrile are used as monomers, and a small amount of solvent is added for polymerization reaction. Controlling a certain monomer conversion rate, devolatilizing the slurry to obtain styrene-acrylonitrile copolymer resin, removing a reaction system of unreacted monomers and a solvent under a vacuum condition, and condensing for recycling.

The polymerization reaction of styrene and acrylonitrile is a strongly exothermic reaction, and in order to ensure the structural and performance stability of the polymer, it is necessary to control the temperature fluctuation due to the exothermic heat of polymerization. In the polymerization stage of SAN resins, heat removal is generally carried out in the following manner: 1) the majority of the heat of polymerization is carried away by the cold monomer feed. 2) Part of heat can be taken away through a jacket refrigerant, but the temperature of the jacket cannot be too low compared with that in the kettle, otherwise, a reaction solution can form a detention layer on the wall of the kettle. 3) A portion of the heat is removed by vapor phase condensation of the monomer and solvent in the kettle. The gas phase condensation heat transfer is a very effective measure for controlling the temperature stability of the polymerization kettle, but also brings certain problems to the process control. At the same temperature, the saturated vapor pressures of styrene and acrylonitrile are different, resulting in a significant difference between the composition of the monomer entering the gas phase space and the liquid phase.

In the research, the silver streak phenomenon is obvious when SAN resin is processed when the polymerization process adopts gas phase condensation for heat transfer. This phenomenon is more prominent particularly when the amount of gas phase condensation is too great, limiting the use of SAN resins in transparent materials (e.g., cosmetic packaging).

By deeply analyzing the craze texture and continuously tracking the polymerization reaction process, the craze texture of SAN resin can be obviously improved by controlling the content of the polymer in the gas phase condensate in the polymerization stage to be at a lower limit value.

Disclosure of Invention

In order to overcome the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a method for preparing a styrene-acrylonitrile copolymer having more excellent optical properties, particularly having very few silver streaks when used alone as a transparent material.

It is another object of the present invention to provide a styrene-acrylonitrile copolymer.

The invention provides a preparation method of a styrene-acrylonitrile copolymer, which comprises the following steps: adding a styrene monomer, an acrylonitrile monomer, an optional chain transfer agent and an optional solvent mixed solution into a reactor, and carrying out polymerization reaction under certain conditions; and volatilizing partial monomer and solvent gas phase in the reactor, condensing to form reactor gas phase condensate, feeding the reactor gas phase condensate into the reactor again for cyclic reaction, feeding the reacted solution into a devolatilization unit to remove volatile components, condensing the volatile components removed by the devolatilization unit, and feeding the condensed volatile components into the reactor again for reaction, wherein the concentration of the polymer in the reactor gas phase condensate is not higher than 100ppm, preferably not higher than 50 ppm.

The reactor of the invention can adopt a full mixing flow reactor, in particular to a stirring type reaction kettle. The reactor can be a single reactor, or two reactors can be connected in series or two reactors can be connected in parallel. For convenience of illustration, the reactors in the examples of the present invention are all single reaction vessels.

In some preferred embodiments of the invention, the reactor adopts a feeding mode of top-in-bottom-out, the filling level of about 60 percent is controlled, and a gas phase space is reserved at the top of the kettle. The top of the reaction kettle is provided with a gas phase condenser, the condenser is a tubular heat exchanger, and the refrigerant is process water at normal temperature.

When the SAN resin is used alone as a transparent material, the silver streaks of a finished piece after injection molding or extrusion processing are very concerned. Researches find that the polymer content in the gas phase condensate of the polymerization kettle can influence the silver streak effect of the formed product. When the polymer content in the gas phase condensate is controlled to be not higher than 100ppm, a polymer product with low silver streak content can be obtained. In order to further improve the crazing effect, it is preferable to control the polymer content in the gas phase condensate to not more than 50 ppm.

In some preferred embodiments of the present invention, a polymerization inhibitor is added to the gas phase volatiles of the reactor, and the polymerization inhibitor is a substance capable of inhibiting free radical polymerization and can be added in any form. But it is preferable from the viewpoint of achieving the effect of the invention to add in the form of a gas, both of which are mixed in the form of a gas phase before the gas phase condensate is not condensed. Preferably, the boiling point of the inhibitor is less than 150 ℃, more preferably less than 135 ℃.

Preferably, the polymerization inhibitor is a hydroxylamine compound, and can be one or more of hydroxyalkyl hydroxylamine, alkyl hydroxylamine and aryl hydroxylamine, and is preferably diethyl hydroxylamine. The polymerization inhibitor is added in such an amount that the concentration of the polymerization inhibitor is 0.1 to 20ppm, preferably 1 to 10ppm, based on the total amount of the monomer and the solvent in the gas phase. When the concentration of the polymerization inhibitor injected is too low, the polymer content of the gas-phase condensate cannot meet the requirement. When the concentration of the polymerization inhibitor injected is too high, the gas phase condensate returning to the polymerization vessel affects the polymerization rate and the color of the final product.

The polymerization inhibitor may be injected alone or after diluted with a solvent, and is preferably injected after diluted with a solvent. Alternative solvents include one or more of toluene, ethylbenzene, tetrahydrofuran, DMF and the like, preferably toluene or ethylbenzene, more preferably solvents compatible with the polymerization reaction. The concentration of the polymerization inhibitor after dilution may be from 0.05% to 10% by weight, such as: 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt%, etc. When the polymerization inhibitor is injected into the gas phase pipeline, the injection temperature is higher than the boiling point of the polymerization inhibitor, and preferably higher than the boiling point of the polymerization inhibitor by more than 10 ℃. The polymerization inhibitor injection pressure is 0.1-1.0MPa, preferably 0.2-0.5 MPa.

In the raw material monomer, there will generally be a trace amount of impurity acid (such as formic acid, acetic acid, mainly as by-products of the production process of styrene and acrylonitrile), and in general, the trace amount of impurity acid will not participate in the polymerization reaction, and will enter the polymerization reaction system again after being removed in the devolatilization stage, so will accumulate in the reaction system continuously and cause the concentration to increase. It was found that the polymer content of the gas phase condensate could not be brought to 100ppm without further removal of acid from the condensate in the case of the addition of a polymerization inhibitor, probably because the acid in the condensate induces polymerization of the styrene and acrylonitrile monomers.

In some preferred embodiments of the invention, polymerization inhibitors are added to the reactor gas phase volatiles and the total acid content of the reactor gas phase condensate recycled to the reactor is not higher than 100ppm, preferably not higher than 50 ppm.

When the acid content in the gas phase condensate is controlled within a certain range and the polymerization inhibitor is added, the generation of polymers in the condenser in the long-term operation process of the device can be reduced, and the styrene-acrylonitrile copolymer with low silver streak content is prepared.

In some preferred embodiments of the present invention, the volatile component condensate of the devolatilization unit and/or the reactor vapor phase condensate is subjected to acid removal by an acid treatment unit prior to entering the reactor. The temperature of the acid treatment unit is 0 to 50 deg.C, preferably 10 to 30 deg.C. The acid component in the SAN reaction process can be continuously accumulated along with the recycling of devolatilization condensate, when an acid treatment unit is added in the devolatilization stage and/or the reaction liquid gas phase condensation stage, an excessive acid component can be removed from a reaction system, and the accumulated acid treatment unit for reducing the acid component can be a packed tower filled with a filler capable of reacting with the acid, preferably a packed tower filled with basic ion exchange resin, and further preferably a packed tower filled with weak basic anion exchange resin. The weakly basic groups of the weakly basic anion exchange resin include, but are not limited to, primary, secondary, and tertiary amine groups. The acid content of the recovered solution can be controlled to a low level after absorption by the ion exchange resin, so that the acid content does not accumulate in the polymerization reaction system.

In the preparation method of the invention, the temperature in the reactor is 130-170 ℃, and preferably 150-160 ℃. The reaction is kept in the reactor for 1 to 3 hours until the outlet conversion rate is 60 to 85 weight percent. When the conversion is too low, the volatile components to be removed are too high, and there are great problems in terms of energy consumption and energy production. When the conversion rate is too high, the viscosity of reaction liquid is high, and the mass and heat transfer in a reactor is difficult, so that the final application performance of a product is influenced. In some preferred embodiments, the first slurry is left to react in the second reactor for 1.5 to 2 hours to a monomer conversion of 70 to 80 wt%.

Preferably, the mass parts of the components added into the reactor are as follows:

60 to 90 parts by mass, preferably 70 to 80 parts by mass of a styrene monomer,

10 to 40 parts by mass, preferably 20 to 30 parts by mass of a vinylcyanide monomer,

0 to 30 parts by mass, preferably 5 to 20 parts by mass of a solvent,

0 to 0.5 parts by mass, preferably 0.05 to 0.25 parts by mass, of a chain transfer agent;

preferably, the styrenic monomer may be styrene, alpha-methylstyrene, preferably styrene. The acrylonitrile-based monomer may be acrylonitrile or methacrylonitrile, and is preferably acrylonitrile.

In order to reduce the viscosity of the slurry in the polymerization stage, a solvent may be added. Alternative solvents include, but are not limited to, benzene, ethylbenzene, cyclohexane, acetonitrile, tetrahydrofuran, N-dimethylformamide, preferably toluene or ethylbenzene. Preferably, the amount of the solvent added is preferably 5 to 20 wt% based on the total amount of the mixed liquid and the recovering liquid fed into the reactor. The solvent is put into operation and is always circulated in the system during the production process.

In the preparation method provided by the invention, the monomer mixed solution is added with the chain transfer agent besides two monomers of styrene and acrylonitrile so as to control the molecular weight of the polymer within a certain range. In some preferred embodiments, the chain transfer agent added is a mercaptan type chain transfer agent, such as tertiary dodecyl mercaptan, which has a better chain transfer capability with respect to both styrene and acrylonitrile monomers. In some more preferred embodiments, the amount of the chain transfer agent added is preferably 0.05 to 0.2 wt% of the total amount of monomers, based on the total mass of monomers in the mixed raw materials, in order to control the weight average molecular weight of the copolymer to be in the range of 8 to 20 ten thousand.

In addition to chain transfer agents, the present invention may optionally include the addition of initiators as desired. Alternative initiators may be azo-type compounds or peroxy-type compounds, with peroxy-type compounds being preferred from the standpoint of raw material source. The choice of initiator can be chosen according to common knowledge in the art with reference to the half-life at the reaction temperature, preferably an initiator having a half-life of 1-30min at the reaction temperature. The amount of initiator added is from 10 to 1000ppm, preferably from 50 to 500ppm, based on the total monomer mass.

In the preparation method provided by the invention, after the polymerization reaction is finished, the obtained slurry is subjected to devolatilization treatment to remove volatile components in the slurry, wherein the volatile components comprise styrene monomers, acrylonitrile monomers, solvents, oligomers, accumulated organic impurities in a reactor and the like. The devolatilization process may be any devolatilization process used in conventional styrene and acrylonitrile copolymerization processes, such as one-stage or multi-stage devolatilization. The alternative devolatilizer may be one or a combination of flash tank, falling film devolatilizer, scraped devolatilizer, twin screw extruder, twin screw devolatilizer. The falling strand devolatilizer is preferably used from the viewpoint of both productivity and cost.

The top of the devolatilizer is provided with a preheater which is needed to preheat the slurry coming out of the polymerizer to the devolatilization temperature so as to improve the supersaturation degree of the slurry. The temperature of the melt in the devolatilization unit is controlled to be 180-240 ℃, and is preferably controlled to be 200-220 ℃. The absolute pressure in the devolatilizer is required to be controlled to be within 5KPa, preferably within 2 KPa. The volatile components after devolatilization are mainly unreacted monomers and solvents, and are recycled after being condensed by a low-temperature refrigerant.

In the preparation method provided by the invention, any type of auxiliary agent with any content commonly used in the field can be added in the process according to the required copolymer performance, including but not limited to a release agent, an ultraviolet absorbent, an antioxidant, a coloring agent and the like.

By controlling the process conditions, the prepared styrene-acrylonitrile copolymer has good mechanical properties (such as tensile strength, bending strength, impact strength and the like) and good optical properties.

Therefore, the invention also provides a styrene-acrylonitrile copolymer prepared by the preparation method of any one of the technical schemes.

The invention also provides a device for preparing the styrene-acrylonitrile copolymer, which comprises a reactor, a devolatilization device, a reactor gas phase condenser, a devolatilization system gas phase condenser and an acid treatment unit, wherein a reactor gas phase outlet is connected with the reactor gas phase condenser, a reactor discharge port is connected with the devolatilization device, a devolatilization device gas phase outlet is connected with the devolatilization system gas phase condenser, and an acid treatment unit is further connected to an outlet pipeline of the devolatilization system gas phase condenser and/or the reactor gas phase condenser.

Preferably, the acid treatment unit is a packed column packed with a basic ion exchange resin, preferably a weakly basic anion exchange resin.

Preferably, the outlet of the reactor gas phase condenser is connected with a reactor gas phase condensate buffer tank, and the reactor gas phase condensate can return to the reactor to continuously participate in the reaction.

Preferably, a devolatilization system gas phase condensate buffer tank is connected between the devolatilization system gas phase condenser and the acid treatment unit, and the devolatilization system gas phase condensate can return to the reactor to continuously participate in the reaction after deacidification is performed by the acid treatment unit.

Preferably, a polymerization inhibitor injection opening is arranged on an inlet pipeline of the reactor gas phase condenser.

Preferably, the devolatilizer may be one of a falling-bar devolatilizer, a falling-film devolatilizer, and a screw extruder, and is preferably a falling-bar devolatilizer.

Preferably, the devolatilization temperature of the devolatilizer is 180-240 ℃, and preferably is 200-220 ℃; the devolatilizer absolute pressure is below 5KPa, preferably below 2 KPa.

Preferably, the temperature of the acid treatment unit is 0-50 ℃, preferably 10-30 ℃; the proper temperature range is controlled to facilitate the absorption of acid. The retention time of the recovery liquid in the acid treatment unit is 0.1-2h, preferably 0.2-1 h. When the residence time is too short, the acid content is difficult to achieve the target requirement. When the residence time is too long, the production efficiency is affected.

In the styrene-acrylonitrile copolymer provided by the invention, the acrylonitrile content in the finally obtained copolymer can be changed according to the addition amount of the acrylonitrile monomer. In some preferred embodiments, the styrene-acrylonitrile copolymer provided by the invention has an acrylonitrile content of 10 to 35 wt%; more preferably, the acrylonitrile content is 20 to 30 wt%. The styrene-acrylonitrile copolymer provided by the invention can be prepared into common products in any form and any type according to a common processing and forming process, can be suitable for any common application field or application occasion, and is particularly suitable for application fields such as cosmetic packaging, food containers, refrigerator fresh-keeping boxes, dust covers, lighters, transparent parts of household appliances and the like.

The styrene-acrylonitrile copolymer prepared by the preparation method of the styrene-acrylonitrile copolymer provided by the invention has excellent optical performance, and particularly has extremely low silver streaks after injection molding. In addition, the preparation method of the invention has simple and convenient process, is easy to control, does not need complex equipment, and is very suitable for large-scale industrial production.

Drawings

FIG. 1 is a schematic view of a system for producing a styrene-acrylonitrile copolymer according to an embodiment of the present invention;

wherein the reference numbers are as follows:

10. monomer mixed solution; 20. a gas phase condensate; 30. devolatilizing the condensate; 40. a polymerization inhibitor injection port and a polymerization inhibitor; 50. SAN resin; r101, a reactor; d101, a devolatilization device; e101, a reactor gas phase condenser; e102, a devolatilizer preheater; e103, a devolatilization system gas phase condenser; v101, a reactor gas phase condensate buffer tank; v102, a devolatilization system gas phase condensate buffer tank; m101, a static mixer; t101 and an acid treatment unit.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the following specific examples.

In the examples of the present invention and the comparative examples, the sources of the raw materials are shown in table 1.

Table 1 raw material source information

Name of raw materials	For short	Rank of	Suppliers of goods
				Styrene (meth) acrylic acid ester	SM	Industrial grade	Qilu petrochemical
Acrylonitrile	AN	Industrial grade	Jilin petrochemical
				Tertiary ten of tenDialkyl mercaptan	t-DDM	Industrial grade	Chevrolet dragon
Toluene	TN	Industrial grade	Qilu petrochemical
				Diethylhydroxylamine	DEHA	Reagent grade	Aladdin
Weakly basic ion exchange resins	IRA96SB	Industrial grade	Chemistry of Dow
				Weakly acidic ion exchange resin	IRC86	Industrial grade	Chemistry of Dow

In the examples and comparative examples of the present invention, the methods for measuring the molecular weight, solid content and monomer conversion of the polymer were as follows:

molecular weight measurement

The molecular weight was measured by liquid gel chromatography (GPC), mobile phase Tetrahydrofuran (THF), detector using a parallax refractometer, and monodisperse polystyrene as a standard.

Solid content and monomer conversion test

The solid content was measured by sampling from the reactor outlet by a sampler, respectively. The test method is as follows: weighing 1g of reaction solution, placing the reaction solution in tin foil paper (the tin foil paper is weighed in advance), placing the tin foil paper in a vacuum oven at 160 ℃, controlling the absolute pressure to be less than 1KPa, vacuumizing for 0.5h, taking out the tin foil paper, cooling the tin foil paper at room temperature, and weighing the dried dry base resin. The solids content can be calculated by dividing the mass of the dry resin by the mass of the reaction solution. The solids content was repeated three times per sample and averaged.

The monomer conversion is obtained by dividing the solid content by the monomer content in the reaction solution (i.e. the total monomer mass divided by the total reaction solution mass).

Acid content test

The acid content is determined by a chemical titration method according to the national standard GB/T7717.5-2008.

Silver streak test

The styrene-acrylonitrile copolymer was processed by an injection molding machine into square sheets of size 80 x 70mm x 3 mm. An injection pressure of 50kgf/cm2 was set by an injection molding machine. And observing the silver stripes in the sheet through a magnifier, classifying the number of the silver stripes with different sizes, and grading the styrene-acrylonitrile copolymer according to the number of the silver stripes. The number of test pieces in each experiment was 6, and the average value was taken.

TABLE 2 injection moulding sheet silver rating Standard

Size of silver line	Class A	Class B	Class C
				5-10mm	≤10	11-20	>20
10-20mm	≤5	6-10	>10
				Greater than 20mm	0	1-2	>2
Total up to	<12	<20	>30

The polymer properties were measured as shown in Table 3.

TABLE 3 Polymer Performance test standards and conditions

Test items	Test standard	Test conditions
			Light transmittance	ISO 13486	3mm
Haze degree	ISO 14782	3mm
			Melt Flow Rate (MFR)	ISO 1133	220℃，10KG
Heat Distortion Temperature (HDT) load	ISO 75	1.8MPa, annealing
			Charpy impact Strength	ISO 179	1eU, no gap
Tensile strength	ISO 527	1A/5
			Elongation at break	ISO 527	1A/5
Bending strength	ISO 527	1A/5
			Yellowing index	ASTM D1925	C/2，3mm

The embodiment 1-2 of the invention adopts a reaction system as shown in fig. 1, which comprises a reactor R101, a devolatilizer D101, a reactor gas-phase condenser E101, a devolatilization system gas-phase condenser E103 and an acid treatment unit T101, wherein a gas-phase outlet of the reactor R101 is connected with the reactor gas-phase condenser E101, the reactor gas-phase condenser E101 is connected with a reactor gas-phase condensate buffer tank V101, a discharge port of the reactor is connected with the devolatilizer D101, the devolatilizer D101 is provided with a devolatilizer preheater E102, a gas-phase outlet of the devolatilizer D101 is connected with the devolatilization system gas-phase condenser E103, an outlet pipeline of the devolatilization system gas-phase condenser E103 is also connected with a devolatilization system gas-phase condensate buffer tank V102 and an acid treatment unit T101, and the devolatilization system gas-phase condensate is treated by the acid treatment unit and then returns to be added into the reactor together with.

And a polymerization inhibitor injection port 40 is arranged on an inlet pipeline of the reactor gas-phase condenser.

In the embodiment of the invention, the acid treatment unit T101 is a packed tower filled with weak base ion exchange resin. The reactor adopts a feeding mode of top-in and bottom-out, the filling liquid level of about 60 percent is controlled, and a gas phase space is reserved at the top of the kettle. The top of the reactor is provided with a gas phase condenser which is a shell and tube heat exchanger, and the refrigerant is process water at normal temperature.