阅读说明：本技术 制备共聚物的方法、由该方法制备的共聚物和包含该共聚物的热塑性树脂组合物 (Method for preparing copolymer, copolymer prepared by the method, and thermoplastic resin composition comprising the copolymer ) 是由 朱玟徹 申珉承 洪晟元 金仁秀 李亨燮 于 2020-10-27 设计创作，主要内容包括：本发明涉及一种制备共聚物的方法、由该方法制备的共聚物和包含该共聚物的热塑性树脂组合物,所述方法包括：步骤(S10),加入芳香族乙烯基类单体和乙烯基氰基类单体以在聚合引发剂的存在下进行聚合,其中,所述聚合引发剂包括至少两种不同种类的聚合引发剂,并且在步骤(S10)中在所述聚合过程中将部分或全部的芳香族乙烯基类单体连续分开加入。(The present invention relates to a method for preparing a copolymer, the copolymer prepared by the method, and a thermoplastic resin composition comprising the copolymer, the method comprising: a step (S10) of adding an aromatic vinyl monomer and a vinyl cyano monomer to perform polymerization in the presence of a polymerization initiator, wherein the polymerization initiator includes at least two different kinds of polymerization initiators, and a part or all of the aromatic vinyl monomer is continuously added separately during the polymerization in the step (S10).)

1. A method of making a copolymer comprising: a step (S10) of adding an aromatic vinyl monomer and a vinyl cyano monomer to carry out polymerization in the presence of a polymerization initiator,

wherein the polymerization initiator includes at least two different kinds of polymerization initiators, and a part or all of the aromatic vinyl-based monomer is continuously and separately added during the polymerization in the step (S10).

2. The method of claim 1, wherein the polymerization initiator comprises a monomer selected from the group consisting of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, di (t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide, di-t-amyl peroxide, dicumyl peroxide, butyl 4, 4-di (t-butylperoxy) valerate, t-butyl peroxybenzoate, 2-di (t-butylperoxy) butane, t-amyl peroxybenzoate, t-butyl peroxyacetate, t-butyl peroxy (2-ethylhexyl) carbonate, t-butyl peroxyisopropylcarbonate, t-butyl peroxy3, 5, 5-trimethylhexanoate, 1-bis (t-butylperoxy) cyclohexane, t-amyl peroxyacetate, t-amyl peroxy (2-ethylhexyl) carbonate, t-amyl peroxycarbonate, and mixtures thereof, 1, 1-bis (t-butylperoxy) -3,5, 5-trimethylcyclohexane, 1-bis (t-amylperoxy) cyclohexane, t-butyl monoperoxymaleate, 1 '-azobis (cyclohexanecarbonitrile), 1' -azobis (cyclohexane-1-carbonitrile), and 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane).

3. The method according to claim 1, wherein the at least two different kinds of polymerization initiators are added in an amount of 0.001 parts by weight to 1.000 parts by weight with respect to 100 parts by weight of the total monomers added.

4. The method of claim 1, wherein the polymerization initiator comprises a first polymerization initiator and a second polymerization initiator, the first polymerization initiator is different from the second polymerization initiator, and the first polymerization initiator and the second polymerization initiator are added in a weight ratio of 10:1 to 1: 10.

5. The method of claim 1, wherein the aromatic vinyl monomer comprises a styrene monomer substituted with an alkyl group.

6. The method according to claim 1, wherein part or all of the aromatic vinyl-based monomer is continuously added separately from a time point at which the polymerization is initiated in step (S10).

7. The method according to claim 1, wherein part or all of the aromatic vinyl monomers are continuously added separately during the polymerization to a time point of 70.00% or less than 70.00% of the total polymerization time in step (S10).

8. The method according to claim 1, wherein 5 to 30 parts by weight of the aromatic vinyl-based monomer is continuously and separately added during the polymerization in the step (S10) with respect to 100 parts by weight of the total monomer added.

9. The method according to claim 1, wherein part or all of the aromatic vinyl monomer is continuously added separately during the polymerization in step (S10) while maintaining a constant rate.

10. A copolymer comprising an aromatic vinyl monomer unit and a vinyl cyano monomer unit,

wherein the heating residue is more than 97.6% as calculated by the following equation 1:

[ equation 1]

Heating residue (%) × 100 (weight of copolymer after retention in oven/weight of copolymer before retention in oven) × 100

Wherein the residence in the oven is performed at 250 ℃ for 2 hours in equation 1 above.

11. The copolymer according to claim 10, wherein a standard deviation of a content of the vinyl cyano monomer unit of the copolymer in the copolymer is 0.20 or less, the content being measured as a change in polymerization time during polymerization.

12. A thermoplastic resin composition comprising: the copolymer of claim 10; and a thermoplastic resin.

Technical Field

Cross reference to related applications

This application claims the benefit of priority from korean patent application No.10-2019-0150368, filed on 21/11/2019, the disclosure of which is incorporated in its entirety by reference into this specification.

The present invention relates to a method of preparing a copolymer, and more particularly, to a method of preparing a copolymer using an aromatic vinyl-based monomer and a vinyl cyano-based monomer, a copolymer prepared by the method, and a thermoplastic resin composition comprising the copolymer.

Background

In general, styrenic copolymers have been widely used in various industrial fields including office automation equipment such as computers, printers and copiers, household electric appliances such as televisions and audio equipment, electric and electronic parts, automobile parts, and other miscellaneous goods because of their excellent moldability, rigidity and electrical characteristics.

In particular, heat-resistant styrene-based copolymers and diene-based graft copolymers such as ABS resins have been mixed and used for articles such as interior or exterior materials of automobiles requiring heat resistance. Here, the heat-resistant styrenic copolymer is prepared by adding a heat-resistant monomer such as a maleimide-based monomer or an α -methylstyrene monomer, but the maleimide-based monomer has a limitation of being expensive and having difficulty in controlling reactivity in polymerization, and the α -methylstyrene monomer has excellent processability and good color, but has a limitation of having low reactivity in polymerization. Further, when a heat-resistant styrenic copolymer using a heat-resistant monomer such as an α -methylstyrene monomer is used by mixing with a diene-based graft copolymer, the heat resistance is superior to the styrenic copolymer, but the thermal stability at the extrusion processing temperature is poor, thereby generating gas during the extrusion processing, and thus there is a disadvantage in that it has an adverse effect on workers who perform the extrusion processing.

Meanwhile, styrenic copolymers comprising a heat-resistant styrenic copolymer are generally prepared by emulsion polymerization, suspension polymerization or bulk polymerization. When the emulsion polymerization method is used, there are advantages in that the prepared particle size is smaller than that by other polymerization methods, and thus the surface area involved in the polymerization is widely distributed so that the temperature of the reaction system is easily controlled and the polymerization can be performed in a short time, stable polymerization is achieved, but unreacted monomers, polymerization additives, etc. remain in the polymer to cause a problem of coloring or discoloration of the copolymer, and since a coagulation process should be performed to prepare a slurry after the polymerization reaction, and a post-treatment process of washing, dehydrating, and drying the slurry should be performed, there are limitations in production efficiency, equipment, and wastewater treatment.

On the contrary, when the suspension polymerization method and the bulk polymerization method are used, there are advantages in that less additives are required during the polymerization process as compared with the emulsion polymerization, and the post-treatment process is simpler than the emulsion polymerization, and thus coloring hardly occurs on the final product. However, when the bulk polymerization method is used, productivity may be superior to other polymerization methods, but there is a limitation in applying the bulk polymerization method to a small-scale batch production. On the other hand, for suspension polymerization, the amount of the additive used is small, the post-treatment process is relatively simple, and suspension polymerization can be easily applied to small-volume batch production.

The suspension polymerization method generally performs polymerization by adding water, a dispersant, a monomer and a polymerization initiator together, and when a monomer partially dissolved in water is used, the ratio of the monomer introduced at the initial stage and the ratio of the monomer participating in the initial polymerization become different. For example, when suspension polymerization is performed using an aromatic vinyl-based monomer and a vinyl cyanide-based monomer, some of the vinyl cyanide-based monomer is dissolved in water, and at the beginning of polymerization reaction, the vinyl cyanide-based monomer participating in polymerization is different from the ratio of addition. As a result, there may occur a defect that a polymer having a non-uniform composition, for example, only the vinyl cyanide-based monomer is continuously bonded to the end of the polymer chain, and thus physical properties of the copolymer are deteriorated and yellowness is increased.

Therefore, when a heat-resistant styrenic copolymer is produced by suspension polymerization, in order to compensate for the disadvantages of the suspension polymerization method as described above, a method of separately adding a heat-resistant monomer such as an α -methylstyrene monomer during polymerization after initiation of polymerization has been proposed, thereby reducing the nonuniformity of monomer units in the copolymer, but the thermal stability at the extrusion processing temperature is still poor.

Therefore, there is a need to develop a method for producing a heat-resistant styrenic copolymer whose monomer units have reduced heterogeneity in the copolymer and improved thermal stability at extrusion processing temperature at the same time.

[ Prior art documents ]

[ patent document ]

(patent document 1) JP3241815B2

Disclosure of Invention

Technical problem

An aspect of the present invention provides a method for preparing a copolymer whose monomer units have reduced heterogeneity in the copolymer and at the same time, have excellent thermal stability.

Technical scheme

According to an aspect of the present invention, there is provided a method of preparing a copolymer, comprising: a step (S10) of adding an aromatic vinyl-based monomer and a vinyl cyano-based monomer to perform polymerization in the presence of a polymerization initiator, wherein the polymerization initiator includes at least two different kinds of polymerization initiators, and a part or all of the aromatic vinyl-based monomer is continuously added separately during the polymerization in the step (S10).

According to another aspect of the present invention, there is provided a copolymer comprising aromatic vinyl-based monomer units and vinyl cyano-based monomer units, wherein the heating residue is 97.6% or more as calculated by the following equation 1:

[ equation 1]

Heating residue (%) × 100 (weight of copolymer after retention in oven/weight of copolymer before retention in oven) × 100

Wherein the residence in the oven is performed at 250 ℃ for 2 hours in equation 1 above.

According to another aspect of the present invention, there is provided a thermoplastic resin composition comprising the copolymer and a thermoplastic resin.

Advantageous effects

When a copolymer is produced by using the method for producing a copolymer according to the present invention, a styrenic copolymer having reduced heterogeneity of monomer units in the copolymer can be produced.

Further, when a copolymer is produced by using the method for producing a copolymer according to the present invention, a heat-resistant styrenic copolymer having excellent thermal stability can be produced.

In addition, since the monomer units in the copolymer are uniformly distributed and excellent in thermal stability, the copolymer prepared according to the present invention has an effect of preventing gas generation during extrusion.

Detailed Description

Hereinafter, the present invention will be described in more detail to help understanding the present invention.

The terms or words used in the present specification and claims should not be construed restrictively as a conventional meaning or a dictionary-based meaning, but should be construed as a meaning and concept conforming to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of the terms to explain the invention in the best way.

Unless otherwise defined, terms and measurement methods used in the present invention may be defined as follows.

The term "composition" as used in the present invention comprises: comprising a substance of corresponding composition and a mixture of reaction products and decomposition products formed from the substance of corresponding composition.

The term "monomer unit" as used in the present invention may refer to a repeating unit formed when a compound used as a monomer participates in a polymerization reaction, as well as a structure or a substance itself derived therefrom.

The term "derivative" used in the present invention may refer to a compound having a structure in which at least one hydrogen atom constituting the original compound is substituted with a halogen group, an alkyl group or a hydroxyl group.

The "polymerization conversion" in the present invention means the degree of polymerization of a monomer by polymerization to form a polymer, which can be calculated from the following equation 2 by taking some polymer in a reactor during polymerization.

[ equation 2]

Polymerization conversion (%) - (total amount of charged monomer-total amount of reacted monomer)/total amount of charged monomer ] × 100

The present invention provides a method for producing a copolymer whose monomer units have reduced nonuniformity in the copolymer and which has excellent thermal stability.

The method for producing a copolymer according to the present invention may be a method for producing a styrenic copolymer, and as a specific example, may be a method for producing a heat-resistant styrenic copolymer.

The method for preparing a copolymer according to the present invention is characterized by comprising: a step (S10) of adding an aromatic vinyl monomer and a vinyl cyano monomer to perform polymerization in the presence of a polymerization initiator, wherein the polymerization initiator includes at least two different kinds of polymerization initiators, and a part or all of the aromatic vinyl monomer is continuously added separately during the polymerization in the step (S10).

According to one embodiment of the present invention, the polymerization in the step (S10) may be performed by a suspension polymerization method. Suspension polymerization has the advantages of using small amounts of additives, relatively simple work-up procedures and easy application to even small batch production. The suspension polymerization method is a batch polymerization, which is carried out by adding the reactants including the monomer for polymerization to the reactor together before initiation of the polymerization. In this case, the vinyl cyanide-based monomer having small water solubility is dissolved in the water-soluble solvent, so that the aromatic vinyl-based monomer and only some of the vinyl cyanide-based monomer participate in the polymerization reaction in the initial stage of the polymerization, and only the vinyl cyanide-based monomer keeps continuing the polymerization reaction as the polymerization reaction proceeds to the later stage. Therefore, only the vinyl cyano-based monomer unit is continuously bonded to the terminal of the copolymer, and thus a copolymer in which monomer units forming the copolymer have unevenness is prepared, thereby having a limitation in color, for example, an increase in yellowness.

Therefore, when a copolymer is produced by a suspension polymerization method, in order to compensate for the above-mentioned disadvantages of the suspension polymerization method, a method of separately adding a heat-resistant monomer such as an α -methylstyrene monomer during polymerization after initiation of polymerization has been proposed, and thus the heterogeneity of monomer units in the copolymer has been reduced, but the thermal stability at the extrusion processing temperature is still poor.

However, according to the method of preparing a copolymer of the present invention, when at least two different kinds of polymerization initiators are added as the polymerization initiators, a low-temperature polymerization initiator that initiates polymerization at a relatively low temperature among the at least two kinds of polymerization initiators initiates polymerization from an initial stage of the polymerization reaction, and even if the low-temperature polymerization initiator is insufficient at a later stage of the polymerization reaction (for example, a time point at which the polymerization conversion rate is 50% to 100%), a high-temperature polymerization initiator that initiates polymerization at a relatively high temperature among the at least two kinds of polymerization initiators makes up for the insufficient low-temperature polymerization initiator, so that the polymerization reaction can be maintained while the polymerization reaction rate is not decreased at the later stage of the polymerization reaction. When a part or all of the aromatic vinyl monomers are continuously and separately added during the polymerization, the content of the aromatic vinyl monomers capable of participating in the polymerization reaction in the reaction system is controlled according to the polymerization conversion rate and the polymerization reaction rate, and thus the monomer units in the copolymer can be uniformly formed, thereby having the effects of reducing the non-uniformity of the monomer units in the prepared copolymer and achieving excellent thermal stability.

Meanwhile, even though at least two different kinds of polymerization initiators are added as the polymerization initiators, unlike the method of preparing the copolymer according to the present invention, when a part or all of the aromatic vinyl-based monomers are co-added before initiating polymerization, monomer units in the copolymer are still non-uniform due to a difference in reactivity between each monomer.

According to an embodiment of the present invention, the polymerization initiator may include a monomer selected from the group consisting of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, di (t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide, di-t-amyl peroxide, dicumyl peroxide, butyl 4, 4-di (t-butylperoxy) valerate, t-butylperoxybenzoate, 2-di (t-butylperoxy) butane, t-amyl peroxybenzoate, t-butyl peroxyacetate, t-butyl peroxy (2-ethylhexyl) carbonate, t-butyl peroxyisopropylcarbonate, t-butyl peroxy3, 5, 5-trimethylhexanoate, 1-bis (t-butylperoxy) cyclohexane, t-amyl peroxyacetate, t-amyl peroxy (2-ethylhexyl) carbonate, t-amyl peroxycarbonate, 1, 1-bis (t-butylperoxy) -3,5, 5-trimethylcyclohexane, 1-bis (t-amylperoxy) cyclohexane, t-butyl monoperoxymaleate, 1 '-azobis (cyclohexanecarbonitrile), 1' -azobis (cyclohexane-1-carbonitrile), and 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane). For example, the polymerization initiator may include a low-temperature polymerization initiator that initiates polymerization at a relatively low temperature and a high-temperature polymerization initiator that initiates polymerization at a relatively high temperature. In this case, the low-temperature polymerization initiator and the high-temperature polymerization initiator may be respectively selected from the polymerization initiators listed above, a polymerization initiator that initiates polymerization at a relatively low temperature among the selected polymerization initiators may be a low-temperature polymerization initiator, and a polymerization initiator that initiates polymerization at a relatively high temperature among the selected polymerization initiators may be a high-temperature polymerization initiator. As more specific examples, the polymerization initiator may be 1, 1-bis (t-butylperoxy) cyclohexane and t-butylperoxybenzoate, in which case 1, 1-bis (t-butylperoxy) cyclohexane may be a low-temperature polymerization initiator and t-butylperoxybenzoate may be a high-temperature polymerization initiator. When the polymerization is initiated by including at least two of the above-listed polymerization initiators, the polymerization reaction temperature is maintained within a suitable range, thus preventing depolymerization that may occur at a high polymerization temperature (e.g., above 110 ℃) and preventing reduction in polymerization reactivity that may occur at a low polymerization temperature (e.g., below 90 ℃), thereby having an effect of being able to produce a copolymer at a high polymerization conversion rate.

Further, according to an embodiment of the present invention, the polymerization initiators of at least two different kinds may be added in an amount of 0.001 parts by weight to 1.000 parts by weight, 0.1000 parts by weight to 1.000 parts by weight, or 0.500 parts by weight to 0.700 parts by weight, relative to 100 parts by weight of the total monomers added, and have the effect of being able to produce a copolymer at a high polymerization conversion rate within the above range. Here, the addition amount of the at least two different kinds of polymerization initiators may be the addition amount of the whole polymerization initiators.

Meanwhile, according to an embodiment of the present invention, each of the at least two different kinds of polymerization initiators may be added in an amount of 0.001 parts by weight to 1.000 parts by weight, 0.010 parts by weight to 0.800 parts by weight, or 0.100 parts by weight to 0.500 parts by weight, relative to 100 parts by weight of the total monomer added amount, and the addition amount of each polymerization initiator may be selected within the above range of the total polymerization initiator added amount.

According to an embodiment of the present invention, the polymerization initiator may include a first polymerization initiator and a second polymerization initiator different from each other, and the first polymerization initiator and the second polymerization initiator may be added in a weight ratio of 10:1 to 1:10, 10:1 to 1:5, or 5:1 to 1: 5. In this case, the first polymerization initiator may be a low-temperature polymerization initiator, and the second polymerization initiator may be a high-temperature polymerization initiator, in the above-mentioned weight ratio range, having the following effects: even if the low-temperature polymerization initiator is insufficient at the latter stage of the polymerization reaction (for example, at a time point at which the polymerization conversion is 50% to 100%), the high-temperature polymerization initiator compensates for the insufficient low-temperature polymerization initiator, so that the polymerization reaction can be maintained at the latter stage of the polymerization reaction without a decrease in the polymerization reaction rate.

According to an embodiment of the present invention, the aromatic vinyl monomer may be at least one selected from the group consisting of styrene, α -methylstyrene, α -ethylstyrene, p-methylstyrene, o-tert-butylstyrene, bromostyrene, chlorostyrene, trichlorostyrene and derivatives thereof.

According to an embodiment of the present invention, the aromatic vinyl monomer may include a styrene monomer substituted with an alkyl group. The styrene monomer substituted with an alkyl group may be at least one selected from the group consisting of α -methylstyrene, α -ethylstyrene, p-methylstyrene, o-methylstyrene and o-tert-butylstyrene, and may be a heat-resistant monomer for imparting heat resistance to the copolymer.

Further, according to an embodiment of the present invention, the aromatic vinyl-based monomer may include: styrene; and at least one selected from the group consisting of alpha-methylstyrene, alpha-ethylstyrene, p-methylstyrene, o-methylstyrene and o-tert-butylstyrene.

According to an embodiment of the present invention, part or all of the aromatic vinyl monomer may be continuously added separately from the time point of polymerization initiation in the step (S10) or from the time point of 10.00% or more than 10.00% of the total polymerization time during the polymerization in the step (S10). As another embodiment, a part or all of the aromatic vinyl-based monomer is continuously and separately added in step (S10) from the time point of polymerization initiation or from the time point of polymerization conversion rate of 5% or more than 5% according to polymerization. Therefore, when a part or all of the aromatic vinyl-based monomer is continuously and separately added from the initial stage of the polymerization reaction, there is an effect of improving the uniformity of monomer units in the prepared polymer to improve thermal stability.

Further, according to an embodiment of the present invention, a part or all of the aromatic vinyl-based monomer may be continuously added separately from a time point of initiation of polymerization in step (S10) or from a time point of 10.00% to 20.00% or 10.00% to 16.67% of the total polymerization time during polymerization in step (S10). As another embodiment, part or all of the aromatic vinyl-based monomer is continuously and separately added in step (S10) from the time point of polymerization initiation or from the time point of polymerization conversion rate of 5% to 40% or 5% to 31% according to polymerization.

Further, according to an embodiment of the present invention, as a preferred embodiment, part or all of the aromatic vinyl monomer may be continuously added separately from the time point of polymerization initiation in the step (S10), and in this case, the content of the aromatic vinyl monomer capable of participating in the polymerization reaction in the reaction system may be more easily controlled according to the polymerization conversion rate and the polymerization reaction rate, thereby having the effects of reducing the non-uniformity of monomer units in the produced copolymer and achieving excellent thermal stability.

Here, the time point of polymerization initiation in the step (S10) may refer to: the point in time at which the initial temperature is reached when the temperature is raised to the polymerization temperature for carrying out the polymerization reaction, in the presence of added monomers, before the initiation of the polymerization. In addition, in the course of raising the temperature to the polymerization temperature for carrying out the polymerization reaction, some polymerization may be carried out before reaching the initial temperature, and in this case, the point of time at which the initial temperature is reached may be a point of time at which the polymerization conversion rate is 5% or less. That is, according to an embodiment of the present invention, a part or all of the aromatic vinyl-based monomer may be continuously added separately from the time point when the initial temperature is reached in the step (S10).

According to an embodiment of the present invention, part or all of the aromatic vinyl monomer may be continuously and separately added during the polymerization to a time point of 70.00% or less than 70.00% of the total polymerization time in step (S10). As another embodiment, part or all of the aromatic vinyl-based monomer may be continuously added separately in step (S10) to a point of time when the polymerization conversion rate according to the polymerization is 85% or less than 85%. When part or all of the aromatic vinyl-based monomer is continuously and separately added up to the time point, the copolymer in the reaction system polymerized according to the polymerization conversion rate is smoothly mixed with the continuously and separately added monomer, so that it is possible to prevent the preparation of a polymer (e.g., oligomer, single polymer, etc.) different from the copolymer in the reaction system. Therefore, there is an effect of preventing deterioration of physical properties and occurrence of haze, which may occur due to the residue of monomers not participating in the polymerization reaction and polymers different from the copolymer in the reaction system.

Further, according to an embodiment of the present invention, part or all of the aromatic vinyl monomer may be continuously and separately added during the polymerization to a time point of 50.00% to 70.00% or 50.00% to 66.67% of the total polymerization time in step (S10). As another embodiment, part or all of the aromatic vinyl monomer is continuously and separately added in the step (S10) to a point of time when the polymerization conversion rate according to the polymerization is 71% to 85%.

Further, according to an embodiment of the present invention, part or all of the aromatic vinyl-based monomer may be continuously and separately added during the polymerization from the time point of polymerization initiation to the time point of 70.00% or less than 70.00% of the total polymerization time in the step (S10), or may be continuously and separately added from the time point of polymerization initiation to the time point of polymerization conversion of 85% or less than 85% in the step (S10).

Further, according to an embodiment of the present invention, the aromatic vinyl monomer may be continuously and separately added from a time point of polymerization initiation to a time point of 50.00% or less than 66.67% of the total polymerization time during the polymerization in step (S10), or may be continuously and separately added from a time point of polymerization initiation to a time point of polymerization conversion of 71% to 85% in step (S10).

Further, according to an embodiment of the present invention, the aromatic vinyl-based monomer may be added in an amount of 50 to 90 parts by weight, 60 to 80 parts by weight, or 70 to 80 parts by weight, relative to 100 parts by weight of the total monomers. Here, the addition content of the aromatic vinyl-based monomer may be the addition content of the aromatic vinyl-based monomer when all the aromatic vinyl-based monomers are continuously and separately added in the polymerization process of the step (S10), or the addition content of the aromatic vinyl-based monomer may be the total content of the aromatic vinyl-based monomer which is commonly added before the initiation of polymerization in the step (S10) when part of the aromatic vinyl-based monomers are continuously and separately added in the polymerization process of the step (S10), and the aromatic vinyl-based monomer which is continuously and separately added in the polymerization process in the step (S10).

Further, according to an embodiment of the present invention, the aromatic vinyl-based monomer may be continuously and separately added in the polymerization process in the step (S10) by 5 parts by weight to 30 parts by weight, 10 parts by weight to 30 parts by weight, or 15 parts by weight to 25 parts by weight with respect to 100 parts by weight of the total monomer added amount, and in this case, since the polymerization rate may be maintained at a suitable rate by preventing the polymerization rate from being sharply increased, there is an effect that a copolymer can be prepared at a high polymerization conversion rate. Here, the addition content of the aromatic vinyl monomer may be a content of the aromatic vinyl monomer which is continuously and separately added during the polymerization in step (S10) when part of the aromatic vinyl monomer is continuously and separately added during the polymerization in step (S10).

Further, according to an embodiment of the present invention, part or all of the aromatic vinyl-based monomer may be continuously and separately added while maintaining a constant rate during the polymerization in step (S10). Here, the constant rate may refer to an addition rate of the aromatic vinyl monomer continuously and separately added, and as a specific example, the constant rate may refer to a constant flow rate. That is, according to an embodiment of the present invention, when a part or all of the aromatic vinyl monomer is continuously added separately while maintaining a constant rate, the part or all of the aromatic vinyl monomer may be continuously added while maintaining a constant flow rate from a start point to an end point when the part or all of the aromatic vinyl monomer is separately added. Therefore, in the case where part or all of the aromatic vinyl-based monomers are continuously added separately while maintaining a constant rate, the content of the aromatic vinyl-based monomers remaining in the reaction system can be appropriately controlled, as compared with the case where the monomers are added separately together in a certain amount at a specific time point, so that the difference in polymerization rate due to the difference in reactivity between the monomers can be minimized. Therefore, there is an effect of reducing the nonuniformity of monomer units in the produced copolymer and achieving excellent thermal stability while the polymerization rate is kept constant.

According to an embodiment of the present invention, the vinyl cyano-based monomer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and derivatives thereof, and may be acrylonitrile as a specific example.

Further, according to an embodiment of the present invention, the vinyl cyano-based monomer may be added in an amount of 10 parts by weight to 50 parts by weight, 20 parts by weight to 40 parts by weight, or 20 parts by weight to 30 parts by weight, relative to 100 parts by weight of the total monomers added, within this range, having the following effects: the copolymer can be obtained at a high polymerization conversion rate and has excellent compatibility with the thermoplastic resin while the mechanical properties of the copolymer are maintained.

Further, according to an embodiment of the present invention, the vinyl cyano-based monomers may be co-added before polymerization in step (S10).

Meanwhile, according to an embodiment of the present invention, the method of preparing the copolymer may be performed by a suspension polymerization method, and thus may be performed in the presence of at least one additive selected from a water-soluble solvent as a solvent for polymerization, a molecular weight controlling agent, and a dispersing agent.

According to one embodiment of the present invention, the water-soluble solvent may be ion-exchanged water or deionized water.

Further, according to an embodiment of the present invention, the molecular weight controller may be at least one selected from the group consisting of α -methylstyrene dimer, t-dodecylmercaptan, n-dodecylmercaptan, octylmercaptan, carbon tetrachloride, methylene chloride, dibromomethane, tetraethylthiuram disulfide, dipentamethylenethiuram disulfide, and diisopropylxanthogen disulfide, and may be t-dodecylmercaptan as a specific example.

According to an embodiment of the present invention, the molecular weight controlling agent may be used in an amount of 0.01 to 0.15 parts by weight, 0.05 to 0.15 parts by weight, or 0.05 to 0.10 parts by weight, relative to 100 parts by weight of the total monomer added, within which a copolymer having a suitable weight average molecular weight may be prepared.

Further, according to an embodiment of the present invention, the dispersing agent may be at least one selected from the group consisting of water-soluble polyvinyl alcohol, partially saponified polyvinyl alcohol, polyacrylic acid, a copolymer of vinyl acetate and maleic anhydride, hydroxypropylmethyl cellulose, gelatin, calcium phosphate, tricalcium phosphate, hydroxyapatite, sorbitan monolaurate, sorbitan trioleate, polyoxyethylene, sodium lauryl sulfate, sodium dodecylbenzenesulfonate and sodium dioctyl sulfosuccinate, and may be tricalcium phosphate as a specific example.

According to an embodiment of the present invention, the dispersant may be used in an amount of 0.5 parts by weight to 2.0 parts by weight, 0.5 parts by weight to 1.5 parts by weight, or 1.0 part by weight to 1.5 parts by weight, relative to 100 parts by weight of the total monomer added, within which the dispersion stability of the monomers in the polymerization system may be improved, thereby preparing a copolymer having more uniform particles.

Further, according to an embodiment of the present invention, the method of preparing the copolymer may be performed by further including a dispersion aid during polymerization, and the dispersion aid may be a polyoxyethylene-based dispersion aid as a specific example, and may be a polyoxyethylene alkyl ether phosphate as a more specific example, and in this case, has an effect of achieving excellent polymerization stability.

The present invention provides a copolymer prepared by the above-mentioned method for preparing a copolymer. The copolymer may be a styrene-based copolymer, and as a specific example, a heat-resistant styrene-based copolymer.

The copolymer according to the present invention is characterized by comprising an aromatic vinyl-based monomer unit and a vinyl cyano-based monomer unit, wherein the heating residue calculated by the following equation 1 is 97.6% or more.

[ equation 1]

Heating residue (%) × 100 (weight of copolymer after retention in oven/weight of copolymer before retention in oven) × 100

Wherein the residence in the oven is performed at 250 ℃ for 2 hours in equation 1 above.

According to an embodiment of the present invention, the heating residue of the copolymer calculated from the above equation 1 may be 97.6% or more, 97.6% to 100.0%, or 97.6% to 98.1%, within which range there is an effect of achieving excellent thermal stability.

According to an embodiment of the present invention, each of the aromatic vinyl monomer unit and the vinyl cyanide monomer unit may refer to a repeating unit formed by polymerization of the aromatic vinyl monomer and the vinyl cyanide monomer, respectively. As a specific example, the polymerization reaction may be a radical polymerization reaction, and thus the monomer unit may refer to a repeating unit derived from a carbon-carbon double bond present in the aromatic vinyl-based monomer and the vinyl cyano-based monomer.

According to an embodiment of the present invention, the copolymer may be a random copolymer, and the aromatic vinyl-based monomer unit and the vinyl cyano-based monomer unit may have a uniform composition in the copolymer. The uniform composition of the monomer units may mean that the proportion of each monomer unit present in a polymer grown by polymerization of the monomers remains uniform. As a specific example, as polymerization proceeds, i.e., as polymerization time varies during polymerization, the proportion of each monomer unit forming the polymer may remain uniform when some of the polymer in the reactor is withdrawn.

The uniformity of the composition of the monomer unit in the present invention is expressed as a standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer measured as a change in polymerization time during the polymerization. The standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer measured as a function of the polymerization time during the polymerization can be confirmed from the square root of the value obtained as follows: the average value of the contents of the vinyl cyano monomer units in the copolymer measured as a function of the polymerization time during the polymerization is calculated, and the average value of the square deviations of the calculated average values of the contents of the vinyl cyano monomer units is calculated. The standard deviation of the content of the vinyl cyano monomer unit in the copolymer measured as a change in polymerization time during polymerization is small, which means that the change in the content of the vinyl cyano monomer unit in the copolymer is small for each polymerization time (i.e., for each polymerization conversion), which can mean that the ratio of each monomer unit of the copolymer to the polymerization-completed copolymer is maintained uniform for each polymerization time.

According to an embodiment of the present invention, the variation of the polymerization time may refer to a variation of time points, which are a time point of polymerization initiation, 60 minutes (1 hour), 120 minutes (2 hours), 240 minutes (4 hours), 480 minutes (8 hours), 600 minutes (10 hours), and 720 minutes (12 hours) after the polymerization initiation.

According to an embodiment of the present invention, the standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer of the copolymer, which is measured as a change in polymerization time during polymerization, may be 0.20 or less, 0.01 to 0.20, or 0.09 to 0.17, within which the composition of each monomer unit in the copolymer is uniform, thus having an effect of achieving excellent heat resistance.

The present invention provides a thermoplastic resin composition comprising the copolymer and a thermoplastic resin. As a specific example, the thermoplastic resin composition may contain the copolymer and a diene-based graft copolymer.

Further, according to an embodiment of the present invention, the diene-based graft copolymer may be an acrylonitrile-butadiene-styrene-based copolymer, and the acrylonitrile-butadiene-styrene-based copolymer is used to impart excellent moldability and impact resistance to the thermoplastic resin composition, and may be a graft copolymer having a core-shell structure, including: a core comprising conjugated diene monomer units; and a shell surrounding the core and including an aromatic vinyl-based monomer unit and a vinyl cyano-based monomer unit.

According to an embodiment of the present invention, the aromatic vinyl monomer of the diene graft copolymer may be at least one selected from the group consisting of styrene, α -methylstyrene, α -ethylstyrene, p-methylstyrene, o-tert-butylstyrene, bromostyrene, chlorostyrene, trichlorostyrene and derivatives thereof, and may be styrene as a specific example.

According to an embodiment of the present invention, the vinyl cyanide-based monomer of the diene-based graft copolymer may be at least one selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and derivatives thereof, and as a specific example, acrylonitrile.

According to an embodiment of the present invention, the conjugated diene monomer of the diene-based graft copolymer may be at least one selected from the group consisting of 1, 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, 2-ethyl-1, 3-butadiene, 1, 3-pentadiene and isoprene, and may be 1, 3-butadiene as a specific example.

Further, according to an embodiment of the present invention, the acrylonitrile-butadiene-styrene copolymer may be prepared by emulsion polymerization and emulsion graft polymerization, and may be prepared as follows: for example, a conjugated diene monomer is emulsion-polymerized to prepare a core (or seed), which is a rubbery polymer, and a vinyl cyano monomer and an aromatic vinyl monomer are added to the core and emulsion graft-polymerized.

In addition, the acrylonitrile-butadiene-styrene copolymer may include: a core comprising 30 to 70% by weight of units derived from a conjugated diene monomer; and a shell surrounding the core, the shell including 30 to 70 wt% of a unit from an aromatic vinyl-based monomer and a unit from a vinyl cyano-based monomer, and the shell may include the unit from the aromatic vinyl-based monomer and the unit from the vinyl cyano-based monomer in a weight ratio of 7:3 to 8:2, and in this case, the impact resistance, mechanical properties, and moldability of the copolymer may be more excellent.

Meanwhile, the thermoplastic resin composition according to one embodiment of the present invention may further include at least one additive selected from the group consisting of an impact modifier, a lubricant, a heat stabilizer, an anti-dripping agent, an antioxidant, a light stabilizer, a UV blocker, a pigment and an inorganic filler, as needed. And in this case, the additive may be used in an amount of 5.0 parts by weight or less or 0.1 parts by weight to 1.0 part by weight with respect to 100 parts by weight of the copolymer and the thermoplastic resin.

Further, a specific substance of the additive may be used without particular limitation as long as it is used in the thermoplastic resin composition, but for example, as the anti-dripping agent, at least one selected from polytetrafluoroethylene, polyamide, polycrystalline silicon, Polytetrafluoroethylene (PTFE) and tetrafluoroethylene-hexafluoropropylene (TFE-HFP) copolymer may be used for further improving flame retardancy, and as the inorganic filler, at least one selected from barium sulfate, barium glass filler and barium oxide may be used.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

Examples

Example 1

To the reactor, 114 parts by weight of ion-exchanged water, 48 parts by weight of α -methylstyrene, 32 parts by weight of acrylonitrile, 0.5 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane as a first polymerization initiator, 0.1 parts by weight of t-butyl peroxybenzoate as a second polymerization initiator, 0.005 parts by weight of polyoxyethylene alkyl ether phosphate and 1.3 parts by weight of tricalcium phosphate were charged, and polymerization was initiated at 100 ℃. After two hours from the initiation of polymerization (31% of polymerization conversion), 20 parts by weight of α -methylstyrene were continuously added for 6 hours while maintaining the rate of 3.33 parts by weight/hour. After the addition of α -methylstyrene was completed (polymerization conversion: 85%), the polymerization was further carried out for 4 hours, formic acid was added thereto to make the pH of the polymer syrup to 2.5, and then the polymer syrup was washed, dehydrated and dried to prepare a copolymer in a powder form.

Here, the parts by weight are parts by weight relative to 100 parts by weight of the added amount of the whole monomers.

Example 2

Example 2 was performed in the same manner as in example 1, except that in example 1, when the polymerization was initiated, 20 parts by weight of α -methylstyrene was continuously added for 8 hours while maintaining the rate of 2.50 parts by weight/hour. Here, the polymerization conversion when the addition of α -methylstyrene was completed was 85%.

Example 3

Example 3 was performed in the same manner as in example 1, except that in example 1, when the polymerization was initiated, 20 parts by weight of α -methylstyrene was continuously added while maintaining the rate of 3.33 parts by weight/hour for 6 hours, and after the addition of α -methylstyrene was completed (the polymerization conversion was 71%), the polymerization was further performed for 6 hours.

Comparative example 1

To the reactor, 114 parts by weight of ion-exchanged water, 68 parts by weight of α -methylstyrene, 32 parts by weight of acrylonitrile, 0.2 part by weight of 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane as a polymerization initiator, 0.005 part by weight of polyoxyethylene alkyl ether phosphate and 1.3 parts by weight of tricalcium phosphate were charged and polymerization was initiated at 100 ℃. The polymerization reaction was performed for 12 hours, formic acid was added thereto so that the pH of the polymer syrup became 2.5, and then the polymer syrup was washed, dehydrated and dried to prepare a copolymer in a powder form.

Here, the parts by weight are parts by weight relative to 100 parts by weight of the added amount of the whole monomers.

Comparative example 2

Comparative example 2 was conducted in the same manner as in comparative example 1, except that in comparative example 1, 0.4 parts by weight of 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane was added instead of 0.2 parts by weight.

Comparative example 3

Comparative example 3 was conducted in the same manner as in comparative example 1, except that in comparative example 1, 0.6 parts by weight of 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane was added instead of 0.2 parts by weight.

Comparative example 4

Comparative example 4 was conducted in the same manner as in comparative example 1, except that in comparative example 1, polymerization was initiated at 105 ℃.

Comparative example 5

Comparative example 5 was conducted in the same manner as in comparative example 4, except that in comparative example 4, 0.4 part by weight of 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane was added instead of 0.2 part by weight.

Comparative example 6

Comparative example 6 was conducted in the same manner as in comparative example 4, except that in comparative example 4, 0.6 parts by weight of 2, 2-bis (4, 4-di-tert-butylperoxycyclohexane) propane was added instead of 0.2 parts by weight.

Comparative example 7

Comparative example 7 was conducted in the same manner as in comparative example 1, except that in comparative example 1, 0.6 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane was added instead of 0.2 parts by weight of 2, 2-bis (4, 4-di-t-butylperoxy cyclohexane) propane.

Comparative example 8

Comparative example 8 was conducted in the same manner as in example 1, except that in example 1, 0.6 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane was added instead of 0.5 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane and 0.1 parts by weight of t-butyl peroxybenzoate.

Here, the polymerization conversion rate was 36% after two hours from the initiation of the polymerization, and the polymerization conversion rate was 85% when the addition of α -methylstyrene was completed.

Comparative example 9

Comparative example 9 was conducted in the same manner as in example 1, except that in example 1, 0.6 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane was added instead of 0.5 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane and 0.1 parts by weight of t-butyl peroxybenzoate, 20 parts by weight of α -methylstyrene was continuously added for 6 hours while maintaining the rate of 3.33 parts by weight/hour when the polymerization was initiated, and the polymerization was further conducted for 6 hours after the addition of α -methylstyrene was completed (the polymerization conversion was 71%).

Comparative example 10

Comparative example 10 was conducted in the same manner as in example 2, except that in example 2, 0.6 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane was added instead of 0.5 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane and 0.1 parts by weight of t-butyl peroxybenzoate.

Here, the polymerization conversion when the addition of α -methylstyrene was completed was 85%.

Comparative example 11

Comparative example 11 was conducted in the same manner as in comparative example 1, except that in comparative example 1, 0.5 parts by weight of 1, 1-bis (t-butylperoxy) cyclohexane was added as the first polymerization initiator instead of 0.2 parts by weight of 2, 2-bis (4, 4-di-t-butylperoxycyclohexane) propane as the polymerization initiator.

Examples of the experiments

For the copolymers prepared in examples 1 to 3 and comparative examples 1 to 11, the heating residue was measured as follows, and the results are shown in tables 1 and 2.

Further, when the copolymers of example 1 to example 3 and comparative example 1 to comparative example 11 were prepared, the content of the vinyl cyano-based monomer unit in each copolymer was measured from the copolymer at the following time points by the following method: the standard deviation (AN standard deviation) of the copolymers prepared at the polymerization initiation time point, 60 minutes (1 hour), 120 minutes (2 hours), 240 minutes (4 hours), 480 minutes (8 hours), 600 minutes (10 hours) after the polymerization initiation, and 720 minutes (12 hours) after the polymerization initiation was calculated, and the results are shown in tables 1 and 2.

1) Heating the residue (%): 4g of the copolymer was charged into the oven, held at 250 ℃ for 2 hours, and then the heating residue was calculated using the following equation 1:

[ equation 1]

Heating residue (%) × 100 (weight of copolymer after retention in oven/weight of copolymer before retention in oven) × 100

2) Content of vinyl cyano-based monomer units in the copolymer (wt%): after 0.02g of a sample was taken out of the copolymer at the polymerization initiation time point, at the time points of 60 minutes (1 hour), 120 minutes (2 hours), 240 minutes (4 hours), 480 minutes (8 hours), 600 minutes (10 hours) and 720 minutes (12 hours) after the initiation of the polymerization, a sample in the form of a thin Film was prepared at 220 ℃ using a Universal Film Maker, and the content of the vinyl cyano monomer unit in the copolymer was measured by fourier transform infrared spectroscopy (FT-IR).

[ Table 1]

[ Table 2]

As in the above tables 1 and 2, it can be confirmed that the copolymers of examples 1 to 3 prepared according to the method of preparing a copolymer of the present invention have excellent heat resistance because the heating residue after the residence of the copolymer in an oven remains high and show a very low standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer, which is measured as a change in polymerization time during the polymerization, and thus the monomer units in the copolymer are uniform.

On the other hand, it was confirmed that comparative example 1 used only one polymerization initiator and all the aromatic vinyl-based monomers were added together before initiation of polymerization when preparing the copolymer, and comparative example 1 had poor heat resistance due to low heating residue.

Further, it was confirmed that, in order to improve heat resistance as compared with comparative example 1, comparative examples 2 and 3 are different from the present invention in that only the addition amount of the polymerization initiator is increased and also have an increased standard deviation of the content of the vinyl cyano group-based monomer unit in the copolymer, and thus the nonuniformity of the monomer unit in the copolymer is increased.

Further, it was confirmed that, in order to improve heat resistance, comparative examples 4 and 6 are different from the present invention in that the polymerization temperature is increased and the standard deviation of the content of the vinyl cyano group-based monomer unit in the copolymer is also increased, as compared with comparative examples 1 to 3, and thus the nonuniformity of the monomer unit in the copolymer is increased.

Further, it was confirmed that, in order to improve heat resistance as compared with comparative example 1, comparative example 7 is different from the present invention in that the kind of the polymerization initiator is changed and the added amount thereof is increased, and also has an increased standard deviation of the content of the vinyl cyanide-based monomer unit in the copolymer, and thus the nonuniformity of the monomer unit in the copolymer is increased.

Further, it was confirmed that, even if a part of the aromatic vinyl-based monomer was continuously added separately during the polymerization process when the copolymer was prepared, comparative examples 8 to 10 using only one polymerization initiator exhibited high standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer, and thus the effect of improving the nonuniformity of the monomer unit in the copolymer was slight.

This is explained because when only one polymerization initiator is used, the residual polymerization initiator in the reaction system is insufficient at the latter stage of the polymerization reaction, and thus the polymerization reaction rate is lowered.

Further, even when only two polymerization initiators were used when preparing the copolymer, comparative example 11 in which all the aromatic vinyl-based monomer was co-added before the initiation of polymerization exhibited a high standard deviation of the content of the vinyl cyano-based monomer unit in the copolymer, and thus the nonuniformity of the monomer unit in the copolymer was sharply increased.

This is explained that, since the vinyl cyano-based monomer is dissolved in the ion-exchanged water which is a water-soluble solvent, the aromatic vinyl-based monomer and only some of the vinyl cyano-based monomer participate in the polymerization reaction at the initial stage of the polymerization, and as the polymerization proceeds to the later stage, only the vinyl cyano-based monomer remains to continue the polymerization reaction.

As a result, it was confirmed that, when at least two polymerization initiators are used as polymerization initiators and part or all of the aromatic vinyl-based monomers are continuously separated during polymerization to prepare a copolymer according to the method of preparing a copolymer of the present invention, the nonuniformity of monomer units in the copolymer can be reduced and, at the same time, a heat-resistant styrenic copolymer having excellent thermal stability can be prepared.