KR102015091B1

KR102015091B1 - Preparation method of heat-resistant styrene copolymer and heat-resistant styrene copolymer produced by the same

Info

Publication number: KR102015091B1
Application number: KR1020150143555A
Authority: KR
Inventors: 최은정; 강병일; 성다은; 한창훈
Original assignee: 주식회사 엘지화학
Priority date: 2015-10-14
Filing date: 2015-10-14
Publication date: 2019-08-27
Also published as: KR20170043901A

Abstract

The present invention relates to a method for producing a heat resistant styrene copolymer having excellent heat resistance and a heat resistant styrene copolymer prepared therefrom. In this way, by adding a second monomer mixture to prepare a heat-resistant styrene copolymer by the second polymerization step to improve the polymerization reactivity to improve the conversion rate and at the same time can be produced a styrene-based copolymer having excellent heat resistance. .

Description

Preparation method of heat-resistant styrene copolymer and heat-resistant styrene copolymer produced therefrom {Preparation method of heat-resistant styrene copolymer and heat-resistant styrene copolymer produced by the same}

The present invention relates to a method for producing a heat resistant styrene copolymer having excellent heat resistance and a heat resistant styrene copolymer prepared therefrom.

In general, heat-resistant styrene-based copolymers have excellent moldability, rigidity, and electrical properties, and various industrial fields including OA devices such as computers, printers, and copiers, home appliances such as televisions and audio, electric and electronic parts, automobile parts, and sundries. Widely used in. In particular, heat-resistant styrene-based copolymers that can withstand high external temperatures by increasing the heat resistance are used for special applications such as home appliance housings and automotive interior materials.

In order to obtain a styrenic copolymer having high heat resistance, α-methylstyrene (AMS) is commonly used. α-methylstyrene is relatively inexpensive and has excellent heat resistance. However, due to the low ceiling temperature (Tc), the α-methylstyrene is polymerized at a temperature lower than that of the conventional heat resistant styrene-based copolymer. There is a problem that the polymerization reaction should proceed and the polymerization conversion is greatly reduced, as well as low molecular weight of the polymer produced and pyrolysis can easily occur.

Thus, the production method through the emulsion polymerization using a batch process that is easy to control the polymerization temperature and polymerization time was mainly used. However, such emulsion polymerization requires a long polymerization reaction time due to low reaction temperature, high agglomeration temperature conditions, and impurities such as emulsifiers and flocculants are contained in the resin and are easily decomposed due to heat discoloration when processed by extrusion or injection. There is a problem such as this occurs. In addition, the emulsion polymerization may not perform the process of recovering the unreacted monomer, the heat resistance may be lowered due to the unreacted monomer remaining in the resin, it contains a large amount of acrylonitrile in the unreacted monomer, it is easily discolored by heat However, there is a problem that the acrylonitrile remains as an insoluble gel and acts as a foreign material that damages the appearance.

Therefore, in order to easily apply the heat-resistant styrenic copolymer to the industry to compensate for the disadvantage of the low ceiling temperature of α-methylstyrene to improve the polymerization conversion of the heat-resistant styrene-based copolymer to increase the productivity while inherently heat-resistant styrene-based copolymer There is a need for a technology that does not lower the mechanochemical properties of the polymer, that is, a technology that improves only the polymerization conversion rate and does not cause deformation in the heat resistant styrene copolymer.

KR 10-2006-0074752 A

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a production method capable of producing a heat resistant styrene copolymer having excellent heat resistance while improving the polymerization conversion rate.

Another object of the present invention is to provide a heat resistant styrene copolymer prepared by the above production method.

In order to solve the above problems, the present invention comprises the steps of first polymerizing a first monomer mixture comprising α-methylstyrene and acrylonitrile to prepare a polymer (step 1); And a second monomer mixture comprising α-methylstyrene and methacrylonitrile and secondary polymerization to the polymer (step 2). .

In addition, the present invention provides a heat resistant styrene copolymer prepared by the above production method.

In the production method according to the present invention, by adding a second monomer mixture to prepare a heat-resistant styrene copolymer by the second polymerization step to improve the polymerization reactivity to improve the conversion rate and at the same time to produce a styrene-based copolymer having excellent heat resistance Can be.

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

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

The present invention provides a production method capable of producing a heat resistant styrene copolymer having excellent heat resistance with improved conversion and improved productivity.

Heat-resistant styrene-based copolymers are also widely applied to special applications such as automotive interior materials, home appliance housing. Although α-methylstyrene (AMS) is commonly used to obtain a styrene-based copolymer having high heat resistance, the α-methylstyrene is significantly lower than the polymerization temperature of a conventional styrene-based copolymer due to a low ceiling temperature (Tc). Since the polymerization is carried out at a temperature, there is a problem that the conversion rate is greatly decreased. Low conversion rates directly lead to lower productivity, which poses a major obstacle to industrial applications.

Therefore, in order to easily apply the heat-resistant styrene copolymer to the industry, there is a need for a technology that improves the conversion rate of α-methylstyrene to increase productivity while not deteriorating the mechanochemical properties of the heat-resistant styrene copolymer.

Accordingly, the present invention provides a method for producing a heat resistant styrene copolymer capable of producing a heat resistant styrene copolymer having excellent heat resistance at a high conversion rate.

The preparation method according to an embodiment of the present invention comprises the steps of first polymerizing a first monomer mixture comprising α-methylstyrene and acrylonitrile to prepare a polymer (step 1); And adding a second monomer mixture including α-methylstyrene and methacrylonitrile to the polymer and performing secondary polymerization (step 2).

In addition, the production method is characterized in that the second monomer mixture is added at the time when the polymerization conversion rate of the first monomer mixture is 50% or more.

In addition, the production method according to an embodiment of the present invention may be carried out by a continuous bulk polymerization, for example, at least two stirring tanks in a batch while continuously adding a material to be polymerized using a continuous reactor connected in series It may be carried out by polymerization.

Hereinafter, the manufacturing method according to an embodiment of the present invention will be described in detail by dividing step by step.

Step 1 is a step for preparing a polymer by first polymerizing a first monomer mixture including α-methylstyrene and acrylonitrile.

Specifically, the first monomer mixture may include 60 wt% to 75 wt% of α-methylstyrene and 25 wt% to 40 wt% of acrylonitrile.

The α-methylstyrene (AMS, alpha-methylstyrene) is an alkylated styrene compound represented by the following Chemical Formula 1, and has excellent heat resistance properties so that it may be used as a chemical intermediate or raw material for imparting heat resistance when preparing resins and polymers. have.

[Formula 1]

As described above, the α-methylstyrene may have excellent heat resistance and may serve to improve excellent heat resistance of the finally produced heat-resistant styrene-based copolymer. However, the α-methylstyrene has a very low ceiling temperature (Tc, 66 ° C.), so that when it is polymerized alone, the α-methylstyrene has to be polymerized for a long time at low temperature, and the polymerized polymer is not only unstable but also has low polymerization conversion rate. There is a problem of low productivity. Thus, according to an embodiment of the present invention, a polymer is prepared by first polymerizing acrylonitrile together with the α-methylstyrene, and then, a second monomer mixture including α-methylstyrene and methacrylonitrile. Input and secondary polymerization resulted in further mechanical and chemical properties improvement and improved conversion and heat resistance.

As used herein, the term “ceiling temperature (Tc)” refers to an upper limit of the temperature range that enables the exothermic reaction to proceed thermodynamically in a reversible reaction. If the depolymerization rate is the same and above the ceiling temperature, the depolymerization rate is faster than the polymerization rate, so that the polymerization is inhibited and polymerization to the desired polymer may not easily occur.

The first monomer mixture may include 60 wt% to 75 wt% of α-methylstyrene. If the α-methylstyrene is included in less than 60% by weight, the effect of improving heat resistance may be insignificant, and when the α-methylstyrene is included in an amount of more than 75 parts by weight, the content of acrylonitrile, which will be described later, may be relatively reduced. The effect of improving the conversion is negligible, resulting in a reduction in weight average molecular weight and a large amount of residual monomer due to low polymerization conversion.

The acrylonitrile (acrylonitrile) is a kind of unsaturated nitrile-based compound, excellent in reactivity and polymerizability may be widely used as a raw material of synthetic rubber, synthetic resin.

In the present invention, the acrylonitrile may increase the weight average molecular weight of the heat-resistant styrenic copolymer finally prepared while supplementing the low ceiling temperature of the α-methylstyrene to facilitate polymerization. It can play a role in improving mechanochemical properties such as impact strength and chemical resistance.

As described above, the first monomer mixture may include 25 wt% to 40 wt% of the acrylonitrile. If the acrylonitrile is included in less than 25% by weight, the polymerization may be incomplete, resulting in an increase in unreacted monomers, and the finally produced heat-resistant styrene-based copolymer may not have a sufficiently high weight average molecular weight. Problems of deterioration may occur. On the other hand, when the acrylonitrile is included in excess of 40% by weight, the content of the α-methylstyrene is relatively reduced, which may cause a decrease in heat resistance.

The first polymerization may be performed by continuously adding the first monomer mixture to the polymerization reactor and bulk polymerization. In this case, the first polymerization may be to perform a bulk polymerization by using a polymerization initiator and a reaction medium further, if necessary, the polymerization initiator and the reaction medium is continuously added to the polymerization reactor simultaneously with the first monomer mixture. Alternatively, the first monomer mixture may be sequentially added and the polymerization initiator and the reaction medium may be continuously added. In addition, the polymerization initiator and the reaction medium may be added to the first monomer mixture and mixed before being added to the polymerization reactor, and the mixture may be continuously added to the polymerization reactor in the form of a mixture.

The polymerization initiator is not particularly limited, but may be, for example, 0.1 parts by weight to 0.3 parts by weight with respect to 100 parts by weight of the first monomer mixture. Specifically, the polymerization initiator may be a polyfunctional group-containing organic peroxide initiator, and is not particularly limited, for example, 1,1-bis (tertarybutylperoxy) cyclohexane, 1,1-bis (tertarybutylperoxy) 2-methylcyclohexane, 1,1-bis (tertiarybutylperoxy) -3,3,5-trimethylcyclohexane, 2,2-bis (tertiarybutylperoxy) butane and 2,2-bis ( It may be one or more selected from the group consisting of 4,4-dibutyl butyl peroxycyclohexane) propane.

The reaction medium may be used in an amount of 10 parts by weight or less based on 100 parts by weight of the first monomer mixture, but is not limited thereto. In addition, the reaction medium is an aromatic compound such as ethylbenzene, benzene, toluene, xylene; Methyl ethyl ketone, acetone, n-hexane, chloroform, cyclohexane and the like, but is not limited thereto.

The first polymerization may be performed for a reaction time of 4 hours to 6 hours in the temperature range of 100 ℃ to 120 ℃, it is not limited thereto. At this time, the reaction time may be the same as the residence time in the polymerization reactor, it can be controlled by adjusting the flow rate of the first monomer mixture is introduced.

Step 2 is a step for preparing a heat-resistant styrene copolymer with improved conversion rate, it can be carried out by adding a second monomer mixture to the polymer prepared in step 1 and secondary polymerization.

The second monomer mixture may include α-methylstyrene and methacrylonitrile, and the α-methylstyrene and methacrylonitrile in the second monomer mixture may have a weight ratio of 6.5: 3.5 to 8: 2. Can be. In addition, the weight ratio of α-methylstyrene in the second monomer mixture may represent a weight ratio of 5% to 10% reduced relative to the weight ratio of α-methylstyrene in the first monomer mixture. For example, when the total weight of the first monomer mixture is 10 and the weight ratio of α-methylstyrene in the first monomer mixture is 8, the weight ratio of α-methylstyrene in the second monomer mixture (total weight 10) is 7.2 to It may be a weight ratio of 7.6. If the weight ratio of α-methylstyrene and methacrylonitrile in the second monomer mixture is outside the above range, the effect of improving heat resistance and conversion may be insignificant.

The secondary polymerization may be performed by adding a second monomer mixture to the polymer prepared in Step 1 and bulk polymerization. In this case, the second monomer mixture may be added in an amount of 20 parts by weight or less relative to 100 parts by weight of the first monomer mixture, and specifically, may be added in an amount of 10 parts by weight to 20 parts by weight.

In addition, as described above, the second monomer mixture may be added at a time when the polymerization conversion rate of the first monomer mixture is 50% or more. If the second monomer mixture is added at a time when the polymerization conversion rate of the first monomer mixture is less than 50% and the second polymerization is performed, a problem may occur in which the polymerization conversion rate is decreased.

Here, the polymerization conversion rate represents the polymerization conversion rate of the first monomer mixture, that is, the degree to which the α-methylstyrene and acrylonitrile polymerized in the first monomer mixture polymerize to form a polymer. The weight and the weight of the polymer after dehydration and drying were measured and calculated as the ratio of the two weights.

The secondary polymerization may be performed under elevated temperature conditions compared to the primary polymerization. Specifically, the temperature may be performed under elevated temperature conditions of 2 ° C. to 10 ° C. relative to the temperature of the first polymerization.

According to an embodiment of the present invention, a heat-resistant styrene-based copolymer finally prepared by the methacrylonitrile is prepared by adding a second monomer mixture including α-methylstyrene and methacrylonitrile and subjecting it to secondary polymerization. The heat resistance of can be further improved. In addition, the conversion can be further improved by further participating in unreacted α-methylstyrene in the reaction.

In addition, the manufacturing method according to an embodiment of the present invention may further include a devolatilization process step after step 2.

The devolatilization process is for recovering and removing impurities such as a monomer, a reaction medium, and the like, and is not particularly limited, and may be performed under appropriate conditions for easily recovering and removing the impurities. Specifically, the temperature may be performed under a temperature of 240 ° C to 300 ° C and a vacuum pressure of 30 torr or less.

The present invention also provides a heat resistant styrene copolymer prepared by the above production method.

The heat resistant styrene-based copolymer according to an embodiment of the present invention is characterized in that the glass transition temperature is 126 ℃ or more.

Here, the glass transition temperature was raised to 20 ℃ / min from room temperature to 160 ℃ using a differential scanning calorimetry (DSC) Ta instrument Q10 and then reduced to 20 ℃ / min to 40 ℃, and again The highest variation point of the heat flow was measured when the temperature was raised to the first 10 ℃ / min.

Meanwhile, the heat resistant styrene-based copolymer according to an embodiment of the present invention may be used as a base resin of a rubbery polymer to impart heat resistance to the rubbery polymer.

The rubbery polymer is not particularly limited, but may be, for example, acrylonitrile-butadiene-styrene-based copolymer (ABS) or acrylate-styrene-acrylonitrile copolymer (ASA).

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following Examples and Experimental Examples are provided to illustrate the present invention, and the scope of the present invention is not limited only to these examples.

Example 1

100 parts by weight of the first monomer mixture comprising 70% by weight of α-methylstyrene and 30% by weight of acrylonitrile, 0.2 part by weight of 1,1-bis (tertiarybutylperoxy) -3,3,5-trimethylcyclohexane And 3 parts by weight of toluene were continuously added to the first polymerization reactor with a stirrer and first polymerized at 110 ° C. At this time, the input flow rate was adjusted so that the time of staying in the first polymerization reactor was 5 hours. Thereafter, all the polymers of the first polymerization reactor were transferred to the second polymerization reactor, and 20 parts by weight of the second monomer mixture was added at a time when the conversion rate of the first monomer mixture polymerization was 50%, thereby performing secondary polymerization at 112 ° C. for 3 hours. It was. The second monomer mixture was prepared by mixing α-methylstyrene and methacrylonitrile in a weight ratio of 6.5: 3.5. After completion of the polymerization, a devolatilization process was performed at a temperature of 250 ° C. and 30 torr vacuum pressure to recover and remove unreacted monomer and toluene, and a pellet-type heat-resistant styrene copolymer was prepared through an exhaust pump extruder.

Example 2

A heat resistant styrenic copolymer in the form of pellets was prepared in the same manner as in Example 1, except that a first monomer mixture including 72 wt% of α-methylstyrene and 28 wt% of acrylonitrile was used.

Example 3

Except for using the second monomer mixture in 15 parts by weight, a heat-resistant styrene copolymer of pellet form was prepared in the same manner as in Example 1.

Comparative Example 1

100 parts by weight of a monomer mixture comprising 70% by weight of α-methylstyrene and 30% by weight of acrylonitrile, 0.2 parts by weight of 1,1-bis (tertiarybutylperoxy) -3,3,5-trimethylcyclohexane and toluene 3 parts by weight were added and mixed, then continuously added to a polymerization reactor, and bulk polymerization was performed at 110 ° C. After the polymerization was completed, a devolatilization process was performed at a temperature of 250 ° C. and a vacuum pressure of 30 torr to recover and remove unreacted monomers and toluene, and a pellet-type heat-resistant styrene copolymer was prepared through a discharge pump extruder.

Comparative Example 2

Heat-resistant styrene-based copolymer in pellet form through the same method as Comparative Example 1, except that a monomer mixture including 70 wt% of α-methylstyrene, 25 wt% of acrylonitrile, and 5 wt% of methacrylonitrile was used. Was prepared.

Comparative Example 3

Except for using a styrene monomer instead of the second monomer mixture was prepared in the pellet-type heat-resistant styrenic copolymer in the same manner as in Example 1.

Comparative Example 4

Except for using the α-methylstyrene instead of the second monomer mixture was prepared in the pellet-type heat-resistant styrenic copolymer in the same manner as in Example 1.

Comparative Example 5

A pellet-type heat resistant styrene copolymer was prepared in the same manner as in Example 1, except that the second monomer mixture was added at the time of 40% conversion of the first monomer mixture.

Experimental Example

In order to compare and analyze the physical properties of each of the heat-resistant styrenic copolymers prepared in Examples 1 to 3 and Comparative Examples 1 to 5, the conversion rate (%), weight average molecular weight (Mw, g) of each copolymer / mol) and the glass transition temperature (Tg, ° C.) were measured. The results are shown in Table 1 below.

1)% conversion

The conversion rate was determined by measuring the total weight of the polymer before the devolatilization process after the completion of the polymerization and by measuring the weight of the heat-resistant styrene copolymer prepared after the devolatilization process.

2) Weight average molecular weight (g / mol)

The weight average molecular weight was obtained by dissolving each copolymer in tetrahydrofuran as a relative value to a standard polystyrene sample by gel osmosis chromatography (GPC).

3) Glass transition temperature (℃)

The glass transition temperature was increased from 20 ° C./min to 160 ° C. using a Differential Scanning Calorimetry (DSC) Ta instrument Q10, and then decreased to 20 ° C./min to 40 ° C., followed by a second 10 ° C. / When the temperature is raised to min, the highest variation of the heat flow is measured during the phase change.

division % Conversion Weight average molecular weight (g / mol) Glass transition temperature (℃) Example 1 66.2 91000 127.2 Example 2 64.1 87500 128.1 Example 3 65.2 89500 126.1 Comparative Example 1 61 89000 124.2 Comparative Example 2 50.1 78000 127.3 Comparative Example 3 67.2 93000 118.5 Comparative Example 4 53.5 79000 126.1 Comparative Example 5 64 90000 125.6

As shown in Table 1, the heat conversion of the heat-resistant styrene copolymer of Examples 1 to 3 according to an embodiment of the present invention compared to the heat-resistant styrene copolymer of Comparative Examples 1 to 5 overall It was confirmed that the increase and high glass transition temperature.

Specifically, in the case of the heat-resistant styrene-based copolymer of Comparative Example 1 prepared through a conventional general method without proceeding the secondary polymerization using the second monomer mixture, the conversion rate of the heat-resistant styrene-based copolymer of Example 1 is 8% The glass transition temperature decreased by about 2%.

In addition, the heat-resistant styrene-based copolymer of Comparative Example 2, which is a terpolymer obtained by using methacrylonitrile, showed a glass transition temperature similar to that of the heat-resistant styrene-based copolymer of Example 1, but the conversion rate of Example 1 It was significantly reduced to about 75% compared to the heat resistant styrene copolymer.

In addition, the heat-resistant styrene-based copolymer of Comparative Example 3 using the styrene monomer instead of the second monomer mixture showed a similar degree of conversion compared to the heat-resistant styrene-based copolymer of Examples 1 to 3, but the glass transition temperature is 7% ~ The heat resistant styrene copolymer of Comparative Example 4 using α-methylstyrene was reduced by about 8%, and the glass transition temperature was similar to that of the heat resistant styrene copolymers of Examples 1 to 3, but the conversion was 18 %%. It showed a tendency to decrease.

In addition, the glass transition temperature of the heat resistant styrene copolymers of Examples 1 to 3 also polymerized by adding a second monomer mixture at a time point deviated from the time point presented in the present invention to polymerize the comparative examples 5 It was confirmed that is reduced.

Claims

1) preparing a polymer by first polymerizing a first monomer mixture including α-methylstyrene and acrylonitrile; And
2) adding a second monomer mixture including α-methylstyrene and methacrylonitrile to the polymer and performing secondary polymerization;
The second monomer mixture is a method for producing a heat-resistant styrenic copolymer which is added at the time when the polymerization conversion rate of the first monomer mixture is 50% or more.

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The method according to claim 1,
The second monomer mixture is a method of producing a heat-resistant styrene copolymer is added to the amount of 20 parts by weight or less relative to 100 parts by weight of the first monomer mixture.

The method according to claim 1,
The second monomer mixture is α-methyl styrene and methacrylonitrile in a weight ratio of 6.5: 3.5 to 8: 2 method of producing a heat-resistant styrene copolymer.

The method according to claim 1,
Wherein the first monomer mixture comprises 60 wt% to 75 wt% of α-methylstyrene and 25 wt% to 40 wt% of acrylonitrile.

The method according to claim 1,
The secondary polymerization is a method of producing a heat-resistant styrene copolymer is carried out under elevated temperature conditions compared to the first polymerization.

The method according to claim 1,
The manufacturing method is a method of producing a heat-resistant styrene crab copolymer further comprising a devolatilization step step after step 2).

The method according to claim 7,
The devolatilization process is a method of producing a heat-resistant styrene copolymer is carried out under a temperature of 240 ℃ to 300 ℃ and a vacuum pressure of 30 torr or less.

The method according to claim 1,
The manufacturing method is a method of producing a heat-resistant styrene copolymer that is carried out by a continuous bulk polymerization.

The method according to claim 1,
Wherein the primary polymerization is carried out in the presence of a multifunctional group-containing organic peroxide initiator.

The method according to claim 10,
The polyfunctional group-containing organic peroxide initiator may be 1,1-bis (tert-butyl peroxy) cyclohexane, 1,1-bis (tert-butyl peroxy) -2-methylcyclohexane, 1,1-bis (tertary) Butyl peroxy) -3,3,5-trimethylcyclohexane, 2,2-bis (tertiarybutylperoxy) butane and 2,2-bis (4,4-dibutylbutyloxyoxyhexane) propane Method for producing a heat-resistant styrene copolymer is one or more selected from the group.

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