KR101064778B1 - Styrenic Copolymer With Heat-Resistant And Transparency And Method For Preparing The Same - Google Patents

Abstract

The present invention relates to a styrenic copolymer having excellent heat resistance and transparency, and a method of manufacturing the same, and more particularly, when (meth) acrylic acid is copolymerized to styrene using continuous bulk polymerization in order to add heat resistance to the styrene resin. Heat resistance and transparency characterized by applying alkyl (meth) acrylate, a typical transparent polymer monomer, as a comonomer in order to solve problems such as a decrease in transparency due to the gel component due to thermal crosslinking and discoloration by light. The excellent styrene copolymer and its manufacturing method are related. According to the present invention, there is an effect of providing a styrenic copolymer excellent in heat resistance, transparency and processability.

Transparency, acrylic acid, methacrylic acid, alkyl (meth) acrylate, acrylate, continuous bulk polymerization, styrene copolymer

Description

Styrenic copolymer with excellent heat resistance and transparency and its manufacturing method {Styrenic Copolymer With Heat-Resistant And Transparency And Method For Preparing The Same}

The present invention relates to a styrene copolymer having excellent heat resistance and transparency, and a method for producing the same, and more particularly, to copolymerize (meth) acrylic acid to styrene using a continuous process in order to add heat resistance to the styrene resin. Styrene, which is prepared by applying alkyl (meth) acrylate, a typical transparent polymer monomer, as a comonomer in order to solve problems such as transparency deterioration and discoloration due to light due to thermal crosslinking. It relates to a system copolymer and a production method thereof.

Styrene-based polymers such as polystyrene having heat resistance and transparency are usually produced by a bulk polymerization method, in particular by a continuous bulk polymerization method. In order to improve heat resistance with respect to such a styrene polymer, the method of copolymerizing maleic anhydride or methacrylic acid with a styrene monomer as a comonomer is widely known.

However, when the styrene monomer is copolymerized with maleic anhydride, there is a disadvantage in that discoloration occurs easily due to heat, and thus there is a limitation in using the transparent resin. In order to prevent thermal deformation of maleic anhydride, introduction of a tubular imide, which is a thermally stable functional group, has been in the spotlight. In other words, primary amine is applied to the copolymer of styrene-maleic anhydride and converted into styrene-maleimide. However, this method is difficult to design a variety of polymers, and requires a new equipment for the imidization reaction, as well as a high purification means for the removal of reaction by-products and water generated by the imidization reaction.

On the other hand, when styrene monomer is copolymerized with methacrylic acid, insoluble gel is formed by condensation reaction between methacrylic acid in the volatilization process for recovering unreacted monomer, thereby reducing the transparency of the resin and forming the resin into a product. If there is a problem that the appearance physical properties of the product is lowered.

In this regard, U.S. Patent 4,195,169 proposes a method of injecting water, alcohol, etc. into the volatilizer in order to inhibit gel formation after copolymerizing styrene and methacrylic acid. However, in order to inject water or alcohol into the gasoline tank, there is a constraint that a separate stirring device is added to the input line at the front of the gasoline tank.

In addition, U.S. Patent 4,937,298 discloses that the surface of the injection molding was improved by connecting several reactors in series and branching methacrylic acid and polymerization inhibitor into each reactor. However, this cannot be seen as a fundamental solution to the problem of gel formation in volatilization.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a styrene-based copolymer excellent in heat resistance and transparency and a manufacturing method thereof.

In order to achieve the above object, in the styrenic copolymer having excellent heat resistance and transparency of the present invention and a method for producing the same, 25 to 50% by weight of the styrene monomer, 5 to 10% by weight of (meth) acrylic acid, based on the total monomer weight It provides a styrene copolymer and a method for producing the styrene copolymer, characterized in that the haze of the styrene copolymer prepared and prepared by copolymerizing% and 50 to 70% by weight of alkyl (meth) acrylate is 0.1 to 0.5.

As described above, according to the present invention, in the production of a styrene copolymer by copolymerizing a styrene monomer with (meth) acrylic acid by continuous bulk polymerization, the amount of the polymer does not significantly reduce other physical properties such as heat resistance and processability. By adding alkyl (meth) acrylate as a comonomer, it is possible to prevent deterioration of resin transparency due to gel formation by condensation reaction of (meth) acrylic acid in the volatilization process for removal of unreacted monomer and reaction medium, thereby improving heat resistance, transparency and There is an effect that can produce a styrenic copolymer excellent in workability.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Styrene-based copolymer of the present invention is prepared by copolymerizing 25 to 50% by weight of styrene-based monomer, 5 to 10% by weight of (meth) acrylic acid and 50 to 70% by weight of alkyl (meth) acrylate based on the total monomer weight As a result, sufficient heat resistance, excellent transparency, and workability are satisfied at the same time.

Styrene-based monomers used in the present invention are not only styrene but also styrene derivatives such as α-methylstyrene, α-ethylstyrene, p-methylstyrene, p-ethylstyrene, halogenated styrene compounds, o-methoxystyrene, and the like. It is preferable to use, and more preferably α-methylstyrene can be used to maximize the heat resistance.

Such styrene monomer is a basic component of the styrenic copolymer of the present invention, the styrene monomer used in the present invention is preferably used 25 to 50% by weight based on the total weight of the monomer, more preferably 30 ~ 45% by weight can be used. If the content is too small, it is difficult to obtain the basic physical properties to be obtained by the polystyrene resin, if the content is too much, the amount of the comonomer for obtaining heat resistance is too small to improve the heat resistance.

The (meth) acrylic acid used in the present invention is a comonomer added to improve the heat resistance of the polystyrene resin, and methacrylic acid is more preferable than acrylic acid. In order to improve the heat resistance of the styrene resin, it is required to add more (meth) acrylic acid, but as described below, when too much (meth) acrylic acid is added, the (meth) The gel is produced by the condensation of acrylic acid, so that the desired transparency cannot be obtained. In this case, in order to prevent gel formation, more alkyl (meth) acrylate may be added. However, the content of the styrene monomer becomes too small to obtain desired physical properties. On the other hand, when the content of (meth) acrylic acid is too small, the degree of heat resistance improvement is insignificant.

Alkyl (meth) acrylate used in the present invention has excellent compatibility with (meth) acrylic acid, thereby preventing the hydrogen bond between (meth) acrylic acid, thereby greatly reducing the chance of condensation reaction between (meth) acrylic acid. Therefore, in the present invention, the condensation reaction between unreacted (meth) acrylic acid hardly occurs in the volatilization process due to the action of such alkyl (meth) acrylate, so that an increase in haze or a decrease in transparency does not occur. When the content of alkyl (meth) acrylate used in the present invention is too small, the degree of preventing the hydrogen bonding between (meth) acrylic acid is not so large that the effect of preventing gel formation due to condensation reaction between (meth) acrylic acid is insignificant. Done. On the other hand, when the content of alkyl (meth) acrylate is too high, the effect of preventing gel formation is excellent, but other properties such as MI (Melt Index) and water content become poor, or the content of styrene monomer, which is a basic monomer, becomes smaller. Will be different.

In addition, when the styrene-based copolymer of the present invention is applied to the production of the light diffusion plate by mixing with the light diffusing agent, if the content of alkyl (meth) acrylate, especially methyl methacrylate is too high, Since there is less than the refractive index required there is a disadvantage that must mix more light diffusing agents.

The alkyl (meth) acrylate used in the present invention may play the same role as described above, and is not particularly limited so long as it is not contrary to the required physical properties, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl meth Acrylate, propyl acrylate, propyl methacrylate and the like are preferable, and methyl methacrylate can be used more preferably.

The styrenic copolymer according to the present invention has a haze of 0.1 to 0.5, and preferably a MI (Melt Index) of 10 to 25, a heat deflection temperature (HDT) of 100 to 110 ° C, and a glass of 120 to 130 ° C. It has a transition temperature, a yellow index of 0.1 to 0.4 and can be used for manufacturing optical diffusers.

Such a styrenic copolymer of the present invention can be prepared by a bulk polymerization method, in particular a continuous block polymerization method. In general, the methods used for polymerization are known as a bulk polymerization method, solution polymerization method, emulsion polymerization method and suspension polymerization method. Among these, emulsion polymerization and suspension polymerization cannot obtain a polymer having excellent transparency. Solution polymerization has advantages such as easy control of polymerization heat, but the cost is increased due to the use of a solvent, and the polymerization rate is lowered and produced. The polymer has a disadvantage of low molecular weight, so that the bulk polymerization method is mainly used to prepare a styrene polymer having excellent heat resistance and transparency.

The bulk polymerization method has a disadvantage in that it is not easy to control the heat of polymerization, temperature and viscosity, but it is particularly advantageous in manufacturing a transparent resin because it is economically advantageous such as a simple device, fast reaction, high yield and high purity polymer. Suitable.

The present invention is to produce a heat-resistant styrene copolymer having high transparency using such a bulk polymerization method, in particular a continuous block polymerization method. That is, the production method of the styrene-based copolymer of the present invention, based on the total weight of the monomers, 25 to 50% by weight of the styrene monomer, 5 to 10% by weight of (meth) acrylic acid and 50 to 70% by weight of alkyl (meth) acrylate % Is copolymerized by continuous bulk polymerization in the presence of 0.001 to 0.1% by weight of the molecular weight regulator and 0.001 to 0.2% by weight of the radical polymerization initiator, to obtain a styrene-based copolymer as described above.

The radical polymerization initiator used in the production method of the present invention may include generally known organic peroxides and azo compounds. The amount of the initiator used may be selected in consideration of the half-life of the initiator, the reaction temperature and the molecular weight of the polymer to be obtained, the reaction time and the like. The molecular weight regulator can be selected from those generally used as molecular weight regulators, and typically mercaptan compounds can be used as molecular weight regulators. The quantity of a molecular weight modifier can be suitably selected according to the molecular weight of the target polymer.

In the present invention, the continuous bulk polymerization is, for example, a step of putting a portion of the monomers together with the molecular weight regulator and the initiator in the first polymerization reactor to undergo a first polymerization reaction, the reaction mixture is a secondary polymerization reactor To the secondary polymerization reactor and the remaining amount of the monomers into the secondary polymerization reactor together with the molecular weight regulator and the initiator to undergo a secondary polymerization reaction, and then the reaction mixture is transferred to a volatilizer to remove the unreacted monomer pellets It may comprise the step of preparing a styrenic copolymer in the form.

In the above, the amount of monomers, molecular weight regulators and initiators to be introduced into the primary and secondary polymerization reactors can be variously changed as desired. In some cases, the molecular weight regulator and the initiator may be added only to the primary polymerization reactor, the initiator may be added only to the primary polymerization reactor, and the molecular weight regulator may be added to both the primary and the secondary polymerization reactors in different amounts.

As such, it is possible to obtain a polymer having various physical properties by designing various processes. The polymerization reaction may be carried out at a temperature of 100 to 200 ° C, preferably at a temperature of 130 to 150 ° C.

In the bulk polymerization, an organic solvent having a suitable boiling point as a reaction medium may be added in an amount of about 5 to 20 wt% based on the total weight of the monomers. Examples of such a reaction medium include aromatic organic solvents such as toluene, benzene, and the like, and other organic solvents may be used.

In the present invention, when the final reactor, for example, having two reactors, the final polymerization conversion rate at the outlet of the secondary reactor is preferably 60 to 70%. If the polymerization conversion rate is too low, it is not economical in itself, and a high cost is required for the recovery of unreacted monomers. On the other hand, the polymerization conversion ratio is advantageously as high as possible from an economic point of view, but in the case of bulk polymerization, when the polymerization conversion ratio is too high, it is difficult to control the polymerization reaction due to reaching a high viscosity, and it is difficult to process the obtained polymer and also a small amount of Polymerization conversion has a limit because the removal of the reaction monomers and by-products is not easy and the physical properties of the polymer may be lowered due to their residuals. Usually, in bulk polymerization, it is not easy to obtain a polymerization conversion of 90% or more.

The polymerization mixture in the final polymerization reactor is then transferred to a volatilization tank to remove unreacted monomers, reaction medium and volatile reaction byproducts. At this time, the final polymerization conversion rate is usually about 60 to 70% so that a sufficient amount of (meth) acrylic acid remains in the polymerization mixture transferred to the volatilization tank.

According to the prior art in which only styrene and methacrylic acid are copolymerized, gel formation by condensation reaction of methacrylic acid in this process cannot be prevented without special operation by a special addition device, but in the present invention, only the above-mentioned content By adding alkyl (meth) acrylate as a comonomer, gel formation can be prevented by preventing the condensation reaction of (meth) acrylic acid in this step. For this reason, high transparency which cannot be obtained by the prior art can be obtained.

The volatilization in the volatilization can be carried out typically at a temperature of at least 150 ℃, preferably at a temperature of 200 ℃ or more.

The styrene-based copolymer of the present invention prepared as described above has high heat resistance and transparency and is therefore particularly suitable for application to a light diffusion plate.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only specific examples of the present invention, which should not be construed as limiting the scope of the present invention.

Example

Example 1

43 parts by weight of styrene, 7 parts by weight of methacrylic acid, and 50 parts by weight of methyl methacrylate, 100 parts by weight of the monomer mixed solution, 10 parts by weight of toluene as a reaction solvent, n-octyl mercaptan as a molecular weight regulator 0.02 Part by weight and 0.02 parts by weight of t-butyl peroxy-2-ethyl hexanoate as an organic peroxide initiator were added to prepare a reaction mixture, followed by a rate of 14 l / hr in a 26 L reactor. After the addition, the polymerization was carried out at a temperature of 140 ° C. in one step, followed by polymerization at the same temperature of 140 ° C. in the second step. When the polymerization conversion rate after the polymerization was more than 60%, unreacted monomers and reaction solvents remaining in the reactants were recovered and removed at a temperature of 210 ° C. in a volatilizer to prepare a styrene copolymer in pellet form. The physical properties of the resin thus prepared were measured, and the results are shown in Table 1.

[Example 2]

Except that 33 parts by weight of styrene, 7 parts by weight of methacrylic acid and 60 parts by weight of methyl methacrylate were prepared in the same manner as in Example 1 to measure the physical properties of the styrene-based copolymer, the results are shown in Table 1 Indicated.

Example 3

Except for using 33 parts by weight of styrene, 9 parts by weight of methacrylic acid and 58 parts by weight of methyl methacrylate to prepare a transparent copolymer in the same manner as in Example 1 and measured the physical properties, the results are shown in Table 1 It was.

Comparative Example 1

Styrene-based copolymers were prepared in the same manner as in Example 1 except that 93 parts by weight of styrene and 7 parts by weight of methacrylic acid were used as the monomer without methyl methacrylate, and the physical properties thereof were measured. It was.

Comparative Example 2

Except for using 83 parts by weight of styrene, 7 parts by weight of methacrylic acid and 10 parts by weight of methyl methacrylate to prepare a styrene copolymer in the same manner as in Example 1 to measure the physical properties, the results are shown in Table 1 Indicated.

[Comparative Example 3]

Except for using 63 parts by weight of styrene, 7 parts by weight of methacrylic acid and 30 parts by weight of methyl methacrylate to prepare a styrene copolymer in the same manner as in Example 1 to measure the physical properties, the results are shown in Table 1 Indicated.

[Comparative Example 4]

Except for using 3 parts by weight of styrene, 7 parts by weight of methacrylic acid and 90 parts by weight of methyl methacrylate to prepare a styrene copolymer in the same manner as in Example 1 to measure the physical properties, the results are shown in Table 1 Indicated.

Properties of the copolymer prepared as described above were measured by the following method.

(1) Haze-It measured according to ASTM 1003 method.

(2) MI (Melting Index)-10 minutes at 220 ℃, 10 kg load was measured according to the ASTM D1238 method.

(3) Gel Number-The number of gels contained in 0.1 m ² was measured using FS-5 (Film Quality Testing Systems) of Optical Control Systems.

(4) HDT (Heat Deflection Temperature)-1/4 "specimens were measured at 18.6 kg / cm ² load according to ASTM D648 method.

(5) Tg (glass transition temperature)-Pyris 6 Differential Scanning Calorimeter (DSC) by Perkin Elmer.

(6) Yellow index (b)-An injection test piece having a thickness of 3 mm was produced and measured according to ASTM 1003.

 TABLE 1

As shown in Table 1, the styrene copolymer of the present invention obtained by polymerizing monomers having a content range according to the present invention by continuous bulk polymerization is not only excellent in heat resistance and transparency, but also during the reaction by continuous bulk polymerization. It was confirmed that the number of gels produced was small. In addition, it can be seen that the styrenic copolymer according to the present invention is also excellent in workability.

On the contrary, in the case of Comparative Example 1, in which methyl methacrylate was not added, it was confirmed that the gel was poor and many gels were produced. In addition, the comparative example 4 to which too much methyl methacrylate is added is excellent in preventing gel formation, but other physical properties such as MI (Melt Index) and water content are not good and the content of styrene monomer, which is a basic monomer, is decreased. It can be seen that the physical properties will be different.

Claims (12)

It is prepared by copolymerizing 25 to 45% by weight of styrene monomer, 5 to 10% by weight of (meth) acrylic acid and 50 to 70% by weight of alkyl (meth) acrylate, based on the total weight of monomers, and having a haze of 0.1 to 0.5. Characterized by Styrenic copolymer delete delete The method of claim 1, It has a MI (Melt Index) of 10 to 25 Styrenic copolymer The method of claim 1, Characterized by having a glass transition temperature of 120 ~ 130 ℃ Styrenic copolymer The method of claim 1, The styrene monomer is at least one selected from the group consisting of styrene, α-methyl styrene, α-ethyl styrene, p-methyl styrene, p-ethyl styrene, halogenated styrene compound and o-methoxy styrene Styrenic copolymer The method of claim 1, The alkyl (meth) acrylate is at least one selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate and propyl methacrylate Styrenic copolymer The method of claim 1, The styrene-based copolymer is characterized in that the styrene, methacrylic acid and methyl methacrylate is prepared by copolymerization Styrenic copolymer Based on the total weight of the monomers, 25 to 45% by weight of styrene-based monomers, 5 to 10% by weight of (meth) acrylic acid and 50 to 70% by weight of alkyl (meth) acrylate are copolymerized by continuous bulk polymerization to produce a haze of 0.1 to 0.5. It characterized in that it comprises the step of preparing a styrene-based copolymer Method for producing styrene copolymer delete The method of claim 9, Final polymerization conversion rate in the final reactor outlet of the continuous bulk polymerization is characterized in that 60 to 70% Method for producing styrene copolymer The method of claim 9, The number of gels contained in 0.1 m ² of the styrenic copolymer, generated from the continuous process, characterized in that 0 to 10 Method for producing styrene copolymer