JP2007063335A - Method for producing styrenic polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a styrenic polymer, by which the polymer capable of exhibiting excellent impact resistance, while retaining a high mol. wt., a high cross link degree, and good moldability, can be obtained in good productivity. <P>SOLUTION: This method for producing the styrenic polymer, comprising polymerizing a styrenic monomer or a monomer mixture of the styrenic monomer with a vinylic monomer capable of being copolymerized with the styrenic monomer, is characterized by using a t-alkylperoxy monocarbonate having a conjugated double bond at the terminal as a polymerization initiator. The t-alkylperoxy monocarbonate is preferably a compound represented by the general formula (1) [R is H or methyl; R' is a 4 to 12C tertiary alkyl or a tertiary aralkyl; X is a 1 to 4C straight chain or branched alkylene; (n) is an integer of 1 to 4]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a styrenic polymer that can be used as a molding material and has a high molecular weight, a high degree of branching, a polymer having good moldability and excellent impact resistance, and high productivity. Is.

  Since styrene-based polymers are inexpensive and excellent in transparency and processability, they are used in a wide range of fields as one of general-purpose plastics. In recent years, however, various performances as molding materials, particularly impact resistance and heat resistance, have been demanded higher than before.

  In order to improve the impact resistance and heat resistance of styrene polymers, it is effective to increase the molecular weight of the polymer. On the other hand, increasing the molecular weight increases the viscosity at the time of melting and decreases the molding cycle. It was difficult to achieve both.

  As a method for satisfying these conflicting performances, it is generally known that a polymer having many branched portions, that is, a branched polymer is effective. As a method for obtaining such a polymer, a method for obtaining a polymer having a high molecular weight and a high degree of branching using a polyfunctional polymerization initiator has been proposed (see, for example, Patent Document 1). Examples of such polyfunctional polymerization initiators include polyfunctional peroxyketals such as 2,2-bis (4,4-bis-t-butylperoxycyclohexyl) propane, and polyfunctionals such as trimethylolpropane and pentaerythritol. Polyfunctional polymerization initiators such as polyfunctional peroxymonocarbonate having alcohol as a central skeleton are mentioned.

As another method, a method is known in which a peroxide having a polymerizable substituent, for example, a peroxy ester having a double bond such as t-alkyl peroxycinnamate is used as a polymerization initiator ( For example, see Patent Document 2). In this method, a double bond, which is a polymerizable substituent, is incorporated into a polymer by decomposing and reacting with a peroxide, and then copolymerized with another monomer or polymer, thereby causing the above-mentioned multiple. It is possible to obtain a polymer having a higher degree of branching than when a functional polymerization initiator is used.
Japanese Patent Laid-Open No. 10-17545 (pages 2 and 4) JP-A-11-279224 (Pages 2 and 5)

  However, in the method disclosed in Patent Document 1, although a polymer having a relatively high molecular weight is obtained, a polymer having a branch number equal to or greater than the number of functional groups of the polymerization initiator is basically not obtained. There was a problem that the melt viscosity of the coalescence could not be sufficiently suppressed and the moldability could not be improved.

  In the method disclosed in Patent Document 2, although a polymer obtained by using a peroxyester having a double bond as a polymerization initiator is sufficiently branched, it has excellent moldability. Due to the structure of the ester, the polymerization rate decreases in the latter half of the polymerization when the polymerization conversion is 50% or more. For this reason, in terms of molecular weight, it does not exceed the case where the polyfunctional polymerization initiator is used, and there is a problem that impact resistance cannot be sufficiently improved and production efficiency is lowered.

  Therefore, the object of the present invention is to provide a styrene-based polymer with high productivity and high molecular weight, high branching degree, and good polymerizability while maintaining good moldability. It is providing the manufacturing method of a polymer.

  As a result of intensive studies, the present inventors have used a peroxymonocarbonate having a specific structure, that is, a peroxymonocarbonate having a conjugated double bond at the terminal, as a polymerization initiator, thereby allowing a styrene-based polymer having a high molecular weight and a high branching degree. It has been found that coalescence can be obtained efficiently, and the present invention has been completed.

  That is, the method for producing a styrenic polymer according to the first aspect of the present invention is the method for producing a styrenic polymer in which a styrene monomer is produced by polymerizing a styrene monomer using a polymerization initiator. The agent is a t-alkyl peroxymonocarbonate having a conjugated double bond at the terminal.

  The method for producing a styrenic polymer of the second invention is characterized in that, in the first invention, the polymerization initiator further contains another polymerization initiator other than the t-alkylperoxymonocarbonate. It is.

  The method for producing a styrenic polymer of the third invention is characterized in that, in the first or second invention, the t-alkyl peroxymonocarbonate is a compound represented by the following chemical formula (1). It is.

（但し、Ｒは水素原子又はメチル基を表し、Ｒ´は炭素数４〜１２の第３級アルキル基又は第３級アラルキル基を表し、Ｘは炭素数１〜４の直鎖又は分岐のアルキレン基を表し、ｎは１〜４の整数を表す。）
第４の発明のスチレン系重合体の製造方法は、第１から第３のいずれかの発明において、前記スチレン系重合体は屈折率検出器を用いたゲルパーミエーションクロマトグラフィ（ＧＰＣ）により検量線に基づいて求めた質量（重量）平均分子量が３０万〜１００万であり、かつ多角度光散乱式検出器を用いてＧＰＣにより求めた質量（重量）平均分子量を前記屈折率検出器を用いたＧＰＣにより検量線に基づいて求めた質量平均分子量で除した値が１．２〜２．０であることを特徴とするものである。

(However, R represents a hydrogen atom or a methyl group, R ′ represents a tertiary alkyl group or a tertiary aralkyl group having 4 to 12 carbon atoms, and X represents a linear or branched alkylene having 1 to 4 carbon atoms. Represents a group, and n represents an integer of 1 to 4.)
According to a fourth aspect of the invention, there is provided a method for producing a styrenic polymer according to any one of the first to third aspects, wherein the styrenic polymer is converted into a calibration curve by gel permeation chromatography (GPC) using a refractive index detector. The mass (weight) average molecular weight determined on the basis of 300,000 to 1,000,000, and the mass (weight) average molecular weight determined by GPC using a multi-angle light scattering detector was used as the GPC using the refractive index detector. The value obtained by dividing by the mass average molecular weight determined on the basis of the calibration curve is 1.2 to 2.0.

According to the present invention, the following effects can be exhibited.
In the method for producing a styrenic polymer of the first invention, a t-alkyl peroxymonocarbonate having a conjugated double bond at the terminal is used as a polymerization initiator, so that a peroxide bond (OO bond) is used during polymerization. Among radicals generated by cleavage of, a radical on the side having a conjugated double bond is added to the styrenic monomer to produce a polymer chain having a conjugated double bond. This conjugated double bond is copolymerized with another styrene monomer or polymer chain to obtain a styrene polymer having a high molecular weight and a high degree of branching. In general, styrenic polymers have low impact resistance and are susceptible to cracking, so it is necessary to further increase the molecular weight compared to other polymers. Can demonstrate its sexuality.

  Since the resulting styrenic polymer has a high degree of branching, the apparent bulk of the molecule is reduced, and the probability of entanglement with each other is reduced, so that the movement of the molecular chain is not inhibited. Therefore, even when the styrene-based polymer has a high molecular weight, the viscosity at the time of melting can be kept low, and good moldability can be exhibited. In this way, by using the specific polymerization initiator, high polymerization initiation efficiency is maintained even when the viscosity increases in the latter half of the polymerization when the polymerization conversion rate is 50% or more, and the increase in the molecular weight and the degree of branching proceed. The copolymerization in the latter half of the polymerization proceeds efficiently, and as a result, a high molecular weight, highly branched styrene polymer can be produced with high productivity.

  In the method for producing a styrenic polymer of the second invention, in addition to the effects of the first invention, by further containing a polymerization initiator other than the t-alkylperoxymonocarbonate as a polymerization initiator. The polymerization temperature and the physical properties of the styrene polymer can be adjusted.

  In the method for producing a styrenic polymer of the third invention, since the t-alkyl peroxymonocarbonate is a compound represented by the chemical formula (1), the effect of the first or second invention is improved. Can do.

  In the method for producing a styrene polymer of the fourth invention, the styrene polymer has a mass average molecular weight of 300,000 to 1,000,000 determined based on a calibration curve by GPC using a refractive index detector. The value obtained by dividing the mass average molecular weight determined by GPC using a multi-angle light scattering detector by the mass average molecular weight determined based on the calibration curve by GPC using the refractive index detector is 1.2-2. .0. For this reason, in addition to the effects of any one of the first to third inventions, the degree of branching and the molecular weight of the styrene polymer can be sufficiently increased.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The method for producing a styrene polymer of the present embodiment is a method for producing a styrene polymer by polymerizing a styrene monomer using a specific polymerization initiator. Such a polymerization initiator is a t-alkyl peroxymonocarbonate having a conjugated double bond at the terminal (hereinafter also referred to as conjugated percarbonate). The conjugated percarbonate includes all polymerization initiators as long as it is a t-alkyl peroxymonocarbonate having a conjugated double bond at the terminal. Among them, a compound represented by the following chemical formula (1) is preferable.

（但し、Ｒは水素原子又はメチル基を表し、Ｒ´は炭素数４〜１２の第３級アルキル基又は第３級アラルキル基を表し、Ｘは炭素数１〜４の直鎖又は分岐のアルキレン基を表し、ｎは１〜４の整数を表す。）ここで、化学式（１）において、一端側のＣ＝ＣとＣ＝Ｏとが共役二重結合を形成している。

(However, R represents a hydrogen atom or a methyl group, R ′ represents a tertiary alkyl group or a tertiary aralkyl group having 4 to 12 carbon atoms, and X represents a linear or branched alkylene having 1 to 4 carbon atoms. Represents a group, and n represents an integer of 1 to 4.) Here, in the chemical formula (1), C = C and C = O on one end side form a conjugated double bond.

  Specific examples of the conjugated percarbonate include t-butylperoxyacryloyloxyethyl carbonate, t-butylperoxyacryloyloxypropyl carbonate, t-butylperoxymethacryloyloxyethyl carbonate, t-butylperoxymethacryloyloxypropyl carbonate, t -Amylperoxyacryloyloxyethyl carbonate, t-amylperoxyacryloyloxypropyl carbonate, t-amylperoxymethacryloyloxyethyl carbonate, t-amylperoxymethacryloyloxypropyl carbonate, 2-methylpentyl-2-peroxyacryloyloxy Ethyl carbonate, 2-methylpentyl-2-peroxyacryloyloxypropyl carbonate, 2 Methylpentyl-2-peroxymethacryloyloxyethyl carbonate, 2-methylpentyl-2-peroxymethacryloyloxypropyl carbonate, 2,4,4-trimethylpentyl-2-peroxyacryloyloxyethyl carbonate, 2,4,4- Trimethylpentyl-2-peroxyacryloyloxypropyl carbonate, 2,4,4-trimethylpentyl-2-peroxymethacryloyloxyethyl carbonate, 2,4,4-trimethylpentyl-2-peroxymethacryloyloxypropyl carbonate, 2- Examples thereof include phenylpropyl-2-peroxymethacryloyloxyethyl carbonate and 2-phenylpropyl-2-peroxymethacryloyloxypropyl carbonate.

  As conjugated percarbonate, t-butyl peroxy (1-ethylacryloyloxyethyl) carbonate, t-butyl peroxy (1-ethylacryloyloxypropyl) carbonate, t-butyl peroxy (not included in the chemical formula (1)) 1-phenylacryloyloxyethyl) carbonate, t-butylperoxy (1-phenylacryloyloxypropyl) carbonate, and the like can also be used. Among the above conjugated percarbonates, from the viewpoint of polymerization initiation efficiency and production cost, in chemical formula (1), R is a methyl group, R ′ is an alkyl group having 4 to 8 carbon atoms, and X is 2 or 3 carbon atoms. A compound in which an alkylene group and n is 1 is preferable. Specifically, t-butyl peroxymethacryloyloxyethyl carbonate, t-butyl peroxymethacryloyloxypropyl carbonate, and 2-methylpentyl-2-peroxymethacryloyloxyethyl carbonate are preferable.

  The compounding quantity of a conjugated percarbonate is 0.005-0.5 mass part normally with respect to 100 mass parts of styrene-type monomers, Preferably it is 0.01-0.2 mass part. If the blending amount is less than 0.005 parts by mass, the amount of branched polymer produced will be small, and if it exceeds 0.5 parts by mass, branching due to copolymerization will proceed excessively and a gel polymer will tend to be produced. is there.

  In addition, conjugated percarbonate and other polymerization initiators can be used in combination as long as the object of the present invention is not impaired. Thereby, the polymerization temperature, the physical properties of the styrene polymer, and the like can be adjusted. Other polymerization initiators can be used without problems as long as they are usually used for the production of styrene polymers, but those having a 10-hour half-life temperature in the temperature range of 70 to 130 ° C. are usually used. . Specific examples of such a polymerization initiator include diacyl peroxides such as benzoyl peroxide and toluyl peroxide; t-butyl peroxyacetate, t-butyl peroxybenzoate, di-t-butyl peroxyisophthalate, Peroxyesters such as t-butyl peroxylaurate, t-hexyl peroxyacetate, t-hexyl peroxy 2-ethylhexanoate, t-hexyl peroxybenzoate; t-butyl peroxyisopropyl monocarbonate, t -Peroxyesters such as butyl peroxy 2-ethylhexyl monocarbonate, t-hexyl peroxyisopropyl monocarbonate; 1,1-bis-t-butylperoxy 3,3,5-trimethylcyclohexane, 1,1-bis -T-Buchi Peroxycyclohexane, 2,2-bis-t-butylperoxybutane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (4,4-bis-t-butyl) Peroxyketals such as peroxycyclohexyl) propane; di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-di-t-butylperoxy 2,5-dimethylhexane, dicumyl peroxide, etc. Dialkyl peroxides; azo compounds such as 2,2-azobisisobutyronitrile. An appropriate polymerization initiator can be selected from these polymerization initiators according to the polymerization temperature and the physical properties required of the polymer.

  The amount of the polymerization initiator to be used in combination is not particularly limited, but if the amount is too much with respect to the conjugated percarbonate, the effect of the conjugated percarbonate is reduced, so the amount is 10 times the amount based on the amount of radical generated with respect to the conjugated percarbonate. The following is preferable, and the amount of 5 times or less is more preferable. Moreover, the polymerization initiator used together with the conjugated percarbonate may be added by mixing with the conjugated percarbonate at the initial stage of polymerization, or may be added during the polymerization.

  The combined amount of the conjugated percarbonate and the polymerization initiator used in combination therewith, that is, the total amount of polymerization initiator, is an amount that can achieve the desired polymerization conversion rate. The amount of the total polymerization initiator is usually 0.005 to 1 part by mass, preferably 0.01 to 0.5 part by mass with respect to part. When the total amount of the polymerization initiator is less than 0.005 parts by mass, the effect of the polymerization initiator cannot be sufficiently obtained. On the other hand, when the amount exceeds 1 part by mass, there are cases where the polymerization proceeds excessively and partly gels, or the transparency of the resulting styrenic polymer is lowered or colored.

  Next, the monomer used as a polymerization raw material is a monomer mixture of a styrene monomer or a styrene monomer and a vinyl monomer copolymerizable therewith. Examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and the like. Among these styrenic monomers, styrene is particularly preferable because of its high polymerizability and easy to obtain a high molecular weight polymer.

  Examples of vinyl monomers include acrylic monomers such as acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate. Methacrylic monomers such as methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, octyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, fumaric acid ester, maleic acid ester, acrylonitrile, And methacrylonitrile. In addition, the said styrene-type monomer can also be used as a vinyl-type monomer. In that case, different types of styrenic monomers are used in combination. Specific examples of the resulting copolymer include styrene / acrylonitrile copolymer, styrene / α-methylstyrene copolymer, styrene / butyl acrylate copolymer, α-methylstyrene / acrylonitrile copolymer, and the like.

  Furthermore, it is also possible to use a polymer raw material in which a rubber such as polybutadiene rubber, styrene / butadiene block copolymer rubber, SBR, NBR, EPDM or the like is dissolved in a styrene monomer or a monomer mixture. Content of the said rubber | gum is 2-40 mass% normally with respect to a styrene-type monomer, Preferably it is 5-30 mass%. Further, if necessary, additives usually used for the polymerization of styrene monomers, for example, additives such as chain transfer agents, antioxidants, ultraviolet absorbers and the like can be blended.

  As the polymerization method, a bulk polymerization method, a solution polymerization method or a suspension polymerization method is adopted, and a combination of these polymerization methods is also adopted. In these cases, both the continuous polymerization method and the batch polymerization method are adopted, but industrially, the continuous polymerization method with good production efficiency is advantageous. In particular, in the continuous polymerization method, the polymerization temperature is usually 70 to 180 ° C, preferably 80 to 170 ° C, more preferably 90 to 160 ° C. When the polymerization temperature is less than 70 ° C., the polymerization rate is slow, so the productivity is lowered. On the other hand, when the polymerization temperature exceeds 180 ° C., chain transfer to the styrene monomer tends to occur, and the production of branched polymers tends to decrease, or the molecular weight of the resulting polymer tends to decrease. is there. Other conditions for the polymerization method are carried out according to a conventional method in the method for producing a styrene polymer.

  The styrene polymer obtained by the above production method preferably has a mass average molecular weight determined based on a calibration curve by gel permeation chromatography (GPC) using a refractive index detector, preferably from 300,000 to 1,000,000, more preferably 350,000 to 800,000. Here, gel permeation chromatography (GPC) is gel permeation chromatography and is one of the molecular weight measurement methods. The molecular weight obtained is a constant value even if the measuring device (refractive index detector) is different, because a calibration curve to be measured in advance is used. Further, the value obtained by dividing the mass average molecular weight determined by GPC using a multi-angle light scattering detector by the mass average molecular weight determined based on the calibration curve by GPC using the refractive index detector is preferably 1.2. It is -2.0, More preferably, it is 1.4-2.0.

  The mass average molecular weight obtained by GPC using the refractive index detector based on the calibration curve is the retention time of linear polystyrene with a known molecular weight, so-called standard polystyrene (hereinafter abbreviated as standard PS), and the molecular weight is unknown. It is obtained by comparing and referring to the retention time of the sample, and is generally called a standard PS equivalent molecular weight. This method is simple and widely used. However, the refractive index detector only measures the concentration of the sample that has been eluted, and on the principle of GPC that the retention time is determined by the bulkiness of the molecules, even if molecules having the same molecular weight are branched, When the apparent bulk of the molecule is reduced due to a high degree of reason or the like, the retention time is increased, so that the molecular weight is evaluated to be smaller than the true value.

  On the other hand, the multi-angle light scattering detector irradiates a sample solution with laser light from a plurality of angles and measures how light is scattered by the sample molecules contained therein. Since light scattering is determined by the number and size of sample molecules, the absolute molecular weight of the molecules can be obtained by combining with information on the retention time of GPC. The degree of deviation of the mass average molecular weight of the same sample determined by these two types of measurement methods is an index representing the degree of molecular branching. There are several methods for evaluating the degree of divergence, but the method of dividing the absolute molecular weight by the standard PS-converted molecular weight and obtaining the ratio is the simplest.

  When the standard PS conversion molecular weight of the obtained styrene polymer is less than 300,000, the impact resistance and heat resistance of the styrene polymer are insufficient. On the other hand, when the standard PS-converted molecular weight exceeds 1,000,000, the molecular weight of the styrenic polymer is increased, the melt viscosity is increased, gelation occurs in part, and the moldability tends to deteriorate. In addition, when the value obtained by dividing the absolute molecular weight by the standard PS-converted molecular weight is less than 1.2, the viscosity at the time of melting of the styrenic polymer is increased, and when the molding process is continuously performed by extrusion molding, the workability is increased. Deteriorating and lengthening the molding cycle is undesirable, resulting in poor productivity. On the other hand, when the value obtained by dividing the absolute molecular weight by the standard PS equivalent molecular weight exceeds 2.0, the production conditions of the styrenic polymer become difficult and the productivity tends to deteriorate.

  Now, the operation of the present embodiment will be described. The styrene polymer is produced by heating a styrene monomer in the presence of a polymerization initiator and performing radical polymerization. At that time, since a t-alkyl peroxymonocarbonate having a conjugated double bond at the terminal is used as a polymerization initiator, a peroxide bond (OO bond) is cleaved during polymerization to generate a radical, and a conjugated double bond is generated. The radical on the side having a bond is added to the styrenic monomer to form a polymer chain having a conjugated double bond. This conjugated double bond is copolymerized with another styrene monomer to produce a styrene polymer having a high molecular weight and a high degree of branching.

  Since the styrenic polymer produced in this way has a high degree of branching, it is presumed that the apparent bulk of the molecule is reduced and the probability of entanglement with each other is reduced, and the movement of the molecular chain is not inhibited. Therefore, even when the styrene-based polymer has a high molecular weight, the viscosity at the time of melting can be kept low, and good moldability can be exhibited. In particular, even when the viscosity increases in the latter half of the polymerization conversion rate of 50% or more, the high polymerization initiation efficiency is maintained, and the latter half of the polymerization where the increase in the molecular weight and the degree of branching progresses efficiently. A highly branched styrenic polymer is obtained.

  Conventional peroxyesters and peroxyketals are subject to reactions such as β-cleavage and decarboxylation after cleavage of the peroxide bond, and part of them are easily converted to alkyl radicals to cause deactivation reactions called cage reactions. When the viscosity of the polymerization solution increases in the latter half of the polymerization, the ratio of this cage reaction increases, and the number of radicals that are deactivated is greater than the number of radicals that initiate polymerization, resulting in a decrease in polymerization initiation efficiency. In contrast, the conjugated percarbonate of the present embodiment hardly causes reactions such as β-cleavage and decarboxylation, and does not cause subsequent deactivation reactions. For this reason, regardless of the viscosity of the polymerization solution, most of the generated radicals contribute to the initiation of polymerization, and as a result, a high polymerization initiation efficiency is maintained until the end of the polymerization.

The effects exhibited by the above embodiment will be described collectively below.
-In the method for producing a styrenic polymer of this embodiment, conjugated percarbonate is used as a polymerization initiator, so that radicals generated by cleaving the peroxide bond during polymerization are added to the styrenic monomer and conjugated. A polymer chain having a double bond is formed. This conjugated double bond is copolymerized with another styrene monomer or polymer chain to obtain a styrene polymer having a high molecular weight and a high degree of branching. In general, styrenic polymers have low impact resistance and are susceptible to cracking, so it is necessary to further increase the molecular weight compared to other polymers. And good heat resistance can be exhibited.

  Moreover, since the resulting styrenic polymer has a high degree of branching, the apparent bulk of the molecule is reduced and entanglement with each other is reduced, and the movement of the molecular chain is not inhibited, and the styrenic polymer has a high molecular weight. Even if it exists, the viscosity at the time of a fusion | melting is low, and favorable moldability can be exhibited. Thus, by using the specific polymerization initiator, high polymerization initiation efficiency is maintained even if the viscosity increases in the latter half of the polymerization when the polymerization conversion rate is 50% or more, and the copolymerization in the latter half of the polymerization proceeds efficiently. As a result, a styrene polymer having a high molecular weight and a high degree of branching can be produced with high productivity (high polymerization conversion).

  -Moreover, the polymerization temperature and the physical property of a styrene-type polymer can be adjusted by further containing other polymerization initiators other than the said t-alkyl peroxymonocarbonate as a polymerization initiator.

-The said effect can be improved by using the compound represented by the said Chemical formula (1) as t-alkyl peroxymonocarbonate which is a polymerization initiator.
-Furthermore, the above-mentioned standard PS conversion molecular weight is 300,000 to 1,000,000, and the value obtained by dividing the absolute molecular weight by the standard PS conversion molecular weight is 1.2 to 2.0. The molecular weight can be sufficiently increased.

  Hereinafter, the embodiment will be described in more detail with reference to examples and comparative examples, but the invention is not limited to these examples. The molecular weight, MFR and Izod impact strength of the styrene polymer were measured by the following methods.

  1) Molecular weight of styrene polymer: After dissolving the styrene polymer in tetrahydrofuran so that the concentration becomes 0.1 wt / v%, the column temperature is set to 38 ° C. and the flow rate of the eluent (tetrahydrofuran) is set to 1.0 mL / min. 150 μL was injected into each of the molecular weight measuring devices.

  MwR: Refractive index detector (GPC apparatus: HLC-8020 manufactured by Tosoh Corporation), separation column: three TSKgel-GMHXL manufactured by Tosoh Corporation connected, detector: HLC-8020 manufactured by Tosoh Corporation Mass average molecular weight determined as a standard PS equivalent molecular weight based on a calibration curve prepared in advance using standard PS using a built-in differential refractive index detector.

  MwL: Multi-angle light scattering detector (GPC apparatus: HLC-8020 manufactured by Tosoh Corporation), separation column: three separation columns manufactured by Tosoh Corporation TSKgel-GMHXL connected, detector: manufactured by Tosoh Corporation Absolute molecular weight measured by GPC using an angle light scattering detector LS-8000, scattering angle: 5 °, light source: 5 mW (He—Ne laser), sampling pitch: 1 / 0.4 (times / second).

Branching degree: MwL / MwR, the larger the value, the higher the branching degree of the styrenic polymer.
2) MFR (melt flow rate, g / min): Measured according to JIS K7210 (200 ° C., 5 kg load). The larger the value, the higher the fluidity.

3) Izod impact strength (notched) (kg · cm / cm): It was carried out according to ASTM D256. The larger the value, the higher the impact strength.
The abbreviations used in Tables 1 and 2 showing the results of Examples and Comparative Examples are as follows. In addition, all the usage-amounts described the value converted into the pure product as a mass part.
(Polymerization initiator)
B-MEC: 40 mass% toluene diluted product of t-butylperoxymethacryloyloxyethyl carbonate.

H-MEC: 2-methylpentyl-2-peroxymethacryloyloxyethyl carbonate diluted with 40% by mass of toluene.
B-MPC: 40% by weight toluene diluted product of t-butylperoxymethacryloyloxypropyl carbonate.

B-Z: t-butyl peroxybenzoate [Nippon Yushi Co., Ltd., brand name: perbutyl Z].
HC: 1,1-bis-t-butylperoxycyclohexane [Nippon Yushi Co., Ltd., brand name: Perhexa C].

B-CI: t-butyl peroxycinnamate (50% ethylbenzene diluted product).
TA: 2,2-bis (4,4-bis-t-butylperoxycyclohexyl) propane diluted with 20% ethylbenzene [manufactured by NOF Corporation, trade name: Pertetra A].
(Monomer)
St: Styrene [made by Wako Pure Chemical Industries, Ltd.].
[Production Example 1, Synthesis of t-butylperoxymethacryloyloxyethyl carbonate (B-MEC)]
A mixed solution was prepared by mixing 0.34 parts by mass of 2-hydroxyethyl methacrylate and 0.51 parts by mass of toluene, and 0.29 parts by mass of a 70% toluene solution of t-butyl hydroperoxide was added thereto at room temperature. After the mixture was cooled to 10 ° C., 0.50 parts by mass of a 20% aqueous potassium hydroxide solution was added dropwise with care so that the liquid temperature was kept almost constant. After completion of the dropping, the reaction solution was stirred for 45 minutes while keeping the temperature constant, and then the aqueous layer was separated. The oil layer was washed 3 times with distilled water and dehydrated with anhydrous sodium sulfate. As a result, 1.0 part by mass of a toluene solution of t-butylperoxymethacryloyloxyethyl carbonate as a target product was obtained (concentration 40% by mass). The amount of active oxygen in this solution was measured by iodometry and found to be 2.60%.
[Production Example 2, synthesis of 2-methylpentyl-2-peroxymethacryloyloxyethyl carbonate (H-MEC)]
The same procedure as in Production Example 1 was carried out except that 0.26 parts by mass of 2-methylpentyl-2-hydroperoxide (purity 90%) was used in place of t-butyl hydroperoxide in Production Example 1. As a result, 1.0 part by mass of 2-methylpentyl-2-peroxymethacryloyloxyethyl carbonate was obtained (concentration 40%). When the amount of active oxygen in this solution was measured by the iodometry method, it was 2.33%.
[Production Example 3, Synthesis of t-butylperoxymethacryloyloxypropyl carbonate (B-MPC)]
In Production Example 1, t-butylperoxymethacryloyloxypropyl which is the target product was carried out in the same manner as in Production Example 1 except that 0.38 parts by mass of 2-hydroxypropyl methacrylate was used instead of 2-hydroxyethyl methacrylate. 1.0 part by mass of carbonate was obtained (concentration 40%). When the amount of active oxygen in this solution was measured by the iodometry method, it was 2.46%.
(Example 1, continuous polymerization of styrene)
The polymerization stock solution dissolved at a ratio of 86 parts by mass of styrene, 0.024 parts by mass of B-MEC (1 mmol / L) and 14 parts by mass of ethylbenzene was degassed, and the polymerization temperature was set in a continuous reaction tank with a stirrer having an internal volume of 1 liter. While maintaining the temperature at 130 ° C., the polymerization was continuously carried out so that the average residence time was 5 hours. After polymerization, the polymerization solution was degassed under reduced pressure at 230 ° C. and 10 mmHg, and pelletized (granulated) with an extruder. The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 86%. Table 1 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Examples 2 and 3, continuous polymerization of styrene)
It implemented according to Example 1 except having changed the polymerization initiator in Example 1 respectively as Table 1 (all polymerization initiator density | concentrations are 1 mmol / L). Table 1 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Example 4, continuous polymerization of styrene)
In Example 1, 0.012 parts by mass (0.5 mmol / L) of B-MEC and 0.02 parts by mass of HC (0.8 mmol / L, bifunctional initiator) were used in combination as polymerization initiators. Except for the above, it was carried out according to Example 1. The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 79%. Table 1 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Example 5, continuous polymerization of styrene)
In Example 1, 0.012 parts by mass (0.5 mmol / L) of B-MEC and 0.015 parts by mass (0.8 mmol / L) of BZ were used as polymerization initiators. It carried out according to 1. The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 80%. Table 1 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Comparative example 1, continuous polymerization of styrene)
In Example 1, it implemented according to Example 1 except having used B-CI 0.024 mass part (1 mmol / L) instead of B-MEC. The polymerization conversion rate determined from the quantitative result of the residual styrene content by gas chromatography was 77%. Table 2 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Comparative Example 2, continuous polymerization of styrene)
In Example 2, it implemented according to Example 2 except having used 0.012 mass part (0.5 mmol / L) of B-CI instead of B-MEC. The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 75%. Table 2 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Comparative Example 3, continuous polymerization of styrene)
In Example 3, it implemented according to Example 3 except having used 0.012 mass part (0.5 mmol / L) of t-butylperoxycinnamate instead of t-butylperoxymethacryloyloxyethyl carbonate. . The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 79%. Table 2 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.
(Comparative Example 4, continuous polymerization of styrene)
In Example 1, it implemented according to Example 1 except having used 0.014 mass part (0.25 mmol / L, tetrafunctional polymerization initiator) of TA instead of B-MEC. The polymerization conversion rate determined from the result of quantitative determination of the amount of residual styrene by gas chromatography was 70%. Table 2 shows the results of measuring the molecular weight, degree of branching, MFR and Izod impact strength of the obtained styrene polymer.

実施例１〜３と比較例１、４との比較、或いは実施例４と比較例２との比較より、重合開始剤として共役パーカーボネートを使用することにより、従来の共役パーオキシエステル、或いは多官能重合開始剤を用いた場合に比べて重合転化率や得られる重合体の分子量が十分に向上し、それに伴って耐衝撃性が向上することが明らかとなった。分子量が大きく増大している分、実施例１と比較例１、４との比較ではＭＦＲは若干の低下が認められるが、実施例１のスチレン重合体は成形が十分に可能であった。さらに、例えば実施例４と比較例３とを比較すると、実施例４ではＭＦＲを損なうことなく分子量が増大し、耐衝撃性が向上していることがわかる。加えて、実施例１の重合転化率は、比較例１の重合転化率より９％もの高い値を示しており、生産性の良い点が裏付けられた。ちなみに、重合時間をさらに延長すると、実施例１の共役パーカーボネートでは重合転化率が高くなるのに対して比較例１のパーオキシエステルでは重合転化率がそれ以上高くならないため、それらの差が一層大きくなるものと予測される。

From the comparison between Examples 1 to 3 and Comparative Examples 1 and 4, or the comparison between Example 4 and Comparative Example 2, it is possible to use conventional conjugated peroxyesters, It has been clarified that the polymerization conversion rate and the molecular weight of the resulting polymer are sufficiently improved as compared with the case of using a functional polymerization initiator, and the impact resistance is improved accordingly. Since the molecular weight was greatly increased, the MFR was slightly decreased in the comparison between Example 1 and Comparative Examples 1 and 4, but the styrene polymer of Example 1 was sufficiently capable of being molded. Further, for example, when Example 4 and Comparative Example 3 are compared, it can be seen that in Example 4, the molecular weight increases without impairing the MFR, and the impact resistance is improved. In addition, the polymerization conversion rate of Example 1 was 9% higher than the polymerization conversion rate of Comparative Example 1, confirming the good productivity. Incidentally, when the polymerization time is further extended, the polymerization conversion rate of the conjugated percarbonate of Example 1 increases, whereas the peroxyester of Comparative Example 1 does not increase the polymerization conversion further, so that the difference between them is further increased. Expected to grow.

  From these results, it was found that the method for producing a styrene polymer using the conjugated percarbonate in each example can increase the molecular weight without impairing the moldability of the polymer and achieve an improvement in impact resistance.

In addition, the said embodiment can also be changed and actualized as follows.
A plurality of t-alkyl peroxymonocarbonates having a conjugated double bond at the terminal may be used in combination.

A polyfunctional peroxide having a plurality of peroxide bonds may be used in combination with the conjugated peroxide.
Furthermore, the technical idea grasped from the embodiment will be described below.

  In the chemical formula (1), R is a methyl group, R ′ is an alkyl group having 4 to 8 carbon atoms, X is an alkylene group having 2 or 3 carbon atoms, and n is 1. Item 5. A method for producing a styrene polymer according to Item 4. In this case, in addition to the effect of the invention according to claim 3 or claim 4, the polymerization initiation efficiency can be increased, and the production cost can be reduced.

  A polymerization initiator used in the method for producing a styrenic polymer according to claim 1 and comprising a t-alkyl peroxymonocarbonate having a conjugated double bond at a terminal. In this case, the polymerization initiator can exert the effect of the invention according to claim 1 in the production of the styrene polymer.

Claims (4)

A styrene polymer is produced by polymerizing a styrene monomer or a monomer mixture of a styrene monomer and a vinyl monomer copolymerizable therewith using a polymerization initiator. In the manufacturing method,
The method for producing a styrenic polymer, wherein the polymerization initiator is a t-alkyl peroxymonocarbonate having a conjugated double bond at a terminal. The method for producing a styrenic polymer according to claim 1, further comprising a polymerization initiator other than the t-alkyl peroxymonocarbonate as a polymerization initiator. The method for producing a styrenic polymer according to claim 1 or 2, wherein the t-alkyl peroxymonocarbonate is a compound represented by the following chemical formula (1).

(However, R represents a hydrogen atom or a methyl group, R ′ represents a tertiary alkyl group or a tertiary aralkyl group having 4 to 12 carbon atoms, and X represents a linear or branched alkylene having 1 to 4 carbon atoms. Represents a group, and n represents an integer of 1 to 4.) The styrenic polymer has a mass average molecular weight of 300,000 to 1,000,000 determined based on a calibration curve by gel permeation chromatography (GPC) using a refractive index detector, and uses a multi-angle light scattering detector. The value obtained by dividing the mass average molecular weight determined by GPC by the mass average molecular weight determined based on the calibration curve by GPC using the refractive index detector is 1.2 to 2.0. The method for producing a styrenic polymer according to any one of claims 1 to 3.