JPH072803B2 - Method for producing styrene-based prepolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention aims to improve the performance and functionality of products in the field of manufacturing molding materials, paints, adhesives and other polymeric materials. The present invention relates to a method for producing a styrene-based prepolymer, which is an important means and is particularly important as a synthetic intermediate for a graft polymer.

[Conventional technology and its problems]

Attempts have been made for a long time to use block polymers and graft polymers to enhance the functionality of polymer materials, but block polymers by ionic polymerization have many restrictions in production, so graft polymers are not suitable for the development of functional polymers. Was desired.

The macromonomer means an oligomer or polymer having a polymerizable functional group at the terminal, and is an abbreviation of Macrolecure Monomer. Since about 20 years ago, research on oligomers with a double bond at one end has been carried out, but the topic was Milkovich.
After that research. Their method is to make living polymer anions such as styrene, α-methylstyrene, butadiene, and isoprene react with allyl chloride, epichlorohydrin, methacrylic acid chloride, etc., to produce various terminal polymerizable groups such as allyl group, methacryloyloxy group, and styryl. Group, glycidyl group and other macromonomers are synthesized. Co
rn Product registered a trademark of Macromer for this kind of oligomer and applied for numerous patents (Japanese Patent Publication No. 50-116586).
No.

Macromonomers have been of great industrial importance since their research as a dispersant in the manufacture of high solid paints at ICI, UK. Typically, a radical-polymerizable monomer such as methyl methacrylate is polymerized in the presence of mercaptoacetic acid as a chain transfer agent to obtain an oligomer of a terminal carboxylic acid, which is converted into a macromonomer with glycidyl methacrylate (hereinafter abbreviated as GMA). (Japanese Patent Publication No. 43-11224, Japanese Patent Publication No. 43-16147, etc.). As a method similar to this ICI method, there is a du Pont method in which a hydroxyl group-terminated oligomer with mercaptoethanol is converted into an isocyanate with toluylene diisocyanate and then converted into a macromonomer with hydroxyethyl methacrylate.

In Japan, the energetic research of Yamashita et al.
General interest has also grown significantly over the last few years. They are
Various comb-type graft polymers were synthesized using several kinds of macromonomers synthesized by the above-mentioned Milkovich ionic polymerization method and ICI radical polymerization method, and applied to the surface modification of polymer materials. According to their research, the usefulness of the graft polymer using macromonomer, that is, the structure is clearly controlled and the graft polymer with a small content of homopolymer can be easily produced. It has been clarified that the effect of reforming is excellent (JP-A-57-179246, Macromol).
ecule 13 , 216 (1980) etc.).

As described above, the importance of macromonomers is clear, and in the last few years, their importance in the polymer manufacturing industry has been deeply recognized, and the development of practical applications has also been promoted. It is progressing.

Polystyrene resin has a wide range of uses as general-purpose plastics, and is a polymer material that boasts a huge amount of consumption along with polyolefin and polyvinyl chloride, and is used as a molding material as well as a paint vehicle or for a wide range of other uses. Has been done. Therefore, it should be the polymer segment that should be taken up first, especially when considering practicality in the synthesis of macromonomers. In fact, there are numerous examples of styrene macromonomer synthesis and applications found in the literature and patents.

However, most of these styrene macromonomers adopt the above-mentioned Milkovich method or a partially improved method thereof, that is, a synthetic method by anionic polymerization. There are some reasons why the ICI or du Pont method, which can easily control the synthesis conditions and is closer to the industrial use, that is, the anionic polymerization method is used exclusively instead of the radical polymerization method. This is because the chain transfer reaction, which is a key point in synthesizing macromonomers by radical polymerization, is difficult to occur uniformly in the case of styrene.

In the ICI method, mercaptans are used as a chain transfer agent, and methacrylic acid and methacrylic acid esters and acrylic acid and acrylic acid esters have appropriate chain transfer constants (0.1 to 3), so the molecular weights are uniform. Prepolymers and macromonomers can be easily produced. However, since the chain transfer constant of styrene for mercaptans is generally 10 or more, the chain transfer agent is consumed very early in the polymerization, and a macromonomer with a uniform molecular weight cannot be produced. Therefore, the styrene macromonomer is
It doesn't work even if I try to synthesize it simply by the method.
In fact, as far as the present inventors know, there is no example of synthesizing a styrene macromonomer by the ICI method using a mercaptan chain transfer agent.

Focusing on this point, Yamashita et al. Have changed the chain transfer agent during prepolymer synthesis from mercaptoacetic acid to monoiodoacetic acid and synthesized a styrene macromonomer by radical polymerization (Polym.J., 14 , 255 (1982)). In this case, the chain transfer constant is 0.4 to 0.6, and a uniform chain transfer reaction can occur. However, in this method, the focus is on the release of iodine derived from the chain transfer agent, and its practicality is poor.

(B) Structure of the Invention [Means for Solving Problems] A styrene prepolymer and a styrene macromonomer are produced by a radical polymerization method advantageous for industrial production, using a mercaptan compound which is a highly versatile chain transfer agent. I examined how to do it.

In order to produce styrene macromonomer simply and economically, we considered the following points.

1) Use a radical polymerization method that allows easy control of manufacturing conditions.

2) As a chain transfer agent, a mercaptan compound is used because of problems with stability such as coloring and availability.

3) The chain transfer constants of vinyl monomers for mercaptan compounds are reported to be 14 to 19 for styrene, while that for methyl methacrylate; 0.63, methyl acrylate; 0.78, acrylonitrile; 0.73. Therefore, it is considered that the mercaptan compound will be consumed in a very short time in the polymerization reaction system of styrene.

4) For the reason of 3), in order to keep the concentration of the chain transfer agent in the reaction system at a constant level, the chain transfer agent is continuously supplied over the entire polymerization reaction time.

5) For the same reason 3), in order to reduce the molecular weight distribution of the macromonomer, the consumption rate of styrene by polymerization and the supply rate of the chain transfer agent are made close to each other.

6) Since styrene has a smaller polymerization rate than (meth) acrylic acid ester and acrylonitrile, a large amount of radical generation source, that is, an initiator is required for ordinary solution polymerization at a relatively low temperature. Due to this, by-products derived from the polymerization termination reaction increase and the purities of the prepolymer and macromonomer decrease, so that the polymerization reaction is carried out under substantially solvent-free conditions. In the field where the prepolymer or the macromonomer derived from the prepolymer is required as a powder, solvent-free conditions are preferable for producing the prepolymer or macromonomer. It is extremely difficult to industrially obtain a powdery prepolymer or macromonomer by removing the solvent from the organic solvent solution of the prepolymer or macromonomer. From this point of view, therefore, it is a very important point to carry out the polymerization reaction under substantially solvent-free conditions.

7) In order to prevent the polymer component generated in the latter stage of the reaction from solidifying or becoming so viscous that stirring is impossible, the prepolymer is kept in a molten state at a high temperature for the polymerization reaction.

By taking the above points into consideration, we were able to obtain styrene-based prepolymers with relatively uniform molecular weight and less impurity components, as well as styrene-based macromonomers.

That is, the present invention continuously or intermittently supplies a functional group-containing mercaptan chain transfer agent into a radical polymerization reaction system of a styrene-based monomer, and in the presence of a solvent of 0 to 10% by weight in the polymerization reaction system. The number average molecular weight (hereinafter referred to as Mn) is 1000 to 20000 and the ratio of the weight average molecular weight (hereinafter referred to as Mw) is Mw / Mn, which is characterized by performing a radical polymerization reaction.
= 1.5 to 4.0, a method for producing a styrene-based prepolymer.

The Mw and Mw of the above styrene-based prepolymer are measured values by the following gel permeation chromatography (hereinafter abbreviated as GPC).

Column: Polystyrene gel (eg Toyo Soda Kogyo Co., Ltd. trade name G4000H8, G3000H8) Elution solvent: Tetrahydrofuran Outflow rate; 1.0 ml / min Column temperature; 40 ° C Detector; RI detector Mw / Mn of styrene-based prepolymer The ratio is between 1.5 and 4.0, preferably between 1.5 and 3.0. It is difficult to produce a prepolymer having a ratio of less than 1.5, and when it exceeds 4.0, a prepolymer having no functional group based on a chain transfer agent at the polymer end or a by-product having a functional group at both ends of the polymer is produced.

The Mn of the styrenic prepolymer of the present invention is 1000 to 2000.
It is 0. When Mn is less than 1000, the physical properties of the polymer are insufficient and the raw material cost increases, which is not preferable. Mn
If it exceeds 20000, the purity of the prepolymer is lowered, and it is not preferable because troubles at the time of production are likely to occur due to an increase in melt viscosity. [Raw material] Styrene-based monomers used in the present invention include styrene, o-, m- or Alkylated styrenes such as p-methylstyrene, o-, m- or p-ethylstyrene, p-tert-butylstyrene, etc., monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, o-, m- or Halogenated styrene such as p-chlorostyrene, α-methylstyrene, etc., which can be used alone or in combination of two or more kinds, and the styrene-based monomer is used for commonly available polymerization or other purposes. The purity is not particularly limited. Also, a small amount of a monomer other than the styrene-based monomer may be added for the purpose of copolymerization. As the copolymerization monomer, methacrylic acid ester, acrylic acid ester, acrylonitrile, etc. can be used, and the amount used is preferably 0 to 40% by weight based on the total amount of the monomers.

Next, a functional group-containing mercaptan chain transfer agent is described. One of the examples is a chain transfer agent having a carboxyl group as a functional group at the terminal, specifically, mercaptoacetic acid, 2-mercaptopropionic acid, A mercaptan compound having a carboxyl group such as 3-mercaptopropionic acid is used. As the carboxyl group-containing mercaptan compound, 2-mercaptopropionic acid or 3-mercaptopropionic acid is preferably used because of the problem of coloring the macromonomer and the availability.

Another example of a chain transfer agent suitable for use is a chain transfer agent having a hydroxyl group at the terminal, and there is a hydroxyl group-containing mercaptan compound. Among them, 2-mercaptoethanol is preferable because of its easy availability. Used.

As the functional group-containing mercaptan-based chain transfer agent, various mercaptan compounds can be used depending on the type of the intended polystyrene end. For example, if the group to be introduced at the polymer end is a carboxyl group, mercaptopropionic acid as a chain transfer agent, thiomalic acid as a chain transfer agent if a dicarboxyl group, 2-mercaptoethanol as a chain transfer agent if a hydroxyl group, and a chain transfer agent if a dihydroxyl group. For thioglycerin and amino groups, 2-aminoethanethiol may be used as a chain transfer agent, and in other cases, the desired prepolymer can be obtained by selecting the mercaptan compound having the desired functional group. be able to.

Usual azo initiators and peroxide initiators can be used as polymerization initiators during prepolymer production, but the reaction temperature should be 100
When the temperature is set to be higher than 0 ° C, the initiator may not be used. When an initiator is used, an azo-based initiator is preferable in order to avoid the reaction of the chain transfer agent with the mercaptan compound. As the azo-based initiator, 2,2-azobisisobutyronitrile, (hereinafter abbreviated as AIBN) 4,4′-azobis-
4-Dianovaleric acid (hereinafter abbreviated as ACVA), 1-azobis-1-cyclohexanecarbonitrile (hereinafter abbreviated as ACHN) and the like are preferably used.

The prepolymer in the present invention is produced under the substantially solvent-free condition of 0 to 10% by weight of solvent in the polymerization reaction system.
The solvent present in the polymerization reaction system should be as small as possible, but if it is a small amount of solvent, a solid chain transfer agent insoluble in the styrene-based monomer may be continuously added for the purpose of reducing the viscosity of the molten state in the latter stage of the reaction. It is allowed to be used for supplying to the reaction system.

The amount of solvent is 0 to 10% by weight in the polymerization reaction system, and 5% by weight
The following is preferable, and 1% by weight or less is more preferable. When the amount of solvent exceeds 10% by weight, the control of the polymerization reaction itself becomes easy, but the polymerization rate decreases due to the lowering of the reflux temperature and the lowering of the monomer concentration, and the purity of the styrenic prepolymer produced decreases. It is not preferable.

As the solvent that may be contained in a small amount, a general organic solvent that dissolves a styrene-based prepolymer is used, and examples thereof include toluene, xylene, benzene, methyl ethyl ketone, butyl acetate, and N, N-dimethylformamide.

[Production of styrene-based prepolymer]

The synthesis of the styrenic prepolymer (hereinafter simply referred to as a prepolymer) in the present invention, that is, the radical polymerization of styrene is performed by bulk polymerization in the substantial absence of a solvent. The styrene may be charged all at once at the beginning of the polymerization, or a part or all of the styrene may be continuously supplied to the reaction system for the purpose of preventing runaway of the polymerization reaction. Similarly, the method of charging the polymerization initiator is not particularly limited.

On the other hand, the chain transfer agent must be fed continuously or intermittently throughout the polymerization reaction. If the supply of the chain transfer agent is cut off, the chain transfer agent in the reaction system will be consumed in a short time, and the molecular weight of the polystyrene produced thereafter cannot be controlled by the continuous transfer agent. It becomes a polymer that does not have. as a result,
The molecular weight distribution of the product is disturbed and the GPC spectrum shows multiple peaks. Therefore, continuous or intermittent supply of the chain transfer agent is necessary to obtain a macromonomer having a uniform molecular weight.

However, when the polymerization initiator is kept at a high temperature for the purpose of crushing the residual initiator which becomes an obstacle in the next reaction step after the completion of the polymerization reaction, it is not necessary to continuously supply the chain transfer agent.

Further, in order to obtain a prepolymer having a uniform molecular weight distribution, it is desirable that the ratio of the reaction amount of styrene per unit time and the supply amount of the chain transfer agent per unit time be as constant as possible. For that purpose, it is preferable to take the following two means.

1) Keep the supply rate of the chain transfer agent constant, and devise the supply method of styrene and the initiator to keep the consumption rate of styrene polymerization (consumption of styrene per unit time) constant.

2) The feed rate of the chain transfer agent is changed according to the consumption rate of styrene.

In the case of 1), the time-conversion rate curve in the polymerization of styrene approaches a straight line in consideration of the polymerization conditions of styrene, for example, the charging method and charging amount of styrene monomer / initiator / solvent, reaction time, reaction temperature, etc. Just devise it.
In the case of 2), a time-conversion rate curve is drawn for the polymerization of styrene under a certain condition, and the chain transfer agent may be continuously supplied to the reaction system in accordance with this.

However, if a prepolymer with a narrow molecular weight distribution is not particularly required, such a method for supplying the chain transfer agent is not necessary.

Initiators without a carboxyl group such as AIB
When using N, ACHN, etc., it is preferable to keep the total amount of the initiator charged to a level lower than the total amount of the chain transfer agent. This is because when the initiator is present in a large amount relative to the chain transfer agent, the probability of initiating the polymerization directly from the initiator is increased, and as a result, the polymer molecule having the initiator segment rather than the desired functional group at the polymer end is obtained. Is increased and the purity of the prepolymer is reduced.

The acceptable amount of initiator in this case depends on the type of initiator,
It cannot be stated unequivocally because it is affected by the type of chain transfer agent, the concentration of monomers and initiators / chain transfer agents, the reaction temperature, the charging method, etc., but as a guideline, it should be less than the charged amount of chain transfer agent. The smaller the amount of the initiator used, the more preferable, and it is preferable not to use the initiator at a high temperature at which the polymerization reaction proceeds even without using the initiator. In the case of an initiator having a carboxyl group in the molecule, such as ACVA, there is no such restriction on the amount of the initiator, but on the other hand, its solubility in ordinary organic solvents is inferior, so there is a limitation in use.

[Use of prepolymer]

The prepolymer itself can be used as a raw material for adhesives, paints, molding materials, etc., but the main use of the prepolymer is for the production of macromonomers.

A macromonomer is a reaction with a polymerizable compound having both a polymerizable double bond and a functional group derived from a chain transfer agent in a prepolymer, which can be easily obtained by a conventional method. You can

As the compound having a polymerizable functional group used during the production of the macromonomer, when the terminal of the prepolymer is a carboxyl group, a compound having an epoxy group which easily reacts with the carboxyl group and a polymerizable functional group is used. For example, glycidyl methacrylate (hereinafter abbreviated as GMA), glycidyl acrylate, allyl glycidyl ether and the like are preferably used. When the terminal functional group of the prepolymer is a hydroxyl group, a compound having an isocyanate group and a polymerizable functional group which have good reactivity with the hydroxyl group is used. Isocyanatoethyl methacrylate is preferably used.

The reaction catalyst used during the production of macromonomers is
In the case of the reaction between the carboxylic acid at the polymer terminal and the epoxy group, a tertiary amine, a quaternary ammonium salt or the like can be used. In order to prevent coloring of the macromonomer, it is preferable to use a quaternary ammonium salt such as tetrabutylammonium bromide (hereinafter abbreviated as TBAB). Further, in the case of the reaction between the hydroxyl group of the polymer terminal and the isocyanate group, a tin-based catalyst such as dibutyltin dilaurate or dibutyltin diacetate is preferably used, but no catalyst is also acceptable.

Any reaction solvent may be used as long as it can dissolve the macromonomer, and may be appropriately selected. When the reaction is carried out in a high temperature molten state, it may not be used.

In addition to these, in order to prevent polymerization during the production of the macromonomer, it is preferable to add a radical polymerization inhibitor such as hydroquinone or hydroquinone monomethyl ether (hereinafter abbreviated as MQ) at the macromonomerization reaction stage.

The molecular weight of the macromonomer is the molecular weight of the prepolymer plus the molecular weight of the polymerizable compound that reacts with it, and the range is almost the same as that of the prepolymer.
The molecular weight ratio Mw / Mn of the macromonomer is almost the same as that of the prepolymer.

As mentioned above, there are two types of reaction: a) terminal carboxyl group prepolymer + epoxy group-containing compound b) terminal hydroxyl group prepolymer + isocyanate group-containing compound. preferable. This is because the isocyanate compound used in the reaction b) is sensitive to water and easily produces a bifunctional compound.

In the case of a), the reaction is carried out in the molten state of the polymer after production of the prepolymer or after dissolution in a suitable solvent. A radical polymerization inhibitor such as MQ, an epoxy compound such as GMA, and a catalyst such as TBAB may be charged into this prepolymer and reacted. In this case, the amount of MQ charged is preferably 10 to 1000 PPM with respect to the total amount of the reaction solution. The amount of GMA charged is 0.9 to the carboxyl groups in the reaction solution.
3.0 times equivalent is preferable. TBAB amount is based on the total amount of reaction solution
0.02 to 2.0% by weight is preferable.

During the reaction, the reaction system may be bubbled with an oxygen-containing gas in order to prevent polymerization of the generated macromonomer. Usually, the reaction temperature is preferably in the range of 50 ° C to 200 ° C.
0 ° C to 180 ° C is more preferable.

As an example of the reaction method in the case of b), 0.9 to 3.0 times equivalent amount of isocyanate ethyl methacrylate with respect to the hydroxyl groups in the reaction solution in the reaction solution or the melt after the prepolymer production, and the total amount of the reaction solution The target styrene macromonomer can be obtained by charging 0 to 3.0% by weight of dibutyltin dilaurate and reacting the mixture at room temperature to 180 ° C. for several minutes to several hours. In this case, since the isocyanate group is unstable, it is preferable to carry out the solution reaction at a relatively low temperature.

The macromonomer produced by the solution reaction may be used in the next reaction as it is, or may be taken out as a solid product after being purified by precipitation in a poor solvent or by removing volatile components and drying as it is. .

Further, the graft polymer can be easily obtained by radically copolymerizing the macromonomer obtained as described above and various radically polymerizable monomers by a conventional method.

[Examples and Comparative Examples]

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, all% described in each example represent% by weight, and part represents part by weight.

Example 1 1) Production of Styrene-based Prepolymer Having Carboxyl Group at Terminal End In a glass flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, 333 parts of styrene and 3-mercaptopropionic acid (hereinafter referred to as MPA) 3.2 parts were charged, and a mixture of 667 parts of styrene and 14.8 parts of MPA was put into the dropping funnel. The reaction solution was refluxed by heating the flask. The mixed solution of the dropping funnel was added dropwise thereto over 4 hours. During this time, the reaction temperature gradually increased from the initial reflux temperature of 146 ° C.
After reaching 0 ° C., the temperature was kept constant thereafter. After the dropping was completed, 3.2 parts of MPA was continuously fed to the reaction system over 3 hours. The reaction was terminated by further aging for 3 hours to obtain a prepolymer having a terminal carboxyl group. The amount of solvent in this prepolymer was zero. It was The styrene polymerization conversion determined by gas chromatography was 97.0%, and the molecular weight determined by GPC was Mn = 5880, Mw = 11700.
And Mw / Mn = 1.99.

2) Production of macromonomer 1000 parts of toluene was gradually added to the reaction melt of 1) to form a solution having a solid content of about 50%. MQ0.51 part, GMA26.6 part, TBA
10 parts of B was charged and reacted at 90 ° C for 8 hours while bubbling air. The reaction conversion obtained from the acid value by titration is
It was 96.6%. The reaction solution was dried under reduced pressure at 80 ° C to obtain 972 parts of solid styrene macromonomer. The polystyrene reduced molecular weight by GPC is Mn = 5910, Mw = 11900 and Mw /
It was Mn = 2.01.

The polystyrene reduced molecular weight by GPC is Mn = 5910, Mw = 119
00 and Mw / Mn = 2.01.

3) Confirmation of polymerizability a. 2 parts of the produced styrene macromonomer, 2 parts of styrene monomer, 4 parts of toluene, and 0.04 part of ACHN were charged into a polymerization tube, and after deaeration and sealing, reaction was carried out at 90 ° C for 3 days. Of this solution
It was confirmed from the GPC chart that the peak of the macromonomer had disappeared, and the polymerizability of the macromonomer was proved.

b. Polymerizability of macromonomer was confirmed in the same manner as in a except that AIBN was used instead of ACHN and the reaction temperature was 80 ° C. The product had Mw / Mn = 2.10.

Example 2 1) Production of a styrene-acrylonitrile copolymer prepolymer having a carboxyl group at the terminal A glass flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer was equipped with 150 parts of styrene, 50 parts of acrylonitrile, MPA1. .27 parts were charged and styrene 75 was added to the dropping funnel.
Part, acrylonitrile 25 parts, MPA 3.39 parts, and ACHN 0.15 parts were mixed. The reaction solution was refluxed by heating the temperature of the slasco. The mixed solution of the dropping funnel was added dropwise thereto over 4 hours. After the dropping was completed, 1.7 parts of MPA was continuously fed to the reaction system over 2 hours. The reaction temperature during this time is the initial reflux temperature.
The temperature rises gradually from 101 ℃, and when it reaches 160 ℃, the temperature is kept constant thereafter. Then, the reaction was completed by aging for 2 hours to obtain a styrene-acrylonitrile copolymer prepolymer having a carboxyl group at the terminal. The amount of solvent in this prepolymer was zero.

The polymerization conversion of styrene determined by gas chromatography was 94.8%, and the molecular weight determined by GPC was M
n = 7310, Mw = 16500 and Mw / Mn = 2.26.

2) Production of macromonomer 300 parts of toluene was gradually added to the reaction melt obtained in 1) to form a solution having a solid content of about 50%. MQ0.12 part, GMA7.95 part, TBA
B3.0 parts were charged, and the mixture was reacted at 90 ° C for 3 hours while bubbling air. The reaction conversion obtained from the acid value by titration is
It was 97.1%. The reaction solution was dried under reduced pressure at 80 ° C to obtain 290 parts of solid styrene macromonomer. The molecular weights determined by GPC were Mn = 7400, Mw = 17000 and Mw / Mn = 2.30.

3) Confirmation of Polymerizability The same procedure as in Example 1 was performed to confirm the polymerizability.

Example 3 (Production of styrene-based prepolymer having terminal dicarboxyl group) A glass flask equipped with a stirrer, a reflux condenser, two dropping funnels and a thermometer was charged with 333 parts of styrene and 4.5 parts of thiomalic acid. Then, 667 parts of styrene was placed in one dropping funnel (designated dropping funnel A), and a mixture of 21 parts of thiomalic acid and 79 parts of distilled water was placed in the other dropping funnel (designated dropping funnel B). The reaction solution was refluxed by heating the flask. The mixed solution of the dropping funnels A and B was added dropwise thereto over 4 hours. After completion of dropping, thiomalic acid 4.
A mixed solution of 5 parts and 17 parts of distilled water was supplied to the reaction system over 3 hours. During the dropwise addition of the thiomalic acid aqueous solution, the reaction was proceeded while separating and removing the distilled water with the H tube. During this period, the reaction temperature gradually increased from the initial reflux temperature of about 135 ℃, and when it reached 170 ℃, it was kept constant. The reaction was completed after aging for 2 hours. The amount of solvent in the obtained prepolymer was 0. The polymerization conversion of styrene determined by gas chromatography was 95.0%, and the molecular weights determined by GPC were Mn = 5530, Mw = 16400 and Mw / Mn = 2.97.

The molten product was taken out of the flask, allowed to cool, solidify, and pulverized to obtain 946 parts of a solid prepolymer having a dicarboxyl group at its end.

Comparative Example 1 1) Production of prepolymer having terminal carboxyl group by solution polymerization method 500 parts of styrene and methyl isobutyl ketone (in a glass flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a gas inlet). Hereinafter abbreviated as MIBK) 300
Parts, and one part of the dropping funnel (hereinafter referred to as dropping funnel A) has 500 parts of styrene, and the other dropping funnel (hereinafter referred to as dropping funnel B) has 12.5 parts of AIBN and 21.2 parts of MPA and M.
A mixture of 250 parts of IBK was added. After introducing the nitrogen gas, the dropping funnel A was dropped for 4 hours and the dropping funnel B was dropped for 10 hours while the temperature of the flask was increased by heating to keep the reaction liquid at 90 ° C.

In order to decompose AIBN existing in the reaction system, heating was further performed for 2 hours to obtain a prepolymer having a terminal carboxyl group. The polymerization conversion of styrene determined by gas chromatography was 92.5%, and the molecular weights determined by GPC were Mn = 4840, Mw = 9540 and Mw / Mn = 1.97.

2) Production of macromonomer 0.3 parts of MQ, 27.0 parts of GMA and 7.5 parts of TBAB were charged into the reaction melt of 1), and the mixture was reacted at 90 ° C for 9 hours while bubbling air. The reaction conversion rate determined by titration was 91.0%.
This reaction solution was precipitated in 10 volumes of methanol. It was dried under reduced pressure at 80 ℃ to obtain 912 parts of solid styrene macromonomer. The polystyrene reduced molecular weight by GPC is Mn = 470
0, Mw = 9400 and Mw / Mn = 2.0.

3) Confirmation of polymerizability When polymerized by the method a) in 3) of Example 1, the reaction solution gelled and became insoluble in the solvent.

Further, when polymerized by the method b) of Example 1 3),
The reaction liquid did not gel, and the polymerizability was confirmed, but the product was
Mw / Mn = 3.0.

Since the unreacted styrene macromonomer remains, the Mw / Mn ratio seems to have increased apparently.

(C) Effect of the Invention According to the present invention, a high-purity prepolymer having a carboxyl group or a hydroxyl group at the terminal can be easily obtained. The number average molecular weight of this prepolymer is Since it matches very well with the calculated value of the molecular weight calculated from the polymerization conversion rate of the monomer, the molecular weight of this prepolymer can be surely controlled, and the molecular weight distribution of this prepolymer is relatively narrow. In addition to that, it is a high-purity product that contains less bifunctional by-products that may cause gelation due to the crosslinking reaction, as compared with products manufactured in the presence of a large amount of solvent. .

Such prepolymers themselves can be used as molding materials, adhesives, paints and other functional polymer materials,
It is industrially useful as a raw material for macromonomers and graft polymers.

Claims (1)

[Claims] 1. A mercaptan chain transfer agent containing a functional group is continuously or intermittently supplied to a radical polymerization reaction system of a styrene monomer, and the polymerization reaction system is subjected to the presence of a solvent in an amount of 0 to 10% by weight. Characterized by performing a radical polymerization reaction,
The number average molecular weight (Mn) is 1000 to 20000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight is Mw / Mn = 1.5 to 4.0
A method for producing a styrene-based prepolymer.