JP2001048935A - Fumarate diester-based polymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a fumarate diester-based polymer which can dispense with, e.g. a procedure for eliminating the unreacted fumarate diester, and also to provide fumarate diester-based polymer containing a limited quantity of the unreacted fumarate diester and having a low number- average molecular weight. SOLUTION: This fumarate diester-based polymer is produced by polymerizing a monomer composition containing fumprate diester in the presence of a solvent and initiator for the polymerization. The solvent dissolves the monomer composition containing fumarate diester and essentially does not dissolve the fumarate diester-based polymer. The fumarate diester-based polymer produced by the method for producing the fumarate diester-based polymer is powdery, and has a number-average molecular weight of 500 to 50,000 and particle size of 5 to 100 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not require an operation for removing unreacted fumaric acid diester and the like. The present invention relates to a fumaric acid diester polymer having a small number of fumaric acid diesters and a small number average molecular weight.

[0002]

2. Description of the Related Art Fumaric acid diester polymers have been known as resins having excellent heat resistance. This fumaric acid diester polymer is disclosed in, for example, Japanese Patent Publication No. 4-3041.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2 (1994) -1990, the polymer is produced by a bulk polymerization method without using a polymerization solvent. Further, the fumaric acid diester polymer is also produced by a suspension polymerization method using water as a polymerization solvent or a solution polymerization method using an organic solvent such as benzene or toluene as a polymerization solvent.

[0003]

[Problems to be solved by the invention]
In the bulk polymerization method disclosed in Japanese Patent No. 30412, the polymerization reaction of fumaric acid diester is particularly slow in the late stage of polymerization, and unreacted fumaric acid diester remains in the obtained fumaric acid diester polymer. In order to remove the unreacted fumaric acid diester, there was a problem that extra operations such as reprecipitation purification and filtration had to be performed.

[0004] In the suspension polymerization method, since the diffusion of fumaric acid diester becomes rate-determining in the latter stage of the polymerization, the polymerization reaction of fumaric acid diester is restricted, and unreacted fumaric acid diester remains. Moreover, the fumaric acid diester-based polymer produced by the suspension polymerization method has a problem that the number average molecular weight is high and the solubility in solvents such as benzene, toluene, tetrahydrofuran, and chloroform is low.

Further, in the solution polymerization method, since the polymerization solvent used dissolves both the monomer and the polymer, a chain transfer to the polymerization solvent occurs during the polymerization, and the polymerization reaction of fumaric diester is carried out. However, there is a problem that unreacted fumaric acid diester remains.

The present invention has been made by paying attention to the problems existing in the prior art described above. The objective is to eliminate the need for an operation to remove unreacted fumaric acid diester, etc., to obtain a fumaric acid diester-based polymer efficiently and to obtain an unreacted fumaric acid diester. To provide a fumaric acid diester polymer having a low number and a small number average molecular weight.

[0007]

Means for Solving the Problems In order to achieve the above object, a method for producing a fumaric acid diester polymer according to the first invention comprises a method for producing a fumaric acid diester in the presence of a polymerization solvent and a polymerization initiator. In the method for producing a fumaric acid diester polymer for polymerizing a monomer composition, the polymerization solvent dissolves the monomer composition containing the fumaric acid diester, and substantially converts the fumaric acid diester polymer. Insoluble.

Further, the fumaric acid diester polymer according to the second invention is a powdery fumaric acid diester polymer obtained by the method for producing a fumaric acid diester polymer according to the first invention. Average molecular weight 500-50,000
And the particle size of the powder is 0.5 to 100 μm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. The fumaric acid diester polymer is obtained by polymerizing a monomer composition containing a fumaric acid diester in the presence of a polymerization solvent and a polymerization initiator. The polymerization solvent used is one that dissolves the monomer composition containing the fumaric acid diester and makes the fumaric acid diester-based polymer substantially insoluble.

As the raw material, all known fumaric acid diesters can be used, but a compound represented by the following general formula (1) is preferred.

[0011]

Embedded image In the general formula (1), R ¹ represents an alkyl group or a cycloalkyl group, R ² represents an alkyl group, a cycloalkyl group or an aryl group, and R ¹ and R ² may be the same or different.

The alkyl group represented by R ¹ or R ² is preferably an alkyl group having 2 to 12 carbon atoms, which may be linear or branched, and further having a substituent. It may be. Examples of the substituent having a substituent include a halogen atom (F, Cl), an alkoxy group (such as a methoxy group, an ethoxy group, a propoxy group, and a butoxy group), and an aryl group (such as a phenyl group).

Specific examples of the alkyl group include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
sec-butyl group, tert-butyl group, n-pentyl group (n-amyl group), sec-amyl group, isopentyl group, neopentyl group, tert-pentyl group, n-hexyl group, 4-methyl-2-pentyl group , Heptyl, octyl, nonyl, decyl, undecyl, dodecyl, trifluoroethyl, hexafluoroisopropyl, perfluoroisopropyl, perfluorobutylethyl, perfluorooctylethyl, 2-chloroethyl , 1-butoxy-2-propyl group, methoxyethyl group, benzyl group and the like.

The cycloalkyl group represented by R ¹ or R ² is preferably a cycloalkyl group having 3 to 14 carbon atoms, and may be a single ring or a bridged ring. May be provided. Examples of the substituent in this case include the same substituents as those exemplified above for the alkyl group.

Specific examples of the above cycloalkyl group include:
Examples include a cyclopentyl group, a cyclohexyl group, an adamantyl group, and a dimethyladamantyl group. The aryl group represented by R ² preferably has 6 to 18 carbon atoms and is preferably a monocyclic ring, but may be a polycyclic ring (condensed ring or ring assembly) or may have a substituent. Good. In this case, the substituents are the same as those exemplified for the alkyl group and the cycloalkyl group.

Specific examples of the aryl group include a phenyl group and a benzyl group. As R ¹ or R ² , an alkyl group and a cycloalkyl group are preferable. As the alkyl group, a branched alkyl group is preferable, and an isopropyl group, a tert-butyl group, and the like are preferable. Further, as the cycloalkyl group, a cyclohexyl group or the like is preferable.

Specific examples of the fumaric acid diester represented by the general formula (1) include diethyl fumarate, di-n-propyl fumarate, di-n-hexyl fumarate, isopropyl-n-hexyl fumarate, and diisopropyl fumarate. Fumarate, di-n-butyl fumarate, di-sec-butyl fumarate, di-tert-butyl fumarate, di-sec-amyl fumarate, n-butyl isopropyl fumarate, sec-butyl isopropyl fumarate,
tert-butyl-4-methyl-2-pentyl fumarate, tert-butyl isopropyl fumarate, sec
-Amyl isopropyl fumarate, di-4-methyl-2
-Pentyl fumarate, diisoamyl fumarate, di-
Dialkyl fumarate such as 4-methyl-2-hexyl fumarate, tert-butyl isoamyl fumarate;
Dicycloalkyl fumarate such as dicyclopentyl fumarate, dicyclohexyl fumarate, dicycloheptyl fumarate, cyclopentyl cyclohexyl fumarate, bis (adamantyl) fumarate, bis (dimethyladamantyl) fumarate; cyclohexyl isopropyl fumarate, adamantyl isopropyl fumarate Alkylcycloalkyl fumarate such as dimethyl adamantyl isopropyl fumarate and cyclohexyl-tert-butyl fumarate; alkyl aryl fumarate such as isopropylphenyl fumarate; aralkyl such as benzyl-tert-butyl fumarate and benzyl isopropyl fumarate Alkyl fumarate; ditrifluoroethyl fumarate, dihexafluoroisopropyl fumarate Difluoroalkyl fumarate such as diperfluoroisopropyl fumarate and diperfluorobutylethyl fumarate; alkylfluoroalkyl fumarate such as isopropyl perfluorooctylethyl fumarate and hexafluoroisopropylisopropyl fumarate; 1-butoxy-2 -Propyl-t
and alkyl-substituted alkyl fumarate such as tert-butyl fumarate, isopropylmethoxyethyl fumarate, 2-chloroethyl isopropyl fumarate and the like. These fumaric diesters are classified into a liquid type and a solid type.

Among them, diisopropyl fumarate, dicyclohexyl fumarate, di-sec-butyl fumarate, di-tert-butyl fumarate, cyclohexyl isopropyl fumarate, tert-butyl isopropyl fumarate, sec-butyl cyclohexyl fumarate, etc. It is particularly preferred in terms of ease of synthesis and polymerization rate.

The fumaric acid diester can be synthesized by combining known esterification techniques and isomerization techniques. In obtaining the fumaric acid diester polymer of the present invention, the above fumaric acid diester may be used alone or in combination of two or more.

The content of the fumaric acid diester in the monomer composition is preferably 80% by weight or more in order to improve the heat resistance of the resulting fumaric acid diester polymer.

Further, another vinyl monomer having a copolymerizability with the fumaric acid diester can be contained in the monomer composition. All such other vinyl monomers are included as long as they have copolymerizability, but a compound represented by the following general formula (2) is preferable.

[0022]

Embedded image In the general formula (2), X represents a hydrogen atom or a methyl group, and Y represents a hydrogen atom, a chlorine atom, a fluorine atom, an alkyl group, an aryl group, a nuclear-substituted aryl group, an acetyl group (-C
OCH ₃ ), acyl group (—COR ₃ ), alkoxy group (—OR ₃ ), alkoxycarbonyl group (—COO)
R ₃ ) or an alkylcarbonyloxy group (—OCO
R ₃ ). Here, R ₃ represents an alkyl group having 1 to 8 carbon atoms or a branched alkyl group having 3 to 8 carbon atoms, an aryl group, or a nucleus-substituted aryl group.

As the vinyl monomer represented by the general formula (2), specifically, vinyl acetate, vinyl pivalate,
Vinyl carboxylates such as vinyl 2,2 dimethylbutanoate, vinyl 2,2 dimethylpentanoate, vinyl 2-methyl-2-butanoate, vinyl propionate, vinyl stearate, and vinyl 2-ethyl-2-methylbutanoate; p-tert-
Aromatic vinyl monomers such as butyl vinyl benzoate and vinyl benzoate; α such as styrene, o-, m-, p-chloromethylstyrene, α-methylstyrene, and nuclear-substituted products thereof
Substituted styrene derivatives; alkyl nuclei such as o-, m- and p-methylstyrene; substituted styrenes; α-olefins such as vinyl chloride and vinyl fluoride; halogen nuclei such as o-, m- and p-halogenated styrene Substituted styrenes; vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether and cyclohexyl vinyl ether; naphthalene derivatives such as α, β vinyl naphthalene; alkyl vinyl ketones such as methyl vinyl ketone, isobutyl vinyl ketone and butyl vinyl ketone; butadiene; Dienes such as isoprene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth)
(Meth) acrylates such as acrylate and phenyl (meth) acrylate; and the like.

Among them, vinyl pivalate, p-ter
Vinyl t-butyl benzoate, styrene, cyclohexyl vinyl ether and the like are particularly preferred because of their high polymerization rate.

In using the vinyl monomer, one or more of the vinyl monomers represented by the general formula (2) can be selected and used. The content of the other vinyl monomer in the monomer composition is usually preferably less than 20% by weight. If the content of the other vinyl monomer is 20% by weight or more, the heat resistance of the resulting fumaric acid diester polymer is undesirably reduced.

Next, when producing the fumaric diester polymer, the polymerization solvent for the polymerization reaction dissolves the monomer composition containing the fumaric diester and substantially dissolves the fumaric diester polymer. Everything is included unless otherwise noted. By selecting a polymerization solvent satisfying such specific conditions, only the degree of polymerization can be reduced without lowering the polymerization rate.

Specific examples of such a polymerization solvent include alcohols such as methanol, ethanol and isopropanol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; acetates such as methyl acetate and ethyl acetate; And hydrocarbons such as hexane and cyclohexane. Of these, preferred are alcohols and ketones. When using these polymerization solvents, one kind or two or more kinds can be selected and used. When two or more kinds of polymerization solvents are used, water can be used as one component as long as it is soluble in the polymerization solvent.

Here, the polymerization solvent dissolves the monomer composition containing the fumaric acid diester and makes the fumaric acid diester-based polymer substantially insoluble as described above. Specifically, the solubility of the monomer composition in 100 parts by weight of the polymerization solvent is usually more than 5 parts by weight, preferably more than 10 parts by weight,
The solubility of the fumaric acid diester polymer in 100 parts by weight of the polymerization solvent is usually 5 parts by weight or less, preferably 3 parts by weight or less. The solubility varies depending on the type of fumaric acid diester, the type of polymerization solvent, the number average molecular weight of the fumaric acid diester-based polymer, and the like, but is appropriately selected depending on the purpose.

The amount of the polymerization solvent to be used with respect to the monomer composition containing the fumaric acid diester is usually in the range of 0.1 to 10 times by weight, preferably 0.2 to 10 times, in order to promote the polymerization smoothly. The range is five times.

Next, the polymerization initiator is preferably an organic peroxide having a 10-hour half-life temperature of 35 to 80 ° C. and an azo polymerization initiator. Specific examples include benzoyl peroxide, di-
Organics such as n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyisobutyrate and tert-butylperoxypivalate Peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 1,1 And azo-based polymerization initiators such as' -azobis (cyclohexane-1-carbonitrile) and dimethyl 2,2'-azobisisobutyrate.

Among them, benzoyl peroxide, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, tert-butylperoxypivalate, 2,2'-azobisisobutyronitrile and the like are 10 hours half-life temperature. Is particularly preferred since the boiling point is not higher than the boiling point of the polymerization solvent.

The method of using the polymerization initiator includes, for example, a method of dissolving it in a polymerization solvent in advance, a method of adding it all at once at the start of polymerization, and a method of adding it separately. Considering the polymerizability, the split addition is preferred.

The amount of the polymerization initiator used is preferably from 1 to 30% by weight, more preferably from 1 to 10% by weight, based on the monomer composition containing the fumaric acid diester. The polymerization in the production of the fumaric acid diester polymer is preferably carried out by substituting with an inert gas, for example, nitrogen, carbon dioxide, helium, argon or the like, or in an atmosphere thereof.

The polymerization temperature varies depending on the type of polymerization initiator, but is usually 35 to 80 ° C, preferably 40 to 60 ° C. Further, the polymerization time is preferably in the range of 1 to 24 hours, more preferably 1 to 10 hours.

The fumaric acid diester polymer obtained by the above production method has a low degree of polymerization and a relatively narrow range. That is, the number average molecular weight is usually 500
50,000, preferably 1,000 to 30,000. If the number average molecular weight is less than 500, the fumaric acid diester polymer becomes tacky due to its low melting point, making it difficult to handle. On the other hand, when the number average molecular weight exceeds 50,000, the solution viscosity of the fumaric acid diester-based polymer becomes extremely high, which makes handling inconvenient.

The particle size of the powder is relatively small, usually 0.5 to 100 μm, preferably 5 to 100 μm.
It is in the range of 50 μm. When the particle size is less than 0.5 μm, the yield of the fumaric acid diester-based polymer is reduced due to deterioration in filterability, and when it exceeds 100 μm, the monomer remains inside the particles of the fumaric acid diester-based polymer. Gelation occurs due to an increase in the polymerization rate.

The effects obtained by the above embodiment will be described below. According to the method for producing a fumaric acid diester polymer, the polymerization solvent is one that makes the fumaric acid diester polymer substantially insoluble,
The produced polymer precipitates quickly from the polymerization solvent. For this reason, a side reaction of the chain transfer agent or the like to the polymer is suppressed, the polymerization conversion rate is increased, and the unreacted fumaric diester is reduced. Therefore, an operation of removing unreacted fumaric acid diester is not required, and a fumaric acid diester-based polymer can be obtained efficiently.

A monomer composition containing a fumaric acid diester in the presence of a polymerization initiator in a polymerization solvent in which the monomer composition containing the fumaric acid diester is dissolved and the polymer is insoluble. By performing the above polymerization, the polymerization can be carried out smoothly with a high polymerization conversion rate.

The fumaric acid diester polymer obtained by the method for producing a fumaric acid diester polymer described above has a small amount of unreacted fumaric acid diester.

When the molecular weight of the fumaric acid diester-based polymer gradually increases in the polymerization solution and reaches a certain molecular weight during the polymerization, the polymer precipitates from the solution.
For this reason, the polymer deposited does not proceed any more, and the resulting polymer has a number average molecular weight of 500 to 5000.
It is as small as 0.

Further, the rate of precipitation from the polymerization solvent is higher than the rate of aggregation of the fumaric acid diester polymer during polymerization. For this reason, the resulting polymer has a particle size of 0.5 to 1
It becomes a fine particle powder as small as 00 μm.

The fumaric acid diester polymer obtained by the above-mentioned production method has a high glass transition temperature, a small amount of unreacted fumaric acid diester, and does not have a fragment of a molecular weight modifier at a molecular chain terminal, and thus has a high heat resistance. Excellent in nature. Therefore, the fumaric acid diester-based polymer is suitable for applications such as resin materials.

Further, the fumaric acid diester-based polymer has a small number average molecular weight, has excellent solubility in solvents such as benzene, toluene, tetrahydrofuran and chloroform, and has high solubility.

[0044]

EXAMPLES Hereinafter, the embodiments will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these. Example 1 500 g of methanol and dicyclohexyl fumarate (hereinafter referred to as DcH) were placed in a 500 ml four-necked flask.
After 100 g of F) and 5 g of diisopropyl peroxydicarbonate (hereinafter abbreviated as IPP) were charged and the atmosphere was replaced with nitrogen, the temperature was raised to 40 ° C. with stirring. Stirring was continued for 8 hours. Thereafter, the mixture was cooled, and the generated white powder was filtered. This powder was washed with methanol and dried under reduced pressure to obtain 94.5 g of white fine particles.

The physical properties of the fumaric acid diester polymer were measured by the following methods. (Number average molecular weight Mn) It was calculated and calculated from standard polystyrene using GPC (gel permeation chromatography). (Amount of residual monomer) Approximately 0.1 g was precisely weighed and dissolved by adding toluene, and the residual monomer was quantified by gas chromatography using n-tridecane as an internal standard. (Powder particle size)
It was measured by a scattering type particle size distribution analyzer [manufactured by Horiba, Ltd.]. (Solubility in chloroform) The amount of the fumaric acid diester polymer dissolved in 100 g of chloroform was measured. (Thermal decomposition temperature) TG / DTA [Seiko Electronic Industry Co., Ltd.
Was used to measure the thermal decomposition temperature.

Table 1 shows the physical properties described above. (Examples 2 to 23) Polymerization was carried out in the same procedure as in Example 1 except that the type and amount of fumaric acid diester, the type and amount of polymerization solvent, and the polymerization conditions were changed. Tables 1 to 5 show the polymerization conditions and the measurement results of physical properties. Table 1
Abbreviations in Table 5 are as shown below. DiPF: diisopropyl fumarate DsBF: di-sec-butyl fumarate DtBF: di-tert-butyl fumarate cH-iPF: cyclohexyl isopropyl fumarate tB-iPF: tert-butyl isopropyl fumarate VPi: vinyl pivalate VtBB: p- tert-butyl vinyl benzoate St: styrene CHVE: cyclohexyl vinyl ether IPA: isopropanol NPP: di-n-propylperoxydicarbonate BPO: benzoyl peroxide AIBN: 2,2′-azobisisobutyronitrile PV: tertbutylperoxypi Valate (Comparative Example 1) 10 g of DcHF and BPO as a polymerization initiator were placed in a polymerization tube made of Pyrex glass having an internal volume of 20 ml.
0.1 g was charged, and the inside was sufficiently purged with nitrogen gas and then sealed. This polymerization tube was placed in a shaking water bath maintained at 70 ° C. ± 0.05 ° C., and was subjected to bulk polymerization for 8 hours. The polymerization tube was opened, and the contents were taken out. Table 5 shows the measurement results of physical properties.
It was shown to. Comparative Example 2 A 500 ml four-necked flask was charged with 300 g of a 0.2% by weight aqueous solution of partially saponified polyvinyl alcohol, and after purging with nitrogen, 100 g of DcHF and I
After adding 1 g of PP dissolved therein, suspension polymerization was carried out with stirring for 10 hours while maintaining the temperature in the reaction system at 40 ± 0.5 ° C. After the completion of the polymerization reaction, the particulate polymer was separated by filtration, and washed with water. Table 5 shows the measurement results of the physical properties.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5] As shown in Tables 1 to 5, in all of Examples 1 to 23, the fumaric acid diester-based polymer having a small number average molecular weight (low polymerization degree) and a small number of residual monomers was obtained in high yield. Obtained. The particle size of the powder was in the range of 0.5 to 100 μm, and the solubility in chloroform was high.

On the other hand, in Comparative Example 1, the amount of unreacted residual monomer was large, and in Comparative Example 2, the number average molecular weight of the formed fumaric acid diester polymer was large and the particle size was 200%.
It was as large as μm, indicating low solubility in chloroform.

The technical idea grasped from the embodiment will be described below. The polymerization solvent has a solubility of the monomer composition in 100 parts by weight of the polymerization solvent of more than 100 parts by weight and a solubility of the fumaric acid diester polymer in 100 parts by weight of the polymerization solvent of 100 parts by weight or less. The method for producing a fumaric acid diester polymer according to claim 1.

According to this production method, there is no need for an operation for removing unreacted fumaric acid diester, etc.
A fumaric acid diester-based polymer can be reliably obtained.

The method for producing a fumaric acid diester polymer according to claim 1, wherein the content of the fumaric acid diester in the monomer composition is 80% by weight or more. According to this production method, physical properties such as heat resistance of the fumaric acid diester polymer can be exhibited well.

The method for producing a fumaric acid diester polymer according to claim 1, wherein the polymerization solvent is an alcohol or a ketone. According to this production method, the polymerization can be carried out efficiently, the unreacted fumaric diester in the obtained polymer can be reduced, and the number average molecular weight can be reduced.

The method for producing a fumaric acid diester-based polymer according to claim 1, wherein the polymerization initiator is an organic peroxide or an azo-based polymerization initiator having a 10-hour half-life temperature of 35 to 80 ° C.

According to this production method, the polymerization can be carried out efficiently, the unreacted fumaric diester in the obtained polymer can be reduced, and the number average molecular weight can be reduced.

The method for producing a fumaric acid diester-based polymer according to claim 1, wherein the polymerization initiator is a compound having a 10-hour half-life temperature not higher than the boiling point of the polymerization solvent. According to this production method, the polymerization can be carried out promptly, the unreacted fumaric acid diester in the obtained polymer can be reduced, and the number average molecular weight can be reduced.

[0060]

As described above, the present invention has the following advantages. According to the method for producing a fumaric acid diester polymer of the first invention, it is possible to efficiently obtain a fumaric acid diester polymer without requiring an operation for removing unreacted fumaric acid diester.

According to the fumaric acid diester polymer of the second invention, since the fumaric acid diester polymer is obtained by the production method of the first invention, the amount of unreacted fumaric acid diester is small. In addition, the number average molecular weight is small.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4J011 HA03 HA04 HB16 HB22 4J100 AB00Q AB02Q AB03Q AB04Q AB08Q AC03Q AC23Q AE02Q AE04Q AE09Q AF10Q AG02Q AG04Q AG08Q AL03Q AL11Q AL34P AL39P AS02Q AS03Q BA04P BCBC BCBCBC DA01 EA05 FA03 FA19

Claims (2)

[Claims] 1. A method for producing a fumaric acid diester polymer in which a monomer composition containing a fumaric acid diester is polymerized in the presence of a polymerization solvent and a polymerization initiator, wherein the polymerization solvent contains a fumaric acid diester. A method for producing a fumaric acid diester polymer, which dissolves the monomer composition to be formed and makes the fumaric acid diester polymer substantially insoluble. 2. A powdery fumaric acid diester polymer obtained by the process for producing a fumaric acid diester polymer according to claim 1, wherein the number average molecular weight is 500 to 5
0000, a fumaric acid diester polymer having a powder particle size of 0.5 to 100 μm.