JPH0586105A - Preparation of maleimide copolymer - Google Patents

Abstract

PURPOSE:To prevent a maleimide copolymer from having impaired heat resistance, giving a discolored molding, and causing mold fouling, by sufficiently decreasing the content of a residual maleimide monomer at the completion of the polymerization for producing the maleimide copolymer. CONSTITUTION:At least one of an aromatic vinyl monomer (a), a maleimide monomer (b), and other vinyl monomer(s) (c) copolymerizable therewith is introduced into a reaction system, and copolymerization is conducted while feeding the remainder of the monomers gradually to the system. After the whole of the remainder has been fed, a polymerization inhibitor is added to the system to conduct a maturing reaction. Thus, the amount of the residual monomer (b) is reduced while inhibiting the polymerization of the monomer (a).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a maleimide copolymer having high heat resistance and impact resistance and excellent heat stability. More specifically, the present invention relates to a molding material,
The present invention relates to a method for producing a maleimide copolymer, which is effective as a material for improving various properties such as heat resistance by being mixed with a thermoplastic resin, and in which an unreacted maleimide monomer is extremely small.

[0002]

2. Description of the Related Art A maleimide-based copolymer obtained by copolymerizing a maleimide-based monomer and an aromatic vinyl-based monomer is known to be a thermoplastic resin having a high heat distortion temperature and thermal decomposition temperature. Has been. When radical polymerization of a maleimide-based monomer and an aromatic vinyl-based monomer is performed, the molar ratio of the maleimide-based monomer unit and the aromatic vinyl-based monomer unit is 1: because the alternating copolymerization is high. The alternating copolymer of 1 is preferentially obtained, and thereafter, a homopolymer of excess monomer is obtained. Since the 1: 1 alternating copolymer has a high heat distortion temperature, it requires an extremely high temperature for melt molding and has a drawback of being brittle. Further, a heterogeneous copolymer in which a 1: 1 alternating copolymer and a homopolymer are mixed has a drawback that it has poor toughness.

Various proposals have hitherto been made for obtaining a copolymer having a homogeneous composition. For example, in US Pat. No. 2,971,939, a vinyl-based monomer is charged into a reaction system to start polymerization, and then a maleimide-based monomer is uniformly added to the reaction system at a rate slower than the polymerization rate of the vinyl-based monomer. Then, a method of polymerizing is proposed. Further, according to JP-A-58-162616, the consumption rate of a vinyl monomer from a maleimide monomer to a reaction system containing a vinyl monomer mainly composed of an aromatic vinyl monomer. A method of feeding and polymerizing at a slower rate than that has been proposed. Further, according to JP-A-2-51514, in order to obtain a maleimide-based copolymer having a specific composition, at least one of an aromatic vinyl-based monomer and a methacrylic acid ester-based monomer is added to a reaction system. A seed and an organic solvent are charged, and at least a maleimide-based monomer of a maleimide-based monomer and other vinyl-based monomer is continuously dropped and supplied at a specific ratio to polymerize, a solvent use ratio, a polymerization conversion. It has been shown that the amount of the remaining maleimide-based monomer is reduced by controlling the rate and the like within a specific range and further post-polymerizing after the dropping of the maleimide-based monomer is completed.

[0004]

According to the method described in the above-mentioned U.S. Patent and JP-A-58-162616, one maleimide monomer unit and one aromatic vinyl monomer unit are used.
Although it becomes difficult to obtain a copolymer having a molar ratio of 1: 1, the content of the maleimide monomer unit in the copolymer changes with the progress of the reaction, and finally the aromatic vinyl monomer The copolymer has a wide distribution from molecules rich in body units to molecules rich in maleimide-based monomer units, and the proportion of molecules in which the content of maleimide-based monomer units is almost equal to the average value is extremely high. It becomes low. Such a copolymer does not satisfy all of heat resistance, moldability and impact resistance.

If the maleimide-based monomer remains in the maleimide-based copolymer, there is a problem that heat resistance is lowered, a molded product is colored, and molds are easily contaminated. The maleimide-based monomer is generally solid at room temperature or has a very high boiling point, so that it is difficult to remove by evaporation. For this reason, in the invention of JP-A-2-51514, the content of the maleimide-based monomer is reduced by carrying out post-polymerization after completion of dropping. However, since the amount of the maleimide-based monomer remaining at the end of the dropping is very large, the reduction of the content of the maleimide-based monomer is insufficient even after the post-polymerization, and a polymerization initiator is present. Since the post-polymerization is carried out in the state, the reaction of the aromatic vinyl-based monomer existing in excess also progresses, and the aromatic vinyl-based monomer homopolymer or the aromatic vinyl-based monomer is contained in a large amount. Another problem is that the copolymer is formed and the average composition of the obtained copolymer varies.

Further, in the examples described in JP-A-63-90557, cooling is performed with addition of a polymerization inhibitor,
By stopping the polymerization reaction, fluctuations in the composition of the copolymer are reduced. However, such a method has a problem that the residual amount of the maleimide-based monomer is large. This invention can sufficiently reduce the content of the residual maleimide-based monomer at the end of the polymerization reaction, can prevent the above-mentioned problems caused by the residual maleimide-based monomer, and can reduce the composition of the copolymer. An object of the present invention is to provide a method for producing a maleimide-based copolymer that can narrow the distribution.

[0007]

In order to solve the above-mentioned problems, the present invention provides an aromatic vinyl monomer (a), a maleimide monomer (b) and other vinyl copolymerizable therewith. A method for producing a maleimide-based copolymer, in which at least a part of the monomers (c) is charged in the reaction system and the rest of the monomers are gradually fed into the reaction system for copolymerization. In the above, after all the remaining monomers have been supplied to the reaction system, a polymerization inhibitor is added to the reaction system to carry out an aging reaction, thereby suppressing the polymerization of the monomer (a) and the monomer. Provided is a method for producing a maleimide-based copolymer, which is characterized by reducing the residual amount of (b).

The monomer (b) used in the present invention has the following formula:

[0009]

[Chemical 1]

Compounds represented by, for example, maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, N-tertiarybutyl. Maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide,
Examples thereof include N-bromophenylmaleimide, N-naphthylmaleimide, N-laurylmaleimide, 2-hydroxyethylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide and N-nitrophenylmaleimide. It is possible to use one or more of these.

The monomer (a) used in the present invention is represented by the following formula 2:

[0012]

[Chemical 2]

Compounds represented by, for example, styrene; o-methylstyrene, m-methylstyrene, p-
Methylstyrene (o-, m-, p-methylstyrene is also called vinyltoluene), 1,3-dimethylstyrene,
2,4-dimethylstyrene, ethylstyrene, p-third
Alkyl styrenes such as primary butyl styrene; α-methyl styrene, α-ethyl styrene, α-methyl-p-methyl styrene; vinylnaphthalene; o-chlorostyrene,
Examples thereof include halogenated styrenes such as m-chlorostyrene, p-chlorostyrene, and 2,4-dibromostyrene; halogenated alkylstyrenes such as 2-methyl-4-chlorostyrene, and one or two of these. The above can be used. From the viewpoint of the balance between productivity and physical properties, styrene, vinyltoluene and α-
It is desirable to use at least one selected from the group consisting of methylstyrene. When an aliphatic vinyl monomer is used instead of an aromatic vinyl monomer, the reactivity of the monomer is low, and the heat resistance of the obtained copolymer is low,
Moreover, there is a problem that the hygroscopicity is large.

In the present invention, other vinyl type monomer (c) copolymerizable with the monomer (a) and the monomer (b) can be used, if necessary. Monomer (c)
Is a compound having an ethylenically unsaturated bond other than the monomer (a) and the monomer (b), and is used for the purpose of improving impact resistance, solvent resistance and compatibility. .. Examples of the monomer (c) include unsaturated nitriles such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and phenylacrylonitrile; and an alkyl group having 1 to 18 carbon atoms including a cycloalkyl group and a benzyl group ( (Meth) acrylic acid ester (for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate,
Amyl (meth) acrylate, isoamyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate,
Lauryl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, etc.); olefins such as ethylene, propylene, isobutylene, diisobutylene; dienes such as butadiene and isoprene; vinyl chloride, vinylidene chloride, Vinyl halides such as vinyl bromide and vinyl fluoride; vinyl ethers such as methyl vinyl ether and butyl vinyl ether; vinyl acetate,
Vinyl esters of saturated monocarboxylic acids such as vinyl propionate; allyl esters or methallyl esters of saturated aliphatic monocarboxylic acids such as allyl acetate and allyl propionate; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) Acrylate, divinylbenzene, diallyl phthalate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dimethacrylate of ethylene oxide or propylene oxide adduct of bisphenol A, halogenation Di (meth) acrylate of ethylene oxide or propylene oxide adduct of bisphenol A, tri (meth) acrylate of isocyanurate Polyvalent (meth) acrylates such as di- or tri (meth) acrylates of ethylene oxide or propylene oxide adducts of isocyanurate; polyvalent arylates such as triallyl isocyanurate; glycidyl (meth) acrylate, allyl glycidyl ether, ( Examples thereof include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esterified products thereof, and one kind or two or more kinds may be used depending on the purpose. It may be selected within a range not deviating from.

The amount of the aromatic vinyl monomer (a) used is
The range of 40 to 70 wt% is preferable. The amount of the maleimide-based monomer (b) used is preferably in the range of 30 to 60 wt%.
The amount of the monomer (c) used is preferably in the range of 0 to 20 wt%. However, the total amount of the monomers (a), (b) and (c) is 100 wt%. If the amount of the monomer (a) used exceeds the above range, the heat resistance of the maleimide-based copolymer to be formed may be lowered, and the compatibility when blended with the thermoplastic resin may be lowered. Workability and / or impact resistance may decrease. If the amount of the monomer (b) used exceeds the above range, the molding processability of the maleimide-based copolymer produced may deteriorate and the impact resistance may decrease. There is a possibility that sufficient heat resistance cannot be imparted to the product. When the amount of the monomer (c) used exceeds the above range,
There is a possibility that it may be difficult to obtain a balance of physical properties such as processability and impact resistance of the resulting maleimide-based copolymer.

In the present invention, the polymerization is carried out as follows. Aromatic vinyl monomer (a), a reaction system such as a reaction vessel,
At least a part of the maleimide-based monomer (b) and another vinyl-based monomer (c) copolymerizable therewith are charged. Copolymerization is carried out while gradually supplying the rest of the monomers to this reaction system.
Here, the method of gradually supplying the monomer is not particularly limited, and for example, a method such as dropping at a uniform rate or controlling the dropping rate while monitoring the monomer composition in the reaction system may be used. Adopted. Monomer (a),
When (b) and (c) are gradually supplied, they may all be supplied separately, or at least two may be mixed and supplied, and there is no particular limitation.

Incidentally, the maleimide system produced by carrying out the copolymerization while gradually supplying the monomer and keeping the concentration ratio of the monomer (a) and the monomer (b) in the reaction system constant. The composition of the copolymer can be controlled so as to be uniform. To do so, for example, 10 to 80 wt% of the total amount of the aromatic vinyl-based monomer (a) used is charged into the reaction system, and the maleimide-based monomer (b) is added to the reaction system. It is preferable to gradually supply the total amount and the remaining amount of the aromatic vinyl monomer (a). When the charged amount of the aromatic vinyl-based monomer (a) is less than 10 wt% of the total amount, the ratio of the unreacted aromatic vinyl-based monomer is too low, so that the polymerization rate becomes slow and the productivity decreases. There is a risk. Since the concentration of the unreacted aromatic vinyl-based monomer in the reaction system increases as the initial charging amount of the aromatic vinyl-based monomer (a) increases, the feed rate of the maleimide-based monomer (b) increases. It is possible to control the composition of the resulting copolymer to be uniform by increasing the polymerization rate, but the initial charge of the aromatic vinyl monomer (a) is 80 wt% of the total amount.
When the amount exceeds the above, the ratio of the maleimide-based monomer (b) in the liquid gradually supplied as a dropping liquid becomes large and the supply rate of the maleimide-based monomer (b) becomes too fast. The amount of heat generated during polymerization increases. Therefore, in industrial production, an excessive cooling capacity is required, and adjustment of the internal temperature at the start of polymerization becomes complicated.

When gradually supplying the aromatic vinyl-based monomer (a) and the maleimide-based monomer (b), the aromatic vinyl-based monomer and the maleimide-based monomer are supplied separately or as a mixture. Or a method in which a maleimide-based monomer is dissolved or dispersed in an aromatic vinyl-based monomer or an organic solvent and supplied. The ratio of the aromatic vinyl-based monomer and the maleimide-based monomer gradually supplied is, for example, 10 to 70 wt% of the aromatic vinyl-based monomer (a) and 30 to 90 wt% of the maleimide-based monomer (b). %. Further, when the organic solvent is used, the organic solvent is, for example, 0 to 50 wt% with respect to the weight of all the monomers in the supply liquid.

In the present invention, during the polymerization reaction, the dissolved oxygen in the reaction system is removed by an inert gas (usually nitrogen gas) to carry out the polymerization. This is because oxygen acts as a polymerization inhibitor. The reaction system may be charged with only the aromatic vinyl-based monomer (a), or may be charged with the monomer (a) and an organic solvent, if necessary. In this case, the amount of the organic solvent is preferably such that the weight ratio of organic solvent / [organic solvent + aromatic vinyl-based monomer (a)] is 0.40 to 0.98. This is because it is convenient to obtain a maleimide-based copolymer having a maleimide-based monomer unit (B) content of 40.0 to 65.0 wt%. Such a maleimide-based copolymer is particularly excellent in heat resistance, and has the advantage that the heat resistance of the resin composition can be effectively improved by blending it with a thermoplastic resin. If the weight ratio of organic solvent / [organic solvent + aromatic vinyl-based monomer (a)] is less than 0.40, the solution viscosity of the reaction system may increase, or the composition distribution may be broadened due to poor stirring. If it exceeds 0.98, the ratio of the aromatic vinyl-based monomer becomes low, and the reaction rate may decrease.

The composition of the maleimide copolymer is determined by the monomer molar ratio (b) / (a) in the reaction system. That is, the larger the monomer molar ratio, the more the maleimide-based copolymer having a higher content of the maleimide-based monomer unit (B) is produced. Therefore, when a copolymer having a large content of the monomer unit (B) is produced, the amount of the residual monomer (b) also increases. In such a case, by using a large amount of an organic solvent, the residual amount of the monomer (b) at the end of the monomer supply is reduced, and the monomer (b) to be removed by aging is removed. It is better to reduce it in advance.

As the organic solvent, for example, toluene,
Aromatic solvents such as xylene and ethylbenzene; ketones such as methyl ethyl ketone (abbreviated as MEK), methyl isobutyl ketone and cyclohexanone; polar solvents such as dimethylformamide, dimethylacetamide and dimethylsulfoxide are used. The use of organic solvents is
For example, it is carried out for the purpose of increasing the solubility of the maleimide-based copolymer, preventing the viscosity of the reaction solution from decreasing, and preventing gelation during polymerization.

The method of adding the copolymerizable monomer (c) is not particularly limited. By considering the copolymerizability of the monomer (c) to be used and setting the allocation between the initially charged amount and the gradually supplied amount, it is possible to allow the monomer (c) to uniformly exist in the copolymer.
In this invention, a polymerization initiator, a chain transfer agent, etc. may be present in the reaction system. As the polymerization initiator, for example, 1,1-bis (t-butylperoxy) -3,3,3
5-trimethylcyclohexane, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxy Peroxides such as 2-ethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate; azobisisobutyronitrile, azobisdimethylvaleronitrile, azobis A compound usually used for the polymerization of a maleimide monomer and an aromatic vinyl monomer, such as an azo compound such as -1-cyclohexanecarbonitrile, is used in a usual amount. The whole amount of the polymerization initiator may be charged in the reaction system in advance, or may be supplied during the reaction.

The present invention can employ polymerization methods such as solution polymerization, bulk polymerization and emulsion polymerization, but is particularly effective in solution polymerization. The polymerization is performed, for example, at a temperature of 60 to 200 ° C. for 1 to 20 hours. The polymerization conversion rate of all the monomers put in the reaction system is, for example, 50 to 95 wt.
% Is preferable. After gradually supplying all of the monomers, an aging reaction is performed.

In the present invention, the aging reaction carried out after the completion of the supply of all the monomers is carried out by adding a polymerization inhibitor to the reaction system. This aging reaction reduces the residual amount of the monomer (b) while suppressing the polymerization of the monomer (a). In particular, it is preferable that the residual amount of the maleimide-based monomer (b) is about 1/10 or less of that when not matured, for example, the residual amount of the monomer (b) is 0.1 wt% or less. Monomer (b)
If the residual amount of the above is more than 0.1 wt%, the obtained maleimide-based copolymer may be easily colored.

When a maleimide copolymer having a high maleimide monomer unit content in the molecular structure is to be obtained, the amount of the maleimide monomer remaining in the reaction system tends to increase.
The present invention is particularly effective in such a case. The polymerization inhibitor used in the present invention is, for example, diphenylpicrylhydrazyl, di-p-fluorophenylamine,
Tri-p-nitrophenylmethyl, p-benzoquinone,
Methyl-p-benzoquinone, 2,5-dimethyl-p-benzoquinone, methoxy-p-benzoquinone, chloranil, p-t-butylcatechol, 3-phenylcatechol, hydroquinone, m-dinitrobenzene, p-phenyldiamine, 2, 5-di-t-butylhydroquinone,
Examples thereof include dichloronitrophenol and hydroquinone monomethyl ether, which may be used alone or in combination of two or more kinds. The addition amount of the polymerization inhibitor is, for example, 0.001 to 100 parts by weight of the monomer that is gradually fed and remains at the end of the feeding.
1 part by weight is preferable, and 0.002 to 0.5 part by weight is more preferable. If the amount is out of this range, the effect of the present invention may not be sufficiently obtained, and conversely, the amount may cause coloring.

The temperature at which the aging reaction is carried out is, for example, 80 to
It is carried out in a temperature range of 180 ° C, preferably at a temperature equivalent to the polymerization temperature. If it is heated to a temperature higher than this temperature range, another reaction such as a thermal polymerization reaction proceeds, so the amount of the polymerization inhibitor must be increased in order to prevent this reaction as well, which adversely affects the physical properties of the product. There is. If the temperature is lower than the above temperature range, it takes time to reduce the maleimide-based monomer (b), the residual amount increases, and the viscosity of the polymer solution increases, which makes the operation difficult. The time for performing the aging reaction is, for example, preferably 10 minutes to 10 hours, and more preferably 15 minutes to 5 hours. Outside this range, the effects of the present invention may not be fully exhibited.

Catechols and hydroquinones used as polymerization inhibitors such as styrene and phenylmaleimide are known to exert a sufficient polymerization inhibiting effect in the coexistence of oxygen, and particularly in reducing coloring. Catechols are preferred. Therefore, in the present invention, it is preferable to carry out the aging reaction in the presence of oxygen, and the amount of oxygen at that time is preferably 0.1 to 10% by volume of oxygen concentration in the gas phase, and 0.3 to 5% by volume. More preferable. If the oxygen concentration is too low, the effect of suppressing the polymerization of the monomer (a) may be small, and if it is too high, the risk of ignition with a solvent and explosion will increase. As oxygen, only molecular oxygen may be supplied, but a mixed gas containing molecular oxygen such as air may be supplied. Normally, oxygen is supplied by bubbling a mixed gas of N ₂ and air into the polymerization liquid.

After completion of the aging reaction, the reaction solution is cooled and the reaction solution is added to a solvent such as methanol to precipitate a polymer, which is separated from the solution by filtration or the like, and then the solvent or the like is removed by vacuum drying or the like. A maleimide-based copolymer can be obtained.
In addition, unreacted monomers and solvents can be removed by an ordinary desolvation method, and by sufficiently reducing the residual amount of the maleimide-based monomer (b) in the aging reaction step, the devolatilization step can be performed. By appropriately controlling the temperature, the degree of vacuum, the residence time, etc., it is possible to obtain a maleimide-type copolymer from which the residual monomer components that cause coloring are removed.

The maleimide-based copolymer produced as described above is preferably an aromatic vinyl-based monomer unit (A) 35.0 to 60.0 wt% and a maleimide-based monomer unit (B). 40.0 to 65.0 wt% and other vinyl monomer units (C) 0 to 20 wt%, and the residual amount of aromatic vinyl monomer (a) is 0.1 wt%.
Below, preferably 0.05 wt% or less, the residual amount of the maleimide-based monomer (b) is 0.1 wt% or less, preferably 0.0
2 wt% or less, residual amount of vinyl monomer (c) is 0.1 wt
% Or less, preferably 0.05 wt% or less. The aromatic vinyl-based monomer unit (A) is obtained from the aromatic vinyl-based monomer (a), and the maleimide-based monomer unit (B) is obtained from the maleimide-based monomer (b). Quantity unit (C)
Are derived from the vinyl-based monomer (c). The aromatic vinyl-based monomer unit (A), the maleimide-based monomer unit (B), and the vinyl-based monomer unit (C) may be randomly arranged or may have a block portion. Absent.

The maleimide-based copolymer obtained by the production method of the present invention has, for example, a weight average molecular weight of 50,000 to 1
It has physical properties of, 000,000, a number average molecular weight of 20,000 to 300,000, a viscosity at a temperature of 260 ° C of 200 to 1,000,000 poise, and a glass transition temperature of 130 to 220 ° C. The maleimide-based copolymer obtained by the production method of the present invention has good moldability and excellent heat resistance and impact resistance, and further has ABS resin (acrylonitrile-butadiene-styrene resin) and MBS resin (methyl methacrylate- It also has excellent miscibility with rubber-modified resins represented by butadiene-styrene resin). Therefore, the maleimide-based copolymer obtained by the present invention can be blended with a rubber-modified resin to produce a heat-resistant and impact-resistant resin having a high heat distortion temperature and higher impact resistance. When this maleimide-based copolymer is blended with a rubber-modified resin, a device such as a twin-screw extruder is used, and 10-100 parts by weight of the maleimide-based copolymer is added to 100 parts by weight of the rubber-modified resin under normal operating conditions. Blend in proportion.
Further, the maleimide copolymer obtained by the present invention has high heat resistance and excellent moldability (fluidity).
Since it also has, it can be used as a modifier. For example, methyl methacrylate resin, methyl methacrylate-styrene resin, polycarbonate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene oxide resin, vinyl chloride resin, chlorinated vinyl chloride resin, acrylonitrile-styrene resin, acrylonitrile-methyl methacrylate resin, styrene. When used as a modifier for a methacrylic acid resin, a styrene-methacrylic acid-acrylonitrile resin, an unsaturated polyester resin, etc., heat resistance is improved. In particular, it has excellent miscibility with a crystalline resin such as a polyamide resin, a polyethylene terephthalate resin, and a polybutylene terephthalate resin, and the heat resistance can be improved without impairing the characteristics of these resins, and the moldability can be improved. preferable. When used as a modifier as described above, a device such as a twin-screw extruder is used, and under normal operating conditions,
The maleimide copolymer is mixed in an amount of 10 to 100 parts by weight with respect to 100 parts by weight of the resin to be modified.

[0031]

After the monomers (a), (b) and (c) have all been gradually supplied to the reaction system, a polymerization inhibitor is added to the reaction system to carry out an aging reaction to obtain a single amount. While suppressing the polymerization of the body (a), the amount of the maleimide-based monomer (b) remaining in the polymerization reaction can be reduced and the composition distribution of the copolymer can be narrowed.

At least 10 to 80 wt% of the total amount of the monomer (a) among the monomer (a) and the monomer (c) is charged into the reaction system, and the monomer (a) and the monomer (a) are added. The residual amount of the monomer (c) and the total amount of the monomer (b) are polymerized while being supplied to the reaction system so that the residual amount of the maleimide-based monomer is reduced and the maleimide having a uniform composition is obtained. A system copolymer can be obtained.

[0033]

EXAMPLES Specific examples and comparative examples of the present invention will be shown below, but the present invention is not limited to the following examples.
Unless otherwise specified, "part" is "part by weight" and "%" is "% by weight". -Examples 1 to 6- An initially charged monomer and a solvent having the composition shown in Table 1 were charged into a polymerization reaction tank equipped with a condenser, a stirrer and two dropping funnels, sufficiently dissolved, and the inside was replaced with nitrogen.
The inside of the polymerization reaction tank was heated to the temperature shown in Table 1, an initial polymerization initiator was added to start the reaction, and the dropping raw material mixtures I and II having the two compositions shown in Table 1 were fed from separate dropping funnels. Polymerization was carried out by uniformly dropping the mixture over the time period shown in 1. Table 2 shows the composition of the reaction solution, the conversion of polymerization and the structure of the copolymer at the end of the dropping. After completion of the dropping, aging was carried out under the conditions shown in Table 3 to obtain a reaction liquid containing a maleimide copolymer. In Table 3, when the presence / absence column of oxygen is “Yes”, a mixed gas in which air and nitrogen are mixed at a volume ratio of 1: 4 is added to the reaction liquid at a volume of 1/5 of the reaction tank per minute. Bubbling to. Composition of reaction solution at the end of aging, polymerization conversion rate, structure of copolymer, and rate of change in content of maleimide monomer unit (B) (here, N-phenylmaleimide unit) before and after aging (according to equation 1) Is shown in Table 4.

The reaction solution obtained was provided with a vent having a diameter of 44 mm.
Using a screw extruder, the temperature of the copolymer is 270 to 300 ° C,
The operation was performed at a vacuum degree of 20 Torr to obtain a pellet-shaped maleimide-based copolymer.

[0035]

[Equation 1]

Comparative Example 1 A pelletized maleimide copolymer was obtained in the same manner as in Example 1 except that aging was not performed after the dropping. -Comparative Example 2-A pellet-shaped maleimide-based copolymer was obtained in the same manner as in Example 1 except that after dripping, aging was performed without adding a polymerization inhibitor.

Each of the pellets obtained in the above Examples and Comparative Examples was dissolved in the solvent shown in Table 1 and the volatile content was measured by gas chromatography. The volatile content was reduced to 0.5% by weight or less in the pellet. Was. Regarding the composition of the reaction solution at the end of dropping and at the end of aging, a part of the reaction solution was sampled and the amount of unreacted monomer and the amount of solvent were measured by gas chromatography. The composition of the copolymer was calculated from the charged amount of monomer and the amount of unreacted monomer.

The abbreviations of the compounds in Table 1 are as follows. ST: Styrene AN: Acrylonitrile PMI: N-Phenylmaleimide CHMI: N-Cyclohexylmaleimide MEK: Methylethylketone Tol: Toluene PBO: t-Butylperoxy-2-ethylhexanoate BIC: t-Butylperoxyisopropylcarbonate PHM: 1 , 1-bis (t-butylperoxy) -3,
3,5-trimethylcyclohexane

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

As shown in Tables 1 to 4, in Examples 1 to 6, the maleimide-based monomer was 0.1
%, And the variation in the composition of the copolymer before and after aging was small. In Comparative Example 1, since the aging was not performed, a large amount of maleimide-based monomer remained. In Comparative Example 2, the maleimide-based monomer was reduced to 0.1% or less, but the composition of the copolymer before and after aging varied greatly.

The glass transition temperature, colorability and transparency of each copolymer obtained in Examples and Comparative Examples were examined as follows. The glass transition temperature is D manufactured by Rigaku Denki Co., Ltd.
It was determined by the midpoint method from a DSC curve measured using SC-8230 under a nitrogen stream with α-alumina as a reference at a heating rate of 5 ° C / min. The colorability and transparency were visually evaluated on the obtained pellets. The evaluation criteria are as follows. The results are shown in Table 5. Colorability ◎… Slightly yellow ○… Light yellow ×… Brown transparency ○… Transparent ×… Muddy

[0045]

[Table 5]

In each of Examples 1 to 6, pellets having a high glass transition temperature, high transparency and little coloring were obtained.
In Comparative Example 1, colored pellets having a low glass transition temperature were obtained, and in Comparative Example 2, pellets having a low glass transition temperature and poor transparency were obtained.

[0047]

According to the method for producing a maleimide-based copolymer of the present invention, the content of the residual maleimide-based monomer at the end of the polymerization reaction can be sufficiently reduced and the composition is uniform. A copolymer can be obtained.

Claims (5)

[Claims] 1. A monomer of at least a part of an aromatic vinyl monomer (a), a maleimide monomer (b) and another vinyl monomer (c) copolymerizable therewith. The body is charged into the reaction system, and the remaining monomer is gradually fed to the reaction system to perform copolymerization. In the method for producing a maleimide-based copolymer, all the remaining monomers are completely fed to the reaction system. After that, a polymerization inhibitor is added to the reaction system to carry out an aging reaction to suppress the polymerization of the monomer (a) while reducing the residual amount of the monomer (b). Method for producing copolymer. 2. Monomers (a) and (c) are charged in an amount of 10 to 80 wt% of the total amount of monomers (a) among monomers (a) and (c). The method for producing a maleimide-based copolymer according to claim 1, wherein the polymerization is carried out while gradually supplying the remaining amount of and the total amount of the monomer (b) to the reaction system. 3. The method for producing a maleimide copolymer according to claim 1, wherein the aging reaction is carried out in the presence of oxygen. 4. The method for producing a maleimide-based copolymer according to claim 3, wherein catechols are used as the polymerization inhibitor. 5. A monomer (a) 40 to 70 wt%, a monomer (b) 30 to 60 wt%, and a monomer (c) 0 to 20.
The method for producing a maleimide-based copolymer according to any one of claims 1 to 4, which is used in a wt% ratio (however, the total of (a), (b) and (c) is 100 wt%).