JPH0684409B2 - Method for producing heat-resistant thermoplastic resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-resistant thermoplastic resin having excellent transparency.

[Conventional technology and problems]

Vinyl-based polymers such as polystyrene and polymethylmethacrylate, and vinyl-based copolymers such as styrene-methylmethacrylate copolymer are resins with excellent transparency and moldability, and are used for automobiles, office automation parts, daily sundries, etc. Is used for
Its use is limited due to its low heat distortion temperature.

Therefore, many studies have been made to improve the heat distortion temperature. For example, a method of copolymerizing methyl methacrylate and α-methylstyrene (US Pat. No. 3,135,723).
Specification), a method of copolymerizing methyl methacrylate, α-methylstyrene and maleic anhydride (Japanese Patent Publication No. 45-3).
1,953), a method of copolymerizing methyl methacrylate, α-methylstyrene and maleimide, and the like have been reported. However, these methods have not been put into practical use because the polymerization rate is extremely slow, the heat distortion temperature is not sufficient, the obtained resin is strongly colored, and the transparency is impaired.

On the other hand, it is known that a copolymer of a maleimide type monomer and a vinyl type monomer has a high heat distortion temperature. However, because maleimide-based monomers and aromatic vinyl monomers such as styrene are easy to form alternating copolymers (Polymer Papers, Vo
L.33, No.11, 685 ~ 691), it is very brittle and lacks practical strength.

As a method for improving this, a method of supplying a maleimide monomer to a polymerization system in which an aromatic vinyl monomer is present at a rate slower than the consumption rate of the vinyl monomer (JP-A-58-16).
No. 2,616), and a method in which styrene is added during the polymerization of a mixture of monomers such as α-methylstyrene, N-substituted maleimide-based monomer, and acrylonitrile (JP-A-60-147,41).
No. 4) is proposed. However, the former needs to be diluted or dissolved with a solvent such as ethyl methyl ketone or a vinyl-based monomer such as styrene and supplied, so that a separate dissolution tank is required or a solvent recovery facility is required. Therefore, it becomes costly and impractical. Further, in the latter case, since it is essential to use acrylonitrile as a monomer for polymerization, the resin obtained after the completion of polymerization is strongly colored and the transparency is impaired.

[Means for solving problems]

In view of the current situation, the present inventors have conducted intensive research,
During the process of copolymerizing N-substituted maleimide, α-methylstyrene, methacrylic acid ester and aromatic vinyl-based monomer in a specific ratio, methacrylic acid ester or a part thereof and aromatic vinyl-based monomer are continuously added. Or, the resin obtained after the completion of the polymerization by intermittently adding,
The inventors have found an unexpected effect that not only the heat resistance is excellent, but also the transparency and molding processability are well-balanced, and the coloring is small, which led to the invention.

The present invention includes (a) 5 to 40 parts by weight of N-substituted maleimide, (b) α
-When copolymerizing 5 to 35 parts by weight of methylstyrene, 40 to 85 parts by weight of (c) methacrylic acid ester, and 0 to 50 parts by weight of (d) an aromatic vinyl monomer other than α-methylstyrene,
First, the total amount of (a) and (b), the total amount of (c) and a part of (d) or (c)
And a monomer mixture consisting of the whole amount or a part of (d) are copolymerized, and then a part of the remaining (d) or a part of (c) or a part of (c) and (d). The present invention provides a method for producing a thermoplastic resin, characterized in that a part of the above is continuously or intermittently supplied to the copolymerization system for copolymerization.

That is, according to the method of the present invention, the above (a), (b) and
When (c) or (a), (b), (c) and (d) are copolymerized, at least one of (c) and (d) is divided and supplied to the copolymerization system. Therefore, when (d) is not copolymerized, (c) must be added in portions. The thermoplastic resin produced according to this method has excellent heat resistance and is particularly excellent in transparency.

Hereinafter, the present invention will be described in more detail.

The (a) N-substituted maleimide-based monomer used in the present invention includes
N-methylmaleimide, N-ethylmaleimide, Nt
-N-alkylmaleimide such as butylmaleimide, N-
N-aromatic maleimides such as N-cycloalkylmaleimides such as cyclohexylmaleimide, N-phenylmaleimides, N-o-methylmaleimides, Np-methylmaleimides, No-chlorophenylmaleimides and Np-chlorophenylmaleimides Etc., but N-alkylmaleimide and N-cyclohexylmaleimide, which cause little coloration of the obtained resin, are preferable.

(c) Methacrylic acid ester includes methyl methacrylate,
Examples thereof include ethyl methacrylate and butyl methacrylate, and methyl methacrylate is preferable in the present invention for the purpose of improving the heat distortion temperature.

Examples of the (d) aromatic vinyl-based monomer other than α-methylstyrene include styrene-based monomers such as styrene, p-methylstyrene, o-methylstyrene and p-chlorostyrene, but styrene is preferred. Is.

In the present invention, the composition ratio of the monomers (a) to (d) charged is required to be 5 to 40% by weight, preferably 10 to 30% by weight, for the (a) N-substituted maleimide. N-substituted maleimide is 5
If the content is less than 10% by weight, the heat resistance of the obtained resin is insufficient, and
If it exceeds 5% by weight, the resin becomes brittle and the practical strength is poor. Further, (b) α-methylstyrene is required to be 5 to 35% by weight, preferably 10 to 30% by weight. α-methylstyrene is 5
If it is less than 5% by weight, the heat resistance is not sufficient, and if it exceeds 35% by weight, not only the reaction rate is remarkably slowed but also the practical strength is deteriorated. (c) Methacrylic acid ester is required to be 40 to 85% by weight, preferably 45 to 80% by weight. If the amount of the methacrylic acid ester is less than 40% by weight, not only the excellent surface gloss of the methacrylic resin is impaired, but also the practical strength is significantly deteriorated. The aromatic vinyl-based monomer other than (d) α-methylstyrene is preferably 0 to 50% by weight. If it exceeds 50% by weight, a resin having excellent transparency cannot be obtained even with the present invention, and the heat resistance is extremely poor.

The method of polymerizing the heat-resistant thermoplastic resin having excellent transparency according to the present invention is not particularly limited, and the monomer mixture having the above specific ratio is subjected to the bulk polymerization method, suspension polymerization method, emulsion polymerization method, solution polymerization method, etc. Although a generally well-known polymerization method can be arbitrarily used, a suspension polymerization method is preferable because the operation during polymerization and the easy recovery of the polymer are easy.

The copolymerization reaction is carried out under general polymerization conditions, for example, a radical polymerization initiator having a 10-hour half-life of 30 to 150 ° C. Examples of this type of initiator include benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, 1,1-bis-t-butylperoxy-hexahydro-3,3,5-trimethyl-cyclohexane, t-butylperoxy. Organic peroxides and azo such as 2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, t-butylperoxyacetate, ethyl-3,3-di- (t-butylveroxy) butyrate One or more kinds of azo compounds such as bisisobutyronitrile, azobisvaleronitrile and azobiscyclohexylnitrile may be optionally used.

Further, in order to maintain good moldability, it is necessary to appropriately adjust the molecular weight of the polymer. Therefore, if necessary,
A chain transfer agent such as dodecyl mercaptan, octyl mercaptan, or α-methylstyrene dimer may be added.

As the suspension stabilizer, a calcium phosphate such as calcium hydroapatite, an inorganic dispersant such as magnesium phosphate, magnesium oxalate, or magnesium sulfate, or an organic dispersant such as partially saponified polyvinyl alcohol or polyvinylpyrrolidone may be used alone or in combination. Can be used for. Further, if necessary, a surfactant such as sodium dodecylbenzenesulfonate and a dispersion aid such as magnesium persulfate may be used.

In the method of the present invention, first of all the monomers (a) and (b) and (c) all or part and (d) all or part (however, at least (c) and (d) A monomer mixture consisting of one of them is used as a part) to start the polymerization, and the remaining part of (c) and / or part of (d) is continuously added during the polymerization. Alternatively, it is necessary to intermittently add and polymerize.
For example, when the total amount of (a) to (d) is supplied to the copolymerization system from the initial stage, first, the monomers (a) and (d) are mainly consumed, and (b) and (c) in the latter stage. Since a copolymer mainly composed of the monomer (1) is produced, the refractive index of the polymer produced in the early stage of polymerization is significantly different from that of the polymer produced in the latter stage of the polymerization, resulting in poor transparency of the obtained resin. Even if (d)
Even when not supplied to the copolymerization system, the monomers (a) and (c) are first consumed mainly, and a copolymer centered on (c) is produced in the latter stage, so that Inferior in transparency of resin.
Further, when (b) α-methylstyrene is added during the polymerization, the copolymerizability with other monomers is poor, the polymerization rate is remarkably slowed, and the polymerization rate of the obtained resin is lowered.

As a method of continuously or intermittently adding the aromatic vinyl monomer other than (c) the methacrylic acid ester and / or (d) the α-methylstyrene, a pump such as a plunger pump is used. Any method such as a method and a method of applying a pressure to a copolymerization system by using a gas such as N ₂ gas which has no influence on the polymerization system may be used. However, the monomers (c) and / or (d) supplied to the copolymerization system during the polymerization are 5% or more, preferably 10% or more, of the total amount of (c) and (d) supplied to the copolymerization system. The above is necessary. If it is less than 5%, the monomer (a)
A resin having excellent transparency cannot be obtained, as in the case where all the amounts of (d) to (d) are initially supplied to the copolymerization system.

Thus, by pelletizing or sheeting the heat-resistant thermoplastic resin obtained by the method of the present invention, a molding material having a good balance of transparency, heat resistance and molding processability and less coloring can be obtained. Further, the thermoplastic resin obtained in the present invention may be blended with rubber-modified polystyrene, MBS resin, ABS resin or the like to improve heat resistance.

Further, to the thermoplastic resin of the present invention, if necessary, an antioxidant such as hindered phenol-based, phosphorus-based, or inun-based, a reinforcing agent such as glass fiber, an ultraviolet absorber, a flame retardant, a pigment, etc. may be added. You can

〔Example〕

The effects of the present invention will be described in more detail below with reference to Examples and Comparative Examples. The heat distortion temperature in the examples is ASTM-D.
-648-56, total light transmittance ASTM-D-1003, bending strength ASTM-D-790, tensile strength ASTM-D-638 Metho
Followed d.

Example 1 N-cyclohexylmaleimide 900 g, α-methylstyrene 600 g, methyl methacrylate 2700 g, styrene 1200 g, water
6000g, di-t-butylperoxy-hexahydro-
15.6 g of terephthalate, 3 g of t-butyl peroxyacetate, 6 g of t-dodecyl mercaptan, 42 g of tricalcium phosphate and 0.24 g of potassium persulfate were charged into a nitrogen-substituted 15 autoclave and heated to 90 ° C. with stirring. After maintaining the temperature at 90 ° C for 4 hours with continuous stirring, 600 g of styrene was added to the copolymerization system, and after maintaining at 90 ° C for 5 hours, the temperature was raised to 125 ° C, and the temperature was maintained at 125 ° C for 2 hours. finished.

After dehydration and drying, the resin pelletized by the extruder was molded by a 2 ounce molding machine, and its performance was evaluated. The results are shown in Table 1.

Example 2 The method of Example 1 was followed except that N-cyclohexylmaleimide was changed to N-methylmaleimide. The results of evaluating the performance of the obtained resin are shown in Table 1.

Example 3 Example 1 was followed except that N-cyclohexylmaleimide was changed to Nt-butylmaleimide. The results of evaluating the performance of the obtained resin are shown in Table 1.

Comparative Example 1 In Example 1, 600 g of styrene supplied to the copolymerization system was initially added during the polymerization, and the charged amount of styrene was 1800 g.
The procedure of Example 1 was followed, except that styrene was not added during the polymerization. The results are shown in Table 1. The obtained resin was cloudy and not practical.

Example 4 N-cyclohexylmaleimide 600 g, α-methylstyrene 1200 g, methyl methacrylate 2700 g, styrene 600 g, water
6000 g, 1,1-bis-t-butylperoxy-hexahydro-3,3,5-trimethyl-cyclohexane 24 g, t-butyl-peroxyacetate 3 g, tricalcium phosphate 42
g and 0.48 g of potassium persulfate were charged into a nitrogen-substituted 15 autoclave, and the temperature was raised to 95 ° C. with stirring. After maintaining at 95 ° C for 10 hours with continuous stirring, 300 g of styrene,
A mixture of 600 g of methyl methacrylate was continuously subjected to copolymerization over 1 hour, and the mixture was kept at 95 ° C. for 2 hours, then 125
After the temperature was raised to ℃ and kept for 2 hours, the polymerization was terminated.

After dehydration and drying, the resin pelletized by the extruder was molded by a 2 ounce molding machine, and its performance was evaluated. The results are shown in Table 1.

Comparative Example 2 In Example 4, a monomer mixture consisting of 300 g of styrene and 600 g of methyl methacrylate to be used in the copolymerization system in the course of polymerization was initially added, and the charged amount of styrene was 900 g and the charged amount of methyl methacrylate was 900 g. The method of Example 1 was followed except that the amount was changed to 3300 g and the monomer mixture during the polymerization was not added. The results are shown in Table 1, which was not practical because clouding occurred.

Example 5 N-Cyclohexylmaleimide 1800 g, α-methylstyrene 600 g, methyl methacrylate 2400 g, water 6000 g, t-butylperoxy-2-ethylhexanoate 12 g, t-
Butyl peroxyacetate 3g, t-dodecyl mercaptan 6g, tricalcium phosphate 42g, potassium persulfate 0.2
4 g was charged into 15 autoclaves whose atmosphere was replaced with nitrogen, and the temperature was raised to 85 ° C. with stirring. 1 at 85 ℃ with continuous stirring
After maintaining for a period of time, 900 g of styrene was subjected to the copolymerization system, and after 1 hour and 30 minutes, 300 g of styrene was subjected to the copolymerization system for 1 hour.
After the temperature was maintained at 85 ° C, the temperature was raised to 130 ° C and the temperature was maintained for 2 hours, after which the polymerization was completed.

After dehydration and drying, the resin pelletized by the extruder was molded by a 2 ounce molding machine, and its performance was evaluated.

The results are shown in Table 1.

Comparative Example 3 Example 5 was carried out except that the charged amount of styrene was 1650 g and the amount of styrene supplied to the copolymerization system during the polymerization was 150 g. The obtained resin was cloudy and impractical.

Example 6 N-cyclohexylmaleimide 1200 g, α-methylstyrene 1200 g, methyl methacrylate 3000 g, water 6000 g, di-
t-butyl peroxy-hexahydro-terephthalate
15.6 g, t-butyl peroxyacetate 3 g, t-dodecyl mercaptan 3 g, tricalcium phosphate 42 g, and
Charge 0.24 g of potassium persulfate into 15 autoclaves replaced with nitrogen, raise the temperature to 90 ° C. with stirring, and keep at 90 ° C. for 6 hours with continuous stirring.
After 600g was put into the copolymerization system and kept at 90 ° C for another 2 hours,
The temperature was raised to 5 ° C. and the temperature was maintained at 125 ° C. for 2 hours, and then the polymerization was terminated.

After dehydration / drying, the resin pelletized with an extruder was molded with a 2 ounce molding machine, and its performance was evaluated. The results are shown in Table 1.

Comparative Example 4 N-cyclohexylmaleimide 180 g, α-methylstyrene 300 g, methyl methacrylate 1020 g, styrene 2400 g, water
6000g, di-t-butylperoxy-hexahydro-
15.6 g of terephthalate, 3 g of t-butyl peroxyacetate, 6 g of t-dodecyl mercaptan, 42 g of tricalcium phosphate and 0.24 g of potassium persulfate were replaced with nitrogen 15.
Was charged into the autoclave and heated to 95 ° C with stirring. After maintaining at 95 ° C for 2 hours with continuous stirring, styrene
1800g is used for the copolymerization system over 1 hour, and then for 3 hours 95
The temperature was maintained at 125 ° C., the temperature was raised to 125 ° C., and the temperature was maintained at 125 ° C. for 2 hours, and then the polymerization was completed.

After dehydration / drying, the resin pelletized with an extruder was molded with a 2 ounce molding machine, and its performance was evaluated. The results are shown in Table 1, but the heat resistance, which is one of the objects of the present invention, was not sufficient.

Comparative Example 5 N-cyclohexylmaleimide 2700 g, α-methylstyrene 600 g, methyl methacrylate 2100 g, water 6000 g, t-butyl-2-ethylhexanoate 12 g, t-butylperoxyacetate 3 g, tricalcium phosphate 42 g, and
0.24 g of potassium persulfate was charged into 15 autoclaves purged with nitrogen, and the temperature was raised to 85 ° C. with stirring. While continuing stirring, the mixture was kept at 85 ° C for 2 hours, then 600 g of methyl methacrylate was supplied to the copolymerization system, further kept at 85 ° C for 2 hours and then heated to 125 ° C, and kept for 2 hours, and then the polymerization was completed. did.

After dehydration / drying, the resin pelletized with an extruder was molded with a 2 ounce molding machine, and its physical properties were evaluated. The results are shown in Table 1, but the obtained resin had low tensile strength and was not practical.

〔The invention's effect〕

As described in detail above, the heat-resistant thermoplastic resin of the present invention has excellent transparency, heat resistance, and molding processability, and its industrial value is extremely large.

Claims (1)

[Claims] 1. (a) 5-40 parts by weight of N-substituted maleimide,
(B) 5 to 35 parts by weight of α-methylstyrene, (c) 40 to 85 parts by weight of methacrylic acid ester, and (d) 0 to 50 parts by weight of an aromatic vinyl monomer other than α-methylstyrene are copolymerized. In this case, first, the total amount of (a) and (b), the total amount of (c) and a part of (d), or the monomer mixture consisting of a part of (c) and the total amount of (d) or a part thereof is mixed. Polymerization, and then the remaining part of (d) or part of (c) or part of (c) and part of (d) are continuously or intermittently supplied to the copolymerization system to carry out copolymerization. What to do (however, first (a),
(D) is not 0 parts by weight when the whole amount of (b) and (c) is copolymerized).