JP2840645B2 - Heat resistant thermoplastic resin and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is excellent in heat resistance and molding processability, and is transparent,
The present invention relates to a thermoplastic resin having excellent color fastness and a method for producing the same.

[Conventional technology and problems]

Vinyl-based polymers such as polystyrene are resins with excellent transparency and moldability,
Its applications are wide, such as parts and daily necessities. However, due to its low heat distortion temperature, vinyl polymers are limited in their applications.

Therefore, studies have been made to improve the heat distortion temperature of vinyl polymers. For example, a method of copolymerizing methyl methacrylate and α-methylstyrene (U.S. Pat.
3,135,723), a method of copolymerizing methyl methacrylate, α-methylstyrene and maleic anhydride (JP-B-45-31,953), methyl methacrylate, α-
Methods for copolymerizing methylstyrene and maleimide (unsubstituted) have been reported.

However, these methods have not been put to practical use because the polymerization rate is extremely slow, the heat distortion temperature is insufficient, the obtained resin is strongly colored, and the transparency is impaired.

It has been known that a copolymer comprising a vinyl-based monomer and a maleimide-based monomer has excellent moldability and heat resistance. However, when a mixture of a vinyl monomer and a maleimide monomer is performed under ordinary radical polymerization, an alternating copolymer is preferentially formed, followed by a homopolymer of the remaining monomer. Eventually, an opaque or translucent copolymer having a heterogeneous copolymer composition is obtained. Moreover, the copolymer having this heterogeneous chemical composition,
There is a disadvantage that heat resistance is poor.

[Means for solving the problem]

In view of these problems, the present inventors have conducted intensive studies, and as a result, by copolymerizing styrene and / or α-methylstyrene having a specific compounding ratio with N-cyclohexylmaleimide by a specific method. The obtained copolymer is not only excellent in heat resistance and molding processability,
Surprisingly, they have found that an effect that the transparency and productivity of the resin are excellent and the coloration of the resin is small can be obtained, and the present invention has been accomplished.

That is, one of the present inventions And a structural unit represented by In a molar ratio of 65 to 97:35 to 3, the structural unit represented by the formula is linear and irregularly arranged styrene having a weight average molecular weight of 50,000 to 500,000 and / or α-methylstyrene and N-cyclohexylmaleimide. A heat-resistant thermoplastic resin having a haze value of 3% or less, which is a polymer, and another invention of the present invention is a method for producing the heat-resistant thermoplastic resin, N-cyclohexylmaleimide is continuously or intermittently supplied to a polymerization system in which styrene and / or α-methylstyrene are present and copolymerized. The present invention relates to a method for producing a thermoplastic resin. (However, in the above formula
R ₁ is a hydrogen atom or a methyl group, and R ₂ is a cyclohexyl group. Hereinafter, the present invention will be described in more detail.

It is essential that the copolymer of the present invention contains N-cyclohexylmaleimide in an amount of 3 to 35 mol%, preferably 5 to 25 mol%.

Structural units constituting the copolymer which is the resin of the present invention N-cyclohexylmaleimide used to produce (In the formula, R ₂ is a cyclohexyl group.) Maleimide monomer of R ₂ is other than cyclohexyl group, for example N- phenylmaleimide aromatic maleimide monomers such as, O- chlorophenyl maleimide, O-
When a halogenated alkylmaleimide monomer such as bromophenylmaleimide is used, a copolymer using the same is strongly colored and the transparency is impaired. However, even when the alkylmaleimide-based monomer is used in less than 3 mol%,
If the heat resistance of the produced copolymer resin is poorly improved, and if it exceeds 35 mol%, the resin becomes intensely colored and has low mechanical strength, which is not practical. In the present invention, which aims at a resin having transparency and heat resistance, N-cyclohexylmaleimide is preferred.

Structural units that make up the copolymer Styrene and / or α-
Methylstyrene has the general formula (Wherein, R ₁ is a hydrogen atom or a methyl group).

In the present invention, styrene and / or α-methylstyrene are used. Since α-methylstyrene has a large effect of improving heat resistance,
When 25% by weight is contained, the invention for improving the heat resistance of the resin becomes remarkable. However, when the content of α-methylstyrene exceeds 25%, the polymerization rate is remarkably slow and the amount of residual monomers of α-methylstyrene increases, which is unfavorable for various properties such as heat resistance.

The heat-resistant thermoplastic resin having excellent transparency according to the present invention can be obtained by copolymerizing styrene and / or α-methylstyrene with N-cyclohexylmaleimide. The continuous or intermittent supply of maleimide is required. In this case, the supply rate is preferably such that the differential composition ratio of the copolymer is constant in the Mayo-Lewis copolymer composition formula. There are no particular restrictions on the supply method,
A method of supplying N-cyclohexylmaleimide directly or by diluting it with a solvent such as methyl ethyl ketone, styrene, or α-methylstyrene can be employed.

In the method for producing the copolymer of the present invention, generally well-known polymerization methods such as a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and a solution polymerization method can be optionally used. A suspension polymerization method that allows easy operation and recovery of the polymer is preferable.

The suspension polymerization reaction is performed under general polymerization conditions, for example, using 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, cumene hydroperoxide, t-butylbenzoate, t-butylperoxy-2-ethylhexanoate, di-t-butylperoxide. Organic peroxides such as oxyhexahydroterephthalate, t-butylperoxyacetate, ethyl-3,3-di- (t-butylperoxy) butyrate, azobisisobutyronitrile, azobisvaleronitrile, and azobis One or more of azo compounds such as cyclohexylnitrile may be optionally used.

In order to maintain good moldability of the copolymer resin,
The weight average molecular weight of the polymer is 50,000 to 500,000, preferably 100,000 to
It is preferable to adjust to 250,000. Therefore, if necessary, a chain transfer agent such as dodecyl mercaptan or octyl mercaptan may be added.

As the suspension stabilizer, an inorganic dispersant such as calcium phosphate such as calcium hydroabatite, magnesium phosphate, magnesium oxalate, or magnesium sulfate, or an organic dispersant such as partially saponified polyvinyl alcohol is used.

In the method for producing a copolymer of the present invention, the polymerization temperature is not particularly limited, but is in the range of 60C to 160C.

Further, by forming the thermoplastic resin of the present invention into a pellet or a sheet, a molding material having excellent transparency, heat resistance and moldability can be obtained. The thermoplastic resin obtained in the present invention is a styrene-butadiene copolymer, styrene-
It is also possible to further improve heat resistance by blending in a butadiene-methyl methacrylate copolymer (MBS resin), a styrene-butadiene-acrylonitrile copolymer (ABS resin), or the like.

Further, the thermoplastic resin of the present invention, if necessary, hindered phenol-based, phosphorus-based, or sulfur-based antioxidant, reinforcing agent such as glass fiber, ultraviolet absorber, flame retardant,
Pigments can also be added.

〔Example〕

Hereinafter, the effects of the present invention will be described in more detail with reference to Examples and Comparative Examples. The heat distortion temperature in Examples and Comparative Examples is ASTM D-648-56, and the haze and total light transmittance are AST.
MD-1003, flexural strength according to ASTM D-790Method.

The weight average molecular weight was determined by a GPC method in terms of polystyrene.

Example 1 3000 g of styrene, 6000 g of water, 6 g of t-butylperoxybenzoate, 42 g of tribasic calcium phosphate and 0.24 g of potassium persulfate were charged into a 15-autoclave which was purged with nitrogen and stirred vigorously.

Separately, a 20% by weight styrene solution of N-cyclohexylmaleimide was prepared and charged into a dropping funnel.

Next, the temperature in the autoclave was kept at 110 ° C., and while stirring, the N-cyclohexylmaleimide-styrene solution was added to the solution from a dropping funnel using a plunger pump.
The solution was dropped at a rate of 0 g / hr for 6 hours. The monomer composition ratio at this time was styrene: N-cyclohexylmaleimide = 93.9: 6.1 in molar ratio. The temperature was further raised to 130 ° C., and after maintaining for 2 hours, the polymerization was terminated. After dehydration and drying, the composition of the polymer was confirmed by elemental analysis and ¹³ C-NMR, which was equal to the monomer composition ratio.

After pelletizing the obtained polymer with an extractor, molding was performed with a 2 oz. Injection molding machine. Its performance was evaluated.
Table 1 shows the results.

Example 2 The procedure of Example 1 was followed except that the styrene was changed to 2500 g and the α-methylstyrene was changed to 500 g. The monomer composition at this time was a molar ratio of styrene: α-methylstyrene: N-
Cyclohexylmaleimide = 86.1: 7.7: 6.1. The composition of the polymer was confirmed by elemental analysis and ¹³ C-NMR, and was found to be equal to the monomer composition ratio. Table 1 shows the physical properties.

Example 3 6,000 g of water, 42 g of tribasic calcium phosphate, and 0.24 g of potassium persulfate were charged and stirred in a 15-autoclave purged with nitrogen.

Separately, a mixed solution of 1200 g of N-cyclohexylmaleimide, 4800 g of styrene and 6 g of t-butylperoxybenzoate was prepared and charged in a dropping funnel.

Next, while maintaining the temperature in the autoclave at 110 ° C. and stirring, 500 g of an N-cyclohexylmaleimide-styrene solution was dropped from the dropping funnel using a plunger pump.
The solution was dropped at a rate of / hr for 12 hours. The monomer composition ratio at this time was a molar ratio of styrene: N-cyclohexylmaleimide = 87.3: 12.7. The temperature was further raised to 130 ° C., and after maintaining for 2 hours, the polymerization was terminated. After dehydration and drying, the composition of the polymer was confirmed by elemental analysis and ¹³ C-NMR, which was equal to the monomer composition ratio.

The obtained polymer was pelletized by an extractor and then performed by a 2 oz. Injection molding machine. Table 1 shows the results of evaluating the performance.

Comparative Example 1 The procedure of Example 1 was followed except that N-cyclohexylmaleimide was changed to N-phenylmaleimide and tertiary calcium phosphate was changed to 8 g of partially saponified polyvinyl alcohol. The monomer composition ratio at this time was styrene: N- in molar ratio.
Phenylmaleimide = 93.8: 6.2. Table 1 shows the results of evaluating the performance. From this table, it can be seen that the yellowness is deep and is not practical as a transparent material.

Comparative Example 2 The method of Comparative Example 1 was followed except that N-phenylmaleimide was changed to N-O-chlorophenylmaleimide. At this time, the monomer composition ratio was styrene: NO-
Chlorophenylmaleimide = 94.8: 5.2. Table I shows the results of the performance evaluation. From this table, it can be seen that the yellowness is deep and is not practical as a transparent material.

Comparative Example 3 N-cyclohexylmaleimide 600 g, styrene 5400
g, 6000 g of water, 6 g of t-butylperoxybenzoate, 42 g of tribasic calcium phosphate and 0.24 g of potassium persulfate were charged into a 15-autoclave which was purged with nitrogen and stirred vigorously. At this time, the monomer composition ratio is a molar ratio, styrene: N-
Cyclohexylmaleimide = 93.9: 6.1.

After keeping the temperature in the autoclave at 110 ° C for 6 hours,
C. and the polymerization was terminated after maintaining for 2 hours. After dehydration and drying, molding was performed, and the physical properties are shown in Table 1.

Comparative Example 4 Example 1 was followed except that a 8% by weight styrene solution of N-cyclohexylmaleimide was charged into the dropping funnel.
The monomer composition ratio at this time is a molar ratio of styrene: N-cyclohexylmaleimide = 97.6: 2.4. Table 1 shows the physical property values. It can be seen from the table that sufficient heat resistance cannot be obtained.

Comparative Example 5 The procedure of Example 1 was followed except that a slurry of 20% by weight of N-cyclohexylmaleimide was charged into a dropping funnel and dropped at a rate of 2500 g / hr. The monomer composition ratio at this time was styrene: N-cyclohexylmaleimide = 63:
3: 36.7. Table 1 shows the physical property values. The table shows that the strength is inferior.

[Effect] As described above, the copolymer resin of the present invention has heat deformation resistance,
Excellent transparency and moldability. This resin is expected to be used in applications requiring heat-resistant deformation, such as heat-resistant PSP for microwave ovens, heat-resistant OPS, and automotive applications, and is useful.

Continuation of front page (56) References JP-A-2-138321 (JP, A) JP-A-61-278509 (JP, A) JP-A-58-162219 (JP, A) JP-A-61-157550 (JP, A) , A) JP-A-61-76512 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08F 12/00-12/12 C08F 212/00-212/12 C08F 22/00 -22/40 C08F 222/00-222/40

Claims (2)

(57) [Claims] (1) And a structural unit represented by In a molar ratio of 65 to 97:35 to 3, the structural unit represented by the formula is linear and irregularly arranged styrene having a weight average molecular weight of 50,000 to 500,000 and / or α-methylstyrene and N-cyclohexylmaleimide. A heat-resistant thermoplastic resin which is a polymer and has a haze value of 3% or less. (However,
In the above formula, R ₁ is a hydrogen atom or a methyl group, and R ₂ is a cyclohexyl group. ) 2. The heat-resistant thermoplastic according to claim 1, wherein N-cyclohexylmaleimide is continuously or intermittently supplied to the polymerization system in which styrene and / or α-methylstyrene are present to copolymerize. Method of manufacturing resin.