JPH0796582B2 - Method for producing transparent heat-resistant resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a methacrylic resin,
The resin obtained by the production method of the present invention has little yellowing during molding and has excellent transparency and heat resistance.
It is suitable as a material for optical elements such as lenses, optical disks and optical fibers.

(Prior art and problems) Since methacrylic resin containing methyl methacrylate as a main component has excellent optical properties, mechanical properties, and moldability,
It is used as a material for optical elements such as lenses, optical disks, and optical fibers. However, conventional methacrylic resins have a low heat distortion temperature, so lenses made of these materials undergo heat distortion during hard coating treatment to prevent scratches, and optical discs are subject to creep during use. Surrection is seen. Many attempts have been made to improve the heat resistance of methacrylic resins, for example, a method of copolymerizing methyl methacrylate with α-methylstyrene and maleic anhydride (Japanese Patent Publication No.
No. 10156).

However, the resin obtained by this method has difficulty in thermal stability,
Resin often decomposes and fires during molding.

Further, a method of copolymerizing methyl methacrylate with an N-aromatic substituted maleimide (Japanese Patent Publication No. Sho 43-9753, JP-A No. 61-1417).
No. 15, JP-A-61-171708) is also known, but the N-aromatic substituted maleimide monomers used in the disclosed examples of these publications are often colored by themselves, and these Since the resin obtained by polymerization has a yellowish tint, its commercial value is significantly impaired.

(Means for Solving Problems) Therefore, the inventors of the present invention diligently studied a method for obtaining a methacrylic resin having excellent transparency and heat resistance without such inconvenience. As a result, surprisingly, the N-substituted aromatic group By copolymerizing an N-aromatic substituted maleimide monomer having an alkyl group having 2 or more carbon atoms at the ortho position with an alkyl methacrylic acid ester, yellowing during molding is extremely small, and transparency and heat resistance are improved. They have found that an excellent resin can be obtained and have reached the present invention.

That is, the present invention has the general formula (R ₁ : an alkyl group having 1 or more carbon atoms) monomer (I) 30 to 95% by weight, general formula 1 to 60% by weight of the monomer (II) represented by (R ₂ , R ₃ : an alkyl group having 2 or more carbon atoms), and the monomer (I) or (II)
To a method for producing a transparent heat-resistant resin having an extremely low degree of yellowing during molding and processing, which comprises copolymerizing a monomer group consisting of 0 to 60% by weight of a monomer (III) copolymerizable with It is a thing.

Here, the group of monomers constituting the resin will be described.

As the monomer (I), those having an alkyl group in which R ₁ is 1 or more in the general formula can be used, and among them, particularly preferred is methyl methacrylate. As the monomer (II), those in which R ₂ and R ₃ in the general formula are alkyl groups having 2 or more carbon atoms can be used, and among them, preferred one is N- (2,
6-diethylphenyl) maleimide. Examples of the monomer (III) copolymerizable with the monomer (I) or (II) include styrene, α-methylstyrene, vinyltoluene,
Examples thereof include halogen-substituted derivatives thereof, acrylic acid, methacrylic acid, acrylic acid alkyl esters having an alkyl group having 1 or more carbon atoms, maleic anhydride, and acrylonitrile. Of these, styrene and α-methylstyrene are preferable.

The proportion of the monomers (I) and (II) in the monomer group is
(I) 30 to 95% by weight, preferably 40 to 90% by weight, (II)
1 to 60% by weight, preferably 2 to 50% by weight, and the transparency of the resin obtained when the monomer (I) is less than 30% by weight or the monomer (II) exceeds 60% by weight. However, the moldability is remarkably lowered and the birefringence is increased, which is not preferable. On the other hand, when (I) exceeds 95% by weight or (II) is less than 1% by weight, the heat resistance of the resin is insufficient and the refractive index is not increased, which is not preferable. The monomer group includes monomers (I) and (I
Although I) is an essential component, the addition of monomer (III) as described above to the extent that it does not exceed 60% by weight does not deteriorate the excellent properties of the resulting resin, and also improves the refractive index. Sometimes it can be increased.

Next, a method of copolymerizing these monomer groups will be described. For the polymerization, any of known bulk polymerization method, emulsion polymerization method, suspension polymerization method and solution polymerization method can be adopted, but in the bulk polymerization method, it is difficult to remove the heat of polymerization, and thus the emulsion polymerization method and the suspension polymerization method are used. In the case of the polymerization method, since the polymerization is carried out in an aqueous system, the N-aromatic substituted maleimide is hydrolyzed, and the physical properties of the obtained resin are poor. In addition, especially when a highly hydrophilic monomer such as methyl methacrylate is used in the suspension polymerization method, the suspension stabilizer may be mixed in the polymer beads produced, and the transparency of the resulting resin is Is damaged. On the other hand, in the solution polymerization method, it is easy to remove the heat of polymerization, and if appropriate desolvation measures are taken after the completion of the polymerization, it is easy to remove impurities such as unreacted monomers and initiator residues, and high purity. The resin can be obtained, and a material particularly suitable for optical element applications can be provided. The recommended desolvation method is a method of volatilizing the solvent by rapidly discharging a heated and pressurized polymer solution through an orifice into a low temperature decompression space, and an extruder equipped with a devolatilizer for the polymer solution. There is a method in which the solvent is continuously supplied to the hopper port to perform desolvation and pelletization of the resin at the same time (for example, JP-A-60-243102). In the latter case, the resin can be directly recovered as pellets from the solution. This is preferable because it has an advantage and the residual monomer which causes the coloring of the resin can be removed by appropriately controlling the cylinder temperature of the extruder and the degree of pressure reduction at the devolatilization port. In order to prevent coloration, it is preferable to reduce the residual monomer in the resin as much as possible, and it is particularly preferable that the residual amount of the monomer (II) in the resin is 5000 ppm or less. Can be achieved.

As the solvent that can be used in the solution polymerization method, acetone, methyl ethyl tetone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, butyl cellosolve, dimethylformamide, isopropyl alcohol,
Examples thereof include butyl alcohol, benzene, toluene, xylene, and ethylbenzene. Among these, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone are particularly preferable. These solvents are used in an amount of 5 to 400 parts by weight, preferably 10 to 250 parts by weight, per 100 parts by weight of the monomer. If it is less than 5 parts by weight, the viscosity of the system is extremely high depending on the monomer composition, and it is difficult to remove the heat of polymerization. If it exceeds 400 parts by weight, the polymerization rate is slow and the molecular weight of the obtained polymer is low. As a polymerization initiator, a common organic peroxide such as benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-
Butylcumyl peroxide, dicumyl peroxide, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxybenzoate, 2,5-dimethyl-2,5 -Di (benzoylperoxy) hexane, t-
Butyl peroxy isopropyl carbonate, 2,2-di- (t-butyl peroxy) butane, di-t-butyl peroxy-hexahydroterephthalate, di-t-butyl peroxyazelate, or azobis compounds, such as 2, 2'-azobis (2,4-dimethylvaleronitrile), (1-phenylethyl) azodiphenylmethane,
2,2'-azobisisobutyronitrile, dimethyl 2,2'-
Azobisisobutyrate, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo)-
Isobutyronitrile, 2,2'-azobis (2,4,4-trimethylpentane) and the like can be used. The preferred amount of use is 0.01 to 2 parts by weight with respect to 100 parts by weight of the monomer,
It is more preferably 0.05 to 1 part by weight. If it is less than 0.01% by weight, the polymerization rate is slow, and if it exceeds 2 parts by weight, impurities (initiator residue) in the resin increase and it becomes unsuitable for optical element use.

The polymerization temperature can be appropriately set in the range of 50 ° C to 150 ° C depending on the decomposition temperature of the initiator.

Incidentally, the resin obtained in the present invention, if necessary,
A heat stabilizer such as a hindered phenol compound or an organic (sub) phosphoric acid ester, a benzotriazole-based UV absorber, a hindered amine-based UV stabilizer, and various lubricants may be added.

(Examples) Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

All parts and% in the examples are expressed on a weight basis.

Example 1 Methyl methacrylate in an autoclave equipped with a stirrer
30 parts, N- (2,6-diethylphenyl) maleimide 15
Part, cyclohexanone 50 parts, and 2,2′-azobisisobutyronitrile 0.1 part were charged, and after the system was replaced with nitrogen gas,
The mixture was stirred at room temperature for 30 minutes to dissolve N- (2,6-diethylphenyl) maleimide. After heating to 80 ° C. and continuing stirring for 3 hours, a mixture of 55 parts of methyl methacrylate, 60 parts of cyclohexanone and 0.5 parts of 2,2′-azobisisobutyronitrile was continuously added over 5 hours. . After addition, 110
The temperature was raised to 0 ° C. and the mixture was further stirred for 3 hours to obtain a viscous copolymer solution. A part of the solution was sampled and the amount of unpolymerized monomer was quantified by gas chromatography. As a result, the polymerization rates were 99.0% for methyl methacrylate and 98.5% for N- (2,6-diethylphenyl) maleimide. The copolymer solution was supplied to the hopper port of a co-rotating twin-screw extruder equipped with a devolatilizer through a closed system pipe whose interior had been previously replaced with nitrogen, and the solvent was removed and the copolymer resin was pelletized at the same time. It was The cylinder temperature of the extruder was set to 240 ° C., and the devolatilization port provided in the middle of the cylinder was designed so that the degree of vacuum was always 700 mmHg or more. The content of impurities in the obtained resin pellets was analyzed by gas chromatography to find that N
-(2,6-Diethylphenyl) maleimide was 0.07% and cyclohexanone was 0.02%, and methyl methacrylate was not detected.

The obtained pellets were injection-molded, various physical properties were measured, and the results are shown in Table 1.

Example 2 Methyl methacrylate was placed in the same autoclave as in Example 1.
25 parts, N- (2,6-diethylphenyl) maleimide 30
Part, cyclohexanone 55 parts, and 2,2′-azobisisobutyronitrile 0.1 part were charged, and after the system was replaced with nitrogen gas,
The mixture was stirred at room temperature for 30 minutes to dissolve N- (2,6-diethylphenyl) maleimide. After heating to 80 ° C. and stirring for 2 hours, a mixture of 45 parts of methyl methacrylate, 50 parts of cyclohexanone and 0.5 parts of 2,2′-azobisisobutyronitrile was continuously added in 6 hours. . 110 ℃ after addition
The temperature was raised to 0, and the mixture was further stirred for 4 hours to complete the polymerization.

When the polymerization rate was determined in the same manner as in Example 1, it was 99.6% for methyl methacrylate and 99.0% for N- (2,6-diethylphenyl) maleimide. Through the same operation as in Example 1, the resin pellet was recovered. As impurities in the pellet, N- (2,6-diethylphenyl) maleimide, 0.06
%, And cyclohexanone 0.02%. Various physical properties of the pellets after injection molding are shown in Table 1.

Example 3 Methyl methacrylate was placed in the same autoclave as in Example 1.
25 parts, N- (2,6-diethylphenyl) maleimide 15
Part, cyclohexanone 50 parts, and 2,2′-azobisisobutyronitrile 0.1 part were charged, and after the system was replaced with nitrogen gas,
The mixture was stirred at room temperature for 30 minutes. After heating to 80 ° C and stirring for 3 hours, 50 parts of methyl methacrylate, 10 parts of styrene,
A mixture of 60 parts of cyclohexanone and 0.5 parts of 2,2'-azobisisobutyronitrile was added continuously over 5 hours. After the addition, the temperature was raised to 110 ° C. and stirring was continued for another 3 hours to complete the polymerization. Polymerization rate is 99.3% methyl methacrylate,
N- (2,6-diethylphenyl) maleimide was 98.7% and styrene was 98.0%. Impurities in the resin recovered as pellets in the same manner as in Example 1 were N- (2,6-diethylphenyl) maleimide 0.05% and cyclohexanone.
0.03% and styrene 0.01% were recognized. Table 1 shows the physical properties after molding.

Comparative Example 1 Methyl methacrylate was placed in the same autoclave as in Example 1.
30 parts, N- (2-chlorophenyl) maleimide 15 parts, cyclohexanone 35 parts, and 2,2'-azobisisobutyronitrile 0.06 parts were charged, the system was replaced with nitrogen gas, and the mixture was stirred at room temperature for 30 minutes. . After heating to 80 ° C and stirring for 1 hour, 55 parts of methyl methacrylate, 70 parts of cyclohexanone,
A mixture of 0.55 parts of 2,2'-azobisisobutyronitrile was added continuously over 4 hours. After the addition, the temperature was raised to 110 ° C. and stirring was continued for 2 hours to complete the polymerization. The polymerization rate was 99.5% for methyl methacrylate and 98.2% for N- (2-chlorophenyl) maleimide.

Resin pellets were obtained in the same manner as in Example 1 and injection-molded to measure the physical properties. The results are shown in Table 1. In addition,
Impurities in the pellet were 0.06% N- (2-chlorophenyl) maleimide and 0.02% cyclohexanone.

Comparative Example 2 A resin pellet was obtained by the same procedure as in Example 1 except that 15 parts of N- (2,6-diethyl) phenylmaleimide was changed to 15 parts of N-phenylmaleimide. The physical properties of the injection-molded products are shown in Table 1. Impurities in the pellet were 0.05% N-phenylmaleimide and 0.03% cyclohexanone.

Example 4 160 parts of pure water, 0.08 part of 1% sodium dodecylbenzenesulfonate aqueous solution, 1% of potassium persulfate in an autoclave
Aqueous solution 0.05 parts, tricalcium phosphate 10% slurry liquid 7.
5 parts were added. Furthermore, 30 parts of methyl methacrylate, N-
15 parts of (2,6-diethyl) phenylmaleimide and 0.2 parts of 2,2'-azobisisobutyronitrile were added and stirred to 80
The temperature was raised to ° C. After the internal temperature reached 80 ° C., 55 parts of methyl methacrylate was continuously added over 3 hours. Then, after adding 0.15 parts of a 1% aqueous solution of potassium persulfate and 0.5 parts of 2,2'-azobisisobutyronitrile, the temperature was raised to 110 ° C and further 3
I kept it for hours. After the completion of the polymerization, a bead-shaped resin having a diameter of about 0.5 mm was obtained. The beads were separated by filtration, dried, and then extruded with a single-screw extruder to form pellets. Impurities in the pellets were 0.21% of methyl methacrylate, N- (2,
It was 0.64% of 6-diethyl) phenylmaleimide. Table 1 shows the physical properties after injection molding.

Comparative Example 3 (Synthesis of methyl methacrylate homopolymer) Methyl methacrylate 100 was placed in an autoclave equipped with a stirrer.
Parts, cyclohexanone 250 parts, and 2,2′-azobisisobutyronitrile 0.3 parts were charged, the system was purged with nitrogen, and the temperature was raised to 80 ° C. with stirring and kept for 10 hours. After that, solvent removal and pelletization were performed in the same manner as in Example 1. The physical properties of the injection molded product are summarized in Table 1.

Reference Example 1 Polycarbonate of Mitsubishi Gas Chemical Co., Inc., Iupilon H4
000 was injection molded and the birefringence was measured.

The various physical properties were measured by the following methods.

(1) Tg (glass transition temperature): Using a differential scanning calorimeter (DSC-2 type) manufactured by PERKIN ELMER, a temperature rising rate of 10 ° / in a nitrogen atmosphere.
Measured in minutes. The sample used the pellet extruded by the extruder.

(2) Refractive index and number of Abpe: Pellets were molded into a plate with a thickness of 2 mm by an injection molding machine (J10S type manufactured by Nikko Shoji Co., Ltd.) and measured by an Abpe refractometer.

(3) Total light transmittance, haze: The molded piece having a thickness of 2 mm obtained in (2) was measured by Nippon Denshoku Industries Co., Ltd. NDH-Σ80 COLOR MEASURING SYSTEM TYPE II.

(4) Yellowness: Using the molded product obtained in (2), Nippon Denshoku Industries Co., Ltd. Σ80 C
It was measured by OLOR MEASURING SYSTEM TYPE II.

(5) Bending strength: According to ASTM-D790-71.

(6) Heat distortion temperature: According to ASTM-D648.

(7) Birefringence: Toshiba Machine IS100E-3A injection molding machine [50Z, cylinder temperature setting 230-270 ℃ (Iupilon H40
00 only 280-320 ℃)], a disk substrate is molded using a center gate mold (mold temperature 70 ℃) with a diameter of 130 mm and a thickness of 12 mm, and from the center of the disk substrate with a Shinko Seiki SFII polarimeter. The birefringence at a position of 30 mm was measured.

(Effect of the Invention) General formula according to the present invention (R ₁ : an alkyl group having 1 or more carbon atoms), a monomer (I), and a general formula As shown in Table 1, resins obtained by copolymerizing the monomer (II) represented by (R ₂ , R ₃ : an alkyl group having 2 or more carbon atoms) as an essential constituent component have various transparency, heat resistance and various properties. Since it has excellent optical properties (refractive index, birefringence) and extremely low yellowness, it is suitable as a material for optical elements such as optical fibers, lenses and optical disks.

Claims (1)

[Claims] 1. A general formula (R ₁ : an alkyl group having 1 or more carbon atoms) monomer (I) 30 to 95% by weight, general formula 1 to 60% by weight of the monomer (II) represented by (R ₂ , R ₃ : an alkyl group having 2 or more carbon atoms), and the monomer (I) or (II)
A method for producing a transparent heat-resistant resin having an extremely low degree of yellowing during molding, which comprises copolymerizing a monomer group composed of 0 to 60% by weight of a monomer (III) copolymerizable with