JPH02127407A - Heat-resistant thermoplastic resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin having excellent heat-resistance, moldability, transparency and productivity, resistant to discoloration and useful for automobile use, etc., by copolymerizing an aromatic vinyl monomer and an alkylmaleimide monomer at a specific ratio. CONSTITUTION:The objective resin having a weight-average molecular weight of 50,000-500,000 and containing the unit of formula I (R1 is H, methyl or ethyl; R2 is aromatic hydrocarbon group) and the unit of formula II (R3 is 1-15C alkyl or cycloalkyl) at a molar ratio of (65-97):(35-3) in linearly and randomly arranged state is produced by copolymerizing an aromatic vinyl monomer (preferably styrene, etc.) and an alkylmaleimide monomer (preferably N- cyclohexylmaleimide). The resin is produced preferably by carrying out suspension polymerization while continuously or intermittently supplying the alkylmaleimide monomer to the polymerization system. The polymerization temperature is usually preferably 60-160 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermoplastic resin that has excellent heat resistance and moldability as well as excellent transparency.

[Conventional technology and problems]

Vinyl polymers such as polystyrene are resins with excellent transparency and moldability, and are used in automobile parts, OA
Its uses are wide, including parts and daily necessities.

However, the use of vinyl polymers is limited due to their low heat distortion temperatures.

Therefore, research is being conducted to improve the heat distortion temperature of vinyl polymers. For example, a method of copolymerizing methyl methacrylate and α-methylstyrene (U.S. Patent No. 3
．． 135.723), methyl methacrylate, α
- Method of copolymerizing methylstyrene and maleic anhydride (Japanese Patent Publication No. 4531.953), methyl methacrylate, α-methylstyrene and maleimide (unsubstituted)
A method of copolymerizing these has 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, and the resulting resin is strongly colored and loses transparency.

Furthermore, it has been known that copolymers made of vinyl monomers and maleimide monomers have excellent moldability and heat resistance. However, when a mixture of vinyl monomers and maleimide monomers is subjected to normal radical polymerization, alternating copolymers are preferentially formed, followed by homopolymers of the remaining monomers. Finally, an opaque or translucent copolymer with a heterogeneous copolymer composition is obtained.

Moreover, this copolymer having a non-uniform chemical composition has the disadvantage of poor heat resistance.

[Means for solving problems]

In view of these problems, the present inventors conducted intensive research and found that a copolymer obtained by copolymerizing an aromatic vinyl monomer with a specific blending ratio and an alkylmaleimide monomer. It was discovered that the polymer not only has excellent heat resistance and molding processability, but also surprisingly produces resins with excellent transparency and productivity, and has low color discoloration, which led to the present invention. Ta.

That is, the present invention is a copolymer consisting of an aromatic vinyl monomer and an alkylmaleimide monomer with a ratio of 65 to 97:3.
A heat-resistant thermoplastic resin having a weight average molecular weight of 50,000 to 500,000 arranged irregularly in a linear manner at a molar ratio of 5 to 3 (wherein R in the above formula is a hydrogen atom, a methyl group or an ethyl group, R
2 is an aromatic hydrocarbon group, and R3 has 1 to 1 carbon atoms.
15 alkyl group or cycloalkyl group. ) regarding.

This copolymer has excellent transparency and a haze value of 3% or less.

The present invention will be explained in more detail below.

The copolymer of the present invention essentially contains 3 to 35 mol%, preferably 5 to 25 mol%, of alkylmaleimide monomer units.

The structural unit R:I alkylmaleimide monomer constituting the copolymer which is the resin of the present invention has the general formula % (in the formula, P is an alkyl group or a cycloalkyl group having 1 to 15 carbon atoms) ). A maleimide monomer in which R1 is an alkyl group or other than a cycloalkyl group, for example, an aromatic maleimide monomer such as N-phenylmaleimide, a halogenated alkylmaleimide monomer such as O-chlorophenylmaleimide, O-bromophenylmaleimide, etc. If a copolymer is used, the copolymer made using it will be strongly colored and its transparency will be impaired. However, even if an alkylmaleimide monomer is used, if it is less than 3 mol%, the heat resistance of the resulting copolymer resin will be poorly improved, and if it exceeds 35 mol%, the color of the resin will change. In the present invention, which aims to produce a resin with transparency and heat resistance, N-cyclohexylmaleimide is suitable.

is represented by the general 2 CH2=C (wherein R3 is a hydrogen atom, a methyl group or an ethyl group, and Rt is an aromatic hydrocarbon group).

Examples of aromatic vinyl monomers include styrene, p
-Methylstyrene, α-methylstyrene, 0-chlorostyrene, p-chlorostyrene, 0-bromostyrene, p
-bromostyrene, p-cyclohexylstyrene, p-
Examples include phenylstyrene, but styrene and α-
One or more methylstyrenes are preferred. In addition, α-methylstyrene has a great effect on improving heat resistance, so
When α-methylstyrene is contained in an amount of 5 to 25% by weight, the heat resistance of the resin is significantly improved. However, if the content of α-methylstyrene exceeds 25%, the polymerization rate will be extremely slow and the residual monomer of α-methylstyrene will increase, which will have an adverse effect on various physical properties such as heat resistance, which is not preferable.

It can be obtained by copolymerizing alkylmaleimide monomers, but the production method requires continuous or intermittent supply of the alkylmaleimide monomer to the polymerization system. At this time, it is preferable that the feed rate is such that the differential composition ratio of the copolymer becomes constant in the Mayo-Lewis copolymerization formula. There are no particular limitations on the supply method (the alkylmaleimide monomer can be supplied directly or after being diluted with a solvent such as methyl ethyl ketone or an aromatic vinyl monomer such as styrene or α-methylstyrene).

For the polymerization to produce the copolymer of the present invention, any polymerization method well known for boat fishing can be used, such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization.
Suspension polymerization is preferred because it facilitates operation during polymerization and recovery of polymerized products.

Further, the suspension polymerization reaction is carried out under general polymerization conditions, for example, using a radical polymerization initiator having a 10-hour half-life of 30 to 150°C. Initiators of this type include benzoyl peroxide, lauroyl ate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxy hexahydroterephthalate, t-butyl peroxy acetate, ethyl-33 - Optionally use one or more of organic peroxides such as di(t-butylperoxy)butyrate, and ab-based compounds such as azobisisobutyronitrile, azobiscyclonyl-IJ, azobiscyclohexylnitrile, etc. It's fine.

Further, in order to maintain good moldability of the copolymer resin, a chain transfer agent such as dodecyl mercaptan or octyl mercaptan may be added if necessary.

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

The polymerization temperature for producing the heat-resistant thermoplastic resin of the present invention is not particularly limited, but is in the range of 60°C to 160°C.

Furthermore, by forming the thermoplastic resin of the present invention into pellets or sheets, a molding material with excellent transparency, heat resistance, and moldability can be obtained. In addition, the thermoplastic resins obtained in the present invention are styrene-butadiene copolymer, styrene-butadiene-methyl methacrylate copolymer (MBS resin), styrene-butadiene-acrylonitrile copolymer (
It is also possible to further improve heat resistance by blending it with ABS resin.

In addition, the thermoplastic resin of the present invention may optionally contain a hindered phenol-based, phosphorus-based, or sulfur-based antioxidant,
Reinforcing agents such as glass fiber, ultraviolet absorbers, flame retardants, and pigments can also be added.

[Example] The effects of the present invention will be explained in more detail with reference to Examples and Comparative Examples below. In addition, the heat distortion temperature in Examples and Comparative Examples is ASTM D-648-56, haze value and total light transmittance is ASTM D-1003, and bending strength is ASTM D-648-56.
D-790Method was followed.

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

Example 1 3000 g of styrene, 6000 g of water, 6 g of t-butyl peroxybenzoate, 42 g of tertiary calcium phosphate
and 15f in which 0.24 g of potassium persulfate was replaced with nitrogen.
The mixture was placed in an autoclave and stirred vigorously.

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

Next, while maintaining the temperature inside the autoclave at 110°C and stirring, 50% of the N-cyclohexylmaleimide-styrene solution was added from the dropping funnel using a plunger pump.
The mixture was added dropwise at a rate of 0 g/hr for 6 hours. The monomer composition ratio at this time was styrene diN-cyclohexylmaleimide-93,9=6.1 in molar ratio. The temperature was further raised to 130°C and maintained for 2 hours, after which the polymerization was completed. After dehydration and drying,
When the composition of the polymer was confirmed by elemental analysis and C-NMR, it was found to be equal to the monomer composition ratio.

The resulting polymer was pelletized using an extractor and then molded using a 2-ounce injection molding machine. Its performance was evaluated. The results are shown in Table 1.

Example 2 2500 g of styrene, 500 g of α-methylstyrene
The method of Example 1 was followed except that g was changed. The monomer composition at this time is styrene: α-methylstyrene diN-cyclohexylmaleimide = 86.1 in molar ratio:
7.776.1, and the composition of the polymer was determined by elemental analysis and "
When confirmed by C-NMR, it was found to be equal to the seven-mer composition ratio. The physical properties are shown in Table 1.

Example 3 6000 g of water, 42 g of tertiary calcium phosphate, and 0.24 g of potassium persulfate were charged into a 151 autoclave purged with nitrogen and stirred.

On the other hand, 1200 g of N-cyclohexylmaleimide,
A mixed solution of 4,800 g of styrene and 6 g of t-butylperoxybenzony was prepared and charged into a dropping funnel.

Next, while maintaining the temperature inside the autoclave at 110°C and stirring, 50% of the N-cyclohexylmaleimide-styrene solution was added from the dropping funnel using a plunger pump.
The mixture was added dropwise at a rate of 0 g/hr for 12 hours. The monomer composition ratio at this time is styrene:N-cyclohexylmaleimide=87.3:12.7 in terms of molar ratio. Another 130
The temperature was raised to .degree. C. and maintained for 2 hours, after which the polymerization was completed. After dehydration and drying, the composition of the polymer was confirmed by elemental analysis and C-NMR, and it was found to be equal to the monomer composition ratio.

The resulting polymer was pelletized using an extractor and then molded using a 2-ounce injection molding machine. Table 1 shows the results of evaluating the performance.

Comparative Example I The method 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 is styrene diN-
Phenylmaleimide=93.8:6.2. Table 1 shows the results of performance evaluation. From this table, it can be seen that the yellow color is deep and it 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-0-chlorophenylmaleimide. The monomer composition ratio at this time is styrene:N-0-
Chlorophenylmaleimide = 94.8:5.2.

Table 1 shows the results of performance evaluation. From this table, it can be seen that if the yellowness is too deep, it is not practical as a transparent material.

Comparative example 3 N-cyclohexylmaleimide 1000g, styrene 5
000 g, water 6000 g, t-butyl peroxybenzoate 6 g, tertiary calcium phosphate 42 g and potassium persulfate 0.24 g were charged into a 151 autoclave purged with nitrogen and stirred vigorously. The monomer composition ratio at this time was styrene diN-cyclohexylmaleimide-93.9:6.1 in terms of molar ratio.

After keeping the temperature inside the autoclave at 110℃ for 6 hours,
The temperature was raised to 30°C and maintained for 2 hours, after which the polymerization was completed. 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 styrene solution containing 8% by weight of N-cyclohexylmaleimide was charged into the dropping funnel. The monomer composition ratio at this time was styrene diN-cyclohexylmaleimide-97.6:2.4 in terms of molar ratio. The physical property values are shown in Table 1. It can be seen from the table that sufficient heat resistance cannot be obtained.

Comparative Example 5 Example 1 was followed except that a slurry containing 20% by weight of N-cyclohexylmaleimide was charged into the dropping funnel. The monomer composition ratio at this time was styrene diN-cyclohexylmaleimide = 63.3:36.1 in molar ratio. The physical property values are shown in Table 1. It can be seen from the table that the strength is inferior.

〔effect〕

As mentioned above, the copolymer resin of the present invention has excellent heat resistance, shapeability, transparency, and moldability. This resin is expected to be useful in applications that require heat deformation resistance, such as heat-resistant PSP for microwave ovens, heat-resistant OPS, and automobile applications.

Claims (1)

[Scope of Claims] 1. A copolymer consisting of an aromatic vinyl monomer and an alkylmaleimide monomer, which comprises a structural unit represented by the formula ▲, which includes mathematical formulas, chemical formulas, tables, etc.▼, and the formula ▲ A heat-resistant thermoplastic resin with a weight average molecular weight of 50,000 to 500,000, in which the structural units shown by ▼ are linearly and irregularly arranged in a molar ratio of 65 to 97:35 to 3. (However, in the above formula, R_1 is a hydrogen atom, a methyl group, or an ethyl group, R_2 is an aromatic hydrocarbon group, and R_3 is an alkyl group or cycloalkyl group having 1 to 15 carbon atoms.) 2. The heat-resistant thermoplastic resin according to claim 1, which has a haze value of 3% or less.