JP2565377B2 - Method for producing α-methylstyrene-acrylonitrile copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is mainly applied to the production of α-methylstyrene-acrylonitrile heat-resistant copolymer, and has good transparency with no coloration and a residual monomer content. The present invention relates to an industrially advantageous copolymerization method in which a tetrafunctional organic peroxide is used as a polymerization initiator in order to obtain a high-polymerization degree copolymer having a small body weight.

(Prior Art) Conventionally, in order to improve heat resistance, that is, to obtain a copolymer with acrylonitrile containing a large amount of α-methylstyrene, which has a high heat distortion temperature and good thermal stability, organic peroxides have been used. There is a method of using a substance, and t-butylperoxybenzoate, t-butylperoxyacetate, benzoyl peroxide and the like are used.

(Problems to be Solved by the Invention) However, in the method using these polymerization initiators, it is necessary to use a large amount of the polymerization initiator regardless of the polymerization temperature. Therefore, the obtained copolymer is strongly colored, and The degree of polymerization of the copolymer was extremely low, industrially satisfactory copolymer physical properties could not be obtained, and the situation was poor for practical use.

On the other hand, an emulsion polymerization method is employed to obtain an α-methylstyrene-acrylonitrile-based copolymer having a high degree of polymerization and a high polymerization conversion rate. However, although the obtained copolymer is certainly a high degree of polymerization, it is unavoidable from the manufacturing method that an emulsifier, a salting-out agent, or the like is mixed in, and it is not satisfactory from the viewpoint of transparency, and it is industrially used. Has limitations. These are the reasons why it is desired to establish a method for producing a copolymer having good transparency and high heat distortion temperature without coloring by the suspension or bulk polymerization method.

(Means for Solving the Problem) In the process for producing an α-methylstyrene-acrylonitrile-based copolymer, the present inventors have no particular coloring, and have excellent transparency, a high polymerization conversion rate and a high polymerization degree. As a result of searching various organic peroxides for obtaining a copolymer, it was found that it is extremely effective to carry out the polymerization using a tetrafunctional organic peroxide having a specific structure, and to complete the present invention. Arrived

That is, the present invention is represented by the general formula (I) in copolymerizing a mixture of α-methylstyrene and acrylonitrile, or at least one monomer selected from monomers copolymerizable therewith. Is a method for producing an α-methylstyrene-acrylonitrile copolymer using a tetrafunctional organic peroxide.

(In the formula, R represents an alkyl group having 1 to 5 carbon atoms or a phenyl group R ₁ or R ₂ represents an alkyl group having 1 to ₂ carbon atoms).

As the tetrafunctional organic peroxide having a specific structure represented by the general formula (I), that is, perketal in the present invention, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane 2 , 2-Bis (4,4-di-t-amylperoxycyclohexyl) propane 2,2-bis (4,4-
Di-t-octylperoxycyclohexyl) propane
2,2-Bis (4,4-di-α-cumylperoxycyclohexyl) propane 2,2-bis (4,4-di-t-butylperoxycyclohexyl) butane 2,2-bis (4,4- The-t-
Examples include octylperoxycyclohexyl) butane. These perketals can be synthesized relatively easily based on the production methods described in JP-B-40-19013 and JP-B-41-19511. That is, the general formula (I
Diketone compounds represented by I) (In the formula, R ₁ and R ₂ are as defined in the general formula (I).)
And tertiary hydroperoxide, for example, t-butyl hydroperoxide, t-amyl hydroperoxide, cumene hydroperoxide, t-octyl hydroperoxide, etc. can be obtained by reacting in the presence of an acid catalyst. .

The amount of the tetrafunctional organic peroxide represented by the general formula (I) used as a polymerization initiator is preferably 0.1% by weight to 3.0% by weight based on the total amount of the mixture monomers. If it is less than 0.1% by weight, the polymerization conversion cannot be increased and it is not practical. On the other hand, when it is 3.0% by weight or more, the polymerization rate becomes remarkably high, it becomes difficult to control the polymerization reaction, and intense coloring occurs.

The organic peroxide according to the present invention can be used as a mixture of two kinds. Further, the organic peroxide according to the present invention can be used in combination with other organic peroxides other than the organic peroxide represented by the general formula (I) and in combination with an azo polymerization initiator.

It is preferable to carry out the polymerization in a temperature range of 80 ° C. or higher and lower than 120 ° C. in order to obtain good transparency without coloring and a high polymerization conversion / high polymerization degree copolymer. Furthermore, it is still effective to carry out the polymerization at a temperature obtained by adding 10 ° C. to the 10-hour half-life temperature of the organic peroxide used. Further, a polymerization method according to a temperature rising scheme can also be adopted. It should be noted that polymerization in a temperature range of less than 80 ° C is not practical because the conversion rate does not increase. Meanwhile, 120 ° C
In the above cases, the coloring is severe and the physical properties of the obtained copolymer are not satisfactory.

The monomers that can be used in the present invention are mainly α-methylstyrene and acrylonitrile, and a monomer copolymerizable with them can be added if necessary. α-Methylstyrene is preferably 40 to 80% by weight, acrylonitrile is preferably 10 to 40% by weight, and the copolymerizable monomer is preferably 0 to 40% by weight. Specific examples of the copolymerizable monomer include acrylic acid esters such as styrene, ethyl acrylate and butyl acrylate, methacrylic acid esters such as methyl methacrylate and butyl methacrylate, and vinyltoluene.

The polymerization method may be either suspension polymerization or bulk polymerization, and can also be used in a bulk-suspension polymerization system.

EXAMPLES Next, the present invention will be described with examples. The results of these polymerizations are summarized in Table 1. Prior to the description of the embodiment,
The polymerization method and the evaluation method of the copolymer will be described below.

Polymerization method The polymerization adopted the ampoule method. That is, a predetermined amount of α-methylstyrene (hereinafter abbreviated as αMS) and acrylonitrile (hereinafter abbreviated as AN) and, if necessary, a copolymerizable monomer are charged together with a polymerization initiator into an ampoule for polymerization, and nitrogen is added. After replacement with gas, sealing was performed. Polymerization was carried out for a predetermined time in an oil bath set to a predetermined temperature, and after completion of the polymerization, the ampoule was taken out and cooled. The contents were taken out as needed, and after pretreatment, they were used as respective evaluation (analysis / measurement) samples. The amount of the polymerization initiator added was% by weight (equivalent to a pure product), which was expressed as the total weight of the monomer. The charging ratio of αMS / AN was expressed as the weight ratio. The temperature scheme for the polymerization used a constant temperature format, and in some examples also a temperature rising format.

Evaluation Method of Copolymer The polymerization conversion rate (%) of the copolymer; it was calculated back from the measurement results of residual αMS and AN amount by gas chromatography.

Reduced viscosity (ηsp / C); 0.2% solution of N, N′-dimethylformamide was measured with an Ubbelohde viscometer at 25 ° C.,
It was used as a standard for comparison of copolymer molecular weight.

Hue (Yellowness: YI): The degree of yellowness was determined by the white plate reflection method using an ampoule and a color difference meter. The correlation between YI and the hue (degree of coloring) of the copolymer is as follows.

Comprehensive Judgment Criteria: Those satisfying the following three item criteria were evaluated as good (marked with ⊚), and if even one of the three items was not satisfied, judged as defective (marked with ×).

Examples 1 to 5. Bulk Polymerization of αMS / AN System As shown in Table 1, various organic peroxides were used as polymerization initiators to carry out polymerization according to the above-mentioned polymerization method. The polymerization temperature scheme is a constant temperature format.

Examples 6 and 7. Bulk polymerization of αMS / AN system As shown in Table 1, Example 6 is the case of the elevated temperature polymerization temperature scheme, and Example 7 is the case of the two-component combination initiator system.

Comparative Examples 1 to 5. Bulk Polymerization of αMS / AN System All were carried out based on the above-mentioned polymerization method. Comparative Example 1
3 is an example of using an organic peroxide having a structure other than the organic peroxide according to the present invention, and Comparative Examples 4 and 5 are examples where the polymerization conditions according to the present invention are not satisfied.

The physical properties of the copolymers obtained in Examples 1 to 7 and Comparative Examples 1 to 5, that is, the conversion, reduced viscosity, and hue were
It is described in Table 1 together with the polymerization conditions.

Example 8. αMS / AN Suspension Polymerization 300 g of deionized water and 4 g of tricalcium phosphate were charged into an autoclave equipped with a stirrer and thoroughly stirred while blowing nitrogen gas. Next, 2 g of 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane and αMS of 280
g and AN120g were charged, and the inside of the autoclave was made a nitrogen gas atmosphere. Immediately heat and heat the contents to 100 ° C, 1
Polymerization was continued at 00 ° C for 15 hours. After the completion of the polymerization, the copolymer was cooled to 40 ° C., dehydrated and dried, and various properties of the obtained copolymer were evaluated. As a result, the conversion was 99.6%, the polymerization average molecular weight (w) was 152000, the heat distortion temperature was 125 ° C, and the impact strength was 2.4 kg · cm / cm.

Comparative Example 6. αMS / AN Suspension Polymerization As a polymerization initiator, 1,2-bis (4,4-di-t-butylperoxycyclohexyl) propane was used in place of 1,1
A copolymer was obtained in the same manner as in Example 8 except that -di-t-butylperoxy 3,3,5 trimethylcyclohexane was used. As a result of evaluation of various physical properties, the conversion was 98.9%, the weight average molecular weight (w) was 123000, the heat distortion temperature was 119 ° C., and the impact strength was 2.0 kg · cm / cm.

In Example 8 and Comparative Example 6, the conversion rate of the copolymer was determined by gas chromatography, the weight average molecular weight was determined by GPC using polystyrene as the standard, and the heat distortion temperature and impact strength were measured by ASTM D -D-648, ASTM-D-2
56, respectively.

As shown in Examples 1 to 8, each of the copolymers obtained by using the organic peroxide according to the present invention as a polymerization initiator,
It was found that the degree of conversion was much higher than that of the copolymer obtained by the conventional polymerization initiator, and it was a high degree of polymerization with no coloring and good transparency. It was also found that the copolymer obtained by suspension polymerization has a high heat distortion temperature and at the same time has a sufficiently high impact strength.

(Effect of the invention) Since the organic peroxide according to the present invention is a so-called tetrafunctional type having four —OO— bonds, that is, four polymerization initiation points in one molecule,
When polymerization is carried out using such a polymerization initiator, a plurality of polymerization initiations occur and a growth reaction also occurs in a plurality of molecules in one molecule. Therefore, the polymer obtained as a result of the termination reaction is a conventional monofunctional compound.
A polymer having a higher degree of polymerization can be obtained as compared with a bifunctional or trifunctional type polymerization initiator. Therefore, the physical properties of the obtained copolymer are improved, and the copolymer is not colored and has good transparency.

That is, according to the present invention, a copolymer having more excellent physical properties can be easily produced as compared with a copolymer produced by a conventional polymerization initiator, and its industrial utility value is extremely large. Especially, it is suitable for applications where heat resistance is not satisfied with polystyrene resin, acrylic resin, and AS resin.

Claims (1)

(57) [Claims] 1. α-Methylstyrene and acrylonitrile,
Alternatively, in copolymerizing a mixture of at least one monomer selected from monomers copolymerizable therewith, an organic peroxide represented by the general formula (I) is used. -A method for producing a methylstyrene-acrylonitrile-based copolymer. (In the formula, R represents an alkyl group having 1 to 5 carbon atoms or a phenyl group, and R ₁ and R ₂ represent an alkyl group having 1 to ₂ carbon atoms).