JP3083608B2 - Production method of aromatic vinyl-vinyl cyanide copolymer. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION

The present invention relates to a method for continuously producing a styrenic copolymer. More specifically, the present invention relates to a method for producing the same resin with less deterioration and coloration in the devolatilization step.

[0002]

2. Description of the Related Art Styrene-based copolymers comprising a polymer of styrene or a monomer mixture comprising a predominant amount of styrene are mainly produced by a method such as suspension polymerization, emulsion polymerization, bulk polymerization (including solution polymerization) and the like. Manufacturing has been put to practical use. Especially in recent years,
From the viewpoints of environmental problems, production costs, and the like, a continuous bulk polymerization method has attracted attention.

[0003]

Generally, when the polymerization rate increases, the concentration of the monomer decreases, and as a result, the polymerization rate decreases, so that the production efficiency deteriorates. This problem is particularly pronounced in the case of bulk polymerization. In addition, especially in the case of bulk polymerization, the viscosity of the reaction solution is significantly increased, so that handling becomes difficult. Therefore, in continuous bulk polymerization, it is common practice to introduce a reaction solution into a devolatilizer without completing the polymerization and to remove volatile components such as unreacted monomers and / or solvents under reduced pressure. At that time, the temperature of the reaction solution in the devolatilizer must be kept much higher than the polymerization temperature in order to handle the high-viscosity resin from which volatile components have been removed and improve the devolatilization efficiency. This is one of the causes of deterioration and coloring.

[Summary of the Invention]

Means for Solving the Problems The present inventors have made intensive studies in view of such a situation, and as a result, regarding the deterioration and coloring of the resin in the devolatilization step, the radicals in the reaction solution to be devolatilized Has been found to have a significant impact. Based on such findings, the inventors have found that the above-mentioned problems can be solved by using an initiator that satisfies certain conditions described later, and have reached the present invention.

<Summary> That is, the method for producing an aromatic vinyl-vinyl cyanide copolymer according to the present invention comprises 60 to 90 parts by weight of an aromatic vinyl monomer, 40 to 10 parts by weight of a vinyl cyanide monomer, And 0 to 20 parts by weight of other monomers copolymerizable with these monomers are continuously bulk-polymerized in the presence or absence of an organic solvent using a polymerization initiator containing no aromatic group. After the reaction, the unreacted monomer and / or
In the method for producing a styrenic copolymer to remove the solvent,
The decomposition rate constant k at the polymerization temperature of the polymerization initiator used satisfies the following expression.

[0006] k: Decomposition rate constant of polymerization initiator at polymerization temperature [sec- ¹ ] RT: Average residence time of polymerization step [sec]

<Effect> By using a polymerization initiator whose decomposition rate constant k is specified in relation to the polymerization temperature and the average residence time in the polymerization step, a problem in the above-mentioned devolatilization step is obtained. Was solved.

That is, according to the method of the present invention, since the polymerization initiator is almost consumed in the polymerization step and the amount of the residual polymerization initiator introduced into the devolatilization step can be reduced, the resin in the devolatilization step using the residual polymerization initiator can be reduced. Polymerization, deterioration, coloring and discoloration can be reduced to a negligible level. That is, when continuously polymerizing a styrene-based monomer and a vinyl cyanide-based monomer, and other monomers copolymerizable with these monomers, a polymerization initiation meeting a specific condition is satisfied. By using the agent, it is possible to obtain a copolymer with very little deterioration and coloring, and an improvement in the quality of the resin is realized.

[Specific description of the invention] <Monomer type> The present invention relates to a bulk of an aromatic vinyl monomer, a vinyl cyanide monomer and, if necessary, a monomer copolymerizable therewith. It relates to polymerization.

As aromatic vinyl monomers, nucleus or (and) side chain-substituted styrene (substituent is a lower alkyl group,
Lower alkoxy groups, halogen atoms, and others are typical). Specific examples include styrene and α-
Examples include methylstyrene, p-methylstyrene, o-chlorostyrene, p-chlorostyrene, 2,4-dimethylstyrene, t-butylstyrene and the like, with styrene being preferred.

The vinyl cyanide monomer in the present invention includes acrylonitrile, methacrylonitrile and the like, and among them, acrylonitrile is preferable.

Other monomers that may be used as required in the present invention include monomers other than the above-mentioned aromatic vinyl monomers and vinyl cyanide monomers, such as acrylic acid and methyl acrylate. And alkyl acrylates such as ethyl acrylate (the alkyl group is preferably a chain having about C _{1 to} C ₆ ), and alkyl methacrylates such as methacrylic acid, methyl methacrylate, ethyl methacrylate, and cyclohexyl methacrylate ( The alkyl group is C
Preferably from ₁ -C ₆ about chain or cyclic), maleic anhydride, alpha, such as itaconic anhydride, beta-unsaturated dicarboxylic acid anhydride, N- phenylmaleimide, N- substituted such as N- methylmaleimide And maleimides.

These monomers may be used as a mixture of two or more kinds in each group.

These monomers are aromatic vinyl monomers 6
0 to 90 parts by weight, preferably 65 to 85 parts by weight, vinyl cyanide monomer 40 to 10 parts by weight, preferably 35 to 1 part by weight.
5 parts by weight and 0 to 20 parts by weight, preferably 0 to 10 parts by weight, of other monomers copolymerizable with these monomers are copolymerized. In addition, these quantitative ratios are 100 parts by weight of the total of the aromatic vinyl monomer, the vinyl cyanide monomer, and other monomers copolymerizable with these monomers.

<Polymerization Initiator> Polymerization initiators which can be used for bulk polymerization of the above monomers are well known. The present invention has a major feature in that these well-known polymerization initiators whose decomposition constants satisfy specific conditions are selected and used. Since the decomposition rate constant of the polymerization initiator at the polymerization temperature matters, the polymerization initiator used in the present invention falls in the category of the radical polymerization initiator.

The polymerization initiator used in the present invention has a decomposition rate constant k at a given polymerization temperature that satisfies the following equation. k: Decomposition rate constant of polymerization initiator at polymerization temperature [sec- ¹ ] RT: Average residence time of polymerization step [sec]

When an initiator that does not satisfy this condition is used, the polymerization initiator remaining without being consumed in the polymerization step is decomposed in a very short time during the high-temperature treatment in the next devolatilization step. To generate a lot of radicals,
Side reactions such as the formation and crosslinking reaction of low molecular weight polymer and polymer of heterogeneous composition and the oxidation of polymer occur, causing deterioration, coloration, discoloration, etc. of the finally formed copolymer, lowering product value Let it.

When a multi-reactor reactor is used, the polymerization temperature may not be at the same level over the entire range of the average residence time. When the polymerization temperature is changed for each polymerization vessel as described above, the polymerization temperature based on the decomposition rate constant of the polymerization initiator is based on the highest polymerization temperature in the polymerization vessel.

The decomposition rate constant k mentioned here is obtained as follows. A solution having a polymerization initiator concentration of about 0.1 mol / l is prepared using a solvent relatively inert to radicals, for example, benzene or toluene, and sealed in a nitrogen-substituted glass tube. When immersed in a thermostat set at a predetermined temperature and thermally decomposed, this reaction can be approximately treated as a primary reaction. At this time, assuming that the amount of the decomposition polymerization initiator is x [mol / l], the decomposition rate constant is k [sec ^-1 ], the time is t [sec], and the initial concentration of the polymerization initiator is a [mol / l], The formula holds.

In a / (a−x) = kt Therefore, thermal decomposition is performed at a certain temperature, and the time t versus the ln
The relationship of a / (ax) is plotted, and the decomposition rate constant k at that temperature can be obtained from the slope of the obtained straight line.

The average residence time in the polymerization step as referred to herein is a value obtained by dividing the volume [m ³ ] of the reactor by the supply volume rate [m ³ / sec] of the reaction solution. The average residence time of this polymerization step, expressed in minutes, is preferably 30 to 120 minutes, more preferably 40 to 90 minutes. If the time is shorter than 30 minutes, the polymerization rate becomes too high to obtain an economical polymerization rate, and it is difficult to control the polymerization. If the time is longer than 120 minutes, the film is susceptible to thermal degradation during the polymerization. Here, the capacity of the reactor means the total capacity when the reactor is composed of multiple cans.

The polymerization initiator used in the present invention has a decomposition rate constant k at the polymerization temperature.

(Equation 2) k: decomposition rate constant of polymerization initiator at polymerization temperature [sec
^-1 ] RT: It is selected from those satisfying the formula of average residence time [sec] of the polymerization step. Specifically, for example, peroxyesters such as t-butylperoxy (2-ethylhexanoate), t-hexylperoxy (2-ethylhexanoate), and t-butylperoxypivalate; Examples include azo compounds such as bisisobutyronitrile. These may be used as a mixture of two or more in each group and / or between each group. In addition, even if the decomposition rate constant k satisfies this condition, the aromatic polymerization initiator such as benzoyl peroxide is eventually formed by the decomposition to form a chromophore containing an aromatic ring. It may cause deterioration, coloration, discoloration and the like of the copolymer, which may lower the product value. Therefore, as the polymerization initiator used in the present invention, a polymerization initiator containing no aromatic group in the polymerization initiator compound is used.

<Continuous Bulk Polymerization> The process for producing an aromatic vinyl-vinyl cyanide copolymer according to the present invention involves a devolatilization step except that the polymerization initiator used is specific. It is essentially the same as continuous bulk polymerization of species monomers.

Therefore, the present invention can be carried out according to a well-known bulk polymerization technique except for the selection criteria of the polymerization initiator.

Specifically, for example, the amount of the polymerization initiator to be used is preferably 0.05 to 0.5 part by weight, preferably 0.1 to 0.5 part by weight, based on 100 parts by weight of a reaction solution comprising a monomer and optionally an organic solvent. 1 to 0.3 parts by weight is more preferred. 0.0
If the amount is less than 5 parts by weight, the polymerization rate becomes low, which is not economical. If the amount is more than 0.5 part by weight, the polymerization rate becomes too high, and control becomes difficult. Further, the method of supplying the polymerization initiator to the reactor may be supplied at once at the beginning of the polymerization step, or may be divided and supplied in the middle.
The polymerization temperature is preferably from 90 to 135 ° C, and from 100 to 125 ° C.
C is more preferred. If the temperature is lower than 90 ° C., a large amount of a polymerization initiator is required to increase the polymerization rate, which is not economical. When the temperature is higher than 135 ° C., a side reaction occurs during polymerization, and the polymer is easily affected by thermal deterioration. Note that the devolatilization temperature and the degree of pressure reduction in the devolatilization step may be sufficient as long as necessary devolatilization is performed under given devolatilization conditions.

Although the process of the present invention basically belongs to the category of bulk polymerization, the polymerization may be carried out in the presence of an organic solvent.
Therefore, the "bulk polymerization" referred to in the present invention includes a case where the polymerization is carried out in the presence of such an organic solvent.

As described above, in practicing the present invention,
A suitable organic solvent can be used. Examples of the organic solvent include aromatic vinyl monomers and vinyl cyanide monomers, other monomers copolymerizable with these monomers, and / or solvents capable of dissolving the resulting copolymer. Is preferable, but a poor solvent for the produced copolymer may be used in some cases, and there is no particular limitation.
Representative examples include aromatic hydrocarbon solvents such as toluene, ethylbenzene, and xylene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; and alcohol solvents such as methanol and ethanol. The amount of the organic solvent used is preferably 0 to 30% by weight based on the total amount of the monomers. If it exceeds 30% by weight, chain transfer to the solvent and a decrease in the polymerization rate will be caused, and the devolatilization step will be overloaded,
Not efficient.

Further, in practicing the present invention, a suitable molecular weight modifier can be used. Typically, tertiary decyl mercaptan, normal dodecyl mercaptan, α-methylstyrene dimer, terpinolene, octyl thioglycolate and the like can be mentioned. Further, a stabilizer such as an antioxidant can be added in the polymerization step and / or the devolatilization step.

The molecular weight of the polymer obtained by radical polymerization generally varies depending on the polymerization conditions such as the polymerization temperature and the amount of the polymerization initiator used. As the aromatic vinyl-vinyl cyanide copolymer, those having a weight average molecular weight in terms of styrene of preferably 3 × 10 ^{4 to} 7 × 10 ⁵ are preferable, and especially 5 ×.
Since those having a range of 10 ^{4 to} 5 × 10 ⁵ are preferable, it is desirable to set the polymerization conditions so as to obtain a polymer having such a molecular weight.

<Production Copolymer> The copolymer obtained according to the present invention may be used alone or as a mixture with other polymers and / or other copolymers.
It is provided for the formation of office equipment, parts of electric appliances, housing materials and packaging materials, and structures such as automobile interior and exterior parts.

Since there is little deterioration and coloring of the resin, it can be applied to applications utilizing its special characteristics.

[0032]

The following examples serve to illustrate the invention in more detail. The present invention is not limited by these.

Example 1 61.5% by weight of styrene, 23.5% by weight of acrylonitrile, 15.1% by weight of methyl ethyl ketone were placed in a completely mixed stirred reactor having a content of 2 liters.
0% by weight of a total of 100 parts by weight, t-butyl peroxy (2-ethylhexanoate) as a polymerization initiator
A mixed liquid containing 0.225 parts by weight of terpinolene as a molecular weight modifier and 0.3 part by weight of terpinolene was continuously supplied so that the average residence time was 48 minutes in minutes. For the k value of this polymerization initiator, see Table 1 (hereinafter the same).

The polymerization temperature is set to 120 ° C., and the polymerization conversion rate is 75
The polymerization reaction liquid was continuously taken out, immediately sent to a devolatilizer at 230 ° C. and 50 Torr to separate unreacted monomers and an organic solvent (methyl ethyl ketone), and then pelletized.

As a result of analysis, the obtained pellet was a binary copolymer having a styrene / acrylonitrile composition of 74/26 by weight.

The obtained copolymer was injected into a 4.7 oz. Rotary ram in-line screw type injection molding machine (Nissei FS8
0) 62 × 74 × 2.5 at a barrel temperature of 220 ° C.
It was molded into a mm plate.

The color tone (YI) of these plate samples
Value) was measured by a white plate holding reflection method using an SM color computer manufactured by Suga Test Instruments according to JIS K7105.
The results are shown in Table 1 and FIG. 1 together with general physical properties. The smaller the YI value, the smaller the degree of yellowish coloring.

Example 2 In the example described in Example 1, the polymerization initiator to be added was t-hexylperoxy (2
(Ethylhexanoate) A binary copolymer having a styrene / acrylonitrile composition of 74/26 by weight% was obtained in the same manner as in the same example except that the amount was changed to 0.255 parts by weight.

The color tone of the obtained copolymer was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. 1 together with general physical properties.

Example 3 The procedure of Example 1 was repeated, except that the polymerization initiator to be added was changed to 0.17 parts by weight of azobisisobutyronitrile to produce styrene / acrylonitrile. Composition is 7% by weight
A 4/26 binary copolymer was obtained.

The color tone of the obtained copolymer was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. 1 together with general physical properties.

Comparative Example 1 Styrene / acrylonitrile was prepared in the same manner as in Example 1 except that the polymerization initiator to be added was changed to 0.39 parts by weight of t-butylperoxyisopropyl carbonate. Was obtained in a weight ratio of 74/26.

The color tone of the obtained copolymer was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. 1 together with general physical properties.

Comparative Example 2 In the example described in Example 1, the polymerization initiator to be added was 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane.
Except for changing to 133 parts by weight, the composition of styrene / acrylonitrile was 74% by weight in the same manner as in the same example.
/ 26 was obtained.

The color tone of the obtained copolymer was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. 1 together with general physical properties.

Comparative Example 3 The composition of styrene / acrylonitrile was changed in the same manner as in Example 1 except that the polymerization initiator to be added was changed to 0.24 parts by weight of benzoyl peroxide. 7% by weight
A 4/26 binary copolymer was obtained.

The color tone of the obtained copolymer was evaluated in the same manner as in Example 1. Table 1 shows the results together with general physical properties.

In the case of the styrene / acrylonitrile copolymers listed in Examples 1-3 and Comparative Examples 1-3, Table 1
As shown in FIG. 1, it is apparent that the copolymer obtained by the production method under the conditions of the present invention has a better color tone than the copolymer obtained by the production method outside the conditions of the present invention. It is. Note that the k value according to the present invention exists in the region on the right side of the chain line in the figure.

Table 1 _{Decomposition rate} experiment _{of polymerization initiator} Constant [sec- ¹ ] YI value Haze Tensile strength ^* MFR ^** Example 1 3.27 × 10 ⁻³ 12 0.9 700 25 Example 2 5.90 × 10 ⁻³ 12 1.0 700 26 Example 3 1.26 × 10 ⁻² 11 0.9 710 27 Comparative example 1 6.30 × 10 ^-4 17 1.3 700 24 Comparative Example 2 1.12 × 10 ^-4 18 1.4 700 28 Comparative Example 3 4.20 × 10 ^-3 40 1.7 700 23

* The polymerization initiator used in the present invention under the conditions of the examples and comparative examples: * kg / cm ² , in accordance with JIS K-7113 ** g / 10 minutes (220 ° C, 10 kg) JIS K-7
Complies with 210

[0051]

The process for producing a styrenic copolymer according to the present invention, that is, when a styrene-based monomer and a monomer copolymerizable with the styrene-based monomer are continuously bulk-polymerized,
By a method for producing a styrene-based copolymer using a polymerization initiator satisfying certain conditions, it is possible to obtain a copolymer having very little deterioration and coloration, and an improvement in the quality of the resin is realized. This is as described above in the section of “Summary of the Invention”.

[Brief description of the drawings]

FIG. 1 is a graph showing the color tone (YI value) of a styrene / acrylonitrile copolymer as a function of the k value of a polymerization initiator used.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/00-2/02

Claims (1)

(57) [Claims] 1 to 60 parts by weight of an aromatic vinyl monomer, 40 to 10 parts by weight of a vinyl cyanide monomer, and 0 to 20 parts by weight of another monomer copolymerizable with these monomers. The aromatic
After performing bulk polymerization continuously in the presence or absence of an organic solvent using a polymerization initiator containing no group, unreacted monomers and / or solvent are removed in a devolatilization step under high temperature and reduced pressure. Wherein the decomposition rate constant k at the polymerization temperature of the polymerization initiator used satisfies the following expression: an aromatic vinyl-vinyl cyanide copolymer Manufacturing method. (Equation 1) k: decomposition rate constant of polymerization initiator at polymerization temperature [sec
^-1 ] RT: average residence time in the polymerization step [sec]