JPH0987307A - Method for controlling rate of styrene monomer polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for easily regulating the rate of polymerization in a short time in styrene resin production while keeping specific the average mol.wt. of the resin being yielded. SOLUTION: A monomer feedstock consisting of styrene alone or styrene and one or more monomers copolymerizable therewith is polymerized in a reactor of complete mixing type under conditions satisfying x>=(0.3t+6×(a-1)+12), wherein t is a polymerization temp. ( deg.C), (x) is a polymer concentration in the reaction mixture, and (a) is the ratio of a regulated polymerization rate to the rate of polymerization conducted at t deg.C and (x) in the absence of any radical polymerization initiator, provided that (t) is kept substantially constant, and that the rate of monomer feeding is (a) times as high as that in the polymerization conducted in the absence of any radical polymerization initiator. The amount of the radical polymerization initiator to be added is regulated to be in the range of from (0.1/n)×10<-3> to (2.0/n)×10<-3> mol per liter of the monomer fed (wherein (n) is the number of functional groups per molecule of the initiator which generate free radicals) so as to keep (x) substantially constant.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a styrene resin by a continuous polymerization method in the presence of a radical polymerization initiator. More specifically, the present invention relates to a method for controlling the polymerization rate of a styrene resin, which can easily and freely adjust the polymerization rate, that is, the production amount per unit time by using an arbitrary radical polymerization initiator.

[0002]

BACKGROUND OF THE INVENTION Styrenic resins are widely used as various molding materials because of their excellent balance between price, mechanical strength and moldability. Mechanical strength and moldability are determined by the average molecular weight of the styrene resin. The higher the average molecular weight, the better the mechanical strength, and the lower the average molecular weight, the better the moldability. Therefore, various average molecular weights are used depending on the application, and a method for efficiently producing a styrene resin having a desired average molecular weight at low cost is demanded. In order to produce efficiently at low cost, it is necessary to finely adjust the polymerization rate according to the demand situation. In addition, in the case of equipment trouble, etc., it is required that the polymerization rate be promptly lowered without changing the average molecular weight of the product and promptly increased after the recovery. Therefore, there is a demand for a method of easily adjusting the polymerization rate in a short time.

By the way, a thermal polymerization method or an initiator polymerization method has been conventionally known as an industrial production method of a styrene resin. In the thermal polymerization method, in order to adjust the polymerization rate without changing the average molecular weight of the produced resin, it is necessary to change the volume of the polymerization solution while keeping the polymerization temperature constant, but it is not possible to increase the volume of the polymerization solution. There is a limit due to the size of the polymerization tank, and the production rate cannot be changed freely. Further, it takes a long time to adjust the volume of the polymerization solution.
Regarding the initiator polymerization method, in addition to the method of changing the volume of the polymerization solution in the same manner, a method of changing the amount of the polymerization initiator added to the polymerization reactor has been proposed. However, this method has a disadvantage that the polymerization temperature must be changed at the same time in order to keep the average molecular weight of the produced resin constant, and as a result, the polymerization rate cannot be freely adjusted.

A method for increasing the polymerization rate by using a specific polyfunctional organic peroxide as a polymerization initiator is disclosed in JP-B-41-19511, JP-B-52-42834, and JP-B-52-34. It is disclosed in Japanese Patent Publication No. 52-797, Japanese Patent Publication No. 55-7455 and Japanese Patent Publication No. 2-21401. However, even if these methods are used, the range in which the polymerization rate can be adjusted is widened, but it is still necessary to change the polymerization temperature. The two parameters, the polymerization rate and the average molecular weight of the styrene resin, are simultaneously adjusted by operating the three parameters at the same time, and it is not easy to adjust the polymerization conditions. further,
Since the polymerization initiator used is a specific polyfunctional initiator, there is a problem that other inexpensive polymerization initiators cannot be used and the production cost is increased.

[0005]

In view of such circumstances, the inventors of the present invention have earnestly studied the method for adjusting the polymerization rate, and as a result,
While keeping the average molecular weight of the resulting styrene resin constant, we found a method to easily adjust the polymerization rate in a short time,
The present invention has been completed.

That is, in the present invention, the polymerization temperature t (° C.),
When the ratio of the adjusted polymerization rate to the polymerization rate when the polymerization is performed without using the radical polymerization initiator at the polymer concentration x in the polymerization solution is a, the polymerization temperature is kept substantially constant at t, The supply rate of the styrene monomer or the styrene monomer and the monomer copolymerizable therewith is set to be a times the polymerization rate when the polymerization is performed without using the radical polymerization initiator, and x ≧
In order to satisfy 0.3t + 6 × (a-1) +12 and keep x substantially constant, the addition amount of the radical polymerization initiator is set to (0.1 / liter) with respect to the monomer 1 (liter) supplied.
n) × 10 ⁻³ to (2.0 / n) × 10 ⁻³ mol (where n is the number of functional groups that generate radicals in one molecule of the radical polymerization initiator). In a continuous radical polymerization reaction of a styrene monomer or a styrene monomer and a monomer copolymerizable therewith using a completely mixed reactor, the polymerization rate can be obtained without substantially changing the average molecular weight of the obtained polymer. And a method for producing a styrene resin using this method.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The continuous radical polymerization reaction of the styrene monomer or the styrene monomer and the monomer copolymerizable therewith in the present invention is carried out in a completely mixed reactor. When this reaction is carried out in two or more reactors connected in series, if the first-stage reactor is a complete mixing type, the second and subsequent stages are other than the perfect mixing type, for example, a plug flow type. It may be of any type such as a loop type or the like which is used in a usual polymerization reaction. As the first stage, a plurality of completely mixed reactors may be arranged in parallel. In the case where the first stage is a reactor other than the complete mixing type, for example, a plug flow type tubular reactor, a loop type reactor using a static mixer, etc.,
It is impossible to adjust the reaction rate while keeping the average molecular weight of the styrene resin produced constant without changing the polymerization temperature. The complete mixing type reactor is equipped with a stirring means in the reactor, and by using this reactor, the complete mixed state of the polymerization reaction in the present invention is achieved. Here, the completely mixed state means a state in which the concentration and temperature of the polymer in the reactor are substantially kept uniform. Further, in the present invention, when a continuous radical polymerization reaction is carried out in a completely mixed reactor, the solution in the reactor is simply referred to as “polymerization liquid”, and the concentration of the polymer in the polymerization liquid is simply referred to as “polymer concentration”. There are times. The fully mixed reactor is a stirred tank reactor (stir).
It is also called a red tank reactor, and its stirring method, heat removal method, etc. are not particularly limited as long as the above-mentioned completely mixed state can be realized. For example, pages 10 to 11, pages 19 to 21 and pages 206 to 21 of "Industrial reaction device" (edited by Kenji Hashimoto, published by Baifukan Co., Ltd. in 1984).
Specific examples include those described on page 1. Examples of the raw material monomer used in the present invention include a styrene monomer or a mixture of a styrene monomer and a monomer copolymerizable with the styrene monomer (hereinafter, these may be collectively referred to simply as “the monomer”). it can. Examples of the monomer copolymerizable with the styrene monomer include substituted styrenes such as α-methylstyrene and p-methylstyrene, vinyl monomers such as acrylonitrile, methacrylonitrile, methacrylic acid, methyl methacrylate and vinyl acrylate, and maleic anhydride. Examples thereof include acids and maleimides. Further, a solvent, a rubber-like elastic body, a mineral oil, an antioxidant, which is soluble in the monomer or which can be finely dispersed in the slurry in the monomer before being fed to the reaction in advance or directly in the polymerization reactor. ,
Colorants, internal lubricants, etc. may be added. Thermal polymerization in the present invention, without adding a radical polymerization initiator,
Polymerization carried out by heating. When a preset adjusted polymerization rate ratio with respect to the polymerization rate of thermal polymerization using a completely mixed reactor of the monomer at a polymerization temperature t (° C.) and a polymer concentration x is represented as a, The adjustment can be performed by following the procedure below without substantially changing the average molecular weight of the obtained polymer. That is, the polymerization temperature t (° C.) is kept substantially constant at this temperature. The supply rate of the monomer is a times that at the time of the thermal polymerization, and the polymer concentration x is represented by the following inequality (1).
The rate of introducing the radical polymerization initiator (hereinafter, may be simply referred to as a polymerization initiator or an initiator) is adjusted so as to keep the above condition substantially constant. x ≧ 0.3t + 6 × (a−1) +12 (1) In the formula, a is a number larger than 1 and is appropriately selected. X
Is usually in the range of 50 to 90% by weight, preferably 60 to 8
It is in the range of 0% by weight.

The polymerization initiator is charged at a rate of the monomer 1
Displaying in terms of the concentration of radical polymerization initiator having n functional groups (n is the number of functional groups generating radicals in one molecule of radical polymerization initiator) with respect to (liter),
Preferably (0.1 / n) × 10 ⁻³ to (2.0 / n) ×
10 ⁻³ mol, more preferably (0.1 / n) × 10 ⁻³
(1.5 / n) × 10 ⁻³ mol. It is preferable that the change in the polymer concentration with the change in the polymerization rate is small, and it is more preferable that the change is almost constant. The polymerization temperature is preferably in the range of 110 to 160 ° C., more preferably 120 to 15 ° C.
It is in the range of 5 ° C, and usually before and after adjusting the polymerization rate,
It is preferable to keep it almost constant.

The feeding rate of the monomer is as described above.
Since it is automatically determined by the supply rate in the thermal polymerization and the previously set desired polymerization rate to be adjusted, the parameter to be adjusted in the present invention is only the introduction rate of the radical polymerization initiator, which facilitates the control. The volume of the polymerization liquid in the completely mixed reactor is usually set to be substantially constant from the viewpoint of controlling the polymerization rate. The volume of the polymerization liquid can be set arbitrarily.

When the polymer concentration does not satisfy the inequality (1), it is difficult to adjust the polymerization rate without changing the average molecular weight of the obtained styrene resin, and this can be achieved without changing the temperature. Will not be possible.

[0011]

The radical polymerization initiator used in the present invention includes any organic peroxide and azo compound.
As the organic peroxide, for example, a monofunctional radical polymerization initiator (n-n, such as t-butylperoxybenzoate, benzoyl peroxide, di-t-butylperoxide) is used.
= 1), 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane (n = 2), 2,2-bis (4,4di-t-butylperoxycyclohexyl) propane ( n
= 4) and other polyfunctional radical polymerization initiators (n ≧ 2). Examples of azo compounds include monofunctional radical polymerization initiators (n = 1) such as 1,1-azobis (cyclohexane-1-carbonitrile) and azobisisobutyronitrile. Among them, monofunctional radical polymerization initiators such as di-t-butyl peroxide are preferable in terms of easy availability and low cost.

The polymerization initiator may be dissolved in the raw material monomer in advance using a stirring tank or the like and then used in the reaction, or it may be diluted with an appropriate solvent such as ethylbenzene, or the raw material monomer may be supplied as it is. It may be injected into the line or directly into the reactor.

[0014]

As described in detail above, according to the present invention,
Only by adjusting the addition amount of the radical polymerization initiator under specific conditions in the complete mixing type reactor, the polymerization rate, that is, the production amount per unit time can be maintained while keeping the average molecular weight of the styrene resin produced constant. It can be adjusted freely and easily.

[0015]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. The weight average molecular weight is an average molecular weight obtained by gel permeation chromatography (GPC) method. Example 1 A continuous polymerization apparatus comprising one completely mixed stirring polymerization tank having an internal volume of 30 L and a flash type degassing tank was used to continuously prepare a monomer solution containing 95% by weight of styrene monomer and 5% by weight of ethylbenzene. It is supplied to the stirring polymerization tank and the polymerization temperature is
C., the volume of the polymerization solution was kept at 24 L, and the monomer supply amount was adjusted so that the polymer concentration of the polymerization solution was 63% by weight, and continuous thermal polymerization was carried out. Furthermore, without changing the polymerization temperature, the volume of the polymerization solution, and the polymer concentration, the 1,1-di-t-t is adjusted so that the polymerization rate is 1.2 to 1.8 times the thermal polymerization reaction rate.
-Butylperoxy-3,3,5-trimethylcyclohexane was injected into the monomer supply line to the concentration shown in Table 1, and the supply rate of the monomer solution was changed in proportion to the polymerization rate. In addition, 1, used as a radical polymerization initiator
The number of functional groups (n) in one molecule of 1-di-t-butylperoxy-3,3,5-trimethylcyclohexane is 2. The results are shown in Table 1.

[0016]

[Table 1] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 145 145 145 145 145 145 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 63 63 63 63 63 0.3t + 6 ・ (a-1 ) +12 (wt%) 55.5 56.7 57.9 59.1 60.3 Feed rate of the monomer solution (L / hr) 4.5 5.4 6.3 7.2 8.1 Concentration of radical initiator (***) 0 0.21 0.39 0.57 0.72 Weight average molecular weight of polymer (10,000) 26 26 26 26 26 ─────────────────────────────────── ***: 10 ^-3 mol / the monomer Solution 1L

Example 2 1,1-di-t-butylperoxy as radical polymerization initiator
The same procedure as in Example 1 was carried out except that t-butylperoxybenzoate was used instead of -3,3,5-trimethylcyclohexane. The number of functional groups (n) in one molecule of t-butyl peroxybenzoate is 1. Table 2 shows the results.

[0018]

[Table 2] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 145 145 145 145 145 145 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 63 63 63 63 63 0.3t + 6 ・ (a-1 ) +12 (wt%) 55.5 56.7 57.9 59.1 60.3 Feed rate of the monomer solution (L / hr) 4.5 5.4 6.3 7.2 8.1 Concentration of radical initiator (***) 0 0.37 0.70 1.02 1.25 Weight average molecular weight of polymer (10,000) 26 26 26 26 26 ─────────────────────────────────── ***: 10 ^-3 mol / the monomer Solution 1L

Example 3 1,1-di-t-butylperoxy as a radical polymerization initiator
The same procedure as in Example 1 was carried out except that 1,1-azobis (cyclohexane-1-carbonitrile) was used instead of -3,3,5-trimethylcyclohexane. Number of functional groups in one molecule of 1,1-azobis (cyclohexane-1-carbonitrile) (n)
Is 1. The results are shown in Table 3.

[0020]

[Table 3] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 145 145 145 145 145 145 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 63 63 63 63 63 0.3t + 6 ・ (a-1 ) +12 (wt%) 55.5 56.7 57.9 59.1 60.3 Feed rate of the monomer solution (L / hr) 4.5 5.4 6.3 7.2 8.1 Concentration of radical initiator (***) 0 0.40 0.72 1.08 1.37 Weight average molecular weight of polymer (10,000) 26 26 26 26 26 ─────────────────────────────────── ***: 10 ^-3 mol / the monomer Solution 1L

Comparative Example 1 The procedure of Example 1 was repeated, except that the polymer concentration of the polymerization solution was kept at 30% by weight. The results are shown in Table 4.

[0022]

[Table 4] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 145 145 145 145 145 145 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 30 30 30 30 30 0.3t + 6 ・ (a-1 ) +12 (wt%) 55.5 56.7 57.9 59.1 60.3 Monomer solution supply rate (L / hr) 20 24 28 32 36 Radical initiator concentration (***) 0 0.21 0.39 0.57 0.72 Weight average molecular weight of polymer (10,000) 27 26 25 24 23 ─────────────────────────────────── ***: 10 ^-3 mol / monomer solution 1L

Comparative Example 2 In order to obtain a styrene resin having the same weight average molecular weight,
The procedure of Comparative Example 1 was repeated except that the polymerization temperature was adjusted.
Table 5 shows the results.

[0024]

[Table 5] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (° C) 145 143 141 139 137 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 30 30 30 30 30 0.3t + 6 ・ (a-1 ) +12 (wt%) 55.5 56.1 56.7 57.3 57.9 Supply rate of the monomer solution (L / hr) 20 24 28 32 36 Concentration of radical initiator (***) 0 0.33 0.63 0.92 1.25 Weight average molecular weight of polymer (10,000) 27 27 27 27 27 ─────────────────────────────────── ***: 10 ^-3 mol / the monomer Solution 1L

Example 4 The procedure of Example 1 was repeated, except that the polymerization temperature was maintained at 120 ° C. and the polymer concentration was maintained at 60% by weight. Table 6 shows the results.

[0026]

[Table 6] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 120 120 120 120 120 Polymerization liquid volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 60 60 60 60 60 0.3t + 6 ・ (a-1 ) +12 (wt%) 48 49.2 50.4 51.6 52.8 Supply rate of the monomer solution (L / hr) 1.9 2.2 2.6 3.0 3.3 Concentration of radical initiator (***) 0 0.12 0.21 0.27 0.33 Weight average molecular weight of polymer (10,000) 40 40 40 40 40 ─────────────────────────────────── ***: 10 ^-3 mol / the monomer Solution 1L

Comparative Example 3 The procedure of Example 4 was repeated, except that the polymer concentration of the polymerization solution was kept at 30% by weight. Table 7 shows the results.

[0028]

[Table 7] ─────────────────────────────────── Polymerization rate ratio (a) (−) 1.0 1.2 1.4 1.6 1.8 Polymerization temperature (t) (℃) 120 120 120 120 120 Polymer volume (L) 24 24 24 24 24 Polymer concentration (x) (wt%) 30 30 30 30 30 0.3t + 6 ・ (a-1 ) +12 (wt%) 48 49.2 50.4 51.6 52.8 Supply rate of the monomer solution (L / hr) 4.6 5.5 6.4 7.4 8.3 Concentration of radical initiator (***) 0 0.12 0.24 0.33 0.42 Weight average molecular weight of polymer (10,000) 41 40 39 38 37 ──────────────────────────────────── ***: 10 ^-3 mol / Monomer solution 1L

Claims (7)

[Claims] 1. When the ratio of the adjusted polymerization rate to the polymerization rate at the polymerization temperature t (° C.) and the polymer concentration x in the polymerization liquid without using a radical polymerization initiator is a, the polymerization is performed. The temperature was kept substantially constant at t, and the supply rate of the styrene monomer or the styrene monomer and the monomer copolymerizable therewith was set to a times the polymerization rate without using a radical polymerization initiator, and x ≧ 0. 3t + 6 × (a-
1) +12 and (0.1 / n) × 10 ⁻³ to (2) with respect to 1 (liter) of the monomer to which the radical polymerization initiator is added so as to keep x substantially constant. ．
0 / n) × 10 ⁻³ mol (where n is the number of functional groups that generate radicals in one molecule of the radical polymerization initiator), and a completely mixed reactor is used. A method of controlling the polymerization rate in a continuous radical polymerization reaction of a styrene monomer or a styrene monomer and a monomer copolymerizable therewith without substantially changing the average molecular weight of the obtained polymer. 2. The method according to claim 1, wherein t is any temperature in the range of 110 to 160 ° C. 3. The method of claim 1 wherein t is any temperature in the range of 120-155 ° C. 4. A radical polymerization initiator is added in an amount of (0.1 / n) × 10 ⁻³ to 1 (liter) of the monomer.
The method according to claim 1, which is adjusted in the range of (1.5 / n) × 10 ⁻³ mol. 5. The method according to claim 1, wherein the radical polymerization initiator is a monofunctional radical polymerization initiator. 6. The monofunctional radical polymerization initiator is di-t-butylperoxide, 1,1-di-t-butylperoxy-3,
3,5-Trimethylcyclohexane, t-butylperoxybenzoate or 1,1-azobis (cyclohexane
-1- Carbonitrile). 7. A continuous radical polymerization reaction of a styrene monomer or a styrene monomer and a monomer copolymerizable therewith using a completely mixed reactor, according to claim 1, 2, 3, 4, 5 or 6. A method for producing a styrene-based resin, which comprises controlling the polymerization rate by the method described.