JP2000248018A - Method for producing brominated polystyrene - Google Patents

Abstract

(57) [Problem] To provide a method for producing brominated polystyrene having good hue and high bromine content with high productivity without gelation. SOLUTION: The number average molecular weight is 10,000 to 30,0.
A solution in which polystyrene having a molecular weight distribution of 1.0 to 3.0 is dissolved in a halogen-based organic solvent at a concentration of 11 to 30% by weight, and 2.0 to 4 mol per mol of a styrene skeleton unit of the polystyrene. A method for producing a brominated polystyrene, comprising mixing 0.5 mol of bromine or chlorine bromide in the presence of a Lewis acid catalyst to carry out a bromination reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing brominated polystyrene. More specifically, the present invention relates to a method for producing a brominated polystyrene having excellent productivity, a high bromine content and a good hue.

[0002]

2. Description of the Related Art Basically, two kinds of production methods have been disclosed for brominated polystyrene. One is a method of brominating styrene monomer and polymerizing it, and the other is
This is a method of brominating polystyrene. For example, as an example of the former, German Patent 1,544,694 discloses a method of brominating a styrene monomer and subsequently polymerizing the obtained monomer. However, this method requires a step of producing a brominated styrene monomer as a raw material, which increases the price, and requires strict control of the polymerization reaction itself in the process. Is difficult to increase, and the flame retardancy as a flame retardant has not been achieved.

On the other hand, several examples of the latter are disclosed. For example, Japanese Patent Application Laid-Open No. Sho 53-60986 discloses a method in which a styrene monomer is polymerized and then brominated.
However, in this method, specifically, the average molecular weight of the styrene polymerization product is in the range of 800 to 8000, and the resulting brominated polystyrene contains residual monomers or oligomers, and has insufficient color and heat stability. When kneading and molding such a brominated polystyrene into a resin, problems such as mold contamination may occur.

After dissolving polystyrene in a solvent,
A method for brominating in the presence of a catalyst is disclosed in
Japanese Patent No. 29202 discloses bromination of polystyrene having a low degree of polymerization, and specifically discloses the use of a polystyrene having a degree of polymerization of 6 to 200. The assay is described and it is believed that the substantial number average molecular weight is between 400 and 8000. That is, it can be understood as a polystyrene having a molecular weight containing a styrene oligomer as in the above publication.

Further, Japanese Patent Application Laid-Open No. 54-100492 discloses that in a method of dissolving polystyrene in a solvent and then brominating in the presence of a catalyst, the average molecular weight of the polystyrene preferably used is in the range of 50,000 to 500,000. Specifically, it is disclosed that bromination of, for example, polystyrene having a molecular weight of 150,000 with a dichloromethane solution having a concentration of 25% by weight is performed. However, in this case, the amount of added bromine is small, and the brominated polystyrene obtained has a low bromine content of 61.5%.

Also, in US Pat. No. 5,723,549, in a method in which polystyrene is dissolved in a solvent and then brominated in the presence of a catalyst, the molecular weight of polystyrene is described as being in the range of 5 to 1.5 million. , Without any substantial limitation. Specifically, polystyrene having a weight average molecular weight of 300,000 was brominated with a 1,2-dichloroethane solution having a concentration of 10% by weight, and
It has been shown that a brominated polystyrene having a high bromine content of at least% is obtained.

On the other hand, when bromination is performed with a high-concentration solution when obtaining brominated polystyrene having a high bromine content using conventional ordinary polystyrene, the reaction system becomes a gel, and the reaction system becomes substantially more concentrated. Bromination reaction becomes difficult,
It is necessary to perform the bromination reaction with a low-concentration solution, and there is a problem that productivity is reduced. In addition, even when the solution is in a dissolved state, if the solution viscosity is extremely increased, the diffusion of bromine becomes insufficient, and therefore, in addition to bromine substitution on the aromatic ring, substitution on the main chain or formation of an unsaturated bond may occur. When such a brominated polystyrene is mixed with a resin and heat-molded, coloring and generation of an inorganic bromine-based gas occur.

Therefore, there is a need for a method for producing brominated polystyrene having good hue and high bromine content with high productivity.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing brominated polystyrene having a good hue and a high bromine content with high productivity without gelation. The present inventor has conducted intensive studies as an attempt to achieve the above object, and as a result, when performing a bromination reaction using polystyrene having a specific number average molecular weight and a molecular weight distribution,
The present inventors have found that even when the solution concentration of the raw material polystyrene is high, gelation does not occur, and a brominated polystyrene having a high hue and a good hue can be obtained with good productivity, and the present invention has been achieved.

[0010]

That is, according to the present invention, polystyrene having a number average molecular weight of 10,000 to 30,000 and a molecular weight distribution of 1.0 to 3.0 is added to a halogen-based organic solvent in an amount of 11 to 11. A solution dissolved at a concentration of 30% by weight is mixed with 2.0 to 4.5 moles of bromine or chlorine bromide per mole of the styrene skeleton unit of the polystyrene in the presence of a Lewis acid catalyst to perform a bromination reaction. And a method for producing a brominated polystyrene.

The polystyrene used as a raw material in the production method of the present invention has a number average molecular weight of 10,000 to 30,
Styrene, preferably having a molecular weight distribution of 1.0 to 3.0, preferably 1.0 to 2.8. Such polystyrene can be synthesized by various methods such as radical polymerization, anionic polymerization, and cationic polymerization. Here, the number average molecular weight and the molecular weight distribution (weight average molecular weight / number average molecular weight) are obtained by measurement by size exclusion chromatography.

The raw material polystyrene has a number average molecular weight of 10,
If it is less than 000, the color of the obtained brominated polystyrene deteriorates, possibly due to the unstable structure of the brominated polystyrene, and the amount of gas generated during heating is undesirably large. If the number average molecular weight exceeds 30,000, the solution viscosity of the reaction solution will be extremely increased, the operability will be reduced, gelation will occur, and the productivity will be poor, which is not preferable. The progress of the reaction in a homogeneous state is hindered, and it becomes difficult to obtain the intended brominated polystyrene having a high bromine content, which is not preferable. Also,
If the molecular weight distribution exceeds 3.0, a low molecular weight component or a high molecular weight component is contained in a large amount, so that gelation occurs during the bromination reaction or the hue of the obtained brominated polystyrene is not preferable.

[0013] For the bromination reaction, a usual aromatic nucleus bromination technique is used, and as a solvent to be used, a halogen-based organic solvent which is inert to bromine and a catalyst is used. Examples of such a halogen-based organic solvent include dichloromethane, chloroform, bromoform, bromochloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, and bromoethane. Dichloroethane is preferred. These solvents can be used alone or in combination of two or more. In order not to deactivate the catalyst, the solvent usually used for the reaction is an anhydrous solvent. However, a solvent obtained by dehydrating the recovered solvent to make it substantially anhydrous may be used.

[0014] The number average molecular weight and molecular weight distribution of polystyrene affect the solubility in the above-mentioned solvent. In the case of polystyrene which does not satisfy the number average molecular weight and molecular weight distribution of polystyrene used in the present invention,
The upper limit of the solution concentration during the bromination reaction is approximately 10% by weight. At a concentration higher than 10%, the reaction solution becomes a gel during the bromination reaction, and a substantially uniform reaction cannot be performed. In the production method of the present invention, the solution concentration of polystyrene during the bromination reaction is 11 to 30% by weight, preferably 12 to 2%.
8 wt%, more preferably 13 to 25 wt%, even if the bromination reaction of the polystyrene is carried out at a solution concentration in this range, the reaction solution has an appropriate viscosity and the reaction occurs uniformly without gelation, Operability and productivity are improved. If the solution concentration of polystyrene is less than 11% by weight, the productivity of brominated polystyrene decreases, which is not preferable. If it exceeds 30% by weight, the viscosity of the reaction solution becomes extremely high or gelation occurs and the reaction becomes uneven, which is not preferable. .

As the brominating agent used in the production method of the present invention, bromine or bromine chloride is used. These may be used as solutions dissolved in the above-mentioned halogen-based organic solvents. These brominating agents are used in a substitution reaction of polystyrene with an aromatic ring, and the amount of the brominating agent is 2.0 to 4.0 with respect to 1 mol of styrene skeleton unit of the raw material polystyrene.
5 mol, preferably 2.3 to 4.4 mol, more preferably 2.4 to 4.2 mol, particularly preferably 2.5 to 4.0 mol.
Is a mole. By using the brominating agent in such a range, a brominated polystyrene having a desired bromine content of 65 to 68% by weight can be obtained. If such a brominating agent is used in excess, gelation tends to occur during the bromination reaction, and the resulting product is also notably colored, which is not preferable.

The method of mixing bromine or bromine chloride with the polystyrene solution is not particularly limited, and a method of gradually dropping bromine or bromine chloride into the polystyrene solution is preferably employed because the reaction proceeds stably. .

The catalyst used in the production method of the present invention is an ordinary Lewis acid catalyst, which is at least one compound selected from the group consisting of aluminum chloride, aluminum bromide and iron trichloride, and 100 parts by weight of the compound. A catalyst comprising 0 to 100 parts by weight of metal aluminum is preferably used. Of these, aluminum chloride is preferred. Here, the metal aluminum optionally used may react with bromine in the reaction system, and may be substantially modified into aluminum bromide, aluminum chlorobromide or iron aluminum chlorobromide complex. However, the catalytic activity tends to increase with the addition of metallic aluminum. When it is not necessary to increase the catalytic activity, the reaction may be allowed to proceed without adding metallic aluminum.
Therefore, depending on the situation of the reaction system, the state of the bromination reaction can be controlled by adding metal aluminum later. Such a Lewis acid catalyst is preferably a powder having a diameter of 32 μm or less, and is conveniently obtained by sieving through a 440 mesh (pore size 32 μm) sieve in a dry atmosphere. When the diameter of the catalyst is 32 μm or less, the deactivation reaction at the time of deactivation of the catalyst after the bromination reaction is smoothly performed, and the color of the obtained brominated polystyrene is favorable, which is preferable.

From the brominated polystyrene solution obtained by the production method of the present invention, a brominated polystyrene solid can be obtained by a known method, for example, by adding a solution in hot water or boiling water. It is preferably employed because the recovery can be performed simultaneously.

The brominated polystyrene obtained by the production method of the present invention has a good hue and excellent heat stability, and particularly, a polyester resin such as polyamide resin, polyethylene terephthalate, polybutylene terephthalate, etc., which requires high temperature treatment. It is suitably used as a flame retardant, and can provide a flame-retardant resin composition having a good hue.

[0020]

The present invention will be described in detail with reference to the following examples.
The present invention is not limited to these examples. The measurement of various characteristics in the examples was performed by the following methods.

(1) Measurement of number average molecular weight and molecular weight distribution Number average molecular weight was determined by size exclusion chromatography using an HPLC measuring device LC-10A (manufactured by Shimadzu Corporation) equipped with a GPC column KF-805L manufactured by Showa Denko KK Mn and the weight average molecular weight Mw were measured.
It was calculated from the equation of w / Mn. The measurement was performed with THF as the eluent.
Was calibrated using standard polystyrene.

(2) Bromine content The sample was heated with fuming nitric acid in a closed vessel to decompose it, and the hydrobromic acid generated was quantitatively analyzed by a method of titrating with silver nitrate (Carius method).

(3) Hue (APHA) After weighing 0.10 g of the obtained brominated polystyrene,
The solution was dissolved in ml of methylene chloride, and the hue of this solution was measured in comparison with a Hazen color number standard solution. The smaller the value, the better the hue.

Example 1 A polystyrene having 1.68 L of dichloromethane, a number average molecular weight of 20,000 and a molecular weight distribution of 2.5 was placed in a 5 L glass flask equipped with a stirrer, a reflux unit, a thermometer and a dropping funnel. PSt1) 360
g, and 9.7 g of aluminum chloride passed through a sieve having a pore diameter of 32 μm were added (polystyrene solution concentration was 14.0 g).
1.46 kg of bromine (2.6 per mol of styrene skeleton unit) so as to maintain the internal temperature at 5 to 15 ° C.
4 mol) was added dropwise over 1 hour. No gelling occurred during the bromination reaction. After completion of the dropping, the reaction was aged for 40 minutes, and the reaction product was washed with water. Then, the dichloromethane layer was dropped into warm water to obtain a brominated polystyrene solid. The obtained brominated polystyrene was analyzed, and the evaluation results are shown in Table 1. The solution concentration during the bromination reaction was 14.0.
% By weight and excellent in productivity, and the brominated polystyrene obtained had a bromine content of 67.5% by weight.
Was 10 and the hue was good.

Example 2 1.81 L of dichloromethane
Use a catalyst with a pore size of 3 instead of aluminum chloride.
Brominated polystyrene was obtained in the same manner as in Example 1 except that 11.8 g of iron trichloride passed through a 2 μm sieve was used. Table 1 shows the evaluation results of the obtained brominated polystyrene.
It was shown to.

Example 3 The procedure was carried out except that a mixture of 9.8 g of aluminum bromide passed through a sieve having a pore size of 32 μm and 0.98 g of metallic aluminum passed through a sieve having a pore size of 32 μm was used instead of aluminum chloride as the catalyst. Brominated polystyrene was obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained brominated polystyrene.

[Example 4] The same as Example 1 except that 1.06 kg of chlorine bromide (BrCl) (2.64 mol per mol of styrene skeleton unit) was used as a brominating agent instead of bromine. Brominated polystyrene was obtained by the method. Table 1 shows the evaluation results of the obtained brominated polystyrene.

Example 5 Brominated polystyrene was obtained in the same manner as in Example 1 except that 1.77 L of 1,2-dichloroethane was used instead of dichloromethane as a solvent. Table 1 shows the evaluation results of the obtained brominated polystyrene.

Example 6 PS was used as a raw material polystyrene.
555 g of polystyrene (PSt2) having a number average molecular weight of 11,000 and a molecular weight distribution of 2.4 instead of t1
Using 15.0 g of aluminum chloride and 2.25 kg of bromine (2.64 mol per mol of styrene skeleton unit), which had passed through a sieve having a pore size of 32 μm (polystyrene solution concentration was 20.0% by weight). Brominated polystyrene was obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained brominated polystyrene.

Example 7 Bromination was carried out in the same manner as in Example 1 except that aluminum chloride having an average particle size of 40 μm (average particle size was determined from the particle size distribution by sieving) was used as a catalyst. Polystyrene was obtained. Compared to the brominated polystyrene obtained in Example 1, the APHA of the brominated polystyrene obtained in this example was slightly lowered, and the bromine polystyrene having a slightly lower hue but a high bromine content was obtained. . Table 1 shows the evaluation results.

COMPARATIVE EXAMPLE 1 A polystyrene having 1.68 L of dichloromethane, a number average molecular weight of 22,000 and a molecular weight distribution of 3.2 was placed in a 5 L glass flask equipped with a stirrer, a reflux unit, a thermometer and a dropping funnel. PSt3) 360
g, and 9.7 g of aluminum chloride passed through a sieve having a pore diameter of 32 μm were added (polystyrene solution concentration was 14.0 g).
1.46 kg of bromine (2.6 mol per mol of styrene skeleton unit) so as to keep the internal temperature at 5 to 15 ° C.
(4 mol) was dropped over 1 hour, and gelation occurred.

Comparative Example 2 1.81 L of dichloromethane was used.
Use a catalyst with a pore size of 3 instead of aluminum chloride.
When a bromination reaction was carried out in the same manner as in Comparative Example 1 except that 11.8 g of iron trichloride passed through a 2 μm sieve was used, gelation occurred.

Comparative Example 3 A comparison was made except that instead of aluminum chloride, a mixture of 9.8 g of aluminum bromide passed through a sieve having a pore size of 32 μm and 0.98 g of aluminum metal passed through a sieve having a pore size of 32 μm was used instead of aluminum chloride. When a bromination reaction was carried out in the same manner as in Example 1, gelation occurred.

Comparative Example 4 A bromination reaction was carried out in the same manner as in Comparative Example 1 except that 1.06 kg of chlorine bromide was used instead of bromine as a brominating agent, and gelation occurred.

Comparative Example 5 A bromination reaction was carried out in the same manner as in Comparative Example 1 except that 1.77 L of 1,2-dichloroethane was used instead of dichloromethane as a solvent, and gelation occurred.

[Comparative Example 6] PS as a raw material polystyrene
Instead of t1, 998 g of polystyrene (PSt2) having a number average molecular weight of 11,000 and a molecular weight distribution of 2.4
26.9 g of aluminum chloride and 4.04 kg of bromine (styrene skeleton unit 1) passed through a sieve having a pore size of 32 μm.
Example 2 in a dichloromethane solution having a polystyrene solution concentration of 31.0% by weight (2.64 mol per mol).
When a bromination reaction was carried out in the same manner as described above, gelation occurred.

[Comparative Example 7] PS as a raw material polystyrene
In place of t1, 555 g of polystyrene (PSt4) having a number average molecular weight of 6,000 and a molecular weight distribution of 2.2 is used (the polystyrene solution concentration is 20.0% by weight),
Aluminum chloride passed through a sieve with a pore size of 32 μm
When a bromination reaction was carried out in the same manner as in Example 1 using 4.9 g and 2.25 kg of bromine (2.64 mol per mol of styrene skeleton unit), gelation did not occur, and brominated polystyrene was used. I got The resulting brominated polystyrene had a high bromine content, but had an APHA of 3
0, and the hue deteriorated. The evaluation results are shown in Table 2.

Comparative Example 8 PS was used as a raw material polystyrene.
Instead of t1, polystyrene (PSt5) having a number average molecular weight of 140,000 and a molecular weight distribution of 3.5
g (a polystyrene solution concentration is 12.0% by weight), 8.2 g of aluminum chloride and 1.23 kg of bromine (2.64 mol per mol of styrene skeleton unit) passed through a sieve having a pore size of 32 μm. When a bromination reaction was carried out in the same manner as in Example 1, gelation occurred.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

According to the present invention, there is provided a method for producing a brominated polystyrene having a good hue and a high bromine content with good productivity, and the obtained brominated polystyrene is suitably used as a high-performance flame retardant for resins. It is used, and the industrial effect it plays is exceptional.

Claims (3)

[Claims] (1) a number average molecular weight of 10,000 to 30,0
A solution in which polystyrene having a molecular weight distribution of 1.0 to 3.0 is dissolved in a halogen-based organic solvent at a concentration of 11 to 30% by weight, and 2.0 to 4 mol per mol of a styrene skeleton unit of the polystyrene. A method for producing a brominated polystyrene, comprising mixing 0.5 mol of bromine or chlorine bromide in the presence of a Lewis acid catalyst to carry out a bromination reaction. 2. The Lewis acid catalyst comprises at least one compound selected from the group consisting of aluminum chloride, aluminum bromide and iron trichloride and 0 to 100 parts by weight of metal aluminum with respect to 100 parts by weight of such a compound. The method for producing brominated polystyrene according to claim 1, wherein the catalyst has passed through a sieve having a pore size of 32 µm. 3. The bromine according to claim 1, wherein the halogen-based organic solvent is dichloromethane, chloroform, bromoform, bromochloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane or bromoethane. For the production of activated polystyrene.