JPH10265509A - Production of styrenic polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing styrenic polymer, excellent in operability in polymerization and handling property in transfer, etc., of powder after polymerization, because formation of mass due to adhesion of powder to powder can be prevented and particle diameter is controlled. SOLUTION: In producing a styrenic polymer mainly having syndiotactic configuration in a synthesis tank having agitating facility, workload per second giving to power and liquid by agitation is set to >=1 kJ/m<3> .sec and when a space distance between the end part of an agitating wing and synthesis tank wall is defined as L and maximum diameter in powder is defined as d, L is set so as to satisfy the formula L<=2d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrenic polymer, and more particularly, to a method for synthesizing a styrenic polymer having a syndiotactic structure.
The present invention relates to a method for producing a styrenic polymer which is excellent in operability during polymerization and handling properties such as transfer of powder after polymerization, because agglomeration due to adhesion of powders can be prevented and the particle size is controlled.

[0002]

2. Description of the Related Art Recently developed styrene-based polymers having mainly a syndiotactic structure (hereinafter sometimes referred to as SPS) are already widely known as engineering plastics having excellent heat resistance and chemical resistance. As a polymerization method, solventless polymerization and slurry polymerization using various catalysts have been proposed.

[0003] It has been pointed out that in the polymerization of SPS, the generated powder tends to adhere to the wall surface of the synthesis tank and the like, and clumping due to the adhesion of the powders tends to occur. In particular, when agglomeration due to the adhesion of powders occurs, stable continuous operation becomes impossible, or the transfer of the powder after polymerization is hindered, and further, when drying is performed as a post-process, It has been regarded as a very serious problem in the process because the inside of the agglomerated powder cannot be sufficiently dried.

[0004] Various methods have been proposed as methods for solving such problems. For example, a method of shifting the charging time of the polymerization catalyst into the reactor (Japanese Patent Application Laid-Open No. 02-255708), or using a self-cleaning type reactor or a reactor having a specific stirring blade, etc. Proposals (JP-A-02-191609, JP-A-02-16)
No. 7314), and a method of polymerizing while applying a shearing force (JP-A-01-207305).

However, even with these methods,
It is not enough to prevent agglomeration due to the adhesion of powders, and when using a self-cleaning type reactor, it is difficult to increase the synthesis capacity or the product itself becomes expensive. However, there is a problem that the cost increase is unavoidable. Therefore, there has been a strong demand for the development of a method that does not cause agglomeration of these powders during polymerization.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to prevent agglomeration due to adhesion of powders, and to control the particle size. It is an object of the present invention to provide a method for producing a styrene-based polymer having excellent handling properties such as powder transfer later.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies under such circumstances, and as a result, the work per second per volume given to the powder and liquid parts by stirring has been set to a predetermined amount or more. In addition, the inventors have found that the above object can be achieved by setting the gap distance between the end of the stirring blade and the wall of the synthesis tank to a predetermined value. The present invention has been made based on such findings.

That is, in the present invention, when a styrene-based polymer having a syndiotactic structure is mainly produced in a synthesis tank having a stirring device, the work per second given to the powder and the liquid part by stirring is defined as 1 kJ per unit volume
/ M ³ · sec or more, and when the gap distance between the end of the stirring blade and the wall of the synthesis tank is L and the diameter of the largest powder in the powder is d, L is set so that L ≦ 2d. An object of the present invention is to provide a method for producing a styrenic polymer having a syndiotactic structure, which is characterized by setting.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. 1. Styrene-based polymer targeted by the present invention The styrene-based polymer targeted by the present invention mainly has a syndiotactic structure, is extracted from the polymerization tank, and contains residual volatile components such as unreacted monomers. It is something that is.

[0010] A syndiotactic structure has a three-dimensional structure.
Syndiotactic structure, ie, from carbon-carbon bonds
A phenyl group or a substituted phenyl group which is a side chain to the main chain to be formed.
Has a steric structure in which phenyl groups are alternately located in opposite directions
And its tacticity is determined by isotope carbon
Nuclear magnetic resonance (¹³C-NMR method). ¹³
Tacticity measured by the C-NMR method is
Existence ratio of multiple structural units following, for example, two
Is diad, 3 is triad, 5 is
Can be indicated by a pentad, but according to the present invention
Styrene polymer having syndiotactic structure and
Is usually at least 75% racemic dyad, preferably
85% or more, or 30% or more in racemic pentad,
Preferably has a syndiotacticity of 50% or more
Polystyrene, poly (alkylstyrene), poly (c
Styrene), poly (halogenated alkylstyrene)
), Poly (alkoxystyrene), poly (vinyl benzoate)
Peroxyesters), their hydrogenated polymers and their blends.
Compounds or copolymers containing these as main components
You. In addition, here, as poly (alkyl styrene),
Poly (methylstyrene), poly (ethylstyrene),
Li (isopropylstyrene), poly (tert-butyl)
Styrene), poly (phenylstyrene), poly (vinyl)
Lunaphthalene), poly (vinylstyrene), etc.
As poly (halogenated styrene), poly (chloros
(Tylene), poly (bromostyrene), poly (fluoros)
(Ethylene). In addition, poly (alkyl halide)
Styrene), such as poly (chloromethylstyrene).
And poly (alkoxystyrene)
(Methoxystyrene), poly (ethoxystyrene), etc.
There is.

Of these, particularly preferred styrene polymers include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tert-butylstyrene), and poly (p-chlorostyrene). , Poly (m-chlorostyrene), poly (p-fluorostyrene), hydrogenated polystyrene and copolymers containing these structural units.

Specifically, a styrene-p-methylstyrene copolymer containing at least 3 mol% of a p-methylstyrene repeating unit is preferable. This styrenic polymer is not particularly limited in molecular weight, but preferably has a weight average molecular weight of 10,000 or more, more preferably 50 or more.
000 or more. Furthermore, the molecular weight distribution is not limited in its width, and various types can be applied.

The method for producing such SPS is not particularly limited. For example, styrene-based monomers (the above-mentioned styrene-based monomers) can be prepared by using various known catalysts in an inert hydrocarbon solvent or in the absence of a solvent. (A monomer corresponding to a polymer). 2. Conditions in the synthesis tank In the synthesis tank for performing polymerization, the following conditions must be satisfied. (1) The work per second given to the powder and the liquid part by stirring is 1 kJ / m ³ · sec or more per unit volume of the powder.

In the present invention, it is necessary to provide a stirring device in the synthesis tank. The type and contents of the stirring equipment are not particularly limited as long as a predetermined work described later can be given to the powder and the liquid part. Specifically, a helical ribbon blade is preferably used. One of the purposes of stirring is to apply a predetermined amount of work to apply a shear to the powder, but by applying an appropriate shear, the powder particles adhere to each other, resulting in a lump like a so-called dango. Can be prevented. The direction in which the shear is applied, that is, the direction of the stirring is not limited.
Furthermore, by performing the stirring, the probability that the powder particles pass through the gap between the extreme end of the stirring blade and the synthesis tank wall increases, and at this time, the powder particles are moved to the extreme end of the stirring blade or the synthesis tank wall. And will be shaved.

Work Amount Provided to Powder and Liquid Part The work amount is given to the powder and liquid part by stirring, and the work amount is 1 kJ / s or more per m ^{3 of} powder.
It is preferably at least 3 kJ, more preferably at least 5 kJ. When the work is smaller than 1 kJ, sufficient shearing is not applied, so that the powder cannot be effectively prevented from agglomerating. Further, when the rotation speed is low and the power that satisfies the work is not given, the probability that the powder particles pass through the gap between the outermost end of the stirring blade and the wall of the synthesis tank decreases, and the outermost end of the stirring blade Since it is hard to be cut by contact with the part or the wall of the synthesis tank, the powder may grow in the synthesis tank and agglomerate.
In particular, when the particle growth rate is high due to the performance of the catalyst, polymerization conditions, and the like, it is desirable to increase the amount of work applied to the powder and liquid parts. The upper limit is not particularly limited, but if it is too large, the calorific value due to stirring becomes too large, which may cause adhesion to the stirring blade or the wall of the synthesis tank.

Method of controlling the amount of work applied to the powder and liquid parts The amount of work applied to the powder and liquid parts means the power by stirring, and the control method is not particularly limited. This is performed by appropriately changing the speed, that is, the number of revolutions of the stirring blade. (2) Gap distance (L) between the end of the stirring blade and the wall of the synthesis tank
Is defined as L ≦ 2d, where (d) is the diameter of the powder having the largest particle diameter among the obtained powders.

As shown in FIG. 1, the gap distance between the outermost end of the stirring blade and the synthesis tank wall is defined as the distance between the outermost portion of the stirring blade and the end plate of the synthesis tank side wall or the synthesis tank bottom. Of the smaller ones. It is necessary to set L so that L ≦ 2d, where L is the gap distance between the end of the stirring blade and the wall of the synthesis tank, and d is the diameter of the largest powder. Here, if the operating conditions under which agglomeration hardly occurs to some extent are selected, the gap distance L can be set to L = 2d. That is, even if the gap distance L is set to twice the diameter of the largest powder, the particle diameter of the powder can be suppressed to d. L <2d
When it is set to, it means that the powder particle size can be efficiently suppressed to within d even under the operating condition in which agglomeration is likely to occur. When L> 2d, the powder particle size cannot be suppressed to d under normal operating conditions. In this case, in order to prevent the powder particle size from increasing, it is possible to avoid agglomeration of the powder particles, to efficiently transmit the stirring power to the powder particles, and to apply a severe shear force to the powder particles effectively. It is necessary to drive under conditions. Specifically, it is necessary to make the liquid content, which will be described later, extremely low, reduce the charging rates of the monomer and the catalyst, and increase the stirring. .

Furthermore, it is desirable that the following conditions are satisfied. (3) The liquid content is 50% by weight or less. The liquid content means liquid part weight × 100 / (powder weight + liquid part weight), and is 50% by weight or less, preferably 30% by weight or less, and more preferably 25% by weight or less. The liquid part refers to the contents of the tank that exist in a liquid state while the polymerization is in progress. All the solvents and the like which exist as the above are applicable, and include those impregnated in powder. The powder is mainly a powder generated by polymerization, and is in a solid state under the progress of polymerization, and the particle size is not limited. Here, when the liquid content exceeds 50% by weight, that is, when the polymerization is performed in a state where the liquid portion is large, the adhesion of the powder particles becomes large, and there is a large possibility that the powder particles are aggregated like a so-called dango. .

[0019]

EXAMPLES The method for producing a styrenic polymer according to the present invention will be described more specifically with reference to examples. [Example 1] A complete mixing tank type reactor having a cleaned helical blade (inner diameter 435 mm, height 740 mm, inner volume 10
0 liter)) was heated to 90 ° C. and dried in vacuum for 3 hours. Next, after the reactor was depressurized with nitrogen gas,
The temperature was lowered to 80 ° C., and 65 liters of SPS powder, which had been sufficiently dried by flowing dry nitrogen gas in advance, was charged into the reactor, and further dried under a nitrogen stream for 2 hours. Subsequently, stirring was started at a stirring speed of 100 rpm, and the temperature in the reactor was adjusted to 70 ° C.

Thereafter, the introduction of the styrene monomer and the catalyst was started. The charging rates of the styrene monomer and each catalyst were as follows. Styrene monomer 7 liter / hour Methylaluminoxane 74 mmol / hour Triisobutylaluminum 52 mmol / hour Pentamethylcyclopentadienyltrimethoxytitanium 0.74 mmol / hour Liquid content during polymerization (liquid part weight × 100 / powder weight) + Liquid part weight) was adjusted to 30% by weight. Also, by stirring, the work per second given to the powder and the liquid part is per unit volume of the powder,
It was 3 kJ / m ³ · second. In order to set the maximum allowable particle diameter (d) of the powder to 8.0 mm, the clearance distance (clearance) between the outermost part of the helical blade and the wall of the synthesis tank (L)
Was set to 15 mm. That is, L ≦ 2d.

The generated powder was discharged intermittently from the bottom of the synthesis tank, and the particle diameter of the obtained powder was measured. All the particle diameters were 8.0 mm or less. Also, no adhesion of powder to the synthesis tank wall or the stirring blade was observed.

[0022]

As described above, the agglomeration due to the adhesion of the powders can be prevented and the particle size is controlled, so that the operability at the time of polymerization and the handling property such as the transfer of the powder after polymerization are excellent. A method for producing a styrenic polymer can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a gap distance between the end of a stirring blade and a wall of a synthesis tank.

[Explanation of symbols]

1: Stirrer blade 2: Synthetic tank wall 3: Gap distance between the outermost part of the stirrer blade and the synthesis tank side wall 4: Gap distance between the outermost part of the stirrer blade and the bottom plate of the synthesis tank bottom

Claims (1)

[Claims] In producing a styrenic polymer having a syndiotactic structure mainly in a synthesis tank having a stirrer, a work per second given to a powder and a liquid part by stirring is per unit volume of the powder. When 1 kJ / m ³ · sec or more, and the gap distance between the end of the stirring blade and the synthesis tank wall is L, and the diameter of the largest powder in the powder is d,
A method for producing a styrenic polymer mainly having a syndiotactic structure, wherein L is set such that L ≦ 2d.