JP3041647B2 - Method for producing styrene-butadiene block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating a styrene-butadiene block copolymer from a copolymer solution by steam stripping and a polymer composition obtained by the method.

[0002]

2. Description of the Related Art Conventionally, a polymer is produced by solution polymerization using a Ziegler catalyst, a lithium catalyst or the like. In solution polymerization, steam stripping is most commonly used as a means for separating and recovering a polymer from a polymer solution. Steel
Mustripping is a method in which a solvent is evaporated by bringing a polymer solution into contact with a steam to solidify the polymer as crumb. In recent years, there has been an increasing demand in the market for rubbery polymers close to resins containing a large amount of polystyrene blocks as rubbery polymers for producing impact-resistant polystyrene resins.

[0003]

When such a rubbery polymer is produced by solution polymerization, and the polymer is separated and recovered from a solution of the polymer by a steam stripping method, the resulting crumb is fine. , And a part thereof is finely divided. As a result, the crumbs do not bite into the dewatering machine, and the crumbs leak from the slits of the dewatering machine. Further, in the drying step, there arises a problem that the dried polymer is scattered as finely divided particles. The present inventors have made efforts to solve such problems and completed the present invention.

[0004]

According to the present invention, styrene having a total styrene content of 15 to 50% by weight and forming ten or more chains analyzed by gel permeation chromatography of an ozonolysis product is provided. Is used for steam stripping a solution of a styrene-butadiene block copolymer having a viscosity of 15 to 200 centipoise of a 5% by weight styrene solution measured at 25 ° C. of 60% by weight or more of the total styrene content. 2 to the copolymer
25% by weight of a viscosity of 38 ° C.
A method for producing a styrene-butadiene block copolymer, characterized by steam stripping in the presence of a liquid polymer having a viscosity of up to 50,000 poise, and the block copolymer obtained by this method and the block copolymer There is provided a polymer composition comprising the liquid polymer in an amount of 2 to 25% by weight based on the weight of the polymer.

The styrene-butadiene block copolymer of the present invention is produced by a known solution polymerization using an ordinary anion polymerization catalyst based on an alkali metal such as lithium. Since the block copolymer of the present invention is used for the production of impact-resistant polystyrene resin, the total styrene content is in the range of 15 to 50% by weight, and the viscosity of a 5% by weight styrene solution at 25 ° C is 15 to 15%. Styrene which forms a block polystyrene chain in which 10 or more styrenes are bound in a range of 200 centipoise is 60% by weight or more of the total styrene content.

The structure of the block copolymer is AB type (A represents a polymer block mainly composed of styrene and B represents a polymer block mainly composed of butadiene). May be clearly distinguished, or the styrene may decrease or increase from A to B or from B to A in a tapered manner. The above-mentioned main component means that a homopolymer of styrene or butadiene containing 50% by weight or more of styrene or butadiene and a copolymer of both are included. Further, AB may have a structure of repeating a plurality of times (AB) n (n represents an integer of 1 or more).

In the present invention, the viscosity of the liquid polymer coexisting when the block copolymer solution is subjected to steam stripping regardless of the type of the polymer (using a B-type viscometer at 38 ° C.) 3 to 50,000
It must be in the range of 0 poise. Depending on the amount used, is less than 3 poise miniaturization of dazzling the block copolymer is not prevented, but more than the finer 5 0,000 poise is prevented, the ease of handling as a liquid rubber At the same time, the characteristics of the impact-resistant polystyrene resin exhibited by the styrene-butadiene block copolymer are lost. Preferably, it is 5 to 10,000 poise.

The amount of the liquid polymer used is in the range of 2 to 25% by weight based on the amount of the block copolymer in the solution. If it is less than 2% by weight, the crumb is not prevented from being finely divided, and 25% by weight.
If it exceeds 50, the effect of preventing crumb fineness does not change even if it is used more than that. Preferably it is 4 to 20% by weight. The liquid polymer is added to the block copolymer solution as it is or as a solution of a block copolymer polymerization solvent or a suitable solvent compatible therewith. As the liquid polymer, liquid polybutadiene, liquid polyisoprene, liquid styrene-isoprene copolymer, liquid styrene-butadiene copolymer, liquid conjugated diene-based polymers such as liquid polychloroprene and copolymers, liquid ethylene-propylene-
Examples thereof include a diene monomer-terpolymer.

The mixed solution of the block copolymer and the liquid polymer thus obtained is subjected to steam stripping. The steam stripping is performed by a known method such as a method of blowing a stream into the mixed solution, a method of injecting a stream through the nozzle into the mixed solution stream injected from the nozzle, and shredding the mixed solution stream. A tripping method is used.

The separated block copolymer crumb has a size of 0.5 to 5 mm, easily penetrates into the dehydrator, and does not leak out from the slit of the dehydrator. Also in the drying step, the block copolymer can be dried in the same manner as a normal rubbery polymer without forming fine powder particles. The polymer composition comprising the block copolymer obtained through a drying step and 2 to 25% by weight of the liquid polymer with respect to the block copolymer, when an impact-resistant polystyrene resin is produced using the same, It is possible to produce an impact-resistant polystyrene resin having better impact resistance than when using the block copolymer containing no liquid polymer.

[0011]

The present invention will be described in more detail with reference to the following examples. In the Examples and Comparative Examples, parts and% are based on weight. The amount of styrene forming a polystyrene chain in which 10 or more styrenes are bonded by ozonolysis (hereinafter referred to as the amount of block styrene) is determined by the method of Tanaka (Preprints of the Society of Polymer Science, Vol. 29, No. 9, No. 2055). -2058, 1980).

Embodiment 1
A polystyrene-polybutadiene block copolymer (complete AB) was prepared by successive monomer addition in cyclohexane at 70 ° C. using n-butyllithium as a polymerization catalyst.
Mold, total styrene content 40%, block styrene content 75
%, A 5% styrene solution at 25 ° C. and a viscosity of 30 centipoise) were polymerized to obtain a polymer solution (1) having a block copolymer concentration of 23%.

This polymer solution (1) was divided into 2 minutes, and one of them was added to a liquid polybutadiene having a viscosity of 5.8 poise measured at 38 ° C. with a B-type viscometer (Polyoil 11 manufactured by Huls Co., Ltd.).
0) was added to the block copolymer in the polymer solution (1) in an amount of 10% and dissolved with stirring to obtain a polymer solution (2).

[0014] The polymer solutions (1) and (2) were steam stripped as follows. That is, each polymer solution is sent to the coagulation tank at a rate of 200 l / hour.
Just before the polymer solution enters the coagulation tank,
Was sprayed onto the polymer solution at a rate of 250 kg / hr.
Water and steam are fed into the coagulation tank so that the temperature of the coagulation tank is 105 ° C., the pressure is 1 kg / cm ² G, and the crumb concentration is 3%, the polymerization solvent is stripped, and the desired block copolymer is prepared. The crumb continuously produced slurry suspended in hot water.

The obtained slurry of the crumb was divided into six types of wire meshes (4.0, 5.5, 7.5, 10.0, 10.0,
20.0, 70.0 mesh) were passed through the coarse mesh to the fine mesh in order, and the distribution of crumb size was measured from the amount of crumb remaining on each mesh. The results are shown in Table 1.

[0016]

[Table 1]

Further, crumbs from each polymer solution are subjected to L / D
(L is the length of the screw, D is the outer diameter of the screw) 5.
6 was placed in a squeezer (dehydrator), and the state of crumb biting was observed. The crumb from the polymer solution (1) (comparative example) has a crumb size that is too fine, resulting in poor penetration,
Further, fine crumbs flowed out from the slits (drain holes) of the squeezer, and the recovery of the block copolymer was reduced.
As a result, the throughput of the entire drying process was significantly reduced.
In the crumb from the polymer solution (2) (Example of the present invention), there was no problem at all, and there was almost no outflow of crumb from the slit, and the recovery of the block copolymer was almost 10
It was 0%. Further, the processing amount of the entire drying step was 1.5 times that of the polymer solution.

Further, the dewatered crumb that has exited the squeezer is adjusted to a cylinder temperature of 140 ° C. and the L / D is 10.
7 was dried using an expansion extrusion dryer. In the crumb of the present invention, the block copolymer could be dried without any problem without any fine powder granulation. On the other hand, in the crumb of the comparative example, the finely divided block copolymer scattered violently.

Example 2 In Example 1, 5% of the same liquid polybutadiene was added to the block copolymer in the polymer solution and steam stripping was performed. The same results as in Example 1 were obtained.

Example 3 A mixture of styrene and butadiene was first polymerized using n-butyllithium as a polymerization catalyst, and after the polymerization was completed, styrene was added and polymerization was carried out to produce a styrene taper block copolymer. As a result, a polymer solution (3) (polymer concentration: 23%) having a total styrene content of 30%, a block styrene content of 70%, and a 5% styrene solution having a viscosity of 120 centipoise at 25 ° C.) was obtained. This solution was divided into 2 minutes, and 5% liquid polyisoprene (Kuraray Co., Ltd., Kuraray LIR-310, viscosity of 9200 poise by a B-type viscometer at 38 ° C., 9200 poise) was added to the copolymer in the solution and dissolved. [Polymer solution (4).

The polymer solutions (3) and (4) were used in Example 1.
Steam stripping was performed in the same manner as described above. The crumb size was measured in the same manner as in Example 1. The results are shown in Table 2. The biteability of the squeezer of the polymer solution (3) crumb was the same as that of the polymer solution (1), and the biteability of the polymer solution (4) was exactly the same as that of the polymer solution (2). Was. Each dehydrated crumb was dried with a box-type ventilation dryer. In the crumb (Comparative Example) from the polymer solution (3), the block copolymer fine powder was very scattered, whereas in the crumb from the polymer solution (4) (Example of the present invention), the fine copolymer powder was dispersed. Was not seen at all, and there was no problem in drying.

[0022]

[Table 2]

[0023]

By carrying out the method of the present invention, the fineness of crumb in steam stripping of the styrene-butadiene block copolymer is prevented, poor penetration into the dehydrator in the dehydration step, and the polymer in the drying step The problem of the formation of fine powder particles is also improved, and the production of the block copolymer becomes easy. The mixture of the block copolymer and the liquid polymer obtained by the method of the present invention is a rubbery polymer composition suitable for producing an impact-resistant polystyrene resin having excellent impact resistance.

Claims (2)

(57) [Claims] 1. A total styrene content of 15 to 50% by weight, styrene forming 10 or more chains analyzed by gel permeation chromatography of an ozonolysis product is 60% by weight or more of the total styrene content at 25 ° C. 5 measured by
When steam-stripping a solution of a styrene-butadiene block copolymer in which the viscosity of a styrene solution having a concentration of 15% by weight is 15 to 200 centipoise, it is measured with a B-type viscometer at 2 to 25% by weight based on the copolymer. 38 ℃
Liquid conjugated diene having a viscosity of 3 to 50,000 poise
A method for producing a styrene-butadiene block copolymer, comprising steam stripping in the presence of a system polymer or a copolymer. 2. A polymer composition comprising the block copolymer obtained by the method of claim 1 and 2 to 25% by weight of the liquid polymer with respect to the block copolymer.