JPS5811447B2 - Post-treatment method for block copolymers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves the solution polymerization of a styrenic hydrocarbon and a conjugated diene in an organic solvent using an organolithium compound as an initiator, and the resulting block copolymer is recovered by a steam stripping method. The method is characterized by the use of a novel dispersant system during the steam stripping.

The block copolymer obtained as described above is precipitated by steam stripping the solvent from a polymerization solution consisting of an organic solvent solution (including a slurry in which a portion of the polymer has precipitated). A method of separating and recovering the waste is adopted.

This method of steam stripping mainly includes a) a batch method in which water and a polymerization solution are charged into a tank in advance and stirred while steam is blown into the tank to raise the temperature and steam strip the solvent; There are three methods: a continuous method in which the polymerization solution is continuously poured into hot water at 95°C;

In either method, a suitable dispersant, such as polyvinyl alcohol (Japanese Unexamined Patent Application Publication No. 1983-1995
90693), Cellulose Derivative C JP-A-1987-
90693), polyether type block copolymer (JP-A-51-37987), polycarboxylic acid (
It has been proposed to use polyphosphoric acid esters (Japanese Patent Application Laid-open No. 141693/1983), polyphosphoric acid esters, etc.

The performance required for a dispersant is, of course, dispersion performance, but it is extremely important that it does not adversely affect the quality, size, transparency, thermal stability, hygroscopicity, odor, etc. of the resulting polymer. It is.

However, the above-mentioned types of dispersants do not necessarily satisfy all of these properties.

In particular, the polyether type block copolymer mentioned above has the advantage that even if it is incorporated to some extent into the polymer, the transparency, which is a characteristic of the above-mentioned target styrene-diene block copolymer, is unlikely to be impaired. This is an interesting dispersant, but
It has the drawback of being unsatisfactory in terms of dispersion performance of the liver and kidneys, making it impractical.

In other words, this dispersant is used in the batch method described above.
Although a good particulate polymer is obtained, a stable dispersion state cannot be maintained in the more economically preferable continuous mode, and a large particle-like or lump-like polymer is obtained.

The present invention provides a novel dispersant system that maintains the advantages of the above-mentioned polyether block copolymer type dispersant and improves the dispersion performance, which is the disadvantage thereof. The purpose is to improve the

According to the research conducted by the present inventors, it has been found that the above-mentioned object can be achieved by using a polyether block copolymer together with a water-soluble salt of the metal as a dispersant.

More specifically, the block copolymer post-treatment method of the present invention involves precipitating and separating a block copolymer of a styrenic hydrocarbon and a conjugated diene by steam stripping the solvent from an organic solvent solution. In doing so, the steam stripping is performed using the following (a) and (
It is characterized in that it is carried out in the presence of a dispersant system containing b).

(a) has a structural formula (% formula %) (where A, m, and n are all integers), an average molecular weight of 4000 to 8000, and a polyoxyethylene content of 2
0 to 40% by weight of a polyether type block copolymer, and (b) a sulfate or carbonate of a metal selected from K, Na, Mg, Ca, Al and Zn.

The present invention will be explained in more detail below.

The block copolymer to be treated in the present invention (hereinafter sometimes referred to as "target polymer" or simply monopolymer").

) consists of a polymer block of styrenic hydrocarbons such as styrene, α-methylstyrene, and vinyltoluene, and a polymer block of conjugated diene such as butadiene and isoprene.

The block copolymer is produced by copolymerizing these styrenic hydrocarbons and conjugated dienes in an organic solvent, especially a low-boiling hydrocarbon such as benzene, cyclohexane, or toluene, using an organolithium metal compound as an initiator by a known method. obtained by.

Generally, when there is a large amount of conjugated diene in the block copolymer,
It exhibits properties as a thermoplastic rubber, and conversely, when the amount is small, it exhibits properties as a thermoplastic resin.

The dispersant system used in the present invention has a specified polyether type block copolymer as a main dispersant, and further contains a water-soluble salt of a specified metal as a dispersion aid.

The polyether block copolymer as the main dispersant is
An ABA type problock copolymer consisting of a polyoxyethylene block and a polyoxypropylene block (B) has an average molecular weight of 4000, with the proportion of A accounting for 20 to 40% (weight %, hereinafter the same). ~80
00.

If the ratio of A is less than 20%, the dispersion performance is poor, and 40%
If it exceeds , the cloud point will be high and the dispersion performance will decrease ((
The bubbling phenomenon during steam stripping is extremely impractical.

If the average molecular weight is less than 4,000, it is not preferable because it reduces the thermal stability of the precipitated polymer and causes yellowing.
If it exceeds 000, the solubility in hot water will be significantly reduced and it will not be practical.

The amount of polyether type block copolymer used is 0.05 to 1.5%, particularly 0.05 to 0.5%, based on the target polymer.
% is preferable.

If it is less than 0.05%, the dispersibility will decrease, and if it exceeds 1.5%, the dispersibility will improve, but it will reduce the transparency of the polymer, so it is not preferable. preferable.

On the other hand, metal salts used as dispersion aids include K and Na.

It consists of a sulfate or carbonate of a metal selected from Mg, Ca, Al and Zn.

The reason why the addition of these water-soluble metal salts gives the dispersibility of the block copolymer solution in hot water, which is significantly improved by the combination with the polyether type block copolymer described above, is not necessarily clear; It is presumed that it has the effect of significantly stabilizing the protective colloid of the main dispersant that is formed around the dispersed droplets of the liquid.

Among them, Na25O, (mirabilite), KAl(SO4)2
(Karimyumban), N a2 C03, K2CO3,
Al2(SO4)3, MgSO4, etc. are preferred.

These water-soluble metal salts are 0.05 to 0.05 to the target polymer.
It is preferable to use it in the range of 0.4%.

If it is less than 0.05%, the effect of addition is poor, and if it is used in excess of 0.4%, it may impair the transparency of the product polymer.

Steam stripping in the method of the present invention can be performed by either the above-mentioned batch method or continuous method.

However, in order to take advantage of the excellent dispersion performance of the dispersant system according to the present invention, it is preferable to apply it to a continuous system, which is economical but more difficult to disperse.

That is, a polymerization solution consisting of an organic solvent solution of the above-described block copolymer of styrenic hydrocarbon and conjugated diene is heated to a temperature higher than the boiling point of the solvent or the azeotropic temperature of this and water, usually 80 to 95°C. The mixture is poured into hot water that is being heated and stirred if necessary, and the above-mentioned dispersant is also added to the hot water.

As a result, the solvent is steam-distilled, and the desired polymer is precipitated in the hot water, and further separated from the hot water by centrifugation or the like.

The crumb-like polymer precipitated and separated by the method of the present invention is
Thereafter, it is dried by a conventional method, and after adding an appropriate molding aid, it is molded and used for the desired purpose.

As described above, according to the present invention, a dispersant that is necessary for the post-treatment of a block copolymer of a styrenic hydrocarbon and a conjugated diene by steam stripping can be used to improve transparency, which is the most important feature of the target polymer. Although polyether block copolymers are the most desirable from the viewpoint of maintenance, they have poor practical use due to unsatisfactory dispersion performance. By combining this with a water-soluble salt of a specific metal, we have developed an excellent dispersant. It was a success in providing a system.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 (Example) Purified benzene 801 was placed in a 1001 autoclave.
was charged, 280 mmol of a dilithium compound of butadiene oligomer was added thereto, and the temperature was maintained at 40°C.

4 kg of butadiene and 16 kg of styrene were introduced into this and polymerized while stirring.

Add a small amount of alcohol to the polymerization solution to stop the polymerization activity.
A thermoplastic resin polymerization solution was obtained.

A 3001 precipitation tank containing hot water with a temperature of 85°C was heated with two stages of turbine blades (diameter 300mm) at a rotation speed of 200r.
The above polymerization solution was mixed at a rate of 301/Hr while stirring under p, m conditions, and Pluronic P-123 (trade name: polyether type block copolymer manufactured by Asahi Denka Kogyo, average molecular weight: 550
0, polyoxyethylene content 30%) in a 5% aqueous solution of 6
00cc/Hr and Glauber's Salt (Na2SO, 10H20)
A 5% aqueous solution of was continuously injected at a rate of 120 c, c,/Hr.

The amounts of Pluronic P-123 and Glauber's salt added correspond to 0.5 and 0.1 pHR (parts by weight per 100 parts by weight of polymer), respectively.

The polymer was stably dispersed in the form of crumbs with a diameter of 3 to 6 mm, no bubbling phenomenon was observed in the precipitation tank, and no deposits on the inner wall of the tank (adhesion to the can) were observed after 10 hours of continuous operation.

Through the above operation, the solvent benzene in the polymerization solution was removed and recovered by steam distillation.

On the other hand, the precipitated crumb-like slurry was subjected to a centrifugal dehydrator to separate and recover the polymer.

After drying the obtained polymer, 0.5 pHR of 2゜6-ditertiary-butyl-4-methylphenol, 0.5 pHR of ToIJ snonylphenylphosphite, and 0.2 pHR of stearic acid were added, and the extrusion temperature was adjusted to 200 pHR. A pelletized product was obtained by pelletizing at °C.

The pellets were injection molded to form a plate with a thickness of 2 mm, and the transparency, hue, and odor of the molded product were evaluated.

Some of the results and conditions of the above tests are summarized in the table below, along with those for the following examples.

Example 2 (Comparative Example) The operation of Example 1 above was repeated under exactly the same conditions except that the aqueous sodium sulfate solution was not supplied.

The dispersion of the polymerization liquid during steam stripping becomes a lump with a TIL diameter of 30 to 50 m within 10 minutes after the start of supply of the polymerization liquid.
I was unable to drive.

In such massive precipitates, solvent volatilization is completely insufficient, and
It could not be used for polymer quality evaluation.

Examples 3 to 5 (Example) In Example 1, the exact same operation as in Example 1 was performed except that the amount of Pluronic P-123 added was changed to 0.05, 1, 0, 2.0 pHR (!). Ta.

Examples 6 to 8 (Example) In Example 1, the amount of mirabilite added was 0.05° and 0.05°, respectively.
The same procedure as in Example 1 was performed except that the pH was 2.0.5.

Examples 9 to 12 (Example) The same operations as in Example 1 were repeated using the same amounts of the following substances instead of Glauber's salt.

Example 9 KANO(SO-.12H20 (potash alum)) Example 10 Na2COs' Example 11 and 2CO3 Example 12 Mg5O.

Example 13 (Example) In Example 1, the method of adding monomers and initiators in the polymerization stage was changed as follows to obtain a polymerization solution for thermoplastic rubber.

In other words, in a 1001 autoclave, purified benzene 8
After preparing 01, first add 3.2 yu of styrene,
Subsequently, 300 mmo of n-butyllithium was added as an initiator.
1 was added, and the temperature in the system was raised to 60°C to complete the polymerization.

Then, after raising the temperature to 40℃, 12 kg of butadiene and 4 styrene were added.
．． 8 kg was added all at once and the temperature was raised to 60°C to carry out polymerization.

After stopping the polymerization by adding a small amount of alcohol, the obtained polymerization liquid was subjected to the steam stripping operation of Example 1, and the same evaluation test was conducted.

Example 14 (Comparative Example) 30 Jl' of the polymerization solution obtained in Example 1 was added to 15 ml of warm water at 40°C.
Pluronic P-1
After adding 3 (l) of 23, the temperature was raised at a rate of 20°C/Hr while stirring and blowing steam, and finally 85
When the temperature was raised to .degree. C., 1 to 2 particles of polymer were obtained.

However, when the inside was observed through the side glass after 5 hours of operation, a film of polymer was observed on the stirring blades and the can wall.

Examples 15 to 17 (Comparative Examples) The same operations as in Example 1 were repeated using the same amounts of the following polyether block copolymer type dispersants in place of Pluronic p-123.

Example 15: Pluronic L-68 (average molecular weight 8500,
- polyoxyethylene content 80%), Example 16: Pluronic L-64 (average molecular weight 8500,
Polyoxyethylene content 10%), Example 17: Pluronic L-61 (average molecular weight 1900,
polyoxyethylene content 10%).

In either case, 30-50 minutes after the start of operation.
A lump of precipitation as large as the diameter of a motor vehicle formed, and operation became impossible.

In addition, after removing the precipitated polymer, a film-like polymer adhered to the can wall and the stirring blade. (Average molecular weight approximately 2200
, polyoxyethylene content 20%), the dispersibility was good, but the molded product obtained from the precipitated polymer was yellowed and had a significant odor.

The results obtained in the above examples are summarized in the table below along with some of the conditions.

Dispersibility The quality of dispersion of the polymerization solution into hot water during stem stripping was visually judged.

In all cases of poor dispersion, the particle size significantly increased halfway through the process, making it impossible to operate.

In addition, for those with good dispersion, the particle diameter of the precipitated polymer was expressed in units of units.

Foaming The operation was carried out so that the liquid level was at the center of the precipitation value sight glass (12 Qmi diameter), and visually judged according to the following criteria.

○: The liquid level is visible during operation.

×: Liquid level cannot be seen due to bubbling.

Can Adhesion After the operation was completed, the contents were tapped, the inside was visually inspected through a sight glass, and the state of polymer adhesion on the can walls and stirring blades was observed and judged based on the following criteria.

○: No adhesion at all, or some adhesion to the stirring blades.

×: Membrane-like adhesion throughout the area.

Transparency A plate with a thickness of 2 mm was injection molded, and its haze value was measured according to the method of ASTM-D-1003 (unit: %).
).

Hue: The b value (yellowness) of a 2 mm thick molded plate was measured using a colorimeter CM-1 [type] using Suga Test Instruments.

Odor 20g of pellets were placed in a 200C, C, flask, and left at 70°C for 2 hours, and the odor immediately after removal was evaluated.

○: There is no odor, or there is a slight odor.

×: Significant off-odor is felt.

Looking at the table above, it can be seen that an excellent dispersant system can be obtained by combining a polyether type block copolymer with a specific molecular weight and polyoxyethylene content and a water-soluble metal salt;
It can also be easily understood that the above-mentioned amount ranges for these two components are particularly preferable when considering the quality of the target polymer, such as transparency.

Claims (1)

[Scope of Claims] 1. When a block copolymer of a styrenic hydrocarbon and a conjugated diene is precipitated and separated from its organic solvent solution by steam stripping the solvent, the steam stripping is performed using the following method (a). ) and (b). (a) has a structural formula (7.m and n are both integers), an average molecular weight of 4000 to 8000, and a polyoxyethylene content of 2
0 to 40% by weight of a polyether type block copolymer, and (b) a sulfate or carbonate of a metal selected from K, Na, Mg, Ca, AI and Zn.