JPS6260402B2 - - Google Patents

Description

[Detailed description of the invention]

A. Industrial Application Field The present invention is directed to the production of internally plastic chlorinated polyolefin by dissolving polyolefin in carbon tetrachloride and chlorinating it to a chlorine content of 50 to 60% by weight. This invention relates to a method for separating and drying polyolefin. B. Conventional technology Conventional chlorinated polyolefin (hereinafter abbreviated as CPO) has good solubility in organic solvents, chemical resistance,
Due to its excellent weather resistance, it is widely used in fields such as paints, printing inks, and adhesives. These CPOs have a high softening point and can be easily separated into solid-liquid powder by known methods such as steam distillation and spray drying. It was essential to use a low molecular weight plasticizer such as paraffin. CPO-based paints that use low molecular weight plasticizers have the drawbacks that when applied, the initial paint film becomes dirty and the plasticizer comes out of the paint film over time, causing cracks in the paint film. ing. Therefore, in order to improve these drawbacks, the inventors of the present invention made extensive studies and found that the single film has flexibility.
CPO was developed and proposed as patent application No. 58-236403. In the case of conventional CPO with a chlorine content of 60% by weight or more, for example, the polymer solution is dried in boiling water using the spray drying method proposed in Japanese Patent Publication No. 45-36310 or the method proposed in Japanese Patent Publication No. 46-4581. add to,
It is well known that CPO can be relatively easily separated from a solvent by a so-called hydrothermal solidification method. C Problems to be Solved by the Invention However, in the case of internally plastic CPO having a relatively low softening temperature with a chlorine content of 50 to 60% by weight, the above-mentioned method cannot be used at a temperature above the softening point of the resin. Due to handling, the resin becomes extremely sticky under these temperature conditions and adheres to the stirring device, vessel walls, etc. during drying, making it impossible to separate and dry using these methods. Other methods include Special Publication No. 39-19230, Special Publication No. 40-
No. 1237 and Japanese Patent Publication No. 12386/1983, there is a method of precipitating and separating the polymer by adding a poor solvent for CPO, such as an alcohol, to the solution. However, in these methods, the polymers aggregate and form nodules, making it impossible to granulate them. Furthermore, solvent purification requires a great deal of time and processing costs, and post-processing such as drying is difficult, making them impractical. Not. As described above, since CPO having internal plasticity, which is the subject of the present invention, exhibits low-temperature softening properties, no satisfactory method for separating it from the reaction solution, drying it, and granulating it has been known so far. In separating internally plastic CPO exhibiting such low-temperature softening properties from its solvent, the present inventors
As a result of extensive research to solve these problems, we have invented a new, simple and rapid separation and drying method that can easily granulate internally plastic CPO that exhibits low-temperature softening properties. D. Means for Solving the Problems Namely, the present invention provides for the production of internally plastic CPO by dissolving polyolefin in carbon tetrachloride and chlorinating it to a chlorine content of 50 to 60% by weight. After that, in the step of separating and drying the produced polymer from the reaction solution, the reaction solution is supplied to a centrifugal thin film evaporator to reduce the carbon tetrachloride concentration to 1.
This is a method for separating and drying internally plastic CPO, which is characterized by drying it to less than % by weight. E Effect The centrifugal thin film evaporator used in the present invention is:
The cylindrical can body has a built-in rotor that rotates while maintaining a small clearance with the can wall, and the can body has an external jacket for heating, and the supplied liquid is stirred by the rotor and heated. This type uses centrifugal force to form a thin liquid film between the tip of the rotor blade and the can wall, and by the time it reaches the outlet, it is heated, the solvent evaporates, and the liquid is concentrated. This is also called a centrifugal thin film evaporator or a stirred thin film evaporator, and specific examples include the Hitachi Control device, Hitachi Zanbai, and Hitachi VL type thin film evaporators manufactured by Hitachi, Ltd. The temperature of the outer jacket of the centrifugal thin film device is preferably kept at 100-180°C, but preferably at 130-160°C to promote efficient solvent evaporation and prevent polymer degradation due to overheating. . Although the solvent evaporation line can be operated under normal pressure or reduced pressure, a degree of reduced pressure of about -10 to -300 mmHg is preferred. The evaporated carbon tetrachloride is condensed and recovered by a condenser. The use of a centrifugal thin film evaporator for drying the reaction solution of internally plastic CPO is particularly suitable because the reaction solution of CPO has a high viscosity and is unstable against prolonged heating. The internally plastic CPO treated in the present invention is a polyolefin such as natural rubber, synthetic isoprene rubber, polypropylene, polyethylene, or a modified polyolefin obtained by grafting these with an oxygen-containing monomer, and is chlorinated to a chlorine content of 50 to 60% by weight. This is what I did. F Example Next, examples of the method of the present invention will be shown, but the present invention is not limited thereto. [Example 1] The reaction solution used for separation and drying was synthesized as follows. In a reactor equipped with a stirrer and a condenser, 1 kg of polyethylene with a molecular weight of 2800 and a density of 0.92 was uniformly dissolved by adding 10 carbon tetrachloride at 90°C under pressure, and the air was completely purged with nitrogen gas to dissolve 3 g of polyethylene.
of benzoyl peroxide was added and thoroughly stirred. Gaseous chlorine was blown into the reactor from the bottom, and the introduction of chlorine gas was stopped when the chlorine content reached 53% by weight. After removing residual chlorine gas with nitrogen gas,
The reaction solution was concentrated to a solid concentration of 40% by weight to obtain a stock solution, which was dried using the following centrifugal thin film device. The centrifugal thin film device used was a Hitachi Vertical Inclined Blade Control Device manufactured by Hitachi, Ltd. This device consists of an upper cylindrical can-shaped evaporation section and a lower vapor chamber. The evaporator has a built-in rotor.
This stirring blade was rotated at a speed of 230 rpm leaving a clearance of 5 mm from the inner wall of the can, thereby forming the solution into a thin film. The outside of the evaporation section was covered with a jacket, and the thin film was heated and dried using a heat transfer area of 0.2 m ² . The stock solution was fed from the upper evaporation section and dried while falling in a thin film inside the can. The vapor chamber and solvent exhaust line were maintained at -260 mmHg by a vacuum pump. Table 1 shows the operating conditions and results at this time. [Example 2] Average molecular weight instead of polyethylene in Example 1
5800, using 1 kg of polypropyne with a density of 0.915,
The same reaction as in Example 1 was carried out to obtain chlorinated polypropylene having a chlorine content of 56% by weight. This reaction solution was concentrated to a solid concentration of 40% by weight to obtain a stock solution. In the same manner as in Example 1, internally plastic chlorinated polypropylene was separated and dried from this stock solution using a Hitachi vertical inclined blade controller. Table 2 shows the operating conditions and results at this time.

【table】

[Table] [Example 3] Instead of the polyethylene used in Example 1, 1 kg of polyethylene having an average molecular weight of 35,000 and a density of 0.913 was reacted until the chlorine content became 55.5% by weight. After removing residual chlorine gas with nitrogen gas, the reaction solution was concentrated to 25% by weight, and the stock solution was dried in the same manner using a centrifugal thin film apparatus. The operating conditions and results at this time are shown in Table 3.

[Comparative example 1]

The same stock solution used in Example 1 was sprayed using a rotating disc type spray dryer, but none of the solutions could be dried, and the undried product adhered to the can body in the drying chamber.
It became colored and decomposed over time. The operating conditions are as follows. In this method, the solvent is not sprayed in granular form, but in the form of strings, so there is almost no solvent evaporation, and the solvent remains undried and adheres to the can body before being fed any further. I couldn't. Further, in this method, even when the stock solution of Example 2 was used, it could not be dried and solidified.

[Comparative example 2]

The same stock solution as in Example 1 was poured into a hot water solidification tank containing boiling water while being stirred, but the solidification process could not be continued because it adhered and deposited on the side walls of the tank and the shaft of the stirrer. . G Effects of the Invention Thus, according to the present invention, internally plastic CPO exhibiting low-temperature softening properties can be easily and quickly separated into a thin film from a carbon tetrachloride solution to a polymer concentration of 99% by weight or more.
Granular shape that can be dried and has excellent hue
This is an extremely useful method industrially as it can provide CPO.

Claims (1)

[Claims] 1. A carbon tetrachloride solution in which a chlorinated polyolefin with internal plasticity with a chlorine content of 50 to 60% by weight is dissolved is supplied to a centrifugal thin film evaporator and dried until the carbon tetrachloride concentration becomes 1% by weight or less. Separation and separation of internally plasticized chlorinated polyolefins
Drying method.