JPS6150963B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a chlorinated polymer, and more particularly, to a method for producing a chlorinated polymer, in which a solution and a solid polymer are separated for the purpose of reducing the amount of carbon tetrachloride remaining in the chlorinated polymer. The present invention relates to a method for reducing the amount of carbon tetrachloride remaining in a chlorinated polymer, characterized by using a system solvent in combination. Aliphatic hydrocarbon polymers or copolymers (e.g. polyisoprene, polypropylene, polyethylene,
When chlorinating polybutadiene, ethylene/propylene copolymer, natural rubber), the commonly used method is to dissolve these polymers in a halogenated solvent, especially carbon tetrachloride, and to react at a reaction temperature of 70 to 130°C.
It consists of introducing a certain amount of chlorine gas into this solution at .degree. The chlorinated polymer obtained by the above chlorination reaction can be easily isolated in solid form by steam distillation, hot water treatment, spray drying, or the like. This solid chlorinated polymer may be dried in a conventional manner, but even after drying, a significant amount (e.g. 5 to 10 parts by weight of carbon tetrachloride per 100 parts by weight of chlorinated polymer) of carbon tetrachloride is present in the chlorinated polymer. remains. This residual carbon tetrachloride may evaporate into the atmosphere as a vapor during use of the chlorinated polymer in some environments, and is generally undesirable due to its harmful nature. For this reason, many attempts have been proposed to reduce residual carbon tetrachloride. Namely, there are 1. Emulsification hot water treatment method, 2. Alcohol solidification method (British patent 1093850), 3. Method for lowering the secondary rearrangement point of chlorinated polymer (Japanese Patent Application Laid-Open No. 1982-68290), etc., but method 1 using an emulsifier is There are many reports, but in all of them, residual emulsifiers lead to deterioration of quality such as deterioration of water resistance and heat resistance. The accompanying decrease in thermal stability is unavoidable. On the other hand, in the method of lowering the secondary rearrangement point by adding other components to the chlorinated polymer, the added component is a low molecular weight substance with a very low secondary rearrangement point, and the amount added is also lower than that of the chlorinated polymer. Due to the large amount of chlorinated polymers, the softening point of the chlorinated polymers is also significantly lowered, and the physical properties of the chlorinated polymers are now different from those of the original chlorinated polymers. As a result of extensive research into a method for producing a chlorinated polymer that reduces residual carbon tetrachloride without changing the physical properties of the original chlorinated polymer, the inventors found that the chlorinated polymer before being subjected to the solvent separation process of carbon tetrachloride solution, at least 20% of the total solvent
The present inventors have discovered that the object can be achieved by adding a halogenated solvent other than carbon tetrachloride to the chlorinated polymer solution so that the halogenated solvent accounts for at least % of carbon tetrachloride. Figure 1 shows chlorinated polyisoprene with a carbon tetrachloride content of 7.6% when separated and recovered from a solution containing only carbon tetrachloride, dissolved in various mixing ratios with carbon tetrachloride and other halogen-based solvents, and the solution This is the result of measuring the total amount of residual solvent after heat-treating the solid chlorinated polymer under the same concentration and temperature conditions as above, and drying the obtained solid chlorinated polymer with air at 110° C. for 60 minutes. Figure 1 shows that chloroform (boiling point 61.2°C) is a solvent relatively close to carbon tetrachloride (boiling point 76.6°C).
℃), 1,2-dichloroethane (boiling point 83.7℃),
1,1,1-trichloroethane (boiling point 74.1℃),
It can be seen that only trichlene (boiling point 87.2°C) has the effect of rapidly reducing the total residual solvent when used in a relatively small amount. Furthermore, as is clear from FIG. 1, the amount of residual solvent formed cannot be reduced in any proportion of percrene (boiling point 121.1°C), which is a high boiling point halogen solvent. On the other hand, methylene chloride (boiling point 41.6°C), which is a low boiling point halogen solvent, is advantageous in normal industrial manufacturing methods because the total amount of residual solvent only falls below 3% when an amount more than four times that of carbon tetrachloride is used. isn't it. It was completely unexpected and surprising that only solvents with relatively close boiling points would rapidly reduce the amount of residual solvent formed. In addition, the permissible concentration of vapor for each solvent is carbon tetrachloride (10 ppm), chloroform (50 ppm), 1,2-dichloroethane (50 ppm), 1,1,1-trichloroethane (200 ppm), and trichlene (50 ppm). Both are less toxic than carbon tetrachloride, and have a great effect on greatly improving safety from a health and safety perspective. Further, the total amount of residual solvent depends on the composition of the solvent, but this amount is preferably 5% or less, preferably 3% or less from the viewpoint of toxicity in subsequent use. The solvent composition of the solution in which the total amount of residual solvent is 3% or less may contain at least 20% or more of a halogen-based solvent excluding carbon tetrachloride. The aliphatic hydrocarbon polymers used as starting materials for the present invention include all known chlorinated polymers, such as the aforementioned polyisoprene, polypropylene, polyethylene, polybutadiene, ethylene/propylene copolymers, and the like. The halogenated solvent used in the present invention has a boiling point of 60
℃ to 90℃, including chloroform, 1,2-dichloroethane, 1,1,1-
Particularly preferred are trichloroethane and trichlene. Further, the chlorinated polymer solution according to the present invention can be obtained by adding a predetermined amount of the halogenated solvent according to the present invention after the chlorination reaction is completed, but if necessary, after distilling a portion of carbon tetrachloride, the halogenated polymer solution By adding , it is possible to avoid increasing the proportion of the halogenated solvent according to the present invention. In addition, in special applications of chlorinated polymers, for example, the total residual solvent content may be 1%.
For the following requirements, it is sufficient to redissolve the chlorinated polymer (residual carbon tetrachloride 7.6%) isolated in a conventional manner in the halogenated solvent of the present invention and then isolate it in solid form. It is something that can meet your needs. In addition, since the boiling point of the halogenated solvent used in the present invention is close to that of carbon tetrachloride, the method for isolating the chlorinated polymer according to the present invention can be carried out using conventional isolation methods such as hot water treatment, steam treatment, and treatment with a spray dryer. There is no problem in using either method. Although conventional methods for drying the isolated solid chlorinated polymer are sufficient, drying is preferably carried out at a temperature approximately 20°C higher than the boiling point of the highest boiling point solvent contained. desirable. Examples are shown below. Example 1 As an aliphatic polymer to be chlorinated, 3 kg of polyethylene with a melt index of 70 and a density of 0.925 and 15 g of benzoyl peroxide were uniformly dissolved in carbon tetrachloride 60 under pressure and converted into a gaseous state at a temperature of 100 to 160°C. After introducing chlorine gas and continuing to introduce chlorine gas until the chlorine content reached 68.0% by weight, hydrochloric acid gas and unreacted chlorine gas were expelled with nitrogen gas. A portion of this reaction solution was taken out, carbon tetrachloride was expelled under reduced pressure and concentrated, and the solid content concentration was determined to be 32.5.
It was %. From this carbon tetrachloride/1,2-
The proportion of dichloroethane is 10/0, 9/1, 8/2, 7/3,
Solutions were prepared such that the ratio was 5/5 and 3/7, and the solid content concentration was 10%. 500 g of each solution was put into a hot water treatment tank equipped with a stirrer at 95° C., and hot water treatment was performed for 3 minutes. The isolated chlorinated polyethylene was dehydrated using a centrifuge and then dried at 50°C for 24 hours and then at 110°C for 60 minutes. The measurement result of the total amount of residual solvent is 6.7 respectively.
%, 4.7%, 2.1%, 1.4%, 0.9%, and 0.8%. Example 2 Concentrated solution prepared in Example 4 (32.5% solids)
The total amount of residual solvent after drying was measured in the same manner as in Example 1 using chloroform and chloroform while changing the concentration, that is, the ratio of carbon tetrachloride/chloroform. The results are shown in Table 1.

[Table] Example 3 70g of degraded cis-1,4-polyisoprene
Uniformly dissolved in carbon tetrachloride of 70-100% under pressure
A predetermined amount of chlorine gas was introduced into the system at a temperature of °C to produce chlorinated cis-1,4-polyisoprene with a chlorine content of 65%. This material was placed in a hot water treatment tank at 95°C, the solid chloride was isolated and dried in the same manner as in Example 1, and the amount of residual carbon tetrachloride was 8.2.
% of chlorinated cis-1,4-polyisoprene was obtained.
This product was redissolved in a mixed solvent of carbon tetrachloride/trichloride at various ratios (all concentrations were adjusted to 15%), and this redissolved solution was subjected to the same operation as in Example 1. , 1-trichloroethane system. The results are shown in Table 2. As a comparative example, the above carbon tetrachloride/triclene system was replaced with carbon tetrachloride/perchloride and carbon tetrachloride/methylene chloride systems, and all other operations were performed in the same way as for the carbon tetrachloride/triclene system, and the total amount of residual solvent was Measurements were made. The results are shown in Table 3.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows the relationship between the ratio of CCl ₄ to each halogen solvent and the total amount of residual solvent in chlorinated polyisoprene (residual carbon tetrachloride content: 7.6%).

Claims (1)

[Claims] 1. Production of a chlorinated polymer, which comprises separating the chlorinated polymer and carbon tetrachloride from a solution obtained by chlorinating an aliphatic hydrocarbon polymer in a carbon tetrachloride solvent. In this method, the chlorinated polymer solution after the completion of the chlorination reaction described above has a boiling point of 60°C to 90°C.
After adding a halogenated hydrocarbon solvent excluding carbon tetrachloride to the total solvent of the solution in an amount of at least 20% by weight, the chlorinated polymer and the solvent are mixed. 1. A method for reducing the amount of residual carbon tetrachloride in a chlorinated polymer, comprising separating it. 2. The method according to claim 1, wherein the total residual amount of solvent is 3% or less. 3 Halogenated hydrocarbon solvents other than carbon tetrachloride include chloroform, 1,2-dichloroethane,
3. The method according to claim 1 or 2, which is one or a mixture of two or more of 1,1,1-trichloroethane and trichlene. 4 Claims 1 to 3, in which the solvent is separated by adding a halogenated hydrocarbon solvent other than carbon tetrachloride to the chlorinated polymer solution at the end of the chlorination reaction and before the solvent separation step. Any one of up to
The method described in section. 5. Any one of claims 1 to 4 in which solvent separation is carried out by adding a halogenated hydrocarbon solvent excluding carbon tetrachloride to a chlorinated polymer solution from which carbon tetrachloride has been partially separated. The method described in Section 1. 6 Claim No. 6 in which solvent separation is carried out by adding a halogenated hydrocarbon solvent other than carbon tetrachloride to a chlorinated polymer with residual carbon tetrachloride isolated by separation from carbon tetrachloride. The method described in any one of paragraphs 1 to 5.