JPH0320132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a method for producing a synthetic resin of excellent quality by regulating the dissolved oxygen concentration in a solution. [Prior art] In methods for producing synthetic resins by interfacial polymerization, solution polymerization, etc. using methylene chloride as a solvent, the methylene chloride solution of the polymer obtained by polymerization is usually diluted with water or the like. Wash and purify.
The purified polymer solution is heated to evaporate methylene chloride, and is then powdered, sheeted, stranded, etc., to obtain a polymer. For example, before a purified polymer solution is powdered using a kneader or the like, it is concentrated to bring the concentration closer to the gelling region so that it can be easily powdered, and then methylene chloride is evaporated using a powdering device such as a kneader. At this time, the concentrator and powderizer are heated at a high temperature of 100°C or higher to efficiently evaporate methylene chloride to obtain polymer powder. The present inventors learned that carbon tetrachloride (CCl ₄ ) is produced during heating and evaporation during concentration and pulverization.
The generated CCl ₄ is distributed between methylene chloride and the polymer, which adversely affects the quality of the product polymer;
We also learned that when methylene chloride is recovered, CCl ₄ accumulates in the methylene chloride, increasing the negative effects. [Object of the Invention] As a result of extensive research by the present inventors in order to avoid the above-mentioned disadvantages, we have found that CCl ₄ can be produced by reducing the dissolved oxygen concentration in the methylene chloride solution of the polymer before concentration and powdering to 20 ppm or less. The present invention was completed based on the knowledge that this can be suppressed. That is, the present inventors aimed to obtain a polymer of excellent quality, and the purpose was to reduce the dissolved oxygen concentration in methylene chloride purified after polymerization and before evaporation removal to 20 ppm or less, and to concentrate and powder it. This is achieved by [Structure of the Invention] The synthetic resins targeted by the present invention include thermoplastic resins such as polycarbonate, polyester polycarbonate, polycarbonate carbamate, and polyarylate, which use methylene chloride as a solvent during resin production. Methylene chloride used here refers to methylene chloride and chlorinated hydrocarbons such as dichlorobenzene, chloroform, tetrachloroethane, trichloroethane, dichloroethane, 1,2 dichloroethylene, or dioxane, tetrahydrofuran, acetophenone, toluene, It includes mixtures with xylene, cyclohexane, acetone, n-heptane, etc., but contains 60% methylene chloride.
A mixture containing the above is preferred, and a mixture containing 100% methylene chloride is particularly preferred. Polycarbonate resins are polymers or copolymers obtained by the phosgene method in which various dihydroxydiaryl compounds and phosgene are reacted, and a typical example is 2,2-bis(4-hydroxyphenyl). ) Polycarbonate resins made from propane (bisphenol A). As the dihydroxydiaryl compound,
In addition to bisphenol A, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis( 4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-
hydroxy-3-methylphenyl)propane,
1,1-bis(4-hydroxy-3-tert-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-
Bis(4-hydroxy-3,5 dibromophenyl)propane, 2,2-bis(4-hydroxy-
Bis(hydroxyaryl)alkanes such as 3,5 dichlorophenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclopentane,
Bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl dihydroxy diaryl ethers such as ethers, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxy-
Dihydroxydiaryl sulfides such as 3,3'-dimethyldiphenyl sulfide, 4,4'-
Dihydroxydiphenyl sulfoxide, 4,4'-
Dihydroxydiaryl sulfoxides such as dihydroxy-3,3'-dimethyldiphenyl sulfoxide, dihydroxydiaryl such as 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone Examples include sulfones. These may be used alone or in combination of two or more, and in addition to these, hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, etc. may be used in combination. The polyester polycarbonate resin is a copolymer obtained by the reaction of various dihydroxydiaryl compounds mentioned in the section of polycarbonate resin, phosgene, and acid chloride (terephthalic acid chloride, isophthalic acid chloride, etc.). The polycarbonate carbamate is a copolymer obtained by the reaction of piperazine (or dipiperidine), a dihydroxydiaryl compound, and phosgene. Polyarylate is a copolymer obtained by the reaction of a dihydroxydiaryl compound and an acid chloride. Normally, the methylene chloride used as a solvent during the production of these resins does not initially contain a large amount of _CCl4 , but when separating the polymer and methylene chloride from a methylene chloride solution of purified polymer, the chlorination of the polymer When a methylene solution is heated to a high temperature, CCl ₄ is formed. This CCl ₄
is dissolved in methylene chloride in any proportion and remains in the polymer solution. When the polymer and methylene chloride are separated, the CCl ₄ remaining in the polymer solution is distributed into the polymer and methylene chloride in a ratio appropriate to the separation conditions. The color tone of pellets and molded pieces obtained from CCl ₄ -containing polymers produced by such a method is not fully satisfactory. For this reason, it is preferable that the CCl ₄ concentration in the polymer solution before separating methylene chloride and the polymer is as low as possible. As a method for lowering the CCl ₄ concentration in the polymer solution, there is a method of reducing the dissolved oxygen concentration in the methylene chloride solution of the polymer when the methylene chloride solution of the polymer is heated and concentrated into powder. At this time, the dissolved oxygen concentration in the methylene chloride solution of the polymer is preferably 20 ppm or less, preferably 10 ppm or less. Typically, the dissolved oxygen concentration in a methylene chloride solution of the polymer is about 30 ppm or more when operating in air. Dissolved oxygen in a methylene chloride solution of this polymer increases as oxygen in the air dissolves. For example, when producing a polymer, polymerization, washing, etc. are performed in a stirring tank. Furthermore, the methylene chloride and the methylene chloride solution of the polymer in the storage tank are circulated to the storage tank using a centrifugal pump, and a portion is sent to the next process. There is a gas phase inside these stirring tanks and storage tanks, and it is impossible to operate them in a completely airtight state. Air entering from the stirring gland, vent pipe, etc. may cause chlorination of the polymer during stirring and liquid circulation. Dissolve in methylene solution. Methods for reducing dissolved oxygen in a polymer methylene chloride solution include using raw materials from which dissolved oxygen has been removed and operating the entire manufacturing process under pressure with inert gas to block oxygen, or concentrating and powdering. There are two methods for removing dissolved oxygen in the methylene chloride solution of the polymer, such as by blowing an inert gas into the solution, and by adding a reducing agent. Specifically, the method of removing dissolved oxygen by adding a reducing agent is not preferred because if the reducing agent is a solid or a liquid with a high boiling point, it may remain in the product polymer and adversely affect the quality of the product. As mentioned above, it is difficult to operate the method in an airtight manner, so it is preferable to remove dissolved oxygen by suctioning an inert gas. Examples of the inert gas include nitrogen gas and argon gas. For example, by inhaling nitrogen gas in an amount twice as much as the methylene chloride solution of the polymer into a methylene chloride solution of the polymer before being concentrated and powdered, the dissolved oxygen concentration in the methylene chloride solution of the polymer decreases to about 1/10. can be removed relatively easily. Note that when methylene chloride is removed by evaporation from a methylene chloride solution of a polymer without removing dissolved oxygen in the methylene chloride solution of the polymer, if the recovered methylene chloride is used as it is, as the number of circulation increases, As CCl ₄ increases, the negative effects on the quality of the produced polymer, such as worsening of the color tone, increase. Next, a method for producing the polymer will be described. Polymerization can be carried out by an interfacial polymerization method in which phosgene or phosgene is reacted with an acid chloride or an acid chloride in the presence of a dihydroxydiaryl compound, a diamine compound, an organic solvent, water, or a caustic alkali, or by an interfacial polymerization method in which a dihydroxydiaryl compound or diamine compound is dissolved and an acid acceptor is reacted. There is a solution polymerization method in which phosgene or phosgene is reacted with acid chloride or acid chloride in an organic alkali and an organic solvent. The polymer solution after polymerization may be diluted with methylene chloride as necessary for washing and purification. In order to remove impurities in the polymer solution, it is washed with an alkaline aqueous solution, an acid aqueous solution, water, etc. Washing is performed using a mixer settler, centrifugal extractor, etc. Before the purified polymer solution is pulverized using a kneader or the like, it is heated to remove methylene chloride and concentrated in order to bring it closer to the gelling region so that it can be easily pulverized. The concentrated polymer solution is powdered by heating the polymer solution with a kneader and powdering it while removing methylene chloride, or by adding a non-solvent to precipitate the polymer. Since the polymer contains methylene chloride, a non-solvent, etc., it is dried according to a conventional method to remove these solvents. [Effects of the Invention] The methylene chloride solution of the polymer having a dissolved oxygen concentration of 20 ppm or less according to the present invention suppresses the production of CCl ₄ when methylene chloride is removed by evaporation. For this reason,
Since the powdered polycarbonate obtained using a methylene chloride solution of this polymer contained almost no CCl ₄ , the resulting pellets and molded pieces had a good color tone and were of almost satisfactory quality. [Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 Pure water 15.3 and caustic soda were placed in 25 glass-lined containers equipped with baffles, a stirrer, a phosgene blowing tube, a thermometer and a discharge pot at the bottom.
1.03 kg (25.7 mol), 3.0 g of sodium hydrosulfite, and 2790 g (12.2 mol) of bisphenol A were added in sequence with stirring and completely dissolved. Next, 10wt/vo1% caustic soda aqueous solution 3.1
(7.65 mol) and methine chloride 7.65 were added, and while keeping the liquid temperature at 20℃ by external cooling, 1.38Kg of phosgene was added.
(13.9 mol) in 60 minutes with stirring, then
66.7 g of paratertiary butylphenol and 3.1 g of triethylamine were added and stirred for 1 hour to polymerize. After polymerization, add methylene chloride to the lower organic phase.
After adding 14.1 and washing once with pure water, add 10% phosphoric acid.
3.0 was added to neutralize the mixture, and the mixture was washed three times with pure water to obtain a purified methylene chloride solution. This 10wt% polymer in methine chloride solution (15)
When analyzed, the dissolved oxygen concentration was 30 ppm, CCl ₄
The concentration was 5 ppm. Inject nitrogen gas into this polymer solution at a rate of 6.0/min.
Measurement of dissolved oxygen concentration after 10 minutes of blowing
It was 0ppm. This was placed in a nitrogen-substituted stainless steel (SUB-316) 20 autoclave.
The temperature was maintained at 180°C for 2 hours without stirring. After heat treatment, cool to room temperature and use Shimadzu GC7A.
CCl ₄ in a methylene chloride solution of the polymer was determined by gas chromatography using
It was 5ppm. This polymer solution of methylene chloride was heated again to distill off the methylene chloride to obtain a powdery polycarbonate. After drying the powdered polycarbonate in a conventional manner, it is not added any additives such as heat stabilizers.
The mixture was kneaded into pellets using a φ extruder (manufactured by Tanabe Plastics Co., Ltd.). (Kneading temperature: 280℃, screw rotation speed: 40r.pm, mixing speed: 1.6Kg/Hr, polymer residence time: 2 minutes) The shape of the generated pellets is 1.3mmφ and 2.5mmL.
It was of (length). The pellets were dried in a conventional manner, and YI (yellowness) was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., model TC-55D). As a result, the YI of the pellets was 6, which was good. Example 2 Nitrogen gas was blown into a methylene chloride solution of 10 wt % polymer produced in the same manner as in Example 1 at 6.0/min for 4 minutes to remove dissolved oxygen. Dissolved oxygen concentration was 5 ppm. A methylene chloride solution of the polymer was placed in a stainless steel 20 autoclave purged with nitrogen gas in the same manner as in Example 1, and held at 180° C. for 2 hours without stirring. As a result, the CCl ₁ concentration in the methylene chloride solution of the polymer after heat treatment was 16 ppm. This methylene chloride polymer solution was pulverized and dried, and then kneaded into pellets using an extruder, and the YI was 7. Example 3 Nitrogen gas was blown into a methylene chloride solution of 10 wt % polymer produced in the same manner as in Example 1 at 6.0/min for 2 minutes to remove dissolved oxygen. Dissolved oxygen concentration was 10 ppm. A methylene chloride solution of the polymer was placed in a stainless steel 20 autoclave purged with nitrogen gas in the same manner as in Example 1, and held at 180° C. for 2 hours without stirring. As a result, the CCl ₄ concentration in the methylene chloride solution of the polymer after heat treatment was 25 ppm. This methylene chloride polymer solution was powdered and dried, and then kneaded into pellets using an extruder, and the YI was 8. Comparative Example 1 Polymer concentration produced by the same method as Example 1 was
A methylene chloride solution of the polymer having a dissolved oxygen concentration of 30 ppm and 10 wt% was placed in the same stainless steel 20 autoclave (without nitrogen substitution) used in Example 1, and held at 180° C. for 2 hours without stirring. As a result, the CCl ₄ concentration in the methylene chloride solution of the polymer after heat treatment was 65 ppm, and the YI of the pellets obtained by kneading this PCM solution with an extruder after powdering and drying was 13, which was poor. The above results are summarized in a table below. 【table】

Claims (1)

[Scope of Claims] 1. After carrying out a polymerization reaction using methylene chloride as a solvent, when obtaining a polymer by removing methylene chloride as a solvent from a methylene chloride solution by evaporation, A method for obtaining a polymer characterized by having a dissolved oxygen concentration of 20 ppm or less. 2. The method for obtaining a polymer according to claim 1, which comprises controlling the dissolved oxygen concentration to 20 ppm or less by blowing inert gas.