JPH08165342A - Method for cleaning and drying resin production apparatus - Google Patents

Abstract

PURPOSE: To obtain a method for cleaning and drying a resin production apparatus whereby a resin attached to the apparatus is cleaned by using a solvent capable of decomposing and dissolving the resin without using a halogenous solvent strictly regulated by waste water regulations. CONSTITUTION: In a resin production apparatus comprising a reaction vessel for the former condensation step and a vented horizontal or vertical twin-screw reactor for the latter condensation step, only the reaction vessel for the former step is cleaned with at least one solvent selected from among phenol, benzyl alcohol, pyridine, dimethylformamide, ethyl acetate, and tetrahydrofuran and dried in the substantial absence of oxygen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning and drying an apparatus for resin production.

[0002]

2. Description of the Related Art Conventionally, there have been some legal restrictions on the method of cleaning resin production equipment in terms of safety and hygiene and toxicity, but with regard to chlorinated solvents, drainage standards have been established except for some of them. There wasn't. However, recently, from the viewpoint of safety and hygiene and toxicity, legal regulations concerning wastewater have become more stringent, and the use of the washing solvent that has been used so far is restricted. For example, since 1994, the use of chlorinated solvents such as dichloromethane as a washing solvent for a resin, particularly a melt polycondensation resin manufacturing apparatus, is restricted due to the strengthening of wastewater standards. Furthermore, since 1997, the effluent standard for chlorinated solvents, especially dichloromethane, will be 0.2 mg / liter.

On the other hand, regarding an aromatic polycarbonate as a typical example obtained by melt polycondensation, the solubility of the aromatic polycarbonate is, first of all, the crystalline state and the properties of the aromatic dihydroxy compound used for the preparation. Depends on. For example, hydroquinone, 4,4 '
Polycarbonates which crystallize rapidly and in large quantities, such as polycarbonates made from -dihydroxy-diphenylmethane, 4,4'-dihydroxy-diphenyl-1,2-ethane, etc., are usually insoluble in any solvent.

State of crystallization inhibition (for example, rapid cooling from liquid or rapid evaporation of solvent from solution)
Thus, polycarbonates made from 4,4'-dihydroxy-diphenylalkanes are some of the commonly used solvents,
For example, it is soluble in methylene chloride, m-cresol, pyridine and dimethylformamide. Most other solvents swell.

Substituents attached to central carbon atoms and / or aromatic residues of 4,4'-dihydroxy-diphenylmethane derivatives generally increase solubility. Polycarbonate
Copolymers also dissolve better than the corresponding homopolymers.

Further, many aromatic polycarbonates and copolycarbonates (for example, a polycarbonate formed from 4,4'-dihydroxy-diphenyl-1,1-cyclohexane and its copolymer with bisphenol A) are used as esters, ketones, cyclic esters, It is soluble in solvents suitable for coatings such as aromatic hydrocarbons. A solution of crystalline polycarbonate having a high solid content gels by crystallization.

In this aromatic polycarbonate having crystallinity, solubility or swelling property is greatly reduced due to a high degree of crystallization or a combination of molecular orientation and crystallinity. None of the aromatic polycarbonates tested so far is soluble in water, aliphatic hydroxy compounds, acids with carboxyl groups, aliphatic and cycloaliphatic hydrocarbons.

Practical solvents for polycarbonates made from bisphenol A include 1,1,2,2-tetrachloroethane, dichloromethane, cis-1,2-dichloroethylene, chloroform, 1,1,2-trichloroethylene.

Solvents having a very limited solubility include 1,2-dichloroethane, thiophene, dioxane, tetrahydrofuran, acetophenone, anisole, benznitrile, cyclohexanone, dimethylformamide and nitrobenzene.

Solvents for which a swelling effect is observed include benzene, chlorobenzene, 1,2-dichlorobenzene and 1-
Examples thereof include chloronaphthalene, tetrahydronaphthalene, diphenyl ether, epichlorohydrin, glycol carbonate, acetone, ethyl acetate, carbon tetrachloride, nitromethane, acetonitrile and 1,1-dichloroethane.

Aliphatic and alicyclic hydrocarbons, ethers,
Acids with carboxyl groups do not dissolve or swell polycarbonates of this family.

On the one hand, the solubility of many aromatic polycarbonates in commonly used solvents, especially methylene chloride, is achieved by solvent evaporation coatings, films, using methods and equipment that are considered standard in the plastics industry. While facilitating processing into fibers, its application is necessarily limited by the fact that it dissolves and swells in the presence of many solvents.

In addition, high molecular weight polyethylene glycol is used as a solvent for the aromatic polyester resin, but it has a problem such as residual after use.

Further, in JP-A-6-56984, a stainless steel reactor is washed with a liquid containing an aromatic hydroxy compound, and then the aromatic dihydroxy compound and the diaryl carbonate are reacted with each other to prevent coloring. It has been proposed to obtain aromatic polycarbonates. However, when a stainless steel reactor is washed with a liquid containing an aromatic hydroxy compound, active iron elements are generated on the surface of the reactor, and a sufficiently satisfactory colorless aromatic polycarbonate cannot be obtained. .

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 6-200008 proposes a method in which, when a polycarbonate is produced by a transesterification method, after completion of the reaction, the reaction apparatus is washed with a phenolic compound. However, the material of the reaction device is not specified, and the part to be cleaned is only described as the liquid contact part of the reaction device, and there is no limitation on what kind of reaction device is cleaned. .

Since the aromatic polycarbonate has a high viscosity, it is general that the pre-condensation step and the post-condensation step are separately produced in the transesterification method. That is, in the precondensation step, a tank reactor having a stirring blade is used, and in the postcondensation step, a horizontal or vertical biaxial postcondensator with a vent is used to obtain a highly viscous and colorless aromatic polycarbonate. . Although it is easy to wash the tank reactor having a stirring blade used in the precondensation step, it is extremely difficult and disadvantageous to wash the vented horizontal or vertical biaxial postcondensator used in the postcondensation step. is there.

That is, a horizontal or vertical biaxial post-condensation machine with a vent is used to increase the viscosity of the aromatic polycarbonate obtained in the pre-condensation step to a high molecular weight with a residence time as short as possible.
The shaft-to-shaft clearance is reduced to improve the surface renewal capability and to provide a high vacuum sealing capability.
If such a post-condensation machine is washed with a solvent, etc., the resin adhering to the clearance between the shafts will no longer be sufficiently washed with the solvent, etc., and it will take a long time to remove the resin, so there will be a seal between them. There is a problem in that the time taken to immerse the sealing portion in relation to the ability in a solvent or the like becomes long, the sealing material deteriorates, and the hermeticity is lost.

[0018]

The inventors of the present invention have found that only the tank-type pre-condensation reactor portion of the resin manufacturing apparatus is used as a washing solvent in, for example, phenol, benzyl alcohol, pyridine, dimethylformamide, ethyl acetate and tetrahydrofuran. One or two or more selected from the above are used, and after washing, they are dried in the substantial absence of oxygen, thereby solving the above problems and eliminating waste water regulations. And completed the invention.

That is, in the present invention, only the tank-type precondensation reactor portion of the resin-manufacturing apparatus in which the resin-manufacturing apparatus includes a tank-type precondensation reactor and a vented horizontal or vertical biaxial postcondensation machine is used as a solvent. The present invention relates to a method for cleaning and drying a resin manufacturing apparatus, which comprises cleaning the resin manufacturing apparatus and drying in the absence of oxygen as a treatment step after cleaning.

In order to produce a high molecular weight polycarbonate, in the first condensation reaction step, the reaction in the initial stage of polymer production is carried out in a tank reactor having an ordinary stirring blade to synthesize a prepolymer, and subsequently, a prepolymer is synthesized. In the second polycondensation reaction step, it is necessary to carry out the polycondensation reaction in an apparatus such as a horizontal or vertical post-condensation machine with a vent. Generally, the first polycondensation reaction step is a batch method, while the second polycondensation reaction step is a continuous method in order to increase the polymer production capacity.

In the present invention, the material of the tank-type precondensation reactor of the resin manufacturing apparatus is such that the iron content is 20% by weight or less, preferably the iron content.
It should be 10% by weight or less. Specific examples of such materials include Hastelloy B (64 wt% nickel, 1 wt% chromium, 28 wt% molybdenum, 5 wt% iron), Hastelloy C-276 (59 wt% nickel, 15.5 wt% chromium, molybdenum). 16% by weight, iron 5.5% by weight), Hastelloy G-30
(Nickel 43 wt%, Molybdenum 7 wt%, Iron 20 wt%, Chromium 22 wt%, Aluminum 12 wt%), Inconel 600 (Nickel 76 wt%, Chromium 15.5 wt%, Iron 8 wt%), Inconel 657 (Nickel 48% by weight, chromium 50% by weight), cupro nickel C-7150 (30% by weight nickel,
Copper 70% by weight), nickel 200 (nickel 99.5% by weight, carbon
0.08% by weight), Monel 400 (66.5% by weight nickel, 31.5% copper)
%, Iron 2% by weight), glass, Teflon, and the like. The content of such iron is 20
The portion forming the material having the composition of less than or equal to% by weight may be integrally formed with these materials, but the same effect can be obtained by forming a layer of these materials on the surface by plating, thermal spraying, clad, etc. Can be obtained. It is also possible to use some of these materials in combination by selecting some from the materials having an iron content of 20% by weight or less.

As the resin, aromatic polycarbonate,
Polyester carbonate, polyarylate, aromatic polyester, nylon, polystyrene, polyvinyl chloride, polyolefin (polyethylene, polypropylene)
, ABS resin, AS resin, polyacetal, acrylic ester, silicon resin and the like. Among these, melt polycondensation resins such as aromatic polycarbonate, polyarylate, aromatic polyester, nylon and polyacetal are effective for the present invention.

The washing solvent for the tank-type precondensation reactor of the resin manufacturing apparatus may be one or more selected from phenol, benzyl alcohol, pyridine, dimethylformamide, ethyl acetate and tetrahydrofuran. Among these, phenol and benzyl alcohol are particularly preferable as the washing solvent for the melt polycondensation resin manufacturing apparatus. Further, for aromatic polycarbonate or polyarylate, phenol produced in the production process is distilled to be used, and for aromatic polyester, benzyl alcohol produced in the production process is distilled to be used. Is possible.

In the present invention, as a treatment step after washing, the remaining solvent is dried and removed by drying under heating and / or non-heating in the substantial absence of oxygen. A preferable example of the method of drying in the substantially absence of oxygen is a method of using nitrogen gas.

[0025]

The resin synthesized by the melting method, particularly aromatic polycarbonate and aromatic polyester, is difficult to dissolve the resin adhering to the inside of the production apparatus unless a halogen-based solvent is used. It is preferable to use a solvent other than the halogen-based solvent after use, since the standards for the drainage contained in the wastewater will become more severe in the future. Furthermore, after washing, by drying in the substantially absence of oxygen, oxidation of the remaining washing solvent is prevented and the synthesized resin is not adversely affected.

Particularly when an aromatic polycarbonate is synthesized by a melt transesterification method using bisphenol A and diphenyl carbonate as raw materials, phenol is produced. By recycling the distilled phenol, the aromatic polycarbonate adhering to the inside of the apparatus can be removed at low cost without using a halogen-based solvent. Further, the remaining phenols can be dried and removed by drying with nitrogen gas substantially free of oxygen under heating and / or without heating.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Synthesis Example 1 of aromatic polycarbonate 2,2-bis (4-hydroxyphenyl) propane 4.57 kg
(20 mol), 4.39 kg (20.5 mol) of diphenyl carbonate and 0.489 g (0.004 mol) of 4-dimethylaminopyridine.
Was placed in a 20-liter nickel-200 tank reactor, melted under nitrogen at 160 ° C, stirred well, and gradually heated up while depressurizing to distill off the phenol produced, and finally 1 torr The reaction was allowed to proceed at 260 ° C to obtain a prepolymer. This prepolymer was cut from the lower part of the reactor through a pole valve, a gear pump and a die by a cutter directly connected to the die in an apparatus under a nitrogen atmosphere at room temperature and pelletized. Contact with air was eliminated until the pellets were sufficiently cooled with nitrogen. The intrinsic viscosity [η] of the prepolymer was 0.3 dl / g. The viscosity average molecular weight (Mv) was 15,300. The hue value was A ₃₈₀ −A ₅₈₀ = 0.06. The hydroxyl group concentration in the prepolymer is 4 × 10 ^-4 mol /
g. The hydroxyl end of all the ends of the prepolymer was 40 mol%. The prepolymer is then mixed with 280
The mixture was sent to a vertical twin-screw post-condenser with a vent made of SOS-316 controlled at 0.1 ° C and 0.1 torr, and the reaction was performed at a residence time of 50 minutes. The obtained resin was colorless and transparent. The hue value was A ₃₈₀ −A ₅₈₀ = 0.09. The intrinsic viscosity [η] of the polymer was 0.5 dl / g. The viscosity average molecular weight (Mv) of the polymer was 28,500. The hydroxyl group concentration in the polymer was 6 × 10 ^-6 mol / g. The hydroxyl end of all the ends of the polymer was 15 mol%.

Synthesis Example 2 of Aromatic Polyester Copolymer 29.15 g (0.15 mol) of dimethyl terephthalate and the following formula

[0030]

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(In the formula, q is a positive number of 10 to 100.) 1.35 g of butanoloxypolydimethylsiloxane at both ends having a number average molecular weight (Mw) of 1247 (5% by weight based on the whole diol component). And 25.65 g of 1,4-butanediol were placed in a Hastelloy C-276 1 liter cylindrical flask, and a solution of isopropyl titanate (Ti (OC ₃ H ₇ ) ₄ ) in isopropyl alcohol (10%) was used as a catalyst. 0.9 g was added. Using a metal bath while introducing nitrogen gas into this mixture 1
The mixture was stirred at 80 ° C for 3 hours. The temperature of the metal bath was further raised to 70 ° C. for 30 minutes, and the pressure was reduced to 15 mmHg with a water-jet pump. After further heating and stirring under reduced pressure at 250 ° C for 1 hour, transfer the solution to a horizontal twin-screw post-condensing machine with a vent, and remove it by 0.3 mm.
After depressurizing to Hg, after reacting at 250 ° C for a residence time of 30 minutes,
The product was removed under nitrogen to give a white, highly viscous polymer.

The J-value of this polymer is phenol / o.
-Using dichlorobenzene (1/1) as a solvent, 25 ℃
It was 99 when measured by. In addition, from the infrared absorption spectrum, the characteristic absorption of polydimethylsiloxane is 800,
A slight absorption was observed at 1000 to 1100 cm ^-1 , 1
By H NMR, absorption of a methyl group bonded to the silyl group of polydimethylsiloxane was observed at 0.1 ppm.

From the above, it was confirmed that this polymer was a copolymer of aromatic polyester and polydimethylsiloxane. This copolymer was used as DSC (Mettler TA-20
00 type and Perkin Elmer 2C type)
It was found that the Tg was 54 ° C and the Tm (melting point) was 223 ° C.

Example 1 In order to remove the adhesion of the aromatic polycarbonate obtained in Synthesis Example 1, 200 m of phenol was added to a tank reactor made of nickel 200.
When 1 was added and the mixture was heated and stirred at the boiling point or below the boiling point for 1 hour, most of the attached aromatic polycarbonate was decomposed and melted into phenol. Then, the phenol solution was distilled off, and the phenol remaining in the tank was dried and removed at 25 to 100 ° C. using nitrogen gas.

Example 2 In order to remove the adhesion of the aromatic polyester copolymer obtained in Synthesis Example 2, benzyl alcohol was added to a cylindrical flask, and the mixture was heated and stirred at the boiling point or below the boiling point for 30 minutes. Most of the copolymer was decomposed and dissolved in benzyl alcohol. Then, the benzyl alcohol solution was distilled off, and the benzyl alcohol remaining in the cylindrical flask was dried and removed by heating the inside of the cylindrical flask to 100 ° C. or higher using nitrogen gas.

By distilling the phenol or benzyl alcohol in which the resin shown in the above Example 1 or 2 is dissolved, phenol or benzyl alcohol in which the resin is not dissolved can be obtained and can be used again.

Comparative Example 1 In order to remove the adhesion of the aromatic polycarbonate obtained in Synthesis Example 1, phenol was added to a tank type reactor made of nickel 200 in a precondensation step and a horizontal biaxial postcondensator with a vent in a postcondensation step. 200 ml and 100 ml were added, and the mixture was heated with stirring at 60 ° C. for 1 hour. Then, the phenol solution in the tank reactor and the post-condenser was distilled off, and the tank reactor and the post-condenser were dried to 100 ° C. while flowing nitrogen gas. As a result, the aromatic polycarbonate adhering to the inside of the tank reactor was almost decomposed and did not remain, but the aromatic polycarbonate inside the vented horizontal biaxial post-condensing machine remained around the shaft. In addition, the seal on the shaft was deteriorated and cracked. A vacuum test of a horizontal twin-screw post-condenser with a vent showed that it was 0.3 mmHg before washing, but
The vacuum level rose only to 00mmHg. It is considered that this is because the seal of the shaft portion was deteriorated.

Claims (11)

[Claims] 1. A resin-manufacturing apparatus including a tank-type pre-condensation reactor and a horizontal or vertical biaxial post-condensation machine with a vent, and only the tank-type pre-condensation reactor portion of the resin-manufacturing apparatus is washed with a solvent, A method of cleaning and drying a resin manufacturing apparatus, which comprises drying in the substantially absence of oxygen as a treatment step after cleaning. 2. The method for cleaning and drying a resin production apparatus according to claim 1, wherein the material of the tank-type precondensation reactor of the resin production apparatus is a metal material having an iron content of 20% by weight or less. 3. The method for cleaning and drying a resin production apparatus according to claim 2, wherein the material of the tank-type precondensation reactor of the resin production apparatus is a metal material having an iron content of 10% by weight or less. 4. The method for cleaning and drying a resin production apparatus according to claim 2, wherein the tank-type precondensation reactor of the resin production apparatus is made of Hastelloy. 5. The method for cleaning and drying a resin manufacturing apparatus according to claim 3, wherein the material of the tank-type precondensation reactor of the resin manufacturing apparatus is nickel 200. 6. The washing solvent for a tank-type precondensation reactor of a resin manufacturing apparatus is one or more selected from phenol, benzyl alcohol, pyridine, dimethylformamide, ethyl acetate and tetrahydrofuran. The method for cleaning and drying the resin manufacturing apparatus according to any one of claims 1 to 5. 7. The resin according to claim 1, which is a melt polycondensation resin.
7. The method for cleaning and drying the resin manufacturing apparatus according to any one of 6 above. 8. The method for cleaning and drying a resin production apparatus according to claim 7, wherein the melt polycondensation resin is aromatic polycarbonate or polyarylate. 9. The method for cleaning and drying a resin production apparatus according to claim 7, wherein the melt polycondensation resin is an aromatic polyester. 10. The method for cleaning and drying a resin production apparatus according to claim 7, wherein the washing solvent for the tank-type precondensation reactor of the molten polycondensation resin production apparatus is phenol. 11. The washing solvent for the tank-type pre-condensation reactor of the melt polycondensation resin production apparatus is benzyl alcohol.
10. The method for cleaning and drying the resin manufacturing apparatus according to any one of items 1 to 9.