JP4344621B2 - Cleaning method for inorganic materials - Google Patents

Description

  The present invention relates to a method for cleaning an inorganic member. More specifically, the thermoplastic resin is removed from an inorganic member (for example, a glass member, a ceramic member, or a metal member) to which a thermoplastic resin having a group of —COO— and / or —CONH— is attached to the polymer main chain. It relates to a method of removing.

  Thermoplastic resins having a group of —COO— and / or —CONH— in the polymer main chain, such as polyester resins, polyamide resins, polyurethane resins, polyurea resins, etc. are excellent in mechanical properties, thermal properties or chemical properties, It is used in various fields such as resin molded products, fibers, and films. Polyethylene terephthalate, which is a typical polymer of polyester resin, is usually bis (2-hydroxyethyl) terephthalate (hereinafter abbreviated as BHET) by esterification reaction of terephthalic acid and ethylene glycol or ester exchange reaction of dimethyl terephthalate and ethylene glycol. And a reaction product based on the oligomer thereof is obtained, and then this is further polycondensed. 6 nylon, which is a typical polymer of polyamide resin, is produced by the self-condensation reaction of ε-caprolactam. Moreover, the polyurethane resin is manufactured by making a polyol and isocyanate react.

  In the production and molding of a thermoplastic resin having a group of —COO— and / or —CONH— in the polymer main chain, a process of handling the thermoplastic resin in a molten state, for example, a resin polymerization process, a transfer process, a filtration process There are molding steps and the like. Inorganic materials used in these processes, such as reactor inner walls, molding machine inner walls, stirrers, thermometers, pressure gauges, pipes, screws, pumps, filters, bases, base packs, etc. are used, broken, inspected, etc. Sometimes needs to be replaced. At that time, adhesion of a thermoplastic resin, particularly a thermoplastic resin having a high melt viscosity cannot be avoided. For example, these members are removed in a state where the resin is fixed. In order to reuse these inorganic members, it is necessary to perform washing in order to remove the thermoplastic resin without damaging the members.

  As a method for removing the fixing resin from the inorganic member, generally, (1) a method of thermally decomposing the fine particles of sand or garnet in a high temperature fluid bath, (2) a method of decomposing in a molten oxide salt bath, (3) strong There are a method of hydrolyzing in an alkaline cleaning bath and a method of (4) decomposing in a hydrolysis furnace using heated steam. Further, (5) a method of dissolving and decomposing a polyester resin with diethylene glycol or triethylene glycol is known (Patent Document 1). However, in any method, in the case of (5), decomposition products accompanying the decomposition of the fixing resin, decomposition products such as oligomers, ethylene glycol, terephthalic acid, carbon dioxide gas, and water are discharged out of the system. In order to prevent emission or atmospheric discharge, it is necessary to install a scrubber and collect it by the scrubber. However, scrubber clogging often occurs and wastewater treatment is also necessary. Further, the consumption of heat energy for maintaining a high temperature is large, and there are also problems in waste treatment such as generation of decomposition residues. Furthermore, in the method of using a potassium nitrate or sodium nitrate type oxidant as the oxidative decomposition agent of (2), the oxidant is brought into contact with an organic substance or aluminum to cause a violent reaction, generating nitrogen oxides, There is a risk of fire and explosion, which is not the preferred method. In the method (3), there are problems such as chemical burns caused by handling of alkali, embrittlement of stainless steel due to alkali and deterioration due to halogen. In the methods (1) to (3), particularly in a pleated filter using a stainless non-woven fabric, damage to the expensive filter due to damage of the stainless non-woven fabric and the opening of the filter become large, and the function as a filter cannot be exhibited. There are problems such as.

  Further, although a physical method is also conceivable as a method for removing the fixed polyester resin from the metal member, according to the results of the study by the present inventors, this method removes the fixed polyester resin without damaging the metal member. It is extremely difficult. These problems similarly exist for glass members, ceramic members, and polyamide resins, polyurethane resins, and the like.

  Therefore, it was necessary to develop a safe cleaning method without damaging the inorganic member, particularly a precise inorganic member. As a result of studying this cleaning method, the present inventors have found that heated ethylene glycol (hereinafter sometimes abbreviated as EG), particularly ethylene glycol heated near the boiling point, has an excellent cleaning effect, (6) A cleaning method was proposed in which the polyester resin fixed to the metal member is depolymerized while boiling ethylene glycol in the presence of a depolymerization catalyst to remove the fixed polyester resin (Patent Document 2).

However, this method is premised on pressurization for implementation at a high temperature, and the scope of application is limited from the viewpoint of handling dangerous materials. In addition, since waste liquid is generated as used EG, it can be reused at a low cost if it is in a location where EG can be refined. It became clear that further improvement is necessary in that it is necessary to respond.
JP 2002-265578 A JP 2003-305424 A

  As a result of further studying this cleaning method, the present inventor, as a method for removing the thermoplastic resin member from the inorganic member to which the thermoplastic resin having a —COO— and / or —CONH— group in the polymer main chain is fixed. The present inventors have found that a method of removing the thermoplastic resin by decomposing it with molten BHET is extremely useful. The inventor has also found that when molten BHET is used, a highly crystallized resin that requires a long time for depolymerization can be easily decomposed. Furthermore, the present inventor believes that the decomposition product of the thermoplastic resin decomposed by molten BHET becomes a brittle solid at room temperature, and therefore it is very easily peeled off from the inorganic member after cooling and is easily soluble in hot water. It has been found that it has the advantage that the finish cleaning after peeling off the object is very easy. In addition, the present inventor has found that the decomposed product after peeling can be repeatedly subjected to decomposing and washing after filtering off insoluble substances after remelting, and has reached the present invention.

  That is, in the present invention, an inorganic member in which a thermoplastic resin having a —COO— and / or —CONH— group is attached to a polymer main chain is brought into contact with molten bis (2-hydroxyethyl) terephthalate, A method for cleaning an inorganic member comprising removing a plastic resin.

  The thermoplastic resin is preferably a polyester resin, a polyamide resin or a polyurethane resin. The inorganic member is preferably a metal, glass or ceramic member. The inorganic member is preferably an inner wall of a thermoplastic resin polymerization reactor or a member provided in the polymerization reactor. Moreover, it is preferable that an inorganic member is piping, a connection member, or a detection end provided in the polymerization process of a thermoplastic resin. Furthermore, the inorganic member is preferably a member provided on the inner wall of the thermoplastic resin melt molding apparatus or in the melt molding apparatus. In addition, the inorganic member is preferably a member provided in the inner wall of the thermoplastic resin melt extruder or in the melt extruder.

  The temperature of molten bis (2-hydroxyethyl) terephthalate is preferably 120 to 300 ° C. After contacting with molten bis (2-hydroxyethyl) terephthalate, it is preferable to wash with ethylene glycol or hot water. After contacting with molten bis (2-hydroxyethyl) terephthalate, it is preferable to wash with ethylene glycol and further with hot water.

  The present invention is further a cleaning agent for an inorganic member comprising a bis (2-hydroxyethyl) terephthalate, wherein a thermoplastic resin having a group of —COO— and / or —CONH— is attached to a polymer main chain. And this invention includes the washing | cleaning method which puts a bis (2-hydroxyethyl) terephthalate in this thermoplastic resin melt extruder, and melt-kneads.

  According to the method of the present invention, the resin can be efficiently removed from the resin-adhered inorganic member. At that time, the temperature and safety operation are almost the same as the conditions in the production and molding of thermoplastic resins (processing under normal pressure is possible), and there is no generation of peculiar waste or exhaust gas. It can be washed away. And the cleaning agent after completion | finish of washing | cleaning has the advantage that it can be repeatedly used by isolate | separating an insoluble matter by methods, such as filtration suitably, in a molten state.

(Inorganic material)
The inorganic member in the present invention is not limited as long as it is an inorganic member to which a thermoplastic resin having a group of —COO— and / or —CONH— is attached to the polymer main chain. It is preferably an inorganic member used in the manufacturing process, transfer process, filtration process or molding process (for example, extrusion molding, injection molding, etc.) of the thermoplastic resin in a molten state. Such a process is stopped when it achieves its purpose or is completed by operation and use for a predetermined period, and also stops due to failure, inspection, etc. At that time, the equipment in the process is washed or parts (inorganic Member) needs to be replaced. In such a case, the inorganic member before washing is in a state where a thermoplastic resin is adhered, and the inorganic member removed from the process is removed in a state where the thermoplastic resin is adhered. Specific examples of the inorganic member include an inner wall of a thermoplastic polymerization reactor of a thermoplastic resin or a member (for example, a stirrer, a thermometer, etc.) provided in the reactor, a transfer or filtration process of the molten thermoplastic resin. Members (for example, pipes, pumps, mixers, filters, thermometers, pressure gauges, etc.), inner walls of thermoplastic resin melt molding apparatuses or members provided in the apparatus (for example, screws, pumps, thermometers, pressures) For example). Examples of the glass member include a beaker, a flask, and a stirring rod used for the polymerization reaction. Examples of the ceramic member include a filter and a static mixer. Examples of the metal member include For example, inner wall of melt polymerization reactor, stirrer, thermometer, pump of transfer process, filter, inner wall of cylinder of melt molding apparatus (for example, extrusion molding machine, injection molding machine, etc.), screw, pressure gauge, thermometer , Molds, caps, cap packs, and the like. Among these, a metal member and a glass member are particularly preferable.

(Thermoplastic resin)
As the thermoplastic resin having a —COO— group in the polymer main chain in the present invention, a polyester resin, a polyamide resin, etc., and the thermoplastic having a —CONH—, or COO— and —CONH— group in the polymer main chain are used. Preferred examples of the resin include polyurethane resins and polyurea resins. Of these, polyester resins and polyamide resins are preferable, and polyester resins are particularly preferable.

  The polyester resin is a resin mainly composed of an ester of an aromatic dicarboxylic acid component (for example, terephthalic acid, 2,6-naphthalenedicarboxylic acid, etc.) and a glycol component (for example, ethylene glycol, tetramethylene glycol, etc.), Specific examples include polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, and polyethylene-2,6-naphthalate. Such a polyester resin is preferably a resin having an average degree of polymerization (the number of bonded ester repeating units) of 10 or more, and more preferably 30 or more. The average degree of polymerization varies depending on the use form of the polyester resin, and there is no particular upper limit, but it is usually preferably 200 or less, more preferably 180 or less. Examples of the polyester resin include polycarbonate (for example, polycarbonate obtained by melt polymerization of bisphenol A and diphenyl carbonate). The molecular weight of such a polycarbonate varies depending on the use form, but is preferably 7,000 or more, more preferably 9,000 or more in terms of number average molecular weight. The upper limit of the molecular weight is not particularly limited, but is preferably 50,000 or less, more preferably 40,000 or less.

  The polyamide resin is a resin mainly composed of an amide of a dicarboxylic acid component (for example, adipic acid) and a diamine component (for example, hexamethylenediamine), for example, by self-condensation of ε-caprolactam. Examples thereof include nylon and polyhexamethylenediamine adipate (6,6 nylon). Such a polyamide resin is preferably a resin having an average degree of polymerization (number of bonded amide repeating units) of 10 or more, and more preferably 30 or more. The average degree of polymerization varies depending on the use form of the polyamide resin, and there is no particular upper limit, but it is usually 300 or less, more preferably 250 or less.

  The polyurethane resin is usually obtained by reacting a long-chain polyol or a short-chain polyol with an isocyanate compound. Examples of the long-chain polyol include ester-based polyols and ether-based polyols. Examples of the ester polyol include polyester using adipic acid as an acid component and one or more of ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol and the like as a glycol component. Examples of ether polyols include polyethylene glycol and polytetramethylene glycol. Examples of the short-chain polyol include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, and glycerin. Such a polyurethane resin is preferably a resin having an average degree of polymerization (number of bonded urethane repeating units) of 10 or more, and more preferably 30 or more. The average degree of polymerization varies depending on the form of use of the polyurethane resin, and there is no particular upper limit, but it is usually 300 or less, more preferably 250 or less.

  In a preferred embodiment of the present invention, the thermoplastic resin is a polyester resin, and the inorganic member to which the polyester resin is attached is provided in a process in contact with the molten polyester resin, or is made of metal or glass that has been removed from the process. Or the cleaning method which is a member made from a ceramic is included.

  Further, the thermoplastic resin is a polyamide resin, and the inorganic member to which the polyamide resin is attached is a metal, glass, or ceramic member that is provided or removed from the process in contact with the molten polyamide resin. Includes certain cleaning methods.

  Further, the thermoplastic resin is a polyurethane resin, and the inorganic member to which the polyurethane resin is attached is a metal, glass, or ceramic member provided or removed from the process in contact with the molten polyurethane resin. Includes certain cleaning methods.

  The thermoplastic resin is easily decomposed by contact with molten BHET by heating to 120 to 300 ° C., preferably 150 to 250 ° C., during the decomposition treatment with molten BHET (cleaning agent). can do. At that time, a decomposition catalyst or a stabilizer may be used. For example, when decomposing a polyester resin, it can be easily decomposed (depolymerized) by using a known transesterification catalyst (for example, caustic soda, caustic potash, sodium carbonate, zinc acetate, etc.), and a phosphorus compound (for example, By adding a stabilizer such as (sub-) phosphoric acid, this alkyl ester or aryl ester), a side reaction of thermal decomposition can be prevented.

  Bis (2-hydroxyethyl) terephthalate (BHET) used for the decomposition treatment is a small proportion (for example, 40% by weight or less, further 30% by weight) of oligomers (degree of polymerization is preferably 10 or less, particularly preferably 6 or less). %), But the proportion of BHET is preferably 90% by weight or more, more preferably 95% by weight or more. Usually, BHET is solid at normal temperature, and the shape thereof is not particularly limited, but is preferably used in the form of pellets, flakes, pulverized products, powders, chips and the like. The temperature of the molten BHET during the decomposition treatment is preferably 120 to 300 ° C, more preferably 150 to 250 ° C.

  In the decomposition (depolymerization) treatment of the thermoplastic resin adhering to the inorganic member in the present invention, usually, a heated container is used, and BHET and the removed inorganic member are put into the container and heated and washed under normal pressure, or the A cleaning process is performed such as heating the inside of the process in which the member is installed and circulating the molten BHET, or heating the inside of the molding machine and passing the molten BHET through. At that time, it is preferable to use BHET at least 4 times by weight, more preferably 6 to 30 times by weight the amount of the thermoplastic resin. The BHET is preferably in a state that always covers the surface of the thermoplastic resin during the cleaning treatment, and from this point, it is more preferable that the amount of the inorganic member is sufficiently immersed.

  In order to clean the inside of the molding machine, a purge agent having an action of physically peeling the thermoplastic resin from the member is usually used, but before using the purge agent or mixing with the purge agent, the molten BHET is removed. You may flow in a molding machine. Thereby, it is also possible to easily remove the thermoplastic resin in a portion that cannot be removed by the purge agent, such as a fine gap in the molding machine or a portion that does not reach the physical action. The purge agent does not melt at the washing temperature. For example, polystyrene resin (PS), polymethyl methacrylate resin (PMMA), acrylonitrile / butadiene / styrene resin (ABS), acrylonitrile / styrene resin (AS), polyethylene / A gel-like resin such as vinyl acetate resin (EVA) is preferred. The mixing ratio of BHET and purge agent is not particularly limited as long as it does not impair the resin supply function (biting property) of the molding machine, but is 1 to 50 parts by weight, more preferably 3 to 40 parts by weight with respect to 1 part by weight of BHET. Part of the purge agent.

  If another thermoplastic resin is used instead of the purge agent, brand switching (color change, resin change, etc.) by the thermoplastic resin can be easily performed.

  Furthermore, when using the heating type container, the molten BHET is forced by a pump or the like including a method of stirring the stirrer so that the stirrer blade and the inorganic member do not contact with each other, and the process in which the inorganic member is installed. In particular, it is desirable to further promote cleaning by renewing the surface of the adhered resin or the like by means of circulating molten BHET.

  The decomposition reaction product is a low molecular weight substance mainly composed of BHET and can be handled as a brittle solid at room temperature. For this reason, the decomposition reaction product can be easily peeled from the inorganic member. Moreover, if an insoluble substance is removed from the decomposition reaction product in a molten state by a method such as filtration, the resulting decomposition reaction product can be used as a cleaning agent (depolymerization agent). Further, the decomposition reaction product can be returned to high purity BHET by a known method and used again as a cleaning agent (depolymerization agent).

In the present invention, after washing with molten BHET, in order to further enhance the washing effect, the decomposition reaction product can be further removed and washed using heated ethylene glycol (cleaning agent). In that case, it is preferable that the temperature of ethylene glycol is 100-190 degreeC, Furthermore, it is preferable that it is 120-180 degreeC. Moreover, it is preferable that the usage-amount of ethylene glycol is 1-10 weight times with respect to the weight of a decomposition reaction product, Furthermore, it is 2-5 weight times.
In the present invention, after performing the above-described washing with molten BHET or heated ethylene glycol, the decomposition reaction product adhering to the inorganic member can be further washed with hot water. In that case, it is preferable that the temperature of hot water is 50-95 degreeC, Furthermore, it is 70-90 degreeC. Moreover, it is preferable that the usage-amount of a hot water is 1-10 weight times with respect to the weight of a decomposition reaction product, Furthermore, it is 2-5 weight times.

Hereinafter, the present invention will be further described with reference to examples. The characteristics in the examples are measured by the following methods.
(1) Optical density of bis (2-hydroxyethyl) terephthalate 5 mg of a sample was dissolved in methanol to give a 10 wt% methanol solution. The cell length was 10 mm by UVmini-1240 (manufactured by Shimadzu Corporation), and the blank was methanol. Using this, the zero point was corrected, and the absorbance of this solution was measured at 380 nm.
(2) Purity of bis (2-hydroxyethyl) terephthalate Weigh accurately 5 mg of sample, prepare a solution of about 100 ppm using chloroform, and column is SILICA SG 80, temperature 40 ° C., flow rate 0.7 ml / min, moving The phase was measured by high performance liquid chromatography (LC-6, manufactured by Shimadzu Corporation) using dichloromethane / dioxane and the detector using an ultraviolet absorptiometer.
(3) Intrinsic viscosity of polymer (IV)
The sample was dissolved in a mixed solvent of phenol / tetrachloroethane = 1/1 (weight ratio) at a concentration of 0.4 g / dl, and the solution viscosity was measured using an Ubbelohde capillary viscometer at a temperature of 25 ° C., and then the above mixing The solution was gradually added to measure the solution viscosity on the low concentration side, and extrapolated to 0% concentration to determine the intrinsic viscosity.

Example 1
SUS304 pleated candle filter (opening 1 μm, diameter 70 mm, height 1,000 mm) used as a filter for removing foreign contaminants of molten polyethylene terephthalate (average polymerization degree: about 110) and 21 kg of the resin adhered The 12 pieces were set on a washing ring stand with the resin outlet of the filter facing down, and a punching plate with a diameter of 800 mm, a straight barrel height of 1,500 mm, and a lower portion of 20 mm in diameter was provided. It put into the washing tank made from SUS304 with a medium jacket. Next, 500 kg of bis (2-hydroxyethyl) terephthalate (BHET; purity: 98% by weight) melted at 160 ° C. was added to this washing tank, and a blade diameter of 200 mm was introduced into an opening of 400 mm in diameter provided at the center of the ring stand. The upper lid was set so that the stirring blades could be accommodated.

  A heating medium of 250 ° C. was passed through the jacket of the washing tank, the internal temperature was gradually increased, and when the temperature exceeded 200 ° C., the stirrer was driven at 60 rpm to start washing. During the washing, the supply amount of the heat medium was adjusted so that the internal temperature was maintained at 200 to 230 ° C. Further, the inside of the tank was observed through a viewing window provided on the upper lid, and after 25 minutes, it was confirmed that the fixing resin was gone and the inner solution became transparent, and stirring and washing were further continued for 10 minutes. After completion of washing, stirring and heating medium supply were stopped.

  Next, the upper lid was opened, the filtering stand was pulled up, drained, and then 12 candle filters were immersed in hot water at 80 ° C., washed and dried. The obtained filter was subjected to a bubble test in isopropanol, and it was confirmed that both pressure loss and bubble generation were normal.

(Example 2)
A stocking made of 6 nylon fibers is cut into several cm squares, and the resulting cut cloth is supplied to a melt extruder (cylinder inner diameter 50 mmφ) and melted at a temperature setting of a supply zone 150 ° C., a melting zone 240 ° C., and a measuring zone 260 ° C. Extrusion and pelletization gave 6 nylon resin pellets. After stopping the extruder after the pelletization process was finished, the extruder was operated for a while after the supply of the cut cloth was stopped, and the resin remaining inside was extruded as much as possible. After that, the temperature of the supply zone is lowered to normal temperature, the temperature of the melting zone is 230 ° C., the temperature of the measuring zone is 230 ° C., and the extrusion screw is kept rotating, and 10 kg of BHET pellets are charged from the charging port and extruded. It was confirmed that the entire amount was discharged. Next, the temperature after the melting zone of the extruder was lowered to 200 ° C., 10 kg of BHET (purity: 98% by weight) pellets were again injected, and extrusion was performed to clean the inside of the extruder. After the cleaning was completed, the extrusion screw was taken out and the surface was observed. As a result, it was not necessary to wipe with a normal metal cloth. Next, the extrusion screw was returned to the extruder and the temperature was returned to the original pelletizing conditions, and then the cut cloth of 6 nylon fibers was supplied and the operation was resumed. There was no foreign matter or abnormal reaction.

(Example 3)
Chemical recycling method of used PET bottles (polyethylene terephthalate bottles) (depolymerization with ethylene glycol, solid impurity removal treatment of depolymerization reaction product solution, activated carbon treatment, ion exchange treatment and crystallization separation to obtain crude BHET; 50 g of high-purity BHET (purity: 98% by weight, optical density: 0.003) obtained by molecular distillation treatment of crude BHET was used as a raw material, and 5 mg of germanium dioxide was used as a polymerization catalyst. (500 ml), the flask was immersed in a hot water bath whose temperature was controlled at 275 ° C., the inside of the flask was maintained at a degree of vacuum of 4 Pa, and the reaction liquid was stirred for 5 hours to carry out the polymerization reaction. After completion of the polymerization reaction, 35 g of the content polymer was scraped from the flask. The obtained polymer (polyethylene terephthalate) had an intrinsic viscosity (IV) of 0.62.

  The separable flask with the polymer that could not be scraped on the inner wall was again immersed in an oil bath whose temperature was controlled at 275 ° C., and 300 g of BHET pellets (purity: 98% by weight) were placed in the separable flask in that state. Was added while melting. After the addition, a separable cover equipped with a stirrer, a condenser and a thermometer was attached to the separable flask. When the internal temperature reached 150 ° C., the stirrer was started and stirred at 180 rpm. While the inside was visually confirmed, the polymer was dissolved and dissolved to become a uniform liquid, and then pulled up from the oil bath. After removing the separable cover, the internal solution was poured out. The liquid adhering to the separable flask, stirring blade, thermometer and the like solidified after cooling, but was immersed and washed in hot water at 90 ° C. and dispersed and dissolved in hot water. After washing with water and drying, it was confirmed that there were no scratches or a polymer thin film on the surface of a separable flask, a stirring blade, a thermometer or the like.

(Example 4)
A stirrer is incorporated, and a separable flask having a three-neck in the lid and having a capacity of 1 liter is charged with 200 g of polyethylene adipate having a hydroxyl group at both ends (molecular weight 2,100), 48 g of diphenylmethane diisocyanate and 44 g of butylene glycol. The reaction mixture was heated in a bath and stirred at a reaction temperature of 115 ° C. for 60 minutes in a nitrogen atmosphere to obtain a hydroxyl group-terminated prepolymer. The viscosity (measured by VT-04E, manufactured by Rion Co., Ltd.) at 70 ° C. of this hydroxyl-terminated prepolymer was 4 Pa · s.

Separately prepared separable flask having the same shape as described above was charged with 400 g of polyethylene adipate having a hydroxyl group at both ends (molecular weight 2,100) and 168 g of diphenylmethane diisocyanate, heated in an oil bath, and stirred at a reaction temperature of 115 ° C. for 60 minutes in a nitrogen atmosphere. Reaction was performed to obtain an isocyanate-terminated prepolymer. The viscosity (measured with VT-04E, manufactured by Rion Co., Ltd.) at 70 ° C. of this isocyanate-terminated prepolymer was 1.5 Pa · s.
292 g of the hydroxyl group-terminated prepolymer and 568 g of the isocyanate-terminated prepolymer thus obtained were charged into a heating medium heating type, a 2 liter scratched surface stirrer and an autoclave having two ports capable of charging raw materials. The reaction was stirred for 30 minutes at a reaction temperature of 190 ° C. in a nitrogen atmosphere. The resulting viscous material was extracted from the lower discharge port with a pump and subjected to test spinning.

  In order to wash the viscous material remaining in the autoclave, 200 g of BHET (purity: 98 wt%) pellets were added to the autoclave, and the mixture was heated to 200 ° C. and stirred for 20 minutes. After 20 minutes, stirring was stopped, and the solution was poured from a lower discharge port into a SUS vat to be solidified. When the undissolved dissolved solution poured out was observed with the naked eye, it was confirmed that the viscous material was uniformly dissolved. Next, the autoclave was lowered to 90 ° C., 200 parts by weight of 90 ° C. warm water was added, and the remaining contents were dissolved by stirring for 10 minutes and discharged to a drain tank. This hot water washing was repeated twice, and then hot air drying was performed. When the autoclave after washing was reused in the synthesis of the polyurethane resin, no abnormal phenomenon was observed, and the reaction was smooth.

(Example 5)
Equipped with a 20mmφ melt extruder and 43mmφ melt extruder, the molten polymers extruded from each extruder are merged in the middle of the transfer pipe, and immediately after that they are mixed by a static mixer and then the two polymers are mixed uniformly. A pellet production facility for producing spinning pellets by extruding the polymer obtained from a nozzle was prepared, and a type having 30 elements of ceramic 1/2 inch blades was set as the static mixer.

  Prepare polyethylene terephthalate (master batch polymer) with intrinsic viscosity (IV) 0.62 containing 30% by weight of carbon black uniformly as a coloring component and polyethylene terephthalate with intrinsic viscosity (IV) 0.62 without carbon black. The master batch polymer was melt-extruded with the 20 mmφ melt extruder at an extrusion temperature of 280 ° C. and an extrusion speed of 6 kg / hr, while the polyethylene terephthalate was extruded with the 43 mmφ melt extruder at an extrusion temperature of 280 ° C. and an extrusion speed of 54 kg / hr. Then, the molten polymers were joined together in the middle of the transfer pipe and further mixed with the static mixer heated to 280 ° C., and extruded as a strand from a 5 mmφ nozzle installed at the tip of the mixer. Cool with water It was prepared black colored polyethylene terephthalate pellets for spinning over the cutter. The resulting black colored polyethylene terephthalate pellets had a carbon black content of 3.0% by weight and an intrinsic viscosity of 0.60.

  After this pellet production was performed for 5 hours, the supply of the polymer to each melt extruder was stopped. In stopping the melt extruder, the charging zone (feeding zone) of each melt extruder is cooled to room temperature, and the zone after the melt zone is cooled to 240 ° C., and then BHET (purity: 98% by weight) 2 kg of the pellets were put into a 20 mmφ melt extruder and 18 kg were put into a 43 mmφ melt extruder and melted and discharged. Subsequently, after the temperature of the zone part after the melting zone of the extruder was lowered to 200 ° C., BHET pellets were charged in the same procedure as described above, and melt discharge was performed again. Next, after the temperature of the zone after the melting zone of the extruder is lowered to 160 ° C., BHET pellets are charged in the same procedure as described above, and the third melt discharge is performed, and the extruder, static mixer, nozzle, and their The piping was cleaned. Coloring with carbon black was not observed in the third melt discharge.

  After performing the third washing treatment, the temperature conditions of the two melt extruders were returned to the original extrusion conditions, and polyethylene terephthalate having an intrinsic viscosity (IV) of 0.62 not containing carbon black was added to each melt extruder. Polyethylene terephthalate pellets for spinning which were not colored by melt extrusion were produced. When this pellet was observed with the naked eye, it was confirmed that carbon black was not mixed, and that not only the metal member but also the ceramic member was sufficiently washed.

(Comparative Example 1)
Aside from using 500 kg of ethylene glycol and 80 g of sodium hydroxide in place of BHET as the cleaning agent, installing a reflux condenser in the cleaning tank, maintaining the internal temperature during cleaning at 198 to 200 ° C., and performing cleaning processing under normal pressure Was carried out in the same manner as in Example 1. After performing this washing process for 2 hours, when the inside was observed through a viewing window provided on the upper lid, the fixing resin still remained and the inner solution was opaque. When the washing process was continued, it was confirmed that the inner solution finally became transparent after 4 hours.

The cleaning method of the present invention is expected to be used in the production of thermoplastic resins having —COO— and / or —CONH— groups in the polymer main chain, or in industries using these resins.

Claims (13)

  Contacting an inorganic member having a thermoplastic resin having a —COO— and / or —CONH— group attached to the polymer main chain with molten bis (2-hydroxyethyl) terephthalate to remove the thermoplastic resin; A method for cleaning an inorganic member comprising:   The cleaning method according to claim 1, wherein the thermoplastic resin is a polyester resin, a polyamide resin, or a polyurethane resin.   The cleaning method according to claim 1, wherein the inorganic member is a metal, glass, or ceramic member.   The cleaning method according to any one of claims 1 to 3, wherein the inorganic member is an inner wall of a polymerization reactor of a thermoplastic resin or a member provided in the polymerization reactor.   The cleaning method according to any one of claims 1 to 3, wherein the inorganic member is a pipe, a connecting member, or a detection end provided in the polymerization step of the thermoplastic resin.   The cleaning method according to claim 1, wherein the inorganic member is an inner wall of a thermoplastic resin melt molding apparatus or a member provided in the melt molding apparatus.   The cleaning method according to claim 1, wherein the inorganic member is an inner wall of a thermoplastic resin melt extruder or a member provided in the melt extruder.   The cleaning method according to claim 7, wherein bis (2-hydroxyethyl) terephthalate is charged into a melt extruder and melt kneaded.   The temperature of molten bis (2-hydroxyethyl) terephthalate is 120-300 degreeC, The washing | cleaning method of any one of Claims 1-8.   The cleaning method according to claim 1, further comprising washing with ethylene glycol after contacting with molten bis (2-hydroxyethyl) terephthalate.   Furthermore, the washing | cleaning method of Claim 1 or 10 which wash | cleans with hot water.   A cleaning agent for inorganic members made of bis (2-hydroxyethyl) terephthalate, wherein a thermoplastic resin having a group of —COO— and / or —CONH— is attached to the polymer main chain. The cleaning agent according to claim 12, wherein the inorganic member is an inner wall of a melt molding apparatus or a member provided in the apparatus.