JP2002240120A - Method for manufacturing recovered polyethylene terephthalate resin injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably manufacturing an injection molding under a good quality control by molding a recovered PET resin having an unevenness of a molecular weight or an unevenness of a moisture due to a drying fault by an injection molding machine. SOLUTION: The method for manufacturing the injection molding comprises the step of injection molding the recovered PET resin by an in-line screw injection molding machine. The method further comprises the steps of holding injection molding conditions constant, measuring a load and/or a movement of a screw of the injection molding machine, and injection molding while confirming that the molecular weight of a material to be molded falls within a predetermined range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a recovered polyethylene terephthalate resin injection molded article. More specifically, the present invention relates to a method for stably producing a recovered polyethylene terephthalate resin injection-molded product with good quality control using an inline screw injection molding machine.

[0002]

2. Description of the Related Art In recent years, various laws such as the Containers and Packaging Recycling Law and the Home Appliances Recycling Law have made it mandatory to recycle synthetic resins, and an effective recycling method has been demanded. Various methods have been proposed and implemented as synthetic resin recycling methods, and for example, a material recycling method, a chemical recycling method, and a thermal recycling method are known. Among them, the material recycling method is the most preferable one because the material is used most effectively and with low energy consumption. By the way, as for the injection molding of polyethylene terephthalate resin (hereinafter abbreviated as PET or PET resin), generally, injection molding of resin mixed with glass fiber is widely performed, and the injection molded product has heat resistance and rigidity. It is widely used in many fields as an excellent engineering plastic molded product. On the other hand, in recent years, a large amount of biaxially stretched PET bottles has been used, and in Japan, the amount of demand currently exceeds 300,000 tons per year.
Recycling of ET bottles is also required by the Containers and Packaging Recycling Law. As a method for reusing the PET bottle, material recycling is most preferable as described above. To recover the biaxially stretched PET bottles, wash and crush the normally used bottles, remove foreign matter, and dry to obtain recycled flakes. Preparation of PET resin has been performed. When the recovered PET resin thus obtained is injection-molded, there is a major problem that the recovered PET resin has an irregular molecular weight. That is, if a trace amount of water is present at the time of heating and melting, the hydrolysis is caused to cause a decrease in the molecular weight, and the molecular weight of the PET once formed and collected is also greatly varied. Further recovered PET
Has a variable moisture content, and in order to reuse the recovered PET resin, it is necessary to sufficiently dry the resin before injection molding. In general, it is required to perform injection molding after drying until the water content becomes 0.005% by weight or less. However, it is sometimes necessary to perform injection molding of PET which is insufficiently dried and has moisture remaining to cause a problem. In such a case, it is inevitable that the molecular weight of the molded article is greatly reduced. Prior to injection-molding the recovered PET resin, it is common practice to confirm the molecular weight by measuring the intrinsic viscosity number (IV value) of the recovered PET resin.
Even in the same lot of the recovered PET resin, there is a large variation in the molecular weight, and the fact is that much effort is required to confirm the molecular weight. On the other hand, a method of increasing the molecular weight by adding a polyfunctional compound to PET has been disclosed as an agent for increasing the molecular weight of PET having a reduced molecular weight (Japanese Patent Publication No. 47-13860). PE
As the injection molding method of T, using a vent type injection molding machine,
A method of performing injection molding while dewatering by suctioning from a vent portion with a vacuum pump during molding (Japanese Patent Application Laid-Open No. 7-608).
03 publication).

[0003]

SUMMARY OF THE INVENTION The present invention relates to a biaxially stretched P
It is an object of the present invention to provide a method for stably producing a recovered PET resin injection molded product with good quality control by using an injection molding machine in material recycling of a PET molded product such as an ET bottle.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has used an in-line screw injection molding machine as an injection molding machine, and kept the injection molding conditions constant, By measuring the load and the movement of the screw, and confirming that the molecular weight of the recovered PET resin is within a predetermined range, it was found that the object can be achieved by injection-molding the recovered PET resin, Based on this finding, the present invention has been completed.
That is, the present invention provides (1) a method for producing a molded article by injection molding a recovered PET resin by an in-line screw injection molding machine, wherein the injection molding conditions are kept constant;
A recovered PET resin injection-molded article characterized by performing injection molding while confirming that the molecular weight of the material to be molded is within a predetermined range by measuring the load applied to the screw of the injection molding machine and / or the movement of the screw. Manufacturing method,
(2) The load applied to the screw of the injection molding machine and / or the movement of the screw is controlled by controlling the screw rotation torque during resin plasticization, the injection pressure at the time of injection while controlling the injection speed, and the injection while controlling the injection pressure. 2. The method according to claim 1, wherein the molecular weight of the material to be molded obtained by measuring the load on the screw of the injection molding machine and / or the movement of the screw is smaller than a predetermined range. 3. The method according to claim 1 or 2, wherein a molecular weight increasing agent is added to the recovered PET resin to be supplied to the injection molding machine so that the molecular weight of the material to be molded falls within a predetermined range, and injection molding is performed. 4.) The production method according to claim 3, wherein the molecular weight-increasing agent comprises a polyfunctional compound, and (5) the polyfunctional compound is one of an epoxy group, an isocyanate group and an acid anhydride group as a functional group. The method of manufacturing the fourth term describes are those having at least one selected et al., As (6) in-line screw injection molding machine, used as vented,
Item 1. Items 1 to 5 in which the dried PET resin is supplied to the hopper by drying the resin by supplying insufficiently dried recovered PET resin and sucking the vent portion or the vent portion and the hopper portion with a vacuum pump. Any one of the production methods described above, and (7) a specific range of a molecular weight of 0.4 as an intrinsic viscosity (IV value) measured at 30 ° C. in o-chlorophenol.
7. The production method according to any one of items 1 to 6, wherein the production method is 5 to 1.0 dl / g.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a recovered PET resin injection molded article of the present invention, the recovered PET resin used as a material to be molded includes, for example, a molded PET molded article, a runner generated during molding, And the like, and collect and pulverize the molded product after the above-mentioned process, or further pelletize the resin. In general, the recovered PET resin often contains paint pieces, printed pieces, hot stamp pieces, and the like, which have been post-processed on the surface of the molded product, and often contains various kinds of dust and different kinds of resins. In the present invention, the recovered PE mixed with foreign matter such as paint pieces is used.
T resin is also included. The base PET resin is a PET resin used for general injection molding, blow molding and the like. Particularly preferred recovered PET resins are PET bottles,
A collected PET resin such as a sheet molded from the bottle-collected product and a vacuum-molded product of the sheet (eg, an egg packaging pack); and a resin obtained by blending various components such as glass fiber with the collected PET resin. In the above PET bottle, PET
Utilizing the slow crystallization speed of the transparent biaxial stretching P
ET is widely used. And this biaxially stretched PE
In molding a T bottle, PET having a high molecular weight is used to prevent crystallization during molding. More recently, the third component has been copolymerized with PET to increase the melt viscosity during molding and to slow down the crystallization rate.
T is also being used. The recovered PET resin used in the present invention is a P resin obtained by copolymerizing such a third component.
ET is also included. Recovered PET used in the present invention
Various additives can be added to the resin as needed. Preferred additives include a crystallization nucleating agent, a crystallization accelerator, a release agent, a stabilizer, a lubricant, a coloring agent, a flame retardant, a glass fiber, and various polymers for blending. The nucleating agent and the crystallization accelerator are for promoting the crystallization of PET having a low crystallization rate, and facilitate the crystallization of the inner core layer even when injection molding is performed at a low mold temperature.

[0006] Since the recovered PET resin is mixed with various elements, the molecular weight generally varies greatly. On the other hand, a certain amount of foreign matter is always mixed in the recovered PET resin, and the mixed amount of the foreign matter is not always constant. Therefore, when manufacturing an injection-molded product using the recovered PET resin, it is necessary to take measures in consideration of the fact that a large amount of foreign matter is mixed. If foreign matter is present on the surface layer of the molded article, the foreign matter acts in a manner similar to the presence of a notch, and the foreign matter easily cracks and cracks, and the impact resistance is reduced. In consideration of these factors, it is preferable that the injection molded product of the recovered PET resin has a large molecular weight and sufficiently high impact resistance. In the present invention, the recovered PET resin is injection-molded using an inline screw injection molding machine. At this time, the injection molding conditions are kept constant, and the load applied to the screw of the injection molding machine and / or the movement of the screw are reduced. By performing measurement, injection molding is performed while confirming that the molecular weight of the material to be molded is within a predetermined range. That is, in such a method, since the molecular weight of the PET resin and the melt viscosity are in a proportional relationship, the injection cylinder temperature, the screw rotation speed, the molding cycle time,
If injection molding conditions such as mold temperature are kept constant, the molecular weight of the PET resin injected into the mold cavity is detected by the load on the screw and the movement of the screw, and the molecular weight of the material being injection-molded is determined. It is possible to know whether the molecular weight is within a predetermined range. Therefore, prior to injection molding, it is not necessary to measure the molecular weight of the resin charged into the hopper every moment, and it is also possible to detect a decrease in the molecular weight in the injection molding machine due to insufficient drying of the resin.

In the present invention, maintaining the injection molding conditions constant means molding while maintaining the injection cylinder temperature, screw rotation speed, molding cycle time, mold temperature and the like constant. The load applied to the screw of the present invention and / or the movement of the screw are the screw rotation torque during plasticization of the resin, the injection pressure when injecting while controlling the injection speed,
It is preferable to select from the injection speed at the time of injection while controlling the injection pressure. The item to be selected is one or more of the above. Note that controlling the injection speed means that injection is performed at a designated change in injection speed for each molding, and a molding method for performing injection in accordance with an injection speed curve according to the lapse of injection time. Show. A typical example of this method is generally VP control (Velo control).
(City → Pressure control), that is, the injection speed is controlled so as to match a certain curve, and the injection speed is switched to a low injection pressure just before the resin fills the mold cavity. There is a molding method that fills the mold cavity at a later time. On the other hand, controlling the injection pressure means that the injection is performed at a designated pressure change for each molding, and indicates a molding method in which the injection is performed according to an injection pressure curve according to the lapse of the injection time. As a typical specific example of this method, there is a method of injecting at a low pressure in the beginning, gradually increasing the pressure, and using a pressure curve in which the pressure is reduced just before the resin fills the mold cavity. The load applied to the screw and / or the movement of the screw include a screw driving force, a screw driving current amount, a screw rotation torque during resin plasticization, an injection pressure and an injection speed during resin injection. When using an all-electric injection molding machine, the load applied to the screw can be easily detected from the current of the screw rotation motor, the current of the screw injection motor, and the like. From this viewpoint, it is preferable to use an all-electric injection molding machine in the present invention. As described above, the molecular weight of the resin can be detected by obtaining the injection pressure at the time of injection while controlling the injection speed, or the injection speed at the time of injection while controlling the injection pressure. That is,
As the molecular weight of the resin increases, the injection pressure increases if the injection speed is controlled, and the injection speed decreases if the injection pressure is controlled. In the present invention, when the molecular weight detected by measuring the load applied to the screw of the injection molding machine and / or the movement of the screw in this way is smaller than a predetermined range, the recovered PET resin supplied to the injection molding machine has a molecular weight It is preferable to add an increasing agent to increase the molecular weight of the recovered PET resin during injection molding by a chemical reaction due to heating and melting in the injection cylinder, maintain the molecular weight within a predetermined range, and perform injection molding. The molecular weight increasing agent used at this time is -OH group at the terminal of PET or-
Polyfunctional compounds that react with COOH groups or both in the molten state in the injection cylinder are preferred. As the polyfunctional compound, a compound having at least one selected from a carboxyl group, an acid anhydride group, an acid halide group, an epoxy group, and an isocyanate group can be used. Among them, those having at least one selected from an epoxy group, an isocyanate group and an acid anhydride group are preferable. Furthermore, it is advantageous to use the polyfunctional compound which is not volatile at the operating temperature.

The polyfunctional compound includes acid anhydrides,
Polyisocyanate compounds and epoxy compounds are preferably used. Here, examples of the acid anhydride include pyromellitic dianhydride, and examples of the polyisocyanate compound include tetramethylene diisocyanate, hexamethylene diisocyanate, tolylene-2,4-diisocyanate, xylylene diisocyanate, and diphenylmethane. Examples thereof include diisocyanate and 2,2-diphenylpropane diisocyanate. Examples of the epoxy compound include compounds generally used as an epoxy resin and having an average of two or more epoxy groups per molecule. These compounds may be any of saturated or unsaturated aliphatic, aromatic and polycyclic compounds, and may have a substituent such as halogen, hydroxy, ether and the like. Particularly preferred epoxy compounds include, for example, glycidyl ether of polyphenol, glycidyl ether of polyphenyl ether, aromatic glycidyl compound, and polynuclear aromatic glycidyl ether. Specifically, a glycidyl ether of dihydroxydiphenyl ether and an epoxy resin prepolymer obtained from bisphenol A and epichlorohydrin are preferably exemplified. In the present invention, the dried PET resin is supplied to the hopper by using a vent type injection molding machine, and the dried PET resin is dried by sucking the vent portion or the vent portion and the hopper portion with a vacuum pump. And a method of injection molding can be used. Patent Publication No. 2640715 and the like, an injection molding method of PET resin using a vent type injection molding machine, that is, PET in which a pressure reducing circuit connected to a vent port is reduced in pressure to about 7 to 20 kPa and vented.
A resin injection molding method can be used favorably.

The present invention is a method for performing injection molding while confirming that the molecular weight is within a predetermined range by measuring the load applied to the screw of the injection molding machine and / or the movement of the screw. The intrinsic viscosity number (IV value) is preferably from 0.5 to 1.0 dl / g, and more preferably from 0.6 to 1.0 dl / g.
In addition, this intrinsic viscosity number (IV value) is a value measured at 30 ° C. in o-chlorophenol. The degree of polymerization of PET is generally represented by an intrinsic viscosity number (IV (dl / g) value). For example, it is represented by a value measured at 30 ° C. in o-chlorophenol, and 0 for soy sauce, sauce and detergent bottle. .65-0.7
5dl / g, 0.75 ~ for carbonated drinks and juice bottles
0.9 dl / g, 0.9 to 1.0 dl / g for cosmetic bottles
Of PET is used. IV (dl
/ G) is a value obtained by subtracting 1 from the relative viscosity ratio of the viscosity of the solvent measured with a 1 g / 1 dl PET solution to the viscosity of the solvent, and the IV value used in the present invention indicates this value. And When the IV value is less than 0.5 dl / g, the impact resistance of the injection molded article of the PET resin becomes low. In particular, in the case of the recovered PET resin used in the present invention, it is preferable to use a resin having a slightly larger molecular weight, considering that a considerable amount of foreign matter is mixed. Next, the method of the present invention will be described with reference to FIG. FIG. 1 shows one example of a method for carrying out the manufacturing method of the present invention.
It is process explanatory drawing of an example. The order shown in FIG. 1, that is, resin → molding condition per molding machine → resin molecular weight detection → molded product will be described in this order. In FIG. 1, the recovered PET resin from a PET bottle or the like is preliminarily dried. The preliminary drying is performed by a method of blowing heated air or a method of partially crystallizing while heating and stirring.

[0010] When PET is heated and melted in a water-containing state, it undergoes hydrolysis to reduce the molecular weight.
Dry until 1% by weight or less, more preferably 0.005% by weight or less. There are various drying methods, one of which is a method of sufficiently drying by dehumidifying drying and / or vacuum drying and then molding by a general in-line screw injection molding machine, and the other is an in-line vented in-line method. There is a method in which a screw injection molding machine is used, and the vent is suctioned by a vacuum pump while molding, and any method can be used. The injection molding conditions are such that the injection cylinder temperature, the screw rotation speed, the molding cycle time, the mold temperature and the like are kept constant. When molded in this manner, the load applied to the screw is proportional to the molecular weight of PET, and it is possible to detect whether the PET resin to be injection-molded falls within a predetermined molecular weight range from the screw rotation torque, the resin injection pressure, and the like. . When the molecular weight of PET decreases, the viscosity of the molten PET injected into the mold cavity also decreases, and filling into the mold cavity at a low injection pressure becomes possible. For example, if injection molding is performed by controlling the injection speed,
It is possible to detect whether the PET molecular weight is within a predetermined range by the injection pressure. That is, one of the injection molding methods generally used at present is to inject a resin by controlling an injection speed and to switch to an injection pressure control immediately before the resin fills a mold cavity (generally referred to as VP control). )
However, if injection molding is performed by this VP control method, the maximum injection pressure and the PET molecular weight are in a proportional relationship. On the other hand, when the injection pressure is controlled to inject the resin, the injection speed and the PET molecular weight are in inverse proportion. By measuring the injection speed and injection pressure, the molecular weight of the resin can be estimated. Injection molded products within the predetermined molecular weight range are regarded as good products, and injection molded products not within the predetermined molecular weight range are excluded as defective products. Recovered PET accepts the molecular weight of injection molded products
In some cases, it may be based on variations in the resin or in some cases based on insufficient drying of the resin during molding, and it has been difficult to sufficiently control the quality of injection-molded products. In the present invention, each injection molded product can be managed individually by detecting a screw rotation torque at the time of plasticizing the resin at the time of injection molding, an injection pressure and an injection speed at the time of resin injection.

Further, in the present invention, when the molecular weight detected by the load applied to the screw or the injection speed is smaller than a predetermined molecular weight range, a PET molecular weight increasing agent such as an epoxy resin is added to the recovered PET resin and injection molding is performed. A method of molding while increasing the molecular weight of the recovered PET resin can also be adopted. Screw rotation torque, the amount of difference between the molecular weight detected by the injection pressure or injection speed and the predetermined molecular weight range, by controlling the amount of the added molecular weight increasing agent to maintain the molecular weight in the predetermined molecular weight range, An automatic control method is preferred. The molecular weight increasing agent,
The raw material may be added at any stage such as when it is added to PET, when it is added after preliminary drying, or when it is added after dehumidification drying and / or vacuum drying. However,
It is important that the molecular weight enhancer does not volatilize significantly during drying. That is, it is important that the molecular weight increasing agent added before the preliminary drying, the dehumidification drying, the vacuum drying, and the like be relatively volatile. Also, when using a vent type injection molding machine for the injection molding machine and molding while suctioning the vent portion with a vacuum pump,
It is important to select a molecular weight increasing agent that is difficult to volatilize as the molecular weight increasing agent to be added to the PET resin. For example, when using an epoxy resin, it is preferable to use an epoxy resin having a relatively large molecular weight.

In the present invention, molding is carried out by setting molding conditions such as injection cylinder temperature, screw rotation speed, molding cycle time, mold temperature and the like constant. In general PET injection molding, the injection cylinder temperature is about 265 to 300 ° C., but in the present invention, injection molding is performed at a selected constant temperature within this range. Then, it is preferable to select a molding condition in which the screw rotation torque and the injection pressure greatly differ depending on the PET molecular weight. When a large amount of a reinforcing agent such as glass fiber is blended with the recovered PET resin and then molded, the injection cylinder temperature is set to be relatively high, and molding is performed while keeping the set temperature constant. The screw rotation speed during resin plasticization is also performed at a constant rotation speed appropriately selected from general molding conditions. As the molding cycle time, it is preferable to set the shortest cycle time in a range in which molding can be performed favorably, and molding is performed at each set constant cycle time. The injection molded article molded by the method of the present invention can be used for various applications. Conventionally, recovered PET resins have been mainly used for low-grade applications where the performance of the resin is not fully utilized, such as buckets, trash cans, and rubble stone (gravel) fences. According to the method of the present invention, since the quality control of each individual injection molded product can be performed, it can be used for applications in which the performance of the PET resin can be exhibited. It absorbs variations in the molecular weight of the recovered PET resin and can be used in various fields such as weak electricity, electronic equipment parts and housing, various industrial parts, furniture, daily necessities, building materials, and civil engineering.

[0013]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Example A flake obtained by pulverizing a PET bottle is used as the recovered PET resin. The molecular weight is IV value, 0.4, 0.6, 0.6.
Prepare three kinds of resins of 9 dl / g. As a mold, a mold cavity is for a box-shaped molded product, and the shape of the molded product is a square having a bottom surface of 100 mm × 100 mm, a rise of 50 mm, a wall thickness of 2 mm, and a bottom surface. The one having a direct gate at the center of was used. As the injection molding machine, "SG125M-HP" manufactured by Sumitomo Heavy Industries, Ltd., which is an in-line screw injection molding, was used. First,
The recovered PET resin was pre-dried at 100 ° C., and then sufficiently dehumidified and dried to reduce the water content in the resin to 0.005% by weight or less. Injection molding was performed under the following constant conditions. The injection cylinder temperature was set to 270 ° C (cylinder front temperature), the screw rotation speed was set to 40 rpm, and the molding cycle time was set to injection 7.
The mold temperature was set to 40 ° C. for 2 seconds, the holding pressure was 4 seconds, the cooling was 20 seconds, and the ejection was 10 seconds. Injection molding was performed by a VP control method, that is, a VP control method in which the injection speed was controlled until just before filling the mold cavity, and pressure control (holding pressure) was switched just before filling the mold cavity. IV value of 0.4, 0.4
6. Injection molding of each recovered PET resin at 0.9 dl / g, and the maximum injection pressure when switching VP is 50
MPa, 70 MPa, and 95 MPa. After cooling in the mold cavity, the molded products protruded from the mold by the protruding pins were automatically taken out, and were automatically classified into good products and defective products according to the injection pressure. That is, the maximum injection pressure is 65 to 10
By setting injection molded products molded at 0 MPa as good products and molding products molded under pressure of less than 65 MPa as defective products, molded products with IV values of 0.6 dl / g and 0.9 dl / g Was obtained as a non-defective product, and a molded product having an IV value of 0.4 dl / g could be excluded as a defective product. With this method, individual injection molded products can be managed individually.

[0014]

The molecular weight of the injection molded product of the recovered PET resin may be based on the variation of the recovered PET resin to be accepted, or may be based on insufficient drying at the time of molding. It was difficult to do. ADVANTAGE OF THE INVENTION According to this invention, each injection molded article can be managed individually by detecting the load applied to the screw, such as the injection speed, injection pressure, or screw rotation torque, at the time of injection molding. Furthermore, when the recovered PET resin is smaller than the predetermined molecular weight range, a good injection molded product can be obtained by adding a molecular weight increasing agent to the PET resin to increase the molecular weight and molding.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a method for carrying out the production method of the present invention.
It is process explanatory drawing of an example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B29K 105: 26 B29K 105: 26

Claims (7)

[Claims] 1. An in-line screw injection molding machine,
In a method of injection molding the recovered polyethylene terephthalate resin and manufacturing a molded product, the injection molding conditions are kept constant, and the load applied to the screw of the injection molding machine and / or the movement of the screw are measured, whereby the material to be molded is obtained. Injection molding while confirming that the molecular weight is within a predetermined range. 2. The method according to claim 1, wherein the load applied to the screw of the injection molding machine and / or the movement of the screw is controlled by controlling the screw rotation torque during resin plasticization, the injection pressure during injection while controlling the injection speed, and the injection pressure. The method according to claim 1, wherein the method is selected from an injection speed at the time of injection. 3. The recovered polyethylene terephthalate resin supplied to the injection molding machine when the molecular weight of the material to be molded obtained by measuring the load applied to the screw of the injection molding machine and / or the movement of the screw is smaller than a predetermined range.
3. The method according to claim 1, wherein a molecular weight-increasing agent is added so that the molecular weight of the material to be molded falls within a predetermined range, followed by injection molding. 4. The method according to claim 3, wherein the molecular weight increasing agent comprises a polyfunctional compound. 5. The method according to claim 4, wherein the polyfunctional compound has at least one selected from an epoxy group, an isocyanate group and an acid anhydride group as a functional group. 6. An in-line screw injection molding machine,
Using a vented type, supplying the recovered polyethylene terephthalate resin which is insufficiently dried to the hopper and drying the resin by suctioning the vent portion or the vent portion and the hopper portion with a vacuum pump, and performing injection molding. Claim 1
6. The production method according to any one of items 1 to 5. 7. An intrinsic viscosity number (IV value) measured at 30 ° C. in o-chlorophenol having a molecular weight within a predetermined range.
The production method according to any one of claims 1 to 6, wherein the pressure is 0.5 to 1.0 dl / g.