JPH0929738A - Manufacture of polycarbonate resin molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate resin molding material having low molecular weight small residual organic solvent in pet, high transparency to impart molding having low dust and excellent transparency useful for an optical grade and transparent component for a vehicle. SOLUTION: To melt, extrude and pelletize polycarbonate resin powder, an extruder with a vent having a barrel including a vent opening of a length of 2 to 15 times as large as a screw diameter is used.

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 polycarbonate resin molding material which has excellent heat resistance and color tone, generates little gas during molding, and does not generate gas from a molded article, and more particularly, polycarbonate. When manufacturing resin pellets, it is possible to improve the devolatilization efficiency by using an extruder configured with a barrel having a specially shaped vent port, and to devolatilize the residual solvent and low molecular weight substances in the powder. It is possible to improve the hue by purging oxygen gas, improve the precision during molding, and improve the production efficiency, and it is particularly suitable as a method for producing a light-colored transparent polycarbonate resin useful for optics and automobile parts. It is something.

[0002]

2. Description of the Related Art Polycarbonate resins are used in a wide range of fields because of their transparency, mechanical properties, flame retardancy, dimensional stability and electrical properties. However, the polycarbonate resin has the property of being colored yellow when it is melt-processed into pellets or formed into a sheet, which deteriorates the appearance.

Conventionally, general-purpose polycarbonate resins have been
Generally, since it is produced by an interfacial polymerization method using an organic solvent, the resin powder obtained from this contains a residual organic solvent and a low molecular weight substance. The low molecular weight product remained, and when processed into a molded product, bubbles were generated in the molded product, and volatile substances derived from the low molecular weight product were generated. In particular, when molding an optical disk substrate, there is a problem that such low molecular weight volatiles cause stains on the stamper, significantly lowering productivity for maintenance and lowering transferability of pits. This low molecular weight volatile is
Polycarbonate oligomers, monomer oligomers, dimers of terminal terminators, etc. have been found to be the most problematic among them, and those having a high content in the polymer are monomer oligomers.

Polycarbonate resins are currently generally produced by reaction polymerization by an interfacial polymerization method. In the interfacial polymerization method, the polycarbonate resin is usually obtained as a solution in an organic solvent, and is usually isolated to obtain a solid. As a method of isolating and obtaining a solid, a method of dropping an organic solvent solution of a polymer into warm water under stirring to evaporate the solvent, or a method of charging into a jacket heating paddle type kneader to perform granulation and drying So many methods have been shown so far.

Methylene chloride is generally used as an organic solvent used when producing a polycarbonate resin by an interfacial polymerization method. Since a solvent represented by methylene chloride has a high affinity with polycarbonate, it is difficult to remove the solvent with a general dryer or a large dryer is required.

Various methods for solving such a problem have been proposed. That is, there is a drying method (Patent Publication No. 53-15899, Japanese Patent Publication No. 55-33966, and Japanese Patent Publication No. 53-137298) using a paddle type dryer having a spiral blade group for progressive feeding and a spiral blade group for backward feeding. , When such a horizontal dryer is used, the fluidity of the powder in the dryer becomes uneven, so burnt dust is generated due to overheating, and dust is generated by forcing the paddle blade and powder to contact. Occurrence is seen. In addition, there is a method of filtering and drying the polycarbonate solid particles in the same dryer using a filter dryer (Japanese Patent Laid-Open No. 61-250025). However,
When this dryer is used, there are many disadvantages such as a long drying time being required, and because the structure of the dryer allows only batch processing, it cannot be applied to continuous production.

Also, the amount of residual organic solvent is reduced during extrusion,
Also, some methods for improving the hue of pellets have been proposed. For example, a method of adding 0.2 to 20 parts by weight of water per 100 parts by weight of the polycarbonate before and / or during the kneading of the polycarbonate resin powder and extruding while degassing under the condition that hydrolysis does not occur (Japanese Patent Publication No.
-27647), a method in which a wet powder containing water and a solvent is charged into an extruder having a high theoretical surface renewal frequency to directly pelletize it (JP-A-1-149827). A method (Japanese Patent Publication No. 7-2364) in which 0.1 to 5 parts by weight of water is injected per 100 parts by weight of polycarbonate between the vent ports is disclosed. However, even if the conventionally known method as described above is used, the effect of reducing the residual solvent in the pellet was small because the contact between the added water and the molten resin and the degree of kneading were insufficient.

In addition to adding phosphorous acid to the polycarbonate resin, water is added to make the water content of the resin 500.
In the method of pelletizing after adjusting to ˜5000 ppm (JP-A-4-81457), the addition of phosphorous acid has the disadvantages of lowering the hydrolysis resistance and lowering the long-term reliability of the optical disc.

[0009]

DISCLOSURE OF THE INVENTION The present invention resides in a method for producing a polycarbonate resin molding material in which the amount of organic solvent and low-molecular-weight volatiles remaining in solid particles of polycarbonate is significantly reduced and the amount of gas generated from the molded product is small. An object of the present invention is to provide a method for removing residual solvent and low-molecular-weight volatiles, which reduces the product cost by reducing the load in the drying process.

That is, the present invention relates to a method for producing a polycarbonate resin molding material which is excellent in heat resistance and color tone, generates little gas during molding, and does not generate gas from a molded product.

[0011]

[Means for Solving the Problems] The method conventionally studied is capable of removing residual solvent and low molecular weight volatiles to some extent during melt extrusion pelletization. The method of adding water has been used. However, the residual amount of residual solvent and low-molecular-weight volatiles does not reach the target level even if the method used conventionally is used. As a factor of this, it has been found that the vent-shaped extruder that has been used in the past cannot sufficiently devolatilize.

The inventors of the present invention have conducted various studies on the shape of the vent portion of the extruder. As a result, the shape of the vent portion has a special structure, and the exposure time of the molten resin in the vacuum state in the portion is changed. In addition, it was found that the devolatilization efficiency of the molten resin was increased.

That is, the present invention relates to a method for producing pellets by melt-extruding a polycarbonate resin powder with an extruder, wherein one vent opening has a length of 2 to 15 times the screw diameter. The present invention relates to a method for producing a polycarbonate resin molding material, which comprises melt-extruding and pelletizing a polycarbonate resin using an extruder configured by a barrel having at least one.

In a further preferred embodiment of the present invention, the vent portion has a vacuum degree of 50 torr or less,
The molten resin temperature at the vent is 280 ° C to 350 ° C
In the zone where the polycarbonate resin is melted, 0.01 part of water is added to 100 parts by weight of the polycarbonate resin.
It is a method of adding (press-fitting) 5 to 5 parts by weight.

In the present invention, a polycarbonate resin powder is used in which the length of one vent opening is 2 times the screw diameter.
The pellets are produced by melt-extruding with an extruder composed of a barrel having a double to fifteen times opening. The extruder is specifically a single-screw extruder with a single-stage or multi-stage vent, or a multi-screw extruder. Machines and the like. Among these, a twin-screw extruder having two or more vents is preferable.

The vent opening length in a general extruder is usually about 0.5 to 1 times the screw diameter, and the width is 0.5 to 1.
This is an extruder consisting of a barrel having about 5 times the opening, but with such a conventional extruder, it is difficult to deaerate low molecular weight volatiles, organic solvents, etc. to a sufficiently low level as described above. However, by using an extruder composed of a barrel having a vent opening in which the length of the vent opening in the present invention is 2 to 15 times the screw diameter, exposure of the molten resin inside the cylinder under vacuum pressure is performed. By increasing the time, the residual solvent and low molecular weight volatiles contained in the molten resin in the portion can be effectively devolatilized.

The width of the vent opening is 0.5 of the screw diameter.
It is possible to more effectively perform devolatilization by doubling. Further, at least one vent opening or more vent openings can be provided in one extruder.

Although the original purpose can be achieved if the vent opening has a structure having the above mechanism, the structure of the screw element prevents vent up (the molten resin rises from the vent port) in the vent part. Therefore, it is preferable to have a structure in which the internal pressure of the barrel is low. Further, it is desirable to use a screw structure having a high carrying capacity in front of these vent portions for the same reason.

Further, the length of the vent opening is preferably 15 times or less the screw diameter in order to prevent foreign matters from entering through the vent opening and vent up, and to keep the screw kneading ability. If the vent opening is smaller than twice the screw diameter, the devolatilization effect is insufficient and sufficient devolatilization is not possible for low molecular weight substances that are less likely to volatilize than organic solvents. In order to reduce the amount of residual solvent and the amount of low molecular weight volatiles remaining, the vacuum degree of the vent is preferably 50 torr or less,
20 by using mechanical booster
It is more preferable that the pressure is not more than torr.

The temperature of the molten resin in the vent opening is particularly preferably 280 ° C. or higher in order to accelerate the volatilization of the organic solvent and low molecular weight substances contained in the resin, and 350 ° C. in order to prevent the decomposition and discoloration of the resin at high temperature. The following is preferable.

The production method of the polycarbonate resin referred to in the present invention is the same as the production method of the conventional polycarbonate resin,
That is, it is produced by a solution method such as an interfacial polymerization method, a pyridine method, and a chloroformate method, which comprises a dihydric phenol compound as a main component, and a small amount of a molecular weight modifier and optionally a branching agent, to react with phosgene. , An aromatic homo- or copolycarbonate resin using an ordinary bisphenol, a further branched one, and a viscosity average molecular weight of 5,000 to 100,000 such as one having a long-chain alkyl group introduced at the end, Preferably 13,0
It is from 00 to 90,000, especially from 7,000 to 35,000.

In these polycarbonate resin production methods, a polycarbonate resin having an active site capable of a graft reaction is obtained by using a monomer having a carbon-carbon double bond or other reactive monomer as an end terminating agent or a comonomer. A grafted polycarbonate obtained by graft-reacting styrene or the like, or a copolymer of polystyrene with a phenolic hydroxyl group or a compound having a graft polymerization initiation point of another polycarbonate resin is used, and a polycarbonate resin is grafted to this. Any one such as a polymerized one can be used.

Preferred dihydric phenol compounds used in the method for producing the polycarbonate resin of the present invention are specifically bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether and bis (4). -Hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl)
Ethane, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A; BPA), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane 2 (TBA), 2-bis ( 4-hydroxyphenyl)
Butane, 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z; BPZ), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4- Hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-
(Hydroxy-3-chlorophenyl) propane, 2,2-
Bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, Bis (4-hydroxyphenyl) diphenylmethane, α, ω-bis [3-
Examples are (O-hydroxyphenyl) propyl] polydimethylsiloxane (PDS) and biphenol.
You may use these in combination of 2 or more types. Among these, Bisphenol A, Bisphenol Z, TBA,
Those selected from PDS are particularly desirable.

Examples of the terminal terminator or molecular weight regulator include compounds having a monovalent phenolic hydroxyl group,
Other than ordinary phenol, P-tert-butylphenol, tribromophenol, etc., long-chain alkylphenol, aliphatic carboxylic acid chloride, aliphatic carboxylic acid, aromatic carboxylic acid, aromatic acid chloride, hydroxybenzoic acid alkyl ester, alkyl ether Examples include phenol.

A compound having a reactive double bond can also be used as a terminal stopper. Examples of these are unsaturated carboxylic acids such as acrylic acid, vinyl acetic acid, 2-pentenoic acid, 3-pentenoic acid, 5-hexenoic acid and 9-undecenoic acid; acrylic acid chloride, sorbic acid chloride, allyl alcohol chloro. Acid chlorides or chloroformates such as formate, isopropenylphenol chloroformate or hydroxystyrene chloroformate; Examples thereof include phenols having a saturated group. These compounds may be used in combination with a conventional end capping agent, and are usually 1 to 25 mol%, preferably 1.5 mol% to 1 mol of the above dihydric phenol compound.
It is used in the range of 10 mol%.

As a solvent inert to the reaction, dichloromethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chloroform, 1,1,1-trichloroethane, carbon tetrachloride, monochlorobenzene, dichlorobenzene. Chlorinated hydrocarbons such as benzene, toluene,
Aromatic hydrocarbons such as xylene and ethylbenzene; ether compounds such as diethyl ether,
Two or more kinds of these organic solvents may be mixed and used. If desired, a solvent having an affinity for water such as ethers, ketones, esters, and nitriles other than those described above may be used as long as the mixed solvent system is not completely compatible with water.

Further, a branching agent is used in an amount of 0.01 to 3 mol%, particularly 0.1 to 3% based on the above dihydric phenol compound.
A branched polycarbonate can also be used in combination within the range of 1.0 mol%. As a branching agent, phloroglucin, 2,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-3,4,6-dimethyl-2,
4,6-tri (4-hydroxyphenyl) heptene-
2,1,3,5-tri (2-hydroxyphenyl) benzole, 1,1,1-tri (4-hydroxyphenyl)
With ethane, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, α, α ′, α ″ -tri (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, etc. Exemplified polyhydroxy compounds, and 3,3-bis (4-hydroxyphenyl) oxindole (= isatin bisphenol), 5-chloroisatin bisphenol, 5,7-dichloroisatin bisphenol, 5-bromoisatin bisphenol Are exemplified.

Examples of the aromatic polycarbonate resin include polycarbonates containing bisphenol A as a main raw material, and polycarbonate copolymers obtained by using, for example, bisphenol Z or tetrabromobisphenol A (TBA) in combination therewith. A branched product or a product modified with a long-chain alkyl at the terminal is preferable.

The polycarbonate resin powder used in the present invention is a powder obtained by solidifying a polycarbonate resin from a purified polycarbonate resin solution. As a method for making powder, the solvent is distilled off from the polycarbonate resin solution. The method of concentrating the mixture into a granular body, adding a poor solvent to the polycarbonate resin solution, adding the mixture to warm water under heating and suspending the mixture in warm water, and distilling the solvent and the poor solvent to solidify There are various methods such as a method of circulating a liquid in a solidification process in a wet pulverizer while producing a water slurry liquid, and pulverizing it. In the present invention, powder obtained by any method can be used. The powder thus obtained varies depending on whether or not it is dried, the type of dryer, and the drying conditions, but in general, the powder has a residual water content of 0.01
10 to 10% by weight, and 0.01 to 4% by weight as a residual solvent.

Polycarbonate powder as a raw material is supplied into the cylinder directly through a hopper or by a side feeder. The powder is melted by heating the cylinder. Since the screw is normally engraved with a screw in the forward direction, the molten resin moves toward the outlet and is guided to the vent portion by the rotation of the screw. In the vent portion, the barrel has a vent opening provided on the top or horizontally. Usually, the inside of the vent opening is evacuated by a vacuum pump. Since the molten resin is kneaded and compressed by the time it reaches the vent opening,
It is rapidly exposed to vacuum pressure to promote devolatilization of residual solvent and low molecular weight volatiles.

In the present invention, water may be added to the raw material powder or the molten resin in order to accelerate the devolatilization of the residual solvent and the low molecular weight volatile matter. From 0.01 to
It is particularly preferable to use the method of adding 5.0 parts by weight of water. The added water can be rapidly gasified at the vent portion to further promote devolatilization. The water may be added at one location, but if it is added at two or more locations, the devolatilization effect will be further improved.

Regarding the kneading time of water and the molten resin, it is preferable to knead the gasified water and the molten resin for 2 to 30 seconds. If the kneading time is shorter than 2 seconds, the kneading of the molten resin and water will be insufficient and the effect of water addition will not be fully exerted. If the kneading time exceeds 30 seconds, hydrolysis of polymer molecules by steam will occur. Occurs and causes coloring.
The kneading time of gasified water and molten resin is determined by the distance from the position where water is added to the vent, the discharge amount of resin, and the screw rotation speed, and the kneading time can be controlled by changing these conditions. it can. Specifically, by performing a tracer response test, the average residence time (T) during which the resin moves by the screw length (L) is calculated for various discharge amounts and screw rotation speeds. The kneading time (t) can be approximated from the distance (d) from the position to the vent using a calculation formula of t = Td / L.

The water added in the present invention is preferably pure water, and has a conductivity of 5 μS / cm or less, particularly preferably 1 μS / cm or less. Water usually contains inorganic salts, and even if these are present in trace amounts,
Since the vapor resistance and heat resistance of the molded product are reduced, it is necessary to reduce the conductivity as much as possible.

In the melt extrusion in the present invention, additives for the purpose of modifying the polycarbonate resin may be added. For example, flame retardants, light stabilizers, antistatic agents, plasticizers, lubricants, compatibilizers, glass agents, foaming agents, carbon fibers, reinforcing agents such as ceramic whiskers, fillers, dyes and pigments, and resins other than polycarbonate. , For example, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polymethylmethacrylate,
ABS resin, polyester, polyphenylene oxide,
In addition, an elastomer or the like can be mixed.

[0035]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto as long as the scope of the present invention is not exceeded.

(Representative Polycarbonate Powder Production Method) Production Example A methylene chloride solution of a polycarbonate resin produced from bisphenol A was purified to obtain a solution having a resin concentration of 20% and a viscosity average molecular weight of 2.1 × 10 ⁴ . This resin liquid 200
To the liter, 40 liters of n-heptane, which was also microfiltered, was added under stirring and uniformly mixed, and then this solution was dropped into warm water under stirring for 10 minutes and pulverized by a wet pulverizer. The temperature of the liquid in the container is 40 ℃ and the internal pressure is 0.1.
It was maintained below kgG / cm ² . After the dropping is completed, the temperature inside the container is raised to about 100 ° C., and the solvent is distilled off in about 15 minutes.
The obtained aqueous slurry of polycarbonate resin was taken out, filtered and drained to obtain a wet powder, which was then dried at 140 ° C. for 4 hours using a hot air circulation dryer,
A dry powder having a residual organic solvent content of n-heptane: 4530 ppm, methylene chloride: 11 ppm and a monomer oligomer content of 0.94% was obtained.

(Measurement Method of Residual Solvent Amount in Pellet) 1 g of the polycarbonate resin pellet was dissolved in dioxane to prepare a 20 mL solution, and quantitative analysis was performed by FID gas chromatography.

(Content of Monomer and Oligomer in Pellet) 100 mg of the pellet was dissolved in 20 ml of chloroform and Waters
GPC (column: Shodex K803L x 2, detector: 4
90 UV detector, 254 nm, AUFS1.0) was used to measure the sample amount: 100 μl, solvent flow rate: 1.0 ml / min. The content rate (%) was calculated.

Examples 1 to 3 Powders having n-heptane: 4530 ppm and methylene chloride: 11 ppm were used as raw material powders, and a twin-screw extruder (screw diameter: 40 mm, L / D =) was used as an extruder.
42, L: total length of screw, D: screw diameter), and having a vent opening with a width of 1.5D at a portion of 20D to 25D from the tip as a barrel shape, 29D to 30
Vent opening of width 0.5D at D, 35D to 36
A barrel having a vent opening with a width of 0.5D was used for D. Discharge rate 30, 40, 50 kg / h, screw speed 2
Extrusion was carried out at a pressure of 00 r.p.m., a vacuum degree of the vent section of 20 torr, and a resin temperature of the vent section of 290 ° C. The residual solvent concentration in the pellet and the monomer oligomer content were measured and the results are shown in Table 1.

Examples 4 to 6 Extrusion pelletization was carried out in the same manner as in Examples 1 to 3 except that extrusion was carried out at a clew rotation speed of 250 rpm and a vent portion resin temperature of 300 ° C., and the pellets remained in the pellets. Solvent concentration,
The monomer oligomer content was measured and the results are shown in Table 1.

Examples 7 to 9 Extrusion pelletization was performed in the same manner as in Examples 1 to 3 except that extrusion was performed at a clew rotation speed of 300 rpm and a vent portion resin temperature of 350 ° C., and the pellets remained in the pellets. Solvent concentration,
The monomer oligomer content was measured and the results are shown in Table 1.

Examples 10 to 12 The extruder used in Examples 1 to 3 was used, and 1 part by weight of pure water was added to 100 parts by weight of the polycarbonate resin in a portion 16D from the tip. Extrusion pelletization was performed in the same manner as in Examples 1 to 3 except for the above. The residual solvent concentration and monomer oligomer content of the extruded pellets were measured, and the results are shown in Table 1.

Examples 13 to 15 As the extruder, the extruder used in Examples 1 to 3 was used, and 0.05 part by weight of pure water was added to the portion 16D from the tip with respect to 100 parts by weight of the polycarbonate resin. Extrusion pelletization is performed in the same manner as in Examples 1 to 3 except that
The residual solvent concentration in the pellet and the monomer oligomer content were measured and the results are shown in Table 1.

Example 16 The extruder used in Examples 1 to 3 was used except that 4.5 parts by weight of pure water was added to 100 parts by weight of the polycarbonate resin in the portion 16D from the tip. Was extruded into pellets in the same manner as in Example 3, the residual solvent concentration in the pellets and the content of the monomer oligomer were measured, and the results are shown in Table 1.

Examples 17-19 Examples 1-19 except that extrusion was carried out at a vent pressure of 5 torr.
Extrusion pelletization was performed in the same manner as in 3, and the residual solvent concentration in the pellets and the content of the monomer oligomer were measured, and the results are shown in Table 1.

Example 20 A powder having n-heptane: 4530 ppm and methylene chloride: 11 ppm was used as a raw material powder, and a twin-screw extruder (screw diameter: 40 mm, L / D =) was used as an extruder.
42, L: total screw length, D: screw diameter), and the barrel shape was a barrel having a vent opening with a width of 1.5D at a portion 21D to 35D from the tip. Discharge rate 50kg / h, screw speed 200r.p.
m., Vent vacuum degree 20 torr, Vent resin temperature 29
Extrusion was carried out at 0 ° C. The residual solvent concentration in the pellet and the monomer oligomer content were measured and the results are shown in Table 1.

Comparative Examples 1 to 3 Extrusion pelletization was carried out in the same manner as in Examples 1 to 3 except that an extruder in which the length of each vent opening was 1.3D was used, and the residual solvent concentration in the pellets, The monomer oligomer content was measured and the results are shown in Table 1.

[0048]

[Table 1]

[0049]

INDUSTRIAL APPLICABILITY In the method of the present invention, extrusion is performed by using an extruder composed of a barrel having a vent opening in which the length of one vent opening is 2 to 15 times the screw diameter. By reducing the amount of residual solvent and low-molecular-weight volatiles in the pellets, it is possible to prevent the formation of bubbles during molding and stains on the stamper, and because the color tone is also highly transparent, optical grade and automotive lenses It is suitable as a method for producing a low-dust transparent material such as

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyoshi Ogawa 2-12-12 Shinshu-cho, Toyonaka-shi, Osaka Mitsubishi Gas Chemical Co., Ltd. Osaka factory

Claims (4)

[Claims] 1. A method for producing pellets by melt-extruding a polycarbonate resin powder with an extruder, wherein the length of one vent opening is from 2 to 15 times the screw diameter.
A method for producing a polycarbonate resin molding material, which comprises melt-extruding and pelletizing using an extruder composed of a barrel having at least one double vent opening. 2. The method according to claim 1, wherein the degree of vacuum of the vent portion is 50 torr or less. 3. The method according to claim 1, wherein 0.01 to 5 parts by weight of water is pressed into 100 parts by weight of the polycarbonate resin in a zone where the polycarbonate resin is melted. 4. The resin temperature of the vent portion is 280 to 350.
The method according to claims 1 to 3, which is at a temperature of ° C.