JP2003082106A - Method for manufacturing regenerated fluorine- containing polymer and pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a recyclable fluorine-containing polymer, free of foaming or coloring, by efficiently modifying unstable groups even in remelt kneading. SOLUTION: The regenerated fluorine-containing polymer is manufactured by melting and kneading a molded fluorine-containing polymer in a kneader containing a modification treatment region where an oxygen-containing gas and water are present. The kneader is preferably a screw extruder. Particularly, the screw type kneader is preferably a twin screw extruder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a regenerated fluoropolymer, and more specifically, it efficiently modifies an unstable group to obtain a reusable fluoropolymer having no bubbles or coloring. It relates to a manufacturing method.

[0002]

Fluorine-containing polymers which can be melt-processed are, for example, copolymers (FEP) of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), TF.
E and perfluoro (alkyl vinyl ether) (PAV
There are many known copolymers (PFA) with E) and copolymers (ETFE) with TFE and ethylene. These have excellent melt processability, heat resistance, chemical resistance, electrical insulation, non-adhesiveness, low friction properties, etc., so they are used not only in the chemical industry, electrical / electronic industry, mechanical industry, but also in space development and aircraft. It is used in a wide range of fields from industry to household products. Among them, FEP is mainly used as a cable covering material because of its melt processability and excellent electrical characteristics.

In recent years, it has become an important subject from the environmental aspect to reduce the amount of waste, that is, to recover and reuse FEP as a covering material from a defective product that is out of specification or a cable that is no longer needed. ing. However, once molded F
When EP is melted and kneaded again, the remolded product is colored and bubbles are generated.

Japanese Unexamined Patent Publication No. 10-292054 discloses that
A method of modifying and whitening a melt-fabricable fluoropolymer resin having an overall unstable fraction of 0.3% or less by extrusion in the presence of an alkali metal nitrate is disclosed. However, even if this method is used for recycling, the polymer to be recycled is already deteriorated,
There was a problem that it could not be stabilized if it had an unstable fraction.

[0005]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems. Even in the case of remelting and kneading, unstable groups are efficiently modified, and reusable compounds containing no bubbles or coloring are contained. It is intended to provide a production method capable of obtaining a fluoropolymer.

[0006]

That is, the present invention is characterized in that a molded fluoropolymer is melt-kneaded in a kneader including a reforming treatment region where a gas containing oxygen and water are present. And a method for producing a regenerated fluorine-containing polymer.

It is preferable to supply a gas containing oxygen into the reforming treatment region.

The kneader is preferably a screw type extruder.

The screw type extruder is preferably a twin screw type extruder.

The absolute pressure in the reforming treatment area is 0.1M.
It is preferably less than Pa.

The absolute pressure in the reforming treatment area is 0.2M.
It is preferably Pa or more.

The gas containing oxygen is preferably air.

A compound containing an alkali metal, an alkaline earth metal or an ammonium salt in the modification treatment region,
Alcohols, amines or salts thereof, or ammonia are preferably present.

The fluorinated polymer is preferably a copolymer composed of at least two kinds of monomers selected from the group consisting of tetrafluoroethylene, hexafluoropropylene and perfluoro (alkyl vinyl ether).

The fluorinated copolymer is preferably a copolymer containing an unstable group produced by an emulsion polymerization method.

It is preferable that the kneader includes a degassing region having an absolute pressure of 0.1 MPa or less downstream of the reforming region.

The present invention also relates to pellets containing the regenerated fluoropolymer produced by the above production method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION As the fluorine-containing polymer used in the present invention, as mentioned above, TFE, HFP, PAVE,
A copolymer obtained by copolymerizing two or more kinds of monomers such as ET, VdF and CTFE, a homopolymer of CTFE (P
CTFE), a homopolymer of VdF (PVdF) and the like are known. Specific copolymers include, for example, TF
E-HFP copolymer (FEP), TFE-HFP-PA
FEP polymer such as VE copolymer; TFE-PAVE
Copolymer (PFA), TFE-PMVE-PAVE (P
Other than MVE) PFA-based polymer such as copolymer; TFE-
ETFE polymer such as ET copolymer (ETFE); C
ECTFE such as TFE-ET copolymer (ECTFE)
Examples include a system polymer; a TFE-VdF copolymer and the like.

As PAVE, a vinyl ether represented by the formula: CF ₂ = CFO (CF ₂ ) _m F (where m is an integer of 1 to 6) (where m is 1 is perfluoromethyl vinyl ether). (hereinafter referred to as PMVE) is), and the formula: CF ₂ = CF- in _{(O-CF 2 CF (CF} 3)) n OC 3 F 7 ( wherein, n is an integer from 1 to 4) The vinyl ethers represented are mentioned. Among them, TFE, HFP, P
It is preferably a copolymer composed of at least two kinds of monomers selected from the group consisting of AVE. Especially PM
VE 0.5 to 13% by weight, PAVE other than the PMVE
It is preferably a copolymer composed of 0.05 to 3% by weight and the balance of TFE. The polymer is polymerized by suspension polymerization, emulsion polymerization or the like. Of these, emulsion polymerization is preferred.

In the production method of the present invention, a fluoropolymer which is once formed into a desired shape by a melt processing method or the like is used. In order to reuse this, melt processing is performed again, but in the production method of the present invention, modification of the unstable group, coloring and bubbles can be prevented.

The fluoropolymer used in the present invention is formed into pellets, films, sheets, foam materials, pipes, tubes, filaments and the like. When these cannot be directly processed, they are crushed by a crusher such as a shredder or a crusher mill into a shape that can be supplied to the kneader. The pulverized fluoropolymer is supplied to a kneader and melt-kneaded. The polymer in the kneader is melted and sheared by heating, which causes unstable end groups in the polymer. The unstable terminal group produces a volatile substance due to heat, which causes bubbles and voids in the molded product.

Here, the types of unstable groups and their reforming reactions will be described including estimation. As the unstable group, a carboxylic acid group (—COOH) derived from a polymerization initiator, a chain transfer agent, etc. remaining in the fluoropolymer, and a vinyl group (—CF) formed by the carboxylic acid group being modified by heat.
= CF ₂ ), an acid fluoride group (—COF) derived from this vinyl group, and the like are known. These labile groups are usually located at the ends of the polymer chains (main chain or side chains). Further, depending on the kind of the polymer and the production method, an unstable bond may occur in the bonding portion in the main chain of the polymer. For example, in a TFE-HFP polymer, TFE and HFP are randomly polymerized, and HF is present in the polymer chain.
There are times when P-HFP binding is repeated and this HFP
The -HFP bond is an unstable bond that is easily broken by mechanical force (shearing force), and it is expected to generate an unstable vinyl group and acid fluoride group.

The reaction for modifying these labile groups is considered as follows.

This reaction is carried out by heating, usually at 200 to 450 ° C.,
It is preferably carried out at 300 to 400 ° C.

In order to accelerate this reaction, it is effective to add a reaction accelerator such as a compound containing an alkali metal, an alkaline earth metal or an ammonium salt, ammonia, an alcohol, an amine or a salt thereof. Is. Among them, a compound containing an alkali metal or an alkaline earth metal is preferable for the reason that the terminal is completely converted to —CF ₂ H. Specifically, potassium hydroxide, hydroxides such as sodium hydroxide, carbonates such as potassium carbonate and calcium carbonate, sulfates such as potassium sulfate, nitrates such as potassium nitrate, ammonium salts such as ammonium hydroxide, ammonia, Examples thereof include alcohols such as methanol and ethanol, amines or salts thereof. -C in the case of an alkali metal or alkaline earth metal compound
It becomes an F ₂ H terminal, and becomes an acid amide terminal group (-CONH ₂ ) in the case of ammonium salt, ammonia, and amine (partially becomes -CF ₂ H terminal at high temperature), and an alkyl ester terminal group (-COOR in the case of alcohol). ).

The reaction accelerator may be added to the fluorine-containing polymer in advance, but it is preferable to add it together with water in the reforming treatment area because it can be uniformly dispersed in the polymer. The amount of addition depends on the type of fluoropolymer to be regenerated, but in the case of alkali metal and alkaline earth metal compounds, it is converted to the number of atoms of alkali metal and alkaline earth metal, and in the case of ammonia the molecule of ammonia In terms of number, in the case of ammonium salt compound, converted to the number of ammonium salt, 10% or less, preferably 0.1 to 10%, of the total number of unstable groups (carboxylic acid end groups) in the fluoropolymer. And particularly preferably 0.2 to 5%.
If the amount of addition is too large, the rate of modification of unstable terminal groups increases, but coloring of the polymer cannot be completely eliminated, and the polymer itself tends to deteriorate and the melt viscosity tends to decrease.

As a method of modifying the carboxylic acid terminal group, there is fluorination treatment with fluorine gas or the like, but fluorination treatment is not carried out in the reforming treatment region of the present invention. Of course, after the modification treatment of the present invention, further fluorination treatment may be performed if necessary.

It is presumed to be caused by the application of heat or shear force from the bond between the vinyl end group carboxylic acid end group and the unstable main chain.

[0029]

This vinyl terminal group is converted to a trifluoromethyl group by fluorination treatment, or converted to a carboxylic acid group via an acid fluoride according to the following reaction formula.

-CF = CF ₂ + O ₂ → -COF + COF ₂ (IV) -COF + H ₂ O → -COOH + HF (V)

The carboxylic acid end groups formed are treated as described above. However, said US Pat. No. 4,675,38
No. 0 is terminated with vinyl end groups in the substantial absence of oxygen to avoid conversion to acid fluoride which complicates processing.

However, when the vinyl terminal group is heated, it undergoes depolymerization as shown in the following formula to generate carbon. Therefore, in US Pat. No. 4,675,380, a dark melt-kneaded product is obtained. ing.

[0034]

Acid Fluoride Terminal Group According to the above formula (V), the carboxylic acid group is once returned to the carboxylic acid group and then modified.

As described above, in many cases, the modification treatment of the fluorine-containing polymer finally results in the reaction of modifying the carboxylic acid end group with water and heat to become a rate-determining reaction, and the vinyl end group is decomposed as much as possible. A method is adopted in which polymerization does not occur. For example, in the method described in the above-mentioned WO98 / 09784 pamphlet, the modification reaction of the carboxylic acid terminal group is prioritized, and the generation of the vinyl terminal group is mildly generated so that carbon causing coloration is not generated by depolymerization, The reforming treatment was carried out under substantially atmospheric pressure (in Examples 1 and 2 described in the pamphlet of WO98 / 09784, the absolute pressure was about 0.1 MPa), and the kneading was further performed with a power coefficient K of 8
Since it is characterized in that it is carried out under a mild condition of less than 000, preferably 7,000 or less, the time required for the modification treatment is long.

In the present invention, on the contrary, by positively and uniformly presenting oxygen and water, the vinyl end group is rapidly converted into acid fluoride (reaction (IV)), depolymerization is reduced, and the generation of carbon is reduced. It suppresses and prevents coloration and accelerates the modification reaction (I) of the carboxylic acid terminal group by applying a pressure.

The reforming treatment region in the present invention is a region in which a gas containing oxygen and water are present in the kneading machine, and in this region, the fluorine-containing polymer is reformed such as stabilizing unstable groups. .

The oxygen used in the present invention is the reaction component necessary to convert the vinyl end groups to acid fluoride end groups. Further, it can be expected that carbon atoms produced by depolymerization of vinyl terminal groups, which are produced to some extent, are oxidized to carbon dioxide.

The amount of oxygen (O ₂ ) present varies depending on the temperature during the reaction, the residence time in the reforming treatment region, the type of extruder, the type and amount of unstable terminal groups, and the like. end groups (-CF = CF ₂₎ and at least equimolar amount, an excess amount considering the amount to be exhausted without contributing to the diffusion loss and reaction, for example 10-fold molar amount or more, and particularly 50 to 500 times the molar amount Is preferred.

The oxygen-containing gas may be supplied by diluting the oxygen gas with an inert gas such as nitrogen gas or argon gas to an appropriate concentration (for example, 10 to 30% by volume), or using air as it is. It is preferable from the economical viewpoint.

When air is used as the oxygen-containing gas, the feed rate to the stabilization treatment area is
It may be appropriately set depending on the throughput, the size and type of the kneading machine, and the like.

It is sufficient that oxygen exists in the reforming treatment area,
It may be contained in the fluoropolymer before being charged into the kneader, or may be supplied after being charged into the kneader. Above all, it is preferable to feed the fluorinated polymer to the kneader after it is charged, because it can be uniformly diffused and dispersed in the raw material resin.
Of course, both may be used together.

The water used in the present invention is used in the reaction (I) for modifying the carboxylic acid end group and the reaction (V) for converting the acid fluoride into the carboxylic acid.

The amount of water added must be in excess of the theoretical amount required for the above reaction, but the amount is greatly dependent on the pressure to be added and the state of the inside of the extruder, and is determined while confirming it in the actual machine. .

The supply rate of water to the stabilization treatment area may be appropriately set depending on the treatment rate of the raw material, the treatment amount, the size and type of the kneader, and the like.

As described above, the reaction (I) for modifying the carboxylic acid terminal group is greatly promoted by adding a reaction accelerator such as an alkali metal compound, and therefore water is in the form of an aqueous solution in which the accelerator is dissolved. Is preferably added.
The concentration of the aqueous solution may be appropriately selected based on the required amount of the above promoter.

Water may be present in the reforming treatment area, and may be contained in the fluoropolymer before being put into the kneader so as to be in a wet state, or after the dried polymer is put into the kneader. May be supplied. Of course, both may be used together. For example, it is also preferable to treat the polymer with an aqueous solution of a reaction accelerator, dry it, and put it in a kneading machine, then supply water and oxygen (air) to knead it.

The amount of water to be supplied can theoretically be modified if the number of molecules is the same as the number of unstable terminal groups generated in the kneader, but in reality, it is excessive, particularly 10 times the number of unstable terminal groups. It is preferable to supply water having the above number of molecules. The upper limit is not particularly limited.

Generally, unless special measures are taken, the polymer supplied to the kneading machine contains air and water similar to the atmosphere, but the present invention can be achieved with such oxygen and water contents. No modification effect is achieved. The reason is probably that in the reforming treatment area of the kneading machine, low molecular weight substances and various additives in the polymer (for example, a polymerization initiator) decompose to generate gas, so that oxygen in the reforming treatment area is generated. It is considered that this is because the partial pressure of is decreased and the contact between the polymer and oxygen becomes insufficient.

As long as the above conditions are satisfied, that is, the gas containing oxygen and water are positively contained in the polymer,
And / or as long as the gas containing oxygen and water are continuously supplied into the reforming treatment region, the reforming treatment region may be under pressure, under reduced pressure, or under atmospheric pressure.

Preferably, the absolute pressure is 0.2 MPa or more,
The pressure is preferably 0.3 MPa or more. By pressurizing, for example, invasion of water or oxygen to be supplied is promoted, and a rapid reforming process becomes possible. The pressure can be measured by a pressure gauge attached to the kneader. The upper limit depends on the condition of the melt seal part and the type of extruder, but it is 1
It is 0 MPa or less, preferably 5 MPa or less. The pressurization can be performed, for example, by injecting an oxygen-containing gas and / or water, which will be described later, or by heating the oxygen-containing gas and / or water and supplying the gas under its own pressure.

In the case where the treatment is carried out under reduced pressure, that is, under an absolute pressure of less than 0.1 MPa, the reforming treatment takes some time, but various decomposed gases and low molecular weight substances generated by heating can be easily added to the system. It is advantageous in that it can be taken out to the outside and that deaeration in the downstream of the reforming treatment region becomes easy. When carrying out the reforming process under reduced pressure, it is difficult to form a reduced pressure if the water supply is introduced in the liquid state,
It is preferable to supply in the form of humidified air obtained by adding water vapor to an oxygen-containing gas.

By melt-kneading under the above conditions, the unstable group can be efficiently modified in a short time regardless of the end group and the unstable bond in the main chain, and the carbon which causes coloring is also generated. The occurrence of can be suppressed.

In the present invention, even if a kneader having a power coefficient K of less than 8000 is used as the kneader, desired results can be obtained as long as the above conditions are satisfied, but in order to further shorten the processing time, the power coefficient is It is preferable to set the kneading conditions such that K is 8,000 or more, and preferably 10,000 or more.

The kneading machine which can be used in the present invention includes a multi-screw kneading machine such as a twin-screw extruder and a kneader having an extremely small effective volume ratio. Of these, a twin-screw extruder is preferable because the residence time distribution is narrow and continuous operation is possible and the pressure in the reaction section can be increased by melt sealing.

The reforming treatment area may be provided, for example, in the screw portion immediately after the melting zone constituted by the kneading disk of the twin-screw type extruder. In addition, it is possible to make a modification such that the melting zone is set to be long and the subsequent flow portion is used as a reforming treatment area.

The treatment time in the reforming treatment area, that is, the residence time, varies depending on the structure of the kneading machine in the reforming treatment area, the method of supplying water or air, the treatment temperature, etc., and usually 10 minutes or less is sufficient, but is preferable. Is 0.2 to 5 minutes. When the residence time becomes long, a large shearing force is applied and the polymer tends to deteriorate.

The temperature of the reforming treatment region is usually 200 to 45.
The temperature is 0 ° C, preferably 300 to 400 ° C. When the temperature of the modification treatment region is lower than 200 ° C., the terminal stabilization reaction to —CF ₂ H tends to be difficult to occur. Also 450 ° C
If it exceeds, the deterioration of the raw material resin is remarkable and the molecular weight tends to decrease.

In the present invention, the gaseous substances generated in the reforming treatment reaction, such as hydrogen fluoride, carbon dioxide gas, and a small amount of monomers generated by the decomposition, are taken out from the inside of the reformed fluorine-containing polymer and the mixture is kneaded. To be discharged to the outside,
It is preferable to provide a deaeration region in which the absolute pressure is kept at 0.1 MPa or less in the kneader after the reforming treatment region. The absolute pressure in the degassing region varies depending on operating conditions such as the molten state of the polymer and the rotation speed of the screw of the extruder, but it is preferable to reduce the pressure so that the polymer does not enter the exhaust nozzle.

The regenerated fluorine-containing polymer obtained by the reforming method of the present invention and discharged from the kneader is usually in the form of pellets, and even if such pellets are subjected to melt molding, the molded article obtained will have air bubbles or voids. Does not occur, and coloring does not occur.

If necessary, the kneaded product (pellets) taken out from the kneader may be subjected to the fluorination treatment.

[0063]

EXAMPLES For the purpose of explaining the present invention, specific examples will be given below, but the present invention is not limited thereto.

Evaluation Method (Volatile Substance Index: VI) As a method for evaluating the amount of volatile substance generated when a polymer is melt-molded, the following volatile substance index (VI) is known (WO98 / 0978).
4 pamphlet etc.)

A 10 g sample of polymer is placed in a heat resistant container and placed in a high temperature block maintained at 380 ° C. to achieve thermal equilibrium. After that, change the pressure by 10 for 60 minutes.
Record every minute and calculate the volatile matter index (VI) value by the following formula.

Volatile substance index = (P ₄₀ −P ₀ ) × V / 10 / W (where P ₀ and P ₄₀ are before insertion (P ₀ ) and 40 minutes after insertion (P ₄₀ ) in the high temperature block, respectively). Pressure (mmH
g), V is the volume of the container (ml), and W is the mass of the sample (g).

The volatile substance index is preferably 25 or less, and when it exceeds 25, the amount of bubbles and voids generated during melt processing becomes a problem.

(Quantification of End Group) US Pat. No. 3,085,
No. 083, U.S. Pat. No. 4,675,380, JP-A-4-20507, and the like, and the infrared spectroscopic analysis method is used to quantify each end group. The evaluation is performed based on the number of each terminal group per 10 ⁶ carbon atoms.

(Degree of Coloring) Using the untreated fluoropolymer before melt-kneading as a standard, the whiteness of the fluoropolymer after re-melt kneading is visually evaluated according to the following steps. A: There is no difference. B: Slightly yellowed. C: Yellowing. D: It is dark brown.

Example 1 TF using ammonium persulfate (APS) as a polymerization initiator
FEP obtained by emulsion-polymerizing E / HFP at 90.2 / 9.8 (molar ratio) was coagulated, dried, and extruded with a twin-screw extruder to obtain pellets (melt viscosity at 372 ° C .: 2. 5K
Pa · s, 3 measured according to ASTM D-2116
Melt flow rate at 72 ° C: 20).

In a twin-screw type extruder having a kneading block (reforming region) having a shaft diameter of 47 mm and a total length of 2468 mm, 20 ppm of potassium carbonate (value converted into potassium amount, which is 4. Equivalent to 3%)
50% of the FEP powder (including air) that was not subjected to any special pre-drying treatment except that it was added so that
It was fed at a rate of kg / hour. Pure water and air (oxygen concentration: about 20%) were supplied to the reforming treatment region at a flow rate of 1.5 kg / hour and 40 NL / min, respectively, on the downstream side of the FEP powder supply port. The setting temperature of the reforming treatment region (kneading block) was 390 ° C., the absolute pressure was 2.5 MPa, and the total time required for the entire treatment including the heating and melting time was 5 minutes (in the reforming treatment region). The residence time is estimated to be about 2 minutes).

The raw material FEP and the modified FEP were evaluated for the volatile matter index (VI), the number of end groups and the coloration by the above-mentioned method. The results are shown in Table 1.

[0073]

[Table 1]

Comparative Example 1 A reforming treatment was performed in the same manner as in Example 1 except that air was not supplied, and the same evaluation was performed. The results are also shown in Table 1.

Example 2 While performing melt-kneading extrusion using the same FEP and extruder as in Example 1, the reforming treatment area in the extruder was once depressurized to 0.098 MPaG with a vacuum pump, and then wet simulated air ( Nitrogen / oxygen (volume) = 80/20, which has been subjected to a moistening treatment corresponding to saturated humidity at 80 ° C.) was introduced into the reforming treatment region under reduced pressure, and the internal pressure of the reforming treatment region was adjusted to 0.05 MPaG It was prepared to be in a reduced pressure state. While maintaining this reduced pressure state, FEP powder was supplied at a rate of 5 kg / hour, and the pseudo air was continuously supplied at 10 NL / min. The set temperature of the reforming treatment area is the same as that of the first embodiment, which is 3
The temperature was 90 ° C. The extrudates obtained were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0076]

[Table 2]

Comparative Example 2 While performing melt-kneading extrusion using the same FEP and extruder as in Example 1, once the reforming treatment area in the extruder was depressurized to 0.098 MPaG to remove oxygen,
Then, a small amount of water (liquid) was introduced into the reforming treatment region under reduced pressure, and the internal pressure of the reforming treatment region was adjusted to 0.09 MPaG under reduced pressure. F while maintaining this reduced pressure
EP powder is supplied at a rate of 5 kg / hour and water is supplied at 0.1 k
It was continuously fed at g / hour. The set temperature of the reforming treatment region was 390 ° C. as in Example 1. The extrudates obtained were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0078]

[Table 3]

Comparative Example 3 While performing melt-kneading extrusion using the same FEP and extruder as in Example 1, once the reforming treatment region in the extruder was depressurized to 0.098 MPaG to remove oxygen,
Then, a small amount of water (liquid) and nitrogen gas are introduced into the reforming treatment region in a reduced pressure state so that the internal pressure of the reforming treatment region is 0.2 MPa.
It was prepared so that the G pressure was applied. While maintaining this pressurized state, FEP powder was supplied at a rate of 5 kg / hour, water was continuously supplied at 0.1 kg / hour, and nitrogen gas was continuously supplied at 10 NL / minute. The set temperature of the reforming treatment region was 390 ° C. as in Example 1. The extrudates obtained were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0080]

According to the modifying method of the present invention, the unstable group of the melt-processable fluoropolymer having the unstable group can be modified rapidly and efficiently. Further, even if the obtained modified polymer is melt-molded again, bubbles or voids do not occur in the molded product, and there is no coloring. Therefore, the fluoropolymer can be reused, the amount of waste can be reduced, and it is environmentally beneficial.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 27:12 B29K 27:12 C08L 27:12 C08L 27:12 (72) Inventor Masayuki Namimatsu Osaka Prefecture 1st 1-1 Nishiichitsuya, Settsu-shi Daikin Industry Co., Ltd. Yodogawa Works (72) Inventor Yoshiyuki Takase 1-1-1 Nishiichitsuya, Settsu City Osaka Prefecture F-term inside Daikin Kogyo Co., Ltd. (reference) 4F070 AA23 AA24 AC03 AC06 AC12 AC16 AC19 AC36 AC46 FA04 FC05 4F201 AA16 AB16 AB19 AH35 AM28 AR02 BA01 BC01 BC02 BC12 BC17 BC25 BD05 BK02 BK13 BK25 BK27 BK36 BK73 4F301 AA18 BF16 BF25 BF31 CA09 CA23 CA01 CA01 4

Claims (12)

[Claims] 1. A method for producing a regenerated fluoropolymer, characterized in that the molded fluoropolymer is melt-kneaded in a kneader including a reforming treatment region in which a gas containing oxygen and water are present. . 2. The method for producing a regenerated fluoropolymer according to claim 1, wherein a gas containing oxygen is supplied into the reforming treatment region. 3. The method for producing a regenerated fluoropolymer according to claim 1, wherein the kneader is a screw type extruder. 4. The method for producing a regenerated fluoropolymer according to claim 3, wherein the screw type extruder is a twin screw type extruder. 5. The absolute pressure in the reforming treatment area is 0.1.
The method for producing a regenerated fluoropolymer according to claim 1, wherein the pressure is less than MPa. 6. The absolute pressure in the reforming treatment area is 0.2.
The method for producing a regenerated fluorine-containing polymer according to claim 1, which has a pressure of at least MPa. 7. The method for producing a regenerated fluoropolymer according to claim 1, 2, 3, 4, 5, or 6, wherein the gas containing oxygen is air. 8. An alkali metal in the reforming treatment area,
The method for producing a regenerated fluorinated polymer according to claim 1, 2, 3, 4, 5, 6 or 7, wherein a compound containing an alkaline earth metal or ammonium salt, an alcohol, an amine or a salt thereof, or ammonia is present. . 9. The fluoropolymer is a copolymer composed of at least two kinds of monomers selected from the group consisting of tetrafluoroethylene, hexafluoropropylene and perfluoro (alkyl vinyl ether). 3. The method for producing a regenerated fluoropolymer according to 3, 4, 5, 6, 7 or 8. 10. The method for producing a regenerated fluoropolymer according to claim 9, wherein the fluorocopolymer is a copolymer containing an unstable group produced by an emulsion polymerization method. 11. The kneading machine includes a degassing treatment area having an absolute pressure of 0.1 MPa or less downstream of the reforming treatment area. Or the method for producing a regenerated fluoropolymer according to item 10. 12. The method according to claim 1, 2, 3, 4, 5, 6, 7,
A pellet containing a regenerated fluoropolymer produced by the production method according to 8, 9, 10 or 11.