JP2006316174A - Method for producing fluorine-containing copolymer by fluorination treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing fluorine-containing copolymer that can stabilize the thermally unstable chain terminal structure and enables the polymer to be melt formed at a forming temperature of lower than 320°C, preferably lower than 300°C and more preferably lower than 280°C. <P>SOLUTION: An amorphous fluorine-including copolymer having substantially perfluoro structure is subjected to the fluorination treatment with fluorine gas under the temperature condition, at 0 to 50°C, preferably in this range and higher than the glass transition point Tg of the copolymer to produce the fluorination-treated, fluorine-containing copolymer. Thereby the produced fluorinated fluorine-containing copolymer is thermally stabilized at the part of thermally unstable chain-terminal structure and the existence ratio of the unstable chain terminal is decreased less than 0.20, preferably less than 0.10 and the melt formation can be carried out at a relatively low temperature as stated above. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a fluorinated fluorinated copolymer. More specifically, the fluorine-containing copolymer which stabilizes the thermally unstable terminal structure and enables melt molding at a relatively low temperature of 320 ° C. or less, preferably 300 ° C. or less, more preferably 280 ° C. or less. The present invention relates to a method for producing a fluorinated fluorinated copolymer capable of forming a polymer.

  Fluorine-containing copolymers, especially those with a perfluoro structure, have excellent chemical resistance and good heat resistance, so tubes, pipes, joints, containers, coatings, linings, films, sheets, round bars, etc. It is used as a molding material. Here, as the fluorine-containing copolymer having a perfluoro structure, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer [PFA], tetrafluoroethylene-hexafluoropropene [FEP] and the like are widely used. Yes.

In general, melt molding of PFA and FEP requires a molding temperature of 300 ° C. or higher, and amorphous fluoropolymers and terpolymers as described in Patent Documents 1 and 2 below have a melt molding temperature of This means that the molding apparatus does not require a sophisticated and expensive corrosion resistance treatment or can be simplified. In addition, it is possible to perform coextrusion molding and fusion / compression treatment at a relatively low temperature with a general-purpose polymer having a low heat-resistant temperature.
Special table 2001-500906 JP 2003-246823 A

  However, in melt molding, especially extrusion molding of tubes, pipes, films, sheets, rods, etc., phenomena called melt fracture, flow mark, streak, die line, bank mark, etc. are likely to occur on the surface of the extruded product. Improvement in the surface smoothness of melt-molded products is demanded so that the merits of low-temperature melt moldability can be fully enjoyed without raising the molding temperature.

Generally, PFA has groups such as -COOH-, -CH ₂ OH, and -COOCH ₃ as terminal groups derived from the polymerization initiator and chain transfer agent used in the copolymerization reaction. It is thermally unstable and heat decomposes during hot melt molding, causing not only foaming and coloration, but also affects rheology, increasing melt viscosity and lowering moldability. It has a beneficial effect.

In order to improve the instability of the end groups found in PFA, it has been proposed to treat PFA with fluorine gas.
Japanese Patent Publication No.62-104822 Japanese Patent No. 2,921,026 Japanese Patent Laid-Open No. 11-116710 JP 2004-161921 A

However, all of these fluorination treatments are performed under high temperature conditions of 150 to 200 ° C., and the tetrafluoroethylene-perfluoro (ethyl vinyl ether) copolymer that has been fluorinated in Patent Document 6 Has a copolymerization ratio of perfluoro (ethyl vinyl ether) of 6.7 to 12.6% by weight (Production Examples 1 to 3), which are described in Patent Document 7 below, that is, the copolymer composition, crystal melting point, and heat of fusion. From the relationship with ΔH, it can be said that it is a fluorine-containing copolymer having a crystalline melting point.
Special table 2002-509557 gazette

  It is an object of the present invention to stabilize the thermally unstable terminal structure and to enable melt molding at a relatively low temperature of 320 ° C. or less, preferably 300 ° C. or less, more preferably 280 ° C. or less. It is providing the manufacturing method of a fluorine copolymer.

  The object of the present invention is to form an amorphous fluorine-containing copolymer having a substantially perfluoro structure at 0 to 50 ° C., preferably at a temperature within this range and at least the glass transition temperature Tg of the fluorine-containing copolymer. This is achieved by performing a fluorination treatment with a fluorine gas under temperature conditions to produce a fluorination-treated fluorine-containing copolymer.

  The fluorinated fluorinated copolymer produced by the method of the present invention stabilizes the thermally unstable terminal structure and has a molding temperature of 320 ° C. or lower, preferably 300 ° C. or lower, more preferably 280 ° C. or lower. There is an effect that enables melt molding at a low temperature.

  In particular, in the fluorination reaction temperature region above the glass transition temperature Tg of the fluorine-containing copolymer, the fluorine-containing copolymer is an amorphous polymer material, so the gas permeability of fluorine gas is higher than that of a crystalline polymer material. It is considered that the stabilization of the thermally unstable terminal structure (supported by IR analysis) was achieved by the fluorination reaction at a relatively low temperature and in a short time.

  In addition, the obtained fluorinated fluorinated copolymer has an abundance ratio of unstable end groups by IR of 0.20 or less, preferably as small as 0.10 or less, and thus enables melt molding at a relatively low temperature as described above. For example, in melt extrusion molding, not only the moldability is improved by eliminating roughening of the extrusion skin due to melt fracture and the like, but improvement of foaming and burning in a higher temperature molding region is also remarkable.

  The amorphous fluorine-containing copolymer to be fluorinated is a substantially amorphous polymer having a perfluoro structure. Examples of the copolymer having a perfluoro structure include tetrafluoroethylene, hexafluoropropene, Carbon atoms such as perfluoro (alkyl vinyl ether), perfluoro (alkoxyalkyl vinyl ether), perfluoro (2,2-dimethyl-1,3-dioxole), etc., where the alkyl group is a methyl group, ethyl group, propyl group, fluorine It is a copolymer of two or more types of monomers that can contain atoms, and further oxygen atoms, and has substantially a perfluoro structure, where a small amount, for example, about 1% by weight for modifying the fluorine-containing copolymer. % Or less functional monomer or polyfluoro monomer is allowed to be copolymerized. The amorphous polymer is a heat of fusion ΔH calculated from an endothermic peak detected by differential scanning calorimetry (DSC) of the fluorine-containing copolymer is about 3 J / g or less, preferably about 1 J / g or less. It points to what is.

  Preferred amorphous fluorine-containing copolymer having a substantially perfluoro structure is tetrafluoroethylene copolymerized with about 20 to 50% by weight, preferably about 30 to 48% by weight of perfluoro (alkyl vinyl ether). More preferred is a copolymer containing tetrafluoroethylene, perfluoro (ethyl vinyl ether) and perfluoro (propyl vinyl ether) as a copolymerization component.

  The fluorination treatment of the fluorine-containing copolymer with fluorine gas is performed at a temperature of 0 to 50 ° C., preferably within this range, and at a temperature not lower than the glass transition temperature Tg of the fluorine-containing copolymer.

  The physical shape of the fluorinated copolymer to be fluorinated can be powder, pellet, or crumb. From the viewpoint of the efficiency of gas-solid contact reaction and the stirring efficiency, it can be powder or pellet. It is preferable that As the fluorination reaction temperature, particularly in the case of a copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether), treatment at around room temperature, generally around 25 ° C. is particularly desirable. In order to perform the above, heating up to 50 ° C. can be performed. Under temperature conditions lower than the fluorination reaction temperature condition defined as 0 to 50 ° C., the batch efficiency per unit treatment amount of the fluorinated copolymer is lowered per hour, while at higher temperature conditions, the fluorinated reaction temperature is decreased. The molecular weight of the polymer is lowered, and the mechanical properties of the melt-molded product are lowered.

  On the other hand, in the fluorination reaction in a relatively high temperature region, although the molecular terminal is stabilized, it is presumed that the lowering of the molecular weight due to the main chain cleavage occurs due to the increased MFR value. When the MFR is increased, the mechanical properties of the melt-molded product are remarkably deteriorated, and in the fluorination treatment at a higher temperature, a foaming phenomenon is observed in the extruded product.

  From the viewpoint of reaction efficiency and handling, the fluorine gas used is preferably diluted with an inert gas such as nitrogen or helium to a concentration of about 2 to 50% by volume, preferably about 10 to 30% by volume. If the fluorine gas concentration is too low, the batch efficiency per unit processing amount of the fluorinated copolymer per hour will be lowered, resulting in poor economic efficiency. On the other hand, if the fluorine gas concentration is too high, the molecular weight of the fluorine-containing copolymer is reduced, and not only the mechanical properties of the melt-molded product are reduced, but the material such as the reaction vessel and the piping material is further improved in fluorine gas resistance. There is a special design cost to grant and it becomes less economical.

  The supply of fluorine gas can be either a batch type or a continuous type, and the treatment time with fluorine gas can be a plurality of gas-solid contact efficiency due to fluorine gas supply amount, stirring mechanism, reactor design, etc. Although it cannot be uniquely determined due to factors, when fluorine gas is continuously supplied using a general-purpose reactor or stirrer, about 1 to 24 hours, preferably about 3 to 10 hours It is most efficient to be a degree. If the fluorination treatment time is shorter than this, the melt processability cannot be sufficiently improved. On the other hand, if the treatment time is longer than this, the molecular weight of the fluorinated copolymer is decreased and the mechanical properties of the melt molded product are reduced. Although a decrease is observed, the degree is lower than the case where the upper limit of the temperature condition range is exceeded, and a long treatment time is a factor that impairs the economy.

  The fluorinated copolymer thus fluorinated enables compression molding at a relatively low molding temperature of 320 ° C. or less, preferably 300 ° C. or less, particularly preferably 280 ° C. or less. Suitable for injection molding, transfer molding, extrusion molding, blow molding, inflation molding, etc. Especially by extrusion molding at relatively low temperature, melt molding of tubes, pipes, films, sheets, rods, etc. with extremely good surface skin can do.

  Next, the present invention will be described with reference to examples.

Examples 1-4, Comparative Examples 1-2
In a 100 L autoclave equipped with a stirrer,
Ion exchange water 50L
100g ammonium pentadecafluorooctanoate
Disodium hydrogen phosphate dodecahydrate 250g
Sodium bisulfite 30g
After charging the vacuum nitrogen replacement three times,
Isopropanol 10g
Tetrafluoroethylene [TFE] 2400g
Perfluoro (ethyl vinyl ether) [FEVE] 2340g
Perfluoro (purpyr vinyl ether) (FPVE) 2650g
And heated to 50 ° C.

After confirming that the internal temperature was 50 ° C. and the internal pressure was 0.85 MPa, 150 g of ammonium peroxodisulfate was charged to initiate the polymerization reaction. When the polymerization reaction proceeds and the internal pressure drops to 0.75 MPa,
TFE / FEVE / FPVE = 54/21/25 (wt%)
Addition of the monomer mixture having the composition ratio of up to 0.85 MPa, and when the internal pressure drops to 0.75 MPa, repeat the same addition until the solid content concentration of the polymerization solution reaches about 30% by weight. Repeated.

  Immediately after completion of the reaction, the unreacted monomer in the autoclave is released, and the recovered aqueous latex is subjected to freezing coagulation, washing with water and drying to obtain a copolymer composition (by IR analysis; see JP2003-246823). TFE / FEVE / FPVE = 54/21/25 (weight%), Tg (using Seiko Denshi Kogyo DSC220C) 15 ° C, melting point (using DSC200C) and heat of fusion ΔH (by DSC method) were not observed, MFR (ASTM 21 kg of a powdery fluorinated copolymer having 1.1 g / 10 min (230 ° C.) based on D1238; using a melt indexer manufactured by Toyo Seiki Seisakusho, and having an unstable terminal group abundance ratio of 0.26 by IR was obtained.

Here, the unstable terminal group peaks derived from the -COOH group (3656cm ^-1) and -CH ₂ OH group includes a plurality of unstable terminal groups peaks containing (3648cm ^-1) "of 3900～2760Cm ^-1 The value obtained by dividing the integral value of broad absorption by the integral value of broad absorption from 2735 to 2185 cm ^-1 derived from the -CF ₂ -group of the copolymer backbone The smaller the value of this index, the smaller the abundance ratio of unstable end groups. In addition, the film and the extrudability are excellent.

  The resulting fluorine-containing copolymer powder is formed at 240, 260, 280, 300, and 320 ° C. molding temperatures (die temperatures), with a die spacing of 0.5 mm, a die width of 120 mm, and a film thickness of approximately 0.1 mm. A film having a width of about 120 mm was extruded by appropriately adjusting the take-up speed as described above. Observe the obtained film surface visually, and indicate the degree of defects such as surface roughness, dimensional accuracy, foaming, streaks, burnt, melt fracture (MF) as △ (slightly), × (many). Those without defects were evaluated as ○.

  In addition, 90 g of the fluorinated copolymer powder has a stirring function and is charged into a degreased 400 ml glass reaction vessel, and after the inside of the reaction vessel is purged with nitrogen, the reactor is set to a predetermined reaction temperature condition. The nitrogen was diluted and 20 volume% fluorine gas diluted with nitrogen was introduced at a flow rate of 100 ml / min for a predetermined time. After completion of the reaction, the inside of the reactor was replaced with nitrogen, and the fluorinated fluorine-containing copolymer was recovered, and the abundance ratio of unstable end groups of MFR (230 ° C.) and IR was measured.

Examples 5-6, Comparative Example 3
In Example 1, as a monomer mixture added during the copolymerization reaction
TFE / FEVE / FPVE = 78/15/17 (wt%)
The copolymer composition is 78/15/17 (wt%), Tg is 35 ° C., melting point and heat of fusion ΔH are not observed, MFR 0.5 g / 10 min (260 ° C.), IR As a result, 23 kg of a powdery fluorocopolymer having an abundance ratio of unstable terminal groups of 0.21 was obtained.

  Using this fluorine-containing copolymer powder, film extrusion and fluorination (however, the flow rate in Example 6 was 150 ml / min) were performed in the same manner as in Examples 1 to 4. The MFR of the fluoride was also measured at 260 ° C.

The results obtained in the above examples and comparative examples are shown in the following table.
table
Real-1 Real-2 Real-3 Real-4 Ratio-1 Ratio-2 Real-5 Real-6 Ratio-3
[Film extrusion]
Molding temperature 320 ° C − − − − − − △ ○ ×
(Burn) (Burn)
300 ° C △ ○ △ ○ × × ○ ○ ○
(Burn) (Foam) (Foam) (Burn)
280 ° C ○ ○ ○ ○ △ ○ ○ ○ △
(Foaming) (MF)
260 ° C ○ ○ ○ ○ ○ △ △ ○ ×
(MF) (MF) (MF)
240 ° C △ ○ ○ ○ ○ × − − −
(MF) (MF)
[Film fluorination]
Fluorination temperature (° C) 0 25 50 50 75 − 25 50 −
Fluorination time (hr) 3 3 3 1 1 − 2 2 −
Fluorinated film
MFR (g / 10 min) 1.1 1.2 3.2 2.1 4.8 1.1 0.5 0.6 0.5
IR unstable terminal group abundance ratio 0.19 0 0 0.03 0 0.26 0.08 0 0.21

Claims (9)

  A method for producing a fluorinated fluorinated copolymer, comprising subjecting an amorphous fluorinated copolymer having a substantially perfluoro structure to fluorination treatment with a fluorine gas at a temperature of 0 to 50 ° C.   The method for producing a fluorinated fluorinated copolymer according to claim 1, wherein the amorphous fluorinated copolymer is a fluorinated copolymer having a heat of fusion ΔH detected by DSC of 3 J / g or less.   The method for producing a fluorinated fluorinated copolymer according to claim 1, wherein the amorphous fluorinated copolymer is a copolymer containing tetrafluoroethylene and perfluoro (alkyl vinyl ether) as a copolymerization component.   4. The copolymer containing tetrafluoroethylene and perfluoro (alkyl vinyl ether) is a copolymer containing tetrafluoroethylene, perfluoro (ethyl vinyl ether) and perfluoro (propyl vinyl ether) as copolymerization components. A process for producing a fluorinated copolymer.   The method for producing a fluorinated fluorinated copolymer according to claim 1, wherein the fluorination is carried out at a temperature in the range of 0 to 50 ° C and at a temperature not lower than the glass transition temperature Tg of the fluorinated copolymer.   A fluorinated fluorinated copolymer which can be melt-molded and produced by the method according to claim 1, 3, 4 or 5. Melting of claim 6, wherein the unstable terminal groups existing ratio by IR (divided by the integral value of the broad absorption in the integral value of the broad absorption of 3900~2760cm ^-1 2735~2185cm ^-1) is 0.20 or less Moldable fluorinated copolymer.   The fluorinated fluorinated copolymer according to claim 6 or 7, which can be melt-molded at a molding temperature of 320 ° C or lower. A molded article melt-molded from the fluorinated fluorine-containing copolymer according to claim 6, 7 or 8.