JPH02163128A - Stabilization of perfluoro polymer - Google Patents

Abstract

PURPOSE:To stabilize the subject polymer at a low cost by irradiating light with a specified wave length on powder or moldings of a perfluoro polymer having unstable terminal groups and capable of melt processing in an atmosphere of gaseous fluorine for fluorination thereof at the room temperatures under the atmospheric pressure. CONSTITUTION:On powder or moldings of a perfluoro polymer [e.g. (co)polymer of tetrafluoroethylene, hexafluoropropylene, etc.] having unstable terminal groups and capable of melt processing, light (preferably mercury vapor lamp or xenon lamp as the light source) with 150-700nm wave length is irradiated in an atmosphere of gaseous fluorine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for stabilizing the terminal ends of a melt-processable perfluoropolymer having unstable terminal groups.

[Prior art] Tetrafluoroethylene (TPE)-hexafluoropropylene (HPP) copolymer and TPE-perfluoro(
Melt-processable perfluoropolymers, such as alkyl vinyl) ether (PPE) copolymers, are resins that can be melt-molded into various types while maintaining the chemical stability and thermal stability of fluorine-containing polymers. It is used in various fields.

Such perfluoropolymers are obtained by copolymerizing perfluoroolefins and perfluoromonomers that can be copolymerized with the perfluoroolefins, but residues of polymerization initiators, chain transfer agents, etc. used at this time remain at the polymer terminals. . Many of these end groups are thermally and chemically unstable, and when the polymer is heated and melted, gas is generated due to thermal decomposition, which may cause foaming in the molded resin. Such unstable end groups include -C001, -CONH2,
-CF2)1, -CP2CHs, -CF2C1.

-CH20H, -COP, etc. are mentioned.

As a method for stabilizing these terminal unstable groups,
-28245 Publication states that by bringing a compound that generates fluorine radicals (2, C0F3, AgF2, halogen fluoride, etc.) into close contact with a perfluoropolymer at a high temperature necessary for generating fluorine radicals, terminal instability is achieved. A method of fluorinating groups up to 10F3 is described. According to this method, it is said that the number of carbon atoms can be reduced to 21 or less per tOS.

In addition, JP-A-62-104822 discloses that after contacting with fluorine gas at 150 to 250°C for 4 to 15 hours to fluorinate unstable groups to 6 or less per 10' carbon atoms, inert gas A method for removing generated fluorine compounds to 3p1) or less is disclosed.

[Problem to be solved by the invention] In the conventional method of stabilizing terminal unstable groups by fluorination using fluorine gas, the fluorination reaction is carried out at high temperature and over a long period of time, which significantly increases the energy cost. In addition to being large, there is a problem in that the reactor and other parts must be made of expensive titanium alloy.

[Means for Solving the Problems] The present invention is a method for stabilizing a perfluoropolymer that solves these problems.
It is characterized by irradiating na light.

[Operations and Examples] The present invention enables excitation and radicalization of terminal unstable groups of a melt-processable perfluoropolymer without heating.
This was accomplished by discovering that fluorine is generated by irradiation with light of 50 to 700 nm, and that if fluorine gas is present at that time, the terminal unstable group undergoes a radical reaction with fluorine, resulting in fluorination and stabilization.

Perfluoropolymers targeted by the present invention include, for example, tetrafluoroethylene, hexafluoropropylene,
trifluoroethylene, chlorotrifluoroethylene,
Homopolymers or copolymers of vinylidene fluoride and vinyl fluoride, these fluoroolefins and ethylene,
Melt-processable perfluoropolymers, such as copolymers with olefins such as propylene or fluoroalkyl ethylene, or fluoroalkyl vinyl ethers, in which terminal unstable groups based on initiators, chain transfer agents, etc. can be stabilized by fluorination. It may be in the form of a powder or a molded body.

As mentioned above, the stabilization method of the present invention uses a wavelength of 150 to 700 nm.
The irradiation is performed by irradiating light of m, but such irradiation can be performed over a wide temperature and pressure range. Particularly preferable temperature and pressure conditions are room temperature and atmospheric pressure from the viewpoints of reaction equipment, operation, and energy costs, but the reaction can also be carried out under heat and pressure.

The fluorine gas to be reacted may be pure, but from the operational point of view it is preferable to dilute it with an inert gas, and the appropriate concentration is 5 to 20% by volume. Examples of the inert gas include nitrogen gas and helium gas. Preferably, the fluorine gas is supplied as an air stream.

The amount of fluorine gas supplied to the perfluoropolymer depends on the type of terminal unstable group, for example -〇〇〇11.

-CONH2, -CF2H, -CF2CH3, -C
Although it varies depending on F2 C1, -C)120il, -cop, etc., it is generally determined as the amount required for substitution to 10F3.

The irradiated light has a wavelength of 150 to 700 nIll, and the light source is preferably one that emits high energy, such as a mercury lamp or a xenon lamp. In the case of powder, the irradiation time is usually about 1 minute, preferably about 5 minutes. However, if the polymer has a plate-like or film-like shape, a longer time is required.

The process according to the invention is preferably carried out in a reactor under light irradiation by passing fluorine gas (which may be diluted with an inert gas), with or without the perfluoropolymer being displaced. However, since the reaction proceeds extremely quickly in the area that is irradiated with one light, it is desirable to renew all surfaces of the polymer powder or molded body so that they are exposed to light.

Next, the stabilization method of the present invention will be explained based on Examples, but the present invention is not limited to these Examples.

In the examples, the copolymer end groups were quantified using the FT-IR difference spectra between a fully fluorinated copolymer film and a sample film (each with a thickness of approximately 0.3 mm). The number of terminal groups per 106 carbon atoms of the copolymer was determined. That is, the number of terminal groups per carbon tOS is calculated from the absorbance obtained from the difference spectrum using the following equation.

C-/f In the formula, C: Number of end groups per 10 carbons = Correction factor f: Thickness of the film (as) In addition, the wave number and coefficient (K )
The following were used.

Type of terminal group Wave number Coefficient (K) - COP
1883cIl-' 390-CH2
01131150cm -' 1800 Examples 1 to 4 and Comparative Example 1 TPO-PPE copolymer was produced by a suspension polymerization method using bis(omega-hydroperfluoroheptanoyl) peroxide (DIIP) as an initiator and methanol as a chain transfer agent. This was then coarsely crushed to obtain a powder with an average particle size of 350μ.

Spread 3 g of this copolymer powder (4) thinly on the bottom of the reactor (1) shown in Figure 1 (inner diameter 150 mm, capacity 1500 cc), and add fluorine gas diluted with nitrogen gas (concentration IO
% by volume) to the reactor at HOcc/min, a 450W high-pressure mercury lamp (3) (manufactured by Ushio Inc., UN-
452, main wavelength 300~400nm, wavelength range 200~
600n) was turned on to carry out the fluorination reaction.

The inside of the reactor was maintained at room temperature and atmospheric pressure.

The reaction time (light irradiation time) was changed to 1 minute, 5 minutes, 15 minutes, and 60 minutes (Examples 1 to 4 above),
The obtained stabilized copolymer was subjected to a foaming test.

In the foaming test, the test copolymer was heated in an electric furnace at 380° C. for 1 hour, and the degree of foaming was visually determined.

The results are shown in Table 1.

When the unstable end groups were quantified for each of the above samples, in the case of Comparative Example 1, it was 10,820 per 10' carbon atoms.
．． 190 of 11 groups were detected, -cop and -COO
Eleven groups were not detected. On the other hand, in the cases of Examples 1 to 4, 1082011 groups per carbon number toe were not detected, and the total amount of -cop and -COOII groups was between 0 and 20 in multiple tests under the same conditions. It was distributed. Comparative Examples 2 to 3 A fluorination reaction using fluorine gas was carried out for 1 hour in the same manner as in Example 1 except that no light was irradiated. However, in Comparative Example 2, the reactor was maintained at room temperature, and in Comparative Example 3, the reactor was immersed in a salt bath and maintained at 200°C. A foaming test was conducted on the obtained copolymer in the same manner as in Example 1.

The results are shown in Table 1.

Table *: Examples 5 to 6 without light irradiation Example 1 TPE-11PP copolymer produced by emulsion polymerization using ammonium persulfate (APS) as an initiator
It was stabilized by fluorination in the same manner as above.

The light source was an IOW low-pressure mercury lamp (υLl-IDQ manufactured by Ushio Inc., with main wavelengths of 185 nm and 254 nm,
The wavelength range was 180 to 600 ns), and the irradiation time was 5 minutes (Example 5) and 30 minutes (Example 6).

When the obtained stabilized copolymers were subjected to a foaming test in the same manner as in Example 1, none of the copolymers foamed at all.

In addition, when quantifying the amount of unstable end groups, it was found that the sample before stabilization had a concentration of 400 to 1000 per 108 carbon atoms.
The sample after stabilization treatment is distributed in the range of 0 to 2.
They were distributed between 5.

[Effects of the Invention] According to the stabilization method of the present invention, the terminal unstable group can be fluorinated at room temperature and under atmospheric pressure, so there is no need to raise the temperature and pressurize the reaction system, and the reaction equipment can be easily fluorinated. In addition to simplifying the process and significantly reducing energy costs, the reactor can be made of inexpensive materials such as stainless steel.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a reaction apparatus used in Examples.

Claims (1)

[Claims] 1. A perfluoropolymer stabilization method in which a powder or molded body of a melt-processable perfluoropolymer having an unstable group at its terminal is irradiated with light having a wavelength of 150 to 700 nm in a fluorine gas atmosphere.