JP2001089531A - Fluorine-containing copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-containing copolymer having chemical resistance and electrical characteristics comparable to those of a tetrafluoroethylene- perfluoroalkyl vinyl ether copolymer (PFA) and improved in moldability. SOLUTION: This fluorine-containing copolymer is a copolymer comprising 60-92 mol% of a monomer unit based on CF2CF2 and 8-40 mol% of monomer unit represented by CF2CF(OCH2Rf) (Rf is a halogenated hydrocarbon group) or a fluorine-substituted copolymer in which at least a part of hydrogen atoms in the above copolymer are substituted by fluorine atoms). The fluorine- containing copolymer has <=1.3 die swell ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel fluorinated copolymer having excellent melt moldability. For more information,
It is a fluorine-containing copolymer having excellent film formability by extrusion molding.

[0002]

2. Description of the Related Art A copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (hereinafter referred to as PFA) has a melt moldability and is excellent in chemical resistance, heat resistance and electric properties. It is well known as a copolymer and is used in a wide range of industrial fields.

However, it is difficult to increase the content of perfluoroalkylvinylether in the above-mentioned PFA due to the limit of the copolymerizability ratio of tetrafluoroethylene and perfluoroalkylvinylether, and there is room for improvement in melt moldability. Was to leave.

On the other hand, as a resin having improved melt moldability of the above-mentioned PFA, JP-A-2-276808 discloses a fluorine-containing vinyl ether having two hydrogen atoms at a carbon atom adjacent to an oxygen atom of an ether bond, and Fluorine-containing copolymers comprising a copolymer with fluoroethylene have been proposed.

[0005] Since the fluorine-containing copolymer contains a hydrogen atom in the fluorine-containing vinyl ether, the copolymerization ratio with tetrafluoroethylene can be adjusted in a wide range, the composition of the fluorine-containing vinyl ether can be increased, and the melt moldability can be improved. It is possible to realize a resin composition with improved properties. In addition, the fluorinated copolymer has chemical resistance and electrical properties comparable to the above-mentioned PFA, despite containing a hydrogen atom in the skeleton.

[0006]

However, the above-mentioned fluorinated copolymer containing an increased amount of the fluorinated vinyl ether component has a considerable effect of improving the melt moldability, but there is still room for improvement. That is, when the above-mentioned fluorinated copolymer is used as a raw material of a thin molded article such as a film, there arises a problem that the film cannot be formed uniformly, and in some cases, the film is easily cut during the formation of the film.

Accordingly, an object of the present invention is to provide a fluorine-containing copolymer which achieves extremely excellent melt moldability and has chemical resistance and electrical properties comparable to those of PFA.

[0008]

Means for Solving the Problems The present inventors have intensively studied to solve the above-mentioned problems. As a result, the fluorinated vinyl ether component was adjusted to a specific range, and the development of a fluorinated copolymer having an extremely low die swell ratio was successfully performed, and the fluorinated copolymer was formed into a film or the like by an extrusion molding method. In the production of a body, it has been found that the composition exhibits excellent melt moldability, which enables a uniform film to be produced with high productivity, and the present invention has been completed.

That is, the present invention relates to a composition comprising 60 to 92 mol% of a monomer unit based on the following general formula (I);
Or a fluorine-substituted copolymer in which at least a part of hydrogen atoms of the copolymer is substituted by fluorine atoms, and the die-swell ratio is 1. It is a fluorine-containing copolymer characterized by being 3 or less.

—CF ₂ CF ₂ — (I) —CF ₂ CF (OCH ₂ Rf) — (II) (where Rf is a halogenated hydrocarbon group)

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the monomer unit represented by the general formula (II) constituting the fluororesin copolymer of the present invention, R
f is not particularly limited as long as it is a halogenated hydrocarbon group,
A group in which part or all of a hydrocarbon such as an alkyl group is substituted with a halogen atom such as fluorine, chlorine, or bromine is preferable.

In the general formula (II), an Rf group particularly preferred in the present invention is a group represented by the following general formula (III).

-C _a F _b X _c H _{(2a + 1-bc)} (III) (where X is a chlorine atom or a bromine atom, a is an integer of 1 or more, and b is an integer of 0 to 2a + 1) And c is 0 or 1 and has a relationship of 1 ≦ b + c ≦ 2a + 1) In the general formula (III), the number of carbon atoms is not particularly limited, but a is 1 because of the availability of the raw material monomer. To 8 are preferred. If Shimese a group represented by Rf in the general formula (II) _{Specifically, -CF 3, -C 2 F 5} , -C 3 F 7, -C 4 F
_{9, -C 5 F 11, -C} 6 F 13, -C 7 F 15, -C 8 F 17, -
_{CF 2 H, -CF 2 Cl,} -CF 2 Br, -C 2 F 4 H, -
_{C 2 F 4 Cl, -C 2} F 4 Br, -C 3 F 6 H, -C 3 F 6 C
_{l, -C 3 F 6 Br,} -C 4 F 8 H, -C 4 F 8 Cl, -C 4
_{F 8 Br, -C 5 F 10} H, -C 5 F 10 Cl, -C 5 F 10 B
_{r, -C 6 F 12 H,} -C 6 F 12 Cl, -C 6 F 12 Br, -
_{C 7 F 14 H, -C 7} F 14 Cl, -C 7 F 14 Br, -C 8 F 16
_{H, -C 8 F 16 Cl,} -C 8 F 16 Br , and the like.

The fluorinated copolymer of the present invention can be used in a molten state in a fluorine nucleus-nuclear magnetic resonance spectrum (hereinafter referred to as ¹⁹ F-NMR).
The absorption is expressed in ppm with the high magnetic field being negative with respect to trichlorofluoromethane. ), The chemical structure can be confirmed.

[0015] That is, for example, Rf is represented by the following general formula _{(IV) - (CF 2)} d CF 3 (IV) (. Where, d is 1 or more is an integer) is a group represented by, at 260 ° C. In the measurement, the absorption of a CF ₃ group fluorine nucleus was around 88 ppm, and the absorption of a CF ₂ group fluorine nucleus adjacent to the CF group was around 122 ppm, 122 pp.
m, the absorption of fluorine nuclei of CF ₂ CF ₂ is 125p
Absorption of the fluorine nucleus of the CF ₂ group sandwiched between the CF ₃ group and the CF ₂ group was observed around pm, and absorption of the fluorine nucleus of the CF group was observed near 138 ppm. It can be calculated from the integrated value of absorption.

The chemical structure of the fluorinated copolymer of the present invention can also be confirmed by measuring its infrared absorption spectrum (hereinafter abbreviated as IR). That 950 cm ^- around ^1> CFOCH ₂ - absorption bands based on group, 2400 cm ^- absorption band based on the group are observed - -CF ₂ near ^1. The content of each monomer unit can also be calculated by quantifying the absorption.

The composition of the fluorinated copolymer of the present invention is such that the monomer unit represented by the general formula (I) is 60 to 92 mol%,
Preferably, 80 to 90 mol%, and the general formula (II)
The monomer unit represented by 8 to 40 mol%, preferably,
10 to 20 mol%. When the amount of the monomer unit represented by the general formula (II) exceeds 40 mol%, properties of the oil start to appear largely, and it becomes difficult to form a film. Conversely, when the monomer unit represented by the general formula (II) is 8
If it is less than mol%, the melt viscosity of the obtained fluorinated copolymer will be high, so that the melt moldability will decrease, and the molding temperature will have to be raised to eliminate this, which is industrially disadvantageous.

In the fluorine-containing copolymer of the present invention, at least a part of the hydrogen atoms of the copolymer having the above-mentioned copolymer composition may be substituted with a fluorine atom.

The greatest feature of the present invention is that the die swell ratio is 1.3 or less, preferably 1.25 or less.

In the present invention, the die swell ratio is:
It is a value measured according to JIS K-7199 at a measurement temperature at which the melt flow rate is 20 g / 10 minutes.

Conventionally, various fluorine-containing copolymers for the purpose of improving melt moldability have been proposed, but none of these conventional fluorine-containing resins has a die swell ratio controlled to 1.3 or less. The die swell ratio reaches 1.5 or more. And even if these fluorinated resins are extruded,
There is a problem that the melt moldability is low, the film may not be uniformly cut, and in some cases, the production of the film itself becomes difficult.

On the other hand, the fluorinated copolymer of the present invention has the above copolymer composition and achieves an extremely low die swell ratio of 1.3 or less.
By using this as a raw material for extrusion molding of a thin molded article such as a film, a film having a uniform thickness can be efficiently produced due to its extremely high melt moldability.

Other characteristics of the fluorine-containing copolymer of the present invention are not particularly limited, but preferable characteristics include the following characteristics.

That is, 260% of the fluorine-containing copolymer of the present invention.
The melt flow rate at 0 ° C is 0.01 to 500 g / 1.
0 minutes is preferable, and the range of 0.01 to 100 g / 10 minutes is more preferable.

The process for producing the fluorine-containing copolymer of the present invention comprises:
Although not particularly limited, the following method may be mentioned as an example of a typical production method.

That is, tetrafluoroethylene (hereinafter TF)
Abbreviated as E. ) And the following general formula (V): CF ₂ ＣＦCFOCH ₂ Rf (V) (where Rf is a halogenated hydrocarbon group). A method of producing a resin having a die swell ratio in a specific range by performing copolymerization while adjusting to a ratio and during or after polymerization, by performing a treatment for homogenizing the molecular weight of the produced copolymer. It is.

In the above formula (V), Rf is selected without particular limitation from the same groups as those exemplified as Rf in the above formula (II).

Used to obtain the copolymer of the present invention
The fluorine-containing vinyl ether represented by the above general formula (V)
Specific examples are as follows. CF_Two= CFOC
H_TwoCF_Three, CF_Two= CFOCH_TwoCF_TwoCF_Three, CF_Two= C
FOCH _TwoCF_TwoCF_TwoH, CF_Two= CFOCH_Two(CF_Two)
_TwoCF_Three, CF_Two= CFOCH_Two(CF_Two)_ThreeCF_Three, CF_Two=
CFOCH_Two(CF_Two)_FourCF_Three, CF_Two= CFOCH_Two(C
F _Two)_FiveCF_Three, CF_Two= CFOCH_Two(CF_Two)₆CF_Three, C
F_Two= CFOCH_Two(CF_Two)₇CF_Three, CF_Two= CFOCH
_TwoCF_TwoCl, CF_Two= CFOCH_TwoCF_TwoBr, CF _Two= C
FOCH_TwoCF_TwoCF_TwoBr, CF_Two= CFOCH_TwoCF_TwoC
F_TwoCl, CF_Two= CFOCH_Two(CF_Two)_TwoCF_TwoBr, C
F_Two= CFOCH_Two(CF_Two)_TwoCF_TwoCl, CF_Two= CFO
CH_Two(CF_Two)_ThreeCF_TwoBr, CF_Two= CFOCH_Two(CF
_Two)_ThreeCF_ThreeCl or the like.

The means for polymerizing the fluorine-containing copolymer is not particularly limited, and any known means can be employed. For example, polymerization means such as a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method may be used.

The organic solvent used in the above polymerization method is not particularly limited, but generally, chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, perfluorocarbon, hydrofluoroether, perfluorotertiary amine and perfluoromorpholine are preferable. Used for For example, chlorofluorocarbons such as trichlorotrifluoroethane, dichlorotetrafluoroethane, trichlorofluoromethane and dichlorodifluoromethane; hydrochlorofluorocarbons such as dichloropentafluoropropane and dichlorotrifluoroethane; hydrofluorocarbons such as decafluoropentane; perfluorobutane Perfluoroalkanes such as perfluoropentane, perfluoroheptane and perfluorooctane or perfluorocycloalkanes such as perfluorocyclobutane and perfluorocyclohexane; methylhexafluoropropyl ether, perfluorobutyl methyl ether and perfluorocarbon Hydrofluoroethers such as butyl ethyl ether; perfluoroto Fluorine-based solvents perfluoro tertiary amines and perfluoromorpholine such as butylamine are preferred.

As the polymerization initiator used in the polymerization, any known radical generator can be used. Among them, for example, diacyl peroxide, peroxyester, peroxydicarbonate and fluorinated diacyl peroxide are preferably used. Specific examples of these include diacyl peroxides such as isobutyryl peroxide; peroxyesters such as cumylperoxyneodecanoate and t-butylperoxyneodecanoate; di-n-propyl purgeoxydicarbonate. Peroxydicarbonate; compounds represented by fluorinated diacyl peroxides such as heptafluorobutyryl peroxide, pentafluoropropyl peroxide and tetrafluoropropyl peroxide.

The amount of such a radical generator used cannot be unconditionally determined by the solvent used, the polymerization conditions, especially the polymerization temperature, but is usually based on the amount of the fluorine-containing alkyl vinyl ether and TFE present in the polymerization tank at the start of the polymerization reaction. , Preferably 0.001 to 0.5 mol%, more preferably 0.003 to 0.2 mol%.

In addition, the radical initiator is generally added all at once during the preparation or intermittently during the reaction. However, depending on the conditions, the polymerization may be difficult to proceed. The radical generator may be added again in the middle.

The pressure of TFE is 0.1 MPa-G to 3 MP
The polymerization reaction proceeds sufficiently within the range of a-G, but the preferred pressure is 0.1 MPa-G to 1 MPa-G.
When the pressure of TFE is lower than the above pressure, the formation rate of the copolymer generally decreases, and when the pressure is high, the formation rate of the copolymer increases. Of course, the polymerization proceeds even if the pressure exceeds the lower limit and the upper limit of the pressure. However, if the pressure is too high, the apparatus becomes considerably expensive and not economical.

The temperature at the time of the polymerization is determined based on the decomposition rate of the radical generator to be used as one standard, and is usually about 0 ° C. to 100 ° C., preferably about 5 ° C. to 80 ° C. Particularly, in the case of a fluorine-containing or perfluoro-based diacyl peroxide having a high decomposition rate even at a low temperature, the temperature is preferably about 5 ° C to 60 ° C.

In the present invention, the method for fluorinating at least a part of the hydrogen atoms of the above copolymer is from 10 to 100
vol. A preferred method is to obtain a fluorine-substituted copolymer having a desired fluorination rate by gradually increasing the temperature from around room temperature over time at a fluorine gas concentration of 10%. It is particularly preferable to control the reaction temperature to less than 100 ° C, preferably to less than 80 ° C.

The method for adjusting the die swell ratio of the fluorine-containing copolymer of the present invention to 1.3 or less is not particularly limited.
During or after the polymerization, there may be mentioned an embodiment in which the treatment for homogenizing the molecular weight of the produced copolymer is performed so that the die swell ratio falls within the above-mentioned specific range.

If the above-mentioned treatment method is specifically shown, a method of heating the copolymer in a fluorine atmosphere after the polymerization of the above-mentioned fluorine-containing copolymer is recommended.

The heating conditions in a fluorine atmosphere generally employ more severe conditions than the above fluorination conditions. The conditions cannot be determined unconditionally depending on the composition of the fluorinated copolymer and the like, but the concentration of the fluorine gas is 0.1 to 5 vol.
% Nitrogen mixed gas at a pressure of 0.01 MPa-G to 0.1
It is preferable to adjust so as to be MPa-G. Further, the temperature is preferably 100 to 200 ° C. Then, the treatment is performed under the above conditions until the die well of the obtained fluorine-containing copolymer becomes 1.3 or less.

When hydrogen atoms are present in the fluorine-containing copolymer, a reaction may occur in which some of the hydrogen atoms are replaced by fluorine in the process for adjusting the die well. Usually, it is 2% or less based on the total hydrogen atom weight in the fluorine-containing copolymer before the treatment.

[0041]

As will be understood from the above description, the fluorinated copolymer of the present invention has the characteristics that it has extremely high melt moldability and that a thin molded article can be favorably molded by an extrusion molding method. Specifically, it is suitably used for extrusion molding of a film, a tube, or the like, and the obtained molded article has a uniform thickness, and its commercial value is extremely high.

[0042]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The physical properties and tests of the fluorinated copolymers produced in the examples and comparative examples were carried out by the following methods. 1. Die well ratio The die well ratio was measured in accordance with JIS K-7199. A capillary having an inner diameter of 9.55 mm, an inner diameter of 1 mm, a length of 10 mm, and an entrance angle of 180 ° was used, and the load was measured at 4 kg. 2. Melt flow rate The melt flow rate (unit: g / 10 minutes; hereinafter abbreviated as MFR) was measured according to JIS K-7210. The measurement load is 5 kg. 3. Formability of film MFR of the sample fluorine-containing copolymer is about 20 g with an extruder
At a temperature of / 10 minutes, a T die (slit width 120 m
m, thickness 0.3 mm). The extruded film was pulled by a roll at a speed of 0.9 m / min to obtain a film.

The following four-stage evaluations were performed on the film formability and the uniformity of the obtained film.

◎ A film having an extremely uniform thickness was obtained. ○ A non-uniform part was present in a part of the film. △ A non-uniform part was present over a considerable part of the film. × The film could not be formed. Comparative Example 1 Dichloropentafluoropropane (hereinafter referred to as HCFC) in a stainless steel 100 L reactor
-3.525 kg), and then charged.
After sufficiently replacing the internal space with nitrogen gas, this is eliminated and 2,2,3,3,3-pentafluoropropyltrifluorovinyl ether (hereinafter abbreviated as FVE)
6.2 kg was put. Keep the system at 27 ° C and stir,
TFE was injected and the pressure inside the reactor was increased to 0.79 MPa-
G was kept.

Here, HCFC-225 solution of isobutyryl peroxide (24.8% by weight) as a polymerization initiator
25.2 g was injected under pressure to initiate polymerization. When the reactor pressure reached 0.63 MPa-G, unreacted monomers,
HCFC-225 and the fluorinated copolymer were recovered and the polymerization was stopped. The concentration of the produced copolymer in the polymerization solution was 8.2% by weight, and the polymerization time was 350 minutes.

The obtained copolymer was heated at 130 ° C. for 15 hours.
It was dried under reduced pressure. TFE in this fluorinated copolymer
Is 85.5 mol%, and FVE is
The ratio of the monomer unit based on was 14.5 mol%. The MFR of the copolymer at a temperature of 260 ° C. is 20.
g / 10 minutes, and the die well ratio was 1.40 (hereinafter, referred to as copolymer A).

As a result of a moldability test using the above-mentioned copolymer A, unevenness in the thickness of the film was observed everywhere, and the result was x.

Example 1 The copolymer A obtained in Comparative Example 1 was placed in a cylinder, and the inside was evacuated. The pressure is 0.05MPa-
G was sealed with a nitrogen mixed gas having a fluorine concentration of 3 vol%. Rotate the cylinder and stir the inside for 15 minutes at a temperature of 1
Heated at 50 ° C.

The copolymer composition of the obtained fluorine-containing copolymer was almost the same as that of Comparative Example 1, and the die swell ratio was 1.08. As a result of performing a moldability test using this fluorinated copolymer, an extremely uniform film could be easily formed, and the evaluation was ◎.

Example 2 The copolymer A of Comparative Example 1 was placed in a cylinder, and the inside was evacuated. A nitrogen mixed gas containing 3 vol% of fluorine was sealed therein until the pressure reached 0.01 MPa-G, and the mixture was heated at a temperature of 150 ° C. for 25 minutes while rotating and rotating the cylinder.

The copolymer composition of the obtained fluorine-containing copolymer was almost the same as that of Comparative Example 1, and the die swell ratio was 1.22. As a result of performing a moldability test using this fluorinated copolymer, an extremely uniform film could be easily formed, and the evaluation was ◎.

Examples 3 to 5 In the method for producing a copolymer of Comparative Example 1, copolymers were produced by changing the composition of each copolymer as shown in Table 1 below. A fluorinated copolymer having a die swell ratio adjusted according to Table 1 was obtained.

Table 1 shows the die swell ratio of the obtained fluorinated copolymer and the results of a moldability test conducted using this fluorinated copolymer.

[0055]

[Table 1]

Claims (2)

[Claims] 1. A monomer unit 6 based on the following general formula (I)
A copolymer comprising 0 to 92 mol% and 8 to 40 mol% of monomer units represented by the following general formula (II), or fluorine in which at least a part of hydrogen atoms of the copolymer is substituted by fluorine atoms: A substituted copolymer having a die swell ratio of 1.3.
A fluorine-containing copolymer characterized by the following. —CF ₂ CF ₂ — (I) —CF ₂ CF (OCH ₂ Rf) — (II) (where Rf is a halogenated hydrocarbon group) 2. A method for producing a film, comprising extruding the fluorine-containing copolymer according to claim 1.