JP3210000B2 - Manufacturing method of high modulus fluororesin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to a method for producing a fluororesin having a high elastic modulus.

[0002]

[Prior art]

Fluororesins are used in various fields due to their excellent heat resistance, chemical resistance, and surface properties, but one of their drawbacks is that they have low elastic modulus. Another drawback is that a fluororesin other than polytetrafluoroethylene (PTFE) flows when heated above its melting point and cannot maintain its shape. PTFE does not flow when heated to above its melting point, but has the drawback that it cannot be melt molded. Thus, it has been desired to develop a fluororesin that can be melt-molded with a high elastic modulus and that does not flow even when heated above its melting point.

[0003] It is considered that these required properties are satisfied by crosslinking the fluororesin after molding, and various crosslinking methods have been proposed so far. For example, in JP-B-62-23772, a fluorine resin is irradiated with an electron beam to crosslink it. However, this method is effective for hydrocarbon resins but is not applicable to perfluoro resins. In Japanese Patent Application Laid-Open No. 61-155410, electron beam crosslinking is performed by adding a crosslinking agent such as triallyl cyanurate to a fluororesin. However, the resin obtained by this method is inferior in chemical resistance and heat resistance due to the presence of the crosslinking agent.

[0004] In JP-A-63-68604 and US Pat. No. 4,204,927, photocrosslinking is performed by adding a photoreactive group to a fluororesin. However, the resins obtained by these methods are inferior in chemical resistance and heat resistance. JP-B-55-23567 describes that a copolymer of tetrafluoroethylene and perfluoroacrylic acid (derivative) is cross-linked by applying heat. However, there is no detailed description of the physical properties of the crosslinked polymer.

[0005]

[Problems to be solved by the invention]

An object of the present invention is to provide a novel method for producing a highly elastic fluororesin which has not been known hitherto.

[0006]

[Means for Solving the Problems]

In the present invention, the unit represented by the following formula (1) (where X is a fluorine atom or a chlorine atom) is 70 to 99.9 mol%, and the following formula (2) (where R _f is divalent fluorine substitution) An organic group, A is an alkyl group having 1 to 3 carbon atoms or 1 to 3 carbon atoms;
Is a fluoroalkyl group) represented by 0.1 to 2
0 mol%, a unit represented by the following formula (3) (where Z is a monovalent fluorine-substituted organic group) (provided that the formula (2)
Is 0 to 10 mol%, and the melt flow rate is 0.01 to 100, and the fluoropolymer is heat treated at a temperature of 200 ° C. or more and the melting point of the fluoropolymer or less. The present invention provides a method for producing a high elastic modulus fluororesin characterized by obtaining a fluororesin having a dynamic elastic modulus of 0.8 × 10 ⁹ dyne / cm ² or more. − [− CF ₂ CFX −] −… (1) − [− CF ₂ CF (OR _f COOA) −] −… (2) − [− CF ₂ CFZ −] −… (3)

In the fluoropolymer used in the production method of the present invention, the unit represented by the formula (1) is 70 to 99.9 mol%, the unit represented by the formula (2) is 0.1 to 20 mol%, It is a fluoropolymer in which the unit represented by (3) is 0 to 10 mol%.

In such a fluoropolymer, X in the formula (1) is more preferably a fluorine atom from the viewpoint of chemical resistance and the like. R _f in the formula (2) is a divalent fluorine-substituted organic group, for example,-(CF ₂ ) _n -,-(CF ₂ ) _m- (OCF (C
F ₃ )) _n −, − (CF ₂ ) _m − (CF ₂ CF (CF ₃ )) _n −, −
(CF ₂ ) _m- (OCF ₂ CF ₂ ) _n -,-(CF ₂ CF (CF ₃ ) O) _m
And a group such as — (CF ₂ ) _n —. Particularly, it is preferably a perfluoro group.

A is an alkyl group having 1 to 3 carbon atoms or a fluoroalkyl group having 1 to 3 carbon atoms. In the present invention, since the fluoropolymer has the group represented by COOA, a fluororesin having a high elastic modulus can be produced by the method described below.

The fluoropolymer used in the production method of the present invention contains the unit of the formula (1) in a proportion of 70 to 99.9 mol% and the unit of the formula (2) in a proportion of 0.1 to 20%. If the amount of the unit represented by the formula (2) is too small, it becomes difficult to obtain a fluororesin having a high elastic modulus even when treated by the method described below. In addition, if the amount is too large, it becomes difficult to maintain the shape during the heat treatment by lowering the melting point of the fluoropolymer, so that precision molding becomes difficult.
Also, the polymer becomes elastomeric and moldability decreases,
Such disadvantages occur.

Further, the fluoropolymer used in the production method of the present invention may be composed of the unit of the above formula (1) and the unit of the formula (2), or may be of the formula (3) And may include a unit other than the unit represented by the formula (2) (hereinafter, simply referred to as a “unit represented by the formula (3)”). When the unit represented by the formula (3) is included, there are advantages such as improvement in melt moldability and improvement in physical properties such as impact resistance and toughness of the fluororesin after heat treatment. However, if the unit represented by the formula (3) is excessively included, the unit becomes elastomeric, so that the unit represented by the formula (3) is set to 10 mol% or less.

The fluoropolymer includes a monomer represented by the formula CF ₂ CFX (X is the same as described above) (hereinafter, referred to as monomer (1 ′)), and a formula CF ₂ CFOR _f COOA (R _f , A is a monomer represented by the same as described above (hereinafter referred to as monomer (2 ')) and, if necessary, a monomer represented by the formula CF ₂ = CFZ (Z is the same as described above); It can be obtained by copolymerizing a monomer other than the monomer (2 ′) (hereinafter, referred to as a monomer (3 ′)) in the presence of a polymerization initiation source.

As the polymerization initiation source, ionizing radiation, a polymerization initiator such as an organic peroxide-based polymerization initiator and an oxidation-reduction-based polymerization initiator can be used. As the polymerization method, suspension polymerization,
Conventionally known polymerization methods such as emulsion polymerization, solution polymerization and bulk polymerization are employed.

Here, the polymerization initiator is preferably a free radical polymerization initiator, for example, bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkylperoxydicarbonates, diacyl peroxides, peroxyesters, And persulfates.

As a polymerization medium, CFC 11 or CFC 11 in solution polymerization is used.
For example, water or a mixed medium of water and another solvent is used in suspension polymerization and emulsion polymerization. The polymerization temperature can be selected from 0 to 100 ° C, and the polymerization pressure can be selected from the range of 0.5 to 30 kg / cm ² G.

In the polymerization reaction, for example, a polymerization medium, a monomer (2 ′), and, if necessary, a monomer (3 ′) and a molecular weight modifier are first charged into an autoclave equipped with a stirrer, and a required amount of the monomer (1) is added. '), And polymerization is started by adding a polymerization initiator. Since the pressure decreases as the polymerization proceeds, the monomer (1 ') is injected so as to compensate for the decrease in the pressure, and the polymerization is continued until a desired amount of the polymer is produced. After the completion of the polymerization, the unreacted monomer is released, and the polymer is washed and dried.

The obtained polymer can be melt-molded by heating it to a temperature higher than the melting point of the polymer. By subjecting the molded article to a heat treatment at a temperature of 200 ° C. or more and a melting point or less for 5 hours or more, it is possible to crosslink without adding a crosslinking agent, and a molded article of a fluororesin which does not flow even at the melting point or more is obtained.

In the present invention, the fluoropolymer has a melt flow rate of 0.01 to 100. The melt flow rate is an extrusion rate (g / min) measured at a temperature equal to or higher than the melting point of the fluoropolymer, and specifically measured by the following method. Using a melt indexer, the fluoropolymer has an inner diameter of 9.
After loading into a 5mm cylinder and holding at 380 ° C for 5 minutes, at that temperature under a 5kg piston load, inner diameter 2.1mm, length 8.0mm
Through an orifice at the extrusion speed (g /
Min) was taken as the melt flow rate.

The melting point was measured using an analyzer (DTA) manufactured by Vacuum Riko. A sample (10 mg) was placed in an aluminum cup and heated at a rate of 10 ° C./minute from room temperature, and the melting endothermic peak temperature was defined as the melting point.
Those having an extremely low melt flow rate, that is, those having an ultra-high molecular weight have extremely low moldability and are not suitable as molding materials. Further, those having an extremely high melt flow rate, that is, those having a low molecular weight, have extremely low mechanical strength.

In the present invention, it is important that the above-mentioned fluoropolymer is heat-treated at a temperature of 200 ° C. or higher and a melting point of the fluoropolymer or lower. By performing such heat treatment, a high elastic modulus fluororesin can be obtained. The heat treatment is preferably performed after forming into a desired shape. If the heat treatment temperature is too low, a sufficiently high elastic modulus cannot be achieved, and if the heat treatment is carried out at an excessively high temperature, a means for maintaining the shape is required during the heat treatment, which is not preferable because the operation becomes complicated. The heat treatment is preferably performed for 5 hours or more. If the heat treatment time is short, it is difficult to sufficiently increase the elastic modulus. The heat treatment may be performed in an inert gas such as a nitrogen gas, or may be performed in air. From the viewpoint of workability, it is preferable to carry out in air.

[0021]

【Example】

The following Examples 1-4 are synthesis examples, Examples 5-8 are Examples, and Examples 9-
10 is a comparative example.

[Example 1] An autoclave having an internal volume of 1200 cc with a stirrer was charged with CFCs.
1474 g of 113, 41.7 g of CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ and 0.83 g of methanol were charged, and the internal space was replaced with nitrogen gas for 1 minute.
E) 60 g was injected, the temperature was raised to 50 ° C., and the mixture was stirred. Add bis (perfluoropropanoyl) peroxide to this
5.5 cc of a polymerization initiator dissolved in wt% Freon 113 was added to initiate polymerization. During the reaction, TFE was successively added as the pressure dropped, so as to maintain a constant pressure. When the sequential addition of TFE reached 74 g, cooling and monomer purging were performed. The obtained slurry solution was washed with Freon 113,
The polymer was obtained by drying at 12 ° C for 12 hours.

The physical properties of the polymer were measured by the following methods. The results of polymerization and the results of measurement of physical properties are shown in Table 1 (the same applies to Examples 2 to 4).

[Melt flow rate] Measured by a melt indexer, the polymer was loaded into a cylinder having an inner diameter of 9.5 mm, kept at 380 ° C. for 5 minutes, and then heated at that temperature under a piston load of 5 kg to an inner diameter of 2.1 mm. length
Extrusion was performed through an 8 mm orifice, and the extrusion speed (g / min) at this time was defined as a melt flow rate.

[Content of Unit Represented by Formula (2)] About 0.8 g of a powder sample was weighed, immersed in a 0.35 N NaOH methanol solution, sealed, and left at 60 ° C. for 2 days. Unreacted NaOH in the solution was determined by titration with a 0.1N aqueous HCl solution.

[Melting Point (° C.)] The melting point was measured using a thermal analyzer (DTA) manufactured by Vacuum Riko. A sample (10 mg) was placed in an aluminum cup and heated at a rate of 10 ° C./minute from room temperature, and the melting endothermic peak temperature was defined as the melting point.

[0027] to give [Example _{2] CF 2 = CFO (CF} 2) 3 COOCH 3 and 25.0g were charged, by the same method as in Example 1 except that charged 1.13g of methanol polymer.

[Example 3] CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ instead of CF ₂ = CFOCF of Example 1
_{2 A} polymer was obtained in the same manner as in Example 1 except that 64.3 g of CF (CF ₃ ) O (CF ₂ ) ₃ COOCH ₃ and 0.64 g of methanol were charged.

Example 4 CF ₂ CCFO (CF ₂ ) ₃ COOCH ₃ was charged with 25.0 g, and CF ₂ FOCFOCF ₂
A polymer was obtained in the same manner as in Example 1 except that 21.7 g of CF ₂ CF ₃ and 0.95 g of methanol were charged.

[0030]

[Table 1]

Examples 5 to 10 In Table 2, the fluoropolymers obtained in Examples 1 to 4 (Examples 5 to 8),
Heat treatment of PFA resin (Example 9) and PTFE resin (Example 10) (300
(° C x 30 hours). In Table 2, the dynamic elastic modulus (unit: 10 ⁹ dyne / cm ² ) is 200 by vibron.
It is a measured value in ° C. In addition, creep resistance (unit:%)
Is a value at a room temperature of 24 hours and a load of 100 kg / cm ² .

[0032]

[Table 2]

By performing the heat treatment, a molded article having a high elastic modulus, not flowing even when heated to a temperature equal to or higher than the melting point, and having excellent heat resistance and chemical resistance was obtained.

[0034]

【The invention's effect】

According to the production method of the present invention, it is possible to obtain a fluororesin which has a high elastic modulus, does not flow even when heated to a temperature equal to or higher than the melting point, and has excellent effects of good heat resistance and chemical resistance.

Claims (2)

(57) [Claims] (1) a unit represented by the following formula (1) (where X is a fluorine atom or a chlorine atom): 70 to 99.9 mol%, and the following formula (2) (where R _f is divalent fluorine) A substituted organic group, A is an alkyl group having 1 to 3 carbon atoms or 1 to 3 carbon atoms;
Is a fluoroalkyl group) represented by 0.1 to 2
0 mol%, a unit represented by the following formula (3) (where Z is a monovalent fluorine-substituted organic group) (provided that the formula (2)
Is 0 to 10 mol%, and the melt flow rate is 0.01 to 100, and the fluoropolymer is heat treated at a temperature of 200 ° C. or more and the melting point of the fluoropolymer or less. And obtaining a fluororesin having a dynamic elastic modulus of 0.8 × 10 ⁹ dyne / cm ² or more. − [− CF ₂ CFX −] −… (1) − [− CF ₂ CF (OR _f COOA) −] −… (2) − [− CF ₂ CFZ −] −… (3) 2. The method according to claim 1, wherein the heat treatment is performed for 5 hours or more.