JP4576665B2 - Method for producing fluorine-containing copolymer - Google Patents

Description

【００３２】
以上の結果から、次のようなことがいえる。
(1)各実施例と比較例1との対比から、亜リン酸ジエステルの存在下で製造された含フッ素共重合体は、同一組成、同程度の結晶性(融点、融解熱量)、同程度の分子量(メルトフローレート)の亜リン酸ジエステル非存在下で製造されたものよりは、より良好な可視光透過性を示すことが分る。
(2)比較例2では、共重合組成をHFPリッチに変更し、結晶性を低下させることにより可視光透過性の改善を図ったが、各実施例のものには及ばなかった。
(3)亜リン酸ジイソプロピルは、亜リン酸ジエチルよりも重合速度が早く、製造コストからみて有利である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a fluorinated copolymer. More specifically, the present invention relates to a method for producing a fluorine-containing copolymer having excellent transparency.
[0002]
[Prior art]
Since the fluorine-containing copolymer is excellent in chemical resistance, oil resistance, weather resistance, heat resistance, etc., the molded product is widely used from industrial use to household use. Among these, copolymers of hexafluoropropene [HFP], chlorotrifluoroethylene [CTFE] or polyfluoro (alkyl vinyl ether) [FVE], such as vinylidene fluoride [VdF] -HFP copolymer, VdF-tetrafluoroethylene [FVE] TFE] -HFP terpolymer, VdF-CTFE copolymer, VdF-TFE-CTFE terpolymer, VdF-FVE copolymer, VdF-TFE-FVE terpolymer, TFE-FVE copolymer, etc. Is known and publicly used as a fluorine-containing elastomer because it exhibits the action of breaking the crystallinity of each VdF or TFE homopolymer.
[0003]
On the other hand, in the region where the copolymerization rate of HFP, CTFE or FVE in these copolymers is low compared to the fluorine-containing elastomer (about 20 mol% or less, generally about 0.5 to 16 mol%), the copolymer is It is known to exhibit properties as a resin having a melting point under room temperature conditions. These resinous copolymers, unlike HFP or TFE homopolymers, are of interest as molding materials having both flexibility and transparency, such as tubes, hoses, films and sheets, etc. Has been.
[0004]
In general, it is effective to increase the copolymerization rate of HFP, CTFE or FVE to give these resinous copolymers a higher degree of flexibility and transparency. Since the mechanical strength of the steel is greatly reduced, there is a limit.
[0005]
On the other hand, various compounds called crystal nucleating agents have been commercially available in recent years. When this compound is blended with a resin and molded, the crystal size of the molded product is reduced and the transparency is improved.
However, when the currently available organophosphorus compound-based crystal nucleating agent is blended and molded into the resinous fluorine-containing copolymer as described above, not only the transparency of the molded product is hardly improved, but conversely the mold release Undesirable side effects such as deterioration of properties and coloring of molded products are observed.
[0006]
[Problems to be solved by the invention]
An object of the present invention is a resinous copolymer of a fluorine-containing monomer such as hexafluoropropene, chlorotrifluoroethylene, polyfluoro (alkyl vinyl ether), etc., and when it is molded, the mechanical strength of the molded product is increased. An object of the present invention is to provide a method for producing a fluorine-containing copolymer capable of improving transparency without lowering.
[0007]
[Means for Solving the Problems]
The object of the present invention is to provide a monomer mixture in the presence of 1/10 to 1 / 100,000 times the molar amount of phosphite diester with respect to the monomer mixture containing at least one kind of fluorine-containing monomer. This is achieved by a method for producing a fluorine-containing copolymer by radical copolymerization reaction.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As the fluorine-containing monomer used for the copolymerization reaction, for example, VdF, TFE, HFP, CTFE, FVE, vinyl fluoride, trifluoroethylene, etc. are used. As FVE, perfluoro (methyl vinyl ether), perfluoro ( Ethyl vinyl ether), perfluoro (propyl vinyl ether), 2,2,3,3,3-pentafluoropropyl trifluorovinyl ether and the like are used.
[0009]
In the present invention, at least one of these fluorine-containing monomers is used for copolymerization reaction. From the viewpoint of imparting transparency to the copolymer molded product, HFP, CTFE, FVE or ethylene [ It is preferable to copolymerize at least one monomer selected from E], propylene [P], alkyl vinyl ether [AVE] and the like to about 20 mol% or less, preferably about 0.5 to 16 mol%.
[0010]
Specifically, VdF-HFP, VdF-TFE-HFP, VdF-CTFE, VdF-TFE-CTFE, VdF-FVE, VdF-TFE-FVE, VdF-P, VdF-TFE-P, TFE-HFP, TFE A combination of -FVE, TFE-P, TFE-AVE, etc. is preferable.
[0011]
The copolymerization reaction can be carried out by any polymerization method such as an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, etc., but in an aqueous medium from the viewpoint of increasing the degree of polymerization and economy. It is preferable to carry out by a polymerization reaction, particularly an emulsion polymerization method.
[0012]
As the polymerization initiator, any organic peroxide, inorganic peroxide, azo compound and the like can be used. However, in order to perform the emulsion polymerization method which is a preferred polymerization form in the present invention, water-soluble peroxide is used. In particular, ammonium peroxydisulfate, potassium peroxydisulfate and the like are preferably used.
[0013]
In the method of the present invention, the radical copolymerization reaction of the monomer mixture containing at least one kind of fluorine-containing monomer is 1/10 to 1 / 100,000 times mole amount, preferably 1 It is carried out in the presence of / 100 to 1 / 100,000 times the molar amount of phosphite diester.
[0014]
Phosphorous acid diesters are known to have hydrogen atoms extracted by radicals generated from peroxides, which undergo addition reactions with fluorine-containing olefins such as TFE, CTFE, VdF, and HFP (J. of Fluorine Chemistry). Vol. 8, pp. 115-124, 1976).
[0015]
In this reaction, since an excess molar amount of dialkyl phosphite is used with respect to these fluorinated olefins, radicals generated by addition to the fluorinated olefin are present from excessive dialkyl phosphite to hydrogen atoms. The reaction is stopped at the stage of the low molecular weight phosphonate, and no polymer is formed.
[0016]
However, in the present invention, by using 1/10 to 1 / 100,000 times the molar amount of phosphite diester with respect to the monomer mixture, the copolymerization reaction of the monomer mixture is made possible. Knowledge has been obtained. Use of phosphorous acid diester at a ratio of 1/10 times the molar amount or more not only makes it impossible to obtain a polymer, but even if a polymer is obtained, the degree of polymerization is practically sufficient. It will be difficult to increase it. The phosphite diester having such a use ratio can be charged in the reactor in advance, or can be charged in small portions during the reaction. The phosphorous acid diester is used in such a proportion that the polymerization initiator is about 1/100 to 100 times the molar amount, preferably about 1/10 to 10 times the molar amount.
[0017]
Examples of phosphorous acid diesters include dialkyl phosphites such as dimethyl phosphite, diethyl phosphite, diisopropyl phosphite and dibutyl phosphite, diaryl phosphites such as diphenyl phosphite, and phosphorous acid. Diaralkyl phosphites such as dibenzyl are used, and it is particularly desirable that dialkyl phosphites, especially diisopropyl phosphite, be used from the viewpoints of polymerization reaction rate, degree of polymerization of the produced copolymer, and the like.
[0018]
In the copolymerization reaction, chain transfer agents such as methanol, ethanol, isopropanol, ethyl acetate, and ethyl malonate for adjusting the molecular weight of the produced copolymer, Na ₂ HPO ₄ for adjusting the pH in the reaction system, NaH ₂ PO ₄ , K ₂ HPO ₄ , KH ₂ PO _{4 and} other electrolytic compound buffering agents, or as long as they do not interfere with the action of phosphite diester, form a redox system with a polymerization initiator When the reducing agent to be added is used as appropriate, and the reaction is carried out by an emulsion polymerization method, at least one emulsifier such as ammonium perfluorooctanoate, ammonium perfluoroheptanoate, ammonium perfluorononanoate is used. Used, preferably ammonium perfluorooctanoate.
[0019]
The polymerization reaction is generally performed under normal temperature or a pressure condition of about 10 MPa or less, preferably about 1 to 5 MPa, and a temperature condition of about 0 to 100 ° C., preferably about 20 to 80 ° C. In the case of emulsion polymerization, an aqueous salt solution such as calcium chloride, sodium chloride, and potassium alum is added to the obtained aqueous dispersion of the fluorine-containing copolymer, and the coagulated product copolymer is added to water, an organic solvent, or these. It is purified by washing with a liquid mixture or the like and drying.
[0020]
The obtained fluorine-containing copolymer is formed into a film, a sheet, a tube, a hose or the like by any molding method such as an injection molding method, a compression molding method, or an extrusion molding method.
[0021]
【The invention's effect】
The resinous fluorine-containing copolymer obtained by the method of the present invention improves the transparency without reducing the mechanical strength when it is molded.
[0022]
【Example】
Next, the present invention will be described with reference to examples.
[0023]
Example 1
In an autoclave with an internal volume of 10 L charged with 5 L of deionized water,
10g ammonium perfluorooctanoate
Disodium hydrogen phosphate 10g
Diisopropyl phosphite 0.27 g (1.62 mmol; fluorine-containing monomer)
(1/15385 times the molar amount of the body mixture)
After the interior space was sufficiently replaced with nitrogen gas, 1 g of isopropanol was injected. Thereafter, a mixed gas consisting of 27.6 mol% of vinylidene fluoride [VdF], 52.4 mol% of tetrafluoroethylene and 20.0 mol% of hexafluoropropene was injected until the internal pressure became 1.0 MPa · G, and the internal temperature was raised to 80 ° C. Allowed to warm.
[0024]
Thereafter, a polymerization initiator aqueous solution in which 0.37 g (1.62 mmol) of ammonium peroxydisulfate was dissolved in 150 ml of water was injected into the autoclave to initiate the polymerization reaction. At this time, the internal pressure was 1.65 MPa · G. When the internal pressure drops to 1.3 MPa · G, the VdF / TFE / HFP (molar ratio 30:57:13) mixed gas is used as the additive gas, and the operation of injecting until the internal pressure becomes 1.4 MPa · G is generated and dispersed. The process was repeated until the solid content concentration in the liquid reached 25% by weight. The time required for the addition was 120 minutes. Immediately after reaching the predetermined solid content concentration, the reaction was stopped by purging the unreacted gas in the autoclave.
[0025]
5 wt% potassium alum water was added to the obtained aqueous dispersion to coagulate the fluorinated copolymer, washed with water and dried. 1700 g 3 terpolymer (polymerization ratio 75%) was obtained, the copolymer composition (elemental analysis, by ^{FT-IR, 19 F-NMR} ) is VdF29 mol%, TFE57 mol%, in HFP14 mol%, the melting point (DSC method by) is 160 ° C., a heat of fusion _(△ H, by DSC method) of 9.0 J / g, also the melt flow rate (265 ° C., load 5Kg) was 8.0 g / 10 min.
[0026]
This fluorine-containing copolymer was subjected to plasticizing conditions at 240 ° C for 5 minutes at a mold temperature of 140 ° C using a small injection molding machine (model CS-183MNX manufactured by Custom Scientific Instruments). A test piece having a thickness of 2 mm was produced by injection molding.
[0027]
The transparency of the prepared specimen was measured as the transmittance of the visible light absorption spectrum at a wavelength of 700 nm, 550 nm or 450 nm, and the normal physical properties [Hardness (Shore A): ASTM D-2240-81 compliant, tensile strength : ASTM D-412-83 compliant, Elongation: ASTM D-412-83 compliant].
[0028]
Example 2
In Example 1, sub instead of diisopropyl equimolar amount of diethyl phosphite 0.224 g; with (1.62 mmol 1/15385 times the molar amount of the fluorine-containing monomer mixture), also the monomer mixture gas partial A copolymerization reaction was carried out at a time required for addition of 150 minutes to obtain a terpolymer having the same copolymer composition. The copolymer had a melting point of 162 ° C., a heat of fusion of 8.0 J / g, and a melt flow rate of 14 g / 10 minutes.
[0029]
Comparative Example 1
In Example 1, the copolymerization reaction was carried out without using diisopropyl phosphite, changing the amount of isopropanol to 1.5 g, and setting the monomer mixture gas addition time to 180 minutes, and having the same copolymer composition. A polymer was obtained. The copolymer had a melting point of 161 ° C., a heat of fusion of 8.5 J / g, and a melt flow rate of 10 g / 10 minutes.
[0030]
Comparative Example 2
In Example 1, without using diisopropyl phosphite, the composition of the mixed monomer mixed gas was changed to VdF / TFE / HFP (molar ratio 29:55:16), and the amount of isopropanol was changed to 0.5 g, respectively. The copolymerization reaction was carried out with a mixed gas addition time of 160 minutes. The copolymerization composition of the obtained terpolymer was VdF 29 mol%, TFE 55 mol%, HFP 16 mol%, melting point 152 ° C., heat of fusion 5.9 J / g, and melt flow rate 17 g / 10 min. .
[0031]
The measurement results in the above examples and comparative examples are shown in the following table.

[0032]
From the above results, the following can be said.
(1) From the comparison between each Example and Comparative Example 1, the fluorine-containing copolymer produced in the presence of phosphite diester has the same composition, the same degree of crystallinity (melting point, heat of fusion), the same degree It can be seen that it exhibits better visible light transmission than that produced in the absence of a phosphite diester having a molecular weight of (melt flow rate).
(2) In Comparative Example 2, the copolymer composition was changed to HFP rich and the crystallinity was lowered to improve the visible light transmission, but it was not as good as that of each Example.
(3) Diisopropyl phosphite has a higher polymerization rate than diethyl phosphite and is advantageous from the viewpoint of production cost.

Claims (5)

Radical copolymerization of the monomer mixture in the presence of 1/10 to 1 / 100,000 times the molar amount of phosphite diester with respect to the monomer mixture containing at least one fluorine-containing monomer A process for producing a fluorine-containing copolymer characterized by the above.   The method for producing a fluorinated copolymer according to claim 1, wherein hexafluoropropene, chlorotrifluoroethylene or polyfluoro (alkyl vinyl ether) is used as the fluorinated monomer. Preparation of the fluorine-containing copolymer according to claim 1, wherein the radical copolymerization reaction is carried out using a 1 / 100-100-fold molar amount of the polymerization initiator to phosphorous acid diester.   The method for producing a fluorinated copolymer according to claim 1, wherein the copolymerization reaction is carried out in an aqueous medium.   A resinous fluorine-containing copolymer produced by the method according to claim 1.