JP2723427B2 - Method for producing fluorine-containing vinyl ether - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a fluorine-containing vinyl ether.

[0002]

2. Description of the Related Art Polytetrafluoroethylene has excellent physical properties such as chemical resistance, heat resistance, surface properties, and electrical properties, but has problems in workability and the like. Therefore,
Copolymers of various comonomers with tetrafluoroethylene have been produced. Among these copolymers, a resin having an alkoxyl group in a side chain is known as a fluororesin having excellent melting properties.
No. 808 proposes a copolymer of tetrafluoroethylene and fluorine-containing vinyl ether as a resin which can be produced with a wide monomer composition. It is known that the fluorine-containing vinyl ether used in the copolymer is produced by reacting a corresponding alkoxide with tetrafluoroethylene (US Pat. No. 2,917,548).

[0003]

The above-mentioned U.S. Pat.
According to the specification of 17548, after the reaction between alkoxide and tetrafluoroethylene, a) the reaction solution is neutralized with an aqueous solution of an inorganic acid, and then the organic layer is separated and the target product is separated by distillation, or b) ) The reaction solution is treated with alcohol, filtered, and the target product is separated by distillation.
In the above-mentioned patents, it is not clear why the treatment is performed after the completion of the reaction, but one possibility is to prevent unreacted alkoxide from reacting with the target fluorine-containing vinyl ether during distillation. Therefore, it can be estimated that the alkoxide is decomposed by the above-described method. However, according to the method of the above patent,
The reaction mixture is brought into contact with water, an acid, or an active hydrogen compound such as an alcohol, and a large amount of RfCH ₂ OCF ₂ CF ₂ H, which is a by-product, is generated in addition to the target substance.
There is a problem that purification is difficult because the boiling point of the target product is close to that of the by-product.

Accordingly, an object of the present invention is to provide a method for suppressing the formation of by-products and obtaining fluorine-containing vinyl ether with good selectivity.

[0005]

The present inventors have conducted intensive studies on the reaction between alkoxide and tetrafluoroethylene. As a result, after reacting the alkoxide with tetrafluoroethylene, the reaction mixture was treated with water, acid, alcohol, and the like. The present inventors have found that a fluorine-containing vinyl ether can be obtained with good selectivity by performing distillation without contact with an active hydrogen compound such as that described above, thereby completing the present invention.

That is, the present invention provides the following general formula [I] RfCH ₂ OM [I] (where Rf is a hydrogen atom, a halogen atom, or a halogenated hydrocarbon group, and M is an alkali metal).
And reacting the alkoxide with tetrafluoroethylene and distilling the reaction product without contacting the compound with an active hydrogen compound. The following general formula [II] RfCH ₂ OCF = CF ₂ [II] ( Here, Rf is a hydrogen atom, a halogen atom, or a halogenated hydrocarbon group.).

In the present invention, one of the raw materials is an alkoxide represented by the above general formula [I]. In the general formula (I), Rf is selected from the group consisting of hydrogen atom, a halogen atom or may be a halogenated hydrocarbon group, but, in the present invention, the following general formula _{-C a F b X c H (} 2a + 1- _bc) (provided that X is a chlorine atom or a bromine atom, a is an integer of 0 or more, b is an integer of 0 to 2a + 1, c is 0 or 1, and b + c ≦ 2a + 1 ) Or a halogenated alkyl group is preferred. In the above formula, a may be an integer of 0 or more, but a is preferably an integer of 0 to 10 from the viewpoint of easy availability of alcohol which is a raw material of the alkoxide represented by the general formula [I]. In the general formula [I], the alkali metal represented by M is preferably Li, Ka, Na, or Cs.

As the alkoxide represented by the general formula [I], a commercially available product may be used as it is, or the alkoxide represented by the following general formula [II]
I] RfCH ₂ OH [III] (where Rf is a hydrogen atom, a halogen atom or a halogenated hydrocarbon group) obtained by reacting an alcohol represented by the formula (I) with an alkali metal or an alkali metal hydride. May be used. The general formula (III)
Rf in the formula is the same as in the general formula [I].

When an alkoxide is produced by reacting an alcohol with an alkali metal or an alkali metal hydride as described above, the alkoxide is produced in the same reaction system prior to the reaction of the present invention, and the alkoxide is produced as it is. There is no problem even if you carry out. However, in this case, if the raw material alcohol remains in the reaction system of the alkoxide and tetrafluoroethylene, there is a problem that the above-mentioned by-products increase. It is preferable to use an excess so that no alcohol remains.

Specific examples of alkoxides which can be suitably used in the present invention are as follows. Sodium methoxide, sodium fluoromethoxide, sodium-1,1,1-trifluoroethoxide, sodium-1,1,1,
2,2-pentafluoropropoxide, sodium-1,1,1,
2,2,3,3-heptafluorobutoxide, sodium-1,1,
1,2,2,3,3,4,4-nonafluoropentoxide, sodium
-1,1,1,2,2,3,3,4,4,5,5-undecafluorohexoxide, sodium-1,1,2,2-tetrafluoropropoxide, sodium-1,1 , 2,2-tetrafluoro-1-chloropropoxide and the like.

In the present invention, a solvent is generally used. The solvent used is a compound that is substantially inert with respect to the reaction of the present invention. The presence of water in the reaction system not only causes the decomposition of the alkoxide represented by the above general formula [I], but also causes an increase in by-products, which may lower the yield of the target product. Therefore, the solvent is preferably dehydrated and dried in advance. Examples of the solvent preferably employed in the present invention include linear ethers such as diethyl ether and glymes; cyclic ethers such as dioxane and tetrahydrofuran; and aromatic hydrocarbon compounds such as benzene, toluene and xylene. Among them, dioxane and tetrahydrofuran can be particularly preferably used.

The reaction pressure of tetrafluoroethylene in the present invention is not particularly limited. However, when the reaction pressure is too high, there is a disadvantage that the apparatus becomes considerably expensive.
Therefore, the pressure of tetrafluoroethylene is 1-30k
g / cm ² -G is practical, particularly preferably 5 to ² g / cm ² -G.
0 kg / cm ² -G. In addition, tetrafluoroethylene may be sealed in a reactor before the reaction, and may not be supplied during the reaction, or may be supplied continuously or intermittently during the reaction. it can. The end of the reaction can be confirmed by stopping the absorption of tetrafluoroethylene.

Next, the reaction temperature is not particularly limited, and the reaction temperature may be selected according to the reaction rate, but is generally in the range of 0 to 120 ° C., particularly in the range of 0 to 80 ° C. Is preferred.

In the reaction of the present invention, when a relatively high pressure is applied to tetrafluoroethylene, the polymerization reaction may occur. In such a case, a polymerization inhibitor is added to the reaction system to prevent polymerization. Is preferably added. The polymerization inhibitor may be added to the reactor prior to the reaction, or may be contained in the introduced tetrafluoroethylene. As the polymerization inhibitor, any compound can be employed without any limitation as long as it is a compound for preventing the polymerization of tetrafluoroethylene. Illustrative polymerization inhibitors preferably used in the present invention, limonene, pinene, cymene,
Terpinene and the like can be mentioned.

The reaction between the alkoxide and tetrafluoroethylene is carried out by the above-mentioned method. The obtained reaction solution is distilled without contacting the active hydrogen compound. The active hydrogen compound in the present invention is a compound having active hydrogen in a molecule and capable of reacting with an alkoxide. Such an active hydrogen compound usually has a pKa of 30 or less.
Specific examples of the active hydrogen compound include, for example, water; inorganic or organic acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, propionic acid, benzoic acid, and lactic acid; and alcohols such as methanol, ethanol, and propanol. it can.

When the reaction solution is distilled without contacting with the active hydrogen compound, the reaction and the distillation need not necessarily be performed in the same vessel. If the contact with the active hydrogen compound is avoided, the reaction solution is distilled from the reaction vessel. It can be moved to the device. In the distillation, rectification for directly isolating the desired fluorine-containing vinyl ether may be carried out, or the fluorinated vinyl ether may be once distilled as a mixture with a solvent, and then isolated by rectification. In the latter case, it is necessary to avoid contact with the active hydrogen compound up to the distillation of the mixture with the solvent, and there is no problem in contacting the active hydrogen compound in the subsequent rectification. Further, in distilling the reaction solution, a solvent inert to the reaction solution may be added without any problem.
Examples of such a solvent include the reaction solvents described above.

[0017]

According to the present invention, by reacting an alkoxide with tetrafluoroethylene and then distilling the reaction solution without contacting with an active hydrogen compound, RfCH ₂ OCF ₂ CF _{2 as} a by-product is obtained. H is hardly generated, and the desired fluorine-containing vinyl ether can be obtained with high selectivity.

In the method of the present invention, there is a concern that unreacted alkoxide reacts with the desired fluorine-containing vinyl ether during distillation to lower the yield of the desired product.
In fact, it is surprising that the yield did not decrease, the generation of by-products was suppressed, and the selectivity of the target product was improved.

[0019]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

EXAMPLE 1 NaH1 was placed in a stainless steel reaction vessel having a capacity of 500 mL.
After adding 3.0 g, the atmosphere was replaced with nitrogen and 1,4-dioxane 15 was added.
0 mL was added and stirring was started. To this, a 1,4-dioxane solution containing 67.5 g of 1,1,1,2,2-pentafluoropropanol and 3 mL of limonene was gradually added dropwise while cooling in an ice bath so as not to raise the temperature of the reactor. After dropping, 3
After stirring was continued for 0 minutes, tetrafluoroethylene was introduced into the reactor to 20 kg / cm ² -G. Thereafter, the reactor was heated to 60 ° C., and tetrafluoroethylene was
The reaction was performed while supplying at g / cm ² -G. After the absorption of tetrafluoroethylene stopped, the pressure was released, and the reactor was heated and distilled to obtain 48.8 g of a fraction having a boiling point of 60 to 61 ° C. The composition of the distillate is C ₂ F ₅ CH ₂ OCF = CF ₂ : C ₂ F ₅
CH ₂ OCF ₂ CF ₂ H = 95.5: 1.5 (molar ratio).

Comparative Example 1 A reaction was carried out in the same manner as in Example 1. After stopping absorption of tetrafluoroethylene, depressurize, pour the reaction mixture into ice water,
After extraction with ether, the boiling point is 60 to 61 ° C. by distillation.
48.1 g of a fraction were obtained. The composition of the distillate is C ₂ F ₅ CH ₂
OCF = CF ₂ : C ₂ F ₅ CH ₂ OCF ₂ CF ₂ H = 87: 1
3 (molar ratio).

Claims (1)

(57) [Claims] 1. The following general formula: RfCH ₂ OM (where Rf is a hydrogen atom, a halogen atom, or a halogenated hydrocarbon group, and M is an alkali metal)
Wherein the reaction product is distilled without contact with an active hydrogen compound after reacting the alkoxide represented by the following formula with tetrafluoroethylene: RfCH ₂ OCF = CF ₂ (where Rf is hydrogen Atom, a halogen atom, or a halogenated hydrocarbon group).