JPH0341488B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel method for producing perfluoropolyether. More specifically, it is a novel perfluoropolyether obtained by reacting tetrafluoroethylene and oxygen in a fluorinated or chlorinated solvent under ultraviolet irradiation, and in which the amount of active oxygen is reduced. Concerning the manufacturing method. [Prior Art] It is already well known to produce perfluoropolyether by reacting tetrafluoroethylene and oxygen in a fluorinated or chlorine-fluorinated solvent under ultraviolet irradiation conditions; It is described in Publication No. 50052, etc. The perfluoropolyether obtained in this way has active fluorine and active oxygen bonds, and its viscosity can be controlled over a wide range, so it can be used as a synthetic intermediate for crosslinking agents, polymeric surfactants, etc. It is useful as In addition, neutral perfluoropolyether, which has its active groups reduced through heat treatment, fluorine treatment, etc., has high chemical and physical stability derived from its structure, and is used as a base oil for high-performance greases, vacuum It has a wide range of industrial applications, including oil for pumps, special lubricants for magnetic disks, and lubricants for rockets. The molecular weight of perfluoropolyether is a big issue when used for each of these uses, but the above patent publication states that the molecular weight is regulated by the amount of ultraviolet rays used in the reaction and the monomer supply rate, and as the amount of ultraviolet rays is increased, the molecular weight It is stated that the molecular weight decreases and that increasing the monomer feed rate increases the molecular weight. Considering this relationship from an equipment design perspective, for example, when trying to obtain a product with a low molecular weight, a large-capacity ultraviolet irradiation equipment must be used, and reducing the supply rate will reduce the manufacturing cost. This means that very unfavorable conditions must be selected from the viewpoints of surface and reaction efficiency. [Problems to be Solved by the Invention] The present inventors have conducted various studies in search of a manufacturing method that does not have such problems when manufacturing low molecular weight perfluoropolyethers, and have found that halogenated hydrocarbon chains It has been found that by employing a telomerization method using a transfer agent as a telogen, this problem can be effectively solved and a perfluoropolyether having a molecular weight within a desired range can be obtained. An object of the present invention is to provide a method for producing a new perfluoropolyether in which the amount of active oxygen in the perfluoropolyether molecule is reduced. [Means for Solving the Problems] The object of the present invention is to provide a compound comprising a combination of the following structural units whose main chain is linearly and irregularly arranged, and which contains 0.1 to 10% by weight of chlorine, bromine or iodine atoms in the molecule.
The new perfluoropolyether having a molecular weight of 200 to 25,000 is bonded to (-CF ₂ CF ₂ O) - _a (-CF ₂ O) - _b (-O) - _c where a + b = 2 to 230 b/ a=0.1~10 c/(a+b)=0.01~1.0 (1) Heat treatment at 150~300°C in an inert gas atmosphere or (2) UV irradiation treatment to remove active oxygen in the molecules from the above c/( This is achieved by producing new perfluoropolyethers whose a+b) values are reduced to between 0 and 0.1. Perfluoropolyethers consisting of a combination of the above structural units are produced by reacting tetrafluoroethylene with oxygen in a fluorinated or chlorinated solvent under ultraviolet irradiation, and the reaction is controlled by a chain transfer constant ( 60℃) is 5
It is carried out in the presence of a halogenated hydrocarbon chain transfer agent of ×10 ⁻⁵ or more. Note that one end group of the perfluoropolyether formed is COF, OCOF, OCF ₃ ,
OCF ₂ COF, Cl, Br, I, CCl ₃ , CBr ₃ , CI ₃ group, etc., and the other terminal group is CF ₃ , COF,
CF ₂ COF, CF ₂ Cl, CF ₂ Br, CF ₂ I, CF ₂ CF ₂ Cl,
CF ₂ CF ₂ Br, CF ₂ CF ₂ I, CF ₂ CCl ₃ , CF ₂ CBr ₃ ,
CF ₂ CI ₃ , CF ₂ CF ₂ CCl ₃ , CF ₂ CF ₂ CBr ₃ ,
It is assumed that there are _three CF ₂ CF ₂ CI groups, and although it is possible to confirm this to some extent, it is difficult to fix it accurately. The reaction of tetrafluoroethylene with oxygen in a fluorinated or chlorinated solvent under ultraviolet irradiation is generally carried out according to conventional methods. The reaction solvent used is one that does not easily undergo chain transfer, such as dichlorotetrafluoroethane, trichlorotrifluoroethane, or dichlorodifluoroethane, and after dissolving or suspending the halogenated hydrocarbon chain transfer agent in these solvents, , about −40
Cool to a temperature of ~10 °C. There, the wavelength is 330nm.
A quartz ultraviolet light source device that effectively emits the following short wavelength ultraviolet light is turned on, and a predetermined concentration of tetrafluoroethylene monomer and oxygen are supplied to start the reaction. The monomer is supplied to the reaction system in gaseous form,
Alternatively, oxygen may be diluted with nitrogen or the like as necessary, or air may be supplied as is. The halogenated hydrocarbon chain transfer agent used is a chlorinated, brominated or iodinated hydrocarbon having a chain transfer constant for methyl methacrylate (C=Ktr/Kp, 60°C) of 5.0×10 ^-5 or more. used. C value for methyl methacrylate: CH ₂ Cl ₂ 1.00×10 ^-5 CHCl ₃ 4.54×10 ^-5 CCl ₄ 9.25×10 ^-5 CBr ₄ 2.7×10 ^-1 CI ₄ (greater than CBr ₄ value) From these values, As the halogenated hydrocarbon chain transfer agent, carbon tetrachloride, carbon tetrabromide, or carbon tetraiodide is preferably used, and the selection is made appropriately depending on the viscosity of the target product. . That is, for the purpose of reducing viscosity,
The larger the atomic number of the halogen atom and the larger the chain transfer constant, the more effectively it acts. on the other hand,
Chloroform having a chain transfer constant below the specified value can hardly achieve its purpose. The amount of chain transfer agent used is determined based on the relationship with ultraviolet light, and is generally between 10 ^-7 and 1W of ultraviolet light output.
It is used on the order of 10 ^-2 mol, preferably on the order of 10 ^-6 to 10 ^-3 mol. The perfluoropolyether obtained in this way has active oxygen and an active halogen derived from a halogenated hydrocarbon chain transfer agent bonded in its molecules.
Calculate the value of c/(a+b) using one of the following methods:
It can be decreased from 0.01-1.0 to 0-0.1. (1) In an inert gas atmosphere such as nitrogen gas,
Method (2) of heat treatment to a temperature of ~300°C, preferably 180 to 240°C Desirably in a fluorinated or chlorinated solvent, about -50 to 100°C, preferably about -30 to 50°C
A method of irradiating ultraviolet rays at a temperature of ℃ As a result of this treatment, the content of active oxygen (c) can be reduced to 0, and in this way, it is possible to reduce the content of active oxygen (c) to 0, and even if it does not have oxidizing power or does not reach that level. It is converted into a perfluoropolyether with limited oxidizing power. The perfluoropolyether from which active oxygen has been removed or reduced is heated at a temperature of about 150 to 300°C, preferably about 180 to 240°C, to a fluorine gas, preferably a fluorine gas, diluted with an inert gas such as nitrogen. By treating with an elementary gas, the active halogen in the molecule can be replaced with fluorine. Although it is possible to obtain a perfluoropolyether that does not contain any active halogen by this method, the processing conditions are generally selected so that it is compatible with the original purpose of the perfluoropolyether and also with intermediate uses. The content of chlorine, bromine or iodine atoms by 0.01
The perfluoropolyether is obtained as reduced to ~1.0% by weight. In other words, when perfluoropolyether is used as an inert fluid, which is its original purpose, the active halogen content is 0.05.
% or less, while for intermediate use it is preferably 0.1% or more. The perfluoropolyethers obtained at each stage through this series of reaction steps were subjected to the following various analyzes in order to specify their structures. As a typical example, the perfluoropolyether obtained in Reference Example 6 below using carbon tetrabromide as a halogenated hydrocarbon chain transfer agent Kinematic viscosity: 35Cst Active oxygen: _I2 by NaI/acetic anhydride system 1.9% as free _I2 by oxidative determination method Molecular weight: Value from solution viscosity in Fc-75 solvent
4900 b/a: Calculated value from the values of a and b by F ¹⁹ -NMR 4.7 Br elemental analysis: Value according to special analysis method for halogen 0.74
% was heat treated at 220℃ for 24 hours in a nitrogen gas stream,
When active oxygen was quantified in the same manner as above, the value as free I ₂ was 0, indicating that this perfluoropolyether no longer exhibited oxidizing properties. In order to analyze the structure of this perfluoropolyether in more detail, we measured its thermal decomposition mass spectrum. In this case, natural bromine contains Br ⁷⁹ and Br ⁸¹ isotopes in a ratio of approximately 1:1, giving a unique mass fragment ion peak, making it possible to obtain particularly accurate structural information. The fragment ion peaks obtained here were assigned as follows. m/e attribution 66 CF ₂ O 69 CF ₃ 100 CF ₂ CF _{2 135} C ₂ F 5 O 201 C ₂ F ₅ OCF ₂ O 235 C ₂ F ₅ OC ₂ F ₄ 251 C ₃ F ₇ OC ₂ F ₄ O 301 C ₂ F ₅ OCF ₂ OC ₂ F ₄ 245 CF ₂ Br ⁷⁹ C ₂ F ₄ O 247 CF ₂ Br ⁸¹ C ₂ F ₄ O 179 CF ₂ Br ⁷⁹ CF ₂ 181 CF ₂ Br ⁸¹ CF ₂ 129 CF ₂ Br ⁷⁹ 131 CF ₂ Br ⁸¹ Here, as a phenomenon specific to the Br element, the mass ion intensities of groups containing Br ⁷⁹ and groups containing Br ⁸¹ are m/e (245, 247), (179, 181), (129, 131)
It was confirmed that the ratio was 1:1. Next, this active oxygen-removed perfluoropolyether was heated to 200°C in a glass reaction vessel, and fluorine gas diluted with nitrogen gas to a concentration of 20% was flowed into it to cause bubbling. A bromine content of 0.1% was measured for the sample after 8 hours of bubbling, but after bubbling was continued for an additional 16 hours,
When the bromine content was measured, the presence of bromine was no longer confirmed, and a neutral perfluoropolyether was obtained. When this perfluoropolyether was subjected to thermal decomposition mass spectrometry analysis, no fragment ion peak containing bromine was observed, indicating that bromine was completely replaced with fluorine. [Effects of the invention] (1) Perfluoropolyether obtained by reacting tetrafluoroethylene and oxygen in a fluorinated or chlorine-fluorinated solvent under ultraviolet irradiation is heated in an inert gas atmosphere. By treatment or ultraviolet irradiation treatment, the amount of active oxygen in the molecule can be significantly reduced, resulting in a neutral perfluoropolyether that is chemically and physically stable and has various uses. (2) Since an active halogen is bonded to the molecule, reactions can be carried out using this group, and if unnecessary, the active halogen can be fluorinated. [Example] Next, the present invention will be explained with reference to an example. Reference Example 1 9 kg of dichlorotetrafluoroethane as a reaction solvent and 10.8 g (0.07 mol) of carbon tetrachloride as a chain transfer agent were charged into an internal irradiation type ultraviolet device having a quartz inner cylinder with a capacity of 6, and the mixture was heated to -20°C. Cooled. Using a 400W high-pressure mercury lamp as a light source and controlling the reaction temperature, tetrafluoroethylene was introduced into the reaction system at a flow rate of 4 mol/hr and oxygen was introduced in gaseous form at a flow rate of 8 mol/hr. I went there. During the reaction, the temperature was controlled at -20°C ± 2°C while keeping the monomer flow rate constant throughout. After the reaction, the solvent was distilled off, and the resulting oily substance was heated to a temperature of 60 to 80°C to remove the solvent. Performed a complete removal. Regarding the obtained oily substance, kinematic viscosity, Fc−75
Reduced viscosity (converted to molecular weight) using a, b, c
The value and active halogen content were measured respectively. Comparative Reference Example 1 In Reference Example 1, carbon tetrachloride was not used. Reference Examples 2 to 4 In Reference Example 1, 0.995 g (0.003 mol), 9.95 g (0.03 mol) or 99.5 (0.3 mol) of carbon tetrabromide was used as a chain transfer agent. Reference Example 5 In Reference Example 3, the reaction vessel capacity is 20, the high pressure mercury lamp output is 300W, the reaction temperature is -25℃±2℃,
The tetrafluoroethylene flow rate was changed to 2.6 mol/hr. Reference Example 6 In Reference Example 5, the amount of carbon tetrabromide is 14.925g
(0.045 mol) with tetrafluoroethylene flow rate
The amount was changed to 1.3 mol/hr. Comparative Reference Examples 2 to 4 In Reference Example 6, carbon tetrabromide was not used,
Tetrafluoroethylene flow rate 0.6 mol/hr, 0.8
The amount was changed to mol/hr or 1.3 mol/hr, respectively. Reference examples 7 to 8 In reference example 6, the high pressure mercury lamp output is set to 200W,
The amount of carbon tetrabromide is 4.64g (0.014mol) or 9.95g
(0.03 mol) with tetrafluoroethylene flow rate
The amount was changed to 1.8 mol/hr or 2.1 mol/hr, respectively. Comparative Reference Example 5 In Reference Examples 7 and 8, carbon tetrabromide was not used and the tetrafluoroethylene flow rate was 2.7 mol/hr.
Changed to Reference examples 9-10 In reference example 6, the high-pressure mercury lamp output is set to 100W,
The amount of carbon tetrabromide is 8.96g (0.027mol) or 17.91
g (0.054 mol), the reaction temperature was -28℃±2℃,
In addition, the tetrafluoroethylene flow rate was 1.6 mol/hr.
changed respectively. Reference Examples 11-12 In Reference Examples 9-10, carbon tetraiodide is 10.39 g (0.02 mol) or 20.79 g as a chain transfer agent.
(0.04 mol) was used, and the reaction temperature was -27℃±2℃
It was changed to . The measurement results for each of the above reference examples and reference comparative examples are shown in the following table.

[Table] From the above results, the following can be said. (1) Carbon tetrachloride, carbon tetrabromide, and carbon tetraiodide are
In this reaction, it acts effectively as a telogen. (2) When the amount of chain transfer agent used decreases, the viscosity and molecular weight increase, but carbon tetrabromide is equally effective as a telogen when used in an amount less than 1/10 of carbon tetrachloride. Ru. (3) A small increase in the tetrafluoroethylene feed rate leads to a rapid increase in the viscosity of the product;
In order to obtain a low viscosity product, it is necessary to keep the supply amount low. (4) In the absence of a chain transfer agent, a decrease in the amount of ultraviolet rays leads to a rapid increase in viscosity and molecular weight, but no such tendency is observed in the presence of a chain transfer agent. Example 1 500g of the product obtained in Reference Example 7 was transferred to a volume of 300g.
ml separable flask, heated to 220°C, and then heat-treated in a nitrogen stream for 24 hours. Kinematic viscosity 61Cst obtained by cooling to room temperature after heat treatment
When the active oxygen content of the product (yield 78%) was analyzed, it was confirmed that the product did not elute iodine from sodium iodide and was non-oxidizing. The active bromine content was 0.74% by weight, which was slightly higher than the value before heat treatment, 0.66% by weight. Example 2 In Example 1, when the heating temperature was changed to 180°C, the kinematic viscosity was 120Cst and the active oxygen content was 0.8% by weight.
of product was obtained in 85% yield. Examples 3 to 6 According to Example 1, using the product obtained in Reference Example 6 as a reaction raw material, heat treatment was performed under the conditions shown in Table 2 below, and the properties shown in Table 2 were obtained. The product was obtained.

[Table] The active bromine content in the product of Example 6 was 0.73% by weight, which was almost the same as the value before heat treatment, 0.74% by weight. Example 7 300 g of the product obtained in Reference Example 6 and 6 kg of trichlorotrifluoroethane were placed in a reactor with a capacity of 6, and irradiated with ultraviolet light through a quartz tube for 24 hours at 0°C using a 400 W high-pressure mercury lamp. did. The obtained product with a kinematic viscosity of 13 Cst no longer exhibited oxidizing properties and was neutral. The active bromine content was 0.75% by weight, which was almost the same as the value before ultraviolet irradiation, which was 0.74% by weight. Examples 8 to 11 According to Example 7, ultraviolet irradiation was performed under the conditions shown in Table 3 below to obtain products having the properties shown in Table 3. However, the amount of solvent used in Example 11 was 2 kg.

[Table] Note that the active bromine content in the product of Example 10 was 0.78% by weight, which was a slight increase of 0.70% by weight from the value before ultraviolet irradiation treatment.

Claims (1)

[Scope of Claims] 1. In the presence of a chlorinated, brominated or iodinated hydrocarbon chain transfer agent having a chain transfer constant (60°C) for methyl methacrylate of 5×10 ^-5 or more, fluorinated or chlorinated hydrocarbon It is obtained by reacting tetrafluoroethylene and oxygen in a solvent under ultraviolet irradiation, and consists of a combination of the following structural units in which the main chain is linearly and irregularly arranged, and contains chlorine, bromine, or iodine atoms in the molecule. A new perfluoropolyether with a _molecular weight of 200 _{to 25,000} in _{which 0.1 to} 10% by weight of = 2 to 230 b/a = 0.1 to 10 c/(a+b) = 0.01 to 1.0 (1) Heat treatment at 150 to 300°C in an inert gas atmosphere or (2) UV irradiation treatment to reduce the activity in the molecule. A method for producing a novel perfluoropolyether, characterized by reducing oxygen to the above c/(a+b) value of 0 to 0.1. 2. The method for producing a novel perfluoropolyether according to claim 1, wherein ultraviolet irradiation is performed on the perfluoropolyether to be treated in a fluorinated or chlorine-fluorinated solvent.