JP2847850B2 - Ethylene-tetrafluoroethylene copolymer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a novel ethylene-tetrafluoroethylene-based copolymer, and more specifically, to an improvement in physical properties obtained by copolymerizing a small amount of a specific fluorovinyl ether. And a novel ethylene-tetrafluoroethylene copolymer.

[Prior art] Conventionally, ethylene tetrafluoride and ethylene are copolymerized by the action of a polymerization initiation source, and an ethylene-tetrafluoroethylene copolymer excellent in chemical resistance, heat resistance, electrical properties, etc. is obtained. Manufacturing methods are known. Since the copolymer can be heated and melt-formed together with its excellent properties, it can be widely used as a material for various molded products, wire coating, lining, coating and the like.

Thus, in order to improve the high-temperature mechanical properties, particularly high-temperature tensile properties, of the ethylene-tetrafluoroethylene-based copolymer, an auxiliary amount having no telogen activity and providing a side chain containing at least two carbon atoms. A method of copolymerizing a copolymerizable vinyl monomer has been proposed. For example,
-23671, U.S. Pat. No. 3,624,250, British Patent No. 1,292,643, and the like. According to such a method,
The disadvantage that the wire coating of the ethylene-tetrafluoroethylene copolymer becomes brittle even at high temperatures and cracks with low stress can be eliminated.

However, when a conventionally proposed vinyl monomer having a bulky side chain is used, advantageous results can be obtained for the improvement of the high-temperature tensile properties, but various disadvantages are recognized for industrial practice. . For example _{CF 2 = CF-C 2 F} 5, CF 2 = C
If the F-C ₄ such as F ₉ formula CF ₂ = CF-Rf (except Rf is a perfluoroalkyl group) with the addition of perfluoroolefin represented by implementing the copolymerization of ethylene and tetrafluoroethylene is The copolymerization reaction rate is significantly reduced. Also, CF
_{2 = CF-CH 2 -C (} CF 3) 2 OH or Such as fluoroolefins, vinyl esters, etc.
Ethylene -4 which has a heat resistance of 200 hours or more in a test (heating temperature of 230 ° C.) for measuring the heat aging time at which the elongation at room temperature is reduced to 50% of the initial value by reducing the heat resistance of the resulting copolymer. Such a disadvantage can be exemplified that the fluoroethylene copolymer is reduced in heat resistance to 80 to 100 hours or less by the introduction of the side chain.

In particular, U.S. Pat.
In the specification of 292643, even a vinyl monomer which gives a bulky side chain, one having a multiple bond in the side chain or one having an acidic group, an ester group or the like is excluded. For example, vinyl esters, unsaturated carboxylic acids, unsaturated carboxylic acid alkyl esters and the like are excluded. Although the reason why such a vinyl monomer is excluded is not always clear, it is considered that the reason is that the heat aging resistance and the like become poor as described above. In practice, it is difficult to improve the high temperature tensile properties of a material such as vinyl acetate without copolymerization in a considerable amount, and as a result, the heat aging resistance and the tensile creep properties are reduced as described above.

[Problems to be Solved by the Invention] As means for suppressing deterioration of heat aging resistance and tensile creep property and improving high-temperature tensile properties, Japanese Patent Publication No. 59-50162 discloses a general formula CF ₂ = CFO (CF ₂ ) _n A method using fluorovinyl ether represented by COX has been proposed. However, this method has a problem that foaming and coloring occur under high molding conditions.

Means for Solving the Invention The present invention has been made to solve the above-mentioned problems, and the molar ratio of units based on ethylene tetrafluoride / units based on ethylene is 70/30 to 40/60. And the general formula The content of the unit based on fluorovinyl ether represented by in the copolymer is 0.1 to 10 mol%, using a Koka type flow tester, 300 ° C., 30 kg / cm ² under a nozzle diameter of 1 mm, An ethylene-tetrafluoroethylene system characterized in that a volume flow rate defined by the volume of the sample extruded per unit time at the time of extruding a 1 g sample from a land 2 mm nozzle is 10 to 500 mm ³ / sec. It is intended to provide a copolymer.

As used herein, the term "volume flow rate"
It is defined as follows and is a measure of the molecular weight. That is, using a Koka type flow tester, is extruded predetermined temperature, under the predetermined load 30kg / cm ^2, nozzle diameter 1 mm, a sample of 1g from the nozzle of the land 2mm extruded, in a unit time at that time The value represented by the volume of the sample is defined as “volume flow rate” and its unit is mm ³ / sec. Here, the predetermined temperature is a temperature range in which a specific ethylene-tetrafluoroethylene-based copolymer can be molded (a temperature range between the flow start temperature and the thermal decomposition start temperature) and close to the flow start temperature. Is adopted. Thus, 300 ° C. is selected for the particular copolymer in the present invention.

In the examples described below, a temperature of 300 ° C. was employed.

In the present invention, the ethylene-tetrafluoroethylene-based copolymer has a content molar ratio of units based on ethylene tetrafluoride / units based on ethylene of 70/30 to 40/60. If the amount of the unit based on ethylene tetrafluoride is too small, the chemical resistance, heat resistance, etc. decrease, which is not preferable. In addition, if the amount is too large, it is practically difficult to produce, and even if it can be produced, the production efficiency deteriorates, which is not preferable. In particular, those having a ratio of 60/40 to 45/55 are preferable.

CF ₂ = CFO (CF ₂ CF (CF ₃ ) O) _n CF ₂ CF ₂ SO ₂ F (n
Is an integer of 1 to 3) and contains a unit based on fluorovinyl ether at a ratio of 0.1 to 10 mol%.

If the content of the unit based on the specific fluorovinyl ether is too small, the effect of improving the high-temperature mechanical properties is not recognized, but if it is too large, tensile creep and heat aging of the ethylene-tetrafluoroethylene-based copolymer are not performed. The properties and the like are reduced, and it becomes excessively soft. The ethylene-tetrafluoroethylene-based copolymer obtained according to the present invention is a high-temperature, e.g., 200 ° C., tensile strength, ultimate elongation of an ethylene-tetrafluoroethylene-based copolymer containing no unit based on a specific fluorovinyl ether. Each degree ~ 20k
g / cm ² , ~ 40%, respectively, 30kg / cm ² or more, especially 40-80kg / cm ² , more than 200%, especially 400-600%, wire coating becomes brittle even at high temperature, The disadvantage of cracking at low stress is eliminated. Especially 0.3 to 5 mol%
Is preferable.

As the specific fluorovinyl ether, n is 1 in view of availability, copolymerization reactivity with ethylene tetrafluoride, and ethylene, that is, Is most preferred.

The novel ethylene-tetrafluoroethylene-based copolymer of the present invention has a volume flow rate of 10 to 500 mm ³ / sec, preferably 20 to 500 mm ³ / sec.
30 mm ³ / sec. Due to this volume flow rate range,
Extrusion molding, hot melt molding such as injection molding is possible,
Baking is also easy in powder coating, dispersion coating and the like. Further, the preferred novel copolymer in the present invention has a flow start temperature of 240 ° C. or higher, preferably 250 to 280.
° C., the thermal decomposition onset temperature is 310 ° C. or more, preferably 330
370 ° C. Therefore, as described above, the heat-melt molding process is easy and the heat resistance is excellent, and the high-temperature tensile properties and the like are improved while maintaining these various properties.

In the present invention, in order to produce a suitable novel copolymer, the reaction molar ratio of ethylene tetrafluoride / ethylene is usually 2.35.
Above, preferably three or more are employed. That is, in a preferred embodiment, the reaction is carried out such that the ratio of the ethylene tetrafluoride monomer to the ethylene monomer in the copolymerization reaction system is kept within the above range. For example, the molar ratio of ethylene tetrafluoride / ethylene is selected from the above range, and the copolymerization reaction is performed while replenishing the amount consumed by the progress of the copolymerization reaction. Therefore, in the method of the present invention,
The charged molar ratio of ethylene tetrafluoride / ethylene is 70/30 to 95 /
5, preferably selected from the range of 75/25 to 85/15, the ethylene tetrafluoride / ethylene molar ratio is 40/6 during the progress of the copolymerization reaction.
It is desirable to carry out the copolymerization reaction while replenishing the monomer mixture from 0 to 70/30, preferably 45/55 to 60/40. Thus, an ethylene-tetrafluoroethylene copolymer having a content of units based on ethylene tetrafluoride of 40 to 70 mol%, particularly 45 to 60 mol%, based on the total of the units based on ethylene tetrafluoride and ethylene is obtained. can get.

It is also desirable to carry out the copolymerization reaction while maintaining the above ratio for the specific fluorovinyl ether, and it is generally preferable to carry out the copolymerization while replenishing the amount consumed by the progress of the copolymerization reaction. In the present invention, a specific fluorovinyl ether is contained in the resulting copolymer by copolymerization in a small amount, but is usually about 0.1 to 10 mol%, particularly 0.3 to 10 mol%.
A content of about 5 mol% is desirable. Therefore, during the copolymerization reaction, the specific fluorovinyl ether is added together with ethylene tetrafluoride and ethylene in an amount of 0.1 to 10 mol%, preferably
It is desirable to replenish at a concentration of 0.3 to 5 mol%. Thus, the specific fluorovinyl ether is 0.1 to 10 mol%,
Preferably, an ethylene-tetrafluoroethylene copolymer copolymerized at 0.3 to 5 mol% is obtained. The content of the specific fluorovinyl ether in the produced copolymer is calculated from the difference between the amount of each monomer introduced into the polymerization tank and the amount of each monomer recovered after the completion of the polymerization.

The copolymerization reaction may be carried out with or without using an inert organic solvent or an aqueous medium, under the action of a polymerization initiator such as a peroxy compound, an azo compound, ultraviolet light, or ionizing radiation. And so on. As the polymerization method, various polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and gas phase polymerization can be adopted.

According to the study of the present inventor, as a copolymerization reaction medium, a solvent composed of a fluorinated saturated hydrocarbon or a fluorinated chlorinated saturated hydrocarbon known as a so-called chlorofluorocarbon-based solvent, preferably It is advantageous to use those having a number of 1 to 4, especially 1 to 2 in terms of producing an ethylene-tetrafluoroethylene-based copolymer having excellent heat resistance, molding processability, chemical resistance and other excellent properties. In addition, it has been recognized that in controlling the reaction conditions and maintaining the copolymerization reaction rate, advantageous results for industrial practice can be obtained. As a chlorofluorocarbon-based solvent, for example, dichlorodifluoromethane,
Trichloromonofluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, chlorotrifluoromethane, fluoroform, tetrafluoroethane,
Trichlorotrifluoroethane, dichlorotetrafluoroethane, hexafluoroethane, fluorochloropropane, perfluoropropane, fluorocyclobutane,
Perfluorocyclobutane and the like can be mentioned, and these are used in one kind or in a mixture of two or more kinds. Thus,
According to the study of the present inventors, dichlorodifluoromethane,
Solvents composed of fluorinated saturated hydrocarbons containing no hydrogen atoms in the molecule or fluorinated chlorinated saturated hydrocarbons, such as trichloromonofluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and perfluorocyclobutane, preferably 1-4 carbon atoms, especially 1-2
It has been recognized that, when individual products are used, it is possible to increase the molecular weight of the produced copolymer, and it is particularly desirable for others.

When using a chlorofluorocarbon-based solvent, the amount thereof is not particularly limited, but usually, the solvent is 0.05 to 20 mol, particularly 1 to 1 mol per 1 mol of a monomer mixture of ethylene tetrafluoride, ethylene and a specific fluorovinyl ether. About 10 mol is employed. It is possible to carry out the copolymerization reaction even if the amount of the solvent used is less than 0.05 mol per mol of the monomer, but it is necessary to increase the copolymerization reaction rate by industrially advantageous operations and conditions. It is advantageous to use more than one mole.
Although it is possible to use more than 20 moles of a solvent, it is advantageous to use 10 moles or less mainly for economic reasons such as solvent recovery after the reaction.

It is also possible to employ a mixture of a fluorocarbon solvent and another organic solvent or aqueous medium. For example, it is possible to employ a mixed reaction medium of a chlorofluorocarbon-based solvent and water, and it is possible to achieve good results by such means as ease of stirring the copolymerization reaction system or removal of reaction heat, and the like.

The copolymerization reaction conditions can be variously changed depending on the polymerization initiation source, the reaction medium, and the like. However, when a CFC-based solvent is used, a reaction temperature of about −50 ° C. to + 150 ° C. is industrially advantageous. Adopted. The type and amount of solvent used,
The appropriate reaction temperature is selected according to the molar ratio of the monomers charged, the amount of the specific fluorovinyl ether added, the type of polymerization initiation source, etc., but if the temperature is too high, the reaction pressure will be excessive, and if the temperature is too low, the copolymerization will occur. It is desirable to adopt the above range, since the reaction rate becomes lower than industrially satisfactory. The reaction pressure may be from normal pressure to a slight pressure, and usually about ^{2 to} 50 kg / cm ² · gauge is employed.

As the polymerization initiation source, various sources can be appropriately adopted according to the polymerization method and the like, and there is no particular limitation. However, if a chlorofluorocarbon solvent is used, cobalt-60
It is desirable to employ ionizing radiation such as γ-rays from cesium-137 or cesium-137, and oil-soluble radical polymerization initiation sources such as peroxy compounds and azo compounds. For example, a dose rate of 10
Ionizing radiation can be employed at up to 10 ⁶ rad / hr, and as the peroxy compound, organic peroxides such as benzoyl peroxide and lauroyl peroxide;
Peroxyesters such as t-butylperoxyisobutyrate, diisopropylperoxydicarbonate and the like are generally used, and as the azo compound, a radical initiator such as azobisisobutyronitrile is generally used. The amount of the radical initiator used must be appropriately selected depending on the polymerization conditions employed, that is, the amount of the specific fluorovinyl ether to be added, the medium used, the polymerization temperature, and the like. Concentrations on the order of ２2% by weight can be employed.

In order to obtain an ethene-tetrafluoroethylene copolymer having a suitable molecular weight, it is preferable to use a molecular weight modifier. As such a molecular weight regulator, a lower alcohol is preferable, and methyl alcohol is particularly preferably used.

In order to obtain a suitable ethylene-tetrafluoroethylene-based copolymer, a fluorocarbon-based solvent is used, and a general formula is used as a polymerization initiation source. (Where R and R ¹ in the formula are aliphatic alkyl groups)
It is particularly preferable to use a peroxyester type radical initiator represented by It is advantageous for the copolymerization reaction rate, various physical properties of the produced copolymer, the copolymerization reaction operation and conditions, and the like. R and R ¹ are aliphatic alkyl groups, and the number of carbon atoms is not particularly limited.
It is desirable that both R and R ¹ are alkyl groups having about 3 to 13 carbon atoms. For example, t-butylperoxyisobutyrate, t-butylperoxyacetate, t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, etc. Can be.

The amount of the peroxyester type radical initiator used is
A concentration of about 0.001 part by weight or more based on 100 parts by weight of all monomers is sufficient. Preferably, the concentration of the radical initiator in the fluorocarbon solvent is about 0.005 to 5 parts by weight per 100 parts by weight of all monomers. The fluorocarbon solvent is used in an amount of about 1 to 10 mol, particularly about 1.5 to 5 mol, per 1 mol of the monomer mixture. The copolymerization reaction temperature is usually 30 to
Although about 120 ° C. can be adopted, it is desirable to select the optimum temperature in consideration of the half-life of the peroxyester type radical initiator used. For example, the temperature is 50 to 80 ° C. for t-butyl peroxyisobutyrate, and 40 to 60 ° C. for t-butyl peroxypivalate. By employing such a reaction temperature, it is possible to obtain a novel copolymer in a good yield without requiring a long time.

When a fluorocarbon solvent is used, the solvent can be easily separated from the produced copolymer together with the unreacted monomer after the completion of the copolymerization reaction. Further, since an excessive reaction pressure such as a copolymerization reaction carried out in an aqueous medium can be suppressed, an ethylene-tetrafluoroethylene copolymer having excellent physical properties can be produced safely without employing high temperature and high pressure. Moreover, in this case, the copolymerization reaction rate is industrially satisfactory as described above. This description does not limit the invention in any way.

Next, examples of the present invention will be described more specifically. However, it is needless to say that the present invention is not limited by the description. In the following examples, the physical properties of the copolymer were measured by the following methods.

[Composition of copolymer] It was determined by elemental analysis and ¹⁹ F-NMR analysis.

[Heat resistance] ・ Appearance of compression molded product Ethylene-tetrafluoroethylene-based copolymer at 320 ° C 10
The appearance (coloring, foaming) after heating and compression for 5 minutes was observed.

Stress cracking 6.4mm in width and 1.3 ± in thickness to 6.4mm in diameter (Mandrel)
A strip-shaped sheet of 0.1 mm and a length of 127 mm is wrapped around, and both ends are fixed to a stretched metal with bolts and nuts. This test piece is
After standing for 96 hours in a furnace maintained at 230 ° C., the presence or absence of cracks was checked. The results were expressed as the number of cracks / the number of tests.

Heat aging resistance The strength and elongation retention after standing for 96 hours in a furnace maintained at 230 ° C were determined. ASTM D-63 for strength and elongation
According to No. 8, the test was performed using a V-shaped dumbbell. The retention rate is
It was determined from the values of strength and elongation before and after standing in a furnace.

[Example] Example 1 CFC 11 was added to an autoclave with a stirrer having a content of 1000 ml.
3 486 g, Freon 11 534 g, [Hereinafter abbreviated as PSVE] 75.3 g was charged, and after sufficiently replacing the internal space with nitrogen gas, this was evacuated and exhausted to obtain 116.4 g of ethylene tetrafluoride [hereinafter abbreviated as TFE], 116.4 g of ethylene
E may be abbreviated.] 8.1 g. The polymerization temperature was raised to 65 ° C., and the initiator t-butyl peroxyisobutyrate was
5 ml of a 10% by weight Freon 113 solution is added to initiate polymerization. During the reaction, ethylene tetrafluoride / ethylene
A mixed gas having a / PSVE molar ratio of 52.0 / 46.2 / 1.8 is introduced, and a polymerization pressure of 13.1 kg / cm ² G is maintained. After 2.4 hours, 88.4 g of a white copolymer was obtained. The composition of the copolymer was TFE / E / PSVE = 52.0
/46.2/1.8 mol%, and the volume flow rate was 20 (mm ³ / sec).

Example 2 Using the autoclave of Example 1, Freon 113 1094 g,
6.45 g of methanol and 90.4 g of PSVE were charged, and the atmosphere was sufficiently replaced with nitrogen gas.
Charge 113.8g and 8.0g ethylene. The polymerization temperature was raised to 65 ° C., and 5 ml of a 10% by weight Freon 113 solution of an initiator t-butyl peroxyisobutyrate was added to initiate polymerization. During the reaction, ethylene tetrafluoride / ethylene
A mixed gas having a / PSVE molar ratio of 51.7 / 45.9 / 2.4 was introduced, and the polymerization pressure was maintained at 13.0 kg / cm ² G. After 2.8 hours, 108.2 g of a white copolymer was obtained. The composition of the copolymer was TFE / E / PSVE = 5
1.7 / 45.9 / 2.4 mol% and the volumetric flow rate was 38 mm ³ / sec.

Comparative Example 1 In Example 1, 630 g of CFC 113 and 426 g of CFC 11 were used.
, 121 g of tetrafluoroethylene as an initially charged monomer,
6.0 g of ethylene, CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ instead of PSVE
[Hereinafter abbreviated as MXM] 59.3 g, and the molar ratio of ethylene tetrafluoride / ethylene / MXM was 51.8 / 46.0 / 2.0 as a monomer to be charged later.
The same operation was repeated except that the mixed gas was introduced to obtain 106.4 g of a white copolymer in a polymerization time of 2.7 hr. The composition of the copolymer was TFE / E / MXM = 51.8 / 46.0 / 2.0 mol%, and the volume flow rate was 45 mm ³ / sec.

Comparative Example 2 In Example 2, 3.83 g of ethanol was used, and 103.4 g of ethylene tetrafluoride and 7.13 g of ethylene were used as initial monomers.
2 g, 98.9 g of MXM instead of PSVE, and the molar ratio of ethylene tetrafluoride / ethylene / MXM was 50.7 / 45.0 / 4.
The same operation was repeated except that the mixed gas of No. 3 was introduced and the polymerization pressure was maintained at 12.0 kg / cm ² G, to obtain 100.0 g of a white copolymer in a polymerization time of 2.1 hr. The composition of the copolymer is TFE / E / MX
M = 50.7 / 45.0 / 4.3 mol%, volume flow rate 13.5mm ³ / sec
Met.

The examination results of the heat resistance of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in the table below.

[Effect of the Invention] The ethylene-tetrafluoroethylene-based copolymer of the present invention is superior in heat resistance to the conventional ethylene-tetrafluoroethylene-based copolymer, and causes coloring and foaming especially during heat molding. This has the effect that there is no occurrence.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI (C08F 214/26 210: 02 216: 14) (58) Investigated field (Int.Cl. ⁶ , DB name) C08F 210/02 C08F 214/26 C08F 216/14 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] (1) The molar ratio of units based on ethylene tetrafluoride / units based on ethylene is from 70/30 to 40/60, and the general formula CF ₂ = CFO (CF ₂ CF (CF ₃ ) O) _n CF The content of the unit based on fluorovinyl ether represented by ₂ CF ₂ SO ₂ F (n is an integer of 1 to 3) in the copolymer is 0.1 to 10 mol%, and using a Koka flow tester, A sample of 1 g is extruded from a nozzle having a nozzle diameter of 1 mm and a land of 2 mm at 300 ° C. and 30 kg / cm ² , and the volume flow rate defined by the volume of the sample extruded per unit time at that time is 10 to 500 mm ³ / sec-ethylene-tetrafluoroethylene copolymer.