JPS631962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluorine-containing elastic copolymer, and more specifically to a fluorine-containing elastic copolymer that has excellent cold and oil resistance and contains specific amounts of units based on tetrafluoroethylene and units based on a specific fluoroallyl ether. The present invention relates to a copolymer that provides an elastic body.

A tetrafluoroethylene/propylene copolymer is known as a typical fluorine-containing elastic copolymer containing tetrafluoroethylene as a backbone monomer. Along with tetrafluoroethylene and propylene, this copolymer can be manufactured from industrially easily available raw materials, and has the advantage of providing an elastic body with excellent heat resistance, chemical resistance, electrical properties, etc. However, it has not always been sufficient in terms of fuel oil resistance and cold resistance.

The present inventors have conducted intensive research based on the recognition of the above problems, and have found that a specific copolymer obtained from tetrafluoroethylene and a specific fluoroallyl ether as raw materials has an elastic property with excellent cold resistance and oil resistance. I discovered an unexpected fact about giving one's body. Moreover, the specific fluoroallyl ether used as a raw material here can be obtained in high yield by adding various fluorine-containing olefins to allyl alcohol, and is therefore highly available. It is not subject to any restrictions.

Thus, the present invention has been completed based on the above findings, and uses a unit based on tetrafluoroethylene and the general formula CH ₂ =CHCH ₂ OR _f (wherein R _f is a fluorine-containing compound having 2 to 10 carbon atoms). A copolymer containing as an essential component a unit based on fluoroallyl ether represented by (representing an alkyl group), wherein the copolymer contains a unit based on tetrafluoroethylene and a unit based on fluoroallyl ether. The object of the present invention is to provide a new fluorine-containing elastic copolymer having a molar ratio of 90/10 to 10/90 and a sum of the contents of both units being 70 mol% or more.

Incidentally, as a fluorine-containing copolymer containing units based on fluoroallyl ether, those containing a trace amount of this unit as a third component are known (see JP-A-50-143889); Copolymers containing units based on fluoroallyl ether as one of the main components, such as the copolymers of the invention, are new, and copolymers with a rigid monomer called tetrafluoroethylene produce elastomers with excellent properties. It was not known that this copolymer could be used as a copolymer.

In the present invention, the fluoroallyl ether represented by the general formula CH ₂ =CHCH ₂ OR _f ,
It is important to use a _fluorine -containing alkyl group having 2 to 10 carbon atoms in terms of reactivity, properties of the resulting copolymer, and ease of availability. Such fluoroallyl ether can be easily synthesized by a method such as a nucleophilic addition reaction of allyl alcohol to a fluoroolefin having 2 to 10 carbon atoms. For example, allyl alcohol is exothermically added to tetrafluoroethylene in the presence of an alkali in a polar solvent such as dimethylformamide to form 2-hydrotetrafluoroethyl allyl ether (CH ₂ =
CHCH ₂ OCF ₂ CF ₂ H) is given almost quantitatively, and the same addition to hexafluoropropylene gives 2-hydrohexafluoropropyl allyl ether (CH ₂ =CHCH ₂ OCF ₂ CFHCF ₃ ).

It is difficult to synthesize the above R _f with 1 carbon number, while those with 11 or more carbon atoms not only reduce the reactivity but also cause disadvantages such as a reduction in the cold resistance of the resulting copolymer. Therefore, neither is preferable. However, from the viewpoint of easy availability, R _f
is −CF ₂ CF ₂ H or −CF ₂ CFHCF ₃ can be preferably employed.

In the present invention, the molar ratio of the content of units based on tetrafluoroethylene and units based on fluoroallyl ether in the copolymer is 90/10 to 90/10.
It is important that the ratio is 10/90, preferably 70/30 to 30/70. If the content of tetrafluoroethylene units is too high outside this range, it will not only be difficult to control the copolymerization reaction, but also cause problems such as loss of elasticity of the resulting copolymer.
Too high a fluoroallyl ether unit content is undesirable because it causes problems such as decreased heat resistance, decreased oil resistance, and difficulty in increasing the molecular weight of the polymer.

In the copolymers of the present invention, in addition to units based on tetrafluoroethylene and fluoroallyl ether, units based on other comonomers are present in less than 30 mol%, preferably 20 mol% of the total amount of the copolymer.
It is possible to contain the content in a range below. Such comonomers include fluoroolefins such as chlorotrifluoroethylene and vinylidene fluoride, olefins such as ethylene and propylene, vinyl ethers such as ethyl vinyl ether, and furthermore 2-chloroethyl vinyl ether and monochlorovinyl acetate. Examples include monomers that provide reactive sites, and they can be used alone or in combination of two or more.

The copolymer of the present invention preferably has a high molecular weight from the viewpoint of mechanical properties as an elastic body, and has an intrinsic viscosity of at least 0.1 dl/g, particularly 0.2 dl/g, as measured at 30°C in tetrahydrofuran. The above is preferable.

The copolymers of the present invention can be produced by acting on a monomer mixture containing tetrafluoroethylene and fluoroallyl ether, and optionally also containing other comonomers, with a radical initiation source. be. Although such a copolymerization reaction may be carried out at high temperature and high pressure, it is preferable to carry out it at a low temperature from the viewpoint of obtaining a high molecular weight copolymer, and various peroxides suitable for low-temperature polymerization can be used as radical initiation sources. It is also possible to use a chemical or azo polymerization initiator as well as ionizing radiation.

Specifically, initiators suitable for low-temperature polymerization include diisopropyl peroxydicarbonate,
Diethylhexyl peroxydicarbonate, acetylcyclohexylsulfonyl peroxide, t-butylperoxypivalate, 2,4-
Organic peroxides such as dichlorobenzoyl peroxide, isobutyryl peroxide, octanoyl peroxide, or azo compounds such as 2,2-azobis(4-methoxy2,4-dimethylvaleronitrile) alone or in combination with a suitable reducing agent. Redox initiators consisting of a combination of inorganic peroxides such as persulfates and appropriate reducing agents, such as persulfates, iron ion sources, ethylenediaminetetraacetic acid or its salts, and sulfinates, etc. Highly active redox initiators are suitable.

The amount of polymerization initiator used is appropriately selected depending on the type, copolymerization reaction conditions, etc., but it is usually the total amount of monomers.
0.005 to 5 parts by weight, especially 0.01 to 100 parts by weight
Approximately 0.5 part by weight is used.

In producing the copolymer of the present invention, any of batch, semi-continuous and continuous polymerization operations can be employed. In addition, any of bulk polymerization, solution polymerization and emulsion polymerization can be employed as the polymerization method, but emulsion polymerization is preferred from the viewpoint of efficiently obtaining a high molecular weight copolymer. As the polymerization temperature
The temperature range is desirably from 60°C or lower to -30°C or higher, particularly from 0°C to 40°C. If the polymerization temperature is too high, it will be difficult to obtain a high molecular weight copolymer, and if it is too low, problems such as solidification of the polymerization medium will occur. In addition, as for the polymerization pressure, the range adopted in normal polymerization reactions can be adopted, but it is less than 150Kg/cm2, especially 100Kg/ ^cm2 or less.
Kg/cm ² or less is sufficient.

Various polymerization media can be used depending on the polymerization method used, but it is desirable to use one that causes chain transfer as little as possible. Examples of polymerization media suitable for solution polymerization include those with small chain transfer constants such as t-butanol, methyl acetate, and chlorofluorocarbons. However, in terms of efficiently obtaining a high molecular weight copolymer, as mentioned above, emulsion polymerization using an aqueous medium is advantageous. It is preferable to use a mixed medium containing an organic solvent. Suitable examples of such additive solvents include t-butanol, methyl acetate, trichlorotrifluoroethane, and the like. Further, when an aqueous medium is employed, it is also possible to use an appropriate PH adjuster, buffer, etc. in order to adjust the PH of the medium depending on the activity of the polymerization initiator.

The copolymer of the present invention can be identified by ¹⁹ F-NMR spectrum. That is, the resonance absorption based on tetrafluoroethylene units is 113 ppm (CCl ₃ F
Several peaks are observed in the vicinity of 122 ppm and 122 ppm, respectively.On the other hand, when the resonance absorption based on the fluoroallyl ether unit is, for example, 2-hydrotetrafluoroallyl ether,
Observed around 92ppm and 132ppm. From the ratio of these peak areas, it is possible to calculate the molar ratio of both units in the copolymer. As a typical example, ^{the 19} F-NMR spectrum of the binary copolymer obtained in Example 1 in which the molar ratio of tetrafluoroethylene/2-hydrotetrafluoroethyl allyl ether is 38/62 is shown in the attached drawing.

The copolymer of the present invention can be crosslinked by irradiation with radiation or by adding a chemical crosslinking agent such as various peroxy compounds. In this case, it is effective to copolymerize a third component that provides a reactive site to improve crosslinking properties, and it is also a preferred embodiment to use a crosslinking accelerator such as a polyallylic compound.

When crosslinking the copolymer of the present invention, various additives commonly used in conventional crosslinking methods may also be added. These additives include metal oxides such as magnesium oxide, lead oxide, reinforcing materials such as carbon black, fine silica, clay, talc, other fillers, pigments, antioxidants, stabilizers, and the like.

When blending the various additives mentioned above with the copolymer of the present invention, it is desirable to mix them sufficiently uniformly. Such mixing may be carried out using a rubber kneading roll or a Banbury mixer that has been conventionally used. Working conditions during mixing are not particularly limited, but usually at a temperature of about 30 to 80°C.
By kneading for 10 to 60 minutes, the additive compound can be sufficiently dispersed and mixed into the fluorine copolymer.

It is also possible to appropriately dissolve and disperse such additives in a solvent to form a suspension. Furthermore, so-called wet mixing is also possible, in which mixing is carried out in the medium from the beginning. In such cases, a suspension-like mixture can be obtained by using a mixer such as a roll, ball mill, or homogenizer. Note that it is desirable that the working conditions and operations during mixing be carried out by selecting optimal conditions according to the types and purpose of the raw materials and ingredients used.

The above compounds can be used in addition to normal mold molding.
It can be molded into molded products such as sheets, pipes, rods, tubes, angles, channels, spread fabrics, coated plates, etc. by continuous molding methods such as extrusion, transfer, roll coating, brushing, and impregnation. However, it can also be molded into irregularly shaped products, special molded products such as sponge-like rubber, etc., using various other molding methods. and,
The thus shaped compound can be made into a vulcanizate by an appropriate vulcanization method as described above. Thus, a vulcanized rubber product can be obtained from the fluorine-containing copolymer of the present invention.

The fluorine-containing copolymer of the present invention provides an elastomer with excellent cold resistance in addition to heat resistance, chemical resistance, and oil resistance, and by taking advantage of such performance, it can be used in a wide range of fields. , may be applied to the purpose. For example, heat resistant, corrosion resistant gaskets, packing, O-
Examples include rings, oil-resistant sealing materials, oil hoses, tubes, diaphragms, heat-resistant and corrosion-resistant rolls, steam-resistant gaskets, heat exchanger gaskets, heat-resistant and oil-resistant electric wires, and the like.

Example 1 In a stainless steel ampoule with a capacity of 100 c.c., 38.6 g of ion-exchanged water, 5 g of t-butanol, 0.5 g of ammonium perfluorononanoate, 1 g of disodium hydrogen phosphate dodecahydrate, and 1.4 g of 5% aqueous sodium hydroxide solution. ,
Ammonium persulfate 0.25g, and ethylenediamine disodium dihydrate 0.009g, ferrous sulfate
Prepare an aqueous solution of 0.0075g and 0.04g of Rongalit dissolved in 5g of water. Thereafter, 2.37 g (0.015 mol) of 2-hydrotetrafluoroallyl ether is added, and the ampoule is capped and solidified and degassed twice with liquid nitrogen. Then tetrafluoroethylene
Introduce 6.00g (0.060 mol). Place the prepared ampoule in a constant temperature shaking water bath at 25°C and shake it. As the temperature rises, the pressure inside the ampoule increases, reaching 22 atmospheres, then gradually decreasing. After 5 hours, the ampoule is removed and unreacted tetrafluoroethylene monomer is purged. The recovered latex is frozen and solidified, and the precipitated polymer is washed and dried. Polymer yield was 1.5g. This copolymer was a soft rubber-like elastic body and had an appearance that was clearly completely different from that of a tetrafluoroethylene homopolymer. The accompanying drawing shows the ¹⁹ F-NMR spectrum of this copolymer in which the H nucleus is decoupled. The numbers in the figure are the chemical shifts (ppm) of each peak based on CFCI ₃ . The intrinsic viscosity ([η]) of this copolymer in tetrahydrofuran at 30℃ is
It was 0.28 dl/g. In addition, the thermal decomposition temperature measured by a differential thermal balance (in heated air at 10°C/min) is as high as 320°C.
Furthermore, the weight increase after immersion in fuel oil B at room temperature for 3 days was only 2.8%. Furthermore, the glass transition temperature was measured by DSC and was found to be -15°C. The molar ratio of tetrafluoroethylene/tetrafluoroallyl ether in this copolymer based on ¹⁹ F-NMR was 38/62.

Example 2 A copolymer was synthesized in the same manner as in Example 1 using a reaction vessel with a capacity of 500 c.c. The charging ratio is exactly the same as in Example 1. 9.2g after 6 hours reaction
of polymer was obtained. [η] of the obtained copolymer is
0.27 dl/g, thermal decomposition temperature was 300°C, and glass transition temperature was -16°C. Using this copolymer, 35phr of carbon and 5phr of triallylisocyanurate were blended using an open roll, and 60Co
It was irradiated for 10 hours at 1×10 ⁵ r/hr. The tensile strength of the crosslinked copolymer is 57Kg/cm ² , the elongation at break is 130%,
In addition, Fuel B swelling (weight) was 1.9%, making it an elastic body with excellent oil resistance.

Example 3 Under the same conditions as Example 1, propylene was added as the third component, and the monomer charges were: 5.8 g (0.058 mol) of tetrafluoroethylene, 1.2 g (0.008 mol) of tetrafluoroallyl ether, and 0.4 g of propylene.
(0.010 mol) was used for polymerization. The obtained copolymer was a rubber-like elastic body with [η] = 0.42 dl/g,
The thermal decomposition temperature was 320°C, the glass transition temperature was -11°C, and the swelling relative to fuel oil B was 34%. As a result of composition analysis by ¹⁹ F-NMR, this copolymer was found to contain 45% tetrafluoroethylene, 40% tetrafluoroallyl ether, and 15% propylene.

Example 4 Under the same conditions as Example 1, 2-hydrohexafluoropropyl allyl ether (CH ₂ =
By charging 3.12 g (0.015 mol) of CHCH ₂ OCF ₂ CFHCF ₃ ) and 6.00 g (0.060 mol) of tetrachloroethylene and reacting for 5 hours, the polymer
Obtained 1.7g. This copolymer was a soft rubber-like elastic body with [η] of 0.22 dl/g. Further, the thermal decomposition temperature was 302°C, and the glass transition temperature was -6°C.
From the results of elemental analysis, the molar ratio of tetrafluoroethylene/hexafluoropropyl allyl ether in the copolymer was determined to be 41/59.

[Brief explanation of the drawing]

The attached drawing shows the H nucleus of the tetrafluoroethylene-2-hydrotetrafluoroethyl allyl ether binary copolymer obtained in Example 1 decoupled.
^19F -NMR spectrum.

Claims (1)

[Scope of Claims] 1. Fluoroallyl ether represented by a unit based on tetrafluoroethylene and the general formula CH ₂ =CHCH ₂ OR _f (wherein R _f represents a fluorine-containing alkyl group having 2 to 10 carbon atoms) A copolymer containing a unit based on as an essential component, the molar ratio of the content of units based on tetrafluoroethylene and units based on fluoroallyl ether in the copolymer being 90/10 to 10/90. A fluorine-containing elastic copolymer characterized in that the sum of the contents of both units is 70 mol% or more. 2. The copolymer according to claim 1 _, wherein R _f is at least _one of _-CF2CF2H and _-CF2CFHCF3 . 3. A copolymer according to claim 1, having an intrinsic viscosity of at least 0.1 dl/g, measured in tetrahydrofuran at 30°C.