JP3063907B2 - Method for producing ethylene-tetrafluoroethylene copolymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an ethylene-tetrafluoroethylene-based copolymer.

[Prior Art] Ethylene-tetrafluoroethylene-based copolymers have conventionally been prepared by solution polymerization in a fluorosaturated hydrocarbon medium or by mixing fluorosaturated hydrocarbons with water, as shown in JP-B-59-50163. It is manufactured by a method such as suspension polymerization in a mixed medium. A method using trichloromonofluoromethane as a molecular weight modifier is also known. This method is advantageous in that an ethylene-tetrafluoroethylene-based copolymer excellent in heat resistance, molding processability, chemical resistance, and the like is produced, and in controlling the reaction conditions and maintaining the copolymerization reaction rate. Was also advantageous for industrial implementation.

[Problems to be Solved by the Invention] In recent years, the molding temperature has been increased for the purpose of improving productivity and the required quality has been enhanced, and the conventional ethylene-tetrafluoroethylene-based copolymer has Improvements have been demanded in respect of the coloring phenomenon of the resin and the heat aging resistance.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and comprises mixing ethylene and ethylene tetrafluoride in a fluoro-saturated hydrocarbon medium or a mixture of fluoro-saturated hydrocarbon and water. A method for producing an ethylene-tetrafluoroethylene copolymer by copolymerization in a medium, characterized in that an aliphatic alcohol having 1 to 3 carbon atoms is used as a molecular weight regulator. An object of the present invention is to provide a method for producing a system copolymer.

In the present invention, ethylene and ethylene tetrafluoride are copolymerized in a fluorosaturated hydrocarbon medium or a mixed medium of fluorosaturated hydrocarbon and water. Here, as the fluorosaturated hydrocarbon, it is particularly preferable to use one having about 1 to 4 carbon atoms. Specifically, fluoromethanes such as dichlorodifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, monochlorotrifluoromethane, tetrafluoromethane, tetrafluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, hexafluoroethane, etc. Examples thereof include fluoroethanes, fluoropropanes such as dichloropentafluoropropane, and fluorobutanes such as perfluorocyclobutane. Especially 1 to 3 carbon atoms
Of these, preferred are fluorosaturated hydrocarbons, especially trichlorotrifluoroethane and dichloropentafluoropropane.

When using a mixed medium of fluorosaturated hydrocarbon and water, the mixing ratio (volume ratio) of the fluorosaturated hydrocarbon and water is 9:
It is preferable that the ratio be 1 to 1: 9, particularly 7: 3 to 3: 7.

The copolymerization ratio of ethylene and ethylene tetrafluoride is such that the units based on ethylene / the units based on ethylene tetrafluoride (molar ratio) in the produced ethylene-tetrafluoroethylene copolymer.
Is preferably about 60/40 to 30/70, because a copolymer having excellent heat resistance, chemical resistance and moldability can be obtained. In order to obtain a copolymer having such a ratio, it is preferable to set the ratio of ethylene tetrafluoride as a high monomer composition before the start of polymerization. In particular, it is preferable that the charged molar ratio of ethylene / ethylene tetrafluoride is about 5/95 to 30/70. Further, as the polymerization reaction proceeds, the amount of the monomer in the polymerization tank decreases. It is preferable to supply a monomer so as to compensate for this decrease. The monomer to be supplied preferably has a molar ratio of ethylene / ethylene tetrafluoride of about 60/40 to 30/70. In the present invention, other monomers may be copolymerized within a range that does not impair the excellent performance of the ethylene-tetrafluoroethylene-based copolymer. When monomers other than ethylene and ethylene tetrafluoride are copolymerized, the content of such monomers is preferably about 10 mol% or less based on all monomers. Such _{monomers, CF 2 = CFR f, CH} 2 = fluoroolefins such as _{CHR f, CF 2 = CFOR f} , CF 2 = CFO (CF 2) n C
OX, And the like. When such a monomer is copolymerized, it is added in an amount of about 10 mol% or less based on the total monomers, and after the polymerization is started, the copolymerization reaction is performed while replenishing the amount consumed by the copolymerization reaction. It is preferred to carry out.

The method of the present invention can be performed under a polymerization initiation source such as a peroxy compound, an azo compound, ultraviolet light, ionizing radiation.

A peroxyester type radical initiator represented by the general formula RC (（O) —O—O—R ¹ (wherein R and R ¹ are aliphatic alkyl groups) is used as a polymerization initiator. When used, 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. However, both R and R ^{1 have} 3 carbon atoms in view of the copolymerization reaction temperature and the like.
Desirably, there are about 13 alkyl groups. 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.

In the case of using ionizing radiation as a polymerization initiating source is suitably about dose rate 10-10 ⁶ Rad / hr, when using azo compounds, about 0.0001% by weight with respect to total monomers is Appropriate.

In the method of the present invention, the copolymerization reaction conditions can be variously changed according to the polymerization initiation source, the reaction medium, and the like, but usually, the reaction temperature of about −50 ° C. to + 150 ° C. is industrially advantageously employed.
Depending on the type and amount of solvent used, the molar ratio of charged monomers, the type of polymerization initiation source, etc., an appropriate reaction temperature is selected, but if the temperature is too high, the reaction pressure becomes excessive, and if the temperature is too low, Since the copolymerization reaction rate is not more than industrially satisfactory, it is preferable to adopt the above range. The reaction pressure may be from normal pressure to a slight pressure, and usually about ^{2 to} 50 kg / cm ² · gauge is employed.

In the method of the present invention, carbon number 1 is used as a molecular weight modifier.
It is important to use ~ 3 aliphatic alcohols. By using such a specific molecular weight modifier, the molecular weight can be controlled to a desired one, and the resulting copolymer is improved in coloration, heat aging resistance and the like. As such a molecular weight modifier, a primary alcohol represented by ROH (R is a methyl group, an ethyl group or a propyl group) is preferable, and methyl alcohol is particularly preferable. The necessary amount of the molecular weight modifier is appropriately determined depending on the required molecular weight, the amount of the polymerization initiation source used, the monomer concentration, and the like. Usually, in order to obtain a copolymer having excellent moldability and mechanical properties, the amount is selected within the range of about 0.001 to 0.2 mol per 100 mol of all monomers.

[Examples] The physical properties of the copolymer were measured as follows.

・ Capacity flow rate Q value At 300 ° C and under 30kg load, using a Koka type flow tester,
The volume (ml / sec) of the copolymer flowing out per unit time from a nozzle having a diameter of 1 mm and a length of 2 mm was measured.

Polymer composition was determined from the F ¹⁹ -NMR and elemental analysis.

・ Heat resistance 1mm thick 10cm square molded sheet in oven 2
A heat resistance test was conducted at 30 ° C. for 4 days to measure the degree of coloring of the molded sheet and the strength and elongation at room temperature. The tensile test is ASTM N
o.5 dumbbells were used at a pulling speed of 200 mm / min at room temperature.

Melting point Using a Perkin Elmer DSC7 apparatus, the melting peak (maximum value) when the temperature was raised at a rate of 10 ° C./min was defined as the melting point.

Example 1 CH ₂ OH 4 was added to a stainless steel autoclave having an internal volume of 10.
4.8 g, trichlorotrifluoroethane (hereinafter, R-113
10.177 kg, 1083 g of ethylene tetrafluoride (hereinafter, referred to as TFE), 75.8 g of ethylene (hereinafter, referred to as E), and 50.7 g of perfluorobutylethylene (CH ₂ = CH-C ₄ F ₉ or less, referred to as PFBE). . The reaction temperature is maintained at 65 ° C. while stirring the mixture well. Next, a 50% by weight R-113 solution of t-butyl peroxyisobutyrate as an initiator was added to 1
Add 5 ml to start polymerization. During the reaction, a mixed gas having a molar ratio of TFE / E / PFBE of 53.0 / 45.5 / 1.5 is introduced into the system according to the pressure drop, and the polymerization pressure is maintained at 13.5 kg / cm ² G. 905 in 7.25 hours
g of a white copolymer was obtained. Melting point of the copolymer = 260 ° C., volume flow rate Q value = 85 (mm ³ / sec), polymer composition, units based on TFE / units based on E / units based on PFBE = 53 / 45.5 / 1.5
(Mol%) Example 2 Using the same autoclave as in Example 1, 60 g of CH ₃ OH,
10.177 kg of R-113, 1059 g of TFE, 74 g of ethylene and perfluorosulfonyl fluoride vinyl ether 841g is prepared. The reaction temperature is maintained at 65 ° C. with sufficient stirring of the mixture. Next, the initiator t-
8.4 ml of a 50% by weight R-113 solution of butyl peroxyisobutyrate is added to initiate polymerization. During the reaction, a mixed gas having a TFE / E molar ratio of 53/47 is introduced into the system according to the pressure drop, and the polymerization pressure is maintained at 13.2 kg / cm ² G. 1298g in 4.6 hours
Was obtained as a white polymer. Melting point of the copolymer = 252 ° C., volumetric flow rate Q value = 59 (mm ³ / sec), unit based on polymer composition TFE / unit based on E / unit based on PSVE = 51.9 / 46.1 / 2.0
(Mol%) Comparative Example 1 Using the same autoclave as in Example 1, 3867 g of trichloromonofluoromethane (hereinafter referred to as R-11), R
Charge 6456 g of -113, 1153 g of TFE, 55.8 g of E and 50.2 g of PFBE. While sufficiently stirring this mixture, raise the reaction temperature to 65 ° C.
To hold. Next, 15 ml of a 50% by weight R-113 solution of t-butyl peroxyisobutyrate as an initiator is added to initiate polymerization. During the reaction, a mixed gas having a molar ratio of TFE / E / PFBE of 52.8 / 45.8 / 1.4 was introduced into the system according to the pressure drop, and the polymerization pressure was 1
Hold 3.4 kg / cm ² G. In 8.1 hours, 890 g of a white copolymer was obtained.

Melting point of the copolymer = 262 ° C., volumetric flow rate Q value = 75 (mm ³ / s
ec), unit based on polymer composition TFE / unit based on E / PF
Unit based on BE = 52.8 / 45.8 / 1.40 (mol%) Table 1 shows the examination results of the polymers of Examples 1 and 2 and Comparative Example 1.

These results indicate that the polymer obtained using CH ₃ OH as a molecular weight regulator has significantly improved heat resistance.

[Effect of the Invention] According to the method of the present invention, an ethylene-tetrafluoroethylene-based copolymer having improved heat resistance such as coloring property and heat aging resistance can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-62584 (JP, A) JP-A-48-15989 (JP, A) JP-A-2-182710 (JP, A) 22586 (JP, B1) JP 40-8138 (JP, B1) WO 89/12240 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 14/00-14 / 28 C08F 214/00-214/28 C08F 2/00-2/60 C08F 10/00-10/14 C08F 210/00-210/18

Claims (1)

(57) [Claims] 1. A process for producing an ethylene-tetrafluoroethylene copolymer by copolymerizing ethylene and ethylene tetrafluoride in a fluorosaturated hydrocarbon medium or a mixed medium of fluorosaturated hydrocarbon and water. 3. The method for producing an ethylene-tetrafluoroethylene copolymer according to claim 1, wherein an aliphatic alcohol having 1 to 3 carbon atoms is used as a molecular weight regulator.