JPH0867721A - Production of soft fluororesin - Google Patents

Abstract

PURPOSE: To provide a simplified process for producing a soft fluororesin by grafting a monomer giving a crystalline polymer onto a specific elastic fluorocopolymer in the form of an aqueous emulsion or a dispersion in a solvent. CONSTITUTION: A monomer comprising at least one fluoromonomer giving a crystalline polymer having a melting point of 130 deg.C or higher us grafted onto an elastic fluorocopolymer containing peroxy bonds in the molecule and having a glass transition temp. not higher than room temp. (and containing 0.1-50wt.% water), the fluoropolymer being in the form of an aqueous emulsion or a dispersion in a solvent. The emulsion or dispersion medium serving as a reaction medium desirably comprises at least t-butyl alcohol and water, and preferably further contains a carboxylic ester, e.g. ethyl acetate or n-butyl acetate, or a chlorinated solvent, e.g. ethylene dichloride or chloroform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a soft fluororesin having flexibility, and more particularly to a reaction solvent for graft copolymerizing a crystalline polymer with a trunk polymer.

[0002]

PRIOR ART At least one fluorine-containing monomer which gives a crystalline polymer having a melting point of 130 ° C. or higher to a fluorine-containing elastic copolymer having a peroxy bond in the molecule and having a glass transition temperature of room temperature or lower. When graft-copolymerizing one or more monomers including a monomer, polymerization in an aqueous emulsion or a dispersion solvent is disclosed in JP-A-58-206615, and specifically, R-113 (1,
The use of 1,2-trichlorotrifluoroethane) is illustrated. Further, in JP-A-1-292013, it is stated that water is used as a solvent because the trunk polymer is produced as a latex by a redox polymerization method and used as it is for graft polymerization. There is.

Japanese Patent Laid-Open No. 3-269008 discloses that
The same graft polymerization is described using a homogeneous mixed solvent of a soluble solvent and an insoluble solvent of the fluorine-containing elastic copolymer, and as a suitable example, t-butanol and ethyl acetate or 1,1,1-trichloroethane is described. Mixed solvents are listed.

[0004]

Problems to be Solved by the Invention JP-A-58-2066
In the method described in Japanese Patent Publication No. 15, the fluorine-containing elastic copolymer produced in the first step is washed and dried to be subjected to the second step graft polymerization, but the elastic copolymer is often heated. It is difficult to apply the accompanying drying operation,
Since the particles aggregate or solidify, and the fluorine-containing elastic copolymer according to the present invention has a peroxy group in the molecule, the heating temperature is limited and it is necessary to use a method such as vacuum drying.

In order to avoid such difficulties, Japanese Patent Laid-Open No.
In JP-A-292013, the latex obtained in the first step is directly applied to the reaction system in the second step. However, in this case, since the initiator and the dispersant are used in the first step and brought into the second step. , Is expected to affect the properties of the produced soft fluororesin.

An object of the present invention is to provide a graft polymerization method capable of avoiding the difficulty of drying a fluorine-containing elastic copolymer which is a trunk polymer of a soft fluororesin.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have found that a fluorine-containing elastic copolymer containing a peroxy bond in the molecule and having a glass transition temperature of room temperature or lower is added to an aqueous emulsion or a dispersion solvent. The simplification of the process of graft-copolymerizing one or more monomers containing at least one fluorine-containing monomer to give a crystalline polymer having a melting point of 130 ° C. or higher was investigated as a reaction medium in the graft copolymerization. As a result, they have found that the step of drying the fluorine-containing elastic copolymer can be omitted by using a specific medium as the above, and completed the present invention.

The fluorine-containing elastic copolymer is obtained as a latex at the end of the first-stage polymerization. Since the latex contains a reaction initiator, a dispersant, an unreacted monomer, etc., these are removed. Therefore, salting out, washing with water or an organic solvent is performed, and drying is performed in relation to the graft polymerization reaction. The drying operation is often performed by vacuum drying in order to avoid decomposition of peroxy groups contained in the fluorine-containing elastic copolymer, but it is a remarkably complicated process because the powder is handled in a vacuum state.

Conventionally, as described in the above-mentioned patent publication, the fluorine-containing elastic copolymer was dried in any case.
The present inventors have come up with the technical and economic effects of omitting this step, and have eagerly searched for a graft copolymerization method capable of using a fluorine-containing elastic copolymer in a water-containing state.

The present invention provides a fluorine-containing elastic copolymer containing a peroxy bond in the molecule and having a glass transition temperature of room temperature or lower, and a melting point of 130 ° C. or higher in an aqueous emulsion or dispersion solvent. Graft copolymerization in which the reaction medium contains at least tert-butyl alcohol and water when graft-copolymerizing one or more monomers containing at least one fluorine-containing monomer giving a crystalline polymer. At this time, when the fluorine-containing elastic copolymer is 0.1
The graft copolymerization method can include ˜50 wt% water.

The reaction medium in the graft copolymerization of the present invention contains at least tert-butyl alcohol and water, but additionally contains a solvent capable of partially or completely dissolving or swelling the fluorine-containing elastic copolymer. is necessary. Such a solvent is a ketone solvent, a carboxylic acid ester, a chlorine solvent, or the like, for example, acetone, methyl ethyl ketone, methyl isopropyl ketone, ethyl acetate, isopropyl acetate, n-butyl acetate, t-butyl acetate, ethyl formate, Methyl propionate, ethyl propionate, ethane dichloride, tetrachloroethylene, trichloroethylene, trichloroethane (including isomers),
Examples thereof include chloroform, methylene chloride, chlorobenzene and the like. Of these, ethyl acetate, methylene chloride and 1,1,1-trichloroethane are particularly preferable.

The ratio of tert-butyl alcohol to water and the other solvent is appropriately selected depending on the composition of the fluorine-containing copolymer, the kind of the monomer to be graft-copolymerized, and the kind of the other solvent. The total weight of tert-butyl alcohol and water is preferably 50 to 95% by weight of the total reaction medium. In these ranges, the fluorine-containing elastic copolymer has a solid surface slightly swelling in the medium and can be dispersed in the medium by agitation by stirring. Moreover, the soft fluororesin produced by the graft copolymerization exists in the medium as fine particles, and the handling of the slurry and the filtration of the resin can be carried out very easily.

The ratio of tert-butyl alcohol to water is appropriately selected depending on the composition of the fluorine-containing copolymer, the type of monomer to be graft-copolymerized, and the type of other solvent. The weight ratio of 3 butyl alcohol / water is 95/5 to 5/95, preferably 90/10 to 2
It is 0/80, more preferably 80/20 to 40/60.

The composition of such a reaction medium containing tertiary butyl alcohol and water is determined so that it exists as a homogeneous system. For example, when ethyl acetate is selected as the other solvent, tertiary butyl alcohol / water is added in a weight ratio of 30/7.
0-60 / 40, and the weight of ethyl acetate in the entire reaction medium is preferably about 25-50%.

The fluorinated monomer which is a copolymerization component of the fluorinated elastic copolymer according to the present invention is a compound having at least one fluorine atom in the molecule and having a polymerizable double bond. It may be present, but a compound in which a part or all of hydrogen atoms of ethylene, propylene or butene is replaced with a halogen atom is particularly preferable. Examples of such compounds include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, tetrafluoroethylene and the like.

The monomer copolymerizable with the above-mentioned fluorine-containing monomer is not particularly limited, and hydrocarbon-based olefins such as ethylene, propylene and butene, hydrocarbon-based conjugated dienes such as butadiene and fluorine-containing vinyl ethers. And the like.

As a copolymer obtained from such a fluorine-containing monomer, a combination which gives a copolymer having the characteristics of fluororubber preferable in the present invention is exemplified by vinylidene fluoride-hexafluoropropylene, fluorinated. Vinylidene-hexafluoropropylene-tetrafluoroethylene, vinylidene fluoride-chlorotrifluoroethylene, tetrafluoroethylene-propylene, tetrafluoroethylene-fluorine-containing vinyl ether, hydrocarbon-based conjugated diene-fluorine-containing monomer and the like. it can. These composition ratios can be appropriately selected based on the mechanical properties of the target fluorine-containing elastic copolymer, particularly flexibility, based on knowledge in the field. For example, in the case of vinylidene fluoride-chlorotrifluoroethylene, 50 to 85 mol% of vinylidene fluoride can be shown as a preferable range exhibiting rubber elasticity.

In the present invention, the unsaturated peroxide to be copolymerized with the fluorine-containing monomer is not particularly limited, but as a specific example, as the unsaturated peroxy ester,
Examples thereof include t-butylperoxymethacrylate, di (t-butylperoxy) fumarate, and t-butylperoxycrotonate, and examples of unsaturated peroxycarbonates include t-butylperoxyallylcarbonate and t-butylperoxyallylcarbonate.
-Hexyl peroxyallyl carbonate, 1,1,
3,3-tetramethylperoxyallyl carbonate,
t-butyl peroxymethallyl carbonate, 1,1,
3,3-tetramethylbutyl peroxymethallyl carbonate, p-menthane peroxyallyl carbonate,
Examples thereof include p-menthane peroxymethallyl carbonate. Of these, t-butyl peroxyallyl carbonate can be mentioned as the most preferable one. Moreover, these can also be used in combination of 1 or more types.

The fluorine-containing elastic copolymer according to the present invention is characterized by having a peroxy bond in its molecule and having a glass transition temperature of room temperature or lower. In the present invention, the amount of the unsaturated peroxide copolymerized with the fluorine-containing monomer is preferably in the range of 0.05 to 20 parts by weight with respect to the monomer, and when it is less than this range, the second In the step, the branch polymer is not efficiently produced, and when the number is large, the properties possessed by the trunk polymer cannot be exhibited, which causes inconvenience.

The method for producing the fluorine-containing elastic copolymer according to the present invention is not particularly limited, and emulsion polymerization using a radical polymerization initiator which is usually carried out in the field of polymer polymerization reaction,
Both suspension polymerization and solution polymerization can be adopted.

As the radical polymerization initiator, radicals need to be generated at a temperature lower than the decomposition temperature of the unsaturated peroxide, and therefore it depends on the selection of the unsaturated peroxide. For example, the activation energy for decomposition is 26 to 33.
15 kcal / mol of benzoyl peroxide, lauroyl peroxide, t-butyl hyponitrite, azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanecarbonitrile, potassium persulfate, ammonium persulfate, etc. ~ 26 kcal / mol hydrogen peroxide-iron (II) salt, persulfate-sodium bisulfite, cumene hydroperoxide-iron (II) salt, benzoyl peroxide-dimethylaniline, diisopropyl peroxy dicarbonate, dicyclohexyl peroxy di Non-limiting examples include 15 kcal / mol peroxide (hydrogen peroxide, hydroperoxide, etc.)-Metal alkyl (triethylaluminum, triethylboron, diethylzinc, etc.), oxygen-metal alkyl, etc., such as carbonate. Kill.

As the polymerization solvent, in the case of emulsion polymerization or suspension polymerization, a medium containing water or water containing a water-soluble solvent such as alcohol is mainly used, but in solution polymerization, a solvent in which chain transfer hardly occurs is used. To be done.

The polymerization temperature and the polymerization time mainly depend on the kind of the initiator and are in the range of 0 to 90 ° C. for about 1 to 50 hours. On the other hand, the polymerization pressure depends on the polymerization method, the method of supplying the raw materials and the kind of the monomer, but is from normal pressure to about 100 Kgf / cm ² .

The reaction liquid after completion of the polymerization is subjected to salting-out for removing an initiator, a solvent, unreacted monomers and the like, a washing treatment with water and / or an organic solvent, and a fluorine-containing elastic copolymer according to a usual method. Purify the polymer. At this time, the fluorine-containing elastic copolymer is preferably adjusted to have a water content of 0.1 to 50% by weight, and most preferably about 25 to 30% by weight. It is difficult to reduce the amount to 0.1% by weight or less and it is not necessary in the method of the present invention, and if the amount is 50% by weight or more, the weight increases and the handling becomes troublesome.

The fluorine-containing monomer or its composition which gives a crystalline polymer having a melting point of 130 ° C. or higher, which is an essential branch polymer for the soft fluororesin of the present invention, is not particularly limited, but for example, , Tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, tetrafluoroethylene-ethylene mixture, chlorotrifluoroethylene-ethylene mixture, tetrafluoroethylene-fluorine-containing vinyl ether mixture, vinylidene fluoride-tetrafluoroethylene mixture , Vinylidene fluoride-chlorotrifluoroethylene mixture, vinylidene fluoride-hexafluoropropylene mixture, vinylidene fluoride-trifluoroethylene mixture, vinylidene fluoride-hexafluoroacetone mixture, vinylidene fluoride-tetrafluoroethylene mixture Oroechiren - hexafluoropropylene mixture can be mentioned. The weight ratio of these branch polymers to the trunk polymer is appropriately selected according to the purpose, but in order to have both flexibility and mechanical strength, it is 20/1.
00-100 / 100 and 40 / 100-80 / 1
00 is preferable.

The method of graft copolymerization onto the trunk polymer is
The procedure is the same as the usual graft polymerization method except that the initiator is not added because the peroxy group of the trunk polymer is the starting group. For example, a fluorine-containing elastic copolymer is introduced into a polymerization reactor together with a reaction medium by using an atomizer such as a homogenizer, and after adding a monomer and other auxiliary materials, the temperature is adjusted while stirring to carry out the reaction. And continue for a predetermined time. The polymerization form is a reaction in a water-based emulsion or dispersion solvent of a homogeneous solvent consisting of tert-butyl alcohol, water and an organic solvent. Further, other auxiliary materials such as a chain transfer agent, a decomposition accelerator for an initiator, an emulsifier, a dispersion stabilizer and the like can be used according to the purpose.

The polymerization temperature and the polymerization time mainly depend on the type of unsaturated peroxide, and are 1 to 5 in the range of 50 to 120 ° C.
It is preferable to adjust the time to about 0 hours. On the other hand, the polymerization pressure depends on the polymerization method, the raw material supply method, and the kind of the monomer, but is usually from normal pressure to about 100 Kgf / cm ² .

The reaction solution after completion of the polymerization is subjected to treatments such as salting out to remove initiators, solvents, unreacted monomers, washing, drying and the like to obtain a purified soft fluororesin.

[0029]

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

[Production Example of Fluorine-Containing Elastic Copolymer] 100
900 g of pure water, 2.9 g of potassium persulfate, 2.2 g of ammonium perfluorooctanoate, 2.7 g of sodium tetraborate, 1.2 g of potassium dihydrogen phosphate and 1.2 g of unsaturated peroxide are placed in a 2 L stainless steel autoclave that can withstand atmospheric pressure. As a solution, 1.8 g of a t-butyl acetate solution of t-butylperoxyallylcarbonate (concentration of t-butylperoxyallylcarbonate: 70% by weight) was added, and after evacuation, chlorotrifluoroethylene monomer 83 was added.
and 182 g of vinylidene fluoride monomer were charged and a polymerization reaction was carried out at a temperature of 50 ° C. with stirring. The internal pressure of the autoclave, which was 40 Kgf / cm ² when the temperature was raised to 50 ° C, decreased with the progress of the polymerization reaction, and when it reached 30 Kgf / cm ² , the temperature was raised to 60 ° C and the pressure reached 7 Kgf / cm ^2. The polymerization reaction was stopped by cooling with and purging the monomer. The polymerization time was about 9 hours. The polymerized product was obtained in the form of a white latex, which was salted out, centrifuged, washed with water and then centrifuged again to obtain 333 g of elastic copolymer particles. The water content of the copolymer particles after centrifugation was measured to be 28%. The yield of this fluorine-containing elastic copolymer is 90.0%
Met.

50 g of the obtained copolymer particles were vacuum dried and then washed with n-hexane to remove unreacted t-butylperoxyallyl carbonate and vacuum dried again.
36 g of a white powder copolymer was obtained. DS of this copolymer
The C curve shows 16 exothermic peaks due to decomposition of the peroxy group.
It has a temperature of 0 to 180 ° C., and the active oxygen content of the copolymer was determined to be 0.039% by the iodometric titration method. The glass transition temperature of the copolymer by DSC at low temperature is -2.
5 ° C.

Example 1 In the next step, the above-mentioned elastic copolymer (appearance: containing 28% water)
342 g, 480 g of t-butanol, 174 g of water and 392 g of ethyl acetate were charged into a 2 L capacity stainless steel autoclave that can withstand 50 atm, and after evacuation, the temperature was raised to 90 ° C., and vinylidene fluoride monomer was added at 20 Kgf / cm.
^It was continuously blown in at a pressure of ² , and when 105 g of it had been consumed, the blowing was stopped, the mixture was cooled rapidly, and the monomers in the reactor were purged to complete the polymerization. After the polymerization, the produced polymer was separated from the solvent and then dried to give 351 g.
Of white powder was obtained.

The melting point of this polymer by DSC is 163.
It was measured to be ° C. The obtained polymer was kneaded with a 4-inch double roll (roll temperature: 180 ° C.) and then press-molded (press temperature 200 ° C.) to form a 1 mm-thick 200 mm-square sheet. A transparent product was obtained. The breaking strength, breaking elongation, tensile modulus, and hardness of this sheet at 23 ° C. were measured and shown in Table 1. [Physical property measuring method] 1) Measurement of breaking strength and breaking elongation In accordance with the method specified in JIS K6301, a No. 3 dumbbell type test piece punched out from a 1 mm thick sheet was used as a tensile tester (manufactured by Shimadzu Corporation). 2 in the autograph)
Measured at 3 ° C. with a pull rate of 200 mm / min. 2) Tensile elastic modulus A 10 mm x 125 mm strip-shaped test piece was cut out from a 1 mm thick sheet and attached to a tensile tester so that the distance between chucks was 100 mm, and the elongation and stress at a tensile speed of 10 mm / min at 23 ° C were measured. A curve representing the relationship was obtained. The tensile elastic modulus (stress / elongation) was calculated from the initial rising slope of this curve.
The smaller this value, the higher the flexibility. 3) Hardness (Shore D hardness) Four 1 mm sheets were stacked and measured according to ASTM D2240. 4) Melt viscosity Using a Koka type flow tester manufactured by Shimadzu Corporation, the graft copolymer resin was charged into a cylinder heated to 200 ° C., preheated for 5 minutes, and then 1 mm at a pressure of 100 Kgf / cm ^2.
The melt viscosity was calculated from the flow rate when extruding from a φ × 10 mmL orifice.

[0034]

[Table 1]

Examples 2 to 4 and Reference Examples 1 to 2 Using the fluorine-containing elastic copolymer produced in the same manner as in the production example of the fluorine-containing elastic copolymer, the same graft copolymerization as in Example 1 was carried out, The reaction medium was changed to one having the composition shown in Table 1, and the same physical properties were measured. The results are also shown in Table 1. The fluorine-containing elastic copolymer used in the reference example was prepared by vacuum drying, washing with n-hexane, and vacuum drying to adjust the water content to less than 0.1%.

[0036]

According to the method of the present invention, since the fluorine-containing elastic copolymer can be graft-copolymerized in a water-containing state without drying, the difficult step of vacuum-drying the elastic resin powder can be omitted and the process can be simplified. It is clear that it has an effect on

Claims (5)

[Claims] 1. A crystalline fluorine-containing copolymer having a peroxy bond in the molecule and having a glass transition temperature of room temperature or lower, and a melting point of 130 ° C. or higher in an aqueous emulsion or a dispersion solvent. A method for graft-copolymerizing one or more monomers containing at least one fluorine-containing monomer which gives a polymer, wherein the fluorine-containing elastic copolymer is 0.1 to 50.
A method for producing a soft fluororesin, which comprises water by weight. 2. The method for producing a soft fluororesin according to claim 1, wherein the reaction medium forming the aqueous emulsion or the dispersion solvent contains at least tert-butyl alcohol and water. 3. The method for producing a soft fluororesin according to claim 2, wherein the reaction medium further contains a carboxylic acid ester or a chlorine-based solvent. 4. Carboxylic acid ester or chlorine-based solvent is ethyl acetate, isopropyl acetate, n-butyl acetate, t-acetate
-Butyl, ethyl formate, methyl propionate, ethyl propionate, ethane dichloride, tetrachloroethylene, trichloroethylene, trichloroethane, chloroform,
The method for producing a soft fluororesin according to claim 2, which is methylene chloride or chlorobenzene. 5. The method for producing a soft fluororesin according to claim 2, wherein the carboxylic acid ester or the chlorine-based solvent is ethyl acetate, 1,1,1-trichloroethane or methylene chloride.