JPH02160810A - Fluoroelastomer - Google Patents

Abstract

PURPOSE:To obtain a fluoroelastomer which is improved in heat resistance, solvent resistance and chemical resistance and gives a vulcanizate improved in physical properties, processability and extrudability by controlling each of the composition, intrinsic viscosity and weight-average MW to number-average MW ratio to be in a specified range an the MW distribution to be multimodal. CONSTITUTION:An inert organic solvent in which a monomer feed as part of a monomer mixture comprising vinylidene fluoride (A) and hexafluoropropylene (B) is dissolved is dispersed in an aqueous medium and an additional monomer feed as the remaining part of said monomer mixture is added to the dispersion. The resulting mixture is suspension-polymerized at 50-60 deg.C under a pressure of 5-17kg/cm<2>.G in the presence of a suspension stabilizer and an oil-soluble catalyst to obtain the title elastomer comprising components A and B, having a weight ratio of component A to component B of (40-80):(60-20) and a multimodal MW distribution having at least two modes, a ratio of a weight-average MW to a number-average MW of 8-20, an intrinsic viscosity of 50-150ml/g, a content of a polymer of an MW of at least 2000000<4wt.% and a ratio of the amount of a low-MW polymer of an MW of at most 50000 to the intrinsic viscosity of 0.30-0.70.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel fluorine-containing elastomer, more specifically, it has good heat resistance, solvent resistance, and chemical resistance, and also has good physical properties and processability of the vulcanizate, especially This invention relates to a fluorine-containing elastomer that also has excellent extrusion moldability.

Conventional technology In general, fluorine-containing elastomers have good heat resistance, solvent resistance,
Due to its excellent physical properties such as chemical resistance, it is widely used as a sealing material for packings and gaskets and diaphragms used under harsh conditions. It not only has excellent mechanical properties such as tensile strength and elongation, dynamic properties such as compression set resistance and bending resistance, but also excellent processability such as roll workability and extrusion moldability. is required.

However, fluorine-containing elastomers generally have the disadvantage of being extremely difficult to process.
Various proposals have been made to solve this problem.

For example, a method of manufacturing a vinylidene fluoride copolymer containing a low molecular weight polymer and a high molecular weight polymer with a wide molecular weight distribution by a continuous emulsion polymerization method in which a chain transfer agent is periodically added (Japanese Patent Publication No. 51-24554) Japanese Patent Publication No. 51-25279 discloses a method for producing a vinylidene fluoride copolymer having a bimodal molecular weight distribution by a cascade two-tank continuous emulsion polymerization method.

However, the fluorine-containing elastomer obtained by such a continuous production method has an extremely wide molecular weight distribution and a high content of ultra-high molecular weight polymer, resulting in large die swell during extrusion molding and a low molecular weight. Since it also contains extremely low polymers, it is not necessarily satisfactory in terms of physical properties of the vulcanizate such as tensile strength.

In general, the extrusion moldability of fluorine-containing elastomers is not good, and one way to improve this extrusion moldability is to increase the content of low molecular weight polymers. This causes problems such as deterioration of the mechanical properties of the vulcanizate and increased tackiness. If the amount of this low-molecular-weight i-polymer is reduced, the above-mentioned problems will be solved, but extrusion moldability such as extrusion speed and extrusion texture will deteriorate. In addition, conventional fluorine-containing elastomers usually contain a large amount of ultra-high molecular weight polymer, and therefore have a problem of large die swell during extrusion molding.

As described above, at present, a fluorine-containing elastomer that can simultaneously fully satisfy processability such as extrusion moldability, and physical properties of vulcanized products such as vulcanizability and mechanical properties has not yet been found.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of conventional fluorine-containing elastomers, has vulcanizability and physical properties of vulcanizate comparable to conventional products, and has improved processability, especially extrusion moldability. This was done with the aim of providing an excellent fluorine-containing elastomer.

Means for Solving the Problems The present inventors have conducted extensive research to develop a fluorine-containing elastomer with an excellent balance of processability, vulcanizability, and vulcanizate physical properties. It has been discovered that the above object can be achieved by a heptadium-containing elastomer having an intrinsic viscosity, a ratio of weight average molecular weight to number average molecular weight, and a specific molecular weight distribution, and based on this knowledge, the present invention has been made. I was able to complete it.

That is, the present invention provides a fluorine-containing elastomer comprising vinylidene fluoride units, hexafluoropropylene units, and, if desired, tetrafluoroethylene units in a proportion not exceeding 35% by weight based on the total amount, (a) vinylidene fluoride units; The weight ratio of do units and hexafluoropropylene units is 40:60 to 80:20.
(b) The molecular weight distribution is a multi-peak type formed from two or more peaks; (c) The weight average molecular weight (Vv) and the number average molecular weight (Mn
) the ratio Ww /Tn is 8 to 20, (d) the intrinsic viscosity is 50 to 150 ml/g, and (e) the amount of high molecular weight polymer with a molecular weight of 2 million or more is less than 4% by weight. and JiM, a low molecular weight polymer with a molecular weight of 50,000 or less.

(wt%) and limiting viscosity [? The present invention provides a fluorine-containing elastomer characterized in that the ratio M, /[η] to (ml/g) is 0.30 to 0.70.

The present invention will be explained in detail below.

The fluorine-containing elastomer of the present invention has vinylidene fluoride units (hereinafter referred to as VdF units) and hexafluoropropylene units (hereinafter referred to as RFP units) of 65 to 10
0% by weight and optionally 35% by weight or less of tetrafluoroethylene units (hereinafter referred to as TFE units), and the weight ratio of VdF units to HFP units is in the range of 40:60 to 80:20. is necessary. The T
When the content of FE units exceeds 35% by weight, the resulting copolymer loses its elastomer properties and becomes resin-like, failing to achieve the object of the present invention. Also, the ratio of the VdF unit is 40% to the total amount of VdF unit and HFP unit.
If it is less than 80% by weight, polymerization will be difficult and it will be difficult to obtain the desired fluorine-containing elastomer, and if it exceeds 80% by weight, the resulting copolymer will lose its properties as an elastomer and become resin-like, thus defeating the purpose of the present invention. not achieved.

Preferred polymer compositions to achieve the objectives of the present invention are:
In the binary copolymer, the weight ratio of VdF units to HFP units is selected in the range of 40:60 to 75:25, more preferably 50:50 to 70:30. On the other hand, in the ternary copolymer, the total amount of VdF units and HFP units is in the range of 65 to 95% by weight, and T
It is desirable that the amount of FE units is in the range of 35 to 5% by weight, and the weight ratio of VdF units to IIFP units is 5% by weight.
It is preferably in the range of 0:50 to 80:20.

The fluorine-containing elastomer of the present invention needs to have a multi-peak molecular weight distribution formed from two or more peaks, as illustrated in the figure. In a fluorine-containing elastomer with a single peak molecular weight distribution, it is extremely difficult to control the ratio of low molecular weight polymer to high molecular weight polymer, and it is difficult to achieve good extrusion moldability, which is the objective of the present invention. Hard to get caught. Moreover, this molecular weight distribution is mainly composed of a low molecular weight peak consisting of a molecular weight of 50,000 or less and a high molecular weight peak consisting of a molecular weight of 50,000 or more. The polymer on the low molecular weight side is necessary to improve fluidity, while the polymer on the high molecular weight side is necessary to maintain mechanical strength.

In the fluorine-containing elastomer of the present invention, the ratio My/
It is necessary that Un be in the range of 8-20. This i
If w/Un is less than 8, the spread of the molecular weight distribution will be small, resulting in poor extrusion speed and extrusion moldability such as extruded membranes, and if it exceeds 20, ultra-high molecular weight polymers and extremely low molecular weight polymers will increase, so extrusion molding will be difficult. The dice swell tends to get worse over time.

A preferable M w /In is selected within the range of 10-17.

In addition, the intrinsic viscosity number [η], which is an index of molecular weight, is 50 to 1
It is necessary that the amount is in the range of 50 ml/g. If the intrinsic viscosity number is less than 50m+2/g, there is a risk of increased stickiness during roll kneading, and if it exceeds 150mQ/g, the molecular weight will be too large, reducing fluidity and making it difficult to perform good extrusion molding. . The intrinsic viscosity for extrusion molding is preferably in the range of 80-120 mg/Q, while for injection molding it is preferably in the range of 50-80 mg/Q.

Furthermore, the amount MS (wt%) of low molecular weight polymers with a molecular weight of 50,000 or less belonging to the low molecular weight peak and the intrinsic viscosity [vl Cr
nQ/g) M s/Ev]]Ha0.3O
-0-70') range. This M,
and [V] influence each other and influence extrusion moldability, and as M becomes larger, extrusion speed and extruded film tend to improve, while as [V] becomes larger, extrusion speed and extrusion performance tend to improve. Both films tend to deteriorate. Therefore, in order to have good extrusion moldability, the value of M5/[vl needs to be within the above range. This M s/ [v
] is less than 0.30, extrusion becomes difficult and the extrusion speed and extruded film are significantly deteriorated. In addition, since there is too much low molecular weight polymer, the low molecular weight polymer is likely to be eluted into a solvent or the like. A preferable Ms/[v] is selected within the range of 0.35 to 0.60.

On the other hand, the amount of high molecular weight polymer with a molecular weight of 2 million or more is M! . .

must be less than 4% by weight.

This M2゜. is closely related to the die swell during extrusion molding, and the M8. . If the amount is 4% by weight or more, the die swell becomes large. Preferable M! . . is 3% by weight or less.

As described above, the heptadium-containing elastomer of the present invention has M, although My/Nn, which represents the molecular weight distribution, is relatively large at 8 to 20. . The frame machine has an extremely small value, and therefore the die swell has a small value.

The fluorine-containing elastomer of the present invention can be produced, for example, by blending a high molecular weight polymer and a low molecular weight polymer that have been produced separately, but it is also possible to produce the fluorine-containing elastomer by, for example, blending a high molecular weight polymer and a low molecular weight polymer that have been produced separately. It is advantageous.

This is because suspension polymerization tends to yield a polymer with a narrow peak molecular weight distribution, and by combining multiple stages of polymerization, a multi-peak type with a relatively sharp molecular weight distribution can be easily obtained.

As described above, the suspension polymerization method is suitable for obtaining a multi-peak type polymer having a small content of ultra-high molecular weight polymer as in the present invention. Such multi-peak type
It can be obtained by changing the polymerization pressure, twisting the catalyst, adding a chain transfer agent, etc. in the polymerization process. Among these, the method of adding a chain transfer agent during the polymerization process is as follows: This is preferable because the molecular weight distribution can be easily controlled.

In this method using a chain transfer agent, for example, in the case of batch polymerization, a chain transfer agent is not used at all or is added in a small amount at the beginning of the polymerization to form a high molecular weight polymer and a predetermined amount of the chain transfer agent is used. A method can be used in which a low molecular weight polymer is formed by adding a large amount of a chain transfer agent after forming the polymer.

As the chain transfer agent, conventionally known ones such as lower alcohols and halogen compounds can be used, but because of their particularly high chain transfer ability, iodine compounds such as short methane and short ethane, dibromomethane and dibromoethane are used. Bromine compounds such as are preferred, and iodine compounds such as short methane are particularly preferred.

Next, a preferred example of the suspension polymerization method for producing the fluorine-containing elastomer of the present invention will be explained. First, an inert organic solvent in which a predetermined mixing agent (charged monomer) is dissolved is added to an aqueous medium. Further, a suspension stabilizer and an oil-soluble catalyst are added, and the temperature is preferably maintained at 50 to 60°C while stirring mechanically, and the pressure is preferably 5 to 17k.
The polymerization is proceeded by adding a new amount of the above-mentioned mixing additive (continuously added monomer) so that the amount remains constant within the range of g/cm2.G.

The composition of monomer units in the produced fluorine-containing elastomer is determined by the relationship between the charged monomer composition and the continuous monomer composition. The charged monomer composition and additional twist monomer composition are measured by gas chromatography, and the composition of monomer units in the fluorine-containing elastomer is measured by F-NMR after dissolving the elastomer in acetone. The molecular weight distribution is adjusted by adding a transfer agent.

The inert organic solvent used in this suspension polymerization method is an organic solvent that does not have carbon-hydrogen bonds that tend to cause radical chain transfer. -Trifluoroethane is preferred in terms of performance and economy. Methylcellulose is preferred as the suspension stabilizer. As the oil-soluble catalyst, dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate are preferred because they have a high decomposition temperature.

The fluorine-containing elastomer of the present invention can be vulcanized with a polyamine compound, a polyol compound, etc., and particularly when vulcanized with a polyol, the improved performance of the fluorine-containing elastomer of the present invention is significantly exhibited.

Hereinafter, a polyol vulcanization method will be explained as an example.

Fluorine-containing elastomer with acid binder, polyol compound,
Add vulcanization accelerator and filler if necessary and knead.
After extrusion molding, it is heated and vulcanized.

As the acid binder, divalent metal oxides or hydroxides, such as oxides or hydroxides of magnesium, calcium, zinc, lead, etc., are used, and the amount used is 1 to 30 parts by weight per 100 parts by weight of the elastomer. Parts by weight, preferably 2-20
Selected based on parts by weight.

Examples of polyol compounds include hydroquinone, 2.2-bis(4-hydroxyphenyl)propane (bisphenol A), 2.2-bis(4-hydroxyphenyl)perfluoropropane (bisphenol AF), and 4.4'-dihydroxydiphenyl. Methane, 2,2-bis(4-hydroxyphenyl)butane, etc. are used in a proportion of 0.1 to 10 parts by weight, preferably 0.6 to 5 parts by weight per 100 parts by weight of elastomer.

Vulcanization accelerators include quaternary onium salt compounds, quaternary phosphonium salts, quaternary ammonium salts or iminium salts, such as tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetrabutyl Ammonium bromide, bis(benzyldiphenylphosphine)iminium chloride, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride, benzyltrioctylphosphonium chloride, etc. are suitable, and 0 per 100 parts by weight of elastomer.
．． It is used in a proportion of 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight. As fillers and reinforcing agents, for example, carbon black, silica, clay talc, etc. are used as necessary. At least one peak on the low molecular weight side of the multi-peak molecular weight distribution of the fluorine-containing elastomer of the present invention
If the polymer is formed by polymerization using a chain transfer agent containing an iodine atom or a bromine atom, peroxide vulcanization using a peroxide becomes possible because the iodine atom or bromine atom has high radical reaction activity. Furthermore, since the fluorine-containing elastomer contains a low molecular weight polymer, a peroxide vulcanization method can be used simultaneously in addition to a polyol vulcanization method using a polyhydroxy compound or a polyamine vulcanization method using a polyamine compound. is possible. In this way, by using the peroxide vulcanization method in combination, it is possible to solve the problem of decreased vulcanizability that occurs with improvement in processability. This peroxide co-vulcanization is higher in the iodine type than in the bromine type.

Next, a case where peroxide vulcanization is performed in combination with polyol vulcanization method or polyamine vulcanization method will be explained. In this case, in addition to the vulcanizing ingredients used for polyol vulcanization and polyamine vulcanization, polyfunctional unsaturated compounds, organic peroxides, and additives used as necessary are used as ingredients for peroxide vulcanization. Further mix and knead.

Examples of the polyfunctional unsaturated compound include triallylcyanurate, triallylisocyanurate, tris(
Diallylamine)-s-triazine and the like are useful;
In particular, triallylisocyanurate is preferably used.

The organic peroxide is preferably one that easily generates peroxy radicals when heated, such as 2,5-dimethyl-2,5-di(t-butylvaoquine)hexyne-3,2,5-dimethyl-2. , 5-di(1-butylperoxy)hexane and the like are preferred.

Examples of additives include carbon black, silica, clay, talc, etc. as reinforcing agents, and waxes as processing aids.

The mixture of the fluorine-containing elastomer and various compounding agents is mixed with a roll or a panburi mixer, and then placed in a mold and pressurized to perform primary vulcanization, and then secondary vulcanization.

In addition, the intrinsic viscosity, M6, and M2° of the fluorine-containing elastomer of the present invention. The molecular weight distribution, which is the basis for calculating -, is based on the values obtained by measurement under the following conditions.

Intrinsic viscosity: 0-1g/using methyl ethyl ketone as a solvent
A solution with a concentration of 100++12 is measured at 35°C using a hair mv viscometer.

Molecular weight distribution: Liquid chromatograph 7: LC-'3A type (manufactured by Kinsei Seisakusho Co., Ltd.) Column: KF-80M (2 pieces) + K F
-800P (precolumn) (manufactured by Showa Denko K.K.) Detector: ERC-751O8 (manufactured by Emul Optical Co., Ltd.) Inch Graternia 000A (manufactured by System Instruments Co., Ltd.) Developing solvent: Tetrahydrofuran concentration = 0.1% by weight Temperature: 35°C Standard polymer for molecular weight calibration curve: Various types of monodisperse polystyrene (manufactured by Toyo Soda Co., Ltd.) (Mw/'1Jn=1.2 (may)
) Effects of the invention The fluorine-containing elastomer of the present invention has a feature of widening the molecular weight distribution without increasing the amount of ultra-high molecular weight polymer. It is possible to improve the die swell during extrusion molding, which was inevitably poor, and the extrusion speed and extrusion surface are also excellent.

Further, the fluorine-containing elastomer of the present invention containing iodine and bromine can increase the vulcanization rate by using peroxide vulcanization in combination, and has excellent properties for injection molding.

As described above, the fluorine-containing elastomer of the present invention has vulcanizability and vulcanizate physical properties comparable to conventional fluorine-containing elastomers, and has excellent processability, especially extrusion moldability such as extrusion speed, extrusion texture, and die swell. Because of its excellent properties, it is particularly suitable for use as a material for fluorine-containing elastomer products that are continuously processed using an extruder. It can also be used as a molding material for injection molding, calendar molding, compression molding, and the like.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

In the present invention, the following conditions were selected as the polyol vulcanization conditions for the fluorine-containing elastomer.

Fluorine-containing elastomer: 100 parts by weight Highly active magnesium oxide = 311 parts by weight Calcium hydroxide
= 6 parts by weight Bisphenol AF:
2 parts by weight Bis(benzyldiphenylphosphine)iminium chloride: 0.375 parts by weight Medium thermal carbon: 20 parts by weight Dimethyl sulfone
: 2 parts by weight mixed wire method
20-roux heat press vulcanization: 160°C
For 145 minutes, the physical properties of the polyol vulcanizate were determined by punching out a No. 3 dumbbell-shaped test piece from a 2-inch-thick vulcanized sheet.
Measurement was performed according to JIS-6301 using a tensile tester (manufactured by Orientic Co., Ltd.) at a tensile speed of 50 cm/min. Hardness was measured using a spring type hardness test A type in accordance with JIS-6301.

The extrusion test was carried out using Brabender extruder IO.
Using the D W type (D-19, 1 fight, L/D = 10),
Using a tube die (outer diameter 9 mm, inner diameter 8 mm),
The test was carried out under the following conditions: screw temperature 60° C., head temperature 100° C., and screw rotation speed 5 Orpm.

Extruded skin is graded into 5 levels based on visual inspection of the fineness of the surface skin (
Ranked from 5 to 1 in descending order of excellence.

The extrusion speed was calculated from the discharge length per unit time, and the die swell was calculated from the tube outer diameter and thickness.

Example 1 An autoclave with an internal volume of about 1,512 mm equipped with an electromagnetic induction stirrer was sufficiently purged with nitrogen gas, and the decompression-nitrogen process was repeated three times to replace the nitrogen with nitrogen, followed by deoxygenated pure water under reduced pressure. 5.44721? , 1.1.2-trichloro-1,2,2-trifluoroethane (hereinafter referred to as Freon 11
3) 1.07721? and methyl cellulose (viscosity 50 cp) as a suspension stabilizer were charged and the temperature was maintained at 50°C while stirring at 600 rpm. Next item vdF unit 14.5% by weight, RFP unit 79
．． 1% by weight and 6.4% by weight of TFE units as the feed gas, 15 hg/cm2・G
I prepared it until it became.

Next, as a catalyst, a Freon 113 solution containing 20.1% by weight of diisopropyl peroxydicarbonate 26.
5 g was charged to start polymerization. Due to polymerization, the pressure increases to 14
．． When it drops to 5kg/cm'G, VdF unit is 43.5
Weight %, HFP units 29.5 weight %, TFE units 27.
A mixed monomer containing 0% by weight was continuously added as a continuous gas, and the pressure was again returned to 15.9/cm"·G. Such operations were repeated to perform a polymerization reaction.

5 hours after the start of polymerization, short methane 4
Add 3g and similarly pressure 14.5-15.0kg/c
The polymerization reaction was continued for an additional 7 hours at m2·G, for a total of 12 hours. After the polymerization reaction was completed, the remaining mixed monomers were scavenged, and the resulting suspension was dehydrated using a centrifugal separator, thoroughly washed with water, and then vacuum dried at IoO'C to obtain an elastomer of approximately 2.8729. . When the obtained fluorine-containing elastomer was analyzed by "F-NMR," V
dF unit: 43.5% by weight, RFP unit: 30.3fI amount%
, 26.2% by weight of TFE units.

[11] of this elastomer is 89 mα/g, the shape of the molecular weight distribution chart is three peaks as shown in the figure, and Vn
is 2.4X 10', Nw/Un is 12.9, M,
is 41.9% by weight, M. . is 1.5% by weight, Mi/[
v] was 0.47.

The fluorine-containing elastomer gave extremely excellent results in an extrusion test. The results are shown in Table 2. Furthermore, when the fluorine-containing elastomer was cured with polyol under standard conditions, good mechanical properties were obtained. The results are also shown in Table 2.

Examples 2 to 4, Comparative Examples 1 to 3 Example 1 except that the polymerization was conducted under the polymerization conditions shown in Table 1.
It was carried out in the same way. Table 2 shows the polymer properties, extrusion properties, and physical properties of the vulcanizate of the obtained elastomer.

Comparative Example 4 As a comparative example, Table 2 shows the results of an extrusion test of a commercially available fluorine-containing elastomer suitable for extrusion processing.

The conditions for polyol vulcanization were as follows.

Fluorine-containing elastomer: 100 parts by weight (Daiel G-555) Highly active magnesium oxide - 3 parts by weight Calcium hydroxide 2 6 parts by weight Medium thermal carbon = 20 parts by weight Other than the above formulation, the polyol vulcanization standard conditions of the example were used. The same procedure was carried out.

[Brief explanation of the drawing]

The figure is a GPC chart showing the molecular weight distribution of one example of the fluorine-containing elastomer of the present invention.

Claims (1)

[Scope of Claims] 1. A fluorine-containing elastomer comprising vinylidene fluoride units and hexafluoropropylene units, in which (a) the weight ratio of vinylidene fluoride units and hexafluoropropylene units is from 40:60 to 80:20. (b) The molecular weight distribution is a multi-peak type formed from two or more peaks; (c) Weight average molecular weight (@M@w) and number average molecular weight (@
M@n) ratio @M@w/@M@n is 8 to 20, (d) the intrinsic viscosity is 50 to 150 ml/g, (e) a polymer with a molecular weight of 2 million or more. The amount of polymer is less than 4% by weight, and (f) the ratio of the amount of low molecular weight polymer with a molecular weight of 50,000 or less M_5 (weight%) to the intrinsic viscosity number [η] (ml/g) M_5/[
η] is 0.30 to 0.70. 2 In a fluorine-containing elastomer consisting of vinylidene fluoride units and hexafluoropropylene units and a proportion of tetrafluoroethylene units not exceeding 35% by weight based on the total amount, (a) the weight ratio of vinylidene fluoride units and hexafluoropropylene units is 40:60 to 80:20; (b) the molecular weight distribution is a multi-peak type formed from two or more peaks; (c) the weight average molecular weight (@M@w) and the number average molecular weight ( @
M@n) ratio @M@w/@M@n is 8 to 20, (d) the intrinsic viscosity is 50 to 150 ml/g, (e) a polymer with a molecular weight of 2 million or more. The amount of polymer is less than 4% by weight, and (f) the ratio of the amount M_5 (weight%) of a low molecular weight polymer with a molecular weight of 50,000 or less to the intrinsic viscosity number [η] (ml/g) M_5/[
η] is 0.30 to 0.70.