Process for preparing fluorine-containing polymer

a technology of fluorine and polymer, which is applied in the field of process for preparing fluorine-containing polymers, can solve the problems of reduced compression set resistance, poor flowability in injection molding, and insufficient prevention of metal die staining, and achieve excellent mold processability, high vulcanization efficiency, and low viscosity

Inactive Publication Date: 2008-10-16
DAIKIN IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The process achieves high vulcanization efficiency, excellent mold processability, and low compression set in vulcanized fluororubber, with a sharp molecular weight distribution and reduced viscosity, enhancing productivity and maintaining desired properties.

Problems solved by technology

However, when only the above fluorine-containing elastomer is used, there were problems regarding mold processing such as roll processability in kneading and mold releasing properties in compression molding are poor, staining of the metal die cannot sufficiently be prevented and flowability in injection molding is poor.
However, by increasing low molecular weight components, compression set resistance decreases and mechanical strength such as tensile strength and elongation and also, solvent resistance tend to become poor.
Compression set is an important factor in evaluating sealing performance and when compression set is high, sealing ability is lost in a short period of time.
Also, in injection molding, excellent flowability is required and when flowability is poor, injecting into the die becomes difficult and more material than necessary must be used.
Also, the thickness of the molded article may become uneven.
However, these methods are not satisfactory with respect to processability other than vulcanizability.
However, even with this method, the problem that processability cannot be improved still remains.
Furthermore, as described above, improvement in flowability has been attempted by lowering the molecular weight, but this is insufficient with respect to compression set resistance and vulcanization efficiency.
According to this method, a fluorine-containing elastomer that is excellent in vulcanization efficiency, mold processability and compression set of a molded article is obtained, but on the other hand, because the polymer obtained by the disclosed polymerization method has composition distribution, there is the problem that the polymer contains components that differ from the target composition.
Furthermore, in order to keep the composition distribution within a specific width, more space than necessary must be acquired and there are problems regarding quality stability and productivity.
However, according to this method, because the gaseous phase composition changes largely before and after polymerization, not only does composition distribution of the polymer occur, but also, there is the problem that a polymer of disadvantageous components tends to be produced by post-polymerization after the reaction.
Also, because the initial monomers also serve as a buffer for composition distribution in polymerization, a constant amount of the gaseous phase must be acquired and as a result, the amount of monomer blow per batch is large.
Thus, productivity is problematic.
On the other hand, the idea behind preparing an elastomer having extremely low viscosity is not disclosed and particularly, as there is no description that a sharp molecular weight distribution Mw / Mn is important, a process for preparing a low viscosity polymer was unknown in reality.

Method used

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  • Process for preparing fluorine-containing polymer
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  • Process for preparing fluorine-containing polymer

Examples

Experimental program
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Effect test

reference example 1

Preparation of Seed Polymer Particles

[0136]A 1.8 liter polymerization vessel equipped with an electromagnetic induction type stirring device as the stirring device was charged with 720 g of deionized water, 290 g of a 10% by weight aqueous solution of ammonium perfluorooctanate and 0.6 g of diethyl malonate. After the system was sufficiently replaced with nitrogen gas, the pressure was reduced. This procedure was repeated 3 times. 20 g of is VdF and 51 g of HFP were added under reduced pressure and the temperature was raised to 80° C. while stirring. Subsequently, 0.02 g of ammonium persulfate (APS) dissolved in 0.6 g of deionized water was injected by nitrogen gas to start polymerization. The polymerization pressure was set to 2 MPa and in order to compensate for the pressure decrease during polymerization, a monomer mixture of VdF / HFP (78 / 22 (% by mol)) was supplied successively and polymerization was conducted while stirring. After 30 minutes, stirring was stopped and the monomer...

reference example 2

Preparation of Seed Polymer Particles

[0137]A 1.8 liter polymerization vessel equipped with an electromagnetic induction type stirring device as the stirring device was charged with 809 g of deionized water, 200 g of a 10% by weight aqueous solution of ammonium perfluorooctanate and 0.6 g of diethyl malonate. After the system was sufficiently replaced with nitrogen gas, the pressure was reduced. This procedure was repeated 3 times. 0.5 mL of isopentane was added under reduced pressure and each of the monomers were added so that the composition inside the vessel at 80° C. became VdF / TFE / HFP=29.0 / 13.0 / 58.0% by mol and the pressure inside the vessel became 1.4 MPa. After the temperature was increased, 0.67 g of ammonium persulfate (APS) dissolved in 20 g of deionized water was injected by nitrogen gas to start polymerization. The polymerization pressure was set to 1.4 MPa and in order to compensate for the pressure decrease during polymerization, a monomer mixture of VdF / TFE / HFP (50 / 20 / ...

example 1

Preparation of Fluorine-Containing Polymer

[0139]A 1.8 liter polymerization vessel equipped with the same stirring device as in Reference Example 1 was charged with 1258 g of deionized water, 26.65 g of an aqueous dispersion of the seed polymer particles prepared in Reference Example 1 (16.3% by weight concentration) and 4.91 g of diethyl malonate. After the system was sufficiently replaced with nitrogen gas, the pressure was reduced. This procedure was repeated 3 times. 76 g of VdF and 323 g of HFP were added under reduced pressure and the temperature was raised to 80° C. while stirring. Subsequently, 0.195 g of APS dissolved in 20 g of deionized water was injected by nitrogen gas to start polymerization and polymerization was continued under the following conditions (a) to (c). After 3 hours, stirring was stopped and the monomers were discharged to stop polymerization.

[0140]The composition ratio (mol) of the gaseous phase monomers VdF / HFP was 36 / 64 before polymerization and 38 / 62 a...

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Abstract

The present invention provides a process for preparing a fluorine-containing polymer having few branched chains and little weight change in high temperatures, which is a new process wherein composition distribution substantially does not occur. The fluorine-containing polymer is prepared by a batch copolymerization process conducted under conditions of reduced temperature of at least 0.95 and reduced pressure of at least 0.80 of the critical constant calculated from critical temperature, critical pressure and composition ratio of each monomer in the gaseous phase of the reaction vessel using the Peng-Robinson formula.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This is a Divisional of application Ser. No. 10 / 521,807 filed Jan. 21, 2005, which is a 371 of PCT Application No. PCT / JP03 / 09315 filed Jul. 23, 2003, the above-noted applications incorporated herein by reference in their entirety.TECHNICAL FIELD[0002]The present invention relates to a process for preparing a fluorine-containing polymer, in which composition distribution, which was a problem in polymerization methods of fluorine-containing polymers under high pressure, essentially does not occur. Also, the present invention relates to a composition comprising the polymer obtained by this process, which gives a vulcanized fluororubber that can be vulcanized efficiently and has small compression set and excellent mechanical properties. Furthermore, the present invention relates to a new fluorine-containing polymer having uniform composition distribution and extremely low Mooney viscosity and a preparation process thereof. The present invent...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C08F214/22C08F2/00C08F14/18C08F214/18
CPCC08F2/00C08F214/18C08F214/22
InventorIRIE, MASAKITOKUNO, SATOSHIIRIE, SADASHIGENISHIMURA, YOSUKEHORI, YOSHINORIKISHINE, MITSURU
OwnerDAIKIN IND LTD