U.S. patent application number 11/370938 was filed with the patent office on 2006-08-03 for acqueous dispersion of vinylidene flouride polymer and preparation process thereof.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Takayuki Araki, Masahiro Kondo, Nobuhiko Tsuda.
Application Number | 20060173117 11/370938 |
Document ID | / |
Family ID | 16961678 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060173117 |
Kind Code |
A1 |
Araki; Takayuki ; et
al. |
August 3, 2006 |
Acqueous dispersion of vinylidene flouride polymer and preparation
process thereof
Abstract
Aqueous dispersion of a vinylidene fluoride (VdF) polymer which
comprises a VdF polymer having a particle size of not more than 200
nm and contains 30 to 50% by weight of solids and not more than 1%
by weight of a fluorine-containing surfactant on the basis of
water. This aqueous dispersion is prepared by emulsion-polymerizing
VdF monomer or a monomer mixture containing VdF under coexistence
of not more than 1% by weight of the fluorine-containing surfactant
and 0.001 to 0.1% by weight of a nonionic non-fluorine-containing
surfactant on the basis of water, and is suitably used for
paints.
Inventors: |
Araki; Takayuki; (Osaka,
JP) ; Tsuda; Nobuhiko; (Osaka, JP) ; Kondo;
Masahiro; (Osaka, JP) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE
SUITE 101
RESTON
VA
20191
US
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka
JP
|
Family ID: |
16961678 |
Appl. No.: |
11/370938 |
Filed: |
March 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09095842 |
Jun 11, 1998 |
|
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11370938 |
Mar 9, 2006 |
|
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08612865 |
Mar 13, 1996 |
5925705 |
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PCT/JP94/01531 |
Sep 16, 1994 |
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09095842 |
Jun 11, 1998 |
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Current U.S.
Class: |
524/462 ;
524/773 |
Current CPC
Class: |
C08F 14/22 20130101;
C08F 14/22 20130101; C08F 2/16 20130101; C09D 127/16 20130101 |
Class at
Publication: |
524/462 ;
524/773 |
International
Class: |
C08K 5/02 20060101
C08K005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 1993 |
JP |
233858/1933 |
Claims
1. An aqueous dispersion of a vinylidene fluoride polymer, which
comprises a vinylidene fluoride polymer having an average particle
size of not more than 320.1 nm, wherein a solid content is from 30
to 50% by weight, and a content of a fluorine-containing surfactant
is not more than 1% by weight on the basis of water.
2. The aqueous dispersion of claim 1, wherein the
fluorine-containing surfactant is at least one member selected from
the group consisting of a fluorine-containing carboxylic acid
represented by the formula: X(CF.sub.2).sub.nCOOH and
Y(CH.sub.2CF.sub.2).sub.mCOOH where n is an integer of 6 to 20, X
is F or H, m is an integer of 6 to 13, and Y is F or Cl, an alkali
metal salt thereof, an ammonium salt thereof, an amine salt thereof
and a quaternary ammonium salt thereof.
3. The aqueous dispersion of claim 1, wherein the
fluorine-containing surfactant is an ammonium salt of
perfluorooctanoic acid.
4. An aqueous dispersion of a vinylidene fluoride polymer, which
comprises a vinylidene fluoride polymer having an average particle
size of not more than 196.3 nm, wherein a solid content is from 30
to 50% by weight, and a content of a fluorine-containing surfactant
is not more than 2% by weight on the basis of water.
5. The aqueous dispersion of claim 4, wherein the
fluorine-containing surfactant is at least one member selected from
the group consisting of a fluorine-containing carboxylic acid
represented by the formula: X(CF.sub.2).sub.nCOOH and
Y(CH.sub.2CF.sub.2).sub.mCOOH where n is an integer of 6 to 20, X
is F or H, m is an integer of 6 to 13, and Y is F or Cl, an alkali
metal salt thereof, an ammonium salt thereof, an amine salt thereof
and a quaternary ammonium salt thereof.
6. The aqueous dispersion of claim 4, wherein the
fluorine-containing surfactant is an ammonium salt of
perfluorooctanoic acid.
7. An aqueous dispersion of a vinylidene fluoride polymer, which
consists essentially of a vinylidene fluoride polymer having an
average particle size of not more than 200 nm and a surfactant,
wherein a solid content is from 30 to 50% by weight, a content of
the surfactant is not more than 1% by weight on the basis of water,
and the surfactant consists essentially of at least one of a
fluorine-containing surfactant.
8. The aqueous dispersion of claim 7, wherein the
fluorine-containing surfactant is at least one member selected from
the group consisting of a fluorine-containing carboxylic acid
represented by the formula: X(CF.sub.2).sub.nCOOH and
Y(CH.sub.2CF.sub.2).sub.mCOOH where n is an integer of 6 to 20, X
is F or H, m is an integer of 6 to 13, and Y is F or Cl, an alkali
metal salt thereof, an ammonium salt thereof, an amine salt thereof
and a quaternary ammonium salt thereof.
9. The aqueous dispersion of claim 7, wherein the
fluorine-containing surfactant is an ammonium salt of
perfluorooctanoic acid.
10. A method for preparing a paint composition, which consists
essentially of blending a coloring agent with an aqueous dispersion
of a vinylidene fluoride polymer, which comprises a vinylidene
fluoride polymer having an average particle size of not more than
200 nm and a surfactant, wherein a solid content is from 30 to 50%
by weight, a content of the surfactant is not more than 1% by
weight on the basis of water, and the surfactant consists
essentially of at least one of a fluorine-containing
surfactant.
11. The method of claim 10, wherein the fluorine-containing
surfactant is at least one member selected from the group
consisting of a fluorine-containing carboxylic acid represented by
the formula: X(CF.sub.2).sub.nCOOH and
Y(CH.sub.2CF.sub.2).sub.mCOOH where n is an integer of 6 to 20, X
is F or H, m is an integer of 6 to 13, and Y is F or Cl, an alkali
metal salt thereof, an ammonium salt thereof, an amine salt thereof
and a quaternary ammonium salt thereof.
12. The method of claim 10, wherein the fluorine-containing
surfactant is an ammonium salt of perfluorooctanoic acid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 09/095,842, filed Jun. 11, 1998, now pending, which is a
continuation of U.S. application Ser. No. 08/612,865, filed Mar.
13, 1996, now U.S. Pat. No. 5,925,705, which is a U.S. national
phase application of International Application No. PCT/JP94/01532
filed Sep. 16, 1994. The entire disclosure of the prior
applications is considered as being part of the disclosure of the
accompanying and is hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present invention relates to an aqueous dispersion of a
fluorine-containing polymer usable for paints. More specifically
the present invention relates to an aqueous dispersion of a
vinylidene fluoride (VdF) type polymer, which comprises a VdF
polymer having a particle size of not more than 200 nm and contains
30 to 50% by weight of solids, and a process for preparation
thereof.
BACKGROUND ART
[0003] Fluorine-containing paints are used as weather-resistive
paints for exterior and interior coating of medium- or low-storied
buildings, and various techniques have been developed for
preparation of the fluorine-containing paints. Though many of the
fluorine-containing paints are in the form of organic solvent
dispersions, there are problems in the use of organic solvents from
safety and environmental protection points of view, and ones of
aqueous dispersion type are preferable. As the methods of preparing
an aqueous dispersion of a fluorine-containing polymer, there are
known the methods mentioned below.
[0004] For example, JP-B-28669/1974 discloses that when vinyl
fluoride is suspension-polymerized in preparation of paints, a
nonionic surfactant is added in an amount of 0.05 to 5% by weight
on the basis of the monomer to increase yield, to prevent
deposition of the polymer onto an inside wall of a polymerization
tank and to control particle size of the polymer.
[0005] Also JP-A-123646/1986 discloses that in preparing a
fluorine-containing copolymer in an aqueous medium, a stable
aqueous emulsion can be obtained by adding a dispersion stabilizing
agent after polymerization of the fluorine-containing copolymer,
but before or during the condensation process of the aqueous
dispersion.
[0006] Further JP-B-55441/1992 discloses that in preparing an
aqueous fluorine-containing polymer dispersion for aqueous paints,
0.05 to 5.0% by weight of surfactants of various kinds including a
nonionic surfactant is added when the seed-polymerization of a
monomer having ethylenically unsaturated bond is carried out.
[0007] Also JP-A-225550/1990 discloses that a mixture of a
fluorine-containing type surfactant and a nonionic type surfactant
is used when copolymerizing a fluorine-containing olefin and a
hydrophilic group-containing non-fluorine-containing olefin.
[0008] Also Koubunshi Ronbun Shu, Vol. 36, No. 11 (1979) discloses
at pages 729 to 737 that when a large amount of surfactants of
various kinds is used in emulsion polymerization, particles of a
polymer latex become smaller, and also that by mixing an anionic
surfactant and a nonionic surfactant in polymerization of an
acrylic monomer, there can be obtained the same effect as in case
of adding an anion surfactant solely.
[0009] However the technique in JP-B-28669/1974 does not relate to
emulsion polymerization, but relates to suspension polymerization
without using a fluorine-containing surfactant, and intends to
obtain a particle size larger than that of the present invention.
The particle size described in the example of this patent
publication is as large as 3.4 to 4.5 .mu.m.
[0010] Also JP-A-123646/1986 discloses that a polymer latex having
a concentration as high as not less than 30% by weight is obtained
by using a fluorine-containing emulsifying agent in polymerization
process. However there is no description as to the use of a
fluorine-containing surfactant for controlling the particles at a
size lower than a certain size. In addition, the invention is
characterized by the use of a specific non-fluorine-containing
dispersion stabilizing agent, and its amount to be used is as much
as 2 to 8% by weight on the basis of a solid content. Usually, the
particle size of a latex tends to increase together with a polymer
concentration, and when the fluorine-containing surfactant is used
solely and if its amount is not more than 1% by weight, there
cannot be obtained a particle size of not more than 200 nm if the
solid content is assumed to be 30 to 50% by weight. Also there is
no description as to controlling of the particle size of the
aqueous latex. It is also described that if the nonionic surfactant
is added in preparing an aqueous emulsion, there is an adverse
effect such as coloring.
[0011] Further in the technique disclosed in JP-B-55441/1992, no
surfactant is used in the polymerization of a fluorine-containing
olefin, and also there is no disclosure as to the use of a
fluorine-containing surfactant as the surfactant to be used in the
seed-polymerization.
[0012] Also the technique specifically disclosed in
JP-A-225550/1990 is one wherein chlorotrifluoroethylene is used as
a fluoroolefin unit and the amount of the nonionic surfactant used
is as relatively much as 3% by weight on the basis of water.
However in copolymerization of VdF, there has been generally known
that there occur problems such that when the nonionic surfactant is
added, the reaction rate is lowered remarkably and the molecular
weight is not increased.
[0013] Also in the techniques disclosed in the above-mentioned
Koubunshi Ronbun Shu, the use of the surfactant in a large amount
causes an adverse effect on water resistance when used for
paints.
[0014] The present invention has been made to solve the
above-mentioned problems, and it is an object of the present
invention to provide an aqueous dispersion of a fluorine-containing
polymer, which comprises a VdF polymer having a particle size as
small as not more than 200 nm and contains solids in an amount as
high as 30 to 50% by weight and a surfactant in an amount as low as
not more than 1% by weight on the basis of water, and its
preparation process.
DISCLOSURE OF THE INVETION
[0015] The present invention relates to an aqueous dispersion of a
VdF polymer, which comprises a VdF polymer having a particle size
of not more than 200 nm, has a solid content of 30 to 50% by weight
and contains a fluorine-containing surfactant in an amount of not
more than 1% by weight on the basis of water.
[0016] It is possible in the present invention that in the known
emulsion polymerization system, notwithstanding that the solid
content is as high as 30 to 50% by weight, the particle size can be
decreased to not more than 200 nm by adding a nonionic
non-fluorine-containing surfactant in a trace amount of 0.001 to
0.1% by weight on the basis of water in the presence of a small
amount of a fluorine-containing surfactant, i.e. not more than 1%
by weight, on the basis of water.
BEST MODE FOR CARRYING OUT THE INVENTION
[0017] As the VdF polymer in the present invention, there are
homopolymer of VdF; a copolymer of VdF monomer and at least one of
the other fluorine-containing monomers such as tetrafluoroethylene
(TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE) and
hexafluoropropylene (HFP); a copolymer of VdF, the other
fluorine-containing monomer and a monomer having an unsaturated
bond which is copolymerizable therewith. The preferable copolymers
are, for example, VdF/TFE copolymer, VdF/TFE/HFP copolymer,
VdF/TFE/CTFE copolymer, VdF/TFE/TrFE copolymer, VdF/CTFE copolymer,
VdF/HFP copolymer, VdF/TFE/HFP/CTFE copolymer,
VdF/TFE/perfluorobutenoic acid copolymer, VdF/TFE/maleic acid
copolymer and the like. The content of VdF units of these
copolymers is preferably not less than 50% by mole, more preferably
not less than 70% by mole. The weight average molecular weight (Mw)
of these VdF polymers is from 1,000 to 1,000,000, preferably from
10,000 to 500,000. When lower than 1,000, mechanical properties and
weatherability when forming a film tend to be inferior, and when
higher than 1,000,000, there are tendencies that the resin does not
flow when forming a film, leveling property is lowered and no gloss
is exhibited.
[0018] The particle size of the VdF polymer is not more than 200
nm, preferably from 150 to 100 run. Since the particle size is as
small as not more than 200 nm, the polymer is excellent in
stability against sedimentation and dispersing property of
additives is excellent. When the particle size is larger than 200
nm, there occurs sedimentation and coagulation of the particles
during storage of the dispersion and the dispersing property of the
additives is poor. Also there is a tendency that gloss of the
formed film is difficult to be obtained.
[0019] The fluorine-containing surfactant used in the present
invention is one or a mixture of compounds containing fluorine
atoms in their structures and having surface activity. For example,
there are an acid represented by X(CF.sub.2).sub.nCOOH (n is an
integer of 6 to 20, X is F or H), its alkali metal salt, ammonium
salt, amine salt or quaternary ammonium salt; an acid represented
by Y(CH.sub.2CF.sub.2).sub.mCOOH (m is an integer of 6 to 13, Y is
F or Cl), its alkali metal salt, ammonium salt, amine salt or
quaternary ammonium salt; or the like. More specifically, there are
used an ammonium salt of perfluoro(octanoic acid), an ammonium salt
of perfluoro(nonanoic acid) or the like. In addition, there can be
used known fluorine-containing surfactants.
[0020] The amount of the fluorine-containing surfactant to be used
is not more than 1.0% by weight on the basis of water, preferably
not more than 0.5% by weight, more preferably not more than 0.2% by
weight. The lower limit is usually 0.01% by weight. When more than
1.0% by weight, there occurs a phenomenon such as precipitation of
the surfactant in the film formed from the aqueous dispersion and
also there is a tendency such that water absorption increases to
make the dispersion whiten. Thus, it is not preferable if the
amount of the fluorine-containing surfactant is more than 1.0% by
weight.
[0021] The solid content of the aqueous dispersion of the present
invention is from 30 to 50% by weight, preferably from 35 to 45% by
weight. When less than 30% by weight, there is a tendency such that
when forming a film, viscosity adjustment is difficult and leveling
property is lowered. When more than 50%, the stability of the
dispersion becomes worse and deposition and coagulation tend to
occur in polymerization process.
[0022] Water to be used for an aqueous dispersion of the present
invention is preferably a deionized water.
[0023] The aqueous dispersion of the VdF polymer of the present
invention can be prepared, for example, by emulsion-polymerizing
VdF monomer or a monomer mixture containing VdF under coexistence
of the above-mentioned fluorine-containing surfactant in an amount
of not more than 1% by weight on the basis of water and a trace
amount of the nonionic non-fluorine-containing surfactant.
[0024] In order to prepare the aqueous dispersion which comprises
the VdF polymer having a particle size of not more than 200 nm and
contains solids in an amount of 30 to 50% by weight, it is usually
necessary to use a large amount of a fluorine-containing
surfactant. However according to the preparation process of the
present invention, it is possible to decrease the amount of the
fluorine-containing surfactant to a small amount of not more than
1% by weight by adding a trace amount of the nonionic
non-fluorine-containing surfactant. Namely, a small particle size
of not more than 200 nm can be attained by adding the nonionic
non-fluorine-containing surfactant.
[0025] As the nonionic non-fluorine-containing surfactant, there
are polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl
ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters,
polyoxyethylene sorbitan alkyl esters, glycerol esters, their
derivatives and the like. More specifically examples of
polyoxyethylene alkyl ethers are polyoxyethylene lauryl ether,
polyoxyethylene cetyl ether, olyoxyethylene stearyl ether,
polyoxyethylene oleyl ether, polyoxyethylene behenyl ether and the
like; examples of polyoxyethylene alkyl phenyl ethers are
polyoxyethylene nonyl phenyl ether, polyoxyethylene oetyl phenyl
ether and the like; examples of polyoxyethylene alkyl esters are
polyethylene glycol monolaurylate, polyethylene glycol monooleate,
polyethylene glycol monostearate and the like; examples of sorbitan
alkyl esters are polyoxyethylene sorbitan monolaurylate,
polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan
monostearate, polyoxyethylene sorbitan monooleate and the like;
examples of polyoxyethylene sorbitan alkyl esters are
polyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitan
monopalmitate, polyoxyethylene sorbitan monostearate and the like;
and examples of glycerol esters are glycerol monomyristate,
glycerol monostearate, glycerol monooleate and the like. Also
examples of their derivatives are polyoxyethylene alkyl amine,
polyoxyethylene alkyl phenyl-formaldehyde condensate,
polyoxyethylene alkyl ether phosphate and the like. Particularly
preferable are polyoxyethylene alkyl ethers and polyoxyethylerte
alkyl esters which have an HLB value of 10 to 18. More particularly
there are polyoxyethylene lauryl ether (EO: 5 to 20. EO stands for
an ethylene oxide unit.), polyethylene glycol monostearate (EO: 10
to 55) and polyethylene glycol monooleate (EO: 6 to 10).
[0026] The amount of the nonionic non-fluorine-containing
surfactant used in the present invention is from 0.001 to 0.1% by
weight on the basis of water, preferably from 0.01 to 0.05% by
weight. When more than 0.1% by weight, it is not practicable
because the rate of reaction is lowered because of chain transfer
reaction and the reaction is stopped. Also when less than 0.001% by
weight, there is almost no effect of making the particle size
fine.
[0027] The emulsion having a relatively high concentration can also
be obtained by polymerizing, in an organic solvent, a monomer
mixture containing an ethylenically unsaturated monomer having an
ionic group or polyalkylene oxide group, then adding water and
distilling off the organic solvent. For example, an emulsion can be
obtained by solution-polymerizing, in ethyl acetate, a mixture of
VdF, TFE and perfluorobutenoic acid
(CF.sub.2.dbd.CF--CF.sub.2COOH), adding aqueous ammonia solution to
neutralize, then pouring dropwise into ion-exchanged water
containing a fluorine-containing surfactant with stirring to
disperse homogeneously, and distilling off ethyl acetate by using
an evaporator.
[0028] In order to polymerize VdF monomer, an initiator is usually
used. As the initiator, particularly there is no restriction if it
serves to generate radicals usable for free radical reaction in an
aqueous medium at a temperature between 20.degree. C. and
90.degree. C. Usually as the water soluble initiator, there are
potassium salt and ammonium salt of persulfuric acid, and hydrogen
peroxide; and as the oil soluble initiator, there are diisopropyl
peroxydicarbonate (IPP), azobisisobutyronitrile (AIBN) and the
like. The amount of the initiator to be added is from 0.005 to 1.0%
by weight on the basis of water, preferably from 0.01 to 0.5% by
weight. When less than 0.005% by weight, the polymerization rate
tends to be lowered extremely; and when more than 1.0% by weight,
there is a tendency such that a concentration of an electrolyte is
increased and thus the particle size is increased.
[0029] In preparing the aqueous dispersion of the VdF polymer of
the present invention, the polymerization temperature is from
20.degree. to 120.degree. C., preferably from 30.degree. to
70.degree. C. When lower than 20.degree. C., in general there is a
tendency such that stability of the formed latex is lowered, and
when higher than 120.degree. C., the polymerization rate tends to
be decreased due to chain transfer reaction. Polymerization is
usually carried out by heating for 5 to 100 hours under a pressure
of 1.0 to 50 kgf/cm.sup.2 (gauge pressure) though it depends on
kind of the polymer.
[0030] The aqueous dispersion of the VdF polymer of the present
invention can be used as water base paints for coating by blending
additives such as pigments, thickeners, dispersing agents,
defoaming agents, antifreezing agents and film forming auxiliaries
or in addition thereto by combining with other high molecular
compounds.
[0031] The present invention is explained further in detail based
on examples, but is not limited thereto.
EXAMPLE 1
[0032] A one-liter pressure resistive reactor equipped with a
stirrer was charged with 500 ml of deionized water, 0.5 g of a
fluorine-containing surfactant, i.e. an ammonium salt of
perfluoro(octanoic acid) (PFOA) and 0.05 g of a nonionic
non-fluorine-containing surfactant, i.e. polyoxyethylene lauryl
ether (MYS40 available from Nikko Chemicals Co., Ltd.), and steps
of introduction of pressurized nitrogen gas and deaeration were
repeated to remove the dissolved air. The inside pressure of the
reactor was then raised to 20 kgf/cm.sup.2 (gauge pressure) at
60.degree. C. by using VdF. Then 0.2 g of an initiator, i.e.
ammonium persulfate was added, VdF was continuously supplied to
maintain the inside pressure of the reactor constant at 20
kgf/cm.sup.2 (gauge pressure), and the reaction was carried out for
20 hours. Afterwards the reaction system was rendered to normal
temperature and normal pressure, and thereby the reaction was
terminated. The intrinsic viscosity [.alpha.]of the obtained
polymer comprising VdF solely, which was measured in a
dimethylfuran (DMF) solvent at 35.degree. C., was 0.63. The
measured characteristic values of the obtained aqueous dispersion
are shown in TABLE 1.
[0033] In TABLE 1, the solid content is represented in percentage
of the weight of the aqueous dispersion after dried at 150.degree.
C. for one hour in a vacuum dryer to its weight before drying. The
particle size is an average size obtained by measuring the particle
sizes with a laser beam scattering particle size analyzer (ELS-3000
available from Otsuka Denshi Kogyo Kabushiki Kaisha). The stability
against sedimentation was evaluated as follows by allowing an
aqueous dispersion to be tested to stand at 25.degree. C. for 60
days. [0034] .largecircle.: There is no change in dispersed state
with naked eyes. [0035] .DELTA.: The dispersion is separated into a
transparent water phase and a dispersed particle phase and it is
possible to re-disperse by shaking. [0036] x: The dispersion is
separated into a transparent water phase and a dispersed particle
phase, and it is impossible to re-disperse by shaking.
EXAMPLE 2
[0037] A one-liter pressure resistive reactor equipped with a
stirrer was charged with 500 ml of deionized water, 0.5 g of an
ammonium salt of perfluoro(octanoic acid) and 0.05 g of
polyoxyethylene lauryl ether, and steps of introduction of
pressurized nitrogen gas and deaeration were repeated to remove the
dissolved air. The inside pressure of the reactor was then raised
to 8 kgf/cm.sup.2 (gauge pressure) at 60.degree. C. by using a
VdF/TFE monomer mixture (80/20% by mole). Then 0.05 g of ammonium
persulfate was added, the above-mentioned monomer mixture was
continuously supplied to maintain the inside pressure of the
reactor constant at 8 kgf/cm.sup.2 (gauge pressure), and the
reaction was carried out for 20 hours. Afterwards the reaction
system was rendered to normal temperature and normal pressure, and
thereby the reaction was terminated. The intrinsic viscosity
[.alpha.]of the obtained VdF/TFE copolymer in a methyl ethyl ketone
(MEK) solution at 35.degree. C. was 1.43. The measured
characteristic values of the obtained aqueous dispersion are shown
in TABLE 1.
EXAMPLE 3
[0038] A one-liter pressure resistive reactor equipped with a
stirrer was charged with 500 ml of deionized water, 0.5 g of an
ammonium salt of perfluoro(octanoic acid) and 0.05 g of
polyoxyethylene lauryl ether, and steps of introduction of
pressurized nitrogen gas and deaeration were repeated to remove the
dissolved air. The inside pressure of the reactor was then raised
to 8 kgf/cm.sup.2 (gauge pressure) at 60.degree. C. by using a
VdF/TFE/HFP monomer mixture (72/20/8% by mole). Then 0.2 g of
ammonium persulfate was added, the above-mentioned monomer mixture
was continuously supplied to maintain the inside pressure of the
reactor constant at 8 kgf/cm.sup.2 (gauge pressure), and the
reaction was carried out for 38 hours. Afterwards the reaction
system was rendered to normal temperature and normal pressure, and
thereby the reaction was terminated. The intrinsic viscosity
[.eta.]of the obtained VdF/TFE/HFP copolymer in an MEK solvent at
35.degree. C. was 1.08. The measured characteristic values of the
obtained aqueous dispersion are shown in TABLE 1.
EXAMPLE 4
[0039] A one-liter pressure resistive reactor equipped with a
stirrer was charged with 500 ml of deionized water, 0.5 g of an
ammonium salt of perfluoro(octanoic acid) and 0.05 g of
polyoxyethylene lauryl ether, and steps of introduction of
pressurized nitrogen gas and deaeration were repeated to remove the
dissolved air. The inside pressure of the reactor was raised to 8
kgf/cm.sup.2 (gauge pressure) at 60.degree. C. by using a
VdF/TFE/CTFE monomer mixture (75/15/10% by mole). Then 0.2 g of
ammonium persulfate was added, the above-mentioned monomer mixture
was continuously supplied to maintain the inside pressure of the
reactor constant at 8 kgf/cm.sup.2 (gauge pressure), and the
reaction was carried out for 40 hours. Afterwards the reaction
system was rendered to normal temperature and normal pressure, and
thereby the reaction was terminated. The intrinsic viscosity
[.eta.] of the obtained VdF/TFE/CTFE copolymer in an MEK solvent at
35.degree. C. was 1.20. The measured characteristic values of the
obtained aqueous dispersion are shown in TABLE 1.
COMPARATIVE EXAMPLES 1 TO 4
[0040] Aqueous dispersions of the VdF polymer were prepared in the
same manner as in EXAMPLES 1 to 4 except that the nonionic
non-fluorine-containing surfactant was not used and the amount of
the fluorine-containing surfactant was changed as shown in TABLE 1.
The measured characteristic values of the obtained aqueous
dispersions are shown in TABLE 1.
COMPARATIVE EXAMPLE 5
[0041] An aqueous dispersion of the VdF polymer was prepared in the
same manner as in EXAMPLE 3 except that CTFE was used instead of
HFP and the amount of the fluorine-containing surfactant was
changed as shown in TABLE 1. The measured characteristic values of
the obtained aqueous dispersion are shown in TABLE 1. As shown in
TABLE 1, these characteristics were preferable, but there was found
precipitation of the fluorine-containing surfactant at drying the
formed film. TABLE-US-00001 TABLE 1 Com. Com. Com. Com. Com. Ex. 1
Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Monomer VdF*.sup.1
100 80 72 75 100 80 72 75 72 (% by mole) TFE*.sup.2 -- 20 20 15 --
20 20 15 20 HFP*.sup.3 -- -- 8 -- -- -- 8 -- CTFE*.sup.4 -- -- --
10 -- -- -- 10 8 Surfactant Fluorine- PFOA.sup.*5 PFOA PFOA PFOA
PFOA PFOA PFOA PFOA PFOA (% by weight) containing type (0.1) (0.1)
(0.1) (0.1) (1.0) (1.0) (1.0) (0.1) (2.0) Nonionic MYS40.sup.*6
MYS40 MYS40 MYS40 -- -- -- -- -- non-fluorine- (0.01) (0.01) (0.01)
(0.01) containing type Aqueous Solid content 30.1 32.1 33.4 42.0
18.5 24.6 32.0 34.6 31.5 dispersion (% by weight) Particle size
180.5 167.3 125.9 165.0 231.7 269.2 234.5 320.1 196.3 (nm)
Stability against .largecircle. .largecircle. .largecircle.
.largecircle. .DELTA. X X X .largecircle. sedimentation
*.sup.1Vinylidene fluoride *.sup.2Tetrafluoroethylene
*.sup.3Hexafluoropropylene *.sup.4Chlorotrifluoroethylene
*.sup.5Ammonium salt of Perfluoro(octanoic acid)
*.sup.6Polyoxsyethylene lauryl ether available form Nikko Chemical
Co., Ltd.
INDUSTRIAL APPLICABILITY
[0042] The aqueous dispersion of the VdF polymer of the present
invention is excellent in stability against sedimentation
notwithstanding a small amount of a surfactant and can provide
coating films excellent in water resistance and leveling property.
According to the preparation process of the present invention, the
above-mentioned aqueous dispersion can be prepared easily by using
a trace amount of a nonionic non-fluorine-containing surfactant
even if the amount of a fluorine-containing surfactant is decreased
greatly.
* * * * *