Aqueous dispersion for water-and-oil repellant and process...

Details Aqueous dispersion for water-and-oil repellant and process... Aqueous dispersion for water-and-oil repellant and process...

2001-06-26

2003-09-23

Lovering, Richard D. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C524S805000, C526S219500, C526S243000, C526S246000

Reexamination Certificate

active

06624268

ABSTRACT:

This application is a 371 of PCT/JP00/07517 filed Oct. 26, 2000 which claims priority based on Japan 11-309562 filed Oct. 29, 1999.
TECHNICAL FIELD
The present invention relates to a water and oil repellent aqueous dispersion.
BACKGROUND ART
As a technique for imparting water and oil repellency to the surface of a textile, application of a polymer (X) having polymer units derived from a polymerizable monomer having a polyfluoroalkyl group (herein after referred to as a R
f
group) in the form of an aqueous dispersion in an aqueous solvent, an organic solution in an organic solvent or a solvent-type dispersion in an organic solvent has been known so far. Especially, application in the form of an aqueous dispersion is recommended in recent years in view of the problem with the working environments and the problem of the impact on the environment.
In direct production of an aqueous dispersion by polymerization of a hardly water-soluble (meth)acrylate (a
1
) having a R
f
group in an aqueous medium, an organic solvent (such as acetone) which is compatible with a (meth)acrylate (a
1
) having a R
f
group and soluble in water is usually incorporated in the aqueous medium as a polymerization co-solvent. However, if acetone is used as a polymerization co-solvent, there is a problem that the flash point of the aqueous dispersion is low.
As a solution to this problem, use of a polymerization co-solvent with a high flash point which is highly compatible with the polymerizable monomer and soluble in water is proposed (JP-A-5-263070). However, the proposed polymerization co-solvent has a problem that it remains on the treated product because of its high boiling point and increases the affinity of the treated product for water. The problem of inadequate wet abrasion durability of the water and oil repellency is m acknowledged with water and oil repellents obtained by conventional processes.
Besides, water and oil repellents obtained by conventional processes have the problem that the water and oil repellency decreases as the emulsion particles coagulate or precipitate due to co-agents such as an acid or an anionic substance (such as a dye fixative agent or an acid dye) in the treatment bath or contaminants or deterioration in the dispersity of the aqueous dispersion and that the textile is not treated evenly due to adhesion of the polymer to the mangle (gum up). To solve these problems, incorporation of a surfactant containing a nitrogen atom, a polyoxyethylene group and at least five oxyalkylene groups is proposed (JP-A-9-59602 and JP-A-9-118877). However, water and oil repellent aqueous dispersions obtained under this proposal still have the problem of inadequate wet abrasion durability of the water and oil repellency.
An water and oil repellent composition obtained by adding a silicone compound to an emulsion obtained by emulsification of a polymerizable monomer such as a perfuloroalkyl acrylate, water, dipropylene glycol monomethyl ether and polyoxyethylene nonyl phenyl ether under pressure followed by polymerization is also proposed (JP-A-10-245783). However, this composition has a problem that it does not function well without the silicone compound. Conventional water and oil repellent compositions are inadequate in terms of the property of draining deposited water as rolling waterdrops (hereinafter referred to as the waterdrop rolling property) and have the problem that waterdrops stay on the surface of the treated product.
DISCLOSURE OF THE INVENTION
The present invention solves the above-mentioned problems and provides a process for producing a water and oil repellent aqueous dispersion excellent in the waterdrop rolling property which shows excellent dispersion stability and water and oil repellency even if contaminated with co-agents and contaminants and forms films with an excellent film-forming property, and a water and oil repellent aqueous dispersion produced by the process.
Namely, the present invention provides a process for producing a water and oil repellent aqueous dispersion, comprising emulsifying a stock composition comprising the following polymerizable monomer (A), the following surfactant (B) and the following aqueous medium (C) under pressure and polymerizing the stock composition to form an aqueous dispersion having a polymer (X) comprising polymer units derived from the polymerizable monomer (A) dispersed in the aqueous medium (C):
polymerizable monomer (A): a polymerizable monomer consisting of a (meth)acrylate (a
1
) having a polyfluoroalkyl group or consisting of a (meth)acrylate (a
1
) having a polyfluoroalkyl group and a polymerizable monomer (a
2
) other than the (meth)acrylate (a
1
) having a polyfluoroalkyl group;
surfactant (B): a surfactant which is a non-fluorine type surfactant containing no aromatic group and contains from 60 to 100 mass % of a nonionic surfactant; and
aqueous medium (C): an aqueous medium consisting of water and a solvent having a viscosity of at least 3 cP at 25° C.
BEST MODE FOR CARRYING OUT THE INVENTION
In this specification, acrylic acid and methacrylic acid are generally referred to as (meth)acrylic acid. Similar general names such as (meth)acrylamide also hold.
The polymerizable monomer (A) in the present invention is a polymerizable monomer consisting of a (meth)acrylate (a
1
) having a R
f
group or a polymerizable monomer consisting of a (meth)acrylate (a
1
) having a R
f
group and a polymerizable monomer other than the (a
1
). The (meth)acrylate (a
1
) having a R
f
group is a compound having a R
f
group on the alcohol residue in the (meth)acrylate. The R
f
group means an alkyl group having at least two hydrogen atoms substituted by fluorine atoms. The carbon number of the R
f
group is preferably from 2 to 20, particularly preferably from 6 to 16.
The R
f
group may be linear or branched, preferably linear. When it is branched, it is preferred that the branch is present at the end of the R
f
group and is a short chain with a carbon number of from about 1 to 4.
The R
f
group may contain a halogen atom other than a fluorine atom. The halogen atom other than the fluorine atom is preferably a chlorine atom. An etheric oxygen atom or a thioetheric sulfur atom may be inserted between a carbon-carbon bond in the R
f
group. The structure of the terminus of the R
f
group may, for example, —CF
2
CF
3
, —CF(CF
3
)
2
, —CF
2
H, —CFH
2
or —CF
2
Cl, preferably —CF
2
CF
3
.
The number of the fluorine atoms in the R
f
group is preferably at least 60%, particularly preferably at least 80%, when it is represented by [(the number of fluorine atoms in the R
f
group)/(the number of hydrogen atoms contained in the corresponding alkyl group having the same carbon number as the R
f
group)]×100(%). Further, the R
f
group is preferably a group having all hydrogen atoms in an alkyl group substituted by fluorine atoms (i.e. a perfluoroalkyl group), or a group having a terminal perfluoroalkyl group.
The carbon number of the perfluoroalkyl group is preferably from 2 to 20, particularly preferably from 6 to 16. If the carbon number is too small, the water and oil repellency tends to be low. If the carbon number is too large, the (meth)acrylate having a R
f
group can be difficult to handle.
Specific examples of the R
f
group include the groups given below.
CF
9
— [which may be any of the structural isomers such as F(CF
2
)
4
—, (CF
3
)
2
CFCF
2
—, (CF
3
)
3
C— and CF
3
CF
2
(CF
3
)CF—],
C
5
F
11
— [such as F(CF
2
)
5
—],
C
6
F
13
— [such as F(CF
2
)
6
—],
C
7
F
15
— [such as F(CF
2
)
7
—],
C
8
F
17
— [such as F(CF
2
)
8
—],
C
9
F
19
— [such as F(CF
2
)
9
—],
C
10
F
21
— [such as F(CF
2
)
10
—],
C
12
F
25
— [such as F(CF
2
)
12
—],
C
14
F
29
— [such as F(CF
2
)
14
—],
C
16
F
33
— [such as F(CF
2
)
16
—],
Cl(CF
2
)
s
— (wherein s is an integer of from 1 to 20),
H(CF
2
)
t
— (wherein t is an integer of from 1 to 20),
(CF
3
)
2
CF(CF
2
)
y
— (wherein y is an integer of from 1 to 17), etc.
Specific examples wherein the R
f
gro

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