Water- and oil-repellent

Details Water- and oil-repellent Water- and oil-repellent

2000-02-04

2001-08-14

Green, Anthony (Department: 1755)

Compositions

Durable finishes for textile materials, or processes of...

Oil or water repellent or soil resistant or retardant

C106S002000, C252S008610, C525S199000, C525S200000, C526S243000, C526S244000, C526S245000, C526S246000

Reexamination Certificate

active

06274060

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a water- and oil-repellent comprising a copolymer as well as textiles treated therewith.
A copolymer of (meth)acrylate (referred to hereinafter as “R
f
group-containing monomer”) containing a fluoroalkyl group (abbreviated hereinafter into “R
f
group”) and a hydrophilic group-containing monomer is known as a soil release agent (also referred to as “SR agent”) which confers water- and oil-repellency on fiber, fabric etc. and makes soil adhering to fibers easily removable by washing (cf. JP-A-53-134786, JP-A-59-204980, and JP-A-62-7782). However, soil releasability (SR property) and the durability of water repellency were not so good.
Recently, soil release agents with improvements in soil releasability and the durability of water repellency were developed (cf. JP-A-3-103411, JP-A-4-68006, and JP-A-6-116340). However, a considerable amount of polymers should be used to achieve satisfactory soil releasability.
Accordingly, the development of a water- and oil-repellent showing high soil releasability and durability even at low concentration had been desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a water- and oil-repellent which can be used as a soil release agent having better soil releasability than the conventional soil release agent.
The present invention provides a water- and oil-repellent comprising, as a major component (active ingredient), a copolymer comprising:
(a) a fluoroalkyl group-containing monomer having a melting point of 60 to 80° C. in the state of a homopolymer, and
(b) a hydrophilic group-containing monomer.
DETAILED DESCRIPTION OF THE INVENTION
The reason why the water- and oil-repellent comprising a copolymer of a R
f
group-containing monomer and a hydrophilic group-containing monomer exhibits higher soil releasability than that of a fluorine-containing water- and oil-repellent not containing the hydrophilic group-containing monomer is speculated by Sherman as follows [P. Sherman, S. Smith, B. Johannessen, Textile Research Journal, 39, 449 (1969)]. Since the R
f
group-containing compound has very low surface free energy, a fabric treated therewith exhibits high water- and oil-repellency in the air. On the other hand, the R
f
group-containing compound hardly exhibits oil-repellency in water. Hence, once oily soil adheres to the fabric, the oily soil is hardly removed by washing.
However, a copolymer comprising the R
f
group-containing monomer and the hydrophilic group-containing monomer can exhibit oil repellency even in water, thus facilitating the removal of oily soil by washing. The reason therefor is supposed to be that the R
f
group in the air emerges on the surface to make adhesion of soil difficult, and the hydrophilic group in water (during washing) emerges on the surface to render the surface hydrophilic, thus facilitating the removal of oily soil. The property that the molecular structure on the surface is altered depending on the environment, that is, in the air or in water, is called “flip-flop property” by Sherman et al.
The present inventors investigated the mechanism of exhibition of water- and oil-repellency and soil releasability in detail. As a result, the inventors proved surface-chemically that the flip-flop property is actually exhibited due to surface characteristics in air and in water, and polymers where the flip-flop property easily occurs are superior in soil releasability. A water- and oil-repellent superior in soil releasability to the conventional soil release agent can be realized by lowering the crystallinity of R
f
group in a polymer thin film to increase the motility of the polymer. On the other hand, if the crystallinity of R
f
group is too low, the oil repellency of the polymer in the air is lost, thus permitting oily soil to penetrate through a polymer thin film into the inside of fibers, and such oily soil is hardly removable by washing. That is, the crystallinity of R
f
group, which gives both good flip-fop property and good oil repellency in the air, is necessary.
The present invention improves further the soil release performance of the conventional soil release agent.
The melting point of a homopolymer arises from the crystallinity of R
f
group and can be measured by differential scanning calorimetry (DSC). The presence of crystals of R
f
group can be also confirmed by observing a peak derived from the self-aggregation thereof by wide-angle X-ray diffraction. Usually, crystallinity is expressed in terms of the degree of crystallization shown in the following equation:
[Degree of crystallization (%)]=
I
Rf
/(
I
Rf
+I
am
)×100
wherein I
Rf
is the intensity of a peak of R
f
group appearing at 2&thgr;=18°, and I
am
is the intensity of a peak of an amorphous region.
The monomer used in the present invention is explained hereinafter.
The monomer (a) is preferably a compound represented by the general formula:
R
f
—R
1
—X—R
2
C═CH
2
wherein R
f
is a C
3
to C
20
straight-chain fluoroalkyl group; R
1
is a C
1
to C
10
straight-chain or branched alkylene group; R
2
is a hydrogen atom or a methyl group; and X is —O—C(═O)— or —SO
2
—N(A
1
)—A
2
— in which A
1
is a C
1
to C
4
alkyl group and A
2
is a direct bond or —A
3
—O—C(═O)— in which A
3
is a C
1
to C
4
alkylene group. The melting point of a homopolymer comprising the monomer (a) is 60 to 80° C., for example 65 to 75° C.
The degree of crystallization of the homopolymer comprising the monomer (a) is preferably 50 to 85%, e.g. 60 to 80%.
The monomer (a) may be a mixture of at least 2 monomers.
A mixture of R
f
group-containing monomers which are different from one another in the chain length of R
f
group has been practically used as a soil release agent. For example, a mixture of fluoroalkyl(meth)acrylates containing C
8
, C
10
and C
12
in the R
f
groups (weight ratio of 5:3:1) has been used. This is because fluoroalkyl intermediates, which are produced industrially by telomerization between tetrafluoroethylene and CF
3
CF
2
I, are obtained as a mixture of perfluoroalkyl iodide telomers which are different from one another in the number of carbons.
The present inventors discovered that those polymers having a lower proportion of monomers having a longer chain of R
f
group (specifically the number of carbons in R
f
group is 10 or 12) among monomers having such a distribution in the chain length of R
f
group exhibit higher polymer motility, thus leading to superior soil releasability. For example, the present inventors discovered that use of fluoroalkyl acrylate having C
8
R
f
group, which is obtained through purification from fluoroalkyl acrylates (those having C
8
, C
10
and C
12
R
f
groups respectively in a weight ratio of 5:3:1) obtained by telomerization, provides a polymer with higher flip-flop property and thus with higher soil releasability than by use of the monomer mixture.
Specific examples of the R
f
group-containing monomer (a) are as follows:
CF
3
(CF
2
)
7
(CH
2
)
2
OCOCH═CH
2
;
a mixture of CF
3
(CF
2
)
5
(CH
2
)
2
OCOCH═CH
2
and
CF
3
(CF
2
)
7
(CH
2
)
2
OCOCH═CH
2
in a weight ratio of 2:8;
a mixture of CF
3
(CF
2
)
7
(CH
2
)
2
OCOCH═CH
2
and
CF
3
(CF
2
)
9
(CH
2
)
2
OCOCH═CH
2
in a weight ratio of 8:2;
a mixture of CF
3
(CF
2
)
7
(CH
2
)
2
OCOCH═CH
2
and
CF
3
(CF
2
)
11
(CH
2
)
2
OCOCH═CH
2
in a weight ratio of 9:1;
CF
3
(CF
2
)
7
SO
2
N(CH
3
)(CH
2
)
2
OCOCH═CH
2
;
CF
3
(CF
2
)
7
SO
2
N(C
2
H
5
)(CH
2
)
2
OCOCH═CH
2
;
CF
3
(CF
2
)
7
(CH
2
)
2
SO
2
N(CH
2
CH
3
)CH═CH
2
;
a mixture of CF
3
(CF
2
)
7
(CH
2
)
2
SO
2
N(CH
2
CH
3
)CH═CH
2
and
CF
3
(CF
2
)
9
(CH
2
)
2
SO
2
N(CH
2
CH
3
)CH═CH
2
in a weight ratio of 8:2;
a mixture of CF
3
(CF
2
)
7
(CH
2
)
2
SO
2
N(CH
2
CH
3
)CH═CH
2
and
CF
3
(CF
2
)
11
(CH
2
)
2
SO
2
N(CH
2
CH
3
)CH═CH
2
in a weight ratio of 9:1; and
CF)
3
(CF
2
)
7
(CH
2
)
2
SO
2
N(CH
3
)CH═CH
2
.
As the R
f
group-containing monomer (a), the monomer wherein the number of

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