Artificial leather

Details Artificial leather Artificial leather

2001-03-21

2003-04-29

Seidleck, James J. (Department: 1711)

Stock material or miscellaneous articles

Composite

Of polyamidoester

C428S446000, C428S447000, C528S044000, C528S070000

Reexamination Certificate

active

06555230

ABSTRACT:

BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to artificial leather, and more specifically to artificial leather excellent in surface properties such as water repellency, oil resistance, abrasion resistance and non-tackiness in which a resin layer arranged on at least one side of a base sheet comprises a novel fluorine-containing polyurethane.
b) Description of the Related Art
Artificial Leather with a polyurethane layer arranged on at least one side of a base sheet such as a woven fabric or non-woven fabric has been used widely for many years. The polyurethane layer of such artificial leather is required to be excellent in stain resistance, waterproofness, abrasion resistance and non-tackiness, and depending on the application, is also required to be low in the coefficient of surface friction.
Polyurethane is obtained basically by reacting a palyol, a polyisocyanate and optionally, a chain extender, and depending on the kinds and combinations of these components, polyurethanes of various physical properties can be provided. It is to be noted that the term “polyurethane” as used herein collectively means polyurethane, polyurea and polyurethane-polyurea.
Processes have been proposed to copolymerize an organic fluorine compound with such polyurethane to impart properties of the organic fluorine compound, such as water repellency and oil repellency, non-tackiness, abrasion resistance and stain resistance, while retaining the inherent good properties of the polyurethane.
For example, polyurethanes each of which is obtained by copolymerizing a one-end diol having a perfluoroalkyl group are proposed in JP S43-26518 B, JP S61-252220 A, etc.
As a conventional process for the preparation of a one-end diol (the term “one-end diol” as used herein means “a compound having two hydroxyl groups at only one end of its molecule”) having a perfluoroalkyl group (which, including a perfluoroalkenyl group, will hereinafter be abbreviated as “the R
f
group”), a process which proceeds following such a reaction scheme as will be described next is known.
As is appreciated from the foregoing, the conventional processes for the preparation of one-end diols having the R
f
group all require many steps. High-purity products of the one-end diols having the R
f
group are hence costly, so that these conventional processes have a problem in their-practical use on an industrial scale.
In polyurethanes each of which is available by copolymerizing a one-end diol having the R
f
group as in the conventional art, on the other hand, any attempt to make the polyurethanes exhibit functions of fluorine by increasing the contents of fluorine in the polyurethanes leads to reductions in certain inherent properties of the polyurethanes such as rubber elasticity and mechanical strength and accordingly, results in artificial leather of inferior flexibility, softness and strength. Such an attempt is therefore not preferred.
This is attributed to properties of the R
f
groups that the resulting polyurethane molecules are not easily bendable, are stiff and tend to orient in a particular direction, because fluorine atoms are very bulky and produce strong repulsion therebetween. As a result, a polyurethane is considered to be reduced in rubber elasticity due to inhibition to the freedom of the thermal motion of soft segments in the molecules and to be reduced in strength due to inhibition to aggregation of hard segments in the molecules. Namely, the above-described problem is considered to be caused for the reason that in a polyurethane, R
f
groups derived from the conventional R
f
-containing one-end diol give strong effects on the polyurethane backbone due to short distances between the R
f
groups and the polyurethane backbone.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to solve the above-described problems of the conventional art and hence, provide artificial leather composed of a polyurethane which is formed of an economical material and is excellent in water repellency and oil repellency, stain resistance, abrasion resistance, non-tackiness and the like.
The present inventors have proceeded with an extensive investigation to develop an economical process for the preparation of a one-end diol having an group, resulting in development of a novel preparation process. Further, the present inventors have also found that use of a fluorine-containing polyurethane, which employs the R
f
-containing one-end diol available from the process, makes it possible to achieve the above-described object, leading to completion of the present invention.
The above-described object can be achieved by the present invention as will be described hereinafter.
In one aspect of the present invention, there is thus provided artificial leather having a base sheet and at least one resin layer arranged on at least one side of the base sheet, wherein the resin layer comprises a polyurethane having side chains derived from a fluorine-containing diol represented by the following formula (I):
wherein R
f
represents a perfluoroalkyl or perfluoroalkenyl group having 1 to 20 carbon atoms; X represents a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenylene group represented by —CH═CH—(CH
2
)
n
— in which n stands for an integer of from 1 to 10, or
in which n stands for an integer of from 0 to 6; Y represents a direct bond, —O—, —NH—, or —R
0
—NH— in which R
0
is an alkylene group having 1 to 6 carbon atoms; Z represents a direct bond or —N(R′)R— in which R is an alkylene group having 1 to 20 carbon atoms and R′ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R
1
and R
2
each independently represent a divalent organic group; and R
3
represents a residual group of an aliphatic, alicyclic or aromatic diisocyanate.
Owing to the formation of the resin layer, which is arranged on the base sheet, with the fluorine-containing polyurethane containing R
f
s in its side chains, the artificial leather according to the present invention is provided with excellent surface properties—such as water repellency and oil repellency, stain resistance, abrasion resistance and non-tackiness—along with the superb rubber elasticity and strength properties inherent to the polyurethane and the fluorine compound, respectively.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The present invention will next be described in further detail based on certain preferred embodiments. The artificial leather according to the present invention is characterized in that the polymer layer arranged on at least one side of the base sheet comprises the polyurethane having side chains derived from the fluorine-containing diol represented by the formula (I), that is, the R
f
-containing one-end diol.
The polyurethane for use in the present invention can be obtained by a conventional process for the production of polyurethanes, namely, by reacting the R
f
-containing one-end diol represented by the formula (1), an active-hydrogen-containing compound and a diisocyanate, optionally in the presence of a chain extender. The R
f
groups in the polyurethane, said R
f
groups being stiff and having strong orientation, are located at ends of side chains and are spaced at least a predetermined distance from the backbone. Moreover, the R
f
groups are each bonded to the backbone of the polyurethane via a urethane bond or a urea bond, so that enhanced compatibility exists between the side chains and the polyurethane backbone and the freedom of motion of soft segments and the aggregation of hard segments in the polyurethane are not inhibited by the R
f
groups. Accordingly, the use of the fluorine-containing polyurethane has made it possible to provide the artificial leather with excellent surface properties—such as water repellency and oil repellency, stain resistance, abrasion resistance and non-tackiness—along with the superb rubber elasticity and strength properties inherent to the polyurethane and the fluorine compound, respectively.

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