Bulk recoverable nonwoven fabric, process for producing the same and method for recovering the bulk thereof

A bulk-recoverable nonwoven fabric comprising a nonwoven fabric of which constituting fiber is bonded to each other by an adhesive agent to bond fibers and which is fixed in a compressed state by a temporary adhesive agent having a melting temperature lower than the melting temperatures of the constituting fiber and the adhesive agent to bond fibers, a process for producing the bulk-recoverable nonwoven fabric and a method for recovering the bulk of the nonwoven fabric.

BACKGROUND OF THE INVENTION 
The present invention relates to a bulk-recoverable nonwoven fabric, a 
process for producing the same and a method for recovering the bulk 
thereof, and more particularly to a bulk-recoverable nonwoven fabric which 
can be preferably used as a wadding, a base material for a brassiere cup, 
a base material for a shoulder pad, a filter and the like, a process for 
producing the same and a method for recovering the bulk thereof. 
A bulky nonwoven fabric containing a large amount of air is generally used 
as a wadding for clothing such as sportswear and the like, a filter, and 
the like. Because the bulky nonwoven fabric contains a large amount of 
air, carrying or storing the bulky nonwoven fabric is the same as carrying 
or storing air. Accordingly, there is a disadvantage for cost because a 
considerable space is necessitated when a large amount of the bulky 
nonwoven fabric is carried stored in a storehouse. There is also a defect 
that it is inconvenient to handle the bulky nonwoven fabric when producing 
clothing and the like because the nonwoven fabric is bulky and soft. 
In order to overcome the above defects, a method for recovering the bulk of 
a bulky nonwoven fabric comprising wrapping the bulky nonwoven fabric with 
a film, removing air from the bulky nonwoven fabric to diminish the bulk 
of the bulky nonwoven fabric so that the nonwoven fabric can be easily 
carried or stored, and recovering the bulk of the nonwoven fabric by 
blowing hot air into the nonwoven fabric when the nonwoven fabric is used, 
is proposed in Japanese Examined Patent Publication No. 58086/1985. 
However, there are some disadvantages in the above method that the 
bulk-diminished nonwoven fabric is poor in recoverability to the original 
shape because the arrangement of the fibers of the bulky nonwoven fabric 
is influenced, and wrinkles or deformations generate when air is removed 
from the bulky nonwoven fabric. The method is also extreme in labour 
effectiveness because two processes of removing air from the nonwoven 
fabric and recovering the bulk of the nonwoven fabric by applying hot air 
are necessitated. The above method also has not yet been improved in 
processability because the nonwoven fabric should be used in a bulky state 
when clothing and the like are actually produced. 
In another method latently crimped fibers are compressed and fixed to each 
other with a powder resin having a low melting point when a nonwoven 
fabric is produced and the powder resin having a low melting point is 
remelted to recover the bulk of the nonwoven fabric by heating the 
nonwoven fabric to a temperature of about 150.degree. C. and then the 
nonwoven fabric is cooled to solidify the melted powder resin to give a 
nonwoven fabric having a novel shape when the nonwoven fabric is actually 
used, is known to the art. 
However, when a wadding is produced in accordance with the above method, 
the nonwoven fabric is fixed in a compressed state or a deformed state at 
the time of being subjected to a post processing of the wadding because 
the powder resin is melted when the wadding is heated. Further, the 
nonwoven fabric produced by the above method has a defect that the 
nonwoven fabric is poor in durability when the nonwoven fabric is 
subjected to dry-cleaning because the powder resin is poor in durability 
against a solvent as well as poor in thermal resistance, and the bonding 
of the fibers formed by the powder resin is destroyed. Also, since the 
fibers of the nonwoven fabric are merely fixed to each other by the powder 
resin, the nonwoven fabric lacks shape stability when the powder resin is 
reheated to melt the resin. Accordingly, it is not suitable for using such 
nonwoven fabric as a wadding. Further, since the bulk of the nonwoven 
fabric is recovered by heating to a temperature of about 150.degree. C., 
the influence of the heat on the fibers of the nonwoven fabric cannot be 
neglected. 
The object of the present invention is to provide a bulk-recoverable 
nonwoven fabric which is excellent in durability after the bulk of the 
nonwoven fabric is recovered, retains shape stability and processability 
when clothing and the like are produced and which can reduce the cost of 
storage, a process for producing the same, and a method for recovering the 
bulk thereof. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a 
bulk-recoverable nonwoven fabric comprising a nonwoven fabric of which 
constituting fibers are bonded to each other by an adhesive means to bond 
the fibers and which is fixed in a compressed state by a temporary 
adhesive agent having a melting temperature lower than that of the 
constituting fibers and the adhesive means used to bond the fibers. 
The present invention provides for a process for producing a 
bulk-recoverable nonwoven fabric comprising blending a constituting fiber 
with a thermally fusible fiber to form a web, bonding the web with an 
adhesive means to bond fibers to form a nonwoven fabric, pressing and 
heating the nonwoven fabric to melt the thermally fusible fiber, and 
fixing the nonwoven fabric in a compressed state. 
The present invention also provides for a method for recovering the bulk of 
the bulk-recoverable nonwoven fabric comprising heating the 
bulk-recoverable nonwoven fabric to a temperature of at least the melting 
temperature of the temporary adhesive agent but below the temperatures at 
which both the constituting fibers and the adhesive means used to bond the 
fibers melt, to recover the bulk of the bulk-recoverable nonwoven fabric.

DETAILED DESCRIPTION 
The bulk-recoverable nonwoven fabric of the present invention comprises 
(A) a nonwoven fabric of which constituting fibers are bonded to each other 
by an adhesive means to bond the fibers and 
(B) a temporary adhesive agent having a melting temperature lower than that 
of the constituting fibers and the adhesive means used to bond the fibers, 
and the nonwoven fabric is fixed in a compressed state by the temporary 
adhesive agent. 
The constituting fiber used in the present invention is not particularly 
restricted. However, it is preferable that the constituting fiber recovers 
the bulk of a nonwoven fabric largely when the temporary adhesive agent is 
melted to release the nonwoven fabric from the compressed state. 
Representative examples of the constituting fiber which can recover the 
bulk of the nonwoven fabric are, for instance, crimped fibers such as a 
highly crimped fiber, and the like. Among the crimped fibers, a latently 
crimped fiber is preferable because the latently crimped fiber reveals 
high crimping when being subjected to heating. 
The crimped fiber shows resilience when the temporary adhesive agent, which 
has been temporary bonded to the constituting fiber, is melted so that the 
adhesive strength of the temporary adhesive agent is lowered because the 
distorted crimped fiber recovers to the original state. The resilience 
acts as a force for recovering the bulk of the nonwoven fabric. 
Accordingly, it is preferable that a crimped fiber having a high 
percentage of crimp, high percentage of residual crimp and high percentage 
of crimp modulus is used. 
The crimped fiber having a high percentage of crimp, high percentage of 
residual crimp and high percentage of crimp modulus is intended to mean a 
crimped fiber having a crimp percentage of 12 to 70%, a residual crimp 
percentage of 7 to 70% and a percentage of crimp modulus of 30 to 100%. 
The values of the crimp percentage, percentage of residual crimp and 
percentage of crimp modulus are intended the mean to values when crimp is 
revealed. In case that crimp is not revealed, values when crimp is 
revealed are shown. 
Examples of the above crimped fiber are, for instance, a hollow fiber, a 
thick fiber having a fineness of at least 6 denier, a fiber having a large 
crimp radius, a fiber showing a three-dimensional spiral structure when 
being subjected to heating or humidifying, which is generally called as a 
highly crimped fiber, and the like. A fiber having a crimp of about 4 to 
about 30 per a length of 25 mm, which is produced by mechanically 
imparting the crimp can also be used other than the above-mentioned 
crimped fibers. 
The percentage of crimp, percentage of residual crimp and percentege of 
crimp modulus are defined as follows. 
A length (a) of a fiber is measured when an initial tension of 2 mgf per 1 
denier is loaded to a sample. A length (b) is measured when a tension of 
500 mgf per 1 denier is loaded to the sample. After the tension of 500 mgf 
is removed and the sample is allowed to stand for one minute, a length (c) 
is measured when an initial tension of 2 mgf per 1 denier is loaded to the 
sample. 
The percentage of crimp (%) and percentage of residual crimp (%) are 
calculated in accordance with the following equations. The test was done 
20 times, and each average of the percentage of crimp and percentage of 
residual crimp is calculated. 
##EQU1## 
The percentage of crimp modulus (%) is calculated in accordance with the 
following equation. 
##EQU2## 
As mentioned above, a fiber having a high percentage of crimp, high 
percentage of residual crimp and high percentage of crimp modulus can be 
preferably used other than a porous fiber, a fiber having a large fineness 
and a fiber having large crimp radius because the fiber is excellent in 
recoverability. 
The terminology "highly crimped fiber" is mainly intended to refer to a 
fiber having a high percentage of crimp, high percentage of residual crimp 
and high percentage of crimp modulus, and a fiber having a 
three-dimensional spiral structure in the instant specification. In the 
present invention, any of fibers having revealed crimps and fibers having 
latent crimps can be used. 
Examples of the fiber showing a three-dimensional spiral structure when the 
fiber is heated to shrink by means of dry heat or wet heat are, for 
instance, a conjugated fiber having revealed crimps, a conjugated fiber 
having latent crimps, a fiber consisting of one component showing crimp 
when being subjected to a specific heat history, and the like. 
Examples of the conjugated fiber are, for instance, a side-by-side type 
conjugated fiber, a core-sheath type conjugated fiber, an eccentric 
conjugated fiber, which are composed of two components of a polyester 
having a low melting point and a polyester having a high melting point, 
and the like. 
The fiber consisting of one component showing crimp when being subjected to 
a specific heat history is intended to mean a fiber to which a heat 
history is imparted by scratching the fiber with a heated edge during 
tensing the fiber or by scratching a heated fiber with an edge so that the 
arrangement of molecules of the fiber is distorted by touching the fiber 
with the edge. 
The fiber is shrunk to generate a three-dimensional spiral structure by 
applying heat in a state of dry heat or wet heat. 
The crimp may be present or latent when a bulk-recoverable nonwoven fabric 
has been produced. The fiber having latent crimps is desirable from the 
viewpoint of recovering the bulk largely because the fiber reveals crimp 
when the fiber is heated to recover the bulk. In general, the thickness of 
the nonwoven fabric in the direction of bulk becomes larger in accordance 
with increasing the number of crimp. To the contrary, the area of the 
nonwoven fabric in the direction of width becomes smaller because 
shrinkage occurs in the direction of width, Accordingly, when the nonwoven 
fabric is particularly required for dimensional stability, it is desirable 
that the crimp is revealed at the time the nonwoven fabric is produced. 
When a conjugated fiber having crimp latently or a fiber consisting of one 
component showing crimp when being subjected to a specific heat history is 
used as a fiber having revealed crimps, the crimp can be revealed by 
heating the fiber to a temperature generating the crimp after a 
bulk-recoverable nonwoven fabric is produced. 
In the present invention, an adhesive means to bond fibers is used in order 
to bond the constituting fibers to each other. The adhesive means used to 
bond the fibers may be either one of a thermosetting resin binder and a 
thermally adhesive fiber. 
The thermosetting resin binder and the thermally adhesive fiber act as a 
means for retaining the original shape of the nonwoven fabric when the 
nonwoven fabric is reheated to recover the bulk of the nonwoven fabric. As 
the adhesive means used to bond the fibers, a means, which is not affected 
by heating for melting the temporary adhesive agent and reheating for 
recovering the bulk of the nonwoven fabric, is used. 
Examples of a thermosetting resin binder are, for instance, 
self-crosslinking acrylic acid ester emulsion, a latex such as 
ethylene-vinyl acetate copolymer latex, polyvinyl acetate latex, polyvinyl 
chloride latex, synthetic rubber latex, polyurethane latex or polyester 
latex, into which a crosslinking agent is added, and the like. 
Among them, acrylic acid ester emulsion can be particularly preferably 
used. The reason why the acrylic acid ester emulsion can be preferably 
used is that the softness of a film of an adhesive agent prepared from the 
acrylic acid ester emulsion can be widely and easily adjusted in addition 
to that the acrylic acid ester emulsion is excellent in adhesion property 
and water resistance against polyester fiber which is frequently used as 
one of the constituting fibers of the nonwoven fabric. A resin binder 
having a melting temperature of at least 10.degree. C. higher than that of 
the temporary adhesive agent also can be used other than the thermosetting 
resin binder because the resin binder is little influenced by heating and 
reheating. 
Examples of a thermally adhesive fiber are, for instance, an all-fusible 
fiber composed of a resin such as non-stretched polyester, polyester 
having a low melting point or polyamide having a low melting point, a 
conjugated fiber of which one component is the above resin, and the like. 
It is desirable that the melting temperature of the thermally adhesive 
fiber is at least 10.degree. C., and preferably at least 20.degree. C., 
higher than that of the temporary adhesive agent. The melting temperature 
of the thermally adhesive fiber is preferably 100.degree. to 230.degree. 
C. 
In particular, when the constituting fiber is composed of a conjugated 
fiber, the component having a low melting point of the conjugated fiber 
can be used as an adhesive means to bond the fibers. In this case, there 
is no necessity to use the thermosetting resin binder and the thermally 
adhesive fiber. However, the melting temperature of the component having a 
low melting point should be higher than that of the temporary adhesive 
agent. 
The terminology "melting temperature" is intended to mean a temperature 
where a solid is melted, and solid phase and liquid phase coexist at 
equilibrium, which is generally referred to as the melting point when the 
solid is subjected to dry heating, or a temperature where a 
non-crystalline material is softened in the presence of water, and solid 
phase and liquid phase of the non-crystalline material which is to be 
liquid phase coexist at equilibrium in the presence of water when the 
non-crystalline material is subjected to wet heating. 
In the present invention, the temporary adhesive agent mentioned later 
should satisfy the above relations when the temporary adhesive agent is 
subjected to dry heating or wet heating. 
An example where a melting temperature at dry heating differs from a 
melting temperature at wet heating is explained hereinafter. The example 
is a case where the temporary adhesive agent is, for instance, polyvinyl 
alcohol. The polyvinyl alcohol shows a melting temperature of about 
120.degree. to about 150.degree. C. at dry heating. To the contrary, the 
polyvinyl alcohol generates adhesive strength at heating with a steam 
having a temperature of about 100.degree. C. because the polyvinyl alcohol 
is swollen and softened and then melted. 
Therefore, when the polyvinyl alcohol is subjected to wet heating, the 
temperature can be adjusted to about 100.degree. C. 
Accordingly, the melting temperature of the temporary adhesive agent 
sometimes depends upon the conditions such as whether the temporary 
adhesive agent is subjected to dry heating or wet heating. 
The temporary adhesive agent used in the present invention acts as an agent 
to temporarily diminish the bulk of the nonwoven fabric, i.e., to form a 
nonwoven fabric having a high density so that the nonwoven fabric can be 
easily treated at first and an agent to lower its adhesive strength to 
recover the bulk of the nonwoven fabric with a resiliency of the crimped 
fiber when the bulk of the nonwoven fabric is finally recovered. 
Therefore, the temporary adhesive agent having a melting temperature, at 
which the constituting fibers of the nonwoven fabric and the adhesive 
means for the fibers are not affected, is necessitated. It is an essential 
condition that the melting temperature of the temporary adhesive agent is 
at least 10.degree. C. lower than the melting temperatures of the 
constutiting fibers of the nonwoven fabric and the adhesive means for the 
fibers. It is particularly preferable that the melting temperature of the 
temporary adhesive agent is at least 20.degree. C. lower than fabric fiber 
melting temperatures. 
In the above conditions, it is preferable that the melting temperature of 
the temporary adhesive agent is at most 100.degree. C. The reason why the 
temperature being at most 100.degree. C. is preferable is because the 
constituting fiber of the nonwoven fabric is little affected and the bulk 
of the nonwoven fabric can be easily recovered by means of a conventional 
heating system when the nonwoven fabric is subjected to sewing. 
Examples of the form of the temporary adhesive agent are, for instance, 
fibrous, powdered, and the like. 
Representative examples of the fibrous temporary adhesive agent are, for 
instance, thermally fusible fiber, and the like. As the form of the fiber, 
a conjugated fiber and a single component fiber are exemplified. When the 
conjugated fiber is used in the present invention, the treatment can be 
easily carried out because only the component having a low melting point 
of the conjugated fiber is melted and the conjugated fiber is not 
excessively melted or adhered to the constituting fiber, therefore, the 
hand-feeling of the nonwoven fabric does not deteriorate. 
Representative examples of the conjugated fiber are, for instance, a 
conjugated fiber composed of polyester having a low melting point and a 
polyester having a high melting point, polyamide having a low melting 
point and a polyester having a high melting point, and the like. Examples 
of the form of the conjugated fibers are, for instance, side-by-side type, 
core-sheath type, islands-in-sea type, and the like. Since the melting 
temperature of the component having a low melting point of the conjugated 
fibers is generally about 80.degree. to about 100.degree. C., heating and 
reheating for recovering the bulk of nonwoven fabric can be carried out at 
a low temperature. Therefore, there are some advantages that energy can be 
reduced and operation efficiency is improved as well as no effect is 
imparted to the constituting fiber. 
It is not desirable that the ratio of the thermally fusible fiber to the 
other constituting fiber be too high because the nonwoven fabric is 
hardened and the constituting fiber is bonded in a deformed state when the 
nonwoven fabric is subjected to dry-cleaning after the bulk of the 
nonwoven fabric is recovered. On the other hand, when the ratio of the 
thermally fusible fiber is too low, the adhesive strength of the temporary 
adhesive agent comes to be insufficient as well as the dispersion of the 
thermally fusible fiber comes to be uneven. Accordingly, it is desirable 
that the content of the thermally fusible fiber in the fibers of the 
nonwoven fabric is 5 to 40% by weight, preferably 10 to 30% by weight. 
Representative examples of the temporary adhesive agent having a powder 
form are a powder resin having a low melting point and a water-soluble 
powder resin. 
Examples of a powder resin having a low melting point are, for instance, a 
powder resin having a melting temperature of at most 100.degree. C., 
preferably 80.degree. to 100.degree. C. or so such as polyamide, 
polyethylene or ethylene and vinyl acetate copolymer, and the like. 
Examples of a water-soluble powder resin are, for instance, water-soluble 
powder resin having a melting temperature of 80.degree. to 110.degree. C. 
or so in a state of wet heating such as polyvinyl alcohol, and the like. 
As mentioned above, the thickness of the nonwoven fabric of which 
constituting fibers are bonded to each other with the adhesive means used 
to bond the fibers can be diminished to 1/5 to 1/30 or so of the original 
thickness of the nonwoven fabric because the compressed state of the 
nonwoven fabric is maintained by the temporary adhesive agent when the 
nonwoven fabric is cooled in a compressed state after the nonwoven fabric 
is heated to a temperature of at most 100.degree. C. and compressed. 
The bulk of the nonwoven fabric can be recovered to 5 to 30 times of the 
bulk of the compressed nonwoven fabric by applying heat having the same 
temperature as mentioned above after the nonwoven fabric is subjected to 
transporting or carring, storing, sewing, and the like. 
The terminology "thickness" is intended to mean a thickness when a load of 
0.01 g per 100 mm.sup.2 of a sample is applied to the sample having a size 
of 250 mm.times.250 mm in the instant specification. 
A process for producing a bulk-recoverable nonwoven fabric of the present 
invention is explained hereinafter. 
The process for producing a bulk-recoverable nonwoven fabric differs 
depending upon whether a thermosetting resin binder or a thermally 
adhesive fiber is used as an adhesive agent to bond fibers, or whether a 
thermally fusible fiber or a powder resin having a low melting point is 
used as a temporary adhesive agent. 
When a thermally adhesive fiber is used as an adhesive agent to bond fibers 
and a thermally fusible fiber is used as a temporary adhesive agent, a web 
is produced by means of carding or the like after blending the 
constituting fiber, the thermally adhesive fiber and the thermally fusible 
fiber. A bulk-recoverable nonwoven fabric is produced by heating the web 
and fusing the thermally adhesive fiber to bond the constituting fibers of 
the web to each other. 
When a thermally adhesive fiber is used as an adhesive agent to bond fibers 
and a resin powder having a low melting point is used as a temporary 
ahdesive agent, a web is produced by means of carding or the like after 
blending the constituting fibers and the thermally adhesive fiber. A 
bulk-recoverable nonwoven fabric is produced by heating the web and fusing 
the thermally adhesive fibers to bond the constituting fiber of the web to 
each other and adding the resin powder having a low melting point to the 
web. 
When a thermosetting resin binder is used as an adhesive agent to bond 
fibers and a thermally fusible fiber is used as a temporary adhesive 
agent, a web is produced by means of carding or the like after blending 
the constituting fiber and the thermally fusible fiber. A bulk-recoverable 
nonwoven fabric is produced by bonding the thermosetting resin binder to 
the web to bond the constituting fibers of the web to each other. 
When a thermosetting resin binder is used as an adhesive agent to bond 
fibers and a resin powder having a low melting point is used a temporary 
adhesive agent, a web is produced by carding the constituting fiber, or 
the like. A bulk-recoverable nonwoven fabric is produced by bonding a 
thermosetting resin binder to the web and adding the resin powder having a 
low melting point thereto. 
In the above processes, it is preferable to blend highly crimped fiber in 
the constituting fiber. In this case, the content of the highly crimped 
fiber in the constituting fibers can be properly adjusted in accordance 
with the uses or useage of the bulk-recoverable nonwoven fabric. 
As mentioned above, when a resin powder having a low melting point is used 
as a temporary adhesive agent, it is difficult to produce a web by means 
of carding after blending the constituting fibers and the resin powder 
having a low melting point. For instance, when a resin powder having a low 
melting point is added to a web and the web is bonded with a thermosetting 
resin binder to give a nonwoven fabric, it sometimes occurs that the 
temporary adhesive agent does not act as an adhesive agent sufficiently 
because the binder envelops and bonds with the resin powder having a low 
melting point. Accordingly, the resin powder is added to a nonwoven fabric 
after the nonwoven fabric is produced in the present invention. 
The amount of the adhesive agent added to the constituting fibers differs 
depending upon the kind thereof. For instance, when the adhesive agent to 
bond fibers is a thermosetting resin binder, the amount (solids content) 
of the thermosetting resin binder is usually adjusted to 3 to 50% by 
weight, preferably 5 to 30% by weight of the nonwoven fabric. When the 
amount of the thermosetting resin binder is less than the above-mentioned 
range, there is a tendency that durability or strength of the nonwoven 
fabric becomes insufficient after the bulk of the nonwoven fabric is 
recovered. When the amount of the thermosetting resin binder is more than 
the above-mentioned range, there are tendencies that it is difficult to 
produce a bulky nonwoven fabric and only a nonwoven fabric having a small 
percentage of bulk recovery is produced, and that the hand-feeling of the 
nonwoven fabric comes to be hard after the bulk of the nonwoven fabric is 
recovered. 
When the adhesive agent is a thermally adhesive fiber, the used amount of 
the thermally adhesive fiber differs depending upon the kind of the 
thermally adhesive fiber. 
When the thermally adhesive fiber is an all-fusible fiber, the amount of 
the all-fusible fiber is adjusted so that the all-fusible fiber is 
contained in a nonwoven fabric in a content of 30 to 55% by weight, 
preferably 35 to 50% by weight. When the amount of the all-fusible fiber 
is less than the above-mentioned range, there is a tendency that 
durability for dry-cleaning and washing deteriorates after the bulk of the 
nonwoven fabric is recovered. When the amount of the all-fusible fiber 
exceeds the above-mentioned range, there is a tendency that producing a 
bulky nonwoven fabric comes to be difficult. 
When the thermally adhesive fiber is a conjugated fiber, the amount of the 
conjugated fiber is adjusted so that the conjugated fiber is contained in 
a nonwoven fabric in a content of 30 to 95% by weight, preferably 40 to 
90% by weight. When the amount is less than the above-mentioned range, 
there is a tendency that durability for dry-cleaning and washing 
deteriorates after the bulk of the nonwoven fabric is recovered. When the 
amount of the conjugated fiber exceeds the above-mentioned range, there 
are tendencies that a sufficient amount of a temporary adhesive agent 
cannot be blended into a nonwoven fabric and that the thickness of a 
nonwoven fabric comes to be so thin after the nonwoven fabric is subjected 
to pressing. 
As to the above-mentioned temporary adhesive agent, when the amount of the 
temporary adhesive agent is so large, there is a tendency that the 
temporary adhesive agent disturbs the bulk recovery of the nonwoven 
fabric, and when the amount of the temporary adhesive agent is so small, 
there is a tendency that a sufficient effect generated by adding the 
temporary adhesive agent is not exhibited. Accordingly, when the temporary 
adhesive agent is a thermally fusible fiber, it is preferable that the 
amount of the thermally fusible fiber is 5 to 40% by weight, desirably 10 
to 30% by weight of a nonwoven fabric. When the above-mentioned temporary 
adhesive agent is a resin powder having a low melting point, it is 
preferable that the amount of the resin powder having a low melting point 
is 5 to 40% by weight, desirably 10 to 30% by weight of a nonwoven fabric. 
Since the weight of the bulk-recoverable nonwoven fabric of the present 
invention depends upon the uses of the bulk-recoverable nonwoven fabric, 
and the like, the weight cannot be absolutely determined. For instance, 
when the bulk-recoverable nonwoven fabric is used as a wadding for 
clothing, it is preferable that the weight is about 30 to about 200 
g/m.sup.2. When the bulk-recoverable nonwoven fabric is used as a filter, 
it is preferable that the weight is about 50 to about 400 g/m.sup.2. 
The nonwoven fabric is heated to a temperature of at least 10.degree. C. 
lower than the melting temperatures of the constituting fiber and the 
adhesive agent to bond fibers, and pressed to give a nonwoven fabric 
having a thickness of 1/5 to 1/30 or so of the original nonwoven fabric. 
When the nonwoven fabric is heated, a part of the thermally fusible fiber 
is melted and the nonwoven fabric is fixed in a compressed state. 
Examples of a heating and pressing method are, for instance, roller 
pressing method, flat pressing method, and the like. The roller pressing 
method is preferable from the viewpoint of productivity because a nonwoven 
fabric can be continuously heated and pressed. 
When the nonwoven fabric is derived from a roller pressing device, flat 
pressing device or belt pressing device for heating and pressing a 
nonwoven fabric, the nonwoven fabric is fixed in a compressed state 
because the temporary adhesive agent is cooled to solidify and fixed at 
that time. It is desirable that the nonwoven fabric is allowed to cool or 
compulsively cooled after the heating while the nonwoven fabric is 
continuously kept in a compressed state in order to fix the nonwoven 
fabric more firmly in a compressed state. If the above heating and 
pressing process can be conducted while the temperature of the heated 
nonwoven fabric is not lowered, a step for pressing can be conducted after 
heating. 
In each of the above heating and pressing processes, the nonwoven fabric 
can be pressed on the whole surface or some spots of the surface. It is 
preferable that a nonwoven fabric is pressed on some spots of the surface 
because the nonwoven fabric is temporarily bonded at the spots, and as the 
result, the bulk of the nonwoven fabric can be easily recovered by 
reheating the nonwoven fabric. 
The thus produced bulk-recoverable nonwoven fabric recovers the bulk when 
the nonwoven fabric is subjected to a heat treatment at a temperature of 
lower than the melting temperatures of the constituting fibers and the 
adhesive means used to bond the fibers. It is preferable that the bulk of 
the nonwoven fabric is recovered by imparting steam in actuality because 
the bulk can be easily recovered. The recovery percentage and expansion 
ratio of the nonwoven fabric, which are defined as follows, are at least 
70% and at least 5 times, respectively. The bulk-recoverable nonwoven 
fabric of the present invention is excellent in various physical 
properties such as durability of washing and dry-cleaning before pressing 
the nonwoven fabric and after recovering the bulk of the nonwoven fabric 
in comparison with conventional nonwoven fabrics. 
##EQU3## 
When the bulk-recoverable nonwoven fabric is used in for instance, clothing 
and the like, it is preferable that the bulk of the nonwoven fabric is 
recovered after sewing is completed from the viewpoint of processability. 
However, when the bulk cannot be recovered after sewing because a heat 
treatment for recovering the bulk affects outer fabric or lining cloth of 
the clothing and the like, the bulk of the nonwoven fabric can be 
recovered after the nonwoven fabric is transported, stored or cut. 
As mentioned above, because the bulk-recoverable nonwoven fabric of the 
present invention can be diminished in the bulk before the nonwoven fabric 
is used, the nonwoven fabric has some advantages that the nonwoven fabric 
is convenient to handle when the nonwoven fabric is transported or stored 
and that costs for transporting or storing the nonwoven fabric can be 
reduce. 
The present invention is more specially described and explained by means of 
the following Examples. It is to be understood that the present invention 
is not limited to the Examples, and various changes and modifications may 
be made in the present invention without departing from the spirit and 
scope thereof. 
EXAMPLE 1 
Fibers comprising 90% by weight of a highly crimped polyester fiber 
(melting point: 256.degree. C., fineness: 3 denier, fiber length: 51 mm) 
as a constituting fiber and 10% by weight of a core-sheath type conjugated 
polyester fiber having a low melting point (core: polyester (melting 
point: 256.degree. C.), sheath: polyester having a low melting point 
(melting point: 87.degree. C.), fineness: 3 denier, fiber length: 51 mm) 
as a temporary adhesive agent were carded to form a web having a weight of 
55 g/m.sup.2. After that, a self-crosslinking acrylic acid ester emulsion 
as a binder was impregnated into the web to bond the constituting fiber of 
the web to each other and a nonwoven fabric having a weight of 60 
g/m.sup.2 was obtained. Some spots of the nonwoven fabric were compressed 
by means of a heating roller having a temperature of 100.degree. C. under 
the condition of a guage pressure of 2 kg/cm.sup.2. After 30 days, a steam 
having a temperature of 100.degree. C. was applied to the nonwoven fabric 
to recover the bulk. At that time, the recovery percentage was 85% and the 
expansion ratio was 11 times. 
The mixing ratio of the core-sheath type conjugated polyester fiber having 
a low temperature to a highly crimped polyester fiber was changed into 3, 
5, 15, 20, 30, 35, 40 or 45% by weight to give a web having a weight of 55 
g/m.sup.2. A self-crosslinking acrylic acid ester emulsion was impregnated 
into each of the webs to bond the constituting fiber of the web to each 
other and nonwoven fabrics having a weight of 60 g/m.sup.2 were obtained. 
Some spots of each of the nonwoven fabrics were compressed and heated in 
the same manner as in Example 1. After 30 days, steam having a temperature 
of 100.degree. C. was imparted to each of the nonwoven fabrics to recover 
the bulk thereof, and recovery percentage and expansion ratio were 
investigated in the same manner as in Example 1. The results are shown in 
Table 1. As is clear from Table 1, it can be seen that when the content of 
the core-sheath type conjugated polyester fiber is 5 to 40% by weight, 
preferable physical properties can be given to the nonwoven fabric. 
TABLE 1 
______________________________________ 
Content of core-sheath 
Experi- 
type conjugated polyester 
Recovery Expansion 
mental 
fiber having low melting 
percentage ratio 
No. point (% by weight) 
(%) (times) 
______________________________________ 
1 3 85 4 
2 5 85 9 
3 10 85 11 
4 15 88 16 
5 20 85 18 
6 30 80 15 
7 35 75 14 
8 40 70 13 
9 45 65 12 
______________________________________ 
After the nonwoven fabric containing 15% by weight of a core-sheath type 
conjugated polyester fiber obtained in Example 1 was allowed to stand for 
30 days, the bulk of the nonwoven fabric was recovered with steam having a 
temperature of 100.degree. C. 
For the reference, a conventional nonwoven fabric, which was neither 
compressed nor bonded, was prepared. 
As to the above two nonwoven fabrics, washing resistance and dry-cleaning 
resistance were examined. As the results, the washing resistance and 
dry-cleaning resistance of each of the above two nonwoven fabrics were 
Class 3 and Class 5, respectively. No change after pressing to bond was 
obserbed. The durability of the nonwoven fabric of the present invention 
was superior to that of the conventional nonwoven fabric. 
The testing methods for examining washing resistance and dry-cleaning 
resistance are as follows. 
[Washing resistance] 
A sample having a size of 250 mm.times.250 mm was prepared from the 
obtained nonwoven fabric. The sample was enveloped in a nylon taffeta and 
it was washed in a high stream of water by means of an automatic 
contrarotating washing machine for 90 minutes under the conditions that 
the temperature of water was 40.degree..+-.3.degree. C., the used amount 
of 0.2% synthetic detergent aqueous solution containing no phosphorous 
compounds was 32 l and loaded cloth was added to the washing machine so 
that the weight ratio of water to the sample and loaded cloth was 50 to 1. 
After the sample was subjected to washing with water, dehydration and air 
drying, the surface of the sample was observed. The evaluation was as 
follows. 
Class 5: No Change on the appearance was observed. 
Class 4: The nonwoven fabric was slightly deformed. 
Class 3: The nonwoven fabric was moderately deformed and unevenness 
generated. 
Class 2: Large deformation of the nonwoven fabric was observed and large 
unevenness generated. 
Class 1: The nonwoven fabric was remarkably deformed and the nonwoven 
fabric was partly destroyed. 
8 Dry-cleaning resistance] 
A sample having a size of 250 mm.times.250 mm was prepared from the 
obtained nonwoven fabric and enveloped in a nylon taffeta. As a detergent, 
a commercially available perchlene dry cleaner was used. Loaded cloth was 
used so that total amount of washing was 500 g. A process comprising 
washing for 8 minutes at a temperature of 25.degree. C., wasting solvent 
for one minute, taking off solvent for 4 minutes, drying for 5 minutes at 
60.degree. C. and deodorizing for 2 minutes was repeated 3 times. After 
that, the surface of the sample was observed. The evaluation was the same 
as in the above-mentioned washing resistance. 
EXAMPLE 2 
A highly crimped polyester fiber (melting point: 256.degree. C., fineness: 
3 denier, fiber length: 51 mm) as a constituting fiber was carded to form 
a web having a weight of 55 g/m.sup.2. A self-crosslinking acrylic acid 
ester emulsion as a binder was impregnated into the web to bond the 
constutiting fiber of the web to each other. After that, polyvinyl alcohol 
powder resin was dispersed onto the surface of the web in an amount of 10 
g/m.sup.2 to give a nonwoven fabric having a weight of 70 g/m.sup.2. Some 
spots of the nonwoven fabric were compressed by means of a heating roller 
having a temperature of 120.degree. C. under the condition of a guage 
pressure of 3 kg/cm.sup.2. After 30 days, steam having a temperature of 
100.degree. C. was applied to the nonwoven fabric to recover the bulk. At 
that time, the recovery percentage was 80% and the expansion ratio was 7 
times. 
The washing resistance and dry-cleaning resistance of the nonwoven fabric 
were Class 3 and Class 5, respectively. The nonwoven fabric exhibited 
excellent durability, which was the same as that of a nonwoven fabric 
which was neither compressed nor fixed. 
Comparative Example 1 
Fibers comprising 80% by weight of a highly crimped polyester fiber 
(melting point: 256.degree. C., fineness: 3 denier, fiber length: 51 mm) 
and 20% by weight of a core-sheath type conjugated polyester fiber having 
a low melting point (core: polyester (melting point: 256.degree. C.), 
sheath: polyester having a low melting point (melting point: 87.degree. 
C.), fineness: 4 denier, fiber length: 51 mm) as a constituting fiber were 
carded to form a nonwoven fabric having a weight of 60 g/m.sup.2. Some 
spots of the nonwoven fabric were compressed by means of a heating roller 
having a temperature of 100.degree. C. under the condition of a guage 
pressure of 2 kg/cm.sup.2. After 30 days, steam having a temperature of 
100.degree. C. was applied to the nonwoven fabric to recover the bulk. At 
that time, the recovery percentage was 40% and the expansion ratio was 6.5 
times. 
The washing resistance and dry-cleaning resistance were Class 1 and Class 
2, respectively. Accordingly, the nonwoven fabric had a problem in 
durability. 
Comparative Example 2 
A highly crimped polyester fiber (melting point: 256.degree. C. fineness: 3 
denier, fiber length: 51 mm) as a constituting fiber was carded to form a 
web having a weight of 49.5 g/m.sup.2. A polyamide powder resin having a 
low melting point was applied onto the web in a ratio of 10.5 g per 1 
m.sup.2 of the web to give a nonwoven fabric having a weigh of 60 
g/m.sup.2. After that, some spots of the nonwoven fabric were compressed 
by means of a heating roller having a temperature of 100.degree. C. under 
the condition of a gauge pressure of 2 kg/cm.sup.2. After 30 days, steam 
having a temperature of 100.degree. C. was applied to the nonwoven fabric 
to recover the bulk. At that time, the recovery percentage was 40% and the 
expansion ratio was 4.5 times. 
When the dry-cleaning resistance of the nonwoven fabric was examined, it 
was Class 2 to 3. The durability of the above nonwoven fabric was inferior 
to that of the nonwoven fabric in which a resin binder was used. 
Since the obtained nonwoven fabric was poor in shape stability, a test of 
washing resistance could not be conducted to the obtained nonwoven fabric. 
EXAMPLE 3 
Fibers comprising 60% by weight of a highly crimped polyester fiber 
(melting point: 256.degree. C., fineness: 3 denier, fiber length: 51 mm), 
30% by weight of a core-sheath type conjugated polyester fiber having a 
low melting point (core: polyester (melting point: 256.degree. C.), 
sheath: polyester having a low melting point (melting point: 110.degree. 
C.), fineness: 4 denier, fiber length: 51 mm) and 10% by weight of a 
core-sheath type conjugated polyester fiber having a low melting point 
(core: polyester (melting point: 256.degree. C.), sheath: polyester having 
a low melting point (melting point: 87.degree. C.), fineness: 3 denier, 
fiber length: 51 mm) were carded to give a web having a weight of 60 
g/m.sup.2. After that, heat having a temperature of 150.degree. C. was 
applied to the web so that the constituting fibers were bonded to each 
other, and a nonwoven fabric was obtained. 
Some spots of the nonwoven fabric were compressed by means of a heating 
roller having a temperature of 100.degree. C. under the condition of a 
guage pressure of 2 kg/cm.sup.2. After 30 days, a steam having a 
temperature of 100.degree. C. was applied to the nonwoven fabric to 
recover the bulk. At that time, the recovery percentage was 45% and the 
expansion ratio was 8 times. 
The washing resistance and dry-cleaning resistance were Class 3 and Class 
3, respectively. The nonwoven fabric exhibited preferable durability which 
was the same as the nonwoven fabric which was not compressed to fix the 
constituting fiber. 
EXAMPLE 4 
Fibers comprising 90% by weight of a core-sheath type conjugated fiber 
having a low melting point (core: polypropylene, sheath: polyethylene 
(melting point: 130.degree. C.), fineness: 14 denier, fiber length: 76 mm) 
as a constituting fiber and 10% by weight of a core-sheath type conjugated 
polyester fiber having a low melting point (core: polyester (melting 
point: 256.degree. C.), sheath: polyester having a low melting point 
(melting point: 87.degree. C.), fineness: 3 denier, fiber length: 51 mm) 
as a temporary adhesive agent were carded to give a web having a weight of 
300 g/m.sup.2. After that, heat having a temperature of 150.degree. C. was 
applied to the web to bond the constituting fibers of the web, and the 
thickness of the web was adjusted by means of a heating roller to give a 
nonwoven fabric having a thickness of 20 mm. 
Some spots of the nonwoven fabric were compressed by means of a heating 
roller having a temperature of 110.degree. C. under the condition of a 
guage pressure of 4 kg/cm.sup.2. After 3 days, steam having a temperature 
of 100.degree. C. was applied to the nonwoven fabric to recover the bulk. 
At that time, the recovery percentage was 105%, and the expansion ratio 
was 11 times. 
As to the nonwoven fabric, initial pressure loss and collection efficiency 
of dust as an air filter were examined. Under the conditions of a wind 
speed of 2.5 m/sec and a dust concentration of 22.3 mg/m.sup.3, the 
initial pressure loss and collection efficiency were examined. As the 
result, the initial pressure loss was 10 mm Aq, and the average collection 
efficiency of dust was 80% until the pressure loss attained to 20 mm Aq. 
As is clear from the above results, the nonwoven fabric satisfies the 
physical properties required for an air filter. 
EXAMPLE 5 
Fibers comprising 10% by weight of a core-sheath type conjugated polyester 
fiber (core: polyester (melting point: 256.degree. C.), sheath: polyester 
having a low melting point (melting point: 87.degree. C.), fineness: 3 
denier, fiber length: 51 mm) as a temporary adhesive agent and 90% by 
weight of a core-sheath type conjugated polyester having a low melting 
point (core: polyester (melting point: 130.degree. C.), sheath: polyester 
having a low melting point (melting point: 125.degree. C.), fineness: 2 
denier, fiber length: 51 mm) as a constituting fiber were carded to give a 
web having a weight of 50 g/m.sup.2. After that, heat having a temperature 
of 150.degree. C. was applied to the web to bond the constituting fibers 
of the web, and some spots of the web were compressed by means of a 
heating roller having a temperature of 100.degree. C. under the condition 
of a guage pressure of 2 kg/cm.sup.2 to give a nonwoven fabric. 
After 3 days, steam having a temperature of 100.degree. C. was applied to 
the nonwoven fabric to recover the bulk. At that time, the recovery 
percentage was 90%, and the expansion ratio was 12 times. 
With respect to the obtained bulk-recoverable nonwoven fabric and a 
conventional nonwoven fabric (weight: 50 g/m.sup.2, produced by applying a 
heat of 150.degree. C.) composed of a polyester fiber (melting point: 
256.degree. C.) of which constituting fiber was not compressed to bond to 
each other, washing resistance and dry-cleaning resistance were examined. 
As the results, each of the washing resistance was Class 4, and each of 
the dry-cleaning resistance was Class 4, respectively. As to the nonwoven 
fabric of the present invention, no change caused by compressing to bond 
was observed. 
Reasonable modification and variation are within the scope of this 
invention which is directed to a novel bulk-recoverable nonwoven fabric.