U.S. patent number RE30,955 [Application Number 06/039,748] was granted by the patent office on 1982-06-01 for fibrous product.
This patent grant is currently assigned to Imperial Chemical Industries Limited. Invention is credited to Harold P. Stanistreet.
United States Patent |
RE30,955 |
Stanistreet |
June 1, 1982 |
Fibrous product
Abstract
A resilient, thermally bonded, non-woven fibrous batt having a
uniform compression modulus in one plane which is more than the
compression modulus measured in a direction perpendicular to that
plane, and a substantially uniform density across its thickness is
obtained by preparing a batt comprising at least 20% by weight of
crimped and/or crimpable conjugate fibres having or capable of
developing a crimp frequency of less than 10 crimps per extended
cm. and a decitex in the range of 5 to 30. The batt is thermally
bonded by subjecting it to an upward flow of a fluid heated to a
temperature sufficient to heat the batt to a temperature in excess
of the softening temperature of the low softening component but
below the softening temperature(s) of the other component(s) of the
conjugate fibre to effect inter-fibre bonding. The thermally bonded
batt is then cooled by an upward flow of cool air.
Inventors: |
Stanistreet; Harold P.
(Harrogate, GB2) |
Assignee: |
Imperial Chemical Industries
Limited (London, GB2)
|
Family
ID: |
10050632 |
Appl.
No.: |
06/039,748 |
Filed: |
May 16, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
673547 |
Apr 5, 1976 |
04068036 |
Jan 10, 1978 |
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Foreign Application Priority Data
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Apr 11, 1975 [GB] |
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14962/75 |
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Current U.S.
Class: |
156/308.2;
156/497; 156/498; 156/555; 442/353; 442/409 |
Current CPC
Class: |
D04H
1/54 (20130101); D04H 1/544 (20130101); D04H
1/549 (20130101); D04H 1/55 (20130101); D04H
1/541 (20130101); Y10T 428/2922 (20150115); Y10T
442/638 (20150401); Y10T 442/608 (20150401); Y10T
442/629 (20150401); Y10T 442/641 (20150401); Y10T
442/637 (20150401); Y10T 442/69 (20150401); Y10T
428/2929 (20150115); Y10T 428/268 (20150115); Y10T
156/1741 (20150115) |
Current International
Class: |
D04H
1/54 (20060101); C09J 005/00 () |
Field of
Search: |
;428/296
;156/308.2,497,498,555 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bell; James J.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What I claim is:
1. In a method for the production of a low-density, high porosity,
resilient, thermally bonded, non-woven fibrous batt having a
substantially uniform density across its thickness by the steps of
forming a lofty fibrous batt from at least 20% by weight of
conjugated staple fibres having a length of 0.5 to 6 inches and
being selected from the group consisting of crimped and potentially
crimpable fibres, the conjugate fibres being composed of at least
two fibre forming polymeric components arranged in distinct zones
across the cross-section of the fibre and substantially continuous
along the length thereof, one of the components having a softening
temperature significantly lower than the softening temperature of a
second component and being located so as to form at least a portion
of the peripheral surface of the fibre, subjecting said batt to a
heat treatment to heat the batt to a temperature in excess of the
softening temperature of the component having the lower softening
temperature but below the softening temperature of the second
component to effect inter-fibre bonding, and then causing .[.or
permitting.]. the batt to cool, the improvement comprising heating
the batt by passing a heated gas upwardly through the batt, the gas
having a temperature sufficient to effect thermal bonding of the
conjugate fibres and having a velocity such that the batt is
supported by the gas in a high-porosity condition without
disintegrating the batt therein .Iadd.and causing the batt to cool
by an upward passage of cooling air through the batt to quench the
fibres and permit them to rapidly redevelop their modulus,
.Iaddend.whereby the resulting batt has substantially uniform
density across its thickness. .[.2. A method for the production of
a resilient, bonded, non-woven fibrous batt as in claim 1 including
cooling the thermally bonded batt by
an updraught of cold air..]. 3. A method for the production of a
resilient, bonded, non-woven fibrous batt as in claim 1
including
compressing the thermally bonded batt before the cooling stage. 4.
A method for the production of a resilient, bonded, non-woven
fibrous batt as in claim 1 wherein the fibres have or are capable
of developing a crimp
frequency of less that 10 crimps per extended centimeter. 5. A
method for the production of a resilient, bonded, non-woven fibrous
batt as in claim 1 wherein the conjugate fibres have or are capable
of developing a crimp frequency of less than 10 crimps per extended
centimeter and a decitex in
the range 5 to 30. 6. A method as in claim 1 wherein the upward
stream of gas blows the batt against a foraminous surface disposed
above the batt. .[.7. An improved low density, high porosity,
resilient, thermally bonded, non-woven fibrous batt having a
substantially non-uniform density across its width, made by the
process of claim 1..].
Description
The present invention relates to the production of a bonded,
non-woven, fibrous batt.
It is known to produce such a batt by compressing an open (e.g.
carded) web or batt comprising crimpable and bondable conjugate
fibres, and then heating the batt to crimp the conjugate fibres and
to effect interfibre bonding. It is also known to produce such a
product by initially heating crimpable and bondable conjugate
fibres at a temperature sufficient to crimp and stabilise the
fibres without effecting interfibre bonding, forming the fibres
into an open (e.g. carded) non-woven web or batt, heating the batt
to a temperature sufficient to effect inter-fibre bonding, and
cooling the batt to form a bonded, integral structure. Moreover, it
is also known to form a batt of heat stabilised, crimped conjugate
fibres, heating the batt to effect interfibre bonding, and
subsequently compressing the batt to the desired density and shape
whilst hot.
By the term "fibre" is meant a fibre of staple length of 0.5 to 6
inches, preferably from 1 to 5 inches. The term "conjugate fibre"
refers to a fibre composed of at least two fibre-forming polymeric
components arranged in distinct zones across the cross-section of
the fibre and substantially continuous along the length thereof,
and wherein one of the components has a softening temperature
significantly lower than the softening temperature(s) of the other
components(s) and is located so as to form at least a portion of
the peripheral surface of the fibre. Types of conjugate fibres
within this definition, for example, include those wherein a
component of low melting temperature is (a) one of two components
arranged side-by-side, or (b) forms a sheath about another
component serving as a core, or (c) forms one or more lobes of a
multilobal fibre. Fibres in which the polymeric components are
asymmetrically arranged in the cross-section thereof are
potentially crimpable in that they tend to develop crimp when
subjected to a heat treatment. In contrast, fibres in which the
polymeric components are symmetrically arranged do not have a
propensity to crimp, and must therefore be crimped by mechanical
action, such as, for example, by the stuffer-box method.
In the known processes for producing a bonded non-woven fibrous
batt interfibre bonding is effected by passing an unbonded batt of
fibres through an oven, especially an oven through which the batt
travels on a brattice and hot fluid, for example steam or air, is
blown downwards onto the batt. This downward flow of hot air tends
to compress the batt and consequently affects the physical
properties of the resultant bonded product, in particular the
density thereof. The process of the present invention seeks to
reduce the degree of compression of the batt during interfibre
bonding and to provide bonded non-woven fibrous batts having new
characteristics.
Therefore, according to the present invention there is provided a
method for the production of a resilient, bonded, non-woven fibrous
batt wherein a batt, comprising at least 20% by weight of crimped
and/or potentially crimpable conjugate fibres (as hereinbefore
defined), is subjected to a heat treatment by the upward passage
through the batt of a fluid having a temperature sufficient to heat
the batt to a temperature in excess of the softening temperature of
the lower softening component but below the softening
temperature(s) of the other component(s) to effect inter-fibre
bonding, and then causing or permitting the batt to cool.
Optionally the hot, bonded fibrous batt may be compressed to a
desired shape and/or density before it is cooled. In a preferred
process, the thermally bonded batt is cooled by an updraught of
cold air to quench the fibres so that they rapidly redevelop their
modulus, and any tendency for the batt to collapse is reduced or
even eliminated.
The conjugate fibres may have or be capable of developing a crimp
frequency in excess of 10 crimps per extended cm. of fibre, but
particularly useful products may be obtained from conjugate fibres
having or capable of developing a crimp frequency of less than 10
crimps per extended cm., and desirably in the range of 2 to 4
crimps per extended cm.
Preferably the initial, unbonded batt comprises at least 50% by
weight of crimped and/or crimpable bondable conjugate fibres, and,
desirably, is composed wholly of such fibres. In those
circumstances where non-conjugate fibres are present, the
non-conjugate fibres are preferably crimped and heat stabilised
under conditions similar to those used for bonding the conjugate
fibres, and, preferably, are also compatibly bondable with the
conjugate fibres.
The crimp of potentially crimpable conjugate fibres may be
developed before the batt is prepared. Thus the uncrimped conjugate
fibres may be carded and formed into a batt by cross-layering and
the batt heated to a temperature sufficient to develop the crimp of
the fibres but not sufficiently high to effect inter-fibre bonding.
The batt is then recarded before being subjected to an upward flow
of hot fluid to bond the fibres. However, the recarding is not
essential since the upward flow of gas tends to keep the batt open
during crimp development.
Normally the fibres may have a decitex within a wide range, for
example 1 to 50 decitex. Conveniently, fibres having a decitex in
the range 5 to 30 are employed. The process is particularly useful
for producing non-woven fibrous products of low density from fibres
having a low decitex.
The density of the batt prior to bonding according to the present
invention is conveniently the natural carded density, i.e. that
normally produced by the carding machine, and which, though
variable, is usually of the order of 0.005 gm/cm.sup.3. If desired,
of course, the density may be varied to suit the density required
of the final product. The batt may be built up to varying
thicknesses, if desired, by utilising a cross-lapping machine.
Inter-fibre bonding is effected by passing the batt through an oven
in which a heated fluid is blown upwards through the batt, for
example, through a fluidized bed of ballotini which evens out the
air flow and acts as a heat exchanger. The velocity of the fluid
should be sufficient to support the batt during its passage through
the oven, and to prevent compacting of the fibres, but not
sufficient to break the batt. Disintegration of the batt by the use
of very high velocities may be reduced by imposing above the batt a
foraminous surface and against which the batt is blown. The fluid
may be any inert gas, such as, for example, air, or it may be
admixed with or comprised solely of a plasticizing agent, for
example steam in the case of nylon fibres. Before cooling, the
bonded fibrous batt may optionally be compressed to a desired
shape, for example, by compressing the batt between heated, shaped
platens, or to a required density, for example, by passing it
through a pair of rollers. Excessive compression is to be avoided
in order to produce a product having a low density, high porosity,
open "sponge-like" structure, and not a high density, "felt-like"
structure.
An advantage of the process of the present invention is that it is
possible to obtain a resilient, thermally bonded, non-woven,
fibrous batt comprising at least 20% by weight of crimped conjugate
fibres, the fibrous batt having a substantially uniform density
across its thickness. The process is particularly useful for
producing bonded batts having a substantially uniform density
across its thickness from carded batts having a thickness greater
than 1.5 cms and especially greater than 4 cms. The process may be
used for bonding carded batts having a thickness of 20 cms. or even
greater.
The process of the present invention is also useful for producing
shaped articles having a minimum thickness of at least 1.5 cm., the
carded batt being thermally bonded by the upward passage of the
heating fluid, and then compressed to the desired shape. In the
resulting product the ratio of number of bonds per unit volume to
the density of the unit volume is substantially constant throughout
the entire product. By contrast, shaping of the unbonded batt by
compression followed by the passage of hot fluid causes tracking of
the fluid which results in uneven thermal bonding.
The products of the invention may be utilized in the production of
pillows, mattresses, and upholstery, for example.
The invention will be further described by way of example with
reference to the following examples.
EXAMPLE 1
A 12 decitex per filament conjugate staple fibre having a length of
2 inches and a crimp level of 3 crimps per extended cm. was
prepared. The fibre was of the sheath/core (1:2) type in which the
core was polyethylene terephthalate and the sheath polyethylene
terephthalate-isophthalate (80:20 mole %). The crimp was produced
by stuffer-box crimping.
The staple fibre was fully opened by one passage through a carding
machine and was built up into a batt having a thickness of 5 cms.
using a lap wheel. Three layers were placed on top of each other,
and the combined layers were heated in an oven in which air at a
temperature of 210.degree. C. and at a flow rate of 15 cfm was
passed through a fluidized bed of ballotini (which acted as a
heated exchanger) and upwards through the non-woven web. The
velocity of the air was sufficient to prevent the fibres from
compacting without displacing the fibres.
After cooling, a 13 cm. cube was cut out of the resulting
non-woven, fibrous batt and each side subjected to a compression
load of 5 kg. The vertical direction, as made, compressed 30% while
at right angles, i.e. horizontal directions, the compression was
only 4%. The product had a density of 0.019 gm per cc.
EXAMPLE 2
Staple conjugate fibre (20 decitex per filament) having a length of
49 mm. and slight crimp was produced from equal proportions of
nylon-66 and nylon-6 spun in a side-by-side configuration, and was
fully opened by one passage through a Tatham (Regd. Trade Mark)
carding machine. The thus obtained web was cross folded to form a
lofty batt having a thickness of 150 mm. which was then subjected
for 1.5 minutes to super-heated steam having a temperature of
230.degree. C. blown vertically upwards through the batt at a
velocity of 30 feet per minute. The steaming caused the fibres to
develop fully their crimp, and to bond to each other. Finally, the
batt was compressed to a thickness of 60 mm., cooled to 180.degree.
C. in steam, and then to ambient temperature by an upward draught
of air. The resulting non-woven fibrous structure had a thickness
of 60 mm. and a density of 0.026 gm. per cc.
EXAMPLE 3
Core/sheath (67:33) conjugate filaments (12 dpf), the core
comprising poly(ethylene terephthalate) and the sheath
polypropylene, were stuffer box crimped (8 crimps per extended
cm.), heat set, and cut to a staple length of 49 mm. The staple was
fully opened by one passage through a Tatham (Regd. Trade Mark)
carding machine and cross-folded to give a batt having a thickness
of 60 mm. The batt was subjected for 1 minute to an up-draught of
air having a temperature of 175.degree. C. and a velocity of 50
feet per minute, by passing it through an up-flow air oven. This
treatment caused the fibres to bond together. Afterwards the batt
was compressed whilst hot to a thickness of 30 mm. and then cooled
by an upward flow of air to give a structure having a density of
0.023 gm. per cc.
EXAMPLE 4
Side/side conjugate filaments (6 dpf) were spun from equal amounts
of poly(ethylene terephthalate) and a copolymer of poly(ethylene
terephthalate) containing 20 moles percent of poly(ethylene
isophthalate), the filaments then being stuffer-box crimped (6
crimps per extended cm), heat set, and cut to a staple length of 50
mm. A mixture of this fibre with an equal weight of the staple
core/sheath fibre of Example 3, was opened and blended using a
Shirley (Regd. Trade Mark) miniature carding machine, and formed
into a batt having a thickness of 120 mm. on a lap wheel. The batt
was subjected for 1.5 minutes in an up-flow oven to an up-draught
of air having a temperature of 215.degree. C. and a velocity of 50
feet per minute. The resulting batt was compressed to a thickness
of 70 mm and cooled to give a non-woven structure having a density
of 0.03 gm. per cc.
EXAMPLES 5 AND 6, AND COMPARATIVE EXAMPLES A AND B
Staple fibre used in Example 2 was carded and formed into a batt
having a thickness of 150 mm. The batt was divided into several
aliquot portions. The samples were heated at different temperatures
in an up flow oven, according to the present invention, or in a
down flow oven according to the known processes of bonding. The air
velocity in the up-flow oven was 50 feet per minute whereas that in
the down flow oven was 500 feet per minute. The average density of
each bonded sample was measured and then cut in a horizontal plane,
the density of the upper and lower halves then being measured.
Conditions of the experiments and the density of the products are
given in table I below.
TABLE I ______________________________________ Temp. of Density
(gm. per cc) Type of Air Aver- Upper Lower Oven (.degree.C.) age
half half ______________________________________ Example 5 207
0.010 0.010 0.010 Up flow Example 6 215 0.012 0.011 0.012
Comparative Examples A Down flow 207 0.023 0.013 0.044 B 215 0.037
0.017 0.063 ______________________________________
The results given in the table clearly show that the non-woven
structures of the present invention have a substantially uniform
density throughout their thickness whereas the structures produced
by known methods vary considerably in density.
EXAMPLES 7 TO 10
Conjugate staple fibres spun from equal proportions of nylon-66 and
nylon-11, and having a decitex of 10 per filament, were converted
into a lofty batt having a thickness of 50 mm. Portions of this
batt were then subjected to an upward flow of air heated to a
temperature of 185.degree.-190.degree. C., the velocity being
varied.
TABLE II ______________________________________ Velocity of air
(feet per min.) Effect on loftiness of batt
______________________________________ Example 7 22 Some reduction
in thickness. 8 61 Very slight reduction in thickness 9 79 No
change in thickness 10 92 Some fibers blown from surface.
______________________________________
The results of the experiments, given in table II, show that the
velocity of the updraught of the bonding fluid has some effect upon
the resultant non-woven structure. The actual effect will depend
upon the conditions employed, such as, the nature of the fibres,
the weight and thickness of the unbonded batt, and the
characteristics of the oven used.
* * * * *