Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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2126-
SYNTHETIC DOWN CL~STERS
FIELD OF THE INVENTION
This invention relates to synthetic down clusters. More
particularly, this invention relates to light-weight thermal
insulation systems achieved by use of fine fibers in low density ~
cluster assemblies. ~ -
BACKGROUND OF THE INVENTION
Donovan, U.S. Patent No. 4,588,63~ presents a useful
discussion of the physics and mechanics of fiber assemblies and
describes and claims a synthetic fiber batt thermal insulation
which contains a specific intimate blend of fibers of two dis~
tinct diameters. The predominant fine microfiber species pro-
vides the thermal barrier characteristics, and the lesser pro~
portion of large diameter macrofiber enhances the mechanical
properties required in a practical insulator. The concept of
providing an optimum combination of thermal and mechanical
performance through the provision of a blend of fine and coarse
fibers was extended in Donovan et al., U.S. Patent No. 4,992,327,
which describes a bonded version of the '635 invention wit~ even
more advantageous mechanical properties.
There has been considerable activity over the past few years
in the gene~al area of high performance thermal insulation, and
several other patents have issued which embody various combina-
' 209~l17~
tions of fibers in a range of configurations, each exploiting andclaiming particular advantages. Examples of such patents include
U.S. Patent No. 4,118,531 to Hauser, U.S. Patent No. 4,304,817 to
Frankosky, U.S. Patent No. 4,551,378 to Carey, and U.S. No.
5,043,207 to Donovan and Skelton. These patents provide a good
overview of this area, which has developed to a high degree of `
sophistication.
One feature which most of the above patents have in common
is that they provide, as an end point, a thermal insulating batt.
That is, the product is available as extended sheets, and it is
usually supplied to the user in roll form. This is highly bene~
ficial to most users since the roll form is easy and convenient
to handle in the layout and cutting stages of the making-up
process, and the cost-effectiveness of the downstream manufac~
turing process is enhanced. However, it is important to realize
that a considerable industry exists which is devoted to the ;;
manufacture of end-use insulating items which utilize down as a ;~
filling agent, and the manufacturing techniques employed by this
traditional segment of the industry are completely different from
those which utilize batts. The essential difference is that down
filling is a collection of discrete individual units, and the
transport and placement of large numbers of these units is nor~
mally carried out using high volume, low velocity air streams,
rather than by direct manipulation of a coherent batt.
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Over the past several years, enormous progress has been made
in devising insulation materials based on synthetic polymeric
fibers which approach or even equal the thermal performance of
down, and the physical parameters which control this performance
are well understood, as reflected in the above mentioned patents.
~here has been much less progress, however, in providing a syn~
thetic insulator which not only exhibits the excellent thermal
properties of down, but also is capable of being handled in the
traditional down processing equipment. One of the above-refer-
enced patents, U.S. No. 4,992,327, describes insulation in
"cluster" form, the particular examples being small rolled balls
having the same fiber characteristics and properties as the batt
insulation which forms the subject of the primary claim. These
clusters exhibit excellent thermal and mechanical performance,
and subsequent investigations have shown that they can be pro-
cessed using commercial down handling equipment. However, the -~
clusters do not have a visual appearance which matches that of ;
down, and they have not yet found acceptance as a viable down
substitute.
~..... . .
Other attempts have been made to imitate the look as well as
the performance of down, and some success has been claimed. U.S.
Patent No. 4,418,103 describes a product and a technique for
achieving this objective, in which a large number of crimped
fibers are joined together at one end and are spread spherical-
ly from the joined end. Various advantageous combinations of
fiber sizes and crimp densities are suggested, and the product
. - .- -- - .' ^: ,
209~ ~7~
described is similar in appearance to some down units. The
thermal performance of the example described is equivalent to
that of medium quality down, and the mechanical behavior is very
good. The process described for the manufacture of these units
does not appear to be particularly cost-effective, and there is
no evidence that a commercial product made according to these
claims has appeared in the U.S. market in the ten years since the
patent issued.
Another attempt to provide ~ true ~synthetic down" is
reflected by U.S. Patent No. 3,892,909. Several embodiments of
possible structures are described, and the principal claims
describe "bodies comprising a myriad of fibers formed into a
rounded configuration which is capable of being repeatedly de~
formed in the manner of a spring ...." This invention, similar
to the previous one mentioned, places emphasis on achieving a
rounded configuration, either cylindrical or spherical, which ;~
attempts to mimic some aspects of natural down. While this may
be of value from both a performance and appearance point of view,
it appears that it can only be achieved by paying a heavy penalty
in terms of slow production rate, and it has not led to commer- ~ -
cial success.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of an embodiment of the - ; -
invention; and
: '
-- 2~9~'i70
Fig. 2 is a schematic flow chart of a preparation procedure
according to the invention.
DESCRIPTION OF THE INVENTION
The present invention concerns a down-like filling material
made up of an assemblage of discrete individual units, each unit `~
having a geometric configuration designed to optimize the ther-
mal insulating properties of the assembly. The individual units
are made up of a supporting member of a predetermined length,
whose dimensions and mechanical properties are such that the
member has sufficient rigidity to maintain its extended configu~
, . . . .
ration, to which is attached an array of fine fibers whose prin~
cipal function is to provide the thermal barrier properties of
the assembly. The two components of the units must act coopera~
tively if the optimum thermal properties are to be achieved.
This can be achieved if the fine fibers form a generally dis~
persed array, and the distribution of fine fibers along the
supporting element is generally uniform. ~he length of the
fringe of fine fibers and the length of the support element can
vary over a wide range, bu~ there are some important limitations
on the relative dimensions and proportions of the two components
if an optimum assembly is required.
The simplest configuration which satisfies the above concept
is a length of monofilament support material to which is adhe-
sively attached a planar array o~ fine, more-or-less parallel
fibers, with the sllpport filament and the fibers that make up the
., ~ , , . .. , . .. , .. . .. ~, .. . ... .. .. .. ... . . ........... . . ... . .
. . , . - ~ , -
~ 2~95~17~
fringe being substantially perpendicular and the support filament
attachment points being located near the center line of the
fringe. While this configuration is simple and symmetrical, it
should not be considered as limiting, and many variations are
possible which still preserve the essential features of the ~ ~
concept. -
The fine fiber array is capable of wide variation within the -~;
essential framework of this invention. One of the simplest and
most direct ways of providing this array is to make use of spread
multifilament tow, using a process similar to that described in
U.S. Patent No. 3,423,795 to Watson, incorporated herein by
reference, but it is also possible to achieve the same effect
through the use of a creel or warp beam which feeds individual
filaments or untwisted multifilament yarns or tows through a reed
in a side-by-side configuration. The essential feature that is
common to these techniques is that they are capable of providing
a thin layer of filaments held in a more-or-less parallel side-
by-side configuration. This layer of filaments is then
subse~uently modified by the attachment of a multiplicity of
bonding and support members which cross the array at a high
angle, after which the partially bonded layer of fila-ments is
subdivided to form a number of separate sub units, each of which
consists of a finite length of bonded support member to which are
attached a large number of crossing fibers and which form one of
-~
the embodiments of this invention.
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The use of spread multifilament tow is a very cost-effective
way of producing large quantities of the thin fiber sheet
material that forms the precursor to the invention, and it is the
preferred means of practicing the art, but under certain circum-
stances the other techniques are appropriate. The provision of a
parallel array of filamentary materials is very common in textile
processing: it is found in the feed systems of weaving looms,
warp knitting machines, and tufting machines, and it is also an
essential component of prepreg lines for the production of
impregnated yarns for composites manufacturing. All of these
systems can be modified to act as the source for the fine fila-
mentary array that provides the starting point for the production
of the units of the present invention.
The simple configuration described above involves a support
member which is a monofilament adhesively attached to the array
of fine crossing filaments. This embodiment is made by laying an
adhesively coated monofilament material down in contact with the `
thin fiber array, so that the monofilament provides both a sup~
port and a bonding function. The actual geometrical configura-
tion of the monofilament is not important. In its usual sense
the word monofilament implies an entity with a generally circular
cross section, but the cross section can be of any shape, and it
is possible to provide the same function with a flattened strip
of polymer with a rectangular or other elongate cross section
shape formed by cutting a narrow ribbon of material from a thin
2 ~ ~ ~ 1 r~
sheet of polymer. In this embodiment it is only necessary to
have an adhesive layer on one side of the ribbon.
In the embodiments described above the monofilaments or
ribbons are provided with a separate layer of adhesive material,
but it is possible to combine the two functions - support and
bonding - into a single entity. In this embodiment a line of
adhesive is laid down directly across the fine filament array
from a suitable nozzle in sufficient quantity that it is capable
of providing the support function in its own right when it is
set, dried and cured. This is equivalent to combining the
extrusion step of a melt spun filament with the laydown step and -~
can provide a highly cost-effective way of making the product if
the material type and disposition are properly chosen. It is
also possible to produce a bonded and supported array of fine
fibers by fusing or bonding a section of the fine fiber in situ
using, for example, a hot wire or an ultrasonic bonder under
carefully controlled conditions. The objective is to melt and
fuse an extended linear region of the fine fibers under con~
trolled conditions so that the partially melted fibers stick
together locally and the resolidified melt line has sufficient
stiffness and integrity to constitute a support member. In this
embodiment no material additional to the fine fiber array is -~
: . : ~ -- -
involved in the system and the weight penalty is minimized, but
it is difficult to achieve all the mechanical requirements of the
support member by this means.
` ~9~'17~
In the discussion above, attention has focused on mono-
filament material or its analogue for the support member. This
is a convenient simplification from the descriptive viewpoint,
but it is not an exclusive one, and the support member can
equally well be a multifilament or spun yarn, or a combination
of the two. The discussion has also dealt almost entirely with
adhesive or other direct ~onding to achieve the necessary integ-
rity. Another way to bond the fine filament array is to use
mechanical entangling to attach the support member to the fine
fiber array, and this can be achieved very effectively by sewing
a line of stitching across the fine fiber array. In this way the `
line of stitching, which may be made up of monofilament or multi-
filament yarn or a combination of the two, not only provides a
mechanical interlocking which holds the fine fiber array in
place, it also can be made sufficiently stiff that it can act as ` ;
the support member without the need for any additional adhesive.
This, too, provides a mec~anically efficient and cost-effective ~ -~
way of practicing the elements of the invention.
The invention can perhaps be better appreciated by refer-
ence to Figs. 1 and 2. A unit assembly 1 comprised an array of
fine fibers 2 which has a support member 3. The array 2 has been
attached in substantially linear fashion to support member 3. ;
2~9~7~
In the schematic flow chart shown in Fig. 2, material com-
prising substantially parallel fibers 10 is treated in step (b)
to space the fibers 10 apart, and macrofibers 11 are interwoven
through fibers 10 in step (c). Then, in step (d), the material
is cut in the area of dotted lines 12, which are substantially
parallel to macrofibers 11. The assemblies 14 resulting from
step (d) are cut perpendicularly, that is, perpendicular to the
longitudinal axis, in step (e) to form the unit assemblies 15
shown in (f).
The materials of choice for the two components of the indi-
vidual units of this invention are preferably polymeric, particu-
larly if a thermal barrier application is contemplated, since the
thermal conductivity of the materials which make up the units can
~ . .
be minimized by this choice. However, the concept is not limited
to polymeric materials, particularly for the fine fiber compo-
, . , ; : , , . .. : ~ :
nent, and fiber arrays of ceramic, carbon or glass materials can
be used. If a polymeric assembly is required, it can be produced
from any of the synthetic fiber-forming polymers in commercial
use, including, without limitation, polyester, nylon, rayon, ace-
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tate, acrylic, modacrylic, polyolefins, spandex, poly-aramides,
polyimides, fluorocarbons, polybenzimidazols, polyvinylalcohols,
polydiacetylenes, polyetherketones, polyimidazols and phenylene
sulphide polymers such as RYTON. The assemblies could also be
made by incorporating any of the natural fibers such as, for
example, silk, cotton, wool or flax, provided that the requisite
dimensional and mechanical criteria for the components are met. ;
~ ~ 2 0 ~ 7 ~)
The range of possible design parameters for the assemblies
of this invention can be estimated by considering the geometric
properties of the assemblies. Consider a unit volume of an
assembly of fibers of density pf, denier d, and total length e:
If the assembly fiber volume fraction is Vf, then:
e = g x 105 V~ pf / d
and for an assembly of polyesters fibers with density pf = 1.41
at a volume fraction Vf = 0.0l, this expression simplifies to: ~ ~ ~
. , ~;. '-
e = 12690/d
The information inherent in this relationship is given in Table Ibelow, which covers the entire range of filament slzes that are
of practical interest:
Table I
nimensional Characterist~cs of Sinale species Fiber Assemblies
_
¦Diameter Total Length
Denier I~Nicrometer~) (cm)
=
0.1 3.2 126900 _
0.5 7.1 25380
l l
1.0 _ 10.0 12690 I ; ,
5.0 22.7 _ 2538 ~ ~
_ I
10.0 31.6 1269
50.0 70.7 254
100.0 100.0 127
500.0 227.0 25.4
l _ l
1000.0 316.0 12.7 l
I . _ ' ~ . '
11
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The information in Table I is valid for unit volume of
assemblies which contain fibers with a single diameter. In the
present invention, there are at least two distinct fiber species
present, and this has an effect on the statistics of the assem-
bly. The fiber units of the invention have a large number of
fine fibers, which contribute the insulating properties of the
material, attached to a support element, which can also be a
fiber, which controls the spacial distribution of these fine
fibers. In order to do this effectively, this support element
must be stiffer, and hence larger in diameter than the fine-fiber
array; consequently, it makes a considerable contribution to the
weight of the assembly and dilutes the insulating properties of ,~
the fine-fiber array. If we are attempting to create a high ~ ~ ;
performance insulator with a low value of thermal conductivity,
then there is an upper limit to the amount of large denier fiber
that can be tolerated. If this can be kept at less than 10% of
the total fiber mass, then the thermal conduc~ivity increase is
held to an acceptable value and the assembly has adequate thermal
performance. The information of Table I can be used to evaluate ~;
some features of assemblies containing both fine and coarse ~-
fibers and to determine those combinations that are practical.
Table I may be divided into two sections on the basis of
diameter. Fibers falling within the range of 0.1 to 5.0 denier
may be considered as insulating fibers, although the insulation
performance at both ends of this range is compromised by the
physics of the heat transfer process, as is explained in U.S.
Patent No. 4,992,327, incorporated by reference. Filaments
12
-~`` 20~5~
falling within the range of so to looo denier may be considered
support fibers. Fibers with linear densities around 10 denier
are not particularly effective providers either of insulation or
mechanical support, and insulating assemblies containing signi~
ficant components of fibers of this size exhibit mediocre all-
around performance. If a mixture containing 90% of insulating
fibers and 10% of support fibers is considered, then the possible
combinations are shown in ~able II below, together with a typical
example, embodying fibers selected near the center of the avail-
able ranges. This example would have a total of approximately -
20,000 cm of fine fibers attached to a total of about lo cm of
support filament contained within each cubic centimeter of fiber
assembly.
Table 11
Dimensional Characteris~ics of Mixed flber Assemblies :~
_ _ r -
Length (om)
Diameter Insulation Support of Fiber in
(Micro- Length~ength Typical
Fun¢tionDenier meters) (90%)~10%) Combination
_ l _ . : ~
0.1 3.2 114210 ~
0.5 7.1 22842 I ;
Insulation 1.0 10.0 11421 -20,000 l
5.0 22.7 2284 _ l ~ -
Transition 10.0 31.6 _
50.0 70.7 25
100.0 100.2 13
Support 500.0 227.0 2.5 ~10
1000.0 316.0 1.3 ~
_ .
The range of these constructional parameters can be narrowed
further by consideration of additional details of the structures
13
. ~ . ` .'.' ; . ;; . j :,;
~9~ 70
of the present invention. One of the preferred techniques for
forming the product of this invention is to attach the support
fiber in a more-or-less perpendicular manner across a thin array
of essentially parallel fine filaments. In order to achieve the
maximum loft in the final configuration, these fine filaments
should be dispersed to the maximum extent possible at the points ~-
where they attach to the supporting fiber. Optimum dispersion
will occur when the fine fibers lie in a single layer at the ~ ~
attachment points, with the mean spacing between individual ~ -
filaments being the maximum that the geometry of the system will
allow. The minimum spacing occurs when this microlayer array of ~ -
fine filaments is in side-by-side contact, and this represents a `
limiting configuration for the array. If a 2 cm lPngth is chosen
as representative for the fine fiber array, the total number of
2 cm fibers per centimeter of support filament can be calculated, ~ ~ ;
as shown in Table II, and if the calculated fine fiber diameter
is used to define the minimum space that a single fiber can ~ -
occupy, we arrive at the minimum total length of support filament
needed to satisfy the maximum dispersion requirement. Better
dispersion would be achieved if the fibers were allowed to spread
more than this. ;~
It can be seen from Table III below that for fine fiber
diameters in the 1.0 denier range, a fiber size that is fine
enough to give good thermal properties and is at the same time
large enough to be handleable by equipment designed to give a
uniform spread sheet of fibers, the side-by-side configuration
requires about 6 cm of support filament in each cubic centimeter ;
14
-~. 2 ~ 7 9
of assembly, which in turn determines that the support filament
can be no larger than about 200 denier. An array in which the ~-
l.o denier fibers are spaced apart by 1 to 2 fiber diameters will
require as much as 20 centimeters of support per cubic centi~
meter, and according to Table III this length is not a~ailable
unless the support filament is considerably smaller than about -~
100 denier. The need to provide a match between the space
required for the array of fine fibers and the available length of
the support filament effectively sets a practical upper limit to
the size of the support filament. At the other end of the range
an adequate level of support cannot be provided mechanically if
the denier drops below the 10 denier level at which the thermal
and support functions have been segregated.
From this consideration of the basic geometric parameters of
the system rational selections for the range of sizes for the
thermal and support elements can be made. The thermal fibers
should be within the range of 0.1 to 5.0 denier, and preferably
within the range 0.5 to 1.5 denier, and the support element must
lie within the range 50 to 1000 denier, and preferably approxi- ~ -
mately 500 denier. If the fiber sizes show any significant
digression beyond these ranges, the geometric relationships be-
come difficult to fulfil and the thermal and mechanical perform~
ance of the assembly will be rapidly compromised.
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_ X A M P L E S ~ -~
:
Examples of down-like clusters in accordance with the pre-
sent inventlon were prepared and their geometric, mechanical and
thermal properties were evaluated. The clusters of these par-
ticular examples were made by laying a thin uniform sheet of
opened continuous filament polyester tow between two sheets of
manilla paper and subsequently sewing through the paper/tow/paper
assembly using parallel lines of stitching running perpendicular
to the general overall direction of the filaments in the spread
tow. Three different tows were used to produce the examples:
Example 1 incorporated a spread tow of 0.5 denier polyester
filaments; Example 2 incorporated a spread tow of 1.2 denier ~`
polyester filaments; and Example 3 incorporated a spread tow of
5.0 denier polyester filaments. In all cases the iines of
stitching were made using 322 denier mercerized, cotton-covered,
polyester-core sewing thread, at a stitch density of 15 to 20
stitches per inch for Example l and 12 stitches per inch for
Examples 2 and 3. The parallel rows of stitching were spaced
apart by about 33 mm in all cases.
After stitching the sandwich assemblies were cut into strips -~ ;
along lines located half way between the rows of stitching. The
outer layers of paper were then removed from the strips to reveal
long lengths of fiber fringes anchored by the lines of stitching.
. . ~,.
17
:
2~'17~
These fringed strips were then cut into short lengths to yield a
collection of down-like clusters. The geometrical and gravi~
metric parameters of clusters of the three examples are given in
Table IV: the measurements were made on 10 samples selected at
random from the various assemblies. The information relative to
the support elements (stems) was found by cutting off the fringe ;
fibers and removing the resi~ual fine fiber material from the
lines of stitching. ; ~;
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L~ ~ = ~ = L~
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2139~ll7~ :
The fine filaments in these three examples are representa-
tive of a range for the practical production of high performance
insulation materials according to the invention. At linear
densities significantly smaller than 0.5 denier the thermal
properties of the low density fiber assemblies begin to increase
because of increased radiative heat transfer; moreover, the
mechanical problems associated with the production of an open
more-or-less parallel array of fibers may become prohibitive.
The 0.1 denier value chosen as the lower limit of fringe fiber
linear density in the tables herein represents a valid and justi~
fiable limit for this particular concept. The fringe length (33
mm) and the length of the support element (45 mm) chosen for
these examples are close to the values used in the representative
calculations leading to the information that is embodied on
Tables I through IV, but these values should not be considered as ;-~
limiting. The fringe fiber length in the practical examples was
chosen as representative of the filament length in natural down
clusters, and it is well suited to the practicality of the
manufacturing technique. The upper level of this parameter has
not been determined, but simple order of magnitude calculations
on the mechanics of deformation of fine fibers suggests that
organized arrays of fine fibers (<0.5 denier) are only marginally
self-supporting if the fiber length exceeds more than a few tens
of millimeters.
2~9&~7~
The length of the clusters may vary. In experimental
studies clusters up to 220 mm in length were investigated, but
most of the work was concentrated on the range 25 to 40 mm, with
the choice again driven by a desire to match the general dimen-
sions of natural down clusters. Experience suggests that this
parameter can be selected on the basis of convenience in the
manufacturing process and practicality in the application stage,
since there does not seem to be any fundamental physical limits
to its value.
The examples of down-like materials described in Table IV
have been evaluated for mechanical and thermal behavior. In
general, an assembly of each of these units behaves very much
like the natural down that it is intended to emulate, in that the
assembly behaves in compression like a semi-coherent mass but
when agitated each of the individual units is free to move with
respect to its neighbor, and this provides an effective mechanism
for the establishment and maintenance of a very low density
assembly. The mechanical and thermal properties of these assem~
blies were measured under standard test conditions, and were
compared with MIL-Spec down and with PRIMALOFT~ insulating
material, a commercial bonded batt insulator available from
Albany International Corp. The test conditions are described
below~
D~nsity: The volume of each insulator sample was
determined by fixing two planar sample dimensions and
21
2 ~ 9 ~
then measuring thickness at 0.014 KPa (0.002 lb/in2)
pressure. The mass of each sample divided by the
volume thus obtained is the basis for density values
reported herein.
Thickness was measured at 0.014 kPa (0.002 lb/in2).
Apparent Thermal Conductivity was measured in accord-
ance with the plate-sample/plate method described by ~-~
ASTM Method C518. In each case the test specimen
thickness was 52.9 mm (2.08 in), the test density was
8.0 Kg/m3 (0.5 lb/ft3), and the heat flow was upward
with a temperature differential of 28C (50F) and a ~ ;
mean temperature of 23C (74F).
Com~ressional Recovery and Work of Compression and Recoverv:
Section 4.3.2 of Military Specification MIL-B-41826E des-
cribes a compressional-recovery test technique for fibrous
batting that was adapted for this work. The essential
difference between the Military Specification method and the
one employed is the lower pressure at which initial thick~
ness and recovered-to-thickness were measured. The measur-
ing pressure in the ~ilitary Specification is 0.07 kPa (0.01
lb/in2) whereas 0.014 kPa (0.002 lb/in2) was used in this
work. - - ~-
The down used throughout the examples was actually a
down/feathers mixture, 80/20 by weight, per MIL-F-43097G, Type II
22
-~ 2~'17~
Class I. This mixture is commonly and commercially referred to
as "down" and is referred to as ~down~' herein.
The three sets of samples described in Table I~ were
evaluated using the test methods described above. The results of :~
the mechanical tests are given in Table V, and the results of the ~ :
thermal tests are given in Table VI. Note that mechanical tests
were carried out on two distinct variants of Examples 2 and 3 in
which only the length of the individual units was changed; in ~ :
each case the short units have a length of 150 to 220 mm and the
long units have a length of 25 to 40 mm.
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q~ ~DI O ~ 1 ~ 1 O ~ I
a~ o ,~ ,~ ,~ ~ ~
_ r _ _ _ I
.~ ~ ~i
I ~7 I r~ ~ ~i ~1 ~r u~ ~ I :
1 D ~O OD D CO U.
I
C .~ ~ . ~ . ;.. ,. .. ,i
a l X . ~ ~
~ ~ r ~ v ~ :~
I ~ I O O
a ~ ¦ ~ ' o ' o ~
I V ~ ~ ~ o ',;
¦ L~ L _ H . ~
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0 I ,~
I _ _ _
h ~ S~ ~ C:
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l~ h I u~ ~ o !~ : ~ :
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___= ' ' : '''
s i~
The most noticeable feature of these results is the low
minimum density and the higher compressional recovery of the
downlike clusters compared with the PRIMALOFT batt, which repre-
sents good performance for fine fibers in a batt configuration.
The low minimum density of the new down-like product is attribut-
able directly to the fact that the assembly is made up of a large
number of discrete, individual units which are free to move inde-
pendently when they are agitatedl and this permits the establish-
ment of a very low density assembly, exactly as is the case with
down. The minimum density achieved in these examples of the new
units is not quite as low as that which is achievable with down,
but there is no doubt that this property could be fine-tuned by ;
manipulation of the geometric parameters of the units. The
PRIMALOFT batt contains a blend of fibers very similar to that
found in Example 1, but the fibers making up ~he PRIMALOFT
assembly are effectively bonded together to create an integral
entity and this bonding, while providing excellent mechanical
stability against disruptive influences, acts to prevent the
establishment of a low density condition by unassisted recovery
or by agitation. Another direct manifestation of the advantages ~ ~ -
of the ability of the new configuration is the high values of
compressional recovery that are given in Table V. In this case
the superiority of the examples over both PRIMALOFT batt and down
is clear, and the values of compressional recovery that are
reported in this table are extraordinarily high.
~r
The thermal behavior of the examples is presented in Table
VI, which also gives comparison data for samples of batt made
from 100% of the same fiber types as were used in the fine fiber
fringes for the various examples of the invention. This permits
a direct evaluation of the deleterious thermal effect of the
presence of the support element that was referred to in an
earlier section, and it is clear that the percentage increase in
thermal conductivity has been held close to the 10% level that
was judged to be acceptable. In addition, thermal data is also
given for the down sample of Table VI as comparison, and it can
be seen that the thermal conductivity of the fine fiber sample is -~
quite similar to that of down and that the thermal behavior is -~
rapidly compromised if the diameter of the fringe fiber is
increased. This finding is in complete agreement with the find~
ings of previous mvestigations of this phenomenon as reported in
U.S. Patents Nos. 4,588,635 and 4,992,327 and emphasi7es that the
ultimate in thermal barrier performance will only be obtained if ~i
fine fibers are used for the fringe. In many cases experience ~
has shown that the mechanical performance of fiber assemblies is ~ -
diminished as the fiber diameter decreases, but this does not
seem to be a significant feature of the assemblies of the new
configurations, as Table V demonstrates. The recovery from
compression is certainly improved as the fiber diameter
increases, but even at the smallest diameters the compressional
recovery is excellent. Accordingly, the most advantageous com-
bination of thermal and mechanical performance for these units
26
--` 2~S~7[)
appears to be associated with fiber at the fine end of the dia-
meter range and the preferred embodiment would make use of fibers
around 0.5 denier. ;
Table Vl
Thermal Proper~ies of Examples o~ Down-like Units
, ~ _ .
Percentage Increases
Apparent ~hermal In Conductivity
Conductivity Attributable to
~ample ~W/m. K~)Support Member
_ ,
#1 0.040
(0.5 denier) 6.9
Comparison 0.037
100% 0.5 denier Fiber
#2 0.044
(1.2 denier) 5.5
Comparison 0.042
100% 1.2 denier Fiber
#3 0.060
(5.0 denier) 10.3
Comparison 0.054 .
100% 5.0 denier Fiber
~ .. ~''''~'~`:'''
Down 0.039 _ : ~ :~
: :. ~: ..:.
:~: .-: ,,: :'
., ~ ~,...
:
27
~` 2 ~ 9 ~
The preceding specific embodiments are illustrative of the
practice of the invention. It is to be understood, however, that
other expedients known to those skilled in the art or disclosed ~ ~
herein, may be employed without departing from the spirit of the ~ ~:
invention or the scope of the appended claims.
- .
~: ~ - : .. ..
:
28
