U.S. patent application number 11/638977 was filed with the patent office on 2007-06-21 for hydroentangled elastic nonwoven sheet.
Invention is credited to Thomas Edward Benim, De-Sheng Tsai.
Application Number | 20070141926 11/638977 |
Document ID | / |
Family ID | 38050213 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070141926 |
Kind Code |
A1 |
Benim; Thomas Edward ; et
al. |
June 21, 2007 |
Hydroentangled elastic nonwoven sheet
Abstract
A method for making an elastic fabric with the steps of
providing a hydroentangled precursor fabric having at least 1% by
weight of binder fibers, heating the precursor fabric to a
temperature above the melting point of the binder fibers and then
drawing the precursor fabric in the machine direction at a ratio
sufficient to reduce the width by more than 20% and at a strain
rate of 10 to 800% per minute to produce an elastic fabric having a
cross-directional extensibility of about 100% up to 500% and a
30-95% recovery under a 50% extension.
Inventors: |
Benim; Thomas Edward;
(Goodlettsville, TN) ; Tsai; De-Sheng;
(Hendersonville, TN) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
38050213 |
Appl. No.: |
11/638977 |
Filed: |
December 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60751070 |
Dec 15, 2005 |
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Current U.S.
Class: |
442/2 ; 156/60;
264/288.4; 442/328; 442/415; 442/50 |
Current CPC
Class: |
Y10T 442/697 20150401;
Y10T 442/601 20150401; D04H 1/49 20130101; D06C 3/00 20130101; D04H
1/54 20130101; Y10T 156/10 20150115; Y10T 442/102 20150401; D04H
1/00 20130101; B29C 55/06 20130101; D04H 3/11 20130101; Y10T
442/184 20150401 |
Class at
Publication: |
442/002 ;
442/328; 442/050; 442/415; 264/288.4; 156/060 |
International
Class: |
D04H 1/00 20060101
D04H001/00; D04H 3/00 20060101 D04H003/00 |
Claims
1. A method for making an elastic fabric comprising the steps of
(a) providing a hydroentangled nonwoven precursor fabric containing
predominantly non-elastomeric base fibers and at least 1% by weight
of thermoplastic binder fibers that have a lower melting point than
the base fibers (b) heating the precursor fabric to a temperature
above the melting point of the binder fibers, (c) drawing the
precursor fabric in the machine direction at a ratio sufficient to
reduce the width of the precursor by at least 20% and to achieve a
cross-direction elongation of above 100% in the resultant elastic
fabric. (d) cooling the stretched web before releasing the tension
to create fixed bond points on binder fibers.
2. The method of claim 1, wherein the processing speed is at least
30 meters per minute and preferably 100-300 meters per minute.
3. The method of claim 2, wherein the processing strain rate is
10-800% per minute.
4. The method of claim 1, wherein the drawing step comprises the
use of two sets of S-wrap rolls.
5. The method of claim 1, wherein the heating step comprises
heating the precursor fabric to a temperature above the melting
point of some base fibers.
6. An elastic fabric composed of non-elastomeric fibers obtained by
applying a draw in the machine direction at an elevated temperature
to a precursor to reduce the width of the precursor and extend the
length from the precursor by more than 20% and achieve in the
elastic fabric an increase of extensibility in cross direction of
more than 50% of the precursor.
7. An elastic nonwoven fabric made from an entangled precursor web
containing non-elastomeric base fibers and less than 30% of
non-elastic thermoplastic binder fibers that have a lower melting
point than the base fibers, wherein the precursor web is drawn in
the machine direction at an elevated temperature above the melting
point of the binder fibers to reduce the width of the precursor by
more than 20% and achieve in the elastic nonwoven fabric a
cross-directional extensibility of 100% to 500% with a 30-95%
recovery from a 50% elongation.
8. The elastic fabric of claim 7, having a 40-85% recovery under a
100% elongation.
9. The elastic fabric of claim 7, having a 15-75% recovery under a
150% elongation.
10. The elastic fabric of claim 7, comprising at least 1% by weight
of binder fibers.
11. The elastic fabric of claim 7 in a form selected from the group
consisting of apertured fabric, mesh fabric, and net fabric.
12. The elastic fabric of claim 7, comprising thermoplastic base
fibers selected from the group consisting of polypropylene,
polyethylene, polyester, acrylic, polystyrene polyamide and
mixtures of thermoplastic fiber and non-thermoplastic fibers
selected from the group consisting of wood pulp, cotton, rayon, and
lyocell.
13. The elastic fabric of claim 7, comprising binder fibers
selected from the group consisting of polypropylene, polyethylene,
polyester, acrylic, polystyrene, polyamide, co-polyester,
sheath/core co-polyester/polyester, sheath/core
polyethylene/polyester, and sheath/core non-elastic
polyolefin/elastomer.
14. The elastic fabric of claim 7, comprising a base fiber blend of
thermoplastic and non thermoplastic fibers selected from the group
consisting of cotton, wood, and synthetics.
15. The elastic fabric of claim 13, wherein the synthetic is an
aramid.
16. The elastic fabric of claim 7, comprising thermoplastic base
fibers of polyester and sheath/core binder fibers, wherein the core
is polyester.
17. The elastic fabric of claim 16, wherein the sheath is a
co-polyester.
18. The elastic fabric of claim 16, wherein the sheath is
polyethylene.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to the preparation of elastic
nonwoven sheets from non-elastic hydroentangled sheets.
[0003] 2. Description of the Related Art
[0004] Elastic fabrics are usually made with rubber or some other
elastomeric material incorporated into or attached to a precursor
fabric. The precursor fabrics can be traditional textiles or
nonwoven fabrics. Other methods of producing elastic nonwovens
included imbedding or attaching elastomeric threads, strips, and
films. These can be attached by adhesives, thermobonding,
lamination, sewing, stitch bonding, etc. However, in all cases, the
process is expensive.
[0005] U.S. Pat. No. 5,244,482 to Hassenboehler et al and EP
1538250 A1 to Tsai et al. on the other hand have shown that
thermoplastic bonded nonwoven fabrics, such as spunbond and carded
webs, can be processed using heat and strain to create a web with
elastic properties. These thermo-mechanical methods describe
passing a thermally bonded precursor web through an oven at an
elevated temperature between the softening temperature and the
melting point and applying a draw in the machine direction to
transversely consolidate the web, whereby the majority of the
fibers are extended and aligned predominantly in the direction of
the draw. Upon cooling the web, the fixation of fibers in the
longitudinally extended configuration creates a position memory at
the thermally bonded points; therefore, the web exhibits recovery
when stretched in the transverse direction. However, these methods
require precursor webs that have been subjected to
thermo-mechanical bonding or calendering and the treatment
temperature has to be lower than the melting point of the fibers.
Otherwise, the web would be plasticized, stiff, brittle, and with
virtually no elasticity, or worse would cause the web to break in
the process. Furthermore, since the tensile strength of such a web
totally relies on the thermal bonding and the heat and strain
treatment aligns the majority of the fibers mostly in the direction
of the draw, it causes serious loss of tearing strength in the
resultant elastic fabric along the draw direction.
[0006] For many applications, a, softer fabric with higher tearing
strength is desired and can be obtained through the use of
entangled fabrics. However, traditional spunlaced and needle
punched fabrics do not gain elasticity by the heat-and-strain
process described in the prior art, because the "bond points" are
formed by entanglement, which provides only frictional and
interlocking contact points that are not permanently altered by
such a process.
SUMMARY OF THE INVENTION
[0007] The invention is directed to a method for making an elastic
fabric by providing a hydroentangled precursor fabric having at
least 1% by weight of thermoplastic binder fibers that has lower
melting temperature than that of the rest of base fibers; and while
heating the precursor fabric to a temperature above the melting
point of the binder fibers, drawing the precursor fabric in the
machine direction at a ratio sufficient to reduce the width of the
precursor by at least 20% and at a strain rate of 10 to 800% per
minute, and then cooling the resultant to ambient temperature to
set the resultant web.
[0008] The invention is directed to an elastic hydroentangled
fabric made by the described method and having an extensibility of
100% to 500% in the cross direction and a 30-95% recovery under a
50% elongation, in the cross direction.
BRIEF DESCRIPTION OF THE DRAWING
[0009] The FIGURE is a schematic illustration of an apparatus for
performing one embodiment of the method of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0010] One object of the present method is to provide a
cost-effective thermo-mechanical process of creating an elastic
spunlaced fabric without the use of true elastomeric fibers as base
fibers. By incorporating in non-elastomeric precursor web a low
percentage of low melting point binder fibers, with or without
being thermally bonded, and conducting a stretch process at
temperature above the melting point of the binder fibers, the
plasticized binder fibers can serve the bonding purpose in the
contacting points and create the position memory for fibers fixed
around the contacting points. Since the percentage of binder fibers
is low, there is no significant stiffness caused by the high
temperature process of this invention.
[0011] The use of spunlaced nonwoven precursor provides thicker,
softer elastic fabrics with a more desirable tearing strength. The
precursor fabric is made of predominantly non-elastomeric base
fibers such as (poly)ethyleneterephthalate (i.e., polyester), or
polyamide staple fibers or a mix of above synthetic fibers with
some percentage of non-thermoplastic fibers such as wood pulp,
cotton, rayon, lyocell, etc. and then blended with at least about
1% binder fibers and preferably about 5% to 30% binder fibers. The
binder fibers are preferably made of thermoplastic fibers such as
polypropylene, polyethylene, co-polyester, acrylic, polyamide,
polyurethane, and polystryene. The binder can be a bi-component
fiber, such as sheath/core, side-by-side, etc. For example, the
binder fibers can be bi-component staple fibers having a
co-polyester sheath and polyester core or polyethylene sheath and
either a polyester or compounded elastomer core. The co-polyester
composition can vary depending on the manufacturer of the fiber and
the desired attributes, but is commonly composed of the copolymer
of poly(ethylene terephthalate) and isophthalate. The percentage of
binder fiber is by weight of the fabric. By incorporating binder
fibers into the fiber web that is further processed into a
spunlaced web and then activating these binder fibers in an in line
dryer, we have made a fabric which can then be converted into an
elastic web. The cross over points of the binder fibers with
themselves and/or the base fibers act similarly to the point bonds
of a spunbonded fabric.
[0012] The present invention provides a process of preparing an
elastic spunlaced (hydro-entangled), nonwoven web. A precursor web
of synthetic and/or wood pulp fibers blended with thermoplastic
binder fibers is processed into a web by opening, carding or other
suitable web forming processes followed by hydroentanglement (also
referred to as spunlacing). The spunlaced web is subjected to an
elevated temperature sufficient to at least partially melt the
binder fibers, but not the base fibers making up the fabric. This
can be accomplished by a hot air treatment or any other suitable
means for achieving the desired elevated temperature. While subject
to a temperature above the melting point of the binder fibers, the
spunlaced fabric is subjected to a drawing treatment in the machine
direction at a drawing ratio sufficient to reduce the web width by
more than 20% (preferably in the range of 55-75%) with a strain
rate of from 10 to 800%/min. The drawing ratio can be 5 to 50%,
preferably 10 to 20%. This step of drawing at an elevated
temperature can be accomplished either in-line with the precursor
web forming process or as a separate off-line process. The method
of heating the precursor web is not particularly limited as long as
the heat transfer may be accomplished in as short a time as
necessary to avoid damage of the web. Heating may be accomplished
by radiation or convection. Radiation heating may be carried out by
using infrared methods. Convection heating may be carried out by a
suitable heating fluid, preferably a gas such as air.
[0013] The process of the invention can be further described with
reference to the FIGURE. Accordingly, an elastic spunlaced fabric 2
is prepared by providing a spunlaced precursor web 1 containing
thermoplastic binder fibers, whereby the precursor web is supported
by unwinding roll 10. Unwinding roll 10 is rotated around its
longitudinal axis whereby the precursor web 1 leaves unwinding roll
10 at a speed A in the machine direction (MD) as indicated by the
arrow. The precursor web travels via S-wrap 15 into a heating means
20, through the heating means and from the exit of the heating
means via S-wrap 25 to the winding roll 30. S-wrap 25 and winding
roll 30 are driven at a speed higher than the unwinding speed A of
unwinding roll 10 and S-wrap 15 by a factor of (1+X %). S-wrap 15
comprises rolls 151 and 152. S-wrap 25 comprises rolls 251 and 252.
The factor (1+X %) determines the drawing ratio of the precursor
web in the process of the present invention. According to the
invention, the precursor web is subjected to a drawing treatment in
a machine direction at a drawing ratio sufficient to reduce the
width by at least 20% and a strain rate within a range of 50 to
800%/min, at a temperature above the melting point of the binder
fibers in order to create in the resultant fabric, elongation at
break in the cross direction of greater than about 100% up to 500%.
Commercially useful recovery of 15-80% with 50-200% extension can
be achieved with the resultant elastic fabrics. Preferably, the
machinery for carrying out the process of the invention is
constructed for commercial capacity with an unwinder roll and a
winding roll(s) installed in a distance of from 3 to 40 m,
preferably about 20-30 m, and a heating device installed between.
The unwinder advantageously runs at commercial speed of more than
30 m/min and up to 300 m/min, preferably at least 100 m/min and up
to 250 m/min, and a draw ratio of 1% to 30%, preferably 10-20%, is
created by increasing the speed of the winding roll. The strain
rate is adjusted to 10 to 800%/min. The draw ratio relates to the
degree of width reduction of the precursor web and the strain rate
relates to the speed of the treatment at a fixed draw ratio. It was
found that when the speed is below the desired range, the web tends
to overheat and to become stiff. On the other hand, if the speed is
above the desired range, the precursor web is not sufficiently
heated and either the web may break during the drawing treatment or
the width reduction is not maintained after the web is released
from the draw tension. The S-wraps 15 and 25 also control the
movement of the nonwoven web, as well as serving as the drawing
means.
[0014] The elastic spunlaced web is characterized by a width
reduction of 20-75% compared to the precursor web and a
cross-direction extensibility of about 100% to 500%. The draw ratio
required to achieve a specific width reduction is very much
dependent on the precursor web structure. Obtaining a width
reduction greater than 20% is important for achieving
cross-direction elongation greater than 100% in the resultant
fabric and the possibility for further making the fabric elastic.
Further, the cross-direction elasticity of the elastic spunlaced
web is characterized by 30-95% recovery under a 50% elongation,
25-75% recovery under a 100% elongation, or 15-75% recovery under a
150% elongation. The resultant elastic spunlaced fabric has a
thickness of 0.2 mm-3.5 mm and a basis weight of 20 to 300
g/m.sup.2.
[0015] The present invention further provides products containing
the elastic nonwoven web of the present invention that greatly
expands the scope of nonwoven substrates available for producing
elastic nonwoven fabrics in a very cost effective manner. The
subject invention has applications in fields such as consumer
goods; cleanrooms; medical face masks, hoods and gloves; substrates
for composites and laminates and coatings such as for synthetic
leather substrates.
Glossary and Test Methods:
[0016] The strain rate (%/t) is generally described as a piece of
fabric being drawn and extended a certain (X) percentage in a
period of time. The extension percentage can be achieved by the
speed ratio of winder or S-wrap (25) to unwind or S-wrap (25), and
the time period of fabric run through can be calculated by dividing
D over the average of unwind speed (A) and winder speed of [(1+X %)
A]. Speed A is generally expressed in m/min as follows: X
%/{D/[A+(1+X %)A]/2}=X %/{2D/[A+(1+X %)A]}={X %.times.[A+(1+X
%)A]}/2D
[0017] The web elasticity is defined by measuring a 5-cm
wide.times.10-cm long strip along the longitudinal axis as follows:
(stretched length-recovered length)/(stretched length-original
length).
[0018] The melting point is the temperature where a thermoplastic
fiber starts to become a liquid.
[0019] The strip tensile test is a measure of breaking strength and
elongation or strain of a fabric when subjected to unidirectional
stress. This testing was conducted on a constant rate of strain
tester, Instron Model 1122. In the current examples, strips of
fabric 2 inches (50 mm) wide and at least 5 inches (150 mm) long
are cut in the machine direction and cross direction of the fabric.
Ten specimens per sample were tested to compute an average value.
This test is known in the art and generally conforms to the
specifications of ASTM Method 5035-95. The results are expressed in
pounds to break and percent of elongation before break. The term
"elongation" means the increase in length of a specimen during a
tensile test expressed as a percentage of the original length. The
term "extensibility" used is the same as the elongation-at-break
measured in the tensile test.
[0020] Tearing strength is measured by the tongue (single rip)
procedure modified from the ASTM 5735 using a rectangular specimen
of 2.times.2.5 inches (50 mm.times.63.5 mm). Ten (10) specimens are
tested per treatment and the results are expressed in pounds.
[0021] The basis weight of each specimen is computed from the
average weight of 10 strip samples or 12 grab samples
respectively.
[0022] Thickness is the average of 10 strip samples or 12 grab
samples respectively. The strip samples are measured using a TMI
automated thickness tester, with a 2 inch diameter contact area and
pressure of 14.7 g/cm.sup.2. The grab samples were measured using
an Ames thickness gauge with a 1-inch diameter contact area and
pressure of 7.46 g/cm.sup.2.
EXAMPLES
[0023] In the following examples, the base fibers are polyester
staple fibers, commercially available from DAK Americas identified
as Dacron(R) Type 612W. The binder fibers are sheath/core
co-polyester/polyester staple fibers commercially available from
FIT, Incorporated and identified as Type 201. The melting point of
the binder fibers is 110.degree. C. (230.degree. F.) and the
precursor spunlaced fabrics contain 15% binder fibers.
Examples 1-10
[0024] Precursors A and E have a basis weight of 1.2 and 1.85 ounce
per square yard, respectively. The results of longitudinal draws at
ambient temperatures are presented in Table 1 below. TABLE-US-00001
TABLE 1 Draw Ratio Width Width Strain Rate Example (%) (in)
Reduction (%) %/min Precursor A 0 76 0 -- 1 10 64 16 60 2 15 52 33
87 3 18 44 42 102 4 20 40 Broke web Precursor E 0 60 0 -- 6 10 55 8
60 7 15 46 23 87 8 18 45 25 102 9 20 43 28 113 10 25 42 Broke
web
[0025] The longitudinal draw at ambient temperatures was varied and
was found to reduce the width to some degree and enhance the
extensibility of the resultant webs. At a width reduction of about
20%, an extensibility of more than 100% in the cross direction of
the resultant webs was achieved, however, no significant elastic
recovery was observed from 50-100% elongation.
Examples 11-23
[0026] Precursors C and D had a basis weight of 0.8 ounce per
square yard (27 g/m.sup.2). The results of longitudinal draw at
elevated temperatures are presented in Table 2 below.
TABLE-US-00002 TABLE 2 Draw Treatment Ratio Width Width Example
Temperature (.degree. F.) (%) (in) Reduction (%) Precursor C 77 0
75 0 11 230 10 33.5 55 12 230 18 17.5 77 13 330 9 34.5 54 14 330 12
25 67 15 330 15 19.5 74 Precursor D 77 0 75 0 16 230 6 52 31 17 230
8 44 41 18 230 10 34.5 54 19 230 18 19 75 20 330 8 42 44 21 330 10
33 56 22 330 14 22.5 70 23 330 16 19.5 74
[0027] In contrast to the results in Tables 1 and 2 above, the
spunlaced precursors without binder fibers processed in the above
conditions were able to achieve similar width reductions and
enhancement of extensibility in the cross direction; however, no
noticeable elastic recovery was found from 50-100% elongation.
Further, in processing the precursors of A,B,C,D at an elevated
temperature but below 230.degree. F. (the melting point of binder
fibers), the resultant fabrics showed only a minor degree of
elasticity.
Examples 24-28
[0028] Precursor spunlaced fabrics as described above were
subjected to a draw ratio of 14% at various draw temperatures and
then tested for elongation and stretch recovery. The results are
presented in Table 3, below. TABLE-US-00003 TABLE 3 Draw Treatment
Width Load at 1st Recovery % BW Ratio Temperature Reduction CD
Elongation at break elongation (lbf) At 1st elongation opsy (%)
(.degree. F.) (%) % lbf 100% 150% 100% 150% Precursor A 1.2 0 77 0
64 56.4 N/A N/A N/A N/A 24 14 230 65 282 10.32 1.300 3.035 50 34.5
25 14 270 66 319 9.20 1.227 2.095 70.6 50 26 14 310 67 317 7.24
1.290 1.960 74.8 59.4 27 14 350 69 352 7.54 1.480 2.068 78 61.1 28
14 400 73 394 4.85 1.156 1.500 77.3 67.8
[0029] The longitudinal draw at elevated temperatures was able to
reduce the width up to about 75% and a draw ratio of about 10% was
shown sufficient to achieve a 50% width reduction. The width
reduction on the resultant example webs was found to be a function
of draw and the temperature and the enhancement of the
extensibility in the cross direction was also found to result from
the draw and the temperature. Further, it was noticeable that the
elasticity (recovery after elongation) increased with higher
temperatures.
Examples 19-38
[0030] Precursor spunlaced fabrics as described above, but with
basis weights of either 0.8 or 1.2 oz/yd.sup.2 (27 or 40.7
g/m.sup.2) were subjected to various draw ratios at various draw
temperatures to achieve the desired width reduction of at least
50%. The examples were then further tested for various elongation
and stretch recovery properties. With the treatment of longitudinal
draw at an elevated temperature of 330.degree. F., the physical
properties of the resultant webs were significantly changed and a
commercially valuable elasticity was shown by the elongation of
under 300%. The results are presented in Table 4, below.
TABLE-US-00004 Resultant Treatment Draw Width Elongation at break
Temperature B.W. Ratio Reduction B.W. Thickness (%) Recovery at 1st
CD elongation (%) Example (.degree. F.) (opsy) % (%) (opsy) (mil)
MD CD 50% 100% 150% 200% 300% Precursor A 1.2 0 0 1.2 18.6 24.3 NA
-- -- -- -- -- 29 230.degree. F. 12 51 2.1 19.3 12.9 245.1 78.6
66.4 47.9 38.8 -- 30 230.degree. F. 18 68 3.3 20.2 10.6 469.7 78 68
60.5 51.2 36.5 31 330.degree. F. 10 50 2.1 21.1 13.2 229.8 85.6
68.8 54.5 -- -- 32 330.degree. F. 14 65 2.9 21.7 13.7 354.6 86.7
67.2 53.9 33.8 16.4 33 330.degree. F. 18 74 3.6 21.2 13.9 497.3
86.8 70.4 65.3 51.8 27.1 Precursor B 1.2 0 0 1.2 18.6 23.6 63.0 --
-- -- -- -- 34 230.degree. F. 12 52 2.2 19.3 13.8 263.9 82 45.2
25.7 18.6 -- 35 230.degree. F. 21 71 3.5 20.8 9.5 484.0 81.6 59.6
52 35.8 19.7 36 330.degree. F. 10 51 2.2 22.0 13.4 240.8 88.4 50.4
28.5 -- -- 37 330.degree. F. 14 66 3.2 22.1 11.5 353.8 88.8 76.8
63.2 44.2 17.5 38 330.degree. F. 18 75 3.6 21.5 13.0 519.0 87.8
74.4 63.5 52 21.2 Precursor C 0.8 0 0 0.8 14.6 22.8 66.7 -- -- --
-- -- 39 230.degree. F. 10 53 1.4 16.4 13.1 214.8 83 50.4 33.3 --
-- 40 230.degree. F. 18 74 2.3 19.0 8.3 485.9 83.3 70.8 61.6 50.8
27.1 41 330.degree. F. 9 54 1.6 18.0 11.3 229.5 90.6 68.4 54.4 31.6
-- 42 330.degree. F. 12 67 1.5 18.0 11.1 314.8 91.3 80 67.2 46 --
43 330.degree. F. 15 73 2.5 20.1 11.8 402.3 91.3 84 72.3 56.2 27.6
Precursor D 0.8 0 0 0.8 13.4 17.7 61.4 -- -- -- -- -- 44
230.degree. F. 10 49 1.4 15.1 12.6 205.0 84 53.2 27 19.6 -- 45
230.degree. F. 18 72 2.1 17.0 6.9 454.2 83 67.6 63.2 52.6 25.8 46
330.degree. F. 10 54 1.7 18.9 11.1 287.0 91.3 67.2 49.1 22.4 -- 47
330.degree. F. 14 70 2.2 18.8 11.5 395.5 90.7 79.2 67.7 56.2 26.3
48 330.degree. F. 16 74 2.4 18.7 11.3 423.5 89.7 80 73.1 56
33.3
* * * * *