U.S. patent application number 09/942103 was filed with the patent office on 2002-09-12 for stretch modified elastomeric netting.
Invention is credited to Cederblad, Hans O..
Application Number | 20020125596 09/942103 |
Document ID | / |
Family ID | 24125652 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020125596 |
Kind Code |
A1 |
Cederblad, Hans O. |
September 12, 2002 |
Stretch modified elastomeric netting
Abstract
Extruded netting having at least some elastomeric strands, the
properties of which have been modified by stretch conditioning.
Inventors: |
Cederblad, Hans O.;
(Minnetonka, MN) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Family ID: |
24125652 |
Appl. No.: |
09/942103 |
Filed: |
August 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09942103 |
Aug 28, 2001 |
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08533366 |
Sep 25, 1995 |
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6280676 |
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Current U.S.
Class: |
264/40.1 ;
264/210.1 |
Current CPC
Class: |
B29D 28/00 20130101;
B29K 2023/0616 20130101; B29C 55/00 20130101; B29K 2009/06
20130101; B29K 2101/12 20130101; B29K 2995/0046 20130101; B29K
2077/00 20130101; B29K 2075/00 20130101; Y10S 264/73 20130101; B29K
2067/00 20130101; B29K 2995/005 20130101 |
Class at
Publication: |
264/40.1 ;
264/210.1 |
International
Class: |
B29C 047/00 |
Claims
What is claimed is as follows:
1. Extruded net comprising at least some elastomeric strands the
strands having been subjected to stretch modification.
2. The net of claim 1 wherein the elastomer is selected from the
group consisting of styrenic block copolymers, thermoplastic
olefins and blends, elastomeric alloys, thermoplastic
polyurethanes, thermoplastic copolyesters and thermoplastic
polyamides.
3. The extruded net of claim 1 wherein all of the strands in one
direction are elastomeric.
4. The extruded net of claim 3 wherein the direction is the MD.
5. The extruded net of claim 3 wherein the direction is the TD.
6. The net of claim 4 wherein the elastomer is a polyether ester
block copolymer.
7. The net of claim 2 wherein the elastomer is VLDPE.
8. The extruded net of claim 1 wherein all of the strands are
elastomeric in both directions.
9. Method of stretch modifying properties of elastomeric strands in
extruded net comprising stretching the net.
10. The method of claim 9 carried out at RT.
11. The method of claim 9 carried out at elevated temperature.
12. The method of modifying the properties of elastomeric extruded
net comprising: providing extruded net of extruded strands in which
at least some of the strands are of the elastomeric composition,
and stretching those strands to a predetermined degree to provide
modified stress/strain properties in the elastomeric strands and
the net.
13. The method of claim 12 carried out at RT.
14. The method of claim 12 carried out at elevated temperature.
15. The method of modifying extruded net containing elastomeric
strands, comprising: providing extruded net having extruded
strands, at least some of which are elastomeric strands; selecting
predetermined final properties for the elastomeric material making
up the elastomeric strands in the net; determining the stretch
conditions necessary to achieve the final properties, and
stretching the elastomeric strands under the determined conditions
to achieve the final properties in the elastomeric strands.
16. The method of claim 15 carried out at RT.
17. The method of claim 15 carried out at elevated
temperatures.
18. In a composite material comprised of a plurality of layers, one
of which is an extruded net of intersecting polymeric strands, the
improvement comprising a net including at least some elastomeric
strands, the strands having been stretch modified.
19. The composite of claim 18 wherein the elastomeric strands are
in one direction.
20. The composite of claim 18 wherein the elastomeric strands are
in both directions.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to extruded polymeric netting and
more particularly to such netting in which at least some of the
strands in at least one direction in the net, preferably all of the
strands, are of an elastomeric polymeric material which may be
stretch modified in accordance with this invention.
[0002] Extruded polymeric netting has been known and used for some
time. U.S. Pat. No. 4,152,479 to Larsen and U.S. Pat. No. 3,252,181
to Hureau describe types of such net. These patents and their
entire content are incorporated herein by reference. Extruded
netting is netting in which the strands are extruded from a die,
the joints therebetween being formed either within the die or
immediately outside the lips of the die.
[0003] In the netting to which these patents relate, the extruded
strands are comprised of orientable polymeric material. Orientation
is a stretching process which can be applied to the net in the
machine direction (MD) and/or the cross direction (CD) or
transverse direction (TD). When oriented in only one direction, the
net is said to be uniaxially oriented. When oriented in both
directions it is said to be biaxially oriented.
[0004] The orientation process is applied to these types of net to
significantly increase net size, both in width and length and to
orient the molecules of the material in the strands from a random
arrangement into a more ordered arrangement. Due to the nature of
the polymeric material used heretofore in extruded netting, the net
when stretched to a larger size remained essentially at the
stretched or enlarged size. That is, such nets do not exhibit any
significant recovery. The ordered arrangement obtained is desirable
because it increases the strength to weight ratio of the net. Some
of the more common materials used in such nets are polypropylene,
nylon and linear low density and high density polyethylene.
[0005] It has recently become desirable to provide extruded net in
which the strands or at least some of the strands in one direction
or both directions are of elastomeric material in order to provide
net exhibiting significant elasticity for a variety of purposes.
One such net is described in co-pending application Ser. No.
08/295,635 entitled BICOMPONENT ELASTOMERIC NETTING which is
assigned to the same assignee as is this invention. The content of
this application is incorporated herein by reference.
[0006] Stretch orientation processing has not been applied to
elastomeric net to modify elastic properties prior to this
invention. It has not been believed that the orientation process
would be useful with respect to extruded elastomeric nets since it
does not provide the traditionally expected results and
benefits.
[0007] In accordance with this invention, it has been discovered
that stretching elastomeric strands in extruded netting produces
beneficial modification of the elastic properties of the net. The
invention most accurately is described herein as "stretch
modification". The same equipment as is used for orientation may be
used for stretch modification when modified to accommodate the
greater stretch involved. Such equipment is described in the
aforenoted Larsen patent. Stretch modification may take place at
room temperature (RT) or at elevated temperatures, similar to the
known orientation process.
SUMMARY OF THE INVENTION
[0008] Stretch modification of extruded elastomeric net allows the
elasticity level of the net to be engineered to predetermined
specification for any desired recovery. It also allows stretch to
be engineered likewise. This is accomplished by stretching the net
in the MD and or CD directions under controlled conditions.
Definition Of Thermoplastic Elastomer
[0009] The ASTM D 1566-66T definition of the term "elastomer" is "a
macromolecular material that returns rapidly to approximately the
initial dimensions and shape after substantial deformation by a
weak stress and release of the stress". A thermoplastic elastomer
is a material that combines the processability of a thermoplastic
resin with the functional performance and properties of a
conventional thermoset rubber. In general, any thermoplastic
elastomer can be used to produce this type of netting. They are
generally covered by the six resin classes listed below.
Thermoplastic Elastomer (TPE) Types
[0010] There are generally considered to be six classes of
commercially available TPE's:
Styrenic Block Copolymers (SBC's)
[0011] The various SBC's include:
[0012] Styrene-Butadiene-Styrene(SBS)
[0013] Styrene-Isoprene-Styrene(SIS)
[0014] Styrene-Ethylene/Butylene-Styrene (SEBS)
[0015] Styrene-Ethylene/Propylene-Styrene (SEPS) (uncommon)
[0016] Tradenames and producers include Kraton (SBS, SIS and SEBS)
by Shell Chemical Co., Finaprene (SBS) by Fina Oil & Chemical,
and Europrene (SBS and SIS) by EniChem Elastomers. Only Shell makes
the SEBS resin (Kraton G).
Thermoplastic Olefins And Blends (TPO's)
[0017] Tradenames and suppliers of traditional TPO's include
Polytrope (a blend of polypropylene and EPDM, a rubber) by A.
Schulman and Telcar (also a blend of polypropylene and EPDM) by
Teknor Apex. These are propylene/EPDM block copolymers. EPDM is
Ethylene Propylene Diene Monomer.
[0018] A new subclass of TPO's are the VLDPE's (very low density),
copolymers with a density of about .ltoreq.0.880 g/cm.sup.3. The
elasticity of polyethylenes increases with decreasing density.
Tradenames and suppliers of these include Exact by Exxon Chemical
Co. and Engage by Dow Plastics.
Elastomeric Alloys
[0019] This class of TPE's consists of mixtures using two or more
polymers that have received proprietary treatment to give them
properties significantly superior to the simple blends of the same
constituents. The two basic types are: Thermoplastic vulcanites
(TPV's), such as Santoprene (polypropylene and crosslinked EPDM) by
Advanced Elastomer Systems, Geolast (polypropylene or nitride
rubber) by Monsanto and melt-processible rubbers (MPR's), such as
Alcryn (polyvinylidene chloride and crosslinked polyvinylacetate
copolymer) by Du Pont Co.
Thermoplastic Polyurethanes (TPU's)
[0020] Tradenames and suppliers include Pellethane (polyurethane
with polyester, polyether, or polycaprolactone copolymers) by Dow
Chemical and Estane by B. F. Goodrich.
Thermoplastic Copolyesters
[0021] Tradenames and producers include Hytrel (polyether-ester
copolymer) by Du Pont Co., and Amitel (polyether-ester copolymer)
by DSM Engineering Plastics.
Thermoplastic Polyamides
[0022] Pebax (a block copolymer of polyamide and polyether) are
made by Elf Atochem.
[0023] Various types of extruded netting may make use of the
invention. For example, an extruded "square" netting that is
extruded using either the "Hureau" process as aforenoted, yielding
an all-elastomeric netting, or the "Bicomponent elastomeric
netting" process as aforenoted, yielding either an all-elastomeric
or a unidirectional elastomeric netting, or any other suitable
netting process.
[0024] This extruded netting may then be uniaxially stretched in
the machine direction in-line with the extruder, or biaxially
stretched (essentially) using Larsen's process above noted, for
example, to modify the properties of the net.
[0025] As already noted, extrusion of elastomeric nettings can
often employ the same extrusion methods as those used for
non-elastomeric nettings, i.e., orientable netting.
[0026] The three process steps of extrusion, MD stretch
modification and TD stretch modification can be performed in two
different ways:
[0027] 1. Extrusion followed by MD and TD stretch at a biaxial
orientor.
[0028] 2. Extrusion followed by in-line MD stretch at ambient
temperature with TD stretch at a (biaxial) orientor, such as that
shown in the Larsen patent.
[0029] Extruded elastomeric nettings utilize thermoplastic
elastomer resins as their raw material for at least some of the
strands. This is possible as a result of the reversible
crosslinking mechanism of thermoplastic elastomers. (Traditional
rubber compounds, such as natural rubber, are vulcanized, resulting
in non-reversible crosslinking.) This invention relates to extruded
elastomeric netting, which in a secondary process step has been
stretch modified. The combination of the use of thermoplastic
elastomer resins and the stretch modification improves many of the
netting's elastomeric properties and enhances other netting
features. In particular, elastomeric nettings with:
[0030] lower set
[0031] higher modulus
[0032] higher force (at an equivalent elongation and weight)
[0033] lower energy loss (per hysterisis cycle)
[0034] lower product weight, and
[0035] wider product width
[0036] can be produced with this method.
[0037] Many thermoplastic elastomers are block copolymers, as
already above identified, with hard and soft segments creating a
crosslinked network. The crosslinked network configuration is
somewhat random, but is also controlled by factors such as hard
phase concentration and processing conditions. The first time a
thermoplastic elastomer netting is stretched and relaxed (its first
hysterisis cycle), some of these crosslinks are broken (probably
due to an unfavorable physical arrangement). This results in a
degree of permanent set from the first hysterisis cycle. In
subsequent hysterisis cycles few additional crosslinks are broken
as long as the netting is not stretched further than in the first
hysterisis cycle. The effect is a lower set and lower energy loss
in the second and subsequent hysterisis cycles, resulting in a
product that performs much more like a true elastomer than the
original product.
[0038] In the stretch modification process, the elastomeric netting
goes through its first hysterisis cycle. It is stretched and
relaxed, and the first cycle set is translated into a slightly
wider width, increased roll length and a reduced MD and TD strand
count. In the stretch modification process, the netting is
typically stretched 100-400%. The resulting product performs best
in applications where it is subjected to less than 100% elongation
in use, as the netting will experience little additional set and
energy loss in this range.
BRIEF DESCRIPTION OF THE FIGURES
[0039] FIG. 1 is a graph showing stress-strain hysterisis curves
for the transverse direction of a netting made with Hytrel 4056, a
polyether-ester thermoplastic elastomer available from the Du Pont
Company
[0040] FIGS. 2A and 2B show two and four cycle stress-strain
hysterisis curves of a netting made with a blend of
styrene-butadiene-styrene block copolymer (SBS) resins (65/25/10:
Vector 7400/Vector 8550/Styron 666D, Vector being from Dexco
polymer and Styron being from Dow).
[0041] FIG. 3 is a pictorial view of a form of the netting
according to the invention used as a reinforcing/elastic element in
a multi-layer composite material or fabric.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Stretch modified extruded elastomeric netting may be used in
numerous ways. It may be used as a component in fabrics and other
materials or used alone to create stretch and recovery in any
direction required. It "bounces back" under vigorous use. It
retains its elasticity to conform to a wide variety of shapes and
sizes. For example, a preferred use of the netting at present is in
mattress pads where it provides a tight fitting pad which does not
come off at the comers. In such a pad, the structure is a layered
or laminated structure of a "sandwich" type including the net
interiorly.
[0043] Hysterisis stress-strain curves illustrate the elastomers
modified according to the invention. By making use of the
invention, i.e. stretch modification, resins and resin blends
making up elastomeric netting or elastomeric/orientable netting
hybrids can be custom engineered for different hysterisis
requirements and product configuration.
Design Principles
[0044] Critical end use performance criteria (load force @ a
specified elongation, unload force @ a specified elongation, set,
stress relaxation, creep, strand count, etc.) must be known for
custom engineering. Once these are established for a particular
application, the following parameters must be taken into
consideration.
Primary Design Parameters
[0045] Raw material: Thermoplastic elastomer (blend) selection
1 Netting weight Processing: Stretch modification ratio (i.e.,
stretch ratio) Stretch modification temperature
Secondary Design Parameters
[0046]
2 Processing: Stretch rate Holding time @ maximum elongation MD
line web tension Line speed Roll wind tension Roll TD width when
wound
[0047] The secondary design parameters affect the final netting
properties, but to a much lesser extent than the primary design
parameters do, and need not be considered further herein in any
detail as they will be apparent to those familiar with this
art.
Design Process
[0048] The selection of a thermoplastic elastomer resin forms the
basis for the netting's performance characteristics. A library of
hysterisis curves for various thermoplastic elastomer resins and
resin blends is useful for product design but not necessary.
Ideally, such hysterisis curves would be available at various
stretch ratios and stretch temperatures. The netting weight may
have to be adjusted to reach a specified force at a specified
elongation (either on the load or unload cycle, or both). The
stretching temperature can be increased to yield a greater first
cycle set, improved dimensional stability and greater product
width. The stretch ratio should generally exceed the stretch range
expected in the netting's end use application. Specifically, the
stretch ratio should be adjusted so that subsequent hysterisis
cycles (at lower stretch rate for the end use application) meets
specified predetermined performance targets. Often (but not
always), the second load cycle follows closely the first cycle
unload curve, this may serve as a first approximation in product
design. Initial design targets may be established by simulating
actual processing and end use conditions using a tensile tester
capable of performing hysterisis testing. After initial product has
been made and tested, the process will typically need to be
fine-tuned. This can usually be done by a slight modification of
the primary or secondary design parameters.
[0049] Referring now to FIG. 1, this graph contains stress-strain
curves for the transverse direction of a netting made with Hytrel
4056, a polyether-ester thermoplastic elastomer, a block
copolymer.
[0050] Curve #1 is the load curve to break. The two downward spikes
are caused by strand slippage in the jaws of the testing
machine.
[0051] Curve #2 shows the first hysterisis cycle to 100% elongation
for the non-stretch modified netting.
[0052] Curve #3 shows the first hysterisis cycle to 375% elongation
for the non-stretch modified netting. This cycle is similar to what
the netting experiences in the TD stretch modification process. The
(return) set is 180%.
[0053] Curve #4 shows a second hysterisis cycle to 100% elongation,
that follows the first cycle to 375% (Curve #3). Curve #4 has been
repositioned, so that it starts @ 0% strain, rather than @ 180%
strain. Curve #4 simulates the first hysterisis cycle in the end
use application of the stretch modified product. When comparing the
stretched product (curve #4) to the non-stretched product (curve
#2), it can be seen that in this case the stretched product
has:
[0054] lower set (18% vs 35%)
[0055] higher modulus (in this example, this only applies to the
20-100% elongation range)
[0056] lower energy loss
[0057] higher force (in this example, this only applies to the
75-100% elongation range)
[0058] than the non-stretched product. It is also a slightly wider,
lower weight product.
[0059] Note that if curve #4 would have started at 180% strain, it
would have extended out to 360% strain (for 100% elongation when
starting the second cycle at 0% strain). Also note that with this
medium hardness resin, the first cycle's load curve shows a
definite yield point. This yield point is eliminated in the second
cycle, and therefore also for a stretch modified elastomeric
netting.
[0060] Referring now to FIGS. 2A and 2B, these two graphs show two
(2A) and four (2B) cycle hysterisis curves of a netting made with a
blend of styrene-butadiene-styrene (SBS) resins. Compared to the
netting in FIG. 1, this netting is relatively soft (low hardness),
has a low force, low modulus, low set, and low energy loss. FIGS.
2A and 2B show that subsequent hysterisis cycles approximately
follow the first cycle unload curve. The additional set (after the
first cycle) is minimal. Most of the energy loss takes place in the
first hysterisis cycle. When this product is stretched, very little
additional width is gained, but set and energy loss are reduced and
close to zero.
[0061] Referring now to FIG. 2A, it includes several curves A, B, C
and D. Curve A represents a first loadcycle applied to an all
elastomeric net in the MD direction in which stretch modification
occurs. Curve B represents a first unload cycle in which the load
applied in Curve A is relaxed and released. Curve C represents a
second load cycle which is representative of load in actual use of
the product. Curve D represents a second unload cycle in which the
load of Curve C is relaxed and released.
[0062] It can be readily seen from the graph that curves A and B,
the first cycle, show some "set" but it is low compared to that
obtained with orientable polymer nets. In subsequent cycles (C-D)
there is low set which does not significantly increase the original
"set" or there is low additional set.
[0063] Also, it can be seen that the energy loss takes place
primarily in the first cycle (A-B) with very little loss occurring
in subsequent cycles.
[0064] The combination of low energy loss and low set makes this a
product that performs very close to a true elastomer.
[0065] Referring now to FIG. 2B, it also includes several curves
1-4 similar to those in FIG. 2A. Curve 1 shows first hysterisis
cycle (both load and unload). Curve 2 shows a second hysterisis
cycle (both load and unload). Curve 3 shows a third hysterisis
cycle (both load and unload). Curve 4 shows a fourth hysterisis
cycle (both load and unload).
[0066] All hysterisis cycles include an upper curve (load cycle)
and a lower curve (unload cycle). What is demonstrated by the
curves of FIG. 2B is that subsequent cycles after the first cycle
do not result in significant changes in the set and energy loss
properties.
Comparison Of Low And Medium Hardness Stretch Modified Elastomeric
Netting
[0067] The performance difference between a netting made from
Hytrel 4056 (a medium hardness thermoplastic elastomer, FIG. 1),
and the netting made from the SBS blend (a low hardness
thermoplastic elastomer, FIGS. 2A and 2B) show a typical
performance range for resins used for stretch modified elastomeric
netting. Within the same resin class:
[0068] The harder the resin, the higher the set, and the greater
the width gained with the stretch modified elastomeric netting.
[0069] The harder the resin, the higher the modulus and force. A
stretch modified elastomeric netting will increase the modulus and
force (at equivalent elongation) further yet.
[0070] The softer the resin, the lower the energy loss. A stretch
modified elastomeric netting will reduce the energy loss further
yet when not exceeding the original stretch modification or first
cycle elongation.
EXAMPLES
EXAMPLE #1
[0071] The starting product is an extruded, square, all-elastomeric
netting made from Hytrel 4056. Hytrel 4056 is a polyether-ester
resin made by Du Pont. The netting is biaxially stretched using
equipment similar to that described in U.S. Pat. No. 4,152,479
(Larsen). The product is stretched in the machine direction
("drafted") at a temperature of 128.degree. F., and an applied MD
stretch ratio of 2.52. The resulting effective MD stretch ratio
(after full product relaxation) is 1.79. The product is then
stretched in the cross direction ("tentered") at a temperature of
150.degree. F., and an applied CD stretch ratio of 4.75. The
resulting effective CD stretch ratio is 2.38. Cf. Example 1 in
Table 1 below.
[0072] Table 1 below includes data for Example 1 and for additional
sets of stretch modification trials, containing information for
additional Examples 2 and 3.
3TABLE 1 POLYETHER-ESTER COPOLYMER Ex. #1 Biaxially Ex. #2 Ex. #3
MD stretched Biaxially Stretched-only Product Description product
product product. Resin Hytrel 4056 Hytrel 3078 Hytrel 4056 Relaxed
strandcount, 2.8 .times. 2.8 2.7 .times. 3.6 6.8 .times. 2.6 MD
.times. TD (per inch) (on roll: 2.5 .times. 2.8) Calculated relaxed
6.7 6.6 16.3 weight (PMSF) (on roll: 5.8) Relaxed width, excluding
30.4 31.5 32.9 edgetrim (in) (on roll: 35.0) Applied/Effective
draft 2.52/1.79 3.35/1.68 3.21/1.92 ratio Applied Effective tenter
4.75/2.38 4.83/2.10 -- ratio (on roll: 2.74) MD stretch temperature
128 70 90 (.degree. F.) TD stretch temperature 150 146 -- (.degree.
F.) MD set @ 35% 5.5 1.7 (est.) 4.0 elongation (%) MD force @ 35%
1,600 210 (est.) 4,220 elongation (g/3 in) MD force @ break 10,300
28,600 (g/3 in) TD force @ break 3,030 2,500 (g/3 in) MD elongation
@ 450 440 break (%) TD elongation @ 220 720 break (%)
EXAMPLE #5
[0073] This all-elastomeric extruded "square" netting is made from
Hytrel 3078. Hytrel 3078 is a polyether-ester resin made by Du Pont
Company. The netting is first MD stretch modified in-line with the
extrusion process, and subsequently CD stretch modified using part
of a biaxial orientor (as in Example #1). The product is stretched
in the machine direction at room temperature (70.degree. F.), and
an applied MD stretch ratio of 3.61. The resulting effective MD
stretch ratio after full product relaxation is 1.67. The product is
stretch modified in the CD at room temperature (70.degree. F.), and
an applied CD stretch ratio of 5.29. The resulting Effective CD
stretch ratio is 1.93. Cf. Example 5 in Table 2 below. Table 2 not
only includes data for Example #5 but for additional stretch
modification trials regarding Examples 4-9.
4TABLE 2 POLYETHER-ESTER COPOLYMER Ex. #5- Ex. #6-CD Ex. #7- Ex. #8
Ex. #9- Ex. #4-CD Biaxially stretch- CD stretch- Biaxially
Biaxially strech-only stretch only only stretched stretched Product
description product product.(1) product product product.(2)
product(2) Resin Hytrel 3078 Hytrel 3078 Hytrel 3078 Hytrel 3078
Hytrel 3078 Hytrel 3078 Relaxed strandcount, 3.0 .times. 6.2 2.9
.times. 3.7 2.5 .times. 6.1 2.6 .times. 5.1 2.6 .times. 3.1 2.7
.times. 3.6 MD .times. TD (per inch) Calculated relaxed 12.6 7.2
10.1 9.0 5.5 6.6 weight (PMSF) Relaxed width, (in) 26.3 27.0 32.0
32.4 32.5 31.5 Applied/Effective 1.00/0.98 3.61/1.67 1.00/1.00
1.00/1.19 3.20/1.96 3.35/1.68 MD stretch ratio Applied/Effective CD
5.29/1.88 5.29/1.93 5.29/2.29 4.83/2.16 4.83/2.17 4.83/2.10 stretch
ratio MD Stretch -- 70 -- -- 70 70 Temperature (.degree. F.) CD
stretch 70 70 153 150 147 146 temperature (.degree. F.) MD set @
25%-50%- 0.7-3.1-6.0 0.9-3.1-5.2- 0.9-2.9-4.8- 75%-100% 8.7 7.0 6.7
elongation (%) TD set @ 25%-50%- 0.6-2.7 0.5-2.6-5.0- 0.9-2.9-5.3-
75%-100% 5.2-7.8 7.4 7.8 elongation (%) MD elastic recovery
1.0-1.2-1.4 1.0-1.2-1.3- 1.0-1.1-1.2- ration for 25%-50%- 1.5 1.4
1.3 75%-100% elongation TD elastic recovery 1.0-1.1-1.3-
1.0-1.1-1.3- 1.0-1.1-1.3- ratio for 25%-50%- 1.4 1.4 1.4 75% 100%
elongation MD force @ 25%- 190-330 120-210- 110-190- 50%-75%-l00%
440-550 300-480 290-240- elongation (g/2 in) TD force @ 25%-
280-490- 210-360 170-290- 50%-75%-100% 670-830 480-630 400-510
elongation (g .multidot. 2 in) MD stress relaxation, 15.1 5 min @
50% elongation (%) TD stress relaxation, 15.5 5 min. @ 50%
elongation (%)
EXAMPLE #12
[0074] This all-elsatomeric extruded "square" netting is made from
Exact 4041, a VLDPE copolymer resin made by Exxon. The netting is
MD stretch modified in-line with the extrusion process, and
subsequently CD stretch modified using part of a biaxial orientor
(as in Example #1). The product is stretched in the MD at room
temperature and an applied MD stretch ratio of 2.11. The resulting
effective MD stretch ratio after full product relaxation is 1.58.
The product is stretch modified in the CD at 130.degree. F., and an
applied CD stretch ratio of 3.49. The resulting effective CD
stretch ratio is 2.37. Cf Example #12 in Table 3 below. Table 3 not
only includes data for Example #12 but for additional stretch
modification trials regarding Examples 10-15.
5TABLE 3 VLDPE COPOLYMER Ex. #10- CD Ex.#11- Ex. #12- Ex. #13- Ex.
#14- stretch- Biaxially Biaxially Biaxially Biaxially Ex. #15
Product only stretch stretch stretch stretched Tenter- description
product product. product. product. product. ed-only Resin Exact
4041 Exact 4041 Exact 4041 Exact 4041 Exact 4041 Exact 4041 Relaxed
3.7 .times. 3.4 3.5 .times. 3.6 3.6 .times. 3.4 5.3 .times. 4.2 4.9
.times. 4.3 4.7 .times. 5.1 strandcount, MD .times. TD (per inch)
Calculated relaxed 5.7 6.0 5.7 5.6 5.3 6.0 weight (PMSF) Relaxed
width, (in) 88.6 91.3 92.5 88.3 93.4 97.8 Finished slit roll 102 95
95 95 95 width (in) Applied/Effective 1.00/ 2.11 2.11/ 2.14 2.14/
1.00/ MD stretch ratio 1.23 1.47 1.58 2.03 1.68 1.02
Applied/Effective 3.53/ 3.58/ 3.49/ 3.49/ 3.56/ 3.57/ CD stretch
ratio 2.30 2.40 2.37 2.26 2.44 2.57 Tenter temperature, 121 127 130
131 134 135 (.degree. F.) MD set @ 25%- 1.3-4.6- 1.8-5.7-11-
1.7-5.3-11- 1.7-5.3-11- 1.6-5.1- 1.3-5.0- 50%-75%-100% 9.6-17 19 18
19 9.8-18 11-21 elongation (%) TD set @ 25%- 2.1-6.5- 2.8-7.2-12-
2.2-6.2-11- 2.0-5.8-11- 2.1-6.2-11- 1.7-5.1- 50%-75%-100% 11-18 19
18 17 19 9.7-17 elongation (%) MD elastic 1.1-1.3- 1.1-1.4-1.8-
1.1-1.3-1.7- 1.1-1.4-1.7- 1.1-1.4- 1.0-1.1- recovery ration for
1.5-1.8 2.0 1.9 2.0 1.7-1.9 1.2-1.3 25%-50%-75%- 100% elongation TD
elastic recovery 1.1-1.4- 1.2-1.4-1.6- 1.1-1.4-1.6- 1.1-1.4-1.6-
1.1-1.4- 1.1-1.4- ratio for 25%-50%- 1.6-1.8 1.8 1.9 1.8 1.6-1.9
1.6-1.9 75%-100% elongation MD force @ 25%- 290-390- 350-460-
410-570- 460-630- 410-560- 270-340- 50%-75%-100% 450-500 510-570
660-730 730-820 650-730 390-420 elongation (g/2 in) TD force @ 25%-
190-290- 150-240- 190-310- 140-220- 160-250- 170-280- 50%-75%-100%
410-550 340-450 440-750 320-440 370-490 400-510 elongation (g
.multidot. 2 in)
[0075] The invention finds a preferred use in composite materials
comprised of multi-layers such as that shown in FIG. 3. Two layer
composites of net and another material may be used but composites
with more than two layers such as shown in the FIG. 3 are most
likely. That composite comprises outer covering layers 60 and 62,
the stretch conditioned elastomer net being indicated at 64. All
such composites are referred to herein generally as composites
comprised of a plurality of layers including net. They may be
manufactured in the known manner as by subjecting them, when
assembled, to heat and pressure. Adhesives may be included.
[0076] The above Examples and disclosure are intended to be
illustrative and not exhaustive. These examples and description
will suggest many variations and alternatives to one of ordinary
skill in this art. All these alternatives and variations are
intended to be included within the scope of the attached claims.
Those familiar with the art may recognize other equivalents to the
specific embodiments described herein which equivalents are also
intended to be encompassed by the claims attached hereto.
* * * * *