U.S. patent application number 10/289922 was filed with the patent office on 2004-05-13 for integral lofty polymer grid and fiber web matrix turf reinforcement mats.
This patent application is currently assigned to Profile Products L.L.C.. Invention is credited to Spittle, Kevin S..
Application Number | 20040091326 10/289922 |
Document ID | / |
Family ID | 32176114 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091326 |
Kind Code |
A1 |
Spittle, Kevin S. |
May 13, 2004 |
INTEGRAL LOFTY POLYMER GRID AND FIBER WEB MATRIX TURF REINFORCEMENT
MATS
Abstract
A turf reinforcement mat comprises a lofty polymer grid having
integrally attached thereto a fibrous mat. The turf reinforcement
mat is preferably produced by needle punching a fibrous mat
containing low melt temperature thermoplastic fibers and a lofty
polymer grid followed by heating to an elevated temperature to fuse
fibers of the fibrous mat to strands of the lofty polymer grid. The
integral TRM does not necessitate stitching to hold the various
layers together in the integral product.
Inventors: |
Spittle, Kevin S.; (Port St
Lucie, FL) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER
TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
Profile Products L.L.C.
Buffalo Grove
IL
|
Family ID: |
32176114 |
Appl. No.: |
10/289922 |
Filed: |
November 7, 2002 |
Current U.S.
Class: |
405/302.7 |
Current CPC
Class: |
E02D 17/202 20130101;
Y10T 442/697 20150401; Y10T 428/31504 20150401; Y10T 428/249921
20150401; Y10T 442/696 20150401 |
Class at
Publication: |
405/302.7 |
International
Class: |
E02D 017/20 |
Claims
What is claimed is:
1. A turf reinforcement mat ("TRM") comprising at least one lofty
polymer grid and at least one fibrous mat, fibers of said fibrous
mat bonded to strands of said lofty polymer grid, or entangled with
strands of said lofty polymer grid to produce an integral TRM, said
lofty polymer grid extending from at least one surface of said
integral TRM.
2. The TRM of claim 1, wherein fibers of said fibrous mat are
entangled within strands of said lofty polymer grid.
3. The TRM of claim 2, wherein said fibrous mat contains 3 weight
percent or more based on the weight of the fibrous mat of low melt
temperature fibers having a melt temperature below the melt
temperature of strands of the lofty polymer grid.
4. The TRM of claim 3, wherein said low melt temperature fibers are
bicomponent fibers.
5. The TRM of claim 4, wherein said fibrous mat contains minimally
5 weight percent of bicomponent fibers.
6. The TRM of claim 1, prepared by the steps of: a) supplying a
fibrous mat containing a fusible thermoplastic; b) supplying a
lofty polymer grid; c) contacting said fibrous mat with said lofty
polymer grid; d) needle punching said fibrous mat and said lofty
polymer grid to entangle fibers of said fibrous mat and strands of
said lofty polymer grid to form an entangled intermediate product;
and e) heating said entangled intermediate product to bond fibers
of said fibrous mat to strands of said lofty polymer grid.
7. The TRM of claim 6, wherein said fusible thermoplastic comprises
low melt temperature thermoplastic fibers.
8. The TRM of claim 7, wherein said low melt temperature
thermoplastic fibers comprise bicomponent fibers.
9. The TRM of claim 6, wherein said fusible thermoplastic comprises
a particulate thermoplastic adhesive.
10. The TRM of claim 1, prepared by the process comprising: a)
supplying a lofty polymer grid; b) supplying a mixture of fibers to
said lofty polymer grid such that a fibrous mat is formed within
said lofty polymer grid; and c) bonding fibers of said fibrous mat
to strands of said lofty polymer grid.
11. The TRM of claim 10, wherein said mixture of fibers contain
minimally 3 weight percent of low melt temperature thermoplastic
fibers, and said step of bonding comprises heating said lofty
polymer grid and fibrous mat within said lofty polymer grid to fuse
fibers of said fibrous mat to strands of said lofty polymer
grid.
12. The process of claim 11, wherein said low melt temperature
thermoplastic fibers comprise bicomponent fibers.
13. The process of claim 10, wherein said mixture of fibers further
comprises a particulate thermoplastic or particulate thermosetting
adhesive, and bonding is accomplished by heating said lofty polymer
grid and said fibrous mat.
14. The process of claim 11, wherein said fiber mixture is supplied
as a dry fiber mixture in an air-laying process.
15. The process of claim 11, wherein said fiber mixture is supplied
as an aqueous suspension in a wet-laying process.
16. A process for the preparation of an integral TRM having a lofty
polymer grid extending from at least one surface thereof and a
fibrous mat intimately associated therewith, said process
comprising: a) supplying at least one lofty polymer grid; b)
juxtaposing on said at least one polymer grid at least one fibrous
mat; c) needle punching said fibrous mat and said lofty polymer
grid to entangle fibers of said fibrous mat with strands of said
lofty polymer grid; and d) when said fibrous mat contains low melt
temperature fibers and/or a thermoplastic or thermosetting
adhesive, heating the product obtained in step c) to bond fibers of
said fibrous mat to strands of said lofty polymer grid.
17. The process of claim 16, wherein said fibrous mat comprises
continuous fibers or fibers of intermediate length, and said needle
punching comprises needle punching with barbed needles, such that
an integral product is prepared without a heating step.
18. The process of claim 16, wherein said fibrous mat contains
minimally 3 weight percent of low melt temperature thermoplastic
fibers and step d) is practiced.
19. The process of claim 18, wherein said low melt temperature
fibers comprise bicomponent fibers.
20. The process of claim 16, wherein said fibrous mat contains a
solid, particulate adhesive activatable at an elevated temperature
and step d) is practiced.
21. A process for the preparation of an integral TRM having a lofty
polymer grid extending from at least one surface thereof and a
fibrous mat intimately associated therewith, said process
comprising: a) providing a lofty polymer grid; b) contacting said
lofty polymer grid with a suspension of fibers in an air-laying or
a wet-laying process to form a fibrous mat within said polymer grid
and entangled with strands of said polymer grid to form an
intermediate product; wherein fibers of said fibrous mat are bonded
to strands of said lofty polymer grid by one or more of the
following: i) fibers of said fibrous mat include low melt
thermoplastic fibers, and the product of step b) is heated to bond
fibers of said fibrous mat to strands of said lofty polymer grid,
ii) a pulverulent thermoplastic or thermoset adhesive is supplied
together with said suspension of fibers in a dry laying process and
cured to bind fibers of said fibrous mat to strands of said lofty
polymer grid, iii) to a dried intermediate product of step b) is
applied a pulverulent thermoplastic or thermoset adhesive which is
cured to bond fibers of said fibrous mat to strands of said lofty
polymer grid.
22. The process of claim 21, wherein a pulverulent thermoplastic
adhesive is supplied together with said suspension of fibers in an
air-laying process and heated to melt said thermoplastic
adhesive.
23. The process of claim 21, wherein a thermosetting adhesive is
employed.
24. The process of claim 23, wherein said thermosetting adhesive is
cured at an elevated temperature.
25. A process for reinforcing a seed bed against runoff, said
process comprising applying to said seed bed the TRM of claim 1,
with an extending polymer grid surface of said TRM installed
adjacent said seed bed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to turf reinforcement
mats.
[0003] 2. Background Art
[0004] Turf reinforcement mats ("TRM") are now in widespread use.
TRM are used to protect the soil surface from severe erosion during
high velocity, surface flow conditions, primary applications being
channels, ditches, steep-long slopes and river bank stabilization.
TRM vary in construction from loosely woven or non-woven plastic
mesh to multiple layers of inorganic netting structures, loose
filled with organic fibers, all stitched together. The use of
plastic mesh or grid-like materials such as colbond, pyramat,
enkabond, and others, provide little assistance in seed
germination: their principal use is in providing reinforcement of
the seed bed once seeds are germinated. By incorporation of such
materials, the root systems are able to withstand much greater
water velocity in overland flow, (water runoff) conditions. However
the open nature of these products does little to reduce sediment
and seed displacement prior to seed bed establishment.
[0005] Fiber mats have been used to assist seed germination and
impair runoff. 100% organic blankets without the inorganic grid
component aren't suitable for turf reinforcement applications. TRM
products can take the place of rip rap or concrete for channel
applications, an aesthetically attractive alternative while
providing permanent long term protection to the channel.
[0006] Establishing seed beds in areas where high runoff is
expected, i.e. on steep slopes, in gulleys, drainage channels,
etc., has often required separate use of one or the aforementioned
synthetic polymer grid-like materials and a separately applied
fiber mat. Such a two-step approach is time and labor intensive,
however, and has not been in widespread commercial use.
[0007] In U.S. Pat. No. 5,849,645, a complex composite mat having a
heavy gauge bottom polymer grid, a heavy gauge top polymer grid,
and a "cuspated" (pleated) "super heavy" gauge polymer netting are
combined with a fiber matrix of coconut fibers to form a multilayer
assembly which is stitched together to form an integral, multilayer
composite structure. This product is widely used, and offers both
runoff protection, assistance in seed germination, and protection
against runoff in established seed beds. However, the product is
expensive to manufacture and adds large quantities of substantially
non-biodegradable materials to the soil due to its construction
which necessarily contains three polymeric layers.
[0008] It would be desirable to provide a TRM product which offers
runoff protection, assistance in germination, and protection
against runoff in established seed beds, which introduces less
synthetic polymer material into the soil and which can be
inexpensively manufactured.
SUMMARY OF THE INVENTION
[0009] It has now been surprisingly discovered that a lofty
synthetic polymer grid or non-woven can be economically combined
with a fibrous mat to form a lofty TRM product. The polymer grid
protrudes from at least one side of the composite product, and the
product is installed with an exposed grid side toward the soil. In
a particularly preferred embodiment, the fibrous mat contains
minimally 5 weight percent of a low melt synthetic fiber and is
thermally bonded to the lofty polymer grid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1a illustrates a lofty non-woven polymer grid which has
been used to prevent runoff;
[0011] FIG. 1b illustrates a side view of the product of FIG. 1a
showing its lofty structure;
[0012] FIG. 2a illustrates a needle punched TRM as shown from the
top;
[0013] FIG. 2b illustrates a needle punched TRM viewed from the
side;
[0014] FIG. 3 illustrates a contact bonded TRM of the subject
invention;
[0015] FIG. 4 illustrates a TRM having two needle punched lofty
polymer grids sandwiching a single fibrous mat;
[0016] FIG. 5 illustrates one embodiment of a needle punching TRM
fabrication process; and
[0017] FIG. 6 illustrates one embodiment of a fabrication process
not employing needle punching.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The polymer mesh, grid, or non-woven will be termed a
"polymer grid" hereafter. Such polymer grids are a lofty product
constructed of synthetic fiber strands or filaments which are
intermeshed and optionally bonded together where the polymer
strands cross over or abut. A preferred polymer grid 1 is shown in
FIGS. 1a and 1b (Prior Art), and has been used alone or together
with a separately applied fiber mat to maintain seed beds and
prevent erosion, as described previously. Such lofty polymer grids
are available from numerous sources, for example as COLBOND.TM.,
ENKAMAT.TM., PYRAMAT.TM., and TENAX.TM., among others.
[0019] The polymer strands 2 of the lofty polymer grid 1 are
generally a single rather thick polymer filament which is kinked
during extrusion or during fabrication of the material to provide a
three-dimensional (i.e., lofty) product. The polymer is generally
one resistant to U.V. light, and many be of polyamide, polyolefin,
polyester, or any suitable thermoplastic. Some polymers,
particularly polyolefins, require incorporation of U.V. protection
agents, as is well known to the art. The polymer may be pigmented
or contain suitable dyes or colorants if desired.
[0020] The fibrous mat of the present invention may comprise but a
single layer of fibers, if desired, or multiple layers of the same
or different construction may be used. A single fibrous mat is
preferred.
[0021] Since in preferred embodiments the fibrous mat must be
thermally bonded to the lofty polymer grid, it is necessary that
the fibrous mat contain or be treated to contain a binder or
binding agent in these embodiments. In the preferred embodiment,
the fibrous mat contains sufficient polymer fiber of low melt
temperature to bond to the strands of the lofty polymer grid so as
to form an integral structure without the need for stitching the
layers together as taught by U.S. Pat. No. 5,849,645, and without
requiring a separate binder. The melting point of the low melt
temperature fibers is low enough to bond to the lofty polymer grid
without causing the latter to melt and/or deform appreciably. Thus,
the melting point will be lower than the melt temperature of the
material of the lofty polymer grid, preferably at least 20.degree.
C. lower, and more preferably 40.degree. C. or more lower. A
melting point in the range of 80.degree. C. to 180.degree. C. is
preferable for the low melt temperature fibers, more preferably
90.degree. C. to 150.degree. C., and most preferably 100.degree. C.
to 130.degree. C.
[0022] The low melt temperature fibers may comprise polyethylene or
polyethylene oligomers, for example, polymers with a melting point
below 130.degree. C., preferably about 110.degree. C. The low melt
temperature fiber generally comprises minimally 3 weight percent of
the fibrous mat, more preferably 10 to 40 weight percent, and most
preferably 10 to 25 weight percent. The entire fibrous mat may
comprise low melt temperature fiber, but this is not preferred.
[0023] The low melt temperature fibers are preferably bicomponent
fibers prepared by coextruding two polymers of different melt
temperature together. One portion of the fiber is a low melt
thermoplastic while another portion has a higher melting point. The
fibers may be extruded with the two different thermoplastics
substantially adjacent each other, or may be in the form of a
core/sheath fiber, with the core of the higher melt temperature
fiber. The latter core/sheath structure is highly preferred. An
example of a core/sheath bicomponent fiber is one with a polyester
core and a polypropylene sheath. A suitable bicomponent fiber is
low melt sheath polyester available from Intercontinental. The
amount of bicomponent fibers is, in general, somewhat higher than
the amount of single component fibers of low melt temperature,
since it is the low melting component which binds the composite
structure together. The fibrous mat must contain an effective
amount to bond to the lofty polymer grid to produce an integral
structure, in general at least 5% by weight, more preferably 10% by
weight or more, and most preferably 15 weight percent or more. The
fibrous mat may constitute up to 100% bicomponent fibers.
[0024] In addition to the low melt temperature fibers, the fibrous
mat preferably contains other fibers as well. In embodiments not
requiring low melt temperature fibers, these "other" fibers will
form the largest part or all of the fibrous mat. These fibers may
be synthetic polymer fibers or natural fibers. The mat may also
contain a small proportion of committed paper such as is contained
in sprayable mulch products, although this is not desired.
[0025] Useful synthetic fibers include fibers which do not have a
low melt temperature in the sense previously described, and thus in
general will not fuse to the lofty polymer grid. These fibers may
be straight or kinked, and may be in the form of single fibers,
bundles of fibers, yarns, tows, or any mixture thereof. The
material of the fibers may be any conventional polymer, including
without limitation, rayon, cellulose acetate, cellulose nitrate,
polyester, polyamide, polyaramide, polyvinyl acetate, polyurethane,
polyacrylamide, poly(meth)acrylate, etc. Crimped fibers are
particularly useful, as these aid in the entanglement of the fibers
in the fibrous mat. In non-bonded needled products as described
hereinafter, low melt temperature fibers may be used as well, but
are not thermally fused to bond the composite together.
[0026] The additional natural fibers are prepared from naturally
occurring sources, with or without additional chemical modification
of the fibers, particularly, with partial digestion with steam or
hot water. Such naturally occurring fibers are well known, and may
include, without limitation, fibers of wood, hemp, jute, coconut,
sisal, flax, corn stalks or leaves, straw, etc. Wood fibers are
preferred.
[0027] A preferred embodiment of the subject invention is
illustrated in FIGS. 2a and 2b, where the strands 2 of a lofty
polymer grid 5 (FIGS. 1a, 1b) are entangled with and thermally
bonded to fibrous mat 7 containing fibers 4. It is noted that some
strands 8 lie within the mat 7.
[0028] The fibrous mat may be prepared by any suitable technique.
Preferred are wet and dry laying of the mat, both processes well
known to those skilled in the art. In wet laying, the fibers are
suspended in water and laid atop a screen through which water
escapes, leaving a damp mat. This process is widely used in paper
making. In dry laying, the fibers are suspended in an air stream
and deposited on a screen or belt. Any process which enables a
suitable mat may be employed. The dry thickness of the mat may be
any thickness which provides a web handleable to produce the final
product and provide the desired seed germination assistance and
water diversion properties. Prior to any needling operations, the
mat may range in thickness from about {fraction (1/50)} inch to
about 1/2 inch, more preferably {fraction (1/32)} inch to 1/4 inch,
and most preferably {fraction (1/16)} inch to 1/4 inch.
[0029] In the laying process, a binding agent may optionally be
employed, and in certain embodiments, is necessary. In the dry
process, for example, particulate binders such as redispersible
polymer powders, preferably polyvinylacetate, ethylenevinylacetate,
or vinylacetate/alkylacrylate copolymers, may be employed. Many
other thermoplastic and thermosettable binders are suitable.
Following laying of the mat, it is exposed to elevated temperature
to activate the dry binder if necessary. In both the wet and dry
laying processes, a separate dry binder may be sprayed onto the
previously laid web.
[0030] In preferred embodiments, the fibrous web containing low
melt temperature fibers and/or binder and the lofty polymer grid
are then contacted an bonded together. Alternatively, the polymer
grid and fibrous mat may be contacted or "married," following which
binder, in dry particulate form, in aqueous dispersion, or in
solution, may be applied. Since only a small proportion of the
strands of the lofty polymer grid will contact the mat due to the
former's lofty nature, thermal bonding by contact with only the
fibrous mat surface may not result in a structurally integral
product, although this method may be suitable with specially
fabricated grids having substantial filaments on a bottom plane
which can contact the mat, or with fibrous mats with a high
proportion of low melt fibers or binder. A test of the degree of
bonding is whether there is any substantial separation of the mat
from the grid during normal handling and installation. It is
generally satisfactory that the grid may be separated from the mat
by purposefully pulling the layers apart by exerting modest tension
between the layers. A contact bonded TRM is shown in FIG. 3 from
the side, where bottommost strands 6 of the lofty grid 5 are
thermally bonded to the mat 7.
[0031] A TRM which is resistant to separation of the fibrous mat
and lofty polymer grid in the manner described, without requiring
stitching to maintain integrity, may be termed an "integral TRM."
However, it would not depart from the spirit of the invention to
additionally stitch the integral TRM, provided that the product
without stitching meets the requirements for an integral TRM.
However, it is more appropriate to produce a bonded composite
product where separation of the lofty polymer grid from the fibrous
mat is quite difficult if not impossible, without destroying the
various components. Such structural integrity is made possible by a
construction wherein the strands or filaments of the lofty polymer
grid penetrate into the fibrous mat. Such penetration may be
accomplished in numerous ways. Two preferred methods of penetration
include entanglement by needle punching and entanglement during the
mat laying process.
[0032] In needle punching, which is presently preferred, the
separate lofty fiber grid and fibrous mat are contacted, preferably
in continuous fashion, and entanglement of the grid strands into
the mat is accomplished by directing the adjacent layer through a
needle board. The latter consists of a single line of posts or
needles, preferably barbed, or an array of the latter, which is
caused to rise and lower repeatedly into and out of the TRM layers.
Such needle punching is well known, and is used, for example, to
prepare felts and other fabrics, and lofty glass mats suitable for
use in thermoplastic impregnated "GMT" products.
[0033] The needle board may be equipped with barbed needles, with
flat headed needles, with posts in lieu of needles, or any type of
extension which will force some of the lofty polymer grid strands
into the fibrous mat, or cause fibers from the fibrous mat to be
entangled with the polymer grid strands. Such a product is
illustrated in FIG. 2b, where strands 2 of the polymer grid are in
intimate contact with fibers 4 of the fibrous mat 3 at locations 8.
Following needle punching, in preferred embodiments, the composite
web is subjected to elevated temperature to bond the web to the
polymer grid, for example at a temperature of 140.degree. C. The
needle punching process has the advantages that it is simple and
economical and involves a process well known in fabric production;
that the degree of entanglement can be easily adjusted; that the
process can be used with multiple layers of fibrous mats and/or
multiple polymer grids sandwiching fibrous mats as shown in side
view in FIG. 4.; and that the structural integrity of the needled
and bonded TRM is very high.
[0034] An alternative method of preparing the TRM of the subject
invention is laying up the fibrous mat directly onto or into the
lofty polymer grid by wet laying or dry laying processes. For
example, in wet laying, the lofty polymer grid is positioned atop a
fiber retaining screen and the aqueous suspension of fibers applied
from the top. The fibers form a mat toward the screen surface, with
fibers being entangled during the laying process within the strands
of the lofty polymer grid. The assembly is then dried and heated to
bond the lofty polymer grid to the mat. Air laying is similar, but
employs air rather than water as a suspending medium for the
fibers.
[0035] A useful variant of the above process is to air or wet lay a
fibrous mat onto and/or within a lofty polymer grid as previously
described. In this variant embodiment, however, the low melt
temperature fibers may be dispensed with provided that they are
replaced by a particulate thermoplastic or thermoset adhesive or by
a soluble resin adhesive, which is then cured, if necessary at
elevated temperature, to bond the fibers of the fibrous mat to the
lofty polymer grid.
[0036] When more than one fibrous mat is employed, the mats may be
of the same or of different composition. When at least two fibrous
mats are employed, it is only necessary that one mat contain low
melt temperature fibers or binder, this mat positioned so as to
sandwich the fibrous mat containing no low melt fibers or binder.
When two polymer grids are employed, the grids should preferably be
positioned on opposite sides of the fiber mat(s).
[0037] The preferred needle punching process is shown schematically
in FIG. 5. In FIG. 5, a roll 10 supplies fibrous mat 11 while a
roll 12 supplies lofty polymer grid 13, the two are allowed to
contact each other, and are entangled by needle board 14, following
which they are bonded by heat source 15 to produce the integral TRM
product 16. The heat source 15 may be a hot air oven, a microwave
oven, or heat lamps, so long as the low melt temperature fibers or
binding agent, when used, is raised to a sufficient temperature to
bond the components together. A hot air oven is preferred. The
fiber mat 11 may be preformed in the same or different location and
supplied in roll form (as shown) or in folded configuration, or may
be continuously produced in an air-laying or wet-laying process and
conveyed to the needle punching station.
[0038] FIG. 6 illustrates a wet-laying process. In FIG. 6, a
suspension 20 of fibers, is supplied to a layer of lofty polymer
grid 21 which lies atop a continuous screen 22, the polymer grid
supplied by roll 23. Water from the fiber suspension flows through
the screen to tank 24, leaving the fibers behind on the screen and
entangled with the polymer grid. The initial product 25 thus
consists of polymer grid 26 entangled with fiber mat 27. This
product then is subjected to elevated temperature, for example in
oven 28 to produce an integral TRM product 29 which may be taken up
on roll 30. The intermediate product may optionally be needle
punched to provide further entanglement prior to bonding.
[0039] In a yet further embodiment, the fibrous mat further
contains continuous or intermediate length fibers, for example but
not by way of limitation, having average fiber lengths of 2 to 3
cm. or longer, and the fibrous mat is primarily attached to the
lofty polymer grid by needle punching with barbed needles, which
thoroughly entangle fibers of the fibrous mat with strands of the
lofty polymer grid. The long fibers may be supplied in forming the
web as a series of overlapping circles of strands of fiber, such as
is used to form GMT intermediate products. Use of at least some
continuous fibers is preferred. The needle punching operation
breaks many of the strands but entangles others, producing a
product where thorough entanglement produces a product wherein the
polymer grid is virtually impossible to separate from the fibrous
mat. Wood and other natural fibers are integrated at the same time.
In this embodiment, no low melt thermoplastic fibers or binding
agents need be used. The entanglement and length of the fibers
employed must be such that the overland flow velocity will not
remove the fibers in substantial amount. At the same time, the
fibers must not be packed so densely that seed emergence is reduced
significantly.
[0040] The advantages of the composite TRM of the subject invention
are many. Unlike the complex multilayer structure of U.S. Pat. No.
5,849,645, requiring numerous steps during the preparation,
including production of a "super heavy" pleated central portion,
and stitching the various layers together, the subject invention
product, in its simplest form, requires but two layers, each
produced by well known processes, which are married together into
an integral structure in a simple process. The product may be
inexpensively produced, and may be cut, for example, without the
possibility of stitching unraveling, thus rendering separation of
the layers in the field less likely. The product may also be
produced with much lower content of thermoplastic, thus being more
environmentally friendly, even though the polymer content is
generally desired to be permanent, as would be required for TRM
which meet industry description of "Permanent Turf Reinforcement
Mats."
[0041] The fibrous mat is preferably of a thickness, after needle
punching when the latter is used, of from about 1/8 inch to 3/4
inch, preferably about {fraction (3/8 )} inch, which, when exposed
to heavy rain or irrigation, breaks up the streams of water
impinging upon the TRM and drastically lowers the ability of the
raindrops to dislodge sediment. Because the layers are intimately
entangled and, in preferred embodiments, bonded, the product is
easy to handle and may be laid down on the ground in but a single
operation. The product is thus economical in application as it is
also in production.
[0042] The fibrous mat also aids in retention of sediment, and
assists seeds in germinating by retention of moisture within the
mat and shielding the soil from direct contact with both sunlight
and the atmosphere, which both bring about evaporation of water
from the ground.
EXAMPLE 1
[0043] A lofty COLBOND.TM. polymer grid from Enka-Engineered
Products is married to a fibrous web composed of 15 weight percent
low melt sheath polyester bicomponent fibers having a low melt
temperature thermoplastic sheath and a high melt temperature
thermoplastic core, available from Intercontinental, and 85 weight
percent wood fiber. The mat has a nominal {fraction (1/16)} inch
thickness. The married layers are needle punched to entangle the
fibers and subsequently heated in an oven to bond the bicomponent
fibers to the strands of the lofty polymer grid. An integral
product wherein the fibrous mat and polymer grid are impossible to
separate without substantially destroying the TRM is produced. As a
result of the needle punching, the ultimate thickness of the fiber
mat is greater than {fraction (1/16)} inch.
EXAMPLE 2
[0044] A lofty polymer grid of COLBOND.TM. is supplied on a belt
and a dry mixture of fibers including 15 weight percent bicomponent
fibers is supplied in an air stream and allowed to settle within
the interstices of the lofty polymer grid. Settling is encouraged
by a modest vacuum applied to the reverse side of the belt, which
is perforated with numerous openings. The product traverses an oven
which bonds the bicomponent fibers to strands of the lofty polymer
grid. An integral TRM with fibers of a fibrous mat entangled with
and bonded to strands of the lofty polymer grid is produced.
EXAMPLE 3
[0045] Example 2 is repeated, except that in lieu of bicomponent
fibers, the dry fiber mixture constitutes 90% by weight wood fibers
and 10% by weight of a pulverulent polyvinylacetate/ethylene
copolymer adhesive. Upon passing through the oven, the particulate
adhesive melts, bonding wood fibers to strands of the polymer grid.
A TRM product having wood fibers entangled within and bonded to
strands of the lofty polymer grid is produced.
EXAMPLE 4
[0046] The process of Example 1 is followed, but two layers of
lofty polymer grid are supplied, one on each side of the fibrous
mat. After needle punching and thermal bonding, an integral TRM is
prepared which is substantially symmetrical, either side of which
may be installed against the earth.
EXAMPLE 5
[0047] A fibrous mat is prepared by air-laying a 3/8 inch layer of
wood fibers and crimped synthetic fibers. The initially formed mat
passes under a distribution head which lays down multiple strands
of continuous synthetic fiber, each strand comprising numerous
filaments. The strands are laid down as overlapping circles, and
constitute about 30 weight percent of the total intermediate fiber
web. A polymer grid of COLBOND.TM. is laid atop the fibrous mat and
exposed to needle punching with barbed needles. The needle punching
operation thoroughly entangles fibers of the fibrous web with
strands of the polymer grid to produce an integral product without
requiring bonding at elevated temperature.
[0048] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
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