U.S. patent application number 10/188941 was filed with the patent office on 2003-01-09 for low binder nonwoven fiber mats, laminates containing fibrous mat and methods of making.
This patent application is currently assigned to Johns Manville International, Inc.. Invention is credited to Bennett, Glenda Beth, Kajander, Richard Emil.
Application Number | 20030008586 10/188941 |
Document ID | / |
Family ID | 23699730 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030008586 |
Kind Code |
A1 |
Kajander, Richard Emil ; et
al. |
January 9, 2003 |
Low binder nonwoven fiber mats, laminates containing fibrous mat
and methods of making
Abstract
A nonwoven fibrous mat containing non-cellulosic fibers such as
glass fibers, mixtures of glass fibers and synthetic polymer
fibers, ceramic fibers, mixtures of glass fibers and natural fibers
and mixtures thereof bound together with a water soluble,
formaldehyde free binder, the binder content of the mat being in
the range of about less than about 4 weight percent of the dry mat
is particularly useful in making wood or wood product laminates.
The mat can also contain limited amounts of cellulosic fibers. The
low binder content produces mat manufacturing efficiencies and
advantages in the wood laminate.
Inventors: |
Kajander, Richard Emil;
(Toledo, OH) ; Bennett, Glenda Beth; (Toledo,
OH) |
Correspondence
Address: |
Johns Manville Corporation
Intellectual Property (R21D)
10100 West Ute Avenue
Littleton
CO
80127
US
|
Assignee: |
Johns Manville International,
Inc.
|
Family ID: |
23699730 |
Appl. No.: |
10/188941 |
Filed: |
July 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10188941 |
Jul 3, 2002 |
|
|
|
09428632 |
Oct 27, 1999 |
|
|
|
Current U.S.
Class: |
442/327 ;
442/415; 442/417 |
Current CPC
Class: |
Y10T 442/697 20150401;
Y10T 442/699 20150401; D04H 1/64 20130101; Y10T 442/60
20150401 |
Class at
Publication: |
442/327 ;
442/415; 442/417 |
International
Class: |
D04H 003/00; D04H
001/00; D04H 005/00; D04H 013/00 |
Claims
We claim:
1. A nonwoven fibrous mat comprising non-cellulosic fibers selected
from the group consisting of glass fibers, mixtures of glass fibers
and synthetic polymer fibers, ceramic fibers, mixtures of glass
fibers and natural fibers and mixtures thereof bound together with
a water soluble, formaldehyde free binder, the binder content of
the mat being in the range of about 0.5-4 weight percent of the dry
mat.
2. The mat of claim 1 wherein the binder content of the dry mat is
within the range of about 1-3 percent.
3. The mat of claim 2 wherein the binder is selected from the group
consisting of polyvinyl alcohol, carboxy methyl cellulose, ethoxy
methyl cellulose and hydroxy ethyl cellulose.
4. A nonwoven fibrous mat comprising non-cellulosic fibers selected
from the group consisting of glass fibers, mixtures of glass fibers
and synthetic polymer fibers, ceramic fibers, mixtures of glass
fibers and natural fibers and mixtures thereof, and cellulosic
fibers, wherein the cellulosic fibers are present in an amount less
than half the total weight fibers per unit area of mat, the fibers
being bound together with a water soluble, formaldehyde free
binder, the binder content of the mat being in the range of about
0.5-4 weight percent of the mat.
5. The mat of claim 2 wherein the mat contains cellulosic fibers in
an amount less than half the total weight of fibers per unit area
of mat.
6. The mat of claim 3 wherein the mat contains cellulosic fibers in
an amount less than half the total weight of fibers per unit area
of mat.
7. The mat of claim 1 wherein the non-cellulosic fibers are glass
fibers.
8. The mat of claim 2 wherein the non-cellulosic fibers are glass
fibers.
9. The mat of claim 3 wherein the non-cellulosic fibers are glass
fibers and the binder is cellulosic.
10. The mat of claim 4 wherein the non-cellulosic fibers are glass
fibers and the binder is cellulosic.
11. A method of making a nonwoven fiber mat comprising forming a
web of fibers, applying an aqueous based, water soluble,
formaldehyde free binder to the web of fibers, and drying the web
and curing the binder to form a finished mat, the binder content
being controlled such that the binder content of the finished mat
is in the range of about 0.5-4 weight percent.
12. A method of making a wood or wood product laminate comprising
placing a fiberous nonwoven mat containing glass fibers and having
a formaldehyde free binder therein on a surface of a wood adhesive
covered wood layer to form a laminate precursor and applying heat
and pressure to the precursor to dry and cure the adhesive, the
improvement comprising that the binder content of said fibrous mat
is within the range of about 0.5-4.0 weight percent of the mat on a
dry basis.
13. The method of claim 12 wherein the binder content is within the
range of about 1-3 wt. percent.
14. A wood laminate or wood product made by the process of claim
12.
15. A wood laminate or wood product made by the process of claim 13
Description
[0001] This application is a continuation of application Ser. No.
09/428,632, filed Oct. 27, 1999.
[0002] The present invention involves nonwoven mats having
particular use in bonding to wood and wood products in making
improved wood laminates and the method of making such mats and
laminates. The mats produced according to this invention are useful
as reinforcement and dimensional stabilizers for making a large
number of products such as wood composites or laminates of all
types, such as structural veneer plywood and hard faced wood
products like laminated veneer lumber, plywood, and various boards
like particle board, OSB, etc. for many uses. The mats are also
useful as stabilizing and reinforcing substrates for various other
wood products.
BACKGROUND
[0003] It is known to make reinforcing nonwoven mats from fibers
and to use these mats as substrates in the manufacture of a large
number of products. Methods of making nonwoven mats are known, such
as the conventional wet laid processes described in U.S. Pat. Nos.
4,112,174, 4,681,802 and 4,810,576, the disclosures of which are
hereby incorporated herein by reference. In these processes a
slurry of glass fiber is made by adding fiber to a typical white
water in a pulper to disperse the fiber in the white water forming
a slurry having a fiber concentration of about 0.2-1.0 weight %,
metering the slurry into a flow of white water to dilute the fiber
concentration to 0.1 or below, and depositing this mixture on to a
moving screen forming wire to dewater and form a wet nonwoven
fibrous mat.
[0004] This wet nonwoven web of fiber is then transferred to a
second moving screen and run through a binder application
saturating station where an aqueous binder mixture, such as an
aqueous urea formaldehyde (UF) resin based binder mixture, is
applied to the mat in any one of several known ways. The binder
saturated mat is then run over a suction section while still on the
moving screen to remove excess binder. The wet mat is then
transferred to a wire mesh moving belt and run through an oven to
dry the wet mat and to cure (polymerize) the UF based resin binder
which bonds the fibers together in the mat. Preferably, the aqueous
binder solution is applied using a curtain coater or a dip and
squeeze applicator, but other methods of application such as
spraying are also known.
[0005] In the drying and curing oven the mat is subjected to
temperatures up to 450 or 500 degrees F. or higher for periods of
time usually not exceeding 1-2 minutes. Alternative forming methods
for nonwoven fiber mats include the use of well known processes of
cylinder forming, continuous strand mat forming which lays
continuous strands of glass fibers in overlapping swirls, and "dry
laying" using carding or random fiber distribution.
[0006] UF resins, usually modified with one or more of acrylic,
styrene butadiene, or vinyl acetate resins, are most commonly used
as a binder for fiber glass mats because of their suitability for
the applications and their relatively low cost. Melamine
formaldehyde resins are sometimes used for higher temperature
and/or chemical resistant applications. To improve the toughness of
the mats, a combination of higher mat tear strength and mat
flexibility, which is needed to permit higher processing speeds on
roofing product manufacturing lines and for maximum roofing product
performance on the roofs and in other applications, it is common to
modify or plasticize the UF resins as described above. The binder
content of these finished mats typically are in the range of 15 to
25 weight percent or higher, based on the dry weight of the
mat.
[0007] Mats made in the above described manner perform well in many
applications, but do not provide the bonding strength desired for
bonding to wood products.
SUMMARY OF THE INVENTION
[0008] The nonwoven mats of the present invention comprise fibers
making up at least 90, preferably at least 95-weight percent or
more of the mat, preferably with at least 80 weight percent of the
fibers being glass or inorganic fibers. The fibers are bonded
together with a very small amount of a resin binder containing
essentially free of urea formaldehyde, phenol formaldehyde melamine
formaldehyde or furfuryl alcohol formaldehyde resins. In this
invention the presence of one or more of these conventional
formaldehyde containing binders is not required and normally would
not be present except as an impurity or trace amount. This is a
substantial advantage in those areas where it is desirable to
eliminate or minimize the presence of compounds containing
formaldehyde from a product.
[0009] The resin binder is preferably a water soluble binder like
polyvinyl alcohol, hydroxy ethyl cellulose, carboxy methyl
cellulose, cellulose gums, polyvinyl pyrilidone, polyvinyl acetate
homopolymer, and mixtures thereof. By a "small amount" is meant
that the binder is no more than about five percent, preferably less
than four percent, and most preferably less than three percent of
the dry mat and usually is at least 0.3 weight percent, most
preferably between about one to three weight percent. All percents
used herein are weight percents unless otherwise stated.
[0010] The preferred fiber is glass fiber, but other fibers
including synthetic fibers of all kinds such as polyester, nylon,
polypropylene, etc., carbon fibers, ceramic fibers, metal fibers,
etc., can be present in amounts up to 100 percent of the fibers. A
minority of the fibers can be cellulosic fibers or fibers derived
from a cellulosic derivative, i.e. less than half the total weight
of fibers per unit area of mat. So called "binder fibers" can be
used in lieu of liquid binder. These binder fibers are typically
made of polyvinyl alcohol, polyvinyl chloride, polyolefins and
their copolymers. Binder fibers can also be bi-component such as a
polyester core covered with a sheath of polyethylene.
[0011] The mats of the present invention have lower physical
properties initially like tensile strength, hot wet strength and
tear strength than conventional mats, but the mats of the present
invention surprisingly produce high bonding strength with wood.
Most importantly, use of the inventive mat produces higher glass
fiber loadings in the "glue line" of wood laminates and composites
than prior art mats for this purpose have produced. The present
invention is based in part on the discovery that limiting the
binder content in the finished mat to a low level greatly improves
the bond strength between the mat and wood, or a wood product,
reduces the amount of undesired organic material in the nonwoven
fiber reinforced glue lines in the resultant wood composite and
increases the amount of desired wood bonding adhesive in nonwoven
glass fiber reinforced glue lines. The low level of resin binder
that is water soluble or water sensitive also allows for limited
movement of the glass fiber network present in the mats of the
invention, instead of rigid fracture during laminate forming, under
high pressure which is characteristic of the thermosetting
formaldehyde containing resin binders.
[0012] The mats of the present invention are particularly suited
for use in the manufacture of wood composites or composites of wood
products or mixtures of wood and wood products as well as wood
veneer laminations. Herein, when wood composite is used it is
intended to include all kinds of composites containing one or more
wood layers, one or more wood product layers and one or more
fibrous nonwoven mat layers. By wood products is meant products
like hardboard, particle board, chip board, oriented strand board,
laminated veneer lumber, gluelam timbers and the like, i.e. where
the major portion of the material is wood in some form. The present
invention also includes precursors of wood laminates or wood
composites containing at least one layer of wood or wood product
and one or more layers of the above described inventive mats.
[0013] By "formaldehyde free" it is meant containing essentially no
formaldehyde, i.e. formaldehyde is not essential in the mats of the
present invention, but might be present as an impurity in trace
amounts. By "water soluble" is meant can be dissolved in water.
[0014] The present invention also includes a process of making the
inventive nonwoven fiber mats described above from a slurry of
fiber, preferably glass fiber, comprising forming a nonwoven web on
a moving, permeable surface and thereafter saturating the fibrous
web with an aqueous based binder, preferably water soluble such as
polyvinyl alcohol binder with or without modification, removing
excess aqueous binder and drying and curing the mat in an oven. The
resultant mat is normally wound into rolls and packaged for
shipment, and/or transported to a point of use.
[0015] The present invention also includes a process wherein one or
more layers of the inventive mat are, after being impregnated with
a normally used conventional wood adhesive, placed in contact with
one or more layers of wood or wood product and the resulting
laminate or precursor are then subjected to high pressure and
sufficient heat to cure the adhesive.
[0016] The present invention also includes wood laminates, wood
composites and veneered wood products containing one or more layers
of mat of the present invention as an intermediate layer bonded
between two or more layers of wood or wood veneer.
[0017] The inventive mats and glue lines of the wood laminates and
composites of the present invention can also contain pigments,
dyes, flame retardants, and other additives so long as they do not
significantly reduce the ability of the mat to bond to a wood
surface. The pigments or other additives can be included in the
fiber slurry, the binder slurry or can be sprayed or otherwise
coated onto the mat later using known techniques or included in the
wood adhesive.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Mats of the present invention contain about 93-99.5,
preferably about 96-99.5, weight percent fibers and about 0.5-4,
preferably 0.75 to less than 3, weight percent binder or binder
fiber, exclusive of any additives like pigments, etc. as described
below. Binder contents in the dry mat in the range of 2-3 wt.
percent are most preferred. The majority of the fibers are
preferably glass fibers, but other fibers can be present. The glass
fibers which can be used to make mats can have various fiber
diameters and lengths dependent on the strength and other
properties desired in the mat. It is preferred that the majority of
the glass fibers have diameters in the range of about 6 up to about
23 microns, with the major portion of the fiber being preferably in
the range of about 10 to 19 microns and most preferably in the
range of about 13 to 17 microns, such as about 15-17 microns.
[0019] The glass fibers can be E glass, C glass, T glass, S glass
or any known glass fiber of good strength and durability in the
presence of moisture. Rotary made fibers of glass, basalt and slag
can also be used, but are not preferred. Preferably, the glass
fibers used are chopped continuous glass fibers, usually all having
about the same target length, such as 0.25, 0.5, 0.75, 1 or 1.25
inch, but fibers of different lengths and different average
diameters can also be used to get different characteristics in a
known manner. Fibers up to about 3 inches in length can be used in
a wet process for making fiber glass mats and even longer fibers
can be used in some dry processes. Generally, the longer the fiber,
the higher the tensile and tear strengths of the mat, but the
poorer the fiber dispersion. Also, continuous strands containing a
plurality of fibers can be introduced into the slurry of fibers
just before forming the mat in a manner known in the wet laid mat
forming industry to produce continuous reinforcement in the fibrous
nonwoven mat.
[0020] While the majority of the fibers used in the present
invention are glass fibers, a minor portion of non-glass fibers can
also be used, such as cellulosic fibers including wood pulp of all
kinds, cotton linters, cellulose derivatives such as cellulose
triacetate, rayon, etc. Man-made organic synthetic polymer fibers
such as nylon, polyester, polyethylene, polypropylene, etc. can
also be used instead of cellulose fibers in any various blends with
one or more cellulosic fibers.
[0021] The binders used to bond the fibers together are preferably
resins that can be put into aqueous solution or emulsion latex and
that are water soluble. Typical resin based binders meeting this
description are polyvinyl alcohol, carboxy methyl cellulose,
hydroxy ethyl cellulose, lignosulfonates, cellulose gums and other
similar resins. Of these, polyvinyl alcohol resin is much preferred
because of its water solubility and the good dry tensile strength
it produces, its bonding strength to fibers, particularly glass
fibers, its reduced levels of volatile organic compound (VOC)
emissions, its phenol-free and formaldehyde-free nature and its
stability in storage.
[0022] A particularly useful polyvinyl alcohol resin for use in
this invention is AIRVOL.TM. 205 resin available from Air Products
and Chemicals, Inc. of Allentown, Pa. AIRVOL.TM. 205 resin is
partially hydrolyzed, highly reactive, water soluble and contains
low levels of volatile components. It has a specific gravity of
about 1.3 grams/cc and has a viscosity of about 5 cps at 4 percent
concentration in water. AIRVOL.TM. 205 resin is fully compatible
and redissolvable in numerous phenolic, urea and melamine resin
based adhesives normally used in bonding layers of wood
together.
[0023] A particularly useful carboxyl methyl cellulose resin for
this invention is CMC AQUALON.TM. 7A available from Hercules, Inc.
of Wilmington, Del. Another binder useful in the present invention
are lignosulfonates, particularly the type used for foundry sand
and ceramic products. Other suitable binders for the mat include
resin based fiber sizings, so called "wet strength"
non-formaldehyde resins used in the paper industry, non-crosslinked
polyvinyl acetate homopolymer latex. Water sensitive or soluble
binder fibers, usually made from PVOH, can also be used in lieu of
resinous binders.
[0024] Processes for making nonwoven fiber glass mats are well
known and some of them are described in U.S. Pat. Nos. 4,112,174,
4,681,802 and 4,810,576, which references are hereby incorporated
into this disclosure by reference, but any known method of making
nonwoven mats can be used. The preferred technique for the making
of mats of the present invention is forming a dilute aqueous slurry
of fibers and depositing the slurry onto an inclined moving screen
forming wire to dewater the slurry and form a wet nonwoven fibrous
mat, on machines like a Hydroformer.TM. manufactured by
Voith-Sulzer of Appleton, WS, or a Deltaformer.TM. manufactured by
Valmet/Sandy Hill of Glenns Falls, N.Y. The examples disclosed
herein were made on a pilot scale model of a wet forming machine,
binder applicator, and oven that produces a mat very similar to a
mat that would be produced from the same slurry and binder on a
production sized Voith-Sulzer Deltaformer.TM. with a curtain coater
binder applicator and a flat bed, permeable conveyor type
convection dryer.
[0025] After forming a web from the fibrous slurry, the wet,
unbonded fibrous nonwoven web or mat is then transferred to a
second moving screen running through a binder application
saturating station where the binder, preferably resin based, in
aqueous solution is applied to the mat. The excess binder is
removed, and the wet mat is transferred to a moving permeable belt
that runs through a convection oven where the unbonded, wet mat is
dried and cured, bonding the fibers together in the mat. In
production, the dry, cured mat is then usually wound into rolls and
packaged such as by stretch or shrink wrapping or by putting into a
plastic bag to keep out moisture and dirt, etc.
[0026] Preferably, the aqueous binder solution is applied using a
curtain coater or a dip and squeeze applicator. In the drying and
curing oven the mat is heated to temperatures of up to about 300
degrees F., but this can vary from about 220 degrees F. to as high
as will not embrittle or deteriorate the binder, usually around 450
degrees F., for periods usually not exceeding 1 or 2 minutes and
frequently less than 40 seconds, preferably significantly less than
30 seconds.
EXAMPLE 1
[0027] A fiber slurry was prepared in a well known manner by adding
one inch long wet E type glass chopped fiber having fiber diameters
averaging about 16 microns and cellulose fibers, standard bleached
softwood kraft fibers, in a ratio of 80 weight percent glass fibers
and 20 weight percent cellulose fibers. These fibers were added to
a known cationic white water containing Natrosol.TM. thickening
agent available from Hercules, Inc. and a cationic surfactant C-61,
an ethoxylated tallow amine available from Cytec Industries, Inc.
of Morristown, N.J., as a dispersing agent to form a fiber
concentration of about 0.2 weight percent. After allowing the
slurry to agitate for about 5-20 minutes to thoroughly disperse the
fibers, the slurry was metered into a moving stream of the same
whitewater to dilute the fiber concentration to a concentration
averaging about 0.2 weight percent before pumping the diluted
slurry to a headbox of a pilot sized machine similar to a Voith
Hydroformer.TM. where a wet nonwoven mat was continuously
formed.
[0028] The wet mat was removed from the forming wire and
transferred to a Sandy Hill Curtain Coater where an aqueous hydroxy
ethyl cellulose resin, NATRASOL.TM.250 LR, available from Hercules,
Inc., at 5 percent concentration was applied in an amount to
provide a binder level in the cured mat of about 2-3 weight
percent. The wet mat was then transferred to an oven belt and
carried through an oven to dry the mat and at a temperature of
about 350-degrees F. The basis weight of the mat produced was 1.5
pounds/100 square feet of mat. This mat is later referred to as A-1
mat.
EXAMPLE 2
[0029] Another mat was made exactly the same as the mat of Example
1, but only glass fibers were used producing a dry mat containing
97-98 wt. percent E glass fibers and 2-3 wt. percent of the HEC
binder used in Example 1. This mat, referred to as A-2 mat, had a
basis weight of 1.5 pounds/100 square feet.
EXAMPLE 3
[0030] A layer of A-2 dry mat and a layer of a conventional,
commercial type 1.7 lb./100 sq. ft. dry fiber glass mat, referred
to as A-3 mat, were used to make mat/particle board laminates. The
A-3 dry mat was made in the same manner as A-1 mat, except the dry
A-3 mat contained about 74 wt. percent 16 micron glass fibers and
about 26 percent of a conventional, cured urea formaldehyde resin
binder. The particle board used to made the laminates was 5/8 inch
thick and had a density of 45 pounds per cubic foot.
[0031] To make the laminates, one surface of a piece of the
particle board was coated with a conventional wood adhesive called
1701 RTU, a water based phenolic adhesive available from Neste
Company of Springfield, Oreg., at an application level of 30 grams
per square foot. A layer of mat was placed against the adhesive
coated face such that there was one layer of mat in the glue line
and these laminate precursors were then put under a pressure of 175
psi and a temperature of 330 degrees F. for seven minutes to dry
and cure the adhesive. After releasing the pressure and cooling,
the laminates and a piece of the particle board had the following
properties in a conventional three point loading test.
1 TABLE Type of Specimen MOE* MOR** Particle Board alone 355,956
2,019 Particle Board/adhesive/A-3 mat 466,520 3,064 Particle
Board/adhesive/A-2 mat 462,035 2,700 *Modulus of Elasticity in
pounds/square inch. **Modulus of Rupture in pounds/square inch.
[0032] These data show that adhering a nonwoven fiber glass mat to
the surface of a wood product, in this case particle board,
enhances the strength of the particle board. This also provides the
particle board with a tougher surface, and if put on both surfaces,
helps stabilize the board from warping due to temperature and/or
humidity or moisture changes. These data also shows that similar
and adequate strength is achieved in the laminate using a mat of
the present invention containing a very low binder content, but
having a substantial advantage of having much less non-adhesive
organics in the glue line resulting in a more flame resistant
laminate. Other advantages of the low binder mat is that it is less
costly to manufacture because the binder is often more costly than
the fiber and mat containing less binder can be dried and cured at
a much faster line speed, with a substantially lower level of
binder emissions during curing.
[0033] Any normally used water based wood adhesive can be used with
the inventive mat to make inventive wood laminates. Another
suitable adhesive is GP 5102 RESI-MIX.TM., a water based phenolic
adhesive available from the Georgia Pacific Corporation of Atlanta,
Ga. Also, the laminate can vary from one layer of wood, plywood,
veneer, or other wood product with an inventive fiber mat bonded to
one, two or all surfaces to provide a tough, reinforced surface(s)
to multiple layers of wood, etc. having many glue lines with one or
more layers of an inventive mat in one or more glue lines, with or
without one or more reinforced surfaces.
[0034] It is not usually practical or economically possible for an
inventor to determine the precise limitations of his invention
because once an attractive result has been found, the effort and
priority shifts to those things necessary to satisfy potential or
actual customer needs with the invention. Therefore, when the word
"about" is used herein to describe a numerical amount, it means the
amount or range stated, or approximately the amount or range
stated, so long as the amount that approximates the numerical
amount or range produces the advantages disclosed for the
invention.
[0035] Having the benefit of the above disclosure, many other
modifications will be obvious to the skilled artisan, all of which
are intended to be included in the scope of the following
claims.
* * * * *