Note: Descriptions are shown in the official language in which they were submitted.
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A FIBROVS Ml\T ESPECIALLY SUITABLE FOR RQO~ING PRODUC'rS
AND A METHOD OF MI~KIN(; THE MAT
Back round of the Invention
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Field of the Invention
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The present invention relates generallY to
fibrous glass mats and more particularlv to an improved
fibrous glass mat especially suitable for use in roofiny
shingles and a method of making such a mat.
Description of the Prior Art
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In the past, most asphalt roofing shingles were
constructed of organic rag felt impregnated and coated with
asphalt or other such bituminous substance, the rag felt,
in most cases, being made on a cylinder paper machine.
More recentl~, the demand for and production of this type
of shingle has increased substantially. For example,
in 1961, the industry produced and sold approximately ;
40 million squares of asphalt shingle for customer use. ~-
A square covers lO0 square feet of roof area and, in 1961, `
cost the contractor approximately seven dollars. In 1971,
approximately 57 million squares of asphalt shingles were
produced and sold at a cost of about nine dollars a s~uare.
The estimated industry production and sale of asphalt `
shingles in 1981 is approximately 74 million squares. It
should be apparent rom these figures that the asphalt
roofing market is highly significant and growing at a
rapid rate.
In responding to the afores-tated increase in
demand and production of asphalt roofing material, industry
has found that the addition of new cylinder paper machines
for producing rag felt is very expensive. Further, in ~ ;~
depleting the supply of materials needed in making rag
felt, the latter has itself become more expensive. For
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1 these r~asons, industry has taken a look at other type~
of shin~le ~ats and particularly mats made of fiber glass.
In developing a new type of glass mat especially
suitable for roofing shingles, there are three basic
objectives which should be achieved. Firstly t the glass
mat should be inexpensive so that competitively priced shingles
can be produced. Secondly, the glass mat should be uniform
so as to avoid production discontinuity and waste which
otherwise increases the manufacturing cost of the mat and
therefore the shingle. Thirdly, the mat should display
sufficient tearing resistance for maintaining integrity
and resistance against blow-offs of the applied shingles
under severe wind conditions.
Heretofore, the prior art has not satisfactorily
met all three of the foregoing objectives. For example,
one suggestion has been to provide a steam-blown glass
fiber mat. While this type of mat is relatively inexpensive
to manufacture, it has been found to display unsatisfactory
tear resistance, thereby resulting in a shingle highly
2~ susceptible to blow-off. On the other hand, a dry forming
process swirl reinforced mat utilizing a web of base fibers
and swirled continuous glass filaments as reinforcement
fibers has also been suggestecl by the prior art. While the
latter type of mat has been found to display better tear
resistance than the steam-blown mat, the dry process utilized
in forming such a mat is expensive and slow. Due to rela- -
tively low production output and relatively high labor re-
quirements utilized with this process, the ultimate product
is relatively expensive. In addition, it has been found
~0 that this type of mat is not reliably uniform in production,
resulting in production discontinulty and waste and therefore
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1 u~necessar~ co~t and delay. For the most part, t~e
prior art h~5 been unable to produce such a ma-t other than
by -the dry process. This drastically limits the ability
to adequately disperse the reinforcement fibers throughout
the base fiher web, resulting in a limitation on the tear
strength of the ultimately produced mat.
Even in view of the foregoing deficiencies,
industry has continued to look towards glass mat for the
production of asphalt shingles. For example, in 1961, the
use of glass mat for this purpose was substantially non-
existent. In 1971, approximately 250,000 squares of
asphalt shingles with glass mat were produced and sold.
The projection for 1981 is that approximately 11 million
squares of asphalt shingle using glass mat will be produced
and sold in that year. Because of this increased demand
for roofing shingles and mat generally and glass mat in
particular, competition in this field has become keener.
In addition, the capability to produce a more economical
and uniform mat with satisfactory tear resistance has become
increasingly more important.
As will be seen hereinafter, the present invention
has overcome many o the problems left unsolved in the prior
art by providing a fibrous glass mat which is more economicallv
and uniforml~ produced and which displays improved teax
resistance. In this manner, a more economical and higher -
quality shingle can be produced.
Ob ects and Summar of the Invention
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In accordance with the foregoing, an object
of the present invention is to provide an economical `~
method of making a uniform fibrous glass mat displaying
improved tear resistance.
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1 ~nother ob~ect of the present invention is to
provide such a mat displayinc3 uniformity and improved
tear resistance.
Yet, another object of the present invention
i5 to provide a roofinc3 product utilizing the aforestated
mat such that the roofing product is economical and dis-
plays improved blow-off resistance.
As will be seen in more detail hereinafter, these
objects, as well as other objects and features, are attained
and manv of the deficiencies of the prior art are eliminated
by the present invention which sets forth a wet forming
process of making a fibrous glass mat especially suitable
for use in shingles. The mat comprises a web of monofila-
ment glass fibers and elongated glass fiber bundles having
ends and binder substance to assist in holding the mono-
filament fibers and fiber bundles together. By making
such a mat by the particular process of the present inven-
tion, the mat can be made in a more economical and uniform
manner. Further, the glass fibers and fiber bundles are
dispersed in a randomly oriented fashion throughout the
web and a majority of the ends of the fiber bundles are
within the confines of the web. This, in turn, increases
the tearing resistance of the mat and therefore the blow-off
resistance of a shingle made with the mat.
Brief Descri tion of the Drawings ;
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Figure 1 is an enlarged perspective view of a
fibrous glass mat designed in accordance with the present
invention.
Figure 2 is a schematic illustration o-f a
method of making the mat in accordance with the present ;
invention.
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1 Figure 3 is a graphic lllustration displaying
tear resistance o an asphalt shingle made with a ylass
mat of the present invention.
Detailed Description
Turning to the drawings, a fibrous glass ma~
constructed in accordance with the present invention is
illustrated in Figure 1 and generally designated by the
reference num~ral 10. The mat is comprised of a web 12
of monofilament glass fibers (base fibers) and elongated ;~
glass fiber bundles 14 (reinforcement bundles) having ends,
the glass fibers and fiber bundles being dispersed through-
out the web in a randomly oriented pattern. In addition,
a suitable binder substance is provided to assist in
holding the base fibers and reinforcement bundles together.
The glass fiber bundles, a majority of which have their
opposite ends terminating well within the confines of the ~ -~
web, provide highly satisfactory tear resistance to the ` ~`
mat, especially where the latter is used as part of an
asphalt shingle. ~ ~
As will be described in more detail hereinafter, '
fibrous glass mat 10 is made by forming a slurry, preferablv
a water slurry, including the base fibers and reinforcement
bundles such that the solids content o the slurry is very
low, preferably approximately 0.2~. Under intense agitation,
the base fibers and reinforcement bundles are substantially
completely dispersed throughout the slurry. After this
dispersing operationl the fiber containing slurry is applied
to a moving screen where, by means of vacuum, a majority of -
the water is removed resulting in the aforedescribed web of
base fibers and reinforcement bundles. After formation of
the web, a binder substance is applied thereto so as to -~
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1 assist in bonding the Fiber5 and Eiber bundles togeth~r.
Thereafter, the bonded web is passecl through a dryer for
evaporating any water remaining in the web and for curing
the binder.
It should be noted that by providing a fibrous
slurry, and preferably a slurry of low fiber content, a
highly uniform mat can be produced, especially in com-
parison to the less uniform mat formed by the dry forming
process. This, of course, minimiæes production dis-
continuity and product wastage and therefore minimizes
manuacturing cost. In addition, by providing this
slurry, the reinforcement bundles, that is, the glass
iber bundles can be readil~ dispersed throughout the
web in the manner described above, thereby resulting
in a mat with improved tear resistance. Further, by pro-
viding a wet forming process of the type described herein,
the rapidity of production can be substantially increased
over that of the dry forming process, in some cases ten
fold, and the re~uirement of producing base fibers simul-
2~ taneously with the production of the mat can be eliminated.
Both of these latter features maximize efficiency and
minimize cost in mat production.
Having briefly described the fibrous glass mat
10 and process for making the same in accordance with the
present invention, attention is now directed to a more
detailed analysis of the components making up the mat.
In this regard, attention is directed to the base fibers ~ ;
which, as set forth above, are~monofilament glass fibers.
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These monofilament fibers are pre-chopped to desired lengths
from continuous strands, preferably in an independent
operation apart from and unrelated to the forming operation
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1 of mat 10. Thi~ independent operation has been found to
be less costly than the simultaneous production of base
fiber and mat typically carried out in the dry forming
process of a glass mat. ~s will be seen hereinafter,
the strands break up into individual monofilament fibers
when placed in the slurry.
While there is no absolute limitation on dis-
crete length of the monofilament fibers, a preferred
broad range is between approximately 12 mm and 60 mm.
With respect to monofilament fibers below 12 mm, it has
been found that the chopping machinery used to date has
been unable to satisactorily chop the continuous filaments ~;
to such shorter lengths. On the other hand, monofilament
fibers above approximately 60 mm tend to cause fiber
entanglement in the slurry and poor dispersion. It has
been found that the best operating range is between approxi-
mately 22 mm and 35 mm. ;~-
Like the length of the monofilament glass fibers ~ ;
or base fibers, there is no ahs~Qlute limitation on the
diameter of these fibers. However, due to practical and ~;
economical considerations, they are preferably between
approximately 12~ and 19~ in diameter. This range includes ;~
the K, M and P filaments, all o which are readily available
and economical to use. In addition, the density of the ~ ~
ultimately produced mat is related to the diameter of the ~;
base ibers and therefore can be regulated by the proper
selection of base fiber diameter.
The preferred amount of base fiber used in
mat 10 is dependent upon the amount o fiber content
provided by the reinforcement fiber bundles. Hence,
this will be discussed hereinafter with respect to the
detailed discussion of the latter.
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1 Attention is now directed to the elongated
cJlass fiber bundles or reinforcement bundles. Each of
-these bundles is macle from a plurality of monofilament
ylass fibers which are preferably in the diameter range
of approximately 12 ~ to l9~L( for the same reasons dis-
cussed above. The exact number of monofilaments provided
in each bundle will depend upon the desired strength and
thickness of the latter. A good working range has been
found to be between approximatel~ 20 and 300 monofilaments
0 per bundle. Since it is important to keep these bundles
intact throughout the mat forming process, they are
coated with a water or other such liquid insoluble binder
of known kind. This keeps the bundles bonded together even
when exposed to the forming slurry.
There is no absolute limitation on the length
of the glass fiber bundles. However, when the fiber bundles
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are below approximately 15 mm in length, their function
as a reinforcement is, in many cases, unreliable, especially
where the ultimately produced mat is to be used as part of
a roofing shingle. On the other hand, when the bundles ~ ;
are above approximately 100 mm in length, they tend to
tangle up in the slurry. ~s a good operating range, the
fiber bundles are preferably between approximately 65 mm
and 75 mm in length.
As stated above, the amount of monofilament
base fibers in mat 10 will depend upon the fiber content
of the reinforcement bundles. In this regard, of the total
fiber content (by dry weight) attributed to the base
fibers and fiber bundles, there can be as little as 5%
fiber content attributed to the bundles or as much as 90%.
Below 5%, the fiber bundles do not contribute any significant
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1 reinforcem~nt to the mat and ab~ve 90% the Eibers tend to
provide an ov~rl~ dense and non-uniform mat.
Where the contemplated use or mat 10 i5 the
carrier material for an asphalk shingle, the pre~erred
range of fiber content atkributed to ~he fiber bundles
i~ between approximately 5% and 30% (by dry weiyht). With
this range, there is adequate xeinorcement for improved
tear resistance in the ultimately produced ma-t but the
mat is not so dense to be unsuitable or shingle use. Within ~-
this latter range, a highly satisfactory mat or use in
shingles has been found to include approximately 15% fiber
content attributed to the reinforcement bundles.
As stated above, the foregoing percentages of
fiber content are those attributed to the fiber bundles
in relation ~o the total of base Eibers and iber bundles.
Hence, the amount of base fiber in any given mat can be ;
readily calculated from the amount of fiber comprising
the reinforcement bundles. These percentages will, of
course, decrease when the binder is taken into consider-
ation. In this regard, mat 10 includes a binder to
cooperate in holding the monofilament base fibers and
fiber bundles together. The amount of binder provided ~`
will depend upon the use of the ultimately formed mat. ~;
As a general range, the mat may include binder as low as
j~ 3% of the total dry weight of the mat or as high as 45%.
' For use in shingles, however, best results are attained
by using binding substance in an amount equal to approxi-
mately 15~ of the total dry weight of the mat. An amount
substantially less than this figure does not adequately
hold the fibers together while an amount substantially
greater than this figure does not appear to he necessary.
Any suitable blnder known by those skilled ~n the art can
be used, such as, ~or example, urea-~ormaldehyde.
With fibrous glass mat 10 constructed ln the
foregoing manner, attention is now d~rected to fI6. 2 which
illustrates a method of making the mat in accordance with
the present invention. Specifically, the aforedescribed mono-
filament base fibers whlch are compressed together in bundles
and reinforcement Fiber bundles, having been provided and
chopped to the preferred lengths, are dispersed into an
opening mixing tank 20 which includes a water slurry. A
suitable dispersan~ such as, for example, a cationic surfac-
tant, for example one designated by the trademark AEROSOL,
is also introduced into the slurry. At this point, the
bundles of monofilament base fibers start to separate into
individual monofilaments in the slurry. Both types of fiber
are carefully metered into the tank in constant relation to ;
the slurry so as to maintain an exact, preferably very low~
fiber concentration. In fact, a preferred ~iber concentration
is approximately 0.2%. The metering operation also measures
and limits the relative amounts by weight of base fibers to
reinforcement fiber bundles to be provided in the slurry,
such as, for example, 85X base ~ibers to 15% fiber bundles.
From opening tank 20, the fibrous slurry is
passed through two larger tanks, a pre-mixing tank 22 and
a main mixing tank 24, where it is intensely agitated so
as to cause the bundles of monofilament base fiber to
completely break up and to achieve complete dispersion of
the fibers generally. As the dispersed fibrous slurry - ~ ;~
passes downstream from main tank 24, the fiber concentra- -
tion is further reduced at point 26 by introduction of
additional water. At this point the fiber concentration
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1 is preferably approximately l/20th of the ori~inal sluxry
concentration.
From polnt 26, the slurry passe~ to a conven-
tionally known head box or h~droformer 28. In the
hydroformer, -the fi~rous slurry passes over a moving
wire screen arranc3ement 30 where most of the water is
removed by vacuum, as indicated at 32, thus forming a
web of base fibers and reinforcement bundles. The water
removed b~ vacuum enters either of two recycle tanks 34
where it can be recirculated to opening tank 20 and point
26.
After the web is formed on moving screen 30, ~;
it is moved downstream where a binder i9 applied thereto
by means of a conventional applicator device 36 which, as
illustrated, may provide recirculation of excess binder.
Downstream from applicator device 36, the bonded fibrous
mat is transferred to a moving conveyor 38 which passes ~;~
the mat through a drying oven for evaporation of water
contained in the mat and curing of the binder.
As set forth above, the reinforcement fiber
bundles are pre~chopped and introduced to the slurry
in the opening tank 20. It is to be understood that the ;~
fiber bundles could also be introduced into the premixing
tank 22, main mixing tank 24 or directly into the ;;
hydroformer 28. However, it has been found that intro-
duction into the opening tank provides best dispersion
of the fibers.
The foregoing method of making mat lO is both
rapid and economical, especially compared to the dry
forming process of making the aforedescribed swirl rein~
forced mat. In addition, by using a slurry of low fiber
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1 concentration in producing mat 10, mat uniEormity can be
readily and consistentl~ a-ttained. F~lrther, the slurry
of low fiber concentration allows -the fiber bundles to
disperse throughout the web of monofilament base ibers
in a randomly oriented pattern such that a subs-tantial
number of the bundles have their ends terminating well
within the con-fine~ oE the web. This substantially increases
the tear resistance of the ultimately produced mat, as will
be shown with respect to Figure 3.
~fter mat 10 has been made, it can be used for ~`
many different purposes. IIowever, a major use for the mat
is its incorporation into bituminous roofing products gen-
erally and asphalt roofiny shingles in particular. In this
case, the mat is preferably 0.035 inches thick and preferablv
displays a weight of approximately 2.05 lbs./100 sq. t. As
stated above, the weight is best regulated by regulating the
diameter of the afore-described monofilament base fibers.
Hence, it has been found that base fibers displaying a
diameter between approxi-mately 14 ~ and 16 ~ are satisfactory
to achieve this weight. ~
The specific methods of making asphalt shingles ~ `
or other roofing products with glass mat are well known
to those skilled in the art. ~lence, a specific dis-
cussion of these methods will not be given herein. It
shall suffice to state that in all cases the mat is
coated with asphalt or other bituminous substance. The
amount and tvpe of asphalt or other such bituminous
substances used will depend on the particular roofing
product made.
Attention is now directed to Figure 3 which
graphically illustrates the tear resistance of asphalt
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1 shingles usln~ glass mat of the present invention, however,
with varying amounts of reinforcement fiber bundles. More
specifically, over forty asphalt shinyle samples were pre- ;
pared from mats. The mats of these shingles had approxi-
mately the same weight (2.00 - 2.40 lbs./100 sq. ft.),
approximately the same length monofilament base fiber (30 mm)
and reinforcement fiber bundle (70 mm) and used the same
amount and type of binder. The mats for the shingles were
made in the manner described above. However, the amount of
fiber content attributed to the reinforcement bundles and
the amount of fiber content attributed to the monofilament `~
base iber have been varied to display their affect or tear
resistance. Specifically, samples were made with 0%, 5%,
10%, 15%, 20% and 25% dry weight fiber content attributed to
the reinforcement fiber bundles of the total of base fiber
and reinforcement fiber. Hence, the samples respectivelv in-
cluded 100%, 95%j 90%, 85%, 80% and 75% fiber content
attributed to the base fiber. All of these samples were
tested for tear resistance (in grams/lb. mat on an Elmendorf
type apparatus in accordance with ASTM No. 1224 Standards.
The results have been graphically displayed in
Figure 3 where a Cartesian coordinate is shown. The
abscissa represents the percent of fiber attributed to the
reinforcement bundles and the ordinate represents the
tearing resistance attained for the given samples in grams/
lb. mat. It should be noted that for each percentage of
reinforcement fiber, a number of test samples were pro-vided,
compiled and averaged out for purposes of the graph. Upon
inspecting the graph, it can be seen that the average tear
strength of those shingles without reinforcement fiber
bundles is approximately 320 grams/lb. mat. At 10% fiber
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1 bundle content, tear resistance im~roves. This improve~
ment continues as more bundles are provided. Hence, at
25% fiber bundle content, the tear strength is approxi-
mately 690 grams/lb. mat. ~t between 10~ and 25~, the
shingle displays tear resistance as good and ln many
cases better than that found with the previously described
swirl mat and, in addition, has the other advantages
described above.
It is to be understood that the foregoing graphlc
display of tear resistance is for illustrative purposes only.
It is set forth only to show how tear resistance is related
to the glass mat of the present invention and particularly
the reinforcement fiber bundles used with the glass mat.
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