Fiberglass Mat

FIG. 1 is a plan view, partly in section in different vertical planes of a fiberglass mat employing randomly oriented fiberglass strands;

FIG. 2 is a view similar to FIG. 1, showing the use of straight longitudinal strands of fiberglass in combination with randomly oriented fiberglass strands;

FIG. 3 is a cross-sectional view of the mat shown in FIG. 1, taken along the line 3--3 thereof;

FIG. 4 is a cross-sectional view of the mat shown in FIG. 2, taken along a line 4--4 thereof;

FIG. 5 is a plan view, partly in section, of tear resistant yarns arranged in a definite spiral or convoluted pattern;

FIG. 6 comprises a view of an alternate embodiment of the present invention, similar to FIG. 2, in which the longitudinal strands are laid in a generally sinusoidal orientation; and

FIG. 7 comprises a plan view of a mat formed in accordance with the alternate embodiment of this invention, illustrating only the longitudinal strands.

For the purposes of this application, the term "vertical", as applied to the mat and its components, shall be considered to refer to mat thickness. On the other hand, "horizontal" shall refer to the length/width of the mat. Obviously, these terms do not define the orientation of the mat or any resulting product. Thus, FIG. 1 is a multi-planar horizontal sectional view and FIG. 3 is a vertical sectional view.

As shown in FIGS. 1 and 3, there is a mat or sheet 10 comprising a base which may be formed of chopped glass fibers indicated by the numeral 11, and bonded together by a suitable bonding agent--many of which are presently known--which is preferably water resistant.

The chopped glass fibers may be of a substantially uniform or standard size and length, as well as of a glass composition normally used as the chopped glass fibers of any well known production process. The fibers may be of a suitable diameter, e.g., within the range of 9-16 microns. The fiber lengths may be within the present standards of 1/4" to 11/4" long. However, these diameters and lengths are not considered to be critical and any desired dimensional relationship may be utilized.

Bonding agents which may be employed in forming the mat or base are such as are commonly found in the industry today. They would include, for example, urea resins, phenolic resins, bone glue, polyvinyl alcohol, polyvinyl acetates, and various coupling and stabilizing agents.

Randomly oriented glass textile strands, yarns, or slivers 12 and 13 may be positioned within the vertical limits of the mat base 10. Preferably, the strands may be laid in layers, such that each layer is within a horizontal plane intermediate and substantially parallel to the top and bottom surfaces of the mat, as shown in FIG. 3. Preferably, the layers or planes may be located near the central plane of the mat. As shown, the layers or planes comprising the strands 12 and 13 are two distinct, separate, and separated layers with a volume of the base or mat material of chopped glass and bonding agent located between the layers as indicated at 16.

With the layers of strands thus separated, and with the volume of mat material located between the layers, there is no weakening or plane of weakness in the central portion of the mat. The body of the mat will have adequate mechanical strength throughout and, because of the strengthening at the central plane of the mat, there will be no separation of the mat body into a plurality of parts, layers, or laminae. These yarns and slivers, or, as may be generally called, "strands of fiberglass", need not be arranged according to a particular pattern, but may be arranged at random in successive circular or oval portions of different sizes, radii, etc. The circular or oval portions may be offset from each other as shown in FIGS. 1, 2 and 5, but the circular or oval portions should preferably be within the same plane as the remainder of the strands. Whenever the strands 12 and 13 of the separate layers cross-over themselves, forming the circular or oval portions, they may be bonded together at those points by the bonding agent. Such bonding crossover points have been indicated at 14 in FIGS. 1 and 2. Preferably, the strands 12 and 13 extend throughout substantially the entire length and width of the mat so that no significant portion of the mat is devoid of these randomly oriented strands.

In FIGS. 2 and 4, the invention has been illustrated as utilizing longitudinal strands of fiberglass which may be substantially parallel and are identified by the numeral 15. The longitudinal strands may be located within their own distinct and separate plane and that plane is preferably separated from the planes which include the random yarn layers 12 and 13.

In this embodiment of the invention, the longitudinal strands 15 may be substantially straight and the layer of strands 15 may be separated from the layer 13 by a volume of mat material 17 in order to give adequate mechanical strength to the mat body. Thus, as shown in FIGS. 2 and 4, the longitudinal strands 15 may be located below the remaining strand layers. Of course, those skilled in the art will realize that the longitudinal strand layers could be located intermediate the layers of strands 12 and 13. If, through a tearing action, a strand is torn loose and would tend to be pulled from the mat, which is highly unlikely, it will be stopped because of the presence of the randomly oriented strands 12 and 13 at the first bonding point 14 and thus prevent pulling loose of the entire strand.

In this form of the invention, the mat is preferably 36" to 48" wide, and three parallel strands along each edge of the mat may be 3/4ths of an inch apart, and the other parallel strands may be 2 inches apart, plus or minus 1/2 inch. The randomly oriented strands may be spaced on center lines about 3/4ths of an inch apart. By putting the strands in three separated layers or planes, the tear strength of the mat is enhanced because of the plurality of bearing surfaces. Since the strands are at different horizontal planar levels between the top and the bottom of the mat, a far superior resistance is available to forces which would tend to tear the mat in a direction across its width, e.g., from left to right in the figures, than is possible when a single layer of yarn is provided. This is also true relative to a mat in which the reinforcing strands are haphazardly or randomly oriented relative to the top and bottom of the mat.

In a final product which may be formed in accordance with this invention, there may be approximately 70% chopped fiberglass, 10% strands 12, 13 and 15, and 20% bonding agent. Of course, the invention is not limited to these percentages and they may be changed as desired. For example, it may be desirable in some forms of the invention to have more than 10% of the reinforcing strands. Likewise, it may be desirable to have the mat or base 10 thicker, in which case the percentage of bonding agent would be more than 70% and 20%, respectively.

FIG. 5 is a plan sectional view of this invention in which the strands of fiberglass 22 and 23 form a definite pattern of spiral portions or convolutions, offset from each other but connected together. In this form of the invention, like the prior forms, the strands 22 and 23 may be in two separate layers. Also, the layers of strands 22 and 23 may be distributed over the entire area so that each portion of the mat or base is tear resistant in all directions.

In the embodiment of the invention illustrated in FIGS. 6 and 7, those structural elements which are substantially identical to those in the above-described embodiments have been provided with similar reference numerals so that no further description thereof is necessary. As shown in FIG. 6, the straight longitudinal strands 15 depicted in FIGS. 2 and 4 have been replaced by longitudinal strands 31, such as are depicted in FIGS. 6 and 7. Broadly speaking, the strands 31 are somewhat longer than is necessary to form a straight longitudinal strand, such as that at 15. This is accomplished to set up the wavy pattern depicted which, for the sake of convenience, shall hereinafter be referred to as "sinusoidal". Those skilled in the art will realize, of course, that the longitudinal strands 31 could be employed without the random strands 12 and 13, with only one of the layers of random strands 12 and 13, or in a position intermediate the random strands 12 and 13. In any event, the strands 31 are preferably within a single horizontal plane intermediate the upper and lower surfaces of the base 10.

It has been found that the semi-straight or sinusoidal longitudinal strands are advantageous for several reasons. Referring to FIG. 2, it can be seen that any of the strands 15 cover only a very narrow area and any bending of the mat along the line parallel to the strands 15 will tend to use one of those strands as a bending line. Consequently, any bending forces in that direction are applied over a very narrow area, resulting in a relatively early failure of the product. For example, the substantially parallel strands 15 act as a ripcord at the junction of the main body of a finished shingle and its exposed edge portion. When the shingle is exposed to wind, the wind will bend it back-and-forth about the straight strand until the exposed edge is eventually sealed down to the roof by its self-sealing adhesive. This problem often occurs in products using absolutely parallel yarns and such shingle failure often occurs during Fall and Winter in northern climates since the adhesive does not have sufficient time to bond in the lower ambient temperatures and high winds.

On the other hand, if bending should occur along a line generally parallel to the longitudinal strands 31, any bend line which might be formed is several hundred times wider than that which would be possible with the embodiment of FIG. 2. This eliminates the possibility of a ripcord effect, since there is so much more material to resist the bending and the ripcording.

This alternate embodiment also has additional advantage when "fishlining" occurs as the result of a hang-up in the strand material as it leaves the spool. When an absolutely straight or parallel strand "hangs up", i.e., stops running momentarily for any number of reasons, it will disorient the chopped fibers located above and below it for some substantial length within the mat. This disorientation is not readily apparent and can later cause the mat product to crack or break apart along that line for a number of feet. This failure often does not show up until the mat is within the finished product and is located, for example, on a roof. Obviously, such a failure can be extremely costly since, at least, a large portion of the roofing material will have to be replaced.

On the other hand, when the semi-straight or sinusoidal strands hang-up or stop running momentarily, any major defect in the mat which might be caused by fishlining, such as is shown at 33 in FIG. 7, can be easily detected by the naked eye. As a result, the defective portion of the mat can be cut away to eliminate the possibility of hidden defects getting into a finished product.

Partly as the result of the use of sinusoidal reinforcing strands, and partly as the result of the distinct separation of the different reinforcing strand configurations into separate planes located between the top and bottom of the mat, products formed in accordance with the present invention have been found to be much stronger than those formed in accordance with the Hogendobler, et al. disclosure described previously. In fact, recent testing of products produced according to these two processes over an extended period of time has disclosed that products formed in accordance with the present invention are far stronger than those formed in accordance with the Hogendobler disclosure. By way of example, the following table sets forth the results of certain testing conducted upon the two types of mat products. A brief review of that table will indicate to those skilled in the art that mats formed in accordance with the alternate embodiment of the present invention are significantly stronger than those formed in accordance with the Hogendobler, et al. disclosure:

Having now reviewed the preceding detailed description, those skilled in the art will be aware of the fact that mats formed in accordance with the present invention may be produced so as to have a variety of configurations, many of which may not even resemble that depicted in the drawings but which, nevertheless, will utilize reinforcing strands in distinct planes and configurations such as have been disclosed here. Those embodiments will, nevertheless, utilize the spirit and teaching of the invention, as found in the following claims.