Non-woven mat having non-uniform basis weight

Abstract

A method of making a non-woven mat having a non-homogenous fiber distribution and, thus, a weight variation therein is disclosed. The method includes forming an aqueous slurry from fiber strands dispersed in water and restricting the amount of the slurry being fed across a width of a porous conveyor in the machine direction. In this manner, more or less fiber content can be fed to parts, or zones, of the mat. Consequently, products, such as shingles, which incorporate the mat can have regions of increased or decreased reinforcement.

Description

NON-WOVEN MAT HAVING NON-UNIFORM BASIS WEIGHT CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 745,982, filed January 16, 2025, the entire disclosure of which is incorporated herein by reference in full.FIELD

[0002] The inventive concepts disclosed herein relate generally to the field of fibrous reinforcement materials, and more specifically to non-woven fibrous mats having a non-homogenous weight distribution.BACKGROUND

[0003] Laminated (also known as architectural) shingles are composed of at least two distinct layers - an uppermost layer (i.e., the overlay) and a lowermost layer (i.e., the underlay). The overlay and underlay are laminated together using an asphalt-based sealant bead. The overlay of one shingle is substantially covered during installation by the underlay of another shingle positioned above it. Thus, the upper surface of an underlay is exposed to the elements once installed, and can tear in high wind conditions.

[0004] Each of the overlay and the underlay are commonly formed by coating a non-woven fibrous mat with an asphaltic coating. Since the overlay and the underlay mats are typically cut from the same larger formed non-woven fibrous mat, they have substantially the same basis weight as one another.

[0005] Non-woven mats may be formed by conventional wet-laid processes. For example, wet-use chopped strand glass fibers (known as WUCS) are dispersed in an aqueous slurry that contains surfactants, viscosity modifiers, defoaming agents, and / or other chemical agents. The slurry containing the chopped fibers is then agitated so that the fibers become dispersedthroughout the slurry. The slurry containing the fibers is transferred to a headbox, which directs and deposits the slurry onto a moving screen. A substantial portion of the water is removed from the slurry by passing through the screen, which leaves a web of randomly arranged fibers on the screen. A binder is then applied to the web. The binder-coated web of fibers then passes through an oven to remove any residual water and to cure the binder, which fixes the web of fibers together and forms the non-woven mat.

[0006] Non-woven fibrous mats are known in the art. Some examples of such mats include the following. CA 2,301,366 to Beuther discloses adding a slurry of fiber to the edges of a wet-formed mat in order to increase the strength in that area. U.S. 5,865,003 discloses adding a binder to sections of a mat to have areas of high binder saturation and low saturation. U.S.7,597,779 discloses using a shake mechanism for glass mats that shakes the mat to ensure the distribution is uniform across the entire width. U.S. 7,833,383 discloses a method of manufacturing a multilayer directionally oriented non-woven mat using a belt modification. U.S. 3,617,437 discloses a process for the manufacture of a composite material having aligned reinforcing fibers.

[0007] It is generally understood that the heavier the non-woven mat (i.e., the more glass it contains), the greater the tear resistance of the shingle. Thus, forming the mat to have a greater basis weight (e.g., by adding more WUCS to the slurry) will tend to increase performance of the shingle. In particular, the exposed underlay portion of the shingle will be less likely to tear when exposed to high wind conditions. However, as noted above, the individual overlay portions and underlay portions are cut from the same mat. Additionally, since the mat is formed by a wet-laid process, the mat (and, thus, the overlay portions and the underlay portions cut therefrom) will have a substantially uniform fiber weight distribution.

[0008] Traditional shingles are tested for tear resistance using several ASTM standards for shingle tear performance (specifically, the ASTM D3642, D1922, and D228 standards). Thesemethods focus on testing the underlay portion, the portion of the shingle which is most likely to have tear failure on the roof as it is exposed to the elements. The testing only assesses the underlay portion of the shingle, but the fiber weight distribution is the same across the entirety of the shingle. Consequently, there exists a performance improvement opportunity to concentrate the glass fibers within those regions of the shingle that are most susceptible to tearing, specifically the underlay. Stated another way, it would be desirable to produce a nonwoven fibrous mat that has a non-uniform fiber weight distribution so that glass fibers can be concentrated in a region of the mat intended for use as an underlay portion of a laminated shingle as compared to a region of the mat intended for use as an overlay portion of the laminated shingle.

[0009] Although fibrous mats are known in the art, there remains a need for a method of making a wet-laid mat that has an increased fiber concentration in those portions of the mat that will be used as an underlay portion of a laminated shingle. This results in a non-woven fibrous mat having a non-homogenous weight distribution (i.e., an increased weight distribution of the fibers in certain regions of the mat), with those regions of the mat being used as the underlay portions of shingles, and those shingles exhibiting more resistance to tearing.SUMMARY

[0010] The present disclosure includes exemplary embodiments of a method of producing a non-woven mat of non-homogenous weight. In particular, the method allows for the controlled distribution of fiber weight throughout the mat. The method includes producing an aqueous slurry including fiber strands therein; and restricting the amount of the slurry along a portion (i.e., the width) of the headbox to the forming screen. By creating restrictive zones along the width of the headbox, a non-woven mat may be produced that has varying weights across its width. In this way, a method is provided that provides for a wet-laid mat that is heavier in certain desired regions as opposed to other regions.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 shows a perspective view of a conventional two-layer (i.e., laminated) shingle.

[0012] Figure 2 shows one pattern of discrete pieces formed on a conventional mat produced on the forming wire prior to the pieces being cut out and assembled to form a shingle.

[0013] Figure 3 shows a side view of the modified headbox and pond regulator.

[0014] Figure 4 shows a front view of the modified headbox and pond regulator of FIG. 3.

[0015] Figure 5 shows an overhead view of the nonwoven mat during formation thereof.

[0016] Figure 6 shows a cross-sectional view of an exemplary nonwoven mat having varying fiber weights across the width of the mat.

[0017] Figure 7 is a table illustrating the varying weights across shingles depending on the heel gap setting.

[0018] Figure 8 is a table illustrating the difference in peak shingle tear of the tending and drive side for Example 2.DETAILED DESCRIPTION

[0019] The inventive concepts will now be described with reference to more detailed exemplary embodiments, as well as the drawings. The invention may be embodied in different forms and should not be construed as limited to the exemplary embodiments set forth herein, nor in any order of preference. Rather, the exemplary embodiments are provided so that the disclosure will be more thorough, and will convey the scope of the inventive concepts to those skilled in the art.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventionbelongs. The terminology used in the description of the invention herein is for describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0021] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties of mats, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from error found in their respective measurements.

[0022] Glass fibers are typically used as a reinforcing substrate (i.e., mat) in shingles. The glass fibers form much of the basis weight of the non-woven mats that later become shingles. Typically, the glass fibers are formed by drawing molten glass into filaments through a bushing or orifice plate and applying an aqueous sizing composition to the filaments. After the sizing composition is applied, the fibers may be gathered into one or more strands and wound into a package or chopped while wet and collected. Strands packaged in their wet condition are known as wet-use chopped strands (WUCS) and may contain hundreds or thousands of individual glass fibers / segments. These wet chopped fibers are typically used in wet-laid processes where the fibers are dispersed in an aqueous slurry that contains surfactants, viscosity modifiers, defoaming agents, and / or other chemical agents. The slurry containing the chopped glass fibers is then agitated to promote uniform dispersion of the fibers within the slurry. The fiber slurry may be transferred to a container, such as a headbox, in which it is held forcontrolled deposition onto a moving porous conveyor or screen (also known as a forming wire). In this manner, the slurry retains a laminar flow as it moves onto the moving porous conveyor. From there, a substantial portion of the water is removed through the screen to form a web of randomly arranged fibers. A binder is then applied to coat / saturate the web of fibers. The web is dried to remove any remaining water and to cure the binder, which forms the non-woven mat. In this way, the non-woven mat is a network of randomly arranged individual glass strands bound together.

[0023] FIG. 1 shows a perspective view of a conventional laminated shingle 100 produced using asphalt-coated non-woven glass fiber mats, which are produced using a wet-laid process as described above. The shingle 100 includes a headlap region 101 and a prime (or exposed) region 102. The headlap region 101 is primarily formed of an upper portion of the overlay sheet 105, while the prime region 102 is formed by a lower portion of the overlay sheet 102 (as tabs 103) and cutouts formed therein to expose portions of the underlay sheet 104. The headlap region 101 is not visible (i.e., is covered) after installation and would ideally use less expensive granules. Conversely, the prime region 102 is visible after installation, and thus is exposed to the elements. As such, the prime region 102 typically uses higher quality granules to meet color and performance specifications. As noted above, the prime region 102 is composed of one or more tabs 103 and portions of the underlay sheet 104 exposed by cutouts in the overlay sheet 105. The overlay sheet 105 includes the headlap region 101 and tabs 103. For aesthetic effect, the tabs 103 form a shadow line 109 with respect to the underlay sheet 104. During the manufacturing process, the overlay sheet 105 is bonded to the underlay sheet 104 using an adhesive 106, and laminated into a single unit (i.e., the shingle 100). This forms a common bond area 107 at or near the center of the newly formed shingle 100. A sealant 108 near the lower edge and on the back of the underlay sheet 104 is used to attach the shingle 100 to anothershingle installed beneath it, such that the bottom of the underlay sheet 104 on the top shingle is substantially aligned with the bottom of the headlap region 101 on the lower shingle.

[0024] FIG. 2 shows one pattern of discrete pieces formed on a conventional mat produced on the forming wire prior to the pieces being cut out and assembled to form a shingle. These discrete pieces (i.e., the overlay and underlay) are cut out and assembled to form two shingles (each comprising one overlay and one underlay). The machine direction (MD) 220 of the nonwoven mat is the same as the MD of the non-woven mat 320, which is perpendicular to the cross direction (CD) 222 and 322 of the respective non-woven mats. As shown in FIG. 2, the underlay portions 201 of the mat are less than half of the total area, necessitating some specificity when seeking to add weight to those particular sections. The forming wire provides MD “lanes” for different treatments to be applied to a non-woven mat as it is being formed.

[0025] FIGS. 3-4 depict an exemplary embodiment of a modified headbox 302 from the side (FIG. 3) and the front (FIG. 4). The headbox 302 is a structure (container) that receives and holds the slurry. The headbox 302 includes a pond regulator 303, which regulates the flow rate of the slurry from the headbox 302 to the forming wire 306. The pond regulator 303 allows the slurry to exit the headbox 302 through an opening of adjustable height 312 onto the forming wire 306. The opening 312 is typically rectangular in shape (i.e., with width greater than its height) and has a width that is less than or equal to the width of the forming wire 306. As stated previously, the forming wire 306 typically moves along the machine direction (MD) 320 and the cross direction (CD) 322 is perpendicular to the MD. The pond regulator 303 includes an angled bar used to regulate the velocity of the slurry as it travels from the headbox 302 to the forming wire 306. The end of the angled bar closer to the center of the headbox 302 is the heel 304; and the end of the angled bar closer to the wire is the toe 305. The heel 304 and toe 305 may be adjusted to control the height of the opening 312 using the heel height setting 308. The heel height setting 308 controls the distance between the heel 304 and the slurry passingthrough the pond regulator 303. Lowering the heel height 308 lowers the heel 304, raises the toe 305, and increases the height of the opening 312. Conversely, raising the heel height 308 raises the heel 304, lowers the toe 305, and further restricts the height of the opening 312.

[0026] In the illustrated embodiment, the headbox 302 has been modified to include a plate 301 across the opening 312. In this way, the addition of the plate 301 allows a user to modify the headbox by covering and occluding the normally homogenous opening 312 in order to create one or more different distribution flows that results in a non-homogenous weight across the non-woven mat. Thus, the resulting non-woven mat may be further treated and modified to form a shingle, having an overlay corresponding to a heavier basis weight and an underlay having a lighter basis weight. Likewise, it is also possible that regions in the overlay and / or the underlay could be formed to have different basis weight portions therein.

[0027] In the illustrated embodiment, the plate 301 modifies the height of the opening 312 along the width of the plate 301, correspondingly decreasing the height of the opening 312 by the height of the plate 301. As such, the plate 301 (and its dimensions, i.e., height and width) creates a restrictive zone 307 that is able to control the amount of slurry that passes from the headbox 302 onto the forming wire 306 within the restrictive zone 307. In the illustrated embodiment, the plate 301 is envisioned as a rectangular plate made of stainless steel; however, the skilled artisan will recognize that the plate 301 is merely one structure that may be used to modify the flow of the slurry passing from the container 302 to the conveyor 306. In other embodiments, the plate 301 may be comprised of any material that is suitable for usage in the desired forming process (i.e., if stainless steel may be inadvisable in an industry, plastic may be used instead). In other embodiments, the plate 301 may be curved, as opposed to rectangular. Further, while the illustrated embodiment may show only one plate 301, in other embodiments, there may more than one plate 301 installed along the headbox opening such that a user could create a plurality of lanes across the conveyor 306, wherein a first plate may occlude a smallerpercentage of the opening 312 than a second plate, which may occlude a smaller percentage of the opening 312 than a third plate. Similarly, it can also be envisioned that a user may create a plate 301 that occludes the entirety of the opening 312 but has several openings that allow the flow of slurry therethrough. Although the plate 301 is fixed flush to the headbox 302 in the illustrated embodiment, in other installations the plate 301 is angled relative to the headbox 302.

[0028] Most importantly, as stated above, is that by using the plate 301 to control the amount of slurry that passes onto the forming wire 306, the fiber weight of the non-woven mat is also controlled; by modifying the headbox 302 to include a restricted zone 307, the modified headbox 302 also enables lanes of varying fiber weights of the non-woven mat across the entire width of the opening 312. In other words, where the plate 301 is engaged, less slurry is deposited onto the forming wire 306 across the width of the restricted zone 307, which also decreases the fiber weight of the resulting non-woven mat across the same width. In some installations, the plate 301 is fixed to the headbox 302. In this manner, the area of the nonwoven mat corresponding with the pattern shown in FIG. 2 can be provided with more or less of the reinforcing fiberglass across the width (i.e., lanes) of the pattern.

[0029] FIG. 5 shows an overhead view of the non-woven mat during formation thereof. The forming wire 306 is divided into two regions: the tending side 309 and the drive side 311. In subsequent experiments to test the effectiveness of restricted zoning (i.e., fiber weight variances), the plate 301 was positioned in the headbox 302 in alignment with the tending side 309 of the forming wire 301, which decreased the fiber distribution (i.e., weight) along the tending side 309. A skilled artisan will recognize, however, that where the goal is to modify the weight of the non-woven along an area eventually corresponding to the underlay of a shingle, the plate 301 should be positioned appropriately to create the proper restrictive zone that gives rise to the desired non-homogeneous weight distribution. This is to say, it may notbe ideal in every situation to position the plate 301 in alignment with the tending side 309 of the forming wire 306.

[0030] Referring now to FIG. 6, there is shown a cross-sectional view of an exemplary nonwoven mat having varying fiber weights across the width of the mat (corresponding to a height of a shingle formed therefrom). As stated above, the width of the weight decrease across a portion of the mat corresponds to the width of the plate 301 installed along the headbox 302 opening 312. In the exemplary mat, the position of the plate 301 corresponded to the tending side 309 of the forming wire 306; thus, the tending side 309 received less slurry, and thus that portion of the mat had a lower basis weight (in this case, 1.45 lbs.), while the portion of the mat formed along the drive side 311 was not restricted and thus had a higher basis weight (in this case, 1.65 lbs.).

[0031] Varying the basis weight across the width of the mat allows the reinforcing fibers to be concentrated in those regions where they are most needed. Conversely, fewer reinforcing fibers could be used where they are less beneficial, as opposed to simply using the needed basis weight across the entire mat body. Consequently, a higher performing shingle could be produced with the same amount of reinforcing fibers. Alternatively, a shingle with the same performance could be produced at a lighter weight. One option may be increasing the basis weight on the underlay region and decreasing it on the overlay region. Doing so would keep the average basis weight across the entire shingle the same. Another option may be to decrease the basis weight on only the overlay region or increase the basis weight on only the underlay region, in turn decreasing or increasing the overall weight, respectively.

[0032] These approaches, which are supported by the invention, are more preferable than the alternative approach of making two different non-woven fibrous mats (i.e., first and second mats), each with a different basis weight, and sourcing all of the underlay portions from the first mat having the desired fiber weight distribution for the underlay portions, and sourcing allof the overlay portions from the second mat having the desired fiber weight distribution for the overlay portions. This alternative approach would likely complicate the shingle production method and would certainly require modification to current shingle production lines. Nonetheless, this alternative approach is encompassed within the general inventive concepts.

[0033] FIG. 7 shows the difference in basis weight between the tending side 309 and drive side 311, which is controlled by the heel height setting 308 and the dimensions of the restrictive plate 301. In the associated experiments, the heel height setting 308 was adjusted to test the efficacy of the addition of the plate 301, wherein a high heel height raised the heel but left the toe at the same height, resulting in a high gap (i.e., allowing more space for the slurry to distribute evenly). Specifically, raising the heel allows the slurry additional space in the headbox, and thus, there is less pressure from the plate 301 to force the slurry along the drive side 311, resulting in a nominal basis weight change across the non-woven mat (e.g., Example 1 in Fig. 7). Conversely, when the heel height setting 308 is low (e.g., Example 3), the slurry under the plate 301 is under a higher pressure and pushes the slurry to the drive side 311, thereby increasing the basis weight along that side. This control of the slurry pressure is another means of using the plate 301 to create a non-homogenous distribution of slurry along the forming wire 306. In the associated experiment, the heel height setting 308 was adjusted at three different heights, wherein the first height was greater than the second, which was greater than third (and consequently, the flow of the slurry became more restricted under the plate 301 as the heel height 308 was lowered). More specifically, a heel height setting 308 of high resulted in a gap measuring 96.5 mm on the heel tending side and 106 mm on the heel drive side. At the toe, the 9.5 mm plate lowered the drive side toe height from 26.2 mm to 16.7 mm on the tending side. A heel height setting 308 of low resulted in a gap measuring 69.5 mm on the heel tending side and 106 mm on the heel drive side. At the toe, the 9.5 mm plate lowered the drive side toe height from 26.2 mm to 16.7 mm on the tending side.; the operating windowof the associated heel gap in the headbox 302 is preferably between 60 mm and 106 mm. A skilled artisan will recognize that these results are specific to the container used in the associated experiments, however, and that a larger or smaller machine with different dimensions may require different ranges for idealized results. In an alternative embodiment, the plate 301 may be installed permanently (i.e., in a non-adjustable manner) and engaged during production of a specific type of non-woven mat (e.g., roofing mat) or disengaged entirely if a standard non-woven mat (i.e., without a basis weight differential) is being produced such as in Example 1.

[0034] FIG. 8 is a table illustrating the improved shingle tear performance in drive side 311 with higher basis weight and more reinforcing fibers. The difference in basis weight is attributed to the heel height setting 308 for this example. The resulting non-woven mats formed in these experiments were tested using the Elmendorf Tear Test (ASTM D3462) in order to determine failure rates depending on each mat’s basis weights. The Elmendorf test involves clamping a mock shingle formed using each mat and utilizing a pendulum to determine the angle and force needed to tear through the shingle underlay 104.

[0035] The above description of specific embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the general inventive concepts and attendant advantages but will also find apparent various changes and modifications to the structures and methods disclosed.

Claims

CLAIMSWhat is claimed is:

1. A method of making a non-woven mat, the method comprising:forming an aqueous slurry comprising a plurality of chopped glass fibers and water; adding the slurry to a container, said container having an opening configured to form an outlet flow of the slurry;blocking a portion of the opening to form a first flow and a second flow from the outlet flow of the slurry;simultaneously feeding the first flow of the slurry and the second flow of the slurry onto a porous conveyor;removing water from the slurry through the porous conveyor to form a web of the chopped glass fibers on the porous conveyor;applying a binder composition to the web; andcuring the web to form the non-woven mat;wherein a first portion of the non-woven mat corresponding to the first flow of the slurry has a lower basis weight than a second portion of the non-woven mat corresponding to the second flow of the slurry.

2. The method of claim 1, further comprising regulating a flow rate of the slurry through the opening.

3. The method of claim 1, wherein a plate is used to cover a portion of the opening.

4. The method of claim 1, wherein the first portion of the non-woven mat corresponds to an overlay of a shingle formed from the non-woven mat and the second portion of the nonwoven mat corresponds to an underlay of the shingle formed from the non-woven mat.

5. The method of claim 3, wherein the plate is affixed to the container.

6. The method of claim 3, wherein the plate covers at least ten percent of the opening.

7. The method of claim 3, wherein the plate covers at least fifty percent of the opening.

8. The method of claim 5, wherein the plate covers at least ten percent of the opening.

9. The method of claim 5, wherein the plate covers at least fifty percent of the opening.

10. The method of claim 3, further comprising a second plate, thereby forming a third flow of the slurry, such that a third portion of the non-woven mat has a basis weight corresponding to the third flow of the slurry.

11. The method of claim 2, wherein regulating the flow through the opening utilizes an angled bar oriented towards the opening, such that a first end of the angled bar is further from the opening and a second end of the angled bar is closer to the opening.

12. The method of claim 11, wherein the angled bar is adjustable, such that adjusting the first end of the angled bar modifies the flow rate of the slurry.

13. The method of claim 12, wherein lowering the first end of the angled bar increases the pressure on the slurry.

14. The method of claim 12, wherein a distance between a base of the container and the first end of the angled bar is between 60 mm and 106 mm.

15. The method of claim 13, wherein a plate is used to cover a portion of the opening.

16. The method of claim 15, wherein lowering the first end of the angled bar increases the pressure on the slurry in the container, thereby decreasing the flow rate of the slurry under the plate.

17. The method of claim 1, wherein the aqueous slurry further comprises a dispersant medium.

18. The method of claim 1, wherein the blocked portion of the opening extends a contiguous one-third the width of the opening.

19. The method of claim 1, wherein the blocked portion of the opening extends a noncontiguous one-third the width of the opening.

20. The method of claim 3, wherein the plate reduces an area of the opening by at least ten percent.

21. The method of claim 3, wherein the plate reduces an area of the opening by between ten percent and fifty percent.

22. The method of claim 3, wherein the plate is stainless steel.

23. The method of claim 1, wherein the first portion of the non-woven mat is greater than the second portion of the non-woven mat by at least 0.1 pounds / 100 sq. ft.

24. The method of claim 1, wherein the first portion of the non-woven mat is less than the second portion of the non-woven mat by at least 0.35 pounds / 100 sq. ft.

25. The method of claim 13, wherein adjusting the angled bar decreases the flow rate of the slurry by at least .

26. A roofing product formed from a non-woven mat made according to the method of any of the preceding claims.

27. The roofing product of claim 26, wherein the roofing product is a shingle.

28. The shingle of claim 27, wherein the shingle is a laminated shingle having an overlay layer and an underlay layer.

29. The shingle of claim 28, wherein a first mat in the overlay layer has a different basis weight than a second mat in the underlay layer of the laminated shingle.

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