Gypsum board with oxidized modified cellulose fibers

Abstract

A system and method for manufacturing a gypsum board having oxidatively modified cellulose fibers is provided. The gypsum board includes a gypsum layer formed from a gypsum slurry, the gypsum layer having a bottom and a top. The gypsum slurry includes oxidatively modified cellulose fibers. The gypsum board further includes a first mat disposed on the bottom of the gypsum layer and a second mat disposed on the top of the gypsum layer.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 63 / 423,820, filed November 9, 2022, and entitled "GYPSUM BOARD HAVING OXIDIZED MODIFIED CELLULOSE FIBERS," which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to the field of gypsum board products, and more particularly to gypsum boards having oxidatively modified cellulose fibers. [Background technology]

[0003] Building panels, such as building exterior panels or roofing panels, include a core material, such as gypsum, and a mat facer, such as a fiberglass mat facer. During manufacturing, the gypsum core material is applied as a slurry to the surface of the mat facer and allowed to set so that the mat facer and gypsum core are bonded at their interfaces. Such panels can experience water intrusion and other performance problems. Summary of the Invention [Problem to be solved by the invention]

[0004] Through the application of hard work, ingenuity, and innovation, applicants have solved problems associated with gypsum board products by developing the solutions embodied in this disclosure, described in detail below. [Means for solving the problem]

[0005] According to one embodiment of the present disclosure, there is provided a gypsum board having oxidatively modified cellulose fiber (OMCF). The gypsum board includes a gypsum layer formed from a gypsum slurry, the gypsum layer having a bottom and a top. The gypsum board further includes a first mat disposed on the bottom of the gypsum layer and a second mat disposed on the top of the gypsum layer.

[0006] In some embodiments, the OMCF comprises a combination of all carboxyl groups or aldehydes and acids. In some embodiments, the gypsum slurry further comprises fibers other than OMCF. In some embodiments, the other fibers comprise organic or inorganic fibers, such as polypropylene, glass E, or ceramic. In some embodiments, the other fibers are larger than the OMCF. In some embodiments, the gypsum slurry further comprises a polymer additive or polymer foam. In some embodiments, the polymer additive or polymer foam comprises styrene butadiene, polystyrene, polyvinyl alcohol, or acrylate. In some embodiments, the electrostatic bonding and mechanical interaction between the OMCF and calcium salts in the gypsum layer of the gypsum board are configured to provide structural integrity to the gypsum board. In some embodiments, the OMCF is added at a rate of 2 to 20 lbs / msf. In some embodiments, the OMCF is added at a rate of up to 8 to 9 lbs / msf. In some embodiments, the OMCF forms an open-ring structure. In some embodiments, the gypsum board further comprises a slate coat having OMCF. In some embodiments, the OMCF is added as a dry additive with the gypsum stucco. In some embodiments, the OMCF is added as a liquid additive or slurry with the gypsum stucco. In some embodiments, the OMCF includes a debonder to facilitate hydropulping. In some embodiments, the first mat or the second mat includes a nonwoven glass fiber mat or a paper facer. In some embodiments, the first mat or the second mat includes a mat coating on the side of the first mat or the second mat opposite the side facing the gypsum layer. In some embodiments, the OMCF is configured to create a low pH local environment that retards biological growth on or within the gypsum board. In some embodiments, the OMCF is configured to retard mold or mildew growth on or within the gypsum board. In some embodiments, the OMCF includes a liquid pulp of OMCF.

[0007] According to yet another embodiment of the present disclosure, there is provided a method for producing a gypsum board having oxidatively modified cellulose fibers. The method includes preparing oxidatively modified cellulose fibers and forming a gypsum layer from a gypsum slurry. The gypsum layer has a bottom and a top, and the gypsum slurry contains the oxidatively modified cellulose fibers. The method further includes positioning a first mat on the bottom of the gypsum layer and a second mat on the top of the gypsum layer.

[0008] Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the present invention, together with its advantages and features, reference is made to the description and drawings.

[0009] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an exemplary gypsum panel according to various embodiments. [Figure 2] FIG. 1 is a cross-sectional view of an exemplary gypsum panel according to various embodiments. [Figure 3] 1 shows an exemplary structure and calcium salt reaction of oxidatively modified cellulose fibers according to various embodiments. [Figure 4] 1 is a chart showing a comparison of cube compression test results relating to exemplary oxidatively modified cellulose fibers, according to various embodiments. [Figure 5A] 1 is a chart showing pullout, wet bond, and compression test results based on a gypsum core incorporating oxidatively modified cellulose fibers, according to various embodiments; [Figure 5B] 1 is a chart showing pullout, wet bond, and compression test results based on a gypsum core incorporating oxidatively modified cellulose fibers, according to various embodiments; [Figure 5C] 1 is a chart showing pullout, wet bond, and compression test results based on a gypsum core incorporating oxidatively modified cellulose fibers, according to various embodiments; [Figure 6] 1 shows an example of a liquid pulp of oxidatively modified cellulose fibers for use in various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention is now described in detail, by way of example only, with reference to the following drawings. Modifications of the various embodiments illustrated within the spirit and scope of the invention will be readily apparent to those skilled in the art.

[0012] Embodiments herein provide strength and reinforcement to gypsum boards (also referred to herein as gypsum panels) by incorporating oxidatively modified cellulose fibers (OMCF). Various examples of modified cellulose fibers are described in U.S. Pat. No. 8,778,136, which is incorporated herein. The use of unmodified cellulose fibers in gypsum boards under appropriate conditions can result in mold and mildew growth. While some applications attempt to incorporate cellulose fibers into gypsum boards, the addition of biocides is the only way to truly prevent mold and mildew growth. Embodiments herein overcome this drawback by oxidizing or partially oxidizing the cellulose fibers to the extent that their structure is modified to make them less susceptible to mold and mildew growth. Embodiments herein can further reduce weight without adversely affecting the strength properties of the gypsum board or panel.

[0013] Embodiments herein provide structural integrity to gypsum boards as a result of chemical (e.g., electrostatic bonding) and mechanical interactions between modified cellulose fibers and calcium salts in the gypsum core of the gypsum board. In some embodiments, modified cellulose fibers can be added at up to 9 lbs / msf. In some embodiments, modified cellulose fibers can be added at between 2 and 20 lbs / msf, either alone or in combination with other fiber systems, polymer additives, or polymer foams. In certain cases, the addition rate of modified cellulose fibers can be between 10 and 15 lbs / msf. In other embodiments, the addition rate can range beyond 20 lbs / msf, for example, up to 30 lbs / msf. Fibers can include organic or inorganic systems, such as polypropylene, glass E, ceramic, etc. Polymers or polyfoams can include styrene butadiene, polystyrene, polyvinyl alcohol, acrylates, styrene-acrylic copolymers, etc.

[0014] Producing oxidatively modified cellulose fibers can involve different levels of oxidation and ring opening. In some embodiments, the oxidized cellulose may have all carboxyl groups or a combination of aldehydes and acids. Oxidation also reduces the size of cellulose fibers by 25% and has better flow rate (e.g., as opposed to non-oxidized cellulose fibers). In some cases, the size of cellulose fibers can be reduced by about 15% to 35%. In other embodiments, the range can be 20% to 30%. In some embodiments, the length range of OMCF is 0.1 microns to 3 millimeters, 1 micron to 2 millimeters, or 100 microns to 1 millimeter.

[0015] In various embodiments, a gypsum core for a gypsum board includes a gypsum slurry and oxidatively modified cellulose fibers (eg, 2-20 lbs / msf).

[0016] In various embodiments, a gypsum core for a gypsum board comprises a gypsum slurry having PVA polymer foam and oxidatively modified cellulose fibers (eg, 2-20 lbs / msf).

[0017] In various embodiments, a gypsum core for a gypsum board comprises a gypsum slurry having styrene butadiene polymer foam and oxidatively modified cellulose fibers (eg, 2-20 lbs / msf).

[0018] In various embodiments, a gypsum core for a gypsum board includes a gypsum slurry having PVA polymer foam, oxidatively modified cellulose fibers (eg, 2-20 lbs / msf), and polypropylene fibers.

[0019] In various embodiments, a gypsum core for a gypsum board includes a gypsum slurry having styrene butadiene polymer foam, oxidatively modified cellulose fibers (eg, 2-20 lbs / msf), and polypropylene fibers.

[0020] In various embodiments, the oxidatively modified cellulose fibers are added only to the slate coat of the gypsum board. In various embodiments, the oxidatively modified cellulose fibers are added to the gypsum core and slate coat of the gypsum board. In various embodiments, the oxidatively modified cellulose fibers are added as a dry additive with the gypsum stucco. In various embodiments, the oxidatively modified cellulose fibers are added to the gypsum stucco as a slurry from a hydropulping process.

[0021] A gypsum panel or board may include a set gypsum core sandwiched between two mats, one or both of which may be coated. The mat coating may be a substantially continuous barrier coating. As used herein, the term "substantially continuous barrier coating" refers to a coating material that is substantially uninterrupted on the surface of the mat.

[0022] During manufacturing, a gypsum slurry may be deposited on the uncoated surface of a facing material, such as a paper sheet or fiberglass mat (which may be pre-coated offline or online), and allowed to solidify to form the gypsum core of the panel. The gypsum slurry may penetrate the thickness of the fiberglass mat or adhere to the paper facing, providing a mechanical bond to the panel. The gypsum slurry may be provided in one or more layers having the same or different compositions, including one or more slate coat layers. As used herein, the term "slate coat" refers to a gypsum slurry having a higher wet density than the remainder of the gypsum slurry that forms the gypsum core.

[0023] In certain embodiments, as shown in FIG. 1 , gypsum panel 100 includes a gypsum core 101 having a first surface and a second, opposing surface, and a first facing material 104 (shown here as a fibrous mat) associated with the first surface of gypsum core 101, such that the gypsum of the gypsum core penetrates at least a portion of first mat 104. The various layers are illustrated as separate layers in the figures for ease of illustration. However, it should be understood that overlap of these materials may occur at their interfaces. In certain embodiments, gypsum panel 100 includes set gypsum core 101 associated with a first surface of first fibrous mat 104, and an optional mat coating 106 applied to a second surface of first fibrous mat 104.

[0024] In some embodiments, as shown in FIG. 1 , the gypsum of the gypsum core 101 penetrates the remainder of the first fibrous mat 104, thereby substantially eliminating voids within the mat 104 and further improving the water resistance of the panel 100. For example, in one embodiment, the first mat 104 has a mat coating 106 on a surface opposite the gypsum core 101, the mat coating 106 penetrating a portion of the first mat 104 and defining the remainder of the first mat 104. That is, the gypsum of the gypsum core 101 can penetrate the remaining fibrous portion of the first fibrous mat 104 such that voids within the first fibrous mat 104 are substantially eliminated. In certain embodiments, the mat 104 is a nonwoven fiberglass mat or a paper facer. In some embodiments, additional ingredients, such as starch, may be added to the gypsum panel 100.

[0025] 1, a gypsum core 101 includes two or more gypsum layers 102, 108. For example, a gypsum core can include various gypsum layers having different compositions.

[0026] In certain embodiments, as shown in Figure 2, gypsum panel 200 includes two fibrous mats 204, 212 associated with gypsum core 201. Second mat 212 is on the side of gypsum core 201 opposite first mat 204. In some embodiments, only first mat 204 has mat coating 206 on its surface. In other embodiments, both mats 204, 212 have coatings 206, 214 on their surfaces opposite gypsum core 201. In some embodiments, gypsum core 201 includes three gypsum layers 202, 208, 210.

[0027] Figure 3 shows an exemplary structure and calcium salt reaction of oxidized modified cellulose fibers according to various embodiments. As shown in Figure 3, oxidized carboxylates are formed with open ring structures. These oxidized carboxylates are structurally and chemically different from native cellulose fibers. [Example]

[0028] Example 1 - Cube Compression Test (Data shown in Figure 4) Figure 4 is a chart showing a comparison of cube compression test results associated with exemplary oxidatively modified cellulose fibers according to various embodiments. For the results in Figure 4, gypsum slurries were prepared by combining stucco with water and other formulation ingredients and fibers under dry and wet conditions of 7-9 lbs / msf. The slurries were then poured into molds and dried in an oven to remove excess water. The dried samples were then analyzed to estimate cube strength. As shown in Figure 4, the sample gypsum boards with oxidatively modified cellulose fibers performed better in cube compression tests and provided the best strength compared to other cellulose-based systems.

[0029] Example 2 - Pull-out Test (Data shown in Figure 5A) Figure 5A shows pullout results based on a gypsum core incorporating oxidatively modified cellulose fibers according to various embodiments. For the results of Figure 5A, gypsum boards were prepared by combining stucco with water and other formulation ingredients as a control sample. Similarly, another formulation with the same stucco-water ratio, other formulation ingredients including oxidatively modified cellulose fibers (approximately 8 lbs / msf), and PVA foam was prepared for testing, reducing the board weight by approximately 20% compared to the control sample.

[0030] A fastener is then inserted through each specimen board, where the fastener holds a metal disc on one side and the fastener is connected to the upper jaw of the testing machine on the other end. The clamp is then ensured to be aligned perpendicular to the square steel cradle holding the specimen board. After the testing machine is used to ensure the board is in a properly secured position, the fastener is pulled through the specimen board. The peak load and failure mode are recorded for each specimen board and each test. The specimens with oxidatively modified cellulose fibers showed improved strength compared to the control specimen.

[0031] Example 3 - Wet Binding Test (Data shown in Figure 5B) Figure 5B shows wet bond results based on a gypsum core incorporating oxidatively modified cellulose fibers according to various embodiments. The wet bond test determines the bond strength between the glass mat and the gypsum core of a gypsum board. For the results in Figure 5B, a gypsum slurry was prepared by combining stucco with water and other formulation ingredients as a control sample. Similarly, another formulation with the same stucco and water ratio was prepared for testing, with other formulation ingredients including oxidatively modified cellulose fibers (approximately 8 lbs / msf) and PVA foam, resulting in a board weight reduction of approximately 20% compared to the control sample. The samples with oxidatively modified cellulose fibers performed better or equally well to the control sample.

[0032] Example 4 - Compression Test (Data Presented in Figure 5C) FIG. 5C shows compression test results based on gypsum cores incorporating oxidatively modified cellulose fibers according to various embodiments. For the results shown in FIG. 5C, a gypsum slurry was prepared by combining stucco with water and other formulation ingredients as a control sample. The slurry was then poured into a mold and dried in an oven to remove excess water. The dried sample was then analyzed to estimate the sample's cube strength. Similarly, another formulation with the same stucco and water ratio, other formulation ingredients including oxidatively modified cellulose fibers (approximately 10 lbs / msf), and PVA foam was prepared for testing, reducing the weight and comparing it to the control sample. The sample with oxidatively modified cellulose fibers performed better or equivalent to the control sample.

[0033] 5A, 5B, and 5C, the sample gypsum boards with oxidized cellulose fibers (and PVA in the gypsum core) performed better in pullout tests, wet bond tests, and compression tests than the gypsum boards without oxidized cellulose fibers and PVA in the gypsum core. Furthermore, the sample gypsum boards with oxidized cellulose fibers (and PVA in the gypsum core) enabled a reduction in the weight of the gypsum boards.

[0034] 6 shows an exemplary liquid pulp of oxidatively modified cellulose fibers 602 stored in a container bowl 604 for use in various embodiments. The liquid pulp of oxidatively modified cellulose fibers 602 can be used in the manufacture of the embodiments described herein.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0036] Corresponding structures, materials, acts, and equivalents of all means or steps and functional elements within the scope of the following claims are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The embodiments have been chosen and described to best explain the principles of the invention and practical application and to enable others skilled in the art to understand the invention in various embodiments with various modifications suited to the particular uses contemplated.

[0037] While preferred embodiments of the present invention have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements that fall within the scope of the following claims, which claims should be construed to maintain appropriate protection for the invention as first described.

Claims

1. A gypsum board, a gypsum layer formed from a gypsum slurry, the gypsum layer having a bottom and a top, the gypsum slurry containing oxidized modified cellulose fiber (OMCF); a first mat disposed on the bottom of the gypsum layer; a second mat disposed on top of the gypsum layer.

2. 10. The gypsum board of claim 1, wherein the OMCF comprises all carboxyl groups or a combination of aldehydes and acids.

3. The gypsum board of claim 1 , wherein the gypsum slurry further comprises fibers other than the OMCF.

4. The gypsum board according to claim 3 , wherein the other fibers include organic or inorganic fibers such as polypropylene, glass E type, or ceramic.

5. The gypsum board according to claim 4, wherein the other fibers are larger than the OMCFs, and the length of the OMCFs ranges from 0.1 microns to 3 millimeters, from 1 micron to 2 millimeters, or from 100 microns to 1 millimeter.

6. The gypsum board of claim 1 , wherein the gypsum slurry further comprises a polymer additive or a polymer foam.

7. 7. The gypsum board of claim 6, wherein the polymer additive or polymer foam comprises styrene butadiene, polystyrene, polyvinyl alcohol, or an acrylate.

8. 10. The gypsum board of claim 1, wherein electrostatic bonding and mechanical interaction between the OMCF and calcium salts in the gypsum layer of the gypsum board is configured to provide structural integrity to the gypsum board.

9. 10. The gypsum board of claim 1, wherein the OMCF is added at a rate of up to 9 lbs / msf.

10. The gypsum board of claim 1 , wherein the OMCF forms an open ring structure.

11. The gypsum board of claim 1 further comprising a slate coat comprising the OMCF.

12. 10. The gypsum board of claim 1, wherein the OMCF is added as a dry additive with the gypsum stucco.

13. 10. The gypsum board of claim 1, wherein the OMCF is added as a liquid additive or slurry with the gypsum stucco.

14. 10. The gypsum board of claim 1, wherein the OMCF includes a debonder to facilitate hydropulping.

15. The gypsum board of claim 1 , wherein the first mat or the second mat comprises a nonwoven fiberglass mat or a paper facer.

16. 10. The gypsum board of claim 1, wherein the first mat or the second mat includes a mat coating on a side opposite the side of the first mat or the second mat that faces the gypsum layer.

17. 10. The gypsum board of claim 1, wherein the OMCF is configured to create a low pH local environment that retards biological growth on or within the gypsum board.

18. 10. The gypsum board of claim 1, wherein the OMCF is configured to retard mold or mildew growth on or within the gypsum board.

19. The gypsum board of claim 1 , wherein the OMCF comprises a liquid pulp of OMCF.

20. 1. A method for manufacturing gypsum board, the method comprising: Preparing oxidatively modified cellulose fibers (OMCF); forming a gypsum layer from a gypsum slurry, the gypsum layer having a bottom and a top, the gypsum slurry containing the OMCF; positioning a first mat on the bottom of the gypsum layer; and positioning a second mat on top of the gypsum layer.

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