Setting joint compound composition with reduced gypsum

Abstract

A snap-setting joint compound having reduced calcium sulfate hemihydrate and enhanced abrasiveness, and methods for constructing wall assemblies and repairing walls using the joint compound.

Description

[Technical Field]

[0001] The present disclosure relates to materials, products, and methods for the construction industry, including hardening joint compounds. The present disclosure also relates to methods for constructing wall assemblies, including, but not limited to, methods for finishing and / or repairing wall surfaces and methods for finishing the joint between two adjacent wall panels. [Background technology]

[0002] Walls, partitions, and ceilings are typically assembled by attaching panels one by one to a frame known as a stud or joint. A variety of panels may be used, including gypsum wallboard (drywall), wood fiber panels, fiberglass mat panels and / or tiles, and many others.

[0003] The seam between two adjacent panels attached to the studs of a wall assembly is called a "joint" or "wall joint." Traditional methods for preparing and finishing joints to create a uniform wall surface and strengthen the wall assembly include various techniques in which adhesives known as joint compounds are used. First, the joint compound is applied into the joint, and then joint reinforcement tape is embedded in the joint compound so that the joint is filled with the joint compound. This joint compound is sometimes called taping-grade joint compound. After the taping-grade joint compound dries, the joint is coated by applying one or more coats of joint compound known as topping or finishing-grade joint compound. Some joint compounds are known as general-purpose joint compounds because they can be used both as tapping joint compounds and as topping joint compounds. Certain joint compounds and methods for filling and coating joints are disclosed in US Pat. No. 8,931,230, the entire disclosure of which is incorporated herein by reference.

[0004] After the final coat of finishing joint compound has dried, the dried joint compound is sanded to produce a uniform wall surface and prepare the wall substrate for painting and / or other decorative finishes.

[0005] Two main types of joint compounds are known in the construction industry: drying joint compounds and setting joint compounds. Dry joint compounds are formulated without calcium sulfate hemihydrate. These compounds dry out as the water evaporates.

[0006] As originally described in U.S. Pat. No. 3,297,601, the entire disclosure of which is incorporated herein by reference, conventional setting joint compounds are typically formulated with calcium sulfate hemihydrate, which may be sourced from calcined gypsum, hereinafter referred to simply as "hemihydrate," and its two forms: alpha calcium sulfate hemihydrate, referred to as "alpha hemihydrate," and beta calcium sulfate hemihydrate, referred to as "beta hemihydrate." In conventional setting joint compounds, calcium sulfate hemihydrate is the major component, used in amounts exceeding 50% by weight of the total setting joint compound, excluding water. The setting joint compound hardens and solidifies when the calcium sulfate hemihydrate interacts with water and rehydrates to calcium sulfate dihydrate.

[0007] The setting joint compound may be formulated in the form of a dry powder to which water is added at the construction site, or as a ready-mix setting joint compound that is premixed with water and one or more inhibitor agents, including those described in U.S. Pat. No. 5,746,822.

[0008] Although various set inhibitors and set activators have been used in the art to improve the set kinetics of setting joint compounds, there remains a need in the art for setting joint compounds that can be used as general purpose joint compounds and have a sufficiently long open time, yet snap set so that waiting time between applications is reduced. Additionally, there is a requirement to maintain a level of compressive strength, but promote greater sandability. Summary of the Invention

[0009] In one aspect, the present disclosure provides a setting joint compound having setting characteristics distinguishable from conventional setting joint compounds. The disclosed setting joint compound retains a workable consistency for an extended period of time before the chemical reaction that initiates solidification or hardening occurs. The time between the onset of solidification and the hardening of the material is compressed, resulting in a "snap set." One skilled in the art will appreciate that the advantage of this "snap set" is that the compound can be worked for longer and can be recoated or sanded as soon as solidification begins. The setting joint compound according to the present disclosure can be used as a general-purpose setting joint compound. Additionally, the setting joint compound according to the present disclosure has improved sandability.

[0010] In one aspect, the present disclosure provides a dry powder setting joint compound comprising calcium sulfate hemihydrate in an amount of 28% to 50% by weight, calcium carbonate in an amount such that the total amount of calcium sulfate hemihydrate and calcium carbonate is 80% to 95% by weight, a starch binder, a redispersible latex binder, one or more of kaolin clay, sepiolite, bentonite, montmorillonite clay, attapulgite clay, or any mixture thereof, a rheology modifier, a cellulose-based thickener, a set retarder, and a set accelerator. Some dry powder setting joint compounds may contain calcium sulfate hemihydrate in an amount of 34% to 46% by weight. In some of these dry powder set joint compounds, the calcium sulfate hemihydrate is a combination of alpha calcium sulfate hemihydrate and beta calcium sulfate hemihydrate, preferably with an alpha to beta ratio ranging from 5:1 to 1:1. In some embodiments, the dry powder set joint compound does not include beta calcium sulfate hemihydrate. In some embodiments, the dry powder set joint compound does not include alpha calcium sulfate hemihydrate.

[0011] Preferred redispersible latex binders for the setting joint compound include, but are not limited to, vinyl acetate ethylene (VAE) copolymer, vinyl acetate / versatic acid vinyl ester (VAE-VeoVa) copolymer, styrene butadiene, acrylic powder, polyvinyl alcohol, or any combination thereof. Preferred starch binders for the setting joint compound include pregelatinized starch binders.

[0012] The dry powder setting joint compound of the present disclosure may further comprise one or more of perlite, resin microspheres, hollow microspheres, or any combination thereof. In some embodiments, the setting joint compound comprises 5% to 20% expanded perlite by weight. In some embodiments, the setting joint compound comprises 0.01% to 5% attapulgite clay by weight. In some embodiments of the dry powder setting joint compound, the rheology modifier is a substituted starch. In some embodiments of the dry powder setting joint compound, the cellulosic thickener comprises one or more of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl cellulose, methylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, cellulosic gum, carboxymethyl cellulose, or any combination thereof.

[0013] In some embodiments of the dry powder set joint compound, the set retarder comprises one or more of Suma retarder, Rochelle salt, ammonium tartrate, sodium citrate, citric acid, sodate retarder, cream of tartar, non-calcium containing phosphate salts, or any mixture thereof.

[0014] In some preferred embodiments of the dry powder setting joint compound, the accelerator comprises ground calcium sulfate dihydrate.

[0015] Any of the dry powder setting joint compounds of the present disclosure may be formulated as a ready-mix setting joint compound with water and one or more non-calcium-containing phosphate salts.

[0016] In a further aspect, the present disclosure provides a method of finishing a joint between two adjacent wall panels, the method comprising: a) mixing a dry powder setting joint compound of the present disclosure with water to form a joint compound paste; b) filling the joint with the joint compound paste; d) embedding joint reinforcement tape in the joint compound paste within the joint; and d) covering the joint with one or more coats of the joint compound paste. After the joint compound paste has set, the joint compound may be sanded.

[0017] In yet another aspect, the present disclosure provides a method for repairing a wall surface, the method comprising: mixing a dry powder setting joint compound of the present disclosure with water to obtain a joint compound paste, or obtaining a ready-mixed setting joint compound of the present disclosure, and mixing the ready-mixed setting joint compound with one or more accelerators, thereby obtaining a ready-mixed joint compound paste; and applying the joint compound paste or ready-mixed joint compound paste to a wall surface. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows the thickening curves of setting joint compounds containing the following amounts of calcium sulfate hemihydrate: 1556A (control, about 54 wt%), 1556B (about 47 wt%), 1556C (about 32 wt%), 1556D (about 47 wt%), 1556E (about 35 wt%), and 1556F (control, about 54 wt%). [Figure 2] 1 illustrates the results of certain tests performed on joint compound samples disclosed herein. [Figure 3] Specific notes regarding the joint compound samples disclosed herein and the results of specific tests performed thereon are provided. [Figure 4] 1 shows the formula for the color difference of joint compound samples, as discussed in Example 2 herein. [Figure 5] 1 shows the thickening curve of the curable joint compound composition disclosed in Example 5 herein. DETAILED DESCRIPTION OF THE INVENTION

[0019] In one aspect, the present disclosure provides a setting joint compound that retains a workable viscosity longer than conventional setting joint compounds. Furthermore, the setting joint compound according to the present disclosure snap sets. The setting joint compound according to the present disclosure can be used as a general-purpose setting joint compound. Furthermore, the setting joint compound according to the present disclosure has improved sandability. In another aspect, the setting joint compound after drying has a compressive strength within 300 psi of a comparable setting joint compound with a similar density and greater than 50% by weight calcium sulfate hemihydrate.

[0020] The setting joint compound of the present disclosure includes a combination of calcium sulfate hemihydrate and calcium carbonate. In the setting joint compound, the total amount of calcium sulfate hemihydrate is less than 50% by weight of the total dry weight of the joint compound, excluding water. Preferably, the setting joint compound of the present disclosure includes calcium sulfate hemihydrate in an amount ranging from about 28% by weight to about 50%, 49%, 48%, 47%, 46%, 45%, or 44% by weight of the total dry weight of the setting joint compound, excluding water. Setting joint compounds containing more than 50% calcium sulfate hemihydrate by weight of the total composition, excluding water, are not suitable.

[0021] Some preferred setting joint compounds contain calcium sulfate hemihydrate in an amount ranging from 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or 36% to 48% by weight of the total dry weight of the setting joint compound excluding water, including any amount of calcium sulfate hemihydrate between 28% and 46% by weight of the total dry weight of the setting joint compound excluding water.

[0022] In this disclosure, "wt. %" means percent by weight. In this disclosure, a settable joint compound can be prepared by mixing the active ingredients and obtaining a dry powder settable joint compound. The settable joint compound can then be mixed with water to obtain a settable joint compound paste. Thus, "wt. % from the total dry weight of the settable joint compound excluding water" means the weight percent from the total of all active ingredients (dry powder settable joint compound), excluding the amount of water that is later added during mixing of the dry powder with water to form a paste. See also Table 1 of this disclosure, where the amounts are listed in wt. % from the total dry weight of the settable joint compound excluding water. In this disclosure, the "composition excluding water" can also be referred to as the dry mix or dry powder, or the dry weight of the entire settable compound excluding water.

[0023] In this disclosure, the term "gypsum" may be used interchangeably with calcium sulfate dihydrate, terra alba, or land plaster. In this disclosure, the term "plaster of Paris" may be used interchangeably with calcined gypsum, stucco, calcium sulfate semihydrate, calcium sulfate half-hydrate, or calcium sulfate hemihydrate. Those skilled in the art will understand that the present setting joint compound compositions include those containing calcium sulfate hemihydrate provided as calcined gypsum in an amount ranging from about 28% to about 50%, about 30% to about 49%, about 28% to about 48%, about 28% to about 47%, about 28% to about 46%, about 28% to about 45%, or about 28% to about 44% by weight of the total composition excluding water (dry powder mix).

[0024] The present setting joint compound must contain less than 50% but more than 28% by weight calcium sulfate hemihydrate based on the total dry weight of the setting joint compound excluding water. Accordingly, the setting joint compound of the present disclosure may be referred to herein as a setting joint compound having a reduced amount of calcium sulfate hemihydrate. It has been unexpectedly discovered that reducing the total amount of calcium sulfate hemihydrate to between 28% and 50% by weight of the total dry weight of the setting joint compound excluding water produces a setting joint compound having a longer period during which the viscosity remains within a workable range for approximately the same Vicat set time. Vicat set time was measured as described later in this disclosure and as known in the art. Surprisingly, the setting joint compound exhibits excellent snap-setting behavior. Furthermore, the setting joint compound of the present disclosure can be easily sanded, and their sandability is improved compared to conventional setting joint compounds containing more than 50% by weight calcium sulfate hemihydrate. Furthermore, the compressive strength of the setting joint compound compositions of the present invention has dry compressive strengths that are comparable to comparable setting joint compounds of similar density and having greater than 50% by weight calcium sulfate hemihydrate.

[0025] This observation is supported by Figure 1, which provides a comparative analysis of a conventional setting joint compound containing 54 wt. % calcium sulfate hemihydrate (see thickening curve 1556A) versus setting joint compounds of the present invention containing 41 wt. %, 31 wt. %, 46 wt. %, or 34 wt. % calcium sulfate hemihydrate (see thickening curves 1556B, 1556C, 1556D, and 1556E, respectively). All amounts are by weight out of the total dry weight of the setting joint compound, excluding water. In Figure 1, Brookfield viscosity was measured as a function of time.

[0026] In FIG. 1 and the remainder of this disclosure, viscosity refers to "Brookfield viscosity" and is measured at room temperature. The term "room temperature" refers to a temperature between 20 and 25 degrees Celsius; preferably, room temperature is 23°C. Skilled practitioners measure viscosity with a viscometer. Viscometers are commercially available from many different sources, including CW Brabender Instruments, Inc., Hackensack, New Jersey, under the trade name Visco-Corder™, which uses a reaction torque for dynamic measurement of viscosity. In this disclosure, including the data shown in FIG. 1, viscosity was measured according to ASTM C474-05, Section 5 (Standard Test Method for Joint Treatments for Gypsum Wall Construction), using a CW Brabender viscometer with a Type A pin, a ½-pint sample cup size with a Brabender Torque-Head with a 250 cm-gm cartridge, and 75 RPM.

[0027] As can be seen in Figure 1, the settable joint compound of the present invention with reduced calcium sulfate hemihydrate maintains a workable viscosity without significant thickening for a longer period of time than the control settable joint compound. Given this, it is also unexpected that the settable joint compound of the present invention snap-sets, meaning that the compound transitions from a workable viscosity compound to a set form within a short period of time. Snap-set can occur in less than 10 minutes, and even more preferably in less than 5 minutes, after the settable joint compound of the present invention maintains a workable viscosity for more than 30 minutes. As can be seen in Figure 1, the control conventional settable joint compound does not possess this snap-set characteristic to the same extent as the settable joint compound of the present invention. The snap-set characteristic of the settable joint compound of the present disclosure is an important technical advantage, as it indicates the time required for the settable joint compound to sufficiently cure before it can be sanded and / or another coat of settable joint compound can be applied.

[0028] As described in U.S. Patent No. 7,754,007, raw gypsum is found in nature in the dihydrate form. In this form, there are approximately two water molecules bound to each calcium sulfate molecule. To produce the hemihydrate form, the gypsum can be calcined to drive off some of the water. As also described in U.S. Patent No. 7,754,007, two different forms of calcium sulfate hemihydrate, namely alpha crystals and beta crystals, can be produced by the calcination process. The alpha crystals are less acicular in shape than the beta crystals. Alpha calcium sulfate hemihydrate has a lower water demand than beta calcium sulfate hemihydrate, and as known in the art, the combination of alpha and beta calcium sulfate hemihydrate controls the amount of water required to form a workable gypsum slurry. [Table 1]

[0029] Some of the present setting joint compounds may include a combination of alpha calcium sulfate hemihydrate and beta calcium sulfate hemihydrate, while other setting joint compounds of the present disclosure may be prepared with alpha calcium sulfate hemihydrate and free of beta calcium sulfate hemihydrate. In further embodiments, the setting joint compounds of the present disclosure may be prepared with beta calcium sulfate hemihydrate and free of alpha calcium sulfate hemihydrate.

[0030] When a combination of alpha calcium sulfate hemihydrate and beta calcium sulfate hemihydrate is used, the alpha to beta ratio can range from 5:1 to 1:1 by weight, respectively. For example, some joint compounds can contain 1 part beta calcium sulfate hemihydrate for every 5 parts alpha calcium sulfate hemihydrate by weight.

[0031] The curable joint compound of the present disclosure includes calcium carbonate as a second required component. The total amount of combined calcium carbonate and calcium sulfate hemihydrate in the curable joint compound can be in the range of 80 to 95% by weight of the total settable joint compound, excluding water, preferably in the range of 80 to 90% by weight of the total settable joint compound, excluding water, and most preferably in the range of 85 to 90% by weight of the total settable joint compound, excluding water. Since calcium sulfate hemihydrate is used in an amount of about 30 to about 50% by weight of the total composition, excluding water, the amount of calcium carbonate in the curable joint compound should be adjusted accordingly so that the total amount of calcium sulfate hemihydrate and calcium carbonate in the composition, excluding water, is in the range of 80 to 95% by weight of the total composition, excluding water, preferably in the range of 80 to 90% by weight of the total composition, excluding water, and most preferably in the range of 85 to 90% by weight of the total composition, excluding water.

[0032] Suitable commercial sources of calcium carbonate include OMYACARB™ (calcium carbonate) from Omya and HUBERCARB™ (calcium carbonate) from Huber Engineered Materials. In some of the setting joint compounds according to the present disclosure, calcium carbonate may be sourced from dolomitic limestone and / or limestone.

[0033] The third required component of the setting joint compound of the present disclosure is a binder. Suitable binders include, but are not limited to, starch, polyvinyl alcohol, acrylic polymers and / or copolymers such as polyacrylamide and polyvinyl acrylate, polyvinyl acetate, ethylene vinyl acetate, or any combination thereof. The setting joint compound of the present disclosure may contain 0.5% to 20% binder by weight, based on the dry weight of the total setting joint compound excluding water.

[0034] Suitable binders according to the present disclosure include redispersible latex powders, which may further be used in combination with one or more starches. Suitable redispersible latex powder binders include, but are not limited to, vinyl acetate ethylene (VAE) copolymers, vinyl acetate / versatic acid vinyl ester (VAE-VeoVa) copolymers, styrene butadiene, acrylic powders, polyvinyl alcohol, or any combination thereof. The setting joint compound of the present disclosure may contain 0.1% to 20% by weight of the redispersible binder, based on the dry weight of the total setting joint compound, excluding water.

[0035] In some embodiments, setting joint compounds according to the present disclosure include one or more starches and one or more redispersible latex powder binders. In some embodiments, setting joint compounds according to the present disclosure include at least one starch binder and one or more of the following redispersible latex powder binders: vinyl acetate ethylene (VAE) copolymer, vinyl acetate / versatate vinyl ester (VAE-VeoVa) copolymer, styrene butadiene, acrylic powder, polyvinyl alcohol, or any combination thereof. In these formulations, the redispersible latex binder may be used in any suitable amount, including 0.1% to 20% by weight, more preferably 0.1% to 1% by weight, of the redispersible latex binder, based on the total dry weight of the setting joint compound excluding water. Suitable redispersible binders include vinyl acetate ethylene (VAE) copolymer and / or polyvinyl alcohol. The starch binder in these formulations may be used in amounts of 0.5% to 20% starch binder by weight, based on the dry weight of the total setting joint compound excluding water. In at least some embodiments, the starch binder may be used without a redispersible latex powder binder.

[0036] Suitable starches include synthetic starches, native starches, modified native starches, or any mixture thereof. Suitable starch binders include, consist essentially of, or consist of wheat starch, corn starch, potato starch, sweet potato starch, rice starch, tapioca starch, or any mixture thereof. Suitable starches can be pregelatinized and / or otherwise chemically modified. Modified starches include alkylated starches, including ethylated or propylated starches, or acid-modified starches. Wheat starch is one of the preferred starches. In some preferred embodiments, the starch binder includes, consists essentially of, or consists of pregelatinized starch.

[0037] Suitable pregelatinized starches include pregelatinized wheat starch, pregelatinized corn starch, pregelatinized potato starch, pregelatinized sweet potato starch, pregelatinized corn starch, rice starch, tapioca starch, or any mixture thereof. A preferred pregelatinized starch is pregelatinized wheat starch, although other modified and / or pregelatinized starches may also be used.

[0038] The setting joint compound may contain from about 0.5% to 20% by weight of one or more starches, based on the dry weight of the total setting compound, excluding water.

[0039] The hardening joint compound can include lightweight materials that can be used to obtain a lightweight hardening joint compound. Suitable lightweight materials include perlite, including expanded perlite, which may be further coated or uncoated. Instead of or in addition to perlite, resin microspheres or hollow microspheres, such as glass bubbles, can be used, as described in U.S. Patent No. 8,931,230.

[0040] Some suitable settable joint compounds of the present disclosure include perlite, more preferably expanded perlite. The use of expanded perlite in lightweight joint compounds is generally known from U.S. Pat. No. 4,454,267, the entire disclosure of which is incorporated herein by reference. The expanded perlite may be further coated, for example, as described in U.S. Pat. No. 4,525,388. The expanded perlite may be used in any amount. In some embodiments, the settable joint compound includes any amount of perlite, preferably expanded perlite, more preferably uncoated expanded perlite, ranging from about 5% to about 20% by weight, based on the dry weight of the total settable joint compound excluding water.

[0041] The setting joint compound preferably also includes a clay. Suitable clays include kaolin clay, sepiolite, bentonite, montmorillonite clay, attapulgite clay, or any mixture thereof. In certain preferred embodiments, the setting joint compound includes attapulgite clay.

[0042] In some embodiments, the setting joint compound may comprise, by dry weight of the total setting compound excluding water, 0.01% to 5%, 0.01% to 4%, 0.01% to 3%, 0.01% to 2%, 0.01% to 1%, 0.1% to 5%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2%, or 0.1% to 1% clay, preferably attapulgite clay.

[0043] The setting joint compound may further include one or more polysaccharide rheology modifiers, which may be substituted starches. The polysaccharide rheology modifiers may be used in any amount necessary to adjust the water retention of the veneer finishing compound. Typically, 0.01% to 2%, 0.01% to 1%, 0.01% to 0.5%, or 0.01% to 0.2% by weight of a polysaccharide rheology modifier, such as a modified starch, based on the total weight of the setting joint compound excluding water, may be used.

[0044] In the present curing joint compound, a suitable polysaccharide rheology modifier is a modified, e.g., substituted, starch. Suitable modifications introduce functional groups, such as anionic groups, into the starch molecule. Modifications may include etherification, esterification, and / or oxidation of the starch molecule. Suitable substituted starches include carboxylated starch, carboxymethyl starch, hydrolyzed starch, starch acetate, hydroxypropyl starch, and phosphated starch. Suitable anionic starches include anionic corn starch.

[0045] The curable joint compound may further include one or more cellulosic thickeners. Any conventional cellulosic thickener may be used. Cellulosic thickeners include cellulose ethers such as carboxymethyl cellulose, methyl cellulose and its derivatives, and hydroethyl cellulose and its derivatives. Suitable cellulosic thickeners include, but are not limited to, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl cellulose, methylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, cellulosic gums, carboxymethyl cellulose, or any combination thereof. The cellulosic thickener may be used in any suitable amount as needed to adjust the consistency of the curable joint compound. In some embodiments, the cellulosic thickener may be used in an amount of 0.01% to 2% by weight, more preferably 0.1% to 1% by weight, based on the dry weight of the total curable joint compound excluding water.

[0046] The setting joint compound of the present disclosure may further include one or more set retarders. Any retarder known for use in conventional setting joint compounds may be used in the present formulations. Suitable retarders include the commercially available Suma retarders, which are protein- and / or amino acid-based retarders common in formulating gypsum-based products. Suma retarders may be used alone or in combination with one or more other known retarders, such as Rochelle salt, ammonium tartrate, sodium citrate, citric acid, and sodate retarders, cream of tartar (potassium bitartrate). The amount of retarder may be adjusted as needed to increase or decrease the period during which the setting joint compound is workable. For ready-mixed setting joint compounds, suitable retarders also include non-calcium-containing phosphates such as zinc hexametaphosphate, potassium tripolyphosphate, tetrasodium pyrophosphate, tetrapotassium pyrophosphate, sodium tripolyphosphate, monoammonium phosphate, monobasic potassium phosphate, or any combination thereof, including as described in U.S. Patent No. 5,746,822, the entire disclosure of which is incorporated herein by reference. Typically, from about 0.01% to about 10% by weight of retarder can be used, based on the dry weight of the total setting joint compound excluding water.

[0047] The setting joint compound of the present disclosure may further include one or more accelerators. Suitable accelerators include, but are not limited to, climatically stable accelerator (CSA), heat-resistant accelerator (HRA), Terra Alba, available from United States Gypsum Company, Chicago, Illinois, containing ground calcium sulfate dihydrate typically used in combination with calcined gypsum, including as described in U.S. Pat. No. 7,754,007, the entire disclosure of which is incorporated herein by reference, and any mixture thereof. Other accelerators particularly suitable for ready-mix setting joint compounds include, for example, zinc sulfate, aluminum sulfate, potassium sulfate, and any mixture thereof, as described in U.S. Pat. No. 5,746,822, the entire disclosure of which is incorporated herein by reference. The amount of accelerator may be adjusted as needed depending on the amount of retarder used. Typically, about 0.001% to about 1% by weight of the accelerator may be used, based on the dry weight of the total setting joint compound excluding water.

[0048] The setting joint compounds of the present disclosure may also include other additives typically used in conventional setting joint compounds, including, but not limited to, fly ash, mica, talc, sand, or any mixture thereof.

[0049] In addition to the above ingredients, the setting joint compound may contain one or more antifoaming agents, humectants such as glycerin and / or polyols, biocides, surfactants, and / or pigments. These ingredients are typically used in amounts of about 0.01% to about 5%, preferably 0.05% to 1%, by weight of the total dry weight of the setting joint compound excluding water.

[0050] The setting joint compound according to the present disclosure may be formulated as a dry powder setting joint compound to which the user then adds water on-site to produce a setting joint compound paste. Water may be added in an amount sufficient to produce a workable mixture. Typically, water is added in an amount sufficient to produce a mixture, typically about 50-70 cc (cubic centimeters) of water per 100 g of dry powder setting joint compound.

[0051] Alternatively, the setting joint compound may be formulated as a ready-mix setting joint compound. The ready-mix setting joint compound is formulated with water during manufacturing and prior to packaging. The ready-mix setting joint compound of the present disclosure may contain the same ingredients as those described for the dry powder formulation. The ready-mix setting joint compound may further contain 20% to 60% by weight of water, more preferably 25% to 55% by weight, and most preferably 30% to 50% by weight, based on the total weight of the ready-mix setting joint compound. The ready-mix setting joint compound is preferably packaged in an airtight container.

[0052] Millediext hardening joint compounds may further include one or more set retarders to prevent premature hardening reactions during storage. Suitable retarders include non-calcium-containing phosphates such as zinc hexametaphosphate, potassium tripolyphosphate, tetrasodium pyrophosphate, tetrapotassium pyrophosphate, sodium tripolyphosphate, monoammonium phosphate, monobasic potassium phosphate, or any combination thereof. Typically, about 0.1% to about 10% by weight of retarder may be used, based on the dry weight of the total hardening joint compound excluding water.

[0053] The setting joint compound of the present disclosure is useful in a variety of applications, including, but not limited to, as a general-purpose joint compound for filling and / or coating (finishing) joints between wall panels. The setting joint compound of the present disclosure may also be used in wall repair projects, for example, as a spackling compound for repairing dents and cracks in walls. The setting joint compound of the present disclosure may also be used as a basecoat for wall panels. The setting joint compound is particularly suited for gypsum wallboard applications. However, the setting joint compound may also be used with other substrates, such as, but not limited to, cementitious substrates, wood fiber panels, roofing tiles, and / or fiberglass mat panels.

[0054] The setting joint compound may be formulated as a paste suitable for application with a hand trowel or as a solution for application as a spray.

[0055] In a further aspect, the present disclosure provides a method in which the presently disclosed setting joint compound is placed in a seam (joint) between two wall panels. In this case, a joint reinforcement tape is embedded in the setting joint compound, allowing the setting joint compound to cure. After the setting joint compound cures, the joint is coated with one or more coats of the setting joint compound. The presently disclosed setting joint compound can be used with various joint reinforcement tapes, such as paper joint reinforcement tape and / or fiberglass mesh joint tape. While the present setting joint compound can be used, for example, as a general-purpose joint compound for taping and finishing joints, the setting joint compound can also be used in combination with other joint compounds. For example, the present setting joint compound can be used as a topcoat (joint finish), while any conventional joint compound can be used for taping and embedding the joint reinforcement tape.

[0056] Any of the methods involving installing walls and / or repairing walls and / or coating joints may further include sanding the hardened joint compound after the compound has sufficiently hardened.

[0057] The setting joint compound may be applied to a substrate, such as a joint and / or wall panel, by troweling, roller application and / or joint knife, or by spraying.

[0058] The curable joint compound can be applied to a substrate to hide small wall defects, such as screw heads, and to fill wall cracks. In a further aspect, the present disclosure provides a method for patching and / or laminating surfaces with the curable joint compound according to the present disclosure. Suitable surfaces include, but are not limited to, wallboard and fiberboard. For these applications, if the curable joint compound is used in powder form, water is added to the powder to mix the curable joint compound paste. Alternatively, a ready-mix curable joint compound can be used. One or more accelerators can be added to the joint compound paste before use. The curable joint compound paste is then applied to a substrate and allowed to cure. Once the curable joint compound paste has hardened, it can be sanded and / or coated with a primer and / or paint.

[0059] This disclosure includes the following non-limiting examples.

[0060] Example 1. Setting Joint Compound with Reduced Calcium Sulfate Hemihydrate Preparation and testing The following hardening joint compound samples were prepared using the amounts of dry cured joint compound listed in Table 2 below. It was prepared by mixing the ingredients. [Table 2]

[0061] As can be seen from Table 2, Sample 1566A was a control sample with a total calcium sulfate hemihydrate content of about 54% by weight of the total composition, excluding water. Sample 1566B contained about 35% by weight of alpha calcium sulfate hemihydrate and about 7% by weight of beta calcium sulfate hemihydrate. Sample 1566C contained about 25% by weight of alpha calcium sulfate hemihydrate and about 7% by weight of beta calcium sulfate hemihydrate. Sample 1566D contained about 47% by weight of alpha calcium sulfate hemihydrate and no beta calcium sulfate hemihydrate. Sample 1566E contained about 35% by weight of alpha calcium sulfate hemihydrate and no beta calcium sulfate hemihydrate. Control Sample 1566F contained the same total amount of calcium sulfate hemihydrate as Control Sample 1566A, but only alpha calcium sulfate hemihydrate was used, not beta calcium sulfate hemihydrate.

[0062] Each of the dry powder setting joint compound samples in Table 2 was mixed with water as listed in Table 3 below. The setting joint compounds were then analyzed for Brookfield viscosity, Vicat set time, dry density, wet density, adhesion to paper tape, shrinkage, compressive strength, and other parameters, as reported in Tables 3 and 4 below and Figures 2 and 3. The thickening curves for each of the samples were also plotted as a function of Brookfield viscosity over time. These thickening curves are shown in Figure 1. Dynamic viscosity has been converted to SI units of Pascal seconds (Pa·s) in Figure 1. Figure 2 shows the results of certain standard joint compound tests known in the art that were applied to the trial materials. All tests in Figure 2 were performed in accordance with ASTM C474. The tests included (a) obtaining three test samples of each trial material to determine the amount of joint compound adhesion to paper tape after X-cutting under the various temperature and relative humidity conditions shown, (b) for each trial material, the total amount of cracking (in inches) when the setting compound was applied in a deep coat (1 / 8 inch thick) on drywall that was forced to dry in a conditioned chamber at 95 degrees Fahrenheit and 10% relative humidity, and (c) the percent shrinkage of each trial material after drying. [Table 3] [Table 4]

[0063] table 3In the table, Vicat set times were measured in minutes according to modified ASTM C-472 (Standard Test Methods for Physical Testing of Gypsum, Gypsum Plaster, and Gypsum Concrete, ASTM International, West Conshohocken, PA, 2014). Vicat set times began when water was added to the dry mixture of setting joint compound. Each sample was scooped into a cup at working viscosity. A 300-gram Vicat needle was held perpendicular to the surface of the joint compound, centered over the surface. The needle was held on the surface, released, and allowed to fall freely under its own weight. Set time was determined when the needle failed to penetrate partway through the joint compound surface. Table 3 As can be seen, the setting joint compounds according to the present disclosure have a longer open time before they set compared to the control light weight (greater than 50% hemihydrate) setting joint compound. One of the technical advantages of the present setting joint compounds is that they maintain a consistent workable viscosity during application.

[0064] FIG. 3 shows a table listing additional tests performed on the samples. One of the measurements was the compressive strength in psi of a dry 2-inch cube per ASTM C-472. The dry density of a 2-inch cube made from the trial material was also measured in pounds per cubic foot (PCF) per ASTM C-474. Also in FIG. 3 are several notes made by the individual who mixed the various samples of trial material. These notes describe, among other things, the workability of the samples as one skilled in the art would understand. The hardness of the samples relative to that of drywall was also measured per ASTM C-474 using a durometer.

[0065] Example 2. Color Test of the Hardening Joint Compound of Example 1 One of the important properties of joint compound is its ability to color blend with the substrate to which it is applied. Typically, walls are color-matched or white. Therefore, a hardening joint compound that is white after the compound dries is required on site. The color difference in hardening joint compound is due to the L * a * b * This method can be measured using a colorimeter such as HunterLab's ColorQUEST®. * a * b * The method is capable of detecting even small differences between the two colors. * a * b * The method defines color difference as a numerical comparison between the sample color and the standard color. It uses three different coordinates: L * indicates lightness (black / white), and L * =100 is pure white, L * =0 is pure black, a * are the red / green coordinates, and a * =-100 is completely green, a * = 100 is completely red, and b * is the yellow / blue coordinate, and b * =100 is completely yellow, b * =-100 is completely blue.

[0066] All measurements are made relative to the standard values ​​provided by the colorimeter for each coordinate. Each of the two samples is * , a * , and b * Then, ΔE is calculated using the formula shown in Figure 4.

[0067] ΔE represents the color difference between the first sample and the second sample. Most humans can easily detect a color change between two colors if the ΔE between those two colors is 3 or higher. Experienced users can detect color changes as low as 0.5 to 1.

[0068] The hardening joint compound of Example 1 is L * a * b * The results of this analysis are reported in Table 5 (color difference of the wet setting joint compound of the present disclosure versus the control conventional setting joint compound) and Table 6 (color difference of the dry setting joint compound of the present disclosure versus the control conventional setting joint compound). [Table 5] [Table 6]

[0069] In the above table, a ΔE value greater than 3 means that the color change was significant and would be discernible by a casual observer. As can be seen from Tables 5 and 6, the setting joint compound with reduced calcium sulfate hemihydrate is a color match to the conventional setting joint compound.

[0070] Example 3. Additional embodiments of setting joint compounds with reduced calcium sulfate hemihydrate exhibiting improved sandability To demonstrate the improved sandability of the compositions of the present invention as measured against an equivalent light-setting joint compound (a control having greater than 50 wt.% hemihydrate), setting joint compounds were prepared by mixing the raw materials with water as shown in Tables 7 and 8. [Table 7] [Table 8] [Table 9] [Table 10]

[0071] The setting joint compound was evaluated for abradability using the device and procedure described by Pelot et al. in U.S. Patent Application Publication No. 2017 / 0241881 A1, which is incorporated herein by reference, with certain modifications. The setting joint compound was abraded on a benchtop apparatus utilizing 150-grit sandpaper to apply a reproducible force along the axis and having an oscillating abrasive member arm weight of 5.5 pounds. The abraded joint compound sample was 7.5 inches long and 2 inches wide. The oscillating abrasive member completed five cycles, and the post-abrasive weight was compared to the initial weight before abrading.

[0072] As shown in Table 9 for the control and inventive formulations 3.1.1 and 3.1.2, respectively, reducing the total amount of hemihydrate from 52.9 wt.% to 49.5 wt.% significantly improves sandability, allowing 2.5 wt.% more material to be sanded away after five passes with 150 grit sandpaper.

[0073] As shown in Table 10, reducing the total amount of hemihydrate from 53.1 wt% to 49.4 wt% significantly improved sandability, allowing 1.2 wt% more material to be sanded away from Formulation 3.2.2 after five passes with 150-grit sandpaper compared to the control sample. Example 4. An embodiment of a setting joint compound with reduced calcium sulfate hemihydrate showing proximity of compressive strength to a comparable setting joint compound with greater than 50 wt.% calcium sulfate hemihydrate [Table 11] [Table 12]

[0074] To demonstrate the proximity of the dry compressive strength of the compositions of the present invention as measured against an equivalent lightweight setting joint compound (a control having greater than 50 wt.% hemihydrate), setting joint compounds were prepared by mixing the raw materials with water as shown in Table 11.

[0075] In Table 12, compressive strength was measured in psi on a dry 2-inch cube according to ASTM C-472.

[0076] The compressive strength of calcium sulfate dihydrate is related to the cube of the density. Data show that two setting joint compounds with hemihydrate levels of 56.44 wt% and 46.52 wt% had a compressive strength of 1.08 PCF, despite the latter sample having significantly less hemihydrate. (17.3 kg / m 3 ) 300 psi from each other with densities apart (21.1 kg / cm 2 ) The 56.44 wt% gypsum mix is ​​slightly denser and has a slightly higher compressive strength. Normalizing this based on density, the lower gypsum mix has a compressive strength of 55.06 PCF. (882.0 kg / m 3 ) 1324.44 in * (55.06 / 53.98) 3 =1405.537psi (98.81903kg / cm 2 ) will have an expected compressive strength of

[0077] Example 5. Additional embodiments of setting joint compounds with reduced calcium sulfate hemihydrate exhibiting improved snap-setting behavior [Table 13]

[0078] Setting joint compounds were prepared by mixing the ingredients with water as shown in Table 13. The consistencies of 1567A, B, and C were 62.5, 62.0, and 60.3 cc, respectively.

[0079] The thickening curves for each of the samples were plotted as a function of dynamic viscosity against time. These thickening curves are shown in Figure 5, where the dynamic viscosity has been converted to SI units of Pascal seconds (Pa s).

[0080] Vicat set time was measured in minutes according to modified ASTM C-472 (Standard Test Methods for Physical Testing of Gypsum, Gypsum Plaster, and Gypsum Concrete, ASTM International, West Conshohocken, PA, 2014). Vicat set time was initiated when water was added to the dry mixture of setting joint compound. Each sample was scooped into a cup at working viscosity. A 300-gram Vicat needle was held perpendicular to the surface of the joint compound, centered over the surface. The needle was held on the surface, released, and allowed to fall freely under its own weight. Set time was determined when the needle failed to penetrate partway through the joint compound surface.

[0081] The thickening curves for the formulations with reduced gypsum show a reduced increase in dynamic viscosity over the processing time of the setting compound. Dynamic viscosity is plotted until the maximum torque of the viscometer is reached. The Vicat sets for the three formulations are 51, 53, and 53 minutes, respectively. The lower hemihydrate formulations (48.59 wt. % and 46.52 wt. % for the 1567B and 1567C trial formulations, respectively) have lower viscosities and do not reach maximum torque as quickly as the 1567A control with over 50 wt. % calcium sulfate hemihydrate, despite having closer Vicat sets. [Appendix 1] 1. A dry powder setting joint compound comprising: calcium sulfate hemihydrate in an amount between 28% and 50% by weight; calcium carbonate in an amount such that the total amount of the calcium sulfate hemihydrate and the calcium carbonate is between 80% and 95% by weight; a starch binder; a redispersible latex binder; one or more of kaolin clay, sepiolite, bentonite, montmorillonite clay, attapulgite clay, or any mixture thereof; a rheology modifier; a cellulose-based thickener; a set retarder; and a set accelerator. [Appendix 2] 2. The dry powder setting joint compound of claim 1, wherein the calcium sulfate hemihydrate is in an amount of 34% to 46% by weight. [Appendix 3] 2. The dry powder setting joint compound of claim 1, wherein the calcium sulfate hemihydrate does not include beta calcium sulfate hemihydrate. [Appendix 4] 2. The dry powder setting joint compound of claim 1, wherein the calcium sulfate hemihydrate does not include alpha calcium sulfate hemihydrate. [Appendix 5] 2. The dry powder cure joint compound of claim 1, wherein the redispersible latex binder comprises one or more of vinyl acetate ethylene (VAE) copolymer, vinyl acetate / versatic acid vinyl ester (VAE-VeoVa) copolymer, styrene butadiene, acrylic powder, polyvinyl alcohol, or any combination thereof. [Appendix 6] 2. The dry powder set joint compound of claim 1, wherein the starch binder is pregelatinized. [Appendix 7] 2. The dry powder setting joint compound of claim 1, wherein the setting joint compound further comprises one or more of perlite, resin microspheres, hollow microspheres, or any combination thereof. [Appendix 8] 2. The dry powder setting joint compound of claim 1, wherein the setting joint compound comprises 5% to 20% by weight of expanded perlite. [Appendix 9] 2. The dry powder setting joint compound of claim 1, wherein the setting joint compound comprises 0.01% to 5% by weight of attapulgite clay. [Appendix 10] 2. The dry powder-setting joint compound of claim 1, wherein the rheology modifier is a substituted starch.

Claims

1. 1. A setting joint compound in the form of a dry powder, comprising: The curable joint compound is calcium sulfate hemihydrate in an amount of 28% to 50% by weight; calcium carbonate, in an amount such that the total amount of calcium sulfate hemihydrate and calcium carbonate is 80% to 95% by weight; 0.5% to 20% by weight of a starch binder; 0.1% to 20% by weight of a redispersible binder comprising one or more of vinyl acetate ethylene (VAE) copolymer, vinyl acetate / versatic acid vinyl ester (VAE-VeoVa) copolymer, styrene butadiene, acrylic powder, polyvinyl alcohol, or any combination thereof; 0.01% to 5% by weight in total of one or more of kaolin clay, sepiolite, bentonite, montmorillonite clay, or attapulgite clay; 0.01% to 2% by weight of a cellulose-based thickener; 0.01% to 10% by weight of a set retarder comprising one or more of protein-based and / or amino acid-based retarders, Rochelle salt, ammonium tartrate, sodium citrate, citric acid, cream of tartar, or a phosphate salt selected from the group consisting of zinc hexametaphosphate, potassium tripolyphosphate, tetrasodium pyrophosphate, tetrapotassium pyrophosphate, sodium tripolyphosphate, monoammonium phosphate, and monobasic potassium phosphate; 0.001% to 1.0% by weight of an accelerator comprising one or more of ground calcium sulfate dihydrate, zinc sulfate, aluminum sulfate, or potassium sulfate; A hardening joint compound comprising:

2. 10. The dry powder setting joint compound of claim 1, wherein the calcium sulfate hemihydrate is in an amount of from 34% to 46% by weight.

3. 10. The setting joint compound of claim 1, wherein the calcium sulfate hemihydrate is free of beta calcium sulfate hemihydrate.

4. 10. The setting joint compound of claim 1, wherein the calcium sulfate hemihydrate is free of alpha calcium sulfate hemihydrate.

5. 10. The setting joint compound of claim 1, wherein the starch binder is pregelatinized.

6. 10. The setting joint compound of claim 1, wherein the setting joint compound further comprises one or more of perlite, resin microspheres, hollow microspheres, or any combination thereof.

7. 10. The settable joint compound of claim 1, wherein the settable joint compound comprises 5% to 20% by weight of expanded perlite.

8. 10. The setting joint compound of claim 1, wherein the setting joint compound comprises 0.01% to 5% by weight of attapulgite clay.

9. 10. The setting joint compound of claim 1, further comprising a rheology modifier comprising carboxylated starch, carboxymethyl starch, hydrolyzed starch, starch acetate, hydroxypropyl starch, and / or phosphated starch used in an amount of 0.01% to 2% by weight.

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