TW201540915A - Building boards with increased surface strength - Google Patents

Abstract

Disclosed is a building board construction with increased surface strength. More specifically, increased nail pull strength is achieved via the application of an external surface coating. The surface coating is ideally applied to a paper faced gypsum building board. In one possible embodiment, the coating is formed from a water soluble polymer.

Description

Building panel with increased surface strength Cross-reference to related applications

This application claims priority from US Application Serial No. 14/143,338, filed on Dec. 30, 2013, entitled "Building Boards with Increased Surface Strength," and some of its subsequent applications, and claims December 30, 2013 The priority of U.S. Application Serial No. 14/143,421, the disclosure of which is incorporated herein by reference in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety.

This invention relates to building panels having increased surface strength. More particularly, the present invention relates to coatings and coating methods that provide increased nail pull strength.

Gypsum board is one of the most widely used and versatile building materials in the world. The basic construction for plaster building panels has remained unchanged for quite some time. The construction includes a calcium sulfate dihydrate core sandwiched between the opposing sheets. In recent years, efforts have been made to increase the strength of gypsum boards. In particular, efforts have been made to increase the strength of the nail pull. The nail pull strength is a standard ASTM measurement. The higher nail pull strength ensures that the panel can be securely fastened to the associated framed component. To date, efforts to increase nail pull have focused on nuclear materials, additives, and nuclear density. A disadvantage of such efforts is that they require a relatively large amount of material and an increased board weight to strengthen the core.

An example of a gypsum board having increased strength is illustrated in Colbert, U.S. Publication No. 2004/0154264. The present disclosure discloses a coated gypsum board having a surfacing sheet. The coating is disposed on at least a portion of the paving sheet and at least a portion of the coating penetrates into In the paving sheet and / or plaster core. In an additional embodiment, the gypsum board further comprises a backing sheet on the second side of the gypsum core. In one aspect, the coating can penetrate into the gypsum core to achieve a substantially uniform depth across the gypsum board area. The gypsum board with this coating exhibits a pull strength value of greater than 80 pounds.

U.S. Publication No. 2005/0233657 to Grove discloses a gypsum or foam end face formed by in-line or off-line coating of a pre-impregnated fibrous network structure mat with a secondary binder system. . The pre-impregnated fibrous web structure is preferably formed from a randomly oriented wet chopped strand fiber material impregnated with a modified urea-formaldehyde binder system. The secondary binder system preferably consists of a low glass transition acrylic or styrene-butadiene-rubber resin that is primarily filled with a filler such as a reinforcing or fiber reinforced panel.

While the invention cited above achieves its own individual goals, they have common disadvantages. That is, none of the prior art can address the use of coating or coating techniques to increase the strength of the pull while minimizing the weight of the panel. The panels for construction of the present invention are designed to overcome these and other deficiencies in the prior art.

The panel for construction of the present invention has the advantage of exhibiting increased surface strength without significantly increasing the overall weight of the panel.

Another advantage is achieved by increasing the strength of the nails of the building panels by applying a surface coating.

One advantage is also achieved by selecting a surface coating that is complementary to the tensile strength of the underlying paper.

Yet another advantage is achieved by increasing the strength of the nail by applying a particular water soluble or water dispersible polymer coating.

Another advantage is achieved by applying a polymer coating after the board has been formed by wet coating techniques.

Another advantage is that the useful strength of the nail pull is found to be lower than found in the prior art. Its coating weight is achieved.

Another possible advantage is achieved by providing a coating that is applied across the surface of the board in a non-uniform manner.

Another advantage is achieved by applying a thicker surface coating at locations where large loads are typically encountered.

Yet another advantage is achieved by reducing the weight and cost of the panel by applying a surface coating through the target.

Another advantage is achieved by providing a construction panel that can be inexpensively manufactured with increased nail pull strength.

Various embodiments of the invention may have or have some or all of these advantages. Other technical advantages of the present invention will be readily apparent to those skilled in the art.

Based on a more complete understanding of the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings in which: FIG. 1 is a diagram showing the relative displacement of the paper panel and the non-paper panel.

Figure 2 is a graph of load relative displacement of a paper panel indicating the failure mode in each measurement area.

Figure 3 is a SEM cross section of the paper panel after the peak load of the nail measurement.

Figure 4 is a graph showing the normal variation in the width of the cross-composite building panel for nail pull strength.

Figure 5 is a graph plotting the pull-out index versus dry weight coverage as applied by airless spray coating techniques.

Figure 6 is a graph plotting nail pull resistance versus panel weight for airless and air atomized spray coating techniques.

Figure 7 is a graph plotting the distance of the puller from the edge of the panel.

The present invention relates to increasing the surface strength of a building panel by applying an outer coating. Paint The layers are ideally applied to the paper building panels to increase the strength of the nail pull. In a possible embodiment, the coating is formed from a water soluble polymer. In yet another embodiment, the coating is applied in a non-uniform manner to account for variable loading across the surface of the panel. The various details of the invention, and the manner in which they are related, are described in more detail below.

In a preferred but non-limiting example, the building panel is a plaster based building panel. The general construction of gypsum board is well known and includes a calcium sulfate dihydrate core sandwiched between opposing sheets. The core was initially deposited as a slurry of calcium sulfate hemihydrate (CaSO4.1⁄2H ₂ O) and water. Once the slurry is deposited, it is immediately rehydrated to form gypsum.

It is also known in the related art to use various additives in the gypsum core. One such additive is starch. Starch can be added prior to rehydration. Starch acts as a binder in the hardened gypsum and obtains a sheet with higher compression and flexural strength. It also enhances the edges of the resulting panels and enhances the combination of paper and core. The gypsum core described herein may optionally comprise an additive such as starch.

The gypsum core of the present invention may also include a plurality of internal pores to reduce the overall weight of the sheet. It is known in the related art to form voids inside the gypsum board as a means for reducing the weight of the board. One technique is described in US Patent 6,706,128 to Sethuraman. Sethuraman '128 discloses a method of adding bubbles having different relative stability whereby the bubbles do not rupture until the slurry is sufficiently hardened to prevent the slurry from filling the void space left by the ruptured bubbles. The result is a gypsum board with internal porosity and reduced weight. Other suitable techniques for pore formation are well known to those skilled in the art.

According to one embodiment, the coating is applied to one of the paper liners. While the coating can be applied to either or both of the liners, the coating is preferably applied to a liner forming the decorative outer surface of the building panel. Any of a variety of wet coating techniques (e.g., spray coating, slot die coating, roll coating, or dip coating) can be used. As explained below, the coating is designed to increase the strength of the nail without significantly increasing the weight of the building panel. The coating can form the decorative outer surface of the panel. In this regard, you can also add various known A matting agent to reduce the gloss of the coating and otherwise make it more aesthetically pleasing. However, the coating does not need to form the outer surface of the resulting sheet. Instead, a coating can be used as a primer or pre-primed to ensure adequate adhesion to subsequent coatings.

Figure 1 shows the load (in pounds of force) relative to the nail pull displacement (in millimeters). The topmost line shows 40 to 50% of the strength of the puller due to the paper liner. This reflects the increased nail pull strength achieved by providing paper. The lower line is reflected in the paperless liner, and 50 to 60% of the strength of the nail is attributed to the nuclear material. In summary, this figure shows that the contribution of the paper shop to the peak load of the nail is more significant than previously known. The present invention takes advantage of this discovery by increasing the strength of the puller by applying a surface coating.

The surface strength is further increased by selecting a coating material that is complementary to the tensile properties of the underlying paper liner. The optimum coating material is not the most sturdy material, but the highest elongation strength required to match the cracking of the paper. By using these coatings, the damage of the liner is delayed as long as possible while the panel is under load. It is also preferred to select a coating that is best adhered to the paper and used to strengthen the cellulose fibers in the paper itself. Preferred coating materials are listed in Table 1 below.

It is also known that the peak pull strength occurs immediately before the crack or tear of the paper surface. This is shown in Figure 2, which shows the relative displacement of the load in the nail pull test. The figure contains a description of the failure process occurring during the test based on a series of SEM cross sections taken at different points during the test. Figure 2 illustrates that the failure mechanism can be broken down into four parts. In the first part, the load causes microcracks to form in the plate. Then, under increasing load, microcrack propagation and internal pores are compressed. In the third part, compression of the core and shear failure of the liner occur. Finally, under peak load, the paper tears.

Figure 3 contains a cross-sectional scanning electron microscope image of the composite building panel immediately after the peak load in the nail pull test. On the right side of the image, it is seen that the paper ruptures just at the surface of the paper that is under tensile strain. This indication can strengthen the surface of the paper or better distribute the tensile load of the coating to significantly increase the peak pull strength.

Table 1 contains a variety of polymers used as coatings on building panels and for nail pull strength The impact. The pull-out (NP) percentage increments relative to the uncoated panels were measured.

Some illustrative examples are listed below.

A comparison with the nail reinforcement of coating numbers 1, 2, and 3 in Table 1 above indicates that only the strength is not sufficient for significant nailing enhancement. Nanocellulose is an extremely high strength material that is effective for paper reinforcement in the application of a coating. Although the tensile strength of the material is extremely high, however, the elongation at break is rather low and thus the material does not increase the strength of the pull. This is because the coating failed before the paper in the nail pull test and the peak load in the nail pull test occurred at the paper break point. Similarly, comparisons with Bostic and Titebond wood adhesives indicate that a tougher, more flexible adhesive significantly enhances nail pull. On the other hand, Titebond, which is strong, hard, and brittle, has no significant effect.

If the extremely hard material has a large coating weight, the nail pull can be increased, but the cost is high. When testing hard epoxy resins, the nail pull strength can be significantly increased, but the peak load is completely derived from the strength of the coating and therefore a large coating weight is required to achieve this result. In the case of very thin tough coatings, the coating desirably fails at the same time as the paper and can be used to increase the strength of the paper itself because it is too thin to provide strength on its own.

A number of conclusions can be drawn from the polyvinyl alcohol (PVOH) coating numbers 4 to 9 in Table 1. One conclusion is that high molecular weight materials are significantly stronger than low molecular weight materials and thus increase the strength of the pull nails (presumably, they have similar degrees of elongation/elongation). Second, the percentage of hydrolysis does not seem to have a major impact. Finally, it has been shown to have an effect at even very low coating weights of ~1 g/ft ² .

Low viscosity vinyl acetate ethylene ("VAE") copolymer coatings are designed to penetrate into the paper and enhance the toughness of the paper. They may be a strong and flexible coating that is crosslinked or uncrosslinked. When cast and dried in air (film numbers 10 to 16 in Table 1), the strength increases with the glass transition temperature ("Tg", measured in degrees Celsius). This implies that the low Tg material is actually slightly soft. However, after IR cross-linking (membrane numbers 17 to 19 in Table 1), the Tg film with a lower Tg film phase is slightly stronger. This implies that the trade-off between strength and ductility can be adjusted by either the polymer Tg or by any of the degrees of crosslinking in the VAE system. Relatively based on nail pull data Cover, film thickness seems to have little effect on nail reinforcement.

As can be seen from Table 1, preferred coating polymers are high molecular weight polyvinyl alcohol (No. 5 to 9), vinyl acetate ethylene (No. 12 to 15) having Tg = 15, and styrene butadiene copolymer ( No. 21). Polymer coatings having a tensile modulus greater than 500 psi at room temperature and an elongation at break greater than 500% are also advantageously provided. The coating may also have a viscosity of between 20 and 2000 centipoise. The VAE based coating is preferably less than 100 microns thick. In the preferred embodiment, the VAE coating applied to the surface of the panel is between 20 and 30 microns thick. In the case of a PVA-based coating, it is preferably 10 microns. Also preferred is a coating thickness greater than 1 g/ft ² and a thickness of about 1.5 g/ft ² is preferred.

It is also preferred to apply the selected coating to the surface of the paper in a non-uniform or non-uniform manner. Ideally, the coating is thicker in areas where it is highly likely to experience maximum surface loading. In other words, the coating coverage is larger in areas such as those having the lowest nail pull strength. Figure 4 contains a plot of the strength of the uncoated composite building panel across the width of the panel. The line drawn shows that the nail pull strength is the weakest in the area around the center of the board. Similarly, the edges of the panels exhibit the greatest amount of nail pull. In accordance with the present invention, the coatings described above can be applied in smaller amounts along the centerline of the panel and in smaller amounts along the edges. In some embodiments, the expected nail pull strength may dictate that no coating is applied in the selected area. The purpose of this target application is to effectively smooth out the lines depicted in Figure 4 to achieve a more uniform pull strength across the entire surface of the board. Other maps having different shapes than those of Figure 4 can be similarly generated based on different plate geometries, core materials, and/or desired uses. The thickness of the surface coating will vary depending on the expected strength of the pull stud across the surface of the board.

Polymer coating formulation

In addition to the polymeric coatings mentioned above, the inventors have also tested a variety of polymer formulations. Broadly speaking, the formulations comprise, in addition to cerium oxide and an antifoaming agent, a polymer as a major component. Various coating techniques were also tested. Table 2 lists formulation 909 #17/02, which is sold primarily by Celanese Corporation of Dallas, Texas under the trademark Dur-o-Set® The composition of the emulsion polymer. In particular, the formulation consisted of about 89.9% Dur-o-Set 909 (expressed as a percentage of total solids). Dur-o-Set 909 is a crosslinked polymer. That is, the polymer crosslinks with itself upon heating. Dur-o-Set 909 performs well because cross-linking does not result in brittleness that is not conducive to nail pull strength. The formulation further comprises water and cerium oxide. In this exemplary formulation, the formulation contained about 9.9% of Acematt® HK400 untreated fine particulate precipitated cerium oxide from Evonik Industries AG. Blue dye is included for testing purposes to make it easier to observe the distribution of the coating on the board. In practice, the dye will be replaced by an antifoaming agent, such as the Foamaster ® 111 brand defoamer from BASF Corporation. Table 2 also lists the components (in grams) based on the total weight and the weight of the solids. Approximately 25.0% of the Table 2 formulations contained solids.

The second formulation (405 #17/02) is listed in Table 3, and in most aspects the same as the 909 #17/02 formulation. However, the Dur-o-Set 909 polymer was replaced by EcoVAE 405, which is a vinyl acetate/ethylene emulsion similarly marketed by Celanese Corporation. However, EcoVAE 405 is a non-crosslinked polymer. EcoVAE 405 is desirable because it produces a tough polymer that complements the strength of the base paper and increases the strength of the pull. Approximately 27.2% of the Table 3 formulations contained solids.

Table 4 lists the results of applying the two coating formulations to the gypsum board and testing the nail removal. In each case, the coating was applied by using a Meyer rod by a primer coating technique. The thickness of the wet coating and the corresponding board weight are also listed. The nail pull index improvement (NPI) lists nail improvement. The NPI was calculated according to the following formula: NPI = NP / Wt × 0.05, where NP is the average nail pull resistance (in pounds force) and Wt is the board weight (in lbs/MSF).

Tables 5 through 6 illustrate the 909 #20/02 coating and the 405 #20/02 coating. These coatings generally correspond to the coating formulations described in Tables 2 through 3 above. The 909 #20/02 formulation contains 24.9% total solids. The 405 #20/02 formulation contained 27.1% total solids. In each case, the coating was applied to the panels using airless spray coating techniques. This results in a much larger coating weight.

Table 7 shows the 909 #20/02 and 405 #20/02 formulations applied by airless spray coating alternately using low and high pressure settings. In each case, the resulting dry coverage (in grams per square foot) was 2.1 g/ft ² or less. The resulting standardized nail pull index (NPI) was changed from a high value of 11.4 to a low value of 5.2.

Air atomized spray coating was also studied. The results of this study are listed in Tables 8 to 11 below. Table 8 describes a coating formulation comprising water, Dur-o-set 909, HK400 cerium oxide, and Foamaster® 111 brand defoamer from BASF Corporation. A small amount of Surfynol 104PG50 surfactant is also included. The total solids are about 25%.

Formulations containing latex binders were also tested as described in Table 9. The specific latex binder used was a latex binder (DL 490NA from Styron).

The results from the two coatings each applied by air atomized spray coating are listed in Below. The table lists the pressure of the air atomized spray coating apparatus and the resulting dry coverage of the panels. Standardized nailing is also listed.

Figure 5 depicts the results of the 909 #20/02 and 405 #20/02 formulations as applied by airless spray coating techniques. The figure shows the actual dry coverage of the nail pull index relative to the panel. It has been determined that lower atomizing air pressures perform better because they leave a sufficient amount of sheets uncoated and thus allow the entrained water vapor to escape through the surface of the sheet during drying. Coatings that are applied through higher pressures result in less satisfactory finer spray patterns and generally result in excessive surface coating. The inventors have found that about 20% of the board surface is left uncoated to achieve sufficient penetration. In the preferred embodiment, between 10% and 20% of the surface of the panel is uncoated. Achieve a 10% or greater improvement in the nail pull index. Figure 6 depicts the nail pull resistance versus plate weight for Dur-o-Set 909 and EcoVAE 405 formulations. Both airless injection and air atomization injection techniques are employed. Significant improvements in nail pull strength have also been achieved.

In a specific test of the 909 #15/08 formulation, the coating was applied by an airless spray coater installed on a gypsum siding factory line at a pressure of about 30 psi. The coating was applied to a gypsum board having an uncoated weight of 1440 lb/MSF (lbs/1000 sq. ft.). The resulting panel had a coating weight of 1448 lb/MSF. The increase in the nail pull index is between 8 and 10%. Therefore, the 909 #15/08 formulation can increase the nail pull strength by up to about 10% but rarely causes the weight of the board to increase. plus. Figure 7 illustrates the nail pull variation across the surface of a production panel with and without a coating.

Table 11 includes information relating to air atomization coating of Styron Latex DL 490NA styrene-butadiene polymer. Table 12 includes information relating to air atomization coating of Dur-o-Set 909. In each case, a 2 bar atomizing air pressure would prove to be a problem in the factory setting, as it would not allow sufficient penetration. An air pressure of about 1.2 bar is considered desirable because it provides a sufficiently rough spray pattern.

Although the present invention has been described in terms of the specific embodiments and the generally associated methods, those skilled in the art will recognize variations and substitutions of the embodiments and methods. Based on this, above The description of the example embodiments does not limit or constrain the invention. Other changes, substitutions, and changes may be made without departing from the spirit and scope of the invention.

Claims (42)

A composite building panel having enhanced nail pull strength, the composite building panel comprising: first and second liners having an outer surface forming a decorative outer surface of the building panel; positioned at the a hardened gypsum core between the first and the second liner and combined with the liner, the hardened gypsum core being formed of a cement slurry mainly composed of calcium sulfate hemihydrate, the hardened gypsum core being formed to have a plurality of Internal voids, the internal pores functioning to reduce the total weight of the building panel; a polymer-based coating applied to the decorative outer surface of the building panel, wherein the coating comprises less than 10 grams per square Feet of polymer. A composite building panel according to claim 1 wherein the coating comprises less than 2 grams per square foot of polymer and the strength of the nail is greater than 10% greater than the uncoated building panel. The composite building panel of claim 2, wherein the coating polymer comprises a synthetic polymer. The composite building board of claim 2, wherein the coating polymer comprises an acrylic and acrylic copolymer, a vinyl acetate polymer and copolymer, a styrene-butadiene polymer and a copolymer, or A polymer of polyvinyl alcohol. The composite building panel of claim 2, wherein the coating polymer comprises one of: a copolymer comprising vinyl acetate and ethylene; a copolymer comprising styrene and butadiene; or a polyvinyl alcohol. A composite building panel according to claim 5, wherein the coating is less than 100 microns thick. The construction panel of claim 3, wherein the coating polymer has a temperature of less than 30 degrees Celsius Glass transition temperature. The construction panel of claim 3, wherein the coating polymer has a glass transition temperature of greater than 5 degrees Celsius and less than 25 degrees Celsius. The construction panel of claim 1, wherein the coating polymer comprises one of: a copolymer comprising vinyl acetate and ethylene; a copolymer comprising styrene and butadiene; or a polyvinyl alcohol. A composite building panel according to claim 9 wherein the coating is less than 100 microns thick. A composite building panel according to claim 3, wherein the coating is less than 100 microns thick. The construction panel of claim 11, wherein the coating is less than 50 microns thick. The composite building panel of claim 3, wherein the coating polymer has a tensile modulus of greater than 500 psi and an elongation at break of greater than 500% at room temperature. The construction panel of claim 13, wherein the coating polymer has an elongation at break of between about 500% and 10,000%. The construction panel of claim 14, wherein the coating polymer has a tensile modulus of between about 500 psi and 10,000 psi. The construction panel of claim 15, wherein the coating polymer further comprises at least one of: a copolymer comprising vinyl acetate and ethylene; a copolymer comprising styrene and butadiene; or a polyvinyl alcohol. The construction panel of claim 16, wherein the coating is less than 100 microns thick. The construction panel of claim 2, wherein the coating is an aqueous solution. The construction panel of claim 2, wherein the coating is an aqueous dispersion. The construction panel of claim 19, wherein the coating has a solids percentage between 10% and 60%. The construction panel of claim 20, wherein the coating has a viscosity of between 25 and 2000 centipoise. The construction panel of claim 21, wherein the coating is applied by spray coating. The construction panel of claim 22, wherein the coating polymer comprises one of: a copolymer comprising vinyl acetate and ethylene; a copolymer comprising styrene and butadiene; or a polyvinyl alcohol. The construction panel of claim 23, wherein the coating is less than 100 microns thick. The construction panel of claim 2, wherein the coating is uneven across the width of the panel. The construction panel of claim 25, wherein the coating is more than 20% thicker at the center of the panel than at the edge. The construction panel of claim 26, wherein the coating polymer comprises one of: a copolymer comprising vinyl acetate and ethylene; a copolymer comprising styrene and butadiene; or a polyvinyl alcohol. The construction panel of claim 27, wherein the coating is less than 100 microns thick. A composite building panel having enhanced nail pull strength, the composite building panel comprising: an outer surface forming a decorative outer surface of the building panel; a hardened gypsum core positioned below the outer surface, the hardened plaster core being mainly A cement slurry of calcium sulfate hemihydrate is formed; a polymer based coating applied to the exterior of the decorative panel of the building, wherein the coating comprises less than 10 grams per square foot of polymer. The composite building panel of claim 1, wherein the first and the second liner are formed by a paper shape to make. A composite building panel having enhanced nail pull strength, the composite building panel comprising: an outer face; a hardened gypsum core positioned below the outer face, the hardened gypsum core being formed from a cement slurry mainly comprising calcium sulfate hemihydrate a polymer-based coating applied to the exterior side of the building panel in a non-uniform manner. The composite building panel of claim 31, wherein the composite building panel comprises a centerline and an opposite lateral edge, and wherein the polymer-based coating is thicker along the centerline. The composite building panel of claim 31, wherein the composite building panel comprises a centerline and opposite lateral edges, and wherein the polymer-based coating is thinner along the opposing lateral edges. The composite building panel of claim 31, wherein the polymeric coating comprises a thicker and thinner region, and wherein the thicker region comprises less than 10 grams per square foot of polymer coating. The composite building panel of claim 31, wherein the hardened gypsum core is formed to have a plurality of internal pores. The composite building panel of claim 31, wherein the exterior surface is formed from paper. A composite building panel having enhanced nail pull strength, the composite building panel comprising: first and second liners having an outer surface forming a decorative outer surface of the building panel; positioned in the first a hardened gypsum core interposed between the second liner and the liner, the hardened gypsum core being formed of a cement slurry mainly composed of calcium sulfate hemihydrate, The hardened gypsum core is formed to have a plurality of internal pores, the internal pores acting to reduce the total weight of the building panel; a polymer-based coating applied to the exterior of the decorative panel of the building panel, The polymer based coating is applied across the exterior in a non-uniform manner. A composite building panel according to claim 37, wherein the coating comprises less than 10 grams per square foot of polymer. The composite building panel of claim 37, wherein the coating polymer comprises a synthetic polymer. The composite building panel of claim 37, wherein the composite building panel comprises a centerline and an opposite lateral edge, and wherein the polymer-based coating is thicker along the centerline. The composite building panel of claim 37, wherein the composite building panel comprises a centerline and opposite lateral edges, and wherein the polymer-based coating is thinner along the opposite lateral edges. The composite building panel of claim 37, wherein the first and second liners are formed from paper.