Gypsum-based board

Abstract

The invention relates to a gypsum-based board. The sheet has a gypsum matrix containing the following additives: glass fibers in an amount greater than 1% by weight relative to gypsum and a synthetic polymer binder in an amount greater than 2.5% by weight relative to gypsum. The glass fibers and the synthetic polymer binder are present in a weight ratio of at least 2 parts of binder to one part of fiber. The amount of sand present in the gypsum matrix is in the range of 0-0.5 wt% relative to gypsum. The amount of cellulosic fibers present in the gypsum matrix is in the range of 0-2% by weight relative to gypsum.

Description

[0001] This application is a divisional application of patent application number 201780028577.5, filed on 06 / 04 / 2017, entitled "Gypsum based board". TECHNICAL FIELD

[0002] The present invention relates to the field of gypsum based materials, and more particularly to the field of gypsum based boards. BACKGROUND

[0003] Lightweight boards such as plasterboard (e.g. gypsum plasterboard), polystyrene boards and fibreboard are commonly used to provide partitions within buildings. Advantages for this application include that they are lightweight and quick to install.

[0004] However, in some cases, such lightweight boards can have the disadvantage that they are not strong enough to support fixtures (e.g. sinks, televisions, radiators, fire extinguishers, shelving and any other items that need to be attached to the board). In these cases, the weight of the fixture can cause the fixing means (e.g. screws) to be pulled out of the board, causing the fixture to fall from the partition.

[0005] Typically, this problem has been addressed by providing a plywood board to increase the fixing strength of the board. In this case, the plywood board is provided on the side of the board opposite to the side on which the fixture is to be placed. The plywood board can provide increased strength to retain one or more fixing means (e.g. screws) used to fix the fixture to the board. Typically, the plywood board is located within the partition frame and the plasterboard is then fixed to the plywood board so that it is located outside of the partition frame.

[0006] As an alternative, metal support means can be provided. These can include a fixing plate, channel, strap or metal fastener. As with the plywood board, the metal support means is typically located on the side of the board opposite to the side on which the fixture is to be fixed and is used to receive and fix the fixing means, e.g. fixing screws, used to attach the fixture to the board.

[0007] Both of these arrangements have the disadvantage that they require the board and the additional support component to be affixed to each other on site. Furthermore, when metal support means are used, a plurality of such support means can be required to support the full complement of fixing means required to fix the fixture to the board. As a result, the installation process can be time consuming and expensive.

[0008] Furthermore, the addition of metal support means or plywood increases the weight and thickness of the partition and / or results in a reduction of the cavity wall space. Typically, the plywood itself must be cut to size on site, thus increasing the time required for installation and potentially resulting in the release of dust and potentially harmful components.

[0009] There is therefore a need to provide an improved panel which is able to retain fixtures and support fixings and which does not require a time consuming installation process.

[0010] It is known (for example from WO 2014 / 188168) to include fibres and / or polymeric additives in a gypsum slurry to increase the fixing strength of the resulting gypsum product.

[0011] Previous developments have resulted in an increase in the fixing strength of gypsum panels, but there remains a need for further improvements in performance, or to maintain performance with a reduced panel weight and / or thickness. For example, it can be desirable to reduce the panel weight and / or thickness by 30-50% whilst maintaining fixing strength. SUMMARY

[0012] It has been surprisingly found that a significant increase in gypsum strength is achieved when fibres and polymeric additives are introduced into a gypsum-based product in unequal amounts. In particular, it has been found that a beneficial effect can be achieved by limiting the amount of fibres introduced into a gypsum-based product such that the polymeric additive is introduced into the gypsum-based product in a significantly greater amount than the fibres additive.

[0013] Thus, in a first aspect, the present invention can provide a panel having a gypsum matrix having contained within it:

[0014] • glass fibres in an amount greater than 1 wt% relative to the gypsum;

[0015] • a synthetic polymeric binder in an amount greater than 4 wt% relative to the gypsum;

[0016] • the glass fibres and synthetic polymeric binder are present in a weight ratio of at least 2 parts binder to one part fibres;

[0017] wherein the amount of sand present in the gypsum matrix is in the range 0-0.5 wt% relative to the gypsum;

[0018] and further wherein the amount of cellulose fibres present in the gypsum matrix is in the range 0-10 wt% relative to the gypsum.

[0019] Preferably, the polymeric binder is polyvinyl acetate.

[0020] Preferably, the amount of acrylic resin present in the gypsum matrix is in the range of 0-1 wt% relative to the gypsum. Typically, the gypsum matrix is essentially free of acrylic resin.

[0021] Preferably, the amount of calcium carbonate present in the gypsum matrix is in the range of 0-5 wt% relative to the gypsum, more preferably 0-1 wt% relative to the gypsum. Typically, the gypsum matrix is essentially free of calcium carbonate.

[0022] Typically, the gypsum matrix is essentially free of sand.

[0023] Preferably, the amount of cellulose fibres present in the gypsum matrix is in the range of 0-1.5 wt% relative to the gypsum, more preferably 0-1 wt%. Typically, the gypsum matrix is essentially free of cellulose fibres. The term "cellulose fibres" is intended to mean both fibres provided within the wood particles (e.g. wood chips and fine sawdust particles) and fibres which are no longer bound by the natural binder present in the wood. Thus, for the avoidance of doubt, the amount of wood particles present in the gypsum matrix is in the range of 0-2 wt% relative to the gypsum, preferably in the range of 0-1.5 wt%, more preferably in the range of 0-1 wt%.

[0024] Preferably, the total weight of additives included in the gypsum matrix is less than the weight of the gypsum in the gypsum matrix. That is, the gypsum is preferably the main component of the board by weight.

[0025] Preferably, the polymeric binder is present in an amount greater than 3.5 wt% relative to the gypsum, preferably greater than 4 wt%, most preferably greater than 5 wt%. It has been found that the addition of polymeric binder leads to a continued improvement in mechanical properties up to at least a level of about 25 wt% of binder relative to the gypsum. Thus, in view of the relatively high cost of synthetic polymeric binders, it is generally preferred that the level of synthetic polymeric binder relative to the gypsum should be 25 wt% or less.

[0026] The glass fibres included in the gypsum matrix are initially added to the gypsum slurry used to form the board. Thus, they are dispersed throughout the gypsum matrix, preferably distributed in a substantially uniform fashion.

[0027] Preferably, the glass fibres are present in an amount greater than 1.5 wt% relative to the gypsum. However, it is believed that high levels of fibres can lead to difficulties in the production of the board, for example, due to the formation of voids. Furthermore, the presence of fibres is believed to increase the force required to score and snap the board to separate them. Thus, it is preferred that the glass fibres are present in an amount less than 6 wt% relative to the gypsum.

[0028] Preferably, the glass fibres have an average length in the range of 3-10 mm.

[0029] Preferably, the glass fibres have a diameter in the range 5-50 microns.

[0030] Preferably, the glass fibres and the polymeric binder are present in a weight ratio of at least 2.5 parts binder to one part fibre, preferably at least 3 parts binder to one part fibre, preferably at least 4 parts binder to one part fibre.

[0031] In certain embodiments, the board can be substantially free of starch. In other embodiments, the board can contain synthetic polymer and starch, wherein the starch is present in an amount less than the amount of synthetic polymer, preferably in an amount less than 5% by weight relative to the amount of synthetic polymer, more preferably in an amount less than 3% by weight relative to the amount of synthetic polymer.

[0032] Typically, the gypsum matrix does not contain any fibres other than glass fibres. However, where the gypsum matrix does contain non-glass fibres, the average length of the non-glass fibres is preferably at least 50%, more preferably at least 80% of the average length of the glass fibres.

[0033] Typically, the board is provided with a facing on one or both sides. The facing can be, for example, a paper facing, which can contain cellulose and optionally glass fibres. Alternatively, the facing can be provided by a mat, for example a glass fibre mat, which is partially or completely embedded at the surface of the board.

[0034] The inclusion of synthetic polymer rather than starch to reinforce the board can have one or more of the following advantages:

[0035] • the board dries more quickly during production, allowing for faster manufacturing speeds;

[0036] • the finished board exhibits less dimensional change with humidity.

[0037] Preferably, the thickness of the board is in the range 6-20mm, more preferably in the range 10-16mm.

[0038] Preferably, the density of the board is in the range 600-1400kg / m 3 , more preferably in the range 700-1200kg / m 3 .

[0039] In a second aspect, the present application can provide a method of manufacturing a board according to the first aspect of the present application, comprising the steps of providing a stucco slurry comprising glass fibres and a synthetic polymer binder, and allowing the slurry to set,

[0040] wherein the amount of lime present in the slurry is in the range 0-0.5% by weight;

[0041] And furthermore wherein the step of providing a plaster slurry comprises adding water to the plaster in an amount less than twice the weight of the plaster.

[0042] Typically, the slurry is substantially free of lime.

[0043] Preferably, water is added to the plaster in an amount less than 1.5 times the weight of the plaster.

[0044] The board produced by the method of the second aspect of the application can comprise one or more of the optional features of the board according to the first aspect of the application.

[0045] The present application comprises the following aspects / embodiments / features in any order and / or in any combination:

[0046] 1. A board having a gypsum matrix having contained within it the following additives:

[0047] • glass fibres in an amount greater than 1 wt% relative to the gypsum;

[0048] • a synthetic polymer binder in an amount greater than 2.5 wt% relative to the gypsum;

[0049] • the glass fibres and synthetic polymer binder are present in a weight ratio of at least 2 parts binder to one part fibre;

[0050] wherein the amount of sand present in the gypsum matrix is in the range 0-0.5 wt% relative to the gypsum;

[0051] and furthermore wherein the amount of cellulose fibres present in the gypsum matrix is in the range 0-2 wt% relative to the gypsum.

[0052] 2. The board of any preceding or subsequent embodiment / feature / aspect, the board being provided with a facing on at least one side.

[0053] 3. The board of any preceding or subsequent embodiment / feature / aspect, wherein the polymer binder is polyvinyl acetate.

[0054] 4. The board of any preceding or subsequent embodiment / feature / aspect, wherein the amount of acrylic resin present in the gypsum matrix is in the range 0-1 wt% relative to the gypsum.

[0055] 5. The board of any preceding or subsequent embodiment / feature / aspect, wherein the amount of calcium carbonate present in the gypsum matrix is in the range 0-1 wt% relative to the gypsum.

[0056] 6. The board of any preceding or subsequent embodiment / feature / aspect, wherein the total weight of the additives contained within the gypsum matrix is less than the weight of the gypsum in the gypsum matrix.

[0057] 7. The board of any preceding or subsequent embodiment / feature / aspect, wherein the polymeric binder is present in an amount greater than 3.5 wt%, preferably greater than 4 wt%, most preferably greater than 5 wt% relative to the gypsum.

[0058] 8. The board of any preceding or subsequent embodiment / feature / aspect, wherein the glass fibres are present in an amount less than 6 wt% relative to the gypsum.

[0059] 9. The board of any preceding or subsequent embodiment / feature / aspect, wherein the glass fibres have an average length in the range 3-10 mm.

[0060] 10. The board of any preceding or subsequent embodiment / feature / aspect, wherein the glass fibres have a diameter in the range 5-50 microns.

[0061] 11. The board of any preceding or subsequent embodiment / feature / aspect, wherein the glass fibres and polymeric binder are present in a weight ratio of at least 3 parts binder to one part fibre, preferably at least 4 parts binder to one part fibre.

[0062] 12. The board of any preceding or subsequent embodiment / feature / aspect, wherein the board is substantially free of starch or contains less than 5 wt% starch relative to the amount of synthetic polymeric binder.

[0063] 13. A method of manufacturing the board of any preceding or subsequent embodiment / feature / aspect, comprising the steps of: providing a plaster slurry comprising glass fibres and a synthetic polymeric binder, and setting the slurry,

[0064] wherein the amount of lime present in the slurry is in the range 0-0.5 wt%;

[0065] and further wherein the step of providing the plaster slurry comprises adding water to the plaster in an amount less than twice the weight of the plaster. DETAILED DESCRIPTION

[0066] The application will now be described by way of example only.

[0067] A gypsum plasterboard was prepared from a gypsum slurry according to the following method:

[0068] 1. Polyvinyl acetate (Vinamul 8481 from Celanese Emulsions) was added to water to form an aqueous suspension;

[0069] 2. Glass fibres were mixed into the aqueous suspension;

[0070] 3. Plaster was added to the aqueous suspension to form a slurry;

[0071] 4. The slurry is mixed in a Kenwood mixer (RTM) for 10 seconds at minimum speed;

[0072] 5. The speed is increased and the slurry is further mixed for 20 seconds;

[0073] 6. The slurry is deposited on a forming surface to form a panel;

[0074] 7. The panel is dried at a temperature of 160°C for 1 hour and further dried at a temperature of 40°C until a constant weight is achieved;

[0075] 8. The panel is conditioned at 23°C and 50% relative humidity until a constant weight is achieved.

[0076] Table 1 details the composition of the slurry and the density of the panel.

[0077] The polyvinyl acetate is added to the slurry in the form of an aqueous suspension. The amount of polyvinyl acetate listed in Table 1 refers to the amount of polyvinyl acetate contained in the aqueous suspension, not the total mass of the suspension added to the slurry.

[0078] Table 1

[0079]

[0080]

[0081] Screw pull-out test

[0082] A screw pull-out test is performed on a 100mm by 100mm measured sample which has been conditioned at a temperature of 23°C and 50% relative humidity. A 50mm single thread wood screw is inserted into the sample using a torque screwdriver, the screw passing through a metal load transfer element located on the surface of the sample. The load transfer element has a first portion configured to sit between the head of the screw and the surface of the sample, and a second portion configured to engage with the testing machine, allowing the load to be applied to the screw along the axis of the screw.

[0083] The test specimen is then mounted in a Zwick Universal Testing Machine and a 10N preload is applied to the screw along the axis of the screw. Subsequently, the load is increased by setting a constant crosshead speed of 10mm / minute until pull-out is achieved.

[0084] Refix pull-out test

[0085] The re-fixity pull-out test was performed using the same procedure as the screw pull-out test with the additional step of immediately after the step of inserting the screw into the sample using a torque screwdriver, removing the screw and re-inserting it into the same location using the torque screwdriver.

[0086] Fatigue test

[0087] The fatigue test was performed using the same procedure as the screw pull-out test with the additional step of 100 load cycles between 10 N and 300 N applied at a crosshead speed of 10 mm / min between the steps of applying a 10 N preload to the screw and setting the crosshead speed to 10 mm / min.

[0088] Hand torque test

[0089] The hand torque test was performed on a 100 mm by 100 mm size sample conditioned at a temperature of 23 °C and a relative humidity of 50%. A 50 mm single thread wood screw was inserted into the sample using a screw gun (screw gun), the screw passing through a steel washer located on the surface of the sample.

[0090] The screw gun was configured to stop when the screw had been inserted into the sample to a depth of 10 mm with the head protruding from the sample. The screw was then turned using a torque controlled hand screwdriver until a sharp increase in the torque reading was observed, when the screw head contacted the sample. Using the hand screwdriver, the screw was then further turned in increments of 1 / 8 of a turn, recording the torque reading after each increment, then resetting to zero. After reaching the maximum torque, the process continued for at least 1.5 turns. The maximum torque was then recorded.

[0091] The results of the mechanical tests are listed in Table 2. The numbers in brackets indicate the number of samples tested.

[0092] Table 2

[0093]

Claims

1. A board having a gypsum matrix, wherein the gypsum matrix contains the following additives: • Glass fiber content greater than 1% by weight relative to gypsum; • Synthetic polymer adhesives in amounts greater than 2.5% by weight relative to gypsum; • The glass fiber and the synthetic polymer adhesive are present in a weight ratio of at least 2 parts adhesive to 1 part fiber; The amount of sand present in the gypsum matrix is ​​in the range of 0-0.5% by weight relative to the gypsum. Furthermore, the amount of cellulose fibers present in the gypsum matrix is ​​in the range of 0-2% by weight relative to the gypsum.

2. The board material according to claim 1, wherein the board material has a decorative surface on at least one side.

3. The sheet material according to claim 1 or 2, wherein the polymer adhesive is polyvinyl acetate.

4. The board according to any one of the preceding claims, wherein the amount of acrylic resin present in the gypsum matrix is ​​in the range of 0-1% by weight relative to the gypsum.

5. The board according to any one of the preceding claims, wherein the amount of calcium carbonate present in the gypsum matrix is ​​in the range of 0-1% by weight relative to the gypsum.

6. The board according to any one of the preceding claims, wherein the total weight of the additives contained in the gypsum matrix is ​​less than the weight of the gypsum in the gypsum matrix.

7. The board according to any one of the preceding claims, wherein the polymer adhesive is present in an amount greater than 3.5% by weight, preferably greater than 4% by weight, and most preferably greater than 5% by weight relative to the gypsum.

8. The sheet material according to any one of the preceding claims, wherein the glass fiber is present in an amount of less than 6% by weight relative to the gypsum.

9. The sheet material according to any one of the preceding claims, wherein the average length of the glass fibers is in the range of 3-10 mm.

10. The sheet material according to any one of the preceding claims, wherein the diameter of the glass fibers is in the range of 5-50 micrometers.

11. The sheet material according to any one of the preceding claims, wherein the glass fiber and the polymer binder are present in a weight ratio of at least 3 parts binder to 1 part fiber, preferably at least 4 parts binder to 1 part fiber.

12. The sheet material according to any one of the preceding claims, wherein the sheet material is substantially free of starch or contains less than 5% by weight of starch relative to the amount of synthetic polymer adhesive.

13. A method for manufacturing a sheet metal according to any one of claims 1-12, comprising the following steps: Provides plastering materials containing glass fibers and synthetic polymer binders, as well as methods for setting the plastering material. The amount of lime present in the slurry is in the range of 0-0.5% by weight; Furthermore, the step of providing the plaster slurry includes adding water to the plaster in an amount less than twice the weight of the plaster.

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