Construction Panel Having Improved Fixing Strength

Abstract

A gypsum product has a first polymeric additive and a second polymeric additive distributed therein, wherein the first polymeric additive is a synthetic polymer and the second polymeric additive is starch. It has been found that the combination of starch and a synthetic polymer may result in one or more of the following advantages in the manufacture and performance of gypsum products: —increased strength; —greater ease of manufacturing due to the increased fluidity of stucco slurries containing both additives; and —increased resistance to hygroscopic expansion.

Claims

1. A gypsum panel comprising a first polymeric additive and a second polymeric additive distributed therein, wherein the first polymeric additive is a synthetic polymer and the second polymeric additive is starch; the gypsum panel having fibres embedded therein in an amount of 2-10 wt % relative to gypsum in the gypsum panel; wherein the total amount of the first and second polymeric additives is greater than 4 wt % relative to the gypsum.

2. A gypsum product according to claim 1, wherein the first polymeric additive is present in an amount equal to or greater than the second polymeric additive.

3. A gypsum product according to claim 1, wherein the total amount of the first and second polymeric additives is 20 wt % or less relative to the gypsum.

4. A gypsum product according to claim 1, wherein the first polymeric additive is polyvinyl acetate.

5. A gypsum product according to claim 1, wherein the second polymeric additive is substituted starch.

6. A gypsum product according to claim 5, wherein the starch is ethylated starch.

7. (canceled)

8. A gypsum product according to claim 1, wherein the fibres are glass fibres.

9. A gypsum product according to claim 8, wherein the fibres are present in an amount of 3-10 wt % relative to the gypsum.

Description

DETAILED DESCRIPTION

[0037] The invention will now be described by way of example only.

[0038] Gypsum plasterboards were prepared using the following general methodology: Stucco and other dry additives were weighed into a bag and shaken to mix them. Water and wet additives were weighed into a bowl. The fibres were weighed, added to the wet additives in the bowl, and mixed together using an electric mixer for 60 s.

[0039] The dry powdered additives were added to the wet additives in the bowl and mixed in with the electric mixer for 30 s.

[0040] The resultant slurry was sandwiched between two sheets of paper liner and allowed to hydrate for 25 minutes measured from the time of mixing. The board was then dried in an oven for 1 hour at 160° C.

[0041] The resulting plasterboards were 15 mm thick.

Example 1

[0042] A gypsum plasterboard was prepared from the following ingredients: [0043] stucco; [0044] polyvinyl acetate in an amount of 6 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Mowilith 51); [0045] starch in an amount of 6 wt % relative to the stucco (the starch is available under the trade name C Flex 03408); [0046] Glass fibres in an amount of 3 wt % relative to the stucco.

Example 2

[0047] A gypsum plasterboard was prepared from the following ingredients: [0048] stucco; [0049] polyvinyl acetate in an amount of 6 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0050] starch in an amount of 6 wt % relative to the stucco (the starch is available under the trade name C Flex 03408); [0051] Glass fibres in an amount of 3 wt % relative to the stucco.

Example 3

[0052] A gypsum plasterboard was prepared from the following ingredients: [0053] stucco; [0054] polyvinyl acetate in an amount of 2.5 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0055] starch in an amount of 2.5 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0056] Glass fibres in an amount of 5 wt % relative to the stucco.

Example 4

[0057] A gypsum plasterboard was prepared from the following ingredients: [0058] stucco; [0059] polyvinyl acetate in an amount of 3.75 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0060] starch in an amount of 1.25 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0061] Glass fibres in an amount of 5 wt % relative to the stucco.

Example 5

[0062] A gypsum plasterboard was prepared from the following ingredients: [0063] stucco; [0064] polyvinyl acetate in an amount of 6.25 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Mowilith SI); [0065] starch in an amount of 6.25 wt % relative to the stucco (the starch is available from Grain Processing Corporation under the trade name Coatmaster K57F); [0066] Glass fibres in an amount of 3% relative to the stucco

Example 6

[0067] A gypsum plasterboard was prepared from the following ingredients: [0068] stucco; [0069] polyvinyl acetate in an amount of 6 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0070] starch in an amount of 0.5 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0071] Glass fibres in an amount of 2 wt % relative to the stucco

Example 7

[0072] A gypsum plasterboard was prepared from the following ingredients: [0073] stucco; [0074] polyvinyl acetate in an amount of 0.5 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0075] starch in an amount of 6 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0076] Glass fibres in an amount of 2 wt % relative to the stucco

Example 8

[0077] A gypsum plasterboard was prepared from the following ingredients: [0078] stucco; [0079] polyvinyl acetate in an amount of 4.5 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0080] starch in an amount of 1.5 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0081] Glass fibres in an amount of 2 wt % relative to the stucco

Example 9

[0082] A gypsum plasterboard was prepared from the following ingredients: [0083] stucco; [0084] polyvinyl acetate in an amount of 1.5 wt % relative to the stucco (the polyvinyl acetate is available under the trade name Vinamul 8481); [0085] starch in an amount of 4.5 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0086] Glass fibres in an amount of 2 wt % relative to the stucco

Comparative Example 1a

[0087] A gypsum plasterboard was prepared from the following ingredients: [0088] stucco; [0089] starch in an amount of 12 wt % relative to the stucco (the starch is available under the trade name C Flex 03408); [0090] Glass fibres in an amount of 3 wt % relative to the stucco.

Comparative Example 3a

[0091] A gypsum plasterboard was prepared from the following ingredients: [0092] stucco; [0093] starch in an amount of 5 wt % relative to the stucco (the starch is available under the trade name Merifilm 102); [0094] Glass fibres in an amount of 5 wt % relative to the stucco.

Comparative Example 5a

[0095] A gypsum plasterboard was prepared from the following ingredients: [0096] stucco; [0097] starch in an amount of 12.5 wt % relative to the stucco (the starch is available from Grain Processing Corporation under the trade name Coatmaster K57F); [0098] Glass fibres in an amount of 3% relative to the stucco

Fluidity

[0099] Slump diameter was measured as an indicator of fluidity of stucco slurry that was used in the production of the plasterboards. The procedure was carried out in line with British Standard EN13963. The diameter was measured before the slurry was subjected to mechanical vibration. The results are set out in Table 1.

TABLE-US-00001 TABLE 1 Example Slump diameter Example 1 102 mm Example 2 102 mm Comparative example 1a  95 mm
Expansion with Humidity

[0100] Expansion with humidity was measured according to ASTM D1037 from initial conditions of 23° C. and 50% relative humidity to final conditions of 20° C. and 90% relative humidity. The samples were 200 mm long and 50 mm thick. The results are set out in Table 2.

TABLE-US-00002 TABLE 2 Example Expansion with humidity Example 3 0.024 Example 4 0.018 Comparative example 3a 0.034

Screw Pull-Out Strength

[0101] Screw pull-out tests were carried out on samples measuring 100 mm by 100 mm that had been 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, passing through a metal load transfer element positioned on the surface of the sample. The load transfer element has a first portion that is configured to lie between the screw head and the surface of the sample, and a second portion that is configured to engage with a testing machine so as to allow a load to be applied to the screw along the axis of the screw. The screw was tightened to a torque of 1 Nm.

[0102] The specimen was then mounted in a Zwick Universal Testing Machine and a 10N pre-load applied to the screw along the axis of the screw. Subsequently, the load was increased by setting a constant cross-head speed of 10 mm/minute until pull out was achieved.

[0103] The results are set out in Table 3. These are averages, each taken from 8 samples.

TABLE-US-00003 TABLE 3 Example Average screw pull-out strength N Example 3 734 Comparative example 3a 674 Example 5 1523 Comparative example 5a 1283 Example 6 797 Example 7 688 Example 8 783 Example 9 604