Gypsum plaster-based material containing casein and activated carbon

Abstract

A plaster-based material, in particular a plasterboard intended for the interior fitting of dwellings, contains a mixture of casein and active charcoal. The plaster-based material is used for reducing the amount of volatile organic compounds present in the atmosphere inside dwellings, offices or public buildings.

Claims

1. A VOC absorbing plaster-based material, comprising: a gypsum plaster material; a mixture of casein and active charcoal; a total amount of casein and active charcoal ranging from 0.01 to 20 parts by weight per 100 parts by weight gypsum plaster and the weight of casein representing from 1.0% to 60% by weight of the mixture of casein and active charcoal.

2. The plaster-based material according to claim 1 further comprising the following additives in the following weight proportions, expressed per 100 parts by weight of plaster: 0.1 to 15 parts of an adhesion agent, 0.001 to 10 parts of a setting accelerator, 0.0001 to 1 part of a foaming agent, 0 to 10 parts of at least one water repellent, 0 to 20 parts of at least one fire retardant, 0 to 20 parts of at least one reinforcer.

3. The plaster-based material according to claim 1, wherein the plaster-based material is in the form of a powder, a paste or a plaster panel.

4. The plaster-based material according to claim 3, wherein the plaster-based material is a plasterboard.

5. The plaster-based material according to claim 1, wherein the total amount of casein and active charcoal ranges from 0.5 to 10 parts by weight per 100 parts by weight of plaster.

6. The plaster-based material according to claim 2, wherein the adhesion agent is a starch, a dextrin or a vegetable flour.

7. The plaster-based material according to claim 6, wherein the starch is pretreated with an acid.

8. The plaster-based material according to claim 2, wherein the setting accelerator is hydrated calcium sulfate or potassium sulfate.

9. The plaster-based material according to claim 2, wherein the foaming agent is sodium lauryl sulfate.

10. The plaster-based material according to claim 2, wherein the at least one water repellent is a siloxane.

11. The plaster-based material according to claim 2, wherein the at least one fire retardant is vermiculite, silica, a clay or metal fibres.

12. The plaster-based material according to claim 2, wherein the at least one reinforcer is polymer fibres, mineral fibres, animal or vegetable fibres.

13. The plaster-based material according to claim 12, wherein the mineral fibres are glass fibres.

Description

EXAMPLES 1 TO 3

(1) a) Manufacture of the Plaster-Based Material

(2) 950 g of calcium sulfate hemihydrate, 5.2 g of starch, 0.1 g of ground gypsum, the compound(s) below and 850 g of water are placed in a mixer.

(3) Casein (25 g)+active charcoal (25 g): Example 1

(4) Casein (50 g): Example 2 (comparative)

(5) Active charcoal (50 g): Example 3 (comparative)

(6) The casein is sold under the reference C3400 by the company Sigma Aldrich.

(7) The active charcoal is sold under the reference Envirocarb 207C 48 by the company Chemviron Carbon. It has a mass per unit surface area equal to 1100 m.sup.2/g and is ground before being introduced into the mixer.

(8) The mixture is stirred for 60 seconds in order to obtain a paste.

(9) The paste is poured into a brass mould (250 mm200 mm) lined on its lower face with a sheet of paper, and a second sheets of paper cut to the sizes of the mould is then applied on the paste.

(10) After setting to a solid, the plasterboard is removed from the mould. It is then dried in an oven whose atmosphere is saturated with water under the following conditions: at 180 C. until 80% of the water has been removed, at 100 C. until 95% of the water has been removed and at 40 C. for 24 hours.

(11) The board is wrapped in an airtight bag that is resistant to ultraviolet rays.

(12) b) Capacity for Trapping Volatile Organic Compounds

(13) The measurement of the capacity for trapping volatile organic compounds (acetaldehyde, acetone and benzene) is performed in a gastight test chamber.

(14) The plasterboard (100 mm20 mm; 125 g) is placed in the test chamber, and chamber is then hermetically closed. A continuous stream of air (relative humidity: 50%) containing 20 ppb of the volatile organic compound to be tested is circulated in the chamber at a rate of 250 ml/min.

(15) The measurement of the amount of volatile organic compound is performed in real-time using an FTICR (Fourier transform ion cyclotron resonance) mass spectrometer equipped with a 1 Tesla magnet. The measurement principle is as follows: a semi-porous flat membrane made of polydimethylsiloxane (PDMS) acting as a barrier between the pressure at the chamber outlet (atmospheric pressure) and the vacuum of the mass spectrometer is used. The pressure difference on either side of the membrane and the semi-porous nature of the membrane are such that the volatile organic compounds migrate more rapidly across the membrane than the other molecules contained in the injected air (oxygen, nitrogen, argon, carbon dioxide and water). This results in and enrichment in volatile organic compounds and hence greater sensitivity of detection by the mass spectrometer.

(16) The results given in the table below correspond to a mean value established on a series of three samples of the same plasterboard. The table indicates the percentage reduction in the content of volatile organic compounds below:

(17) TABLE-US-00001 Acetaldehyde Acetone Benzene (%) (%) (%) Ex. 1 95 92 75 Ex. 2 (comp.) 50 28 0 Ex. 3 (comp.) 3 40 69

(18) It is observed that the mixture of casein and active charcoal (Example 1) makes it possible to reduce the content of volatile organic compounds more substantially than casein (Example 2) or active charcoal (Example 3), for an identical amount. The synergistic effect between the casein and the active charcoal is thus demonstrated.