Composition for plasterboards and products obtained

Abstract

The invention relates to a plaster-based composition comprising nanometric boehmite and/or nanometric aluminium trihydroxide, this composition making it possible to obtain products having better dimensional stability at high and in particular at very high temperature. The invention also relates to the method of obtaining the products, and the products produced.

Claims

1. A plaster-based composition comprising: from 55 to 99.4 wt % hydratable calcium sulfate based on the dry weight of the plaster-based composition; and from 0.6 to 6 wt % particles of nanometric boehmite having a particle size between 20 and 500 nm based on the dry weight of the plaster-based composition, wherein the plaster is a gypsum plaster.

2. The plaster-based composition of claim 1, wherein the plaster-based composition is free of vermiculite fibers, mineral fibers, and refractory fibers.

3. The plaster-based composition of claim 1, wherein a form factor of the particles of nanometric boehmite is in a range of 3-10.

4. The plaster-based composition of claim 1, wherein the plaster-based composition further comprises starch.

5. The plaster-based composition of claim 1, wherein the particles of nanometric boehmite are in a form of plates having parallelpipedal shape.

6. The plaster-based composition of claim 1, wherein the nanometric boehmite is incorporated in a form of a colloidal suspension or in the form of a powder.

Description

REFERENCE EXAMPLE 1

(1) No dry matter was added to the aforementioned composition of plaster, starch and water.

REFERENCE EXAMPLE 2

(2) 3 parts by weight of crude vermiculite with size mainly between 250 and 710 m (sold under the reference Vermiculite grade Micron by the company EFISOL) was added to the composition (before adjusting the density of the mixture).

(3) An improvement in dimensional stability at temperatures reaching 945 and 1049 C. was observed (Table 1) on adding the vermiculite.

REFERENCE EXAMPLE 3

(4) The procedure in reference example 2 was followed, this time adding 5 parts by weight (instead of 3) of vermiculite.

(5) However, measurements of shrinkage could not be carried out (ND signifying not determinable), as the specimens collapsed during the test.

REFERENCE EXAMPLE 4

(6) Instead of increasing the vermiculite as in the preceding example, the procedure in reference example 2 was followed, this time adding 0.8 parts by weight of glass fibres with a length of 12 mm sold under the reference Duracore SF Plus type M300 by the company Johns Mansville, and 2.5 parts by weight of the liquefying agent (in the form of a sodium salt of a polynaphthalene sulphonic acid) sold under the reference Proltor PNS 747L by the company Protex.

(7) An improvement in dimensional stability for temperatures reaching 945 C. was observed on adding the fibres in addition to vermiculite, but conversely this addition of fibres was without consequences at higher temperature.

EXAMPLE 1

According to the Invention

(8) Instead of increasing the vermiculite as in reference example 3 or adding fibres as in reference example 4, the procedure in reference example 2 was followed, this time adding 1 part by weight (per 100 parts by weight of plaster), or about 0.96 wt % relative to the total dry composition (or total dry mixture), of nanometric boehmite (incorporated in the form of a colloidal suspension comprising from 7 to 9 wt % of boehmite, and called B1-sol in the tables) formed from particles (all) having a size below 500 nm (and in particular a high proportion of particles smaller than 200 nm), these particles being in the form of small plates notably having a form factor of the order of 10.

(9) We observed a significant improvement in dimensional stability at very high temperature (above 900 C.here at 945 C., or even above 1000 C.here at 1049 C.) of the products according to the invention relative to those obtained from mixtures using only vermiculite and/or glass fibres for improving the dimensional stability. This example also shows that it is possible if necessary to reduce or omit the fibres for improving the dimensional stability at high and very high temperature owing to the solution according to the present invention.

EXAMPLE 2

According to the Invention

(10) The procedure in reference example 4 was followed, reducing the proportion of vermiculite and adding 1 part by weight of nanometric boehmite B1-sol mentioned in example 1 (i.e. at least about 0.94 wt % of nanometric boehmite relative to the dry total mixture).

(11) Once again, a significant improvement in dimensional stability at very high temperature was observed, relative to the mixture in reference example 4 comprising more vermiculite and not comprising B1-sol. Adding the nanometric boehmite according to the invention therefore also makes it possible to reduce (or even eliminate) the vermiculite used, while preserving and improving the dimensional stability of the products at very high temperature.

EXAMPLE 3

According to the Invention

(12) The procedure in reference example 4 was followed, adding 5 parts by weight (per 100 parts by weight of plaster) of aluminium trihydroxide Al(OH).sub.3 sold under the reference APYRAL 200 by the company Nabaltec (and called ATH3 in Table 1) and having a D50 of (size of 50% of the particles below) about 600 nanometres (or at least about 2.2 wt % of nanometric aluminium trihydroxide relative to the total dry mixture), about 35 wt % of the particles being smaller than 500 nm.

(13) Once again, a significant improvement in dimensional stability at very high temperature was observed, relative to the mixture in reference example 4.

(14) TABLE-US-00001 TABLE 1 ref. ref. ref. ref. ex. ex. ex. 1 2 3 4 1 2 3 Vermiculite 3 5 3 3 1.5 3 Fibres 0.8 0.8 0.8 Liquefying 2.5 2.5 2.5 agent B1 sol 1 1 ATH 3 5 R945 7.2 6.2 ND 4.9 4.4 3.9 4.0 R1049 18.6 13.5 ND 13.8 10.7 10.8 8.8

(15) Table 2 compares the results obtained with the following compositions using various presentations of nanometric boehmite, the foregoing reference example 4 also being taken for comparison, this table giving the shrinkage values expressed as percentages.

EXAMPLE 4

According to the Invention

(16) The procedure in the preceding reference example 4 was followed, adding 1 part by weight of nanometric boehmite powder (called B3 powder in the table) having particles in the form of spheres (all) having a size below 500 nm (and in particular a high proportion of particles smaller than 200 nm), or at least about 0.93 wt % of nanometric boehmite relative to the dry total mixture, these particles having a form factor of the order of 1.

EXAMPLE 5

According to the Invention

(17) The procedure of example 4 was followed, replacing the powder B3 with the same proportion of another nanometric boehmite powder (called B2 powder in the table) this time having rod-shaped particles (all) having a size below 500 nm (and in particular a high proportion of particles smaller than 200 nm), these particles having a form factor of the order of 2.

EXAMPLE 6

According to the Invention

(18) The procedure in example 4 was followed, replacing the powder B3 with the same proportion of another nanometric boehmite powder (called B1 powder in the table) this time having particles in the form of small plates (all) having a size below 500 nm (and in particular a high proportion of particles smaller than 200 nm), these particles having a form factor of the order of 10.

EXAMPLE 7

According to the Invention

(19) The procedure in example 4 was followed, replacing the powder B3 with the same proportion of the nanometric boehmite B1-sol seen previously.

(20) An improvement in dimensional stability at high and very high temperature of the products obtained from the compositions according to the invention was observed, relative to those obtained from the mixture in reference example 4, even greater when the form factor is greater than 2, and improved as well when the boehmite is added in the form of colloidal suspension, compared to addition in the form of powder.

(21) TABLE-US-00002 TABLE 2 ref. 4 ex. 4 ex. 5 ex. 6 ex. 7 Vermiculite 3 3 3 3 3 Fibres 0.8 0.8 0.8 0.8 0.8 Liquefying 2.5 2.5 2.5 2.5 2.5 agent B1 sol 1 B1 powder 1 B2 powder 1 B3 powder 1 R700 1.5 1.1 1.1 0.7 1.1 R945 4.9 4.6 4.1 3.6 3.6 R1049 13.8 13.0 11.3 11.6 9.8

(22) Table 3 compares the results obtained from the following compositions using different proportions of nanometric boehmite (returning to example 1 according to the invention, seen previously, as the starting point), and once again these results were compared with those obtained with non-nanometric aluminium trihydroxide or non-nanometric boehmite, this table giving the values of shrinkage expressed in percentages.

EXAMPLE 8

According to the Invention

(23) The procedure in example 1 was followed, this time adding 2 parts by weight (instead of 1 part) of nanometric boehmite B1-sol, or about 1.9 wt % of nanometric boehmite relative to the total dry mixture.

EXAMPLE 9

According to the Invention

(24) The procedure in example 1 was followed, this time adding 3 parts by weight (instead of 1 part) of nanometric boehmite B1-sol, or about 2.81 wt % of nanometric boehmite relative to the total dry mixture.

EXAMPLE 10

According to the Invention

(25) The procedure in example 1 was followed, this time adding 5 parts by weight (instead of 1 part) of nanometric boehmite B1-sol and adding 0.6 parts by weight of the liquefying agent (for adjusting the viscosity) used in reference example 4, all the vermiculite moreover being removed from the composition, or about 4.71 wt % of nanometric boehmite in the composition relative to the total dry mixture.

(26) It was observed with examples 1, 8, 9 and 10 according to the invention that the improvement in dimensional stability at very high temperature is all the greater as the proportion of boehmite (in this case colloidal) in the composition according to the invention increases. As in Table 1, it was also observed that in parallel, the addition of nanometric boehmite makes it possible to reduce (or even eliminate) the vermiculite used, while preserving and improving the dimensional stability of the products at very high temperature.

EXAMPLE 11

According to the Invention

(27) The procedure in example 10 was followed, replacing the nanometric boehmite B1-sol with the same proportion of a boehmite in the form of powder (called B4 powder in the table), this time having a D50 of about 2.7 m, about 20 wt % of the particles of this boehmite having a size below 750 nm (or at least about 0.94 wt % of nanometric boehmite relative to the dry total mixture), the liquefying agent having been removed as superfluous.

REFERENCE EXAMPLE 5

(28) The procedure in example 11 was followed, replacing boehmite B4-powder with an aluminium trihydroxide Al(OH).sub.3, marketed under the reference SH500 by the company Alcan (and called ATH1 in Table 3), having a D50 of about 50 to 60 microns and not having particles smaller than 1 micron.

REFERENCE EXAMPLE 6

(29) The procedure in example 1 was followed, replacing the nanometric boehmite with a boehmite marketed under the reference PURAL NF by the company Sasol (and called B5 powder in Table 3), having a D50 of about 8-10 microns and not having particles smaller than 1 micron.

(30) A marked improvement in dimensional stability at very high temperature was observed for the products according to the invention relative to the products obtained from compositions using non-nanometric boehmite or non-nanometric aluminium trihydroxide (i.e. formed from particles with size greater than that considered in the present invention).

(31) TABLE-US-00003 TABLE 3 ex. ex. ex. ex. ex. ref. ref. 1 8 9 10 11 5 6 Vermiculite 3 3 3 3 Fibres Liquefying 0.6 agent B1 sol 1 2 3 5 B4 powder 5 ATH1 5 B5 powder 1 R945 4.4 3.8 3.4 2.6 4.6 6.6 8.0 R1049 10.7 9.1 6.9 3.5 7.9 16.9 17.6

EXAMPLE 12

According to the Invention

(32) In order to test a composition intended for the formation of plasterboard joints, plasterboards of 20 cm by 25 cm were prepared by mixing 100 parts by weight of a dry mixture comprising 71.1 wt % of plaster, 24.0 wt % of calcium carbonate and 4.9 wt % of B3 powder (described in example 4) with 48 parts of demineralized water to obtain boards having a density of 1.120.02 after drying for 48 h in the open air.

(33) Samples of parallelepipedal shape, with length equal to 200 mm and width equal to 150 mm, were taken (notably by cutting) and were put in a furnace with a programmed rate of temperature increase according to standard ISO834, the dimensional change of the width of the sample being recorded continuously. After 60 minutes, when the temperature reached 945 C., the shrinkage of the sample R945 was measured. The shrinkage value obtained was 3.1%. After 120 minutes, when the temperature reached 1049 C., the shrinkage of the sample R1049 was measured. The shrinkage value obtained was 4.9%.

REFERENCE EXAMPLE 7

(34) The procedure of example 12 was followed, replacing the dry mixture with a mixture comprising 75 wt % of plaster and 25 wt % of calcium carbonate. The shrinkage values obtained were 6.8% for R945 and 9.2% for R1049.

(35) A strong improvement in dimensional stability at very high temperature for the products according to the invention was thus observed, relative to the products obtained from compositions not using nanometric boehmite or nanometric aluminium trihydroxide.

(36) The composition according to the invention can notably be used advantageously for obtaining fire-resistant plasterboard and intended for forming and/or covering partitions or ceilings of buildings.