Method for producing a prefabricated building material

Abstract

The present invention relates to a method for producing a gypsum-containing foamed prefabricated building material and to a gypsum-containing foamed prefabricated building material.

Claims

1. An aqueous alkyl ketene dimer dispersion comprising (a) an alkyl ketene dimer of the formula (I) ##STR00009## and/or of the formula (II) ##STR00010## in which R.sup.1 and R.sup.2 are identical or different hydrocarbon radicals comprising 10 to 24 carbon atoms; (b) at least one emulsifier having a nitrogen content in the range from 0.05 to 1% by weight and a Brookfield viscosity (20? C.; spindle 61 or 62; 12 rpm) in the range from about 10 to about 500 mPas in a 10% w/w aqueous solution, the emulsifier being selected from the group consisting of a starch, cellulose, starch derivative and cellulose derivative; (c) a condensation product of phenol sulfonic acid and formaldehyde, naphthalene sulfonic acid and formaldehyde or naphthalene sulfonic acid, phenol, formaldehyde and urea wherein sulfonic acid groups of the phenol sulfonic acid and the naphthalene sulfonic acid may optionally be present in protonated or deprotonated or partly in protonated and partly in deprotonated form; wherein the dispersion has a charge density in the range from ?5 to ?150 ?eq/g.

2. The dispersion of claim 1 having a charge density in the range from ?10 to ?120 ?eq/g.

3. The dispersion of claim 1, wherein the at least one emulsifier has a nitrogen content in the range from 0.2 to 0.8% by weight.

4. The dispersion of claim 1, which additionally comprises at least one fatty alcohol alkoxylate, fatty amine alkoxylate or fatty acid alkoxylate.

5. The dispersion of claim 4, wherein the fatty alcohol alkoxylate is a C.sub.8-C.sub.18 alkanol ethoxylate with 10 to 30 ethylene oxide groups.

6. The dispersion of claim 1, which additionally comprises a wax.

7. The dispersion of claim 1, in the form of a gypsum composition which dispersion additionally comprises gypsum hemihydrate or anhydrite or a mixture thereof.

8. The dispersion of claim 7, wherein the gypsum hemihydrate or anhydrite is selected from ?-hemihydrate, ?/?-hemihydrate, ?-hemihydrate, natural anhydrite, synthetic anhydrite, anhydrite obtained from flue gas desulfurization, and/or mixtures of two or more thereof.

9. The dispersion of claim 7, which additionally comprises an aqueous foam.

10. The dispersion of claim 9, wherein a foam having a density from about 50 to 300 g/l is used.

11. The dispersion of claim 10, wherein the foam is obtained from 0.01 to 2 g surfactant per kg gypsum hemihydrate or anhydrite.

12. A method for producing a gypsum-containing foamed prefabricated building material comprising the steps of (a) providing the dispersion in the form of a gypsum composition additionally comprising an aqueous foam as defined in claim 9; and (b) forming, optionally curing and drying the gypsum composition to obtain the foamed prefabricated building material.

13. The method of claim 12, wherein the gypsum composition is obtained by adding the alkylketene dimer of the formula (I) or (II) to components (b) and (c) of the dispersion and then adding the foam.

14. The method of claim 13, wherein the alkyl ketene dimer is employed in the form of an aqueous dispersion.

15. The method of claim 14, wherein the aqueous alkyl ketene dispersion comprises 1 to 60 wt % of ketene dimer, based on the total weight of the dispersion.

16. The method of claim 12, wherein 0.02 to 8.0 wt %, of the alkyl ketene dimer, based on the weight of the gypsum hemihydrate or anhydrite, is used.

17. A prefabricated construction chemical building material comprising a gypsum body hydrophobized with the dispersion of claim 7.

18. A gypsum-containing prefabricated building material obtained from the dispersion according to claim 7.

19. The building material of claim 17 wherein the gypsum body has a core density of 0.4 to 1.1 kg/dm.sup.3.

20. The building material of claim 17 selected from gypsum plasterboard panels, gypsum fiberboard panels, gypsum-containing wallboarding panels, and gypsum-containing moldings.

21. A gypsum-containing foamed prefabricated building material, comprising a gypsum body hydrophobized with the dispersion of claim 9.

Description

EXAMPLE 1 (COMPARATIVE)

(1) A fatty alkyl sulfate-based foam was produced as follows:

(2) A 0.3% strength surfactant solution (based on lauryl sulfate) was converted into foam in a foam generator by rotation of a stator-rotor system (Hobart mixer) and with addition of compressed air. The foam density achieved was 75 g/L.

(3) A gypsum slurry was prepared by introducing 600 g of gypsum ?-hemihydrate obtained from flue gas desulfurization) and 0.16 g of accelerator (finely ground calcium sulfate dihydrate for setting a solidification time) into 443.8 g of water, and the mixture was left at rest for 15 seconds. The Hobart mixer was then used on setting II (285 revolutions per minute) for 30 seconds, and during this stirring time the fatty alkyl ether sulfate-based foam (27.2 g with a density of 75 g/L) was admixed, until the resulting gypsum slurry had a fresh density of 1050+/20 kg/m.sup.3.

EXAMPLE 2 (COMPARATIVE EXAMPLE)

(4) A diluted AKD dispersion was prepared by weighing out 30.0 g of the 24% AKD dispersion I into 420.9 g of water. Then 600 g of gypsum (?-hemihydrate obtained from flue gas desulfurization) and 0.16 g of accelerator (finely ground calcium sulfate dihydrate for setting a solidification time) were introduced into the diluted AKD dispersion I, and the mixture was left at rest for 15 seconds. A Hobart mixer was then used on setting II (285 revolutions per minute) for 30 seconds, and during this stirring time the fatty alkyl ether sulfate-based foam (27.2 g with a density of 75 g/L) was admixed, until the resulting gypsum slurry had a fresh density of 1050+/20 kg/m.sup.3.

EXAMPLE 3 (ACCORDING TO THE INVENTION)

(5) A gypsum slurry was prepared in the same way as in example 2 by using 30 g of AKD dispersion III instead of 30 g AKD dispersion I.

(6) The following experiments were carried out with the gypsum slurries of examples 1 to 3:

(7) Determination of Initial Setting:

(8) Initial setting was determined with the so-called knife-cut method (analogous to DIN EN 13279-2)

(9) Determination of Flow:

(10) Flow was determined after a time of 60 seconds. After mixing at a total time of 45 seconds a cylinder (d=5 cm and h=10 cm) was filled with the slurry up to the top edge and lifted after 60 seconds. At the end the patty diameter was measured with a caliper rule on two perpendicular axes.

(11) The results are shown in table 1 below:

(12) TABLE-US-00001 TABLE 1 Slump flows and initial setting times Slump Parameter flow [cm] Solidification time [min:s] Example 1 (Comparative) 18.1 2:10 Example 2 (Comparative) 15.6 2:05 Example 3 (Invention) 20.5 2:10

(13) Table 1 shows that use of a low cationically charged starch (example 3) leads to improved flow. This is achieved without impact on setting.

EXAMPLE 4 (ACCORDING TO THE INVENTION)

(14) A gypsum slurry was prepared in the same way as in example 2 by using 30 g of AKD dispersion IV instead of 30 g AKD dispersion I.

(15) Slump flow and initial setting times of the gypsum slurries of examples 1, 3 and 4 were determined as described above. The results are given in table 2 below:

(16) TABLE-US-00002 TABLE 2 Slump flows and initial setting times Slump Parameter flow [cm] Solidification time [min:s] Example 1 (Comparative) 18.1 2:10 Example 3 (Invention) 20.5 2:10 Example 4 (Invention) 23.0 2:15

(17) Table 2 shows that the flow behavior could be further improved without negative impact on setting when using the sodium salt of the condensation product of phenolsulfonic acid with formaldehyde, phenol and urea (example 4) instead of the sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde (example 3) as a dispersant in AKD emulsions.

(18) In addition, the water uptake of test specimens prepared from the slurries of examples 3 and 4 was determined as follows:

(19) The dispersion of the hydrophobizing agent was diluted with water in a vessel and homogenized to form a liquid component, to give the amounts of hydrophobizing agent indicated in table 3 below in 443.8 g of waterin other words, the water present in the hydrophobizing agent dispersion was included in the calculation. ?-Hemihydrate (600 g) obtained in flue gas desulfurization was subjected to preliminary homogenization with 0.16 g of finely ground calcium sulfate dihydrate (accelerator for setting a solidification time of about 2.5 minutes) in a mixer to give a dry component. The dry component was sprinkled into the liquid component. After standing for 15 seconds, the resulting gypsum slurry was stirred using a Hobart mixer at setting II (285 revolutions per minute) for 30 seconds, and during this stirring time the fatty alkyl sulfate-based foam (27.2 g with a density of 75 g/L) was admixed. The density of the resulting gypsum slurry was 1050+/?20 kg/m.sup.3. Filling of a cylindrical plastic beaker with a height of 10 cm and a diameter of 8 cm with a portion of the gypsum slurry was followed by curing and drying to form a specimen having a height of about 2 cm. After the specimen has hardened (storage at 20? C. for 15 minutes) it is removed from the plastic mold and dried at 100? C. for 15 minutes and then at around 40? C. to constant mass. The mass of the specimen (M.sub.D) was ascertained by weighing. For the measurement of the water adsorption, the specimen was stored in a water bath at a set temperature of 20? C. The fill level of the water bath was set such that the highest point on the specimen was covered by 3 cm of water. After water bath storage for two hours, the specimen was removed from the water bath, and excess water was removed using a cloth. The mass of the specimen (M.sub.W) was ascertained again by weighing, and the water uptake W in % was determined in accordance with the following formula:
W=100%?((M.sub.W?M.sub.D)/M.sub.D)

(20) The results are given in table 3 below:

(21) TABLE-US-00003 TABLE 3 Water uptake of specimens following addition of different hydrophobizing agents and different amounts of hydrophobizing agent Water absorption Hydrophobizing agent (mass %) (mass % based on ?-hemihydrate) Example 3 Example 4 (invention) 0 57.8 57.8 0.7 13.2 4.2 0.85 6.6 2.9 1.0 3.7 2.6

(22) From table 3 can be seen that for a water uptake of less than 5 wt % it is necessary to add more than 0.85 wt % of the AKD dispersion III, whereas with AKD dispersion IV (with Tamol DN) this figure is already achieved with an addition of less than 0.7 wt %.

EXAMPLE 5 (ACCORDING TO THE INVENTION)

(23) A gypsum slurry was prepared in the same way as in example 2 by using 21.60 g of AKD dispersion III instead of 30 g AKD dispersion I.

EXAMPLE 6 (ACCORDING TO THE INVENTION)

(24) A gypsum slurry was prepared in the same way as in example 2 by using 21.96 g of AKD dispersion V instead of 30 g AKD dispersion I.

(25) Slump flows and initial setting times were determined as described above. The results are given in table 4 below:

(26) TABLE-US-00004 TABLE 4 Slump flows and initial setting times of examples 5 and 6. Parameter Slump flow [cm] Solidification time [min:s] Example 5 (invention) 20.9 2:40 Example 6 (invention) 25.1 2:45

(27) Table 4 shows that by use of a solvent (fatty alcohol ethoxylate) the slump flow could be further improved without influencing the setting time.

(28) In addition, test specimens were prepared and the water uptake thereof was determined as described above using the slurries of examples 3 and 6. The results are given in table 5 below:

(29) TABLE-US-00005 TABLE 5 Water uptake of specimens following addition of different hydrophobizing agents and different amounts of hydrophobizing agent Water absorption Hydrophobizing agent (mass %) (mass % based on ?-hemihydrate) Example 3 Example 6 (invention) 0 53.2 53.2 0.6 10.8 5.7 0.8 3.2 1.5 1.0 1.2 1.1

(30) Table 5 shows that water uptake is reduced by addition of solvent (fatty alcohol ethoxylate). All measured water adsorptions with the slurry of example 6 were lower than for the slurry of example 3.

EXAMPLE 7 (COMPARATIVE EXAMPLE)

(31) Test specimens were prepared as described above using wax dispersion VI.

EXAMPLE 8 (ACCORDING TO THE INVENTION)

(32) Test specimens were prepared and the water uptake determined as described above using AKD dispersion VII. The results are given in table 6 below:

(33) TABLE-US-00006 TABLE 6 Water uptake of specimens following addition of different hydrophobizing agents and different amounts of hydrophobizing agent according to example 4. Water absorption Hydrophobizing agent (mass %) (mass % based on ?-hemihydrate) Example 7 Example 8 (invention) 0 53.2 53.2 0.6 44.6 38.2 0.8 44.3 28.4 1.0 44.0 18.5 1.2 44.4 10.3 1.6 47.3 3.7

(34) Table 6 shows that pure paraffin wax dispersions are not able to achieve water adsorptions below 5% inspite of the presence of the condensation product of naphthalenesulfonic acid and formaldehyde. Even at dispersion dosages of 1.6% by weight stucco the water adsorption was higher than 40%. By use of a mixture of AKD and paraffin wax it is possible to achieve water adsorption values below 5%. For example 8 about 0.6% of AKD/paraffin wax emulsion were enough to achieve water adsorption values below 40%.

(35) Comparative AKD Dispersion VIII (Comparative Dispersion):

(36) Aqueous dispersion of a C.sub.16/C.sub.16 (50:50) alkylketene dimer dispersed with 3 wt % of a highly cationic modified, low-viscose starch (in formula I and II: R.sup.1 and R.sup.2 are C.sub.14 and C.sub.16 alkyl, respectively) and 1 wt % of the sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde (Tamol NN 7718). The average particle diameter is about 1000 nm. The charge density of the dispersion is about +77 ?eq/g. The total solids content is about 24%.

(37) AKD Dispersion IX (According to the Invention):

(38) Aqueous dispersion of a C.sub.16/C.sub.16 (50:50) alkylketene dimer (in formula I and II: R.sup.1 and R.sup.2 are C.sub.14 and C.sub.16 alkyl, respectively) dispersed with 2 wt % of a highly cationically modified, low viscosity starch) and 2 wt % of the sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde (Tamol NN 7718). The average particle diameter is about 1000 nm. The viscosity is about 10 mPas (Method: Brookfield, RVDV-II+PX, spindle 01, 6 rpm, 20? C.). The charge density of the dispersion is about ?80 ?eq/g. The total solids content is about 20%.

EXAMPLE 9 (COMPARATIVE EXAMPLE)

(39) A diluted AKD dispersion was prepared by weighing out 30.0 g of the 24% AKD dispersion VIII into 420.9 g of water. Then 600 g of gypsum (?-hemihydrate obtained from flue gas desulfurization) and 0.16 g of accelerator (finely ground calcium sulfate dihydrate for setting a solidification time) were introduced into the diluted AKD dispersion I, and the mixture was left at rest for 15 seconds. A Hobart mixer was then used on setting II (285 revolutions per minute) for 30 seconds, and during this stirring time the fatty alkyl ether sulfate-based foam (27.2 g with a density of 75 g/L) was admixed, until the resulting gypsum slurry had a fresh density of 1050+/20 kg/m.sup.3.

EXAMPLE 10 (ACCORDING TO THE INVENTION)

(40) A gypsum slurry was prepared in the same way as in example 1 by using 37.5 g of AKD dispersion IX in 413.7 g of water.

(41) Test samples were prepared from the gypsum slurries of examples 1 and 2 and the water-uptake of the samples in [mass %] was determined in accordance with DIN EN 520. The result are given in the following table:

(42) TABLE-US-00007 Hydrophobizing Water absorption agent (mass %) (mass % based Example 10 on ?-hemihydrate) Example 9 (invention) 0 57.8 57.8 0.55 36.7 23.3 0.70 13.5 7.8

(43) As can be seen, the water uptake is reduced by use of anionically charged AKD emulsion (charge density in the range from ?5 to ?150 ?eq/g). All measured values were lower with the example of the invention in comparison to those for example 9.