Polymeric dispersant

Abstract

The invention relates to a dispersant comprising a polymer obtainable by copolymerization of monomers including 5 to 80 mol % of a hydroxyalkyl acrylate phosphate and/or hydroxyalkylacrylamide phosphate (monomer 1), 0 to 20 mol % of a di(hydroxyalkyl acrylate) phosphate and/or di(hydroxyalkylacrylamide) phosphate (monomer 2) and 1 to 80 mol % of a polyalkylene glycol-containing macromonomer comprising an alkene group (monomer 3). Further disclosed is a process for preparing the polymers of the invention and the use thereof as dispersants in calcium sulphate-containing compositions. A further aspect of the invention is a process for producing shaped gypsum bodies, and also shaped gypsum bodies, more particularly gypsum plasterboards and self-levelling screeds, comprising the dispersant of the invention.

Claims

1. A dispersant comprising: a polymer comprising as copolymerized units: 5 to 80 mol % of at least one monomer 1 of formula (1), ##STR00005## 0 to 20 mol % of at least one monomer 2 of formula (2); ##STR00006## and 1 to 80 mol % of at least one monomer 3 of formula (3):
R.sup.3O(C.sub.nH.sub.2nO).sub.mZ(3) wherein R.sup.1 is an alkylene group having 2 to 8 carbon atoms; Y is NR.sup.2; R.sup.2 is a radical from the group of hydrogen, an alkyl group having 1 to 8 carbon atoms, and formula (A), ##STR00007## M.sup.1 and M.sup.2 each independently of one another are hydrogen, an ammonium compound and a mono-, di- or trivalent metal; R.sup.3 is hydrogen, an aliphatic hydrocarbon radical having 1 to 16 C atoms, a cycloaliphatic radical having 5 to 12 C atoms or an aryl radical having 6 to 14 C atoms, the aryl radical optionally having further substituents; n is identical or different and in each case is an integer from 2 to 3; m is an integer between 20 and 160; Z is at least one radical selected from the group consisting of formulae (4), (5), (6) and (7): ##STR00008##

2. The dispersant according to claim 1, wherein the polymer comprises monomer 2.

3. The dispersant according to claim 1, wherein the group R.sup.1 in monomer 1 is an ethylene group.

4. The dispersant according to claim 1, wherein the polymer comprises monomer 2 and group R.sup.1 in both monomer 1 and monomer 2 is an ethylene group.

5. The dispersant according to claim 1, wherein an average molecular weight of the polymer is between 15,000 and 60,000 g/mol, the molecular weight being measured by gel permeation chromatography against a PEG standard.

6. The dispersant according to claim 1, wherein the polymer consists of copolymerized units of monomer 1 and monomer 3.

7. A process for preparing a polymer according to claim 1, comprising: copolymerizing in an aqueous solution at least one monomer 1 of the formula (1), optionally at least one monomer 2 of the formula (2), and at least one monomer 3 of the formula (3).

8. The process according to claim 7, wherein copolymerizing is at a temperature of is from 5 to 100 C. and a pH of is between 0.5 and 8.

9. A calcium sulphate based binder system comprising a calcium sulphate binder and the dispersant according to claim 1.

10. A shaped gypsum body comprising gypsum and the dispersant according to claim 1.

11. The shaped gypsum body according to claim 10, wherein the shaped gypsum body is a gypsum plasterboard.

12. A process for producing a shaped gypsum body, comprising adding the dispersant according to claim 1 to the aqueous gypsum composition.

13. The process according to claim 12, wherein the shaped gypsum body is a gypsum plasterboard.

14. The process according to claim 12, wherein the shaped gypsum body is a calcium sulphate-containing self-levelling screed.

Description

EXAMPLES

Gel Permeation Chromatography (GPC)

(1) Sample preparation for the determination of molar weight was carried out by dissolving copolymer solution in the GPC eluent, to give a polymer concentration in the GPC eluent of 0.5 wt %. This solution was then filtered through a syringe filter with a polyethersulphone membrane and pore size of 0.45 m. The injection volume of this filtrate was 50-100 l.

(2) The average molecular weights were determined by GPC apparatus from Waters, with the model name Alliance 2690, with a UV detector (Waters 2487) and an RI detector (Waters 2410). Columns: Shodex SB-G Guard Column for SB-800 HQ series Shodex OHpak SB 804HQ and 802.5HQ (PHM gel, 8300 mm, pH 4.0 to 7.5) Eluent: 0.05 M aqueous ammonium formate/methanol mixture=80:20 (parts by volume) Flow rate: 0.5 ml/min Temperature: 50 C. Injection: 50 to 100 l Detection: RI and UV

(3) The molecular weights of the copolymers were determined relatively to polyethylene glycol standards from the company PSS Polymer Standards Service GmbH. The molecular weight distribution curves of the polyethylene glycol standards were determined by means of light scattering. The masses of the polyethylene glycol standards were 682,000, 164,000, 114,000, 57,100, 40,000, 26,100, 22,100, 12,300, 6240, 3120, 2010, 970, 430, 194 and 106 g/mol.

(4) Synthesis of 2-Hydroxyethyl Acrylate Phosphate (HEA-P) and 2-Hydroxyethylacrylamide Phosphate (HEAA-P)

(5) A glass reactor is charged with 116 g of 2-hydroxyethyl acrylate, 80 g of polyphosphoric acid are added, and these components are reacted at 40 C. After a reaction time of 2 hours with stirring, the mixture is left to stand at room temperature for a further 24 hours. In the case of the phosphorylation of 2-hydroxyethylacrylamide, an analogous procedure is followed, and the ingredients are reacted in the same molar proportions.

(6) Synthesis of the Inventive Dispersants

Example 1

(7) A glass reactor equipped with stirrer, pH electrode, thermometer, redox electrode and N2 portal is charged with 108.7 g of deionized water and 112.5 g of vinyloxybutylpolyethylene glycol 5800 (VOBPEG 5800) and cooled to a polymerization starting temperature of 15 C. (initial charge).

(8) In a separate feed vessel, 22.12 g of 2-hydroxyethyl acrylate phosphate (HEA-P) are mixed homogeneously with 199.08 g of deionized water and 9.7 g of 50% strength NaOH (solution A). In parallel a 6% strength solution of a mixture of sodium sulphite, the disodium salt of 2-hydroxy-2-sulphinatoacetic acid and the disodium salt of 2-hydroxy-2-sulphonatoacetic acid (Bruggolit FF6 from Brggemann GmbH) in water is prepared (solution B). With stirring and cooling, first 109.53 g of solution A are added to the initial charge, and then 0.77 g of 3-mercaptopropionic acid (MPA) is added to the rest of solution A. Thereafter, in succession, 0.14 g of 3-mercaptopropionic acid and 0.089 g of ironII sulphate heptahydrate (FeSO.sub.4) are introduced into the initial charge solution. This solution is subsequently adjusted with NaOH (50% strength) to a starting pH of 5.3.

(9) With the addition of 0.75 g of hydrogen peroxide (30% strength solution in water) to the initial charge mixture, the reaction is started. At the same time the addition of solution A and solution B to the stirred initial charge is commenced. Solution A is added over 30 minutes. Solution B is added in parallel with a constant metering rate of 13.5 ml/h until peroxide can no longer be detected in the solution. The polymer solution obtained is then adjusted with 50% strength sodium hydroxide solution to a pH of 6.5.

(10) The resulting copolymer is obtained in a solution which has a solids content of 29.3 wt %. The weight-average molar mass of the copolymer is 40,400 g/mol, the polydispersity 1.6.

(11) TABLE-US-00001 TABLE 1 Amounts used for the synthesis of the inventive dispersants Initial charge Example VOBPEG [g] H.sub.2O deionized [g] 1 112.5 108.7 2 112.5 108.7 3 112.5 108.7 4 97.0 93.8 5 90.0 87.0 6 112.5 108.7 Initial Solution A fraction MPA NaOH mono- (to HEA- (50% mer solu- Ex- P HEAA- H.sub.2O strength) solution tion ample [g] P [g] [g] [g] [ml] A) FeSO.sub.4 H.sub.2O.sub.2 MPA 1 22.12 199.1 9.7 109.53 0.70 0.089 0.75 0.08 2 22.12 199.1 9.7 109.53 0.77 0.089 0.75 0.14 3 22.12 199.1 9.7 109.53 0.88 0.089 0.75 0.22 4 22.13 199.1 11.2 65.70 0.37 0.223 1.88 0.08 5 20.53 184.8 10.4 101.65 0.48 0.138 1.16 0.07 6 18.92 170.3 6.1 18.50 0.88 0.133 1.13 0.14 [g] = grams [ml] = millilitres HEAA-P = 2-hydroxyethylacrylamide phosphate MPA = 3-mercaptopropionic acid

(12) TABLE-US-00002 TABLE 2 Overview of the analytical data Example Mw g/mol PD 1 40,400 1.6 2 26,900 1.3 3 26,300 1.2 4 22,300 1.4 5 25,600 1.4 6 32,800 1.3

Example 7

(13) The experimental apparatus consists of a 500 ml double-walled reactor, thermostat, stirring motor with paddle stirrer, temperature and pH probe, and three feed vessels. The reactor is charged with 60 g of water and 73.72 g of 3-methylbut-3-en-1-ol-polyethylene glycol 2200. The contents of the reactor are heated to 55 C. with stirring, and the temperature is maintained.

(14) Then feed A, consisting of 100 g of water, 39.82 g of 2-hydroxyethyl acrylate phosphate (HEA-P) and 0.30 g of 2-mercaptoethanol, is metered over 2 hours, and feed B, consisting of 23 g of water and 2 g of Wako VA-044 (2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride), is metered in over 2 hours and 30 minutes. During the metering of feeds A and B, the pH of the reactor contents is adjusted using feed C, consisting of 9.8 g of sodium hydroxide and 39.2 g of water. The rate at which feed C is metered in is selected such that the pH of the reactor contents is 4.5.

(15) After the end of metering, the reactor contents are stirred at 55 C. for 30 minutes more. Thereafter the reactor contents are cooled to 25 C. and neutralized with a pH of 6. The resulting, colourless, slightly cloudy product has a solids content of 36%. The average molar mass of the polymer is 29,000 g/mol.

Example 8

(16) The experimental apparatus consists of a 500 ml double-walled reactor, thermostat, stirring motor with paddle stirrer, temperature and pH probe, and three feed vessels. The reactor is charged with 55 g of water and 57 g of methallyl-polyethylene glycol 2200. The contents of the reactor are heated to 60 C. with stirring, and this temperature is maintained. When the temperature has been reached, feed A, consisting of 60 g of water, 30.79 g of 2-hydroxyethyl acrylate phosphate (HEA-P) and 0.30 g of 3-mercaptopropionic acid, is metered over 2 hours, and feed B, consisting of 8.4 g of water and 1.6 g of Wako VA-044 (2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride), is metered in over 2 hours. During the metering of feeds A and B, the pH of the reactor contents is adjusted using feed C, consisting of 5.2 g of sodium hydroxide and 20.8 g of water. The rate at which feed C is metered in is selected such that the pH of the reactor contents is 2.5.

(17) After the end of metering, the reactor contents are stirred at 60 C. for 60 minutes more. Thereafter the reactor contents are cooled to 25 C. and neutralized with a pH of 6. The resulting, colourless, slightly cloudy product has a solids content of 39%. The average molar mass of the polymer is 28,800 g/mol.

Example 9

(18) The experimental apparatus consists of a 500 ml double-walled reactor, thermostat, stirring motor with paddle stirrer, temperature and pH probe, and three feed vessels. The reactor is charged with 60 g of water and 81.78 g of 3-methylbut-3-en-1-ol-polyethylene glycol 2200. The contents of the reactor are heated to 55 C. with stirring, and this temperature is maintained.

(19) When the temperature has been reached, feed A, consisting of 100 g of water, 27.61 g of 2-hydroxyethyl acrylate phosphate (HEA-P) and 0.30 g of 2-mercaptoethanol, is metered over 2 hours, and feed B, consisting of 23 g of water and 2 g of Wako VA-044 (2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride), is metered in over 2 hours. After the end of metering, the reactor contents are stirred at 55 C. for 60 minutes more. Thereafter the reactor contents are cooled to 25 C. and neutralized with a pH of 6. The resulting, colourless, slightly cloudy product has a solids content of 35%. The average molar mass of the polymer is 24,000 g/mol.

(20) Prior-Art Dispersant

Example 10

(21) The prior-art dispersant based on 2-hydroxyethyl methacrylate phosphate is prepared in analogy to JP-2000-327386 (Taiheiyo Cement Corp).

(22) 94 g of methoxypolyethylene glycol methacrylate (MPEGMA with 23 EO units) are introduced as an initial charge. Added thereto are 8.8 g of sodium methallylsulphonate and 180 g of water.

(23) 24 g of 2-hydroxyethyl methacrylate phosphate (HEMA-P) are added to the initial charge.

(24) The resulting solution is then adjusted with 30% strength sodium hydroxide solution to a pH of 8.5. When the reaction vessel has been flushed with inert gas, 9 g of ammonium persulphate are added slowing and with stirring. The reaction mixture is subsequently stirred at 60 C. for four hours. The resulting colourless, slightly cloudy product has a solids content of 41.4%. The average molar mass is 32,300 g/mol.

Use Examples

(25) The dispersants from the synthesis examples are investigated for their properties as gypsum plasticizers in a suitable test system.

(26) First, 300 g of -hemihydrate are prehomogenized with finely ground calcium sulphate dihydrate (gypsum) as accelerator, and scattered into 188 g of water. The dispersant is mixed beforehand into the mixing water. The batch is then left to stand for 15 seconds. Then stirring with the Hobart mixer is commenced at level II (285 revolutions per minute) for a further 15 seconds. After a cylinder (h=10 cm, d=5 cm), has been filled, and lifted off after 60 seconds, the slump is ascertained. The solidification time is determined using the method known as the knife method (according to DIN EN 13279-2).

(27) TABLE-US-00003 TABLE 3 Use examples for a water-to-gypsum ratio of 0.63 Knife Dispersant SM % CSA [g] Slump [cm] [min:sec] Example 10 0.130 0.05 19.3 2:30 Example 1 0.055 0.030 19.4 2:15 Example 2 0.060 0.030 19.4 2:10 Example 3 0.060 0.030 19.0 2:15 Example 4 0.058 0.035 19.1 2:15 Example 5 0.048 0.035 19.4 2:15 Example 6 0.100 0.040 20.1 2:20 Example 7 0.045 0.035 19.4 2:20 Example 8 0.055 0.040 19.3 2:15 SM % = Amount of dispersant (solids) used, based on the amount of -hemihydrate in percent by mass CSA = Amount of calcium sulphate dihydrate (gypsum) used as accelerator

(28) The dispersants of the invention exhibit a very good plasticizing effect, evident from the low level of dispersant metered in order to achieve the same slump as compared with a methacrylate-based polyphosphate ether according to the prior art (Example 10).