Alkali-soluble resin (ASR) shell epoxy RDP with divalent metal ions exhibiting improved powder redispersibility

Abstract

The present invention provides multilayer polymer redispersible powder (RDP) particles comprising a major proportion of from 50 to 90 wt. %, preferably, from 60 to 85 wt. %, based on total polymer solids, of epoxy resin resins having a calculated glass transition temperature (Tg) of from 0 to 40 C., a methacrylic acid containing alkali soluble polymer outer layer, and a divalent metal, such as zinc powder, having an aqueous pKa of 9.55 or more, or its acid salt having a pH of 7.0 or less, such as strong acid salts, e.g., chlorides, sulfates or phosphates, or organic acid salts, e.g., acetates, succinates and citrates, as well as to methods of making the same.

Claims

1. A redispersible polymer powder composition comprising as powder multilayer polymer particles of (i) from 50 to 90 wt. %, based on total polymer solids, of epoxy resin compositions having a calculated glass transition temperature (calculated Tg) of from 0 to 40 C., and (ii) from 10 to 50 wt. %, based on polymer solids, of an alkali soluble polymer shell around the epoxy resin, which polymer shell is the copolymerized product of from 5 to 40 wt. % of methacrylic acid or its anhydride, based on the total weight of monomers copolymerized to form the polymer shell, and the remainder of one or more ethylenically unsaturated comonomer, and (iv) an additive chosen from a divalent metal ion (M.sup.2+) having a pKa of 9.55 or higher and its strong acid having a pKa of less than 3.5 or organic acid salt having a pH in water of 7.0 or less, wherein the molar ratio of M.sup.2+ ions to the carboxyl groups from the copolymerized methacrylic acid or its anhydride in the alkali soluble resin shell is from 10 to 200 mole %.

2. The redispersible polymer powder composition as claimed in claim 1, wherein the epoxy resin composition (i) is a blend of two or more epoxy resins.

3. The redispersible polymer powder composition as claimed in claim 1, wherein the calculated Tg of the epoxy resin composition (i) is from 5 to 35 C.

4. The redispersible polymer powder composition as claimed in claim 1, wherein the amount of the epoxy resin composition (i) in the multilayer polymer particle ranges from 60 to 85 wt. %, based on polymer solids.

5. The redispersible polymer powder composition as claimed in claim 1, wherein the alkali soluble polymer that comprises the polymer shell of the multilayer polymer particle has a calculated Tg of from 60 C. to 120 C.

6. The redispersible polymer powder composition as claimed in claim 1, further comprising (iii) from 3 to 25 wt. % of one or more colloidal stabilizer, based on total epoxy resin, alkali soluble polymer and colloidal stabilizer solids.

7. The redispersible polymer powder composition as claimed in claim 1, wherein the divalent metal ion is chosen from calcium, zinc, barium and magnesium.

8. The redispersible polymer powder composition as claimed in any preceding claim 1 wherein the pH of the additive in water is 7.0 or less.

9. A composition comprising cement or hydraulic binder and the redispersible polymer powder composition as claimed in claim 1.

10. A method for making a water dispersible epoxy multilayer polymer particle powder comprising: mechanically dispersing an epoxy resin in an aqueous medium to form an initial aqueous epoxy resin dispersion; charging the initial aqueous epoxy resin dispersion into a reaction vessel; providing in the reaction vessel an ethylenically unsaturated monomer mixture comprising (i) from 5 to 40 wt. % of methacrylic acid or its anhydride and (ii) the remainder of one or more copolymerizable ethylenically unsaturated monomers, each based on the total weight of ethylenically unsaturated monomers copolymerized to form the polymer shell, and one or more addition polymerization catalyst; copolymerizing the monomer mixture in the presence of the initial aqueous epoxy resin dispersion to form an aqueous multilayer polymer particle dispersion; adding an additive chosen from a divalent metal ion (M.sup.2+) having a pKa of 9.55 or higher and its strong acid having a pKa of less than 3.5 or organic acid salt having a pH in water of 7.0 or less to the aqueous multilayer polymer particle dispersion; and, removing the aqueous phase from the resulting multilayer polymer to obtain a water redispersible epoxy polymer powder having an alkali soluble polymer shell, wherein the amounts of epoxy resin and unsaturated monomers are selected so that the resulting water redispersible epoxy polymer powder has from 50 to 90 wt. % of epoxy resin, based on total polymer solids.

11. The process as claimed in claim 10, wherein the ethylenically unsaturated monomer mixture is added by gradual addition to the reaction vessel containing the initial aqueous epoxy resin dispersion.

Description

EXAMPLES

Synthesis Example 1

Batch Mechanical Dispersion

(1) To a stainless steel (300 mL) PARR pressure reactor having a 6.67 cm inside diameter, a Cowles blade stirrer, and equipped with an optional pulley system to allow a mixer speed of up to 1825 rpm was charged either 70.0 g of D.E.R. 661 (type 1 solid bisphenol-A epoxy resin, Mw=1500 g/mol, epoxy equivalent weight=500-560, Dow Chemical, Midland, Mich.) or 70.0 g of an epoxy resin blend of D.E.R. 331 (liquid bisphenol-A epoxy resin, Mw=380 g/mol, EEW=182-192, Dow) and D.E.R. 669E (type 9 solid bisphenol-A epoxy resin, Mw=15000 g/mol, EEW=2500-4000, Dow) and 25.0 g of MOWIOL 4-88 aqueous solution (Polyvinyl alcohol, 88% hydrolyzed, commercially available from Kuraray Europe GmbH, solid content=28.0 wt. %). The Tgs of epoxy resin or blend are shown in Table 1. The stirrer assembly was inserted into the vessel and turned by hand until it spun freely. The Parr reactor assembly was then loaded onto its ring stand and water hoses were attached to the stirrer's cooling sleeve. The thermocouples and stirrer motor were connected, and the heating mantle was lifted into place and tightened. The reactor was sealed and heated to 100 C., and after reaching the temperature the mixture was stirred for 10 minutes to allow sufficient mixing of the epoxy resin and PVOH solution together at 1830 rpm. To this mixture water was added using a HPLC pump at the rate of 1 mL/min for 20 min. The water addition rate was increased to 10 mL/min for 5 min while the heating mantle was removed and the Parr reactor was cooled by air and water. The reactor was cooled down to 50 C. in water bath with stirring. The resultant dispersion was collected by filtration through a 190 m filter and had a 40-45% solids content.

Synthesis Example 2

Continuous Extrusion Dispersion Process

(2) The Epoxy Dispersions were prepared using a KWP (KRUPP WERNER & PFLEIDERER) ZSK25 extruder (60 L/D rotating at 450 rpm) with the formulation components shown in Table 1, below, as follows:

(3) The solid epoxy resin (D.E.R. 669E (type 9 solid bisphenol-A epoxy resin, Mw=15000 g/mol, EEW=2500-4000, Dow) or D.E.R. 667E (type 7 solid bisphenol-A epoxy resin, Mw=10000 g/mol, EEW=1600-1950, Dow) and the semi-crystalline MOWIOL 488 (Polyvinyl alcohol, 88% hydrolyzed, commercially available from Kuraray Europe GmbH)) were supplied to the feed throat of the extruder via a Schenck Mechatron loss-in-weight feeder and then melted blended, and a liquid epoxy stream (D.E.R. 331, liquid bisphenol-A epoxy resin, Mw=380 g/mol, epoxy equivalent weight EEW=182-192) was injected into the melt zone to melt blend with solid epoxy and dispersant before entering the emulsification zone. The initial aqueous stream (IA) was then injected into the emulsification zone, and the melt polymer blend was then emulsified in the presence of water in the extruder. If indicated in the formulations, a co-dispersant E-SPERSE 100 (PEO (14) di- and tristyrenated Phenol ammonium sulfate (from Ethox Chemicals, LLC)) was injected into the emulsification zone together with IA. The emulsion phase was then conveyed forward to the dilution and cooling zone of the extruder where additional water was added to form the aqueous dispersions having solid level levels of less than 60 weight percent. The properties of each of the dispersion components made according to this methods were measured, and reported in Table 1. The initial water and liquid co-dispersants like E-SPERSE 100, and dilution water were all supplied by ISCO 500-D Series dual syringe pumps (500 ml, Teledyne Isco, Lincoln, Neb.). The barrel temperature of the extruder was set to 100 C. After the dispersion exited the extruder, it was further cooled and filtered via a 200 m mesh size bag filter.

(4) TABLE-US-00002 TABLE 1 Summary of Epoxy blend dispersions Dis- Solid in per- Epoxy or blend Dispersant Co- dispersion V.sub.mean sion.sup.2 (pbw) (pbw) dispersant (wt. %) (m).sup.1 A D.E.R. 661 MOWIOL None 39.18 0.323 Tg = 41 C. 488 10 part 100 part B DER669E/DER331 MOWIOL None 40.10 0.350 (3:2); Tg = 28 C. 488 10 part 100 part C DER669E/DER331 MOWIOL None 45.7 0.218 (33/67); Tg = 5 C. 488 10 part 100 part D DER667E/DER331 MOWIOL E-SPERSE 56.94 0.443 (60/40); Tg = 22 C. 488 6.2 part 100 100 part 2 part E DER669E/DER331 MOWIOL E-SPERSE 44.97 0.351 (50/50); Tg = 15 C. 488 6.2 part 100 100 part 2 part .sup.1Volume average particle diameter; .sup.2Dispersions A-C were prepared by the batch dispersion process, and dispersions D-E were prepared by continuous dispersion process.

Example 3

Seed Polymerization

(5) For the dispersions of epoxy resins with alkali soluble polymers listed in Table 2 below, seeded emulsion polymerization of the acrylic monomers was conducted. All polymerizations were conducted by charging into a round bottom flask reactor the indicated amount as solids of the epoxy dispersion and purging with nitrogen gas while maintaining at 60 C. While stirring, add catalyst (in dispersion J, below, for each 36 g of epoxy solids, adding 10 mg of ferrous sulfate as a 1 wt. % aqueous solution). Premix the indicated monomer in the proportions indicated in Table 2 below (in dispersion J, using 6.60 grams of methyl methacrylate and 1.65 grams of methacrylic acid) and inject the mixture into the reactor over 60 minutes. At the same time, feed a redox catalyst pair (in dispersion J, using, for each 36 g of epoxy solids, 2.5 g of 2.5 wt. % aqueous solution of tert-butyl peroxide, and separately 2.5 g of 2.5 wt. % aqueous solution of sodium hydroxymethanesulfinate) so as to add a total of 0.75 wt. % solids of each catalyst component relative to acrylic monomer solids weight into the reactor as a free radical initiator over 90 min. Maintain the reaction at 60 C. for 90 min and then allow to cool to 25 C. and filter through a 190 m filter. The resulting dispersion comprises, for example in dispersion J, epoxy resin particles containing 25 wt. % alkali soluble shell comprising a copolymer of methacrylic acid and methyl methacrylate, with wt. % relative to the epoxy resin.

(6) TABLE-US-00003 TABLE 2 Summary Of Epoxy/Acrylic Hybrid Dispersions Disper- Epoxy or Epoxy V.sub.mean sion.sup.1,2 Blend (pbw) Dispersant ASR shell* (m) F DER661 Tg = 41 C. MOWIOL 488 PMMA- 340 100 part 10 part PMAA (4:1) 20 part G DER669E/331 MOWIOL 488 PMMA- 365 (3:2) Tg = 28 C. 10 part PMAA (4:1) 100 part 20 part H DER669E/DER331 MOWIOL 488 PMMA- 240 (33/67); Tg = 5 C. 10 part PMAA (4:1) 100 part 25 part I DER667E/DER331 MOWIOL 488 PMMA- 458 (60/40); Tg = 22 C. 10 part PMAA (4:1) 100 part E-SPERSE 100 2 25 part part J DER669E/DER331 MOWIOL 488 PMMA- 370 (50/50); Tg = 15 C. 10 part PMAA (4:1) 100 part E-SPERSE 100 2 25 part part K MOWIOL 488 PMMA- 370 10 part PMAA (85:15) E-SPERSE 100 2 25 part part L MOWIOL 488 PMMA- 365 10 part PMAA (4:1) E-SPERSE 100 2 15 part part M MOWIOL 488 PMMA-PAA 365 10 part (4:1) E-SPERSE 100 2 25 part part .sup.1Dispersions F, G, H and I were prepared from dispersions A, B and C, D respectively, and dispersions J, K, L, and M were prepared from Dispersion E. Different amount of acrylic monomers were used in dispersions K, L, and M. Initiator concentrations are the same in all dispersions, each of SFS and t-BuOOH is 0.75 wt. % based on total acrylic monomers; .sup.2For dispersions H-M, additional PVOH was added into the dispersions after polymerization to get 10 part PVOH, based on epoxy resin solids; *Calculated Tg of above ASR shells should be at least 100 C..

Synthesis Example 3

Spray Drying Process

(7) A two-fluid nozzle atomizer was equipped on a MOBILE MINOR 2000 Model H spray dryer (GEA Niro, Denmark). The air pressure to nozzle was fixed at 1 bar with 50% flow which is equivalent to 6.0 kg/hour of air flow. A glass jar was placed under the cyclone with the valve on the bottom of the cyclone open. Each of the aqueous dispersions from Table 2 (about 35-40 wt. % solid content) was pumped into a heated chamber by an emulsion feed pump (from Cole-Parmar Instrument Company, Vernon Hills, Ill.). The spray drying was conducted in N.sub.2 environment with an inlet temperature fixed at 140 C., and the outlet temperature was targeted at 50 C. by tuning the feed rate of the dispersion (feed rate=20-30 mL/min). Simultaneously to the dispersions, kaolin clay powder (KaMin HG-90, Kamin is a trademark of Kamin LLC, Macon, Ga.) was fed into the chamber as an anti-caking agent at 0.5-1.0 g/min. The polymer dispersion was atomized using high air pressure at the nozzle atomizer, while the vacuum fan constantly pulled nitrogen/moisture through the filter, and most of the dry powder was recovered in the glass jar attached on the cyclone. The residual polymer powder having an approximate average particle size of between 10 and 40 m was collected in the filter before ventilation.

(8) The following test methods were used:

(9) Particle Size Analysis for Polymer Dispersions and Redispersions of the RDP Samples:

(10) An epoxy multilayer polymer particle dispersion sample was diluted in de-ionized (DI) water prior to analysis to avoid saturating the detector. Epoxy RDP was dispersed into DI water at 1% solids wt. (at pH=7) and vortexed for 30 seconds twice. In addition, to measure the particle size in alkaline condition, 2 drops of 1 M NaOH solution or cement pore solution shown in Table 3, below, was added into the redispersion to raise the pH to >10. Particle size was measured with a Beckman Coulter LS 13 320 Laser Light Diffraction Particle Size analyzer, using an epoxy resin model predetermined by the instrument software. Solid content analysis was performed on an Ohaus MB45 (Ohaus Corporation, Parsippany, N.J.) moisture analyzer.

(11) TABLE-US-00004 TABLE 3 Cement Pore Solution Ion Concentration (g/l) K.sup.+ 7.1 Na.sup.+ 2.2 Ca.sup.2+ 0.4 SO.sub.4.sup.2 8.2 OH.sup. 2.0

(12) Redispersibility in Cement Solution Vs Alkaline Water with NaOH:

(13) The cement pore solution used is shown in Table 2, above; pH=12.6 (Portland cement at water to cement w/c ratio of 0.5 by weight). Reference: Gretz, M.; Plank, J. Cement and Concrete Research 41 (2011) 184-190. To test redispersibility, a sample of the indicated multilayer polymer particle RDP an indicated additive was added into the RDP dispersion before spray drying in the indicated amounts and redispersibility is a measure of volumetric percentage of RDP particles below 2 m in the redispersion after a period of 1 day at ambient temperature. An acceptable redispersibility reading is 50% or higher, preferably, 75% or higher.

(14) TABLE-US-00005 TABLE 4 Redispersibility Of Multilayer Polymer Particles Additive (molar Redispersibility (%) Multilayer ratio of Aqueous Cement pore Example Polymer RDP M.sup.2+:PMAA).sup.1 NaOH solution 1* From dispersion F None 100 100 2* From dispersion G None 100 <20 3 From dispersion G CaCl.sub.2 (0.25) 100 100 4* From dispersion I None 100 <20 5 From dispersion I Ca(OH).sub.2 0.5 <20 <20 6 From dispersion I CaCl.sub.2 0.5 100 100 7 From dispersion I Ca(Ac).sub.2 0.5 100 50 8 From dispersion I Zn (0.20 mm 100 100 powder) 0.25 9 From dispersion I BaCl.sub.2 (0.25) 100 100 10 From dispersion I CuCl.sub.2 (0.25) <20 <20 11 From dispersion I FeCl.sub.2 (0.25) <20 <20 12* From dispersion I NaCl (0.5) 100 <20 13 From dispersion H CaCl.sub.2 0.5 100 100 *Comparative examples; .sup.1To get mole %, multiply by 100%.

(15) As shown in Table 4, above, the multilayer polymer particle RDP having a Tg of from 5 to 40 C. in Examples 2 and 4 is fully redispersible in an alkaline medium containing NaOH only, but was not redispersible in a cement pore solution. As shown in Examples 3, 6-10 and 12, addition before spray drying of a M.sup.2+ ion soluble metal or acid salt additive having a metal pKa of 9.55 or greater and which has a pH in water of 7.0 or less, at a 1 wt. % aqueous concentration, gives a multilayer polymer particle RDP that exhibits good to excellent redispersibility in a cement pore solution. In Example 13, even a low Tg (5 deg C.) shell in a multilayer polymer particle RDP gave good redispersibility when the additive of the present invention was used. As shown in Example 8, the additive can be used in the form of a fine metal powder. As shown in Example 10, metals having a lower pKa did not aid in redispersibility. In contrast, as shown in Example 5 adding high pH salt like Ca(OH).sub.2 into the epoxy/ASR hybrid dispersion impaired redispersibility. As shown in Example 11, a monovalent metal does not aid in redispersibility.

(16) TABLE-US-00006 TABLE 5 Redispersibility and Acid Monomers Additive.sup.1 (molar Redispersibility (%) Multilayer ratio of Aqueous Cement pore Example Polymer RDP M.sup.2+:PMAA) NaOH solution 14* From dispersion J None 100 <20 15 From dispersion J CaCl.sub.2 0.25 100 100 16* From dispersion K CaCl.sub.2 (0.25)** <20 <20 17 From dispersion K CaCl.sub.2 (0.25) 100 100 18 From dispersion L CaCl.sub.2 (0.25) 100 60 19* From dispersion M CaCl.sub.2 (0.25) *** 20 20 *Comparative examples; **Additive included in emulsion polymerization medium, not free-flowing powder; *** Not free flowing powder; .sup.1To get mole %, multiply by 100%.

(17) As shown in Table 5, above, for the lower alkali soluble polymer shell content in Example 18, a divalent metal additive less effectively aided redispersibility. In comparative Example 16, including the additive during the epoxy seeded emulsion polymerization negatively affected redispersibility. An acrylic acid alkali soluble polymer in comparative Example 19 did not give an multilayer polymer particle RDP having acceptable redispersibility. However, methacrylic acid in alkali soluble polymers gave good redispersibility even at low acid concentrations in Example 17.