WO2020043644A1

WO2020043644A1 - Dry powder composition, putty composition obtainable from such composition, and substrate coated with such putty composition

Info

Publication number: WO2020043644A1
Application number: PCT/EP2019/072668
Authority: WO
Inventors: Kunsheng HUANG; Jian Zhang; Ye HE; Ling Chen
Original assignee: Akzo Nobel Coatings International B.V.
Priority date: 2018-08-29
Filing date: 2019-08-26
Publication date: 2020-03-05
Also published as: CN112638841A

Abstract

The invention relates to a dry powder composition comprising 4% to 20% by weight of cement, wherein the cement is one selected from the group consisting of Portland cement, aluminous cement, and sulfate aluminate cement; 4% to 12% by weight of gypsum; 1.5% to 4.0% by weight of re-dispersible binder polymer particles; 0.02% to 0.04% by weight of a retarder; 0.02% to 0.05% by weight of a viscosity modifying agent selected from the group consisting of xanthan gum, dextran, welan gum, gellan gum, diutan gum, pullanan, and mixtures of two or more thereof; 0.15 to 0.35% by weight of a cellulose ether; and 65% to 85% by weight of a filler having particles with a particle size distribution with a D50 value in the range of from 12 to 300 µm, wherein all percentages by weight are based on the total weight of the composition.The invention further relates to a putty composition obtainable by adding water to such dry powder composition and to a substrate coated with a putty layer deposited from such putty composition.

Description

DRY POWDER COMPOSITION, PUTTY COMPOSITION OBTAINABLE FROM SUCH COMPOSITION, AND SUBSTRATE COATED WITH SUCH

PUTTY COMPOSITION Field of the Invention

The present invention relates to a dry powder composition composition and to a putty composition obtainable by adding water to the dry powder composition that can be used as a levelling and smoothening material. The invention further relates to a substrate coated with a putty layer deposited from such putty composition.

Background of the Invention

Putty is an architecture decorative material. It is widely used for interior and exterior surfaces, in particular on walls and ceilings. Putty provides a very strong and durable foundation for paints and brings out a rich look. It is for example used for filling dents and hair cracks, levelling surface imperfections, and preventing dampness and efflorescence. A putty layer is used to provide a surface with proper strength and water-resistance and to prepare it for further decoration.

There are various types of putty available such as: i. white cement wall putty, which is a white cement, mineral and polymer-based putty formulated to give a white coating and bright, smooth and superior finishes on wall surface for painting; ii. acrylic wall putty, which is an acrylic and water based ready to used putty especially formulated to prepare smooth wall surface for painting; and iii. Plaster Of Paris (POP), which is basically gypsum. Putty is usually provided as a white powder composition to which water is added to form a wet putty composition that can be applied to a surface. The putty sets when mixed with water. Normally wet putty needs to be applied in at least two coats to get a smoot surface. The thickness per wet coat is about 1 mm; strength built-up takes more than 24 hours; re-coat time is around 24 hours after strength built-up. It takes 3-4 days before the pH value of a cement-based dried putty layer has dropped below 10. The pH of gypsum-based putty is generally lower than the pH of cement-based putty. However, gypsum-based putty easily loses strength after contact with water. A high pH value of a dried putty layer may limit the suitability of such putty layer for subsequent treatment, like painting.

Usually, two layers of putty are applied: a first one for levelling of the surface and a second one for smoothening of the surface. Levelling putty has coarse particles and can be applied with a wet layer thickness of more than 1 mm. Due to the presence of coarse particles, it cannot be used to provide a smooth surface. Therefore, smoothness putty has fine particles. The thickness of a smoothness putty layer is preferably less than 1 mm; otherwise cracking of the layer will occur during or after drying.

Traditionally, putty is applied using a trowel. Recently, spray gun and roller application of putty have been introduced to improve the efficiency, although there is still a gap in appearance compared to trowel applied putty. Not all existing putty formulations can be applied by all techniques. After application and drying, a putty layer may be sanded to increase smoothness.

Other powder products like cement or gypsum-based products such as dry mortar and self-levelling materials have been described. CN 107032729, CN 104496388, and CN 104529355 relate to dry mortar, which is used as binder material and has coarse particles and cannot be used to prepare a smooth surface for coating. Main categories of dry mortar are cement-based and gypsum based mortars. Cement-based mortar has a high alkali content. Twenty four hours after its application, an applied layer still has a pH value of 12 to 14, depending on the amount of cement used. CN102010629 describes cement- based putty with a lower alkali content, but with the disadvantage of showing a large cracking tendency. Contrary to putty, applied layers of dry mortar cannot be sanded and hence cannot be used to prepare smooth surfaces.

CN 107963867, CN 101648783, CN 104108918, CN 106587871 , CN

107540329, and CN 104045291 relate to self-levelling putty used as floor material for construction buildings. It has a low viscosity and would result in serious sagging if it would be applied on a wall or ceiling.

WO 2013/040788 and CN 102010629 disclose a mortar composition for exterior insulation finish systems comprising 2 to 10% by weight of aluminate cement,

20 to 40% by weight of Portland cement, 0.5 to 4.5% by weight of calcium sulphate, 1 to 8% by weight of re-dispersible polymer powder, 0.02 to 1 % by weight of a retarder, 0.5 to 5% by weight of an expansive agent, and 40 to 70% by weight of fillers, based on the total dry weight of the mortar composition.

In DE 10 2005 001 101 A1 is disclosed a dry powder mixture for preparation of a putty composition for floors that results in a smooth surface. The dry powder mixture comprises Portland cement, aluminate cement, calcium sulfate

(gypsum) in combination with iron sulfate and/or aluminum sulfate. A

disadvantage of the composition of DE 10 2005 001 101 A1 is that it needs two types of cement and an additional sulfate (iron sulfate and/or aluminum sulfate) to control the size of ettringite crystals formed.

In WO 2006/094528 is disclosed a dry mortar composition for decorative coating comprising gypsum and two types of cement, i.e. Portland cement and calcium aluminate cement, to avoid efflorescence of the coating.

There is a continuous need for putty compositions with improved performance like high initial strength, quick surface dry time, reduction of recoat time, low pH, and water resistance. There is a further need in the art for putty compositions that can be applied by trowel, roller and spray gun application to increase flexibility, have a short dry time to allow recoating within one day, and for putty compositions that can be used both for levelling and smoothening of a surface (so-called two-in-one putty). Depending on the evenness of the surface to be treated, a two-in-one putty can be applied in one or two layers. It is evident that a two-in-one putty composition saves time in its application.

Summary of the Invention

It has now been found that a cement-based putty composition with

advantageous characteristics can be obtained with only one type of cement by carefully controlling the type and amount of ingredients in a dry powder composition for such putty composition.

Accordingly, the invention provides in a first aspect a dry powder composition comprising:

4% to 20% by weight of cement, wherein the cement is one selected from the group consisting of Portland cement, aluminous cement, and sulfate aluminate cement; 4% to 12% by weight of gypsum;

1.5% to 4.0% by weight of re-dispersible binder polymer particles;

0.02% to 0.04% by weight of a retarder;

0.02% to 0.05% by weight of a viscosity modifying agent selected from the group consisting of xanthan gum, dextran, welan gum, gellan gum, diutan gum, pullanan, and mixtures of two or more thereof;

0.15 to 0.35% by weight of a cellulose ether; and

65% to 85% by weight of a filler having particles with a particle size distribution with a D50 value in the range of from 12 to 300 pm,

wherein all percentages by weight are based on the total weight of the composition.

In a second aspect, the invention provides a putty composition obtainable by adding water to the dry powder composition of the first aspect of the invention.

The putty composition obtained by adding water to the dry powder composition can be applied as a two-in-one composition (both leveling and smoothing functionality) and that can be applied by trowel, roller and spray gun. Putty compositions of the invention further have a high initial strength (no sagging), a quick surface dry time, can be recoated after 3-4 hours, have a low pH value (below 10), and meet water-resistance requirements. This combination of features is obtained by a specific combination of ingredients. Especially the amounts of cement and gypsum provide the desired balance in initial strength, drying time, pH, water resistance and non-cracking of the surface.

Viewed from a third aspect, the invention provides a substrate coated with a putty layer deposited from the putty composition of the second aspect of the invention. Once a layer (coat) of the putty composition of the invention is applied, strength builds up uniformly throughout the putty layer which prevents sagging or curling of the putty material. A uniform build-up of strength within the putty layer supports recoating of the surface within one day. The putty composition of the invention may be used for both levelling and smoothening of a surface. It further has a good water resistance, like normal cement based putty, but does not have the long (>24 hours) drying time needed to reduce the pH of the material like cement-based products.

Detailed Description of the Invention

The dry powder composition of the invention is a composition from which a putty composition can be prepared by adding water. Reference herein to a dry powder composition is to a composition with a mass loss during storage for 1 hour in an open container at 105 °C of less than 7 %, preferably less than 5%, more preferably less than 2%, even more preferably less than 1 %. Preferably, the dry powder composition is a free-flowing powder composition. Powder flow ability may be tested using methods known in the art, for example using a powder flow tester. The dry powder composition comprises 4% to 20% by weight of cement. The composition comprises only one type of cement, selected from the group consisting of Portland cement, aluminate cement, and sulfate aluminate cement. Preferably, the cement is Portland cement. Preferably, amount of cement in the dry powder composition is in the range of from 4 to 15 wt%. In one embodiment the cement in the dry powder composition is Portland cement and the amount of cement is in the range of from 4 to 15 wt%, preferably of from 4 to 10 wt%, more preferably of from 5 to 9 wt%. In another embodiment the cement in the dry powder composition is aluminous cement and the amount of cement is in the range of from 4 to 15 wt%, preferably of from 5 to 13 wt%, more preferably of from 6 to 1 1 wt%.

In still another embodiment the cement in the dry powder composition is sulfate aluminate cement and the amount of cement is in the range of from 10 to 20 wt%, preferably of from 1 1 to 19 wt%, more preferably of from 12 to 18 wt%.

The grade of the cement used in the dry powder composition may be any grade suitable for putty manufacturing. Such grades of cement are well known in the art and readily available from various suppliers. If the cement is Portland cement, the grade of Portland cement may for example be 32.5, 32.5R, 42.5, 42.5R, 52.5, 52.5R white cement or gray cement. If the cement is aluminous cement, the grade of cement may for example be 42.5, 52.5, 62.5, or 72.5. If the cement is sulfate aluminate cement, the grade of cement may for example be quick dry sulfate aluminate, high initial sulfate aluminate, or low alkali sulfate aluminate.

The dry powder composition comprises 4 to 12 wt% of gypsum. Any type of gypsum known to be suitable for use in putty formulations can be used. In one embodiment the gypsum is selected from the group consisting of natural gypsum (CaS0₄-.2H₂0), building gypsum (CaS0₄-.½H₂0), desulfurized gypsum, and combinations thereof. Desulfurized gypsum may be obtained in a flue-gas desulfurization process.

Preferably, the gypsum is selected from the group consisting of natural gypsum (CaS0₄-.2H₂0), and building gypsum (CaS0₄-.½H₂0). The dry powder composition comprises 1.5 to 4.0 wt% of of re-dispersible binder polymer particles. Such re-dispersible binder polymer particles are well-known in the art and commercially available. Re-dispersible binder polymer particles are typically available as a free flowing powder and typically obtained by spray drying of an aqueous dispersion of binder polymer particles (often referred to as“latex”), such as aqueous dispersions of vinyl acetate ethylene copolymers such as vinyl acetate ethylene (VAE) copolymers, vinyl acetate/vinyl ester of versatic acid (VAE-VeoVa) copolymers, styrene butadiene, and acrylic polymers.

Re-dispersible binder polymer particles help to improve the properties and performance of the dry powder composition. Re-dispersible binder polymer particles combine the benefits of liquid latex modifiers with the convenience, reliability, and ease of handling and storing of a dry mix system. By adding water, re- dispersible binder polymer particles can be turned back into a liquid latex (aqueous dispersion of polymer particles) with properties essentially identical to those of the original latex.

Preferably, the binder polymer in the re-dispersible binder polymer particles has a minimum film-forming temperature in the range of from 0 to 30°C. Minimum film forming temperature (MFFT) is the lowest temperature at which a polymer self- coalesces in the semi-dry state to form a continuous polymer film, which acts as a binder for the rest of the solids in the paint film. At temperatures at and above the MFFT of the polymer, a film is formed. At temperatures below its MFFT, the polymer cannot coalesce to form a continuous film and thus cannot bind together itself (or any pigments and extenders that may be present) and a "cracked, crazed" powdery layer results. The MFFT can be determined using methods known in the art, e.g. in accordance with the method as described in European Coatings Journal, Issue 03 of 2003, page 1 12.

Preferably, the re-dispersible binder polymer particles are chosen such that a 10 wt% aqueous dispersion of re-dispersible binder polymer particles has a pH value in the range of from 6 to 10, more preferably of from 7 to 9.

Preferably, the binder polymer has a mass-average molecular weight (Mw) in the range of from 500,000 to 1 ,000,000 Dalton, more preferably of from 600,000 to 900,000 Dalton, even more preferably between 700,000 and 800,000 Dalton, as determined using gel permeation chromatography according to ISO 13885-1.

The particle size distribution of the re-dispersible binder polymer particles is preferably such that the D50 value is less than 100 pm, preferably in the range of from 20 to 100 pm, more preferably of from 50 to 80 pm. Reference herein to the D50 value is to the median diameter: 50% by weight of the particles has a smaller diameter and 50% by weight of the particles has a larger diameter). The particle size distribution can be measured by laser diffraction using a suitable particle size analyzer using compressed air to disperse the particles.

The solid polymer content of the re-dispersible binder polymer particles is more than 95% wt%, preferably in the range of from 95 to 99 wt%. The solid polymer content may be determined by measuring the weight loss over 30 minutes of 100 g of re-dispersible binder polymer particles when stored in an open container at 150 °C. Preferably, the binder polymer is an ethylene-vinylacetate copolymer (EVA), a styrene-acrylic copolymer, a vinyl acetate homopolymer, or a copolymer of vinyl acetate and a vinyl ester of versatic acid. The dry powder composition comprises 0.02% to 0.04% by weight of a retarder. Reference herein to a retarder is to an additive to retard setting time of cement and gypsum. A retarder is used to balance drying time and application time of a putty: too fast drying leads to a too short time frame within which the putty can be used.

Too long drying times increase the recoat time. Retarders are well-known in the art and include compounds like tartaric acid, citric acid, sucrose, and lignosulfonate.

The retarder may be any retarder known in the art. In one embodiment the retarder s selected from the group consisting of tartaric acid, citric acid, sucrose, and lignosulfonate. Preferably, the retarder is tartaric acid, citric acid, or a mixture thereof. More preferably the retarder is tartaric acid. It is understood that both D and L tartaric acid may be used as retarder both pure and in combination.

The dry powder composition comprises in the range of from 0.02% to 0.05% by weight, preferably of from 0.03 to 0.04 wt%, of a viscosity modifying agent selected from the group consisting of xanthan gum, dextran, welan gum, gellan gum, diutan gum, pullanan, and mixtures of two or more thereof. In one embodiment, the viscosity modifying agent is xanthan gum; in one embodiment it is dextran; in one embodiment it is welan gum; in one embodiment it is gellan gum; in one embodiment it is diutan gum; in one embodiment it is pullulan.

The dry powder composition comprises 0.15 to 0.35% by weight of a cellulose ether. The cellulose ether may be any suitable cellulose ether known to be used in putty compositions. In one embodiment the cellulose ether is selected from the group consisting of hydroxy propyl methyl cellulose (HPMC) and hydroxyethyl cellulose (HEC). Preferably, the cellulose ether has a dynamic viscosity in the range of from 25,000 to 100,000 centipoise (cP), more preferably from 35,000 to 85,000 cP; as determined using a rotational viscometer (Brookfield viscometer) with spindle 7 at 30 rpm at 25°C.

Preferably, the amount of cellulose ether in the dry powder composition is in the range of from 0.18 to 0.32 wt%, more preferably of from 0.2 to 0.3 wt%. The dry powder composition comprises 65% to 85% by weight of filler. Any filler known to be suitable for putty compositions may be used, for example calcium carbonate, dolomite or silica. Preferably, the filler is selected from the group consisting of calcium carbonate, dolomite, silica, and mixtures thereof. The filler has particles with a particle size distribution with a D50 value in the range of from 12 to 300 pm. D50 value is as specified above. If the particle size is determined by sieve analysis, a D50 value in the range of from 12 to 300 pm is equivalent to a mesh number in the range of from 50 to 800.

Preferably, the D50 value is in the range of from 15 to 150 pm (equivalent to a mesh number of from 100 to 600). Different particle sizes of the putty allow for different types of use. For use as a levelling putty a D50 value in the range of from 75 to 150 pm (mesh number of from 100 to 200) is particularly useful; a D50 value is in the range of from 35 to 75 pm (mesh number of from 200 to 325) is particularly useful for a two-in-one putty; and a D50 value in the range of from 15 to 20 pm (equivalent to a mesh number of from 500 to 600) is particularly useful for a smoothness finishing putty. A 3-4 mm thick wet layer of putty composition can be applied when using a putty composition with a filler with a D50 value in the range of from 75 to 150 pm. A putty composition comprising a combined calcium carbonate and silica sand filler with a D50 value in the range of from 35 to 90 pm pm (equivalent to a mesh number of from 150 to 325) is very suitable as a two-in-one putty leveling and smoothing finishing putty.

The dry powder composition of the invention may further comprise calcium formate, i.e. a calcium salt of formic acid, preferably in an amount in the range of from 0.20 to 0.40 wt% based on the total weight of the dry composition.

The dry powder composition may further comprise one or more additives commonly applied in putty compositions. Examples of such additives are so-called

superplasticizers (also referred to as water reduce agents) such as polycarboxylate ethers and synthetic sulfonates. Superplasticizers are preferably used in an amount in the range of from 0.02 to 0.05% wt%, based on the weight of the dry powder composition. Other examples of additives are hydrophobizing agents (also referred to as water repellent agents) used to improve water resistance and durability of the set putty. Hydrophobizing agents for cement based products are well known in the art and include calcium stearate and emulsions of alkoxy silanes (e.g. SEAL 80 of Elotex). Such hydrophobizing or water repellent agents are preferably used in an amount in the range of from 0.02 to 0.06 wt%, based on the weight of the dry powder composition. The invention further relates to a putty composition obtainable by adding water to the dry powder composition. Any suitable amount of water to obtain the desired viscosity/thickness of the resulting composition may be used. Typically at least 10 wt% of water will be added, preferably in the range of from 20 to 50 wt% of water, more preferably of from 30 to 50 wt%, even more preferably of from 33 to 45 wt%, based on the weight of the dry powder composition.

The invention also relates to a substrate coated with a putty layer deposited from the putty composition according to the invention. The putty layer may be applied by any suitable technique known in the art, such as troweling, rolling or spraying.

If more than one layer of putty composition is applied, a glass fibre sheet may be laid upon a first layer of putty before applying a second layer of putty. In that way extra strength may be introduced to the surface of the object to be coated.

The putty composition of the invention may be applied onto any suitable type of surface material such as for example concrete, cement, brick, wood, metal, gypsum board, no chalking painted wall, or ceramic tile. Preferably it is applied onto concrete, cement or gypsum material.

The invention is further illustrated by means of the following non-limiting examples. Examples

Preparation of putty compositions

Dry powder compositions were prepared by mixing the ingredients in the relative amounts given in the examples below. Putty compositions were then prepared by slowly adding slowly water until a homogeneous slurry with the viscosity suitable for its application method was obtained: 33 wt% water was added for trowel application; 40 wt% water for roller application; and 45 wt% water for spay application (wt% of water based on the weight of the dry powder composition).

EXAMPLE 1

A dry powder composition was prepared by mixing 66 g of a cement (32.5 grade of white normal Portland cement), 120 g gypsum (building gypsum, CaS0₄-½H₂0), 20 g re-dispersible binder polymer powder (Ethylene-Vinyl- Acetate copolymer, MFFT is 12°C, pH value of 6.5-8.5), 2.0 g calcium formate, 0.4 g diutan gum (Kelco-vis™ DG-F biopolymer), 4 g of cellulose ether (HEC; Brookfield viscosity of 70,000 - 100,00 cP), 0.3 g of MELFLUX 2651 F (BASF), 0.4 g of L-tartaric acid, 0.6 g of SEAL 80 (Elotex), 504.7 g of CaCC>₃ (200-325 mesh) and 300 g of silica sand (D50 is 60 pm) at room temperature for 5-8 minutes. Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method.

EXAMPLE 2

A dry powder composition was prepared by combining and mixing (at room temperature for 5-8 minutes): 120 g of a cement (62.5 grade of aluminous cement), 80 g gypsum (desulfurized gypsum), 30 g re-dispersible binder polymer powder (Ethylene-Vinyl- Acetate copolymer, MFFT is 0°C, pH value of 6.5-8.5), 2.0 g calcium formate, 0.5 g of diutan gum (Kelco-vis™ DG-F biopolymer), 5.0 g cellulose ether (HPMC; Brookfield viscosity of 30,000-40,000 cP), 0.3 g of MELFLUX 2651 F, 0.4 g D-tartaric acid, 0.6 of SEAL 80, 18.7 g of CaC0₃ (200-325 mesh), 471 g dolomite, and 292 g silica sand (D50 is 120 pm). Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method. EXAMPLE 3

A dry powder composition was prepared by combining and mixing (at room temperature for 5-8 minutes): 150 g of cement (high initial strength range of sulfate aluminate cement), 80 g gypsum (natural gypsum, CaS0₄-2H₂0), 40 g re-dispersible binder polymer powder (Styrene -Acrylic copolymer, MFFT is 0°C, pH value of 6.5-8.5), 2.0 g calcium formate, 0.5 g of diutan gum (Kelco-vis™ DG-F biopolymer), 4.5 g of cellulose ether (HEC; Brookfield viscosity of 70,000- 100,000 cP), 0.3 g MELFLUX 2651 F, 0.4 g DL-tartaric acid (racemic tartaric acid), 0.6 g SEAL 80, 439 g CaCC>₃ (400-600 mesh), and 282.7 g dolomite. Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method.

EXAMPLE 4

A dry powder composition was prepared by combining and mixing (at room temperature for 5-8 minutes): 66 g of a cement (32.5 grade of white normal Portland cement), 120 g gypsum (build gypsum, CaS0₄-1/2H₂0), 20 g re- dispersible binder polymer powder (Ethylene-Vinyl-Acetate copolymer, MFFT is 12°C, pH value of 6.5-8.5), 2.0 g calcium formate, 0.4 g of diutan gum (Kelco- vis™ DG-F biopolymer), 4.0 g cellulose ether (HEC; Brookfield viscosity of 70,000-100,000 cP) , 0.3 g MELFLUX 2651 F, 1.0 g citric acid, 0.6 g SEAL80, 504.7 g CaC0₃ (200-325 mesh), and 281 g silica sand (D50 is 30 pm). Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method. EXAMPLE 5

A dry powder composition was prepared by combining and mixing (at room temperature for 5-8 minutes): 66 g of a cement (32.5 grade of white normal Portland cement), 120 g gypsum (build gypsum, CaS0₄-1/2H₂0), 20g re- dispersible binder polymer powder (Ethylene-Vinyl- Acetate copolymer, MFFT is 12°C, pH value is 6.5-8.5), 2.0 g calcium formate, 0.4 g of diutan gum (Kelco- vis™ DG-F biopolymer), 4 g cellulose ether (HEC; Brookfield viscosity of 70,000 - 100,000 cP), 0.3 g of MELFLUX 2651 F, 0.4 g L-tartaric acid, 0.6 g of SEAL 80, 504.7 g CaCC>3 (100-200 mesh), and 300 g silica sand (D50 is 45 pm). Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method.

EXAMPLE 6 (comparison)

A dry powder composition was prepared by combining and mixing (at room temperature for 5-8 minutes): 40 g of a cement combination (20 g 32.5 grade of white normal Portland cement combination with 20 g 72.5 grade of aluminous cement), 120 g gypsum (build gypsum, CaS0₄-1/2H₂0), 35 g re-dispersible binder polymer powder (Ethylene-Vinyl- Acetate copolymer, MFFT is 12°C, pH value is 6.5-8.5), 2.0 g calcium formate, 0.4 g diutan gum (Kelco-vis™ DG-F biopolymer), 4 g cellulose ether (HEC; Brookfield viscosity of 70,000 - 100,000 cP), 0.3 g of MELFLUX 2651 F, 0.4 g L-tartaric acid, 0.6 of SEAL 80, 504.7 g CaC0₃ (100-200 mesh), and 300 g silica sand (D50 is 32 pm). Water was added to the thus-prepared dry powder composition as described above, to obtain a homogeneous slurry (putty composition) with a viscosity suitable for its application method.

Applicability test

The applicability of the putty compositions of Examples 1 to 6 was tested by applying the putty compositions onto a concrete ceiling and on a concrete wall of a new-built house. Test surfaces were at least 2m x 2m in size. The applicability (cracking of the surface / smoothening / levelling) of the putty compositions was scored relative to a commercially available putty composition (Dulux Pro water- resistance putty, AkzoNobel), which is normally applied by trowel and requires more than 12 hours before a new coat of putty may be applied (i.e. it is not a two-on-one type putty). The applicability scoring was based on cracking of the putty layer after drying, levelling and smoothening capacity and was rated as indicated in Table 1.

Table 1 - Scoring definition (relative to Dulux Pro water-resistance putty)

The putty composition was applied by trowel, roller and spray gun. Spray gun parameters (GRACO T-Max 657; a maximum air working pressure of 1.7 MPa (250 psi, 17 bar), a maximum fluid working pressure is 5.0- 6.5 MPa (730 psi, 50 bar to 940 psi, 65 bar), a maximum delivery of material of 1.2 to 1.9 grams per minute (4.5 to 7.2 litre/minute), a fluid outlet size of 1.0-1.5 inch).

The results of the applicability tests are shown in Table 2. The scoring of the application of the putty onto a concrete wall and onto a ceiling has been combined, since the relative scoring on these two surfaces was similar.

Table 2 - Applicability of different putty compositions

A levelling layer of all compositions (Examples 1-6) could be recoated with a smoothening layer within 3 to 4 hours after application. Hence two coats (layers) of putty composition could be applied in one day. Furthermore, all compositions could be applied as a two-in-one putty (i.e. both as levelling and smoothening putty). The results further show that compositions of the invention are particularly useful when the putty mortar is applied by roller or spray gun.

The compositions with one type of cement (Examples 1 to 5) have an applicability that is as good as the applicability of a putty composition with two types of cement. Thus, there is no need to combine different types of cement.

Claims

1 . A dry powder composition comprising:

4% to 20% by weight of cement, wherein the cement is one selected from the group consisting of Portland cement, aluminous cement, and sulfate aluminate cement;

4% to 12% by weight of gypsum;

1.5% to 4.0% by weight of re-dispersible binder polymer particles; 0.02% to 0.04% by weight of a retarder;

- 0.02% to 0.05% by weight of a viscosity modifying agent selected from the group consisting of xanthan gum, dextran, welan gum, gellan gum, diutan gum, pullanan, and mixtures of two or more thereof;

0.15 to 0.35% by weight of a cellulose ether; and

65% to 85% by weight of a filler having particles with a particle size distribution with a D50 value in the range of from 12 to 300 pm, wherein all percentages by weight are based on the total weight of the composition.

2. A dry powder composition according to claim 1 , wherein the composition comprises 4 to 15 by weight of cement.

3. A dry powder composition according to claim 1 or 2, wherein the cement is Portland cement. 4. A dry powder composition according to claim 3, wherein the composition comprises in the range of from 4% to 10% of Portland cement. A dry powder composition according to claim 1 or 2, wherein the cement is aluminous cement.

A dry powder composition according to claim 1 , wherein the cement is sulfate aluminate cement and the composition comprises 10 to 20% by weight of sulfate aluminate cement.

A dry powder composition according to any one of the preceding claims, wherein the binder polymer has a minimum film-forming temperature in the range of from 0 to 30°C.

A dry powder composition according to any one of the preceding claims, wherein a 10 wt% dispersion of the re-dispersible binder polymer particles in water has a pH value in the range of from 6 to 10.

A dry powder composition according to any one of the preceding claims, wherein the binder polymer is an ethylene-vinylacetate copolymer (EVA)), a styrene-acrylic copolymer, a vinyl acetate homopolymer, or a copolymer of vinyl acetate and a vinyl ester of versatic acid.

10. A dry powder composition according to any one of the preceding claims, wherein the retarder is tartaric acid and/or citric acid.

1 1 . A dry powder composition according to any one of the preceding claims, wherein the filler is selected from one or more of the group consisting of calcium carbonate, dolomite, and silica.

12. A dry powder composition according to any one of the preceding claims further comprising calcium formate, preferably in an amount in the range of from 0.20 to 0.40 wt%. 13. A putty composition obtainable by adding water to the dry powder

composition according to any one of the preceding claims, preferably by adding in the range of from 30 to 50 wt% water to the dry powder composition, wherein the wt% is based on weight of the dry powder composition.

14. A substrate coated with a putty layer deposited from the putty composition according to claim 13.