WO2020248090A1

WO2020248090A1 - Powder composition

Info

Publication number: WO2020248090A1
Application number: PCT/CN2019/090502
Authority: WO
Inventors: Yufang DUAN (Tina); Zhiliang ZHANG (Jerry); Daqing Sun; Changqing JIN
Original assignee: Wacker Chemie Ag
Priority date: 2019-06-10
Filing date: 2019-06-10
Publication date: 2020-12-17
Also published as: CN113677646A

Abstract

A powder composition comprising 30-60% of redispersible polymer powder, 5-30% of cement, 20-70% of filler and 0-8% of additives. The powder composition is featured by excellent adhesion properties when used for tile laying, especially adhesion property after storage under water immersion condition.

Description

Powder Composition

Field of the Invention

The present disclosure relates to a powder composition and its use in the laying of tiles.

Background of the Invention

Porcelain tiles (the so-called “vitrified tiles” ) are a kind of tiles having a smooth surface and water absorption of less than 0.5%. Due to such low water absorption, it is difficult for porcelain tiles to be firmly bonded to a wall or floor merely using cement mortars which develop bonding strength by penetrating into the pores on the back of porcelain tiles. In order to solve this problem, polymer-modified tile adhesives are usually used for bonding porcelain tiles. In recent years, back glues for tiles plus cement mortars have been used for tile laying.

Tile adhesive, an abbreviation of ceramic tile adhesive, usually refers to a product that meets the requirements of the industry standard JC/T 547-2017 Adhesives for Ceramic Tiles, and is mostly cement-based. They typically comprise cement, sand aggregates and fillers, and can further include a small amount of water-retaining agent, polymers and other additives. CN106673553A, for example, discloses a tile adhesive comprising 15-25 parts of cement, 30-42 parts of river sand, 20-35 parts of ceramic polishing waste residue (CPR) , 1-2 parts of redispersible polymer powder and 0.1-0.5 parts of water-retaining agent. Compared with cement mortars, tile adhesives can be applied by the thin-bed method to significantly reduce the application thickness. However, as the existing wall substrate cannot meet the requirements for flatness, buttering method is still primarily adopted in real-life applications. If tile adhesives are used for both leveling and laying, the cost would go too high. If a cement-based leveling layer is applied on the wall or floor before laying porcelain tiles, it would add a process step and additional waiting time, which is unacceptable in real-life applications.

Back glues for tiles are emerging products in recent years, which are applied to the back of tiles to improve the adhesion between tiles and unqualified bonding materials such as cement mortars. There are a wide variety of back glues for tiles, including one-component products based on polymer emulsions and two-component products based on cement mortar powders combined with polymer emulsions. In addition to polymer materials and inorganic silicates, the two-component products further comprises a small amount of defoamers, water and other additives. For example, CN105969308A discloses a one-component back glue for tiles, comprising 20-40%of micro-nano acrylic emulsions, 20-40%of modified pressure-sensitive adhesive emulsion, 4-10%of styrene butadiene latex, 0.1-0.2%of thickener, 0.2-0.5%of film-forming agent, 0.1-0.3%of defoamer, 0.1-0.5%of preservative, 0.1-0.5%of mold inhibitor, and deionized water. For another example, CN105418031 B discloses a two-component back glue for tiles, wherein the powder component comprises 39-55%of cement, 39-55%of fine sand, 1-5%of polymer powder, 1-5%of additives, 0.1-1%of water-retaining agent, and 1-2%of retarder, while the liquid component comprises 40-70%of acrylic emulsion, 0.1-0.2%of defoamer, 28.4-59.2%of water, 0.2-0.4%of film-forming agent, and 0.5-1%of conditioning agent.

Compared with tile adhesives, back glues for tiles in combination with cement mortars can reduce the laying costs, which therefore has won some market shares. However, there are a wide variety of back glues for tiles of uneven quality, which have not been tested in practice, therefore any improper use may result in quality and safety problems. Moreover, these back glues for tiles require longer application time, as it usually takes more than 2 hours to wait until the glue is tack-free before laying tiles with cement mortars. In addition, the storage and transportation of liquid binders are often subject to temperature, especially in areas below 0 ℃. Therefore, the market calls for a product with excellent adhesion properties that requires short application time and can be easily transported.

CN103466996A discloses a powdery mosaic back glue comprising 100-600 parts of redispersible polymer powder, 200-600 parts of quartz sand, 10-200 parts of sodium chloride, 5-100 parts of bentonite, 1-10 parts of superplasticizer, 1-10 parts of cellulose ether, 0.5-10 parts of defoamer, 1-5 parts of lignocellulose and 1-5 parts of mold inhibitor. In application, the back glue and water are mixed at a ratio of 1: (0.2-0.3) and applied to the wall or floor, and then mosaics are pressed thereon. Compared with liquid back glues, the powdery back glue is much easier for transportation and storage. However, it is only suitable for mosaics and does not suit to large porcelain tiles. Moreover, its adhesion properties are still not good enough, especially after immersed in water, and its cost remains too high.

Summary of the Invention

The powder composition provided by the present disclosure can solve one or more above-mentioned technical problems, which is featured by easy transportation and storage, excellent adhesion properties, especially after immersed in water, and short application time, and higher cost effectiveness than the direct laying with tile adhesive or the laying with existing back glues for tiles in combination with cement mortars.

In the present disclosure, the term "cement mortar" refers to Portland cement mortars not modified by redispersible polymer powders, which is prepared with cement, fine aggregate and water, and lime, admixture or additives added as required, wherein, the fine aggregate has a particle size of less than 4.75 mm, including natural sands such as river sand, sea sand, mountain sand, and artificial sand. Admixtures are classified to two main types: active and inactive. Active mineral admixture is not hydrated to become hardening or is hydrated to become hardening at a slow rate, but can react with calcium hydroxide, precipitated from cement hydration, to form a gelled hydrate. Commonly-used active admixtures are fly ash, granulated blast furnace slag, zeolite powder, silica fume, etc. Inactive admixture has no or very tiny activeness with cement components. Commonly-used inactive admixtures are: limestone, fine quartz sand, etc. Additives can improve the performance of cement mortar. Commonly-used additives are: thickeners, superplasticizers, early strength agents, waterproofing agents, defoamers, and antifreeze agents, etc. Additives herein exclude redispersible polymer powders.

In the present disclosure, the term "porcelain tile" refers to tiles having a water absorption rate of less than or equal to 0.5%, particularly alkali-resistant tiles having a water absorption rate of less than or equal to 0.5%.

In the present disclosure, "not comprise" or “exclude” means a certain ingredient is present in an amount of lower than 0.1 wt%, for example, less than 0.05 wt%, or even lower than 0.01 wt%, based on the total weight of the related substance.

The first aspect of the present disclosure provides a powder composition comprising the following components:

30-60%of redispersible polymer powder,

5-30%of cement,

20-70%of filer, and

0-8%of additives,

all percentages being based on the total weight of the composition.

Redispersible polymer powders

Redispersible polymer powders are prepared from polymer emulsions by a spray-drying process. When mixed with water, they can be redispersed and return to an emulsion state, with properties equivalent or similar to the original emulsions. The redispersible polymer powders are mainly composed of polymers, as well as a small amount of protective colloid, such as polyvinyl alcohol, and optional additives such as plasticizers, film-forming agents, defoamers, and optional anti-caking agents such as fine mineral fillers. Generally, the polymers are present in an amount of around 80-90%, the percentage being based on the total weight of the redispersible polymer powders. In one embodiment herein, the redispersible polymer powder comprises a polymer as the main component and a protective colloid, as well as fine mineral filler, and does not comprise a plasticizer and a film-forming agent.

Suitable polymers are obtained by the polymerization of one or more monomers selected from among: vinyl esters of linear or branched alkyl carboxylic acids having from 1 to 15 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl laurate; olefins, such as ethylene, propylene, 1, 3-butadiene and isoprene; methacrylic esters or acrylic esters of alcohols having from 1 to 10 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate; vinyl aromatic hydrocarbons, such as styrene, methylstyrene, and vinyltoluene; and halogen ethylenes, such as vinyl chloride.

The polymer is preferably prepared by the polymerization of monomers comprising a vinyl ester and ethylene. In one embodiment herein, the polymer is prepared by the copolymerization of a vinyl ester and ethylene, more specifically, by the copolymerization of vinyl acetate and ethylene monomers, wherein the hydrophobic ethylene monomer, if present in a higher amount, can improve the adhesion properties of the powder composition after immersed in water when used for tile laying. In another embodiment herein, the polymer is obtained by the copolymerization of a vinyl ester, ethylene and a third monomer, more specifically by the copolymerization of vinyl acetate, ethylene and a third monomer. In order to achieve better adhesion properties after immersed in water, the third comonomer is preferably a hydrophobic group-containing monomer, such as vinyl butyrate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl laurate, and vinyl chloride.

When necessary, the foregoing polymers may further comprise functional comonomers present in an amount of 0.1 to 10 wt% (based on the total weight of the polymer) , for example, ethylenically unsaturated carboxylic acids and derivatives thereof, such as fumaric acid, maleic acid, maleic anhydride, acrylamide, acrylonitrile; precrosslinking comonomers or postcrosslinking comonomers, such as divinyl adipate, diallyl maleate, allyl methacrylate, triallyl cyanurate, acrylamidoglycolic acid (AGA) , methacrylamide glycolate methyl ester (MAGME) , N-methylol acrylamide (NMA) , N-methylol methacrylamide (NMMA) , N-hydroxymethylallyl carbamate, isobutoxy ethers or esters of N-methylol acrylamide, isobutoxy ethers or esters of N-methylol methacrylamide, isobutoxy ethers or esters of N-methylolallyl carbamate; epoxy-functional comonomers such as glycidyl methacrylate (GAM) and glycidyl acrylate; and silicon-functional comonomers such as vinyl trialkoxysilanes, vinyl methyl dialkoxysilanes. Preferably, the polymers do not comprise other functional comonomers.

In the present disclosure, the glass transition temperature (Tg) of the redispersible polymer powders is not particularly limited, but preferably ranges from -10 ℃ to 20 ℃, for example, from -10 ℃ to 15 ℃, or from -10 ℃ to 10 ℃. In one embodiment of the present disclosure, the redispersible polymer powder has a Tg of from -10 ℃ to 10 ℃. In another embodiment herein, the redispersible polymer powders comprise one having a Tg of from -10 ℃ to 10 ℃ and another one having a Tg of from 0 ℃ to 20 ℃. In the present disclosure, Tg is determined by a differential scanning calorimeter (DSC) in the temperature range of from -70 ℃ to 100 ℃ at a scan rate of 10 ℃/min, unless otherwise specified. The Tg value of the present disclosure is expressed in degree Celsius that corresponds to the midpoint of the slope change in the heat flow-temperature curve, more specifically corresponds to the temperature value of the intersection of the equidistant intermediate line, between the two parallel baselines before and after glass transition, and the heat flow-temperature curve.

The redispersible polymer powders are present in an amount of from 30 to 60%, preferably from 30 to 50%. If the amount of the redispersible polymer powders is lower than the range, the adhesion properties of the obtained powder composition will not be good enough for tile laying after immersed in water; and if higher than the range, the cost of the powder composition will be much high, thereby limiting its applications.

Cement

In the present disclosure, the cement is a conventional Portland cement commonly used in the art, for example, 42.5 grade, 42.5R grade, and 52.5 grade.

The cement is present in an amount of 5-30%, for example, 5%, 10%, 15%, 20%, 25%, 30%. If the amount of the cement is lower than the range, the adhesion properties of the obtained powder composition will not be good enough for tile laying after immersed in water; and if higher than the range, the pot life of the mixture of powder composition and water is short, which is unfavorable for application. In one embodiment of the present disclosure, with the cement present in an amount of greater than or equal to 5%and less than 15%, the mixture of powder composition and water has good workability and improved adhesion properties after immersed in water when used for tile laying. In another embodiment herein, with the cement present in an amount of greater than or equal to 15%and less than or equal to 25%, and more specifically, greater than or equal to 20%and less than or equal to 25%, the powder composition has excellent adhesion properties after immersed in water and good workability when used for tile laying.

Fillers

Non-limiting examples of the fillers include silica sand, quartz powder, calcium carbonate, dolomite, aluminium silicates, talc, mica, or lightweight fillers such as pumice, foamed glass, aerated concrete, perlite, vermiculite, or other fillers comprising natural or synthetic fibers as main ingredients, and mixtures thereof. The “mixture” herein includes the mixture of fillers of different substance types, and the mixture of fillers of the same substance type with the different particle sizes.

As the particle size of the filler is related to the sedimentation behavior of the slurry prepared by mixing the obtained powder composition and water, the particle size of the filler is preferably less than or equal to 0.38 mm, more preferably less than or equal to 0.15 mm, to obtain a better anti-sedimentation property. In one preferred embodiment herein, more than 60%of the filler has a particle size of less than or equal to 0.15 mm, the percentage being based on the total weight of the filler. In another preferred embodiment herein, more than 60%of the filler has a particle size of less than 0.075 mm, and the remaining part of the filler has a particle size of from 0.075 mm to 0.15 mm, the percentage being based on the total weight of the filler.

In one embodiment herein, the filler comprises quartz sand or powder and calcium carbonate. In a more particular embodiment herein, the filler comprises quartz sand or powder with a particle size of from 0.075 mm to 0.27 mm or calcium carbonate with a particle size of less than 0.075 mm.

The filler is present in an amount of 20%, 30%, 40%, 50%, 60%, 70%, preferably 30-60%.

Additives

The powder composition of the present disclosure may further comprise additive as long as the objective of the present invention would not be compromised. The additive may be a thickener, a film-forming agent, a superplasticizer, a defoamer, an mold inhibitor, a preservative, etc.

In one embodiment herein, the additive is a thickener, non-limiting examples of which include unmodified/modified cellulose ethers such as methyl hydroxypropyl cellulose ethers, methyl hydroxyethyl cellulose ethers, and which is present in an amount of preferably 0.05-2%, more preferably 0.05-1%, particularly preferably 0.1-0.5%.

The second aspect of the present disclosure provides use of the powder composition according to the first aspect in the laying of tiles, particularly use for laying tiles in combination with cement mortars or tile adhesives especially cement mortars. The specific application method is as follows:

1) the powder composition and water are mixed at a ratio of 1 : (0.8-1.2) in an arbitrary way, as long as the powder composition and water are mixed evenly;

2) the resulting slurry is applied to the back of tiles, and cement mortar is applied, when the slurry is tack-free, or directly on the wet slurry surface in order to save time;

3) the resulting slurry is applied to a wall or floor, usually a wall, and then the tiles coated with the slurry and cement mortar are laid thereon.

When used for tile laying, the powder composition can increase the adhesion between the porcelain tiles and the cement mortar, especially the adhesion properties after immersed in water, and dramatically reduce the cost (about 0.3-0.4 RMB/m ²) , which is significantly lower than the cost (about 0.7-0.8 RMB/m ²) of other back glues for tiles available on the market .

Detailed Description of the Preferred Embodiments

The present invention is further illustrated by the following examples, but is not limited to the scope thereof. Any experimental methods with no conditions specified in the following examples are selected according to the conventional methods and conditions, or product specifications.

Pull-off bonding strength test

The powder compositions and water were mixed evenly according to the ratio stipulated in Table 1, then the resulting slurries were each applied to both the back of porcelain tiles and the surface of concrete substrate by using a roller, and left to dry for 24 h for later use. Reference sample, Strong Tile Adhesive (the 5th generation quick drying type) from Qingyuan Loubang Building Materials Technology Co., Ltd. (i.e. a back glue for tiles as defined in the present disclosure, hereinafter referred to as “LB” ) were respectively applied to the back of porcelain tiles and the surface of concrete substrate directly by using a roller, then left to dry for 24 h for later use.

Then cement mortar was prepared with reference to the method in section 7.4.1, JC/T 547-2017 Adhesives for Ceramic Tiles. Afterwards the porcelain tiles coated with above slurry or LB were each further applied the cement mortar thereon by using a spatula, and then were laid on the surface of concrete substrate coated with the above slurry or LB. The thickness of the cement mortar layer was controlled to about 5 mm using a mold. Upon forming, they were stored in each case under the following conditions.

Storage under standard conditions: 14 days under standard conditions (s.c. ) , i.e. at 23±2 ℃ and 50%relative humidity.

Storage under water immersion conditions: 7 days of s.c. storage followed by 7 days of storage at 20±2 ℃ in water.

The pull-off bonding strengths were measured in each case at the end of corresponding storage, 24 hours before which a pull head was adhered to each porcelain tile with epoxy adhesive.

The ingredients in Table 1 are all commercially available, with detailed information as follows:

Redispersible polymer powder 1, a powder based on vinyl acetate and ethylene, which contains fine mineral anti-caking agent, but does not comprise a plasticizer or a film-forming agent, -10 ℃ < Tg < 10 ℃, supplied by Wacker Chemicals.

Redispersible polymer powder 2, a powder based on vinyl acetate, ethylene and a third comonomer, which contains fine mineral anti-caking agent, but does not comprise a plasticizer or a film-forming agent, 0 ℃ < Tg < 20 ℃, supplied by Wacker Chemicals.

Methyl hydroxypropyl cellulose ether, having a viscosity of 10,000-100,000 mPa·s.

The amounts in Table 1 are in parts by weight.

The powder compositions of examples and comparative examples were prepared according to table 1. The powder compositions were each mixed with water at a ratio specified in the table below. After stirring uniformly, the resulting slurries were each applied to the back of the porcelain tiles, to test the pull-off bonding strength after storage under different conditions, with the LB as a reference.

Table 1

Table 2

The results show that, compared with the commercially available Loubang liquid back glue, the slurries obtained from the powder compositions of Examples 1-5 have a significantly increased pull-off bonding strength after storage under different conditions. As known from the comparison of Examples 1-2 and Comparative Examples 1-2, when the amount of redispersible polymer powder is less than 30%, the resulting slurry shows a significantly reduced pull-off bonding strength after storage under water immersion conditions and an obviously reduced pull-off bonding strength after storage under standard conditions. As known from the comparison of Examples 3-5 and Comparative Example 3, when the cement content is less than 5%, the pull-off bonding strength of the resulting slurry measured after storage under water immersion conditions is obviously reduced. The formulation of Comparative Example 4 is referenced to that of tile adhesives, and the pull-off bond strengths of the resulting slurry measured after storage under different conditions are obviously reduced.

Claims

A powder composition comprising the following components:

30-60%of redispersible polymer powder,

5-30%of cement,

20-70%of filer, and

0-8%of additives,

all percentages being based on the total weight of the composition.
The powder composition of Claim 1, characterized in that the polymer as the main component of the redispersible polymer powder is prepared by the copolymerization of monomers comprising a vinyl ester and ethylene.
The powder composition of Claim 2, characterized in that the redispersible polymer powder has a Tg of from -10 to 20 ℃.
The powder composition of any one of Claims 1-3, characterized in that the redispersible polymer powder is present in an amount of 30-50%.
The powder composition of any one of Claims 1-4, characterized in that the cement is present in an amount of greater than or equal to 5%and less than 15%.
The powder composition of any one of Claims 1-4, characterized in that the cement is present in an amount of greater than 15%and less than or equal to 25%.
The powder composition of any one of Claims 1-6, characterized in that the filler has a particle size of less than or equal to 0.38 mm.
The powder composition of Claim 7, characterized in that more than 60%of the filler has a particle size of less than or equal to 0.15 mm, the percentage being based on the total weight of the filler.
The powder composition of any one of Claims 1-8, characterized in that the filler comprises quartz sand or powder and calcium carbonate.
Use of the powder composition of any one of Claims 1-9 in the laying of tiles.
The use of Claim 10, characterized in that the powder composition is used in combination with a cement mortar or a tile adhesive for tile laying.
The use of Claim 10 or 11, characterized in that the powder composition and water are mixed at a ratio of 1: (0.8-1.2) and then applied to the back of tiles.
The use of Claim 12, characterized in that the mixture of the powder composition and water is applied respectively to the interface between the tile and the cement mortar, and the interface between the cement mortar and the wall or floor.