Starch-based tile adhesive

Abstract

The present invention provides a starch-based tile adhesive comprising a substituted starch and a filler, and preferably the adhesive is cement-free, although limited amounts of cement may be present. The invention also provides a method for providing the tile adhesive, as well as a method of tiling using the adhesive, and surfaces tiled using the adhesive.

Description

[Technical Field]

[0001] The present invention is in the field of tile adhesives. [Background technology]

[0002] Introduction Currently, there is a growing interest in sustainability and reducing carbon footprints, which has resulted in the construction industry exploring more sustainable alternatives to common building materials. Dry-mix tile adhesives, used to bond tiles to walls and other surfaces, have traditionally been cement-based. Cement production is energy-intensive and has a high associated carbon footprint. In fact, the adhesive properties of cement cannot usually be reused, as the hardening of cement is an irreversible chemical process.

[0003] Cement-based tile adhesives generally contain about 25-40% by weight cement as the adhesive, about 60-75% by weight sand as a filler, and about 0.15-0.50% by weight of a cellulose derivative as a water-retaining agent. Type I (ordinary Portland cement) and Type II cement are commonly used in tile adhesives.

[0004] Small amounts (approximately 0.05-0.25% by weight) of starch ethers can be added to cement-based tile adhesives to prevent the tile from slipping during application. The starch ethers impart a yield stress to the tile adhesive by penetrating between the cement particles. This has the advantage that when the tile is placed on a surface, it stays in place and prevents slipping while the cement hardens. In such applications, the starch ethers do not contribute to adhering the tile to the surface. In such applications, the weight ratio of cement to starch ether is typically at least 100 (or often much higher).

[0005] Cement-based tile adhesives have several drawbacks. Their pot life, also known as workability time (the time the adhesive remains workable after mixing with water), is limited to 1 to 4 hours. After this time, the adhesive begins to harden. Cement-based tile adhesives have an even shorter open time. The open time is the time between applying a layer of tile adhesive to a surface and starting to apply the tile. Therefore, cement-based tile adhesives must be used and applied relatively quickly. Furthermore, any excess tile adhesive left over after application cannot be reused or stored.

[0006] Furthermore, equipment that has held a cement-based adhesive cannot be reused after the cement-based adhesive has hardened, as hardening is an irreversible process, and therefore equipment that is not cleaned in time must be discarded.

[0007] However, cleaning the equipment itself presents challenges. Because cement particles are hard and heavy, the water used for cleaning has a high risk of clogging sewer systems. In many cases, the wastewater from cleaning equipment that uses cement-based tile adhesives ends up in the environment.

[0008] In general, the use of cement-based tile adhesives generates a large amount of waste due to the rapid and irreversible setting, the impossibility of recycling the material, and the fact that tile installers always make excess material.

[0009] Additionally, cement-based tile adhesives typically have a pH of about 13. Skin contact with cement compositions with a pH of 13 can cause dryness and irritation, and inhaling such compositions can lead to lung problems. This presents a problem for construction workers because it is difficult or impossible to completely avoid contact with cement-based tile adhesives.

[0010] Additionally, cement contains chromium-6, which is suspected of causing various health problems, including skin allergies, cancer, and reduced fertility. Chromium-6 can be rendered harmless in cement by adding reducing agents. When mixed with water, these reducing agents convert chromium-6 to harmless chromium-3. However, currently used reducing agents have limited shelf life, which in turn limits the shelf life of the cement itself. Starch is a naturally occurring polymer composed of glucose. Starch exists in the form of granules, which are particles approximately 1 to 100 micrometers in size. Naturally occurring starch granules are commonly referred to as native starch.

[0011] Native starch contains two types of glucose polymers: amylose and amylopectin. Amylose is a linear glucose polymer, while amylopectin is a branched glucose polymer. Typical native potato starch contains approximately 20-25% amylose and 75-80% amylopectin by weight.

[0012] Amylopectin-rich starches are well known. Such starches are commonly called amylopectin starches and contain at least 90% by weight of amylopectin, preferably at least 95% by weight, and more preferably at least 98% by weight of amylopectin. Amylopectin starches are also sometimes called "waxy starches."

[0013] Starch granules contain entangled amylopectin and amylose in crystalline and amorphous regions. Starch granules are insoluble in water at room temperature. The glucose polymers are released from the granules by a process called gelation and can be individually dissolved. Gelatinized starch is starch that has been subjected to a process of gelatinization, i.e., sufficient heat, preferably combined with shear, on starch granules in water, resulting in the dissolution of the starch. The dissolved starch can then be dried to form a gelatinized starch powder ("pregelatinized starch"), which is readily soluble in water at room temperature. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] GB 2 155 944 A Summary of the Invention [Means for solving the problem]

[0015] The present invention provides a tile adhesive that relies on gelled substituted starch to bond tiles to walls, which overcomes the above problems and, unexpectedly, provides superior adhesive properties over conventional cement-based tile adhesives. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention provides a tile adhesive comprising a substituted starch and a filler, wherein the weight ratio of cement to substituted starch is 0 to 2. Preferably, the present invention provides a tile adhesive that does not contain cement (the weight ratio of cement to substituted starch is 0). The terms "weight ratio" and "mass ratio" refer to the same concept and can be used interchangeably.

[0017] The tile adhesive of the present invention has the advantage that the binder is completely renewable. Because less energy is required to manufacture the adhesive and the adhesive is biodegradable, it can be used with significantly reduced environmental impact. The tile adhesive of the present invention has a long pot life and long working time, which offers many advantages. Large quantities of adhesive can be prepared at once and stored and applied over extended periods of time. Excess material can also be stored and reused. The very long open time also reduces time constraints for the applicator, allowing the adhesive to be applied to larger areas than conventional cement-based tile adhesives. Furthermore, the adhesive can be prepared to any desired pH, thereby reducing the risk of contact exposure. The tile adhesive of the present invention is easier to handle than conventional cement-based tile adhesives.

[0018] The equipment used to install tiles using the adhesive does not need to be disposed of and can be washed with water. The discarded adhesive and the waste liquid generated by washing do not cause pollution. As a result, the tile adhesive of the present invention reduces the amount of waste compared to conventional cement-based tile adhesives.

[0019] Therefore, the pot life and open time are significantly longer than those of conventional cement-based adhesives, and the adhesive strength is also high, so the tile adhesive of the present invention leads to reduced waste and is also easy to use.

[0020] The tile adhesive of the present invention is an adhesive for adhering tiles to a surface. Tiles are building materials used for aesthetic or practical purposes and can be attached to surfaces such as walls and floors in a process known as tiling. In this context, the tile adhesive is preferably an adhesive for indoor tiling. More preferably, the tile adhesive is used in a dry indoor area, or at least a dry portion of a room. A dry area refers to any room where the amount of water does not exceed that of a normal living environment. Examples of dry areas include living rooms, hallways, and offices. A dry area is clearly distinguished from a wet area, which is, by definition, a room (or part thereof) where a large amount of water is present. Wet areas commonly include rooms such as (part of) a kitchen or (part of) a bathroom.

[0021] Tiles are commonly known building materials. Any type of tile can be used for tiling using the present invention. Tiles are generally flat objects, meaning that the thickness (or maximum thickness for some tile shapes) is less than 20%, more preferably less than 10%, of the longest linear diameter. Tiles can be any shape, but in most cases tiles are square or rectangular. Tiles can be made of any material. However, tiles made of stone, natural stone, or ceramic are preferred for tiling using the tile adhesive of the present invention.

[0022] The tile may have a porosity expressed as water absorption, which may range from 0.01 to 25% by weight. In a preferred embodiment, the tile may have a water absorption of 0.2 to 20% by weight. In an alternative preferred embodiment, the tile may have a water absorption of 0.5% by weight or less. In another preferred embodiment, the tile may have a water absorption of 10 to 20% by weight, preferably 12 to 18% by weight. In a further preferred embodiment, the water absorption may be greater than 15% by weight.

[0023] Tiling is the process of adhering a tile to a surface. In a tiling process generally known in the art, a tile adhesive is applied, preferably in a substantially uniform layer, to the surface on which the tile will be placed and / or to the tile immediately before it is to be adhered to the surface. The tile is then placed on the surface with a layer of adhesive disposed between the tile and the surface. The adhesive is then allowed to cure ("dry"). After this, the tile is firmly fixed, and if the tile adhesive meets generally accepted adhesion standards, the tile can only be removed with considerable force. In the present invention, the term "curing" is used to refer to a process that results in a strong adhesion of the tile to the surface. Curing of the tile adhesive can be achieved by chemical and / or physical processes.

[0024] The force required to remove a tile, i.e. adhesive strength, is the subject of various standards. The European standard EN12004 states that for the highest quality tile adhesives (C2), an adhesive strength of at least 1 N / mm 2 For low quality tile adhesives (C1), the adhesive strength must be at least 0.5 N / mm 2 This standard is based on a specific type of tile, namely Winkelmann tiles, having a water absorption rate of less than 0.5% by weight. This commonly known EN 12004 standard is used throughout this document when referring to "adhesion strength."

[0025] The tile adhesive of the present invention comprises a substituted starch. In this context, a substituted starch is defined as a starch having one or more substituents, each of which is attached to the starch through a starch hydroxyl group on one of the starch glucose groups by an ether bond, an ester bond, or a carbamate bond. Thus, a substituted starch is a starch in which a group of atoms (substituents) is attached to one of the starch glucose groups through an ester bond, an ether bond, or a carbamate bond, and the group of atoms is not covalently bonded to a different starch glucose group. A substituted starch is a starch substituted with a group of atoms through an ether bond, an ester bond, or a carbamate bond, and the group of atoms is attached to the starch through a covalent bond to one of the starch glucose groups.

[0026] In the present context, the substitution of starch does not result in crosslinking, although in some applications the substituted starch may optionally be further crosslinked with a crosslinking reagent as defined elsewhere in order to fine-tune the rheological properties of the tile adhesive. Substituted starches are reaction products between starch and monofunctional electrophiles suitable for use in nucleophilic substitution or addition reactions.

[0027] Substituted starches can be obtained by activating starch and then reacting it, for example with a base catalyst, with a reagent characterized by the presence of one electrophilic group suitable for nucleophilic substitution, such as an aldehyde, an activated carboxylic acid (such as an acid anhydride, an acyl halide, or a vinyl ester), an epoxy group, an alkyl halide, etc. The reaction product is a starch ether, a starch ester, or a starch carbamate (urethane).

[0028] The reagent used to obtain the substituted starch may be a reagent used in a nucleophilic addition reaction. Suitable reagents are characterized by having an activated double bond. This addition reaction is also known as the Michael addition reaction. Suitable reagents include acrylonitrile, (meth)acrylic acid, methyl (meth)acrylate, maleic acid, and fumaric acid. The reaction product obtained by this addition reaction is a starch ether.

[0029] When starch in solution or starch granules are reacted with a monofunctional electrophilic reagent in a nucleophilic substitution or addition reaction such as those described above, the resulting starch is called a substituted starch. A monofunctional reagent is one that can react with the starch hydroxyl groups only once.

[0030] Known examples of substituted starches suitable for use in the present invention include carboxymethylated starch, hydroxypropylated starch, hydroxyethylated starch, acetylated starch, succinated starch, octenylsuccinate starch, cationic starch and phosphated starch, preferably carboxymethylated starch, hydroxypropylated starch, hydroxyethylated starch, acetylated starch, succinated starch, octenylsuccinate starch and cationic starch.

[0031] The substituted starches preferably have a degree of substitution of 0.01 mol / mol, more preferably at least 0.05 mol / mol. For carboxymethylated, hydroxybutylated, hydroxypropylated, hydroxyethylated, succinated and octenylsuccinate starches, preferably carboxymethylated, hydroxypropylated and hydroxyethylated starches, the degree of substitution is preferably at least 0.1 mol / mol.

[0032] In hydroxypropylated starch, the degree of substitution is preferably at least 0.1, more preferably at least 0.2, more preferably at least 0.3, most preferably 0.3 to 5.0, for example 0.3 to 4.5 mol / mol.

[0033] In carboxymethylated starch, the degree of substitution is preferably at least 0.1, more preferably at least 0.2, most preferably 0.2 to 3.0, for example 0.2 to 2.0, or 0.2 to 1.0 mol / mol.

[0034] In acetylated starch, the degree of substitution is preferably at least 0.05, for example 0.05 to 2.0, or 0.05 to 1.0 mol / mol.

[0035] Degree of substitution ("DS") is the amount of reagent bound to starch, expressed as moles of reagent bound per mole of anhydrous glucose unit (AGU). One mole of AGU has a molecular weight of 162 g / mol. Each AGU has three available hydroxyl groups, so the maximum DS is 3. Degree of substitution can be measured by methods known in the art to quantify the degree of substitution.

[0036] The DS defined above can be calculated from the amount of substituents directly bonded to the oxygen atom of AGU.In this specification, the term DS is used interchangeably with the concept of "molecular substitution (MS)".As is generally known in the art, MS is calculated from the amount of substituents that are covalently bonded to starch through any bond, that are directly bonded to the oxygen atom of AGU, or that are already bonded to AGU.

[0037] Known examples of modified starches where the degree of substitution is expressed as MS and which may exceed 3 include hydroxyalkylated starches and starches to which ethylenically unsaturated monomers have been conjugated. Therefore, for these types of substituted starches, DS in this context should be interpreted as MS.

[0038] The tile adhesive of the present invention further comprises a filler. In this context, filler refers to a solid, inert particulate material. The filler has a particle size, expressed as D50, of preferably at least 1 μm, more preferably at least 5 μm, and even more preferably at least 10 μm. The particle size of the filler is at most 600 μm, preferably at most 500 μm, more preferably at most 300 μm, and even more preferably at most 175 μm. The particle size distribution of the filler is generally measured by sieve classification. Alternatively, the particle size distribution can be measured by laser diffraction measurement of a suspension or dry powder. As used herein, particle size refers to the size of the particles measured by sieve classification.

[0039] Fillers that can be used in the tile adhesive of the present invention include known fillers that are commonly used in cement-based tile adhesives. Examples include sand, clay, calcium carbonate, etc. A further advantage of the tile adhesive of the present invention is that in addition to these known fillers, other types of fillers can also be used. Examples include starch granules, crushed waste concrete, crushed waste plastic, crushed organic fibers, crushed inorganic fibers, sawdust, etc.

[0040] In alternative embodiments, filler-free tile adhesives are also contemplated and disclosed herein. The presence of the substituted starch as a binder is sufficient to adhere the tile to the surface. In such embodiments, the tile adhesive comprises the substituted starch and optional ingredients defined elsewhere.

[0041] In the tile adhesive of the present invention, the weight ratio of cement to substituted starch is 0-2. Cement is a well-known building material used as a support and structural material. Cement mixed with fine fillers is known as mortar, and cement combined with coarse fillers is known as concrete. Cement itself is generally an inorganic material that hardens through an irreversible chemical reaction with water or carbon dioxide. Cement is generally a material containing a mixture of silicates and oxides. In some embodiments, the cement may be a material containing calcium oxide.

[0042] The tile adhesive of the present invention is preferably cement-free, in which case the weight ratio of cement to substituted starch is 0. However, the tile adhesive of the present invention may also contain cement. This can be advantageous where the consumer prefers the presence of at least some cement, such as to provide water or moisture resistance or where irreversible hardening is required.

[0043] However, the tile adhesive of the present invention is primarily a starch-based tile adhesive, and if cement is included, it is considered an additive that may aid adhesion, even though the substituted starch functions as the primary or main binder. The weight ratio of cement to substituted starch is preferably 0 to 2.0, more preferably 0 to 1.5, even more preferably 0 to 1.0, still more preferably 0 to 0.5, more preferably 0 to 0.19, even more preferably 0 to 0.15, and most preferably 0 to 0.1. Most preferably, the tile adhesive of the present invention does not contain cement.

[0044] In some preferred embodiments, the substituted starch is also a cross-linked starch, i.e., the starch used in the tile adhesive of the present invention is capable of undergoing both a substitution process as described elsewhere, and a cross-linking process.

[0045] Starch cross-linking is the process of reacting starch (granular or in solution) with a bifunctional or polyfunctional electrophilic reagent suitable for nucleophilic substitution or addition reactions. Such bifunctional or polyfunctional reagents are called cross-linking agents. Cross-linking agents are capable of reacting with the hydroxyl groups of starch at least twice, thereby cross-linking the amylose or amylopectin chains intramolecularly or intermolecularly. In the context of the present invention, cross-linked starch is distinguished from substituted starch. The cross-linking of starch used in the present invention may be carried out before, during, or after the substitution reaction. Methods for substituting and / or cross-linking starch are well known to those skilled in the art. See, for example, O.B. Wurzburg, CRC Press, 1986, Modified Starches: Properties and Uses.

[0046] Known types of crosslinked starches suitable for use in the tile adhesives of the invention include epichlorohydrin crosslinked starches, trimetaphosphate crosslinked starches, phosphate chloride crosslinked starches, adipic acid crosslinked starches, or starches crosslinked with diglycidyl ethers or polyglycidyl ethers, 1,2-dichloropropanol, dichloroacetic acid, diepoxy or polyepoxy crosslinkers, diisocyanates or polyisocyanates, or dicarboxylic or tricarboxylic acids, or mixtures thereof (e.g., a mixture of adipic acid and acetic anhydride). Known crosslinkers also include glyoxal, zirconium carbonate, borax, and compounds containing multiple polyaldehyde or epoxy groups. The degree of crosslinking ("DC") of the crosslinked starch is at least 0.0001 moles of crosslinker per mole of starch (mol / mol).

[0047] The substituted starch used in the tile adhesive of the present invention may be a degraded starch, which refers to a starch in which the chain length of the glucose polymers has been shortened and the molecular weight has been reduced compared to the original starch. That is, the starch used in the tile adhesive of the present invention may have been subjected to both a substitution process as described elsewhere and a degradation process.

[0048] Starch degradation is well known in the art. See OB Wurzburg, CRC Press, 1986, Modified Starches: Properties and Uses. In a preferred embodiment, the starch is chemically degraded starch (preferably acid-degraded starch), physically degraded starch, or enzymatically degraded starch. All these types of degraded starches and the methods for obtaining them are well known in the art.

[0049] In some embodiments, the starch may be a degraded, cross-linked, and substituted starch.

[0050] In a more preferred embodiment, the starch of the present invention is a cold-water-soluble starch, i.e., a pregelatinized starch. Pregelatinized starch refers to starch that has been made cold-water-soluble by a starch gelatinization process. Starch is originally present in granular form and is dispersible in water but not soluble in water. To function effectively as an adhesive, starch must be gelatinized, i.e., present in a dissolved state at the time of use. Starch gelatinization can be achieved by commonly known methods such as (jet) cooking or other methods well known in the art.

[0051] The starch of the present invention is preferably pregelatinized to render it cold water soluble. Pregelatinization is a process in which a starch suspension is gelled and then dried and powdered. Pregelatinization may occur before, during, or after substitution and / or cross-linking.

[0052] In the case of pregelatinized starch, the starch is gelatinized and then dried to form starch powder or flakes. Pregelatinization can be achieved using techniques well known in the art, such as drum drying, spray drying, spray cooking, and extrusion. Of particular note is drum drying of a slurry of starch granules in water or a paste or solution of gelatinized starch. Drum drying of a starch slurry involves simultaneous dissolution and drying on a heated drum through shear and temperature.

[0053] A thin, dry starch film is obtained by applying a pre-gelatinized starch solution or paste to a rotating, heated drum. Another related method that is particularly useful for preparing cold-water-soluble substituted starches is starch extrusion. Extrusion can be used to convert granular starch into pre-gelatinized starch as a result of the heating and shearing during extrusion. Extrusion can also simultaneously chemically and physically modify granular starch to form pre-gelatinized, cold-water-soluble substituted starch.

[0054] The pregelatinized starch may be ground and sieved into a powder or flakes, the particle size of which is preferably less than 5 mm.

[0055] The substituted starch of the present invention is preferably a pregelatinized starch. In a more preferred embodiment, the substituted starch is a drum-dried starch or an extruded starch. More preferably, the substituted starch may be a pregelatinized and drum-dried starch or a pregelatinized and extruded starch.

[0056] The substituted starch used in the present invention may be of any origin, preferably substituted tuber starch, substituted root vegetable starch, substituted nut starch, substituted cereal starch, or substituted legume starch, more preferably substituted potato starch, substituted sweet potato starch, substituted tapioca starch, substituted corn starch, substituted wheat starch, or substituted pea starch.

[0057] There are no particular limitations on the amounts of substituted starch as a binder and filler in the tile adhesive of the present invention. Generally, the tile adhesive contains 2 to 99% by weight, preferably 2.5 to 75% by weight, more preferably 5 to 50% by weight, of substituted starch, based on the dry weight of the tile adhesive.

[0058] More typically, the tile adhesive comprises 1 to 98% by weight, preferably 25 to 97.5% by weight, more preferably 50 to 95% by weight of filler, based on the dry weight of the tile adhesive.

[0059] In the tile adhesive of the present invention, the mass ratio of filler to substituted starch is preferably 0.25-40, more preferably 0.3-25, and even more preferably 1.0-20.

[0060] The total filler / binder amount is greater than 0.5, preferably greater than 1.0. The "total binder" amount refers to the sum of the amount of substituted starch and the amount of additional binding material, if present. Additional binding materials in this context are, for example, cement, redispersible powders, synthetic polymers, or gums.

[0061] The cement / substituted starch weight ratio is less than or equal to 2, preferably less than or equal to 1.8, more preferably less than or equal to 1.5, and most preferably in the range of 0 to 1. In another preferred embodiment, the tile adhesive of the present invention does not contain any cement.

[0062] The tile adhesive of the present invention may be provided in the form of a dry mix suitable for mixing with water, or alternatively, in the form of an aqueous tile adhesive composition in which the substituted starch is present in a gelled state, the aqueous tile adhesive composition having a viscosity of 300 to 700 Pa.s as measured at 4 rpm and 23°C using a Brookfield Helipath viscometer with a TE spindle.

[0063] A dry mix is ​​the preferred form in which the tile adhesive of the present invention is commercially available. When the tile adhesive is a dry mix, the substituted starch is preferably a pregelatinized substituted starch. This makes it easy to mix the dry mix with water under end-use conditions to obtain a tile adhesive containing dissolved substituted starch. The dry ingredients are as defined above and include at least the substituted starch and the filler.

[0064] Alternatively, the tile adhesive of the present invention may be provided in the form of an aqueous mixture. In the case of an aqueous mixture, the substituted starch may also be a granular substituted starch. The granular substituted starch is mixed with other ingredients, and before the composition is finally used for tiling, the substituted starch must undergo a gelling step. After gelling, the gelled starch solution is added to the other ingredients, or other ingredients are added to the gelled starch. The added ingredients include at least a filler.

[0065] The aqueous tile adhesive composition is the form in which the tile adhesive of the present invention is used for tiling. It may be prepared by mixing with water immediately before tiling, or it may be prepared industrially on a large scale and sold to end consumers in suitable containers. In the aqueous tile adhesive composition, the substituted starch is present as a gelled substituted starch. Preferably, the aqueous tile adhesive composition has a viscosity of 300 to 700 Pa.s, as measured with a Brookfield Helipath viscometer using a TE spindle at 4 rpm and 23°C. This viscosity is advantageous because it minimizes adhesive sagging and slippage and allows for relatively easy application.

[0066] The tile adhesive may further optionally contain a variety of additional ingredients. Suitable ingredients include, but are not limited to, redispersible polymer powders, calcium hydroxide, anhydrous gypsum, and water retention agents such as cellulose ether ((HP / HE)-methylcellulose) and guar gum and its derivatives. Other optional ingredients include calcium formate, glass beads, cellulose fibers, polypropylene fibers, polyethylene terephthalate fibers, polyvinyl alcohol, thickeners, accelerators, retarders, superplasticizers, water repellents, hydrophobic agents, entraining agents, defoamers, pigments, gelatin, proteins, urea-formaldehyde resins, melamine-formaldehyde resins, and synthetic polymer dispersions.

[0067] Optionally, the tile adhesive may include additives to improve the water resistance of the finished adhesive. Such additives may be water repellents, network formers, or hardeners.

[0068] The water repellent agent provides water repellency to the tile adhesive. The agent may be based on additives or emulsions containing fatty acids, or on oils, paraffins, or waxes. Other suitable water repellents include water-based silane, siloxane, and silicone resin-based additives. Still other types are based on synthetic polymer dispersions.

[0069] The network former can improve the water resistance of the tile adhesive by forming a starch network during or after application of the tile adhesive. Suitable network formers induce a crosslinking reaction with the hydroxyl groups of the starch during or after tiling with the adhesive of the present invention. Suitable network formers in this context are those crosslinkers known as starch crosslinkers, described elsewhere, that allow for a crosslinking reaction under the conditions under which the tile adhesive is applied (i.e., ambient temperature in an aqueous environment). One suitable network former is glyoxal. Other suitable starch network formers are zirconium carbonate, borax, and compounds containing multiple aldehyde or epoxy groups.

[0070] Hardeners may be added to induce network formation during or after tiling. For this purpose, proteins such as gelatin or network-forming resins such as urea-formaldehyde resins or melamine-formaldehyde resins may be added. Further suitable hardeners include water glass.

[0071] The tile adhesive of the present invention may contain synthetic binders such as acrylic resins. Preferably, the tile adhesive of the present invention does not contain more than 15% by weight of synthetic binders based on the dry matter of the total composition. In a further preferred embodiment, the adhesive of the present invention is synthetic binder-free.

[0072] The present invention further provides a method for preparing a tile adhesive as defined above, comprising the steps of: providing, in any order, an aqueous solution of substituted starch in water; and homogenizing the dry ingredients in water, the mass ratio of water / total dry ingredients being between 0.1 and 5. The end-use form of the tile adhesive of the present invention is based on an aqueous tile adhesive composition in which the substituted starch is present in solution as gelled substituted starch.

[0073] In either method, the dry ingredients are mixed with water in a mass ratio of water / total dry ingredients of 0.1 to 5, preferably 0.2 to 4, more preferably 0.3 to 3. This mass ratio ensures that the resulting mixture after homogenization has an appropriate viscosity. The dry ingredients are as defined above and include at least the substituted starch and filler.

[0074] The preferred viscosity of the tile adhesive of the present invention at the time of final use is 300 to 700 Pa.s when measured at 4 rpm and 23°C using a Brookfield Helipath viscometer with a TE spindle.

[0075] In some embodiments, the tile adhesive may be entirely starch-based. In such embodiments, the tile adhesive comprises a gelled substituted starch as the binder and granular starch as the filler, preferably a pregelled substituted starch as the binder and granular starch as the filler. The entirely starch-based tile adhesive can be mixed with cold water to provide an aqueous tile adhesive composition, which can be used as detailed elsewhere. The use of granular potato starch as the filler offers the advantage that the tile adhesive is entirely renewable and 100% starch-based.

[0076] The present invention further provides a method for attaching one or more tiles to a surface, said method comprising the steps of: a) providing an aqueous tile adhesive composition comprising a gelled substituted starch, as defined elsewhere, the aqueous tile adhesive composition having a viscosity of 300-700 Pa.s and optionally provided by homogenizing a dry mix of the tile adhesive, as defined elsewhere, with water; b) providing a surface to which one or more tiles are to be attached, or at least one tile to be at least partially tiled to the surface using said aqueous tile adhesive composition; c) applying one or more tiles to a surface; d) allowing the aqueous tile adhesive composition to dry.

[0077] In the method of the present invention for installing one or more tiles on a surface, steps b) to d) represent steps in line with common knowledge in the field of tiling: Step a) represents providing an aqueous tile adhesive composition for use in tiling, which may be provided as is (e.g., an aqueous composition from a suitable container) or by homogenizing a dry mix with water.

[0078] The present invention also provides a surface comprising one or more tiles, said tiles being attached to said surface using a tile adhesive as defined above, said surface comprising one or more tiles and comprising three layers: a base layer, an intermediate layer and a tile layer, wherein the base layer is a surface onto which the tiles can be attached, the intermediate layer comprises dried tile adhesive and the tile layer comprises tiles as defined elsewhere.

[0079] The substrate is the surface layer to which the tiles are adhered using a tile adhesive. The substrate may be made of various types of materials, such as concrete, brick, wood, mortar, or plaster. Tile adhesives are suitable for securing tiles to any substrate, but are particularly suitable for adhering tiles to concrete or wood substrates.

[0080] The intermediate layer comprises a dry tile adhesive and thus includes gelled substituted starch and filler, as well as optional further ingredients as defined elsewhere. [Example]

[0081] The tile adhesives listed below were prepared by dry mixing of the solid ingredients. Cold water soluble starch was used to prepare the water-based tile adhesives. Tap water (20°C) was used. All solid ingredients were used as commercially available dry products.

[0082] Preparation of tile adhesive The mixing procedure is based on EN-120004 and is outlined below. Dry mix all compounds in a plastic bag, close the bag and shake well. Add the required amount of water to the mixing bowl. Attach the paddle to the mixer. · Add the dry mixture to the water, place the bowl in the mixer and start mixing after 30 seconds (t=0). · Operate the mixer according to the following mixing protocol: a. 0-1 / 2 min: Mix the mortar at 140 rpm. b. 1 / 2 to 1 1 / 2 minutes: Rest; lower bowl into mixer and scrape paddle; remove bowl from mixer and scrape inside of bowl. c. 1 1 / 2 to 2 1 / 2 minutes: Mix the mortar again at 140 rpm. d. 2 1 / 2 to 5 minutes: Rest; if thick, scrape down paddle and inside of bowl again. e. 5 to 5 1 / 4 minutes: Final mixing in a mixer at 140 rpm. ·Remove the bowl from the mixer and scrape down the paddle and bowl. If necessary, gently cut the mortar with a silicone spatula to remove any air bubbles and smooth the surface with the tip of the silicone spatula.

[0083] Viscosity measurement Viscosity is measured using a Brookfield Helipath Viscometer with a TE spindle at 4 rpm and 23°C. Viscosity measurements are initiated 7 minutes after the start of adhesive preparation. Measurement points are taken at 1-second intervals. After 18 seconds of stabilization, the viscosity is reported as the average of 10 data points (10 seconds). The water-to-powder ratio (w / p ratio) is selected so that the Brookfield viscosity of the tile adhesive is between 300 and 700 Pa.s.

[0084] Adhesion strength and open time The adhesive strength and open time are measured according to EN12004 using Winckelmans tiles and MOSA tiles. Winckelmans tiles are used for adhesive strength measurements. Winckelmans tiles have (very) low porosity (water absorption less than 0.5% by mass), while the MOSA tiles used for open time have high porosity (water absorption of approximately 15±3%). The use of both high- and low-porosity tiles confirms the general applicability of the tile adhesive of the present invention. Unless otherwise stated, adhesion measurements were carried out on a concrete surface. The summary is as follows:

[0085] 10 minutes after starting the adhesive preparation, apply a layer of tile adhesive onto the surface. Five minutes after applying the adhesive layer, Winckelmans tiles are placed on the adhesive layer. These tiles are used for adhesive strength. Place MOSA tiles on the adhesive layer 5, 30 or 60 minutes after application. These tiles are used for open time.

[0086] Starches used in the examples of the present invention include: [Table 1] DS and DC are the amounts of reagents added to the starch during the reaction, expressed as moles per mole of AGU.

[0087] A conventional cement-based tile adhesive was prepared according to the following formulation: [Table 2]

[0088] Example 1: Types of starch used as tile adhesives A starch-based tile adhesive was prepared according to the following formulation: [Table 3] Starch is added as commercially available dry product, with moisture content varying depending on the starch type: dextrin (11% by weight), maltodextrin (7% by weight), extruded starch (13% by weight), drum-dried starch (6% by weight).

[0089] For all types of starch, the adhesive strength was measured according to EN 12004. The results are shown in Table 1. [Table 4]

[0090] As shown in Table 1, starches 1-7 did not exhibit sufficient adhesion to Winckelmans tiles. Starches 8-18 all exhibited the required adhesive strength to Winckelmans tiles, easily meeting the C2 standard.

[0091] From this, it can be inferred that substituted starches exhibit sufficient adhesive properties under the conditions of EN 12004. It can also be inferred that many starch types, even those that do not contain cement, exhibit higher performance than the reference (cement-based) tile adhesive.

[0092] Further starch modification, such as cross-linking, does not impair the adhesive properties of substituted starches, and cross-linked starches can therefore be used in situations that lead to rheological optimization.

[0093] Example 2: Fillers for use with starch in tile adhesives Starch 9 was used to evaluate the tolerance of the tile adhesive to the presence of different fillers using the formulation of Example 1. The alternative fillers used were Durcal 40 (calcium carbonate with 40 μm D50) or native potato starch. It is noteworthy that the native potato starch was present in granular form in the tile adhesive. The tile adhesive used for the adhesion tests in Experiment 2-2 therefore contained gelled substituted starch as the binder and granular starch as the filler.

[0094] The results are shown in Table 2. [Table 5] These results demonstrate that alternative fillers can be used while still meeting the C2 requirements of EN12004.

[0095] Example 3: Tolerance range for substituted starch / filler ratio Using Starch 9 and Starch 13 as exemplary starches and quartz sand as the filler, different ratios between substituted starch and filler were evaluated, and the results are shown in Table 3.

[0096] The results show that 1% Starch 9 results in insufficient adhesion, while 2.5% to 100% Starch 9 meets the adhesion requirements of the C2 standard. A similar trend is observed for Starch 13. Increasing the starch content (i.e., decreasing the sand content) results in a higher w / p ratio. Of particular note is that filler is not strictly necessary to meet adhesion requirements. [Table 6]

[0097] Example 4: Open Time A starch-based tile adhesive based on Starch 9 in the formulation of Example 1 was compared with a cement-based reference adhesive using MOSA tiles. In both adhesives, the filler was sand (Dorentrup 12 A).

[0098] The results are shown in Table 4. [Table 7]

[0099] Table 4 shows that both the Reference Example (Experiment 4-2) and the Starch 9 Formulation (Experiment 4-5) had a tensile strength of 0.5 N / mm after 30 minutes of open time. 2 These results demonstrate that the required bond strength of 100% or more is met. However, the Starch 9 formulation (Experiment 4-6) easily meets this requirement even after 60 minutes, whereas the cement-based Reference Example does not (Experiment 4-3). Thus, the (starch-based) tile adhesive of the present invention has a longer open time than the cement-based Reference adhesive, allowing the tile installer to work under reduced time constraints and apply adhesive to a larger area than would be possible with conventional cement-based tile adhesives. This also significantly reduces waste generation.

[0100] Example 5: Adhesion to alternative surface materials Various starch-based tile adhesives according to the formulation of Example 1 were tested for adhesion strength to wood (plywood) using the procedure set out in EN12004 and compared with a cement-based reference adhesive.

[0101] The results are shown in Table 5. [Table 8]

[0102] Table 5 and the above examples demonstrate that starch-based tile adhesives can be used on a variety of surfaces, including wood and concrete. The experiments further demonstrate that substituted starch is necessary to adhere tile to wood surfaces, as unsubstituted Starch 7 (drum-dried potato starch) did not exhibit any adhesive strength.

[0103] Example 6: Hybrid tile adhesive The tolerance of the starch-based tile adhesive of the present invention to the presence of cement was evaluated by mixing various ratios of a reference tile adhesive with the formulation of the present invention. The compositions evaluated are shown below: [Table 9]

[0104] This corresponds to adhesion tests carried out using the following compositions, the results of which are shown in Table 6 (formulation amounts are raw weight %): [Table 10]

[0105] The results in Table 6 show that mixtures containing substituted starch, filler, and cement do not always provide sufficient bond strength. However, the presence of cement is tolerated, albeit at the expense of bond strength. Therefore, cement may be present, but preferably in relatively small amounts compared to the substituted starch.

[0106] Example 7: Tolerance for other ingredients The tolerance of the starch-based tile adhesive of the present invention to the presence of other ingredients was evaluated by adding additives commonly used in cement-based tile adhesives, as well as other additives. The types of ingredients and results are shown in Table 7. [Table 11]

[0107] Table 7 shows that the addition of ingredients common in cementitious tile adhesives, such as redispersible powder ("RDP", Vinnapas 5010N) and nanoclay (Cloisite 116), does not adversely affect adhesion. Even ingredients that are not common in cementitious tile adhesives, such as Gelatin 250 Bloom, do not adversely affect adhesion.

Claims

1. A tile adhesive comprising a substituted starch and a filler, wherein the weight ratio of cement to substituted starch is 0-2.

2. 10. The tile adhesive of claim 1, wherein the filler comprises sand, clay, calcium carbonate, granular starch, ground waste concrete, ground waste plastic, ground organic material, ground inorganic material, and / or sawdust.

3. 3. A tile adhesive according to claim 1 or 2, wherein the filler has a particle size, expressed as D50, of at least 1 μm, preferably at least 5 μm, and wherein said particle size is preferably at most 500 μm, more preferably at most 300 μm, even more preferably at most 175 μm.

4. 4. A tile adhesive according to any of claims 1 to 3, wherein the substituted starch is carboxymethylated starch, hydroxybutylated starch, hydroxypropylated starch, hydroxyethylated starch, acetylated starch, octenylsuccinate starch, cationized starch, or any combination thereof, and preferably the degree of substitution of the starch is at least 0.01 mol / mol.

5. 5. Tile adhesive according to claim 4, wherein the substituted starch is also a cross-linked starch, preferably epichlorohydrin cross-linked starch, trimetaphosphate cross-linked starch, phosphate trichloride cross-linked starch, adipic acid cross-linked starch, and / or the substituted starch is also a degraded starch, preferably acid-degraded starch, physically degraded starch or enzymatically degraded starch.

6. A tile adhesive according to any one of claims 1 to 5, wherein the substituted starch is a pregelatinized starch.

7. Tile adhesive according to any of the preceding claims, wherein the substituted starch is a substituted tuber starch, a substituted root vegetable starch, a substituted nut starch, a substituted cereal starch or a substituted legume starch, preferably a substituted potato starch, a substituted sweet potato starch, a substituted tapioca starch, a substituted maize starch, a substituted wheat starch or a substituted pea starch.

8. 8. Tile adhesive according to any of the preceding claims, wherein the amount of substituted starch is from 2 to 99.9% by weight and the amount of filler is from 0.1 to 98% by weight, said amounts being expressed relative to the dry weight of the tile adhesive.

9. Tile adhesive according to any of the preceding claims, wherein the filler / substituted starch mass ratio is between 0.25 and 40, preferably between 0.3 and 25, more preferably between 1.0 and 20.

10. A tile adhesive according to any one of claims 1 to 9, wherein the filler / total binder mass ratio is greater than 0.5, preferably greater than 1.

0.

11. A tile adhesive according to any preceding claim, wherein the tile adhesive is cement-free.

12. 12. The tile adhesive of any of claims 1 to 11, wherein the tile adhesive is a dry mix suitable for mixing with water and the substituted starch is a pregelatinized starch, or wherein the tile adhesive is an aqueous tile adhesive composition and the substituted starch is a gelatinized substituted starch, and the aqueous tile adhesive composition has a viscosity of 300 to 700 Pa s when measured with a Brookfield Helipath viscometer using spindle T-E at 4 rpm and 23°C.

13. 13. A method for preparing a tile adhesive according to any one of claims 1 to 12, comprising, in any order, the steps of providing a substituted starch in water and homogenising at least one dry ingredient in water under conditions where the mass ratio of water to total dry ingredients is between 0.1 and 5.

14. 1. A method of installing one or more tiles on a surface, comprising: a) providing an aqueous tile adhesive composition comprising a gelled substituted starch as defined in claim 12, said aqueous tile adhesive composition optionally being provided by homogenizing said dry mix of tile adhesive as defined in claim 12 with water, b) providing a surface to which one or more tiles will be adhered, or at least one tile for tiling, at least partially by the aqueous tile adhesive composition; c) adhering said one or more tiles onto said surface; d) allowing the water-based tile adhesive composition to dry.

15. A surface comprising one or more tiles, said tiles being adhered to said surface using a tile adhesive as defined in any one of claims 1 to 12.

Images