Process for the preparation and use of a waxy polysaccharide modified material comprising a cellulosic component

Abstract

The present application relates to the field of waxy polysaccharide material, and particularly relates to a preparation method and application of a waxy polysaccharide modified material containing a cellulose component. The preparation method comprises the following steps: dispersing nanocellulose in water to obtain a dispersion; using the dispersion and amylopectin as raw materials, performing cross-linking reaction of the nanocellulose and the amylopectin under the action of a cross-linking agent, separating the product to obtain a primary modified cross-linking material; and performing etherification treatment on the primary modified cross-linking material to obtain the waxy polysaccharide modified material. The waxy polysaccharide modified material obtained by using the preparation method has good water retention capacity, and when used in ceramic tile glue, can give the ceramic tile glue a longer standing time and higher bonding strength.

Description

Technical Field

[0001] This invention relates to the field of waxy polysaccharide materials, and more particularly to a method for preparing and applying a waxy polysaccharide modified material containing cellulose components. Background Technology

[0002] As a decorative material, ceramic tiles have a broad market, and tile adhesive, used in conjunction with them, is a necessary and cost-effective product widely used in the installation of ceramic tiles, wall tiles, floor tiles, and other decorative applications. Its main characteristics include high bonding strength, water resistance, freeze-thaw resistance, good aging resistance, and convenient construction. Compared to cement, it saves more space, effectively reduces waste, and contains no toxic additives, meeting environmental requirements. Therefore, as a new type of ceramic tile adhesive with excellent performance and cost-effectiveness, it has rapidly developed into a leading product.

[0003] Currently, the common formulations of tile adhesives on the market generally consist of cement, river sand, hydroxypropyl methylcellulose (HPMC), EVA (vinyl acetate-ethylene copolymer) latex powder, calcium formate, polyvinyl alcohol (PVA), and styrene-butadiene rubber powder mixed in a certain proportion. Starch ethers, obtained by modifying polysaccharide starch materials, are a high-performance, cost-effective product that can partially replace HPMC. In the construction industry, they can be used as an additive in cement-based, gypsum-based, and lime-based products, exhibiting good compatibility with other building materials and additives. They are particularly suitable for dry-mix building materials such as mortar, adhesives, plaster, and troweling materials. However, existing starch ethers are made by introducing mono- or difunctional groups (such as hydroxypropyl etherification and carboxymethyl etherification) into corn starch or cassava starch. When applied to tile adhesives, they have insufficient water retention, resulting in a short open time (curing time) and low bonding strength. Summary of the Invention

[0004] To address the technical problems of short open time and low bond strength of existing starch ethers used in tile adhesives, this invention provides a method for preparing and applying a waxy polysaccharide-modified material containing cellulose components. The waxy polysaccharide-modified material obtained by this method exhibits good water retention capacity, and when used in tile adhesives, it can impart a longer drying time and higher bond strength to the tile adhesive.

[0005] The specific technical solution of this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a waxy polysaccharide-modified material containing a cellulose component, comprising the following steps:

[0007] (1) Disperse nanocellulose in water to obtain a dispersion;

[0008] (2) Using dispersion and amylopectin as raw materials, crosslinking reaction of nanocellulose and amylopectin is carried out under the action of crosslinking agent, the product is separated, and the initial modified crosslinking material is obtained.

[0009] (3) Etherification treatment of the initially modified crosslinked material to obtain wax polysaccharide modified material.

[0010] This invention uses nanocellulose and branched starch to crosslink and then etherify them, which enables the obtained waxy polysaccharide modified material to have good water retention. This allows the tile adhesive to have a longer drying time and gives it higher bonding strength when used in tile adhesive.

[0011] Specifically:

[0012] 1) Amylopectin is a highly branched polymer in which D-glucanose units are linked together by α-1,4-glycosidic bonds to form a straight chain. This straight chain can then form side chains through α-1,6-glycosidic bonds, and further branched side chains can appear on these side chains. Compared to amylose, the highly branched structure of amylopectin gives it better binding and water retention properties.

[0013] 2) Amylopectin has poor shear stability; under shear force, the starch chains are easily broken, resulting in decreased viscosity and weakened water retention. This invention cross-links amylopectin, forming a wider, more highly cross-linked network structure between starch molecules. This improves structural stability and enhances the shear resistance of amylopectin, enabling it to maintain good stability under shear force. Simultaneously, the formation of this network structure also further improves the water retention of amylopectin.

[0014] 3) Nanocellulose has the characteristics of high surface area and high water retention. In this invention, it is cross-linked with amylopectin, which can stably disperse it in the amylopectin network and improve the network cohesion at the molecular group ends of nanocellulose, thereby improving the water retention and anti-slip properties of the amylopectin network to a greater extent.

[0015] Preferably, in step (2): before the crosslinking reaction, a salt stabilizer is added, and the mass ratio between the amylopectin and the salt stabilizer is 100:1.0 to 1.5; the process of separating the product is to remove water from the filter residue after filtration, without washing.

[0016] By adding a certain amount of salt stabilizer before the crosslinking reaction, the crosslinking agent can be protected from rapid hydrolysis, which would reduce the crosslinking efficiency.

[0017] During the crosslinking reaction, since the outermost electrons of the ionic crystal have usually been gained or lost, it is difficult to gain new electrons. Therefore, the salt stabilizer can exist stably in the system and does not react with other additive phase substances. After the crosslinking reaction is completed, the product is separated by filtration and dehydration without washing. The material obtained after filtration and dehydration is directly subjected to etherification in step (3). This allows the salt stabilizer to remain in the initially modified crosslinked material in large quantities, which accelerates the subsequent etherification reaction and increases the degree of etherification of the wax polysaccharide modified material. When used in tile adhesive, this helps to extend the drying time of the tile adhesive.

[0018] Further, the salt stabilizer includes one or more of hydroxyethyl mercaptan, sodium thiosulfate, sodium chloride, sodium borohydride, sodium metabisulfite, disodium hydrogen phosphate, disodium ethylenediaminetetraacetate, sodium dithionite, sodium fatty alcohol polyether sulfate, and potassium iodide. More preferably, it is one or more of sodium thiosulfate, sodium chloride, disodium hydrogen phosphate, and sodium fatty alcohol polyether sulfate. More preferably, it is one or more of sodium thiosulfate, sodium chloride, and disodium hydrogen phosphate.

[0019] Preferably, step (2) includes the following steps: mixing the dispersion, amylopectin and salt stabilizer, adjusting the pH to 10.6-11.5, then adding a crosslinking agent, wherein the mass ratio of amylopectin to crosslinking agent is 100:0.0005-0.001, and carrying out a crosslinking reaction at 20-50°C for 1-5 hours, separating the product, and obtaining the initial modified crosslinked material.

[0020] Within a certain range, increasing the pH of the cross-linking reaction can increase the degree of cross-linking, thereby improving the water retention of wax polysaccharide modified materials; however, when the pH of the cross-linking reaction is too high, it will cause the degree of cross-linking to be too large, inhibiting the swelling performance of amylopectin, which in turn will shorten the drying time of the tile adhesive and weaken the bonding strength.

[0021] Within a certain range, increasing the amount of crosslinking agent can improve the degree of crosslinking. However, when the amount is too large, it will cause a significant increase in the number of crosslinking bonds in the crosslinking reaction system, making it easier to form a denser network molecular structure. The crosslinking bond energy on the starch molecule groups will increase, and the thermal expansion potential energy of starch will be suppressed, resulting in insufficient viscosity, low bonding strength, and poor application effect.

[0022] Based on the above theoretical analysis and experimental research, this invention adjusts the pH of the reaction system before the crosslinking reaction, controlling it within the range of 10.6 to 11.5, and controls the amount of crosslinking agent at 0.0005 to 0.001 wt% of amylopectin. This can give the wax polysaccharide modified material better performance, enabling it to achieve a longer drying time and higher bonding strength when used in tile adhesive.

[0023] Further, the crosslinking reaction is carried out at a temperature of 23–48°C. More preferably, the crosslinking reaction is carried out at a temperature of 25–45°C for a time of 1–4 hours.

[0024] Further, the crosslinking agent includes one or more of epichlorohydrin, phosphoryl chloride, sodium trimetaphosphate, acetaldehyde, an acetic anhydride-adipic acid mixture, acrolein, carbonyl chloride, dichlorobutene, aliphatic dihalides, cyanuryl chloride, and sodium tetraborate. More preferably, it is one or more of epichlorohydrin, phosphoryl chloride, sodium trimetaphosphate, acetaldehyde, an acetic anhydride-adipic acid mixture, acrolein, aliphatic dihalides, cyanuryl chloride, and sodium tetraborate. More preferably, it is one or more of epichlorohydrin, phosphoryl chloride, sodium trimetaphosphate, and sodium tetraborate.

[0025] Furthermore, the pH adjustment to 10.6–11.5 is achieved by adding a cross-linking catalyst.

[0026] Further, the crosslinking catalyst comprises one or more of calcium oxide, sodium peroxide, magnesium oxide, sodium aluminate, sodium hydroxide, calcium hydroxide, sodium metasilicate, sodium ethoxide, and potassium hydroxide. More preferably, it comprises one or more of calcium oxide, sodium aluminate, sodium hydroxide, calcium hydroxide, and potassium hydroxide. More preferably, it comprises one or more of sodium aluminate, sodium hydroxide, and potassium hydroxide.

[0027] Preferably, the viscosity of a 5wt% aqueous dispersion of the waxy polysaccharide modified material is >6500 mPa·s.

[0028] Preferably, in step (2), the mass ratio between the amylopectin and the nanocellulose in the dispersion is 100:0.003 to 0.01.

[0029] Preferably, in step (1), the content of nanocellulose in the dispersion is 0.0035 to 0.005 wt%.

[0030] By controlling the content of nanocellulose in the dispersion to 0.0035-0.005wt%, the solid content of the system can be avoided to be too low during the crosslinking reaction in step (2), so as to ensure that there is a high probability of collision between the crosslinking agent and nanocellulose and amylopectin, so that the prepared primary modified crosslinking material can reach a moderate degree of crosslinking, thereby giving the wax polysaccharide modified material better water retention performance.

[0031] Preferably, in step (2), the water content of the initial modified crosslinking material is 10-14 wt%.

[0032] Preferably, in step (3): the etherification treatment includes carboxymethyl etherification treatment; after the etherification treatment, an acidifier is added, and the mass ratio between the amylopectin and the acidifier is 100:1.0 to 1.8 to obtain the wax polysaccharide modified material.

[0033] Adding an appropriate amount of acid adjuster after etherification can better maintain and modify the acid-base properties of the etherified material. By adding the acid adjuster, the pH value of the system is lowered, which can better stabilize the system, extend the stability period and shelf life, and also improve the color of the material. However, because the carboxymethyl groups introduced after carboxymethyl etherification are alkali-resistant but not acid-resistant, if the amount of acid adjuster added is too large, it will cause the viscosity of the aqueous dispersion of the wax polysaccharide modified material to be too low. Therefore, when used in tile adhesive, it will result in a short curing time and low bonding strength.

[0034] Further, the acid-adjusting agent includes one or more of citric acid, adipic acid, malic acid, ascorbic acid, fumaric acid, succinic acid, citric acid, tartaric acid, glacial acetic acid, oxalic acid, benzoic acid, salicylic acid, and caffeic acid. More preferably, it is one or more of citric acid, fumaric acid, citric acid, glacial acetic acid, salicylic acid, and caffeic acid. More preferably, it is one or more of fumaric acid, glacial acetic acid, and salicylic acid.

[0035] Preferably, in step (3), the specific process of the etherification treatment includes the following steps: mixing the initial modified crosslinking material, hydroxypropyl etherifying agent and carboxymethyl etherifying agent, wherein the mass ratio between the branched starch, hydroxypropyl etherifying agent and carboxymethyl etherifying agent is 100:10~30:10~15, etherifying under the protection of alcohol, and then removing the alcohol.

[0036] This invention employs a simultaneous semi-dry etherification method using hydroxypropyl and carboxymethyl groups. Theoretically, both anionic and nonionic etherification reactions occur under alkaline conditions, utilizing the ionization reaction of hydroxyl groups on starch molecules (Starch-ONa) followed by attack on the added etherifying agent, resulting in a bimolecular nucleophilic substitution reaction. Using two etherifying agents to modify the cross-linked amylopectin and nanocellulose composite material improves its overall performance, enabling it to achieve longer curing times and higher bonding strength when applied to tile adhesives.

[0037] Furthermore, the hydroxypropyl etherifying agent is ethylene oxide and / or propylene oxide; the carboxymethyl etherifying agent is chloroacetic acid and / or chloroacetic acid salt.

[0038] Furthermore, the etherification temperature is 20–70°C and the time is 2.0–5.0 h.

[0039] Furthermore, the volume fraction of the alcohol is 70-80%, and the mass ratio of the amylopectin to the alcohol is 100:5-30.

[0040] Preferably, in step (3): the content of hydroxypropyl in the wax polysaccharide modified material is 14.0-16.5%, and the degree of substitution of carboxymethyl is 0.15-0.30.

[0041] Preferably, in step (1), the average diameter of the nanocellulose is 10-100 nm and the average length is 2000-20000 nm.

[0042] Preferably, in step (2), the branched content of the amylopectin is >95.0%.

[0043] By using nanocellulose with a large aspect ratio and amylopectin with a high branching content, wax polysaccharide modified materials can be endowed with better water retention and anti-slip properties.

[0044] Preferably, in step (2), the amylopectin is obtained by processing and extracting sorghum, corn, cassava or potato.

[0045] Secondly, the present invention provides a waxy polysaccharide modified material prepared by the aforementioned preparation method.

[0046] Thirdly, the present invention provides the application of the waxy polysaccharide modified material in tile adhesive.

[0047] Preferably, the tile adhesive comprises the following raw materials in parts by weight: 320-380 parts cement, 600-650 parts fine silica sand, 10-15 parts hydroxypropyl methylcellulose, 0.5-1.5 parts EVA latex powder, and 2-5 parts wax polysaccharide modifier.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] (1) The present invention uses nanocellulose and amylopectin to crosslink and then etherification to obtain a wax polysaccharide modified material with good water retention. Therefore, when used in tile adhesive, it can give the tile adhesive a longer drying time and higher bonding strength.

[0050] (2) The present invention adds a certain amount of salt stabilizer before the crosslinking reaction and uses a specific method to separate the products of the crosslinking reaction so that the salt stabilizer remains in the product, which can promote the subsequent etherification reaction, improve the degree of etherification of the wax polysaccharide modified material, and thus make the tile adhesive have a longer drying time.

[0051] (3) By controlling the content of nanocellulose in the dispersion, the amount of crosslinking agent and the pH of the crosslinking reaction system, the present invention can control the degree of crosslinking at a suitable level, thereby giving the wax polysaccharide modified material better water retention performance, so that it can achieve a longer drying time and higher bonding strength when used in tile adhesive. Detailed Implementation

[0052] The present invention will be further described below with reference to embodiments.

[0053] General Implementation Examples

[0054] A method for preparing a waxy polysaccharide-modified material containing cellulose components includes the following steps:

[0055] (1) Disperse nanocellulose in water to obtain a dispersion;

[0056] (2) Using dispersion and amylopectin as raw materials, crosslinking reaction of nanocellulose and amylopectin is carried out under the action of crosslinking agent, the product is separated, and the initial modified crosslinking material is obtained.

[0057] (3) Etherification treatment of the initially modified crosslinked material to obtain wax polysaccharide modified material.

[0058] In one specific implementation, in step (1): the content of nanocellulose in the dispersion is 0.0035 to 0.005 wt%.

[0059] In one specific implementation, in step (1): the average diameter of the nanocellulose is 10-100 nm and the average length is 2000-20000 nm.

[0060] In one specific implementation, in step (1): the amylopectin is obtained by processing and extracting sorghum, corn, cassava or potato, and the amylopectin content is >95.0%.

[0061] As a specific implementation method, the specific process of step (2) includes the following steps: mixing the dispersion, amylopectin and salt stabilizer, wherein the mass ratio between the amylopectin, the nanocellulose in the dispersion and the salt stabilizer is 100:0.003~0.01:1.0~1.5, adding a crosslinking catalyst to adjust the pH to 10.6~11.5, and then adding a crosslinking agent, wherein the mass ratio between the amylopectin and the crosslinking agent is 100:0.0005~0.001, and carrying out a crosslinking reaction at 20~50℃ for 1~5h, filtering and removing water from the filter residue without washing, to obtain a pre-modified crosslinking material with a water content of 10~14wt%.

[0062] In the above specific embodiments, optionally:

[0063] The salt stabilizers include one or more of the following: hydroxyethyl mercaptan, sodium thiosulfate, sodium chloride, sodium borohydride, sodium metabisulfite, disodium hydrogen phosphate, disodium ethylenediaminetetraacetate, sodium dithionite, sodium fatty alcohol polyether sulfate, and potassium iodide.

[0064] The crosslinking agent includes one or more of epichlorohydrin, phosphoryl chloride, sodium trimetaphosphate, acetaldehyde, acetic anhydride-adipic acid mixture, acrolein, carbonyl chloride, dichlorobutene, aliphatic dihalides, cyanuric chloride, and sodium tetraborate.

[0065] The crosslinking catalyst includes one or more of the following: calcium oxide, sodium peroxide, magnesium oxide, sodium aluminate, sodium hydroxide, calcium hydroxide, sodium metasilicate, sodium ethoxide, and potassium hydroxide.

[0066] As a specific implementation method, the specific process of step (3) includes the following steps: mixing the initial modified crosslinking material, hydroxypropyl etherifying agent and carboxymethyl etherifying agent, wherein the mass ratio between the amylopectin, hydroxypropyl etherifying agent and carboxymethyl etherifying agent is 100:10-30:10-15, etherifying under the protection of 70-80% alcohol by volume, at a temperature of 20-70°C for 2.0-5.0 h, wherein the mass ratio between the amylopectin and alcohol is 100:5-30, then removing the alcohol, and then adding an acidifier, wherein the mass ratio between the amylopectin and the acidifier is 100:1.0-1.8, to obtain a waxy polysaccharide modified material with a hydroxypropyl content of 14.0-16.5%, a carboxymethyl substitution degree of 0.15-0.30, and a viscosity of 5wt% aqueous dispersion >6500 mPa·s.

[0067] In the above specific embodiments, optionally:

[0068] The hydroxypropyl etherifying agent is ethylene oxide and / or propylene oxide;

[0069] The carboxymethyl etherifying agent is chloroacetic acid and / or a chloroacetic acid salt;

[0070] The acid-adjusting agent includes one or more of the following: citric acid, adipic acid, malic acid, ascorbic acid, fumaric acid, succinic acid, citric acid, tartaric acid, glacial acetic acid, oxalic acid, benzoic acid, salicylic acid, and caffeic acid.

[0071] A waxy polysaccharide modified material prepared by the above preparation method.

[0072] Application of the above-mentioned waxy polysaccharide modified materials in tile adhesive.

[0073] In one specific embodiment, the tile adhesive comprises the following raw materials in parts by weight: 320-380 parts cement, 600-650 parts fine silica sand, 10-15 parts hydroxypropyl methylcellulose, 0.5-1.5 parts EVA latex powder, and 2-5 parts wax polysaccharide modifier.

[0074] Example 1

[0075] A waxy polysaccharide modified material containing cellulose components was prepared by the following steps (the amount of each substance is based on weight): (1) Using a disperser, 1 part of a nanocellulose aqueous dispersion with a concentration of 0.5wt%, an average d = 50nm, an average L = 9000nm, and an aspect ratio of 180 was added to 140 parts of deionized water and dispersed at a speed of 25000rpm / min for 5min to obtain the dispersion.

[0076] (2) The dispersion was transferred to a conventional stirred reactor. Under stirring conditions, 100 parts of amylopectin (obtained from sorghum through processing, with an amylopectin content of 95.5%) and 1.2 parts of stabilizer (disodium hydrogen phosphate) were added to mix and prepare the slurry. Then, 1.0 parts of crosslinking catalyst (sodium hydroxide) were added to adjust the pH value to 11.0. At 30°C, 0.0005 parts of crosslinking agent (sodium trimetaphosphate) were added. The crosslinking reaction was then carried out at 30°C for 2 hours. The product was filtered, dehydrated and dried to obtain a product with a moisture content of 13.25 wt%, which is the initial modified crosslinking material.

[0077] (3) Add 20 parts of 75 vol% alcohol for protection, 20.0 parts of hydroxypropyl etherifying agent (propylene oxide) and 12.0 parts of carboxymethyl etherifying agent (sodium chloroacetate) to the primary modified crosslinking material, and complete the semi-dry etherification treatment in a high-pressure reactor. The temperature is controlled at 50°C, the pressure is 0.4 MPa and the time is 3.0 h. After removing the alcohol, add 1.5 parts of acidifying agent (citric acid) to the product and mix and stir. After the product is sieved, package the finished product to obtain the wax polysaccharide modified material.

[0078] Examples 2-12 and Comparative Examples 1-5

[0079] Following the steps in Example 1, waxy polysaccharide modified materials of Examples 2-12 and Comparative Examples 1-5 were prepared. The only difference between Examples 2-12 and Comparative Examples 1-5 and Example 1 is that, according to Table 1, the amounts of each raw material were changed, as well as the pH value, crosslinking reaction temperature, and time in step (2). In Table 1, the amounts of each raw material are parts by weight, the temperature is in °C, and the time is in h.

[0080] Table 1

[0081]

[0082]

[0083] Comparative Example 6

[0084] The following steps were used to prepare a waxy polysaccharide modified material containing cellulose components (the amount of each substance is by weight): (1) 140 parts of deionized water were added to a conventional stirred reactor, and 100 parts of amylopectin (obtained from sorghum through processing, with a branched content of 95.5%) and 1.2 parts of stabilizer (disodium hydrogen phosphate) were added under stirring conditions to mix and adjust the slurry. Then, 1.0 parts of crosslinking catalyst (sodium hydroxide) were added to adjust the pH value to 11.0, and 0.0005 parts of crosslinking agent (sodium trimetaphosphate) were added at 30°C. Then, the crosslinking reaction was carried out at 30°C for 2 hours. The product was filtered, dehydrated and dried to obtain a product with a moisture content of 13.25 wt%, which is the initial modified crosslinking material.

[0085] (2) Take one part of a nanocellulose aqueous dispersion with a concentration of 0.5wt%, an average d = 50nm, an average L = 9000nm, and an aspect ratio of 180, filter and dehydrate and dry to obtain nanocellulose with a moisture content of 13.60wt%.

[0086] (3) After mixing nanocellulose and primary modified crosslinking material, 20 parts of 75 vol% alcohol for protection, 20.0 parts of hydroxypropyl etherifying agent (propylene oxide) and 12.0 parts of carboxymethyl etherifying agent (sodium chloroacetate) are added to the mixture. The semi-dry etherification process is completed in a high-pressure reactor at a controlled temperature of 50°C for 3.0 h. After removing the alcohol, 1.5 parts of acidifying agent (citric acid) are added to the product and mixed. The product is then sieved and packaged to obtain the wax polysaccharide modified material.

[0087] Comparative Example 7

[0088] A waxy polysaccharide modified material containing cellulose components was prepared by the following steps (the amount of each substance is based on weight): (1) Using a disperser, 1 part of a nanocellulose aqueous dispersion with a concentration of 0.5wt%, an average d = 50nm, an average L = 9000nm, and an aspect ratio of 180 was added to 140 parts of deionized water and dispersed at a speed of 25000rpm / min for 5min to obtain the dispersion.

[0089] (2) The dispersion was transferred to a conventional stirred reactor. Under stirring conditions, 100 parts of amylopectin (obtained from sorghum through processing, with an amylopectin content of 95.5%) and 1.2 parts of stabilizer (sodium dihydrogen phosphate) were added to mix and prepare the slurry. Then, 1.0 part of crosslinking catalyst (sodium hydroxide) was added to adjust the pH value to 11.0. At 30°C, 0.0005 parts of crosslinking agent (sodium trimetaphosphate) were added. The crosslinking reaction was then carried out at 30°C for 2 hours. The product was filtered, washed three times with deionized water, and dehydrated and dried to obtain a product with a moisture content of 13.25 wt%, which is the initial modified crosslinking material.

[0090] (3) Add 20 parts of 75 vol% alcohol for protection, 20.0 parts of hydroxypropyl etherifying agent (propylene oxide) and 12.0 parts of carboxymethyl etherifying agent (sodium chloroacetate) to the initial modified crosslinking material, and complete the semi-dry etherification treatment in a high-pressure reactor. The temperature is controlled at 50°C and the time is 3.0 h. After removing the alcohol, add 1.5 parts of acidifying agent (citric acid) to the product and mix and stir. After the product is sieved, package the finished product to obtain the wax polysaccharide modified material.

[0091] Application Examples 1-12 and Comparative Application Examples 1-7

[0092] Using the waxy polysaccharide modified materials obtained in Examples 1-12 and Comparative Examples 1-7, respectively, tile adhesives for Application Examples 1-12 and Comparative Examples 1-7 were prepared according to the following formula: 350g of 42.5R cement, 633g of fine silica sand, 13g of HPMC, 1g of EVA latex powder, 3g of waxy polysaccharide modified material, and 260g of tap water. The mixing method was strictly followed according to the technical requirements specified in 6.1 and the mixing method specified in 7.4.1 of standard JC / T547-2017 "Ceramic Tile Adhesives".

[0093] Test Example 1: Performance of Wax Polysaccharide Modified Materials

[0094] The waxy polysaccharide-modified materials prepared in each example and comparative example were tested for moisture and ash content, whiteness, viscosity of 5 wt% aqueous dispersion, hydroxypropyl content, and degree of carboxymethyl substitution (DS). Among them:

[0095] (1) The method for detecting the degree of carboxymethyl substitution (DS) is as follows:

[0096] First, the sample is thoroughly washed until no Cl- is present. Then, the sample is dried and slowly heated in a muffle furnace, gradually increasing the temperature to 700℃. It is then ignited for 1 hour to completely ashed the sample, quantitatively converting it to Na₂O. The ashed material is dissolved with a quantitative amount of standard sulfuric acid solution, and the excess sulfuric acid is titrated with standard NaOH solution. The degree of carboxymethyl substitution of the starch ether is calculated using the following formula:

[0097]

[0098] Where B is the amount of 1 / 2 H2SO4 consumed per gram of sample, and its value is calculated according to the following formula:

[0099]

[0100] in, The molar concentration of the sulfuric acid used is expressed in mol / L. The volume of sulfuric acid used is expressed in mL; C NaOH V represents the molar concentration of sodium hydroxide used, in mol / L. NaOH The volume of sodium hydroxide used is in mL; W is the mass of the starch ether sample dried to constant weight in g.

[0101] (2) Hydroxypropyl content detection method: According to the detection method of cellulose ether group content in Appendix D of JC / T2190-2013 "Cellulose Ethers for Dry Mixed Mortar", under the catalysis of adipic acid, the substituted alkoxy and hydroxyalkoxy groups are quantitatively cleaved by hydroiodic acid, and then the hydroxypropyl content is determined by gas chromatography.

[0102] (3) The viscosity of the 5wt% aqueous dispersion was measured using an NDJ-1 viscometer at a temperature of 20℃.

[0103] The physicochemical properties of the wax polysaccharide-modified material are shown in Table 2. In Table 2, the 5wt% viscosity refers to the 5wt% aqueous dispersion viscosity of the wax polysaccharide-modified material.

[0104] Table 2

[0105]

[0106] Test Example 2: Performance of Tile Adhesive

[0107] The tile adhesives prepared in each application example and comparative application example were tested for drying time, tensile bond strength and slip in accordance with the standard JC / T547-2017 "Ceramic Tile Adhesives". The results are shown in Table 3.

[0108] Table 3

[0109]

[0110]

[0111] Analyzing the performance test results of the wax polysaccharide modified material and tile adhesive in Tables 2 and 3, it can be seen that:

[0112] (1) Compared with Example 1, the amount of deionized water used to disperse nanocellulose was increased in Comparative Example 1. The viscosity of the 5wt% wax polysaccharide modified material was significantly reduced, the drying time of the tile adhesive was shortened, the tensile bond strength was weakened, and the slippage was increased. This may be due to the reduced solid content of the crosslinking reaction system, the reduced probability of collision between the crosslinking agent and the amylopectin and nanocellulose molecules, which led to a decrease in crosslinking efficiency and a decrease in the degree of crosslinking in the initially modified crosslinking material and the wax polysaccharide modified material.

[0113] (2) Compared with Example 1, Examples 5 and 9 increased the pH value of the crosslinking reaction system, significantly prolonging the drying time of the tile adhesive. The tensile bond strength of Example 5 was also improved. This may be because, within a certain range, increasing the pH value of the crosslinking reaction system and appropriately increasing the degree of crosslinking can improve the water retention of the wax polysaccharide modified material. However, Comparative Examples 2 and 4 further increased the pH value. In step (2), the time required for filtration of the crosslinking product was greatly extended, resulting in gelatinization of the filter cake surface, reduced whiteness, and a decrease in the yield of the initial modified crosslinking material from 98.5% in Example 1 to 88% (Comparative Example 2) and 84% (Comparative Example 4). Furthermore, in the later step (3), sieving of the etherified product was difficult, resulting in poor fineness. The 5wt% viscosity of the wax polysaccharide modified material decreased significantly. In addition, the drying time of the tile adhesive was significantly shortened, the tensile bond strength weakened, and the slip increased. This may be due to the excessive degree of crosslinking, which inhibited the expansion performance of the amylopectin, leading to a shortened drying time and weakened bond strength of the wax polysaccharide modified material.

[0114] (3) Compared with Example 1, Comparative Example 3 increased the amount of crosslinking agent. The viscosity of the 5wt% wax polysaccharide modified material decreased significantly, the drying time of the tile adhesive was shortened, the tensile bond strength was weakened, and the slip increased. This may be because when the amount of crosslinking agent is too large, the crosslinking bonds in the crosslinking reaction system will increase significantly, which will easily form a denser network molecular structure. The crosslinking bond energy on the starch molecular groups will increase, the starch thermal expansion potential energy will be suppressed, resulting in insufficient viscosity and poor application effect.

[0115] (4) Compared with Example 1, Comparative Example 1 increased the amount of acidifier added, and the viscosity of the 5wt% wax polysaccharide modified material decreased significantly. The curing time of the tile adhesive was shortened, the tensile bond strength was weakened, and the slip increased. This may be due to the fact that the carboxymethyl group introduced during etherification has some characteristics of being alkali-resistant but not acid-resistant. Therefore, when the amount of acidifier in the system increases, the pH of the system becomes too low, which leads to a significant decrease in the viscosity of the paste. This results in a reduction in application performance. (5) Compared with Example 1, Comparative Example 6 only crosslinked amylopectin alone. There was no crosslinking between amylopectin and nanocellulose. The curing time of its tile adhesive was shortened significantly, the tensile bond strength was weakened, and the slip increased. This may be because the nanocellulose was not effectively crosslinked before mixing with amylopectin, resulting in insufficient network cohesion at the molecular group ends of the nanocellulose, leading to insufficient water retention. To a greater extent, this results in the overall network stretching not meeting the requirements, affecting its subsequent overall performance.

[0116] (6) Compared with Example 1, Comparative Example 7 was washed multiple times during the separation of crosslinking products, which greatly reduced the amount of salt stabilizer remaining in the initial modified crosslinking material. It could not play a better catalytic role in the subsequent etherification reaction, and could not improve the etherification efficiency and modification depth of the wax polysaccharide modified material. When used in tile adhesive, it is beneficial to extend the drying time of the tile adhesive.

[0117] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a waxy polysaccharide-modified material containing cellulose components, characterized in that, Includes the following steps: (1) Disperse nanocellulose in water to obtain a dispersion with a nanocellulose content of 0.0035~0.005wt%; (2) Mix the dispersion, amylopectin and salt stabilizer, adjust the pH to 11.0~11.5, then add the crosslinking agent, and carry out the crosslinking reaction at 20~50℃ for 1~5h. Remove water from the filter residue without washing to obtain the initial modified crosslinking material. The salt stabilizer includes disodium hydrogen phosphate, amylopectin, nanocellulose in the dispersion, and the mass ratio of salt stabilizer and crosslinking agent is 100:0.003~0.01:1.0~1.5:0.0005~0.001; (3) Mix the initial modified crosslinking material, hydroxypropyl etherifying agent and carboxymethyl etherifying agent, and etherify them under the protection of alcohol. Then remove the alcohol and add an acid adjuster to obtain the wax polysaccharide modified material. The mass ratio of amylopectin, hydroxypropyl etherifying agent, carboxymethyl etherifying agent and acid conditioner is 100:10~30:10~15:1.0~1.

8.

2. The preparation method according to claim 1, characterized in that, In step (2): the mass ratio between the amylopectin and the salt stabilizer is 100:1.2 or 100:1.

5.

3. The preparation method according to claim 1, characterized in that, The viscosity of a 5wt% aqueous dispersion of the waxy polysaccharide modified material is >6500 mPa·s.

4. The preparation method according to claim 1, characterized in that, In step (2): the mass ratio between the amylopectin and the nanocellulose in the dispersion is 100:0.005 or 100:0.

009.

5. The preparation method according to claim 1, characterized in that, In step (3): the mass ratio between the amylopectin and the acidifier is 100:1.0 or 100:1.

8.

6. The preparation method according to claim 1, characterized in that, In step (3): the mass ratio between the amylopectin, hydroxypropyl etherifying agent and carboxymethyl etherifying agent is 100:20:12 or 100:30:12 or 100:20:

14.

7. A waxy polysaccharide modified material prepared by the preparation method described in any one of claims 1 to 6.

8. The application of the waxy polysaccharide modified material as described in claim 7 in tile adhesive.

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