An exterior wall putty with progressively increasing strength and its preparation method

Abstract

This invention provides an exterior wall putty with progressively increasing strength. The exterior wall putty comprises the following components by mass fraction: 1.5-2.5% encapsulated potassium silicate, 1.5-2.5% modified redispersible latex powder, 30-40% silicate cement, 35-45% sand, 20-30% heavy calcium carbonate, 0.3-0.5% cellulose ether, 0.03-0.06% starch ether, and 0.05-0.15% sodium gluconate. This invention adds sodium gluconate and encapsulated potassium silicate to a silicate cement system putty. After dissolving, the sodium gluconate inhibits cement hydration. As the cement hydration reaction proceeds slowly, the concentration of calcium ions in the reaction products gradually increases. Simultaneously, the potassium silicate capsule gradually dissolves, and the potassium silicate reacts with calcium ions to form a more stable insoluble compound, thereby increasing the cement hydration reaction rate and overall strength. This reaction continues until the potassium silicate is completely consumed.

Description

Technical Field

[0001] This invention relates to the field of dry powder mortar building materials, and mainly to an exterior wall putty with progressively increasing strength and its preparation method. Background Technology

[0002] Cracking, blistering, and peeling of exterior wall coatings are common problems that seriously affect the overall aesthetics, safety, and service life of buildings. At their root, exterior wall putty is a significant contributing factor. As a material that bridges the gap between the substrate and the paint, exterior wall putty needs to simultaneously maintain both strong adhesion to the substrate and a smooth surface. However, increasing the adhesive strength of the putty also increases the overall strength, making sanding more difficult and compromising surface smoothness; thus, there is a certain trade-off between these two aspects.

[0003] Furthermore, most high-rise buildings currently employ climbing scaffolding construction. The cycle for raising one floor using the climbing scaffolding is typically 4-6 days. To save costs, the exterior wall putty application follows the climbing scaffolding schedule, meaning each layer of exterior wall putty is applied and sanded within 4-6 days. Therefore, the putty should have good sandability within 1-3 days after application, saving time and labor. Additionally, it should possess high strength later on, ensuring adhesion to the substrate and good paint adhesion.

[0004] To meet the above coating requirements, the mainstream approach is to balance the amount of silicate cement and latex powder added to the putty formula, so that the putty's sandability and strength are at a middle value. However, none of these approaches have achieved the most ideal results and have not fundamentally solved the problem.

[0005] In conclusion, it is necessary to develop a new technical solution to address the defects and shortcomings of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to provide an exterior wall putty with progressively increasing strength. The strength increases slowly within the first 3 days of application, which is beneficial for surface sanding and smoothing. The strength increases more rapidly from 3 to 7 days, which is beneficial for the application of subsequent coatings. The strength increases slowly from 7 to 28 days, resulting in high final strength and ensuring the safety of the exterior wall coating.

[0007] One object of the present invention is to provide an exterior wall putty with progressively increasing strength, the exterior wall putty comprising the following components by mass fraction:

[0008]

[0009]

[0010] in,

[0011] The capsule-type potassium silicate is potassium silicate coated with polyvinyl alcohol;

[0012] The modified redispersible latex powder is obtained by reacting vinyl acetate-ethylene-acrylic acid copolymer with tannic acid.

[0013] Furthermore, the sand is river sand or manufactured sand in the 40-140 mesh range.

[0014] Furthermore, the heavy calcium carbonate is calcium carbonate powder in the range of 150-325 mesh.

[0015] Furthermore, the cellulose ether is selected from one or more of methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, or hydroxyethyl methylcellulose.

[0016] Furthermore, the starch ether is potato-modified starch.

[0017] Another object of the present invention is to provide a method for preparing the above-mentioned exterior wall putty with progressively increasing strength, comprising the following steps:

[0018] S1. Mix polyvinyl alcohol with water, heat and stir, add defoamer, stir again to obtain polyvinyl alcohol protective colloid; mix potassium silicate with water, filter to obtain potassium silicate solution;

[0019] S2. The polyvinyl alcohol protective colloid and the potassium silicate solution are mixed, heated and stirred, and an antifoaming agent is added and stirred to obtain a mixed dispersion; the mixed dispersion is spray-dried to obtain a mixed powder, which is then sieved to obtain capsule-shaped potassium silicate.

[0020] S3. Blend vinyl acetate and acrylic acid, evacuate and introduce ethylene, then add an initiator, heat and stir to react, and obtain a vinyl acetate-ethylene-acrylic acid copolymer;

[0021] S4. The vinyl acetate-ethylene-acrylic acid copolymer and tannic acid are blended together, then a catalyst is added and the mixture is heated to react, thereby obtaining modified redispersible latex powder.

[0022] S5. The capsule-shaped potassium silicate, sodium gluconate and heavy calcium carbonate are mixed and stirred evenly to obtain a heavy calcium premix.

[0023] S6. The heavy calcium premix, silicate cement, sand, modified redispersible latex powder, cellulose ether and starch ether are mixed and stirred evenly to obtain an exterior wall putty with progressively increasing strength.

[0024] Furthermore, during use, the exterior wall putty with progressively increasing strength is mixed with water at a weight ratio of 1:(0.3±0.01) and stirred into a uniform paste without particles.

[0025] Further, in step S1, the mass ratio of polyvinyl alcohol to potassium silicate is 1:(6-9).

[0026] Further, in step S3, the mass ratio of vinyl acetate, acrylic acid, and ethylene is (0.5-1.5):(1-3):1.

[0027] Further, in step S4, the mass ratio of the vinyl acetate-ethylene-acrylic acid copolymer to tannic acid is 1:(0.5-1.5).

[0028] Furthermore, in step S1, the heating temperature is 70-90℃.

[0029] Furthermore, in step S2, the heating temperature is 80-100℃.

[0030] Furthermore, in step S3, the heating temperature is 80-100℃.

[0031] Furthermore, in step S4, the heating temperature is 100-120°C.

[0032] The present invention has the following beneficial effects:

[0033] (1) This invention adds sodium gluconate and encapsulated potassium silicate to the putty of the silicate cement system. After the sodium gluconate dissolves, it inhibits the hydration of cement, reducing the hydration rate. As the cement hydration reaction proceeds slowly, the concentration of calcium ions in the reaction products gradually increases. At the same time, the potassium silicate capsule gradually dissolves, and the potassium silicate reacts with calcium ions to form a more stable insoluble compound, increasing the cement hydration reaction rate and overall strength. The reaction continues until the potassium silicate is completely consumed. The macroscopic performance of the exterior wall putty is that the strength is low at 3 days, gradually recovers at 7 days, and is high at 28 days, meeting the requirements of easy sanding in the early stage and high strength in the later stage for building exterior wall putty.

[0034] (2) The modified redispersible latex powder of the present invention is obtained by reacting vinyl acetate-ethylene-acrylic acid copolymer with tannic acid, and introduces a large number of active groups such as hydroxyl groups, which can effectively enhance its viscosity and improve the bonding strength of putty; at the same time, the modified redispersible latex powder and capsule-type potassium silicate have good compatibility, and the hydroxyl groups on the surface of the two can interact with each other, improve the adhesion of putty to the substrate, and enhance the performance of putty.

[0035] Instruction manual illustrations

[0036] Figure 1 The bond strength test results of Example 1 and Comparative Examples 1-5 at 3, 7, 14, 21 and 28 days are shown. Detailed Implementation

[0037] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0038] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0039] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0040] The following raw materials are used in the embodiments and comparative examples of this invention:

[0041] The silicate cement is PO 42.5 lime cement.

[0042] The sand is river sand in the 40-140 mesh range.

[0043] Heavy calcium carbonate is calcium carbonate powder in the range of 150-325 mesh.

[0044] The cellulose ether is hydroxypropyl methylcellulose with a viscosity of 75,000-100,000 mPa·s.

[0045] Starch ether is potato-modified starch with a viscosity of 400-1200 mPa·s.

[0046] Sodium gluconate is a crystalline powder with an effective content of ≥97%.

[0047] The polyvinyl alcohol model is PVA-2488.

[0048] The modulus of fast-dissolving potassium silicate is 2.3-2.5.

[0049] The defoamer is an organosilicon defoamer, brand name F210, purchased from Shanghai Guben Industrial Co., Ltd.

[0050] The release agent was 4000-mesh calcined kaolin, brand name Baixue 80, purchased from Tangshan Madison Kaolin Co., Ltd.

[0051] Example 1

[0052] An exterior wall putty with progressively increasing strength, the exterior wall putty comprising the following components by mass fraction:

[0053]

[0054] The preparation method of the above-mentioned exterior wall putty with progressively increasing strength includes the following steps:

[0055] S1. Pour 960 kg of water into the reactor, heat to 40°C, add 40 kg of polyvinyl alcohol, continue heating to 80°C, stir for 30 min, add 1 kg of defoamer, continue stirring for 10 min to obtain polyvinyl alcohol protective colloid, cool to 30°C, and keep warm for later use; dissolve 300 kg of fast-dissolving potassium silicate in 700 kg of water, filter using a 160 mesh filter to obtain potassium silicate solution;

[0056] S2. Start the reactor, stir and heat to 90℃. Add the polyvinyl alcohol protective colloid and potassium silicate solution to the reactor, mix and stir for 30 minutes, add 1 kg of defoamer, and continue stirring for 10 minutes to obtain a mixed dispersion. Pump the mixed dispersion to a drying tower, control the inlet temperature at 140±5℃, and atomize the mixed dispersion evenly into the tower using a spray device. At the same time, add a separating agent to the airflow. The atomized microdroplets evaporate and dry rapidly, forming a gas-solid mixture, which is discharged from the bottom outlet of the tower to collect the mixed powder. Pass the mixed powder through a 90-mesh sieve to collect particles ≥90 mesh to obtain capsule-type potassium silicate.

[0057] S3. Using water as a solvent, vinyl acetate and acrylic acid are blended, vacuumed and ethylene (vinyl acetate:acrylic acid:ethylene = 1:1:1, m / m) is introduced and pressurized to 5 MPa. Then, 1 wt% of tert-butyl hydrogen peroxide is added to the reactants, and the mixture is heated and stirred at 85°C for 5 h. After filtration, washing and drying, vinyl acetate-ethylene-acrylic acid copolymer is obtained.

[0058] S4. Using dimethyl sulfoxide as solvent, the vinyl acetate-ethylene-acrylic acid copolymer and tannic acid are blended, and p-toluenesulfonic acid is added (vinyl acetate-ethylene-acrylic acid copolymer: tannic acid: p-toluenesulfonic acid = 1:1:0.3, m / m / m). The mixture is reacted at 110°C for 12 hours, filtered, washed, and dried to obtain modified redispersible latex powder.

[0059] S5. According to the above mass fraction, the capsule-shaped potassium silicate, sodium gluconate and heavy calcium carbonate are mixed and stirred evenly to obtain a heavy calcium premix.

[0060] S6. The modified redispersible latex powder, heavy calcium carbonate premix, silicate cement, sand, cellulose ether and starch ether are mixed and stirred evenly to obtain an exterior wall putty with progressively increasing strength.

[0061] Example 2

[0062] An exterior wall putty with progressively increasing strength, the exterior wall putty comprising the following components by mass fraction:

[0063]

[0064] The preparation method of the exterior wall putty with the above-mentioned phased increase in strength is the same as in Example 1.

[0065] Example 3

[0066] An exterior wall putty with progressively increasing strength, the exterior wall putty comprising the following components by mass fraction:

[0067]

[0068]

[0069] The preparation method of the exterior wall putty with the above-mentioned phased increase in strength is the same as in Example 1.

[0070] Comparative Example 1

[0071] An exterior wall putty with progressively increasing strength. The difference between this comparative example and Example 1 is that steps S1-2 are omitted. In step S5, the capsule-type potassium silicate is replaced with a physical mixture of polyvinyl alcohol and fast-dissolving potassium silicate, with the same amount as in step S1. The remaining components and preparation methods are the same as in Example 1.

[0072] Comparative Example 2

[0073] An exterior wall putty with progressively increasing strength is described in this comparative example, which differs from Example 1 in that the capsule-shaped potassium silicate is replaced with heavy calcium carbonate, while the remaining components and preparation method are the same as in Example 1.

[0074] Comparative Example 3

[0075] An exterior wall putty with progressively increasing strength is described in this comparative example, which differs from Example 1 in that the sodium gluconate is replaced by heavy calcium carbonate, while the other components and preparation method are the same as in Example 1.

[0076] Comparative Example 4

[0077] An exterior wall putty with progressively increasing strength is described in this comparative example, which differs from Example 1 in that the capsule-shaped potassium silicate and sodium gluconate are replaced with heavy calcium carbonate, while the remaining components and preparation method are the same as in Example 1.

[0078] Comparative Example 5

[0079] An exterior wall putty with progressively increasing strength is described in this comparative example, which differs from Example 1 in that the modified redispersible latex powder is replaced with a physical mixture of vinyl acetate-ethylene-acrylic acid copolymer and tannic acid, with the same dosage as in steps S3 and S4. The remaining components and preparation method are the same as in Example 1.

[0080] Test case

[0081] 1. Bond strength test

[0082] Test method: The bond strength of Example 1 and Comparative Examples 1-5 was tested at 3, 7, 14, 21 and 28 days in accordance with the bond strength test method in JG / T 157-2009 "Putty for Building Exterior Walls".

[0083] Test results are as follows Figure 1 As shown in Table 1.

[0084] Table 1. Bond strength test results of Example 1 and Comparative Examples 1-5

[0085]

[0086]

[0087] 2. Polishability Test

[0088] The sandability of putty is evaluated by the dusting rate during sanding. The higher the dusting rate, the easier it is to sand, and vice versa.

[0089] The sandability test of putty coating should be conducted according to the following method:

[0090] (1) Test substrate: Asbestos-free cement flat plate with dimensions of 70mm×150mm;

[0091] (2) Film forming mold: outer frame size 70mm×150mm, inner frame size 60mm×140mm, thickness 1mm, forming frame made of stainless steel or acrylic material;

[0092] (3) Coating preparation: Place the mold flat on the cement plate with the edges aligned, pour the mixed material into the mold, and use a steel scraper to compact and smooth the material. The coating should be flat, dense, without defects or bubbles. Make 3 samples for each sample and place them in the curing room for 3 days.

[0093] (4) Maintenance conditions: Temperature 25±2℃, relative humidity 50±5%;

[0094] (5) Sanding test: Use a cube block with a side length of 60mm and a weight of 500g. Attach 240-grit sandpaper to one side, place the side with sandpaper flat on the putty film, align the two sides, and drag the block back and forth. The single drag distance is 80mm. After dragging back and forth 10 times, use a wool brush to clean the dust off the test block.

[0095] (6) Calculation method: Weigh the asbestos-free cement flat plate before making the sample and record it as M0; weigh the test block after it is made and cured for 3 days and record it as M1; weigh the test block after it is polished and cleaned of dust and record it as M2.

[0096]

[0097] (7) Three samples are tested for each sample, and the average of the three values ​​is taken. The difference between the average value and any single value shall not exceed 20%; otherwise, it shall be considered invalid and the test shall be repeated.

[0098] The results of the abrasiveness test for Example 1 and Comparative Examples 1-5, and the powder loss rate are shown in Table 2.

[0099] Table 2. Results of powder loss rate tests for Example 1 and Comparative Examples 1-5

[0100] project Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Powder drop rate % 5.93 2.16 6.02 1.97 3.37 5.87

[0101] The test results above show that the powder shedding rates of Example 1 and Comparative Example 2 are similar, but significantly higher than those of Comparative Example 1, Comparative Example 3 and Comparative Example 4. Example 1 has better grinding properties. Comparative Example 1, because the potassium silicate was not coated, reacts quickly with the cement hydration products after dissolving in water, thus improving early strength. However, it is also affected by the retarding effect of sodium gluconate, so its powder shedding rate is significantly lower than that of Example 1 and higher than that of Comparative Example 3.

[0102] Figure 1 The bond strength test results of Example 1 and Comparative Examples 1-5 at 3, 7, 14, 21, and 28 days are shown; for comparison Figure 1 According to the curves and data in Table 1, the bonding strength of Example 1, Comparative Example 1, and Comparative Example 3 at 28 days was significantly higher than that of Comparative Example 2 and Comparative Example 4.

[0103] comprehensive Figure 1 According to Tables 1 and 2, the present invention exhibits excellent sanding properties 3 days after application and excellent subsequent bonding strength, meeting the coating requirements in practical applications.

[0104] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0105] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An exterior wall putty having a strength that increases in stages, characterized by, The strength stage rising external wall putty comprises the following components by mass fraction: Potassium silicate capsules 1.5-2.5% Modified redispersible latex powder 1.5-2.5% Silicate cement 30-40% Sand 35-45% Heavy calcium carbonate 20-30% Cellulose ether 0.3-0.5% Starch ether 0.03-0.06% Sodium gluconate 0.05-0.15% Wherein, The potassium silicate capsules are polyvinyl alcohol-coated potassium silicate; The modified redispersible latex powder is obtained by the reaction of vinyl acetate-ethylene-acrylic acid copolymer and tannic acid; The strength stage rising external wall putty is prepared by the preparation method comprising the following steps: S1, blending polyvinyl alcohol with water, heating and stirring, adding defoaming agent, stirring to obtain polyvinyl alcohol protective colloid; blending potassium silicate with water, filtering to obtain potassium silicate solution; S2, blending the polyvinyl alcohol protective colloid and the potassium silicate solution, heating and stirring, adding defoaming agent, stirring to obtain a mixed dispersion; spray drying the mixed dispersion to obtain a mixed powder, sieving to obtain potassium silicate capsules; S3, blending vinyl acetate and acrylic acid, vacuumizing and passing in ethylene, then adding initiator, heating and stirring to react to obtain vinyl acetate-ethylene-acrylic acid copolymer; S4, blending the vinyl acetate-ethylene-acrylic acid copolymer and tannic acid, then adding catalyst, heating to react to obtain modified redispersible latex powder; S5, blending the potassium silicate capsules, sodium gluconate and heavy calcium carbonate, stirring uniformly to obtain heavy calcium carbonate premix; S6, blending the heavy calcium carbonate premix, silicate cement, sand, modified redispersible latex powder, cellulose ether and starch ether, stirring uniformly to obtain strength stage rising external wall putty; The mass ratio of the vinyl acetate-ethylene-acrylic acid copolymer and tannic acid is 1:(0.5-1.5).

2. The strength-staged exterior wall putty according to claim 1, characterized in that, The cellulose ether is selected from one or more of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose or hydroxyethyl methyl cellulose.

3. The strength-staged exterior wall joint compound of claim 1, wherein The starch ether is potato modified starch.

4. The strength-staged exterior wall joint compound of claim 1, wherein In step S1, the mass ratio of the polyvinyl alcohol and potassium silicate is 1:(6-9).

5. The strength-staged exterior wall joint compound of claim 1, wherein In step S3, the mass ratio of the vinyl acetate, acrylic acid and ethylene is (0.5-1.5):(1-3):

1.

6. The strength-staged exterior wall joint compound of claim 1, wherein In step S1, the heating temperature is 70-90℃.

7. The strength-staged exterior wall joint compound of claim 1, wherein In step S2, the heating temperature is 80-100℃.

8. The strength-staged exterior wall joint compound of claim 1, wherein In step S3, the heating temperature is 80-100℃.

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