Method for measuring and evaluating the emulsion performance of ethylene-vinyl acetate redispersible latex powder

Abstract

This invention relates to the field of building materials technology, and particularly to a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reconstitution into an emulsion. The method includes the following steps: dissolving ethylene-vinyl acetate redispersible latex powder in water to prepare a latex powder solution of a certain concentration; allowing the latex powder solution to stand for a period of time, then placing it in an ultraviolet spectrophotometer to measure the transmittance, plotting transmittance curves after different standing times, and obtaining the transmittance value of the ethylene-vinyl acetate redispersible latex powder; combining the transmittance curve trend and transmittance value, evaluating the performance of the ethylene-vinyl acetate redispersible latex powder in reconstitution into an emulsion, and providing corresponding application suggestions. The method of this invention is convenient to operate, highly practical, produces stable test results, and has good reproducibility, serving as a reference for the quality evaluation of redispersible latex powder in mortar applications.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion. Background Technology

[0002] Ethylene-vinyl acetate redispersible latex powder is produced by spray drying a polymer emulsion. It can be redispersed and dissolved in water, and is a polymer powder with properties similar to the original emulsion. Currently, this type of powder has the largest application volume in my country. As an important additive in dry-mixed mortar, the emulsion reduction performance of the redispersible latex powder is a crucial factor in its ability to retain the original emulsion's function and is a fundamental basis for its performance in mortar. In applications, "particle size range" is commonly used as an indicator of its ability to reduce to an emulsion. However, the size of the particle size range cannot fully characterize the quality of the redispersible latex powder's ability to reduce to an emulsion. For example, some powder particles may be larger in size due to the spray tower, but can still form a homogeneous emulsion well in aqueous solution. In such cases, the use of particle size range as a measure of the latex powder's ability to reduce to an emulsion is questionable. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems of the present invention, the present invention provides a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion, so as to solve the problem that the existing method of using particle size range as a consideration for the performance of latex powder in reducing it to an emulsion is inaccurate.

[0004] According to a first aspect of the present invention, the present invention provides a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion, comprising the following steps:

[0005] Step (1): Prepare a latex powder solution with a certain concentration by adding water to ethylene-vinyl acetate redispersible latex powder;

[0006] Step (2): After the prepared latex powder solution has been left to stand for a period of time, it is placed in a UV spectrophotometer to measure the transmittance. The transmittance curves after different standing times are plotted to obtain the transmittance value of the ethylene-vinyl acetate redispersible latex powder.

[0007] Step (3): Based on the transmittance curve trend and transmittance value, evaluate the performance of ethylene-vinyl acetate redispersible latex powder in reducing to emulsion and give corresponding application suggestions.

[0008] In the above scheme, the present invention provides a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion. First, the ethylene-vinyl acetate redispersible latex powder is prepared into a latex powder solution. Then, the transmittance value of the ethylene-vinyl acetate redispersible latex powder is measured. Finally, combining the transmittance curve trend and transmittance value, the performance of the ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion is evaluated, and corresponding application suggestions are given. Compared with the traditional consideration of "average particle size" or "fineness" indicators for the emulsion reducing properties of ethylene-vinyl acetate redispersible latex powder, the method of the present invention is convenient to operate, highly practical, produces stable test results, and has good reproducibility. It serves as a reference for the quality evaluation of ethylene-vinyl acetate redispersible latex powder in mortar applications.

[0009] Further, in step (1), the concentration of the latex powder solution is 0.0025%-0.005%.

[0010] In the above scheme, by limiting the concentration of the latex powder solution in step (1) to a reasonable range, it is beneficial to accurately measure the transmittance.

[0011] Furthermore, in step (1), the preparation is carried out using ultrasonic dispersion.

[0012] In the above scheme, the latex powder solution is prepared by using an ultrasonic dispersion method. The high-frequency vibration of ultrasound disperses the material into tiny particles, accelerates dissolution, and achieves a uniform mixing effect, which is beneficial for accurate measurement of light transmittance.

[0013] Furthermore, the ultrasonic dispersion time is 1 min-3 min, and the frequency is 1000 Hz-2000 Hz, preferably 1500 Hz.

[0014] In the above scheme, by limiting the time and frequency of ultrasonic dispersion within a reasonable range, it is more conducive to achieving a uniform mixing effect, and thus more conducive to accurately measuring the transmittance.

[0015] Furthermore, in step (2), the wavelength selected for the ultraviolet spectrophotometer is 550nm-650nm.

[0016] In the above scheme, selecting an appropriate wavelength for measurement is beneficial for accurately measuring transmittance.

[0017] Furthermore, in step (2), the wavelength selected for the ultraviolet spectrophotometer is 590 nm.

[0018] Furthermore, in step (2), the settling time is 1 min to 20 min.

[0019] In the above scheme, by limiting the standing time to a reasonable range, the transmittance at different standing times can be obtained, which is beneficial for drawing a complete transmittance curve and thus for accurately determining the transmittance of the latex powder solution.

[0020] Furthermore, in step (3), the criteria for evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion are as follows:

[0021] When the transmittance value is 30%-65%, the evaluation result is that the performance of reducing ethylene-vinyl acetate redispersible latex powder into emulsion is good, and normal use is recommended;

[0022] When the transmittance value is 66%-80%, the evaluation result is that the performance of reducing ethylene-vinyl acetate redispersible latex powder into an emulsion is poor and it cannot be used.

[0023] In the above scheme, the method of the present invention combines the transmittance curve trend and transmittance value to evaluate the performance of ethylene-vinyl acetate redispersible latex powder to be reduced into an emulsion, and the evaluation method is simple.

[0024] The technical solution provided by this invention has the following beneficial effects:

[0025] Compared to the traditional method of using "average particle size" or "fineness" as indicators to evaluate the performance of ethylene-vinyl acetate redispersible latex powder in reconstitution into an emulsion, the present invention provides a method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reconstitution into an emulsion. This method is convenient to operate, highly practical, produces stable test results, and has good reproducibility. It can serve as a reference for the quality evaluation of ethylene-vinyl acetate redispersible latex powder in mortar applications. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 The transmittance curve of ethylene-vinyl acetate redispersible latex powder A from Example 1 is shown.

[0028] Figure 2 The transmittance curve of ethylene-vinyl acetate redispersible latex powder B in Example 2 is shown.

[0029] Figure 3 The transmittance curve of ethylene-vinyl acetate redispersible latex powder C in Example 3 is shown.

[0030] Figure 4 This is the transmittance curve of ethylene-vinyl acetate redispersible latex powder D from Example 4.

[0031] Figure 5 The transmittance curve of ethylene-vinyl acetate redispersible latex powder E in Example 5 is shown.

[0032] Figure 6 The transmittance curve of ethylene-vinyl acetate redispersible latex powder F in Example 6 is shown.

[0033] Figure 7 This is the transmittance curve of ethylene-vinyl acetate redispersible latex powder G from Example 7. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Example 1

[0036] In this embodiment, an ethylene-vinyl acetate redispersible latex powder A was evaluated for its emulsion properties using the average particle size and the determination and evaluation methods of this invention.

[0037] (1) The average particle size D50 measured by the laser particle size analyzer is 112μm, which does not meet the requirement of GB / T29594-2013 that the average particle size is not greater than 100μm. According to the standard, it is judged as a non-conforming product.

[0038] (2) Add 0.015 g of ethylene-vinyl acetate redispersible latex powder A to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. The transmittance curve was plotted with the standing time and the transmittance of the ethylene-vinyl acetate redispersible latex powder as the X-axis and Y-axis, respectively. Figure 1 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder A can be determined. Its transmittance was measured to be 44% at 590 nm using a 756 spectrophotometer.

[0039] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder A were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The compressive strength of the mortar with and without ethylene-vinyl acetate redispersible latex powder A was measured to be 84% (industry limit not less than 70%), and the tensile bond strength ratio was 158% (industry limit not less than 140%), which is much higher than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder A of this embodiment can be determined to be a redispersible latex powder with good emulsion reduction performance and can be used normally.

[0040] Example 2

[0041] In this embodiment, an ethylene-vinyl acetate redispersible latex powder B was evaluated for its ability to be reduced to an emulsion using the average particle size and the determination and evaluation method of the present invention.

[0042] (1) The average particle size D50 measured by the laser particle size analyzer is 88μm, which meets the requirement of GB / T 29594-2013 that the average particle size is not greater than 100μm. According to the standard, it is judged to be a qualified product.

[0043] (2) Add 0.015 g of ethylene-vinyl acetate redispersible latex powder B to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. The transmittance curve was plotted with the standing time and the transmittance of the redispersible latex powder as the X-axis and Y-axis, respectively. Figure 2 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder B can be determined. Its transmittance was measured to be 73.2% at 590 nm using a 756 spectrophotometer.

[0044] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder B were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The compressive strength of the mortar with and without ethylene-vinyl acetate redispersible latex powder B was measured to be 72% (industry limit not less than 70%), and the tensile bond strength ratio was 134% (industry limit not less than 140%), which is lower than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder B in this embodiment is a redispersible latex powder with poor emulsion reducing properties, and cannot play a good modifying role in mortar, therefore it is unusable.

[0045] Example 3

[0046] In this embodiment, an ethylene-vinyl acetate redispersible latex powder C was evaluated for its ability to be reduced to an emulsion using the average particle size and the determination and evaluation method of the present invention.

[0047] (1) The average particle size D50 measured by the laser particle size analyzer is 74μm, which meets the requirement of GB / T 29594-2013 that the average particle size is not greater than 100μm. According to the standard, it is judged to be a qualified product.

[0048] (2) Add 0.015 g of ethylene-vinyl acetate redispersible latex powder C to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. The transmittance curve was plotted with the standing time and the transmittance of the redispersible latex powder as the X-axis and Y-axis, respectively. Figure 3 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder C can be determined. Its transmittance was measured to be 43% at 590 nm using a 756 spectrophotometer.

[0049] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder C were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The compressive strength of the mortar with and without ethylene-vinyl acetate redispersible latex powder C was measured to be 87% (industry limit not less than 70%), and the tensile bond strength ratio was 152% (industry limit not less than 140%), both higher than the industry average. Based on the measurement and evaluation methods of this invention, the ethylene-vinyl acetate redispersible latex powder C of this embodiment can be determined to be a redispersible latex powder with good emulsion reduction performance and can be used normally.

[0050] Example 4

[0051] Add 0.015 g of ethylene-vinyl acetate redispersible latex powder D to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. Transmittance curves were plotted with standing time and redispersible latex transmittance as the X and Y axes, respectively. Figure 4 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder D can be determined. Its transmittance was measured to be 30.2% at 590 nm using a 756 spectrophotometer.

[0052] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder D were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The tensile bond strength of the mortar with added ethylene-vinyl acetate redispersible latex powder D was measured to be 80% of the compressive strength of the mortar without added ethylene-vinyl acetate redispersible latex powder D (industry limit not less than 70%), and the tensile bond strength ratio was 149% (industry limit not less than 140%), both higher than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder D of this embodiment can be determined to be a redispersible latex powder with good emulsion reducing properties and can be used normally.

[0053] Example 5

[0054] Add 0.015 g of ethylene-vinyl acetate redispersible latex powder E to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. Transmittance curves were plotted with standing time and redispersible latex transmittance as the X and Y axes, respectively. Figure 5 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder E can be determined. Its transmittance was measured to be 64.6% at 590 nm using a 756 spectrophotometer.

[0055] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder E were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The tensile bond strength ratio of the mortar with added ethylene-vinyl acetate redispersible latex powder E to the compressive strength ratio of the mortar without added ethylene-vinyl acetate redispersible latex powder E was 76% (industry limit not less than 70%), and the tensile bond strength ratio was 142% (industry limit not less than 140%), which is higher than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder E of this embodiment can be determined to be a redispersible latex powder with good emulsion reduction performance and can be used normally.

[0056] Example 6

[0057] Add 0.015 g of ethylene-vinyl acetate redispersible latex powder F to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. Transmittance curves were plotted with standing time and redispersible latex transmittance as the X and Y axes, respectively. Figure 6 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder F can be determined. Its transmittance was measured to be 65.8% at 590 nm using a 756 spectrophotometer.

[0058] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder F were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The tensile bond strength ratio of the mortar with added ethylene-vinyl acetate redispersible latex powder F to the compressive strength ratio of the mortar without added ethylene-vinyl acetate redispersible latex powder F was 74% (industry limit not less than 70%), and the tensile bond strength ratio was 136% (industry limit not less than 140%), which is lower than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder F in this embodiment is a redispersible latex powder with poor emulsion reducing properties and is unusable.

[0059] Example 7

[0060] Add 0.015 g of ethylene-vinyl acetate redispersible latex powder G to 400 ml of deionized water and ultrasonically disperse at 1500 Hz for 1 min to obtain a latex powder solution. At the same concentration, the latex powder solution was allowed to stand for 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, and 20 min, respectively. The transmittance of the latex powder solution at 590 nm was measured using a 756 spectrophotometer. Transmittance curves were plotted with standing time and redispersible latex transmittance as the X and Y axes, respectively. Figure 7 As shown, once the transmittance curve trend stabilizes, the transmittance value of ethylene-vinyl acetate redispersible latex powder G can be determined. Its transmittance was measured to be 79.4% at 590 nm using a 756 spectrophotometer.

[0061] 450g of reference cement, 1350g of standard sieved sand, and 36g of ethylene-vinyl acetate redispersible latex powder G were premixed evenly. A certain amount of water was added, and the mortar flowability was controlled at (170±5) mm. Mortar test blocks were prepared. The tensile bond strength ratio of the mortar with added ethylene-vinyl acetate redispersible latex powder G to the compressive strength ratio of the mortar without added ethylene-vinyl acetate redispersible latex powder G was 78% (industry limit not less than 70%), and the tensile bond strength ratio was 130% (industry limit not less than 140%), which is lower than the industry average. Based on the measurement and evaluation method of this invention, the ethylene-vinyl acetate redispersible latex powder G in this embodiment is a redispersible latex powder with poor emulsion reducing properties, which cannot meet the application requirements and is therefore unusable.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining and evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion, characterized in that, Includes the following steps: Step (1): Prepare a latex powder solution with a certain concentration by adding water to ethylene-vinyl acetate redispersible latex powder; Step (2): After the prepared latex powder solution has been left to stand for a period of time, it is placed in an ultraviolet spectrophotometer to measure the transmittance. The transmittance curves after different standing times are plotted to obtain the transmittance value of the ethylene-vinyl acetate redispersible latex powder. Step (3): Based on the transmittance curve trend and transmittance value, evaluate the performance of ethylene-vinyl acetate redispersible latex powder in reducing to emulsion and give corresponding application suggestions. In step (1), the concentration of the latex powder solution is 0.0025%-0.005%; In step (3), the criteria for evaluating the performance of ethylene-vinyl acetate redispersible latex powder in reducing it to an emulsion are as follows: When the transmittance value is 30%-65%, the evaluation result is that the performance of reducing ethylene-vinyl acetate redispersible latex powder into emulsion is good, and normal use is recommended; When the transmittance value is 66%-80%, the evaluation result is that the performance of reducing ethylene-vinyl acetate redispersible latex powder into an emulsion is poor and it cannot be used.

2. The determination and evaluation method according to claim 1, characterized in that, In step (1), ultrasonic dispersion is used for preparation.

3. The determination and evaluation method according to claim 2, characterized in that, The ultrasonic dispersion time is 1 min-3 min, and the frequency is 1000 Hz-2000 Hz.

4. The determination and evaluation method according to claim 1, characterized in that, In step (2), the wavelength selected for the ultraviolet spectrophotometer is 550nm-650nm.

5. The determination and evaluation method according to claim 4, characterized in that, In step (2), the wavelength selected for the ultraviolet spectrophotometer is 590 nm.

6. The determination and evaluation method according to claim 1, characterized in that, In step (2), the settling time is 1 min to 20 min.

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