Zhang Gao Feng
(Sichuan Wilbur Chemical Co., Ltd.)
Preface
The main body of polymer emulsion used for building coatings is synthesized by adding (methyl) acrylic acid, (methyl) acrylate, styrene and other monomers with surfactant and initiator through emulsion polymerization. All these polymers have a certain glass transition temperature (TG) and a minimum film formation temperature (MFT). If the emulsion is lower than the minimum film forming temperature, it will not form a continuous film, that is, it has no use value.
In order to improve its film-forming performance, it is necessary to add suitable film-forming additives to help its real use value. Starting from the development of polymer emulsion, people are constantly choosing various materials as film forming auxiliaries. Therefore, film forming AIDS play an important role in emulsion coatings, which can reduce the film forming temperature of building emulsion coatings and improve the film forming performance of building emulsion coatings. Emulsion paint is mainly a mixture of water dispersion of polymer particles and pigment particles. But they do not have good construction performance, so it is difficult to get good paint film. It is necessary to add various additives to achieve the required construction performance and film-forming quality, and film-forming additives are one of the most important additives in latex paint. At present, the only way which must be passed is to define the definition of VOC. On the critical boundary (250 degrees is the boundary line), the use of high boiling film forming aids to assist the emulsion to form an effective film (boiling point up to 280 degrees or more) is imperative.
In this paper, the author combines the mechanism of emulsion formation, the rational selection of film forming AIDS, the function of film forming AIDS and their influencing factors for many years. The key points are reasonable recommendation and selection techniques, the use of high boiling point environmental protection film forming auxiliaries in architectural coatings, and the specific data obtained from the practical formula.
One
It is imperative to choose suitable film builder for building coating emulsion.
With the improvement of people's living standards, and the increasingly high requirements for environmental protection of coatings in China's chemical industry, especially the strict control of volatile organic compounds (VOC limit), the higher choice of film-forming additives, high boiling point environmental protection film-forming additives have become the choice and demand of many coating manufacturers. With the introduction of the new national mandatory standard (GB18582), the latest definition of the initial boiling point of organic compounds (VOC), the choice of environmentally friendly high boiling point film forming AIDS in building emulsion, these are the R & D personnel and material suppliers of our coatings industry to innovate and develop.
Two
Selection and evaluation of high boiling point environmental friendly film forming AIDS
1. Detection of core technical indicators of high boiling point film forming AIDS (in combination with film forming AIDS brands in the market, select 4 brands of products for the same period)
Table 1. Detection of technical core indexes of high boiling point film forming AIDS
The evaluation results show that: the odor and film-forming efficiency are carried out according to the standard of 1-5, 5 points for the best and 1 point for the worst.
1-1, film forming efficiency (market comparison of styrene acrylic emulsion).
Figure 1. Film forming efficiency
Description: product A products /B performance basically the same, after emulsion membrane drying surface cracks less, C/ products D products appear more cracks, it can be confirmed that different film forming AIDS in the same emulsion, film efficiency has influence, in other words, different film forming AIDS on the emulsion film efficiency has an impact, and relatively large.
1-2 hydrolysis stability test
Table 2 hydrolysis stability test
Note: the overall viscosity and pH value do not change much, both belong to the normal range. The main purpose of this test is to test the application of film forming auxiliaries in emulsion coatings. Because of their poor hydrolysis stability, they are easy to hydrolyze, resulting in hydrolysis of the small components in the film forming AIDS, and complaints of quality problems caused by odor caused by emulsion paint.
2. Application and evaluation of high boiling point environmental protection film builder in emulsion architectural coatings.
2-1. Formulation design of emulsion architectural coatings (test recommended formulation 78%PVC, interior wall latex selection of styrene acrylic emulsion commonly used in the market).
The recommended formula is based on the common formula in the market. The overall formula design meets the needs of most customers. On the same basis, PK test is carried out
Table 3 formula of common architectural coatings
2-2. Detection of finished products of emulsion architectural coatings and design of year-on-year items.
Table 4, design of finished products for emulsion architectural coatings
2-3 comparison of specific test data of each project
2-3-1, preparation of emulsion architectural coatings, basic performance test data comparison:
Table 5. Comparison of basic performance test data of emulsion architectural coatings
2-3-2, preparation of emulsion architectural coatings dry film performance test data comparison:
L low temperature film formation - (see figure below)
Fig. 2 low temperature film formation
The results show that the four samples can form film at low temperature without cracking, and the thick film drying at low temperature is normal.
L water resistance of paint film (see the figure below)
　　　
Fig. 3 water resistance of paint film
Dry for 1 day and soak in water for 7 days
Dry for 7 days and soak in water for 7 days
Note: the four samples dried for 1 day and 7 days have no blistering and falling off after soaking, and have good water resistance.
L paint film powder off at low temperature (see the figure below)
Fig. 4 low temperature powder removal test of paint film
Wipe the board with dry cloth, ten times for each board (left), ten times for each board (right)
　
Product C & gt; product B & gt; product A & gt; product D product C & gt; product B & gt; product A & gt; product D
Note: according to the test results of low temperature powder loss of paint film, product D performs the worst in this area. The choice of film builder agent for emulsion architectural coatings affects the paint film drying at low temperature quickly or slowly, and ultimately affects the film forming performance of lacquer at low temperature.
L color development of paint film (see the figure below)
Fig. 5 test of color development of paint film
　
Note: after the standard finger grind is adopted, the color development is tested by drying. The selected organic color paste and inorganic color paste perform well without obvious difference
L scrub test (3, 5, 7 days)
Table 6. Scrub resistance test
Note: compared with the same period of last year's test, product a and product D showed an upward trend, while the other two decreased with time, and product D, the environmental friendly film-forming assistant with high boiling point and overall washability, performed the best.
Table 7. Scrub resistance test
Note: according to the comparison of relative value year-on-year test, according to product a as the standard, compared with the other three, it is proportional to the absolute value year-on-year, but the overall washability is still the best performance of product D.
L film anti stickiness (see figure below)
Figure 6. Film anti stickiness
Note: through the test of anti backtack, the paint films of the four samples are intact without backtack
L storage stability
Table 8 storage stability
Note: the higher the score, the better the storage performance. Compared with the same period of last year, product D has the best overall thermal storage stability, and other storage properties are basically the same. From the above data, it is concluded that the choice of film builder for emulsion architectural coatings has great influence on its stability.
L paint construction brush sluggish
Table 9 paint construction brush hysteresis
Note: from the above data, the brush's sluggish performance: the lightest net weight of residual paint is the best, the heaviest is the worst, product D is slightly worse than product a and product B, and product C is the worst. In this test, the film builder used in emulsion architectural coatings also has great influence.
2-4. Summary of year-on-year evaluation results of each project
Table 10 year on year evaluation results of each project
The comprehensive score of the 13 items is summarized. The overall performance of the product D is the best. It is also suitable for the application of the current emulsion architectural coatings, but there are still some shortcomings, especially the low temperature dry and wet erasability.
Three
Summary of final test conclusion
In this paper, the high boiling point environmental protection film forming auxiliaries are applied to the emulsion architectural coatings for comprehensive analysis and reasonable application, but only for high PVC coatings, the test application is not comprehensive. At the same time, the film assistant products in the data are also numbered instead. In the determination of market styrene acrylate as the test emulsion, its formulation design only adjusts the products of film forming AIDS, and the other has not changed. The above data obtained under the same conditions, platform and standard should be considered fair and just. Database for technical research and development personnel reference, does not mean the conclusion, of course, if there are better methods and skills, communication with the author, thank you.
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