Rapid test method analysis of calcium ion stability with emulsion in architectural coatings

0 Introduction
latex paint is based on emulsion used in architectural coatings, water as a dispersion medium, added pigments and additives, after a certain process made of coatings. The emulsion used in architectural coatings is the core of latex paint, which binds the components of latex paint together to form a film that is firmly attached to the base. Because emulsion is a polymer dispersed into water in the form of particles, emulsion system is in a thermodynamic sub-stable state, therefore, high-priced electrons, dielectrics, strong mechanical action, low temperature and high temperature, long-term placement, etc., may destabilize the system and lead to broken milk and flocculation

. In the People's Republic of China national standard GB/T 20623-2006 "building coating emulsion" on the emulsion "calcium ion stability" made clear requirements, and standardized testing methods. Through the observation of the latex paint production process and the characteristics of latex paint production equipment, this paper designs a set of rapid detection methods for the stability of calcium ions in emulsions, and compares and analyzes them with the corresponding test methods in the national standard.
1 Test Part
1.1 Experimental Instruments
Dispersion Machine: GFJ-0.4, Shanghai Modern Environmental Engineering Technology Co., Ltd.; Shanghai Modern Environmental Engineering Technology Co., Ltd.; Filter: 80, Hangzhou Daheng Filter Co., Ltd.; Thermometer: 0 to 110 degrees C, Shanghai Glass Instrument Factory; Fine Plate: 0 to 200 m, Shanghai Modern Environmental Engineering Technology Co., Ltd.
1.2 Experimental drug
phenylpropanine emulsion: homemade; film-forming additives: TEXANOL, Qiru Eastman Fine Chemical Co., Ltd.; Heavy calcium carbonate: 1,000, Guangfu Building materials (banana Ridge) refining Co., Ltd.; dispersant SN5040: San Nopco Chemical; Titanium white powder R706: DuPont Titanium Technology (China) Co., Ltd.; cellulose 250 HBR: Aslan Group.
2 Test step
2.1 This test test method
(1) weighs 500 g emulsion with an electronic scale.
(2) filter 500 g lotion with an 80 mesh filter.
(3) pour the filtered emulsion into a stainless steel cup of 1 L.
(4) place the cup containing the lotion in a heated water bath pot at 50 degrees C.
(5) will disperse the disc to 1/3 below the emulsion surface.
(6) turn on the dispersor and adjust the speed to 1,000 r/min.
(7) test the temperature of the emulsion with a thermometer and slowly pour in textANOL 50 g when it reaches 50 degrees C.
(8) continue to spread over 2 min and slowly pour in 500 g of heavy calcium carbonate.
(9) heavy calcium carbonate is added, starts the timing, and stops dispersing after 30 min.
(10) filters the mixed liquid with an 80-mesh filter. And rinse with water. Observe if there are visual sieve residues.
note: (1) the heavy calcium carbonate itself 80 mesh sieve residue to reach 0%, can be used. (2) When testing to step 7 of this method, do not aggravate calcium carbonate, disperse 30 min after filtration, no flocculation.
2.2 National Standard Test Method
In the People's Republic of China national standard GB/T 20623-2006 "Building Coating Emulsion" 4.11 Calcium ion stability test method is: add 30 in the small beech mL emulsion, then add a mass score of 0.5% CaCl2 solution 6 mL, stirred and placed in a 50 mL plug drum, 48 h, to observe the phenomenon of layering, precipitation, flocculation and so on. With the help of a glass rod, the sample can be coated on the glass plate into a uniform thin layer to observe the presence of flocculation.
2.3 paint preparation
(1) inject 300 to 350 g of water into 1 L stainless steel cups.
(2) turn on the disperser to 200 r/min and slowly add 5 to 6 g cellulose.
(3) the speed of the dispersion machine is increased to 2,000 r/min, with 5 to 6 g dispersant, 50 to 100 g titanium white powder, 400 to 450 g calcium carbonate.
(4) disperse 20 min, reduce the speed to 1,000 r/min, add 150 to 200 g emulsion, 10 to 20 g film-forming additives.
dispersion after (5) 5 min and test the fineness when cooling down to (25±2) degrees C.
3 Data Analysis
the effect of calcium ion stability on paint fineness in emulsion can be found in Table 1.
can be clearly seen by Table 1:
(1) analysis from the test results of emulsion A/emulsion B/emulsion C. When the calcium ion stability of the emulsion passes the national standard and passes the test standard of this method, the latex paint made by the emulsion is fine ≤60 m, and the coating film feels smooth and delicate.
(2) analysis of test results from emulsion D/emulsion E/emulsion F. When the calcium ion stability of the emulsion through the national standard standard and may not be able to pass the test standard, the corresponding emulsion paint fineness index has become coarser, paint film feel has a clear grainy feel. This shows that this test method and standard is closer to the actual production requirements.
(3) analysis of test results from emulsion G/Emulsion H/Emulsion I. When the calcium ion stability of emulsion fails to pass the national standard, it must pass the standard of this test method. When the corresponding emulsion is painted, the fineness is poor and the film feels very rough. Therefore, there will not be a lotion did not pass the national standard standard, but through the test method standard misjudgment.
This test method can better reflect the actual production due to the calcium ion stability of emulsion is not good, and make the corresponding emulsion made latex paint fineness difference, the reasons are as follows:
(1) test temperature is different, the national standard test method is carried out at room temperature, this test method is carried out under the conditions of 50 degrees C. In the actual production, due to high-speed dispersion between the powder particles shear friction, resulting in a large amount of heat. Latex paint production equipment is generally not equipped with cooling circulation device, which makes the emulsion added to a large number of powder-based slurry, the temperature is higher, after repeated testing at about 50 degrees C.
(2) different alkaline medium, the national standard test method is to the mass score of 0.5% CaCl2 solution as the alkaline test substance, this test method to heavy calcium carbonate as the alkaline test substance. In the actual production formula of latex paint, a large amount of heavy calcium carbonate is often added as a filling.
(3) Auxiliary reagents are different, the national standard test method does not have auxiliary reagents, and in this test method, the addition of film-forming additive TEXTANOL (2,2,4-3 methyl-1,3 glycol monochloride) is a strong solvent, although the individual effect is difficult to break the emulsion, but under the action of a stronger solvent, heavy calcium carbonate makes the emulsion more sensitive. In the actual production of latex paint, the use of TEXANOL is more common because the finished latex paint can be filmed at more than 5 degrees C, often adding a certain amount of film-forming additives to the formula.
4 Conclusion
building coatings use emulsion as the main raw material in latex paint, which plays a vital role in the quality of latex paint. The indicator of "calcium ion stability" of emulsion affects the fineness of latex after it has been painted into film. In the National Standard GB/T 20623-2006 "Building Coating Emulsion" of the People's Republic of China, the test method and determination criteria for the stability of calcium ions in emulsions are clearly defined, but the test time is longer, it takes more than 48 h. The test method provided in this paper can accurately determine whether the calcium ion stability of the emulsion to be tested is qualified within 2 h. It provides a faster and more practical method for quality managers to quickly detect the stability of calcium ions in emulsions.