Method research on the standard of stain resistance of interior wall coatings

Since the beginning of the 21st century, China's paint industry has made rapid and rapid development, building coatings, industrial coatings, such as the output value and sales of record highs, in the development of the national economy has played an important role. In the construction coatings which are closely related to people's daily life, the stain resistance of interior wall coatings has been paid more and more attention by end consumers, and has become one of the main indicators to evaluate the performance of interior wall coatings.
the anti-fouling properties of the inner wall coating to a large extent determines the decorative effect of the coating film in the process of use,
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. Coatings with excellent anti-fouling properties can not only maintain the long-lasting brightness of the paint decoration effect, but also extend the time interval for coating reapplying, greatly saving human and material costs, reducing waste of resources and reducing environmental pressure. Unfortunately, at present, the domestic architectural coatings industry has no clear testing methods and standards. The anti-fouling performance of inner wall coatings in the market is not defined by uniform indicators, which not only can not meet the needs of consumers, but also is not conducive to the industry quality regulatory authorities and consumers to distinguish the performance of interior wall coatings.
abroad, the industrial developed countries in Europe and the United States attach great importance to the evaluation and research of the anti-fouling properties of building interior wall coatings. In the United States, building interior wall coatings have ASTMD3450, ASTM D4828, ASTM D6578 and other national standards, coating stain resistance and washability assessment, so that the products on the market have a fair and transparent evaluation method; According to these national standards, the famous Consumer Report magazine in the United States continuously compares market products and publishes test results to guide consumers in choosing coatings.
through the study of foreign standards found that foreign testing and evaluation methods and the actual situation at home some differences, in the operation and the representativeness of the selected stains need to be further improved. For example, ASTM D3450 selects only a mixture of carbon black and mineral oil as the only test stain, which makes it difficult to say that the stain represents the most common life stain in people's homes; ASTM D4828 Although 7 life stains such as pencils, ballpoint pens, red potions, water-based marker pens, crayons, lipsticks and a mixture of carbon black and mineral oil are recommended, and after wiping these stains, record the gloss change of the coating film (5 levels), color There are three indicators of variation (5 levels) and breakage (3 levels), but the standard does not regulate these stains: for example, the removability of different brands of ballpoint pens varies widely, making it difficult to guarantee the reproducibility and comparability of test results from different testing
institutions; ASTM D6578 is a test of the graffiti resistance of exterior paint, and the required stains do not represent common life stains. In view of this, this study carried out a study on the building interior wall paint stain resistance testing methods, with a view to establishing a set of in line with China's national conditions and effective standard testing methods, so as to promote the field of architectural coatings to return to consumer-oriented, quality-driven development direction.
1 Stain resistance assessment of interior wall coatings
This study selected common indoor stains as the source of pollution, taking into account the stability and standardity of the source of stains, but also selected some representative single chemical components as the source of pollution, such as alcohol-soluble black CAS 8005 - 02 - 5, this single chemical is the main component used in many oily pens. Apply various stains to a well-maintained coating surface in a standardized coating method, then clean the coating stains with scrub equipment, and test the Y-value (reflectivity) changes before and after the coating is contaminated with a reflectivity tester. Finally, the test results of a variety of selected stains are comprehensively evaluated, and the stain resistance data of the inner wall coating are given.
1. 1 Test instruments and materials
reflectivity tester: in accordance with GB/T 23981-2009 in 4. 1 prescribed tester, Shanghai Modern Environmental Engineering Technology Co., Ltd.; Paint film coater: made of stainless steel, its specifications of 150 m gap, Shanghai Modern Environmental Engineering Technology Co., Ltd.; wash-resistant tester: tester in line with GB/T 9266 regulations, where the test head requirements see Figure 1, Guangzhou Standard Geda Laboratory Equipment Co., Ltd.; Medical skimmed gauze: meets the requirements of YY0331 - 2002; Black polyolefin sheet: Self-made with reference to the plastic sheet specified in the ASTM D2486 - 06 method at 0.25 mm × 432 mm × 165 mm.
the stain resistance test grinding head schematic of the inner wall paint
1. 2 Experiment stains and preparation
(1) green tea: take GB/T 24690-2009 green tea 2 g to add 100 mL boiling water, water quality should comply with GB/T 6682 in the three-level water regulations, soak 30 min to remove the tea bag, cooling spare, using the Leighton brand green tea bag.
(2) vinegar, in accordance with GB/T 18623-2011 regulations. Use Zhenjiang Hengshun brand to eat vinegar.
(3) blue and black ink, QB/T 1745. 1-2011. Use hero brand blue and black ink (number 202).
(4) black neutral water pen: QB/T 1655-2006 standard, using real color brand water pen.
(5) black liquid shoe polish: QB/T2478-2007 compliant, using Redbird liquid shoe polish.
(6) black oily marker pen: QB/T 2777-2006 compliant, using a real color marker pen.
(7) black crayons: QB/T 1336 compliant, using Mapede crayons.
(8) water-soluble melanin: 3% aqueous melanin with CAS 8005 - 03 - 6. According to the calculated amount of water into the container, in the mixing conditions slowly added water-soluble melanin, water and water-soluble melanin mass ratio of 97:3, after adding continue to stir fully, to ensure that melanin completely dissolved. It is recommended to prepare a backup in advance of 24 h, and the use of the prepared solution is valid for 168 h.
(9) Alcohol-soluble melanin: a 10% solution with CAS 8005 - 02 - 5 alcohol-soluble melanin, 30% ethanol and 70% water (mass ratio) mixed solution. According to the calculated amount of water into the container, stirring at the same time add ethanol (analytical pure), mixed evenly after slow addition of alcohol-soluble melanin, water, ethanol, alcohol-soluble melanin mass ratio of 63:27:10, after the addition continued to stir fully, to ensure that melanin completely dissolved. It is recommended to prepare a backup 24 h in advance, and the use of the prepared solution is valid for 168 h.
(10) Vieslin carbon black mixture: add (8 ± 0. 1) g code CAS No. 8052 - 41 - 3 dry cleaning solvent oil and (2.0 ± 0. 1) g in accordance with GB/T 7044-2003, code-named CAS 1333 - 86 - 4 of the medium pigment carbon black (using Yongfeng brand, brand Powcarbon2429G - W). Stir well with a magnetic mixer and add (90 ± 0. 1) g GB/T 1790-1994 medical white Vaselin grease is placed in an oven (70 ± 2) degrees C to heat 30 min until melted into liquid, removed and added to the above dry cleaning solvent oil and carbon black mixture with high-speed dispersion (speed 500 to 600 r /min) fully mixed. Place the mixed stains at room temperature in the laboratory until the stains are solidified. Use is valid for 168 h.
(11) black tea: the test liquid is black tea, take GB/T 24690-2009 black tea 2 g to add 100 mL boiling water, water quality should comply with GB/T 6682 water regulations. Soak 30 min Remove the tea bag, cool the spare, and use the Lytton black tea bag.
1. 3 Test methods
1. 3. 1 Experimental conditions
laboratory temperature: (23 ± 2) degrees C, relative humidity: (50 ± 5).
1. 3. 2 Sample preparation
the experimental sample is evenly coated on a black polyolefin plastic substrate with a 150 m wet film preparer and dried at 168 h.
(a) liquid stain coating
all but Vieslin carbon black mixture are liquid stains. In the parallel direction of the short edge of the test board, the middle part of the coating film is drawn out with 2B pencils in three sections, each section is 20 mm wide, the coating stains, 2 stains are separated by 20 to 30 mm. One test plate for each source of contamination and 3 stains on each plate. The coating shape is shown in Figure 2. When coating, cut the medical gauze into a 120 mm × 20 mm strip and cover the test area with 2 gauze strips. Before coating, stir the stains evenly, and drop the 3 mL liquid stains evenly on the gauze, fully soaking the gauze. Place the stained lacquer film test (along with the liquid-stained gauze strip on the surface of the coating) at 2 h under GB/T 9278 conditions. Remove the gauze carefully. Be careful not to contaminate the coating outside the test area or damage the coating of the test area. Rinse the coating film 20 s with tap water to prevent free stain interaction during the test from affecting the test results and draining for use.
of the coating after the coating test stains
(b) solid stain coating
solid stains: Vieslin carbon black mixture. Cut the polyolefin black plastic diaphragm into 160 mm × 50 mm × 0. The 25 mm rectangle is used as a mold and the inner cavity size is 100 mm × 20 mm, as shown in Figure 3.
Vieslin carbon black mixture coating mold schematic
place the mold in the coating test area, apply stains in the cavity area of the mold, remove the mold placed 2 h, use a paper towel to remove the stain on the surface of the coating film, to be used. When coating stains, care should be taken not to damage the coating film.
1. 3. 3 Experimental step
Test the film reflectivity with a reflectivity tester in the middle of the selected area, testing the film reflectivity once per segment, if the relative error between the 3 results is less than 5%, take the arithmetic average of the 3 test results and record them as Y0. The test plate coating is oriented up, fixed horizontally to the test bench of the wash-resistant tester, the medical gauze is cut into a 90 mm × 50 mm strip, overlapping and fixed to the brush-resistant tester's grinding head for scrub testing. After scrubbing, rinse the test tablets with flowing tap water for 20 s and, after the end, use a paper towel to absorb the remaining water from the surface and place them dry. In the middle part of the contaminated area with a reflectivity tester to test the film reflectivity, each section of the region test 1 time, if the relative error between the 3 results is less than 5%, then take the arithmetic average of 3 test results, recorded as Y1.
1. 3. 4 Calculating
the stain resistance of the coating film to a single stain

: X-coated film on a single stain of stain resistance, retain 3-bit valid value, %; Y1 - Average reflectivity value after testing in the test area; Y0 - The initial average reflectivity value of the test area.
, according to the coating ability to remove various stains, the coating film resistance to a single stain is divided into 1 to 10 levels (i.e. the score value R 1 to 10 points). The X value corresponding to level 1 is the initial value of each stain coating on the paint film, i.e. there is no removal capacity for the stain. Level 10 represents the highest stain removal rate, which is equivalent to removing the vast majority of stains. At the same time, combined with the color card grading standards and the degree of distinction between the naked eye, according to the depth of the stain differentiation grading, that is, when the stain is relatively dark color, the grade difference correspondingly larger, with the improvement of the ability to remove dirt, the higher the grade, the smaller the grade difference.
to determine the score value of the coating film for the stain according to the range of X, refer to Table 1.
of each stain score standard
(2) coating resistance comprehensive evaluation
coating stain resistance comprehensive evaluation by type (2).
: R'-coated film anti-fouling ability, retain 2 bits of valid values; Ri-Coated film's rating of the ith stain; n - The amount of stain.
2 Results and discussions
2. 1 Determination of the test method
2. 1. 1 Determination of brush head quality and number of scrubs
In order to verify the operability of the method, the experiment followed the original wash-resistant tester, but only the brush head was modified for operability, as shown in Figure 1. The quality of the brush head is 1. 0 kg, 1. 5 kg, 2. 0 kg, 100, 200, 300 scrub tests for coatings, as seen in Table 2.
the quality of the brush head and the number of scrubs
according to the test results, a brush head of 1.5 kg was selected for testing and scrubbed 200 times as the experimental cycle.
2. 1. 2 Paint wash-resistant performance determination
taking into account the relatively poor quality paint due to the coating brush broken, will be taken away with stains, resulting in test errors, in order to avoid this situation, the product required to test with this method first through the internal wall paint superior GB/T 9756-2009 wash resistance requirements.
2. 1. 3 Scrub tool selection
scrub tool selection requirements are no damage to the coating film, reproducible good. For example, the brush is easy to damage the coating film, resulting in a large deviation of test data; Sponges with different densities and hardnesses can also cause differences in test results due to the lack of uniform standards, and poor quality sponges themselves are prone to damage during testing.
gauze has the appropriate standards to regulate (YY0331 - 2002 medical strip).