CHENG Yang-pei, ZHANG Cai-mei
(Shunde BATF Industrial Co., Ltd., Foshan 528322, Guangdong, China)
Abstract: By comparing the homogeneous structure of the latex particles with the core-shell structure, it is determined that the dust mite resistant function of the industrial lanolin is obviously related to the structure of the latex particles. But in order to meet the national standard of the inner wall scrubbing resistance, it is determined that when the lanolin dosage is 3%(wt%), the silane coupling agent in the core layer is 0.3%(wt%) and the silane coupling agent in the shell layer is 0.2%(wt%) and that when the core-shell ratio is 3∶7, the dust mite repellency rate of the final emulsion is over 60% and the paint film scrubbing resistance meets the national standard.
With the advent of the intelligent era, the intelligence of the coatings field has gradually attracted attention. The concept of the intelligent coating is proposed. Compared with the one-way traditional coatings that only have protection and decoration functions, the intelligent coatings have one or more special properties in addition to the protection and decoration functions. Therefore, the intelligent coatings It is more able to adapt to the needs of a diversified market, and can carry out controlled positive feedback on the external environment of different needs. Dust mites belong to the family Eugenidae, Chiggeridae, and 34 species have been recorded. Among them, the main species related to human allergic diseases are house dust mites, dust mites, and European mites. Dust mites can not only cause asthma and chest tightness in people, but also easily cause people’s skin to be allergic or suffer from allergic dermatitis. It is worth noting that dust mites are also a vector of various worm diseases.
In response to the current market demand for the dust mite function of coatings, this article uses a method of adding industrial grade lanolin and a core-shell emulsion polymerization process to make a dust mite acrylic emulsion with good basic properties such as adhesion, water resistance, and scrub resistance. It has given acrylic emulsions new functionality, improved the concept of coatings, and expanded the functional boundaries of emulsions, greatly promoting the development of smart emulsions. This product currently has a certain application in the market, mainly used in the bedroom wall paint of consumers with special needs.
1.1 Experimental raw materials (see Table 1)
1.2 Experimental equipment (see Table 2)
1.3 Polymerization process
1.3.1 Reference formula for emulsion preparation (see Table 3)
Table 3 The final solid content of the emulsion = 48% ± 0.5%.
1.3.2 Preparation of pre-emulsion liquid
Weigh the formula amount of anionic emulsifier in the pre-emulsification tank, then weigh the formula amount of deionized water, put the pre-emulsion tank in a mixer, and wait for the anionic emulsification in the pre-emulsification tank. After the agent is completely dissolved, the formulated amounts of styrene, n-butyl acrylate, and acrylic acid are poured into the pre-emulsification tank in order and dispersed and stirred. After stirring for 30 minutes, stop the stirring and remove 5% of the pre-emulsion from the pre-emulsification tank. Emulsion in a small beaker, the remaining pre-emulsion is divided into two components a, b, respectively placed in different mixers and stirred, and then vinyl triethoxysilane and industrial Grade lanolin, add vinyltriethoxysilane to component b, and continue stirring for 30 min.
1.3.3 Preparation of seed emulsion
Use a beaker to weigh the formulated amount of anionic emulsifier, use a certain amount of deionized water, and stir to dissolve the anionic emulsifier in the beaker with a glass rod. After the anionic emulsifier is completely dissolved, dissolve the anionic emulsifier in the beaker. The anionic emulsifier aqueous solution was poured into a 500 mL four-necked flask, and then rinsed with the bottom water of the kettle several times, and a small amount of water was retained as the rinse water, and then sodium bicarbonate was put into the bottom of the kettle.
Adjust the automatic temperature controller to make the temperature inside the flask reach 87-89 ° C, then pour 5% pre-emulsion into the bottom of the kettle at once, rinse with the reserved flushing water, and then pour the initial introduction into the kettle at one time. Bottom, and rinse with the reserved flushing water, keep the system for 30 minutes, until the appearance of the emulsion in the reaction kettle turns blue.
1.3.4 Experimental process flow
After the preparation of the seed emulsion is completed, pre-emulsion a and pre-emulsion b are added dropwise in order, and the pre-emulsion in the pre-emulsification tank and the initiator are simultaneously added into the reaction kettle for a total of 180 min. During the dropwise addition, the internal temperature is maintained at 87-89 ° C; after the dropwise addition is completed, the temperature is maintained for 40 minutes; then the temperature is lowered to 70-75 ° C and post-treatment is performed. The oxidant and the reducing agent are simultaneously added dropwise, and the dropwise addition is continued for 30 minutes. During the dropwise addition, the temperature was maintained at 70 to 75 ° C. After the dropwise addition, the temperature was maintained for 30 minutes. After the temperature was lowered to below 50 ° C, the neutralizer was added dropwise for 30 minutes and then kept for 10 minutes. Then the non-ionic emulsifier was put into the reaction kettle. , Stir for 10 min; finally filter and discharge.
1.4 Detection of Dust Mite Emulsion
1.4.1 Reference formula for coating test (see Table 4)
The PVC of the coating system in Table 5 is 47.7%.
1.4.2 Testing standards for interior wall emulsions
According to GB / T 9756-2009 “Synthetic Resin Emulsion Interior Wall Coatings”, the scrub resistance evaluation of the coatings is conducted to determine whether the self-made emulsion can be applied to interior wall coatings.
18.104.22.168 The scrubbing resistance test method of the coating film refers to GB / T 9756-2009 “Synthetic Resin Emulsion Interior Wall Coatings”.
On an asbestos-free fiber cement flat plate (430 mm × 150 mm × 6 mm), a 120 μm wire rod is used. The first coating film was prepared, and after curing at room temperature for 6 hours, the second coating film was prepared with a wire rod of 80 μm, and the curing film was cured at room temperature for 7 d. After the curing is finished, the asbestos-free fiber cement slab with coating film is placed in the scrub resistance tester specified in GB / T 9266-2009 for scrub resistance test. The test is performed twice in parallel. The average value of the two tests is taken as the final coating film. Scrub resistant results.
22.214.171.124 Evaluation criteria for scrub resistance of coating film
According to GB / T 9756-2009 “Synthetic Resin Emulsion Interior Wall Coatings”, the scrub resistance evaluation standards for coating film are shown in Table 5.
1.4.3 Detection standards for dust mites
According to the relevant national detection standards for dust mites GB / T 24253-2009 “Evaluation of the anti-mite performance of textiles”, the dust mite repellency rate indicators are used to evaluate the protective effect of the emulsion on dust mites. (Tested by a third party).
126.96.36.199 The principle of detection of dust-proof mites on the coating film
refers to GB / T 24253-2009 “Evaluation of Anti-mite Performance of Textiles”. Put the sample and the control sample in a petri dish respectively, and contact the mites at the same time under specified conditions. After a certain period of incubation, the number of mites living in the sample dish and the control dish was counted. According to the experimental method used, the mite repellent rate or mite suppression rate was calculated to evaluate the anti-mite effect of the coating film. .
188.8.131.52 Evaluation Standards for Dust Mites in Coatings
According to GB / T 24253-2009 “Evaluation of Anti-mite Performance in Textiles”, the evaluation standards for dust mites in coatings are shown in Table 6.
1.4.4 Test method for polymer slag output
After the emulsion reaction is completed, the emulsion is cooled to below 50 ° C, the emulsion is filtered with a layer of 350 mesh filter cloth, and the material that does not pass through the filter cloth into the discharge bucket is sucked with filter paper. Dry moisture is weighed in an analytical balance and the corresponding data is recorded.
2 Results and discussion
2.1 Effect of industrial-grade lanolin on dust mites
Experiments 1 to 6 determine the effect of industrial-grade lanolin on dust mites by adjusting the amount of industrial-grade lanolin, as shown in Table 7.
It can be seen from Table 7 that the lanolin-added emulsion has a certain repellent rate against dust mites, and as the amount of industrial-grade lanolin increases, the emulsion-repellent rate against dust mites also increases; The amount of grease increased, and the scrub resistance of the coating film gradually decreased. When the amount of lanolin exceeds 1%, the scrub resistance of the coating film has not reached the national standard.
The reason is that industrial grade lanolin is mainly an ester formed from a mixture of sterols, fatty alcohols, triterpene alcohols and the same amount of fatty acids, so the system is very hydrophobic, although it will not polymerize the emulsion system. It has a great effect, but because there is no double bond in lanolin, lanolin is combined with latex particles in the form of solubilization during the polymerization process. Therefore, as the amount of lanolin increases, the lanolin melts. The amount used in the latex granules also increased. Lanolin in the polymer segment of the latex particles acts as a lubricant similar to the macroscopic effect, so the final latex particles are not tightly wrapped with the powder, so the scrub resistance is reduced.
2.2 Effect of the addition method of industrial grade lanolin on dust mites
According to the experimental results in Table 7, we consider making the emulsion system into a core-shell structure, so m (core layer): m (shell layer) = 3: 7, 1 The ratios of 1: 1, 7: 3, and 3%, 4%, and 5% of the amount of lanolin added were tested.
From Experiments 7 to 9, when the amount of lanolin was 3%, the ratio of m (core layer): m (shell layer) = 3: 7, 1: 1, 7: 3 was shown in Table 8.
From experiment 10 to experiment 12, when the amount of lanolin was 4%, the ratio of m (core layer): m (shell layer) = 3: 7, 1: 1, 7: 3, and the results are shown in Table 9.
From Experiments 13 to 15, when the amount of lanolin was 5%, the ratio of m (core layer): m (shell layer) = 3: 7, 1: 1, 7: 3 was shown in Table 10.
From Tables 8 to 10, it can be seen that there is no significant difference between the core-shell structure and the uniform structure of latex particles in the repellent rate of dust mites. The structure of the granules is irrelevant. At the same time, we can see that as the shell layer thickens, the scrub resistance of the coating film also shows an increasing trend. Therefore, when the amount of lanolin is 3% and the core-shell ratio is 3: 7, the coating film has a certain repellent rate against dust mites, and the scrub resistance is optimal.
The reason is that the film formation process of latex particles is a process of extrusion deformation. Therefore, during the film formation of the coating film, because the shell layer does not densely enclose the core layer, as the latex particles continue to squeeze, the core layer and the The boundaries of the shell gradually become blurred and gradually merge into one , so the repellency rate of the core-shell structure is not significantly different from that of the uniform structure. Because the shell layer has a certain thickness, the scrub resistance of the core-shell structure appears to increase slightly with the increase of the thickness of the shell layer. Increase trend.
2.3 Effect of the amount of nuclear silane coupling agent on scrub resistance
According to the above experimental results, the amount of fixed lanolin is 3%, and m (core layer): m (shell layer) = 3: 7. By adding a certain amount of silane coupling agent to the core layer, the core layer is crosslinked. Density to prevent lanolin from diffusing to the outer layer. Experiments 16 to 20 were designed as shown in Table 11.
According to Table 11, it can be seen that with the increase of the silane coupling agent A-174N in the core layer, the scrub resistance of the coating film has been significantly improved, but when the silane coupling agent in the core layer exceeds 0.3%, the final slag out of the emulsion The amount is gradually increasing. Therefore, when the amount of silane coupling agent in the core layer is 0.3%, the emulsion meets workshop production standards.
The reason is that the reactivity of the silane coupling agent is very strong, and there is a double bond in the front section of the silane coupling agent that can be grafted to the main chain of the polymer, and there are 3 silanol bonds in the back section, which can cause cross-linking. With the increase of the amount of silane coupling agent, the silanol bonds on the latex particles and the surface of the latex particles react with each other and cross-link with each other, thus causing localized flocculation of the latex particles under micro conditions. As the polymerization reaction proceeds, the floc The increase will eventually lead to the formation of slag.
2.4 Effect of the added amount of shell silane coupling agent on scrub resistance
Based on the above experimental results, experiments 21 to 25 were designed. By adding a certain amount of silane coupling agent to the shell layer of latex particles, the scrub resistance of the coating film was achieved. The improvement is shown in Table 12.
It can be seen from Table 12 that as the amount of shell silane coupling agent increases, the scrub resistance of the coating film clearly shows an upward trend. However, as the amount of shell silane coupling agent increases, the final slag amount of the emulsion also increases. Increase. When the amount of shell A-174N is 0.2%, the amount of polymerized slag meets the production standard of our company, and the scrub resistance of the coating film at this time reaches the national standard.
The reason is also that with the increase of the amount of silane coupling agent, the silanol bonds on the latex particles and the surface of the latex particles react with each other and cross-link with each other, thus causing localized flocculation of the latex particles under micro conditions. As the polymerization reaction proceeds, The floc gradually increased, eventually leading to the formation of slag.
Through the above research and experiments, we can conclude that by designing the structure of m (core layer): m (shell layer) = 3: 7 of the latex particles, 3% industrial grade lanolin is wrapped in the core layer of the latex particles. Use 0.3% silane coupling agent to increase the density of the surface of the core layer, so that the emulsion has a certain repellent rate against dust mites, and then use the shell layer 0.2% silane coupling agent to improve the overall resistance of the coating film. Number of scrubs.