Abstract: in this paper, thickening properties, physical and chemical properties and application properties of three synthetic thickeners are tested and discussed in detail. The application properties of thickeners in emulsion coatings are emphatically discussed, so as to adapt different types of coating finishing to select thickeners with corresponding properties, so as to achieve better coating effect and production cost. Key words: coating slurry system; synthetic thickener; physicochemical characteristics; thickening performance; emulsion coating finish; thickening effect
In recent years, with more and more attention paid to pollution, solvent price rising, safety and environmental protection, coating processing is developing from solvent coating to water-based coating. Coating slurry system is usually made of coating agent, such as polyacrylate, water soluble polymer and waterborne polyurethane emulsion, crosslinking agent, thickener and additive, etc. Adding thickener into the coating finishing solution can improve the viscosity and rheology of the coating slurry system, control the fluidity and permeability of the coating adhesive, maintain a stable suspension state, so as to better meet the requirements of (round net) coating processing, make it cover the fabric surface well and improve the processing performance and Application performance. In this paper, the physicochemical characteristics, thickening properties and application of emulsion thickeners in emulsion coating finishing are discussed and evaluated. 1. test part 1.1 test materials and equipment reagents: Thickener R-8 (forest chemical company), T1806 (a brand in Europe and America), P-803 (Jing Yan new material technology), polyacrylate emulsion AM, waterborne polyurethane emulsion LN, crosslinking agent AD, water repellent Sumifluoil SM-30, acetic acid (industrial products). Fabric: 524 pieces of 14.8tex × 14.8tex / 10cm × 283 pieces / 10cm half bleached cotton poplin. Test equipment: viscometer Brookfield DV - Ⅱ + Pro rotor 64 × 3; Japan through well PT-2 hot air dryer, Switzerland Benz double roll electric rolling fluid dryer, Switzerland Mathis coating test machine. 1.2 experimental content and data analysis 1.2.1 performance test of synthetic thickener to determine the physical and chemical indexes, thickening performance, rheology, electrolyte resistance, etc. 1.2.2 thickening emulsion coating application performance test dry coating quantity: quality method test; water pressure according to FZ / T01004-91 "coated fabric permeability test method (hydrostatic pressure test)" test; water repellency according to AATCC-22-1980 method test; washing resistance according to AATCC-83B-1973 method. 2. Discuss and analyze the physical and chemical properties of 2.1 synthetic thickener. Three kinds of polymer synthetic thickeners, i.e. thickenerr-8 (Lin Chemical Co., Ltd.), t1806 (a brand in Europe and America), p-803 (JingZhan Technology), are selected for the test. The physical and chemical properties and physical indexes of each thickener are tested. See Table 1 for the test results. It can be seen from table 1 that the basic properties of the above three synthetic thickeners are very similar, their contents are high, and they are easy to disperse, swell and thicken into colorless transparent body in water.
2.2 the thickening performance of the thickener is to prepare three thickener white pastes with different mass fractions. At room temperature (25 ℃), use Brookfield dv-ii + Pro viscometer (64 rotor) to measure the viscosity value of the thickener at 6 rpm. See Figure 1 for the test results.
Figure 1 thickening performance curve of thickener
As shown in Figure 1, the viscosity of the thickening agents of these three (R-8, T1806, P803) thickeners increased significantly with increasing dosage of synthetic thickeners, indicating that the three thickeners had excellent paste properties and had very strong thickening capability for the coating emulsion. Compared with the thickeners, thickening agent P-803 had the strongest thickening ability, and its viscosity reached 7.50 * 104mPa when its dosage was 1.5%. . s (when 2.0%, the viscosity is more than 10.0 × 104mpa. S), while R-8 is the weakest; the order of thickening ability of three thickeners: p803 > t1806 > thinker R R-8, the thickening force decreases in sequence. Thickener P803 can provide the emulsion viscosity of the round screen coating process at a lower dosage to ensure the smooth finishing of the coating.
2.3 rheology and viscosity index of emulsion after thickening
For coating finishing, the rheological property of coating slurry will directly affect the coating effect of the fabric; especially for the coating slurry of round mesh type, when the coating slurry is not subject to shear force before operation, it should have a high initial viscosity, which is not easy to transfer to the fabric through the screen mesh; during operation, the coating slurry is subject to a certain shear force, and the viscosity drops sharply, which is very easy to be evenly coated on the fabric through the screen mesh As soon as the shear force disappears, the coating slurry in the web and on the fabric immediately returns to the state of high viscosity, which is conducive to the uniformity of the coating finish and the smooth production.
The rheology of thickener raw paste can be expressed by the viscosity index PVI (PVI= ETA 60 / ETA 6). Now the mass fraction of 1.5% thickener is prepared. The viscosity of the original paste is determined by Brookfield DV-II+Pro viscometer and 64# rotor at different speeds. The viscosity index of emulsion is PVI= (60 rpm / S) / (6 RPM), and the thickening emulsion rheological property curve is plotted. The result is shown in Fig. 2.
Fig. 2 rheology curve of thickening agent thickening emulsion is shown in Figure 2. The viscosity of the three synthetic thickeners is sharply decreased with the increase of shear stress, showing good rheology. Thickening agent thickening emulsion belongs to pseudoplastic fluid, that is, shear thinning fluid. The viscosity decreases with the increase of shear rate, which is determined by the properties of thickener emulsion. For coating processing, the rheological properties of the grout directly affect the coating effect. The thickening emulsion of Thickener P-803 and its composite system has smaller PVI value and excellent thixotropy. This kind of thickener fluid has good fluidity and thixotropy. It is applied to the whole cotton compact fabric for scraper coating process under high viscosity, which is conducive to the transfer of coating slurry from the round net to the coated fabric, achieving even wet coating amount, and the coating film has a certain degree of smoothness. 2.4 electrolyte resistance the electrolyte resistance of synthetic thickener is an important index to evaluate its application effect in coating slurry. Prepare the thickener paste with the mass fraction of 1.5% respectively, then add the electrolyte (such as sodium chloride) solution with different mass fractions, stir it evenly, and use Brookfield dv-ii + Pro viscometer and 64 × rotor to measure the corresponding viscosity change value. See Figure 3 for the test results. As shown in Fig. 3, three synthetic thickeners have good electrolyte resistance, among which Thickener P803 > T1806 > R-8; because of the excellent electrolyte resistance of Thickener P-803, the influence of finishing agents on the thickening performance of the coating slurry is reduced, and the finishing emulsion has higher viscosity retention.
Figure 3 electrolyte resistance curve of thickener
3. application of thickener to emulsion coating
According to the formulation of the 3.2 coating process, three kinds of thickeners were prepared according to the different dosage (0.86% Thickener R-8, 0.62% T1806, 0.56% P-803) respectively. The coating emulsion was thickened to a certain viscosity value by adjusting the pH appropriately, and then the cotton poplin fabric was coated and processed under the same equipment condition.
3.1 coating process flow
Two coats of the same condition were used to increase the coating amount of the fabric.
Coating (1) → drying (120 ℃× l-2min) → coating (2) → drying (120 ℃× l-2min) → waterproof treatment (two-step immersion and two-step rolling, pressure 10 kgf / cm2, speed 3 M / min, temperature 28 ℃, rolling liquid rate 65-75%) → drying (120 ℃× l-2min) → curing (160 ℃× 2-3min).
3.2 coating prescription / g
Acrylate emulsion AM 250
Ad 10
Waterborne polyurethane emulsion LN 300
Defoamer JD 2
Synthetic thickener x
Water y
Total 1000g
Water repellent working solution prescription /%:
Sumifluoil SM-30 4%
Fix AT O.3%
PH 5.5-6.0
3.3 coating product performance
According to the coating formula in 3.2, the pure cotton poplin is coated with the coating slurry prepared with the above different synthetic thickeners. The performance of the coating product is tested. The results are shown in Table 2.
The effect of different thickeners on the application performance of emulsion coating is different. It can be seen from table 2 that from the perspective of waterproof performance, at the initial stage of processing, the water repellency of the fabric is more than 95 points, the water pressure resistance is high, and each index performance standard of each thickening system is high, but once washed, it shows certain difference (i.e. the difference of water washing resistance).
In contrast, the thickening system of Thickener P803 composite has better waterproof and durability properties, and the water repellency of its thickened coating product is more than 95 points and its washing resistance is good. From the hand feel, the Thickener T1806 thickening system can obtain a very soft handle; the P803 composite system thickens the emulsion coating, but the handle is slightly inferior, but the fabric surface is dry and even full.
The polyhydroxy structure of the synthetic thickener thickner p803 has affinity with carboxy, hydroxy, nitrile [- C (= O) - O -, oh, - C = n] in fibers and adhesives, which can increase the adhesion and enhance the washability. In addition, when such substances are solidified, they can be partly cross-linked with emulsion polymers and fabrics, especially with emulsion polyacrylate, which can improve the crosslinking degree of polymers, improve their resistance to water pressure and washability, and improve the surface adhesion of coated fabrics. However, due to the high degree of cross-linking, the feel of coated fabrics has a certain negative effect. 4. conclusion 4.1. Three anionic synthetic thickeners have strong thickening effect and good electrolyte resistance for coating emulsion, Thickener The performance of P803 thickener is the best. It is used for thickening coating slurry. It can make the coating slurry have better viscosity and rheology, give the emulsion uniform and stable suspension state, and ensure the uniform coverage and adhesion of the fabric coating film. 4.2 the difference of structure and properties of thickeners will have a certain degree of influence on the properties of coated fabrics. The use of Thickener P803 thickening system functional coatings, such as waterproofing, oil proofing and flame retarding, can improve the crosslinking degree of emulsion polymers and increase their resistance to water pressure and washability. Four point three Due to the differences in composition, structure, polymerization reaction and emulsifier selection, the synthetic thickener has different properties, which should be reasonably selected in the actual coating finishing production practice. The thickener with high reaction performance, strong thickening force, good thixotropy and excellent electrolyte resistance can provide high viscosity and make it fully cross-linked into the macromolecular coating film after curing, so as to enhance the Functional durability of fabric coating. About the author: Peng Zhizhong, a senior engineer of printing and dyeing in Xinyu, Jiangxi Province, has been engaged in dyeing and finishing technology for more than 30 years. He is committed to the research and development of textile dyeing and finishing, new printing technology, application and promotion management, etc. Mobile: 13922372675 wechat same number e-mail: pengzhong7798@126.com