Preparation of acrylic polyurethane coatings with elastic curing agents

China Coatings Online News
Liu Zikang, Wang Xinfeng, Duan Wenfeng (Beijing Oriental Yuhong Waterproof Technology Co., Ltd., Beijing 101309)
Abstract: Introduced a method for the preparation of an elastic curing agent for acrylic polyurethane coatings, which are made of acrylic polyurethane coatings with strong adhesion, weather resistance and elasticity, resistant to the slight cracking of concrete surfaces. The effects of different polyether polyols, different adipose isocyanates, and different -NCO content synthesis curing agents on the performance of paint film were discussed.
key words: elastic curing agent; acrylic polyurethane coating; elastic coating
in the figure classification number: TQ 630.4-93 Document identification code: A article number: 1009-1696 (2014) 11-0022-04
0. Introduction

<1> The traditional acrylic polyurethane coating is rigid coating, suitable for the protective coating of metal surface, and for concrete surface, the hardness is more than enough and the toughness is insufficient, easy to produce micro-cracks and make the protective effect greatly reduced, resulting in repair and maintenance costs increased;
In this paper, an elastic curing agent for acrylic polyurethane coating is developed, and the elastic acrylic polyurethane coating made by it has strong adhesion, weather resistance and elasticity, which can resist the slight cracks on the concrete surface, and the solid content is high, the solvent used is an environmentally friendly solvent, which can be constructed once to achieve the desired thickness and high construction efficiency.
1. Experimental part
1.1 Main raw materials
polyether polyol GE-210, GE-220, GMN-3050, GEP-330N : Industrial Grade, Shanghai Takahashi Petrochemical Company; Polytetrahydrofuran Polyol PTMG1000, PTMG2000: Industrial Grade, Mitsubishi, Japan; Adipose isocyanate HDI (hexymethyl diocyanide) HMDI (4,4'-dicycline methane diocyanate), IPDI (isoprotone diocyanate): industrial grade, Bayer Materials Technology, Germany; 3390: Industrial grade, Bayer Materials Technology, Germany; Hydroxypropyl acrylic resin: industrial grade, Hemings; Catalyst T-12: industrial grade, commercially available; fillers, additives, solvents, etc., commercially available.
the preparation of 1.2 elastic curing agents
the basic formulation of elastic curing agents can be found in Table 1.
add a certain amount of polyether polyols to a four-port cans, heat to 120 to 130 degrees C, open the vacuum pump, dehydrated 3 h at 0.05 to 0.01 MPa vacuum; Adipose isocyanate and solvent, mixed evenly, slowly heated to 75 to 85 degrees C, constant temperature reaction 2.5 h;
1.3 Coating film preparation
the resin parts and curing agent parts mixed evenly and poured into the paint tank, adjust the pressure and flow of the spray gun, the coating evenly sprayed on the silicon isolation film, to ensure that the dry film thickness of 400 to 800 m, the standard conditions of the temperature of 23 degrees C, relative humidity (50±10% maintenance 7 d after the sample test.
1.4 Performance Test
Extrusion Performance Determination: The test piece shape according to GB/T 528-2009 "Sulcanized rubber or thermoplastic rubber stretch stress performance determination" in the I. type dumbbell tailoring, using Shenzhen New Three Thought Metering Technology Co., Ltd. 4104 electronic pull machine to determine stretch performance, the sensor using 200 N range, stretching speed of 250/min.
2. Results and discussion
2.1 Effect of the type of fatty isocyanate on coating performance
HDI, IPDI, HMDI synthesis is different - NCO content of the curing agent, and then mixed with the color paint composition to prepare the coating film, test the extrusion strength and fracture elongation rate of the coating film, the results can be seen in Figure 1, Figure 2.As can be seen from Figure 1 and Figure 2: The extrusion strength of the coating film obtained by the adipose isocyanate synthesis is different - NCO content is gradually increased with the increase of the NCO content, and the fracture elongation rate decreases gradually with the increase of the NCO content. This is due to the increase with the - NCO content, the content of hard segments in the coating film increased, the more microcrystalline regions formed, so its stretch strength and hardness increased, and with the coating film more and more microcrystalline regions, the relative movement between the molecular chain segments becomes more and more difficult, so the fracture elongation rate with the increase of the - NCO content and reduce. Comparing HDI, IPDI, HMDI these three kinds of fat family isocyanate, because HDI is a straight chain structure, the coating film is not easy to form a microcrystalline region, the coating film as a whole is soft, its stretch strength and fracture elongation rate are low; Contains two ring structure, IPDI molecule contains a ring structure, so the coating film with HMDI synthesis has the highest extrusion strength, on the contrary, because HMDI's double ring structure is stronger than IPDI's single ring structure rigidity, so the fracture elongation rate of the coating film using HMDI synthesis is lower than that of the coating film with IPDI synthesis.
effect of 2.2 polyether polyols on coating performance
Selection of different polyether polyols GE-210, GE-220, GMN-3050, GEP-330 N is different from IPDI synthesis - NCO content of the curing agent, and then mixed with the color paint composition to prepare the coating film, to be coated film after the expiration of maintenance, test coating film stretch strength and fracture elongation rate, the results can be seen in Figure 3, Figure 4.
As can be seen from Figure 3 and Figure 4: the curing agent with different polyether polyols and IPDI synthesis - NCO content, the extrusion strength of the resulting coating film gradually increases with the increase of the content of the NCO, and the fracture elongation decreases gradually with the increase of the content of the NCO. Comparing these 4 polyether polyols, the film with polyether polyol GE-210 had the lowest extrusivity and fracture elongation, the polyether polyol GMN-3050 and GEP-330N had the highest elongation strength and fracture elongation, and the polyether polyol GE-220 had the highest extrusivity and fracture elongation. This is because GE-220 is a medium relative molecular mass polyether polyol with secondary energy, the formation of the molecular chain in the coating film is more regular, conducive to the formation of more microcrystalline regions, so its coating film stretch strength is the highest, and when stretched, its molecular chain is linear, so the elasticity of the coating film is also better, the highest fracture elongation rate; Shorter, its coating elasticity is not large enough, resulting in its stretch strength and fracture elongation rate are low, GMN-3050 and GEP-330N are three-degree energy of large relative molecular mass polyether polyol, preparation coating film crosslinking is high, so its fracture elongation and stretch strength is lower than GE-220.
2.3 Effects of polyether polyols and polytehydrofuran polyol synthetic curing agents on coating properties
000, PTMG2000 is different from IPDI synthesis - NCO content of the curing agent, and then mixed with the color paint composition to prepare the coating film, to be coated film maintenance expires, test coating film stretch strength and fracture elongation rate, the results can be seen in Figure 5, Figure 6.can be seen from Figure 5 and Figure 6: Polydihydrofuran polyols with the same relative molecular mass have higher extrusion strength than polyether polyols, but their fracture elongation rate is lower. This is due to the high C-C bond content in the polymer chain of polythihydrofuran polyols, and the content of C-O-C bonds with better softness is less than polyether polyols, so under the same relative molecular quality, the stretch strength of the coating film prepared with polydihydrofuran polyols is higher, and the fracture elongation rate is lower.
2.4 Effects of the mixing of homemade elastic curing agents and rigid curing agents on coating film performance

as can be seen from Figure 7 and Figure 8: N75 and N3390 curing agents with different ratios were added to the homemade elastic curing agent, and the extrusion strength of the coated film gradually increased with the increase of N75 and N3390 content, and the fracture elongation rate decreased gradually with the increase of N75 and N3390 content. This is because N75 and N3390 are small molecular rigid curing agents with three-degree energy, the higher the content, the more cross-linking points in the coating film, the greater the cross-link density between the molecular chains in the coating film, the higher the coating film extrusion strength, the lower the fracture elongation rate. N75 is an HDI shrink-diodes structure with no ring structure in its molecular structure, and N3390 is an HDI trimer structure with a hexaling ring structure in its molecular structure, so add the same amount of N3390 than add N7 The enhancement effect of 5 is good, but the fracture elongation rate is low when the N3390 is added, and when the addition of N75 and N3390 exceeds 15%, the extrusive strength increases significantly, while the fracture elongation decreases significantly. Therefore, the amount of rigid curing agent is appropriate at 15%.
3. Conclusion
Elastic weather-resistant acrylic polyurethane coatings gradually increased with the increase of elastic curing agent-NCO content, fracture elongation decreased gradually with the increase of -NCO content; The strength and fracture elongation were the highest, under the same relative molecular mass, the extrusion strength of the coating film prepared with polyether polyol was higher than that of polyether polyol, and the fracture elongation rate was low, and the extrusion strength of the coating film gradually increased and the fracture elongation rate decreased gradually as the content of rigid curing agent in the homemade elastic curing agent increased. The amount of rigid curing agent is suitable at 15%.
References
. Shang Hanzhang, Bai Yidong, Feng Gang, etc.. Development of fast-drying acrylic polyurethane finish paint, Shanghai Coatings, 2012, 50 (01): 4-6.
, Xia Fanwu. Development and application of high-performance two-component acrylic polyurethane finishes, Shanghai Coatings, 2009, 47 (03): 5-8.
. Song Yonglian. Development of aration-cured acrylic polyurethane coatings. Anhui Chemical, 2001 (05): 29-31.
, Liu Zhong, Zhou Ronghua. Development of high solid acrylic modified polyurethane coatings. Modern coatings and coatings, 2009, 12 (09): 14-18.
, Ding Xuewen, et al. Performance Studies of Polyurethane Acrylic Coatings, Coatings Industry, 2010, 40 (03): 36-40.
, Meng Zhaorong, Zhou Sheng, etc. Development of a new elastic acrylic polyurethane glass and steel primer. Coatings Industry, 2011, 41 (09): 27-29, 33.
, Ma Xiaogu, Stewysheng. Development of ultraviolet cured polyurethane acrylate glass coatings, Coatings Industry, 2005, 35 (02): 15-17.
Zhengbin, Tu Weiping, Yang Zhuru, etc. Research progress in high solid acrylic polyurethane coatings. Modern coatings and coatings, 2002, 28 (01): 15-18.
, Li Wei, Lin Haichao, et al. Acrylic Polyurethane Coatings Corrosion Resistance Research. Journal of Corrosion and Protection of China, 2003, 23 (02): 89-91, 98.