Development of non-tar two-part polyurethane waterproof coating

Ma Jun
(Guangdong Keshun Chemical Industry Co., Ltd., Foshan, Guangdong 528303)
Summary: through a certain proportion of synthesis of polyurethane prepolymer containing NCO as a component A, powder, polyether, MOCA, additives, etc. into
components, A, B components by quality ratio of 1:2 mixed into a non-tar two-component polyurethane

. The effects of NCO content, MOCA, catalytic additives and deboist on two-component polyurethane coatings were discussed, and the results showed that NCO content was 4.0% to 4.6%, MOCA content was 2.5% to 4.0%, catalysts were 0.08% to 0.12%, and de bubble inhibitors were 0.3% to 0.7%.
key words: non-tar; Two-part; Polyurethane coatings; Decosting agent
in the figure classification number: TQ633 Document identification code: A article number: 1007-9548 (2012) 08-0020-03
0 Introduction
NCO/OH type two-part polyurethane coating is now one of the most commonly used polyurethane coatings on the market. It is composed of polyether polyols and isocyanate synthesis containing - NCO pre-polymer for A component and B components containing - OH active group, crosslinking agent, etc. , its basic reaction is - NCO and - OH, - NH2 crosslinking reaction to form a network structure, so that the membrane has a certain strength and elasticity. Therefore, polyurethane coating can be cured at room temperature, the formation of cross-linked structure of the coating film, all kinds of substrates have good adhesion, flexibility, friction resistance, water resistance, solvent resistance, coating outside the sightseeing bright plump. At present, there are still some problems in the two-component polyurethane coating on the market: polyurethane material is mixed with a large amount of coal tar as an active filler, however, coal tar contains volatile aromatic compounds, with a strong irritating odor, in which the components such as radon, radon are extremely harmful to the human body, greatly endangering the health of construction personnel; In the construction and coating drying process of two-part polyurethane
productive coating
, there are always problems of long drying time, slow curing and many bubbles, and the quality of de-foaming has even become a key index of the performance of polyurethane coating.
Based on the above-mentioned problems, this paper prepares a non-tar two-group polyurethane waterproof coating, without harmful active fillers, fast table drying, good performance after curing, film-free bubble-free.
1 test
1.1 main raw materials
polyether binary alcohol (N220), polyether tri-alcohol (330N): Shandong Dongda; Toluene dicycyanate (TDI), dibenzene methane diocyanate (MDI): Imported; Chlorinated Paraffin (52): Hongwang Chemical;
talc powder
: Guangzhou Qijun Chemical; Liquid MOCA (ML-200): Xiangyuan Special Fine Chemicals; Phthalates (DBP): Guangzhou Zhuangda Chemical; Calcination
kaolin
: 100 million peak chemical; Solvent oil (120 s); Alkane oil: Guangzhou Union Zhuo trade; February laurel acid butyl tin (T-12): Huizhou Kesheng trade; DMDEE: Shanghai Xinrui Chemical; Desiccant (ST-530, ST-580): Santo Chemical.
1.2 basic formula
The basic formula for the A and B parts is set out in Table 1.
Table 1 A, B basic formula
1.3 preparation process A part: polyether polyol, talcum powder, chlorinated paraffin, etc. in a certain proportion into a four-mouth bottle, heat up to 120 degrees C and maintain pressure below -0.085MPa dehydrated 2h, cool down to 82 degrees C to add TDI, MDI reaction 3h, cooling material can be.
B components: chlorinated paraffin, polyether polyols, alkane oil, powder, etc. in a certain proportion dispersed, added to four flakes, heated to 120 degrees C dehydrated 2h, cool down to 50 degrees C, add solvent oil, additives, liquid MOCA and other mixing can be evenly distributed.
1.4 performance test
A, B parts by mass ratio of 1:2 mixed stirring 3 to 5min after coating film, under standard test conditions , the temperature (23±2) degrees C, relative humidity (60±15%) maintenance and testing.
coating drying time according to GB /T16777-1997 test, using B method; Stretching performance according to GB /T16777-1997, with WDW-5 electronic all-powerful pull test machine (Guangzhou Auskin Industrial Automation System Co., Ltd.) to determine, stretching speed of 500mm/min; Other performance are in accordance with GB /T19250-2003 "polyurethane waterproof coating" testing.
results and discussion
2.1 test results
according to GB/T19250-2003 performance testing, the results can be seen in Table 2. All testing performance is in line with national standards, especially with excellent impermeability, heat resistance, acid resistance and alkaline resistance.Table
2 double-component polyester coating test results
2.2A components of NCO content on membrane performance
fixed Group B allocating party, with a certain ratio of binary alcohol, tylitol to make different NCO content of A components, A, B components by quality ratio of 1:2 mixed into a membrane, testing its tensile strength and elongation rate, the results are seen in Table 3.
effect of NCO content on film-forming properties in Table 3 A
The content of NCO increased, the stretch strength and elongation increased. When the NCO content is greater than 4.4%, the elongation rate decreases gradually. This is because the NCO content increases, the more complete the crosslink reaction, when the NCO content is greater than 4.4%, the crosslink is too large, resulting in a decrease in the elongation rate. According to GB/T19250-2003, the stretch strength needs to be greater than 1.9MPa, the elongation rate is greater than 450%, so the NCO content should be controlled between 4.0% and 4.8%.
2.3B components of liquid MOCA content on membrane performance
Liquid ML-200 is similar to the chemical structure and physical properties of solid MOCA products, it has a liquid at room temperature, faster reaction speed than solid MOCA, and better safety than solid MOCA characteristics, for its use in the process and environmental safety provides many favorable conditions and factors.
choose the A component with an NCO content of 4.0%, add different contents of MOCA (ML-200) to the formula to get different B components, and group A is divided into membranes, according to the standard detection of physical performance indicators, see Table 4.
effect of table 4 MOCA content on film-forming performance
With the increase of ML-200 content, the cross-linking degree of film-forming increased, so the tensile strength and elongation were enhanced. When the ML-200 content is 3.0%, the elongation rate reaches the maximum value, and the stretch strength continues to increase, because the crosslink is too large, which affects the elongation rate; When the ML-200 content continues to increase and the elongation decreases, the ML-200 content should be controlled between 2.5% and 4.0%.
The effect of catalytic additives on drying time in
2.4B,
selecting the A part with NCO content of 4.0% and the addition of ML-200 in group B is 2.5%, change the ratio and content of the catalyst, divide it into film with group A, test its drying time according to the standard, the results can be seen in Table 5.
Table 5 Catalytic Additives on Drying Time
When only T-12 or DMDEE is used, film-forming drying time is slower, and when using 2 catalysts, the synergy of catalysts greatly improves the table drying and drying time. When T-12:DMDEE is 3:1, the table drying time and curing time are met GB/T19250-2003 requirements, in order to facilitate construction, should control its content in 0.08% to 0.12% is appropriate, can make the coating table dry time between 1 to 4h, the drying time in 12 to 18h.
2.5B components of the desmoulation agent on the effect of the film
because a part of the two-component polyurethane - NCO will react with moisture (moisture) in the air to produce CO2, in the process of surface dry curing, some CO2 failed to overflow the surface of the membrane in time, resulting in the internal appearance of the membrane pores, affecting the physical properties of the membrane, so adding a certain amount of decogrant in the B component will effectively inhibit the film foaming performance. The amount added to the desiccant and the film-forming condition can be found in Table 6.
Table 6 addition and film formation
Desmoulation agent ST-530 and polyurethane mixing effect is good, in the B part, the addition of 0.3% to 0.7% can effectively inhibit the formation of CO2 bubbles, eliminate fish eyes, pinholes and other defects; The desiccant ST-580 is slightly less compatible with polyurethane, and the foam suppression effect is not good, so adding ST-530 content to B can effectively improve the film-forming effect by 0.3% to 0.7%.
3. Conclusion
1) According to the test data, in this Group A allocating party, the NCO content should be controlled between 4.0% and 4.8%, the extrusion strength of the polyurethane film is above 2.2MPa, and the elongation rate is more than 500%.
2) In component B, the controlled MOCA content was between 2.5% and 4.0%, the film extension rate >470% and the stretch strength >2.2MPa were made.
3) In the B-part, the control catalyst ratio T-12:DMDEE is 1:3, the total percentage content is between 0.08% and 0.12%, the drying time of the coating can be adjusted at 1 to 4h, and the drying time is 12 to 18h.
4) In group B, the desculation agent ST-530 added 0.3% to 0.7% can effectively inhibit the bubbles formed by CO2, eliminating defects such as fish eyes, pinholes and so on.
5) The formula designed in this paper does not contain any harmful tar-based active substances, the MOCA used is modified liquid ML-200, greatly reducing the harm to the human body, so this formula is environmentally friendly.
reference:
: Li Shuxian. An initial exploration to improve the drying speed of NCO/OH-type two-part polyurethane coatings. Henan Chemical Industry, 1994 (12): 4-6.
Liu Yijun. Polyurethane Resins and Their Applications: Beijing: Chemical Industry Press, 2012:336.
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