Rapidly-cured polyurethane protective paint as well as preparation method and application thereof

Abstract

The invention provides a quickly cured polyurethane protective paint, and a preparation method and application thereof. The polyurethane protective paint contains a polyurethane soft segment provided by polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate. The mass ratio of the polyurethane hard section to the polyurethane soft section is (1: 2)-(2: 1). By accurately controlling the molecular structure of the resin, the low-temperature fast curing of the repair coating can be effectively realized. Compared with a common repairing coating, the prepared polyurethane paint is faster in curing time, high in heat stability, excellent in film coating performance, good in adhesive force, flexibility, abrasion resistance and weather resistance and capable of guaranteeing the product quality and prolonging the service life.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer coatings, and in particular relates to a fast-curing polyurethane protective paint, a preparation method and application thereof. Background Art

[0002] Polyurethane paint plays an important role in the coating industry due to its excellent coating properties, including good adhesion, flexibility, wear resistance and weather resistance. Among them, polyurethane repair coatings have weather resistance and durability, as well as corrosion resistance, anti-slip, oil resistance, resistance to rapid cooling and rapid heating cycles, and strong hiding power. They are used in various industries, especially the automotive repair industry.

[0003] However, traditional polyurethane paints have problems such as long curing time, need for drying and curing, high energy consumption, high emission of organic compounds, and insufficient adhesion, and cannot meet the needs of rapid repairs. Summary of the invention

[0004] The purpose of the present invention is to provide a fast-curing polyurethane protective paint, a preparation method and application thereof. The polyurethane protective paint of the present invention can be quickly cured at low temperatures, reduce energy consumption and VOC emissions, and provide excellent coating film properties.

[0005] The present invention provides a fast-curing polyurethane protective paint, wherein the polyurethane protective paint contains a polyurethane soft segment provided by a polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate;

[0006] The mass ratio of the polyurethane hard segment to the polyurethane soft segment is 1:2 to 2:1.

[0007] Preferably, the polyether polyol is polyether polyol DEP-330G.

[0008] The present invention provides a method for preparing the fast-curing polyurethane protective paint as described above, comprising the following steps:

[0009] Mixing polyether polyol and chain extender, and removing water from the mixture to obtain material A;

[0010] Dehydrating isophorone diisocyanate to obtain material B;

[0011] A catalyst and material B are added to material A to react to obtain a polyurethane protective paint.

[0012] Preferably, the chain extender is 1,4-butanediol;

[0013] The mass ratio of the polyether polyol to the chain extender is 10:(1-5).

[0014] Preferably, the temperature for dehydrating the mixture is 100-120° C., and the time for dehydrating the mixture is 0.5-2 hours.

[0015] Preferably, the temperature for dehydrating isophorone diisocyanate is 100-120° C., and the time for dehydrating is 0.5-2 hours.

[0016] Preferably, the catalyst is dibutyltin dilaurate;

[0017] The mass of the catalyst is 0.1-3% of the total mass of the A material and the B material.

[0018] Preferably, the reaction temperature is 25 to 80° C., and the reaction time is 20 to 40 seconds.

[0019] The present invention provides an application of a polyurethane protective paint as a repair coating, wherein the polyurethane protective paint is the fast-curing polyurethane protective paint described above.

[0020] Preferably, the curing temperature of the polyurethane protective paint is 20 to 80° C., and the curing time is 40 to 90 seconds.

[0021] The present invention provides a fast-curing polyurethane protective paint, characterized in that the polyurethane protective paint contains a polyurethane soft segment provided by polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate; the mass ratio of the polyurethane hard segment to the polyurethane soft segment is 1:2 to 2:1. The present invention can effectively achieve low-temperature fast curing of the repair coating by accurately controlling the resin molecular structure. The present invention uses polyether polyol as the polyurethane soft segment, isophorone diisocyanate as the isocyanate hard segment, 1,4-butanediol as the chain extender, and dibutyltin dilaurate as the catalyst, and respectively investigates the influence of the catalyst content and the hard-soft segment content ratio on the system curing time to prepare a polyurethane paint that cures quickly at room temperature, and studies its performance. The polyurethane paint prepared by the present invention has a faster curing time than ordinary repair coatings, strong thermal stability, excellent coating performance, good adhesion, flexibility, wear resistance and weather resistance, and can ensure product quality and extend service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 This is a comparison of infrared spectra of IPDI of material B and polyurethane protective paint in Example 2 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the polyurethane protective paint in Example 2 of the present invention;

[0025] Figure 3 This is an enlarged scanning electron microscope image of the polyurethane protective paint in Example 2 of the present invention;

[0026] Figure 4 This is a test curve of the mechanical properties of the polyurethane protective paint in Example 2 of the present invention;

[0027] Figure 5 TG curve of the polyurethane protective paint in Example 2 of the present invention;

[0028] Figure 6 It is the glass transition temperature of the polyurethane protective paint in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a fast-curing polyurethane protective paint, characterized in that the polyurethane protective paint contains a polyurethane soft segment provided by a polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate;

[0030] The mass ratio of the polyurethane hard segment to the polyurethane soft segment is 1:2 to 2:1.

[0031] In the present invention, the polyether polyol is preferably a polyether polyol of the DEP-330G model, and more preferably a polyether polyol of the DEP-330G model produced by Zibo Dexin Federal Chemical Industry Co., Ltd. According to the research of this application, compared with other types of polyols, polyether polyols have a better effect in improving the room temperature curing speed, especially the specific model of DEP-330G polyether polyol selected and used in this application, which has a more prominent advantage in improving the room temperature curing speed.

[0032] In the present invention, the content ratio of the polyurethane hard segment to the polyurethane soft segment is preferably 1:2 to 2:1, more preferably 1:1.5 to 1.5:1. Specifically, in the embodiments of the present invention, it can be 2:3, 1:1 or 3:2.

[0033] The present invention also provides a method for preparing the above-mentioned fast-curing polyurethane protective paint, comprising the following steps:

[0034] Mixing polyether polyol and chain extender, and removing water from the mixture to obtain material A;

[0035] Dehydrating isophorone diisocyanate to obtain material B;

[0036] A catalyst and material B are added to material A to react to obtain a polyurethane protective paint.

[0037] In the present invention, the types of the polyether polyols are consistent with the types of the polyether polyols described above, and the present invention will not be repeated here.

[0038] In the present invention, the chain extender is preferably 1,4-butanediol, and the mass ratio of the polyether polyol to the chain extender is preferably 10:(1-5), more preferably 10:(2-4), such as 10:1, 10:1.5, 10:2, 10:2.5, 10:2.7, 10:3, 10:3.5, 10:4, 10:4.5, 10:5, preferably a range value with any of the above values ​​as the upper or lower limit, and the molecular weight of the polyether polyol is preferably 4000-6000Da, more preferably 5000-5500Da.

[0039] In the present invention, the temperature for removing water from the mixture is preferably 100 to 120° C., more preferably 110 to 115° C., and the time for removing water is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours.

[0040] In the present invention, the temperature for dehydrating the isophorone diisocyanate is preferably 100 to 120° C., more preferably 110 to 115° C., and the time for dehydrating is preferably 0.5 to 2 hours, more preferably 1 to 1.5 hours.

[0041] In the present invention, the catalyst is preferably dibutyltin dilaurate; the mass of the catalyst is preferably 0.1-3% of the total mass of material A and material B, more preferably 0.5-2.5%, such as 0.1%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0042] In the present invention, the reaction temperature is preferably 25-80°C, more preferably 30-50°C, such as 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, preferably a range value with any of the above values ​​as the upper or lower limit; the reaction time is preferably 20-40s, more preferably 30s.

[0043] The present invention also provides an application of the polyurethane protective paint described above as a repair coating. The present invention coats the polyurethane protective paint obtained after the reaction described above on the surface of a substrate and cures the paint to achieve a repairing effect.

[0044] In the present invention, since the polyurethane protective paint has a fast curing speed and can be cured at low temperature (such as room temperature), no high temperature curing conditions are required. Specifically, in the present invention, the curing temperature is preferably 20-80°C, more preferably 20-40°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, preferably a range value with any of the above values ​​as the upper or lower limit; the curing time is shortened to less than 1 minute, specifically 40-90s, more preferably 45-85s.

[0045] The present invention provides a fast-curing polyurethane protective paint, characterized in that the polyurethane protective paint contains a polyurethane soft segment provided by polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate; the mass ratio of the polyurethane hard segment to the polyurethane soft segment is 1:2 to 2:1. The present invention can effectively achieve low-temperature fast curing of the repair coating by accurately controlling the resin molecular structure. The present invention uses polyether polyol as the polyurethane soft segment, isophorone diisocyanate as the isocyanate hard segment, 1,4-butanediol as the chain extender, and dibutyltin dilaurate as the catalyst, and respectively investigates the influence of the catalyst content and the hard-soft segment content ratio on the system curing time to prepare a polyurethane paint that cures quickly at room temperature, and studies its performance. The polyurethane paint prepared by the present invention has a faster curing time than ordinary repair coatings, strong thermal stability, excellent coating performance, good adhesion, flexibility, wear resistance and weather resistance, and can ensure product quality and extend service life.

[0046] In order to further illustrate the present invention, a fast-curing polyurethane protective paint, a preparation method and an application thereof provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] Weigh 10 g of polyether polyol DEP-330G (molecular weight 5000 Da) and 2.6924 g of 1,4-butanediol (BDO), mix them and record them as material A. Pour them into a 100 mL three-necked flask and stir them at a constant temperature of 110° C. for 1 h to remove residual water in the solution.

[0049] Another 7.3076 g of isophorone diisocyanate IPDI was added to another three-necked flask and kept at 110° C. for 1 h to remove the residual water in the solution.

[0050] The A and B materials from which the residual water was removed were cooled to room temperature, and an appropriate amount of catalyst DBTDL (the specific amount of the catalyst is shown in Table 1) was added to the A material, and then the B material was added. The reaction was stirred at 25°C for 30 seconds to obtain a polyurethane prepolymer, i.e., a polyurethane protective paint, in which the mass ratio of the hard and soft segments was 1:1.

[0051] The polyurethane prepolymer was poured into a petri dish or a stainless steel dumbbell (national standard A1) and cured at room temperature to obtain a cured polyurethane paint, and the curing time was recorded. The results are shown in Table 1.

[0052] Table 1 Effect of catalyst dosage on system curing time

[0053]

[0054] It can be seen from Table 1 that under the condition of low concentration of catalyst, as the proportion of catalyst increases, the curing time of P(DEP-BDO-IPDI) polyurethane paint gradually decreases, but when the proportion of catalyst reaches 2%, 2.5%, and 3%, the curing time of polyurethane paint remains basically unchanged, which proves that the increase in the proportion of catalyst can accelerate the curing time of polyurethane paint to a certain extent, but when it reaches a certain proportion, it will basically not enhance the curing time of polyurethane paint.

[0055] Example 2

[0056] Weigh 10 g of polyether polyol DEP-330G and a certain mass of 1,4-butanediol (BDO), mix them and record them as material A. Pour them into a 100 mL three-necked flask and stir them at a constant temperature of 110°C for 1 h to remove the residual water in the solution.

[0057] A certain mass of isophorone diisocyanate IPDI, marked as material B, was added into another three-necked flask and kept at a constant temperature of 110° C. for 1 h to remove the residual water in the solution.

[0058] The material A and material B from which the residual water was removed were cooled to room temperature, and the catalyst DBTDL (the mass of the catalyst was 0.5% of the total mass of the material A and the material B) was added to the material A, and then the material B was added. The reaction was stirred at 25° C. for 30 seconds to obtain a polyurethane prepolymer, i.e., a polyurethane protective paint. The mass ratio of the hard and soft segments in the polyurethane protective paint was specifically shown in Table 2.

[0059] The polyurethane prepolymer was poured into a petri dish or a stainless steel dumbbell (national standard A1), and cured at room temperature and 80°C to obtain a cured polyurethane paint, and the curing time was recorded. The results are shown in Table 2.

[0060] Table 2 Effect of hard and soft segment content ratio on system curing time

[0061]

[0062] It can be seen from Table 2 that within a certain range, as the hard-soft segment content ratio increases, the curing time of P(DEP-BDO-IPDI) polyurethane paint gradually decreases. And under the condition of 80°C, the curing time of polyurethane paint with the same hard-soft segment content ratio is shorter than that at room temperature.

[0063] Infrared spectroscopy

[0064] The qualified sample of P(DEP-BDO-IPDI) polyurethane paint prepared in Experiment No. 1 of Example 2 was analyzed by Fourier transform infrared spectrometer. The wave number range of infrared spectrum test was 4000~500cm -1 , resolution 4cm -1 . Press KBr into a tablet and measure it as a blank background control. Take an appropriate amount of IPDI to make a tablet and put it into the infrared spectrometer for measurement as a peak control experiment. Then mix the sample to be tested with KBr at a ratio of 1:100. Dry for 5 minutes, press into a tablet, and perform infrared spectrum measurement.

[0065] The structure of the prepared P(DEP-BDO-IPDI) polyurethane paint was characterized by Fourier transform infrared spectroscopy. Figure 1 As shown, line A represents P(DEP-BDO-IPDI) polyurethane paint, and line B represents the characteristic absorption peak of B material IPDI-CH2 at 2975-2875 cm -1 , 2934cm -1 The absorption peak at 2260cm corresponds to the stretching vibration peak of -CH2-. -1 Nearby is the characteristic peak of -N=C=O, Figure 1 It can be seen that line A is at 2257cm -1 No characteristic peak of -NCO was found at , indicating that the remaining -NCO reacted completely with BDO. In summary, the infrared spectrum analysis showed that the polyurethane paint was successfully prepared.

[0066] Scanning electron microscope morphology

[0067] The qualified sample of P(DEP-BDO-IPDI) polyurethane paint prepared in Experiment No. 1 of Example 2 was observed using a field emission scanning electron microscope. The microstructure of the polyurethane paint was observed using electron microscope modes of different magnifications. The prepared polyurethane paint was first cut into pieces, placed on a stage, and dried for 12 hours. After drying, the sample on the stage was sprayed with gold. The electron microscope parameters were an acceleration voltage of 10 kV and a magnification of 8 to 10 W times.

[0068] According to the research results, the qualified sample P (DEP-BDO-IPDI) polyurethane paint was selected and observed under a field emission scanning electron microscope (SEM). Figure 2 and Figure 3 , which are SEM images of polyurethane paint at different magnifications. Figure 2 and 3 It can be seen that the prepared P(DEP-BDO-IPDI) polyurethane paint presents a cured block structure.

[0069] Mechanical properties test

[0070] The polyurethane paint sample prepared in Experiment No. 1 of Example 2 was cut into rectangular parallelepiped strips with a length of 25 mm, a width of 5 mm, and a height of 3 mm. The mechanical properties of the protective paint were tested on an electronic universal testing machine. The test temperature was room temperature and the tensile rate was 20 mm*min. -1 To reduce the chance factor, the samples were tested three times.

[0071] The structural difference of polyurethane paint has an important influence on its mechanical properties. The mechanical properties of the prepared qualified polyurethane paint were tested by an electronic universal testing machine. Figure 4 ,Depend on Figure 4 It can be seen that when the sample exhibited the strongest mechanical properties, the tensile stress reached 6.3445MPa and the tensile strain was 675.2%. The average tensile stress of the sample reached 5.3667MPa and the average tensile strain was 499.3%. IPDI has an asymmetric isocyanate structure, which increases the disorder of the protective paint structure, is conducive to the migration of internal chain segments, reduces the mechanical strength of the protective paint, and increases the strain of the protective paint. 1,4-Butanediol as a chain extender improves the mechanical properties of the system, making the experimentally prepared fast-curing P (DEP-BDO-IPDI) polyurethane paint have good application value.

[0072] Thermal performance test

[0073] The qualified samples were tested by thermogravimetric analyzer. The P(DEP-BDO-IPDI) polyurethane paint prepared in Experiment No. 1 of Example 2 was cut into pieces, and the sample mass was weighed to be 7 mg, and placed in an Al2O3 crucible. The instrument parameters were set, the test temperature range was 30-600°C, the heating rate was 10K / min, N2 protection was adopted, and the N2 flow rate was 40mL / min.

[0074] The DSC test was performed using a differential scanning calorimeter. The P(DEP-BDO-IPDI) polyurethane paint was cut into pieces and the sample mass was weighed to be 15 mg. The test temperature range was -150 to 150°C, the heating rate was 10K / min, and N2 protection was adopted with an N2 flow rate of 40mL / min. During the test, the temperature was first raised from room temperature to 150°C, kept for 5 minutes, then cooled to -150°C, kept for 5 minutes, and then raised to 120°C to test the glass transition temperature of the sample.

[0075] like Figure 5 As shown in the figure, the thermodynamic stability of P(DEP-BDO-IPDI) polyurethane paint was analyzed by TG. The polyurethane paint began to decompose at 285.7℃ and the decomposition was completed at 402.2℃. The decomposition rate was fastest at 322.1℃. This section was mainly concentrated in the breakage and decomposition of the ester ring of isocyanate in the molecular structure and the aliphatic group in the polycarbonate structure, indicating that the protective paint has good thermal stability.

[0076] Depend on Figure 6 It can be seen that the Tg of the sample is lower than room temperature, and no crystallization endothermic peak and exothermic peak appear in the entire test range, indicating that the P(DEP-BDO-IPDI) polyurethane paint exhibits good resilience and strong stability.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fast-curing polyurethane protective paint, characterized in that: The polyurethane protective paint contains a polyurethane soft segment provided by a polyether polyol and a polyurethane hard segment provided by isophorone diisocyanate; The mass ratio of the polyurethane hard segment to the polyurethane soft segment is 1:2 to 2:

1.

2. The fast-curing polyurethane protective paint according to claim 1, characterized in that: The polyether polyol is polyether polyol DEP-330G.

3. A method for preparing a fast-curing polyurethane protective paint as claimed in claim 1 or 2, comprising the following steps: Mixing polyether polyol and chain extender, and removing water from the mixture to obtain material A; Dehydrating isophorone diisocyanate to obtain material B; A catalyst and material B are added to material A to react to obtain a polyurethane protective paint.

4. The preparation method according to claim 3, characterized in that: The chain extender is 1,4-butanediol; The mass ratio of the polyether polyol to the chain extender is 10:(1-5).

5. The preparation method according to claim 3, characterized in that: The temperature for dehydrating the mixture is 100 to 120° C., and the time for dehydrating the mixture is 0.5 to 2 hours.

6. The preparation method according to claim 3, characterized in that: The temperature for dehydrating isophorone diisocyanate is 100 to 120°C, and the time for dehydrating is 0.5 to 2 hours.

7. The preparation method according to claim 3, characterized in that: The catalyst is dibutyltin dilaurate; The mass of the catalyst is 0.1-3% of the total mass of the A material and the B material.

8. The preparation method according to claim 3, characterized in that: The reaction temperature is 25-80° C., and the reaction time is 20-40 seconds.

9. The use of polyurethane protective paint as a repair coating, characterized in that: The polyurethane protective paint is the fast-curing polyurethane protective paint described in claims 1 to 2 or the fast-curing polyurethane protective paint prepared by the preparation method described in any one of claims 3 to 8.

10. The use according to claim 9, characterized in that: The curing temperature of the polyurethane protective paint is 20 to 80° C., and the curing time is 40 to 90 seconds.

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