Preparation process of exposed rubber asphalt waterproof coating

Abstract

The invention discloses a preparation process of an exposed rubber asphalt waterproof coating, relates to the technical field of waterproof coatings, and provides a method for introducing a polyurethane prepolymer HS-PU containing dynamic disulfide bonds into a base material system in order to solve the problems that a traditional coating is poor in elastic recovery after being cured and easy to crack at low temperature; the preparation method comprises the following steps: carrying out condensation polymerization on 4, 4 '-diaminodiphenyl disulfide and polytetrahydrofuran glycol to form a reversible cross-linked network; a temperature response type topological structure is constructed in a dynamic curing stage by combining the synergistic ratio of the anionic emulsified asphalt and the SBR emulsion; the preparation method comprises the following steps: preparing an HS-PU prepolymer, mixing base materials, carrying out gradient temperature control curing and carrying out low-temperature grinding, the elastic recovery rate of the obtained coating at-30 DEG C is greater than or equal to 75%; the method is suitable for metal roofs, bridges and other large-temperature-difference scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of waterproof coatings, and in particular to a preparation process for an exposed rubber asphalt waterproof coating. Background Art

[0002] As a key material in the field of building protection, the exposed rubber asphalt waterproof coating has been long-term applied to directly exposed scenarios such as roofs and bridge decks; the traditional process uses SBR rubber latex and anionic emulsified asphalt as the main substrates, and forms a homogeneous system through high-temperature mixing, filler compounding and mechanical grinding.

[0003] However, when the ambient temperature drops suddenly, the crystallization of asphalt components accelerates, and the movement of rubber molecular chain segments is hindered, resulting in irreversible cracks after the coating is bent by external force; such defects are particularly prominent in the northwest region where the day-night temperature difference exceeds 30°C, and the waterproof layer is prone to penetrative damage after winter freeze-thaw cycles; even if the rubber content is increased to more than 25%, the material still faces the contradiction of inversion of elasticity and strength. Although excessive rubber improves flexibility, it causes the bonding strength of the coating to decrease by more than 35%, forming a new leakage hazard;

[0004] To alleviate the problem of elastic recovery, some solutions introduce phthalate plasticizers to improve low-temperature ductility, but small molecule plasticizers continuously migrate and volatilize under the action of ultraviolet rays, and the hardness of the coating increases by more than 40% after 6 months; some solutions externally use thermoplastic elastomers such as SEBS to partially replace SBR, although the elastic modulus at -15°C is improved, the material cost surges by 2 times and the compatibility with asphalt deteriorates; in addition, some solutions add peroxides to initiate chemical cross-linking. Although a three-dimensional network is constructed to improve the resilience, excessive cross-linking leads to an increase in the brittle temperature point of the material, and the cracking risk is aggravated in an environment below 10°C; therefore, there is an urgent need for a preparation process for an exposed rubber asphalt waterproof coating to solve such problems. Summary of the Invention

[0005] In view of the above existing problems, the present invention is proposed.

[0006] The present invention provides a preparation process for an exposed rubber asphalt waterproof coating to solve the problems of high precision requirements for the core-shell filler preparation process and the need for strict control of the addition amount of surface treatment agents in industrialization.

[0007] To solve the above technical problems, the present invention provides the following technical solutions:

[0008] An embodiment of the present invention provides a preparation process for an exposed rubber asphalt waterproof coating, which includes,

[0009] Step S1: React 4,4'-diaminodiphenyl disulfide with polytetrahydrofuran ether glycol in a molar ratio of 1:3 - 1:5 at 60 - 75°C for 2 - 3 hours. Then add isophorone diisocyanate and continue the reaction until the NCO content reaches 3.5 - 4.2% to obtain the HS-PU prepolymer.

[0010] Step S2: Mix anionic emulsified asphalt, SBR rubber latex with the HS-PU prepolymer obtained in Step S1 at a mass ratio of 100:25 - 35:4 - 6 at 40 - 50°C, and control the stirring rate at 200 - 300 rpm.

[0011] Step S3: Sequentially add fumed silica and heavy calcium carbonate to the mixture in Step S2. The mass ratio of fumed silica to heavy calcium carbonate is 1:8 - 1:12, and the total addition amount is 15 - 22% of the solid content of the mixture.

[0012] Step S4: Heat the material obtained in Step S3 to 80 - 85°C, hold for 1.5 - 2 hours and continuously introduce nitrogen for protection, and then cool it to below 50°C.

[0013] Step S5: Grind it with a twin-screw grinder at 40 - 45°C until the fineness is ≤50μm, and finally add an antifoaming agent and a preservative to obtain the product.

[0014] As a preferred scheme of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the number average molecular weight of the polytetrahydrofuran ether glycol in Step S1 is 1500 - 2000 g / mol, and the reaction is carried out in a mixed solvent with a volume ratio of xylene to ethyl acetate of 2:1.

[0015] As a preferred scheme of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the fumed silica in Step S3 is a 1200-mesh product surface-treated with silane coupling agent KH-550, and the addition amount of the surface treatment agent is 1.2 - 1.8% of the mass of the fumed silica.

[0016] As a preferred scheme of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the heating rate in Step S4 is 2 - 3°C / min, and the cooling stage adopts a gradient cooling mode, first cooling to 60°C within 30 minutes and then naturally cooling to below 50°C.

[0017] As a preferred scheme of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the length-diameter ratio of the screw of the twin-screw grinder in Step S5 is 28:1, and the grinding pressure is controlled at 0.15 - 0.25 MPa.

[0018] As a preferred embodiment of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, the preparation process further includes adding epoxidized soybean oil accounting for 0.5-1.2% of the total mass of the mixture as an auxiliary plasticizer in step S3.

[0019] As a preferred embodiment of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the defoamer in step S4 is a polyether-modified silicone defoamer, and its addition amount is 0.1-0.3% of the total mass of the mixture; the preservative is an isothiazolinone compound, and the addition amount is 0.05-0.15%.

[0020] As a preferred embodiment of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, the preparation process further includes adding a light stabilizer after step S3. The light stabilizer is a compound system composed of a hindered amine and a benzotriazole, and the total addition amount is 0.5-1.5% of the mass of the filler, wherein the mass ratio of the hindered amine to the benzotriazole is 2:1-3:1.

[0021] As a preferred embodiment of the preparation process of the exposed rubber asphalt waterproof coating described in the present invention, wherein: the penetration of the anionic emulsified asphalt at 25°C is 60-80, 0.1mm, the softening point ≥ 85°C, the solid content of the SBR rubber latex is 45-50%, and the glass transition temperature Tg is -45°C to -50°C.

[0022] In the second aspect, the present invention also provides an exposed rubber asphalt waterproof coating, which is prepared based on the above-mentioned preparation process of the exposed rubber asphalt waterproof coating. The coating contains a dynamic disulfide bond cross-linked structure with a mass fraction of 2.1-3.5%. The dynamic disulfide bond cross-linked structure is formed by the thiol-ene click reaction between the HS-PU prepolymer and the double bond in the SBR rubber latex, and the cross-linking point spacing is 8-15nm; the filler dispersion phase of the coating contains a core-shell structure of fumed silica and heavy calcium carbonate, wherein the fumed silica coats the surface of the calcium carbonate in a dendritic form, and the dendritic length ≤ 200nm.

[0023] The beneficial effects of the present invention are as follows: in the present invention, the dynamic disulfide bond cross-linked network endows the coating with reversible deformation ability; the core-shell structure of fumed silica dendrites coating calcium carbonate, with dendrites ≤ 200nm, synergistically with the dynamic cross-linked network enables the crack width ≤ 0.1mm after 50 freeze-thaw cycles; the gradient temperature-controlled curing at 80-85°C and the twin-screw low-temperature grinding ≤ 45°C are compatible with the existing production line, the hindered amine / benzotriazole compounded light stabilizer enables the yellowing index Δb < 2.0 after 500h of ultraviolet aging, and the strength retention rate of the dynamic cross-linked network after thermal aging > 90%. Description of the Drawings

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0025] Figure 1 It is a schematic flow chart of the preparation process of the exposed rubber asphalt waterproof coating in Example 1. Specific Embodiments

[0026] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will provide a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification.

[0027] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0028] Secondly, a so-called embodiment or an embodiment herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. Appearing in different places in this specification, an embodiment does not necessarily refer to the same embodiment, nor is it a separate or selectively exclusive embodiment from other embodiments.

[0029] Example 1, referring to Figure 1 , this example provides a preparation process for an exposed rubber asphalt waterproof coating, including the following steps:

[0030] 1. Preparation of HS-PU prepolymer:

[0031] Add 4,4'-diaminodiphenyl disulfide (0.2 mol) and polytetrahydrofuran ether glycol (Mn = 1800, 0.8 mol) to the reaction kettle, and add 300 mL of a xylene / ethyl acetate (2:1) mixed solvent;

[0032] Heat up to 65 °C and react for 2.5 hours, then add isophorone diisocyanate (0.5 mol), and maintain at 70 °C until the NCO content reaches 3.8%;

[0033] Remove the solvent under reduced pressure to obtain a light yellow viscous liquid;

[0034] 2. Base material mixing:

[0035] Take 100 kg of anionic emulsified asphalt (solid content 60%), 30 kg of SBR rubber latex (solid content 48%), and 5 kg of HS-PU prepolymer, and stir and mix them at 45 °C at 250 rpm for 40 minutes;

[0036] 3. Filler dispersion:

[0037] Add 3 kg of 1200-mesh fumed silica treated with KH-550 and 27 kg of heavy calcium carbonate, and stir and disperse until the fineness is ≤80 μm;

[0038] 4. Dynamic crosslinking and curing:

[0039] Heat the material to 83 °C at a rate of 2.5 °C / min, and cure it under nitrogen protection for 1.8 hours, then cool it down to 45 °C step by step;

[0040] 5. Grinding and modulation:

[0041] Use a twin-screw grinder with a length-to-diameter ratio of 28:1 to grind to a fineness of 45 μm at a pressure of 0.2 MPa and a temperature of 42 °C;

[0042] Add 0.3 kg of silicone defoamer and 0.1 kg of isothiazolinone preservative, and mix evenly to obtain the finished product;

[0043] Example 2, this example provides a preparation process for an exposed rubber asphalt waterproof coating, including the following steps:

[0044] 1. In the preparation of HS-PU prepolymer, adjust the molar ratio of 4,4'-diaminodiphenyl disulfide to polytetrahydrofuran ether glycol to 1:4.5, and raise the reaction temperature to 72 °C;

[0045] 2. In the base material mixing stage, increase the addition amount of SBR latex to 35 kg and reduce the HS-PU prepolymer to 4.2 kg;

[0046] 3. Add 0.8 kg of epoxy soybean oil during filler dispersion, and replace heavy calcium carbonate with an equal amount of mica powder;

[0047] 4. Lower the curing temperature to 80 °C and extend the time to 2 hours;

[0048] 5. Control the grinding pressure at 0.18 MPa, and the final fineness reaches 48 μm;

[0049] Example 3, this example provides a preparation process for an exposed rubber asphalt waterproof coating, including the following steps:

[0050] 1. Use polytetrahydrofuran ether glycol with a number average molecular weight of 2000, and increase the NCO end value to 4.1% during the preparation of HS-PU prepolymer;

[0051] 2. During the base material mixing stage, the dosage of anionic emulsified asphalt is increased to 120 kg, and the stirring rate is simultaneously increased to 280 rpm;

[0052] 3. The total filler addition amount is adjusted to 20% of the solid content, and the proportion of fumed silica is increased to 1:7;

[0053] 4. The curing process uses programmed temperature control: 80°C × 1 h → 85°C × 0.5 h;

[0054] 5. After grinding, 2 kg of silicon carbide whiskers (diameter 0.3 μm) are additionally added to enhance the mechanical properties;

[0055] Experimental Example 1

[0056] The elastic recovery rate is tested according to the improved method in GB / T 528-2009 "Rubber, vulcanized or thermoplastic - Determination of tensile stress - strain properties";

[0057] Experimental group: The coatings prepared in Examples 1 - 3 are coated on an aluminum plate with a thickness of 2 mm and cured for 7 days (23 ± 2°C, RH 50%);

[0058] Control group: Traditional process coatings (without adding HS - PU prepolymer, with the same other components);

[0059] The specimen is placed in an environmental chamber at - 30°C and kept at a constant temperature for 4 hours;

[0060] Using a universal material testing machine, the specimen is bent 180° at a rate of 10 mm / min and then immediately released;

[0061] Record the angle recovery value within 30 seconds, calculation formula:

[0062]

[0063] Record the experimental data:

[0064] Experimental group: Example 1 is 84 ± 2%, Example 2 is 81 ± 3%, Example 3 is 79 ± 2%;

[0065] Control group: 53 ± 5%.

[0066] Experimental Example 2

[0067] Refer to Appendix B of JC / T 975 - 2005 "Waterproof coatings for road and bridge" for the freeze - thaw cycle crack resistance test; The coating specimen (thickness 1.5 mm) is fixed on a deformable fixture, and a pre - applied tensile strain of 0.5% is applied; Cycle conditions: - 25°C freezing for 4 h → 23°C water bath thawing for 4 h, a total of 50 cycles;

[0068] Failure analysis:

[0069] Experimental group: Only microcracks less than 0.1 mm appeared on the surface of the specimens in Examples 1-3, and there was no through damage;

[0070] Control group: The crack width reached 1.2 - 1.8 mm, and delamination and spalling occurred at the edges;

[0071] The cross-section was observed by an electron microscope (SEM, ×500): The crack path in the experimental group showed a zigzag extension (energy dissipation characteristic), while that in the control group was a straight brittle crack.

[0072] Experimental Example 3

[0073] The stability of the dynamic cross-linked network was verified, and the storage modulus (E’) and loss factor (tanδ) were measured by a dynamic mechanical analyzer (DMA); Temperature scanning range: -50 °C to 100 °C, heating rate 3 °C / min;

[0074] The glass transition temperature (Tg) was monitored:

[0075] Example 1: Tg of the SBR phase = -45.2 °C, Tg of the HS-PU phase = 12.5 °C (the bimodal peak characterizes the two-phase separation structure);

[0076] Control group: Single Tg = -38.7 °C (indicating that no effective dynamic cross-linking was formed);

[0077] Cross-linking density: Calculated according to the rubber elasticity theory, the cross-linking density of the experimental group was 2.1×10 -4 mol / cm 3 , which was 62% higher than that of the control group (1.3×10 -4 mol / cm 3 );

[0078] In summary, combining the experimental examples and verification data, it can be seen that the reversible cross-linked network constructed by dynamic disulfide bonds significantly improves the low-temperature elastic recovery ability of the coating, meeting the long-term service requirements of exposed waterproof coatings.

[0079] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation process for an exposed rubber asphalt waterproof coating, characterized in that: Including, Step S1: React 4,4'-diaminodiphenyl disulfide with polytetrahydrofuran ether glycol at a molar ratio of 1:3 - 1:5 at 60 - 75 °C for 2 - 3 hours, then add isophorone diisocyanate and continue the reaction until the NCO content reaches 3.5 - 4.2% to obtain an HS-PU prepolymer; Step S2: Mix anionic emulsified asphalt, SBR rubber latex with the HS-PU prepolymer obtained in Step S1 at a mass ratio of 100:25 - 35:4 - 6 at 40 - 50 °C, and control the stirring rate at 200 - 300 rpm; Step S3: Sequentially add fumed silica and heavy calcium carbonate to the mixture in Step S2. The mass ratio of fumed silica to heavy calcium carbonate is 1:8 - 1:12, and the total addition amount is 15 - 22% of the solid content of the mixture; Step S4: Heat the material obtained in Step S3 to 80 - 85 °C, hold for 1.5 - 2 hours and continuously pass nitrogen for protection, and then cool to below 50 °C; Step S5: Grind with a twin-screw grinder at 40 - 45 °C until the fineness ≤ 50 μm, and finally add an antifoaming agent and a preservative to obtain the product.

2. The preparation process of an exposed rubber asphalt waterproof coating according to claim 1, characterized in that: In Step S1, the number-average molecular weight of the polytetrahydrofuran ether glycol is 1500 - 2000 g / mol, and the reaction is carried out in a mixed solvent with a volume ratio of xylene to ethyl acetate of 2:

1.

3. The preparation process of an exposed rubber asphalt waterproof coating as described in claim 1, characterized in that: In Step S3, the fumed silica is a 1200-mesh product surface-treated with silane coupling agent KH-550, and the addition amount of the surface treatment agent is 1.2 - 1.8% of the mass of the fumed silica.

4. The preparation process of an exposed rubber asphalt waterproof coating as claimed in claim 1, characterized in that: In Step S4, the heating rate is 2 - 3 °C / min, and the cooling stage adopts a gradient cooling mode. First, cool to 60 °C within 30 min, and then naturally cool to below 50 °C.

5. The preparation process of an exposed rubber asphalt waterproof coating as claimed in claim 1, characterized in that: In Step S5, the length-diameter ratio of the screws of the twin-screw grinder is 28:1, and the grinding pressure is controlled at 0.15 - 0.25 MPa.

6. The preparation process of an exposed rubber asphalt waterproof coating as claimed in claim 1, wherein It also includes adding 0.5 - 1.2% of epoxidized soybean oil based on the total mass of the mixture as an auxiliary plasticizer in Step S3.

7. The preparation process of an exposed rubber asphalt waterproof coating as claimed in claim 4, characterized in that: In Step S4, the antifoaming agent is a polyether-modified silicone antifoaming agent, and its addition amount is 0.1 - 0.3% of the total mass of the mixture. The preservative is an isothiazolinone compound, and the addition amount is 0.05 - 0.15%.

8. The preparation process of an exposed rubber asphalt waterproof coating as claimed in claim 7, characterized in that, The preparation process also includes adding a light stabilizer after Step S3. The light stabilizer is a compound system of hindered amines and benzotriazoles, and the total addition amount is 0.5 - 1.5% of the mass of the filler, where the mass ratio of hindered amines to benzotriazoles is 2:1 - 3:

1.

9. The preparation process of an exposed rubber asphalt waterproof coating as described in claim 8, characterized in that: The penetration of the anionic emulsified asphalt at 25 °C is 60 - 80, 0.1 mm, the softening point ≥ 85 °C, the solid content of the SBR rubber latex is 45 - 50%, and the glass transition temperature Tg is -45 °C to -50 °C.

10. An exposed rubber asphalt waterproof coating, based on the preparation process of an exposed rubber asphalt waterproof coating according to any one of claims 1 to 9, characterized in that, The coating contains a dynamic disulfide cross-linked structure with a mass fraction of 2.1-3.5%. The dynamic disulfide cross-linked structure is formed by the thiol-ene click reaction between the HS-PU prepolymer and the double bonds in the SBR rubber latex, and the crosslinking point spacing is 8-15 nm. The filler dispersion phase of the coating contains a core-shell structure of fumed silica and heavy calcium carbonate, where the fumed silica coats the surface of calcium carbonate in a dendritic form, and the dendritic length ≤ 200 nm.

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