Nano silicon dioxide modified flame-retardant coating and preparation method thereof

Abstract

The invention relates to the technical field of silicon dioxide flame-retardant coatings, in particular to a nano silicon dioxide modified flame-retardant coating which is prepared from the following raw materials in parts by mass: 70 to 90 parts of waterborne polyurethane emulsion, 5 to 20 parts of functionalized nano silicon dioxide, 0.3 to 1 part of dispersing agent, 0.1 to 0.5 part of flatting agent and 0.1 to 0.3 part of defoaming agent, according to the nano silicon dioxide modified flame-retardant coating, the high length-diameter ratio gt of wormlike mesoporous silicon dioxide; according to the present invention, the ratio of the components is 10: 1, the components are interlocked in the coating to form the physical barrier, the flame propagation path is prolonged, the pore size is 10-20 nm, the high specific surface area loading site can be provided, the aging resistance is substantially improved, and the carbon layer density is at least improved by 3 times.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon dioxide flame retardant coatings, and in particular to a nano silicon dioxide modified flame retardant coating and a preparation method thereof. Background Art

[0002] Flame-retardant coatings are a crucial material for reducing casualties and property damage. When a fire breaks out, they form a protective layer, making the coated surface less prone to burning or ignition, slowing the spread of the fire and allowing firefighters ample time to extinguish and rescue. Furthermore, flame-retardant coatings reduce the release of harmful substances. Smoke and harmful gases produced by fires are a major cause of casualties. The use of flame-retardant coatings can slow the rate of combustion, reducing the amount of smoke and harmful gases produced to a certain extent. Therefore, the flame-retardant properties of flame-retardant coatings are crucial for fire prevention. They can effectively protect against fires caused by natural disasters and human factors, preventing the spread and spread of fires and minimizing casualties and property damage.

[0003] However, existing flame-retardant coatings generally use spherical nano-silica as a flame-retardant filler. Although it can improve the thermal stability of the coating, it has three major defects: 1. Morphological limitations: spherical particles are easy to agglomerate and randomly disperse in the coating, and cannot form a continuous barrier layer; 2. Single function: It only relies on the physical barrier effect of silica, or adds small molecule flame retardants through physical mixing, which leads to the migration and precipitation of flame retardants; 3. No antibacterial function: microorganisms erode the coating and accelerate the degradation of the flame retardant structure. In view of this, we propose a nano-silica modified flame-retardant coating and its preparation method. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies mentioned in the above background technology and to provide a nano-silicon dioxide modified flame retardant coating and a preparation method thereof.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A nano-silicon dioxide modified flame retardant coating, wherein the mass fractions of the raw material components of the nano-silicon dioxide modified flame retardant coating are as follows:

[0007]

[0008] The functionalized nano-silica has an aspect ratio of >10:1, a pore size of 10-20 nm, and a specific surface area of ​​≥400 m 2 / g.

[0009] Preferably, the preparation steps of the functionalized nano-silica are specifically as follows:

[0010] Step 1: Place worm-like mesoporous silica in a 250ml three-necked flask, add 100ml of anhydrous ethanol, and ultrasonically disperse until no precipitation occurs;

[0011] Step 2: Add silane coupling agent and replace air with nitrogen, react in an oil bath and magnetic stirring for 4 hours, then centrifuge, wash with ethanol three times, and vacuum dry to obtain amino silica;

[0012] Step 3: Disperse the amino-silica in anhydrous toluene, add hexachlorocyclotriphosphazene and protect with nitrogen, then place in an oil bath, condense and reflux for 6 hours, then collect the solid by centrifugation, wash with toluene and ethanol in sequence, and dry in vacuum to obtain the phosphazene-silica;

[0013] Step 4: Disperse the phosphazene silica in DMF and add bromododecane, then stir in an oil bath for 8 hours, then centrifuge and wash alternately with DMF / ethanol three times, and finally vacuum dry for 12 hours to obtain functionalized nano-silica.

[0014] Preferably, the preparation steps of the worm-like mesoporous silica are as follows: preparing a template with hexadecyltrimethylammonium bromide / sodium dodecyl sulfate, carrying out a hydrothermal reaction at a temperature of 160-180° C. for a reaction time of 12-24 h, and calcining to remove the template.

[0015] Preferably, the dispersant is BYK-190.

[0016] Preferably, the leveling agent is BYK-346.

[0017] Preferably, the defoaming agent is based on mineral oil.

[0018] Preferably, the functionalized nano-silica is oriented in the coating by shear electric field induction to form a multi-layer barrier network parallel to the substrate.

[0019] A preparation method of a nano-silica modified flame-retardant coating comprises the following specific steps: uniformly mixing an aqueous polyurethane emulsion, functionalized nano-silica, and a dispersant, adding a defoamer and a leveling agent, and continuously stirring at a speed of 400-600 r / min for 15-25 minutes to obtain the nano-silica modified flame-retardant coating.

[0020] Preferably, the mixing temperature is 40-60°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This nano-silica modified flame retardant coating has a high aspect ratio of >10:1 of worm-like mesoporous silica, which interlocks in the coating to form a physical barrier, extending the flame propagation path. The pore size is 10-20nm, which can provide high specific surface area loading sites, greatly improving aging resistance and increasing the carbon layer density by at least 3 times.

[0023] 2. The quaternary ammonium salt modification layer can destroy the cell membrane of microorganisms and decompose to produce NH3 to dilute oxygen. The antibacterial rate is ≥99.8%, and the flame retardant / antibacterial life is extended to 2 times that of conventional coatings. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] The present invention describes the above technical solution in detail through the following embodiments:

[0026] Example 1

[0027] A nano-silicon dioxide modified flame retardant coating, wherein the mass fractions of the raw material components of the nano-silicon dioxide modified flame retardant coating are as follows:

[0028]

[0029] Among them, the functionalized nano-silica is a worm-like mesoporous silica with phosphorus-nitrogen-silicon ternary flame retardant and quaternary ammonium salt antibacterial group grafted on the surface, with an aspect ratio of >10:1, a pore size of 10-20nm, and a specific surface area of ​​≥400m 2 / g.

[0030] It should be noted that the worm-like mesoporous silica has a high aspect ratio of >10:1, which interlocks in the coating to form a physical barrier, extending the flame propagation path, and has a pore diameter of 10-20nm, which can provide high specific surface area loading sites, greatly improving aging resistance, and increasing the carbon layer density by at least 3 times.

[0031] Among them, the phosphazene grafted layer allows thermal decomposition to release PO· free radicals to interrupt the combustion chain reaction, promote dehydration and carbonization, and form a Si-OP ceramic layer.

[0032] Among them, the quaternary ammonium salt modification layer can destroy the cell membrane of microorganisms and decompose to produce NH3 to dilute oxygen. The antibacterial rate is ≥99.8%, and the flame retardant / antibacterial life is extended to 2 times that of conventional coatings.

[0033] The preparation steps of the functionalized nano-silica are as follows:

[0034] Step 1: Select 10g of worm-like mesoporous silica and place it in a 250ml three-necked flask. Add 100ml of anhydrous ethanol and disperse it by ultrasonication (power 300W, 30min) until there is no precipitation.

[0035] Step 2: Add 1.2 g of KH-550 and replace the air with nitrogen. React in an oil bath at 70 ± 2 ° C with magnetic stirring (500 rpm) for 4 h, then centrifuge (8000 rpm × 10 min), wash three times with ethanol, and dry in vacuo at 60 ° C for 6 h to obtain amino silica.

[0036] Step 3: Disperse 5 g of amino-silica in 80 ml of anhydrous toluene, add 2.38 g of hexachlorocyclotriphosphazene and protect with nitrogen, in an oil bath at 110±1°C, reflux under condensation for 6 h, then collect the solid by centrifugation, wash with toluene and ethanol in sequence, and dry in vacuo at 60°C to obtain phosphazene-silica;

[0037] Step 4: Disperse 4 g of phosphazene silica in 60 ml of DMF and add bromododecane (molar ratio of bromododecane: HCCP = 1.2:1), then stir in an oil bath at 60±1°C for 8 h, then centrifuge and wash alternately with DMF / ethanol three times, and finally dry in vacuum at 40°C for 12 h to obtain functionalized nano-silica.

[0038] The preparation steps of the worm-like mesoporous silica are as follows: preparing a template with hexadecyltrimethylammonium bromide / sodium dodecyl sulfate, carrying out a hydrothermal reaction at a temperature of 160-180° C. for a reaction time of 12-24 hours, and calcining to remove the template.

[0039] Among them, the functionalized nano-silica is oriented in the coating through shear electric field induction to form a multi-layer barrier network parallel to the substrate. The angle between the electrode plate and the substrate plane is 0-15°, so that the long axis of the worm-like mesoporous silica is parallel to the substrate. The worm-like particles are polarized in the electric field, and the long axis is oriented along the electric field line → mechanical shear force destroys the oriented agglomeration → forming a dense layered structure.

[0040] Unless otherwise specified, the components and raw materials used in the examples and comparative examples of the present invention are all commercially available raw materials.

[0041] A method for preparing a nano-silica modified flame-retardant coating comprises the following specific steps: uniformly mixing an aqueous polyurethane emulsion, functionalized nano-silica, and a dispersant at a mixing temperature of 60°C, adding a defoamer and a leveling agent, and continuously stirring at a speed of 400-600 rpm for 15-25 minutes to obtain the nano-silica modified flame-retardant coating.

[0042] Example 2

[0043] The only difference between this embodiment and embodiment 1 is that 10 parts of functionalized nano-silica are added in this embodiment, and other conditions are the same.

[0044] Example 3

[0045] The only difference between this embodiment and embodiment 1 is that 15 parts of functionalized nano-silica are added in this embodiment, and other conditions are the same.

[0046] Example 4

[0047] The only difference between this embodiment and embodiment 1 is that 20 parts of functionalized nano-silica are added in this embodiment, and other conditions are the same.

[0048] Comparative Example 1

[0049] The only difference between this comparative example and Example 1 is that this comparative example uses commercially available nano-silicon dioxide flame retardant coating.

[0050] Comparative Example 2

[0051] The only difference between this comparative example and Example 1 is that spherical nano-silica is used to replace the functionalized nano-silica in this comparative example, and other conditions are the same.

[0052] Comparative Example 3

[0053] The only difference between this comparative example and Example 1 is that in this comparative example, the functionalized nano-silica is not aligned in the coating layer by induction of shear electric field, and other conditions are the same.

[0054] The nano-silica modified flame retardant coatings prepared in Examples 1-4 and Comparative Examples 1-3 were applied to substrates and subjected to the following performance tests. The results are shown in Tables 1 and 2, respectively.

[0055] Test items:

[0056] 1. Limiting Oxygen Index (LOI): According to GB / T 2408-2021 standard, apply the coating to a 100×10×3mm 3 Glass fiber reinforced epoxy board, dry film thickness 80±5μm; the sample is fixed vertically to the combustion tube, and an O2 / N2 mixed gas is introduced; the oxygen concentration is adjusted, and the minimum oxygen concentration of the sample during continuous combustion for ≥3 minutes is measured (repeat 3 times and take the average value).

[0057] 2. Vertical burning (UL94): According to ANSI / UL 94-2018 standard, specimen size 125×13×3mm 3, hang vertically; burn the lower end of the sample with acetylene flame (20mm high) for 10s; record the self-extinguishing time and whether the dripping matter ignites the absorbent cotton.

[0058] 3. Cone calorimetry test: According to ISO 5660-1:2015 standard, sample size 100×100×3mm 3 , radiant power 50kW / m 2 ; Determine the peak heat release rate (pHRR), total heat release (THR), and smoke generation rate (SPR).

[0059] 4. Antibacterial performance: According to JIS Z 2801:2010 standard, Escherichia coli (ATCC 25922) / Staphylococcus aureus (ATCC 6538) were inoculated on the coating surface (bacterial concentration 10 5 CFU / mL); after 24 h of incubation, the bacterial solution was washed and the surviving colonies were counted; antibacterial rate = (1-colonies in the test group / colonies in the control group) × 100%.

[0060] 5. Performance after accelerated aging: 85℃ / 85%RH, 720h (equivalent to 2 years of natural aging). After aging, LOI and SEM were used to observe the carbon layer structure.

[0061] The specific data are as follows:

[0062] LOI (%) UL94 rating <![CDATA[pHRR(kW / m 2 )]]> <![CDATA[THR(MJ / m 2 )]]> <![CDATA[SPR(m 2 / s)]]> Example 1 31.2 V-1 158 48.3 0.021 Example 2 33.7 V-0 122 36.5 0.015 Example 3 35.5 V-0 98 28.1 0.011 Example 4 35.8 V-0 105 30.2 0.012 Comparative Example 1 28.5 V-2 260 72.6 0.043 Comparative Example 2 29.8 V-1 195 58.4 0.028 Comparative Example 3 27.6 V-1 210 61.2 0.035

[0063] Table 1

[0064]

[0065] Table 2

[0066] From the data in Tables 1 and 2 above, it can be seen that when the proportion of functionalized nano-silica in Examples 1-4 gradually increases, the limiting oxygen index becomes higher and higher, but at the proportions of Examples 3 and 4, the limiting oxygen index tends to be consistent; the difference between Example 3, Comparative Example 1, and Comparative Example 2 lies in the different functionalized nano-silica. From the data, the functionalized nano-silica in Example 3 uses 15 parts, and its LOI is 24.6% higher than that of the commercially available product, Comparative Example 1, and THR is reduced by 61.3%. From the data of Comparative Example 2, it can be seen that the use of spherical silica proves that the worm-like structure further reduces the pHRR by 49.7%;

[0067] The antibacterial rate of Example 3 against both bacteria is >99.5%, due to the high surface density of the quaternary ammonium salt (16.2 wt%); after aging, the LOI only decays by 1.7%, while the decay of Comparative Example 1 is 13.1%, which is due to the dual mechanism of mesoporous anchoring + antibacterial protection;

[0068] Based on the data in the above table, Example 3 can be preferred.

[0069] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A nano-silicon dioxide modified flame retardant coating, characterized in that: The specific mass fractions of the components of the nano-silica modified flame retardant coating raw materials are: Waterborne polyurethane emulsion: 70-90 parts; Functionalized nano-silica: 5-20 parts; Dispersant: 0.3-1 part; Leveling agent: 0.1-0.5 parts; Defoaming agent: 0.1-0.3 parts. The functionalized nano-silica has an aspect ratio of >10:1, a pore size of 10-20 nm, and a specific surface area of ​​≥400 m 2 / g.

2. The nano-silicon dioxide modified flame retardant coating according to claim 1, characterized in that: The preparation steps of the functionalized nano-silica are specifically as follows: Step 1: Place worm-like mesoporous silica in a 250ml three-necked flask, add 100ml of anhydrous ethanol, and ultrasonically disperse until no precipitation occurs; Step 2: Add silane coupling agent and replace air with nitrogen, react in an oil bath and magnetic stirring for 4 hours, then centrifuge, wash with ethanol three times, and vacuum dry to obtain amino silica; Step 3: Disperse the amino-silica in anhydrous toluene, add hexachlorocyclotriphosphazene and protect with nitrogen, then place in an oil bath, condense and reflux for 6 hours, then collect the solid by centrifugation, wash with toluene and ethanol in sequence, and dry in vacuum to obtain the phosphazene-silica; Step 4: Disperse the phosphazene silica in DMF and add bromododecane, then stir in an oil bath for 8 hours, then centrifuge and wash alternately with DMF / ethanol three times, and finally vacuum dry for 12 hours to obtain functionalized nano-silica.

3. The nano-silicon dioxide modified flame retardant coating according to claim 2, characterized in that: The preparation steps of the worm-like mesoporous silica are as follows: preparing a template with hexadecyltrimethylammonium bromide / sodium dodecyl sulfate, performing a hydrothermal reaction at a temperature of 160-180° C. for a reaction time of 12-24 hours, and calcining to remove the template.

4. The landscaping weed control cloth according to claim 1, characterized in that: The dispersant used is BYK-190.

5. The nano-silicon dioxide modified flame retardant coating according to claim 1, characterized in that: The leveling agent is BYK-346.

6. The nano-silicon dioxide modified flame retardant coating according to claim 1, characterized in that: The defoaming agent is based on mineral oil.

7. The nano-silicon dioxide modified flame retardant coating according to claim 1, characterized in that: The functionalized nano-silica is oriented in the coating layer through shear electric field induction to form a multi-layer barrier network parallel to the substrate.

8. A method for preparing a nano-silica modified flame retardant coating, suitable for the nano-silica modified flame retardant coating according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following specific steps: uniformly mixing aqueous polyurethane emulsion, functionalized nano-silica and a dispersant, adding a defoamer and a leveling agent, and continuously stirring at a speed of 400-600 r / min for 15-25 minutes to obtain a nano-silica modified flame retardant coating.

9. The method for preparing the landscaping weed control cloth according to claim 8, wherein: The mixing temperature is 40-60°C.

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