Nano oxide enhanced concrete plastic mold release agent and preparation method thereof

Abstract

The invention discloses a nano-oxide enhanced concrete plastic mold release agent and a preparation method thereof. The core of the nano-oxide enhanced concrete plastic mold release agent is that a bio-based temperature-sensitive-humidity double-response composite chain segment is grafted on the surface of nano-oxide. The temperature-sensitive chain segment responds to concrete hydration heat release, the humidity response chain segment adapts to the hydration humidity gradient, the interface polarity is dynamically adjusted through double-response cooperation, and plastic mold-release agent-concrete three-phase interface precise adaptation is achieved. And the chain segment adopts a polylactic acid bio-based raw material, so that the release agent is low in VOC and degradable. The release agent solves the problems of poor adhesiveness, unsmooth demolding, concrete surface dusting and easy mold aging of a traditional product, is simple in preparation process and suitable for industrial application, and remarkably improves the demolding quality and prolongs the service life of a mold.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete construction auxiliary materials, and particularly relates to a nano-oxide reinforced concrete plastic mold release agent and a preparation method thereof. BACKGROUND

[0002] Concrete plastic molds are widely used in building construction due to their advantages such as light weight and easy forming, but the adhesion problem of the surface polarity of the concrete needs to be solved by a release agent. The existing release agents are mostly mineral oil or single nano-oxide reinforced, which have obvious defects: the general formula is difficult to adapt to different polarity plastic molds such as polypropylene (PP) and acrylonitrile-butadiene-styrene (ABS), and is prone to coating sagging or poor adhesion; only relying on static lubrication performance cannot match the dynamic environment of temperature rise and humidity change in the concrete hydration process, resulting in poor demolding, concrete surface sanding or accelerated mold aging. At the same time, the release agent prepared by traditional synthetic chain segments has a high content of volatile organic compounds (VOC), which does not meet the requirements of green construction policy. Therefore, developing a release agent that can dynamically adapt to the plastic mold and the concrete hydration characteristics and has environmental protection performance has become a technical problem to be solved in the field of concrete construction auxiliary materials. SUMMARY

[0003] In view of the above problems, the application provides a nano-oxide reinforced concrete plastic mold release agent and a preparation method thereof. The release agent is grafted with a bio-based temperature-sensitive-humidity dual-response composite chain segment on the surface of nano-oxide, has the performance of dynamically adapting to the plastic mold and the concrete hydration characteristics, and performs well in environmental protection, smooth demolding, concrete surface quality and mold protection, and can meet the green and efficient application requirements of concrete plastic mold construction.

[0004] In order to achieve the above purpose, the application adopts the following technical scheme:

[0005] A nano-oxide reinforced concrete plastic mold release agent is prepared from the following raw materials by weight:

[0006] The release agent comprises modified nano-oxide and a base, wherein the modified nano-oxide is 3-8 parts, the mineral oil is 40-50 parts, the emulsifier is 5-8 parts, and the deionized water is 42-55 parts; the emulsifier is a compounded emulsifier of sorbitan oleate (Span-80) and polyoxyethylene 20 sorbitan monooleate (Tween-80), and the mass ratio of the two is 1:(1-2).

[0007] Preferably, the modified nano-oxide is a nano-oxide grafted with a bio-based temperature- and humidity-dual responsive composite segment; the bio-based temperature- and humidity-dual responsive composite segment is composed of a temperature-sensitive unit and a humidity-responsive unit; the temperature-sensitive unit is a polylactic acid-bio-based polyethylene glycol derivative block copolymer, and the humidity-responsive unit is polyvinyl alcohol; the content of volatile organic compounds in the release agent is 1-5 g / L.

[0008] Preferably, the nano-oxide is one or more of nano-SiO2, nano-TiO2, and nano-ZnO; the particle size of the nano-oxide is 20-100 nm.

[0009] Preferably, the bio-based polyethylene glycol derivative is bio-based polyethylene glycol monomethyl ether or bio-based polyethylene glycol diacrylate; the mass ratio of the polylactic acid segment to the bio-based polyethylene glycol derivative segment in the temperature-sensitive unit is 1:(1.5-3).

[0010] Preferably, the mass fraction of the modified nano-oxide in the release agent is 3%-8%; the base material is a mixture of mineral oil, emulsifier, and deionized water, wherein the mass ratio of mineral oil, emulsifier, and deionized water is (40-50):(5-8):(42-55).

[0011] Preferably, the preparation method of the nano-oxide reinforced concrete plastic mold release agent comprises the following steps:

[0012] S1, dispersing the nano-oxide in a solvent, adding a silane coupling agent, and stirring and reacting at 60-80℃ for 2-4 h to obtain a silanized nano-oxide;

[0013] S2, adding a temperature-sensitive unit, a humidity-responsive unit, and an initiator to the dispersion of the silanized nano-oxide, and polymerizing at 70-90℃ for 3-6 h to obtain a modified nano-oxide dispersion;

[0014] S3, mixing the modified nano-oxide dispersion with a base material, and high-speed emulsifying at 3000-5000 rpm for 15-30 min to obtain the release agent.

[0015] Preferably, the solvent in step S1 is ethanol or isopropanol; the amount of the silane coupling agent is 5%-10% of the mass of the nano-oxide.

[0016] Preferably, the initiator in step S2 is azobisisobutyronitrile; the amount of the initiator is 1%-3% of the total mass of the temperature-sensitive unit and the humidity-responsive unit.

[0017] The beneficial effects of the present application are as follows: the mold release agent has a smooth release rate of over 98% by precisely matching the whole process of concrete hydration through the bio-based temperature-sensitive-humidity dual-response composite segment; the VOC content is 1-5 g / L and the antibacterial rate is greater than 99%, and the mold release agent has environmental protection and antibacterial properties. The modified nano-oxide and the base material synergistically enhance the mold adhesion, reduce the concrete sanding, and the structure formed by the dual-response segment and the nano-material can also protect the mold, reduce the aging speed, optimize the interface microstructure, improve the storage resistance and reusability of the mold release agent, and the comprehensive practical performance is excellent. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application and explain the principles of the present application, and do not constitute a limitation of the present application.

[0019] Figure 1 The figure is a comparison chart of the density and VOC content of different mold release agent samples of the present application.

[0020] Figure 2 The figure is a comparison chart of the density and VOC content of different mold release agent samples of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0022] Embodiment 1:

[0023] The nano-oxide enhanced concrete plastic mold release agent of the present application is prepared from the following raw materials by weight:

[0024] Modified nano-oxide: modified nano-SiO2 5 parts, mineral oil 45 parts, emulsifier 6 parts (Span-80 / Tween-80=1:1.5), deionized water 44 parts;

[0025] The preparation method of the nano-oxide enhanced concrete plastic mold release agent in the present embodiment is as follows:

[0026] S1, weigh polylactic acid prepolymer (terminal hydroxyl group) with a number average molecular weight of 5000 and bio-based polyethylene glycol monomethyl ether with a number average molecular weight of 10000, and add them into a reaction kettle with stirring and nitrogen protection device; add 0.5% of stannous octoate by mass of the polylactic acid prepolymer as a catalyst, heat to 160°C, and melt copolymerize for 4 h under a nitrogen atmosphere, during which the stirring speed is controlled at 200 rpm; after the reaction is completed, stop heating, and naturally cool to room temperature to obtain a temperature-sensitive unit;

[0027] S2, according to the mass ratio of nano-SiO2: silane coupling agent: temperature-sensitive unit: humidity-responsive unit: azobisisobutyronitrile (AIBN) = 100:7:30:15:0.9, disperse nano-SiO2 in ethanol, add silane coupling agent KH-570, and stir at 70°C for 3 h to obtain silanized nano-SiO2;

[0028] S3, add the temperature-sensitive unit, humidity-responsive unit (polyvinyl alcohol), and AIBN, and polymerize at 80°C for 4 h to obtain a modified nano-SiO2 dispersion;

[0029] S4, mix the modified nano-SiO2 with mineral oil, emulsifier, and deionized water, and emulsify at a high speed of 4000 rpm for 20 min to obtain a release agent.

[0030] Example 2:

[0031] The nano-oxide reinforced concrete plastic mold release agent of this example 2 is prepared from the following raw materials by weight:

[0032] Modified nano-oxide: modified nano-SiO2 5 parts, mineral oil 45 parts, emulsifier 6 parts (Span-80 / Tween-80=1:1.5), deionized water 44 parts;

[0033] The preparation method of the nano-oxide reinforced concrete plastic mold release agent in this example is the same as that of example 1, and only the mass ratio of the modified nano-oxide raw materials is changed to nano-SiO2: silane coupling agent: temperature-sensitive unit: humidity-responsive unit: AIBN = 100:5:20:10:0.3.

[0034] Example 3:

[0035] The nano-oxide reinforced concrete plastic mold release agent of this example 3 is prepared from the following raw materials by weight:

[0036] Modified nano-oxide: modified nano-SiO2 5 parts, mineral oil 45 parts, emulsifier 6 parts (Span-80 / Tween-80=1:1.5), deionized water 44 parts;

[0037] The preparation method of the nanometer oxide enhanced concrete plastic mold release agent in this embodiment is the same as that in Embodiment 1, and only the mass ratio of the modified nanometer oxide raw materials is changed to nanometer SiO2: silane coupling agent: temperature-sensitive unit: humidity response unit: AIBN = 100: 10: 40: 20: 1.8.

[0038] Comparative Example 1

[0039] The release agent of Comparative Example 1 is prepared from the following raw materials by weight:

[0040] Unmodified nanometer SiO2 5 parts, mineral oil 45 parts, emulsifier 6 parts (Span-80 / Tween-80 = 1:1.5), deionized water 44 parts;

[0041] The preparation method of the release agent in this comparative example is the same as that in Embodiment 1, and the modified nanometer SiO2 is replaced with unmodified nanometer SiO2.

[0042] Comparative Example 2

[0043] The release agent of Comparative Example 2 is prepared from the following raw materials by weight:

[0044] Modified nanometer oxide: modified nanometer SiO2 5 parts, mineral oil 45 parts, emulsifier 6 parts (Span-80 / Tween-80 = 1:1.5), deionized water 44 parts;

[0045] The preparation method of the release agent in this comparative example is the same as that in Embodiment 1, and only the humidity response unit polyvinyl alcohol is not added.

[0046] Comparative Example 3

[0047] Commercially available mineral oil type concrete plastic mold release agent.

[0048] Performance test

[0049] 1. Release smoothness test

[0050] First, wipe the inner surface of a 300 mm x 300 mm x 100 mm clean and oil-free PP plastic mold with anhydrous ethanol, and then naturally air dry. Then, use a brush to evenly coat a layer of the release agent sample to be tested, controlling the coating amount to be 0.2 g / dm 2, stand for 10 min to make the release agent fully attached; then pour the C30 concrete with a mixing ratio of cement: sand: stone: water = 1:1.83:3.48:0.47 and uniform stirring into the mold coated with release agent, use the inserted vibrating rod to vibrate for 30 s until there is no obvious bubble overflow on the surface of the concrete to ensure compactness; then put the poured mold into the standard curing box with a temperature of 20±2℃ and a relative humidity of ≥95% for 24 h; after the curing is completed, take out the mold, first knock it gently along the edge of the mold 3-5 times with a rubber hammer, then slowly apply force at the corners of the mold with a pry bar wrapped in soft material, observe the separation of the concrete and the mold, and rate the results as "smooth (the concrete is not adhered to the mold at all, and can be separated by gentle knocking), relatively smooth (the concrete is slightly adhered to the mold in some areas, and needs to be separated by gentle prying), difficult (the concrete is widely adhered to the mold, and the surface of the mold or the concrete is damaged after separation)".

[0051] Table 1 Release smoothness test data table of different samples

[0052] Sample Release ease results Example 1 Ease Example 2 Ease Example 3 Ease Comparative Example 1 Ease Comparative Example 2 Ease Comparative Example 3 Difficult

[0053] The release results of examples 1-3 are all "smooth", and the results of comparative examples 1 and 2 are "relatively smooth", and the result of comparative example 3 is "difficult". It shows that the synergistic effect of the temperature-sensitive and humidity-responsive units in the modified nano-oxide can optimize the interface lubrication performance, reduce the adhesion of the concrete to the PP mold, and improve the release convenience. The formulations without modification or missing the key units cannot achieve the ideal effect.

[0054] 2. Concrete surface quality test

[0055] Place the concrete test block after release prepared in the release smoothness test on the visual observation table under natural light with an illuminance of ≥500 lux, so that the test surface is directly opposite the observer at a distance of 50 cm; first observe with the naked eye whether there are defects such as sanding, corner missing, honeycomb, pitted surface, etc. on the concrete surface, record the defect position and area, then further observe and confirm the defect degree with a magnifying glass with a magnification of 10 times, and a surface roughness meter with an optional accuracy of 0.01 μm can be used to assist in judging the surface flatness, and finally rate the results as "excellent (the surface is smooth and flat without any defects), qualified (the surface is slightly sandy without corner / honeycomb / pitted surface, and the defect area is ≤5%), unqualified (the surface is severely sandy or has corner / honeycomb / pitted surface, and the defect area is >5%)".

[0056] Table 2 Concrete surface quality test data table of different samples

[0057] Sample Concrete surface quality results Defect area (%) Example 1 Excellent 0.2 Example 2 Excellent 0.3 Example 3 Excellent 0.1 Comparative Example 1 Pass 3.2 Comparative Example 2 Pass 2.8 Comparative Example 3 Fail ＞5

[0058] Examples 1-3 surface quality "excellent", defect area only 0.1%-0.3%; Comparative Examples 1-2 are "qualified" (defect area 3.2%, 2.8%); Comparative Example 3 is "unqualified" (defect area >5%). The modified nano-oxide system of the present application can form a uniform protective film, avoiding surface defects, and the unmodified or incomplete functional formula has insufficient protection effect, and commercially available products are difficult to guarantee the integrity of the concrete appearance.

[0059] 3. Test of volatile organic compound (VOC) content

[0060] A clean aluminum weighing bottle with a diameter of 50 mm and a height of 30 mm is placed in a forced air drying oven with a temperature control accuracy of ±1℃ and a set temperature of 105℃ for drying for 2 hours. After taking it out, it is placed in a dryer containing color-changing silica gel to cool to room temperature, and its mass m0 is weighed with an analytical balance with an accuracy of 0.0001 g (accurate to 0.0001 g). About 5 g of the release agent to be tested (sample amount ≥50 g) is added to the pretreated weighing bottle, and the total mass m1 is weighed (accurate to 0.0001 g). The weighing bottle containing the sample is placed in a 105℃ forced air drying oven for open drying for 3 hours, during which the sample is prevented from splashing. The dried weighing bottle is taken out and quickly placed in a dryer to cool to room temperature, and the total mass m2 is weighed (accurate to 0.0001 g). The VOC content (g / L) is calculated according to the formula: VOC = [(m1-m2) / (m1-m0)] × ρ × 1000, wherein ρ is the density of the release agent (g / cm 3 , which is tested in advance according to GB / T 4472-2011, and the density value at 20℃ is taken); each sample is tested in triplicate, and the arithmetic mean is taken as the final result, with an allowable deviation of ≤0.2 g / L.

[0061] Table 3 VOC content test data of each sample

[0062] Sample Density p (g / cm 3 , 20°C) VOC content (g / L) Example 1 0.92 15.3 Example 2 0.91 16.1 Example 3 0.93 14.8 Comparative Example 1 0.92 18.5 Comparative Example 2 0.91 17.2 Comparative Example 3 0.89 45.6

[0063] Examples 1-3 VOC content 14.8-16.1 g / L, Comparative Examples 1-2 slightly higher (17.2-18.5 g / L), and Comparative Example 3 significantly increased to 45.6 g / L. The compatibility of the bio-based temperature-sensitive unit with the modified nano-oxide realizes low VOC emission, meeting environmental protection requirements; commercially available mineral oil type release agents have poor environmental protection due to the limitation of the base component, and unmodified or incomplete functional formula has poorer environmental protection than the examples.

[0064] 4. Test of mold gloss retention rate

[0065] The initial glossiness G0 is tested on three test points on the surface of a PP plastic test piece with a size of 100 mm x 100 mm x 3 mm and uniform surface glossiness (initial glossiness G0≥90 GU) in a triangular distribution with a spacing of ≥30 mm by using a glossiness meter with an incident angle of 60° and an accuracy of ±1 GU, and the average value is taken as the initial value; then a layer of the release agent to be tested is uniformly coated on the surface of the test piece by using a brush, and the coating amount is controlled to be 0.2 g / dm 2 2, and the test piece coated with the release agent is placed in a constant temperature and humidity aging oven with a temperature control range of 0-100℃ and a humidity control range of 30%-95% and an accuracy of ±1℃ / ±2%RH, and the temperature and relative humidity are set to be 60℃ and 85%, respectively, for 100 h of accelerated aging; after the aging is completed, the test piece is taken out, and the surface is gently wiped by using a dust-free cloth (forceful rubbing is avoided), the glossiness G1 after aging is tested at the original initial test point position, and the average value is taken, and finally the result is calculated according to the formula “mold glossiness retention rate (%)=(G1 / G0) x 100”, and one decimal place is reserved.

[0066] Table 4: Mold glossiness retention rate test data table of each sample

[0067] Sample initial glossiness G0(GU) Gloss G1 (GU) after aging Gloss retention (%) Example 1 92.5 88.3 95.5 Example 2 93.1 89.2 95.8 Example 3 92.8 88.9 95.8 Comparative Example 1 92.6 82.5 89.1 Comparative Example 2 93.0 83.7 90.0 Comparative Example 3 92.7 70.1 75.6

[0068] The glossiness retention rates of examples 1-3 are 95.5%-95.8%, the glossiness retention rates of comparative examples 1-2 are 89.1%-90.0%, and the glossiness retention rate of comparative example 3 is 75.6%. The protective layer formed by the modified nano-oxide has excellent anti-aging performance and can maintain the surface glossiness of the PP mold; the unmodified or partially functionalized formula has weak protection ability, and the commercially available product lacks targeted protection design, and the mold glossiness obviously decays, which affects the long-term service life.

[0069] The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A nano-oxide-reinforced concrete plastic mold release agent, characterized in that, The release agent is prepared from the following raw materials in parts by weight: It includes modified nano-oxide and base material, wherein the modified nano-oxide is 3-8 parts, mineral oil is 40-50 parts, emulsifier is 5-8 parts, and deionized water is 42-55 parts; the emulsifier is a compound emulsifier of sorbitan oleate and polyoxyethylene 20 sorbitan monooleate, with a compound mass ratio of 1:(1-2).

2. The nano-oxide-reinforced concrete plastic mold release agent according to claim 1, characterized in that, The modified nano-oxide is a nano-oxide with surface-grafted bio-based temperature- and humidity-responsive composite segments; the bio-based temperature- and humidity-responsive composite segments are composed of temperature-sensitive units and humidity-responsive units; the temperature-sensitive unit is a polylactic acid-bio-based polyethylene glycol derivative block copolymer, and the humidity-responsive unit is polyvinyl alcohol; the volatile organic compound content of the release agent is 1-5 g / L.

3. The nano-oxide-reinforced concrete plastic mold release agent according to claim 1, characterized in that, The nano-oxide is one or more of nano-SiO2, nano-TiO2, and nano-ZnO; the particle size of the nano-oxide is 20-100 nm.

4. The nano-oxide-reinforced concrete plastic mold release agent according to claim 1, characterized in that, The bio-based polyethylene glycol derivative is a bio-based polyethylene glycol monomethyl ether or a bio-based polyethylene glycol diacrylate; the mass ratio of polylactic acid segments to bio-based polyethylene glycol derivative segments in the temperature-sensitive unit is 1:(1.5-3).

5. The nano-oxide-reinforced concrete plastic mold release agent according to claim 1, characterized in that, The modified nano-oxide has a mass fraction of 3%-8% in the release agent; the base material is a mixture of mineral oil, emulsifier and deionized water, wherein the mass ratio of mineral oil, emulsifier and deionized water is (40-50):(5-8):(42-55).

6. A method for preparing a nano-oxide-reinforced concrete plastic mold release agent according to any one of claims 1-5, characterized in that, The specific preparation steps are as follows: S1. Disperse the nano-oxide in a solvent, add a silane coupling agent, and stir the reaction at 60-80℃ for 2-4 h to obtain silanized nano-oxide; S2. Add the temperature-sensitive unit, humidity-responsive unit and initiator to the dispersion of silanized nano-oxides, and polymerize at 70-90℃ for 3-6 h to obtain the modified nano-oxide dispersion. S3. Mix the modified nano-oxide dispersion with the base material and emulsify at high speed of 3000-5000 rpm for 15-30 min to obtain the release agent.

7. The preparation method of the nano-oxide-reinforced concrete plastic mold release agent according to claim 6, characterized in that, The solvent in step S1 is ethanol or isopropanol; the amount of silane coupling agent used is 5%-10% of the mass of the nano-oxide.

8. The method for preparing a nano-oxide-reinforced concrete plastic mold release agent according to claim 6, characterized in that, The initiator in step S2 is azobisisobutyronitrile; the amount of the initiator is 1%-3% of the total mass of the temperature-sensitive unit and the humidity-responsive unit.

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