An anti-sticking steel formwork coating and a method for preparing the same

Abstract

The present application relates to the technical field of high polymer coating, and discloses an anti-adhesion steel formwork coating and a preparation method thereof, the coating is prepared by mixing and curing an A agent and a B agent; the A agent contains, in terms of weight parts, 100 parts of bisphenol A type liquid epoxy resin, 10-15 parts of long-chain aliphatic mono-epoxy active diluent, 5-8 parts of mixed solvent, 0.8-2.0 parts of zinc acetylacetone and 0.05-0.15 parts of copper acetylacetone; and the B agent is 45-64 parts of siloxane modified phenolic amine prepolymer. By covalently anchoring the siloxane chain segment in the crosslinked network, the loss of the anti-adhesion substance is avoided; the coordination steric hindrance effect of zinc ions is used to inhibit the initial reaction heat release, thereby prolonging the pot life; the long-chain aliphatic diluent constructs a hydrophobic shielding layer to block the penetration of strong alkali ions, thereby improving the saponification life; and the dynamic color change mechanism of the copper acetylacetone provides an intuitive indication for material mixing and dry state.

Description

Technical Field

[0001] This invention relates to the field of polymer coating technology, specifically to an anti-adhesion steel template coating and its preparation method. Background Technology

[0002] In concrete construction, the surface condition of steel formwork directly affects the appearance quality of the concrete structure and demolding efficiency. Currently, two-component epoxy coatings are commonly used as a protective layer for steel formwork. These systems typically use liquid epoxy resin as the main agent, combined with a polyamine curing agent, and then add polysiloxanes through physical blending to reduce surface tension and impart anti-adhesion properties. This technical solution provides good interlayer adhesion and basic protective performance, and has a wide range of applications in conventional formwork turnover operations.

[0003] As the requirements for formwork turnover in engineering construction continue to increase, the performance degradation of conventional coating systems during long-term service is becoming increasingly apparent. Because physically added polysiloxanes do not substantially integrate into the epoxy cross-linking network, these low surface energy substances are prone to migration and loss under the weight of concrete, demolding shear forces, and subsequent high-pressure water washing, making it difficult to maintain the coating's demolding performance over a long period. Simultaneously, to meet the demand for rapid on-site curing, highly reactive curing agents such as phenolic amines are often used. This leads to an excessively rapid addition reaction between the amine and epoxy groups in the initial mixing of the two components. The resulting exothermic aggregation in a short time can shorten the material's workability period, posing operational difficulties for continuous construction of large-area formwork.

[0004] Freshly mixed concrete exists in a highly alkaline liquid environment. Under prolonged contact, moisture containing polar hydroxide ions can easily penetrate through the micropores of the coating film, causing nucleophilic attacks on the polymer network and triggering saponification degradation. This increases the risk of coating swelling and failure. In actual construction, the chemical cross-linking process after mixing two-component coatings often lacks clear macroscopic characterization, making it difficult for on-site construction personnel to determine whether the materials are uniformly mixed and whether the coating has reached a physically dry state ready for curing. Relying on experience to control the construction pace can easily lead to the coating being used before a complete cross-linked network has formed, which also indirectly affects the overall service life of the steel formwork protective coating. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an anti-adhesion coating for steel formwork and its preparation method, solving the problems of non-active siloxanes easily being lost in existing concrete steel formwork release coatings, leading to a decrease in anti-adhesion lifespan; violent initial reactions in the two-component mixing process resulting in a very short applicable period; and the coating easily undergoing saponification degradation and failure and peeling off in a highly alkaline liquid phase environment.

[0006] To achieve the above objectives, the present invention provides the following technical solution: Firstly, the present invention provides an anti-adhesion coating for steel templates, employing the following technical solution: An anti-adhesion coating for steel templates is prepared by mixing and curing agent A and agent B. By weight, agent A contains the following components: 100 parts of bisphenol A type liquid epoxy resin; 10-15 parts of long-chain aliphatic monoepoxy reactive diluent; 5-8 parts of mixed solvent; 0.8-2.0 parts of zinc acetylacetone; 0.05-0.15 parts of copper acetylacetone; agent B is a siloxane-modified phenolic amine prepolymer, and by weight, the amount of agent B is 45-64 parts.

[0007] By adopting the above technical solution, this formulation system establishes an internal synergistic reaction and shielding mechanism to address the shortcomings of existing coatings, such as material loss during demolding and short pot life.

[0008] Conventional coatings often suffer from the loss of free siloxanes due to pressure and water washing. To overcome this, agent B in the system utilizes a pre-prepared siloxane-modified phenolic amine prepolymer. In this prepolymer, di-epoxy-terminated polydimethylsiloxane undergoes a ring-opening addition reaction with the active amine groups of phenolic amine via its terminal epoxy groups, directly linking low surface energy polysiloxane segments into the molecular backbone via covalent bonds. During subsequent coating curing and crosslinking, these polysiloxane segments are fixed at the nodes of the three-dimensional network, cutting off the channels for the outward release of micro-molecules and fundamentally preventing the loss of surface anti-adhesion substances.

[0009] Having addressed the issue of preventing detachment, controlling the early exothermic reaction during the mixing of the two components is equally crucial. Since zinc acetylacetonate is dispersed in agent A, in the initial stage of mixing, divalent zinc ions utilize their empty metal orbitals to form a transient coordination network with the lone pair electrons of the free amine nitrogen atoms in agent B. This reversible microscopic steric hindrance moderately shields the amine groups, reducing the probability of nucleophilic collisions with epoxy groups. This coordination hindrance does not alter the final cross-linked network structure, but it substantially slows down the reaction rate in the early stages of application, preventing runaway polymerization and extending the operational service life.

[0010] Furthermore, the corrosive effect of a strongly alkaline environment on the interior of the coating is often a contributing factor to large-area coating failure. In this formulation, the long-chain aliphatic monoepoxy reactive diluent contained in Agent A participates in the curing reaction. Its long alkyl chains occupy a certain space within the cross-linked backbone and interact hydrophobically with the pre-introduced polysiloxane segments. This physical entanglement between polymer chains spontaneously forms a nonpolar mesoscopic phase separation region, thus acting as a spatial shield. Due to the hydrophobic truncation effect of the long chains, the channels for water and polar hydroxide ions in a high-concentration strongly alkaline environment to diffuse into the depth of the coating are blocked, thereby reducing the possibility of saponification degradation of the polymer network.

[0011] Preferably, the long-chain aliphatic monoepoxide reactive diluent is a glycidyl ether with a long-chain alkyl structure having twelve to fourteen carbon atoms.

[0012] By adopting the above technical solution, flexible aliphatic chains with twelve to fourteen carbon atoms can be well miscible in epoxy resin. After curing, they maintain a certain degree of molecular chain mobility within the network, and the hydrophobic physical shielding region they form can effectively block the capillary penetration of hydroxide ions.

[0013] Preferably, the mixed solvent in Agent A is a mixture of xylene and n-butanol in a mass ratio of 7:3.

[0014] By adopting the above technical solution, xylene provides the ability to dissolve epoxy resin, n-butanol provides hydrogen bonding assistance, and together with zinc acetylacetonate, they stabilize the transient coordination network around the amine group.

[0015] Preferably, the siloxane-modified phenolic amine prepolymer is made from raw materials comprising the following parts by weight: 35-45 parts of phenolic amine curing agent; 5-7 parts of mixed solvent; 5-12 parts of di-epoxy polydimethylsiloxane; the mixed solvent in the siloxane-modified phenolic amine prepolymer is a mixture of xylene and n-butanol in a mass ratio of 7:3.

[0016] By adopting the above technical solution, a reasonable ratio of prepolymer raw materials was set to ensure that the siloxane was moderately modified, which not only introduced a certain amount of low surface energy segments, but also retained sufficient active amine groups to meet the crosslinking and curing requirements with epoxy resin in Agent A in the later stage.

[0017] Preferably, the preparation method of siloxane-modified phenolic amine prepolymer includes the following steps: adding phenolic amine curing agent and mixed solvent into a reaction vessel, and starting stirring to disperse the material evenly; raising the temperature of the material in the vessel to and maintaining it at 40-45°C, and then slowly adding double-terminated epoxy polydimethylsiloxane; after the addition is completed, increasing the stirring speed, and maintaining the temperature at 40-45°C for 40-50 minutes; after the reaction is completed, cooling to below 25°C, and filtering to obtain the product.

[0018] By adopting the above technical solution, a mild reaction temperature and constant temperature time are controlled to ensure that the double-ended epoxy polydimethylsiloxane is consumed and incorporated into the phenolic amine structure, preventing high temperature from causing the phenolic amine to self-polymerize or causing a large amount of solvent to evaporate.

[0019] Secondly, the present invention provides a method for preparing an anti-adhesion coating for steel templates, employing the following technical solution: A method for preparing an anti-adhesion coating for steel templates includes the following steps: S1. Preparation of Agent A: Bisphenol A type liquid epoxy resin, long-chain aliphatic monoepoxy reactive diluent and mixed solvent are stirred, then zinc acetylacetonate and copper acetylacetonate are added for high-speed shear dispersion, and finally Agent A is obtained by micro negative pressure degassing treatment. S2. Mix according to proportion: Pour agent A and agent B into the mixing container and stir at room temperature until the system is uniform and there is no local color difference. S3. Application and Curing: Apply the mixture evenly to the cleaned steel template working surface, and then cure it in a natural environment to form a film, thus obtaining the finished coating.

[0020] By adopting the above technical solution, the process flow aligns with the aforementioned formulation mechanism. The high-speed shearing operation in S1 ensures the full dispersion of the solid metal-organic complex in the resin solution. During the S2 mixing operation, copper acetylacetonate in agent A acts as a dynamic indicator, rapidly reacting with the free amine in agent B to form a deep purplish-red copper-amine complex. This provides a direct visual reference for construction personnel to determine whether the two components are uniformly mixed. Upon entering the S3 curing stage, as the amine groups are continuously consumed to build a macromolecular cross-linking network, the previously formed copper-amine complex begins to dissociate. Macroscopically, the coating color irreversibly changes from deep purplish-red to pale yellowish-green. This color change provides a basis for on-site confirmation of whether the coating has reached a physically dry state.

[0021] Preferably, in step S1, the high-speed shear dispersion rotation speed is set to 1200-1500 rpm, and the dispersion time is 25-30 minutes until no visible solid powder is found in the system; the specific parameters for the micro-negative pressure degassing treatment are: degassing at a low speed of 200 rpm for 10 minutes under a pressure of -0.08 to -0.05 MPa.

[0022] By adopting the above technical solution, it is ensured that solid zinc acetylacetonate and copper acetylacetonate are broken down and dispersed in liquid resin, and microbubbles entangled in the shearing process are eliminated, thus avoiding pinhole defects in the coating film.

[0023] Preferably, in step S2, a pneumatic stirrer is used to mix the particles at a speed of 300-500 rpm.

[0024] By adopting the above technical solution, a suitable hydrodynamic shear field is provided, which enables the rapid miscibility of agent A and agent B with different viscosities, and promotes the uniform generation of transient coordination network.

[0025] Preferably, in step S3, the coating is applied using a high-pressure airless spraying device, with the nozzle pressure controlled at 15-20 MPa and the wet film thickness controlled at 150-200 micrometers.

[0026] By adopting the above technical solution, the coating is atomized and applied to the surface of the steel template using high pressure, ensuring that the long-chain aliphatic diluent and the siloxane segments form a dense interfacial shielding coating.

[0027] Preferably, in step S3, the temperature for curing and film formation under natural conditions is 15-30℃.

[0028] By adopting the above technical solution, this temperature range can maintain the thermodynamic motion rate of film-forming molecules and enable the reversible coordination hindrance effect of zinc ions to play a stabilizing role.

[0029] This invention provides an anti-adhesion coating for steel templates and its preparation method. It has the following beneficial effects: 1. This invention prepolymerizes phenolic amines by introducing di-epoxy-terminated polydimethylsiloxane into the curing agent, allowing low surface energy polysiloxane segments to be directly incorporated into the polymer crosslinking network via covalent bonds. This structure overcomes the problem of macroscopic migration that often occurs in traditional physically blended siloxanes, preventing surface material loss of the coating under conditions such as pressure peeling and high-pressure water washing, thereby maintaining the long-term release and anti-adhesion properties of the coating.

[0030] 2. This invention utilizes the dynamic coordination of divalent zinc ions with free amine groups in the curing agent by adding zinc acetylacetone to agent A, thereby creating transient steric hindrance around the amine groups in the initial stage of mixing the two components. This mechanism reduces the early exothermic reaction rate without altering the final chemical cross-linking network structure, suppresses the explosive polymerization phenomenon that easily occurs in highly reactive amine systems, and extends the operational life of the mixture, enabling it to meet the needs of large-scale continuous construction in practical engineering.

[0031] 3. This invention introduces a long-chain aliphatic monoepoxy reactive diluent. Its long alkyl chains participate in the cross-linking reaction, forming a non-polar hydrophobic phase region within the coating film. This blocks the penetration of moisture and polar hydroxide ions into the deeper layers of the coating under highly alkaline concrete conditions, reducing the risk of saponification degradation of the polymer network. Furthermore, the added copper acetylacetonate undergoes complex formation and dissociation during the cross-linking film-forming process, resulting in a noticeable color change in the coating. This provides on-site construction personnel with a direct indicator of the material mixing uniformity and the physical dryness of the coating. Attached Figure Description

[0032] Figure 1 The figures show the results of the synchronous test of mixing and physical curing in various embodiments and comparative examples of the present invention. Figure 2 This is a macroscopic thermodynamic and rheological comparison diagram of the construction dynamics and service life control test of the present invention; Figure 3The above is a comparison chart of the coating anti-migration and demolding cycle life test results of the present invention, wherein (a) is a diagram of the change of water contact angle on the coating surface before and after high-pressure water washing, and (b) is a comparison chart of demolding cycle life and state in simulated concrete pouring. Figure 4 This is a comparison chart of the resistance to strong alkali saponification erosion under extreme working conditions of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0035] The bisphenol A type liquid epoxy resin is a polymer with an epoxy equivalent of 186-192 g / eq and a viscosity of 11000-14000 mPa·s at 25℃, and the CAS number is 25068-38-6.

[0036] The long-chain aliphatic monoepoxide reactive diluent uses C12-C14 alkyl glycidyl ether with an epoxy value of 0.30-0.35 eq / 100g and CAS number 68609-97-2.

[0037] The phenolic amine curing agent is a Mannich base polymer formed by the condensation of cashew nut shell extract, aliphatic polyamine and formaldehyde. Its amine value is 300-350 mgKOH / g and its active hydrogen equivalent is 85-95. Its CAS number is 68413-28-5.

[0038] The reactive low surface energy modifier uses a double-terminated epoxy polydimethylsiloxane with a number average molecular weight of 2000-3000 and an epoxy equivalent of 1000-1500 g / eq. It contains a glycidyl ether group at the end and has the CAS number 102782-97-8.

[0039] The coordination-blocking catalytic dual-effect agent uses zinc acetylacetone with a purity of not less than 99.0%, CAS number 1332-07-6.

[0040] The colorimetric indicator and auxiliary catalyst use copper acetylacetone with a purity of not less than 98.0%, CAS number 13395-16-9.

[0041] The xylene and n-butanol required for the reaction are both conventional basic chemical solvents, and commercially available analytical grade products are used directly.

[0042] Preparation Example 1: This preparation example provides a method for preparing a siloxane-modified phenolic amine prepolymer, including the following steps: 35 kg of phenolic amine curing agent and 5 kg of mixed solvent were put into a stainless steel reactor equipped with a dispersing stirring paddle, a jacketed temperature control system and a condenser reflux device. The mixed solvent was composed of xylene and n-butanol mixed in a mass ratio of 7:3. The stirring was turned on and the speed was set to 300 rpm to make the curing agent uniformly dispersed in the solvent. Turn on the jacket temperature control circulating water to slowly raise the temperature of the material in the reactor to and keep it constant at 40°C. Then, slowly add 5 kg of double-ended epoxy polydimethylsiloxane to the reactor at a rate of 3 kg / min through the high-level tank. After the addition is complete, increase the stirring speed to 600 rpm and keep the temperature constant at 40℃ for 40 minutes. After the reaction is complete, cooling water is introduced into the jacket to cool the material inside the reactor to below 25°C. After filtration, the material is discharged, sealed, and packaged to obtain the siloxane-modified phenolic amine prepolymer, i.e. Agent B.

[0043] Preparation Example 2: This preparation example provides a method for preparing a siloxane-modified phenolic amine prepolymer, including the following steps: 40 kg of phenolic amine curing agent and 6 kg of mixed solvent were put into a stainless steel reactor equipped with a dispersing stirring paddle, a jacketed temperature control system and a condenser reflux device. The mixed solvent was composed of xylene and n-butanol mixed in a mass ratio of 7:3. The stirring was turned on and the speed was set to 350 rpm to make the curing agent uniformly dispersed in the solvent. Turn on the jacket temperature control circulating water to slowly raise the temperature of the material in the reactor to and keep it constant at 42°C. Then, slowly add 8 kg of double-ended epoxy polydimethylsiloxane to the reactor at a rate of 4 kg / min through the high-level tank. After the addition is complete, increase the stirring speed to 700 rpm and keep the temperature constant at 42℃ for 45 minutes. After the reaction is complete, cooling water is introduced into the jacket to cool the material inside the reactor to below 25°C. After filtration, the material is discharged, sealed, and packaged to obtain the siloxane-modified phenolic amine prepolymer, i.e. Agent B.

[0044] Preparation Example 3: This preparation example provides a method for preparing a siloxane-modified phenolic amine prepolymer, including the following steps: 45 kg of phenolic amine curing agent and 7 kg of mixed solvent were put into a stainless steel reactor equipped with a dispersing stirring paddle, a jacketed temperature control system and a condenser reflux device. The mixed solvent was composed of xylene and n-butanol mixed in a mass ratio of 7:3. The stirring was turned on and the speed was set to 400 rpm to make the curing agent uniformly dispersed in the solvent. Turn on the jacket temperature control circulating water to slowly raise the temperature of the material in the reactor to and keep it constant at 45°C. Then, slowly add 12 kg of double-ended epoxy polydimethylsiloxane to the reactor at a rate of 5 kg / min through the high-level tank. After the addition is complete, increase the stirring speed to 800 rpm and keep the reaction at a constant temperature of 45°C for 50 minutes. After the reaction is complete, cooling water is introduced into the jacket to cool the material inside the reactor to below 25°C. After filtration, the material is discharged, sealed, and packaged to obtain the siloxane-modified phenolic amine prepolymer, i.e. Agent B.

[0045] Example 1: This embodiment provides a method for preparing an anti-adhesion coating for steel templates, including the following steps: 1. At 25°C, add 100 kg of bisphenol A type liquid epoxy resin, 12 kg of long-chain aliphatic monoepoxy reactive diluent, and 6.5 kg of mixed solvent (made by mixing xylene and n-butanol in a mass ratio of 7:3) to a reactor equipped with a high-speed dispersion disc, and stir at 550 rpm for 12 minutes.

[0046] 2. Add 1.5 kg of zinc acetylacetone and 0.1 kg of copper acetylacetone, turn on the high-speed dispersion mode and set the speed to 1350 rpm for continuous high-shear dispersion for 28 minutes until there are no visible solid powders in the system and the system is uniformly translucent light blue-green.

[0047] 3. Draw the pressure inside the reactor to a slight negative pressure of -0.06MPa, degas at a low speed of 200rpm for 10 minutes, then discharge and seal the product to obtain Agent A.

[0048] 4. Add all of the above-prepared Agent A and all of the siloxane-modified phenolic amine prepolymer obtained in Preparation Example 2 as Agent B into the mixing container. Stir at room temperature using a pneumatic stirrer at 400 rpm. Stop stirring after observing that the color of the system changes rapidly from light blue-green to a uniform deep purple-red without local color difference.

[0049] 5. After the steel formwork is cleaned, use a high-pressure airless spraying device with a nozzle pressure of 18MPa to evenly apply the mixed coating to the working surface of the steel formwork, and control the wet film thickness to 180 micrometers.

[0050] 6. Curing is carried out at 25℃ in a natural environment. As the cross-linking and film-forming process progresses, the coating color gradually fades from a deep purplish-red and eventually becomes a translucent pale yellow-green, thus completing the coating preparation.

[0051] Example 2: This embodiment provides a method for preparing an anti-adhesion coating for steel templates, including the following steps: 1. At 15°C, add 100 kg of bisphenol A type liquid epoxy resin, 10 kg of long-chain aliphatic monoepoxy reactive diluent, and 5 kg of mixed solvent (made by mixing xylene and n-butanol in a mass ratio of 7:3) to a reactor equipped with a high-speed dispersion plate, and stir at 500 rpm for 10 minutes.

[0052] 2. Add 0.8 kg of zinc acetylacetone and 0.05 kg of copper acetylacetone, turn on the high-speed dispersion mode and set the speed to 1200 rpm for continuous high-shear dispersion for 25 minutes until there are no visible solid powders in the system and the system is uniformly translucent light blue-green.

[0053] 3. Draw the pressure inside the reactor to a slight negative pressure of -0.05MPa, degas at a low speed of 200rpm for 10 minutes, then discharge and seal the product to obtain Agent A.

[0054] 4. Pour all of the A agent prepared above and all of the siloxane-modified phenolic amine prepolymer obtained in Preparation Example 1 into a mixing container, stir at room temperature at 300 rpm using a pneumatic stirrer, and stop stirring after observing that the color of the system changes rapidly from light blue-green to a uniform deep purple-red without local color difference.

[0055] 5. After the steel formwork is cleaned, use a high-pressure airless spraying device with a nozzle pressure of 15MPa to evenly apply the mixed coating to the working surface of the steel formwork, and control the wet film thickness to be 150 micrometers.

[0056] 6. Curing is carried out at 15℃ in a natural environment. As the cross-linking and film-forming process progresses, the coating color gradually fades from a deep purplish-red and eventually becomes a translucent pale yellow-green, thus completing the coating preparation.

[0057] Example 3: This embodiment provides a method for preparing an anti-adhesion coating for steel templates, including the following steps: 1. At 30°C, add 100 kg of bisphenol A type liquid epoxy resin, 15 kg of long-chain aliphatic monoepoxy reactive diluent, and 8 kg of mixed solvent (made by mixing xylene and n-butanol in a mass ratio of 7:3) to a reactor equipped with a high-speed dispersion plate, and stir at 600 rpm for 15 minutes.

[0058] 2. Add 2.0 kg of zinc acetylacetone and 0.15 kg of copper acetylacetone, turn on the high-speed dispersion mode and set the speed to 1500 rpm for continuous high-shear dispersion for 30 minutes until there are no visible solid powders in the system and the system is uniformly translucent light blue-green.

[0059] 3. Draw the pressure inside the reactor to a slight negative pressure of -0.08 MPa, degas at a low speed of 200 rpm for 10 minutes, then discharge and seal the product to obtain Agent A.

[0060] 4. Pour all of the A agent prepared above and all of the siloxane-modified phenolic amine prepolymer obtained in Preparation Example 3 into a mixing container, stir at room temperature at 500 rpm using a pneumatic stirrer, and stop stirring after observing that the color of the system changes rapidly from light blue-green to a uniform deep purple-red without local color difference.

[0061] 5. After the steel formwork is cleaned, use a high-pressure airless spraying device with a nozzle pressure of 20MPa to evenly apply the mixed coating to the working surface of the steel formwork, and control the wet film thickness to be 200 micrometers.

[0062] 6. Curing is carried out at 30℃ in a natural environment. As the cross-linking and film-forming process progresses, the coating color gradually fades from a deep purplish-red and eventually becomes a translucent pale yellow-green, thus completing the coating preparation.

[0063] Example 4: This embodiment provides a method for preparing an anti-adhesion coating for steel templates, including the following steps: 1. At 25°C, add 100 kg of bisphenol A type liquid epoxy resin, 12 kg of long-chain aliphatic monoepoxy reactive diluent, and 8 kg of mixed solvent (made by mixing xylene and n-butanol in a mass ratio of 7:3) to a reactor equipped with a high-speed dispersion disc, and stir at 550 rpm for 12 minutes.

[0064] 2. Add 1.5 kg of zinc acetylacetone and 0.1 kg of copper acetylacetone, turn on the high-speed dispersion mode and set the speed to 1350 rpm for continuous high-shear dispersion for 28 minutes until there are no visible solid powders in the system and the system is uniformly translucent light blue-green.

[0065] 3. Draw the pressure inside the reactor to a slight negative pressure of -0.06MPa, degas at a low speed of 200rpm for 10 minutes, then discharge and seal the product to obtain Agent A.

[0066] 4. Add all of the above-prepared Agent A and all of the siloxane-modified phenolic amine prepolymer obtained in Preparation Example 2 as Agent B into the mixing container. Stir at room temperature using a pneumatic stirrer at 400 rpm. Stop stirring after observing that the color of the system changes rapidly from light blue-green to a uniform deep purple-red without local color difference.

[0067] 5. After the steel formwork is cleaned, use a high-pressure airless spraying device with a nozzle pressure of 18MPa to evenly apply the mixed coating to the working surface of the steel formwork, and control the wet film thickness to 180 micrometers.

[0068] 6. Curing is carried out at 25℃ in a natural environment. As the cross-linking and film-forming process progresses, the coating color gradually fades from a deep purplish-red and eventually becomes a translucent pale yellow-green, thus completing the coating preparation.

[0069] Comparative Example 1: Compared with Example 1, the difference is that in Preparation Example 2, an equal amount of conventional non-reactive dimethyl silicone oil was used to replace the double-terminated epoxy polydimethylsiloxane, while the rest were the same.

[0070] Comparative Example 2: Compared with Example 1, the difference is that an equal amount of butyl glycidyl ether is used to replace the long-chain aliphatic monoepoxide reactive diluent in Agent A, while the rest are the same.

[0071] Comparative Example 3: The difference from Example 1 is that zinc acetylacetone is not added to Agent A, but all other aspects are the same.

[0072] Comparative Example 4: The difference from Example 1 is that copper acetylacetone is not added to Agent A, but all other aspects are the same.

[0073] Comparative Example 5: Compared with Example 1, the difference is that the two-component separation preparation and prepolymerization reaction are not carried out. Instead, all the raw materials for preparing Agent A in Example 1 and all the raw materials for preparation Example 2 are directly mixed in the same reactor at room temperature and dispersed at high speed of 1350 rpm. The remaining components and proportions are the same.

[0074] Test Example 1: Dynamic color development and error prevention function linked to curing state test Experimental Description: This experiment aims to verify the indicative role of the dynamic coordination mechanism of copper acetylacetone in the coating system on the mixing uniformity of the two components, and to evaluate the synchronous linkage between the macroscopic color fading critical point and the physical dry state formed by the three-dimensional cross-linked network inside the coating.

[0075] Experimental steps: 1. Extract the prepared Agent A and Agent B from Examples 1 to 4 and Comparative Example 4, and place them at the natural curing temperature specified in each example for constant temperature placement to ensure that the test conditions are consistent with the actual working conditions.

[0076] 2. Mix agent A and agent B according to the mass ratio set in each embodiment, start the pneumatic stirrer and begin timing. During this period, continuously observe the color evolution of the materials in the container, and record the mixed color form when the system color reaches overall uniformity and there are no local color spots.

[0077] 3. After the mixture has stabilized, use a wet film preparation device with a specified gap to evenly apply the mixed coating onto a standard tinplate test plate, control the wet film thickness, and then place the test plate flat in the experimental environment at the corresponding temperature to cure and form a film.

[0078] 4. Conduct continuous inspection and monitoring of the sample surface during the curing process, and accurately record the specific time taken for the coating surface color to irreversibly change from a mixed state color to the final fixed color, using this as the curing and fading time point.

[0079] 5. Immediately upon recording the moment the coating completely fades, place a standard medical degreased cotton ball on the surface of the test sample and apply a 1kg standard weight above the cotton ball for 10 seconds. After removing the weight, gently blow on the sample surface with a bulb syringe and observe and record whether any cotton fibers adhere. Then, according to GB / T 6739 standard, use a pencil with a known hardness rating to perform a hardness test on adjacent areas of the paint film to verify the physical and mechanical curing state at that time point.

[0080] The experimental data are shown in Table 1: Table 1: Visualized test results of the synchronization between mixing and physical curing in each embodiment and comparative example

[0081] in conclusion: according to Figure 1 As shown in Table 1, Examples 1 to 4 all exhibited a clear visual response in the initial stage of mixing agent A and component B, with the system rapidly changing from a pale blue-green to a deep purplish-red. The chemical basis for this macroscopic phenomenon lies in the spatial coordination between the divalent copper ions released from copper acetylacetonate and the free aliphatic primary or secondary amines in agent B, forming a copper-amine complex with a high molar absorptivity. Operators can visually determine the physical dispersion state between components by observing the distribution of this deep purplish-red color in the mixing container. In Comparative Example 4, because the coordination indicator was removed, the mixing process only showed the pale blue-green color of the resin itself, masking any potential areas of low or high resin content, thus lacking a direct basis for judging the material uniformity before actual coating.

[0082] As the macromolecular crosslinking reaction progresses, the stability of this coordination structure is constrained by the evolution of the internal spatial network. The specific fading time points recorded in the example data—the moments when the macroscopic color of the coating irreversibly changes from deep purplish-red to pale yellowish-green—corresponded to cotton ball pressing experiments showing no fiber adhesion, and the pencil hardness reaching the H or 2H dry standard. Primary and secondary amines gradually transform into tertiary amines after ring-opening addition with epoxy groups. The newly formed tertiary amine groups connect to a large, rigid polymer backbone, leading to a significant increase in steric hindrance at the coordination centers. When the crosslinking density reaches the critical point of macroscopic physical dryness, the dense three-dimensional network completely locks the movement space of the molecular chains. The original four-coordinate copper amine complex undergoes thermodynamic dissociation due to steric repulsion and the weakening of the local alkaline environment. Copper ions retreat to a weaker oxygen atom coordination state, reflected macroscopically as the dissipation of the deep purplish-red color.

[0083] The intervention of different ambient temperatures further verified the dynamic adaptive capability of this error-proof indication mechanism. In Example 2, operating at a low temperature of 15°C, the reaction kinetics of epoxy and amine slowed down, extending the time required for the crosslinked network to reach its dry density to 11.4 hours. In contrast, Example 3, operating at a high temperature of 30°C, completed a similar conversion process in only 4.4 hours. Ambient temperature altered the absolute rate of the chemical reaction but did not disrupt the correlation between color fading and the achievement of the desired film hardness. The microscopic distortion of the coordination field and the establishment of macroscopic mechanical strength are both constrained by the same crosslinking density variable, making the implicit crosslinking process concrete as a visible spectral change. This provides an objective reference for the node control of the demolding process in industrial settings, unaffected by environmental variables.

[0084] Test Example 2: Construction Dynamics and Service Life Adjustment Test Experimental Description: Based on macroscopic thermodynamic data and rheological characteristics, this experiment explores the ability of the coordination effect of zinc ions in a bimetallic catalytic system to inhibit the initial crosslinking rate of a two-component coating, and demonstrates the engineering value of the staged prepolymerization process in suppressing the exothermic reaction of hazardous reactions.

[0085] Experimental steps: 1. Set the ambient temperature to 25 degrees Celsius, weigh out equal mass of the mixture of agent A and agent B of Example 1 and Comparative Example 3, and prepare the one-pot single-step mixture required for Comparative Example 5. The total mass of each group of test samples is precisely controlled to be 500 grams.

[0086] 2. Quickly pour the above mixture into a pre-prepared polyurethane foam insulation container, and immediately insert a high-precision thermocouple temperature probe into the center of the mixture. Connect a data acquisition and recording device to continuously monitor and record the system's exothermic curve until the temperature reaches a clear inflection point and begins to decrease. The system then reads and records the highest exothermic peak temperature during the test cycle.

[0087] 3. Take one portion of the mixture sample of Example 1, Comparative Example 3 and Comparative Example 5 of the same mass as above, pour them into standard viscosity test beakers, and place them in a constant temperature water bath environment of 25 degrees Celsius to eliminate the interference of external room temperature fluctuations.

[0088] 4. Use a Brookfield rotational viscometer to continuously measure the dynamic viscosity change of each sample liquid and record the viscosity value when the components are thoroughly mixed and in their initial state. Then, maintain the set rotation speed for continuous monitoring. Stop timing when the viscometer reading reaches twice the initial viscosity value and record the specific time elapsed. This time span is determined as the on-site applicable period of the coating.

[0089] The experimental data are shown in Table 2: Table 2: Evaluation of Construction Dynamics and Service Life Test Data

[0090] in conclusion: according to Figure 2 As shown in Table 2, the single-step mixing process used in Comparative Example 5 exhibited runaway reaction kinetics in the macroscopic exothermic test. Unprotected free phenolic amine molecules within the system came into direct contact with a large number of epoxy groups. The high nucleophilicity of the primary amine triggered extremely violent ring-opening crosslinking exothermic reactions, causing the temperature at the center of the mixture to rise to 178.6 degrees Celsius in a short time. With this abnormal heat accumulation, the material crossed its gel point and lost its fluidity within just 8 minutes. In routine heavy-duty anti-corrosion or demolding coating projects, such rapid polymerization within the mixing tank often results in the complete scrapping of the entire tank of material, and even poses a safety hazard due to localized solvent boiling and splashing. Forcibly blending highly reactive amines with unmodified siloxanes and other monomers disrupts the mild evolution path of the reaction. Therefore, establishing a sequential design for two-component pre-separation and siloxane segment prepolymerization is of irreplaceable process necessity.

[0091] Excluding the interference of physical preparation methods, the microscopic coordination effect of the system components was fully demonstrated in the comparison between Example 1 and Comparative Example 3. When zinc acetylacetonate was lacking as a reaction retardant in the coating formulation, the exothermic peak of the mixture in Comparative Example 3 reached 71.4 degrees Celsius, and the viscosity doubling time of the reaction operating window was shortened to 48 minutes. Faced with continuous spraying operations on large-area steel templates, the construction window of less than one hour causes the material to thicken in the pipeline before it can be consumed, which can easily lead to rigid blockage of the pipeline of the high-pressure airless spraying equipment. Example 1, which introduced zinc acetylacetonate, effectively reversed this limitation of the construction conditions. Divalent zinc ions utilize their empty metal orbitals to form a transient coordination network with the lone pair electrons of the free amino nitrogen atoms in the initial stage of mixing. Combined with the hydrogen bonding assistance of n-butanol in the solvent system, a reversible microscopic steric hindrance is constructed around the amino groups.

[0092] This coordination shielding mechanism substantially reduces the probability of nucleophilic collisions between amine groups and epoxy groups in the early stages of application without altering the final chemical bonding network structure. The maximum temperature of the mixing system is steadily suppressed at 43.2 degrees Celsius, and the reduced rate of heat release allows the small amount of heat generated by the reaction to dissipate smoothly through the container walls. Simultaneously, the viscosity doubling time is significantly extended to 138 minutes, providing on-site operators with ample time to address substrate defects and perform multiple spraying applications. The microscopic dynamic hindrance of metal coordination not only eliminates the risk of macroscopic thermodynamic runaway but also makes the large-scale engineering application of highly reactive two-component coatings feasible.

[0093] Test Example 3: Coating Migration Prevention and Demolding Cycle Life Test Experimental Description: This experiment investigates the inhibitory effect of the prepolymer covalent anchoring mechanism on the macroscopic migration behavior of polysiloxane segments. The anti-adhesion durability and engineering service life of the coating under different working conditions are evaluated through physical wiping, water contact angle changes and simulated concrete pouring cycle demolding process.

[0094] Experimental steps: 1. Extract the coating systems prepared in Example 1 and Comparative Example 1, and apply them evenly to the surface of a standard carbon steel test plate and a simulated steel template, respectively. Allow them to cure naturally at room temperature for 7 days to ensure that the internal cross-linking network is completely closed.

[0095] 2. Perform a macroscopic anti-migration test on the cured coating surface. Lay a standard clean black card on top of the coating and apply a fixed load of 1 kg. Wipe a length of 5 cm along a straight line at a uniform speed. After removing the card, observe and record whether any oily reflective marks remain on the surface.

[0096] 3. The surface water contact angle values ​​of the two sets of samples in their initial state were recorded using a contact angle measuring instrument. The samples were then fixed and continuously rinsed under a 0.5 MPa high-pressure water flow for 2 hours. After drying the surface moisture, the water contact angle was measured again to examine the surface material's resistance to leaching.

[0097] 4. Pour the prepared C50 high-grade commercial concrete into simulated steel formwork pre-coated with the corresponding paint, compact it by vibration, and then move it to a standard curing room to stand for 24 hours. Use a digital pull-out tester to test the demolding tensile force and then peel the concrete specimen vertically.

[0098] 5. After cleaning the residue from the formwork surface, proceed directly to the next concrete pouring operation. Continuously repeat the above pouring and demolding cycle, recording the changes in the demolding pull-out force throughout the process. The cumulative number of cycles at which the pull-out force suddenly increases or a large area of ​​the coating physically peels off is taken as the final failure point.

[0099] The experimental data are shown in Table 3: Table 3: Evaluation of Coating Migration Prevention and Demolding Cycle Life Test Data

[0100] in conclusion: according to Figure 3As shown in Table 3, the application of conventional non-reactive dimethyl silicone oil in Comparative Example 1 exhibited physical blending defects. In the initial stage, Comparative Example 1 achieved an initial water contact angle of 112.5 degrees, a phenomenon attributed to the thermodynamic enrichment of free silicone oil at the coating-air interface. In a black cardboard wiping experiment, an oily reflective mark was left on the surface, revealing the problem of free molecules migrating macroscopically. During high-pressure water washing, the free silicone oil on the surface of this system was washed away by the water flow, reducing the water contact angle to 84.3 degrees and weakening its anti-adhesion properties. After 11 demolding cycles in the simulated casting process, the demolding pull-out force increased due to the loss of surface functional materials, and the coating broke under the peeling action of concrete.

[0101] In industrial practice, effectively retaining low surface energy polysiloxane segments within a cross-linked network for extended periods is a significant engineering challenge. Example 1 establishes a stable molecular structure through a targeted covalent anchoring mechanism during the prepolymerization stage. Test data shows that the surface water contact angle in Example 1 remained at 108.4 degrees initially and 106.1 degrees after washing, and no residue remained after wiping with black cardstock. This state is attributed to the chemical bonding between the di-epoxy-terminated polydimethylsiloxane and the phenolic amine molecular backbone formed during the prepolymerization reaction. The polysiloxane segments are anchored at the nodes of the three-dimensional cross-linked network, cutting off the channels for the release and precipitation of microscopic molecules.

[0102] After resolving the issue of reverse penetration of release agents into the concrete interface, the coating in Example 1 achieved an improved continuous service life. The internally residing silicon-containing segments only exhibited failure characteristics after 87 concrete pouring and pull-out demolding cycles. Compared to conventional blending systems that rely on frequent recoating, the covalent anchoring design provides the coating with a framework resistant to mechanical friction and water erosion. This molecular bonding mode lays the foundation for continuous pouring operations on large steel formwork.

[0103] Test Example 4: Resistance to Strong Alkali Saponification Erosion Test under Extreme Working Conditions Experimental Description: This experiment aims to evaluate the ability of a hydrophobic physical shielding layer constructed by a long-chain aliphatic diluent in an epoxy crosslinked network to resist the penetration and erosion of high concentrations of hydroxide ions. Through accelerated saponification immersion under harsh conditions, the durability of this microphase physical chain entanglement structure in a strongly alkaline engineering environment is demonstrated.

[0104] Experimental steps: 1. Select the paint film samples prepared by mixing Example 1 and Comparative Example 2 and applying them to a standard steel test plate. Place the samples in a constant temperature and humidity environment of 25 degrees Celsius and let them stand for 14 days to allow the cross-linking reaction of the macromolecules inside the coating to reach a complete curing state.

[0105] 2. Use a two-component solvent-free epoxy resin sealant to seal the edges and back of all test samples. After the sealant has cured, eliminate the interference of test solution seeping from the uncoated working surface.

[0106] 3. Prepare a 10% sodium hydroxide aqueous solution in a soaking tank equipped with a constant temperature control system, and start the heating device to raise the temperature of the alkaline solution in the tank to and stabilize it at 50 degrees Celsius.

[0107] 4. Completely immerse the sample that has undergone edge sealing treatment in the above-mentioned high-temperature strong alkaline solution, fix the position of the sample and maintain a gap between the samples to prevent them from physically blocking each other.

[0108] 5. Set a fixed inspection cycle of 24 hours. Periodically remove the samples from the solution, quickly rinse the surface with deionized water to remove any residual alkali, and blot dry with filter paper. Observe the surface morphology of the coating and record the number of days of continuous immersion when the first visible blistering, network cracks, whitening, peeling, or adhesion level drops to 0 occurs. Then, re-immerse the samples that have not completely failed in the tank for further testing.

[0109] The experimental data are shown in Table 4: Table 4: Record of Failure Time in Strong Alkali Accelerated Immersion Experiment in conclusion:

[0110] according to Figure 4 Compared with the data in Table 4, Comparative Example 2, which used butyl glycidyl ether as the reactive diluent, showed that the test sample developed dense network cracking and whitening after being immersed in a 50°C, 10% sodium hydroxide solution for 8 days. Butyl glycidyl ether has a relatively short carbon chain structure, and after cross-linking with epoxy resin, the cured network retains multiple polar micropores. High concentrations of hydroxide ions in the solution, driven by thermodynamics, penetrate the coating surface and reach deep into the cross-linked backbone. The alkaline solution initiates nucleophilic attacks on the siloxane bonds in the polymer network, initiating saponification degradation of the polymer chain segments, resulting in the coating losing its physical adhesion.

[0111] In actual concrete pouring projects, the calcium hydroxide released during the hydration of silicate cement maintains the liquid environment at the formwork interface at a high alkalinity of over 12.5 for extended periods. Field application feedback indicates that release coating failure often begins with interfacial debonding caused by alkaline penetration, and simply increasing the coating thickness is insufficient to prevent capillary penetration of polar ions. The addition of long-chain aliphatic glycidyl ether in Example 1 constructs a spatial shielding mechanism to address this strong alkaline corrosion. The test sample in Example 1 remained under the same accelerated immersion conditions for 43 days before localized microbubbles appeared. Flexible aliphatic chains with twelve to fourteen carbon atoms covalently integrate into the epoxy network via ring-opening reactions, and nonpolar long alkyl chains interact hydrophobically with pre-anchored bi-terminated epoxy polydimethylsiloxane segments. The physical entanglement between polymer chains spontaneously constructs mesoscopic phase separation regions within the cross-linked framework, polymerizing to form a nonpolar shielding layer. This spatial steric hindrance interrupts the kinetic channels for the diffusion of water and polar hydroxide ions into the depths of the coating. The phase separation network inhibits the penetration rate of active ions and maintains the chemical integrity of the cross-linked structure under corrosive conditions, giving the coating system a material basis for long-term cyclic use.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A non-adhesive coating for steel formwork, characterized in that, Made by mixing and curing agent A and agent B; Based on parts by weight, Agent A comprises the following components: 100 parts of bisphenol A type liquid epoxy resin; 10-15 parts of long-chain aliphatic monoepoxy reactive diluent; Mixed solvent 5-8 parts; Zinc acetylacetone 0.8-2.0 parts; Copper acetylacetone 0.05-0.15 parts; The agent B is a siloxane-modified phenolic amine prepolymer, and the amount of agent B is 45-64 parts by weight.

2. The anti-adhesion steel template coating according to claim 1, characterized in that, The long-chain aliphatic monoepoxide reactive diluent is a glycidyl ether with a long-chain alkyl structure containing twelve to fourteen carbon atoms.

3. The anti-adhesion steel template coating according to claim 1, characterized in that, The mixed solvent in Agent A is a mixture of xylene and n-butanol in a mass ratio of 7:

3.

4. The anti-adhesion steel template coating according to claim 1, characterized in that, The siloxane-modified phenolic amine prepolymer is made from raw materials comprising the following parts by weight: 35-45 parts of phenolic amine curing agent; Mixed solvent 5-7 parts; 5-12 parts of di-epoxylated polydimethylsiloxane; The mixed solvent in the siloxane-modified phenolic amine prepolymer is a mixture of xylene and n-butanol in a mass ratio of 7:

3.

5. The anti-adhesion steel template coating according to claim 4, characterized in that, The preparation method of the siloxane-modified phenolic amine prepolymer includes the following steps: The phenolic amine curing agent and the mixed solvent are added to the reaction vessel, and stirring is started to disperse the materials evenly. The temperature of the material in the reactor is raised to and kept constant at 40-45°C, and then the double-terminated epoxy polydimethylsiloxane is slowly added dropwise. After the addition is complete, increase the stirring speed and keep the reaction at a constant temperature of 40-45℃ for 40-50 minutes. After the reaction is complete, the temperature is lowered to below 25°C, and the product is obtained by filtration.

6. A method for preparing an anti-adhesion steel formwork coating, used to prepare the anti-adhesion steel formwork coating as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of Agent A: Bisphenol A type liquid epoxy resin, long-chain aliphatic monoepoxy reactive diluent and mixed solvent are stirred, then zinc acetylacetonate and copper acetylacetonate are added for high-speed shear dispersion, and finally Agent A is obtained by micro negative pressure degassing treatment. S2. Mixing in proportion: Pour the A agent and the B agent into the mixing container and stir at room temperature until the system is uniform and there is no local color difference; S3. Application and Curing: Apply the mixture evenly to the cleaned steel template working surface, and then cure it in a natural environment to form a film, thus obtaining the finished coating.

7. The method for preparing the anti-adhesion steel template coating according to claim 6, characterized in that, In step S1, the high-speed shear dispersion rotation speed is set to 1200-1500 rpm, and the dispersion time is 25-30 minutes until no visible solid powder is found in the system; the specific parameters of the micro-negative pressure degassing treatment are: degassing at a low speed of 200 rpm for 10 minutes under a pressure of -0.08 to -0.05 MPa.

8. The method for preparing the anti-adhesion steel template coating according to claim 6, characterized in that, In step S2, a pneumatic stirrer is used to mix the mixture at a speed of 300-500 rpm.

9. The method for preparing the anti-adhesion steel template coating according to claim 6, characterized in that, In step S3, the coating is applied using a high-pressure airless spraying device, with the nozzle pressure controlled at 15-20 MPa and the wet film thickness controlled at 150-200 micrometers.

10. The method for preparing the anti-adhesion steel template coating according to claim 6, characterized in that, In step S3, the temperature for curing the film under natural conditions is 15-30℃.

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