A method for preparing an interpenetrating network type PVDC emulsion

Abstract

The application discloses a preparation method of an interpenetrating network type PVDC emulsion, and comprises the following steps: (1) preparing reaction raw materials for standby; (2) preparing an emulsifier aqueous solution; (3) preparing a polymerization initiator aqueous solution; (4) preparing a residual-removing initiator aqueous solution; (5) seed emulsion polymerization; (6) feeding polymerization; and (7) emulsion residual removal. The application has the advantages of simple process, good product stability, high barrier performance, excellent adhesion, good water resistance and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a method for preparing an interpenetrating network type PVDC emulsion. Background Technology

[0002] Steel, as an important structural material, plays a vital role in our production and daily life. However, steel is highly susceptible to corrosion by corrosive media such as oxygen, moisture, and salt spray, leading to loss of strength, safety accidents, and economic losses. Statistics show that global economic losses due to steel corrosion reach as high as $250 million annually, making the exploration of simple and efficient corrosion prevention technologies crucial. Polyvinylidene chloride (PVDC) possesses good structural symmetry, resulting in high crystallinity. Combined with the strong polarity and hydrophobicity of its carbon-chlorine bonds, PVDC exhibits excellent barrier properties against water vapor and oxygen. Therefore, many industry experts are exploring the application of PVDC in the field of steel corrosion protection.

[0003] For example, CN108129926A discloses a barrier coating, its preparation method, and its application. The barrier coating, by weight, comprises the following raw material components: 10-30 parts styrene-butadiene emulsion, 60-80 parts polyvinylidene chloride emulsion, 5-10 parts ethylene-vinyl acetate copolymer, and 0.5-2 parts additives. This invention blends styrene-butadiene emulsion and ethylene-vinyl acetate copolymer in a suitable ratio to form a cross-penetrating mixed system. The resulting barrier coating exhibits strong adhesion, good flexibility, and water vapor and oxygen barrier properties. The coating applied using this barrier coating demonstrates good water and oxygen barrier properties. However, this invention simply mixes several emulsions, resulting in poor compatibility. Furthermore, the strength and water resistance of the film need further improvement.

[0004] For example, CN105669890A discloses a polyvinylidene chloride emulsion for preparing water-based metal anti-corrosion coatings and its preparation method. Polyvinylidene chloride, acrylate monomers, hydroxyethyl methacrylate phosphate, N-hydroxymethyl acrylamide, emulsifier, and deionized water are pre-emulsified. Under the action of an initiator, a seed emulsion polymerization method is used to obtain a polyvinylidene chloride emulsion with good emulsion stability. By introducing polar monomers, the adhesion between the emulsion and the substrate is increased. The prepared water-based anti-corrosion coating uses water as the main dispersion medium, does not contain volatile organic solvents, is environmentally friendly and non-toxic, and adheres firmly to the metal substrate. The drawback is that although the introduction of acrylate phosphate monomers improves the adhesion of the coating to the steel substrate, the water resistance and film strength are relatively poor. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of existing technologies and provide a method for preparing an interpenetrating network PVDC emulsion with good product stability, high barrier performance, excellent adhesion, and good water resistance.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: a method for preparing an interpenetrating network PVDC emulsion, comprising the following steps:

[0007] (1) Prepare reaction raw materials for later use.

[0008] The composition of the reactants, by weight, is as follows:

[0009]

[0010] (2) Preparation of emulsifier aqueous solution: Prepare an emulsifier aqueous solution by mixing the emulsifier with 30-35% deionized water;

[0011] (3) Preparation of polymerization initiator aqueous solution: Prepare a polymerization initiator aqueous solution by mixing 50% initiator with 5.5-6.5% deionized water;

[0012] (4) Prepare an aqueous solution of residual initiator: Mix the remaining initiator with 4-5% deionized water to prepare an aqueous solution of residual initiator;

[0013] (5) Seed emulsion polymerization: Add the remaining deionized water, styrene, organosilicon monomer, 1-3% vinylidene chloride monomer, 4-12% acrylate phosphate monomer, 4.5-10.5% crosslinking monomer, 2-12% comonomer, 20-40% hydrophilic monomer, and 5-10% emulsifier aqueous solution to the polymerization kettle. Disperse the emulsion cold for 15-35 minutes at a stirring speed of 80-150 rpm, raise the temperature to 45-75℃, add 5-10% polymerization initiator aqueous solution to react, and react for 0.5-2.5 h to obtain seed emulsion;

[0014] (6) Additive polymerization: At a temperature of 45-75℃ and a stirring speed of 80-150rpm, the remaining vinylidene chloride monomer, the remaining acrylate phosphate monomer, the remaining crosslinking monomer, the remaining comonomer, the remaining hydrophilic monomer, the remaining emulsifier aqueous solution, and the remaining polymerization initiator aqueous solution are added to the above seed emulsion for reaction. The reaction time is 12-15h to obtain the reaction product.

[0015] (7) Emulsion residue removal: At a temperature of 45-75℃ and a stirring speed of 80-150rpm, add an aqueous solution of residue removal initiator to the reaction product obtained in step (6) for reaction time of 0.5-1.5h, cool down, filter, and obtain the product.

[0016] In a preferred embodiment of the present invention, the polymerization reactor is evacuated before the seed emulsion polymerization.

[0017] In a preferred embodiment of the present invention, the organosilicon monomer is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and methylvinyldichlorosilane.

[0018] In a preferred embodiment of the present invention, the acrylate phosphate monomer is at least one of 2-hydroxyethyl methacrylate phosphate, methacrylate phosphate, and ethoxyethyl 2-methacrylate phosphate.

[0019] In a preferred embodiment of the present invention, the hydrophilic monomer is at least one of acrylic acid and methacrylic acid.

[0020] In a preferred embodiment of the present invention, the crosslinking monomer is at least one of ethylene glycol diacrylate, divinylbenzene, methylenebisacrylamide, and diallyl maleate.

[0021] In a preferred embodiment of the present invention, the comonomer is at least two of acrylonitrile, methyl acrylate, butyl acrylate, ethyl acrylate, hydroxymethyl acrylate, hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate.

[0022] In a preferred embodiment of the present invention, the emulsifier is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, sodium pentadecyl sulfate, and sodium dodecyl sulfate.

[0023] In a preferred embodiment of the present invention, the initiator is a mixture of tert-butyl hydroperoxide and sodium thiosulfate.

[0024] In a preferred embodiment of the present invention, the mesh size of the filter used in step (7) is 250 to 450 mesh.

[0025] The preparation method of the interpenetrating network PVDC emulsion of the present invention optimizes the polymerization method by optimizing the feed formulation and factors affecting the polymerization reaction, such as polymerization process, reaction temperature and time, stirring speed, and feeding method. By introducing crosslinking monomers, the molecular chains of the shell and core layers form an interpenetrating network structure, resulting in an interpenetrating network PVDC emulsion with good stability, high barrier properties, excellent adhesion and water resistance, and good flexibility. The interpenetrating network PVDC emulsion obtained by the present invention is particularly suitable for the field of steel corrosion protection.

[0026] In this invention, during the seed emulsion polymerization stage, the crosslinking monomer containing two double bonds reacts with seed monomers such as styrene, organosilicon monomers, vinylidene chloride monomers, phosphate acrylate monomers, comonomers, and hydrophilic monomers. The crosslinking monomer consumes one double bond, leaving one remaining. Thus, a reactive molecular chain containing one double bond is formed during the seed emulsion polymerization stage. During the feed polymerization stage, the monomers in the feed polymerization stage have a swelling effect on the latex particles formed in the previous seed emulsion polymerization stage (polymerization and swelling occur simultaneously). The reactive molecular chains in the latex particles formed during the seed emulsion polymerization stage react with the feed monomers such as vinylidene chloride monomers, phosphate acrylate monomers, crosslinking monomers, comonomers, and hydrophilic monomers from the feed polymerization stage, forming new reactive molecular chains on top of the original molecular chains. This process repeats, and combined with the swelling effect of the feed monomers on the seeds, ultimately forming an interpenetrating network structure with vinylidene chloride, styrene, organosilicon monomers, and phosphate acrylate monomers as the shell layers and vinylidene chloride, comonomers, and phosphate acrylate monomers as the core layers.

[0027] Compared with existing technologies, the present invention has the following advantages:

[0028] 1. The latex particles of the interpenetrating network PVDC emulsion prepared by this invention have an interpenetrating network structure, which gives the coating good water resistance and strength. This invention first uses seed monomers such as styrene, organosilicon monomers, and crosslinking monomers for seed polymerization to synthesize seeds with reactive molecular chains. Then, feed monomers such as VDC, acrylate monomers, and crosslinking monomers are swollen and then subjected to feed polymerization. This forms a shell layer and a core layer, with an interpenetrating network structure between the two molecular chains, which significantly improves the water resistance and strength of the coating. The steel anti-corrosion coating prepared using the PVDC emulsion of this invention has a 3.5% salt water resistance of over 140 hours and a pencil hardness of over 1H.

[0029] 2. The obtained PVDC emulsion has good stability. The introduction of hydrophilic monomers such as acrylic acid and methacrylic acid makes the latex particles easy to disperse in water and less likely to settle and break down, thus losing their application performance. The PVDC emulsion obtained by this invention can be stored at room temperature for more than 8.5 months.

[0030] 3. The resulting coating has strong adhesion. The acrylate phosphate monomers and acrylic monomers introduced into the PVDC emulsion in this invention can interact with substrates such as steel to improve the adhesion between the coating and the substrates such as steel. The resulting coating has an adhesion level of 0 or higher.

[0031] 4. The resulting coating has excellent rust prevention effect. This invention introduces phosphate acrylate monomers into the PVDC emulsion. During the film formation process, the phosphate ester functional groups can form a dense phosphate protective film with the steel substrate, which passivates the steel substrate and achieves a good rust prevention effect.

[0032] 5. The resulting coating exhibits excellent barrier properties. This invention, through cross-linking, reduces the mobility of molecular chains, making it more difficult for water vapor and oxygen to migrate within the coating, thus better protecting the steel substrate. The resulting coating has an oxygen permeability of 35 cm⁻¹. 3 / m 2 • For days below, the water vapor transmission rate is 11 g / m 2 • Day or less.

[0033] Specific Implementation Examples

[0034] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0037] (1) Prepare reaction raw materials for later use.

[0038] The raw material formula is as follows:

[0039]

[0040] (2) Preparation of emulsifier aqueous solution: Weigh 20 kg of sodium dodecyl sulfate and prepare sodium dodecyl sulfate aqueous solution with 200 kg of deionized water for later use;

[0041] (3) Prepare the polymerization initiator aqueous solution: Weigh 85g of TBHP and prepare TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 85g of SFS and prepare SFS aqueous solution with 20Kg of deionized water for later use.

[0042] (4) Prepare the solution of the residue removal initiator: Weigh 400g of TBHP and prepare a TBHP solution with 10KG of deionized water for later use; Weigh 400g of SFS and prepare an SFS solution with 20KG of deionized water for later use.

[0043] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 10Kg vinylidene chloride, 27.5Kg styrene, 2.5Kg vinyltrimethoxysilane, 2.5Kg ethoxyethyl phosphate of 2-methacrylate, 4.85Kg methyl acrylate, 175g divinylbenzene, 2.5Kg methacrylic acid and 5% sodium dodecyl sulfate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 90rpm for 30 minutes, and maintain this speed to raise the temperature to 55℃, and then uniformly add 5% TBHP aqueous solution prepared in step (3) and 5% SFS aqueous solution prepared in step (3) within 13h to react for 1h to obtain seed emulsion;

[0044] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 55℃ and the stirring speed at 90 rpm. Add the remaining sodium dodecyl sulfate aqueous solution, the remaining vinylidene chloride, 47.5 kg butyl acrylate, the remaining methyl acrylate, 9.5 kg acrylic acid, the remaining ethoxyethyl phosphate of 2-methacrylate, the remaining divinylbenzene, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 13 h to end the reaction and obtain the reaction product;

[0045] (7) Residue removal from emulsion: Under the condition of maintaining the temperature of the polymerization reactor at 55°C and the stirring speed at 90 rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization reactor within 20 minutes. After the feeding is completed, the temperature is kept at 0.5 h, then cooled to 20°C. The product is obtained by filtering with a 300-mesh filter. The performance is shown in Table 1.

[0046] Example 2

[0047] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0048] (1) Prepare reaction raw materials for later use.

[0049] The raw material formula is as follows:

[0050]

[0051]

[0052] (2) Preparation of emulsifier aqueous solution: Weigh 22Kg sodium pentadecyl sulfate and prepare sodium pentadecyl sulfate aqueous solution with 200Kg deionized water for later use;

[0053] (3) Prepare the polymerization initiator aqueous solution: Weigh 90g of TBHP and prepare TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 90g of SFS and prepare SFS aqueous solution with 20Kg of deionized water for later use.

[0054] (4) Prepare the aqueous solution of the residue removal initiator: Weigh 420g of TBHP and prepare an aqueous solution of TBHP with 10KG of deionized water for later use; Weigh 420g of SFS and prepare an aqueous solution of SFS with 20KG of deionized water for later use.

[0055] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 10.8Kg vinylidene chloride, 36.6Kg styrene, 3.6kg vinyltriethoxysilane, 2.4Kg phosphate methacrylate, 2.76Kg butyl acrylate, 240g ethylene glycol diacrylate, 3.6Kg acrylic acid and 6% of sodium pentadecyl sulfate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 100rpm for 20 minutes. Maintain this speed and raise the temperature to 50℃. Then, add 6% of TBHP aqueous solution prepared in step (3) and 6% of SFS aqueous solution prepared in step (3) at a uniform rate within 13h to react. The reaction time is 1.2h to obtain seed emulsion;

[0056] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 50℃ and the stirring speed at 100rpm. Add the remaining sodium pentadecyl sulfate aqueous solution, the remaining vinylidene chloride, the remaining butyl acrylate, 62.04kg methyl acrylate, 9.4Kg methacrylic acid, the remaining phosphate methacrylate, the remaining ethylene glycol diacrylate, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 12.5h to end the reaction and obtain the reaction product;

[0057] (7) Residue removal from emulsion: Under the condition of maintaining the temperature of the polymerization reactor at 50°C and the stirring speed at 100 rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization reactor within 30 minutes. After the feeding is completed, the temperature is kept for 1 hour, then cooled to 30°C, and filtered with a 350-mesh filter to obtain the product. The performance is shown in Table 1.

[0058] Example 3

[0059] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0060] (1) Prepare reaction raw materials for later use.

[0061]

[0062] (2) Preparation of emulsifier aqueous solution: Weigh 24Kg sodium dodecyl sulfonate and prepare sodium dodecyl sulfonate aqueous solution with 200Kg deionized water for later use;

[0063] (3) Prepare the polymerization initiator aqueous solution: Weigh 100g of TBHP and prepare a TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 100g of SFS and prepare an SFS aqueous solution with 20Kg of deionized water for later use.

[0064] (4) Prepare the aqueous solution of the residue removal initiator: Weigh 430g of TBHP and prepare an aqueous solution of TBHP with 10KG of deionized water for later use; Weigh 430g of SFS and prepare an aqueous solution of SFS with 20KG of deionized water for later use.

[0065] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 11.64Kg vinylidene chloride, 53.6Kg styrene, 3.2kg vinyltriethoxysilane, 2.4Kg 2-hydroxyethyl methacrylate phosphate, 4Kg butyl acrylate, 360g methylenebisacrylamide, 4.8Kg acrylic acid and 8% sodium dodecyl sulfate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 110rpm for 25 minutes. Maintain this speed and raise the temperature to 60℃. Then, add 8% TBHP aqueous solution prepared in step (3) and 8% SFS aqueous solution prepared in step (3) at a uniform rate within 13h to react for 1.5h to obtain seed emulsion;

[0066] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 60℃ and the stirring speed at 110 rpm. Add the remaining sodium dodecyl sulfate aqueous solution, the remaining vinylidene chloride, the remaining butyl acrylate, 50.6 kg methyl acrylate, the remaining acrylic acid, the remaining 2-hydroxyethyl methacrylate phosphate, the remaining methylene bisacrylamide, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 13 h to end the reaction and obtain the reaction product.

[0067] (7) Residue removal from emulsion: Under the condition of maintaining the polymerization kettle temperature at 60℃ and stirring speed at 110rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization kettle within 25 minutes. After the feeding is completed, the temperature is kept at 0.75h, then cooled to 25℃, and filtered with a 400-mesh filter to obtain the product. The performance is shown in Table 1.

[0068] Example 4

[0069] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0070] (1) Prepare reaction raw materials for later use.

[0071] The raw material formula is as follows:

[0072]

[0073]

[0074] (2) Prepare an aqueous solution of emulsifier: Weigh 25 kg of sodium dodecylbenzene sulfonate and prepare an aqueous solution of sodium dodecylbenzene sulfonate with 200 kg of deionized water for later use;

[0075] (3) Prepare the polymerization initiator aqueous solution: Weigh 120g of TBHP and prepare a TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 120g of SFS and prepare an SFS aqueous solution with 20Kg of deionized water for later use.

[0076] (4) Prepare the aqueous solution of the residue removal initiator: Weigh 450g of TBHP and prepare an aqueous solution of TBHP with 10KG of deionized water for later use; Weigh 450g of SFS and prepare an aqueous solution of SFS with 20KG of deionized water for later use.

[0077] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 21Kg vinylidene chloride, 55Kg styrene, 5kg vinyltrimethoxysilane, 4Kg 2-hydroxyethyl methacrylate phosphate, 9.5Kg butyl acrylate, 500g methylenebisacrylamide, 5Kg acrylic acid and 10% sodium dodecylbenzenesulfonate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 120rpm for 25 minutes, and maintain this speed to raise the temperature to 70℃. Then, add 10% TBHP aqueous solution prepared in step (3) and 10% SFS aqueous solution prepared in step (3) at a uniform rate within 13h to react for 2h to obtain seed emulsion;

[0078] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 70℃ and the stirring speed at 120rpm. Add the remaining sodium dodecylbenzenesulfonate aqueous solution, the remaining vinylidene chloride, the remaining butyl acrylate, 9Kg methyl acrylate, the remaining acrylic acid, the remaining 2-hydroxyethyl methacrylate phosphate, the remaining methylene bisacrylamide, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 14h to end the reaction and obtain the reaction product.

[0079] (7) Residue removal from emulsion: Under the condition of maintaining the temperature of the polymerization reactor at 70°C and the stirring speed at 120 rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization reactor within 30 minutes. After the feeding is completed, the temperature is kept for 1 hour, then cooled to 25°C, and filtered with a 450 mesh filter to obtain the product. The performance is shown in Table 1.

[0080] Example 5

[0081] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0082] (1) Prepare reaction raw materials for later use.

[0083] The raw material formula is as follows:

[0084]

[0085]

[0086] (2) Preparation of emulsifier aqueous solution: Weigh 22Kg sodium pentadecyl sulfate and prepare sodium pentadecyl sulfate aqueous solution with 200Kg deionized water for later use;

[0087] (3) Prepare the polymerization initiator aqueous solution: Weigh 90g of TBHP and prepare TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 90g of SFS and prepare SFS aqueous solution with 20Kg of deionized water for later use.

[0088] (4) Prepare the aqueous solution of the residue removal initiator: Weigh 420g of TBHP and prepare an aqueous solution of TBHP with 10KG of deionized water for later use; Weigh 420g of SFS and prepare an aqueous solution of SFS with 20KG of deionized water for later use.

[0089] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 12.6Kg vinylidene chloride, 42.7Kg styrene, 4.2kg vinyltriethoxysilane, 3.22Kg butyl acrylate, 2.8Kg 2-hydroxyethyl methacrylate phosphate, 4.2Kg acrylic acid, 280g ethylene glycol diacrylate and 7% of the sodium pentadecyl sulfate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 100rpm for 20 minutes, and maintain this speed to raise the temperature to 50℃, and then uniformly add 7% of the TBHP aqueous solution prepared in step (3) and 7% of the SFS aqueous solution prepared in step (3) within 13h to react for 1.2h to obtain seed emulsion;

[0090] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 50℃ and the stirring speed at 100rpm. Add the remaining sodium dodecyl sulfate aqueous solution, the remaining vinylidene chloride, the remaining butyl acrylate, 65.8Kg methyl acrylate, 9.4Kg methacrylic acid, the remaining 2-hydroxyethyl methacrylate phosphate, the remaining ethylene glycol diacrylate, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 12.5h. The reaction is then stopped to obtain the reaction product.

[0091] (7) Residue removal from emulsion: Under the condition of maintaining the temperature of the polymerization reactor at 50°C and the stirring speed at 100 rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization reactor within 30 minutes. After the feeding is completed, the temperature is kept for 1 hour, then cooled to 30°C, and filtered with a 350-mesh filter to obtain the product. The performance is shown in Table 1.

[0092] Example 6

[0093] A method for preparing an interpenetrating network PVDC emulsion includes the following steps:

[0094] (1) Prepare reaction raw materials for later use.

[0095] The raw material formula is as follows:

[0096]

[0097] (2) Preparation of emulsifier aqueous solution: Weigh 22Kg sodium pentadecyl sulfate and prepare sodium pentadecyl sulfate aqueous solution with 200Kg deionized water for later use;

[0098] (3) Prepare the polymerization initiator aqueous solution: Weigh 90g of TBHP and prepare TBHP aqueous solution with 20Kg of deionized water for later use; Weigh 90g of SFS and prepare SFS aqueous solution with 20Kg of deionized water for later use.

[0099] (4) Prepare the aqueous solution of the residue removal initiator: Weigh 420g of TBHP and prepare an aqueous solution of TBHP with 10KG of deionized water for later use; Weigh 420g of SFS and prepare an aqueous solution of SFS with 20KG of deionized water for later use.

[0100] (5) Seed emulsion polymerization: First, put the remaining deionized water into the polymerization kettle, evacuate the polymerization kettle to -0.095Mpa, and under this vacuum, pump 16.2Kg vinylidene chloride, 54.9Kg styrene, 5.4Kg vinyltriethoxysilane, 5.4Kg acrylic acid, 3.6K methacrylate-2-hydroxyethyl phosphate, 4.14Kg butyl acrylate, 360g ethylene glycol diacrylate and 9% of the sodium pentadecyl sulfate aqueous solution prepared in step (2) into the polymerization kettle, and cold disperse at a stirring speed of 100rpm for 20 minutes, and maintain this speed to raise the temperature to 50℃, and then uniformly add 9% of the TBHP aqueous solution prepared in step (3) and 9% of the SFS aqueous solution prepared in step (3) within 13h to react for 1.2h to obtain seed emulsion;

[0101] (6) Addition polymerization: Keep the temperature of the polymerization kettle at 50℃ and the stirring speed at 100rpm. Add the remaining sodium pentadecyl sulfate aqueous solution, the remaining vinylidene chloride, the remaining butyl acrylate, 60.06kg methyl acrylate, 9.1Kg methacrylic acid, the remaining ethylene glycol diacrylate, the remaining 2-hydroxyethyl methacrylate phosphate, the remaining TBHP aqueous solution and SFS aqueous solution prepared in step (3) to the seed emulsion obtained in step (5) and react for 12.5h. The reaction is then stopped to obtain the reaction product.

[0102] (7) Residue removal from emulsion: Under the condition of maintaining the temperature of the polymerization reactor at 50°C and the stirring speed at 100 rpm, the TBHP aqueous solution and SFS aqueous solution prepared in step (4) are uniformly fed into the polymerization reactor within 30 minutes. After the feeding is completed, the temperature is kept for 1 hour, then cooled to 30°C, and filtered with a 350-mesh filter to obtain the product. The performance is shown in Table 1.

[0103] Comparative Example 1

[0104] The emulsion obtained in Comparative Example 1 was prepared according to the method described in Example 1 of CN105669890A, and its properties are shown in Table 1.

[0105] Performance testing

[0106] The PVDC emulsions obtained in Examples 1-6 and Comparative Example 1 were used to prepare anti-corrosion coatings for steel. The preparation process is as follows: 100 parts of PVDC emulsion, 30 parts of general-purpose water-based colorant (medium yellow), 0.5 parts of multi-branched polysiloxane, 8 parts of dipropylene glycol butyl ether, 0.3 parts of pectin, 0.4 parts of silicone defoamer, 0.8 parts of sodium bicarbonate, and an appropriate amount of deionized water were mixed to form an anti-corrosion coating for steel with a solid content of 40%. The coating was applied by spraying with a nozzle diameter of 2 mm and a spraying pressure of 0.4 MPa. A 30 μm wet film was prepared, and the performance of the coating film was tested. The performance is shown in Table 2.

[0107] Adhesion test: Performed according to the method specified in GB / T9286-1998 "Paints and varnishes, cross-cut test of paint film";

[0108] Salt water resistance test: Performed according to the method specified in GB / T10834-2008 "Determination of salt water resistance of marine paints - Salt water and hot salt water immersion method";

[0109] Flexibility test: Performed according to the method specified in GB / T1731-2020 "Test Method for Flexibility of Paint Film and Putty Film";

[0110] Pencil hardness test: The test was conducted according to the method specified in GB / T6739-2006 "Paints and varnishes - Pencil method for testing the hardness of paint film".

[0111] Oxygen barrier performance test: Performed according to the method specified in GB / T1038-2000 "Test method for gas permeability of plastic films and sheets - differential pressure method";

[0112] Water vapor barrier performance test: Performed according to the method specified in GB / T1037-1988 "Test method for water vapor permeability of plastic films and sheets - cup method".

[0113] The performance indicators of the examples and comparative examples are shown in Tables 1 and 2. Table 2 shows that the adhesion of Examples 1-6 and Comparative Example 1 is relatively good. This is because Examples 1-6 and Comparative Example 1 introduce phosphate ester monomers, which can react with the steel substrate, resulting in better adhesion of the coating. Examples 1-6 exhibit better salt water resistance, oxygen permeability, and water vapor permeability than Comparative Example 1. This is because Examples 1-6 possess an interpenetrating network structure, exhibiting better water resistance and barrier properties, thus better delaying the penetration of salt spray, water vapor, and oxygen. Examples 1-6 have higher hardness than Comparative Example 1 because they possess an interpenetrating network structure, resulting in higher film hardness and better scratch resistance. Examples 1-6 have better flexibility than Comparative Example 1 because they possess an interpenetrating network structure, forming strong links between molecular chains, thereby improving the flexibility and strength of the molecular chains.

[0114] Table 1. Performance indicators of the emulsions from the examples and comparative examples.

[0115]

[0116]

[0117] Table 2. Primer performance indicators for the examples and comparative examples.

[0118]

[0119] Note: The dry film thickness is 20µm when conducting water permeability and oxygen permeability tests.

Claims

1. A process for the preparation of an interpenetrating network type PVDC emulsion, characterized in that, Includes the following steps: (1) Prepare reaction raw materials for later use. The composition of the reactants, by weight, is as follows: 650-850 parts of vinylidene chloride monomer 20-60 parts of styrene 2-6 parts of organosilicon monomer 25-55 parts of acrylate phosphate monomers 3-5.5 parts of cross-linked monomer 10-25 parts of hydrophilic monomer 100-150 parts of comonomer 10-30 parts emulsifier Initiator 0.5~1.5 parts 550-750 parts of deionized water The crosslinking monomer is methylenebisacrylamide containing two double bonds, the hydrophilic monomer is at least one of acrylic acid and methacrylic acid, and the comonomer is at least two of acrylonitrile, methyl acrylate, butyl acrylate, ethyl acrylate, hydroxymethyl acrylate, hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. (2) Preparation of emulsifier aqueous solution: Prepare an emulsifier aqueous solution by mixing the emulsifier with 30-35% deionized water; (3) Preparation of polymerization initiator aqueous solution: Prepare a polymerization initiator aqueous solution by mixing 50% initiator with 5.5~6.5% deionized water; (4) Prepare an aqueous solution of residual initiator: Mix the remaining initiator with 4-5% deionized water to prepare an aqueous solution of residual initiator; (5) Seed emulsion polymerization: Add the remaining deionized water, styrene, organosilicon monomer, 1-3% vinylidene chloride monomer, 4-12% acrylate phosphate monomer, 4.5-10.5% crosslinking monomer, 2-12% comonomer, 20-40% hydrophilic monomer, and 5-10% emulsifier aqueous solution to the polymerization kettle. Disperse the emulsion cold for 15-35 minutes at a stirring speed of 80-150 rpm. Heat the emulsion to 45-75℃ and add 5-10% polymerization initiator aqueous solution to react for 0.5-2.5 h to obtain seed emulsion. Methylenebisacrylamide containing two double bonds reacts with styrene, organosilicon monomer, vinylidene chloride monomer, acrylate phosphate monomer, comonomer, and hydrophilic monomer to form a molecular chain containing one double bond with reactive activity. (6) Additive polymerization: At a temperature of 45~75℃ and a stirring speed of 80~150rpm, the remaining vinylidene chloride monomer, the remaining phosphate acrylate monomer, the remaining crosslinking monomer, the remaining comonomer, the remaining hydrophilic monomer, the remaining emulsifier aqueous solution, and the remaining polymerization initiator aqueous solution are added to the above seed emulsion for reaction. The reaction time is 12~15h to obtain the reaction product. The reactive molecular chains in the latex particles formed in the seed emulsion polymerization stage react with the vinylidene chloride monomer, phosphate acrylate monomer, crosslinking monomer, comonomer, and hydrophilic monomer. (7) Residue removal from emulsion: At a temperature of 45~75℃ and a stirring speed of 80~150rpm, add an aqueous solution of residue removal initiator to the reaction product obtained in step (6) for reaction. The reaction time is 0.5~1.5h. After cooling and filtration, an interpenetrating network PVDC emulsion product with a core-shell structure is obtained.

2. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The polymerization reactor was evacuated before the seed emulsion polymerization.

3. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The organosilicon monomer is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and methylvinyldichlorosilane.

4. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The acrylate phosphate monomer is at least one of 2-hydroxyethyl methacrylate phosphate and 2-ethoxyethyl methacrylate.

5. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The acrylate phosphate monomer is methacrylate phosphate.

6. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The emulsifier is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, sodium pentadecyl sulfate, and sodium dodecyl sulfate.

7. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The initiator is a mixture of tert-butyl hydroperoxide and sodium thiosulfate.

8. The method for preparing the interpenetrating network PVDC emulsion according to claim 1, characterized in that, The mesh size of the filter used in step (7) is 250 to 450 mesh.

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