An expandable polystyrene antibacterial coating agent and its application method

Abstract

This application relates to the field of polymer material additives, specifically disclosing an expandable polystyrene antibacterial coating agent and its application method. The expandable polystyrene antibacterial coating agent comprises component A and component B. Component A includes the following raw materials in parts by weight: 10-20 parts mono- and diglycerides of fatty acids, 12-20 parts tristearate, 10-18 parts stearate, 0.5-1.5 parts ethylene bis-stearamide, 20-35 parts nano-silica, and 45-65 parts antibacterial agent; component B is a polyethylene wax-carbon nanotube composite emulsion, which contains polyethylene wax and carbon nanotubes in a mass ratio of 5-10:100. The antibacterial coating agent of this application is used to prevent adhesion and agglomeration of different types of polystyrene particles, increase the lubricity and flowability of the particles, and simultaneously impart excellent antibacterial properties, expanding the application of foamed particles in food contact materials and medical devices.

Description

Technical Field

[0001] This application relates to the field of polymer material additives technology, and more specifically, it relates to an expandable polystyrene antibacterial coating agent and its application method. Background Technology

[0002] Foamed polystyrene products are currently highly valuable insulation, heat insulation, thermal insulation, and packaging cushioning materials. Moreover, polystyrene foam has advantages such as low water absorption, excellent dielectric properties, and high mechanical strength, making it widely used in building walls, roof insulation, composite board insulation, cold storage, air conditioning, vehicle and ship insulation, floor heating, and decorative carving.

[0003] During the pre-expansion process of expandable polystyrene, when the temperature reaches above 90℃, the polystyrene reaches an elastic state. Static electricity exists on the particle surface, and factors such as physical contact between particles and the loss of blowing agent and additives cause the polystyrene particles to easily stick together, clump, and become difficult to demold. This not only affects the flowability of the polystyrene but also leads to uneven foaming during the foaming process. Uneven foaming creates gaps between the foam particles filled in the mold, resulting in voids in the finished product and affecting its usability. Furthermore, most expandable polystyrene currently contains pentane as a blowing agent. In industrial methods, the amount of blowing agent used is 6-7% of the weight of styrene monomer, but pentane-based blowing agents can have adverse environmental impacts.

[0004] To prevent polystyrene particles from sticking together and clumping during foaming, coating agents are often added to the particle surface. Traditional coating agents such as monoglycerides, triglycerides, and zinc stearate have poor compatibility with the polystyrene matrix, easily migrate to the material surface and escape, and have little effect on improving the clumping and sticking of polystyrene particles. Moreover, they cannot reduce the volatilization of pentane. In addition, expandable polystyrene particles have poor antibacterial ability, which limits their application in fields with high hygiene requirements such as food packaging and medical devices. Summary of the Invention

[0005] In order to increase the flowability of expandable polystyrene particles, reduce their clumping and adhesion, reduce the volatilization of pentane-based foaming agents, and increase their antibacterial properties, so as to make them applicable in fields with high requirements for hygiene and safety, this application provides an expandable polystyrene antibacterial coating agent and its application method.

[0006] In a first aspect, this application provides an expandable polystyrene antibacterial coating agent, employing the following technical solution:

[0007] An expandable polystyrene antibacterial coating agent comprises the following raw materials in parts by weight: 10-20 parts mono- and diglycerides of fatty acids, 12-20 parts tristearate, 10-18 parts stearate, 0.5-1.5 parts ethylene bis-stearamide, 20-35 parts nano-silica, 45-65 parts antibacterial agent, and 3-5 parts polyethylene wax-carbon nanotube composite emulsion, wherein the polyethylene wax-carbon nanotube composite emulsion comprises polyethylene wax and carbon nanotubes in a mass ratio of 5-10:100.

[0008] By employing the above technical solution, nano-silica, with its large specific surface area and high surface energy, preferentially adsorbs zinc stearate molecules, fixing them to the surface. Zinc stearate acts as a lubricant for the nano-silica, making it easier to spread evenly on the surface of expandable polystyrene particles. Meanwhile, the nano-silica provides a strong, non-migrating physical barrier. The combination of these two technologies utilizes the lubricity of stearate while simultaneously addressing the migration problem of stearate with the help of nano-silica powder, significantly improving the anti-blocking effect and durability. Polyethylene wax itself is an excellent anti-blocking agent. When dispersed in water, after spraying and water evaporation, the polyethylene wax, in the form of fine solid particles, physically adsorbs onto the EPS surface, forming a microporous, discontinuous surface layer on the expandable polystyrene particles, rather than a sealed film. During the foaming of expandable polystyrene granules, the foaming agent can easily escape from the gaps between the wax granules without hindering expansion, while also exhibiting excellent anti-caking and lubrication properties. The carbon nanotubes, bound by the polyethylene wax, form a rough physical barrier on the surface of the polystyrene granules, reducing the contact area between the granules and effectively preventing adhesion caused by softening and pressure at room temperature. Furthermore, carbon nanotubes are excellent conductors; even at very low concentrations, the resulting conductive network can efficiently conduct and dissipate static charges, thereby reducing the likelihood of static electricity generated by friction between the polystyrene and the wax, leading to mutual adsorption, clumping, and difficulty in flow. Additionally, the solid polyethylene wax granules act as micro-bearings on the surface of the polystyrene granules, significantly reducing the coefficient of friction and improving the flowability and lubrication of the polystyrene granules.

[0009] Ethylene bis-stearamide is a highly efficient lubricant that reduces friction and resistance in expandable polystyrene particles during flow. It provides excellent internal and external lubrication, significantly improving flowability and mold release properties, allowing for smooth filling and demolding of expandable polystyrene in molds. Furthermore, the amide groups in ethylene bis-stearamide give it antistatic properties, reducing static electricity buildup from friction and minimizing adhesion and agglomeration caused by electrostatic adsorption. Mono- and diglyceride fatty acid esters, used as emulsifiers, can mix uniformly with various components to form a stable coating system. During foaming, they distribute evenly on polystyrene particles, improving film quality. The lubricating film formed between polystyrene particles by these esters also enhances film durability. Triglycerides can uniformly coat the surface of expandable polystyrene particles, reducing the loss of foaming agents and other additives, ensuring stable performance of expandable polystyrene during subsequent processing, and preventing adhesion and agglomeration. This maintains particle independence and flowability, significantly improving molding efficiency during polystyrene molding, resulting in products with better quality and performance.

[0010] Optionally, polyethylene wax is heated to 120-130℃ until completely melted, then deionized water is added and homogenized to emulsify, thus obtaining a polyethylene wax emulsion.

[0011] Carbon nanotubes were added to deionized water, sonicated, cellulose nanocrystals were added, and the mixture was sonicated and then filtered to obtain pretreated carbon nanotubes.

[0012] Pretreated carbon nanotubes were added to a polyethylene wax emulsion and stirred until homogeneous to obtain a composite emulsion.

[0013] By adopting the above technical solution, the surface of cellulose nanocrystals is rich in hydroxyl groups, which can be adsorbed onto the surface of carbon nanotubes through physical entanglement, hydrogen bonding, or electrostatic interaction, effectively separating carbon nanotube clusters and preventing their aggregation. Moreover, the pure carbon nanotube coating is hard and brittle. When polystyrene particles are foamed, the internal pressure rises sharply, and the hard carbon nanotube thin layer expands accordingly, which needs to overcome its own hardness and will restrict the foaming of polystyrene particles. In contrast, cellulose nanocrystals are rigid rod-shaped crystals. When mixed with carbon nanotubes, they can form a three-dimensional network with better flexibility and deformability. When the internal foaming agent vaporizes and generates pressure, the elastic network is expected to be stretched and expanded rather than being brittlely destroyed, thus not affecting particle expansion. Furthermore, the introduction of cellulose nanocrystals can form a more loose and porous network structure, which is beneficial for the escape of the foaming agent and the merging of cells in the later stages.

[0014] Optionally, the concentration of the polyethylene wax emulsion is 10-15%.

[0015] By adopting the above technical solution, the appropriate concentration of polyethylene wax emulsion can form a uniform and complete coating layer on the surface of polystyrene particles, providing better lubrication and isolation effects. If the concentration is too low, the anti-sticking effect is not obvious, and if the concentration is too high, the coating is too thick, affecting the fusion performance of subsequent molding processes.

[0016] Optionally, the mass ratio of the cellulose nanocrystals to the carbon nanotubes is 1-2:1.

[0017] By adopting the above technical solution, the cellulose nanocrystals used can more completely adsorb, encapsulate and isolate carbon nanotubes, forming a stable hybrid structure. The carbon nanotube clusters are broken down to form a stable dispersion, making it easier for carbon nanotubes to form a uniform and efficient conductive network on the surface of expandable polystyrene. Furthermore, the well-dispersed cellulose nanocrystals and carbon nanotube network are more elastic and can be stretched by internal pressure during foaming, rather than rigidly breaking, thereby minimizing the inhibition of the foaming ratio.

[0018] Optionally, the method for pretreating carbon nanotubes with cellulose nanocrystals is as follows:

[0019] Polyethyleneimine, acrylic acid, N,N-methylenebisvinylamide, quaternary ammonium salt chitosan and photoinitiator were added to deionized water and mixed evenly to obtain the treatment solution.

[0020] Pretreated carbon nanotubes were added to the treatment solution, ultrasonically dispersed, filtered, irradiated with ultraviolet light, and then soaked in sodium carbonate solution, filtered, and washed.

[0021] By employing the above technical solution, a treatment solution is prepared using polyethyleneimine, acrylic acid, etc., and ultraviolet light irradiation is used to induce the formation of hydrogels on the surfaces of cellulose nanocrystals and carbon nanotubes. Acrylic acid can rapidly absorb water molecules under humid conditions to form a hydrophilic gel, effectively reducing the friction coefficient and hydrophilicity of the carbon nanotube and cellulose nanocrystal surfaces. Polyethyleneimine and acrylic acid undergo a cross-linking reaction. The polyelectrolytes with opposite charges have a large number of anionic -COO- and cationic -NH3+ groups, which can form strong cohesive and adhesive electrostatic effects, forming strong adhesion on the surfaces of cellulose nanocrystals and carbon nanotubes. This further enhances the anti-detachment effect of the two on the surface of polystyrene particles, enhances lubrication and anti-adhesion capabilities, and this hydrogel has excellent toughness and strength. When expandable polystyrene particles foam and expand, the hydrogel is not easily damaged or cracked, exhibiting strong adhesion and good stability. The cations in chitosan quaternary ammonium salts, along with the positively charged polyethyleneimine, can interact with the negatively charged components on the bacterial surface through electrostatic interactions, thereby disrupting the fluidity and permeability of the bacterial cell membrane, effectively inhibiting bacterial growth and proliferation, and enhancing antibacterial capabilities.

[0022] Optionally, the antibacterial agent is silver-loaded silicate.

[0023] By adopting the above technical solution, silver ions in silver-loaded silicate can destroy the structure of microbial cells and achieve slow and controllable release of silver, which has durable antibacterial and antistatic properties. Silver-loaded silicate itself is a micron or nano-sized inorganic rigid particle. When it is uniformly dispersed on the surface of polystyrene particles, it plays a physical isolation role and can also act like a ball bearing, reducing the direct contact area of ​​polystyrene particles, lowering the friction coefficient between particles, increasing fluidity, and preventing them from sticking together and clumping due to surface softening during storage, especially under pressure. It also makes the particle processing process smoother and reduces blockage. In synergy with polyethylene wax, it can provide more durable anti-stick protection.

[0024] Optionally, the silver-loaded silicate undergoes the following pretreatment:

[0025] Oleic acid and ethanol were reacted to prepare an oleic acid-ethanol solution, which was then added dropwise to silver-loaded silicate while stirring. The solution was then dried under vacuum. The mass ratio of oleic acid to silver-loaded silicate was 0.03-0.05:1.

[0026] By adopting the above technical solution, silver-loaded silicate can increase the anti-adhesion effect by sealing the capillaries on the surface of EPS particles. However, the interfacial bonding force between the silver-loaded silicate and the EPS particles is weak. The coating is prone to peeling off due to friction during particle transportation and pre-foaming, resulting in adhesion between particles. Or the peeled silver-loaded silicate may mix into the foaming equipment, causing wear or blockage of the equipment. Oleic acid is a long-chain unsaturated fatty acid with an amphiphilic molecular structure, which can act as a bridge to reconcile the interfacial contradiction between the silver-loaded silicate and the EVA emulsion. The carboxyl group of the oleic acid molecule can undergo an esterification reaction with the hydroxyl group on the surface of the silver-loaded silicate to form a stable bond, so that the oleic acid molecule is firmly anchored on the surface of the silver-loaded silicate, completing its coating modification. The oleic acid is fully dissolved in ethanol and dripped into the silver-loaded silicate, so that the oleic acid molecule reacts fully with the hydroxyl group on the surface of the silver-loaded silicate through the carboxyl group. Then, the ethanol is removed by vacuum drying, so that the surface of the silver-loaded silicate is hydrophobic, with a delicate feel and no obvious agglomeration.

[0027] Optionally, the stearate is selected from at least one of zinc stearate, magnesium stearate, sodium stearate, aluminum stearate, and calcium stearate.

[0028] Secondly, this application provides a method for applying an expandable polystyrene antibacterial coating agent, employing the following technical solution:

[0029] A method for applying an expandable polystyrene antibacterial coating agent includes the following steps:

[0030] Tristearate, antibacterial agent, mono- and diglyceride fatty acid esters, nano-silica, stearate and ethylene bis-stearamide are mixed evenly to prepare material A;

[0031] After mixing expandable polystyrene granules with material A for 30-50 minutes, spray the mixture with a polyethylene wax-carbon nanotube composite emulsion and let it dry.

[0032] By adopting the above technical solution, various solid materials are mixed with expandable polystyrene particles, and then a polyethylene wax-carbon nanotube composite emulsion is sprayed on. After drying, an anti-slip coating is formed, which effectively improves the lubricity of the polystyrene particle surface and reduces adhesion and clumping.

[0033] Optionally, the amount of component A is 0.1-0.5% of the mass of expandable polystyrene granules, and the amount of component B is 0.05-0.25% of the mass of expandable polystyrene granules.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. This application uses mono- and diglyceride fatty acid esters, stearates, nano-silica to form an adhesive layer with lubricating and dispersing effects on the surface of expandable polystyrene particles, and then uses polyethylene wax-carbon nanotube emulsion spraying to form a film, which reduces the adhesion and agglomeration of particles and increases the lubrication effect.

[0036] 2. In this application, cellulose nanocrystals are preferably used to pretreat carbon nanotubes to improve the dispersibility and elasticity of carbon nanotubes, reduce the impact on the foaming rate of polystyrene particles, and treat the blend of cellulose nanocrystals and carbon nanotubes with polyethyleneimine, acrylic acid, etc. to form a hydrogel on the surface of the two, which not only increases the adhesion between cellulose nanocrystals and carbon nanotubes and polystyrene particles, but also further weakens the impact on the foaming ratio.

[0037] 3. In this application, silver-loaded silicate is preferably used as an antibacterial agent, which can block the capillary pores of polystyrene particles, reduce the volatilization of foaming agent, and at the same time impart antibacterial properties to polystyrene particles, making polystyrene foam products more widely applicable. Detailed Implementation

[0038] The following embodiments provide a further detailed description of this application.

[0039] Preparation Examples of Polyethylene Wax-Carbon Nanotube Composite Emulsions 1-7

[0040] In the preparation example, the polyethylene wax was selected from Jinan Shanhai Chemical Technology Co., Ltd., model F-110; the carbon nanotubes were selected from Jiaxing Bona New Materials Co., Ltd., model NACODC8, catalog number NACODC8-1; the cellulose nanocrystals were selected from Nanjing Tianlu Nanomaterials Co., Ltd., model TL-003; the polyethyleneimine was selected from Hubei Handafei Biotechnology Co., Ltd., MW=100000; the quaternary ammonium salt chitosan was selected from Hubei Langbowan Biomedical Co., Ltd., model KMK; and the acrylic acid was selected from Maclean's reagent.

[0041] Preparation Example 1: (1) 10g of polyethylene wax was heated to 130°C and stirred until it was completely melted. Deionized water preheated to 90°C was added and homogenized at 8000rpm to obtain a polyethylene wax emulsion with a concentration of 15%.

[0042] (2) Add 0.5g of carbon nanotubes to 99.5g of deionized water, sonicate for 30min, add 0.5g of cellulose nanocrystals, sonicate for another 30min, filter, and obtain pretreated carbon nanotubes.

[0043] (3) Add pretreated carbon nanotubes to polyethylene wax emulsion and stir at 500 rpm for 60 min to obtain composite emulsion.

[0044] Preparation Example 2: (1) 10g of polyethylene wax was heated to 130°C and stirred until it was completely melted. Deionized water preheated to 90°C was added and homogenized at 8000rpm to obtain a polyethylene wax emulsion with a concentration of 10%.

[0045] (2) Add 1g of carbon nanotubes to 98g of deionized water, ultrasonically disperse for 30min, add 1g of cellulose nanocrystals, continue ultrasonication for 30min, filter, and obtain pretreated carbon nanotubes.

[0046] (3) Add pretreated carbon nanotubes to polyethylene wax emulsion and stir at 500 rpm for 60 min to obtain composite emulsion.

[0047] Preparation Example 3: The difference from Preparation Example 1 is that the polyethylene wax emulsion was prepared by heating 10g of polyethylene wax to 130°C, stirring until it was completely melted, adding deionized water preheated to 90°C, and homogenizing and emulsifying at 8000rpm, with a concentration of 30%.

[0048] Preparation Example 4: The difference from Preparation Example 1 is that the amount of cellulose nanocrystals added is 6g.

[0049] Preparation Example 5: The difference from Preparation Example 1 is that the pretreated carbon nanotubes underwent the following pretreatment before being added to the polyethylene wax emulsion:

[0050] 20g of polyethyleneimine, 20g of acrylic acid, 0.04g of N,N-methylenebisvinylamide, 3g of quaternary ammonium salt chitosan and 0.5g of photoinitiator I2959 were added to 56.46g of deionized water and mixed evenly to obtain the treatment solution.

[0051] Pretreated carbon nanotubes were added to the treatment solution, ultrasonically dispersed for 30 min, filtered, irradiated under ultraviolet light of λ=365nm for 20 min, and then soaked in a 10% sodium carbonate solution to convert the carboxyl groups into sodium carboxylate. The solution was then filtered and washed with deionized water.

[0052] Preparation Example 6: The difference from Preparation Example 5 is that no quaternary ammonium salt chitosan was added.

[0053] Preparation Example 7: The difference from Preparation Example 5 is that polyethyleneimine was not added.

[0054] Example

[0055] Example 1: An expandable polystyrene antibacterial coating agent, comprising component A and component B. Component A contains 15g of mono- and diglycerides of fatty acids, 18g of triglycerides of stearate, 16g of stearate, 1g of ethylene bis-stearamide, 24g of nano-silica, and 50g of antibacterial agent. The stearate is zinc stearate, and the antibacterial agent is silver-loaded silicate. Component B is a polyethylene wax-carbon nanotube composite emulsion, which is prepared from Preparation Example 1.

[0056] Example 2: An expandable polystyrene antibacterial coating agent, comprising component A and component B. Component A contains 10g of mono- and diglycerides of fatty acids, 12g of triglycerides of stearate, 10g of stearate, 0.5g of ethylene bis-stearamide, 25g of nano-silica, and 45g of antibacterial agent. The stearate is zinc stearate, and the antibacterial agent is silver-loaded silicate. Component B is a polyethylene wax-carbon nanotube composite emulsion, which is prepared from Preparation Example 1.

[0057] Example 3: An expandable polystyrene antibacterial coating agent, comprising component A and component B. Component A contains 20g of mono- and diglycerides of fatty acids, 20g of tristearate, 18g of stearate, 1.5g of ethylene bis-stearamide, 35g of nano-silica, and 65g of antibacterial agent. The stearate is zinc stearate, and the antibacterial agent is silver-loaded silicate. Component B is a polyethylene wax-carbon nanotube composite emulsion, which is prepared from preparation example 2.

[0058] Example 4: An expandable polystyrene antibacterial coating agent, comprising component A and component B. Component A contains 15g of mono- and diglycerides of fatty acids, 12g of triglycerides of stearate, 14g of stearate, 1g of ethylene bis-stearamide, 21g of nano-silica, and 50g of antibacterial agent. The stearate is zinc stearate, and the antibacterial agent is silver-loaded silicate. Component B is a polyethylene wax-carbon nanotube composite emulsion, which is prepared from Preparation Example 1.

[0059] Example 5: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that the polyethylene wax-carbon nanotube emulsion is prepared in Preparation Example 3.

[0060] Example 6: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that the polyethylene wax-carbon nanotube emulsion is prepared in Preparation Example 4.

[0061] Example 7: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that the polyethylene wax-carbon nanotube emulsion is prepared in Preparation Example 5.

[0062] Example 8: An expandable polystyrene antibacterial coating agent, which differs from Example 7 in that the polyethylene wax-carbon nanotube emulsion is prepared in Preparation Example 6.

[0063] Example 9: An expandable polystyrene antibacterial coating agent, which differs from Example 7 in that the polyethylene wax-carbon nanotube emulsion is prepared in Example 7.

[0064] Example 10: An expandable polystyrene antibacterial coating agent, differing from Example 7 in that the silver-loaded silicate undergoes the following pretreatment:

[0065] Add 2.5g of oleic acid to 50g of anhydrous ethanol and stir at 300rpm for 10min to form a transparent oleic acid-ethanol solution.

[0066] Add 50g of silver-loaded silicate to a high-speed mixer and stir at 800rpm. Slowly add an acid-ethanol solution at a rate of 10ml / min. After the addition is complete, continue stirring for 30min. Then, vacuum dry at 80℃ and -0.08MPa for 4h.

[0067] Comparative Example

[0068] Comparative Example 1: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that it does not contain polyethylene wax-carbon nanotube emulsion.

[0069] Comparative Example 2: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that it does not use polyethylene wax-carbon nanotube emulsion, and nano-silica is not added to component A.

[0070] Comparative Example 3: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that a polyethylene wax emulsion is used instead of a polyethylene wax-carbon nanotube emulsion as component B.

[0071] Comparative Example 4: An expandable polystyrene antibacterial coating agent, which differs from Example 1 in that component B is a carbon nanotube suspension. 0.5g of carbon nanotubes is dispersed in 99.5g of deionized water and ultrasonicated for 30min to form a carbon nanotube suspension.

[0072] Performance testing

[0073] Anti-slip treatment is applied to expandable polystyrene of different types and particle sizes. Expandable polystyrene is divided into light-grade, flame-retardant grade, and ordinary grade. The light-grade expandable polystyrene granules are selected from Jiasheng Industrial, Jiachang brand, model B, with a particle size of 1.4mm (grade B-103), 0.8mm and 1.25mm (grades B-104), and 0.55mm (grade B-106). The flame-retardant expandable polystyrene is also from Jiasheng Industrial, Jiachang brand, model C, with a particle size of... The particle size is 1.5mm, grade C-103; 1.1mm, grade C-104; 0.8mm, grade C-106; and 0.5mm, grade C-107. Ordinary grade expandable polystyrene is selected from Jiasheng Industry, Jiachang brand, grade A, with particle sizes of 1.5mm (grade A-103), 1.25mm (grade A-104), 0.8mm (grade A-106), and 0.6mm (grade A-107).

[0074] The antibacterial coating agent prepared in Example 1 was used to treat different types of expandable polystyrene particles for anti-slip treatment according to the following method:

[0075] Tristearate, antibacterial agent, mono- and diglyceride fatty acid esters, nano-silica, stearate and ethylene bis-stearamide are mixed evenly to prepare material A;

[0076] After mixing expandable polystyrene particles with material A for 50 minutes, the mixture is sprayed with a polyethylene wax-carbon nanotube composite emulsion and then dried.

[0077] The dosage of expandable polystyrene, the dosage of antibacterial coating agent, the mixing time, and the discharge time during the anti-slip treatment are shown in Table 1. The scoring criteria for whether the expandable polystyrene particles adhere to each other after anti-slip treatment are as follows: 4-5 points: Particles are completely independent and do not adhere; 3-4 points: Slight adhesion, with slight contact between a few particles; 2-3 points: Moderate adhesion, with obvious contact between multiple particles, but they can be easily separated; 1-2 points: Severe adhesion, with a large number of particles tightly adhered and difficult to separate; 0-1 points: Complete adhesion, with particles forming large clumps that cannot be separated. Five sets of data were tested for each example or comparative example, and the test results were taken as the average of the five sets of data. The test results are recorded in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] As can be seen from the data in Table 1, the antibacterial coating agent prepared in Example 1 can effectively reduce the adhesion and clumping of polystyrene particles and improve their lubricity when used for surface lubrication treatment of different types of expandable polystyrene particles.

[0082] Following the anti-slip treatment method for expandable polystyrene particles using the antibacterial coating agent in Example 1, the expandable polystyrene particles were treated using the coating agents prepared in Examples 2-8 and Comparative Examples 1-2. Taking light-grade expandable polystyrene with a particle size of 1.4 mm and grade B-103 as an example, the mixture weight was 400 kg, the coating agent addition amount was 0.7 kg of component A and 0.7 kg of component B, the discharge time was 170 min, and the mixing time was 270 min. The adhesion between particles was evaluated according to the above scoring criteria, and the performance was tested according to the following method. The test results are recorded in Table 2.

[0083] 1. Lubrication effect: Expandable polystyrene particles treated with antibacterial coating agent were subjected to 50 reciprocating friction cycles at room temperature under conditions of 1N load and 1Hz frequency. The friction coefficient was tested using a friction coefficient tester. The friction pair consisted of stainless steel balls.

[0084] 2. Antibacterial properties: Expandable polystyrene particles of the same mass treated with antibacterial coating agent were placed on solid culture media coated with Escherichia coli and Staphylococcus aureus suspensions, respectively, and then incubated at 37°C for 12 hours. Finally, the antibacterial properties of expandable polystyrene were evaluated by the size of the inhibition zone; the larger the diameter of the inhibition zone, the better the surface antibacterial properties, and vice versa.

[0085] Table 2

[0086]

[0087] As can be seen from the data comparison in Table 2, when the antibacterial coating agents prepared in Examples 1-4 are used to treat light expandable polystyrene particles, the polystyrene particles are not easy to stick together, have a high adhesion score, and have a low pre-expansion density and a high foaming ratio. At the same time, they have a low coefficient of friction, good lubricity and fluidity, and have good antibacterial ability against Escherichia coli and Staphylococcus aureus.

[0088] Compared with Example 1, Example 5 used the composite emulsion prepared in Preparation Example 3, in which the concentration of polyethylene wax emulsion was increased. It can be seen that the foaming density of polystyrene particles increased and the foaming ratio decreased, indicating that the increase of polyethylene wax emulsion concentration will affect the foaming ratio of polystyrene particles.

[0089] In Example 6, the composite emulsion prepared in Preparation Example 4 was used. Compared with Example 1, the antibacterial coating agent prepared in Example 6, when applied to expandable polystyrene particles, resulted in an increased pre-expansion basis weight, a decreased foaming ratio, an increased coefficient of friction, and a decreased adhesion score. This indicates that increasing the amount of cellulose nanocrystals affects the foaming effect of polystyrene particles and also affects their flowability and lubricity.

[0090] Compared with Example 1, Example 7 used the composite emulsion prepared in Preparation Example 5, in which pretreated carbon nanotubes were pretreated with polyethyleneimine, acrylic acid, etc. It can be seen that the adhesion of expandable polystyrene particles on the surface is reduced, the score is increased, the coefficient of friction is reduced, the lubricity is enhanced, the antibacterial ability is increased, and the pre-foaming weight is reduced and the foaming ratio is increased. This indicates that polyethyleneimine and the like form an elastic hydrogel on the surface of carbon nanotubes and cellulose nanocrystals, which can reduce the binding of polystyrene particles during foaming.

[0091] Compared to Example 1, Example 8 used the composite emulsion prepared in Preparation Example 6. Compared to Example 7, no quaternary ammonium salt chitosan was added for pretreatment of carbon nanotubes. As can be seen from the data in Table 2, the adhesion score of expandable polystyrene particles pretreated with the antibacterial coating agent prepared in Example 8 did not change significantly, and the antibacterial ability decreased. In Example 9, the composite emulsion prepared in Preparation Example 7 was used. Compared to Example 7, no polyethyleneimine was added. It can be seen that its foaming ratio decreased and the coefficient of friction increased, indicating that the hydrogel formed by polyethyleneimine crosslinking can significantly increase the elasticity of carbon nanotubes and cellulose nanocrystals, reduce the influence on the foaming ratio, and increase the lubrication effect.

[0092] Compared with Example 7, Example 10 uses oleic acid to pretreat silver-loaded silicate. As shown in Table 2, the adhesion score of expandable polystyrene particles treated with the antibacterial coating agent prepared in Example 10 increases and the coefficient of friction decreases. It can be seen that the lubricity and fluidity of polystyrene particles are enhanced, and the anti-adhesion and anti-caking ability is increased.

[0093] In Comparative Example 1, without the addition of polyethylene wax-carbon nanotube emulsion, the foaming density of expandable polystyrene particles decreased, but its lubrication effect decreased, the adhesion score decreased, and the coefficient of friction increased.

[0094] Compared with Example 1, Comparative Example 2 did not add polyethylene wax-carbon nanotube emulsion, nor did it add nano silica. As shown in Table 2, after the antibacterial coating agent prepared in Comparative Example 2 was used to treat expandable polystyrene particles for anti-slip treatment, the surface lubricity and fluidity of the polystyrene particles were reduced.

[0095] Compared with Example 1, Comparative Example 3 used only polyethylene wax emulsion without adding carbon nanotubes. It can be seen that when the antibacterial coating agent prepared therefrom is applied to the surface of expandable polystyrene particles, the adhesion score of the expandable polystyrene particles decreases and the surface lubrication effect is weakened.

[0096] Compared with Example 1, Comparative Example 4 only used carbon nanotube suspension as component B. Compared with Example 1, the antibacterial coating agent prepared on the surface of expandable polystyrene particles had reduced lubrication and anti-sticking effects.

[0097] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An expandable polystyrene antibacterial coating agent, characterized in that, The product comprises two components, A and B. Component A includes the following raw materials in parts by weight: 10-20 parts mono- and diglycerides of fatty acids, 12-20 parts tristearate, 10-18 parts stearate, 0.5-1.5 parts ethylene bis-stearamide, 20-35 parts nano-silica, and 45-65 parts antibacterial agent. Component B is a polyethylene wax-carbon nanotube composite emulsion, wherein the polyethylene wax-carbon nanotube composite emulsion contains polyethylene wax and carbon nanotubes in a mass ratio of 5-10:

100. The preparation method of the polyethylene wax-carbon nanotube composite emulsion is as follows: Polyethylene wax is heated to 120-130℃ until completely melted, then deionized water is added and homogenized to emulsify, thus obtaining a polyethylene wax emulsion. Carbon nanotubes were added to deionized water, sonicated, cellulose nanocrystals were added, and the mixture was sonicated and then filtered to obtain pretreated carbon nanotubes. Pretreated carbon nanotubes were added to a polyethylene wax emulsion and stirred until homogeneous to obtain a composite emulsion.

2. The expandable polystyrene antibacterial coating agent according to claim 1, characterized in that: The concentration of the polyethylene wax emulsion is 10-15%.

3. The expandable polystyrene antibacterial coating agent according to claim 1, characterized in that: The mass ratio of cellulose nanocrystals to carbon nanotubes is 1-2:

1.

4. The expandable polystyrene antibacterial coating agent according to claim 3, characterized in that: Before being added to the polyethylene wax emulsion, the pretreated carbon nanotubes undergo the following pretreatment: Polyethyleneimine, acrylic acid, N,N-methylenebisvinylamide, quaternary ammonium salt chitosan and photoinitiator were added to deionized water and mixed evenly to obtain the treatment solution. Pretreated carbon nanotubes were added to the treatment solution, ultrasonically dispersed, filtered, irradiated with ultraviolet light, and then soaked in sodium carbonate solution, filtered, and washed.

5. The expandable polystyrene antibacterial coating agent according to claim 1, characterized in that: The antibacterial agent is silver-loaded silicate.

6. The expandable polystyrene antibacterial coating agent according to claim 5, characterized in that: The silver-loaded silicate undergoes the following pretreatment: Oleic acid was added to ethanol to prepare an oleic acid-ethanol solution, which was then added dropwise to silver-loaded silicate while stirring. The solution was then dried under vacuum. The mass ratio of oleic acid to silver-loaded silicate was 0.03-0.05:

1.

7. The expandable polystyrene antibacterial coating agent according to claim 1, characterized in that: The stearate is selected from at least one of zinc stearate, magnesium stearate, sodium stearate, aluminum stearate, and calcium stearate.

8. The method of applying the expandable polystyrene antibacterial coating agent according to any one of claims 1-7, characterized in that: Includes the following steps: Tristearate, antibacterial agent, mono- and diglyceride fatty acid esters, nano-silica, stearate and ethylene bis-stearamide are mixed evenly to prepare material A; After mixing expandable polystyrene granules with material A for 30-50 minutes, spray the mixture with a polyethylene wax-carbon nanotube composite emulsion and let it dry.

9. The application method of the expandable polystyrene antibacterial coating agent according to claim 8, characterized in that, The amount of component A is 0.1-0.5% of the mass of expandable polystyrene granules, and the amount of component B is 0.05-0.25% of the mass of expandable polystyrene granules.

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