Environment-friendly positioning emulsion as well as preparation method and application thereof

Abstract

The invention relates to the technical field of grafted modified urea-formaldehyde resin adhesives, in particular to an environment-friendly positioning emulsion and a preparation method thereof. The preparation method comprises the following steps: mixing formaldehyde, urea, melamine, polyvinyl alcohol and a solvent, and carrying out condensation polymerization to obtain urea-formaldehyde resin; the preparation method comprises the following steps: mixing urea-formaldehyde resin, ethylene glycol terephthalate and an acidic substance, and carrying out esterification reaction to obtain grafted modified urea-formaldehyde resin; and mixing the graft modified urea-formaldehyde resin with waterborne polyurethane, and adjusting the pH value to 6.0-9.0 to obtain the environment-friendly positioning emulsion. The mechanical property, flexibility, alkali resistance, water resistance and high-temperature setting performance of the environment-friendly positioning emulsion are improved through esterification reaction of urea resin and ethylene glycol terephthalate, meanwhile, water resistance, flame retardance, flexibility and adhesion of the environment-friendly positioning emulsion are further improved through introduction of waterborne polyurethane, and the environment-friendly positioning emulsion is suitable for being applied to the field of building materials. The problems that in the prior art, a coating agent is poor in flexibility and poor in adhesion effect on glass fibers are solved.

Description

Technical Field

[0001] The invention relates to the technical field of grafted modified urea-formaldehyde resin adhesives, and in particular to an environmentally friendly positioning emulsion, a preparation method thereof, and an application thereof. Background Art

[0002] Glass fiber mats, glass fiber mesh, glass fiber nonwovens, and other glass fiber products are all organic products made from a woven glass fiber mesh substrate, coated with a polymer emulsion, and then dried. These materials are widely used in building foundations, as well as for fire protection, waterproofing, thermal insulation, and crack resistance. However, due to their brittleness and poor flexibility, these materials are easily corroded by the alkaline medium of construction cement, resulting in a shortened service life.

[0003] In order to solve the above problems, the prior art often adopts coating a layer of coating agent, also known as positioning emulsion, on the surface of the glass fiber mesh cloth to improve and increase the performance and service life of the glass fiber mesh cloth.

[0004] Patent CN1560158A discloses a water-based silicone rubber emulsion for coating glass fiber cloth, which is prepared using linear polysiloxane rubber, surfactant, dispersant, emulsifier, gasoline, and silane coupling agent. The water-based silicone rubber emulsion for coating glass fiber cloth prepared by this method has strong adhesion, thick coating, and high mechanical strength. However, there are problems such as poor flexibility of the coated glass fiber mesh cloth, high adhesion between the glass fiber mesh cloths, and poor flame retardancy.

[0005] Patent CN101696549A discloses a flame-retardant glass fiber mesh, which is prepared using chlorinated partial emulsion, reinforced positioning emulsion, nano-inorganic filler, synergistic flame retardant and dispersant. This method is easy to operate and control and has good flame retardancy, but the flame-retardant glass fiber mesh has the problems of poor flexibility, unsatisfactory adhesion to glass fiber materials and poor alkali resistance.

[0006] Patent CN102603959A discloses a method for preparing a modified coating agent for glass fiber mesh. The preparation method comprises: first, modifying aluminum hydroxide with ammonium dihydrogen phosphate to obtain modified aluminum hydroxide powder; second, weighing the core monomer and shell monomer, an emulsifier, and water according to the formula to prepare a core-shell pre-emulsion; then, weighing 1 / 2 of the core pre-emulsion, an initiator, and the modified aluminum hydroxide powder, and the remaining core pre-emulsion according to the formula to prepare a core emulsion; finally, combining the core emulsion and the shell pre-emulsion to prepare a modified coating agent. The glass fiber mesh modified coating agent prepared by this invention is applied to the glass fiber mesh, resulting in the glass fiber mesh having good flexibility, non-stickiness, excellent flame retardancy, and high alkaline retention. However, the preparation process is complex, and the water resistance and setting effect under high temperature conditions are poor. Summary of the Invention

[0007] To address the shortcomings of the existing technology, the present invention provides an environmentally friendly positioning emulsion, its preparation method, and its application. The present invention uses formaldehyde, urea, melamine, and polyvinyl alcohol as raw materials to produce a urea-formaldehyde resin through a polycondensation reaction. The urea-formaldehyde resin is then esterified with ethylene terephthalate under acidic conditions to produce a grafted urea-formaldehyde resin. Finally, the grafted urea-formaldehyde resin is mixed with water-based polyurethane and the pH is adjusted to produce the environmentally friendly positioning emulsion. The urea-formaldehyde resin prepared by the present invention has good environmental performance and high adhesion to glass fiber; at the same time, the grafted modified urea-formaldehyde resin with a three-dimensional network structure is formed through an esterification reaction, which improves the mechanical properties, alkali resistance, flexibility, water resistance, flame retardancy and high-temperature setting properties of the environmentally friendly positioning emulsion; at the same time, by introducing water-based polyurethane and mixing it with the grafted modified urea-formaldehyde resin, the flexibility, water resistance, alkali resistance and flame retardancy of the environmentally friendly positioning emulsion are further improved, effectively solving the problems of insufficient flexibility and poor adhesion to glass fiber materials of the positioning emulsion in the prior art, and significantly improving the water resistance of the environmentally friendly positioning emulsion.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: The first object of the present invention is to provide a method for preparing an environmentally friendly positioning emulsion, comprising the following steps: S1. Using formaldehyde and urea as raw materials, melamine and polyvinyl alcohol as modifiers, in the presence of a solvent, formaldehyde, urea, melamine and polyvinyl alcohol are mixed, and urea, melamine and polyvinyl alcohol are subjected to a condensation reaction with formaldehyde to obtain urea-formaldehyde resin. In order to ensure the quality and performance of the urea-formaldehyde resin, the optimal mass ratio of formaldehyde, urea, melamine and polyvinyl alcohol is 11.2~13.5:8.3~8.9:1:0.15~0.20.

[0009] S2. Mixing urea-formaldehyde resin, ethylene terephthalate and an acidic substance, and performing an esterification reaction to obtain a graft-modified urea-formaldehyde resin.

[0010] S3. Mixing the grafted modified urea-formaldehyde resin and waterborne polyurethane, and adjusting the pH to obtain an environmentally friendly positioning emulsion.

[0011] Preferably, when the properties of the urea-formaldehyde resin are modified by grafting, the mass ratio of the urea-formaldehyde resin to the ethylene terephthalate is 85-100:4.5-6.5:1.

[0012] Preferably, the mass ratio of urea-formaldehyde resin to acidic substance is 85-100:1.

[0013] Preferably, the acidic substance is selected from ammonium chloride, ammonium sulfate, ammonium bisulfate or hydrochloric acid.

[0014] Preferably, the mass ratio of the grafted modified urea-formaldehyde resin to the waterborne polyurethane is 150~180:1; within this range, the environmentally friendly positioning emulsion has excellent adhesion, flexibility and high mechanical strength, and its high temperature resistance and environmental protection are also optimized.

[0015] Preferably, the polycondensation reaction is carried out at 70° C. to 80° C. for 0.5 h to 1.0 h.

[0016] Preferably, the esterification reaction conditions are: reaction at 90° C. to 95° C. for 1.0 h to 1.5 h.

[0017] Preferably, the graft-modified urea-formaldehyde resin and the waterborne polyurethane are mixed under the following conditions: stirring at 75° C. to 85° C. for 0.5 h to 1.0 h.

[0018] Preferably, the pH adjustment treatment is performed by mixing an alkaline solution with the environmentally friendly positioning emulsion to adjust the pH value of the environmentally friendly positioning emulsion to 6.0-9.0. Within this pH value range, the environmentally friendly positioning emulsion can be stably stored for a long time, thereby effectively extending its service life and maintaining the stability of its performance.

[0019] Preferably, the temperature of the pH adjustment treatment is 50°C to 60°C.

[0020] Preferably, the mass fraction of formaldehyde is 35% to 37%. Preferably, the solvent is water. Water is often used as a reaction medium in the preparation of urea-formaldehyde resin to control the reaction process.

[0021] The second object of the present invention is to provide an environmentally friendly positioning emulsion prepared by the above preparation method.

[0022] The third object of the present invention is to provide an environmentally friendly positioning coating, which is obtained by spraying the above-mentioned environmentally friendly positioning emulsion on glass fiber and drying and shaping it.

[0023] Preferably, the drying and shaping temperature is 180°C to 220°C.

[0024] Preferably, the glass fiber product is selected from glass fiber mat, glass fiber mesh or glass fiber non-woven fabric.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a method for preparing an environmentally friendly positioning emulsion, which comprises the following steps: using formaldehyde and urea as raw materials, and melamine and polyvinyl alcohol as modifiers; mixing formaldehyde, urea, melamine and polyvinyl alcohol in the presence of a solvent; and subjecting urea, melamine and polyvinyl alcohol to a condensation reaction with formaldehyde to obtain a urea-formaldehyde resin; wherein urea reacts with formaldehyde to form the main chain structure of the urea-formaldehyde resin, i.e., the urea-formaldehyde segment; introducing a triazabenzene ring structure into melamine and copolymerizing with the urea-formaldehyde segment, thereby significantly improving the water resistance, heat resistance and bonding strength of the urea-formaldehyde resin; and forming a semi-interpenetrating structure with the urea-formaldehyde segment network through ether bonds in the flexible segment of the polyvinyl alcohol, thereby improving the toughness of the urea-formaldehyde resin.

[0026] Urea-formaldehyde resin is mixed with ethylene terephthalate, and the hydroxyl groups of the urea-formaldehyde resin react with the carboxyl groups of the ethylene terephthalate to form an esterification reaction, thereby forming a graft copolymer with a three-dimensional network structure, thereby obtaining a grafted modified urea-formaldehyde resin; this three-dimensional network structure not only enhances the cross-linking density of the molecular chain of the grafted modified urea-formaldehyde resin, making it difficult for the molecular chain to be destroyed when eroded by acid and alkali, thereby significantly improving its alkali resistance; at the same time, it also gives the grafted modified urea-formaldehyde resin higher thermal stability, so that it can still maintain a stable molecular structure under high temperature conditions, and is not prone to thermal degradation or softening, thereby significantly improving its high-temperature setting properties.

[0027] After mixing the grafted modified urea-formaldehyde resin with waterborne polyurethane, the pH value was adjusted to 6.0-9.0 to produce an environmentally friendly positioning emulsion. By introducing waterborne polyurethane and mixing it with the grafted modified urea-formaldehyde resin, the flame retardancy, flexibility, and adhesion of the environmentally friendly positioning emulsion were further improved, addressing the problems of poor flexibility and poor adhesion to glass fibers in existing coatings.

[0028] 2. The environmentally friendly positioning emulsion of the present invention is sprayed on the glass fiber, and the environmentally friendly positioning coating formed after curing exhibits excellent comprehensive performance. The environmentally friendly positioning coating not only has a uniform and controllable thickness, but also has high mechanical strength, excellent flexibility and good flame retardant properties. In particular, the environmentally friendly positioning coating is also resistant to high temperatures and does not soften even in a high temperature environment of 250°C. The excellent performance of the environmentally friendly positioning coating of the present invention is mainly attributed to the fact that the present invention successfully grafted a polyethylene terephthalate segment with excellent mechanical properties onto the molecular structure of urea-formaldehyde resin, so that the environmentally friendly positioning emulsion has the advantages of high strength, alkali corrosion resistance, high temperature resistance and environmental friendliness of polyethylene terephthalate materials.

[0029] 3. The environmentally friendly positioning emulsion of the present invention is applied to the glass fiber for coating treatment. The environmentally friendly positioning emulsion of the present invention can efficiently adhere to and stabilize the glass fiber during the high-temperature drying process. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solution of the present invention in conjunction with the data in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0032] Although a variety of surface coatings for glass fiber products, such as glass fiber mats, glass fiber meshes, and glass fiber non-woven fabrics, are now available on the market, these coatings still suffer from issues such as insufficient flexibility, high adhesion between mesh products, poor flame retardancy, poor alkali resistance, and unsatisfactory water resistance and high-temperature setting properties. These issues limit the application range and service life of glass fiber products.

[0033] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for preparing an environmentally friendly positioning emulsion, comprising the following steps: using formaldehyde and urea as raw materials, and melamine and polyvinyl alcohol as modifiers, in the presence of a solvent, mixing the formaldehyde, urea, melamine and polyvinyl alcohol, and subjecting the urea, melamine and polyvinyl alcohol to a condensation reaction with the formaldehyde to obtain a urea-formaldehyde resin; mixing the urea-formaldehyde resin, ethylene terephthalate and an acidic substance, and under the catalytic action of the acidic substance, allowing the hydroxyl groups of the urea-formaldehyde resin to undergo an esterification reaction with the carboxyl groups of the ethylene terephthalate to obtain a grafted modified urea-formaldehyde resin; mixing the grafted modified urea-formaldehyde resin and water-based polyurethane, and adjusting the pH value to 6.0-9.0 to obtain the environmentally friendly positioning emulsion.

[0034] In terms of alkali resistance and high-temperature setting properties, the esterification reaction of urea-formaldehyde resin, ethylene terephthalate, and an acidic substance is used to generate a grafted modified urea-formaldehyde resin. This significantly improves the mechanical properties and alkali resistance of the urea-formaldehyde resin, overcoming the problem in the prior art that glass fiber mesh cloth is susceptible to erosion by alkaline media. Specifically, during the esterification reaction, the active groups of the urea-formaldehyde resin undergo an esterification reaction with the carboxyl groups of ethylene terephthalate, forming a graft copolymer with a three-dimensional network structure, namely the grafted modified urea-formaldehyde resin. This structure not only enhances the cross-linking density of the molecular chain, making the grafted modified urea-formaldehyde resin less susceptible to damage when attacked by acids and alkalis, thereby significantly improving its alkali resistance; at the same time, the three-dimensional network structure also gives the grafted modified urea-formaldehyde resin higher thermal stability, allowing it to maintain a stable molecular structure under high temperature conditions, making it less susceptible to thermal degradation or softening, thereby significantly improving its high-temperature setting properties.

[0035] In terms of flexibility and adhesion, the present invention utilizes flexible segments of polyvinyl alcohol to form a semi-interpenetrating structure with the urea-formaldehyde resin network through ether bonds, thereby improving the toughness of the urea-formaldehyde resin. Furthermore, the esterification reaction also introduces flexible segments that deform when the grafted urea-formaldehyde resin is subjected to external forces, absorbing and dispersing stress, further enhancing the flexibility of the environmentally friendly positioning emulsion.

[0036] In addition, the present invention forms good compatibility and interaction between the flexible segments introduced into the grafted modified urea-formaldehyde resin and the molecular segments of the waterborne polyurethane. This interaction not only retains the original strength and chemical resistance of the grafted modified urea-formaldehyde resin, but also gives the environmentally friendly positioning emulsion excellent flexibility. At the same time, the polar groups in the waterborne polyurethane can form hydrogen bonds or chemical bonds with the active groups on the surface of the glass fiber material, thereby enhancing the wettability and adhesion of the environmentally friendly positioning emulsion to the glass fiber material and significantly improving its adhesion. By adjusting the mass ratio of the grafted modified urea-formaldehyde resin to the waterborne polyurethane, the flexibility and adhesion of the environmentally friendly positioning emulsion can be further optimized, so that it can exhibit better flexibility and strong adhesion to the glass fiber material while maintaining sufficient mechanical strength.

[0037] As for the preparation method, compared with the preparation method of the prior art, the preparation method of the present invention is relatively simple. Through polycondensation reaction, esterification reaction and mixing of water-based polyurethane, an environmentally friendly positioning emulsion can be obtained, and the conditions of each step are clearly controlled and easy to operate.

[0038] In terms of water resistance, the grafted urea-formaldehyde resin of the present invention forms a three-dimensional network structure through an esterification reaction. This three-dimensional network structure significantly increases the crosslink density of the molecular chains, making the grafted urea-formaldehyde resin less susceptible to hydrolysis or swelling when exposed to water, thereby enhancing water resistance. Furthermore, polar groups in the waterborne polyurethane, such as urethane groups, form hydrogen bonds or chemical bonds with the grafted urea-formaldehyde resin, further strengthening intermolecular interactions. This synergistic effect enables the environmentally friendly positioning emulsion to form a dense membrane structure after curing, reducing the channels for water penetration.

[0039] In terms of flame retardancy, the present invention utilizes the halogen-free flame retardant melamine and grafted modified urea-formaldehyde resin, resulting in an environmentally friendly positioning emulsion with excellent flame retardancy. The grafted modified urea-formaldehyde resin decomposes at high temperatures to produce nitrogen oxides, an inert gas. This forms an insulating char layer, blocking the transfer of oxygen and heat, thereby enhancing flame retardancy. Furthermore, the urethane groups in the waterborne polyurethane decompose at high temperatures to produce ammonia, which dilutes oxygen concentration and further enhances the flame retardancy.

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] Example 1 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. In a reactor, add 1000 kg of environmentally friendly formaldehyde with a mass fraction of 37%, 420 kg of water, 260 kg of urea, 30 kg of melamine and 5 kg of polyvinyl alcohol respectively under stirring, heat to 70 ° C, and react for 0.5 h to obtain urea-formaldehyde resin.

[0042] S2. After heating the urea-formaldehyde resin to 95° C., 40 kg of ethylene terephthalate and 9 kg of ammonium chloride were added respectively, and the mixture was subjected to esterification reaction at 90° C. for 1 hour to obtain a graft-modified urea-formaldehyde resin.

[0043] S3. After cooling the grafted modified urea-formaldehyde resin to 80°C, add 10 kg of waterborne polyurethane, mix for 0.5 h, and then cool to 50°C. Use sodium hydroxide solution to adjust the pH in the reactor to 7.2, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0044] Example 2 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. Add 1000 kg of environmentally friendly formaldehyde (37% by mass), 400 kg of water, 255 kg of urea, 28 kg of melamine, and 6 kg of polyvinyl alcohol into a reactor under stirring, heat to 75°C, and react for 0.5 h to obtain urea-formaldehyde resin.

[0045] S2. After heating the urea-formaldehyde resin to 90° C., 38 kg of ethylene terephthalate and 8 kg of ammonium chloride were added respectively, and the mixture was subjected to esterification reaction at 90° C. for 40 min to obtain a graft-modified urea-formaldehyde resin.

[0046] S3. After cooling the grafted modified urea-formaldehyde resin to 85°C, add 15 kg of waterborne polyurethane, mix for 1.0 h, and then cool to 45°C. Use sodium hydroxide solution to adjust the pH in the reactor to 7.5, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0047] Example 3 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. In a reactor, add 1000 kg of environmentally friendly formaldehyde (35% by mass), 405 kg of water, 265 kg of urea, 32 kg of melamine and 6 kg of polyvinyl alcohol under stirring, heat to 80°C, and react for 1.0 h to obtain urea-formaldehyde resin.

[0048] S2. After heating the urea-formaldehyde resin to 95° C., 42 kg of ethylene terephthalate and 8 kg of ammonium bisulfate were added respectively, and the mixture was esterified at 90° C. for 45 min to obtain a graft-modified urea-formaldehyde resin.

[0049] S3. After cooling the grafted modified urea-formaldehyde resin to 75°C, add 12 kg of waterborne polyurethane, mix for 0.5 h, and then cool to 40°C. Use sodium hydroxide solution to adjust the pH in the reactor to 6.5, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0050] Example 4 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. In a reactor, add 1000 kg of environmentally friendly formaldehyde (35% by mass), 410 kg of water, 250 kg of urea, 30 kg of melamine and 5 kg of polyvinyl alcohol under stirring, heat to 75 ° C, and react for 45 minutes to obtain urea-formaldehyde resin.

[0051] S2. After heating the urea-formaldehyde resin to 90° C., 45 kg of ethylene terephthalate and 9 kg of ammonium bisulfate were added respectively, and the mixture was subjected to esterification reaction at 90° C. for 1 hour to obtain a graft-modified urea-formaldehyde resin.

[0052] S3. After cooling the grafted modified urea-formaldehyde resin to 85°C, add 15 kg of waterborne polyurethane, mix for 45 minutes, and then cool to 50°C. Use sodium hydroxide solution to adjust the pH in the reactor to 8.0, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0053] Example 5 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. In a reactor, add 1000 kg of environmentally friendly formaldehyde (37% by mass), 410 kg of water, 265 kg of urea, 32 kg of melamine and 7 kg of polyvinyl alcohol under stirring, heat to 70 ° C, and react for 45 minutes to obtain urea-formaldehyde resin.

[0054] S2. After heating the urea-formaldehyde resin to 95° C., 42 kg of ethylene terephthalate and 10 kg of ammonium sulfate were added respectively, and the mixture was subjected to esterification reaction at 90° C. for 50 min to obtain a graft-modified urea-formaldehyde resin.

[0055] S3. After cooling the grafted modified urea-formaldehyde resin to 75°C, add 12 kg of waterborne polyurethane, mix for 1.0 h, and then cool to 50°C. Use sodium hydroxide solution to adjust the pH in the reactor to 8.5, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0056] Example 6 A method for preparing an environmentally friendly positioning emulsion specifically comprises the following steps: S1. In a reactor, add 1000 kg of environmentally friendly formaldehyde (35% by mass), 430 kg of water, 270 kg of urea, 35 kg of melamine and 7 kg of polyvinyl alcohol respectively under stirring, heat to 80°C, and react for 50 minutes to obtain urea-formaldehyde resin.

[0057] S2. After heating the urea-formaldehyde resin to 90° C., 45 kg of ethylene terephthalate and 8 kg of ammonium sulfate were added respectively, and the mixture was subjected to esterification reaction at 90° C. for 1.5 h to obtain a graft-modified urea-formaldehyde resin.

[0058] S3. After cooling the grafted modified urea-formaldehyde resin to 75°C, add 10 kg of waterborne polyurethane, mix for 50 minutes, and then cool to 45°C. Use sodium hydroxide solution to adjust the pH in the reactor to 9.0, and cool to 40°C to obtain an environmentally friendly positioning emulsion.

[0059] Examples 1 to 6 of the present invention all produced environmentally friendly positioning emulsions, and their main properties all met the technical indicators in Table 1. Taking the environmentally friendly positioning emulsion produced in Example 5 as an example, its emulsion properties were tested, and the test results are shown in Table 2.

[0060] Table 1 Performance index of environmentally friendly positioning emulsion Table 2 Performance data of the environmentally friendly positioning emulsion prepared in Example 5 Combining Table 1 and Table 2, it can be concluded that the environmentally friendly positioning emulsion prepared by the present invention exhibits excellent performance in terms of film-forming temperature, heat resistance, and tensile strength in warp and weft directions.

[0061] Taking the environmentally friendly positioning emulsion prepared in Example 1 and two commonly used positioning agents on the market as examples, they were applied to glass fiber mesh to study their application performance: Coating Method: A 25 cm x 25 cm glass fiber mesh was placed on a clean glass plate. Two commonly used positioning agents, Changhai and Taian, and the environmentally friendly positioning emulsion prepared in Example 1 were evenly applied to the glass fiber mesh using a paint spray gun. The glass fiber mesh was then placed in an oven and baked at 120°C for 10 minutes to obtain an environmentally friendly positioning coating. The thickness of the environmentally friendly positioning coating was 0.5 mm.

[0062] Detection method: (1) Softness test: 20 evaluators with a sensitive sense of touch were selected and divided into 5 groups to conduct double-blind sensory evaluation. At room temperature, the evaluators touched the glass fiber mesh with environmentally friendly positioning coating with their hands to judge its softness.

[0063] The scoring criteria are: soft: 10 points to 8 points; relatively soft: 8 points to 6 points; relatively hard: 6 points to 4 points.

[0064] (2) Adhesion test: stack three pieces of glass fiber mesh cloth with environmentally friendly positioning coating, place a 2 kg weight on top, keep warm at 60 ° C for 24 hours, take out and observe.

[0065] The judging criteria are: glass fiber mesh that can be peeled off freely or by gently shaking is rated as level one; that cannot be peeled off freely but can be peeled off easily by hand is rated as level two; that is difficult to peel off is rated as level three.

[0066] (3) Flame retardancy test: An automatic oxygen index tester is used to measure the limiting oxygen index of the glass fiber mesh cloth with environmentally friendly positioning coating.

[0067] (4) Alkali retention rate: Place the glass fiber mesh cloth with environmentally friendly positioning coating in an alkaline solution containing 3.5g potassium hydroxide, 0.9g sodium hydroxide and 0.5g calcium hydroxide per liter, soak it at 80℃ for 6h, take it out, wash it and dry it, and then use a BZ2.5 / TNIS material testing machine to measure its value.

[0068] Calculation formula for alkali resistance retention rate: ; Among them, the tensile strength meter is L 2 , the tensile strength before natron is L 1 .

[0069] (5) Mechanical strength: The tensile strength of the glass fiber mesh cloth with environmentally friendly positioning coating was measured using an electronic fabric strength tester before being soaked in caustic soda.

[0070] The test results of the application performance of the environmentally friendly positioning emulsions and Changhai and Taian brand positioning agents prepared in Examples 1 to 6 are shown in Table 3: Table 3 Test results of the application performance of the environmentally friendly positioning emulsions prepared in Examples 1 to 6 and the Changhai and Taian brand positioning agents As shown in Table 3, compared with the commonly used Changhai brand positioning agents and Tai'an brand positioning agents on the market, the environmentally friendly positioning emulsions prepared in Examples 1 to 6 of the present invention show significant advantages in various properties. Specifically, in terms of softness, the scores of Examples 1 to 6 are higher than those of the Changhai brand positioning agents and Tai'an brand positioning agents, showing better softness; in terms of adhesion, the environmentally friendly positioning emulsions of the present invention all meet the first-level standard, which is better than the second-level standard of the Changhai brand positioning agents and Tai'an brand positioning agents; in terms of limiting oxygen index and alkaline retention number, the environmentally friendly positioning emulsions of the present invention generally have higher values than the Changhai brand positioning agents and Tai'an brand positioning agents, indicating that they have better flame retardancy and alkali resistance; in terms of radial and latitudinal tension, the radial and latitudinal tensions of the environmentally friendly positioning emulsions of the present invention are both higher than 2000N, much higher than those of the Changhai brand positioning agents and Tai'an brand positioning agents, indicating that they have stronger mechanical properties. Therefore, the environmentally friendly positioning emulsion prepared by the present invention is superior to the Changhai brand positioning agents and Taian brand positioning agents commonly used in the market in terms of softness, adhesion, flame retardancy, alkali resistance and mechanical properties.

[0071] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Claims

1. A method for preparing an environmentally friendly positioning emulsion, characterized in that: The steps include: Using formaldehyde and urea as raw materials, melamine and polyvinyl alcohol as modifiers, in the presence of a solvent, formaldehyde, urea, melamine and polyvinyl alcohol are mixed, and urea, melamine and polyvinyl alcohol are subjected to a condensation reaction with formaldehyde to obtain urea-formaldehyde resin; Mixing urea-formaldehyde resin, ethylene terephthalate and an acidic substance, and under the catalytic action of the acidic substance, esterification reaction occurs between the hydroxyl group of the urea-formaldehyde resin and the carboxyl group of the ethylene terephthalate to obtain a grafted modified urea-formaldehyde resin; After the grafted modified urea-formaldehyde resin is mixed with waterborne polyurethane, the pH value is adjusted to 6.0-9.0 to obtain an environmentally friendly positioning emulsion.

2. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The mass ratio of formaldehyde, urea, melamine and polyvinyl alcohol is 11.2~13.5:8.3~8.9:1:0.15~0.

20.

3. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The mass ratio of urea-formaldehyde resin to ethylene terephthalate is 85-100:4.5-6.

5.

4. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The mass ratio of grafted modified urea-formaldehyde resin to waterborne polyurethane is 150~180:

1.

5. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The acidic substance is selected from ammonium chloride, ammonium sulfate, ammonium bisulfate or hydrochloric acid.

6. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The conditions for the esterification reaction are: reaction at 90°C~95°C for 1h~1.5h.

7. The method for preparing the environmentally friendly positioning emulsion according to claim 1, characterized in that: The conditions for the polycondensation reaction are: reaction at 70°C~80°C for 0.5h~1.0h.

8. An environmentally friendly positioning emulsion, characterized in that: The environmentally friendly positioning emulsion is prepared by the preparation method of any one of claims 1 to 7.

9. An environmentally friendly positioning coating, characterized in that: The environmentally friendly positioning emulsion according to claim 8 is sprayed on glass fiber and dried to shape.

10. The environmentally friendly positioning coating according to claim 9, characterized in that: The drying and shaping temperature is 180℃~220℃.

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