Low-cost water-resistant tert-vinegar core-shell emulsion for tree trunk whitening agent, preparation method of low-cost water-resistant tert-vinegar core-shell emulsion and latex powder

Abstract

The invention discloses low-cost water-resistant redispersible latex powder for a tree trunk whitening agent. The latex powder comprises the following components in parts by weight: 145 parts of a tert-vinegar core-shell process emulsion, 1-5 parts of polyvinyl alcohol and 16-20 parts of an anti-caking agent. According to the latex powder prepared in the invention, in the design of a polymerization structure, the core layer and the shell layer of the latex particle adopt different monomer components, the vinyl acetate homopolymer with poor water resistance is used in the core layer structure of the latex particle and accounts for 60-80% of the total monomer, and the cost is low; vinyl versatate and vinyl acetate which are high in water resistance are copolymerized in a shell structure of the emulsion particle and account for 20-40% of the total monomer amount, the content of vinyl versatate in a shell is 40-50%, and the water resistance of the emulsion particle is improved by utilizing the excellent water resistance of vinyl versatate; and finally, the water absorption rate of an adhesive film can be further reduced after the polymer forms a film by using added hydrophobic silane, so that the cost of the raw materials is reduced, and meanwhile, a relatively good water-resistant effect is achieved, and the synthesized emulsion and the latex powder prepared from the emulsion can be used for preparing a tree trunk whitening agent, so that the water resistance of the whitening agent can be remarkably improved; the action duration and the service life of the whitening agent are prolonged, so that the re-brushing frequency is reduced, and the greening cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of emulsion synthesis and powder spraying, in particular to a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent, a preparation method thereof and latex powder. Background Art

[0002] Dry powder tree trunk whitening agent is easy to transport and can be applied by adding water and stirring on site. It is a commonly used whitening agent in recent years. It uses redispersible latex powder as a binder, which plays a role in adhering and anchoring various components in the ingredients that inhibit pests and kill bacteria on the tree trunk. However, it is often encountered that after rain, the latex powder has poor water resistance and will fall off or be washed away by rain, especially in areas with frequent rain in the south. Therefore, the development of redispersible latex powder with good water resistance and adhesion, which can withstand 3-5 months of sun and rain, is a product that the market urgently needs; at the same time, because the product price is not high, the cost should be reduced as much as possible.

[0003] In view of the above problems, in the redispersible latex powder system, tert-butyl vinyl carbonate has not been widely used because of its high unit price, which makes the tert-butyl vinyl acetate powder costly and the limited performance improvement. The trunk whitewash agent needs to be repainted every year due to the growth of trees and the requirements of pest control and sterilization. In fact, it only needs to withstand a few months of rain. Summary of the invention

[0004] The object of the present invention is to provide a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent and a preparation method and latex powder thereof, so as to solve one or more of the above-mentioned prior art problems.

[0005] The present application provides a method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent, comprising the following steps: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature of the mixed solution between 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise add the shell monomer to the prepared mixed solution B for polymerization. The shell monomer needs to be added dropwise within 70-90 minutes; d. After the addition of the shell monomer is completed, the initiator is continued to be added dropwise for 15-20 minutes while maintaining the reaction temperature until the initiator is exhausted; e. After 90-120 minutes of heat preservation and aging, the temperature is lowered to 60°C, hydrophobic silane is added, and the mixture is fully stirred for 30 minutes, and the temperature is lowered again to discharge the material. After filtering, a low-cost tertiary ester core-shell emulsion with a solid content of 50-55% is obtained. It can be seen that in the vinyl acetate emulsion polymerization applied, the core-shell copolymerization free radical polymerization process is adopted, tertiary ester vinyl carbonate is copolymerized in the outer layer of the particles, and hydrophobic silane is added to prepare the polymer emulsion, which can be obtained by centrifugal spray drying process.

[0006] Preferably, the preparation method comprises the following steps: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature of the mixed solution between 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise add the shell monomer to the prepared mixed solution B for polymerization. The shell monomer needs to be added dropwise within 70-90 minutes; d. After the addition of the shell monomer is completed, the initiator is continued to be added dropwise for 15-20 minutes while maintaining the reaction temperature until the initiator is exhausted; e. After 90-120 minutes of heat preservation and aging, the temperature is lowered to 60°C, and hydrophobic silane is added. After sufficient stirring and mixing for 30 minutes, the temperature is lowered again and the material is discharged. After filtering, a low-cost tertiary vinegar core-shell emulsion with a solid content of 50-55% is obtained.

[0007] Preferably, the core monomer accounts for 60-80% of the mass of the main monomer, the core monomer includes vinyl acetate, and the shell monomer accounts for 20-40% of the mass of the main monomer, and the above ratios are the mass ratios of each substance to the main monomer; the shell monomer is prepared by copolymerization of vinyl acetate and tert-butyl vinyl carbonate, wherein tert-butyl vinyl carbonate accounts for 40-50% of the mass of the shell monomer. Therefore, the core polymerization is mainly based on vinyl acetate, accounting for 60-80% of the total monomer ratio, and the cost is relatively low; the shell polymerization adopts vinyl acetate and tert-butyl vinyl carbonate copolymerization, accounting for 20-40% of the total monomer amount, and the content of tert-butyl vinyl carbonate in the shell is 40-50%, thereby increasing the water resistance of the latex particles.

[0008] Preferably, the protective colloid is polyvinyl alcohol, and its alcoholysis degree is 86-90%, and its polymerization degree is 300-2400. According to the requirements for viscosity in actual conditions, polyvinyl alcohol with different polymerization degrees is selected as the protective colloid to ensure that the emulsion viscosity is suitable, which is conducive to powder spraying, provides convenience for the later production of latex powder, and improves the powder spraying efficiency.

[0009] Preferably, the hydrophobic silane is one or a combination of octylsilane, dodecylsilane, hexadecylsilane and octadecylsilane.

[0010] Preferably, the initiator is one of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide or tert-butyl hydroperoxide.

[0011] On the other hand, the present application provides a low-cost water-resistant tertiary vinegar core-shell emulsion prepared by the above method, wherein the raw materials of the core-shell emulsion include the following components by weight: 8-20 parts of versatate, 80-92 parts of vinyl acetate, 7-15 parts of protective colloid, 0.5-1 parts of initiator, 100-130 parts of water, and 2-8 parts of hydrophobic silane.

[0012] Preferably, the latex powder comprises the following ingredients in parts by weight: 145 parts of tertiary vinegar core-shell emulsion, 1-5 parts of polyvinyl alcohol and 16-20 parts of anti-caking agent.

[0013] Preferably, the anti-caking agent is one or a combination of calcium carbonate, kaolin, and silicon dioxide, and the fineness of the anti-caking agent is not less than 800 mesh.

[0014] The beneficial effects of the present invention are: The latex powder prepared in the present application adopts different monomer components in the core layer and shell layer of the latex particles in the polymerization structure design, and the vinyl acetate homopolymer with poor water resistance is made in the core layer structure of the latex particles, accounting for 60-80% of the total monomer ratio, and the cost is relatively low; the versatate vinyl carbonate and vinyl acetate copolymers with high water resistance are made in the shell layer structure of the latex particles, accounting for 20-40% of the total monomer amount, and the content of versatate vinyl carbonate in the shell layer is 40-50%, and the excellent water resistance of versatate vinyl carbonate is used to improve the water resistance of the latex particles; finally, the added hydrophobic silane can further reduce the water absorption rate of the film after the polymer film is formed, thereby reducing the cost of raw materials and having a good water resistance effect. The synthesized emulsion can be made to meet the requirements of the tree trunk whitewashing agent, which can significantly improve the water resistance of the whitewashing agent, extend the effect time and service life of the whitewashing agent, thereby reducing the number of re-painting and saving greening costs. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail by examples below. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0017] The present application provides a method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for a tree trunk whitening agent, comprising the following steps: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature of the mixed solution between 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise add the shell monomer to the prepared mixed solution B for polymerization. The shell monomer needs to be added dropwise within 70-90 minutes; d. After the addition of the shell monomer is completed, the initiator is continued to be added dropwise for 15-20 minutes while maintaining the reaction temperature until the initiator is exhausted; e. After 90-120 minutes of heat preservation and aging, cool down to 60°C, add hydrophobic silane, stir and mix thoroughly for 30 minutes, cool down again, discharge, and filter to obtain a low-cost tertiary ester core-shell emulsion with a solid content of 50-55%. In the present application, in the vinyl acetate emulsion polymerization, a core-shell copolymerization free radical polymerization process is used to copolymerize tertiary ester carbonate in the outer layer of the particles, and hydrophobic silane is added to prepare a polymer emulsion. The emulsion is subjected to a centrifugal spray drying process to obtain a low-cost water-resistant redispersible latex powder.

[0018] Therefore, in the steps of the present application, in the polymer structure design, the vinyl acetate homopolymer with poor water resistance is made in the core layer of the latex particles, the tert-butyl vinyl carbonate and vinyl acetate copolymer with high water resistance is made in the shell layer of the latex particles, and a certain amount of hydrophobic silane is added to reduce the water absorption rate of the latex particles, thereby reducing the cost of raw materials and having a good water resistance effect. The synthesized emulsion can produce a redispersible latex powder that meets the requirements of the tree trunk whitening agent. At the same time, the latex powder prepared by the present invention can be used in the formulation of the tree trunk whitening agent to significantly improve the water resistance of the whitening agent, extend the duration and service life of the whitening agent, thereby reducing the number of re-painting and saving greening costs.

[0019] As an achievable preferred method, the specific preferred steps of this application may be: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature of the mixed solution between 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise add the shell monomer to the prepared mixed solution B for polymerization. The shell monomer needs to be added dropwise within 70-90 minutes; d. After the addition of the shell monomer is completed, the initiator is continued to be added dropwise for 15-20 minutes while maintaining the reaction temperature until the initiator is exhausted; e. After heat preservation and aging for 90-120 minutes, cool to 60°C, add hydrophobic silane, stir and mix thoroughly for 30 minutes, cool again and discharge, filter to obtain a low-cost tertiary vinegar core-shell emulsion with a solid content of 50-55%. Among them, the protective colloid is preferably polyvinyl alcohol, with a degree of alcoholysis of 86-90% and a degree of polymerization of 300-2400. The hydrophobic silane is preferably one or a combination of octylsilane, dodecylsilane, hexadecylsilane and octadecylsilane. The initiator is preferably one of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide or tert-butyl hydroperoxide.

[0020] It should be noted that the core layer structure is mainly composed of vinyl acetate, which accounts for 60-80% of the mass of the main monomer; the shell layer polymerization adopts copolymerization of vinyl acetate and versatate vinyl carbonate, and the shell layer monomer accounts for 20-40% of the mass of the main monomer. The above ratios are the mass ratios of each substance to the main monomer; the shell layer monomer is prepared by copolymerization and mixing of vinyl acetate and versatate vinyl carbonate, wherein versatate vinyl carbonate accounts for 40-50% of the mass of the shell layer monomer.

[0021] On the other hand, the present application also provides a low-cost water-resistant tertiary vinegar core-shell emulsion obtained by the above-mentioned preparation method, which can be used in a tree trunk whitening agent, and the emulsion can be made into latex powder, which is used for tree trunk whitening agents. The raw materials of the core-shell emulsion include the following components by weight: 8-20 parts of tertiary ethylene carbonate, 80-92 parts of vinyl acetate, 7-15 parts of protective colloid, 0.5-1 part of initiator, 100-130 parts of water, and 2-8 parts of hydrophobic silane. The tertiary vinegar core-shell emulsion can be prepared by centrifugal spray drying for a low-cost water-resistant redispersible latex powder for a tree trunk whitening agent, and the latex powder includes the following components by weight: 145 parts of tertiary vinegar core-shell emulsion, 1-5 parts of polyvinyl alcohol, and 16-20 parts of an anti-caking agent. Among them, the anti-caking agent is one or a combination of two of calcium carbonate, kaolin, and silicon dioxide, and the fineness of the anti-caking agent is not less than 800 meshes.

[0022] The preparation of low-cost tertiary vinegar core-shell emulsion A includes: 8 parts of tertiary vinyl carbonate and 92 parts of vinyl acetate, 10 parts of protective colloid, 0.5 parts of initiator; 8 parts of dodecyl triethoxysilane; the protective colloid is polyvinyl alcohol with an alcoholysis degree of 86% and a polymerization degree of 300; the initiator is potassium persulfate; and 96 parts of deionized water.

[0023] The preparation steps are: a. Mix the protective colloid with water and heat to 90°C to dissolve the protective colloid; b. Keep the temperature stable at 80°C and start to drop the initiator continuously. At the same time, drop 80 parts of vinyl acetate as the core layer monomer; c. After the core layer monomer was added dropwise for 150 minutes, the shell layer monomer consisting of 12 parts of vinyl acetate and 8 parts of vinyl ester was immediately added dropwise, and the dropwise addition was completed within 70 minutes. During this period, the reaction temperature was maintained at 82-85°C by controlling the dropwise addition speed. After the dropwise addition, the temperature was maintained and the initiator was continued to be added dropwise for 15-20 minutes until the initiator was exhausted; d. After 90 minutes of heat preservation, cool to 60 ° C, add 8 parts of dodecyl triethoxysilane, and stir thoroughly for 30 minutes; e. Cool down to 40℃ and discharge the material. After filtering, a low-cost tertiary vinegar core-shell emulsion with a solid content of 55% is obtained.

[0024] After the synthesis of the tertiary ester core-shell emulsion A, the redispersible latex powder A is prepared by spray drying. The latex powder includes the following components by weight: 145 parts of tertiary ester core-shell emulsion, 2 parts of polyvinyl alcohol and 18 parts of anti-caking agent. The anti-caking agent used is 10 parts of calcium carbonate and 8 parts of kaolin with a fineness of 1250 mesh. It is added by air delivery during centrifugal spray drying, and the obtained rubber powder is sieved through a 60-mesh sieve for standby use. The rotary spray drying conditions are: the inlet temperature is 150°C and the outlet temperature is 80°C.

[0025] The preparation of low-cost tertiary vinegar core-shell emulsion B includes 20 parts of tertiary vinyl carbonate and 80 parts of vinyl acetate, 15 parts of protective colloid, 0.5 parts of initiator, 10 parts of hexadecyltriethoxysilane, the protective colloid is polyvinyl alcohol with an alcoholysis degree of 86% and a polymerization degree of 300, the initiator is potassium persulfate, and 100 parts of deionized water.

[0026] The preparation steps are: a. Mix the protective colloid with water and heat to 90°C to dissolve the protective colloid; b. Keep the temperature stable at 80°C and start to drop the initiator continuously. At the same time, drop 60 parts of vinyl acetate as the core layer monomer; c. After the core layer monomer is added dropwise for 130 minutes, the shell layer monomer consisting of 20 parts of vinyl acetate and 20 parts of vinyl ester is immediately added dropwise, and the dropwise addition is completed within 90 minutes. During this period, the reaction temperature is maintained at 82-85°C by controlling the dropwise addition speed. After the dropwise addition, the temperature is maintained and the initiator is continued to be added dropwise for 15-20 minutes until the initiator is exhausted; d. After 90 minutes of heat preservation, cool to 60 ° C, add 10 parts of hexadecyltriethoxysilane, and stir thoroughly for 30 minutes; e. Cool down to 40°C and discharge the material. After filtering, a low-cost tertiary vinegar core-shell emulsion B with a solid content of 55% is obtained.

[0027] After the synthesis of the tertiary ester core-shell emulsion B, the redispersible latex powder B is prepared by spray drying. The latex powder includes the following components by weight: 145 parts of tertiary ester core-shell emulsion B, 5 parts of polyvinyl alcohol and 20 parts of anti-caking agent. The anti-caking agent used is 10 parts of calcium carbonate and 10 parts of kaolin with a fineness of 1250 mesh, which are added by air during rotary spray drying. The obtained rubber powder is sieved through a 60-mesh sieve for standby use. The rotary spray drying conditions are: the inlet temperature is 150°C and the outlet temperature is 80°C.

[0028] Preparation of low-cost tertiary vinegar core-shell emulsion C: 12 parts of tertiary vinyl carbonate and 88 parts of vinyl acetate, 12 parts of protective colloid, 0.5 parts of initiator; 10 parts of hexadecyl triisopropoxy silane; the protective colloid is polyvinyl alcohol with a degree of alcoholysis of 86% and a degree of polymerization of 300; the initiator is potassium persulfate; and 100 parts of deionized water.

[0029] The preparation steps are: a. Mix the protective colloid with water and heat to 90°C to dissolve the protective colloid; b. Keep the temperature stable at 80°C and start to drop the initiator continuously. At the same time, drop 70 parts of vinyl acetate as the core layer monomer; c. After the core layer monomer was added dropwise for 140 minutes, the shell layer monomer consisting of 18 parts of vinyl acetate and 12 parts of vinyl ester was immediately added dropwise for 80 minutes, during which the reaction temperature was kept at 82-85°C by controlling the dropwise addition speed; after the dropwise addition, the temperature was maintained and the initiator was continued to be added dropwise for 15-20 minutes until the initiator was exhausted; d. After 90 minutes of heat preservation, cool to 60 ° C, add 10 parts of hexadecyl triisopropoxysilane, and stir thoroughly for 30 minutes; e. Cool down to 40°C and discharge the material. After filtering, a low-cost tertiary vinegar core-shell emulsion C with a solid content of 55% is obtained.

[0030] After the synthesis of the tertiary ester core-shell emulsion C, the redispersible latex powder C is prepared by spray drying. The latex powder includes the following components by weight: 145 parts of tertiary ester core-shell emulsion C, 3 parts of polyvinyl alcohol and 20 parts of anti-caking agent. The anti-caking agent used is 10 parts of calcium carbonate and 10 parts of kaolin with a fineness of 1250 mesh. It is added by air delivery during rotary spray drying, and the obtained rubber powder is sieved through a 60-mesh sieve for standby use. The rotary spray drying conditions are: the inlet temperature is 150°C and the outlet temperature is 80°C.

[0031] Preparation of low-cost tertiary vinegar core-shell emulsion D: 12 parts of tertiary vinyl carbonate and 88 parts of vinyl acetate, 12 parts of protective colloid, 0.5 parts of initiator; 10 parts of octyl triisopropoxy silane; the protective colloid is polyvinyl alcohol with a degree of alcoholysis of 86% and a degree of polymerization of 300; the initiator is potassium persulfate; and 100 parts of deionized water.

[0032] The preparation steps are: a. Mix the protective colloid with water and heat to 90°C to dissolve the protective colloid; b. Keep the temperature stable at 80°C and start to drop the initiator continuously. At the same time, drop 60 parts of vinyl acetate as the core layer monomer; c. After the core layer monomer was added for 140 minutes, the shell layer monomer consisting of 28 parts of vinyl acetate and 12 parts of vinyl ester was immediately added, and the dropwise addition was completed in 80 minutes. During this period, the reaction temperature was kept at 82-85 ° C by controlling the dropwise addition speed. After the dropwise addition, the temperature was maintained and the initiator was continued to be added for 15-20 minutes until the initiator was exhausted; d. After 90 minutes of heat preservation, cool to 60 ° C, add 10 parts of octyl triisopropoxy silane, and stir thoroughly for 30 minutes; e. Cool down to 40°C and discharge the material. After filtering, a low-cost tertiary vinegar core-shell emulsion D with a solid content of 55% is obtained.

[0033] After the synthesis of the tertiary ester core-shell emulsion D, the redispersible latex powder D is prepared by spray drying. The latex powder includes the following components by weight: 145 parts of tertiary ester core-shell emulsion C, 2 parts of polyvinyl alcohol and 20 parts of anti-caking agent. The anti-caking agent used is 10 parts of calcium carbonate and 10 parts of kaolin with a fineness of 1250 mesh, which are added by air during rotary spray drying. The obtained rubber powder is sieved through a 60-mesh sieve for standby use. The rotary spray drying conditions are: the inlet temperature is 150°C and the outlet temperature is 80°C.

[0034] Comparative Example 1 Tertiary vinegar emulsion E, whose components and preparation method are substantially the same as those in Example 1, differs only in that, in steps b and c of the emulsion synthesis, the core-shell stepwise addition is not adopted, but all the vinyl acetate and tertiary carbonate are mixed and added dropwise in one step to obtain tertiary vinegar emulsion E, and latex powder E is prepared according to Example 1.

[0035] Comparative Example 2 Tertiary vinegar emulsion F, whose components and preparation method are substantially the same as those of Example 2, differs only in that, in steps b and c of the emulsion synthesis, the core-shell stepwise addition is not adopted, but all the vinyl acetate and tertiary carbonate are mixed and added dropwise in one step to obtain tertiary vinegar emulsion F, and latex powder F is prepared according to Example 2.

[0036] Comparative Example 3 Vinyl acetate emulsion G: In this embodiment, no versatate vinyl carbonate is used in the components, and all vinyl acetate monomers are added dropwise. The other components and preparation method are substantially the same as those in Example 3 to obtain vinyl acetate emulsion G, and latex powder G is prepared according to Example 3.

[0037] Comparative Example 4 Tertiary vinegar emulsion H, whose components and preparation method are substantially the same as those of Example 4, differs only in that, in the emulsion preparation step d, no hydrophobic silane is added. The other raw materials and synthesis steps are the same as those of Example 4 to obtain tertiary vinegar emulsion H, and prepare latex powder H according to Example 4.

[0038] Comparative test The samples prepared by Examples 1-4 and Comparative Examples 1-4 were tested for particle size using a Malvern laser particle size analyzer; the viscosity of the emulsion was tested using a rotational viscometer; a film with a thickness of 0.5 mm was made using the emulsion, and after curing for 7 days, the water absorption rate was tested by weighing method, as shown in Table 1 below.

[0039] Table 1. Comparison of synthetic emulsion tests of various embodiments and comparative examples It can be seen from the data results in Table 1 that compared with Comparative Examples 1-4, emulsion F of Examples 1-4 is a full vinyl acetate monomer and has the highest water absorption rate; the water absorption rate of the film of tertiary vinegar emulsions A, B, C, and D is greatly reduced, and the water resistance is better. In horizontal comparison, the thicker the shell, the better the water resistance effect; Examples 1 and 2 and Comparative Examples 1 and 2 show that the core-shell process increases the shielding effect of the outer layer of the latex particles on water, and the water resistance effect is better; Example 3 and Comparative Example 3 show that tertiary vinyl carbonate has the effect of reducing the water absorption of latex particles; Example 4 and Comparative Example 4 show that hydrophobic silane has a significant hydrophobic and water absorption reducing effect, and has good compatibility with the emulsion, and the emulsion particle size and viscosity are stable.

[0040] The latex powder samples of Examples 1-4 and Comparative Examples 1-4 were used in the formulation of tree trunk whitewashing agents and performance tests were performed.

[0041] Refer to JGT 157-2009 "Putty for Building External Walls" standard for water absorption test (standard ≤ 2.0g / 10min); According to the tree whitening agent formula, the bamboo tube was sprayed on the outer layer and dried for one week. The bamboo tube was exposed to rain for one month to check the condition of the whitening agent and test the water absorption. The test data is shown in Table 2 below: Table 2 According to the water absorption test results in Table 2 and the coating conditions on the outer surface of the bamboo tube: The tertiary vinegar latex powders A, B, C, and D prepared in Examples 1-4 were prepared according to the core-shell process of the present invention, and their water absorption was less than 2 g / 10 min. They performed well on the bamboo tube, and it was basically not seen that they were obviously washed off by rain. Comparative Example 2 is a tertiary acetic acid emulsion that does not use the core-shell process. The water absorption is also less than 2g / 10min, but the content of tertiary ethylene carbonate in the outer layer of the latex particles is low. In the actual rain test, there are a few traces of being washed off. The difference between Example 1 and Comparative Example 1 in the synthesis process makes it possible to achieve significant effects even when a small amount of tert-butyl vinyl carbonate is added. Comparative Example 3 From the rain test, the effect of the prepared latex powder G is the worst, because it is a vinyl acetate emulsion without adding tertiary carbonate, and it is easily eroded by rain and falls off; The latex powder H of Comparative Example 4, without the addition of hydrophobic silane, also showed obvious traces of rain washing and coating shedding, indicating that the hydrophobic silane in the latex particles has the effect of preventing water from intruding.

[0042] It will be clear to those skilled in the art that various modifications to the above embodiments may be made without departing from the overall spirit and concept of the present invention. All of these modifications fall within the scope of protection of the present invention. The protection scheme of the present invention shall be subject to the claims attached to the present invention.

Claims

1. A method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent, characterized in that: The following steps are involved: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature range of 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise adding the shell monomer to the prepared mixed solution B for polymerization, the shell monomer needs to be added dropwise within 70-90 minutes; d. After the shell monomer is added, the reaction temperature is maintained and the initiator is continued to be added for 15-20 minutes until the initiator is exhausted; e. After 90-120 minutes of heat preservation and aging, the temperature is lowered to 60°C, and hydrophobic silane is added. After sufficient stirring and mixing for 30 minutes, the temperature is lowered again and the material is discharged. After filtering, a low-cost tertiary vinegar core-shell emulsion with a solid content of 50-55% is obtained.

2. The method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for a tree trunk whitening agent according to claim 1, characterized in that: The following steps are involved: a. Mix the protective colloid with water and raise the temperature to 90°C to dissolve the protective colloid to obtain a mixed solution A. b. After adding the emulsifier to the mixed solution A and stirring and mixing, the initiator is continuously added dropwise at a temperature range of 80-85°C, and the core layer monomer is simultaneously added dropwise for polymerization to obtain a mixed solution B, wherein the core layer monomer needs to be added dropwise within 130-150 minutes; c. Immediately dropwise adding the shell monomer to the prepared mixed solution B for polymerization, the shell monomer needs to be added dropwise within 70-90 minutes; d. After the shell monomer is added, the reaction temperature is maintained and the initiator is continued to be added for 15-20 minutes until the initiator is exhausted; e. After 90-120 minutes of heat preservation and aging, the temperature is lowered to 60°C, and hydrophobic silane is added. After sufficient stirring and mixing for 30 minutes, the temperature is lowered again and the material is discharged. After filtering, a low-cost tertiary vinegar core-shell emulsion with a solid content of 50-55% is obtained.

3. A method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for a tree trunk whitening agent according to claim 1, characterized in that: The core layer monomer accounts for 60-80% of the mass of the main monomer, the core layer monomer includes vinyl acetate, and the shell layer monomer accounts for 20-40% of the mass of the main monomer, and the above ratios are all mass ratios of each substance to the main monomer; the shell layer monomer is prepared by mixed copolymerization of vinyl acetate and versatate vinyl carbonate, wherein the versatate vinyl carbonate accounts for 40-50% of the mass of the shell layer monomer.

4. The method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for a tree trunk whitening agent according to claim 1, characterized in that: The protective colloid is polyvinyl alcohol, the alcoholysis degree of which is 86-90% and the polymerization degree of which is 300-2400.

5. The method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent according to claim 1, characterized in that: The hydrophobic silane is one or a combination of octylsilane, dodecylsilane, hexadecylsilane and octadecylsilane. The method for preparing a low-cost water-resistant tertiary vinegar core-shell emulsion for tree trunk whitening agent according to claim 1, characterized in that the initiator is one of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide or tert-butyl hydroperoxide.

6. A low-cost water-resistant tertiary vinegar core-shell emulsion obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The raw materials of the core-shell emulsion include the following components by weight: 8-20 parts of versatate, 80-92 parts of vinyl acetate, 7-15 parts of protective colloid, 0.5-1 parts of initiator, 100-130 parts of water, and 2-8 parts of hydrophobic silane.

7. A low-cost water-resistant redispersible latex powder for tree trunk whitening agent, prepared by using the low-cost water-resistant tertiary vinegar core-shell emulsion according to claim 7, characterized in that: The latex powder comprises the following components in parts by weight: 145 parts of tertiary vinegar core-shell emulsion, 1-5 parts of polyvinyl alcohol and 16-20 parts of anti-caking agent.

8. The low-cost water-resistant redispersible latex powder for tree trunk whitening agent according to claim 8, characterized in that: The anti-caking agent is one or a combination of calcium carbonate, kaolin and silicon dioxide, and the fineness of the anti-caking agent is not less than 800 meshes.

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