Polyvinyl acetate emulsions, methods of making and using the same

Abstract

The application relates to the field of emulsion polymerization and discloses a polyvinyl acetate emulsion, characterized in that the polyvinyl acetate emulsion comprises latex particles and an emulsifier; the latex particles are polyvinyl acetate, and the emulsifier is polyvinyl alcohol; the polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B; the polyvinyl alcohol A has a polymerization degree of 400-1000 and an alcoholysis degree of 83-88 mol%; and the polyvinyl alcohol B has a polymerization degree of 1500-2000 and an alcoholysis degree of 92-99 mol%. The polyvinyl acetate emulsion has excellent water resistance.

Description

Technical Field

[0001] This invention relates to the field of emulsion polymerization, specifically to a polyvinyl acetate emulsion, a method for preparing a polyvinyl acetate emulsion, the polyvinyl acetate emulsion prepared by the method, and the application of the polyvinyl acetate emulsion. Background Technology

[0002] Emulsion polymerization, as a highly efficient and widely used polymerization method, relies on emulsifiers to uniformly disperse monomers in an aqueous phase. Initiators then facilitate the polymerization reaction in this aqueous phase, ultimately generating polymers and forming a stable emulsion system. This technology not only simplifies the polymerization process but also significantly improves the uniformity and stability of the polymer products, thus holding a crucial position in the field of polymer material preparation.

[0003] Polyvinyl acetate emulsions, as a typical product of emulsion polymerization technology, have broad application prospects. However, in existing technologies, although polyvinyl acetate emulsions can be prepared by adding surfactants (such as anionic and nonionic surfactants) as emulsifiers to carry out emulsion polymerization reactions, their stability and water resistance still face certain challenges. Specifically, existing emulsifiers cannot improve the water resistance of polyvinyl acetate emulsions.

[0004] Therefore, it is of great significance to research and develop a water-resistant polyvinyl acetate emulsion with excellent stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of poor water resistance in existing polyvinyl acetate emulsions, and to provide a polyvinyl acetate emulsion, its preparation method, and its application. The polyvinyl acetate emulsion includes polyvinyl alcohol A and polyvinyl alcohol B with specific degrees of polymerization and alcoholysis, resulting in excellent water resistance.

[0006] To achieve the above objectives, the first aspect of the present invention provides a polyvinyl acetate emulsion, wherein the polyvinyl acetate emulsion comprises latex particles and an emulsifier;

[0007] The latex particles are polyvinyl acetate, and the emulsifier is polyvinyl alcohol.

[0008] The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of hydrolysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of hydrolysis is 92-99 mol%.

[0009] A second aspect of the present invention provides a method for preparing a polyvinyl acetate emulsion, the method comprising the following steps:

[0010] (1) In the presence of a solvent, polyvinyl alcohol, a reducing agent and vinyl acetate are mixed to obtain a first liquid phase;

[0011] (2) Under the conditions of emulsion polymerization, an oxidant and a reducing agent are added to the first liquid phase to obtain a polyvinyl acetate emulsion;

[0012] The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of hydrolysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of hydrolysis is 92-99 mol%.

[0013] A third aspect of the present invention provides a polyvinyl acetate emulsion prepared by the method described in the second aspect.

[0014] The fourth aspect of this invention provides an application of the polyvinyl acetate emulsion described in the first or third aspect in the field of construction or packaging.

[0015] Through the above technical solutions, the polyvinyl acetate emulsion and its preparation method of the present invention achieve the following beneficial effects.

[0016] (1) The polyvinyl acetate emulsion provided by the present invention contains polyvinyl alcohol A and polyvinyl alcohol B with specific degrees of polymerization and degree of alcoholysis. The two work together as emulsifiers, and their interaction makes the polyvinyl acetate emulsion have excellent water resistance.

[0017] (2) Preferably, the polyvinyl acetate emulsion provided by the present invention contains a specific proportion of polyvinyl alcohol A and polyvinyl alcohol B, which are combined in a certain proportion to more effectively improve the water resistance of the polyvinyl acetate emulsion.

[0018] (3) Preferably, the average particle size, pitch and dispersion index of the latex particles in the polyvinyl acetate emulsion of the present invention meet specific requirements, thereby further improving the water resistance of the polyvinyl acetate emulsion.

[0019] (4) In the preparation method of polyvinyl acetate emulsion provided by the present invention, polyvinyl alcohol A and polyvinyl alcohol B are used together as emulsifiers, so as to better control the polymerization process of vinyl acetate and make the prepared polyvinyl acetate emulsion have excellent water resistance.

[0020] (5) Preferably, in the preparation method of polyvinyl acetate emulsion, the present invention further controls the mass ratio of reducing agent and oxidizing agent, thereby more effectively controlling the polymerization reaction process of vinyl acetate, so that the prepared emulsion has more suitable average particle size, pitch and dispersion index, as well as better water resistance.

[0021] (6) Preferably, in the preparation method of polyvinyl acetate emulsion, the present invention further limits the mass ratio of reducing agent and oxidant, thereby more effectively controlling the polymerization reaction process of vinyl acetate, so that the prepared emulsion has more suitable volume average particle size, pitch and dispersion index, as well as better water resistance.

[0022] (7) Preferably, the present invention further limits the addition time of the reducing agent and the oxidizing agent, thereby more effectively controlling the reaction rate of the emulsion polymerization reaction, so that the prepared emulsion has a more suitable volume average particle size, pitch and dispersion index, as well as better water resistance. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of the present invention provides a polyvinyl acetate emulsion, wherein the polyvinyl acetate emulsion comprises latex particles and an emulsifier;

[0025] The latex particles are polyvinyl acetate, and the emulsifier is polyvinyl alcohol.

[0026] The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of hydrolysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of hydrolysis is 92-99 mol%.

[0027] In this invention, the inventors discovered that using polyvinyl alcohol A and polyvinyl alcohol B, which have specific degrees of polymerization and hydrolysis, together as emulsifiers in polyvinyl acetate emulsions can give polyvinyl acetate emulsions excellent water resistance.

[0028] In this invention, the test methods for the degree of hydrolysis and degree of polymerization are as follows: the degree of hydrolysis is tested according to GB / T 12010.3-2010 Plastic Polyvinyl Alcohol Materials (PVAL) Part 3: Specifications, and the degree of polymerization is tested according to GB / T 12010.3-2010 Plastic Polyvinyl Alcohol Materials (PVAL) Part 5: Determination of Average Degree of Polymerization.

[0029] According to a particularly preferred embodiment of the present invention, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 0.5-2.5:1. Using polyvinyl alcohol A and polyvinyl alcohol B in the above-mentioned mass ratio as emulsifiers can better improve the water resistance of the polyvinyl acetate emulsion. Further, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 1-2:1.

[0030] According to a particularly preferred embodiment of the present invention, the degree of polymerization of polyvinyl alcohol A is 400-500, and the degree of hydrolysis is 86-88 mol%; the degree of polymerization of polyvinyl alcohol B is 1500-1700, and the degree of hydrolysis is 96-98 mol%. Adopting the above-mentioned ranges of degree of polymerization and degree of hydrolysis allows for better synergistic effects between polyvinyl alcohol A and polyvinyl alcohol B, thereby resulting in superior water resistance of the polyvinyl acetate emulsion.

[0031] In this invention, the polymer emulsion further includes a solvent.

[0032] In this invention, a wide range of solvents can be selected, and those skilled in the art can choose according to actual needs. Preferably, the solvent is water.

[0033] According to a particularly preferred embodiment of the present invention, the solid content of the polymer emulsion is 48-56 wt%.

[0034] In this invention, the solid content of the polymer emulsion refers to the content of non-volatile substances in 100 parts by weight of polyvinyl acetate emulsion, wherein the non-volatile substances include latex particles and emulsifiers.

[0035] In this invention, the method for measuring the content of nonvolatile matter is as follows: testing is performed according to "GB T 27573-2011 Vinyl acetate-ethylene copolymer emulsion".

[0036] According to a particularly preferred embodiment of the present invention, the viscosity-average molecular weight of the polyvinyl acetate is 300,000 to 600,000. Adopting a viscosity-average molecular weight within this range can better improve the water resistance of the polyvinyl acetate emulsion. Further, the viscosity-average molecular weight of the polyvinyl acetate is 400,000 to 500,000.

[0037] In this invention, the method for testing the viscosity-average molecular weight is as follows: Weigh 25g of the sample to be tested into a 100mL beaker, add 50g of potassium sulfate solution with a concentration of 10wt%, and stir evenly; after the latex particles break down, let stand for 15min, filter, wash the filter cake with 100mL of deionized water, repeat the washing 3 times, then transfer the filter cake into a 500mL Erlenmeyer flask, add 300mL of water, and extract in a 90℃ water bath for 24h; filter the above liquid, weigh 1g of the filter cake and add 100g of acetone, reflux in a Soxhlet extraction tube for 72h; after filtering the extract, test the viscosity-average molecular weight at 25℃ using a multi-point method with an Ubbelohde viscometer.

[0038] According to a particularly preferred embodiment of the present invention, the density of the polyvinyl acetate emulsion is 1.04-1.07 g / cm³. 3 .

[0039] In this invention, the density is tested according to GB-T 6750-2007 Determination of density of paints and varnishes - Specific gravity bottle method.

[0040] According to a particularly preferred embodiment of the present invention, the apparent viscosity of the polyvinyl acetate emulsion at 25°C is 3500-6000 mPa·s.

[0041] In this invention, the apparent viscosity is tested according to GB / T 27573-2011 Vinyl acetate-ethylene copolymer emulsion.

[0042] In this invention, when the density and / or apparent viscosity of the polyvinyl acetate emulsion meet the above-mentioned range, the water resistance of the polyvinyl acetate emulsion can be significantly improved.

[0043] According to a particularly preferred embodiment of the present invention, the density of the polyvinyl acetate emulsion is 1.05-1.06 g / cm³. 3 .

[0044] According to a particularly preferred embodiment of the present invention, the apparent viscosity of the polyvinyl acetate emulsion at 25°C is 4000-5500 mPa·s.

[0045] According to a particularly preferred embodiment of the present invention, the average particle size of the latex particles is 0.5-1.5 μm, preferably 0.8-1 μm.

[0046] According to a particularly preferred embodiment of the present invention, the diameter of the latex particles is 0.5-1.5, more preferably 0.8-0.9.

[0047] In this invention, the radial distance is used to characterize the distribution width of latex particles, and its calculation formula is as follows:

[0048] (D90-D10) / D50

[0049] In the formula, D10 is the particle size of the latex particles when the cumulative particle size distribution percentage reaches 10%.

[0050] D50 is the particle size of latex particles when the cumulative particle size distribution percentage reaches 50%.

[0051] D90 is the particle size of latex particles when the cumulative particle size distribution percentage reaches 90%.

[0052] According to a particularly preferred embodiment of the present invention, the dispersion index of the latex particles is not greater than 0.5, more preferably not greater than 0.3.

[0053] In this invention, the average particle size, particle size distribution, and dispersion index of the latex particles were measured using a Malvern 2000 particle size analyzer. The measured volume-average particle size is the average particle size described in this invention, and the uniformity is the dispersion index described in this invention.

[0054] A second aspect of the present invention provides a method for preparing a polyvinyl acetate emulsion, the method comprising the following steps:

[0055] (1) In the presence of a solvent, polyvinyl alcohol, a reducing agent and vinyl acetate are mixed to obtain a first liquid phase;

[0056] (2) Under the conditions of emulsion polymerization, an oxidant and a reducing agent are added to the first liquid phase to obtain a polyvinyl acetate emulsion;

[0057] The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of alcoholysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of alcoholysis is 92-99 mol%.

[0058] In this invention, by adding the reactants according to the above steps, the reaction process can be effectively controlled, resulting in a uniform polymerization reaction. In particular, when the polyvinyl alcohol includes polyvinyl alcohol A and polyvinyl alcohol B, which have specific degrees of polymerization and alcoholysis, the prepared polyvinyl acetate emulsion can have excellent water resistance while ensuring a uniform polymerization reaction.

[0059] In this invention, a wide range of solvents can be selected, and those skilled in the art can choose according to actual needs. Preferably, the solvent is water.

[0060] According to a particularly preferred embodiment of the present invention, the amount of polyvinyl alcohol is 1.8-2.6 parts by mass, the amount of vinyl acetate is 50-55 parts by mass, the amount of oxidant is 0.001-0.1 parts by mass, the amount of reducing agent is 0.01-0.1 parts by mass, and the amount of co-reducing agent is 0.0001-0.001 parts by mass. In this invention, controlling the amount of each reactant to meet the above ranges allows for better control of the emulsion polymerization process, resulting in a polyvinyl acetate emulsion with superior water resistance.

[0061] Further, the amount of polyvinyl alcohol used is 2-2.5 parts by mass, the amount of vinyl acetate used is 50-55 parts by mass, the amount of oxidant used is 0.005-0.03 parts by mass, the amount of reducing agent used is 0.02-0.06 parts by mass, and the amount of co-reducing agent used is 0.0004-0.0006 parts by mass.

[0062] In this invention, the range of solvent dosage is relatively wide, as long as it can evenly disperse the reactants. Those skilled in the art can select the appropriate amount based on actual needs. Preferably, relative to the amount of reactants within the above range, the amount of solvent is such that the total mass of the prepared polyvinyl acetate emulsion is 100 parts by mass.

[0063] According to a particularly preferred embodiment of the present invention, the polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 0.5-2.5:1.

[0064] In this invention, controlling the mass ratio of polyvinyl alcohol A and polyvinyl alcohol B to meet the above-mentioned range enables a better synergistic effect between polyvinyl alcohol A and polyvinyl alcohol B, thereby improving the water resistance of the prepared polyvinyl acetate.

[0065] Furthermore, the polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 1-2:1.

[0066] According to a particularly preferred embodiment of the present invention, the degree of polymerization of polyvinyl alcohol A is 400-500 and the degree of hydrolysis is 86-88 mol%; the degree of polymerization of polyvinyl alcohol B is 1500-1700 and the degree of hydrolysis is 96-98 mol%.

[0067] In this invention, controlling the degree of polymerization and degree of alcoholysis of polyvinyl alcohol A and polyvinyl alcohol B to meet the above-mentioned range can enable polyvinyl alcohol A and polyvinyl alcohol B to have a better synergistic effect, thereby improving the water resistance of the prepared polyvinyl acetate.

[0068] In this invention, the reducing agent is ferrous sulfate. Using the above-mentioned type of reducing agent allows for a more superior water resistance in the prepared polyvinyl acetate emulsion.

[0069] In this invention, the oxidant can be a conventional peroxide in the art; preferably, when the peroxide is selected from at least one of hydrogen peroxide, tert-butylhydrogen peroxide, and benzoyl peroxide, the prepared polyvinyl acetate emulsion can have better water resistance.

[0070] In this invention, the reducing agent can be a conventional inorganic acid salt and / or organic acid in the art; preferably, the reducing agent is selected from at least one of sodium styrax, sodium persulfate, isoascorbic acid, and tartaric acid.

[0071] In this invention, there are no particular limitations on the mixing method of polyvinyl alcohol, reducing agent, and vinyl acetate, as long as the mixing of the three can be achieved. Preferably, stirring is performed during the mixing process.

[0072] In this invention, there is no particular limitation on the mixing order of polyvinyl alcohol, reducing agent, and vinyl acetate, as long as the mixing of the three can be achieved. Preferably, polyvinyl alcohol is mixed with a solvent to obtain a mixture, and then the reducing agent and vinyl acetate are added to the mixture.

[0073] In this invention, there is no particular limitation on the mixing temperature of polyvinyl alcohol and solvent, as long as complete dissolution of polyvinyl alcohol can be achieved. Those skilled in the art can select the appropriate temperature according to actual needs. Preferably, the mixing temperature of polyvinyl alcohol and solvent is 80-90°C.

[0074] In this invention, there is no particular limitation on the mixing time of polyvinyl alcohol and solvent, as long as complete dissolution of polyvinyl alcohol is achieved. Those skilled in the art can select the appropriate time according to actual needs. Preferably, the mixing time of polyvinyl alcohol and solvent is 40-90 minutes.

[0075] In this invention, there is no particular limitation on the mixing temperature of the reducing agent and vinyl acetate with the mixed solution, as long as complete dissolution of the reducing agent and vinyl acetate can be achieved. Those skilled in the art can select the appropriate temperature according to actual needs. Preferably, the mixing temperature of the reducing agent and vinyl acetate with the mixed solution is 40-50°C.

[0076] According to a particularly preferred embodiment of the present invention, in step (2), the emulsion polymerization reaction conditions include: the emulsion polymerization temperature is 80-90°C.

[0077] According to a particularly preferred embodiment of the present invention, the mass ratio of reducing agent to oxidizing agent is 2-4:1. Adopting a mass ratio within this range allows for better control of the emulsion polymerization process, thereby further improving the average particle size, particle size distribution, dispersion index, and water resistance of the prepared polyvinyl acetate emulsion. Further, the mass ratio of reducing agent to oxidizing agent is 2.5-3.5:1.

[0078] According to a particularly preferred embodiment of the present invention, the mass ratio of the co-reducing agent to the oxidizing agent is 0.02-0.08:1. Adopting a mass ratio within this range allows for better control of the emulsion polymerization process, thereby further improving the average particle size, particle size distribution, dispersion index, and water resistance of the prepared polyvinyl acetate emulsion. Further, the mass ratio of the co-reducing agent to the oxidizing agent is 0.025-0.067:1.

[0079] According to a particularly preferred embodiment of the present invention, step (2) further includes dispersing the oxidant and the reducing agent separately in a solvent. By taking the above steps, the polymerization reaction rate can be better controlled, resulting in a polyvinyl acetate emulsion with more suitable average particle size, particle size distribution, and dispersion index, as well as superior water resistance.

[0080] In this invention, there is no particular limitation on the amount of solvent used to disperse the oxidant, as long as the oxidant is completely dispersed in the solvent.

[0081] In this invention, there is no particular limitation on the amount of solvent used to disperse the reducing agent, as long as the reducing agent is completely dispersed in the solvent.

[0082] According to a particularly preferred embodiment of the present invention, in step (2), the dispersion containing the oxidant and the dispersion containing the reducing agent are each added to the first liquid phase independently and at a uniform rate.

[0083] In step (2) of this invention, there is a wide range of options for the method of adding the oxidant and the reducing agent to the first liquid phase, and those skilled in the art can choose according to actual needs. Preferably, the method of addition is dropwise addition.

[0084] According to a particularly preferred embodiment of the present invention, in step (2), the oxidant and the co-reducing agent are each added to the first liquid phase independently for 180-420 min. Using the above-mentioned time range allows for better control of the polymerization reaction rate, resulting in a polyvinyl acetate emulsion with suitable average particle size, particle size distribution, and dispersion index. Further, the oxidant and the co-reducing agent are each added to the first liquid phase independently for 200-300 min.

[0085] In this invention, the oxidant and the reducing agent can be added to the first liquid phase at the same or different times, but preferably at the same time.

[0086] In this invention, the reaction time of the emulsion polymerization reaction is controlled by the time when the oxidant and / or reducing agent is added to the first liquid phase.

[0087] According to a particularly preferred embodiment of the present invention, step (2) further includes adding the oxidant and the reducing agent to the first liquid phase and then keeping it at a constant temperature.

[0088] According to a particularly preferred embodiment of the present invention, the temperature of the heat preservation is 85-95°C.

[0089] In this invention, there is no particular limitation on the heat preservation time; those skilled in the art can select it according to actual needs. Preferably, the heat preservation time is 10-80 minutes, more preferably 20-50 minutes.

[0090] The method for preparing polyvinyl acetate emulsion of the present invention is described below with reference to preferred embodiments:

[0091] (a) Polyvinyl alcohol is mixed with a solvent at 80-90°C to obtain a mixture;

[0092] (b) At 40-50°C, under stirring conditions, the reducing agent and vinyl acetate are mixed evenly with the mixture to obtain the first liquid phase;

[0093] (c) Disperse the oxidant and the reducing agent in a solvent to obtain an oxidant dispersion system and a reducing agent dispersion system, respectively.

[0094] (d) At 80-90℃, the oxidant dispersion system and the reducing agent dispersion system are added to the first liquid phase at a uniform rate for 180-420 min.

[0095] (e) After the addition is complete, keep warm at 85-95℃ for 10-80 minutes to obtain polyvinyl acetate emulsion.

[0096] A third aspect of the present invention provides a polyvinyl acetate emulsion prepared by the method described in the second aspect.

[0097] The fourth aspect of the present invention provides the application of the polyvinyl acetate emulsion described in the first or third aspect in the field of construction or packaging, preferably in at least one of coatings, adhesives or paper coatings.

[0098] The present invention will be described in detail below through embodiments. Unless otherwise specified, all raw materials used in the following embodiments are commercially available.

[0099] In the following examples and comparative examples, the volume-average particle size, pitch, and dispersion index were measured using a Malvern 2000 particle size analyzer.

[0100] Water resistance is expressed as weight loss rate. The test method is as follows: Polyvinyl acetate emulsion is uniformly coated onto a glass plate using a 500μm coating applicator, then dried at 40℃ for 2 hours and weighed to obtain a film, recorded as W1. The film is then immersed in deionized water at 25℃ for 48 hours, the surface moisture is wiped off, and it is dried at 40℃ for 2 hours and weighed again, recorded as W2. Weight loss rate ΔW=(W1-W2) / W1×100%.

[0101] Example 1

[0102] (i) Add 38 parts by weight of water and polyvinyl alcohol to a reaction vessel, heat to 80°C for 60 min to dissolve, and obtain a mixture.

[0103] (ii) After cooling the mixture to room temperature, add ferrous sulfate and vinyl acetate, stir until homogeneous, and obtain the first liquid phase.

[0104] (iii) The oxidant is mixed with 2.5 parts by weight of water to obtain a dispersion containing the oxidant; the reducing agent is mixed with 2.5 parts by weight of water to obtain a dispersion containing the reducing agent.

[0105] (iv) Raise the temperature of the first liquid phase to 80°C, and then add the dispersion containing the oxidant and the dispersion containing the reducing agent to the first liquid phase at the same rate for 300 min.

[0106] (v) After the addition is complete, keep warm at 85°C for 30 minutes and then discharge to obtain polyvinyl acetate emulsion S1.

[0107] The reaction raw materials and reaction conditions are shown in Tables 1 and 2. The relevant parameters of polyvinyl acetate emulsion S1 and the weight loss rate of the film obtained after drying are shown in Table 3.

[0108] Examples 2-11, Comparative Examples 1-2

[0109] The preparation steps are the same as in Example 1, except that the amount of water in step (1) is adjusted so that the prepared polyvinyl acetate emulsion is 100 parts by weight. The remaining reaction raw materials and reaction conditions are shown in Tables 1 and 2, and polyvinyl acetate emulsions S2-S11 and D1-D2 are obtained.

[0110] The relevant parameters of polyvinyl acetate emulsions S2-S11 and D1-D2, as well as the weight loss rate of the film obtained after drying, are shown in Table 3.

[0111] Table 1

[0112]

[0113]

[0114] Table 2

[0115]

[0116] Table 3

[0117]

[0118]

[0119] Within the scope of this invention, a polyvinyl acetate emulsion with a volume average particle size of 0.5-1.0 μm, a particle size distribution of 0.8-0.9 μm, and a dispersion coefficient of no more than 0.5 was obtained. The dried film lost less than 5 wt% of weight after being soaked in deionized water at 25°C for 48 hours. This indicates that the emulsion has good water resistance. Compared with existing polyvinyl acetate emulsions, the emulsion of this invention has significantly improved in terms of water resistance.

[0120] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polyvinyl acetate emulsion, characterized in that, The polyvinyl acetate emulsion includes latex particles and an emulsifier; The latex particles are polyvinyl acetate, and the emulsifier is polyvinyl alcohol. The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of hydrolysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of hydrolysis is 92-99 mol%.

2. The polyvinyl acetate emulsion according to claim 1, wherein, The mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 0.5-2.5:1, preferably 1-2:1; Preferably, the degree of polymerization of polyvinyl alcohol A is 400-500 and the degree of hydrolysis is 86-88 mol%; the degree of polymerization of polyvinyl alcohol B is 1500-1700 and the degree of hydrolysis is 96-98 mol%. Preferably, the polymer emulsion has a solid content of 48-56 wt%.

3. The polyvinyl acetate emulsion according to claim 1 or 2, wherein, The viscosity-average molecular weight of the polyvinyl acetate is 300,000-600,000, preferably 400,000-500,000; Preferably, the density of the polyvinyl acetate emulsion is 1.04-1.07 g / cm³. 3 More preferably, it is 1.05-1.06 g / cm³. 3 ; Preferably, the apparent viscosity of the polyvinyl acetate emulsion at 25°C is 3500-6000 mPa·s, more preferably 4000-5500 mPa·s.

4. The polyvinyl acetate emulsion according to any one of claims 1-3, wherein, The average particle size of the latex particles is 0.5-1.5 μm, preferably 0.8-1 μm; Preferably, the diameter of the latex particles is 0.5-1.5, more preferably 0.8-0.9; Preferably, the dispersion index of the latex particles is not greater than 0.5, more preferably not greater than 0.

3.

5. A method for preparing a polyvinyl acetate emulsion, characterized in that, The method includes the following steps: (1) In the presence of a solvent, polyvinyl alcohol, a reducing agent and vinyl acetate are mixed to obtain a first liquid phase; (2) Under the conditions of emulsion polymerization, an oxidant and a reducing agent are added to the first liquid phase to obtain a polyvinyl acetate emulsion; The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the degree of polymerization of polyvinyl alcohol A is 400-1000 and the degree of hydrolysis is 83-88 mol%; and the degree of polymerization of polyvinyl alcohol B is 1500-2000 and the degree of hydrolysis is 92-99 mol%.

6. The method for preparing polyvinyl acetate emulsion according to claim 5, wherein, The amount of polyvinyl alcohol used is 1.8-2.6 parts by weight, the amount of vinyl acetate used is 50-55 parts by weight, the amount of oxidant used is 0.001-0.1 parts by weight, the amount of reducing agent used is 0.01-0.1 parts by weight, and the amount of co-reducing agent used is 0.0001-0.001 parts by weight. Preferably, the amount of polyvinyl alcohol used is 2-2.5 parts by weight, the amount of vinyl acetate used is 50-55 parts by weight, the amount of oxidant used is 0.005-0.03 parts by weight, the amount of reducing agent used is 0.02-0.06 parts by weight, and the amount of co-reducing agent used is 0.0004-0.0006 parts by weight; Preferably, the polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, wherein the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is 0.5-2.5:1, more preferably 1-2:1; Preferably, the degree of polymerization of polyvinyl alcohol A is 400-500 and the degree of hydrolysis is 86-88 mol%; the degree of polymerization of polyvinyl alcohol B is 1500-1700 and the degree of hydrolysis is 96-98 mol%.

7. The method for preparing polyvinyl acetate emulsion according to claim 5 or 6, wherein, The oxidant is a peroxide; Preferably, the peroxide is selected from at least one of hydrogen peroxide, tert-butylhydrogen peroxide, and benzoyl peroxide; Preferably, the reducing agent is ferrous sulfate; Preferably, the reducing agent is an inorganic acid salt and / or an organic acid; Preferably, the reducing agent is selected from at least one of sodium styrax, sodium persulfate, isoascorbic acid, and tartaric acid.

8. The method for preparing polyvinyl acetate emulsion according to any one of claims 5-7, wherein, In step (2), the emulsion polymerization reaction conditions include: the emulsion polymerization temperature is 80-90℃; Preferably, the mass ratio of reducing agent to oxidizing agent is 2-4:1, more preferably 2.5-3.5:1; Preferably, the mass ratio of the reducing agent to the oxidizing agent is 0.02-0.08:1, more preferably 0.025-0.067:1; Preferably, the oxidant and the reducing agent are each added to the first liquid phase independently in the form of a dispersion; Preferably, in step (2), the dispersion containing the oxidant and the dispersion containing the reducing agent are each added to the first liquid phase independently and at a uniform rate. Preferably, in step (2), the time for adding the dispersion containing the oxidant and the dispersion containing the reducing agent to the first liquid phase are each independently 180-420 min, more preferably 200-300 min.

9. A polyvinyl acetate emulsion prepared by the method of any one of claims 5-8.

10. The use of the polyvinyl acetate emulsion according to any one of claims 1-4 or 9 in the field of construction or packaging, preferably in at least one of coatings, adhesives or paper coatings.

Images