Preparation method of large-particle-size polyvinyl acetate emulsion and product

Abstract

According to the preparation method and the product of the large-particle-size polyvinyl acetate emulsion, compared with the prior art, seed polymerization reaction does not need to be repeatedly carried out, an agglomerating agent does not need to be added, the particle size distribution of the emulsion is narrow, and the average particle size of the polymer emulsion can be adjusted in a large range through the rotating speed of a homogenizer; the polymerization reaction process flow is simple, the production cost is low, and industrial production is easy to realize.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer emulsion polymerization, and particularly relates to a preparation method and product of a large-particle polyvinyl acetate emulsion. Background Art

[0002] Polyvinyl acetate (PVAc) emulsion is a polymer emulsion obtained by using water as a dispersion medium and vinyl acetate (VAc) as a monomer under the action of protective colloids, emulsifiers and initiators, commonly known as white latex. Polyvinyl acetate emulsion has the advantages of simple synthesis process, wide application, low environmental pollution and low production cost. It is one of the most produced varieties of synthetic resin emulsion. The latex particle diameter of traditional polyvinyl acetate emulsion is generally between 0.1 and 1.0 μm, which makes it easy for the emulsion to penetrate into the narrow pores of materials such as wood, paper, fiber, leather, ceramics, and building materials, thereby achieving a good bonding effect. Polyvinyl acetate emulsion has been widely used in papermaking, textile, home improvement, coatings, glue, chemical and other industries.

[0003] Traditional vinyl acetate emulsion polymerization generally uses polyvinyl alcohol as a protective agent, OP-10 as an emulsifier, and ammonium persulfate as an initiator for free radical polymerization. After chain initiation, growth, termination and other elementary reactions, a polyvinyl acetate latex with a milky white appearance and a latex particle diameter between 0.1 and 1.0 μm is finally obtained. However, in practical applications, large-particle-size emulsions (several microns to tens of microns) are often used. For example, in cosmetics, large-particle-size latex particles can play a role in scrubbing the stratum corneum, filling wrinkles and smoothing the skin. In the bonding process of glass fiber chopped strand mat, it can improve the bonding strength and reduce the penetration loss of the emulsion. In some coating products, it can also increase the texture of the coating and improve the gloss of the coating. Synthesizing large-particle-size polyvinyl acetate emulsions has important practical application significance.

[0004] At present, conventional methods for synthesizing large-particle polyvinyl acetate emulsions mainly include seed emulsion polymerization (seed expansion method) and one-step emulsion agglomeration method. Seed emulsion polymerization method is to add monomers to seed emulsion, use vinyl acetate monomer to swell seed latex particles and continue polymerization, and then use this emulsion as a seed to repeat swelling polymerization expansion in multiple steps until the desired particle size is reached. In this way, polyvinyl acetate emulsion with a particle size greater than 1 μm can be obtained by repeated seed emulsion polymerization in multiple steps, but this method has many reaction steps, is very time-consuming, and is complicated to operate. It is necessary to strictly control the amount of emulsifier used, the production efficiency is low and the cost is high, which is not conducive to flexible production. The one-step emulsion agglomeration method is to add an agglomerating agent to the original primary emulsion, aggregate the colloid particles in the emulsion into large particles through physical or chemical adsorption, and further adsorb monomers to undergo polymerization until they grow to the desired particle size. Although the one-step method has simple steps and high production efficiency, the emulsion obtained by this method has poor stability and a wide distribution of latex particle size. It is difficult to produce an emulsion with a particle size greater than 1 μm, and it is actually difficult to meet the wide range of needs in large-scale industrial production and applications.

[0005] Patent CN102115506A discloses a method for producing large-particle polymer emulsions by emulsion agglomeration, wherein the agglomerating agent is a copolymer of alkyl acrylate and carboxyl monomer. The method uses fatty acid soap and alkyl sulfonate composite emulsifiers, and finally obtains a polymer emulsion with a particle size of 500nm to 1000nm by combining the first-stage water-soluble initiator with the second-stage oil-soluble initiator. This method has many production steps, the agglomerating agent needs to be synthesized by itself, the process operation is complicated, and the particle size of the obtained emulsion is difficult to exceed 1000nm. Patent CN106632814A discloses a method for using in-situ electrical neutralization technology to neutralize the surface charge of latex particles with a charged second functional monomer, induce the particles to aggregate and produce a large-particle polymer emulsion, but the polymer emulsion produced by this method has a small particle size, only between 270nm and 580nm. Patent CN114031709A discloses a method for preparing a large-particle polyvinyl acetate emulsion by modifying acrylic resin. The method adopts a core-shell copolymerization process and utilizes ordinary mechanical stirring. In the early stage of the reaction, pure vinyl acetate is used for base emulsification. In the later stage, a monomer containing an acrylic ester crosslinking agent is added dropwise. Through strict temperature control and initiator addition procedures, and the addition of humectants, plasticizers, preservatives, defoamers, buffers and other additives, a polyvinyl acetate emulsion with an average particle size of 3 to 4 μm is finally obtained. However, ordinary mechanical stirring cannot guarantee the uniformity of the emulsion particle size distribution, and this method has many production steps and complex process operation requirements, which is not conducive to large-scale industrial production. Summary of the invention

[0006] In view of this, the present invention aims at the deficiencies of the current technology and provides a method for synthesizing a large-particle polyvinyl acetate emulsion with simple reaction steps.

[0007] In a first aspect, the present invention provides a method for preparing a large-particle polyvinyl acetate emulsion, the steps of which include:

[0008] A1. 5000 parts by mass of deionized water, 50 to 250 parts by mass of polyvinyl alcohol, 12 parts by mass of sodium dodecylbenzene sulfonate, and 3 parts by mass of polyethylene glycol monolaurate were uniformly mixed to prepare an aqueous phase solution.

[0009] A2. 2500 to 5000 parts by mass of vinyl acetate and 50 to 100 parts by mass of an initiator are uniformly mixed to prepare an oil phase solution;

[0010] A3. The aqueous phase solution and the oil phase solution were mixed, and dispersed in an ice water bath using a homogenizer at a speed of 5000 to 23000 rpm for 15 min to obtain a vinyl acetate emulsion.

[0011] A4. The vinyl acetate emulsion obtained in step A3 is transferred to a reaction tube, and nitrogen is continuously bubbled into the vinyl acetate emulsion for deoxygenation for 30 minutes. The reaction solution in the tube is then heated to 30-50° C. and stirred under ordinary mechanical stirring for 5-8 hours, preferably at a stirring speed of 200 rpm.

[0012] A5. Cooling the reaction solution to room temperature to obtain the large-particle polyvinyl acetate emulsion.

[0013] Preferably, the initiator in A2 is one of bis(4-tert-butylcyclohexyl) peroxydicarbonate, azodimethoxyisoheptanenitrile, and diisobutyryl peroxide, or a mixture in any proportion.

[0014] In a second aspect, the present invention provides a product of the above-mentioned preparation method, wherein the latex particle size of the large-particle polyvinyl acetate emulsion as the product is between 1 and 10 μm.

[0015] Compared with the prior art, the synthesis method of the large-particle polyvinyl acetate emulsion of the present invention does not require repeated seed polymerization reaction, nor does it require the addition of agglomerating agent. The average particle size of the polymer emulsion can be adjusted within a wide range by the speed of the homogenizer, so that the particle size distribution of the emulsion is narrow. The polymerization reaction process is simple, the production cost is low, and it is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a microscopic appearance of a large-particle polyvinyl acetate emulsion of the present invention.

[0017] Figure 2 This is a curve showing the relationship between reaction conversion rate and time during the vinyl acetate polymerization reaction in Example 1.

[0018] Figure 3 This is the appearance of the large-particle polyvinyl acetate emulsion after the polymerization reaction in Example 1 is completed. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described in detail below through specific implementation methods. The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] In the embodiment of the present invention, the homogenizer used is a T25 digital display homogenizer produced by IKA of Germany.

[0021] Example 1

[0022] The process of preparing large particle size polyvinyl acetate emulsion is as follows:

[0023] A1. 50.0 g of deionized water, 1.5 g of polyvinyl alcohol, 120.0 mg of sodium dodecylbenzene sulfonate, and 30.0 mg of polyethylene glycol monolaurate were mixed uniformly to prepare an aqueous phase solution.

[0024] A2. 37.0 g of vinyl acetate and 500.0 mg of bis(4-tert-butylcyclohexyl)peroxydicarbonate as an initiator were uniformly mixed to prepare an oil phase solution;

[0025] A3. The aqueous phase solution and the oil phase solution were mixed, and dispersed in an ice water bath using a homogenizer at a speed of 5000 to 23000 rpm for 15 min to obtain a vinyl acetate emulsion.

[0026] A4. The vinyl acetate emulsion was transferred to a reaction tube, and nitrogen was continuously bubbled into the emulsion for deoxygenation for 30 min. The emulsion was then heated to 35°C and reacted for 5 h under ordinary mechanical stirring at 200 rpm.

[0027] A5. Cooling the reaction solution to room temperature to obtain the large-particle polyvinyl acetate emulsion.

[0028] B. Characterize the product of the above preparation process, the steps are as follows:

[0029] B1. Determination of reaction product yield (Yield.%)

[0030] The reaction conversion rate (Conv.%) of vinyl acetate emulsion polymerization is calculated using the differential weight method. The calculation formula is as follows:

[0031] Conv.%=(a+b)·m2 / a·m1×100%;

[0032] Wherein: m2 is the mass of polyvinyl acetate obtained after vacuum drying of the emulsion sample during the polymerization process, m1 is the mass of the sampled emulsion, a is the mass of vinyl acetate monomer added to the formula, and b is the mass of the water phase added to the formula.

[0033] B2. Observation of the morphology of polyvinyl acetate latex particles

[0034] The prepared polyvinyl acetate emulsion was diluted 5 times with distilled water and then photographed and observed using an XP-213 trinocular microscope produced by Jiangnan Yongxin Optical Co., Ltd.

[0035] B3. Determination of particle size of polyvinyl acetate emulsion latex

[0036] The prepared polyvinyl acetate emulsion was diluted 100 times with distilled water, and the particle size was measured using a Malvern Mastersize 3000 particle size analyzer.

[0037] The appearance of the large-particle polyvinyl acetate emulsion obtained after the polymerization reaction is completed is as shown in the attached figure. Figure 1 shown; from Figure 1 It can be seen that the large-particle polyvinyl acetate emulsion has a milky white appearance. Figure 2 shown; from Figure 2 It can be seen that the polymerization reaction can reach a conversion rate of more than 80% within 2 hours, and the final conversion rate after 5 hours of reaction is 92.4%. The morphology of the latex particles of large-size polyvinyl acetate emulsion under a microscope is shown in the attached figure. Figure 1 As shown (scale bar length: 50 μm); Figure 1 It can be seen that the latex particles of the large-particle polyvinyl acetate emulsion are regular spherical particles with a particle size ranging from about 1 μm to 5 μm. The average particle size of the polyvinyl acetate emulsion latex particles measured by Malvern's particle size analyzer is 3.83 μm.

[0038] Example 2

[0039] The same method as in Example 1 was used to prepare and test the large-particle polyvinyl acetate emulsion, wherein the raw material composition formula of the polymerization reaction was as follows: vinyl acetate: 37.0 g; deionized water: 50.0 g; polyvinyl alcohol: 0.5 g; sodium dodecylbenzene sulfonate: 120.0 mg; polyethylene glycol monolaurate: 30.0 mg; initiator bis(4-tert-butylcyclohexyl) peroxydicarbonate: 800.0 mg

[0040] IKA homogenizer speed 12000rpm; polymerization temperature: 50℃; reaction time: 5h. After the polymerization reaction is completed, the obtained polyvinyl acetate emulsion has a milky white appearance. The final conversion rate of the polymerization reaction is 86.6%. The latex particle morphology of the polyvinyl acetate emulsion is regular spherical particles. The average particle size of the latex particles measured by the particle size analyzer is 4.34μm.

[0041] Example 3

[0042] The same method as in Example 1 was used to prepare and test the large-particle polyvinyl acetate emulsion, wherein the raw material composition formula of the polymerization reaction was as follows: vinyl acetate: 50.0 g; deionized water: 50.0 g; polyvinyl alcohol: 2.0 g; sodium dodecylbenzene sulfonate: 120.0 mg; polyethylene glycol monolaurate: 30.0 mg; initiator azodimethoxyisoheptanenitrile: 800.0 mg

[0043] IKA homogenizer speed 18000rpm; polymerization temperature: 35℃; reaction time: 6h. After the polymerization reaction is completed, the obtained polyvinyl acetate emulsion has a milky white appearance. The final conversion rate of the polymerization reaction is 83.9%. The latex particle morphology of the polyvinyl acetate emulsion is regular spherical particles. The average particle size of the latex particles measured by the particle size analyzer is 2.77μm.

[0044] Example 4

[0045] The same method as in Example 1 was used to prepare and test the large-particle polyvinyl acetate emulsion, wherein the raw material composition formula for the polymerization reaction was as follows: vinyl acetate: 40.0 g; deionized water: 50.0 g; polyvinyl alcohol: 2.0 g; sodium dodecylbenzene sulfonate: 120.0 mg; polyethylene glycol monolaurate: 30.0 mg; initiator diisobutyryl peroxide: 1.0 g

[0046] IKA homogenizer speed 23000rpm; polymerization temperature: 30℃; reaction time: 8h. After the polymerization reaction is completed, the obtained polyvinyl acetate emulsion has a milky white appearance. The final conversion rate of the polymerization reaction is 88.6%. The latex particle morphology of the polyvinyl acetate emulsion is regular spherical particles. The average particle size of the latex particles measured by the particle size analyzer is 1.03μm.

[0047] Example 5

[0048] The large-particle polyvinyl acetate emulsion was prepared and tested using the same method as in Example 1, wherein the raw material composition formula for the polymerization reaction was as follows: vinyl acetate: 25.0 g; deionized water: 50.0 g; polyvinyl alcohol: 2.5 g; sodium dodecylbenzene sulfonate: 120.0 mg; polyethylene glycol monolaurate: 30.0 mg; initiator bis(4-tert-butylcyclohexyl) peroxydicarbonate: 300.0 mg, diisobutyryl peroxide: 200.0 mg, and azodimethoxyisoheptanenitrile: 300.0 mg.

[0049] IKA homogenizer speed: 8000 rpm; polymerization temperature: 40°C; reaction time: 8 h.

[0050] After the polymerization reaction is completed, the obtained polyvinyl acetate emulsion has a milky white appearance. The final conversion rate of the polymerization reaction is 82.8%. The latex particles of the polyvinyl acetate emulsion are regular spherical particles. The average particle size of the latex particles measured by the particle size analyzer is 7.79 μm.

[0051] Example 6

[0052] The large-particle polyvinyl acetate emulsion was prepared and tested using the same method as in Example 1, wherein the raw material composition formula for the polymerization reaction was as follows: vinyl acetate: 40.0 g; deionized water: 50.0 g; polyvinyl alcohol: 2.0 g; sodium dodecylbenzene sulfonate: 120.0 mg; polyethylene glycol monolaurate: 30.0 mg; initiator bis(4-tert-butylcyclohexyl) peroxydicarbonate: 800.0 mg.

[0053] IKA homogenizer speed: 5000 rpm; polymerization temperature: 35°C; reaction time: 8 h.

[0054] After the polymerization reaction is completed, the obtained polyvinyl acetate emulsion has a milky white appearance. The final conversion rate of the polymerization reaction is 85.4%. The latex particles of the polyvinyl acetate emulsion are regular spherical particles. The average particle size of the latex particles measured by the particle size analyzer is 9.82μm.

Claims

1. A method for preparing a large-particle polyvinyl acetate emulsion, comprising the steps of: A1. 5000 parts by mass of deionized water, 50 to 250 parts of polyvinyl alcohol, 12 parts of sodium dodecylbenzene sulfonate, and 3 parts of polyethylene glycol monolaurate were uniformly mixed to prepare an aqueous solution; A2. 2500 to 5000 parts by mass of vinyl acetate and 50 to 100 parts by mass of an initiator are uniformly mixed to prepare an oil phase solution; A3. The aqueous phase solution and the oil phase solution were mixed and dispersed in an ice water bath with a homogenizer at a speed of 5000 to 23000 rpm for 15 min to obtain a vinyl acetate emulsion; A4. The vinyl acetate emulsion obtained in step A3 is transferred to a reaction tube, nitrogen is continuously bubbled into the vinyl acetate emulsion for deoxygenation for 30 min, and then the reaction solution in the tube is heated to 30-50° C. and reacted for 5-8 h under mechanical stirring; A5. Cooling the reaction solution to room temperature to obtain the large-particle polyvinyl acetate emulsion.

2. The method for preparing a large-particle polyvinyl acetate emulsion according to claim 1, characterized in that : The initiator described in A2 is one of bis(4-tert-butylcyclohexyl) peroxydicarbonate, azodimethoxyisoheptanenitrile, and diisobutyryl peroxide, or a mixture in any proportion.

3. The product of the method for preparing a large-particle polyvinyl acetate emulsion according to claim 1, characterized in that: The mechanical stirring described in step A4 is to stir the reaction at a rotation speed of 200 rpm.

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