阅读说明：本技术 一种低固低粘乙酸乙烯酯-乙烯共聚乳液的制备方法 (Preparation method of low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion ) 是由 袁大兵 蒋红光 何盛教 苏猛 石显伟 韦忠国 韦慧 牙金艳 黄栋 文志康 何伟忠 于 2021-08-26 设计创作，主要内容包括：本发明公开了一种低固低粘乙酸乙烯酯-乙烯共聚乳液的制备方法：(1)将初始单体乙酸乙烯酯和表面活性剂溶液加入反应器中进行预乳化,加氧化剂过氧化氢溶液引发反应,搅拌反应,在反应过程中均匀分段加入连续单体乙酸乙烯酯,在熟化期阶段加入次硫酸锌甲醛水溶液,熟化期结束即反应结束；(2)加水、过氧化苯甲酸叔丁酯、碳酸氢钠、调节反应液酸碱度、消泡剂等调节反应液不挥发组分含量、乙酸乙烯酯等,搅拌均匀后过滤去滤渣,得到低粘低固的乙酸乙烯酯-乙烯共聚乳液GW-707A。本发明低固低粘乙酸乙烯酯-乙烯共聚乳液GW-707A具有更好流变学性能,在保持乳液的低粘度,降低固含量,使乳液的流平性更优异。(The invention discloses a preparation method of low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion, which comprises the following steps: (1) adding initial monomer vinyl acetate and a surfactant solution into a reactor for pre-emulsification, adding an oxidant hydrogen peroxide solution for initiating reaction, stirring for reaction, uniformly and sectionally adding continuous monomer vinyl acetate in the reaction process, adding a zinc sulfoxylate formaldehyde aqueous solution in the curing period, and finishing the reaction after the curing period is finished; (2) adding water, tert-butyl peroxybenzoate, sodium bicarbonate, adjusting the pH value of the reaction solution, adjusting the nonvolatile component content of the reaction solution by using a defoaming agent and the like, and vinyl acetate and the like, uniformly stirring, filtering and removing filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A. The low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A has better rheological property, maintains the low viscosity of the emulsion, reduces the solid content and ensures that the leveling property of the emulsion is more excellent.)

1. A preparation method of a low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion is characterized by comprising the following operation steps:

(1) adding initial monomer vinyl acetate and a surfactant solution into a reactor for pre-emulsification, continuously adding an oxidant hydrogen peroxide solution under the conditions of an ethylene atmosphere and a pressure of 1.5-6.0MPa to initiate a reaction, stirring for reaction for 100-120min, uniformly and sectionally adding continuous monomer vinyl acetate in the reaction process, controlling the temperature to be 78-82 ℃ in the reaction process, after the continuous monomer vinyl acetate is completely added, enabling the reaction temperature to be lower than 77 ℃ and the adding rate of the oxidant hydrogen peroxide solution to be increased to 100%, enabling the production to enter a curing period, adding a zinc sulfoxylate formaldehyde aqueous solution in the curing period, and ending the reaction after the curing period;

(2) and (2) placing the reaction liquid obtained after the curing period in the step (1) in a flash evaporator to remove residual ethylene, adding water to adjust the content of non-volatile components in the reaction liquid, adding tert-butyl peroxybenzoate to reduce the content of vinyl acetate in the reaction liquid, adding sodium bicarbonate to adjust the pH value of the reaction liquid, adding an antifoaming agent to remove residual fine bubbles in the reaction liquid, uniformly stirring, filtering and removing filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A.

2. The method of claim 1, wherein: the surfactant solution in the step (1) is a mixed solution obtained by uniformly mixing water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and a reducing agent zinc formaldehyde sulfoxylate and heating to 75-85 ℃; the mass ratio of water in the surfactant solution, the compound polyvinyl alcohol, the octyl phenol polyoxyethylene ether and the reducer zinc formaldehyde sulfoxylate is 275-283.3: 13.5-15.0: 1.67-1.94: 1.

3. the method of claim 2, wherein: the compound polyvinyl alcohol is prepared by mixing polyvinyl alcohol 05-88 and polyvinyl alcohol 17-88 according to the mass ratio of 11-12: 1-1.5.

4. The method of claim 1, wherein: in the step (1), the mass percentage of the oxidant hydrogen peroxide is 1.2-2.0%, and the total mass of the oxidant hydrogen peroxide is 8.0-9.5% of the total mass of the monomer vinyl acetate added in the step (1).

5. The method of claim 1, wherein: the mass ratio of the initial vinyl acetate to the total mass of the continuous monomer vinyl acetate in the step (1) is 2.0-2.4: 1.

6. The method of claim 1, wherein: adding continuous monomer vinyl acetate in three batches in the reaction process in the step (1), wherein the adding amount of each batch is equal; the specific adding time is that the reaction is added when the reaction is carried out for 10min, 30min and 50min, the adding time is 15min at each time interval, and then the adding is stopped for 5min and is continued.

7. The method of claim 1, wherein: the mass percentage of the zinc sulfoxylate formaldehyde aqueous solution added in the curing period in the step (1) is 4-5%, and the mass ratio of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution to the total mass of the monomer vinyl acetate is 0.75%.

8. The method of claim 1, wherein: the addition amount of the tert-butyl peroxybenzoate is 0.15-0.3 kg per ton of the reaction solution in the step (2); the addition amount of the sodium bicarbonate is 1.5-2.2 kg per ton of the reaction liquid in the step (2); the addition amount of the defoaming agent is 1.5-2.0 kg per ton of the reaction liquid in the step (2); the addition amount of the deionized water is 30-50 kg per ton of the reaction liquid in the step (2).

Technical Field

The invention relates to a preparation method of vinyl acetate-ethylene copolymer emulsion, in particular to a preparation method of low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion.

Background

Vinyl acetate-ethylene copolymer emulsion (namely VAE) introduces ethylene molecular chains into polyvinyl acetate molecules, so that acetyl groups generate discontinuity, the rotational freedom degree of a high molecular chain is increased, the space obstruction is small, the main chain of a high molecular chain becomes soft, and the rheological property is improved. Meanwhile, ethylene is used as an internal plasticizer of the copolymer, so that the VAE polymer has internal plasticization, and the plasticizer cannot migrate, thereby avoiding the aging of the polymer performance. The VAE emulsion not only has good stability to ultraviolet rays, but also has good acid and alkali resistance, and is widely applied to the fields of adhesives, waterproof coatings, interior decoration, outdoor heat preservation, carpets, non-woven fabrics, paper industry processing, cement modification and the like.

At present, vinyl acetate-ethylene copolymer emulsion products are in a plurality of types, and each type has unique performance advantages. The non-volatile matter of the prior vinyl acetate-ethylene copolymer emulsion of various brands is more than or equal to 54 percent, and the mechanical stability of the emulsion, no matter the emulsion is low in viscosity and high in solid content or high in viscosity and low in solid content, the film-forming hardness is high due to the high curing speed, the flexibility is insufficient, the smoothness is poor during construction, the ageing resistance is reduced, and the waterproof effect is poor. In the aspect of production control, the proportion of a reaction system formed by an initial surfactant, a vinyl acetate monomer and ethylene influences the viscosity and the solid content of the copolymerization emulsion; in order to obtain the low-solid low-viscosity copolymer emulsion, the ratio of vinyl acetate monomer to ethylene must be reduced, the initial surfactant is related to the balance of the whole system, the emulsion is exploded due to excessive use amount, and the emulsion breaking occurs in an emulsion system due to insufficient use amount, which becomes a difficulty of the production process.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention overcomes the production difficulty of reaction system balance, provides a preparation method of low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion, and prepares the vinyl acetate-ethylene copolymer emulsion GW-707A which has good rheological property, strong bonding force, good film forming flexibility, difficult after-tack and can be used in low-temperature areas. The invention makes up the defect that vinyl acetate-ethylene copolymer emulsion products have higher requirements on the flexibility of waterproof coatings, adhesive plates and textile coatings, and provides an emulsion raw material with better performance for adhesives and spray-coating.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a method for preparing a low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion comprises the following operation steps:

(1) adding initial monomer vinyl acetate and a surfactant solution into a closed reactor for pre-emulsification, continuously dropwise adding an oxidant hydrogen peroxide solution under the ethylene atmosphere and the pressure of 1.5-6.0MPa to initiate a reaction, stirring for reaction for 100-120min, uniformly and sectionally adding continuous monomer vinyl acetate in the reaction process, controlling the temperature to be 78-82 ℃ in the reaction process, after the continuous monomer vinyl acetate is completely added, enabling the reaction temperature to be lower than 77 ℃ and the adding rate of the oxidant hydrogen peroxide solution to be increased to 100%, enabling the product to enter a curing period, adding a zinc sulfoxylate formaldehyde (ZFS) aqueous solution in the curing period, improving the conversion rates of the monomer vinyl acetate (initial monomer vinyl acetate + continuous monomer vinyl acetate) and ethylene, and ending the reaction after the curing period;

(2) placing the reaction liquid obtained after the curing period in the step (1) in a flash evaporator to remove residual ethylene, adding deionized water to adjust the content of non-volatile components in the reaction liquid, adding tert-butyl peroxybenzoate to reduce the content of vinyl acetate in the reaction liquid, adding sodium bicarbonate to adjust the pH value of the reaction liquid, adding a defoaming agent to remove residual fine bubbles in the reaction liquid, uniformly stirring, filtering and removing filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A.

Preferably, the surfactant solution in the step (1) is a mixed solution obtained by uniformly mixing deionized water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and reducing agent zinc formaldehyde sulfoxylate and heating to 75-85 ℃; the mass ratio of deionized water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and reducer zinc formaldehyde sulfoxylate in the surfactant solution is 275-283.3: 13.5-15.0: 1.67-1.94: 1.

preferably, the compound polyvinyl alcohol is prepared by mixing polyvinyl alcohol 05-88 and polyvinyl alcohol 17-88 according to the mass ratio of 11-12: 1-1.5.

Preferably, the mass percentage of the oxidant hydrogen peroxide in the step (1) is 1.2-2.0%, and the total mass of the oxidant hydrogen peroxide is 8.0-9.5% of the total mass of the monomer vinyl acetate added in the step (1) (initial monomer vinyl acetate and continuous monomer vinyl acetate).

Preferably, the ratio of the mass of the initial vinyl acetate to the total mass of the continuous monomeric vinyl acetate in step (1) is 2.0-2.4: 1.

Preferably, the continuous monomer vinyl acetate is added in three batches in the reaction process in the step (1), and the addition amount of each batch is equal; the specific adding time is that the reaction is added when the reaction is carried out for 10min, 30min and 50min, the adding time is 15min at each time interval, and then the adding is stopped for 5min and is continued.

Preferably, the mass percentage of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution added in the curing period in the step (1) is 4-5%, and the ratio of the mass of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution to the total mass of the vinyl acetate monomers (initial vinyl acetate monomer + continuous vinyl acetate monomer) is 0.75%.

Preferably, the addition amount of the tert-butyl peroxybenzoate is 0.15-0.3 kg per ton of the reaction solution in the step (2); the addition amount of the sodium bicarbonate is 1.5-2.2 kg per ton of the reaction liquid in the step (2); the addition amount of the defoaming agent is 1.5-2.0 kg per ton of the reaction liquid in the step (2); the addition amount of the deionized water is 30-50 kg per ton of the reaction liquid in the step (2).

Compared with the prior art, the invention has the following beneficial effects:

1) the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A has better rheological property, maintains the low viscosity of the emulsion, reduces the solid content and ensures that the leveling property of the emulsion is more excellent; the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A prepared by the invention has the characteristics of good rheological property, low solid content, low viscosity, high flexibility and good film forming property;

2) the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A makes up the defects of large film forming hardness and insufficient flexibility of the existing vinyl acetate-ethylene copolymer emulsion model due to high mechanical stability and high curing speed, and provides an emulsion raw material with better performance for the adhesive type and the spray type;

3) the invention optimizes the performance of the vinyl acetate-ethylene copolymer emulsion on the premise of not changing the raw material components of the original vinyl acetate-ethylene copolymer emulsion, has simple preparation process and is easy to realize industrialization.

Detailed Description

The following detailed description is to be read in connection with specific embodiments, but it should be understood that the scope of the invention is not limited to the specific embodiments. The raw materials and reagents used in the examples were all commercially available unless otherwise specified. The oxidant hydrogen peroxide solution used in the following examples is 150kg of hydrogen peroxide solution with a mass concentration of 35%, and the hydrogen peroxide solution is diluted to prepare a hydrogen peroxide solution with a mass concentration of 1.2-2.0%.

The vinyl acetate purity used in the following examples was 99.5%; wherein the initial monomer vinyl acetate and the continuous monomer vinyl acetate are the same substance, and the addition sequence is different, so the names are different; the monomer vinyl acetate described in the examples refers to the generic term of initial monomer vinyl acetate + continuous monomer vinyl acetate.

Example 1

A preparation method of a low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion comprises the following specific operation steps:

(1) 4500kg of monomeric vinyl acetate was received in a monomer batch tank; taking deionized water as a solvent, uniformly mixing 258kg of compound polyvinyl alcohol (obtained by mixing 05-88 and 17-88 of polyvinyl alcohol according to a mass ratio of 12: 1) with 31.2kg of octylphenol polyoxyethylene ether and 18kg of zinc sulfoxylate formaldehyde serving as a reducing agent in a container, and heating to 85 ℃ to prepare 5000-5100 kg of mixed solution, namely surfactant solution, for later use; the mass ratio of deionized water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and reducer zinc formaldehyde sulfoxylate in the surfactant solution is 277.8-283.3: 14.3: 1.73: 1; then adding 150kg Zinc Formaldehyde Sulfoxylate (ZFS) and 2850kg deionized water into the post-addition tank to prepare a 5% zinc formaldehyde sulfoxylate aqueous solution for later use;

adding 2750kg of initial monomer vinyl acetate and 5000kg of the standby surfactant solution into a polymerization kettle with a stirrer and an external heat removal device for pre-emulsification, starting the stirrer and a circulating pump, heating to 50-60 ℃, stopping heating, introducing ethylene, boosting the pressure to 3.8MPa, dropwise adding 1.82% by mass of oxidant hydrogen peroxide solution to initiate reaction, stirring for 100min, adding continuous monomer vinyl acetate (the continuous vinyl acetate is added in three batches, the adding amount of each batch is equal, the adding time is 10min, 30min and 50min after the reaction, the adding time is 15min at each time interval, stopping adding for 5min, and continuing adding) 1250kg, wherein the ratio of the mass of the initial vinyl acetate to the mass of the continuous monomer vinyl acetate is 2.2:1, heat is released during the reaction, and the reaction temperature is finally controlled to be 78-82 ℃ for reaction, cooling by using circulating cooling water of a reactor heat exchanger when the reaction is overheated, continuously adding ethylene, boosting the pressure to 5.9MPa, stopping adding the ethylene, setting the pressure of the reactor to be 1.8MPa when the reaction time reaches 70min, automatically controlling the adding rate of an oxidant by an oxidant feeding pump according to the reaction temperature, adjusting the rate of adding the oxidant to be 100% when the reaction time reaches 100min, adding the oxidant to be 14min, controlling the total adding amount of a hydrogen peroxide solution with the mass percentage of 1.82% to be 320-380 kg (namely the total adding amount of the hydrogen peroxide is 8.0-9.5% of the total mass of the monomer vinyl acetate added in the step (1)), after finishing adding the hydrogen peroxide solution of the oxidant, controlling the reaction temperature to be lower than 77 ℃ and the adding rate of the hydrogen peroxide solution of the oxidant to be 100%, then generating the mixture to enter a curing period, and adding 29.2kg of the standby zinc sulfoxylate formaldehyde (ZFS) aqueous solution with the mass percentage of 5% in the curing period, the mass ratio of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution to the total mass of the monomer vinyl acetate is 0.75 percent, the conversion rate of the monomer vinyl acetate and the ethylene is improved, and the reaction is finished after the curing period is finished;

(2) placing the reaction liquid obtained after the curing period in the step (1) in a flash evaporator to remove residual ethylene, adding 45kg of deionized water into each ton of the reaction liquid to adjust the content of non-volatile components in the reaction liquid, adding 0.15kg of tert-butyl peroxybenzoate into each ton of the reaction liquid to reduce the content of vinyl acetate in the reaction liquid, adding 1.8kg of sodium bicarbonate into each ton of the reaction liquid to adjust the pH value of the reaction liquid, adding 1.5kg of defoaming agent into each ton of the reaction liquid to remove residual fine bubbles in the reaction liquid, stirring uniformly, filtering and removing filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A.

Example 2

A preparation method of a low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion comprises the following operation steps:

(1) 4500kg of monomeric vinyl acetate was received in a monomer batch tank; taking deionized water as a solvent, and uniformly mixing 243kg of compound polyvinyl alcohol (obtained by mixing 05-88 parts of polyvinyl alcohol and 17-88 parts of polyvinyl alcohol according to a mass ratio of 111.5) with 30kg of octyl phenol polyoxyethylene ether and 18kg of zinc formaldehyde sulfoxylate serving as a reducing agent in a container, and heating to 75 ℃ to prepare 4950-5000 kg of mixed solution, namely surfactant solution, for later use; the mass ratio of deionized water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and reducer zinc formaldehyde in the surfactant solution is 275-277.8: 13.5: 1.67-1.94: 1; then adding 120kg Zinc Formaldehyde Sulfoxylate (ZFS) and 2880kg deionized water into the post-addition tank to prepare a 4% zinc formaldehyde sulfoxylate aqueous solution for later use;

adding 2800kg of initial monomer vinyl acetate and 5000kg of the standby surfactant solution into a polymerization kettle with a stirrer and an external heat removal device for pre-emulsification, starting the stirrer and a circulating pump, heating to 50-60 ℃, stopping heating, introducing ethylene, boosting the pressure to 1.5MPa, dropwise adding an oxidant hydrogen peroxide solution with the mass percentage of 1.2% to initiate reaction, stirring for reaction for 116min, beginning to add continuous monomer vinyl acetate (the continuous vinyl acetate is added in three batches, the adding amount of each batch is equal, the adding time is 10min, 30min and 50min after the reaction, the adding time is 15min at each time interval, stopping adding for 5min, and continuing to add) 1400kg, wherein the ratio of the mass of the initial vinyl acetate to the mass of the continuous monomer vinyl acetate is 2.0:1, heat is released in the reaction process, and the reaction temperature is finally controlled to react at 78-82 ℃, cooling by using circulating cooling water of a reactor heat exchanger when the reaction is overheated, continuously adding ethylene, boosting the pressure to 5.9MPa, stopping adding the ethylene, setting the pressure of the reactor to be 1.8MPa when the reaction time reaches 70min, automatically controlling the adding rate of an oxidant by an oxidant feeding pump according to the reaction temperature, adjusting the rate of adding the oxidant to be 100% when the reaction time reaches 116min, adding the oxidant to be 14min, controlling the total adding amount of a hydrogen peroxide solution with the mass percentage of 1.2% to be 336-399 kg (namely the total adding amount of the hydrogen peroxide to be 8.0-9.5% of the total mass of the monomer vinyl acetate added in the step (1)), after finishing adding the hydrogen peroxide solution of the oxidant, controlling the reaction temperature to be lower than 77 ℃ and the adding rate of the hydrogen peroxide solution of the oxidant to be 100%, then generating the mixture to enter a curing period, and adding 31.5kg of the standby zinc sulfoxylate formaldehyde (ZFS) aqueous solution with the mass percentage of 4% in the curing period, the mass ratio of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution to the total mass of the monomer vinyl acetate is 0.75 percent, the conversion rate of the monomer vinyl acetate and the ethylene is improved, and the reaction is finished after the curing period is finished;

(2) and (2) placing the reaction liquid obtained after the curing period in the step (1) in a flash evaporator to remove residual ethylene, adding 30kg of deionized water into each ton of the reaction liquid to adjust the content of non-volatile components in the reaction liquid, adding 0.3kg of tert-butyl peroxybenzoate into each ton of the reaction liquid to reduce the content of vinyl acetate in the reaction liquid, adding 1.5kg of sodium bicarbonate into each ton of the reaction liquid to adjust the pH value of the reaction liquid, adding 1.8kg of defoaming agent into each ton of the reaction liquid to remove residual fine bubbles in the reaction liquid, stirring uniformly, and filtering to remove filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A.

Example 3

A preparation method of a low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion comprises the following operation steps:

(1) 4500kg of monomeric vinyl acetate was received in a monomer batch tank; taking deionized water as a solvent, uniformly mixing 270kg of compound polyvinyl alcohol (obtained by mixing 05-88 and 17-88 of polyvinyl alcohol according to a mass ratio of 12: 1) with 34.92kg of octyl phenol polyoxyethylene ether and 18kg of zinc sulfoxylate formaldehyde serving as a reducing agent in a container, and heating to 80 ℃ to prepare 5005-5045 kg of mixed solution, namely surfactant solution, for later use; the mass ratio of deionized water, compound polyvinyl alcohol, octyl phenol polyoxyethylene ether and reducer zinc formaldehyde in the surfactant solution is 278-280: 15.0: 1.94: 1; then adding 150kg Zinc Formaldehyde Sulfoxylate (ZFS) and 2850kg deionized water into the post-addition tank to prepare a 5% zinc formaldehyde sulfoxylate aqueous solution for later use;

adding 2880kg of initial monomer vinyl acetate and 5000kg of the standby surfactant solution into a polymerization kettle with a stirrer and an external heat removal device for pre-emulsification, starting the stirrer and a circulating pump, heating to 50-60 ℃, stopping heating, introducing ethylene, boosting the pressure to 6.0MPa, dropwise adding an oxidant hydrogen peroxide solution with the mass percentage of 2.0% to initiate reaction, stirring for 120min, beginning to add continuous monomer vinyl acetate (the continuous vinyl acetate is added in three batches, the adding amount of each batch is equal, the adding time is 10min, 30min and 50min, the adding time is 15min in each time interval, stopping adding for 5min, and continuing adding) 1200kg of initial vinyl acetate, the mass ratio of the initial vinyl acetate to the continuous monomer vinyl acetate is 2.4:1, releasing heat in the reaction process, and finally controlling the reaction temperature to be 78-82 ℃ for reaction, cooling by using circulating cooling water of a reactor heat exchanger when the reaction is overheated, continuously adding ethylene, boosting the pressure to 5.9MPa, stopping adding the ethylene, setting the pressure of the reactor to be 1.8MPa when the reaction time reaches 70min, automatically controlling the adding rate of an oxidant by an oxidant feeding pump according to the reaction temperature, adjusting the rate of adding the oxidant to be 100% when the reaction time reaches 120min, adding the oxidant to be 14min, controlling the total adding amount of a hydrogen peroxide solution with the mass percentage of 2.0% to be 326-387.6 kg (namely the total adding mass of the hydrogen peroxide is 8.0-9.5% of the total mass of the monomer vinyl acetate added in the step (1)), after finishing adding the hydrogen peroxide solution as the oxidant, controlling the reaction temperature to be lower than 77 ℃ and the adding rate of the hydrogen peroxide solution as the oxidant to be increased to be 100%, then producing to enter a curing period, and adding 30.6kg of the standby zinc sulfoxylate formaldehyde (ZFS) aqueous solution with the mass percentage of 5% in the curing period, the mass ratio of the zinc sulfoxylate formaldehyde (ZFS) aqueous solution to the total mass of the monomer vinyl acetate is 0.75 percent, the conversion rate of the monomer vinyl acetate and the ethylene is improved, and the reaction is finished after the curing period is finished; (ii) a

(2) Placing the reaction liquid obtained after the curing period in the step (1) in a flash evaporator to remove residual ethylene, adding 50kg of deionized water into each ton of the reaction liquid to adjust the content of non-volatile components in the reaction liquid, adding 0.25kg of tert-butyl peroxybenzoate into each ton of the reaction liquid to reduce the content of vinyl acetate in the reaction liquid, adding 2.0kg of sodium bicarbonate into each ton of the reaction liquid to adjust the pH value of the reaction liquid, adding 2.0kg of defoaming agent into each ton of the reaction liquid to remove residual fine bubbles in the reaction liquid, stirring uniformly, filtering and removing filter residues to obtain the low-viscosity low-solid vinyl acetate-ethylene copolymer emulsion GW-707A.

The comparison table of the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A prepared by the method and the conventional GW-707 shows the test results of important quality performance indexes of the emulsion in the following table 1:

TABLE 1

The quality performance test results of the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A prepared by the invention are shown in the table 2:

TABLE 2

Analysis item	Index (I)
		Appearance of the product	White homogeneous emulsion
pH value	4～6
		Non-volatile matter,%	45.0-50.0
Content of ethylene%	16±2％
		Viscosity (25 ℃), mPa.s	800～1000
Residual monomer content%	≤0.1
		Dilution stability,% of	≤2.0
Particle size, μm	≤0.8
		Tensile strength, MPa	5.25
Elongation at break,%	612

As can be seen from the data in Table 1, the ratio of the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707A to the conventional GW-707 is lower, the softness of the product after film forming is better, the rheological property is obviously better than that of the conventional GW-707, the leveling property is better, and the low-solid low-viscosity vinyl acetate-ethylene copolymer emulsion GW-707 is suitable for being used as a spray coating of textiles and paper industry; as can be seen from the data in Table 2, GW-707A belongs to low-viscosity low-solid-content emulsion, has good rheological property, good tensile strength and elongation at break and ideal soft and moist performance, and can meet the industrial requirements of more waterproof coatings, adhesives and textile coatings.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.