Vinyl acetate-ethylene emulsion, preparation method thereof and vinyl acetate-ethylene emulsion film

Abstract

The invention relates to the field of vinyl acetate-ethylene emulsion, and discloses vinyl acetate-ethylene emulsion, a preparation method thereof and a vinyl acetate-ethylene emulsion film. The vinyl acetate-ethylene emulsion comprises a vinyl acetate-ethylene copolymer, vinyl acetate, ethylene, a protective colloid, an emulsifier, a reducing agent, an oxidizing agent, a pH regulator, a chelating agent, water and a bactericide. Wherein the chelating agent is selected from citric acid and / or EDTA (Ethylene Diamine Tetraacetic Acid). The chelating agent in the components of the vinyl acetate-ethylene emulsion can inhibit yellowing of the vinyl acetate-ethylene emulsion, and the yellowing index of a vinyl acetate-ethylene emulsion film prepared from the vinyl acetate-ethylene emulsion is reduced.

Description

Technical Field

[0001] The present invention relates to vinyl acetate-ethylene emulsion, and specifically relates to a vinyl acetate-ethylene emulsion, a preparation method thereof, and a vinyl acetate-ethylene emulsion film. Background Art

[0002] Vinyl acetate-ethylene (VAE) emulsion has good low-temperature film-forming property, flexibility and adhesiveness, and is widely used in fields such as construction (including latex powder, waterproof coating, interior wall coating), adhesives (including packaging, woodworking, cigarette glue), textiles (including material compounding, printing, carpet, non-woven fabric, coating, etc.).

[0003] When VAE emulsion is used in the textile field, with the gradual enhancement of people's environmental awareness, more and more users require that VAE emulsion does not contain formaldehyde. However, VAE emulsion is prone to yellowing or even browning during the film-forming process. If the color of the composite adhesive material is very light, it will seriously affect the appearance and quality of textiles, and the yellowing resistance of VAE emulsion becomes very important.

[0004] CN111073020A mixes polyolefin powder with an aqueous solution of an organic acid (acetic acid, propionic acid or butyric acid), heats (80-150°C) and refluxes under stirring conditions, then cools, filters, washes and dries to promote the complexation of acid radical ions with metal ions, especially heavy metal ions, and then separates them from the material, so that the color of the polyolefin material is significantly improved, and the problems of product yellowing and unstable melt index can be successfully overcome.

[0005] CN110964133A controls the content of soluble organic carbon (≤5000 ppm) or soluble organic carbon and iron ions (≤10 ppm) in ABS rubber powder by washing with water or alkali solution or acid solution (aqueous solution of acetic acid, hydrochloric acid or sulfuric acid) to obtain an ABS resin with a low yellow index ≤18.

[0006] There are ferrous ions in the above materials, and they all solve the yellowing caused by ferrous ions, but cannot solve the yellowing caused by the vinyl acetate-ethylene polymerization reaction itself. Summary of the Invention

[0007] The purpose of the present invention is to overcome the yellowing phenomenon existing in the use of vinyl acetate-ethylene emulsion in the prior art, and provide a vinyl acetate-ethylene emulsion, a preparation method thereof, and a vinyl acetate-ethylene emulsion film, so that the vinyl acetate-ethylene emulsion film has a lower yellowing index.

[0008] The first aspect of the present invention provides a vinyl acetate-ethylene emulsion, wherein the emulsion comprises: vinyl acetate-ethylene copolymer, vinyl acetate, ethylene, protective colloid, emulsifier, reducing agent, oxidizing agent, pH regulator, chelating agent, water and bactericide;

[0009] Among them, the chelating agent is selected from citric acid and / or EDTA.

[0010] The second aspect of the present invention provides a method for preparing a vinyl acetate-ethylene emulsion. Among them, the preparation method includes:

[0011] S1. Polymerize vinyl acetate monomer and ethylene monomer by semi-continuous method to obtain a vinyl acetate-ethylene pre-emulsion;

[0012] S2. After defoaming the vinyl acetate-ethylene pre-emulsion, add a post-treatment aid and a chelating agent to obtain the vinyl acetate-ethylene emulsion;

[0013] Among them, the chelating agent is selected from citric acid and / or EDTA.

[0014] The third aspect of the present invention provides a vinyl acetate-ethylene emulsion prepared by the aforementioned preparation method.

[0015] The fourth aspect of the present invention provides a vinyl acetate-ethylene emulsion film. Among them, the vinyl acetate-ethylene emulsion film is obtained by drying the aforementioned vinyl acetate-ethylene emulsion.

[0016] Through the above aspects, the present invention has achieved the following beneficial effects:

[0017] (1) In the specific vinyl acetate-ethylene emulsion of the present invention, the chelating agent can inhibit the yellowing of the vinyl acetate-ethylene emulsion and reduce the yellowing index of the vinyl acetate-ethylene emulsion film prepared from the vinyl acetate-ethylene emulsion. It is speculated that the reason is that the reducing agent causes the yellowing of the vinyl acetate-ethylene emulsion, and the chelating agent can chemically react with the reducing agent to inhibit the yellowing of the vinyl acetate-ethylene emulsion caused by the reducing agent.

[0018] (2) The present invention adds a chelating agent after the post-treatment of the vinyl acetate-ethylene emulsion, which does not affect the previous polymerization reaction and production efficiency, and the addition method is simple; further, adding vinyl acetate monomer step by step can make the polymerization reaction easier to control;

[0019] Further, it is speculated that due to the specific dosages of the reducing agent and the chelating agent, the reducing agent can ensure the smooth progress of the polymerization reaction, and can fully react with the chelating agent after the reaction ends, inhibiting the yellowing phenomenon that may be caused by the reducing agent, so that the prepared vinyl acetate-ethylene emulsion film has a lower yellowing index. Specific embodiments

[0020] The endpoints and any values in the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0021] The first aspect of the present invention provides an ethylene-vinyl acetate emulsion, wherein the emulsion comprises: an ethylene-vinyl acetate copolymer, vinyl acetate, ethylene, a protective colloid, an emulsifier, a reducing agent, an oxidizing agent, a pH regulator, a chelating agent, water, and a bactericide;

[0022] Wherein, the chelating agent is selected from citric acid and / or EDTA.

[0023] In the present invention, the inventors unexpectedly found that adding a chelating agent can inhibit the yellowing of the ethylene-vinyl acetate emulsion. It is speculated that the reason is that the reducing agent causes the yellowing of the ethylene-vinyl acetate emulsion, and the chelating agent can undergo a chemical reaction with the reducing agent.

[0024] In the present invention, the weight parts of the oxidizing agent and the reducing agent are relatively small, and there is a certain probability of mutual contact. Also, due to the relatively long half-life, although the subsequent redox reaction is still ongoing, it consumes slowly over a long time, so they can coexist within several days or months.

[0025] According to the present invention, in the ethylene-vinyl acetate emulsion, the weight part of the ethylene-vinyl acetate copolymer is 100, the weight part of vinyl acetate is 40 - 50, the weight part of ethylene is 9 - 10, the weight part of the protective colloid is 2 - 2.5, the weight part of the emulsifier is 0.25 - 0.3, the weight part of the reducing agent is 0.05 - 0.1, the weight part of the oxidizing agent is 0.05 - 0.08, the weight part of the pH regulator is 0.03 - 0.05, the weight part of the chelating agent is 0.06 - 0.08, the weight part of water is 38 - 42, and the weight part of the bactericide is 0.1 - 0.5.

[0026] In the present invention, when the contents of the components of the ethylene-vinyl acetate emulsion meet the above ranges, it can further inhibit the yellowing of the ethylene-vinyl acetate emulsion.

[0027] Further, in the vinyl acetate-ethylene emulsion, the weight parts of the vinyl acetate-ethylene copolymer are 100, the weight parts of vinyl acetate are 42-48, the weight parts of ethylene are 9.2-9.8, the weight parts of the protective colloid are 2.1-2.4, the weight parts of the emulsifier are 0.26-0.29, the weight parts of the reducing agent are 0.06-0.09, the weight parts of the oxidizing agent are 0.06-0.07, the weight parts of the pH regulator are 0.035-0.045, the weight parts of the chelating agent are 0.065-0.075, the weight parts of water are 39-41, and the weight parts of the bactericide are 0.2-0.4.

[0028] According to the present invention, the protective colloid is selected from polyvinyl alcohol and / or cellulose, preferably polyvinyl alcohol.

[0029] According to the present invention, the emulsifier is selected from at least one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, and fatty alcohol polyoxyethylene ether, preferably selected from fatty alcohol polyoxyethylene ether and / or octylphenol polyoxyethylene ether.

[0030] According to the present invention, the reducing agent is selected from at least one of ascorbic acid, isoorange ascorbate, and tartrate.

[0031] In the present invention, the vinyl acetate-ethylene emulsion prepared by a general formaldehyde-free reducing agent in the art has a slow reaction rate and causes yellowing. The specific reducing agent ensures that the vinyl acetate-ethylene emulsion in the present invention is a formaldehyde-free environmentally friendly emulsion. However, due to the degradation of the reducing agent, the generated ketone substances are prone to non-enzymatic browning to form brown pigments, which will cause yellowing of the vinyl acetate-ethylene emulsion.

[0032] According to the present invention, the isoorange ascorbate is selected from at least one of zinc isoorange ascorbate, sodium isoorange ascorbate, and magnesium isoorange ascorbate, preferably sodium isoorange ascorbate.

[0033] According to the present invention, the tartrate is selected from at least one of zinc tartrate, sodium tartrate, potassium tartrate, and magnesium tartrate, preferably potassium tartrate.

[0034] Further, the reducing agent is selected from at least one of ascorbic acid, sodium isoorange ascorbate, and potassium tartrate.

[0035] According to the present invention, the oxidizing agent is selected from organic peroxides or / and inorganic peroxides.

[0036] Further, the oxidizing agent is selected from at least one of tert-butyl hydroperoxide, hydrogen peroxide, potassium persulfate, and ammonium persulfate, preferably tert-butyl hydroperoxide.

[0037] According to the present invention, the pH regulator is selected from at least one of bicarbonate, acetate, phosphate and sodium hydroxide, and preferably sodium hydroxide.

[0038] According to the present invention, the bactericide is selected from Kathon and / or 1,2-benzisothiazol-3-one, and preferably Kathon.

[0039] A second aspect of the present invention provides a method for preparing a vinyl acetate-ethylene emulsion, wherein the preparation method includes:

[0040] S1. Polymerize vinyl acetate monomer and ethylene monomer by semi-continuous method to obtain a vinyl acetate-ethylene pre-emulsion;

[0041] S2. After defoaming the vinyl acetate-ethylene pre-emulsion, add post-treatment aids and chelating agents to obtain the vinyl acetate-ethylene emulsion;

[0042] Wherein, the chelating agent is selected from citric acid and / or EDTA.

[0043] The vinyl acetate-ethylene emulsion prepared by the specific preparation method of the present invention has good yellowing resistance on the premise of meeting the use standards. It is speculated that the reason is that the chelating agent reacts chemically with the reducing agent and post-treatment reagent that cause yellowing, inhibiting the yellowing of the vinyl acetate-ethylene emulsion.

[0044] In the present invention, the defoaming conditions include: defoaming after reducing the pressure to 0.1013 MPa.

[0045] In the present invention, the addition of reactants and the polymerization reaction are both carried out under stirring conditions. The stirring conditions are the conventional stirring time and stirring temperature in the art, and sufficient mixing can be achieved by stirring.

[0046] According to the present invention, in S1, the semi-continuous method includes: first carrying out a first polymerization reaction on the first vinyl acetate monomer and ethylene monomer, and then carrying out a second polymerization reaction on the second vinyl acetate monomer and ethylene monomer.

[0047] According to the present invention, the first polymerization reaction includes: heating water, protective colloid, emulsifier and the first vinyl acetate monomer to a first temperature and introducing ethylene to increase the pressure to a first pressure, and then adding an oxidizing agent and a reducing agent to carry out the first polymerization reaction.

[0048] In a particularly preferred embodiment of the present invention, several polyvinyl alcohols (protective colloids) with different molecular weights are added to adjust the viscosity of the system, providing suitable conditions for the polymerization reaction; the system refers to the entire solution including water, protective colloid, emulsifier and the first vinyl acetate monomer.

[0049] According to the present invention, the second polymerization reaction includes: heating the product of the first polymerization reaction to a second temperature, introducing ethylene to increase the pressure to a second pressure, adding a second vinyl acetate monomer, and performing the second polymerization reaction.

[0050] In the present invention, both the "first vinyl acetate monomer" and the "second vinyl acetate monomer" are vinyl acetate monomers. This definition is only for distinction; adding vinyl acetate monomers step by step can make the polymerization reaction easier to control, and the polymerization reaction starts after adding the first vinyl acetate monomer.

[0051] In the present invention, during the preparation process, the oxidant, the reductant, the protective colloid, and the post-treatment auxiliary agent are all formulated into solutions for addition. Formulating into solutions for addition is a conventional addition method in the art, which is to dissolve solid raw materials into liquids for easy pumping; or to dilute high-concentration liquid raw materials, making it easier to add them evenly.

[0052] A particularly preferred method for preparing the protective colloid solution is: first add an appropriate amount of water and the protective colloid, heat to 80 - 95 °C, dissolve for 60 - 120 min, and then cool to 30 - 60 °C for use.

[0053] According to the present invention, the post-treatment auxiliary agent includes a post-treatment oxidant and a post-treatment reductant.

[0054] According to the present invention, in the post-treatment auxiliary agent, the weight ratio of the post-treatment oxidant to the post-treatment reductant is 0.7 - 1.5, preferably 0.9 - 1.3.

[0055] According to the present invention, in S1, the first temperature is 48 - 56 °C, preferably 50 - 54 °C; the first pressure is 3 - 4 MPa, preferably 3.2 - 3.9 MPa.

[0056] According to the present invention, in S1, the second temperature is 75 - 90 °C, preferably 80 - 85 °C; the second pressure is 4 - 8 MPa, preferably 5 - 6 MPa.

[0057] According to the present invention, in S1, the time of the first polymerization reaction is 10 - 40 min, preferably 20 - 30 min.

[0058] According to the present invention, in S1, the conditions of the second polymerization reaction are: the time of the second polymerization reaction is 150 - 350 min, preferably 200 - 300 min.

[0059] According to the present invention, in S2, after adding the post-treatment auxiliary agent and the chelating agent, there are also steps of cooling, adding a pH regulator, and a bactericide.

[0060] According to the present invention, in S2, the process of cooling includes: cooling the defoamed vinyl acetate-ethylene pre-emulsion to a third temperature, where the third temperature is 30-50°C, preferably 35-40°C.

[0061] According to the present invention, the post-treatment aid includes a post-treatment reducing agent and a post-treatment oxidizing agent.

[0062] According to the present invention, the reducing agent and the post-treatment reducing agent are each independently selected from at least one of ascorbic acid, isascorbate, and tartrate.

[0063] Further, the isascorbate is selected from at least one of zinc isascorbate, sodium isascorbate, and magnesium isascorbate, preferably sodium isascorbate.

[0064] Further, the tartrate is selected from at least one of zinc tartrate, sodium tartrate, and magnesium tartrate, preferably potassium tartrate.

[0065] Further, the reducing agent and the post-treatment reducing agent are each independently selected from at least one of ascorbic acid, sodium isascorbate, and potassium tartrate.

[0066] Further, the oxidizing agent and the post-treatment oxidizing agent are each independently selected from organic peroxides or / and inorganic peroxides.

[0067] Further, the oxidizing agent and the post-treatment oxidizing agent are each independently selected from at least one of tert-butyl hydroperoxide, hydrogen peroxide, potassium persulfate, and ammonium persulfate, preferably tert-butyl hydroperoxide.

[0068] In the second aspect of the present invention, the components and dosages in the vinyl acetate-ethylene emulsion are mostly the same as those in the first aspect of the present invention, and will not be elaborated here.

[0069] The reducing agent and the post-treatment reducing agent cannot be distinguished in the emulsion, and the oxidizing agent and the post-treatment oxidizing agent cannot be distinguished in the emulsion either. In the vinyl acetate-ethylene emulsion, the reducing agent comes from the added reducing agent and the added post-treatment reducing agent; the oxidizing agent comes from the added oxidizing agent and the added post-treatment oxidizing agent.

[0070] In the third aspect of the present invention, there is provided a vinyl acetate-ethylene emulsion prepared by the aforementioned preparation method.

[0071] In the fourth aspect of the present invention, there is provided a vinyl acetate-ethylene emulsion film, wherein the vinyl acetate-ethylene emulsion film is obtained by drying the aforementioned vinyl acetate-ethylene emulsion.

[0072] In the present invention, before drying, the vinyl acetate-ethylene emulsion also undergoes filtration and packaging, and the methods of filtration and packaging are both conventional operations in the art.

[0073] In the present invention, the preparation of the vinyl acetate-ethylene emulsion film is a conventional method for preparing emulsion films in the art. A particularly preferred embodiment is to form a wet film from the product emulsion and place it on a clean glass plate, and then place the glass plate in a blower drying oven at 180-190°C for drying. After cooling, the vinyl acetate-ethylene emulsion film is peeled off.

[0074] According to the present invention, the thickness of the vinyl acetate-ethylene emulsion film is 0.05-0.3 mm, preferably 0.08-0.15 mm.

[0075] According to the present invention, the yellowing index of the vinyl acetate-ethylene emulsion film is ≤15, preferably ≤13.

[0076] According to the present invention, the drying conditions include: the drying temperature is 5-200°C, preferably 80-180°C; the drying time is 1-60 min, preferably 2-10 min.

[0077] The present invention will be described in detail below through examples.

[0078] Test method for yellow index: Refer to "GB / T39294-2020 Determination of discoloration (yellowing) performance of adhesives", specifically the colorimeter method.

[0079] Vinyl acetate, ethylene, polyvinyl alcohol-1: grade PVA088-20, polyvinyl alcohol-2: grade PVA088-05, octylphenol polyoxyethylene ether: weight average molecular weight of 646.86 g / mol, tert-butyl hydroperoxide, ascorbic acid, citric acid, ethylenediaminetetraacetic acid, sodium hydroxide, Kathon, and deionized water are all commercially available.

[0080] Example 1

[0081] (1) Add deionized water, polyvinyl alcohol-1, polyvinyl alcohol-2, octylphenol polyoxyethylene ether, and the first vinyl acetate monomer, stir evenly, heat up to 50°C, introduce ethylene to increase the pressure to 3.9 MPa, and dropwise add tert-butyl hydroperoxide (rate 1.7×10 -4 parts by weight / min), dropwise add ascorbic acid (rate 2.8×10 -4 parts by weight / min) for the first polymerization reaction. The first polymerization reaction time is 25 min, heat up to 85°C, add the second vinyl acetate monomer, introduce ethylene to increase the pressure to 5 MPa, and carry out the second polymerization reaction. The second polymerization reaction time is 210 min to obtain a vinyl acetate-ethylene pre-emulsion;

[0082] (2) When the temperature is 83 °C and the pressure is 3.5 MPa, it enters the finishing period. After the vinyl acetate-ethylene pre-emulsion is defoamed (the pressure has dropped to 0.1013 MPa during defoaming), tert-butyl hydroperoxide, ascorbic acid and citric acid are added, and the temperature is lowered to 40 °C. Then sodium hydroxide and Kathon are added to obtain a vinyl acetate-ethylene emulsion;

[0083] In the vinyl acetate-ethylene emulsion, the weight parts of vinyl acetate-ethylene are 100, the weight parts of vinyl acetate are 45, the weight parts of ethylene are 9.5, the weight parts of polyvinyl alcohol are 2.3, the weight parts of octylphenol polyoxyethylene ether are 0.28, the weight parts of ascorbic acid are 0.08, the weight parts of tert-butyl hydroperoxide are 0.07, the weight parts of sodium hydroxide are 0.04, the weight parts of citric acid are 0.07, the weight parts of water are 40 and the weight parts of Kathon are 0.3;

[0084] (3) The vinyl acetate-ethylene emulsion is filtered, packaged and dried at 160 °C for 5 min to obtain a vinyl acetate-ethylene emulsion film N1.

[0085] Example 2

[0086] (1) Deionized water, polyvinyl alcohol-1, polyvinyl alcohol-2, octylphenol polyoxyethylene ether and the first vinyl acetate monomer are added and stirred evenly. The temperature is raised to 50 °C, ethylene is introduced to increase the pressure to 3.9 MPa, and tert-butyl hydroperoxide (rate 1.7×10 -4 parts by weight / min) and ascorbic acid (rate 2.8×10 -4 parts by weight / min) are added dropwise for the first polymerization reaction. The time of the first polymerization reaction is 10 min. The temperature is raised to 85 °C, and the second vinyl acetate monomer is added. Ethylene is introduced to increase the pressure to 5 MPa for the second polymerization reaction. The time of the second polymerization reaction is 150 min to obtain a vinyl acetate-ethylene pre-emulsion;

[0087] (2) When the temperature is 83 °C and the pressure is 3.5 MPa, it enters the finishing period. After the vinyl acetate-ethylene pre-emulsion is defoamed (the pressure has dropped to 0.1013 MPa during defoaming), tert-butyl hydroperoxide, ascorbic acid and citric acid are added, and the temperature is lowered to 30 °C. Then sodium bicarbonate and Kathon are added to obtain a vinyl acetate-ethylene emulsion;

[0088] In the vinyl acetate-ethylene emulsion, the weight parts of vinyl acetate-ethylene are 100, the weight parts of vinyl acetate are 50, the weight parts of ethylene are 9, the weight parts of polyvinyl alcohol are 2.5, the weight parts of octylphenol polyoxyethylene ether are 0.25, the weight parts of ascorbic acid are 0.1, the weight parts of tert-butyl hydroperoxide are 0.08, the weight parts of sodium bicarbonate are 0.03, the weight parts of citric acid are 0.08, the weight parts of water are 42 and the weight parts of Kathon are 0.5;

[0089] (3) Filter, package the vinyl acetate-ethylene emulsion, and dry it at 200 °C for 1 min to obtain the vinyl acetate-ethylene emulsion film N2.

[0090] Example 3

[0091] (1) Add deionized water, polyvinyl alcohol-1, polyvinyl alcohol-2, octylphenol polyoxyethylene ether, and the first vinyl acetate monomer, stir evenly, heat up to 50 °C, introduce ethylene to increase the pressure to 3.9 MPa, and dropwise add tert-butyl hydroperoxide (rate 1.7×10 -4 parts by weight / min), dropwise add ascorbic acid (rate 2.8×10 -4 parts by weight / min) to carry out the first polymerization reaction. The first polymerization reaction time is 40 min, heat up to 85 °C, add the second vinyl acetate monomer, introduce ethylene to increase the pressure to 5 MPa, and carry out the second polymerization reaction. The second polymerization reaction time is 350 min to obtain the vinyl acetate-ethylene pre-emulsion;

[0092] (2) At a temperature of 83 °C and a pressure of 3.5 MPa, enter the finishing period. After the vinyl acetate-ethylene pre-emulsion is defoamed (the pressure has dropped to 0.1013 MPa during defoaming), add tert-butyl hydroperoxide, ascorbic acid, and ethylenediaminetetraacetic acid, cool down to 50 °C, add sodium acetate and Kathon to obtain the vinyl acetate-ethylene emulsion;

[0093] In the vinyl acetate-ethylene emulsion, the parts by weight of vinyl acetate-ethylene are 100, the parts by weight of vinyl acetate are 40, the parts by weight of ethylene are 10, the parts by weight of polyvinyl alcohol are 2, the parts by weight of octylphenol polyoxyethylene ether are 0.3, the parts by weight of ascorbic acid are 0.05, the parts by weight of tert-butyl hydroperoxide are 0.05, the parts by weight of sodium acetate are 0.05, the parts by weight of ethylenediaminetetraacetic acid are 0.06, the parts by weight of water are 38, and the parts by weight of Kathon are 0.1;

[0094] (3) Filter, package the vinyl acetate-ethylene emulsion, and dry it at 5 °C for 60 min to obtain the vinyl acetate-ethylene emulsion film N3.

[0095] Example 4

[0096] (1) Add deionized water, polyvinyl alcohol-1, polyvinyl alcohol-2, octylphenol polyoxyethylene ether, and vinyl acetate monomer, stir evenly, heat up to 50 °C, introduce ethylene to increase the pressure to 3.9 MPa, and dropwise add tert-butyl hydroperoxide (rate 1.7×10 -4 parts by weight / min), dropwise add ascorbic acid (rate 2.8×10 -4Heat to 85°C at a rate of [[weight parts / min]], introduce ethylene, increase the pressure to 5 MPa, and carry out a polymerization reaction for 235 min to obtain a vinyl acetate-ethylene pre-emulsion;

[0097] (2) Obtain a vinyl acetate-ethylene emulsion in the same manner as in (2) of Example 1;

[0098] In the vinyl acetate-ethylene emulsion, the weight parts of vinyl acetate-ethylene are 100, the weight parts of vinyl acetate are 45, the weight parts of ethylene are 9.5, the weight parts of polyvinyl alcohol are 2.3, the weight parts of octylphenol polyoxyethylene ether are 0.28, the weight parts of ascorbic acid are 0.08, the weight parts of tert-butyl hydroperoxide are 0.07, the weight parts of sodium hydroxide are 0.04, the weight parts of citric acid are 0.07, the weight parts of water are 40, and the weight parts of Kathon are 0.3;

[0099] (3) Obtain a vinyl acetate-ethylene emulsion film N4 in the same manner as in (3) of Example 1.

[0100] Example 5

[0101] (1) Add deionized water, polyvinyl alcohol-1, polyvinyl alcohol-2, and octylphenol polyoxyethylene ether, stir evenly, heat to 50°C, introduce ethylene, increase the pressure to 3.9 MPa, and dropwise add tert-butyl hydroperoxide (rate 1.7×10 -4 weight parts / min) and dropwise add ascorbic acid (rate 2.8×10 -4 weight parts / min), heat to 85°C, add vinyl acetate monomer, introduce ethylene, increase the pressure to 5 MPa, and carry out a polymerization reaction for 235 min to obtain a vinyl acetate-ethylene pre-emulsion;

[0102] (2) Obtain a vinyl acetate-ethylene emulsion in the same manner as in (2) of Example 1;

[0103] In the vinyl acetate-ethylene emulsion, the weight parts of vinyl acetate-ethylene are 100, the weight parts of vinyl acetate are 40, the weight parts of ethylene are 10, the weight parts of polyvinyl alcohol are 2.1, the weight parts of octylphenol polyoxyethylene ether are 0.25, the weight parts of ascorbic acid are 0.1, the weight parts of tert-butyl hydroperoxide are 0.08, the weight parts of sodium hydroxide are 0.06, the weight parts of citric acid are 0.04, the weight parts of water are 41, and the weight parts of Kathon are 0.2;

[0104] (3) Obtain a vinyl acetate-ethylene emulsion film N5 in the same manner as in (3) of Example 1.

[0105] Example 6

[0106] (1) Obtain a vinyl acetate-ethylene pre-emulsion in the same manner as in (1) of Example 1;

[0107] (2) In the same manner as in (2) of Example 1, except that "citric acid and ethylenediaminetetraacetic acid" is used to replace "citric acid", a vinyl acetate-ethylene emulsion is obtained.

[0108] (3) In the same manner as in (3) of Example 1, a vinyl acetate-ethylene emulsion film N6 is obtained.

[0109] Example 7

[0110] (1) In the same manner as in (1) of Example 1, except that "zinc tartrate" is used to replace "ascorbic acid";

[0111] (2) In the same manner as in (2) of Example 1, a vinyl acetate-ethylene emulsion is obtained.

[0112] (3) In the same manner as in (3) of Example 1, a vinyl acetate-ethylene emulsion film N7 is obtained.

[0113] Comparative Example 1

[0114] (1) In the same manner as in (1) of Example 1, a vinyl acetate-ethylene pre-emulsion is obtained.

[0115] (2) In the same manner as in (2) of Example 1, except that "citric acid" is not added, a vinyl acetate-ethylene emulsion is obtained.

[0116] (3) In the same manner as in (3) of Example 1, a vinyl acetate-ethylene emulsion film D1 is obtained.

[0117] Comparative Example 2

[0118] (1) In the same manner as in (1) of Example 3, a vinyl acetate-ethylene pre-emulsion is obtained.

[0119] (2) In the same manner as in (2) of Example 3, except that "disodium ethylenediaminetetraacetate" is used to replace "ethylenediaminetetraacetic acid", a vinyl acetate-ethylene emulsion is obtained.

[0120] (3) In the same manner as in (3) of Example 3, a vinyl acetate-ethylene emulsion film D2 is obtained.

[0121] Vinyl acetate-ethylene emulsion films are prepared by the methods of Examples 1-6 and Comparative Examples 1-2, and their thickness and yellowness index are tested. The results are shown in Table 1.

[0122] Thickness (mm) Yellow Index YI Example 1 0.05 10.35 Example 2 0.1 10.85 Example 3 0.3 12.81 Example 4 0.2 11.56 Example 5 0.1 11.28 Example 6 0.1 10.09 Example 7 0.1 11.83 Comparative Example 1 0.05 38.72 Comparative Example 2 0.3 35.66

[0123] It can be seen from the results in Table 1 that by comparing Example 1 with Comparative Example 1, it is known that adding a chelating agent can inhibit the yellowing of vinyl acetate-ethylene emulsion and reduce the yellowing index of the vinyl acetate-ethylene emulsion film prepared from the vinyl acetate-ethylene emulsion.

[0124] By comparing Example 1 with Comparative Example 2, it is known that not any similar structure can achieve the inhibition of yellowing. Only a specific type of chelating agent can inhibit the yellowing of the vinyl acetate-ethylene emulsion film.

[0125] Furthermore, by comparing Example 1 with Example 6, it is known that the effect of inhibiting yellowing is better when two specific chelating agents are used together.

[0126] By comparing Example 1 with Example 3, it is known that the content of specific components in the emulsion and the film-forming method will further affect the yellowing index of the vinyl acetate-ethylene emulsion film.

[0127] By comparing Example 1, Example 4 and Example 5, it is known that adding vinyl acetate monomer in specific steps can further improve the inhibitory effect on the vinyl acetate-ethylene emulsion film.

[0128] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A vinyl acetate-ethylene emulsion, characterized in that, the emulsion comprises: vinyl acetate-ethylene copolymer, vinyl acetate, ethylene, protective colloid, emulsifier, reducing agent, oxidizing agent, pH regulator, chelating agent, water and fungicide; wherein, the chelating agent is selected from citric acid and / or EDTA.

2. The vinyl acetate-ethylene emulsion according to claim 1, wherein, in the vinyl acetate-ethylene emulsion, the weight parts of the vinyl acetate-ethylene copolymer is 100, the weight parts of the vinyl acetate is 40-50, the weight parts of the ethylene is 9-10, the weight parts of the protective colloid is 2-2.5, the weight parts of the emulsifier is 0.25-0.3, the weight parts of the reducing agent is 0.05-0.1, the weight parts of the oxidizing agent is 0.05-0.08, the weight parts of the pH regulator is 0.03-0.05, the weight parts of the chelating agent is 0.06-0.08, the weight parts of the water is 38-42 and the weight parts of the fungicide is 0.1-0.5; Preferably, in the vinyl acetate-ethylene emulsion, the weight parts of the vinyl acetate-ethylene copolymer is 100, the weight parts of the vinyl acetate is 42-48, the weight parts of the ethylene is 9.2-9.8, the weight parts of the protective colloid is 2.1-2.4, the weight parts of the emulsifier is 0.26-0.29, the weight parts of the reducing agent is 0.06-0.09, the weight parts of the oxidizing agent is 0.06-0.07, the weight parts of the pH regulator is 0.035-0.045, the weight parts of the chelating agent is 0.065-0.075, the weight parts of the water is 39-41 and the weight parts of the fungicide is 0.2-0.

4.

3. The vinyl acetate-ethylene emulsion according to claim 1 or 2, wherein, the protective colloid is selected from polyvinyl alcohol and / or cellulose, preferably polyvinyl alcohol; Preferably, the emulsifier is selected from at least one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, preferably selected from fatty alcohol polyoxyethylene ether and / or octylphenol polyoxyethylene ether; Preferably, the reducing agent is selected from at least one of ascorbic acid, isascorbate and tartrate; Preferably, the isascorbate is selected from at least one of zinc isascorbate, sodium isascorbate and magnesium isascorbate, preferably sodium isascorbate; Preferably, the tartrate is selected from at least one of zinc tartrate, sodium tartrate, potassium tartrate and magnesium tartrate, preferably potassium tartrate; Preferably, the reducing agent is selected from at least one of ascorbic acid, sodium isascorbate and potassium tartrate; Preferably, the oxidizing agent is selected from organic peroxides or / and inorganic peroxides; Preferably, the oxidizing agent is selected from at least one of tert-butyl hydroperoxide, hydrogen peroxide, potassium persulfate and ammonium persulfate, preferably tert-butyl hydroperoxide; Preferably, the pH regulator is selected from at least one of bicarbonate, acetate, phosphate and sodium hydroxide, preferably sodium hydroxide; Preferably, the bactericide is selected from Kathon and / or 1,2-benzisothiazol-3-one, preferably Kathon.

4. A method for preparing vinyl acetate-ethylene emulsion, characterized in that, the preparation method includes: S1. Polymerize vinyl acetate monomer and ethylene monomer by semi-continuous method to obtain vinyl acetate-ethylene pre-emulsion; S2. After defoaming the vinyl acetate-ethylene pre-emulsion, add post-treatment aids and chelating agents to obtain the vinyl acetate-ethylene emulsion; wherein, the chelating agent is selected from citric acid and / or EDTA.

5. The preparation method according to claim 4, wherein, in S1, the semi-continuous method includes: first carry out the first polymerization reaction on the first vinyl acetate monomer and ethylene monomer, and then carry out the second polymerization reaction on the second vinyl acetate monomer and ethylene monomer; Preferably, the first polymerization reaction includes: heating water, protective colloid, emulsifier and the first vinyl acetate monomer to the first temperature and introducing ethylene to increase the pressure to the first pressure, and then adding an oxidizing agent and a reducing agent to carry out the first polymerization reaction; Preferably, the second polymerization reaction includes: heating the product of the first polymerization reaction to the second temperature and introducing ethylene to increase the pressure to the second pressure, and adding the second vinyl acetate monomer to carry out the second polymerization reaction; Preferably, in S1, the first temperature is 48-56 °C, preferably 50-54 °C; the first pressure is 3-4 MPa, preferably 3.2-3.9 MPa; Preferably, in S1, the second temperature is 75-90 °C, preferably 80-85 °C; the second pressure is 4-8 MPa, preferably 5-6 MPa; Preferably, in S1, the time of the first polymerization reaction is 10-40 min, preferably 20-30 min; Preferably, in S1, the time of the second polymerization reaction is 150-350 min, preferably 200-300 min; Preferably, in S2, after adding the post-treatment aids and the chelating agent, there are also steps of cooling, adding a pH regulator and a bactericide; Preferably, in S2, the cooling process includes: cooling the defoamed vinyl acetate-ethylene pre-emulsion to the third temperature, and the third temperature is 30-50 °C, preferably 35-40 °C.

6. The preparation method according to claim 4 or 5, wherein, in the vinyl acetate-ethylene emulsion, the weight parts of the vinyl acetate-ethylene copolymer are 100, the weight parts of vinyl acetate are 40-50, the weight parts of ethylene are 9-10, the weight parts of the protective colloid are 2-2.5, the weight parts of the emulsifier are 0.25-0.3, the weight parts of the reducing agent are 0.05-0.1, the weight parts of the oxidizing agent are 0.05-0.08, the weight parts of the pH regulator are 0.03-0.05, the weight parts of the chelating agent are 0.06-0.08, the weight parts of water are 38-42 and the weight parts of the bactericide are 0.1-0.5; Preferably, in the vinyl acetate-ethylene emulsion, the weight parts of the vinyl acetate-ethylene copolymer are 100, the weight parts of vinyl acetate are 42-48, the weight parts of ethylene are 9.2-9.8, the weight parts of the protective colloid are 2.1-2.4, the weight parts of the emulsifier are 0.26-0.29, the weight parts of the reducing agent are 0.06-0.09, the weight parts of the oxidizing agent are 0.06-0.07, the weight parts of the pH regulator are 0.035-0.045, the weight parts of the chelating agent are 0.065-0.075, the weight parts of water are 39-41, and the weight parts of the bactericide are 0.2-0.

4.

7. The preparation method according to any one of claims 4-6, wherein, the protective colloid is selected from polyvinyl alcohol and / or cellulose, preferably polyvinyl alcohol; Preferably, the emulsifier is selected from at least one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether, preferably fatty alcohol polyoxyethylene ether and / or octylphenol polyoxyethylene ether; Preferably, the post-treatment aid comprises a post-treatment reducing agent and a post-treatment oxidizing agent; Preferably, the reducing agent and the post-treatment reducing agent are each independently selected from at least one of ascorbic acid, isascorbate and tartrate; Preferably, the isascorbate is selected from at least one of zinc isascorbate, sodium isascorbate and magnesium isascorbate, preferably sodium isascorbate; Preferably, the tartrate is selected from at least one of zinc tartrate, sodium tartrate and magnesium tartrate, preferably potassium tartrate; Preferably, the reducing agent and the post-treatment reducing agent are each independently selected from at least one of ascorbic acid, sodium isascorbate and potassium tartrate; Preferably, the oxidizing agent and the post-treatment oxidizing agent are each independently selected from organic peroxides or / and inorganic peroxides; Preferably, the oxidizing agent and the post-treatment oxidizing agent are each independently selected from at least one of tert-butyl hydroperoxide, hydrogen peroxide, potassium persulfate and ammonium persulfate, preferably tert-butyl hydroperoxide; Preferably, the pH regulator is selected from at least one of bicarbonate, acetate, phosphate and sodium hydroxide, preferably sodium hydroxide; Preferably, the bactericide is selected from carbopol and / or 1,2-benzisothiazol-3-one, preferably carbopol.

8. A vinyl acetate-ethylene emulsion prepared by the preparation method according to any one of claims 4-7.

9. A vinyl acetate-ethylene emulsion film, characterized in that, the vinyl acetate-ethylene emulsion film is obtained by drying the vinyl acetate-ethylene emulsion according to any one of claims 1-3 and 8.

10. The vinyl acetate-ethylene emulsion film according to claim 9, wherein, the thickness of the vinyl acetate-ethylene emulsion film is 0.05-0.3 mm, preferably 0.08-0.15 mm; Preferably, the yellowing index of the vinyl acetate-ethylene emulsion film is ≤15, preferably ≤13; Preferably, the drying conditions include: the drying temperature is 5-200°C, preferably 80-180°C; the drying time is 1-60 min, preferably 2-10 min.