Method for relieving film-forming yellowing of vinyl acetate-ethylene copolymer emulsion

Abstract

The invention discloses a method for relieving film-forming yellowing of vinyl acetate-ethylene copolymer emulsion. The method comprises the step of adding a chelating agent into the vinyl acetate-ethylene copolymer emulsion subjected to polymerization reaction for treatment. According to the invention, the problem of yellowing of a polymer film is solved, and the polymerization reaction and the production efficiency are not influenced.

Description

Technical Field

[0001] The invention relates to a vinyl acetate-ethylene copolymer emulsion, and in particular to a method for reducing film yellowing of the vinyl acetate-ethylene copolymer emulsion. Background Art

[0002] Vinyl acetate-ethylene copolymer emulsion (VAE emulsion) has good low-temperature film-forming properties, flexibility and adhesion, and is widely used in construction (including latex powder, waterproof coatings, interior wall coatings), adhesives (including packaging, woodworking, cigarette adhesives), textiles (including material composites, printing, carpets, non-woven fabrics, coatings, etc.) and other fields.

[0003] When VAE emulsion is used in the textile field, it is generally necessary to subject the composite material to high temperature setting. Some VAE emulsions with special formulas are prone to yellowing or even browning during the high-temperature film-forming process. If the color of the composite adhesive material is very light, it will seriously affect the appearance and quality of the textile. Therefore, the yellowing resistance of VAE emulsion is very important.

[0004] Chinese patent document CN112708002A discloses a vinyl acetate-ethylene copolymer emulsion having excellent compatibility with cement at high temperature, which is prepared from raw materials including monomers, an initiator system, an emulsifying system, water, a pH regulator, a buffer and a post-processing aid.

[0005] Chinese patent document CN104892831A discloses a styrene acrylic emulsion for sponge and cloth composite and a preparation method thereof. The styrene acrylic emulsion is emulsified with an anionic emulsifier, and an excessive amount of carboxyl-containing material is added to the system to achieve the purpose of reducing the emulsion particle size and alkali thickening to form a paste-like translucent emulsion; an amide-containing material is added to the system, and hot pressing and curing self-crosslinking is performed, and adding a hydroxyl-containing material can crosslink with the carboxyl group by hot pressing and curing, and the polymer film has high strength; a hydrogen peroxide-tartaric acid initiation system is used, and the polymer film is resistant to yellowing.

[0006] The prior art has the following deficiencies: the prior art method is to solve the problem of yellowing of polymer film by using functional additives, emulsifiers and initiators in the polymerization reaction system; however, the problem of yellowing of polymer film solved by this method, the addition of functional additives will have an adverse effect on the polymerization reaction and production efficiency of the emulsion. Summary of the invention

[0007] The invention provides a method for alleviating the yellowing of vinyl acetate-ethylene copolymer emulsion film, which solves the problem of yellowing of polymer film and does not affect polymerization reaction and production efficiency.

[0008] To achieve the above object, the technical solution of the present invention is: On the one hand, the present invention provides a method for reducing the yellowing of vinyl acetate-ethylene copolymer emulsion film, comprising adding a chelating agent to the vinyl acetate-ethylene copolymer emulsion after polymerization for treatment.

[0009] Furthermore, a chelating agent is added to the defoamed vinyl acetate-ethylene copolymer emulsion for treatment.

[0010] Furthermore, a chelating agent is added to the vinyl acetate-ethylene copolymer emulsion after the degassing and the addition of the post-treatment auxiliary agent for reaction for treatment.

[0011] Furthermore, the content of the chelating agent is 0.06%-0.08% of the content of the vinyl acetate-ethylene copolymer emulsion, calculated by mass.

[0012] Furthermore, the chelating agent is citric acid or ethylenediaminetetraacetic acid.

[0013] Furthermore, the chelating agent is citric acid.

[0014] Furthermore, the film-forming yellowness index YI of the vinyl acetate-ethylene copolymer emulsion is 11-13.23.

[0015] Furthermore, it also includes post-treatment with a pH regulator, a defoaming agent and a bactericide.

[0016] Furthermore, the content of the defoamer is 0.1%-0.16% of the content of the vinyl acetate-ethylene copolymer emulsion, and the content of the bactericide is 0.1%-0.4% of the content of the vinyl acetate-ethylene copolymer emulsion, both in parts by mass.

[0017] Furthermore, the method comprises the following steps: adding a chelating agent to the vinyl acetate-ethylene copolymer emulsion after the reaction of adding a post-treatment auxiliary agent after degassing, stirring evenly, controlling the temperature at 20°C-40°C, and then adding a pH regulator, a defoaming agent and a bactericide.

[0018] The present invention has the following beneficial effects.

[0019] 1) In the present invention, the chelating agent is added after the post-treatment of the VAE emulsion is completed, which does not change the polymerization reaction system itself and does not affect the polymerization reaction and production efficiency.

[0020] 2) The method used in the present invention can significantly reduce the yellowing of VAE emulsion during film formation without affecting the production cost and quality performance of VAE products. DETAILED DESCRIPTION

[0021] The examples are provided to better illustrate the content of the present invention, but the content of the present invention is not limited to the examples. Therefore, those skilled in the art can make non-essential improvements and adjustments to the implementation scheme according to the above content of the invention, which still fall within the protection scope of the present invention.

[0022] The pH regulator added in the present invention is not specifically limited, and is a conventional pH regulator, including sodium hydroxide, bicarbonate, acetate or dihydrogen phosphate; preferably sodium hydroxide.

[0023] The defoaming agent is selected from at least one of mineral oil, polyether, amide, silicone, alcohol, and fatty acid defoaming agents; preferably, mineral oil.

[0024] The fungicide is isothiazolinone, benzisothiazolinone, bronopol, preferably isothiazolinone.

[0025] Detection method: Referring to "GB / T39294-2020 Determination of discoloration (yellowing) properties of adhesives", a self-developed yellowness index test method for VAE films was developed. Example

[0026] The specific preparation steps of the present invention are as follows, wherein the parts or percentages mentioned are all parts by mass or percentage by mass; A. Raw material preparation Prepare oxidant solution: add oxidant and water into oxidant tank and stir to dissolve; Prepare reducing agent solution: add reducing agent and water into reducing agent tank and stir to dissolve; Prepare protective colloid solution: add water and protective colloid into the dissolving tank in sequence under stirring, heat to 80-95℃ and dissolve for 60-120min, then cool to 30-60℃ for standby use; Preparation of post-treatment additives: adding oxidant and water into a post-treatment oxidant tank, stirring and dissolving; adding reductant and water into a post-treatment reductant tank, stirring and dissolving; B. Feed production Under stirring, add water, protective colloid solution and emulsifier, stir evenly and add 42-52 parts of vinyl acetate monomer, raise the temperature and pressure. When the temperature reaches 52-54°C and the pressure reaches 3.2-3.6MPa, add oxidant and reductant at the same time. When the temperature reaches 80-85°C and the ethylene pressure rises to 5-6MPa, add 34-64 parts of vinyl acetate monomer within 60-150 minutes, and continuously add initiator at a rate of 0.5×10 -4 -3.0×10 -4After the monomer addition is completed, the finishing period begins; after degassing, the post-treatment additives are continuously added within 30-60 minutes; the chelating agent is added, and then the pH regulator and bactericide are added after cooling, and the material is discharged, filtered, and packaged; C. Yellowness index of emulsion film test A VAE emulsion film was prepared on a clean glass plate using a 0.1 mm wet film preparation device, and was placed in a forced air drying oven set at 180°C-190°C for 10 minutes before being taken out. After cooling, the film was removed for a yellowness index test of the VAE film.

[0027] The "post-treatment of the degassing tank" described in Examples 1-3 and Comparative Examples 1-3 of the present invention means: after degassing, the post-treatment additive is continuously added within 30-60 minutes for reaction; Example 1.

[0028] After the VAE emulsion is processed in the degassing tank, 0.06 kg of citric acid is added to every 100 kg of emulsion under stirring; after cooling, 60 g of sodium hydroxide, 130 g of DF-691 defoamer, 250 g of Kasson, etc. are added, and the material is discharged, filtered, and packaged; Example 2.

[0029] After the VAE emulsion is processed in the degassing tank, 0.07 kg of citric acid is added to every 100 kg of emulsion under stirring; after cooling, 60 g of sodium hydroxide, 100 g of DF-691 defoamer, 100 g of Kasson, etc. are added, and the material is discharged, filtered, and packaged; Example 3.

[0030] After the VAE emulsion is processed in the degassing tank, 0.08 kg of citric acid is added to every 100 kg of emulsion under stirring; after cooling, 60 g of sodium hydroxide, 160 g of DF-691 defoamer, 400 g of Kasson, etc. are added, and the material is discharged, filtered, and packaged; Comparative example 1.

[0031] After the VAE emulsion is processed in the degassing tank, citric acid is not added; after cooling, 60g sodium hydroxide, 130g DF-691 defoamer, 250g Kasson, etc. are added, and the material is discharged, filtered, and packaged; Comparative example 2.

[0032] After the VAE emulsion is processed in the degassing tank, 0.03 kg of citric acid is added to every 100 kg of emulsion under stirring; after cooling, 60 g of sodium hydroxide, 100 g of DF-691 defoamer, 100 g of Kasson, etc. are added, and the material is discharged, filtered, and packaged; Comparative example 3.

[0033] After the VAE emulsion is processed in the degassing tank, 0.1 kg of citric acid is added to every 100 kg of emulsion under stirring; after cooling, 60 g of sodium hydroxide, 130 g of DF-691 defoamer, 100 g of Kasson, etc. are added, and the material is discharged, filtered and packaged.

[0034] VAE emulsions were prepared by the methods of Examples 1-3 and Comparative Examples 1-3. The yellowness index of the emulsion film test is shown in Table 1: Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yellow Index YI 11.35 11.16 13.23 42.67 22.82 20.59 As can be seen from Table 1, the yellowness index of the VAE emulsion film obtained by the emulsion film prepared in Examples 1-3 of the present invention is 11.16-13.23; the yellowness index of the VAE emulsion film obtained by the emulsion film prepared in Comparative Examples 1-3 is 20.59-42.67, and the yellowness index of the VAE emulsion film obtained by the emulsion film prepared in Examples 1-3 of the present invention is significantly reduced by 1.55-3.82 times compared with Comparative Examples 1-3; thus, it is proved that the method used in the present invention can not only significantly reduce the yellowing of the VAE emulsion in the film-forming process, but also does not affect the production cost and quality performance of the VAE product.

[0035] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film, characterized in that: A chelating agent is added to the vinyl acetate-ethylene copolymer emulsion after the polymerization reaction for treatment.

2. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to claim 1, characterized in that: A chelating agent is added to the defoamed vinyl acetate-ethylene copolymer emulsion for treatment.

3. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to claim 2, characterized in that: A chelating agent is added to the vinyl acetate-ethylene copolymer emulsion after degassing and adding a post-treatment auxiliary agent for reaction for treatment.

4. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to any one of claims 1 to 3, characterized in that: The content of the chelating agent is 0.06%-0.08% of the content of the vinyl acetate-ethylene copolymer emulsion, calculated by mass.

5. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to any one of claims 1 to 4, characterized in that: The chelating agent is citric acid or ethylenediaminetetraacetic acid.

6. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to claim 5, characterized in that: The chelating agent is citric acid.

7. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to any one of claims 1 to 6, characterized in that: The film-forming yellowness index YI of the vinyl acetate-ethylene copolymer emulsion is 11-13.

23.

8. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to any one of claims 1 to 7, characterized in that: Post-treatment with pH adjusters, defoamers and bactericides is also included.

9. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to claim 8, characterized in that: The content of the defoamer is 0.1%-0.16% of the content of the vinyl acetate-ethylene copolymer emulsion, and the content of the bactericide is 0.1%-0.4% of the content of the vinyl acetate-ethylene copolymer emulsion, both in parts by mass.

10. The method for reducing yellowing of vinyl acetate-ethylene copolymer emulsion film according to any one of claims 1 to 9, characterized in that: The following steps are involved: After degassing and adding post-treatment additives, the chelating agent is added to the vinyl acetate-ethylene copolymer emulsion after the reaction, and the mixture is stirred evenly. The temperature is controlled at 20° C.-40° C., and then a pH regulator, a defoaming agent and a bactericide are added.