Preparation method and application of waterborne acrylic emulsion for glove coating

Abstract

The invention discloses a preparation method of a water-based acrylic emulsion for a glove coating. The preparation method comprises the following steps: preparing a pre-emulsion; adding an initiator into the pre-mixing system; adding a small part of the pre-emulsion; dropwise adding the residual pre-emulsion and an aqueous solution of an initiator II at the same time, and carrying out heat-preservation reaction; cooling and adjusting the pH value; and continuously cooling, adding a functional crosslinking reagent aqueous solution, stirring and discharging. According to the invention, the initiator is firstly added into the pre-mixing system, and then the pre-emulsion is added, so that the reaction process does not release heat violently, the emulsion particles are uniformly dispersed, the formed emulsion particles are uniform in size, and the formed acrylic emulsion coating can provide excellent smoothness for the PVC gloves. And the coating is excellent in water resistance, high in crosslinking density and relatively good in stability, can form a film at a low temperature, and is lower in cost compared with a polyurethane emulsion.

Description

Technical Field

[0001] The invention relates to the field of coatings, and in particular to a method for preparing a water-based acrylic emulsion for glove coatings and an application field thereof. Background Art

[0002] Disposable PVC gloves are widely used in medical examinations, laboratories, electronic product processing, and the food industry. Currently, the inner coating of PVC gloves is mostly polyurethane emulsion, which has a high cost and is generally sold at more than 20 yuan / kg. In order to reduce production costs, a new type of inner coating for gloves is urgently needed. Existing glove coatings that use acrylic emulsions instead of polyurethane emulsions have poor water resistance and poor slippery feeling when putting on and taking off. Therefore, it is very important to develop a low-cost acrylic emulsion that has good water resistance, excellent slippery feeling, and can form a film at low temperature.

[0003] Chinese invention patent CN105332287A discloses a coating resin and preparation method for high-temperature resistant, high-adhesion, wet-hand-wearable PVC gloves. Dehydrated polyol and isocyanate are added to a container for reaction to obtain a polyurethane prepolymer, the prepolymer is neutralized with an amine, and water is added to emulsify to obtain an aqueous polyurethane emulsion, which is applied to the PVC gloves. The coating resin has the characteristics of no irritation, high adhesion, high temperature resistance, water resistance, and excellent slippery performance, but the production cost of the polyurethane emulsion is relatively high. Chinese invention patent CN112063283A discloses a preparation method for a powder-free water-based coating of polyvinyl chloride gloves, which is composed of a water-based hydroxy acrylic resin, a wetting agent, a leveling agent, a film-forming aid, a thickener, deionized water, a defoamer, a filler, and a water-based isocyanate curing agent. The water-based hydroxy acrylic coating with less VOC emissions is used to replace the existing talcum powder and starch coating, avoiding the problem of easy adhesion of polyvinyl chloride gloves during use, but the obtained slipperiness and water resistance are not as good as the powder-containing coating. Summary of the invention

[0004] In order to develop a low-cost acrylic emulsion with good water resistance, excellent smoothness and low-temperature film formation, the first aspect of the present invention provides a method for preparing an aqueous acrylic emulsion for glove coating, comprising the following steps:

[0005] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0006] S2: uniformly mix the emulsifier II, the initiator I, the buffer and water to obtain a premixed system;

[0007] S3: 0.5-1 wt% of the total mass of the pre-emulsion is slowly added dropwise to the pre-mixed system and reacted for 5-15 minutes;

[0008] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the addition time is 1-3 hours;

[0009] After the addition of S5 is completed, the reaction is kept warm for 1-2 hours;

[0010] S6: Cool down after the heat preservation, and adjust the pH with ammonia water;

[0011] S7: After adjusting the pH, continue to cool down, add the functional cross-linking reagent aqueous solution to the reaction system, stir for 5-15 minutes and then discharge the material.

[0012] As a preferred embodiment, the method for preparing the aqueous acrylic emulsion for the glove coating comprises the following steps:

[0013] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0014] S2: uniformly mix the emulsifier II, the initiator I, the buffer and water to obtain a premixed system;

[0015] S3: Take 0.5-1wt% of the total mass of the pre-emulsion and slowly add it dropwise into the pre-mixed system. After the system emits a slight blue light, keep the temperature and react for 10 minutes.

[0016] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the addition time is 2 hours;

[0017] After the addition of S5 is completed, the reaction is kept warm for 1 h;

[0018] S6: Cool down after the heat preservation, and adjust the pH with ammonia water;

[0019] S7: After adjusting the pH, continue to cool down, add the functional cross-linking reagent aqueous solution to the reaction system, stir for 10 minutes and then discharge the material.

[0020] As a preferred embodiment, the heat preservation reaction is to maintain the reaction system in a water bath heated to 80-90° C. Preferably, the heat preservation reaction is to maintain the reaction system in a water bath heated to 85° C.

[0021] As a preferred embodiment, the speed of slow dripping in step S3 is 1-3 g / 10 min.

[0022] As a preferred embodiment, the slow dripping speed in step S3 is 1-2 g / 10 min.

[0023] As a preferred embodiment, the slow dripping speed in step S3 is 1 g / 10 min.

[0024] As a preferred embodiment, the mass concentration of initiator I in the premixed system of step S2 is 0.1-0.3%, and the mass concentration of the initiator II aqueous solution is 1-3%.

[0025] As a preferred embodiment, the mass concentration of initiator I in the premixed system of step S2 is 0.199%, and the mass concentration of the initiator II aqueous solution is 2%.

[0026] The inventors found during the experiment that in the process of preparing acrylic emulsion, the initiator is first added to the premixed system and then the pre-emulsion is added. There will be no severe heat release during the reaction, the emulsion particles are evenly dispersed, the size of the formed emulsion particles is uniform, and the formed acrylic emulsion coating can provide excellent slippery properties for PVC gloves. If the pre-emulsion is added first and then the initiator is added, the reactions will occur simultaneously, the system will show obvious heat release, the size of the formed emulsion particles is inconsistent, and the slippery effect cannot be achieved inside the PVC gloves.

[0027] As a preferred embodiment, during the dropping process of step S4, when the dropping is continued for 1-2 hours, a monomer mixture of a diacetone acrylamide aqueous solution and a methacrylic acid monomer is added dropwise to the pre-emulsion, and the mixture is continued to be dropped after being stirred evenly.

[0028] As a preferred embodiment, the mass concentration of the diacetone acrylamide aqueous solution is 0.1-0.2%, and the mass concentration of the methacrylic acid monomer in the monomer mixture is 15-25%.

[0029] As a preferred embodiment, the mass concentration of the diacetone acrylamide aqueous solution is 0.1%, and the mass concentration of the methacrylic acid monomer in the monomer mixture is 18.18%.

[0030] The inventors further discovered during the experiment that adding diacetone acrylamide solution and methacrylic acid simultaneously during the preparation of acrylic emulsion can improve the water resistance of the emulsion. The reason may be that adding diacetone acrylamide solution and methacrylic acid simultaneously can create an acidic reaction system, enhance the cross-linking density between chain segments from the molecular structure, enhance the cross-linking degree of the emulsion, and thus improve the water resistance of the acrylic emulsion.

[0031] As a preferred embodiment, the temperature of step S6 is 40-50° C. and the pH value is 7-8.

[0032] As a preferred embodiment, the temperature of step S6 is 45° C. and the pH value is 7.5.

[0033] As a preferred embodiment, the temperature of step S7 is 20-40° C., and the mass ratio of the functional cross-linking reagent to water in the functional cross-linking reagent aqueous solution is 1:(1-2).

[0034] As a preferred embodiment, the temperature of step S7 is 30° C., and the mass ratio of the functional cross-linking reagent to water in the functional cross-linking reagent aqueous solution is 1:1.

[0035] As a preferred embodiment, the functional cross-linking reagent aqueous solution is adipic acid dihydrazide aqueous solution.

[0036] The inventors first lowered the temperature and then added adipic acid dihydrazide in the later stage of preparing the acrylic emulsion, which can increase the crosslinking density while achieving good stability, low gel rate, and good practicality. The reason may be that lowering the temperature before adding adipic acid dihydrazide can reduce the intensity of the reaction, and the added adipic acid dihydrazide can be secondary crosslinked with the formed preliminary polymer, further increasing the crosslinking degree of the molecular structure, reducing the gel rate, and having good practicality.

[0037] As a preferred embodiment, the acrylic monomer composition includes methyl methacrylate, butyl acrylate, methacrylic acid, acrylamide and water; the mass ratio of methyl methacrylate, butyl acrylate, methacrylic acid, acrylamide and water is (40-60): (20-40): (1-3): (0.1-1): (40-60).

[0038] As a preferred embodiment, the mass ratio of methyl methacrylate, butyl acrylate, methacrylic acid, acrylamide and water is 50:30:1:0.5:50.

[0039] As a preferred embodiment, the emulsifier I and the emulsifier II both include one or a combination of two of anionic surfactants and / or nonionic surfactants.

[0040] As a preferred embodiment, the emulsifier I and the emulsifier II are both a combination of sodium lauryl sulfate and polyoxyethylene ether OP-10.

[0041] As a preferred embodiment, the weight ratio of sodium lauryl sulfate to polyoxyethylene ether OP-10 in the emulsifier I is (0.3-0.8):1; preferably, the weight ratio of sodium lauryl sulfate to polyoxyethylene ether OP-10 is 0.5:1.

[0042] As a preferred embodiment, the weight ratio of sodium lauryl sulfate to polyoxyethylene ether OP-10 in the emulsifier II is 0.1:(0.1-0.3); preferably, the weight ratio of sodium lauryl sulfate to polyoxyethylene ether OP-10 is 0.1:0.2.

[0043] As a preferred embodiment, the buffer is sodium bicarbonate. The initiator I and initiator II are both ammonium persulfate.

[0044] The second aspect of the present invention provides an application of a method for preparing an aqueous acrylic emulsion for a glove coating, wherein the prepared aqueous acrylic emulsion is applied to an inner coating of a powder-free PVC glove.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The aqueous acrylic emulsion of the glove coating of the present invention is prepared by first adding an initiator to a premixed system and then adding the pre-emulsion. During the reaction, no intense heat is released, the emulsion particles are evenly dispersed, and the formed emulsion particles have uniform size. The formed acrylic emulsion coating can provide excellent slipperiness for PVC gloves.

[0047] (2) The aqueous acrylic emulsion of the glove coating of the present invention can improve the water resistance of the emulsion by adding diacetone acrylamide solution and methacrylic acid simultaneously during the preparation of the acrylic emulsion. The coating has excellent adhesion to the gloves after being immersed in water at 70° C. for 1 hour.

[0048] (3) The aqueous acrylic emulsion of the glove coating of the present invention is cooled down in the later stage of preparing the acrylic emulsion and then adipic acid dihydrazide solution is added, so that the cross-linking density can be increased while having good stability, low gel fraction and good practicality.

[0049] (4) The aqueous acrylic emulsion of the glove coating of the present invention has a glass transition temperature of 25°C and can form a film at low temperature.

[0050] (5) The aqueous acrylic emulsion of the glove coating of the present invention achieves excellent gloss effect through seed emulsion polymerization, and has excellent stability and no stratification during centrifugation. Compared with polyurethane emulsion, it has lower cost and is more conducive to large-scale and extensive application in multiple industries. DETAILED DESCRIPTION

[0051] Example 1

[0052] A method for preparing an aqueous acrylic emulsion for glove coatings comprises the following steps:

[0053] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0054] S2: uniformly mix emulsifier II, 0.4 g initiator I, 0.3 g buffer, and 200 g water to obtain a premixed system;

[0055] S3 Take 1g of pre-emulsion and slowly add it dropwise into the pre-mixed system for 10 minutes. After the system emits a slight blue light, keep the temperature and react for 10 minutes.

[0056] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the dropping time is 2 hours. During the dropping process, when the dropping reaches 1 hour, a monomer mixture of a diacetone acrylamide aqueous solution and 1g of methacrylic acid monomer is added to the pre-emulsion, and the mixture is stirred evenly before continuing to dropwise;

[0057] After the addition of S5 is completed, the reaction is kept warm for 1 h;

[0058] S6: Cool down after the heat preservation, and adjust the pH with ammonia water;

[0059] S7: After adjusting the pH, continue to cool down, add 0.5 g of functional cross-linking reagent aqueous solution to the reaction system, stir for 10 minutes and then discharge the material.

[0060] The acrylic monomer composition includes 50 g of methyl methacrylate, 30 g of butyl acrylate, 1 g of methacrylic acid, 0.5 g of acrylamide, and 50 g of water.

[0061] The emulsifier I includes 0.5 g of sodium dodecyl sulfate and 1 g of polyoxyethylene ether, wherein the polyoxyethylene ether is OP-10 purchased from Sinopharm Chemical Reagent Co., Ltd.

[0062] The emulsifier II includes 0.1 g of sodium dodecyl sulfate and 0.2 g of polyoxyethylene ether, wherein the polyoxyethylene ether is OP-10 purchased from Sinopharm Chemical Reagent Co., Ltd.

[0063] The initiator I is ammonium persulfate. The buffer is sodium bicarbonate.

[0064] The initiator II aqueous solution includes 0.4 g of ammonium persulfate and 20 g of water.

[0065] The diacetone acrylamide aqueous solution includes 0.5 g of diacetone acrylamide and 5 g of water.

[0066] The temperature of step S6 is 45° C. and the pH value is 7.5.

[0067] The temperature of step S7 is 30° C., and the functional cross-linking reagent aqueous solution is adipic acid dihydrazide aqueous solution, including 0.25 g of adipic acid dihydrazide and 0.25 g of water.

[0068] Comparative Example 1

[0069] A method for preparing an aqueous acrylic emulsion for glove coatings comprises the following steps:

[0070] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0071] S2: uniformly mix emulsifier II, 0.3 g buffer, and 200 g water to obtain a premixed system;

[0072] S3 Take 1g of pre-emulsion and slowly drop it into the pre-mixed system for 10 minutes. After mixing evenly, add 0.4g of initiator I. After the system temperature starts to drop, proceed to the next step.

[0073] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the dropping time is 2 hours. During the dropping process, when the dropping reaches 1 hour, a monomer mixture of a diacetone acrylamide aqueous solution and 1g of methacrylic acid monomer is added to the pre-emulsion, and the mixture is stirred evenly before continuing to dropwise;

[0074] After the addition of S5 is completed, the reaction is kept warm for 1 h;

[0075] S6: Cool down after the heat preservation, and adjust the pH with ammonia water;

[0076] S7: After adjusting the pH, continue to cool down, add 0.5 g of functional cross-linking reagent aqueous solution to the reaction system, stir for 10 minutes and then discharge the material.

[0077] The rest of the implementation is the same as Example 1.

[0078] Comparative Example 2

[0079] A method for preparing an aqueous acrylic emulsion for glove coatings comprises the following steps:

[0080] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0081] S2: uniformly mix emulsifier II, 0.4 g initiator I, 0.3 g buffer, and 200 g water to obtain a premixed system;

[0082] S3 Take 1g of pre-emulsion and slowly add it dropwise into the pre-mixed system for 10 minutes. After the system emits a slight blue light, keep the temperature and react for 10 minutes.

[0083] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time. The addition time is 2 hours. During the addition process, when the addition reaches 1 hour, the aqueous solution of diacetone acrylamide is added to the pre-emulsion, and the mixture is stirred evenly before continuing to be added dropwise.

[0084] After the addition of S5 is completed, the reaction is kept warm for 1 h;

[0085] S6: Cool down after the heat preservation, and adjust the pH with ammonia water;

[0086] S7: After adjusting the pH, continue to cool down, add 0.5 g of functional cross-linking reagent aqueous solution to the reaction system, stir for 10 minutes and then discharge the material.

[0087] The rest of the implementation is the same as Example 1.

[0088] Comparative Example 3

[0089] A method for preparing an aqueous acrylic emulsion for glove coatings comprises the following steps:

[0090] S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion;

[0091] S2: uniformly mix emulsifier II, 0.4 g initiator I, 0.3 g buffer, and 200 g water to obtain a premixed system;

[0092] S3 Take 1g of pre-emulsion and slowly add it dropwise into the pre-mixed system for 10 minutes. After the system emits a slight blue light, keep the temperature and react for 10 minutes.

[0093] S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the dropping time is 2 hours. During the dropping process, when the dropping reaches 1 hour, a monomer mixture of a diacetone acrylamide aqueous solution and 1g of methacrylic acid monomer is added to the pre-emulsion, and the mixture is stirred evenly before continuing to dropwise;

[0094] After the addition of S5 is completed, the reaction is kept warm for 1 h;

[0095] After the S6 heat preservation is completed, 0.5 g of functional cross-linking reagent aqueous solution is added to the reaction system and stirred for 10 min;

[0096] S7 is cooled to 45°C, and the pH is adjusted to 7.5 with aqueous ammonia before discharging the material.

[0097] In step S6, the temperature is not lowered.

[0098] The rest of the implementation is the same as Example 1.

[0099] Performance Testing

[0100] 1. Gel rate: The aqueous acrylic emulsions prepared in Example 1 and Comparative Examples 1-3 were passed through a 200-mesh sieve. Gel rate = (mass of material on the sieve / total mass) × 100%

[0101] 2. Centrifugal stability: The aqueous acrylic emulsions prepared in Example 1 and Comparative Examples 1-3 were centrifuged at 3000 rpm for 15 min, the stratification was observed, and the height of the sediment at the bottom of a 10 mL flat-top centrifuge tube was measured. The inner diameter of the centrifuge tube was 16 mm.

[0102] 3. Particle size: The latex was diluted with distilled water at a ratio of 1:10, and then the particle size of the diluted acrylic emulsion was tested and analyzed using a Malvern Nano Particle Size Analyzer (ZS Nano S produced by Malvern Instruments Ltd., UK) at room temperature.

[0103] The emulsion particle sizes of the aqueous acrylic emulsions prepared in Example 1 and Comparative Examples 1-3 were measured using the method.

[0104] 4. Water resistance: The aqueous acrylic emulsions prepared in Example 1 and Comparative Examples 1-3 were coated on a glass substrate, dried and cured at 60° C. for 4 h to form a film, and then immersed in 70° C. water for 1 h to observe the film surface.

[0105] 5. Glossiness: The glossiness of the film surfaces of the aqueous acrylic emulsions prepared in Example 1 and Comparative Examples 1-3 was tested using a gloss meter.

[0106] 7. Friction coefficient: Use a friction coefficient meter to test the friction coefficient between two film surfaces.

[0107] 8. Glass transition temperature: In the temperature range of -20℃~100℃, at a heating rate of 10K / min, in N 2 Under protection, the glass transition temperature was tested.

[0108] The test results are shown in Table 1.

[0109] Table 1

[0110]

Claims

1. A method for preparing an aqueous acrylic emulsion for glove coating, characterized in that: The following steps are involved: S1: uniformly dispersing the acrylic monomer composition and the emulsifier I to obtain a pre-emulsion; S2: uniformly mix the emulsifier II, the initiator I, the buffer and water to obtain a premixed system; S3: 0.5-1 wt% of the total mass of the pre-emulsion is slowly added dropwise to the pre-mixed system and reacted for 5-15 minutes; S4 After the reaction in step S3, the remaining pre-emulsion and the aqueous solution of initiator II are added dropwise at the same time, and the addition time is 1-3 hours; After the addition of S5 is completed, the reaction is kept warm for 1-2 hours; S6: Cool down after the heat preservation, and adjust the pH with ammonia water; S7: After adjusting the pH, continue to cool down, add the functional cross-linking reagent aqueous solution to the reaction system, stir for 5-15 minutes and then discharge the material.

2. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: The speed of slow dripping in step S3 is 1-3 g / 10 min.

3. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: The mass concentration of the initiator I in the premixed system of step S2 is 0.1-0.3%, and the mass concentration of the initiator II aqueous solution is 1-3%.

4. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: During the dropping process of step S4, when the dropping is continued for 1-2 hours, a monomer mixture of a diacetone acrylamide aqueous solution and a methacrylic acid monomer is dropped into the pre-emulsion, and the mixture is continued to be dropped after being stirred evenly.

5. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 4, characterized in that: The mass concentration of the diacetone acrylamide aqueous solution is 0.1-0.2%, and the mass concentration of the methacrylic acid monomer in the monomer mixture is 15-25%.

6. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 4, characterized in that: The temperature of step S6 is 40-50° C., and the pH value is 7-8.

7. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: The temperature of step S7 is 20-40° C., and the mass ratio of the functional cross-linking reagent to water in the functional cross-linking reagent aqueous solution is 1:(1-2).

8. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: The acrylic monomer composition comprises methyl methacrylate, butyl acrylate, methacrylic acid, acrylamide and water; the mass ratio of the methyl methacrylate, butyl acrylate, methacrylic acid, acrylamide and water is (40-60): (20-40): (1-3): (0.1-1): (40-60).

9. The method for preparing the aqueous acrylic emulsion for glove coating according to claim 1, characterized in that: The emulsifier I and the emulsifier II both include one or a combination of anionic surfactants and / or nonionic surfactants.

10. An application of the method for preparing the aqueous acrylic emulsion for glove coating according to any one of claims 1 to 9, characterized in that: The prepared water-based acrylic emulsion was applied in the inner coating of powder-free PVC gloves.

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