Modified VAE emulsion and preparation method thereof

Abstract

The invention discloses a modified VAE emulsion and a preparation method thereof, the modified VAE emulsion comprises the following raw material components: a reaction monomer, an initiator, an emulsifier and a protective colloid, the reaction monomer comprises vinyl acetate and ethylene, and the modified VAE emulsion also comprises vinyloxy alkyl polypropylene glycol as a functional comonomer. Vinyloxy alkyl polypropylene glycol is used as a functional comonomer, the usage amount is small, the reaction pressure is low, the glass transition temperature of the VAE emulsion can be effectively reduced, when the modified VAE emulsion is used for preparing a JS waterproof coating, the usage of an external plasticizer can be avoided, the phenomena of hardening and aging of a coating film are improved, and the performance of the JS waterproof coating is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of vinyl acetate-ethylene copolymer emulsions, and specifically relates to a modified VAE emulsion and a preparation method thereof. Background Art

[0002] VAE emulsion is a polymer dispersion commonly used in polymer cement waterproof coatings (JS waterproof coatings). It is a high molecular emulsion made from vinyl acetate and ethylene monomers as basic raw materials and other auxiliary materials through high-pressure emulsion polymerization.

[0003] JS waterproof coatings prepared with existing VAE emulsions usually have the following shortcomings: large polymer-cement ratio (i.e. large amount of polymer) but low elasticity, usually liquid-to-powder ratio of 10:7 (polymer-cement ratio = 1-2), elongation of only 150%-200%; coating film softens significantly after long-term immersion in water, strength decreases; weak UV resistance and poor weather resistance, some products become hard and elongation decreases after two or three years of exposure on the roof. Therefore, it is necessary to modify conventional VAE emulsions to improve the performance of VAE emulsion-based JS waterproof coatings.

[0004] In the formulation design of JS waterproof coatings, in order to achieve better flexibility and qualified elongation, a certain amount of plasticizer must be added in many cases. Plasticizers will migrate over time, causing the polymer coating to harden and age, and the greater the amount of plasticizer used, the more obvious this phenomenon is. If the glass transition temperature of the VAE emulsion itself is low, the amount of plasticizer can be reduced relative to the emulsion with a high glass transition temperature. To reduce the glass transition temperature of the VAE emulsion, the first method is to increase the ethylene content as much as possible, but due to the pressure of the polymerization reactor and the key core process control of the polymerization reaction, the ethylene content of the VAE emulsion produced under the existing conditions is generally less than 20%, and the glass transition temperature is 0°C, which cannot meet the use requirements. Another method is to introduce functional flexible monomers, which can not only reduce the glass transition temperature of the VAE emulsion, but also avoid the problem of plasticizer migration over time.

[0005] Therefore, it is of great significance to explore suitable functional flexible monomers to prepare modified VAE emulsions in order to reduce the glass transition temperature of VAE emulsions used in JS waterproof coatings. Summary of the invention

[0006] In view of the problems existing in the existing VAE emulsion, the present invention provides a modified VAE emulsion and a preparation method thereof, aiming to reduce the glass transition temperature of the VAE emulsion.

[0007] To achieve the purpose, the present invention adopts the following technical solution:

[0008] The invention firstly discloses a modified VAE emulsion, the raw material components of which include reaction monomers, initiators, emulsifiers and protective colloids. The reaction monomers include vinyl acetate and ethylene, and also include ethyleneoxyalkyl polypropylene glycol as a functional comonomer.

[0009] Furthermore, the initiator comprises an oxidant and a reductant. The oxidant is at least one of ammonium persulfate, potassium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide, and the reductant is one of zinc formaldehyde sulfoxylate, sodium formaldehyde sulfoxylate, isoascorbic acid, and tartrate, or a combination of any two thereof.

[0010] Further, the emulsifier is a combination of anionic emulsifier and nonionic emulsifier. The anionic emulsifier is one or a combination of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium vinyl sulfonate, sodium allyl sulfonate and ethoxylated ether ammonium sulfate. The nonionic emulsifier is one or a combination of nonylphenol polyoxyethylene ether (OP-10), octylphenol polyoxyethylene ether, Span 60, Span 80, MS-1 emulsifier.

[0011] Furthermore, the protective colloid includes polyvinyl alcohol and at least one of hydroxyethyl cellulose and polyether, wherein the degree of polymerization of the polyvinyl alcohol is 200-3500 and the degree of alcoholysis is between 80% and 99%.

[0012] Furthermore, the composition of each raw material component by weight is:

[0013] Reactive monomers: 55-75 parts of vinyl acetate; 10-30 parts of ethylene; 5-40 parts of functional comonomer;

[0014] Initiator: 0.05-0.4 parts of oxidant, 0-0.2 parts of reducing agent;

[0015] Emulsifier: anionic emulsifier 0.2-1 part; nonionic emulsifier 0.5-1 part;

[0016] Protective colloid: polyvinyl alcohol 0.3-1 part; hydroxyethyl cellulose and / or polyether: 0-1 part;

[0017] pH regulator: 0.05-0.1 parts;

[0018] Deionized water: 40-90 parts.

[0019] The present invention also discloses a method for preparing the modified VAE emulsion, comprising the following steps:

[0020] Step 1: Preparation of initiator solution, protective colloid solution, emulsifier solution, mixed monomer, and pre-emulsified monomer

[0021] Preparation of initiator solution: add 0.05-0.4 parts of oxidant and 10-30 parts of deionized water into the oxidant tank, stir until completely dissolved, and obtain an oxidant solution; add 0-0.2 parts of reductant and 10-20 parts of deionized water into the reductant tank, stir until completely dissolved, and obtain a reductant solution; use 30%-50% of the oxidant solution and the reductant solution as the initial oxidant solution and the initial reductant solution respectively;

[0022] Preparation of protective colloid solution: add 0.3-1 parts of polyvinyl alcohol, 0-1 parts of hydroxyethyl cellulose and / or polyether into a protective colloid preparation tank, add 10-15 parts of deionized water, heat to 60-90°C, stir until completely dissolved, and obtain a protective colloid solution;

[0023] Preparation of emulsifier solution: add 0.2-1 part of anionic emulsifier, 0.5-1 part of nonionic emulsifier and 10-25 parts of deionized water into the emulsifier solution preparation tank, heat to 40-50°C, stir to mix evenly, and obtain emulsifier solution;

[0024] Preparation of mixed monomers: add 55-75 parts of vinyl acetate and 5-35 parts of ethyleneoxyalkyl polypropylene glycol into a mixed monomer preparation tank according to metered amounts, stir thoroughly until the mixture is uniform, and obtain a mixed monomer; use 10%-60% of the mixed monomers as initial mixed monomers, and the rest as continuous mixed monomers;

[0025] Step 2: Feeding and production

[0026] After replacing the air in the reactor with ethylene, pump all the protective colloid solution and emulsifier solution into the reactor, stir to make them fully mixed, then pump in the initial mixed monomer, and stir rapidly at a speed of 150r / min-350r / min for 30-60min; start heating, and at the same time open the ethylene control valve to charge ethylene into the system, and control the pressure in the reaction process at 2.0-6.0MPa by controlling the amount of ethylene added; when the temperature of the reactor reaches 40-50°C and the pressure rises to 2.0-4.0MPa, start adding the initial oxidant solution and the reducing agent solution in parallel; When the temperature of the reactor rises to 65-80°C, start to drop the continuous mixed monomer and the remaining oxidant solution and reducing agent solution; the feeding time of the continuous mixed monomer is 100-150min, and during the feeding process, the reaction temperature is maintained at 70-80°C and the pressure is maintained at 4.0-6.0MPa by controlling the feeding rate of the oxidant and reducing agent and the temperature of the water exchange water; after the continuous mixed monomer is added, turn off the ethylene, and continue to drop the remaining oxidant solution and reducing agent solution until they are added; when the pressure of the reactor drops below 1.5MPa, the reaction ends, and then the temperature is lowered, degassed, and filtered;

[0027] The obtained emulsion is transferred to a defoaming barrel, a defoaming agent is first added for defoaming, hydrogen peroxide or tert-butyl hydroperoxide is then added to remove residual monomers, and finally a pH regulator is added to adjust the pH of the emulsion to 4.0-6.5 to obtain a modified VAE emulsion.

[0028] The beneficial effects of the present invention are embodied in:

[0029] (1) The present invention uses ethyleneoxyalkyl polypropylene glycol as a functional comonomer, which can effectively reduce the glass transition temperature of the VAE emulsion.

[0030] (2) The use of the modified VAE emulsion of the present invention to prepare JS waterproof coatings can avoid the use of external plasticizers, improve the phenomenon of coating film hardening and aging, and effectively improve the performance of JS waterproof coatings.

[0031] (3) The product of the present invention has a simple process, is easy to realize industrial production, and has a good application prospect. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific examples, which are intended to illustrate the present invention rather than to further limit the present invention. Those skilled in the art may make non-essential improvements and adjustments to the implementation scheme based on the above invention content, which still fall within the scope of protection of the present invention.

[0033] The performance testing methods of the products obtained in the following examples are listed below:

[0034] Appearance detection method: white or slightly yellow emulsion, without coarse particles, foreign matter and sediment.

[0035] Solid content detection method: refer to GB / T 2793 "Determination of non-volatile matter content of adhesives".

[0036] Viscosity detection method: The temperature is set at 25±0.5℃, and the BROOLFIELD rotational viscometer is used with the speed set at 60r / min. The rest refers to GB / T 2794 "Determination of viscosity of adhesives - Single cylinder rotational viscometer method".

[0037] pH detection method: refer to GB / T 8325 "Measurement method for pH value of aqueous dispersions of polymers and copolymers".

[0038] Detection method of residual VAc: refer to the method specified in 6.10 of GB / T 11175 "Test methods for synthetic resin emulsions".

[0039] The particle size was measured using a MasterSizer 2000 laser particle size analyzer.

[0040] Glass transition temperature (Tg) test method: let the cured film stand for 48 hours and then use differential scanning calorimeter to test. During the test, the temperature range is set to -60℃ to 100℃ and the temperature is increased at a rate of 10℃ / min.

[0041] Example 1

[0042] This embodiment provides a modified VAE emulsion, the raw materials of which are composed of the following in parts by weight:

[0043] Reactive monomers: 60 parts of vinyl acetate; 15 parts of ethylene; 10 parts of vinyloxyalkyl polypropylene glycol;

[0044] Initiator: 0.2 parts of hydrogen peroxide, 0.1 parts of sodium formaldehyde sulfoxylate;

[0045] Emulsifier: 0.1 part of sodium lauryl sulfate, 0.1 part of sodium allyl sulfonate; 0.2 part of OP-10, 0.3 part of Span 60;

[0046] Protective colloid: 0.1 parts of PVA1788; 0.1 parts of PVA0588; 0.3 parts of PVA0488:

[0047] pH regulator: 0.06 parts of NaHCO3;

[0048] Deionized water: 60 parts in total.

[0049] The preparation method of the modified VAE emulsion of this embodiment comprises the following steps:

[0050] Step 1: Preparation of initiator solution, protective colloid solution, emulsifier solution, mixed monomer, and pre-emulsified monomer

[0051] Preparation of initiator solution: add 0.2 parts of hydrogen peroxide and 15 parts of deionized water to the oxidant tank, stir until completely dissolved, to obtain an oxidant solution; add 0.1 parts of sodium formaldehyde sulfoxylate and 10 parts of deionized water to the reductant tank, stir until completely dissolved, to obtain a reductant solution. 30% of the oxidant solution and the reductant solution are used as the initial oxidant solution and the initial reductant solution, respectively.

[0052] Preparation of protective colloid solution: Add 0.1 parts of PVA1788, 0.1 parts of PVA0588 and 0.3 parts of PVA0488 into the protective colloid preparation tank, then add 10 parts of deionized water, heat to 85°C, stir until completely dissolved, and obtain a protective colloid solution.

[0053] Preparation of emulsifier solution: Add 0.1 parts of sodium dodecyl sulfate, 0.1 parts of sodium allyl sulfonate, 0.2 parts of OP-10, 0.3 parts of Span 60 into the emulsifier solution preparation tank, then add 25 parts of deionized water, heat to 40°C, stir to fully dissolve, and obtain an emulsifier solution.

[0054] Preparation of mixed monomers: Add 60 parts of vinyl acetate and 10 parts of ethyleneoxyalkyl polypropylene glycol into a monomer preparation tank, stir thoroughly until mixed evenly, and obtain a mixed monomer. 20% of the mixed monomer is used as the initial mixed monomer, and the rest is used as the continuous mixed monomer.

[0055] Step 2: Feeding and production

[0056] After replacing the air in the reactor with ethylene, pump all the protective colloid solution and emulsifier solution into the reactor, stir to mix them thoroughly, then pump in the initial mixed monomers, and stir rapidly at 200r / min for 30min. Start heating, and open the ethylene control valve to charge ethylene into the system at the same time. By controlling the amount of ethylene added, the pressure during the reaction is controlled at 2.0-5.0MPa. When the reactor temperature reaches 40°C and the pressure rises to 2.2MPa, start adding the initial oxidant solution and the reducing agent solution in parallel. When the reactor temperature rises to 80°C, start dripping the continuous mixed monomers and the remaining oxidant solution and reducing agent solution at a certain rate, and at the same time pass ethylene to increase the pressure to 4.2MPa. The feeding time of the continuous mixed monomer is 150min. During the feeding process, the reaction temperature is maintained at 80°C and the pressure is maintained at 4.2MPa. After the continuous addition of the mixed monomers, turn off the ethylene and continue to drop the remaining oxidant solution and reducing agent solution until they are finished; the reaction is completed when the pressure of the reactor drops below 1.5 MPa, and then the temperature is lowered, degassed, and filtered.

[0057] The obtained emulsion was transferred to a defoaming barrel, and a defoaming agent was first added for defoaming, and then hydrogen peroxide was added to remove residual monomers. Finally, 0.06 parts of pH adjuster NaHCO3 was added to adjust the pH of the emulsion to 5.5 to obtain a modified VAE emulsion.

[0058] Example 2

[0059] In this example, the modified VAE emulsion was prepared according to the same formula and preparation method as in Example 1, except that the amount of ethyleneoxyalkyl polypropylene glycol used was 20 parts.

[0060] Example 3

[0061] In this example, the modified VAE emulsion was prepared according to the same formula and preparation method as in Example 1, except that the amount of ethyleneoxyalkyl polypropylene glycol used was 30 parts.

[0062] Example 4

[0063] In this example, the modified VAE emulsion was prepared according to the same formula and preparation method as in Example 1, except that the amount of ethyleneoxyalkyl polypropylene glycol used was 40 parts.

[0064] Comparative Example 1

[0065] In this comparative example, a modified VAE emulsion was prepared according to the same formula and preparation method as in Example 1, except that no functional comonomer was used, that is, the amount of ethyleneoxyalkyl polypropylene glycol used was 0.

[0066] Comparative Example 2

[0067] In this comparative example, a modified VAE emulsion was prepared according to the preparation method of Example 1, except that no ethyleneoxyalkyl polypropylene glycol functional comonomer was used, ethylene was 25 parts, and the pressure of the reaction system controlled by introducing ethylene was increased from 4.2 MPa to 7.5 MPa.

[0068] The properties of the modified VAE emulsions obtained in various examples and comparative examples are shown in Table 1.

[0069] Table 1 Test results of modified VAE emulsion performance

[0070] Detection indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Appearance White emulsion White emulsion White emulsion White emulsion White emulsion White emulsion Ethylene content 15％ 15％ 15％ 15％ 15％ 25％ Solid content / % 55.6 56.7 55.0 57.8 55.2 54.6 Viscosity / mpa·s 2600 2300 2100 1950 2570 2890 pH 5.2 5.0 5.1 5.0 4.9 5.0 Residual VAc / % 0.043 0.043 0.048 0.040 0.044 0.049 Tg / ℃(midpoint) -8.9 -15.7 -22.3 -32.0 10.5 -21

[0071] It can be seen from Table 1 that in Comparative Example 1, under the same reaction pressure, when no ethyleneoxyalkyl polypropylene glycol is added, the Tg of the product is 10.5°C. It can be clearly seen from Examples 1, 2 and 3 that under the same reaction pressure, after using ethyleneoxyalkyl polypropylene glycol as a functional comonomer, the Tg of the VAE emulsion is significantly reduced. When the addition amount of ethyleneoxyalkyl polypropylene glycol increases from 0 parts to 40 parts, the Tg of the product decreases from 10.5°C to -32.0°C, indicating that the introduction of the functional comonomer ethyleneoxyalkyl polypropylene glycol can significantly reduce the glass transition temperature of the VAE emulsion.

[0072] It can be seen from Example 3 and Comparative Example 2 that, in order to achieve a glass transition temperature below -20°C without using ethyleneoxyalkylpolypropylene glycol, the pressure of the kettle must reach 7.5 MPa, and the amount of ethylene used must be extremely large.

[0073] The above description is only an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A modified VAE emulsion, characterized in that: The raw material components include reaction monomers, initiators, emulsifiers and protective colloids; the reaction monomers include vinyl acetate and ethylene, and also include ethyleneoxyalkyl polypropylene glycol as a functional copolymer monomer.

2. The modified VAE emulsion according to claim 1, characterized in that: The initiator includes an oxidizing agent and a reducing agent.

3. The modified VAE emulsion according to claim 2, characterized in that: The oxidant is at least one of ammonium persulfate, potassium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide, and the reducing agent is one of zinc formaldehyde sulfoxylate, sodium formaldehyde sulfoxylate, isoascorbic acid, and tartrate, or a combination of any two thereof.

4. The modified VAE emulsion according to claim 1, characterized in that: The emulsifier is a combination of an anionic emulsifier and a nonionic emulsifier.

5. The modified VAE emulsion according to claim 4, characterized in that: The anionic emulsifier is one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium vinyl sulfonate, sodium allyl sulfonate and ethoxylated ether ammonium sulfate, or a combination of any of them; the nonionic emulsifier is one of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, Span 60, Span 80, MS-1 emulsifier, or a combination of any of them.

6. The modified VAE emulsion according to claim 1, characterized in that: The protective colloid comprises polyvinyl alcohol and at least one of hydroxyethyl cellulose and polyether, wherein the polymerization degree of the polyvinyl alcohol is 200-3500 and the alcoholysis degree is between 80% and 99%.

7. The modified VAE emulsion according to claim 1, characterized in that The composition of each raw material component by weight is: Reactive monomers: 55-75 parts of vinyl acetate; 10-30 parts of ethylene; 5-40 parts of functional comonomer; Initiator: 0.05-0.4 parts of oxidant, 0-0.2 parts of reducing agent; Emulsifier: anionic emulsifier 0.2-1 part; nonionic emulsifier 0.5-1 part; Protective colloid: polyvinyl alcohol 0.3-1 part; hydroxyethyl cellulose and / or polyether: 0-1 part; pH regulator: 0.05-0.1 parts; Deionized water: 40-90 parts.

8. A method for preparing the modified VAE emulsion according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Preparation of initiator solution, protective colloid solution, emulsifier solution and mixed monomer Preparation of initiator solution: add 0.05-0.4 parts of oxidant and 10-30 parts of deionized water into the oxidant tank, stir until completely dissolved, and obtain an oxidant solution; add 0-0.2 parts of reductant and 10-20 parts of deionized water into the reductant tank, stir until completely dissolved, and obtain a reductant solution; use 30%-50% of the oxidant solution and the reductant solution as the initial oxidant solution and the initial reductant solution respectively; Preparation of protective colloid solution: add 0.3-1 parts of polyvinyl alcohol, 0-1 parts of hydroxyethyl cellulose and / or polyether into a protective colloid preparation tank, then add 10-15 parts of deionized water, heat to 60-90°C, stir until completely dissolved, and obtain a protective colloid solution; Preparation of emulsifier solution: add 0.2-1 part of anionic emulsifier, 0.5-1 part of nonionic emulsifier and 10-25 parts of deionized water into the emulsifier solution preparation tank, heat to 40-50°C, stir to mix evenly, and obtain emulsifier solution; Preparation of mixed monomers: add 55-75 parts of vinyl acetate and 5-35 parts of ethyleneoxyalkyl polypropylene glycol into a monomer preparation tank according to metered amounts, stir thoroughly until the mixture is uniform, and obtain a mixed monomer; 10%-60% of the mixed monomer is used as an initial mixed monomer, and the rest is used as a continuous mixed monomer; Step 2: Feeding and production After replacing the air in the reactor with ethylene, pump all the protective colloid solution and emulsifier solution into the reactor, stir to make them fully mixed, then pump in the initial mixed monomer, and stir rapidly at a speed of 150r / min-350r / min for 30-60min; start heating, and at the same time open the ethylene control valve to charge ethylene into the system, and control the pressure in the reaction process at 2.0-6.0MPa by controlling the amount of ethylene added; when the temperature of the reactor reaches 40-50°C and the pressure rises to 2.0-4.0MPa, start adding the initial oxidant solution and the reducing agent solution in parallel; When the temperature of the reactor rises to 65-80°C, start to drop the continuous mixed monomer and the remaining oxidant solution and reducing agent solution; the feeding time of the continuous mixed monomer is 100-150min, and during the feeding process, the reaction temperature is maintained at 70-80°C and the pressure is maintained at 4.0-6.0MPa by controlling the feeding rate of the oxidant and reducing agent and the temperature of the water exchange water; after the continuous mixed monomer is added, turn off the ethylene, and continue to drop the remaining oxidant solution and reducing agent solution until they are added; when the pressure of the reactor drops below 1.5MPa, the reaction ends, and then the temperature is lowered, degassed, and filtered; The obtained emulsion is transferred to a defoaming barrel, a defoaming agent is first added for defoaming, hydrogen peroxide or tert-butyl hydroperoxide is then added to remove residual monomers, and finally a pH regulator is added to adjust the pH of the emulsion to 4.0-6.5 to obtain a modified VAE emulsion.