Application of DAAM DAAM is involved in lotion copolymerization and the introduction of ketone carbonyl which reacts with adipic hydrazide. The introduction of ketone carbonyl to the water emulsion polymer molecule is not only a monomer of DAAM, but also includes (methyl) acrolein (aldehyde group can also form hydrazone with hydrazide to achieve cross linking), methyl vinyl ketone, (methyl) acrylic acid acetyl, acetoxyethyl ester, (methyl) acrylic acid acetyl, acetaminoethyl ester, etc. However, DAAM has low toxicity and simple synthetic materials, which are particularly beneficial for enhancing the adhesion performance of coatings. Therefore, DAAM is mainly used as a monomer for introducing ketone carbonyl groups.
Crosslinker DAAM modified polymer lotion Crosslinkers include hydrazides of binary and polycarboxylic acids, such as dihydrazide carbonate, oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, N-amino polyacrylamide containing about 10mol% hydrazide with polymerization degree below 100, N (CH2CH2CONHNH2) 3 and (H2NHNCOCH2CH2) 2NCH2CH2N (CHCHCONHNH2) 2, etc. Generally, binary and multicomponent acylhydrazide are soluble in water, and the acylhydrazide groups within the molecule should not be too crowded to avoid hindering the reaction with ketone carbonyl groups. Polyhydrazide has better crosslinking effect than dihydrazide, but considering cost and performance, adipic hydrazide is still generally used. The ketone carbonyl reaction on the latex particles in the aqueous solution of adipic hydrazide and the aqueous lotion is a heterogeneous reaction, so it is necessary to consider whether the ketone carbonyl group on the latex particles is on the surface or embedded in the latex particles. The content of ketone carbonyl group is measured with hydroxylamine hydrochloride (NH2OH · HCL). It is found that the content of ketone carbonyl group in general lotion copolymerization is only 60% -80% of the theoretical amount, that is, the exposed surface can react with hydrazide only 60% -80% of the theoretical amount. Therefore, during the synthesis of lotion, segmented or core-shell lotion polymerization is adopted to concentrate a large amount of DAAM in the later stage or shell polymer, so that the ketone carbonyl group on DAAM can be more fully utilized. The amount of hydrazide used is generally equivalent to 0.8-1.0 equivalents of ketone carbonyl groups on the polymer.
In addition, it should be considered that in heterogeneous reactions, reagents must have good compatibility with reactants or reaction zones, otherwise it is difficult to react. Due to the strong polarity and hydrophilicity of hydrazide, it cannot dissolve with water-insoluble polymers. However, if there are many hydrophilic groups such as carboxyl groups near the ketone carbonyl group of the polymer, the aqueous solution of hydrazide can still be compatible for reaction in this region. For example, the modified polyvinyl alcohol aqueous solution with DAAM unit is added with adipic hydrazide equivalent to ketone carbonyl to form a water resistant film after drying at room temperature for 4h, while the polyacrylate lotion with DAAM and acrylic acid unit, and the lotion film with adipic hydrazide equivalent to ketone carbonyl to fully solidify in about a week. Here, the surface of the latex particles contains more acrylic acid units, and the curing is faster. Therefore, DAAM is often used together with acrylic acid in the synthesis of water insoluble polymer lotion.
In order to prevent premature crosslinking of polymer lotion with DAAM unit added with adipic hydrazide from reducing the stability of lotion, diacetone alcohol equivalent to 1.5 equivalent of adipic hydrazide (boiling point 168 ℃, soluble in water) is added to lotion. This is because diacetone alcohol is a low molecular weight ketone that can react with hydrazine to form a hydrazone, but does not cause cross-linking, thus reducing the cross-linking effect of hydrazine. However, this low molecular weight hydrazone can also undergo exchange reactions with ketone carbonyl groups in the polymer, while diacetone alcohol evaporates and can still cause crosslinking.
Because the molecular structure of diacetone alcohol is very similar to the structure near the ketone carbonyl group on the lotion polymer, it can be compatible with the ketone carbonyl group. In addition, diacetone alcohol can dissolve adipic hydrazide and its dihydrazone, so it can help adipic hydrazide and the hydrazone of diacetone alcohol of adipic hydrazide react with the ketone carbonyl group on the polymer. Therefore, the addition of diacetone alcohol not only increased the stability of the lotion, but also did not seriously reduce the crosslinking speed.
The reaction between hydrazine and ketone carbonyl groups needs to be carried out under weak acid or weak base conditions, that is, around pH 6 or pH 8. Neutrality is not good because this reaction requires catalysis from weak acids or bases, but strong acids or bases can cause many side reactions. Therefore, after polymerization of lotion, it should be carefully neutralized with ammonia to reach about pH6 or pH8. Excessive ammonia has adverse effects on post crosslinking. Because ammonia can also react with ketone carbonyl groups to form imines.
The speed of this reaction is greatly affected by temperature, with fast crosslinking at high temperatures and slow crosslinking at low temperatures. It usually takes about 7 days to complete cross-linking at a room temperature of 25 ℃. Forced drying, with a temperature of 80 ℃, baking for 10 minutes, and then leaving at room temperature for 12 hours, can basically complete crosslinking. There is also a situation where the water resistance test still shows whitening after being dried for the specified time, but it passes the water resistance test by allowing it to dry again. This may be because soaking in water allows the fixed reactants to move to a certain extent, and then drying allows for smooth cross-linking.
The emulsifiers used for lotion polymerization are hydrophilic. After polymerization, these emulsifiers are still attached to the surface of the latex particles and brought into the film after film formation, thus affecting the water resistance of the film. But use polymerizable active emulsifiers.
The above introduces the mechanism and precautions of the application of DAAM and ADH in the post crosslinking of water emulsion and water-soluble polymers. Below, we will briefly introduce some important applications of this method.
Scope of application Synthesis of water-based one liquid room temperature curing lotion exterior wall coating Synthesis of water-based one liquid room temperature curing lotion exterior wall coating with water resistance, pollution resistance and weather resistance.
The pollution resistance of coatings is related to the Tg of their constituent polymers. A high Tg is beneficial for pollution resistance, but not for film formation, and is also related to the hydrophilicity of their polymer surfaces. High hydrophilicity is beneficial for pollutants to be washed away by rainwater, but not for water resistance. Both of these contradictions can be resolved through post crosslinking. If too much acrylic acid is used to improve the hydrophilicity, it is difficult to solve the problem of water resistance. Therefore, lotion polymerization is adopted to drip in sections, so that the latex particles contain less acrylic acid and DAAM inside, but more acrylic acid and DAAM outside. After crosslinking with adipic hydrazide, the film formed has both high hydrophilicity, water resistance and high Tg. This method can be roughly understood from the formula and performance in Table 1 below. The synthesis of water-based coatings for wood is generally limited by the minimum film-forming temperature required, and the Tg of the resulting coating is relatively low, making it difficult to obtain coatings with high hardness. The invention first prepares polyacrylate copolymer lotion with Tg up to 85 ℃ through segmented lotion copolymerization. Then continue to add materials for copolymerization, and the outer layer of the copolymer has a Tg of 3 ℃, forming an inner hard and outer soft polyacrylate copolymer composite. Both the inner and outer layers of the copolymer contain DAAM units, with the inner layer accounting for 7.5% of the polymer and the outer layer accounting for 3%. The amount of soft hard copolymer used is 1:1. Then it is mixed with self dispersible polyurethane in the water lotion, on which there are UV curable acrylate double bonds and semicarbazone groups that can be crosslinked with ketone carbonyl groups. The dosage of polyurethane and copolymer is 30:70. Add adipic hydrazide equivalent to 50% ketocarbonyl equivalent in this lotion and mix it with 3% photoinitiator (1173) of polyurethane weight. This lotion is coated on the board with a wet thickness of 125 μ m, dried rapidly at 60 ℃, and then passed through the high-pressure mercury lamp (120W/cm) at 10m/min to obtain a cross-linked coating. The stability of the lotion was tested to be excellent, the hardness was tested with a pendulum hardness tester for 108s, the resistance to xylene wiping was 67 times, and the anti adhesion: good before UV curing, excellent after UV curing. It is used to synthesize water resistant, solvent resistant, one liquid room temperature curing water-based lotion resin for general and plastic paint inks. This synthesis uses self emulsifying polyurethane as the seed polymer to carry out the lotion copolymerization of DAAM, a small amount of divinylbenzene, methacrylic acid and acrylate. In addition to the post crosslinking agent adipic hydrazide, the lotion is also added with diacetone alcohol to improve the stability of the lotion. The formula and performance are shown in Table 2.
Coatings with excellent waterproof performance for underground substrates generally have poor sealing properties due to the hardened film formed by water-based coatings. In this synthesis, when DAAM is copolymerized with other acrylate lotion, not only water-soluble initiators such as (NH4) 2S2O8, but also oil soluble initiators such as azoisobutyronitrile or benzoyl peroxide are used, so that there are latex particles and nearly water-soluble fine particles in the obtained lotion, and the ketone carbonyl group exposed on the surface is also increased (reaching more than 90% of the feeding amount), which is convenient for plugging pores and fully cross-linking. The crosslinking agent used here is a tri functional amino urea obtained by trimerization of diisocyanate and addition of hydrazine. The coating has excellent normal adhesion, wet adhesion, and water permeability tests when used on flexible boards and calcium silicate boards. The synthesis of polyvinyl alcohol modified with diacetone acrylamide and DAAM modified polyvinyl alcohol is a widely used polymer. It is a copolymerization of vinyl acetate in methanol solution with azoisobutyronitrile as initiator, dropping the methanol solution of DAAM at 60 ℃ for about 5h to 6h to complete the polymerization, then steaming the unreacted vinyl acetate with methanol steam, using a small amount of NaOH methanol solution as catalyst, carrying out alcohol exchange reaction at 40 ℃ to obtain DAAM vinyl alcohol gel like copolymer precipitation, filtering out methanol, methyl acetate and lye, washing and drying them with methanol to obtain DAAM modified polyvinyl alcohol. DAAM modified polyvinyl alcohol is used as the active dispersant DAAM modified polyvinyl alcohol is used as the active dispersant to manufacture polymer lotion, and is matched with crosslinking agents such as adipic hydrazide, which can improve the water resistance and bonding strength of the generated film, especially the bonding strength in wet conditions.
For example, the polyvinyl acetate lotion (solid content 50%) is prepared with DAAM modified polyvinyl alcohol (modification degree 5.0mol%, saponification degree 98.4mol, 20 ℃ 4% aqueous solution viscosity 26.8mPa · s) as the dispersant, and then acetylhydrazine (to improve the stability of the lotion) and adipic acid hydrazine are added. In addition, it is modified into polyvinyl acetate lotion prepared with unmodified polyvinyl alcohol (saponification degree 98.5mol, 20 ℃ 4% aqueous solution viscosity 26.6mPa · s), but without hydrazide, that is, commercially available polyvinyl acetate lotion.
If DAAM is added to vinyl acetate, the normal and water resistant shear bond strength of the obtained lotion can reach 85 and 83 kgf/cm2 respectively, and the solvent resistance is good. It can be used as adhesive for non-woven fabrics, wood, paper, cloth, chlorinated bed bricks, tile adhesive, putty, coating, etc. DAAM modified polyvinyl alcohol is used as a waterproof coating agent for paper. 100 parts of DAAM modified polyvinyl alcohol with a saponification degree of 98mol, viscosity of 25.6mPa · s, and a modification degree of 1.0mol are dissolved in 900 parts of water. 2.0 parts of carbonic acid hydrazide and 1.0 part of malonic acid hydrazide are added, and mixed and dissolved to obtain the waterproof coating agent for paper. Apply 1g/m2 onto paper and dry it for 50 minutes. The test results are as follows:
Hot water insolubility rate of membrane/% 88.3
Good water resistance of coated paper
The stability of waterproof coating is above 120 days
(gel time)
The comprehensive evaluation shows that DAAM modified polyvinyl alcohol is suitable for use as a layered film for air resistance under particularly high humidity conditions, such as polyester and polypropylene. It is suitable for food, medicine, and other applications. DAAM modified polyvinyl alcohol with a modification degree of 5.0mol, a polymerization degree of 1600, and a saponification degree of 98.4mol is prepared into a 15% aqueous solution. 0.75 parts of adipic hydrazide are added to 100 parts of the solution and mixed well. Apply a 12 μ m thick coating onto a biaxially oriented polyester (PET) film using a coating rod. A 2 μ m thick laminated film was obtained by drying at 150 ℃ for 1 minute. Through testing, its water resistance is good, and its oxygen barrier permeability is excellent at a relative humidity of Technolo 265% and good at a relative humidity of 85%. The polyvinyl alcohol modified with DAAM instead of polyvinyl alcohol is classified as poor and medium, respectively
Modified polyolefin film with DAAM modified polyvinyl alcohol synthetic paper suitable for offset printing: 100 parts of DAAM modified polyvinyl alcohol, 58 parts of silicon oxide (average particle size 3 μ m), 38 parts of colloidal silicon oxide, and 4 parts of adipic hydrazide with a modification degree of 6.3 mol, a polymerization degree of 1780, and a saponification degree of 99 mol were coated on the corona treated polyolefin film, and the coating amount after drying was 3g/m2. After testing, the solvent resistance: the edge height is 0mm, the water resistance: wipe with a cotton swab for more than 30 times, and the ink drying time is 3h, all of which are excellent. A photosensitive resin plate was manufactured using DAAM modified polyvinyl alcohol with a modification degree of 5.0 mol, saponification degree of 98.4 mol, and viscosity of 6.8 mPa · s. 250 parts of DAAM modified polyvinyl alcohol, 90 parts of hydroxyethyl methacrylate, 10 parts of ethylene glycol dimethacrylate, 0.05 parts of hydroquinone monomethyl ether, 3 parts of benzoin isopropyl ether (photoinitiator), and 200 parts of water (pH 3) were mixed and dissolved into a solution at 90 ℃. After defoaming, the plate was coated on an aluminum plate and dried at 80 ℃ for 30 minutes to obtain a 0.5mm thick coating photosensitive resin plate. DAAM modified polyvinyl alcohol has good compatibility with other components, excellent photo curing properties, low extraction rate, no peeling of hardened film, and excellent image reproducibility.
Post time: Aug-28-2026