Silicone type (silicone oil)
Commonly used silicone oils are polydimethylsiloxane and polymethylphenylsiloxane. Paint, ink used in the polydimethylsiloxane. Polymethylphenylsiloxane, although good compatibility, but does not have the surface state control ability, so the leveling agent is basically not used, and more for high temperature.
Although there is a good surface state control, but there are many shortcomings, compatibility is not good, will affect the coating luster, but also often appear shrinkage, layer adhesion problems. Polydimethylsiloxane has a different molecular weight and its compatibility and use. Organic modified polydimethylsiloxane and silicone oil compared to the obvious advantages, both to retain the advantages of siloxanes, but also with modified products to overcome its shortcomings, played a number of special functional effects. The performance and use of modified siloxanes is the key to the molecular weight of silicone, type, the type of modified compounds and the location in the molecule, the modification of the way is a lot.
Polyether Polyester Modified Organosiloxane
Belonging to the comb structure of the organopolysiloxane. n + m is about 50-250, and the molecular weight is between 1000 and 150,000. Its compatibility is to rely on polyether and polyester to adjust the chain the longer the better compatibility. Most of these polyether modification, usually using ethylene oxide and propylene oxide. With the increase in ethoxyl content, its compatibility with water also increased, so it is also possible to synthesize water-soluble siloxanes leveling agent. Ethylene oxide and propylene oxide may be used singly or in combination, and they may be used to control the hydrophilic and lipophilic. If both ethoxyl and propoxy groups are present, a leveling agent for silicone-based oils and fats is made, for example, the 10801090 series products of Mau Keng Chemical.
The greater the molecular weight, the stronger the surface state control capability, the better the slip resistance and the anti-blocking properties, such as the 1070,1071 series of products.
Modified polyester or polyether and silicone coupling in two ways: a silicone key; the other is a silicon carbon chain, in general, the former thermal stability and water resistance as the latter is good.
With the polyether, polyester modified silicone and resin compatibility has been greatly improved, reduce the surface tension, the ability to control the surface flow, slip, anti-shrinkage, anti-adhesion effect is also very good , There are inter-layer adhesion problems of individual products. Especially polyether modified polysiloxane, thermal stability is not good, easy to bubble. In the application must pay attention to the negative impact of these products.
Alkyl modified organosiloxanes
Some of the shortcomings of polyether-modified polysiloxanes have been mentioned earlier; alkyl-modified polysiloxanes have the advantages of these aspects.
This series of polysiloxane products also belong to comb structure. The molecular weight of these products is relatively small, around 10,000, n + m is about 30-50. The purpose of the alkyl modification is mainly to improve the thermal stability, compatibility and instability of foam, and even defoaming function. But with the growth of modified alkyl chain, its ability to reduce the surface tension also decreased. The relationship between the length of the alkyl chain and the surface tension is shown in Table 1-1
Table 1-1 Relationship between the length of the alkyl chain and the surface tension
Modified alkyl chain
The general carbon chain is controlled between C1 and C14, so the molecular weight is not too large.
The above describes the polydimethylsiloxane three kinds of modification methods, different modification methods, the amount of different modifier and structure of its products are different performance, three different methods of production of leveling agent, Its heat resistance is also very different. Mo Chemical Chemical 1060 Silicone Modified Polysiloxane has good heat resistance, heat resistant temperature range of 200-220 ° C used within the temperature range.
To provide excellent smoothness of the end-modified silicone in order to give the film a good slip, Mo Chemical Chemical introduced a number of terminal modified silicone.
Reactive leveling agent
In the radiation curing coating, ink system, there is poor substrate wetting, not smooth, easy to scratch, poor leveling defects. In response to these problems, Mo Neng Chemical Company provides a series of reactive organic modified polysiloxane acrylic leveling agent, with the energy of chemical products 1073,1074, the former good compatibility, poor slip. The latter is poor, good slip.
From the structural formula can be seen that the modified organic matter is acrylic, with its adjustment of its mobility and compatibility, her slip is determined by the silicone. The double bond of the acrylic group may participate in the polymerization of the radical, and the coating film formed together with the resin is firmly anchored to the surface of the coating film.
Resin type surface flow control agent, mostly linear resin polymer, mainly acrylic resin, urea resin and melamine formaldehyde resin. In the general system, the compatibility of these resins is limited, they will accumulate on the surface to form a new layer of resin film, so that the surface tension of the coating tends to balance, but they do not reduce the surface tension, so does not affect The flow of paint, mostly known as flow promoters. Such a leveling agent in the acrylic resin as the main body.
Acrylic leveling agents not only promote the flow and leveling of the coating, but also does not affect the adhesion of the coating layer, and also defoaming effect.
The compatibility of the acrylic leveling agent is an important indicator of its ability to control the surface state of the coating film. Compatibility is good, soluble in the coating, will not form a new interface in the coating surface, can not provide leveling effect; poor compatibility, can not be evenly distributed in the coating surface, will gather together , Prone to shrinkage-like defects. Will make the coating gloss decreased, resulting in fog and other adverse side effects. Only the ideal controlled compatibility, will form a new interface layer on the surface of the coating, play a leveling role.
The control of the acrylic leveling agent is achieved by varying the molecular weight and polarity. Homopolymer compatibility is not as good as the copolymer, such as homogeneous acrylic acid and epoxy, polyester, polyurethane and other coatings used in the resin compatibility is poor, if it is physically mixed will form a surface Bad state of the matt film, so the acrylic homopolymer is not suitable for leveling agent. The ideal leveling agent is more commonly used in the copolymer, which can be a terpolymer or a modified copolymer. Only the copolymer can change the polar glass heating temperature of the polymer by different monomers.
Usually, the number average molecular weight of the acrylic leveling agent is controlled between 6000 and 20000, the molecular weight distribution is relatively narrow, the glass flower temperature is controlled below -20 ℃, and the surface tension is 25-26 mN / m or less. This compatible, acrylic copolymer is considered to be a good leveling agent.
The acrylate leveling agent may be a homopolymer or a copolymer; it may be of a linear structure or a branched chain; it may be random copolymer or block copolymerized.
1) fluorine modified acrylic leveling agent such leveling agent is widely used, with fluorine modified acrylic acid to the advantages and disadvantages of fluoride and acrylic acid complementary, so that these leveling agents more perfect. The advantages and disadvantages of acrylic and fluorine leveling agents are shown in Table 1-1
Table 1-1 Advantages and disadvantages of acrylic and fluoride leveling agents
Acrylic leveling agent
Strong leveling, more defoaming ability, does not affect the adhesion between layers
Poor substrate wetting, can not eliminate shrinkage
Fluoride leveling agent
Good wetting properties of the substrate, anti-shrinkage ability
Stable foam, poor adhesion between the layers, can not be recoated, expensive
Through the modified leveling agent, with good surface control ability, unstable foam, can be recoated, with good anti-shrinkage and substrate wetting ability. Representative products are the energy of the chemical industry 1154.
2) the application of acrylic leveling agent Pure acrylic leveling agent because of its little effect on the surface tension so much for the flow and leveling aids, especially the Indian iron coating, coil coating, the elimination of roller marks Is helpful There are also brushing the wood paint to eliminate the brush marks is also helpful.
Application should pay special attention to compatibility with the paint, the general situation is poor compatibility of molecular weight, but the flow and leveling is good; good molecular weight compatibility, but the flow and leveling to worse.
Acrylic leveling agent can not only be used for oily coatings, water-based paints, but also commonly used in powder coatings leveling agent, such products are energy-saving.