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Various of the inorganic and organic dispersants

Date:2014年8月11日 09:19

A dispersant having in the molecule at the same time both a lipophilic and hydrophilic nature of the surfactant opposite. Uniform dispersion may be difficult to dissolve in the liquid that inorganic, solid organic pigment particles, but also to prevent sedimentation of solid particles and agglomerate to form a stable suspension of the desired agent.

Explain

Interpretation tool book

Makes the material particles are uniformly dispersed in a medium to form a stable suspension agent. Dispersing agents are generally classified into inorganic dispersants and organic dispersant two

Categories. Conventional inorganic dispersants silicate (e.g. water glass) and alkali metal phosphates (e.g., sodium tripolyphosphate, sodium hexametaphosphate and sodium pyrophosphate, etc.). Organic dispersing agents include triethyl hexyl phosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, Gul gel, polyethylene glycol fatty acid esters and the like.

Interpretation of the academic literature

Defined dispersants are dispersants can reduce the dispersion of solid or liquid particles aggregated material. Dispersing agents and suspending agents in the preparation of emulsifiable concentrates and wettable powders tend to form dispersions and suspensions, and functions to maintain a relatively stable dispersion system.

Dictionary of interpretation

Can enhance and improve the dispersibility of the solid material or liquid additives. When the solid dye grinding, dispersing agents, can help prevent the particles have been crushed and broken particle aggregation while maintaining dispersion stability. An oily liquid insoluble in water under high shear mixing, may be dispersed into small droplets after stopping stirring rapidly under the action of interfacial tension delamination, and the mixture was stirred after adding a dispersing agent, is able to form a stable emulsion. Its main role is to reduce the liquid - liquid and solid - liquid interfacial tension between. Thus the dispersant is a surfactant. Species are anionic, cationic, nonionic, amphoteric, and polymer type. Anionic most used.

Dispersant selected

An excellent dispersant should meet the following requirements:

 

1, good dispersion, prevent mutual aggregation between the filler particles;

2, with the resin, a suitable filler compatibility; good thermal stability;

3, the flowability during molding is good; not cause color drift;

4, does not affect the performance of the products; non-toxic and inexpensive.

The amount of dispersing agent is generally 5% by mass of the masterbatch

Type of dispersant

Fatty acids, fatty amides and esters

Stearylamine with higher alcohol can be improved lubricity and thermal stability, the amount (mass fraction) of 0.3% -0.8%, the slip agent can be made of polyolefin; hexenyl bis stearamide, and said ethylene bis stearamide (EBS), the lubricant is a high melting point, the amount of 0.5% to 2%; oleic acid; glyceryl monostearate (GMS), glyceryl tristearate (HTG) the amount of acid of 0.2% to 0.5%; hydrocarbon wax solid, mp 57 ~ 70 ℃, insoluble in water, soluble in an organic solvent, a resin dispersion, compatibility and thermal stability are poor, the dosage is generally 0.5% or less

Paraffin

Although part of the outer wax lubricant, a straight-chain non-polar hydrocarbons, but not wet the metal surface, that does not prevent the adhesion of metal such as polyvinyl chloride resin, a wall, and only stearic acid, calcium stearate, when used, in order to achieve synergy

Liquid paraffin: freezing point -15¯-35 ℃, during extrusion and injection molding, poor compatibility with the resin, the addition amount is generally 0.3% to 0.5%, when too much, but to make the deterioration of workability

Microcrystalline wax: obtained from the petroleum refining process, the greater the relative molecular mass, and there are many isomers, melting point 65-90 ℃, good lubricity and thermal stability, but poor dispersion, the amount is usually 0.1 % -0.2%, more preferably with butyl stearate, higher fatty acids and use.

Metal soaps

Metal salts of higher fatty acids, referred to as metal soaps such as barium stearate (BaSt) for a variety of plastics, in an amount of about 0.5%; zinc stearate (ZnSt) is adapted to a polyolefin, ABS, etc., in an amount of 0 .3%; calcium stearate (CaSt) adapted for common plastic, external lubrication, the amount of 0.2% ¯1.5%; other soaps such as stearate, stearic acid cadmium (CdSt), magnesium stearate (MgSt), copper stearate (CuSt).

Low molecular weight waxes

Based on a variety of low molecular weight polyethylene wax (homopolymer or copolymer), polypropylene, polystyrene, or other polymer-modified products as raw materials, pyrolysis, oxidation from a series of oligomers with different properties

Its main products are: homopolymers, oxide homopolymers, ethylene - acrylic acid copolymer, ethylene - vinyl acetate copolymer, low molecular weight ionomer five categories. Among them, polyethylene wax, polyethylene wax chemical name polyethylene glycol, Molecular PEG (Poly Ethylene Glycol) is most commonly

Commonly used polyethylene wax (polyethylene glycol) average relative molecular mass of 1500-4000, a softening point of 102 ℃; polyethylene wax average relative molecular mass of other specifications of 10,000 to 20,000, a softening point of 106 ℃; oxidation long-chain molecules with a certain amount of polyethylene wax ester or soap, so PVC, PE, PP, ABS internal and external lubrication of more balanced, better, resistance or transparency. Since many different types of practical applications and environments dispersant, selection of the appropriate dispersing agent is very important.

Polyethylene glycol 200 or 400 (molecular weight of about 190-420) is a good dispersion of water-soluble dispersant / solubilizer / wetting agent / solvent. Polyethylene glycol 200 or 400 is pro-oil can be very good with a lower hydrophilic-lipophilic balance (HLB value) of the dispersion to form a stable dispersion.

Dispersing agent mechanism

1 adsorbed on the surface of the solid particles, the surface of the agglomerated solid particles easy to wet.

2 polymer dispersant on the surface of the adsorption layer is formed of solid particles, the solid particles of the charge surface is increased to improve the reaction between the particle formation of the steric hindrance.

3 formed on the surface of the solid particles in the bilayer structure, the polarity of the outer end of the dispersant has a strong affinity with water, increasing the level of the solid particles are wetted with water. Due to electrostatic repulsion between the solid particles away from the

4. make uniform system, increased suspension performance, no precipitation, so that the whole system of the same physical and chemical properties

Described above, can be dispersed using a dispersing agent of solid particles in a liquid stably.

The basic principle of the dispersant:

In our paint production process, the pigment dispersion is a very major production areas, it is directly related to the paint store, construction, appearance, and the film's performance, so a reasonable choice of dispersing agent is a very important production processes. But the quality is not only dispersed slurry coating and dispersants are related, and the development and selection of raw materials in coating formulations have a relationship. Gu dispersant inconceivable that the various powders are dispersed in a solvent is reasonably exclusion principles, or steric effects of polymer through certain charge, so that a variety of solid suspended in the solvent is stable (or dispersion) of the.

Principle of double layer

An aqueous dispersing agent used must be water-soluble coatings which are selectively adsorbed on the powder and water interface. The most commonly used anionic, they form ionized anions in water, has some surface activity and adsorption were powder surface. After the adsorption surface of the particles of powder dispersant to form a double layer, the particle surface is tightly adsorbed anions, are known as surface ions. Oppositely charged ions are called counter-ions in the medium. They are surface ions through electrostatic attraction, part of the counter ions in the surface of the particles and ions bind more closely, they said bound counter-ion. Movement in them in the medium, with a negative charge, the counter ion is surrounded by the other part in the area, they are called free counter ion, to form a diffusion layer. Thus between the surface ions and counter-ions to form an electric double layer.

Dynamic potential: the negatively charged particles carried by positively charged and brought about the formation of a diffusion layer electric double layer, called electrokinetic potential. Thermal potential: The electric double layer is formed between the anion and cation of all, the corresponding potential.

Since dispersion is dynamic potential rather than thermodynamic potential, and dynamic potential charge is not balanced, there is a charge exclusion, and thermodynamic potentials are charge-balancing phenomenon. If increasing the concentration of counter ions in the medium, and the anti-diffusion layer of the free ions bound by electrostatic repulsion is forced into the counter-ion layer, so that the electric double layer is compressed, moving the electric potential was decreased, when all of the free counter ions becomes bound after the counter-ion, and dynamic potential is zero, called isoelectric point. No charge repulsion, flocculation system is not stable.

Steric effect

Forming a stable dispersion system, in addition to electrostatic repulsion, i.e., the particles adsorbed on the surface of the negative charges repel each other, to prevent adsorption of the particles and between the particles / aggregates to form large particles and finally layered / settling outside, but also the use theoretical steric effects, that is, when the adsorption of negatively charged particles have close to each other, so that they are shifted from each other slide, such steric hindrance effect of the surfactant is typically nonionic surfactants. Flexible use of the theory of electrostatic repulsion with steric hindrance, either to form a highly stable dispersion.

Polymer adsorption layer has a certain thickness, each block can be effectively adsorbed particles, mainly by the polymer solvent layer when the adsorption layer of the powder surface 8-9nm, the repulsive force between them can not protect the particles flocculation. Therefore, the polymer dispersing agent is better than the conventional surface active agent.

TypeInfo: Industry News

Keywords for the information:The kind of dispersant