Organic silicon defoamer

Defoamer (English name Defoamers, Defoaming Agent) is an additive, its function is to eliminate the formation of foam in the production process of materials, silicone defoamer (English name organic silicon defoamer), its main component is called silicone oil silicone components, silicone oil is not volatile at room temperature oily liquid in water, animal and plant oils and mineral oils are insoluble or very soluble in both high and low temperatures. In water, animal and vegetable oils and mineral oils are insoluble, or solubility is very small, both high temperature resistance, but also low temperature resistance. It is chemically inert, physically stable and biologically inactive.
Silicone defoamer is a white viscous emulsion. It has been used in various industrial fields since the 1960s, but large-scale and comprehensive rapid development began in the 1980s. As a silicone antifoam agent, its application field is also very wide, and it is more and more emphasized by various industries. In the chemical industry, paper, paint, food, textiles, pharmaceuticals and other industrial sectors organosilicon antifoam agent is an indispensable auxiliary in the production process, it is not only able to remove the foam on the liquid surface of the production process process media, thereby improving filtration, washing, extraction, distillation, evaporation, dehydration, drying and other processes of separation, gasification, liquid discharge and other effects, to ensure that all types of materials, the capacity of the handling container.

Principle of action

Whenever we stir the liquid or be passed into the gas, it will be in the surface area of the liquid within the generation of many bubbles, some liquids produce bubbles, quickly broken and disappeared. Some liquids not only do not disappear, and more and more, forming bubbles. Foam is a large number of bubbles dispersed in the liquid and the formation of the dispersion system, the dispersion phase for the gas, the continuous phase for the liquid. The volume fraction of the foaming liquid is very small, and the foam occupies a large volume. The gas is separated by a continuous liquid film, forming bubbles of varying sizes, which accumulate to form foam.

The media that can foam are such as surfactants, a layer of surfactant molecules adsorbed on the surface of the bubble in a directional arrangement, when it reaches a certain concentration, the bubble wall forms a solid film. Surfactant adsorbed on the gas-liquid interface, resulting in a decrease in the surface tension of the liquid surface, thereby increasing the gas-liquid contact surface, so that the bubbles are not easy to merge. The relative density of the bubbles is much smaller than the liquid itself, and when the rising bubbles pass through the liquid surface, they adsorb a layer of surfactant molecules on the liquid surface. Therefore, exposed to the air adsorbed surfactant bubble film and solution bubble film is not the same, it is wrapped with two layers of surfactant molecules, forming a bimolecular membrane, the adsorbed surfactant on the liquid membrane has a protective effect. Antifoam agent is to destroy and inhibit the formation of this film, antifoam agent into the foam bimolecular oriented membrane, destroying the mechanical equilibrium of the oriented membrane to achieve the effect of bubble-breaking.

The defoamer must be a substance insoluble in the foaming medium, which can be dispersed into the foaming medium in the form of droplets, or droplets wrapped in solid mass, or solid mass. Antifoam agent has a lower surface tension than the foaming medium, and can spontaneously enter the liquid film and rupture the bubbles.

Antifoam agent is easy to spread on the surface of the solution, automatically spread on the surface of the foam, will take away a layer of solution on the neighboring surface, so that the liquid film becomes locally thin, reaching the critical thickness, the liquid film rupture, foam destruction. The faster the defoamer spreads on the surface of the solution, the thinner the liquid film becomes, the speed of foam destruction is accelerated, and the defoaming effect is strengthened. Therefore, the reason for defoaming on the one hand is easy to spread, adsorption of antifoam agent molecules to replace the foaming agent molecules, the formation of a poor strength of the film. At the same time in the spreading process to take away part of the neighboring surface layer of the solution, so that the foam liquid film becomes thin, reducing the stability of the foam, so that it is easy to destroy.

An excellent antifoam agent must be both anti-foam and foam inhibition, that is, it should not only quickly destroy the foam, but also prevent foam generation for a long time. The reason for this situation may be related to whether the critical micelle concentration of the foaming agent (surfactant) in the solution exceeds. In the solution exceeding the critical micelle concentration, the antifoaming agent (generally an organic liquid) may be solubilized to the extent that it loses the role of spreading on the surface, and the antifoaming effectiveness is greatly reduced. After a period of time, as the defoamer is gradually solubilized, the defoaming effect is correspondingly weakened.

Components and Functions

Antifoam agent is generally composed of a variety of components with different functions, i.e., main antifoam agent, auxiliary antifoam agent, carrier, emulsifier or unfolding agent, stabilizer or cooperating agent.
(1) Main antifoam agent: the main active component, usually insoluble granular substances, such as hydrophobic silica treated with silicone oil, fatty amines, paraffin, etc..
(2) Auxiliary antifoam agent: It is the active component that plays a regulating role, improves the surface effect of the main antifoam agent, and plays a synergistic role for the main antifoam agent. Such as fatty alcohols, fatty acid esters, etc.
(3) Carrier: the main and auxiliary defoamers play a supporting role, water is the most convenient and economical carrier.
(4) Emulsifier and unfolding agent: It is to make the active component of antifoam agent immediately dispersed in the medium of foaming, faster and more contact surface, so as to improve the unfolding efficiency of antifoam agent. Commonly used emulsifiers are organic esters and ethyl oxide products.
(5) Stabilizers and cooperating agents: additives to improve the stability and storage time of defoamers, water-based defoamer stabilizers are often a preservative to prevent the product from being destroyed by bacteria in the storage process. Commonly used cooperating agents are oleic acid, hexanediol and so on.

3 silicone defoamer active components and performance:
(1) active component: the main component of the silicone antifoam agent is a linear polysiloxane (English name: Polysiloxane, Silicones) (also known as silicone oil) that can remain liquid at room temperature as an active agent, polysiloxane mainly has the following types;
Polydimethylsiloxane: the molecular formula is as follows:
Me3SiO(Me2SiO)nSiMe3

Fluorosiloxane: The molecular formula is as follows:

Glycol silicone: the molecular formula is as follows:

Silicone oil is a non-volatile oily liquid at room temperature, insoluble in water, animal and vegetable oils and mineral oils, or very small solubility, can withstand both high and low temperatures. Chemical properties inert, stable physical properties, no biological activity.
(2) Organosilicon antifoam agent performance: organosilicon antifoam agent has three kinds of functions: foam-breaking, defoaming and foam-suppressing.
(3) Characteristics of organosilicon defoamer
Appearance】White viscous emulsion
PH】6-8
Water dilution]: 0.5%-5.0% of the foaming liquid dilution.
Volatility] Non-volatiles
Stability]: 3000rpm/20mins without delamination
Ionic properties]: Non-ionic
Temperature resistance]: 130℃, no emulsion breakage, no oil bleaching, no delamination.

Vantage

(1) Wide range of applications: due to the special chemical structure of silicone oil, neither with water or substances containing polar groups are soluble, nor with hydrocarbons or organic substances containing hydrocarbon groups are soluble. Because of the insolubility of silicone oil on all kinds of substances, and therefore a wide range of applications, both using water system defoaming, but also can be used in the oil system.
(2) Small surface tension: the surface capacity of silicone oil is generally 20-21 dynes/cm, which is smaller than the surface tension of water (72 dynes/cm) and general foaming liquid, with good defoaming efficiency.
(3) Good thermal stability: the commonly used dimethyl silicone oil, for example, it can withstand 150 ℃ for a long time, a short time can withstand more than 300 ℃, its Si-O bond does not decompose. This ensures that the silicone defoamer can be used in a wide range of temperatures.
(4) good chemical stability: due to the Si-O bond is relatively stable, so the chemical stability of silicone oil is very high, it is difficult to chemical reaction with other substances. Therefore, as long as the formulation is reasonable, silicone antifoam agent is allowed to be used in the system containing acid, alkali and salt.
(5) Physiological inertia: Silicone oil has been proved to be non-toxic to humans and animals, and its half-lethal dose is more than 34 g/kg. So silicone defoamer (in the appropriate non-toxic emulsifiers, etc. with) can be safely used in food, medical, pharmaceutical and cosmetic industries.
(6) strong defoaming power: silicone antifoam agent can not only effectively break the foam has been generated, but also can significantly inhibit the foam, to prevent the generation of foam. It is used in very small quantities, as long as the addition of foaming medium weight of one millionth (1ppm), that can produce an antifoaming effect. It is commonly used in the range of 1 to 100 ppm, which is not only low cost but also does not contaminate the defoamed material.

Type

Polyether-modified silicone defoamer

Polyether-modified silicone is a polyether-siloxane copolymer (referred to as silicone ether copolymer) made by introducing polyether chain segments into the siloxane molecule. Polyether modified organosilicon antifoam agent is a new type of efficient antifoam agent that combines the advantages of both organically. It is a new type of high efficient defoamer that combines the advantages of the two organically. It is an antifoamer composed of polyether with strong foam inhibition ability and dimethylsilicone oil with strong hydrophobicity and rapid foam breakage, matched with emulsifiers, stabilizers and other components that can make silicone oil and polyether combine organically. It has the characteristics of low surface tension, rapid defoaming, long foam suppression time, low cost, low dosage and wide application. Polyether modification of silicone, so that it has the advantages of two types of antifoam agent, become a kind of excellent performance, have a wide range of prospects for the application of antifoam agent.

In the molecule of the silicone ether copolymer, the siloxane segment is a lipophilic group and the polyether segment is a hydrophilic group. The poly(ethylene oxide) chain in the polyether chain segment provides hydrophilicity and foaming, and the poly(ethylene oxide) chain provides hydrophobicity and permeability, and has a strong effect on reducing surface tension. The groups at the end of the polyether chain also have a great influence on the properties of the silicone ether copolymer. Common end groups are hydroxyl, alkoxy, etc. Adjusting the relative molecular mass of the siloxane segment in the copolymer can make the copolymer accentuate or attenuate the silicone properties. Similarly, changing the relative molecular mass of the polyether segment will increase or decrease the proportion of silicone in the molecule, which will also have an effect on the performance of the copolymer. Polyether-modified silicone defoamers emulsify easily in water and are also called “self-emulsifying defoamers”. Above its cloud point temperature, it loses solubility in water and mechanical stability, and is resistant to acids, alkalis and inorganic salts, so it can be used for defoaming under harsh conditions.

In order to improve the lipophilicity for water-based inks, coatings, cutting fluids, etc., some of the methyl groups in the copolymer molecules of polyether-modified silicones are replaced with long-chain alkyl groups, so that the antifoaming effect can be more effectively realized. In order to make in the turbidity point temperature can also have a better defoaming, commercial self-emulsifying antifoam agent are usually equipped with dimethylsiloxane — silica paste, then in the turbidity point temperature polyether modified organosilicone surfactant can also be used as an emulsifier of dimethylsiloxane oil to play the role of dispersion, emulsification.

Application

Silicone antifoam agent uses and applications in a wide range of fields, in erythromycin, Zeomicin, avermectin, gentamicin, penicillin, hygromycin, tetracycline mold, tylosin, glutamic acid, lysine, citric acid, xanthan gum, and other fermentation industry used as defoamer. It is also used in textile, printing and dyeing, coating, dyestuff, paper making, printing ink, oil field, sewage treatment and other fields. When used in printing and dyeing, it has good compatibility with the additives in the dyeing bath, and does not affect the color light and dyeing fastness.

Silicone used as spray dyeing defoamer, there have been a number of literature reports. The old dyeing process, generally applying dimethylpolysiloxane defoamer, can achieve satisfactory defoamer effect and ensure uniform dyeing. The new dyeing process, however, uses high-temperature and high-pressure machinery, in which the dyed material is subjected to the movement of the jet of dyeing liquid and is dyed at the same time. Although the foam generated can be defoamed by ordinary silicone defoamer, under high temperature and high pressure, ordinary silicone defoamer will produce film-like precipitation and make the dyed material produce spots. Application of block copolymers can overcome the above shortcomings, because these defoamer components can be soluble in cold water, but not in hot water, so it can play a role in defoaming. But only with this copolymer antifoam agent defoaming effect is not satisfactory, if the copolymer in the addition of a certain amount of mist SiO2, you can achieve satisfactory defoaming effect, and the production of uniformly dyed fabrics. It is used for defoaming in high temperature dyeing process and fermentation process of polyester fabric. In addition, it can also be used in the defoaming of diethanolamine desulfurization system and the defoaming of all kinds of oils, cutting fluids, non-freezing liquids, water-based inks and other systems, and is also suitable for the defoaming of washing off the uncured resin in the printing industry after the plate making of photopolymer resin, which is a very representative, excellent performance and wide range of silicone defoamer.

Packaging, Storage and Transportation

Packed in 25kg plastic drums or 200kg plastic-coated iron drums; stored in a cool place and transported as non-toxic and non-dangerous goods, pay attention to anti-freezing.