What Is a Release Agent?

Release agent is a functional substance between the mold and the finished product. The release agent is chemically resistant and will not dissolve when in contact with the chemical composition of different resins (especially styrene and amines). The release agent also has heat resistance and stress properties, and is not easy to decompose or wear; the release agent is adhered to the mold without being transferred to the processed part, and does not hinder painting or other secondary processing operations. Due to the rapid development of injection molding, extrusion, calendering, molding, lamination and other processes, the amount of release agent has also increased significantly.

Chinese name: Release agent
Foreign name: mold discharging agent; releasing agent



Classification: Internal release agent, external release agent
Features: Good mold release and durability

Basic introduction of release agent

Release agent is an interface coating used on the surfaces of two objects that are easy to adhere to each other. It can make the surface of the object easy to detach, smooth and clean.

Release agents are widely used in various molding operations such as metal die casting, polyurethane foam and elastomers, glass fiber reinforced plastics, injection molded thermoplastics, vacuum foamed sheets and extruded profiles. During molding, sometimes other plastic additives such as plasticizers will ooze out to the interface, and a surface remover is required to remove it.

Theoretical basis of release agent

In theory, the release agent has a large tensile strength, so that it is not easy to be polished when it is in frequent contact with the molding resin. This is especially true when the resin has a frosted mineral filler or glass fiber reinforcement. The release agent is chemically resistant and will not dissolve when in contact with the chemical composition of different resins (especially styrene and amines). The release agent also has heat resistance and stress properties, and is not easy to decompose or wear; the release agent is adhered to the mold without being transferred to the processed part, and does not hinder painting or other secondary processing operations. The specific working principle of the release agent is as follows:

1. The polar chemical bond interacts with the mold surface to form an adsorption film with regenerative force;

2. The silicon-oxygen bond in polysiloxane can be regarded as a weak dipole (Si + -O-). When the release agent is spread into a unidirectional arrangement on the mold surface, the molecule adopts a unique extended chain configuration;

3. The free surface is covered by densely packed alkyl groups, and the demolding ability increases with the density of the alkyl group; but when the alkyl group occupies a large steric hindrance, the stretched configuration is limited, and the demolding ability is reduced;

4. The molecular weight and viscosity of the release agent are also related to the release ability. When the molecular weight is small, the spreadability is good, but the heat resistance is poor.

Release agent classification

1. Classified by usage: internal release agent, external release agent;

2. Classified by life: conventional release agent, semi-permanent release agent;

3. Classification by form: solvent-based release agent, water-based release agent, solvent-free release agent, powder release agent, paste release agent

4. Classification by active substance:

Silicone series-mainly silicone compounds, silicone oil, silicone resin methyl branched silicone oil, methyl silicone oil, emulsified methyl silicone oil, hydrogen-containing methyl silicone oil, silicone grease, silicone resin, silicone rubber, silicone rubber toluene solution ,

Wax series-plants, animals, synthetic paraffin; microcrystalline paraffin; polyethylene wax, etc.

Fluorine series-the best isolation performance, less pollution to the mold, but high cost polytetrafluoroethylene; fluororesin powder; fluororesin coating, etc.

Surfactant seriesmetal soap (anionic), EO, PO derivatives (non-ionic)

Inorganic powder series-talc, mica, clay, white clay, etc.

Polyether series-mixture of polyether and fatty oil, which is chemically resistant to heat and is mostly used in certain rubber industries that have restrictions on silicone oils. The cost is higher than the silicone oil series.

5.Other

Masking agent-containing water-based release agent: Use the masking agent to fix water molecule. Durable release agent: silicone oil + silicone resin system, 800 times or more multilayer composite release agent: halogenated hydrocarbon film + polyethylene release agent + polymer Vinyl alcohol mold release agent, aromatic polysulfone mold release agent, mold release agent, halogen-containing polyether mold release agent: lower vapor pressure, increase decomposition temperature, will not cause charged contact with carbonyl alkylsilane mold release agent: internal Releasing release agent to improve the adhesion to the surface of water-based inks: After coating, it chemically reacts to form a film and adheres to the mold surface at the same time. The above are some representative release agents. They have their own characteristics, and They can be used separately according to the application. For example, it can be used as a back surface treatment agent for fiber adhesive tape, release paper, anti-sticking agent (telephone pole, telephone box, signboard, sign), anti-pollution (inner and outer wall coating, vehicles, barricades, road barriers, etc.) Residual tack around the adhesive.

Release agent performance requirements

The role of the release agent is to smoothly separate the cured product from the mold, so as to obtain a smooth and flat product, and ensure that the mold is used repeatedly. The specific performance requirements are as follows:

1. Demoldability (lubricity). When forming a uniform thin film and a complex shape, the dimensions are accurate.

2. Good mold release persistence.

3. The appearance of the formed object is smooth and beautiful, and does not cause dust adhesion due to the application of sticky release agent.

4. Superior secondary workability. When the release agent is transferred to the molded product, it has no adverse effects on processed products such as electroplating, hot stamping, printing, coating, and adhesion.

5. Easy to coat.

6, heat resistance.

7. Pollution resistance.

8. Good forming and high production efficiency.

9. Good stability. When used with compounding agents and materials, its physical and chemical properties are stable.

10. Non-combustibility, low odor and low toxicity. Plastic release agent

Release agent selection method

Selection of Release Agents There are three types of release agents commonly used: inorganics, organics and polymers.

Inorganic mold release agents, such as talc, mica powder, and clay, white clay, etc. are the main components of the compound, mainly used as rubber release film release agent, semi-finished release agent.

Organic release agents include fatty acid soaps (potassium soap, sodium soap, ammonium soap, zinc soap, etc.), fatty acids, paraffin, glycerin, vaseline and the like.

Polymer release agents, including silicone oil, polyethylene glycol, low molecular weight polyethylene, etc., their release agent efficiency and thermal stability are much better than organic release agents.

Release agents are usually divided into powder, semi-solid and liquid. The powder and semi-solid can be applied to the mold surface with a brush or hand like wax grease. The liquid can be sprayed on the surface of the mold with tools such as a spray or a brush to form a barrier film. The liquid release agent is preferably sprayed.

Most developed countries in the international industry use release agents filled with metal spray cans. Due to the better sealing performance of the metal spray can, the release agent can be prevented from being oxidized or mixed with impurities, which can ensure the purity of the release agent when it leaves the factory. Large-scale injection equipment is installed indoors, and the ambient temperature changes little, which has no effect on the use of spray release agent. However, the temperature of the mold for compression molding must be considered, and a mold release agent with good thermal stability must be selected. Generally, the thermal decomposition temperature of the mold release agent is higher than the temperature of the mold. Otherwise charring will occur. For high-end products and secondary processing (such as spray painting and printing), select a release agent suitable for secondary processing. In order to prevent environmental pollution, it is necessary to choose a release agent that is not easy to burn, and has low odor and toxicity. In the selection of mold release agents, economics is an important factor that cannot be ignored. Poor quality release agent will cause cracks and wrinkles on the surface of the product, affect the appearance of the product and the service life of the mold, and bring environmental pollution. Selecting a high-quality spray release agent has a higher price, but a high comprehensive economic benefit.

In summary, the main points for the selection of release agents are:

1. Excellent release property, surface tension for spray release agent is between 17 and 23 N / m.

2, with heat resistance, no carbonization and decomposition when heated.

3. Stable chemical properties, no chemical reaction with molded products.

4. Does not affect the secondary processing performance of plastics.

5. Does not corrode the mold, does not pollute the product, and has low odor and toxicity.

6, the appearance is smooth and beautiful;

7, easy coating, high production efficiency;

Release agent considerations

Since most liquid internal release agents are acidic, pay attention to the following issues in use:

1. When using acid-sensitive pigments, it will cause color changes;

2. When using alkaline fillers, such as calcium carbonate, acidic release agents will react with it, causing the viscosity of the mixture to increase, but it will not affect the release effect;

3. If the filler is aluminum hydroxide, in addition to increasing the viscosity of the mixture, the acidic release agent will release water during the curing process of the mixture, causing problems such as bubbles and cracks.

Generally, the initial amount of internal release agent is 1% of the resin amount, and the effective addition range is 0.75-2% based on the weight of the resin. Should be adjusted appropriately according to the actual situation.

1. For thin-walled simple profiles, the dosage can be appropriately less, such as 0.8% or less;

2, thick-walled or complex shapes need to add more.

3. In high filler systems, the amount of internal release agent should be increased, but too much internal release agent will delay curing.

4. In the pultrusion production, if the resistance is too large and no reason can be found, it is necessary to appropriately increase the amount of release agent. When using it, pay attention to the order of addition. Before adding the curing agent, filler and other resin additives, add the internal release agent to the resin system and mix well. This can achieve the best demoulding effect.

Release agent solution

-Caused by uneven spraying: improve coating;

Caused by spray flow: adjust spray amount;

-Caused by wiping: choose the hardness of the release agent and the solvent system;

-Caused by evaporation: different solids have different solubility or different solvent dissolving ability, orange peel phenomenon, can not form a uniform film when solids precipitate during evaporation, adjust dispersant and solvent;

Resin flow: easy to appear at the turning point, overcome in mold design;

-Caused by air bubbles: There are many fine bubble pits on the surface of the product, raw material problems or defoaming properties of the release agent, air between the release agent and the mold, or rough mold surface, etc., to improve the hardness of the release agent;

Product shrinkage: shrinkage stress exceeds anti-tension, concentric spots, material shrinkage and injection pressure are mainly selected for adjustment;

-Caused by the heat capacity of the mold material: The heat capacity distribution of the mold reinforcement material is different, the stored heat is different, and the reaction occurs at high temperature, which is caused by the rapid release;

Release agent plastic release agent

Plastic release agent is specially used for the release from the mold during the process of injection molding, blistering and plastic products production. Most of these products are sprayed in iron cans, which are easy to use and easy to use.

First, the structural formula or composition

High viscosity polysiloxane, surfactant, water

Product

Plastic release agent is an aqueous emulsion made by reacting high-viscosity polysiloxane, environmentally-friendly surfactant and high-efficiency emulsifier.

Performance characteristics

1.Environmental protection

2. Does not affect the basic properties of the additive system.

3. Good diffusibility and permeability, and good compatibility with water.

4, good heat resistance (can withstand 300 degrees high temperature), chemical stability, strong oxidation resistance.

5, no physiological activity, no corrosion, no toxicity, no adverse side effects, non-combustible, non-explosive, high safety.

Application

It is mainly used for demoulding and anti-sticking when cutting rubber, plastic, EVA, printing paste, wire and cable, hot-melt adhesive products and adhesive tape.

Fifth, packaging, storage and transportation

450ml, 500ml iron can spray. Store in a cool and dry place to avoid direct sunlight. The storage period is one year. Transport as general goods.

Silicone release agent

Silicone release agent is specifically used to prevent the phenomenon that it is not easy to remove the product from the cavity when the molded vulcanized silicone product is released. In silicone vulcanization, it can quickly achieve clean and mold release from the mold, and can increase production efficiency and reduce mold maintenance and repair costs, while also maintaining excellent lubrication between metal and non-metal.

First, advantages

1. Silicone release agent is a new product developed mainly for the release of silicone rubber parts, trademark rubber molds, and silicone keypad production. It has the characteristics of excellent mold release, smooth surface, and no pollution.

2. It is not easy to contaminate the mold, reducing the number of times the mold is cleaned, and the secondary processing is easy.

3. Reduce the defective rate of molded products.

4. Just apply a thin layer, it will not accumulate in the corner, so it can improve the accuracy of the size

5.The release agent is colorless, odorless, non-toxic, does not hurt the skin, and is harmless to the human body.

6. Due to the extremely low surface tension and excellent thermal stability, it can be widely used in harsh temperatures, because this product has extremely high stability and safety, and it is not irritating and harmful at all, so you can use it with confidence. .

7, the product has the characteristics of easy dispersion, low addition ratio, etc., but also improve the product's glue effect. The product can also be used in food-grade products.

Product parameters

Colorless transparent liquid, white paste.

Ingredients: 3% (fluorine)

Specific gravity (25 ^o C): 1.01

PH: 10

Diluted solvent: water

The most appropriate dilution ratio: 3 ~ 5 times

Third, use

1. Dilution method: adjust the required concentration with water, and stir well.

2. After dilution with water, spray on the mold surface; the specific dilution ratio should be selected according to the ease of mold release of the silicone product. The amount of spray of the release agent during use will not cause the surface of the product after molding White appearance, cracks, watermarks, spitting, etc.

Fourth, matters needing attention

1. Avoid high temperature, direct sunlight, and keep away from sources of fire, strong acids, metal oxides, amines and flammable materials. It should be stored in a well-ventilated place at room temperature (preferably below 25 ° C).

2. The addition ratio is strictly controlled. Too many addition ratios of this product are prone to produce frosting and seriously affect the appearance. If this phenomenon occurs in the product, it can be eliminated by boiling, secondary vulcanization, etc.

Release agent thinner

Dichloromethane

CH2Cl2, boiling point 39.75, relative density 1.326, no flash point, surface tension 28.12mN / m, chemical stability, no oxidation or cracking at 290 degrees, strong dissolving ability, no burning; high concentration of steam causes poisoning, causing greenhouse effect.

Petroleum ether

It is a low boiling point fraction of petroleum. It is a lower alkane mixture. It is divided into three types according to different boiling points: 30-60 ° C, 60-90 ° C, and 90-120 ° C. It has low boiling point, high volatility, and toxicity similar to lower alkane.

120 # gasoline

C4-C11 is a mixture of alkanes, olefins, naphthenes and aromatic hydrocarbons. The main ingredients are pentane, hexane, heptane, and octane. It is highly volatile and irritating odors. A large amount of inhalation affects nerves.

Naphtha

The aromatic hydrocarbon mixture obtained from the coal tar light oil fraction has a boiling point of 120-200 ° C and is composed of toluene, ethylbenzene, etc., to avoid fire and affect the nerves.

Release agent

Heptane

C7H16, boiling point 98.4 , chemically stable, flash point -4 , surface tension 19.6mN / m, low toxicity.

Xylene

C8H10, an isomer, has a distillation range of about 140 ° C and a density of about 0.86. It has a high flash point, is flammable, has low toxicity, and has an effect on the skin.

Examples of release agent formulations

Formula One : Water-based ^[1] Release Agent

Basic components: 5 to 20 parts of paraffin, 5 to 8 parts of stearic acid, 5 to 10 parts of vegetable oil, 5 to 8 parts of co-emulsifier, calculated amount of potassium hydroxide, appropriate amount of other excipients, appropriate amount of paraben ethyl ester, to Ionized water to 100 parts.

Heat paraffin, stearic acid, co-emulsifier, auxiliary oily materials in one container to 60-80 ° C and melt. Put water, alkali agent, auxiliary water-based materials in another container, mix and heat to 80-90. ; keep the temperature of oil phase and water phase basically the same, and then slowly add water phase to oil phase under vigorous stirring, slowly emulsifying and inverting phase, the stirring speed will gradually slow down as the emulsification temperature decreases, stir to room temperature After the product, a white oil-in-water emulsion was obtained. The results show that the demolding effect and performance test are very good.

Formulation 2: Polyurethane water-based release agent

Polyurethane water-based release agent, composed of the following weight percentages:

Emulsified wax liquid: 10% to 15%; methyl silicone oil emulsion: 15% to 20%; modified silicone oil emulsion: 5% to 8%; deionized water: 50% to 55%; emulsifier: 4.5% to 6% ; Additives: 0.5% to 1%; Preservatives: 0.3% to 0.5%. This kind of water-based release agent is mainly used in the production of polyurethane products to release the mold after casting, giving most polyurethane molding a good release effect. Its characteristics are that the product uses water as the dispersed phase, and the formed water-soluble substance not only has the function of releasing the polyurethane foam, but also has biodegradability, no harmful substances such as VOC, and strong environmental protection; and water as a diluent, no pollution Easy to get, low cost.

Laws and regulations for release agents

Although the release agent industry has always focused on environmental protection, since the 1990s, global attention has been paid to reducing harmful vapors in the working environment and eliminating the use of chlorofluorocarbons (CFCS) compounds that have a damaging effect on the ozone layer in the atmosphere. By the end of 1989, release agents and suppliers had generally banned the use of chlorofluorocarbons from sprays and solvent carriers. Instead, other solvents are acceptable to the general public under the 1987 (Montreal Convention) guidelines.

Government (US) regulations tend to further reduce common solvents such as chlorinated hydrocarbons by the mid-1990s. Chlorine-containing solvents are widely used as fast-drying, non-flammable solvent carriers for release agents and mold cleaning agents. Because many active release ingredients are only soluble in a few agents, this may cause problems in release agent formulations. CFCS and some other chlorine-containing solvents belong to this class of solvents because of their solubility in release agents and their rapid volatility. However, many formulations have introduced new water-based release agents into a wide range of thermoset resin applications, such as unsaturated polyesters, epoxy resins, phenolics, and polyurethanes.

In addition, in the effort to stop using external mold release agents, resin suppliers and molders have become increasingly aware of and accepted the concept that mold release can be achieved by adding internal mold release agents directly to the resin. purpose.