Aluminate coupling agent is used for the modification of inorganic filler surface activity. Its structure is similar to that of titanate coupling agent, There are two kinds of active groups in the molecule. One can interact with the surface of inorganic filler; The other can be entangled with resin molecules, resulting in coupling between inorganic filler and matrix resin. It has the characteristics of light color, non-toxic and easy to use. Its thermal stability is better than that of titanate coupling agent, and the price is only half of that of titanate coupling agent.

Aluminate coupling agent 

Performance characteristics

1. Non toxic, low taste, synergistic thermal stability and lubricity to PVC, wide application range, no diluent, easy to use and low price.

It is applicable to the surface activation modification of various inorganic fillers (such as calcium carbonate, wollastonite powder, talc powder, kaolin, bentonite, gypsum powder, alumina, etc.), inorganic flame retardants (such as magnesium hydroxide, aluminum hydroxide, zinc borate, antimony trioxide, etc.) and pigments (such as iron oxide red, lithopone, titanium dioxide, zinc oxide, lithopone, etc.). The modified fillers, flame retardants and pigments can be applied to composite products such as plastics, rubber, coatings, inks, laminated products and adhesives.

2. Various inorganic powders activated and modified by aluminate coupling agent produce an organic molecular layer due to chemical or physicochemical action on their surface, which changes from hydrophilicity to organophilicity. Practice has proved that when the surface of inorganic powder is modified by aluminate coupling agent and used in composite products, the inorganic friendly end and organic friendly end of coupling agent can react with the surface of inorganic filler and organic resin respectively or form entanglement structure, which enhances the interface compatibility between inorganic powder and organic resin. Therefore, aluminate coupling agent is used for modification, It can not only improve the processing performance of plastic products filled with inorganic powder, but also significantly improve the physical and mechanical properties of products, reduce the water absorption, oil absorption and uniform dispersion of fillers. For some low filled plastic products, generally, the amount of filler can be greatly increased (double or more than double the original filling amount), the processing performance can be improved (the melt viscosity is reduced, the die wear is reduced), the product quality can be improved and the production cost can be reduced, so it has obvious economic benefits.

3. In the grinding process of pigment and ink, the measured coupling agent can be directly input to improve the dispersion of pigment (filling), shorten the grinding time, improve the fineness, brightness and reduce the viscosity.

Product consumption:

The amount of aluminate coupling agent is generally 0.3% ~ 1.0% of the filler amount of composite materials. For plastic hard products molded by injection or extrusion, it is about 1.0% of the filler, and for products molded by other processes, soft products and foamed products, it is 0.3% ~ 0.5% of the filler. Fillers with high specific surface such as aluminum hydroxide, magnesium hydroxide and white carbon black can be used for 1.0% ~ 1.3%. Its dosage is not in direct proportion to the effect. If it is too much, the coupling agent will be surplus, but the performance will be reduced (the tensile and impact resistance will be reduced in plastics, and the adhesion will be greatly reduced in coatings). If it is too small, the effect will not be significant due to incomplete coating. Therefore, the best dosage should be tested in application, so as to be economical and effective.

Before selecting the coupling agent, the moisture content of the filler used shall be measured first, and the specific variety shall be determined according to the moisture content state and the characteristics of the above aluminate coupling agents. The dry filler should be monoalkoxy type, and the wet filler can be chelated type or monoalkoxypyrophosphate type. When selecting aluminate coupling agent, the melting point, crystallinity, molecular weight, polarity, aromaticity, fat foot and copolymerization structure of the polymer should also be considered. For thermosetting polymers, the curing temperature and curing mechanism should also be considered.

Before selecting the coupling agent, the moisture content of the filler used shall be measured first, and the specific variety shall be determined according to the moisture content state and the characteristics of the above aluminate coupling agents. The dry filler should be monoalkoxy type, and the wet filler can be chelated type or monoalkoxypyrophosphate type. When selecting aluminate coupling agent, the melting point, crystallinity, molecular weight, polarity, aromaticity, fat foot and copolymerization structure of the polymer should also be considered. For thermosetting polymers, the curing temperature and curing mechanism should also be considered.

The shape, specific surface, moisture content, acid-base and chemical composition of the filler can affect the coupling effect. Generally, the coupling effect of coarse particle fillers is not as good as that of fine particles, but there is the opposite phenomenon for ultra-fine fillers (such as CaCO3 ≥ 2000 mesh).

Usage methods:

1. Mixing method: it is to directly mix polymer, filler or pigment and other additives with aluminate coupling agent. This method is relatively simple. It does not need to increase equipment and change the original processing technology. The disadvantage is that the dispersion is not ideal, because other additives have competitive reaction with coupling agent.

2. Pretreatment method: firstly, the filler or pigment is pretreated with coupling agent, and then processed and mixed with polymer and other additives. This method has many advantages. It is especially suitable for some engineering plastics with complex polymer components or high processing temperature. It can prevent unnecessary side reactions. The decomposition point of coupling agent and filler will be greatly improved after pretreatment.

① Dry mixing method: in order to evenly cover a small amount of Titanate on the surface of pigments and fillers, a small amount of diluent is generally added. When the dosage ratio of the diluent to the coupling agent is 1:1, a small amount of titanate can be evenly distributed on the surface of fillers. The fillers cannot be evenly covered without diluent. The diluent can use the solvent and lubricant in the original process formula.

② Wet mixing method: monoalkoxy type, coordination type and other coupling agents can be diluted with solvent oil, petroleum ether, benzene alcohol and other solvents to soak the pigment, and then remove the solvent by heating or decompression. For water-soluble chelating type, dilute and soak with water, and then remove the water. This method is relatively complete, but it costs too much in industrial production and is not economical.

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