Background and overview

Globally, Iron Oxide is the second largest inorganic pigment after Titanium Dioxide and the first largest color inorganic pigment. Iron oxide pigments mainly include iron oxide red, yellow, black and brown with iron oxide as the basic material. Iron oxide yellow, also known as hydroxyl iron oxide (FeOOH), will be dehydrated and decomposed into red at about 177 ℃, so the application of ordinary iron yellow pigment in high-temperature occasions such as plastic processing and baking coatings is limited. Iron oxide yellow pigment can improve its temperature resistance through surface coating, so as to expand the application field of iron oxide yellow pigment.

The chemical formula of iron oxide yellow (also known as hydroxyl iron) is α- Fe2O3 · H2O or α- FeOOH, with needle like structure and yellow powder, is a kind of particle size less than 0.1 μ m. Iron series pigment with good dispersibility in transparent medium has strong coloring power, high covering power, insoluble in alkali and slightly soluble in ACID. Synthetic iron oxide yellow has the characteristics of light resistance, good dispersion, non-toxic, tasteless and difficult to be absorbed by human body. It is widely used in coatings, plastics, ink and pharmaceutical industry.

Physical and chemical properties and structure

1. Iron oxide yellow pigment has acid and alkali resistance, resistance to general weak and dilute acids, and is very stable in alkaline solution of any concentration.

2. Iron oxide yellow pigment has certain light resistance, heat resistance and weather resistance. Its coating color is durable and can keep the coating from being damaged in light. Iron oxide yellow pigment is stable in a certain temperature range, but beyond the limit temperature, its color begins to change, and the degree of change is more significant with the increase of temperature. Iron oxide yellow pigment is not affected by cold, heat, dry and wet weather conditions.

3. Iron oxide yellow pigment is very stable in any ambient atmosphere (such as gases containing H 2S, Co, so 2, HCl, no, etc.). And resistant to pollution, water, oil and solvent penetration, insoluble in water, mineral oil or vegetable oil.

4. Iron oxide yellow pigment has strong coloring power and high hiding power. With the decrease of pigment particle size, its coloring power is stronger.

application

Nano iron oxide yellow has the characteristics of acid resistance, alkali resistance, non toxicity and low price. It is widely used in coatings, plastics and rubber. The particle size of nano iron yellow is less than 100 nm, which makes it have some unique characteristics. When light shines on its surface, transmission and diffraction will occur, showing transparent yellow, and can strongly absorb ultraviolet rays, Therefore, it can be used as a functional pigment for the surface paint of high-grade cars, precision instruments, bicycles, motorcycles, cosmetics, food, drugs and other coloring additives.

Pure PVB is non-toxic and harmless to human body. In addition, ethyl acetate or alcohol can be used as solvent, so PVB is widely used in printing ink of food containers and plastic packaging in European and American countries.

Storage safety properties

PVB can be stored for two years without affecting its quality as long as it is not in direct contact with water; PVB shall be stored in a dry and cool place and avoid direct sunlight. Heavy pressure shall be avoided during PVB storage.

Solubility

PVB is soluble in alcohol, ketone, ester and other solvents. The solubility of various solvents changes according to the functional group composition of PVB itself. Generally speaking, alcohol solvents are soluble, but methanol is more insoluble for those with high acetal groups; The higher the acetal group, the easier it is to dissolve in ketone solvents and ester solvents;

PVB is easily soluble in cellosolve solvents; PVB is only partially dissolved in aromatic solvents such as xylene and toluene; PVB is insoluble in hydrocarbon solvents.

Viscosity characteristics of PVB solution

The viscosity of PVB solution is greatly affected by the formula of solvent and the type of solvent; Generally speaking, if alcohol is used as solvent, the higher the molecular weight of alcohol, the higher the viscosity of PVB solution;

Aromatic solvents such as xylene and toluene and hydrocarbon solvents can be used as diluents to reduce the viscosity of PVB solution; The effect of PVB chemical composition on viscosity is summarized as follows: under the same solvent and the same content of each base, the higher the degree of polymerization, the higher the solution viscosity; Under the same solvent and the same degree of polymerization, the higher the acetal group or acetate group, the lower the solution viscosity.

Dissolution method of PVB

Where mixed solvents are used, the dissolution step is to first put aromatic solvents (such as xylene, toluene, etc.) or ester solvents (such as n-butyl acetate, ethyl acetate, etc.) into the mixing, slowly put PVB into the mixing, and then add alcohol solvents (such as n-butanol, ethanol, etc.) after PVB is dispersed and expanded,

At this time, the dissolution time can be shortened by heating; Using this dissolution method, the formation of lumpy PVB can be avoided (because the dissolution time will be several times after the formation of lumpy PVB), so the dissolution speed can be accelerated. Generally, the ratio of aromatic and alcohol solvents is 60 / 40 ~ 40 / 60 (weight ratio), and PVB solution with low viscosity can be prepared.

The solvent composition contains 2 ~ 3wt% water, which can improve the hydrogen bonding strength of alcohol solvents and help the solubility of PVB.

Processing properties

Although PVB resin is a thermoplastic, it has little processability before plasticizer is added. Once plasticizer is added, its processability is very easy.

The purpose of general coatings and adhesives is to change the resin characteristics by adding plasticizers to meet the application requirements, such as film softness, reducing the TG point of the resin, reducing the heat sealing temperature, maintaining low-temperature softness, etc.

Compatibility

PVB can be compatible with a variety of resins, such as phenolic resin, epoxy resin, alkyd resin and MELAMINE resin.

B-08sy, b-06sy and b-05sy with high acetal degree can be mixed with nitrocellulose in any proportion. PVB and alkyd resin are partially compatible. General PVB is compatible with low molecular weight epoxy resin, while high molecular weight epoxy resin needs PVB with high acetal degree to be compatible with each other.