Polyvinyl Butyral Resin (PVB) is a solvent-based Resin synthesized by the acetal reaction of Polyvinyl Alcohol (PVA) and butyraldehyde in contact with coal.
Because Pvb Resin itself contains a lot of hydroxyl groups, it can bridge with some thermosetting resins to improve the properties of chemicals and film hardness.
Because PVB resin has the above excellent properties, it is widely used in the adhesive safety glass intermediate film of automobiles and buildings, rust primer, baking varnish, wood paint, printing ink, electronic ceramic and printed circuit board adhesive, metal to metal, metal to plastic adhesive, modifier of hot-melt adhesive, textile Tiewei waterproof processing, etc. New uses in various industries are also continuously developed and applied.
The general characteristics of PVB are as follows:
The appearance of polyvinyl butyral (PVB) resin is white spherical porous particles or powder with a specific gravity of 1:1; However, the filling density is only 0.20~0.35g/ml.
Thermal Properties
The glass transfer temperature (Tg) of polyvinyl butyral (PVB) resin ranges from 50 ℃ for low degree of recombination to 90 ℃ for high degree of recombination; The glass transfer temperature can also be adjusted to lower than 10 ℃ by adding an appropriate amount of Plasticizer.
Mechanical Properties
The film of polyvinyl butyral (PVB) resin has good water resistance, resistance and oil resistance (resistance to aliphatic, mineral, animal and vegetable oils, but not to sesame oil). PVB is widely used in printing inks and coatings because of its high hydroxyl content and good dispersion of pigments.
In addition, its chemical structure also contains hydrophobic acetal group, acetic group and hydrophilic hydroxyl group, so PVB has good adhesion with glass, metal, plastic, leather and wood.
Chemical Reaction
Any chemical that can react with secondary alcohol will also react with PVB. Therefore, in many applications of PVB, it is often combined with thermosetting resin to make it bridge and harden with the hydroxyl group of PVB to achieve chemical resistance, solvent resistance and water resistance.
Of course, depending on the type of heat-hardening resin and the mixing ratio with PVB, the coating film with different characteristics (such as hardness, toughness, impact resistance, etc.) can be prepared.
Safety Properties
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 the 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 should be stored in a dry and cool place and avoid direct sunlight. PVB should be stored without heavy pressure.
Solubility
PVB is soluble in alcohols, ketones, esters and other solvents. The solubility of various solvents varies according to the functional group composition of PVB itself. Generally speaking, all alcohol solvents are soluble, but methanol is more insoluble for those with high acetal group; The higher the acetal group, the easier it is to dissolve in ketone solvent and ester solvent;
PVB is easily soluble in alcohol ether solvent; 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 and type of solvent; In general, 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 influence of PVB chemical composition on viscosity is summarized as follows: under the same solvent and the same content of each group, the higher the degree of polymerization, the higher the solution viscosity; In the same solvent and the same degree of polymerization, the higher the acetal or acetate group, the lower the solution viscosity.
Dissolution method of PVB
When mixed solvents are used, the dissolution step is to put aromatic solvents (such as xylene, toluene, etc.) or ester solvents (such as n-butyl acetate, ethyl acetate, etc.) into PVB slowly in mixing, and then add alcohol solvents (such as n-butyl alcohol, ethanol, etc.) after PVB is dispersed and expanded,
At this time, the dissolution time can be shortened by heating; Using this dissolution method can avoid the formation of lumpy PVB (because the dissolution time will be several times shorter after the formation of lumpy PVB), thus the dissolution rate 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 solvent and help the solubility of PVB.
Processing Properties
Although PVB resin is a thermoplastic, it has almost no workability before adding plasticizer, but its workability is very easy after adding plasticizer.
The purpose of general coatings and adhesives is to change the resin properties by adding plasticizers to meet the application requirements, such as film softness, reducing the Tg point of the resin, reducing the temperature of heat sealing, and maintaining low-temperature flexibility.
Compatibility
PVB can be compatible with various resins, such as phenolic resin, epoxy resin, alkyd resin and MELAMINE resin.
B-08SY, B-06SY and B-05SY with higher acetality 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 requires high acetal PVB to be compatible.
