Polyvinyl Butyral Resin (PVB for short) is a solvent-based resin synthesized by acetal reaction of polyvinyl alcohol (PVA for short) and butyraldehyde under action of coal contact.
Because PVB resin itself contains a large proportion of hydroxyl groups, it can react with some thermosetting resins to improve chemical properties and film hardness.
Because PVB resin has above-mentioned various excellent properties, it is widely used in glued safety glass interlayer film of automobiles and buildings, rust primer, baking varnish, wood paint, printing ink, electronic ceramics and printed circuit board adhesive, adhesive between metal and metal, metal and plastic, modifier of hot melt adhesive, and waterproof processing of textile iron. New applications in various industries are continuously being developed and applied.

 

Appearance of polyvinyl butyral (PVB) resin is white spherical porous particles or powder, and its specific gravity is 1:1; but packing density is only 0.20~0.35g/ml.

Glass transition temperature (Tg) of polyvinyl butyral (PVB) resin ranges from 50℃ for low coincidence to 90℃ for high coincidence; glass transition temperature can also be adjusted by adding an appropriate amount of plasticizer to reduce it to below 10℃.

Coating film of polyvinyl butyral (PVB) resin has good water resistance, resistance and oil resistance (resistant to aliphatic, mineral, animal and vegetable oils, but not resistant to sesame oil). Because PVB contains high hydroxyl groups and has good dispersibility for pigments, it is widely used in printing inks and coatings.
In addition, its chemical structure contains both hydrophobic acetal and acetate groups as well as hydrophilic hydroxyl groups, so PVB has good adhesion to glass, metal, plastic, leather and wood.

Any chemical that can react with secondary alcohols will also react with PVB. Therefore, in many PVB applications, it is often used with thermosetting resins to bridge and harden hydroxyl groups of PVB to achieve chemical resistance, solvent resistance and water resistance.
Of course, depending on the type of thermosetting resin and mixing ratio with PVB, coating films with different characteristics (such as hardness, toughness, impact resistance, etc.) can be adjusted.

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

As long as PVB is not in direct contact with water, it can be stored for two years without affecting its quality; PVB should be stored in a dry and cool place, avoid direct sunlight, and PVB should be stored without heavy pressure.

PVB is soluble in alcohols, ketones, esters and other solvents, its solubility in various solvents varies depending on composition of PVB's functional groups. Generally speaking, alcohol solvents are easy to dissolve, but methanol is more difficult to dissolve in high acetal groups; the higher 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 soluble in aromatic solvents such as xylene and toluene; PVB is not soluble in hydrocarbon solvents.

Viscosity of PVB solution is greatly affected by solvent formula and type of solvent; in general, if alcohol is used as solvent, the higher molecular weight of alcohol, the higher viscosity of PVB solution;
Aromatic solvents such as xylene and toluene and hydrocarbon solvents can be used as diluents to reduce viscosity of PVB solution; influence of PVB chemical composition on viscosity is summarized as follows. Under same solvent and same content of each group, the higher degree of polymerization, the higher solution viscosity; under same solvent and same degree of polymerization, the higher acetal or acetate group, the lower solution viscosity.

When mixed solvents are used, dissolving step is to first put aromatic solvents (such as xylene, toluene, etc.) or ester solvents (such as n-butyl acetate, ethyl acetate, etc.) into PVB while stirring, then add alcohol solvents (such as n-butanol, ethanol, etc.) after PVB is dispersed and swelled.
At this time, temperature can be increased to shorten dissolution time; using this dissolution method can avoid formation of lumps (lumps) of PVB (because dissolution time will be several times longer after formation of lumps of PVB), thus speeding up dissolution. Generally, ratio of aromatic and alcohol solvents is 60/40～40/60 (weight ratio), and PVB solution with lower viscosity can be prepared.
Solvent composition contains 2 to 3 wt% of water, which can increase hydrogen bonding strength of alcohol solvents (hydrogen bonding) and help solubility of PVB.

Although PVB resin is a thermoplastic plastic, it has almost no processability before adding a plasticizer. Once plasticizer is added, its processability is very easy.
In general coatings and adhesives, plasticizers are added to change characteristics of resin to meet application requirements, such as film flexibility, lowering Tg point of resin, lowering heat sealing temperature, and maintaining low-temperature flexibility.

PVB is compatible with many resins, such as phenolic resin, epoxy resin, Alkyd resin and Melamine resin.
B-08SY, B-06SY and B-05SY with higher acetal degree can be mixed with nitrocellulose in any ratio. PVB and alkyd resins are partially compatible. General PVB is compatible with low-molecular-weight epoxy resins, while high-molecular-weight epoxy resins need to choose high acetal PVB to be compatible.