Polyvinyl Butyral Resin (PVB) is a solvent type Resin synthesized by acetal reaction of Polyvinyl Alcohol (PVA) and butyral under the action of coal contact.
Because Pvb Resin itself contains a large proportion 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-mentioned excellent characteristics, it is widely used in the adhesive safety glass intermediate film of automobiles and buildings, rust cutting primer, baking paint, wood paint, printing ink, adhesive of electronic ceramics and printed circuit boards, adhesive between metal and metal, adhesive between metal and plastic, modifier of hot-melt adhesive, and waterproof processing of textiles. A variety of new industrial applications 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; But 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 ℃ of low degree of gravity to 90 ℃ of high degree of gravity; The glass transfer temperature can also be adjusted by adding an appropriate amount of Plasticizer to reduce it to below 10 ℃.
Mechanical properties
The coating film of polyvinyl butyral (PVB) resin has good water resistance, water resistance and oil resistance (it is resistant to aliphatic, mineral, animal and vegetable oils, but not to sesame oil). PVB is widely used in printing inks and coatings because it contains high hydroxyl groups and has good dispersibility to pigments.
In addition, its chemical structure contains hydrophobic acetal group, Acetic Acid group and hydrophilic hydroxyl group, so PVB has good adhesion to 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 used 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 thermosetting resin and the mixing ratio with PVB, films 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 food containers and plastic packaging printing inks in Europe and America.
Storage properties
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, and avoid direct sunlight. PVB should be stored under heavy pressure.
Solubility
PVB is soluble in alcohol, ketone, ester and other solvents. The solubility of various solvents varies with the functional group composition of PVB itself. Generally speaking, alcohol solvents are easy to dissolve, but methanol is more difficult to dissolve with high acetal groups; The higher the acetal group, the more easily dissolved in ketone solvents and ester solvents;
PVB is easily dissolved in cellosolve solvents; PVB is only partially dissolved in aromatic solvents such as xylene and toluene; PVB is not soluble in hydrocarbon solvents.
Viscosity characteristics of PVB solution
The viscosity of PVB solution is greatly affected by the formulation 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 influence of PVB chemical composition on viscosity can be summarized as follows: under the same solvent and the same content of each group, the higher the degree of polymerization, the higher the viscosity of the solution; Under the same solvent and the same polymerization degree, the higher the acetal group or acetic ACID group, the lower the solution viscosity.
Dissolution method of PVB
When mixed solvents are used, the dissolving step is to put aromatic solvents (such as xylene, toluene, etc.) or ester solvents (such as n-butyl acetate, ethyl acetate, etc.) into the mixture and slowly add PVB. After PVB is dispersed and expanded, alcohol solvents (such as n-butanol, ethanol, etc.) are added,
At this time, the dissolution time can be shortened by heating; Using this dissolution method, it is possible to avoid forming lumpy PVB (because the dissolution time will be several times shorter after forming lumpy PVB), and thus 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 plastic, it has almost no processability before the plasticizer is added. Once the plasticizer is added, its processability is very easy.
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 softness.
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 to choose PVB with high acetal degree to be compatible.
