PVB Chemische Eigenschaften,Einsatz,Produktion Methoden
R-Sätze Betriebsanweisung:
R36/37/38:Reizt die Augen, die Atmungsorgane und die Haut.
S-Sätze Betriebsanweisung:
S26:Bei Berührung mit den Augen sofort gründlich mit Wasser abspülen und Arzt konsultieren.
S36:DE: Bei der Arbeit geeignete Schutzkleidung tragen.
S24/25:Berührung mit den Augen und der Haut vermeiden.
Beschreibung
Polyvinyl butyral (PVB) is a synthetic resin obtained by the condensation reaction
of PVA and butyraldehyde in the presence of acid catalyst. Since the acetalization
reaction cannot be carried out completely, the molecular chain of PVB contains three
functional groups, butyral, alcohol hydroxyl and acetate, the latter two of which come
from PVA. The chemical structure is:
The proportion of these three groups can be controlled by changing the reaction conditions, but they are randomly distributed in the long molecular chain. The proportion and distribution of the three are different, and the properties of PVB are also
different.
Chemische Eigenschaften
PVB resin is white or slightly yellow amorphous powder, with a particle size of
40–200 μm, fluidity and a density of 1.11 kg.m–1. It is a thermoplastic material, the
softening temperature is 60–65°C, the glass transition temperature is 70–78°C, the
molding temperature is 120–170°C, and the temperature adaptation range is 10–80°C.
PVB resin is insoluble in water, but soluble in a variety of organic solvents such as
alcohols, esters, benzene and ketones. It is miscible with various plasticizer including
phthalates, phosphates, and fatty acid ester. It has good compatibility with various
resins such as phenolic resin, urea–formaldehyde resin, melamine resin, epoxy resin,
nitrocellulose and natural resin. By mixing these resins in an appropriate ratio, the
physical and chemical properties are improved, and the cost is reduced.
PVB resin has certain chemical stability, but it can be decomposed in acidic or
alkaline (especially acidic) medium. It starts to decompose thermally after being
heated to 100°C, and will be almost completely decomposed at 200–240°C. Hydrolysis can occur in dilute acid, at this time intermolecular cross-linking can occur, a
small amount of double bonds is formed in the chain, and the acetate group will be
further hydrolyzed. Heated in concentrated acid to form a transparent solution, while
decomposing into aldehydes. Upon heating in dilute alkali solution with alkali concentration less than 1%, the free acid in PVB resin is neutralized and the thermal
stability of the resin is improved. However, when PVB resin is heated with 3% alkaline
solution to boiling, the acetate groups can be further hydrolyzed and saponified.
Verwenden
The main application of poly(vinyl butyral) is as interlayers in safety glass
laminates. In this application, a pure (colourless, light-stable) product with
high hydroxyl content (for good adhesion) is required. Such material is
preferably prepared from poly(vinyl alcohol) rather than directly from
poly(vinyl acetate). In a typical process, completely hydrolysed poly(vinyl
alcohol) is suspended in ethanol and then butyraldehyde and a small quantity of sulphuric acid (catalyst) are added. The mixture is heated at 800℃ for 6
hours. Water is then added to the product with rapid agitation and the
poly(vinyl butyral) is precipitated as granules, which are washed with alkali
and dried.
Poly(vinyl butyral) is generally softer than
poly(vinyl formal) with lower softening point, hardness and tensile strength.
In commercial polymers the hydroxyl content exerts a major influence on the
solubility characteristics. Most grades are soluble in alcohols, glycol ethers
and dioxan and as the hydroxyl content decreases the polymers become more
soluble in ketones and esters.
Poly(vinyl butyral) used in safety glass generally has 78-80% butyral
content, 18-19% hydroxyl content and less than 2% acetate content. For this
application the polymer is plasticized with an ester such as dibutyl sebacate
to the extent of about 30 parts of plasticizer per 100 parts of polymer; the
compound is then sheeted by calendering. To produce safety glass, the sheet is
placed between two pieces of glass and the laminate is then bonded under
heat and pressure.
PVB Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
