Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1995-02-27
1997-01-21
Nakarani, D. S.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
2641761, 428141, 428436, 428437, 524502, 524503, 525154, 525155, B32B 516, B32B 2730, C08F 828
Patent
active
055958184
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to sheet containing polyvinyl butyral (PVB) and more particularly to the roughened surface of such sheet and to a process for producing it.
Plasticized sheet containing PVB is known as an impact-dissipating layer for use with glass or rigid plastic panels (hereinafter "laminating panel(s)") in laminated safety glazings.
It is likewise known to roughen the major planar surface(s) of such sheet to facilitate deairing during preparation of such laminated glazings. More particularly, minute channels between the smooth surface of the laminating panel and the extremities of minute valleys in the face of a rough surface of the contiguous PVB sheet permit air between the two members to escape when pressure or vacuum is applied to the interface.
U.S. Pat. No. 4,654,179 discloses crosslinked PVB for generating surface roughness during extrusion. A single PVB phase is used with roughness described therein as a function of PVB molecular weight distribution, the broader the distribution obtained by increasing the crosslink level, the lower the magnitude of surface roughness. In such '179 patent, crosslinked and uncrosslinked PVB are chemically, molecularly integral in a homogenous mass. According to this patent, roughness is adjusted by changing crosslinking agent concentration used during synthesis of the PVB, the greater such concentration the lower the sheet roughness.
While this technique has been successful, it would be desirable to provide a more versatile way to regulate PVB sheet roughness using crosslinked PVB which does not solely rely on changing the chemistry of the resin during its synthesis.
SUMMARY OF THE INVENTION
Now improvements have been made in roughening one or both surfaces of PVB sheet which mitigate shortcomings of the prior art.
Accordingly, a principal object of this invention is to provide PVB sheet having a rough surface wherein crosslinked PVB is responsible for generating roughness.
Another object is to provide a tractable process for making such PVB sheet wherein the parameters defining roughness quality (including amplitude and pitch) can be readily changed.
Other objects will in part be obvious and will in part appear from the following detailed description and claims.
These and other objects are accomplished by a sheet comprising a plasticized polyvinyl butyral matrix containing discrete particles of crosslinked PVB which are integrally, randomly dispersed in the matrix and microscopically protrude from the surface of the sheet forming a rough surface thereon. The amount of the particle fraction is preferably 1 to 40 weight percent of the combined weight of matrix and particles; the size of the particles is 1 to 100 microns and the stiffness, measured by the concentration of crosslinking agent present in synthesizing the particles, is that resulting from a concentration of about 0.06 to 0.30 parts crosslinking agent per 100 parts polyvinyl alcohol.
Also provided in the process of preparing PVB sheet by extruding a plasticized formulation containing PVB through a die opening is the step in combination therewith of adding to the formulation before extrusion, a fraction of stiffly resilient particles of crosslinked PVB which during extrusion form a different phase from the balance of the PVB of the formulation and which on exiting the die opening mechanically interfere with and roughen the surface of the sheet being formed.
BRIEF DESCRIPTION OF THE DRAWINGS
In describing the overall invention, reference will be made to the accompanying drawing which is a photomicrograph of the surface of sheet according to the invention taken at a magnification of 100 times.
DETAILED DESCRIPTION OF THE INVENTION
The formulation of the sheet of the invention is a heterogeneous polymer mixture comprising first and second PVB components admixed with plasticizer, the first PVB component forming a matrix phase in which a minor weight amount (based on the combined weight of the first and second components) of particles of the second PVB component are
REFERENCES:
patent: 4654179 (1987-03-01), Cartier et al.
patent: 5482767 (1996-01-01), Karagiannis et al.
Hopfe Harold H.
Karagiannis Aristotelis
Monsanto Company
Murphy Michael J.
Nakarani D. S.
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