Note: Descriptions are shown in the official language in which they were submitted.
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SOLUBLE POLYMER INTERLEAVING MATERIAL
B ground of the Invention
The present invention relates generally to the art of protecting
glass surfaces from staining and scratches, and more particularly to the
art of protecting glass surfaces without permanently altering the glass
surfaces.
U.S. Patent No. 3,723,312 to Hay discloses the use of dedusted
agglomerated salicylic acid in conjunction with an inert particulate sepa-
rator material, such as wood flour or polystyrene, to prevent staining of
stacked glass sheets. U.S. Patent No. 3,798,112 to Hay discloses agglom-
erating salicylic acid with polyethylene oxide to produce an interleaving
material which further comprises an inert particulate separating material
such as wood flour or polystyrene to prevent staining of stacked glass
sheets.
U.S. Patent No. 4,011,359 to Simpkin et al discloses an inter-
leaving material for separatlng glass sheets and protecting them from
staining and scratches which comprises a porous, finely divided support
material, impregnated with a weakly acidic material, and fine particles of
a chemically inert plastic material.
U.S. Patent No. 4,200,670 to Albach describes a method for pro-
tecting glass sheets during packing, shipping and storing. The methodinvolves applying water, a stain inhibiting material, and dry, finely
divided particles of a mechanical separator to the surfaces of glass sheets
prior to stacking them, in a plurality of sequential steps that produce`an
adherent coating which acts as a protective interleaving between facing
glass surfaces when the sheets are stacked.
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U.S. Patent No. 4,263,371 to Franz discloses a method for reduc-
ing the surface energy of glass by chemisorption of an alkyltin compound at
the glass surface. U.S. Patent No. 4,360,544 to Franz discloses a method
for protecting the surfaces of stacked glass sheets by chelDisorption of an
organotin compound on the glass surfaces, and separation of adjacent glass
surfaces with an inert interleaving material.
Su ry of the Inventio
The present invention provides effective temporary protection
to a surface, as well as an interleaving material for protection and sepa-
ration of adjacent surfaces. The present invention involves forming a
soluble polymer film on the substrate surface. The soluble polymer film
may further comprise inert, insoluble spacer particles such as polyethylene
or acrylic beads, as well as stain inhibitors such as adipic acid, or
hydrophobic additives such as chemically reacted colloidal silica. The
protective film of the present invention is applied to a substrate surface
prior to handling, storage, shipping, installation, and so on to protect
the surface from staining,- scratches, dirt, fingerprints, and other con-
taminants. When the substrate has reached its final destination, the
soluble protective film is easily renoved by ordinary washing procedures.
description of the Preferred Embodiments
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Substrates preferably glass sheets, are provided with temporary
protection Erom staining and scratches by application of a protective film
of a soluble polymer. Preferably, glass sheets are contacted with a solu-
tion of a water soluble film-forming polymer, and the solvent evaporated to
form a water soluble film on a glass surface before the glass is subjected
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to fabrication, finishing, handling, stacking, storage, transportation or
installation. A preferred polymer is polyvinylpyrrolidone, and preferred
solvents Include water and water miscible alcohols and ketones such as
methanol, ethanol, propanol, acetone and methyl ethyl ketone. Suitable
application techniques include spraying, dipping and roll coating. The
~olym~r film preferably comprises Inicrosized inert, insoluble organic
polymer particles to act as spacer material when glass surfaces are brought
together as in stacking for storage or shipment. Preferred polymer spacer
materials include polyethylene or acrylic beads.
In one preferred embodiment of the present invention, glass
sheets are contacted with a solution of a water soluble film-forming
polymer containing inert, insoluble polyethylene particles and hydrophobic
colloidal silica. The particles act as spacers when the glass sheets are
stacked for storage and shipment. When the glass sheets are installed ;n
architectural applications, the hydrophobic colloidal silica minimizes
wetting of the glass surfaces and thereby protects the glass surfaces from
staining ordinarily caused by concrete or mortar run-off and other contami-
nants generally encountered at construction sites.
In a second preferred embodiment of the present invention, where
glass sheets are to be silk-screened, a protective film is applied in accord-
ance with tlle present invention prior to such processing. In this embodi-
Kent, the protective film is applied to one surface of the glass sheets,
and must not transfer to the opposite surface. In addition, it is preferred
that the polymer film-former, as well as the particulate spacer, burn off
without residue during a tempering cycle. A preferred protective film in
this embodiment of the present invention comprises polyvinylpyrrolidone
film and polyethylene particles.
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In another preferred embodiment of the present invention where
a protective film of water soluble polymer acts essentially as an inter-
leaving material, the polymer film preferably comprises, in addition to
particulate spacing material, a stain inhibiting material such as an organic
aeid. A particularly preferred protective film incorporates polyvinyl-
pyrrolidone as the film-former, polyethylene as the particulate spacer, and
adipic acid as the stain inhibitor.
The present invention will be further understood from the descrip-
tions of specific examples which follow.
EXAMPLE I
A solution is prepared comprising 2 percent polyvinylpyrrolidone
and 2 pereent interleaving material in propanol. The interleaving material
is an equal weight mixture of acrylic beads and adipic acid. This composi-
tion is sprayed onto metal oxide coated surfaces of glass sheets. After 11
weeks of exposure at 140F. and 90 pereent relative humidity, the treated
glass surfaces show no scum or stain. By comparison, adjacent gIass sur-
faces separated by newsprint exhibit light scum, and adjacent surEaces
separated by other conventional interleaving materials show even greater
surface deterioration.
EXAMPLE II
A solution is prepared comprising 2 percent polyvinylpyrrolidone,
2 percent polyethylene particles, 2 percent hydrophobic colloidal silica,
and 0.2 percent wetting agent (ZONYL-FSN from DuPont) in isopropanol. The
composition is sprayed onto metal oxide coated surfaces of glass sheets to
protect them from concrete and mortar run-off at construction sites. To test
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the protection afforded by the soluble film, the treated sheets are placed
in a horizontal position and contacte(l with a cement slurry which is
allowed to dry on the coated glass surface. The sheets are then placed in
a humidity chamber at 120F. (48.9G.) and 100 percent relative humidity
for 2 weeks. when the samples are removed from the chamber and washed, the
cement washes off and the coated glass surface is clean with no stain.
EXAMPLE III
To protect glass surfaces from staining and scratches prior to
silk screening and tempering, a protective film on one surface of the glass
is required which will not transfer to an adjacent glass surface, does not
interfere with the silk-screening process, and burns off residue-free
during the tempering cycle. A suitable protective film is deposited on
glass surfaces from a solution of 2 percent polyvinylpyrrolidone, 2 percent
polyethylene particles and 0.2 percent wett;ng agent (ZONYL-FSN from DuPont).
This composition is sprayed onto one surface of a number of glass sheets.
The protective film formed prevents staining and scratching of the glass,
does not transfer to adjacent glass sheet surfaces, can be handled with
vacuum equipment, does not interfere with silk screening and burns off
residue-free in the tempering cycle.
The above examples are offered to illustrate the present invention,
which encompasses various modifications. For example other soluble poly-
mers may be employed, such as polyvinylalcohols or copolymers of polyvinyl-
pyrrolidone. Other solvents may be used, preferably water or water-miscible
ketones and alcohols such as acetone, methyl ethyl ketone, rnethanol or
ethanol. Other inert spacing material may be utilized such as acrylic
beads or wood flour. Other optional wetting agents may be e~nployed, as
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well as other hydrophobic additives. Substrates other than glass may be
protected with films in accordance with the present invention, the scope of
which is defined by the following claims.
