Note: Descriptions are shown in the official language in which they were submitted.
THIN PLASTIC GELATIN LAMII~JATE MATERIAL
. . _
AND METHOD FOR MAKI~ SAME
The invention relates to the production of a thin stock
sheet material and in particular to continuous methods
of producing thin, reinforced sheets of plastics which
flow before setting but not after.
5 The class of plastic material which includes thermoset-
ting plastics and catalyst cured plastics are materials
which readily flow before setting, but not afterwards.
This class includes materials such as epoxy, melamine
formaldehyde, melamine phenolic, phenolic, polybutadiene,
10 thermosetting polyesters, thermosetting polyimide,
polyurethane, silicone and urea. For convenience, this
class will be termed "fluid-setting plastics" for this
application.
Previously, fluid-setting plastics have been sold
- 15 primarily as cast pieces. This implies high unit cost
because of batch processing. Fluid setting plastics
tend to have low tensile strength when cast in thin
sheets. This has limited the ability of manufacturers
to produce fluid-setting plastics in large thin sheets.
20 One approach in solving the problem of low tensile
strength is to add reinforcing fibers to the material.
Cast epoxy reinfored with glass or graphite fibers
is a wel] known high strength material. Another
approach is to form a laminate which reinforces the
25 low strength fluid setting material. Many epoxy
laminates are known.
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The present invention provides a method for making a
reinforced epoxy laminate comprising the steps of:
applying a non-bonding layer of gelatin to a substrate;
applying a bonding fluid layer of epoxy to said gelatin
5 layer; curing said epoxy to form a dimensionally stable
laminate with said gelatin layer; and separating said
gelatin layer from said substrate, thereby producing
a cured gelatin-epoxy laminate.
The present invention further provides a gelatin-epoxy
10 laminate material comprising, a uniformly thick layer
of gelatin bonded on a first side to a uniformly thick
layer of epoxy.
.
The invention resulted through the discovery that a
layer of fluid-setting plastic may be supported by a
lS layer of gelatin to form a plastic-gelatin laminate
sheet. The fluid-setting plastic may easily flow
onto a moving layer of supported gelatin to form a
continuous sheet of plastic-gelatin laminate where the
fluid-setting plastic creates the shape and the
20 dimensional stability after setting and the gelatin adds
- the desired tensile strength to the laminate sheet and
creates a substrate for a continuous sheet. It was also
discovered that gelatin has the important property as a
substrate for continuous sheets that if it is coated
25 onto plastic without the use of a subbing layer to
cause adherence, the gelatin may be separated from the
film base by mechanical force.
First a~layer of gelatin is applied to a non-bonding
plastic flexible base and then a uniform coating of a
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fluid-setting plastic is applied over the gelatin layer.
The combination of gelatin on the plastic film base
resembles a photographic film. The fluid-setting
plastic is then cured, forming a self-supporting
5 reinforced plastic-gelatin laminate. This combination
may be separated from the non-bonded plastic base to
form the desired laminate.
There are several possible alternative procedures that
may be followed. For example, the gelatin could be
lO coated with another layer of fluid-setting plastic on
the opposite side, thereby sandwiching the gelatin.
Another alternative involves passing the laminate
through water near its boiling point to remove the
gelatin leaving a thin fluid-setting plastic sheet.
151An advantage of these thin sheet plastics is their long
length, light weight per unit length and low cost
compared to cast sheets made by batch processing.
In the drawings, Figure l is a plan view of a process
for making an epoxy-gelatin laminate material;
20 Figure 2 is a plan view of a process for making an
epoxy-gelatin-epoxy "sandwich" laminate material;
Figure 3 is a plan view of a process for making
reinforced sheet epoxy;
Figure 4 is a top view of an example of an epoxy-gelatin
25 laminate article on a glass substrate;
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Figure 5 is a sectional view of the article of Figure 4
taken along lines 5-5; and
.
Figure 6 shows an epoxy-gelatin laminate article,
- derived from the article shown in Figure 5, after
5 removal of a glass substrate.
The present invention contemplates the use of gelatin
as a reinforcing material for fluid-setting plastics,
either as a temporary support or as a permanent laminate,
in order to form thin stock of the desired material.
10 Gelatin derived from cattle is a well-known material used
in photography to hold photosensitive materials in photo-
graphic films and papers. Gelatin acts very much like a
high polymer as described in "The Macromolecular
Chemistry of Gelatin" by Arthur Veis, Academic Press,
15 1964, Chapter II. It has great tensile strength when
dry. It also dissolves in water near 100C.
In the discussion below, epoxy is used as an example
of a fluid-setting plastic which may be reinforced and
continuously produced in accord with the present
20 invention. Other fluid-setting plastics could be used,
so long as they strongly adhere to gelatin when placed
in contact with that material. It is believed that all
fluid-setting plastics will do so.
The epoxy material discussed herein is the combination
25 of an epoxy resin and a curing agent. Many types of
epoxy resins are known and any of which may be used for
purposes described herein. For general applications,
epoxies which are clear or not clear may be used.
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In accord with the present invention, thin epoxy layers
are provided with the necessary mechanical strength for
forming sheets of epoxy stock material. With refere~ce
to Figure 1, epoxy is formulated in vat 11 which
5 receives constituent materials from supply tanks 13, 15.
Supply tank 13 contains the selected epoxy resin while
supply tank 15 contains the selected curing agent. The
curing agent which is selected should have good sta-
bility and be easy to handle, such as an acid anhydride.
10 Both are dispensed in appropriate chemical ratios into
vat 11, wherein the two constituents are mixed by
mechanical means. Vat 11 has an extrusion nozzle at
its lower end for distributing a coating onto a passing
substrate. Although not shown, extrusion may occur
15 under pressure conditions.
The starting material 17 comprises a plastic base 19
with a gelatin coating 21 thereon. The plastic base 19
may be any plastic support, whether opaque or trans-
parent, as long as the base is flexible, similar to
20 common photographic film base materials, such as
polyester, polyterephthalate, polycarbonate and
cellulose triacetate, except that the base 19 need not
be restricted to the common dimensions of film. To
that base, a gelatin layer 21 is applied, in a
25 conventional manner, except that no subbing layer
is applied to the plastic base 19. When the gelatin
is used only for reinforcement, the gelatin layer
contains no photosensitive material. However, photo-
sensitive material such as silver halide may be
30 contained within the gelatin if a photographic film
on an epoxy base is desired. In photographic film
manufacture, a subbing layer is usually applied in
1146~32;~
order to adhere a gelatin emulsion layer to a film base
layer. However, in the present case, separation of the
gelatin emulsion from the base layer is desired, so that
no subbing layer is used. Base 19 is referred to as a
5 non-bonding base.
The gelatin layer 21 is applied in a conventional manner,
in usual thicknesses characteristic of photographic
films. The starting material 17 is fed beneath vat 11
where a thin coating 31 of epoxy is applied. The
10 application is made as uniform as possible through
an extrusion nozzle under positive pressure.
The extruded epoxy coating 31 immediately begins to
cure, but the curing process may be aided, depending
upon the curing agent, by an oven 23 which directs
15 infrared radiation or hot air onto the epoxy coating,
as the base 19 moves the material overlying it down-
stream of the applicator station where vat 11 is
located.
Starting material 17 i5 continuously moved past the
20 extrusion nozzle of vat 11 by means of a conveyor 25
which contacts plastic base 19 with sufficient friction
to drive it forward beneath a fixed roller 27. Beneath
roller 27, the gelatin coating 21 is pulled from plastic
base 19. The gelatin coating 21 perferentialiy adheres
25 to the epoxy coating 31 which is pulled at roll~r 27
away from the plastic film base 19. The plastic base
19 continues in the same direction as previously,
around rollers 33 and 35 for subsequent cleaning and
re-use. Thus, plastic base 19 may be an endless loop.
30 On the other hand, the epoxy layer 31 has a gelatin
layer 21 adhered to it, forming a plastic-gelatin
laminate.
11~63~i.
Epoxies are very useful as the plastic in this plastic
gelatin laminate. They have superior adhesion and
high flexural strength. The increasingly stringent
requirements for flame retardancy and higher tempera-
5 ture resistant systems are being met by specia]lycontrolled molecular weight distribution and higher
bromine content systems.
Figure 2 shows the making of an epoxy-gelatin-epoxy
"sandwich" composite sheet. Such a composite sheet
10 material has essentially the same utility as the
epoxy-gelatin laminate sheet of Figure 1, with the
additional characteristic that the gelatin, which is
absorptive of water, is now shielded on both sides
by epoxy which is generally impervious to water.
15 Figure 2 shows the application of an epoxy coating
to the composite sheet which is the product of the
process of Figure 1. In particular, the composite
sheet 41 comprises an epoxy layer 31 and a gelatin
layer 21. A conveyor 45 advances this starting material
20 in the direction indicated by the arrow A toward vat 43
which receives constituent materials from supply tanks
47, 49. Supply tank 47 contains the selected epoxy
resin while supply tank 49 contains the selected
curing agent. The curing agent which is selected
25 should have good stability and be easy to handle, such
as an acid anhydride. Both constituents are dispensed
in appropriate chemical ratios into the vat 43, wherein
the two constituents are mixed by mechanical means.
Vat 43 has an extrusion nozzle at its lower end for
30 distributiny a coating onto the starting material 41.
Although not shown, extrusion may occur under pressure
conditions.
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The extrusion is an epoxy coating 51 over the starting
material 41. Immediately after extrusion, the coating
begins to cure, but may be aided, depending upon the
curing agent, by an oven 53 which directs infrared
5 radiation or hot air onto the extruded coating. The
finished material consists of a layer of epoxy 51 over
a layer of gelatin 21 which is over a layer of epoxy 31.
The thickness of the epoxy layers 31 and 51 may be the
same or may be different depending upon the use for the
10 material.
Note that in Figure 2 the layer 51 may be the same
fluid-setting plastic as layer 31 or may be a different
one. Figure 3 illustrates a method of making
reinforced epoxy wherein reinforcement comes not from
15 gelatin, because the gelatin is removed, but from
internal fibers.
The starting material 17 comprises a plastic base 19
with a gelatin coating 21 thereon, just as in Figure 1.
Once again, no subbing layer is used so that film base
20 19 is a non-bonding base. The starting material 17
is fed beneath vat 11 which supplies epoxy constituents
from supply tanks ]3 and 15. Supply tank 13 contains
the selected epoxy resin while supply tank 15 contains
the selected curing agent. Supply tank 14 dispenses
25 strengthening fibers, such as glass fibers so that the
epoxy will be self-reinforcing. Such glass reinforced
epoxy is known in the prior art. However, contrary to
the prior art, such an epoxy layer can be made thinner
because support is provided by the gelatin layer 21.
30 For example, the epoxy layer 32 may be as thin as 0.5
;32:~
g
millimeters or less, although the present method is not
limited to such thin epoxy layers,
The extruded epoxy coating 32 immediately begins to
cure, but curing may be aided by an oven 23 which
5 directs infrared radiation or hot air onto the epoxy
coating. Beneath roller 27 the gelatin coating 21 is
separated from the plastic base 19 with the gelatin
coating 21 perferentially adhering to the epoxy coating
32 which is pulled at roller 27 away from the plastic
10 base 19 and toward roller 61. From roller 61 the
composite epoxy-gelatin sheet is directed toward
roller 63 in a bath 65 maintained near 100C which will
p ca~ ~ ~;emoval of the gelatin from the epoxy, without
~ffocting the stability of the epoxy. The epoxy is
15 pulled out of the bath around roller 67, then about
roller 69 and wound on a spool or otherwise stored.
The same processes described above are suitable for
reinforcing other fluid-setting plastics, namely
melamine formaldehyde, melamine phenolic, phenolic,
20 polybutadiene, thermosetting polyesters, thermosetting
polyimide, polyurethane, silicone and urea. In each
case a laminate with improved tensile properties is
produced. If the thin stock fluid-setting plastic
produced as described herein has sufficient intrinsic
25 tensile strength for a desired application the gelatin
backing may be removed as described.
This application describes continuous processes for
making plastic-gelatin laminate materials. It will be
realized that casting methods may also be used to
30 produce these laminates. As an example, a disk which
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may be used as an optical recording medium may be made
as follows. A flat piece of glass is coated with a
layer of gelatin without any intervening subbing
layer. This intermediate product is similar to a
5 photographic plate in appearance. Next, two concentric
rings of equal height are placed on the gelatin, the
height of a desired epoxy layer. Next, liquid epoxy
is poured into the annular region between the two rings
and the epoxy is then cured. The epoxy is then peeled
10 from the glass and the gelatin will preferentially
adh~ere to the epoxy. The rings are left in place as
part of the disk. The final product is a gelatin-epoxy
disk. If the gelatin contains a photosensitive emulsion
an optical medium, suitable for recording data, is
15 formed.
The following is an example of a use for the gelatin-
epoxy laminate of the present invention. With reference
to Figure 4, a square plate 71 is shown which consists
of a flat piece of glass which is coated with a uniform
20 layer of gelatin without a subbing layer. Glass is
not necessary; a plastic substrate may be used. The
gelatin layer is smooth and continuous and has
approximately the same thickness as a gelatin layer on
a photographic plate. For the purpose of making an
25 optical recording medium, the gelatin may contain an
unexposed silver-halide black and white emulsion for
photographically recording data. Two concentric rings
73, 75 are placed on the gelatin. The outer ring 75
could be as large as to be tangent with edges of plate
30 71 or can be as small as to permit several disks to
be made on the same glass substrate. The height of
the rings 73, 75 corresponds to the height of an epoxy
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layer.
The gelatin is coated with a thin layer of fluid
setting epoxy which is poured between the rings 73
and 75. After the epoxy is cured, a sharp instrument,
5 like a razor blade, is used to cut the gelatin around
the outer diameter of the outer ring 75 and around
the inner diameter of the inner ring 73. Then the
epoxy-gelatin laminate is peeled from the glass
substrate. The glass substrate may be reused.
10 Depending upon the application the epoxy may be opaque
or clear. When it is opaque its thickness need not
be uniform and some bubbles may exist in the epoxy
without detrimental effect. If the epoxy must be
clear for recording or reading data through it, then
15 it must be optically flat and devoid of bubbles in the
active area of the disk. For application where the
disk forms a photosensitive medium, the gelatin would
typically be under eight microns thick and at least one
micron thick. The epoxy coating would typically be
~ 20 greater than 250 microns thick and less than 2500
; microns thick.
Figure 5 shows a sectional view of a portion of the
disk of Figure 4 with a glass substrate 91 supporting
the laminate. The laminate consists of the gelatin
25 layer 93 and the epoxy layer 95 on top of it.
In Figure 6, the laminate of Figure 5 is shown to have
been separated from the glass substrate. What remains
is the epoxy layer 95 adhearing to the gelatin layer
93. The finished disk is gelatin epoxy laminate which
30 has good dimensional stability required for use as a
data recording medium.
