Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Backs,~round of the Invention ~
Field of the Invention ~ ;
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This invention relates to a coated foam sheet in which the resin in ~ -
each of the layers is at least predominantly a styrene-maleic anhydride
10 copolymer. A process of producing such a sheet is disclosed.
Prior Art
- Related to the process and product disclosed herein is the process s~.
and product disclosed in Whelan et al IJ.S. Patent 3,616,020.
An object of this invention is to provide a thermoformable coated --
15 foam sheet of improved properties. A furt:her object is to provide such a
sheet which uill remain flat for use as is or which can be thermoformed
and thereafter retQin the new shape.` A further object is to provide a sheet
which can be laminated to other materials to provide stiffness to the ~J~
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resulting composite if the material to which it is laminated is flexible. ;`-
The product of our invention can be used m automobile headliners, ` -
as aluminum siding backerboard, in the production of disposable pallets, , .. ..
as display board, etc. ' ~.
Summary of the Invention ,. .
Broadly our invention comprises an essentially flat plastic laminate
~ .:
25 ~ which is flexible and thermoformable having an intermediate foam layer
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; formed by extruding a foamable resin mixture comprising, on a weight
! - . : . ::
'i basis, at least 60% of a styrene-maleic anhydrlde copolymer, up to 20% of -
l~ reclaim resin from said sheet, up to 20~ of crystal polystyrene\, and a
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film coating on each side of a resin comprising at least 90% of a styrene
maleic-anhydride copolymer, said sheet having~ a total thickness 0. 7 to ;
7mm, with each film having a thickness of 0 . 03 to 4mm, the weight
. ~ .
oî said laminate being 200 to 1,500 g/m2 with the foam weight being -;
150 to 600 g/m2, the adhesion of film to foam being an average of at
least 30 newtons/meter with no value less than 20 newtons/meter when -~testing both sides in machine and transverse directions at an angle
of 90 at a test rate of 300 mm/minutes, said laminate having a flatness
factor of 5 cnl for a sheet having dimensions of 1. 5 by 3 meters . The
balance of each resin layer can be crystal polystyrene. The styrene-
maleic anhydride copolymer contains from 5 to 20% by weight of bound
maleic anhydride . The solid resin coating preferably contains 1. 5 to
10% by weight of a rubbery polymer such as high cis-polybutadiene.
Drawing ~`
The drawing includes: ~ ~
Figure 1, a cross section of a final product of our invention; 1;
Figure 2, a perspective view of apparatus suitable for producing
foam coated with film; ~.
Figure 3, a top view of the foam extrusion and slitting system;
and ,~.
Figure 4, a side view of the system of Figure 3.
Preferred Embodiment ~ ;~
Referring to Figure 1, we have illustrated in cross section the ,
product produced according~ to our invention as it is incorporated in
an automobile heaclliner. This Figure shows the foam layer 10 with
solid resin layers 11 and 12 fused to the foam layer 10. 13onded to
solid resin layer 12- is a rubbery foam layer 13 and bonded to layer
13 is a cloth layer 14. For its ultimate use, this composite structure
of l:igure 1 is thermoformed to form an automobile headliner.
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The process of the invention can be used to produce such a
composite structure containing layers 10, 11, and 12. For the head-
.. . . .
liner application, it is preferred that the laminate have a weight of :~
2 2
640 g/m with the foam having a weight of 210 g/m . The solid resin
layers 11 and 12 have a thickness of 0. 2mm and the laminate have a
thickness of 3 . 8mm maximum .
The resulting sheet containing layers 10, 11, and 12 should have
a flatness factor of not over 5cm. The flatness factor is a measurement
of the amount of upward bowing in a sheet having dimensions of 1. 5 by
3 meters.
The thickness of rubbery foam sheet 13 is generally substantially
thicker than the composite coated foam sheet but this is dependent upon
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the amount of padding desired in the final product. The cloth layer 14 :
is any suitable material having decorating properties for use in an " : `~
15 automobile headliner.
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Drawing attention to Figure 2, the principal steps of the process -~
can be seen. The process comprises mixing the resin with a nucleating
agent and feeding this mixture to extruder 20 wherein a blowing agent is
added. Those skilled in the art will recognize that a number of
systems can be used for nucleating and blo~,ving. We prefer to use, on "~
a weight basis based on the resin, O.1 to ll~o sodium bicarbonate, O.1 to ~ ~-1% citric acid, and 2 to 3% isopentane. This mixture is extruded through
circular die 21 and the tube foams and expands over a sizing mandrel
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(now shown) to produce a tubular foam structure 22. Tension is
maintained on tube 22 in S ~rrap rollers 23, 24, and 26 after passing
over roller 27. Figures 3 and 4 show top ~md side views of the system.
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The tube is slit at the top by knife 25 after it lcaves the cooling mundrel.
Therenfter~ the sheet passes over rollers 28 and 29 before entering a
polish roll stack comprising rolls 30, 31, and 32. Into the nip between
rolls 30 and 31, a sheet of unfoamed resin 33 extruded from the extruder 39,
5 is fused to the sheet 31 by the pressure at said nip. This foam sheet, now
coated on one side, is passed over rolls 42, 43, 44, and 46 and into a second
polish roll stack comprising rolls 47, 48, and 49. From die 50, a sheet 51
is extruded into the nip by the rolls ~7 and 48, this applying a second i
solid resin coating~ to the foam. This coated foam now having solid resin
10 on both sides thereof, and shown at 52 passes over roll 55 and into
tension control roll system comprising rolls 53 and 54. The proper tension ~ ¦
is adjusted to produce a flat wrinkle-free sheet without snapping the web.
Obviously, the sheet at this stage has the first coating as the top layer.
Thereafter, the sheets are cut to length in shear means 58 and passed
15 into the finish stack 59.
The resins use~ in the production of the preferred article prepared -
according to this invention are styrene-maleic anhydride copolymers
containing approximately 10 percent of bound maleic anhydride. For the
foam, we prefer to use a resin having the following properties: -;
ASTM Typical
Properties MethodValues -
.:
Tensile Strength, psi D-638 7,800
Tensile Elongation, % D-638 2.0
Tensil Modulus, 105 psi D-638 4. 5
Flexural Strength, psi D-790 13,50û
llexural Modulus, 105 psi D-790 4.7
Izod Impact Strength, D-255 o. 4
Ft . I.bs . /In .
' Dcflection Temperature D-618 237
Under Load, F., 264 psi
Annealed at 90C.
,, (1/2" x 1/2" x 5" Bar)
30 l, -4-
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! ASTMTypical
' Properties Me~hodValues
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Vicat, C. D-1525 120
F. 248
Specific Gravity, D-792 1.08
23/23C. ~:
Water ~bsorption, Wt . ~6 D-57Q 0.11 . .:
Mold Shrinkag~e, In . /In . D-955 0.005
:: .~.....
Rockwell Hardness, D-785 108 -
"L" Scale -,
For the coating, we also use a styrene-maletic anhydride
copolymer containing approximately 10 percent bound maleic anhydride
. .
and approximately 3 percent of a rubbery modifier, high
cis-polybutadiene being most commonly used. The following properties
describe a suitable material:
ASTM Typical
Properties MethodValues
Tensile Strength, psi D-638 5,000
Utlimate Elongation, % D-638 25 ;~
Tensile Modulus, 10 psi D-638 3.2
Flexural Strength, psi D-790 8,900
Flexural Modulus, 105 psi D-790 3.4 ` ~
I~od Impact Strength D-256 3.4 '
Ft. Lbs . /Inch
Deflection Temperature D-618 239
Under Load, F. 264 psi
Annealed at 90C.
(1/2" x 1/2" x 5" Bar)
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Vicat Softening Point, C. D-1525 121 ~ -
, F. 250
Specific Gravity, 23/23 C D-792 1.06
Wntcr Absorption, Wt. g; D-570 0.12
` Mold Shrinkage, In./In. D-955 0.006 - 0.007
Rockwell Hardness, "L" Scale D-785 80
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j~ ~xample
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jl Using a 6" extruder with a 3. 75 inch diameter die opening, a
mixture of the styrene-maleic acid copolymer containing, on a weight
basis, 0. 5 percent citric acid and 0 . 5 percent sodium carbonate as a
nucleating agent and 4 percent isopentane ns a blowing agent was
extruded . The circumference of the tube of the blown material expanded ~ ~ ~
to 52 inches. This tube was then slit and opened up. It has a weight 1~, ,`
of 210 grams per square meters. The average pore size in the foam was
approximately 0 . 2mm in diameter, this diameter providing maximum
10 bond strength to the coating subsequently added without excessive
brittleness which would result from larger cell size. This sheet was
passed between rolls 30, 31, and 32 which were supplied with cooling
water at 115, 175, and 175F. from top to bottom. The coating 38 was
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supplied to the nip between rolls 30 and 31 with a 0.100 inch gap at the
coating sizes. Thereafter, the foam sheet having a coating on one side
~vas passed to roll stack containing rolls 47, 48, 49, these rolls being
supplied with coolant at a temperature of 205F, 140F, and 205F from
top to bottom . The nip between rolls 47 and 48 was 0 . 060 inch . The two
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nip gaps set forth were determined by experimentation to provide
mlaximum bond strength without sacrificing thickness. ~s excessive gap ~-
diminishes bond strength and as the gap decreases, bond strength -:
increases to a point limited by the cell structure although more and more
foam is destroyed by the hot melt. The roll stack temperatures are -
selected to achieve a good bond on the first coat and sheet flexibility
25 ~ ancl, on the second stack, the temperatures control the coating temperature
on both sides as the coated foam leaves the stack which, in turn, affects
sheet flatness.
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For the foam, we hnve referred to specific styrene-malcic
anhydride copolymers and these are preferred. ~lowever, it is
possible to operate using up to 20 percent of crystal polystyrene
and up to 20 percent reclaim, all on a weight basis in the -foam without
5 adversely affecting the properties of the final product. Further, reclaim
sheet can be used with the virgin resin in an amount up to 20 percent
by weight.
While we have described our invention in specific terms, it is
apparent that modifications in the sheet can be made without departing
10 from the invention.
