Artificial marble sheet, method of manufacturing the same and artificial marble molding product

An artificial marble sheet is formed of a pair of carrier films, an SMC layer and a resin concrete layer which has plasticity but does not contain glass fibers laminated between the carrier films. A method of manufacturing the artificial marble sheet as defined above which includes forming a resin concrete layer which has plasticity but does not contain glass fiber on a first carrier film, forming an SMC layer on a second carrier film and bringing the resin concrete layer and the SMC layer into an intimate contact to each other. Carrier films are removed from the artificial marble sheet and press molding is applied under heating such that the resin concrete layer is located on the side of the surface of the product.

FIELD OF THE INVENTION 
The present invention concerns an artificial marble sheet, a method of 
manufacturing the same and an artificial marble molding product. 
DESCRIPTION OF THE PRIOR ART 
Molding products utilizing sheet molding compounds (hereinafter simply 
referred to as "SMC") have been used generally, for example, for bath 
tubs, water proof pans, laundry pans, counter tops and decks. 
As shown in FIG. 4, an SMC sheet in the prior art has a constitution 
comprising a pair of carrier films 1 and 2 and an SMC layer 3 interposed 
therebetween. The SMC layer is a uniform mixture layer in which glass 
fibers, resins and, if necessary, fillers are blended. 
FIG. 3 is a side elevational view showing a method which is most similar 
among various manufacturing methods for SMC sheet, to a method of 
manufacturing an artificial marble sheet according to the present 
invention. 
A first carrier film 5 is continuously fed by a conveyor belt 6, on which a 
layer of a resin paste 7 is formed by a doctor blade 8 and chopped strands 
11 are scattered thereon by cutting rovings 9 by a chopper 10. 
On the other hand, a layer of a resin paste 13 is also formed on a second 
carrier film 12 by a doctor blade 14. The second carrier film 12 is 
disposed opposite to the first carrier film 5 such that the layer of the 
resin paste 13 is laid over the chopped strands 11 and then they are 
pressed between compaction rolls 15. By the press contact, the resins 
constituting the layers of the resin pastes 7, 13 are impregnated into the 
chopped strands 11 to form a uniform SMC layer. The resultant SMC sheet 16 
is taken up by a winding device 17. 
Further, the SMC sheet 16 is put to an aging treatment usually at 
40.degree.-50.degree. C. for 24-48 hours and hardened such that the SMC 
layer can be press molded. 
For manufacturing a molding product by using the thus manufactured SMC 
sheet 16, the carrier films 5 and 12 are peeled off, and the remaining 
portion of the sheet is cut into an appropriate size, arranged properly on 
a molding die and then press molded under heating. 
In the molding products molded from the SMC sheet in the prior art as 
described above, the glass fibers are uniformly dispersed in the cross 
sectional direction of the molding products and the products lack in the 
feeling of transparency or feeling of depth due to the material. Further, 
since the glass fibers are present as far as the surface layer of the 
molding products, minute undulating unevenness is present at the surface. 
OBJECT AND SUMMARY OF THE INVENTION 
An object of the present invention is to overcome the foregoing problems of 
the SMC sheet in the prior art and provide an artificial marble sheet 
having a surface layer capable of manufacturing an artificial marble 
molding product with the feeling of transparency and feeling of depth and 
having a smooth surface and high quality feeling, a manufacturing method 
thereof and an artificial marble molding product using such an artificial 
marble. 
The artificial marble sheet according to the present invention comprises a 
pair of carrier films, an SMC layer and a resin concrete layer which has 
plasticity but does not contain glass fibers. Both of the layers are 
laminated and arranged between the films. 
A method of manufacturing an artificial marble sheet according to the 
present invention comprises a step of forming a resin concrete layer which 
has plasticity but does not contain glass fibers on a first carrier film, 
and a step of forming an SMC layer on a second carrier film and bringing 
the resin concrete layer and the SMC layer into an intimate contact to 
each other. 
The artificial marble molding product according to the present invention is 
prepared by removing the carrier films from the artificial marble sheet of 
the present invention as described above and then press molding the 
remaining portion of the layer with the resin concrete layer being 
situated on the side of the surface of the product. 
In the artificial marble sheet according to the present invention, the SMC 
layer and the resin concrete layer of high transparency are laminated. 
Accordingly, in the molding product obtained by press molding the 
laminate, a two layer structure can be attained in which the side of the 
surface of the product comprises a layer which does not contain glass 
fibers and has a high transparency derived from the resin concrete layer 
and a non-transparent FRP layer derived from the SMC layer is disposed to 
the rear side of the surface layer. 
Accordingly, the molding product has a feeling of high transparency at the 
surface layer, a feeling of depth due to the transparent resin concrete 
layer at the surface and the non-transparent SMC layer on the rear side, 
and has a smooth surface and can be treated as high quality product. 
Especially, when a pattern is applied to the surface, the pattern can be 
emphasized to obtain a molding product of excellent decorative nature. 
Further, since the molding product has a high strength reinforced with the 
FRP layer, reinforcing treatment after molding, such as blowing of glass 
fibers, for example, by a hand lay-up method is no longer necessary. In 
addition, such a high quality product of great strength can be 
manufactured by press molding for once. 
According to the method of the present invention, the artificial marble 
sheet can be manufactured with ease.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Description will now be made more in details to the present invention with 
reference to the accompanying drawings. 
FIG. 1 is a cross sectional view illustrating a preferred embodiment of an 
artificial marble sheet according to the present invention and FIG. 2 is a 
side elevational view illustrating an example of a method of manufacturing 
an artificial marble sheet according to the present invention. In FIGS. 1 
and 2, members having the same performances as those in FIGS. 3 and 4 
carry the same reference numerals. 
As shown in the drawings, the artificial marble sheet according to the 
present invention comprises a pair of carrier films 1 and 2, and an SMC 
layer 3 and a resin concrete layer 4 which has plasticity but does not 
contain glass fibers. 
In the artificial marble sheet according to the present invention, the SMC 
layer 3 can be formed with the same material as those for the SMC layer 
that constitutes the SMC sheet in the prior art and, specifically, it is 
prepared by blending a resin such as an unsaturated polyester resin with 
glass fibers and, if required, fillers such as calcium carbonate, aluminum 
hydroxide, glass powder, frit and silica beads, viscosity improvers such 
as magnesium hydroxide, magnesium oxide, calcium hydroxide and calcium 
oxide, and internal releasing agents such as zinc stearate. The blending 
amount of the glass fibers is about 5-40% by weight based on the total 
amount of the SMC layer constituent materials. Further, as the filler, 
calcium carbonate or aluminum hydroxide is preferred since such material 
is inexpensive. 
On the other hand, the resin concrete layer 4 comprises the material used 
for the SMC layer described above except for the glass fibers. There is no 
particular restriction for the kind and the addition amount of the filler, 
the viscosity improver and other additives. Preferably, it is constituted 
with the resin of the same material as that for the SMC layer but 
different resin may also be used. In particular, in a case of making the 
resin concrete layer transparent, it is important to use colorless filler 
such as aluminum hydroxide, glass powder, frit and silica beads. 
In the present invention, the ratio of the thickness between the SMC and 
the resin concrete layer is preferably about 1:1 to 10. The entire 
thickness of the artificial marble sheet according to the present 
invention is, usually about 5 to 30 mm. 
The artificial marble sheet of the present invention can be manufactured 
with ease in accordance with the method, for example, as shown in FIG. 2. 
In the method shown in FIG. 2, a first carrier film 5 is continuously 
delivered by a conveyor belt 6, on which a layer of a resin paste 7A for 
forming a resin concrete layer is formed by a doctor blade 8. On the other 
hand, a layer of resin paste 13A for forming an SMC layer is formed also 
on a second carrier film 12 by a doctor blade 14, on which chopped strands 
11 prepared by cutting roving 9 by a chopper 10 are scattered, and the 
chopped strands are impregnated into the resin paste 13A. The second 
carrier film 12 is opposed to the first carrier film 5 such that the layer 
of the resin paste 13A is laminated with the layer of the resin paste 7A 
and then they are pressed between the compaction rolls 15. By the press 
contact, the resin constituting the layer of the resin paste 13A is 
impregnated into or mixed with the chopped strands 11 to form a 
homogeneous SMC layer. 
On the other hand, the resin constituting the layer of the resin paste 7A 
is not impregnated into the chopped strands 11 and is put to press contact 
with the SMC layer to form a laminate sheet 20, which is taken up to a 
winding device 17. Accordingly, it is important to properly control the 
viscosity for each of the resin pastes, for example, by adjusting the 
addition ratio of the viscosity improver or the like, so that the resin 
paste 13A constituting the SMC layer can be impregnated easily into the 
chopped strands 11, while the resin paste 7A constituting the resin 
concrete layer is not impregnated into the chopped strands 11. 
The laminate sheet 20 taken up on the winding device 17 is further put to 
an aging treatment at 40.degree.-50.degree. C. for about 24-48 hours and 
hardened to such an extent as capable of press molding, to form an 
artificial marble sheet. 
When the artificial marble molding product according to the present 
invention is manufactured by using the artificial marble sheet of the 
present invention thus manufactured, the carrier films 5 and 12 are peeled 
off and the remaining portion of the sheet is cut into an appropriate 
size, properly arranged on a molding die such that the resin concrete 
layer is located on a front side of the product and then press molded 
under heating. 
The artificial marble molding product according to the present invention is 
especially suitable to plate-like press molding products such as counter 
tops, decks, water proof pans and laundry machine pans. That is, in such 
plate-like press molding products, the SMC layer and the resin concrete 
layer are not mixed to each other upon press molding and satisfactory 
molding products can be obtained. 
As has been described above specifically, according to the artificial 
marble sheet and an artificial marble molding product obtained by molding 
the sheet, the following excellent advantageous effects can be provided: 
(1) Since the surface layer comprises a resin concrete layer not containing 
glass fibers, a high quality molding product having a smooth surface with 
no undulation and having feeling of transparency and feeling of depth can 
be provided. 
(2) When a pattern is applied to the surface, the pattern can be emphasized 
to obtain a product of excellent decorative nature. 
(3) Since the rear side is reinforced with the SMC layer, no reinforcing 
treatment is necessary after molding. 
In the method of manufacturing the artificial marble sheet according to the 
present invention, an artificial marble sheet capable of obtaining an 
artificial marble molding product having such high performance can be 
manufactured with ease.