TITLE: Compositions for artificial marbles and process for producing
artificial marbles therefrom
European Patent EP0173290
 B1

ABSTRACT:
Abstract not available for EP0173290
Abstract of corresponding document: US4678819
A composition for artificial marble which comprises a polymer
composition in which an inorganic substance and an organic polymer are
firmly bound in one body and a vinyl compound, said polymer composition
being obtained by polymerizing a polymerizable vinyl monomer, in the
presence of at least one monomer selected from the group consisting of
carboxylic acid monomer, sulfonic acid monomer, and sulfonate monomer,
in an aqueous polymerization system containing an inorganic substance
dispersed therein; and a processs for producing artificial marble from
said composition by cast polymerization with the addition of a
polymerization initiator.

INVENTORS:
Sasaki, Isao (1665-98, Ohno-cho Saiki-gun, Hiroshima-ken, JP)
Mukai, Nobuhiro (2-6-203 Kurokawa 3-chome, Ohtake-shi, Hiroshima-ken,
JP)

APPLICATION NUMBER: EP19850110713
PUBLICATION DATE: 07/10/1991
FILING DATE: 08/26/1985

ASSIGNEE: MITSUBISHI RAYON CO., LTD. (3-19, Kyobashi 2-chome Chuo-Ku, Tokyo, 104,
JP)
INTERNATIONAL CLASSES: C04B26/04; (IPC1-7): C04B26/04; C04B26/06
EUROPEAN CLASSES: C04B26/04

DOMESTIC PATENT REFERENCES:
EP0067690 Methacrylate polymer concrete mix with reduced shrinkage
 during cure.

FOREIGN REFERENCES:
DE2160612A
FR2342948A
GB2092602A
3839065 ADHESIVE CEMENT

OTHER REFERENCES:
CHEMICAL ABSTRACTS, vol. 89, no. 26, 25th December 1978, page 282,
abstract no. 219907x, Columbus, Ohio, US; & JP-A-78 104 621 (NIPPON
GAKKI CO. LTD) 12-09-1978
O.A. NEUMÜLLER: "Chemie-Lexikon H. Römpp", edition 8, part 1: "A-CI",
1979, Franck'scher Verlag, Stuttgart, pages 1-768
Attorney, Agent or Firm:
TER MEER - MÜLLER - STEINMEISTER & PARTNER (Mauerkircherstrasse 45,
München, 81679, DE)

CLAIMS:
1. A filler for the manufacture of artificial marble comprising an
organic substance-bound inorganic filler obtained by polymerizing a
vinyl monomer capable of radical polymerization in the presence of at
least one monomer selected from the group consisting of carboxylic acid
monomers, sulfonic acid monomers and sulfonate monomers, in an aqueous
polymerization system containing an inorganic substance dispersed
therein.
2. The filler as claimed in claim 1, wherein the carboxylic acid
monomer has either of the following formulae (I) and (II): in which
R[1]and R[2] are H, C[1]-C[1][5] alkyl groups, COOY (where Y is H,
NH[4], or an alkali metal atom), halogen atoms, phenyl groups, or
substituted phenyl groups wherein at least one of R[1] and R[2] is H;
R[3] is H, a methyl group, a halogen atom, a phenyl group, or a
substituted phenyl group; and X is H, NH[4], or an alkali metal atom;
and in which R[4] and R[5] are H, C[1]-C[1][5] alkyl groups, halogen
atoms, phenyl groups, or substituted phenyl groups, wherein at least
one of R[4] and R[5] is H.
3. The filler as claimed in claim 1, wherein the sulfonic acid monomer
or the sulfonate monomer has the following formula (III): in which
R'[1]is H, a C[1]-C[2][0] alkyl group, a phenyl group, a substituted
phenyl group, or a halogen atom; X' is (where R'[2] and R'[3] are H or
C[1]-C[1][5] alkyl groups, and R'[4] is a C[1]-C[1][5] alkylene group),
COO(CH[2])[m] (where m is an integer of 1 to 20), or (CH[2])[n] (where
n is an integer of 0 to 20); and Y has the same meaning as defined in
claim 2.
4. The filler as claimed in claim 1, wherein the vinyl monomer is
acrylic acid, methacrylic acid, or crotonic acid.
5. The filler as claimed in claim 1, wherein the sulfonic acid monomer
or the sulfonate monomer is 2-acrylamide-2-methylpropanesulfonic acid,
sodium 2-methacryloylethanesulfonate, or sodium
3-methacryloylpropanesulfonate.
6. The filler as claimed in claim 1, wherein the vinyl monomer is
methyl methacrylate or a monomer mixture composed mainly of methyl
methacrylate.
7. The filler as claimed in claim 1, wherein the inorganic substance is
at least one substance selected from the group consisting of calcium
sulfite, calcium sulfate, barium sulfate, silicon dioxide, quartz,
calcite, feldspar, titanium oxide, antimony trioxide, talc, clay,
aluminium oxide, calcium carbonate, nickel powder, iron powder, zinc
powder, copper powder, iron oxide, zinc oxide, aluminium hydroxyde,
magnesium hydroxide, glass powder, glass beads, glass fibers, barium
salt-or lead salt-containing glass filler, silica gel, zirconium oxide,
tin oxide, and gypsum.
8. The filler as claimed in claim 1, wherein the vinyl compound is
methyl methacrylate or a mixture or partial polymer composed of 80 to
100% by weight of methyl methacrylate and 0 to 20% by weight of
copolymerizable vinyl compound.
9. The filler as claimed in claim 1, wherein the amount of the
inorganic substance based on the total weight of composition is 20 to
95% by weight.
10. The filler as claimed in claim 1, wherein the amount of the
carboxylic acid monomer, sulfonic acid monomer, or sulfonate monomer
used for the production of the organic substance-bound filler is 0.05
to 100% by weight based on the total amount of the inorganic substance
and vinyl monomer.
11. The filler as claimed in claim 1, wherein the weight ratio of the
vinyl monomer to the inorganic substance in the production of the
organic substance-bound filler is 250 : 1 to 1 : 5.
12. The filler as claimed in claim 1, wherein the amount of the organic
polymer bound to the inorganic substance is 0.01 to 100 % by weight.
13. The filler as claimed in claim 1, which further comprises at least
one of silane, titanate, aluminate and zircoaluminate coupling agents
in an amount of 0.01 to 10 % by weight on the total weight of the
composition.
14. A process for producing an artificial marble comprising casting and
polymerizing a composition comprising the inorganic filler according to
one of claims 1 to 13, a vinyl compound and a polymerization initiator.
15. The process as claimed in claim 14, wherein the composition is
incorporated with 0.01 to 10 % by weight based on the total weight of
the composition, of at least one of silane, titanate, aluminate, and
zircoaluminate coupling agents.
16. The process as claimed in claim 14, wherein the amount used of the
polymerization initiator is 0.01 to 10 % by weight based on the amount
of the vinyl compound.

DESCRIPTION:
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a filler for the manufacture for
artificial marbles and a process for producing artificial marbles. More
particularly, this invention relates to a filler which can provide
artificial marbles having superior mechanical properties and external
appearances, and to a process for producing artificial marbles by cast
polymerization.
2. Description of the Prior Art:
Conventionally, various kinds of the so-called artificial marble have
been developed, in which methyl methacrylate (MMA)is blended with an
inorganic filler comprising various inorganic substances such as
aluminum hydroxide, alumina, calcium carbonate, etc. for the purpose of
providing the artificial marble primarily with design effects, flame
retardancy and rigidity. (See U.S. Patent Nos. 3,775,364 and
3,847,865.)
In these conventional types of artificial marble, internal affinities
such as miscibility, adhesion, ect. are poor due to substantial
differences in properties between the inorganic filler and organic
resin, so that the conventionally used inorganic filler has often
exhibited no sufficient improving effect in relation to the mechanical
properties of the artificial marble, particularly its bending strength
and impact strength. In order to improve the foregoing shortcomings
resulting from the use of the conventional types of inorganic fillers,
an artificial marble has been proposed, which is produced by
surface-treating the inorganic filler with, for example, a silane
coupling agent and then incorporating it in, for example MMA resin, but
no adequate improvement has been accomplished as yet. (See J. G.
Marsuen, Appl. Polym. Symposia 14, pp. 108-109(1970). UCC Technical
Bulletin, F-43598A.)
In EP-A-0 067 690 a shrinkage compensated polymer concrete is
disclosed. The concrete comprises a filler consisting essentially of
silica sand (flour) and an acrylic polymer (MMA-EA-copolymer). Finally,
in DE-A-2 160 612 a method for preparing a polymer concrete from sand
or gravel and a two-pot hardenable acrylic resin system is revealed.

SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned
problems. Accordingly, it is an object of this invention to provide a
filler for the manufacture for artificial marble which comprises an
organic substance-bound filler, in which an inorganic substance and an
organic polymer are firmly bound in one body obtained by polymerizing a
radical polymerizable vinyl monomer in an aqueous polymerization system
with an inorganic substance dispersed therein in the presence of at
least one monomer selected from the group consisting of carboxylic acid
monomers, sulfonic acid monomers and sulfonate-monomers, and a process
for producing artificial marbles comprising cast polymerization of a
composition comprising the above filler, a vinyl compound and a
polymerization initiator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Carboxylic acid monomers, sulfonic acid monomers and sulfonate monomers
are used for the formation of the organic substance-bound filler of the
invention, the carboxylic acid monomer having either of the following
formulae (I) and (II), and the remaining two of above having the
following formula (III).
in which R[1] and R[2] are H,- C[1]-C[1][5] alkyl groups, COOY (where Y
is H, NH[4], or an alkali metal atom), halogen atoms, phenyl or
substituted phenyl groups; R[3] is H, a methyl group groups, halogen
atoms, phenyl groups, or substituted phenyl groups; and X is H, NH[4],
or alkali metal atoms;
in which R[4] and R[5] are H, C[1]-C[1][5] alkyl groups, halogen atoms,
phenyl groups, or substitued phenyl groups;
in which R'[1] is H, a C[1]-C[2][0] alkyl group, a phenyl group, a
substituted phenyl group, or a halogen atom; X' is CONH,
(where R'[2] and R'[3] are H or C[1]-C[1][5] alkyl groups, and R'[4] is
a C[1]-C[1][5] alkylene group), COO(CH[2])[m] (where m is an integer of
1 to 20), or (CH[2])[n] (where n is an integer of 0 to 20); and Y has
the same meaning as defined before.
It is essential for the above-mentioned carboxylic acid monomer, which
has either of the above-mentioned formulae (I) and (II) and is used to
form the organic substance-bound filler in the composition of this
invention, to have one or more carboxyl groups as the active site for
polymerization and a double bond as the active site for firmly binding
the resulting polymer and the inorganic substance. Such carboxylic acid
monomer may be any of those compounds having these functional groups
and includes acrylic acid, methacrylic acid, crotonic acid, tiglic
acid, cinnamic-acid, maleic anhydride, and citraconic anhydride, among
which acrylic acid, methacrylic acid, and crotonic acid are most
preferable because of their high polymerization activity.
It is also essential for the above-mentioned sulfonic acid monomer or
sulfonate monomer, which has the above-mentioned formula (III) and is
used to form the organic substance-bound filler of this invention, to
have a sulfonic group as the active site for polymerization and a
double bond as the active site for firmly binding the polymer and the
inorganic substance. Such sulfonic acid monomer may be any of the
compounds having these functional groups and includes
2-acrylamide-2-methylpropanesulfonic acid (AMPS), sodium
2-methacrylethanesulfonate (SEM·Na), sodium 3-methacrylpropanesulfonate
(SPS), sodium 2-propenesulfonate (NaAS), and sodium
2-methyl-2-propenesulfonate (NaMS). Out of these, particularly AMPS
including the amide bond, and SEM·Na and SPS both including the ester
bond are desirable because they develop a remarkable secondary
aggregation ability as well as an extremely high polymerization
activity.
The inorganic substances used to form the organic substance-bound
filler include simple substances of elements from Groups I, II, III,
IV, and V of the Periodic Table, transition metals, and their oxides,
hydroxides, chlorides, sulfates, sulfites, carbonates, phosphates, and
silicates, and the mixtures and double salts thereof. Preferred among
them are calcium sulfite, calcium sulfate, barium sulfate, silicon
dioxide, quartz, calcite, feldspar, titanium oxdie, antimony trioxide,
talc, clay, aluminum oxide, calcium carbonate, nickel powder, iron
powder, zinc powder, copper powder, iron oxide, zinc oxide, aluminum
hydroxide, magnesium hdyroxide, glass powder, glass beads, glass fiber,
barium salt-or lead salt-containing glass filler, silica gel, zirconium
oxide, tin oxide, and gypsum, since they are particularly outstanding
in activating the vinyl monomer and assuring an effect of firm binding
with the polymer.
According to the invention, the inorganic substance may be added in an
amount of 20 to 95 wt%, preferably 30 to 90 wt%, based on the total
weight of the composition. Their shape and size may be properly
selected.
The vinyl monomer used to form the organic substance-bound filler may
be any vinyl monomer which is capable of radical polymerization. Methyl
methacrylate is particularly preferred because it has high
polymerization activity and its polymer has high affinity for the
inorganic substance. Where a mixture of two or more kinds of vinyl
monomers are used, at least one of them may preferably be methyl
methacrylate and, more preferably, it may constitute a major component
in the mixture. This is preferable because of its polymerization
activity. Methyl methacrylate may be used in combination with styrene,
substituted styrene, acrylonitrile, vinyl acetate, acrylic ester having
a C[1]-C[2][0] alkyl group, and methacrylic ester having a C[2]-C[2][0]
alkyl group.
The organic substance-bound filler is obtainable by polymerizing one or
more of carboxylic acid monomers, sulfonic acid monomers and sulfonate
monomers and one or more of polymerizable vinyl monomers in a
polymerization system with an inorganic substance dispersed therein. In
other words, it is essential that the polymerization is effected in the
presence of an inorganic substance.
One example of a preferred process of producing said organic
substance-bound filler may represent a method of causing heterogeneous
polymerization in an aqueous system and thus effecting polymerization
during certain predetermined hours by suspending and dispersing said
vinyl monomer and said inorganic substance in an aqueous medium at
temperatures in such a range that no thermal polymerization takes place
and then by adding and stirring one or more of carboxylic acid monomer,
sulfonic acid monomer and sulfonate monomer.
For the formation of the organic substance-bound filler, the carboxylic
acid monomer, sulfonic acid monomer or sulfonate monomer may be used in
an amount of about 0.05 to 100 wt%, preferably 0.1 to 50 wt%, more
preferably 0.5 to 30 wt%, based on the total weight of the inorganic
substance and vinyl monomer. In most cases, it is preferred to increase
the amount of carboxylic acid monomer, sulfonic acid monomer or
sulfonate monomer in correspondence with an increase in the vinyl
monomer component. The weight ratio of the inorganic substance to the
vinyl monomer or monomers may be varied in a wide range, for example,
from about 500 : 1 to about 1 : 5, preferably from 250 : 1 to 1 : 5,
and more preferably about 50: 1 to about 1 : 1.
The amount of water as the reaction medium may be about 1 wt% to
hundredsfold, preferably about 10 wt% to tensfold, based on the total
weight of the inorganic substance and vinyl monomer. The polymerization
reaction may preferably be effected under an inert gas such as nitrogen
at about 10 to 100°C, preferably 20 to 80°C, for 30 minutes to about 15
hours. The organic substance-bound filler thus formed may be dried at
about 10 to 300°C, preferably about 50 to 200°C.
The interaction between the inorganic substance and the polymer in the
organic substance-bound filler is more than a simple adsorption or
physical bonding caused by the van der Waals force. This is evidenced
by the fact that only a small amount of polymer can be dissolved when
the organic substance-bound filler is subjected to extraction with a
hot benzene which is a good solvent for vinyl polymers. The firm
binding effect between the inorganic substance and the polymer in the
organic substance-bound filler is not achieved if the inorganic
substance is coated with a separately produced polymer which is
considered to be identical to that polymerized in the presence of the
inorganic substance. This is apparent from the fact that most of the
polymer is dissolved when the organic filler is similarly subjected to
extraction.
In the organic substance-bound filler, the amount of the polymer that
is chemically bound to the inorganic substance may be 0.01 to 100 wt%,
preferably 0.05 to 50 wt%, more preferably 0.1 to 30 wt%. With less
than 0.01 wt% of the polymer, the organic substance-bound filler is
poor in mechnical properties; and with more than 100 wt%, the organic
substance-bound filler is extremely high in oil absorption, so that the
composition will be of low flowability, thus resulting in difficulty in
handling.
According to the invention, the vinyl compound being incorporated in
the above mentioned organic-substance bound filler may be methyl
methacrylate or a mixture of methyl methacrylate in a major amount and
a copolymerizable monomer in a minor amount, or a partial polymer
thereof (hereinafter referred to as methacrylate syrup). The
copolymerizable monomer is a monofunctional vinyl compound such as
styrene; acrylonitrile; vinyl acetate; methyl acrylate; ethyl acrylate
and methacrylate; butyl acrylate and methacrylate;
2-ethyl-hexylacrylate and methacrylate; lauryl acrylate and
methacrylate; stearyl acrylate and methacrylate; hydroxyethyl acrylate
and methacrylate; methoxyethyl acrylate and methacrylate; glycidyl
acrylate and methacrylate; and methacryloxyethyl trimellitic acid and
acid anhydride thereof.
According to the invention, optionally a multifunctional vinyl compound
may additionally be used. It is represented, for example, by the
following formula (IV):
(where R[6] is H or a methyl group, and p is an integer of 1 to 20),
and includes ethylene glycol diacrylate and dimethacrylate; diethylene
glycol diacrylate and dimethacrylate; triethylene glycol diacrylate and
dimethacrylate; and polyethylene glycol diacrylate and dimethacrylate.
These acrylates and methacrylates may be used alone or in combination.
Moreover, it is also possible to add a liquid polybutadiene.
The monofunctional vinyl compound may be used in an amount of 20 wt% or
less based on the amount of methyl methacrylate, and the
multifunctional vinyl compound may be used in an amount of 0.01 to 10
wt% based on the total amount or the vinyl compound used in
polymerization. The methacrylate syrup used may contain 95 to 2 wt% of
the polymer, preferably 85 to 15 wt% of the polymer.
The filler of this invention may preferably further comprise at least
one of silane, titanate, aluminate, and zircoaluminate coupling agents
in order to reduce the viscosity. The amount of the coupling agent may
be 0.01 to 10 wt%.based on the total amount of the composition.
The filler of this invention may optionally comprise a coloring matter,
polymerization inhibitor, ultraviolet absorber, antioxidant, etc.
The composition for artificial marble prepared according to this
invention which comprises said organic substance-bound filler and vinyl
compound is converted, by cast polymerization, into a cured molding to
be used as artificial marble. According to this process, a uniform
dispersion and stabilization of the filler in the composition, which
has been very difficult to attain in the conventional technique, is
obtained, and the cured molding may also exhibit its outstanding
properties. The organic substance-bound filler may be mixed with a
methacrylate resin and the resulting mixture may be made into a molded
product by pressure molding with heat-melting. The product thus
obtained, however, is inferior in terms of mechanical strength to the
product obtained by cast molding.
In order to obtain a desired cured molding using the filler of this
invention a polymerization catalyst that polymerizes the vinyl compound
in the composition is used. Although any of the known polymerization
catalysts can be used, when the polymerization is effected by heating,
the polymerization catalyst which may be used is a substance which
initiates polymerization upon decomposition at a high temperature and
includes, for example, benzoyl peroxide, cumene hydroperoxide, t-butyl
hydroperoxide, dicumyl peroxide, acetyl peroxide, lauroyl peroxide, and
azobisisobutyronitrile, and when the polymerization is effected at
normal temperatures, the polymerization catalyst which may be used is a
combination of a peroxide and amine, a peroxide and sulfinic acid, or a
peroxide and cobalt compound.
In addition, the filler of this invention may be incorporated further
with a photosensitizer such as benzoin methyl ether, benzoin ethyl
ether, and benzoin propyl ether, so that it can be cured by irradition
of ultraviolet light.
For the cast polymerization of the composition comprising the filler of
this invention, the polymerization initiator may be used in an amount
of 0.01 to 10 wt% based on the amount of the vinyl compound. The cast
polymerization is effected by heating the composition at 50 to 80°C for
1 to 5 hours and further heating it at 100 to 140°C for 0.5 to 3 hours.
The composition for artificial marble contains as the filler the
organic substance-bound filler of the invention in which an inorganic
compound and an organic polymer are firmly bound in one body;
therefore, the affinity at interfacial boundary between the filler and
the vinyl compound is greatly improved, with the result that the filler
is dispersed uniformly and stably in the composition and that the
workability of the composition is greatly improved. Upon curing, the
composition can provide the artificial marble of superior mechanical
properties and external appearances which has not been obtained using
the conventional material for artificial marble.
According to this invention, inorganic substances that cannot
effectively be treated with a common coupling agent can be used as an
inorganic substance for the organic substance-bound filler.
The invention will be described in more detail with reference to the
following Examples, in which amounts are to be understood as parts by
weight. The mechanical strengths of the cured product were evaluated by
measuring the bending strength and Izod impact strength according to
JIS K6911.

EXAMPLES 1 and 2 and COMPARATIVE EXAMPLES 1 and 2
In a 5-liter four-mouth flask equipped with a condenser, nitrogen
introduction tube, stirrer, and thermocouple was placed 4,000 ml of
demineralized water. In this water was dispersed and suspended 1,200 g
of aluminum hydroxide powder (Hydilite H-210, a trademark of Showa
Light Metal Co., Ltd.) as an inorganic substance. The flask was purged
with nitrogen for 30 minutes. Then, 215 g of methyl methacrylate as a
vinyl monomer was added with vigorous stirring under a nitrogen stream.
The contents of the flask were heated to 60°C in a water bath. After
methyl methacrylate had uniformly been dispersed, a solution of 57 g of
methacrylic acid as a carboxylic acid monomer in 100 ml of
demineralized water was slowly added, and the polymerization reaction
was effected at 60°C for 8 hours.
After the completion of the polymerization reaction, the reaction
product was filtered off under reduced pressure, washed thoroughly with
demineralized water, and dried at 105°C with a steam drier, to yield
1370 g of an organic substance-bound filler. The polymer content of the
organic substance-bound filler was measured by calcination and was 12%,
while the polymer content of the organic substance-bound filler after
extraction with hot benzene for 50 hours by a Soxhlet extractor was
10%. This indicates that the aluminum hydroxide powder and most of the
polymer formed on the powder surface by the polymerization reaction are
firmly bound in one body.
The organic substance-bound filler thus obtained was mixed with
methacrylate syrup (rate of polymerization= 33.4%, intrinsic viscosity
of polymer = 0.033 l/g, viscosity at 23°C = 680 cp) and
azobisisobutyronitrile in the ratio as indicated in Table 1 (Example
1). The mixture was mechanically mixed to prepare a dope for cast
polymerization.
In Example 2, 1 wt% of 3-methacryloxypropyltrimethoxysilane (coupling
agent) was added to the organic substance-bound filler to lower the
viscosity of the dope.
Each dope prepared in Examples 1 and 2 was cast into a mold formed of
tempered glass applied with a polyethylene terephthalate film and
gasket. The dope was then cured at 65°C for 3 hours in a water bath and
further at 130°C for 2 hours in an oven. The bending strength and Izod
impact strength of the cured product were measured. The results are
shown in Table 1.
In Comparative Example 1, the organic substance-bound filler used in
Examples 1 and 2 was replaced by the aluminum hydroxide powder which
has been used for the preparation of that filler, and in Comprative
Example 2, the aluminum hydroxide powder and the same silane coupling
agent as in Example 2 were used for the preparation of a dope.
The amount used of the filler in comparative Example 1 was made to
correspond to the content of the aluminum hydroxide powder in the
organic substance-bound filler in Example 1, that is, 409 parts x 0.88
= 360 parts. On the other hand, the amount used of the methacrylate
syrup in Comparative Example 1 was made greater than that in Example 1,
by the amount corresponding to the amount of the polymer in the
above-mentioned organic substance-bound filler, that is, 409 parts -
360 parts = 49 parts. In Example 2 and Comparative Example 2, on the
basis of the similar calculations, the amounts of the filler and the
methacrylate syrup were determined.
Each dope prepared in Comparative Examples 1 and 2 was cast and cured
in the same manner as in Example 1, and the bending strength and Izod
impact strength of the cured product were measured. The results are
shown in Table 1.
It will be noted from Table 1 that the dope incorporated with the
organic substance-bound filler according to the Examples of the present
invention can provide cured products for artificial marble having
mechanical properties superior to those provided by the dopes of the
Comparative Examples incorporated with untreated filler. Because of
excellent wettability to the liquid resin, the organic substance-bound
filler is readily intimately mixed with the resin to form the
artificial marble having much better external appearances than with the
Comparative Examples.

EXAMPLES 3 and 4 COMPARATIVE EXAMPLES 3 and 4
The heterogeneous polymerization in an aqueous system was carried out
in the same manner as in Example 1, except that 1,200 g of quartz
powders (Crystalite A-2, a trademark of Tatsumori Co., LTD.) was used
as the inorganic substance, to obtain 1,333 g of the organic
substance-bound filler containing 10% of a polymer. The polymer content
of this filler after extraction with a hot benzene for 50 hours by a
Soxhlet extractor was 9%. The dopes of Examples 3 and 4 and Comparative
Examples 3 and 4 were prepared by compounding the filler of the quartz
powders with the methacrylate syrup and azobisisobutyronitrile
according to the formulation shown in Table 2. The dopes were cast and
cured in the same manner as in Example 1. The mechanical properties of
the cured products were measured, the results being shown in Table 2.
It can be seen from Table 2 that each dope prepared in Comparative
Examples 3 and 4 provides the cured product having strength properties
considerably lower than with each dope prepared in Examples 3 and 4.
That is, the organic substance-bound filler in these Examples
effectively improves the mechanical properties of artificial marble.
Because of excellent wettability to the liquid resin, the organic
substance-bound filler is readily intimately mixed with the resin to
form the artificial marble having much better external appearances than
with the Comparative Examples.

EXAMPLE 5 and COMPARATIVE EXAMPLES 5 and 6
The heterogeneous polymerization in an aqueous system was carried out
in the same manner as in Example 1, except that 1,200 g of magnesium
hydroxide powders (special grade chemical) was used as the inorganic
substance, to obtain 1,412 g of organic substance-bound filler
containing 15% of a polymer. The polymer content of this filler after
extraction with a hot benzene for 50 hours by a Soxhlet extractor was
13%. The dopes of Example 5 and Comparative Examples 5 and 6 were
prepared by compounding the organic substance-bound filler or the
magnesium hydroxide powders with the methacrylate syrup and
azobisisobutyronitrile according to the formulation shown in Table 3.
The dopes were cast and cured in the same manner as in Example 1. The
mechanical properties of the cured products were measured. The results
are shown in Table 3.
It will be noted from Table 3 that the dopes of Comparative Examples 5
and 6 where the magnesium hydroxide powders are used as the filler
provide the cured products having a considerably low level of strengths
as compared with those of Examples 5. That is, the organic
substance-bound filler in Example 5 effectively improves the mechanical
properties of artificial marble. Because of its good wettability to the
liquid resin, the organic substance-bound filler is readily intimately
mixed with the resin to form artificial marble having much better
external appearances than with the Comparative Examples.

COMPARATIVE EXAMPLE 7
50 g of methyl methacrylate and 13 g of methacrylic acid were
copolymerized by bulk polymerization in the presence of 0.6 g of
azobisisobutyronitrile as a polymerization initiator. The resulting
copolymer (49 g) was dissolved in 191 g of the methacrylate syrup (the
methacrylate syrup is the same as used in Example 1). The
copolymer-containing methacrylate syrup (240 g) was used to prepare a
dope and the dope was cured in the same manner as in Comparative
Example 2. The mechanical properties of the cured product were
measured, the results being shown in Table 4.
It will be noted from Table 4 that the cured product in Comparative
Example 7 is inferior in strength to that in Example 2. In addition,
because of poor wettability, the filler does not uniformly disperse but
precipitates, resulting in a strikingly bad appearance of the cured
product.

REFERENTIAL EXAMPLE 1
The organic substance-bound filler obtained in Example 1 was mixed with
a pearl-like methyl methacrylate resin, and the resulting mixture was
subjected to pressure molding by heat-melting. The mechanical strength
of the resulting product was measured in the same manner as in Example
1. The results are shown in Table 5.
It will be noted from Table 5 that the molded product obtained by
pressure molding is superior in mechanical strength to those obtained
in Comparative Examples; but it is still inferior to that obtained by
cast polymerization. That is, the composition of this invention is
suitable for molding by cast polymerization.

EXAMPLES 6 and 7
Into a 5-liter four-mouth flask equipped with a condenser, a nitrogen
introduction tube, a stirrer, and a thermocouple was charged with 4,000
ml of demineralized water. In this water was dispersed and suspended
1,200 g of aluminum hydroxide powders (Hydilite H-210, a trademark of
Showa Light Metal Co., Ltd.) as an inorganic substance. The flask was
purged using nitrogen for 30 minutes. Then, 215 g of methyl
methacrylate as a vinyl monomer was added with vigorous stirring under
a nitrogen stream. The contents of the flask were heated to 60°C in a
water bath. After methyl methacrylate had been uniformly dispersed, a
solution of 57 g of SEM·Na as a sulfonate monomer in 100 ml of
demineralized water was slowly added, and polymerization reaction was
effected at 60°C for 8 hours.
After the completion of the polymerization reaction, the reaction
product was filtered off under reduced pressure, washed thoroughly with
demineralized water, and dried at 105°C in a steam drier, to give 1,310
g of organic substance-bound filler. Upon calcination, this filler was
found to contain 8% of a polymer. The polymer content of this filler
was 7% even after extraction with a hot benzene for 50 hours by a
Soxhlet extractor. This indicates that aluminum hydroxide powder and
most of the polymer formed on the surface of the powder by the
polymerization reaction are firmly bound in one body.
The organic substance-bound filler thus obtained was mixed with
methacrylate syrup (rate of polymerization = 33.4%, intrinsic viscosity
of polymer = 0.033 l/g, viscosity at 23°C = 680 cp) and
azobisisobutyronitrile in the ratio as indicated in Table 6 (Example
6). The mixture was mechanically mixed to prepare a dope for cast
polymerization.
In Example 7, 1 wt% of 3-methacryloxypropyltrimethoxysilane (coupling
agent) was added to the organic substance-bound filler to lower the
viscosity of the dope.
Each dope prepared in Examples 6 and 7 were cast into a mold formed of
tempered glass applied with a polyethylene-terephthalate film and
gasket. The dope was cured at 65°C for 3 hours in a water bath and
further at 130°C for 2 hours in an oven. The bending strength and Izod
impact strength of the cured product were measured, the results being
shown in Table 6
It will be noted from Table 6 that the cured artificial marbles in
Examples 6 and 7 are superior in mechanical properties. Because of its
good wettability to the liquid resin, the organic substance-bound
filler is readily intimately mixed with the resin to form the
artificial marble having excellent external appearance.

EXAMPLES 8 and 9
The heterogeneous polymerization in an aqueous system was carried out
in the same manner as in Example 6, except that 1,200 g of quartz
powder (Crystalite A-2, a trademark of Tatsumori Co., Ltd.) was used as
the inorganic substance, to obtain 1,328 g of organic substance-bound
filler containing 9% of a polymer. The polymer content of this filler
after extraction with a hot benzene for 50 hours by a Soxhlet extractor
was 8%. The dopes of Examples 8 and 9 were prepared by compounding the
organic substance-bound filler or quartz powders with a methacrylate
syrup and azobisisobutyronitrile according to the formulation shown in
Table 7 The dopes were cast and cured in the same manner as in Example
6. The mechanical properties of the cured products were measured, the
results being shown in Table 7.
It will be noted from Table 7 that the cured products in Examples 8 and
9 are superior in strength. That is, the organic substance-bound filler
prepared in Examples 8 and 9 effectively improves the mechanical
properties of artificial marble. Because of its good wettability to the
liquid resin, the substance-bound filler is readily intimately mixed
with the resin to form the artificial marble having excellent external
appearance.

EXAMPLE 10
The heterogeneous polymerization in an aqueous system was effected in
the same manner as in Example 6, except that 1,200 g of magnesium
hydroxide powders (special grade chemical) was used as the inorganic
substance, to obtain 1,400 g of organic substance-bound filler
containing 14% of a polymer. The polymer content of this filler after
extraction with a hot benzene for 50 hours by a Soxhlet extractor was
still 12%. A dope was prepared by compounding the organic
substance-bound filler with a methacrylate syrup and
azobisisobutyronitrile according to the formulation shown in Table 8.
The dope was cast and cured in the same manner as in Example 6. The
mechanical properties of the cured product were measured. The results
are shown in Table 8.
It will be noted from Table 8 that the composition of this invention
provides artificial marble superior in mechanical properties. Because
of its good wettability to the liquid resin, the organic
substance-bound filler used in the present invention is readily
intimately mixed with the resin to form the artificial marble having
excellent external appearance.

COMPARATIVE EXAMPLE 8
50 g of methyl methacrylate and 13 g of SEM·Na were copolymerized by
bulk polymerization in the presence of 0.6 g of azobisisobutyronitrile
as a polymerization initiator. The resulting copolymer (49 g) was
dissolved in 191 g of a methacrylate syrup as in Example 2. The
copolymer-containing methacrylate syrup (240 g) was compounded into a
dope and the dope was cured in the same manner as in Comparative
Example 2. The mechanical properties of the cured product were
measured, the results being shown in Table 9.
It can be seen from Table 9 that the cured product in Comparative
Example 8 is inferior in strength to that in Example 7. In addition,
because of its poor wettability, the filler does not uniformly disperse
but precipitates, resulting in the artificial marble having a poor
external appearance.

REFERENTIAL EXAMPLE 2
The organic substance-bound filler obtained in Example 6 was mixed with
a pearl-like methyl methacrylate resin, and the resulting mixture was
subjected to pressure molding by heat-melting. The mechanical strength
of the resulting product was measured in the same way as in Example 1.
The results are shown in Table 10.
It will be noted from Table 10 that the molded product obtained by
pressure molding is inferior to that obtained by cast polymerization.
This indicates that the composition of this invention is more suitable
for molding by cast polymerization.
Examples 11 - 18
The same procedure as in Example 1 was repeated to prepare the organic
substance-bound fillers but using, as a carboxylic acid monomer,
acrylic acid, maleic anhydride, 2-acrylamide-2-methylpropane sulfonic
acid (AMPS) and a mixed monomer of methacrylic acid and AMPS (50 : 50
by weight), respectively, in place of methacrylic acid. The cured
products prepared by cast polymerization of the mixtures of the fillers
prepared above and the same methacrylate syrup as used in Example 1,
were evaluated for the bending strength and Izod impact strength, the
results being given in Table 11.
Table 11 indicates that the organic substance-bound fillers according
to the present Examples can provide the cured products having the
excellent mechanical properties. In addition, the fillers prepared in
accordance with the Examples have excellent wettability to the liquid
resin, so that they are readily intimately mixed with the resin and the
cured test pieces prepared had the strikingly good external
appearances.