Molding sand mixtures

This invention relates to mixtures of molding sand which comprise a mixture of a molding sand with a rapid hardening cement containing calcium aluminate as amorphous glass and/or crystals, and/or calcium haloaluminate, a polymer water holding agent and a lime, or mixture of a molding sand with the above-mentioned rapid hardening cement, a polymer water reducing agent, a lime, and, if necessary, a foaming agent, and in either case with water. The mixture also provides a method of mixing the ingredients except for water and then kneading the mixture with water.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of preparing molding sand mixtures and 
the mixtures thereby obtained. More particularly, it relates to molding 
sand mixtures which harden in a short period of time, providing molds with 
high strength and good surface stability. 
2. Description of the Prior Art 
Prior art molding sand mixtures suffer from disadvantages in that their 
coefficients of utilization of floor area and operation efficiencies are 
low. This is true because when making molds of portland cement, long 
periods of time are consumed until the molds attain the desired 
compressive strength. As an earlier improved method to eliminate these 
disadvantages, we have developed self-hardening molding sand mixtures 
which comprise a mix of molding sand with a mixture of sulfate, or of 
sulfate and an organic carboxylic acid, with clinker powder containing 
calcium haloaluminate (11CaO.7Al.sub.2 O.sub.3.CaX.sub.2), or by further 
addition of a water reducing agent such as a .beta.-naphthalenesulfonic 
acid-formalin condensation product. The molds made from these mixtures are 
hardened rapidly; but they have a disadvantageous tendency toward 
insufficient stability, especially when hardened at low temperatures. This 
is because of the deficiency of water necessary for the cement to hydrate 
near the surface and of the resulting incomplete bonding among the sand 
grains. 
SUMMARY OF THE INVENTION 
As a result of further studies for improvements in molding sand mixtures 
using not only rapid hardening cement containing calcium haloaluminate 
(11CaO.7Al.sub.2 O.sub.3.CaX.sub.2, X = halogen), but also rapid hardening 
cement containing calcium aluminate in the form of amorphous glass and/or 
crystals, we have found that a molding sand mixture is rapidly hardened to 
provide molds with proper strength and excellent surface stability, when 
made by first mixing the molding sand with a polymer water holding agent 
and a lime in addition to the aforementioned rapid hardening cements, 
followed by kneading with water. Also disclosed is that the use of a 
polymer water reducing agent in place of the aforementioned polymer water 
holding agent provides the molding sand mixture with better moldability, 
thereby permitting the formation of a hardened material with proper 
strength and molds with good surface stability. In addition, we have found 
that molds having better properties are made with higher efficiency, when 
a foaming agent which fluidizes the molding sand mixture is added to the 
molding sand mixtures containing the polymer water reducing agent. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description of experimental results is typical of the results 
of various experiments. 
The rapid hardening cements employed in the experiments described below are 
jet cement (a product of Onoda Cement Company, Limited, mineral 
composition: 11CaO.7Al.sub.2 O.sub.3.CaF.sub.2 20.6%, 3CaO.SiO.sub.2 
50.7%, CaSO.sub.4 15.3%) (hereinafter referred to as rapid hardening 
cement A) and the cement (hereinafter referred to as rapid hardening 
cement B) prepared as follows. The rapid hardening cement B is prepared by 
mixing normal portland cement and the following strength-improving agent 
in a ratio by weight of 1:3, 0.06 part by weight of potassium carbonate 
and 0.04 part by weight of citric acid as bench life controlling agents, 
with 100 parts by weight of silica sand. The aforementioned 
strength-improving agent is produced by fusing a mixture of white bauxite, 
lime stone and fluorite and then immediately cooling to afford a glassy 
material (SiO.sub.2 4.8%, Al.sub.2 O.sub.3 52.6%, Fe.sub.2 O.sub.3 0.8%, 
CaO 40.2%, MgO 0.5%, F 1.0%). The glassy material is ground to the Blaine 
specific surface area of 4900 cm.sup.2 /g. Then anhydrous gypsum with a 
Blaine specific surface area of 6800 cm.sup.2 /g is mixed with the ground 
glassy material in the ratio by weight of 1:1.1. 
EXPERIMENT 1 
100 parts by weight of Kawamura silica sand (No. 5) was mixed with 8 parts 
by weight of the rapid hardening cement A, 0 or 0.2 parts by weight of 
methylcellulose as a polymer water holding agent and 0 or 0.3 parts by 
weight of quicklime. Subsequently the mixture was kneaded with 6 parts by 
weight of water and the resultant sand mixtures were hardened as a test 
piece according to JIS Z-2604. On the other hand, 8 parts by weight of the 
rapid hardening cement B was employed in place of the rapid hardening 
cement A to form a mix with the same components as above. The resultant 
sand mixtures were hardened as a test piece under the same conditions. The 
hardened test pieces thus formed were tested for compressive strength and 
surface stability. (24 hours after kneading. All the tests of surface 
stability hereinafter are conducted on samples 24 hours after kneading). 
The results are listed in Table 1. 
As the strength test of this invention, compressive strength was measured 
according to JIS Z-2604 (Japan Industrial Standard Z-2604). Surface 
stability was measured with a 6-mesh sieve mounted on a Sieve Analysis 
Machine provided with a vibrator. After 24 hours, each test sample was 
placed on the sieve and vibration was applied to the sieve and sample for 
one minute. Then the weight of sample was measured. 
Surface Stability = W/W0 .times. 100 (%) where 
W0 is the initial weight of sample, and 
W is the weight of sample after vibration 
Table 1 
______________________________________ 
Water Quick 
holding lime Compressive 
Kind agent part, strength Surface 
of part, by (kg/cm.sup.2) 
stability 
cement by weight weight 1hr. 2hrs. 
24hrs. 
(%) 
______________________________________ 
Rapid 0 0 0.2 4.0 20.2 87.3 
hardening 
0 0.3 2.7 6.9 19.2 90.9 
cement A 
0.2 0 0.2 4.1 22.6 97.4 
0.2 0.3 1.9 5.8 23.1 98.7 
______________________________________ 
Rapid 0 0 0.4 1.8 14.4 85.4 
hardening 
0 0.3 0.6 2.3 17.7 90.2 
cement B 
0.2 0 0.4 3.0 17.6 98.8 
0.2 0.3 0.6 3.9 17.7 99.4 
______________________________________ 
EXPERIMENT 2 
100 parts by weight of Kawamura silica sand (No. 5) was mixed with 8 parts 
by weight of the rapid hardening cement A, 0 or 0.2 parts by weight of the 
polymer water reducing agent calcium methylnaphthalenesulfonate-formalin 
condensation product (the average number of naphthalene rings was 8), and 
0 or 0.1 part by weight of quicklime. Subsequently the mix was kneaded 
with 6 parts by weight of water and the resultant sand mixtures were 
hardened on the pattern as a test piece. Additionally, 8 parts by weight 
of the rapid hardening cement B was mixed in place of the rapid hardening 
cement A as described above and the resultant sand mixtures were hardened 
as a test piece under the same conditions. The hardened materials thus 
formed were tested for compressive strength and surface stability with the 
results shown in Table 2. 
Table 2 
______________________________________ 
Water Quick 
reducing lime Compressive 
Kind agent part, strength Surface 
of part, by (kg/cm.sup.2) 
stability 
cement by weight weight 1hr. 2hrs. 
24hrs. 
(%) 
______________________________________ 
Rapid 0 0 0.2 4.0 20.2 87.3 
hardening 
0 0.1 1.5 5.1 24.7 91.4 
cement A 
0.2 0 0.3 3.2 29.4 98.2 
0.2 0.1 1.3 7.8 36.0 99.3 
______________________________________ 
Rapid 0 0 0.3 1.8 14.4 85.4 
hardening 
0 0.3 0.6 2.3 17.7 90.2 
cement B 
0.2 0 0.4 3.0 18.7 98.0 
0.2 0.3 0.8 4.8 20.9 98.9 
______________________________________ 
The above results demonstrate that the addition of either a water holding 
agent and quicklime or a water reducing agent and quicklime to the rapid 
hardening cement A or B results is an increase in the compressive strength 
and surface stability when compared with the results obtained when only 
one or more of these reagents is added. 
This invention is based on these findings and relates to the process of 
molding and sand mixtures, and the resultant mixtures, which comprise 
either mixing the molding sand with a rapid hardening cement containing 
calcium aluminate as an amphorous glass and/or calcium haloaluminate as a 
rapid hardening component, a polymer water holding agent and a lime, or by 
mixing the molding sand with the above-mentioned rapid hardening cement, a 
polymer water reducing agent, a lime and, if necessary, a foaming agent, 
and thereafter kneading the mixture with water. 
In this invention, the rapid hardening cement containing calcium aluminate 
in the form of amorphous glass as a rapid hardening component is prepared 
by adding to portland cement, fly ash cement, blast furnace cement or 
silica cement and if necessary, a bench life controlling agent, the 
following strength-improving agents. These strength-improving agents are 
prepared by adding 3-96% of anhydrous gypsum to an amorphous glass of 
calcium aluminate which was made by cooling a fused material consisting of 
CaO (20-80%) and Al.sub.2 O.sub.3 (80-20%). The rapid hardening cement 
thus produced should contain preferably over 2% calcium aluminate 
amorphous glass. 
In this invention, the rapid hardening cement containing crystals of 
calcium aluminate as the rapid hardening component can be formed by adding 
one or more kinds of CaO.2Al.sub.2 O.sub.3, CaO.Al.sub.2 O.sub.3, 
12CaO.7Al.sub.2 O.sub.3 and the like, or a mixture of one or more kinds of 
CaO.2Al.sub.2 O.sub.3, CaO.Al.sub.2 O.sub.3, 12CaO.7Al.sub.2 O.sub.3 and 
the like to portland cement or anhydrous gypsum. On the other hand, the 
rapid hardening cement containing calcium haloaluminate is produced by 
adding anhydrous gypsum to clinker powder (obtained by heating a mixture 
of clay, lime stone, a halogenated compound and the like; mineral 
composition: 3CaO.SiO.sub.2 solid solution, 2CaO.SiO.sub.2 solid solution, 
2CaO.Fe.sub.2 O.sub.3 - 6CaO.2Al.sub.2 O.sub.3.Fe.sub.2 O.sub.3 solid 
solution in addition to calcium haloaluminate (11CaO.7Al.sub.2 
O.sub.3.CaX.sub.2)) so that the Al.sub.2 O.sub.3 /SO.sub.3 mol. ratio in 
the cement is 0.5-2.0, and, if desired, further mixing with a bench life 
controlling agent. The rapid hardening cement thus produced should contain 
over 2% 11CaO.7Al.sub.2 O.sub.3.CaX.sub.2. 
Suitable bench life controlling agents include carboxylic acids, 
oxycarboxylic acids, weak inorganic acids or their salts such as citric 
acid, sodium citrate, sodium gluconate, diketogluconic acid, tartaric 
acid, adipic acid, boric acid and sodium borate, hemihydrate gypsum, or 
sodium or potassium carbonate, sulfate and nitrite. The bench life 
controlling agent is employed in suitable amounts to control the handling 
time and the hardening time of the molding sand mixtures. 
Suitable polymer water holding agents include methylcelluloses, polyvinyl 
alcohols, alginic acids, sodium alginates, polyethylene oxides or 
water-soluble melamine resins without water reducibility (for example, 
Melment F 300, a product of Showa Denko Company). 
Suitable polymer water reducing agents include naphthalenesulfonic 
acid-formalin condensation products (salt, the number of naphthalene 
rings, over 5), methylnaphthalenesulfonic acid-formalin condensation 
products (salt, the number of naphthalene rings, over 5), 
methylnaphthalenesulfonic acid-naphthalenesulfonic acid-formalin 
copolycondensates (salt, the number of naphthalene rings, over 5), 
condensate salts of alkylaldehyde and creosote oil fractionated at b.p. of 
200.degree.-315.degree. C. (55% of creosote oil), or polymer surface 
active agents such as water soluble melamine resins having not only water 
reducibility, but also water holdability (for example, Melment F 10, a 
product of Showa Denko Company). 
Suitable limes include quicklime and slaked lime. 
Suitable foaming agents include anionic, nonionic or cationic surface 
active agents such as polyoxyethylene nonylphenyl ether and high alcohol 
sulfonic acid esters. 
In this invention the rapid hardening cements should be employed in amounts 
of 2-20 parts by weight relative to 100 parts by weight of the molding 
sand. Fewer than 2 parts by weight are not sufficient to harden the 
molding sand and more than 20 parts by weight are not suitable, since the 
gas permeability and refractoriness of the molds are reduced, although the 
strength of the hardened mold increases. A suitable amount of the polymer 
water holding agent is 0.01-1.0 parts by weight as an effective component 
relative to 100 parts by weight of the molding sand. Less than 0.01 part 
by weight is not sufficient for suitable effect, and more than 1.0 part by 
weight is also not suitable, since the desirable effect is not great and 
the gas permeability of the mold is reduced. The polymer water reducing 
agents should be used in amounts of 0.03-2.0 parts by weight as an 
effective component relative to 100 parts by weight of the molding sand. 
The addition of less than 0.03 parts by weight has little effect on the 
surface stability and strength of the molds, while the use of more than 
2.0 parts by weight does not display the desirable effect to a great 
extent and is accompanied by increase of gas evolution from the mold 
during casting. Limes are preferably used within the range of 0.01 to 3.0 
parts by weight relative to 100 parts by weight of the molding sand. The 
ratio of the amount of lime to the amount of molding sand is preferred to 
be adjusted corresponding to the temperature wherein the molding sand 
mixture is to be hardened. When it is hardened at or near room 
temperature, a suitable amount of the lime is 0.01-1.0 parts by weight 
relative to 100 parts by weight of the molding sand, but more than 1.0 
parts by weight has little improving effects. When hardening is at 
temperatures lower than about 5.degree. C., a suitable amount is 1.0-3.0 
parts by weight and the use of less than 1.0 part by weight has the 
disadvantage that a long time is required for hardening. 
Water is preferably added in amounts of 3-15 parts by weight relative to 
100 parts by weight of the molding sand. 
To 100 parts by weight of the molding sand, 0.01-1.0 part by weight of the 
bench life controlling agents and 0.01-0.5 parts by weight of the foaming 
agents are preferably employed. 
Although it is not clear why the molding sand mixtures made according to 
the invention reduce hardening time and provide the molds with proper 
strength and good surface stability, it is theorized that the molding sand 
mixtures possessing a suitable moldability may be formed by the use of 
relatively small amounts of water, because of a synergistic action of the 
polymer water holding agents or the polymer water reducing agents and lime 
on the rapid hardening cements in the presence of water and because of 
retardance of the evaporation of the water from the surface of the 
mixtures and the molds until hardening starts. The polymer water reducing 
agents provide the molds with better properties than the polymer water 
holding agents do, probably because the former agents possess an ability 
to increase the strength of the cement in addition to the water 
holdability. 
The use of the molding sand mixtures prepared according to this invention 
permits reduction of the hardening time of the molds and provides the 
molds with excellent surface stability.

EXAMPLE 1 
To kawamura silica sand (No. 5 according to JIS) were added a rapid 
hardening cement, a polymer water holding agent, a lime and a bench life 
controlling agent in the ratio given in Table 3 and the mixture was 
kneaded with water in the ratio shown in the same Table. The resulting 
molding sand mixes were tested for their bench lives together with the 
compressive strength and surface stability of the hardened materials. The 
results are presented in Table 4. 
Table 3 
______________________________________ 
Mixture No. 1 2 3 
______________________________________ 
Kawamura silica sand 100 100 100 
(No.5) part, by weight 
______________________________________ 
kind I II III 
Rapid hardening 
part, 
cement by weight 18 12 6 
______________________________________ 
Limes 
Quick lime part, 
by weight 0 0.1 0.3 
Slaked lime 
part, 
by weight 0.3 0 0 
______________________________________ 
Soluble 
Sodium 
Polymer kind Poval melamine 
alginate 
holding agent 
part, resin 
by weight 0.25 0.8 0.05 
______________________________________ 
Water part, 
by weight 12 8 5 
______________________________________ 
Note 
(1) The rapid hardening cements were produced by adding a variety of bench 
life controlling agents to jet cement which was also employed in the 
Experiments. The ratio of the bench life controlling agents to silica sand 
100 parts by weight are as follows: I, boric acid 0.05 parts by weight; 
II, sodium gluconate 0.02 parts by weight; III, 0. 
(2) The water-soluble melamine resin employed as a polymer water holding 
agent in Melton F 300, a product of Showa Denko Company. 
Table 4 
______________________________________ 
No. 1 2 3 
______________________________________ 
Compressive 1 hr 8.4 3.3 1.4 
strength 2hrs 18.3 10.5 5.9 
(kg/cm.sup.2) 24hrs 62.6 40.4 15.4 
______________________________________ 
Surface stability(%) 97.3 98.8 90.4 
______________________________________ 
EXAMPLE 2 
Rapid hardening components were prepared by grinding two kinds of glassy 
materials (a) and (b) (listed in Table 5) which were made of white 
bauxite, lime stone and fluorite, to the Blaine specific surface area of 
4900 cm.sup.2 /g and mixing with anhydrous gypsum (Blaine specific surface 
area of 6800 cm.sup.2 /g) in the ratio of 1:1 and 1:1.1, respectively. 
Commercially available normal portland cement was mixed with the 
components thus obtained as a strength improving agent in the ratio by 
weight of 1:3 to produce the cements (a') and (b'). The cement (a') or 
(b') was mixed with a variety of bench life controlling agents to provide 
three kinds of cements, (a') - I, (a') - II and (b'). 
Table 5 
______________________________________ 
Component 
(1) SiO.sub.2 
Al.sub.2 O.sub.3 
Fe.sub.2 O.sub.3 
CaO MgO F Total 
______________________________________ 
Composition 
of glass (a) 
4.1 45.0 0.7 48.7 0.6 0.9 100.0 
______________________________________ 
Composition 
of glass (b) 
4.8 52.6 0.8 40.2 0.5 1.0 99.9 
______________________________________ 
To Kawamura silica sand (No. 5) were added the aforementioned three rapid 
hardening cements, limes and the polymer water holding agents in the ratio 
given in Table 6 followed by adding water. Table 4 shows the results of 
tests for the bench lives of the molding sand mixtures thus prepared, and 
the compressive strength and surface stability of the hardened materials. 
Table 6 
______________________________________ 
Mixture No. 1 2 3 
______________________________________ 
Kawamura silica sand 
(No. 5) part, by weight 
100 100 100 
______________________________________ 
kind (a') - I (a') - II 
(b') 
Rapid hardening 
part, 
cement by weight 10 15 6 
______________________________________ 
part, 
Slaked lime by weight 0.1 0.25 0.3 
______________________________________ 
Poly- 
kind Methyl ethylene 
Poval 
Polymer water cellulose 
oxide 
holding agent 
part, 
by weight 0.1 0.5 0.4 
______________________________________ 
part, 
Water by weight 6 10 5 
______________________________________ 
Note: 
(1) The rapid hardening cement (a') - I was mixed with potassium carbonate 
0.08 parts by weight and gluconic acid 0.02 parts by weight as the bench 
life controlling agents based on the silica sand 100 parts by weight. The 
rapid hardening cement (a') - II was mixed with potassium sulfate 0.4 
parts by weight in place of the bench life controlling agent in case of 
(a') - I. The rapid hardening cement (b') was mixed with sodium nitrite 
0.1 parts by weight and tartaric acid 0.04 parts by weight as the bench 
life controlling agents based on the silica sand 100 parts by weight. 
(2) Of the polymer water holding agents, methyl cellulose is a product of 
Shin-etsu Chemical Industry Company (Metholose) and polyethylene oxide, a 
product of Seitetsu Kagaku Company and Poval, a product of Kuraray 
Company. 
Table 7 
______________________________________ 
Property No. 1 2 3 
______________________________________ 
1hr 1.1 1.7 0.4 
Compressive 2hrs 3.8 5.1 1.2 
strength(kg/cm.) 
24hrs 22.8 30.2 10.8 
______________________________________ 
Surface stability 
(%) 93.8 95.9 93.3 
______________________________________ 
EXAMPLE 3 
Asari silica sand (No. 5) was mixed with the rapid hardening cements, the 
polymer water reducing agents, and limes, followed by being kneaded with 
water in the ratio shown in Table 8 to prepare the molding sand mixtures. 
Table 9 shows the results of tests for the bench lives of the mixtures, 
and the compressive strength and surface stability of the hardened 
materials. 
Table 8 
__________________________________________________________________________ 
Mixture 
No. 1 2 3 4 5 
__________________________________________________________________________ 
Kawamura 
silica sand 
(No.5) part, 100 100 100 100 100 
by weight 
__________________________________________________________________________ 
Rapid kind IV V VI VII VIII 
hardening 
part, 
cement by weight 
10 8 15 6 4 
__________________________________________________________________________ 
kind 0 0 0.10 
0.02 
0.25 
Limes part, 
by weight 
3 0.05 0 0.02 
0 
__________________________________________________________________________ 
Polymer 
water kind A A+B C C D 
reducing 
part, 
agent by weight 
0.1 0.15+0.05 
0.6 0.8 0.5 
__________________________________________________________________________ 
part, 
Water by weight 
6 5 10 4 4 
__________________________________________________________________________ 
Note 
(1) The rapid hardening cements (IV-VIII) were prepared by adding a variety 
of bench life controlling agents to jet cement which was employed in the 
Experiments. The controlling agents and the ratio to the silica sand 100 
parts by weight are as follows, IV, sodium borate 0.02 parts by weight; V, 
boric acid 0.025 parts by weight; VI, citric acid 0.05 parts by weight; 
VII, tartaric acid 0.01 parts by weight; VIII, no bench life controlling 
agent. 
(2) Of the polymer water reducing agents, A is sodium 
.beta.-naphthalenesulfonate-formalin condensation product (the average 
number of naphthalene rings, 8); A + B, calcium 
.beta.-naphthalenesulfonate-calcium .beta.-naphthalenesulfonate-formalin 
copolycondensate (the average number of naphthalene rings, 8); C, Melment 
F 10, a water-soluble melamine resin (a product of Showa Denko Company); 
and D, Pozzolith NL 1400. a polycyclic sulfonic acid salt (a product of 
Nisso-Master Builders Co., Ltd.). 
Table 9 
______________________________________ 
Property No. 1 2 3 4 5 
______________________________________ 
Bench life time (min) 
10 30 10 25 60 
______________________________________ 
Compressive 1hr 5.8 0.5 13.2 1.2 -- 
strength 2hrs 10.2 8.2 15.1 4.8 0.4 
(kg/cm.sup.2) 
24hrs 39.3 37.6 72.0 20.1 6.2 
______________________________________ 
Surface stability (%) 
95.9 99.1 99.2 96.9 81.2 
______________________________________ 
EXAMPLE 4 
Asari silica sand (No.5) 100 parts by weight was mixed with 8 parts by 
weight of jet cement with the same composition as employed in Example 1, 
sodium methylnaphthalenesulfonate-formalin condensation product or methyl 
cellulose 0.2 parts by weight, and quicklime 2.5 parts by weight, followed 
by adding water 5 parts by weight at 5.degree. C. to provide two kinds of 
molding sand mixtures. Table 10 shows the results of tests for the bench 
lives of the mixtures, and the compressive strength and surface stability 
of the hardened materials. For comparison, the molding sand mixture made 
in the absence of quicklime was tested under the same conditions and the 
results are also listed in Table 10. 
Table 10 
______________________________________ 
Quick Bench 
lime life Compressive Surface 
part, time strength (kg/cm.sup.2) 
stability 
by weight (min) 1hr 2hrs 24hrs (%) 
______________________________________ 
1 2.5 10 1.3 7.2 39.6 99.8 
2 0 180 -- -- 24.0 90.2 
3 2.5 10 1.4 3.5 21.3 96.2 
4 0 180 -- -- 11.2 88.4 
______________________________________ 
Note: 
In No.1 and No.2 is used sodium methylnaphthalenesulfonate-formalin 
condensation product (the average number of naphthalene rings, 8). In No.3 
and No.4 methyl cellulose is employed. 
EXAMPLE 5 
To Enshu silica sand (No.6) were added the rapid hardening cements, limes, 
the polymer water reducing agents and then the mixture was kneaded with 
water in the ratio shown in Table 11 to provide the molding sand mixtures. 
Table 11 shows the results of tests for the bench lives of the mixtures, 
and the compressive strength and surface stability of the hardened 
materials. 
Table 11 
______________________________________ 
Mixture No. 1 2 3 4 
______________________________________ 
Enahu silica sand 100 100 100 100 
(No.6) part, 
by weight 
______________________________________ 
Rapid hardening 
kind (a')-III 
(a')-IV 
(b')-I 
(b')-II 
cement part, 
by weight 10 8 18 6 
______________________________________ 
Polymer water 
kind C D A B 
reducing agent 
part, 
by weight 0.8 0.6 0.1 0.2 
______________________________________ 
kind Quick Slaked 
Quick Quick 
lime lime lime lime 
Limes part, 
by weight 0.3 0.1 0.05 0.2 
______________________________________ 
Water part, 
by weight 5 5 8 5 
______________________________________ 
Note 
(1) Of the rapid hardening cements, (a')-III was produced by adding K.sub.2 
CO.sub.3 0.08 parts by weight and citric acid 0.03 parts by weight (based 
on the silica sand 100 parts by weight) as the bench life controlling 
agents to the cement prepared by mixing the glassy material (a) (made in 
Example 2) with anhydrous gypsum and normal portland cement; (a')-IV, 
produced by the use of potassium sulfate 0.3 parts by weight in place of 
the bench life controlling agents employed for the preparation of 
(a')-III; (b')-I, produced by adding sodium nitrite 0.12 parts by weight 
and malic acid 0.08 parts by weight (based on the silica sand 100 parts by 
weight) as the bench life controlling agents to the cement made of the 
glassy material (made in Example 2), anhydrous gypsum and normal portland 
cement; (b')-II, produced by the use of potassium carbonate 0.1 parts by 
weight and boric acid 0.01 part by weight in place of the bench life 
controlling agents used for the preparation of (b')-I. 
(2) The polymer water reducing agents, A, C and D are the same as employed 
in Example 3, and B is sodium methylnaphthalenesulfonate-formalin 
condensation product (the average number of naphthalene rings, 8). 
Table 12 
______________________________________ 
Property No. 1 2 3 4 
______________________________________ 
Bench life time (min) 
20 30 25 10 
1hr 1.3 0.4 2.9 0.7 
______________________________________ 
Compressive 
strength 2hrs 4.2 2.8 8.3 2.7 
(kg/cm.sup.2) 
24hrs 25.4 16.5 38.8 12.2 
______________________________________ 
Surface stability (%) 
99.2 92.4 93.6 97.8 
______________________________________ 
EXAMPLE 6 
The molding sand mixes formed of the components and water in the ratio 
shown in Table 3 were poured into a wooden pattern for test piece of 
.phi.50mm .times. 50mm and capped. The pattern was stripped off 40 minutes 
after kneading to provide samples for tests. Table 14 shows the results of 
tests for the compressive strength, gas permeability and surface 
stability. 
Table 13 
______________________________________ 
Mixture No. 1 2 3 
______________________________________ 
Kozu silica sand 
(No.4) part, by weight 
100 100 100 
______________________________________ 
Rapid hardening 
cement part, by weight 
10 8 6 
______________________________________ 
Polymer water 
kind B B A+B 
reducing agent 
part, by weight 
0.2 0.1 0.2 
______________________________________ 
kind Slaked Slaked Quick 
Limes lime lime lime 
part, by weight 
0.8 0.5 0.5 
______________________________________ 
kind a b c 
Forming agent 
part, by weight 
0.05 0.2 0.1 
______________________________________ 
Water part, by weight 
6 5.5 5 
______________________________________ 
Note 
(1) The rapid hardening cement has the same composition as used in Example 
1. 
(2) The polymer water reducing agents, B and A+B are the same as used in 
Example 3. 
(3) The foaming agents, a, b and c are a higher alcohol-sulfuric acid 
ester, a polyoxyethylene nonylphenyl ether and a mixture of nonionic and 
anionic surface active agents, Reoflude A (a product of Takemoto Resin 
Company), respectively. 
Table 14 
______________________________________ 
Property No. 1 2 3 
______________________________________ 
Slump (%) 82 78 80 
______________________________________ 
Compressive 1 hr. 8.1 4.2 1.2 
strength(kg/cm.sup.2) 
24hrs 22.4 16.2 7.5 
______________________________________ 
Gas permeability 915 1020 1080 
Surface stability (%) 98.8 97.6 93.3 
______________________________________ 
EXAMPLE 7 
The rapid hardening cement employed in composed of the components shown in 
Table 15. 
Table 15 
__________________________________________________________________________ 
11CaO.7Al.sub.2 O.sub.3.CaF.sub.2 
3CaO.SiO.sub.2 
2CaO.SiO.sub.2 
4CaO.Al.sub.2 O.sub.3.Fe.sub.2 O.sub.3 
CaSO.sub.4 
__________________________________________________________________________ 
35% 23% 4% 8% 28% 
__________________________________________________________________________ 
A mixture of Amino silica sand (No.5), the above-mentioned rapid hardening 
cement, a lime, and either a polymer water reducing agent or polymer water 
holding agent was kneaded with water in the ratio shown in Table 16 to 
prepare molding sand mixes. Table 17 shows the results of tests for the 
bench lives of the mixes, and the compressive strength and surface 
stability of the hardened materials. 
Table 16 
______________________________________ 
Mixture No. 1 2 
______________________________________ 
Amino silica sand 
part, by weight 100 100 
Rapid hardening cement 
part, by weight 6 6 
Slaked Lime 
part, by weight 0.1 0.2 
Polymer water reducing agent 
part, by weight 0.2 -- 
Polymer water holding agent 
part, by weight -- 0.15 
Water part, by weight 5 6 
______________________________________ 
Note 
(1) The polymer water reducing agent employed is sodium 
.beta.-naphthalenesulfonate-formalin condensation product (the average 
number of naphthalene rings, 8). 
(2) The polymer water holding agent employed is Metholose, a product of 
Seitetsu Kagaku Company. 
Table 17 
______________________________________ 
Property No. 1 2 
______________________________________ 
1hr 5.8 6.4 
______________________________________ 
Compressive 
strength 
(kg/cm.sup.2) 2hrs 17.7 15.3 
______________________________________ 
24hrs 39.7 29.3 
Surface stability (%) 
99.2 97.9 
______________________________________ 
EXAMPLE 8 
Water (50g) and concentrated sulfuric acid (200g) were poured into a 
creosote oil fractionated at 200.degree.-275.degree. C. and the mixture 
was heated for 3 hours at 160.degree.-170.degree. C. After dropwise 
addition of 37.2% formalin (100g), the mixture was reacted for 10 hours at 
100.degree. C. Following additional addition of water (30g), the mixture 
was heated for 20 hours with stirring and the product was converted to the 
sodium salt by liming sodation. The salt was dried in vacuo and employed 
as a polymer water reducing agent. Kawamura silica sand (No.5) was mixed 
with the polymer water reducing agent thus obtained, the rapid hardening 
cement, and a lime, and the mixture was kneaded with water in the ratio 
shown in Table 18 to give the molding sand mixture. The hard material made 
of the mix was tested for the compressive strength and surface stability, 
and the results are listed in Table 19. 
Table 18 
______________________________________ 
Kawamura silica sand 
part, by weight 100 
Rapid hardening cement 
part, by weight 8 
Polymer water reducing 
agent part, by weight 0.2 
Slaked lime 
part, by weight 0.3 
Water part, by weight 5 
______________________________________ 
Note: Jet cement is employed as a rapid hardening cement. 
Table 19 
______________________________________ 
1hr 2.2 
Compressive 
strength 2hrs 8.4 
(kg/cm.sup.2) 24hrs 34.8 
______________________________________ 
Surface stability (%) 99.0 
______________________________________ 
EXAMPLE 9 
To Enshu silica sand (No.6) 100 parts by weight, a variety of rapid 
hardening cements, a polymer holding agent and a bench life controlling 
agent were added, and the mixture was kneaded with water in the ratio 
given in Table 20 to prepare molding sand mixes. Table 21 shows the 
results of tests for the bench lives of the mixes and the compressive 
strength and surface stsbility of the resulting molds. 
Table 20 
__________________________________________________________________________ 
Mixture No. 1 2 3 4 5 
__________________________________________________________________________ 
Enshu silica sand (No.5) 
(part, by weight) 100 100 100 100 100 
__________________________________________________________________________ 
Alumina cement 
(part. by weight) 
3 2 5 2 2 
kinds Normal Portland Cement 
of (part, by weight) 
8 8 2 4 0 
rapid Jet Cement 
hardening 
(part. by weight) 
6 0 0 0 2 
cement Anhydrous gypsum 
(part, by weight) 
0 0.8 0 0.6 0 
Quick lime 
(part, by weight) 
0.8 0 0 0.8 0.5 
Slaked lime 
(part, by weight) 
0 0.2 0.05 0 0 
__________________________________________________________________________ 
kind methyl 
Polyvinyl 
Methyl 
Water-soluble 
Polyvinyl 
Polymer water cellulose 
alcohol 
cellulose 
melamine 
alcohol 
holding agent 
part, by weight 
0.05 0.1 0.2 0.1 0.3 
__________________________________________________________________________ 
Tartaric 
Boric Adipic 
Potassium 
Bench life 
kind acid acid acid carbonate 
-- 
controlling citric acid 
agent part, by weight 
0.04 0.04 0.02 0.1 -- 
+0.01 
__________________________________________________________________________ 
Water part, by weight 
10 7 6 6 5 
__________________________________________________________________________ 
Table 21 
______________________________________ 
Property No. 1 2 3 4 5 
______________________________________ 
1hr 1.0 0.4 0.2 0.5 0.3 
Compressive 
2hrs 7.5 3.9 3.4 2.3 1.7 
strength 6hrs 18.4 18.2 10.3 6.8 2.9 
(kg/cm.sup.2) 
24hrs 48.8 24.6 19.3 15.6 7.7 
______________________________________ 
Surface stability (%) 
90.4 93.7 97.2 98.7 92.1 
______________________________________ 
EXAMPLE 10 
With Kozu silica sand (No.4) 100 parts by weight, a variety of rapid 
hardening cements, polymer water reducing agents, bench life controlling 
agents and a foaming agent were mixed in the ratio given in Table 22 and 
the mixture was kneaded with water in the ratio shown in the same Table to 
prepare molding said mixes. Table 23 shows the results of tests for the 
strength and surface stability of the molds formed of the mixes. 
Table 22 
__________________________________________________________________________ 
Mixture No. 1 2 3 4 5 
__________________________________________________________________________ 
Kozu silica sand (No.4) 
(part, by weight) 100 100 100 
100 
100 
Alumina cement 
(part, by weight) 
4 2 1.5 
3 2 
Normal portland cement 
Kinds (part, by weight) 
12 4 2.5 
6 0 
of Jet cement 
rapid (part, by weight) 
0 0 0 0 6 
hardening 
Anhydrous gypsum 
cement (part, by weight) 
0 1 0.5 
0 0 
Quick lime 
(part, by weight) 
0 0.5 0.5 
0 0 
Slaked lime 
(part, by weight) 
0.4 0.3 0 0.6 
0.6 
__________________________________________________________________________ 
Polymer water 
kind A B C A B 
reducing agent 
part, by weight 
1.2 0.1 0.4 
0.8 
0.25 
__________________________________________________________________________ 
Bench life 
kind Malic acid 
Boric acid 
-- -- Citric acid 
controlling 
agent part, by weight 
0.04 0.01 -- -- 0.03 
__________________________________________________________________________ 
Foaming kind -- -- -- a -- 
agent part, by weight 
-- -- -- 0.2 
-- 
__________________________________________________________________________ 
Water part, by weight 
10 4.5 4 7 5 
__________________________________________________________________________ 
Note 
(1) The polymer water reducing agents A - C are as follows: 
A: water-soluble melamine resin (Melment F 10, a product of Showa Denko 
Company). 
B: calcium methylnaphthalenesulfonate-formalin condensation product (the 
average number of naphthalene rings, 8). 
C: calcium salt of methylnaphthalenesulfonic acid and naphthalenesulfonic 
acid-formalin copolycondensate (mol ratio, 1:1, the average number of 
naphthalene rings, 8). 
(2) The foaming agent designated by "a" is polyoxyethylene nonylphenyl 
ether. 
Table 23 
______________________________________ 
Property No. 1 2 3 4 5 
______________________________________ 
Compressive 
1hr 1.3 0.4 0.4 1.2 0.3 
strength 2hrs 8.7 2.4 2.3 3.6 5.2 
(kg/cm.sup.2) 
24hrs 54.3 20.8 12.2 15.2 30.4 
______________________________________ 
Surface stability (%) 
97.7 95.2 91.0 96.9 98.9 
______________________________________ 
Note: The slump of sample No.5 is 78%.