CA1103405A - Inorganic foam and preparation thereof - Google Patents

Abstract

NOVEL INORGANIC FOAM AND PREPARATION THEREOF

Abstract of the disclosure:

A highly expanded inorganic foam containing discrete cells with an average diameter of 3 mm or less, being non-flammable with excellent thermal insulating property, heat resistant property as well as water resistance is found to be prepared by foaming and setting simultaneously at normal temperature by adding a suitable amount of a polyvalent metal carbonate to a stable aqueous solution dispersion of a metal phosphate with a specific atomic ratio of metal, to phosphorus and a specific ratio of metal valences relative to phosphate ion valences.

Description

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This invention relates to a novel inorganic foamed material and a process for producing the same.
More particularly, this invention is concerned with a novel inorganic foam comprising metallic salts of phos-phoric acid, containing discrete cells with a high degree of expansion ratio and being non-flammable with excellent thermal insulating and heat-resistant properties and also to a process for producing the same under conditions of normal pressure and temperature.
Organic foamed materials such as polyurethane foams, polystyrene foams or polyethylene foams have been known to have excellent thermal insulating properties and are useful for various materials such as construction materials, various lagging materials, etc. Among them, compositions for polyurethane foams are foa~able and settable at normal temperature and very useful when structural fabrication is to be accomplished at the site at which the compositions are prepared. All of these materials, however, are inflammable since they are organic in nature and also have no satisfactory thermal resistance. In particular, damages caused by soot and toxic gases generated from organic materia~s at the time of fire are becoming great problems in recent years. In the field of thermal insulating materials, there have been made great efforts to make them non-flammable.
On the other hand, inorganic foams such as glass foams, light porous concrete and the like have also been developed as materials excellent in non-flammability and heat resistance. Any of these materials jrc:"~,~J

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is produced under conditions of high temperature and hiqh pressure to result in products of open cellular structure, which are high in water absorption and inferior in thermal insulating property. Furthermore, such a method involves a drawback that there can be produced only products of limited shapes.
U.S. Patent 3" 48,996 (Vukasovich et al) discloses a composition for inorganic foams, which is foamable and settable at normal temperature, comprisin~
an acidic metal phosphate sllch as acidic aluminum phosphate, fine powders of calcium silicate and a liquid vehicle such as water. According to a typical example, 50 parts by weight of an aqueous aluminum phosphate solution are mixed with 50 parts hy weight (in amounts sufficient to set completely said aluminum phosphate solution) of calcium silica-te powders and, after partial setting of the mixture, about 5 parts by weight of calcium carbonate are added to the mixture to effect foaming, whereby a foamed product havinq specific ~ravity of 0.29 is obtained.
U~S. Patent 3,330,675 (Magder) discloses another compositlon for inorganic foams, which is improved in several physical properties over the composition of Vukasovich et al, by replacing calcium silicate in Vukasovich et al with a basic compound which completely neutralizes free P2O5 in acidic Qluminum phosphate solution. The density of the Eoamed product obtained from this composition is as high as 0.~1 g/cm3 at its minimum.
The ohject of the present invention is to provide jrc:~u~, an inorganic foamed material with a high degree of foaminq having a specific gravity of 0.15 or less, containing discrete cells and being non-flammable with excellent thermal insulating as well as *hermal resistant properties and also to provide a process for producing the same.
It has now been found that an aqueous acidic solution of a metal phosphate having specific atomic ratio of metals to phosphor (M/P ratio) and specific equivalent ratio (E ratio) can be foamed with a basic metal carbonate excellently to give a foamed product with a high degree of expansion. The present invention has been accomplished based on such a finding.
The particular feature o e the process of the present invention resides in that there is first formed a stable aqueous solution of metal phosphate having specific M/P ratio and E ratio which is not self-settable even on storage for a long time ~and the~thus formed stable solution is then subjected to simu]taneous foam-ing and setting by addition of a basic carbonate of polyvalent metals. In contrast, according to the processes of prior art as mentioned above for producing foamed inorganic materials, it is essentially required to use stoichiometric amounts (i.e., E ratio = 1) of hardening agents (calcium silicate or basic compound) to effect complete hardening of the phosphate composition. Further, foaming is commenced after hardening has proceeded to some extend or alternatively foaming and setting are commenced simultaneously by mixinq at the same time the hardening agent and the foaming agent with the phosphate composition. :[t is entirely unexpected that j ~c: t~

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a highly expanded foam can be produced by simultaneous ~oaming and setting o~ a stable aqueous metal phosphate solution specifically prepared according to the present .invention.
According to the present invention, there is provided an inorganic foam comprisinq metallic salts of phosphoric acid, being characterized in that (a) the ratio of the total number of metal atoms constitutinq said salts to that of phosphor atoms is in the range from ?/3 to 2/1;
(b) the metals constituting.said salts comprise polyvalent metals and have a composition such that the equivalent ratio of the total valences of metals relative to the -total valences of phosPhate ions : is from 0.65 to 0.95;
(c) said foam contains discrete cells with an average diameter.of 3 mm or lessl and (d) said foam has a specific grav.ity of 0.15 or less.
:2~ The inorganic foam provided by the present invention is distinguished in structure from any of the inorganic foams known in the art. The difference may be better understood by referring to the accompanying drawings, in which:
E'ig. 1 shows a microscopic photograph (X 13) of a cross-section of the foamed product (Example 8) of the present invention;
Fig. 2 shows microscopic photograph (X 13) of a cross-section of the foamed product produced by foaming at normal temperature according to the process of prior ~' jrc~ JI~

art (comparative example 6); and Fig. 3 shows a microscopic photograph (X 13) of a cross-section of commercially available calcium silicate board produced under conditions of a hiah pressure and a high temperature.
By comparison among Fig. 1, Fig. 2 and Fig. 3, it is apparently seen that the cells of the foam according to the present invention are discrete and uniform in size as compared with those of prlor art as shown in Fig. 2 and Fig. 3, indicating a high deqree of expansion ratio of the foam according to the present invention. Due to such a difference in structure, the foam provided by the present invention is novel foam having a low specific gravity, excellent thermal insulating and heat resistant properties and being low in water absorption.
The inorganic ~oam of the present invention can be produced by a process which comprises allowing a mixture comprising (A) a metal phosphate containing at least one polyvalent metal,~the ratio of the total number of metallic atoms to the number of phosphorus atoms in said metal phosphate being from 1/3 to 3/2 and the e~uivalent ratio of the total valences of the metallic atoms to the total valences of phosphate ion in said metal phosphate from 1j3 to 3/4; (B) a polyvalent metal carbonate and (C) water to foam and set at normal temperature, the amount of the polyvalent metal carbonate being controlled within the range such that the ratio of the total number of metallic atoms to the number of phosphorus atoms in the resultant foam may be from 2/3 to 2/1 and the equivalent ratio of the total valences ~ jrc~

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of metals relative to the total valences of phosphate ion in said resultant foam may be from 0.65 to 0.95.
The process accordino to the present invention can be generally practised by allowing a composition comprising 100 parts by weight of the metal phosphate (A), 5 to 50 parts by weigh~ of the carbonate (B) and 20 to 200 parts by weight of water (C).
Typical examples of -the polyvalent metal phos !phates (A) to be used in the present invention are primary phosphates, e.g. primary magnesium phosphate, primary calcium phosphate, primary strontium phosphate, primary barium phosphate, primary zinc phosphate, primary aluminum phosphate, etc. and a `mixture of said primary polyvalent metal phosphate with a secondary phosphate, tertiary phosphate or pyrophosphate of such metals as magnesium, calcium, strontium, barium, aluminum, zinc, iron, manganese, etc. These polyvalent metal phosphates may optionally be modified with oxides, hydroxides or , silicates of mono- or polyvalent metals such as alkali metals (e.g. lithium, sodium, potassium), ma~nesium, calcium, strontium, barium, aluminum, zinc, iron, manganese, etc.
Thus, the polyvalent metal in the metal phos-phate is general]y selected from di-valent and tri-valent metals. Among them, magnesium, zinc and aluminum are preferred from the standpoint of mechanical strength of the foam obtained. Calcium is also preferably used since it is available at low cost.
Of course, the above metal phosphates can be obtained directly from the reaction between an aqueous ,~ - 6 -, jrc:'hu~, ~3~S
phosphoric acid solution and oxides, hydroxides or salts of said metals. In any case, it is critical that the ratio of the total number of metal atoms (M atom) to the number of phosphorus atoms (P atom) in the metal phosphate is required to ~e M/P = 1/3 to 3/2.
If M/P ratio in the startin~ metal phosphate is less than 1/3, setting reaction accompanied at the time of foaming does not proceed sufficiently and it is difficult to maintain a good balance between foaming and setting. As the result, it is difficult to obtain a foamed product having uniform and fine foamed cells but there is obtained only foamed products inferior in water resistance and heat resistance. On the contrary, with M/P ratio exceeding 3/2, the aqueous solution of such a salt is extremely unstable. In other words, the aqueous solution tends to be self-settable, whereby it is also difficult to maintain a good balance between foaming and setting with the result that there is obtained only a foamed product with low degree of expansion.
Furthermore, the equivalent ratio E, which is defined as the total valences of metals relative to those of phosphate ions as expressed by the following equation, in the starting metal phosphate is desired to be from 1/3 to 3~4.

E - ~i x Ei 3 x Np (wherein Np represents the numbar of phosphorus atoms in said metal phosphate, i the valance of each metal and Ei the number of the metal having a valence of i).

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3~i The polyvalent metal carbonates to be used in the present invention are exemplified by magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, zinc carbonate, iron carbonate, cobalt carbonate, zirconium carbonate, basic magnesium carbonate, basic cobalt carbonate and the like. The carbonates to be used in the present invention are required to be those of a metal having the valence of two or more in order that they can function simultaneously as a foaming agent which generates carbon dioxide by reaction with the aforesaid phosphate and as a hardening agent for setting said metal phosphate.
The quantity of the carbonates to be used in the present invention is intimately related with the M/P ratio and the equivalent ratio E as described abové.
Namely, when a n.etal phosphate having larger M/P
ratio and equivalent ratio E, the balance between foaming and setti.ng can be maintained well by use of a small amount of the carbonate. On the other hand, when the M/P ratio and equivalent ratlo E are smaller, it is necessary to use a relatively large amount of the carbonate in order to maintain a good balance between foaming and setting. By analysis of the data obtained, .-it has now been found that satisfactorv results can be obtained by increasing the equivalent ratio E of the starting metal phosphate which is within the range from 1/3 to 3/4 to the range from 0.65 to 0.95 by addition of the carbonate. Fur-ther, for the purpose of generating bubbles of carbon dioxide to effect sufficient expansion, it is also desirable to use the carbonate in a quantity jrc~

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sufficient to increase the equivalent ratio by at least - 0.06, preferably 0.15 or more. ~hile satisying the requirements as mentioned above, from 5 to 50 parts by weight of the carbonate are generally used per 100 parts by weight of the metal phosphate.
According to a preferred embodiment oE the present invention, the process o the present invention is practised by first forming an aqueous solution or dispersion of the aforesaid metal phosphate. It is important to mix homogeneously the components and it is also important that the resultant aqueous solution or dispersion should have an appropriate viscosity.
If the viscosity is too low, there may occur shrinkage of foamed product before setting. On the other hand, if the viscosity is too high it is difficult to mix with the foaming agent. In either of such cases, no favorable foamed produot can be obtained. For obtaining a suitable viscosity, from 20 to 200 parts by weight of water is used per 100 parts by weight of the aforesaid phosphate or modified phosphate. Furthermore, analysis o the data shows that the most favorable result can be obtained by adding the carbonate to an aqueous solution or dispersion of the phosphate or modified phosphate, in which the M/P ratio is from 1/3 to 3/2, the equivalent ratio E is from 1/3 to 3/4 and said M/P ratio is not less than the equivalent ratio E and not more than 2/3 times the equivalent ratio E, in an amount to increase the equivalent ratio F. by at least 0.06 to an equivalent ratio E of the resultant foam within the range from 0.65 to 0.g5.

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The aqueous solution or dispersion of the metal phosphate having the composition within the preferred range as mentioned above can exist stably on storage for a long time and shows no self-setting tendency. Such a stable aqueous solution or dispersion of the metal phosphake is found to be foamable to a high degree of expansion and simultaneously settable by addition of the metal carbonate as mentioned above. Usually, the aforesaid carbonate is added while stirring at a high speed the aqueous phosphate ~,~olution or dispersion to be completely mixed therewith and the resultant mix is cast in a'mold of a desired shape to allow foaming and setting at normal temperature.
Within several seconds to some 10 minutes after mixing, foaming usually commences and complete setting occurs within 10 minutes to 10 hours. The degree of expansion, the speed of expansion and the speed of setting can be freely controlled by~varying the composition of the phosphate, the carbonate to be employed and its amount and the~stirring speed at the time of mixing. ' The ~norganic foam of the present invention may also preferably contain hydrophobic groups chemically bonded to phosphate groups. As such hydrophobic groups, the reaction products between the phosphate groups and the compound selected from the group of the compounds as represented by the following formula (I) are found to impart excellent water repellency to the foamed product:
R

(1, ' I

' R'~()m~Q ()k (I) ()n I

R"

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3~5 wherein Q represents phosphorus or nitrogen and k, Q, and n are integers o~ O or 1 and, when ~ is phosphorus, (1) k is O or 1, Q and m are 1, n is O or 1, R and R' are each hydrogen, and R" is an alkyl, an aryl, a substituted al~yl or a substituted aryl; or

(2) k is O or 1, Q is 1, m and n are each O or 1, R is hydrogen and R' and R" are each an alkyl, an aryl, a substituted alkyl or a substituted aryl, and when Q is nitrogen, k, Q, m and n are 0, R, R' and R" are each hydrogen, an alkyl, an aryl, a substi~uted alkyl or a subst.ituted aryl, with proviso that the case where R, R' and R" are all hydrogens is excluded.
Typical examples of the compounds of the formula (I) include the compounds as classified below:

Rl~ ~0 R / ~ OH

R -O ~ O
(b) / P
R3-0 \ OH

p (c) -OH

Rl- O
(d) / P-OH

R~

(e) R5 N

(wherein Rl represents an alkyl, an aryl, a substituted alkyl, or a substituted aryl; R2 hydroxy, an alkyl, an aryl, a substituted alkyl, or a substituted aryl; R3 hydrogen, an alkyl, an aryl, a substituted alkyl, or a substituted aryl; and each of R4, R5 and R6 represents irc: ~J.~, ~39L~5 hydrogen, an alkyl, an aryl, a substituted alkyl, or a substituted aryl excluding the case where all of R4, R5 and R6 are hydrogens).
Inorganic foamed or porous materials of prior art have a common drawback that they have poor water resistance and are espeçially liable to absorb water or moisture.
Thus, while they possess inherently good thermal insulat-ing properties, they become frequently degraded in thermal insulating properties as the result of absorption of water or moisture when they are practically applied.
Improvement of water resistance has been proposed by incorporating a hydrophobic compound such as paraffin wax, mineral oil or silicone oil in an inorganic material such as cement or gyps~n. The greatest drawback o~ this method is that it is extremely difficult to mix homogeneously the hydrophobic compound with the inorganic material. A mixture which appears to be homogeneously mixed by macroscopic observation may sometimes fail to be homogeneous from microscopic observation. Thus, the improvement o~ water resistance is ~uite limited. In particular, for porous or foamed materials having a structure which will readily absorb water, it is entirely impossible to improve water resistance thereof by such a method as described above.
The water resistance exhibited by the inorganic foam of the present invention is effected by homogeneous dispersion of the compound of the general formula (I) which has in combination hydrophobic groups and functional groups reactive with the metal phosphate, as substantially different from the method of prior art. The effect of " j -, .....
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addition of such a compound can be achie~ed by an extremely small amount thereof and such an effect remains almost permanently since the compound is chemically bonded to the inorganic material. It is therefore critical that the compound of the formula ~I) should contain hydrophobic groups together with functional groups which are reactive with the metal phosphate. A compound having only hydro-phobic groups will not give the excellent result o~ the present invention The hydrophobic groups herein mentioned include alkyl groups, aryl groups, substituted alkyl groups and substituted aryl groups. Other groups such as alkyl silyl groups (R-~i-) may also be included. The functional groups reactive with the metal phosphate are amino groups which can be chemically bound by neutralization reaction with phosphoric acid groups in the metal phosphate, or phosphoric hydroxide groups which can be chemically bound by neutralization or exchange reaction with metallic ions in the metal phosphate. Typical examples of the compounds as represented by the general formula (I) are organic amines such as mono-~or di- or tri-)butyl amine, mono-(or di- or tri-)hexyl amine, mono-(or di- or tri-)octyl amine, mono-(or di- or tri-)lauryl amine, mono-~or di- or tri-) palmityl amine, aniline, or myristyl phenyl amine, etc.;
organic phosphoric acids such as mono-(or di-)phenyl phosphoric acid or mono-(or di-)phenyl phosphoric acid, etc.; phosphoric acid esters such as phosphoric acid mono-(or di-) butyl ester, phosphoric acid mono-(or di-) oleyl ester, etc.; organic phosphorous acids such as mono-(or di-)stearyl phosphorous acid, mono-(or di-) dodecylphenyl phosphorous acid, etc.; and phosphorous ,, , jrc~

~L~q;D 3~5 acid esters such as phosphorous acid (octyl)(dodecyl) ester, phosphorous acid (butyl)(nonylphenyl) ester, phosphorous acid steryl ester, etc.
The compound represented by the above formula (I) is used in an amount of 0.01 to 10 parts by weight, preferably from 0.1 to 5 parts by weight, based on 100 parts by weight of the metal phosphate. With an amount less than 0.01 parts by weight, no significant effect can be obtained. On the contrary, an amount in excess of 10 parts by weight will make homogeneous mixing or reaction impossible and may, in an extreme case, damage the inherent properties such as excellent thermal insulating properties of non-flammability.
The compound of the formula (I) may be added at any time during the preparation of the foamed product as described above. For example, it~ may be present in the original aqueous metal phosphate solution or dlsper-sion or alternatively it may be added by mixing with the carbonate which is to be added to saicl aqueous metal phosphate solution or dispersion.
As mentioned above, the excellent ef~ect o the present invention can be imparted by use of a compound having hydrophobic groups in combination with functional groups reactive with the metal phosphate. Thus, the hydrophobic compounds having reactivity with the metal phosphate such as alcoho]s, epoxy compounds, weak acid salts of amines and the ]ike may also be available to form in situ the compound of the formula (I) to achieve the effect of the present invention.
The inorganic foam of the present inven-tion ;
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In particular, physical properties such as thermal insulating property may frequently be deteriorated and there should be paid due consideration as to the selection of the reinforcing material to be used and its quantity. The reinforcing materials which may be used in the present invention in d ude fihrous reinforcing materials such as qlass fibers, ashestos fibers, rock wool fibers, fibrous calcium silicate, cellulose fibers, synthetic fibers (e.g. polyester, polyamide, etc.) and others; and powdery reinforcing materials such as fly ash, talc, kaolinite, zircon sand, alumina, silica, pearlite and others.~ The quantity of the reinforcing material to be used in the present invention is desired to fall within the range from 1 to 1000 parts by weight based on 100 parts by weight of the aforesaid phosphate.
Particularly, fibrous reinforcing materials may have an extremely bad influence on the state of foaming when they are employed in excessive amount, although they can remarkably improve the strength of the foam on the other hand. Hence, they should be used in amounts from 1 to 25 parts by weight. In contrast, powdery reinforcing materials do not improve the strength of the foam to a remarkable extent by addition of a small amount thereof, but have no bad influence on the resultant foam when the amount is increased. Hencej they are desired to be ~rc: ~Sl~

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used inamounts from 10 to 1000 parts by weight. It is not preferred to use an amount of the reinforcing material in excess of 1000 parts by weight, because workability is poor and the foams obtained are inferior in expansion ratio and thermal conductivity. It should further be noted that the upper limit of the reinforcing material is further limited when it contains metallic species having reactivity with the metal phosphate of the present invention.
As mentioned~above, ~y use of the composition according to the present invention, there can be obtained inorganic foams with various complicated shapes, which have not been attainable by the inorganic foams of prior art, at normal temperature and under normal pressure.
Further, they are very useful slnce they are excellent in non-flammability, thermal~insulating properties, heat resistance and also water~reslstance as well ~s mechanical stren~th.
The particular feature of the present~invention can further be exhibited by making into a composite with other materials. As mentioned above, the composition of - the present invention is foamable under conditions of normal temperature and pressure and therefore there can s~mply be obtained a composite by casting the composition into the space between other materials and a1lowing it to expand and set. This is also one of the remarkable effects of the present invention which is entirely impossible according to the inorganic foams of prior - art. Thus, by casting the composition into a space defined between other materials having various complicated jrc: ~1JlJ

, 3~5 , structures, including not only plane structure but also other structures such as curved structure or honeycomb structure and permitting said composition to foam and set, there can be obtained composite materials with light weight and excellent thermal insulatin~ property which can be utilized for various uses, especially as lagging material. Furthermore, in practising the present invention, it is not required to use a large scale equipment and there~re the composition of the present invention is useful for thermal insulating material for heat reservoir, thermal insulating material for ship or fire-retardant thermal insulating material for steel-frame, for which structural fabrication is desired to be accomplished at the site where the compo-sition is prepared.
Other materials as mentioned above to be used in combination with the present composition may include metals, glasses, cement products, gypsum products, plastic materials, woods, papers, cloths and others.
The inorganic foam shows excellent adhesiveness with these other materials.
The present invention is illustrated in further detail by the following Examples, in which all parts and "%" are by weight and thermal conductivity is measured by the method according to ASTM-C 518. The test methods for evaluation of water resistance are explained below:
(1) Measurement of water absorption:
A test block of 5 cm x 5 cm x 5 cm is cut from the sample and, after measurement of its weight and apparent volume, dipped into water at 25C for 3 hours, jrc:~L~

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followed by weighing again of the block. The amount of water absorbed is measured per 100 cm3 of the test block by the following equation:
Weight after Weight before Water absorption _ absorption(g) absor~tion(q) ~g/100 cm3) Apparent volume of test block x 100 before absorption(cm3) (2) Red ink penetration test:
A test block of 3 cm x 3 cm x 6 cm is cut from the sample, dipped in commercially available aqueous red lnk for 12 hours and thereafter the block is cut to observe cross-section of the test block to examine penetration of red ink into the test block.
Example 1 Primary aluminum phosphate150 parts (50% aqueous solution) Tertiary magnesium phosphate 50 parts Tertiary calcium phosphate40 parts The above components with M/P ratio = 0.91, E ratio = 0.67, are completely mixed at normal temperature and then mixed completely with 20 parts of basic magnesium carbonate. The mixture is taken out and left to stand.
Foaming begins immediately and has substantially completed within 15 minutes to obtain a foam (~/P = 1007, E = 0.77).
The properties of the foam are shown in Table 1.
Thermal conductivit~ is measured at average temperature of 35C and evaluation of heat resistance is conducted by the changes after leaving the foam in an electric surface set at 1000 C for 2 hours. For comparison, the properties of polystyrene foam (Styrofoam: trade mark) are also shown in Table 1.

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Table 1 Expan- Thermal con-sion Specific ductivity Sample ratio ~ravity (kcal/m.hr. C) Heat resistance Example 19.5 0.11 0.035 no change at 1000C ~or . 2 hours Poly- 25.0 0.04 0.030 completely de-foam formad at 110C
after 5 minutes Examples 2-3, Comparative examples 1-2 Phosphoric acid 91.4 parts (75~ aqueous solution) Aluminium hydroxide 11.4 parts Zinc oxide .11.4 parts Magnesium oxide 7.5~parts The above components are completely mixed and reacted at normal temperature to obtain a transparent, viscous solution with~M/P ratio = 0.66 and E = 0.50.
Then, this solution is mixed with various parts of calcium carbonate as shown i:n Table 2.
Table 2 ~ .
Comparative Comparative example 1 Example 2 Example 3 exam le 2 20 . Amount of calcium 4 parts 23 parts 34 parts 51 parts carbonate The properties of the foams obtained are shown in Table 3.

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Table 3 Speci- Thermal fic conductivity gra ty M/P E (kcal/m~hr-C) Foamin~
Compara- - 0.73 0.54 - foamed, but tive not set example .
Example 2 0.09 1.00 0.72 0.038 uniEorm dis-crete cells average cell size 2.1 mm Example 3 0.05 1.16 0.83 0.033 uniform dis crete cells average cell size 1.5 mm Compara- - 1_40 0.99 - impossible to tive mix example Example 4 - 9 Various aqueous metal phosphate compositions as shown in Table 4 are prepared.
Table 4 -:
Example ~Example Example Example Example Example

4 _ 5 _ 6 _ 7 8 _ 9 Phosphoric acid(7596 140 140 140 140 160 160 aqueous parts parts parts parts parts parts solution) Aluminium 40 30 25 20 20 20 hydroxide parts parts parts parts parts parts Magnesium 10 20 25 30 oxide parts parts parts parts Zinc 35 35 oxide - ~ - - parts }?arts Sodium 40 hydroxide - - - - - parts Water 50 50 50 50 20 parts parts parts parts - parts M/P 0.70 0.81 0.87 0.93 0.55 1.38 E 0.63 0.66 0.68 0.70 0.44 0.72 jrc: t~ J

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All of these metal phosphate compositions are stable solutions and neither increase of viscosity nor setting is observed in any of these compositions after 24 hours.
To each composition is added basic magnesium carbonate in various parts as shown in Table 5.
Each mixture is well mixed to obtain respective foamsO The properties of each Eoam are shown in Table 5.
_able 5 ::iExample Example Ex = Example Example Example Basic magnesium 40 35 30 25 80 20 carbonate parts parts parts parts parts parts .
M/P 1.08 1.15 1.16 1.17 1.23 1.59 E 0.89 0.88 0.87 0.86 0.89 0.83 Specific gravity'Ø08 0.07 0.07 0.06 0.04 0.09 Average cell size 1.1 mm 1.0 mm 1.5 mm 1.0 mm l.S mm 2.0~.mm Comparative examples 3 - 5 Various metal phosphate compositions as shown in Table 6 are prepared.

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Table 6 Comparative Comparative Comparative example 3 example 4 example 5 . . _ Primary aluminium phosphate (S0% 100 parts 100 parts 100 parts aqueous solution~
Magnesium oxide 12.9 parts - -Zinc oxide - 26.9 parts Calcium silicate - - 100 parts M/P 1.00 1.03 2.1 E 0.78 0.80 1.5 All of these metal phosphate compositions are unstable and set in a few minutes. With these composi-tions, substantially no foaming occurs by addition of a polyvalent metal carbonate.
Comparative example 6 ~ .
Primary aluminium phosphate 100 parts ~50% aqueous solution) Calcium sllicate 100 parts The above components (M/P = 2.1, E = 1.5~ are completely mixed and then mixed completely with 10 parts of calcium carbonate prior to complete setting of above components.
The properties of the obtained foam are shown in Table 7.
_able 7 Specific Average Thermal conductivity qravity cell size (kcal/m hr C~
0.48 5.0 mm 0.115 - 22 ~
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The above results of Comparative examples 3 - 6 show that there can be obtained no highly ex~anded foam with small speclfic gravity from a self-setting starting composition with M/P ratio and E ratio exceeding the ranges of the present invention~ -Comparative example 7 Example 1 is repeated except that sodium carbonate is used instead of basic magnesium carbonate in the same amount.
Foaming occurs but the composition is not hardened even after a long period of time, failing to give a solidified foam. Thus, it is critical to use a polyvalent metal carbonate which also functions as a hardening agent.
Example 10 Primary zinc phosphate 450 parts tS0% aqueous solution) Tertiary magnesium phosphate 150 parts Tertiary calcium phosphate 120 parts The above components with M/P ratio = 1.01, E = 0.6~ are completely mixed and further mixed completely with addition of 75 parts of magnesium carbonate.
The resultant mixture is cast into annular space between double walls formed by double pipes of steel erected vertically (outer pipe being 300 mm in height, 100 mm in diameter and 1 mm thick; inner pipe being 300 mm in height, 50 mm in diameter and 1 mm thick).
After 10 seconds, foamina begins until settin~ is completed after 45 minutes. The space between the double walls is completely filled with the ~oam (M/P = 1.22, E = 0.81) jrc~

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~33~5 which is strongly adhered to the walls. A part of the foam is taken out for measurement of expansion ratio, whi.ch is found to be 18.5.
Example 11 Phosphoric acid (75% aqueous 80 parts solution) Aluminum hydroxide 15 parts Zinc oxide 25 parts Phosphoric acid mono-lauryl ester 0.5 part ..
. The above components are completely mixed and reacted at normal temperature to obtain a transparent viscous so]ution with M/P ratio = 0.79, E = 0.56. When this solution is mixed with 20 parts of basic magnesium carbonate, foaming immediately begins and aft~r 10 minutes ~oaming is substantially completed to glve the foam (M/P = 1.13, E = 0.87) havin~ the properties as shown in Tab~.e 8.
Table 8 Thermal con- Compressive Water resistance Density ductivity strength Water absorp- Red.ink (g/cm3) (kcal/m-hr-C) _(kg/cm2) tion ( /100 cm3) ~enetration 0.08 0.035 0.5 1.5 no pen-etration Examples 12 - 17, Comparative examples 8 - 14 Example 1 is repeated except that various compounds as shown in Table 9 are used in place of phosphoric acid mono-lauryl ester. The results of evaluation of these foams are set forth in Table 10.

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O X O ~'0 ~ C) Q ,1:~ v2 v2 r~
~1 O O ~ ' " O-- V~ = O

. ~ v~o--~ . o~ a) r~
~rl a~ ~ 3 5~ ~ ~ ~
~C .S O ~ v2 o ~ Q c~ d N
~1 p~ d ~1 ~d r l O X O O '.~ r-1 Q) ~1 u2 u~ C>
r~
r~ rl -5 ~ ~ 11

5:~ 0~0--P~ --O ~ O--V
E S ~ ~ E~ E ~d ~d ~
X C ~d~ O X 1~ ~ r-l ~dr-l ~d r~ .
O ~V r-l O ~ c.> ~3 O~rl O r1 ~ t~ ~ ,L, O

Table 10 Evaluation of water resistance .
Water absorption (g/100 cm3) Red ink penetration Example 12 4.1 No penetration Example 13 1.1 No penetration Example 14 3.7 No penetration Example 15 1.3 No penetration Example 16 3.8 No penetration 10 Example 17 2~9 No penetration Comparative example 8 30.1 Penetration Comparative example 9 34.6 Penetration . -Comparative example 10 36.1 Penetration Comparative example 11 31.9 Penetration Comparative 20~. example 12 ~2.6 Penetration Comparative example 13 30.9 Penetration "' Comparative example 14 32.3 Penetration Example 18 A test block o-f 3 cm x 3 cm x 6 cm is cut from the foam obtained in Example 11 and placed in a Soxhlet's extractor and extracted with 200 m~ o-f isoproply alcohol for 24 hours. The test strip is dried after extraction and its water resistance is evaluated to ~ive the result as shown in Table 11.

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Table ll Water absorption Red ink (q/100 cm3) penetration Remarks Example 18 1.6 No penet- After ration extraction Example 11 1.5 No penet- Before ration extra~tion Examples 19 - 21, Comparative examples 15 - 16 Primary aluminum phosphate 160 parts :(50% aqueous solution) Magnesium oxide 15 parts Zinc silicate ~ 5 parks The above components are mixed and reacted thoroughly to prepare a transparent and viscous solution with M/P ratio = 0.87, E = 0.68. Several tests are conducted by adding various amounts of phosphoric acid distearyl ester as shown in Table 12, followed by :
complete dispersing in said solution, and adding 25 parts of calcium carbonate to perform foaming and setting.
Each foam has M/P ratio of 1.20 and E ratio of 0.90.
Table 12 .
Compara- Com~ara-tive tive example Example Example Example example . 15 19 20 21 16 . . .
Phosphoric acid di-stearyl 0.0050.05 0.1 5.0 15.0 ester (parts) The foams obtained are evaluated for water resistance and also for heat resistance by heating at 800C for 10 minutes to give the results as shown in - Table 13.

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Table 13 Water resistance evalua-tion Heat resistance .
Water absor~tion ~ed ink _ _g/100 cm ) penetration Comparative Nothing example 1525.n Penetration abnormal Example 192.1 No Nothinq Penetration abnormal Example 201.4 No Nothing penetration abnormal . .
Example 211.0 No Nothing penetration abnormal Comparative example lZ0.8 No Soot and bad penetration odor generated Example 22 Phosphoric acid (75% aqueous 80 parts solution) Aluminom hydroxide 15 parts Magnesium oxide 10 parts Zinc oxide 15 parts Octyl amine 1.0 part The above components are completely mixed and reacted at normal temperature to obtain a se:mi-transpar~nt viscous solution with M/P ratio = 1.0, E = 0.79. After 3.0 parts of paper pulp are added to this solution and completely dispersed, the mixture is mixed with 10 parts of calcium carbonate and cast into the space between two aluminum plates of 300 mm x 300 mm x 1 mm to prepare a sandwich composite with thickness of 50 mm. The foam (M/P = 1.18, E - 0.90) is strongly adhered to aluminum plates and a part of the foam is cut out for measurement of its density, thermal conductivity, water resistance jrc~

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and com~ressive strength to qive the results set forth in Table 14.

Table 14 Thermal Density conductivity Red ink Compressive (g/cm3) (kcal/m hr~C) penetration strength(kg/cm2) _ _ _ _ -- _ _ 0.]1 0.041 No 2.5 penetration Example 23 Phosphoric acid (75% aqueous 80 parts solution) `~ Aluminum hydroxide 15 parts Zlnc oxide 25 parts The above components are completely mixed and reacted to prepare a transparent viscous solution with M/P ratio = 0.79, E~= 0~66. Flve parts of glass fibers (produced by Asahi Glass Piber Co., Japan) are added to this solution and completely dispersed therein.
Then, the mixture is mixed with 20 parts of basic magnesium carbonate. When the mixture is taken out and left to stand, foaming begins immediately and is completed substantially after 10 minutes. The resultant foam (M/P - 1.13, E = 0.87) is found to have a density of 0.09 g/cm , thermal conductivity of 0.039 kcal/m-hr C
and compression strength of 2.0 kg/cm .
Examples 24 - 27 Phosphoric acid (75% aqueous 80 parts ;
solution) Aluminum hydroxide lS parts Magnesium oxide 10 parts Zinc oxide 15 parts jrc:~)v~

~3~5 The above components are completely mixed and reacted at normal temperature to prepare a semi-transparent viscous solution with M/P ratio = 1.0, E = 0.79.
Examples 24 to 27 are carried out by adding various amounts of paper pulp as shown in Table 15 to this solution, followed by complete dispersing, then mixing with 10 parts of calcium carbonate and allowing the mixture to foam and set. Each foam has ~/P ratio of 1.18 and E
ratio of 0.90. The properties of the foams are also shown in Table 15.
Table 15 Paper Thermal Compressive pulp Density conductivity strength (parts) (g/cm3) (kcal/m hr C) (kg/cm2?
Example 24 0 0.06 0.033 0.5 Example 25 2.5 0.07 0.033 1.5 Example 26 5.0 0.09 0.037 2.0 Example 27 20 0.15 0.041 7.5 Examples 28 - 30, ~omparative example 17 Primary aluminum phosphate160 parts (50% aqueous solution) Magnesium oxide 15 parts Zinc silicate 5 parts The above components are completely mixed and reacted to give a transparent viscous solution with M/P
ratio = 0.87, E = 0.67. Several experiments are carried out by adding various amounts as shown in Table 16 of kaolinite (S1O2 72.10%,.A12O3 19.57%, Fe2O3 0.39%, CaO
0.80%, MgO 0.54%) to be completely dispersed therein and each mixture i5 admixed with 30 par-ts of basic magnesium jrc~

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carbonate and allowed to foam and set. Each foam is Eound to have M/P ratio oE 1.13 and E ratio of 0.84.
The foams obtained have the properties as shown in Table 16.
Table 16 K~ Thermal Compressive nite Density conductivity strength (parts) (g/cm3) (kcal/m-hr-C) (ka/cm2) _ Example 280 0.05 0.032 0.4 Example 2950 0.07 0.035 2.5 ~,,xample 30 100 0.09 0.038 2.7 Comparative example 171250 0.47 0.078 9.3 Example 31 Phosphoric acid (75% aqueous 80 parts solution) Aluminum hydroxide 15 parts Magnesium oxide 10 parts Zinc oxide 15 ~arts The above components are completely mixed and reacted at normal temperature to obtain a semi-transparent viscous solution with M/P ratio = 1.0, E = 0.79.
After 3.0 parts of paper pulp are added to this solution and completeIy dispersed, the mixture is mixed with 10 parts of calcium carbonate and cast into the space between two aluminum plates of 300 mm x 300 mm x 1 mm to prepare a sandwich composite with thickness oE 50 mm.
The foam (M/P - 1.18, E = 0.90) is found to be strongly adhered to aluminum plates.

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Claims (18)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An inorganic foam comprising metallic salts of phosphoric acid, being characterized in that:
(a) the ratio of the total number of metal atoms constituting said salts to that of phosphorus atoms is in the range from 2/3 to 2/1;
(b) the metal constituting said salts comprises at least one polyvalent metal and the equivalent ratio of the total valences of the metal relative to the total valences of phosphate ion is from 0.65 to 0.95;
(c) said foam consists of discrete cells with an average diameter of 3 mm or less; and (d) said foam has a specific gravity of 0.15 or less.

2. An inorganic foam as in Claim 1, wherein the polyvalent metal is at least one selected from the group consisting of di-valent and tri-valent metals.

3. An inorganic foam as in Claim 2, wherein the polyvalent metal contains magnesium, zinc, aluminum or a combination thereof.

4. An inorgnaic foam as in Claim 3, wherein the polyvalent metal further contains calcium.

5. An inorganic foam as in any of Claims 2 to 4, wherein the metal phosphate further contains at least one alkali metal.

6. An inorganic foam as in any of Claims 2 to 4, wherein there is incorporated at least one additive selected from the group consisting of aggregates, reinforcing materials and fillers, said additive being incorporated in an amount of from about 1 to about 1000 parts by weight per 100 parts by weight of phosphoric acid metallic salt.

7. An inorganic foam as in Claim 1, wherein the foam contains hydrophobic groups chemically bonded to the metal phosphate.

8. An inorganic foam as in Claim 7, wherein the hydrophobic groups are formed by reaction between the metal phosphate and a compound of the formula (I):

(I) wherein Q represents phosphorus or nitrogen and k, ?, m and n are integers of 0 or 1 and, when Q is phosphorus, (1) k is 0 or 1, ? and m are 1, n is 0 or 1, R and R' are hydrogen atoms, and R" is a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups; or (2) k is 0 or 1, ? is l, m and n are each 0 or 1, R is hydrogen and R' and R" are each a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups; and when Q is nitrogen, k, ?, m and n are 0, R, R' and R" are each hydrogen, a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups, with the proviso that the case where R, R' and R" are all hydrogen is excluded.

g. A process for producing an inorganic foam comprising metallic salts of phosphoric acid by allowing a foamable composition to foam and set at normal temperature, said composition comprising:
(A) a metal phosphate containing at least one polyvalent metal, the ratio of the total number of metallic atoms to the number of phosphorus atoms in said matel phosphate being from 1/3 to 3/2 and the equivalent ratio of the total valences of the metallic atoms to the total valences of phosphate ions in said metal phosphate from 1/3 to 3/4;
(B) a polyvalent metal carbonate; and (C) water, the amount of the polyvalent metal carbonate (B) being controlled within the range such that the ratio of the total number of metallic atoms to the number of phosphorus atoms in the resultant foam maybe from 2/3 to 2/1 and the equivalent ratio of the total valences of the metallic atoms to the total valences of phosphate ions in said resultant foam may be from 0.65 to 0.95, the amount of water (C) being in the range of from about 20 to about 200 parts by weight per 100 parts by weight of metal phosphate (A), said composition having been compounded by mixing the components in an order selected from the group consisting of (i) (A + C) + B; and (ii) (A + C) + (B + C).

10. A process for producing an inorganic foam as in Claim 9, wherein the polyvalent metal is at least one selected from the group consisting of di-valent and tri-valent metals.

11. A process for producing an inorganic foam as in Claim 10, wherein the polyvalent metal contains magnesium, zinc, aluminum or a combination thereof.

12. A process for producing an inorganic foam as in Claim 11, wherein the polyvalent metal further contains calcium.

13. A process for producing an inorganic foam as in any of Claims 10 to 12, wherein the metal phosphate further contains at least one alkali metal.

14. A process for producing an inorganic foam as in any of Claims 10 to 12, wherein the metal phosphate is modified with oxides, hydroxides or silicates of mono- or poly-valent metals.

15. A process as in any of Claims 10 to 12, wherein the composition further contains an additive selected from the group consisting of aggregates, reinforcing materials and fillers, said additive being present in an amount of from about 1 to about 1000 parts by weight per 100 parts by weight of phosphoric acid metallic salt.

16. A process as in any of Claims 10 to 12, wherein the polyvalent metal carbonate is at least one selected from the group consisting of magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, zinc carbonate, iron carbonate, cobalt carbonate, basic magnesium carbonate, basic zinc carbonate and basic cobalt carbonate.

17. A process as in Claim 9, wherein the composition contains a water repellent agent of a compound having a hydrophobic group and a functional group which is reactive with the metal phosphate in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of said metal phosphate.

18. A process as in Claim 17, wherein there is further contained in the mixture a compound of the formula (I):

wherein Q represents phosphorus or nitrogen and k, ?, m and n are integers of 0 or 1 and, when Q is phosphorus, (1) k is 0 or 1, ? and m are 1, n is 0 or 1, R and R' are each hydrogen and R" is a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups; and (2) k is 0 or 1, ? is 1, m and n are each 0 or 1, R is hydrogen and R' and R" are each a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups; and when Q is nitrogen k, ?, m and n are 0, R, R' and R" are each hydrogen, a C4-75 alkyl, a C4-75 aryl or a C4-75 alkyl or aryl substituted with at least one moiety selected from the group consisting of halogen, nitro, cyano, alkoxy, phenoxy and silyl groups, with the proviso that the case when R, R ' and R" are all hydrogen is excluded.