Foam cross-linked with metal salt and process for production

Details Foam cross-linked with metal salt and process for production Foam cross-linked with metal salt and process for production

1999-10-15

2003-04-29

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S092000, C521S093000, C521S125000, C521S906000, C521S907000

Reexamination Certificate

active

06555591

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a novel foam which is useful for such applications as a heat insulating material, a structural material, a protective material and a sound insulating material.
BACKGROUND ART
Generally, as a foam, polyurethane foam, polyurea foam, polystyrene foam, polyolefin foam and polycyclopentadiene foam, among others are known. Moreover, as a kind of polyolefin foam providing for improved productivity, an ion-crosslinked polyethylene foam which can be produced by reacting an ethylene-carboxylic acid copolymer with a metal carbonate (Japanese Kokoku Publication Hei-2-11621) has been proposed.
However, the conventional foams not only involves the use of starting materials with high ecological loads but cannot avoid generation of noxious gases and soot owing to incomplete combustion in incineration, destruction of the incinerator through generation of the excess heat of combustion, and generation of static electricity, all of which cause a problem that a burden on the environment is high.
The ion-crosslinked polyethylene foam disclosed in Japanese Kokoku Publication Hei-2-11621 has an expansion ratio of as much as about 2 to 5 and, therefore, the low-density series cannot be provided. Moreover, if an attempt is made to increase the expansion ratio of the carboxylic acid-containing copolymer by combining other blowing agent, the foam strength is so short that cells are destroyed and low-density foams cannot be provided. In addition, because the foam density cannot be lowered, the temperature-time area and the emitting smoke factor are remarkably high so that criteria of the flame retardance test (JIS A-1321) for Grade 1 to Grade 3 cannot be satisfied.
SUMMARY OF THE INVENTION
The inventors of the present invention intensively examined a foam of reduced ecological burden and of low density and found that a metal bound to an organic polymer contributes a great deal to flame retardance and have developed the present invention.
The present invention relates to a foam comprising an organic polymer expanded matrix (I) and at least one kind of inorganic substance (II) selected from the group consisting of metals, metal compounds and non-metal inorganic fillers, wherein
said expanded matrix (I) contains metal salt-crosslinks and
the relation between the weight percentage (M) of the metal forming said metal salt-crosslinks in the expanded matrix (I) based on the total weight of the expanded matrix (I) and the inorganic substance (II) and the weight percentage (S) of the inorganic substance (II) based on the total weight of the expanded matrix (I) and the inorganic substance (II) satisfies the following expression.
M≧
10
−S/
4  (1)
wherein M≦50 and S≧5.
The present invention further relates to a process for producing a metal salt-crosslinked foam which comprises subjecting an organic polymer containing a metal salt-crosslinkable functional group to crosslinking with a metal or a metal compound and expansion in the presence of an inorganic substance (II) optionally together with a blowing agent.
The present invention relates, in a further aspect, to a process for producing a metal salt-crosslinked foam which comprises subjecting a metal salt-crosslinkable functional group-containing monomer to concurrent polymerization, crosslinking with a metal or a metal compound and expansion in the presence of an inorganic substance (II) optionally together with a blowing agent.
The present invention further relates to a process for producing a metal salt-crosslinked foam which comprises subjecting a metal salt-crosslinked monomer to concurrent polymerization and expansion in the presence of an inorganic substance (II) and a blowing agent.
DETAILED DESCRIPTION OF THE INVENTION
The foam of the present invention comprises an organic polymer expanded matrix (I) and an inorganic substance (II). The expanded matrix (I) mentioned above contains metal salt-crosslinks. The term “metal salt-crosslinks” as used in this specification means chemical bonds formed between functional groups of an organic polymer through the intermediary of a metal. The mode of chemical bond involved may for example be ionic bond or coordination bond.
In the foam of the present invention, the relation between the weight percentage (M) of the metal forming said metal salt-crosslinks in the expanded matrix (I) and the weight percentage (S) of the inorganic substance (II) which are based on the total weight of the expanded matrix (I) and the inorganic substance (II) should satisfy the following expression (1),
M≧
10
−S/
4  (1)
wherein M≦50, S≧5.
Unless the above expression (1) is satisfied, the flame retardance of the foam is insufficient. Therefore, the above relation should be complied with.
More preferably, the following expression (2) should be satisfied.
M≧
12
−S/
4  (2)
Referring to the above expressions (1) and (2), if M is greater than 50, the quantity of the metal forming said metal salt-crosslinks in the expanded matrix (I) will be so large that the foam will become brittle. If S is less than 5, the inorganic substance (II) will be so little that the flame retardance will be short.
The weight percentage (M) of the metal forming said metal salt-crosslinks and the weight percentage (S) of the inorganic substance (II) in the foam of the present invention can be determined by the X-ray diffraction analysis described hereinafter.
The above expanded matrix (I) and inorganic substance (II) are now explained in that order.
Expanded Matrix (I)
In the present invention, the expanded matrix (I) has metal-salt crosslinks. The metal in the metal-salt crosslinks may be one derived from any of various metals and metal compounds.
The metal or metal compound mentioned above is not particularly restricted but includes polyvalent metals, for example alkaline earth metals such as magnesium, calcium, barium, etc.; Group IIIa and Group IVa metals such as aluminum, germanium, tin, etc.; transition metals such as iron, cobalt, nickel, copper, zinc, etc.; and various salts, oxides and hydroxides of those metals.
The metal salt mentioned above is not particularly restricted but includes the carbonates, sulfates, acetates, borates, phosphates, nitrates and other salts of metals.
Preferred, among them, is the salt, oxide or hydroxide of at least one polyvalent metal selected from the group consisting of calcium, magnesium, zinc, barium, aluminum and iron.
The expanded matrix (I) mentioned above is obtained by an expansion using a substance having a blowing action. The substance having a blowing action may be the metal compound used for the formation of said metal salt-crosslinks provided that it has a blowing action. It is also possible to use a blowing agent.
As the blowing agent, there can be used, for example, at least one member selected from the group consisting of metal carbonates and metal hydrogencarbonates. The metals of said metal carbonates or metal hydrogencarbonates may be monovalent metals such as alkali metals (e.g. sodium, potassium, rubidium) and polyvalent metals such as the above-mentioned alkaline earth metals, Group IIIa and Group IVa metals, and transition metals. Among them, polyvalent metals are preferred. In this case, the metal salt not only acts as a blowing agent but forms metal salt-crosslinks with metal salt-crosslinkable functional groups, for example, carboxyl groups. More preferably, the polyvalent metal is at least one member selected from the group consisting of calcium, magnesium, barium, zinc, aluminum and iron.
As the blowing agent mentioned above, not only metal carbonates and metal hydrogencarbonates but also the known blowing agents can be employed. For example, azide compounds such as sodium azide; azo compounds such as AIBN, azobiscyanovaleric acid, azodicarbonamide, azobisamidinopropane salt, etc.; carbonates or hydrogencarbonates of monovalent bases, such as ammonium carbonate; gases such as chlorofluorocarbon gases, butane gas, etc.; low-boiling solvents; and water can be mentioned.
The above-mentioned exp

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