Composition for Producing Self-Supporting Stiff Expanded Materials

This invention relates to a composition for the production of expanded materials which are stiff and self-supporting. More particularly, this invention relates to a composition based on an unsaturated polyester resin, an isocyanate, and a filler material. Unsaturated polyester resins have been used in the prior art in the manufacture of products such as building sheets, automobile fenders, boats, and the like, and have been used together with aqueous metal silicates, such as sodium silicate, for the production of laminated products containing reinforcing fibers or a core of expanded metal lath (see U.S. Pat. No. 4,011,195).

Plastic materials have been formed from compositions containing hydroxyl-terminated linear polyesters, an isocyanate, an aqueous alkali metal silicate and fillers (see U.S. Pat. Nos. 4,042,536; 4,097,422; 4,142,030; 4,057,519). These plastic materials contain aqueous alkali metal silicates, preferably sodium or potassium silicate, which chemically react with other components, and are used for products which may have a low strength compared to their specific density. The plastic materials obtained by such compositions are generally used as insulating panels or foams for coating buildings owing to their good fire and heat resistance.

As it is well-known from the prior art in the matter of expanded materials, the synthetic compositions often used as basic materials are characterized by the presence of isocyanates associated with polyols, and such materials can be expanded up to 10 times their original volume. The expanded materials thus obtained with a density of not more than 100 kg/m.sup.2 have a mechanical strength which is inadequate for a technically satisfactory use as structural materials and they do not have physical properties conducive to the production from them of articles of a large size and having self-supporting properties. On the contrary, there are obtained, as a rule, expanded products of a small size, which tend to crumble and do not hold screws, so that they are virtually incapable of withstanding ordinary mechanical stresses.

It is to be noted, in particular, that the defect of brittleness, in addition to restricting the field of application of the expanded materials to that of sound-absorbing and/or self-extinguishing fillers, requires the use of expensive metal supporting members such as zinc or aluminum to ensure adequate supporting strength. This has undesirable results during the manufacturing operations including an increase in scrap produced.

It is thus an object of the present invention to provide a composition, based on an unsaturated polyester resin, which does away with the above-indicated shortcomings, or at least reduces them to a neglectable degree, while affording special advantages.

It is another object of this invention to provide a composition based on an unsaturated polyester resin capable of forming a cellular, expanded material which combines thermal and acoustic insulation with considerable stiffness and mechanical strength. It is still another object of this invention to provide a composition capable of use in casting relatively large cellular bodies.

It is yet another object to provide a composition having electrical insulation properties and which resists weathering, and attack by acids and brine of marine origin.

In accordance with this invention there is provided a composition consisting essentially of:

an unsaturated polyester resin in the amount of 28 to 46 percent by weight;

an isocyanate in the amount of 12 to 28 percent by weight;

an inert anhydrous filler in the amount of 12 to 40 percent;

a catalyst in the amount of about 0.5 to about 2.5 percent by weight;

a self-extinguishing compound in the amount of about 3.5 to about 11 percent by weight; and

styrene in the amount of 0 to about 6 percent by weight.

Optionally the composition may contain as other constituents polyols, soybean oils, hydrogen peroxide, and an accelerator, alone or in combination with each other. The polyol, which may be present in the amount up to 18 percent, preferably about 3 to about 9 percent by weight, serves as a priming agent for the expansion reaction rather than as a basic constituent of the expanded material, and is most preferably present in a low concentration, e.g., about 3 to about 4 percent by weight. The glycerols such as 1, 2, 3-propanetriol and the sugar alcohols are typically useful polyols. Polyol is intended to include the resinous polymaleate compounds commercially available, such as for example that sold under the trademark CARADOL 30 by Shell Co.

The soybean oil which may be present in an amount up to about 3.5 percent, is an epoxidized oil, and serves to increase the shock-resistance of the product.

Hydrogen peroxide, which may be present in an amount up to 2.0 percent accelerates the expansion of the composition.

The accelerator, which may be present in an amount up to about 0.3 percent increases the rate of reaction of the catalyst, and is selected to be compatible with the catalyst.

The resulting composition according to the invention produces, quite surprisingly, an expanded material which provides a useful combination of the usual properties of thermal and acoustic insulation with a considerable stiffness and mechanical strength, which was quite unpredictable on the basis of the cellular structure of such a product.

Among the several advantages afforded by the stiff expanded material as obtained by virtue of the composition according to this invention, there can be mentioned the possibility of obtaining, by casting, articles of very large size, such as laminates of the size of 300 by 120 by 5 cm weighing approximately 120 kg, and slabs having a thickness of from 2 to 15 cm, all such articles being capable of receiving external coatings of a number of materials (wood, asbestos-cement, plastics, laminates, aluminum and many others) and more particularly coatings of marble grit and polyester resin on a substrate of glass fibers.

Other advantages are the resistance to weathering agents, acids, brine of marine origin, and the electric insulation properties. The combination of such properties provides the possibility of using the stiff, expanded materials obtained according to this invention with surprisingly outstanding results in many different fields, such as:

(a) components of self-supporting panels for partition walls, wall coverings, ceilings and false-ceilings and the like in the building industry;

(b) supporting structures for veneers and plastic laminates in the furniture industry;

(c) self-supporting insulating layers in the refrigeration industry; and

(d) dielectrics in the electrical, electronic, telephonic and like industries.

Their possible applications in the railway signal manufacture and in maritime and harbor installations are also important.

The present invention is based on (a) an unsaturated polyester resin, (b) an isocyanate, (c) an inert filler, (d) a catalyst, (e) a self-extinguishing compound, and (f) styrene.

The unsaturated resin component is added as solution a, and according to the present invention the term "unsaturated polyester resin" refers to a solution of a linear polyester in a vinylic monomer, preferably styrene. The vinylic monomer is preferably present in the amount of about 25 to about 50 percent by weight.

The unsaturated polyester resin used in accordance with this invention is of the type disclosed in U.S. Pat. No. 4,011,195, and may be obtained by polycondensation of one or more diols with one or more, and usually two, dicarboxylic acids, at least one of which is unsaturated. Typically useful diols are ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol and polypropylene glycol. Typically useful dicarboxylic acids are maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, fumaric acid, adipic acid and succinic acid.

The unsaturated polyester resin is preferably an orthophthalic polyester resin and a typically useful resin composition is produced by a diol in the amount of about 32 to about 38 percent by weight, maleic anhydride in the amount of about 15 to about 20 percent by weight, phthalic anhydride in the amount of about 23 to about 25 percent by weight, and styrene as a solvent in the amount of 25 to 35 percent by weight. Especially useful in this invention is an unsaturated orthophthalic polyester consisting of propylene glycol, phthalic anhydride, and maleic anhydride in a mol ratio of 1 to 0.5 to 0.5 respectively.

The following Table illustrates typical resin compositions which may be used in accordance with this invention.

The polyester resin and styrene are mixed in amounts of 55-70 parts resin to 45-30 parts styrene after having added a suitable inhibitor, usually hydroquinone.

The isocyanate may be any of the diisocyanates useful in the production of polyurethane foams, and is preferably one of the commercially available isocyanates as exemplified by tolylene-2-4-diisocyanate, tolylene-2-6-diisocyanate, polyphenyl-polymethylene-isocyanate, 4, 4' diphenylmethane diisocyanate, and 1, 5 naphthalene diisocyanate. Other useful isocyanates are disclosed in U.S. Pat. Nos. 3,981,831 and 4,042,536. Especially preferred is methylene-diphenyl diisocyanate sold under the tradenames CARADATE (Shell Co.) and TEDIMONTI 31 (Monteconti of Italy).

The filler is an inert, high temperature particulate material such as anhydrous silicates, obsidian, vitreous trachyte, pearlite, ground fire clay, kaolin, ceramics, glass or quartz hollow spheres such as are sold under the trademark SFERULINE. The preferred filler is an inert anhydrous silicate.

The term "inert anhydrous silicate" refers to silicates which are non-aqueous and chemically inert with respect to other components in the composition. The preferred silicates are the alumina silicates as exemplified by phyllites, a typical composition for which is:

silica (SiO.sub.2): 61%

alumina (Al.sub.2 O.sub.3): 30%

alkali (Na.sub.2 O): 5%

ferric oxide (Fe.sub.2 O.sub.3): 4%

The physical properties of this inert silicate are:

bulk density: 2.85 gram/cm3

diameter (microns): 300

melting point .degree.C.: 1200

hardness (Mohs): 5

The particle size of the inert filler is preferably in the size range of 100 to 400 microns and has a melting point higher than about 1000.degree. C.

Other fillers such as expanded polystyrene beads, cork, and ash may optionally be used with the above-mentioned fillers.

The fillers may be present in the amount of from about 12 to about 40 percent by weight, and in the preferred composition from about 24 to about 35 percent by weight.

The catalyst may be any of the peroxides well-known in processes for hardening polyester resins, and the preferred catalysts are the peroxides of the ketones. Typically useful catalysts are benzoyl peroxide, cyclohexonone peroxide, and methyl ethyl ketone peroxide. The concentration of catalyst may suitably range from about 0.5 to 2.5 percent by weight of the composition. If an accelerator is used with the catalyst the accelerator selected will be based upon the catalyst used, and the combination may be any of the pairs usually used in hardening polyester resins. Typically useful combinations are benzoyl peroxide and dimethylaniline; cyclohexanone peroxide and cobalt nathphenate; and methyl ethyl ketone peroxide and cobalt octoate.

The self-extinguishing compound refers to flame-retardant compounds and the preferred compounds are the chlorophosphoric compounds. The preferred compounds are the resins having the general formula: ##STR1## known in the trade as PHOSGARD-C-22R which is typically employed with the polyester resins in a percentage up to 15%; however, in the case of the composition according to this invention a percentage as low as about 3.5 percent by weight of such self-extinguishing material is sufficient.

As regards the production technology of the expanded materials according to the invention the hardening of the resin in the presence of the catalyst-accelerator may take place at a constant temperature of 22.degree. C..+-.1.degree. C. and at a relative humidity of 55 to 60 hygrometric degrees. For industrial requirements, the polymerization of the expanded material can be accelerated by using ovens with a controlled temperature up to 70.degree. C. The pressures exerted by the expanded material during expansion vary, according to the percentages of the compounding ingredients, from 60 kg/m.sup.2 to 200 kg/m.sup.2.

By varying the percentages of the compounding ingredients, there can be obtained apparent specific gravities variable from 180 to 300 kg/m.sup.3. The increase of the specific gravity involves an improvement of the mechanical strength so that the end product is a stiff, compact and well cross-linked expanded material having a closed-cell structure and physical properties definitely improved over those of the materials of this kind previously produced.

The stiff expanded material thus obtained can be machined with the tools which are conventional in the processing of wood.

The cold reaction of the compound takes place according to the following stages:

liquidity stage: 13 seconds

expansion time: 71 seconds

condensation: 85 seconds

The weight drop from the liquid state to the solid state is in the order of about 8%.

Tests of the product as to flame resistance give the following results:

when the product is subjected to penetration by the flame the high phosphorus content delays the penetration of the heat;

when the material is subjected to a test for flame propagation the high content of chlorine extinguishes the flame; and

no toxic gas or black smoke are produced.

Having described the invention the following Examples are offered to illustrate it in more detail.

Into a mixer there are contemporaneously introduced from suitable dosage hoppers:

The components are mixed for 13 seconds, and the composition is poured into a die having a cavity of 100.times.100.times.8 cm and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds. The resulting panel has a gross density of 230 kg/m.sup.3, a compression strength of 54 kg/cm.sup.2 and a K-factor of 0.024.

Into a mixer there are contemporaneously introduced from suitable dosage hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 210.times.80.times.5 cm and compressed at a pressure of 100 kg/cm2 for 60 seconds.

The resulting panel has a gross density of 250 kg/m.sup.3, a compression strength of 43 kg/cm.sup.2 and a K-factor of 0.026.

Into a mixer there are contemporaneously introduced from suitable dosage hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 300.times.80.times.5 cm provided with male and female joints and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds.

The panel has well shaped joint cavity and protuberance, a gross density of 301 kg/m.sup.3, a compression strength of 52 kg/cm.sup.2 and a K-factor of 0.025.

The possibility of attaining, during the pressing of the panel, a well-shaped joint cavity and protuberance is of fundamental importance for maintaining the same K-factor practically for unlimited time, inasmuch as there are thus avoided heat insulation interruptions in the assembled panels.

Into a mixer there are contemporaneously introduced from suitable dosage hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 300.times.80.times.5 cm provided with male and female joints and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds.

The panel has a gross density of 282 kg/m.sup.3, a compression strength of 45 kg/cm.sup.2 and a K-factor of 0.027.

Into a mixer there are contemporaneously introduced from separate dosage hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 210.times.77.times.3.8 cm and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds.

The panel has a gross density of 217 kg/m.sup.3 and is particularly well-adapted for the doors.

Into a mixer there are contemporaneously introduced from separate dosage hoppers:

The components are mixed for 13 seconds and the composition is poured into a die having a cavity of 300.times.80.times.4 cm and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds.

The panel has a gross density of 200 kg/m.sup.3 and is particularly adapted for the movable partition walls.

Into a mixer there are contemporaneously introduced from separate dosage hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 80.times.300.times.5 cm and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds. The panel has a gross density of 360 kg/m.sup.3 and is a particularly well-adapted structural element for the building industry.

Into a mixer there are contemporaneously introduced from separate hoppers:

The components are mixed for 13 seconds, the composition is poured into a die having a cavity of 80.times.270.times.3 cm and compressed at a pressure of 100 kg/cm.sup.2 for 60 seconds. The panel has a gross density of 180 kg/m.sup.3 and is adapted for light partition walls.