| 摘要 |
A method of forming a refractory foamed product suitable for a coating on missiles or spaceships comprises mixing together a foamable thermosetting resin comprising a polyester of an alpha, beta-ethylenically-unsaturated dicarboxylic acid, a blowing agent therefore and a pulverulent inorganic filler which is sinterable to provide a continuous but foamed coating and curing the resin to provide a foamed thermoset mass wherein the filler constitutes from about 30 to about 80% by weight of the combined binder and filler. The inorganic filler is usually a glass-forming material such as silica and a flux. The thermoset compositions if heated sufficiently will burn or char to give a carbonaceous skeleton loaded with powdered glass or glass-forming agents. If the temperature is further increased the organic material burns out, at least in the surface layers leaving the inorganic particles to sinter into a continuous cellular state which follows the pattern of the original foam and comprises a heat-resistant coating. The coating before charring and the glass formed of residual filler can form ablating agents which gradually evaporate. In some cases articles are prepared for use by applying the coating and then playing a flame on the surface or by passage through an oven at 1200 DEG to 2000 DEG F. to char or burn out the organic material. Suitable inorganic materials are synthetic and natural silicates such as glass, blast-furnace slag, perlite, obsidian, nepheline, syenite, feldspar and china clay. Calcium oxide, barium oxide, boric oxide, lead oxide and antimony trioxide are suitable fluxes. Suitable blowing agents are CCl3F, CCl2F2, ammonium bicarbonate, or, preferably, an alkali metal carbonate or bicarbonate with a carboxylic acid or a carboxylic anhydride and water. Cellulose acetate butyrate, ethyl cellulose, benzyl cellulose, polyethylene glycol and chlorinated rubber may be added to the foamable mixture. A preferred thermoset resin is a mixture of a polyester and a >C=CH2 monomer. The polyester may be prepared from a ,b -unsaturated acid as the sole acid, or from a mixture containing saturated acid. Inhibitors, quaternary compounds, siccatives and peroxidic catalysts may also be present. In a typical example, a polyester from maleic anhydride, isophthalic acid and triethylene glycol (containing excess acid) containing hydroquinone and copper naphthenate is thinned with styrene and mixed with silica, sodium bicarbonate, and methyl ethyl ketone peroxide. A coating from the mixture sets to a resin. Exposure to an open flame gives a gray char and this, in the flame of an acetylene torch provides a vitreous skin. Illustrated are sections of coatings applied to a steel bar or shell of a missile, of compositions referred to above. On heating, there are formed a layer of continuous glass as the outer surface, a cellular glass layer below, and unburned or only charred material next to the metal body.ALSO:A method of forming a refractory foamed product suitable for a coating on missiles or spaceships comprises mixing together a foamable thermosetting resin comprising a polyester of an alpha, beta-ethylenically unsaturated dicarboxylic acid, a blowing agent therefor and a pulverulent inorganic filler which is sinterable to provide a continuous but foamed coating and curing the resin to provide a foamed thermoset mass wherein the filler constitutes from about 30 to about 80% by weight of the combined binder and filler. The inorganic filler is usually a glass-forming material such as silica and a flux. The thermoset compositions if heated sufficiently will burn or char to give a carbonaceous skeleton loaded with powdered glass or glass-forming agents. If the temperature is further increased the organic material burns out, at least in the surface layers, leaving the inorganic particles to sinter into a continuous cellular state which follows the pattern of the original foam and comprises a heat-resistant coating. The coating before charring and the glass coating formed of residual filler can form ablating agents which gradually evaporate. In some cases artices are prepared for use by applying the coating and then playing a flame on the surface or by passage through an oven at 1200 DEG to 2000 DEG F. to char or burn out the organic material. Suitable inorganic materials are synthetic and natural silicates such as glass, blast-furnace slag, perlite, obsidian, nepheline, syenite, feldspar and china clay. Calcium oxide, barium oxide, boric oxide, lead oxide and antimony trioxide are suitable fluxes. Suitable blowing agents are CCl3F, CCl2F2, ammonium bicarbonate, or, preferably, an alkali metal carbonate or bicarbonate with a carboxylic acid or a carboxylic anhydride and water. Cellulose acetate butyrate, ethyl cellulose, benzyl cellulose, polyethylene glycol and chlorinated rubber may be added to the foamable mixture. A preferred thermoset resin is a mixture of a polyester and a >C = CH2 monomer. The polyester may be prepared from a ,b -unsaturated acid as the sole acid, or from a mixture containing saturated acid. Inhibitors, quaternary compounds, siccatives and peroxidic catalysts may also be present. In a typical example a polyester from maleic anhydride, isophthalic acid and triethylene glycol (containing excess acid) containing hydroquinone and copper naphthenate is thinned with styrene and mixed with silica, sodium bicarbonate, and methyl ethyl ketone peroxide. A coating from the mixture sets to a resin. Exposure to an open flame gives a gray char and this, in the flame of an acetylene torch provides a vitreous skin. Illustrated are sections of coatings applied to a steel bar or shell of a missile, of compositions referred to above. On heating there are formed a layer of continuous glass as the outer surface, a cellular glass layer below, and unburned or only charred material next to the metal body.ALSO:A method of forming a refractory foamed product suitable for a coating on missiles or spaceships comprises mixing together a foamable thermosetting resin comprising a polyester of an alpha,beta-ethylenically unsaturated dicarboxylic acid, a blowing agent therefor and a pulverulent inorganic filler which is sinterable to provide a continuous but foamed coating and curing the resin to provide a foamed thermoset mass wherein the filler constitutes from about 30% to about 80% by weight of the combined binder and filler. The inorganic filler is usually a glass-forming material such as silica and a flux. The thermoset compositions if heated sufficiently will burn or char to give a carbonaceous skeleton loaded with powdered glass or glass-forming agents. If the temperature is further increased the organic material burns out, at least in the surface layers leaving the inorganic particles to sinter into a continuous cellular state which follows the pattern of the original foam and comprises a heat-resistant coating. The coating before charring and the glass coating formed of residual filler can form ablating agents which gradually evaporate. In some cases articles are prepared for use by applying the coating and then playing a flame on the surface or by passage through an oven at 1200-2000 DEG F. to char or burn out the organic material. Suitable inorganic materials are synthetic and natural silicates such as glass, blast-furnace slag, perlite, obsidian, nepheline, syenite, feldspar and china clay. Calcium oxide, barium oxide, boric oxide, lead oxide and antimony trioxide are suitable fluxes. Suitable blowing agents are CCl3F, CCl2F2, ammonium bicarbonate, or, preferably, an alkali metal carbonate or bicarbonate with a carboxylic acid anhydride and water. Cellulose acetate butyrate, ethyl cellulose, benzyl cellulose, polyethylene glycol and chlorinated rubber may be added to the foamable mixture. A preferred thermoset resin is a mixture of a polyester and a >C=CH2 monomer. The polyester may be prepared from a ,b -unsaturated acid as the sole acid, or from a mixture containing saturated acid. Inhibitors, quaternary compounds, siccatives and peroxidic catalysts may also be present. In a typical example a polyester from maleic anhydride, isophthalic acid and triethylene glycol (containing excess acid) containing hydroquinone and copper naphthenate is thinned with styrene and mixed with silica, sodium bicarbonate, and methyl ethyl ketone peroxide. A coating from the mixture sets to a resin. Exposure to an open flame gives a gray char and this, in the flame of an acetylene torch provides a vitreous skin. Illustrated are sections of coatings applied to a steel bar or shell of a missile, of compositions referred to above. On heating there are formed a layer of continuous glass as the outer surface, a cellular glass layer below, and unburned or only charred material next to the metal body. |
