Basic metal nitrate, process for producing the same and gas generating agent composition

Abstract

Provided is a basic metal nitrate suitable as an oxidizing agent for a gas generating agent, which is a basic metal nitrate having a good thermal stability and meeting at least one requirement of the following (a) to (d): (a) a particle diameter of 0.5 to 40 μm; (b) a degree of crystallinity having 0.4 deg or less of a half band width of the peak in the X-ray analysis; (c) an initiation temperature of weight loss being 220° C. or higher according to TG-DTA analysis; and (d) an impurity content of 1,000 ppm or less based on Na atom. Further provided is a gas generating composition which has a low toxicity, a high burning rate and a low combustion temperature and which is used in a gas generator for an air bag. The gas generating composition comprises (a) tetrazole derivatives, guanidine derivatives or a mixture thereof, (b) a basic metal nitrate and (c) a binder and/or a slag-forming agent.

1 . A method of improving thermal stability or ignition properties in a gas generating composition, said method comprising the steps of:
 (a) providing a basic metal nitrate having a decomposition temperature-improving particle diameter or ignition-property improving particle diameter in the range 0.5 to 40 μm; and   (b) combining from 40 to 90 weight-% of said basic metal nitrate with from 10 to 60 weight-% of nitroguanidine to form a gas generating composition comprising from 10 to 60 weight-% nitroguanidine and from 40 to 90 weight-% basic metal nitrate, said gas generating composition having improved thermal stability or improved ignition properties.   
   
   
       2 . The method according to  claim 1  of improving thermal stability or ignition properties in a gas generating composition, further comprising including a binder and/or a slag-forming agent in the gas generating composition having improved thermal stability or ignition properties formed in step (b). 
   
   
       3 . The method according to  claim 1  of improving thermal stability or ignition properties in a gas generating composition, wherein said gas generating composition having improved thermal stability or ignition properties has at least one feature selected from the following features (1) to (3):
 (1) a weight loss ratio of the gas generating composition, when the gas generating composition is retained in a closed state at 90° C. for 1,000 hours or at 110° C. for 400 hours, of 2.0% or less,   (2) concentrations of trace gases contained in a gas generated by the combustion of the gas generating composition, as values measured in a 2,800-liter tank, of 400 ppm or less for CO, 40 ppm or less for NO, 8 ppm or less for NO2 and 100 ppm or less for NH3, and   (3) a maximum internal pressure in a gas generator on the combustion of the gas generating composition of 7,840 to 22,500 kPa.   
   
   
       4 . The method according to  claim 3  of improving thermal stability or ignition properties in a gas generating composition, further comprising including a binder and/or a slag-forming agent in the gas generating composition having improved thermal stability or ignition properties formed in step (b). 
   
   
       5 . The method of improving thermal stability or ignition properties in a gas generating composition as claimed in claim  1  or  3 , wherein the basic metal nitrate provided in step (a) is at least one member selected from the group consisting of a basic copper nitrate, a basic cobalt nitrate, a basic zinc nitrate, a basic manganese nitrate, a basic iron nitrate, a basic molybdenum nitrate, a basic bismuth nitrate, and a basic cerium nitrate. 
   
   
       6 . The method of improving thermal stability or ignition properties in a gas generating composition as claimed in  claim 2  or  4 , comprising including a non-crosslinkable binder in the gas generating composition having improved thermal stability or ignition properties formed in step (b). 
   
   
       7 . The method according to  claim 2  of improving thermal or ignition properties in a gas generating composition, wherein the binder and/or the slag-forming agent included in the gas generating composition having improved thermal stability or ignition properties formed in step (b) is a member selected from the group consisting of carboxymethylcellulose, sodium carboxymethylcellulose, potassium carboxymethylcellulose, ammonium carboxymethylcellulose, cellulose acetate, cellulose acetatebutyrate, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethylhydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethylethyl cellulose, fine crystalline cellulose, polyacrylic amide, aminated compounds of polyacrylic amide, polyacrylic hydrazide, a copolymer of an acrylic amide and a metal salt of acrylic acid, a copolymer of polyacrylic amide and polyacrylic ester, polyvinyl alcohol, acrylic rubber, guar gum, starch, polysaccharides, silicone, molybdenum disulfide, Japanese acid clay, talc, bentonite, diatomaceous earth, kaolin, calcium stearate, silica, alumina, sodium silicate, silicon nitrate, silicon carbide, hydrotalcite, mica, a metal oxide, a metal hydroxide, a metal carbonate, a basic metal carbonate, and a molybdate. 
   
   
       8 . The method according to  claim 2  of improving thermal stability or ignition properties in a gas generating composition, wherein the gas generating composition having improved thermal stability or ignition properties formed in step (b) comprises
 nitroguanidine,   a basic copper nitrate, and   sodium carboxymethylcellulose.   
   
   
       9 . The method according to  claim 8  of improving thermal stability or ignition properties in a gas generating composition, wherein the gas generating composition having improved thermal stability formed in step (b) comprises
 15 to 55% by weight of nitroguanidine,   45 to 70% by weight of a basic copper nitrate, and   0.1 to 15% by weight of sodium carboxymethylcellulose.   
   
   
       10 . The method according to  claim 8  of improving thermal stability or ignition properties in a gas generating composition, wherein the gas generating composition having improved thermal stability formed in step (b) comprises
 nitroguanidine,   a basic copper nitrate,   sodium carboxymethylcellulose binder, and further comprises   a second binder or slag-forming agent selected from the group consisting of carboxymethylcellulose, potassium carboxymethylcellulose, ammonium carboxymethylcellulose, cellulose acetate, cellulose acetatebutyrate, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethylhydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethylethyl cellulose, fine crystalline cellulose, polyacrylic amide, aminated compounds of polyacrylic amide, polyacrylic hydrazide, a copolymer of an acrylic amide and a metal salt of acrylic acid, a copolymer of polyacrylic amide and polyacrylic ester, polyvinyl alcohol, acrylic rubber, guar gum, starch, polysaccharides, silicone, molybdenum disulfide, Japanese acid clay, talc, bentonite, diatomaceous earth, kaolin, calcium stearate, silica, alumina, sodium silicate, silicon nitrate, silicon carbide, hydrotalcite, mica, a metal oxide, a metal hydroxide, a metal carbonate, a basic metal carbonate, and a molybdate.