Container sealant composition
Disclosed is a container sealant composition with improved can sealing performance and reduced hot water absorption. The composition comprises a latex of a carboxylated styrene-butadiene rubber, a filler (preferably kaolin clay), an organosilane, and a tackifier. Also disclosed is a method of sealing a can with the aforedescribed container sealant composition.
1. A container sealant composition comprising:
a latex of a carboxylated styrene-butadiene rubber (CSBR) solids;
a kaolin clay filler in combination with one or more fillers consisting of materials selected from the group consisting of clay, precipitated silica, silica gel, titanium dioxide, calcium carbonate, alumina white, calcium sulfate, aluminum hydroxide, and talc;
an organosilane; and
a tackifier;
wherein the container sealant composition further comprises an additional filler, different from the kaolin clay filler and the one or more fillers, wherein the additional filler comprises at least one material selected from the group consisting of titanium dioxide, calcium carbonate, alumina white, calcium sulfate, aluminum hydroxide and talc, and wherein the container sealant composition comprises 5-150 parts by weight of the additional filler per 100 parts by weight of the carboxylated styrene-butadiene rubber (CSBR) solids, and
wherein the container sealant composition has a weight ratio of the carboxylated styrene-butadiene rubber (CSBR) solids to fillers that ranges from 100:5 to 100:80; the container sealant composition being a stabilizer-free aqueous liquid and comprising less than 0.5% by weight of colloidal silica.
2. The container sealant composition according to claim 1 , wherein the weight ratio of the carboxylated styrene-butadiene rubber (CSBR) solids to the fillers ranges from 100:10 to 100:50.
3. The container sealant composition according to claim 1 , wherein the organosilane has the general formula
wherein X is a functional group selected from the group consisting of an amino group, a polyamino alkyl group, a mercapto group, a polysulfide group, an epoxy group, a hydroxy group, a vinyl group, an acryloxy group and a methacryloxy group; y is 0 to 8; and Z 1 , Z 2 and Z 3 are each independently selected from the group consisting of hydrogen, C 1 to C 18 alkyl, aryl such as phenyl, benzyl and the like, cycloalkyl such as cyclopentyl, cyclohexyl, or aryl, alkoxy or halo substituted alkyl, and C 1 to C 8 alkoxy group, with the proviso that at least one of Z 1 , Z 2 or Z 3 must be one of the foregoing alkoxy groups or one of the Z's must be a halogen, hydroxyl, or hydrogen group.
4. The container sealant composition according to claim 3 , wherein the organosilane is selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyldihydroxymethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and N-methyl-aminopropyltrimethoxysilane.
5. The container sealant composition according to claim 3 , wherein the organosilane is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.
6. The container sealant composition according to claim 1 , comprising 1 to 15 parts by weight of the organosilane per 100 parts by weight of the filler.
7. The container sealant composition according to claim 1 , wherein the tackifier is at least one member selected from the group consisting of rosin-based resins, terpene-based resins, phenol-formaldehyde-based resins, and petroleum hydrocarbon-based resins and the 10-150 parts by weight of the tackifier per 100 parts by weight of the carboxylated styrene-butadiene rubber (CSBR) solids.
8. The container sealant composition according to claim 1 , wherein the carboxylated styrene-butadiene rubber (CSBR) has a gel content of 0 to 70 wt. %, a Mooney viscosity of 30 to 150 (ML 1+4 , 100° C.) and a styrene content of 20 to 60 wt. %.
9. The container sealant composition according to claim 1 , wherein the composition is free of crosslinking agent.
10. The container sealant composition according to claim 1 , wherein the composition contains less than 0.1% by weight of colloidal silica.
11. A method for sealing a can which comprises coating a curl area of a can cap with an aqueous dispersion of the container sealant composition according to claim 1 , drying the container sealant composition, placing the can cap onto a can body filled with contents, and sealing the can by seaming a flange area of the can body and the curl area of the can cap to obtain a sealed can containing the contents.
12. The method according to claim 11 additionally comprising subjecting the sealed can to a heat treatment to sterilize the contents.