Coating processes – Mold coating
Reexamination Certificate
2000-04-24
2001-11-27
Beck, Shrive P. (Department: 1762)
Coating processes
Mold coating
C427S387000, C427S397700
Reexamination Certificate
active
06322850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the use of organo-silanes as mold release agents. More particularly, it refers to aqueous compositions and methods of using select organo-silanes for coating mold surfaces and thereafter obtaining clean mold surfaces after repeated ejections of plastic parts from the mold.
2. Description of Prior Art
In the process of preparing molded products such as urethanes, natural rubber, silicones, neoprene, and other synthetic elastomers, it is necessary to coat the core surfaces of a mold to prevent the molded product from sticking to the mold. Coatings used to prevent such molded products from sticking to molds are called mold release agents. Most prior art mold release agents were organic solvent based compositions. This caused undesirable vapors dangerous to the environment and particularly to the mold operators.
An advance in non-solvent based mold release agents was disclosed in U.S. Pat. No. 5,219,925. Methyltriethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane and vinyltrimethoxysilane were each disclosed as an active component in an aqueous mold release composition. These compositions have been readily accepted in the marketplace and one or more is used in mold release compositions commercially. One is identified as CRYSTAL® 1053, containing methyltriethoxysilane. Although these compositions are ideal for use in repeated mold releases of plastic products and elastomers, the molds themselves have sometimes become discolored. Another composition that will have satisfactory mold release properties and prevent mold discoloration is needed.
SUMMARY OF THE INVENTION
The present invention is the discovery of nine unique silanes promoting multiple releases of plastic products from molds coated with a composition containing the unique silanes, but at the same time causing the mold surface to retain its luster. The unique silanes are:
ethyltriethoxysilane,
dimethyldiethoxysilane,
methyldiethoxysilane,
trimethylmethoxysilane,
trimethylethoxysilane,
dimethyldimethoxysilane,
diphenyldimethoxysilane,
aminopropyltriemethoxysilane, or
aminopropyltriethoxysilane.
The composition contains one of the above unique silanes in an aqueous reaction mixture with a multi-functional polydimethyl siloxane emulsified polymer, a surfactant, ethanol and water.
DETAILED DESCRIPTION OF THE INVENTION
The composition of this invention is a reaction mixture of a multi-functional polydimethyl siloxane emulsified polymer, and a unique silane from the group consisting of:
ethyltriethoxysilane,
dimethyldiethoxysilane,
methyldiethoxysilane,
trimethyimethoxysilane,
trimethylethoxysilane,
dimethyldimethoxysilane,
diphenyldimethoxysilane, aminopropyltrithoxysilane,
aminopropyltriethoxysilane. In addition the composition contains a compatible surfactant, ethanol and the major component of water.
The composition contains the ingredients as a percent by weight in the following ranges:
0.5 to 12% of a silane selected from the group of unique silanes set forth above,
1 to 8% of a multi-functional polydimethylsiloxane emulsified polymer,
0.1 to 2.5% of a first compatible surfactant such as substituted nonyl or octyl phenol derivative surfactant,
0.1 to 2.5% of a second compatible surfactant such as synthetic ethoxylated amine surfactant
0.1 to 30% ethanol and the remainder water.
Other compatible surfactants such as ethoxylated nonionic fluorosurfactant (ZONYL® FSO, (ZONYL® FS-300) obtained from E.I. duPont de Nemours and Company, may be substituted for the nonyl phenol, octyl phenol or ethoxylated amine.
Three to five grams of the composition is applied to each square foot of a compression or injection molding core surface and then heated to about 320 degrees F. or dried to remove the water to form an interpenetrating network.
The preferred composition is prepared by mixing the following ingredients (% by weight) in water:
3% ethyltriethoxysilane,
1.8% decamethylcyclopentasiloxane,
1.6% octamethylcyclotetrasiloxane,
0.6% dodecamethylcyclohexasiloxane,
1.5% surfactants which are a substituted nonyl or octyl phenol derivative and synthetic ethoxylated amines,
3.0% ethanol, and
88.5% water.
The ethyltriethoxysilane reacts with the water to produce additional ethanol. The mixture is sprayed on a clean mold core surface and heated to 320 degrees F. or dried with air to vaporize the water and coat the mold core.
The ethyltriethoxysilane can be substituted with:
dimethyldiethoxysilane,
methyldiethoxysilane, trimethylmethoxysilane,
trimethylethoxysilane,
dimethylditnethoxysilane,
diphenyldimethoxysilane,
aminopropyltrimethoxysilane, or aminopropyltriethoxysilane.
to achieve substantially the same results in the mixture and on spraying the resulting mixture on a mold core.
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patent: 3883628 (1975-05-01), Martin
patent: 3905823 (1975-09-01), Piskoti
patent: 3959242 (1976-05-01), Watts et al.
patent: 4110095 (1978-08-01), Stengle, Jr.
patent: 4267297 (1981-05-01), Hanada et al.
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patent: 4822646 (1989-04-01), Clark et al.
patent: 5425848 (1995-06-01), Haisma et al.
patent: 5601641 (1997-02-01), Stephens
Bertolucci Patricia R.
Stephens William D.
Beck Shrive P.
Crockford Kirsten A.
Larson James E.
Larson & Larson P.A.
TSE Industries, Inc.
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