Patent Application
20080029213
The invention is directed to colorless primer compositions and methods of using such compositions with plastic pipes prior to joining the pipes with adhesives. As will be evident to those of ordinary skill in the art, substitutions, omissions and additions will be possible in order to provide adhesives with customized selected properties.
Preferred embodiments of the invention should comprise, but are not limited to, a solvent component and a dye component. Compositions in accordance with the invention can also include a UV light stabilizer component. The inclusion of the UV light stabilizer component is not necessary for the function of the primer.
A solvent component in accordance with preferred embodiments of the invention can include a combination of solvents commonly used in primers in the plumbing and construction trades industry. Preferred solvents can include combinations of 0-80% tetrahydrofuran (THF), 0-80% cyclohexanone (CYH), 0-100% acetone and/or 0-100% methyl ethyl ketone (MEK), preferably 1-20% tetrahydrofuran (THF), 1-20% cyclohexanone (CYH) and 20-50% acetone and 20-50% methyl ethyl ketone (MEK), most preferably 5-15% of tetrahydrofuran (THF), 5-15% of cyclohexanone (CYH) and 35-45% each of acetone and methyl ethyl ketone (MEK). Of these, the most preferred blend is 10% tetrahydrofuran, 10% cyclohexanone, 40% methyl ethyl ketone and 40% acetone.
The dye component can include a single component dye or a multi-component combination dye. Both components should fluoresce under black light to appear as a purple color consistent with IPC and UPC building codes. An example of the dye component is the combination of DFSB-C7 (red), DFSB-C0 (blue) and DFLQ-C2 (yellow), as supplied by Risk Reactor of Huntington Beach, Calif. The single component dyes, such as LX 10522 Pylakrome white or S 5 Pylakor White, supplied by Pylam Products Company, Inc. of Tempe, Ariz., are also examples of dyes suitable for the colorless purple primer. A preferred dye component includes a combination of red dye and blue dye, such as DFSB-C7 and DFSB-C0, each with the total weight in the range of 0.00005-0.02%, preferably between 0.0001-0.1% of the solvent mixture. The ratio between the blue dye and the red dye can range from 4:1 to 1:4. The preferred ratio for the best expression of purple color is about 1:1.
Dyes used in the current invention should not interfere with the primer process as described in ASTM D2564 or F403. They should be safe to use for potable water as according to NSF 61. These dyes should react to black light when black light is applied from a simple black light torch at a reasonable distance (e.g., less than about three feet) to allow an inspector to perform visual inspection. The selected dye or dyes should also have the attribute of being stable for prolonged periods of time in the primer solvent solution, even when exposed to either light or air. When applied to a porous surface, such as vinyl or stone, these dyes should not produce a discoloration over time when exposed to natural, incandescent or fluorescent light. Preferred compositions will remain colorless on surfaces such as PVC for more than six months for testing purposes, preferably more than a year.
An example of the colorless primer composition includes a combination of acetone and MEK with a minimal amount of red dye (DFSB-C7) and blue dye (DFSB-C0), i.e., about a 1:1 ratio, totaling 0.0001% of the solvent mixture.
Colorless primer in accordance with the invention also can advantageously include an UV stabilizer. Although the dyes selected should show no instability in either their storage can or on exposure to air or light, the UV stabilizer can be added as a precaution to ensure stability. The UV light stabilizer component is exemplified by the class of hindered amine light stabilizers (HALS). Examples of preferred UV light stabilizers include a hindered phenol based phosphite such as Irganox 1010, supplied by Ciba Geigy of Hawthorne, N.Y., and/or hindered quinone exemplified by Irgafos 168, also supplied by Ciba Geigy of Hawthorne, N.Y. A preferred UV stabilizer is Irganox 1010 at a weight percent of 0.005-0.2, most preferably 0.01-0.1% of the solvent mixture.
The colorless primer should not require special handling or packaging. It should be able to be supplied in a standard metal container with dauber as currently used in the industry. Daubers and cans are exemplified by the daubers supplied by National Novelty Brush, Lancaster, Pa., and the metal cans by Prime Packaging Group, Kearney, N.J.
The colorless primer can be applied exactly as described by ASTM F656. The incorporation of the fluorescent dye should not change the routine operations of the user as described in ASTM F656. Once applied and dried, the minute levels of fluorescent dye left on the surface of the plastic pipe should respond to black light and exhibit a color under black light. Removal of the black light returns the plastic pipe to a natural, colorless state.
Examples of the black light employed in order to induce fluorescence in the applied primer is Model No. BNBNS flash light, supplied by Risk Reactor of Huntington Beach, Calif., or the pen light model # BL-900 supplied by Fortune Products, Inc., Lake Stevens, Wash. Black light Model No. BNBNS is recommended for its convenience of size and illumination.
Unlike the traditional purple primer employed by the industry, the appearance of the purple color should only be generated by the application of black light. The dye should be selected so that, if the colorless primer containing the fluorescent dye is accidentally applied or spilled to a porous surface other than the plastic pipe, upon evaporation of the solvent, although fluorescent dye remains on the porous surface, it should not respond to a broad range of light typified by natural light, incandescent light or light from fluorescent bulbs. Thus, the affected surfaces should appear without any color under normal lighting conditions.
The resistance to any permanent purple color development has been tested over a period of one year with no appearance of any purple color induced by a presence of light other than from a black light.
The following example is provided for the purpose of illustration only and is not intended to be construed as limiting the scope of the invention.
The stability of the colorless purple primer to a light source other than black light is measured by performing exposure tests utilizing a variety of light sources. CPVC and PVC pipe sections were applied with the colorless primer listed in Table 1. These sections were then exposed to a variety of light sources, including natural light, incandescent light and florescent light to test whether exposure to light, other than black light would result in the appearance of a dye related color. During the tests, primer coated sections are periodically exposed to black light to ensure that the fluorescent dye had not deteriorated and was still visible under black light. As can be seen from Table 2, there was no generation of any color during the one-year testing period. The activity of the fluorescent dye did not deteriorate and was maintained during the one-year study.
To test the stability of the colorless primer to light and water, 500 ml of samples of colorless purple prime composition were placed in two 1 L Erlenmeyer flasks. In the first flask, the colorless primer example was subjected to compression expressed through a gas frit. This was continued for a 24-hour period. In the second flask, 10% by weight of distilled water was added to the flask and the solution was then subjected to exposure to compressed air for 24 hours. After 24 hours, the two example primers from the flasks were applied to PVC coupons, dried and subjected to black light. In both cases, the application of the black light induced fluorescent behavior exhibiting the desired color.
A third test was performed to test the performance of the colorless primer composition against ASTM D-XXXX. Using the primer described in Table 1, a PVC pipe assembly was used for testing under a variety of pressures and fluids contained in the pipe. The pipe assembly included a 2-inch PVC pipe. On one end of the pipe, an end cap was connected and sealed with the colorless purple primer example and regular body regular set PVC pipe cement. The other end of the PVC pipe was connected to a hydraulic pump. The hydraulic pump employed was a Simpson Model No. 70 manufactured by Templeton, Kelly and Co. of Broadview, Ill., which is capable of producing up to 10,000 psi of pressure. A needle valve and gauge was connected between the hydraulic pump and the PVC pipe to control and measure the pressure.
The test was conducted at 80 psi twice, once while the pipe assembly contained air and once when the pipe assembly contained water. The pressure was held for 24 hours. In both cases, the pressure was maintained over the time period tested, demonstrating that the colorless purple primer does not lose the desired characteristics over time.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and, since certain changes may be made in carrying out the above method and in the compositions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
Particularly it is to be understood that in said claims, ingredients or compounds recited in the singular are intended to include compatible mixtures of such ingredients wherever the sense permits.
