Patent Application
20070282065
This polymer produced with this procedure is used in the examples below. To a three liter four-neck flask equipped with a mechanical stirrer, a condenser, a nitrogen sweep, a thermometer and inlets for the gradual additions of monomer, initiator and sodium hypophosphite solutions, was added 710 grams of deionized water. A chain regulator stock solution was prepared by dissolving 2500 grams of sodium hypophosphite monohydrate in 3056 grams of deionized water. A total of 486.4 g was removed form the stock solution and half (243.2) of this solution was added to the water charge and heated to 93° C. The remaining half of the chain regulator solution was used as co-feed solution. A monomer charge of 1216 grams of glacial acrylic acid was prepared. An initiator solution was prepared by dissolving 12.16 grams of sodium persulfate in 30.7 grams of DI water.
The acrylic acid, sodium persulfate and sodium hypophosphite charges were added linearly and separately over two hours to the stirring water charge. Temperature was maintained at 93°÷1° C.
The resultant polymer solution was allowed to cool to room temperature and diluted with 274 grams of deionized water. The solution had a solids content of 52.71%, pH of 3.2, viscosity of 210 centipoises and residual monomer content of less than 0.01%. The number average (Mn) molecular weight by GPC was 660.
The following samples in Table 1B-D illustrate compositions of this invention.
1>99% solids
245% solids
393% solids
Aqueous curable composition samples A-D were evaluated for wet and dry tensile strength as follows. Glass microfiber filter paper sheets (20.3×25.4 cm, Cat No. 1820 866, Whatman International Ltd., Maidstone, England) were dipped in each sample binder composition and run through a roll padder with roll pressures of 10 lbs. The coated sheets were then heated at 90° C. for 90 seconds in a Mathis oven. Post drying weight was determined to calculate binder add-on (dry binder weight as a percentage of filter paper weight). Dried sheets were then cured in a Mathis oven at specified times and temperatures.
The cured sheets were cut into I inch (cross machine direction) by 4 inch (machine direction) strips and tested for tensile strength in the machine direction in a Thwing-Albert Intelect 500 tensile tester. The fixture gap was 2 inches and the pull rate was 2 inches/minute. Strips were tested either “as is” (dry tensile) or immediately after a 30 minute soak in water at 85.degree. C. Tensile strengths were recorded as the peak force measured during parting (Table 1). Data reported are averages of 7 test strips for each binder composition tested.
Wet tensile strength of a curable composition-treated glass microfiber filter paper which is a substantial fraction of dry tensile strength of a similarly treated glass microfiber filter paper indicates that a composition has cured, and that useful high temperature performance of the cured aqueous composition-treated glass microfiber filter paper results. Samples B-D of this invention cured at 210° C. exhibit comparable cured properties (wet tensile strengths) relative to Comparative Sample A (without urea), also cured at 210.degree. C.
As to viscosity, data in Table 2 show that viscosity can be considerably reduced by adding urea. This means that urea can lower viscosity to make the binder more sprayable onto a substrate. Viscosity was measured according to the Brookfield method, ASTM D2196-68. Specifically, viscosity was measured using a low sheer Brookfield LVDT rheometer. Formulation samples were prepared at 50% weight solids and allowed to equilibrate to room temperature prior to testing (22° C.±1° C.). Each sample was measured using spindle #2 at 100 rpm. Viscosity in centipoise was recorded once the reading stabilized.
When we measure total solids by weight, we used the ASTM D-2369 method as follows.
Place sample in 150° C. oven for 30 minutes.
Formaldehyde-free thermosetting resin systems have been developed that either use diethanolamine or ethanol amine as the polyol crosslinker or utilize polyol crosslinkers that contain residual diethanolamine (DEA) or ethanol amine (EA). As typically supplied and used in the industry, triethanolamine contains a low level of approximately 1.5% DEA and 0.1% EA; Unfortunately, DEA is environmentally unfriendly at certain levels, and can be a skin irritant. Urea is very reactive with ethanolamine (EA) or diethanolamine (DEA) and as such has a potentially sallutory effect of acting as a reactive scavenger for ethanolamine and diethanolamine in the formaldehyde-free thermosetting resin. In such a formulation, urea can react with the diethanolamine or ethanol amine as to produce hydroxyureas which can then crosslink into the binder system reducing the already low levels of free diethanolamine or ethanolamine.
This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/811,605, filed on Jun. 06, 2006, the disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60811605 | Jun 2006 | US |
