Patent Application
20080097038
Two tests were used to demonstrate the effectiveness of the PASA catalysts in promoting the crosslinking of moisture-curable systems. The first test utilizes a Brookfield viscometer to measure rate and degree of silane crosslinking. It screens a variety of catalysts under well controlled conditions, and it is designed to simulate the cure of moisture-curable formulations for wires, cables, fibers, foams and adhesives. Examples 1-2 and Comparative Examples 1-4 use this Brookfield viscometer-based screening method.
The second test used lab plaques of the same materials and under similar processing conditions to those currently employed in wire and cable insulation products. The plaque method is also utilized to demonstrate the effectiveness of the disclosed catalysts in a preferred embodiment of this invention, i.e., as silane-crosslinking catalysts in wire and cable insulation products that provide cure rates that are appreciable faster at ambient conditions than existing catalysts, namely di-butyl tin dilaurate (DBTDL). Examples 3-4 and Comparative Examples 5-6 are based on this plaque screening method.
In the case of Comparative Examples 1-3 and Examples 1-2, varying amounts of catalysts were added to dry n-octane to make 1000 mg (1.422 ml) of solution, and the contents were stirred with a spatula. The amounts of catalyst used to make the “catalyst solution” are reported in Table 1 below (the residual amount is octane).
1Di-n-butyldilauryl tin
2Not Available
3Available from King Industries (#17097)
4C20-24 alkyl toluene sulfonic acid
5C20-24 alkyl benzene sulfonic acid
A water-saturated sample of n-octane was prepared by mixing the n-octane with 1 volume percent (vol %) water, and stirring for 1 hour at room temperature (22° C.). The two-phase mixture was allowed to settle for at least 1 hour, and the upper layer was then decanted carefully to collect the water-saturated octane (the “wet octane”). The solubility of water in octane at 22° C., as determined by Karl-Fischer titration, is 50 ppm. The wet octane (4.5 grams) was used to dissolve 500 mg of poly(ethylene-co-octene) grafted with 1.6 weight percent (wt %) vinyltriethoxysilane (POE-g-VTES) at about 40° C. to obtain a clear and colorless solution comprising 1:9 w:w (weight ratio) polymer:octane. In the case of Comparative Examples 1-3 and Examples 1-2, a fixed amount (0.200 mL) of the catalyst solution described above was added and mixed with the 5.0 grams of POE-g-VTES/octane solution using a syringe.
Comparative Example 4 was prepared differently by directly adding 50 mg of 2-acrylamido-2-methyl-1-propane sulfonic acid (which is a solid at room temperature) to the 5.0 gram of POE-g-VTES/octane solution (instead of first dissolving in n-octane), and then mixing with an ultrasonic cleaner at 40° C. for 5 minutes. A 1.5 ml portion of the final solution was loaded into a preheated (40° C.) Brookfield-HADVII cone and plate viscometer, and a CP 40 spindle was lowered onto the sample. The motor was started and the speed of rotation of the spindle was maintained at 2.5 rpm. The torque reading in mV was monitored over time. The increase in torque over time is a measure of the rate of crosslinking. The effective catalyst concentrations are reported in Table 2 below.
The results from the Brookfield viscometer are presented in Table 3 below.
Assuming a linear effect of catalyst concentration on cross-linking kinetics, Table 4 reports the corresponding times per mg of catalyst.
The sulfonic acids of Examples 1 and 2 yielded not only a desirably fast cross-linking, but the rate of cross-linking was better than that of the sulfonic acids of Comparative Examples 2 and 3. In contrast, the insoluble sulfonic acid compositions in Comparative Example 4 was not very effective at accelerating crosslinking.
These examples and comparative examples were based on the plaque method which utilizes the same materials that are used for the fabrication of a wire and cable product. However, instead of extruding the insulation onto wire and monitoring cure, the polymer composition is prepared as plaques. The polymer composition was prepared in a 250 g mixing bowl that was purged with nitrogen. The ethylene/silane-base resin (DFDA-5451) was added to the bowl and fluxed at 150° C. and then the antioxidant (Lowinox 22IB46) and catalyst wee added to the melt. The polymer composition was mixed for 5 minutes, and then it is immediately transferred into a 30 mil mold at 150° C. Dogbone plaques were then cut out of these forms, cured under ambient conditions (23° C., 70% relative humidity), and evaluated for cure using Hot Set by methods well known in the art, e.g., CEI/IEC 60502-1, Ed. 1.1 (1998), International Electrotechnical Commission, Geneva, Switzerland.
Table 5 lists the percent by weight of each component that was used in preparing Examples 3-4 and Comparative Examples 5-6. The ethylene-silane copolymer (DFDA-5451) is a reactor copolymer prepared with 1.5% vinyltrimethoxysilane (VTMS), and it constituted the polymer embodiment of each system. As can be seen in Table 5, all of the compositions used the same level of copolymer, antioxidant (Lowinox 221B46 which is isobutylidene(4,6-dimethylphenol) supplied by Great Lakes Chemical) and catalyst by weight, so that each could be evaluated under a weight equivalence factor. Comparative Example 5 was prepared with DBTDL so that its performance could be compared directly with the catalysts of the invention. Comparative Example 6 was prepared with Nacure B201, a sulfonic acid catalyst supplied by King Industries, and it was expected to perform faster than DBTDL. The Aristonate F and Witconate AS304 are Examples 3 and 4 of the invention, and they represent the first and second instances, respectively, of the catalysts used in the practice of the instant invention.
Table 6 reports the Hot Set or creep measured following curing of each of these polymer compositions under ambient conditions. All the samples were tested prior to conditioning (0 days) in order to verify that none had crosslinked. A sample was considered a failure if it either broke during the test or achieved a Hot Set value of greater than 175%. As shown in Table 6, the compositions prepared with Witconate AS304 and Aristonate F passed Hot Set within 16 hours, while the Nacure B201 passed within 1 day. The DBTDL-cure took a week to pass the test. The substantially faster cure rate of the polymer compositions comprising Witconate AS304 or Aristonate F not only validated that Witconate AS304 and Aristonate F are suitable catalysts for the crosslinking of moisture curable systems under ambient conditions, but their passing Hot Set in less time than that required for compositions comprising Nacure B201 catalyst indicates they are preferable over other sulfonic acid catalysts.
Although the invention has been described in considerable detail through the preceding examples, this detail is for the purpose of illustration and is not to be construed as a limitation upon the invention as described in the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/27008 | 8/1/2005 | WO | 00 | 6/7/2007 |
| Number | Date | Country | |
|---|---|---|---|
| 60599000 | Aug 2004 | US |
