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Resins which are in situ catalytically produced blends of broad bimodal molecular weight distribution ethylene resin are produced. The resins of the invention are characterized by a blend of low molecular weight component and high molecular weight component with HMW component weight fraction which is greater than 0 (zero). Generally, the LMW/HMW weight fraction can be controlled within a very broad range. The resin has a molecular weight distribution, which is characterized as MFR or Mw/Mn. The bimodal molecular weight resins can be processed into films on existing equipment, and exhibit good processability in blown film production and provide film product of excellent FQR. The resin of the invention exhibits reduced tendency towards die-lip buildup and smoking in on-line operations.
1. A product in the form of particles, characterized by a weight average particle diameter in the range of 0.01 to 0.04 inches,
each particle comprising a resin which is selected from the group consisting of polymer of ethylene, copolymer of ethylene and admixtures thereof,
wherein the resin has a density of 0.89 to 0.97; has a Mw/Mn of 2.5 to 60, and has FI of 1 to 100,
wherein said resin comprises two components of different molecular weight wherein one of said two components is a high molecular weight component (HMW) and wherein another of said two components is a low molecular weight component (LMW) with a molecular weight less than that of HMW, wherein said resin is characterized by Mw and Mw/Mn;
wherein the HMW component has a calculated FI of 0.005 to 50 and the LMW component has calculated MI of 0.1 to 20,000 and calculated Mw /Mn of 2 to 5; and
wherein the Mw and the Mw /Mn of said resin in said particles is substantially constant over said range of weight average particle diameter;
wherein the blend is formed in situ in a single reactor by a catalyst comprising a metallocene transition metal.
2. The product of claim 1, wherein the resin has a density which ranges from 0.930 to 0.970 g/cc.
3. The product of claim 1, wherein the resin has a density which ranges from 0.940 to 0.970.
4. The product of claim 1, wherein the resin has a density which ranges from 0.930 to 0.940.
5. The product of claim 1, wherein the Mw/Mn of the resin ranges from 10 to 40.
6. The product of claim 1, wherein the Mw/Mn of the resin ranges from 15 to 30.
7. The product of claim 1, wherein the polymer or copolymer has a total unsaturation measured by IR which ranges from 0.1 to 3.0 per 1000 carbon atoms.
8. The product of claim 1, which is crosslinkable.
9. The product of claim 1, wherein the calculated molecular weight distribution Mw /Mn of the LMW fraction ranges from 2 to 3.5.
10. The product of claim 1 wherein the calculated molecular weight distribution Mw /Mn of the LMW fraction ranges from 2 to 2.5.
11. The product of claim 1 which is a homopolymer of ethylene.
12. The product of claim 1 which is a copolymer of ethylene and an alpha olefin of 3 to 10 carbon atoms.
13. The product of claim 1 which is a copolymer of ethylene and an alpha olefin of 4 to 8 carbon atoms.
14. The product of claim 1 which is a copolymer of ethylene and an alpha olefin which is selected from the group consisting of propylene, 1-butene, 1-hexene, 1-octene, 4-methylpentene and admixtures thereof.
15. The product of claim 1 which is a copolymer of ethylene and 1-hexene.
16. The product of claim 12, wherein the copolymer comprises 0 to 20 weight percent of alpha olefin.
17. The product of claim 5 wherein the calculated molecular weight distribution of the LMW fraction ranges from 2 to 2.5
18. The product of claim 6 wherein the calculated molecular weight distribution of the LMW fraction ranges from 2 to 2.5.
19. The product of claim 1 wherein the resin contains 0.1 to 10 ppm of said metallocene transition metal.
20. The product of claim 19, wherein the resin further comprises 1 to 30 ppm titanium.
21. The product of claim 1, wherein the resin has a density in the range of 0.918 to 0.929.
22. A film formed of the product of claim 1 having FQR of less than 50.
23. An article blow molded from the product of claim 1.
This is a continuation of application Ser. No. 08/139,132, filed on Oct. 21, 1993, now abandoned.
The invention relates to a catalytically produced blend comprising a high molecular weight component and low molecular weight component. These blends may be characterized as exhibiting bimodal or broad molecular weight distribution. The blend comprises polymers and copolymers of ethylene and admixtures thereof. The catalyst which is used contains two different transition metals. The catalyst allows for the production of the blend in a single reactor. The resulting blends embrace a broad spectrum of product compositions, determined by the weight fractions and molecular weights of the individual components. The blends can be processed into films of excellent appearance, exhibiting very low gel levels.
Bimodal molecular weight distribution of a resin indicates that a resin comprises to components of different molecular weight, and implicitly requires a relatively higher molecular weight component (HMW) and low molecular weight (LMW) component. Physical blending of two different polymers will produce a bimodal blend. Such a concept appears in U.S. Pat. No. 4,461,873. Those physically produced blends contain high gel levels. Accordingly, their actual application in film production is of theoretical interest only because of film appearance due to those gels.
To replace physical blending, the art shows a development by which such bimodal resin blends are produced by process techniques, sometimes referenced as tandem process polymerization. Such a process relies on a two (or more) reactor set up; in one reactor, one of the two components of the bimodal blend is produced under a set of conditions maintained in the first reactor, and transferred to a second reactor, where under a different set of conditions from those in the first reactor the second component is produced, with a different molecular weight. Compared to bimodal HMW-high density polyethylene [HMW HDPE] produced by physical blending, blends produced in a tandem operation may have relatively improved film appearance. However, the film appearance is dependent on the HMW component being a major component, greater than 50 percent by weight fraction, of the blend. U.S. Pat. No. 4,307,209 discusses some of the constraints on composition which the tandem mode of operation imposes on product because of the presence of gels.
The problems which inhere in tandem produced products, as discussed in U.S. Pat. No. 4,307,209, may be due to a function of particles of product which have varying LMW/HMW ratios. It is difficult to avoid having particles that have not incorporated LMW species, particularly, when the HMW component is produced in the first reactor. This may be due to deactivation of the HMW reactor particles or because of their bypassing the LMW reactor. Such particles with fairly high viscosity appear as gels and would be incorporated (through deformation) only if the bulk matrix viscosity was high enough. The latter requires that the weight fraction of the HMW component be fairly high (greater than 55 percent).
The desirability of bimodal products resides in product strength and processability, which are provided by the individual components of the blend. Processability relates to the capacity of the resin to be used in existing lines efficaciously.
In accordance with the invention, broad, and preferably bimodal molecular weight distribution ethylene resin is produced catalytically; moreover, the catalysis can be conducted in one reactor. As a result of catalysis in a single reactor the product has greatly improved inter particle composition homogeneity. This is because the catalyst itself provides sites for catalysis of each of the LWM and HWM component, in the constant process conditions and environment of one reactor. Since these sites are relatively uniform in concentration in the catalyst particle, the polymerization (or copolymerization) product particles will have substantially constant HMW:LMW ratios. This means that the Mw and the Mw/Mn of said resin in said particles is substantially constant over the range of weight average particle diameter of the particles.
The resins of the invention are characterized by a chemical blend of low molecular weight component and a high molecular weight component with the HMW component weight fraction being greater than 0 (zero). Generally, the HMW component weight fraction can be controlled within a very broad range. The resin has a molecular weight distribution, which is characterized as MFR or Mw/Mn. MFR is the ratio I21/I2 [determined by ASTM 1238]. Mw is weight average molecular weight and Mn is number average molecular weight as determined by Gel Permeation Chromatography (GPC).
The resins which are (broad) bimodal molecular weight resins can be processed into films on existing equipment, and exhibit good processability, in blown film production and provide film product with a low gel level (excellent FQR). The resin of the invention exhibits reduced tendency towards die-lip buildup and smoking in on-line operations. The resin of the invention exhibits these unexpected advantages over a broader range of HMW/LMW composition than that produced by either physical blends or tandem series reactor technology.
The FIGURE is a GPC [gel permeation chromatograph] curve of a resin of the invention.
The resins herein are mainly comprised of ethylene. The resins may be homopolymers, copolymers or admixtures of homopolymers and copolymers. Copolymers of ethylene contain at least 70 weight percent ethylene and an alpha olefin of 3 to 10 carbon atoms. Preferred alpha olefins include 1-butene, 1-hexene, 1-octene and 4 methyl-pentene.
The resins produced herein have a specific density in the range of 0.89 to 0.970. The resins which can be produced in accordance with the invention can exhibit densities of high density, medium density or low density resins, respectively. Accordingly, the resins can be produced which exhibit specific density in the range of 0.89 to 0.929 [low density], 0.930 to 0.940 [medium density], and 0.940 to 0.970 [high density.]
The resins of the invention are characterized by a blend of HMW and LMW component with the high molecular weight component weight fraction which is greater than 0 (zero). Generally, the HMW component weight fraction can be controlled within a very broad range, while maintaining excellent properties in ultimate applications, such as film production. The weight fraction of HMW component can range from 0.01 to 0.99, preferably from 0.4 to 0.7 and most preferably from 0.5 to 0.6. The resin has a molecular weight distribution, which is characterized as MFR or Mw/Mn. The MFR of resin products of the invention can range from 20 to 300, preferably from 60 to 200, and most preferably from 80 to 150. The Mw/Mn of resin products of the invention can range from 2.5 to 60, preferably from 10 to 40, and most preferably from 15 to 30.
The MFR of the low molecular weight component of the resin products of the invention can range from 15 to 40, preferably from 15 to 30, and most preferably from 15 to 20. The Mw/Mn of the low molecular weight component of the resin products of the invention can range from 2 to 30, preferably from 2 to 3.5, and most preferably from 2 to 2.5. The low molecular weight component of resin product of the invention is much narrower in molecular weight distribution, than that produced by a conventional Ziegler Natta catalyst containing only one transition metal such as titanium and/or that produced by a conventional tandem two-reactor process. The narrow MWD of the LMW component is a result of the single site metallocene catalyst component. This narrower molecular weight distribution of the low molecular weight component of the resin of the invention may be responsible for the reduced tendency towards die-lip buildup and smoking because of the absence of very low molecular weight tails. That narrower distribution also enables production of much lower molecular weight component, as the LMW component, without encountering the die-lip buildup problem. The MFR of the high molecular weight component of the resin products of the invention can range from 25 to 90, preferably from 30 to 50, and most preferably from 30 to 40. The Mw/Mn of the high molecular weight component of the resin products of the invention can range from 3 to 30, preferably from 3 to 10, and most preferably from 3 to 6.
The molecular weight of the LMW component as reflected and expressed herein as MI [ASTM D1238 (190� C./2160 g)] can range generally from 0.1 to 20,000, usually from 20 to 20000, preferably 100 to 5000, and most preferably 2000 to 3000. The FI [ASTM D1238 (190� C./21600 g)] of the high molecular weight component can range from 0.005 to 50, preferably from 0.1 to 5 and most preferably from 0.2 to 1.0.
The resin product of the invention is unsaturated and crosslinkable. The resin product of the invention has an unsaturation measured by IR which ranges from 0.1 to 3.0, generally 0.20 to 3.0, preferably ranges from 0.2 to 2 and most preferably ranges from 0.4 to 1.5 (unsaturation per 1000 carbon atoms). The high levels of unsaturation allow for facile cross-linking of resin products of the invention.
When blown into films, these resins exhibit unexpected FQR values. FQR is a qualitative ranking of gel level, ranging from 10 to 60, where 10 FQR indicates no gels and 60 FQR indicates an unacceptably high number of gels. As noted below in the Examples, the FQR of resin products of the invention is superior to those of tandem process produced resins. Generally, the FQR is less than 50, usually less than 30, preferably less than 20 and most preferably 10. In addition to excellent FQR values, the products exhibit excellent dart drop impact resistance.
The resin products of the invention can be referred to as in situ catalytically produced blends of bimodal molecular weight distribution. As noted above, the resins are produced by a catalyst which comprises two different transition metals. In a preferred embodiment at least one of the transition metals is provided in the form of a metallocene compound. In a preferred embodiment at least one of the transition metals is provided in the form of a metallocene compound of a transition metal zirconium or hafnium. Accordingly, the resin product of the invention will contain 0.01 to 10 ppm usually 1 to 5, and generally 1 to 3 ppm (weight of the transition metal (e.g. Hf, Zr, Ti) which is provided in the catalyst as the metallocene. It will contain 1 to 30 ppm titanium, preferably 1 to 20, and more preferably 1 to 10 ppm titanium provided as a non-metallocene or as TiCl4.
The preferred catalysts comprise a cocatalyst comprising an aluminum alkyl compound, such as a trialkyl aluminum free of alumoxane, e.g. TMA, and a catalyst precursor comprising a carrier, an alumoxane, at least one metallocene and a non-metallocene transition metal source.
The carrier material is a solid, particulate, porous, preferably inorganic material, such as an oxide of silicon and/or of aluminum. The carrier material is used in the form of a dry powder having an average particle size of from about 1 micron to about 250 microns, preferably from about 10 microns to about 150 microns. The surface area of the carrier is at least about 3 square meters per gram (m2 /gm), and preferably at least about 50 m2 /gm up to about 350 m2 /gm. The carrier material should be dry, that is, free of absorbed water. Drying of the carrier material can be effected by heating at about 100� C. to about 1000� C., preferably at about 600� C. When the carrier is silica, it is heated to at least 200� C., preferably about 200� C. to about 850� C. and most preferably at about 600� C. The carrier material must have at least some active hydroxyl (OH) groups to produce the catalyst composition of this invention.
In the most preferred embodiment, the carrier is silica which, prior to the use thereof in the first catalyst synthesis step, has been dehydrated by fluidizing it with nitrogen and heating at about 600� C. for about 16 hours to achieve a surface hydroxyl group concentration of about 0.7 millimoles per gram (mmols/gm). The silica of the most preferred embodiment is a high surface area, amorphous silica (surface area=300 m2 /gm; pore volume of 1.65 cm3 /gm), and it is a material marketed under the tradenames of Davison 952 or Davison 955 by the Davison Chemical Division of W.R. Grace and Company. The silica is in the form of spherical particles, e.g., as obtained by a spray-drying process.
When the catalyst contains two transition metals components, one of which is a metallocene, and one of which is non-metallocene (free of unsubstituted or substituted cyclopentadienyl groups) the impregnation of the alumoxane in accordance with the unique method described above is preferably undertaken after hydroxyl groups of the carrier material are reacted with an organomagnesium compound and the non-metallocene transition metal compound. In this embodiment, the amount of Al, provided by alumoxane, is sufficient to provide an Al:transition metal (provided by metallocene) mole ratio ranging from 50 to 500, preferably 75 to 150. The carrier material, having said (OH) groups, is slurried in a non-polar solvent and the resulting slurry is contacted with at least one organomagnesium composition having the empirical formula below. The slurry of the carrier material in the solvent is prepared by introducing the carrier into the solvent, preferably while stirring, and heating the mixture to about 25� to about 70� C., preferably to about 40� to about 60� C. Temperatures here are critical with respect to the non-metallocene transition metal which is subsequently added; that is temperatures in this slurry of about 90� C. result in deactivation of the transition metal added subsequently. The slurry is then contacted with the aforementioned organomagnesium composition, while the heating is continued at the aforementioned temperature.
The organomagnesium composition has the empirical formula
Rm MgR'n
where R and R' are the same or different C2 -C12 alkyl groups, preferably C4 -C10 alkyl groups, more preferably C4 -C8 normal alkyl groups, and most preferably both R and R' are n-butyl groups, and m and n are each 0, 1 or 2, providing that m+n is equal to the valence of Mg.
Suitable non-polar solvents are materials in which all of the reactants used herein, i.e., the organomagnesium composition, and the non-metallocene transition metal compound, are at least partially soluble and which are liquid at reaction temperatures. Preferred non-polar solvents are alkanes, such as isopentane, hexane, n-heptane, octane, nonane, and decane, although a variety of other materials including cycloalkanes, such as cyclohexane, aromatics, such as benzene, toluene and ethylbenzene, may also be employed. The most preferred non-polar solvent is isopentane. Prior to use, the non-polar solvent should be purified, such as by percolation through silica gel and/or molecular sieves, to remove traces of water, oxygen, polar compounds, and other materials capable of adversely affecting catalyst activity.
In the most preferred embodiment of the synthesis of this catalyst it is important to add only such an amount of the organomagnesium composition that will be deposited--physically or chemically--onto the support since any excess of the organomagnesium composition in the solution may react with other synthesis chemicals and precipitate outside of the support. The carrier drying temperature affects the number of sites on the carrier available for the organomagnesium composition--the higher the drying temperature the lower the number of sites. Thus, the exact molar ratio of the organomagnesium composition to the hydroxyl groups on the carrier will vary and must be determined on a case-by-case basis to assure that only so much of the organomagnesium composition is added to the solution as will be deposited onto the support without leaving any excess of the organomagnesium composition in the solution. Furthermore, it is believed that the molar amount of the organomagnesium composition deposited onto the support is greater than the molar content of the hydroxyl groups on the support. Thus, the molar ratios given below are intended only as an approximate guideline and the exact amount of the organomagnesium composition in this embodiment must be controlled by the functional limitation discussed above, i.e., it must not be greater than that which can be deposited onto the support. If greater than that amount is added to the solvent, the excess may react with the non-metallocene transition metal compound, thereby forming a precipitate outside of the support which is detrimental in the synthesis of our catalyst and must be avoided. The amount of the organomagnesium composition which is not greater than that deposited onto the support can be determined in any conventional manner, e.g., by adding the organomagnesium composition to the slurry of the carrier in the solvent, while stirring the slurry, until the organomagnesium composition is detected as a solution in the solvent.
For example, for the silica carrier heated at about 600� C., the amount of the organomagnesium composition added to the slurry is such that the molar ratio of Mg to the hydroxyl groups (OH) on the solid carrier is about 0.5:1 to about 4:1, preferably about 0.8:1 to about 3:1, more preferably about 0.9:1 to about 2:1 and most preferably about 1:1. The organomagnesium composition dissolves in the non-polar solvent to form a solution from which the organomagnesium composition is deposited onto the carrier.
It is also possible to add such an amount of the organomagesium composition which is in excess of that which will be deposited onto the support, and then remove, e.g., by filtration and washing, any excess of the organomagnesium composition. However, this alternative is less desirable than the most preferred embodiment described above.
After the addition of the organomagnesium composition to the slurry is completed, the slurry is contacted with a non-metallocene transition metal compound, free of substituted or unsubstituted cyclopentadienyl groups. The slurry temperature must be maintained at about 25� to about 70� C., preferably to about 40� to about 60� C. As noted above, temperatures in this slurry of about 80� C. or greater result in deactivation of the non-metallocene transition metal. Suitable non-metallocene transition metal compounds used herein are compounds of metals of Groups IVA, and VA, of the Periodic Chart of the Elements, as published by the Fisher Scientific Company, Catalog No. 5-702-10, 1978, providing that such compounds are soluble in the non-polar solvents. Non-limiting examples of such compounds are titanium and vanadium halides, e.g., titanium tetrachloride, TiCl4, vanadium tetrachloride, VCl4, vanadium oxytrichloride, VOCl3, titanium and vanadium alkoxides, wherein the alkoxide moiety has a branched or unbranched alkyl radical of 1 to about 20 carbon atoms, preferably 1 to about 6 carbon atoms. The preferred transition metal compounds are titanium compounds, preferably tetravalent titanium compounds. The most preferred titanium compound is titanium tetrachloride. The amount of titanium or vanadium, in non-metallocene form ranges from a Ti/Mg molar ratio of 0.5 to 2.0, preferably from 0.75 to 1.50.
Mixtures of such non-metallocene transition metal compounds may also be used and generally no restrictions are imposed on the transition metal compounds which may be included. Any transition metal compound that may be used alone may also be used in conjunction with other transition metal compounds.
Incorporation of the alumoxane-metallocene can be directly to this slurry. Alternatively, and in accordance with the unique method of infusion of alumoxane into the pores of the carrier, the carrier slurry can be stripped of solvent, after the addition of the non-metallocene transition metal compound, to form a free-flowing powder. The free flowing powder can then be impregnated by determining the pore volume of the carrier and providing a metallocene-alumoxane solution in a volume equal to or less than that of the pore volume of the carrier, and recovering a dry catalyst precursor. The amount of solution of aluminoxane activated zirconocene is to obviate the formation of a slurry containing the silica supported titanium in the solution of the activated zirconocene; the actual volume of solution (of activated zirconocene) can be 30% greater than the total pore volume of silica supported titanium without slurry formation.
The resulting free-flowing powder, referred to herein as a catalyst precursor, is combined with an activator (sometimes referred as a cocatalyst). The activator is a monomeric anhydrous aluminum compound. The aluminum compound can be a trialkylaluminum, dialkylaluminum hydride, dialkylaluminum halide, alkylaluminum dihydride or alkylaluminum dihalide, in which alkyl is 1 to 6 carbon atoms, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, straight and branched pentyl and hexyl groups. Specific examples include triethylaluminum, triisobutylaluminum and trimethylaluminum. The amount of cocatalyst is sufficient to activate the precursor containing the non-metallocene source of transition metal. Practically, the amount of activator (or cocatalyst) ranges from 80 to 800 ppm, preferably from 200 to 300 ppm, based on the ethylene feed. Preferably, trimethylaluminum (TMA) is the cocatalyst or activator. The amount of the TMA activator is sufficient to give an Al:Ti molar ratio of about 10:1 to about 1000:1, preferably about 15:1 to about 300:1, and most preferably about 20:1 to about 100:1. The catalyst exhibits high activity for long periods of time and exhibits little deactivation.
In a preferred embodiment, the metallocene is added to a solution of the alumoxane prior to impregnating the non-metallocene transition metal supported carrier with the solution. The class of alumoxanes comprises oligomeric linear and/or cyclic alkylalumoxanes represented by the formula: R--(Al(R)--O)n --AlR2 for oligomeric, linear alumoxanes and (--Al(R)--O--)m for oligomeric cyclic alumoxane wherein n is 1-40, preferably 10-20, m is 3-40, preferably 3-20 and R is a C1 -C8 alkyl group and preferably methyl (MAO). It is a mixture of oligomers with a very wide distribution of molecular weights and usually with an average molecular weight of about 1200. MAO is typically kept in solution in toluene. While the MAO solutions remain liquid at fluid bed reactor temperatures, the MAO itself is a solid in the absence of toluene.
Again the maximum volume of the alumoxane solution also including the metallocene is the total pore volume of the carrier material sample. That maximum volume of the alumoxane solution insures that no slurry of silica is formed. Accordingly, if the pore volume of the carrier material is 1.65 cm3 /g, then the volume of alumoxane will be equal to or less than 1.65 cm3 /gram of carrier material. As a result of this proviso, the impregnated carrier material will appear dry immediately following impregnation although the pores of the carrier will be filled with inter alia solvent. The mole ratio of alumoxane provided aluminum, expressed as Al, to metallocene metal expressed as M (e.g. Zr), ranges from 50 to 500, preferably 75 to 300, and most preferably 100 to 200. An added advantage of the present invention is that this Al:Zr ratio can be directly controlled. In a preferred embodiment the alumoxane and metallocene compound are mixed together at a temperature of about 20� to 80� C., for 0.1 to 6.0 hours, prior to use in the infusion step. The solvent for the metallocene and alumoxane can be appropriate solvents, such as aromatic hydrocarbons, halogenated aromatic hydrocarbons, ethers, cyclic ethers or esters, preferably it is toluene.
The metallocene compound has the formula Cpm MAn Bp in which Cp is an unsubstituted or substituted cyclopentadienyl group, M is zirconium or hafnium and A and B belong to the group including a halogen atom, hydrogen or an alkyl group. In the above formula of the metallocene compound, the preferred transition metal atom M is zirconium. In the above formula of the metallocene compound, the Cp group is an unsubstituted, a mono- or a polysubstituted cyclopentadienyl group. The substituents on the cyclopentadienyl group can be preferably straight-chain C1 -C6 alkyl groups. The cyclopentadienyl group can be also a part of a bicyclic or a tricyclic moiety such as indenyl, tetrahydroindenyl, fluorenyl or a partially hydrogenated fluorenyl group, as well as a part of a substituted bicyclic or tricyclic moiety. In the case when m in the above formula of the metallocene compound is equal to 2, the cyclopentadienyl groups can be also bridged by polymethylene or dialkylsilane groups, such as --CH2 --, --CH2 --CH2 --, --CR'R"-- and --CR'R"--CR'R"-- where R' and R" are short alkyl groups or hydrogen, --Si(CH3)2 --, Si(CH3)2 --CH2 --CH2 --Si(CH3)2 -- and similar bridge groups. If the A and B substituents in the above formula of the metallocene compound are halogen atoms, they belong to the group of fluorine, chlorine, bromine or iodine. If the substituents A and B in the above formula of the metallocene compound are alkyl groups, they are preferably straight-chain or branched C1 -C8 alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl or n-octyl.
Suitable metallocene compounds include bis(cyclopentadienyl)metal dihalides, bis(cyclopentadienyl)metal hydridohalides, bis(cyclopentadienyl)metal monoalkyl monohalides, bis(cyclopentadienyl)metal dialkyls and bis(indenyl)metal dihalides wherein the metal is zirconium or hafnium, halide groups are preferably chlorine and the alkyl groups are C1 -C6 alkyls. Illustrative, but non-limiting examples of metallocenes include bis(cyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)hafnium dichloride, bis(cyclopentadienyl)zirconium dimethyl, bis(cyclopentadienyl)hafnium dimethyl, bis(cyclopentadienyl)zirconium hydridochloride, bis(cyclopentadienyl)hafnium hydridochloride, bis(pentamethylcyclopentadienyl)zirconium dichloride, bis(pentamethylcyclopentadienyl)hafnium dichloride, bis(n-butylcyclopentadienyl)zirconium dichloride, cyclopentadienylzirconium trichloride, bis(indenyl)zirconium dichloride, bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, and ethylene-[bis(4,5,6,7-tetrahydro-1-indenyl)] zirconium dichloride. The metallocene compounds utilized within the embodiment of this art can be used as crystalline solids, as solutions in aromatic hydrocarbons or in a supported form.
Solvent may be removed from the alumoxane impregnated pores of the carrier material by heating and/or under a positive pressure induced by an inert gas, such as nitrogen. If employed, the conditions in this step are controlled to reduce, if not to eliminate, agglomeration of impregnated carrier particles and/or crosslinking of the alumoxane. In this step, solvent can be removed by evaporation effected at relatively low elevated temperatures of above about 40� and below about 50� to obviate agglomeration of catalyst particles and cross-linking of the alumoxane. Although solvent can be removed by evaporation at relatively higher temperatures than that defined by the range above 40� and below about 50� C., very short heating times schedules must be employed to obviate agglomeration of catalyst particles and cross-linking of the alumoxane.
The catalyst composition of this invention is used to polymerize either ethylene alone or ethylene in conjunction with higher monomers, such as any one of C3 -C10 alpha-olefins, e.g., propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene or 1-octene, preferably 1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene and most preferably 1-hexene. The polymerization reaction may be carried out using any suitable, conventional olefin polymerization process, such as a slurry, particle form or vapor phase, e.g., fluid bed reactor, but preferably it is carried out in a vapor phase, fluid bed reactor. The reaction is conducted substantially in the absence of catalyst poisons, such as moisture, carbon monoxide and acetylene, with a catalytically effective amount of the catalyst at a temperature and pressure conditions sufficient to initiate the polymerization reaction. A particularly desirable method for producing polymers according to the present invention is in a fluid bed reactor. Such a reactor and means for operating it are described by Levine et al. U.S. Pat. No. 4,001,382, Karol et al., U.S. Pat. No. 4,302,566, and Nowlin et al, U.S. Pat. No. 4,481,301, the entire contents of all of which are incorporated herein by reference. The polymer produced in such a reactor contains catalyst particles since the catalyst is not separated from the polymer.
In order to achieve density ranges of about 0.915 to about 0.965 g/cc in the copolymers, it is necessary to copolymerize enough of the C3 or higher comonomer with ethylene to achieve a level of about 0.1 to about 25 mole percent of the C3 -C10 comonomer in the copolymer. The amount of comonomer needed to achieve this result will depend on the particular comonomer(s) being employed. Further, the various intended comonomers have different reactivity rates, relative to the reactivity rate of ethylene, with respect to the copolymerization thereof with the catalysts of the present invention. Therefore, the amount of comonomer used in the stream of monomers fed to the reactor will also vary depending on the reactivity of the comonomer.
In the most preferred embodiment, the catalyst of the present invention is used to polymerize 1-hexene and ethylene to obtain polymers having the density of about 0.930 to about 0.955 g/cc, and high load melt index (HLMI), I21, values of about 3 to about 12, preferably about 6 to about 8, which are especially suitable for the production of high strength films.
Hydrogen may be used in the polymerization reaction of the present invention in such amounts that the ratio of hydrogen to ethylene is between about 0 to about 2.0 moles of hydrogen per mole of the ethylene monomer in the gas stream. Any gas inert to the catalyst and reactants may also be present in the feed stream.
It is essential to operate the fluid bed reactor at a temperature below the sintering temperature of the polymer particles. For the production of ethylene copolymers in the process of the present invention an operating temperature of about 30� to 115� C. is preferred, and a temperature of about 75� to 100� C. is most preferred. Temperatures of about 70� to 85� C. are used to prepare products having a density of about 0.89 to 0.930, and temperatures of about 80� to 95� C. are used to prepare products having a density of about 0.93 to 0.94, and temperatures of about 90� to 115� C. are used to prepare products having a density of about 0.94 to 0.96.
The fluid bed reactor is operated at pressures of up to about 1000 psi, and is preferably operated at a pressure of from about 150 to 350 psi, with operation at the higher pressures in such ranges favoring heat transfer since an increase in pressure increases the unit volume heat capacity of the gas.
The partially or completely activated catalyst is injected into the bed at a point above the distribution plate at a rate equal to its consumption. Since the catalysts used in the practice of this invention are highly active, injection of the fully activated catalyst into the area below the distribution plate may cause polymerization to begin there and eventually cause plugging of the distribution plate. Injection into the bed, instead, aids in distributing the catalyst throughout the bed and precludes the formation of localized spots of high catalyst concentration.
The production rate of polymer in the bed is controlled by the rate of catalyst injection. Since any change in the rate of catalyst injection changes the rate of generation of the heat of reaction, the temperature of the recycle gas is adjusted to accommodate the change in rate of heat generation. Complete instrumentation of both the fluidized bed and the recycle gas cooling system is, of course, necessary to detect any temperature change in the bed so as to enable the operator to make a suitable adjustment in the temperature of the recycle gas.
Since the rate of heat generation is directly related to product formation, a measurement of the temperature rise of the gas across the reactor (the difference between inlet gas temperature and exit gas temperature) is determinative of the rate of particulate polymer formation at a constant gas velocity.
Under a given set of operating conditions, the fluidized bed is maintained at essentially a constant height by withdrawing a portion of the bed as product at a rate equal to the rate of formation of the particulate polymer product.
The compositions of the invention can be extruded and injection or blow molded into articles or extruded and blown into films. Films can be produced which are 0.2 to 5.0 mils, preferably 0.5 to 2.0 mils, thickness. Blow molded articles include bottles, containers, fuel tanks and drums.
A particularly desirable method for producing linear low density polyethylene polymers according to the present invention is in a single fluid bed reactor unit which is shown and is also described in U.S. Pat. No. 4,481,301, which is relied upon and incorporated by reference herein.
For film production, the products may contain any of various additives conventionally added to polymer compositions such as lubricants, microtalc, stabilizer, antioxidants, compatibilizers, pigments, etc. These reagents can be employed to stabilize the products against oxidation. For example, additive packages comprising 400-1200 ppm hindered phenol(s); 200-2000 ppm phosphites; 250 to 1000 ppm antistats and 250-2000 ppm stearates, for addition to the resin powders, can be used for pelletization. The polymers can be added directly to a blown film extruder, e.g., an Alpine extruder, to produce films having a thickness, for example of about 0.2 to 5 mils.
The following Examples further illustrate the essential features of the invention. However, it will be apparent to those skilled in the art that the specific reactants and reaction conditions used in the Examples do not limit the scope of the invention.
The properties of the polymers produced in the Examples were determined by the following test methods:
______________________________________Density ASTM D-1505 - a plaque is made and conditioned for one hour at 100� C. to approach equilibrium crystallinity. Measurement for density is then made in a density gradient column; reported as gms/cc.Melt Index ASTM D-1238 - (190� C./2160 g)(MI), I2 Measured at 190� C. - reported as grams per 10 minutes.High Load ASTM D-1238 - (190� C./21600 g)Melt Index Measured at 10 times the weight used in(HLMI), I21 the melt index test above.or FI ##STR1## ##STR2##______________________________________
The following examples C and D are in examples of U.S. patent application Ser. No. 07/997,421, filed Dec. 28, 1992.
This catalyst was prepared in two stages.
(Step I) 495 grams of Davison grade 955 silica, previously calcined with dry nitrogen for about 12 hours at 600� C., was added to a 2 gallon stainless steel autoclave under a slow nitrogen purge to eliminate oxygen and moisture from the catalyst preparation vessel. Then, 4.0 liters of dry isopentane (IC5) was added to the autoclave and the silica/IC5 were slurried at about 100 rpm and the internal temperature was maintained at about 55�-60� C. Next, 469 ml of a 0.76 molar solution of dibutylmagnesium in heptane was added to the silica/IC5 slurry and stirring was continued for 60 minutes. Next, 39.1 ml of neat titanium tetrachloride was diluted with about 40 ml of IC5 and this solution was added to the autoclave and stirring was continued for 60 minutes. Finally, the solvents were removed with a nitrogen purge through a vent line and 497 grams of a brown free-flowing powder were obtained. Ti found was 2.62 wt %; Mg found was 1.33 wt % and Ti/Mg molar ratio was 1.0.
(Step II) 492 grams of the product of the first stage was added to a 1.6 gallon glass catalyst preparation vessel fitted with a temperature jacket and an internal stirrer. The product of the first stage had an estimated pore volume of 1.5 cc/g (i.e. 738 cc of pore volume). Then into a stainless steel Hoke bomb was added 13.93 grams of (BuCp)2 ZrCl2 (34.4 mmol Zr) and 717.5 ml of a methylalumoxane solution (3,444 mmol of Al) in toluene (4.8 Molar). Note: The total volume of the methylalumoxane/toluene solution is equal to or less than the total pore volume of the product of the first step. Next, the toluene solution containing the methylalumoxane and the zirconium compound were mixed and then the solution was added to the product of the first step in approximately 5 ml aliquots over 90 minutes; (during this time, the product of the first step remains completely dry and always consists of a free-flowing powder). Finally, nitrogen is purged through the glass vessel for about 5 hours with the jacket temperature at about 45� C. Yield: 877 grams of a free-flowing powder. Ti found was 1.85 wt %; Zr found was 0.30 wt %.
This catalyst was also prepared in a two step process as described in EXAMPLE C. Step I was the same as EXAMPLE C, but in Step II we used 406 grams of reaction product from the first step, 826 mls of methylalumoxane solution and 15.6 grams of (BuCp)2 ZrCl2 were used. Yield: 568 grams of a brown free-flowing powder. Ti found was 1.58 wt % Zr found was 0.45 wt %.
This catalyst was also prepared in a two step process as described in EXAMPLE C. Step I was the same as EXAMPLE C, but in Step II we used 506 grams of reaction product from the first step, 921 mls of methylalumoxane solution and 17.5 grams of (BuCp)2 ZrCl2 were used. Yield: 866 grams of a brown free-flowing powder. Ti found was 1.64 wt %, Zr found was 0.43 wt %.
The catalyst described in Example C was examined in a pilot plant fluid bed gas phase reactor under the following conditions:
______________________________________ethylene partial pressure 180 psihydrogen/ethylene 0.005-0.008hexene/ethylene 0.015reactor temperature 95� C.TMA 200 ppm______________________________________
The resin prepared at a productivity of about 1400 g polymer/g catalyst had the following characteristics:
______________________________________average particle size 0.017 inchesresin metal (Ti) content 13.0 ppmHLMI (I21) 5.3MFR (I21/I2.16) 113Density 0.949 g/cc______________________________________
Properties of films of the product of Example D are compared to the commercially produced product OxyChem L5005 in the following table.
______________________________________Sample Ti/Zr OxyChem L5005______________________________________I21 5.3 8.0MFR 113 160Density 0.949 0.950Throughput, lb/hr 98 120Melt Pressure (at 120 lb/hr), psi 7550 6450FQR 15 15Dart Drop, 1 mil. g 565 3250.5 mil, g 410 420MD Elmendorf Tear, 0.5 mil. g/mil 37 25______________________________________
The GPC results show that the Example D bimodal product has a high molecular weight component with higher molecular weight than that produced in the tandem two reactor process. The film of Example D is substantially reduced in, if not free of, gel content. The film of the Example D product has improved dart impact [as measured by dart drop ASTM D1709 (Method A)] and Elmendorf Tear (ASTM-1992).
A catalyst similar to that described in Example C with a higher MAO loading (9.5 mmol Al/g silica at an Al/Zr ratio of 100) was examined in a pilot plant fluid bed gas phase reactor under the following conditions:
______________________________________ethylene partial pressure 185 psihydrogen/ethylene ratio .007hexene/ethylene ratio .004reactor temperature 95� C.TMA 263 ppm______________________________________
The resin prepared had the following characteristics:
______________________________________average particle size 0.017 in.resin Ti content 12 ppmHLMI (I21) 26 g/10 minMFR (I21 /I2) 259 g/10 minDensity 0.960 g/cc______________________________________
Resin was fabricated into 28 g bottles on a reciprocating Improved blow molding machine. Properties of the resin and bottles of the product of Example E are compared to the commercially produced product USI 734 in the following table.
______________________________________ Commercial Invention Product ProductSample Ti/Zr USI LR734______________________________________I21 26 34MFR 259 110Density .960 .954Bent Strip ESCR*, F50, hrs 128 <21(10% Igepal with slit)Net Bottle Weight, g 26.3 27.7Top Pinch Width, in 2.177 2.188______________________________________ *Bent Strip ESCR ASTM D1693
The above results show that the invention product has a significantly improved ESCR at higher stiffness (density) compared to a commercial blow molding product at comparable processability (swell characteristics).
This example illustrates the superior inter-particle homogeneity of the in-situ blends produced by the bimetallic catalyst over that of the tandem reactor resins.
Presently, commercial samples of HDPE with a bimodal MWD are produced in a tandem reactor process. In that process, two reactors are run in series and the catalyst is exposed to ethylene polymerization conditions in one reactor, and the resulting polymer-catalyst particles are transferred to a second reactor for additional polymerization. One of the main process differences in the two different reactors, is that the amount of hydrogen is different in the two different reactors. Relatively lower molecular weight product is produced in the reactor containing more hydrogen, because the hydrogen acts as a chain transfer agent; whereas relatively higher molecular weight product is produced in the reactor containing lesser relative amounts of hydrogen.
The reactor samples were sieved to segregate them as a function of particle size. The individual sieved fractions were analyzed by GPC to determine their molecular weight distribution. The results are tabulated below:
______________________________________Resin Mw* Mw/Mn xx______________________________________xxxxTandem Reactor Process#18 sieve 277600 18.30#60 sieve 236000 18.9#120 sieve 222700 18.0#170 sieve 196000 17.8xxxBimetallic Catalyst C-2#18 sieve 276800 35.8#35 sieve 269200 33.6#60 sieve 290700 32.7#120 sieve 267400 33.0#200 sieve 285200 37.5______________________________________ *Mw is weight average molecular weight measured by GPC. xxMn is number average molecular weight measured by GPC. xxxCatalyst C2 (above) xxxxThis process used a catalyst which was a silicasupported Ti/Mg comple which was not prereduced or partially activated with trin-hexylaluminum. The catalyst precursor contained 1.13 wt. % Ti, 1.95 wt. % Mg, 8.22 wt. % C1, 15.4 wt. % THF, and 1.41 wt.% A1.
The particles of product are characterized by weight average particle diameter ranging from 0.01 inches to 0.04 inches, but can range from 0.015 to 0.022 inches.
For the bimetallic catalyst resin particles, the Mw of the highest molecular weight sieved fraction is only 8.7 percent higher than the Mw of the lowest molecular weight fraction. On the other hand, for the tandem resin, the highest molecular weight fraction has a Mw which is 41.6 percent higher than the Mw of the lowest molecular weight fraction. In addition, unlike the bimetallic resins, the molecular weight of the tandem resin fractions decreases with decreasing particle size. Thus, the tandem resin particles are more heterogeneous than the corresponding bimetallic (Ti/Zr) catalyzed resin particles.
The differences in the heterogeneity of the two bimodal products is also reflected in the appearance of the films produced from these resins. The film quality rating (FQR) of the Ti/Zr film was 10 while the tandem resin film sample had a FQR of 50. The higher FQR denotes higher gel levels and thus poorer film appearance. The low FQR of the Ti/Zr film is truly impressive considering the fact that it has a significantly broader MWD (Mw/Mn of 36 versus 18) with more distinct bimodality.
We also studied particle heterogeneity of the bimodal HMW-HDPE resin produced with the Ti/Zr catalyst (of U.S. Pat. No. 5,032,562 assigned to Mobil) with the MAO cofed externally. We characterized the MWD of the individual sieved fractions of a sample which would be similar to the one described in Example 4 of that patent. The results are as follows:
______________________________________Sieve # Mw Mw/Mn______________________________________18 327811 8.1760 242030 14.49120 97412 12.88200 77986 10.52pan (>200 sieve) 11907 1.8______________________________________
This analysis shows that the particles made by the MAO cofeed process are very heterogeneous. In Example 1, the resin made from a Ti/Zr containing the preactivated Zr had only a 9 percent difference between the Mw of the lowest molecular weight fraction and the Mw of the highest molecular weight fraction. In contrast, the result with product of U.S. Pat. No. 5,032,562 shows that the Mw of the highest molecular weight fraction is almost 30 times the Mw of the lowest molecular weight fraction. Also, there is a wide variation in the Mw/Mn of the fractions: 1.8-14.49.
This example demonstrates the broad range of products that are possible with the Ti/Zr catalyst system. By proper selection of the-catalyst formulation and reactor conditions, we were able to produce resins covering a broad range of FI, MFR and density. These resins also represented a broad range of component weight fractions and molecular weights (FI, MI). The following equations illustrate the versatility of the technology:
______________________________________1. Den = 0.944 + 0.19(H2 /C2) -0.25(C6 /C2)+0.00027(T-90) +.0063 (log10 FI)T-value 1.9 7.1 3.1R square = 892. Ln FI-HMW = -1.6 + 75(H2 /C2) + 0.063(T-90)T-value 7.3 6.8R square = 923. Ln MI-LMW = 7.5 + 166(H2 /C2) - 41(C6 /C2) +0.03(T-90)T-value 11.9 10.3 1.8R square = 984. XHMW = 0.979 - 2.2(H2 /C2) -2.4(C6 /C2)+0.008(T-90)-0.039(PZ*)T-value 2.3 6.1 4.4 4.3R square = 96______________________________________ *PZ = mmol (A1)/g precursor; at an A1/Zr ratio of 100.
Using the appropriate control variables, it is possible to make resins with a HMW weight fraction range of 0.1-0.8, a HMW FI range of 0.01 to 4 and a LMW MI range of 20 to 20,000.
A brief description of the mathematical technique that is used to estimate the composition (Molecular weight and weight fraction) of the bimodal molecular weight distribution produced by the bimetallic catalyst appears in Computer Applications in Applied Polymer Science, ACS Symposium Series, 197, T. Provder, 45, 1982, which is expressly incorporated herein by reference.
In this example, we compare the level of unsaturation encountered in the Ti/Zr resin with that of typical tandem resin. These measurements were made on granular resins with standard FTIR spectroscopy techniques.
______________________________________ Total Unsaturation Level,Sample per 1000 carbons______________________________________Ti/Zr .92Tandem .18______________________________________
This example illustrates the narrow MWD of the LMW component in the bimodal product produced by the Ti/Zr catalyst. The attached GPC curve clearly shows (by its relative sharpness) that the LMW peak for the bimodal Ti/Zr resin is significantly narrower in MWD when compared to the LMW MWD of a typical tandem resin. The MWD of the LMW component in the Ti/Zr catalyzed resin is expected to be narrower in distribution because it is made by the Zr catalyst component. The metallocene Zr catalyst is known to produce resins with substantially narrower MWD compared to a typical Ziegler Natta based Ti catalyst. The latter are used in producing both the HMW and LMW components in the tandem process. The MWD of the LMW component can also be deduced by deconvoluting the bimodal GPC curve into its component. With this technique, the molecular weights and molecular weight distribution of each component can be estimated. This technique also shows the LMW component to be narrower in MWD for the Ti/Zr catalyzed resins. The LMW component in Ti/Zr catalyzed resins has Mw/Mn range of 2-3.5, while the LMW component in a typical tandem resin has Mw/Mn range of 4-6.
Thus it is apparent that there has been provided, in accordance with the invention, a process that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
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There is one month left in Dog College Level 100 but it's not too late to register. Do it today and get 1,000 Club Dog points just for joining. Prove you are the smartest dog around and you could earn a years' worth of dog food for your favorite canine companion. Don't delay… sign up today!
so glad we can be friends. Here's a vote for you and I hope to hear from you soon.
~:*:~Blessings, Angel Indigo~:*:~
Come visit me, ♥ Yukon & Peaka ♥, ., .., Indigo ♥ In Most Loving Memory ♥
Hello, Marley, I'm Angel Indigo. I'm really sorry about Jenny. Believe me, it wasn't easy for her to make that decision. I was wondering if you and I could be friends??? I don't understand what you mean be you's "lost all your friends". No you haven't, Marley. Just go and answer all the blogs you haven't and ask lots and lots of doggies on DC if they'd like to be friends with you. That always works and it's so much talking to old friends again. And new ones, too!! Lots of my old friends have left DC too but then it's time to find new ones! Well, I really hope we can be friends.
Here's a vote for you. Oh, btw, how is your Dad's daughter (with leukemia) doing?
~*✗*~Angel Indigo~*✗*~
Never to be removed~ Jenny girl's avatar in my dog park. Or the picture down there... I remember that night..
Come visit me, Angel Marley .Heartbroken...Goodbye 4ever, Angel Marriesoul *In the need of friends*, Angel Toki
Once upon a time, I believe it was a Tuesday
When I caught your eye
And we caught onto something, I hold on to the night
You looked me in the eye and told me you loved me
Were you just kidding? 'Cause it seems to me
This thing is breaking down, we almost never speak
I don't feel welcome anymore
Baby, what happened? Please tell me
'Cause one second it was perfect
Now you're halfway out the door
And I stare at the phone and he still hasn't called
And then you feel so low, you can't feel nothin' at all
And you flashback to when he said, forever and always
Oh, oh
Oh, and it rains in your bedroom, everything is wrong
It rains when you're here and it rains when you're gone
'Cause I was there when you said forever and always
Was I out of line? Did I say something way too honest
That made you run and hide like a scared little boy?
I looked into your eyes, thought I knew you for a minute
Now I'm not so sure
So here's to everything, coming down to nothing
Here's to silence that cuts me to the core
Where is this going? Thought I knew for a minute
But I don't anymore
And I stare at the phone and he still hasn't called
And then you feel so low, you can't feel nothin' at all
And you flashback to when he said forever and always
Oh, oh
Oh, and it rains in your bedroom, everything is wrong
It rains when you're here and it rains when you're gone
'Cause I was there when you said forever and always
You didn't mean it, baby, I don't think so
Oh, oh
Oh, back up, baby, back up, did you forget everything?
Back up, baby, back up, did you forget everything?
'Cause it rains in your bedroom, everything is wrong
It rains when you're here and it rains when you're gone
'Cause I was there when you said forever and always
Oh, I stare at the phone and he still hasn't called
And then you feel so low, you can't feel nothin' at all
And you flashback to when we said forever and always
And it rains in your bedroom, everything is wrong
It rains when you're here and it rains when you're gone
'Cause I was there when you said forever and always
You didn't mean it, baby, you said forever and always
I never thought i could loose everything. Everything of mine has gone away or forgotten about me. My old friends? Forgot about me. I dont blame them. I couldnt get on often... But even when they didnt blog me I was alright because i still had jenny. then... i wasnt online and on December 29, Jenny left me. I dont blame her for her actions because i couldnt get on. And now i've literally relized that I've lost everything. My friends, My love, My LIFE (im an angel). ........
but this will be my last blog to you. You blogged me once since our wedding. (and that was begging me to stay with you and not be with Ollie Pop)
You haven't blogged me in forever. You usually never blogged me that often anyway though. And you haven't been on DC for 22 days! You took off all your pictures. (I know, you told me why.) DC weddings are different than weddings in real life. Because you're not in my life anymore, Marley. It's hard to stay with you when you don't ever come on and I can't see your face. I'm not taking my page off because you're not blogging anymore but that's a part of it. My family is wishing your Dad and daughter a Happy New Year and we hope you had a good Christmas. We hope you start coming on DC again and blog your old friends. But please don't try to get Jenny back...there's not use in it.
Oh honey!!! I almost cried when I read your blog to me! Sweetheart, I wouldn't trade you for a million dollars. I wouldn't trade you up for all the stars in the world and every happy feeling that ever as felt by everything in the world and every happy moment that ever will ever be!! You are everything to me. You are more to me than all those things. My life without you...would NEVER be the same!!!! You make me smile through my tears when I'm sad. You make me a thousand times happier when I'm already happy. You've made me the luckiest dog in the universe and I understand everything you've ever told me! The way you love me is just the way I love you, Marley!! It's just I can't explain my love for you like you can for me. Do you know what I mean? You always know my love so I'm sure you know now. You are the best one, the sweetest one, the ONLY one for ME!! I have got a few blogs like that from different annoying boys telling me how much they "love me and want me" but I don't believe them, Marley!! And I NEVER will! None of them are like YOU, Marley! You are everything to me an I mean it. I believe you with my whole heart and sole when you tell me that you love me. I believe everything everything everything...everything you say. I don't believe anyone else like you. You are my husband and forever you will always be. A river I'd swim, the tallest mountain I'd climb! Just to be with you forever!!!
I am so very sorry that Ollie Pup blogged that to me. I don't believe him, Marley! I am so sorry he made you worry like that. If a girl left that on your page I would be so mad and worried. I love you Marley more than everything I have or ever have had or ever will!
Together and forever with my love since 4/10/09.
♥ Your wife, Jenny ♥
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subset: commoncrawl


text:
A catheter for diagnosis or treatment of a vessel or organ is provided in which a flexible elongated body includes a tri-axial force sensor formed of a housing and a plurality of optical fibers associated with the housing that measure changes in the intensity of light reflected from the lateral surfaces of the housing resulting from deformation caused by forces applied to a distal extremity of the housing. A controller receives an output of the optical fibers and computes a multi-dimensional force vector corresponding to the contact force.
1. A catheter for exploration or treatment of a vessel or organ, the catheter comprising:
a flexible elongated body having a proximal end and a distal extremity; and
a tri-axial force sensor disposed within the distal extremity, the tri-axial force sensor having a housing including a plurality of laterally-oriented members coupled to a plurality of longitudinally-oriented members, at least some of the laterally-oriented members having reflective surfaces, and a plurality of optical fibers disposed relative to the laterally-oriented members to emit light onto, and to collect light reflected from, the reflective surfaces,
wherein the intensity of the light collected from the reflective surfaces varies as a function of a degree of deformation imposed by a contact force on the housing.
2. The catheter of
3. The catheter of
4. The catheter of
5. The catheter of
6. The catheter of
7. The catheter of
8. The catheter of
9. The catheter of
10. The apparatus of
11. Apparatus for exploration or treatment of a vessel or organ, the apparatus comprising:
a flexible elongated body having a proximal end and a distal extremity;
a tri-axial force sensor disposed within the distal extremity and comprising a housing including a plurality of laterally-oriented members having reflective surfaces and a plurality of optical fibers disposed to emit light onto, and to collect reflected light from, the reflective surfaces; and
a controller operatively coupled to receive a signal corresponding to the intensity of the reflected light collected from the reflective surfaces, the controller programmed to compute a multi-dimensional force vector corresponding to a contact force applied to the distal extremity.
12. The apparatus of
13. The apparatus of
14. The apparatus of
15. The apparatus of
16. The apparatus of
17. The apparatus of
18. The apparatus of
19. The apparatus of
20. The apparatus of
The present invention relates to a catheter for exploring and treating a vessel or a bodily organ that permits the detection and computation of the contact forces between a sensor affixed to an extremity of the catheter and a wall of the vessel or organ.
Catheter-based diagnostic and treatment systems have made possible the exploration and treatment of various bodily vessels and organs. Such catheters are introduced through a vessel leading to the cavity in the target organ, or may alternatively be introduced directly into the organ through an incision made in the wall of the organ. These procedures avoid the trauma to the patient and the extended recuperation times typically associated with an open surgical procedure.
To provide effective diagnosis or therapy, it is frequently necessary to first map the zone to be treated with great precision. Such mapping may be performed, for example, when it is desired to selectively ablate current pathways within a heart to treat atrial fibrillation. Often, the mapping procedure is complicated by difficulties in locating the zone(s) to be treated because of the periodic movements of the heart throughout the cardiac cycle.
Previously-known systems for mapping the interior of a vessel or organ are described, for example, in U.S. Pat. Nos. 6,546,271 and 6,226,542. The catheters described in those patents employ electro-magnetic, magnetic or acoustic sensors to map the position of a distal end of the catheter in space and then construct a three-dimensional visualization of the vessel or organ interior.
One drawback of such previously known mapping systems is that they require manual feedback from the catheter and/or impedance measurements to determine when the catheter is properly positioned relative to the wall of the vessel or organ. Those previously-known systems do not measure contact forces with the vessel or organ wall nor do they detect contact forces applied by the catheter against the organ or vessel wall, which may modify the true location of the wall. Instead, previously known mapping methods are time-consuming, highly dependent upon the skill of the clinician, and are unable to compensate for artifacts created by excessive contact forces.
It therefore would be desirable to provide apparatus and methods for detecting and monitoring contact forces between a mapping catheter and the wall of an organ or vessel, so to enable faster and more accurate mapping. It also would be desirable to provide apparatus and methods that permit the process to be automated, thereby improving registration of measured electro-physiologic values and spatial coordinates, for example, by recording such values only where the contact forces fall within a predetermined range.
Once the topography of the vessel or organ is mapped, either the same or a different catheter may be employed to effect treatment. Depending upon the specific treatment to be applied to the vessel or organ, the catheter may comprise any of a number of end effectors, such as radio frequency ablation electrodes, a rotary cutting head, laser ablation system, injection needle or cryogenic fluid delivery system. Exemplary systems are described, for example, in U.S. Pat. Nos. 6,120,520, 6,102,926, 5,575,787, 5,409,000 and 5,423,807.
Because the effectiveness of such end effectors often depends on having the end effector in contact with the wall of the organ or vessel, many previously-known treatment systems include expandable baskets or hooks that stabilize the extremity of the catheter in contact with the wall. Such arrangements, however, may be inherently imprecise due to the motion of the organ or vessel. Moreover, the previously-known systems do not provide the ability of sense the load applied to the distal extremity of the catheter by movement of the tissue wall.
For example, in the case of a cardiac ablation system, at one extreme the creation of a gap between the end effector of the treatment system and the tissue wall may render the treatment ineffective and inadequately ablate the tissue zone. At the other extreme, if the end effector of the catheter contacts the tissue wall with excessive force, if may inadvertently puncture the tissue, resulting in cardiac tamponade.
In view of the foregoing, it would be desirable to provide a catheter-based diagnostic or treatment system that permits sensing of the load applied to the distal extremity of the catheter, including periodic loads arising from movement of the organ or tissue. It further would be desirable to have a load sensing system coupled to control operation of the end effector, so that the end effector is operated, either manually or automatically, only when the contact force is detected to fall within a predetermined range.
U.S. Pat. No. 6,695,808 proposes several solutions to measure the force vector arising from contact with a tissue surface, including mechanical, capacitive, inductive and resistive pressure sensing devices. One drawback of such devices, however, is that they are relatively complex and must be sealed to prevent blood or other liquids from disturbing the measurements. In addition, such load sensing devices may result in an increase in the insertion profile of the distal extremity of the catheter. Still further, sensors of the types described in that patent may be subject to electromagnetic interference.
One previously-known solution for dealing with potential electromagnetic interference in the medical environment is to use light-based systems rather than electrical measurement systems, such as described in U.S. Pat. No. 6,470,205 to Bosselman. That patent describes a robotic system for performing surgery comprising a series of rigid links coupled by articulated joints. A plurality of Bragg gratings are disposed at the articulated joints so that the bend angle of each joint may be determined optically, for example, by measuring the change in the wavelength of light reflected by the Bragg gratings using an interferometer. Calculation of the bend angles does not require knowledge of the characteristics of the rigid links.
International Publication No. WO 01/33165 to Bucholtz describes an alternative spatial orientation system wherein wavelength changes measured in a triad of optical fiber strain sensors are used to compute the spatial orientation of a catheter or other medical instrument.
An article by J. Peirs et al., entitled "Design of an Optical Force Sensor for Force Feedback during Minimally Invasive Robotic Surgery," published by Katholieke Universiteit Leuven, Belgium, describes a tri-axial force sensor for use generating force feedback systems in a robotic surgery system. The apparatus includes a plurality of optical fibers that direct light onto a mirrored surface disposed adjacent to a distal tip of the device. The intensity of the light reflected from the mirrored surface is measured and may be correlated to the force required to impose a predetermined amount of flexure to the distal tip. The article describes a flexible and compact structure that supports the mirrored surface and produces variations in light intensity responsive to contact forces that deform the structure.
In view of the drawbacks of the previously known catheters, it would be desirable to provide diagnostic and treatment apparatus, such as a catheter, that permits sensing of loads applied to a distal extremity of the apparatus, but which do not substantially increase the insertion profile of the apparatus.
It further would be desirable to provide diagnostic and treatment apparatus, such as a catheter, that permits the computation of forces applied to a distal extremity of the apparatus, and which is substantially immune to electromagnetic interference.
It also would be desirable to provide a catheter having force-sensing capability that includes a compact and flexible force measurement structure that may be used to modulate reflected light intensities responsive to contact forces arising from contact between a distal end of the catheter and a target organ or vessel.
In view of the foregoing, it is an object of the present invention to provide a diagnostic or treatment catheter that permits a tri-axial sensing of the forces applied to an extremity of the catheter, including periodic loads arising from movements of the organ or tissue.
It is another object of this invention to provide a catheter for detecting and monitoring contact forces between the catheter and the wall of an organ or vessel, to facilitate the speed and accuracy of such mapping.
It is a further object of the present invention to provide a catheter having a load sensing system coupled to an end effector of a diagnostic or treatment catheter, so that the end effector is operated, either manually or automatically, only when the contact force is detected to fall within a predetermined range.
It is also an object of this invention to provide a diagnostic and treatment catheter that permits sensing of loads applied to an extremity of the catheter, but which do not substantially increase the insertion profile of the apparatus.
It is yet another object of the present invention to provide a catheter for use in a hollow-body organ, such as the heart, that permit sensing of loads applied to an extremity of the catheter during movement of the organ, so as to optimize operation of an end effector disposed within the distal extremity.
It is a further object of this invention to provide a catheter having force-sensing capability that includes a compact and flexible force measurement structure that may be used to modulate reflected light intensities responsive to contact forces arising from contact between a distal end of the catheter and a target organ or vessel.
These and other objects of the present invention are accomplished by providing a catheter comprising a flexible elongated body and a tri-axial force sensor affixed to an extremity of the flexible elongated body. The tri-axial force sensor includes a housing having a plurality of mirrored surfaces and optical fibers associated therewith. The optical fibers are disposed relative to the housing to detect light intensity changes resulting from longitudinal and radial deformations of the housing. A controller is provided to compute a force vector responsive to-detected light intensity changes.
In one embodiment, the housing comprises a plurality of columnar members narrowly spaced from each other and extending longitudinally between a proximal ring and a distal ring. Preferably, the columnar members are spaced equi-distant around the longitudinal axis and define a parallelogram-shaped structure. Each columnar structure preferably includes a pair of longitudinal beams that are substantially parallel and joined to a pair of lateral beams that are also substantially parallel.
One of the longitudinal beams extends longitudinally to join the parallelogram-shaped structure to the proximal ring and an opposite longitudinal beam also extends longitudinally to join the parallelogram-shaped structure to the distal ring. Preferably, the longitudinal beams have a larger cross-section than the lateral beams. The housing additionally may comprise mating tongue-and-groove indentations between neighboring longitudinal beams to protect the optical fibers from axial overload.
The tri-axial forces sensor further comprises a reflective surface disposed within the housing that reflects differing amounts of light to the optical fibers responsive to the contact forces applied to the housing. In a preferred embodiment, at least one of the optical fibers is disposed so as to detect a variation in reflected light intensity due to a change in the size of a gap between two columnar members, and at least one of the optical fibers is disposed to detect a variation in reflected light intensity due to a change in the size of a gap between a lateral beam and a proximal or distal ring. Preferably, two of the optical fibers are spaced equi-distant apart around the circumference of the housing, e.g., 90 degrees or 120 degrees.
The extremely small dimensions of the optical fibers and compact design of the housing provide ample space in the distal extremity of the catheter to house one or more end effectors for other diagnostic or treatment purposes, for example, an electrode to measure an electric potential (e.g., to perform an endocavity electrocardiogram), an electrode configured to ablate tissue by deposition of radiofrequency energy, an irrigation channel, and/or a three-dimensional positioning sensor.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:
The present invention is directed to a catheter for the diagnosis and treatment of a bodily vessel or organ, in situations where it is desired to detect and measure contact forces between a distal extremity of the catheter and a wall of the organ or vessel. The force sensing capability of the catheter may be used intermittently to measure the contact forces at discrete points, or alternatively, used to continuously monitor contact forces to assist in the manipulation and operation of the device.
In a preferred embodiment, the catheter of the present invention may be manually operated by a clinician and employs a visual or audio cue generated by the output of the tri-axial force sensor so to determine, e.g., an optimum position for measuring an electro-physiologic value or for performing a treatment. Advantageously, a catheter equipped with the force sensing system of the present invention is expected to permit faster, more accurate diagnosis or treatment of a vessel or organ, with improved registration between spatial locations and applied pressures.
For example, a catheter having the inventive force measuring capability would enable the application of adequate pressure against a tissue or an organ without perforating or damaging the tissue or organ because of the clinician's lack of tactile response to the applied pressure. This causes the results of the insertion process to be less dependent on the skill of the individual clinician and facilitates automated procedures.
Referring to
In one preferred application, catheter 10 is configured as an electrophysiology catheter for performing cardiac mapping and ablation. In other embodiments, the catheter may be configured to deliver drugs or bioactive agents to a vessel or organ wall or to perform minimally invasive procedures such as transmyocardial revascularization or cryo-ablation.
Referring now also to
The distal ends of optical fibers 21 are disposed relative to the housing 20 to emit light onto reflective surfaces of housing 20 and to collect light reflected from those surfaces. Optical fibers 21 may be arranged in pairs, with one optical fiber coupled to an emitter, e.g., a light source such as a LED or a tunable laser diode, and another optical fiber coupled to a receiver, e.g., a photodiode, to generate a signal corresponding to the intensity of the reflected light. The emitters and receivers for each pair of optical fibers may be located either in proximal portion 15 of the catheter or controller 17. Alternatively, the emitter and receiver may be optically coupled to a single optical fiber disposed in catheter 10 via a suitable optocoupler, thereby reducing the number of optical fibers extending through flexible elongated body 12.
Still referring to
Columnar members 30 extend between distal ring 31 and proximal ring 32, and each have parallelogram-shaped structure 33. Each parallelogram structure 33 comprises two substantially parallel longitudinal beams 34 and 36 and two substantially parallel lateral beams 38 and 40. The connection of columnar members 30 to distal and proximal rings 31 and 32, respectively, is provided by having longitudinal beam 34 extend to connect to distal ring 31, and longitudinal beam 36 extend to connect to proximal ring 32.
Columnar members 30 are arranged so that when closed to form a circular cylinder, as in
Optical fiber 21 c likewise extends through aperture 47 so that light is emitted into gap 48 and impinges upon the reflective surface of mid-span 49 of another of lateral beams 38. Optical fibers 21 a-21 c collect light reflected from free edges 46 and mid-span 49, and provide signals corresponding to the intensity of light reflected from those surfaces to controller 17 for processing, as described below.
The mode of deformation of columnar members 30 is depicted in
Likewise, when radial force Fradial is applied to columnar member 30, longitudinal beams 34 and 36 deflect elastically towards or away from one another, while lateral beams 38 and 40 remain essentially undeformed. This movement of longitudinal beams 34 and 36 will reduce or increase the size of gaps 48 between longitudinal beams 34 and 36 of adjacent columnar members 30. Consequently, light reflected to optical fibers 21 a and 21 b, positioned to collect light reflected from free edges 46 of adjacent columnar members 30, will increase or decrease in intensity as gaps 48 change size. The change in gap size 48 also may be empirically correlated to the applied radial force, so that a given change in reflected light detected by optical fibers 21 a and 21 b may be used to compute an applied radial force.
In view of the foregoing, it will be understood that when a force having both radial and axial components is applied to housing 20, columnar members 30 will experience both longitudinal and radial displacement, as depicted in
In a preferred embodiment, gaps 45 and 48 typically are less than 100 μm. For example, for a housing having a length of 8.85 mm, an outer diameter of 5 mm and a wall thickness of 0.5 mm for the columnar member, gaps 45 and 48 may be in a range of approximately 50 μm to 100 μm, and may have a usable range of applied axial and radial forces from about 0.1 N to 5 N.
As described above, housing 20 of the tri-axial force sensor of the present invention is configured to decompose contact forces applied to distal extremity 13 of catheter 10 into radial and axial components that result in deflections of the longitudinal and lateral beams of the columnar members. These deflections, which are detected based upon changes in the intensity of reflected light collected by optical fibers 21 a-21 c, may then be used by controller 17 to determine the contact force applied to the distal extremity.
In a preferred embodiment, controller 17 is preprogrammed or uses catheter-specific algorithms or look-up tables to convert the light intensity changes to corresponding force components. Controller 17 further may be programmed to use these force components to compute a multi-dimensional force vector quantifying the contact force. The resulting force vector then may be displayed in real-time in any of a variety of formats, useful to the clinician, on a display screen associated with controller 17.
For example, controller 17 may provide the values for the measured contact forces as numerical values that are displayed on a screen associated with controller 17. Alternatively or in addition, the display screen may include a graphic including a variable size or colored arrow that points at a position on the circumference of a circle to visualize the magnitude and direction of the transverse force applied to the distal extremity of the catheter. By monitoring this display, the clinician may continuously obtain feedback concerning the contact forces applied to distal extremity of the catheter.
Because the light intensity-force conversion table or algorithm may be housing specific, it is contemplated that it may be necessary to generate a catheter-specific table or algorithm during manufacture of the catheter. This information, which is then supplied to the controller when the catheter is used, may be stored with the catheter in the form of a memory chip, RFID tag or bar code label associated with the catheter or its packaging.
Turning now to
Housing 50 preferably is formed by laser cutting or electro-discharge machining ("EDM") a titanium alloy tube, such as Ti6Al4V, and includes stops 51, consisting of mating tongue-and-groove indentations sculpted in longitudinal gaps 68. Stops 51 limit axial deflections of the beams of housing 50 to prevent axial force overloads that could impose plastic strains and thus ruin the tri-axial sensor. Circular openings 52 may be provided as starting openings when using an EDM process to machine gaps 45 and 48, and various other slits. Housing 50 includes apertures (not shown) that permit placement of the optical fibers to measure light intensity changes resulting from deformation of the housing, as discussed above with respect to the embodiment of
While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.
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The studio space of the Architecture + Health program is located in 104 Lee hall. The studio was recently renovated in the fall of 2010, bringing a healthy and modern space both students and faculty. New features from the renovation include operable windows, access to the exterior balcony, comfortable lighting, new workstations/computers, a simple kitchen, and an advanced media center. Keeping with our ethos of healthy and creative collaboration, the studio of the MA students is adjacent to the MS/P.h.D students and the research lab.
Check out more images of our studio on our Interactive Floor plan (flash file)!
Opening its doors in fall 2005, the Clemson University Schools of Nursing and Architecture + Health established a collaborative partnership in designing and in constructing the new CLRC. The Architecture + Health program has an ongoing collaboration with the CLRC as it houses a patient room prototype mockup that is used for study and research in the patient environment.
More images of the CLRC - Interactive Floor Plan (flash file).


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Secrets of the Dead: Blackbeard's Lost Ship DVD
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Easter Island has mystified the world ever since the first Europeans arrived in 1722. How and why did the ancient islanders build and move nearly 900 giant statues, and how did they transform a presumed paradise into a treeless wasteland, bringing ruin upon their island and themselves? NOVA explores controversial recent claims that challenge decades of previous thinking about the islanders.More >
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Description : La Thérapie pour les cheveux Rare Blend Oil d'Ojon est une huile pour les cheveux aux multiples bienfaits qui renferme 7 huiles naturelles pour procurer une hydratation intense et favoriser la brillance des cheveux. À qui ce produit s'adresse-t-il : Ce produit s'adresse aux personnes qui ont les cheveux très secs et abîmés. Effets : Ce produit contient 7 huiles : de l'huile d'Ojon, d'oleifera rouge, de monoï tahitien, de marula, de melon du Kalahari, de kukui et de ximénia qui proviennent du monde entier et qui sont connues pour leur composition unique. Elles vous aident à faire face à toute une gamme de préoccupations relatives aux cheveux. Vous obtiendrez des boucles brillantes et nourries en un clin d'œil! Comprend : • Thérapie pour les cheveux Rare Blend Oil (45 mL)
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Par Shopaholic
de edmonton
This oil is not only amazing,but awesome ,u can't believe how soft it makes ur hair,even after showering,not greasy at all an only need a little,u must try it!!!!
En résumé
Oui, je recommanderais ceci à un ami
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Great stuff
Par Bush Bunny
de LODGEPOLE, AB
I have just purchased this for the first time and I wish I had done so a long time ago. My hair is very fine and no matter what I do I have trouble combing after I wash it. With or without cream rinse I got some breakage. I tried this on wet hair and put a comb through it right away. Amazing is all that I can say. With over 36 inches of hair you are bound to get breakage but this oil has all but stopped the problems with my hair. Thanks Ojon. I so wish that were staying on the Channel.
ojon rare blend oil
Par barbara
de courtice, ontario
this product works well on its own or with other ojon products, but you only need a small drop, I put too much on and my hair looks oily, I use after shampooing and styling my hair is much easier
ojon rare blend oil total hair therapy
this product works very well, only use a tiny drop as I used too much first time, made my hair look oily, have color treated hair and short hair, use after shampoo and my thick hair is easy to style and makes my hair shiny and healthy looking, also smells great, great product
Not for me!
Par Sandy
de Calgary, AB
I was disappointed, I have used Ojon for years, until they changed the original formula. I Tried this when my hair was wet and also when it was dry, I have long blonde fine hair, I found it weighed my hair down! I would not recommend this product. Sorry.
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Non, je ne recommanderais pas ceci à un ami
( 3 of 3 clients ont trouvé ce commentaire utile)
Great for fine, thin frizzy hair.
Par Lori
de Montreal
I got a sample of this product in the Summer Cosmetics bag. I have fine short curly hair and have been on the lookout for years for a product that makes my hair dry hair shine. It's hard to get curly hair to shine without using heavy products that are greasy. I have used Moroccain oil and others and find them heavy. I used this on damp hair and could not believe how shiny and moisturized my hair was after I blew it dry! The ends were sealed, my highlights were brilliant and it kept the frizz away better than most serums. At 51, I have literally tried everything, money being no object- and this is the best hands down.
( 2 of 2 clients ont trouvé ce commentaire utile)
A dab will do ya
Par Jewels
de Toronto
Smells nice, makes hair shiny, put just a bit on fingertip and massage thru, use every day. Great product.
( 4 of 4 clients ont trouvé ce commentaire utile)
Best finishing product
Par Anna
de Edmonton
This is the best finishing product I've used, and it's a very good complement to the Damage Reverse Restorative Shampoo and Conditioner. It brings back the look of young, healthy hair better than any other similar product I've tried. And the smell is gentle and delicious. Please note: it's a light OIL, NOT a serum with all the usual fillers that we've all tried. As another reviewer mentioned, the amount that sticks to your finger from the opening when you shake it up is usually enough even for my longish hair. I bet everyone uses too much the first time.This is my all time second favorite hair product after the Ojon Rare Blend Deep Conditioner (see review).
wonderful stuff
Par Janice
de Caledonia Ontario
This product along with the shampoo and conditioner is the first product I have found that make my dry frizzy hair controllable. The rare oil lets me for the first time be able to flat iron my hair so that it actually looks smooth and silky.
Rare Blend Oil is a winner
Par Jacquie
de Mississauga, On
Lovely and light for daily useI only have to use a little and it goes a long wayI love the benefits my hair is softer smoother and so manageable.


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It is that time of the year again. Time to travel! As YOU, our fans, embark on some amazing vacations and adventures this summer, we at Bobsled want to remind you about staying in touch. Flights can be long and arduous, trust us we know. There is nothing more annoying than not having access to communication for 6 – 10 hours while you sit in your passenger seat.
In a time where we are more connected than ever, a question begs to be answered: When is it not appropriate to be on your cell phone? First, we were curious about dating. Do you use your cell phone on a date, or do you abide by a strict "phone's off" policy?
Have you ever wondered why we say what we say? Who decided the greeting when answering your phone should be "Hello"? Someone had to! We thought we'd explore a little bit of history, and what we found was pretty interesting.
Spring break has finally ended and it is now officially Spring Quarter! You know what that means, time to study abroad. According to a recent survey, roughly ¼ of college students in the United States went off to study abroad programs in 2011!
Bobsled connects many different people, including long-lost friends. How? By connecting your Bobsled account to your Facebook account, you can easily leave voicemails for your old friends on their timelines!
First, Bobsled would like to thank military families for all the sacrifices you make in order to keep our families safe and our country free.