1. A cellular polyisocyanate polyadduct prepared by
(1) reacting (a) one or more diisocyanates with (b) one or more polyether alcohols to form a prepolymer comprising isocyanate groups and an NCO content of less than 10%, and
(2) reacting said prepolymer in a mold with a crosslinking component comprising (e) water and, optionally, (d) one or more sulfated fatty acid esters;
wherein said (b) one or more polyether alcohols comprises a mixture of (b1) and (b3) and optionally (b2), wherein:
(b1) is a polytetrahydrofuran having a molecular weight of from 1800 to 2100 gmol; and
(b2) is a polyether alcohol having a molecular weight of from 500 to 7000 gmol, based on ethylene oxide andor propylene oxide; and
(b3) is a polytetrahydrofuran having a molecular weight of from 800 to 1200 gmol
wherein said cellular polyisocyanate polyadduct has a density, according to DIN EN ISO 845, of from 200 to 800 kgm3; a tensile strength, according to DIN EN ISO 1798, of greater than or equal to 2.0 Nmm2; an elongation at break, according to DIN EN ISO 1798, of greater than or equal to 200%; and a tear propagation resistance, according to DIN ISO 34-1 B (b), of greater than or equal to 8 Nmm.
2. The cellular polyisocyanate polyadduct of claim 1, wherein the weight ratio of (b1) to the sum of (b2) and (b3), wherein the weight of (b2) is optionally 0, is from 11:1 to 2:1.
3. The cellular polyisocyanate polyadduct of claim 1, wherein said (b) one or more polyether alcohols further comprises a polyether alcohol (b2) having a hydroxyl number of less than 500 mg KOHg.
4. The cellular polyisocyanate polyadduct of claim 3, wherein said polyether alcohol (b2) is based on ethylene oxide andor propylene oxide and glycerol andor trimethylolpropane as an initiator.
5. The cellular polyisocyanate polyadduct of claim 1, wherein said mixture comprising (b1) and (b3) has a number average molecular weight of from 1500 gmol to 1900 gmol.
6. The cellular polyisocyanate polyadduct of claim 1, wherein said prepolymer further comprises allophanate groups.
7. The cellular polyisocyanate polyadduct of claim 1, wherein said crosslinking component further comprises catalysts (f) and, optionally, (c) polysiloxanes, (g) blowing agents, andor (h) assistants.
8. The cellular polyisocyanate polyadduct of claim 1, wherein said crosslinking component further comprises tin compounds.
9. The cellular polyisocyanate polyadduct of claim 7, wherein said crosslinking component further comprises amine catalysts.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A vacuum vessel for a magnetic resonance imaging (MRI) system, the vacuum vessel comprising:
a housing configured to receive therein a magnet assembly; and
an end flange forming an end of the housing, wherein the end flange include an outer surface, an inner surface, and a core coupled between the outer and inner surfaces, the core having a greater stiffness than the outer surface and the inner surface.
2. The vacuum vessel of claim 1, wherein the end flange is generally planar.
3. The vacuum vessel of claim 1, wherein the outer and inner surfaces are formed from a metal material and the core is formed from a composite material.
4. The vacuum vessel of claim 3, wherein the metal material is stainless steel.
5. The vacuum vessel of claim 3, wherein the metal material has a thickness of about two millimeters.
6. The vacuum vessel of claim 1, wherein the outer and inner surfaces are formed from fiberglass.
7. The vacuum vessel of claim 1, wherein the core is formed from a metal in a honeycomb type configuration.
8. The vacuum vessel of claim 7, wherein the metal is aluminum.
9. The vacuum vessel of claim 1, wherein the outer surface comprises a flammability resistant material.
10. The vacuum vessel of claim 1, wherein the outer surface defines an outer housing of the vacuum vessel and not including a cover.
11. The vacuum vessel of claim 1, wherein the outer surface, the inner surface, and the core are coupled together in a sandwiched arrangement and having an overall thickness of about ten millimeters.
12. A magnet system for a magnetic resonance imaging (MRI) device, the magnet system comprising:
a vacuum vessel having at least one end flange formed from a non-solid core having outer and inner surfaces forming planar walls, the non-solid core having a greater stiffness than the outer and inner surfaces;
a cryogen vessel having liquid helium therein, the cryogen vessel within the vacuum vessel; and
a superconducting magnet within the cryogen vessel.
13. The magnet system of claim 12, wherein the outer and inner surfaces are formed from a metal material and the non-solid core is formed from a composite material.
14. The magnet system of claim 13, wherein the metal material is stainless steel and has a thickness of about two millimeters, and the outer surface, the inner surface, and the core are coupled together in a sandwiched arrangement and having an overall thickness of about ten millimeters.
15. The magnet system of claim 12, wherein the outer and inner surfaces are formed from fiberglass.
16. The magnet system of claim 12, wherein the non-solid core is formed from a metal in a honeycomb type configuration.
17. The magnet system of claim 12, wherein the outer surface comprises a flammability resistant material.
18. The magnet system of claim 12, wherein the outer surface defines an outer housing of the vacuum vessel and not including a cover.
19. A method of manufacturing a flange for a vacuum vessel for a magnet resonance imaging (MRI) system, the method comprising:
forming a core, an outer surface and inner surface of a vacuum vessel flange, the core having a greater stiffness than the outer surface and the inner surface; and
coupling together the core with the outer and inner surfaces, the core between the outer and inner surfaces and together defining a generally planar vacuum vessel flange.
20. The method of claim 19, wherein the outer and inner surfaces are formed from a metal material and the core is formed from a composite material, the core coupled together in a sandwiched arrangement with the outer and inner surfaces and having an overall thickness of about ten millimeters.