1. A process for preparing methacrylic acid, comprising:
reacting a liquid reaction mixture comprising methacrylamide and water,
wherein the reacting is effected continuously in a vertically aligned tubular reactor, wherein there is a pressure difference within the tubular reactor in the flow direction of the reaction mixture, and
wherein the pressure difference is generated by hydrostatic pressure between the top and bottom of the tubular reaction.
2. The process according to claim 1, wherein the pressure difference between the inlet of the reactants and the outlet of the products from the tubular reactor is at least 1 bar.
3. The process according to claim 1, wherein the reactants are reacted at a high pressure at the start of the reaction and at a lower pressure at the end of the reaction.
4. The process according to claim 1, wherein the temperature is measured and regulated in at least two regions.
5. The process according to claim 1, wherein the reacting is effected at a temperature within the range of 90\xb0 C. to 150\xb0 C.
6. The process according to claim 5, wherein the reacting is effected at a temperature in the range of 90 to 130\xb0 C. at the start of the reaction and in the range of 110 to 150\xb0 C. at the end of the reaction.
7. The process according to claim 1, wherein the reactants are reacted at a lower pressure at the start of the reaction than at the end of the reaction.
8. The process according to claim 7, wherein the temperature at the end of the reaction is at least 5\xb0 C. higher than at the start of the reaction.
9. The process according to claim 7, wherein the temperature at the end of the reaction is at most 25\xb0 C. higher than at the start of the reaction.
10. The process according to claim 1, wherein the reaction is effected at a pressure in the range of 1.5 bar to 6 bar.
11. The process according to claim 10, wherein the reacting is effected at a pressure in the range of 2 to 6 bar at the start of the reaction and at a pressure in the range of 1.5 to 5 bar at the end of the reaction.
12. The process according to claim 1, wherein the tubular reactor is flowed through from the bottom upward.
13. The process according to claim 1, wherein the reaction is catalysed with acid.
14. The process according to claim 1, wherein the reaction mixture comprises at least one stabilizer.
15. The process according to claim 1, wherein the molar ratio of water to methacrylamide in the reaction mixture is in the range of 1:1 to 7:1.
16. The process according to claim 1, wherein a mixture is reacted which comprises
10 to 40% by weight of methacrylamide,
20 to 50% by weight of water,
30 to 65% by weight of sulphuric acid and
0 to 5% by weight of additional additives.
17. The process according to claim 1, wherein the pH during the reacting is in the range of 1 to 2.
18. The process according to claim 1, wherein the residence time in the reactor is in the range of 10 minutes to 2 hours.
19. The process according to claim 1, wherein the tubular reactor is vertically aligned with less than 5\xb0 deviation from 90\xb0.
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 passively stabilized wheeled object comprising
an object body;
at least one primary wheel assembly comprising two wheels, spaced apart from each other and mounted to the object body to rotate about a common axis, the primary wheel assembly being defined by a first set of coordinates x, y and z, wherein x is the direction of motion, y is vertical and z is the direction along the common axis of the primary wheel assembly and a second set of coordinates x1, y1 and z1 defined relative to the earth, such that when the object is at rest, the coordinates x, y and z substantially match y1, x1 and z1, respectively, and when the object tips, an angle \u03b8 between the z and z1 axes is greater than zero; and
at least one secondary wheel assembly comprising at least two secondary wheels, disposed on opposite sides of, and spaced further apart than the wheels of the primary wheels assembly, each of the secondary wheels is further defined by a cant axis and an angle \u03c8 that is not equal to zero and represents rotation about the cant axis in a direction away from the x axis such that the secondary wheel assembly is not aligned with the direction of motion;
wherein the secondary wheel assembly restores the angle \u03b8 to zero when the object tips.
2. The apparatus of claim 1 wherein the cant axis is defined by an angle \u03be which is the angle between the coordinate axis x1 and the cant axis, and expressed in the coordinates system attached to the wheeled object as follows:
x1=cos \u03be
y1=sin \u03be
z1=0.
3. The apparatus of claim 2 wherein the angle \u03be is chosen to be about 90-\u03c6 degrees, where \u03c6 is the \u201cusual\u201d pitch angle of the wheeled object when towed by its user.
4. The apparatus of claim 1, wherein the absolute value of the angle \u03c8 is in the range of about 5 degrees to about 55 degrees.
5. The apparatus of claim 1, wherein the absolute value of the angle \u03c8 is in the range of about 10 degrees to 40 degrees.
6. The apparatus of claim 1 wherein the primary wheels rotate about a primary axis and the secondary wheels rotate about secondary axes, and wherein the secondary axis of each of the secondary wheels is displaced vertically from the primary axis of the primary wheels.
7. The apparatus of claim 1 wherein the primary wheels rotate about a primary axis and the secondary wheels rotate about secondary axes, and wherein the secondary axis of each of the secondary wheels is displaced laterally from the primary axis of the primary wheels.
8. The apparatus of claim 1 wherein the diameter of each of the secondary wheels is smaller than the diameter of the primary wheels.
9. The apparatus of claim 1 wherein the apparatus further comprises more than one set of secondary wheels.
10. The apparatus of claim 1 wherein the object body further comprises a luggage container.