Spiral tube winding

Adhesive, Dextrin (Spiral Tube Winding for Ammunition Containers) US Spec MIL-A-13374C (June 1969)... 

The tackified polyvinyl alcohols, introduced in the early 1960s, rapidly replaced starch/urea formaldehyde adhesives in solid fiber laminating and dextrine, compounded polyvinyl acetate and sodium silicate adhesives in spiral tube winding. The new adhesives demonstrated superior adhesion over silicates and dextrines to a wide variety of paper substrates. These adhesives reduce warp in solid fiber laminating and shrinkage in spiral tubes because of the low adhesive application rate and, thus, low amount of water added to the laminations. The low application rate and low resin level also made these adhesives very economical. 

The influence of spiral tube diameter d on separation efficiency is greater than that of screw diameter D. The optimum design parameters of the device are the tube diameter 8 mm, screw diameter 300 mm, and number of windings N can be chose according to the actual separation system. The separation efficiency of this device can reach 0.63. 

Tube winding is either spiral (a continuous winding where adhesive is applied to outer plies as they are wrapped on a cylindrical mandrel), or convolute (where the sheet is as wide as the mandrel is long, and the mandrel wraps the sheet over itself). The tube is removed from the mandrel by a pusher arm. Convolute adhesives are usually used cold, while spiral adhesives may be used at 131°F (55°C). Many starch products may be used, but 50% solids borated dextrins are common, as seen in Table 4. 

The upper outlet for water from the condenser should be above the jacket so as to ensure that the condenser is full of water. If the rubber tube, which carries the waste water to the sink, tends to kink, a short copper spiral, made by winding a length of copper wire round a glass tube, may be slipped over the end attached to the condenser. 

Prepare a coil of copper wire by winding several turns around a glass tube. Heat the coil in the oxidising flame of a Bunsen burner for 1-2 minutes and plunge the spiral, whilst still red hot, into a test-tube containing a solution of 1 ml. of methyl alcohol and 5 ml. of water. Stopper the test-tube loosely, cool, remove the wire, and repeat the process two or three times. Observe the odour of the solution and use it (or formalin diluted with water) to carry out the following tests. 

It is often easier to wind a spiral on a mandrel or former of carbon, metal tubing or glass tubing wrapped with asbestos paper. A right-angle bend is made in the tube to give a short portion at the end which... 

Spiral winding calls for skill and concentration. Thin-walled glass quickly overheats and loses its uniform shape, so it is better to practise with medium-walled tube and to make successive turns about 5 mm apart. 

Should a spiral be required of such dimensions that a 5 ft length of tubing will not suffice, then the join should be made before winding begins. This join must be quite uniform in wall-thickness and diameter, since otherwise it will not bend smoothly and will show up as an obvious defect in the finished coil. 

FIQ. 8.13. (Left) Spiral coils, "(a) Shows tlie small U-bend ready to hook into the metal loop on tlie forming tool, (b) Tlie elevation of tlie tube at tlie beginning, (c) Tlie elevation of tlie tube when winding is under way. 

C) Oxidation of Methanol. Place 1 ml of methanol and 5 ml of water into a test tube. Prepare a spiral of copper wire by winding it around a glass tube. Heat the spiral until it is red hot and plunge it immediately into the dilute alcohol. Repeat the operation three times. Note the odor of the solution. Filter and test the solution with Tollen s reagent and Schiff s reagent according to sections (B) and (E), Experiment 34. 

---