Laminate tubes

Heat and oil resistance coupled with its low swell have led automotive apphcations into laminated tubing and hoses (11) with this material. This resistance to the effects of ASTM No. 3 oil at service temperatures of 200°C makes it competitive with fluorocarbons and with the tetrafluoroethylene—propylene copolymer. Fluorosihcones are used to make exhaust gas recirculation (EGR) diaphragms for some passenger cars. 

Figure 4. Head conduction through a laminated tube with fluid at temperature inside and fluid temperature Tj outside. (From Transport Phenomena by R. B. Bird, W. E. Stewart, andE. N. Lightfoot, p. 287, John Wiley Sons, Inc., 1960. Used with permission.)...

Semi-solid products have been traditionally packed in collapsible tin tubes. Metal tubes are a potential source of metal particles in ophthalmic products, and so the tubes have to be cleaned carefully prior to sterilisation. Also, the final product must meet limits for the number of metal particles found. Plastic tubes are not suitable because of their non-collapsible nature, which causes air to enter the tube after withdrawal of each dose. However, collapsible tubes made from laminates of plastic, aluminium foil and paper are a good alternative to tin tubes. Laminated tubes fitted with polypropylene caps can be sterilised by autoclaving, whereas tubes fitted with polyethylene caps are sterilised by gamma irradiation. The tubes are usually filled aseptically, sealed with an adhesive and then crimped. 

In addition to internal or external coatings, barrier enhancers can be incorporated into the plastic as additives. These can include various metal oxides, glass fibre, mica, etc. Incorporating a foil ply between layers of plastic is a further way of obtaining excellent barrier properties, e.g. multilayer laminated tubes, cold formed blisters, and additional overwraps should not be ignored. 

Good gas and odour barrier. Good moisture value when dry, but as moisture is absorbed, moisture barrier properties reduce. Relatively expensive. Usually used as a central ply in coextrusion processes. Replacing foil layer in some laminated tubes. Good barrier to certain flavours peppermint, spearmint, etc. 

One of the more complex laminates used consisted of clear LDPE/LDPE white/paper/LDPE/LDPE copolymer/30-50 Pm, EVOH or A1 foil/LDPE copolymer/ LDPE clear. As another example, many laminated tubes now consist of five layers e.g. two plies LDPE/40 4m foil/two plies LDPE. 

The properties of metal and plastic have been combined in the form of a laminated tube, which consists of a polyethylene/ aluminium foil/polyethylene or similar laminated body fitted with a polyethylene nozzle and is less permeable than a conventional polyethylene tube with less tendency to draw air back. To date the main usage of laminated tubes has been for toothpastes, but wider pharmaceutical applications are now found. 

The use of laminates for collapsible tubes is an example of the success of a new approach. The fact that the word collapsible has been maintained indicates that the pack may be subjected to rather severe handling. It is for this reason that the usually central foil ply is 40 4m thick. Most laminated tubes are five to seven plies with the decoration being a sandwich print. 

Laminated tubes are made from multilayer materials that usually contain paper as well as plastic, and often also include aluminum foil as a barrier layer. The preprinted tube bodies are sealed into a cylinder, with the edges of the sleeve overlapped and compressed, squeezing some of the plastic out around the raw edges of the foil and paper to make a good seal. Next the tube is cut to length, and finally the head is molded and assembled to the body. To improve the barrier in the head, a premolded insert of polybutylene terephthalate or urea can be incorporated in the injection mold when the head is formed. 

Brief mention may be made here of a compression test that measures the cohesion between layers of laminated tube as given in BS 2782. Method. 346A. This is covered more fully in Chapter 18. 

In the broad sense, interlaminar adhesion means the adhesion between any laminations of similar or dissimilar materials and hence could be taken to include just about any adhesion test. One particular type for fiber-reinforced plastics, which is known as interlaminar shear strength, is normally considered as a short beam flexural test (sec Chapters 9 and 18). A method peculiar to laminated plastics tube is given in BS 2782, Method 346A [59] and called cohesion between layers of laminated tube. A sample of tube is subjected to compression to induce shear forces between layers and delamination observed by eye,... 

BS 2782. Method 346A, 1984. Cohesion between layers of laminated tube. 

D348 Laminated tubes D704 Melamine-formaldehyde molding... 

Filament winding on molds is used to produce large laminated tubes and storage tanks. The continuous glass fiber is guided into a tank filled with resin and then through an orifice to remove excess resin, and finally is wound onto a core. The part is cured in an oven, the core is removed, and additional finishing steps are completed. 

Fiber Cans and Tubes. The basic material used for fiber tubes and cans is a bending board. The body of a fiber can usually is of paperboard and the ends usually are of metal, paperboard, or plastic. The constmction of the body may be one of three general types sprial-wound tubes and cans, convolutely wound tubes and cans, or laminated or lap-seam cans. 

Adhesives for paper tubes, paperboard, cormgated paperboard, and laminated fiber board are made from dispersions of clays suspended with fully hydrolyzed poly(vinyl alcohol). Addition of boric acid improves wet tack and reduces penetration into porous surfaces (312,313). The tackified grades have higher solution viscosity than unmodified PVA and must be maintained at pH 4.6—4.9 for optimum wet adhesion. 

Elimination. Since laminations result from steel-making and steelforming processes, little can be done to eliminate defects once they have survived quality inspections at the mill. If laminations are suspected, ultrasonics or radiography may disclose them. They may also be observed visually at cut ends of plate, pipe, or tubes if the cut intersects the lamination. 

H. Ozonizalion of organic compounds. The ozonization of each unsaturated organic compound is more or less an individual problem, but some general comments may be made. Organic ozonides are highly explosive, and hence it is safest to carry out the ozonization in a solvent which dissolves both the original compound and the ozonide. In all cases, a shatterproof screen of laminated safety glass should be placed between the operator and the tubes H, I, and J. A second screen should be placed back of the tubes to protect other pieces of the apparatus. 

Current usage is almost entirely associated with the good adhesion to aluminium. Specific applications include the bonding of aluminium foil to plastics films, as the adhesive layer between aluminium foil and polyethylene in multilayer extrusion-laminated non-lead toothpaste tubes and in coated aluminium foil pouches. Grades have more recently become available for manufacture by blown film processes designed for use in skin packaging applications. Such materials are said to comply with FDA regulations. 

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