AU7790491A - Binder for absorbing oily liquids - Google Patents

Description

Binder for absorbing oily liquids

The invention relates to a process for manufacturing a recyclable binder made from hydrophobic polymer fibres for absorbing crude oil and derivatives thereof or other oily liquids, from water, from a water surface or from the ground. The invention also relates to a recyclable binder made from hydrophobic polymer fibres.

Crude oil and derivatives thereof, such as for example heating oil, diesel oil, petrol and other motor fuels, but also other oily substances, also referred to in brief as oily liquids or oils in the text which follows, are transported to land and water more and more frequently, in increasing amounts and in larger containers. Damage which may lead to environmental catastrophes is a threat in the event of an accident. However, damage, which assumes a large dimension, may occur even in the case of smaller transport containers, if it cannot be prevented rapidly and using simple means. In this context, the oil fighters of local fire brigades, which have to take the first measures for the prevention of water pollution and protection of drinking water facilities, should be mentioned by way of example.

German Auslegeschrift 1 939 490 describes fibre mixtures for limiting or eliminating contaminating oil from a water surface. The fibre mixture may contain plastic fibres. Polypropylene or polyethylene fibres, even for covering nets, are emphasised in particular. Finally, squeezing out is mentioned for the re-use of absorption devices.

United States application 3 539 013 mentions that absorption pads made from polymer fibres, in particular polypropylene fibres of high density, which are randomly orientated, are used for absorbing oil. Special device features are described which relate to coverings, reinforcing ropes for coverings and the like.

Experiments using a comparable make from the roll (PULPLUS, a DUPONT product) have shown that the absorption capacity of a compact nonwoven is very limited for oil. Thus it has been shown, for example that an amount of oil, which corresponds approximately to the polyethylene tape nonwoven's own weight, may be absorbed after one hour of immersion in diesel oil and five minutes draining.

The inventor is faced with the object of providing a process of the type mentioned in the introduction by means of which a binder, which may absorb many times its own weight of oily liquid with a high retention capacity, is produced for absorbing oily liquids. The simple and economical process should make available a binder which permits ecologically harmless recycling of the oily liquid or removal.

With respect to the process, the object is achieved according to the invention in that wet polyolefin fibrils cooled in water are placed on a water-permeable tape continuously circulating over at least two rollers, guided on a heated roller of large diameter while draining the water, dried on the surface thereof to form a compact, tape-like nonwoven, then compressed and wound or cut into sections, which nonwoven is passed to a comminuting or disintegrating machine for impacting, after appropriate storage, a loosened, flaked, hydrophobic pulp being produced which has a large absorption capacity for oily liquids. Special embodiments and further developments of the invention are the object of dependent patent claims. The compact, tape-like or cut starting nonwoven is preferably passed to a hammer mill or a mixer of conventional construction.

The polyolefin fibrils of the pulp flakes leaving a comminuting or disintegrating machine in the form of flakes are preferably joined to one another at points by melt adhesion, this is also termed thermobonding. A pulp thus attains a certain dimensional stability, even after the absorption of oil it does not fall apart. However, the number of point adhesions is measured so that the pulp remains expandable and the absorption capacity for oil is not reduced or is reduced only imperceptibly.

The point adhesion is carried out advantageously by partially melting fibrils in a hot stream of air or by contacting with at least one heating surface which may be a stationary (plate) or a moving (roller, belt) shaping surface.

The preferred temperature for the thermobonding known per se is in the range from 160 - 220°C, which is advantageously used for 1 to 2 minutes to prevent the fibres from melting to too great an extent.

The pulp flakes may be joined together to form a flat pulp in accordance with processes known per se at the same time as or after thermobonding. This loosened flat pulp is preferably designed to be like a tape, also continuous, it may be wound or stacked folded, even after applying a tear-resistant outer shell.

The PULPLUS product from Messrs. DUPONT mentioned above is particularly suitable as a compact starting nonwoven of about 1 mm thickness. Experiments using loosened pulps arranged in an oil-permeable covering or having a flat shape manufactured according to the process of the present invention, have shown that the oil absorption capacity is increased considerably using binders manufactured according to the invention. Hence, for example a pulp made from polyethylene fibrils impacted using a hammer mill, absorbed approximately ten times its own weight of diesel oil within just one hour after five minutes draining.

The full absorption capacity of a loosened pulp manufactured according to the invention is at least 15 times, preferably at least 20 to 30 times its own weight, the oily liquids being absorbed with retention capacity. However, no water an also no other hydrophilic moisture or liquid is absorbed to a appreciable extent because of the hydrophobic nature of the polyolefin fibrils.

The loosened pulp used as absorption material reacts differently depending on the nature and the viscosity of the oil. The full absorption capacity may usually be achieved after about 2 to 4 hours.

The polyolefin fibrils preferably consist of polyethylene or polypropylene of high density, they are advantageously about 1 mm long and have a diameter of 1 - 20 p.

The solution of the invention is characterised with reference to the recyclable binder in that the polyolefin fibrils are joined to one another at points by means of thermobonding.

A pulp fully soaked with an oily liquid floating on a water surface remains intertwined or linked, in as far as it is treated by means of thermobonding, no powder or other oil-soaked components sink. The pulp may be distributed intact or in larger pieces, and may be collected without difficulty for recycling or removal. The pulp is preferably designed as a flat layer and is stored as stacks or rolled up as a tape and transported.

According to a preferred embodiment of the invention, a pulp is embedded in an all-round liquid-permeable, flexible outer shell or a net for improved handling during storage, transport and before, during and after use and to achieve a greater mechanical resistance. This outer shell, nets are also shells, is tear-resistant and resistant to chemicals. It consists of a nonwoven, textile, knitted fabric or net, preferably made from a plastic, such as lor example a polyester or polypropylene.

A flat pulp arranged in a shell may comprise one or more premanufactured layers. The shell must be able to expand several times as much when the oily liquid is absorbed, because of the large oil absorption capacity of the pulp. The shell is therefore folded, for example like a bellows, either in pad or tube form. The shell further advantageously comprises at least one carrying or suspension device for manual or machine transport.

To prevent compression of the fibrils during transport they may be interspersed by a fine grain, neutral powder or by appropriate fibres, for example cellulose fibres treated with sand, polystyrene powder and/or treated to be water repellent. Here neutral means that neither the powder nor the fibres, which are used as a lining, are able to bind water or oil. Sand is also a weighting agent for binders used on land.

The elements of the pulp are designed in dimensions such that they may be carried by one or at the most two people, even when fully soaked, for use on land, for example by oil fighters. For use on water where work is carried out by machine, larger dimensions are possible and they are only limited by the tear resistance of the shell or its drawing reinforcements and suspensions. Drawing reinforcements in the shell serve for pulling, for example two external wires, ropes or chains are integrated to be resistant to pulling, in particular for long elements.

Long sacks or tubes for the pulps are advantageously formed to position a oil barrier, intermediate walls for the formation of chambers preferably being provided at intervals. The intervals of the intermediate walls are preferably between 0.2 and 1 m. This prevents the flowable absorber oil mass from bulging out too much when the sacks or tubes, which may be continuous, are pulled out.

Shorter flat elements with the pulp arranged in a shell may also be preferably releasably connected to one another, or may be fitted with premanufactured devices for connecting to a couple of handles, for the formation of an oil barrier in water as well as on land. An oil fighting stand-by team has elements available which are advantageously connected to one another, these may be carried before use without difficulty in larger, for example rolled up or folded units. Of course individual units as well as open pulps may also be introduced as barrier material.

The shell of a flat element may also have fastening devices for means to hold, pull, float and.^"or weigh down, next to or in addition to carrying or suspension devices. For use on water, in particular for a moving surface, oil barriers are advantageously positioned so that they are not carried off course. Furthermore, it may be advantageous to attach floats to prevent sagging. For oil barriers on land, in particular on roads or squares having collecting channels and/or manholes, it may prove to be necessary to weigh down and/or to fix the elements at critical points.

According to a further variant, elements having covered pulps made from polyolefin fibrils are arranged in the flow cavity of a container having an inlet and an outlet to purify water contaminated with an oily liquid during rinsing. This method is particularly suitable for small amounts of oil in water.

The oil absorption pads can be used universally, they are required for use everywhere where crude oil or derivatives thereof are used, for example in petrol stations, in airports, intermediate stations of pipelines, tankers, garages, in the fire brigade, in particular oil fighting and in civil defence.

The oil soaked up by the pulp can be recovered with lower recycling costs and can be re-used. The pulp raw materials can also be re-used many times without further expense after the oil has been removed.

The invention is explained in more detail using the exemplary embodiments, which are also objects of the dependent patent claims, shown in the drawing.

- Figure 1 shows schematically the manufacture known per se of a compact tape made from polyethylene fibrils,

- Figure 2 shows schematically the principle of impacting this tape using a hammer mill,

- Figure 3 shows schematically a tape-like loosened nonwoven,

- Figure 4 shows schematically a section through a covered, loosened polyolefin pulp, - Figure 5 shows schematically a view of a covered element having polyethylene fibrils,

- Figure 6 shows schematically a cross-section through Figure 5 at VI-VI,

- Figure 7 shows schematically a view of an element folded like a bellows before oil absorption,

- Figure 8 shows schematically a section through an element according to Figure 7 after oil absorption,

- Figure 9 shows schematically a section from an element designed as a continuous tube in longitudinal section, and

- Figure 10 shows schematically a cross-section X-X through the tube according to Figure 9.

Figure 1 shows wet polyolefin fibrils 10, which are placed in direction 12 on a continuous, water-permeable tape 14. This tape 14 designed as a sieve runs in the direction of the arrow 16 around two rollers 18, 20, at least one of which is driven. The wet polyolefin fibrils drain initially on the tape 14, this is characterised by water droplets 24. The residual water of the wet polyolefin fibrils 10 is subsequently evaporated.

The heart of the machine, which essentially corresponds to a paper manufacturing machine, is a heatable roller 22 which has a large diameter, usually about 5 - 10 m. The polyolefin fibrils 10 are compressed to form a compact tape on the surface of the roller. This tape has the same characteristics as cardboard.

The compact tape nonwoven 28 leaving the roller surface 26 is wound onto a reel 30 and stored until it is used. The cardboard-like tape nonwoven 28 is impacted in a hammer mill characterised by an arrow 32 according to Figure 2. The individual fibres are exposed in this manner and form pulp flakes 34 having a loose structure.

Figure 3 shows pulp flakes 34 joined to a loosened pulp tape 36. The pulp flakes 34 are joined, for example using thermobonding, with the formation of numerous joining points. The structure remains very loose and hence the absorption capacity for an oil is large.

Figure 4 shows a bag 38 or tube having an outer shell 40 known per se and permeable to oily liquids and which is adhered on three sides to form a hem 42. The structure of the enclosed pulp flakes 34 remains loose and ensures a large absorption capacity for oil.

Figures 5 and 6 show an element 44 which comprises several flat pulps or pulp tapes 36 layered one on another. These are held together by a shell 40 made from an all-round water-permeable nonwoven of tear-resistant plastic fibres. The pulps 36 are dry, hence they have not as yet absorbed any oil.

The two halves of the shell 40 form a surrounding hem 42 which is formed from two watertight exterior shell sides adhered one on another.

The upper hem 42 is broader, it may have a space reserved for a handle 46, which is shown by a dotted line. Of course several handles 46 are also possible, in particular two.

Overall the element 44 is flat, it may be stacked so as to take up a small volume and be transported. After absorbing an oily substance the shell 40 bulges out so far that the element 44 is virtually spherical. Figures 7 and 8 show an element 44 filled with pulp 36 and provided with a shell 40 before and after absorbing oil. The element 44 lying on the ground 50 has a side wall 48 folded like a bellows and which is stretched slightly or completely when oil is absorbed.

A further one to six carrying flaps may be attached in the region of the upper part of the shell 40 (not shown).

Before use elements 44 joined to one another may be rolled up or folded, this saves space, permits easy transport and is suitable for spreading out rapidly.

Figure 9 shows an element 44 which is designed as a continuous tube. There is an intermediate wall 52 approximately every 50 cm, by means of which the chambers containing pulp 36 are formed. The pulp 36 is shown greatly enlarged in a chamber. In addition to the polyethylene fibrils 10, fine grain sand 54 can be seen which prevents the fibrils 10 from being compressed during transport.

It can also be seen from the cross-section according to Figure 10, that the element 44 designed as a continuous tube floating on the water surface 56 having an oil film 60 has two lateral drawing reinforcements 56, which, for example are present in the form of a wire, a rope or a chain.

A continuous tube may be arranged, for example on a ship, which absorbs the oil resorbed by the surrounding tube. Hence the tube may absorb and release several hundred times more oil from water 62, and this is a significant economic and ecological advance.

Claims (10)

Patent claims

1. Process for the manufacture of a recyclable binder made from hydrophobic polymer fibres for the absorption of crude oil, derivatives thereof or other oily liquids, from water (62), from a water surface (58) or from the ground (50), characterised in that wet polyolefin fibrils (10) cooled in water (24) are placed on a water-permeable tape (14) continuously circulating over at least two rollers (18, 20), guided on a heater roller (22) of large diameter while draining the water (24), dried on the surface (26) thereof to form a compact, tape-like nonwoven (28), then compressed and wound or cut into sections, which nonwoven (28) is passed to a comminuting or disintegrating machine (32) for impacting,, after appropriate storage, a loosened, flaked, hydrophobic pulp being produced which has a large absorption capacity for oily liquids.

2. Process according to claim 1, characterised in that the compact nonwoven (28) made from polyolefin fibrils, preferably from polyethylene or polypropylene fibrils, is passed to a hammer mill (32) or a mixer.

3. Process according to claim 1 or 2, characterised in that the polyolefin fibrils of the loosened, flake-like pulp (34) are joined to one another partially at points by means of heat treatment, preferably in a hot stream of air or by contacting with at least one heating surface.

4. Process according to claim 3, characterised in that the thermobonding is carried out at a temperature of 160 to 220°C, preferably for 1 to 2 minutes.

5. Process according to one of claims 1 - 4, characterised in that the pulp flakes (34) are joined to form a loosened, tape-like pulp (36), preferably to form a continuous tape having an outer shell (40).

6. Recyclable binder made from at least one element (44) having a hydrophobic pulp (36) of intertwined and linked polyolefin fibrils (10) of high density and a diameter of less than 40 μm, which forms a fine-pored expandable cavity for absorbing crude oil and derivatives thereof or other oily liquids, from water (62), from a water surface (58) or from the ground (50), characterised in that the polyolefin fibrils (10) are joined together at points by means of thermobonding.

7. Binder according to claim 6, characterised in that the polyolefin fibrils (10) consist of polyethylene or polypropylene.

8. Binder according to claim 6 or 7, characterised in that the polyethylene fibrils (10) are approximately 1 mm long and have a diameter of 1 to 20 μm.

9. Binder according to one of claims 6 - 8, characterised in that at least one preferably flat pulp (36) is arranged in a liquid-permeable, flexible outer shell (40) or a net, which is tear-resistant, resistant to chemicals and has at least one carrying or suspension device (46), and preferably has intermediate walls (52) forming chambers at an interval of 0.2 to 1 m.

10. Binder according to claim 9, characterised in that the pulp (36) is continuously surrounded by the tear- resistant outer shell (38).