ABSORBENT ELEMENT, ASSEMBLY AND FABRICATION PROCESS

Abstract

Absorbent element for spilled petroleum or its derivatives comprising an oil-absorbent, hydrophobic and oleophilic material, essentially based on polyurethane foam, having a specific weight in the range of 15-30 g/l and delimiting open cells and closed cells, the latter being in a percentage equal to or lower than 10% of the total cells. The invention further relates to an assembly comprising a plurality of such elements and a method for fabricating an oil-absorbent material.

Claims

1. Absorbent element for spilled petroleum or its derivatives comprising an oil-absorbent, hydrophobic and oleophilic material, essentially based on polyurethane foam, having a specific weight in the range of 15-30 g/l and delimiting open cells and closed cells, the latter being in a percentage equal to or lower than 10% of the total cells.

2. Element according to claim 1, wherein the percentage of open cells is between 92-99% of the total cells, and wherein the specific weight is in the range of 15-25 g/l.

3. Element according to claim 1, wherein, adsorbed at the surface of the open cells, said material comprises polypyrrole, graphene, calcium carbonate or mixtures thereof in order to improve the oleophilia of said material.

4. Element according to claim 1, comprising at least a reinforcement cord or tape that extends along the predominant direction of extension of this element, in order to increase at least its tensile strength, said cord/tape being at least partially incorporated in the oil-absorbent material or at least partially glued to the surface of said material.

5. Element according to claim 1, wherein the oil-absorbent material is at least partially contained in an outer wrapper of non-woven fabric of average density between 100-200 g/m2, said non-woven fabric comprising polypropylene fibres optionally mixed with styrene fibres, the latter for example of a diameter of 6-14 micrometres.

6. Element according to the claim 5, wherein the oil-absorbent material and the outer wrapper are glued by means of at least a hot-melt adhesive.

7. Element according to claim 1, wherein the oil-absorbent material is contained in a polyolefin fibre or biodegradable fibre netting, preferably of a tubular shape.

8. Assembly comprising a plurality of absorbent elements according to claim 5, joined together in an articulated and releasable manner, each outer wrapper or each netting comprising complementary means for modular interconnection with other wrappers or nettings.

9. Process for the fabrication of an oil-absorbent, hydrophobic and oleophilic material, essentially based on polyurethane foam comprising a step of reaction between: one or more poly-isocyanates; one or more poly-oils or one or more compounds containing reactive hydrogens; at least one oleophilic nano filler, for example, graphene, or at least one oleophilic polymer such as poly-pyrrole; at least one cell-regulator emulsifier; at least one amine catalyst; and as expander, water and optionally at least one fluoro-derivative compound.

10. Process according to the claim 9, wherein said polyisocyanate is selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, 2,2-diphenylmethane diisocyanate, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, polymethylene polyphenyl polyisocyanate or mixtures thereof.

11. Process according to claim 9, wherein said polyol is selected from the group consisting of polyester polyols, polyether polyols, grafted polyols, special polyols or mixtures thereof.

12. Process according to the claim 11, wherein the polyether polyols are linear or branched with a molecular weight in the range 1000-6000, and with a number of hydroxide functionalities between 15-900, for example between 30-150.

13. Process according to claim 12, wherein the polyether polyols are obtained by reaction of alkylene oxides with 2-4 carbon atoms in the alkylene radical with a starter molecule containing at least two reactive hydrogens, said alkylene oxides comprising in particular tetrahydrofuran, 1,2 butylene oxide, 2,3 butylene oxide, propylene oxide and ethylene oxide, or combinations thereof, preferably a PO/EO mixture in a 70/30 or 80/20 mixture.

14. Process according to claim 11, wherein the special polyol is obtained according to one of the following procedures a) or b): a) ester obtained by esterification of a linear aliphatic acid with 10-20 carbon atoms in the molecule, saturated or unsaturated, with an alcohol with 2-20 carbon atoms in the molecule, for example palmitic acid, stearic acid, oleic acid and their mixtures; b) liquid polybutadiene homopolymer with hydroxyl groups, particularly poly-butadiene, that react with di- and poly-isocyanates in order to obtain an oil-absorbent material of high resilience.

15. Process according to claim 11, comprising at least a mixture of at least one polyether polyol and at least one grafted polyol in a ratio of about 65/35, the polyether polyol having an hydroxyl number of about 55, the grafted polyol containing about 25% polystyrene, 10% polyacrylonitrile and about 65% ethylene oxide and/or propylene oxide.

16. Process according to claim 11, wherein said reaction step is conducted by pre-polymer technique, or by one-shot technique.

Description

Example 1: Preparation of the Oil-absorbent Material Using the Pre-polymer Technique

[0083] In the expansion process via pre-polymer the hydroxyl compound is reacted with an excess of isocyanate (NCO/OH ratio about 2:1) forming a pre-polymer with terminal free isocyanate in defined amount. This compound will be defined as pre-polymer (A).

[0084] A compound containing 100 parts by weight of polyols and catalysts, emulsifiers, cell regulators, pigments, water, blowing agents, fillers and any other additives will be called compound (B).

[0085] The value of the sum of the equivalent weights of the compound (B) will require an equivalent weight of pre-polymer (A) and, after fast mixingbetween 8 and 16 secondsof the two components, the mixture that is not yet in cream time is discharged in a mould wherein it will reach the desired volume after several minutes and the cross-linking of the foam in the next 48 hours for cutting operations to be started.

[0086] The stoichiometric ratio (A)/(B) provides an index of the isocyanate pre-polymer equal to 100. The variation above or below the value of the isocyanate with respect to the stoichiometric amount required by the properties of the foam is referred to as NCO-index.

[0087] The isocyanates employable in this example are: diphenylmethanediisocyanate (MDI) in its isomeric forms 2,4-,4,4-2,2, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, polyfunctional isocyanates obtained by the dimerisation or trimerisation reaction or containing urethane groups, or mixtures thereof.

[0088] The use of technical grade mixtures of diphenylmethane diisocyanate and polymethylene polyisocyanate (crude MDI) is preferred. The MDI index, which is the ratio of the amount used in the formulation and the theoretical stoichiometric amount can vary between 75 and 125.

Example 2: Possible Formulations of the Oil-Absorbent Material According to this Invention

[0089] Eight different formulations of oil-absorbent material were prepared according to this invention, whose compositions are summarised in FIG. 1.

[0090] After obtaining them, these materials were tested as discussed in Example 3.

Example 3: Control Tests for Absorption of Oil and Salt Water (25g NaCl in 1000 cc of Water) of the Samples of Example 2

[0091] The values reported in accompanying FIG. 2 correspond to an average obtained on three different samples.

[0092] From the consideration of this table, it appears evident that the oil-absorbent material, in addition to possessing an advantageous ratio between closed cells and open cells, further presents a high degree of hydrophobia with an equally high oleophilia (exceeding thirty times the weight of the absorbent material).

[0093] Innovatively, the absorbent element of this invention is able to brilliantly overcome the drawbacks noted in relation to the prior art.

[0094] More precisely, this element has excellent buoyancy in water both before and after contact with and absorption of petroleum, is configurednot only by virtue of its own cellsto allow easy access and penetration of the oil, but also to resist desorption of the oil during removal from the water.

[0095] Advantageously, the absorbent element of this invention has a surface tension that allows it to be both hydrophobic and oleophilic.

[0096] Advantageously, the absorbent element of this invention selectively absorbs the oil but not the water of the water body to be reclaimed, despite the presence of open cells.

[0097] Advantageously, the absorbent element of this invention has a marked ability to reduce the enlargement of the oil spilled in water.

[0098] Advantageously, the absorbent element of this invention is characterised by a high rate of oil absorption, so as to prevent an undesirable mixing of oil and the water body.

[0099] Advantageously, the absorbent element of this invention is distinguished for a high solid-liquid contact surface, as well as an equally marked ratio of absorbent material weight/weight of adsorbed oil.

[0100] Advantageously, the absorbent element of this invention is designed to allow a remarkable ease of separation of the oil from the absorbent material so as to allow the recovery of the oil spill and reuse of the absorbent material.

[0101] Advantageously, the absorbent element of this invention has low weight and ease of transport with reduced volumes.

[0102] In fact, not only by virtue of the compression set (evaluated according to ASTM D395) that characterises it, the absorbent element described allows it to be transported under vacuum with an extremely reduced total volume, but it quickly resume its internal volume in order to perform its absorbent function.

[0103] It follows that this element is a candidate to be, for all effects, standard safety equipment for all structures used for the transportation, extraction or processing of petroleum and its derivatives.

[0104] Advantageously, the absorbent element of this invention has high mechanical properties, so that it can be dragged and literally squeezed to cause the exit of the oil from the cells.

[0105] Therefore, advantageously, following the above mentioned squeezing, the element is once again available for a new absorption cycle.

[0106] Advantageously, the aforesaid material is designed to withstand not less than five cycles of squeezing and re-use.

[0107] Advantageously, the compression set of the absorbent element of this invention allows drastically reducing the volume transported, resuming its original shape after the oil has been removed by the procedure mentioned above.

[0108] Advantageously, the use of a wrapper or netting allows making the absorbent material and the related covering work synergistically, so as to considerably increase the mechanical properties of the absorbent element of this invention.

[0109] Advantageously, the use of tapes or ropes in the manner described allows discharging part of the draft forces to structures other than the oil-absorbent material, so as to avoid an unintentional squeezing of the oil, and reducing the risk of lacerations of the material.

[0110] Advantageously, the modular system described above allows obtaining an assembly of variable length depending on the contingencies, for example based on the magnitude of the contaminated area to be reclaimed or the volume of spilled oil.

[0111] In addition to this, the element described above allows a rapid replacement of the absorbent areas that are deteriorated or damaged, allowing an easy recovery of absorbent capacity.

[0112] Advantageously, the absorbent element of this invention even allows the use of waste from the production of the absorbent material.

[0113] Advantageously, the use of technical grade mixtures of the polyisocyanates described above has proved to be favourable both for toxicological reasons and for convenience of use.

[0114] To the embodiments of the aforesaid element, oil-absorbent material and process, one skilled in the art, in order to meet specific needs, may make variants or substitutions of elements with others functionally equivalent.

[0115] Even these variants are contained within the scope of protection; as defined by the following claims.

[0116] Moreover, each of the variants described as belonging to a possible embodiment can be realised independently of the other variants described.