HK1016571B - Process for removing pollutant from water, sand and/or rocks - Google Patents

Description

Method for removing contaminants from water, sand and/or rock

The present invention relates to the field of polymers. More particularly, the present invention relates to methods of using certain polymers to remove contaminants from water, sand, and/or rock.

It has been described in GB 1170959 and US 3869385 to spray formulations suitable for making polyurethane foams onto water or sand to remove oil.

DE3315596 discloses the use of polyurethane prepolymers made from polyether polyols containing from 70 to 95% by weight of ethylene oxide units and polyisocyanates as flocculants for the purification of water containing industrial waste. The flocculated waste is precipitated and thus difficult to recover. Two prepolymers are used, having an NCO value of 7% by weight and prepared from a polyol comprising EO and PO units in a weight ratio of 75/25, having a nominal functionality of 3 and a molecular weight of 4000; one prepolymer was prepared from toluene diisocyanate and the other prepolymer was prepared from a mixture of 2, 4 '-and 4, 4' -diphenylmethane diisocyanate 50/50 (by weight). The amount of prepolymer used is small.

EP-415127 also discloses the use of prepolymers as flocculants.

EP-370349 discloses the use of isocyanate-terminated prepolymers for removing hydrocarbons, especially oils, by preparing gels. Since the gel is relatively weak in strength, its removal is troublesome. EP-370349 discloses the use of prepolymers having an NCO value of 4.2% by weight, which are prepared from toluene diisocyanate and about 2% by weight of a propylene oxide-terminated polyether polyol. It is also disclosed that the prepolymer may be mixed with water prior to contacting it with the oil. In the examples the prepolymer was combined with water and mixed thoroughly for 25 seconds before combining with the oil. It is believed that premixing with water is performed to achieve some degree of pre-reaction of the prepolymer and water, and without such long mixing times, the mixing times under field conditions would be impractically long and would only yield unrecoverable chips.

The pending application PCT/EP95/01517 discloses the use of prepolymers made from 4, 4' -MDI and polyols having an oxyethylene content of 50 to 85% by weight for removing tall oil from water. It is also disclosed to contact the prepolymer with oil/water as a froth, the froth being obtained by adding water to the prepolymer. We have surprisingly found that the process of removing oil from water by using the prepolymer can be further improved by adding a certain amount of water to the prepolymer shortly before the prepolymer is contacted with the oil/water. The application of water lowers the viscosity of the prepolymer, changing the surface tension to such an extent that the prepolymer is easily brought into contact with oil/water: obtaining a suitable spray pattern (droplets) in which the prepolymer and water are mixed and a sufficiently high discharge of prepolymer from such a spray gun is obtained, particularly when a spray gun is used; if there is no water, the shot size will be low and the prepolymer will leave the nozzle as a jet. It has also been shown that foams of oil-containing materials obtained after combining the prepolymer/water mixture with oil/water retain the oil well after removal of the foam from the water surface. Since the addition of water to the prepolymer is performed a short time before the prepolymer is contacted with the oil/water, no significant pre-reaction occurs, particularly when water is added at a temperature of 5-35 ℃.

The present invention therefore relates to a process for removing unwanted material from wanted material in the presence of water by: by contacting an isocyanate-containing prepolymer with the substance, reacting the prepolymer with at least part of the water to form a flexible foam, and removing the foam obtained from the desired substance, wherein the prepolymer has an NCO value of 2 to 10% by weight, preferably 5 to 10% by weight, and is the reaction product obtained by reacting an excess of polymethylene polyphenylene polyisocyanate containing at least 25% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof with a polyether polyol having an average nominal hydroxyl functionality of from 2 to 4, a number average hydroxyl equivalent of from 500 to 3000 and an ethylene oxide content of at least 50% by weight, the amount of prepolymer used being from 5 to 200 parts by weight per 100 parts by weight of undesired substances, the process being characterized in that the prepolymer is mixed with from 2 to 100 and preferably from 5 to 50 parts by weight of water per part by weight of prepolymer for up to 20 seconds before contacting the substance, preferably at most 10 seconds and most preferably at most 5 seconds. Mixing of 2-100 parts water and 1 part prepolymer can be accomplished by methods known in the art. The prepolymer may be added to water or water may be added to the prepolymer before it is contacted with the material, and then optionally stirred. It is advantageously possible to use a device capable of applying a liquid spray in the form of droplets to a surface, such as a spray gun, which is connected to a water supply and a prepolymer supply, which are combined into one supply before the nozzle of the entire device.

Thus, according to one aspect of the invention, the invention relates to a process for removing contaminants from water, sand and/or rock in the presence of water by contacting an isocyanate-containing prepolymer with the material, reacting the prepolymer with at least part of the water to form a flexible foam and removing the foam obtained from the water, sand and/or rock, wherein the prepolymer has an NCO value of 2 to 10% by weight and is the reaction product obtained by reacting an excess of polymethylene polyphenylene polyisocyanate containing at least 25% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof with a polyether polyol having an average nominal hydroxyl functionality of 2 to 4, a number average hydroxyl equivalent weight of 500 to 3000, an ethylene oxide content of at least 50% by weight, the amount of prepolymer used being 5 to 200 parts by weight per 100 parts by weight of unwanted material, characterized in that the prepolymer is mixed with 2 to 100 parts by weight of water per part by weight of prepolymer for at most 20 seconds before being brought into contact with the substance.

According to one embodiment of the invention, the amount of prepolymer in the process of the invention is 10 to 100 parts by weight per 100 parts by weight of contaminants.

According to another embodiment of the invention, the polyisocyanate in the process of the invention comprises at least 85% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof.

According to still another embodiment of the present invention, the polyol in the process of the present invention has an oxyethylene content of 50 to 85% by weight.

According to another embodiment of the invention, the polyol in the process of the invention is a random polyoxyethylene polyoxypropylene polyol.

According to a further embodiment of the invention, water is contacted with the prepolymer in the process of the invention for up to 5 seconds before the prepolymer is contacted with the material in an amount of from 5 to 50 parts of water per part of prepolymer.

According to another embodiment of the invention, the NCO value of the prepolymer in the process of the invention is between 5% and 10% by weight.

It has surprisingly been found that a large amount of water maintained at room temperature (5-35 ℃) delays the reaction with the prepolymer for a very long time, allowing the water to act as a viscosity reducer for the polyisocyanate prepolymer.

The invention further relates to the use of water as a viscosity reducer for prepolymers having an NCO value of 2 to 10% by weight and being the reaction product of an excess of polymethylene polyphenylene polyisocyanate containing at least 25% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof with a polyether polyol having an average nominal hydroxyl functionality of 2 to 4, a number average hydroxyl equivalent of 500 to 3000 and an ethylene oxide content of at least 50% by weight, the amount of water being 2 to 100 parts by weight per part by weight of prepolymer.

Although other materials than water may be applied together with the prepolymer, it is preferred to use the prepolymer without further substances in the process according to the invention.

An undesired substance within the scope of this application is a substance that is in contact with another substance, i.e., a desired substance, is considered a contaminant of the desired substance and thus needs to be removed or separated from the desired substance.

The desired substance is a substance from which the undesired substance is to be removed or separated.

Combinations of unwanted/wanted substances are e.g. oil/water, paint/water, ink/water, oil/sand (beach), oil/rock, other petroleum products/water and industrial waste/water.

In particular, the process is useful for removing oils or other water-insoluble hydrocarbons from water.

The amount of the prepolymer used is 5 to 200 parts by weight, preferably 10 to 100 parts by weight, most preferably 20 to 80 parts by weight, per 100 parts by weight of the undesired substances. The amount of actually undesired substances can be estimated. The process can be repeated if the estimated amount is too low and some additional foam is formed if the estimated amount is too high.

The prepolymer/water mixture may be contacted with the material in any known manner. Such as spraying, pouring and whipping. If desired, a prepolymer may be mixed with the material. The prepolymer is preferably allowed to react under ambient conditions. The process can be carried out even at low ambient temperatures, provided there is sufficient liquid-water. The prepolymer is reacted with a portion of the water to form a flexible foam. The reaction is generally completed within 1 to 15 minutes. The foams obtained contain undesirable substances: it is entrapped, absorbed and/or adsorbed on the foam. The flexible foam is then removed from the desired material in any known manner. The flexible foam may be removed or removed from the desired material, dried and cut into smaller sections and/or compressed. The collected foam is preferably used for energy recovery after drying.

The polyisocyanate used to prepare the prepolymer may be selected from polymethylene polyphenylene polyisocyanates containing at least 25, preferably at least 50, most preferably at least 85% by weight of 4, 4 '-diphenylmethane diisocyanate (4, 4' -MDI) or a liquid variant thereof. Preferably, the polyisocyanate has an isocyanate functionality of 2.0 to 3, more preferably 2.0 to 2.3, most preferably 2.0 to 2.1.

Within the scope of the present invention, the term polymethylene polyphenylene polyisocyanate includes diphenylmethane diisocyanate and oligomers thereof, known in the art as crude or polymeric MDI, having an isocyanate functionality of greater than 2.

The polyisocyanate may consist essentially of pure 4, 4 ' -diphenylmethane diisocyanate or a mixture of such isocyanates with other diphenylmethane diisocyanate isomers, for example the 2, 4 ' -isomer optionally together with the 2, 2 ' -isomer. The polyisocyanate may also be a MDI derived from a polyisocyanate containing at least 25%, preferably at least 50%, most preferably at least 85% by weight of 4, 4' -diphenylmethane diisocyanate. MDI variants are well known in the art and, depending on the use in the present invention, comprise in particular liquid products obtained by adding uretonimine and/or carbodiimide groups to the polyisocyanate, such carbodiimide and/or uretonimine modified polyisocyanates preferably having an NCO value of at least 25% by weight and/or modified polyisocyanates obtained by reacting such polyisocyanates with one or more polyols having a hydroxyl functionality of from 2 to 6 and a molecular weight of from 62 to 1000 in order to obtain modified polyisocyanates preferably having an NCO value of at least 25% by weight. The polyisocyanate may contain minor amounts of polymethylene polyphenylene polyisocyanates having an isocyanate functionality greater than 2; preferably, the amount is such that the total polyisocyanate has an isocyanate functionality of from 2.0 to 2.5, more preferably from 2.0 to 2.3, most preferably from 2.0 to 2.1.

The polyol used to prepare the prepolymer preferably has an average nominal hydroxyl functionality of 2 to 4, and most preferably 2.5 to 3.5, a number average hydroxyl equivalent weight of 1000 to 3000, and an ethylene oxide content of 50 to 85% by weight. Polyether polyols used in the preparation of the prepolymer include products prepared by the polymerization of ethylene oxide optionally with additional epoxides such as tetrahydrofuran, butylene oxide, preferably propylene oxide, in the presence of polyfunctional initiators. Suitable initiator compounds contain a plurality of active hydrogen atoms and include water, butanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, toluene diamine, diethyl toluene diamine, phenyl diamine, diphenylmethane diamine, 1, 2-ethylene diamine, cyclohexane dimethanol, resorcinol, bisphenol A, glycerol, trimethylolpropane, 1, 2, 6-hexanetriol, and pentaerythritol. Mixtures of initiators may be used.

The polyols may be obtained by the simultaneous or sequential addition of ethylene oxide and other epoxides to the initiator. The sequential addition may be performed in any order. Sequential addition will give a polyol of the so-called block copolymer type, while addition will give a polyol of the so-called random type. Most preferred are random polyoxyethylene polyoxypropylene polyols having an oxyethylene content of 50-85% by weight.

To obtain the most preferred polyols having an average nominal hydroxyl functionality of 2.5 to 3.5, a polyol or mixture of polyols having a nominal hydroxyl functionality of 3 may be used, as long as the mixture is in the range of 2.5 to 3.5 functionalities for the mixture, wherein each polyol may have another average nominal hydroxyl functionality.

The term "average nominal hydroxyl functionality" is used herein to refer to the average functionality (number of hydroxyl groups per molecule) of the polyol assuming that the average functionality of the polyoxyalkylene polyol present therein is equivalent to the average functionality (number of active hydrogen atoms per molecule) of the initiator used in its preparation, although in practice the polyoxyalkylene polyol will have less functionality than the initiator due to some terminal unsaturation. The term "average" is used in this specification to mean the average.

The prepolymer is prepared by conventional methods at a temperature preferably between 40 and 100 ℃ by means of the polyisocyanate and the polyol in relative amounts such that an NCO value of 2 to 10%, preferably 5 to 10%, by weight is obtained. The prepolymer thus prepared is liquid at ambient conditions. Polyisocyanates, polyols, prepolymers and processes for their preparation are known per se, see for example EP-547765.

The invention is illustrated by the following examples.Example 1

The prepolymer was prepared by reacting 30 parts by weight of 4, 4' -MDI with 70 parts by weight (pbw) of an EO/PO polyol (random) having a molecular weight of 4000, a nominal functionality of 3 and a content of 75% by weight Eo. The NCO value of the prepolymer was 7.8% by weight (prepolymer 1).

A1 liter plastic cup was filled with 120ml of water plus 40 grams of used motor oil. 400 g of water and 20 g of prepolymer 1 were added to the cup after mixing for 5 seconds. The contents of the plastic cup were then mixed thoroughly and allowed to react. After 5 minutes the sticky flexible foam, which contained all the oil, was removed from the water surface. The foam also retains the oil for more than one day after removal from the water surface.Comparative example 2

A vessel having a diameter of 170cm was filled with water (the height of the water amount was 40cm from the bottom of the vessel). 1 liter of used engine oil was poured into the water and spread out on the surface. Then 300 g of prepolymer 1 were added through a spray gun with a gas nozzle. The gun is 12cm long and 7mm in diameter; the nozzle was kept 1 meter from the oil surface. The maximum achievable output of prepolymer is 150 g per minute (8 bar absolute of the lance pressure used). The prepolymer leaves the nozzle as a jet. The prepolymer was allowed to react for 10 minutes. Part of the prepolymer sinks to the bottom of the vessel and forms debris as the foam is formed. A portion of the flexible foam is removable from the surface, the foam containing less than 2/3 oil.Example 3

Example 2 was repeated, but with the water being combined with the prepolymer at the beginning of the spray gun (and thus 12cm from the nozzle) in a weight ratio of 20: 1. The prepolymer/water mixture exited the nozzle as a fine droplet spray at an output of 21 liters per minute. Spraying was carried out at 6 bar absolute for 30 seconds. The time between the prepolymer and water combination and the combination and oil/water contact can be calculated to be 0.1 seconds. Removing the viscous flexible foam containing all oils. No debris was found at the bottom. The foam is capable of retaining all oils for more than one day.Example 4

Example 3 was repeated, but with the spray gun having a simple nozzle (no air cap). The results were the same.

Claims (7)

1. Process for removing contaminants from water, sand and/or rock in the presence of water by contacting an isocyanate-containing prepolymer with the material, reacting the prepolymer with at least part of the water to form a flexible foam and removing the foam obtained from the water, sand and/or rock, wherein the prepolymer has an NCO value of 2 to 10% by weight and is the reaction product obtained by reacting an excess of polymethylene polyphenylene polyisocyanate containing at least 25% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof with a polyether polyol having an average nominal hydroxyl functionality of 2 to 4, a number average hydroxyl equivalent weight of 500 to 3000, an oxyethylene content of at least 50% by weight, the amount of prepolymer used being 5 to 200 parts by weight per 100 parts by weight of contaminants, characterized in that the prepolymer, prior to contacting with the material, mixing with 2-100 parts by weight of water per part by weight of the prepolymer for at most 20 seconds.

2. The method of claim 1, wherein the amount of the prepolymer is 10 to 100 parts by weight per 100 parts by weight of the contaminant.

3. A process according to claims 1-2, characterized in that the polyisocyanate comprises at least 85% by weight of 4, 4' -diphenylmethane diisocyanate or a liquid variant thereof.

4. A process according to claims 1 to 3, characterized in that the polyol has an oxyethylene content of 50 to 85% by weight.

5. A process according to claim 1 to 4, characterised in that the polyol is a random polyoxyethylene polyoxypropylene polyol.

6. A process according to claims 1 to 5, characterised in that the water is contacted with the prepolymer for up to 5 seconds before the prepolymer is contacted with the material, in an amount of from 5 to 50 parts of water per part of prepolymer.

7. A process according to claim 1 to 6, wherein the prepolymer has an NCO value of 5 to 10% by weight.