IE42690B1 - Improvements in or relating to oil absorbing materials - Google Patents

Abstract

1513645 Material for absorbing oil on water MITSUI TOATSU CHEMICALS Inc 13 May 1976 [22 May 1975] 19649/76 Heading C1C [Also in Division Dl] An oil-absorbing material is prepared by mixing vegetable fibres i.e. grass peat, flax, coconut shell, straw or grass fibres with up to 35% by weight, based on the dry fibre, of an olefin polymer and then heating the mixture to impregnate the fibres with the molten polymer. Specified olefin polymers are homopolymers or copolymers of ethylene, propylene, isobutylene or butene and copolymers of ethylene with vinyl acetate, acrylic acid or salts or esters thereof and methacrylic acid or salts or esters thereof. The materials are used for treating oil-on-water pollution.

Description

This invention relates to a process for producing oil-absorbing materials which are useful for collecting oils on the surface of water or those dispersed in water as oil particles.

Various types of oil-absorbing materials have previously been used for collecting and removing various oils that have been spilled onto a water surface, for example, the spillage of heavy oils onto the sea. Oil-absorbing materials in general use are structures composed of natural fibers or synthetic fibers in the form of, for example, a mat or a barrier. Known natural fibers used for this purpose include, for example, grass peat fibers, wood Wool, and straw; polypropylene and polyethylene fibers, for example, are known as the synthetic fibres.

Since these oil-absorbing materials are evaluated not only by their, ability to absorb oils, but also by their combustability after oil absorption, oil-absorbing materials composed of the natural fibers are preferred to those made of the synthetic fibers. The oil-absorbing materials of the synthetic fibers melt during combustion, and it is difficult to burn them off. Furthermore, they produce black smoke or hazardous substances during combustion, and therefore, a special combustion furnace or special equipment for the removal of the hazardous sub25 stances is required. - 3 On the other hand, since oil-absorbing materials made of natural fibers are hydrophilic, they absorb not only oils but also water when put into a water area polluted by oils, and consequently, their ability to g absorb oils is restricted.

This defect can be overcome to some extent by subjecting the natural fibers to a water-repelling treatment using a chemical consisting mainly of an emulsion-type water repellent of, for example, the aliphatic wax or silicone type. However, when oil-absorbing materials produced from the natural fibers so treated float on the water surface for long periods of time while being tossed about in the waves of the sea and in contact with oils, the water-repellent itself is dissolved and removed out of the oil-absorbing materials so that the water-repelling effect does not last sufficiently . In addition, emulsifiers, heavy metal salts, and other ingredients contained in the treating chemicals may dissolve in the water, and cause adverse effects. Accordingly, the use of the water20 repelling chemicals is undesirable.

It is an object of this invention therefore to provide a process for producing oil-absorbing materials which retain the ability to hold oils in water for long periods of time, have good combustibility after oil absorption, 25 and do not produce hazardous substances during combustion.

According to this invention, there is provided a process for producing an oil-absorbing material which comprises mixing vegetable fibers selected from grass peat fibers, flax fibers, coconut shell fibers, straw, and 3q grass fibers with not more than 35% by weight, based on the dry weight of the fibers, of a solid olefin polymer and heating the resulting mixture to melt the olefin polymer and thereby impregnate the vegetable fibers with the molten olefin polymer.

Examples of the solid polyolefin polymers are homopolymers or copolymers preferably having a weight-average molecular weight of at least 15,000 of ethylene, propylene - 4 isobutylene and butene, copolymers of ethylene with one or more of vinyl acetate, acrylic acid, acrylates (salts or esters), methacrylic acid, methacrylates (salts or esters), and mixtures of these homopolymers and copolymers.

When olefin polymers having a molecular weight of less than 15,000 are used, the durability of the water-repellency of the resulting oil-absorbing materials is somewhat reduced. Desirably, the olefin polymers are crystalline. The amount of the solid olefin polymer is not more than 35% by weight, preferably 2 to 30% by weight, based on the dry weight of the vegetable fibers.

Mixing of the vegetable fibers and the solid olefin polymer is performed, for example, by using a stirrer or a cardihg machine. Preferably, the solid olefin poly15 mer is used in the form of a powder having a size of not greater than 50 mesh on the ASTM standard (hereinafter referred to as ASTM mesh), or fibers having a length of not more than 10 mm. Water contained in the vegetable fibers evaporates off during the heating operation, and 2o therefore, it is not necessary to restrict the moisture content of the vegetable fibers. The vegetable fibers well mixed with the solid olefin polymer are heated to a temperature above the melting point of the solid olefin polymer. This heating results in the melting of the solid olefin polymer and consequently its impregnation in the vegetable fibers, .

Since the.amdunt of the olefin polymer impregnated in the vegetable fibers is not more than 35% by weight, preferably 2 to 30% by weight, the porosity and surface roughness of the vegetable fibers themselves remain in the resulting structure. A microscopic observation of this structure shows that apparently adhesion of fibers to one another ascribable to the impregnated olefin polymer occurs only to a small exteht, and the olefin polymer does not cover the surface bf the vegetable fibers. Accordingly, the oil-holding ability of the vegetable fibers themselves is not reduced, and the olefin polymer once impregnated into - 6 the fibers is not likely to dissolve even during its longterm residence in water. Thus, a long-lasting stable waterrepellency is imparted to the vegetable fibers. When the amount of the olefin polymer exceeds 35% by weight, the wick effect of the vegetable fibers becomes insufficient during burning so that the fibers generate a black smoke and the olefin polymer partly drips from the vegetable fibers.

The oil-absorbing material obtained can be used as packed in a suitable receptacle so as to collect oils dispersed as oil droplets in water. Or it can be pressformed into a mat-like structure, or further wrapped by a net to prevent the breakage of the mat in water, and in this form, can be used to absorb oils on the water surface. Or the mat so obtained may be placed on the water surface as an oil-absorbing barrier with a suitable float so as to use it to prevent the diffusion of floating oils on the water surface.

Thus, there can easily be obtained an oil-absorbing material which has water-repellency durable for long periods of time in water, good oil-absorbing ability inherent to the vegetable fibers, and good combustibility after oil absorption, and which does not produce a hazardous substance during combustion.

Examples IA, IB and 1C.

IA. Polypropylene powder (lOOg) having a size of not greater than 100 ASTM mesh and a weight-average molecular weight of 25,000 was added to 1.4 Kg of grass peat fibers (water content 40% by weight) obtained by heating grass peat in water and separating the fibers from the humus. They were thoroughly mixed by a carding machine.

The resulting mixture was maintained in a hot air dryer at 180°C for 15 minutes to melt the polypropylene and impregnate it in the peat fibers. The resulting polypropyleneimpregnated peat fibers are designated as an oil-absorbing material A.

- £ IB. The above procedure was repeated using 42 g of an ethylene/vinyl acetate copolymer powder (10% by weight of vinyl acetate; melting point 95°C) with the heatmelting temperature being maintained at 105°C. Thus, grass peat fibers impregnated with the above copolymer were obtained. These fibers are designated as an oil-absorbing material B.

IC. When the above procedure was repeated using 42 g of an ethylene/zinc methacrylate copolymer powder (10% LO of zinc methacrylate; melting point 113°C) with the heatmelting temperature being maintained at 123°c, grass peat fibers impregnated with the above copolymer were obtained. These fibers are designated as an oil-absorbing material C.

Examples 2D and 2E. .5 2D. 1.2 Kg of grass peat fibers (water content % by weight) obtained by the same method as set forth in Example 1 and 100 g of fibrillated fibers of polypropylene having a weight-average molecular weight of 30,000 with an average fiber diameter of 3 mm were thoroughly mixed in a Henschel mixer. The resulting mixture was maintained in a hot air dryer at 180°C for 15 minutes to melt the polypropyl ene fibers and impregnate them in the peat fibers. The resulting polypropylene-impregnated peat fibers are designated as an oil-absorbing material D. !5 2E. The above procedure was repeated using 48 g pf fibrillated fibers of polyethylene having an average mole cular weight Of 20,000 with an average fiber length of 2 mm with the heat-melting temperature being maintained at 140°C. Thus, polyethylene impregnated grass peat fibers were ob0 tained. These fibers are designated as an oil-absorbing material E.

Example 3F. 0.9 Kg of flax fibers (water content 40%) and 160 g of polybutene-1 powder having a weight-average molecular weight of 50,000 and a size of not greater than 100 ASTM mesh were mixed, and maintained in a farinfrared furnace at - 7 15O°C for 15 minutes to melt the polybutene-1 and impregnate it into the flax fibers, to form a product containing about 29% of polybutene-1 by weight of the dry fibers. The resulting impregnated flax fibers are designated as an oil5 absorbing material F.

Comparative Example 1.

A paraffin wax emulsion having the composition indicated below was diluted with water, and the same grass peat fibers as used in Example 1 were immersed in the dilu10 ted emulsion. Then, the immersed peat fibers were squeezed by rolls to the desired paraffin wax content, and heated at 100°C to melt the paraffin wax adhering to the peat fibers and impregnate it into the peat fibers. In this manner, products with a paraffin wax content of 2% by weight and 4% by weight were obtained. These products are designated as oil-absorbing materials I and II, repsectively.

Formulation of the paraffin wax emulsion.

Paraffin (m.p. 54.5°C) 90% Beef tallow free fatty acid 38.8% 2θ Monoethanolamine 3.35% Water 48.85% Comparative Example 2.

A commercially available silicone emulsion for water-repellent finishing of textiles (Toshiba TSW 83) and a commercially available catalyst (Toshiba CW 80) were mixed in a volume ratio of 1:1. The same grass peat fibers as used in Example 1 were immersed in the mixture, dried at 100°C for 10 minutes, and then heat-treated at 180°C for 5 minutes to form a product having a silicone pick-up of 3% by weight based on the peat fibers. The product is designated as an oil-absorbing material III.

Comparative Example 3.

A waxy substance having a weight-average molecular weight of 6,000 obtained as a by-product in the production _ of polyethylene was dissolved in naphtha by heating to form -βα 30% by weight solution. The same grass peat fibers as used in Example 1 were immersed in the resulting solution, squeezed, cooled, and then crumpled to remove the excess of the waxy substance and thereby to obtain a product with a waxy substance pick-up of 150%. The product is designated as an oil-absorbing material IV.

The above procedure was repeated using a 10% by weight solution of 'the wax substance,thereby to obtain a product having a waxy substance pick-up Of 10% which is designated as an oil-absorbing material V.

Comparative Example 4 Atactic polypropylene having a weight-average molecular weight of 10,000 obtained as a by-product in the production of polypropylene was dissolved irt toluene by heating to form a -30% by weight solution of the atactic polypropylene. The same grass peat fibers as used in Example 1 were immersed in the solution, and dried in air to remove the toluene and thereby to obtain a product with an atactic polypropylene pick-up of 100%. The product is designated as an oil-absorbing material VI.

The above procedure was repeated using a 10% by weight toluene solution of the atactic polypropylene thereby, to form a product having an atactic polypropylene pick-up of 10%. The product is designated as an oil-absorbing material VII.

Comparative Example 5.

The same procedure as in Example 3 was repeated except that the amount of the polybutene-1 added was changed to 220 g. Thus, flax fibers impregnated with about 41% polybutene-1 by weight based on the dry fibers were obtained. This product is designated as an oil-absorbing material VIII.

Text Example 1 (test for the durability of water repellency). 128 g each of the oil-absorbing materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5 was wrapped in a net made of polyethylene filaments and formmed Into a square mat measuring 40 cm in each side and 1 cm in thickness. The mats obtained were each tested for the durability of water repellency in the following manner.

The mat was allowed to stand in a water tank in which waves with a height of 30 cm, a length of 200 cm and a period of 1.2 seconds were artificially produced. The time that elapsed until the mat completely submerged in water was measured. When the mat did not submerge, the state of the mat after performing the test for 78 hours was observed.

The same grass peat fibers (a) and flax fibers (b) as used in Examples 1 and 3 respectively were also tested in the same way as above. The results are shown in Table 1.

TABLE 1 Oil-absorbing material Time that elapsed until the complete submerging of the mat (hours) State of the mat after the end of the test A - Completely floating B - Submerged to about 1/8 C - I Submerged to about 1/8 D Submerged to about 1/10 E Submerged to about 1/10F - Completely floating a 15 b 11 1 I 20 i II 33 j III 38 IV - Submerged to j about 3/4 j - 10 TABLE I (Contd.) Oil-absorbing material Time that elapsed until the complete submerging of the mat (hours) State of the mat after the end of the test V 45 VI Submerged to 1 about 1/4 VII 68 - VIII Completely floating Test Example 2 (test for the ability to absorb oils and water). g each of the oil-absorbing materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5 was wrapped in a net made of polyethylene filaments and formed into a square mat measuring 10 cm in each side and 1 cm in thickness. The mats obtained were each tested for the ability to absorb oils and water in the following manner.

The mat was immersed forcibly in oil-free water for a 10 predetermined period of time, and oscillated with an amplitude of 4 cm at 100 strokes/minute. The mat so treated was allowed to stand for 5 minutes so as to remove water, and then put into. a water tank in which a floating film of heavy.oil A meeting Japanese Industrial Standard K-2205 with a thickness of 0.5 mm was formed on.the water surface to cause it to absorb the oil. The mat was pulled up from the tank, and allowed to stand for 5 minutes. The final contents of the oil and water in the mat were determined on the basis of the weight of the mat, A similar oil and water absorption determination was made for mats which had not been subjected to the initial immersion in oil-free water.

The same grass peat fibers (a) and flax fibers (b) as used in Examples 1 and 3 were tested in the same way as above. The results obtained are shown in Table 2. 4269ο - 11 TABLE 2.

Time for immersing the mat in water Oil-ab- sorbing material Amount of the oil held by the mat (g-oil/g-mat) Amount of water held by the mat (g-water/ g/mat) A 9.13 0.50 B 9.51 0.48 C 9.05 0.55 D 9.55 0.45 E 9.70 0.40 0 (in the dry F 9.38 0.58 state) a 6.58 1.27 b 7.48 1.71 I 6.13 1.50 7.26 1.08 m 7.83 0.95 IV 4.58 0.55 V 8.06 0.59 VI 5.05 0.37 VII' 8.59 0.56 . i VIII 8.23 0.45 ί A 9.66 0.70 5 minutes 1 ί B 9.62 0.73 i c 9.00 0.68 i D 9.60 0.70 ! E 9.35 0.65 I i F 9.65 0.59 a 0.54 7.34 i b 0.63 7.24 1 I 6.27 2.05 i II 6.66 2.13 j III 7.50 ! 1.24 IV 4.38 j 0.65 V 7.53 : 1.15 5 minutes VI 4.87 0.61 VII 8.13 i 1.24 ‘ - 12 TABLE 2 (Contd.) Time for immersing the mat in water Oil-ab- sorbing material Amount of the oil held by the mat (g-oil/ g-mat) Amount of water held by the mat (g-water/ g-mat) VIII 8.16 0.56 A 9.50 0.75 B 9.55 0.78 c · 8.92 0.72 1 day D 9.52 0.70 j E 9.67 0.66 | F . 9.38 0.62 ι a 0.49 9.01 i b 0.55 8.22 I ‘ 3.59 5.03 II 4.06 4.37 in 5.32 3.48 iv, 4.08 1.19 ! V 6.47 2.31 VI 4.75 0.88 VII 7.49 2.05 VIII 8.08 0.70 ί i t A 9.22 0.81 f B 9.23 0.83 10 days C 8.53 0.85 D 9.15 0.80 j E 9.68 0.68 F 9.30 0.71 a 0.43 8.93 b 0.48 8.35 I 1.15 7.48 II 1.52 7.11 I 10 days III 2.19 6.65 . IV 3.81 1.86 V 2.89 6.14 - 13 TABLE 2 (Contd.) Time for immersing the mat in water "-'- 1 Oil absorbing material Amount of the oil held by the mat (g-oil/g-mat) j Amount of ί water held by the mat (g-water/ g-mat) VI 4*51 1.25 j VII 3.26 1 6.47 _ VIII 8.01 } L 0.75 Xn the above Table, and also in Tables 3 and 4 hereinafter, 0 (in the dry state) means the mats were tested by immersion in oil/water without initially being immersed in oil-free water.

Text Example 3 (test for combustibility) Mats were produced in the same way as in Test Example using the oil-absrobing materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5. Each of the mats was placed on a wire gauze, and ignited. The mats made of the oil-absorbing materials A to Ρ, I to XXI, V and VII showed a good burning state without producing any smoke, but the mat made of the oil-absorbing material VIII burned while generating some black smoke. The mats made of the other oil-absorbing materials IV and VI produced a large quantity of black smoke, and a part of the polymer impregnated melted, and dripped from the Wire gauze.

Example 4. 2,5 Kg of the same grass peat fibers (water content 40% by weight) as used in Example 1 and 120 g of a powder with a size of not greater than 100 ASTM mesh of a propylene/ethylene copolymer (ethylene content 10%) having a weight-average molecular weight of 40,000 were mixed, and maintained in a hot air oven at 160°C for 15 minutes to melt the polymer and impregnate it into the peat fibers. The resulting oil-absorbing material was packed into a cylindrical receptacle having a diameter of 260 mm and a - 14 height of 400 mm. Water having suspended therein 40 ppm of a lubricating oil as fine particles was flowed at a rate of 700 liters/hour through the receptacle. Even after the passage of 150 hours, the oil content at the exit of the receptacle did not exceed 5 ppm.

Example 5. 200 g of a polyethylene powder having a size of hot. greater than 100 ASTM mesh and a weight-average molecular weight of 18,000 was added to 1.4 Kg of coconut shell fibres (water content 40% by weight), and they were thoroughly mixed by a Henschel mixer. The resulting mixture was hot-pressed at 125°C, and maintained for 15 minutes in a compressed state such that 10 g of the mixture was converted to a square mat measuring 10 cm in each side and 1 cm in thickness. Thus, a mat composed of the coconut shell fibers impregnated with the molten polyethylene (oilabsorbing material G) was obtained. The mat was tested for its ability to absorb oils and water in the same way as in Test Example 2 using heavy oils B and C in accordance 2q with Japanese Industrial Standard K-2205. The results are shown in Table 3.

For comparison, a square mat measuring 10 cm in each side and 1 cm in thickness was made from 10 g qf non-treated coconut shell fibers (Η), and its ability to absorb water and oils was tested in the same way. The results are also shown in Table 3. . - 15 TABLE 3 Time for immersing the mat in water Oil-ab- sorbing material Type of heavy oil l Amount of oil held by the mat (g-oil/ I g-mat) Amount of water held by the mat (g-water/ g-mat) 0 (in the dry state) G B I c 8.73 11.53 0.30 0.28 H θ c 6.50 9.85 1.03 0.97 10 days G B c 8.62 11.08 0.65 0.56 H B C 1.77 2.53 7.52 7.48 The above mats were subjected to the same test for the durability of water repellency as in Test Example 1.

As a result, the mat prepared from the oil-absorbing material G submerged to a depth of only about 1/10, but the mat prepared from the oil-absorbing material II completely Submerged in 12 hours.

After the test for the ability to absorb oils and water, the mat prepared from the oil-absorbing material G showed a good burning state without the generation of any black smoke.

Text Example 4 (test for the ability to absorb a fish oil) A square mat measuring 10 cm in each side and 1 cm in thickness was made from 10 g of the oil-absorbing material B in the same way as in Test Example 2, and tested for its ability to absorb a sardine oil and water in the same way as in Test Example 2. The results are shown in Table 4. 42600 - 16 TABLE 4.

Time for immersing the mat in water Amount of the sardine oil held by the mat (g-oil/g-mat) Amount of water held by the mat (g-water/g-mat) 0 (in the dry state) 8.79 1.05 5 minutes 8.26 1.24 4 days 7.95 1.45

Claims (6)

1. CLAIMS;1. A process for producing an oil-absorbing material, which comprises mixing vegetable fibers selected from grass peat fibers, flax fibers, coconut shell fibers, 5 straw, and grass fibers with not more than 35% by weight based on the dry weight of the fibers, of a solid olefin polymer, and heating the resulting mixture to melt the ole*£in polymer and thereby impregnate the molten olefin polymer in the vegetable fibers. 10 2. Λ process according to Claim i, wherein said olefin polymer has a weight-average molecular weight of at least 15,000. 3. A process according to any one of Claim 1 or Claim

2. , wherein said olefin polymer is a homopolymer or copoly15 mer of ethylene, propylene, isobutylene or butene, a copolymer of ethylene with one or more of vinyl acetate, acrylic acid, acrylic acid salts, acrylic acid esters, methacrylic acid, a methacrylic acid salt or a methacrylic acid ester, or a mixture thereof. 20 4. A process according to any one of the preceding claims, wherein said olefin polymer is in the form of a powder having a size of not greater than 50 ASTM mesh, or fibers having a length of not more than 10 mm.

3. 5. A process according to any one of the preceding 25 Claims, wherein the amount of said olefin polymer is 2 to 30% by weight based on the vegetable fibers.

4. 6. A process for producing an oil-absorbing material substantially as hereinbefore described with reference to any one of Examples IA, IB, 1C, 2D, 2E, 3F, 4 and 5. ,-181

5. 7. An oil-absorbing material produced by a process according to any one of the preceding Claims.

6. 8. A method of absorbing oil, wherein the oil is absorbed in a material according to Claim 7.