WO2000039206A1

WO2000039206A1 - Process for polyurethane recycling

Info

Publication number: WO2000039206A1
Application number: PCT/BR1999/000105
Authority: WO
Inventors: Luiz Carlos Oliveira Da Cunha Lima
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-23
Filing date: 1999-12-21
Publication date: 2000-07-06
Anticipated expiration: 2001-06-23
Also published as: AU1763000A; BR9805620A

Abstract

Invention relating to 'PROCESS FOR POLYURETHANE RECYCLING' based on the capacity of polyurethanes to lower their resistance to shearing and hydrolysis by absorption of solvents. The shearing equipment considered as suitable for this process are, in particular, ball mills, sphere mills, plate mills, hammer and that equipment which enable material flowing through slots, holes, screens, sintering microporous plates, such as injectors, pumps and extruding machines, under pressure. The hydrolyzing agent added to the polyurethane shearing or comminuting processes comprise, acid solutions and, alkalis solutions. The process of this invention allows the obtention of polyurethane powder, or else, regenerated polyurethane under mild conditions that will enable a new integration to the basic formulation while ensuring a minimum loss in the product original characteristics.

Description

PROCESS FOR POLYURETHANE RECYCLING

BACKGROUND OF THE INVENTION Technical Field This invention relates to a process for polyurethane recycling based on the capacity of polyurethanes to lower their resistance to shearing and hydrolysis by absorption of solvents. Description of the Related Art The first information available on polyurethane obtention dates back to 1848, when it was first synthetized by A. Wurtz. Only in the next century, namely, in 1937, Bayer started with polyurethane commercial production. Polyurethane has by far the widest range of applications when compared to existing synthetic polymers. It is used to produce following products:

1. Foams or rigid and flexible foamed _products .

2. Elastomers . 3. Sealants

4. Coatings .

5. Fibers

The ever growing utilization of polyurethanes has made it necessary an economically feasible process for recycling of industrial waste and out- of-use, discarded products .

Most polyurethane plants currently use scrap recycling processes, whereby the polyurethane is crushed into small pieces and agglomerated with a certain portion of the unreacted virgin product. The process for discarded polyurethane scrap recycling utilizes about 90 to 60 percent of polyurethane scrap and 10 to 40 percent of the virgin unreacted raw material. A reaction takes place next on said mixture, whereby the crushed polyurethane is agglomerated. However_τ this is not a sound solution, inasmuch as this product has characteristics inferior to those of the virgin product, must be sold at a price lower than that of the original product, which labour costs are twice as high as those of the original product.

Other processes available for polyurethane scrap recycling involve opening; or breaking of the polymer chain so as to obtain polyols, as stated in the following patents:

1)- "Cleavage of polyurethane scrap"- German patent number 2.542.001_r claimed by -Schneider, Gottfried, awarded on March 24, 1977. Polyurethane scraps are easily and economically recycled to yield polyhydroxylated compounds, by cleavage with adducts of caprolactams with ethylene or diethylene glycol and methylene diamine. The reaction takes place at 130° C, 2)- "Polyurethane scrap processing". Russian patent number 1.224,309, claimed by Dunaevsky and co-workers, awarded on April 15, 1986.

Polyurethane scraps are processed by adding heated prepolymer to small piece-s of cru-shed polyurethane with subsequent cross-linking agent. The reaction is obtained under vacuum. The method Is simplified and accelerated by activation in the presence of dimethylketone or methylenechloride between 18 and 20° C.

3)- "Decomposition of polyurethanes"- German patent number 2.541.10-0, claimed by -Sakai Kasuvoshi and co-workers, awarded on April 1, 1976. Polyurethane scraps are decomposed at between 50 to 1-8-0° C in the presence of alcoholates, and, whenever applicable, of alkali metal hydroxydes and/or amines, and amides. 4)- "Decomposition of polyurethanes". Japanese patent number 7675, 769, claimed by Murachi Tatsuya and co- workers, awarded on June 30, 197-6.

Decomposition of polyurethane scraps in the presence of group III-VII metal hydroxydes and aminoalcohols .

5)- "Recovery of polyurethane scrap polyols by heating at 140 to 2Q0° C, mixed with high-molecular weight alcohols and tin organic derivatives. With the exception of the process whereby comminuted polyurethane is mixed with unreacted polyurethane, all other polyol-yielding processes are rarely utilized for commercial purposes as they have proved to be expensive.

So far the world has not been able to solve the problem which involves significant losses incurred in the recycling of both, industrial and post- consumption waste. This leads to the prevailing practice of incinerating excess polyurethane, thus incurring pollution risks through toxic gases whenever the required combustion process is carried out inadequately. Polyurethane plants utilize inert fillers that are mixed with certain compositions in order to lower formulation costs. Filler users prefer fine mesh precipitated calcium carbonate, silica and silicates, kaolin, gypsum, etc. All of these fillers do indeed lower costs, but at the expenses of product characteristics ^such as, permanent set and flexural strength. SUMMARY OF THE INVENTION

The present invention relates to a polyurethane recycling process whereby the polyurethane is comminuted into very fine particles that are perfectly compatible with the original product. Polyurethane comminuting is done by swelling the polyurethane with a solvent and further comminuting the resulting scraps by shearing, with or without processing in the presence of hydrolyzing agents.. In case said sc aps are not -further processed in the presence of hydroylizing agents, the product obtained is polyurethane powder, an inert filler. On the other hand, whenever said scrap is processed in the presence of an -hydrolyzing agent., an active filler is obtained, that is, micro polyurethane containing OH radicals .

The present invention refers also to a process for polyurethane scrap regeneration, whereby a high-quality final product is obtained that can be incorporated into the original composition while maintaining compatible characteristics. DESCRIPTION OF PREFERRED EMBODIMENTS More specifically, present invention relates to a process for polyurethane comminuting and/or regeneration, characterized by the fact hat the polyurethane is crushed in the presence-, or absence_y of hydrolyzing agents. Particle size may vary from 1 milimeter to 0,01 micron, more specifically from 0,1 mm to 0,1 micron.

The material so regenerated can be further utilized to make either-, compact objects or foamed polyurethane. Whereas producing compact objects requires only the material to b moulded under pressure and lieated during a certain period of time, foamed polyurethante production requires the material to be mixed with polyisocianates; more specifically, it is first mixed with polyol and further mixed with polyisocianates, although it can also be mixed with prepolymers.

Comminuting of the carbon chains of the solvent--swollen polyurethane ma-cromolecule_y combined with hydrolyzing action, makes it possible to obtain OH radicals, as herein presented. This is therefore a new achievement and has the advantage of providing the addition of said product to nri gi nal fnrmnl a .i nns without incurring quality downgrading.

All organic solvents, concentrated or dilute, pure or blended, that are able to swell the polyurethane to a greater or lesser degree are considered solvents for the purpose of this invention, as listed in following examples:

- Acids; formic acid, acetic acid.

Ketones: dimethylketone, diethylketone, methylethylketone, m thylbutylketone.

-Alcohols: methanol, ethanol, isopropanol, propanol, butanol, isobutanol, glycols.

-Ethers: dietylether.

-Esters: ethylacetate, propylacetate, butylacetate, butylphthalate, tricresylphosphate .

-Vegetable oils. -Hallogenated derivatives: carbon tetrachloride, chloroform, trichloroethylene, chlorobenzene, methylenchloride .

-Aromatic hydrocarbons: toluene, xylenes, cresols.

-Paraffin hydrocarbon _: hexane,, ±Lepthane-, octane^ - Naphthenic hydrocarbons: cyclopentane, cyclohexane, dipentene, turpentine.

-Amines: aniline.

- Amides: dimethylformamide, dimethylacetalde.

- Nitrated derivatives: nitrobenzene. - Sulphur derivatives: carbon disulphide.

Mentioned swelling agents may be used alone or in blends, the purpose always being to swell high molecular weight chains and/or to dissolve low molecular weight chains, thus weakening the mechanical properties imported by cross-li king.

Depending on the polyurethane type, a suitable_* pure or blended solvent is applicable, that is, a solvent that can more efficiently swell the polyurethane and favour the size reductio process. Given the wide range of polyurethane scrap mixture characteristics, a suitable solvent or solvent mixture can be selected experimentally.

Another important issue to be considered when choosing the swelling solvent or the solvent-swollen mixture is that of pricing, although involved costs will only play a significant role upon plant start up, and, as the process evolves, the solvent can be regenerated during drying phase and further recycled, once again.

The swelling solvents must be present at approximately 1 to 20 parts of polyurethane, preferably_* at about 4 to 8 parts by weight.

The time required for polyurethane swelling with a solvent depends on the solvent type used and on the state of the polyurethane particles or scraps, as well as on the polyurethane consistency - whether it is in compact or foamed state - and on polyurethane particle or scrap size. Whenever a high-viscosity polyurethane is used, the polyurethane particles are large and compact_* and it will take longer to he absorbed, maybe-, hours or days; in this case, it is convenient to heat the solvent so as to reduce viscosity rates. Also, in this case, it is convenient to use, say, petroleum aromatic extract as a solvent. When using a fluid solvent and foamed polyurethane, absorption takes place almost immediately; in this case a trichloroethylene at ambient temperature should be used on the foamed polyurethane. When the hydrolysing agents are present as a solution to be mixed with the solvent-swollen polyurethane, they act simultaneously with the polymer carbon chain shearing process_* reduces the molecular weight size, and the hydrolyzing process thus takes place. For purpose of this invention, it is considered as hydroly-zing elements those acid solutions and alkalis which are employed in ester hydrolysing. The process, considers acids_* such as, sulfuric acid, hydrochlroric acid and their derivatives. The alkalis considered in the process are hidroxydes, such as, sodium hydroxyde, potassium hydroxyde and derivatives .

The addition of the hydrolyzing agents of above mentioned products occurs at above 0.001%- by polyurethane, preferably, at about 0,01% by weight.

Different kinds of eguipment are used in the polyurethane regeneration, whereas it is extremely important for the polyurethane to get in contact with the hydrolyzing agent. Equipment used are ball, bar, sphere and plate mills, indented plate comminutors, perforated cylinders, compression-driven gears and machines, such as extruding machines_* pumps and injectors that may subject the swollen polyurethane to restrictions, such as, slots, grades,_* holes, screens,, interized or sponged material. During polymer chain breaking process by pressure-driven pumps and injectors_* comminuting may also occur by decompression (flash) after the swollen polyurethane release through mentioned -restrict] ons.

The time required for polyurethane regeneration by hydrolyzing agents depends- on the eguipment used in the regeneration process. For instance, it can take centesimal .of a second_* when the swollen polyurethane is pressed through restriction means with simultaneous particle comminuting and hydrolysis, or else, it can take hours, when shearing and/or regeneration are processed at ball mills.

Other important factors in the regeneration process are: hydrolyzing agent temperature, pressure and quantity. Regeneration time is conversely proportional to the same factors_* that is, the higher (or larger) these factors are, the shorter is regeneration time. Following examples will evidence the workability of the process of this invention and the new concepts comprised therein, whereby the quality of the polyurethane scrap thus obtained by mentioned recycling process is very similar to that of the original products without radicalizing the regeneration process to the point of restoring its original products such as polyols, amines, etc., which is quite slow and expensive. Table I below shows the characteristics of each example, with the purpose of illustrating the practical aspects of the recycling process by both, polyurethane size reduction and regeneration, respectively_* whereas said considerations should not be considered as limiting factors what concerns the definition of this invention. .As -evidenced in Table I, the size reduction process alone produces an inert filler only -compatible with the polyurethane_* but downgrades prevailing characteristics, whereas the regeneration process maintains the guality of original polyurethane to some extent.

Weight measure units will apply to this invention whenever no measure unit is herein indicated.

Basic Material Following formulation was prepared to subsidize subseguent experiments :

Characteristics of Table 1.

The foamed polyurethane that was yielded according with the material basic formulation was crushed into pieces of approximately 1cm³, start point for following examples, that illustrate embodiments of the present invention but are not to be construed as limiting the scope thereof. Example 1 About 100 g of crushed polyurethane was swollen with 1 liter of acetone and crushed -a.t porcelain ball mills at ambient temperature during 24 hours. The crushed material was dried and resulting scattered powder was mixed with polyol at 10, 20 and 30% by weight. Completing the basic formulation_* following results were obtained: Table 1. Example 2

About 100 g. of crushed polyurethane was swollen with 1 liter of ethyl acetate_* wherein lOg of a solution containing about 0.01 g of hydrochloric acid was added, and the mate-rial was next crushed at a .stainless steel bar mill at ambient temperature during 24 hours. The crushed material 4«*as dried and resulting -scattered powder was then mixed with polyol at 10, 20 30% by weight. Completing the basic fprmulation, following characteristics were obtained: Table 1 Example 3 About 100 g of crushed polyurethane was swollen with 1 liter of toluene-, wherein 20g of a solution containing about 0,01 g of potassium hydroxide was added, and the material ^w next -crushed at stainless ball mill at a temperature of 40° C during 12 hours. The crushed material was dried and resulting scattered powder was further mixed with polyol at 10, 20 30% by weight. Completing the basic formula following characteristics 4«/ere obtained: Table 1 Example 4 About 100 g of crushed polyurethane was swollen with 1 liter of nitrobenzene_* wherein 15g of -a solution of about 0.1 g of sulphuric acid was added, and the material was next crushed at a stainl ess steel ball mill at ambient temperature during 4 hours . The crushed material was dried and resulting scattered powder was mixed with poliol at 10, 20 and 30% by weight. Completing the basic formulation, following characteristics were obtained. Table 1 Example 5

About lOOg of crushed polyurethane was swollen with 1/2 liter of carbon sulphide and 17-2 liter of ethanol. It was next crushed at stainless steel, bar mills, at a drying oven, at 55° C, at a pressure about 0.3 kg/cm³, during 6 hours. The crushed material was next dried and resulting scattered powder was then mixed with polyol at 10_* 20 and 30% by weight. Completing the basic formulation, following characteristics were obtained-: Table 1 Example 6

About lOOOg of polyurethane crushed into 1mm particles was swollen -with 10 liters of trichlor-oet ylene, wherein 85 g of a 0.1% of hydrochloric acid solution was added. Then the material was sieved three times through stainless steel screens with decreasing restrict!io s at a pressure -about 150 kg/cm² and 183 ml/sec. of flow rate. Duration of each sieving operation equals to approximately one minute. The micro-comminuted material was -dried and resulting scattered powder was then mixed with polyol at 10, 20, 30% by weight. Completing the basic formulation_* following characteristics were obtained: Table 1 Example 7

About 1000 g of crushed polyurethane was swollen with 10 liters -of -ethyl alcohol-, wherein 50 g of a solution containing about 0.2% soda-ash was added. The material was next sieved three times through micro-sintered bronze plates with decreasing restrictions at a pressure about 100 kg/cm³ and 122 ml/sec of flow rate. Duration of each sieving operation equals to one and a half minutes. The micro-comminuted material -was olried and resulting scattered powder was mixed with polyol at 10, 20 and 30% by weight. Completing the -basic formulation-, following characteristics were obtained Table 1 Example -8

About 100 g of crushed polyurethane was swollen with 1 liter of cyclohexane_* whero-i fig of a solution containing about 0.1 g of potassium hydroxide was added, and the material was next crushed at -a glass ball mill -during A hours. Following, the material was dried and mixed with 30 g of polyol -through _a three--ro11 er mi 11 till a compact .and homogeneous mass was formed. Completing the basic formulation, additional -quantities -equivalent to 10, 2 30% by weight were added, and following characteristics were obtained-: Table 1: Example 9 About 1000 g of crushed polyurethane previously swollen with 5 liters of ethyl alcohol and 5 liters of cyclohexane was sieved three times through stainless screen with decreasing granulometry at a pressure about 150 kg/cm². Duration of each sieving operation equals to approximately one minute . The comminuted material was dried and resulting scattered powder was mixed with polyol at 10, 20 and 30% by weight Completing the basic formulation, following characteristics were obtained. Table 1

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i υ TABLE 1

CHARACTERISTICS Unit Basic Example Example Example Example Material 1 2 3 4

Reg. Polyurethane 0,0 10,0 20,0 30,0 10,0 20,0 30,0 10,0 20,0 30,0 10,0 20,0 3 Tensile strenght kg/cm² 1,4 0,9 0,8 0,8 1,3 1,1 1,1 1,1 1,0 1,0 1,1 1,0 Module at 100% kg/cm² 1,2 0,0 0,0 0,0 1,1 1,0 1,0 1,0 0,9 0,9 1,0 0,9 Elongation 120,0 95,0 95,0 90,0 110,0110,0105,0 120,0105,0110,0 110,0120,011 Swelling (*) 250,0 200,0190,0190,0 240,0220,0220,0 240,0245,0230,0 235,0235,023

CO CARACTERISTICS Unit Example Example Example Example Example 5 6 7 8 9

Tensile strenght kg/cm² 1,2 1,1 1,1 1,1 1,0 1,1 1,1 1,0 1,0 1,2 1,1 1,1 0,7 0,6 Module at 100% kg/cm² 0,0 0,0 0,0 1,0 1,1 1,0 1,0 0,9 0,9 1,0 1,0 0,9 0,0 0,0 Elongation % 95,0 95,0 90,0 110,0110,0105,0 120,0110,0110,0 110,0120,0110,0 85,0 80,0 8

Swelling (*) % 190, 0180, 0170, 0 230,0220,0210,0 245,0240,0235,0 230,0225,0220,0 190,0180,018 (*) Swelling with Dimethylacetamide

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Claims

1. Process for polyurethane recycling, characterized in that it comprises the initial polyurethane swelling with organic solvent, and the comminuting or shearing of said material in order to reduce the polymer macromolecule chain.

2. Process for polyurethane recycling, characterized in that it comprises the initial polyurethane swelling with organic solvent, and the comminuting or shearing of this material, and its regeneration by means of hydrolyzing agents.

3. Process cr.ordi ng to claims 1 and 2_* characterized in that the comminuting and/or regeneration processes are carried out within 4-8 hours and 0.01 seconds.

4. Process according to claim 3, characterized in that the comminuting process is carried out within 24 hours and 0.1 seconds.

5. Process according to claim 2, characterized in that the hydrolyzing agent employed consists of acid or, alkalis solution.

6. Process according to claim 2, characterized in that the hydrolyzing agent consists of, acid or alkalis derivatives.

7. Process according to claims 1 and 2, characterized in that the organic solvent is an aromatic, naphthenic_* paraffinic_* hallogenated_* nitrate, sulphide, alcohol, ester, ether, ketone, amine, amide derivative, pure, mixed or dilute.

8. Process according to claim 7, characterized in that the process employs ethanol, ethylacetate, trichloroethylene, ketone, hexane, cyclohex-ane, toluene_*- -pure_* mixed or dilute.

9. Process according to claim 7, characterized in that the quantity of organic solvent used in the process corresponds to 1 to 10 parts of polyurethane by weight.

10. Process according to claim 9, characterized in that the quantity of organic solvent used corresponds to 4 to 8 parts of polyurethane by weight.

11. Process according to claims 1 and 2, characterized in that the comminuting and/or shearing systems used consist of sphere, h>all_* and bar mills, comminutors, injectors and pumps that apply pressure through the restrictions.

12. Process according to claim 9, characterized in that the pump applies pressure through restrictions such as sintered plates, perforated plates, metallic foams, screens.

13. Process according to claim 9, characterized in that the polyurethane comminuting is done by decompression (flash) at the injector or pump outlet.

14. Process according to claims 1 and

2, characterized in that the polyurethane is comminuted into particles of 1mm to 0.01 micron.

15. Process according to claim 8, characterized in that the polyurethane is comminuted into particles of 0.1mm to 1 micron.

16. Process according to claims 1 and 2, characterized in that the comminuting is carried out at a temperature of 0 to 150° C.

17. Process according to claim 15, characterized in that the temperature lies between 20 and

60°C.