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Title:
PROCESS FOR RECYCLING PRODUCTS HAVING COMPOSITE MATERIALS, COMPOUNDS OR RESINS CONTAINING ABSORBENT POLYMERS
Document Type and Number:
WIPO Patent Application WO/2018/102898
Kind Code:
A1
Abstract:
The used absorbent products, such as diapers and sanitary napkins, containing cellulose pulp and other polymers, are submitted to the steps of: immersion in a solution with controlled pH range and radiation for sterilization of the products; crushing; washing with the use of washing liquid under agitation to separate the cellulose pulp from the other materials of the absorbent products; and forced drying/dehydration. According to the process, the different materials resulting from the drying step can be further submitted to the steps of: mixing homogeneously and in the necessary proportions, the different materials resulting from the drying step; melting in a new blend or composite material; processing the blend or composite material into granules; and molding the granules in final products/test bodies.

Inventors:
CUNHA, Kátia Lúcia Da Silva Gonçalves (Avenida Dr. Washington Luis, 173 - Ap. 42 - Vila Caminho do Mar, -040 São Bernardo Do Campo - SP, 09618-040, BR)
Application Number:
BR2017/050371
Publication Date:
June 14, 2018
Filing Date:
December 06, 2017
Export Citation:
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Assignee:
INSTITUTO PRESBITERIANO MACKENZIE (Rua da Consolação, 896 - Consolação, -907 São Paulo - SP, 01302-907, BR)
WISEWASTE CONSULTORIA AMBIENTAL LTDA. (Rua do Radium, 72 - Bairro Jardim Petrópolis, -050 São Paulo - SP, 04637-050, BR)
CUNHA, Kátia Lúcia Da Silva Gonçalves (Avenida Dr. Washington Luis, 173 - Ap. 42 - Vila Caminho do Mar, -040 São Bernardo Do Campo - SP, 09618-040, BR)
International Classes:
C08L101/00; A61L2/08; A61L11/00; B02C19/11; B02C23/18; B09B3/00; C02F11/12; C05F9/00; C05F17/00; C08L23/06; C08L23/12; C08L27/06; C08L97/02; D21B1/32
Domestic Patent References:
WO1995024967A11995-09-21
WO2001091809A22001-12-06
Foreign References:
CN103756350A2014-04-30
CN102503072A2012-06-20
US5322225A1994-06-21
US5292075A1994-03-08
US5558745A1996-09-24
KR20140107119A2014-09-04
CN101709006A2010-05-19
Attorney, Agent or Firm:
ARNAUD, Antonio M. P. (Rua José Bonifácio, 93 - 8° Floor, -901 São Paulo - São Paulo - SP, 01003-901, BR)
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Claims:
CLAIMS

1. Process for recycling products having composite materials, compounds or resins containing absorbent polymers, such as disposable diapers and sanitary napkins, containing cellulose pulp and one or more other polymers, characterized in that it comprises the steps of:

- submitting the used absorbent products to immersion in a solution with a controlled pH range and to a radiation in an appropriate dose necessary and sufficient to promote sterilization of the product being processed;

- submitting the absorbent products, sterilized by radiation and withdrawn from the controlled pH solution, to a crushing in a crusher-shredder equipment;

- submitting the sterilized and crushed absorbent products to a washing step with the use of a washing liquid under agitation, until the release of the cellulose pulp occurs, separating it from the other materials of the absorbent products being processed; and

- submitting the different separate materials obtained from the sterilized, crushed and washed absorbent products to a forced drying/dehydration step.

2. Process according to claim 1, characterized in that it further comprises the steps of:

- mixing the dried different materials, homogeneously and in the necessary proportions;

- melting the different blended materials into a new blend or composite material of homogeneous structure;

- processing the blend or composite material into granules; and

- processing the blend or composite granules into final products/test bodies.

3. Process according to any one of claims 1 or 2, characterized in that the drying step is carried out in a kiln at a temperature from 50°C to 100°C, preferably 80°C.

4. Process according to any one of claims 1 to 3, characterized in that the immersion of the absorbent products is carried out in a solution having a pH range of 5 to 7.

5. Process according to claim 4, characterized in that the pH of the solution is controlled with hydrochloric acid and sodium hydroxide.

6. Process according to any one of claims 1 to 5, characterized in that the absorbent products immersed in the solution are submitted to a radiation of 25 to 50 kGy.

Description:
"PROCESS FOR RECYCLING PRODUCTS HAVING COMPOSITE MATERIALS, COMPOUNDS OR RESINS CONTAINING ABSORBENT POLYMERS"

Technical field

[001] The present invention relates to a process for the hygienic and economically feasible recycling of products having composite materials, compounds or resins having an absorbent function, such as disposable diapers and sanitary napkins, containing cellulose pulp and one or more other absorbent polymers without requiring the prior disposal of solid waste eventually aggregated into the composite product and allowing recovery of the cellulose pulp and other polymeric materials of interest which constitutes the product to be recycled.

Background art

[002] The increasing concern with the environment, due to the increasing difficulty of landfilling, has encouraged the search for alternatives to waste through recycling. Although the need for waste recovery is not new, the issue of adequate disposal of composite absorbent products, such as disposable diapers, sanitary napkins and other products having similar construction and use, generally discarded with liquid and solid wastes, is still of little importance.

[003] Although 90% of the superabsorbent polymers are intended for absorbent sanitary products, such as disposable diapers and absorbents for women, their use extends to a wide variety of applications, such as in agriculture, hydroponic product cultivation and soil moisture retention, in the pharmaceutical drug-releasing, civil construction, food packaging, electronic cables and cosmetics industry among others (LOPES et . al . , 2007, KHOYLOU; NAIMIAN, 2009) . [004] The main characteristic of the superabsorbent polymers is the great absorption and retention of water. However, a characteristic that makes the disposal of superabsorbent polymers an environmental problem is their durability, that is they take a long time to decompose in nature .

[005] Absorbent composite products, even with a variety of recyclable materials, are still widely disposed of in dumps or landfills, generating known environmental problems and their consequences in economic and public health terms.

[006] When such products are used in hospital environments, their disposal is usually accomplished through incineration, a relatively costly procedure that prevents the recovery of a wide variety of high quality and high value natural and synthetic polymer materials.

[007] The technologies currently known to recycle such composite materials, for example, disposable diapers, are not satisfactory because they are difficult to implement, generate large amounts of pollutants and organic waste, consume large amounts of energy and have significant safety deficiencies for those involved in the handling of waste. Examples of such known technologies for recycling absorbent composite products can be found in US5292075 and US5322225.

[008] As can be seen, such known recycling technologies require relatively complex steps and equipment which considerably limit their implementation in small-scale processing units.

Summary

[009] Due to the limitations of the known recycle processes of absorbent composites considered herein, the present invention has the object of providing a recycling process for said products containing at least one superabsorbent polymer, said process being carried out in a relatively simple and cost-effective manner, allowing its economic viability in small applications in specific areas of intensive use of such products and without submitting the operators of the recycling process and the environment to contamination risks in the treatment of the products in recycling .

[0010] The present invention resulted from the research of new technologies for the recycling of absorbent composite products, such as, for example, disposable diapers, using appropriate dose radiation, with the observation of the effects of this radiation on the mechanical, thermal, rheological and morphological properties of the blends

(mixtures) and the compounds to be obtained from the recycling process.

[0011] The process comprises the characterization of the components of the absorbent composite for the determination of aspects to be considered in the processing, such as a controlled pH solution, the preparation of the absorbent composite (such as disposable diapers), the application of radiation in the appropriate dosage, mechanical recycling, in order to obtain mixtures and composites, with the possibility of further characterization of samples of such mixtures and composites resulting from the recycling process.

Description of the drawings

[0012] The invention will now be described with reference to the accompanying drawing in which:

[0013] Figure 1 shows a block diagram representing the different steps of the present recycling process.

Detailed description of the invention

[0014] According to the present invention, the recycling process is applied to absorbent products containing, in their composition, cellulose pulp and, usually, other polymer materials (plastics) . The process is initiated by submitting used absorbent products, such as disposable diapers or other sanitary absorbent products, by carrying impurities or liquid and/or solid wastes immersed in a controlled pH variation solution to a dose radiation step, for example a radiation of 25 to 50 kGy, necessary and sufficient to promote the sterilization of the product being processed.

[0015] The sterilization can be done with gamma radiation in an industrial irradiator, the pH of the solution being controlled between 5 and 7 with hydrochloric acid and/or sodium hydroxide.

[0016] The results showed that the radiation acts differently and in isolation in each component of the absorbent product in the presence of a controlled pH solution, causing significant changes in the superabsorbent polymers, improving the mechanical recycling process and allowing the reduction of costs. Recycling such products, such as disposable diapers, can maintain some properties and change others. It has been observed that removal of superabsorbent polymer improves not only the recycling steps but also the thermal and mechanical properties of the final product to be obtained by recycling.

[0017] After the radiation sterilization step, the sterilized absorbent products are subjected to a crushing step in any commercially available crusher-shredder equipment suitable for the type of material being processed. The materials that make up the absorbent products are not resistant and are easily crushed. In this way, the main requirement is that the equipment be constructed of stainless material, because the diapers will be crushed in the humid condition, requiring that the equipment be easily sanitized.

[0018] The sterilized and comminuted absorbent products are then subjected to a washing step, with the use of washing liquid, which may be defined, for example, by water and biodegradable neutral detergent. During washing, carried out in any suitable washing tank, the absorbent products should be submitted to agitation so that the detachment of the materials that are arranged in layers and, mainly, of the cellulose pulp takes place. In this agitated washing step, the different materials of the crushed absorbent products, for example, disposable diapers, are separated by density difference, with the moist cellulose pulp tending to sink and other plastics (other polymers) tend to float. The washing should occur in a washing tank having sufficient dimensions to allow the decantation of materials and be further provided with an outlet opening, to allow the washing liquid to be released from the tank over at least one sieve to separate the washing liquid from the decanted cellulose pulp and the plastic materials, both crushed.

[0019] The crushed materials, defined by the cellulose pulp and the plastic materials of the absorbent product, are then subjected to a forced drying/dewatering step, preferably in an oven and at a temperature between 50° C and 100° C, usually 80° C for diapers and other absorbent disposable products, of personal use. The average drying time may vary depending on the load, the degree of humidity and the temperature of the drying kiln or oven.

[0020] After the drying step, the crushed materials obtained from the recycling of the absorbent products, can have different destinations and be used, for example, for the development of blends and composites, in varied compositions, depending on the desired properties and functions.

[0021] For the development of blends and composites, the different crushed materials must be homogeneously mixed in the required proportions and in any suitable blending equipment, to be then melted into a new composite material of homogeneous structure, to be used as a raw material for molding, for injection or other processes of different products. For this purpose, this mass of molten composite material, which has already been cooled, must be granulated with the aid of a mill or other similar processing equipment, so that the granules obtained can be traced to conventional polymer molding steps or obtaining test bodies, such as extrusion and injection, molding the desired final product obtained by recycling the absorbent products used.

[0022] As can be seen from the foregoing, the process in question contemplates important steps for the recovery of the materials comprising the sanitary absorbent products, steps such as the step of irradiating the absorbent products used in a controlled pH solution.

[0023] The effects of radiation on the component materials of the sanitary napkins, under appropriate conditions, render the mechanical recycling steps feasible, including the steps of crushing in shredder, washing and separating equipment by difference in density and/or solubility and drying, preferably in a kiln. This behavior of the superabsorbent polymer, induced by radiation in controlled pH solution, promotes a satisfactory process in relation to the implementation problems listed by other authors, since it uses less washing liquid, usually water with neutral detergent, simple separation step and lower energy consumption for drying, since the washing liquid is no longer held by the superabsorbent polymer. As previously mentioned, the present process, unlike those known, is very efficient in promoting the safety of those involved in the handling of contaminated waste.

[0024] Although only one embodiment of the present process has been described, it should be understood that changes of parameters may be made in the processing steps without departing from the inventive concept defined in the enclosed claim set .