A.REUSE OF ACRYLIC SCRAP FROM SHEET MANUFACTURE FOR SHEET MANUFACTURE

Acrylic, also known as  poly methyl methacrylate (PMMA), is a clear, colorless transparent plastic with a higher softening point, better impact strength, and better weatherablility than polystyrene (PS). Acrylic is widely used in many application fields, such as transparency roof, automobile parts,  etc. The principal commercial processes for the production acrylic sheets are extrusion and casting . The manufacturing of transparent acrylic sheet is normally produced by cell casting process, which utilizes two flat glass plates separated by an elastomeric gasket. The flexible gasket permits filling of the cell with monomer or syrup,prevents leakage, and controls thickness of the acrylic sheet. In general, gasket is used only once and must be removed from finished product by cutting in order to make a require sheet size. Most of acrylic scrap, residual acrylic material stick around unusable gasket, generated during cutting step and comprises of approximately 10% of total final production, which becomes as an industrial waste plastic.

In order to conserve and reduce the quantity of acrylic waste from the production process, the concept of cleaner technology could be  applied to demonstrate the alternative way to reduce the processing cost of acrylic cast sheet and decrease an industrial waste by using acrylic scrap recycle within the acrylic cast sheet process.

Approximately  10% of acrylic scrap is generated during cutting step. Recycling of acrylic waste scrap within the production process is a technical option that can  reduce the generation of acrylic waste scrap.

The acrylic monomer solution viscosity increases with increasing the concentration of acrylic waste scrap. According to the industrial preparation of acrylic cast sheet, the appropriate viscosity of acrylic syrup before pouring into a casting cell is in the range of 500-3000 cp, therefore the appropriate concentration of acrylic monomer solution mixed with acrylic waste scrap should almost reach that of industrial standard viscosity value. The appropriate concentrations of acrylic waste scrap mixed within the acrylic monomer solution are in the range of 4% and 5%, which give the viscosity values in the range of 500-1611 cp.

In experimental studies the acrylic waste scrap did not affect the impact strength and hardness properties of the acrylic cast sheet product although the tensile strength property of the acrylic cast sheet product increased with increasing the amount of acrylic waste.

The acrylic waste scrap did not affect  the transparency property of the acrylic cast sheet.

Acrylic waste scrap affects the UV resistance property but did not affect the heat resistance property. However, the UV resistance property of the acrylic cast sheet product mixed with the acrylic waste scrap can be improved by the addition of UV stabilizer additive, which is usually added to the final product of acrylic cast sheet before sale to customer.

Environmental Impact Evaluation of the Acrylic Scrap Recycle

According to data available for Pan Asia Industrial Co., Ltd, Thailand,  16,000 kg of acrylic monomer isfed into a batch reactor and approximate 1,600 kg of acrylic waste scrap is generated during the productionprocess per day.  5% (800kg/day) of acrylic waste scrap was the maximum concentration that can be recycled as a part of raw material for produces acrylic cast sheet. By using the material balance analysis  and the material grouping for simplified product life cycle assessment, the environmental impact evaluation of the 5% of acrylic scrap recycle was calculated.   5% of acrylic waste scrap recyclable can reduce the costs of raw material (acrylic monomer), waste disposal, processing, and transportation, which are approximate 6-7% saving of the total cost. It can be concluded that the recycling of acrylic waste scrap within the acrylic production process generates a double outcomes to industry both in environmental and economical aspects. In environmental aspect, company can minimize the waste and pollutions.  Economical aspect, company can optimize resource use while increasing resource productivity. This ensures that more product/or services areobtained from less energy and raw material input.

B.ACRYLIC POWDER FROM SCRAP RECYCLE AS FILLER IN THE MANUFACTURE OF BATHROOM FIXTURES.

Composite plastic scrap (vacuum formed acrylic plastic with glass fibre reinforcement) has low density and thus has to be precrushed to save transportation and landfilling costs. Reprocessing of problematic plastic scrap (composite plastics) by using mechanical methods like milling by collision in disintegrators has been tried successfully.For the milling of composite plastic scrap, different disintegrator mills wereused [9]. for the size reduction of the acrylic plastic constituent and on the separation of the glass fibre constituent. Plastic powder with a particle size of about 1–2 mm can beproduced by two step milling and 95 mass % of the glass fibre content can be separated by final selective milling.

The total amount of separated GFP was 45 mass %.As a result, we can use 55 mass % of acrylic plastic from the composite plastic scrap. GFP can be reused in the production of polymeric concrete products as reinforcement.

Industrial PMMA scrap can be divided into two groups: pure acrylic plastic scrap forms about 20% and reinforced acrylic plastic scrap about 80% of the total amount. PMMA scrap without technological additives cannot be recycled and reextruded to produce new PMMA sheet material because of the amorphous structure of this thermoplastic material. Heating up an acrylic plastic material overglass transition temperature (100 °C) converts the plastic into a rubber-like state, which makes this material ideal for vacuum forming. Continued heating causes thermal degradation of the material instead of melting.

Acrylic powder has found application as  as a new fillermaterial in  the Solid Surface casting technology for producing  bathroom washbasins. Commonly, washbasins are made from a composite material consisting of a binder agen(unsaturated polyester resin), a filler material (dolomite powder),and a catalyst agent added to the resin to accelerate hardening. The mixing ratios of the binder agent and the filler material are 25/75 mass %. The traditional filler material, used in the casting technology, is a high-white dolomite filler, composed of CaMg(CO3)2 with a density of 2850 kg/m3 and particle sizes of coarse fractions 0.2–0.6 mm and 0.1–0.3 mm, and of the fine fraction less than 0.1 mm. Acrylic powder was used to substitute for the high white dolomite filler. The best flow characteristics of the mixture were obtained with 50 mass % of acrylic filler and 50 mass % of matrix, but the best surface quality and hardness after polishing was achieved with a mixture of 66 mass % of the acrylic filler and 34 mass % of the resin matrix.

Flow characteristics of the mixture 66/34 could be improved by using a lower viscosity matrix.Based on the results of tensile and hardness tests, two composite materials, 34/66 and 40/60 were selected for the abrasive resistance test. This test showed that the composite 40/60 had the best relative wear resistance properties ( 0.94), v e = which were closest to the reference material PMMA. Reprocessed plastics washbasins, produced from the new composite material, will increase the wear resistance of the working surface. At the same time, as compared to the dolomite filler, double reduction in weight can be achieved.

Aditional Readings

[1] National Pollution Prevention Center for Higher Education (2006), Industrial Ecology, Available
online: http://www.umich.edu/~nppcpub/
[2] Kasakura, T., Noda, R. and Hashiudo, K. (1999), Trends in Waste Plastics and Recycling, J. Mater.
Cycles Waste Manag., vol. 1, pp. 33-37.
[3] Noda, R., Komatsu, M., Sumi, E. and Kasakura, T. (2001), Evaluation of Material Recycling for
Plastics: Environmental Aspects, J. Mater. Cycles Waste Manag., vol. 3, pp. 118-125.
[4] Billmeyer, F. W. Jr. (1984). Textbook of Polymer Science, John Wiley & Sons Inc, Singapore.
[5] UNEP (1993), Cleaner Production Worldwide, UNEP, Paris.
[6] Ross, S. and Evans, D. (2003), The Environmental Effect of Reusing and Recycling a Plastic-Based
Packaging System, Journal of Cleaner Production, vol. 11, pp. 561-571.
[7] Sun, M., Rydh, C. J. and Kaebernick, H. (2003), Material Grouping for Simplified Product Life
Cycle Assessment, The Journal of Sustainable Product Design, vol. 3, pp. 45-58.
[8] Rydh, C. J. and Sun, M. (2005), Life Cycle Inventory Data for Materials Grouped According to
Environmental and Material Properties, Journal of Cleaner Production, vol. 13, pp. 1258-1268
[9] Patel, M., von Thienen, N., Jochem, E. and Worrell, E. Recycling of plastics in Germany.
Resources Conservat. Recycl., 2000, 29, 65–90.
[10] Subramanian, P. M. Plastics recycling and waste management in the US. Resources Conservat.
Recycl., 2000, 28, 253–263.
[11] Okuwaki, A. Feedstock recycling of plastics in Japan. Polymer Degrad. Stabil., 2004, 85, 981–
988.
[12] Smolders, K. and Baeyens, J. Thermal degradation of PMMA in fluidised beds. Waste Manag.,
2004, 24, 849–857.
[13] Kang, H.-Y. and Schoenung, J. M. Electronic waste recycling: a review of U.S infrastructure
and technology options. Resources Conservat. Recycl., 2005, 45, 368–400.
[14] Broekel, J. and Scharr, G. The specialities of fibre-reinforced plastics in terms of product
lifecycle management. J. Mater. Process. Technol., 2005, 162–163, 725–729.
[15] Directive 2002/96/EC of the European Parliament and of the Council on waste electrical and
electronic equipment (WEEE). Official Journal of the European Union, L37, 2003, 24–38.
[16] Rosato, D. Reinforced Plastics Handbook. Elsevier, Oxford, 2005.
[17] Tamm, B. and Tümanok, A. Impact grinding and disintegrators. Proc. Estonian Acad. Sci. Eng.,
1996, 2, 209–223.
[18] Kers, J. and Kulu, P. Retreatment of industrial plastic wastes by high energy disintegrator mills.
In Proc. Global Symposium on Recycling, Waste Treatment and Clean Technology
(Gabllah, I. and Mishra, B., eds.). Madrid, 2004, vol. 3, 2795–2797.
[19] Kulu, P. and Tymanok, A. Treatment of different materials by disintegrator systems. Proc.
Estonian Acad. Sci. Eng., 1999, 5, 222–242.
[20] Tümanok, A. and Tamm, J. Choice of rational distribution function for describing of granulometry
of ground material. Izv. Sib. Otd. Akad. Nauk SSSR, Khimiya, 1983, 6, 8–11 (in
Russian).
[21] Wojnar, L. Image Analysis: Applications in Materials Engineering. CRC Press LLC, Boca
Raton, 1999.
[22] EVS-EN ISO 6506-1:2006. Metallic materials – Brinell hardness test – Part 1: test method.
[23] ASTM–G–65–94. Standard test method for measuring abrasion using the dry sand/rubber wheel
apparatus, 1994.
[24]Jaan Kersa, Priit Kulua, Dimitri Goljandina and Valdek Miklib-Reprocessing technology of composite plastic
scrap and properties of materials from recycled plastics-Proc. Estonian Acad. Sci. Eng., 2007, 13, 2, 105–116
[25]K. Charmondusit, P. Arleewong-The application of cleaner technology in th acrylic cast sheet production production:Case study of Acrylic cast sheet company in Thailand.International Conference on Green and sustainable innovation.  November 29th – December 1st, 2006

As of estimates made in 2002, India had more than 3000 tanneries with a total capacity of 700000 tonnes of hides and skins per year. The annual income from leather trade in India was about Rs 20000 crores. More than 90% of the tanneries were small or medium with a processing capacity of less then 2 to 3 tonnes of hides/skins per day. Most of the tanneries are located near river banks. The highest concentration of tanneries in India is on the banks of Ganga river (Kanpur, Unnao) in North India and the Palar river system in Tamilnadu.

Leather Production Technology and Pollution:

An animal skin consists of about 61% water, 34% fibrous proteins, 1% globular proteins, 2% lipids, 1% natural salts and some other ingredients including pigments. Out of three layers, the epidermis, dermis and the hypodermis it is the dermis which is later transformed into leather. The epidermis primarily composed of keratin has hair which is removed and the hypodermis has flesh and blood vessels which is also removed. In leather processing, the basic operations revolve round cleaning the skin of unwanted inter fibrillary material through a set of pre-tanning operations in the Beam House, processing the leather permanently by means of tanning and adding aesthetic value during the post tanning process. The starting material in most cases is raw hide or skin which has been preserved temporarily by the addition of common salt.

1. The Beam House process involves the removal of salt, dirt and hair  in the following processes:

(a)   Desalting and Soaking the hides to remove salt and other foreign material such as dirt and also to remove the moisture content.  This process uses a large amount of water about 20 m³ per ton of hide and generates conspicuous pollution. Soaking generates about 6-9 m³ per ton of effluents with a BOD from 1100 to 2500 mg/l, a COD of 3000-6000 mg/L, very high total solids and suspended solids, 15000 to 30000 mg/l of chlorides and 800-1500 mg/l of sulphates.

(b)   Unhairing and Liming – The process yields one of the most polluting effluent streams from tanneries. Liming opens up the collagen structure by removing interstitial material, fleshing removes excess tissue from the interior of the hide.  Unhairing is done by treating soaked hides in a bath containing sodium sulphide / Hydrogen sulphide and lime. About 3 to 5 m³ of effluent per tonne of hide/skin is expected to be discharged with a high pH of 10.0 to 12.8, a BOD of 5000 to 10000 mg/l and COD of 10000 – 25000 mg/l. The concentration of sulphides ranges from 200 to 500 mg/l, the total solids (24000 to 48000 mg/l) and sulphates (600-1200 mg/L) are also high.

(c)    Deliming and bating: A bath of ammonium salts and proteolytic enzymes is used to process the pelt. About 1.5 m³ of effluents are generated in the process at a pH of 7 to 9. The pollutants from the process include Calcium salts, Sulphide residues (30 to 60 mg/l), degraded proteins, residual proteolytic enzymatic agents, Chloride (1000 to 2000 mg/l), Sulphates (2000 to 4000 mg/l), BOD (1000 – 3000 mg/l) and COD (2500 to 7000 mg/l). Nitrogen based deliming agents are considered a long term environmental threat because of their impact on soil NOx values.

Sulphates are an important content of pretanning waste waters. They readily get reduced to sulphide under anaerobic conditions in waste water treatment plants like anaerobic lagoons, contact filters or up flow anaerobic sludge blanket reactors. A build up of sulphides makes the biomethanation of organic materials less effective apart from adding to the COD load. Ammonia is also given off as an air pollutant in the process.