S. Basu, S. Malik, G. Joshi et al.
Carbohydrate Polymer Technologies and Applications 2 (2021) 100050
flocculant, paper coating agent and a rheology modifier for high size press in paper manufacturing ( Castro & Cheng, 2014 ; Lachke, 2004 ; Mukherjee et al., 2014 ; Taggart et al., 1992 ).
and paper industries when compared with synthetic chemical additives. With the constantly increasing price of petro-chemicals and fossil fuel based chemicals, it is important to understand the economic and envi- ronmental need to switch from chemical to renewable bio-based poly- mers. Most of these bio-materials are abundant and cheap (e.g. cellu- lose and starch based products). Furthermore, these bio-polymers can be obtained/ recycled from natural and household wastes. Recent re- search ( Díez-Pascual, 2019) highlighted these aspects while discussing the production, impact and economical significance of bio-based poly- mers in the manufacture of bio-composites. It was mentioned that al- though the cost of production of bio-polymers is a matter of concern, the same can be compensated from the functional diversity, properties and eco-friendliness. The approximate average price range of various commercially available biopolymers has been reviewed from the latest price lists of reputed manufactures and listed in Table 3 to provide a per- spective on the commercial viability of bio-based polymers. However, a comparative economic blue-print comprising the utilization of syn- thetic and bio-based polymers has not yet been devised. Hence, there is an ample scope of research and analysis in order to design sustainable industrial practices in future.
7. Other bio-based polymeric additives of importance
Molasses extracted from sugarcane have recently been explored as a potential additive in paper industry ( Fahmy, 2014 ). It comprises of around 32–44% sucrose, besides trace amount glucose and fructose. Mo- lasses also contains 3–5% gums (and starch). Sucrose interactions with cellulose fibrils happen to enhance breaking length and water uptake of paper. Molasses at a concentration of 15–20% (w/w) has been reported to increase the dry breaking length (by − 10%), wet breaking length (by ∼ 6%) and water retention value (by ∼ 30%) in paperboards ( Allan et al., 2005 ; Allan, Stoyanov, Ueda & Yahiaoui, 2001 ; Fahmy, 2014 , 2006 ). Tamarind kernel powder or tamarind kernel polysaccharide (TKP) is another commercially available xyloglucan obtained by husking and milling seed kernels of Tamarindus indica Linn . TKP blended with algin and guar has been used a size press solution, pigment coating formula- tion, ink hold-out agent and water retention additive in paper manufac- turing ( Yin & Lewis, 1981 ). This novel blend imparts properties as thick- ener, emulsifier, stabilizer, lubricator, binder and chemical stabilizers. Crude TKP has successfully substituted the conventional wet end addi- tives like starch and galactomannans in paper-making. TKP xyloglucan when used with NFC has been found to enhance the tensile strength and TEA of unbeaten softwood pulp by ∼ 20–30% ( Goyal, Kumar & Sharma, 2008 ; Sehaqui, 2013 ; Yin & Lewis, 1981 ).
10. Future strategy
The consistently high consumption of paper and paper based prod- ucts eventually increases the demand of chemical additives in order to meet the needs of the industry. As discussed in this review, ad- ditives perform a wide array of functions starting from surface engi- neering (surface strength, barrier properties, sizing, coating, enhanc- ing the shelf-life, recyclability etc.) to mechanical strength enhance- ment (tear, tensile etc.) and from retention aid (for fines, filler, other additives etc.) to paper rheology modifications. Hence, additives form an inseparable domainin pulp and paper manufacturing. The produc- tion, availability, chemistry and specific utility of chemical additives are well known to paper technologists and are extensively utilized in paper manufacturing ( Bajpai, 2015 ; Hubbe, Nanko & McNeal, 2009 ; Pelton & Hong, 2002 ). However, it is important to understand the conse- quences of using these harmful chemicals on an environmental perspec- tive. Hundreds of hazardous chemicals and their derivatives are gener- ated during the papermaking process and are released as mill effluents ( Ali & Sreekrishnan, 2001 ). Although effluent recycling and treatments are devised to minimize such risks, the same measures are unable to completely mitigate the potential long term hazards of these harmful chemicals ( Bajpai, 2017 ; Cesaro, Belgiorno, Siciliano & Guida, 2019 ). Hence, to cut-down the hazards of chemical additives, the present re- view discusses the significance of polymers derived from nature that are potential functional substitutes of chemical additives in paper in- dustries. Besides being eco-friendly and biologically benign, the striking feature of bio-polymeric additives is their versatility i.e., one biopoly- mer can be used to impart diverse functions even at very low concentra- tions. In other words, a single bio-polymer additive carries the potential to substitute a group of chemical additives used in paper production ( Table 2 ). Secondly, the chemical make-up of bio-polymers shows com- patibility with cellulose fibrils and synergism with other bio-polymers; hence can be used in innumerable combinations as per requirement. Finally, bio-polymers can be obtained from abundant, and renewable resources. However, modified bio-polymers, are often criticized on a commercial perspective considered their higher production cost. Hav- ing considered such limitations, wide array of bio-polymers are avail- able that can be concurrently produced in paper industries (e.g., modi- fied cellulose, modified starch, modified gums etc.), hence transforming a paper mill into an integrated one for additional revenue and employ- ment opportunities ( Hamaguchi, 2013 ). Table 4 summarises the sources and application of potential bio-polymeric additives that can be used in paper industries.
8. Environmental perspective
The pulp and paper industry has been designated as one of the most notoriously polluting industries on a global scale. The intense manufac- turing processes not only generate hazardous chemicals, gases and toxic water in leaps and bounds but also produces huge amount of sludge com- prised of fibres ( Bajpai, 2017 ; Hashim & Sen Gupta, 1998 ; Veluchamy & Kalamdhad, 2017 ). Adsorbable organic halides (AOX), heavy met- als, sulphide gases, phenolics, suspended particles, acids and various other detrimental compounds are produced and released in the environ- ment. These compounds not only pollute the habitat and disrupt the food chain, but also affect the systemic and genetic make-up of microscopic to large organisms adversely ( Antoni Ginebreda et. al., 2006 ; Lacorte et al., 2003 ). A unique utility of biopolymers was devised by researchers that fo- cuses on the recycling of fibres from effluents. In their study, commonly used bio-polymeric additives like guar gum, xanthan gum and locust bean gum were employed to recover cellulosic fibres from paper-mill effluent. Guar gum proved to be the most promising bio-polymeric floc- culent as compared to chemical flocculent (alum) with a capability of removing turbidity of paper-mill effluent by ∼ 95% ( Mukherjee et al., 2014 ). Recently, Dixit, Gupta, Liu and Shukla (2019) have brilliantly highlighted the environmental health aspect of pulp and paper mill pollutants in detail. The study also describes state of art techniques in waste recycling and the scope of eco-friendly measures. In this context, the commonly used chemical additives and the potential environmen- tal threats from them can be overviewed. Table 2 represents some of the functional chemical additives used widely in paper industry, the po- tential hazards from these chemicals and corresponding bio-polymeric additives that have the potential to execute similar functions.
9. Economy and prospects
The commercialization of biopolymers on a global scale is still at its naive stage. Moreover, there is no authentic scientific report that dis- cusses the economy related to the application of bio-polymers in pulp
11
Made with FlippingBook - Online magazine maker