Elsevier

Carbohydrate Polymers

Volume 99, 2 January 2014, Pages 617-623
Carbohydrate Polymers

TEMPO-mediated oxidation of oat β-d-glucan and its influences on paper properties

https://doi.org/10.1016/j.carbpol.2013.08.070Get rights and content

Highlights

  • Bonding agents can improve the strength of paper products.

  • Beta-d-glucan, an oat byproduct, is shown to be an effective bonding agent.

  • The performance of beta-d-glucan is greatly improved by oxidation.

  • Strength benefits of oxidation were observed even after recycling of the fibers.

Abstract

An enhanced bonding agent for papermaking was prepared by selective oxidation of a hemicellulose-rich byproduct of oat processing, which will be identified here by its primary component, β-d-glucan. The β-d-glucan was treated sequentially with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and sodium hypochlorite, or alternatively just with sodium hydroxide. When added to a slurry of unbleached softwood kraft fibers, in combination with an optimal dosage of aluminum sulfate, the oxidized β-d-glucan yielded greater increases in tensile strength and folding endurance in comparison to untreated β-d-glucan. NaOH treatment also improved dry-strength performance of the β-d-glucan, except for folding endurance. The improvements were attributed to increased charge density of the treated polyelectrolytes, leading to better distribution and retention on fibers prior to sheet formation. Modified β-d-glucan also enhanced the strength of recycled sheets when the treated paper was repulped and formed into recycled paper with no further chemical addition.

Introduction

Bonding between cellulosic fibers is known to play a critical role in meeting the strength requirements of paper products (Page, 1969). Though the strength of paper also depends on the strength of the component fibers, the inter-fiber bonds frequently can be considered as the “weak link” in a paper structure (Helle, 1963, Howard and Jowsey, 1989). Kraft pulp fibers suffer a reduction in their bonding ability when they are recycled (Weise and Paulapuro, 1996, Hubbe et al., 2007). Further demands are placed on paper's inter-fiber bonding ability due to increasing levels of mineral fillers (Shen, Song, Qian, & Liu, 2009), and also a gradual trend toward reduction in the mass per unit area of various paper and paperboard products (Nahrath, 2004, Kerman et al., 2009, Li et al., 2012).

It is well known that paper's inter-fiber bonding strength can be increased by addition of certain water-soluble polyelectrolytes such as cationic starch or acrylamide copolymers; these products are added as solutions to the fibrous slurry before formation of the sheet (Hubbe, 2006). It has been shown that related beneficial effects can be achieved by the addition of hemicellulose products as dry-strength agents (Denis et al., 2003, Suurnäkki et al., 2003, Bai et al., 2012). Hemicelluloses serve as a natural bonding agent when they are a component in ordinary kraft pulp fibers. Thus, it has been shown that excessive removal of hemicellulose, as in the case of overly aggressive “pre-extraction” treatments, can lead to paper that exhibits relatively low inter-fiber bond strength (Oksanen et al., 1997, Al-Dajani and Tschirner, 2008, Yoon and Van Heiningen, 2008).

Another approach that can be used to enhance the strength of paper is chemical modification. It has been shown, for example, that the dry strength properties of paper can be enhanced by TEMPO-mediated oxidation of bleached hardwood kraft fibers (Song & Law, 2010). The treatment was found to benefit not only the strength of paper made from never-dried fibers, but it also had a beneficial effect on recycled paper made from the same fibers. Best results were obtained when the oxidation of the fiber surfaces was carried out before the initial drying of the fibers.

The present work concerns the possible usage of a bonding agent prepared from a hemicellulose-rich byproduct of oat processing, a β-d-glucan product. The authors surmised that a more effective dry-strength additive could be prepared from a commercially available β-d-glucan-rich product by subjecting it to TEMPO-mediated oxidation (Isogai & Kato, 1998). In other words, the natural polysaccharide product was subjected to a form of oxidation that mainly affects the C6 position on the accessible glucopyranose units of the polysaccharide, leaving the polyelectrolyte chains and other single bondOH groups largely unaffected. The increased anionic charge of the treated β-d-glucan product was intended to allow the material to be dissolved more readily in water, which is one criterion for selection of promising candidate materials to be evaluated as dry-strength agents (Hubbe, 2006). The additional negatively charged carboxylate groups also provide more handles by which the polyelectrolytes later can be retained during the papermaking process (Linke, 1968). The described approach was used for the first time as a strengthening system for papermaking.

Section snippets

Materials

Oat β-d-glucan was obtained from the Biovelop Company, Kimstad, Sweden. The molecular weight of the β-d-glucan was 1,300,000 Da. The compositional data were as follows: 32–35% of dietary fiber (soluble β-d-glucan), 34–37% of total dietary fiber, 54–56% of carbohydrate (maltodextrin), 2.5–3.5% of protein, 3–4% of ash, and 0.5–1% of fat. Kraft pulp of loblolly pine was prepared under the following laboratory conditions: liquor ratio 1:4.5, alkali dosage 19%, sulfidity 25%, and an H-Factor of 180.

Molecular weight of oxidized β-d-glucan

The viscosity data for the oxidized oat β-d-glucan are presented in Table 1. As shown, the viscosity values were decreased by 8.7%, 42.4%, and 64.4%, respectively, compared with the original β-d-glucan after thermal treatment, oxidation treatment (30 min), and alkali treatment. The decreases in viscosity values for oxidized oat β-d-glucan increased with increasing time of oxidation. These results indicate that the conditions of thermal treatment, oxidation, and alkali treatment were sufficient

Conclusions

The following main conclusions may be drawn from this study:

  • 1.

    Oxidized β-d-glucan prepared by TEMPO-mediated oxidation was effective in improving paper physical properties. Tensile index and folding endurance were increased by 36.0% and 125.4%, respectively, when the oxidized time was 30 min. Oxidation was confirmed by FTIR and elemental analyses.

  • 2.

    The dosage of oxidized β-d-glucan played the most important role in papermaking. Tensile index, burst index, and folding endurance of handsheets

Acknowledgements

Dr. Xianliang Song was supported in this work by Beijing Forestry University and China Scholarship Council. The authors also thank North Carolina State University for providing laboratory facilities for much of the described research.

References (29)

  • M.A. Hubbe

    Bonding between cellulosic fibers in the absence and presence of dry-strength agents – A review

    Bioresources

    (2006)
  • A. Isogai et al.

    Preparation of polyuronic acid from cellulose by TEMPO-mediated oxidation

    Cellulose

    (1998)
  • L. Johannson et al.

    Structural analysis of water-soluble and -insoluble beta-glucans of whole-grain oats and barley

    Carbohydrate Polymers

    (2004)
  • N. Kerman et al.

    First operational experience with the high efficiency synthetic dry strength agents

    Wochenblatt für Papierfabrikation

    (2009)
  • Cited by (27)

    • Structural analysis of a glucoglucuronan derived from laminarin and the mechanisms of its anti-lung cancer activity

      2020, International Journal of Biological Macromolecules
      Citation Excerpt :

      Methacrylated laminarin microparticles provide an effective support for cell attachment and expansion [15]. TEMPO-mediated reaction has been widely used for the oxidation of oat β-D-glucan [16], lignin [17], softwood cellulose [18–20], curdlan [21], cornstarch [22], and chitin [23]. TEMPO-mediated reactions are useful for determining the degree of substitution at the C6 position in different modified polysaccharides because it selectively oxidizes primary hydroxyl groups [21,24].

    • Strengthening effects of carboxymethylated hemicellulosic fractions on paper strength

      2018, Industrial Crops and Products
      Citation Excerpt :

      Cationic galactomannan- and xylan-type hemicelluloses are beneficial to improve the mechanical strength of paper (Bigand et al., 2013). Carboxymethylated and oxidized glucomannan or β-D-glucan could also significantly improve the mechanical strength of handsheets (Song and Hubbe, 2014a, 2014b; Wang et al., 2015a, 2015b). Carboxymethylation is an excellent method for hemicelluloses modification, which can increase their solubility in water.

    • Interaction between two oppositely charged starches in an aqueous medium containing suspended mineral particles as a basis for the generation of cellulose-compatible composites

      2017, Industrial Crops and Products
      Citation Excerpt :

      The morphologies of samples (i.e., cellulosic networks and starches) were observed by using a JEOL JEM-2100 high-performance transmission electron microscope (TEM) and a QUANTA 200 scanning electron microscope (SEM). In accordance with the global trend in various sectors towards a green economy, the efficient use of biopolymers or their composites in the production of cellulosic paper-based products fits into the widely known concept of sustainability (Arboleda et al., 2014; El-Wakil et al., 2015; Hu et al., 2015; Lackinger et al., 2011; Liu et al., 2015; Salam et al., 2015; Song and Hubbe, 2014a,b; Sun et al., 2015; Vallejos et al., 2016; Wang et al., 2015). In this context, the simple concept of using two low-cost, oppositely charged biopolymers (cationic starch and anionic starch) for the treatment of mineral filler particles as a basis for enhancing the compatibility and hydrogen-bondability of filler particles with cellulosic fibers was proposed, which is schematically illustrated in Fig. 2.

    View all citing articles on Scopus
    View full text