Production of high quality packaging paper from bamboo asam pulp with cellulose nanocrystals
Bamboo is a non-wood fiber that has been proven to be a viable alternative source for pulp and paper industry. However, due to the large variation in species, anatomical structure and chemical composition, significant variations in the performance of paper made from bamboo have been reported. Lik...
محفوظ في:
| المؤلف الرئيسي: | |
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| التنسيق: | أطروحة |
| اللغة: | English |
| منشور في: |
2016
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| الموضوعات: | |
| الوصول للمادة أونلاين: | http://psasir.upm.edu.my/id/eprint/69870/1/IPTPH%202016%208%20-%20IR.pdf |
| الوسوم: |
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| الملخص: | Bamboo is a non-wood fiber that has been proven to be a viable alternative source for
pulp and paper industry. However, due to the large variation in species, anatomical
structure and chemical composition, significant variations in the performance of paper
made from bamboo have been reported. Like softwood, paper made from bamboo can
have excellent properties particularly in stiffness, bending quality, tear strength, and
crush resistance, which are found suitable for paperboard. Kraft pulping is the most
common method used for bamboo because it generates relatively high pulp yield and
kappa number with value approximately 46.4% and 24.6, respectively. Kraft paper
however tends to be lower in initial brightness and has limited chemical penetration.
Having strong bundle sheathes, impenetrable epidermis, a complete absence of ray
cells, and limited area of conducting tissues, bamboo requires a more rigorous pulping
regime as compared to wood.
This study employed alkaline sulfite anthraquinone with methanol (ASAM) method
of pulping for bamboo (Gigantochloa scortechinii) with a main aim to develop high
performance paper for packaging application. ASAM pulping process has combined
advantages of suitable paper properties obtained from kraft pulping, and higher initial
pulp brightness, obtained from sulfite pulping. Low kappa number, high pulp yield,
and high paper strength are the main advantages of ASAM pulping in comparison with
kraft. In addition, ASAM pulping reduces the bad odor from methyl mercaptan that is
generated in kraft pulping. The objectives of the study were: (I) to characterize the
basic properties of Gigantochloa scortechinii bamboo fiber (II) to determine optimum
pulping condition with maximum pulp yield and under less severe pulping conditions
(III) to develop high strength bleached bamboo papers by applying minimum beating
revolution (IV) to evalutate the effects of cellulose nanocrystals (CNC) on the
properties of bamboo paper.
The study was divided into: (1) evaluation of biometric characteristics and chemical
composition Gigantochloa scortechinii bamboo; (2) determination of the effect of
pulping conditions on the pulp and paper properties, (3) evaluation of beating and bleaching effects on the pulp and paper properties, and (4) improvement of paper
properties by adding cellulose nanocrystals (CNC). Compared to cellulose fiber, CNC
has many advantages such as unique optical properties, high specific strength, and
high surface area. Therefore, in this study, CNC was prepared from bleached bamboo
ASAM pulps and applied as an additive to improve paper properties such as the
permeability, tensile, burst, and tear indices.
Franklin (1954) and TAPPI standard methods were used to determine the biometric
characteristics and chemical compositions of bamboo culms, respectively. The results
show that bamboo has fiber length similar to that of softwood (1980 - 4000 μm), a
runkel ratio of 0.86 and and flexibility ratio of 50.19. Bamboo contains 47.67%
cellulose, 68.33% holocellulose, 26% lignin and 3.69% solvent extractive, which are
also within the range of wood from softwoods species. The pulping was conducted using ASAM process at 170C and alkali ratio
(Na2SO3/NaOH: anthraquinone: methanol) of (80/20: 0.1%: 15%). It was found that the highest yield
(52.36%) was achieved by applying 14% sodium hydroxide and 90 min cooking time whilst the lowest
kappa number (10.38) was observed using 18% and 120 min. Further increase of both alkali
and cooking time resulted in marked decrease in both kappa number and pulp yield. The optimum
pulping condition was obtained at 16% alkali and 90 min cooking time with resulting kappa number of
14.17
and pulp yield of 49.06%. The tear, tensile, and burst indices of unbleached bamboo ASAM paper were within the range of
26.33-18.64 mN.m²/g, 24.8-17.87 Nm/g, and 10.83-9.27 kPa.m²/g, respectively, which is
suitable for packaging paper. The study revealed that the optimum ASAM pulping parameters
was at 16% NaOH and 90 min cooking time, resulting in paper having tensile index of 20.86 Nm/g,
tear index of 22.64 mN.m²/g
and brightness of 39.32%. Bleaching study was conducted on bamboo pulps that have been digested using the optimized pulping
conditions, 170°C, 16% NaOH and 90 min. The final brightness of bamboo ASAM pulp was 84% ISO
suggesting an almost pure cellulose have been obtained. To improve the paper properties of
bleached-beaten bamboo paper, cellulose nanocrystals (CNC) was added. The same ASAM bleached bamboo
pulp was used to produce the CNC. For this purpose, the bleached pulp was reacted with sulfuric
acid (64%) at 45C for 45 min with dynamic stirring. The CNC was analysed under UTHSCSA
image Tool and the final diameter of the CNC was found to be between 10 to 20 nm.
Based on the paper properties, bamboo appears to require high level of beating (as high as 9,500
revolutions) in order to achieve acceptable properties for packaging application. Bamboo
pulp fibers have very small lumen diameter therefore, the swelling of the cell wall is very
difficult. On the other hand, bamboo culms have two major types of vascular bundles, type III
(sclerenchyma sheaths, and one fiber strands) and type IV (sclerenchyma sheaths and two fiber
strands). Type IV was located in the middle part of culm wall, whilst type III in the inner and
outer parts of the culm wall. The distributions of vascular bundle type III is higher than type IV
by 71.05%. Fiber
strands was found to have a much larger cross-section area than the sclerenchyma sheaths. Thus, the swelling of b mboo pulp fibers is more difficult consequently
require higher number of beating. Since beating significantly affects the paper strength, as well as require high energy, CNC was
added to help reinforce the paper with minimum beating. For this purpose, three different types of
bamboo pulp were prepared: Type 1 – fully beaten pulp, Type 2 - slightly beaten pulp without
reinforcement by CNC, and Type 3 - slightly beaten pulp with reinforced by CNC. The results show
that the mechanical properties of paper reinforced with CNC (Type 3) were similar to those of paper
made from beaten pulp (Type 1). The tensile, tear, burst indices, and folding endurance of the
former were 20
- 48.3 Nm/g, 19 - 24.6 mN.m²/g, 1.96 - 4.40 kPa.m²/g, and 20 - 353 double folds,
respectively as compared to 50.70 Nm/g, 17.10 mN.m²/g, 4.48 kPa.m²/g, and 446
double folds, in the latter. In summary, ASAM was found to be a suitable pulping process for bamboo compared to kraft as it
produced pulps at higher yield and lower kappa number. The bleaching of ASAM pulp is relatively
easy when compared to kraft. In ASAM pulping process, the initial delignification phase proceeds
very fast and more than 50% of the lignin
was removed in bulk delignification phase. This method also produced pulp with high
hemicellulose content and low residual lignin content which can easily be bleached to
a brightness of 80% ISO. The paper produced from ASAM pulping process has
properties suitable for packaging paper, however the pulps require a substantial
amount of beating. The addition of CNC was able to improve the final paper properties
at low levels of beating (<7,000 revolutions) by creating better fiber-to-fiber bonding
among the pulp fibers. |
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