Jute pulp, also called hemp pulp, it is the generic terms of paper pulp made from bast-fiber. The hemp belongs to the bast fiber, it has long and strong fiber. The bast-fibers for papermaking generally use the wastes of different hemp, not the raw hemp, such as sten fiber, old hemp rope, waste jute bag, and etc. The jute pulp can be applied to manufacture various fine papers and industrial and technical paper like banknote paper and cigarette paper.
Jute pulp types
In general, the different kind of jute pulp is all named after the name of raw material like flax pulp, kenaf pulp, jute pulp, hemp pulp, etc.
Kenaf pulp
Kenaf pulp is made from kenaf. Kenaf is also known as bimlipatam, China jute, is the annual herb. The kenaf husk can be used to make fine chemical pulp with long fiber and is processed into high-grade culture paper, cigarette paper, etc. The kenaf stalk and Kenaf core can be made into chem-mechanical pulp, CTMP, mechanical pulp, etc. Due to the pulp is light-colored, easy to bleach, and its physical strength is close to hardwood pulp, so it can be applied to manufacture newspaper and other kinds of cultural paper.
Jute pulp
Jute fiber is one of the most low-cost natural fiber, the planting and applications are only less than cotton. The jute belongs to bast fiber just like kenaf, hemp, flax, and ramie. Jute pulp is easier than wood pulp, and no need of sulfide. The whole stalk jute pulp can apply for making fine printing paper, writing paper and cigarette paper, security paper, etc. For some countries or regions that are short of wood fiber, the jute is the most potential material for papermaking.
Jute pulp market
The most kinds of hemp can be applied to paper and pulp making, currently, the whole stalk jute or whole stalk kenaf is widely used. In 1960, the United States confirmed that kenaf is most suitable non-wood fiber for papermaking among 500 different kinds of therophyte. Bangladesh and India are two main jute and kenaf growing countries in the world. These countries try to replace bamboo, wood with jute or jute fibers.
Jute pulp processing
Jute pulp processing can be divided into material storage, material preparation, pulp cooking, pulp washing and pulp bleaching.
Material preparation
The hemp cutter is necessary for material preparation. The modern hem cutter will improve the yield, and it is easy to feed and with no winding. If whole jute stalk has the large content of water, the yield will be lower; if the content water is smaller, it will be easy to cut, but also easy to separate stalk and husk.
Pulp cooking process
The study of jute pulping shows that Kraft pulping, soda cooking of whole jute stalk is available. CNBM has 50 years' experience in paper pulp production line customization and paper pulper machines manufacture. We summed different cooking processes and related working conditions.
Kraft pulping
The Kraft delignification of whole jute stalk includes three stages: initial stage, main stage and last stage, the total delignification rate reach 92.1%. In the Kraft pulping process, the main delignification of jute is sooner than wood and later than wheat straw. Meanwhile, the carbohydrate dissolution also can be classified into three stages including temperature-raised stage, first insulation stage and second insulation stage.
As for the cooking equipment, the rotary digester is widely applied, obtained pulp has high quality but low yield. The pulp made by common vertical pulp digester has bad evenness. Some large-scale paper and pulp mills, they usually adopt the continuous cooking system. The cooking condition of rotary digester as below:
| NaOH | 20% |
|---|---|
| sulfidity | 25% |
| ball load | 110kg/m³ |
| temperature rise time | 2.0h |
| soaking time | 1.5h |
| unscreened yield | 50-55% |
Soda pulping
Compared to wood pulp, the whole jute stalk pulp require less alkali number in the soda cooking, pulp yield is higher and is easier to obtain. Compared to the straw pulp, the jute pulp needs more alkali number, the strength of jute pulp is better than straw pulp's and hardwood pulp's, but worse than softwood pulp's. The cooking condition of soda pulping as following:
| NaOH | 16% |
|---|---|
| ball load | 110kg/m³ |
| temperature rise time | 2.0h |
| soaking time | 1.5h |
| unscreened yield | 54.4% |
Pulp washing
Whole jute stalk pulp has high adaptability to washing equipment and good drainability. Common washing equipment for the jute pulping process includes vacuum drum washer and belt filter press, horizontal belt filter. The horizontal belt filter has high efficiency and a high clean degree.
Pulp bleaching
From the point of pulp bleaching process, the total chlorine dosage is about 8%. Through the CEH or CEPH three-stage bleaching, the bleaching degree can reach 82.84%, the whiteness up to 75-79% after reversion. If the jute pulp adopts CEPH three-stage bleaching, there are two advantages, firstly, improve the brightness of jute pulp. Secondly, jute pulp has less fiber loss.
Excepting for the jute pulp, there are other plant fiber materials that can be used to making paper pulp, such as wood pulp, bamboo pulp, wheat straw pulp, sugarcane bagasse pulp, cotton pulp. etc.