In recent years, with the economic growth and improvement of people's living standards, China's paper mill industry process has also developed rapidly-- production capacity and yield has increased; production technology and equipment has also been improved. However, due to excessive expansion of production capacity, there has been a stage of overcapacity, the entire industry market competition continuing to intensify, product sales prices continuing to decline and the company's pressure of production and operation continuing to increase. In response to the highly competitive market situation, companies are actively developing new products and differentiated products in order to be able to make the whole industry market bigger, permit the differentiated products to obtain reasonable sales prices and profits, and expand their respective businesses shares; at the same time, the industry's well-known and large enterprises are expanding their own industry and do more product publicity and have done a lot of work in guiding the market and consumption, which plays an active role in the development of the entire paper industry.
Since 2014, the unbleached household paper has become a major highlight of the differentiated products. From the number of the business exhibitors in the annual meeting by the China National Household Paper Industry Association(CNHPIA for short), it can be clearly seen that it has been increasing rapidly year by year.
In the 2016 Nanjing household paper annual meeting, over 20 enterprises exhibited unbleached household papers who were mainly made of bamboo pulp, straw pulp, cane pulp, etc and are mainly Sichuan household paper enterprises with bamboo as raw material; Shandong with straw pulp and Guangxi with cane pulp.
Under the great promotion and guidance to consumers from these enterprises, the unbleached household paper products has gradually come into the consumers’ vision and has been received by a part of consumers who are mainly concentrated in the high-end consumers caring about environmental protection and sustainable development.
At present, the unbleached household paper market is gradually growing and has injected new vitality to the development of the China’s paper industry; the price of unbleached paper products has excelled white paper products. In addition, from the recent communication between the businesses and the Secretariat, the businesses with unbleached household paper products will continue to increase.
The unbleached paper and white paper are both environmentally friendly and safe.
1) An introduction to the basic procedures of pulping making process and bleaching
1, The raw materials of pulping are divided into wood and non-wood categories. Wood category includes coniferous wood and hardwood; non-wood category includes rice-wheat-straw, bamboo, bagasse, reed, hemp and other plants.
2, Simply speaking, pulping is a lignin and fiber separation process out of the wood or non-wood raw materials. Pulping methods include chemical, mechanical methods, or a combination of both.
The most commonly used chemical pulping method is sulfate cooking method with chemical agents of sodium hydroxide and sodium sulfide.
In order to achieve a certain paper pulp yield and strong performance, the cooking process does not need to separate all the lignin and there will be residual lignin. In addition, kraft pulp in the cooking process makes the lignin become very dark, so the resulting unbleached pulp is yellow or brown, with high lignin content and poor performance.
3, In order to improve the pulp whiteness, performance and purification, the pulp needs to be bleached after cooking which is to remove the residual lignin. Bleaching is the process of removing the residual lignin in the pulp or changing the structure of the color gene in the lignin by chemicals with oxidative or reductive properties. The removal of lignin during the chemical pulp bleaching process can be regarded as a further action of cooking.
4, Pulp bleaching methods can be divided into two categories. One is "dissolved lignin bleaching". That is, through the role of chemicals the lignin in the pulp is dissolved , so that the fiber structure of the chromophore and other colored material can be completely destroyed and dissolved.
The dissolution of this kind of lignin usually uses oxidative bleaching agents such as chlorine, hypochlorite, chlorine dioxide, peroxide, oxygen, ozone and the like. The other is " lignin retaining bleaching", which is, without the removal of lignin, to change or damage the chromophore in the pulp , reducing its absorbance ability and increasing the reflection ability. In this process, oxidative bleaching agent hydrogen peroxide and reductive bleaching agents dithionite, sulfite and boron hydride are usually used.
5, ECF and TCF bleaching
The traditional bleaching method with chlorine as bleach is economical and effective, but it can produce large amounts of organic chlorides ,AOX, in the waste water . In order to reduce AOX in the waste water, the most effective way is to reduce or non-use of chlorine for bleaching. The traditional bleaches containing element chlorine have become less and less and elemental chlorine free (ECF) and totally chlorine-free (TCF) bleaching methods are now used.
ECF and TCF use bleaches which are most environmentally freindly drugs, such as H2O2, peracetic acid, xylanase, etc.. Some bleaches has existed in nature, such as oxygen and ozone. These bleaching agents will not cause pollution when discharged into the river and the air . The products after the degradation of pulps are also basically non-toxic and cause no pollution to the air and easy to biodegradate. Data shows that the current European and American, Canadian and other international pulp mills and the large-scale domestic pulp mills are basically using ECF or TCF bleaching process.
(1) ECF uses ClO2 to replace chlorine to bleach pulp and this method will greatly reduce the content of organic chloride in the bleaching waste water. Modern ECF pulp bleaching factories emit AOX reduced to 0.1 ~ 0.5kg / t pulp. Pulp bleached by ECF has high whiteness, good strength, little impact on the environment, relatively low cost , so ECF bleaching technology has been rapidly promoted. With the advancement of technology, ECF technology continues to improve. In more modern factories, deep delignification and oxygen delignification are used. That is, pulp is firstly bleached with chloride-free bleaching agents (such as ozone and H2O2) , and only in the last step ClO2 is used. Thus this can further improve the quality of waste water, and waste water from factories can be reduced by 70% to 90%, most of which can be recycled.
TCF means chlorine-free bleaching, which is, not to use any chlorine bleach and uses H2O2, ozone and acetic acid and other oxygenated chemicals for bleaching. Due to the increasing environmental protection requirements and the increasing demands for high whiteness bleached chemical pulp, the bleached chemical pulps, especially for the production of food packaging paper and paperboard , are not allowed to contain organic chloride. To this end, many countries have carried out researches and applications of all chlorine-free bleaching technologies, which mainly use mature oxygen delignification technologies, as well as the successful ozone bleaching technologies and H2O2 bleaching chemical pulp technology. And other technologies include a combination of acid bleaching technology and xylanase biobleaching technology to produce high whiteness chlorine-free bleached pulp to meet the needs of the market.
Bleached waste water by TCF is detected without AOX, so it can be reused as pulp-washing water and attenuant water for boiled chemicals. The water in the pulp mills can be used in a closed cycle, and achieve "zero emission".
2) White paper is also environmentally friendly which consumers can use at ease.
Most of China's domestic paper companies are buying bleached pulp for sale as raw materials. The bleaching process is done in the pulp mill. A small amount of harmful substances produced by bleaching are mainly found in bleach waste water which needs further processing to meet the discharge requirements. After the washing process of the bleached pulp, harmful substances in the pulp and the final product are too small to cause harm to the user, like the fact that the residual disinfectant dose in the swimming pool will not cause harm to the human body.
In addition, imported pulp bought by the current paper enterprises and the pulp process in the domestic large enterprises are basically chlorine-free and of no chlorine bleaches, which will not cause AOX pollution in water and do no harm to people's health by the products in the bleaching . So the white household paper is also healthy, environmentally friendly and safe.
On the other hand, in 2015 the wood pulp rate in the fiber as raw materials in China’s household papers has reached 80%. The integration of wood pulp and paper is also fully in line with the requirements of eco-friendly. Compared to straw pulp and bamboo pulp, wood pulp household papers have better softness and strength, more suitable for the production of high-quality tissue paper and high-speed operation requirements of the modern paper machinery and processing equipment.
3) The unbleached pulp and unbleached household paper
Some open pulp-making technology information of unbleached household papers include Shandong Quan Lin Paper Co., Ltd. With wheat straw as raw materials, Shaogan Group Shaoguan Nanxiong Zhuji Paper Co., Ltd. With bamboo as raw materials, Ningxia Bauhinia Paper Co., Ltd. with wheat straw as raw materials, Sichuan Jiajiang HSBC Paper Co., Ltd. with bamboo as raw materials, and Sichuan Yongfeng Paper Co., Ltd. with bamboo as raw materials. These enterprises mostly use non-wood fiber raw materials. Whiteness reaches 20% ISO or less after boiling, and then after one or two oxygen delignifications to reduce the hardness of pulp, the whiteness increases by 10% to 20% ISO and up to 30% to 50% ISO
Through the oxygen delignification to improve the pulp cleanliness and whiteness, the oxygen delignification of the waste water can be incorporated in the cooking section of the alkali recovery and it will not produce AOX and other harmful substances. So it reduces pollutant emissions, reducing the cost of waste water treatment, protecting the environment, in addition to reducing the consumption of chemical raw materials, saving cost and so on. Therefore, it is worth advocating in terms of the preservation of chemicals and energy consumption, especially in the production of toilet paper and hand paper. The wheat straw pulp and bamboo pulp unbleached papers take the comprehensive utilization of agricultural straw and bamboo resources, thus having undoubtedly a positive significance in environmental protection.
In addition, with the improvement of production technologies, unbleached paper in the cleanliness , softness, delicacy has also been greatly improved. Unbleached paper is generally more difficult to even the color. It’s mainly due to the quality of raw materials or pulping process conditions fluctuations, which often result in different batches of the color paste. There is a no follow-up bleaching process to adjust the color , so inevitably there is color differentiation. Unbleached paper is generally more difficult to even the color. It’s mainly due to the quality of raw materials or pulping process conditions fluctuations, which often result in different batches of the color paste. There is a no follow-up bleaching process to adjust the color , so inevitably there is color differentiation.
Unbleached paper is generally more difficult to even the color. It’s mainly due to the quality of raw materials or pulping process conditions fluctuations, which often result in different batches of the color paste. There is a no follow-up bleaching process to adjust the color , so inevitably there is color differentiation.