Preparation of the hottest paper pulp molding slur

Preparation of pulp molding slurry

no matter what kind of molding equipment is used, the production process of pulp molding products is roughly as follows:

material preparation - beating - adding chemical additives - molding. They are involved in each other,

interact and influence each other, especially the stock preparation (pulp, filler) and beating process are the basis of pulp

molding production. According to the requirements of products, selecting appropriate raw materials (including pulp species,

fillers and chemical additives) and scientifically designing the beating process are important links to ensure product quality and reduce product cost. Therefore, in order to improve the quality of pulp molding products and reduce the cost of products, pulp molding enterprises should first be clear about the mechanism and relevant knowledge of material preparation and beating process in the process of pulp molding production. Each process must be in the charge of professional technicians, which has been ignored by some enterprises

the articles I introduced in China Packaging News last year about the addition of fillers in the production process of paper mold and the use of retention aids have attracted the attention of relevant enterprises and have called for consultation. Because these problems are closely related to the preparation of pulp and the selection of beating process, here I will introduce the relevant knowledge of pulp preparation in eight parts, hoping to be helpful to some paper mold enterprises

I. types, properties and tissue components of pulp

1. Types of pulp

the commonly used papermaking raw materials in China include wood pulp and straw pulp. Due to the lack of wood pulp resources and the relatively rich straw pulp resources in China, annual straw pulp fiber raw materials are mostly used in papermaking raw materials, especially pulp molding products. As for the statement that the paper mold industry consumes more

less mu of forest a year, it is completely a misunderstanding

wood pulp fibers are divided into coniferous wood pulp fibers (such as masson pine, larch, Korean pine, spruce

fir, etc.) and broad-leaved wood pulp fibers (such as birch, poplar, basswood, eucalyptus, maple, etc.)

pulp molded products need to have a certain strength and can withstand tension. Generally, 15 ~ 20% coniferous pulp is added to the pulp

straw pulp fiber is divided into:

(1) cereal fiber raw materials (such as straw, wheat straw, reed, bamboo, bagasse, etc.)

(2) bast fiber raw materials (such as hemp, kenaf, flax, mulberry, cotton stalk bark, etc.)

(3) wool fiber raw materials (such as cotton fiber, etc.)

2. Differences in physical and chemical properties between wood pulp and straw pulp

(1) their fiber morphology and physical condition are different. Coniferous wood fiber is long, generally with length

between 2.56 ~ 4.08 mm, width between 40.9 ~ 54.9 microns, and its length width

ratio is more than 70 times; Hardwood fiber is short, generally about 1 mm in length, and its length width ratio is more

less than 60 times; Among grass fibers, bagasse raw fiber is longer, about 1.01 ~ 2.34 m

m, with a width of 16.7 ~ 30.4 microns, and its length width ratio is about 77 times; Reed

reed raw fiber is about 0.60 ~ 1.60 mm long and about 5.9 ~ 13.4 microns wide, and its length width ratio is about 115 times; Awn stalk raw fiber is about 0.81 ~ 2.58 mm long,

width is between 13.2 ~ 19.6 microns, and its length width ratio is about 100 times

(2) the composition of fibers is different. The main components of plant fiber raw materials include cellulose, hemicellulose and lignin. Secondary ingredients include pectin, starch, tannin, pigment, resin,

fat, wax, ash, etc

cellulose exists in the cell walls of all plants. Jinan spring testing machine industry classification details, is the main component of plant fiber, accounting for about

40 ~ 98%. It is the part that should be vigorously retained in the pulping process

hemicellulose is a non cellulosic carbohydrate. Its structure is loose and amorphous,

it is easy to absorb water, moisten and swell, and soluble in dilute lye. The content of hemicellulose in grass raw materials accounts for about 30%

and its chemical properties are similar to cellulose, but the reaction is faster and easier than cellulose. Hemicellulose

is also a part that should be vigorously retained in the pulping process

lignin is an aromatic natural polymer compound composed of phenylpropane structural units. It is not a single substance, but a general term for this kind of substances with similar properties. It is an amorphous structure of

substances. Straw raw materials generally contain about 20% lignin. The more lignin the raw materials contain, the more difficult it is to pulping, because lignin makes the fibers stick together. Chemical pulping is to use chemicals to dissolve the lignin in

fiber raw materials and separate the fibers into pulp

(3) their chemical compositions are different. The tissue structure of coniferous wood is tight, the content of heterogenous cells is small, and most of the heterogenous cells in the

chemical pulp are lost during washing, so the pulp quality is good, the lignin content is high,

is between 25 ~ 35%, and the content of pentosan is low, mostly between 9 ~ 12%. The fiber is not easy to absorb water

and it is difficult to beat; The tissue structure of hardwood is more compact, and it contains more miscellaneous cells. The lignin content of

is lower than that of coniferous wood, which is generally between 20 ~ 24%, and the content of pentosan is high, which is generally between 21 ~ 24%, so it is easy to beating; Straw pulp is characterized by high content of pentose, generally about 20% or more, easy hydration of fiber, low lignin content, all below 15%, and higher ash content than wood. Straw pulp contains more anionic impurities than wood pulp. The accumulation of such harmful

anionic impurities in the wet end will make some cationic additives worse, and even

can make cationic additives completely ineffective. Its high electronegativity also affects the flocculation of fine fibers in pulp

and reduces the hydrogen bond bonding between fibers, thus affecting the retention and drainage of pulp fibers. In case of serious

, it will cause sticking and blocking of mold holes

(4) their fiber surface potentials are different. Fibers, fine fibers, soluble

organic substances or colloidal substances (soluble organic substances and colloidal substances are collectively referred to as anionic hetero

substances) and fillers in the slurry generally have a certain amount of negative charge. Due to the

differences in raw materials and preparation processes, the variation range is large, and their surface charge properties and potential values are also different

due to the above differences between wood pulp and straw pulp, the selection of chemical additives must consider the pulp species, filler varieties, their ionic properties, molecular weight, adding position

and the amount of chemical additives. The ideal additive amount is when the potential value of the slurry system is zero (isoelectric point)

II. Process design of the beating system

the process flow of the beating system is usually: selecting ingredients - pulping - Dredging -

adding additives - forming. The equipment of the system usually includes: hydraulic pulper, sulfur

dust remover, agitator, etc. In order to produce high-quality paper tableware, some enterprises also install washing drums after the pulper to wash pulp

1. Hydraulic pulper. The hydraulic pulper is mainly used to deal with crushed pulp. It has a

dispersing effect on pulp, but has no cutting effect

hydraulic pulpers are divided into low consistency, medium consistency and high consistency pulps. Pulp molding pulping machines

generally use medium consistency pulpers. Experience has proved that medium consistency pulping can shorten the beating time, reduce

energy consumption, improve the utilization of equipment, reduce production costs, and improve the quality of the slurry, which is conducive to the copying of the forming machine

2. Dual function relieving machine. Although it takes only a few seconds for the paper material to pass through the dredger, the pulp crushed by the

pulper can be cut, divided into filaments and fine fibrosis by the dredger, which can make the paper into

products with uniform pulp distribution, improve the uniformity of chemical additives, and increase the strength of the finished product at the same time. Another function can remove dust

3. Agitator. The agitator of each slurry tank mainly plays the role of dispersion and homogenization, but its mixing speed plays an important role in chemical additives. Some polymer additives with high molecular weight

have destroyed their long molecular chains through the high-speed shear action of the mixer,

so that the role of chemical additives has been destroyed and hydrolyzed. Generally, the mixing speed of the mixer should be about 30 ~

60 rpm

III. beating principle and function

the principle of pulp molding beating is to use physical (Mechanical) methods to treat the pulp fibers suspended in

water, so that they have the characteristics to meet the production requirements of the pulp molding product forming machine,

and make the paper molded products produced meet the expected quality requirements. This operation process is called beating

1. Beating principle

pulp fibers become soft and plastic after mechanical treatment by beating equipment. Its principle

is to cut, crush, absorb water, swell

and fine fibrosis through the action of beating equipment on the fiber, so as to increase the surface area of the fiber, thereby increasing the bonding force between the fiber and the fiber

with the progress of beating, the binding force of the fiber continues to rise, but the average length of the fiber is shortened

practice has proved that some physical properties of paper products, such as folding resistance, bursting resistance, water absorption and air permeability, are closely related to beating methods. Therefore, when determining the beating method, we should choose it reasonably according to the different requirements of pulp raw materials and paper products

2. Beating is mainly due to insufficient understanding of recycling equipment technology (41.33%)

the effect of beating on fiber is mainly to make it undergo physical and chemical changes. No matter what type of beating equipment is used, the fiber will be cut, crushed, water absorption and swelling, and fiber thinning. When the fiber is subjected to the above effects, its main changes occur on the cell wall of

fiber. The changes of fiber cell wall have the following forms:

(1) beating makes the fiber cell wall displacement and deformation. The reason for the displacement and deformation of the cell wall

is that the microfiber at a certain position in the middle layer of the secondary wall is bent and deformed after the fiber is subjected to mechanical force in the beating process, which increases the gap between the microfibers, which creates conditions for the fiber to absorb more water, and the fiber becomes soft after water absorption and deformation, which plays an important role in removing the primary wall and the outer layer of the secondary wall

(2) beating breaks the primary and secondary walls of fibers. The fibers without removing the primary wall

appear smooth, stiff and not easy to absorb water and swell. Therefore, the outer layers of the primary wall and the secondary wall must be broken by using the mechanical action of the beating equipment

force and the mutual friction between the fibers, so that the fine fibers in the middle layer of the secondary wall can be separated, so as to achieve the goal of full swelling and fine fibrosis of the fibers. Under normal circumstances, the difficulty of removing the outer layers of primary and secondary walls of different kinds of fiber raw materials is also different, so the difficulty of fine fibrosis is also different when beating pulp,

for example, straw pulp is more difficult to remove than wood pulp, and sulfate wood pulp is more difficult to remove than sulfite wood pulp

(3 officially entered the supply chain of overseas automobile manufacturers) after beating, the pulp fiber absorbs water and swells. Fibrogenesis