The additives in the paper industry

Update: 06-10-2015 10:10:40 + GMT7

To improve the properties of paper, reduce the cost of products, to meet the diverse capabilities in all areas of the paper used in the paper production process involves adding to the cellulose raw material and auxiliary substances

The raw material for paper production include glue group, the color group fillers and other additives.

* Group glue: is the substance with adhesive on the surface or internal sizing paper, in order to increase the ability of waterproofing liquid (water) of paper.

* Group fillers means substances mixed into the paper pulp as it had replaced less amount of paper fibers and increase smoothness, opacity, surface uniformity.

* Group, additives, food coloring means substances added to the mixture to make paper pulp with higher quality, increased some aesthetic properties as color, luster, reduce product cost. The proportion of group which makes up a small amount of paper

Paper production environment (acid or neutral, alkaline) different, the use of additives is also different
* Comparison of the additives used in the calculation of acid and alkaline manufacturing process of paper pulp:
The method has several advantages alkaline than acid method as follows:
- For operators:
+ Easy to grind more flour
+ Drainage and faster drying
+ More stable PH
+ Additional water in hydraulic crusher is taken directly from the recovery of waste equipment flour without the preliminary treatment

Environment sizing additives, additive
PH = 4.5 6.5
(The acidic properties)

PH = 7,28,4

(The neutral, alkaline)
Adhesive glue resin, rosin modified, resin dispersion AKD (Alkyl Keten Dimer), ASA
Using alum to coagulate more glue and glue on fiber Sometimes one little used to neutralize the negative charge
Kaolin Fillers crushed or precipitated CaCO3
Auxiliaries Cationic reserves, Polyacrylamide (Percol, Cataretin ...) The system reserves the microparticles, or reserve system 2 component (Bentonite ...)
Cationic starches Increase Increase reliability is the reservation of the main AKD
Use more Brightener Use less
No different pigments different None
Biocides Biocide Use more normal Use

- For quality paper

 

+ More White, smoother

+ Reliability higher

+ Time for longer storage

- Economy:

+ Higher amount of fillers saving flung Profile

+ Brightener less than

+ Consuming fewer materials

+ Save water

+ Higher Productivity

Therefore in recent years, technology has made the paper a great change from paper production technology into alkaline acid. However, alkaline method also has some difficulties as the strong development of bacteria generate operational problems. The transportation and storage of glue to hold on to £ AKD 15oC. In addition, some types of products, the sizing in acidic or rosin sizing still get the advantages irreplaceable. As the kraft paper, the common duct or modified rosin or a product of this glue line still gives the best properties Vietnamese much for using AKD sizing. Plastic products after rosin sizing is testing is right quality, the paper reviews the stiffer, or the platform increases. With Kraft products are rosin sizing has brought many more advantages.

 

1. Activated Adhesive AKD

 

1.1. To introduce:

As we all know, to make paper with water resistant adhesive it has been at the paper. Sizing method can be internal sizing or surface sizing, the internal paper sizing additives typically resin glue, glue substance diffusion and active as: AKD, ASA.

Adhesive resins are used in the paper industry since the early 19th century was the modern alkaline sizing begun over 30 years. But it has grown rapidly and is gradually replacing the glue resin in an acid environment. Currently it is known that about 90% fine paper in Europe and 50% fine paper in North America are produced by the method of alkaline sizing. in Asia, many countries such as Japan, South Korea, Taiwan, Indonesia, Thailand and growing method has many advantages alkaline than acidic calculation method.

Glue paper AKD make better permeability, giving the surface a layer fibers prevent aqueous dispersion, on the other hand it is also used to increase endurance, increase links between wet and produce fibers surface glossy paper.

These characteristics give AKD glue as follows:

- Appearance: white emulsion solution

- The composition of solids: 15 ¸ 40%

- Nature: Cationic

- The rate at 25oC (kg / l): 11.03

- PH: 57

- Freezing point (oC): 0

- Viscosity at 25

twelfth. Structural formula

* Glue AKD (alkyl ketene dimer) with the following structural formula:

R1 - CH = C - CH -R2

O - C = O

R1, R2: C14 - C18

1.3. Features and characteristics of glue

The development process sizing effect ADK includes 3 consecutive steps:

- Stick to stick: glue initial contact with fibers due to the coagulation of the colloidal particle surface positively charged fibers negatively charged.

- Long thin: This process occurs when the water is evaporated by the drying that creates a thin layer, the thickness of one molecule size.

- Reaction: Occurs when the molecular monolayer formed chemical bonds created between the political assimilation and cellulose glue.

1. Stick grip 2. Flattening 3. Reaction

AKD glue glue huge effectively so very low dosage at only 0.05 ¸ 0.2% by dry glue. Special paper sizing AKD maintain the original whiteness and its durability over time, so it is used in the production of paper for storage. AKD Adhesive paper is also suitable for high sizing requirements and good paper containing CaCO3 fillers.

AKD glue is not suitable for mechanical pulp, mechanical pulp mill, chemical or mechanical pulp. Particularly thermomechanical pulp chemicals can wash gel ADK.

In actual use, additional points in the pulp glue AKD is very important, as a rule it should be added to the powder flow characteristics in a short cycle before powder diluted a very short time. This will make the tack fast and reduce the minimum separation of colloidal particles from the fiber surface.

The reaction between the glue and cellulose can be catalyzed by an additive, such as a number of amine groups polymebazo with HCO3- ions available in the pulp. When using CaCO3 as filler, also catalyses good quality, but if supplemented with Na2 CO3 or NaHCO3 to increase alkalinity better.

industrial scale, using AKD with PCC (precipitated CaCO3) must interested in glue. It means that the adhesive is reduced hydrophobic lost for a while. Although the adhesive is guaranteed as he produces, but after a few weeks or months hydrophobic no longer be guaranteed. This phenomenon should be overcome by the process depending on the intended use. Sizing process is considered effective when the amount of glue used least and still achieve the necessary adhesive. The level of glue too limited not only wasteful but environmentally polluting production.

In industrial scale, using PCC as filler paper have increased profit by reducing the amount of fiber, thanks to this cheap fillers. In these kinds of PCC as an additive, the crystal structure type is the most widely used. With its open architecture, porous PCC crystals scatter light efficiently and make the filler has high turbidity. PCC particle diameter of 1.4 mm most common. Due to the tight precipitate PCC fillers should have some narrow distribution in size and has high homogeneity. Conversely GCC (CaCO3 crushed stone) from limestone or marble with heterogeneous grain structure. GCC standard type used as fillers for papermaking average particle diameter of 0.7 mm or higher and particle size distribution of about 2 mm. Glue AKD has a melting point of approximately 46.11oC (1150F). Factors decreasing the sizing of alkaline paper are: retention, dispersion and adhesion of the glue on the fiber surface.

According to a pilot study, the colloidal particles are smaller than AKD melt and staging 1mm brush up the fibers and fillers in the drying process. The ability to create double bonds between hydroxyl groups of the cellulose and the lactone ring of AKD molecules are described as follows:

AKD sizing degree of degradation over time due to the influence of the additives are present in powder. The interaction between AKD with fillers carbonate (CaCO3) and the influence of AKD hydrolysis products do not participate in the reaction of the paper hydrophobic, so it is common to choose the sizing before the filler and process meal for animal closer to the grid point, the better.

When referring to the mutual issues between AKD and fillers, which studies show that the AKD to cover the surface of carbonate fillers, the weak adhesive effect. Because mounting surfaces AKD fillers with hydrophobic part of the molecule outward fillers. The chemistry between AKD and cellulose express that AKD associated with carbonate fillers and produces ketone beta calcium salt. This connection is not stable and lasting for dime into Distearon denatured by acid hydrolysis of the beta ketone.

Ramping glue hydrolyzate decreased because this form does not engage in hydrophobic properties of paper. Humidity and temperature are factors that promote the process of change Distearon.

Look at the impact of the effective drying temperature via ADK glue for paper containing GCC or PCC filler is used at 10%. Sizing degree decreases as temperature increases drying using PCC fillers. In case of using the adhesive GCC increased when the drying temperature increase from 180oF 210oF dispatch. As temperatures rise, the greater the spread of AKD. Part of the glue may seep down and be retained in the structure of the filler pipe. As the temperature increases, the various sizing create. Compared with the adhesive when using 2-temperature carbonate type 180oF, the PCC found that the higher level of household glue. But at higher temperatures than this temperature, the paper with the GCC more dominant. The drying temperature is usually higher than 180oF, if compared between the 2 types of fillers are easier to implant sizing GCC PCC fillers.

 

2. Cationic starch

 

As a type of hydrocarbon synthesis in corn, potatoes, cassava and other foods by the synthesis of glucose units, with structural formula (C6H12O6) n. Starch has two parts: a linear section called: a linear section called amylose consists of approximately 500 units chain, partially branched amylopectin called for several thousand units link.

Amylose easy recovery format, ie the dissolved elements to precipitate back to its original state to cause the hard phrase, so one must use enzymes to form of amylopectin, also known as modified starches.

Starch is a polymer, also exist hydroxyl alcohol (plant) as cellulose, so they stick together and form a strong link Xenluloza- cellulose-starch. The result is a dry paper increases as the burst strength, tensile strength, hardness, surface durability, smoothness ... as in will sharpen.

Currently the external starch use traditional whitening of paper strength, it also applies to the reserved aid components in a mixture of pulp.

When sizing AKD is effective cationic starch improve reserves of glue a lot, so it is required to use because of high retention, the new glue effectively dropped.

Also starch acts as an auxiliary reserve so we selected fibers soi.Do starch positions immediately after the glue to ensure both reserves are not doing the glue and cotton of long fiber.

Dose cationic starch used from 0.6 ¸ 1.2%. If the excessive cationic starch also leads to difficulties in running the machine and the stability of the wet part.

The following figure explains why the starch in the paper:

 

4. Methyl Cellulose carbonyl (CMC)

 

CMC is a cellulose derivatives. It exists in two forms and insoluble in water. Water-soluble type is associated with the link type alkaline (Na, Ca or Al). CMC taking big swell, so the challenge to stir constantly with great speed. CMC beyond the effect of increasing the durability of the paper, it is also effective to reduce grinding time, so I entered before perusing fine (in tank mixtures).

 

5. / Assistant reserved

 

Due to the size of the filler is smaller than the eye vulnerable luoiva short fibers pass through the grid according to the white water in the process of production that should be reserved for short fibers by combining fibers of cotton short while fillers are retained.

So often reserved fillers low, particularly on paper machines double mesh generation are very strong drainage capacity. On long net paper machine, the result was due to lower reserves distribution is uneven between the underside and the top, which affects the quality of printing. Besides the low reserve levels also lead to fillers, fine fibers in the lower drainage drainage grid, particularly for producing paper printing (using large amount of filler) significantly reduces drainage capacity of mesh powder on luck, lead to speed and operating capacity of paper machines, funding costs for wastewater treatment ...

To improve the effectiveness of the reserves fillers and flung smooth application in paper, normally the reserve of chemical auxiliaries used. It is extremely necessary in the current paper technology, especially the kind of paper used many fillers.

Auxiliaries used reserve is Percol 182, Percol 47, Hydrocol OC (Bentonite)

To not make the cotton of long fiber (He drank to the nature of the paper), then we give as close as possible to the grid point powder, here we choose to enter into the ark before pressurizing.

* Product Features:

- White powder

- Is the high molecular weight polyacrylamide

- Nature: Cationic

- Gravity: 600700 g / l

- PH: 4

Structure flocculation

- The cotton by neutralizing the charge:

Since fibers and fillers are negatively charged, they repel each other fillers not attached to the surface fibers are. To suppress repulsion between them and strengthen distribution power

The figure illustrates the mechanism of aid to cotton reserves

I put alum canopy and to neutralize starch and electricity tich.Tuy However, flocculation is also limited because the cohesive force between them and the fibers are not strong enough to hold on to the paper machine mesh nets with double speed elevation, drainage strong

- The Cotton bridge:

Therefore, Polyacrylamide high molecular weight is included to create linkages between the needs of this filler particles with different filler particles and the fibers on the basis of electrostatic adsorption formed between the vast cotton fibers and the small fillers in grid

The amount of reserves to support in paper machines have been tested before in laboratory as if for less, do not work, if for more than offensive drainage on the grid due to too much cotton, flux for about 0, 03% / ton of product.

 

Reserve calculation formula:

The inorganic fillers, flowing powder, white is widely used in the manufacture of paper and cacton improving quality indicators of product and reduce production costs.

Paper is padded to increase the physical and optical properties of the paper. Thanks to the small diameter, the particles will fill the hole filler mix between the fibers are cut to make paper, soft, smooth, white and higher turbidity. Fillers used in paper production will replace part of fibers leading to lower costs of product due to its cost cheaper than the cost of the fiber.

However, the proportion of filler in the paper section is also limited by the paper to produce inferior durability and reduced quality of glue. In fact the amount of filler used in about 5 ¸ 15% weight paper. Particularly as paper filler 20-25% volume weight paper.

* Technical requirements for fillers:

+ As hard substances dissolved in water.

+ There must be at least whiteness of flour whiteness.

+ Being durable chemical substances, capable of high reserves in the paper.

+ Particle size small enough.

* Fillers commonly used in the paper industry.

 

6.1. Kaolin: (Al2O3.SiO3.2H2O)

- The most inexpensive fillers, abundant resources, stable and easy to use, it gives a lot of good properties paper. Kaolin is used in the paper production process in an acid environment.

6.2. Gypsum (CaO4)

- There is a high brightness, low cost, but has the disadvantage of low retention on the paper.

 

6.3. Powdered calcium carbonate (CaCO3):

- Only use alkaline and neutral properties, due to CaCO3 dissolved in an acid environment. It has white and opaque concentrations higher than kaolin, it is especially used in the manufacture of paper for long term use because of their ability to neutralize acids generated in the aging process of destroying the paper.

 

6.4. The oxide - titanium dioxide (TiO2):

Having the highest brightness and the best turbidity but high cost. It is only used for the type of paper requires less amount of filler but opacity, high whiteness. The level of 2-3% only use fillers

- Powder Talc (Magnesium Silicate-3MgO.4SiO2.H2O) mean fillers create softness to the paper, talc have good affinity with plastic, so it is used to prevent the adhesion of plastic in system paper manufacturing system. Recently, however, limited talc use and harmful to human health when inhaling it into the lungs.

6.5 The other additives

In slightly alkaline environment, the bacteria grow very strong, especially the dirt bacteria. As the bacteria grow they cause an accumulation of material on the surface or into the device, a pipe or disintegrated pulp in places less rotation, resulting in occlusion device, clogging mesh blankets , reduces the ability to run the machine, increased corrosion, reduces paper quality, increase maintenance costs. So moving to the alkaline program needs to have a microbial control more closely. Biocide agents commonly used to control the growth of bacteria.

* From these characteristics we can see when producing coated paper surface sizing in an alkaline environment, is essential to use padded CaCO3 than Vietnam.

7.Hon right sizing (sizing system)

The surface of the paper can be processed by coating, polishing, surface laminated onto a sheet of paper or starch for paper running through many of these lots slot pressed highly polished to increase durability, balls, and other characteristics (optical cross stitch pressed).

Ordinary glue or used for surface treated paper at this stage is the oxidation of starch to improve strength, smoothness, and ensuring the proportion of paper.