A surface sizing process for tissue paper using corn starch as raw material

Abstract

This invention belongs to the field of new papermaking processes, specifically relating to a surface sizing process for thin paper using corn starch as raw material. The main improvements are as follows: 1) During the corn starch dissolution stage, 25-35 kg of high-molecular-weight polyol polymer is added to each ton of starch as a starch modifier; 2) A heating system is added to the feeding station to raise the temperature of the sizing starch solution from 55℃ to 65℃, thereby improving fluidity; 3) Novozymes CWB-3515 cellulase is added to the starch solution at a dosage of 2-3 ppm per ton of starch to decompose paper fibers. Through the comprehensive application of these methods, the problem of corn starch not being suitable for surface sizing of thin paper using a film transfer sizing machine is solved; simultaneously, the problem of protein flocculation causing clogging of the sizing metering rod grooves is prevented, the metering rod lifespan is increased by 20 times, the sizing amount is increased by 1 time, the uniformity of the coating width is increased by 4 times, and the paper surface strength is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of new papermaking processes, specifically providing a surface sizing process for thin paper using corn starch as raw material. Background Technology

[0002] The main technical characteristics of thin paper are as follows: it has low basis weight, high physical strength, excellent uniformity and good surface properties. However, because there is no standard for sizing degree for thin paper, it also has the following difficult-to-solve technical problems: thin sizing coating, poor sizing uniformity, large consumption of metering rods in film transfer sizing machines, large changes in paper surface strength, and easy to produce powder and lint during printing and use. The above defects are increasingly unsuitable for the requirements of the printing industry for paper.

[0003] Using corn starch to replace cassava starch in papermaking surface sizing technology is an effective way to reduce production costs. It has been widely used in dip sizing machines and high-coating paper. However, when using a film transfer sizing machine to produce thin paper, due to the limitations of paper absorbency (the total thickness of the sizing film coating transferred to the paper is 0.2-0.5μm), higher requirements are placed on coating uniformity, sizing solution viscosity, and flowability.

[0004] Because corn starch is prone to aging after gelatinization, the viscosity of the starch solution increases rapidly during film transfer sizing and pressing of the paper. This makes it easier for paper fibers and dust on the paper surface to be adsorbed and carried into the sizing and feeding system, affecting the stable operation of the sizing system and the absorption performance of the paper. At the same time, the grooves of the sizing metering rod become severely clogged. These factors cause many problems when using corn starch as raw material to produce thin paper using a film transfer sizing machine, especially posing new challenges to the sizing process. How to improve the above defects has become a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the problems existing in the above-mentioned technology, this invention provides a surface sizing process for thin paper using corn starch as raw material, mainly employing the following improved process: 1) During the corn starch dissolution stage, 25-35 kg of high molecular weight polyol polymer is added to each ton of starch as a starch modifier; 2) A heating system is added to the feeding station to raise the temperature of the sizing starch solution from 55℃ to 65℃, thereby improving fluidity; 3) Novozymes CWB-3515 cellulase is added to the starch solution used at a dosage ratio of 2-3 ppm per ton of starch to decompose paper fibers. By comprehensively applying the above methods, the problem of starch aging caused by the high amylose content of corn starch was solved, thereby resolving the issue that corn starch could not be used for surface sizing of thin paper using a film transfer sizing machine. Simultaneously, it prevented protein flocculation from clogging the grooves of the sizing metering rod, increasing the metering rod's lifespan by 20 times, doubling the sizing amount, improving the uniformity of the coating width by 4 times, significantly enhancing paper surface strength, and noticeably reducing powder buildup on printing rollers and blankets. The cleaning efficiency for printing plates and blankets increased from 10,000 impressions to 50,000 impressions, greatly improving production efficiency and equipment lifespan while reducing equipment maintenance costs.

[0006] After research, the inventors discovered that the amylose content in corn starch is four times that of cassava starch (corn starch contains approximately 40% amylose, while cassava starch contains no more than 10%), which is the main factor causing the rapid aging of corn starch solution. Simultaneously, corn starch contains a certain amount of fat (0.3%) and protein (0.4%), which can flocculate and cross-link with paper fibers and dust, causing blockage of the grooves in the sizing metering rod. This is the main problem encountered when using corn starch to replace cassava starch in papermaking surface sizing technology. Based on the above findings, the applicant's final specific technical solution for this invention is as follows:

[0007] A surface sizing process for thin paper using corn starch as raw material, mainly including the following improvements:

[0008] 1) During the corn starch dissolution stage, add 25-35 kg of high molecular weight polyol polymer to each ton of starch as a starch improver;

[0009] 2) The addition of a heating system to the feeding station raises the temperature of the sizing starch solution from 55℃ to 65℃, thereby improving its fluidity;

[0010] 3) Add Novozymes CWB-3515 cellulase to the corn starch sizing compound at 2-3 ppm per ton of dry starch to decompose paper fibers.

[0011] In addition, the sizing process for thin paper used in this application is the same as the existing conventional sizing process, and the specific process can be referred to as follows:

[0012] Dry corn starch is fed into a discharge hopper and then transported to a starch storage hopper via a pneumatic conveying system. The starch is added via a metering screw, along with the specified proportion of amylase. After dispersion, it is filtered through a basket filter to remove impurities and then fed into a jet cooker. The heated starch is maintained at 70-85°C and enters a reaction tank for reaction. After a certain reaction time, the high molecular weight raw starch is broken down into low molecular weight chains, producing cross-linked starch molecules. This is then pumped into the jet cooker for high-temperature gelatinization. The gelatinized starch paste enters a steam separator via a serpentine coil and then flows into a starch storage tank for insulated storage. Stirring is maintained within the starch storage tank to ensure uniform concentration and temperature of the finished starch paste. The sizing starch is pumped from the storage tank into the feeding tank. The liquid level controls the frequency of the finished sizing material feeding rotor pump to keep the liquid level in the feeding tank at a normal level. The sizing material in the feeding tank is filtered and descaled by the feeding pump into the pressure screen. The clean sizing material enters the feeding beam of the sizing machine through the feeding pipe. The amount of sizing liquid on the sizing roller is controlled by the metering rod. When the paper is transferred through the film transfer sizing press, the sizing film is transferred to the paper surface. The returned sizing material is returned to the feeding station through the vibrating screen to complete the sizing process.

[0013] Compared with existing technologies, this application first uses corn starch for papermaking surface sizing technology, replacing the existing conventional cassava starch. More specifically, the steps for preparing the sizing solution using corn starch are as follows:

[0014] Corn starch and high-molecular-weight polyol polymer are added to a dispersion tank via a metering screw. Simultaneously, α-amylase (enzyme activity 2000-3000 u / g) is added at a ratio of 0.2-0.5 kg / ton of starch. The amount of water added is controlled so that the starch concentration in the dispersion tank is 20-30 wt%. After continuous dispersion in the tank, the mixture is filtered through a basket filter to remove impurities. It is then sent to a first-stage jet cooker for heating, with the starch temperature controlled at 70℃~80℃. Finally, it is sent to an enzyme reaction tank. Enzymatic reaction is performed; after 15-20 minutes of enzymatic reaction, the high molecular weight corn starch is broken down into low molecular weight starch molecules, achieving the viscosity required for surface sizing. It is then fed into a jet cooker for high-temperature gelatinization at 115-135℃, 1.7-3.0 bar, and 2-4 minutes. Simultaneously, the high temperature terminates the enzyme reaction in the starch solution. The gelatinized starch slurry flows through a serpentine coil into a steam separator and then into a sizing starch storage tank for insulated storage. The starch storage tank requires stirring to ensure uniform concentration and temperature of the finished starch slurry. Three rotary pumps are connected after the finished product tank to feed the paper machine, with variable frequency flow control.

[0015] In addition, a heating system is added to the starch compound feeding station to raise the temperature of the starch sizing solution from 55℃ to 65℃, thereby improving fluidity. The heating system can use various methods such as electric heating or coil heating, with electric heating being preferred for better temperature control. Furthermore, Novozymes CWB-3515 cellulase can be added to the corn starch compound at a rate of 2-3 ppm per ton of starch, either within the feeding station or in the vibrating screen of the sizing solution return system.

[0016] The high molecular weight polyol polymer used above is selected from KSK1511 starch modifier from Zhejiang Kesike High-Tech Materials Co., Ltd.

[0017] After adopting the above improvements, the technical effects that this application can achieve are as follows:

[0018] After using the above starch modifier, corn starch forms "molecular bridges" between the amylose molecular chains, similar to modifying amylose into amylopectin; at the same time, it can emulsify the vegetable fat in corn starch and decompose the protein encapsulating the corn starch, so that they are dispersed in the starch liquid in a small molecule state to prevent flocculation, thereby avoiding clogging of the metering rod grooves, and improving fluidity, ensuring sizing uniformity and coating thickness.

[0019] Increasing the temperature of the feeding station can improve the fluidity of the sizing solution, making it more suitable for sizing solutions prepared from corn starch. It can also increase the reaction rate of cellulase, thereby increasing the amount of sizing agent and the thickness of the surface sizing layer.

[0020] Adding the corresponding cellulase to the corn starch adhesive breaks down paper fibers, preventing the paper fibers from mixing with the adhesive and clogging the metering rod, and further ensuring uniform sizing.

[0021] In summary, by comprehensively applying the above methods, the inventors have solved the problem of starch aging caused by the high amylose content of corn starch, thereby solving the problem that corn starch cannot be used for surface sizing of thin paper using a film transfer sizing machine. Simultaneously, they have prevented the problem of protein flocculation causing clogging of the sizing metering rod grooves, increased the metering rod lifespan by 20 times, doubled the sizing amount, improved the uniformity of the coating width by 4 times, significantly improved the surface strength of the paper, and significantly reduced powder accumulation on the printing rollers and blankets. The cleaning efficiency of printing plates and blankets has increased from 10,000 impressions to 50,000 impressions, greatly improving production efficiency and equipment lifespan while reducing equipment maintenance costs. Detailed Implementation

[0022] The following detailed embodiments further illustrate the above-described content of the present invention, but should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Unless otherwise specified, the following embodiments are all implemented using conventional prior art. Unless otherwise specified, all percentages below are weight percentages.

[0023] The amylases used in the following examples are all mesophilic α-amylases with enzyme activity of 2000-3000 u / g, purchased from Buckman Laboratories Chemical (Shanghai) Co., Ltd. (α-amylases produced by other companies can also be used, with enzyme activity of 3000-4000 u / g, 2000-3000 u / g, 1500-2000 u / g, and other specifications).

[0024] The high molecular weight polyol polymer used is selected from KSK1511 starch modifier from Zhejiang Kesike High-Tech Materials Co., Ltd.;

[0025] The cellulase used was Novozymes CWB-3515 cellulase (enzyme activity > 4500 u / g).

[0026] The thin paper used in the following examples has a specification of 36-40 g / m², a width of 5960 mm, a winding speed of 1100 m / min, and an adhesive application rate of 0.8-0.9 g / m² on one side.

[0027] When applying the sizing agent, control the starch viscosity to 9-14 Pa·s (40℃) and the starch solution concentration to 15-20%.

[0028] Example 1:

[0029] A surface sizing process for thin paper, using corn starch as the sizing solution, includes the following steps:

[0030] Dry corn starch is fed into a discharge hopper and then transported to a starch storage hopper via a pneumatic conveying system. Starch is added via a metering screw, maintaining a starch solution concentration of 25 wt%. Amylase is added at a ratio of 0.35 kg / t starch. The cooking process is automatically controlled. 25 kg / t starch-based polyol polymer is added to a dispersion tank, dispersed, and then filtered through a basket filter to remove impurities. The resulting starch is then fed into a jet cooker, where its temperature is controlled at 80°C before entering a reaction tank for reaction. After 20 minutes of reaction, the high-molecular-weight raw starch is broken down into low-molecular-weight chains, producing some cross-linked starch molecules. This is then pumped into the jet cooker for high-temperature gelatinization at 120°C, 2.5 bar, and 2-3 minutes. The gelatinized starch paste then flows through a serpentine coil into a steam separator and then into a sizing starch storage tank for insulated storage. The starch storage tank requires stirring to ensure uniform concentration and temperature of the finished starch paste.

[0031] The starch for sizing is pumped from the storage tank into the feeding tank (which has an electric heating device to keep the starch solution at about 65°C). The frequency of the finished sizing material feeding rotor pump is controlled by the liquid level to keep the liquid level in the feeding tank at about 50%. The sizing material in the feeding tank is then pumped into the pressure screen for filtration and slag removal. The clean sizing material enters the feeding beam of the sizing machine through the feeding pipe. At the same time, 2 ppm of cellulase is added to the sizing material according to the amount of dry starch per ton. The amount of sizing material on the sizing roller is controlled by the metering rod. When the paper is transferred through the film transfer sizing press, the sizing film is transferred to the paper surface. The returned sizing material is returned to the feeding station through the vibrating screen, completing the sizing process.

[0032] Example 2:

[0033] A surface sizing process for thin paper, using corn starch as the sizing solution, includes the following steps:

[0034] Dry corn starch is fed into a discharge hopper and then conveyed to a starch storage hopper via a pneumatic conveying system. Starch is added via a metering screw, controlling the starch solution concentration at 28 wt%. Amylase is added at a ratio of 0.50 kg / t starch. The cooking process is automatically controlled. In a dispersion tank, 35 kg / t starch-based polyol polymer is added, dispersed, and then filtered through a basket filter to remove impurities. The resulting starch is then fed into a jet cooker, where its temperature is controlled at 70°C before entering a reaction tank. After 10 minutes of reaction, the high-molecular-weight raw starch is broken down into low-molecular-weight chains, producing some cross-linked starch molecules. This is then pumped into the jet cooker for high-temperature gelatinization at 130°C, 2.0 bar, and 3-4 minutes. The gelatinized starch paste then flows through a serpentine coil into a steam separator and then into a sizing starch storage tank for insulated storage. The starch storage tank requires stirring to ensure uniform concentration and temperature of the finished starch paste.

[0035] The starch for sizing is pumped from the storage tank into the feeding tank (which has a heating device to keep the starch solution at about 65°C). The frequency of the finished sizing material feeding rotor pump is controlled by the liquid level to keep the liquid level in the feeding tank at about 70%. The sizing material in the feeding tank is then pumped into the pressure screen for filtration and slag removal. The clean sizing material enters the feeding beam of the sizing machine through the feeding pipe. The amount of sizing material on the sizing roller is controlled by the metering rod. When the paper is pressed through the film transfer sizing process, the sizing film is transferred to the paper surface. The returned sizing material is returned to the feeding station through the vibrating screen (with 3ppm cellulase / t of dry starch added), thus completing the sizing process.

[0036] Comparative Example 1

[0037] A surface sizing process for thin paper, using cassava starch as the sizing solution, includes the following steps:

[0038] Dry cassava starch is fed into a discharge hopper and then transported to a starch storage hopper via a pneumatic conveying system. The starch is added via a metering screw, maintaining a starch concentration of 28 wt%. Amylase is added at a ratio of 0.40 kg / t starch. The cooking process is automatically controlled, dispersing the starch in a dispersion tank. After dispersion, it is filtered through a basket filter to remove impurities and then fed into a jet cooker. The heated starch is maintained at 80°C and then enters a reaction tank for reaction. After 20 minutes of reaction, the high molecular weight raw starch is broken down into low molecular weight chains, producing some cross-linked starch molecules. This is then pumped into the jet cooker for high-temperature gelatinization at 130°C, 2.0 bar, and 3-4 minutes. The gelatinized starch paste is then fed into a steam separator via a serpentine coil and then flows into a starch storage tank for insulated storage. The starch storage tank requires stirring to ensure uniform concentration and temperature of the finished starch paste.

[0039] The sizing starch is pumped from the storage tank into the feeding tank. The liquid level controls the frequency of the finished sizing material feeding rotor pump to keep the liquid level in the feeding tank at about 50%. The sizing material in the feeding tank is then filtered and descaled by the feeding pump into the pressure screen. The clean sizing material enters the feeding beam of the sizing machine through the feeding pipe. The amount of sizing liquid on the sizing roller is controlled by the metering rod. When the paper is pressed through the film transfer sizing process, the sizing film is transferred to the paper surface. The returned sizing material is returned to the feeding station through the vibrating screen, completing the sizing process.

[0040] Comparative Example 2

[0041] A surface sizing process for thin paper, the specific steps of which are as follows:

[0042] Dry corn starch is fed into a discharge hopper and then transported to a starch storage hopper via a pneumatic conveying system. The starch is added via a metering screw, maintaining a starch concentration of 25 wt%. Amylase is added at a ratio of 0.35 kg / t starch. The cooking process is automatically controlled, dispersing the starch in a dispersion tank. After dispersion, it is filtered through a basket filter to remove impurities and then fed into a jet cooker. The heated starch is maintained at 80°C and then enters a reaction tank for reaction. After 20 minutes of reaction, the high molecular weight raw starch is broken down into low molecular weight chains, producing some cross-linked starch molecules. This is then pumped into the jet cooker for high-temperature gelatinization at 120°C, 2.5 bar, and 2-3 minutes. The gelatinized starch paste enters a steam separator via a serpentine coil and then flows into a starch storage tank for insulated storage. The starch storage tank requires stirring to ensure uniform concentration and temperature of the finished starch paste.

[0043] The sizing starch is pumped from the storage tank into the feeding tank. The liquid level controls the frequency of the finished sizing material feeding rotor pump to keep the liquid level in the feeding tank at about 50%. The sizing material in the feeding tank is then filtered and descaled by the feeding pump into the pressure screen. The clean sizing material enters the feeding beam of the sizing machine through the feeding pipe. The amount of sizing liquid on the sizing roller is controlled by the metering rod. When the paper is pressed through the film transfer sizing process, the sizing film is transferred to the paper surface. The returned sizing material is returned to the feeding station through the vibrating screen, completing the sizing process.

[0044] Comparative Example 3 directly uses the un-sizing thin paper from the above-described examples and comparative examples.

[0045] Experimental Example

[0046] The relevant data were tested on the tissue paper obtained in Examples 1 and 2 and Comparative Examples 1-3. The results are as follows: the adhesive solution of Example 1 was used for 36 g / m² tissue paper, the adhesive solution of Example 2 was used for 40 g / m² tissue paper, and Comparative Examples 1 and 2 were used for 36 g / m² and 40 g / m² tissue paper, respectively. The specific test data are as follows:

[0047]

[0048]

[0049] As shown in the table above, the technical solution of this application solves the problem of starch aging caused by the high amylose content of corn starch, thus solving the problem that corn starch cannot be used for surface sizing of thin paper using a film transfer sizing machine. Simultaneously, it prevents the problem of protein flocculation causing clogging of the sizing metering rod grooves. Compared with directly using native corn starch as the sizing liquid, the metering rod lifespan is increased by 20 times, the sizing amount is increased by 1 time, the uniformity of the coating width is increased by 4 times, the paper surface strength is significantly improved, and the accumulation of powder on the printing rollers and blankets is significantly reduced. The frequency of cleaning the printing plate and blanket is increased from 10,000 impressions / time to 45,000-50,000 impressions / time, greatly improving production efficiency and equipment lifespan, and reducing equipment maintenance costs. Compared with using cassava starch as the sizing liquid, the performance improvements are also significant, and it can effectively replace cassava starch as a sizing liquid raw material.

[0050] Without departing from the spirit and essence of this invention, those skilled in the art can make various equivalent modifications or substitutions to the embodiments of this invention, and all such modifications or substitutions should be within the scope of this invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this invention should also be covered within the protection scope of this invention. Therefore, the protection scope of this invention should be determined by the scope of the claims.

Claims

1. A process for surface sizing of tissue paper using corn starch as raw material, characterized by, Meanwhile, the following three improvement schemes are adopted: 1) 25-35 kg of high-molecular polyol polymer is added to each ton of starch as a starch modifier during the corn starch dissolving stage; 2) A heating system is added to the feeding station to increase the temperature of the sizing starch solution from 55℃ to 65℃; 3) 2-3 ppm of cellulase is added to the corn starch sizing material according to the absolute dry weight of one ton of starch; The sizing material enters the sizing machine feeding beam through the feeding pipeline, the sizing roller glue liquid amount is controlled by the metering rod, the glue film is transferred to the paper surface when the paper passes through the film transfer sizing press, the backflow sizing material is backflowed to the feeding station through the vibrating screen, and the sizing is completed; The high-molecular polyol polymer used is KSK1511 starch modifier from Zhejiang Kexike High-tech Materials Co., Ltd.; The cellulase used is Novozymes CWB-3515; The steps of preparing the sizing solution with corn starch are as follows: The corn dry starch and high-molecular polyol polymer are added to the dispersing tank through the metering screw, and 0.2-0.5 kg of α-amylase is added according to the proportion of 0.2-0.5 kg per ton of starch, the water amount is controlled to make the starch concentration in the dispersing tank 20-30 wt%, the above mixture is continuously dispersed in the dispersing tank and then filtered through the basket filter to remove impurities, then it is sent to the first jet cooker for heating, the temperature of the heated starch is controlled at 70-80℃, and finally it is sent to the enzyme reaction tank for enzyme reaction; After 15-20 min of enzyme reaction, the high-molecular chain corn starch is cut into low-molecular chain starch molecules, which can meet the viscosity requirement for surface sizing; Then it is sent to the jet cooker for high-temperature gelatinization, the gelatinization temperature is 115-135℃, the pressure is 1.7-3.0 bar, and the gelatinization time is 2-4 min, and the high-temperature terminates the enzyme reaction in the starch solution; The gelatinized starch sizing material flows into the sizing starch storage tank for heat preservation and storage after entering the steam separator through the snake-shaped coil.

2. The process for surface sizing of tissue paper using corn starch as raw material as claimed in claim 1 wherein: The heating system used is electric heating or coil heating.

3. The process for surface sizing of tissue paper using corn starch as claimed in claim 2 wherein: The heating system used is electric heating.

4. The process for surface sizing of tissue paper using corn starch as claimed in claim 1 wherein: The used tissue paper format was 36-40 g / m 2 2, width 5960 mm, reel speed 1100 m / min, sizing amount 0.8-0.9 g / m 2 2 per side.

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