CN111101402A

CN111101402A - Food cardboard and preparation method thereof

Info

Publication number: CN111101402A
Application number: CN201911273605.7A
Authority: CN
Inventors: 朱国忠; 田维实; 王俊明; 周雪林; 仇如全; 刘继春
Original assignee: Ningbo Asia Pulp and Paper Co Ltd
Current assignee: Ningbo Asia Pulp and Paper Co Ltd
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2020-05-05

Abstract

The application discloses food card paper and a preparation method thereof, the food card paper comprises a paper layer and a coating, the paper layer comprises a bottom layer, a core layer and a surface layer which are sequentially stacked, and the coating is coated on the surface layer. The core layer is made of core layer raw materials, wherein the core layer raw materials comprise bleached needle sulfate pulp, bleached broad-leaf sulfate pulp and 90-95% by mass of bleached chemithermomechanical pulp, and the bulk of the prepared food paperboard is 1.70-1.75. The bulk of the food paperboard can be improved by improving the dosage of the bleached chemithermomechanical pulp, so that the quality of the food paperboard is improved.

Description

Food cardboard and preparation method thereof

Technical Field

The application relates to the field of medium-high grade food packaging paperboards, in particular to an ultrahigh-bulk food paperboard and a preparation method thereof.

Background

With the vigorous development of social economy, the requirements of people on paper quality are increasingly enhanced, the requirements on food packaging are higher and higher, and the requirements of food packaging and various printing are met, so that the improvement of the process of making paper by using food paperboard is particularly important, and the food paperboard packaging meeting the requirements of people is manufactured.

Through long-term research by the inventor of the application, the paper paperboard has the advantages that the loose thickness and the stiffness of the paper are obviously different due to different pulp mixing of the paper layer and the coating, and the loose thickness, the stiffness and the printing adaptability range are narrow due to the pulp mixing of the common paper layer, so that the quality of the food paperboard is reduced, and the use requirement is not met.

Disclosure of Invention

The application provides a food paperboard and a preparation method thereof, which can improve the bulk of the food paperboard.

In order to solve the technical problem, a technical scheme that this application adopted provides a food card paper, including ply and coating, the ply is including the bottom, sandwich layer and the surface course that stack gradually the setting, on the coating surface course. The core layer is made of core layer raw materials, wherein the core layer raw materials comprise bleached softwood kraft pulp (NBKP), bleached broadleaf kraft pulp (LBKP) and bleached chemithermomechanical pulp (BCTMP) with the mass percentage of 90-95%.

Wherein, the core layer raw material alsoComprises cationic starch with the dosage of 10-17 kg/T, wherein the cationic starch with the dosage of 10-17 kg/T is that each ton of oven-dried pulp contains 10-17kg of cationic starch, and the coating weight of the coating is 29-36.2 g/m²。

Wherein, the refining freeness of LBKP is 250 +/-30 ml.

Wherein the bulk of the obtained food cardboard is 1.70-1.75.

The surface layer is made of 20-40% of NBKP and 60-80% of LBKP by mass percentage, the core layer is made of 0-2% of NBKP, 5-10% of LBKP and 90-95% of BCTMP by mass percentage, and the bottom layer is made of 20-40% of NBKP and 60-80% of LBKP by mass percentage.

The preparation method of the food cardboard comprises the following steps:

respectively preparing a bottom layer, a core layer, a surface layer and the coating.

And sequentially laminating the bottom layer, the core layer and the surface layer together, and coating paint on the surface layer to form a coating, thereby obtaining the food paperboard.

Wherein the step of preparing the core layer comprises:

providing core layer raw materials, wherein the core layer raw materials comprise NBKP, LBKP and BCTMP with the mass percent of 90-95%;

and mixing the core layer raw materials together to obtain the core layer by papermaking.

Wherein, the core layer raw material also comprises cationic starch with the dosage of 10-17 kg/T.

Wherein the coating weight of the coating on the surface layer is 29-36.2 g/m²。

Wherein, the refining freeness of LBKP is 250 +/-30 ml.

Wherein the bulk of the prepared food cardboard is 1.70-1.75.

Wherein the step of preparing the bottom layer comprises:

providing 20-40% of NBKP and 60-80% of LBKP in percentage by mass;

mixing 20-40% of NBKP and 60-80% of LBKP by mass percent together to obtain a bottom layer by papermaking.

A step of preparing a core layer comprising:

providing NBKP with the mass percent of 0-2%, LBKP with the mass percent of 5-10% and BCTMP with the mass percent of 90-95%;

mixing 0-2% of NBKP, 5-10% of LBKP and 90-95% of BCTMP together by mass percent to obtain a core layer by papermaking.

A step of preparing a facing comprising:

providing 20-40% of NBKP and 60-80% of LBKP in percentage by mass;

mixing 20-40% of NBKP and 60-80% of LBKP together by mass percent to obtain the surface layer by papermaking.

The beneficial effect of this application is: be different from prior art's condition, this application is through the mode that adopts improvement BCTMP quantity to optimize cardboard sandwich layer thick liquids ratio, can promote the bulk of food card paper, and then promote the quality of food card paper.

Drawings

FIG. 1 is a schematic perspective view of an embodiment of a food card of the present application;

FIG. 2 is a schematic flow diagram of an in-line process flow of a core layer mixing system for preparing an embodiment of a food paperboard of the present application;

fig. 3 is a schematic flow chart of a preparation method of an embodiment of the present application for preparing food cardboard.

Wherein in figures 1 and 2, 10-ply, 11-bottom, 12-core, 13-top, 20-coat, 21-precoat, 22-midcoat, 23-top, 31-mixer, 32-chest, 33-fan pump, 34-chest, 35-fan pump.

Detailed Description

The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

Referring to fig. 1, the food cardboard provided by the embodiment of the present application may be formed by combining a paper layer 10 and a coating layer 20, and the paper layer 10 may include a bottom layer 11, a core layer 12, and a surface layer 13, which are sequentially stacked. Core layer 12 may be placed on bottom layer 11, face layer 13 may be placed on core layer 12, and coating layer 20 may coat face layer 13. The coating 20 may include a precoat layer 21, a midcoat layer 22, and a topcoat layer 23 disposed from below and above. The midcoat layer 22 may be disposed over the precoat layer 21 and the topcoat layer 23 may be disposed over the midcoat layer 22.

The food paperboard with ultrahigh bulk is mainly used for cake boxes, milk tea boxes and ice cream packages, and if the bulk size is too low, the packaged food is easily affected by moisture under the low-temperature condition. Therefore, in the field of middle-high-end food packaging, the bulk of the food paperboard is very necessary to be improved.

As is well known, the bulk and smoothness of a sheet are contradictory, and a smaller compression of a stack of sheets indicates a greater bulk, meaning a large gap between sheets. By bulk is meant the degree of porosity of the paper, and it is possible to increase the thickness at a given basis weight, for example, by increasing the stock freeness, by reducing the filler load, by reducing the semi-wet calender line pressure, etc.

The embodiment of the present application is to obtain the food cardboard with the ultrahigh bulk, wherein the core layer 12 may be made of a core layer raw material (not shown), and the core layer raw material may include NBKP, LBKP and 90-95% by mass of BCTMP, so that the bulk of the food cardboard may be increased by optimizing the ratio of BCTMP in the slurry of the core layer 12, specifically, the mass percentage of BCTMP in the core layer raw material may be 90%, 91%, 92%, 94%, 95%, and the like, and is not limited herein. The bulk of the food cardboard may be 1.70 to 1.75, and specifically, the bulk may be 1.71, 1.72, 1.74, or the like.

In the paper industry, BCTMP is a high yield wood pulp impregnated with mild chemicals, refined and bleached. LBKP is also produced by the sulfate process, except that the starting material used is hardwood. It is well known that "eucalyptus pulp" sold in brazil, i.e. wood pulp, can be used alone or in combination with bleached pulp for making various high-grade printing papers, etc. NBKP is chemical paper pulp prepared by using needle-leaved wood as a raw material and adopting a sulfate method to cook and bleach. It is the most widely used pulp, and the bleached pulp is "the king of pulp" according to different coniferous trees, cooking and bleaching processes and operating conditions, and can be used for producing almost all kinds of paper, except special varieties.

In order to obtain a high yield of the corresponding pulp of the bottom layer 11, the core layer 12 and the face layer 13, broke of different mass percentages, NBKP, LBKP and BCTMP can be mixed, which broke can be converted to the corresponding pulp proportions. The surface layer 13 may be made of 20 to 40 mass% of NBKP and 60 to 80 mass% of LBKP, specifically, the mass% of NBKP may be 20%, 25%, 30%, 40%, etc., and the mass% of LBKP may be 60%, 65%, 70%, 80%, etc. The core layer 12 may be made of NBKP of 0 to 2% by mass, LBKP of 5 to 10% by mass, and BCTMP of 90 to 95% by mass, specifically, NBKP may be 0, 1%, 2%, etc., LBKP may be 5%, 6%, 8%, 10%, etc., and BCTMP may be 90%, 91%, 93%, 95%, etc., by mass. The bottom layer 11 may be made of 20 to 40 mass% of NBKP and 60 to 80 mass% of LBKP, specifically, the mass% of NBKP may be 20%, 25%, 30%, 40%, etc., and the mass% of LBKP may be 60%, 65%, 70%, 80%, etc. According to the actual situation, NBKP, LBKP and BCTMP with different mass percentages are used, and the NBKP, LBKP and BCTMP with different mass percentages are mixed to respectively obtain the slurry required by the corresponding surface layer, the core layer and the bottom layer. Of course, during the actual process of preparing the surface layer 13, the core layer 12 and the bottom layer 11, other raw materials may be further added according to the requirement, and are not specifically limited herein.

Further, in order to improve the bonding strength between the pulp of the core layer 12, it is essential to use a reinforcing agent in the paper industry, for example, cationic starch may be added to the core layer raw material, because cationic starch has a specific structure and has a positive charge itself, and it can adsorb negatively charged fibers, fine fibers, fillers and other anionic trash in the paper making slurry. The added cationic starch can be beneficial to fiber dehydration in the slurry, filler fixation and interlayer strength improvement, the cationic starch with the addition amount of 10-17 kg/T can be adopted for matching, and the cationic starch with certain concentration can be matched according to actual conditions.

It should be noted that common enhancing drugs may include self-converted starch, cationic starch, and enhancing agents, etc. Different application scenes can adopt different enhanced medicines, and compared with a common white card, the enhanced medicine addition contrast table 1 is as follows:

TABLE 1

The common white card is added with 8-12 kg/T self-converted starch and 10-35 kg/T reinforcing agent, while the food card paper is only added with 10-17 kg/T cationic starch, specifically, the concentration of the cationic starch can be 10kg/T, 12kg/T, 15kg/T, 17kg/T and the like, so that the fiber bonding strength in the core layer 12 is improved.

In addition, in order to increase the bulk of the food cardboard and the stiffness of the paper layer 10, so that the food cardboard can maintain the required hardness even at low temperature, and the folding function of the box produced by the food cardboard is not affected, the coating weight of the coating layer 20 can be controlled to be 29-36.2 g/m²Specifically, the coating amount may be 29g/m²、31g/m²、34.8g/m²、36.2g/m²Etc., the main purpose of controlling the coating amount is: 1) on the premise of meeting the printing requirements, the coating weight is reduced, and the base paper quantity is increased, so that the bulk and the stiffness of the base paper are improved; 2) the coating amount is obviously lower than that of the common white card, and the phenomenon that the coating 20 bursts when the box is folded is reduced under the conditions of high bulk and stiffness of the food card paper.

In the paper making industry, the refining freeness can represent the water filtering speed or strength of pulp, the unit is ml, 3g of absolute dry pulp is diluted to 1 liter, and the volume of filtrate obtained by filtering is adopted.

In order to improve the bonding strength and thickness of the core layer 12, prevent the paper layer 10 from tearing, prevent delamination and foaming in the subsequent process, prevent the grinding and cutting powder, and maintain the low-layer fiber structure, the general condition is that the broken paper is 300ml, the grinding freeness is 350ml, and the smaller the grinding freeness value is, the poorer the drainage is, and the better the strength is. Therefore, in the present application, in order to improve the bonding strength of the core layer 12, the refining freeness of the broke and the LBKP may be reduced to 250 ± 30ml, and specifically, the refining freeness of the broke and the LBKP may be 220ml, 230ml, 260ml, 280ml, and the like, so that the fibers between the core layers 12 may be sufficiently devillized, and the bonding strength between the fibers may be improved to enhance the bonding strength between the core layers 12.

To more visually demonstrate the difference compared to conventional white card-sized pulp, the pulp formulation process diagram is as follows in comparison to table 2:

TABLE 2

According to the pulp matching ratio, the 20 gram weight of the front coating of the common white card can reach 42 +/-1 g/m²The gram weight of the food card paper can reach 29 to 36.2g/m²Is lighter than the front coating 20 of the common white card, so the slurry can be saved; the core layer 12 of the common white card can be made of 2-5% of NBKP, 5-10% of LBKP and 75-85% of BCTMP by mass percentage, and the core layer 12 of the food cardboard can be made of 0-2% of NBKP, 5-10% of LBKP and 90-95% of BCTMP by mass percentage, that is, the mass percentage of NBKP is reduced, the mass percentage of BCTMP is improved, and thus the bulk of the food cardboard can be improved.

Since the food cardboard is used for packaging food, the requirements of food packaging paper are required to be met, wherein one detection is fluorescence detection, and the requirement is to achieve non-fluorescence. The fluorescent tube control requirement of the food paperboard is an important index in the quality inspection and manufacturing process of the paperboard, and mainly comprises the fluorescent substance detection R457 of less than or equal to 0.3 percent or the fluorescent substance area detection (254nm and 365nm, any one 100cm part)²Fluorescence area of sample) is less than or equal to 5mm². Thus the conventional paper machine processWhen producing the paper board or the paper board, only the thorough cleaning of a process system, the serial washing and the fluorescent whitening agent addition are adopted for the fluorescent control. Coated food cardboard requires more that no whitening agent be added to the coating and the coating supply system requires thorough washing and cleaning.

The latex is used as an adhesive, can be used for preparing a coating raw material, has heavy odor for the latex used by a common white card, and is not suitable for food packaging, so the latex in the food paperboard coating formula adopts the same type of latex with low odor, such as low-odor styrene-butadiene latex, the proportion in the formula is unchanged, and the requirement of the food paperboard on paper can be met.

Referring to fig. 2, a schematic flow chart of a flow line process of the core layer 12 in a slurry mixing system is shown, where the slurry mixing system is to provide slurry corresponding to the bottom layer 11, the core layer 12, and the surface layer 13 for the flow system, so that to prepare the bottom layer 11, the core layer 12, and the surface layer 13, the flow lines corresponding to the bottom layer 11, the core layer 12, and the surface layer 13 may be operated simultaneously to obtain a bottom layer raw material, a core layer raw material, and a surface layer raw material corresponding to the bottom layer 11, the core layer 12, and the surface layer 13, respectively.

The mixing system may comprise a mixer 31, a stock chest 32, a slurry pump 33, a machine chest 34, a machine pump 35. The broke, the NBKP, the LBKP and the BCTMP can flow into the mixer 31 through the inlet of the mixer according to a certain proportion, the mixer 31 can be connected with the slurry mixing tank 32, the slurry mixing tank 32 can be used for mixing the pulp raw materials on the one hand, and can be used for storing the pulp raw materials on the other hand, so as to provide the slurry mixing pump 33 with stirring raw materials, the slurry mixing pump 33 can be provided with a concentration meter for detecting the concentration of the pulp raw materials in the slurry mixing pump 33, the concentration meter can be connected with a concentration controller, the concentration controller can be connected with an automatic valve, when the concentration is detected to be higher, the automatic valve can be opened through the concentration controller, the dilution water can flow into the slurry mixing pump 33, and the pulp in the slurry mixing pump 33 can be provided to the pulp mixing pump 34.

The paper machine pulp pond 34 can be used for stabilizing the thick liquids concentration, and paper machine pulp pond 34 liquid level can have a level gauge, and the level gauge can be connected with liquid level controller, and liquid level controller is connected with the fan pump 33, can be used for controlling fan pump 33 to open or close, and the level gauge can be through the pressure that detects 34 liquid levels in paper machine pulp pond and bottom, and the pressure that detects forms current signal and can feed back to liquid level controller. When the level gauge detects that the level of the stock chest 34 drops, indicating that the now mixed stock is gradually supplied to the approach flow system by the stock pump 35, the opening of the stock pump 33 can be controlled to meet the requirements of the stock chest 34 on the level and stock concentration.

In order to obtain the food cardboard with the bottom layer 11, the core layer 12, the surface layer 13 and the coating layer 20 stacked in sequence, the components and the structure of the food cardboard can be obtained from the above embodiments of the present application, which are not described herein again, and referring to fig. 3, the preparation method of the food cardboard may include:

step S11: respectively preparing a bottom layer 11, a core layer 12 and a surface layer 13 by using the obtained bottom layer raw material, core layer raw material and surface layer raw material, and preparing a coating for subsequent use;

step S12: sequentially laminating the bottom layer 11, the core layer 12 and the surface layer 13 together, and coating the coating on the surface layer 13 to form a coating 20, thereby obtaining the food paperboard;

wherein the step of preparing the core layer 12 comprises:

providing a core layer raw material, wherein the core layer raw material comprises NBKP, LBKP and BCTMP with the mass percentage of 90-95%, specifically, the mass percentage of the BCTMP can be 90%, 91%, 93%, 95% and the like;

the core layer raw materials are mixed together to produce the core layer 12 by paper making.

In order to enhance the fiber strength between the core layers 12, the core layer raw material also comprises cationic starch with the dosage of 10-17 kg/T.

In addition, in order to increase the bulk of the food cardboard and the stiffness of the paper layer 10, so that the food cardboard can maintain the required hardness even at low temperatures, and the folding function of the box produced from the food cardboard is not affected, the coating amount of the coating on the surface layer 13 is 29-36.2 g/m²Specifically, the coating amount may be 29g/m²、31g/m²、34.8g/m²、36.2g/m²Etc. in this wayThe bulk of the prepared food cardboard is 1.70-1.75, and specifically, the bulk can be 1.71, 1.72, 1.74 and the like.

It should be noted that in order to enable the surface of the paper layer 10 of the food paperboard to have good plasticity in terms of printing function in the food packaging later, the coating layer 20 may include a precoat layer 21, a middle coating layer 22 and a top coating layer 23 arranged from below. The coating is sequentially coated with the obtained solid continuous film through the adhesion of the low-odor latex, the surface layer 13 and the coating 20 can be bonded, the paper layer 10 coated with the coating 20 is flat and smooth in surface and high in color purity, and fine smooth dots can be obtained during printing, so that the layering sense of the original can be well reproduced.

In order to improve the bonding strength and thickness of the core layer 12, prevent the paper layer 10 from being torn, prevent delamination and foaming in the subsequent process, prevent powder falling by grinding and cutting, and maintain the low-layer fiber structure, the broken paper is 300ml in general, the grinding freeness is 350ml, when the grinding freeness value is smaller, the drainage is worse, and the strength is better. Therefore, in the present application, in order to improve the bonding strength of the core layer 12, the refining freeness of the broke and the LBKP may be reduced to 250 ± 30ml, and specifically, the refining freeness of the broke and the LBKP may be 220ml, 230ml, 260ml, 280ml, and the like, and the fibers between the core layers 12 may be fully devillicate and broomed, so that the bonding strength between the fibers is improved to enhance the bonding strength of the core layer 12.

Further, the step of preparing the bottom layer 11 includes:

providing 20-40% of NBKP and 60-80% of LBKP, specifically, the NBKP can be 20%, 25%, 30%, 40% and the like, and the LBKP can be 60%, 65%, 70%, 80% and the like;

mixing 20-40% of NBKP and 60-80% of LBKP by mass percent together to obtain a bottom layer 11 by papermaking;

the step of preparing the core layer 12 includes:

providing 0-2% by mass of NBKP, 5-10% by mass of LBKP and 90-95% by mass of BCTMP, specifically, the mass percent of NBKP can be 0, 1%, 2%, etc., the mass percent of LBKP can be 5%, 6%, 8%, 10%, etc., and the mass percent of BCTMP can be 90%, 91%, 93%, 95%, etc.;

mixing 0-2% of NBKP, 5-10% of LBKP and 90-95% of BCTMP together by mass percent to obtain a core layer 12 by papermaking;

a step of preparing the face layer 13, comprising:

mixing 20-40% of NBKP and 60-80% of LBKP by mass percent together to obtain the surface layer 13 by papermaking.

In papermaking, the unfilled paper consists mainly of fibers and air. The filler is used for making paper to obtain specific properties such as whiteness, opacity, paper strength, bulk, smoothness and the like, and meanwhile, the filler is added to reduce and thin the internal space of the paper, so that the ink absorptivity of the paper is increased, and the ink absorptivity is even. The water-insoluble or slightly water-soluble minerals usually added to the stock are present in the printing paper in amounts of about 10% to 25%, and can vary widely from paper to paper. Common inorganic fillers include talc, clay, titanium dioxide and calcium carbonate. Wherein, the titanium dioxide is an expensive high-quality filler; organic synthetic fillers are some high molecular substances.

Air exists in pores among fibers, and because the refractive indexes of the fibers and the air are different, when a light beam irradiates the surface of the paper, part of light is scattered on the interface between the fibers and the air, so that the paper is endowed with low opacity and is reflected in printing, and the printing is mainly represented as extremely easy strike-through. After the filler with the refractive index larger than that of the cellulose is added into the paper, the number of light scattering interfaces in the paper is increased, namely three different interfaces between the fiber and the air, between the filler and the fiber and between the filler and the air exist, and the difference of the refractive index between the filler and the air is larger in the three interfaces. The light is thus maximally scattered at the interface between the filler and the air, resulting in an increase in opacity.

The density of the paper fibers is 1g/cm³The density of the filler is usually 2.5 to 3.0g/cm³. The addition of fillers will reduce the bulk of the paper. However, when a smaller amount of filler is added, the bulk increases with increasing filler amount, and short fiber papers are particularly noticeable. The network formed by interweaving the fibers always has a large number of pores and surface unevenness, and the softness and plasticity of the paper can be improved after adding the fine particle filler, and the calendering treatment can be better carried out, so that the smoothness of the calendered paper can be improved.

Therefore, in order to increase the bulk of the food cardboard and fully consider the plasticity of the surface printing of the food cardboard, a filler may be added as needed according to the actual situation.

In order to more vividly show that the physical indexes of the quantitative distribution, the size proportioning, the enhanced medicine, the coating amount and the main quality of the food cardboard of the present application are different from those of the ordinary social cardboard, the above embodiments are compared with two specific groups of examples and comparative examples, and the comparison table is shown in table 3, wherein the weight of the paper of comparative example 1 and example 1 is 250g, and the weight of the paper of comparative example 2 and example 2 is 350g, but not limited to the scope of the present application.

TABLE 3

By comparing the parameters of quantitative distribution, slurry ratio, physical indexes of main quality and the like of comparative example 1 and example 1, and comparative example 2 and example 2, it can be known that:

first, the bulk of example 1 is 1.7, the bulk of comparative example 1 is 1.43, the bulk of example 2 is 1.75, and the bulk of comparative example 2 is 1.43, it can be seen that the mixed pulp of NBKP of 0-2% by mass, LBKP of 5-10% by mass, and BCTMP of 90-95% by mass provides a higher bulk for the food cardboard.

Second, the interlayer strength of example 1 was 202J/m²While comparative example 1 had an interlayer strength of 185J/m²The interlayer strength of example 2 was 235J/m²While comparative example 2 had an interlayer strength of 190J/m²Therefore, the prepared food paperboard has better interlayer strength by adding the cationic starch with the dosage of 10-17 kg/T and reducing the grinding freeness of broken paper and LBKP to be 250 +/-30 ml.

Thirdly, the mass percent of ash after combustion of example 1 is 15.8%, while the mass percent of ash after combustion of comparative example 1 is 26.5%, the mass percent of ash after combustion of example 2 is 12.6%, and the mass percent of ash after combustion of comparative example 2 is 26.3%, so that the same weight of cardboard can be seen, and the pulp and forest resources can be saved more by the cardboard made of food.

Therefore, through comparison, the preparation method of the application can not only improve the bulk of the food paperboard, but also improve the interlayer strength between the paper layers 10, and save more slurry, which means more saving of papermaking resources and more environmental protection.

In the paper making industry, Alkenyl Succinic Anhydride (ASA) can modify starch under wet conditions, ASA is grafted to starch by using an esterification reaction, and a hydrophobic group is introduced on the starch to synthesize a novel starch modified surface sizing agent. The modified starch long-chain hydrophobic groups are arranged outwards on paper, the surface energy of fibers is reduced, the sizing performance of the paper is improved, the modified product can be directly pasted and sized, the modified starch long-chain hydrophobic groups can be used in pulp and can be used as a surface sizing agent, the modified starch long-chain hydrophobic groups have an obvious reinforcing effect, and the effects of water resistance and water resistance are achieved.

After the thick liquids stream in thoughtlessly thick liquids system sent to the drifting system, can adopt the edulcorator to detach unnecessary impurity, send into the head box through the pressure stopper, the thick liquids is tiled on the net section, and the press section is squeezed the shaping, then is dried, surface sizing, carries out the supercalence again, sets up coating 20 on ply 10, then carries out soft press polish reinforcing surface friction and increment surface, the printing of being convenient for, then batches into paper.

The rolled paper can be sprayed with polyethylene or polypropylene on the 11 surfaces of the bottom layer of the paper board to be coated, so that the air tightness and tensile strength of the paper board are better improved, and after the paper board is treated by a special process, the surface of the paper board is covered with a high-pressure polyethylene electrostatic film layer to form a coating film, so as to prevent oil and water and realize heat sealing, for example: when the food paperboard is used, the edible vegetable oil at 80 ℃ does not leak oil for 10 minutes. When used for packaging, the waterproof property is taken, and when used for packaging by an automatic packaging machine, the heat-sealable property is taken, and the specific property is not limited herein.

The above description is only for the purpose of illustrating embodiments of the present application and is not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application or are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims

1. A food card stock, comprising: the paper layer comprises a bottom layer, a core layer and a surface layer which are sequentially stacked, and the coating is coated on the surface layer;

the core layer is made of core layer raw materials, and the core layer raw materials comprise bleached needle sulfate pulp, bleached broadleaf sulfate pulp and 90-95% by mass of bleached chemithermomechanical pulp.

2. The food paperboard according to claim 1, wherein the core layer material further comprises cationic starch in an amount of 10-17 kg/T;

the coating weight of the coating is 29-36.2 g/m²；

The refining freeness of the bleached broadleaf sulfate pulp is 250 +/-30 ml.

3. The food cardboard of claim 1, wherein the bulk of the food cardboard is 1.70 to 1.75.

4. The food paperboard of claim 1, wherein the face layer is made of 20-40% by mass of bleached softwood kraft pulp and 60-80% by mass of bleached hardwood kraft pulp;

the core layer is made of 0-2% of bleached softwood kraft pulp, 5-10% of bleached broadleaf kraft pulp and 90-95% of bleached chemithermomechanical pulp by mass percentage;

the bottom layer is made of 20-40% by mass of bleached softwood kraft pulp and 60-80% by mass of bleached hardwood kraft pulp.

5. The preparation method of the food paperboard is characterized by comprising the following steps of sequentially stacking a bottom layer, a core layer, a surface layer and a coating layer, wherein the preparation method comprises the following steps:

respectively preparing the bottom layer, the core layer, the surface layer and the coating;

sequentially stacking the bottom layer, the core layer and the surface layer together, and coating the coating on the surface layer to form the coating, so as to obtain the food paperboard;

wherein the step of preparing the core layer comprises:

providing a core layer raw material, wherein the core layer raw material comprises bleached softwood kraft pulp, bleached hardwood kraft pulp and 90-95% by mass of bleached chemithermomechanical pulp;

6. The preparation method according to claim 5, wherein the core layer raw material further comprises cationic starch in an amount of 10-17 kg/T.

7. The method according to claim 5, wherein the coating material is applied to the surface layer in an amount of29～36.2g/m²。

8. The method as claimed in claim 5, wherein the bleached broadleaf kraft pulp has a refining freeness of 250 ± 30 ml.

9. The preparation method according to claim 5, wherein the bulk of the prepared food cardboard is 1.70-1.75.

10. The method of claim 5, wherein the step of preparing the bottom layer comprises:

providing 20-40% by mass of bleached softwood kraft pulp and 60-80% by mass of bleached hardwood kraft pulp;

mixing the bleached softwood kraft pulp with the mass percentage of 20-40% and the bleached hardwood kraft pulp with the mass percentage of 60-80% together to obtain the bottom layer by papermaking;

a step of preparing the core layer, comprising:

providing 0-2% by mass of bleached softwood kraft pulp, 5-10% by mass of bleached hardwood kraft pulp and 90-95% by mass of the bleached chemithermomechanical pulp;

mixing the bleached softwood kraft pulp with the mass percentage of 0-2%, the bleached hardwood kraft pulp with the mass percentage of 5-10% and the bleached chemithermomechanical pulp with the mass percentage of 90-95% together to obtain the core layer by papermaking;

a step of preparing the facing comprising:

and mixing the bleached softwood kraft pulp with the mass percentage of 20-40% and the bleached hardwood kraft pulp with the mass percentage of 60-80% together to obtain the surface layer by papermaking.