CN113445361A

CN113445361A - Color household paper and preparation method thereof

Info

Publication number: CN113445361A
Application number: CN202110747973.1A
Authority: CN
Inventors: 罗士余; 刘猛; 贾荣智; 藏亚伟; 孟双
Original assignee: Shandong Sun Household Paper Ltd; SHANDONG TAIYANGZHIYE CO Ltd
Current assignee: Shandong Sun Household Paper Ltd; SHANDONG TAIYANGZHIYE CO Ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2021-09-28

Abstract

The present disclosure provides a preparation method of color household paper, which comprises the following specific steps: (1) dispersing slurry; (2) removing slag and grinding into thick liquid; (3) pulp preparation and dyeing; (4) grinding the mixture into thick liquid; (5) fixing color; (6) shaping on the net; (7) squeezing; (8) drying; (9) wrinkling; (10) and (4) coiling. The present disclosure ensures that less dye is used at low grammage, ensures uniform dyeing, good finished paper, fast fastness to sunlight, fast bleeding, and less white water load.

Description

Color household paper and preparation method thereof

Technical Field

The disclosure relates to the field of papermaking, in particular to color household paper and a preparation method thereof.

Background

Along with the development of social economy, the demand of paper towels as fast-moving products is increased day by day, the usage amount is increased, the consumption level of people is improved, the demand of wiping is not met, the quality grade and the personalized use demand of the paper towels are increased, and more market segments are brought to the consumption of mainstream primary wood pulp paper towels. The color napkin gradually appears in high-grade hotels, restaurants and the like, and grows to be part of pursuit of individuality and promotion of life colors for modern people.

The dyeing technology of cultural paper, wrapping paper and the like is common, and mainly comprises off-pulp dyeing such as roller coating, and has the main disadvantages of insecure dyeing, large dye consumption, fading in water, environmental pollution caused by large water consumption for dyeing after paper forming and the like. With the development of the technology, the in-pulp dyeing gradually becomes the mainstream, but the in-pulp dyeing is applied to the paper types or paperboards with larger gram weights such as cultural paper, wrapping paper and the like, and various problems of uneven dyeing, unstable bleeding, sun-proof property and the like can occur if the process technology is not in place with the larger gram weights.

Most process flows conflict with the medium-alkaline papermaking process under the acidic condition, and the production improvement brings a plurality of difficulties such as system series washing on papermaking. The process is established, and more materials are added, which does not meet the relevant specifications of daily paper for close contact with human bodies.

The present disclosure provides low basis weight colored tissue. Less dye is used at low grammage to ensure uniform dyeing, good lightfastness and bleed fastness of the finished paper, and less white water load.

Disclosure of Invention

The invention provides a preparation method of color household paper, which comprises the following steps of pulp dispersing, slag removing and pulp grinding, pulp preparation and dyeing, pulp re-grinding, color fixing, net surfing and forming, squeezing, drying, wrinkling and reeling:

(1) slurry dispersing: dispersing bleached sulfate softwood pulp and bleached sulfate hardwood pulp to a concentration of 5-6 mass% respectively by a hydrapulper;

(2) deslagging and pulping: the bleached sulfate softwood pulp and the bleached sulfate hardwood pulp are subjected to deslagging and then respectively enter a pulping machine for pulping, wherein the pulping concentration of the bleached sulfate softwood pulp is controlled to be 3.6-5.5 mass%, and the pulping concentration of the bleached sulfate hardwood pulp is controlled to be 3.5-5 mass%;

(3) pulp preparation and dyeing: after deslagging and pulping, mixing bleached sulfate softwood pulp and bleached sulfate hardwood pulp in a mixed pulp tank according to a certain proportion, and adding direct dye on line through a screw pump;

(4) and (3) grinding the mixture into thick liquid: feeding the wood pulp slurry in the mixed pulp tank into a pulping machine for re-pulping, controlling the pulping degree of the pulp to be 28-35 DEG SR, adding a wet strength agent, and feeding the pulp obtained by re-pulping into a paper machine pulp tank;

(5) and (3) fixation: adding a fixing agent into a pulp tank of a paper machine to promote the dye to be fixed on the surface of the fiber, wherein the final concentration of the fixing agent is 8-15 mass%, and adjusting the pH value to 7.5-8.5;

(6) and (3) net surfing and forming: the pulp in the pulp tank of the paper machine is further diluted and screened by an external white water tank and a paper machine screen, then is distributed by a head box, is formed and dewatered by an upper net to form a uniform wet paper web, and then is conveyed by a coarse cloth to enter the next unit;

(7) squeezing: the wet paper web enters a pressing area for further dehydration, and the strength of the wet paper web is improved through the extrusion of a vacuum press roll;

(8) and (3) drying: drying the paper web by using a heating drying cylinder and a hot air hood;

(9) wrinkling: the dried paper web is peeled off from the drying cylinder under the action of a wrinkling scraper, and the wrinkling effect is brought under the action of the wrinkling scraper, so that the softness of the paper web is achieved, and the bulk of the finished paper is increased;

(10) coiling: and winding the wrinkled paper web onto a paper winding shaft through a paper winding cylinder for winding.

The sulfate wood pulp is prepared by taking various coniferous trees and broad-leaved trees as raw materials and cooking by a sulfate method.

Kraft pulps can be generally classified into both bleached and unbleached. The bleached sulfate wood pulp can be used for manufacturing high-grade printing paper, newspaper, offset paper, writing paper and the like.

In a preferred embodiment, the bleached kraft wood pulp includes bleached kraft softwood pulp and bleached kraft hardwood pulp.

In a preferred embodiment, in step (1), the bleached sulfate softwood pulp has an aspect ratio of 65 or greater and the bleached sulfate hardwood pulp has an aspect ratio of 35 or greater.

If the aspect ratio of the wood pulp is smaller, for example, when the aspect ratio of the bleached sulfate softwood pulp is less than 65 and the aspect ratio of the bleached sulfate hardwood pulp is less than 35, the fiber material is short and coarse, and under the same refining power and concentration, the fibrillation capability of the fiber is reduced, so that the beating degree is reduced, and the paper strength is influenced. The pulping power consumption needs to be improved to reach the same pulping degree, and excessive cutting of fibers is inevitably caused in the pulping process, so that the increase of fine fibers is brought. Aspect ratio (ratio of individual fiber length to width) is a method of screening fiber stock for quality. The aspect ratio is optimized, so that the beating degree of the fibers can be better improved in the pulping process, and the content of fine fibers after cutting can be reduced.

Bleached sulfate softwood pulp is abbreviated as bleached softwood pulp, and is abbreviated as NBKP in English. The chemical paper pulp is 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 in commercial paper pulp, and the bleached needle pulp is "the king of paper pulp" according to different coniferous trees, cooking bleaching process and operation conditions, and can be used for producing almost all paper varieties (except special varieties).

Bleached sulfate hardwood pulp, abbreviated as bleached pulp, and abbreviated as LBKP in english, is also produced by the sulfate method, except that the raw material is hardwood. The "goldfish" brand commercial pulp (eucalyptus pulp) sold in brazil is well known and can be used alone or in combination with a bleached needle pulp to make various high-grade printing papers, etc.

The bleached sulfate softwood pulp is selected from wood pulp of coniferous plants such as Korean pine, white pine, Larix gmelini, southern pine, etc., and spruce, fir, hemlock, etc. The bleached sulfate hardwood pulp is selected from the group consisting of eucalyptus wood, poplar hardwood pulp.

In a preferred embodiment, in step (2), the bleached kraft softwood pulp has a freeness of 25 to 30 ° SR.

In a preferred embodiment, in step (2), the bleached sulfate hardwood pulp has a freeness of 20 to 25 ° SR.

The softwood pulp fibers are longer, the viscosity pulping improves the pulping degree, the fiber length is kept as much as possible, the fibrillation is realized, the skeleton effect is realized, the fine fibers are intercepted, and the loss is avoided.

In a preferred embodiment, in step (3), the kraft softwood pulp is bleached: the proportion of bleached sulfate hardwood pulp is 20-50: 50-80.

In a preferred embodiment, in the step (3), the direct dye is dissolved at a temperature of 55 to 80 ℃ at a final concentration of 3 to 6% by mass for a stirring time of 30 to 60 min.

In a preferred embodiment, in step (3), the amount of direct dye used is from 8 to 20kg/t of paper. The direct dye is a dye which can be heated and boiled in neutral and weak bond phase media without the help of a mordant and can be dyed, the direct dye is formed by combining the hydrogen bond between the direct dye and cotton fiber and Van der Waals force, and is mainly applied to industries of fiber, silk, cotton spinning, leather and the like, and is also applied to industries of paper making and the like. Direct dyes can be classified into azo, stilbene and the like according to their structures, and mainly include common direct dyes, direct light-fast dyes and direct azo dyes according to their application classification. In a preferred embodiment, the direct dye is selected from direct fast dyes.

In a preferred embodiment, in step (4), the wet strength agent is used in an amount of 5 to 10kg/t of paper. Wet strength agents are used primarily in the paper industry. The amount of different paper used varies widely, such as sanitary paper, fruit bag paper, board paper, wet tissue paper, etc. The wet strength agent is a common nontoxic and tasteless papermaking auxiliary agent capable of greatly improving the dry and wet strength of the paper, is suitable for the production of various papers with wet strength requirements, and can be used as a retention aid and a filter aid in the papermaking process due to the characteristics of retention aid and filter aid. The wet strength agent is selected from polyamide epichlorohydrin series, preferably polyamide polyamine epichlorohydrin resin.

In a preferred embodiment, in step (4), the refiner is a disc mill or a cone mill.

In a preferred embodiment, in step (5), the amount of the fixing agent is 100-200kg/t of paper. In a preferred embodiment, in step (5), the fixing agent is one of polyaluminium chloride and aluminium sulphate.

In a preferred embodiment, in step (5), the pH is controlled to be 7.5 to 8.5. Preferably, the pH is controlled to be 7.5-8.0. The pH may be adjusted by adding a base solution selected from one or more of sodium hydroxide, sodium carbonate, sodium hydrogen phosphate.

In a preferred embodiment, in step (7), the press line pressure is 90 to 93N/mm.

In a preferred embodiment, in step (9), the cylinder speed is 1100-1800 m/min, the creping rate is 9-16%, the creping doctor angle is 8-15 °, and the blade pressure is 0.5-3.0N/mm.

Has the advantages that:

the present disclosure provides a low grammage colored tissue. Less dye is used under low gram weight, so that the dyeing uniformity, good finished paper, firm sun-proof property, firm color bleeding and less white water load are ensured. The fiber retention rate is improved, the fiber loss is reduced, and the fiber is prevented from being cut off to form fine fibers. The dye is fixed on the fiber as much as possible by adjusting the flow of the fixing agent, so that the loss is avoided, and the using amount of the dye is reduced.

The pH value control in the preparation method process is the key point of the process control, and is the basis and key point of dyeing uniformity and color bleeding fastness. The inventor ensures the dyeing uniformity and the color bleeding fastness by controlling the pH value in sections and controlling the adding points and the flow of the matched dye and the fixing agent. Secondly, the proportion of the fixing agent and the dye in the system is also important, the fixing agent has strong positive charge, the excess of the fixing agent can cause the instability of the system, the excess of the dye can cause uneven color, color difference among rollers, incomplete water absorption and low water fastness, and the like.

The fiber raw material/chemical particles can not become paper by 100 percent, certain fine fibers and chemical particles are inevitably dehydrated by the screen press part and enter water circulation to form white water, and the white water load of the color paper comes from residues of the color fibers, the chemical particles and the like caused by adding dyes. The color difference is harmful to a paper machine, namely, the color difference influence is brought when the color paper is changed. Therefore, the conventional method can discharge most of the white water with color, and replenish clean water to accelerate circulation, thereby increasing the load of external water treatment and being not good for environmental protection. The inventor of the present application reduced the white water load by:

1. the fiber retention rate is improved as much as possible, and the loss of the fiber is reduced. The beating degree, the fiber proportion and the raw material selection (length-width ratio) are adjusted to prevent the fibers from being cut into fine fibers as much as possible.

2. The dye is fixed on the fiber as much as possible by adjusting the flow of the fixing agent, the loss is avoided, the dye consumption is reduced, the optimal dye is kept at 7.5-8.0 by detecting the pH value of the system, and the adding position of the fixing agent is also important.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.

Fig. 1 is a flow chart showing the preparation of the color household paper of the present disclosure.

Fig. 2 is a preparation schematic diagram showing an exemplary embodiment of the color household paper of the present disclosure.

Fig. 3 is a schematic view showing an approach system for preparing a conventional colored household paper.

Detailed Description

The present disclosure will be described in further detail with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the present disclosure. It should be further noted that, for ease of description, only those portions relevant to the present disclosure are shown in the drawings.

In addition, the features of the embodiments and modes in the present disclosure may be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Examples

(3) pulp preparation and dyeing: after deslagging and pulping, mixing bleached sulfate softwood pulp and bleached sulfate hardwood pulp in a mixed pulp tank according to a certain proportion, adding direct dye on line through a screw pump, wherein the dissolution temperature of the direct dye is 55-80 ℃, the dissolution final concentration is 3-6 mass%, and the stirring time is 30-60 min;

(5) and (3) fixation: adding a fixing agent into a paper machine pulp chest, wherein the final concentration of the fixing agent is 8-15 mass%, and adjusting the pH value to 7.5-8.5;

Example 1

13 g/square meter paper towel paper and pomegranate red are prepared as described above.

The bleached sulfate hardwood pulp was eucalyptus urophylla pulp with an aspect ratio of 48.

Bleached sulfate softwood pulp is pinus koraiensis: spruce wood pulp (7: 3) with an aspect ratio of 80.

Bleaching sulfate softwood pulp: the mass ratio of bleached sulfate hardwood pulp is 35: 65.

The beating degree of bleached sulfate hardwood pulp is 22 DEG SR, and the concentration is as follows: 4.2% by mass.

Beating degree of bleached sulfate softwood pulp: 27 ° SR, concentration: 4.5% by mass.

And (3) uniform beating degree: 32 ° SR, concentration: 3.5% by mass.

Paper machine speed: 1500m/min, the wrinkling rate is 11%.

Type of direct dye used: scarlet R, which was added after being filtered as a 6.5 mass% solution directly diluted with condensed water. The flow rate of the liquid supply pump is 13200 ml/min.

The fixing agent used was aluminum sulfate: the incoming material concentration is 8 mass percent, and the flow rate is 2300 ml/min.

The usage amount of the wet strength agent is as follows: 6kg/t paper.

Adding alkali liquor:

an external white water tank: sodium hydrogen phosphate solution (15 mass%) 150ml/min + sodium hydroxide solution (30 mass%) 20ml/min, maintaining pH: 7.3.

needle leaf stores up thick liquid pond: sodium hydrogen phosphate solution (15 mass%) 45ml/min, pH maintained: 7.0.

the paper color index L is 46.21, a is 47.0 and b is 24.2; the color difference between the rollers is less than 0.4.

Example 2

The paper towel with the purple color is prepared into the paper towel with the purple color of 15g per square meter.

Bleached sulfate hardwood pulp is eucalyptus pulp, mainly (eucalyptus globulus labill, eucalyptus leuca) 8:2, length to width ratio 52.

The bleached kraft softwood pulp was radiata pine pulp with an aspect ratio of 83.

Bleaching sulfate softwood pulp: the mass ratio of bleached sulfate hardwood pulp is 30: 70.

The beating degree of bleached sulfate softwood pulp is 30 DEG SR, and the concentration: 4.5% by mass.

And (3) uniform beating degree: 35 ° SR, concentration: 3.5% by mass.

Paper machine speed: 1400m/min, the wrinkling rate is 12%.

Type of direct dye used: violet B, which was diluted directly with condensed water to a 6.5 mass% solution, was filtered and added for use. The flow rate of the liquid supply pump is 11500 ml/min.

The fixing agent used was aluminum sulfate: the incoming material concentration was 8 mass%, and the flow rate was 1900 ml/min.

The usage amount of the wet strength agent is as follows: 5kg/t paper.

Adding alkali liquor:

an external white water tank: sodium hydrogen phosphate solution (15 mass%) 200ml/min + sodium hydroxide solution (30 mass%) 30ml/min, maintaining pH: 7.5.

the paper color index L is 58.30, a is 10.2, b is 17.5; the color difference between the rollers is less than 0.4.

Example 3

The paper towel paper with 18g per square meter is prepared in the above way, and is light green.

Bleaching sulfate softwood pulp: the mass ratio of bleached sulfate hardwood pulp was 26: 74.

The beating degree of bleached sulfate hardwood pulp is 20 DEG SR, and the concentration is as follows: 4.2% by mass.

Beating degree of bleached sulfate softwood pulp: 30 ° SR, concentration: 4.5% by mass.

And (3) uniform beating degree: 30 ° SR, concentration: 3.4% by mass.

Paper machine speed: 1100m/min, the wrinkling rate is 13%.

Type of direct dye used: light green N, which was diluted directly with condensed water to a 6.5 mass% solution, was added after filtration. The flow rate of the liquid supply pump is 8500 ml/min.

The fixing agent used was aluminum sulfate: the incoming material concentration was 8 mass%, and the flow rate was 1200 ml/min.

The usage amount of the wet strength agent is as follows: 7kg/t paper.

Adding alkali liquor:

the finished paper color index L is 62.0, a is-10.5, and b is 16.35; the color difference between the rollers is less than 0.4.

Comparative example 1

According to the production technology and practice of colored napkin paper of Wubao Ying et al.

1. The production flow comprises the following steps:

(1) pulping system

Hydropulper → water → magnesium sulfate → pulp board → dye → aluminum sulfate → fixing agent → 1# pulp tank;

(2) slurry in a No. 1 pulp tank → a high-concentration slag separator → a double-disc mill → 2 pulp tank → 3, #4 pulp tank → 5 papermaking pulp tank;

(3) slurry internet surfing system

See the approach system of fig. 3.

2. The production process requires:

(1) beating process parameters

Proportioning the slurry: 100% of long fibers and 5% of pulping concentration.

Pulping current: 140A + -5A, throughput: 45 +/-1 m³H, refining concentration: 3.5 percent.

(2) Technological requirements for papermaking

Paper machine speed: 500m/min, winding speed: 405m/min, pulp speed: 535 m/min.

(3) Dyes and drug additives

Adding a certain amount of water into a pulper;

② adding MgSO₄；

Thirdly, adding the pulp into a pulper, and crushing for about 8 min;

fourthly, adding the solid dye into the pulper, and mixing for 8 min;

adding Al₂(SO₄)₃Mixing for about 2 min;

sixthly, adding a color fixing agent, mixing for 5-10min, and then discharging the slurry.

Wherein bleached kraft softwood pulp: the mass ratio of the bleached sulfate hardwood pulp is 10:90, and the dye is Chinese red.

Comparative example 2

The experiment was performed according to comparative example 1, except that bleached kraft softwood pulp: bleached kraft broad-leaved wood pulp mass ratio 60:40, dye light green (available from tianjinxiangri).

Comparative example 3

The experiment was performed according to comparative example 1, except that bleached kraft softwood pulp: the mass ratio of bleached sulfate broad-leaved wood pulp was 70:30, and the dye was violet (available from tianjin auspicious company).

Wherein, dyeing is intermittent dyeing, mixed pulp pond wood pulp is lifted to a dyeing pond by a pulp pump, a dye and a fixing agent which are dissolved in a fixed volume are added under the state of maintaining the liquid level and the concentration of the pulp pond to be stable, and the mixed pulp pond wood pulp is lifted to a paper machine pulp pond by the pulp pump after being uniformly stirred. The dyeing method has simple process operation, but has the defects;

1. the intermittent addition cannot keep up with the paper machine production when the production is increased due to the speed of the paper machine. The existing paper machines are developed in the direction of high speed and high width, and the continuous addition is a normal state.

2. The machine table is smaller, the sealing performance of the white water is poorer, the color accumulation of the white water has smaller influence on the color difference, the white water recycling rate of the large machine table is higher, and the intermittent addition can cause the problems of the same dye addition but obvious color difference in the later production period. And the white water is discharged more, so the loss is more, the dye consumption is large, and the pollution load is large.

3. Neglecting the consideration of the pH value of the system to the fastness of fixation, the change of the pH value of the paper machine system can cause color difference. Intermittent dyeing and uneven stirring of a pulp tank can also cause dyeing uniformity. There is no room for adjustment.

Test method

And (3) decoloring test verification:

the detection method comprises the following steps: the paper towel international 20808 promulgated draft (to replace the current 20808-2011 version).

(1) 1 piece of tissue was arbitrarily cut into a 100mm × 100mm sample of a finished ply. When cutting, a printing or dyeing part (except for the natural color paper towel) is selected. The samples were placed into 200mL beakers containing simulated sweat, simulated saliva, respectively, so that the samples were completely submerged. After soaking for 10min, the above two sample soaking solutions were poured into two colorimetric tubes, respectively. In the test process, a constant-temperature water bath kettle is adopted to ensure that the temperature of the sample soaking solution is maintained at (40 +/-2).

(3) Blank test was performed as above.

(3) And respectively comparing the colorimetric tubes containing the sample soaking solution and the blank soaking solution, and observing whether the two sample soaking solutions are dyed with colors.

(4) Two specimens were tested per sample.

Table 1: experimental results of decolorizing performance test

Nature of the solution

Example 1

Example 2

Example 3

Comparative example 1

Comparative example 2

Comparative example 3

Simulated saliva

No decolorization

Simulated sweat

No decolorization

The experimental conditions were maintained and the water temperature was only raised to 100 ℃. The decolorization capability under the condition exceeding the national standard experiment is verified.

Table 2: test of decolorizing performance at 100 deg.C water temperature

Nature of the solution

Example 1

Example 2

Example 3

Comparative example 1

Comparative example 2

Comparative example 3

Simulated saliva

No decolorization

Decolorization of

Simulated sweat

No decolorization

Decolorization of

The decolorization standard is judged in the national standard: comparing the colorimetric tubes containing the sample soaking solution and the blank soaking solution, observing whether the sample soaking solutions are dyed with colors or not, and visually observing that the solutions at 100 ℃ have a decolorization phenomenon, wherein in order to better explain the decolorization effect, a spectrophotometer 450nm (the visible light region is 380-780nm) is used for measuring the light absorption value of the sample solutions, and the measurement results are as follows:

table 3: determination of solution absorbance

Nature of the solution	Blank sample	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
								Simulated saliva	0(A)	0	0	0	0.053	0.040	0.063
Simulated sweat	0(A)	0	0	0	0.060	0.051	0.085

Compared with the conventional color household paper in the field, the color household paper disclosed by the invention uses less dye under low gram weight, and ensures uniform dyeing, good finished paper, firm sun-proof property, firm color bleeding and less white water load.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, a schematic representation of the above terms does not necessarily refer to the same embodiment/manner or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of illustration of the disclosure and are not intended to limit the scope of the disclosure. Other variations or modifications may occur to those skilled in the art, based on the foregoing disclosure, and are still within the scope of the present disclosure.

Claims

1. A preparation method of color household paper comprises pulp dispersing, slag removing and pulp grinding, pulp preparation and dyeing, pulp grinding again, color fixing, net surfing and forming, squeezing, drying, wrinkling and reeling, and is characterized by comprising the following specific steps:

(6) and (3) net surfing and forming: the pulp in the pulp tank of the paper machine is further diluted and screened by an external white water tank and a paper machine screen, then is distributed by a head box, is formed and dewatered by an upper wire to form a uniform wet paper web, and then is conveyed by a coarse cotton cloth to enter the next unit;

(7) squeezing: the wet paper web enters a pressing area for further dehydration, and the strength of the wet paper web is improved through the extrusion of a vacuum pressing roller;

2. The method of claim 1, wherein in step (1), the bleached sulfate softwood pulp has an aspect ratio of 65 or more and the bleached sulfate hardwood pulp has an aspect ratio of 35 or more.

3. The method of claim 1, wherein in the step (2), the beating degree of bleached sulfate softwood pulp is 25-30 ° SR, and the beating degree of bleached sulfate hardwood pulp is 20-25 ° SR.

4. The production method according to claim 1, wherein in the step (3), the bleached kraft softwood pulp: the proportion of bleached sulfate hardwood pulp is 20-50: 50-80.

5. The method of claim 1, wherein in the step (3), the amount of the direct dye is 8 to 20kg/t of paper.

6. The production method according to claim 1, wherein in the step (3), the direct dye is dissolved at a temperature of 55 to 80 ℃ at a final dissolved concentration of 3 to 6% by mass for a stirring time of 30 to 60 min.

7. The process according to claim 1, wherein in step (4), the wet strength agent is used in an amount of 5 to 10kg/t of paper.

8. The method as claimed in claim 1, wherein in the step (5), the fixing agent is used in an amount of 100-200kg/t paper.

9. The production method according to claim 1, wherein in the step (5), the pH is controlled to 7.5 to 8.0.

10. The production method according to claim 1, wherein, in the step (7), the press line pressure is 90 to 93N/mm.