A kind of white offset paper and preparation method thereof

Abstract

The present application relates to the technical field of papermaking, and provides a white offset paper and a preparation method thereof. The method comprises: mixing and beating coniferous wood pulp, hardwood wood pulp and eucalyptus pulp to obtain a first mixed pulp; adding a fiber modifier to the first mixed pulp, and stirring and mixing for 10 to 90 minutes at a temperature of 45 to 95°C and a pH value of 8 to 11 to obtain a second mixed pulp; adding a composite filler and a retention and drainage aid to the second mixed pulp, mixing evenly, and obtaining a third mixed pulp; wet paper sheeting with the third mixed pulp to obtain a wet paper sheet; pressing, primary drying, surface sizing, secondary drying, and calendering the wet paper sheet in sequence to obtain the white offset paper. The white offset paper prepared by the present application has the advantages of high opacity, soft color, ability to protect readers' eyesight, good recognition, etc., which is conducive to the promotion and application of the white offset paper.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking, and in particular to a white offset paper and a preparation method thereof. Background Art

[0002] Natural white offset paper, also known as natural white offset paper, is widely used in textbooks, teaching materials and office paper because of its certain vision protection effect.

[0003] The traditional preparation process of white offset paper generally uses a large amount of dyes (such as royal blue and basic violet) to color the pulp raw materials so that the offset paper produced can meet the opacity requirements of white offset paper. Although the opacity of the paper will increase with the increase of the amount of dye, the opacity of the paper will increase slowly or even remain unchanged after increasing the amount of dye to a certain extent, so the effect is not ideal; and the color tone of the offset paper produced is not soft enough, which is not conducive to the promotion and application of white offset paper. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a white offset paper and a preparation method thereof. The preparation method of the present application modifies the pulp raw material by adding a specific fiber modifier to the first mixed slurry, and at the same time adds a specific composite filler and a retention and filtration aid to treat the second mixed slurry. The prepared white offset paper has high opacity and soft color, can protect the reader's eyesight, has good recognition and other advantages, and is conducive to the promotion and application of the white offset paper. Compared with the traditional white offset paper preparation process, the preparation method of the present application can reduce the use of dyes and even does not need to add additional dyes to color the pulp raw materials, which is conducive to saving the investment cost of dyes.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides a method for preparing white offset paper, comprising:

[0007] Mixing and beating coniferous wood pulp, hardwood wood pulp and eucalyptus pulp to obtain a first mixed pulp; wherein the mass ratio of coniferous wood pulp, hardwood wood pulp and eucalyptus pulp is 25-35:40-50:30-40;

[0008] Adding a fiber modifier to the first mixed slurry, and stirring and mixing for 10 to 90 minutes at a temperature of 45 to 95° C. and a pH value of 8 to 11 to obtain a second mixed slurry; wherein the amount of the fiber modifier added is 0.1% to 1% of the total mass of the first mixed slurry;

[0009] Adding a composite filler and a retention and drainage aid to the second mixed slurry, mixing them evenly, to obtain a third mixed slurry; wherein the amount of the composite filler added is 10% to 30% of the total mass of the second mixed slurry; the amount of the retention and drainage aid added is 0.2% to 0.4% of the total mass of the second mixed slurry; the composite filler includes at least two of light calcium carbonate, cationic ground calcium carbonate or porous silica; the retention and drainage aid includes at least two of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate or modified corn starch;

[0010] The third mixed slurry is used to make wet paper sheets to obtain wet paper sheets;

[0011] The wet paper sheets are sequentially subjected to pressing, primary drying, surface sizing, secondary drying and calendering treatment to obtain white offset paper.

[0012] In a second aspect, an embodiment of the present application provides a white offset paper, which is prepared according to the preparation method of the white offset paper of the first aspect.

[0013] The beneficial effects of this application include at least:

[0014] The preparation method of the white offset paper provided in the embodiment of the present application modifies the pulp raw material by adding a specific fiber modifier to the first mixed slurry, and at the same time adds a specific composite filler and a retention and drainage aid to treat the second mixed slurry. The prepared white offset paper has high opacity and soft color, can protect the reader's eyesight, has good recognition and other advantages, and is conducive to the promotion and application of the white offset paper. Compared with the traditional white offset paper preparation process, the preparation method of the present application can reduce the use of dyes and even does not need to add additional dyes to color the pulp raw materials, which is conducive to saving the investment cost of dyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 It is a schematic diagram of the production process of white offset paper provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but the implementation methods of the present application are not limited thereto.

[0018] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which this application belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the amounts of experimental reagents, unless otherwise specified, are all the amounts of reagents used in conventional experimental operations; and the experimental methods, unless otherwise specified, are all conventional methods.

[0019] In a first aspect, the present application provides a method for preparing white offset paper, comprising:

[0020] S1. Mix and beat coniferous wood pulp, hardwood wood pulp and eucalyptus pulp to obtain a first mixed pulp; wherein the mass ratio of coniferous wood pulp, hardwood wood pulp and eucalyptus pulp is 25-35:40-50:30-40;

[0021] S2. Adding a fiber modifier to the first mixed slurry, and stirring and mixing for 10 to 90 minutes at a temperature of 45 to 95° C. and a pH value of 8 to 11 to obtain a second mixed slurry; wherein the amount of the fiber modifier added is 0.1% to 1% of the total mass of the first mixed slurry;

[0022] S3, adding a composite filler and a retention and drainage aid to the second mixed slurry, mixing them evenly, to obtain a third mixed slurry; wherein the amount of the composite filler added is 10% to 30% of the total mass of the second mixed slurry; the amount of the retention and drainage aid added is 0.2% to 0.4% of the total mass of the second mixed slurry; the composite filler includes at least two of light calcium carbonate, cationic ground calcium carbonate or porous silica; the retention and drainage aid includes at least two of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate or modified corn starch;

[0023] S4, making wet paper sheets from the third mixed slurry to obtain wet paper sheets;

[0024] S5. The wet paper sheets are sequentially pressed, dried once, sizing is applied on the surface, dried twice, and calendered to obtain white offset paper.

[0025] In some embodiments, in step S1, the coniferous pulp may be bleached sulfite coniferous pulp; the hardwood pulp may be bleached sulfite hardwood pulp; and the eucalyptus pulp may be bleached sulfate eucalyptus pulp.

[0026] Optionally, the coniferous wood pulp may be Canadian "Continental" or "Lion" coniferous chemical pulp.

[0027] Optionally, the hardwood pulp may be Brazilian "Goldfish" or Canadian "Knight" hardwood chemical mechanical pulp.

[0028] In some embodiments, in step S1, the mass ratio of coniferous wood pulp, hardwood wood pulp, and eucalyptus pulp can be 25:40:35, 28:42:30, 30:50:40, 35:40:40, etc.

[0029] In some embodiments, coniferous wood pulp, broadleaf wood pulp, and eucalyptus pulp may be mixed in a mass ratio of 25-35:40-50:30-40, and then beaten with a pulper to obtain a first mixed pulp.

[0030] The beating degree of the first mixed pulp is 40°SR to 55°SR. The beating degree, also known as the beating degree, refers to the effect of the pulping process such as fiber cutting, splitting, swelling, and hydration after the reaction pulp passes through the pulping machine.

[0031] In some embodiments, in step S2, the fiber modifier is prepared as follows:

[0032] Dissolving plant starch in water to prepare a starch suspension having a solid content of 20% to 50%;

[0033] The starch suspension is reacted with 2,3-oxypropyl-N-alkyl-N,N-dimethylammonium chloride in an alkaline medium at a temperature of 20-45° C. for 8-16 hours to obtain a fiber modifier.

[0034] The alkaline medium may be at least one of sodium carbonate, sodium hydroxide or potassium hydroxide. For example, the alkaline medium may be sodium carbonate, sodium hydroxide, or a mixture of sodium carbonate and sodium hydroxide in any proportion.

[0035] The degree of substitution of the fiber modifier of the embodiment of the present application is 0.02-0.06, where the degree of substitution is determined by the average number of substituents of the hydroxyl group of each D-pyranose glucopyranosyl unit of the plant starch.

[0036] Optionally, the vegetable starch is corn starch, tapioca starch or other vegetable starches.

[0037] The above-mentioned fiber modifiers can interact with fibers and other components (for example, electrostatic attraction, van der Waals force, hydrogen bond formation, etc.). The fiber modifiers are tightly combined with the fibers, which can increase the number and strength of fiber-to-fiber bonding, which is beneficial to improving the mechanical strength and dehydration efficiency of the fibers.

[0038] By adding the above-mentioned specific fiber modifier to the first mixed slurry, the number and strength of the bonding between the fibers in the first mixed slurry can be increased. When the first mixed slurry modified by the fiber modifier enters the subsequent papermaking process, the fiber modifier adsorbed in the fiber can still retain its special properties, so that the mechanical strength and dehydration and drying efficiency of the paper sheet can be increased, which is beneficial to improving production efficiency. In addition, the fiber modifier is adsorbed in the fibers and cellulose of the slurry, which can reduce the space gap between the fibers, thereby facilitating the improvement of the opacity of the paper.

[0039] By using coniferous wood pulp, hardwood pulp and eucalyptus pulp in a specific ratio as raw materials and adding the above-mentioned specific fiber modifier for modification, the amount of dye used to color the pulp can be greatly reduced. Even without the need to add additional dye to color the pulp, white offset paper with a soft tone and a whiteness that meets the whiteness index requirements of white offset paper can be produced.

[0040] In some embodiments, in the preparation step of the fiber modifier, the mass ratio of the starch suspension to 2,3-oxypropyl-N-alkyl-N,N-dimethylammonium chloride is 100:1 to 2. For example, it can be 100:1, 100:1.5 or 100:2.

[0041] In some embodiments, the mass ratio of the alkaline medium, the starch suspension and the 2,3-oxypropyl-N-alkyl-N,N-dimethylammonium chloride is 0.01:100:1 to 2. For example, it can be 0.01:100:1, 0.01:100:1.5, 0.01:100:2, etc.

[0042] In some embodiments, in step S3, the composite filler includes light calcium carbonate, cationic ground calcium carbonate and porous silica; the mass ratio of light calcium carbonate, cationic ground calcium carbonate and porous silica is 10-15:5-7:2-3. For example, the mass ratio of light calcium carbonate, cationic ground calcium carbonate and porous silica can be 10:5:2, 10:7:2, 15:5:2, 15:5:3 or 12:6:2, etc.

[0043] Optionally, the light calcium carbonate is a precipitated calcium carbonate with a triangular shape and a particle size of 1.5 μm to 1.9 μm. The particle size of the cationic ground calcium carbonate is 0.7 to 1.5 μm.

[0044] The opacity of paper can be improved by adding a composite filler consisting of light calcium carbonate, cationic ground calcium carbonate and porous silica during the papermaking process and controlling the addition amount of the composite filler to be 10% to 30% of the total mass of the second mixed slurry.

[0045] In some embodiments, in the above step S3, the retention and drainage aids include tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch; the mass ratio of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch is 20 to 36: 0.04 to 0.06: 1 to 2. Exemplarily, the mass ratio of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch is 20: 0.04: 1, 20: 0.05: 2, 25: 0.04: 1, 25: 0.05: 2, 36: 0.04: 1 or 36: 0.05: 2, etc.

[0046] Among them, the molecular weight of tertiary amine type amphoteric polyacrylamide is 2.02 million, the degree of hydrolysis is 4%, and the cationic degree is 21.8%.

[0047] The modified corn starch can be NSP-01 modified starch. NSP-01 modified starch is a corn starch that has been subjected to a double grafting modification reaction, where ester groups and amino groups are introduced into the starch base material to modify the starch. The starch also has free active groups that combine with fiber molecules and initiate "fiber-fiber" bonding.

[0048] By adding a retention and drainage aid composed of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch during the papermaking process, and controlling the addition amount of the retention and drainage aid to be 0.2% to 0.4% of the total mass of the second mixed slurry, the first-pass retention rate of the composite filler can be increased to more than 50%, which is beneficial to improving the opacity of the paper.

[0049] In some embodiments, in the above step S4, the web concentration is 0.7-1.1%, the web pH is 8-9, the pulp-to-web speed ratio is 0.9-0.96, the operating speed is 380-400 m / min, the white water concentration under the web is ≤0.3%, the dryness of the web outlet is ≥20%, and the papermaking basis weight is 60-80 g / m 2 .

[0050] In some embodiments, in the above step S5, in the process of surface sizing, the surface sizing agent used is a composition of paraffin, 13-18 alkyl ketene dimer and modified sodium sulfate in a mass ratio of 0.02-0.05:0.5-0.6:20-25; the single-sided coating amount of the surface sizing agent is 2-5 g / m 2 .

[0051] The modified sodium sulfate is prepared by modifying sodium sulfate with chitosan and organic salt.

[0052] By adding a surface sizing agent composed of paraffin wax, 13-18 alkyl ketene dimer and modified sodium sulfate in a specific ratio to the wet paper sheet, not only the film-forming property is good, but also the surface strength and visual whiteness of the paper can be improved.

[0053] In a second aspect, the embodiments of the present application further provide an off-white offset paper, which is prepared according to the preparation method of the off-white offset paper of the first aspect.

[0054] The white offset paper prepared by the preparation method of the embodiment of the present application has the advantages of high opacity, soft color tone, can protect the reader's eyesight, and has good recognition, which is conducive to the promotion and application of the white offset paper.

[0055] Figure 1 It is a schematic diagram of the production process of white offset paper provided in an embodiment of the present application.

[0056] See also Figure 1 The process system for implementing the preparation method of the white offset paper of the embodiment of the present application includes a pulp preparation tank 101, a pulp adjustment tank 102, a slag removal system 103, a fourdrinier section 104, a pressing section 105, a first drying section 106, a surface sizing machine 107, a second drying section 108, a calender 109 and a paper reel 110 which are sequentially connected through pipelines (pipes) or connecting components (such as conveyor belts, etc.).

[0057] The preparation method of the white offset paper provided in the embodiment of the present application comprises:

[0058] Step 1, pulping: First, add coniferous wood pulp, broadleaf wood pulp and eucalyptus pulp into the pulping tank 101 in a mass ratio of 25-35:40-50:30-40 for mixing, then use a pulping machine (such as a double disc refiner) to beat the pulp to obtain a first mixed pulp, and then convey the obtained first mixed pulp to the pulping tank 102.

[0059] Step 2, slurry adjustment: First, add a fiber modifier to the first mixed slurry in the slurry adjustment tank 102, and stir and mix for 10 to 90 minutes at a temperature of 45 to 95°C and a pH value of 8 to 11 to obtain a second mixed slurry, wherein the amount of the fiber modifier added is 0.1% to 1% of the total mass of the first mixed slurry. Then, add a composite filler and a retention and drainage aid to the second mixed slurry, mix them evenly, obtain a third mixed slurry, and convey the obtained third mixed slurry to the slag removal system 103; wherein the amount of the composite filler added is 10% to 30% of the total mass of the second mixed slurry; the amount of the retention and drainage aid added is 0.2% to 0.4% of the total mass of the second mixed slurry; the composite filler includes at least two of light calcium carbonate, cationic ground calcium carbonate or porous silica; the retention and drainage aid includes at least two of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate or modified corn starch.

[0060] Step 3, deslagging: In the deslagging system 103, the third mixed slurry is deslagging to obtain the deslagging third mixed slurry, and the deslagging is transported to the fourdrinier wire section 104. The deslagging can ensure the surface flatness and smoothness of the paper produced subsequently.

[0061] Process 4: Wet paper sheet making, pressing, and primary drying: The third mixed pulp after slag removal passes through the fourdrinier wire section 104, is formed into a wet paper sheet, and the wet paper sheet is sequentially transported to the pressing section 105 and the first drying section 106 for pressing, dehydration, and primary drying. The process conditions for wet paper sheet making are: the concentration of the web is 0.7-1.1%, the pH value of the web is 8-9, the pulp-to-web speed ratio is 0.9-0.96, the operating speed is 380-400 m / min, the concentration of white water under the web is ≤0.3%, the dryness of the web outlet is ≥20%, and the paper making basis weight is 60-80 g / m 2 The primary drying temperature is controlled at 60-90°C.

[0062] Step 5: Surface sizing: The paper sheet that enters the surface sizing machine 107 after primary drying in the first drying section 106 is subjected to surface sizing. In the surface sizing process, the surface sizing agent used is a composite of paraffin wax, 13-18 alkyl ketene dimer and modified sodium sulfate in a mass ratio of 0.02-0.5:0.5-0.6:20-25; the single-side coating amount of the surface sizing agent is 2-5 g / m 2 .

[0063] Step 6: Secondary drying, calendering, and winding: After the surface sizing treatment in the surface sizing machine 107, the paper sheets are sequentially sent to the second drying section 108, the calender 109, and the paper winding machine 110 for secondary drying, calendering, and winding to obtain finished paper. The pressure of the calendering treatment is controlled at 30-60 kg / cm 2 The temperature of the secondary drying is controlled at 70-80℃.

[0064] The present application has been tested for many times, and part of the test results are now cited as a reference to further describe the invention in detail, and the following is a detailed description in conjunction with specific embodiments.

[0065] Example 1

[0066] See also Figure 1 The preparation method of the white offset paper provided in this embodiment is as follows:

[0067] Process 1: Slurry preparation:

[0068] Bleached sulfite coniferous pulp, bleached sulfite broadleaf pulp and bleached sulfate eucalyptus pulp are added to the pulping tank 101 in a mass ratio of 25:40:35 for mixing, and then beaten by a pulper to obtain a first mixed pulp with a beating degree of 40°SR~55°SR, and the first mixed pulp is conveyed to the pulping tank 102.

[0069] Process 2: Slurry preparation:

[0070] Add fiber modifier to the first mixed slurry in the slurry mixing tank 102 (the added amount is 0.1% of the total mass of the first mixed slurry), heat it to 45°C, adjust the pH value of the mixed slurry in the slurry mixing tank 102 to 8, stir and mix for 10 minutes to obtain a second mixed slurry.

[0071] Afterwards, composite fillers (including light calcium carbonate with a triangular shape and a particle size of 1.5 μm, cationic ground calcium carbonate with a particle size of 0.7 μm and porous silica, and their mass ratio is 10:5:2) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, and their mass ratio is 20:0.04:1) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 10% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.2% of the total mass of the second mixed slurry.

[0072] Process 3: Slag removal:

[0073] In the deslagging system 103 , the third mixed slurry is deslagging to obtain the deslagging third mixed slurry, which is then transported to the Fourdrinier wire section 104 .

[0074] Process 4: Wet paper making, pressing and primary drying:

[0075] The third mixed pulp after the slag removal system 103 is transported to the fourdrinier wire section 104 for papermaking and forming to obtain a wet paper sheet; the online concentration is controlled to be 0.7%, the online pH value is 8, the pulp-to-wire speed ratio is 0.9, the operating speed is 380m / min, the white water concentration under the wire is ≤0.3%, the dryness of the outlet wire is ≥20%, and the papermaking basis weight is 60-80g / m 2 The obtained wet paper sheets are transported to the pressing section 105 for pressing and dehydration, and then passed through the first drying section 106 for primary drying at a temperature of 60°C.

[0076] Process 5: Surface sizing:

[0077] The paper sheet is dried once in the first drying section 106 and then transported to the surface sizing machine 107 to obtain a surface sized paper sheet, wherein the surface sizing agent is a composition of paraffin wax, 13-18 alkyl ketene dimer (AKD) and modified sodium sulfate in a mass ratio of 0.02:0.5:20. The single-side coating amount of the surface sizing is 5g / m 2 .

[0078] Process 6: Secondary drying, calendering and coiling:

[0079] The surface sized paper sheet is conveyed to the second drying section 108 for secondary drying at a temperature of 70° C., and then calendered and finished by the calender 109 , and finally wound up by the paper winder 110 to obtain the finished white offset paper.

[0080] Example 2

[0081] See also Figure 1 The preparation method of the white offset paper provided in this embodiment is as follows:

[0082] Process 1: Slurry preparation:

[0083] Bleached sulfite coniferous pulp, bleached sulfite broadleaf pulp and bleached sulfate eucalyptus pulp are added to the pulping tank 101 in a mass ratio of 28:42:30 for mixing, and then beaten by a pulper to obtain a first mixed pulp with a beating degree of 40°SR~55°SR, and the first mixed pulp is conveyed to the pulping tank 102.

[0084] Process 2: Slurry preparation:

[0085] A fiber modifier is added to the first mixed slurry in the slurry mixing tank 102 (the added amount is 1% of the total mass of the first mixed slurry), the temperature is raised to 55° C., and the pH value of the mixed slurry in the slurry mixing tank 102 is adjusted to 9. The mixture is stirred and mixed for 20 minutes to obtain a second mixed slurry.

[0086] Afterwards, composite fillers (including triangular light calcium carbonate with a particle size of 1.9 μm, cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica, and their mass ratio is 10:7:2) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, and their mass ratio is 20:0.05:2) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 20% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.2% of the total mass of the second mixed slurry.

[0087] Process 3: Slag removal:

[0088] In the deslagging system 103 , the third mixed slurry is deslagging to obtain the deslagging third mixed slurry, which is then transported to the Fourdrinier wire section 104 .

[0089] Process 4: Wet paper making, pressing and primary drying:

[0090] The third mixed pulp after the slag removal system 103 is transported to the fourdrinier wire section 104 for papermaking and forming to obtain a wet paper sheet; the online concentration is controlled to be 0.8%, the online pH value is 9, the pulp-to-web speed ratio is 0.96, the operating speed is 400m / min, the white water concentration under the wire is ≤0.3%, the dryness of the outlet part is ≥20%, and the papermaking basis weight is 60-80g / m 2 The obtained wet paper sheets are transported to the pressing section 105 for pressing and dehydration, and then passed through the first drying section 106 for primary drying at a temperature of 70°C.

[0091] Process 5: Surface sizing:

[0092] The paper sheet is dried once in the first drying section 106 and then transported to the surface sizing machine 107 for surface sizing treatment to obtain a surface sized paper sheet, wherein the surface sizing agent is a composition of paraffin wax, 13-18 alkyl ketene dimer (AKD) and modified sodium sulfate in a mass ratio of 0.03:0.5:25. The single-side coating amount of the surface sizing is 2 g / m 2 .

[0093] Process 6: Secondary drying, calendering and coiling:

[0094] The surface sized paper sheet is conveyed to the second drying section 108 for secondary drying at a temperature of 70° C., and then calendered and finished by the calender 109 , and finally wound up by the paper winder 110 to obtain the finished white offset paper.

[0095] Example 3

[0096] See also Figure 1 The preparation method of the white offset paper provided in this embodiment is as follows:

[0097] Process 1: Slurry preparation:

[0098] Bleached sulfite coniferous pulp, bleached sulfite broadleaf pulp and bleached sulfate eucalyptus pulp are added to the pulping tank 101 in a mass ratio of 35:40:40 for mixing, and then beaten by a pulper to obtain a first mixed pulp with a beating degree of 40°SR~55°SR, and the first mixed pulp is conveyed to the pulping tank 102.

[0099] Process 2: Slurry preparation:

[0100] A fiber modifier (the amount added is 0.8% of the total mass of the first mixed slurry) is added to the first mixed slurry in the slurry mixing tank 102, the temperature is raised to 55°C, and the pH value of the mixed slurry in the slurry mixing tank 102 is adjusted to 11, and stirred and mixed for 90 minutes to obtain a second mixed slurry.

[0101] Afterwards, composite fillers (including light calcium carbonate with a triangular shape and a particle size of 1.9 μm, cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica, and their mass ratio is 12:6:2) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, and their mass ratio is 36:0.05:2) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 30% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.4% of the total mass of the second mixed slurry.

[0102] Process 3: Slag removal:

[0103] In the deslagging system 103 , the third mixed slurry is deslagging to obtain the deslagging third mixed slurry, which is then transported to the Fourdrinier wire section 104 .

[0104] Process 4: Wet paper making, pressing and primary drying:

[0105] The third mixed pulp after the slag removal system 103 is transported to the fourdrinier wire section 104 for papermaking and forming to obtain a wet paper sheet; the online concentration is controlled to be 0.8%, the online pH value is 8.5, the pulp-to-wire speed ratio is 0.96, the operating speed is 400m / min, the white water concentration under the wire is ≤0.3%, the dryness of the outlet wire is ≥20%, and the papermaking basis weight is 60-80g / m 2 The obtained wet paper sheets are transported to the pressing section 105 for pressing and dehydration, and then passed through the first drying section 106 for primary drying at a temperature of 80°C.

[0106] Process 5: Surface sizing:

[0107] The paper sheet is dried once in the first drying section 106 and then transported to the surface sizing machine 107 to obtain a surface sized paper sheet, wherein the surface sizing agent is a composition of paraffin wax, 13-18 alkyl ketene dimer (AKD) and modified sodium sulfate in a mass ratio of 0.05:0.6:25. The single-side coating amount of the surface sizing is 4g / m 2 .

[0108] Process 6: Secondary drying, calendering and coiling:

[0109] The surface sized paper sheet is conveyed to the second drying section 108 for secondary drying at a temperature of 70° C., and then calendered and finished by the calender 109 , and finally wound up by the paper winder 110 to obtain the finished white offset paper.

[0110] Example 4

[0111] See also Figure 1 The preparation method of the white offset paper provided in this embodiment is as follows:

[0112] Process 1: Slurry preparation:

[0113] Bleached sulfite coniferous pulp, bleached sulfite broadleaf pulp and bleached sulfate eucalyptus pulp are added to the pulping tank 101 in a mass ratio of 30:50:40 for mixing, and then beaten by a pulper to obtain a first mixed pulp with a beating degree of 40°SR~55°SR, and the first mixed pulp is conveyed to the pulping tank 102.

[0114] Process 2: Slurry preparation:

[0115] Add fiber modifier to the first mixed slurry in the slurry mixing tank 102 (the added amount is 0.5% of the total mass of the first mixed slurry), heat it to 75°C, adjust the pH value of the mixed slurry in the slurry mixing tank 102 to 10, stir and mix for 60 minutes to obtain a second mixed slurry.

[0116] Afterwards, composite fillers (including light calcium carbonate with a triangular shape and a particle size of 1.9 μm, cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica, and their mass ratio is 15:5:3) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, and their mass ratio is 25:0.05:2) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 25% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.3% of the total mass of the second mixed slurry.

[0117] Process 3: Slag removal:

[0118] In the deslagging system 103 , the third mixed slurry is deslagging to obtain the deslagging third mixed slurry, which is then transported to the Fourdrinier wire section 104 .

[0119] Process 4: Wet paper making, pressing and primary drying:

[0120] The third mixed pulp after the slag removal system 103 is transported to the fourdrinier wire section 104 for papermaking and forming to obtain a wet paper sheet; the online concentration is controlled to be 1.1%, the online pH value is 8.5, the pulp-to-web speed ratio is 0.96, the operating speed is 400m / min, the white water concentration under the wire is ≤0.3%, the dryness of the outlet wire is ≥20%, and the papermaking basis weight is 60-80g / m 2 The obtained wet paper sheets are transported to the pressing section 105 for pressing and dehydration, and then passed through the first drying section 106 for primary drying at a temperature of 80°C.

[0121] Process 5: Surface sizing:

[0122] The paper sheet is dried once in the first drying section 106 and then transported to the surface sizing machine 107 for surface sizing treatment to obtain a surface sized paper sheet, wherein the surface sizing agent is a composition of paraffin wax, 13-18 alkyl ketene dimer (AKD) and modified sodium sulfate in a mass ratio of 0.04:0.5:24. The single-side coating amount of the surface sizing is 3g / m 2 .

[0123] Process 6: Secondary drying, calendering and coiling:

[0124] The surface sized paper sheet is conveyed to the second drying section 108 for secondary drying at a temperature of 70° C., and then calendered and finished by the calender 109 , and finally wound up by the paper winder 110 to obtain the finished white offset paper.

[0125] Comparative Example 1

[0126] This comparative example provides a white offset paper, and its preparation method is basically the same as that of the above-mentioned Example 3, the only difference being that: step 2 is replaced by: adding 100 ml / t of royal blue dye (first mixed slurry) and 40 ml / t of basic violet dye (first mixed slurry) to the first mixed slurry in the slurry mixing tank 102 for color adjustment to obtain a second mixed slurry.

[0127] Afterwards, composite fillers (including light calcium carbonate with a triangular shape and a particle size of 1.9 μm, cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica, and their mass ratio is 12:6:2) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, and their mass ratio is 36:0.05:2) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 30% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.4% of the total mass of the second mixed slurry.

[0128] Comparative Example 2

[0129] This comparative example provides a white offset paper, and its preparation method is basically the same as that of the above-mentioned Example 3, except that: step 2 is replaced by: adding a fiber modifier to the first mixed slurry in the slurry mixing tank 102 (the added amount is 0.8% of the total mass of the first mixed slurry), heating to 55°C, and adjusting the pH value of the mixed slurry in the slurry mixing tank 102 to 11, stirring and mixing for 90 minutes, and obtaining a second mixed slurry.

[0130] Afterwards, fillers (light calcium carbonate with a triangular shape and a particle size of 1.9 μm) and retention and drainage aids (including tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch, with a mass ratio of 36:0.05:2) are added to the second mixed slurry, mixed evenly, to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the filler is 30% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.4% of the total mass of the second mixed slurry.

[0131] Comparative Example 3

[0132] This comparative example provides a white offset paper, and its preparation method is basically the same as that of the above-mentioned Example 3, except that: step 2 is replaced by: adding a fiber modifier to the first mixed slurry in the slurry mixing tank 102 (the added amount is 0.8% of the total mass of the first mixed slurry), heating to 55°C, and adjusting the pH value of the mixed slurry in the slurry mixing tank 102 to 11, stirring and mixing for 90 minutes, and obtaining a second mixed slurry.

[0133] Afterwards, composite fillers (including triangular light calcium carbonate with a particle size of 1.9 μm, cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica, and their mass ratio is 12:6:2) and retention and drainage aids (tertiary amine type amphoteric polyacrylamide) are added to the second mixed slurry, mixed evenly to obtain a third mixed slurry, and the obtained third mixed slurry is conveyed to the slag removal system 103; wherein, the added amount of the composite filler is 30% of the total mass of the second mixed slurry, and the added amount of the retention and drainage aid is 0.4% of the total mass of the second mixed slurry.

[0134] Comparative Example 4

[0135] This comparative example provides a white offset paper, the preparation method of which is basically the same as that of the above-mentioned embodiment 3, except that step 5 is replaced by: surface sizing is performed on the paper sheet that is once dried in the first drying section 106 and then transported to the surface sizing machine 107 to obtain a surface sized paper sheet, wherein the surface sizing agent is 13-18 alkyl ketene dimer (AKD). The single-sided coating amount of the surface sizing is 4g / m 2 .

[0136] The following performance index tests were conducted on the white offset papers prepared in the above Examples 1 to 4 and Comparative Examples 1 to 4, and the test results are shown in Tables 1 and 2. Each index was tested in accordance with relevant national standards.

[0137] Table 1

[0138]

[0139]

[0140] Table 2

[0141]

[0142] As can be seen from Table 1 and Table 2, the thickness deviation, cross-sectional thickness difference, opacity, color (original white), smoothness difference on both sides, transverse stretchability and other indicators of the white offset paper prepared in Examples 1 to 4 of the present application are significantly better than the indicator requirements (standard requirements). It can be seen that the white offset paper prepared by the preparation method provided in the examples of the present application has good quality, high opacity, the highest (Example 3) can reach 90.0%, soft color, can protect the reader's eyesight, and has good recognition.

[0143] From the comparison results of Example 3 and Comparative Example 1, it can be seen that by using a specific fiber modifier to modify the first mixed pulp, it is beneficial to improve the mechanical strength, whiteness and opacity of the paper, and at the same time, it can reduce or eliminate the need for additional addition of dyes for color adjustment, thereby saving the investment cost of dyes.

[0144] From the comparison results of Example 3 and Comparative Example 2, it can be seen that the composite filler formed by compounding a specific proportion of triangular light calcium carbonate with a particle size of 1.9 μm, a cationic ground calcium carbonate with a particle size of 1.5 μm and porous silica is beneficial to improving the mechanical strength and opacity of paper compared to using only triangular light calcium carbonate with a particle size of 1.9 μm as a filler.

[0145] From the comparison results of Example 3 and Comparative Example 3, it can be seen that by using a composition prepared by mixing tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch in a specific proportion as a retention and drainage aid, compared with using tertiary amine type amphoteric polyacrylamide alone as a retention and drainage aid, it is beneficial to improve the opacity and mechanical strength of the paper.

[0146] From the comparison results of Example 3 and Comparative Example 4, it can be seen that by using a composition prepared by mixing paraffin, 13-18 alkyl ketene dimer (AKD) and modified sodium sulfate in a specific ratio as a surface sizing agent, compared with using 13-18 alkyl ketene dimer (AKD) alone as a surface sizing agent, it is beneficial to improve the opacity and visual whiteness of paper.

[0147] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing white offset paper, characterized in that: include: Mixing and beating coniferous wood pulp, hardwood wood pulp and eucalyptus pulp to obtain a first mixed pulp; wherein the mass ratio of coniferous wood pulp, hardwood wood pulp and eucalyptus pulp is 25-35:40-50:30-40; Adding a fiber modifier to the first mixed slurry, and stirring and mixing for 10 to 90 minutes at a temperature of 45 to 95° C. and a pH value of 8 to 11 to obtain a second mixed slurry; wherein the amount of the fiber modifier added is 0.1% to 1% of the total mass of the first mixed slurry; Adding a composite filler and a retention and drainage aid to the second mixed slurry, mixing them evenly, to obtain a third mixed slurry; wherein the addition amount of the composite filler is 10% to 30% of the total mass of the second mixed slurry; the addition amount of the retention and drainage aid is 0.2% to 0.4% of the total mass of the second mixed slurry; the composite filler includes at least two of light calcium carbonate, cationic ground calcium carbonate or porous silica; the retention and drainage aid includes at least two of tertiary amine type amphoteric polyacrylamide, dimethyl sulfate or modified corn starch; The third mixed slurry is used to make wet paper sheets to obtain wet paper sheets; The wet paper sheets are sequentially subjected to pressing, primary drying, surface sizing, secondary drying and calendering treatment to obtain white offset paper.

2. The method for preparing white offset paper according to claim 1, characterized in that: The preparation steps of the fiber modifier are as follows: Dissolving plant starch in water to prepare a starch suspension having a solid content of 20% to 50%; The starch suspension is reacted with 2,3-oxypropyl-N-alkyl-N,N-dimethylammonium chloride in an alkaline medium at a temperature of 20 to 45° C. for 8 to 16 hours to obtain the fiber modifier.

3. The method for preparing white offset paper according to claim 2, characterized in that: The mass ratio of the starch suspension to 2,3-oxypropyl-N-alkyl-N,N-dimethylammonium chloride is 100:1-2.

4. The method for preparing white offset paper according to claim 1, characterized in that: The composite filler comprises light calcium carbonate, cationic ground calcium carbonate and porous silica; The mass ratio of the light calcium carbonate, the cationic ground calcium carbonate and the porous silicon dioxide is 10-15:5-7:2-3.

5. The method for preparing white offset paper according to claim 4, characterized in that: The particle size of the light calcium carbonate is 1.5 μm to 1.9 μm.

6. The method for preparing white offset paper according to claim 1, characterized in that: The retention and drainage aids include tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch; The mass ratio of the tertiary amine type amphoteric polyacrylamide, dimethyl sulfate and modified corn starch is 20-36:0.04-0.06:1-2.

7. The method for preparing white offset paper according to claim 1, characterized in that: The beating degree of the first mixed slurry is 40°SR-55°SR.

8. The method for preparing white offset paper according to claim 1, characterized in that: In the step of making a wet paper sheet from the third mixed slurry to obtain a wet paper sheet: The concentration of the net is 0.7-1.1%, the pH value of the net is 8-9, the pulp-to-net speed ratio is 0.9-0.96, the operating speed is 380-400 m / min, the white water concentration under the net is ≤0.3%, the dryness of the outlet part is ≥20%, and the papermaking basis weight is 60-80 g / m 2 .

9. The method for preparing white offset paper according to claim 1, characterized in that: In the process of surface sizing, the surface sizing agent used is a composition of paraffin wax, 13-18 alkyl ketene dimer and modified sodium sulfate in a mass ratio of 0.02-0.05:0.5-0.6:20-25; The single-sided coating amount of the surface sizing agent is 2 to 5 g / m 2 .

10. A white offset paper, characterized in that: The white offset paper is prepared according to the method for preparing the white offset paper according to any one of claims 1 to 9.

Images