AU2020103872A4 - Method for preparing light-coated paper with high bulkiness - Google Patents

Abstract

The present disclosure relates to the technical field of papermaking, and particularly relates to a method for preparing light-coated paper with high bulkiness, including coating base paper, drying, winding, and slitting, where one layer of air knife coating is applied on each side. The present disclosure provides a method for preparing light-coated paper with high bulkiness by air knife coating. A coating is prepared from polystyrene pigment, mineral pigment, adhesive and other coating aid. Obtained light-coated paper has strong fiber feel on the surface and high bulkiness. The present disclosure provides a process having low energy consumption in production, simple and easy-to-obtain equipment, and simple process flow, enabling mass production. Moreover, the entire process of the present disclosure is a completely closed cycle without causing any pollution.

Description

AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION INNOVATION PATENT METHOD FOR PREPARING LIGHT-COATED PAPER WITH HIGH BULKINESS

The following statement is a full description of this invention, including the best method of performing it

known to me:

METHOD FOR PREPARING LIGHT-COATED PAPER WITH HIGH BULKINESS TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of papermaking, and particularly relates to a method for preparing light-coated paper with high bulkiness.

BACKGROUND OF THE PRESENT INVENTION

[0002] Light-coated paper is high-grade coated printing paper with its surface feeling like natural fiber. It features high bulkiness, low smoothness, light and stiff hand feel, and low visual fatigue. In addition, it has a same printing effect as coated printing paper, and provides accurate natural color reproduction and excellent presentation, enabling bright ink dots and three-dimensional beautiful images. Therefore, it is widely used in printed materials such as high-end picture albums, samples, invitations, posters, real estate brochures, and advertisements.

[0003] The light-coated paper is different from copper printing paper in that it has a simple production process. In order to maintain a fiber feel of the paper surface, a single side of the paper is usually coated with 10-15 g/m of air knife coating. After coating, there is no need for calendering treatment, which avoids the visual fatigue caused by high gloss of copper printing paper while achieving printing effect of copper printing paper.

[0004] In the prior art, there is also similar research on production process of light-coated paper. For example, CN101581059A discloses a method for producing light-coated paper in which 5-10% of velvet additive is added to coatings to give a fluffy smooth and delicate hand feel of finished paper and an elegant matte printing visual effect. CN10125085A discloses a method for producing light-coated paper, which uses titanium dioxide and china clay as pigments and styrene butadiene latex and starch as adhesives to prepare light-coated paper by air knife coating. The method allows for 15g/m 2 of coatings on a single side on base paper having bulkiness of 1.5 cm 3/g to obtain finished coated paper having bulkiness of about 1.1 cm 3/g. CN101581058A relates to a method for producing lightweight light-coated paper. The method uses titanium dioxide and china clay as pigments, styrene butadiene latex and starch as adhesives, and lightweight paper as base paper with bulkiness of 1.8 cm 3/g to prepare light-coated paper by air knife coating. Finished paper has bulkiness of 1.4 cm 3/g.

[0005] The light-coated paper produced by existing methods uses mineral pigments for coating, leading to a great bulkiness loss of the paper after coating. This cannot meet current requirements of light-coated paper with high bulkiness.

SUMMARY OF PRESENT INVENTION

[0006] In order to solve the problem that there is a great bulkiness loss of finished coated light-coated paper produced in existing methods, the present disclosure provides a method for preparing light-coated paper with high bulkiness, where a synthetic resin pigment is used for coating to obtain finished paper having a small bulkiness loss after coating.

[0007] The present disclosure is implemented by a method for preparing light-coated paper with high bulkiness, including coating base paper, drying, winding, and slitting; where

[0008] a coating process includes:

[0009] coating mode: one layer of air knife coating on each side,

[0010] coating speed: 150-250 m/min,

[0011] coating amount: 10-15 g/m2 on each side,

[0012] parameters of coating: solid content of 35-45%, viscosity of 30-80 mPa-S (at 40C); and

[0013] raw materials having the following parts by weight based on absolute dry weight:

[0014] 65-85 parts of pigment, 15-30 parts of adhesive and 2-5 parts of aid.

[0015] According to the preparation method, the pigment preferably includes the following raw materials in parts by weight: 20-40 parts of calcium carbonate, 0-10 parts of kaolin, 0-20 parts of titanium dioxide, and 20-50 parts of polystyrene pigment.

[0016] The polystyrene pigment is a pigment product with both pigment and adhesive properties, having a particle size of 0.5 [m, a refractive index of 1.59, a whiteness of 95%, and an outstanding density of 1.05 g/cm3 . Traditional mineral pigments have higher densities, for example calcium carbonate has a density of 2.7g/cm 3, kaolin (china clay) has a density of 2.58 g/cm 3, and titanium dioxide has a density of 4.2 g/cm3 , which is several times the density of the polystyrene pigment. The polystyrene pigment has excellent fluidity and can improve ink absorption of a coating due to its lipophilicity.

[0017] The present disclosure uses the polystyrene pigment to replace or partially replace mineral pigment, and uses carboxyl styrene butadiene latex, starch, polyvinyl alcohol (PVA) as adhesives, carboxymethyl cellulose (CMC)as water retaining agent, together with other coating aid, to form a coating liquid according to a certain proportion. The coating liquid is coated on base paper in an air knife coating manner to prepare light-coated paper with high bulkiness.

[0018] In the preparation method, a weight ratio of raw materials in the adhesive is preferably: carboxyl styrene butadiene latex : starch : PVA = (8-15):(6-15):(0-5).

[0019] In the preparation method, a weight ratio of raw materials in the aid is preferably: water retaining agent : dispersant : defoamer : water repellent : lubricant= (0.2-0.5):(02-0.5):(0.01-0.05):(0.5-0.8):(3-5).

[0020] In the preparation method, the base paper preferably has bulkiness > 1.90 cm 3/g, picking strength >2 m/s, and surface absorbency <25 g/cm.

[0021] Production of base paper for the light-coated paper in the present disclosure uses well-known papermaking technology. However, the light-coated paper with high bulkiness is high-end printing paper showing better performance than conventional coated paper. The production process of the light-coated paper with high bulkiness attaches great importance to finished paper evenness and paper defects. Specifically, it is required that the finished paper meet requirements of surface strength, bulkiness and surface absorbency. In the pigment for coating, the calcium carbonate selected may be double 90-grade liquid calcium commonly used for coating (whiteness greater than 90 degrees, and portion of pigment having particles with a size <2 m accounting for greater than 90% of the total pigment used), the titanium dioxide may be anatase ultrafine titanium dioxide (particle size <2 m), and the polystyrene pigment may have a particle size <0.5 m and whiteness of >95. In the adhesive, the carboxyl styrene butadiene latex may be a hydrophilic latex, the PVA may be a 17-99 type high alcoholysis polyvinyl alcohol, and the starch may be a highly rheological coated oxidized starch.

[0022] Beneficial effects:

[0023] (1) According to the method for preparing light-coated paper with high bulkiness by air knife coating, the coating is prepared from polystyrene pigment, mineral pigment, adhesive and other coating aid. Obtained light-coated paper has strong fiber feel on the surface and high bulkiness.

[0024] (2) The light-coated paper prepared by the present disclosure ensures outstanding three-dimensional printing, light, high-end and excellent printing quality, and is the first choice for high-end clothing samples, picture albums, invitations and the like.

[0025] (3) The process provided by the present disclosure has low energy consumption in production, simple and easy-to-obtain equipment, and simple process flow, enabling mass production. Moreover, the entire process of the present disclosure is a completely closed cycle without causing any pollution.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] Polystyrene pigment greatly improves bulkiness of paper.

[0027] The polystyrene pigment in use can increase viscosity of a coating. To ensure basic performance of the coating, when amount of the polystyrene pigment is increased, amount of adhesive, especially the PVA, can be appropriately reduced. The PVA is also an important factor that causes the viscosity of the adhesive to increase. It is also possible to reduce solid content of the coating to control the viscosity.

[0028] The polystyrene pigment itself also has adhesive properties and a certain film-forming property. Therefore, as the amount of the polystyrene pigment increases, water resistance can also be improved.

[0029] The polystyrene pigment itself has high whiteness, which significantly increases whiteness of paper after a coating is formed.

[0030] The titanium dioxide affects opacity most obviously. For papers that require high opacity, amount of the titanium dioxide can be appropriately increased.

[0031] As basis weight of base paper increases, bulkiness of the base paper itself has a greater effect on bulkiness of finished paper.

[0032] To facilitate better understanding, the present disclosure is further described below with reference to 5 Examples and 1 Comparative Example.

[0033] Example 1:

[0034] Step 1: production of base paper

[0035] Slurry ratio: chemical hardwood pulp: chemical softwood pulp = 80:20.

[0036] Beating degree:45°SR with chemical hardwood pulp, and 36°SR with chemical softwood pulp.

[0037] Slurries were combined, subjected to a three-stage residual removal treatment, and filled with light calcium carbonate in an amount of 50 Kg/ton paper. Cationic starch in an amount of 10 Kg/ton paper, alkylketene dimmer (AKD) in an amount of 20 Kg/ton paper and cationic polyacrylamide (c-PAM) in an amount of 0.5 Kg/ton paper were metered and added before a slurry pump. A mixture was supplied to a net through rotary wing screen-headbox, with a pulp-to-net speed ratio controlled to be 1.01, and finally dried into paper.

[0038] Main indicators of finished paper included basis weight of 81 g/cm2 , bulkiness of 1.92 cm 3/g, picking strength of 2.5 m/s, and surface absorbency of 23 g/cm 2 .

[0039] Step 2: coating treatment

[0040] Coating formula: (based on absolute dry weight proportion of coating)

[0041] calcium carbonate: porcelain clay: polystyrene pigment: carboxyl styrene butadiene latex : coating starch : PVA=30 parts : 10 parts : 40 parts : 12 parts : 7 parts : 1 part.

[0042] Coating preparation process:

[0043] Calcium carbonate, titanium dioxide and dispersant at a 70% concentration were dispersed by a high-speed disperser at a shear speed of 17 m/s for 30 min. A 50% solid content of polystyrene pigment was slowly added, dispersed at a low speed for 15 min, and then mixed with carboxy styrene butadiene latex, boiled coating starch glue liquid and PVA glue liquid. Stirring was maintained while adding water retaining agent, water repellent, defoamer, lubricant, bactericide, toner and other coating aid.

[0044] Coating indicators: solid content was 38 0.2%, viscosity was 50 2.5 mPa.s, and coating temperature was 40 0.5°C.

[0045] Coating process: prepared coating was passed through vibrating frame screen-pressure screen-feeding device-premeter device-air knife-drying box-conditioning cylinder-winding.

[0046] Coating process requirements: coating amount was 12+0.2 g/m 2 per single side, coating amount difference between two sides was 0.3 g/m2 , vehicle speed was 180 m/min and finished paper dryness was 94%.

[0047] Example 2:

[0048] Step 1: production of base paper

[0049] Slurry ratio : chemical hardwood pulp : chemical softwood pulp : poplar alkaline peroxide mechanical pulp (APMP) = 50:30:20.

[0050] Beating degree: 45°SR with chemical hardwood pulp, 36°SR with chemical softwood pulp and 55°SR with poplar APMP.

[0051] Slurries were combined, subjected to a three-stage residual removal treatment, and filled with light calcium carbonate in an amount of 80 Kg/ton paper. Cationic starch in an amount of 10 Kg/ton paper, AKD in an amount of 25 Kg/ton paper and c-PAM in an amount of 0.5 Kg/ton paper were metered and added before a slurry pump. A mixture was supplied to a net through rotary wing screen-headbox, with a pulp-to-net speed ratio controlled to be 1.01, and finally dried into paper.

[0052] Main indicators of finished paper included basis weight of 175 g/cm2 , bulkiness of 1.91 cm 3/g, picking strength of 3.7 m/s, and surface absorbency of 24 g/cm 2 .

[0053] Step 2: coating treatment

[0054] Coating formula: (based on absolute dry weight proportion of coating)

[0055] calcium carbonate: titanium dioxide: polystyrene pigment: carboxyl styrene butadiene latex : coating starch : PVA=30 parts : 20 parts : 30 parts : 14 parts : 5 parts : 1 part.

[0056] A coating preparation process was the same as that in Example 1.

[0057] Coating indicators:

[0058] solid content was 40 0.2%, viscosity was 55 2.5 mPa.s, and coating temperature was 0.50 C.

[0059] Coating process requirements were the same as those in Example 1:

[0060] coating amount was 12.5+0.2 g/m 2 per single side, coating amount difference between two sides was 0.3 g/m 2 , vehicle speed was 150 m/min andfinished paper dryness was 94%.

[0061] Example 3:

[0062] Coating was applied on the base paper (as substrate) of Example 1.

[0063] Coating formula: (based on absolute dry weight proportion of coating)

[0064] calcium carbonate: titanium dioxide: polystyrene pigment: carboxyl styrene butadiene latex : coating starch : PVA=40 parts : 20 parts : 20 parts : 10 parts : 5 parts : 5 parts.

[0065] A coating preparation process was the same as that in Example 1.

[0066] Coating indicators:

[0067] solid content was 42 0.2%, viscosity was 60 2.5 mPa.s, and coating temperature was 0.50 C.

[0068] Coating process and requirements were the same as those in Example 1.

[0069] Example 4:

[0070] Coating was applied on the base paper (as substrate) of Example 1.

[0071] Coating formula: (based on absolute dry weight proportion of coating)

[0072] calcium carbonate : titanium dioxide : polystyrene pigment: carboxyl styrene butadiene latex : coating starch : PVA=20 parts : 10 parts : 50 parts : 10 parts : 10 parts : 1 part.

[0073] A coating preparation process was the same as that in Example 1.

[0074] Coating indicators:

[0075] solid content was 35 0.2%, viscosity was 55 2.5 mPa.s, and coating temperature was 0.50 C.

[0076] Coating process and requirements were the same as those in Example 1.

[0077] Example 5:

[0078] Coating was applied on the base paper (as substrate) of Example 1.

[0079] Coating formula: (based on absolute dry weight proportion of coating)

[0080] calcium carbonate : titanium dioxide : polystyrene pigment : carboxyl styrene butadiene latex : coating starch : PVA=35 parts : 0 part : 50 parts : 8 parts : 6 parts : 1 part.

[0081] A coating preparation process was the same as that in Example 1.

[0082] Coating indicators:

[0083] solid content was 42 0.2%, viscosity was 55 2.5 mPa.s, and coating temperature was 0.50 C.

[0084] Coating process and requirements were the same as those in Example 1.

[0085] Comparative Example: the base paper of Example 1 was used in this example.

[0086] Coating formula: (based on absolute dry weight proportion of coating)

[0087] calcium carbonate : titanium dioxide : carboxyl styrene butadiene latex : coating starch: PVA= 60 parts : 20 parts : 12 parts : 7 parts : 1 part.

[0088] Coating preparation process:

[0089] Calcium carbonate, titanium dioxide and dispersant at a 65% concentration were dispersed by a high-speed disperser at a shear speed of 17 m/s for 30 min, and mixed with carboxy styrene butadiene latex, boiled coating starch glue liquid and PVA glue liquid. Stirring was maintained while adding water retaining agent, water repellent, defoamer, lubricant, bactericide, toner and other coating aid.

[0090] Coating indicators: solid content was 45 0.2%, viscosity was 60 2.5 mPa.s, and coating temperature was 40 0.50 C.

[0091] A coating process was the same as that of Example 1.

[0092] Final finished paper indicators:

Surface Dustiness Bulkiness Detection Basis absorbency Whiteness Opacity (0.2-1.0 Bulkiness ofbase item weight Front Back mn2 )< paper side side Unit g/m2 g/m2 g/mz % % /Mz cm 3/g cm3/g Example 1 104.9 22.4 22.6 85.2 96.6 8 1.72 1.92 Example 2 200.3 23.5 23.6 85.6 98.5 8 1.73 1.91 Example 3 104.9 24.2 24.3 84.2 97.8 8 1.52 1.92 Example 4 104.9 2.1 22.2 87.3 96.5 8 1.75 1.92 Example 5 104.9 22.5 22.6 87.2 95.3 8 1.82 1.92 Comparative 104.9 23.6 23.8 87.3 98.2 8 1.28 1.92 Example

[0093] It can be seen from the finalfinished paper indicators that, the bulkiness of thefinished paper produced in each Example and the Comparative Example was lower than that of the base paper. Bulkiness loss of paper was due to factors such as high density of the coating itself, filling of the coating in gaps of paper surface, migration of glue liquid to the inside of the paper during the coating process and z-direction pressure on the paper.

[0094] Compared with the Comparative Example, different proportions of polystyrene pigment were added in the Examples, leading to higher bulkiness. Among the Examples, the polystyrene pigment accounting for the largest proportions in Example 4 and Example 5 yielded significantly higher bulkiness than other Examples. Compared with Example 5, Example 4 had a larger amount of titanium dioxide, which led to finished paper with slightly lower bulkiness than Example 5.

[0095] Compared with Example 1, Example 2 had a higher basis weight of base paper, a higher amount of titanium dioxide and a higher proportion of base paper in the finished paper, which ultimately led to that the bulkiness of finished paper of Example 1 was slightly lower than that of Example 2.

[0096] Example 2 had the highest opacity, mainly due to the high amount of titanium dioxide and the high basis weight. Similarly, compared with other examples, the opacity of the Comparative Example was significantly increased due to the higher amount of titanium dioxide.

[0097] Examples 4 and 5 had the highest whiteness and the lowest absorbency. This was also due to the high proportion of the polystyrene pigment which increased paper whiteness.

[0098] The above embodiments are preferred implementations of the present disclosure. However, the embodiments of the present disclosure are not limited by the above embodiments. Any change, modification, combination, substitution and simplification and the like made without departing from the spiritual essence and principle of the present disclosure should be an equivalent replacement manner, and all are included in a protection scope of the present disclosure.

Claims (10)

1. The claims for defining the invention are as follows: 1. A method for preparing light-coated paper with high bulkiness, comprising coating base paper, drying, winding, and slitting; wherein a coating process comprises: coating mode: one layer of air knife coating on each side, coating speed: 150-250 m/min, coating amount: 10-15 g/m2 on each side, parameters of coating: solid content of 35-45%, viscosity of 30-80 mPa-S (at 40°C); and raw materials having the following parts by weight based on absolute dry weight: -85 parts of pigment, 15-30 parts of adhesive and 2-5 parts of aid.
2. 2. The method according to claim 1, wherein the pigment comprises the following raw materials in parts by weight: -40 parts of calcium carbonate, 0-10 parts of kaolin, 0-20 parts of titanium dioxide, and 20-50 parts of polystyrene pigment.
3. 3. The method according to claim 1, wherein a weight ratio of raw materials in the adhesive is: carboxyl styrene butadiene latex : starch: polyvinyl alcohol (PVA)= (8-15):(6-15):(0-5).
4. 4. The method according to claim 1, wherein a weight ratio of raw materials in the aid is: water retaining agent : dispersant : defoamer : water repellent : lubricant =

   (0.2-0.5):(0.2-0.5):(0.01-0.05):(0.5-0.8):(3-5).
5. 5. The method according to claim 1, wherein the base paper has bulkiness > 1.90 cm 3/g, picking strength >2 m/s, and surface absorbency <25 g/cm2 .
6. 6. The method according to claim 1, wherein the calcium carbonate has whiteness >90 degrees, and portion of pigment having particles with a size <2 m accounting for greater than 90% of the total pigment used.
7. 7. The method according to claim 1, wherein the titanium dioxide is anatase ultrafine titanium dioxide with a particle size <2 m.
8. 8. The method according to claim 1, wherein the polystyrene pigment has a particle size <0.5 Im and whiteness >95.
9. 9. The method according to claim 1, wherein the carboxyl styrene butadiene latex is a hydrophilic latex.
10. 10. The method according to claim 1, wherein the PVA is a 17-99 type high alcoholysis polyvinyl alcohol.