CN112127211A

CN112127211A - Stone paper, calcium carbonate slurry and preparation method thereof

Info

Publication number: CN112127211A
Application number: CN202011032837.6A
Authority: CN
Inventors: 姚梁; 姚强
Original assignee: Shanxi Yuhao Environmental Protection Paper Co ltd
Current assignee: Shanxi Yuhao Environmental Protection Paper Co ltd
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2020-12-25
Anticipated expiration: 2040-09-27
Also published as: CN112127211B

Abstract

The invention provides stone paper and calcium carbonate slurry and a preparation method thereof, wherein the preparation method comprises the following steps: preparing calcium carbonate superfine powder with the particle size of not more than 6 mu m; step two: mixing, shearing and dispersing the calcium carbonate ultrafine powder in a stirring tank to obtain initial slurry, wherein the stirring speed is 800-; step three: and grinding the initial slurry by a sand mill to obtain calcium carbonate slurry. The invention realizes the accurate control of the fineness, the viscosity and the like of the particle size of the ground slurry by accurately controlling the stirring speed and the particle size of the calcium carbonate ultrafine powder. The obtained calcium carbonate slurry does not have the defects of precipitation, coarse particles and the like in the long-time storage process. Through coating application and coating appearance detection of the stone paper, the defects of paper powder falling, particles and the like which influence printing are avoided.

Description

Stone paper, calcium carbonate slurry and preparation method thereof

Technical Field

The invention relates to the technical field of stone paper production, in particular to stone paper, calcium carbonate slurry and a preparation method thereof.

Background

The stone paper is a novel material between paper and plastic, can replace the traditional partial functional paper and professional paper, and can also replace the traditional most plastic packing materials. The method has the characteristics of low cost and controllable degradation, can save a large amount of cost for users, and does not produce pollution.

The stone paper is printed and packaged to enter the market, the printing effect is necessarily involved, and indexes such as ink absorbability and the like meet requirements. The stone paper substrate has low surface tension, low adhesion fastness of direct printing ink and poor printing effect. In order to improve the printing effect, the stone paper base material is subjected to corona treatment, so that the surface tension is improved, and the adhesive force of the coating is increased. As calcium carbonate slurry for coating stone paper, the calcium carbonate slurry is used as a pigment filler and film-forming substances such as adhesives and the like in the whole coating treatment system, is uniformly stirred and mixed, and is coated on a stone paper substrate to play a good role in protection and good absorption with ink. The existing heavy calcium slurry in the market has the defects of high solid content, high viscosity and uneven dispersion in different degrees. And high requirements are put forward on the fluidity of the coating treatment of the stone paper and the appearance quality of the coating. The fluidity and dispersibility indexes of the calcium carbonate slurry for coating the stone paper become a technical barrier for restricting the production of the stone paper.

Based on this, the prior art still remains to be improved.

Disclosure of Invention

The invention aims to provide stone paper, calcium carbonate slurry and a preparation method thereof, and aims to solve the technical problem that the calcium carbonate slurry for coating stone paper in the prior art is poor in flowability and dispersibility.

In order to solve the above problems, in one aspect, the present invention provides a method for preparing a ground calcium carbonate slurry for stone paper coating, which adopts the following technical scheme:

a preparation method of ground calcium carbonate slurry for stone paper coating comprises the following steps

Step one, preparing calcium carbonate ultrafine powder with the particle size not more than 6 mu m;

step two, mixing, shearing and dispersing the calcium carbonate ultrafine powder in a stirring tank to obtain initial slurry, wherein the stirring speed is 800-1000 rpm/min;

and step three, grinding the initial slurry by a sand mill to obtain calcium carbonate slurry.

Further, in the first step, the preparation of the calcium carbonate ultrafine powder comprises: after the calcium carbonate raw material is ground by a dry method, the superfine powder meeting the requirement of the particle size is cut out after secondary classification.

Further, in the second step, after adding pure water and a dispersing agent into the stirring tank, adding the calcium carbonate ultrafine powder for mixing, shearing and dispersing.

Further, in the second step, the adding amount of the pure water, the dispersing agent and the calcium carbonate ultrafine powder is calculated according to the solid content of the oven-dried pigment of 70-75 percent; the addition amount of the dispersant is 0.9-1.2% of the mass of the calcium carbonate ultrafine powder. Considering the flowing property of the prepared heavy calcium slurry, the design range of the solid content is generally 70-75 percent; the solid content is too low, the slurry concentration is low, grinding media in the system collide with each other and are abraded, the grinding loss is large, and the grinding efficiency is low; the solid content is too large, the fluidity of system slurry is poor, and the system blockage phenomenon exists; in summary, a solids content of 70% is relatively reasonable. The addition amount of the calcium carbonate and the dispersant is 0.9 to 1.2 percent of the mass of the calcium carbonate ultrafine powder.

Further, the dispersant comprises sodium polyacrylate; the molecular weight of the sodium polyacrylate is 2000-.

Furthermore, in the third step, the particle size of the calcium carbonate slurry particles is D50 of 0.3-0.7 μm, D98 is less than or equal to 3 μm, 2 μm is more than or equal to 95%, and the whiteness is more than or equal to 93%.

Further, in step three, the step of grinding the initial slurry through a sand mill comprises:

2 sand mills connected in series sequentially carry out two procedures of coarse grinding and fine grinding, and the proportion of the dispersant added in the two grinding stages is 0.15-0.3 percent and 0.15-0.3 percent of the solid content of the oven-dried pigment respectively. The addition of the dispersing agent is too little, the mutual agglomeration tendency of the slurry is serious, and the dispersion uniformity is poor; excessive dispersant is added, so that a dispersed stable balance system is damaged, and secondary agglomeration is easy to occur.

On the other hand, the embodiment of the invention also discloses a preparation method of the stone paper, which comprises the preparation method of the ground calcium carbonate slurry for coating the stone paper.

The embodiment of the invention also discloses a ground calcium carbonate slurry for coating stone paper, wherein the particle size of the particles is D50 of 0.3-0.7 mu m, D98 is less than or equal to 3 mu m, 2 mu m is more than or equal to 95 percent, and the whiteness is more than or equal to 93 percent; the particle size distribution curve is a bimodal normal distribution.

The embodiment of the invention also discloses stone paper which is prepared by coating the calcium carbonate slurry.

The invention has the beneficial effects that:

the invention realizes the accurate control of the fineness, the viscosity and the like of the particle size of the ground slurry by accurately controlling the stirring speed and the particle size of the calcium carbonate ultrafine powder. The obtained calcium carbonate slurry does not have the adverse defects of precipitation, coarse particles and the like in the long-time storage process. Through coating application and coating appearance detection of the stone paper, the defects of paper powder falling, particles and the like which influence printing are avoided. The particle size of the ground calcium carbonate slurry provided by the invention can be accurately controlled, the dispersion uniformity is good, the viscosity is controllable, the fluidity is good, and the requirements of a stone paper coating treatment process can be met.

Drawings

FIG. 1 is a flow chart of an embodiment of the present invention.

Fig. 2 is a particle size distribution curve diagram of a normal distribution of calcium carbonate slurry obtained in an embodiment of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.

As shown in figure 1, the embodiment of the invention discloses a ground calcium carbonate slurry for coating stone paper and a preparation method thereof, which comprises the following steps

mixing, shearing and dispersing the calcium carbonate ultrafine powder in a stirring tank to obtain initial slurry, wherein the stirring speed is 800 rpm/min;

In the embodiment, the particle size fineness, the viscosity and the like of the grinding slurry are accurately controlled by accurately controlling the stirring speed and the particle size of the calcium carbonate ultrafine powder. The obtained calcium carbonate slurry does not have the adverse defects of precipitation, coarse particles and the like in the long-time storage process.

In the ground calcium carbonate slurry for stone paper coating and the preparation method thereof disclosed in some preferred embodiments of the present invention, on the basis of the above embodiments, in the first step, the preparation of the calcium carbonate micropowder comprises: after the calcium carbonate raw material is ground by a dry method, the superfine powder meeting the requirement of the particle size is cut out after secondary classification.

And step two, adding pure water and a dispersing agent into the stirring tank, and then adding the calcium carbonate ultrafine powder for mixing, shearing and dispersing. And mixing, shearing and dispersing by a dispersion disc attached to the stirring rotor to obtain uniformly dispersed initial slurry. The stirring speed of the stirring tank can be controlled at 800-.

In the second step, the adding amount of the pure water, the dispersing agent and the calcium carbonate ultrafine powder is calculated according to the solid content of oven-dried pigment of 70-75 percent (the solid content in the whole water-based paint system is 70-75 percent); the addition amount of the dispersant is 0.9-1.2% of the mass of the calcium carbonate ultrafine powder. The main component of the dispersant can be a sodium polyacrylate high molecular substance; the molecular weight of the sodium polyacrylate is preferably 2000-.

In step three, the step of grinding the initial slurry by a sand mill comprises the following steps:

2 sand mills connected in series sequentially carry out two procedures of coarse grinding and fine grinding, and the proportion of the dispersant added in the two grinding stages is 0.3 percent and 0.3 percent of the solid content of the oven-dried pigment respectively. During grinding, the solid content of the slurry is 65-66%, the viscosity of the slurry after grinding is less than or equal to 200cps, and the PH is controlled to be 9.0-9.5. Wherein, during coarse grinding, the rotating speed of the main motor is controlled to be 1000-; during fine grinding, the rotating speed of the main motor is controlled to be 700-;

the particle size of the obtained calcium carbonate slurry is 0.3-0.7 mu m of D50, less than or equal to 3 mu m of D98, more than or equal to 95 percent of 2 mu m and more than or equal to 93 percent of whiteness; the particle size distribution curve is a bimodal normal distribution.

According to the invention, the dispersant is added in the grinding of the calcium carbonate slurry, and the electrolyte is adsorbed on the surface of the powder particles by generating, so that good adsorption is formed. Reduces or prevents particle flocculation, enables pigment particles, namely calcium carbonate particles to be stably suspended in a liquid medium, maintains the dispersed state in the later production process and maintains the stability of the slurry. By controlling the usage amount of the dispersing agent, the dispersing agent is added in batches according to the grinding process requirements of different stages of mixing, dispersing, coarse grinding and fine grinding, so that good adsorption of the new fracture surface of the grinding powder is ensured in different grinding stages, and the defects of agglomeration or poor dispersion are prevented. Through controlling a main motor of the grinding machine, the feeding amount is reasonably adjusted, good collision and shearing between the grinding slurry and the grinding medium are ensured, the grinding efficiency is improved, and the particle size and fineness of the powder are accurately controlled within a required range.

Examples

Grinding calcium carbonate by a dry method, and then cutting the superfine powder to obtain superfine powder with the maximum particle size of not more than 6 microns, namely calcium carbonate superfine powder; adding water and a dispersing agent into a stirring tank according to the designed slurry concentration, slowly adding calcium carbonate ultrafine powder after uniformly stirring, keeping a stirring rotor in the stirring tank to operate at a high speed, enabling the added powder to have a good wetting and dispersing effect, and stirring for 30min to obtain a preliminary pre-dispersing effect. And starting a shearing pump to ensure that the uniformly mixed slurry is further well sheared and dispersed, and simultaneously operating a stirring rotor for 45-60 min. The slurry with good shearing dispersion firstly enters the grinding stage of the coarse grinding process, 0.15-0.3% of dispersing agent is added according to grinding viscosity and particle size indexes, and the slurry enters the final fine grinding process after reaching the required particle size (the viscosity is less than or equal to 100 cps; 2 mu m%: 80-85%), wherein 0.15-0.3% of dispersing agent is added according to the grinding viscosity and particle size indexes as described above. The parameters of the obtained calcium carbonate slurry are shown in tables 1, 2 and 3, and the particle size distribution curve of the normal distribution of the calcium carbonate slurry is shown in fig. 2. The grain diameter D98 of the obtained slurry grains is less than or equal to 3 mu m, the grain diameter D50 is 0.3-0.7 mu m, the 2 mu m is more than or equal to 95 percent, and the whiteness is more than or equal to 93 percent; through the field viscosity test of the slurry, the viscosity is less than or equal to 100cps, and the PH: and 9.2, the coating meets the use requirement of stone paper coating. Standing the slurry, and testing the viscosity for 24h to ensure that the viscosity of the slurry is stable; sampling to test the settling property, basically presenting a suspension stable state, inserting a stirring rod into the heavy calcium carbonate slurry, and when the slurry is lifted, the color and consistency of the adhered slurry are uniform without precipitation.

TABLE 1

TABLE 2

Particle size of mum	Interval%	Cumulative%	Particle size of mum	Interval%	Cumulative%	Particle size of mum	Interval%	Cumulative%
									0.020-0.024	0.15	0.15	0.911-1.161	9.32	80.3	44.04-56.13	0	100
0.024-0.030	3.77	3.92	1.161-1.479	8.67	88.97	56.13-71.52	0	100
									0.030-0.039	11.15	15.07	1.479-1.885	6.44	95.41	71.52-91.14	0	100
0.039-0.049	12.88	27.95	1.885-2.403	3.47	98.88	91.14-116.1	0	100
									0.049-0.063	8.73	36.68	2.403-3.062	1.05	99.93	116.1-147.9	0	100
0.063-0.080	4.42	41.1	3.062-3.902	0.07	100	147.9-188.5	0	100
									0.080-0.102	1.92	43.02	3.902-4.972	0	100	188.5-240.3	0	100
0.102-0.131	0.8	43.82	4.972-6.336	0	100	240.3-306.2	0	100
									0.131-0.167	0.29	44.11	6.336-8.074	0	100	306.2-390.2	0	100
0.167-0.212	0.03	44.14	8.074-10.28	0	100	390.2-497.2	0	100
									0.212-0.271	0.05	44.19	10.28-13.11	0	100	497.2-633.6	0	100
0.271-0.345	0.45	44.64	13.11-16.70	0	100	633.6-807.4	0	100
									0.345-0.440	2.32	46.96	16.70-21.28	0	100	807.4-1028	0	100
0.440-0.561	5.98	52.94	21.28-27.12	0	100	1028-1311	0	100
									0.561-0.715	8.77	61.71	27.12-34.56	0	100	1311-1670	0	100
0.715-0.911	9.27	70.98	34.56-44.04	0	100	1670-2000	0	100

TABLE 3

The stone paper prepared by coating the calcium carbonate slurry has good adhesion effect between a coating and a base material, and a tensile machine is adopted to test the indexes of stripping and adhesion, wherein the stripping index is more than or equal to 450gf, and the adhesion is less than or equal to 100, so that the stone paper meets the printing use requirement; the paper product after printing has good ink absorptivity, good ink glossiness, moderate ink drying speed and no printing back sticky dirty condition; the phenomenon of hair and powder falling is avoided, the bonding force between the ink and the base material is smaller than that between the coating and the base material, and the possibility that the coating is pulled up is avoided.

The stone paper prepared by adopting the calcium carbonate slurry has the advantages that the calcium bicarbonate slurry is uniformly dispersed, the film forming substance has carboxyl groups and hydrophilic groups, the water layers around the particles can be adsorbed, the film forming substance is negative charges and is the same as the charges of the particles in the coating, the flocculation is not easy, the stability is improved, the film forming substance is uniformly coated on the surface of the pigment and filler, the slurry and the film forming substance have good compatibility, and the storage and dispersion uniformity is good.

According to some embodiments of the invention, the particle size fineness and viscosity of the ground slurry are accurately controlled by controlling the stirring speed to be 800-1000rpm/min, the slurry concentration, the stirring time to be 45-60 min, the main motor current of the sand mill to be 40-50A, the total dispersant proportion to be 1.2% and other parameters. The obtained calcium carbonate slurry has good stability, and does not have the adverse defects of precipitation, particle coarsening and the like in the long-time storage process. Through coating application and coating appearance detection of the stone paper, the defects of paper powder falling, particles and the like which influence printing are avoided. The dispersion uniformity is good, the viscosity is controllable, the fluidity is good, and the requirements of a stone paper coating treatment process can be met.

The above embodiments are only for illustrating the invention and are not to be construed as limiting the invention, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention, therefore, all equivalent technical solutions also belong to the scope of the invention, and the scope of the invention is defined by the claims.

Claims

1. The preparation method of the ground calcium carbonate slurry for stone paper coating is characterized by comprising the following steps

2. The method for preparing ground calcium carbonate slurry for stone paper coating as claimed in claim 1, wherein in step one, the preparation of calcium carbonate micropowder comprises: after the calcium carbonate raw material is ground by a dry method, the superfine powder meeting the requirement of the particle size is cut out after secondary classification.

3. The method for preparing ground calcium carbonate slurry for stone paper coating as claimed in claim 1, wherein in the second step, after adding pure water and a dispersant into a stirring tank, the calcium carbonate ultra-fine powder is added for mixing, shearing and dispersing.

4. The method for preparing the ground calcium carbonate slurry for stone paper coating as claimed in claim 3, wherein in the second step, the amounts of pure water, dispersant and calcium carbonate micropowder added are calculated in accordance with a solid content of 70-75% of oven dried calcium carbonate micropowder.

5. The method for preparing the ground calcium carbonate slurry for stone paper coating as claimed in claim 3, wherein the dispersant comprises sodium polyacrylate; the molecular weight of the sodium polyacrylate is 2000-.

6. The method for preparing the ground calcium carbonate slurry for coating stone paper as claimed in claim 1, wherein in the third step, the particle size of the calcium carbonate slurry is D50:0.3-0.7 μm, D98 is not more than 3 μm, 2 μm is not less than 95%, and the whiteness is not less than 93%.

7. The method for preparing the ground calcium carbonate slurry for stone paper coating according to claim 1, wherein in step three, the step of grinding the initial slurry by a sand mill comprises the following steps:

2 sand mills connected in series sequentially carry out two procedures of coarse grinding and fine grinding, and the proportion of the dispersant added in the two grinding stages is 0.15-0.3 percent and 0.15-0.3 percent of the solid content of the absolute dry calcium carbonate pigment respectively.

8. A method for preparing stone paper, which is characterized by comprising the method for preparing the ground calcium carbonate slurry for coating stone paper as claimed in any one of claims 1 to 7.

9. The ground calcium carbonate slurry for stone paper coating is characterized in that the particle size of the particles is 0.3-0.7 mu m of D50, the particle size of D98 is less than or equal to 3 mu m, the particle size of 2 mu m is more than or equal to 95 percent, and the whiteness is more than or equal to 93 percent; the particle size distribution curve is a bimodal normal distribution.

10. Stone paper, characterized in that it is prepared by coating the calcium carbonate slurry according to claim 9.