CN115570863B - Easy-to-print PP synthetic paper and preparation method thereof - Google Patents

Abstract

The invention provides an easy-to-print PP synthetic paper and a preparation method thereof. The easy-to-print PP synthetic paper comprises an upper surface layer, a base material layer and a lower surface layer which are sequentially laminated, wherein at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler, and micropores are formed in at least one of the upper surface layer and the lower surface layer. The synthetic paper has better ink absorption and ink fixation performance on the basis of not adding a printing coating.

Description

Easy-to-print PP synthetic paper and preparation method thereof

Technical Field

The invention belongs to the technical field of printing paper, and in particular relates to an easy-to-print PP synthetic paper and a preparation method thereof.

Background Art

PP synthetic paper is made of thermoplastic polypropylene and inorganic particles such as calcium carbonate and titanium dioxide through double-drawing, blow molding, cast or calendering processes. Compared with traditional paper, it has the disadvantages of poor ink absorption and ink fixation. In order to achieve good printing effects, a printing coating is generally added to the surface of PP synthetic paper to improve the wettability and adsorption of ink, so as to achieve efficient ink absorption and ink fixation. However, the addition of a coating process will reduce the economic efficiency of PP synthetic paper; and due to the high content of inorganic particles in the coating, there is a risk of powder loss during the printing process.

Summary of the invention

The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, one object of the present invention is to provide an easy-to-print PP synthetic paper and a preparation method thereof. The synthetic paper has good ink absorption and ink fixing performance without adding a printing coating.

In one aspect of the present invention, the present invention provides an easy-to-print PP synthetic paper. According to an embodiment of the present invention, the easy-to-print PP synthetic paper comprises an upper surface layer, a substrate layer and a lower surface layer stacked in sequence, at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler, and at least one of the upper surface layer and the lower surface layer is formed with micropores.

According to the embodiment of the present invention, the easy-to-print PP synthetic paper comprises an upper surface layer, a substrate layer and a lower surface layer which are stacked in sequence, wherein at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler. Since the tough polyolefin resin contains more amorphous regions with low density and low rigidity, on the one hand, it can make charged particles easier to penetrate during corona, and on the other hand, it is easier to be roughened by high-voltage and high-frequency electric spark impact, so the surface energy and roughness are easier to reach a suitable range, which can improve the corona effect of the synthetic paper, that is, by improving the surface energy and roughness of the synthetic paper surface layer, the wettability and infiltration of the ink are improved, thereby providing basic conditions for the ink absorption and fixation of the porous inorganic filler. At the same time, the porous inorganic filler has a high specific surface area and a good fixation effect on the ink, and at least one of the upper surface layer and the lower surface layer is formed with micropores, and the presence of the micropores further improves the ink absorption and fixation performance of the porous inorganic filler. Therefore, the synthetic paper has good ink absorption and fixation performance without adding a printing coating.

In addition, the easy-to-print PP synthetic paper according to the above embodiment of the present invention may also have the following technical features:

In some embodiments of the present invention, at least one of the upper surface layer and the lower surface layer further comprises at least one of ultrafine calcium carbonate, a dispersant, an antioxidant and an ultraviolet absorber. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, based on the total weight of the upper surface layer or the lower surface layer, the tough polyolefin resin accounts for 40 to 60 parts by weight, the ultrafine calcium carbonate accounts for 20 to 30 parts by weight, the porous inorganic filler accounts for 20 to 30 parts by weight, the dispersant accounts for 0.5 to 1 part by weight, the antioxidant accounts for 0.05 to 0.1 part by weight, and the ultraviolet absorber accounts for 0.05 to 0.1 part by weight. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the flexural modulus of the tough polyolefin resin is 0.065 to 1.3 GPa. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the particle size of the porous inorganic filler is 0.02-1.0 μm. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the specific surface area of the porous inorganic filler is 10-60 m ² /g. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the particle size of the ultrafine calcium carbonate is 0.02-0.1 μm. Thus, synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the tough polyolefin resin includes at least one of random polypropylene (PPR), ethylene propylene copolymer (POE), low density polyethylene (LDPE) and linear low density polyethylene, preferably linear low density polyethylene. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the porous inorganic filler includes at least one of diatomaceous earth, white carbon black and carbon black, preferably white carbon black. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the ultrafine calcium carbonate includes light calcium carbonate. Thus, synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the dispersant includes at least one of zinc stearate and calcium stearate.

In some embodiments of the present invention, the antioxidant comprises a hindered phenol antioxidant.

In some embodiments of the present invention, the ultraviolet absorber includes at least one of UV-234, UV-326 and UV-900.

In some embodiments of the present invention, the density of the linear low-density polyethylene is in the range of 0.91 to 0.93 g/cm ³ , preferably 0.91 to 0.92 g/cm ³ . Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the particle size of the white carbon black is 0.02-0.1 μm. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the particle size of the light calcium carbonate is 0.02-0.1 μm. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, based on the total weight of the substrate layer, the substrate layer includes: 60 to 80 parts by weight of polypropylene resin, 10 to 20 parts by weight of ultrafine calcium carbonate, 10 to 20 parts by weight of nano titanium dioxide, and 0.6 to 1.3 parts by weight of processing aids.

In some embodiments of the present invention, the thickness ratio of the upper surface layer or the lower surface layer to the substrate layer is 1:(6-8). Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In some embodiments of the present invention, the total thickness of the upper surface layer, the lower surface layer and the substrate layer is 0.1-0.3 mm. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained.

In another aspect of the present invention, the present invention provides a method for preparing the above-mentioned easy-to-print PP synthetic paper. According to an embodiment of the present invention, the method comprises:

(1) stacking an upper surface layer, a substrate layer and a lower surface layer, wherein at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler, so as to obtain a three-layer structure thick film;

(2) The three-layer thick film is heated, longitudinally stretched, and then corona-treated to obtain an easily printable PP synthetic paper.

Therefore, by heating the three-layer thick film and then stretching it longitudinally, micropores are formed on the upper and lower surface layers. The presence of the micropores further improves the ink absorption and ink fixing properties of the porous inorganic filler. This method can be used to prepare synthetic paper with better ink absorption and ink fixing properties.

In addition, the method for preparing easy-to-print PP synthetic paper according to the above embodiment of the present invention may also have the following technical features:

In some embodiments of the present invention, in step (2), the longitudinal stretching ratio is 1.5 to 2.

Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

FIG. 1 is a structural diagram of an easy-to-print PP synthetic paper according to an embodiment of the present invention.

DETAILED DESCRIPTION

The embodiments of the present invention are described in detail below, which are intended to explain the present invention but should not be construed as limiting the present invention.

In one aspect of the present invention, the present invention provides an easy-to-print PP synthetic paper. According to an embodiment of the present invention, referring to FIG1 , the easy-to-print PP synthetic paper includes an upper surface layer 100, a substrate layer 200, and a lower surface layer 300 stacked in sequence, at least one of the upper surface layer 100 and the lower surface layer 300 includes a tough polyolefin resin and a porous inorganic filler, and at least one of the upper surface layer 100 and the lower surface layer 300 is formed with micropores.

According to an embodiment of the present invention, at least one of the upper surface layer 100 and the lower surface layer 300 includes a tough polyolefin resin and a porous inorganic filler. Since the tough polyolefin resin contains more amorphous regions with low density and low rigidity, on the one hand, it can make charged particles easier to penetrate during corona, and on the other hand, it is easier to be roughened by high-voltage and high-frequency electric sparks. Therefore, the surface energy and roughness are easier to reach a suitable range, which can improve the corona effect of the synthetic paper, that is, by improving the surface energy and roughness of the synthetic paper surface, the wettability and infiltration of the ink are improved, thereby providing basic conditions for the ink absorption and fixation of the porous inorganic filler. At the same time, the porous inorganic filler has a high specific surface area and a good fixation effect on the ink, and at least one of the upper surface layer 100 and the lower surface layer 300 is formed with micropores, and the presence of the micropores further improves the ink absorption and fixation performance of the porous inorganic filler. Therefore, the synthetic paper has good ink absorption and fixation performance without adding a printing coating. It is understandable to those skilled in the art that both the upper surface layer 100 and the lower surface layer 300 are formed with micropores, and the resulting synthetic paper has better performance, which will not be elaborated here.

According to an embodiment of the present invention, the bending modulus of the tough polyolefin resin is 0.065 to 1.3 GPa. The inventors found that when the bending modulus of the polyolefin resin is in the range of 0.065 to 1.3 GPa, there are more amorphous regions with low density and low rigidity in the resin, which can make charged particles easier to penetrate during corona on the one hand, and on the other hand, it is easier to be roughened by high-voltage and high-frequency electric spark impact, so the surface energy and roughness are easier to reach a suitable range, showing a good corona effect. Thus, synthetic paper with good ink absorption and ink fixing properties can be obtained. It can be understood by those skilled in the art that the tough polyolefin resin is a conventional resin in the field. On the basis of meeting the above conditions, those skilled in the art can select the type of specific tough polyolefin resin according to actual conditions, for example, the tough polyolefin resin includes at least one of random polypropylene, ethylene propylene copolymer, low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), preferably linear low-density polyethylene. Furthermore, the density of the linear low-density polyethylene is in the range of 0.91 to 0.93 g/cm ³ , preferably 0.91 to 0.92 g/cm ^3. The inventors have found that when the density of the linear low-density polyethylene is relatively low, the comonomer concentration is high and the short-chain density is higher. The oxidation of the polymer during the corona process tends to occur at the weak branches of the molecular structure. Therefore, the linear low-density polyethylene with a lower density has a better corona effect and better ink wettability. Therefore, the linear low-density polyethylene with a density range of 0.91 to 0.93 g/cm ³ is used in this application, which can have a better corona effect. Specifically, the melt index (MFI) of the above-mentioned linear low-density polyethylene is 1.0 to 5.0 g/10 min (2.16 kg, 190°C), and commercially available LLDPE can be selected, such as ExxonMobil's Exceed4518 (MFI 4.5 g/10 min; density 0.918 g/cm ³ ), 218BJ (MFI 2.0 g/10 min; density 0.918 g/cm ³ ) of Dow Chemical, USA 4601 (MFI 1.0 g/10 min; density 0.912 g/cm ³ ) of Dow Chemical.

According to an embodiment of the present invention, the particle size of the porous inorganic filler is 0.02 to 1.0 μm. The inventors found that if the particle size of the porous inorganic filler is too large, the packing density of the particles will be reduced, thereby affecting the adsorption uniformity of the ink, thereby affecting the uniformity of image printing; if the particle size of the porous inorganic filler is too small, the dispersion effect is poor, and it is easy to aggregate into large particles, which will also affect the uniformity of image printing. Therefore, the present application adopts a porous inorganic filler with a particle size of 0.02 to 1.0 μm, and a synthetic paper with good ink absorption and ink fixing properties can be obtained. It should be noted that the porous inorganic filler is a conventional filler in the field, and those skilled in the art can select it according to actual conditions. For example, the porous inorganic filler includes at least one of diatomaceous earth, white carbon black and carbon black, preferably white carbon black, and more preferably hydrophilic white carbon black, which can make white carbon black easy to separate from the matrix resin during the stretching process of the synthetic paper, so that micropores can be obtained by a lower stretching ratio.

According to an embodiment of the present invention, the specific surface area of the porous inorganic filler is 10 to 60 m ² /g. The inventors have found that if the specific surface area of the porous inorganic filler is too small, the ink absorption is poor; if the specific surface area of the porous inorganic filler is too high, it is difficult to disperse in the resin and the processability is deteriorated. Therefore, the present application selects a porous inorganic filler with a specific surface area of 10 to 60 m ² /g, and a synthetic paper with good ink absorption and ink fixing performance can be obtained.

According to an embodiment of the present invention, at least one of the upper surface layer and the lower surface layer also includes at least one of ultrafine calcium carbonate, a dispersant, an antioxidant and an ultraviolet absorber. It can be understood by those skilled in the art that the upper surface layer and the lower surface layer both include ultrafine calcium carbonate, a dispersant, an antioxidant and an ultraviolet absorber, and the performance of the obtained synthetic paper is better, which will not be repeated here. It should be noted that the dispersant, the antioxidant and the ultraviolet absorber are conventional materials in the field, and those skilled in the art can select them according to actual conditions. For example, the dispersant includes at least one of zinc stearate and calcium stearate, the antioxidant includes a hindered phenol antioxidant, and the ultraviolet absorber includes at least one of UV-234, UV-326 and UV-900.

According to an embodiment of the present invention, the particle size of ultrafine calcium carbonate is 0.02 to 0.1 μm. The inventors found that if the particle size of ultrafine calcium carbonate is too small, it is not easy to disperse in the resin, the ink absorption is poor, and it will also aggregate in large quantities, affecting the uniformity of image printing; if the particle size of ultrafine calcium carbonate is too large, it is easy to agglomerate and affect the uniformity of image printing, and the processability deteriorates. Therefore, the present application adopts ultrafine calcium carbonate with a particle size of 0.02 to 0.1 μm, and synthetic paper with good ink absorption and ink fixing properties can be obtained. It can be understood by those skilled in the art that, while meeting the above-mentioned particle size requirements, those skilled in the art can select the specific type of ultrafine calcium carbonate according to actual conditions, for example, ultrafine calcium carbonate includes light calcium carbonate, and further, the particle size of light calcium carbonate is 0.02 to 0.1 μm, and the whiteness is not less than 95%.

According to an embodiment of the present invention, based on the total mass of the upper surface layer or the lower surface layer, the tough polyolefin resin accounts for 40 to 60 parts by weight, the ultrafine calcium carbonate accounts for 20 to 30 parts by weight, the porous inorganic filler accounts for 20 to 30 parts by weight, the dispersant accounts for 0.5 to 1 part by weight, the antioxidant accounts for 0.05 to 0.1 part by weight, and the ultraviolet absorber accounts for 0.05 to 0.1 part by weight. The inventors found that the proportion of tough polyolefin resin is within 40-60 parts by weight, which can not only ensure that the porous inorganic filler has a good dispersion effect, thereby avoiding the uniformity of the micropore size after the inorganic particles agglomerate, and then affecting the uniformity of the printed image, but also ensure a certain micropore density and provide conditions for high ink fixation; the proportion of porous inorganic filler is within 20-30 parts by weight, on the one hand, it can ensure that the surface layer has a high micropore density, thereby having high ink fixation; on the other hand, the porous inorganic filler has a good dispersion effect, avoiding the uniformity of the micropore size after the inorganic particles agglomerate; the proportion of ultrafine calcium carbonate is within 20-30 parts by weight, which can not only reduce material costs and improve economy, but also can use the high adsorption of calcium carbonate to ensure that the ink fixation ability does not decay. Therefore, by using the upper surface layer or lower surface layer of the above-mentioned component formula, a synthetic paper with good ink absorption and ink fixation performance can be obtained.

According to an embodiment of the present invention, based on the total weight of the substrate layer, the substrate layer includes: 60 to 80 parts by weight of polypropylene resin, 10 to 20 parts by weight of ultrafine calcium carbonate, 10 to 20 parts by weight of nano titanium dioxide, and 0.6 to 1.3 parts by weight of a processing aid. Thus, a synthetic paper with good ink absorption and ink fixing properties can be obtained. It should be noted that polypropylene resin, ultrafine calcium carbonate, nano titanium dioxide and processing aids are conventional materials in the art, and those skilled in the art can select them according to actual conditions. For example, polypropylene resin includes homopolypropylene, and the melt index of homopolypropylene is 4-7g/10min (2.16kg, 230°C); commercially available products can be directly selected, such as C1007 (MFI 7.0g/10min) of Shanghai Secco, YC37F (MFI 6.0g/10min) of Liaoning Huajin, and J440 (MFI 4.0g/10min) of Korea Hyosung; ultrafine calcium carbonate includes light calcium carbonate, nano titanium dioxide includes rutile nano titanium dioxide, and the particle size range is 0.1-0.3μm; processing aids include dispersants, antioxidants and ultraviolet absorbers.

According to an embodiment of the present invention, the thickness ratio of the upper surface layer or the lower surface layer to the substrate layer is 1:(6-8). The inventors have found that if the thickness ratio of the upper surface layer or the lower surface layer to the substrate layer is too large, the processing stability is poor; if the thickness ratio of the upper surface layer or the lower surface layer to the substrate layer is too small, it is easy to cause cost increase. Therefore, by adopting the thickness ratio of the upper surface layer or the lower surface layer to the substrate layer of the present application of 1:(6-8), a synthetic paper that can be stably produced, has good economic efficiency, and has good ink absorption and ink fixing properties can be obtained. Furthermore, the total thickness of the upper surface layer, the lower surface layer and the substrate layer is 0.1-0.3 mm, so the production has high economic efficiency.

In another aspect of the present invention, the present invention provides a method for preparing the above-mentioned easy-to-print PP synthetic paper. According to an embodiment of the present invention, the method comprises:

S100: Lay the upper surface layer, the base material layer and the lower surface layer in layers

In this step, the upper surface layer, the substrate layer and the lower surface layer are stacked, wherein at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler. Since the tough polyolefin resin contains more amorphous regions with low density and low rigidity, on the one hand, it can make the charged particles easier to penetrate during corona, and on the other hand, it is easier to be roughened by high-voltage and high-frequency electric spark impact, so the surface energy and roughness are easier to reach a suitable range, which can improve the corona effect of synthetic paper, that is, by improving the surface energy and roughness of the surface layer of synthetic paper, the wettability and infiltration of ink are improved, thereby providing basic conditions for the ink absorption and fixation of porous inorganic fillers, and at the same time, the porous inorganic fillers have a good fixing effect on the ink due to their high porosity and high specific surface area. It should be noted that the stacking of the upper surface layer, the substrate layer and the lower surface layer in this step is not a simple stacking. It can be understood by those skilled in the art that the granulation extrusion casting film-forming process is commonly used in this field to granulate and extrude the materials of the upper surface layer, the substrate layer and the lower surface layer and tightly integrate them into a three-layer thick film.

S200: Heating the three-layer thick film, then longitudinally stretching it and corona treating it

In this step, the three-layer thick film is heated and then longitudinally stretched for corona treatment, so that micropores are formed on the upper and lower surface layers. The presence of the micropores further improves the ink absorption and ink fixing properties of the porous inorganic filler.

According to an embodiment of the present invention, the longitudinal stretching ratio is 1.5 to 2. The inventors found that if the longitudinal stretching ratio is too small, the pores are too small, affecting the permeability of the ink; if the longitudinal stretching ratio is too large, it will affect the thermal shrinkage of the synthetic paper, thereby affecting the printing accuracy. Therefore, by adopting the longitudinal stretching ratio of 1.5 to 2 of the present application, a synthetic paper with good ink absorption and accurate printing can be obtained.

Therefore, the method can be used to prepare synthetic paper with good ink absorption and ink fixing performance. It should be noted that the characteristics and advantages described for the above-mentioned easy-to-print PP synthetic paper are also applicable to this method, and will not be repeated here.

The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

The PP synthetic paper of Examples 1-7 and Comparative Examples 1-3 is prepared by three-layer co-extrusion casting and longitudinal stretching process, and the upper surface layer and the lower surface layer of the synthetic paper are the same. The specific steps are as follows:

(1) Vacuum dry the materials and stir and mix them to form granules

In this step, first, each material is dried at a vacuum degree of 0.05 MPa and a temperature of 80°C to 90°C for 8 hours, and then the formula materials of the upper surface layer, the lower surface layer and the substrate layer are added to a strong mixer for stirring and mixing, and then a twin-screw extruder is used for extrusion and pelletizing, and finally, the material is dried at a vacuum degree of 0.05 MPa and a temperature of 80°C to 90°C for 4 hours for use.

(2) The pelletized material is co-extruded and cast, then cooled and shaped.

In this step, the formulated materials of each layer after the above granulation are respectively conveyed to the single screw extruder of ABC three-layer co-extrusion, wherein the surface layer formulated materials are added to the A and C machines, and the substrate layer formulated materials are added to the B machine, and then melted and plasticized at 210°C and cast into a thick film through a T-type die (the melt of the A/C machine passes through the upper and lower flow channels, and the melt of the B machine passes through the middle flow channel), and cooled and shaped. The layer thickness ratio of each layer of the melt is adjusted by the melt pump and the distributor, and the total thickness is adjusted by the extrusion amount and the rotation speed of the shaping roller, so as to obtain a three-layer thick film with an upper surface layer/substrate layer/lower surface layer of a certain thickness and layer thickness ratio.

(3) Heating and longitudinally stretching the three-layer thick film and then corona

In this step, the cooled and shaped three-layer thick film is transported online to a longitudinal stretching machine, heated to 120-130°C by infrared rays, and then longitudinally stretched. Finally, the stretched sample is corona treated, trimmed and rolled to obtain an easy-to-print PP synthetic paper. The porous inorganic filler and the resin matrix are separated by the longitudinal low-magnification stretching process, so that micropores are formed on the surface of the synthetic paper, and the porous inorganic filler can efficiently absorb and fix ink.

Example 1

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 1 is shown in Table 1.

Table 1

Example 2

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 2 is shown in Table 2.

Table 2

Example 3

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 3 is shown in Table 3.

Table 3

Example 4

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 4 is shown in Table 4.

Table 4

Example 5

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 5 is shown in Table 5.

Table 5

F800EPS- ternary random copolymer polypropylene, produced by Sinopec.

Example 6

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 6 is shown in Table 6.

Table 6

POE/0201-Polyolefin elastomer, produced by ExxonMobil.

Example 7

The material formula of the upper surface layer/lower surface layer and the substrate layer of Example 7 is shown in Table 7.

Table 7

1C7A-Low-density polyethylene, produced by Sinopec.

Comparative Example 1

The difference between Comparative Example 1 and Example 4 is that the tough polyolefin resin in the formula of the upper surface layer/lower surface layer in Comparative Example 1 adopts polypropylene resin (homopolymer polypropylene/YC37F).

Comparative Example 2

The difference between Comparative Example 2 and Example 4 is that the porous inorganic filler in the upper surface layer/lower surface layer formula in Comparative Example 1 is replaced by ultrafine calcium carbonate (light calcium carbonate/particle size 0.08 μm).

Comparative Example 3

The difference between Comparative Example 3 and Example 4 is that no stretching process is adopted, that is, the stretching ratio is 0.

The performance test of the synthetic paper of Examples 1-7 and Comparative Examples 1-3 was conducted in the following manner:

(1) Printing uniformity

HP Indigo 3550 printing press was used to print N1, N2, N3, N4, N5, N6, N7, and N8 images defined in GB/T 18721-2002, and the image surface was visually inspected for deprinting and white spots. The printing uniformity was divided into four levels according to the integrity of the printed image: severe deprinting, partial deprinting, white spots, and no white spots.

(2) Image fastness

HP Indigo 3550 printing press was used to print cyan (100% C), magenta (100% M), yellow (100% Y), and black (100% K) images, and left for 2 hours; 3M SCOTCH 600P tape was used to stick to the images, compacted, and the tape was torn off to observe the ink shedding. According to the ink shedding situation, the image fastness was divided into three levels: complete shedding, partial shedding, and no shedding.

The synthetic paper performance tests of Examples 1-7 and Comparative Examples 1-3 are shown in Table 8.

Table 8

It can be seen from Table 8 that the printing uniformity and image fastness of the PP synthetic paper of Examples 1-7 are better than those of Comparative Examples 1-3, indicating that the PP synthetic paper of the present application has good ink absorption and ink fixing properties, and achieves good printing effect even without adding a printing layer.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims (8)

1. An easy-to-print PP synthetic paper, characterized in that it comprises an upper surface layer, a base material layer and a lower surface layer stacked in sequence, at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler, and at least one of the upper surface layer and the lower surface layer is formed with micropores; Based on the total weight of the upper surface layer or the lower surface layer, the tough polyolefin resin accounts for 40 to 60 parts by weight, the ultrafine calcium carbonate accounts for 20 to 30 parts by weight, the porous inorganic filler accounts for 20 to 30 parts by weight, the dispersant accounts for 0.5 to 1 part by weight, the antioxidant accounts for 0.05 to 0.1 part by weight, and the ultraviolet absorber accounts for 0.05 to 0.1 part by weight; The flexural modulus of the tough polyolefin resin is 0.065 to 1.3 GPa; The particle size of the porous inorganic filler is 0.02 to 1.0 μm; The specific surface area of the porous inorganic filler is 10 to 60 m ² /g; The particle size of the ultrafine calcium carbonate is 0.02 to 0.1 μm; The tough polyolefin resin includes at least one of random polypropylene, ethylene propylene copolymer, low density polyethylene and linear low density polyethylene; Based on the total weight of the substrate layer, the substrate layer comprises: 60 to 80 parts by weight of polypropylene resin, 10 to 20 parts by weight of ultrafine calcium carbonate, 10 to 20 parts by weight of nano titanium dioxide, and 0.6 to 1.3 parts by weight of a processing aid. 2. The easy-to-print PP synthetic paper according to claim 1, characterized in that the porous inorganic filler comprises at least one of diatomaceous earth, white carbon black and carbon black; the ultrafine calcium carbonate comprises light calcium carbonate; The dispersant includes at least one of zinc stearate and calcium stearate; The antioxidant includes a hindered phenol antioxidant; The ultraviolet absorber includes at least one of uv-234, uv-326 and uv-900. 3 . The easy-to-print PP synthetic paper according to claim 2 , wherein the density of the linear low-density polyethylene is in the range of 0.91 to 0.93 g/cm ³ . 4 . The easy-to-print PP synthetic paper according to claim 3 , wherein the density of the linear low-density polyethylene is in the range of 0.91 to 0.92 g/cm ³ . 5 . The easy-to-print PP synthetic paper according to claim 1 , wherein a thickness ratio of the upper surface layer or the lower surface layer to the substrate layer is 1:(6-8). 6 . The easy-to-print PP synthetic paper according to claim 1 , wherein the total thickness of the upper surface layer, the lower surface layer and the base material layer is 0.1 to 0.3 mm. 7. A method for preparing the easy-to-print PP synthetic paper according to any one of claims 1 to 6, comprising: (1) stacking an upper surface layer, a substrate layer and a lower surface layer, wherein at least one of the upper surface layer and the lower surface layer comprises a tough polyolefin resin and a porous inorganic filler, so as to obtain a three-layer structure thick film; (2) The three-layer thick film is heated, longitudinally stretched, and then corona-treated to obtain an easily printable PP synthetic paper. 8. The method according to claim 7, characterized in that in step (2), the longitudinal stretching ratio is 1.5 to 2.