Polypropylene synthetic paper and method of making and using same

Abstract

The present application relates to the paper base of image material, provide a kind of PP synthetic paper base and its preparation method and application.The PP synthetic paper base includes first emulsion receiving layer, first tonal adjustment layer, light barrier layer, second tonal adjustment layer and second emulsion receiving layer arranged in sequence;Wherein, light barrier layer is formed by including first polypropylene resin, light barrier agent, first filler and first auxiliary;First tonal adjustment layer and second tonal adjustment layer are independently formed by including second polypropylene resin, second filler and second auxiliary;First emulsion receiving layer and second emulsion receiving layer are independently formed by including polyethylene resin, polyolefin elastomer, titanium dioxide master batch, color master batch and third auxiliary, and polyethylene resin matrix includes linear low density polyethylene.Therefore, the synthetic paper base can realize with contact layer and have good coating firmness, and light barrier effect is good.

Description

TECHNICAL FIELD

[0001] The present application relates to a paper base of image material, and in particular to a PP synthetic paper base and a preparation method and application thereof. BACKGROUND

[0002] Image materials are divided into photosensitive materials, inkjet materials and printing materials, and can also be divided into single-sided image materials and double-sided image materials, and the requirements for the paper base are different. The single-sided image material has no requirement for the light resistance of the paper base, while the paper base of the double-sided image material must have a certain light resistance. The PP synthetic paper base is widely used in image materials due to its excellent light resistance, soft texture and low price. For example, the double-sided photosensitive paper uses the PP synthetic paper base to replace the traditional pulp base paper as the base material, which greatly improves the light resistance of the base material, simplifies the coating structure of the double-sided photosensitive paper, improves the whiteness and color tone of the photosensitive paper, and improves the overall photographic performance, so that it is more suitable for laser exposure. On the other hand, the softness of the double-sided photosensitive paper is more obvious, and the unique book hand feeling is more favored by the high-end personalized image market.

[0003] Although the current PP synthetic paper base has better light resistance than the traditional pulp base paper, when it is applied to double-sided photosensitive materials, inkjet materials or printing materials, there is still interference between the double-sided images. In addition, the PP synthetic paper base is usually a single-layer calendering product with polypropylene as the main raw material, and the adhesion of the coating layer of the contact layer is low. Therefore, a polymer layer with polyethylene as the main resin needs to be coated on both sides of the PP synthetic paper base. However, due to the low adhesion between polypropylene and the polymer with polyethylene as the main resin, the polymer layer and the base material layer are prone to delamination during the production and use of the double-sided photosensitive paper. SUMMARY

[0004] The present application aims to at least partially solve one of the problems in the related art.

[0005] According to one aspect of the present application, the present application provides a PP synthetic paper base, which comprises a first emulsion receiving layer, a first color tone adjusting layer, a light resistance layer, a second color tone adjusting layer and a second emulsion receiving layer which are sequentially stacked; wherein the light resistance layer is formed by light resistance layer raw materials comprising a first polypropylene resin, a light resistance agent, a first filler and a first auxiliary agent; the first color tone adjusting layer and the second color tone adjusting layer are each independently formed by color tone adjusting layer raw materials comprising a second polypropylene resin, a second filler and a second auxiliary agent; and the first emulsion receiving layer and the second emulsion receiving layer are each independently formed by emulsion receiving layer raw materials comprising a polyethylene resin, a polyolefin elastomer, a titanium dioxide master batch, a color master batch and a third auxiliary agent, and the polyethylene resin comprises a linear low density polyethylene. Thus, the synthetic paper base can have good coating adhesion with the contact layer and good light resistance effect.

[0006] According to an embodiment of the present application, the first polypropylene resin and the second polypropylene resin each independently comprises a homopolymer polypropylene.

[0007] According to an embodiment of the present application, the first filler and the second filler each independently comprises a rigidifying filler and / or a high hiding filler.

[0008] According to an embodiment of the present application, the first auxiliary agent, the second auxiliary agent and the third auxiliary agent each independently comprises an antioxidant and / or a dispersing agent.

[0009] According to an embodiment of the present application, the color masterbatch comprises at least one of a blue masterbatch, a magenta masterbatch and a fluorescent whitening masterbatch.

[0010] According to an embodiment of the present application, the light-blocking agent comprises a medium tone carbon black.

[0011] According to an embodiment of the present application, in the light-blocking layer raw material, the first polypropylene resin is 50-80 parts by mass, the light-blocking agent is 0.02-0.1 parts by mass, the first filler is 20-45 parts by mass, the first auxiliary agent is 0.55-1.1 parts by mass, and the total mass of the light-blocking layer raw material is 100 parts.

[0012] According to an embodiment of the present application, the first filler comprises a rigidifying filler and a high hiding filler, the rigidifying filler is 15-30 parts by mass, and the high hiding filler is 5-15 parts by mass.

[0013] According to an embodiment of the present application, the first auxiliary agent comprises an antioxidant and a dispersing agent, the dispersing agent is 0.5-1 parts by mass, and the antioxidant is 0.05-0.1 parts by mass.

[0014] According to an embodiment of the present application, in each of the tone adjusting layer raw materials, the second polypropylene resin is 40-70 parts by mass, the second filler is 30-55 parts by mass, and the second auxiliary agent is 0.55-1.1 parts by mass, and the total mass of each of the tone adjusting layer raw materials is 100 parts.

[0015] Further, the second filler comprises a rigidifying filler and a high hiding filler, the rigidifying filler is 15-30 parts by mass, and the high hiding filler is 15-25 parts by mass.

[0016] Further, the second auxiliary agent comprises an antioxidant and a dispersing agent, the dispersing agent is 0.5-1 parts by mass, and the antioxidant is 0.05-0.1 parts by mass.

[0017] According to the embodiment of the present application, in each of the emulsion receiving layer raw materials, the polyethylene resin is 50-70 parts by mass, the polyolefin elastomer is 10-15 parts by mass, the titanium dioxide master batch is 15-25 parts by mass, the color master batch is 3.5-6 parts by mass, and the third auxiliary agent is 0.55-1.1 parts by mass, and the total mass of each of the emulsion receiving layer raw materials is 100 parts.

[0018] Further, the color master batch includes a blue master batch, a magenta master batch, and a fluorescent whitening master batch, the blue master batch accounts for 2-3 parts, the magenta master batch accounts for 1-2 parts, and the fluorescent whitening master batch accounts for 0.5-1 part.

[0019] Further, the third auxiliary agent includes an antioxidant and a dispersant, the dispersant accounts for 0.5-1 part, and the antioxidant accounts for 0.05-0.1 part.

[0020] According to the embodiment of the present application, the rigidifying filler includes at least one of silicon dioxide, aluminum hydroxide, magnesium hydroxide, kaolin, barium sulfate, calcium carbonate, and talc.

[0021] According to the embodiment of the present application, the dispersant includes at least one of zinc stearate and calcium stearate.

[0022] According to the embodiment of the present application, the polyolefin elastomer includes at least one of an ethylene-α-olefin copolymer and a propylene-α-olefin copolymer.

[0023] According to the embodiment of the present application, the linear low-density polyethylene has a density of 0.91-0.93 g / cm 3 , and a melt index of 1.0-5.0 g / 10 min at 2.16 kg and 190°C.

[0024] According to the embodiment of the present application, the polyolefin elastomer has a melt index of 1.0-10.0 g / 10 min at 2.16 kg and 190°C.

[0025] According to the embodiment of the present application, the thickness ratio of the first emulsion receiving layer, the first color tone adjusting layer, the light-blocking layer, the second color tone adjusting layer, and the second emulsion receiving layer is 2:(5-6):(7-8):(5-6):2.

[0026] According to the embodiment of the present application, the PP synthetic paper base has a thickness of 0.18-0.3 mm.

[0027] According to another aspect of the present application, the present application provides a method for preparing the above-mentioned PP synthetic paper base, which comprises: feeding raw materials of each layer to a five-layer co-extrusion device; extruding the raw materials of each layer, and extruding products are cast onto a setting roller to form by the five-layer co-extrusion device. Thus, by designing a light-blocking layer between layers through a multi-layer co-extrusion technology, an emulsion receiving layer is arranged at the outermost side, and the PP synthetic paper base prepared by the method can realize good coating firmness with the contact layer and good light-blocking effect.

[0028] According to still another aspect of the present application, the present application provides an application of the PP synthetic paper base in image materials. The image materials have all the features and advantages of the above-mentioned PP synthetic paper base, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0029] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0030] Figure 1 Structure diagram of the PP synthetic paper base according to some embodiments of the present application;

[0031] Figure 2 Test results diagram of firmness with the contact layer of the PP synthetic paper base according to embodiments 1-4 and comparative examples 1-4 of the present application;

[0032] Figure 3 Flow chart of the method for preparing the PP synthetic paper base according to some embodiments of the present application.

[0033] BRIEF DESCRIPTION OF DRAWINGS

[0034] 1: first emulsion receiving layer; 2: first color tone adjusting layer; 3: light-blocking layer; 4: second color tone adjusting layer; 5: second emulsion receiving layer. DETAILED DESCRIPTION

[0035] Embodiments of the present application are described in detail below. The embodiments described below are exemplary only, and are intended to explain the present application, but should not be understood as a limitation of the present application. If a specific technique or condition is not mentioned in the embodiments, the technique or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not mentioned by the manufacturer, it is a conventional product that can be obtained by purchase.

[0036] In a first aspect, the present application provides a PP synthetic paper base. According to embodiments of the present application, referring to Figure 1The PP synthetic paper base comprises a first emulsion receiving layer 1, a first color tone adjusting layer 2, a light blocking layer 3, a second color tone adjusting layer 4 and a second emulsion receiving layer 5 which are sequentially stacked. The light blocking layer 3 is formed by a light blocking layer raw material comprising a first polypropylene resin, a light blocking agent, a first filler and a first auxiliary agent. The first color tone adjusting layer 2 and the second color tone adjusting layer 4 are each independently formed by a color tone adjusting layer raw material comprising a second polypropylene resin, a second filler and a second auxiliary agent. The first emulsion receiving layer 1 and the second emulsion receiving layer 5 are each independently formed by an emulsion receiving layer raw material comprising a polyethylene resin, a polyolefin elastomer, a titanium dioxide master batch, a color master batch and a third auxiliary agent, and the polyethylene resin comprises linear low density polyethylene (LLDPE). Thus, the synthetic paper base can achieve good coating firmness with the contact layer and good light blocking effect.

[0037] In the present application, the first polypropylene resin is the resin matrix of the light blocking layer 3, and the second polypropylene resin is the resin matrix of the first color tone adjusting layer 2 and the second color tone adjusting layer 4. The first polypropylene resin and the second polypropylene resin can be the same or different. In some embodiments, the first polypropylene resin and the second polypropylene resin independently comprise homopolymer polypropylene. Further, the homopolymer polypropylene has a melt index (MFI) of 3-9 g / 10 min (2.16 kg, 230°C). The homopolymer polypropylene preferably has a flexural modulus of not less than 1500 MPa. Preferably, the first polypropylene resin and the second polypropylene resin use the same homopolymer polypropylene. In addition, the homopolymer polypropylene can be directly selected from commercially available products, such as HMC Polymers HP520M (MFI 8.0 g / 10 min), flexural modulus 1550 MPa; LyondellBasell HA849K (MFI 3.5 g / 10 min), flexural modulus 2150 MPa, HJ8005 of Liaoning Huajin (MFI 5.0 g / 10 min), flexural modulus 1800 MPa.

[0038] In some embodiments, the first filler and the second filler are the same or different, and each independently comprises a rigidifying filler and / or a high hiding filler.

[0039] Further, the rigidifying filler comprises at least one of silica, aluminum hydroxide, magnesium hydroxide, kaolin, barium sulfate, calcium carbonate and talc master batch.

[0040] Further, the high hiding filler comprises nano titanium dioxide. In addition, the nano titanium dioxide has a D50 particle size of 0.1-0.3 μm, and the nano titanium dioxide is preferably rutile type nano titanium dioxide.

[0041] In some specific embodiments, the high-hiding filler in the first filler can include nano-titanium dioxide with a whiteness (L*) of not less than 95 (for example, commercially available Zhonghe Titanium White R-215, R-2219, etc.); the high-hiding filler in the second filler can include nano-titanium dioxide with a whiteness of not less than 98 (for example, commercially available Zhonghe Titanium White R-2196+). In this way, the addition of nano-titanium dioxide can achieve the adjustment of the color tone of the light-blocking layer, avoiding the phenomenon of low color tone of the light-blocking layer.

[0042] In the present application, the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent can include processing aids in a polyolefin-based matrix composition. In some embodiments, the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent are the same or different, and each independently includes an antioxidant and / or a dispersant. Among them, the antioxidant can be at least one of hindered phenolic antioxidants, such as commercially available antioxidant 1010, antioxidant 1098, etc.

[0043] In some embodiments, the dispersant includes at least one of zinc stearate and calcium stearate.

[0044] In some embodiments, the dispersant is zinc stearate and calcium stearate, and the mass ratio of zinc stearate to calcium stearate is 1:(0.8-1.2), for example, 1:1.

[0045] In some embodiments, in the emulsion receiving layer (the first emulsion receiving layer 1 and the second emulsion receiving layer 5), the D50 particle size of the titanium dioxide master batch can be 0.13-0.35 μm, and the whiteness is not less than 95.

[0046] In some embodiments, in the emulsion receiving layer, the color master batch includes at least one of blue master batch, magenta master batch, and fluorescent whitening master batch. Various color master batches can be commercially available color master batches, such as color master batches produced by Ningbo Color Master, Meilian New Materials, Guangdong Colorful Co., Ltd., etc. Those skilled in the art can select them according to actual conditions, as long as they meet the process requirements of the present application.

[0047] According to an embodiment of the present application, in the light-blocking layer 3, the first polypropylene resin (such as homopolymer polypropylene) in the light-blocking layer raw material is 50-80 parts (such as 50 parts, 54 parts, 60 parts, 62 parts, 70 parts, 71 parts, 79 parts and 80 parts, etc.) by mass, the light-blocking agent is 0.02-0.1 parts (such as 0.02 parts, 0.03 parts, 0.05 parts, 0.08 parts and 0.1 parts, etc.) by mass, the first filler is 20-45 parts (such as 20 parts, 25 parts, 30 parts, 35 parts, 40 parts and 45 parts, etc.) by mass, the first additive is 0.55-1.1 parts (such as 0.55 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and 1.1 parts, etc.) by mass, and the total mass of the light-blocking layer raw material is 100 parts. Under the condition that the light-blocking layer raw material has the above parameters, the light-blocking layer can play a role in blocking light transmission in the overall structure, and at the same time, as part of the overall paper base, it can also meet the support of the overall stiffness of the paper base during use, thereby meeting the requirements of the paper base for light-blocking.

[0048] Preferably, in the light-blocking layer raw material, the first filler is a rigidifying filler and a high-hiding filler, the rigidifying filler is 15-30 parts (such as 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts and 30 parts, etc.) by mass, and the high-hiding filler is 5-15 parts (such as 5 parts, 8 parts, 10 parts, 12 parts and 15 parts, etc.) by mass.

[0049] Preferably, in the light-blocking layer raw material, the first additive is an antioxidant and a dispersant, the antioxidant is 0.05-0.1 parts (such as 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts and 0.1 parts, etc.) by mass, and the dispersant is 0.5-1 parts (such as 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts and 1.0 parts, etc.) by mass.

[0050] In some embodiments, the light-blocking agent is a medium-tone carbon black. In addition, the D50 diameter of the medium-tone carbon black can be 1-20 nm, such as Cabot BLACK PEARLS 900, 800, 717, 4840. In this way, the addition of the light-blocking agent can meet the requirements of the paper base for light-blocking, and compared with the scheme of improving light-blocking by simply increasing the amount of filler, it can reduce the introduction of part of the high-hiding filler, which is conducive to the dispersion of the resin system and the stability of subsequent processing; and the medium-tone carbon black and the high-hiding filler can produce a synergistic effect to improve the blocking effect of the light-blocking layer.

[0051] According to the embodiment of the present application, in the raw material of each of the color tone adjusting layers (the first color tone adjusting layer 2 and the second color tone adjusting layer 4), the second polypropylene resin is 40-70 parts by mass (such as 40 parts, 44 parts, 50 parts, 52 parts, 60 parts, 61 parts, 69 parts and 70 parts, etc.), the second filler is 30-55 parts by mass (such as 30 parts, 35 parts, 40 parts, 45 parts, 50 parts and 55 parts, etc.), and the second auxiliary agent is 0.55-1.1 parts by mass (such as 0.55 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and 1.1 parts, etc.), and the total mass of the raw material of each color tone adjusting layer is 100 parts.

[0052] Preferably, in the raw material of each of the color tone adjusting layers, the second filler is a rigid reinforcing filler and a high hiding filler, the rigid reinforcing filler is 15-30 parts by mass (such as 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts and 30 parts, etc.), and the high hiding filler is 15-25 parts by mass (such as 15 parts, 18 parts, 20 parts, 22 parts and 25 parts, etc.). By adding the high hiding filler to the color tone adjusting layer, the influence of the low color tone caused by the addition of carbon black in the light blocking layer can be reduced.

[0053] Preferably, in the raw material of each of the color tone adjusting layers, the second auxiliary agent includes an antioxidant and a dispersant, the antioxidant is 0.05-0.1 parts by mass (such as 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts and 0.1 parts, etc.), and the dispersant is 0.5-1 parts by mass (such as 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts and 1.0 parts, etc.).

[0054] According to the embodiment of the present application, in the raw material of each of the emulsion receiving layers (the first emulsion receiving layer 1 and the second emulsion receiving layer 5), the polyethylene resin is 50-70 parts by mass (such as 50 parts, 54 parts, 59 parts, 60 parts, 63 parts and 70 parts, etc.), the polyolefin elastomer is 10-15 parts by mass (such as 10 parts, 11 parts, 12 parts, 13 parts, 14 parts and 15 parts, etc.), the titanium dioxide master batch is 15-25 parts by mass (such as 15 parts, 16 parts, 18 parts, 20 parts, 22 parts and 25 parts, etc.), the color master batch is 3.5-6 parts by mass (such as 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts and 6 parts, etc.), the third auxiliary agent is 0.55-1.1 parts by mass (such as 0.55 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts and 1.1 parts, etc.), and the total mass of the raw material of each emulsion receiving layer is 100 parts.

[0055] Preferably, in each of the emulsion substrate raw materials, the color masterbatch includes blue masterbatch, magenta masterbatch, and fluorescent whitening masterbatch. By weight, the blue masterbatch is 2-3 parts (e.g., 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, and 3 parts, etc.), the magenta masterbatch is 1-2 parts (e.g., 1 part, 1.2 parts, 1.5 parts, 1.8 parts, and 2 parts, etc.), and the fluorescent whitening masterbatch is 0.5-1 part (e.g., 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, and 1 part, etc.).

[0056] Preferably, in each of the emulsion substrate raw materials, the third auxiliary agent includes an antioxidant and a dispersant. By weight, the dispersant is 0.5 to 1 part (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, and 1 part, etc.), and the antioxidant is 0.05 to 0.1 part (e.g., 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1 parts, etc.).

[0057] In this invention, linear low-density polyethylene (LLDPE), which is easily corona-electrified, is introduced as the main resin in the emulsion substrate raw material. This improves the corona effect on the paper base, thereby enhancing the coating adhesion to the emulsion contact layer. This effectively addresses the problem of corona difficulties caused by polypropylene as the surface resin in existing paper substrates, which leads to insufficient adhesion to the contact layer and necessitates a polymer coating layer. Simultaneously, since the main resin of the emulsion substrate is linear low-density polyethylene, a polyolefin elastomer is introduced into this layer as a compatibilizer between polyethylene and polypropylene to maintain good interlayer adhesion with the color adjustment layer during co-extrusion. This avoids the problem of low adhesion of the polymer coating layer on the paper base surface in traditional methods and eliminates the need for a polymer coating process. Furthermore, the addition of titanium dioxide masterbatch adjusts the whiteness value of this layer. To further meet the color requirements of the paper base substrate, different color masterbatches are added to this layer, thereby achieving the color standard of the paper base polymer coating layer.

[0058] In some embodiments, the density of linear low-density polyethylene is 0.91–0.93 g / cm³. 3 The melt flow index is 1.0–5.0 g / 10 min (2.16 kg, 190 °C). Commercially available linear low-density polyethylene (LLDPE), such as ExxonMobil, can be directly selected. TM LLDPE LL 1002YB (MFI 2.0g / 10min; density 0.918g / cm³) 3 ), LLDPE 6318BE (MFI 3.2g / 10min; density 0.920g / cm³) 3 ) and Dow Chemical's 4601 (MFI 1.0g / 10min density 0.912g / cm³) 3). Linear low density polyethylene has higher content of comonomer per unit mass at smaller density compared with linear high density polyethylene, thus has higher branch chain density; and oxidation of polyolefin structure material during the corona process easily occurs at weak branch chain of molecular structure, thus linear low density polyethylene with higher branch chain density has better corona effect than other structures and has better interlayer adhesion with the contact layer, so that the coating polymer layer can be omitted.

[0059] In some embodiments, the polyolefin elastomer comprises at least one of ethylene-α-olefin copolymer and propylene-α-olefin copolymer, and the melt index of the polyolefin elastomer is 1.0-10.0 g / 10 min (2.16 kg, 190°C). The polyolefin elastomer can be directly selected from commercially available products, such as DOW AFFINITY TM EG 8200G, ExxonMobil Vistamaxx TM Performance Polymer 3980FL, Sabic COHERE TM 8380, etc. The elastomer has good compatibility with polyethylene resin and polypropylene resin, and can improve the problem of low interlayer adhesion in the multilayer co-extrusion process.

[0060] In the present application, the thickness of the first emulsion receiving layer 1 and the second emulsion receiving layer 5 can be the same or different, and the thickness of the first color tone adjusting layer 2 and the second color tone adjusting layer 4 can be the same or different.

[0061] In some specific embodiments, the first emulsion layer 1 and the second emulsion layer 5 are formed by the same emulsion layer raw material. The first color tone adjusting layer 2 and the second color tone adjusting layer 4 are formed by the same color tone adjusting layer raw material. In this way, the requirement of the double-sided imaging paper base for the uniformity of the two surfaces can be further met.

[0062] According to the embodiments of the present application, the thickness ratio of the first emulsion receiving layer 1, the first color tone adjusting layer 2, the light blocking layer 3, the second color tone adjusting layer 4 and the second emulsion receiving layer 5 is 2:(5-6):(7-8):(5-6):2.

[0063] Further, the thickness of the PP synthetic paper base is 0.18-0.3 mm, such as 0.18 mm, 0.2 mm, 0.22 mm, 0.25 mm and 0.3 mm, etc.

[0064] In another aspect of the present application, the present application provides a method for preparing the above-mentioned PP synthetic paper base, comprising:

[0065] supplying the raw materials of the layers to a five-layer co-extrusion equipment;

[0066] The raw materials of the layers are extruded, and the extruded product is cast onto a setting roller to form a film by the five-layer co-extrusion equipment.

[0067] Optionally, the method further comprises pre-mixing, granulating and drying the components in the raw materials of the layers. Specifically, the step can comprise adding the above-mentioned formulations of the layers into a mixer to stir uniformly, then melt-extruding and pelletizing by a twin-screw extruder, and finally drying by a dew-point dryer.

[0068] Optionally, the method further comprises post-processing, which can comprise corona treatment, edge cutting and winding of the product after setting.

[0069] In some embodiments, the five-layer co-extrusion equipment has two planar and completely consistent steel rollers or rubber rollers to meet the requirement of two-sided imaging paper base for two-sided planar consistency.

[0070] According to an embodiment of the present application, with reference to Figure 3 The method comprises:

[0071] S1: pre-drying

[0072] The raw materials of the layers are dried by a dew-point dryer, with a drying air dew point of -40℃ to -50℃, and dried for 4-6 hours to control the moisture content to be ≤300ppm.

[0073] S2: mixing and granulating

[0074] The raw materials of the above-mentioned layers are respectively added into a powerful mixer to stir to mix uniformly, then extruded and pelletized by a twin-screw extruder, and finally dried by a dew-point dryer for 4-6 hours.

[0075] S3: five-layer co-extrusion

[0076] The granulated raw materials of the layers in step S2 are fed into the extruders of the ABCDE five-layer co-extrusion equipment, wherein the raw materials of the emulsion receiving layer are added into the A machine and the E machine, the raw materials of the color tone adjusting layer are added into the B and D machines, and the raw materials of the light blocking layer are added into the C machine. After melt plasticization at a temperature of 200℃ to 220℃, a thick film is cast by a T-shaped die and cooled and set. The layer thickness ratio of the melts of the layers is adjusted by a melt pump and a distributor, and the total thickness is adjusted by the extrusion amount and the rotation speed of the setting roller, so as to obtain a sample of ABCBA five-layer structure thick film with a certain thickness and layer thickness ratio.

[0077] S4: post-processing

[0078] The sample obtained in step S3 is subjected to corona treatment, edge cutting and winding to obtain a PP synthetic paper base.

[0079] Therefore, the PP synthetic paper prepared by the method can realize good coating firmness with the contact layer and good light blocking effect. It should be noted that the features and advantages described above for the PP synthetic paper also apply to the method, which will not be described here.

[0080] According to another aspect of the present application, the present application provides the use of the PP synthetic paper in image materials. The PP synthetic paper applied to the image materials can realize good coating firmness with the contact layer and good light blocking effect.

[0081] The present application will be described below with reference to specific examples, and it should be noted that these examples are merely descriptive and do not limit the present application in any way.

[0082] Examples 1-4

[0083] According to the corresponding formulations in Table 1 below, a PP synthetic paper was prepared by a five-layer co-extrusion casting process, wherein the thickness ratio of the first emulsion receiving layer, the first color tone adjusting layer, the light blocking layer, the second color tone adjusting layer and the second emulsion receiving layer was 2:5:8:5:2, and the thickness of the PP synthetic paper was 0.22 mm. The first emulsion receiving layer and the second emulsion receiving layer had the same formulation, which were collectively referred to as "emulsion receiving layer" in Table 1; the first color tone adjusting layer and the second color tone adjusting layer had the same formulation, which were collectively referred to as "color tone adjusting layer" in Table 1.

[0084] The specific steps of preparing the PP synthetic paper by the five-layer co-extrusion casting process are as follows:

[0085] (1) Pre-drying

[0086] The raw materials of each layer were dried by a dew point dryer, the drying air dew point was -45℃, and the drying time was 6 hours, and the moisture content was controlled to be ≤300ppm.

[0087] (2) Mixing and granulation

[0088] The raw materials of each layer were added to a strong mixer for stirring and mixing uniformly, then extruded and pelletized by a twin-screw extruder, and further dried by a dew point dryer for 6 hours for standby.

[0089] (3) Five-layer co-extrusion

[0090] The raw materials of each layer after granulation in step (2) were transported into the five-layer co-extrusion extruder ABCDE, wherein the emulsion receiving layer raw material was added to A and E machines, the color adjusting layer raw material was added to B and D machines, and the light blocking layer raw material was added to C machine. After being melt-plasticized at 210°C, the thick film was cast through a T-shaped die and cooled and shaped. The layer thickness ratio of each layer of the melt was adjusted through a melt pump and a distributor, and the total thickness was adjusted through the extrusion amount and the shaping roller speed, so as to obtain a five-layer structure thick film sample with a certain thickness and layer thickness ratio.

[0091] (4) Post-treatment

[0092] The sample obtained in step (3) was subjected to edge cutting and winding after being subjected to corona treatment, so as to obtain a PP synthetic paper base with a target thickness.

[0093] Comparative Example 1

[0094] The PP synthetic paper base was prepared according to the formulation and five-layer co-extrusion casting process of Example 3, except that no light blocking agent was added when preparing the light blocking layer.

[0095] Comparative Example 2

[0096] The PP synthetic paper base was prepared according to the formulation and five-layer co-extrusion casting process of Example 3, except that the linear low-density polyethylene of the emulsion receiving layer was replaced with the homopolypropylene of the light blocking layer when preparing the emulsion receiving layer.

[0097] Comparative Example 3

[0098] The product after polyethylene resin coating on a common PP paper base:

[0099] The surface of the PP synthetic paper base (model: BCC) of Nan Ya Plastic was coated with a polyethylene layer (this layer was used to characterize the interlayer peeling strength between the polyethylene layer and the PP synthetic paper base, and only pure LLDPE resin (model: 4601) was used without adding color masterbatch) through a single-layer coating device. The thickness of the polyethylene layer was 0.02 mm.

[0100] Comparative Example 4

[0101] The PP paper base (model: BCC) of Nan Ya Plastic was used as a comparative example.

[0102]

[0103]

[0104] Performance evaluation:

[0105] The performance evaluation was mainly for testing the main indicators related to the double-sided paper, involving the opacity in the physical performance and the interlayer adhesion test with the contact layer.

[0106] 1. Opacity and transmission density test

[0107] Opacity and transmission density are the main means to evaluate the light shielding effect of duplex paper base, wherein,

[0108] Opacity is tested according to the method specified in standard GB / T 7975, using PF-10 colorimeter or equivalent instrument, selecting UVI setting.

[0109] Transmission density is measured using X-Rite 310 densitometer in M state.

[0110] 2. Interlayer adhesion test with contact layer

[0111] Test method: after corona treatment of the sample, the contact layer primer (formula as shown in Table 2) is coated, dried and then treated in constant temperature and humidity (30°C, 80% RH) for 30 min, then immersed in hot water at 40°C for 3 min, dyed with dyeing solution (methylene blue solution), then longitudinally scratched with a steel ball, and then transversely rubbed with hands to observe the peeling of the primer. OK and NG are used to represent OK means only scratch, no primer peeling, NG means scratch and primer peeling.

[0112] Table 2 Formulation of contact layer primer

[0113] Ingredients Amount Pure water 81g Gelatin 15g Surfactant 10% 0.3g Kathon 0.3g Citric acid solution 10% 0.3g Chromium vanadium solution 10% 0.27g Fixative 2.1% 1.3g

[0114] 3. Interlayer peeling strength test

[0115] The interlayer peeling strength between the emulsion receiving layer and the color tone adjusting layer in Examples 1-3 and Comparative Examples 1-2 and the adhesion between the polyethylene layer and the PP synthetic paper base in Comparative Example 3 are tested using a universal tensile testing machine LK-103B from Shenzhen Xinsisai Material Testing Co., Ltd., and the test is carried out in accordance with test standard GB / T 2790.

[0116] Table 3 Test results of physical properties of each example and comparative example

[0117]

[0118] From the test results of each example and comparative example in Table 3, it can be seen that the PP synthetic paper base of Examples 1-4 has good hiding property, cannot be peeled off with the emulsion receiving layer, and has good adhesion with the contact layer, which can eliminate the need for coating a polymeric layer, and meets the requirements of duplex paper for paper base.

[0119] Herein, the terms "first", "second", "third", etc. are used only for the purpose of facilitating description and explanation, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, the features defined with "first", "second", "third" can explicitly or implicitly include one or more of the features.

[0120] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "certain embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In the present specification, the illustrative expressions of the above terms are not necessarily directed to the same embodiment. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments. In addition, the person skilled in the art can combine and combine the different embodiments described in the present specification and the features of the different embodiments without contradiction.

[0121] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A PP synthetic paper base, characterized in that, It includes a first emulsion receiving layer, a first tone adjustment layer, a light-blocking layer, a second tone adjustment layer, and a second emulsion receiving layer, which are stacked sequentially; wherein, The light-blocking layer is formed from light-blocking layer raw materials consisting of a first polypropylene resin, a light-blocking agent, a first filler, and a first additive. The first tone-adjusting layer and the second tone-adjusting layer are each independently formed from tone-adjusting layer raw materials consisting of a second polypropylene resin, a second filler, and a second additive; The first emulsion receiving layer and the second emulsion receiving layer are each independently formed from emulsion receiving layer raw materials of polyethylene resin, polyolefin elastomer, titanium dioxide masterbatch, color masterbatch and third additive, and the polyethylene resin includes linear low-density polyethylene. In each of the emulsion bonding layer raw materials, by mass parts, the polyethylene resin is 50-70 parts, the polyolefin elastomer is 10-15 parts, the titanium dioxide masterbatch is 15-25 parts, the color masterbatch is 3.5-6 parts, the third auxiliary agent is 0.55-1.1 parts, and the total mass of each of the emulsion bonding layer raw materials is 100 parts; In the light-blocking layer raw material, by mass parts, the first polypropylene resin is 50-80 parts, the light-blocking agent is 0.02-0.1 parts, the first filler is 20-45 parts, the first auxiliary agent is 0.55-1.1 parts, and the total mass of the light-blocking layer raw material is 100 parts. The masterbatch includes blue masterbatch, magenta masterbatch and fluorescent whitening masterbatch, wherein the blue masterbatch is 2-3 parts, the magenta masterbatch is 1-2 parts, and the fluorescent whitening masterbatch is 0.5-1 parts; The light-blocking agent is medium-toned carbon black; The second filler includes a high-coverage filler, which is nano-titanium dioxide.

2. The PP synthetic paper base according to claim 1, characterized in that, Both the first polypropylene resin and the second polypropylene resin independently comprise homopolymer polypropylene; Optionally, the first packing includes stiffening packing and / or high-coverage packing, and the second packing includes stiffening packing; Optionally, the first, second, and third adjuvants each independently include an antioxidant and / or a dispersant.

3. The PP synthetic paper base according to claim 1 or 2, characterized in that, The first packing material includes stiffening packing and high-coverage packing, wherein the stiffening packing material is 15-30 parts and the high-coverage packing material is 5-15 parts; Optionally, the first adjuvant includes an antioxidant and a dispersant, wherein the dispersant is 0.5 to 1 part and the antioxidant is 0.05 to 0.1 part.

4. The PP synthetic paper base according to claim 1 or 2, characterized in that, In each of the color-adjusting layer raw materials, the second polypropylene resin is 40-70 parts, the second filler is 30-55 parts, the second auxiliary agent is 0.55-1.1 parts, and the total mass of each of the color-adjusting layer raw materials is 100 parts. Optionally, the second packing includes stiffening packing and high-coverage packing, wherein the stiffening packing is 15-30 parts and the high-coverage packing is 15-25 parts; Optionally, the second adjuvant includes an antioxidant and a dispersant, wherein the dispersant is 0.5 to 1 part and the antioxidant is 0.05 to 0.1 part.

5. The PP synthetic paper base according to claim 1 or 2, characterized in that, The third adjuvant includes an antioxidant and a dispersant, wherein the dispersant is 0.5 to 1 part and the antioxidant is 0.05 to 0.1 part.

6. The PP synthetic paper base according to claim 2, characterized in that, The stiffening filler includes at least one of silicon dioxide, aluminum hydroxide, magnesium hydroxide, kaolin, barium sulfate, calcium carbonate, and talc. Optionally, the dispersant includes at least one of zinc stearate and calcium stearate.

7. The PP synthetic paper base according to claim 5, characterized in that, The polyolefin elastomer includes at least one of ethylene-α-olefin copolymer and propylene-α-olefin copolymer; Optionally, the linear low-density polyethylene has a density of 0.91~0.93 g / cm³. 3 The melt index at 2.16 kg and 190℃ is 1.0~5.0 g / 10 min; Optionally, the polyolefin elastomer has a melt index of 1.0~10.0 g / 10 min at 2.16 kg and 190 °C.

8. The PP synthetic paper base according to claim 1, characterized in that, The thickness ratio of the first emulsion receiving layer, the first tone adjustment layer, the light blocking layer, the second tone adjustment layer and the second emulsion receiving layer is 2:(5~6):(7~8):(5~6):2; Optionally, the thickness of the PP synthetic paper base is 0.18~0.3mm.

9. A method for preparing the PP synthetic paper base according to any one of claims 1 to 8, characterized in that, include: The raw materials from each layer are supplied to the five-layer co-extrusion equipment; The raw materials of each layer are melt-extruded, and the extruded product is cast onto the shaping roller through the five-layer co-extrusion equipment.

10. The application of the PP synthetic paper base according to any one of claims 1 to 8 in imaging materials.

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