Waterproof, acid-base-resistant and scratch-resistant thermo-sensitive paper and preparation method thereof

Abstract

The invention discloses water-proof, acid-proof, alkali-proof and scratch-proof thermo-sensitive paper and a preparation method thereof, and belongs to the technical field of thermo-sensitive papers, the surface of the thermo-sensitive paper is sequentially coated with a thermo-sensitive paper coating and a water-proof, acid-proof and alkali-proof coating, and the thermo-sensitive paper coating comprises a color developing agent, a dye precursor and a sensitizer. The thermo-sensitive paper is waterproof, acid-base-resistant, scratch-resistant and high-temperature-resistant, and the color development of a coating of the thermo-sensitive paper is not influenced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-sensitive paper, in particular to a waterproof, acid and alkali resistant, and scratch-resistant heat-sensitive paper and a preparation method thereof. BACKGROUND

[0002] The printing process of heat-sensitive paper mainly relies on heat-sensitive printing technology, which is a kind of inkless printing method that makes the heat-sensitive coating on the paper react chemically and show color by heating a specific area. Heat-sensitive paper is a common special paper widely used in receipts, labels, and fax machines and other equipment. The principle of this phenomenon involves the chemical reaction of heat-sensitive materials and the transfer of heat. The main components of heat-sensitive paper include: base paper: this is the base layer of heat-sensitive paper, usually made of ordinary paper or synthetic paper; heat-sensitive coating: a layer of chemicals coated on the base paper that can change color when heated, the heat-sensitive coating mainly contains the following components: dye precursor: a colorless chemical that reacts with color developer to show color. Color developer: a substance that can react with the dye precursor to cause it to show color. Sensitizer: a substance that can lower the temperature of the color development reaction, causing the color development reaction to occur at a lower temperature.

[0003] In an acidic or alkaline environment, the color developer and dye precursor will react chemically with the acid and alkali substances in the environment. For example, the acidic substances in the color developer may be neutralized by the alkaline substances, preventing the color development reaction with the dye precursor, and in a strong alkaline environment, the dye precursor will undergo an alkaline reaction to produce a colorless product, losing its color development ability; the dye precursor may also react with acidic substances prematurely, losing the effect of the color developer. Phenolic compounds such as bisphenol A are common dye precursors. In an acidic environment, bisphenol A reacts with acidic substances such as protons H + ) to form a colored phenolphthalein structure. However, in a strong alkaline environment, bisphenol A may undergo a hydrolysis reaction to form a colorless phenolphthalein sodium salt, losing its color development ability. Fluorane compounds are another common dye precursor. In an acidic environment, fluorane compounds react with acidic substances to form a colored fluorane structure. However, in a strong alkaline environment, fluorane compounds may undergo an alkaline reaction to produce a colorless product, losing their color development ability. SUMMARY

[0004] As described in the prior art above, one of the purposes of the present application is to provide a waterproof, acid and alkali resistant, and scratch-resistant heat-sensitive paper that can prevent water, acid and alkali, and scratching, and is resistant to high temperatures without affecting the color development of the heat-sensitive paper coating.

[0005] The second purpose of the present application is to provide a manufacturing method for a waterproof, acid and alkali resistant, and scratch-resistant heat-sensitive paper, which is simple in steps and reliable in quality.

[0006] One of the purposes of the present application is achieved by using the following technical solution: The waterproof, acid and alkali resistant and scratch resistant thermal paper, the surface of which is coated with a thermal paper coating and a waterproof and acid and alkali resistant coating in sequence, the thermal paper coating comprising a color developer, a dye precursor and a sensitizer.

[0007] Further, the thermal paper coating further comprises a rare earth oxide and an antioxidant.

[0008] Further, the rare earth oxide is one of Gd2O3 and Nd2O3.

[0009] Further, the waterproof and acid and alkali resistant coating comprises polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), nano-silicon dioxide (SiO2) modified by a silane coupling agent and nano-titanium dioxide (TiO2) modified by a silane coupling agent.

[0010] Further, the mass ratio of the PVDF and PMMA is 8:2, and the doping amount of the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in the polyvinylidene fluoride and the polymethyl methacrylate is 0.22wt%.

[0011] Further, the dye precursor is 3-dibutylamino-6-methyl-7-anilinofluoran, the color developer is bisphenol A, and the sensitizer is dimethyl terephthalate.

[0012] The second purpose of the present application is achieved by the following technical scheme: The preparation method of the waterproof, acid and alkali resistant and scratch resistant thermal paper comprises the following steps: S1, biodegradable high-density paper is made from environment-friendly pulp through an environment-friendly process, and the surface thereof is subjected to flattening treatment to obtain base paper; S2, preparation of a transparent hydrophobic aqueous solution: S21, a mixture of PVDF and polymethyl methacrylate (PMMA) (7.11% based on the weight of the solvent) is added to dimethyl carbonate (DMC), and stirring is carried out at 60℃ until the PVDF and PMMA are completely dissolved; S22, then trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS) is added, and the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane is stirred at room temperature for 30 minutes; S23, nano-silicon dioxide modified by a silane coupling agent and nano-titanium dioxide modified by a silane coupling agent are added to the above solution, and stirring is carried out until uniform, to obtain the transparent hydrophobic aqueous solution; S3, the transparent hydrophobic aqueous solution is coated onto one side of the base paper with a coating device to form a smooth coating layer uniformly, and then placed into a curing oven at 100 DEG C for curing to form the waterproof acid and alkali resistant coating layer, thereby obtaining the waterproof acid and alkali resistant scratch-resistant thermal paper.

[0013] Compared with the prior art, the present application has the following advantages: (1) The waterproof acid and alkali resistant scratch-resistant thermal paper provided by the present application mixes nanomaterials (such as nanosilica and nanotitanium dioxide) with waterproof acid and alkali resistant polymers (polyvinylidene fluoride and polymethyl methacrylate), and ensures uniform dispersion of the nanomaterials in the waterproof acid and alkali resistant polymers by mechanical stirring, ultrasonic dispersion and other methods, so as to prepare a transparent waterproof acid and alkali resistant coating layer. This coating layer not only has good waterproof acid and alkali resistant performance, but also maintains a certain degree of transparency, reduces interference with the color developing effect of the thermal paper coating layer, and prevents acid and alkali substances in the environment from directly contacting the color developing agent and dye precursor of the thermal paper coating layer, thereby affecting the function of the thermal paper coating layer.

[0014] (2) The waterproof acid and alkali resistant scratch-resistant thermal paper provided by the present application adds rare earth oxides to the thermal paper coating layer, which can effectively prevent the thermal paper coating layer from decomposing at high temperatures, and maintain uniform distribution of the color developing agent and dye precursor.

[0015] (3) The waterproof acid and alkali resistant scratch-resistant thermal paper provided by the present application uniformly coats the thermal paper coating layer on one surface of the base paper, and coats Brazil palm wax on the other surface of the base paper. The Brazil palm wax has waterproof performance, which avoids the influence of moisture on the performance of the base. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application, the drawings required by the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0017] Figure 1 is a light transmittance measurement result graph of the waterproof acid and alkali resistant coating layer containing different proportions of polyvinylidene fluoride and polymethyl methacrylate in the present application embodiment 1; Figure 2 is a light transmittance measurement result graph of the waterproof acid and alkali resistant coating layer in the present application embodiment 1 with different contents of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane; Figure 3 is a contact angle measurement result graph of the waterproof acid and alkali resistant coating layer in the present application embodiment 1 with different contents of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane. DETAILED DESCRIPTION

[0018] The application will be further described below in conjunction with specific embodiments. It should be noted that the embodiments described below or technical features thereof can be combined with each other to form new embodiments without conflict.

[0019] Embodiment 1 The embodiment provides a waterproof, acid- and alkali-resistant and scratch-resistant thermal paper. The surface of the thermal paper is coated with a thermal paper coating and a waterproof and acid- and alkali-resistant coating in sequence. The thermal paper coating comprises a color developing agent, a dye precursor and a sensitizer. The waterproof and acid- and alkali-resistant coating comprises polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), nano-silicon dioxide (SiO2) modified by a silane coupling agent and nano-titanium dioxide (TiO2) modified by a silane coupling agent.

[0020] In the embodiment, the mass ratio of PVDF and PMMA is 8:2, and the doping amount of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in polyvinylidene fluoride and polymethyl methacrylate is 0.22 wt%.

[0021] The waterproof and acid- and alkali-resistant coating: a protective coating of waterproof and acid- and alkali-resistant is coated on the surface of the thermal paper. For example, a chemical corrosion resistant polymer material such as polyvinylidene fluoride (PVDF) is used to prevent the acid and alkali substances in the environment from directly contacting the color developing agent and the dye precursor in the inner layer.

[0022] PVDF (polyvinylidene fluoride) is a semi-transparent or white powder or particle with a compact arrangement between molecular chains and strong hydrogen bonds. The oxygen index is 46%, it is non-flammable, the crystallinity is 65%~78%, the density is 1.77~1.80 g / cm3, the melting point is 172℃, the heat distortion temperature is 112~145℃, and the long-term use temperature is -40~150℃.

[0023] The transparency of the PVDF coating is moderate to high. The alternating CH2 and CF2 units in the PVDF molecular structure make the scattering effect of light relatively small, so that light can pass through to a certain extent, showing good transparency.

[0024] The molecular chain of PMMA is relatively flexible, the intermolecular force is relatively strong, and the internal structure is relatively uniform. Light can directly penetrate the waterproof and acid- and alkali-resistant coating through less scattering.

[0025] However, due to the easy crystallization of PVDF, its light transmittance is not high, and the visible light transmittance of pure PVDF film is only 61.5% at a wavelength of 380-760 nm. From the perspective of microstructure, there are rod-like structures on the surface of the film. PMMA has the advantages of high transparency and low price, and can effectively inhibit the crystallization of PVDF. The light transmittance measurement results of the waterproof and acid-base resistant coating of different proportions of PVDF / PMMA are shown in FIGS. Figure 1 The greater the proportion of added PMMA, the higher the light transmittance; however, excessive addition of PMMA will cause a small amount of protrusions or wavy textures on the surface of the waterproof and acid-base resistant coating, therefore, a proportion of 8:2 is selected to prepare the waterproof and acid-base resistant coating, and the visible light transmittance of the waterproof and acid-base resistant coating reaches 86%. Due to the extremely low surface tension of TMEHFDS, it is selected to modify the hydrophobicity of the waterproof and acid-base resistant coating, a certain amount of TMEHFDS is added to the polypropylene solution and stirred, when the doping amount of TMEHFDS is 0.22wt%, the waterproof and acid-base resistant coating has good hydrophobicity, the water contact angle can reach 105° or more, and has very high transparency, the transmittance in the visible light range (380-760 nm) can reach 90% or more, as shown in FIGS. Figure 2 and Figure 3 With the increase of the thickness of the waterproof and acid-base resistant coating, the transmittance of the waterproof and acid-base resistant coating decreases, while the hydrophobic angle changes little, when the coating thickness is 0.5 mm, the transmittance of the waterproof and acid-base resistant coating film is the highest, and the transmittance in the visible light range is 94% or more.

[0026] DMSO is a colorless and transparent liquid with good solubility and transparency, which is suitable for preparing transparent coatings, and DMC is usually cheaper than DMSO, if the performance of the coating is not affected, DMC can be considered to reduce the cost, a small amount of DMC (such as 10%-20%) is added to DMSO.

[0027] In this embodiment, the dye precursor is 3-dibutylamino-6-methyl-7-anilino fluorophore, the color developing agent is bisphenol A, and the sensitizer is dimethyl terephthalate. The dye precursor and the color developing agent will undergo structural changes when heated, releasing active groups; the dye precursor reacts with these active groups to generate colored products; and dimethyl terephthalate as a sensitizer can promote this process and realize color development at a lower temperature.

[0028] The thermal paper may be subjected to friction during use, therefore, the wear resistance of the waterproof and acid-base resistant coating is also important. A small amount of nano filler (such as silica or titanium dioxide nanoparticles) is added to the mixture of PVDF and PMMA to enhance the wear resistance of the waterproof and acid-base resistant coating.

[0029] Nano-silica (Si02): Nano-silica has high specific surface area, good dispersibility and chemical stability, and it can enhance the mechanical properties (such as hardness and wear resistance) of the waterproof and acid-alkali resistant coating, and improve the transparency of the waterproof and acid-alkali resistant coating.

[0030] Nano-titanium dioxide (Ti02): Nano-titanium dioxide has excellent optical properties (such as high refractive index and good transparency), chemical stability and antibacterial properties, and it can improve the weather resistance and ultraviolet resistance of the waterproof and acid-alkali resistant coating, while maintaining the transparency.

[0031] The particle size of nano-silica and nano-titanium dioxide is usually between 10-100 nanometers, which is much smaller than the wavelength of visible light (about 400-700 nanometers), so these nano-materials will not scatter visible light in the waterproof and acid-alkali resistant coating, thereby maintaining the transparency of the coating. The silane coupling agent modified nano-silica and nano-titanium dioxide can reduce the adsorption of acidic substances, making it easier for acidic substances to diffuse.

[0032] In this embodiment, the coating material in the thermal paper usually needs to develop color quickly at a certain temperature. The selection of stabilizers with high thermal stability, such as rare earth oxides (Gd203 and Nd203), can effectively prevent the decomposition of the thermal paper coating at high temperature, thereby maintaining the uniform distribution of the color developer and dye precursor. Since the thermal paper will instantaneously contact the high-temperature print head during printing, the high-thermal-stability stabilizer can ensure that the thermal paper coating does not decompose at high temperature, maintaining its physical structure and color development performance.

[0033] In this embodiment, the addition of antioxidants, such as aluminum dihydrogen phosphate, in the thermal paper coating can effectively prevent the contact of oxidative gases with the thermal paper coating, preventing oxidative decomposition of the thermal paper coating at high temperature and maintaining its color development effect.

[0034] The embodiment also provides a preparation method of the waterproof, acid-alkali resistant and scratch-resistant thermal paper, which comprises the following steps: S1, biodegradable high-density paper is made from environmentally friendly pulp through an environmentally friendly process, and the surface of the paper is flattened to obtain a base paper; S2, preparation of transparent hydrophobic aqueous solution: S21, a mixture of PVDF and polymethyl methacrylate (PMMA) (7.11% based on the weight of the solvent) is added to dimethyl carbonate (DMC), and stirred at 60°C until the PVDF and PMMA are completely dissolved; S22, then add trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), stir trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane at room temperature for 30 minutes, and then keep the solution at room temperature for 3 hours; S23, adding silane coupling agent modified nano-silica and silane coupling agent modified nano-titanium dioxide to the above solution, stirring uniformly, obtaining a transparent hydrophobic aqueous solution; S3, coating the transparent hydrophobic aqueous solution to one side of the base paper with a coating device to uniformly form a smooth coating layer, and then placing it in a curing oven at 100°C for curing to form a waterproof and acid-alkali resistant coating layer, obtaining a waterproof, acid-alkali resistant and scratch-resistant thermal paper.

[0035] Embodiment 2 The embodiment provides a waterproof, acid-alkali resistant and scratch-resistant thermal paper. The surface of the thermal paper is coated with a thermal paper coating layer and a waterproof and acid-alkali resistant coating layer in sequence. The thermal paper coating layer comprises a color developing agent, a dye precursor and a sensitizer, and further comprises rare earth oxide Gd2O3 and antioxidant aluminum dihydrogen phosphate. The waterproof and acid-alkali resistant coating layer comprises polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), silane coupling agent modified nano-silica (SiO2) and silane coupling agent modified nano-titanium dioxide (TiO2).

[0036] The embodiment further provides a preparation method of a waterproof, acid-alkali resistant and scratch-resistant thermal paper, comprising the following steps: S1, preparing biodegradable high-density paper from environment-friendly pulp through an environment-friendly process, and performing planarization treatment on the surface of the biodegradable high-density paper to obtain base paper; S2, preparation of a transparent hydrophobic aqueous solution: S21, adding a PVDF and polymethyl methacrylate (PMMA) mixture (7.11% based on the weight of the solvent) to dimethyl carbonate (DMC), and stirring at 60°C until the PVDF and PMMA are completely dissolved; S22, then adding trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), stirring the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane at room temperature for 30 minutes, and then keeping the solution at room temperature for 3 hours; S23, adding silane coupling agent modified nano-silica and silane coupling agent modified nano-titanium dioxide to the above solution, stirring uniformly, obtaining a transparent hydrophobic aqueous solution; S3, coating the transparent hydrophobic aqueous solution to one side of the base paper with a coating device to uniformly form a smooth coating layer, and then placing it in a curing oven at 100°C for curing to form a waterproof and acid-alkali resistant coating layer, obtaining a waterproof, acid-alkali resistant and scratch-resistant thermal paper.

[0037] In this embodiment, the mass ratio of PVDF and PMMA is 8:2, and the doping amount of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in polyvinylidene fluoride and polymethyl methacrylate is 0.22wt%.

[0038] Embodiment 3 The present embodiment provides a waterproof, acid and alkali resistant and scratch resistant thermal paper. The surface of the thermal paper is coated with a thermal paper coating and a waterproof and acid and alkali resistant coating in sequence. The thermal paper coating comprises a color developing agent, a dye precursor and a sensitizer, and further comprises rare earth oxide Nd2O3 and antioxidant aluminum dihydrogen phosphate. The waterproof and acid and alkali resistant coating comprises polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), nano-silicon dioxide (SiO2) modified by a silane coupling agent and nano-titanium dioxide (TiO2) modified by a silane coupling agent.

[0039] The present embodiment also provides a preparation method of a waterproof, acid and alkali resistant and scratch resistant thermal paper, comprising the following steps: S1, preparing biodegradable high-density paper from environmentally friendly pulp through an environmentally friendly process, and performing flattening treatment on the surface of the paper to obtain base paper; S2, preparation of transparent hydrophobic aqueous solution: S21, adding a mixture of PVDF and polymethyl methacrylate (PMMA) (7.11% based on the weight of the solvent) to dimethyl carbonate (DMC) and stirring at 60°C until the PVDF and PMMA are completely dissolved; S22, then adding trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (TMEHFDS), stirring the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane at room temperature for 30 minutes, and then keeping the solution at room temperature for 3 hours; S23, adding nano-silicon dioxide modified by a silane coupling agent and nano-titanium dioxide modified by a silane coupling agent to the above solution and stirring uniformly to obtain a transparent hydrophobic aqueous solution; S3, coating the transparent hydrophobic aqueous solution onto one side of the base paper using a coating device to uniformly form a smooth coating layer, and then placing it in a curing oven at 100°C for curing to form a waterproof and acid and alkali resistant coating layer, thereby obtaining a waterproof, acid and alkali resistant and scratch resistant thermal paper.

[0040] In this embodiment, the mass ratio of PVDF and PMMA is 8:2, and the doping amount of trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in polyvinylidene fluoride and polymethyl methacrylate is 0.22wt%.

[0041] The above embodiments are only the preferred embodiments of the present application, and cannot be used to limit the protection scope of the present application, and any non-essential changes and replacements made by those skilled in the art on the basis of the present application shall fall within the protection scope of the present application.

Claims

1. A waterproof, acid and alkali resistant, scratch resistant thermal paper, characterized in that, The surface of the heat-sensitive paper is coated with a heat-sensitive paper coating and a waterproof and acid-alkali resistant coating in sequence, the heat-sensitive paper coating comprises a color developer, a dye precursor and a sensitizer.

2. The waterproof, acid and alkali resistant, scratch resistant thermal paper of claim 1, wherein, The heat-sensitive paper coating further comprises a rare earth oxide and an antioxidant.

3. The waterproof, acid and alkali resistant, scratch resistant thermal paper of claim 2, wherein, The rare earth oxide is one of Gd2O3 and Nd2O3.

4. The waterproof, acid and alkali resistant, scratch resistant thermal paper of claim 1, wherein, The waterproof and acid-alkali resistant coating comprises polyvinylidene fluoride, polymethyl methacrylate, trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane, nano-silicon dioxide modified by a silane coupling agent and nano-titanium dioxide modified by a silane coupling agent.

5. The waterproof, acid and alkali resistant, scratch resistant thermal paper of claim 4, wherein, The mass ratio of the polyvinylidene fluoride and the polymethyl methacrylate is 8:2, and the doping amount of the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane in the polyvinylidene fluoride and the polymethyl methacrylate is 0.22wt%.

6. The waterproof, acid and alkali resistant, scratch resistant thermal paper of claim 1, wherein, The dye precursor is 3-dibutylamino-6-methyl-7-anilino fluorophore, the color developer is bisphenol A, and the sensitizer is dimethyl terephthalate.

7. A method for preparing a waterproof, acid- and alkali-resistant, and scratch-resistant thermal paper according to any one of claims 1-6, characterized in that, The method comprises the following steps: S1, biodegradable high-density paper is made from environment-friendly pulp through an environment-friendly process, and the surface of the paper is subjected to flattening treatment to obtain base paper; S2, preparation of a transparent hydrophobic aqueous solution: S21, a mixture of polyvinylidene fluoride and polymethyl methacrylate is added to dimethyl carbonate, and stirring is performed at 60℃ until the polyvinylidene fluoride and the polymethyl methacrylate are completely dissolved; S22, then trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane is added, the trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane is stirred at room temperature for 30 minutes, and the solution is then kept at room temperature for 3 hours; S23, nano-silicon dioxide modified by a silane coupling agent and nano-titanium dioxide modified by a silane coupling agent are added to the above solution, and stirring is performed until uniformity is achieved, to obtain the transparent hydrophobic aqueous solution; S3, the transparent hydrophobic aqueous solution is coated onto one side of the base paper by using a coating device to uniformly form a smooth coating layer, and then the base paper is placed into a curing oven at 100℃ for curing to form the waterproof and acid-alkali resistant coating, thereby obtaining the waterproof and acid-alkali resistant and scratch-resistant heat-sensitive paper.

8. The method for preparing a waterproof, acid- and alkali-resistant, and scratch-resistant thermal paper as described in claim 7, characterized in that, The coating device is one of a slot coater or a spraying device.

9. The method for preparing a waterproof, acid- and alkali-resistant, and scratch-resistant thermal paper as described in claim 7, characterized in that, Brazilian palm wax is coated on the other side of the base paper.

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