TW202134298A - Composite particle, coating composition and thermal paper - Google Patents

Abstract

A composite particle, a coating composition and a thermal paper are provided. In the presence of an initiator and at least one carbohydrate, the composite particle is obtained by subjecting a styrene monomer and an acrylate monomer to an emulsion polymerization reaction. The composite particle has a glass transition temperature of at least higher than 40℃, and the composite particle demonstrates homogeneous transparency above the glass transition temperature.

Description

Composite particles, coating composition and thermal paper

The present invention relates to a composite particle, a coating composition and a thermal paper, and particularly relates to a composite particle, a coating composition and a thermal paper that are relatively thermally stable through emulsion polymerization.

In the conventional technology, the use of chemical raw materials to coat the thermal paper can change the color of the thermal paper due to heat, without the need to use ink or ink. Thermal paper can be used in thermal printers, and is particularly suitable for fax machines, cash registers, or credit card terminals to print invoices or credit card signing and other documents. However, most of the thermal paper coatings contain bisphenol A, which is a chemical substance that may cause endocrine interference and has potential adverse effects on the human body. In addition, the color on the thermal paper is in a meta-stable state and will gradually fade over time. Therefore, it is only suitable for printing purposes that do not require long-term storage.

Based on the above, the development of a coating composition for thermal paper has no adverse effects on the human body and has better thermal stability, which is an urgent development goal for those skilled in the art.

The invention provides a composite particle, a coating composition and a thermal paper. The composite particle is formed by emulsifying and polymerizing carbohydrates, styrene monomers and acrylate monomers. Therefore, there is no adverse effect on the human body and the thermal stability is relatively high. good.

The composite particles of the present invention are obtained by emulsifying and polymerizing styrene monomers and acrylate monomers in the presence of an initiator and at least one carbohydrate. The composite particles have a glass transition temperature of at least higher than 40°C. , And have homogeneous transparency above the glass transition temperature.

In an embodiment of the present invention, the glass transition temperature of the composite particles is between 40°C and 95°C.

In an embodiment of the present invention, carbohydrates include modified starch, positive starch, dextrin, sucrose, carboxymethyl cellulose, tapioca starch, or a combination thereof.

In an embodiment of the present invention, the composite particles are obtained from 70 to 95 weight percent of styrene monomer and 5 to 30 weight percent of acrylic monomer through emulsion polymerization.

In an embodiment of the present invention, the composite particles are obtained from 70 to 80 weight percent of styrene monomer and 20 to 30 weight percent of acrylic monomer through emulsion polymerization.

In an embodiment of the present invention, the acrylic monomer is selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, ( One or more of the group consisting of 2-ethylhexyl meth)acrylate and 2-hydroxyethyl acrylate.

In an embodiment of the present invention, the particle size of the composite particles is 150 nm to 1000 nm.

In an embodiment of the present invention, the initiator of the emulsion polymerization reaction includes ammonium persulfate, sodium persulfate or potassium persulfate.

In an embodiment of the present invention, acrylic acid is added during the emulsion polymerization reaction.

The present invention also provides a coating composition comprising the above-mentioned composite particles, and the coating composition can be used for coating paper.

In an embodiment of the present invention, the coating composition includes one or more additives selected from the group consisting of binders, lubricants, thickeners and dispersants.

The present invention further provides a thermal paper, at least one side of the thermal paper is coated with the above-mentioned coating composition.

Based on the above, the composite particles of the present invention are obtained by emulsification polymerization of styrene monomers and acrylic monomers in the presence of an initiator and at least one carbohydrate. Therefore, when used as a coating for thermal paper When the composition contains the composite particles of the present invention, there is no adverse effect on the human body and the thermal stability is better.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, some embodiments are given below, which are described in detail as follows.

Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are illustrative, and the present disclosure is not limited thereto.

In this article, the range represented by "a value to another value" is a general way to avoid listing all the values in the range one by one in the specification. Therefore, the record of a specific numerical range covers any numerical value in the numerical range and the smaller numerical range defined by any numerical value in the numerical range, as if the arbitrary numerical value and the smaller numerical value are written in the description in the specification. The numerical range is the same.

The invention provides a composite particle, which is obtained by emulsification polymerization of styrene monomer and acrylic monomer in the presence of an initiator and at least one carbohydrate. The composite particles have a glass transition temperature of at least higher than about 40°C, and have homogeneous transparency above the glass transition temperature. For example, the glass transition temperature of the composite particles is, for example, between 40°C and 95°C. In more detail, the carbohydrate may include modified starch, positive starch, dextrin, sucrose, carboxymethyl cellulose, tapioca starch, or a combination thereof. The initiator of the emulsion polymerization reaction may include ammonium persulfate, sodium persulfate or potassium persulfate. Acrylic monomers are selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethyl (meth)acrylate One or more of the group consisting of hexyl ester and 2-hydroxyethyl acrylate. In this embodiment, the composite particles are obtained, for example, from 70 to 95 weight percent of styrene monomer and 5 to 30 weight percent of acrylic monomer through emulsion polymerization. In more detail, the composite particles are preferably obtained, for example, from 70 to 80 weight percent of styrene monomer and 20 to 30 weight percent of acrylic monomer through the emulsion polymerization reaction. The composite particles are, for example, solid particles, the particle size is, for example, 150 nm to 1000 nm, and the solid content is, for example, between 20% and 60%.

The method of the composite particle of the present invention may include the following steps. First, prepare carbohydrates as a paste (the viscosity of the paste is, for example, less than 10 cps), place it in a reaction tank, bubbling with nitrogen and heating to about 75°C to 80°C. After reaching the reaction temperature, add part of the initiator dropwise (if the total amount of the initiator is, for example, 1 aliquot, at this time, for example, add 0.3 aliquot of the initiator), the initiator can include ammonium persulfate, persulfuric acid Sodium or potassium persulfate, but the present invention is not limited to this. After that, add the remaining starter together with styrene monomer and acrylate monomer (if the total amount of the starter is, for example, 1 equal part, at this time, for example, add 0.7 equal part of the starter) . Next, after cooling at room temperature, the composite particles of the present invention can be obtained.

When the above-mentioned emulsion polymerization reaction is in progress, a small amount of acrylic acid can be further added, for example, based on acrylate monomers, no more than 5 weight percent, which will help increase the viscosity and improve the composition of styrene monomers and acrylate monomers. Cohesion.

The present invention also provides a coating composition comprising the above-mentioned composite particles. In order to meet the requirements of coating on various surfaces, those skilled in the technical field of the present invention can add one or more additives by themselves. The additives include the following substances: adhesives, lubricants, thickeners and dispersants. According to the present invention, the binder can be selected from the conventional water-soluble starch and its starch derivatives, carboxyethyl cellulose, polyvinyl alcohol and its modified derivatives, acrylamide, methacrylate copolymer, styrene-acrylic latex , Styrene-butadiene latex, polyvinyl acetate copolymer, acrylate, etc. Lubricants can be selected from conventional fatty acid salts, mica powder, calcium stearate, alkyd resin, epoxy resin, acrylic resin, polyester, phenolic resin, urea-formaldehyde resin, polyurethane, silicone, polytetrafluoroethylene, Polyimide, polyphenylimidazole, polyphenylene sulfide, polyparaben, etc. The thickener can be selected from conventional methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, acrylic acid, maleic acid or maleic anhydride, methacrylic acid, acrylate, Styrene, N,N-methylenebisacrylamide, butylene diacrylate or dipropylene phthalate, polysaccharides, polyethylene glycol, glycerin, polyurethane, etc. The dispersant can be selected from conventional silicates, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphoric acid, sodium lauryl sulfate, methylpentanol, cellulose derivatives, poly Acrylamide, Guer gum, fatty acid polyethylene glycol ester, etc. However, the present invention is not limited to this.

According to an embodiment of the present invention, based on the total wet weight of the coating composition, the amount of composite particles added is, for example, 60 to 90 weight percent, the amount of binder added is, for example, 10 to 50 weight percent, and the amount of lubricant added is, for example, 1 to 10% by weight, the addition amount of the thickener is, for example, 1 to 10% by weight, and the addition amount of the dispersant is, for example, 0.1 to 2% by weight.

The present invention also provides a thermal paper with a base color layer (which can be blue or black, but the present invention is not limited to this). The application method of the above-mentioned coating composition containing composite particles is coating On the base color layer, the coating composition after coating is opaque and can mask the color of the base color layer. When the instantaneous temperature is heated to a temperature in the range of, for example, about 100°C to 200°C, the composite particles have homogeneous transparency, and therefore, the color of the base color layer can be displayed. In more detail, as an embodiment of the present invention, ^{white paper with a basis weight of 40 g/m 2} to 60 g/m ² is used, and black ink is coated at a specification of 1 g/m ² to 3 g/m ^2. After drying at a temperature of 100°C to 150°C and a time of 30 seconds to 60 seconds. After that, take out the bottom paper and perform the calendering condition 100bar/2 times (the roughness is controlled below 2 μm) to complete the primer coating process. Next, the coating composition of the present invention is coated with a specification of 6 g/m ² to 10 g/m ² to form a color developing layer, and then dried at a temperature of 80°C to 120°C for a time of 30 seconds to 60 seconds, namely The surface coating process can be completed to form the thermal paper of the present invention.

Hereinafter, the composite particles and coating composition proposed in the above embodiments will be explained in detail through experimental examples. However, the following experimental examples are not intended to limit the present invention. Preparation of composite particles Preparation example 1

Add water to prepare a 15% solution of dextrin and stir to dissolve it (the viscosity of the paste is less than 10 cps), place it in the reaction tank, pour in nitrogen and heat to 75°C. After reaching the reaction temperature, add a portion of the initiator (if the total amount of the initiator is 1 aliquot, add 0.3 aliquots of the initiator), and the initiator is ammonium persulfate. After the temperature rises back to 75°C, add the remaining starter together with styrene monomer and 2-ethylhexyl acrylate monomer (2-EHA) together (addition ratio of 75%: 25%) ( If the total amount of the starter is 1 equal part, add 0.7 equal part of the starter at this time), and drop it within 3 hours, hold the temperature for 2 hours and then cool at room temperature to obtain the desired product. The prepared composite particles have a Tg of 52.49°C, a particle size of 350 nm, and a solid content of 35%. Preparation example 2

The addition ratio of styrene monomer and 2-ethylhexyl acrylate monomer (2-EHA) is 70%: 30%, and the rest of the preparation process is the same as Preparation Example 1. The prepared composite particles have a Tg of 41.03°C, a particle size of 340 nm, and a solid content of 35%. Preparation example 3

The positive starch is added with sulfuric acid, and the pH value of the paste liquid is adjusted to about 1.35 for operation. After gelatinization and hydrolysis for 1 hour, sodium bicarbonate was added to adjust the pH to 5.5-7. Place the paste in the reaction tank, pour nitrogen into it and heat it to 75°C. After reaching the reaction temperature, add a portion of the initiator (if the total amount of the initiator is 1 aliquot, add 0.3 aliquots at this time) Initiator), the initiator is ammonium persulfate. After the temperature rises back to 75℃, add the remaining starter together with styrene monomer and 2-ethylhexyl acrylate monomer (2-EHA) together (addition ratio 80%: 20%) (if The total amount of the starting agent is 1 equal part, at this time, 0.7 equal parts of the starting agent is added), and the dripping is completed within 3 hours. After holding the temperature for 2 hours, it is cooled at room temperature to obtain the desired product. The prepared composite particles have a Tg of 66.54°C, a particle size of 250 nm, and a solid content of 35%. Preparation Example 4

Sucrose was prepared by adding water to a 15% solution, stirred and dissolved, placed in the reaction tank, filled with nitrogen and heated to 75°C. After reaching the reaction temperature, add part of the initiator (if the total amount of initiator is 1 equal part) At this time, add 0.3 equal parts of the initiator), the initiator is ammonium persulfate. After the temperature rises back to 75℃, add the remaining starter together with styrene monomer and 2-ethylhexyl acrylate monomer (2-EHA) together (addition ratio 80%: 20%) (if The total amount of the starting agent is 1 equal part, at this time, 0.7 equal parts of the starting agent is added), and the dripping is completed within 3 hours. After holding the temperature for 2 hours, it is cooled at room temperature to obtain the desired product. The prepared composite particles have a particle size of 560 nm and a solid content of 35%. Preparation Example 5

Sucrose and dextrin were added with water to prepare a 15% solution after stirring and dissolving, and then placed in the reaction tank, vented with nitrogen and heated to 75°C. After reaching the reaction temperature, add a portion of the initiator (if the total amount of the initiator is 1 aliquot, add 0.3 aliquots of the initiator), and the initiator is ammonium persulfate. After the temperature rises back to 75℃, add the remaining starter together with styrene monomer and 2-ethylhexyl acrylate monomer (2-EHA) together (addition ratio 80%: 20%) (if The total amount of the starting agent is 1 equal part, at this time, 0.7 equal parts of the starting agent is added), and the dripping is completed within 3 hours. After holding the temperature for 2 hours, it is cooled at room temperature to obtain the desired product. The prepared composite particles have a Tg of 62.4°C, a particle size of 460 nm, and a solid content of 35%. Preparation Example 6

After the tapioca starch is added with water to prepare a paste, add concentrated sulfuric acid, heat to 80°C and hold the temperature for 1 hour. Add NH ₄ OH aqueous solution to the reactor to neutralize, and lower the temperature to 70°C. When the temperature is 70°C, add part of the initiator (if the total amount of the initiator is 1 aliquot, add 0.3 aliquots of the initiator), and the initiator is ammonium persulfate. Hold the temperature for 10 minutes, add the remaining starter together with styrene monomer and butyl acrylate monomer (BA) dropwise (addition ratio is 80%: 20%) (if the total amount of starter is 1 equal part, at this time, add 0.7 equal part of the initiator), continue to add and complete the addition within 3 hours. After the addition is completed, the temperature is maintained at 70°C for 1.5 hours, the temperature is increased to 85°C for 0.5 hours, and the temperature is cooled down to obtain the desired product. The prepared composite particles have a Tg of 69.1°C, a particle size of 312 nm, and a solid content of 35.3%. Preparation of coating composition

The coating compositions of Examples 1 to 4 were prepared according to the components and contents in Table 1 below, in which styrene-acrylic latex, acrylic latex and PVA were binders. The number of parts is a ratio based on dry weight. Table 1 Solid content% Example 1 Example 2 Example 3 Example 4 Number of copies Number of copies Number of copies Number of copies Composite particles (preparation example 3) 35 100 0 0 0 Composite particles (preparation example 1) 35 0 100 0 0 Composite particles (preparation example 4) 35 0 0 100 0 Composite particles (preparation example 5) 35 0 0 0 100 Styrene acrylic latex 50 10 0 8 0 Acrylic latex 62 0 0 6 0 PVA 10 0 13 0 8 Dispersant 47 1 0 0 0 Lubricant 45 5 5 5 5 Thickener 7 3 0.5 0.5 0.5 Preparation of thermal paper

Use white paper with a basis weight of 40 g/m ² to 60 g/m ² to coat black ink with a specification of 1 g/m ² to 3 g/m ² , and then pass the temperature 100 ℃ to 150 ℃, time 30 seconds to 60 Dry in seconds. After that, take out the bottom paper and perform the calendering condition 100bar/2 times (the roughness is controlled below 2 μm) to complete the primer coating process. Next, the coating composition of the present invention is coated with a specification of 6 g/m ² to 10 g/m ² to form a color layer, and then dried at a temperature of 80°C to 120°C for a time of 30 seconds to 60 seconds, namely The surface coating process can be completed to form thermal paper. Nature assessment

Evaluate the pre-printing-color density value (opaque layer), post-printing-color density value (black layer), contrast (%), and paper whiteness of the finished thermal paper, and list the evaluation results in Table 2 below . The commercially available product is Blue4est®.

The color density value is evaluated using the X-Rite eXact color density instrument, and the test conditions are as follows: 1. Equipment name: X-Rite (eXact) basic version density meter 2. Equipment specifications: Optical analyzer: DRS spectrum engine Spectral range: 400nm~700nm (10nm interval) Optical components: light source, gas-filled tungsten lamp (light source type A) and UV LED Calibration: Automatically open mode Density repeatability: The density of CMYK is +/-0.01D (measure the color every 5 seconds and take the average of 10 times, the maximum error is compared with this value) Operating temperature: 10°C to 35°C (maximum relative humidity 30% to 85%) 3. Measurement method: measure the color density of the coated paper before printing (opaque layer) and the color density after printing (black base color layer) 4. Contrast formula (%) = (color density after printing-color density before printing) / (color density after printing + color density before printing) * 100

The test conditions for rough measurement are as follows: 1. Equipment name: L&W PPS roughness measuring instrument 2. Measuring method: measuring the roughness of the paper on the coated surface 3. Use TAPPI T555-om99 Roughness of paper and paperboard (Print-surf method)-Grayhall standard detection method

The test conditions for paper whiteness measurement are as follows: 1. Equipment name: L&W ELREPHO spectrophotometer 2. Measurement method: measuring paper whiteness value on coated surface 3. Use TAPPI T452 om-98 Brightness Of Pulp, Paper And Paperboard ( directional Reflectance At 457 nm) standard detection method table 2 Test items Commercial products Example 1 Example 2 Example 3 Example 4 Before printing-color density value (opaque layer) 0.46 0.38 0.53 0.46 0.33 After printing-color density value (black layer) 1.31 1.44 1.39 1.61 1.61 Contrast (%) 48.02 58.42 44.79 55.56 65.98 Paper whiteness (Br) 45.13 45.73 42.08 49.84 52.17

From Table 2 above, it can be seen that the color density values of Example 1, Example 2, Example 3, and Example 4 of the present invention after printing are all higher than those of the commercially available products. High, the black of the base color layer can be more clearly presented. In contrast, Example 1, Example 3, and Example 4 of the present invention are significantly better than the commercially available products, showing that the black layer develops more clearly and has a higher resolution. Furthermore, the whiteness of the commercially available paper is relatively low and appears blue to the naked eye. The composite particles of the present invention can improve the whiteness of the paper after being coated. For sale.

In summary, the composite particles of the present invention are obtained by emulsification polymerization of styrene monomers and acrylate monomers in the presence of an initiator and at least one carbohydrate. When prepared in the form of a coating composition , It can be coated on the paper surface to obtain a thermal paper, which has no adverse effects on the human body, and has the advantages of excellent thermal stability, higher paper whiteness, and improved resolution after printing.

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Claims (12)

A composite particle obtained by emulsifying and polymerizing styrene monomer and acrylate monomer in the presence of an initiator and at least one carbohydrate, the composite particle having a glass transition temperature of at least higher than 40°C , And have homogeneous transparency above the glass transition temperature. The composite particle as described in item 1 of the scope of patent application, wherein the glass transition temperature of the composite particle is between 40°C and 95°C. The composite particle according to the first item of the patent application, wherein the carbohydrate includes modified starch, positive starch, dextrin, sucrose, carboxymethyl cellulose, tapioca starch, or a combination thereof. The composite particles described in item 1 of the scope of patent application are obtained from 70 to 95 weight percent of styrene monomer and 5 to 30 weight percent of acrylic monomer through the emulsion polymerization reaction. The composite particles described in item 4 of the scope of the patent application are obtained from 70 to 80 weight percent of styrene monomer and 20 to 30 weight percent of acrylic monomer through the emulsion polymerization reaction. As described in the first item of the patent application, the acrylic monomer is selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (meth)acrylate, and (meth)acrylate. One or more of the group consisting of butyl acrylate, 2-ethylhexyl (meth)acrylate and 2-hydroxyethyl acrylate. The composite particle as described in item 1 of the scope of patent application, wherein the particle size of the composite particle is 150 nm to 1000 nm. The composite particle as described in the first item of the patent application, wherein the initiator of the emulsion polymerization reaction includes ammonium persulfate, sodium persulfate or potassium persulfate. The composite particle as described in the first item of the scope of patent application, wherein acrylic acid is added during the emulsion polymerization reaction. A coating composition comprising: The composite particles as described in any one of items 1 to 9 of the scope of the patent application. The coating composition as described in item 10 of the scope of the patent application includes one or more additives selected from the group consisting of binders, lubricants, thickeners and dispersants. A thermal paper, wherein at least one side of the thermal paper is coated with the coating composition described in item 10 or 11 of the scope of the patent application.