Photoinitiator, preparation method, application and ink composition

Abstract

The invention discloses a photoinitiator, an ink composition and application of the photoinitiator, the photoinitiator is 3-methyl-4 '-phenyl benzophenone, the 3-methyl-4'-phenyl benzophenone has specific particle distribution, and the ink composition prepared from the photoinitiator particles has high wear resistance and alcohol resistance.

Description

Technical Field

[0001] The present invention belongs to the field of polymer composite materials, and in particular relates to a photoinitiator, a preparation method, an application and an ink composition. Background Art

[0002] With economic development, people's expectations for a better life are growing. Whether for logo or decoration, plastic products require printing. Plastic printing refers to printing on plastic rolls such as films, sheets, artificial leather, and wallpaper. Flexographic and gravure printing are commonly used, and the basic principles are the same as those for paper printing.

[0003] However, the ink used for plastic printing is different from the ink used for paper printing. The ink used for plastic printing is mainly suitable for use on rotogravure printing machines. The compatibility of the ink used for plastic printing with the printing machine, the curing performance of the ink, and the adhesion performance of the ink on the plastic surface all affect the product quality of the printed plastic. In particular, poor wear resistance and poor alcohol resistance limit the application of ink used for plastic printing.

[0004] Different plastic products have different relative effects on printing inks due to the differences in plastic resins and modifiers, as well as different plastic molding processes. The PET resin commonly used in the market is widely used in daily plastic products due to its good plasticity, but its surface properties are poor. Products printed or copied by ink through a printing press have poor surface properties and adhesion properties, especially its wear resistance and alcohol resistance are poor, and the ink is easily scratched and falls off.

[0005] Among the types of inks, photocurable ink is an important branch. The wear resistance and alcohol resistance of photocurable ink and its adhesion to plastic materials are important factors affecting plastic printing products.

[0006] Therefore, it is a technical problem that those skilled in the art need to solve urgently to prepare a light-curable ink suitable for printing that has good wear resistance, alcohol resistance and plastic adhesion. Summary of the Invention

[0007] The purpose of the present invention is to provide a photoinitiator for preparing ink, which can significantly improve the wear resistance and alcohol resistance of the ink and the adhesion to plastic materials.

[0008] Necessarily, the present invention also provides a method for preparing the above-mentioned photoinitiator.

[0009] Necessarily, the present invention also provides the use of the above-mentioned photoinitiator.

[0010] More importantly, the present invention also provides an ink composition prepared using the above-mentioned photoinitiator.

[0011] The present invention provides a photoinitiator.

[0012] The photoinitiator is 3-methyl-4'-phenylbenzophenone, which has the following structural formula:

[0013]

[0014] The particle distribution of the 3-methyl-4'-phenylbenzophenone satisfies,

[0015]

[0016] The range of a is 1.2-2.0, preferably 1.3-1.5.

[0017] The particle size distributions D10, D50, D75, and D90 of the photoinitiator are all well-known in the art, where the particle size distribution D50, also known as the average particle size or median particle size, indicates that the photoinitiator particles with a particle size below this value account for 50% of the total volume; the particle size distribution D10 indicates that the photoinitiator particles with a particle size below this value account for 10% of the total volume; the particle size distribution D75 indicates that the photoinitiator particles with a particle size below this value account for 75% of the total volume; and the particle size distribution D90 indicates that the photoinitiator particles with a particle size below this value account for 90% of the total volume.

[0018] The numerator of the formula The difference between D90 and D50 is calculated. This difference reflects the distribution range of larger particle sizes. The larger the difference, the wider the range of large particles in the particle size distribution; the denominator of the formula The difference between D75 and D10 was calculated. This part reflects the distribution of particles with smaller particle sizes. The larger the difference, the greater the variation in particle size between small particles. By calculating the ratio of these two parts, parameter a is used to measure the distribution difference in different particle size ranges. Specifically, the size of the a value reflects the difference in distribution width between large particles and small particles. Parameter a is used to measure the uniformity and concentration of particle distribution. If the a value is large, it means that the particle size distribution is wider and the particle size difference is larger; conversely, a smaller a value means that the particle size distribution is more concentrated and the size difference is smaller. The optimal range of a value is 1.3 to 1.5, which means that within this range, the distribution of particles is neither too concentrated nor too dispersed, and the best physical properties can be achieved. Parameter a can be used to quantify the distribution characteristics of particles very well.

[0019] Wherein, the particle distribution of the 3-methyl-4'-phenylbenzophenone further satisfies:

[0020] The full width at half maximum (FWHM) is 130-310 μm, preferably 190-240 μm.

[0021] The full width at half maximum (FWHM) is the half-maximum width of the interval size distribution curve of the photoinitiator. It is the difference between the two particle sizes corresponding to half the maximum height of the interval size distribution curve of the photoinitiator particles. The interval size distribution of a photoinitiator is well known in the art and is defined as a curve plotted with particle size as the abscissa and volume percentage as the ordinate. It can accurately reflect the particle size distribution characteristics of the photoinitiator particles. The above particle size parameters can be measured using a laser particle size analyzer.

[0022] Parameters a and FWHM measure the range of the particle size distribution. A larger FWHM indicates a wider and more dispersed particle size distribution, with greater variation in particle size; a smaller FWHM indicates a more concentrated particle size distribution, with more uniform particle size. The value of parameter a is related to this; a larger a value also reflects greater variability in the particle size distribution. Parameter a quantifies particle uniformity by comparing the distribution variation within different size bins. Its calculation takes into account the width of the particles between different size distribution percentiles (such as D10, D50, D75, and D90). FWHM directly measures the width of the overall distribution curve at the midpoint (half-height). Together, they reflect the breadth and concentration of the particle size distribution. A smaller FWHM indicates a more concentrated particle size distribution, and the value of a tends to be smaller in these cases because the variation between large and small particles is smaller. If the particle size distribution curve exhibits a significant skew or bimodal shape, the value of a may be larger because the particle size variation between bins is greater, and the FWHM may not clearly reflect this asymmetry. Conversely, if the distribution is relatively symmetrical and concentrated, FWHM and a may provide a relatively consistent reflection of the particle size distribution. In practical applications, FWHM is often used to directly measure and characterize the width of the particle size distribution, while a can provide a more detailed analysis, especially when differentiating between large and small particle distributions. Combining the two provides a more comprehensive picture of the physical distribution of particles, helping to assess and optimize particle quality.

[0023] The present invention also provides a method for preparing the photoinitiator, comprising the following steps:

[0024] Ethanol is added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4-6 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture is stirred at a constant temperature of 65°C for 30-40 minutes at a stirring speed of 40-60 r / min. After 15-20 minutes, 0.5 mol / L hydrochloric acid is added dropwise in an amount of 2-4 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture is cooled to 12°C at a cooling speed of 3-5°C / 5 minutes under a stirring speed of 10-20 r / min. After crystallization, the mixture is filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0025] The present invention also provides an ink composition comprising the following components in parts by weight:

[0026] 2-6 parts of the above-mentioned photoinitiator;

[0027] 53-61 parts of resin;

[0028] 36-40 parts of acrylic acid ester monomer;

[0029] 0.1-0.3 parts of additives.

[0030] The resin is selected from one or more mixtures of modified rosin resin, allyl ester prepolymer (molecular weight 30,000-60,000), polyketone resin, modified epoxy acrylate, polyester acrylate, alkyd resin, and styrene acrylate.

[0031] Wherein, the acrylate monomer is selected from one or more of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, ditrimethylolpropane acrylate, tripropylene glycol diacrylate, propoxylated neopentyl glycol diacrylate.

[0032] Wherein, the auxiliary agent is an amine co-initiator.

[0033] The ink composition further comprises 0.2-0.3 parts of a dispersant, 0.2-0.3 parts of a leveling agent and 0.2-0.3 parts of an antioxidant.

[0034] The photoinitiator of the present invention is used to improve the wear resistance and alcohol resistance of ink.

[0035] Compared with the prior art, the photoinitiator of the present invention has a reasonable particle size distribution. The ratio of the arithmetic square root of the square number between D90 (μm) and D50 (μm) and the arithmetic square root of the square number between D7 (μm) and D10 (μm) is within a reasonable range, indicating that the photoinitiator has a suitable particle size and particle size uniformity.

[0036] Photoinitiator molecules have a certain light absorption capacity in the ultraviolet region (250-400nm) or visible light region (400-800nm). After directly or indirectly absorbing light energy, the initiator molecules transition from the ground state to an excited singlet state, and then to an excited triplet state via intersystem crossing. After undergoing unimolecular or bimolecular chemical reactions in the excited singlet or triplet state, they produce active fragments capable of initiating monomer polymerization. These active fragments can be free radicals, cations, anions, etc. Based on their initiation mechanism, photoinitiators can be divided into free radical polymerization photoinitiators and cationic photoinitiators, with free radical polymerization photoinitiators being the most widely used.

[0037] The inventors of this patent discovered that during the preparation of photocurable inks, the particle size distribution of the photoinitiator has a significant impact on the ink's ultimate performance. The main components of photocurable inks include monomers, initiators, and additives. Due to environmental protection requirements, photocurable inks are free of volatile organic compounds (VOCs) and, therefore, lack traditional organic solvents. Under these circumstances, the dissolution behavior of the photoinitiator in the ink differs significantly from that of inorganic salts in water. When inorganic salts, such as table salt, dissolve completely into ions, forming a uniform solution; however, the dissolution process of the photoinitiator is more complex. In the ink system, due to the lack of a benign organic solvent, the dissolution behavior of the photoinitiator is actually a process similar to "swelling," whereby the initiator molecules partially enter the molecular spaces between monomers or oligomers, while still retaining some of their solid-state aggregated state characteristics. This "mixed state" causes the distribution of the photoinitiator in the monomer to differ from that of inorganic salts in water, resulting in the photoinitiator existing as swollen particles.

[0038] The particle size of the photoinitiator has a significant effect on its solubility behavior in the monomer and the polymerization reaction. Since the photoinitiator exists in a swollen form, its particle size and distribution will affect the diffusion and action range of the initiator in the monomer:

[0039] (1) Light absorption capacity and photoinitiation efficiency: The particle size of the photoinitiator directly affects its light absorption capacity in the monomer. If the particles are too small, although the specific surface area is large and the light absorption capacity is strong, the swollen particles absorb light too quickly, which may cause local monomer polymerization to be too rapid, forming an uneven polymerization network. On the contrary, if the particles are too large, the light absorption capacity and speed are insufficient, which may lead to incomplete reaction. Therefore, the appropriate distribution of particle size (for example, the a value range of 1.3-1.5 is preferred in the embodiment) can ensure that the photoinitiator generates free radicals after absorbing light energy, making the polymerization reaction of the monomer more uniform.

[0040] (2) Influence of swelling behavior and aggregation state: The particle size of the photoinitiator affects its swelling degree in the monomer and its ability to maintain an aggregated state. Larger particles, due to their limited swelling degree, can maintain more solid aggregate structures. This aggregated state can provide stable active sites in the photoinitiation reaction, thereby better controlling the generation rate and concentration distribution of free radicals or cations, which is crucial for ensuring overall uniform curing and excellent physical properties of the ink.

[0041] When particles maintain an appropriate size and distribution, they form a uniform network structure within the ink, improving the ink's overall performance. If the particles are too small, the cured ink layer may become brittle, while if they are too large, uneven curing or stratification may occur. Furthermore, due to the photoinitiator's characteristic swelling behavior in the monomer, reprecipitation may occur after the photoinitiator dissolves. The particle size and distribution of this reprecipitate are directly influenced by the properties of the initial particles. Properly controlling the initiator's particle size distribution can effectively avoid the uneven performance caused by reprecipitation and ensure the overall quality of the ink.

[0042] The present invention can obtain photoinitiator particles with a specific particle size distribution through various methods such as graded sieve screening. For example, a recrystallization method can be used to dissolve 3-methyl-4'-phenylbenzophenone powder in ethanol. After dissolution, the powder is stirred at a constant temperature of 65°C for 30-40 minutes at a stirring speed of 40-60 r / min. After 15-20 minutes, 0.5 mol / L hydrochloric acid is added dropwise, and the added content of the hydrochloric acid is 2-4 wt% of the 3-methyl-4'-phenylbenzophenone. The powder is cooled to 12°C at a cooling speed of 3-5°C / 5 minutes under a stirring speed of 10-20 r / min. After crystallization, the powder is filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles with a specific distribution that can achieve the purpose of the present invention.

[0043] After the 3-methyl-4'-phenylbenzophenone is dissolved, the particle size of the 3-methyl-4'-phenylbenzophenone particles is controlled by adjusting the stirring speed, the content and addition timing of hydrochloric acid, the cooling rate, etc. The polarity of the hydrochloric acid molecules affects the crystallization rate of the 3-methyl-4'-phenylbenzophenone in ethanol, thereby affecting the particle size of the 3-methyl-4'-phenylbenzophenone particles.

[0044] Plastic film has low surface tension and poor ink-holding properties. Printed ink on plastic film easily de-inks and has poor adhesion. Plastic film is also prone to bending, which can easily lead to de-inking or scratching. The film is not resistant to ink solvents or acid-base additives, making it prone to ink dispersion or dissolution. The distribution of the ink's photoinitiator particles affects the light absorption capacity and speed, which in turn influences the degree of crosslinking in the polymerization reaction between the ink resin and acrylate monomers, thus affecting the ink's surface properties on the plastic film, such as abrasion resistance and alcohol resistance.

[0045] However, the present invention found that when the photoinitiator satisfies a certain distribution pattern, it can achieve the best initiation effect on the polymerization of the ink, and the obtained ink has higher wear resistance and alcohol resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a particle size distribution diagram of 3-methyl-4'-phenylbenzophenone particles prepared in Example 3. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with specific implementation methods.

[0048] The raw materials used in the examples and comparative examples are described as follows:

[0049] 3-Methyl-4'-phenylbenzophenone: Aladdin reagent;

[0050] Leveling agent: BYK, Germany, model: UV3500 (BYK);

[0051] Antioxidant: BHT, commercially available;

[0052] Dispersant: Lubrizol Solsperse 24000 hyperdispersant from the United States;

[0053] Resin: polyester acrylate, Changxing, Taiwan, China, 6353;

[0054] Acrylate monomers: ethoxylated trimethylolpropane triacrylate, Aladdin reagent;

[0055] The remaining raw materials were commercially available.

[0056] Example 1

[0057] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 30 minutes at a stirring rate of 40 r / min. At the 15th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 20 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0058] Example 2

[0059] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring rate of 60 r / min. At the 17th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0060] Example 3

[0061] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 6 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 35 minutes at a stirring rate of 50 r / min. At the 18th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 4 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 3°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0062] Example 4

[0063] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5.5 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 35 minutes at a stirring rate of 55 r / min. At the 18th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2.5 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 4°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0064] Example 5

[0065] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount 4.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 35 minutes at a stirring rate of 45 r / min. At the 16th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3.5 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 13 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0066] Example 6

[0067] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 35 minutes at a stirring rate of 48 r / min. At the 15th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 16 r / min at a cooling rate of 4°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0068] Example 7

[0069] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring rate of 55 r / min. At the 20th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 18 r / min at a cooling rate of 3°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0070] Example 8

[0071] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount 4.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring rate of 45 r / min. At the 15th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3.5 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 11 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0072] Example 9

[0073] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring rate of 55 r / min. At the 15th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 5°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0074] Example 10

[0075] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 38 minutes at a stirring rate of 52 r / min. At the 18th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2.5 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 18 r / min at a cooling rate of 4°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0076] Example 11

[0077] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount 4.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 38 minutes at a stirring rate of 48 r / min. At the 15th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3.5 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 13 r / min at a cooling rate of 4°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0078] Example 12

[0079] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 5 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 38 minutes at a stirring rate of 52 r / min. At the 16th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 3 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 4°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0080] Example 13

[0081] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount 4.5 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 30 minutes at a stirring rate of 44 r / min. At the 17th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 17 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0082] Example 14

[0083] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring rate of 40 r / min. At the 20th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 2 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 15 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0084] Example 15

[0085] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 6 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 30 minutes at a stirring speed of 60 r / min. At the 20th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 4 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring speed of 20 r / min at a cooling rate of 3°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0086] Comparative Example 1

[0087] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring speed of 60 r / min. The mixture was then cooled to 12°C at a stirring speed of 15 r / min at a cooling rate of 5°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0088] Comparative Example 2

[0089] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 40 minutes at a stirring speed of 60 r / min. At the 20th minute, 0.5 mol / L of sodium hydroxide was added dropwise in an amount of 3 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring speed of 15 r / min at a cooling rate of 5°C / 5 min. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0090] Comparative Example 3

[0091] Ethanol was added to 3-methyl-4'-phenylbenzophenone powder in an amount of 4 times the amount of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture was stirred at a constant temperature of 65°C for 45 minutes at a stirring rate of 30 r / min. At the 10th minute, 0.5 mol / L hydrochloric acid was added dropwise in an amount of 6 wt% of the 3-methyl-4'-phenylbenzophenone. The mixture was cooled to 12°C at a stirring rate of 5 r / min at a cooling rate of 6°C / 5 minutes. After crystallization, the mixture was filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles.

[0092] The products obtained in Examples 1-15 and Comparative Examples 1-3 were subjected to particle size statistics.

[0093] The measuring instrument is an OMEC particle size analyzer. All prepared samples are added to the sample cell of the injector. After the shading ratio is stabilized, the samples are measured immediately to obtain the data, see Table 1.

[0094] Table 1

[0095]

[0096]

[0097] The 3-methyl-4'-phenylbenzophenone particles prepared in Examples 1-15 and Comparative Examples 1-3 were used to prepare inks (as shown in the ink formula table in Table 2 below):

[0098] 3-Methyl-4'-phenyl benzophenone particles, resin (polyester acrylate), acrylate monomer (ethoxylated trimethylolpropane triacrylate), amine co-initiator (6422TF, Changxing Special Materials (Zhuhai) Co., Ltd.), dispersant (Lubrizol Solsperse 24000 hyperdispersant, USA), leveling agent (UV3500 (BYK)), and antioxidant (antioxidant BHT) were mixed uniformly according to the weight parts shown in Table 2 to obtain an ink.

[0099] The photoinitiators in Experimental Examples 1 to 15 were the 3-methyl-4'-phenylbenzophenone particles prepared in Examples 1 to 15, respectively. The photoinitiators in Experimental Examples 16 and 17 were the 3-methyl-4'-phenylbenzophenone particles prepared in Example 3.

[0100] The photoinitiators of Comparative Experimental Examples 1, 2 and 3 respectively used the 3-methyl-4'-phenylbenzophenone particles prepared in Comparative Examples 1, 2 and 3.

[0101] Table 2 Ink composition ratio table (unit: weight parts)

[0102]

[0103] Test methods for ink performance

[0104] 1. Gloss test (QB573-83)

[0105] The gloss of ink is measured in accordance with the "QB573-83 Ink Gloss Test Method". The ink is placed on a PET plastic film and scraped into thin layers of printed samples of the same size. The gloss is measured using a DTH-80 glossmeter. Under the illumination of a fixed light source, the ratio of the reflected luminous flux of the sample to that of the standard surface is used to express the gloss of the sample ink (the reflected luminous flux of the standard surface is taken as 100%). The higher the gloss, the better its gloss performance.

[0106] 2. Wear resistance (adhesion)

[0107] Abrasion resistance testing was performed according to GB 1768-1979 Test Method for Abrasion Resistance of Coatings. The specific steps are as follows: ink was evenly rolled onto PET plastic films of equal size and allowed to dry before use. The sample was fixed to the work turntable of the abrasion tester using an MCJ-01A friction tester (provided by Jinan Languang Electromechanical Technology Co., Ltd.), with the parameters set to 200 times and 40N. After the test, the sample was removed, brushed to remove debris, and weighed. The difference in weight before and after the test was the ink weight loss. The smaller the ink weight loss, the better the abrasion resistance.

[0108] 3. Alcohol resistance

[0109] The sample was immersed in 75% alcohol (25° C.) for 12 hours, taken out, rinsed, dried, and then tested for gloss and abrasion resistance (adhesion) according to the above test method.

[0110] Gloss reduction rate = |(gloss before alcohol resistance treatment - gloss after alcohol resistance treatment)| / gloss before alcohol resistance treatment; adhesion reduction rate = |(adhesion before alcohol resistance treatment - adhesion after alcohol resistance treatment)| / adhesion before alcohol resistance treatment.

[0111] Table 3 Test results

[0112]

[0113]

[0114] The above data show that the photoinitiator prepared by the present invention, by using a photoinitiator with a specific particle distribution as an ink photoinitiator, can produce ink with high gloss, and in particular, the ink on the surface of the produced plastic film has good abrasion resistance and alcohol resistance.

[0115] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A photoinitiator, characterized in that: The photoinitiator is 3-methyl-4'-phenylbenzophenone, having the following structural formula: The particle distribution of the 3-methyl-4'-phenylbenzophenone satisfies: The range of a is 1.2-2.

0.

2. The photoinitiator according to claim 1, characterized in that: The range of a is 1.3-1.

5.

3. The photoinitiator according to claim 1, characterized in that: The particle distribution of the 3-methyl-4'-phenylbenzophenone also satisfies: The half-width (FWHM) is 130-310 μm, preferably 190-240 μm.

4. The method for preparing the photoinitiator according to any one of claims 1 to 3, characterized in that: The following steps are involved: Ethanol is added to 3-methyl-4'-phenylbenzophenone powder, wherein the added mass of ethanol is 4-6 times that of the 3-methyl-4'-phenylbenzophenone powder. After dissolution, the mixture is stirred at a constant temperature of 65° C. for 30-40 minutes at a stirring speed of 40-60 r / min. At the 15th to 20th minute, 0.5 mol / L hydrochloric acid is added dropwise, wherein the added content of the hydrochloric acid is 2-4 wt % of the 3-methyl-4'-phenylbenzophenone solution. The mixture is cooled to 12° C. at a stirring speed of 10-20 r / min at a cooling speed of 3-5° C. / 5 min. After crystallization, the mixture is filtered and dried to obtain 3-methyl-4'-phenylbenzophenone particles satisfying the particle size distribution.

5. An ink composition, characterized in that: The components include the following by weight: 2-6 parts of the photoinitiator according to any one of claims 1-3; Resin 15-50 parts; 15-30 parts of acrylic acid ester monomer; Additives 0.1-3 parts.

6. The ink composition according to claim 5, characterized in that: The resin is selected from one or more mixtures of modified rosin resin, allyl ester prepolymer, polyketone resin, modified epoxy acrylate, polyester acrylate, alkyd resin, and styrene acrylate.

7. The ink composition according to claim 5, characterized in that: The acrylate monomer is selected from one or more of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, ditrimethylolpropane acrylate, tripropylene glycol diacrylate, and propoxylated neopentyl glycol diacrylate.

8. The ink composition according to claim 5, characterized in that: The auxiliary agent is an amine auxiliary initiator.

9. The ink composition according to claim 5, characterized in that: The ink composition further comprises 0.2-2 parts of a dispersant, 0.05-0.1 parts of a polymerization inhibitor and 0.1-0.3 parts of an antioxidant.

10. Use of the photoinitiator according to any one of claims 1 to 3 in preparing ink for printing on plastic products.

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