A bio-based LED light-cured top-coat pencil lacquer, a preparation method and application thereof

Abstract

The application discloses a kind of bio-based LED light-cured top-dipping pencil paint and its preparation method and application, including the following mass fraction of composition: epoxy acrylate: 27%~40%, epoxy soybean oil acrylate: 12%~15%, di-functional polyurethane acrylate: 8%~30%, dipropylene glycol diacrylate: 10%~20%, fumed silica: 0.2%~0.5%, inorganic filler: 10%~20%, photoinitiator: 5%~10%, auxiliary agent: 0.5%~1%. The pencil paint of the application meets the requirements of relevant laws and regulations for pencil paint export, the bio-based carbon content is greater than or equal to 15%, uses LED lamp to cure, is energy-saving and environment-friendly, the paint film has high flexibility, can be used for eyebrow pencil, and there is no risk of subsidence.

Description

Technical Field

[0001] This invention belongs to the field of pencil light-curing coatings, specifically relating to a bio-based LED light-curing adhesive pencil paint for coating and protecting the tip of a pencil. Technical Background

[0002] Ultraviolet (UV) radiation curing technology is an environmentally friendly technology, and UV-cured coatings produced using this technology are simply called UV coatings. While mercury lamps are the mainstream UV curing lamps, they have several drawbacks: mercury lamps experience rapid intensity decay, have a short lifespan, and high maintenance costs; they also have slow start-up times, high power consumption, high equipment temperatures, and high surface temperatures on the irradiated components, potentially causing deformation; furthermore, mercury lamps contribute to mercury and ozone pollution. LED lamps, on the other hand, offer advantages such as low energy consumption, long lifespan, instantaneous response, high output, and are mercury-free and ozone-free. As an energy-saving and environmentally friendly curing technology, LED curing is increasingly being used in UV coatings, especially in fields with high environmental and energy-saving requirements, such as pencils, children's toys, and children's furniture.

[0003] In the pencil industry, traditional solvent-based coatings (such as patent document CN107474636A) are gradually being replaced by water-based coatings due to their poor environmental performance caused by solvents. For example, patent documents CN113249001A and CN113185907A both disclose a water-based pencil tip paint. However, both solvent-based and water-based coatings have drawbacks such as low coating efficiency, slow drying speed, thin film, many coats required, low hardness, and generally poor fullness. Therefore, more and more customers are demanding UV coatings as a protective coating for pencil tips.

[0004] A single application of UV coatings yields a high-hardness, full-bodied paint film with rapid curing, significantly reducing drying time and eliminating the influence of weather humidity. This improves the surface quality of the pencils and increases production efficiency. Then, depending on the desired color effect, a second layer of water-based color paint can be applied.

[0005] Currently, the use of UV coatings in my country's pencil industry is relatively limited; they are only applied to the tips of pencils, while mercury lamps remain the primary curing method. For example, patent document CN1580159A discloses a single-component UV-curable topcoat, comprising 27%–40% epoxy acrylate resin as the active oligomer, 40%–53% trimethylolpropane triacrylate or tripropylene glycol diacrylate as the active diluent, plus 20% 3136 alkyd resin and 1%–2% photosensitizer, wherein the photosensitizer is at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxy-cyclohexyl-phenyl ketone. This document incorporates a photosensitive material, resulting in rapid curing, excellent effect, full top coating, and good adhesion without peeling after light exposure.

[0006] With increasing environmental awareness, leading companies in the pencil industry have raised the demand for bio-based LED-cured topcoat pencil paints: 1. Compliant with relevant export laws and regulations for pencil paints, passing various chemical tests. 2. Using bio-based materials, which can be used as a selling point. 3. Cured using only LED lamps, without mercury lamps. 4. Excellent adhesion to the substrate and top water-based coatings; no stringing, dripping, uneven application, or sinking.

[0007] Patent document CN111154384A discloses an LED pencil tip paint and its preparation method, comprising the following components in parts by weight: 50-70 parts of bisphenol A epoxy acrylate resin; 18-30 parts of polyester acrylate resin; 0.3-0.7 parts of defoamer; 9-12 parts of acrylate monomer (hydroxyethyl methacrylate or diethylene glycol diacrylate); 1.5-2.5 parts of photoinitiator; 2-4 parts of reactive amine co-initiator; 1.2-1.6 parts of thickener; and 2-3 parts of functional additives (isooctyltriethoxysilane and tetrabutyl titanate in a mass ratio of 1:(3-5)). This invention solves the problems of poor surface drying and poor deep curing when thick coatings are applied, which are easily caused by oxygen inhibition during the curing process of the tip paint. However, this paper also has the following problems: The pencil paint is not environmentally friendly enough: the polyester acrylic resin and thickener are very likely to contain CMR substances, and hydroxyethyl methacrylate cures very slowly, which can easily cause monomer residues; the pencil paint does not contain bio-based components; the pencil paint is not suitable for eyebrow pencils because the tip of the eyebrow pencil has a hole, which needs to be filled with a certain amount of powder, and the paint film has high flexibility requirements, otherwise there will be a risk of sinking.

[0008] Patent document CN111440512A discloses a UV glossy gold paint coating for pencil tips, comprising: epoxy acrylate: 45%–65%, fatty acid modified epoxy acrylate: 10%–20%, polyester acrylate: 20%–30%, defoamer: 0.2%–0.3%, and photoinitiator: 4.0%–7.0%. However, this document also has the following problems: the pencil paint is not environmentally friendly enough; the polyester acrylate resin is very likely to contain CMR substances; the pencil paint does not contain bio-based components; the pencil paint is not suitable for eyebrow pencils because eyebrow pencils have holes at the tip, requiring a certain amount of powder to fill them, and the paint film requires high flexibility, otherwise there is a risk of sagging; the pencil paint is cured with a mercury lamp, not an LED lamp; the pencil paint does not contain monomers, has a very high viscosity, and in winter it is easy to cause a high coating amount, affecting adhesion, and there is also a risk of stringing. Summary of the Invention

[0009] To meet the above requirements, this invention provides a bio-based LED light-curing top-coating pencil paint and its preparation method. The raw materials selected comply with the relevant laws and regulations for pencil paint exports. The formula needs to meet the requirements of pure LED curing, no stringing, no deviation, no sinking, good fullness, good adhesion to the substrate, and good adhesion to the top water-based coating, and contains bio-based materials.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The present invention discloses a bio-based LED light-curable top-coating pencil paint, characterized in that it comprises the following components in the indicated mass fractions: epoxy acrylate: 27%–40%, epoxy soybean oil acrylate: 12%–15%, difunctional polyurethane acrylate: 8%–30%, dipropylene glycol diacrylate: 10%–20%, fumed silica: 0.2%–0.5%, inorganic filler: 10%–20%, photoinitiator: 5%–10%, and additives: 0.5%–1%.

[0012] The epoxy acrylate is an epoxy acrylate with a functionality of 1 to 3, prepared by ring-opening esterification of acrylic acid or methacrylic acid with epoxy resin, and a viscosity of 20,000 to 50,000 cps, such as S6101 produced by Zhuhai Zhancheng New Materials Co., Ltd.

[0013] The epoxidized soybean oil acrylate is an epoxidized soybean oil acrylate with a functionality of 1 to 3 and a viscosity of 20,000 to 40,000 cps, produced by esterification reaction of epoxidized soybean oil with acrylic acid or methacrylic acid, such as ETERCURE 6265 produced by Changxing Chemical.

[0014] The difunctional polyurethane acrylate is a difunctional polyurethane acrylate produced by reacting aliphatic polyurethane prepolymer with hydroxyethyl acrylate, with a viscosity of 30,000 to 50,000 cps, such as CR92099NT produced by Guangdong Haohui New Materials.

[0015] The dipropylene glycol diacrylate is a bifunctional monomer with CAS number 57472-68-1.

[0016] The fumed silica refers to hydrophobic fumed silica powder modified by silane treatment, such as Evonik's R972;

[0017] The inorganic filler is one or both of talc and transparent powder;

[0018] The photoinitiator refers to a substance that can cause overall drying, surface drying, and deep drying of the coating system under LED light irradiation, such as photoinitiator TPO, photoinitiator 819, photoinitiator ITX, and active amines (such as HL-P115 from Dongtou Hengli).

[0019] The additives include dispersants, anti-settling agents, wetting agents, and other conventional additives in the art. The specific dosage of each additive can be adjusted according to the actual situation during use, within the range of conventional dosages in the art.

[0020] The preparation method of the bio-based LED light-curing adhesive pencil paint of the present invention includes the following steps: epoxy acrylate, epoxy soybean oil acrylate, difunctional polyurethane acrylate, dipropylene glycol diacrylate, fumed silica, ultrafine inorganic filler, photoinitiator and additives are added into a reaction vessel in proportion, heated to 40-50°C, and dispersed at a high speed of 1500-2000 rpm for 1-2 hours until uniform and free of oil shrinkage, thereby obtaining the bio-based LED light-curing adhesive pencil paint.

[0021] This invention provides a bio-based LED light-curing top-coating pencil paint suitable for pencils of various substrates. Simply apply one coat to the tip of the pencil, cure it with an LED lamp, and a uniform and full paint film can be obtained. Then, apply a water-based coating.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The bio-based LED light-curing top-coating pencil paint of this invention uses epoxy acrylate as the main resin, giving the paint film high curing speed and high hardness. It is then combined with difunctional polyurethane to improve the flexibility and adhesion of the paint film. A small amount of epoxy soybean oil acrylate is added to further improve the flexibility of the paint film and to reduce the curing of the paint film surface, thereby improving interlayer adhesion with water-based coatings. Additionally, talc is added to roughen the paint film surface, further improving interlayer adhesion with water-based coatings. Dipropylene glycol diacrylate is added to adjust the viscosity and coating amount, ensuring that the paint does not string, drip, deviate, or sink, and has good fullness and adhesion.

[0024] The pencil paint of this invention complies with the relevant laws and regulations for pencil paint exports and has passed various chemical tests, including: formaldehyde, CMR substances, phthalates, polycyclic aromatic hydrocarbons, organotin compounds, cadmium and its compounds, lead and its compounds, specific element migration, VOCs, free monomers and free photoinitiators, etc., ensuring the environmental friendliness of the paint; it uses bio-based materials with a bio-based carbon content of ≥15%, responding to the green and sustainable development strategy; it uses LED lamps for curing, which is energy-saving and environmentally friendly, and in particular, the paint film has high flexibility, so it can be used in eyebrow pencils without the risk of sagging.

[0025] Specific construction methods:

[0026] The present invention will be further illustrated below by way of embodiments. It should be noted that the embodiments of the present invention are only for explanation and illustration of the content of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0027] The raw materials used in the following examples are all commercially available products, including: epoxy acrylate: S6101 produced by Zhuhai Zhancheng New Materials Co., Ltd., 2-functionality, viscosity 20,000-30,000 cps; epoxy soybean oil acrylate: ETERCURE 6265 produced by Changxing Chemical, 2-functionality, viscosity 30,000-40,000 cps; difunctional polyurethane acrylate: CR92099NT produced by Guangdong Haohui New Materials, viscosity 40,000-50,000 cps; fumed silica: Evonik's R972; inorganic filler: talc powder, KB-10-2 from Guangxi Guilin Guiguang Talc Development Co., Ltd., particle size 20-30 μm; photoinitiators: photoinitiator TPO, photoinitiator 819, and photoinitiator ITX produced by Jiuri.

[0028] Examples 1-4

[0029] The components and mass fractions of the bio-based LED light-curing adhesive pencil paints in Examples 1-4 are listed in Table 1. Preparation of the bio-based LED light-curing adhesive pencil paint: The epoxy acrylate, epoxy soybean oil acrylate, difunctional polyurethane acrylate, dipropylene glycol diacrylate, fumed silica, ultrafine inorganic filler, photoinitiator, and additives are sequentially added to a reaction vessel in proportion. The mixture is heated to 40-50°C and dispersed at a high speed of 1500-2000 rpm for 1-2 hours until uniform and free of oil shrinkage, thus obtaining the bio-based LED light-curing adhesive pencil paint.

[0030] In Example 1, the pencil substrate was poplar, birch, or pine; in Example 2, the pencil substrate was linden; in Example 3, the pencil was a large carbon lead pencil; and in Example 4, the pencil was an eyebrow pencil. A layer of bio-based LED-cured topcoat pencil paint was applied to the tip of the pencil, cured by an LED lamp, followed by a layer of water-based pencil paint. The pencil was then dried in an infrared oven to complete the coating process.

[0031] Table 1. Components of the top-coating pencil paints in Examples 1-4, wt%.

[0032]

[0033]

[0034] After the bio-based LED light-curing adhesive pencil paint applied in Examples 1-4 was cured, it was sent to a testing institution for testing of phthalates, polycyclic aromatic hydrocarbons, organotin compounds, cadmium and its compounds, lead and its compounds, migration of specific elements, VOCs, free monomers and free photoinitiators.

[0035] After the bio-based LED light-curing adhesive pencil paint applied in Examples 1 to 4 is cured, observe whether there are any abnormalities such as stringing, sagging, tilting, or sinking of the paint film, and then see if the paint film is easily peeled off when scratched with a fingernail.

[0036] After the bio-based LED light-curing top pencil paint applied in Examples 1-4 is cured, another layer of water-based pencil paint is applied. After it is completely dried, the adhesion is tested by scratching the paint film with a fingernail.

[0037] Based on the addition ratio of epoxidized soybean oil acrylate (bio-based resin) in the formulations designed in Examples 1-4 and the coating process, the bio-based carbon content can be calculated using the bio-based carbon calculation method. The test results obtained above are listed in Table 3.

[0038] Comparative Examples 1-4

[0039] The components and mass fractions of LED-cured top-coating pencil paints used in Comparative Examples 1–4 are listed in Table 2, and the test results are listed in Table 4.

[0040] Table 2. Components of top-coating pencil paints in Comparative Examples 1–4, wt%.

[0041]

[0042]

[0043] Table 3 Test results of Examples 1-4

[0044]

[0045]

[0046] Table 4 shows the test results of Comparative Examples 1 to 4.

[0047]

[0048] A comparison of the test results from the examples and comparative examples shows that: when the pencil substrate is poplar, birch, or pine, reducing epoxy acrylate and increasing difunctional polyurethane acrylate will decrease the curing speed and the cross-linking density of the paint film, resulting in poorer adhesion to the substrate; when the pencil substrate is linden, reducing the talc content and increasing the epoxy soybean oil acrylate will decrease the curing speed and increase the curing shrinkage rate of the paint film, resulting in poorer adhesion to the substrate; when the pencil is a large carbon lead pencil, reducing the talc content and increasing the epoxy acrylate will increase the hardness and cross-linking density of the paint film, resulting in poorer adhesion to the water-based paint layer; when the pencil is an eyebrow pencil, reducing the talc content and increasing the epoxy acrylate will increase the curing shrinkage rate of the paint film and reduce the filling of the small holes at the tip of the eyebrow pencil, resulting in sagging.

[0049] In summary, the bio-based LED light-cured top-coating pencil paint of this invention complies with the relevant laws and regulations for pencil paint exports and has passed various chemical tests, ensuring the environmental friendliness of the coating. Furthermore, it responds to the green and sustainable development strategy, as the coating contains bio-based carbon with an average content of ≥15%. On different pencil substrates, using the coating method described in the above embodiments, it exhibits no stringing, no sagging, no unevenness, no sinking, good fullness, good adhesion to the substrate, and good adhesion between water-based paint layers, fully meeting customer needs.

Claims

1. A bio-based LED light-curable top-coating pencil paint, characterized in that, It is made from the following components in the indicated mass fractions: epoxy acrylate: 27%–40%, epoxy soybean oil acrylate: 12%–15%, difunctional polyurethane acrylate: 8%–30%, dipropylene glycol diacrylate: 10%–20%, fumed silica: 0.2%–0.5%, inorganic filler: 10%–20%, photoinitiator: 5%–10%, and additives: 0.5%–1%. The epoxy acrylate is an epoxy acrylate with a functionality of 1-3, prepared by ring-opening esterification of acrylic acid or methacrylic acid with epoxy resin, and a viscosity of 20,000-50,000 cps; the epoxy soybean oil acrylate is an epoxy soybean oil acrylate with a functionality of 1-3, prepared by esterification reaction of epoxy soybean oil with acrylic acid or methacrylic acid, and a viscosity of 20,000-40,000 cps; the difunctional polyurethane acrylate is a difunctional polyurethane acrylate prepared by reacting aliphatic polyurethane prepolymer with hydroxyethyl acrylate, and a viscosity of 30,000-50,000 cps; the inorganic filler is one or both of talc powder and transparent powder.

2. The bio-based LED light-curable top-coating pencil paint according to claim 1, characterized in that, The fumed silica refers to hydrophobic fumed silica powder modified by silane treatment; the photoinitiator is photoinitiator TPO, photoinitiator 819, photoinitiator ITX or an active amine.

3. The bio-based LED light-curable top-coating pencil paint according to claim 1, characterized in that, The additives include dispersants, anti-settling agents, and / or wetting agents.

4. The preparation method of the bio-based LED light-curable top-coating pencil paint according to any one of claims 1 to 3, characterized in that, Includes the following steps: The epoxy acrylate, epoxy soybean oil acrylate, difunctional polyurethane acrylate, dipropylene glycol diacrylate, fumed silica, inorganic filler, photoinitiator and additives are added to a reaction vessel in a certain proportion, heated to 40-50°C, and dispersed at a high speed of 1500-2000 rpm for 1-2 hours until uniform and free of oil shrinkage, thus obtaining the bio-based LED light-curing top pencil paint.

Images