Primer with high adhesive force and high heat resistance as well as preparation method and application of primer to pre-coating film

Abstract

The invention discloses a primer with high adhesive force and high heat resistance as well as a preparation method and application of the primer to a pre-coating film. The primer is prepared from the following raw materials in parts by weight: 60 to 80 parts of 2-functionality polyurethane acrylate A, 20 to 40 parts of acrylate reactive diluent, 0.5 to 5 parts of photoinitiator and 0 to 10 parts of pigment filler, the polyurethane acrylate A with the functionality degree of 2 is polyether polyester modified polyurethane acrylate A with the functionality degree of 2. Through cooperation of molecular structure design and process, balance between high rigidity (Tg is greater than or equal to 40 DEG C) and moderate flexibility (elongation at break is greater than or equal to 20%) of the coating is realized. The moderate elongation at break is kept while the higher Tg is maintained, so that the heat resistance and the adhesive force are balanced.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and in particular, to a primer with high adhesion and high heat resistance, a preparation method thereof, and an application on a pre-coated film. Background Art

[0002] With the wide application of pre-coated film technology in the fields of furniture, PVC floors, automotive interiors, etc., the performance requirements for primers are becoming increasingly stringent. Traditional primers are prone to problems such as softening and decreased adhesion in high-temperature environments, while in low-temperature or thermal cycling conditions, the coatings are prone to brittle cracking and peeling due to insufficient toughness, severely restricting their reliability under extreme working conditions. In the prior art, research on improving the performance of primers mainly focuses on single-performance optimization, but it is often difficult to balance multiple requirements such as low-temperature and high-temperature toughness, heat resistance, and adhesion. The specific limitations are as follows: 1. The contradiction between heat resistance and toughness: Existing high-heat-resistant primers mostly adopt high-crosslinking-density epoxy resins or phenolic systems (such as CN112375429A). Although they can withstand temperatures above 200°C, the molecular chain segments are too rigid and are prone to brittle fracture under low temperature or thermal shock. The elongation at break is generally less than 10%, and they cannot adapt to wide-temperature-range application scenarios. 2. The bottleneck in improving adhesion: Conventional adhesion-enhancing means (such as phosphate ester coupling agents or silane treatment) can improve the interfacial bonding between the primer and the substrate (CN113736285A), but in long-term high-low temperature cycling, due to the difference in the thermal expansion coefficients of the resin and the substrate, stress concentration is easily caused, resulting in adhesion attenuation. For example, the adhesion of a modified acrylic primer decreased from an initial 5B to 2B (ASTM D3359) after 100 thermal cycling tests. 3. Insufficient adaptability to pre-coated film substrates: Pre-coated film substrates (such as BOPP, PET, metallized films) have low surface energy and a weak boundary layer, and it is difficult for traditional primers to form a dense anchoring structure. Patent CN114456739A improves the roughness by introducing nano-silica, but excessive filling will sacrifice the flexibility of the coating, instead reducing the low-temperature impact performance by more than 30%.

[0003] In view of the above problems, the present patent innovatively proposes a primer with both high adhesion and heat stability. Through multi-scale interfacial enhancement design and dynamic crosslinking network regulation, it breaks through the bottleneck of performance imbalance in traditional technologies and provides a reliable solution for the long-term service of pre-coated films in extreme environments. Summary of the Invention

[0004] The purpose of the present invention is to provide a primer with high adhesion and wide-temperature-range toughness, a preparation method thereof, and an application on a pre-coated film, which solves the problems of poor low-temperature impact resistance, poor high-temperature thermal stability, and insufficient adhesion or flexibility of existing primers.

[0005] The present invention achieves the above purpose through the following technical solutions:

[0006] A primer with high adhesion and high heat resistance, comprising the following components in parts by weight:

[0007] 60 to 80 parts by weight of difunctional polyurethane acrylate A, 20 to 40 parts by weight of acrylate active diluent, 0.5 to 5 parts by weight of photoinitiator, 0 to 10 parts by weight of pigment filler; the difunctional polyurethane acrylate A is difunctional polyether polyester modified polyurethane acrylate A.

[0008] The present invention has no particular limitation on the parts by weight of difunctional polyether polyester modified polyurethane acrylate A. For example, it can be difunctional polyether polyester modified polyurethane acrylate A with a mass of 60 to 80 parts by weight. Exemplarily, the mass percentage of the difunctional polyether polyester modified polyurethane acrylate A is 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, and any value within the range formed by any two of these point values.

[0009] The present invention has no particular limitation on the parts by weight of acrylate active diluent. For example, it can be acrylate active diluent with a mass of 20 to 40 parts by weight. Exemplarily, the mass percentage of the acrylate active diluent is 20 parts by weight, 30 parts by weight, 40 parts by weight, and any value within the range formed by any two of these point values.

[0010] The present invention has no particular limitation on the parts by weight of photoinitiator. For example, it can be photoinitiator with a mass of 0.5 to 5 parts by weight. Exemplarily, the mass percentage of the photoinitiator is 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, and any value within the range formed by any two of these point values.

[0011] The present invention has no particular limitation on the parts by weight of pigment filler. For example, it can be pigment filler with a mass of 0 to 10 parts by weight. Exemplarily, the mass percentage of the pigment filler is 0 parts by weight, 2 parts by weight, 4 parts by weight, 6 parts by weight, 8 parts by weight, 10 parts by weight, and any value within the range formed by any two of these point values.

[0012] According to a preferred embodiment of the present invention, the bifunctional polyether polyester modified polyurethane acrylate A is prepared by reacting the following components: IPDI, where IPDI is isophorone diisocyanate; PCL 1000, where PCL 1000 is a polycaprolactone polyol with a molecular weight of 1000; PCL 2000, where PCL 2000 is a polycaprolactone polyol with a molecular weight of 2000; CHDM, where CHDM is 1,4-cyclohexanedimethanol; HEA, where HEA is hydroxyethyl acrylate with a content of 97%; polymerization inhibitor, where the polymerization inhibitor is BHT, MEHQ; BHT is dibutylhydroxytoluene, and MEHQ is p-methoxyphenol; catalyst, where the catalyst is DBTL, and DBTL is dibutyltin dilaurate.

[0013] According to a preferred embodiment of the present invention, the molar ratio of the IPDI, the PCL 1000, the PCL 2000, the CHDM, the HEA, the BHT, the MEHQ, and the DBTL is: 1:1.2:1:1:0.067:0.0136:0.0399:0.00158.

[0014] According to a preferred embodiment of the present invention, the amounts of the IPDI, the PCL 1000, the PCL 2000, the CHDM, the HEA, the BHT, the MEHQ, and the DBTL are as follows: 0.1 mol of IPDI, where IPDI is isophorone diisocyanate; 0.12 mol of PCL 1000, where PCL 1000 is a polycaprolactone polyol with a molecular weight of 1000; 0.1 mol of PCL 2000, where PCL 2000 is a polycaprolactone polyol with a molecular weight of 2000; 0.1 mol of CHDM, where CHDM is 1,4-cyclohexanedimethanol; 0.8 ml of HEA, where HEA is hydroxyethyl acrylate with a content of 97%; polymerization inhibitor, where the polymerization inhibitor is 0.3 g of BHT and 0.6 g of MEHQ; 0.1 g of catalyst.

[0015] According to a preferred embodiment of the present invention, the catalyst is DBTL; BHT is dibutylhydroxytoluene, MEHQ is p-methoxyphenol, and DBTL is dibutyltin dilaurate.

[0016] In the solution of the present invention, the specific content of the PCL 1000 improves the reaction activity of the solution of the present invention. The specific content of the PCL 2000 enhances the chain segment flexibility, synergistically optimizing the coating elasticity and adhesion. The hydroxyl functional groups contained in the PCL 1000 and / or PCL 2000 react with the IPDI to generate a polyurethane prepolymer, forming a coating skeleton structure.

[0017] In the solution of the present invention, the CHDM with a specific content is used as a chain extender to adjust the regularity of molecular chain segments during the reaction, enhance the hardness and scratch resistance of the coating; its cyclic structure can reduce the thermal shrinkage stress.

[0018] In the solution of the present invention, the HEA with a specific content introduces acrylic double bonds and hydroxyl groups during the reaction, participates in the synthesis of polyurethane prepolymers, and provides active sites for UV curing.

[0019] In the solution of the present invention, the BHT / MEHQ with a specific content inhibits the pre-polymerization initiated by free radicals during storage or reaction to ensure the stability of the formulation.

[0020] In the solution of the present invention, the DBTL with a specific content accelerates the polycondensation reaction of isocyanate and hydroxyl groups during the reaction, shortens the reaction time and reduces the risk of side reactions.

[0021] According to a preferred embodiment of the present invention, the reaction includes the following steps:

[0022] S1. Mix the PCL 1000, PCL 2000, and CHDM, heat up, dehydrate under vacuum, and cool to obtain mixture 1;

[0023] S2. Mix the mixture 1 obtained in step S1 with IPDI, stir and heat up, and then add the DBTL to obtain mixture 2;

[0024] S3. Add HEA, BHT, and MEHQ to the mixture 2 obtained in step S2 to obtain the bifunctional polyether-polyester modified polyurethane acrylate A.

[0025] According to a preferred embodiment of the present invention, in step S1, after mixing, heat up to 110 °C, dehydrate under vacuum for 40 minutes, and cool to 25 °C.

[0026] According to a preferred embodiment of the present invention, in step S2, the reaction temperature is 55 - 60 °C, and the reaction is carried out for 0.5 h.

[0027] According to a preferred embodiment of the present invention, in step S3, the reaction temperature is 65 - 70 °C, and the reaction is carried out for 0.5 h.

[0028] In the present invention, in step S2, the reaction temperature is 55 - 60 °C, for example, it can be 55 °C, 57 °C, 60 °C, and any value within the range formed by any two of these point values.

[0029] In the present invention, in step S3, the reaction temperature is 65 - 70 °C, for example, it can be 65 °C, 67 °C, 70 °C, and any value within the range formed by any two of these point values.

[0030] The present invention also provides a method for preparing the primer, which includes mixing a difunctional polyether-polyester modified polyurethane acrylate A with an acrylate active diluent, a photoinitiator, and a pigment filler.

[0031] In the solution of the present invention, the acrylate active diluent with a specific content, as an active diluent, reduces the viscosity of the system to improve the workability; and participates in the UV curing crosslinking through homopolymerization or copolymerization to adjust the balance between the flexibility and hardness of the coating.

[0032] According to a preferred embodiment of the present invention, the acrylate active diluent is at least one of a monofunctional active diluent TMCHA, a monofunctional active diluent IBOA, and a monofunctional active diluent CTFA.

[0033] According to a preferred embodiment of the present invention, the photoinitiator is selected from at least one of MBP, 184, and TPO-L; and the pigment filler is SiO2.

[0034] In the solution of the present invention, the photoinitiator with a specific content decomposes under UV light to generate free radicals, triggering the polymerization reaction of the acrylic double bond to achieve rapid curing.

[0035] In the solution of the present invention, the pigment filler with a specific content provides color covering power; excessive addition may reduce the flexibility and curing efficiency of the coating.

[0036] The present invention also provides an application of the primer on a pre-coated film.

[0037] The beneficial effects of the present invention are as follows:

[0038] Through the coordination of molecular structure design and process, the present invention realizes the balance between high rigidity (Tg≥40°C) and moderate flexibility (elongation at break≥20%) of the coating. The specific technical effects are as follows: Isophorone diisocyanate (IPDI) and 1,4-cyclohexanedimethanol (CHDM) are used to construct a rigid skeleton, improving the crosslinking density and thermal stability; flexible chain segments are introduced through polycaprolactone polyol (PCL 1000 / 2000) with a molecular weight gradient distribution to absorb stress deformation and avoid brittle fracture. Hydroxyethyl acrylate (HEA) provides double bond active sites, and cooperates with monofunctional acrylate monomers to regulate the crosslinking network, achieving second-level curing in combination with a photoinitiator, while maintaining high adhesion of the coating to metal / plastic substrates. The aliphatic structure of IPDI avoids yellowing, the BHT / MEHQ double inhibitor inhibits free radical side reactions during storage and reaction, and the DBTL catalyst precisely controls the polycondensation rate of the prepolymer to ensure a uniform molecular weight distribution. The process of controlling temperature in stages and vacuum dehydration eliminates the interference of the moisture of the polyol, improves the purity of the prepolymer, and the pigment filler can be added in a customized manner to enhance the covering or functionality. Specific Embodiments

[0039] I. Main raw materials:

[0040] IPDI (Isophorone diisocyanate): Molecular weight 222.29, purchased from Wanhua Chemical Group Co., Ltd.

[0041] PCL 1000 (Polycaprolactone polyol): Molecular weight 1000, purchased from Guangzhou Haoyi Chemical Technology Co., Ltd. PCL 2000 (Polycaprolactone polyol): Molecular weight 2000, purchased from Hunan Juren Chemical New Materials Technology Co., Ltd.

[0042] CHDM (1,4 - Cyclohexanedimethanol): Molecular weight 144.21, purchased from Greenlink (Jining) Chemical Technology Co., Ltd.

[0043] HEA (Hydroxyethyl acrylate, 97%): Molecular weight 116.11, purchased from Jinan Aochen Chemical Co., Ltd.

[0044] BHT (Dibutylhydroxytoluene): Molecular weight 220.35, purchased from Hunan Jushuo Biotechnology Co., Ltd.

[0045] MEHQ (p - Hydroxyanisole), Molecular weight 138.16, purchased from Hubei Dechao Chemical Co., Ltd.

[0046] DBTL (Dibutyltin dilaurate): Molecular weight 631.56, purchased from Shandong Jinyuanyuan New Materials Co., Ltd.

[0047] Monofunctional active diluent TMCHA: Purchased from Changxing Chemical Industry (Guangdong) Co., Ltd.

[0048] Monofunctional active diluent IBOA: Purchased from Changxing Chemical Industry (Guangdong) Co., Ltd.

[0049] Monofunctional active diluent CTFA: Purchased from Changxing Chemical Industry (Guangdong) Co., Ltd.

[0050] TPO - L: Purchased from Wuhan Xinyang Ruihe Chemical Technology Co., Ltd.

[0051] 184: Purchased from Hubei Hongxin Ruiyu Fine Chemical Co., Ltd.

[0052] MBP: Purchased from Hunan Juren Chemical New Materials Technology Co., Ltd.

[0053] SiO2: Molecular weight 60.08, purchased from Wuhan Jinqu New Materials Co., Ltd.

[0054] Bifunctional polyether polyurethane acrylate (Confluence HU9807): Purchased from Dongguan Confluence New Materials Co., Ltd.

[0055] 2-functional polyether polyurethane acrylate (Zicai ZC6487): Purchased from Shenzhen Zicai Technology Co., Ltd.

[0056] II. Examples

[0057] Example 1

[0058] A method for preparing a primer with high adhesion and high heat resistance, which includes first preparing 2-functional polyether polyester modified polyurethane acrylate A, and then mixing 2-functional polyether polyester modified polyurethane acrylate A with acrylate active diluent, photoinitiator, pigment and filler to prepare the primer.

[0059] 1. The preparation steps of the 2-functional polyether polyester modified polyurethane acrylate A include:

[0060] S1. Mix 0.12 mol of PCL 1000, 0.1 mol of PCL 2000, and 0.1 mol of CHDM, then heat up to 110 °C, dehydrate under vacuum for 40 minutes, and cool to 25 °C to obtain mixture 1;

[0061] S2. Mix the mixture 1 obtained in step S1 with 0.1 mol of IPDI, stir and heat up to 55 - 60 °C, react for 0.5 h, and then add 0.1 g of DBTL to obtain mixture 2;

[0062] S3. Add 0.8 ml of hydroxyethyl acrylate with 97% HEA content, 0.3 g of BHT, and 0.6 g of MEHQ to the mixture 2 obtained in step S2, and react at 65 - 70 °C for 0.5 h to obtain 2-functional polyether polyester modified polyurethane acrylate A;

[0063] 2. The primer preparation steps include:

[0064] S4. Repeat the above steps to prepare 70 g of 2-functional polyether polyester modified polyurethane acrylate A. Take 70 g of 2-functional polyether polyester modified polyurethane acrylate A, 29 g of monofunctional active diluent TMCHA, 0.2 g of MBP, 0.3 g of 184, 0.5 g of TPO-L, and 2 g of SiO2, mix them evenly in a dispersion kettle to obtain the finished primer.

[0065] Example 2

[0066] 1. The preparation steps of the 2-functional polyether polyester modified polyurethane acrylate A include:

[0067] S1. Mix 0.12 mol of PCL 1000, 0.1 mol of PCL 2000, and 0.1 mol of CHDM, then heat up to 110 °C, dehydrate under vacuum for 40 minutes, and cool to 25 °C to obtain mixture 1;

[0068] S2. Mix the mixture 1 obtained in step S1 with 0.1 mol of IPDI, stir and heat up to 55 - 60 °C, react for 0.5 h, and then add 0.1 g of DBTL to obtain mixture 2;

[0069] S3. Add 0.8 ml of hydroxyethyl acrylate with 97% HEA content, 0.3 g of BHT, and 0.6 g of MEHQ to the mixture 2 obtained in step S2, and react at 65 °C for 0.5 h to obtain bifunctional polyether polyester modified polyurethane acrylate A;

[0070] 2. The steps for preparing the primer include:

[0071] S4. Repeat the above steps to prepare 69 g of bifunctional polyether polyester modified polyurethane acrylate A. Take 69 g of bifunctional polyether polyester modified polyurethane acrylate A, 28 g of monofunctional active diluent TMCHA, 0.2 g of MBP, 0.3 g of 184, 0.5 g of TPO-L, and 2 g of SiO2, mix them evenly in a dispersion kettle to obtain the finished primer.

[0072] Example 3

[0073] 1. The steps for preparing the bifunctional polyether polyester modified polyurethane acrylate A include:

[0074] S1. Mix 0.12 mol of PCL 1000, 0.1 mol of PCL 2000, and 0.1 mol of CHDM, then heat up to 110 °C, dehydrate under vacuum for 40 minutes, and cool to 25 °C to obtain mixture 1;

[0075] S2. Mix the mixture 1 obtained in step S1 with 0.1 mol of IPDI, stir and heat up to 55 - 60 °C, react for 0.5 h, and then add 0.1 g of DBTL to obtain mixture 2;

[0076] S3. Add 0.8 ml of hydroxyethyl acrylate with 97% HEA content, 0.3 g of BHT, and 0.6 g of MEHQ to the mixture 2 obtained in step S2, and react at 65 °C for 0.5 h to obtain bifunctional polyether polyester modified polyurethane acrylate A;

[0077] 2. The steps for preparing the primer include:

[0078] S4. Repeat the above steps to prepare 60 g of bifunctional polyether polyester modified polyurethane acrylate A. Take 60 g of bifunctional polyether polyester modified polyurethane acrylate A, 39 g of monofunctional active diluent TMCHA, 0.2 g of MBP, 0.3 g of 184, 0.5 g of TPO-L, and 2 g of SiO2, mix them evenly in a dispersion kettle to obtain the finished primer.

[0079] Comparative Example 1

[0080] Take 60 g of difunctional polyether polyurethane acrylate (Huahui HU9807), 38 g of monofunctional reactive diluent IBOA, 0.5 g of MBP, 0.7 g of 184, 0.8 g of TPO-L, and 2 g of SiO2, mix them in a dispersion kettle and stir evenly to obtain the finished primer.

[0081] Comparative Example 2

[0082] Take 60 g of difunctional polyether polyurethane acrylate (Huahui HU9807), 10 g of difunctional polyether polyester modified polyurethane acrylate A, 29 g of monofunctional reactive diluent CTFA, 0.2 g of MBP, 0.3 g of 184, 0.5 g of TPO-L, and 2 g of SiO2, mix them in a dispersion kettle and stir evenly to obtain the finished primer.

[0083] Comparative Example 3

[0084] Take 70 g of difunctional polyether polyurethane acrylate (Zicai ZC6487), 29 g of monofunctional reactive diluent CTFA, 0.2 g of MBP, 0.3 g of 184, 0.5 g of TPO-L, and 2 g of SiO2, mix them in a dispersion kettle and stir evenly to obtain the finished primer.

[0085] III. Performance Tests

[0086] Methods for Testing Tg and Elongation at Break

[0087] Due to interference from external curing factors, the data of Tg and elongation at break of the coating after the primer is cured have slight fluctuations. The coatings for testing Tg and elongation at break are obtained by the following method: coat the paint on a high-gloss PET film, cover it with a high-gloss OPP release film, and cure the coating with a high-pressure mercury lamp in an oxygen-free environment.

[0088] Specific steps:

[0089] 1. Coating preparation: Uniformly coat the primer paint on the surface of the high-gloss PET film, control the wet film thickness (it is recommended to use a wire bar or a doctor blade, with a thickness tolerance of ±5 μm); cover the high-gloss OPP release film to avoid oxygen penetration interference during the curing process and ensure an oxygen-free environment; perform photocuring using a high-pressure mercury lamp, and control the light intensity (such as 80 - 120 mW / cm 2 ) and the exposure time (adjust according to the resin photoinitiator system). Curing environment control: Keep the temperature at 25 ± 2 °C and the humidity at 50 ± 5% throughout the curing process to reduce the influence of temperature and humidity on the curing rate and internal stress of the coating; after curing, peel off the release film and let it stand for 24 hours to eliminate the residual stress.

[0090] 2. Glass transition temperature (Tg) test

[0091] Cut a 5-10 mg sample from the coating, avoiding contamination or mechanical damage; encapsulate it in an aluminum crucible to ensure good contact with the DSC instrument, heat from 15 °C to 250 °C at a rate of 10 °C / min; cool to 15 °C at the same rate; heat to 250 °C again at a rate of 10 °C / min, and record the heat flow curve. Take the inflection point or midpoint of the second heating curve as the Tg value and compare the baseline calibration data.

[0092] 3. Tensile Elongation at Break Test (Tensile Test)

[0093] According to ASTM D638 or ISO 527 standards, cut the coating into dumbbell-shaped specimens (gage section width 10 mm, length 50 mm), use laser scribing or non-contact optical marking for the gage (line width ≤ 0.1 mm) to avoid stress concentration introduced by mechanical scribing. Use a universal material testing machine, set the tensile rate to 5 mm / min (flexible coating) or 50 mm / min (rigid coating), ensure the coaxiality deviation ≤ 0.2 mm / m when clamping the specimen to avoid early yielding, record the stress-strain curve, read the gage length at break, and calculate the tensile elongation at break according to the formula: 100%(Lbreak - L0) / L0, where L0 is the initial gage length and Lbreak is the gage length after break.

[0094] (2) Results of Tg and Tensile Elongation at Break:

[0095] Table 1: Results of Tg and Tensile Elongation at Break for Each Example and Comparative Example

[0096]

[0097] As can be seen from Table 1, for the primer prepared in Example 1 of the present invention, the Tg (°C) of its coating can reach 43 °C and the tensile elongation at break is 29.3%, and both its Tg and tensile elongation at break are very excellent and achieve a balance. For Comparative Example 3, the commercially available bifunctional polyether polyurethane acrylate (Zicai ZC6487) is used, and the Tg (°C) of its coating drops to -17 °C and the tensile elongation at break is 26.7%, indicating that bifunctional polyether polyester modified polyurethane acrylate A is very important for the Tg of the material. For Comparative Example 1, the bifunctional polyether polyurethane acrylate (Huihe HU9807) is used, and its tensile elongation at break drops to 15.60%. In summary, bifunctional polyether polyester modified polyurethane acrylate A achieves a balance between the Tg (°C) and tensile elongation at break of the coating of the material. A high tensile elongation at break indicates that the coating has good flexibility and deformation ability, can adapt to the stress generated by the thermal expansion or mechanical deformation of the substrate, reduce the risk of interface cracking, maintain a relatively high Tg while retaining an appropriate tensile elongation at break, so as to balance heat resistance and adhesion.

[0098] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention.

Claims

1. A primer with high adhesion and high heat resistance, characterized in that, Comprising the following components in parts by weight: 60 - 80 parts by weight of difunctional polyurethane acrylate A, 20 - 40 parts by weight of acrylate active diluent, 0.5 - 5 parts by weight of photoinitiator, 0 - 10 parts by weight of pigment filler; The difunctional polyurethane acrylate A is difunctional polyether polyester modified polyurethane acrylate A.

2. The primer according to claim 1, wherein, The difunctional polyether polyester modified polyurethane acrylate A is prepared by reacting the following components: IPDI, where IPDI is isophorone diisocyanate; PCL 1000, where PCL 1000 is polycaprolactone polyol with a molecular weight of 1000; PCL 2000, where PCL 2000 is polycaprolactone polyol with a molecular weight of 2000; CHDM, where CHDM is 1,4 - cyclohexanedimethanol; HEA, where HEA is hydroxyethyl acrylate with a content of 97%; Polymerization inhibitor, where the polymerization inhibitor is BHT, MEHQ; BHT is dibutylhydroxytoluene, and MEHQ is p - methoxyphenol; Catalyst, where the catalyst is DBTL, and DBTL is dibutyltin dilaurate.

3. The primer according to claim 2, wherein, The molar ratio of the IPDI, the PCL 1000, the PCL 2000, the CHDM, the HEA, the BHT, the MEHQ, and the DBTL is: 1:1.2:1:1:0.067:0.0136:0.0399:0.00158.

4. The primer according to claim 3, wherein, The reaction includes the following steps: S1. Mix the PCL 1000, PCL 2000, and CHDM, then raise the temperature, dehydrate under vacuum, and cool to obtain mixture 1; S2. Mix the mixture 1 obtained in step S1 with IPDI, stir and raise the temperature, then add the DBTL to obtain mixture 2; S3. Add HEA, BHT, and MEHQ to the mixture 2 obtained in step S2 to obtain the difunctional polyether polyester modified polyurethane acrylate A.

5. The primer according to claim 4, wherein, In step S1, after mixing, raise the temperature to 110°C, dehydrate under vacuum for 40 minutes, and cool to 25°C.

6. The primer according to claim 4, wherein, In step S2, the reaction temperature is 55 - 60°C, and the reaction time is 0.5 h.

7. The primer according to claim 4, wherein, In step S3, the reaction temperature is 65 - 70°C, and the reaction time is 0.5 h.

8. A method for preparing the primer according to any one of claims 1-7, characterized in that, Including mixing the difunctional polyether polyester modified polyurethane acrylate A with acrylate active diluent, photoinitiator, and pigment filler.

9. The method according to claim 8, wherein, The photoinitiator is selected from at least one of MBP, 184, and TPO - L; the pigment filler is SiO2.

10. Use of the primer according to any one of claims 1-7, characterized in that, The application of the primer on the pre - coated film.

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