UV pressure-sensitive adhesive for protective film and preparation method of UV pressure-sensitive adhesive

Abstract

The invention discloses a UV pressure-sensitive adhesive for a protective film and a preparation method of the UV pressure-sensitive adhesive. The UV pressure-sensitive adhesive for the protective film comprises polyether polyol, aliphatic diisocyanate, dibutyltin dilaurate, hydroxyl acrylate, methylhydroquinone, an acrylate reactive diluent, a bifunctional crosslinking monomer and a photoinitiator. The pressure-sensitive adhesive is prepared by three steps of synthesizing urethane acrylate, preparing glue and preparing a protective film, the viscosity of the pressure-sensitive adhesive at 25 DEG C is 500-2000 mPas, and the pressure-sensitive adhesive is good in flowability, suitable for a high-linear-speed coating process, free of organic solvent, environmentally friendly, low in carbon, capable of being prepared by mixing at room temperature and short in process. The pressure-sensitive adhesive provided by the invention has the advantages of no residual adhesive, no fog shadow, excellent cohesive strength, high temperature resistance and weather resistance, solves the problems of high VOC emission, difficulty in balancing low viscosity and high performance and the like of the traditional pressure-sensitive adhesive, and is suitable for the limit protection requirement of a super-sensitive surface.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision protective materials technology, specifically to a UV pressure-sensitive adhesive for protective films and its preparation method. Background Technology

[0002] Pressure-sensitive adhesives (PSA) are adhesives that bond under slight pressure and maintain their tack for a long time. They are widely used in various protective films to protect the surfaces of items from scratches, contamination, or chemical damage during transportation, processing, or storage.

[0003] For the protection of high-gloss surfaces (such as glass, polished metal, and optical components), the pressure-sensitive adhesive used for the protective film must have extremely low initial tack and peel strength. This ensures easy and effortless peeling without insufficient cohesion leading to adhesive layer damage and residue, or excessive tack causing surface damage or "ghosting" (i.e., uneven adhesive transfer marks). Traditional low-tack pressure-sensitive adhesives often use solution-based or emulsion-based acrylate systems, but these suffer from environmental pollution due to solvent evaporation, high energy consumption, and difficulties in balancing cohesion and low tack in certain applications. UV curing technology offers advantages such as high efficiency, environmental friendliness, and low energy consumption. Therefore, developing a pressure-sensitive adhesive that combines low tack, high cohesion, and good adaptability to UV curing processes has become a pressing technical problem in this field. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] Therefore, the purpose of this invention is to provide a UV pressure-sensitive adhesive for protective films and a method for preparing the same, so as to solve the problems mentioned in the background art.

[0006] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0007] A UV pressure-sensitive adhesive for protective films is composed of the following components in the following mass ratio: 60-70 parts polyether polyol, 10-35 parts aliphatic diisocyanate, 0.02-0.05 parts dibutyltin dilaurate, 1-10 parts hydroxy acrylate, 0.1-0.5 parts methyl hydroquinone, 25-45 parts acrylate reactive diluent, 5-10 parts bifunctional crosslinking monomer, and 1-3 parts photoinitiator.

[0008] As a preferred embodiment of the UV pressure-sensitive adhesive for protective film described in this invention, the polyether polyol is polypropylene glycol or polytetrahydrofuran ether glycol, and is one or a mixture thereof with a number average molecular weight of 600-2000.

[0009] As a preferred embodiment of the UV pressure-sensitive adhesive for protective film described in this invention, the aliphatic diisocyanate is one or a mixture of IPDI, HDI, and HMDI.

[0010] In a preferred embodiment of the UV pressure-sensitive adhesive for protective film described in this invention, the hydroxy acrylate is one or a mixture of two of hydroxyethyl acrylate and hydroxybutyl acrylate.

[0011] In a preferred embodiment of the UV pressure-sensitive adhesive for protective film described in this invention, the acrylic reactive diluent is a mixture of at least two of butyl acrylate, isooctyl acrylate, isobornyl acrylate, and methacrylate.

[0012] As a preferred embodiment of the UV pressure-sensitive adhesive for protective film described in this invention, the dual-energy crosslinking monomer is one of 1,6-hexanediol diacrylate or tripropylene glycol diacrylate.

[0013] As a preferred embodiment of the UV pressure-sensitive adhesive for protective film according to the present invention, the photoinitiator is one or a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0014] A method for preparing a UV pressure-sensitive adhesive for a protective film, comprising the following steps:

[0015] S1. Synthesis of polyurethane acrylate: In a dry nitrogen-protected reactor, polyether polyol is added and heated to 120°C. While stirring, vacuum dehydration is carried out for 2 hours. The temperature is then lowered to 50°C, and a mixture of aliphatic diisocyanate and dibutyltin dilaurate is slowly added dropwise. After the addition is complete, the temperature is slowly raised to 80°C and the reaction is maintained for 3 hours. The temperature is then lowered to 50°C-60°C, hydroxy acrylate and polymerization inhibitor are added, and the temperature is raised to 80°C-85°C and maintained for 4 hours. The reaction is then stopped, and the temperature is lowered to below 40°C. The product is then discharged to obtain polyurethane acrylate.

[0016] S2. Prepare the adhesive: In a clean, light-proof environment, at 25°C, mix polyurethane acrylate, acrylate reactive diluent, bifunctional crosslinking monomer and photoinitiator in sequence at low speed and stir slowly for 2 hours to remove bubbles and obtain a clear, water-like adhesive solution.

[0017] S3. Preparation of protective film: In a clean and light-proof environment, the adhesive is applied to a 50μm PET carrier film using a slit coating method, with a dry adhesive thickness of 10μm. Then, under nitrogen protection, it is cured with a 395nm LED light source at an energy of 600 mJ / cm².

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The pressure-sensitive adhesive provided by this invention can easily control the viscosity of 500-2000 mPa·s at 25℃, with excellent fluidity. It is suitable for advanced processes such as high-speed microgravure and slot coating, with good coating uniformity and no defects such as stringing or orange peel. The entire system does not require any organic solvents to reduce viscosity, truly achieving environmental protection, safety and low carbon emissions.

[0020] 2. By using self-made low-viscosity PUA and high-efficiency monofunctional diluent, the traditional perception that low viscosity necessarily means low performance is broken. The cured adhesive layer has excellent resistance to damp heat due to the presence of PUA skeleton and cross-linking network. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0022] Figure 1 These are test graphs showing the performance parameters of the pressure-sensitive adhesives prepared in Examples 1-4 and the comparative examples of the present invention. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] Synthesis of polyurethane acrylate: In a dry nitrogen-protected reactor, 65 parts of polypropylene glycol with a molecular weight of 1000 were added and heated to 120°C. The mixture was then vacuum-dehydrated for 2 hours while stirring. The temperature was lowered to 50°C, and a mixture of 23 parts of IPDI and 0.05 parts of dibutyltin dilaurate was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80°C and maintained for 3 hours. The temperature was then lowered to 50°C-60°C, and 5 parts of hydroxyethyl acrylate and 0.1 parts of methylhydroquinone were added. The temperature was raised to 80°C-85°C and maintained for 4 hours. The reaction was stopped, and the temperature was lowered to below 40°C. The product was then discharged to obtain polyurethane acrylate.

[0026] Preparation of adhesive: In a clean, light-protected environment, at 25°C, mix 50 parts of polyurethane acrylate, 13 parts of isoborneol acrylate, 30 parts of isooctyl acrylate, 5 parts of 1,6-hexanediol diacrylate, and 2 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in sequence at low speed and stir slowly for 2 hours to remove bubbles, resulting in a clear, water-like adhesive solution.

[0027] Preparation of protective film and performance testing: In a clean and light-proof environment, the adhesive was applied to a 50μm PET carrier film using a slit coating method, with a dry adhesive thickness of 10μm. Subsequently, under nitrogen protection, the film was cured using a 395nm LED light source with an energy of 600 mJ / cm². The protective film sample was then bonded to a mirror stainless steel plate, and a 180° peel force test was conducted according to the national standard GB / T2792-1998. Its heat resistance and weather resistance were also examined.

[0028] Example 2

[0029] Synthesis of polyurethane acrylate: In a dry nitrogen-protected reactor, 60 parts of polytetrahydrofuran ether diol with a molecular weight of 650 were added and heated to 120°C. The mixture was then vacuum-dehydrated for 2 hours while stirring. The temperature was lowered to 50°C, and a mixture of 25 parts HDI and 0.02 parts dibutyltin dilaurate was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80°C and maintained for 3 hours. The temperature was then lowered to 50°C-60°C, and 9 parts hydroxybutyl acrylate and 0.1 parts methylhydroquinone were added. The temperature was raised to 80°C-85°C and maintained for 4 hours. The reaction was stopped, and the temperature was lowered to below 40°C. The product was then discharged to obtain polyurethane acrylate.

[0030] Preparation of adhesive: In a clean, light-proof environment, at 25°C, mix 45 parts of polyurethane acrylate, 13 parts of methacrylate, 32 parts of butyl acrylate, 8 parts of tripropylene glycol diacrylate, and 2 parts of 1-hydroxycyclohexylphenyl ketone in sequence at low speed and stir slowly for 2 hours to remove bubbles and obtain a clear, water-like adhesive solution.

[0031] Preparation of protective film and performance testing: In a clean, light-protected environment, the adhesive was applied to a 50μm PET carrier film using a slit coating method, resulting in a dry adhesive thickness of 10μm. Subsequently, under nitrogen protection, the film was cured using a 395nm LED light source at an energy of 600 mJ / cm². The protective film sample was then bonded to a mirror-finished stainless steel plate, and a 180° peel strength test was conducted according to the national standard GB / T2792-1998. Its heat resistance and weather resistance were also investigated.

[0032] Example 3

[0033] Synthesis of polyurethane acrylate: In a dry nitrogen-protected reactor, 60 parts of polypropylene glycol with a molecular weight of 600 were added and heated to 120°C. The mixture was then vacuum-dehydrated for 2 hours while stirring. The temperature was lowered to 50°C, and a mixture of 35 parts of HMDI and 0.05 parts of dibutyltin dilaurate was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80°C and maintained for 3 hours. The temperature was then lowered to 50°C-60°C, and 6 parts of hydroxybutyl acrylate and 0.1 parts of methylhydroquinone were added. The temperature was raised to 80°C-85°C and maintained for 4 hours. The reaction was stopped, and the temperature was lowered to below 40°C. The product was then discharged to obtain polyurethane acrylate.

[0034] Preparation of adhesive: In a clean, light-protected environment, at 25°C, mix 55 parts of polyurethane acrylate, 12 parts of isoborneol acrylate, 25 parts of butyl acrylate, 6 parts of 1,6-hexanediol diacrylate, and 2 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone in sequence at low speed and stir slowly for 2 hours to remove bubbles, and obtain a clear, water-like adhesive solution.

[0035] Preparation of protective film and performance testing: In a clean, light-protected environment, the adhesive was applied to a 50μm PET carrier film using a slit coating method, resulting in a dry adhesive thickness of 10μm. Subsequently, under nitrogen protection, the film was cured using a 395nm LED light source at an energy of 600 mJ / cm². The protective film sample was then bonded to a mirror-finished stainless steel plate, and a 180° peel strength test was conducted according to the national standard GB / T2792-1998. Its heat resistance and weather resistance were also investigated.

[0036] Example 4

[0037] Synthesis of polyurethane acrylate: In a dry nitrogen-protected reactor, 70 parts of polytetrahydrofuran ether diol with a molecular weight of 2000 were added and heated to 120°C. The mixture was then vacuum-dehydrated for 2 hours while stirring. The temperature was lowered to 50°C, and a mixture of 13 parts IPDI and 0.05 parts dibutyltin dilaurate was slowly added dropwise. After the addition was complete, the temperature was slowly raised to 80°C and maintained for 3 hours. The temperature was then lowered to 50°C-60°C, and 3 parts hydroxyethyl acrylate and 0.1 parts methylhydroquinone were added. The temperature was raised to 80°C-85°C and maintained for 4 hours. The reaction was stopped, and the temperature was lowered to below 40°C. The product was then discharged to obtain polyurethane acrylate.

[0038] Preparation of adhesive: In a clean, light-protected environment, at 25°C, mix 60 parts of polyurethane acrylate, 15 parts of methacrylate, 13 parts of isooctyl acrylate, 10 parts of 1,6-hexanediol diacrylate, and 2 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone in sequence at low speed and stir slowly for 2 hours to remove bubbles, and obtain a clear, water-like adhesive solution.

[0039] Preparation of protective film and performance testing: In a clean, light-protected environment, the adhesive was applied to a 50μm PET carrier film using a slit coating method, resulting in a dry adhesive thickness of 10μm. Subsequently, under nitrogen protection, the film was cured using a 395nm LED light source at an energy of 600 mJ / cm². The protective film sample was then bonded to a mirror-finished stainless steel plate, and a 180° peel strength test was conducted according to the national standard GB / T2792-1998. Its heat resistance and weather resistance were also investigated.

[0040] Comparative Example

[0041] The following is the preparation process of a commercially available general-purpose acrylic solvent-based protective film pressure-sensitive adhesive:

[0042] Synthesis of acrylate polymer: Add 140 parts of ethyl acetate to a reactor, then add 75 parts of butyl acrylate (BA), 15 parts of methyl methacrylate (MMA), 2 parts of acrylic acid (AA), 2 parts of hydroxyethyl acrylate (HEA), and 0.3 parts of initiator AIBN in proportion. Stir to mix evenly, heat the reactor to 75-80℃, and maintain the reflux reaction at this temperature for 6-8 hours; stop the reaction, cool to below 40℃ and discharge to obtain the acrylate polymer.

[0043] Prepare the protective film adhesive: Take 100 parts of the above acrylate polymer, add 0.5 parts of L75 (Covestro) and 20 parts of ethyl acetate, and stir thoroughly for 30 minutes to obtain the target adhesive.

[0044] Preparation of protective film and performance testing: Take the above adhesive and apply it evenly to a 50μm thick PET film using a slit coating method. Place it in an oven at 120℃ and cure for 2 minutes to form a protective film sample with a dry adhesive thickness of about 10μm. After curing at 50℃-60℃ for 3 days, the protective film sample is then bonded to a mirror stainless steel plate. The 180° peel strength test is performed according to the national standard GB / T2792-1998, and its heat resistance and weather resistance are also examined.

[0045] The performance parameters of the pressure-sensitive adhesives prepared in Examples 1-4 and comparative examples are as follows: Figure 1 As shown, by Figure 1 As can be seen, Examples 1-4 of the present invention successfully controlled the peel force precisely within the target range of 3g-5g, and exhibited excellent stability and zero residue characteristics, fully meeting the extreme requirements of ultra-precision surface protection. Furthermore, it has low viscosity at 25°C, excellent flowability, and good coating uniformity. The entire system does not require any organic solvents to reduce viscosity, achieving environmental protection, safety, and low carbon emissions. Although the comparative examples meet the low peel force requirements, the system contains a large amount of solvent, resulting in high VOC emissions and poor high-temperature resistance. Therefore, the present invention can completely replace traditional protective film adhesives in protective film applications.

[0046] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A UV pressure-sensitive adhesive for a protective film, characterized by comprising: According to the mass ratio, it is composed of 60-70 parts of polyether polyol, 10-35 parts of aliphatic diisocyanate, 0.02-0.05 parts of dibutyltin dilaurate, 1-10 parts of hydroxy acrylate, 0.1-0.5 parts of methylhydroquinone, 25-45 parts of acrylic acid ester active diluent, 5-10 parts of bifunctional crosslinking monomer, and 1-3 parts of photoinitiator.

2. The UV pressure-sensitive adhesive for a protective film according to claim 1, characterized by The polyether polyol is a mixture of one or more of polypropylene glycol or polytetrahydrofuran ether glycol with a number average molecular weight of 600-2000.

3. The UV pressure-sensitive adhesive for a protective film according to claim 1, characterized by The aliphatic diisocyanate is a mixture of one or more of IPDI, HDI, HMDI.

4. The UV pressure-sensitive adhesive for a protective film according to claim 1, characterized by The hydroxy acrylate is a mixture of one or both of hydroxyethyl acrylate or hydroxybutyl acrylate.

5. The UV pressure-sensitive adhesive for a protective film according to claim 1, characterized by The acrylic acid active diluent is a mixture of at least two of butyl acrylate, isooctyl acrylate, isobornyl acrylate, and methacrylate.

6. The UV pressure sensitive adhesive for a protective film according to claim 1, characterized by, The bifunctional crosslinking monomer is one of 1,6-hexanediol diacrylate or tripropyleneglycol diacrylate.

7. The UV pressure-sensitive adhesive for a protective film according to claim 1, characterized by The photoinitiator is a mixture of one or more of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

8. A method for preparing a UV pressure-sensitive adhesive for a protective film according to any one of claims 1 to 7, characterized by, The steps are as follows: S1, synthesis of polyurethane acrylate: in a dry nitrogen protection reaction kettle, polyether polyol is heated to 120℃, stirred and vacuum dehydrated for 2 hours, cooled to 50℃, slowly added with a mixture of aliphatic diisocyanate and dibutyltin dilaurate, after the addition is completed, slowly heated to 80℃, and reacted for 3h; cooled to 50-60℃, added with hydroxy acrylate and polymerization inhibitor, heated to 80-85℃, and reacted for 4h, then stopped the reaction, cooled to below 40℃, discharged, and polyurethane acrylate was obtained; S2, configuration of glue: in a clean and light-proof environment, at 25℃, polyurethane acrylate, acrylic acid ester active diluent, bifunctional crosslinking monomer, and photoinitiator are sequentially mixed at low speed for 2 hours, defoamed, and a clear glue solution is obtained; S3, preparation of protective film: in a clean and light-proof environment, the glue solution is coated on a 50μm PET carrier film by slot coating, the dry glue thickness is 10μm, and then cured under nitrogen protection with a 395nm LED light source at an energy of 600 mJ / cm².

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