Directly-received easy-to-unwind polyurethane pressure-sensitive adhesive protective film and preparation method thereof

Abstract

The present application relates to pressure sensitive adhesive protective film technical field, especially to a kind of direct-receiving easy-to-unwind polyurethane pressure sensitive adhesive protective film and preparation method thereof.Protective film includes substrate and polyurethane pressure sensitive adhesive layer;Polyurethane pressure sensitive adhesive layer is mainly prepared by prepolymer 100 parts, solvent 70-200 parts, polyisocyanate 3-15 parts and catalyst 0.01-0.02 parts;Prepolymer is mainly prepared by dihydric alcohol 10-40 parts, trihydric alcohol 2-10 parts, functional monomer 2-8 parts, polyisocyanate 5-20 parts, antistatic agent 0.1-1 part, catalyst 0.001-0.03 parts and solvent 20-50 parts;The molar number of NCO in polyisocyanate in prepolymer is less than the sum of the molar number of OH in dihydric alcohol, trihydric alcohol and functional monomer.The protective film of the present application has low peeling performance, lower unwinding force, can meet the requirements of direct-coating direct-receiving protective film to pressure sensitive adhesive, and can save release film related structure and process.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesive protective film technology, and in particular to a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film and its preparation method. Background Technology

[0002] As China's electronics industry continues to expand its market share and new electronic products emerge in endless streams, the demand for protective films, especially polyurethane protective films, is gradually increasing to prevent contamination of components such as glass panels, back panels, lenses, and touch screen modules. Pressure-sensitive adhesives used in protective films mainly fall into three categories: acrylic, silicone, and polyurethane. Acrylic pressure-sensitive adhesives offer a wide range of controllable peel strength, but their wettability on smooth surfaces such as glass is insufficient, and they are prone to showing spots after aging. Silicone pressure-sensitive adhesive protective films have excellent wettability, air release, and high-temperature aging resistance, but there is a risk of silicone residue, thus limiting their application in the electronics field. Polyurethane pressure-sensitive adhesive protective films have excellent wettability, stable mechanical properties, and good antistatic properties, making them widely used in the protection of electronic products, especially various glass panels.

[0003] Polyurethane pressure-sensitive adhesive protective film is made by uniformly coating polyurethane pressure-sensitive adhesive onto a film substrate, drying and curing it at high temperature, laminating it with a release film, and then rolling it up and packaging it. When using it, the release film needs to be peeled off before applying it to the surface to be protected. Therefore, the release film mainly serves to protect the adhesive surface. If the protective film can be directly rolled up and used after the adhesive surface is dry, nearly half of the raw material cost can be saved. Furthermore, it can be directly unwound and used later without needing to peel off the release film, which not only saves materials and simplifies the process, making it convenient to use, but also improves production efficiency.

[0004] In view of the advantages of the above-mentioned direct-winding protective film, the formulation of polyurethane pressure-sensitive adhesive needs to be adjusted accordingly: after the polyurethane pressure-sensitive adhesive is coated on the polymer substrate and dried at high temperature, the adhesive layer is required to have antistatic properties, and the peel force needs to be stabilized immediately. Otherwise, after direct winding, uneven winding, difficulty in unwinding, or excessive static electricity during unwinding and use will occur, leading to greater losses.

[0005] To address the difficulty of direct unwinding, existing methods involve directly applying polyurethane pressure-sensitive adhesive to the non-release surface of the release film, eliminating the need for a separate release film. However, this approach still suffers from issues such as residue buildup and a long curing time, and offers no cost advantage.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One objective of this invention is to provide a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film to solve the technical problems existing in the prior art, such as long curing time, long time required for peel force stabilization, need for composite release film for winding, and difficulty in unwinding.

[0008] Another object of the present invention is to provide a method for preparing a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film.

[0009] To achieve the above-mentioned objectives of the present invention, the present invention provides a direct-winding and easy-to-unwind polyurethane pressure-sensitive adhesive protective film, comprising a substrate and a polyurethane pressure-sensitive adhesive layer disposed on the surface of the substrate;

[0010] The polyurethane pressure-sensitive adhesive layer is mainly composed of the following components in parts by weight:

[0011] The composition includes 100 parts prepolymer, 70-200 parts solvent, 3-15 parts polyisocyanate, and 0.01-0.02 parts catalyst.

[0012] The prepolymer is mainly prepared from the following components in parts by weight:

[0013] 10-40 parts of diol, 2-10 parts of triol, 2-8 parts of functional monomer, 5-20 parts of polyisocyanate, 0.1-1 part of antistatic agent, 0.001-0.03 parts of catalyst and 20-50 parts of solvent;

[0014] The functional monomers include at least one of oleic acid diethanolamine, octadecyl diethanolamine, lauroyl glutamate, and octyl glycol;

[0015] In the prepolymer, the number of moles of NCO in the polyisocyanate is less than the sum of the number of moles of OH in the diol, the triol, and the functional monomer;

[0016] In the polyurethane pressure-sensitive adhesive layer, the number of moles of OH in the prepolymer is less than the number of moles of NCO in the polyisocyanate.

[0017] In a specific embodiment of the present invention, the mass ratio of the triol to the diol is 1:(1-5).

[0018] In a specific embodiment of the present invention, the diol includes at least one of polyethylene glycol, polypropylene glycol, polytetrahydrofuran, and poly(neopentyl glycol adipate-1,6-hexanediol) ester diol.

[0019] In a specific embodiment of the present invention, the triol includes at least one of trimethylolpropane, polyglycerol, and polycaprolactone triol.

[0020] In a specific embodiment of the present invention, the polyisocyanate in the prepolymer is selected from aromatic isocyanates and / or aliphatic isocyanates. Further, the aromatic isocyanate includes at least one selected from 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,4-tetramethylxylene diisocyanate, 1,3-tetramethylxylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated phenylmethane diisocyanate; the aliphatic isocyanate includes at least one selected from trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,2-methylene diisocyanate, 2,3-methylene diisocyanate, 1,3-methylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylene diisocyanate.

[0021] In a specific embodiment of the present invention, the polyisocyanate in the polyurethane pressure-sensitive adhesive includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, and trimethylene diisocyanate.

[0022] In a specific embodiment of the present invention, the catalyst in the polyurethane pressure-sensitive adhesive and the catalyst in the prepolymer are each independently selected from at least one of dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethylethoxytin, tributylethoxytin, stannous octoate, trioctyltin oxide, trioctyltin chloride, tributyltin trichloroacetate, and 2-ethylhexanoate.

[0023] In a specific embodiment of the present invention, the solvent in the polyurethane pressure-sensitive adhesive and the solvent in the prepolymer are each independently selected from at least one of ethyl acetate, butyl acetate, toluene, xylene, butanone, cyclohexanone, cyclohexane, acetone, and acetylacetone.

[0024] In a specific embodiment of the present invention, the antistatic agent is selected from ionic liquids. Further, the ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-hexyl-3-methylimidazolium di(trifluoromethanesulfonyl)imide.

[0025] In a specific embodiment of the present invention, the method for preparing the prepolymer includes:

[0026] (a) Under nitrogen protection, the diol, functional monomer, polyisocyanate and solvent are mixed evenly, heated to 50-60°C, some catalyst is added, and the reaction is carried out at 80-90°C for 2-3 hours.

[0027] (b) Cool down to 50-60°C, add triol and the remaining catalyst, react at 80-90°C for 2-8 hours, add antistatic agent, stir evenly, and discharge.

[0028] In a specific embodiment of the present invention, the mass ratio of the partial catalyst in step (a) to the remaining catalyst in step (b) is 1:(1.5 to 2.5).

[0029] In a specific embodiment of the present invention, the substrate includes at least one of polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polypropylene (BOPP), and polyolefin (PO).

[0030] In a specific embodiment of the present invention, the thickness of the polyurethane pressure-sensitive adhesive layer is 1 to 15 μm.

[0031] The present invention also provides a method for preparing any one of the above-described direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective films, comprising the following steps:

[0032] The polyurethane pressure-sensitive adhesive is evenly coated onto the substrate surface and then baked at high temperature.

[0033] The preparation method of the polyurethane pressure-sensitive adhesive includes: mixing the prepolymer with a solvent, adding a polyisocyanate and a catalyst, stirring evenly to obtain the polyurethane pressure-sensitive adhesive.

[0034] In a specific embodiment of the present invention, the high-temperature baking temperature is 80-130°C, and the high-temperature baking time is 3-8 minutes.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The polyurethane pressure-sensitive adhesive protective film of the present invention can reasonably adjust the hardness of the prepolymer molecular chain, the polymer and the crosslinking density by using a certain amount of diol, triol and specific functional monomers; and control the NCO in the prepolymer to be less than OH, so as to avoid the reaction of residual NCO in the prepolymer with water in the environment or solvent, resulting in uncontrollable adhesive performance; when making pressure-sensitive adhesive, control the excess NCO and OH, so that the polymer functional groups can react fully, and after high temperature baking, the protective film product can quickly reach a low peel stability state;

[0037] (2) The functional monomers of the present invention, in combination with the other components, can effectively improve the degree of polymerization of the molecular chain, improve the flexibility and degassing of the molecular chain, thereby improving the electrostatic discharge effect of the protective film; at the same time, an antistatic agent is added in the preparation of the prepolymer, which further improves the antistatic properties and low tear voltage of the obtained polyurethane pressure-sensitive adhesive protective film.

[0038] (3) The protective film of the present invention quickly achieves low peel performance after coating and drying. After coating and drying, the adhesive surface is in a solidified and stable state, with low unwinding force. It can meet the requirements of pressure-sensitive adhesive for direct coating and direct winding protective film, and can save on release film related structures and processes.

[0039] (4) The polyurethane pressure-sensitive adhesive of the present invention has good wettability and is suitable for direct coating on the surface of low surface energy materials such as PE, BOPP, and PO, thus broadening the application range of the product. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0041] The present invention provides a direct-winding and easy-to-unwind polyurethane pressure-sensitive adhesive protective film, comprising a substrate and a polyurethane pressure-sensitive adhesive layer disposed on the surface of the substrate;

[0042] The polyurethane pressure-sensitive adhesive layer is mainly composed of the following components in parts by weight:

[0043] The composition includes 100 parts prepolymer, 70-200 parts solvent, 3-15 parts polyisocyanate, and 0.01-0.02 parts catalyst.

[0044] The prepolymer is mainly prepared from the following components in parts by weight:

[0045] 10-40 parts of diol, 2-10 parts of triol, 2-8 parts of functional monomer, 5-20 parts of polyisocyanate, 0.1-1 part of antistatic agent, 0.001-0.03 parts of catalyst and 20-50 parts of solvent;

[0046] The functional monomers include at least one of oleic acid diethanolamine, octadecyl diethanolamine, lauroyl glutamate, and octyl glycol;

[0047] In the prepolymer, the number of moles of NCO in the polyisocyanate is less than the sum of the number of moles of OH in the diol, triol, and functional monomer;

[0048] In polyurethane pressure-sensitive adhesive layers, the number of moles of OH in the prepolymer is less than the number of moles of NCO in the polyisocyanate.

[0049] The polyurethane pressure-sensitive adhesive protective film of the present invention, through a certain amount of diol, triol and specific functional monomers, can reasonably adjust the hardness of the prepolymer molecular chain, the polymer and the crosslinking density; and control the NCO in the prepolymer to be less than OH, avoiding the reaction of residual NCO in the prepolymer with water in the environment or solvent, which would lead to uncontrollable adhesive performance; when making pressure-sensitive adhesive, controlling the excess NCO and OH allows the polymer functional groups to react fully, and after high-temperature baking, the protective film product can quickly reach a low-peel stability state.

[0050] Furthermore, by combining functional monomers, diols, and triols, the resulting prepolymer molecular weight is ensured to have a certain degree of polymerization, while also taking into account flexibility and air permeability. This improves the electrostatic discharge effect of the protective film, enhances its antistatic properties, and reduces the tear-off voltage, thus meeting the usage requirements of polyurethane pressure-sensitive adhesive protective films.

[0051] In different embodiments, the amounts of the components used to prepare the polyurethane pressure-sensitive adhesive layer, by weight, relative to 100 parts of the prepolymer, can be as follows:

[0052] The amount of solvent can be 70 parts, 80 parts, 100 parts, 120 parts, 150 parts, 180 parts, 200 parts, or any combination thereof;

[0053] The amount of polyisocyanate can be 3 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, or any combination thereof;

[0054] The amount of catalyst can be 0.01 parts, 0.012 parts, 0.015 parts, 0.018 parts, 0.02 parts, or any combination thereof.

[0055] The amount of solvent can be adjusted according to actual needs. It is preferable to use solvent to dilute the prepolymer so that the solid content after dilution reaches 15% to 35%.

[0056] In different implementation methods, the amounts of each component used in preparing the prepolymer, by weight, can be as follows:

[0057] The amount of diol used can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, or any combination thereof.

[0058] The amount of triol can be 2 parts, 4 parts, 5 parts, 8 parts, 10 parts, or any combination thereof;

[0059] The amount of functional monomer can be 2 parts, 4 parts, 5 parts, 6 parts, 8 parts, or any combination thereof;

[0060] The amount of polyisocyanate can be 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, or any combination thereof;

[0061] The amount of antistatic agent can be 0.1 parts, 0.2 parts, 0.5 parts, 0.8 parts, 1 part, or any combination thereof;

[0062] The amount of catalyst can be 0.001 parts, 0.005 parts, 0.01 parts, 0.02 parts, 0.03 parts, or any combination thereof;

[0063] The amount of solvent used can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any combination thereof.

[0064] In practice, the molar number of NCO in the polyisocyanate of the prepolymer can be 95%, 90%, 80%, 70%, or any combination thereof, representing the sum of the molar numbers of OH in the diol, triol, and functional monomer. It should be noted that OH here includes both alcoholic hydroxyl and carboxylic hydroxyl groups.

[0065] In the polyurethane pressure-sensitive adhesive layer, the molar number of OH groups in the prepolymer can be within the range of 98%, 95%, 90%, 85%, 80%, or any combination thereof, which is the molar number of NCO in the polyisocyanate used to prepare the polyurethane pressure-sensitive adhesive layer. It should be noted that OH groups here include both alcoholic hydroxyl groups and carboxylic hydroxyl groups.

[0066] In a specific embodiment of the present invention, the mass ratio of triol to diol is 1:(1-5).

[0067] In different embodiments, the mass ratio of triol to diol can be 1:1, 1:2, 1:3, 1:4, 1:5, or any combination thereof. By further limiting the mass ratio of triol to diol, the hardness and crosslinking density of the prepolymer molecular chains can be reasonably adjusted.

[0068] In a specific embodiment of the present invention, the diol includes at least one of polyethylene glycol, polypropylene glycol, polytetrahydrofuran, and poly(neopentyl glycol adipate-1,6-hexanediol) diol.

[0069] In a specific embodiment of the present invention, the triol includes at least one of trimethylolpropane, polyglycerol, and polycaprolactone triol.

[0070] In practice, if diols and triols are made of polymerized polyols, the molecular weight is not limited as long as the corresponding purpose can be achieved. For example, the number average molecular weight can be in the range of 400 to 4000, such as 400, 1000, 2000, 3000, 4000 or any combination thereof.

[0071] In a specific embodiment of the present invention, the polyisocyanate in the prepolymer is selected from aromatic isocyanates and / or aliphatic isocyanates. Further, aromatic isocyanates include at least one selected from 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,4-tetramethylxylene diisocyanate, 1,3-tetramethylxylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated phenylmethane diisocyanate; aliphatic isocyanates include at least one selected from trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,2-methylene diisocyanate, 2,3-methylene diisocyanate, 1,3-methylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylene diisocyanate.

[0072] In a specific embodiment of the present invention, the polyisocyanate in the polyurethane pressure-sensitive adhesive includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, and trimethylene diisocyanate.

[0073] In specific embodiments of the present invention, the catalyst in the polyurethane pressure-sensitive adhesive and the catalyst in the prepolymer are each independently selected from at least one of dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethylethoxytin, tributylethoxytin, stannous octoate, trioctyltin oxide, trioctyltin chloride, tributyltin trichloroacetate, and 2-ethylhexanoate. The type of catalyst is not limited to these, as long as it can catalyze the reaction of OH with NCO.

[0074] In a specific embodiment of the present invention, the solvent in the polyurethane pressure-sensitive adhesive and the solvent in the prepolymer are each independently selected from at least one of ethyl acetate, butyl acetate, toluene, xylene, butanone, cyclohexanone, cyclohexane, acetone and acetylacetone.

[0075] In a specific embodiment of the present invention, the antistatic agent is selected from ionic liquids. Further, the ionic liquid includes at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-hexyl-3-methylimidazolium di(trifluoromethanesulfonyl)imide.

[0076] In a specific embodiment of the present invention, the method for preparing the prepolymer includes:

[0077] (a) Under nitrogen protection, the diol, functional monomer, polyisocyanate and solvent are mixed evenly, heated to 50-60°C, some catalyst is added, and the reaction is carried out at 80-90°C for 2-3 hours.

[0078] (b) Cool down to 50-60°C, add triol and the remaining catalyst, react at 80-90°C for 2-8 hours, add antistatic agent, stir evenly, and discharge.

[0079] In the preparation of the prepolymer of this invention, adding diol and functional monomer at the initial stage of the reaction, followed by adding triol during secondary catalysis, can increase the crosslinking density of the polymer. Simultaneously, the catalyst is added in batches at different reaction times, allowing the raw materials to react and crosslink gradually. This enables the polymer to quickly reach a stable performance state after baking and drying, significantly reducing the curing time of the protective film.

[0080] In a specific embodiment of the present invention, the mass ratio of the partial catalyst in step (a) to the remaining catalyst in step (b) is 1:(1.5 to 2.5).

[0081] In different embodiments, the mass ratio of the partial catalyst in step (a) to the remaining catalyst in step (b) can be 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, or any combination thereof.

[0082] In a specific embodiment of the present invention, the substrate includes at least one of polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polypropylene (BOPP), and polyolefin (PO).

[0083] In a specific embodiment of the present invention, the thickness of the polyurethane pressure-sensitive adhesive layer is 1 to 15 μm.

[0084] In practice, the thickness of the polyurethane pressure-sensitive adhesive layer can be adjusted according to the actual needs of the polyurethane pressure-sensitive adhesive protective film. For example, the thickness of the polyurethane pressure-sensitive adhesive layer can be 1μm, 2μm, 5μm, 8μm, 10μm, 12μm, 15μm or any combination thereof.

[0085] This invention also provides a method for preparing any of the above-mentioned direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective films, comprising the following steps:

[0086] The polyurethane pressure-sensitive adhesive is evenly coated onto the substrate surface and then baked at high temperature.

[0087] The preparation method of polyurethane pressure-sensitive adhesive includes: mixing prepolymer with solvent, adding polyisocyanate and catalyst, stirring evenly to obtain polyurethane pressure-sensitive adhesive.

[0088] In practice, after high-temperature baking, a polyurethane pressure-sensitive adhesive layer of a certain thickness is formed and then it can be directly rolled up without the need for an additional release film.

[0089] In a specific embodiment of the present invention, the high-temperature baking temperature is 80-130°C, and the high-temperature baking time is 3-8 minutes.

[0090] In different embodiments, the high-temperature baking temperature can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C or any combination thereof, and the high-temperature baking time can be 3 min, 4 min, 5 min, 6 min, 7 min, 8 min or any combination thereof.

[0091] The direct-winding and easy-to-unwind polyurethane pressure-sensitive adhesive protective film of the present invention quickly achieves stable peel force after coating and drying. It can achieve easy winding and unwinding without the need for a release film, which not only saves one layer of release film, but also greatly shortens the post-curing time, improves the production efficiency of polyurethane protective film, and is convenient and environmentally friendly to use.

[0092] Example 1

[0093] This embodiment provides a method for preparing a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film, including the following steps:

[0094] (1) Preparation of prepolymer: Polyethylene glycol (600), trimethylolpropane, 2,4-toluene diisocyanate, etc., were placed in reaction flasks and the water was removed by vacuum distillation. Under nitrogen protection, 30 parts by weight of polyethylene glycol (600), 8 parts by weight of lauroyl glutamic acid, 18 parts by weight of 2,4-toluene diisocyanate, 20 parts by weight of toluene, and 14 parts by weight of ethyl acetate were added to the reaction vessel and mixed evenly. The temperature was raised to 60°C and after 1 hour, 0.005 parts by weight of stannous octoate was added, the temperature was raised to 80°C and reacted for 3 hours. The temperature was lowered to 60°C, 10 parts by weight of trimethylolpropane and 0.01 parts by weight of dibutyltin dilaurate were added, the temperature was raised to 80°C and reacted for 2 hours. The temperature was lowered to 50°C, 0.3 parts by weight of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide was added, the mixture was stirred evenly, filtered, and discharged to obtain the prepolymer.

[0095] (2) Preparation of polyurethane pressure-sensitive adhesive: Weigh 100 parts by weight of the prepolymer obtained in step (1), then add 100 parts by weight of ethyl acetate, stir evenly, add 8 parts by weight of hexamethylene diisocyanate and 0.01 parts by weight of tin 2-ethylhexanoate, stir evenly to obtain polyurethane pressure-sensitive adhesive.

[0096] (3) Preparation of polyurethane pressure-sensitive adhesive protective film: The polyurethane pressure-sensitive adhesive obtained in step (2) is uniformly coated on the surface of a 50μm thick transparent PET film, and then baked at 120℃ for 5min to cure and form a 10μm thick polyurethane pressure-sensitive adhesive layer, thus obtaining a polyurethane pressure-sensitive adhesive protective film.

[0097] Example 2

[0098] This embodiment provides a method for preparing a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film, including the following steps:

[0099] (1) Preparation of prepolymer: Polyethylene glycol (600), 1,2-methylene diisocyanate, polycaprolactone triol, etc. are placed in reaction flasks and the water is removed by vacuum distillation. Under nitrogen protection, 40 parts by weight of polyethylene glycol (600), 3 parts by weight of diethanolamine oleate, 20 parts by weight of 1,2-methylene diisocyanate, 20 parts by weight of toluene, and 22 parts by weight of ethyl acetate are added to the reaction vessel and mixed evenly. The temperature is raised to 50°C and after 1 hour, 0.01 parts by weight of dioctyltin dilaurate is added. The temperature is raised to 80°C and reacted for 2 hours. The temperature is lowered to 60°C and 10 parts by weight of polycaprolactone triol and 0.02 parts by weight of 2-ethylhexanoate are added. The temperature is raised to 90°C and reacted for 6 hours. The temperature is lowered to 50°C and 1 part by weight of 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide is added. The mixture is stirred evenly, filtered, and discharged to obtain the prepolymer.

[0100] (2) Preparation of polyurethane pressure-sensitive adhesive: Weigh 100 parts by weight of the prepolymer obtained in step (1), then add 70 parts by weight of ethyl acetate, stir evenly, add 7 parts by weight of hexamethylene diisocyanate and 0.015 parts by weight of tin 2-ethylhexanoate, stir evenly to obtain polyurethane pressure-sensitive adhesive.

[0101] (3) Preparation of polyurethane pressure-sensitive adhesive protective film: The polyurethane pressure-sensitive adhesive obtained in step (2) is uniformly coated on the surface of a 75μm thick transparent PET film, and then baked at 130℃ for 4min to cure and form a 15μm thick polyurethane pressure-sensitive adhesive layer, thus obtaining a polyurethane pressure-sensitive adhesive protective film.

[0102] Example 3

[0103] This embodiment provides a method for preparing a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film, including the following steps:

[0104] (1) Preparation of prepolymer: Place the raw materials polyethylene glycol (600), 2,4,4-trimethylene diisocyanate, polycaprolactone triol, etc. into reaction flasks, remove water by vacuum distillation, and set aside for use. Under nitrogen protection, 30 parts by weight of polyethylene glycol (600), 5 parts by weight of octadecyl diethanolamine, 15 parts by weight of 2,4,4-trimethylene diisocyanate, 6 parts by weight of acetylacetone, and 30 parts by weight of ethyl acetate were added to a reaction vessel and mixed thoroughly. The mixture was heated to 55°C and after 1 hour, 0.01 parts by weight of tin 2-ethylhexanoate was added, the temperature was raised to 80°C, and the reaction was carried out for 3 hours. The temperature was then lowered to 60°C, 6 parts by weight of polycaprolactone triol and 0.02 parts by weight of stannous octoate were added, the temperature was raised to 80°C, and the reaction was carried out for 2.5 hours. The temperature was then lowered to 50°C, and 0.4 parts by weight of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt was added. The mixture was stirred thoroughly, filtered, and discharged to obtain the prepolymer.

[0105] (2) Preparation of polyurethane pressure-sensitive adhesive: Weigh 100 parts by weight of the prepolymer obtained in step (1), then add 200 parts by weight of ethyl acetate, stir evenly, add 10 parts by weight of hexamethylene diisocyanate and 0.02 parts by weight of dibutyltin dilaurate, stir evenly to obtain polyurethane pressure-sensitive adhesive.

[0106] (3) Preparation of polyurethane pressure-sensitive adhesive protective film: The polyurethane pressure-sensitive adhesive obtained in step (2) is uniformly coated on the surface of a 45μm thick transparent PE film, and then baked at 90℃ for 8min to cure and form a polyurethane pressure-sensitive adhesive layer with a thickness of 4μm, thus obtaining a polyurethane pressure-sensitive adhesive protective film.

[0107] Example 4

[0108] This embodiment provides a method for preparing a direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film, including the following steps:

[0109] (1) Preparation of prepolymer: Polyethylene glycol (600), trimethylolpropane, 2,4-toluene diisocyanate, etc., were placed in reaction flasks and the water was removed by vacuum distillation. Under nitrogen protection, 30 parts by weight of polyethylene glycol (600), 8 parts by weight of lauroyl glutamic acid, 18 parts by weight of 2,4-toluene diisocyanate, 20 parts by weight of toluene, and 14 parts by weight of ethyl acetate were added to the reaction vessel and mixed evenly. The temperature was raised to 60°C and after 1 hour, 0.025 parts by weight of stannous octoate was added and the temperature was raised to 80°C. The reaction was carried out for 3 hours, and 10 parts by weight of trimethylolpropane were added. The reaction was continued for 2 hours. The temperature was lowered to 50°C and 0.3 parts by weight of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide was added. The mixture was stirred evenly, filtered, and discharged to obtain the prepolymer.

[0110] (2) Preparation of polyurethane pressure-sensitive adhesive: Weigh 100 parts by weight of the prepolymer obtained in step (1), then add 100 parts by weight of ethyl acetate, stir evenly, add 8 parts by weight of hexamethylene diisocyanate, stir evenly, and obtain polyurethane pressure-sensitive adhesive.

[0111] (3) Preparation of polyurethane pressure-sensitive adhesive protective film: The polyurethane pressure-sensitive adhesive obtained in step (2) is uniformly coated on the surface of a 50μm thick transparent PET film, and then baked at 120℃ for 5min to cure and form a 10μm thick polyurethane pressure-sensitive adhesive layer, thus obtaining a polyurethane pressure-sensitive adhesive protective film.

[0112] Example 5

[0113] This embodiment refers to the preparation method of the direct-winding and easy-to-unwind polyurethane pressure-sensitive adhesive protective film of Embodiment 3. The only difference is that in step (1), the amounts of polyethylene glycol (600) and polycaprolactone triol are different.

[0114] In this embodiment, the amount of polyethylene glycol (600) is 31 parts by weight and the amount of polycaprolactone triol is 5 parts by weight.

[0115] Comparative Example 1

[0116] Comparative Example 1 refers to the preparation method of the direct-winding and easy-to-unwind polyurethane pressure-sensitive adhesive protective film of Example 3, the only difference being that the amount of 2,4,4-trimethylene diisocyanate and polyethylene glycol (600) is different in step (1).

[0117] In this comparative example, the amount of 2,4,4-trimethylene diisocyanate was 20 parts by weight and the amount of polyethylene glycol (600) was 25 parts by weight.

[0118] Comparative Example 2

[0119] Comparative Example 2 uses the same preparation method as Example 3, except that octadecyl diethanolamine is not added in the preparation of the prepolymer in step (1).

[0120] Comparative Example 3

[0121] Comparative Example 3 was prepared using the same method as Example 3, except that the antistatic agent 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt was not added.

[0122] Experimental Example

[0123] The performance of each embodiment and comparative example was tested and compared. The relevant test items and methods are as follows, and the test results are shown in Table 1:

[0124] Surface resistance: Use a surface resistivity meter to place it on the adhesive surface of the protective film and measure the surface resistance directly;

[0125] Peel strength at 180°: After the polyurethane pressure-sensitive adhesive protective film is prepared, that is, after the polyurethane pressure-sensitive adhesive is baked and dried on the surface of the polymer film to form a pressure-sensitive adhesive layer, after cooling, the peel strength at 180° is tested according to GB / T 2792-2014.

[0126] Stable peel strength: After the polyurethane pressure-sensitive adhesive protective film is dried and rolled up, it is cured at room temperature for 7 days and the peel strength at 180° is tested according to the national standard GB / T2792-2014.

[0127] Unwinding force: After the polyurethane pressure-sensitive adhesive protective film is dried, the same film material (the same as the base film material coated with polyurethane pressure-sensitive adhesive) is directly laminated onto the adhesive surface. After curing at room temperature for 7 days, the 180° peel force of the single-layer protective film from the surface of the composite film is tested according to the national standard GB / T2792-2014. When the unwinding force is ≥100g / 25mm, it is considered that the unwinding force is too large.

[0128] Peel-off voltage: Apply the polyurethane pressure-sensitive adhesive protective film to the glass surface, let it stand for 24 hours, and then peel it off quickly at a speed of not less than 500 m / min. Use a static voltage tester to test the static voltage on the glass surface.

[0129] Table 1 Comparison of data from different embodiments and comparative examples.

[0130]

[0131]

[0132] The test results above show that the polyurethane pressure-sensitive adhesive protective film prepared in the embodiments of the present invention has similar lower peel strength and stable peel strength, and the unwinding force when directly wound is very small (e.g., <5g / 25mm), making it easy to achieve smooth unwinding. Moreover, the tearing voltage can reach less than 100V, which is very friendly to the protected material. The preparation formula and process of polyurethane pressure-sensitive adhesive have a great influence on the performance of the protective film, especially the lower peel strength, unwinding force and tearing voltage.

[0133] Comparing Examples 1 and 4, it can be seen that in the preparation of the prepolymer, the catalyst is added at once, and the initial chain extension catalytic reaction rate is too fast, resulting in a low molecular chain crosslinking density and a large molecular weight distribution width. After coating onto the substrate, the peel force after unwinding is too large, leading to a larger unwinding force.

[0134] Comparing Examples 3 and 5, it can be seen that when the ratio of diol to triol exceeds a certain range, it will affect the peel strength and unwinding force of the protective film to a certain extent.

[0135] Comparative Examples and Comparative Example 1 show that during the preparation of the prepolymer, the molar number of NCO in the isocyanate is greater than the sum of the molar numbers of OH in the diol, triol and functional monomer, resulting in poor film-forming properties and excessive peel force and unwinding force, making it unsuitable for direct coating and winding of protective films.

[0136] Comparative Examples 1 and 2 show that no functional monomers were added during the preparation of the prepolymer, resulting in insufficient wettability and electrostatic conductivity. Therefore, when the surface tension of the base film is low, insufficient adhesion is likely to occur, and the tear-off voltage will also be too high.

[0137] Comparative examples and Comparative Example 3 show that without the addition of antistatic agent, the film-tearing voltage is higher, but the adhesive surface still has a certain antistatic effect. This is mainly because the functional monomers selected in the pressure-sensitive adhesive have a long-chain structure, which has a certain air-venting and electrostatic conduction effect.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A straight take easy-to-unwind polyurethane pressure-sensitive adhesive protective film, characterized by, Includes a substrate and a polyurethane pressure-sensitive adhesive layer disposed on the surface of the substrate; The polyurethane pressure-sensitive adhesive layer is mainly composed of the following components in parts by weight: The composition includes 100 parts prepolymer, 70-200 parts solvent, 3-15 parts polyisocyanate, and 0.01-0.02 parts catalyst. The prepolymer is mainly prepared from the following components in parts by weight: 10-40 parts of diol, 2-10 parts of triol, 2-8 parts of functional monomer, 5-20 parts of polyisocyanate, 0.1-1 part of antistatic agent, 0.001-0.03 parts of catalyst and 20-50 parts of solvent; The functional monomer includes at least one of oleic acid diethanolamine, octadecyl diethanolamine, and lauroyl glutamic acid; the mass ratio of the triol to the diol is 1:(1-5); the antistatic agent is selected from ionic liquids; In the prepolymer, the number of moles of NCO in the polyisocyanate is less than the sum of the number of moles of OH in the diol, the triol, and the functional monomer; In the polyurethane pressure-sensitive adhesive layer, the number of moles of OH in the prepolymer is less than the number of moles of NCO in the polyisocyanate; The method for preparing the prepolymer includes: (a) Under nitrogen protection, the diol, the functional monomer, the polyisocyanate and the solvent are mixed evenly, heated to 50-60°C, a portion of the catalyst is added, and the mixture is reacted at 80-90°C for 2-3 hours. (b) Cool down to 50-60°C, add the triol and the remaining catalyst, react at 80-90°C for 2-8 hours, add the antistatic agent, stir evenly, and discharge; The mass ratio of the partial catalyst described in step (a) to the remaining catalyst described in step (b) is 1:(1.5 to 2.5).

2. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The diol includes at least one of polyethylene glycol, polypropylene glycol, polytetrahydrofuran, and poly(neopentyl glycol adipate-1,6-hexanediol) diol.

3. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The triol includes at least one of trimethylolpropane, polyglycerol, and polycaprolactone triol.

4. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The polyisocyanate in the prepolymer is selected from aromatic isocyanates and / or aliphatic isocyanates.

5. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The polyisocyanate in the polyurethane pressure-sensitive adhesive includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, and trimethylene diisocyanate.

6. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The catalyst in the polyurethane pressure-sensitive adhesive and the catalyst in the prepolymer are each independently selected from at least one of dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethylethoxytin, tributylethoxytin, stannous octoate, trioctyltin oxide, trioctyltin chloride, tributyltin trichloroacetate, and 2-ethylhexanoate. And / or, the solvent in the polyurethane pressure-sensitive adhesive and the solvent in the prepolymer are each independently selected from at least one of ethyl acetate, butyl acetate, toluene, xylene, butanone, cyclohexanone, cyclohexane, acetone and acetylacetone.

7. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The ionic liquid comprises at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-hexyl-3-methylimidazolium di(trifluoromethanesulfonyl)imide.

8. The direct-winding, easy-to-unwind polyurethane pressure-sensitive adhesive protective film according to claim 1, characterized in that, The substrate includes at least one of polyethylene, polyethylene terephthalate, polyimide, and polypropylene; And / or, the thickness of the polyurethane pressure-sensitive adhesive layer is 1 to 15 μm.

9. The method for preparing the direct-winding, easily unwindable polyurethane pressure-sensitive adhesive protective film according to any one of claims 1 to 8, characterized in that, Includes the following steps: The polyurethane pressure-sensitive adhesive is evenly coated onto the substrate surface and then baked at high temperature. The preparation method of the polyurethane pressure-sensitive adhesive includes: mixing the prepolymer with a solvent, adding a polyisocyanate and a catalyst, stirring evenly to obtain the polyurethane pressure-sensitive adhesive.

10. The preparation method according to claim 9, characterized in that, The high-temperature baking temperature is 80-130℃, and the high-temperature baking time is 3-8 minutes.

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