Polyurethane film and method for manufacturing same

Abstract

Disclosed are a polyurethane film having excellent constructability and weather resistance, and a method for manufacturing same. The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at the end thereof and a first curing agent, and is characterized in that, according to ASTM D882 standards, a polyurethane film having a width of 1 inch has a tensile force of 15-35 N when stretched by 15% in the machine direction (MD) or transverse direction (TD).

Description

Polyurethane film and method for producing the same

[0001] The present invention relates to a polyurethane film for advertising and a method for producing the same.

[0002] Polyurethane films for advertising are constructed with a thickness of less than 30%, and most of the films used are PVC films.

[0003] PVC film has excellent processability and satisfies stable weather resistance when exposed outdoors by using plasticizers.

[0004] However, plasticizers have migration properties, which can reduce the weatherability of PVC layers, limiting their ability to meet the weatherability requirements of advertising printing. Furthermore, PVC film is prone to tearing and difficult to stretch during construction.

[0005] To improve these problems, thermoplastic polyurethane (TPU) films or olefin elastomer films are being used.

[0006] However, thermoplastic polyurethane films have elasticity and resilience, making them difficult to extrude in film thicknesses commonly used in advertising printing. Furthermore, their low cost of processing hinders their commercial viability. Furthermore, thermoplastic polyurethane films have a higher initial tensile strength than PVC films, making them less susceptible to stretching during construction.

[0007] In addition, olefin elastic film has lower tensile properties and toughness properties and lower heat resistance than PVC film, making it unsuitable for advertising films.

[0008] Therefore, there is a need for research on films that have excellent workability, weather resistance, and heat resistance and can be applied to advertising films.

[0009] The purpose of the present invention is to provide a polyurethane film with excellent workability and weather resistance and a method for manufacturing the same.

[0010] In addition, the purpose of the present invention is to provide a polyurethane film and a method for manufacturing the same, which can suppress the soft properties and impart hardness while maintaining the elongation at break, thereby suppressing the adhesion of polyurethane films to each other during winding.

[0011] Another object of the present invention is to provide a method for producing a polyurethane film that can be produced by a casting process.

[0012] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned above can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objectives and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0013] The polyurethane film according to the present invention is a cured product of a composition including a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized in that, according to ASTM D882 standard, the polyurethane film having a width of 1 inch has a tensile strength of 15 to 35 N when stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0014] The polyurethane resin having a hydroxyl group at the terminal may be a copolymer of a polyol, a diol containing C4 to C12, and a second curing agent.

[0015] The elongation at break according to ASTM D882 can be 90 to 250%.

[0016] The breaking strength according to ASTM D882 can be 15 to 30 MPa.

[0017] After exposing the above polyurethane film for 3,000 hours according to the ISO04892-2 standard, when the color change value for the polyurethane film before exposure is △E, △E < 3.0 may be obtained.

[0018] After exposing the above polyurethane film for 14 days under constant temperature and humidity conditions of 85°C and 85%, when the color change value for the polyurethane film before exposure is △E, △E ≤ 3.0 may be achieved.

[0019] When the above polyurethane films are laminated so that they face each other and peeled off after 5 seconds, there may be no residue on the surface of the polyurethane films. (The above residue is defined as having a size of 0.1 mm or more.)

[0020] The first curing agent may include a prepolymer having isocyanate groups (NCO) at both terminals.

[0021] The second curing agent may include at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexylmethane diisocyanate (H12MDI).

[0022] The first solid content of the above polyurethane resin is 30 to 40 wt%, and may include 5 wt% or less of the first curing agent per 100 wt% of the above polyurethane resin.

[0023] The polyurethane film according to the present invention is characterized in that, in accordance with ASTM D882 standard, the polyurethane film having a width of 1 inch has a tensile strength of 15 to 35 N when stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0024] The polyurethane film according to the present invention is characterized in that, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction, the tensile strength is 15 to 35 N, and the elongation at break according to ASTM D882 is 90 to 250%.

[0025] The polyurethane film according to the present invention is characterized in that, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction, the tensile strength is 15 to 35 N, and the breaking strength according to ASTM D882 is 15 to 30 MPa.

[0026] The polyurethane film according to the present invention is characterized in that, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction according to ASTM D882 standard, the tensile strength is 15 to 35 N, and when the polyurethane film is exposed for 3,000 hours according to ISO04892-2 standard, when the color change value for the polyurethane film before exposure is △E, △E < 3.0.

[0027] The polyurethane film according to the present invention is characterized in that, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction according to ASTM D882 standard, the tensile strength is 15 to 35 N, and when the polyurethane film is exposed to 85°C and 85% constant temperature and humidity conditions for 14 days, when the color change value for the polyurethane film before exposure is △E, △E ≤ 3.0.

[0028] The polyurethane film according to the present invention is characterized in that, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction according to ASTM D882 standard, the tensile strength is 15 to 35 N, and when the polyurethane films are laminated so as to face each other and peeled off after 5 seconds, there is no residue on the surface of the polyurethane film.

[0029] The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and the polyurethane resin having a hydroxyl group at a terminal is characterized in that it is a copolymer of a polyol, a diol containing C4 to C12, and a second curing agent.

[0030] The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized by having an elongation at break of 90 to 250% according to ASTM D882.

[0031] The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized by a breaking strength of 15 to 30 MPa according to ASTM D882.

[0032] The polyurethane film according to the present invention is a cured product of a composition including a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized in that when the color change value of the polyurethane film before exposure is △E after exposing the polyurethane film for 3,000 hours according to the ISO04892-2 standard, △E < 3.0.

[0033] The polyurethane film according to the present invention is a cured product of a composition including a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized in that when the polyurethane film is exposed for 14 days under constant temperature and humidity conditions of 85°C and 85%, the color change value for the polyurethane film before exposure is △E, and △E ≤ 3.0.

[0034] The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized in that when the polyurethane films are laminated so as to face each other and peeled off after 5 seconds, there is no residue on the surface of the polyurethane film.

[0035] The polyurethane film according to the present invention is a cured product of a composition comprising a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, wherein the first solid content of the polyurethane resin is 30 to 40 wt%, and the first curing agent is comprised in an amount of 5 wt% or less with respect to 100 wt% of the polyurethane resin.

[0036] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; and, according to ASTM D882 standard, the polyurethane film having a width of 1 inch is characterized in that the tensile strength is 15 to 35 N when stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0037] The polyurethane resin having a hydroxyl group at the terminal may be a copolymer obtained by copolymerizing 40 to 60 wt% of polyol, 9 to 20 wt% of diol containing C4 to C12, and 30 to 42 wt% of a second curing agent.

[0038] The number average molecular weight of the above polyol may be greater than 1000 g / mol and less than or equal to 3000 g / mol.

[0039] The first curing agent may include a prepolymer having isocyanate groups (NCO) at both terminals.

[0040] The first solid content of the above polyurethane resin is 30 to 40 wt%, and a composition can be prepared by mixing 100 wt% or less of an organic solvent and 5 wt% or less of a first curing agent with respect to 100 wt% of the above polyurethane resin.

[0041] The weight average molecular weight of the above polyurethane resin may be 40,000 to 60,000 g / mol.

[0042] The second curing agent may include at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexylmethane diisocyanate (H12MDI).

[0043] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein the polyurethane resin having a hydroxyl group at a terminal is characterized in that it is a copolymer of a polyol, a diol containing C4 to C12, and a second curing agent.

[0044] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; and is characterized in that the elongation at break according to ASTM D882 is 90 to 250%.

[0045] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; and is characterized in that the breaking strength according to ASTM D882 is 15 to 30 MPa.

[0046] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein, after exposing the polyurethane film for 3,000 hours according to the ISO04892-2 standard, when the color change value for the polyurethane film before exposure is △E, △E < 3.0.

[0047] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at the terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein after exposing the polyurethane film under constant temperature and humidity conditions of 85°C and 85% for 14 days, when the color change value for the polyurethane film before exposure is △E, △E ≤ 3.0.

[0048] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein when the polyurethane films are laminated so as to face each other and peeled off after 5 seconds, there is no residue on the surface of the polyurethane film.

[0049] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein the first curing agent comprises a prepolymer having isocyanate groups (NCO) at both terminals.

[0050] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) preparing a polyurethane film by coating the composition on a substrate; wherein the first solid content of the polyurethane resin is 30 to 40 wt%, and the composition is prepared by mixing 100 wt parts or less of the organic solvent and 5 wt parts or less of the first curing agent with respect to 100 wt parts of the polyurethane resin.

[0051] A method for producing a polyurethane film according to the present invention comprises the steps of (a) preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent; and (b) coating the composition on a substrate to produce a polyurethane film; wherein the polyurethane resin is characterized in that the weight average molecular weight is 40,000 to 60,000 g / mol.

[0052] The polyurethane film according to the present invention has excellent workability due to low initial tensile strength and excellent weather resistance. In addition, the polyurethane film comprises a polyurethane resin copolymerized from 40 to 60 wt% of polyol, 9 to 20 wt% of diol containing C4 to C12, and 30 to 42 wt% of a second curing agent, thereby imparting hardness while maintaining the basic elongation at break of the polyol, thereby having the effect of suppressing adhesion of the polyurethane films to each other during winding.

[0053] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0054] Figure 1 is a cross-sectional view showing a structure in which a polyurethane film according to the present invention is applied to advertising materials.

[0055] [Explanation of symbols]

[0056] 10: Polyurethane film

[0057] 12: Adhesive layer

[0058] 14: Lee Hyeong-ji

[0059] 20: Car paint surface

[0060] 30: Advertising printing layer

[0061] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0062] Hereinafter, the phrase "any configuration is placed on (or below)" a component or "on (or below)" a component may mean that any configuration is placed in contact with the upper surface (or lower surface) of said component, and that other configurations may be interposed between said component and any configuration placed on (or below) said component.

[0063] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0064] Hereinafter, a polyurethane film and a method for manufacturing the same according to some embodiments of the present invention will be described.

[0065] The polyurethane film of the present invention can replace existing PVC, thermoplastic polyurethane film (TPU), and olefin elastomer film, has excellent workability due to low initial tensile strength, and can secure hardened surface properties while maintaining elongation at break by using a polyurethane resin with a diol content of 9 to 20 wt%.

[0066] Additionally, weather resistance can be secured by controlling the type of second curing agent used to polymerize polyurethane resin.

[0067] A method for producing a polyurethane film according to the present invention comprises the steps of preparing a composition by mixing a polyurethane resin having a hydroxyl group at a terminal, an organic solvent, and a first curing agent, and the steps of coating the composition on a substrate to produce a polyurethane film, and is characterized in that, according to ASTM D882 standard, the polyurethane film having a width of 1 inch has a tensile strength of 15 to 35 N when stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0068] A step of preparing a composition by mixing a polyurethane resin having a hydroxyl group at the terminal, an organic solvent, and a first curing agent.

[0069] The polyurethane resin having a hydroxyl group at at least one terminal may be a copolymer of 40 to 60 wt% of polyol, 9 to 20 wt% of diol containing C4 to C12, and 30 to 42 wt% of a second curing agent, based on 100 wt% of the total.

[0070] The polyol may include at least one of polycarbonate polyol, polyester polyol, polyether polyol, acrylic polyol, and polycaprolactone polyol, and preferably may include polycarbonate polyol.

[0071] Since the polyurethane resin contains polycarbonate polyol, the tensile properties of the polyurethane film can be secured, and accordingly, when construction is required for stretching or when construction is performed on a curved surface, the tensile force is 15 to 35 N at 15% tension, resulting in excellent construction properties.

[0072] 15% tensile strength refers to a 15% elongation compared to the original length, i.e., an elongation of 15%. Tensile strength refers to the force that stretches or pulls a material.

[0073] In the case of construction films, it is easy to stretch the film if the force applied when stretching to the initial stretch amount (15%) is low during stretching construction. Accordingly, in the present invention, the tensile force (N), which is the force applied to the polyurethane film when stretched by 15%, was confirmed as a substitute for the construction characteristics. Accordingly, according to the ASTM D882 standard, when a polyurethane film having a width of 1 inch is stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction), the tensile force may be 15 to 35 N, and preferably 18 to 32 N. If the tensile force is less than 15 N, the film stretches too easily, which has the disadvantage of making roll-to-roll production impossible.

[0074] Additionally, according to ASTM D882, the tensile strength of a polyurethane film having a width of 1 inch may be 20 to 40 N, and preferably 22 to 38 N, when stretched 100% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0075] When 100% tension is applied, the tensile force is 20 to 40 N more, which has the effect of improving constructability.

[0076] Since the polyurethane film of the present invention is coated by casting rather than extrusion, the tensile strength is the same when pulled in the MD (Machine Direction) and TD (Transverse Direction) directions.

[0077] Polycarbonate polyol has a carbonate (-O-(C=O)-O-) group in the main chain, at least one functional group selected from hexanediol and pentanediol, and may have hydroxyl groups (OH) at both terminals. Here, polyol refers to a compound having two or more hydroxyl groups. For example, polycarbonate polyol may include a reaction product of at least one carbonate derivative selected from hexanediol and pentanediol and a diol.

[0078] The number average molecular weight of such polycarbonate polyol may be more than 1000 g / mol and less than or equal to 3000 g / mol, preferably 1500 to 2500 g / mol, and more preferably 1800 to 2200 g / mol.

[0079] The number average molecular weight is the total weight divided by the number of chains, which is the product of the average degree of polymerization of the chain and the molecular weight of the repeating unit.

[0080] By satisfying the number average molecular weight of the polycarbonate polyol of 1000 g / mol to 3000 g / mol or less, it can exhibit low tensile strength at 15% elongation.

[0081] In this range, the hydroxyl value (OH value) of the polycarbonate polyol may be 46 to 66 mgKOH / g, and preferably 50 to 60 mgKOH / g.

[0082] The hydroxyl value is the number of milligrams of potassium hydroxide required to acetylate 1 g of oil and neutralize the acetic acid produced by hydrolysis.

[0083] The hydroxyl value is determined by the type of polyol, the number of functional groups, and the molecular weight, and the hydroxyl value can impart flexibility (softness) to the polyurethane film.

[0084] Polyurethane resin is a copolymerization reaction of a mixture of 40 to 60 wt% polyol, 9 to 20 wt% diol containing C4 to C12, and 30 to 42 wt% of a second curing agent, and has an advantageous effect in securing low tensile strength and flexibility when stretched by 15%.

[0085] Meanwhile, since polycaprolactone polyol has such high flexibility, there is a concern that the elongation rate of the polyurethane film during construction will be significantly high.

[0086] Diol is a chain extender with a short chain, which serves to provide rigidity to polyurethane films, and may contain C4 to C12, preferably C4 to C6. Diol is a compound having two hydroxyl groups, with C4 to C12 present in the main chain and hydroxyl groups present at both ends.

[0087] Since the polyurethane resin contains a diol, the polyurethane resin contains a hard segment, which has the effect of suppressing adhesion of the polyurethane films to each other during winding while hardening the surface properties.

[0088] In particular, it is preferable that the molar content of the diol in the polyurethane resin be greater than the molar content of the polyol, which can satisfy 9 to 20 wt% of the diol containing C4 to C12. Then, the coating layer becomes hard, which can manufacture a polyurethane film that can be used in a roll-to-roll process during the process. In addition, since the amount of polyol remains the same, the basic elongation at break of the polyol can be maintained. By satisfying 9 to 20 wt% of the diol containing C4 to C12, it can be manufactured using only one sheet of substrate (carrier film) in a roll-to-roll process, which has a great advantage in cost.

[0089] If the molar content of the diol is lower than that of the polyol, or if it exceeds 9 to 20 wt% of the diol, the surface of the polyurethane film will stick to the guide roll of the coating machine after coating (drying), making normal manufacturing impossible. To prevent this, a release film can be laminated after coating (drying), but this has the disadvantage of increasing the manufacturing cost of the release film. In particular, when the diol content exceeds 20 wt%, the elongation at break decreases as the hardening increases.

[0090] In addition, when a polyurethane resin is manufactured by copolymerization reaction in the absence of a diol and then a diol is added in the mixing step with the second curing agent described later, the surface properties of the polyurethane film become softer and tend to become tacky because no reaction occurs.

[0091] Specifically, the polyurethane resin may contain 9 to 20 wt% of a diol containing C4 to C12, and preferably 9 to 16 wt%. By containing 9 to 20 wt% of a diol containing C4 to C12, there is a beneficial effect in ensuring hardening of the polyurethane film.

[0092] The second curing agent forms a crosslinking reaction through a polyol and diol and urethane curing reaction, imparting weather resistance to the polyurethane film.

[0093] In this way, the second curing agent is added together with the polyol and diol to manufacture a polyurethane resin, and the polyol, diol, and the second curing agent can undergo a copolymerization reaction to form a polyurethane group.

[0094] The second curing agent affects the reaction rate in the copolymerization reaction and can promote the structural formation of the polyurethane resin.

[0095] The second curing agent is preferably a non-yellowing monomer, and preferably includes an aliphatic compound having two isocyanate groups without a double bond in the compound, wherein the double bond of the isocyanate can be excluded. From this perspective, the second curing agent may include at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexylmethane diisocyanate (H12MDI).

[0096] The second curing agent may not include aromatic isocyanates such as 1,5-naphthalene diisocyanate (NDI), xylene diisocyanate (XDI), toluene diisocyanate (TDI), and methylene diphenyl diisocyanate (MDI) which have low weather resistance.

[0097] The polyurethane resin may contain 30 to 42 wt% of a second curing agent, preferably 32 to 40 wt%.

[0098] The weight average molecular weight of the polyurethane resin may be 40,000 to 60,000 g / mol, and preferably 45,000 to 55,000 g / mol. By satisfying the weight average molecular weight of the polyurethane resin of 40,000 to 60,000 g / mol, there is an advantageous effect in securing a break elongation and low tensile strength at 15% elongation.

[0099] Weight average molecular weight can be measured using gel permeation chromatography (GPC).

[0100] And the hydroxyl value (OH value) of the polyurethane resin may be more than 0 and less than or equal to 10 mgKOH / g, and preferably 2 to 8 mgKOH / g.

[0101] In this way, a polyurethane resin can be synthesized by copolymerizing 40 to 60 wt% of polyol, 9 to 20 wt% of diol containing C4 to C12, and 30 to 42 wt% of a second curing agent, and the synthesized polyurethane resin can be mixed with an organic solvent under an inert atmosphere, and the first solid content can be 30 to 40 wt% while dissolved in the organic solvent.

[0102] For example, the first solid content of a polyurethane resin dissolved in an organic solvent may be 40%. The solid content refers to a solute or solid excluding the organic solvent, and refers to, for example, a copolymer of a polyol, a diol, and a second curing agent.

[0103] To adjust the first solid content to 30 to 40 wt%, the organic solvent may include at least one of toluene, xylene, cyclohexanone, ethyl acetate, butyl acetate, butyl cellosolve, methyl ethyl ketone, methyl isobutyl ketone, and isopropyl alcohol.

[0104] In order to improve the coating properties of the synthesized polyurethane resin, a composition can be prepared by mixing an organic solvent for viscosity control and a first curing agent for improving the density of the coating layer.

[0105] For 100 parts by weight of a polyurethane resin having a first solid content of 30 to 40% by weight, 100 parts by weight or less of an organic solvent and 5 parts by weight or less of a first curing agent can be mixed, and preferably, more than 0 to 80 parts by weight or less of an organic solvent and more than 0 to 3 parts by weight or less of a first curing agent can be mixed.

[0106] By including 5 parts by weight or less of the first curing agent, the degree of curing of the polyurethane film formed from the coating layer can be increased, which can be advantageous in improving physical properties.

[0107] The solvent may include one or more of the organic solvents described above, such as toluene, xylene, cyclohexanone, ethyl acetate, butyl acetate, butyl cellosolve, methyl ethyl ketone, methyl isobutyl ketone, and isopropyl alcohol.

[0108] The first curing agent may include a prepolymer having isocyanate groups (NCO) at both terminals.

[0109] The first curing agent is added together with the polyurethane resin to manufacture a polyurethane film. It accelerates the curing reaction of the polyurethane resin, and this curing reaction can stabilize the film structure. Furthermore, the first curing agent can control the curing speed of the polyurethane resin and impart the necessary physical properties to the polyurethane film.

[0110] Here, physical properties may mean at least one of strength, hardness, flexibility, elasticity, and chemical resistance.

[0111] In particular, the first curing agent increases the curing reaction and imparts a degree of curing to the coating layer, i.e., the polyurethane film, so it is advantageous in securing the properties that the polyurethane film should have.

[0112] Prepolymers are products of a reaction between isocyanate compounds, and have a relatively lower degree of polymerization and weight average molecular weight than polymers, but a higher degree of polymerization and weight average molecular weight than second curing agents.

[0113] When a prepolymer is used as the first curing agent, the curing reaction is fast and the physical properties of the coating layer after curing are excellent.

[0114] As a first curing agent, the prepolymer having isocyanate groups (NCO) at both ends may include a known curing agent. For example, the first curing agent may include at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (H12MDI), 1,5-naphthalene diisocyanate (NDI), xylene diisocyanate (XDI), and methylene diphenyl diisocyanate (MDI), and preferably, at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexylmethane diisocyanate (H12MDI), but is not limited thereto.

[0115] The second solid content of the composition may be 30 to 40 wt%, and the second solid content at this time may be lower than the first solid content.

[0116] For example, the second solid content of the composition may be 35%.

[0117] A step of manufacturing a polyurethane film by coating the composition on a substrate

[0118] A composition containing a polyurethane resin, an organic solvent, and a first curing agent is coated on a substrate and dried.

[0119] By manufacturing a polyurethane film using a casting method and a drying method that apply a composition on a flat substrate, workability can be improved and price competitiveness can be enhanced.

[0120] Typically, films are manufactured by extruding thermoplastic polyurethane at high temperatures and high pressures, but this has the disadvantage of reducing process efficiency and increasing manufacturing costs due to the elasticity of polyurethane.

[0121] To overcome these shortcomings, the present invention provides a polyurethane resin-based composition with soft and hard properties, and by applying the composition by casting and then drying it to remove the organic solvent, a polyurethane film can be manufactured that has improved workability and can be applied to advertising materials while maintaining properties equivalent to or better than those of a film manufactured by a conventional extrusion method.

[0122] The substrate may be a carrier film such as PET film.

[0123] The casting method for applying the composition can be performed by one of various methods such as slot die coating, comma coating, and micro gravure coating.

[0124] The thickness of the polyurethane film manufactured by the casting method may be 30 to 80 μm, and preferably 30 to 60 μm.

[0125] Since the thickness of the polyurethane film satisfies 30 to 80㎛, it has the advantage of exhibiting low tensile strength and hardened surface characteristics at 15% tension while maintaining the elongation at break, and can be applied to advertising materials that can protect the printed layer.

[0126] After applying the composition, the organic solvent can be removed at 80 to 150°C to produce a polyurethane film, but is not limited thereto.

[0127] The polyurethane film according to the present invention is a cured product of a composition including a polyurethane resin having a hydroxyl group at a terminal and a first curing agent, and is characterized in that, according to ASTM D882 standard, the polyurethane film having a width of 1 inch has a tensile strength of 15 to 35 N when stretched by 15% in the MD (Machine Direction) or TD (Transverse Direction) direction.

[0128] The polyurethane resin having a hydroxyl group at the terminal may be a copolymer obtained by copolymerizing a polyol, a diol containing C4 to C12, and a second curing agent.

[0129] Polyurethane resin is a copolymer manufactured by copolymerizing a polyol, a diol containing C4 to C12, and a second curing agent, and can satisfy the characteristics of a polyurethane film for post-processing. From this perspective, the polyurethane film can have a breaking elongation of 90 to 250% according to ASTM D882, and preferably more than 100% and less than 200%. By satisfying a breaking elongation of 90 to 250%, the film is not easily torn, so it has excellent detachability without residue on the surface. The breaking elongation, also called elongation, is the ratio of elongation without breaking in a tensile test.

[0130] Additionally, the breaking strength according to ASTM D882 may be 15 to 30 MPa, preferably 15 to 25 MPa. Breaking strength, also called fracture strength, refers to the maximum stress until the material breaks.

[0131] Regarding weather resistance, after exposing the polyurethane film for 3,000 hours according to the ISO04892-2 standard, when the color change value for the polyurethane film before exposure is △E, △E may be < 3.0, and preferably △E may be < 2.0.

[0132] ΔE(L*, a*, b*) ={(ΔL*) 2 +(Δa*) 2 +(Δb*) 2} 1 / 2

[0133] In the formula, L*: brightness, a*: green, red color coordinates, b*: yellow, blue color coordinates (based on CIE Lab color space). When △E < 3.0, it exhibits excellent weather resistance.

[0134] By satisfying △E < 3.0, the polyurethane film has little color change even after exposure to high temperature and light, and has excellent UV resistance, resulting in almost no discoloration.

[0135] Regarding heat and moisture resistance, after exposure for 14 days under constant temperature and humidity conditions of 85℃ and 85%, when the color change value for the polyurethane film before exposure is △E, △E may be ≤ 3.0, and preferably △E may be ≤ 2.2.

[0136] ΔE(L*, a*, b*) ={(ΔL*) 2 +(Δa*) 2 +(Δb*) 2} 1 / 2

[0137] In the formula, L*: brightness, a*: green, red color coordinates, b*: yellow, blue color coordinates (based on CIE Lab color space). When △E ≤ 3.0, it exhibits excellent heat and moisture resistance.

[0138] Regarding hardening, when polyurethane films are laminated facing each other and peeled off after 5 seconds, there may be no residue on the surface of the polyurethane films. (The residue is defined as having a size of 0.1 mm or more.)

[0139] The first curing agent may include a prepolymer having isocyanate groups (NCO) at both terminals, the details of which are the same as described above.

[0140] The second curing agent may include at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexylmethane diisocyanate (H12MDI), and the details thereof are the same as those described above.

[0141] The first solid content of the polyurethane resin is 30 to 40 wt%, and may include 5 wt% or less of the first curing agent per 100 wt% of the polyurethane resin, and the details thereof are the same as those described above.

[0142] Figure 1 is a cross-sectional view showing a structure in which a polyurethane film according to the present invention is applied to advertising materials.

[0143] As shown in Fig. 1, a polyurethane film (10) can be attached to a car paint surface (20) and can also be attached to the top layer to protect an advertising print layer (30).

[0144] In order to apply polyurethane film to advertising materials, the polyurethane film can be produced in a form in which an adhesive layer and a release paper are attached.

[0145] For example, a polyurethane film (10) is manufactured by casting on a substrate.

[0146] An adhesive layer (12) is formed by coating an acrylic copolymer on a release paper (14), and then the polyurethane film (10) is laminated and cured. Both sides are cut to fit the width and the substrate is removed.

[0147] Here, specific examples of polyurethane films and their manufacturing methods are as follows.

[0148] 1. Manufacturing of polyurethane film

[0149] ① As in the composition of [Table 1], in specimen a-1, polycarbonate diol (Caffaro PCD, trade name REVECARB 107) with Mn 2,000 g / mol and 50 to 60 mgKOH / g was used as the polyol. Mitsubishi Chemical 1,4-butanediol was used as the diol, and Evonik IPDI (isophorone diisocyanate) was used as the second curing agent to carry out urethane polymerization.

[0150] Specimens a to f were synthesized using polyurethane resin (solid content 40 wt%) under the same conditions as Specimen a-1, except for the conditions described in Table 1.

[0151] Specimen g was synthesized using polyurethane resin (solid content 40 wt%) under the same conditions as Specimen e, except for the conditions described in Table 1.

[0152] The mixed solution was placed in a reactor and reacted for 24 hours in a nitrogen atmosphere to produce a polyurethane resin having a weight average molecular weight of 50,000 g / mol and a hydroxyl value of 2.5 mgKOH / g or more and less than 5 mgKOH / g. The organic solvent used at this time was 50 parts by weight of methyl ethyl ketone (MEK) and 50 parts by weight of toluene.

[0153] For 100 parts by weight of the manufactured polyurethane resin, 50 parts by weight of methyl isobutyl ketone (MIBK), 20 parts by weight of acetylacetone, 25 parts by weight of toluene, and 5 parts by weight of a first curing agent (Asahi Kasei TLA100, HDI series polyisocyanate) were mixed to manufacture a coating agent having a solid content of 35% by weight.

[0154] The prepared coating solution was applied to a 140 μm thick PET film, a substrate with silicone release treatment, before drying. The film was then dried in a drying oven at 120°C for 2 minutes and 30 seconds to obtain a 50 μm thick dry film. Films were manufactured using the same method for the remaining materials.

[0155] ② Specimen h was manufactured as a film under the same conditions as specimen a-1, except that the content of the first curing agent was 10 parts by weight.

[0156] [Table 1]

[0157]

[0158] 1) The elongation at break and the strength at break were measured using a UTM (universal tensile machine) instron 5969, and the test was performed at 500 mm / min according to ASTM D882.

[0159] Tensile strength was measured at 15% tension and 100% tension in the MD (Machine Direction) or TD (Transverse Direction) direction of a 1-inch wide polyurethane film according to ASTM D882.

[0160] 2) After exposing the polyurethane film for 3,000 hours according to the ISO04892-2 standard, the color change value for the polyurethane film before exposure was designated as △E. If △E < 3.0, the weather resistance is excellent.

[0161] The ISO04892-2 standard used a xenon arc lamp as a light source, and performed one cycle (total 120 minutes) of 102 minutes of drying without water spray conditions and 18 minutes of water spray conditions without drying, and was performed in a chamber (38℃, 50% conditions).

[0162] ΔE(L*, a*, b*) ={(ΔL*) 2 +(Δa*) 2 +(Δb*) 2} 1 / 2

[0163] In the formula, L*: brightness, a*: green, red color coordinates, b*: yellow, blue color coordinates (based on CIE Lab color space).

[0164] 3) After exposing the polyurethane film to constant temperature and humidity conditions of 85℃ and 85% for 14 days, the color change value for the polyurethane film before exposure was designated as △E. If △E ≤ 3.0, the heat and moisture resistance is excellent.

[0165] ΔE(L*, a*, b*) ={(ΔL*) 2 +(Δa*) 2 +(Δb*) 2} 1 / 2

[0166] In the formula, L*: brightness, a*: green, red color coordinates, b*: yellow, blue color coordinates (based on CIE Lab color space).

[0167] 3) Surface characteristics: When polyurethane films are laminated facing each other and peeled off after 5 seconds, if there is no residue on the surface of the polyurethane film, it is marked as “hard.” If there is residue due to adhesive properties, it is marked as “soft, tacky.” Residue is considered to be 0.1 mm or larger in size.

[0168] [Table 2]

[0169]

[0170] From the results in Table 2, specimens a-1, b, and c are specimens that satisfy the configuration of the present invention, and showed excellent results in elongation at break, strength at break, tensile strength at 15% and 100% tensile strength, weather resistance, heat and moisture resistance, and surface properties.

[0171] Specimen a is a specimen with a diol content of less than 9 wt%, and its surface properties were soft and sticky as the elongation at break was too high.

[0172] Specimen b-1 is a specimen that used caprolactone polyol instead of polycarbonate polyol, and showed poor properties in terms of weather resistance and heat and moisture resistance, and its surface characteristics were soft and sticky.

[0173] Specimen d is a specimen with a number average molecular weight of 1000 g / mol of polycarbonate polyol, and its elongation at break was considerably low.

[0174] Specimen e is a specimen with a diol content exceeding 20 wt%, and showed a low elongation at break due to high hardening.

[0175] Specimen f was a specimen that used toluene diisocyanate as a second curing agent, and showed low properties in terms of weather resistance and heat and moisture resistance.

[0176] Specimen g is a specimen with the same conditions as Specimen e, but with a different diol type. Specimen g has a harder property, and its breaking strength exceeds 30 MPa.

[0177] Specimen h is a specimen in which the content of the first hardener exceeds 5 parts by weight. Specimen h showed low heat and moisture resistance.

[0178]

[0179] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

1. A cured product of a composition comprising a polyurethane resin having a hydroxyl group at the terminal and a first curing agent. A polyurethane film having a tensile strength of 15 to 35 N when stretched 15% in the MD (Machine Direction) or TD (Transverse Direction) direction, with a width of 1 inch, according to ASTM D882.

2. In paragraph 1, Polyurethane resin having a hydroxyl group at the terminal A polyurethane film which is a copolymer of a polyol, a diol containing C4 to C12, and a second curing agent.

3. In paragraph 1, Polyurethane film having an elongation at break of 90 to 250% as per ASTM D882.

4. In paragraph 1, Polyurethane film having a breaking strength of 15 to 30 MPa according to ASTM D882.

5. In paragraph 1, A polyurethane film in which, after exposing the above polyurethane film for 3,000 hours according to the ISO04892-2 standard, the color change value for the polyurethane film before exposure is △E, and △E < 3.

0.

6. In paragraph 1, A polyurethane film in which, after exposing the polyurethane film to constant temperature and humidity conditions of 85°C and 85% for 14 days, the color change value for the polyurethane film before exposure is △E, and △E ≤ 3.

0.

7. In paragraph 1, A polyurethane film having no residue on the surface of the polyurethane film when the polyurethane films are laminated so that they face each other and peeled off after 5 seconds. (The above residue is defined as having a size of 0.1 mm or more.) 8. In paragraph 1, A polyurethane film comprising a prepolymer having isocyanate groups (NCO) at both terminals, wherein the first curing agent is 9. In paragraph 2, A polyurethane film wherein the second curing agent comprises at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexyl methane diisocyanate (H12MDI).

10. In paragraph 1, The first solid content of the above polyurethane resin is 30 to 40 wt%, A polyurethane film comprising 5 parts by weight or less of a first curing agent per 100 parts by weight of the polyurethane resin. 11.(a) A step of preparing a composition by mixing a polyurethane resin having a hydroxyl group at the terminal, an organic solvent, and a first curing agent; and (b) a step of manufacturing a polyurethane film by coating the composition on a substrate; A method for producing a polyurethane film having a tensile strength of 15 to 35 N when stretched 15% in the MD (Machine Direction) or TD (Transverse Direction) direction, with a width of 1 inch, according to ASTM D882.

12. In paragraph 11, Polyurethane resin having a hydroxyl group at the terminal A method for producing a polyurethane film, which is a copolymer obtained by copolymerizing 40 to 60 wt% of a polyol, 9 to 20 wt% of a diol containing C4 to C12, and 30 to 42 wt% of a second curing agent.

13. In paragraph 12, A method for producing a polyurethane film wherein the number average molecular weight of the polyol is more than 1000 g / mol and less than or equal to 3000 g / mol.

14. In paragraph 11, A method for producing a polyurethane film, wherein the first curing agent comprises a prepolymer having isocyanate groups (NCO) at both terminals.

15. In paragraph 11, The first solid content of the above polyurethane resin is 30 to 40 wt%, A method for producing a polyurethane film, comprising: preparing a composition by mixing 100 parts by weight or less of an organic solvent and 5 parts by weight or less of a first curing agent with respect to 100 parts by weight of the above polyurethane resin.

16. In paragraph 11, A method for manufacturing a polyurethane film, wherein the weight average molecular weight of the polyurethane resin is 40,000 to 60,000 g / mol.

17. In paragraph 12, A method for producing a polyurethane film, wherein the second curing agent comprises at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4-dicyclohexyl methane diisocyanate (H12MDI).

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