Thermoplastic polyurethane film and method for producing the same

Abstract

To provide a thermoplastic polyurethane film which is thick and is low in stress at initial elongation, allowing easy processing, and a production method therefor.SOLUTION: The present invention relates to a thermoplastic polyurethane film which has a tensile strength of 0.2 MPa to 1.5 MPa at an initial elongation of 5% to 10% and can be easily processed due to low stress at initial elongation, and a production method therefor.SELECTED DRAWING: None

Description

Technical Field

[0001] This specification claims the benefit of the filing date of Korean Patent Application No. 10-2017-0033596, filed with the Korean Intellectual Property Office on March 17, 2017, and all of its contents are incorporated herein by reference.

[0002] The present invention relates to a thermoplastic polyurethane film having low stress during initial stretching and a method for manufacturing the same.

Background Art

[0003] Thermoplastic polyurethane (TPU) films are excellent in mechanical properties such as strength, elongation characteristics, toughness, and abrasion resistance, and are mainly used in the automotive field and the like.

[0004] Generally, polyurethane pellets extruded and formed are dissolved in a solvent to produce a polyurethane solution, and the polyurethane solution is applied onto a substrate to produce a thermoplastic polyurethane film. However, since high molecular weight polyurethane pellets are not well dissolved in the solvent, the solid content of the produced polyurethane solution is as low as about 15% or less. Since it is impossible to apply a polyurethane solution having a low solid content onto a substrate with a thickness of a certain thickness or more, there is a problem that it is difficult to produce a thick thermoplastic polyurethane film. In addition, since it is difficult for an additional polymerization reaction to proceed in the polyurethane pellets, it is not easy to control the physical properties of the thermoplastic polyurethane film produced from the polyurethane solution, and there is a problem that a highly toxic solvent must be used to dissolve the high molecular weight polyurethane pellets.

[0005] On the other hand, in order to apply a thermoplastic polyurethane film to automotive parts, engineering parts, etc., a process of processing the thermoplastic polyurethane film into a curved surface or the like is required. Therefore, there is a situation where a thermoplastic polyurethane film having a greater thickness and easy processability is required.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention provides a thermoplastic polyurethane film that is thick, has low stress during initial stretching, and is easy to process, and a method for producing the same.

[0007] Moreover, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0008] One embodiment of the present invention provides a thermoplastic polyurethane film comprising a cured product of a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent, and having a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial stretching rate of 5% or more and 10% or less.

[0009] Another embodiment of the present invention provides a method for producing a thermoplastic polyurethane film, comprising steps of producing a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent, applying the polyurethane resin composition onto a base film and heat-treating to form a polyurethane resin layer, and further curing the polyurethane resin layer.

Advantages of the Invention

[0010] The thermoplastic polyurethane film according to one embodiment of the present invention has a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial stretching rate of 5% or more and 10% or less, and has the advantage of low stress during initial stretching and excellent processability.

[0011] The method for producing a thermoplastic polyurethane film according to one embodiment of the present invention can produce a thermoplastic polyurethane film with low stress during initial stretching and easy processing.

[0012] Furthermore, the effects of the present invention are not limited to the effects described above, and effects not mentioned can be clearly understood by those skilled in the art from the specification of the present application and the attached drawings.

Embodiments for Carrying Out the Invention

[0013] Throughout the present specification, when a certain part "includes" a certain component, this means that, unless otherwise stated, it does not exclude other components, and may further include other components.

[0014] Throughout the present specification, when a certain member is located "on" another member, this includes not only the case where a certain member is in contact with another member, but also the case where there is another member between the two members.

[0015] Throughout the present specification, the unit "weight %" means the weight ratio of the components contained in the member to the total weight of the member.

[0016] Throughout the present specification, the unit "parts by weight" means the weight ratio between the respective components.

[0017] Throughout the present specification, the term "polymerization unit" means the form in which monomers have reacted within the polymer, specifically, the form in which the monomers have formed the backbone of the polymer, for example, the main chain or side chain, through a polymerization reaction.

[0018] Throughout this specification, the "weight average molecular weight" and "number average molecular weight" of a certain compound can be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, put tetrahydrofuran (THF) and the compound into a 1 ml glass bottle to prepare a sample with a compound concentration of 1% by weight. After filtering the standard sample (polystyrene) and the sample through a filter (pore size 0.45 mm), inject them into a GPC injector, and compare the elution time of the sample with the calibration curve of the standard sample to obtain the molecular weight and molecular weight distribution of the compound. At this time, Infinity II 1260 (Agilent) can be used as the measuring instrument, and the flow rate can be set at 1.00 mL / min and the column temperature at 40.0 °C.

[0019] Hereinafter, this specification will be described in more detail.

[0020] One embodiment of the present invention includes a cured product of a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent, and provides a thermoplastic polyurethane film having a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial elongation rate of 5% or more and 10% or less.

[0021] The thermoplastic polyurethane film according to one embodiment of the present invention has a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial elongation rate of 5% or more and 10% or less, and has the advantage of low stress during initial stretching and excellent processability.

[0022] According to an embodiment of the present invention, the thermoplastic polyurethane film may have a tensile strength of 0.2 MPa or more and 0.5 MPa or less at a elongation rate of 5%, and a tensile strength of 0.4 MPa or more and 1.5 MPa or less at an elongation rate of 10%. Specifically, the tensile strength of the thermoplastic polyurethane film at an elongation rate of 5% may be 0.25 MPa or more and 0.45 MPa or less, 0.3 MPa or more and 0.4 MPa or less, 0.2 MPa or more and 0.3 MPa or less, or 0.35 MPa or more and 0.45 MPa or less. Also, the tensile strength of the thermoplastic polyurethane film at an elongation rate of 10% may be 0.5 MPa or more and 1.25 MPa or less, 0.7 MPa or more and 1.1 MPa or less, 0.4 MPa or more and 0.7 MPa or less, or 0.85 MPa or more and 1.25 MPa or less. Therefore, since the thermoplastic polyurethane film has a low tensile strength during initial stretching, it can be easily processed by a relatively small external force.

[0023] According to an embodiment of the present invention, the thermoplastic polyurethane film is excellent in durability. Specifically, the tensile strength at break of the thermoplastic polyurethane film may be 20 MPa or more and 45 MPa or less. The thermoplastic polyurethane film whose tensile strength at break satisfies the above-mentioned range has the advantage of being excellent in impact absorption against external forces and durability.

[0024] Therefore, the thermoplastic polyurethane film has a low tensile strength during initial stretching and is excellent in processability, and has a high tensile strength at break and is excellent in durability.

[0025] According to one embodiment of the present invention, the content of the first isocyanate-based curing agent may be 2.5 parts by weight or more and 5 parts by weight or less, or 3 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the polyurethane resin. By adjusting the content of the first isocyanate-based curing agent within the above-described range, a thermoplastic polyurethane film having a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial elongation rate of 5% or more and 10% or less can be realized. That is, by adjusting the content of the first isocyanate-based curing agent in the polyurethane resin composition within the above-described range, a thermoplastic polyurethane film having excellent processability can be realized.

[0026] According to one embodiment of the present invention, the first isocyanate-based curing agent may contain 2 or more and 6 or less isocyanate functional groups. For example, the first isocyanate curing agent may contain at least one of H12MDI, a bifunctional isocyanate-based curing agent of Evonik, MHG-80B, a hexafunctional isocyanate-based curing agent of Asahi KASEI, MFA-100, a hexafunctional isocyanate-based curing agent of Asahi KASEI, and TKA-100, a trifunctional isocyanate-based curing agent of Asahi KASEI.

[0027] According to one embodiment of the present invention, the polyurethane resin may be a copolymer of a mixture containing a polyol having a number average molecular weight of 1,800 g / mol or more and 2,200 g / mol or less; a chain extender containing a diol having 4 or more and 10 or less carbon atoms; and a second isocyanate-based curing agent.

[0028] According to one embodiment of the present invention, the polyurethane resin may be a block copolymer containing a soft segment and a hard segment. Specifically, the soft segment of the polyurethane resin may contain polymerization units derived from the polyol and the second isocyanate-based curing agent, and the hard segment of the polyurethane resin may contain polymerization units derived from the chain extender and the second isocyanate-based curing agent.

[0029] According to one embodiment of the present invention, the number average molecular weight of the polyol may be 1,800 g / mol or more and 2,200 g / mol or less, 1,950 g / mol or more and 2,050 g / mol or less, or 1,900 g / mol or more and 2,100 g / mol or less. When the number average molecular weight of the polyol is within the above-described range, a thermoplastic polyurethane film having low tensile strength at the initial stretching and excellent processability can be realized. Further, by adjusting the number average molecular weight of the polyol to the above-described range, it is possible to suppress a decrease in the elongation rate of the thermoplastic polyurethane film.

[0030] According to one embodiment of the present invention, the polyol may include a diol containing two hydroxy groups. Specifically, the polyol may include one or more of polycarbonate diol, polycaprolactone diol, polyester diol, and polyether diol.

[0031] According to one embodiment of the present invention, the content of the polyol may be 60% by weight or more and 75% by weight or less based on the weight of the mixture. Specifically, the content of the polyol may be 62.5% by weight or more and 73% by weight or less, 65% by weight or more and 71% by weight or less, or 68% by weight or more and 74.5% by weight or less based on the weight of the mixture. By adjusting the content of the polyol in the mixture to the above-described range, a thermoplastic polyurethane film having low tensile strength at the initial stretching can be produced. Further, by adjusting the content of the polyol to the above-described range, it is possible to suppress an excessive increase in the content of the hard segment contained in the polyurethane resin and prevent an increase in the tensile strength at the initial stretching of the thermoplastic polyurethane film.

[0032] According to one embodiment of the present invention, the chain extender may include a diol having 4 to 10 carbon atoms or a diol having 4 to 6 carbon atoms. The chain extender containing a diol having the carbon number within the above-mentioned range can effectively extend the chain of the second isocyanate-based curing agent. Specifically, the chain extender may include at least one of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,1-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0033] According to one embodiment of the present invention, the content of the chain extender may be 5% by weight or more and 10% by weight or less based on the weight of the mixture. Specifically, it may be 5% by weight or more and 8% by weight or less, or 6% by weight or more and 7.5% by weight or less. By adjusting the content of the chain extender in the mixture within the above-mentioned range, the weight average molecular weight of the polyurethane resin can be improved, and an increase in the tensile strength during the initial stretching of the thermoplastic polyurethane film can be suppressed.

[0034] According to one embodiment of the present invention, the second isocyanate-based curing agent may contain 2 to 6 isocyanate functional groups. Specifically, the second isocyanate-based curing agent may contain 2 isocyanate functional groups. For example, the second isocyanate-based curing agent may include at least one of isophorone diisocyanate (IPDI), methylene diphenyl-4,4'-diisocyanate, 4,4'-methylenebis(cyclohexyl diisocyanate), xylene diisocyanate (XDI), naphthalene-1,5-diisocyanate, and cyclohexane diisocyanate.

[0035] According to one embodiment of the present invention, the content of the second isocyanate-based curing agent may be 20% by weight or more and 30% by weight or less based on the weight of the mixture. Specifically, the content of the second isocyanate-based curing agent may be 20.5% by weight or more and 27.5% by weight or less, 20% by weight or more and 25% by weight or less, or 22.5% by weight or more and 25% by weight or less based on the weight of the mixture. By adjusting the content of the second isocyanate-based curing agent within the above-described range, the polymerization reaction of the polyurethane resin can be stably carried out, and a thermoplastic polyurethane film having low stress during initial stretching can be produced.

[0036] According to one embodiment of the present invention, the mixture may further contain a catalyst. As the catalyst, a catalyst used in the art can be used without particular limitation. For example, dibutyl tin dilaurate (DBTDL) can be used. Further, the content of the catalyst may be 0.005 parts by weight or more and 0.02 parts by weight or less, or 0.008 parts by weight or more and 0.015 parts by weight or less based on 100 parts by weight of the mixture.

[0037] According to one embodiment of the present invention, the weight average molecular weight of the polyurethane resin may be 40,000 g / mol or more and 70,000 g / mol or less. By adjusting the weight average molecular weight of the polyurethane resin, physical properties such as the tensile strength and durability of the thermoplastic polyurethane film can be easily controlled.

[0038] According to one embodiment of the present invention, the organic solvent may contain at least one of acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, toluene, xylene, ethylene glycol monomethyl ether (methyl cellosolve), and ethylene glycol monoethyl ether (ethyl cellosolve).

[0039] According to one embodiment of the present invention, the content of the organic solvent may be 30 parts by weight or more and 80 parts by weight or less with respect to 100 parts by weight of the polyurethane resin. By adjusting the content of the organic solvent within the above-described range, the solid content of the polyurethane resin composition can be controlled, and the coating property of the polyurethane resin composition can be improved.

[0040] According to one embodiment of the present invention, the solid content of the polyurethane resin composition may be 20% or more and 70% or less, specifically, 30% or more and 60% or less, or 40% or more and 55% or less. In this specification, the "solid content" means a solute or solid matter obtained by removing a solvent from the entire solution. Specifically, the solid content of the polyurethane resin composition may be a general term for the polyurethane resin, the first isocyanate-based curing agent, and additives such as a catalyst excluding the organic solvent. When the solid content of the polyurethane resin composition is within the above-described range, the polyurethane resin composition can be thickly applied onto a substrate, whereby a thick thermoplastic polyurethane film can be produced.

[0041] According to one embodiment of the present invention, the thickness of the thermoplastic polyurethane film may be 10 μm or more and 250 μm or less. Specifically, the thickness of the thermoplastic polyurethane film may be 20 μm or more and 200 μm or less, or 30 μm or more and 180 μm or less. That is, the thermoplastic polyurethane film is thicker than existing polyurethane films.

[0042] Another embodiment of the present invention provides a method for producing a thermoplastic polyurethane film, including steps of producing a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent, applying the polyurethane resin composition onto a substrate film and performing heat treatment to form a polyurethane resin layer, and additionally curing the polyurethane resin layer.

[0043] According to one embodiment of the present invention, a method for manufacturing a thermoplastic polyurethane film can produce a thermoplastic polyurethane film with low stress during initial stretching and easy processing. Specifically, the thermoplastic polyurethane film produced by the method for manufacturing the thermoplastic polyurethane film may have a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial stretching ratio of 5% or more and 10% or less. The thermoplastic polyurethane film whose tensile strength during initial stretching satisfies the above-mentioned range has the advantage of excellent processability.

[0044] According to one embodiment of the present invention, the content of the first isocyanate-based curing agent may be 2.5 parts by weight or more and 5 parts by weight or less, or 3 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the polyurethane resin. By adjusting the content of the first isocyanate-based curing agent within the above-mentioned range, the tensile strength during initial stretching of the thermoplastic polyurethane film can be effectively reduced.

[0045] According to one embodiment of the present invention, the solid content of the polyurethane resin composition may be 20% or more and 70% or less, specifically, 30% or more and 60% or less, or 40% or more and 55% or less. When the solid content of the polyurethane resin composition is within the above-mentioned range, the polyurethane resin composition can be thickly coated on a substrate, thereby producing a thick thermoplastic polyurethane film.

[0046] According to one embodiment of the present invention, the polyurethane resin used in the method for manufacturing the thermoplastic polyurethane film can be produced by copolymerizing a mixture containing a polyol having a number average molecular weight of 1,800 g / mol or more and 2,200 g / mol or less; a chain extender containing a diol having 4 or more and 10 or less carbon atoms; and a second isocyanate-based curing agent in an organic solvent.

[0047] In addition, the polyol, chain extender, first isocyanate-based curing agent, second isocyanate-based curing agent, organic solvent, catalyst, etc. used in the method for producing the thermoplastic polyurethane film may be the same as those of the polyol, chain extender, first isocyanate-based curing agent, second isocyanate-based curing agent, organic solvent, catalyst, etc. in the thermoplastic polyurethane film.

[0048] According to one embodiment of the present invention, since the number of carbon atoms constituting the diol used as the chain extender is smaller than the number of carbon atoms constituting the polyol, the diol has higher fluidity than the polyol in the mixture. Thereby, in the mixture, the reaction between the chain extender and the second isocyanate-based curing agent occurs prior to the reaction between the polyol and the second isocyanate-based curing agent. Specifically, when butanediol is used as the chain extender, as one of the two hydroxy groups of butanediol reacts with the isocyanate group of the second isocyanate-based curing agent and binds, and the unreacted hydroxy group of the butanediol binds to a new isocyanate group of the second isocyanate-based curing agent, a second isocyanate-based curing agent having a long extended chain structure can be formed as the process is repeated. Thereafter, the second isocyanate-based curing agent having a long extended chain structure reacts with the polyol to form a polyurethane resin with an increased weight average molecular weight.

[0049] According to one embodiment of the present invention, the copolymerization reaction for producing the polyurethane resin can be carried out at a temperature of 50°C or higher and 70°C or lower. By adjusting the copolymerization reaction temperature to the aforementioned range, the polyurethane resin can be polymerized stably, and since the polyurethane resin can be polymerized at a relatively low temperature, the manufacturing cost and manufacturing time of the thermoplastic polyurethane film can be reduced.

[0050] According to an embodiment of the present invention, the content of the polyol may be 60% by weight or more and 75% by weight or less, 62.5% by weight or more and 73% by weight or less, 65% by weight or more and 71% by weight or less, or 68% by weight or more and 74.5% by weight or less based on the weight of the mixture. By adjusting the content of the polyol in the mixture within the above-mentioned range, the polymerization reaction of the polyurethane resin can be stably carried out, and a thermoplastic polyurethane film with low tensile strength during initial stretching can be produced.

[0051] According to an embodiment of the present invention, the content of the chain extender may be 5% by weight or more and 10% by weight or less, 5% by weight or more and 8% by weight or less, or 6% by weight or more and 7.5% by weight or less based on the weight of the mixture. By adjusting the content of the chain extender in the mixture within the above-mentioned range, the weight average molecular weight of the polyurethane resin can be improved, and an increase in the tensile strength during initial stretching of the thermoplastic polyurethane film can be suppressed.

[0052] According to an embodiment of the present invention, the content of the second isocyanate-based curing agent may be 20% by weight or more and 30% by weight or less, 20.5% by weight or more and 27.5% by weight or less, 20% by weight or more and 25% by weight or less, or 22.5% by weight or more and 25% by weight or less based on the weight of the mixture. By adjusting the content of the second isocyanate-based curing agent in the mixture within the above-mentioned range, the polymerization reaction of the polyurethane resin can be stably carried out, and a thermoplastic polyurethane film with low stress during initial stretching can be produced.

[0053] According to one embodiment of the present invention, the mixture may further contain a catalyst. Through the catalyst, the polymerization reaction of the polyurethane resin and the reaction between the polyurethane resin and the first isocyanate-based curing agent can be promoted. The content of the catalyst may be 0.005 parts by weight or more and 0.02 parts by weight or less, or 0.008 parts by weight or more and 0.015 parts by weight or less, based on 100 parts by weight of the mixture. By adjusting the content of the catalyst within the above-mentioned range, the polymerization reaction of the polyurethane resin can be effectively promoted, and the polyurethane resin can be polymerized at a relatively low temperature.

[0054] According to one embodiment of the present invention, the polymerization reaction of the polyurethane resin can be carried out in an organic solvent. When a water-soluble solvent is used to produce a thermoplastic polyurethane film, urethane particles must be processed into beads having a diameter of several tens of nm to several hundreds of nm and dispersed on the water-soluble solvent. At this time, in order to effectively disperse the urethane particles on the water-soluble solvent, additives such as various surfactants and monomers must be used, which complicates the manufacturing process of the thermoplastic polyurethane film and increases the manufacturing time and cost.

[0055] In contrast, according to one embodiment of the present invention, the polyurethane resin is in a state of being dissolved in the organic solvent, and it is not necessary to add additives of a dispersion stability system such as additional dispersants and surfactants to the polyurethane resin composition. Therefore, the manufacturing time and cost of the thermoplastic polyurethane film can be reduced.

[0056] According to one embodiment of the present invention, the content of the organic solvent may be 30 parts by weight or more and 80 parts by weight or less, based on 100 parts by weight of the polyurethane resin. By adjusting the content of the organic solvent within the above-mentioned range, it is possible to suppress the phenomenon that the polyurethane resin composition is rapidly dried and the organic solvent swells during the heat treatment step of the polyurethane resin composition, and prevent the thickness of the thermoplastic polyurethane film from becoming thin.

[0057] According to an embodiment of the present invention, the mixture can be reacted in an organic solvent to produce a composition containing a polyurethane resin and an organic solvent, and a first isocyanate-based curing agent can be added to the composition to produce the polyurethane resin composition. That is, the organic solvent in the polyurethane resin composition may be the organic solvent that remains after being used in the production of the polyurethane resin.

[0058] According to an embodiment of the present invention, the weight average molecular weight of the polyurethane resin may be 40,000 g / mol or more and 70,000 g / mol or less. By adjusting the number average molecular weight of the polyol, the number of carbon atoms of the diol used as the chain extender, the content of the polyol in the mixture, the content of the chain extender, the content of the second isocyanate-based curing agent, etc., the weight average molecular weight of the polyurethane resin can be controlled. By adjusting the weight average molecular weight of the polyurethane resin, physical properties such as the tensile strength and durability of the thermoplastic polyurethane film can be easily controlled.

[0059] According to an embodiment of the present invention, the method of applying the polyurethane resin composition onto the base film is not particularly limited, and for example, any one of bar coating, blade coating, slot die coating, spray coating, spin coating, and gravure coating can be used.

[0060] According to one embodiment of the present invention, the polyurethane resin composition can be applied onto the base film to a thickness of 20 μm or more and 500 μm or less. The polyurethane resin composition applied onto the base film can be heat-treated to form a polyurethane resin layer having a thickness of 10 μm or more and 250 μm or less. In the process of heat-treating the polyurethane resin composition, the organic solvent contained in the polyurethane resin composition volatilizes, whereby the thickness of the produced polyurethane resin layer decreases. Therefore, considering the thickness of the polyurethane resin layer that decreases due to the volatilization of the organic solvent, the thickness of the polyurethane resin composition applied onto the base film can be adjusted.

[0061] According to one embodiment of the present invention, the polyurethane resin composition applied onto the base film can be heat-treated at a temperature of 100°C or more and 150°C or less to form a thermoplastic polyurethane resin layer. By heat-treating the polyurethane resin composition within the above-described temperature range, the organic solvent contained in the polyurethane resin composition can be effectively volatilized to form a semi-cured polyurethane resin layer. Further, by heat-treating the polyurethane resin composition within the above-described temperature range, the occurrence of yellowing in the polyurethane resin layer can be suppressed.

[0062] According to one embodiment of the present invention, the polyurethane resin layer can be additionally cured at a temperature of 25°C or more and 40°C or less for a time of 48 hours or more and 72 hours or less. The polyurethane resin layer formed by heat-treating the polyurethane resin composition is in a semi-cured state, and it can be additionally cured to produce a finally cured thermoplastic polyurethane film.

[0063] In the process of further curing the polyurethane resin layer, the polyurethane resin contained in the polyurethane resin layer reacts with the first isocyanate curing agent, or the remaining trace amounts of polyol, chain extender, first isocyanate curing agent, and second isocyanate curing agent react to provide a thermoplastic polyurethane film containing a polyurethane resin with an increased weight average molecular weight.

[0064] According to one embodiment of the present invention, by further curing the polyurethane resin layer under the above-described temperature and time conditions, the polyurethane resin and the first isocyanate curing agent can be effectively reacted.

[0065] According to one embodiment of the present invention, the thickness of the thermoplastic polyurethane film may be 10 μm or more and 250 μm or less. Specifically, the thickness of the thermoplastic polyurethane film may be 20 μm or more and 200 μm or less, or 30 μm or more and 180 μm or less.

[0066] According to one embodiment of the present invention, it may further include the step of removing the base film after further curing the polyurethane resin layer. That is, through the manufacturing method of the thermoplastic polyurethane film, a laminate in which the thermoplastic polyurethane film is laminated on the base film can be manufactured, and by removing the base film, a thermoplastic polyurethane film with low stress during initial stretching can be provided.

Examples

[0067] Hereinafter, in order to specifically explain the present invention, examples will be given and described in detail. However, the examples according to the present invention can be deformed into various other forms, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those with average knowledge in the industry.

[0068] Example 1 Manufacture of Polyurethane Resin Composition As the polyol, polycarbonatediol (PCDL, manufactured by Asahi Kasei) with a number average molecular weight of 2,050 g / mol was prepared. As the chain extender, 1,4-butanediol (1,4BD, manufactured by BASF) was used. As the first isocyanate-based curing agent, H12MDI (manufactured by Evonik) containing two isocyanate functional groups was used. As the second isocyanate-based curing agent, isophorone diisocyanate (IPDI, manufactured by Evonik) was used. Dibutyl tin dilaurate (DBTDL) was used as the catalyst, and methyl ethyl ketone was used as the organic solvent. Then, a mixture with a polyol content of about 70.03 wt%, a chain extender content of about 6.64 wt%, and a second isocyanate-based curing agent content of about 23.33 wt% was manufactured. 100 parts by weight of the mixture and 50 parts by weight of the organic solvent were mixed to produce a mixed solution.

[0069] The manufactured mixed solution was charged into a reactor, and the temperature was raised to 55 °C and maintained. While maintaining the temperature, 0.005 parts by weight of the catalyst was added to 100 parts by weight of the mixture. Then, the reaction was carried out at 57 °C for 25 hours to produce a composition containing a polyurethane resin with a weight average molecular weight of about 51,000 g / mol. Then, about 3 parts by weight of the first isocyanate-based curing agent was added to 100 parts by weight of the manufactured polyurethane resin to produce a polyurethane resin composition. The solid content of the manufactured polyurethane resin composition was about 45%.

[0070] Manufacture of Thermoplastic Polyurethane Film The manufactured polyurethane resin composition was coated on a polyethylene terephthalate (PET) film, which is a base film, at about 200 μm. Then, the polyurethane resin composition was heat-treated at 100 °C to form a polyurethane resin layer, and the polyurethane resin layer was additionally cured at 50 °C for 48 hours to finally produce a thermoplastic polyurethane film with a thickness of 95 μm.

[0071] Examples 2 to 5 To produce the polyurethane resin composition, a thermoplastic polyurethane film was produced in the same manner as in Example 1, except that a polyol, a chain extender, a first isocyanate-based curing agent, a second isocyanate-based curing agent, and a catalyst were used as shown in Table 1 below. In Table 1 below, TKA-100 is a trifunctional isocyanate-based curing agent manufactured by Asahi KASEI Corporation.

[0072] Comparative Example 1 To produce the polyurethane resin composition, a thermoplastic polyurethane film was produced in the same manner as in Example 1, except that a polyol, a chain extender, a first isocyanate-based curing agent, a second isocyanate-based curing agent, and a catalyst were used as shown in Table 1 below. In Table 1 below, MHG-80B is a hexafunctional isocyanate-based curing agent manufactured by Asahi KASEI Corporation.

[0073]

Table 1

[0074] Measurement of Tensile Strength of Thermoplastic Polyurethane Film To measure the tensile strength of the thermoplastic polyurethane film, thermoplastic polyurethane films produced in Examples 1 to 5 and Comparative Example 1 were processed according to ASTM D-638 standards to produce test pieces. Then, using an Ultimate Tensile Machine (UTM) (Model 3343, INSTRON), one end of the test piece was fixed, and the other end was pulled at a speed of 300 mm / min, and the tensile strength corresponding to the degree of stretching of the thermoplastic polyurethane film was measured.

[0075] The tensile strength corresponding to the elongation rate of the thermoplastic polyurethane films produced in Examples 1 to 5 and Comparative Example 1 is shown in Table 2 below.

[0076]

Table 2

[0077] Referring to Table 2, it was confirmed that the thermoplastic polyurethane films produced in Examples 1 to 5 of the present invention satisfied a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial elongation rate of 5% or more and 10% or less. Specifically, it was confirmed that the thermoplastic polyurethane films produced in Examples 1 to 5 of the present invention satisfied a tensile strength of 0.2 MPa or more and 0.5 MPa or less at a 5% elongation rate and a tensile strength of 0.4 MPa or more and 1.5 MPa or less at a 10% elongation rate. On the other hand, it was confirmed that the thermoplastic polyurethane film produced in Comparative Example 1 exceeded 1.5 MPa at a 10% elongation rate. Further, it was confirmed that the thermoplastic polyurethane film produced in Comparative Example 1 exceeded 0.5 MPa in tensile strength at a 5% elongation rate.

[0078] Therefore, it can be seen that the thermoplastic polyurethane film according to one embodiment of the present invention has a low tensile strength during initial stretching and excellent processability.

Claims

1. A method for manufacturing a thermoplastic polyurethane film, comprising: producing a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent; coating the polyurethane resin composition on a base film and performing heat treatment to form a polyurethane resin layer; and performing additional curing on the polyurethane resin layer. The additional curing is carried out at a temperature of 25°C or higher and 40°C or lower for a time of 48 hours or longer and 72 hours or shorter. The polyurethane resin is produced by copolymerizing a mixture containing a polyol having a number average molecular weight of 1,800 g / mol or more and 2,200 g / mol or less, a chain extender containing a diol having 4 to 10 carbon atoms, and a second isocyanate-based curing agent in an organic solvent. The thermoplastic polyurethane film contains a cured product of a polyurethane resin composition containing a polyurethane resin, a first isocyanate-based curing agent, and an organic solvent. The polyurethane resin is a copolymer of a mixture containing a polyol having a number average molecular weight of 1,800 g / mol or more and 2,200 g / mol or less, a chain extender containing a diol having 4 to 10 carbon atoms, and a second isocyanate-based curing agent. The content of the polyol is 70.03% by weight or more and 74.08% by weight or less based on the weight of the mixture. The content of the chain extender is 5.34% by weight or more and 6.64% by weight or less based on the weight of the mixture. The content of the second isocyanate-based curing agent is 20.58% by weight or more and 23.33% by weight or less based on the weight of the mixture. The weight average molecular weight of the polyurethane resin is 40,000 g / mol or more and 70,000 g / mol or less. The thermoplastic polyurethane film has a tensile strength of 0.2 MPa or more and 1.5 MPa or less at an initial elongation rate of 5% or more and 10% or less, a thickness of 10 μm or more and 250 μm or less. The tensile strength is measured by fixing one end of a specimen produced according to ASTM D-638 standard, pulling the other end at a speed of 300 mm / min, and measuring the tensile strength corresponding to the degree of stretching of the thermoplastic polyurethane film. A method for manufacturing a thermoplastic polyurethane film.

2. The heat treatment is carried out at a temperature of 100°C or higher and 150°C or lower. The method for manufacturing a thermoplastic polyurethane film according to Claim 1.

3. ​ ​ ​ ​ The method for producing a thermoplastic polyurethane film according to claim 1, wherein the copolymerization reaction is carried out at a temperature of 50°C or higher and 70°C or lower.

4. The method for producing a thermoplastic polyurethane film according to claim 1, wherein the content of the first isocyanate-based curing agent is 2.5 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the polyurethane resin.

5. The method for producing a thermoplastic polyurethane film according to claim 1, wherein the first isocyanate-based curing agent contains 2 or more and 6 or less isocyanate functional groups.

6. The method for producing a thermoplastic polyurethane film according to claim 1, wherein the solid content of the polyurethane resin composition is 20% or more and 70% or less.

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