Film

Abstract

A film according to an embodiment includes a first polymer resin and a second polymer resin as dissimilar resins, the first polymer resin including a polyamide-based repeating unit and a polyether-based repeating unit, and the second polymer resin including, in a branched chain, any one selected from the group consisting of a hydroxyl group, an acetal group, and a combination thereof, the tensile recovery rate at N% elongation is derived according to formula 1, and when N% is 60%, the tensile recovery rate of the film is 90% or more. [Formula 1] Stretch recovery rate (%) = (LfN-LiN) / (LfN-Li). In formula 1, LfN is the length of the film stretched at an N% elongation, LiN is the length when the stretched film is recovered, and Li is the length of the film before stretching. The film according to an embodiment can maintain excellent optical properties and excellent mechanical properties for a relatively long period of time.

Description

Technical Field

[0001] The implementation method relates to a thin film with excellent mechanical properties.

[0002] [Cross-references to related applications] This document claims priority to Korean Patent Application No. 10-2023-0129043, filed on September 26, 2023, and Korean Patent Application No. 10-2023-0129042, filed on September 26, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0003] To protect painted surfaces such as those on automobiles, film laminates containing materials like polyurethane (TPU) and polyvinyl chloride (PVC) have traditionally been applied. However, when these polyurethane and PVC film laminates are applied to painted surfaces, their elastic properties change significantly due to external environmental factors, particularly temperature variations, hindering the application process. While internal air conditioning and localized heating devices can be used to manage the temperature of the work area during winter, these methods still offer shortcomings in terms of ease of use, completion rate, and quality.

[0004] The background technology described above is technical information held by the inventor for the purpose of deriving embodiments or acquired during the deriving process, and is not necessarily publicly known technology disclosed to the general public before this invention application.

[0005] As relevant prior art, there is Korean Patent Publication No. 10-2012-0022141, "Release Film for Automotive Coating Protective Film", etc. Summary of the Invention

[0006] Technical issues The purpose of this implementation is to provide a thin film with excellent mechanical properties such as tensile recovery rate and strain rate.

[0007] Solution to the problem To achieve the above objectives, the film according to one or more embodiments is a film comprising a first polymer resin and a second polymer resin as dissimilar resins, wherein the first polymer resin comprises polyamide repeating units and polyether repeating units, and the second polymer resin comprises any one selected from the group consisting of hydroxyl groups, acetal groups, and combinations thereof in its side chains.

[0008] The tensile recovery rate at N% elongation is derived according to Equation 1 below. When N% is 60%, the tensile recovery rate of the film can be 90% or more.

[0009] [Formula 1] Tensile recovery rate (%) = (LfN - LiN) / (LfN - Li) In Formula 1 above, LfN is the length of the film stretched with an elongation of N%, LiN is the length of the film when it is restored after stretching, and Li is the length of the film before stretching.

[0010] The stress of the aforementioned thin film at a strain rate of 100% can be 1 N / mm. 2 the following.

[0011] After being placed at 60°C for 7 days, the haze value of the above-mentioned film can be below 3%.

[0012] When N% is 100%, the tensile recovery rate of the film can be above 75%.

[0013] Based on the sum of the first polymer resin and the second polymer resin, the film may contain more than 10% by weight of the polyether repeating units.

[0014] The attenuation coefficient of tensile recovery rate (20-40) between the above-mentioned 20% elongation and the above-mentioned 40% elongation is derived according to the following formula 2, and the attenuation coefficient of tensile recovery rate (20-40) of the above-mentioned film can be 0.3 or less.

[0015] [Equation 2] Tensile recovery rate attenuation coefficient (20-40) =

[0016] In Equation 2, A 20 A represents the tensile recovery rate (%) of the above film at 20% elongation. 40 The tensile recovery rate (%) of the above film at 40% elongation.

[0017] To achieve the above objectives, the film according to one or more embodiments comprises a polyether block amide copolymer resin and a polyvinyl acetal resin, wherein the stress can be 7 N / mm when the strain rate is 20%. 2 the following.

[0018] The value of the stress at a strain rate of 100% minus the stress at a strain rate of 20% for the aforementioned thin film can be 5 N / mm. 2 the following.

[0019] The ratio of the stress at a strain rate of 100% to the stress at a strain rate of 300% can be 1.4 or higher.

[0020] The above-mentioned film can be a coating protection film.

[0021] The effects of the invention The thin film of the embodiments can maintain excellent optical properties and excellent mechanical properties for a relatively long time. However, the effects of the embodiments are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description. Detailed Implementation

[0022] The following detailed description is provided to enable those skilled in the art to readily implement the embodiments. However, the embodiments can be implemented in many different forms and are not limited to the examples described herein.

[0023] In the specification, when it is mentioned that a certain composition "includes" another composition, unless otherwise stated, this does not mean that other compositions are excluded, but rather that other compositions may be further included.

[0024] In this specification, when it is mentioned that one component is "connected" to another component, this includes not only the case of "direct connection" but also the case of "connection with other components in between".

[0025] In this specification, "B is located on A" means that B is located on A in direct contact with A or in the presence of other components therebetween, and should not be limited to the interpretation that B is in contact with the surface of A.

[0026] In this specification, the term "combination thereof" in the Markush form of expression refers to at least one mixture or combination of the group of constituent elements described in the Markush form of expression, meaning that it includes at least one of the group of constituent elements described above.

[0027] In this specification, the reference to "A and / or B" means "A, B, or A and B".

[0028] In this specification, the terms “first,” “second,” or “A,” “B,” etc., are used to distinguish the same terms from one another unless otherwise specified.

[0029] In this specification, the singular expression is interpreted, unless otherwise specified, to include the meaning of singular or plural as interpreted from the context.

[0030] In this instruction manual, room temperature is based on approximately 20°C, and ambient temperature is based on approximately 25°C.

[0031] In this specification, the text and / or numbers listed together with the name of the compound refer to the abbreviation of the compound name.

[0032] The term "resin" as used in this specification is interpreted to include both the resin itself and compounds derived from it. For example, the polyether block amide copolymer resin described in this specification refers to polyether block amide copolymer resin and its derivatives.

[0033] In this specification, the amount of hydroxyl groups is evaluated by measuring the amount of vinyl groups bound to the hydroxyl groups of the polyvinyl acetal resin according to the method of JIS K6728.

[0034] To achieve the above objectives, the film according to the embodiments comprises a first polymer resin and a second polymer resin as dissimilar resins.

[0035] The aforementioned first polymer resin comprises polyamide repeating units and polyether repeating units.

[0036] The aforementioned second polymer resin contains any one of the groups selected from hydroxyl, acetal, and combinations thereof in its branched chain.

[0037] The first polymer resin containing polyamide repeating units and polyether repeating units can impart excellent characteristics such as film durability and dimensional stability.

[0038] When surface protective films are applied to objects, stretching operations are often involved. The surface of the object being protected may have curved or bent surfaces, and the film attached to these parts will inevitably undergo localized film stretching.

[0039] When the first polymer resin described later is applied in the form of a film, it is sometimes observed that the film loses its elasticity and cannot return to its original length when the elongation is high.

[0040] If the tensile recovery rate of the film decreases, it may damage the appearance of the object on which the film is applied, and spaces such as air bubbles may form between the object and the film, making it difficult to adequately protect the object from external influences.

[0041] In order to suppress the decrease in tensile recovery rate, the inventors tried various methods and confirmed that, as described in the embodiments, methods such as mixing dissimilar resins and thinning them into films can substantially suppress the decrease in tensile recovery rate.

[0042] The implementation method will be described in more detail below.

[0043] Composition of the film To achieve the above objectives, the film according to the embodiments includes a first polymer resin and a second polymer resin.

[0044] The first polymer resin comprises amide repeating units and polyether repeating units.

[0045] In the first polymer resin, the aforementioned amide repeating units can help improve the hardness of the film. In the first polymer resin, the aforementioned ester repeating units can help impart flexibility and elasticity to the film.

[0046] The first polymer resin may contain 80% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 70% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 60% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 50% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 40% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 30% by weight or less of the aforementioned amide repeating units. The first polymer resin may contain 0% or more of the aforementioned amide repeating units, and may contain 10% or more of the aforementioned amide repeating units.

[0047] The aforementioned amide repeating units may contain amide residues.

[0048] The first polymer resin may contain amide residues of 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less by weight. Alternatively, the first polymer resin may contain 0% or more, or 10% or more, of amide residues.

[0049] The aforementioned amide residues may, by way of example, be aliphatic amide residues, semi-aromatic amide residues, semi-crystalline polyamide residues, amorphous polyamide residues, or mixtures thereof.

[0050] The aforementioned first polymer resin may contain 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of aliphatic amide residues, semi-aromatic amide residues, semi-crystalline polyamide residues, and amorphous polyamide residues. Alternatively, the aforementioned first polymer resin may contain 0% or more, or 10% or more, of aliphatic amide residues, semi-aromatic amide residues, semi-crystalline polyamide residues, and amorphous polyamide residues.

[0051] Aliphatic amide residues can be, for example, polycaprolactam (PA 6) residues, polyundecanamide (PA 11) residues, polylauryllactam (PA 12) residues, polybutylene adipamide (PA 46) residues, polyhexamethylene adipamide (PA 66) residues, polyhexamethylene azelamide (PA 69) residues, polyhexamethylene sebacamide (PA 610) residues, polyhexamethylene dodecanediamide (PA 612) residues, polydecamethylene dodecanediamide (PA 1012) residues, and polydecamethylene sebacamide (PA 1012) residues. The residues of PA 1010, polydodecamethylene dodecanediamide (PA 1212), PA 11 / NHUA residues as polyamide copolymers, PA BACM6 residues, PA BACM10 residues, PA BACM12 residues, PA 6 / 66 residues or PA 6 / 12 residues.

[0052] The semi-aromatic amide residue can be a PA 6 / 6T residue, a PA 66 / 6T residue, a PA 6T / 6I residue, a PA 66 / 6T / 6I residue, a PA 11 / 6T residue, a PA 12 / 6T residue, a PA MXD6 residue, or a PA MXD10 residue.

[0053] The semi-crystalline polyamide residues can be PA 6 residues, PA 11 residues, PA 12 residues, PA 10.10 residues, PA 10.12 residues, PA 6.10 residues, or PA 6.12 residues.

[0054] The amorphous polyamide residues can be polyhexamethylene isophthalamide (PA 6I) residues, polytrimethylhexamethylene terephthalamide (PA TMHMDAT) residues, or PA BACM12 residues as polyamides; or PA 6 / BMACPI residues, PA 6 / BAMNT residues, PA 11 / BMACMI residues, PA 11 / BMACMT / BMACMI residues, PA 11 / BACM.I / IPDA.I residues, PA 12 / BMACM.I residues, PA 12 / BACMT / BACMI residues, PA12 / BMACMT / BACMI residues, PA 12 / BACMI / IPDAI residues, PA 6T / 6I / BACMI residues, or PA 6T / 6I / BACMT / BACMI residues as amide copolymers.

[0055] Based on the sum of the first polymer resin and the second polymer resin, the first polymer resin may contain 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, or 35% or more of the aforementioned polyether repeating units. Based on the sum of the first polymer resin and the second polymer resin, the first polymer resin may contain 50% or less or 45% or less of the aforementioned polyether repeating units.

[0056] The aforementioned polyether repeating units may contain tetramethylene oxide residues, ethylene oxide residues, and / or propylene oxide residues.

[0057] The aforementioned first polymer resin may contain 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, or 70% or more of the sum of the aforementioned tetramethylene oxide residues, ethylene oxide residues, and propylene oxide residues. Alternatively, the aforementioned first polymer resin may contain less than 100% or less, or less than 90% by weight, of the sum of the aforementioned tetramethylene oxide residues, ethylene oxide residues, and propylene oxide residues.

[0058] For example, the polyether repeating unit described above may include -CH2-CH2-CH2-CH2-O-, -CH2-CH2-O- and / or -CH2(-CH2)-CH2-O-.

[0059] The aforementioned first polymer resin may contain 20% or more, 30% or more, 40% or more, 50% or more, or 70% or more of the sum of -CH2-CH2-CH2-CH2-O-, -CH2-CH2-O-, and -CH2(-CH2)-CH2-O-. The aforementioned first polymer resin may contain less than 100% or less, or less than 90% of the sum of -CH2-CH2-CH2-CH2-O-, -CH2-CH2-O-, and -CH2(-CH2)-CH2-O-.

[0060] The first polymer resin mentioned above can be a polyether block amide resin. When the first polymer resin is a polyether block amide resin, the content of tetramethylene oxide residues, ethylene oxide residues, and / or propylene oxide residues contained in the resin can be less than 40% by weight, less than 30% by weight, or less than 20% by weight based on the total amount of the resin. In this case, the polyester film including the first polymer resin can be endowed with flexible and elastic properties.

[0061] The first polymer resin described above can, by way of example, be a polyether ester copolymer layer. The first polymer resin can be a polyether ester copolymer resin.

[0062] As the first polymer resin mentioned above, PEBAX from Arkema France can be used. ® 25R53, PEBAX ® 35R53, PEBAX ® 40R53, PEBAX ® 55R53, PEBAX ® 72R53, PEBAX ® Clear1200, Rilsan ® BESNO or equivalent products, etc.

[0063] The second polymer resin contains any one of the groups selected from hydroxyl groups, acetyl groups, and combinations thereof in its branched chain.

[0064] Specifically, the second polymer resin can be a polyvinyl alcohol resin or a polyvinyl alcohol acetal resin. Polyvinyl alcohol acetal resin can be obtained by synthesizing polyvinyl alcohol and aldehydes.

[0065] The degree of polymerization of the aforementioned second polymer resin can be below 3,500.

[0066] Among the aforementioned second polymer resins, those with a low degree of polymerization can be used to form coating films, while those with a degree of polymerization of a certain level or higher can be used for film making through extrusion or other methods.

[0067] In this embodiment, the first polymer resin and the second polymer resin are mixed and applied, and both grades can be used.

[0068] For example, the second polymer resin may be a polyvinyl alcohol resin with a degree of polymerization of 200 to 3,500. Alternatively, the second polymer resin may be a polyvinyl alcohol acetal resin obtained by acetalizing a polyvinyl alcohol resin with a degree of polymerization of 200 to 3,500 with an aldehyde.

[0069] For example, the second polymer resin may be a polyvinyl alcohol resin with a degree of polymerization of 1,600 to 3,000. Alternatively, the second polymer resin may be a polyvinyl alcohol acetal resin obtained by acetalizing a polyvinyl alcohol resin with a degree of polymerization of 1,600 to 3,000 with an aldehyde.

[0070] For example, the second polymer resin may be a polyvinyl alcohol resin with a degree of polymerization of 1,700 to 2,500. Alternatively, the second polymer resin may be a polyvinyl alcohol acetal resin obtained by acetalizing a polyvinyl alcohol resin with a degree of polymerization of 1,700 to 2,500 with an aldehyde.

[0071] When this resin is applied to a second polymer resin, the mechanical properties of the film can be significantly improved.

[0072] The aldehyde mentioned above can be any one selected from the group consisting of n-butyraldehyde, isobutyraldehyde, n-pentanaldehyde, 2-ethylbutyraldehyde, n-hexanaldehyde, and their blends. When n-butyraldehyde is used as the aldehyde mentioned above, the prepared polyvinyl butyral resin can have excellent optical properties.

[0073] The aforementioned second polymer resin contains hydroxyl groups.

[0074] The hydroxyl content of the aforementioned second polymer resin can be 2% or more by weight, 5% or more by weight, 8% or more by weight, 10% or more by weight, 15% or more by weight, 16% or more by weight, or 19% or more by weight. Furthermore, the hydroxyl content of the aforementioned second polymer resin can be 60% by weight, 50% by weight, 40% by weight, or less than 30% by weight.

[0075] The acetyl content of the aforementioned second polymer resin can be 0.01% by weight or more, 1.5% by weight or more, 3% by weight or more, 5% by weight or more, or 10% by weight or more. Alternatively, the acetyl content of the aforementioned second polymer resin can be 20% by weight or less, 15% by weight or less, or 12% by weight or less.

[0076] Using a second polymer resin with these properties can improve miscibility with the plasticizer described later and effectively suppress the reduction in optical properties of the film caused by haze changes. This is believed to be because the hydroxyl groups arranged on the branches inhibit the migration of unreacted polyether monomers (or oligomers), thereby helping to suppress the induction of haze changes.

[0077] Furthermore, if a second polymer resin with this property is used, the first polymer resin can be given flexibility and elasticity, thereby effectively suppressing the decrease in the tensile recovery rate of the film caused by stretching.

[0078] The aforementioned film may further include a plasticizer. The content of the plasticizer, based on 1 part by weight of the second polymer resin, may be 0.5 parts by weight or less.

[0079] The content of the aforementioned plasticizer, based on 1 part by weight of the second polymer resin, can be 0.01 parts by weight or more, 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.12 parts by weight or more, or 0.15 parts by weight or more. Alternatively, the content of the aforementioned plasticizer, based on 1 part by weight of the second polymer resin, can be 0.5 parts by weight or less, 0.4 parts by weight or less, 0.35 parts by weight or less, or 0.3 parts by weight or less.

[0080] The aforementioned film is based on 100 parts by weight of a base resin consisting of a first polymer resin and a second polymer resin, including the following amounts of plasticizer.

[0081] Based on 100 parts by weight of the aforementioned base resin, the film may include 0.1 parts by weight or more, 0.3 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more of a plasticizer. Additionally, based on 100 parts by weight of the aforementioned base resin, the film may include 20 parts by weight or less, 17 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less of a plasticizer.

[0082] Specifically, as the aforementioned plasticizer, a plasticizer selected from triethylene glycol bis(ethylene glycol) can be used. 2 Ethylhexanoate (3G8), tetraethylene glycol diheptanoate (4G7), triethylene glycol bis-2-ethylbutyrate (3GH), triethylene glycol bis-2-heptanoate (3G7), dibutoxyethoxyethyl adipate (DBEA), butyl carbitol adipate (DBEEA), dibutyl sebacate (DBS), dihexyl adipate (DHA), and combinations thereof. Specifically, the plasticizer may include any one selected from the group consisting of triethylene glycol bis-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol bis-2-heptanoate, and combinations thereof. More specifically, triethylene glycol bis-2-ethylbutyrate can be used as the plasticizer. 2 Ethylhexanoate (3G8). This plasticizer exhibits excellent miscibility with the second polymer resin and can simultaneously improve workability and optical properties.

[0083] To achieve the above objectives, the film according to one embodiment comprises a first polymer resin and a second polymer resin as dissimilar resins. Specific descriptions of the first and second polymer resins are repeated above, and therefore detailed descriptions are omitted.

[0084] The aforementioned film, based on 1 part by weight of the first polymer resin, may include 2.5 parts by weight or less of the second polymer resin. Specifically, the aforementioned film, based on 1 part by weight of the first polymer resin, may include 2.5 parts by weight or less, 2.3 parts by weight or less, 2 parts by weight or less, 1.8 parts by weight or less, 1.6 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, 0.67 parts by weight or less, or 0.5 parts by weight or less of the second polymer resin. The aforementioned film, based on 1 part by weight of the first polymer resin, may include 0.001 parts by weight or more, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.3 parts by weight or more of the second polymer resin.

[0085] By preparing the film in the proportions described above, the migration of unreacted polyether monomers (including oligomers) can be minimized. Furthermore, it helps to effectively suppress the degradation of the film's optical properties caused by haze changes. In addition, by preparing the film in the proportions described above, the reduction in the film's tensile recovery rate due to stretching can be effectively suppressed.

[0086] The thickness of the aforementioned film can be 1,000 µm or less. Specifically, the thickness of the aforementioned film can be 500 µm or less, 250 µm or less, or 150 µm or less. The thickness of the aforementioned film can be 1 µm or more, 10 µm or more, 20 µm or more, 30 µm or more, 40 µm or more, or 50 µm or more, and can be 100 µm or more. When the aforementioned film is prepared with such thickness, it is possible to provide a thin and lightweight film that also possesses excellent impact resistance and other properties, as well as low haze.

[0087] Physical properties of the film According to one or more embodiments, the film can have a tensile recovery rate of over 90% at 60% elongation.

[0088] The tensile recovery rate of the film at N% elongation can be derived from Equation 1 below.

[0089] [Formula 1] Tensile recovery rate (%) = (LfN - LiN) / (LfN - Li) In Equation 1 above, LfN is the length of the film stretched with an elongation of N%, LiN is the length of the film after it has recovered from stretching, and i is the length of the film before stretching.

[0090] The elongation rate mentioned above is a percentage (%) of the length of the film stretched by applying tension in one direction to the length of the film in one direction before the tension was applied.

[0091] An exemplary method for measuring tensile recovery force is described. A film sample with a length of 60 mm to 100 mm is prepared. After marking a length of 50 mm, tension is applied using the aforementioned elongation rate. In other words, tension is applied to the film sample until it reaches a length of LfN and stretched, held for 10 seconds. The tension applied to the stretched film is then removed, and the film is left at room temperature for 5 minutes. The marked length of the film after this period is measured and taken as the length of the film after recovery, i.e., LiN.

[0092] When N% is 20%, the tensile recovery rate of the film can be 90% or more, 95% or more, 96% or more, or 97% or more. The tensile recovery rate can be less than 100% or less than 99%.

[0093] When N% is 40%, the tensile recovery rate of the film can be 85% or more, 90% or more, or 95% or more. The tensile recovery rate can be less than 100% or less than 99%.

[0094] When N% is 60%, the tensile recovery rate of the film can be 80% or more, 85% or more, 90% or more, or 93% or more. The tensile recovery rate can be less than 100% or less than 99%.

[0095] When N% is 80%, the tensile recovery rate of the film can be 75% or more, 80% or more, 85% or more, or 90% or more. The tensile recovery rate can be less than 100% or less than 99%.

[0096] When N% is 100%, the tensile recovery rate of the film can be 75% or more, 80% or more, 82% or more, or 84% or more. The tensile recovery rate can be less than 100% or less than 99%.

[0097] With this stretch recovery rate, even when performing operations such as stretching and attaching the film, the degree of plastic deformation generated in the film can be minimized. Furthermore, the formation of spaces such as air bubbles between the object being attached and the film can be substantially suppressed.

[0098] The attenuation coefficient (20-40) of the tensile recovery rate between the aforementioned 20% elongation and 40% elongation can be derived from Equation 2 below. (Unitless.)

[0099] [Equation 2] Tensile recovery rate attenuation coefficient (20-40) =

[0100] In Equation 2, A 20 A represents the tensile recovery rate (%) of the above film at 20% elongation. 40 The tensile recovery rate (%) of the above film at 40% elongation.

[0101] The tensile recovery rate attenuation coefficient (20-40) of the above-mentioned film can be less than 0.3, less than 0.2, or less than 0.1. The tensile recovery rate attenuation coefficient (20-40) of the above-mentioned film can be greater than 0.01.

[0102] The attenuation coefficient (40-60) of the tensile recovery rate between the above-mentioned 40% elongation and the above-mentioned 60% elongation can be derived according to Equation 3 below. (Unitless.)

[0103] [Formula 3] Tensile recovery rate attenuation coefficient (40-60) =

[0104] In Equation 3, A 40 A represents the tensile recovery rate (%) of the above film at 40% elongation. 60 The tensile recovery rate (%) of the above film at 60% elongation.

[0105] The tensile recovery rate attenuation coefficient (40-60) of the above-mentioned film can be below 0.3, below 0.2, or below 0.1. The tensile recovery rate attenuation coefficient (40-60) of the above-mentioned film can be above 0.01.

[0106] For optimal application as a surface protective film, the film should ideally possess high strength and be easy to install.

[0107] The strength of a thin film is related to its effectiveness in protecting the surface of an object from external impacts (e.g., stones, car door collisions, etc.). This is related to the film stress at high strain rates in the stress-strain rate curve.

[0108] To ensure smooth adhesion of the film to surfaces including curved and bent surfaces, the film is preferably easily deformable within a small strain rate range suitable for application. This relates to the film stress at small strain rates in the stress-strain rate curve.

[0109] In a stress-strain rate curve, the low strain rate region refers to the strain rate region below approximately 100% or approximately 80%.

[0110] In a stress-strain rate curve, the high strain rate region refers to the strain rate region of approximately 200% to approximately 400%.

[0111] When the strain rate is 20%, the stress of the above-mentioned thin film can be 7 N / mm. 2 Below, 6.5N / mm 2 Below, 6N / mm 2 Below, 5.5N / mm 2 Below or 5N / mm 2 The stress described above can be 1 N / mm. 2 above.

[0112] When the strain rate is 50%, the stress of the above-mentioned thin film can be 8 N / mm. 2 Below, 7.5N / mm 2 Below or 7N / mm 2 The stress described above can be 2 N / mm. 2 above.

[0113] When the strain rate is 300%, the stress of the above-mentioned thin film can be 6 N / mm. 2 Above, 7N / mm 2 Above, 8N / mm 2 Above, 9N / mm 2 Above or 10N / mm 2 The above. The stress can be 20 N / mm. 2 the following.

[0114] The value of the stress at a strain rate of 100% minus the stress at a strain rate of 20% can be 5 N / mm². 2 The difference mentioned above can be 5 N / mm. 2 Below, 4N / mm 2 Below, 3.4N / mm 2 Below, 3N / mm 2 Below or 2.5N / mm 2 The difference mentioned above can be 1.2 N / mm. 2 This means that stress changes are relatively small in the low strain rate range, and films with this characteristic can have excellent workability when used as protective coatings.

[0115] Using the stress at a strain rate of 100% as a baseline, the ratio of stress at a strain rate of 20% can be 0.45 or higher. This ratio can be 0.45 or higher, 0.5 or higher, or 0.55 or higher. Alternatively, it can be 0.85 or lower, or 0.8 or lower. This means that the difference between the stress of the film in the low strain rate range and the stress at a strain rate of 100% is not significant, and films with this characteristic can exhibit excellent workability.

[0116] The ratio of stress at a strain rate of 300% to the stress at a strain rate of 100% can be 1.4 or higher. This ratio can be 1.4 or higher, 1.45 or higher, or 1.5 or higher. Alternatively, the ratio can be 3 or lower, or 2.2 or lower. This indicates that the stress at a strain rate of 300% is considerably high compared to the stress at 100% strain rate, and this characteristic enables the provision of thin films with excellent strength.

[0117] Films with this stress value exhibit excellent workability and high strength, making them highly suitable for surface protection. It is believed that films with this stress value are obtained through the application of dissimilar resins and plasticizers.

[0118] The haze value of the aforementioned film at room temperature can be below 3%. Specifically, the haze value of the aforementioned film at room temperature can be below 2.5% or below 2%. The haze value of the aforementioned film at room temperature can be above 0% or above 0.1%. The aforementioned film can ensure a level of transparency suitable for optical film applications.

[0119] The haze value of the above-mentioned film after being placed at 60°C for 7 days can be below 3%. Specifically, the haze value of the above-mentioned film after being placed at 60°C for 7 days can be below 2.5% or below 2%. The haze value of the above-mentioned film after being placed at 60°C for 7 days can be above 0% or above 0.1%.

[0120] The difference in haze value of the aforementioned film before and after being placed at 60°C for 7 days can be less than 1%. Specifically, the difference in haze value of the aforementioned film before and after being placed at 60°C for 7 days can be less than 0.5%, less than 0.3%, less than 0.1%, less than 0.05%, less than 0.01%, or less than 0.001%. The difference in haze value of the aforementioned film before and after being placed at 60°C for 7 days can be greater than 0% or greater than 0.0001%.

[0121] In this case, even when the above-mentioned film is exposed to a film application environment with a temperature higher than that of room temperature for a long time, the change in haze value is small, which can minimize the degradation of optical performance.

[0122] Use of the film The above-mentioned film can be used as a surface protection film.

[0123] The upper surface protective film can be applied to automobiles, aircraft, electronic products, furniture, etc. (hereinafter referred to as articles). The surface of the aforementioned articles may include at least a portion of a coated surface with paint or the like. The upper surface protective film can be attached to the coated surface to protect the coating of the aforementioned articles from being peeled off.

[0124] A protective film can be applied to the substrate (object, coated surface). This prevents the surface of the substrate from being exposed to the outside.

[0125] A coating film can be formed on the surface of the substrate. A protective film can be disposed on the coating film. This prevents the coating film from being exposed to the outside, thereby preventing damage to the coating film.

[0126] An adhesive layer may be added between the surface of the substrate and the upper surface protective film. The adhesive layer may be attached to the surface of the substrate in a manner formed on one side of the surface protective film.

[0127] Method of preparing the film The method for preparing a film includes: a preparation step of preparing a mixture of a film composition comprising a first polymer resin and a second polymer resin; and a molding step of extruding the mixture into a sheet form.

[0128] The specific descriptions of the first polymer resin and the second polymer resin mentioned above are repeated in the above content, so their detailed descriptions are omitted.

[0129] The above-mentioned film composition may further include a plasticizer.

[0130] The specific details and contents of the first polymer resin, second polymer resin, plasticizer, etc., included in the film composition are repeated in the above description, so their detailed description is omitted.

[0131] The above mixture is formed by mixing a first polymer resin and a second polymer resin.

[0132] The mixture described above may be formed by mixing a second polymer resin mixed with a plasticizer with a first polymer resin.

[0133] The second polymer resin can have viscous properties. When the second polymer resin, which is mixed with a plasticizer, is mixed with the first polymer resin, the miscibility of the composition can be further improved.

[0134] The above composition may optionally further include a light absorber. The light absorber can mitigate the degradation of the optical and mechanical properties of the film caused by ultraviolet radiation exposure.

[0135] The aforementioned light absorber may include any one selected from the group consisting of benzotriazole compounds, oxaloylaniline compounds, hydroxybenzophenone compounds, hydroxyphenyltriazine compounds, benzoic acid ester compounds, and combinations thereof. This compound exhibits excellent compatibility with polyether block amide copolymer resins and effectively absorbs ultraviolet light, thereby stably preventing film degradation.

[0136] For example, BASF's Tinuvin 234, Tinuvin 312, Tinuvin 329, Tinuvin P, Tinuvin 1130, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 571, Tinuvin 99-DW, Tinuvin 1600, Tinuvin 1577, etc., can be used as light absorbers.

[0137] The composition, based on 100 parts by weight of the sum of the first polymer resin and the second polymer resin, may include 0.1 parts by weight or more, 0.2 parts by weight or more, 0.35 parts by weight or more, or 0.5 parts by weight of the aforementioned light absorber. The composition, based on the aforementioned sum of 100 parts by weight, may include 5 parts by weight or less, 3 parts by weight or less, or 2 parts by weight or less of the aforementioned light absorber. In this case, the yellowing and hardening rate of the prepared film can be effectively slowed down.

[0138] The aforementioned films may further include additives commonly used in the film industry. Examples of such additives include lubricants, anti-blocking agents, heat stabilizers, antistatic agents, and impact modifiers.

[0139] The molding step is the step of molding the above composition into a sheet form.

[0140] The above molding step can be exemplarily described as the step of extruding the above mixture in a molten state and forming it into a sheet form through a T-die.

[0141] The above molding step can be exemplarily described as the step of extruding the above mixture in a molten state, arranging it on a carrier film, and forming it into a sheet form between rollers.

[0142] In the molding step, the melt extrusion temperature of the mixture can be from 150°C to 300°C. The sheet formed by the above melt extrusion process can be used as the film described above.

[0143] The film in this embodiment can be an extruded film. Extruded films offer the advantages of easier mass production and the ability to form laminated films that further include other layers. When preparing an extruded film, film thickness control is easier, and compared to casting methods, it is advantageous to prepare relatively thick films with good overall thickness control. For example, the thickness of the extruded film can be 80µm or more, 90µm or more, or 100µm or more.

[0144] The film of the embodiment can be a film that further includes a plasticizer. The plasticizer can adjust the modulus of the film. Specifically, a film including a plasticizer can reduce the modulus, which can improve the workability of the surface protective film.

[0145] The following detailed description uses specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto.

[0146] Preparative example: preparation of the film As the first polymer resin, a polyether block amide copolymer resin was used. Specifically, PEBAX was used. ® 40R53 or PEBAX ® 35R53. PEBAX ® 40R53 contains approximately 46% by weight of PA11 residues as amide residues and approximately 54% by weight of polytetramethylene glycol residues. It is a polyether block amide resin manufactured and commercially available by Arkema, France, and is abbreviated as 40R53. PEBAX ® 35R53 contains approximately 31% by weight of PA11 residues as amide residues and approximately 69% by weight of polytetramethylene glycol residues. It is a polyether block amide resin manufactured and commercially available by Arkema, France, and is simply referred to as 35R53.

[0147] As the second polymer resin, a polyvinyl alcohol acetal resin composition was used. Specifically, polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 99 and n-butyraldehyde were used to synthesize polyvinyl alcohol butyraldehyde resin (PVB) through a conventional synthesis process. The above-mentioned polyvinyl alcohol butyraldehyde resin has a hydroxyl content of 20.3% by weight, a butyraldehyde group content of 78.9% by weight, and an acetyl group content of 0.8% by weight, and is simply referred to as PVB.

[0148] Triethylene glycol bismuth substituent was used as a plasticizer. 2 Ethylhexanoate, abbreviated as 3G8.

[0149] The contents were as shown in Table 1 below, and the mixture was prepared by extruding the composition. The mixture was melt-extruded using an extruder owned by SK Microworks Solutions Co., Ltd. to prepare a sheet form for film application as an example.

[0150] For comparative examples, either a film formed by molding polyether block amide copolymer resin into a film (Comparative Example 1) or commercially available TPU (Comparative Example 2) was used. The TPU used was Argotec's 49510 product.

[0151] [Table 1]

[0152] Experimental example: evaluation of the physical properties The stress-strain rate curves were measured using an Instron universal testing machine, etc. The results are shown in Table 2.

[0153] [Table 2]

[0154] The tensile recovery rate was evaluated using the sample from Example 2.

[0155] Prepare film samples with a length of 60 mm to 100 mm. Mark a length of 50 mm and then apply tension using the elongation rates shown in Table 3. In other words, apply tension to the film sample and stretch it to a length of LfN, holding for 10 seconds. Then remove the tension applied to the stretched film and allow it to stand at room temperature for 5 minutes. Measure the marked length of the film after standing, which is taken as the recovered length of the stretched film, LiN. The tensile recovery rate is calculated using Equation 1 below.

[0156] [Formula 1] Tensile recovery rate (%) = (LfN - LiN) / (LfN - Li) In Equation 1 above, LfN is the length of the film stretched with an elongation of N%, LiN is the length of the film after it has recovered from stretching, and Li is the length of the film before stretching.

[0157] [Table 3]

[0158] Referring to Tables 1 to 3 above, when comparing the physical properties with those of TPU previously used as a surface protective film, it was confirmed that Examples 1, 2, 4, and 5 containing plasticizers exhibited lower stress at low strain rates such as 10% and 20%, further improving workability.

[0159] In addition, referring to Examples 1 and 2 and Comparative Example 1, the stress at high strain rates was at a similar level to that when the first polymer resin was used alone, but the stress at low strain rates was reduced, confirming that workability was improved.

[0160] Referring to the results of Comparative Example 1 and Examples 1 to 6, by mixing the second polymer resin, the stress was appropriately reduced in the range of low strain rate while the stress was increased in the range of high strain rate. It was confirmed that by mixing the first polymer resin with the second polymer resin, the effect of simultaneously improving workability and strength can be obtained, so as to facilitate its use as a surface protective film.

[0161] While the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention as defined in the appended claims also fall within the scope of the present invention.

Claims

1. A thin film, characterized in that, Includes: a first polymer resin and a second polymer resin as dissimilar resins, The aforementioned first polymer resin comprises polyamide repeating units and polyether repeating units. The aforementioned second polymer resin contains any one of the groups selected from hydroxyl, acetal, and combinations thereof in its branched chain. The tensile recovery rate at N% elongation is derived from Equation 1 below. When N% is 60%, the tensile recovery rate of the film is over 90%. [Formula 1] Tensile recovery rate (%) = (LfN - LiN) / (LfN - Li) In Equation 1 above, LfN is the length of the film stretched with an elongation of N%, LiN is the length of the film when it is restored after stretching, and Li is the length of the film before stretching.

2. The thin film according to claim 1, characterized in that, When the strain rate is 100%, the stress is 1 N / mm. 2 the following.

3. The thin film according to claim 1, characterized in that, After being placed at 60°C for 7 days, the haze value of the above film was less than 3%.

4. The thin film according to claim 1, characterized in that, When N% is 100%, the tensile recovery rate of the film is 75% or higher.

5. The thin film according to claim 1, characterized in that, Based on the sum of the first polymer resin and the second polymer resin, the film contains 10% by weight or more of the polyether repeating units.

6. The thin film according to claim 1, characterized in that, The attenuation coefficient (20-40) of the tensile recovery rate between the aforementioned 20% elongation and the aforementioned 40% elongation is derived from Equation 2 below. The tensile recovery rate attenuation coefficient (20-40) of the above-mentioned films is below 0.3: [Equation 2] Tensile recovery rate attenuation coefficient (20-40) = In Equation 2, A 20 The tensile recovery rate (%) of the above film at 20% elongation. A 40 The tensile recovery rate (%) of the above film at 40% elongation.

7. A thin film, characterized in that, include: Polyether block amide copolymer resin; as well as Polyvinyl acetal resin, When the strain rate is 20%, the stress is 7 N / mm. 2 the following.

8. The thin film according to claim 7, characterized in that, The difference between the stress at 100% strain rate and the stress at 20% strain rate is 5 N / mm². 2 the following.

9. The thin film according to claim 7, characterized in that, The ratio of stress at a strain rate of 300% to stress at a strain rate of 1.4 or higher is based on the stress at a strain rate of 100%.

10. The thin film according to claim 1 or claim 7, characterized in that, The above-mentioned film is a protective coating film.

Images