JP2019001015A - Polyurethane multilayer film - Google Patents

Abstract

To provide an improved multilayer film.SOLUTION: A multilayer film has a first layer containing polyester thermoplastic polyurethane (A) as the main component, and a second layer disposed on one principal surface of the first layer and containing polyester thermoplastic polyurethane (B) as the main component. The surface of the first layer has a Shore D hardness of 50 or more, and the surface hardness of the second layer is smaller than the surface hardness of the first layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyurethane multilayer film. More particularly, the present invention relates to a multilayer film used for protecting a surface, in particular, a film used for protecting a surface (for example, painted surface) of a vehicle (for example, an automobile, an aircraft, a ship, a train, etc.).

  The coated product has a protective film on the painted surface (painted surface, paint film) to prevent damage during storage, transportation, or processing, and to prevent deterioration or fading due to light, heat, or moisture. The painted surface is protected by sticking.

  Polyurethane has been conventionally used as a base material for protective films because it can follow a complicated shape due to the mechanical properties peculiar to polyurethane and thereby has excellent shock absorption. For example, Patent Documents 1 to 3 have developed a plurality of surface protecting films made of a multilayer film including a polyurethane layer.

  In recent years, a coating protective film in which a self-repairing functional film is laminated on the surface has been proposed with the aim of further increasing the functionality. For example, Patent Document 4 proposes a coating agent that can form a surface layer excellent in self-repairing property and antifouling property by being applied to a substrate surface such as thermoplastic polyurethane and cured. The said coating agent is comprised including a urethane (meth) acrylate type resin, a fluorine-type compound, and a photoinitiator.

JP 2008-539107 A JP 2004-516958 A JP 2002-529277 A International Publication No. 2016/159023

  When a self-healing layer is formed on the surface of a film substrate having a low surface hardness, there is a tendency that the self-healing function is hardly exhibited and / or the self-healing layer is difficult to be applied. On the other hand, when the hardness of the surface of the film base material is increased, the stretchability and flexibility of the protective film are lowered, and there is a problem that the handling property when the paint protective film is applied is lowered.

  There is still a need for improved multilayer film technology.

  As a result of intensive studies to solve the above problems, the present inventors have arranged a high-hardness polyester-based thermoplastic polyurethane layer on the surface and a low-hardness polyester-based thermoplastic polyurethane layer on the inner layer. As a result, the present inventors have found that the above problems can be solved, and have completed the present invention. That is, the present invention is as follows, for example.

[1] a first layer containing a polyester-based thermoplastic polyurethane (A) as a main component;
A second layer disposed on one main surface of the first layer and comprising a polyester-based thermoplastic polyurethane (B) as a main component,
The surface of the first layer has a Shore D hardness of 50 or more,
A multilayer film in which the surface hardness of the second layer is smaller than the surface hardness of the first layer.
[2] The layer thickness ratio (first layer / second layer) between the first layer and the second layer is 0.05 to 0.6, and the total layer thickness of the first layer and the second layer is 30 to 300 μm. The multilayer film according to [1].
[3] The multilayer film according to [1] or [2], wherein the surface of the first layer has a Shore D hardness of 50 to 60.
[4] The multilayer film according to any one of [1] to [3], wherein the surface of the second layer has a Shore A hardness of 70 to 95.
[5] The multilayer film according to any one of [1] to [4], wherein the first layer and the second layer are laminated and integrated.
[6] The multilayer film according to any one of [1] to [5], wherein the first layer and the second layer are laminated by coextrusion molding.
[7] The multilayer film according to any one of [1] to [6], having an adhesive layer on a surface opposite to the surface on which the first layer of the second layer is disposed.
[8] The multilayer film according to [7], wherein the pressure-sensitive adhesive layer contains a pressure-sensitive adhesive.
[9] The multilayer film [10] according to any one of [1] to [8], having a self-healing layer on a surface opposite to the surface on which the second layer of the first layer is disposed. The multilayer film according to [9], which is transparent or colored.
[11] The self-healing layer is composed of a polyurethane resin, an acrylic transparent rubber resin, a silicone rubber resin, an olefin elastomer, and a soft synthetic resin selected from a styrene elastomer. [9] The multilayer film according to [10].
[12] The multilayer film according to any one of [1] to [11], wherein the thickness of the first layer is 10 to 100 μm.
[12-1] The multilayer film according to any one of [1] to [12], wherein the second layer has a thickness of 20 to 200 μm.
[13] The multilayer film according to any one of [1] to [12], which is used for protecting coating.
[14] A vehicle body portion having a coating film protected by the multilayer film according to any one of [1] to [13].
[15] A molding material (A) containing the polyester-based thermoplastic polyurethane (A) constituting the first layer and a molding material (B) containing the polyester-based thermoplastic polyurethane (B) constituting the second layer are co-used. The manufacturing method of the multilayer film in any one of [1]-[13] including extrusion.

The present invention has one or more of the following effects.
(1) A polyurethane multilayer film having sufficient surface hardness and excellent handling properties can be obtained.
(2) It is possible to form a self-healing layer that can exhibit excellent self-healing properties.
(3) An interface failure between polyurethane layers hardly occurs and a polyurethane multilayer film having a good appearance can be obtained.

It is sectional drawing which shows schematic structure of the multilayer film of one Embodiment of this invention. It is sectional drawing which shows schematic structure of the multilayer film of one Embodiment of this invention. It is sectional drawing which shows schematic structure of the multilayer film of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

One embodiment of the present invention relates to a multilayer film. The multilayer film according to the embodiment is disposed on one main surface of a first layer including a polyester-based thermoplastic polyurethane (A) (hereinafter also simply referred to as “polyurethane (A)”) as a main component, and the first layer. And a second layer containing, as a main component, a polyester-based thermoplastic polyurethane (B) (hereinafter also simply referred to as “polyurethane (B)”). In the multilayer film of the embodiment, the surface of the first layer has a Shore D hardness of 50 or more, and the surface hardness of the second layer is smaller than the surface hardness of the first layer. The first layer is a layer (outer layer) provided on the outer side (outer surface side of the multilayer film), and the second layer is a layer (inner layer) provided on the inner side of the first layer.
Note that “including as a main component” means that the content of the polyester-based thermoplastic polyurethane exceeds 50% by mass with respect to the total mass of the layer. Preferably, in the first layer and the second layer, the content of the polyester-based thermoplastic polyurethane is preferably 75% by mass or more, more preferably 90% by mass or more, and 95% by mass or more with respect to the total mass of each layer. Is more preferable, and it is particularly preferable that the first layer and the second layer substantially consist of a polyester-based thermoplastic polyurethane.

Conventionally used polyurethane protective films having a Shore A hardness of about 90 are the mainstream, and those having a self-healing layer on polyurethane of this hardness have been developed. However, since the self-healing function of the self-healing layer is difficult to develop on the surface with a Shore A hardness of about 90 and / or the construction of the self-healing layer is difficult, a paint protective film with further excellent self-healing properties has been developed. In order to do this, the surface of the polyurethane paint protective film needs to have a higher hardness. However, if the hardness of the urethane layer is higher, the elongation and flexibility tend to be lowered, so it is difficult to achieve both higher hardness and flexibility of the surface.
On the other hand, the present inventors have found that high hardness and flexibility of the surface can be achieved by laminating two kinds of polyester-based thermoplastic polyurethane layers having high hardness and low hardness. Further, when a plurality of thermoplastic resin layers having different hardnesses are laminated, an interface defect between the layers tends to occur, and appearance defects such as streaks and blurring tend to occur. The present inventors have also found that interfacial defects between layers can be suppressed by using a polyester-based thermoplastic polyurethane which is the same kind of material. According to the present invention, it is possible to obtain a polyurethane multilayer film having excellent handling properties and a high hardness surface without impairing the appearance.

  The handling property of the multilayer film can be evaluated by, for example, a tensile elastic modulus. The multilayer film of the present invention preferably has an elastic modulus of 4 N / mm or more and 14 N or less, more preferably 7 N / mm or more and 9 N when applied with 50% strain measured according to JIS K 7161-1: 2014. / Mm or less.

  FIG. 1 is a cross-sectional view illustrating a schematic configuration of a multilayer film according to an embodiment. The multilayer film 10 of the present embodiment includes at least a first layer 11 containing polyurethane (A) as a main component and a second layer 12 containing polyurethane (B) as a main component. One main surface of the first layer 11 is preferably bonded to one main surface of the second layer 12, and the first layer and the second layer are preferably laminated and integrated.

  FIG. 2 is a cross-sectional view illustrating a schematic configuration of a multilayer film according to another embodiment. As shown in this embodiment, the multilayer film 10 includes a first layer 11 containing at least a polyurethane (A) as a main component and a second layer 12 containing a polyurethane (B) as a main component, in addition to the second layer. The adhesive layer 14 may be included on the surface opposite to the surface on which one layer is disposed. Preferably, one main surface of the first layer is bonded to one main surface of the second layer, and an adhesive layer is bonded to the opposite main surface of the second layer so that the second layer is the first layer. Be sandwiched between the layer and the adhesive layer.

  FIG. 3 is a cross-sectional view illustrating a schematic configuration of a multilayer film according to another embodiment. As shown in this embodiment, the multilayer film 10 includes, in addition to the first layer 11 containing at least polyurethane (A) as a main component, the second layer 12 containing polyurethane (B) as a main component, and the adhesive layer 14, The self-healing layer 13 may be included on the surface opposite to the surface on which the second layer of the first layer is disposed. Also in this embodiment, one main surface of the first layer 11 is bonded to one main surface of the second layer 12, and the first layer 11 and the second layer 12 are laminated and integrated. preferable.

In the embodiment of FIGS. 1 to 3, other layers may be interposed between the self-healing layer 13, the first layer 11, the second layer 12, and the adhesive layer 14.
Hereinafter, the configuration of each layer will be specifically described.

  Thermoplastic polyurethane (TPU) is a rubber elastic body obtained by reaction of polyisocyanate, high molecular weight polyol and chain extender. Various physical properties (for example, elastic modulus, abrasion resistance, mechanical strength (such as tensile strength)) can be adjusted by changing the type and blending ratio of polyisocyanate, high molecular weight polyol and chain extender, and the degree of polymerization When it decreases, the surface hardness tends to increase, and when it increases, the surface hardness tends to decrease.

(Polyester thermoplastic polyurethane)
Thermoplastic polyurethane (TPU) is a thermoplastic resin generally obtained by reacting a polyol (long chain diol component), polyisocyanate, and a chain extender (short chain diol component). When the polyol and the polyisocyanate are heated, the hydroxyl group of the polyol and the isocyanate group of the polyisocyanate form a urethane bond to form a thermoplastic polyurethane. The chain extender and polyisocyanate react to form a hard segment, and the polyol and polyisocyanate react to form a soft segment.

In the present invention, polyester polyurethane is used as the thermoplastic polyurethane.
A polyol (hereinafter, also referred to as “polyester polyol”) used for producing a polyester-based polyurethane is a polyol having an ester structure. Examples of polyester polyols include condensed polyester polyols and polycaprolactone polyols.

  Examples of the condensed polyester polyol include polycarboxylic acids such as adipic acid, isophthalic acid, and terephthalic acid, and ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexanediol, trimethylolpropane, neopentyl glycol, and glycerin. Examples thereof include condensation reaction products obtained by reacting with polyols such as.

The polycaprolactone polyol is a polyol having a polycaprolactone structure obtained by ring-opening polymerization of caprolactone. Polycaprolactone includes a structure represented by the following (i).

The polycaprolactone polyol contains at least two or more hydroxyl groups, and the hydroxyl group is preferably at the end of the polycaprolactone polyol. Examples of the polycaprolactone having two or more hydroxyl groups include polycaprolactone diols represented by the following formula (ii), polycaprolactone triols represented by the following formula (iii), and other tetrafunctional polycaprolactone polyols. .
(In the formula, m + n represents an integer of 4 to 35, and R represents _C1-8 alkylene, _C1-4 alkylene-O- _C1-4 alkylene.)
(In the formula, l + m + n represents an integer of 3 to 30, and R represents a trivalent group derived from a C _1-8 alkyl chain.)

  In addition, polyethers having a hydroxyl group at the terminal and having a molecular weight of 400 to 10,000, polyester amides, polyether esters, polycarbonates, and the like may be used in combination.

  Examples of polyisocyanates include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate and the like, and aromatic diisocyanates composed of these isomers, 1,6-hexamethylene diisocyanate, 1, Aliphatic diisocyanates such as 12-dodecane diisocyanate, trimethyl-hexamethylene diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, norbornane-diisocyanate methyl, 4,4′-methylenedicyclohexyl diisocyanate (H12MDI) Alicyclic diy Or the like can be mentioned cyanate. Moreover, the isocyanate group terminal compound by reaction of these compounds and an active hydrogen group containing compound, or the polyisocyanate modified body by reaction of these compounds, for example, a carbodiimidization reaction, etc. can be mentioned. Also include polyisocyanates partially stabilized with a blocking agent having one active hydrogen in the molecule, such as methanol, n-butanol, benzyl alcohol, ethyl acetoacetate, ε-caprolactam, methyl ethyl ketone oxime, phenol, cresol, etc. Can do.

  The amount of polyisocyanate relative to the polyol is selected in an amount that is approximately stoichiometrically equivalent, although other ratios (eg, excess polyisocyanate or excess polyol) may be used.

  Examples of the chain extender include ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, bis-β-hydroxyethoxybenzene, 3- And compounds having a molecular weight of less than 400, such as methyl-1,5-pentanediol, neopentyl glycol, N-phenyldiisopropanolamine, monoethanolamine, 1,4 cyclohexyldimethanol.

  When manufacturing thermoplastic polyurethane (TPU), a catalyst can be added as needed. Examples of the catalyst include amines such as triethylamine, triethylenediamine, N-methylimidazole, N-ethylmorpholine, 1,8-diazabicyclo-5,4,0-undecene-7 (DBU), potassium acetate, stannous octet And organometallics such as dibutyltin dilaurate, and phosphorus compounds such as tributylphosphine, phospholene, and phospholene oxide.

  The production method of thermoplastic polyurethane (TPU) is not particularly limited, and known TPU production methods such as one-shot method, prepolymer method, batch reaction method, continuous reaction method, kneader method, extruder method, etc. The method can be adopted. For example, in the method using a kneader, a polymer polyol and a chain extender are charged into a kneader, and after heating, a polyisocyanate is added, reacted for a specific time, and cooled to produce a powdery or block-like TPU. it can. A catalyst such as dibutyltin dilaurate may be used as necessary. These powdery or blocky resins can be formed into pellets by an extruder or the like, if necessary.

(First layer)
The surface of the first layer has a Shore D hardness of 50 or more, preferably 50-60. Thereby, the surface hardness of a multilayer film can be raised. On the surface of the first layer having such a high surface hardness, it is easy to form a self-healing layer, and the self-healing function can be sufficiently exhibited.
The Shore D hardness of the surface can be measured by the method of JIS Z 2246.

  The first layer contains a polyester-based thermoplastic polyurethane (A) as a main component. The polyurethane (A) is not particularly limited as long as a desired surface hardness can be obtained. For example, those described above (polyester thermoplastic polyurethane) can be used.

Of the above, the polyurethane (A) is preferably in the form of pellets.
As the polyurethane (A), for example, commercially available products such as ProGran (Huntman), Elastollan (BASF), and Estane (Lublizol) can be used, and ProGran (Huntman) and Estane (Lublizol) are preferable.
Examples of the polyester-based thermoplastic polyurethane are disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-299026, and the disclosed polyester-based thermoplastic polyurethane and a modified version thereof can also be used in the present invention. .

  The first layer may contain other components as necessary. Other components include ABS resin, SAN resin, vinyl chloride resin, polypropylene, polyethylene, polystyrene, polyacetal, polyamide, polyester, polyester ether, polycarbonate, epoxy resin, amino resin, phenol resin, silicone resin, fluorine resin, etc. Ingredients. These resin components are preferably less than 50% by mass and more preferably 25% by mass or less based on the total mass of the first layer. In addition, as other components, antioxidants, ultraviolet absorbers, heat resistance improvers, plasticizers, lubricants, antistatic agents, conductivity-imparting agents, colorants, inorganic and organic fillers, fiber-based reinforcing materials, hydrolysis inhibitors And additives such as reaction retardants.

  The content of the thermosetting polyurethane in the first layer is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and particularly preferably substantially free of thermosetting polyurethane. In such a case, there is an advantage regarding handling property.

  The thickness of the first layer is not particularly limited as long as sufficient surface hardness and handling properties are ensured. As an example, the thickness of the first layer is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of maintaining the surface hardness. On the other hand, the thickness of the first layer is preferably 100 μm or less, and more preferably 40 μm or less from the viewpoint of handling properties.

(Second layer)
The second layer is disposed on one main surface of the first layer.
The second layer has a smaller surface hardness than the first layer. As a result, the surface of the multilayer film (the surface of the first layer) can be made to have a high hardness without impairing the extensibility and / or flexibility of the multilayer film, thereby exhibiting excellent self-healing properties. A self-healing layer can be formed.

For example, the surface of the second layer has a Shore D hardness of less than 50. Preferably, Shore A hardness is 70-95. Note that the Shore A hardness 95 has a smaller surface hardness than the Shore D hardness 50.
The Shore A hardness of the surface can be measured by the method of JIS Z 2246.

  The second layer contains a polyester-based thermoplastic polyurethane (B) as a main component. The polyurethane (B) is not particularly limited as long as the desired surface hardness can be obtained. For example, the polyurethane (B) described above (polyester thermoplastic polyurethane) can be used. In one embodiment, the polyurethane (B) is different from the polyurethane (A) constituting the first layer in at least one of polymerization degree, molecular weight, and polyol / isocyanate composition ratio. The polyurethane (B) preferably contains the same reactants (polyisocyanate, high molecular weight polyol and chain extender) as the polyurethane (A) constituting the first layer.

As the polyurethane (B), for example, commercially available products such as ProGran (Huntman), Elastollan (BASF) and Estane (Lublizol) can be used, and ProGran (Huntman) and Estane (Lublizol) are preferable.
it can.

  The second layer may contain other components as necessary. Other components include ABS resin, SAN resin, vinyl chloride resin, polypropylene, polyethylene, polystyrene, polyacetal, polyamide, polyester, polyester ether, polycarbonate, epoxy resin, amino resin, phenol resin, silicone resin, fluorine resin, etc. Ingredients. These resin components are preferably less than 50% by mass, more preferably 25% by mass or less, based on the total mass of the second layer. In addition, as other components, antioxidants, ultraviolet absorbers, heat resistance improvers, plasticizers, lubricants, antistatic agents, conductivity-imparting agents, colorants, inorganic and organic fillers, fiber-based reinforcing materials, hydrolysis inhibitors And additives such as reaction retardants.

  The content of the thermosetting polyurethane in the second layer is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and particularly preferably substantially free of thermosetting polyurethane. In such a case, there is an advantage that the coating process can be reduced.

  The thickness of the second layer is not particularly limited. As an example, the thickness of the second layer is preferably 20 μm or more. On the other hand, the thickness of the second layer is preferably 300 μm or less.

  The total layer thickness of the first layer and the second layer is preferably 30 to 300 μm.

  The layer thickness ratio (first layer / second layer) between the first layer and the second layer is preferably 0.05 to 0.6 from the viewpoint of handling properties. For example, the layer thickness ratio (first layer / second layer) may be 0.1 to 0.5 or 0.2 to 0.55. The layer thickness ratio (first layer / second layer) is particularly preferably 0.2 to 0.4.

  The first layer and the second layer are preferably laminated by coextrusion molding. By coextrusion molding, a laminated integrated multilayer film in which the first layer and the second layer are directly bonded is manufactured. In addition, by co-extrusion of two types of polyester-based thermoplastic polyurethane layers as the first layer and the second layer, there are few interface defects between the first layer and the second layer, and streaks and blurring are reduced. A multilayer film having an excellent appearance can be obtained. The degree of interface failure can be quantified by, for example, a defect inspection apparatus provided with a threshold value (for example, Neurosensor K5000 manufactured by Technos Co., Ltd.).

(Self-healing layer)
The multilayer film may have a self-healing layer on the surface opposite to the surface on which the second layer of the first layer is disposed. In the present specification, the “self-healing layer” means a layer having self-healing properties (self-healing properties), and is usually composed of a soft resin in order to develop a self-healing function. “Self-repairing” means the property that a wound once has disappeared over time.

  It is known that the degree of self-healing can be measured by a method using a scratch tester (for example, HEIDON from Shinto Kagaku Co., Ltd.). For example, the self-healing layer preferably has a self-healing property of 10 g or more as measured with a scratch tester using a diamond tip having a tip diameter of 15 μm as a wound body in an atmosphere of 23 ° C. and 50% (relative humidity). Furthermore, it is preferable that the time for the scratches applied to the self-healing layer to disappear by the measurement method described above is 15 seconds or less. The lower limit of the scratch disappearance time is a time that can be recognized by visual observation that the scratch has disappeared, and is, for example, about 0.2 to 0.5 seconds.

  The thickness of the self-healing layer is not particularly limited, but is preferably in the range of 10 to 60 μm, and more preferably in the range of 15 to 50 μm.

  The material for forming the self-healing layer is not particularly limited. For example, soft synthetic resins are known to have self-healing properties. Examples of such resins include soft synthetic resins such as polyurethane resins, acrylic transparent rubber resins, silicone rubber resins, olefin elastomers, and styrene elastomers.

  The self-healing layer may be transparent or colored.

  Examples of the self-healing layer are disclosed in, for example, Japanese Patent Application Laid-Open No. 2013-27998. In the present invention, the disclosed self-healing layer and a modified version thereof can be used.

(Adhesive layer)
The multilayer film may have an adhesive layer on the surface opposite to the surface on which the first layer of the second layer is disposed. The multilayer film can be fixed to a protective surface (for example, a coating surface) via the adhesive layer.

The pressure-sensitive adhesive layer preferably contains a pressure-sensitive adhesive, and more preferably contains a pressure-sensitive adhesive at room temperature (eg, about 10 to about 35 ° C.).
Alternatively, the adhesive layer may contain an adhesive such as an acrylic adhesive, a rubber adhesive, a polyester adhesive, a urethane adhesive, and a silicone adhesive. The thickness of the adhesive layer is not particularly limited.

(Other layers)
The multilayer film may have a layer other than the above.
For example, functional layers such as an antireflection layer, an antiglare layer, an antifouling layer, and an antifingerprint layer can be laminated on the self-healing layer or the first layer. The thickness of the other functional layer is preferably less than 0.15 μm, more preferably less than 0.1 μm, and particularly preferably less than 0.08 μm.
For example, the multilayer film is formed of a polyester resin film, cellulose, between layers (for example, between a self-healing layer and a first layer, between a first layer and a second layer, and between a second layer and an adhesive layer). Other resin films such as a resin film, polyethylene, polyolefin resin film, acrylic resin film, polycarbonate resin film, polyimide resin film, polyetherimide resin film, and polyamide resin film may be interposed. The thickness of the resin film is not particularly limited, but is preferably in the range of 10 to 100 μm.

(Production method)
Another embodiment of the present invention relates to a method for producing a multilayer film. For example, in the multilayer film, the raw material of the first layer and the raw material of the second layer are melted and kneaded in separate extruders, and the respective melts are guided to a feed block or a multi-manifold die, Are formed by extruding into a film with a die, cooling and solidifying with a cooling roll to form a film.

The manufacturing method of one embodiment includes a molding material (A) containing a polyester-based thermoplastic polyurethane (A) constituting the first layer and a molding material containing a polyester-based thermoplastic polyurethane (B) constituting the second layer ( B) and coextrusion. By using the same type of polyester-based thermoplastic polyurethane, it is possible to obtain a multilayer polyurethane film excellent in appearance with very few interface defects during multilayer film formation by coextrusion molding.
For example, the molding material (A) containing the polyurethane (A) in the molten state and the molding material (B) containing the polyester-based polyurethane (B) are heated, co-extruded from the die, and cooled with a cooling roll, A multilayer film in which the first layer containing the polyester-based thermoplastic polyurethane (A) and the second layer containing the polyester-based thermoplastic polyurethane (B) are laminated and integrated can be obtained.

Specifically, first, the polyurethane (A) and the polyurethane (B) are heated and melted by separate extruders, and are coextruded from a die for coextrusion molding and laminated.
The temperature to be melted by heating in the extruder may be a temperature that is 80 to 150 ° C. higher than the glass transition temperature (Tg) of each resin temperature of polyurethane (A) and polyurethane (B).
As a method of co-extrusion of two types of molten resins, a known method such as a feed block method or a multi-manifold method can be employed.
For example, in the case of the feed block method, the molten resin laminated in the feed block is guided to a sheet forming die such as a T die and formed into a sheet shape, and then flows into a forming roll (polishing roll) whose surface is mirror-finished. Then, a bank may be formed, and the roll surface may be transferred to a film and cooled while passing through the forming roll.
In the case of the multi-manifold system, the molten resin laminated in the multi-manifold die may be formed into a sheet shape inside the die, and then surface finishing and cooling may be performed with a forming roll.

  Subsequently, the sheet-like or film-like laminate coextruded from the die is wound around at least one cooling roll and cooled and solidified to obtain a laminate (multilayer film) of the first layer and the second layer. It is done.

  Alternatively, the first layer containing the polyurethane (A) and the second layer containing the polyurethane (B) are separately formed into a film shape by extrusion, casting or molding (for example, injection molding), and the first layer and The second layer may be multilayered by lamination, or both layers may be laminated via an adhesive.

  Although it does not restrict | limit especially as an adhesive, Acrylic adhesive, rubber adhesive, polyester adhesive, urethane adhesive, silicone adhesive, etc. are mentioned.

The method for disposing the adhesive layer on the surface of the second layer is not particularly limited, and can be carried out by a known method.
In a preferred embodiment, the main surface of the second layer opposite to the first layer can be pre-corona treated to improve bonding with the adhesive layer. Specifically, it is desirable to subject the surface of the second layer to a surface treatment by corona treatment or the like (for example, air or nitrogen corona treatment) and to heat laminate the second layer main surface to be bonded to the adhesive layer. Specifically, the main surface of the second layer of the TPU film is exposed and then the wettability of the film surface is modified by corona discharge treatment or the like to improve the coating characteristics.

  The multilayer film of the present invention may be a paint protective film used for paint protection. For paint protection applications, the multilayer film is typically transparent, but may be translucent. The multilayer film of the present invention may also be transparent, translucent, or opaque for other surface protection or reinforcement applications. For some applications, it may be desirable for the multilayer film of the present invention to be colored. The film of the present invention may be colored by, for example, one or more of the films further comprising a pigment or other colorant.

  For example, when used as a paint protective film, the multilayer film of the present invention is preferably sized and shaped along the surface to be protected. The multi-layer film pieces of the present invention that have been preliminarily sized and shaped are suitable for various body parts of vehicles such as automobiles, aircrafts, ships, etc., especially flying fragments (eg sand, stones, etc.), insects, etc. It can be used for paint surface protection of exposed vehicle bodies (eg, front hood tips and other tip surfaces, rocker panels, etc.). For example, the multilayer film of the present invention is used by being attached to various body portions of a vehicle. One embodiment may be a vehicle body part having a coating protected by a multilayer film.

Hereinafter, although the present invention is explained in full detail with reference to an example, the technical scope of the present invention is not limited to this.
Moreover, each physical property in Examples and Comparative Examples was measured by the following method.

<Test and evaluation>
(Physical properties: Evaluation of elastic modulus)
Based on JIS K7161-1: 2014, a tensile test was performed with a tensile tester using a No. 5 dumbbell-shaped piece. At that time, the elastic modulus was measured when 50% strain (strain = displacement / distance between marked lines × 100) was applied to the sample.
An elastic modulus of 6 N / mm or more and 10 N / mm or less is preferable from the viewpoint of handling properties, and a range of 7 N / mm to 9 N / mm is particularly preferable.

(Handling properties)
Evaluation on the workability as a paint protection film was carried out. In the evaluation, particular emphasis was placed on “feel of touch”, “feel of stickiness” and the like. Very good ones were marked with “◎”, good ones with “◯”, and bad ones with “×”.

(Evaluation of sheet interface)
Visual appearance was evaluated about the appearance defect which arises in an interface. At that time, when there is almost no appearance defect that seems to be caused by interface failure such as streaks, it is `` ◎ '', when it is slightly occurring but it is not worrisome, `` ○ '', when many are occurring It was set as “x”.

Example 1
Polyester thermoplastic polyurethane (TPU1) with Shore D hardness 52 as the first layer (Product name: PN343-200 manufactured by Huntsman, Polyester thermoplastic polyurethane (TPU2) with Shore A hardness 90 as the second layer (Product name: PN3429-218 (manufactured by Huntsman) was melt-kneaded in separate extruders, and two types of TPU (TPU1 and TPU2) were laminated in two layers with a multi-manifold die and coextruded into a film. The mixture was cooled and solidified with a cooling roll to obtain a two-layer film composed of two types of TPU1 and TPU2 having a total thickness of 100 μm.

(Examples 2 to 4)
A two-layer film was produced by the same production method as in Example 1 except that the thickness of the two-layer TPU (TPU1 and TPU2) was changed.

(Comparative Example 1)
The same material as in Example 1 is used as the first layer, and a polyether thermoplastic polyurethane having a Shore A hardness of 88 (product name: manufactured by D91F88 Lubrizol) is used as the second layer. A thick film was obtained. At that time, the layer ratio was the same as in Example 1.

(Comparative Example 2)
A polyester-based thermoplastic polyurethane having a Shore A hardness of 88 (product name: manufactured by NY988 BASF) is used as the first layer, and the same material as in Comparative Example 1 is used for the second layer. A film having a thickness of 100 μm was obtained. At that time, the layer ratio was the same as in Example 1.

(Comparative Example 3)
A single layer 150 μm thick film was obtained using the same material as that used for the first layer of Example 1.

(Comparative Example 4)
A single layer 150 μm thick film was obtained using the same material as used for the second layer of Example 1.

  Table 1 summarizes the structures of the films obtained in the above Examples and Comparative Examples and the evaluation results of the obtained films.

(Discussion)
The following is confirmed from the examples and comparative examples.
(1) The two-layer films of Examples 1 to 4 in which a high hardness layer (first layer) made of a polyester-based thermoplastic polyurethane and a low hardness layer (second layer) made of a polyester-based thermoplastic polyurethane are laminated, It is confirmed that the handling property is good. Further, it was found that the use of polyester thermoplastic polyurethane for the first layer and the second layer makes it difficult for defects occurring at the interface to occur and a multilayer thermoplastic polyurethane film having a good appearance can be obtained.
(2) The appearance of the two-layer films of Examples 1, 3, and 4 in which the layer thickness ratio of the high hardness layer (first layer) / low hardness layer (second layer) is in the range of 0.2 to 0.54. Especially good.
(3) The two-layer films of Examples 3 to 3 having a layer thickness ratio of high hardness layer (first layer) / low hardness layer (second layer) in the range of 0.18 to 0.33 have particularly good handling properties. Met.
(4) The two-layer films of Comparative Examples 1 and 2 configured using thermoplastic polyurethanes other than polyester-based materials have good handling properties, but interface failure occurs between the first layer and the second layer. And the appearance was poor.
(5) In Comparative Examples 3 and 4 configured with a single layer of polyester-based thermoplastic polyurethane, the elastic modulus was outside the desired range (6 to 10 N / mm), and handling properties were inferior.

  The polyurethane multilayer film of the present invention includes a protective film for vehicles such as automobiles, airplanes, ships, snowmobiles, trucks, trains, etc., metal plates, resin plates, painted plates, decorative steel plates, glass, liquid crystal panels, and various liquid crystals. It is suitable as a protective application in the transportation and processing of members.

DESCRIPTION OF SYMBOLS 10 Multilayer film 11 1st layer 12 2nd layer 13 Self-healing layer 14 Adhesive layer

Claims (15)

A first layer containing a polyester-based thermoplastic polyurethane (A) as a main component;
A second layer disposed on one main surface of the first layer and comprising a polyester-based thermoplastic polyurethane (B) as a main component,
The surface of the first layer has a Shore D hardness of 50 or more,
A multilayer film in which the surface hardness of the second layer is smaller than the surface hardness of the first layer.   The layer thickness ratio (first layer / second layer) between the first layer and the second layer is 0.05 to 0.6, and the total layer thickness of the first layer and the second layer is 30 to 300 μm. The multilayer film according to claim 1.   The multilayer film according to claim 1 or 2, wherein the surface of the first layer has a Shore D hardness of 50 to 60.   The multilayer film according to any one of claims 1 to 3, wherein the surface of the second layer has a Shore A hardness of 70 to 95.   The multilayer film according to claim 1, wherein the first layer and the second layer are laminated and integrated.   The multilayer film according to any one of claims 1 to 5, wherein the first layer and the second layer are laminated by coextrusion molding.   The multilayer film as described in any one of Claims 1-6 which has an adhesion layer in the surface on the opposite side to the surface where the 1st layer of a 2nd layer is arrange | positioned.   The multilayer film according to claim 7, wherein the pressure-sensitive adhesive layer contains a pressure-sensitive adhesive.   The multilayer film as described in any one of Claims 1-8 which has a self-healing layer in the surface on the opposite side to the surface where the 2nd layer of a 1st layer is arrange | positioned.   The multilayer film according to claim 9, wherein the self-healing layer is transparent or colored.   The self-healing layer is made of a soft synthetic resin selected from a polyurethane resin, an acrylic transparent rubber resin, a silicone rubber resin, an olefin elastomer, and a styrene elastomer. Multilayer film.   The multilayer film as described in any one of Claims 1-11 whose layer thickness of a 1st layer is 10-100 micrometers.   The multilayer film as described in any one of Claims 1-12 used for protection of coating.   The vehicle body part which has a coating film protected by the multilayer film as described in any one of Claims 1-13.   Co-extrusion of a molding material (A) containing a polyester-based thermoplastic polyurethane (A) constituting the first layer and a molding material (B) containing a polyester-based thermoplastic polyurethane (B) constituting the second layer The manufacturing method of the multilayer film as described in any one of Claims 1-13 containing this.