JP4739846B2 - Polyester film for automotive interior materials - Google Patents

Description

  The present invention relates to a polyester film used as a component of an automobile interior material, particularly a molded ceiling that covers the interior side of a roof of a car body of an automobile. More specifically, the present invention relates to an automobile interior material that involves drawing with a mold in a machining process, and particularly to a polyester film used for a component member of a molded ceiling of an automobile.

  In the interior of an automobile ceiling, an automobile molded ceiling is usually attached to the inside of the vehicle body ceiling outer plate to give heat insulation and decorativeness.

  As the molded ceiling, a base material made of polypropylene, hard urethane foam sheet, soft urethane foam sheet, glass fiber mat, thermosetting resin sheet material, etc., surface material made of fabric such as polyester fiber, plastic sheet or non-woven fabric In general, a laminate obtained by laminating a back material with a hot melt film is integrated and shaped by pressing with a hot press mold. Many of these molded ceilings are provided with openings called sunroofs or moon roofs.

  In automotive ceilings, the front and back materials are bright colors, and the base material is made of light-colored foam or transparent glass fibers. In addition, the hot melt film is colorless and transparent. ing. However, due to variations in the molding conditions of the molded ceiling and variations in mounting to the vehicle body, the periphery of the opening of the sunroof or moon roof or other edge portions are not completely sealed with the vehicle body outer plate, but slightly. It was inevitable that a gap was formed in the surface. Therefore, the so-called light leakage phenomenon, in which the peripheral edge or edge of the opening of the molded ceiling appears to be thinly transparent from the inside of the vehicle by external light that has entered the peripheral edge of the opening or other edge of the molded ceiling from the slight gap. Occurs and the appearance of the molded ceiling and the interior of the vehicle deteriorates.

  Therefore, in order to prevent this light leakage, before assembling the molded ceiling and before assembling, light leakage prevention tape such as black felt tape on the periphery and edge of the opening of the back of the molded ceiling where light leakage is expected to occur. Light leakage prevention work such as sticking as a cover is performed.

  However, the method by sticking the light leakage prevention tape requires an extra work of light leakage prevention work, and there is a problem that it takes not only labor but also extra material costs and equipment costs. Moreover, since the said light leakage prevention tape is affixed partially from the point of economical efficiency or workability | operativity, it is the present condition that it has not come to prevent the said light leakage reliably.

JP-A-8-1877 JP 7-68689 A JP 2003-34192 A

  The present invention has a sufficient light-shielding property without performing light leakage prevention processing by attaching a light leakage prevention tape to the periphery or edge of an opening of a sunroof or the like as a component of an automobile interior material, particularly a molded ceiling of an automobile. Another object of the present invention is to provide an automobile interior material that has sufficient rigidity and heat resistance without using a glass fiber mat, is lightweight, and has a high degree of deep drawing processability.

That is, the present invention provides a film optical density of 0.4 or more, Ri crystalline orientation degree 0.20 to 0.65 der in the thickness direction of the film, automotive interior the film thickness and wherein 50~188μm der Rukoto It is a polyester film for materials.

  The present invention has a sufficient light-shielding property without performing light leakage prevention processing by attaching a light leakage prevention tape to the periphery or edge of an opening of a sunroof or the like as a component of an automobile interior material, particularly a molded ceiling of an automobile. Another object of the present invention is to provide a polyester film for automobile interior materials, which has sufficient rigidity and heat resistance without using a glass fiber mat, and is lightweight and has a high degree of deep drawing processability.

Hereinafter, the present invention will be described in detail.
[polyester]
The polyester film for automobile interior materials of the present invention comprises a polyester film. This polyester is a general term for polymers in which a monomer residue, which is a main bond in the main chain, and a covalent bond that connects the monomer residue is an ester bond. Polyester can be obtained by polycondensation reaction of a dicarboxylic acid compound and a dihydroxy compound, or a dicarboxylic acid ester compound and a dihydroxy compound.

  Examples of the dicarboxylic acid compound include aromatics such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoterephthalic acid, and phthalic acid. Dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, and paraoxybenzoic acid and other oxycarboxylic acids Can be mentioned.

  Examples of dicarboxylic acid ester compounds include esterified products of the above dicarboxylic acid compounds, such as dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, and maleate. Examples include diethyl acid and dimethyl dimer acid.

  Examples of the dihydroxy compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexane. Aliphatic dihydroxy compounds such as diol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, alicyclic dihydroxy compounds such as cyclohexanedimethanol, and fragrances such as bisphenol A and bisphenol S Group dihydroxy compounds may be mentioned.

  Among these, as dicarboxylic acid compounds, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid or dimethyl ester compounds thereof are used, and as dihydroxy compounds, ethylene glycol, 1,3-propanediol, 1,4- Butanediol, polytetramethylene glycol, neopentyl glycol, and cyclohexanedimethanol can be preferably used.

  Polyester may be used individually by 1 type and may be used in mixture of 2 or more types. When mixing two or more types, the polymer polymerized separately in advance may be blended and melted in the state of chips, and the melted materials in separate extruders are merged to form an obvious laminated structure. Alternatively, they may be mixed with a static mixer.

  Among the polyester films made of these polyesters, those having an optical density of 0.4 or more, preferably 0.5 or more, more preferably 0.6 or more are used in the present invention. When the optical density is less than 0.4, the effect of preventing light leakage of the film is low, and the light shielding effect cannot be obtained. On the other hand, the higher the optical density is, the more effective it is for preventing light leakage. However, if it exceeds 2.0, the optical density is at most about 2.0 because it is excessively high and economically unsuitable.

  The polyester film in the present invention has a degree of crystal orientation in the thickness direction of the film of 0.20 to 0.65, preferably 0.25 to 0.55. If the degree of crystal orientation is less than 0.20, the orientation is excessively low, and the heat resistance during molding is insufficient. If it exceeds 0.65, the moldability becomes insufficient, and the film is easily cut during the drawing.

The crystal orientation in the film thickness direction is measured as follows. First, the crystal orientation index <cos ² Φ _j , 100> in three directions (longitudinal direction MD, width direction TD, thickness direction ND) of the crystal plane (100) of the film is determined using an X-ray diffractometer. Then, the crystal orientation degree fi ^{, k} is ^obtained from the following equation. In this measurement, the degree of crystal orientation in three directions is measured using a pole sample table.
f ^{i, k} = 2/3 <cos ² Φ _j , 100> −1/2
(However, i = MD, TD or ND, k = 100)

When the white pigment is titanium dioxide, the reflection peak due to the titanium dioxide particles is close to the copolyester (100) of anatase (101) and rutile (110). Assuming that the reflection peak of (100) of the polymerized polyester is due to the reflection intensity of titanium dioxide (I _TiO2 , _{α = 0} ), the intensity of all positions α and β up to 90 ° is reduced to I _TiO2 , _{α = 0} . Thus, the degree of crystal orientation is calculated.
here,
_ITiO2 , _{α = 0} = 1/2 ( _ITiO2 , _{α = 0} , _MD + _ITiO2 , _{α = 0} , _TD )
And
In the above, α is a pole sample stage, α = 90 ° represents the case where (100) is arranged in parallel to the film surface, and α = 0 ° represents the case where it is arranged perpendicular to the film surface. Further, β represents the direction in the MD and TD planes of the film, β = 0 was defined as MD, and β = 90 ° was defined as the TD direction. Note that the degree of crystal orientation is represented by the value of ND.

  The melting point of the polyester film in the present invention is preferably 200 to 270 ° C, more preferably 210 to 260 ° C, and particularly preferably 220 to 250 ° C. When the melting point is less than 200 ° C., since the heat resistance is poor, there is a possibility that fusion to the mold may occur during the molding process. Is unsuitable and not preferred. On the other hand, if the melting point exceeds 270 ° C., the productivity is inferior, which is not preferable.

The apparent density of the polyester film in the present invention is preferably 1400 to 1700 kg / m ³ , more preferably 1450 to 1650 kg / m ³ , and particularly preferably 1490 to 1600 kg / m ³ . If it is less than 1400 kg / m ³ , the heat resistance of the film is inferior, so that fusion to the mold may occur during molding, which is not preferable. If it exceeds 1700 kg / m ³ , the crystallinity of the film becomes so high that the molding processability is lowered, which is not preferable.

  The polyester film satisfying these optical density, melting point, crystal orientation degree and apparent density is, for example, a total of 25 mol% or less, preferably 5 to 20 mol% of polyethylene terephthalate or copolymer components containing fine particles. As described later, the polymerized copolymerized polyethylene terephthalate can be obtained by stretching and heat-treating under specific conditions for stretching temperature, stretching ratio, and stretching speed during stretching.

  In this case, as the copolymer component, for example, isophthalic acid or naphthalene dicarboxylic acid can be used as the dicarboxylic acid component, and for example, neopentylene glycol or cyclohexane dimethanol can be used as the diol component.

The thickness of the polyester film is preferably 12 to 250 μm, more preferably 50 to 188 μm, from the viewpoints of economy, productivity, moldability, and the like.
Polyester film may be subjected to corona discharge treatment from the viewpoint of obtaining good adhesion to other materials and laminate materials that make up automotive interior materials, especially automotive molded ceiling materials, and surface treatment by in-line coating or offline coating. May be applied.

[Fine particles]
The polyester film preferably contains fine particles in order to improve handleability, processability, and optical density. The fine particles may be any of internally precipitated fine particles, inorganic fine particles, and organic fine particles, but inorganic fine particles are preferred.

  As the inorganic fine particles, for example, wet and dry silica, colloidal silica, aluminum silicate, alumina, titanium oxide, zinc sulfide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, and clay can be used. May be titanium oxide, zinc sulfide, barium sulfate, wet and dry silica, aluminum silicate, and alumina. As the organic fine particles, for example, particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinyl compound as constituent components can be used.

  Two or more kinds of fine particles may coexist. From the viewpoint of obtaining good handleability and workability without causing defects in the film and obtaining the optical density required for the present invention, the average particle size of the fine particles is preferably 0.01 to 5 μm, more preferably The content of fine particles is preferably 3.0 to 40% by weight, more preferably 5.0 to 35% by weight.

  Various methods can be used to contain the fine particles in the present invention. For example, a method of adding before transesterification or esterification reaction at the time of polyester synthesis or adding before the start of polycondensation reaction, a method of adding to polyester and melt-kneading, a master in which a large amount of additives are added in these methods A method of producing pellets, kneading with polyester not containing particles, and adding a predetermined amount of additives can be used.

[Film Production Method]
The polyester film for automobile interior materials of the present invention can be produced, for example, as follows.
First, a polyester chip to which fine particles are added to a desired concentration is dried for 7 hours at 130 ° C. in a nitrogen atmosphere or under vacuum, and is supplied to an extruder and melted. The resin melted in the extruder is subjected to removal of foreign matters and leveling of the amount of extrusion through a filter and a gear pump, and discharged and extruded in a sheet form from a T-die onto a cooling drum to obtain an unstretched sheet. At that time, a wire electrode, a tape-like electrode or a needle-like electrode is used to apply static electricity and adhere to the cooling drum, a casting method in which a water film is provided between the cooling drum and the extruded polymer sheet, and the cooling drum temperature. The sheet-like polymer is brought into close contact with the cooling drum by a method of adhering a polymer extruded from the glass transition point of polyester to (glass transition point-20 ° C.) or a combination of these methods.

  Next, the unstretched film is biaxially stretched. Biaxial stretching may be performed by, for example, a sequential biaxial stretching method by stretching in the longitudinal direction and then stretching in the width direction, or stretching in the width direction and then stretching in the longitudinal direction. May be performed by a simultaneous biaxial stretching method in which stretching is performed almost simultaneously. The stretching ratio in the stretching is preferably 1.6 to 4.0 times, more preferably 2.4 to 3.8 times, and particularly preferably 2.8 to 3.5 times in each direction. The stretching temperature ranges from the glass transition point of the polyester to (glass transition point + 100 ° C.), preferably 80 to 170 ° C., particularly preferably 90 to 150 ° C. in the longitudinal direction and 100 to 150 in the width direction. ℃. In order to impart excellent formability to the film, it is particularly preferable that the stretching temperature in the longitudinal direction is 100 to 130 ° C., and particularly in a range where crystallization is not performed for about 1 to 100 seconds at a temperature of 100 ° C. or more before longitudinal stretching. It is preferable to stretch after preheating. If it does in this way, the outstanding flatness by uniform extending | stretching and the outstanding moldability by orientation spot suppression can be obtained.

  The polyester film thus biaxially stretched is subjected to heat treatment. The heat treatment can be performed, for example, on a heated roll in an oven. The heat treatment temperature is usually a temperature that is 30 ° C. or more lower than the melting point of the raw material. For example, when a polymer having a melting point of 256 ° C. is used as the raw material, the heat treatment temperature is less than 226 ° C. The temperature of the heat treatment is more preferably from the stretching temperature to (melting point of raw material −30 ° C.), more preferably 100 to 225 ° C., and particularly preferably 120 to 205 ° C. By setting the temperature within this range, a film excellent in molding processability and impact resistance can be obtained. When the heat treatment temperature is lower than this temperature, the heat resistance and dimensional stability may be deteriorated, which is not preferable. When the heat treatment temperature is high, the degree of crystal orientation increases and the molding processability may be deteriorated. The heat treatment time is preferably 1 to 30 seconds. This heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction. Thereafter, a corona discharge treatment may be further performed. This corona treatment is preferable in terms of improving the adhesion with other materials.

Hereinafter, the present invention will be described in more detail with reference to examples.
The physical properties of the polymer and film and the properties of the film and processed product were measured and evaluated by the following methods.

(1) Melting point (Tm) of polyester film
About 20 mg of polyester film was measured with a differential scanning calorimeter (Du Pont Instruments 910 DSC) at a heating rate of 20 ° C./min, and the endothermic peak temperature was defined as the melting point (Tm).

(2) Crystal orientation in the film thickness direction Three directions (longitudinal direction MD, width direction TD, thickness direction ND) of the crystal plane (100) of the film using an X-ray diffractometer (ROTAFLEX RINT2500HL manufactured by Rigaku Corporation) ) Crystal orientation index <cos ² Φ _j , 100> and the crystal orientation degree f ^{i, k} was obtained from the following equation.
f ^{i, k} = 2/3 <cos ² Φ _j , 100> −1/2
(However, i = MD, TD or ND, k = 100)
The crystal orientation in the three directions was measured using a pole sample table (Rigaku Denki Multipurpose Sample Table).
In the measurement, when the white pigment is titanium dioxide, the reflection peak due to the titanium dioxide particles is close to the copolyester (100) of anatase (101) and rutile (110), so α = 0 in the pole figure. Assuming that the reflection peak of (100) of the copolyester is due to the reflection intensity of titanium dioxide (I _TiO2 , _{α = 0} ), the intensity at all positions α and β up to α = 90 ° is _expressed as I _TiO2 , _{α = 0} . The degree of crystal orientation was calculated by subtracting.
here,
_ITiO2 , _{α = 0} = 1/2 ( _ITiO2 , _{α = 0} , _MD + _ITiO2 , _{α = 0} , _TD )
It was.
Here, α is a pole sample stage, α = 90 ° represents the case where (100) is arranged in parallel to the film surface, and α = 0 ° represents the case where it is arranged perpendicular to the film surface. Further, β represents the direction in the MD and TD planes of the film, β = 0 was defined as MD, and β = 90 ° was defined as the TD direction. The degree of crystal orientation was represented by the value of ND.

(3) Optical density V (Visual) optical density in the three primary colors of the film sample was measured using an optical densitometer (TR-310 type manufactured by X-Rite).

(4) Apparent density 10 cm × 10 cm taking the size of the sample, and measuring the thickness of the試科a micrometer, determine the volume of the sample, then measuring the weight of試科, calculate the weight per 1 m ³ did. The number of samples was five, and the average value was the apparent density.

(5) Formability Vacuum forming was performed using a headliner mold. First, a polyester film and a plate-shaped urethane foam for thermoforming (thickness 5 mm, specific gravity 0.035) were dry laminated by an ordinary method using an epoxy adhesive to prepare a two-layer structure. The resulting structure was heated so that the polyester film would be on the mold side and both edge portions were gripped with clips while the surface temperature was 170 ° C., and the depth of the concave curved portion was 1800 mm × 1400 mm wide. A 50 mm thick automobile ceiling material was molded. The appearance was evaluated by visually confirming that wrinkles and blisters did not occur and that the shape followed the shape of the mold, and the moldability was determined according to the following criteria.
○: The thickness of the ceiling material is uniform and the appearance is good.
Δ: The thickness of the ceiling material is uneven or part of the appearance is defective.
X: Some of the ceiling material has cracks or the whole does not follow the mold.

[Examples 1 to 4 and Comparative Examples 1 to 5]
Using dimethyl terephthalate, ethylene glycol, and the copolymer components shown in Table 1, tetrabutoxy titanium and germanium dioxide were used as polymerization catalysts, and orthophosphoric acid was used as a stabilizer, and an intrinsic viscosity (o-chlorophenol, 35 C.) A polyester composition of 0.67 was produced. This polyester contained titanium oxide as shown in Table 1, and 0.06% by weight of true spherical silica having an average particle size of 1.7 μm.

  After drying the above polyester at 160 ° C. for 4 hours, it is supplied to an extruder hopper, melted at a melting temperature of 275 ° C., extruded onto a cooling drum having a surface temperature of 20 ° C. using a die, and rapidly cooled to obtain an unstretched film. It was. This unstretched film was longitudinally stretched under the conditions shown in Table 1, and then supplied to a stenter for transverse stretching, followed by heat setting while relaxing 3% to obtain a biaxially stretched polyester film. In Example 3 and Comparative Example 1, homopolyethylene terephthalate was used as a raw material.

  The properties of the obtained stretched polyester film are shown in Table 1. In Comparative Example 1 and Comparative Example 2, the heat setting temperature was too high, so that the degree of crystal orientation increased and the molding processability was poor. In Comparative Example 3, since the melting point and the heat setting temperature were too low, the degree of crystal orientation was lowered and the heat resistance at the time of molding was poor. In Comparative Example 5, the amount of particles added was too high, so that cutting occurred frequently in the stretching process, and a stretched film could not be collected. In Comparative Example 4, the optical density is too low because the amount of particles added is small, so that a complicated work such as applying a black felt tape after molding the molded ceiling as described in the section of the prior art must be performed. The leakage was inferior.

  The polyester film for automobile interior materials of the present invention has sufficient concealability and rigidity, is light and can be easily molded, and can be suitably used as an automobile interior material. In particular, when it is used as a core material for a molded ceiling of an automobile, it is possible to omit the work of preventing light leakage, which has conventionally required complicated mounting.

  For example, in the structure of the film / urethane foam / nonwoven fabric layer of the present invention or the film / nonwoven fabric layer of the present invention, a laminate is obtained by thermal lamination or dry lamination with an adhesive, and this is deep-drawn with a mold. It is possible to obtain an automobile interior material having a sufficient concealing property, particularly a molded ceiling of an automobile. Furthermore, in this molding, since the conventional film can be processed so as to break without causing any defects, the film of the present invention can provide sufficient rigidity without using a glass fiber mat. And can be used as an interior material for automobiles having excellent environmental suitability.

  The polyester film for automobile interior materials according to the present invention can produce a lightweight automobile interior material that has excellent concealability and mechanical properties, and is also useful for reducing environmental load, such as easy disposal and recycling. .

Claims (3)

Film optical density 0.4 above, Ri degree of crystal orientation in the thickness direction from 0.20 to 0.65 der film, a polyester film for automobile interior material film thickness and wherein 50~188μm der Rukoto.   The polyester film for automobile interior materials according to claim 1, wherein the melting point of the film is 200 to 270 ° C. The polyester film for automobile interior materials according to claim 1, wherein the apparent density is 1400 to 1700 kg / m ³ .