KR20260020375A - Automobile interior material comprising composite having reduced cell size - Google Patents

Abstract

The present invention relates to an automotive interior material using a composite material with a reduced cell size, comprising: a foam layer having a cell size of 400 ㎛ or less and a density of 500 kg/㎥ or less; a surface layer laminated on one side of the foam layer; and a back layer laminated on the other side of the foam layer, wherein lamination of the foam layer and the surface layer and lamination of the foam layer and the back layer are each independently performed through an extrusion coating layer, a hot melt adhesive film, or flame lamination, and the automotive interior material has a total thickness of 3 mm or more.

Description

Automobile interior material comprising composite having reduced cell size

The present invention relates to an automobile interior component using a composite material with a reduced cell size.

Automotive interior materials typically use PP (Poly Propylene) boards, natural fiber-reinforced boards (HS Felt), glass fiber PP boards, and PU (Poly Urethane) foam as substrates, while PET nonwoven fabrics are used for surface and backing materials. Composite materials, which combine the substrate and surface materials, are then molded into automotive parts. Recently, with the eco-friendly trend, there has been a growing need for lightweight materials that improve fuel efficiency and recyclable single-material solutions.

Automotive interior materials typically use foam layers as a substrate for weight reduction. A single material can be manufactured by combining a PET foam layer substrate with PET nonwoven fabric. For example, automotive interior components such as luggage sides, headliners, and underbody components require properties such as breakability, deep formability, flexural strength, sound absorption, and heat resistance.

Accordingly, the purpose of the present invention is to provide a lightweight automobile interior material having excellent physical properties such as breakability, formability, flexural strength, sound absorption, and heat resistance.

In order to achieve the above-described object, the present invention provides an automobile interior material comprising: a foam layer having a cell size of 400 ㎛ or less and a density of 500 kg/㎥ or less; a surface layer laminated on one surface of the foam layer; and a back layer laminated on the other surface of the foam layer, wherein lamination of the foam layer and the surface layer and lamination of the foam layer and the back layer are each independently performed through an extrusion coating layer, a hot melt adhesive film, or flame lamination, and the total thickness is 3 mm or more.

In the present invention, the foam layer can be formed of a foaming composition including a polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener.

In the present invention, the intrinsic viscosity (IV) of the PET resin may be 0.7 ㎗/g or more.

In the present invention, the PET resin may be a PET resin in which the proportion of molecules having a molecular weight of 10,000 or more, as indicated by a differential molecular weight distribution, accounts for 60 wt% or more of the total weight of the PET resin.

In the present invention, the size of the nucleating agent may be 10 μm or less.

In the present invention, the content of the nucleating agent may be 1 to 10 parts by weight based on 100 parts by weight of PET resin.

In the present invention, the content of the thickener may be 0.3 to 10 parts by weight based on 100 parts by weight of PET resin.

In the present invention, the surface layer and the back layer may each be PET nonwoven fabric, and the extrusion coating layer may be a PET coating layer.

In the present invention, the basis weight of the surface layer may be 100 to 1000 g/㎡, the basis weight of the back layer may be 10 to 500 g/㎡, and the thickness of the extrusion coating layer may be 50 to 200 ㎛.

In the present invention, the surface layer and the back layer may include PET having a melting temperature of 200°C or higher and low-melting point PET having a melting temperature of less than 200°C.

The automobile interior material according to the present invention may additionally include a reinforcing layer at least one of between the surface layer and the extrusion coating layer and between the back layer and the extrusion coating layer.

In the present invention, the crystallinity of the foam layer may be 20% or more, and the ratio of the major axis length/minor axis length of the cells of the foam layer may be 20 or less.

The maximum bending load of the automobile interior material according to the present invention may be 10 N or more.

The sound absorption coefficient of the automobile interior material according to the present invention may be greater than 0.2 at 2000 Hz and greater than 0.3 at 6000 Hz.

In addition, the present invention provides a method for forming an automobile interior material by cold forming a composite material having the above-described laminated structure under the conditions of a heater temperature of 200°C or higher, a heater residence time of 90 seconds or higher, a composite surface temperature of 150°C or higher, a press gap of 3 mm or higher, a press temperature of 40°C or lower, and a press time of 20 seconds or higher.

The automobile interior material according to the present invention can provide a foam layer having a small cell size and a low density by using a size and content of a nucleating agent, a content of a thickener, and a viscosity and molecular weight distribution of a resin within a specific range, and can also provide an automobile interior material having excellent properties such as breakage resistance, moldability, flexural strength, sound absorption, and heat resistance by using a specific laminated structure, material, lamination method, and molding conditions.

Figure 1 illustrates a laminated structure of a composite material for automotive interior materials according to one embodiment of the present invention.
Figure 2 illustrates a laminated structure of a composite material for automotive interior materials according to another embodiment of the present invention.
Figure 3 is a cross-sectional view of an automobile interior material according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

Referring to FIG. 1, a composite material (10) for automotive interior materials according to one embodiment of the present invention may be sequentially composed of a back layer (11), a foam layer (12), an extrusion coating layer (13), and a surface layer (14) from below. Specifically, the surface layer (14) is laminated on one side of the foam layer (12), the back layer (11) is laminated on the other side of the foam layer (12), the foam layer (12) and the surface layer (14) are bonded by the extrusion coating layer (13), and the foam layer (12) and the back layer (11) can be directly melt-bonded.

The laminated structure and lamination (or lamination or adhesion or bonding) method of FIG. 1 are only one embodiment, and the lamination of the foam layer (12) and the surface layer (14) and the lamination of the foam layer (12) and the back layer (11) are not limited to FIG. 1. Specifically, the lamination of the foam layer (12) and the surface layer (14) and the lamination of the foam layer (12) and the back layer (11) can each be independently achieved through an extrusion coating layer (13), a hot melt adhesive film, or flame lamination. For example, both the lamination of the foam layer (12) and the surface layer (14) and the lamination of the foam layer (12) and the back layer (11) can be achieved through an extrusion coating layer (13), and also both can be achieved through flame lamination.

The foam layer (12) is a base material of the composite material (10) and is characterized by having a small cell size and low density.

The cell size of the foam layer (12) may be 400 μm or less, 350 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. The lower limit of the cell size may be, for example, 50 μm or more, 80 μm or more, or 100 μm or more. The cell size may mean an average cell size, and specifically, may mean an average value of the major axis length and the minor axis length of the cell.

The density of the foam layer (12) may be 500 kg/㎥ or less, 450 kg/㎥ or less, 400 kg/㎥ or less, 350 kg/㎥ or less, 300 kg/㎥ or less, 250 kg/㎥ or less, or 200 kg/㎥ or less. The lower limit of the density may be, for example, 50 kg/㎥ or more, 100 kg/㎥ or more, or 150 kg/㎥ or more.

The thickness of the foam layer (12) may be 15 mm or less, 12 mm or less, 10 mm or less, 8 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, or 3 mm or less. The lower limit of the thickness may be, for example, 0.5 mm or more, 1 mm or more, 1.5 mm or more, 2 mm or more, or 2.5 mm or more.

The surface roughness Ra of the foam layer (12) may be 2 µm or less, 1.8 µm or less, 1.6 µm or less, or 1.4 µm or less. The lower limit of the surface roughness Ra may be, for example, 0.5 µm or more, 0.8 µm or more, or 1 µm or more. The surface roughness may be a centerline surface roughness.

The elongation of the foam layer (12) at 200°C for 60 seconds may be 300% or more, 350% or more, 400% or more, 450% or more, or 500% or more. The upper limit of the elongation may be, for example, 700% or less, 650% or less, 600% or less, or 550% or less. The elongation at 200°C for 60 seconds may refer to the elongation measured after allowing the sample to remain at a temperature of 200°C for 60 seconds.

The maximum bending load of the foam layer (12) may be 5 N or more, 6 N or more, 7 N or more, 8 N or more, or 9 N or more. The upper limit of the maximum bending load may be, for example, 15 N or less, 14 N or less, 13 N or less, or 12 N or less.

The foam layer (12) can be formed from a foam composition containing polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener. By using PET resin, it is environmentally friendly and can be easily reused.

The intrinsic viscosity (IV) of the PET resin may be 0.7 ㎗/g or more, 0.72 ㎗/g or more, 0.74 ㎗/g or more, 0.76 ㎗/g or more, 0.78 ㎗/g or more, or 0.8 ㎗/g or more. The upper limit of the intrinsic viscosity may be, for example, 1.0 ㎗/g, 0.95 ㎗/g, 0.9 ㎗/g, 0.85 ㎗/g, or 0.82 ㎗/g. Preferably, the intrinsic viscosity (IV) of the PET resin may be 0.76 to 0.82 ㎗/g. When the intrinsic viscosity is low, low-density foaming may be difficult, cell size and surface roughness may increase, and stretchability may be reduced.

The melting point of the PET resin may be 250°C or higher, 252°C or higher, 254°C or higher, or 256°C or higher. The upper limit of the melting point may be, for example, 300°C, 290°C, 280°C, 270°C, or 260°C.

The weight average molecular weight (Mw) of the PET resin may be 20,000 to 200,000, preferably 50,000 to 150,000, and more preferably 60,000 to 100,000. The weight average molecular weight can be measured by gel permeation chromatography (GPC, analysis equipment HLC-8320), and polymethyl methacrylate (PMMA) can be used as a standard sample. The molecular weight unit can be g/mol or Da.

The PET resin may be a PET resin in which the proportion of molecules having a molecular weight of 10,000 or more, expressed by a differential molecular weight distribution, accounts for 60 wt% or more of the total weight of the PET resin. That is, the proportion of molecules having a molecular weight of 10,000 or more in the PET resin may be 60 wt% or more, and the proportion of molecules having a molecular weight of less than 10,000 may be less than 40 wt%. The proportion of molecules having a molecular weight of 10,000 or more may be preferably 65 wt% or more, more preferably 70 wt% or more. The upper limit of the proportion of molecules having a molecular weight of 10,000 or more may be, for example, 100%, 95%, 90%, 85%, 80%, or 75%. If the proportion of molecules having a molecular weight of 10,000 or more is low, the maximum bending load may decrease. The proportion of molecules having a molecular weight of less than 10,000 may be preferably less than 35 wt%, more preferably less than 30 wt%. The lower limit of the abundance of molecules having a molecular weight of less than 10,000 may be, for example, 0%, 5%, 10%, 15%, 20%, or 25%.

Differential molecular weight distribution is a method of expressing the molecular weight distribution of a polymer substance using a differential molecular weight distribution curve. A differential molecular weight distribution curve is a curve that expresses the quantity representing the number of grams of a substance with a molecular weight M in 1 g of a substance as a function of M.

Particularly preferably, the PET resin may be a PET resin that satisfies the above properties simultaneously, that is, has an intrinsic viscosity (IV) of 0.7 ㎗/g or more, a melting point of 250°C or more, a weight average molecular weight of 20,000 or more, and a proportion of molecules having a molecular weight of 10,000 or more expressed by a differential molecular weight distribution of 60 wt% or more based on the total weight of the PET resin.

Nucleating agents are added to control cell size, etc., and examples of nucleating agents include inorganic compounds such as talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, sodium bicarbonate, and glass beads. Preferably, talc can be used as the nucleating agent.

The content of the nucleating agent may be 1 to 10 parts by weight, preferably 2 to 7 parts by weight, and more preferably 3 to 5 parts by weight, based on 100 parts by weight of PET resin. If the content of the nucleating agent is low, the cell size and surface roughness may increase, and the maximum bending load and elongation may decrease.

The size of the nucleating agent may be 10 μm or less, 8 μm or less, 6 μm or less, 4 μm or less, or 3 μm or less. The lower limit of the nucleating agent size may be, for example, 0.1 μm or more, 0.5 μm or more, or 1 μm or more. A larger nucleating agent size may increase the cell size and surface roughness and reduce the ductility. The size of the nucleating agent may refer to an average size, and specifically, may refer to an average value of the major axis length and the minor axis length of the nucleating agent.

A thickener is added to control the melt viscosity of the foam composition, etc., and examples of thickeners that can be used include pyromellitic dianhydride (PMDA), epoxy, etc.

The content of the thickener may be 0.3 to 10 parts by weight, preferably 1 to 5 parts by weight, and more preferably 2 to 3 parts by weight, based on 100 parts by weight of PET resin. If the content of the thickener is low, foaming may not occur properly, and the density, cell size, and surface roughness may increase.

A foaming agent is added to foam the composition and control the density of the foam layer (12), and for example, gases such as N ₂ , CO ₂ , and Freon; physical foaming agents such as butane, pentane, neopentane, hexane, isohexane, heptane, isoheptane, and methyl chloride; and chemical foaming agents such as azodicarbonamide-based compounds, P,P'-oxybis(benzenesulfonylhydrazide)-based compounds, and N,N'-dinitrosopentamethylenetetramine-based compounds can be used.

The content of the foaming agent may be 0.1 to 5 parts by weight, preferably 0.5 to 4 parts by weight, and more preferably 1 to 3 parts by weight, based on 100 parts by weight of PET resin.

In addition, the raw material of the foam layer (12) may additionally include a surfactant, a UV blocker, a hydrophilizing agent, a flame retardant, a heat stabilizer, a waterproofing agent, a cell size expander, an infrared attenuator, a plasticizer, a fire retardant chemical, a pigment, an elastic polymer, an extrusion aid, an antioxidant, a filler, an anti-foaming agent, a UV absorber, etc. for the purpose of imparting a hydrophilizing function, a waterproofing function, a flame retardant function, a UV blocking function, etc.

The foam layer (12) can be formed through bead foaming or extrusion foaming. Bead foaming is a method of heating beads to foam them first, allowing them to mature for an appropriate period of time, filling them into a mold such as a plate or cylinder, heating them again, and fusing and molding them through secondary foaming to create a product. Extrusion foaming simplifies the process steps by continuously extruding and foaming a resin melt, enabling mass production, and preventing cracks and granular destruction between beads during bead foaming, thereby realizing superior compressive strength.

Preferably, the foam layer (12) can be manufactured using extrusion foaming and a circular die. By extrusion foaming with a circular die, a foam layer (12) having smooth surfaces on both the upper and lower surfaces can be obtained.

Meanwhile, when extruded and foamed using a slit-shaped die, a board-type foam having a thickness of 5 mm or more is formed. When the foam board is cut to a thickness of less than 5 mm, at least one surface may have traces of cell cutting, preventing a smooth surface.

In this way, the foam layer (12) according to the present invention can provide a foam layer (12) having a small cell size, low density, and thin thickness by using a size and content of a nucleating agent, a content of a thickener, and a viscosity and molecular weight distribution of a resin within a specific range, thereby improving the physical properties of the foam layer (12) such as breakability and stretchability.

The foam layer (12) may have closed cells. Having closed cells means that more than 90% of the cells in the foam layer (12) are closed cells (DIN ISO4590). For example, the percentage of closed cells in the foam layer (12) may be 90 to 100%, 95 to 100%, 97 to 100%, or 99 to 100%. By having closed cells within this range, excellent lightness, durability, and rigidity can be satisfied.

The back layer (11) and the surface layer (14) may each be PET nonwoven fabric, and the extrusion coating layer (13) may be a PET coating layer. In this way, the entire layers of the back layer (11), the foam layer (12), the extrusion coating layer (13), and the surface layer (14) constituting the composite material (10) may all be made of PET material.

The type of nonwoven fabric used for the back layer (11) and the surface layer (14) is not particularly limited, but a needle-punched nonwoven fabric can be used when considering sound insulation and sound absorption performance and prevention of delamination between layers. In the needle-punching process, the penetration depth of the needle can be 7 to 13 mm, the inlet speed can be 3.0 to 5.0 m/min, and the outlet speed can be 3.5 to 6.0 m/min. Within these condition ranges, damage to the needles does not occur, and an automobile interior material having good sound insulation and sound absorption performance can be provided. The needle density can be 5000 to 8000 needles/㎡. If the needle density is denser than this, it may be difficult to penetrate multiple layers, and if the needle density is lower, the process efficiency may be reduced.

The maximum point load of the nonwoven fabric of the back layer (11) and the surface layer (14) may be 200 to 1000 N, 350 to 750 N, 550 to 750 N, or 300 to 400 N in the machine direction (MD), and may be 200 to 1200 N, 300 to 1000 N, 800 to 1100 N, or 300 to 400 N in the cross direction (CD). The maximum point stress may be 1 to 8 N/mm2, or 2 to 6 N/mm2 in the machine direction (MD), and may be 1 to 8 N/mm2, or 2 to 7 N/mm2 in the cross direction (CD). The elongation may be from 30 to 100%, or from 40 to 80%, in the machine direction (MD), and from 30 to 200%, or from 40 to 160%, in the cross direction (CD).

The surface layer (14) is the visible surface of the interior material when the interior material is installed on the floor of the vehicle, etc., and thus, a nap may be formed on the surface to provide a soft feel when the driver's or passenger's feet or hands or other body parts come into contact with it. In addition, since the surface layer (14) should provide a cushioning feeling rather than a hard feeling to the driver or other person, it is preferable to have elasticity to reduce the impact when an item is dropped on the interior floor. To provide elasticity, the surface layer (14) may be used such that the PET fibers maintain a gap between each other and are not tightly adhered.

The weight (weight per unit area) of the surface layer (14) may be 100 to 1000 g/m2, 200 to 900 g/m2, 250 to 800 g/m2, 300 to 700 g/m2, 350 to 600 g/m2, 400 to 500 g/m2, 100 to 300 g/m2, or 150 to 200 g/m2.

The back layer (11) has the function of absorbing and insulating noise generated while the vehicle is running, and also functions as a bonding layer that is positioned at the bottom of the interior material and bonded to the foam layer (12) positioned at the top. The back layer (11) is made of a single PET material, which can improve the recyclability, and by integrating the sound-absorbing and insulating materials to form a sound-absorbing and insulating layer, the weight reduction rate can be improved.

The nonwoven fibers of the back layer (11) may have a fineness of 3 to 15 denier and a length of 51 to 64 mm. The basis weight of the back layer (11) may be 10 to 500 g/m2, 20 to 400 g/m2, 30 to 300 g/m2, 40 to 250 g/m2, or 50 to 200 g/m2.

The backing layer (11) and the foam layer (12) can be directly melt-bonded without the intervention of another layer, such as an adhesive layer. This melt-bonding can be performed, for example, by a method such as flame lamination. In addition, the lamination of the backing layer (11) and the foam layer (12) can be achieved through an extrusion coating layer (13) or a hot melt adhesive film.

In addition, the surface layer (14) and the back layer (11) may include PET high-melting fibers having a melting temperature of 200°C or higher, and low-melting fibers made of PET having a melting temperature of less than 200°C. For example, the surface layer (14) and the back layer (11) may include 50 to 90 wt% of PET high-melting fibers and 10 to 50 wt% of PET low-melting fibers. If the amount of low-melting fibers is small, it may be difficult to have a bonding force, and if it is too large, the amount of high-melting fibers may decrease, which may lower the strength.

Low-melting point fibers that can be used in the surface layer (14) and the back layer (11) have a melting point in the range of 110 to 180°C. When a plurality of layers forming the interior material are laminated and preheated for molding, the low-melting point fibers can melt and flow between the high-melting point fibers to perform the function of bonding the high-melting point fibers.

The extrusion coating layer (13) refers to a layer in which a molten resin layer extruded from a T-die is coated on the foam layer (12) (or surface layer (14)) and, at the same time, the surface layer (14) (or foam layer (12)) is laminated on top of it to bond the foam layer (12) and the surface layer (14) in a sandwich manner. The extrusion coating layer (13) enables deep drawing when cold forming is performed and prevents peeling of the surface layer (14) and the foam layer (12). In addition, it plays a role in improving sound insulation performance.

In addition, the lamination of the foam layer (12) and the surface layer (14) can be achieved through a hot melt adhesive film or flame lamination in addition to the extrusion coating layer (13).

The thickness of the extrusion coating layer (13) may be 50 to 200 ㎛, 80 to 190 ㎛, 100 to 180 ㎛, 120 to 170 ㎛, or 140 to 160 ㎛. The basis weight of the extrusion coating layer (13) may be 50 to 1000 g/m2, 100 to 800 g/m2, 100 to 600 g/m2, or 100 to 400 g/m2. Within this range, weight reduction and molding processability can be secured. The crystallinity of the extrusion coating layer (13) may be 5 to 10%. If the crystallinity is too low, the strength of the final molded product may be low, and if the crystallinity is too high, the moldability may be poor.

Referring to FIG. 2, a composite material (20) according to another embodiment of the present invention may be sequentially composed of a back layer (21), a foam layer (22), an extrusion coating layer (23), a reinforcing layer (25), and a surface layer (24) from below. Specifically, the surface layer (24) is laminated on one side of the foam layer (22), the back layer (21) is laminated on the other side of the foam layer (22), the foam layer (22) and the surface layer (24) are bonded by the extrusion coating layer (23), and the foam layer (22) and the back layer (21) may be directly melt-bonded.

The lamination of the foam layer (22) and the surface layer (24) and the lamination of the foam layer (22) and the back layer (21) are not limited to FIG. 2. Specifically, the lamination of the foam layer (22) and the surface layer (24) and the lamination of the foam layer (22) and the back layer (21) can each be independently achieved through an extrusion coating layer (23), a hot melt adhesive film, or flame lamination. For example, the lamination of the foam layer (22) and the surface layer (24) and the lamination of the foam layer (22) and the back layer (21) can both be achieved through an extrusion coating layer (23), and can also both be achieved through flame lamination.

The back layer (21), foam layer (22), extrusion coating layer (23), and surface layer (24) are the same as those described above in Fig. 1, and thus a detailed description thereof will be omitted. The reinforcing layer (25) may be a PET latex coating layer, and may maintain the stability of the fibers of the surface layer (24) and provide sound absorption and cushioning. The basis weight of the reinforcing layer (25) is preferably in the range of 50 to 200 g/㎡.

PET latex coating layers can be manufactured by injecting air into a suspension containing PET to form a foam, coating the foam on a surface layer, and then drying it. The process for manufacturing PET latex is described, for example, in Korean Patent Publication No. 2299625.

In addition, the present invention provides a method for manufacturing a composite including a back layer, a foam layer, and a surface layer, wherein the method may include the steps of forming a foam layer having closed cells; laminating the foam layer and the surface layer through an extrusion coating layer, a hot melt adhesive film, or flame lamination; and laminating the foam layer and the back layer through an extrusion coating layer, a hot melt adhesive film, or flame lamination.

The step of forming a foam layer may include a step of preparing a resin melt by mixing PET resin, a nucleating agent, a thickener, a foaming agent, etc.; and a step of extruding and foaming the resin melt using an extruder.

The step of preparing the resin melt can be performed at a temperature of 260 to 300°C. In addition, the PET resin can be in the form of pellets, granules, beads, chips, etc., and in some cases, can be in the form of powder.

The extrusion and foaming step can be performed by cooling the foamable melt to 220 to 260°C to facilitate foaming, and then passing the cooled foamable melt through a die. Additionally, the formed foam sheet can be cooled using a mandrel and an air ring to maintain its shape. The foaming temperature can be 225 to 280°C, 225 to 275°C, or 225 to 265°C.

The step of forming an extrusion coating layer between the foam layer and the surface layer or the foam layer and the back layer and laminating the foam layer and the surface layer or the foam layer and the back layer can be performed using a known method. For example, the extrusion coating can be performed by extruding PET between the foam layer and the surface layer or the foam layer and the back layer using a T-die, and then laminating the foam layer and the surface layer or the foam layer and the back layer. The extrusion temperature can range from 260 to 380°C, and the thickness of the extrusion coating layer can be 50 to 200 μm. In order to uniformly coat, it is preferable to sufficiently dry the PET before putting it into the extrusion cylinder.

The step of bonding the foam layer and the surface layer, or the foam layer and the back layer, using flame lamination can also be performed using a known method. For example, the interface between the foam layer and the surface layer, or the foam layer and the back layer, can be bonded through a flame lamination process having a flame temperature of 700 to 1000°C and a calorific value of 15,000 to 70,000 kcal.

One surface of the foam layer and the surface layer or the foam layer and the back layer is heated with a laminating flame generator to make the interface into a molten state, and then the bonding force at this time can be used to bond and heat-fuse the interface of the foam layer and the surface layer or the foam layer and the back layer. When bonding the foam layer and the surface layer or the foam layer and the back layer through a flame lamination process using a flame generator, the peeling force between the interfaces can be improved compared to the method of bonding the interfaces using an adhesive film, and the cost can be reduced and the weight can be reduced because another adhesive layer is not used. In particular, when the coating amount of the extruded coating layer is low, it is necessary to appropriately control the flame height and winding speed in order to prevent delamination between the interfaces.

The present invention also provides an automotive interior material using the composite material described above. The automotive interior material may include, but is not limited to, a luggage partition, a luggage side, a luggage board, a package tray, a headliner, or an underbody.

Referring to Fig. 3, the automotive interior material (30) is a molded product, particularly a cold molded product, processed from a composite material (31) according to the present invention having a predetermined thickness (T). The molded automotive interior material may have one or more recessed portions (32). The recessed portions (32) may have various depths, and the distance to the deepest point thereof may be defined as the maximum depth (D). In one specific example, the automotive interior material of the present invention may satisfy the following general formula 1.

[General Formula 1]

D/T > 3

In the above formula, D represents the maximum depth of the concave portion formed in the automobile interior material, and T represents the thickness of the automobile interior material.

The above D/T may be 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more. The larger the value, the deeper the concave portion can be formed, which means that deep drawing forming is possible.

The overall thickness of the automotive interior material may be 3 mm or more, 3.5 mm or more, 4 mm or more, 4.5 mm or more, or 5 mm or more. The upper limit of the overall thickness may be, for example, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, or 6 mm or less.

The crystallinity of the foam layer of the automotive interior material may be 20% or more, 22% or more, 24% or more, or 26% or more. The upper limit of the crystallinity may be, for example, 40% or less, 35% or less, 30% or less, or 28% or less. Excellent strength can be provided within the above range.

The ratio of the major axis length/minor axis length of the cells of the foam layer of the automobile interior material may be 20 or less, 15 or less, 10 or less, 8 or less, or 6 or less. The lower limit of the ratio may be, for example, 1 or more, 2 or more, 3 or more, or 4 or more. If the clearance of the mold is low, the ratio may be increased due to compression.

The maximum flexural load of the automotive interior material may be 10 N or more, 11 N or more, 12 N or more, 13 N or more, 14 N or more, or 15 N or more. The upper limit may be 40 N or less, 35 N or less, 30 N or less, 25 N or less, or 20 N or less. The tensile strength (MS341-19 4.4) of the automotive interior material may be 25 kgf/cm2 or more in the MD direction, for example, 30 to 50 kgf/cm2.

The sound absorption coefficient of the automotive interior material may be greater than 0.2, greater than 0.21, greater than 0.22, greater than 0.23, greater than 0.24, or greater than 0.25 at 2000 Hz, and the upper limit may be 0.4 or less, 0.35 or less, or 0.3 or less. The sound absorption coefficient of the automotive interior material may be 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more at 6000 Hz, and the upper limit may be 1 or less, 0.9 or less, or 0.8 or less.

In addition, the present invention provides a method for manufacturing an automobile interior material, the method including the steps of preheating a composite material; and cold-forming the preheated composite material using a mold.

The step of preheating the composite can be performed using a heater having heating sources at the top and bottom. The step of preheating can be performed, for example, by adjusting the heating sources at the top and bottom to 200 to 400°C, or 250 to 350°C, and heating for about 90 to 300 seconds, or 150 to 250 seconds, thereby controlling the surface temperature of the composite to be about 150 to 250°C.

The step of cold forming using a mold can be performed by controlling the temperature of the mold at room temperature, for example, 10 to 40°C, and applying pressure for about 20 to 60 seconds to form it into a desired shape.

Preferably, a composite having the above-described laminated structure can be cold-formed under the following conditions: a heater temperature of 200°C or higher, a heater residence time of 90 seconds or higher, a composite surface temperature of 150°C or higher, a press gap of 3 mm or higher, a press temperature of 40°C or lower, and a press time of 20 seconds or higher. Here, the press gap refers to a mold press gap or a mold gap.

The conditions for cold forming with low press temperature may be specifically a heater temperature of 300±50℃, a heater residence time of 160±30 seconds, a composite surface temperature of 190±30℃, a press gap of 3.5±1 mm, a press temperature of 20±10℃, and a press time of 40±20 seconds.

In this way, in the present invention, by applying a foam layer with a reduced cell size, breakability can be improved, by laminating nonwoven fabric on both sides of the foam layer, ductility (30 cm deep formability) can be excellent, and by applying flame lamination and coating lamination, flexural strength can be improved.

In addition, in the present invention, by setting the mold gap to about 3.5 to 5 mmT, the flexural strength can be improved, the cell size can be maintained (the major axis/minor axis ratio can be 20 or less), the cell shape is maintained, so the flexural strength is excellent, and the thickness is maintained, so the sound absorption is excellent.

In addition, the automobile material according to the present invention is lightweight (40% lighter than existing polypropylene (PP) products) while having excellent rigidity and superior sound absorption (especially in the high-frequency range) compared to existing PP products.

Hereinafter, the present invention will be described in more detail by way of examples.

[Examples and Comparative Examples]

1. PET foam layer

Foam layers of examples and comparative examples having the properties described in Tables 1 and 2 were manufactured by extrusion foaming using the compositions described in Tables 1 and 2.

2. Composite materials

Composites having each layer composition and bonding method in Tables 3 and 4 were manufactured.

The surface layer and back layer each used needle-punched nonwoven fabric. The needle-punched nonwoven fabric was manufactured by passing a PET fiber web through a pair of bed plates and interlocking the PET fibers through needles mounted on a needle board that reciprocates up and down. In addition, a PET latex coating layer was formed as a reinforcing layer on the surface layer nonwoven fabric.

The manufactured surface layer and foam layer were bonded with a PET extrusion coating layer. For extrusion coating, PET was dried at 150°C for more than 4 hours, and then the dried PET was sequentially fed into an extrusion cylinder controlled at 280 to 330°C and extruded through a T-die.

A multilayer composite was manufactured by bonding a backing layer to the back of a foam layer to which a surface layer was bonded using a flame lamination device including three individually driven lamination rollers, two flame treatment sections, and a gap control device (conditions: flame height 1.8 to 2.5 mm, flame amount 130 to 210 g/㎥, gap 2.5 to 2.6 mm, line speed 30 to 40 m/min).

3. Plastic surgery

By molding the composite using the heater and press conditions of Tables 5 and 6, composite molded products (automotive interior materials) of the examples and comparative examples having the properties described in Tables 5 and 6 were obtained.

The methods for measuring each property are as follows.

(1) Intrinsic viscosity (IV)

The intrinsic viscosity was measured at 35°C using an Ubbelohd viscometer by dissolving the sample in a mixed solution of phenol and tetrachloroethane (mixing ratio = 1:1 by volume) at a concentration of 0.5 wt%.

(2) Molecular weight

The molecular weight was measured by dissolving the sample in a mixed solution of chloroform and phenol (mixing ratio = 1:1 by volume) and using gel permeation chromatography (GPC, analytical equipment HLC-8320) at 254 nm. PMMA was used as the standard sample.

(3) Density

Density was measured under KS M ISO 845 conditions.

(4) Cell size

Cell size was determined by measuring the length of the long and short axes of the cell using a scanning electron microscope (SEM), and the average value was used as the cell size.

(5) Crystallinity

The melting enthalpy at the melting temperature and the crystallization enthalpy at the cooling crystallization temperature were measured using differential scanning calorimetry (DSC), and the degree of crystallization was calculated according to the following equation.

Crystallinity = ΔHm - ΔHc / ΔHm

ΔHm represents the enthalpy of melting, ΔHc represents the enthalpy of crystallization, and ΔHm represents the standard enthalpy of melting (140 J/g).

(6) Formability

Formability was evaluated by visually observing the molded product to determine whether breakage or cracking occurred.

(7) Fragility

The brittleness was measured using the flexural maximum load flexural measurement method. The specimen size was manufactured as 150 × 50 mm, and 5 sheets were measured in each vertical and horizontal direction for each specimen. The support span of the measured specimen was fixed at 50 mm, and a flexural load was applied at a rate of 20 mm/min. After the test was terminated at a point where the specimen was deformed 40 mm from the initial specimen, the number of cracks was measured by visually observing the surface of the sample.

(8) Flexural strength

According to ASTM D 790, the support span of the specimen was fixed at 100 mm, and while applying a flexural load at a rate of 5 mm/min, the maximum load until 10% deformation was achieved with respect to the initial specimen was measured.

(9) Sound absorption

Absorption was measured using the KS F 2805 reverberation chamber measurement method, and the noise reduction coefficient (NRC) value was calculated. NRC was measured at 2,000 and 6,000 Hz, respectively.

(10) Heat resistance cycle

The 80℃ heat resistance cycle was evaluated by maintaining the molded part in the same condition as the actual car, setting the following conditions as 1 cycle, performing 3 cycles, observing the appearance, and determining whether there was any change in shape.

*Heat resistance cycle: 3 hours at 80±2℃, 1 hour at 23±2℃, 3 hours at -30±2℃, 1 hour at 23±2℃, 15 hours at 50±2℃, 95~100% RH, 1 hour at 23±2℃

division Example 1 Example 2 Example 3 PET
profit Intrinsic viscosity (IV) ㎗/g 0.8 0.8 0.8 Molecular weight 10,000 or more weight% 72 72 72 thickener PMDA Weight division 2.5 2.5 2.5 Nuclear agent Talc content Weight division 3 3 3 Talc size ㎛ 1 1 5 blowing agent butane Weight division 2.2 2.2 2.2 PET foam layer density kg/㎥ 160 160 160 thickness mm 3 3 3 Average cell size ㎛ 100~200 100~200 200~400

division Comparative Example 1 Comparative Example 2 Comparative Example 3 PET
profit Intrinsic viscosity (IV) ㎗/g 0.8 PP
1200 gsm
1.2 mmT 0.8 Molecular weight 10,000 or more weight% 72 72 thickener PMDA Weight division 2.5 2.5 Nuclear agent Talc content Weight division 3 3 Talc size ㎛ 1 1 blowing agent butane Weight division 2.2 2.2 PET foam layer density kg/㎥ 160 160 thickness mm 3 3 Average cell size ㎛ 100~200 100~200

division Example 1 Example 2 Example 3 surface layer Needle punching + latex coating (weight) g/㎡ 180 180 180 Lamination method PET coating layer (thickness) ㎛ 150 150 150 foam layer PET foam layer (basis weight) g/㎡ 480 480 480 Lamination method Flame Rami - Flame Rami Flame Rami Flame Rami back layer Needle punching (weight) g/㎡ 60 60 60

division Comparative Example 1 Comparative Example 2 Comparative Example 3 surface layer Needle punching + latex coating (weight) g/㎡ 180 180 180 Lamination method PET coating layer (thickness) ㎛ 150 Nonwoven lamination during PP extrusion 150 foam layer PET foam layer (basis weight) g/㎡ 480 480 Lamination method Flame Rami - Flame Rami Flame Rami back layer Needle punching (weight) g/㎡ 60 60 60

division Example 1 Example 2 Example 3 plastic surgery
condition Heater temperature ℃ 300 300 300 Heater time candle 160 160 160 Composite surface temperature ℃ 190 190 190 Press interval mm 3.5 5 3.5 Press temperature ℃ 20 20 20 Press time candle 40 40 40 foam layer Crystallinity % 27 25 27 Cell size Long/short axis ratio - 7 5 7 composite materials
part Formability No breakage or cracking - Good Good Good Fragility MD direction broken Number 0 0 0 TD direction broken Number 0 0 0 Total thickness mm 3.9 5.2 3.7 Flexural strength Maximum load (MD direction) N 14 15 13 sound absorption Absorption coefficient (2000Hz) - 0.23 0.25 0.21 Absorption coefficient (6000Hz) - 0.63 0.75 0.61 Heat resistance cycle - Pass Pass Pass

division Comparative Example 1 Comparative Example 2 Comparative Example 3 plastic surgery
condition Heater temperature ℃ 300 300 300 Heater time candle 160 160 80 Composite surface temperature ℃ 190 190 140 Press interval mm 1.2 1.2 3.5 Press temperature ℃ 20 20 20 Press time candle 40 40 40 foam layer Crystallinity % 27 - 19 Cell size Long/short axis ratio - 25 - 7 composite materials
part Formability No breakage or cracking - Good Good Good Fragility MD direction broken Number 0 0 0 TD direction broken Number 0 0 0 Total thickness mm 1.5 1.2 3.8 Flexural strength Maximum load (MD direction) N 4 3.5 14 sound absorption Absorption coefficient (2000Hz) - 0.19 0.2 0.23 Absorption coefficient (6000Hz) - 0.5 0.23 0.63 Heat resistance cycle - Pass Pass Fail

As can be seen in the table above, the foam layer of the example had a small cell size and low density by using a nucleating agent size and content, a thickener content, and a resin viscosity and molecular weight distribution within an appropriate range. In addition, the composite of the example had excellent breakage resistance, formability, flexural strength, sound absorption, and heat resistance by using an appropriate laminated structure, material, lamination method, and molding conditions.

However, in the case of Comparative Example 1, the mold gap was small, so the major axis/minor axis ratio of the cell size increased, and the flexural strength and sound absorption of the composite molded product decreased.

In the case of Comparative Example 2, the flexural strength and sound absorption of the composite molded product were reduced by using the existing PP product.

In the case of Comparative Example 3, the crystallinity of the foam layer and the heat resistance of the composite molded product were reduced due to the conditions (heater time, composite surface temperature) being outside the appropriate molding conditions.

10, 20, 31: composite material, 11, 21: backing layer, 12, 22: foam layer, 13, 23: extrusion coating layer, 14, 24: surface layer, 25: reinforcing layer, 30: automotive interior material, 32: concave part

Claims (11)

A foam layer having a cell size of 250 ㎛ or less and a density of 500 kg/㎥ or less;
A surface layer laminated on one side of the foam layer; and
Including a back layer laminated on the other side of the foam layer,
The lamination of the foam layer and the surface layer is achieved through an extrusion coating layer, and the lamination of the foam layer and the back layer is achieved through flame lamination.
The total thickness is 3 mm or more,
The foam layer is formed of a foam composition containing polyethylene terephthalate (PET) resin, a nucleating agent, and a thickener.
PET resin is a PET resin in which the proportion of molecules having a molecular weight of 10,000 or more, as indicated by the differential molecular weight distribution, is 60 wt% or more with respect to the total weight of the PET resin, and the proportion of molecules having a molecular weight of less than 10,000 is less than 40 wt% with respect to the total weight of the PET resin.
The content of the nucleating agent is 2 to 10 parts by weight based on 100 parts by weight of PET resin.
Automobile interior material having a thickener content of 2 to 10 parts by weight based on 100 parts by weight of PET resin. In the first paragraph,
Automotive interior materials with an intrinsic viscosity (IV) of PET resin of 0.7 ㎗/g or more. In the first paragraph,
Automobile interior materials with a nucleus size of 10 ㎛ or less. In the first paragraph,
An automobile interior material in which the surface layer and back layer are each made of PET nonwoven fabric, and the extrusion coating layer is a PET coating layer. In the first paragraph,
An automobile interior material having a surface layer having a basis weight of 100 to 1000 g/㎡, a back layer having a basis weight of 10 to 500 g/㎡, and an extrusion coating layer having a thickness of 50 to 200 ㎛. In the first paragraph,
An automobile interior material in which the surface layer and the back layer include PET having a melting temperature of 200°C or higher and low-melting point PET having a melting temperature of less than 200°C. In the first paragraph,
An automotive interior material additionally comprising a reinforcing layer between the surface layer and the extruded coating layer. In the first paragraph,
An automobile interior material having a crystallinity of 20% or more in the foam layer and a ratio of the major axis length/minor axis length of the foam layer cells of 20 or less. In the first paragraph,
Automobile interior materials with a maximum bending load of 10 N or more. In the first paragraph,
Automotive interior materials having a sound absorption coefficient of more than 0.2 at 2000 Hz and more than 0.3 at 6000 Hz. A method for forming an automotive interior material, comprising cold forming a composite material having a laminated structure according to Article 1, under the conditions of a heater temperature of 200°C or higher, a heater residence time of 90 seconds or higher, a composite surface temperature of 150°C or higher, a press gap of 3 mm or higher, a press temperature of 40°C or lower, and a press time of 20 seconds or higher.