KR20240105546A - Automobile crash pad core and manufacturing method thereof - Google Patents

Abstract

The present invention is a crash pad core for a vehicle manufactured by core-back foam injection of a polypropylene resin composition containing long glass fibers, wherein the polypropylene resin composition contains 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers. It relates to a crash pad core for a vehicle and a method of manufacturing the same, wherein the polypropylene resin includes 20 to 100% by weight of a highly crystalline polypropylene polymer and 0 to 80% by weight of an ethylene-propylene block copolymer.

Description

Automotive crash pad core and manufacturing method thereof {Automobile crash pad core and manufacturing method thereof}

The present invention relates to a crash pad core for a vehicle manufactured by core-back foam injection of a polypropylene resin composition and a method of manufacturing the same.

The crash pad is an automobile interior part that is mounted on the front lower part of the driver's seat and has a shape that can accommodate an instrument panel that integrates instruments such as a speedometer, fuel gauge, and water temperature gauge, as well as an air conditioning system, radio, clock, ashtray, and small items. It is designed and manufactured, and the parts installed on the crash pad are manipulated and checked while driving. Therefore, crash pads are very important automobile parts in terms of design, convenience, and safety.

Conventional crash pads are made of various methods and materials in line with the trends of eco-friendliness, high sensitivity, lightweight, and high functionality, and continuous development is in progress. Crash pads are generally soft depending on the manufacturing method and applied materials and structure. It is divided into two types, soft type crash pad and hard type crash pad, and various manufacturing methods can be selected depending on the vehicle type and construction method specifications.

The soft type crash pad is composed of three layers including skin, foam, and core, and has a beautiful appearance and a soft cushioning feel to the touch, while the hard type crash pad is made up of three layers: skin, foam, and core. Crash pads are simply made up of one layer (core) and are manufactured through a plastic injection process, so they have the disadvantage of poor emotional quality.

Among the conventional soft IP specifications, IMG (In Mold Graining) and leather-wrapped crash pad cores are manufactured by general injection molding of a material called PPF (PP + rubber + TD). In addition, in order to include a passenger airbag (PAB), it was manufactured by fusing a PAB suit door injection molded with a separate TPO (Thermoplastic Olefin) material.

In this way, conventional crash pad materials are manufactured by making individual parts from PPF material containing expensive rubber components and TPO material and fusing them together. PPF contains about 25% rubber in polypropylene (PP) and includes inorganic fillers (talc, whiskers, etc.) to reinforce rigidity, and TPO contains about 40% or more rubber to improve the impact resistance of polypropylene. Contains ingredients.

Crash pads require rigidity as a structure, but there is also the problem of a high dependence on structural reinforcement of parts due to loss of rigidity due to the addition of rubber. In addition, tensile/flexural modulus and impact strength usually have a trade-off relationship, so the PPF of the crash pad core functions to secure rigidity, and the TPO of the PAB chute door functions to supplement impact resistance performance. In addition, conventional crash pad cores were manufactured through general injection molding and considering the mechanical properties of PPF material, so there were limitations in lightening them.

Therefore, there is a need for the development of a resin composition for automobiles that does not contain rubber components and can simultaneously secure weight reduction and economic efficiency. In addition, there is a need to develop a foamed resin composition that can integrate the crash pad core and PAB chute door into a single material, thereby simplifying the process and improving production efficiency.

The purpose of the present invention is to provide a method of manufacturing a crash pad core for a vehicle that can ensure both lightness and economic efficiency.

Another object of the present invention is to provide a method of manufacturing a crash pad for a vehicle that can achieve weight reduction using a foam coreback injection molding method rather than thinning the design thickness for weight reduction.

Another object of the present invention is to provide a lightweight crash pad for vehicles while maintaining high strength and rigidity, thereby improving vehicle performance.

According to one aspect of the present invention, a crash pad core for a vehicle is manufactured by core-back foam injection of a polypropylene resin composition containing long glass fibers, wherein the polypropylene resin composition includes 65 to 85% by weight of polypropylene resin and long glass fibers. 15 to 35% by weight, and the polypropylene resin includes 20 to 100% by weight of a highly crystalline polypropylene polymer and 0 to 80% by weight of an ethylene-propylene block copolymer.

According to examples, the average diameter of the glass filaments is preferably in the range of 3 to 100 and the average length is preferably in the range of 5 to 20 mm.

According to an embodiment, the passenger airbag (PAB) suit and core may be injected as one piece through core bag foam injection, or may be injected as separate pieces.

According to the example, the crash pad core for vehicles manufactured by core bag foam injection was tested at a test speed of 50 mm/min in accordance with ISO 527 standards. The tensile strength measured may be 85 MPa or more.

According to the example, the crash pad core for vehicles manufactured by core bag foam injection was tested at a test speed of 2 mm/min in accordance with ISO 178 standards. The flexural modulus measured by may be 4,500 MPa or more.

According to another aspect of the present invention, preparing a polypropylene resin composition containing 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers; placing the polypropylene resin composition in a mold for a crash pad core; Injecting; and manufacturing a crash pad core by molding the movable axis of the mold and foaming and injecting the core bag. A method of manufacturing a crash pad core for a vehicle is provided.

Coreback foam injection is characterized by the ability to adjust the thickness of the foam by adjusting the mold angle.

According to an embodiment, in the method of manufacturing a crash pad, the passenger airbag (PAB) suit and core may be injected as one piece, or may be injected as separate pieces.

The polypropylene resin used to manufacture the crash pad core for a vehicle may include 20 to 100% by weight of a highly crystalline polypropylene polymer and 0 to 80% by weight of an ethylene-propylene block copolymer.

The glass filaments used in the production of vehicle crash pad cores preferably have an average diameter in the range of 3 to 100 and an average length in the range of 5 to 20 mm.

In coreback foam injection molding, foaming can be either chemical foaming or physical foaming. The foaming agent used in chemical foaming may be one or more selected from the group consisting of sodium bicarbonate, sodium bicarbonate and citric acid, azodicarbonamide (ADCA), hydrazodicarbonamide, and azobisisobutyronitrile. It may be added in the range of 1 to 3% by weight based on the total amount of the polypropylene resin composition, but is not particularly limited thereto.

Additionally, in the case of physical foaming, the foaming agent may be one or more selected from the group consisting of nitrogen, carbon dioxide, and water.

The method of manufacturing a crash pad for a vehicle according to the present invention has the advantage of being able to achieve weight reduction by using a foam coreback injection molding method rather than a thinner design for weight reduction.

Additionally, when manufacturing a crash pad using the core bag foam injection method according to the present invention, the passenger airbag (PAB) suit and core may be injected as one piece or as separate pieces. When a crash pad is manufactured by integrating the passenger airbag (PAB) suit and core using the propylene resin composition according to the present invention, the process is simplified and production efficiency is improved.

Molded parts for automobiles manufactured by foam injection of the polypropylene resin composition according to the present invention can maintain high strength and rigidity while achieving a weight reduction of about 25% compared to conventional products using rubber materials, and thus can be used for the development of high-performance automobiles. You can contribute.

In addition, molded parts for automobiles manufactured using the polypropylene resin composition according to the present invention are economical because raw material costs can be reduced because expensive rubber materials are not used.

Meanwhile, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

Figure 1 is a schematic diagram showing the change in thickness of the crash pad core before and after injection foaming of the core bag according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples and drawings. However, the following examples are provided by way of example to aid understanding of the present invention, and the scope of the present invention is not limited thereto. The present invention may be subject to various changes and may be implemented in various different forms. It should be understood to include all changes, equivalents, or substitutes included in the spirit and technical scope of .

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that it does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as having an ideal or excessively formal meaning unless explicitly defined in the present application. No.

The present invention includes the mechanical properties of the material, molding characteristics, and structure of the component to satisfy the performance required by the soft IP crash pad core and maximize the lightweight effect. The crash pad core according to an embodiment of the present invention can be applied to IMG, leather wrapping, and urethane foam specifications classified as SOFT IP specifications.

In the present invention, the crash pad core is formed using a foam injection molding method to reduce the weight of the part. More specifically, when the molten resin is completed filling the mold with nitrogen or CO ₂ gas, the movable side of the mold is opened by a certain amount, forming micropores inside the molded product and simultaneously expanding the volume of the molded product. This reduces the amount of material input compared to existing parts and expands only the volume while maintaining the mass of the molded product through the core back, thereby satisfying the designed dimensions and performance required by the crash pad core.

Because foaming is accompanied by a decrease in mechanical properties, in the prior art, the PAB part had the inconvenience of having to design a product/mold structure to minimize foaming. However, in the examples according to the present invention, the loss of physical properties was overcome by using a resin composition containing polypropylene resin and glass filaments of a specific composition that can realize high tensile strength and flexural modulus compared to conventionally used materials.

The coreback foam injection molding of the vehicle crash pad core according to the present invention will be described in more detail as follows.

In general, airbag devices are installed in vehicles for the safety of passengers, and among them, the passenger airbag (PAB) is a device to protect passengers sitting in the passenger seat. This passenger airbag is installed in the crash pad, and has a structure that deploys through the airbag door of the PAB suit in case of emergency.

The foam injection molding method according to the present invention can be applied to both chemical foaming and physical foaming methods.

In one embodiment, a chemical foaming method was applied in which foaming occurs through a chemical reaction by adding a small amount of a chemical foaming agent to the product material (e.g., PPF), and a core-back method commonly used in foam molding was adopted.

The core-back method refers to a method of injecting product material into a mold and then finely opening the mold to the thickness (setting distance) of the product through control of the injection machine. In other words, this is a method of molding the moving mold into a fixed mold, injecting the product material into the cavity, and then foaming the moving mold by opening the mold as finely as the setting distance in the opening direction.

As an embodiment, the crash pad core has a structure in which a chute door made of TPO material is formed separately and fused together as before for PAB deployment performance, and the structure of the chute door is included within the crash pad core to form an integrated structure with the above material. It can be applied as a structure.

When the crash pad includes an integrated PAB chute door structure, the interior is made of foam with micropores. This method is called short-shot foam injection, in which molten resin is completely filled into the mold with nitrogen or CO2 gas to form a foam, and after injection of molten resin, the movable side of the mold is opened by a certain amount to reduce the thickness of the PAB door part. There are two methods of so-called core-back foam injection that maximize the weight reduction effect by increasing the amount of micropores inside the molded product.

The former has a minimal weight reduction effect due to a reduction in specific gravity of about 1 to 7% compared to existing general injection molding, but the latter can secure a weight saving effect of up to 20 to 45% depending on the mold angle of the product.

Referring to the drawing, the mold angle and thickness of the injection molded product during the foaming process are explained.

In Figure 1, ⓐ is the product thickness direction, ⓑ is the mold withdrawal direction, that is, the coreback direction, and ⓒ is the mold angle. Also, d1 is the thickness before core back, and d2 is the thickness after core back.

The correlation between the amount of thickness increase and the amount of core back in the core back foam injection process is as follows.

[Equation 1] Thickness increase = amount of core bag x sin ⓒ

As an example, when the product thickness direction and the mold removal direction are different (ⓐ ≠ ⓑ), the amount of thickness increase is small compared to the mold removal direction. For example, in the case of a thickness of 2.8mm, a core back of 1.5mm, and a mold angle of 30°, a 20% weight reduction can be achieved with a final thickness of 3.5mm.

As another example, if the product thickness direction and the mold removal direction are the same (ⓐ = ⓑ), the thickness increases by the mold removal direction. The amount of thickness increase is the core bag amount. For example, if the thickness is 2mm, the core back is 1.5mm, and the mold angle is 0˚, the final thickness is 3.5mm, which can achieve a 43% weight reduction.

As an embodiment, a crash pad core for a vehicle is manufactured by core-back foam injection of a polypropylene resin composition containing long glass fibers, and the polypropylene resin composition contains 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers. % by weight, and the polypropylene resin may include 20 to 100 wt% of highly crystalline polypropylene polymer and 0 to 80 wt% of ethylene-propylene block copolymer.

If the content of the highly crystalline polypropylene polymer and the ethylene-propylene block copolymer is outside the above range, the tensile strength and flexural modulus of the crash pad core are reduced.

Glass filaments preferably have an average diameter in the range of 3 to 100 ㎛ and an average length in the range of 5 to 20 mm. If the length of the fiber is less than the above range, the impact strength and strength are drastically lowered, and if the length of the fiber is longer than the above range, it becomes difficult to input it into the injection machine.

According to the embodiment, the vehicle crash pad core manufactured by core bag foam injection was tested at a test speed of 50 mm/min according to the ISO 527 standard. The tensile strength measured may be 85 MPa or more.

In addition, according to the embodiment, the vehicle crash pad core manufactured by foam injection of the core bag was tested at a test speed of 2 mm/min according to the ISO 178 standard. The flexural modulus measured by may be 4,500 MPa or more.

Depending on the embodiment, manufacturing a crash pad using the core-back foam injection method has the advantage of being able to reduce the weight by about 25% compared to existing crash pad products, while maintaining high flexural modulus and impact strength.

When manufacturing a crash pad using the core bag foam injection method, the passenger airbag (PAB) suit and core can be injected as one piece or as separate pieces. In the case of manufacturing an integrated crash pad using a propylene resin composition containing long glass fibers according to the present invention, the crash pad core and the passenger airbag (PAB) suit door are integrated into a single material, and the PAB suit integrated core is injection molded. Since the manufacturing process can be simplified, process efficiency can be improved and manufacturing costs can be reduced.

As an embodiment, a method of manufacturing a crash pad core for a vehicle includes preparing a polypropylene resin composition containing 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers; applying the polypropylene resin composition to a crash pad core Injecting into a mold; and manufacturing a crash pad core by opening the movable axis of the mold and foaming and injecting the core bag.

The polypropylene resin used to manufacture the crash pad core for a vehicle may include 20 to 100% by weight of a highly crystalline polypropylene polymer and 0 to 80% by weight of an ethylene-propylene block copolymer.

The glass filaments used to manufacture the crash pad core for vehicles preferably have an average diameter in the range of 3 to 100 ㎛ and an average length in the range of 5 to 20 mm.

Coreback foam injection is characterized by the ability to control the thickness of the foam by adjusting the mold angle.

According to an embodiment, the average thickness of the crash pad core before foam injection of the core back may range from 1.5 to 2.5 mm, and the average thickness of the crash pad core after foam injection of the core back may range from 2.5 to 4 mm.

In coreback foam injection molding, the foaming method can be either chemical foaming or physical foaming. Chemical foaming agents may be, for example, selected from the group consisting of sodium bicarbonate, sodium bicarbonate and citric acid, azodicarbonamide (ADCA), hydrazodicarbonamide, and azobisisobutyronitrile, but are not particularly limited thereto. That is not the case.

The foaming agent used in chemical foaming may be added in the range of 1 to 3% by weight based on the total amount of the polypropylene resin composition.

In addition, the physical foaming agent that can be used may be, for example, one or more selected from the group consisting of nitrogen, carbon dioxide, and water, but is not particularly limited thereto.

When a crash pad core is manufactured by core-back foam injection of the resin composition according to the present invention, there is an advantage in that it is possible to reduce the weight compared to existing crash pad products while maintaining high flexural modulus and impact strength.

In this way, automobile molded products manufactured by foam injection of a polypropylene resin composition can achieve approximately 25% weight reduction compared to conventional products using rubber materials while maintaining high strength and rigidity, thereby contributing to the development of high-performance automobiles. there is.

In particular, the method of manufacturing a crash pad for a vehicle according to the present invention has the advantage of being able to achieve weight reduction by using a foam core back injection molding method rather than a thinner design for weight reduction.

Although the above description focuses on the examples, this is only an example and does not limit the examples, and those skilled in the art will understand that there are various options not exemplified above without departing from the essential characteristics of the examples. You will see that variations and applications of branches are possible. For example, each component specifically shown in the examples can be modified and implemented. And these variations and differences related to application should be interpreted as being included in the scope of the embodiments set forth in the appended claims.

Claims (13)

A vehicle crash pad core manufactured by core-back foam injection of a polypropylene resin composition containing long glass fibers,
The polypropylene resin composition includes 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers, and the polypropylene resin includes 20 to 100% by weight of highly crystalline polypropylene polymer and ethylene-propylene block copolymer 0. A crash pad core for a vehicle, comprising from 80% by weight. According to paragraph 1,
The crash pad core for a vehicle, wherein the glass filament has an average diameter in the range of 3 to 100 ㎛ and an average length in the range of 5 to 20 mm. According to paragraph 1,
Test speed 50mm/min according to ISO 527 standard. Automotive crash pad core with a tensile strength of 85 MPa or more, as measured by . According to paragraph 1,
Test speed 2mm/min according to ISO 178 standard. A crash pad core for vehicles with a flexural modulus of more than 4,500 MPa, as measured by . Preparing a polypropylene resin composition containing 65 to 85% by weight of polypropylene resin and 15 to 35% by weight of long glass fibers;
Injecting the polypropylene resin composition into a mold for a crash pad core; and
A method of manufacturing a crash pad core for a vehicle comprising: manufacturing a crash pad core by molding the movable axis of the mold and foaming and injecting the core bag. According to clause 5,
The coreback foam injection method is a method of manufacturing a crash pad core for a vehicle, characterized in that the thickness of the foam is adjusted by adjusting the mold angle. According to clause 5,
The average thickness of the crash pad core before foam injection of the core back is in the range of 1.5 to 2.5 mm, and the average thickness of the crash pad core after foam injection of the core back is in the range of 2.5 to 4 mm. According to clause 5,
The method of manufacturing a crash pad core for a vehicle, wherein the polypropylene resin includes 20 to 100% by weight of a highly crystalline polypropylene polymer and 0 to 80% by weight of an ethylene-propylene block copolymer. According to clause 5,
The method of manufacturing a crash pad core for a vehicle, wherein the glass long fiber has an average diameter in the range of 3 to 100 ㎛ and an average length in the range of 5 to 20 mm. According to clause 5,
A method of manufacturing a crash pad core for a vehicle, wherein the foaming is chemical foaming or physical foaming. According to clause 10,
The foaming agent used in the chemical foaming is one or more selected from the group consisting of sodium bicarbonate, sodium bicarbonate and citric acid, azodicarbonamide (ADCA), hydrazodicarbonamide, and azobisisobutyronitrile. Method of manufacturing the core. According to clause 10,
The method of manufacturing a crash pad core for a vehicle, wherein the foaming agent used in the chemical foaming is added in the range of 1 to 3% by weight based on the total amount of the polypropylene resin composition. According to clause 10,
A method of manufacturing a crash pad core for a vehicle, wherein the foaming agent used for the physical foaming is one or more selected from the group consisting of nitrogen, carbon dioxide, and water.