A plastic composite resin composition, a method for manufacturing a plastic molded article, and a plastic molded article for radar absorption produced by the method

Abstract

The present invention relates to a plastic composite resin composition, a method for manufacturing a plastic molded article using the same, and a radar-absorbing plastic molded article manufactured by the method. More specifically, the present invention is characterized by providing a method to improve radar absorption rate by manufacturing a plastic molded article having internal pores formed using a plastic resin comprising polyamide, a filler comprising carbon nanotubes, and a foaming agent.

Description

Technology Field

[0001] The present invention relates to a plastic composite resin composition, a method for manufacturing a plastic molded article using the same, and a radar-absorbing plastic molded article manufactured by the method. More specifically, the present invention is characterized by providing a method to improve radar absorption rate by manufacturing a plastic molded article having internal pores formed using a plastic resin comprising polyamide, a filler comprising carbon nanotubes, and a foaming agent. Background Technology

[0002] Vehicles are equipped with electronic control units (ECUs) that electronically control various devices. These units receive information from sensors or switches installed in the vehicle, process the received information, and perform control functions to improve vehicle safety and steering feel. A radar device, which senses the distance between the vehicle and surrounding objects by transmitting electromagnetic waves and receiving the reflected waves, is essential. In particular, the function of the absorber component within the radar device, which directly absorbs the reflected electromagnetic waves, is considered to be of great importance.

[0003] Specifically, radar absorbers can be used for two purposes. For the first purpose, absorbers mounted on the outer perimeter of the radar device prevent false detections by absorbing noise reflected from vehicle wheels, back beams, and road surfaces during radar radiation. For the second purpose, absorbers located inside the EMI shield absorb noise from the RF chip that generates electromagnetic waves, helping the radar beam pattern to be formed into the desired shape and thereby ensuring the reliability of radar detection performance.

[0004] Conventionally, such absorber materials widely utilize polybutylene terephthalate (PBT) plastic with carbon fiber (CF) fillers. However, these absorber materials are very expensive, and because a very large amount of filler is used to enhance absorption performance, significant deformation occurs during manufacturing, resulting in a disadvantage of a very high defect rate during radar device assembly.

[0005] Korean Patent Publication No. 10-2019-0114809 relates to a radar device and is characterized by providing a radar device that reduces noise in the low-frequency range and lowers manufacturing costs by utilizing plastics, carbon fibers, and carbon nanotubes; however, there is still a problem in that it cannot present the desired radar absorption rate. Prior art literature

[0006] Korean Patent Publication No. 10-2019-0114809 The problem to be solved

[0007] According to the present invention, the purpose is to provide a method for manufacturing a plastic capable of increasing radar wave absorption performance.

[0008] According to the present invention, the purpose is to provide a plastic resin composition that can reduce production costs while maintaining high radar wave absorption performance.

[0009] According to the present invention, the purpose is to provide a plastic molded article for absorbing radar waves with maximized dimensional stability.

[0010] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become clearer from the following description and will be realized by the means and combinations thereof described in the claims. means of solving the problem

[0012] According to the present invention, a plastic composite resin composition is provided, comprising a plastic resin; and a filler; wherein the plastic resin comprises a polyamide.

[0013] The above filler may include carbon nanotubes.

[0014] The above plastic composite resin may comprise 97 to 99 weight percent of plastic resin and 1 to 3 weight percent of filler.

[0015] The above plastic composite resin composition may further include a foaming agent.

[0016] The above foaming agent may include a foaming material containing sodium bicarbonate.

[0017] The above foamed material may be contained in any one carrier selected from the group consisting of low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), and combinations thereof.

[0018] The above foaming agent may be included in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin.

[0019] According to the present invention, a method for manufacturing a plastic molded article for radar absorption is provided, characterized by comprising the steps of: preparing the above-mentioned plastic composite resin; introducing, mixing, and injecting a foaming agent into the above-mentioned plastic composite resin to form a molded article; and foaming the above-mentioned foaming agent to manufacture a foamed molded article.

[0020] The above foaming agent may include a foaming material containing sodium bicarbonate, and the foaming agent may be added in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin.

[0021] In the step of manufacturing a foamed molded product, a foaming agent may be foamed to form pores within the molded product.

[0022] The volume of the above pores may account for 10 to 50 percent of the total volume of the foamed molded product.

[0023] The major axis length of the above pore may be 0.3 to 1.0 mm.

[0024] According to the present invention, a plastic molded article for radar absorption is provided, characterized by being manufactured by the above-described manufacturing method.

[0025] The above plastic molded article includes pores, and the pores may be included in a volume of 10 to 50 percent relative to the plastic molded article.

[0026] The radar absorption rate (%) of the above plastic molded product may be 60% or higher. Effects of the invention

[0027] According to the present invention, a method for manufacturing a plastic capable of enhancing radar wave absorption performance can be provided.

[0028] According to the present invention, a plastic resin composition can be provided that can reduce production costs while maintaining high radar wave absorption performance.

[0029] According to the present invention, a plastic molded article for absorbing radar waves with maximized dimensional stability can be provided.

[0030] The effects of the present invention are not limited to those mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description. Brief explanation of the drawing

[0031] Figure 1 shows a plastic molded article of the present invention. Figure 2 shows the cross-section of the specimen of Comparative Example 7. Figure 3 shows the cross-section of the specimen of Example 2. Specific details for implementing the invention

[0032] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0033] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0034] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0035] In this specification, where a range is described for a variable, it will be understood that the variable includes all values ​​within the described range, including the described endpoints of the range. For example, the range “5 to 10” will be understood to include not only the values ​​5, 6, 7, 8, 9, and 10, but also any sub-ranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and any values ​​between integers valid for the category of the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Also, for example, the range “10% to 30%” will be understood to include all integers including values ​​such as 10%, 11%, 12%, 13%, etc. and up to 30%, as well as any sub-range such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between valid integers within the stated range category such as 10.5%, 15.5%, 25.5%, etc.

[0037] The present invention relates to a plastic composite resin composition, a method for manufacturing a plastic molded article using the same, and a radar-absorbing plastic molded article manufactured by the method.

[0039] Plastic composite resin composition

[0040] The plastic composite resin composition of the present invention is characterized by comprising a plastic resin and a plastic composite resin comprising a filler.

[0042] The above plastic resin comprises one selected from the group consisting of polyethylene, polypropylene, polystyrene, polyalkylene terephthalate, polyamide, polyacetal, polycarbonate, polysulfone, polyimide, and combinations thereof, and preferably, the above plastic resin comprises one selected from the group consisting of polyamide, polybutylene terephthalate, and combinations thereof. More preferably, the above plastic resin may comprise polyamide, which enables the induction of even dispersion of the foaming agent, thereby allowing small-sized pores to be evenly distributed within the manufactured molded article.

[0043] The above filler may include any one of carbon fibers, carbon fibers, and carbon nanotubes, but preferably includes carbon nanotubes.

[0044] The above plastic composite resin preferably comprises 97 to 99 weight percent of plastic resin and 1 to 3 weight percent of filler.

[0046] The plastic composite resin composition of the present invention preferably further comprises a foaming agent.

[0047] The foaming agent comprises a foaming material containing sodium bicarbonate, and preferably, the foaming material may be contained in a carrier selected from the group consisting of low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), and combinations thereof, and more preferably, the carrier may contain polyethylene.

[0048] The above foaming agent is preferably included in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin.

[0050] Method for manufacturing a plastic molded article for radar absorption

[0051] The method for manufacturing a radar-absorbing plastic molded article of the present invention is characterized by comprising the steps of: preparing a plastic composite resin of the present invention; introducing, mixing, and injecting a foaming agent into the plastic composite resin to form a molded article; and foaming the foaming agent to manufacture a foamed molded article.

[0053] Preparation stage

[0054] The plastic composite resin of the present invention preferably comprises a plastic resin and a filler.

[0055] The above plastic resin may preferably include polyamide, and the plastic composite resin of the present invention preferably includes 97 to 99 weight percent of the above plastic resin.

[0056] The above filler may preferably include carbon nanotubes, and the plastic composite resin of the present invention preferably includes 1 to 3 weight percent of the above filler.

[0058] Molding product formation stage

[0059] This is the step of manufacturing a molded product by injecting and mixing a foaming agent into a prepared plastic composite resin and injection molding it.

[0060] The above foaming agent comprises a foaming material containing sodium bicarbonate, wherein the foaming agent may preferably be included in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin.

[0061] The above plastic composite resin and foaming agent are mixed to evenly disperse the foaming agent within the plastic composite resin, and the plastic composite resin in which the foaming agent is dispersed is injected to form a molded product in the shape of a desired molded product.

[0062] In the present invention, the mixing environment and injection environment of the plastic composite resin and foaming agent are not specifically limited.

[0064] Foam molded product manufacturing step

[0065] This is a step of manufacturing a foamed molded product by foaming a foaming agent contained within an injection-molded product. More specifically, it is a step of forming pores within the molded product by foaming the foaming agent.

[0066] It is preferable that the volume of the above pores accounts for 10 to 50 percent of the total volume of the foamed molded product, and more preferably, the above pores account for 12 to 35 percent of the total volume of the foamed molded product.

[0067] The volume of the above pores may be affected by the temperature and speed of injecting the plastic composite resin, but since this does not align with the main point of the present invention, it will be excluded.

[0068] The length of the major axis of the above pore is preferably 0.3 to 1.0 mm, and more preferably 0.3 to 0.55 mm. At this time, if the length of the major axis of the pore is formed to be 0.3 mm or less, the pore interface to which the electromagnetic wave comes into contact becomes smaller, so a problem may arise in which the absorption effect is reduced.

[0070] Radar-absorbing plastic molded product

[0071] The radar-absorbing plastic molded article of the present invention preferably comprises a plastic resin and a filler.

[0072] The above plastic resin comprises one selected from the group consisting of polyethylene, polypropylene, polystyrene, polyalkylene terephthalate, polyamide, polyacetal, polycarbonate, polysulfone, polyimide, and combinations thereof, and preferably, the plastic resin comprises one selected from the group consisting of polybutylene terephthalate, polyamide, and combinations thereof. More preferably, the plastic resin may comprise polyamide, which enables the induction of even dispersion of the foaming agent, thereby allowing small-sized pores to be evenly distributed within the manufactured molded article.

[0073] The above filler may include any one of carbon fibers, carbon fibers, and carbon nanotubes, but it is preferable to include carbon nanotubes to improve absorption performance and ensure dimensional stability.

[0074] A plastic molded article manufactured by the method for manufacturing a radar-absorbing plastic molded article of the present invention preferably comprises pores. Air is contained within the spaces of the pores, and since the dielectric constant (ε) of the pores is lower than the dielectric constant of the plastic resin, refraction or reflection of radio waves occurs at the interface.

[0075] Figure 1 shows the plastic molded article of the present invention and the expected path of absorbed radio waves. Referring to this, it can be understood that since the pores are evenly distributed in small sizes within the plastic molded article, the absorbed radio waves undergo multiple reflections at the interface between the pores and the plastic resin, causing the propagation path to become longer. Consequently, as multiple reflections of the radio waves proceed, additional radio waves are absorbed. If there are no pores, or if they are not evenly formed within the plastic resin, it can be expected that some of the radio waves absorbed into the molded article will escape to the outside of the molded article with only a single reflection.

[0076] The present invention also has the feature of being able to obtain a high absorption rate through the pores while minimizing the content of the filler.

[0077] It is preferable that the above pores be included in a volume of 10 to 50 percent relative to the plastic molded product. More preferably, the above pores are included in a volume of 12 to 35 percent relative to the total volume of the plastic molded product. In this case, if the volume of the above pores is 10 percent or less, the radar absorption performance intended cannot be achieved, and if it exceeds 50 percent, problems such as wrinkles and sinks may occur on the surface of the molded product due to excessive pores created inside.

[0078] In addition, the length of the major axis of the pore is 0.3 to 1.0 mm, and more preferably 0.3 to 0.55 mm. At this time, if the length of the major axis of the pore is formed to be 0.3 mm or less, the pore interface to which the electromagnetic wave comes into contact becomes smaller, so a problem may arise in which the absorption effect is reduced.

[0079] The absorption rate of the radar-absorbing plastic molded article manufactured in the present invention is preferably 60% or higher.

[0082] The present invention will be explained in more detail below through specific embodiments. However, these embodiments are intended to illustrate the present invention and do not limit the scope of the present invention.

[0084] Examples and Comparative Examples

[0085] Specimens were prepared using plastic composite resin compositions with the contents of Tables 1 and 2 below. Sodium hydrogen carbonate with a polyethylene (PE) carrier that does not generate harmful gases was used as the blowing agent.

[0086] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 plastic resin PBT (weight%) X X X X X X X X PA6 (weight%) 99 97 97 97 97 97 97 97 Filler CNT (weight%) 1 3 3 3 3 3 3 3 CF(weight%) X X X X X X X X blowing agent* Content (parts by weight*) 2 2 3 4 2 2 2 2 Volume (%) 20 20 20 20 15 29 20 20 Major axis length (mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.35 0.55 * Foaming agent = Sodium bicarbonate contained in PE acceptor * parts by weight = Relative content based on the total weight of the polystyrene resin and filler being 100 parts by weight

[0088] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 plastic resin PBT (weight%) 60 X X X X X X X PA6 (weight%) X 97 97 100 94 97 97 97 Filler CNT (weight%) X 3 3 X 6 3 3 3 CF(weight%) 40 X X X X X X X blowing agent* Content (parts by weight*) X X 5 X 2 2 2 2 Volume (%) X X 20 X 20 9 60 20 Major axis length (mm) X X 0.4 X 0.4 0.4 0.4 0.2 * Foaming agent = Sodium bicarbonate contained in PE acceptor * parts by weight = Relative content based on the total weight of the polystyrene resin and filler being 100 parts by weight

[0090] Experimental results

[0091] Radar transmittance / absorption / reflectance evaluation and bending evaluation were performed on the specimens prepared in the above examples and comparative examples, and the results are shown in Tables 3 and 4 below.

[0092] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 plastic resin PBT (weight%) X X X X X X X X PA6 (weight%) 99 97 97 97 97 97 97 97 Filler CNT (weight%) 1 3 3 3 3 3 3 3 CF(weight%) X X X X X X X X blowing agent* Content (parts by weight*) 2 2 3 4 2 2 2 2 Volume (%) 25 25 25 25 15 29 25 25 Major axis length (mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.35 0.55 Appearance measurement Good Good Good Good Good Good Good Good Pore ​​measurement generation generation generation generation generation generation generation generation Absorption rate (%) 62 63 63 64 62 65 63 63 reflectivity(%) 38 37 37 36 38 35 37 37 Transmittance (%) 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less Bending evaluation (mm) 0.18 0.18 0.17 0.16 0.18 0.18 0.18 0.18 *Appearance Measurement = Visually observing external deformation of the specimen *Pore Measurement = Observing the presence of pores by cutting a cross-section of the specimen (if the pore area exceeds 80%, it is considered 'non-occurring') *Transmittance / Absorption / Reflectance Measurement Method = Electromagnetic waves are generated using a Vector Network Analyzer, and the signals radiated from the transmitter are received by the receiver antenna to measure transmittance, reflection, and absorption rates. The electromagnetic wave frequency band was adjusted to 76–77 GHz. *Bending Measurement Method = Laser scanning is applied to the upper buttocks of the specimen, and the degree of bending is evaluated using the delta values ​​of the high and low points on the Z-axis.

[0094] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 plastic resin PBT (weight%) 60 X X X X X 97 X PA6 (weight%) X 97 97 100 94 97 X 97 Filler CNT (weight%) X 3 3 X 6 3 3 3 CF(weight%) 40 X X X X X X X blowing agent* Content (parts by weight*) X X 5 X 2 1 2 2 Volume (%) X X 53 X 10 9 20 20 Major axis length (mm) X X 0.4 X 0.4 0.4 0.4 0.2 Appearance measurement Good Good Defect (Sink) Good Good Good Good Good Pore ​​measurement Non-occurrence Non-occurrence generation Non-occurrence generation generation Non-occurrence generation Absorption rate (%) 12 45 65 10 58 56 11 50 reflectivity(%) 88 55 35 90 42 44 89 50 Transmittance (%) 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less 0.01% or less Bending evaluation (mm) 0.55 0.35 0.15 0.12 0.20 0.20 0.15 0.15 *Appearance Measurement = Visually observing external deformation of the specimen *Pore Measurement = Observing the presence of pores by cutting a cross-section of the specimen (if the pore area exceeds 80%, it is considered 'non-occurring') *Transmittance / Absorption / Reflectance Measurement Method = Electromagnetic waves are generated using a Vector Network Analyzer, and the signals radiated from the transmitter are received by the receiver antenna to measure transmittance, reflection, and absorption rates. The electromagnetic wave frequency band was adjusted to 76–77 GHz. *Bending Measurement Method = Evaluating the degree of bending of the specimen by scanning the top of the specimen and checking the high and low points along the Z-axis.

[0095] It can be confirmed through Comparative Example 1 and Comparative Example 7 that when PBT is used as the plastic resin, the water absorption rate is very low and almost no pores are formed. Figure 2 shows the observation of pore formation through the cross-section of the specimen in Comparative Example 7. Referring to Figure 2, it can be seen that no pores were formed in the area within the dotted line. Through this, it can be expected that when PA6 is used as the plastic resin, the dispersion of the foaming agent proceeds evenly, and as a result, pores are formed uniformly.

[0096] Figure 3 shows the observation of pore formation through a cross-section of the specimen of Example 2. Referring to Figure 3, it can be seen that pores are formed and evenly distributed throughout.

[0097] Overall, it can be seen that the absorption rate is significantly lower compared to the examples in the case of specimens where almost no pores occur or where no pores are present due to the absence of a foaming agent. In particular, even when a foaming agent is used, it can be confirmed that the absorption rate does not exceed 60% if the pore volume is less than 20%. However, if the pore volume is excessively large, the absorption rate may increase, but it can be observed that the appearance of the specimen becomes poor and sinks occur.

[0098] In addition, it can be confirmed that when the major axis length of the generated pores is short, the contact interface of the electromagnetic waves is relatively reduced, resulting in a decrease in absorption rate.

[0099] In the evaluation of the bending of the specimens, it can be seen that the values ​​of the comparative examples, in which no pores were formed or unevenly formed, are much larger than those of the examples in which pores were formed evenly, which suggests that the dimensional stability of the specimens can be improved due to the even formation of pores.

Claims

Claim 1 A plastic molded article for radar absorption comprising a plastic composite resin including a plastic resin and a filler, wherein the plastic resin includes polyamide, pores exist inside, the volume of the pores occupies 10 to 50% of the total volume, and the major axis length of the pores is 0.3 to 1.0 mm. Claim 2 A radar-absorbing plastic molded article according to claim 1, wherein the filler comprises carbon nanotubes. Claim 3 A radar-absorbing plastic molded article according to claim 1, wherein the plastic composite resin comprises 97 to 99 weight% of plastic resin and 1 to 3 weight% of filler. Claim 4 In claim 1, the above-described radar-absorbing plastic molded article is a radar-absorbing plastic molded article formed by foaming a plastic composite resin composition comprising the above-described plastic composite resin and a foaming agent. Claim 5 In paragraph 4, the above foaming agent comprises a foaming material containing sodium bicarbonate, for a radar-absorbing plastic molded article. Claim 6 In paragraph 5, the above foamed material is a radar-absorbing plastic molded article contained in a carrier selected from the group consisting of low-density polyethylene (LDPE), polyethylene (PE), polypropylene (PP), and combinations thereof. Claim 7 A radar-absorbing plastic molded article according to claim 4, wherein the foaming agent is included in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin. Claim 8 A method for manufacturing a radar-absorbing plastic molded article comprising: a step of preparing a plastic composite resin including a plastic resin and a filler; a step of introducing, mixing, and injecting a foaming agent into the plastic composite resin to form a molded article; and a step of foaming the foaming agent to manufacture a foamed molded article; wherein the plastic resin includes polyamide, and in the step of manufacturing the foamed molded article, the foaming agent is foamed to form pores within the molded article, the volume of the pores occupies 10 to 50% of the total volume of the foamed molded article, and the major axis length of the pores is 0.3 to 1.0 mm. Claim 9 A method for manufacturing a radar-absorbing plastic molded article according to claim 8, wherein the foaming agent comprises a foaming material containing sodium bicarbonate, and the foaming agent is added in an amount of 2 to 4 parts by weight based on 100 parts by weight of the plastic composite resin. Claim 10 A method for manufacturing a radar-absorbing plastic molded article according to claim 8, wherein a foaming agent is foamed to form pores within the molded article during the step of manufacturing the foamed molded article. Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 A radar-absorbing plastic molded article according to claim 1, wherein the radar absorption rate (%) of the radar-absorbing plastic molded article is 60% or higher.

Images