US20140306142A1

US20140306142A1 - Polyamide resin composition for sound insulation

Info

Publication number: US20140306142A1
Application number: US13/946,230
Authority: US
Inventors: Jee-Young Youn; Sang-lll Lee
Original assignee: Hyundai Motor Co; Kia Motors Corp
Current assignee: Hyundai Motor Co; Kia Corp
Priority date: 2013-04-12
Filing date: 2013-07-19
Publication date: 2014-10-16
Also published as: CN104098895A; KR101526953B1; KR20140123341A; DE102013107386B4; DE102013107386A1

Abstract

Disclosed is a polyamide resin composition for sound insulation, which includes a polyamide 66 or polyamide 6 resin, a glass fiber for improving mechanical and heat resistance properties of the composition, and barium sulfate for improving a sound insulation property of the composition. The polyamide resin composition can further include one or more of an antioxidant for preventing deterioration of the composition, a heat resistant stabilizer for improving heat resistance, and a lubricant for reducing friction to improve moldability. The polyamide resin composition thus has excellent mechanical properties, heat resistance, noise and vibration insulation performance, and can further be injection molded to thereby provide weight reduction and allow for the formation of complicated shapes.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2013-0040585, filed on Apr. 12, 2013, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND

(a) Technical Field
The present invention relates to a polyamide resin composition for sound insulation that effectively insulates engine sounds and noise generated in an engine room of a vehicle, and more specifically, to a polyamide resin composition for sound insulation which includes polyamide 66 or polyamide 6 resins, glass fibers and barium sulfates.
(b) Background Art
A partition of an engine room of a vehicle is a wall disposed between the engine room and a dash board to insulate transfer of noise generated in the engine room into an interior of the vehicle. The partition, thus, improves the comfort level for passengers in the vehicle.
A partition of an engine room of a vehicle is conventionally made of a steel material. However, the weight of such a steel partition is excessively large, thus reducing fuel efficiency and ride comfort of the vehicle. Further, it is difficult to manufacture a complicated form from such a steel material.
In attempt to solve the above-described problems, a composition including polypropylene, a glass fiber, and iron oxide (Fe₂O₃) having high specific gravity has been used as a vehicle partition. Such a composition, is more easily processed than metal, is lightweight, can be provided in various and simple designs and design effects, and is less expensive due to its high productivity. However, it provides inadequate mechanical stiffness, heat resistance and injection moldability.
Generally, since a high-filling material having high specific gravity is useful for insulating noise and vibration, a filler such as iron oxide (Fe₂O₃, specific gravity: 4 to 4.5) and barium sulfate (BaSO₄, specific gravity: 4 to 4.5) is commonly used to increase the weight of a material.
Iron oxide and barium sulfate have a higher specific gravity as compared to talc or wollastonite (specific gravity: 2.6 to 2.9). Thus, these fillers are extensively used because a sound insulation property can be improved by increasing the specific gravity of a plastic material.
However, Moh's hardness of iron oxide is about 7, which is significantly high. Thus, screws and molds of injection molding machines are easily abraded during extrusion and molding of products which include iron oxide due to the high hardness provided thereby. As such, operation and maintenance of the injection molding machine for high hardness materials is costly.
Korean Unexamined Patent Application Publication No. 2010-41588 describes a polyamide resin composition for a vehicle engine cover, including a polyamide 6 resin, a glass fiber, carbon nanotube and a heat resistant stabilizer. However, the composition is problematic in that a sound insulation property is not sufficient even though heat resistance is excellent. Further, Japanese Unexamined Patent Application Publication No. 1999-43602 describes a polyamide resin composition including a polyamide resin, a glass fiber and barium sulfate. However, the content of barium sulfate is low, and thus there is a disadvantage in that a sufficient sound insulation property is not provided.

SUMMARY OF THE DISCLOSURE

The present invention provides a polyamide resin composition for sound insulation, which includes a polyamide 66 or polyamide 6 resin, a glass fiber for improving mechanical and heat resistance properties of the composition, and barium sulfate for improving a sound insulation property of the composition. According to various embodiments, the composition can further include one or more of an antioxidant for preventing deterioration of the composition, a heat resistant stabilizer for improving heat resistance, and a lubricant for reducing friction to improve moldability. The composition of the present invention, thus, provides excellent mechanical properties, heat resistance, noise and vibration insulation performance, degree of freedom in design, and injection moldability. The present invention further provides a partition for a vehicle fabricated from the present composition, wherein the partition effectively insulates engine sound generated in an engine room, and thus provides a more comfortable driving environment.
According to one aspect, the present invention provides a polyamide resin composition for sound insulation comprising about 15 to 20 parts by weight of a glass fiber, and about 45 to 50 parts by weight of barium sulfate, based on 100 parts by weight of a polyamide 66 or polyamide 6 resin.
The glass fiber can be any conventional glass fibers that provide the desired mechanical and heat resistance properties, and according to preferred embodiments, the glass fiber has an average length of about 1 mm to 5 mm and an average diameter of a cross section of about 10 to 13 μm.
According to various embodiments, the glass fiber is coated with a silane-based coupling agent. Preferably, a weight of the silane-based coupling agent is about 0.1 to 0.3 wt % based on a total weight of the glass fiber.
According to various embodiments, an average diameter of barium sulfate particles is about 20 to 30 μm.
According to various embodiments, the polyamide resin composition for sound insulation further includes one or more of about 0.3 to 0.5 parts by weight of an antioxidant, about 0.3 to 0.5 parts by weight of a heat resistant stabilizer, and/or about 0.2 to 0.4 parts by weight of a lubricant.
According to preferred embodiment, the antioxidant is a mixture of a phenol-based antioxidant and a phosphite-based antioxidant.
The present invention having the above-described constitution of a polyamide 66 or polyamide 6 resin, a glass fiber and barium sulfate (BaSO₄) having high specific gravity, provides excellent mechanical properties, heat resistance and noise and vibration insulation performance.
According to a further aspect, the present invention provides a partition for a vehicle fabricated of the composition. According to various embodiments, such a partition provides a weight reduction effect of about 2.6 kg per one vehicle as compared to a conventional partition made of iron. Further, since injection molding can be performed to implement a complicated shape using the present composition, there is an effect in that the excellent degree of freedom in design can be ensured in a narrow space in an engine room.
According to various embodiments, the composition utilizes a barium sulfate having Moh's hardness of about 3. The use of such a barium sulfate provides excellent injection moldability, as compared to a conventional polypropylene composition including iron oxide having Moh's hardness of 7.
Other aspects and exemplary embodiments of the invention are discussed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a mimetic diagram showing a partition of an engine room of a vehicle;

FIG. 2 is a graph showing the magnitude of noise insulated at a left of a driver's seat for each frequency;

FIG. 3 is a graph showing the magnitude of noise insulated at a right of the driver's seat for each frequency;

FIG. 4 is a graph showing the magnitude of noise insulated at a left of a front passenger seat for each frequency;

FIG. 5 is a graph showing the magnitude of noise insulated at a back seat for each frequency;

FIG. 6 is a graph showing the magnitude of noise insulated at a left of a VIP seat of the back seat for each frequency;

FIG. 7 is a graph showing the magnitude of noise insulated at a right of the VIP seat of the back seat for each frequency;

FIG. 8 is a graph showing the magnitude of noise insulated directly behind a left engine room for each frequency; and

FIG. 9 is a graph showing the magnitude of noise insulated directly behind a right engine room for each frequency.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.
In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

The terms and the words used in the specification and claims should not be construed with common or dictionary meanings, but construed as meanings and conception coinciding the spirit of the invention based on a principle that the inventors can appropriately define the concept of the terms to explain the invention in the optimum method.
It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.
Hereinafter, the present invention will be described in detail.
The present invention relates to polyamide resin composition for sound insulation having excellent mechanical stiffness, heat resistance and noise insulation function. More specifically, the present invention relates to polyamide resin composition which includes a polyamide 66 or polyamide 6 resin, a glass fiber and barium sulfate (BaSO₄) having high specific gravity in order to increase mechanical stiffness, heat resistance and injection moldability. According to preferred embodiments, the composition further includes one or more of an antioxidant, a heat resistant stabilizer and/or a lubricant.
To be more specific, it is preferable that the content of the glass fiber is about 15 to 20 parts by weight, the content of barium sulfate is about 45 to 50 parts by weight, the content of the antioxidant is about 0.3 to 0.5 parts by weight, the content of the heat resistant stabilizer is about 0.3 to 0.5 parts by weight and the content of the lubricant is about 0.2 to 0.4 parts by weight, based on 100 parts by weight of the polyamide 66 or polyamide 6 resin.
Hereinafter, constitution components of the present invention and the contents thereof will be described in detail.
1. Constitution Component
(1) Polyamide 66 or Polyamide 6
Any polyamide resin known in the art may be used as the polyamide resin component. However, it is preferable that polyamide 66 or polyamide 6 resin is used. As described herein, the polyamide 66 or polyamide 6 resin is a material that is a basis of the present invention. The polyamide resin is a material having excellent general mechanical and heat resistance properties such as tensile strength, flexural strength, flexural modulus, heat resistance, chemical resistance, and moldability. As such, the polyamide resin is extensively used in various fields such as vehicles, airplanes, space and sports.
Further, there are advantageous in that the mechanical and heat resistance properties may be easily improved by including a reinforcing agent, such as a glass fiber, in the polyamide 66 or polyamide 6 resin.
(2) Glass Fiber
The glass fiber functions to improve the mechanical properties of the polyamide resin composition, such as tensile strength, flexural strength, flexural modulus and impact strength, as well as the heat resistance properties, such as a heat distortion temperature (HDT). Any glass fiber known in the art may be used as the glass fiber. In addition, it is preferable that the surface of the glass fiber is coated with a silane-based coupling agent in order to increase an interface adhesion property between the polyamide resin and the glass fiber.
Herein, it is preferable that the content of the glass fiber is about 15 to 20 parts by weight based on 100 parts by weight of polyamide 66 or polyamide 6. In the case where the content of the glass fiber is less than about 15 parts by weight, the mechanical and heat resistance properties of the composition may be reduced. On the other hand, in the case where the content is more than about 20 parts by weight, fluidity of the composition may be reduced to deteriorate the appearance quality of molded products.
Further, it is preferable that an average diameter of a cross section of the glass fiber is about 10 to 13 μm. In the case where the average diameter of the cross section is less than about 10 μm, since a breakage ratio of the glass fiber is high, the mechanical property of the composition may be reduced. On the other hand, in the case where the average diameter is more than about 13 μm, the appearance quality of the composition may be reduced.
Any conventional glass fiber may be used in the present invention. Further, while any length of the glass fiber may be used, it is preferable that the glass fiber be a long glass fiber such as one having an average length of about 1 mm to 5 mm in order to improve impact strength and a dimensional stability effect of the composition. In the case where the average length of the glass fiber is less than about 1 mm, the mechanical and heat resistance properties of the composition may be reduced and a distortion phenomenon may occur in large-sized products. On the other hand, in the case where the average length is more than about 5 mm, a significant difference occurs between glass fiber alignment on the surface of the composition and the glass fiber alignment in the composition. This results in a difference in physical properties between the surface and the inside of the composition.
According to preferred embodiments, the content of the silane-based coupling agent is about 0.1 to 0.3 wt % based on the total weight of the glass fiber. In the case where the content of the silane-based coupling agent is less than about 0.1 wt %, mechanical and heat resistance properties of the composition may be reduced. On the other hand, in the case where the content is more than about 0.3 wt %, moldability may be reduced due to an increase in viscosity of the composition.
(3) Barium Sulfate
Barium sulfate (BaSO₄) is an inorganic filler that improves moldability and dimensional stability of the present composition and that further increases specific gravity of the composition, thus improving a sound insulation property. Since the sound insulation property is generally increased in proportion to an increase in specific gravity of the material, it is preferable to use a barium sulfate having a high specific gravity in order to improve the sound insulation property.
Barium sulfate has Moh's hardness of about 3, which is smaller than the Moh's hardness of about 7 for iron oxide used as a conventional inorganic filler. As such, friction of screws of injection molding machines and molds is reduced during an extrusion process and molding of the present composition to improve moldability.
It is preferable that the content of barium sulfate is about 45 to 50 parts by weight based on 100 parts by weight of polyamide 66 or polyamide 6. In the case where the content of barium sulfate is less than about 45 parts by weight, the specific gravity of the composition may be reduced to reduce the sound insulation property. On the other hand, in the case where the content is more than about 50 parts by weight, appearance quality and physical properties may be reduced.
In addition, it is preferable that the average diameter of the particles of barium sulfate is about 20 to 30 μm. In the case where the average diameter is less than about 20 μm, moldability and dimensional stability may be reduced. On the other hand, in the case where the average diameter is more than about 30 μm, a surface area of barium sulfate is reduced, and effective sound insulation property cannot be obtained.
(4) Antioxidant
The antioxidant functions to suppress a reaction of oxidative degradation during extrusion and injection processes of the composition. Any conventional antioxidant may be used in the present invention, but it is preferable to use a mixture of a phenol-based antioxidant and a phosphate-based antioxidant.
The phenol-based antioxidant is reacted with radicals generated in plastics to discharge hydrogen in the phenol-based antioxidant, thereby stabilizing the radicals, and the antioxidant is converted into the radicals and remains in a stable form through a resonance effect or re-arrangement of electrons.
Any conventional phenol-based antioxidant may be used in the present invention, but it is preferable that the phenol-based antioxidant is N,N′-1,6-hexanediylbis(3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene-propaneamide or bis-(3,3-bis-(4′-hydroxy-3′-tetrabutylphenyl)butanoic acid)-glycolester.
Further, the phosphite-based antioxidant performs a function of a hydroperoxide decomposer to prevent the radicals from being generated. Further, if the phosphite-based antioxidant is used together with the phenol-based antioxidant, a synergistic effect can be expected and stability of cross-linked plastics and stability to UV are increased.
Any conventional phosphite-based antioxidant may be used in the present invention, but it is preferable that the phosphite-based antioxidant is tris-(2,4-di-tertiary-butylphenyl)-phosphite or tetrakis(2,4-di-tertiary-butylphenyl)-4,4′-biphenylene diphosphite.
According to a preferred embodiment, the composition contains about 0.3 to 0.5 parts by weight and more preferably 0.4 parts by weight of the mixed antioxidant, based on 100 parts by weight of polyamide 66 or polyamide 6. In the case where the content of the antioxidant is less than about 0.3 parts by weight, the antioxidant cannot sufficiently prevent oxidation, and where the content is more than about 0.5 parts by weight, physical properties and the quality of appearance may be reduced.
(5) Heat Resistant Stabilizer
The heat resistant stabilizer functions to improve heat resistance of the composition, and any matter known in the art may be used as the heat resistant stabilizer. According to preferred embodiments, the heat resistant stabilizer is an iodine-based heat resistant stabilizer. According to an exemplary embodiment, the heat resistant stabilizer is copper iodide (CuI).
The content of the heat resistant stabilizer is preferably about 0.3 to 0.5 parts by weight and more preferably about 0.2 parts by weight based on 100 parts by weight of the polyamide 66 or polyamide 6 resin. In the case where the content of the heat resistant stabilizer is less than about 0.3 parts by weight, the heat resistance properties, such as the heat distortion temperature, of the composition may be reduced. On the other hand, in the case where the content is more than about 0.5 parts by weight, the mechanical properties and the appearance quality may be reduced.
(6) Lubricant
The lubricant functions to adjust friction between the compositions or between the composition and a metal when the composition is heated and molded to improve fluidity and a release property to thereby facilitate processing. Any conventional lubricant may be used in the present invention, and according to preferred embodiments, an olefine-based lubricant, more preferably ethylene bisstearamide, is used.
The content of the lubricant is preferably about 0.2 to 0.4 parts by weight and more preferably about 0.2 parts by weight based on 100 parts by weight of the polyamide 66 or polyamide 6 resin. In the case where the content of the lubricant is less than about 0.2 parts by weight, the fluidity and the release property may be reduced, and thus it may be difficult to mold large-sized products. In the case where the lubricant content is more than about 0.4 parts by weight, mechanical properties and weld strength may be reduced.
2. Use
The present invention provides excellent sounds insulation properties and may be applied in various ways so as to provide sound insulation. In particular, it is preferred that the present invention is applied to a partition of an engine room of a vehicle.
3. Manufacturing Method
Hereinafter, in another aspect, the present invention relates to a method of manufacturing a polyamide resin composition for sound insulation.
The polyamide resin composition for sound insulation may be appropriately manufactured by a person of ordinary skill in the art with reference to known technologies. Specifically, it is preferable that the polyamide resin composition for sound insulation is manufactured so as to include about 15 to 20 parts by weight of a glass fiber, preferably a glass fiber coated with a silane-based coupling agent, about 45 to 50 parts by weight of barium sulfate, about 0.3 to 0.5 parts by weight of antioxidant, preferably a mixture of a phenol-based antioxidant and a phosphite-based antioxidant, about 0.3 to 0.5 parts by weight of the heat resistant stabilizer and about 0.2 to 0.4 parts by weight of the lubricant, based on 100 parts by weight of the polyamide 66 or polyamide 6 resin.
Hereinafter, the present invention will be described in further detail with reference to examples. It will be obvious to a person having ordinary skill in the art that these examples are illustrative purposes only and are not to be construed to limit the scope of the present invention.

EXAMPLE

FIG. 1 is a mimetic diagram showing the partition 100 of the engine room of the vehicle which was formed from the polyamide resin compositions of the Examples and Comparative Examples. The components and contents of the Examples and Comparative Examples are shown in the following Table 1. Thereafter, physical properties thereof were compared, and set forth in the following Table 2.

	TABLE 1

		Comparative
	Example	Example

Classification	Unit	1	2	3	1	2	3

Resin	Polyamide	Part by	100	100	100	—	100	100
	66	weight
	Poly-	Part by	—	—	—	100	—	—
	propylene	weight
Anti-	Phenols	Part by	0.2	0.2	0.2	0.2	0.2	0.2
oxidant	weight
	Phosphites	Part by	0.2	0.2	0.2	0.2	0.2	0.2
		weight

Heat resistant	Part by	0.5	0.5	0.5	0.5	0.5	0.5
stabilizer	weight
Lubricant	Part by	0.3	0.3	0.3	0.3	0.3	0.3
weight
Glass fiber (short	Part by	15	20	—	25	15	15
fiber)	weight
Glass fiber (long	Part by	—	—	15	—	—	—
fiber)	weight
Barium sulfate	Part by	50	45	50	—	—	—
(BaSO₄)	weight
Iron oxide (Fe₂O₃)	Part by	—	—	—	50	50	—
	weight
Wollastonite	Part by	—	—	—	—	—	25
	weight

Table 1 is a table comparing the components and the contents of the Examples and the Comparative Examples. The antioxidant, the heat resistant stabilizer and the lubricant of the above-described Table 1 were included in the same content in the Examples and the Comparative Examples, and polypropylene was only included in Comparative Example 1. Further, barium sulfate for improving the sound insulation property was only included in the Examples (in accordance with the present invention), while iron oxide and wollastonite were instead included in the Comparative Examples (not in accordance with the present invention).
Physical and heat resistance properties of the Examples and the Comparative Examples compared through tests, and are described below.

TABLE 2

Test		Comparative
method	Example	Example

Classification	(ASTM)	Unit	1	2	3	1	2	3

Specific gravity	D792	—	2.06	2.05	2.06	2.15	2.10	1.83
Tensile strength	D638	MPa	104	122	120	38	100	101
Flexural strength	D790	MPa	152	166	158	50	150	155
flexural modulus	D790	MPa	8620	10200	9400	5500	9475	9921
Impact strength	D256	MPa	45	48	72	31	33	30
(+23□)
heat distortion	D648	° C.	243	243	245	155	242	238
(1.82 MPa)

Table 2 is a table in which physical and heat resistance properties of the Examples and the Comparative Examples are numerically represented through the specific tests, and compared.
The specific gravity was measured according to ASTM D792, and the tensile strength was measured according to ASTM D638 under the condition of the temperature of 23±2° C., relative humidity of 50%, atmospheric pressure, and a speed of 5 mm/min.
The flexural strength and the flexural modulus were measured according to ASTM D790, and the cross head speed was measured under the condition of a speed of 5 mm/min.
The impact strength was measured according to ASTM D256 as a value obtained by dividing energy when the specimen was broken by unit thickness by an Izod notch method at 23±2° C.
The heat distortion temperature was obtained by measuring the temperature in the case where the specimen was distorted when the ambient temperature was increased at the rate of 2° C./min under the condition of a load of 1.82 MPa on the specimen according to ASTM D648.
According to Table 2, the specific gravity was highest in Comparative Example 1, but the tensile strength, the flexural strength, the flexural modulus and the impact strength were superior in the Examples. In particular, one of the most important properties of a composition applied to the engine room of the vehicle is heat resistance. Based on the result that the heat resistance of the Examples was much better than the heat resistance of the Comparative Examples, it was demonstrated that the Examples were better than the Comparative Examples in terms of the mechanical and heat resistance properties. Further, it was demonstrated that in the case of Example 3 to which the long glass fiber was applied, all properties were better than Example 1 to which the short glass fiber was applied.

	TABLE 3

	400 Hz to 6300 Hz (dB RMS)

						Left of		Left	Right
		Left of	Right of	Left of the		the VIP	Right of	behind	behind
		the	the	front		seat of	the VIP	the left	the right
		driver's	driver's	passenger	Back	the back	seat of the	engine	engine
Classification	Unit	seat	seat	seat	seat	seat	back seat	room	room

Example 3	dB	76	76.4	75.9	78.5	78	78.4	25.2	32.4
No	dB	67.8	67.6	66.9	72.8	72.3	71.3	13.4	13.5
partition
Difference	dB	8.2	8.8	9	5.7	5.7	7.1	11.8	18.9

Table 3 is a table in which sound insulation performances of the Examples are compared. After the high-power speaker for tests having the frequency range of 400 Hz to 6300 Hz was installed in a direction of the inside of the vehicle at a position of the engine of the engine room of the vehicle, noise was generated. The insulation of noise by the partition, to which the present invention was applied, was then measured by imaging the insulated sound. That is, the magnitude of insulated noise was increased as the measured numerical value is was increased, and the magnitude of insulated noise was reduced as the measured numerical value was reduced.
In Table 3, in the case of Example 3 to which the partition was applied, the measured numerical value was higher than that of the case where the partition was not applied, which means that a large amount of noise is insulated by the higher numerical value. Accordingly, it was confirmed that in the case of Example 3 to which the partition was applied, the measured noise was reduced at all positions in the vehicle and right behind the engine room as compared to the case where the partition was not applied.
To be more specific, the drawings showing graphs which classify the magnitudes of noise insulated at each position for each frequency in Table 3 are provided below. FIG. 2 is a graph showing the magnitude of noise insulated at a left of a driver's seat for each frequency, FIG. 3 is a graph showing the magnitude of noise insulated at a right of the driver's seat for each frequency, FIG. 4 is a graph showing the magnitude of noise insulated at a left of a front passenger seat for each frequency, FIG. 5 is a graph showing the magnitude of noise insulated at a back seat for each frequency, FIG. 6 is a graph showing the magnitude of noise insulated at a left of a VIP seat of the back seat for each frequency, FIG. 7 is a graph showing the magnitude of noise insulated at a right of the VIP seat of the back seat for each frequency, FIG. 8 is a graph showing the magnitude of noise insulated directly behind a left engine room for each frequency, and FIG. 9 is a graph showing the magnitude of noise insulated directly behind a right engine room for each frequency. As seen in FIGS. 2 to 9, even though there was a difference between frequencies, from the average values, it was demonstrated that in the case where the partition was applied (200) a high noise insulation effect was provided as compared to the case where the partition was not applied (300) in all graphs.
Further, it was confirmed that in view of only the position of the driver's seat, the partition of Example 3 (which was in accordance with the present invention) was positioned between the engine room and the dash board, and thus the noise flowing from the engine room to the position of the driver's seat was reduced by an average of 8 to 8.8 dB.
The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes or modifications may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A polyamide resin composition for sound insulation comprising:

about 15 to 20 parts by weight of a glass fiber, based on 100 parts by weight of polyamide 6.6 or polyamide 6,

about 45 to 50 parts by weight of barium sulfate, based on 100 parts by weight of the polyamide 6.6 or polyamide 6 resin, and

one or more of about 0.3 to 0.5 parts by weight of an antioxidant, about 0.3 to 0.5 parts by weight of a heat resistant stabilizer, or about 0.2 to 0.4 parts by weight of a lubricant, based on 100 parts by weight of the polyamide 6.6 or polyamide 6,

wherein an average length of the glass fiber is about 1 mm to 5 mm,

wherein an average diameter of a cross section of the glass fiber is about 10 to 13 μm,

wherein the glass fiber is coated with a silane-based coupling agent,

wherein a weight of the silane-based coupling agent is about 0.1 to 0.3 wt % based on a total weight of the glass fiber,

wherein an average diameter of particles of the barium sulfate is about 20 to 30 μm.

2-7. (canceled)

8. The polyamide resin composition for sound insulation according to claim 1, the antioxidant comprises a mixture of a phenol-based antioxidant and a phosphite-based antioxidant.