JP2012061940A - Waterproof cover and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waterproof cover which is excellent in both sound absorbing properties and sound insulating properties, and a simple method for manufacturing the same.SOLUTION: This is the waterproof cover 1 interposed between an inner panel 4 of an automobile door 2 and a door trim 6. The waterproof cover is composed of a first film 7, a second film 8, and sound absorbing materials 10, the sound absorbing materials 10 are pinched between the first film 7 and the second film 8, a thickness of the first film 7 is thinner than that of the second film 8, and the first film 7 is opposed to the door trim 6, and the second film 8 is opposed to the inner panel 4 to form the waterproof cover 1 so interposed.

Description

  The present invention relates to a waterproof cover that is interposed between an inner panel of an automobile door and a door trim and prevents water from entering the vehicle interior, and a method of manufacturing the same.

  In order to prevent water from entering the vehicle interior from the automobile door, a waterproof cover is disposed between the inner panel of the automobile door and the door trim. Conventionally, a polyethylene sheet or the like has been used as such a waterproof cover. After being cut, the polyethylene sheet is placed in a three-dimensional shape or a cap attached as necessary, and then fixed to the inner panel using butyl tape or the like.

  Further, in recent years, there has been a demand for a waterproof cover having sound insulation and sound absorption properties in order to improve the quietness in the passenger compartment. So far, a waterproof sheet that has improved sound insulation by using a thick sheet, a waterproof sheet that has improved sound absorption by pasting a nonwoven fabric or foamed urethane onto a polyethylene sheet, and the like are known. However, many of these have been improved only in either the sound insulation property or the sound absorption property. Since the waterproof cover used in the automobile door is limited in weight and space, it is difficult to improve both sound insulation and sound absorption.

  Patent Document 1 describes a waterproof sheet (water deflector sheet) having sound insulation characteristics in which high-strength linear low-density polyethylene films of the first layer and the second layer are bonded to opposite sides of an open-cell urethane foam. Has been. Moreover, it is suitable that the thickness of the low density polyethylene film of a 1st layer and a 2nd layer shall be 1-10 mil (25.4-254 micrometers), and the thickness of an open cell urethane foam is 50-500 mil ( 1270 to 12700 μm). In the said waterproof sheet, it is supposed that the sound absorption property of the said waterproof sheet will improve by using an open cell urethane foam as a center layer. Moreover, it is supposed that the low density polyethylene film of a 1st layer and a 2nd layer has the effect | action which prevents the penetration | invasion of the water | moisture content to an open cell urethane foam. However, it has been difficult to make both the sound absorption property and the sound insulation property of the waterproof sheet good under the limitation of weight and space.

  Patent Document 2 describes a sound-absorbing material obtained by laminating resin films on both surfaces of a substrate in which small pieces of a foam from which a cell film has been removed are bonded with a binder. Here, it is described that the foam is preferably made of a soft polyurethane foam. Further, it is described that the small pieces of the foam are prevented from falling off by the resin film, and sound absorption is improved by the membrane vibration of the resin film. The example describes a sound absorbing material in which a polyethylene terephthalate resin film having a thickness of 30 μm is bonded to both surfaces of the substrate having a thickness of 10 mm by laminating, and the sound absorbing material has a low frequency (500 Hz, 1000 Hz). ) Was considered to have good sound absorption. However, the sound absorbing material has insufficient sound insulation.

JP-A-8-58378 JP 2008-32977 A

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a waterproof cover excellent in both sound absorption and sound insulation and a simple manufacturing method thereof.

  The above-described problem is a waterproof cover interposed between an inner panel of an automobile door and a door trim, and the waterproof cover includes a first film, a second film, and a sound absorbing material. The sound absorbing material is sandwiched between the first film, the first film is thinner than the second film, the first film and the door trim face each other, and the second film and the inner panel face each other. It is solved by providing a waterproof cover characterized in that.

  At this time, it is preferable that the sound absorbing material is sandwiched by adhering the first film and the second film in a blank portion where the sound absorbing material is not disposed.

  In the waterproof cover of the present invention, the thickness of the first film is 20 to 100 μm, the thickness of the second film is 50 to 300 μm, and the ratio of the thickness of the first film to the second film (first / 2) is preferably 0.8 or less. It is also preferable that the sound absorbing material is a porous material, and it is more preferable that the porous material is made of a fiber aggregate or a foam.

  The said subject is also solved by providing the manufacturing method of the waterproof cover which heat-seal | fuses a 1st film and a 2nd film.

  The waterproof cover of the present invention is lightweight and thin, and has excellent sound absorption and sound insulation properties. Therefore, such a waterproof cover is preferably used as a waterproof cover for an automobile door, which has severe restrictions on weight and space, and the quietness in the vehicle interior of the automobile in which the waterproof cover is arranged is improved. Furthermore, according to the manufacturing method of the present invention, such a waterproof cover can be easily obtained.

It is a disassembled perspective view which shows the outline of the motor vehicle door containing the waterproof cover of this invention. It is a perspective view of the waterproof cover of this invention. It is a figure which shows the relationship between Example 1 and 2 and the frequency of an incident sound, and a sound absorption factor in the waterproof cover of Comparative Examples 1-4. It is a figure which shows the relationship between the frequency of an incident sound, and the transmission loss in the waterproof cover of Examples 1 and 2 and Comparative Examples 1-4. It is a figure which shows the relationship between Example 3 and 4, and the frequency of an incident sound, and a sound absorption factor in the waterproof cover of Comparative Examples 5-7. It is a figure which shows the relationship between the frequency of an incident sound, and the transmission loss in Example 3 and 4 and the waterproof cover of Comparative Examples 5-7.

  FIG. 1 is an exploded perspective view showing an outline of an automobile door 2 including a waterproof cover 1 of the present invention. An example of the usage mode of the waterproof cover 1 of the present invention will be briefly described using this. The automobile door 2 includes a door body 5 including an outer panel 3 made of a steel plate and an inner panel 4, and a door trim 6 for makeup mounted on a side surface on the vehicle interior side below the window opening of the inner panel 4. Is done. A waterproof cover 1 is interposed between the inner panel 4 and the door trim 6 to prevent water from entering the vehicle interior. At this time, the waterproof cover 1 is interposed such that the first film 7 and the door trim 6 face each other, and the second film 8 and the inner panel 4 face each other. In the space between the outer panel 3 and the inner panel 4, equipment components such as a window regulator that raises and lowers the window glass and a speaker 9 are accommodated.

  The waterproof cover 1 includes a first film 7, a second film 8, and a sound absorbing material 10. The second film 8 is disposed so as to face the inner panel 4 and prevents water from entering the vehicle interior. The sound absorbing material 10 is disposed between the first film 7 and the second film 8. In the blank portion 11 where the sound absorbing material 10 is not disposed, the sound absorbing material 10 is sandwiched, for example, by bonding the first film 7 and the second film 8 together.

  The waterproof cover 1 is usually provided with a speaker insertion hole 12, and the speaker 9 is inserted into the speaker insertion hole 12 so that water does not leak between the speaker 9 and the waterproof cover 1. . The speaker 9 is mounted in an opening 13 provided in the inner panel 4, and waterproof means is provided so that water can be prevented from entering the speaker 9. Further, cap insertion holes 14 and 15 are opened in the waterproof cover 1 as necessary. The caps 16 and 17 are inserted into the cap insertion holes 14 and 15 and adhered so that water does not leak. In the caps 16 and 17, cushioning materials 18 and 19 for absorbing a shock from the side are inserted. Here, instead of using the caps 16 and 17, the second film 8 may be formed to form a recess, and the cushioning materials 18 and 19 may be inserted into the recess. In addition, a slit through which wiring or the like passes is provided as necessary.

  The waterproof cover of the present invention comprises a first film, a second film, and a sound absorbing material, the sound absorbing material is sandwiched between the first film and the second film, and the thickness of the first film is greater than the thickness of the second film. It is thin, and the first film and the door trim are opposed to each other, and the second film and the inner panel are opposed to each other.

  As for the waterproof cover of this invention, the 1st film and the 2nd film are arrange | positioned on both sides of the sound-absorbing material. By forming such a double wall structure with the first film and the second film, the waterproof cover of the present invention has a sound insulating property superior to the sound insulating property predicted by the mass law. In the waterproof cover of the present invention, of the two films, the first film having a smaller thickness faces the door trim. That is, the first film is disposed on the vehicle compartment side. The first film having a small thickness has little sound reflection and excellent sound absorption. Therefore, the waterproof cover of the present invention is excellent in sound absorption for noise in the vehicle interior. By adopting such a configuration, it is possible to provide a waterproof sheet that is excellent in sound insulation against noise from outside the vehicle and also excellent in sound absorption against noise once entering the vehicle interior.

  Examples of the resin that is the material of the first film include linear low density polyethylene (LLDPE), high density polyethylene (HDPE), polyethylene such as low density polyethylene (LDPE), polyolefin such as polypropylene; polyamide; polyester; polyurethane; Resin etc. are mentioned. Among them, polyethylene having excellent water resistance and low cost is preferable, and LLDPE having excellent flexibility and strength is particularly preferable. When the first film is flexible, chatter noise derived from speaker vibration and vibration noise due to wind during driving are reduced.

  The resin may further contain another resin. As the other resin to be contained in the resin, a flexible resin having an elastic modulus lower than that of the resin is suitable. By including such a flexible resin, the first film becomes flexible, and chatter noise derived from speaker vibration and vibration noise due to wind during driving are reduced. Such a flexible resin may be an elastomer, and among them, a thermoplastic elastomer is suitable. As the flexible resin to be contained when the resin that is the material of the first film is a polyolefin, a flexible polyolefin or a polyolefin-based thermoplastic elastomer is suitable. In this case, the compatibility is good. Of these, an ethylene-α-olefin copolymer or an ethylene-α-olefin-diene copolymer is particularly suitable. The content of the flexible resin contained in the resin that is the material of the first film is preferably 2 to 50% by weight. When the content of the flexible resin is less than 2% by weight, the effect of making the first film flexible may not be obtained. On the other hand, when the content of the flexible resin exceeds 50% by weight, the strength of the first film may be reduced.

  The resin that is the material of the first film preferably further contains an inorganic filler. Thereby, the slipperiness between the first films is improved, and blocking when the first films are stacked and stored can be prevented. As the inorganic filler, talc, clay, kaolin, calcium carbonate, silica, alumina, magnesium hydroxide, magnesium oxide and the like can be used. The content of the inorganic filler in the resin is preferably 0.1 to 10% by weight. When the content of the inorganic filler in the resin is less than 0.1% by weight, the effect of improving the sliding property between the first films may not be obtained, and more preferably 0.3% by weight. That's it. On the other hand, when content of an inorganic filler exceeds 10 weight%, there exists a possibility that the intensity | strength of a 1st film may fall, More preferably, it is 5 weight% or less.

  The resin may contain other additives as long as the effects of the present invention are not impaired. Examples of the additive include a lubricant. The content of such additives is usually 10% by weight or less.

  A first film is formed using the resin. Although the molding method at this time is not particularly limited, the molding is usually performed by extrusion molding using a T die, inflation molding or the like. The obtained first film is usually cut into a shape corresponding to the outer shape of the sound absorbing material. When the sound absorbing material is sandwiched by adhering the first film and the second film at the margin, when the first film is overlapped with the sound absorbing material, the sound absorbing material is placed outside the outer periphery of the sound absorbing material. It is necessary to cut so that a blank portion where only one film is arranged is formed. Moreover, the slit for wiring penetration etc. can be simultaneously provided with respect to a 1st film.

  The thickness of the first film is preferably 20 to 100 μm. If the thickness of the first film is in such a range, the first film vibrates strongly when the sound wave reaches. At this time, a sound absorbing effect is obtained by converting a part of sound energy into heat energy. In particular, the sound absorption for sounds having a frequency of 2500 Hz or less is improved. Since most of the noise in the passenger compartment is in such a frequency range, the quietness in the passenger compartment is improved. Moreover, if the thickness of a 1st film is said range, reflection of the sound which reaches | attains from a vehicle interior is reduced more. When the thickness of the first film is less than 20 μm, chatter noise derived from speaker vibration may increase and the strength of the first film may decrease. The thickness of the first film is more preferably 25 μm or more. On the other hand, if the thickness of the first film exceeds 100 μm, the sound absorption effect due to membrane vibration may be reduced, or reflection of sound reaching from the passenger compartment may be increased, and the sound absorption of the waterproof cover may be reduced. There is. The thickness of the first film is more preferably 80 μm or less.

  The second film faces the inner panel. That is, the second film is disposed outside the vehicle. Of the two films constituting the waterproof cover, the thicker second film has better sound insulation than the first film. Therefore, the second film improves the sound insulation of the waterproof cover against noise from outside the vehicle. Further, the second film covers the inner panel, thereby preventing water from entering the vehicle interior.

  As the resin that is the material of the second film, those described above as the material of the first film can be used. Among them, polyethylene having excellent water resistance and low cost is preferable, and LLDPE having excellent flexibility and strength is particularly preferable. Since the second film is flexible, chatter noise derived from speaker vibration and vibration noise due to wind during driving are reduced. LLDPE is also excellent in moldability.

  The resin may further contain another resin. As the other resin to be contained in the resin, a flexible resin having an elastic modulus lower than that of the resin is suitable. By including such a flexible resin, the second film becomes flexible, and chatter noise derived from speaker vibration and vibration noise due to wind during driving are reduced. As the flexible resin to be contained in the resin that is the material of the second film, those described above as the material of the first film can be used. The content of the flexible resin contained in the resin that is the material of the second film is preferably 2 to 50% by weight. If the content of the flexible resin is less than 2% by weight, the effect of making the second film flexible may not be obtained. On the other hand, when content of flexible resin exceeds 50 weight part, there exists a possibility that the intensity | strength of a 2nd film may fall.

  The resin that is the material of the second film preferably further contains an inorganic filler. Thereby, the slidability between the second films is improved, and blocking when the second films are stacked and stored can be prevented. As an inorganic filler, what was mentioned above as a material of the 1st film can be used. The content of the inorganic filler in the resin is preferably 0.1 to 10% by weight. When the content of the inorganic filler in the resin is less than 0.1% by weight, the effect of improving the slipperiness between the second films may not be obtained, and more preferably 0.3% by weight. That's it. On the other hand, when content of an inorganic filler exceeds 10 weight%, there exists a possibility that the intensity | strength of a 2nd film may fall, More preferably, it is 5 weight% or less.

  The resin may contain other additives as long as the effects of the present invention are not impaired. Examples of the additive include a lubricant. The content of such additives is usually 10% by weight or less.

  A second film is formed using the resin. Although the shaping | molding method at this time is not specifically limited, A 2nd film is shape | molded by the method mentioned above etc. as a method of shape | molding a 1st film.

  The obtained second film is cut corresponding to the dimensions of the door. In the case of a passenger car door, the cut dimensions are usually about 500 to 600 mm in length and about 600 to 800 mm in width. Moreover, when providing a speaker insertion hole and a cap insertion hole in a waterproof cover, it is preferable to punch out these insertion holes simultaneously with cutting. The size of the speaker insertion hole is usually about 100 to 200 mm in diameter, and the size of the cap insertion hole is usually about 50 to 300 mm in the vertical direction and about 50 to 300 mm in the horizontal direction. A small hole for other wiring penetration etc. can be simultaneously provided in the 2nd film.

  Unevenness is formed in the second film thus cut as necessary. The position where the irregularities are formed is not particularly limited, but is usually a portion where no sound absorbing material is disposed. The unevenness may be formed after the second film is formed, or after the second film is formed and the sound absorbing material is sandwiched between the obtained second film and the first film. The method for forming the irregularities is not particularly limited, and either thermoforming or cold forming can be employed. Examples of thermoforming include vacuum forming and pressure forming. Examples of cold forming include cold drawing and press forming. A cushioning material or the like for absorbing an impact from the side can be inserted into the irregularities formed in this way.

  The thickness of the second film is preferably 50 to 300 μm. When the thickness of the second film is included in such a range, the waterproof cover of the present invention has excellent sound insulation. If the thickness of the second film is less than 50 μm, the strength of the second film may be insufficient or the sound insulation properties may be reduced. The thickness of the second film is more preferably 60 μm or more. On the other hand, when the thickness of the second film exceeds 300 μm, the waterproof cover may be heavy or the cost may be increased. The thickness of the second film is more preferably 200 μm or less, and further preferably 170 μm or less.

  In the waterproof cover of the present invention, it is necessary that the thickness of the first film is thinner than the thickness of the second film. Thereby, it is possible to obtain a waterproof cover excellent in both sound absorption and sound insulation. Since the first film having a small thickness faces the door trim, the sound incident from the vehicle interior side is effectively absorbed by the membrane vibration of the first film. Further, since the first film is thin, most of the sound not absorbed by the membrane vibration is transmitted and absorbed by the sound absorbing material. On the other hand, since the thicker second film faces the inner panel, the sound insulation of the waterproof cover is improved. Moreover, since the waterproof cover of the present invention has a double wall structure, the sound insulation is further improved. By having such a configuration, the waterproof cover of the present invention has excellent sound absorption and sound insulation properties even if it is lightweight and thin.

  At this time, it is preferable that the thickness ratio (first / second) of the first film and the second film is 0.8 or less. If the ratio of the thickness of the first film to the second film (first / second) is greater than 0.8, it may be difficult to achieve both the sound absorbing property and the sound insulating property of the waterproof cover. The ratio of the thickness of the first film to the second film (first / second) is more preferably 0.7 or less, and further preferably 0.5 or less. On the other hand, the thickness ratio (first / second) of the first film and the second film is usually 0.1 or more.

  The sound absorbing material is not particularly limited, but is preferably a porous material. Since the porous material is excellent in sound absorbing property and lightweight, it is suitably used as the sound absorbing material of the present invention. More preferably, the porous material is made of a fiber aggregate or foam.

The fiber assembly used as the sound absorbing material is not particularly limited, and examples thereof include a nonwoven fabric and felt. Especially, a nonwoven fabric is suitable and a melt blown nonwoven fabric is more suitable. Melt blown non-woven fabrics are excellent in sound absorption because the fiber diameter is extremely fine. From the viewpoint of recyclability, the melt blown nonwoven fabric is preferably made of polyolefin fibers. At this time, the fiber which consists of other thermoplastic resins other than polyolefin may be contained. The suitable content rate when the fiber which consists of another thermoplastic resin is included is 50-90 weight part of polyolefin fibers, and the fiber which consists of another thermoplastic resin is 10-50 weight part. Examples of fibers made of other thermoplastic resins include polyester fibers and polyamide fibers, but polyester fibers are preferably blended from the viewpoint of high elastic modulus and maintaining the bulkiness of the nonwoven fabric. The thickness of the nonwoven fabric is preferably ^{3 to 30} mm as measured under a load of 1.37 × 10 ⁻³ N / cm ² . In order to improve sound absorption, it is more preferably 5 mm or more. On the other hand, if considering the weight of the vehicle body, the size of the space in the door, etc., it is more preferably 20 mm or less.

  The material of the foam used as the sound absorbing material is not particularly limited, and a foam of rubber or resin can be used. From the viewpoint of sound absorption, a rubber foam is preferable, and a polyurethane foam is particularly preferable. It is preferable that the foam has a thickness of 3 to 30 mm. In order to improve sound absorption, it is more preferably 5 mm or more. On the other hand, if considering the weight of the vehicle body, the size of the space in the door, etc., it is more preferably 20 mm or less.

  The area covered by the sound absorbing material is preferably 50% or more of the area of the waterproof cover from the viewpoint of sound absorption. On the other hand, the waterproof cover is often affixed while aligning with the inner panel, and in order to allow it to be affixed while checking the position of various wirings, sound absorbing material is affixed around the periphery. It is preferable that the remaining part remains. Therefore, the area covered by the sound absorbing material is preferably 90% or less of the area of the waterproof sheet.

  The sound absorbing material is sandwiched between the first film and the second film. Thereby, the first film, the second film, and the sound absorbing material are integrated. The method for sandwiching the sound absorbing material is not particularly limited, but it is preferable that the sound absorbing material is sandwiched by bonding the first film and the second film in a blank portion where the sound absorbing material is not disposed. It is.

  At this time, as the first film, a film cut so as to have a blank portion where only the first film is arranged outside the outer periphery of the sound absorbing material when the first film is overlapped with the sound absorbing material is used. When the sound absorbing material is sandwiched between the first film and the second film, the first film and the second film are in contact with each other in the blank portion. In the margin, the sound absorbing material is sandwiched by adhering the first film and the second film. The margin is preferably formed outside the outer periphery of the sound absorbing material so as to go around the sound absorbing material, and the width of the margin at this time is preferably 1 to 5 cm.

  According to such a method, since the sound absorbing material is fixed without adhering the sound absorbing material to the first film or the second film, the number of steps can be reduced. In this case, since the first film and the sound absorbing material are not bonded to each other, the first film vibrates more strongly when sound reaches the first film. Therefore, the sound absorption of the waterproof cover is further improved. When the first film and the second film are bonded, the outer side of the outer periphery of the sound absorbing material may be bonded without any gap, and the sound absorbing material may be sealed with the first film and the second film. Moreover, you may adhere | attach the 1st film and the 2nd film partially. From the viewpoint of protecting the sound absorbing material from water intrusion and dust adhesion, it is more preferable that the sound absorbing material is sealed.

  The method for adhering the first film and the second film is not particularly limited. Examples thereof include a method of using an adhesive and an adhesive sheet, a method of thermally fusing the first film and the second film, and the like.

  Especially, it is suitable to manufacture a waterproof sheet by heat-seal | fusing a 1st film and a 2nd film. According to such a method, the first film and the second film can be bonded firmly in a short time, and the cost is low. Specifically, after placing the first film on a heat plate on which a heat source is arranged so as to correspond to the bonded portion, and further placing the sound absorbing material and the second film in this order, 2 The method of lightly pressing from above the film is preferred.

  It is also preferable that the sound absorbing material is sandwiched by bonding the first film and the sound absorbing material and bonding the second film and the sound absorbing material. At this time, it is preferable that the first film and the sound absorbing material are locally bonded. Specifically, it is preferable that the sound absorbing material is bonded in a linear shape or a dot shape at the peripheral portion. When the entire surface of the sound absorbing material is bonded to the first film, there is a possibility that the first film is less likely to vibrate when sound reaches. On the other hand, the second film and the sound absorbing material may be locally bonded, or the entire surface of the sound absorbing material may be bonded to the second film. Adhesion between the first film and the sound absorbing material and adhesion between the second film and the sound absorbing material can be performed by using an adhesive or heat-sealing. It is selected as appropriate.

  The waterproof cover of the present invention thus manufactured is interposed between the inner panel of the automobile door and the door trim. Specifically, an embodiment in which a double-sided adhesive tape made of butyl rubber is attached to an inner panel, the waterproof cover of the present invention is pressed against the inner panel, and the periphery of the waterproof cover is adhered with an adhesive tape is suitable. At this time, wiring or the like may penetrate the waterproof cover. In that case, it is preferable to seal the penetration portion of the wiring so that water does not enter. The door trim is installed after the waterproof cover is bonded to the inner panel.

  In order to improve the quietness of the interior of the vehicle, the waterproof cover needs to have excellent sound absorbing properties against noise once entering the vehicle interior as well as sound insulation against noise from outside the vehicle. Further, the waterproof cover disposed in the automobile door is limited in weight and thickness. The waterproof cover of the present invention, which is lightweight and thin, and has both excellent sound absorption and sound insulation, has excellent characteristics as a waterproof cover for automobile doors. Moreover, such a waterproof cover can be easily manufactured by thermally fusing and bonding the first film and the second film.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Measurement of sound absorption characteristics]
The sound absorption characteristics of the waterproof cover were measured using a 4206 type impedance tube manufactured by Brüel & Kjær Co., Ltd., based on JIS: A1405-2.

[Measurement of transmission loss characteristics]
The sound insulation of the waterproof cover was evaluated by measuring the transmission loss characteristics of the waterproof cover. For measurement of the transmission loss characteristic, a 4206T type impedance tube manufactured by Brüel & Kjær was used. The measurement was performed by the 4-microphone transfer coefficient method. As the measurement sample, a portion of the waterproof cover where the sound absorbing material is disposed is punched into a circular shape (φ29 mm). The measurement sample was attached to the sample holder placed between the sound source tube and the sound receiving tube. Sound is emitted from the sound source (loudspeaker) attached to the end of the sound source tube (the end to which the sample holder is not connected) at the four measurement positions (two on the sound source tube and two on the sound receiving tube). Sound pressure was measured. The transmission loss was calculated from the measured values obtained.

Example 1

  Raw material of first film 7 [Linear low density polyethylene (Nippon Polyethylene, “Novatech LL UH410”): 100 parts by weight, Linear low density polyethylene with talc (talc content 20% by weight): 3 parts by weight ] Was injected into an inflation molding machine to perform inflation molding. The molding conditions at this time were a resin temperature of 210 ° C. and an extrusion rate of 50 to 60 kg / hr. The thickness of the obtained first film 7 was 70 μm.

  The first film 7 was punched with a Thomson blade according to the outer shape of the first film 7 shown in FIG. The outer shape of the first film 7 at this time corresponds to the outer shape of the sound absorbing material, and is 2 cm larger than the outer shape of the sound absorbing material on the entire circumference.

  A second film 8 was obtained by the same raw material and molding method as those of the first film 7 except that the setting of the film thickness at the time of inflation molding was changed. The thickness of the obtained second film 8 was 150 μm.

  The second film 8 was punched with a Thomson blade according to the outer shape of the second film 8 shown in FIG.

As the sound absorbing material 10, a polyurethane foam (thickness: 10 mm, apparent density: 22 kg / m ³ ) having no skin layer on the surface was used. The polyurethane foam was punched with a Thomson blade according to the outer shape of the sound absorbing material 10 shown in FIG.

  As shown in FIG. 2, the first film 7 is placed on a hot plate in which heat rays are arranged at a position corresponding to the bonding portion 20 that is about 1 cm inside (about 1 cm outside the outer periphery of the sound absorbing material 10) from the outer periphery of the first film 7. Placed. Further, the sound absorbing material 10 is formed on the first film 7 so that a blank portion 11 having a width of about 2 cm in which only the first film 7 is disposed is formed outside the outer periphery of the sound absorbing material 10. Placed. Furthermore, the 2nd film 8 was mounted on it. A plate was placed on the second film 8 and the plate was lightly pressed down by air pressure, whereby the first film 7 and the second film 8 were fused at the bonding portion 20. In FIG. 2, the bonded portion 20 is indicated by a broken line, but is actually bonded linearly, and the sound absorbing material 10 is sealed by the first film and the second film.

  The sound absorption characteristics and transmission loss characteristics of the waterproof cover 1 thus obtained were measured. When measuring the sound absorption characteristics, sound was incident on the first film 7 side. When measuring the transmission loss characteristic, sound was incident on the second film 8 side. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover 1.

Example 2
A waterproof cover 1 was produced in the same manner as in Example 1 except that a film having a thickness of 30 μm was used as the first film 7 and a film having a thickness of 70 μm was used as the second film 8. At this time, the thickness of the 1st film 7 and the 2nd film 8 was adjusted by changing the setting of the film thickness at the time of inflation molding. The sound absorption characteristics and transmission loss characteristics of the waterproof cover 1 obtained were measured in the same manner as in Example 1. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover 1.

Comparative Example 1
A waterproof cover was produced in the same manner as in Example 1 except that a film having a thickness of 150 μm was used instead of the first film 7 (thickness: 70 μm). The sound absorption characteristics and transmission loss characteristics of the obtained waterproof cover were measured in the same manner as in Example 1. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

Comparative Example 2
A waterproof cover was produced in the same manner as in Example 1 except that a film having a thickness of 30 μm was used instead of the first film 7 and the second film 8. The sound absorption characteristics and transmission loss characteristics of the obtained waterproof cover were measured in the same manner as in Example 1. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

Comparative Example 3
An adhesive is applied around the sound absorbing material 10 (punched with a Thomson blade) made of polyurethane foam used for the waterproof cover 1 of Example 1, and the sound absorbing material 10 is used for the waterproof cover 1 of Example 1. A waterproof cover was prepared by adhering to the same film as the second film 8 (one punched with a Thomson blade). The sound absorption characteristics and transmission loss characteristics of the obtained waterproof cover were measured. When measuring the sound absorption characteristics, sound was incident on the sound absorbing material side. When measuring the transmission loss characteristics, sound was incident on the film side. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

Comparative Example 4
The sound absorption characteristics and transmission loss characteristics of the sound absorbing material 10 (made by punching with a Thomson blade) made of polyurethane foam used for the waterproof cover of Example 1 were measured. FIG. 3 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 4 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

  The waterproof cover 1 of Example 1 and Example 2 is an example in which a polyurethane foam is used as the sound absorbing material 10. As shown in FIG. 3, the waterproof cover 1 of Example 1 [first film: 70 μm, second film: 150 μm] and Example 2 [first film: 30 μm, second film: 70 μm] has a frequency of 2500 Hz or less. In the frequency domain, the water-absorbing cover (Comparative Example 3) not having the first film 7 and the sound-absorbing property superior to those of only the sound-absorbing material made of polyurethane foam (Comparative Example 4) were obtained. As shown in FIG. 4, the waterproof cover 1 of Examples 1 and 2 is only a waterproof cover (Comparative Example 3) that does not have the first film 7 and a sound-absorbing material made of polyurethane foam in all frequency regions. The sound insulation was superior to that of Comparative Example 4 (Comparative Example 4). On the other hand, the waterproof cover (Comparative Example 1) in which the sound-absorbing material is sandwiched between a film having a thickness of 150 μm and a film having a thickness of 150 μm was excellent in sound insulation (FIG. 4), but sound-absorbing (FIG. 3). ) Was low. In addition, the waterproof cover (Comparative Example 2) in which the sound absorbing material is sandwiched between the film having a thickness of 30 μm and the film having a thickness of 30 μm was excellent in sound absorption (FIG. 3), but sound insulation (FIG. 4). ) Was low.

Example 3
A waterproof cover 1 was produced in the same manner as in Example 1 except that a melt blown nonwoven fabric was used as the sound absorbing material 10 instead of the polyurethane foam. The melt blown nonwoven fabric used at this time is a melt blown nonwoven fabric “Synthrate Embossed Type TAI-2047” manufactured by Sumitomo 3M Limited. The nonwoven fabric is a nonwoven fabric produced by the melt blown method containing 65% by weight of polypropylene and 35% by weight of polyester, and having a thickness of 10 mm measured under a load of 1.37 × 10 ⁻³ N / cm ^2. It is. The sound absorption characteristics and transmission loss characteristics of the waterproof cover 1 obtained were measured in the same manner as in Example 1. FIG. 5 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 6 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover 1.

Example 4
Example 1 except that a film having a thickness of 30 μm is used as the first film 7, a film having a thickness of 70 μm is used as the second film 8, and a melt blown nonwoven fabric is used as the sound absorbing material 10 instead of the polyurethane foam. A waterproof cover 1 was produced in the same manner. The melt blown nonwoven fabric used at this time is the same as that used for the waterproof cover 1 of Example 3. The sound absorption characteristics and transmission loss characteristics of the waterproof cover 1 obtained were measured in the same manner as in Example 1. FIG. 5 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 6 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover 1.

Comparative Example 5
A waterproof cover in the same manner as in Example 1 except that a film having a thickness of 150 μm was used instead of the first film 7 (thickness 70 μm), and a melt blown nonwoven fabric was used as the sound absorbing material instead of the polyurethane foam. Was made. The melt blown nonwoven fabric used at this time is the same as that used for the waterproof cover 1 of Example 3. The sound absorption characteristics and transmission loss characteristics of the waterproof cover 1 obtained were measured in the same manner as in Example 1. FIG. 5 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 6 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

Comparative Example 6
A sound-absorbing material similar to the sound-absorbing material 10 made of the melt-blown nonwoven fabric used in the waterproof cover 1 of Example 3 (punched with a Thomson blade) is placed on a hot plate in which heat wires are arranged at positions corresponding to the periphery of the sound-absorbing material. Further, a film similar to the second film 8 used for the waterproof cover of Example 1 (those punched with a Thomson blade) was placed thereon. A plate was placed on the film, and the plate and the sound absorbing material were fused by lightly pressing the plate with air pressure. The sound absorption characteristics and transmission loss characteristics of the obtained waterproof cover were measured. When measuring the sound absorption characteristics, sound was incident on the sound absorbing material side. When measuring the transmission loss characteristics, sound was incident on the film side. FIG. 5 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 6 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

Comparative Example 7
The sound absorption characteristics and transmission loss characteristics of the sound-absorbing material (punched with a Thomson blade) made of a Ruthblon nonwoven fabric used for the waterproof cover 1 of Example 3 were measured. FIG. 5 shows the relationship between the frequency of the incident sound obtained by the measurement and the sound absorption coefficient, and FIG. 6 shows the relationship between the frequency of the incident sound and the transmission loss. Table 1 shows the evaluation of sound absorption and sound insulation of the waterproof cover.

  The waterproof cover 1 of Example 3 and Example 4 is an example in which a melt blown nonwoven fabric is used as the sound absorbing material 10. As shown in FIG. 5, the waterproof cover 1 of Example 3 [first film: 70 μm, second film: 150 μm] and Example 4 [first film: 30 μm, second film: 70 μm] is 2500 Hz or less ( In the frequency range of Example 3) or 3500 Hz or less (Example 4), it is superior to the waterproof cover (Comparative Example 6) not having the first film 7 and only the sound-absorbing material made of meltblown nonwoven fabric (Comparative Example 7). It had a good sound absorption. Further, as shown in FIG. 6, the waterproof covers of Examples 3 and 4 have only a sound-absorbing material made of a waterproof cover (Comparative Example 6) that does not have the first film 7 and a melt-blown nonwoven fabric in all frequency regions. It had better sound insulation than (Comparative Example 7). On the other hand, the waterproof cover (Comparative Example 5) in which a sound absorbing material is sandwiched between a film having a thickness of 150 μm and a film having a thickness of 150 μm has excellent sound insulation (FIG. 6), but has a sound absorbing property (FIG. 5). ) Was low.

  Regardless of whether the sound absorbing material 10 is a polyurethane foam or a melt blown nonwoven fabric, the sound absorbing property and sound insulating property of the waterproof cover 1 are greatly changed by changing the thicknesses of the first film 7 and the second film 8.

DESCRIPTION OF SYMBOLS 1 Waterproof cover 2 Automotive door 3 Outer panel 4 Inner panel 5 Door main body 6 Door trim 7 1st film 8 2nd film 9 Speaker 10 Sound absorption material 11 Blank part 12 Speaker insertion hole 13 Opening part 14, 15 Cap insertion hole 16, 17 Cap 18 , 19 Cushioning material 20 Adhesive part

Claims (6)

A waterproof cover interposed between an inner panel and a door trim of an automobile door,
The waterproof cover comprises a first film, a second film and a sound absorbing material,
The sound absorbing material is sandwiched between the first film and the second film,
The thickness of the first film is thinner than the thickness of the second film,
A waterproof cover, wherein the first film and the door trim face each other, and the second film and the inner panel face each other.   The waterproof cover according to claim 1, wherein the sound absorbing material is sandwiched by adhering the first film and the second film in a blank portion where the sound absorbing material is not disposed.   The thickness of the first film is 20 to 100 μm, the thickness of the second film is 50 to 300 μm, and the ratio of the thickness of the first film to the second film (first / second) is 0. The waterproof cover according to claim 1, wherein the waterproof cover is 8 or less.   The waterproof cover according to claim 1, wherein the sound absorbing material is a porous material.   The waterproof cover according to claim 4, wherein the porous material is made of a fiber assembly or a foam.   The manufacturing method of the waterproof cover of Claim 2 which heat-seal | fuses a 1st film and a 2nd film.

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