Sound-absorbing cover and sound source component

Abstract

To provide an inexpensive sound absorbing cover covering a sound source side component such as an engine cover of a vehicle, which can reduce overall thickness and simplify manufacturing work by eliminating need for laminating nonwoven fabrics.SOLUTION: A sound absorbing cover 10 covering a sound source side component 41 such as an engine cover is composed of a body 11 made of molded polyurethane foam, a support portion 21 supporting the body 11 away from a surface 43 of the sound source side component 41, and an air layer 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sound-absorbing cover and a sound source component.

Background Art

[0002] Conventionally, there is a sound-absorbing cover that uses an air layer to improve the sound absorption of low frequencies below 1000 Hz. For example, there is an engine cover that improves sound absorption by providing a urethane foam resin layer and a PET non-woven fabric on the surface facing the direct injection engine in the cover body covering the direct injection engine, and using the air layer formed between the urethane foam resin layer and the PET non-woven fabric (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Those that improve sound absorption by the air layer formed between the urethane foam resin layer and the PET non-woven fabric have a problem that the overall thickness increases due to the urethane foam resin layer and the PET non-woven fabric, and also require a welding operation for bonding the urethane foam resin layer and the PET non-woven fabric, resulting in an increase in manufacturing work and product cost.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a sound-absorbing cover and a sound source component having a new configuration that can reduce the overall thickness and simplify and reduce the manufacturing work.

Means for Solving the Problems

[0006] The first means is characterized in that in a sound-absorbing cover that covers a sound source side member, it includes a main body formed of polyurethane foam, a support portion that supports the main body away from the surface of the sound source side member, and an air layer. The second means is a sound source component that includes the sound-absorbing cover of the first means and has an air layer between the main body and the sound source side member.

Advantages of the Invention

[0007] According to the sound-absorbing cover of the present invention, since it includes a main body formed of polyurethane foam, a support portion that supports the main body away from the surface of the sound source side member, and an air layer, the overall thickness of the sound-absorbing cover can be reduced. Also, since bonding of non-woven fabric or the like is unnecessary, the manufacturing work can be simplified, and the sound-absorbing cover can be made inexpensive.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described. The sound-absorbing cover 10 of an embodiment shown in FIGS. 1 and 2 is composed of a main body 11, a support portion 21, and an air layer 31, and is provided to cover the surface 43 of a sound source side member 41 such as an engine, battery, transmission, intake manifold, exhaust manifold, etc. of a vehicle.

[0010] The main body 11 is made of molded polyurethane foam (molded polyurethane foam). The molding is a molding method in which a polyurethane foam raw material containing polyol, catalyst, foaming agent, foam stabilizer, and polyisocyanate is mixed, injected into a mold, and foamed in the mold. Note that the molding methods of polyurethane foam include mold molding and slab molding. Slab molding is a molding method in which raw materials of polyurethane foam are mixed and discharged onto a belt conveyor, and foamed under atmospheric pressure at room temperature.

[0011] As the polyol, a polyol for polyurethane foam can be used. For example, any of polyether polyol, polyester polyol, polyether ester polyol, and polymer polyol may be used, and one or more of them may be used.

[0012] Examples of the polyether polyol include polyether polyols obtained by adding alkylene oxides such as ethylene oxide (EO) and propylene oxide (PO) to polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose.

[0013] Examples of the polyester polyol include polyester polyols obtained by polycondensation from aliphatic carboxylic acids such as malonic acid, succinic acid, and adipic acid and aromatic carboxylic acids such as phthalic acid, and aliphatic glycols such as ethylene glycol, diethylene glycol, and propylene glycol. In addition, examples of the polyether ester polyol include those obtained by reacting the polyether polyol with a polybasic acid for polyesterification, or those having both polyether and polyester segments in one molecule.

[0014] Polymer polyol is a polyol in which polyacrylonitrile or polystyrene is dispersed in the polyol. When trying to increase the rigidity of polyurethane foam by blending polymer polyol, the foam becomes brittle and the physical properties deteriorate. Therefore, when using it, it is preferably used in combination with other polyols, and less than 20 parts by weight, more preferably less than 10 parts by weight, per 100 parts by weight of the polyol is preferred. The polyol is not limited to one type, and a plurality of types may be used in combination.

[0015] As the catalyst, urethanization catalysts known for use in polyurethane foam can be used in combination. For example, amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine, tin catalysts such as stannous octoate and dibutyltin dilaurate, and metal catalysts such as phenylmercury propionate or lead octoate (also referred to as organometallic catalysts) can be mentioned. Either only one of the amine catalyst and the metal catalyst, or a combination of both, may be used. The amount of the catalyst is preferably 0.5 to 3 parts by weight per 100 parts by weight of the polyol.

[0016] As the blowing agent, water, alternative CFCs, or hydrocarbons such as pentane can be used alone or in combination. In the case of water, carbon dioxide gas is generated during the reaction of the polyol and the polyisocyanate, and foaming is caused by the carbon dioxide gas. The amount of water as the blowing agent is preferably 1 to 10 parts by weight, more preferably 1 to 7 parts by weight, per 100 parts by weight of the polyol.

[0017] The foam stabilizer may be any one used in polyurethane foam, and examples include silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, and known surfactants. The compounding amount of the foam stabilizer is preferably 0 to 2 parts by weight per 100 parts by weight of the polyol.

[0018] As the polyisocyanate, an aliphatic or aromatic polyisocyanate having two or more isocyanate groups, a mixture thereof, and a modified polyisocyanate obtained by modifying them can be used. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexane methane diisocyanate, etc., and examples of the aromatic polyisocyanate include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate, polymeric MDI (crude MDI), etc. In addition, other prepolymers can also be used.

[0019] The isocyanate index (INDEX) is preferably 80 to 120, more preferably 90 to 110. The isocyanate index is a value obtained by multiplying the value obtained by dividing the number of moles of isocyanate groups in the isocyanate by the total number of moles of active hydrogen groups such as hydroxyl groups of the polyol by 100, and is calculated by [NCO equivalent of isocyanate / active hydrogen equivalent × 100].

[0020] Various additives can be mentioned as components appropriately contained in the polyurethane foam raw materials. Examples of the additives include crosslinking agents, flame retardants, pigments, fillers, etc. Examples of the crosslinking agent include glycerin, trimethylolpropane, 1,2,4-butanetriol, 2-methyl-2,3,4-butanetriol, diethanolamine, triethanolamine, pentaerythritol, etc., and one kind or a combination of a plurality of kinds may be used. The blending amount of the crosslinking agent is preferably 0 to 5 parts by weight with respect to 100 parts by weight of the polyol.

[0021] Examples of the flame retardant include halogenated diphenyl ethers such as degabromodiphenyl ether and octabromodiphenyl ether, halogen compounds such as halogenated polycarbonate, inorganic compounds such as antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, and aluminum hydroxide, triazine ring-containing compounds, metal hydroxides, phosphate ester-based flame retardants, condensed phosphate ester-based flame retardants, phosphate-based flame retardants, inorganic phosphorus-based flame retardants, dialkylphosphinates, silicone-based flame retardants, metal oxides, boric acid compounds, expanded graphite, etc. From the perspective of environmental protection, non-halogen-based flame retardants are preferred. For example, non-halogen-based phosphate esters and non-halogen-based condensed phosphate esters are preferred, and non-halogen-based flame retardants containing nitrogen atoms in addition to phosphorus atoms can be mentioned. The flame retardant in the form of a liquid or powder with a phosphorus content of 10% to 22% by weight is preferred.

[0022] Examples of the pigment include carbon black, titanium oxide, etc. Examples of the filler include graphite, alumina, melamine, etc.

[0023] The support portion 21 supports the main body 11 away from the surface of the sound source side member 41 and forms an air layer 31 between the main body 11 and the sound source side member 41. The support portion 21 is not particularly limited and may have an appropriate shape such as a columnar shape. Examples include grommets made of resin such as rubber and plastic, and clips. The support portion 21 can be fixed to the polyurethane foam by insert molding in which the support portion 21 is set on the mold surface during the mold molding of the polyurethane foam constituting the main body 11, or a resin washer or the like can be insert molded, and a clip or the like as the support portion 21 can be fixed to the washer or the like. A locking portion 45 composed of a hole or the like for engaging the tip side of the support portion 21 is provided on the surface of the sound source side member 41.

[0024] The interval a of the support part 21 is preferably 100 to 400 mm, more preferably 100 to 300 mm. If the interval a of the support part 21 is too narrow, the air layer 31 becomes small, and the sound absorption effect by the air layer 31 becomes small. Also, as the number of support parts 21 increases, the number of required parts increases, resulting in an increase in product weight, product cost, and deterioration of assemblability. On the other hand, if the interval a of the support part 21 is too wide, the polyurethane foam constituting the main body 11 is likely to bend between the support parts 21.

[0025] The amount of deflection c of the polyurethane foam between the support parts 21 (shown in Fig. 2) is preferably 0 to 5 mm, more preferably 0 to 1.5 mm, when the polyurethane foam is horizontally supported by the support parts 21 with the interval a of the support parts 21 being 250 mm. When the amount of deflection c becomes large, the air layer 31 becomes small, and the sound absorption effect at low frequencies by the air layer 31 becomes small.

[0026] The thickness of the air layer 31, that is, the interval b between the polyurethane foam supported by the support part 21 and the surface 43 of the sound source side member 41 is preferably 10 to 30 mm. When the interval b becomes narrow, the air layer 31 becomes small. On the other hand, when the interval b becomes wide, the sound absorption material 10 becomes bulky.

[0027] Since the polyurethane foam is likely to bend between the support parts 21 when its rigidity is low, the result of the three-point bending test is preferably 5 N or more. The measuring method of the three-point bending test is to measure the maximum load based on JIS K 7221-2:2006 with a sample cut to 50×150×10 mm and a support point distance of 100 mm.

[0028] The polyurethane foam preferably has an open-cell structure with the surface of the cells open. By making the surface (more preferably both surfaces) of the polyurethane foam an open-cell structure, the air permeability of the polyurethane foam can be improved, the sound is more likely to enter the polyurethane foam, and the sound absorption performance of the polyurethane foam can be further enhanced.

[0029] As a method for making the surface of a polyurethane foam into an open-cell structure, there is a method in which, during mold forming, a mold release agent containing a linear hydrocarbon wax is applied to the mold surface of a mold, and the polyurethane foam raw material is injected and foamed. Examples of the linear hydrocarbon wax include paraffin wax, Fischer-Tropsch wax, Sasol wax, etc., and a solvent-based mold release agent dispersed in an organic solvent, an aqueous mold release agent dispersed in water using an emulsifier, etc. can be used.

[0030] The polyurethane foam preferably has an air permeability (conforming to JIS K 6400-7 Method B: 2012) of 2.5 to 15 ml / cm 2 / s, more preferably 5 to 10 ml / cm 2 / s. If the air permeability is too low or too high, it will affect the sound absorption at low frequencies. The air permeability can be adjusted by the amount of foam stabilizer, etc.

[0031] The thickness of the polyurethane foam is preferably 5 to 40 mm, more preferably 10 to 20 mm. If the thickness of the polyurethane foam is too thin, the sound absorption at low frequencies will be low, while if the thickness is too large, it will become bulky.

[0032] The density of the polyurethane foam (JIS K7222:2005) is preferably 70 to 200 kg / m 3 and more preferably 90 to 120 kg / m 3 If the density of the polyurethane foam is low, the rigidity of the polyurethane foam will decrease, and the polyurethane foam will be easily bent by its own weight between the support portions 21. As a result, the polyurethane foam approaches the surface 43 of the sound source side member 41 between the support portions 21, and the air layer 31 between the polyurethane foam and the sound source side member 41 becomes small, and the sound absorption effect by the air layer 31 becomes small. On the other hand, if the density of the polyurethane foam is too high, the air permeability of the polyurethane foam will decrease. The density of the polyurethane foam can be adjusted by the injection amount (packing rate) of the polyurethane foam raw material into the mold. The packing rate (%) into the mold is calculated by [injection amount into the mold / molding space volume in the mold × 100].

[0033] It is preferable that the main body 11 made of polyurethane foam is molded into a shape such that the edge of the sound-absorbing cover 10 closes the gap between the surface 43 of the sound source side member 41.

[0034] The sound source component of the present invention includes the sound-absorbing cover of the present invention and has an air layer between the main body of the sound-absorbing cover and the sound source side member.

Example

[0035] From the polyurethane foam raw materials having the compositions of each of the examples shown in FIG. 3 and Comparative Example 1, a polyurethane foam (without a support portion) which is the main body of the sound-absorbing cover was injection molded. The mold used for injection molding consisted of a lower mold and an upper mold and had a molding space (cavity) of 500 × 500 × 10 mm. The temperature of the mold 20 was heated to 60° C. by warm water circulating inside the mold. After applying a mold release agent containing a linear hydrocarbon wax, product name: T-626, manufactured by Chukyo Yushi Co., Ltd. as a mold release agent to the mold surface of the mold, the polyurethane foam raw materials were mixed and injected into the open mold, and then the mold was closed to foam the polyurethane foam raw materials in the molding space inside the mold. Then, the mold was opened and a 500 × 500 × 10 mm polyurethane foam was demolded. Regarding Comparative Example 2 and Comparative Example 3, the slab-molded polyurethane foam was cut into 500 × 500 × 10 mm and used.

[0036] The details of each component used in the composition shown in FIG. 3 are as follows. · Polyol: Polyether polyol, functional group number 3, number average molecular weight 5000, EO ratio 14%, hydroxyl value 34 mgKOH / g, product name: Sannix FA-703, manufactured by Sanyo Chemical Industries, Ltd. · Catalyst: Amine type, product name: DABCO 33LSI, manufactured by Evonik Japan KK · Crosslinking agent: Amine type, functional group number 2, number average molecular weight 105, hydroxyl value 34 mgKOH / g, product name: Diethanolamine, manufactured by Dow Chemical Japan Ltd. · Foaming agent: Water · Blowing agent: silicone-based, product name; B8738LF2, manufactured by Evonik Japan Co., Ltd. · Flame retardant: non-halogenated condensed phosphate ester, phosphorus content: 17%, white powder (average particle size 3 - 4 μm) · Isocyanate: modified MDI, NCO%: 29.5%, product name; Millionate MTL, manufactured by Tosoh Corporation

[0037] Regarding the polyurethane foams of each example and each comparative example, the cell state, density, air permeability, heat resistance, flammability, maximum load, deflection amount, and sound absorption rate (800 Hz) of the front and back surfaces were judged or measured as follows.

[0038] The cell state of the front and back surfaces was judged by visually observing the front and back surfaces of the polyurethane foam to determine whether it was in an open state or a closed state. The density was measured for samples cut into 100×100×10 mm based on JIS K7222:2005. The air permeability was measured with the surface on the sound source side as the front surface based on JIS K 6400-7 B method: 2012.

[0039] The heat resistance was tested based on JIS K 6400-8:2014 under the condition of heat aging at 135°C for 600 hours. The tensile strength and elongation after heat aging were measured based on JIS K 6400-5:2012, and when the tensile strength was 100 N / m 2 or more and the elongation rate was 15% or more, it was marked as "〇"; otherwise, it was marked as "×". The flammability was measured based on UL94. When it met the V-0 condition excluding cotton ignition by dripping materials, it was marked as "〇"; otherwise, it was marked as "×".

[0040] The rigidity (three-point bending test) was measured for samples cut into 50×150×10 mm with a support span of 100 mm based on JIS K 7221-2:2006 to measure the maximum load.

[0041] The deflection amount was measured by arranging support parts made of a plastic square prism with dimensions of 10×10×10 mm in height at the number and intervals of the support part distances shown in Fig. 3, horizontally placing a sample made by pasting four 500×500 mm samples together to form a 1000×1000 mm sample on the support parts, and measuring the deflection amount due to the self-weight of the sample at the central position between the support parts. Note that the deflection amount was set with the position of the height of the support part as the zero deflection position, and the distance from that position to the lower surface of the sample was taken as the deflection amount.

[0042] For the sound absorption rate, samples with dimensions of 1000×1000×10 mm were used. For Examples 1 to 9 and Comparative Examples 2 and 3, an air layer of 10 mm was provided between the floor surface and the sample, 10 mm away from the floor surface, and the reverberation room sound absorption rate was measured based on JIS A 1409. As a specific measurement method, the air layer was obtained by arranging support parts made of a plastic square prism with dimensions of 10×10×10 mm in height at the number and intervals of the support part distances shown in Fig. 3 and horizontally placing the sample on the support parts. Also, to evaluate the sound absorption performance per exactly 1000 mm 2 To prevent the intrusion of sound from the side surface into the space between the sample and the floor surface, aluminum bars were installed on the four edges of the sample. For Comparative Example 1, the sample was placed in contact with the floor surface, and the reverberation room sound absorption rate was measured with the air layer between the sample and the floor surface eliminated.

[0043] A comprehensive judgment was made for the polyurethane foams of each example and each comparative example. The criteria for the comprehensive judgment were: when the deflection amount was 5 mm or less and the sound absorption rate was 0.80 or more, the comprehensive judgment was "◎"; when the deflection amount was 5 mm or less and the sound absorption rate was less than 0.70 to 0.80, the comprehensive judgment was "〇"; when the deflection amount was greater than 5 mm or the sound absorption rate was less than 0.70, the comprehensive judgment was "×".

[0044] The configurations and measurement results, etc. of each example and each comparative example will be described. Examples 1 to 8 are examples with 5×5 support parts and a support part distance of 250 mm. The cell state of the front and back surfaces of the polyurethane foam is open cell, the density is 75 to 140 kg / m 3 , and the air permeability is 3 to 14 ml / cm 2 / s, heat resistance "〇", flammability "〇", rigidity (3-point bending test) 5 - 9 N, deflection amount 3 mm or less, sound absorption rate (800 Hz) 0.70 - 0.85, overall judgment "◎" or "〇", less deflection, good sound absorption property.

[0045] Particularly in Examples 1 to 4, the air permeability of the polyurethane foam is adjusted by the addition amount of the blowing agent. In Examples 1 to 3, the air permeability is 5 - 9 ml / cm 2 / s, and the overall judgment is "◎", showing particularly excellent sound absorption property. In addition, in Example 1 and Examples 5 to 8, the density of the polyurethane foam is adjusted. In Example 1 and Examples 6 to 7, the density is 90 - 120 kg / m 3 and the overall judgment is "◎", with a good balance between the deflection amount and air permeability, showing particularly excellent sound absorption property.

[0046] Example 9 is an example with 4×4 support parts and a support part distance of 333 mm. The cell state on the front and back surfaces of the polyurethane foam is open cell, the density is 100 kg / m 3 , the air permeability is 7.5 ml / cm 2 / s, heat resistance "〇", flammability "〇", rigidity (3-point bending test) 7 N, deflection amount 3 mm, sound absorption rate (800 Hz) 0.79, overall judgment "〇", less deflection, good sound absorption property.

[0047] Comparative Example 1 uses the polyurethane foam of Example 9, arranges the polyurethane foam without support parts, and eliminates the air layer. Comparative Example 1 has a sound absorption rate (800 Hz) of 0.65 and an overall judgment of "×". Due to the absence of the air layer, its sound absorption property is inferior to that of Example 9.

[0048] Comparative Example 2 and Comparative Example 3 are examples of slab-shaped polyurethane foams, with densities of 35 kg / m 3 and 100 kg / m 3 , air permeabilities of 132 ml / cm 2 / s and 9.5 ml / cm 2 / s, heat resistance, and flammability are all "×", rigidity (3-point bending test) is 0.4 N and 2 N, deflection amount is greater than 10 mm and 7 mm, sound absorption rate (800 Hz) is 0.19 and 0.41, and the comprehensive judgment is "×". It has large deflection and poor sound absorption.

[0049] In this way, the present invention can reduce the overall thickness of the sound absorption cover, simplify the manufacturing operation, and make the sound absorption cover inexpensive. Note that the present invention is not limited to the above-described embodiments and can be modified without departing from the spirit of the invention. [1] In a sound-absorbing cover that covers a sound source side member, a main body formed of polyurethane foam, a support portion that supports the main body away from the surface of the sound source side member, and an air layer, characterized by a sound-absorbing cover. [2] The sound-absorbing cover according to [1] above, wherein the polyurethane foam has a deflection amount of 0 to 5 mm when horizontally supported by the support portion with a spacing of 250 mm. [3] The sound-absorbing cover according to [1] or [2] above, wherein the polyurethane foam has a result of a three-point bending test of 5 N or more. [4] The polyurethane foam has an open cell structure on the surface, and the air permeability is 2.5 to 15 ml / cm 2 / s, and the density is 70 to 200 kg / m 3 , characterized by the sound-absorbing cover according to any one of [1] to [3] above. [5] A sound source component including the sound-absorbing cover according to any one of [1] to [4] above, and having an air layer between the main body and the sound source side member.

Explanation of Reference Numerals

[0050] 10 Sound absorption cover 11 Polyurethane foam 21 Support part 31 Air layer 41 Sound source side member 43 Surface of the sound source side member 45 Locking part a Spacing between support parts b Spacing between the polyurethane foam and the surface of the sound source side member c Deflection amount

Claims

1. In a sound-absorbing cover that covers a sound source side member, a main body formed of molded polyurethane foam, a support portion that supports the main body away from the surface of the sound source side member, and an air layer, a sound-absorbing cover characterized in that the reverberation room sound absorption rate (800 Hz, air layer 10 mm) measured based on JIS A1409 is 0.80 or more.

2. A sound source component including the sound-absorbing cover according to Claim 1, and having an air layer between the main body and the sound source side member.

Images