Sound absorbing cover and sound source parts

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 part. [Background technology]

[0002] Conventionally, some sound-absorbing covers utilize an air layer to improve sound absorption at low frequencies below 1000 Hz. For example, there is an engine cover that has a urethane foam layer and a PET nonwoven fabric on the surface of the cover body that covers the direct injection engine, facing the direct injection engine, and improves sound absorption by the air layer formed between the urethane foam layer and the PET nonwoven fabric (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2007-255189 Summary of the Invention [Problem to be solved by the invention]

[0004] Products that improve sound absorption by using an air layer formed between a urethane foam layer and a PET nonwoven fabric have the problem that the overall thickness increases due to the urethane foam layer and the PET nonwoven fabric. In addition, welding work is required to bond the urethane foam layer and the PET nonwoven fabric, which increases the manufacturing work and product costs.

[0005] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a sound absorbing cover and a sound source component having a novel configuration that can reduce the overall thickness and can be manufactured simply and inexpensively. [Means for solving the problem]

[0006] The first means is a sound-absorbing cover that covers a sound source side member, characterized in that it comprises a main body formed of polyurethane foam, a support part 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 part 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. Effect of the Invention

[0007] The sound-absorbing cover of the present invention comprises a main body formed of polyurethane foam, a support part that supports the main body away from the surface of the sound source side member, and an air layer, so that the overall thickness of the sound-absorbing cover can be made thin, and since there is no need to bond nonwoven fabrics, the manufacturing process is simplified and the sound-absorbing cover can be made inexpensively. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of a sound absorbing cover according to one embodiment. [Diagram 2] 6 is a cross-sectional view showing the deflection of the sound absorbing cover. FIG. [Diagram 3] 1 is a table showing the configurations and physical properties of each of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described below. A sound absorbing cover 10 of one embodiment shown in Figures 1 and 2 comprises a main body 11, a support portion 21, and an air layer 31, and is provided to cover a surface 43 of a sound source side member 41 such as a vehicle engine, a battery, a transmission, an intake manifold, or an exhaust manifold.

[0010] The main body 11 is made of a molded polyurethane foam. The mold molding is a molding method in which polyurethane foam raw materials containing polyol, catalyst, blowing agent, foam stabilizer, and polyisocyanate are mixed and injected into a mold to be foamed within the mold. There are two methods for molding polyurethane foam: mold molding and slab molding. Slab molding is a molding method in which polyurethane foam raw materials are mixed and discharged onto a belt conveyer, and foamed at atmospheric pressure and room temperature.

[0011] The polyol may be a polyol for polyurethane foam, for example, any one of polyether polyol, polyester polyol, polyether ester polyol, and polymer polyol, and one or more of these may be used.

[0012] Examples of polyether polyols 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 polyester polyols include polyester polyols obtained by polycondensation of an aliphatic carboxylic acid such as malonic acid, succinic acid, or adipic acid, or an aromatic carboxylic acid such as phthalic acid, and an aliphatic glycol such as ethylene glycol, diethylene glycol, or propylene glycol. Examples of the polyether ester polyol include those obtained by reacting the above-mentioned polyether polyol with a polybasic acid to form a polyester, and those having both polyether and polyester segments in one molecule.

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

[0015] The catalyst may be used in combination with a known urethane catalyst for polyurethane foam. 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 and lead octenate (also called organometallic catalysts), and either one of the amine catalyst and the metal catalyst, or both may be used in combination. The amount of the catalyst is preferably 0.5 to 3 parts by weight per 100 parts by weight of the polyol.

[0016] The blowing agent may be water, a fluorocarbon substitute, or a hydrocarbon such as pentane, either alone or in combination. In the case of water, carbon dioxide gas is generated during the reaction of polyol with polyisocyanate, and the foaming is caused by the carbon dioxide gas. The amount of water used 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 polyol.

[0017] The foam stabilizer may be any foam stabilizer that is used in polyurethane foam, including silicone foam stabilizers, fluorine-containing compound foam stabilizers, and known surfactants. The amount of foam stabilizer is preferably 0 to 2 parts by weight based on 100 parts by weight of 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. As the aliphatic polyisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexamethane diisocyanate, etc. can be mentioned, and as the aromatic polyisocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate, polymeric MDI (crude MDI), etc. can be mentioned. In addition, prepolymers can also be used.

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

[0020] Various additives can be included as components that may be appropriately contained in the polyurethane foam raw material. Examples of the additives include a crosslinking agent, a flame retardant, a pigment, and a filler. Examples of the crosslinking agent include glycerin, trimethylolpropane, 1,2,4-butanetriol, 2-methyl-2,3,4-butanetriol, diethanolamine, triethanolamine, pentaerythritol, etc., and one or more of them may be used in combination. The amount of the crosslinking agent is preferably 0 to 5 parts by weight based on 100 parts by weight of the polyol.

[0021] Examples of the flame retardant include halogenated diphenyl ethers such as degabrom diphenyl ether and octabrom diphenyl ether, halogenated compounds such as halogenated polycarbonates, inorganic compounds such as antimony trioxide, antimony tetraoxide, antimony pentoxide, sodium pyroantimonate, and aluminum hydroxide, triazine ring-containing compounds, metal hydroxides, phosphate flame retardants, condensed phosphate flame retardants, phosphate flame retardants, inorganic phosphorus flame retardants, dialkyl phosphinates, silicone flame retardants, metal oxides, boric acid compounds, and expandable graphite. From the viewpoint of environmental protection, non-halogen flame retardants are preferred, such as non-halogen phosphate esters and non-halogen condensed phosphate esters, and non-halogen flame retardants containing nitrogen atoms in addition to phosphorus atoms. Liquid or powder flame retardants with a phosphorus content of 10% by weight to 22% by weight are preferred.

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

[0023] The support part 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 part 21 is not particularly limited, and may be, for example, a columnar or other suitable shape, and may be a grommet or clip made of resin such as rubber or plastic. The support part 21 may be fixed to the polyurethane foam by insert molding, which is performed by setting the polyurethane foam on the mold surface during molding of the polyurethane foam constituting the main body 11, or a resin washer or the like may be insert molded and a clip or the like as the support part 21 may be fixed to the washer or the like. A locking part 45 consisting of a hole or the like for engaging the tip side of the support part 21 is provided on the surface of the sound source side member 41.

[0024] The interval a between the support parts 21 is preferably 100 to 400 mm, and more preferably 100 to 300 mm. If the interval a between the support parts 21 is too narrow, the air layer 31 becomes small, and the sound absorbing effect of the air layer 31 becomes small. Furthermore, an increase in the number of support parts 21 increases the number of necessary parts, which increases the product weight and cost, and deteriorates the ease of assembly. On the other hand, if the interval a between the support parts 21 is too wide, the polyurethane foam constituting the main body 11 becomes easily deflected between the support parts 21.

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

[0026] The thickness of the air layer 31, i.e., the distance b between the polyurethane foam supported by the support portion 21 and the surface 43 of the sound source side member 41, is preferably 10 to 30 mm. If the distance b is narrower, the air layer 31 becomes smaller. On the other hand, if the distance b is wider, the sound absorbing material 10 becomes bulky.

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

[0028] The polyurethane foam preferably has an open cell structure with open cells on the surface. By making the surface of the polyurethane foam (preferably both surfaces) an open cell structure, the breathability of the polyurethane foam can be improved, making it easier for sound to enter the polyurethane foam, thereby further increasing the sound absorption properties of the polyurethane foam.

[0029] One method for making the surface of polyurethane foam have an open cell structure is to apply a release agent containing linear hydrocarbon wax to the mold surface during molding, and then inject and foam the polyurethane foam raw material. Examples of linear hydrocarbon wax include paraffin wax, Fischer-Tropsch wax, and Sasol wax. Solvent-based release agents dispersed in an organic solvent, and water-based release agents dispersed in water using an emulsifier can be used.

[0030] The polyurethane foam has a breathability of 2.5 to 15 ml / cm (JIS K 6400-7 B method: 2012 compliant). 2 / s, and more preferably 5 to 10 ml / cm 2 / s. If the air permeability is too low or too high, it affects the low frequency sound absorption. 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, and more preferably 10 to 20 mm. If the polyurethane foam is too thin, the sound absorption properties at low frequencies will be low, while if the polyurethane foam is too thick, it will be bulky.

[0032] The density of polyurethane foam (JIS K7222:2005) is 70 to 200 kg / m 3 is preferable, and more preferably 90 to 120 kg / m 3 If the density of the polyurethane foam is low, the rigidity of the polyurethane foam decreases, and the polyurethane foam becomes more likely to bend under its own weight between the support parts 21. As a result, the polyurethane foam approaches the surface 43 of the sound source side member 41 between the support parts 21, the air layer 31 between the polyurethane foam and the sound source side member 41 becomes smaller, and the sound absorbing effect of the air layer 31 becomes smaller. On the other hand, if the density of the polyurethane foam is too high, the breathability of the polyurethane foam decreases. The density of the polyurethane foam can be adjusted by the amount of polyurethane foam raw material injected into the mold (pack rate). The pack rate (%) into the mold is calculated by [amount injected into the mold / molding space volume in the mold x 100].

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

[0034] The sound source part of the present invention includes the sound absorbing cover of the present invention, and an air layer is provided between the main body of the sound absorbing cover and the sound source side member. EXAMPLES

[0035] The polyurethane foam raw material having the composition shown in FIG. 3 for each of the Examples and Comparative Example 1 was molded into a polyurethane foam (without a supporting portion) which is the main body of the sound absorbing cover. The mold used for 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 adjusted to 60° C. by warm water circulating inside the mold. After applying a mold release agent containing linear hydrocarbon wax (product name: T-626, manufactured by Chukyo Yushi Co., Ltd.) to the mold surface of the mold, polyurethane foam raw materials were mixed and injected into the open mold, which was then closed to allow the polyurethane foam raw materials to foam in the molding space inside the mold. The mold was then opened, and the 500×500×10 mm polyurethane foam was demolded. In Comparative Examples 2 and 3, the slab-molded polyurethane foam was cut to 500×500×10 mm and used.

[0036] The components used in the formulation shown in FIG. 3 are as follows: Polyol: Polyether polyol, functionality 3, number average molecular weight 5000, EO ratio 14%, hydroxyl value 34mgKOH / g, product name: Sannix FA-703, manufactured by Sanyo Chemical Industries, Ltd. Catalyst: Amine type, Product name: DABCO 33LSI, Evonik Japan Crosslinking agent: Amine type, functional group number 2, number average molecular weight 105, hydroxyl value 34mgKOH / g, product name: diethanolamine, manufactured by Dow Chemical Japan Co., Ltd. Foaming agent: Water Foam stabilizer: Silicone type, product name: B8738LF2, manufactured by Evonik Japan Co., Ltd. Flame retardant: non-halogen condensed phosphate ester, phosphorus content: 17%, white powder (average particle size 3-4μm) Isocyanate: Modified MDI, NCO%: 29.5%, Product name: Millionate MTL, Tosoh Corporation

[0037] For the polyurethane foams of each Example and Comparative Example, the cell state on the front and back surfaces, density, breathability, heat resistance, flammability, rigidity (maximum load in three-point bending test), deflection amount, and sound absorption coefficient (800 Hz) were judged or measured as follows.

[0038] The cell state on the front and back surfaces of the polyurethane foam was judged to be open or closed by visually observing the front and back surfaces. The density was measured based on JIS K7222:2005 for a sample cut to 100 x 100 x 10 mm. The breathability was measured based on JIS K 6400-7 Method B:2012, with the sound source side as the front surface.

[0039] Heat resistance was evaluated by heat aging at 135°C for 600 hours in accordance with JIS K 6400-8:2014. The tensile strength and elongation after heat aging were measured in accordance with JIS K 6400-5:2012, and the tensile strength was 100N / m 2 If the test result was above this level and the elongation rate was 15% or more, it was marked as "O", otherwise it was marked as "X". Flammability was measured based on UL94. If the V-0 criteria were met, excluding cotton ignition due to dripping, the material was rated as "Good" and if not, it was rated as "Poor."

[0040] Rigidity (three-point bending test) was measured on samples cut to 50 x 150 x 10 mm with a support distance of 100 mm, based on JIS K 7221-2:2006, and the maximum load was measured.

[0041] The amount of deflection was measured by arranging supports consisting of plastic rectangular columns of 10x10x10mm height with the number and distance between supports shown in Figure 3, placing a sample made of four 500x500mm samples pasted together to make a 1000x1000mm sample horizontally on the supports, and measuring the amount of deflection due to the weight of the sample at the center between the supports. Note that the position at the height of the supports was defined as the position of zero deflection, and the amount of deflection was measured as the distance from that position to the bottom surface of the sample.

[0042] The sound absorption coefficient was measured using a sample measuring 1000×1000×10 mm, and for Examples 1 to 9 and Comparative Examples 2 and 3, the sample was separated from the floor by 10 mm, providing an air gap of 10 mm between the floor and the sample, and the sound absorption coefficient in a reverberation room was measured based on JIS A 1409. As a specific measurement method, the air gap was obtained by arranging supports made of plastic rectangular columns measuring 10×10×10 mm in height with the number and distance between the supports shown in FIG. 3, and placing the sample horizontally on the supports. 2 In order to evaluate the sound absorption performance around the floor, aluminum bars were placed on the four edges of the sample to prevent sound from entering between the sample and the floor from the sides. For Comparative Example 1, the sample was placed in contact with the floor, eliminating the air gap between the sample and the floor, and the sound absorption coefficient in the reverberation room was measured.

[0043] An overall judgment was made for the polyurethane foams of each Example and Comparative Example. The criteria for the overall judgment were as follows: when the deflection amount was 5 mm or less and the sound absorption coefficient was 0.80 or more, the overall judgment was "◎", when the deflection amount was 5 mm or less and the sound absorption coefficient was 0.70 to less than 0.80, the overall judgment was "◯", and when the deflection amount was more than 5 mm or the sound absorption coefficient was less than 0.70, the overall judgment was "×".

[0044] The configuration and measurement results of each of the examples and comparative examples will be described. Examples 1 to 8 are examples in which the number of support parts is 5 × 5, the distance between the support parts is 250 mm, the cell state of the front and back surfaces of the polyurethane foam is open cell, and the density is 75 to 140 kg / m 3 , breathability 3~14ml / cm 2 / s, heat resistance "Good", flammability "Good", rigidity (three-point bending test) 5 to 9 N, deflection amount 3 mm or less, sound absorption coefficient (800 Hz) 0.70 to 0.85, and overall judgment "◎" or "Good", with little deflection and good sound absorption.

[0045] In particular, in Examples 1 to 4, the breathability of the polyurethane foam is adjusted by the amount of foam stabilizer added. 2 / s, the overall rating was "◎", indicating particularly excellent sound absorption properties. In addition, the density of the polyurethane foam is adjusted in Example 1, and Examples 5 to 8. In Examples 1, 6, and 7, the density is 90 to 120 kg / m 3 The overall rating was "◎", with a good balance between the amount of deflection and breathability, and especially excellent sound absorption.

[0046] Example 9 is an example in which the number of support parts is 4 × 4, the distance between the support parts is 333 mm, the cell state of the front and back surfaces of the polyurethane foam is open cell, and the density is 100 kg / m 3 , breathability 7.5ml / cm 2 / s, heat resistance "Good", flammability "Good", rigidity (three-point bending test) 7N, deflection amount 3mm, sound absorption coefficient (800Hz) 0.79, overall judgment "Good", with little deflection and good sound absorption.

[0047] Comparative Example 1 is an example in which the polyurethane foam of Example 9 was used, the polyurethane foam was arranged without a support portion, and an air layer was eliminated. Comparative Example 1 had a sound absorption coefficient (800 Hz) of 0.65 and an overall rating of "x", and was inferior in sound absorption to Example 9 due to the absence of an air layer.

[0048] Comparative Example 2 and Comparative Example 3 are examples of slab molded polyurethane foams, each having a density of 35 kg / m 3 and 100 kg / m 3 , breathability is 132ml / cm 2 / s and 9.5ml / cm 2The test pieces were rated as "x" for vibration / s, heat resistance and flammability, stiffness (three-point bending test) was 0.4N and 2N, deflection was greater than 10mm and 7mm, and sound absorption coefficient (800Hz) was 0.19 and 0.41. The overall verdict was "x", with a large deflection and poor sound absorption.

[0049] In this way, the present invention can reduce the overall thickness of the sound absorbing cover, and the manufacturing process is simple, resulting in a low-cost sound absorbing cover. The present invention is not limited to the above-described embodiment, and can be modified without departing from the spirit and scope of the invention. [Explanation of symbols]

[0050] 10 Sound absorbing cover 11 Polyurethane foam 21 Support part 31 Air Layer 41 Sound source side components 43 Surface of sound source component 45 Locking part a Support spacing b) Distance between polyurethane foam and the surface of the sound source c Deflection amount

Claims

1. In the sound absorbing cover that covers the sound source side member, A body formed of polyurethane foam; a support portion that supports the main body at a distance from a surface of the sound source side member; and an air layer; The polyurethane foam has an open cell structure on the front and back sides and a density of 70 to 140 kg / m ３ A sound-absorbing cover characterized by:

2. In the sound absorbing cover that covers the sound source side member, A body formed of polyurethane foam; a support portion that supports the main body at a distance from a surface of the sound source side member; and an air layer; The polyurethane foam has a breathability of 5 to 15 ml / cm ２ / s, density is 70-140kg / m ３ A sound-absorbing cover characterized by:

3. The sound-absorbing cover according to claim 1 or 2, wherein the polyurethane foam has a deflection of 0 to 5 mm when supported horizontally by the support parts spaced 250 mm apart, and / or the polyurethane foam has a maximum load of 5 N or more in a three-point bending test.

4. A sound source component comprising the sound absorbing cover according to any one of claims 1 to 3, and an air layer between the main body and the sound source side member.

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