JP7710078B2 - Sound absorbing cover and sound source parts - Google Patents

Description

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

Conventionally, some sound absorbing covers utilize an air layer to improve sound absorption at low frequencies of 1000 Hz or less.
For example, there is an engine cover in which a urethane foam layer and a PET nonwoven fabric are provided on the surface of a cover body that covers a direct injection engine, facing the direct injection engine, and the air layer formed between the urethane foam layer and the PET nonwoven fabric improves sound absorption (Patent Document 1).

Patent Publication 2007-255189

Products that improve sound absorption by forming an air layer between a urethane foam resin layer and a PET nonwoven fabric have the problem that the overall thickness increases due to the urethane foam resin layer and the PET nonwoven fabric, and because welding work is required to bond the urethane foam resin layer and the PET nonwoven fabric together, there are problems with increased manufacturing work and product costs.

The present invention has been made in consideration of the above points, and aims to provide a sound-absorbing cover and sound source component with a new configuration that allows for a thin overall thickness and simplifies and reduces manufacturing costs.

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.

The sound-absorbing cover of the present invention has a main body made of polyurethane foam, a support part that supports the main body away from the surface of the sound source member, and an air layer, so 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.

FIG. 2 is a cross-sectional view of a sound absorbing cover according to one embodiment. 6 is a cross-sectional view showing the deflection of the sound absorbing cover. FIG. 1 is a table showing the configurations and physical properties of each of the examples and comparative examples.

The following describes an embodiment of the present invention. The sound-absorbing cover 10 of one embodiment shown in Figures 1 and 2 is made up 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 a vehicle engine, battery, transmission, intake manifold, or exhaust manifold.

The main body 11 is made of a molded polyurethane foam. The mold molding is a molding method in which polyurethane foam raw materials including a polyol, a catalyst, a blowing agent, a foam stabilizer, and a 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.

The polyol may be a polyol for polyurethane foam, such as polyether polyol, polyester polyol, polyether ester polyol, or polymer polyol, and one or more of these may be used.

Examples of polyether polyols include polyether polyols in which alkylene oxides such as ethylene oxide (EO) and propylene oxide (PO) are added to polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose.

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.

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

The catalyst can be used in combination with a known urethane catalyst for polyurethane foam. Examples include amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine, tin catalysts such as stannous octoate and dibutyltin dilaurate, and metal catalysts (also called organometallic catalysts) such as phenylmercury propionate and lead octenate. Either the amine catalyst or the metal catalyst, or both may be used in combination. The amount of catalyst is preferably 0.5 to 3 parts by weight per 100 parts by weight of polyol.

The blowing agent can be water, a fluorocarbon substitute, or a hydrocarbon such as pentane, either alone or in combination. When water is used, carbon dioxide gas is generated during the reaction of the polyol with the 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 the polyol.

The foam stabilizer may be any foam stabilizer that is used in polyurethane foams, 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 per 100 parts by weight of polyol.

As polyisocyanates, aliphatic or aromatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them can be used. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexamethane diisocyanate, etc., and examples of aromatic polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate, polymeric MDI (crude MDI), etc. Other prepolymers can also be used.

The isocyanate index (INDEX) is preferably 80 to 120, and more preferably 90 to 110. The isocyanate index is calculated 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 in the polyol, and multiplying the result by 100, and is calculated as [NCO equivalent of isocyanate / active hydrogen equivalent x 100].

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.

Examples of flame retardants include halogenated diphenyl ethers such as degabromdiphenyl ether and octabromdiphenyl ether, halogen 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 ester flame retardants, condensed phosphate ester 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% to 22% by weight are preferred.

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

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.

The spacing a between the support parts 21 is preferably 100 to 400 mm, and more preferably 100 to 300 mm. If the spacing a between the support parts 21 is too narrow, the air layer 31 will be small, and the sound absorbing effect of the air layer 31 will be reduced. Furthermore, an increase in the number of support parts 21 will increase the number of parts required, resulting in increased product weight and cost, and poorer assembly. On the other hand, if the spacing a between the support parts 21 is too wide, the polyurethane foam that constitutes the main body 11 will be more likely to bend between the support parts 21.

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. If the amount of deflection c is large, the air layer 31 becomes smaller, and the sound absorbing effect of the air layer 31 at low frequencies becomes smaller.

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.

If the polyurethane foam has low rigidity, it will be easily bent between the support parts 21, so it is preferable that the result of the three-point bending test is 5N or more. The measurement method for the three-point bending test was to measure the maximum load on a sample cut to 50 x 150 x 10 mm with a support distance of 100 mm, based on JIS K 7221-2:2006.

The polyurethane foam preferably has an open cell structure with open cells on the surface.
By making the surface (preferably both surfaces) of the polyurethane foam have 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 enhancing the sound absorption properties of the polyurethane foam.

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.

The polyurethane foam preferably has an air permeability (JIS K 6400-7 B method: 2012 compliant) 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 affects low frequency sound absorption. The air permeability can be adjusted by the amount of foam stabilizer, etc.

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, it will have poor sound absorption properties at low frequencies, while if it is too thick, it will become bulky.

The density of the polyurethane foam (JIS K7222:2005) is preferably 70 to 200 kg/m ³ , 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 is easily bent by 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 small, and the sound absorbing effect of the air layer 31 becomes small. 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 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 x 100].

It is preferable to mold the main body 11 made of polyurethane foam 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.

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.

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 a linear hydrocarbon wax (product name: T-626, manufactured by Chukyo Yushi Co., Ltd.) to the mold surface of the mold, the polyurethane foam raw material was mixed and injected into the open mold, and the mold was closed to allow the polyurethane foam raw material to foam in the molding space inside the mold. Thereafter, the mold was 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 a size of 500×500×10 mm and used.

The components used in the formulation shown in FIG.
Polyol: polyether polyol, number of functional groups: 3, number average molecular weight: 5000, EO ratio: 14%, hydroxyl value: 34 mg KOH/g, product name: Sannix FA-703, manufactured by Sanyo Chemical Industries, Ltd. Catalyst: amine-based, product name: DABCO 33LSI, manufactured by Evonik Japan Co., Ltd. Crosslinking agent: amine-based, number of functional groups: 2, number average molecular weight: 105, hydroxyl value: 34 mg KOH/g, product name: diethanolamine, manufactured by Dow Chemical Japan Co., Ltd. Foaming agent: water Foam stabilizer: silicone-based, product name: B8738LF2, manufactured by Evonik Japan Co., Ltd. Flame retardant: non-halogen-based condensed phosphate ester, phosphorus content: 17%, white powder (average particle size: 3 to 4 μm)
Isocyanate: Modified MDI, NCO%: 29.5%, Product name: Millionate MTL, manufactured by Tosoh Corporation

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.

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 100×100×10 mm.
The air permeability was measured based on JIS K 6400-7 Method B:2012, with the surface facing the sound source as the front surface.

Heat resistance was evaluated by heat aging at 135°C for 600 hours according to JIS K 6400-8:2014. The tensile strength and elongation after heat aging were measured according to JIS K 6400-5:2012. If the tensile strength was 100 N/m2 or ^more and the elongation rate was 15% or more, it was marked as "Good", and otherwise it was marked as "Poor".
Flammability was measured based on UL94. If the conditions of V-0 were met except for cotton ignition due to dripping, it was marked as "good" and if not, it was marked as "poor."

The 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.

The amount of deflection was measured by arranging the support parts consisting of plastic rectangular pillars measuring 10 x 10 x 10 mm in number and at intervals between the support parts as shown in Figure 3, placing a sample made of four 500 x 500 mm samples glued together to a size of 1000 x 1000 mm horizontally on the support parts, and measuring the amount of deflection due to the weight of the sample at the center position between the support parts. Note that the position at the height of the support parts was defined as the position of zero deflection, and the amount of deflection was measured as the distance from that position to the underside of the sample.

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, a 10 mm air gap was provided between the floor and the sample at a distance of 10 mm from the floor, 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 plastic supports made of 10×10×10 mm high rectangular columns at intervals shown in FIG. 3, and placing the sample horizontally on the supports. In order to accurately evaluate the sound absorption performance per 1000 ^mm2 , aluminum bars were installed 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 a reverberation room was measured.

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

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

Particularly in Examples 1 to 4, the breathability of the polyurethane foam was adjusted by the amount of foam stabilizer added. Examples 1 to 3 had a breathability of 5 to 9 ml/cm ² /s, and were rated as "◎" overall, showing particularly excellent sound absorption properties.
Furthermore, the density of the polyurethane foam was adjusted in Example 1 and Examples 5 to 8. Example 1 and Examples 6 to 7 had a density of 90 to 120 kg/ ^m3 , and were rated as "◎" overall, exhibiting a good balance between the amount of deflection and air permeability, and exhibiting particularly excellent sound absorption properties.

Example 9 is an example in which the number of support parts is 4 × 4 and the distance between the support parts is 333 mm. The cell state on the front and back sides of the polyurethane foam is open cell, the density is 100 kg/ ^m3 , the air permeability is 7.5 ml/ ^cm2 /s, the heat resistance is "good", the flammability is "good", the rigidity (three-point bending test) is 7 N, the deflection amount is 3 mm, the sound absorption coefficient (800 Hz) is 0.79, and the overall judgment is "good", with little deflection and good sound absorption.

Comparative Example 1 is an example in which the polyurethane foam of Example 9 was used, with no support, and the air layer was eliminated. Comparative Example 1 had a sound absorption coefficient (800 Hz) of 0.65 and an overall rating of "x", and because there was no air layer, it had inferior sound absorption properties compared to Example 9.

Comparative Examples 2 and 3 are examples of slab-molded polyurethane foams, with densities of 35 kg/ ^m3 and 100 kg/ ^m3 , air permeabilities of 132 ml/ ^cm2 /s and 9.5 ml/ ^cm2 /s, heat resistance and flammability both rated as "x", rigidity (three-point bending test) of 0.4 N and 2 N, deflection of more than 10 mm and 7 mm, sound absorption coefficient (800 Hz) of 0.19 and 0.41, and the overall verdict was "x", indicating large deflection and poor sound absorption.

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.
[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;
A sound-absorbing cover comprising an air layer.
[2]
The sound-absorbing cover according to the above-mentioned [1], characterized in that the polyurethane foam has a deflection of 0 to 5 mm when supported horizontally by the support parts spaced 250 mm apart.
[3]
The sound-absorbing cover according to the above-mentioned [1] or [2], wherein the polyurethane foam has a result of 5N or more in a three-point bending test.
[4]
The sound-absorbing cover according to any one of the above [1] to [3], wherein the polyurethane foam has an open cell structure on the surface, an air permeability of 2.5 to 15 ml/cm ² /s, and a density of 70 to 200 kg/m ³ .
[5]
A sound source component comprising the sound absorbing cover according to any one of the above [1] to [4], and an air layer between the main body and the sound source side member.

REFERENCE SIGNS LIST 10 sound absorbing cover 11 polyurethane foam 21 support portion 31 air layer 41 sound source member 43 surface of sound source member 45 engagement portion a distance between support portions b distance between polyurethane foam and surface of sound source member c amount of deflection

Claims (2)

In the sound absorbing cover that covers the sound source side member,
a body formed from molded 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;
A sound-absorbing cover characterized in that the reverberation chamber sound absorption coefficient (800 Hz, air layer 10 mm) measured based on JIS A1409 is 0.80 or more. A sound source component comprising the sound absorbing cover according to claim 1 and having an air layer between the main body and the sound source side member.