WO2021132387A1

WO2021132387A1 - Polyurethane foam and soundproofing material for vehicle

Info

Publication number: WO2021132387A1
Application number: PCT/JP2020/048266
Authority: WO
Inventors: 崇志 ▲高▼田; 幸宏藤原; 澁谷　崇; 孝太郎兒玉
Original assignee: Ａｇｃ株式会社
Priority date: 2019-12-26
Filing date: 2020-12-23
Publication date: 2021-07-01
Also published as: CN114846042A; DE112020006330T5; JPWO2021132387A1

Abstract

Provided are: a polyurethane foam having a good sound absorption coefficient in a low-frequency band of 500-2000 Hz, enabling weight reduction while maintaining sound absorption performance equivalent to or higher than that of conventional products, and having a skin layer that can be used as a soundproofing material for a vehicle; and a soundproofing material for a vehicle.　This polyurethane foam and this soundproofing material for a vehicle each have a skin layer and an internal foam layer formed inside the skin layer, a thickness of 3-25 mm, a normal incidence sound absorption coefficient at a frequency of 1000 Hz of not less than 0.40 at a thickness of 10 mm, and a skeleton coefficient ratio SS/SI of 2.8-5.0 where the skeleton coefficient of the skin layer is defined as SS and the skeleton coefficient of the internal foam layer is defined as SI.

Description

Polyurethane foam and soundproofing material for vehicles

The present invention relates to polyurethane foam and soundproofing material for vehicles.

Soundproofing materials are installed as undercovers and fender liner covers on vehicles such as automobiles for the purpose of suppressing noise from motors, engines, tires, etc. to the outside of the vehicle. As the soundproofing material, a non-woven fabric of polyester fiber or polyolefin fiber or polyurethane foam is used. Polyurethane foam is cheaper than polyester fiber and polyolefin fiber, but has been used as a composite with a sheet of rubber, thermoplastic elastomer, or thermoplastic resin because it alone lacks sound absorption performance in the low frequency region. .. However, the composite of polyurethane foam and other materials has problems such as an increase in manufacturing cost and an increase in mass.

Patent Document 1 describes a polyurethane foam produced by foaming in a sealed mold using a raw material composition containing a high molecular weight polyoxyalkylene polyol, an organic polyisocyanate compound, a foaming agent and a catalyst. On the other hand, Patent Document 2 describes a sound absorbing body including a porous inner body and a dense skin formed on the surface of the inner body.

Japanese Unexamined Patent Publication No. 2005-113134 Japanese Unexamined Patent Publication No. 10-121597

Patent Document 1 describes a polyurethane foam having good sound absorption around 500 Hz. Sound absorption in a low frequency region of around 500 Hz can be achieved by increasing the thickness of the sound absorbing material, but in Patent Document 1, the film is thickened to 26 mm in order to exhibit sufficient sound absorption. There is a need. On the other hand, although the sound absorbing body described in Patent Document 2 exhibits excellent sound absorbing characteristics in the medium to high frequency region (2000 Hz or more), the sound absorbing performance in the low frequency region (1000 Hz or less, particularly 500 Hz or less) is that of the sound absorbing body. It was not enough to increase the thickness to 30 mm.
Therefore, when the sound absorbing material described in Patent Document 1 or Patent Document 2 is applied to an application requiring a thin film of up to about 10 mm (for example, a fender liner for a vehicle, an undercover, etc.), it is sufficient in a low frequency region. It was difficult to develop a good sound absorption performance.

The present invention has been made in view of the above circumstances, has a good sound absorption coefficient in a low frequency region (500 to 2000 Hz), can be made thinner and lighter while maintaining sound absorption performance equal to or higher than the conventional one, and can be used as a soundproof material for vehicles. An object of the present invention is to provide a flexible polyurethane foam and a soundproofing material for vehicles.

The problem is solved by the following configuration.
[1] A polyurethane foam having a skin layer and an internal foam layer formed inside the polyurethane foam, having a thickness of 3 to 25 mm and a vertically incident sound absorption coefficient at a frequency of 1000 Hz of 0.40 with a thickness of 10 mm. As described above, the polyurethane is characterized in that the skeleton ratio SS / SI is 2.8 to 5.0 when the skeleton ratio of the epidermis layer is SS and the skeleton ratio of the internal foam layer is SI. Form.
[2] The polyurethane foam according to [1], wherein the skeleton ratio SS / SI is 2.8 to 4.0.
[3] The polyurethane foam according to [1] or [2], wherein the skeleton ratio SS of the epidermis layer is 60% to 85%.
[4] The polyurethane foam according to any one of [1] to [3], wherein the internal foam layer has a skeleton ratio SI of 24% to 30%.
[5] The polyurethane foam according to any one of [1] to [4], wherein the skeleton ratio immediately below the epidermis layer is 40% or more.
[6] The polyurethane foam according to any one of [1] to [5], which has a density of 20 to 120 kg / m ^3.
[7] The polyurethane foam according to any one of [1] to [6], wherein the residual film ratio of the foam cell of the internal foam layer is 40% or more and less than 94%.
[8] The value obtained by dividing the average skeleton diameter of the foam cell by the average cell diameter is 0.10 to 0.50, and the average cell diameter of the foam cell is 100 to 400 μm, according to [7]. Polyurethane foam.
[9] A soundproofing material for vehicles containing the polyurethane foam according to any one of [1] to [8].
[10] A fender liner provided with the vehicle soundproofing material according to [9].

The polyurethane foam of the present invention has good sound absorption characteristics in the low frequency range of 500 to 2000 Hz even if it has a thin thickness, and is therefore suitable as a soundproofing material for vehicles. Since the frequency with good sound absorption coefficient is the frequency band of road noise, it is suitable for use in fender liner and undercover applications, especially in fender liner applications.

Hereinafter, embodiments of the present invention will be described, but the technical scope of the present invention is not limited to the embodiments described below, and various modifications can be made without departing from the spirit of the present invention. Is.

[Polyurethane foam]
The polyurethane foam of the present invention has a dense skin layer and an internal foam layer formed inside the polyurethane foam.
The skin layer is formed so as to cover the outer surface of the polyurethane foam. The skin layer is a layer that greatly contributes to the improvement of sound absorption characteristics. The thickness of the epidermis layer is defined by the thickness from the sample surface to the portion where the skeleton ratio is less than 50% in the skeleton ratio measurement described later.
The thickness of the epidermis layer is not particularly limited, but is preferably 0.2 to 1 mm, more preferably 0.2 to 0.6 mm. When the above value is within this range, the polyurethane foam of the present invention can secure sound absorption performance in a low frequency region of 500 to 2000 Hz.
The inner foam layer refers to a porous inner body formed inside the epidermis layer.

The thickness of the polyurethane foam of the present invention is 3 to 25 mm, preferably 3 to 20 mm.
When the thickness is at least the above lower limit value, good sound absorption performance can be exhibited. On the other hand, when the thickness is not more than the above upper limit value, the polyurethane foam of the present invention is easy to exhibit good sound absorption performance while being lightweight.
The polyurethane foam of the present invention has a vertically incident sound absorption coefficient at a frequency of 1000 Hz, which is 0.40 or more at a thickness of 10 mm. The vertically incident sound absorption coefficient is preferably 0.40 to 1, more preferably 0.50 to 1.
When the sound absorption coefficient is within this range, the polyurethane foam of the present invention is excellent in sound absorption performance in a low frequency region of 500 to 2000 Hz.
The polyurethane foam having a sound absorption coefficient within this range is suitable for use as a soundproofing material for vehicles. In particular, when the installation site is a narrowed portion or a complicated shape, it will be used in a thin state, and the advantages of the polyurethane foam of the present invention will be utilized.

The sound absorption coefficient is determined by a method based on JIS A 1405-2: 2007 "Measurement of sound absorption coefficient and impedance by acoustic tube" using a measurement sample having a thickness of 10 mm obtained by cutting polyurethane foam with a sharp blade. Measure.

The polyurethane foam of the present invention has a skeleton ratio SS / SI of 2.8 to 5.0 and 2.8 to 4 when the skeleton ratio of the epidermis layer is SS and the skeleton ratio of the internal foam layer is SI. .0 is preferable.
When SS / SI is above the lower limit, the density of the epidermis layer that affects sound absorption is high, so that the transmission of sound in the low frequency region to the internal foam layer is blocked, and the internal foam layer is interacted by inertial force. The low frequency sound absorption characteristics are improved.
On the other hand, when SS / SI is not more than the upper limit value, the influence of sound reflection in the epidermis layer can be suppressed. Furthermore, the strength of the internal foam layer can be maintained.
As a result, the polyurethane foam of the present invention further improves the sound absorption performance in the low frequency region of 500 to 2000 Hz.

The skeleton ratio is calculated from the result of cutting the polyurethane foam with a sharp blade to make a sample for measurement and imaging the cross section in the thickness direction of the sample using an optical microscope. The detailed calculation method will be described later.

The skeletal ratio SS of the epidermis layer is defined by the average value of the skeletal ratio measured at a depth of 0.3 mm from the surface of the sample. The SS is not particularly limited, but is preferably 60% to 85%, more preferably 70% to 85%.
When the above value is within this range, the polyurethane foam of the present invention further improves the sound absorption performance in the low frequency region of 500 to 2000 Hz.

The skeletal ratio SI of the inner foam layer is defined by the average value of the skeletal ratios measured at a depth of 3.5 to 4.5 mm from the surface of the sample. The SI is not particularly limited, but is preferably 24% to 30%, more preferably 25% to 29%.
When the above value is within this range, the polyurethane foam of the present invention further improves the sound absorption performance in the low frequency region of 500 to 2000 Hz.

The skeletal ratio directly below the epidermis layer is defined as the position directly below the epidermis layer at a depth twice the thickness of the epidermis layer, and is defined by the average value of the skeletal ratio measured at the depth directly below the epidermis layer from the surface of the sample. The skeleton ratio immediately below the epidermis layer is not particularly limited, but is preferably 40% or more, and more preferably 40 to 70%.
When the above value is within this range, the polyurethane foam of the present invention further improves the sound absorption performance in the low frequency region of 500 to 2000 Hz.

The density of the polyurethane foam of the present invention is 20 ~ 120kg / ^{m 3,} preferably 30 ~ 100kg / ^{m 3,} more preferably 55 ~ 90kg / ^{m 3.}
When the density is within this range, the polyurethane foam of the present invention can be reduced in weight while maintaining the sound absorption performance equal to or higher than the conventional one.
In particular, recent vehicle soundproofing materials are strongly required to be lightweight, and the advantages of the polyurethane foam of the present invention can be utilized. It can also be used for parts with complicated shapes such as fender liners.

^{The density is a density (unit: kg / m 3} ) measured according to JIS K 7222: 2005 “Foam Plastics and Rubber-How to Obtain Apparent Density”.

The residual film ratio of the foam cell in the internal foam layer of the polyurethane foam of the present invention is 40% or more and less than 94%, preferably 40 to 90%, more preferably 50 to 85%, still more preferably 55 to 85%.
When the residual film ratio of the foamed cell is within this range, the polyurethane foam of the present invention is excellent in sound absorption performance in a low frequency region of 500 to 2000 Hz.
Further, when the residual film ratio is within this range, shrinkage is less likely to occur during molding of the polyurethane foam, and molding is easy.
The residual film ratio of the foam cell is calculated from the result of imaging the cross section of the measurement sample using an optical microscope. Detailed calculation conditions will be described later.

The average cell diameter of the foam cells of the internal foam layer is not particularly limited, but is preferably 100 to 400 μm, more preferably 150 to 350 μm, and even more preferably 150 to 300 μm. When the average cell diameter of the foamed cell is within this range, the polyurethane foam of the present invention is excellent in sound absorption performance in a low frequency region of 500 to 2000 Hz.

The value obtained by dividing the average skeleton diameter of the foamed cells of the inner foam layer by the average cell diameter is not particularly limited, but is preferably 0.10 to 0.50, more preferably 0.15 to 0.45, and 0.27 to 0.27 to 0.45. 0.45 is more preferable.
When the above value is within this range, the polyurethane foam of the present invention further improves the sound absorption performance in the low frequency region of 500 to 2000 Hz.

The average skeleton diameter and average cell diameter of the internal foam layer are calculated from the results of imaging the cross section of the measurement sample using an optical microscope. Detailed calculation conditions will be described later.

[Manufacturing method of polyurethane foam]
The polyurethane foam of the present invention can be produced by foaming using, for example, a raw material composition G containing a polyoxyalkylene polyol A, an organic polyisocyanate compound B, a foaming agent C and a catalyst D.

<Raw material composition G>
The raw material composition G contains a polyoxyalkylene polyol A, an organic polyisocyanate compound B, a foaming agent C and a catalyst D. The raw material composition G is usually prepared by mixing a polyol system liquid H containing a raw material other than the organic polyisocyanate compound B and an organic polyisocyanate compound B.

(Polyoxyalkylene polyol A)
Polyoxyalkylene polyol A (hereinafter referred to as "polyol A") is usually synthesized by ring-opening addition polymerization of an alkylene oxide as an initiator in the presence of a catalyst.
Polyol A contains a trifunctional polyoxyalkylene polyol, that is, a polyoxyalkylene polyol having three hydroxyl groups in one molecule. The polyoxyalkylene polyol other than the trifunctional polyoxyalkylene polyol is not particularly limited, and is, for example, a bifunctional or tetrafunctional or higher functional polyoxyalkylene polyol.
The number of hydroxyl groups per molecule of polyol A (hereinafter referred to as "average number of hydroxyl groups") is not particularly limited as long as it is 2 or more, but 2 to 8 is preferable, 2 to 4 is more preferable, and 2.2 to 3.9 is preferable. Is more preferable, and 2.4 to 3.7 is even more preferable.
When the average number of hydroxyl groups is within this range, the softness of the polyurethane foam becomes more appropriate, the compression set is further improved, the mechanical properties such as elongation are improved, and the soundproofing performance tends to be further improved. .. The number of hydroxyl groups in one molecule of the polyoxyalkylene polyol is the same as the number of active hydrogen-containing groups of the initiator used in the synthesis of the polyoxyalkylene polyol.

The number average molecular weight of the polyol A is not particularly limited, but is preferably 1000 to 20000, more preferably 1000 to 16000, and even more preferably 1500 to 12000. When the molecular weight is within this range, the residual film ratio of the foamed cell in the polyurethane foam is likely to be in an appropriate range, and the sound absorption performance in the low frequency region of 500 to 2000 Hz is likely to be improved.

The number average molecular weight per hydroxyl group of polyol A (hereinafter referred to as "molecular weight / number of hydroxyl groups") is not particularly limited, but is usually 500 or more, preferably 500 to 5000, and more preferably 1000 to 3500. When the molecular weight / number of hydroxyl groups is within this range, the polyurethane foam is less likely to shrink and the elasticity becomes better. In the present invention, a polyoxyalkylene polyol having a molecular weight / number of hydroxyl groups of less than 500 is usually classified as a cross-linking agent F described later.

The initiator used in the production of polyol A is preferably a compound having 2 to 8 active hydrogen-containing groups in one molecule. As such a compound, a 2- to 8-valent polyhydric alcohol, a polyhydric phenol or an amine is preferable.
Examples of the divalent to octavalent polyhydric alcohols include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, dipropylene glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin, meso-erythritol, and methyl. Examples include, but are not limited to, glucoside, glucose, dextrose, sorbitol or sucrose.
Examples of the multivalent phenol include, but are not limited to, bisphenol A, bisphenol F, pyrogallol or hydroquinone.
Examples of the amine include, but are not limited to, polyamines such as ethylenediamine, diethylenediamine, diaminodiphenylmethane, hexamethylenediamine and propylenediamine, and condensation compounds obtained by condensing polyamine with a phenol resin or novolak resin. ..
Further, the polyhydric alcohol, the polyhydric phenol, or a low molecular weight polyether polyol having a hydroxyl group at the terminal of the molecular chain obtained by ring-opening addition polymerization of a small amount of alkylene oxide to the amine can also be used as an initiator. The molecular weight per hydroxyl group of such a low molecular weight polyether polyol is usually 1200 or less, preferably 200 to 500, and more preferably 200 to 350.

As the initiator, a compound having 2 to 4 hydroxyl groups in one molecule is more preferable, and a dihydric to tetravalent polyhydric alcohol or a 2 to 4 valent low molecular weight polyether polyol is preferable. Among them, the polyol produced by using a trihydric or higher-valent alcohol or a low molecular weight polyether polyol as an initiator has a better balance of soundproofing performance, foaming stability and physical properties of polyurethane foam. One type of initiator may be used alone, or two or more types may be used in combination.

The alkylene oxide is not particularly limited, but one or more selected from ethylene oxide, propylene oxide, butylene oxide and styrene oxide is preferable, and one or more selected from ethylene oxide and propylene oxide are more preferable. As the ethylene oxide content increases, the crystallinity of the polyoxyalkylene chain tends to improve and the soft segment of polyurethane tends to become rigid. The content of the unit derived from ethylene oxide (hereinafter referred to as “EO content”) of the polyoxyalkylene chain of polyol A is not particularly limited, but is preferably 0 to 20% by mass of the total mass of the polyoxyalkylene chain. More preferably 0 to 15% by mass. When the EO content is within this range, the hydrophilicity of the polyoxyalkylene chain becomes more preferable, and the residual film ratio of the foamed cell in the obtained polyurethane foam tends to be within a more appropriate range.

A conventionally used catalyst is used as a catalyst for ring-opening addition polymerization of an alkylene oxide as an initiator. Examples of the catalyst include, but are not limited to, potassium hydroxide, sodium hydroxide, cesium hydroxide, phosphazenium compound, boron trifloride compound or complex metal cyanide complex.

Polyol A may contain polymer fine particles dispersed in polyol A. In the polymer fine particles, the polymer fine particles are stably dispersed in the base polyol as a dispersion medium. Examples of the polymer fine particles include addition polymerization type polymers and polycondensation type polymers. Examples of the polymer constituting the polymer fine particles include addition polymerization polymers such as homopolymers or copolymers of acrylonitrile, styrene, alkyl methacrylate, alkyl acrylates and other vinyl monomers, or reduced polymerization polymers such as polyester, polyurea, polyurethane or melamine resin. Is preferable, and homopolymers or copolymers of acrylonitrile and styrene are more preferable.

In the method for producing a polyurethane foam of the present invention, a polyol other than polyol A may be used in combination. Examples of such a polyol include other high molecular weight polyols such as polyester polyol. The amount of the polyol other than the polyol A to be used is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and 0 parts by mass, that is, not used, based on 100 parts by mass of the total of the polyol A. preferable.

Hereinafter, the content of the components other than the polyol A in the raw material composition G is defined as the content with respect to 100 parts by mass of the polyol A.
One type of polyol A may be used alone, or two or more types may be used in combination.

(Organic Polyisocyanate Compound B)
The organic polyisocyanate compound B used for producing the polyurethane foam of the present invention is not particularly limited. At least one selected from the group consisting of the obtained modified polyisocyanate and polyisocyanate can be mentioned.
Examples of the organic polyisocyanate compound B include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl isocyanate (commonly known as crude MDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HMDI). ), Prepolymer modified products of these polyisocyanates, isocyanurate modified products, urea modified products and carbodiimide modified products, and at least one selected from the group consisting of TDI, MDI, crude MDI and modified products thereof. It is preferable in terms of availability. The TDI may be either 2,4-TDI or 2,6-TDI, or a mixture. The MDI may be any of 2,2'-MDI, 2,4'-MDI and 4,4'-MDI, and may be a mixture of two or three of these. As the organic polyisocyanate compound B, TDI is particularly preferable.

The content of the organic polyisocyanate compound B in the raw material composition G is not particularly limited, but is a value obtained by dividing the total number of moles of the isocyanate groups of the organic polyisocyanate compound B by the total number of moles of the hydroxyl groups of the polyol A and multiplying by 100. The amount of (isocyanate index) is preferably 75 to 120, more preferably 80 to 120, and even more preferably 80 to 110. When the isocyanate index is within this range, curing can proceed sufficiently, and a foam having an appropriate degree of curing can be obtained without excessive curing progressing.
As the organic polyisocyanate compound B, one type may be used alone, or two or more types may be used in combination.

(Foamant C)
The foaming agent used in the production of the polyurethane foam of the present invention contains water.
Further, a foaming agent other than water can be used for the purpose of lowering the density of the foam. As the foaming agent other than water, an inert compound having a low boiling point is preferable. Such an inert compound further includes, for example, an inert gas and a hydrocarbon compound having a boiling point of 70 ° C. or lower and a carbon number of 8 or less, and is one of the hydrogen atoms bonded to the carbon atom of the hydrocarbon compound. Examples thereof include saturated hydrocarbons whose portions may be substituted with halogen atoms (hereinafter referred to as “saturated hydrocarbons X”). The halogen atom is, for example, a chlorine atom or a fluorine atom.
Examples of the saturated hydrocarbon X include, but are not limited to, butane, pentane, hexane, dichloromethane (methylene chloride), trichloroethane and various chlorofluorocarbon compounds.

The content of water as the foaming agent C in the raw material composition G is preferably 1.5 parts by mass or more, more preferably 2 to 5 parts by mass, based on 100 parts by mass of the polyol A. Within this range, foaming can proceed sufficiently and the density of the foam can be easily set within a desired range.
The content of the foaming agent other than water in the raw material composition G is not particularly limited, but is preferably 0 to 25 parts by mass, more preferably 0 to 20 parts by mass with respect to 100 parts by mass of the polyol A.
One type of foaming agent C may be used alone, or two or more types may be used in combination.

(Catalyst D)
The catalyst D used in the production of the polyurethane foam of the present invention is at least one selected from the group consisting of amine-based catalysts and tin-based catalysts.
The catalyst D is a catalyst used when reacting a polyoxyalkylene polyol with an organic polyisocyanate compound.
As the catalyst D, one type may be used alone, or two or more types may be used in combination.

Examples of the amine-based catalyst include triethylenediamine, bis (2-dimethylaminoethyl) ether, N, N, N', N'-tetramethylhexamethylenediamine, N, N-dimethylaminoethoxyethoxyethanol, N, N-. Dimethylamino-6-hexanol, N, N-dimethylaminoethoxyethanol, N, N-dimethylaminoethoxyethanol plus 2 mol of ethylene oxide, or 5- (N, N-dimethyl) amino-3-methyl- 1-Pentanol, but is not limited to these.

The content of the amine-based catalyst in the raw material composition G is not particularly limited, but is preferably 0.1 to 5.0 parts by mass and 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the polyol A. More preferred.
One type of the amine-based catalyst may be used alone, or two or more types may be used in combination.

Examples of the tin-based catalyst include tin 2-ethylhexanoate, di-n-butyltin oxide, di-n-butyltin dilaurate, di-n-butyltin diacetate, di-n-octyltin oxide, and di-n-octyltin. Examples include, but are not limited to, dilaurate, monobutyltin trichloride, di-n-butyltin dialkyl mercaptan and di-n-octyl tin dialkyl mercaptan.

The content of the tin-based catalyst in the raw material composition G is not particularly limited, but is preferably 1.0 part by mass or less, more preferably 0.005 to 1.0 part by mass, based on 100 parts by mass of polyol A. preferable.
One type of the tin-based catalyst may be used alone, or two or more types may be used in combination.

(Foaming agent E)
The raw material composition G used for producing the polyurethane foam of the present invention may further contain a defoaming agent E.
Examples of the defoaming agent E include, but are not limited to, a silicone-based defoaming agent or a fluorine-containing compound-based defoaming agent.
When the raw material composition G contains the antifoaming agent E, good bubbles can be formed.
The content of the foam stabilizer E in the raw material composition G is not particularly limited, but is preferably 0.1 to 5.0 parts by mass and 0.3 to 4.0 parts by mass with respect to 100 parts by mass of the polyol A. Parts are more preferable, and 0.5 to 3.0 parts by mass are further preferable.
One type of foam stabilizer E may be used alone, or two or more types may be used in combination.

(Crosslinking agent F)
The raw material composition G used for producing the polyurethane foam of the present invention may further contain a cross-linking agent F. As the cross-linking agent F, a compound having two or more active hydrogen-containing groups selected from a hydroxyl group, a primary amino group and a secondary amino group is preferable. The number of active hydrogen-containing groups is preferably 2 to 8. The molecular weight of the cross-linking agent per active hydrogen-containing group is preferably less than 500.

Examples of the cross-linking agent F include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, pentaerythritol, and di. Glycerin, monoethanolamine, diethanolamine, triethanolamine, bisphenol A, ethylenediamine, 3,5-diethyl-2,4-diaminotoluene, 3,5-diaminotolu, 6-diaminotoluene, 2-chloro-p-phenylene Diamine, 3,5-bis (methylthio) -2,4-diaminotoluene, 3,5-bis (methylthio) -2,6-diaminotoluene, 1-trifluoromethyl-3,5-diaminobenzene, 1-tri Fluoromethyl-4-chloro-3,5-diaminobenzene, 2,4-toludiamine, 2,6-toludiamine, bis (3,5-dimethyl-4-aminophenyl) methane, 4,4'-diaminodiphenylmethane , M-xylylene diamine, 1,4-diaminohexane, 1,3-bis (aminomethyl) cyclohexane and isophoronediamine, but are not limited thereto. Further, as the cross-linking agent F, the above-mentioned polyoxyalkylene polyol having a molecular weight / number of hydroxyl groups of less than 500 can also be used.

The content of the cross-linking agent F in the raw material composition G is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the polyol A. As the cross-linking agent F, one type may be used alone, or two or more types may be used in combination.

(Additive)
The raw material composition G used for producing the polyurethane foam of the present invention may further contain an additive.
Examples of the additive include an emulsifier, an antioxidant, an antioxidant such as an ultraviolet absorber, a filler such as calcium carbonate or barium sulfate, a plasticizer, a colorant, a flame retardant, an antifungal agent or a foam breaking agent. Examples of the above-mentioned various known additives or auxiliaries can be mentioned, but the present invention is not limited to these, and additives conventionally used for polyurethane foam can be used.
The content of the additive or the like in the raw material composition G is not particularly limited as long as it does not interfere with the effects of the present invention.

<Molding method>
In the method for producing a polyurethane foam of the present invention, a molding method in which the raw material composition G is injected into a closed mold is preferable. Examples of this molding method include a molding method called mold foaming.

[Soundproofing material for vehicles]
The vehicle soundproofing material of the present invention includes the polyurethane foam described above.
As the vehicle, an automobile is preferable.
The polyurethane foam of the present invention has a thin thickness and good sound absorption characteristics in a low frequency region of 500 to 2000 Hz, and is therefore suitable as a soundproofing material for vehicles. Since the frequency with good sound absorption coefficient is the frequency band of road noise, it is suitable for use in fender liner and undercover applications, especially in fender liner applications.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the technical scope of the present invention is not limited to the Examples described later, and various modifications may be made without departing from the spirit of the present invention. It is possible.

[Synthesis example]
A polyoxyalkylene polyol was synthesized according to the following procedure.

<Synthesis example 1>
In the presence of a potassium hydroxide catalyst, propylene oxide was subjected to ring-opening addition polymerization using glycerin as an initiator, and then ethylene oxide was further subjected to ring-opening addition polymerization to synthesize a polyoxyalkylene polyol A1.

<Synthesis example 2>
Using the polyoxyalkylene polyol A1 obtained above as a dispersion medium, acrylonitrile polymer fine particles (30% by mass) were dispersed to obtain a polyoxyalkylene polyol A2.

<Synthesis example 3>
A composite metal cyanide complex catalyst (hereinafter referred to as “DMC catalyst”) was produced by the production method described in JP-A-2016-006203, [0021] to [0034].
In the presence of a DMC catalyst, propylene oxide was subjected to ring-opening addition polymerization using glycerin as an initiator, and then ethylene oxide was subjected to ring-opening addition polymerization using KOH to obtain a polyoxyalkylene polyol A3.

<Synthesis example 4>
In the presence of a potassium hydroxide catalyst, propylene oxide was subjected to ring-opening addition polymerization using glycerin as an initiator, and then ethylene oxide was further subjected to ring-opening addition polymerization to synthesize a polyoxyalkylene polyol A4.

<Synthesis example 5>
Polyoxyalkylene polyol A5 was synthesized by ring-opening addition polymerization of propylene oxide using glycerin as an initiator in the presence of a potassium hydroxide catalyst.

<Synthesis example 6>
In the presence of a potassium hydroxide catalyst, propylene oxide was subjected to ring-opening addition polymerization using glycerin as an initiator, and then ethylene oxide was further subjected to ring-opening addition polymerization to synthesize a polyoxyalkylene polyol A6.
The number average molecular weights of the polyoxyalkylene polyols A1 to A6, the number of hydroxyl groups per molecule, the molecular weight per hydroxyl group, and the EO content are as shown in Table 1, respectively.

In Table 1, the EO content refers to the content (% by mass) of a unit derived from ethylene oxide in the polyoxyalkylene chain of the polyoxyalkylene polyol. The PO content refers to the content (% by mass) of a unit derived from propylene oxide in the polyoxyalkylene chain of the polyoxyalkylene polyol.

[Example 1]
An aluminum mold having a length, a width of 150 mm, and a height of 10 mm was prepared.
As shown in Table 2, 60 parts by mass of the polyoxyalkylene polyol A1, 40 parts by mass of the polyoxyalkylene polyol A2, 3 parts by mass of the foaming agent C1, 0.3 parts by mass of the catalyst D1 and 0. 05 parts by mass, 3 parts by mass of the foam stabilizer E2 and 3 parts of the cross-linking agent F1 were placed in a container and mixed at 3000 rpm for 30 seconds using a high-speed mixer. A mixture containing a raw material other than the organic polyisocyanate compound (hereinafter referred to as "polyol system liquid 1") was obtained.
39.4 parts by mass of the organic polyisocyanate compound B2 was added to the polyol system liquid 1 and mixed at 3000 rpm for 5 seconds using a high-speed mixer (described above). A raw material composition (hereinafter referred to as "raw material composition 1") was obtained.
After heating the upper and lower mold temperature of the mold prepared in advance to 60 ° C., the raw material composition 1 was added and foamed and cured. After 3 minutes, the cured product was taken out from the mold, crushed and degassed to obtain a flexible polyurethane foam (hereinafter referred to as "polyurethane foam 1").
The polyol system liquid 1, the raw material composition 1, and the polyurethane foam 1 were all produced in an environment of 25 ° C. at both room temperature and liquid temperature.

[Example 2]
A mixture containing a raw material other than the organic polyisocyanate compound (hereinafter referred to as "polyol system liquid 2") in the same manner as in Example 1 except that the amount of the foaming agent C1 added is changed to 1 part and the catalyst D2 is not used. Got In the same manner as in Example 1, 18.5 parts by mass of the organic polyisocyanate compound B2 was added to obtain a raw material composition (hereinafter referred to as “raw material composition 2”). A flexible polyurethane foam (hereinafter referred to as "polyurethane foam 2") was obtained in the same manner as in Example 1 except that the raw material composition 2 was used.

[Example 3]
A mixture containing a raw material other than the organic polyisocyanate compound (hereinafter referred to as "polyol system liquid 3") was obtained in the same manner as in Example 2 except that the amount of the foaming agent C1 added was changed to 5 parts. In the same manner as in Example 2, 60.2 parts by mass of the organic polyisocyanate compound B2 was added to obtain a raw material composition (hereinafter referred to as “raw material composition 3”). A flexible polyurethane foam (hereinafter referred to as "polyurethane foam 3") was obtained in the same manner as in Example 1 except that the raw material composition 3 was used.

[Example 4]
As shown in Table 2, 8 parts by mass of the polyoxyalkylene polyol A3, 3 parts by mass of the polyoxyalkylene polyol A4, 72 parts by mass of the polyoxyalkylene polyol A5, 20 parts by mass of the polyoxyalkylene polyol A6, and the foaming agent C1. 2.35 parts by mass of the catalyst D1, 0.6 parts by mass of the catalyst D1, 0.3 parts by mass of the catalyst D3, 0.3 parts by mass of the catalyst D4 and 0.4 parts by mass of the foam stabilizer E1. And mixed at 3000 rpm for 30 seconds using a high speed mixer. A mixture containing a raw material other than the organic polyisocyanate compound (hereinafter referred to as "polyol system liquid 4") was obtained.
To the polyol system liquid 4, 29.9 parts by mass of the organic polyisocyanate compound B1 was added, and the mixture was mixed at 3000 rpm for 5 seconds using a high-speed mixer (described above). A raw material composition (hereinafter referred to as “raw material composition 4”) was obtained. A flexible polyurethane foam (hereinafter referred to as “polyurethane foam 4”) was obtained in the same manner as in Example 1 except that the raw material composition 4 was used.
Polyurethane foams 1 to 4 were left in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH for 24 hours or more.

The meanings of the symbols in Table 2 are as follows.
A: Polyoxyalkylene polyol A1 Polyoxyalkylene polyol A1 synthesized in Synthesis Example 1
-A2 Polyoxyalkylene polyol A2 synthesized in Synthesis Example 2
-A3 Polyoxyalkylene polyol A3 synthesized in Synthesis Example 3
-A4 Polyoxyalkylene polyol A4 synthesized in Synthesis Example 4
-A5 Polyoxyalkylene polyol A5 synthesized in Synthesis Example 5
-A6 Polyoxyalkylene polyol A6 synthesized in Synthesis Example 6

B: Organic polyisocyanate compound-Mixture of B1 TDI and MDI (Coronate 1025, manufactured by Tosoh Corporation)
A mixture of 2,4-TDI, 2,6-TDI and Crude MDI having a mass ratio of 2,4-TDI / 2,6-TDI / Crude MDI = 40/10/50 Isocyanate group content 39.7% by mass
・ Mixture of B2 TDI and MDI (Coronate 1021, manufactured by Tosoh Corporation)
A mixture of 2,4-TDI, 2,6-TDI and Crude MDI having a mass ratio of 2,4-TDI / 2,6-TDI / Crude MDI = 64/16/20 Isocyanate group content 44.8% by mass

C: Foaming agent, C1 water

D: Catalyst-D1 Triethylenediamine dipropylene glycol solution (TEDA (registered trademark) L-33, manufactured by Tosoh Corporation) Amine-based catalyst-tin D2 2-ethylhexanoate (DABCO (registered trademark) T-9, manufactured by EVONIK) )
-Dipropylene glycol solution of D3 bis [(2-dimethylamino) ethyl] ether (TOYOCAT (registered trademark) ET, manufactured by Tosoh Corporation)
-D4 1-isobutyl-2-methylimidazole (NC-IM, manufactured by Sankyo Air Products & Chemicals)

E: Defoaming agent / E1 Silicone-based defoaming agent (SRX-274C, manufactured by Dow Corning)
・ E2 Silicone-based defoaming agent (TEGOSTAB (registered trademark) B8737 LF2, manufactured by EVONIK)

F: Cross-linking agent / F1 cross-linking agent (molecular weight 400, number of functional groups 4, EO content 100% by mass polyol) However, the EO content 100% by mass of F1 is a unit derived from alkylene oxide in the polyoxyalkylene chain. It means that the unit derived from ethylene oxide is 100% by mass.

[Evaluation method]
The polyurethane foams 1 to 4 obtained in Examples 1 to 4 were cut with a sharp cutting tool to prepare a sample for measurement. The thickness of any 5 points of this measurement sample was measured with a dial thickness gauge type film thickness meter (manufactured by Ozaki Seisakusho Co., Ltd., model: G), and the average value was calculated to obtain a thickness of 10 mm. there were. Using this measurement sample, sound absorption coefficient, density, residual film ratio, average cell diameter, average skeleton diameter, value obtained by dividing the average skeleton diameter by the average cell diameter, skeleton ratio (epidermal layer skeleton ratio SS, internal foamed layer skeleton ratio) SI, SS / SI, skeletal ratio directly below the epidermis layer) and epidermis layer thickness were evaluated by the methods described below, and the results are shown in Table 3.

<Sound absorption rate>
The vertically incident sound absorption coefficient (sound absorption coefficient) was measured in the 500 to 2000 Hz region by a method based on JIS A 1405-2: 2007 “Measurement of sound absorption coefficient and impedance by acoustic tube”. The equipment used for the measurement is as follows.
・ Vertically incident sound absorption measuring tube (40 mmφ, manufactured by Nippon Acoustic Engineering Co., Ltd.)
・ Analysis software (WinZacMTX VER.5.0, manufactured by Nippon Acoustic Engineering Co., Ltd.)
・ Power amplifier (AP15d, manufactured by FOSTEX)
・ Microphone (46BD, manufactured by GRAS)
・ Microphone amplifier (12AQ, manufactured by GRAS)
・ Audio interface (Fireface UC, manufactured by RME)

<Density>
Density was measured according to JIS K 7222: 2005 "Foam Plastics and Rubber-How to Obtain Apparent Density". Density measurements were made on the entire polyurethane foam.

<Residual film ratio>
A cross section of the measurement sample was imaged using an optical microscope 1 (VHX-1000, manufactured by KEYENCE CORPORATION) at a magnification of 150 times. Of the internal foamed layers, the part where the cell skeleton could be confirmed over the entire circumference and the peripheral skeleton was not clearly destroyed was used as the observation target.
If there was an undamaged membrane on the inner circumference of the cell skeleton to be observed, it was judged that there was a residual membrane.
If there was no membrane on the inner circumference of the cell skeleton to be observed, or if the membrane was partially torn, it was judged as "no residual membrane".
The cross section of the measurement sample is imaged at 10 points, 100 cell skeletons are observed, the number of "with residual film" and "without residual film" is counted, and the ratio of "with residual film" is calculated as a percentage. did. The calculated percentage was taken as the residual film ratio.

<Average skeleton diameter>
A cross section of the measurement sample was imaged using an optical microscope 1 at a magnification of 150 times. Of the internal foam layer, the portion where the boundary between the skeleton portion, the cell portion, and the membrane portion could be clearly observed was set as the observation target. The average skeleton diameter of the skeleton to be observed was measured using image processing software (ImageJ, manufactured by the National Institutes of Health). For the skeleton having a constricted shape, the smallest diameter portion was defined as the skeleton diameter of the skeleton portion.
The cross section of the measurement sample was imaged at 10 places, the skeleton diameters of 70 observation objects were measured, and the average skeleton diameter was calculated by the arithmetic mean.

<Average cell diameter>
A cross section of the measurement sample was imaged using an optical microscope 1 at a magnification of 150 times. Of the internal foam layer, the part where the cell skeleton can be confirmed over the entire circumference was used as the observation target.
The contour of the inner circumference of the cell to be observed was extracted using image processing software (ImageJ, manufactured by the National Institutes of Health), and the area surrounded by the contour was calculated. The diameter of a circle with an area equal to the calculated area (circle-equivalent diameter) was calculated and defined as the cell diameter of the cell to be observed.
The cross section of the measurement sample was imaged at 10 places, the cell diameters of 80 observation objects were measured, and the average cell diameter was calculated by the arithmetic mean.

<Average skeleton diameter / average cell diameter>
From the average skeleton diameter and the average cell diameter obtained by the above method, a value obtained by dividing the average skeleton diameter by the average cell diameter was calculated.

<Skeletal ratio>
The cross section of the measurement sample was imaged using an optical microscope 1. Then, using image processing software (ImageJ, manufactured by the National Institutes of Health, USA), the captured image was cut out in an area of 2.5 mm × 3.5 mm.
The cut-out image was binarized by a discriminant analysis method (binarization of Otsu).
In the above binarized image, the area ratio of the black part is calculated for each area of 0.02 mm × 3.5 mm, and the area ratio at each position is obtained while scanning the analysis area in the sample thickness direction by 0.02 mm. The distribution of the skeletal ratio in the sample thickness direction (skeletal ratio profile) was calculated.
The cross section of the measurement sample was imaged at five or more places, and the skeleton ratio was calculated by the arithmetic mean of the skeleton ratio profile obtained from each image.

<Epidermal skeleton ratio SS>
The epidermal layer skeleton ratio SS was calculated from the arithmetic mean of the skeletal ratio profiles measured at a depth of 0.3 mm from the surface of the polyurethane foam.

<Internal foam layer skeleton ratio SI>
The internal foam layer skeleton ratio SI was calculated from the arithmetic mean of the skeletal ratio profiles measured at a depth of 3.5 to 4.5 mm from the surface of the polyurethane foam.

<SS / SI>
From the epidermis layer skeleton ratio SS and the internal foam layer skeleton ratio SI obtained by the above method, a value obtained by dividing the epidermis layer skeleton ratio SS by the internal foam layer skeleton ratio SI was calculated.

<Epidermis layer thickness>
In the skeletal ratio profile obtained by the above method, the thickness from the sample surface to the portion where the skeletal ratio is less than 50% is calculated while scanning the analysis region in the sample thickness direction by 0.02 mm to obtain the epidermis layer thickness. did.

[Explanation of results]
Example 1 corresponds to an embodiment, and Examples 2 to 4 correspond to a comparative example.
It can be seen that the polyurethane foam of Example 1 has a residual film ratio within a specific range and is excellent not only in sound absorption characteristics at a low frequency of 1000 Hz but also in sound absorption performance in a low frequency region. Further, since the polyurethane foam of Example 1 has high sound absorption performance even if it is thin, a high sound absorption environment can be achieved by introducing it into a portion requiring weight reduction or thinning.
Although the polyurethane foam of Example 2 has a higher density than the polyurethane foam of Example 1, SS / SI does not meet the scope of the present invention and the residual film ratio is also high, so that sufficient sound absorption characteristics can be obtained. There wasn't.
The polyurethane foam of Example 3 has insufficient SS / SI, and has a lower density and a lower residual film ratio than the polyurethane foam of Example 1, so that the sound absorption characteristics in the low frequency region are insufficient. Met.
Although the polyurethane foam of Example 4 has a higher density than the polyurethane foam of Example 1, the SS / SI is outside the range of the present invention, so that sufficient sound absorption characteristics cannot be obtained.

The polyurethane foam of the present invention has a thin thickness and good sound absorption characteristics in a low frequency region of 500 to 2000 Hz, and is therefore suitable as a soundproofing material for vehicles. Since the frequency with good sound absorption coefficient is the frequency band of road noise, it is suitable for use in fender liner and undercover applications, especially in fender liner applications.
The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2019-236123 filed on December 26, 2019 are cited here and incorporated as disclosure of the specification of the present invention. Is.

Claims

A polyurethane foam having an epidermis layer and an internal foam layer formed inside the epidermis layer.
The thickness is 3 to 25 mm, and the vertical incident sound absorption coefficient at a frequency of 1000 Hz is 0.40 or more at a thickness of 10 mm.
A polyurethane foam having a skeleton ratio ratio SS / SI of 2.8 to 5.0 when the skeleton ratio of the epidermis layer is SS and the skeleton ratio of the internal foam layer is SI.
The polyurethane foam according to claim 1, wherein the skeleton ratio SS / SI is 2.8 to 4.0.
The polyurethane foam according to claim 1 or 2, wherein the skeleton ratio SS of the epidermis layer is 60% to 85%.
The polyurethane foam according to any one of claims 1 to 3, wherein the skeleton ratio SI of the internal foam layer is 24% to 30%.
The polyurethane foam according to any one of claims 1 to 4, wherein the skeleton ratio immediately below the epidermis layer is 40% or more.
The polyurethane foam according to any one of claims 1 to 5, which has a density of 20 to 120 kg / m 3.
The polyurethane foam according to any one of claims 1 to 6, wherein the residual film ratio of the foam cell of the internal foam layer is 40% or more and less than 94%.
The polyurethane foam according to claim 7, wherein the value obtained by dividing the average skeleton diameter of the foam cells by the average cell diameter is 0.10 to 0.50, and the average cell diameter of the foam cells is 100 to 400 μm. ..
A soundproofing material for vehicles containing the polyurethane foam according to any one of claims 1 to 8.
A fender liner provided with the vehicle soundproofing material according to claim 9.