JP2013134427A - Sound absorbing material having laminated body of aliphatic polyester nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin sound absorbing material which has excellent sound absorbing characteristics in a low spectrum and which can reduce an environmental load.SOLUTION: A sound absorbing material has layers of a laminated body of a nonwoven fabric made of aliphatic polyester which is preferably a polyglycolic acid or a polylactic acid, has other layers as desired, and has a sound absorption peak of 1,100 Hz or less.

Description

  The present invention relates to a sound-absorbing material that is thin, has excellent sound-absorbing characteristics in a low frequency range, and can reduce environmental burden.

  Noise is a familiar problem as one of the uncomfortable factors along with vibration, and the demand for a sound absorbing material for solving it is still high. In addition, there are a wide variety of required characteristics depending on applications and purposes. Recently, a material having a high sound absorption performance in a low frequency region typified by an engine of an automobile or a construction machine, a motor in a factory, a machine, or the like is desired.

  Conventionally, as a sound absorbing material, for example, a material formed by forming a fiber into a cotton or board shape, such as glass wool or rock wool, a polymer foam such as polyurethane foam, or a porous material such as porous ceramic, etc. Are known. When sound waves are incident on these sound absorbing materials, the sound waves vibrate the air in the gaps in the material, so part of the vibration energy is converted to heat energy and dissipated by the viscosity of the air itself and the friction with the surroundings, resulting in a sound absorbing effect. Is obtained. However, for example, glass wool, which is widely used as a sound absorbing material, has an excellent sound absorption coefficient at a frequency of 1,000 Hz or higher, but a sound absorption coefficient in a low frequency region of less than 1,000 Hz is not sufficient.

As a sound absorbing material having an excellent sound absorption rate in a low frequency region, Patent Document 1 specifies a through-hole provided in a frame as a sound absorbing material having a sound absorption rate of 0.5 or more in a low frequency region of 500 Hz or less. What is covered with a sound-absorbing material having a storage elastic modulus defined by the following formula is disclosed, and a frame body formed of a resin or the like and provided with a cylindrical through-hole having a diameter of 20 mm or more and a thickness of 3 mm or more is described. Patent Document 2 includes a non-breathable vibration thin film made of a compound film formed by polymer blending a thermoplastic elastomer and plastic, and a nonwoven fabric that adheres to the vibration thin film and supports the vibration thin film. A sound-absorbing material is disclosed, and the sound-absorbing peak of a sound-absorbing material comprising 1 to 5 compound films having a thickness of 20 to 200 μm and a nonwoven fabric having a thickness of 10 mm and a basis weight of about 30 g / m ² is in the range of 800 to 1,300 Hz. It is described to control. Patent Document 3 discloses that a sound absorption coefficient at a frequency of 1,000 Hz obtained by bonding a face material made of a laminated nonwoven fabric including at least one ultrafine fiber layer and a base material made of a short fiber nonwoven fabric is 50% or more. A certain composite sound-absorbing material is disclosed, and the laminated nonwoven fabric (face material) is made of thermoplastic fibers having an average fiber diameter of 10 to 30 μm, and has a thickness of 0.1 to 0.3 mm and a basis weight of 50 to 120 g / m ² . A sound-absorbing material having a high sound-absorbing property in a low frequency region of 500 to 1,500 Hz, in which the base material has a thickness of 20 to 50 mm and a basis weight of 500 to 1,500 g / m ² is described.

On the other hand, Patent Document 4 discloses a nonwoven fabric A having a basis weight of 100 to 1,000 g / m ² and a thickness of 5 to 50 mm mainly composed of polylactic acid fibers, and a nonwoven fabric having a basis weight of 50 to 500 g / m ² mainly composed of polylactic acid fibers. A sound-absorbing material is disclosed in which the non-woven fabric B is laminated on the front side, and a sound-absorbing material having excellent sound-absorbing property in the frequency range of 1,000 to 2,500 Hz, easy recyclability, and low environmental load is described. Yes.

  Since aliphatic polyesters such as polylactic acid and polyglycolic acid disclosed in Patent Document 4 are decomposed by microorganisms or enzymes existing in nature such as soil and sea, and finally converted to water and carbon dioxide, In recent years, it has attracted attention as a biodegradable polymer material with a low environmental impact. Since these biodegradable aliphatic polyesters have biodegradable absorbability, they are used as medical polymer materials such as surgical sutures and artificial skin. Further, attention has been focused on applications utilizing the nature of gradual disappearance in nature without requiring special disposal processing operations. As a sustained-release fertilizer container, as a civil engineering material such as a rope or cement decorative frame that can be left in the mountains, fields, or cities after use, as an agricultural material such as a nursery net or greenhouse film, and more recently, as a magnetic card or packaging It is used as a daily miscellaneous material such as materials or as a golf course member such as a marker, and contributes to a reduction in environmental load.

  As described above, in recent years, the demand for sound-absorbing material with high sound-absorbing performance in the low-frequency region is required to be based on a complex combination of thick materials. Was not obtained. Therefore, it has been desired to provide a sound-absorbing material that is rich in resource saving and recyclability and that can further reduce the environmental load.

JP 2010-26258 A JP 2010-237418 A JP 2010-128005 A JP 2006-98890 A

  An object of the present invention is to provide a sound-absorbing material that is thin, has excellent sound-absorbing characteristics in a low frequency range, and can reduce environmental burden.

  As a result of earnest research on solving the above-mentioned problems, the present inventors have found that the problem can be solved by providing a layer of a nonwoven fabric laminate formed from aliphatic polyester as the sound absorbing material. Was completed.

  That is, according to the present invention, there is provided a sound absorbing material having a layer of a nonwoven fabric laminate formed from aliphatic polyester and having a sound absorption peak of 1,100 Hz or less.

Moreover, according to this invention, the sound-absorbing material of the following (1)-(10) is provided as an embodiment.
(1) The sound absorbing material, wherein the aliphatic polyester is polyglycolic acid or polylactic acid.
(2) The said sound-absorbing material whose nonwoven fabric formed from aliphatic polyester is a melt blown nonwoven fabric.
(3) The sound absorbing material, wherein the nonwoven fabric formed from the aliphatic polyester has a basis weight of 1 to 500 g / m ² and a fiber diameter of 300 nm to 100 μm.
(4) Aliphatic polyester has (a) weight average molecular weight (Mw) of 10,000 to 800,000, (b) ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn) The above sound-absorbing material having a molecular weight distribution of 1.5 to 4 and (c) a melt viscosity (measured at a melting point + 50 ° C. temperature and a shear rate of 122 sec ⁻¹ ) of 100 to 2,000 Pa · s.
(5) The sound absorbing material, wherein the laminate is formed by adhering and laminating the entire surface of a nonwoven fabric formed from an aliphatic polyester.
(6) The sound absorbing material, wherein the laminate is formed by partially bonding and laminating a nonwoven fabric formed from an aliphatic polyester.
(7) The said sound-absorbing material whose thickness is 5 cm or less.
(8) At a frequency (f) of 200 Hz to 700 Hz, the sound absorption coefficient (A) is expressed by the following formula (formula) A ≧ 10 ⁻¹³ × f ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² + 0.0002 × f−0.0059
The sound absorbing material satisfying the above.
(9) The sound-absorbing material that does not include any other layer than the layer of the laminate.
(10) The above-described sound absorbing material wrapped with a moisture-proof packaging material.

  The present invention is a sound-absorbing material having a non-woven laminate layer formed from aliphatic polyester and having a sound-absorbing peak of 1,100 Hz or less, thus having a thin thickness and excellent sound-absorbing characteristics in a low frequency range. In addition, there is an effect that a sound absorbing material capable of further reducing the environmental load is provided.

It is a graph which shows the sound absorption rate with respect to the frequency of the sound-absorbing material of this invention. It is a graph which shows the sound absorption rate with respect to the frequency about the other example of the sound-absorbing material of this invention. It is a graph which shows the sound absorption rate with respect to the frequency about the other example of the sound-absorbing material of this invention.

1. Aliphatic polyester The sound-absorbing material of the present invention includes a laminate layer of a nonwoven fabric (hereinafter sometimes referred to as “aliphatic polyester nonwoven fabric”) formed from an aliphatic polyester. Examples of the aliphatic polyester forming the nonwoven fabric include polyglycolic acid (hereinafter sometimes referred to as “PGA”) composed of glycolic acid repeating units and polylactic acid composed of lactic acid repeating units (hereinafter referred to as “PLA”). ) Hydroxycarboxylic acid polyesters, lactone polyesters such as polyε-caprolactone, diol / dicarboxylic acid polyesters such as polyethylene succinate and polybutylene succinate, and copolymers thereof, for example, glycolic acid repeating units A copolymer composed of lactic acid repeating units is known.
Many of these aliphatic polyesters are biodegradable aliphatic polyesters having biodegradability, and biodegradable aliphatic polyesters are preferred from the viewpoint of further reducing the environmental burden.

  Among biodegradable aliphatic polyesters, PLA is obtained from L-lactic acid, which is a raw material, at low cost by fermentation from corn, straw, etc. The resulting poly L-lactic acid is characterized by high rigidity and good transparency. Further, PGA has characteristics such as excellent hydrolytic and biodegradable properties, mechanical strength such as heat resistance and tensile strength, and excellent gas barrier properties when used as a film or sheet.

  The biodegradable aliphatic polyester will be described in more detail. Glycolic acids including glycolic acid and glycolide (GL) which is a bimolecular cyclic ester of glycolic acid; lactic acid including lactide which is a bimolecular cyclic ester of lactic acid and lactic acid. In addition to ethylene oxalate (ie, 1,4-dioxane-2,3-dione), lactones (eg, β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone) , Β-methyl-δ-valerolactone, ε-caprolactone etc.), carbonates (eg trimethylene carbonate etc.), ethers (eg 1,3-dioxane etc.), ether esters (eg dioxanone etc.) etc. 3-hydroxypropanoic acid, 4-hydroxybutanoic acid, 6- Hydroxycarboxylic acids such as droxycaproic acid or alkyl esters thereof; aliphatic diols such as ethylene glycol and 1,4-butanediol (butylene glycol); and aliphatic dicarboxylic acids such as succinic acid and adipic acid or alkyl esters thereof A homopolymer or copolymer of aliphatic ester monomers such as: Specifically, for example, the formula: (—O—CHR—CO—) [R is a hydrogen atom or a methyl group. ] The biodegradable aliphatic polyester which has 50 mass% or more of the glycolic acid or lactic acid repeating unit represented by these, polylactone, polyhydroxybutyrate, polyethylene succinate, polybutylene succinate, etc. are mentioned. Of these, biodegradable aliphatic polyesters having 50% by mass or more of glycolic acid or lactic acid repeating units are preferable. Specifically, PGA, that is, a homopolymer of glycolic acid, or a copolymer having a glycolic acid repeating unit of 50% by mass or more; a homopolymer of poly L-lactic acid or poly D-lactic acid, L-lactic acid or D -PLA, such as a copolymer having a repeating unit of lactic acid of 50% by mass or more, or a mixture thereof; and a mixture of PGA and PLA; Particularly preferred is PGA or PLA from the viewpoint of excellent sound absorption in a low frequency region (hereinafter, simply referred to as “sound absorption”), mechanical strength, heat resistance, decomposability, and the like.

  These aliphatic polyesters can be synthesized, for example, by dehydration polycondensation of α-hydroxycarboxylic acids such as glycolic acid and lactic acid known per se. Further, in order to efficiently synthesize a high molecular weight aliphatic polyester, a method of synthesizing a bimolecular cyclic ester of α-hydroxycarboxylic acid and subjecting the cyclic ester to ring-opening polymerization is generally employed. For example, PLA is obtained by ring-opening polymerization of lactide, which is a bimolecular cyclic ester of lactic acid. PGA is obtained by ring-opening polymerization of glycolide, which is a bimolecular cyclic ester of glycolic acid.

  PLA can be synthesized by the above-mentioned method. Examples of commercially available products include “Lacia” (registered trademark) series (such as Lacia H-100, H-280, H-400, H-440) ( "Ingeo" (registered trademark) (manufactured by Natureworks), such as 3001D, 3051D, 4032D, 4042D, 6201D, 6251D, 7000D, and 7032D, Ecoplastic U'z S-09, S-12 "Eco-plastic U'z series" (manufactured by Toyota Motor Corporation), "Viro Ecole (registered trademark)" (manufactured by Toyobo Co., Ltd.), etc., such as S-17, etc., sound absorption, strength, flexibility and heat resistance It is preferably selected from the viewpoint of sex balance.

  Hereinafter, although PGA will be further described as an example of the aliphatic polyester, PLA and other aliphatic polyesters can take a form for carrying out the invention according to PGA.

[Polyglycolic acid (PGA)]
In the present invention, PGA preferably used as a raw material of the aliphatic polyester forming the aliphatic polyester nonwoven fabric is a homopolymer of glycolic acid composed only of a glycolic acid repeating unit represented by the formula: (—O—CH ₂ —CO—). In addition to a polymer (including a ring-opened polymer of glycolide (GL), which is a bimolecular cyclic ester of glycolic acid), a PGA copolymer containing 50% by mass or more of the glycolic acid repeating unit is included.

  Examples of comonomers that give a PGA copolymer together with glycolic acid monomers such as glycolide include ethylene oxalate (ie, 1,4-dioxane-2,3-dione), lactides, lactones, carbonates, and ethers. , Ether esters, amides and other cyclic monomers; lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid and other hydroxycarboxylic acids or alkyl esters thereof; ethylene glycol A substantially equimolar mixture of an aliphatic diol such as 1,4-butanediol and an aliphatic dicarboxylic acid such as succinic acid or adipic acid or an alkyl ester thereof; or two or more of these Can do. These comonomers can be used as a starting material for giving a PGA copolymer together with the glycolic acid monomer such as glycolide.

  The glycolic acid repeating unit in the PGA used in the present invention is 50% by mass or more from the above, preferably 70% by mass or more, more preferably 85% by mass or more, still more preferably 95% by mass or more, particularly Preferably it is 98% by weight or more, and most preferably 99% by weight or more is a substantially PGA homopolymer. If the proportion of the glycolic acid repeating unit is too small, the sound absorption property, strength, and decomposability in the low frequency region expected for PGA may be poor. The repeating unit other than the glycolic acid repeating unit is 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less, still more preferably 5% by mass or less, and particularly preferably 2% by mass or less. Most preferably, it is used in a proportion of 1% by mass or less, and may not contain any repeating unit other than the glycolic acid repeating unit.

  PGA used in the present invention is preferably PGA obtained by polymerizing 50 to 100% by mass of glycolide and 50 to 0% by mass of the other comonomer described above in order to efficiently produce a desired high molecular weight polymer. The other comonomer may be a cyclic monomer between two molecules, or may be a mixture of both instead of a cyclic monomer, but in order to obtain a PGA nonwoven fabric used in the present invention, a cyclic monomer is preferable. . Hereinafter, PGA obtained by ring-opening polymerization of 50 to 100% by mass of glycolide and 50 to 0% by mass of other cyclic monomers will be described in detail.

[Glycolide]
Glycolide that forms PGA by ring-opening polymerization is a bimolecular cyclic ester of glycolic acid, which is a kind of hydroxycarboxylic acid. Although the manufacturing method of glycolide is not specifically limited, Generally, it can obtain by thermally depolymerizing a glycolic acid oligomer. As a thermal depolymerization method for glycolic acid oligomers, for example, a melt depolymerization method, a solid phase depolymerization method, a solution depolymerization method or the like can be employed, and glycolide obtained as a cyclic condensate of chloroacetate is also used. be able to. If desired, glycolide containing glycolic acid can be used up to 20% by mass of the glycolide amount.

  The PGA used in the present invention may be formed by ring-opening polymerization of glycolide alone, but may also be formed by simultaneously ring-opening polymerization using another cyclic monomer as a copolymerization component. In the case of forming a copolymer, the proportion of glycolide is 50% by mass or more, preferably 70% by mass or more, more preferably 85% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass. % Or more, and most preferably 99% by mass or more of a substantially PGA homopolymer.

[Other cyclic monomers]
Other cyclic monomers that can be used as a copolymerization component with glycolide include lactones (for example, β-propiolactone, β-butyrolactone, in addition to bimolecular cyclic esters of other hydroxycarboxylic acids such as lactide). Cyclic monomers such as pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, trimethylene carbonate, 1,3-dioxane and the like can be used. Other preferable cyclic monomers are bimolecular cyclic esters of other hydroxycarboxylic acids. Examples of hydroxycarboxylic acids include L-lactic acid, D-lactic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α- Hydroxyvaleric acid, α-hydroxycaproic acid, α-hydroxyisocaproic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid, and these Examples include alkyl-substituted products. Another particularly preferable cyclic monomer is lactide, which is a bimolecular cyclic ester of lactic acid, and may be any of L-form, D-form, racemate, and a mixture thereof.

  The other cyclic monomer is 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less, still more preferably 5% by mass or less, particularly preferably 2% by mass or less, and most preferably 1% by mass. Used in the following proportions. By ring-opening copolymerization of glycolide and another cyclic monomer, the melting point of PGA (copolymer) can be lowered to lower the processing temperature, and the extrusion processability and stretch processability can be improved. However, if the use ratio of these cyclic monomers is too large, the sound absorption property, heat resistance, mechanical strength, etc. of the PGA (copolymer) nonwoven fabric formed from PGA (copolymer) are lowered. In addition, when PGA is formed from glycolide 100 mass%, another cyclic monomer is 0 mass%, and this PGA is also included in the scope of the present invention.

(Ring-opening polymerization reaction)
The ring-opening polymerization or ring-opening copolymerization of glycolide (hereinafter sometimes collectively referred to as “ring-opening (co) polymerization”) is preferably carried out in the presence of a small amount of a catalyst. Although the catalyst is not particularly limited, for example, a tin-based compound such as tin halide (for example, tin dichloride, tin tetrachloride, etc.) or organic carboxylate (for example, tin octoate such as tin 2-ethylhexanoate). A titanium compound such as alkoxy titanate; an aluminum compound such as alkoxyaluminum; a zirconium compound such as zirconium acetylacetone; an antimony compound such as antimony halide and antimony oxide; The usage-amount of a catalyst is a mass ratio with respect to cyclic ester, Preferably it is 1-1000 ppm, More preferably, it is about 3-300 ppm.

  Ring-opening (co) polymerization of glycolide is a molecular weight regulator for controlling higher molecular weights such as molecular weight and melt viscosity of PGA to be produced, and higher alcohols such as lauryl alcohol, other alcohols, and protic compounds such as water. Can be used as Glycolide usually contains trace amounts of water and hydroxycarboxylic acid compounds composed of glycolic acid and linear glycolic acid oligomers as impurities, and these compounds also act on the polymerization reaction. Therefore, the concentration of these impurities is quantified as a molar concentration by, for example, neutralizing titration of the amount of carboxylic acid in these compounds, and based on this quantified value, alcohols or The molecular weight and the like of the produced PGA can be adjusted by adding water and controlling the molar concentration of all protic compounds with respect to glycolide. Moreover, you may add polyhydric alcohols, such as glycerol, for a physical property improvement.

  The ring-opening (co) polymerization of glycolide may be bulk polymerization or solution polymerization, but in many cases, bulk polymerization is employed. There are various types of polymerization equipment for bulk polymerization, such as an extruder type, a vertical type with paddle blades, a vertical type with helical ribbon blades, a horizontal type such as an extruder type and a kneader type, an ampoule type, a plate type and a tubular type. The device can be selected as appropriate. Moreover, various reaction tanks can be used for solution polymerization.

  The polymerization temperature can be appropriately set according to the purpose within a range from 120 ° C. to 300 ° C. which is a substantial polymerization start temperature. The polymerization temperature is preferably 130 to 270 ° C, more preferably 140 to 260 ° C, and particularly preferably 150 to 250 ° C. If the polymerization temperature is too low, the molecular weight distribution of the produced PGA tends to be wide. If the polymerization temperature is too high, the produced PGA is susceptible to thermal decomposition. The polymerization time is in the range of 3 minutes to 50 hours, preferably 5 minutes to 30 hours. If the polymerization time is too short, the polymerization does not proceed sufficiently and a predetermined molecular weight cannot be realized. If the polymerization time is too long, the produced PGA tends to be colored.

  After making the produced PGA into a solid state, solid phase polymerization may be further carried out if desired. The solid phase polymerization means an operation of performing heat treatment while maintaining a solid state by heating at a temperature lower than the melting point (Tm) of PGA described later. By this solid phase polymerization, low molecular weight components such as unreacted monomers and oligomers are volatilized and removed. The solid phase polymerization is preferably performed for 1 to 100 hours, more preferably 2 to 50 hours, and particularly preferably 3 to 30 hours.

[Weight average molecular weight (Mw)]
In the present invention, the aliphatic polyester such as PGA that forms the aliphatic polyester nonwoven fabric preferably has a weight average molecular weight (Mw) in the range of 10,000 to 800,000, and more preferably in the case of PGA. Those in the range of 20,000 to 600,000, more preferably 30,000 to 400,000, particularly preferably 50,000 to 300,000 are selected. In the case of PLA, the range is more preferably 20,000 to 700,000, still more preferably 40,000 to 600,000, still more preferably 60,000 to 500,000. If the weight average molecular weight (Mw) is too small, the sound absorbing property and strength of the nonwoven fabric and the sound absorbing material provided with the nonwoven fabric may be insufficient. If the weight average molecular weight (Mw) is too large, it is difficult to perform biodegradation in a short time, and the environmental load may not be sufficiently reduced. The weight average molecular weight (Mw) of the aliphatic polyester is determined using a gel permeation chromatography (GPC) analyzer. As a specific example, a PGA sample is dissolved in hexafluoroisopropanol (HFIP) in which sodium trifluoroacetate is dissolved at a predetermined concentration, and then filtered through a membrane filter to obtain a sample solution. The weight average molecular weight (Mw) is calculated from the result of injecting into the GPC analyzer and measuring the molecular weight.

[Molecular weight distribution (Mw / Mn)]
The molecular weight distribution (Mw / Mn) represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of an aliphatic polyester such as PGA or PLA that forms the aliphatic polyester nonwoven fabric in the present invention. Mn) is in the range of 1.5 to 4 by reducing the amount of polymer components in the low molecular weight region, which are susceptible to degradation at an early stage, and polymer components in the high molecular weight region where the degradation rate is slow. This is preferable because the decomposition rate of the material can be controlled. If the molecular weight distribution (Mw / Mn) is too large, the moldability may be deteriorated. If the molecular weight distribution (Mw / Mn) is too small, it may be difficult to maintain the sound absorption and strength of the nonwoven fabric and the sound absorbing material provided with the nonwoven fabric for a required period of time. The molecular weight distribution (Mw / Mn) is preferably 1.6 to 3.7, more preferably 1.65 to 3.6, still more preferably 1.67 to 3.5, and particularly preferably 1.7 to 3. 4. The molecular weight distribution (Mw / Mn) can be determined using a GPC analyzer in the same manner as the weight average molecular weight (Mw).

[Melting point (Tm)]
The melting point of the aliphatic polyester such as PGA or PLA used in the present invention is usually 145 to 245 ° C., and it is preferable to adjust the melting point according to the type of aliphatic polyester, particularly the type and content ratio of the copolymer component. When the aliphatic polyester is PGA, it is more preferably 160 to 245 ° C, further preferably 200 to 240 ° C, particularly preferably 205 to 235 ° C, and particularly preferably 210 to 230 ° C. The melting point of the homopolymer of PGA is usually about 220 ° C. The melting point of PLA is more preferably 145 to 185 ° C, further preferably 150 to 182 ° C, particularly preferably 155 to 180 ° C. If the melting point is too low, the strength in the production of aliphatic polyester fibers such as PGA fibers, the production of non-woven fabrics and other processing may be insufficient, or the temperature management in the production process or the like may be difficult. If the melting point is too high, it may be difficult to produce aliphatic polyester fibers or nonwoven fabrics, or the sound absorbing material provided with the nonwoven fabric and the laminate layer of the nonwoven fabric may be insufficient. The melting point (Tm) of the aliphatic polyester is determined in a nitrogen atmosphere using a differential scanning calorimeter (DSC). Specifically, crystal melting is detected in a temperature rising process in which a sample of an aliphatic polyester is heated from room temperature to a temperature near melting point (Tm) + 60 ° C. at a temperature rising rate of 20 ° C./min in a nitrogen atmosphere. It means the temperature of the endothermic peak associated with. When a plurality of absorption peaks are observed, the peak having the largest endothermic peak area is defined as the melting point (Tm).

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) of PGA, PLA, etc. used in the present invention is usually 25 to 75 ° C., and in the case of PGA, it is preferably 30 to 55 ° C., more preferably 35 to 50 ° C. In the case of PLA, it is preferably 45 to 75 ° C, more preferably 50 to 70 ° C, still more preferably 55 to 65 ° C. The glass transition temperature (Tg) can be adjusted by the weight average molecular weight (Mw), the molecular weight distribution, the type and content ratio of the copolymer component. The glass transition temperature (Tg) is determined in a nitrogen atmosphere using a differential scanning calorimeter (DSC), similarly to the measurement of the melting point (Tm). Specifically, a glass state detected in a temperature rising process in which a sample of an aliphatic polyester is heated in a nitrogen atmosphere at a temperature rising rate of 20 ° C./min from room temperature to a temperature near melting point (Tm) + 60 ° C. The glass transition point (Tg) is the temperature at which the secondary transition of heat in the secondary transition region corresponding to the transition region from the rubber state to the rubber state begins. When the glass transition temperature (Tg) is too low, the surface of the formed aliphatic polyester nonwoven fabric may be excessively softened.

[Melt viscosity]
In the present invention, the melt viscosity (measured at a melting point + 50 ° C. temperature and a shear rate of 122 sec ⁻¹ ) of an aliphatic polyester such as PGA or PLA is usually in the range of 30 to 5,000 Pa · s, preferably 50 to 3 1,000 Pa · s, more preferably in the range of 100 to 2,000 Pa · s. If the melt viscosity of the aliphatic polyester is too large, it may be difficult to obtain an aliphatic polyester fiber, a nonwoven fabric or a laminate thereof. If the melt viscosity of the aliphatic polyester is too small, the strength, heat resistance, etc. of the aliphatic polyester fiber, nonwoven fabric or laminate thereof may be insufficient.

Accordingly, the aliphatic polyester such as PGA and PLA forming the aliphatic polyester nonwoven fabric provided in the sound absorbing material of the present invention is preferably (a) having a weight average molecular weight (Mw) of 10,000 to 800,000, (b). It is an aliphatic polyester having a molecular weight distribution (Mw / Mn) of 1.5 to 4 and (c) a melt viscosity (measured at a melting point + 50 ° C. temperature and a shear rate of 122 sec ⁻¹ ) of 100 to 2,000 Pa · s. .

  In the present invention, the aliphatic polyester forming the aliphatic polyester nonwoven fabric may further contain other resins and additives as long as the characteristics thereof are not significantly impaired. Examples of the other resins include aromatic polyesters such as polyethylene terephthalate / butylene terephthalate copolymer and polybutylene terephthalate; polyglycols such as polyethylene glycol and polypropylene glycol; modified polyvinyl alcohol; polyurethane; polyamide such as poly L-lysine. And the like. The compounding quantity of other resin is 60 mass parts or less normally with respect to 100 mass parts of aliphatic polyester, Preferably it is 40 mass parts or less, More preferably, it is 30 mass parts or less. Additives include pigments, heat stabilizers, antioxidants, end-capping agents, weathering agents, flame retardants, plasticizers, lubricants, mold release agents, antistatic agents, UV absorbers, colorants, crystallization There are usually added additives such as accelerators, hydrogen ion concentration regulators, fillers and the like. The compounding amount of these additives is usually 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and 5 parts by mass or less or 1 part by mass or less with respect to 100 parts by mass of the aliphatic polyester. In some cases, it may be sufficient.

  In particular, it is preferable to add a carboxyl group terminal blocking agent as the terminal blocking agent because the strength, heat resistance and long-term storage stability of the formed aliphatic polyester nonwoven fabric are improved. That is, by adding a carboxyl group terminal blocking agent, the water resistance of the formed aliphatic polyester nonwoven fabric is improved, and the molecular weight reduction during storage can be further suppressed. As a carboxyl group terminal blocker, a compound having a carboxyl group terminal blocker and known as a water resistance improver for aliphatic polyesters can be used. Examples of the carboxyl group end capping agent include carbodiimide compounds such as N, N-2,6-diisopropylphenylcarbodiimide; 2,2′-m-phenylenebis (2-oxazoline), 2,2′-p-phenylene Oxazoline compounds such as bis (2-oxazoline), 2-phenyl-2-oxazoline and styrene / isopropenyl-2-oxazoline; oxazine compounds such as 2-methoxy-5,6-dihydro-4H-1,3-oxazine; And epoxy compounds such as N-glycidylphthalimide, cyclohexene oxide, and tris (2,3-epoxypropyl) isocyanurate; Among these carboxyl group end-capping agents, carbodiimide compounds are preferred, and aromatic, alicyclic, and aliphatic carbodiimide compounds are also used, but aromatic carbodiimide compounds are particularly preferred, and those with particularly high purity are used. Gives water resistance improvement effect. A carboxyl group terminal blocker is 0.01-5 mass parts normally with respect to 100 mass parts of aliphatic polyester, Preferably it is 0.05-3 mass parts, More preferably, it is a ratio of 0.1-1 mass part. Used.

  In addition, it is more preferable to add a heat stabilizer to the aliphatic polyester, since the long-term storage stability of the sound-absorbing material provided with the formed aliphatic polyester nonwoven fabric and the laminate of the nonwoven fabric is further improved. As thermal stabilizers, cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) ) Phosphate, phosphate ester having a pentaerythritol skeleton structure such as cyclic neopentanetetraylbis (octadecyl) phosphite; mono- or di-stearyl acid phosphate, or a mixture thereof, preferably having 8 to 8 carbon atoms Phosphoric acid alkyl ester or phosphorous acid alkyl ester having 24 alkyl groups; Metal carbonates such as calcium carbonate and strontium carbonate; Bis [2- (2-hydroxybenzoyl) hydrazine] generally known as a polymerization catalyst deactivator Dodecanoic acid, N, N ' Hydrazine compounds having a -CONHNH-CO- unit such as bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine; 3- (N-salicyloyl) amino-1,2, And triazole compounds such as 4-triazole; triazine compounds; and the like. The heat stabilizer is usually 3 parts by mass or less, preferably 0.001 to 1 part by mass, more preferably 0.005 to 0.5 parts by mass, particularly 100 parts by mass of aliphatic polyester such as PGA and PLA. Preferably, it is used at a ratio of 0.01 to 0.1 parts by mass (100 to 1,000 ppm).

2. Nonwoven Fabric Formed from Aliphatic Polyester The sound absorbing material of the present invention comprises a layer of a nonwoven fabric laminate formed from an aliphatic polyester. The aliphatic polyester nonwoven fabric is a nonwoven fabric formed mainly from aliphatic polyester fibers such as PGA and PLA, and is a nonwoven fabric containing 50% by mass or more of aliphatic polyester fibers. The nonwoven fabric preferably contains 70% by mass or more of aliphatic polyester fiber, more preferably 80% by mass or more, and still more preferably 90% by mass or more, and may be a nonwoven fabric formed only from aliphatic polyester fiber. The aliphatic polyester nonwoven fabric in the present invention may contain fibers other than aliphatic polyester fibers and the like in an amount of 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less. In addition, fibers other than aliphatic polyester fibers may not be contained. Examples of fibers other than aliphatic polyester fibers include well-known fibers such as polyethylene terephthalate (PET) fibers, polyamide fibers, and acrylic fibers, low-temperature fusible fibers, and the like. A cloth formed in advance may be used. If the content of the aliphatic polyester fiber is too small, the sound absorption and strength in a low frequency region may be insufficient, or the biodegradability and water resistance may be reduced, resulting in an increase in environmental load. Therefore, the aliphatic polyester nonwoven fabric in the present invention is preferably a PGA nonwoven fabric, a PLA nonwoven fabric, or a mixed nonwoven fabric of PGA and PLA.

  Examples of the aliphatic polyester nonwoven fabric in the present invention include a melt blown nonwoven fabric, a spunbond nonwoven fabric, a needle punched nonwoven fabric, a three-dimensional entangled nonwoven fabric by water flow or air flow, and may also be a nonwoven fabric manufactured by a papermaking method. A melt blown nonwoven fabric or a spunbonded nonwoven fabric is preferred, and a melt blown nonwoven fabric is particularly preferred because the desired fiber diameter and porosity can be easily obtained.

The aliphatic polyester nonwoven fabric in the present invention is preferably an aliphatic polyester nonwoven fabric having a basis weight of 1 to 500 g / m ² and a fiber diameter of 300 nm to 100 μm.

1) basis weight aliphatic polyester nonwoven fabric in the present invention, basis weight, but is preferably in the range of from 1 to 500 g / ^{m 2,} more preferably 2~400g / ^{m 2,} more preferably 3~300g / ^{m 2,} particularly preferably Is in the range of 4 to 200 g / m ² . The basis weight of the nonwoven fabric is measured according to JIS L1096. If the basis weight of the nonwoven fabric is less than 1 g / m ² , the strength may be insufficient. If the basis weight of the nonwoven fabric is larger than 500 g / m ² , it is not possible to obtain a thin sound-absorbing material, and it is too heavy to handle poorly, or it takes a long time to decompose the sound-absorbing material after use. It may be necessary.

2) Fiber diameter The aliphatic polyester nonwoven fabric in the present invention preferably has a fiber diameter in the range of 300 nm to 100 μm, more preferably 500 nm to 70 μm, still more preferably 800 nm to 50 μm, and particularly preferably 1 to 30 μm. is there. If the fiber diameter of the nonwoven fabric is less than 300 nm, the nonwoven fabric may be too dense, and sound absorption in a low frequency region may be insufficient. If the fiber diameter is more than 100 μm, the nonwoven fabric becomes excessively rough, and the sound absorbing property for the low frequency region may be insufficient. The fiber diameter is measured by sampling 10 fibers so that they do not overlap in the width direction and longitudinal direction of the nonwoven fabric, measuring 10 fiber diameters from an electron micrograph magnified 1,000 times, and totaling 100 points. Is the average fiber diameter and the fiber diameter of the nonwoven fabric.

3) Thickness The thickness of the aliphatic polyester nonwoven fabric in the present invention is not particularly limited, but is preferably 50 to 1,000 μm, more preferably 65 to 700 μm, and still more preferably 75 to 500 μm. If the thickness of the nonwoven fabric is too small, the sound absorbing property and strength of the sound-absorbing material provided with the laminate layer of the nonwoven fabric may be insufficient. If the thickness of the non-woven fabric is too large, it will not be possible to obtain a thin sound absorbing material, it will be too heavy and handleability will be insufficient, or it will take a long time to decompose the sound absorbing material after use, etc. There is. The thickness of the nonwoven fabric is measured at a load of 0.7 kPa according to JIS L1096.

4) Manufacturing method of aliphatic polyester nonwoven fabric The manufacturing method of the aliphatic polyester nonwoven fabric according to the present invention is not particularly limited. As described above, the melt-blowing method, the spunbonding method, the needle punching method, the water flow or the airflow 3 Known non-woven fabric manufacturing methods such as dimensional entanglement and paper making can be used. Moreover, when the aliphatic polyester nonwoven fabric in the present invention contains fibers other than aliphatic polyester fibers, composite fibers such as a core-sheath structure are used, or spun aliphatic polyester fibers and aliphatic polyester fibers. A nonwoven fabric can be produced by a method known per se using fibers other than those.

  The melt-blowing method or the spunbond method is preferred because the desired fiber diameter and fiber density can be easily obtained.In particular, from the viewpoint of producing a nonwoven fabric that is lightweight and has a high sound-absorbing property, the melt-blowing method is used. More preferred. In addition, it is preferable to manufacture in consideration of the moisture content not increasing by a method such as nitrogen gas purging.

  Furthermore, it is good also as a heat-processed nonwoven fabric by heat-processing for the predetermined time at required temperature using the heat processing machine with respect to the manufactured nonwoven fabric containing the aliphatic polyester fiber. The heat treatment temperature and treatment time are not necessarily constant depending on the melting point and content of the fibers contained in the nonwoven fabric, but in order not to decrease the porosity of the nonwoven fabric, it is preferable to be less than the melting point, Heat treatment is preferably performed at a temperature of 70 to 200 ° C. for 1 second to 60 minutes, more preferably at a temperature of 80 to 180 ° C. for 3 seconds to 40 minutes, and still more preferably at a temperature of 90 to 150 ° C. for 5 seconds to 30. What is necessary is just to heat-process for minutes.

3. Nonwoven Fabric Laminate Formed from Aliphatic Polyester The sound-absorbing material of the present invention comprises a laminate of an aliphatic polyester nonwoven fabric. The layer of the laminate provided in the sound absorbing material of the present invention is a layer of a laminate in which two or more of the above aliphatic polyester nonwoven fabrics are integrally laminated. There is no upper limit on the number of laminated layers as long as it has a sound absorbing property and strength in a low frequency range and a thin thickness can be obtained, and the optimum thickness depends on the thickness of the aliphatic polyester nonwoven fabric and the desired thickness of the sound absorbing material. The number of stacked layers may be determined. The number is usually 10 or more, and may be 20 or more, 40 or more, 80 or more, 120 or more, 180 or more, or 250 or more. As a method of obtaining the layer of the laminated body of the aliphatic polyester nonwoven fabric, the laminated body is obtained by laminating by bonding or joining the entire surface of the nonwoven fabric by an adhesion method using an adhesive, a conventional joining method such as a heat welding method, or the like. Alternatively, the laminated body may be obtained by laminating the non-woven fabrics partially by bonding or joining them by discretely applying an adhesive or performing discrete heating. From the viewpoint of making the sound absorption performance in a low frequency range higher, it is preferable to form a laminate by partially bonding or bonding the nonwoven fabric and laminating. Depending on the mode of use, there may be a case where bonding such as adhesion is not required only by overlaying the aliphatic polyester nonwoven fabrics.

  Moreover, the layer of the laminated body of the aliphatic polyester nonwoven fabric in the sound-absorbing material of the present invention further comprises a plurality of laminated layers of the above-mentioned aliphatic polyester nonwoven fabric (the number of laminated layers may be the same or different). -It is good also as a laminated body of an aliphatic polyester nonwoven fabric by joining. Lamination and bonding of a pre-formed aliphatic polyester non-woven fabric laminate is performed by adhering or joining the entire surface of the non-woven fabric laminate using an adhesive bonding method or a conventional bonding method such as a heat welding method. It is good also as a layer of a body, and it is good also as a layer of a laminated body by adhere | attaching or joining the laminated body of a nonwoven fabric partially.

4). A sound-absorbing material having a layer of a nonwoven fabric laminate formed from aliphatic polyester and having a sound absorption peak of 1,100 Hz or less The sound-absorbing material of the present invention has a layer of a laminate of aliphatic polyester nonwoven fabric, and has a sound absorption peak. The sound absorbing material has a frequency of 1,100 Hz or lower. The sound-absorbing material of the present invention may be a sound-absorbing material comprising only the layer of the above-mentioned aliphatic polyester nonwoven fabric, that is, a sound-absorbing material having no other layers other than the layer of the above-mentioned aliphatic polyester nonwoven fabric. The sound absorbing material may be provided with a layer of the laminated body of the aliphatic polyester nonwoven fabric and another layer.

  When the sound-absorbing material of the present invention is a sound-absorbing material that does not have other layers other than the layer of the aliphatic polyester nonwoven fabric laminate, one or more of the aliphatic polyester nonwoven fabric laminates, It is fixed with a predetermined attachment or the like to make a sound absorbing material. When the sound-absorbing material of the present invention is a sound-absorbing material comprising a layer of a laminate of a plurality of aliphatic polyester nonwoven fabrics, the laminate of the plurality of aliphatic polyester nonwoven fabrics is simply stacked and placed, According to the conventional method, it may be fixed by a predetermined attachment or the like, and may be used as a sound absorbing material. It is also possible to use a sound absorbing material.

  When the sound-absorbing material of the present invention is a sound-absorbing material comprising a layer of an aliphatic polyester nonwoven fabric laminate and another layer, it may be a pre-formed laminate of aliphatic polyester nonwoven fabric (one or a plurality, In the case of a sheet, it may be simply placed on top of each other, or the entire surface or a part thereof may be bonded.) And a member forming a layer other than the laminate of the aliphatic polyester nonwoven fabric are integrated. In this state, the sound absorbing material is obtained by fixing it with a predetermined attachment or the like according to a conventional method. The laminated body of the aliphatic polyester non-woven fabric and the member forming the other layer may be simply stacked and placed, or the entire surface or a part thereof may be bonded.

  The member forming the other layer is not particularly limited as long as a sound absorbing material having a sound absorption peak of 1,100 Hz or less can be provided, and a layered member usually used for the sound absorbing material may be used. it can. For example, resin films, metal foils, fabrics, and the like can be used, and fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics are preferable from the viewpoint of sound absorption and handling of sound absorbing materials, and ease of disposal and reduction of environmental load In view of the above, aliphatic polyester woven or knitted fabric is more preferable. The thickness (weight per unit area) of members forming other layers such as aliphatic polyester woven fabric or knitted fabric can be appropriately selected in consideration of the sound absorbing property and thickness of the entire sound absorbing material.

  The sound-absorbing material of the present invention is thin and has excellent sound-absorbing characteristics in a low frequency range, preferably 5 cm or less, more preferably 4 cm or less, still more preferably 3 cm or less, most preferably 2.5 cm. It is desirable that The sound-absorbing material of the present invention is not particularly limited as long as the strength of the sound-absorbing material is maintained, but from the viewpoint of handleability, the thickness is usually 0.5 mm or more, and in many cases 1 mm or more.

  The sound absorbing material of the present invention is a sound absorbing material having a sound absorption peak of 1,100 Hz or less. In accordance with JIS A1405, the sound absorption peak of the sound-absorbing material is 50 to 1, using a sound absorption coefficient measurement system Type 4206 by Brüel & Kjær Corporation using a two-microphone method (the acoustic tube used is a large tube having an inner diameter of 100 mm). The sound absorption coefficient (A) at 600 Hz is determined based on the sound absorption coefficient (A) of the sound absorbing material.

  The sound-absorbing material of the present invention has excellent sound-absorbing properties in a low frequency range of 1,000 Hz or less when the sound-absorbing peak is 1,100 Hz or less. The sound absorption peak of the sound absorbing material is preferably 1,000 Hz or less, more preferably 900 Hz or less, and still more preferably 700 Hz or less. Moreover, it is especially preferable that the sound absorbing material of the present invention has a sound absorption rate at 500 Hz of 0.3 or more.

The sound absorbing material of the present invention has a sound absorption coefficient (A) of the following formula (formula) A ≧ 10 ⁻¹³ × f ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × at a frequency (f) of 200 Hz to 700 Hz. By satisfying 10 ⁻⁷ × f ² + 0.0002 × f−0.0059, it is possible to provide a sound-absorbing material that is extremely excellent in sound-absorbing properties in a low frequency range as compared with conventionally used glass wool. be able to.

  The sound-absorbing material of the present invention is covered with a bag or film formed from a moisture-proof material in order to prevent unintended biodegradation or hydrolysis from occurring while it is installed in a place that requires sound absorption. And it can also be set as the sound-absorbing material covered with the packaging material. In this case, the laminated body of aliphatic polyester nonwoven fabrics can be used as a sound absorbing material in a state where the nonwoven fabrics are simply overlapped and covered with a packaging material without adhering the nonwoven fabrics.

EXAMPLES The present invention will be further described below with reference to examples and reference examples, but the present invention is not limited to the examples.
The measuring method of the physical property or characteristic of the sound-absorbing material, the nonwoven fabric formed from the aliphatic polyester, and the aliphatic polyester in Examples and Reference Examples is as follows.

(1) Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn):
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the aliphatic polyester were measured using a gel permeation chromatography (GPC) analyzer under the following conditions. A sample of aliphatic polyester 10 mg is dissolved in hexafluoroisopropanol (HFIP) in which sodium trifluoroacetate is dissolved at a concentration of 5 mM to make 10 ml, and then filtered through a membrane filter to obtain a sample solution. Was injected into a GPC analyzer and the molecular weight was measured under the following measurement conditions.

<GPC measurement conditions>
Apparatus: Showa Denko GPC104
Column: Showa Denko HFIP-806M 2 (in series connection) + Precolumn: HFIP-LG 1 Column temperature: 40 ° C
Eluent: HFIP solution in which sodium trifluoroacetate is dissolved at a concentration of 5 mM Detector: Differential refractometer Molecular weight calibration: Prepared using 5 types of polymethyl methacrylate (manufactured by Polymer laboratories Ltd.) with different molecular weights Using the calibration curve data of the measured molecular weight

(2) Melting point (Tm) and glass transition temperature (Tg)
Using a differential scanning calorimeter (DSC; DSC-60, manufactured by Shimadzu Corporation), 10 mg of a sample was heated from room temperature to a melting point (Tm) + 60 ° C. in a nitrogen atmosphere at a rate of temperature increase of 20 ° C./min. The secondary transition region corresponding to the transition region from the glass state to the rubber state detected from the endothermic peak detected during the temperature rising process and the melting point (Tm) detected during the temperature rising process. The glass transition temperature (Tg) was detected from the onset temperature of the second order transition of calorie. When a plurality of melting points (Tm) were observed, the temperature of the peak having the largest endothermic peak area was defined as the melting point (Tm).

(3) Melt Viscosity The melt viscosity of the aliphatic polyester was measured using “Capillograph 1-C” manufactured by Toyo Seiki Seisakusho Co., Ltd. equipped with a capillary (1 mmφ × 10 mL). About 20 g of a sample was introduced into a device heated to a temperature of melting point (Tm) + 50 ° C., held for 5 minutes, and then the melt viscosity at a shear rate of 122 sec ⁻¹ was measured.

(4) Fabric weight of nonwoven fabric The fabric weight of the nonwoven fabric was measured according to JIS L1096.

(5) Fiber diameter of non-woven fabric The fiber diameter of the non-woven fabric is 10 points from the electron micrograph obtained by sampling 10 fibers and enlarging 1,000 times so that they do not overlap in the width and longitudinal directions of the non-woven fabric. The average value of 100 points in total was taken as the average fiber diameter, and the fiber diameter of the nonwoven fabric.

(6) Thickness of the nonwoven fabric The thickness of the nonwoven fabric was measured at a load of 0.7 kPa according to JIS L1096.

(7) Sound absorption rate The sound absorption rate of the sound absorbing material is measured according to JIS A1405 using a sound absorption rate measurement system Type 4206 by Bruel Care Co. using a two-microphone method (the acoustic tube used is a large tube with an inner diameter of 100 mm). Then, it was performed by measuring the sound absorption coefficient at 50 to 1,600 Hz or 50 to 1,000 Hz.

(8) Biodegradability The sound-absorbing material is biodegradable by burying the sound-absorbing material having a diameter of 10 cm in soil kept at 40 ° C., excavating it one month later, and visually observing the state of the sound-absorbing material. did.

[Reference example]
(Measurement of sound absorption coefficient of glass wool sound absorbing material)
The sound absorption coefficient at 50 to 1,600 Hz of a glass wool sound absorbing material (MAG Co., Ltd. MAGB * 3225) having a thickness of 25 mm was measured, and an approximate curve was obtained by a curve fitting method. ) Is the following formula (formula) A = 10 ⁻¹³ × f ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² + 0.0002 × f−0.0059
It was found that

[Example 1]
(Manufacture of non-woven fabric)
Pellet PGA (manufactured by Kureha Co., Ltd., Mw: 210,000, Mw / Mn: 2.3, melt viscosity (measured at a temperature of 270 ° C. and a shear rate of 122 sec ⁻¹ ): 610 Pa · s, melting point: 220 ° C., glass transition (Temperature: 43 ° C.) was melted with an extruder, discharged from a die having a spinneret, and stretched fibers were collected on a belt conveyor to prepare a melt blown nonwoven fabric. At that time, the amount of lamination was controlled by adjusting the discharge amount and the speed of the belt conveyor to prepare a PGA nonwoven fabric having a basis weight of 15 g / m ² and a thickness of 92 μm. The fiber diameter of the nonwoven fabric was 4.4 μm.

(Manufacture of nonwoven fabric laminates)
After pasting 50 sheets of the prepared PGA nonwoven fabric cut out to A4 size, tape glue (dot liner long made by KOKUYO S & T Co., Ltd.) on each nonwoven fabric, and 2cm long at 5cm intervals, Were laminated together to obtain a laminate of non-woven fabric, and then punched out into a circle having a diameter of 10 cm. The total thickness of a laminate of non-woven fabrics formed by partially adhering 50 nonwoven fabrics and punched into a circle (hereinafter referred to as “partially bonded nonwoven fabric laminate”) was 6 mm.

(Manufacture of sound absorbing material)
The sound absorbing material which consists only of the laminated body (total number of nonwoven fabrics 200 sheets, total thickness of 24 mm) of the nonwoven fabric formed from the aliphatic polyester was obtained by stacking four partially bonded nonwoven fabric laminates.

(Measurement of sound absorption rate)
The result of measuring the sound absorption coefficient at 50 to 1,600 Hz of the obtained sound absorbing material is a graph showing the sound absorption coefficient for the reference example, that is, the sound absorption coefficient (A) at the frequency (f) is expressed by the following formula (formula). A = 10 ⁻¹³ × f ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² + 0.0002 × f−0.0059
FIG. 1 shows a graph that satisfies the following (hereinafter referred to as “reference example graph”).

(Biodegradable)
The obtained sound absorbing material was embedded in soil kept at a temperature of 40 ° C., excavated one month later, and the state of the sound absorbing material was visually observed. As a result, the sound absorbing material was partially separated. The shape was not retained, and when the end of the sound absorbing material was grabbed with tweezers, it was broken and could not be removed.

[Example 2]
Three partially bonded nonwoven fabric laminates in Example 1 were stacked to obtain a sound-absorbing material composed of a laminate of nonwoven fabrics formed from aliphatic polyester (total number of nonwoven fabrics 150 sheets, total thickness 18 mm). The result of having measured the sound absorption rate in 50-1600Hz of the obtained sound-absorbing material is shown in FIG. 1 with a reference example graph. The results of the biodegradability test were the same as in Example 1.

[Example 3]
Two partially bonded nonwoven fabric laminates in Example 1 were stacked to obtain a sound-absorbing material composed of a laminate of nonwoven fabrics formed from aliphatic polyester (total number of nonwoven fabrics 100, total thickness 12 mm). The result of having measured the sound absorption rate in 50-1600Hz of the obtained sound-absorbing material is shown in FIG. 1 with a reference example graph. The results of the biodegradability test were the same as in Example 1.

From the results shown in FIG. 1, the sound absorbing materials of Examples 1 to 3 having the nonwoven fabric laminate formed from aliphatic polyester have sound absorption peaks of 400 Hz, 500 Hz, and 800 Hz, respectively, and low frequencies of 1,000 Hz or less. From the reference example graph, the entire region was found to have a high sound absorption coefficient. In particular, the sound absorbing material of Example 1 having a total thickness of 24 mm has a sound absorption coefficient (A) of the following formula (formula) A ≧ 10 ⁻¹³ over the entire region of the frequency (f) of 200 Hz to 700 Hz. Xf ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² + 0.0002 × f−0.0059, a sound-absorbing material that has a high sound-absorbing property in an extremely low frequency range of 500 Hz or less. I found out. Moreover, since the sound-absorbing material of Examples 1 to 3 is provided with biodegradability, it was found that treatment after disposal is easy and contributes to reduction of environmental load.

[Example 4]
(Manufacture of nonwoven fabric laminates)
Spray paste (spray paste 77 manufactured by Sumitomo 3M Co., Ltd.) was applied to the entire surface of each nonwoven fabric 50 sheets of non-woven fabric cut to a size of A4 size from a PGA nonwoven fabric having a basis weight of 15 g / m ² and a thickness of 92 μm prepared in Example 1. After spray coating and pasting together to obtain a nonwoven fabric laminate, it was punched out into a circle having a diameter of 10 cm. The total thickness of a laminate of non-woven fabrics formed by bonding the entire surface of 50 non-woven fabrics and punched into a circle (hereinafter referred to as “full-surface adhesive nonwoven fabric laminate”) was 6 mm.

(Manufacture of sound absorbing material)
Four sheets of the above-mentioned whole surface bonded nonwoven fabric laminate were stacked to obtain a sound-absorbing material composed of a laminate of nonwoven fabrics formed from aliphatic polyester (total number of nonwoven fabrics 200, total thickness 24 mm).

(Measurement of sound absorption rate)
The result of having measured the sound absorption rate in 50-1600 Hz of the obtained sound-absorbing material is shown in FIG. 2 with the said reference example graph.

(Biodegradable)
The obtained sound absorbing material was embedded in soil kept at a temperature of 40 ° C., excavated one month later, and the state of the sound absorbing material was visually observed. As a result, the sound absorbing material was partially separated. The shape was not retained, and when the end of the sound absorbing material was grabbed with tweezers, it was broken and could not be removed.

[Example 5]
Three sound-adhesive nonwoven fabric laminates in Example 4 were stacked to obtain a sound-absorbing material composed of a laminate of nonwoven fabrics formed from aliphatic polyester (total number of nonwoven fabrics 150 sheets, total thickness 18 mm). The result of having measured the sound absorption rate in 50-1600 Hz of the obtained sound-absorbing material is shown in FIG. 2 with the said reference example graph. The results of the biodegradability test were the same as in Example 4.

[Example 6]
Two sound-absorbing nonwoven fabric laminates in Example 4 were stacked to obtain a sound-absorbing material composed of a laminate of nonwoven fabrics (total number of nonwoven fabrics 100, total thickness 12 mm) formed from aliphatic polyester. The result of having measured the sound absorption rate in 50-1600Hz of the obtained sound-absorbing material is shown in FIG. 2 with a reference example graph. The results of the biodegradability test were the same as in Example 4.

From the results shown in FIG. 2, the sound absorbing materials of Examples 4 to 6 having the nonwoven fabric laminated layer formed from aliphatic polyester have sound absorption peaks of 600 Hz, 630 Hz, and 1,000 Hz, respectively, and 1,000 Hz or less. From the reference example graph, it was found that the sound absorption coefficient was high over the entire low frequency range. In particular, the sound absorbing material of Example 4 having a total thickness of 24 mm has a sound absorption coefficient (A) of the following formula (formula) A ≧ 10 ⁻¹³ over the entire frequency (f) region of 200 Hz to 700 Hz. Xf ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² + 0.0002 × f−0.0059, a sound-absorbing material that has a high sound-absorbing property in an extremely low frequency range of 500 Hz or less. I found out. Moreover, since the sound-absorbing materials of Examples 4 to 6 are provided with biodegradability, it has been found that treatment after disposal is easy and contributes to reduction of environmental load.

[Example 7]
(Manufacture of non-woven fabric)
Instead of pellet PGA, pellet PLA (4032D manufactured by NatureWorks, Mw: 180,000, Mw / Mn: 2.3, melt viscosity (measured at a temperature of 225 ° C. and a shear rate of 122 sec ⁻¹ ): 505 Pa · s (the melt viscosity was adjusted by humidity conditioning), melting point: 175 ° C., glass transition temperature: 58 ° C.), and a basis weight of 15 g / m ² and a thickness of 82 μm in the same manner as in Example 1. A PLA nonwoven fabric was prepared. The fiber diameter of the nonwoven fabric was 4.5 μm.

(Manufacture of nonwoven fabric laminates)
A laminate of PLA nonwoven fabrics prepared by spray-coating 50 sheets of the above prepared PLA nonwoven fabric cut out in A4 size and spraying paste (spray glue 77 manufactured by Sumitomo 3M Co., Ltd.) over the entire surface of each nonwoven fabric. After being obtained, it was punched into a circle having a diameter of 10 cm. The total thickness of the laminate of PLA nonwoven fabrics formed by adhering the entire surface of 50 PLA nonwoven fabrics and punched into a circle (hereinafter referred to as “full-surface-adhesive PLA nonwoven fabric laminate”) was 5.5 mm.

(Manufacture of sound absorbing material)
Four sound-absorbing materials comprising a laminate of PLA nonwoven fabric (total number of nonwoven fabrics, total thickness of 22 mm) formed of aliphatic polyester were obtained by stacking four sheets of the above-mentioned whole surface bonded PLA nonwoven fabric laminate.

(Measurement of sound absorption rate)
The result of having measured the sound absorption rate in 50-1,000 Hz of the obtained sound-absorbing material is shown in FIG. 3 with the said reference example graph.

[Example 8]
Three sound-absorbing material laminates (total number of nonwoven fabrics 150, total thickness 16.5 mm) of nonwoven fabrics formed from aliphatic polyesters were obtained by stacking three sheets of PLA whole-bonded nonwoven fabric laminates in Example 7. The result of having measured the sound absorption rate in 50-1,000 Hz of the obtained sound-absorbing material is shown in FIG. 3 with a reference example graph. The results of the biodegradability test were the same as in Example 7.

[Example 9]
Two sheets of the PLA whole-bond nonwoven fabric laminate in Example 7 were stacked to obtain a sound absorbing material composed of a laminate of nonwoven fabrics (total number of nonwoven fabrics 100, total thickness 11 mm) formed from aliphatic polyester. The result of having measured the sound absorption rate in 50-1,000 Hz of the obtained sound-absorbing material is shown in FIG. 3 with a reference example graph. The results of the biodegradability test were the same as in Example 7.

  From the results shown in FIG. 3, the sound absorbing materials of Examples 7 to 9 including the nonwoven fabric laminate formed from the aliphatic polyester PLA have sound absorption peaks at 500 Hz, 630 Hz, and 630 Hz, respectively, and 1,000 Hz. It turned out that it has a high sound absorption coefficient over the following low frequency area | regions. In particular, it was found that the sound-absorbing material has a high sound-absorbing property over the entire extremely low frequency range of 50 Hz to 200 Hz. Moreover, since the sound-absorbing material of Examples 7-9 is provided with biodegradability, it turned out that the process after disposal is easy and contributes to reduction of an environmental load.

  The present invention is a sound-absorbing material having a non-woven laminate layer formed from aliphatic polyester and having a sound-absorbing peak of 1,100 Hz or less, thus having a thin thickness and excellent sound-absorbing characteristics in a low frequency range. Furthermore, since a sound absorbing material capable of reducing the environmental load is provided, the industrial applicability is high.

Claims (11)

  A sound absorbing material having a layer of a nonwoven fabric laminate formed from aliphatic polyester and having a sound absorption peak of 1,100 Hz or less.   The sound absorbing material according to claim 1, wherein the aliphatic polyester is polyglycolic acid or polylactic acid.   The sound absorbing material according to claim 1 or 2, wherein the nonwoven fabric formed from the aliphatic polyester is a melt blown nonwoven fabric. The sound-absorbing material according to any one of claims 1 to 3, wherein the nonwoven fabric formed from the aliphatic polyester has a basis weight of 1 to 500 g / m ² and a fiber diameter of 300 nm to 100 µm. The aliphatic polyester is represented by (a) a weight average molecular weight (Mw) of 10,000 to 800,000, and (b) a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn). The molecular weight distribution is 1.5 to 4, and (c) the melt viscosity (measured at a melting point + 50 ° C. temperature and a shear rate of 122 sec ⁻¹ ) is 100 to 2,000 Pa · s. The sound-absorbing material according to Item.   The sound-absorbing material according to any one of claims 1 to 5, wherein the laminate is formed by adhering and laminating the entire surface of a nonwoven fabric formed from an aliphatic polyester.   The sound-absorbing material according to any one of claims 1 to 5, wherein the laminate is formed by partially bonding and laminating a nonwoven fabric formed from an aliphatic polyester.   The sound-absorbing material according to any one of claims 1 to 7, wherein the thickness is 5 cm or less. At a frequency (f) of 200 Hz to 700 Hz, the sound absorption coefficient (A) is expressed by the following formula (formula) A ≧ 10 ⁻¹³ × f ⁴ −6 × 10 ⁻¹⁰ × f ³ + 8 × 10 ⁻⁷ × f ² +0 .0002 × f−0.0059
The sound-absorbing material according to claim 1, wherein:   The sound-absorbing material according to any one of claims 1 to 9, wherein no other layer other than the layer of the laminate is provided.   The sound-absorbing material according to any one of claims 1 to 10, wherein the sound-absorbing material is covered with a moisture-proof packaging material.

Images