JP4003831B2 - Electroacoustic transducer member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a member for an electroacoustic transducer, such as a speaker diaphragm and a speaker edge material, and a manufacturing method thereof.

  Electroacoustic transducers (speakers, etc.) and their components (speaker edge materials, speaker diaphragms, etc.) have good linearity, are lightweight, do not emit unique sounds, and have sufficient reliability. There are demands for conditions such as having a low cost, easy manufacture and low cost. In such an electroacoustic transducer or a member thereof, for example, as a speaker edge material (an edge material provided on the outer peripheral portion of the speaker diaphragm), various free edge materials have been proposed and put into practical use ( Patent Literature 1 to Patent Literature 2).

As said free edge material, the free edge material etc. which are shown by following (1)-(4) etc. are mentioned, for example.
(1) A natural or synthetic fiber woven fabric is coated with a relatively soft and high internal loss material such as rubber or acrylic resin, and if necessary, impregnated with a thermosetting resin for hardness control. Coated fabric edge material (woven fabric edge material) obtained by heat-molding the sheet material into a predetermined edge shape
(2) Foamed urethane edge material (urethane edge material) made by heat-molding a foamed urethane sheet into a predetermined edge shape
(3) A vulcanized rubber edge material obtained by vulcanizing and molding a rubber admixture containing a raw rubber and a vulcanizing agent into a predetermined edge shape. (4) A rubber admixture containing a raw rubber, a vulcanizing agent and a foaming agent. Foam rubber edge material that has been vulcanized and foam molded into a predetermined edge shape

Japanese Patent Laid-Open No. 11-69483 JP 2002-159093 A

However, each conventionally used free edge material has the following drawbacks.
(1) With the coated fabric edge material, the coating agent application work is complicated, and the resulting products vary.
(2) The foamed urethane edge material has a problem that it is inferior in weather resistance and water resistance.
(3) In the vulcanized rubber edge material, the weight of the product itself is increased due to the molding material. Therefore, there is a problem that it is impossible to follow the vibration, and as a result, the sensitivity of the speaker is lowered.
(4) Like the vulcanized rubber edge material, the foamed rubber edge material has a problem that it is heavier than the coated cloth edge material and the urethane foam edge material, and lowers the sensitivity of the speaker.

  Thus, various conventional speaker edge materials (sometimes simply referred to as “edge materials”) have their respective problems.

  Therefore, among various demands, members for electroacoustic transducers such as speaker edge materials and speaker diaphragms are required to have excellent durability, high quality, and light weight. In particular, in recent years, the downsizing and digitization of speakers including mobile phones and personal computers and audio has progressed. In addition to the weight of the speakers themselves, it is also necessary to reduce the weight of the components for electroacoustic transducers such as speaker edge materials. It has been.

However, the conventional electroacoustic transducer member using a rubber component as a raw material has a weight of about 1200 g / m ² , and even if it is foamed, it is 600 g / m ^2. In the case of foamed urethane foam, those of about 200 to 400 g / m ² are known, and even those made of the most lightweight woven fabric are 160 to 200 g. / M ² or so. If the thickness is simply reduced to reduce the weight, the strength is lowered and the durability is lowered, and a high-quality electroacoustic transducer member cannot be obtained. For this reason, only members that are heavy due to the material are known as electroacoustic transducer members (speaker edge members and the like), and those having a weight of 150 g / m ² or less are not known.

  JP-A-11-69483 describes a speaker diaphragm obtained by foaming with carbon dioxide in a supercritical state. Japanese Patent Laid-Open No. 2002-159093 discloses a foamed speaker diaphragm edge material made of a foamed sheet mainly composed of an olefinic thermoplastic elastomer, which is produced by foaming with carbon dioxide in a supercritical state. Is disclosed. However, even such a diaphragm for a speaker or an edge material of a foamed speaker diaphragm cannot satisfy both high quality and light weight.

Accordingly, an object of the present invention is to provide a member for an electroacoustic transducer that maintains a high quality even if it is lightweight, and a method for manufacturing the same.
Another object of the present invention is to provide a member for an electroacoustic transducer that has good strength, excellent durability, and is lightweight, and a method for manufacturing the same.

  As a result of intensive studies to achieve the above object, the present inventors use a polyolefin resin foam containing a specific amount of an inorganic filler, and maintain a high quality when its weight is a specific amount or less. However, it has been found that the weight can be reduced. The present invention has been completed based on these findings.

That is, the present invention is an electroacoustic transducer member used as a support system member of an electroacoustic transducer, and includes a polymer component containing a polyolefin resin and an inorganic filler of 5% by weight or more based on the entire foam. And a weight for the electroacoustic transducer is 30 g / m ² or more and 120 g / m ² or less .

  The polymer component preferably includes a polyolefin resin and a rubber component and / or a thermoplastic elastomer component, and the polyolefin resin is preferably a non-crosslinked body. The electroacoustic transducer member has a tensile strength measured according to JIS K 6301 (punching each sheet with dumbbell No. 1, tensile speed: 500 mm / min, temperature: 23 ° C., thickness: 1 mm), It is preferable that it is 6N or more. Furthermore, the polyolefin resin foam may be formed by foaming using a high-pressure gas.

  The present invention is also a method for producing the member for an electroacoustic transducer, comprising a polymer component containing a polyolefin resin and an inorganic filler of 5% by weight or more based on the whole foam. The manufacturing method of the member for electroacoustic transducers characterized by including the process of foaming a resin composition or its non-foaming molding is provided.

  In the method for producing a member for an electroacoustic transducer, foaming can be performed using a high-pressure gas. As the high-pressure gas, a high-pressure gas using carbon dioxide or nitrogen is preferable, and in particular, carbon dioxide in a supercritical state is used. It can be used suitably.

  According to the member for an electroacoustic transducer of the present invention, high quality is maintained even if it is lightweight. Specifically, the electroacoustic transducer member of the present invention has good strength, excellent durability, and light weight.

The electroacoustic transducer member of the present invention is formed of a polyolefin resin foam containing a polymer component containing a polyolefin resin and 5 wt% or more of an inorganic filler with respect to the entire foam, The weight is 150 g / m ² or less. As described above, since the weight of the electroacoustic transducer is as light as 150 g / m ² or less, the weight of the speaker itself can be reduced, and the sensitivity of the electroacoustic transducer (speaker, etc.) can be reduced. It can also contribute to improvement. Therefore, the member for electroacoustic transducers of the present invention is lightweight and has high quality as a member for electroacoustic transducers. As the weight of the electro-acoustic transducer member it is not particularly limited as long as 150 g / m ² or less, is preferably 100 g / m ² or less. The lower limit of the weight of the electroacoustic transducer member is not particularly limited, and may be, for example, 30 g / m ² or more (preferably 50 g / m ² or more).

  Moreover, the member for electroacoustic transducers of this invention can have the intensity | strength equivalent to the member for conventional electroacoustic transducers. If the thickness of the electroacoustic transducer member is simply reduced to make it lighter, its strength decreases and cannot be used as an electroacoustic transducer member, but the electroacoustic transducer member of the present invention Even if it is lightweight, its strength can be maintained at a good level. Specifically, as a member for an electroacoustic transducer of the present invention, for example, tensile strength measured according to JIS K 6301 (each sheet is punched with dumbbell No. 1, tensile speed: 500 mm / min, temperature: 23 ° C., thickness: 1 mm) can be 6 N or more (preferably 8 N or more). Thus, since it can have intensity | strength equivalent to the member for conventional electroacoustic transducers, it can be used without a problem in workability, durability, etc. If the tensile strength measured according to JIS K 6301 (punching each sheet with dumbbell No. 1, tensile speed: 500 mm / min, temperature: 23 ° C., thickness: 1 mm) is less than 6N, the strength is insufficient. In case of use under severe conditions such as continuous use, tearing may occur and damage may occur.

  Furthermore, the electroacoustic transducer member of the present invention is also excellent in durability. For example, even if it is exposed for 2000 hours in an atmosphere at a temperature of 60 ° C. and a humidity of 95% RH, the state does not change. .

  Therefore, although the member for electroacoustic transducers of the present invention is lightweight, it has excellent strength and excellent durability. That is, the electroacoustic transducer member maintains high quality even if it is lightweight.

  As described above, such a member for an electroacoustic transducer foams a polyolefin resin composition containing a polymer component containing a polyolefin resin and 5% by weight or more of an inorganic filler with respect to the entire foam. It is formed by the polyolefin resin foam obtained by making it. Such a polyolefin resin foam is not particularly limited as long as it is formed by a polyolefin resin composition containing a polymer component containing a polyolefin resin and an inorganic filler, but in particular, a polyolefin resin and a rubber It can be suitably formed by a polyolefin resin composition containing a polymer component containing a component and / or a thermoplastic elastomer component, and an inorganic filler. Of course, since it is a foam (foamed sheet or the like), it is important that it is foamed and molded for formation.

(Polymer component)
In the polymer component of the polyolefin-based resin composition forming the polyolefin-based resin foam, the polyolefin-based resin is not particularly limited as long as the resin contains at least an olefin (such as ethylene or propylene) as a monomer component. Any type of polyolefin resin such as a polyolefin resin having a broad molecular weight distribution and having a shoulder on the high molecular weight side, a post-crosslinking polyolefin resin, and a long-chain branched polyolefin resin may be used.

  Specifically, examples of the polyolefin resin include polyethylene resins such as low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene; polypropylene resins such as polypropylene; poly-4-methylpentene- Other polyolefin resins such as 1; other than olefin copolymers such as copolymers of ethylene and propylene, terpolymers of ethylene, propylene and other α-olefins other than these And olefins such as a copolymer of ethylene and a monomer component other than α-olefins, and olefinic copolymers of monomer components other than olefins. Polyolefin resins can be used alone or in combination of two or more.

  In addition, in the olefin-type copolymer only by olefins, as alpha-olefin other than ethylene and propylene, for example, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1- Heptene, 1-octene, etc. are mentioned.

  Moreover, in the olefin copolymer by olefins and monomer components other than olefins, as monomer components other than α-olefins, for example, vinyl esters such as vinyl acetate; (meth) acrylic acid (acrylic acid, methacrylic acid) Acid), itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and other carboxyl group-containing monomers or anhydrides thereof (maleic anhydride, itaconic anhydride, etc.); (meth) methyl acrylate, (meth) Ethyl acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t- (meth) acrylic acid Butyl, (meth) acrylic acid pentyl, (meth) acrylic acid hexyl, (meth) a Heptyl tollate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth ) (Meth) acrylic acid alkyl esters such as isodecyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and (meth) acrylic esters such as cyclohexyl (meth) acrylate and phenyl (meth) acrylate Vinyl alcohols such as vinyl alcohol; maleic acid (mono or di) esters such as monomethyl maleate, monoethyl maleate and diethyl maleate; fumaric acid (mono or di) esters such as monomethyl fumarate and monoethyl fumarate; styrene , Aromatic styrene such as substituted styrene Nyl compounds; dienes such as butadiene, isoprene and isobutylene; vinyl chloride; vinyl ethers such as vinyl alkyl ether; hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; Hydroxyl group-containing monomers such as glycerol dimethacrylate; epoxy group-containing monomers such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; acrylamide, Amide group-containing monomers such as methacrylamide, N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide; Amino group-containing monomers such as aminoethyl (meth) acrylate and (meth) acryloylmorpholine; cyclohexyl Reimido, imide group-containing monomers such as isopropyl maleimide; a sulfonic acid group-containing monomers such as sodium vinyl sulfonate and the like. Olefins and monomer components other than olefins can be used alone or in combination of two or more.

  Therefore, in the olefin copolymer by olefins and monomer components other than olefins, specific examples thereof include, for example, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-ethyl acrylate copolymer, and other ethylene- Vinyl acetate copolymer; ethylene-α, β-unsaturated carboxylic acid copolymer such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid-ethyl acrylate copolymer Ethylene-α, β-unsaturated carboxylic acid ester copolymers such as ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer; ethylene-vinyl alcohol copolymer; A polymer etc. are mentioned.

  As the polyolefin-based resin, a polyethylene-based resin and a polypropylene-based resin can be preferably used from the viewpoints of heat processability at the time of foam molding, shape fixability after foaming, and the like, and polypropylene is particularly preferable.

  As described above, it is preferable to use a rubber component and / or a thermoplastic elastomer component together with the polyolefin resin as the polymer component. Thus, by using a rubber component or a thermoplastic elastomer component, the cushioning property (impact absorbability) of the foamed sheet can be improved.

  As the rubber component, natural rubber or synthetic rubber can be used. More specifically, examples of the rubber component include natural rubber and synthetic rubber such as polyisobutylene, polyisoprene rubber, chloroprene rubber, butyl rubber, and nitrile butyl rubber. A rubber component can be used individually or in combination of 2 or more types.

  Examples of the thermoplastic elastomer component include olefin-based thermoplastic elastomers such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, and chlorinated polyethylene; styrene -Butadiene (SB) copolymer, styrene-isoprene (SI) copolymer, styrene-isoprene-styrene block (SIS) copolymer, styrene-butadiene-styrene block (SBS) copolymer, styrene-ethylene-butylene -Styrenic thermoplastic elastomers such as styrene block (SEBS) copolymer, styrene-ethylene-propylene-styrene block (SEPS) copolymer, styrene-ethylene-propylene block (SEP) copolymer; polyester-based thermoplastic elastomer Tomah; polyamide thermoplastic elastomers; thermoplastic polyurethane elastomer; include various thermoplastic elastomers such as thermoplastic acrylic elastomer. A thermoplastic elastomer component can be used individually or in combination of 2 or more types.

  As the rubber component and / or the thermoplastic elastomer component used together with the polyolefin-based resin, an olefin-based thermoplastic elastomer (in particular, an ethylene-propylene copolymer or an ethylene-propylene-diene copolymer) can be suitably used. . The olefin thermoplastic elastomer is, for example, an elastomer having a structure in which an olefin component and ethylene-propylene rubber are microphase-separated, and has good compatibility with the polyolefin resin.

  When the rubber component and / or the thermoplastic elastomer component are used together with the polyolefin resin in the polymer component of the polyolefin resin composition forming the polyolefin resin foam, the ratio of the rubber component and / or the thermoplastic elastomer component As, for example, it can be selected from the range of 150 parts by weight or less (for example, 10 to 150 parts by weight), preferably 30 to 100 parts by weight with respect to 100 parts by weight of the polyolefin resin. If the ratio of the rubber component and / or the thermoplastic elastomer component exceeds 150 parts by weight with respect to 100 parts by weight of the polyolefin-based resin, it becomes difficult to obtain a high foam because gas tends to escape during foaming. In addition, the cushioning property as a foam can be improved by making the ratio of a rubber component and / or a thermoplastic elastomer component into 10 weight part or more with respect to 100 weight part of polyolefin resin.

  In the present invention, the polymer component (particularly polyolefin resin) is preferably a non-crosslinked product. If the polymer component (especially polyolefin resin) is a non-crosslinked product, the flexibility inherent in the polyolefin resin is not impaired, so that excellent processability can be exhibited, and reuse is also possible. Since it becomes easy to do, it can have the advantage of being excellent in recyclability.

(Inorganic filler)
As described above, the polyolefin resin composition forming the polyolefin resin foam contains an inorganic filler in a proportion of 5% by weight or more based on the entire foam. The inorganic filler has a function as a nucleating agent (foaming nucleating agent or bubble nucleating agent) at the time of foam formation. That is, in the present invention, the inorganic filler is mainly used to function as a foam nucleating agent (or a cell nucleating agent).

  The proportion of the inorganic filler is not particularly limited as long as it is 5% by weight or more based on the whole foam, but is preferably 8% by weight or more based on the whole foam. By setting the proportion of the inorganic filler to 5% by weight or more with respect to the entire foam, a uniform foam (for example, a foam having excellent cell structure uniformity) can be easily obtained. Become.

The upper limit of the proportion of the inorganic filler is not particularly limited, but is desirably 70% by weight or less (preferably 60% by weight or less) with respect to the entire foam. When the proportion of the inorganic filler exceeds 70% by weight with respect to the entire foam, the weight of the electroacoustic transducer member may not be 150 g / m ² or less. In addition, the viscosity of a polyolefin resin composition containing a polymer component containing a polyolefin resin and an inorganic filler is remarkably increased, and gas escape may occur during foam molding, which may impair foaming characteristics.

  Specifically, as the inorganic filler, for example, talc, silica, stone powder, zeolite, alumina, aluminum powder, iron powder, and carbonate metal salts such as calcium carbonate, magnesium carbonate, magnesium carbonate-calcium, and barium carbonate. Metal salts of sulfuric acid such as magnesium sulfate and barium sulfate; metal oxides such as zinc oxide, titanium oxide and magnesium oxide; metal water such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide and barium hydroxide Oxides; metal hydrates (hydrated metal compounds) such as magnesium oxide-nickel oxide hydrate, magnesium oxide-zinc oxide hydrate, and the like.

  As the inorganic filler, a flat plate shape may be used, but in order to effectively exhibit the function as a foam nucleating agent (or a cell nucleating agent), a granular material can be suitably used. In the granular inorganic filler, the particle size is preferably, for example, 0.1 to 10 μm. When the particle size of the inorganic filler is less than 0.1 μm, the functionality as a foam nucleating agent is lowered. On the other hand, when the particle size exceeds 10 μm, there is a case where gas is lost during foam formation.

(Other ingredients)
Since the polyolefin resin foam is composed of a polyolefin resin composition mainly composed of an organic polymer component, it can be said that the polyolefin resin foam has a drawback that it is easy to burn. Therefore, when an electroacoustic transducer member formed of a polyolefin-based resin foam is used in an application (especially for a vehicle) in which it is essential to impart flame retardancy, the electroacoustic transducer member (or polyolefin-based component) It is preferable that a flame retardant is contained in the resin foam). As such a flame retardant, flame retardants such as bromine flame retardants, chlorine flame retardants, phosphorus flame retardants, antimony flame retardants, and the like that are conventionally known can be used, but bromine flame retardants and chlorine flame retardants. However, there is a problem that gases that are harmful to human body and corrosive to equipment are generated during combustion. On the other hand, phosphorus flame retardants and antimony flame retardants have problems such as toxicity and explosiveness. Therefore, a non-halogen / non-antimony flame retardant can be preferably used. A flame retardant can be used individually or in combination of 2 or more types.

  As the non-halogen / non-antimony flame retardant, inorganic flame retardants such as metal hydroxides and metal hydrates are suitable. Examples of the inorganic flame retardant include metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal hydrates such as magnesium oxide-nickel oxide hydrate and magnesium oxide-zinc oxide hydrate (water Japanese metal compounds). Such a metal hydroxide or metal hydrate as a flame retardant may be subjected to a known or conventional surface treatment.

  In addition, when a metal hydroxide or metal hydrate is used as the inorganic filler, the metal hydroxide or metal hydrate can also function as a flame retardant. Therefore, when a metal hydroxide or metal hydrate is used as the inorganic filler, the function as a flame retardant can be exhibited together with the function as a foam nucleating agent. Even when it is used in applications where it is essential to impart the property, it is not necessary to add a new flame retardant, which is advantageous in terms of cost, and retains excellent characteristics as a member for an electroacoustic transducer. be able to.

  Various additives may be blended in the polyolefin resin composition forming the polyolefin resin foam, if necessary. The additive is not particularly limited, and various additives that can be used for various foamed sheets can be appropriately selected and used. Examples of such additives include crystal nucleating agents, plasticizers, lubricants, colorants, ultraviolet absorbers, antioxidants, other fillers, reinforcing agents, and antistatic agents. The addition amount of the additive can be appropriately selected within a range that does not impair the formation of bubbles and the like, and the addition amount used for molding a normal thermoplastic resin can be adopted.

  The polyolefin resin composition for forming the polyolefin resin foam has a melting point [Tm (° C.) of the polyolefin resin composition in order to prevent the bubble wall from being destroyed during foam formation and to foam at a high expansion ratio. )] The melt tension when measured at a temperature [Tm to (Tm + 20)] within 20 ° C. on the higher temperature side is desirably 20 cN or more, particularly 25 cN or more (for example, 25 to 70 cN), especially 30 cN or more. (For example, 30 to 50 cN) is preferable. The melt tension of the polyolefin resin composition is said to be measured at a temperature [Tm to (Tm + 20)] within 20 ° C. higher than the melting point [Tm (° C.)] of the polyolefin resin composition. This is because when the temperature is lower than the melting point, it does not enter a molten state, and when the temperature is higher than the melting point of the polyolefin resin composition by 20 ° C., it becomes a completely fluidized region and hardly produces tension. The melt tension of the polyolefin resin composition may be 20 cN or more at at least one of the temperatures [Tm to (Tm + 20)] within 20 ° C. higher than the melting point of the polyolefin resin composition.

  Furthermore, when the melt tension of the polyolefin resin composition is 20 cN or higher at a temperature [Tm to (Tm + 20)] within 20 ° C. higher than the melting point of the polyolefin resin composition, the inorganic filler grows in bubbles. As a starting point, the effect of making the bubble structure more uniform is also exhibited. This is particularly effective when high-pressure gas (particularly, supercritical carbon dioxide) is used as a foaming agent to be described later, and particularly fine and uniform bubbles can be formed as compared with conventional foaming methods.

(Method for producing electroacoustic transducer member)
The electroacoustic transducer member of the present invention can be formed using the polyolefin resin foam. The polyolefin resin foam for forming the member for an electroacoustic transducer can be obtained by foaming the polyolefin resin composition. In the foaming, a foaming agent can be used. Such a foaming agent is not particularly limited as long as it is usually used when foaming a polyolefin-based resin, but it is preferable to use a high-pressure gas from the viewpoints of environmental protection and low contamination to the foamed body. . In the present invention, the high-pressure gas is used to include a supercritical fluid.

  The high-pressure gas is not particularly limited as long as it is impregnated into the polyolefin resin and a polymer component such as a rubber component and / or a thermoplastic elastomer component under high pressure, but a high-pressure inert gas is preferably used. Can do. More specifically, examples of the high pressure gas include high pressure gas using carbon dioxide, nitrogen, air, and the like. These high-pressure gases may be mixed and used. Carbon dioxide and nitrogen are preferred as the components of the high-pressure gas, and in particular, the amount of impregnation of the polymer component (polyolefin resin, rubber component and / or thermoplastic elastomer component) used as the foam material is large, and the impregnation rate Carbon dioxide is preferred from the standpoint of a high speed. Further, from the viewpoint of increasing the impregnation rate into the resin, the high-pressure gas (for example, carbon dioxide) is preferably in a supercritical state. Carbon dioxide has a critical temperature of 31 ° C. and a critical pressure of 7.4 MPa.

  When a gas in a supercritical state (supercritical fluid) is used, the solubility of the gas in the resin (polymer component) increases, and high concentration can be mixed, and at the time of a sudden pressure drop after impregnation, Since the concentration is high, the generation of bubble nuclei is increased, and the density of bubbles formed by the growth of the bubble nuclei is increased even if the porosity is the same, so that fine bubbles can be obtained.

  The method for producing a polyolefin resin foam is not particularly limited as long as it can be formed by foaming using the polyolefin resin composition. For example, the method is performed by any one of a batch method and a continuous method. May be.

  A method for producing a polyolefin resin foam in a batch system using a high-pressure gas as a foaming agent is shown below. First, a polyolefin resin composition containing a polyolefin resin and, if necessary, a polymer component containing a rubber component and / or a thermoplastic elastomer component, and an inorganic filler, a single screw extruder, a twin screw extruder, etc. An unfoamed molded product (such as a resin sheet for foam molding) is produced by extruding using an extruder. Alternatively, a polyolefin resin composition containing a polyolefin resin and, if necessary, a polymer component containing a rubber component and / or a thermoplastic elastomer component, and an inorganic filler, is made into a roller, a cam, a kneader, a Banbury type blade. Kneaded uniformly using a kneading machine provided with a non-foamed molded product (such as a resin sheet for foam molding) by press molding to a predetermined thickness using a hot plate press or the like Is made. The unfoamed molded product thus obtained is placed in a pressure-resistant container, and high-pressure gas (for example, high-pressure inert gas such as carbon dioxide, nitrogen, air, etc.) is introduced or injected, and the high-pressure gas is unfoamed. Impregnation into the molding. At this time, the high-pressure gas may be introduced continuously or discontinuously. Thereafter, when the high-pressure gas is sufficiently impregnated, the pressure is released (usually up to atmospheric pressure), and bubble nuclei are generated in the base resin. Bubble nuclei may be grown at room temperature as they are, or may be grown by heating as necessary. As a heating method, a known or conventional method using a water bath, an oil bath, a hot roll, a hot air oven, far infrared rays, near infrared rays, microwaves, or the like can be employed. After the bubbles are grown in this way, the polyolefin resin foam sheet can be obtained by rapidly cooling with cold water or the like to fix the shape.

  In addition, in such a batch system, the unfoamed molded product (unfoamed product) to be used for foaming is not limited to a sheet shape, and can have various shapes depending on the application. Moreover, the unfoamed molded product (unfoamed product) to be subjected to foaming can be produced by other molding methods such as injection molding, as well as extrusion molding and press molding.

  A method for producing a polyolefin resin foam in a continuous manner using a high-pressure gas as a foaming agent is shown below. Extrusion of a polyolefin resin composition containing a polyolefin resin and, if necessary, a polymer component containing a rubber component and / or a thermoplastic elastomer component, and an inorganic filler, such as a single screw extruder or a twin screw extruder Injecting high-pressure inert gas while kneading using a machine, sufficiently impregnating the gas in the resin, then extruding to release pressure (usually up to atmospheric pressure), foaming and molding simultaneously Yes, and in some cases, the bubbles are grown by heating. After growing the bubbles, the polyolefin resin foam sheet can be obtained by rapidly cooling with cold water or the like to fix the shape. In addition,

  In such a continuous method, foam molding can be performed by other molding methods such as injection molding in addition to extrusion molding. The shape of the foam is not limited to the sheet shape, and may be various shapes depending on the application, and may be, for example, a prismatic shape.

  Thus, as a method for producing a member for an electroacoustic transducer of the present invention, a polyolefin resin composition containing a polymer component containing a polyolefin resin and an inorganic filler of 5% by weight or more based on the entire foam. The method which foams the thing or its non-foaming molded article, and performs the foaming using high-pressure gas can be adopted suitably. As described above, when foaming is performed using high-pressure gas, the method for producing the member for an electroacoustic transducer includes a gas impregnation step of impregnating the high-pressure gas and a pressure reduction step of foaming the resin by reducing the pressure after the step. , And if necessary, a heating step of growing bubbles by heating can be provided.

  In the gas impregnation step, the pressure when impregnating the non-foamed molded product or the resin kneaded product (polyolefin-based resin composition) with the high-pressure gas can be appropriately selected in consideration of the type and operability of the high-pressure gas. For example, when a high-pressure gas using carbon dioxide is used as the high-pressure gas, the pressure is, for example, 6 MPa or more (for example, about 6 to 100 MPa), preferably 8 MPa or more (for example, about 8 to 100 MPa). When the pressure is lower than 6 MPa, the bubble growth during foaming is remarkable and the bubble diameter becomes too large. This is because, when the pressure is low, the amount of gas impregnation is relatively small compared to when the pressure is high, and the number of bubble nuclei formed is reduced due to a decrease in the bubble nucleus formation rate. This is because the bubble diameter becomes extremely large. Further, in the pressure region lower than 6 MPa, the bubble diameter and the bubble density change greatly only by slightly changing the impregnation pressure, so that it is difficult to control the bubble diameter and the bubble density.

  The temperature in the gas impregnation step varies depending on the high-pressure gas used, the polymer component (polyolefin resin, etc.), etc., and can be selected in a wide range, but is, for example, about 10 to 350 ° C. in consideration of operability. For example, the impregnation temperature in the case of impregnating a non-foamed molded product such as a sheet with high pressure gas is about 10 to 200 ° C. (preferably 40 to 200 ° C.) in a batch system. Moreover, the continuous impregnation temperature in the case where foaming and molding are simultaneously performed by extruding a mixture containing a molten polymer impregnated with a high-pressure gas is generally about 60 to 350 ° C. In addition, when using the high pressure gas by a carbon dioxide as a high pressure gas, in order to maintain a supercritical state, it is preferable that the temperature at the time of impregnation is 32 degreeC or more (especially 40 degreeC or more).

  In the decompression step, the decompression rate is not particularly limited, but is preferably about 5 to 300 MPa / second in order to obtain uniform fine bubbles. Moreover, the heating temperature in the said heating process is about 40-250 degreeC (preferably 60-250 degreeC), for example.

  Thus, since the polyolefin resin foam for producing the member for an electroacoustic transducer of the present invention is obtained by a method of foaming using a high-pressure gas, it can be a foam with a high expansion ratio. . Therefore, according to the method for producing a polyolefin resin foam as described above, a foam having a large thickness can be produced. That is, for example, when a polyolefin resin foam is produced in a continuous manner, a high pressure gas is injected while the polyolefin resin composition is kneaded, and the resin is sufficiently impregnated with the high pressure gas and then extruded. In this case, in order to maintain the pressure inside the extruder, the die gap at the tip of the extruder needs to be as narrow as possible (usually about 0.1 to 1.0 mm). Therefore, in order to obtain a thick foam, an unfoamed composition extruded through a narrow gap must be foamed at a high magnification. The foam has been limited to a thin one (for example, about 0.5 to 2.0 mm).

  On the other hand, the polyolefin resin foam in the present invention can continuously obtain a foam having a final thickness of 0.50 to 5.00 mm. In order to obtain such a thick foam, it is desirable that the relative density of the foam (density after foaming / density in an unfoamed state) is 0.15 or less (preferably 0.10 or less). . The lower limit of the relative density of the foam is not particularly limited, but is usually 0.02 or more. When the relative density of the polyolefin resin foam exceeds 0.15, foaming is insufficient. On the other hand, when the relative density is less than 0.02, the strength may be remarkably lowered.

  Depending on the type of high-pressure gas, polyolefin resin, rubber component, thermoplastic elastomer component, etc. used, the thickness, relative density, etc. of the polyolefin resin foam can be controlled by, for example, temperature, pressure, time, etc. in the gas impregnation process. It can be adjusted by appropriately selecting and setting conditions, operating conditions such as pressure reduction speed, temperature and pressure in the pressure reduction process, and heating temperature after pressure reduction.

  The member for electroacoustic transducers of the present invention can be produced by molding into a predetermined shape using the polyolefin resin foam. For example, after polyolefin resin foam is punched into a predetermined shape as necessary, it is placed in a molding die and molded into a predetermined shape as a member for an electroacoustic transducer (heat molding, pressure molding, The member for electroacoustic transducers can be produced by heating and pressing. In this molding, the heating conditions and pressure conditions are the composition and composition ratio of the polyolefin resin composition for obtaining the polyolefin resin foam (such as the types and proportions of the blended components) and the thickness of the molded product. The heating conditions can be set to 80 to 160 ° C., the pressurizing conditions can be set to 0.098 to 0.98 MPa, and the treatment time can be set to 0.02 to 30 minutes.

  Of course, when the polyolefin resin foam itself has a predetermined shape as an electroacoustic transducer member, the electroacoustic transducer member can be obtained by using the polyolefin resin foam as it is. it can.

  The member for an electroacoustic transducer of the present invention is used as a support system member for an electroacoustic transducer (such as a speaker). Specifically, the electroacoustic transducer member can be suitably used as a speaker dust plate (particularly a speaker edge material), in addition to a speaker diaphragm and a speaker edge material.

  The internal loss (tan δ) of the electroacoustic transducer member is appropriately determined depending on the composition and composition ratio of the polyolefin-based resin composition for obtaining the polyolefin-based resin foam (such as the types and ratios of the blended components). The internal loss (tan δ) can be adjusted. The internal loss (tan δ) is defined by storage elastic modulus (E ′) / loss elastic modulus (E ″). The member for electroacoustic transducers of the present invention can have a high internal loss (tan δ), and can exhibit excellent acoustic characteristics. Specifically, the electroacoustic transducer member has, for example, an internal loss (tan δ) measured at a frequency of 128 Hz or 256 Hz of 0.2 or more (preferably 0.3 or more, more preferably 0.4 or more). It can be. In measuring the internal loss (tan δ) of the electroacoustic transducer member, a trade name “ARES” manufactured by Rheometric Co., Ltd. can be used as a dynamic viscoelasticity measuring device. As measurement conditions, the temperature is 23 ° C., the measurement frequency is 128 Hz or 256 Hz, the sample thickness is about 1.0 mm, the strain is 0.1% (23 ° C.), the plate is a parallel plate having a diameter of 7.9 mmφ. The jig conditions can be adopted.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The melt tension and relative density were determined by the following methods.

(Melting tension)
The melt tension was measured at room temperature (23 ° C.) using a capillary rheometer manufactured by Toyo Seiki Co., Ltd. (device name “capillograph; capillary die size: diameter (φ) 1 mm, L / D = 10; die diameter: 10 mm). Using a load from above the capillary and extruding into a strand at a constant speed of 20 m / min, sending the extrudate through a tension detection pulley and winding it on a roll. Gradually increase (1 to 100 m / min) The speed is increased until cutting, and the tension immediately before cutting is generally the melt tension, but here the tension at the winding speed of 2 m / min Is adopted.

(Relative density)
The relative density was determined by the following formula.
Relative density = [density after foaming (density of foam) (g / cm ³ )] ÷ [density before foaming (density of sheet before foaming) (g / cm ³ )]

Example 1
Polypropylene [melt flow rate (MFR; temperature; 230 ° C .; load: 2.16 kg): 0.35 g / 10 min]: 45 parts by weight, olefin-based thermoplastic elastomer [ethylene-propylene copolymer; melt flow rate (MFR) Temperature: 230 ° C .; load: 2.16 kg): 6 g / 10 min; JIS-A hardness: 79 °]: 55 parts by weight and magnesium hydroxide (average particle size: 0.7 μm): 10 parts by weight The mixture was kneaded at a temperature of 200 ° C. in a twin-screw kneader manufactured by Japan Steel Works (JSW), then extruded into a strand shape, water-cooled, cut into a pellet shape, and molded. When the melting point (Tm; ° C.) of the kneaded product (compound) of the pellets was determined by DSC (differential scanning calorimeter), it was 170 ° C., and the melt tension was 182 ° C. (12 ° C. higher than the melting point). When calculated, it was 31.1 cN.

The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected in a 220 ° C. atmosphere at a pressure of 22 (19 after injection) MPa / cm ² . After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and extruded from a die to obtain a foam (foamed sheet). In this foam, the relative density was 0.05. The die gap was 0.3 mm, and the thickness of the foam (foamed sheet) at that time was 2.2 mm.

  After mounting a predetermined mold on the air press machine, the foam (foamed sheet) is placed in the mold and heat-molded under the conditions of 110 ° C. × 10 seconds to obtain a thickness of 1.0 mm. The speaker edge material was produced.

(Example 2)
Polypropylene [melt flow rate (MFR; temperature; 230 ° C .; load: 2.16 kg): 0.35 g / 10 min]: 45 parts by weight, olefin-based thermoplastic elastomer [ethylene-propylene copolymer; melt flow rate (MFR) Temperature; 230 ° C .; load: 2.16 kg): 6 g / 10 min; JIS-A hardness: 79 °]: 55 parts by weight and magnesium hydroxide (average particle size: 0.7 μm): 120 parts by weight After being kneaded at a temperature of 200 ° C. by a twin-screw kneader manufactured by Nippon Steel Co., Ltd., it was extruded into a strand shape, cooled with water, cut into a pellet shape, and molded. When the melting point (Tm; ° C.) of the kneaded product (compound) of the pellets was determined by DSC (differential scanning calorimeter), it was 170 ° C., and the melt tension was 182 ° C. (12 ° C. higher than the melting point). When calculated, it was 31.4 cN.

The pellets were put into a single screw extruder manufactured by Nippon Steel Works, and carbon dioxide gas was injected in a 220 ° C. atmosphere at a pressure of 19 (16 after injection) MPa / cm ² . After sufficiently saturating the carbon dioxide gas, it was cooled to a temperature suitable for foaming and extruded from a die to obtain a foam (foamed sheet). In this foam, the relative density was 0.120. The die gap was 0.3 mm, and the thickness of the foam (foamed sheet) at that time was 1.7 mm.

  After mounting a predetermined mold on the air press machine, the foam (foamed sheet) is placed in the mold and heat-molded under the conditions of 110 ° C. × 10 seconds to obtain a thickness of 1.0 mm. The speaker edge material was produced.

(Comparative Example 1)
As the speaker edge material, a resin-coated woven fabric (thickness: 0.3 mm) was used.

(Comparative Example 2)
A foamed urethane foam (thickness: 8 mm) is placed in a predetermined mold attached to an air press and press molded under the conditions of 110 ° C. × 10 seconds to provide a speaker edge material with a thickness of 1.0 mm. Was made.

(Comparative Example 3)
An unvulcanized rubber sheet (thickness: 1.2 mm) is placed in a predetermined mold mounted on an air press machine, and press-molded under conditions of 170 ° C. × 5 minutes. A speaker edge material made of 0.0 mm vulcanized rubber was prepared.

(Comparative Example 4)
An unvulcanized rubber sheet (thickness: 1.2 mm; foamed rubber edge material of Nitto Denko Co., Ltd. ethylene-propylene-diene copolymer system) is placed in a predetermined mold mounted on an air press machine. A speaker edge material made of foamed rubber having a thickness of 1.0 mm was produced by press molding under the conditions of 205 ° C. × 45 seconds.

(Evaluation)
About the speaker edge material produced by Examples 1-2 and Comparative Examples 1-4, durability, weight, and intensity | strength were evaluated with the following evaluation method or the measuring method. The evaluation results are shown in Table 1.

(Durability evaluation method)
Place the speaker edge material in an incubator at a temperature of 60 ° C. and a humidity of 95% RH for 2000 hours, and visually observe the state before and after that. If there is no change in the state (shape or strength) In Table 1, “NG” indicates that the shape was observed to change or the strength was deteriorated.

(Weight measurement method)
The weight of the speaker edge material was measured and converted per 1 m ² .

(Measurement method of strength)
For speaker edge materials, according to JIS K 6301 (vulcanized rubber test method), tensile strength (punch each sheet with dumbbell No. 1, tensile speed: 500 mm / min, temperature: 23 ° C., thickness: 1 mm) is measured. did.

  As apparent from Table 1, the speaker edge materials according to Examples 1 and 2 are formed by foaming a polyolefin resin composition containing an inorganic filler in an amount of 5% by weight or more based on the whole foam. Compared with the speaker edge material (conventional speaker edge material) according to Examples 1 to 4, the speaker edge material has stable durability and is very light in weight. Also, the strength is 6N or more, which is good. Therefore, the speaker edge material according to Examples 1 and 2 has high quality even if it is lightweight, and is optimal as a lightweight speaker edge material.

Claims (9)

A member for an electroacoustic transducer used as a support system member for an electroacoustic transducer, comprising a polymer component containing a polyolefin resin and an inorganic filler of 5% by weight or more based on the entire foam A member for an electroacoustic transducer, which is formed of a resin foam and has a weight of 30 g / m ² or more and 120 g / m ² or less . The electroacoustic transducer member according to claim 1, wherein the polymer component includes a polyolefin-based resin and a rubber component and / or a thermoplastic elastomer component. The member for electroacoustic transducers according to claim 1 or 2, wherein the polyolefin resin is a non-crosslinked body. The tensile strength (punching each sheet with dumbbell No. 1, tensile speed: 500 mm / min, temperature: 23 ° C., thickness: 1 mm) measured according to JIS K 6301 is 6N or more. The electroacoustic transducer member according to any one of the items. The member for electroacoustic transducers according to any one of claims 1 to 4, wherein the polyolefin resin foam is formed by foaming using a high-pressure gas. A method for producing a member for an electroacoustic transducer according to any one of claims 1 to 5, wherein the polymer component includes a polyolefin-based resin and the inorganic filler is 5% by weight or more based on the entire foam. A process for producing a member for an electroacoustic transducer, comprising a step of foaming a polyolefin-based resin composition containing or an unfoamed molded product thereof. The manufacturing method of the member for electroacoustic transducers of Claim 6 which foams using a high pressure gas. The method for producing a member for an electroacoustic transducer according to claim 6 or 7, wherein the high pressure gas is a high pressure gas of carbon dioxide or nitrogen. The method for producing a member for an electroacoustic transducer according to any one of claims 6 to 8, wherein the high-pressure gas is carbon dioxide in a supercritical state.