JP7277093B2 - Method for producing nonwoven fabric for sound absorbing or heat insulating material, and nonwoven fabric for sound absorbing or heat insulating material - Google Patents

Description

The present invention provides a method for producing a nonwoven fabric for a sound absorbing material or a heat insulating material, which has a low bulk density, excellent sound absorbing properties or heat insulating properties, and does not allow heat-expandable fine particles to fall off (powder falling off) from the nonwoven fabric, and The present invention relates to a nonwoven fabric for sound absorbing material or heat insulating material.

Nonwoven fabrics having sound absorbing properties are used as sound absorbing materials in various places such as the interior and exterior of automobiles, audiovisual equipment, building materials such as floor materials, wall materials, and ceiling materials. In addition, especially when the sound absorbing material is incorporated in equipment, etc., "lightening" is required.

Conventional sound absorbing materials made of non-woven fabric are known in which microfibers with a fiber diameter of about 2 μm are combined to control air permeability and staple fibers with a fiber diameter of 20 to 30 μm are combined to control thickness. However, the sound absorbing material has a high bulk density and cannot sufficiently meet the demand for "lightening".

As a nonwoven fabric having a low bulk density, that is, a bulky and lightweight nonwoven fabric, for example, Patent Document 1 describes microcapsules in which a nonwoven fabric obtained by needle punching a long fiber web (spunbond web) contains a thermally expandable gas. is disclosed which is filled with a resin containing Further, Patent Document 2 discloses a composite sound absorbing material in which a synthetic resin foam layer in which thermally expandable microcapsules are mixed is formed on the surface of a fiber base material.

JP-A-04-281054 JP 2016-045450 A

However, in the nonwoven fabric of Patent Document 1, unless a large amount of microcapsules containing a thermally expandable gas are used, a bulky nonwoven fabric cannot be obtained by foaming, and the microcapsules after expansion fall off from the nonwoven fabric (powdering). I was afraid. Conversely, if the number of microcapsules is reduced in order to avoid powder falling off, there is a risk that the expansion will be insufficient and the sound absorption will decrease, making it difficult to achieve both prevention of powder falling off and sound absorption properties.

The composite sound absorbing material of Patent Document 2 is coated with a highly viscous synthetic resin emulsion on the surface of a high-density fiber base material. there were.

Under such circumstances, an object of the present invention is to provide a nonwoven fabric for sound absorbing or heat insulating material, which is easy to reduce weight, and can achieve both excellent sound absorbing properties and prevention of falling powder, and a method for producing the same. listed as.

As a result of extensive research to solve the above problems, the inventors of the present invention used a nonwoven fabric substrate obtained by mixing and thermally bonding a nonwoven fabric substrate fiber and a fiber having a lower melting point than the nonwoven fabric substrate fiber. , while the thickness of the non-woven fabric substrate is 5 mm or more, the content of the thermally expandable fine particles after expansion is 20 g/m ² or less, thereby reducing weight, excellent sound absorption properties, and excellent heat insulation properties; The inventors have found that it is possible to produce a nonwoven fabric for sound absorbing material or heat insulating material that can achieve less powder falling off, and have completed the present invention.

That is, the method for producing a nonwoven fabric for a sound absorbing material or a heat insulating material according to the present invention has the following points.
[1] A nonwoven fabric substrate obtained by mixing and thermally bonding nonwoven fabric substrate fibers and fibers having a lower melting point than the nonwoven fabric substrate fibers is impregnated with a coating liquid containing thermally expandable fine particles to obtain the thermally expandable fine particles. is expanded to make the thickness of the nonwoven fabric substrate 5 mm or more, and the content of the thermally expandable fine particles after expansion is 20 g/m ² or less. manufacturing method.
[2] The nonwoven fabric for sound absorbing or heat insulating material according to [1], wherein the nonwoven fabric for sound absorbing or heat insulating material has a bulk density of 0.001 to 0.050 g/cm ³ due to the expansion of the thermally expandable fine particles. manufacturing method.
[3] The method for producing a nonwoven fabric for sound absorbing material or heat insulating material according to [1] or [2], wherein the nonwoven fabric substrate fibers are discontinuous fibers having a fineness of 0.8 to 30 dtex.
[4] The method for producing a nonwoven fabric for sound absorbing or heat insulating material according to any one of [1] to [3], wherein the fibers having a lower melting point than the nonwoven fabric base fibers have a fineness of 1.0 to 20 dtex.
[5] The method for producing a nonwoven fabric for sound absorbing material or heat insulating material according to any one of [1] to [4], wherein the thermally expandable fine particles have a median particle size of 20 to 70 μm.
[6] Comprising thermally bonded nonwoven fabric substrate fibers and internal hollow resin capsules present in a dispersed state between the nonwoven fabric substrate fibers, having a thickness of 5 mm or more and a bulk density of 0.001 to 0.050 g. /cm ³ for sound absorbing or heat insulating non-woven fabrics.
[7] The nonwoven fabric for sound absorbing or heat insulating material according to [6], wherein the nonwoven fabric substrate fibers are discontinuous fibers having a fineness of 0.8 to 30 dtex.
[8] The inner hollow resin capsules have an average median particle diameter of 170 to 200 μm, a content of the inner hollow resin capsules per unit area of 2000/cm ² or less, and an air permeability of 50.0 cc/cm. The nonwoven fabric for sound absorbing or heat insulating material according to [6] or [7], which is cm ² ·sec or less.
[9] The nonwoven fabric for sound absorbing or heat insulating material according to any one of [6] to [8], wherein the thermal bond nonwoven fabric has a normal incident sound absorption coefficient at 1600 to 5000 Hz of 0.300 or more.

According to the present invention, a nonwoven fabric substrate obtained by mixing and thermally bonding nonwoven fabric substrate fibers and fibers having a lower melting point than the nonwoven fabric substrate fibers is impregnated with a coating liquid containing thermally expandable fine particles, and the heat By expanding the expandable fine particles to make the thickness of the non-woven fabric base material 5 mm or more, and by setting the content of the thermally expandable fine particles after expansion to 20 g/m ² or less, weight reduction is facilitated, It is possible to produce a nonwoven fabric for a sound absorbing material or a heat insulating material that can achieve both excellent sound absorbing properties or heat insulating properties and prevention of falling powder.

FIG. 1 is a graph showing the normal incident sound absorption coefficient measurement results of nonwoven fabrics for sound absorbing or heat insulating materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4. FIG. FIG. 2 is a stereomicrograph of the surface of the nonwoven fabric for sound absorbing material or heat insulating material obtained in Example 4. FIG. FIG. 3 is a stereomicrograph of the cross section of the nonwoven fabric for sound absorbing material or heat insulating material obtained in Example 4. FIG. 4 is a stereoscopic micrograph of the surface of the nonwoven fabric for sound absorbing material or heat insulating material obtained in Comparative Example 5. FIG. FIG. 5 is a stereomicrograph of the cross section of the nonwoven fabric for sound absorbing material or heat insulating material obtained in Comparative Example 5. As shown in FIG. FIG. 6 is a stereomicrograph of the surface of the nonwoven fabric for sound absorbing material or heat insulating material obtained in Comparative Example 6. FIG. 7 is a stereomicrograph of a cross section of the nonwoven fabric for sound absorbing or heat insulating material obtained in Comparative Example 6. FIG. FIG. 8 is a graph showing the measurement results of the heat insulation performance of the sound absorbing or heat insulating nonwoven fabrics obtained in Example 5 and Comparative Example 7. FIG.

The method for producing a nonwoven fabric for a sound absorbing material or a heat insulating material according to the present invention includes: A coating liquid containing thermally expandable fine particles is impregnated and heat-treated to expand the thermally expandable fine particles to make the thickness of the nonwoven fabric base material 5 mm or more, while the content of the thermally expandable fine particles after expansion is reduced to It is characterized by being 20 g/m ² or less. The present invention will be described in detail below.

<<Nonwoven base material>>
The nonwoven fabric substrate constituting the nonwoven fabric for sound absorbing material or heat insulating material of the present invention contains nonwoven fabric substrate fibers and low-melting-point fibers. When the nonwoven fabric substrate is heat-processed, part or all of the low melting point fibers contained in the nonwoven fabric substrate are thermally melted, and the intersections of the fibers contained in the nonwoven substrate are bonded (fused) and bonded by thermal bonding. be able to.

<Nonwoven fabric base fiber>
Non-woven fabric substrate fibers include, for example, natural fibers, regenerated fibers, and synthetic fibers. Specifically, for example, natural fibers such as cotton, hemp, wool, and silk; regenerated fibers such as rayon, polynosic, cupra, and leyocell; semi-synthetic fibers such as acetate fibers and triacetate fibers; polyamides such as nylon 6 and nylon 66. Fiber; polyester fiber such as polyethylene terephthalate fiber, polybutylene terephthalate fiber, polylactic acid fiber, polyarylate fiber; acrylic fiber such as polyacrylonitrile fiber, polyacrylonitrile-vinyl chloride copolymer fiber; polyolefin fiber such as polyethylene fiber and polypropylene fiber polyvinyl alcohol fibers such as vinylon fibers and polyvinyl alcohol fibers; polyvinyl chloride fibers such as polyvinyl chloride fibers, vinylidene fibers and polychloral fibers; synthetic fibers such as polyurethane fibers; polyethers such as polyethylene oxide fibers and polypropylene oxide fibers A system fiber etc. can be illustrated.

The melting point of the non-woven fabric substrate fiber is preferably higher than the melting point of the low-melting-point fiber described later by, for example, 30° C. or more, and more preferably 50° C. or more. If the melting point difference becomes small, depending on the heating conditions, both the nonwoven fabric substrate fibers and the low melting point fibers may melt or soften and the entire nonwoven fabric substrate may solidify when heat treatment is performed to melt the low melting point fibers. Alternatively, neither the non-woven fabric substrate fibers nor the low-melting-point fibers are melted or softened, and there is a possibility that the bonding strength of the fibers in the non-woven fabric substrate may be weakened, which is not preferable.

Non-woven fabric substrate fibers are preferably discontinuous fibers (so-called short fibers) because they have a high degree of freedom of movement. If the non-woven fabric substrate fibers are discontinuous fibers, they are preferable because they do not hinder the thermal expansion of the thermally expandable fine particles. The fiber length of the nonwoven fabric substrate fibers is preferably 200 mm or less, more preferably 100 mm or less, and preferably 10 mm or more, more preferably 30 mm or more.

The fineness of the nonwoven fabric substrate fiber is preferably 0.8 dtex or more, more preferably 1.0 dtex or more, still more preferably 1.1 dtex or more, preferably 30 dtex or less, more preferably 22 dtex or less, and still more preferably. is 15 dtex or less, more preferably 10 dtex or less, and particularly preferably 6 dtex or less. It is preferable that the fineness of the nonwoven fabric substrate fiber is equal to or higher than the above-mentioned lower limit, since sufficient strength as a nonwoven fabric substrate can be obtained. If the fiber fineness of the nonwoven fabric base material is equal to or less than the above upper limit, the nonwoven fabric base material has low air permeability, which is preferable in terms of sound absorption or heat insulation. Furthermore, if the fiber fineness of the nonwoven fabric base material is equal to or less than the above upper limit, the number of fibers in the nonwoven fabric base material is appropriately increased, so that the thermally expandable fine particles are easily distributed uniformly in the nonwoven base material, and the thermal expansion is reduced. When the fine particles are thermally expanded, the fibers can move flexibly, so that expansion is less likely to be inhibited, which is preferable.

As the nonwoven fabric substrate fiber, one type of nonwoven fabric substrate fiber or a combination of multiple types of nonwoven fabric substrate fibers can be used.

<Low melting point fiber>
The low-melting-point fiber will be described. In the present specification, the low-melting-point fiber refers to a heat-fusible fiber having a melting point of 80° C. or higher and 200° C. or lower, for example, a melting point of 80° C. or higher, more preferably 95° C. or higher, further preferably 110° C. or higher. Fibers having a temperature of preferably 120° C. or higher and 200° C. or lower, more preferably 190° C. or lower, and still more preferably 180° C. or lower.

The melting point of the low-melting-point fiber is preferably lower than the maximum expansion temperature of the thermally expandable fine particles, which will be described later. If the melting point of the low-melting-point fibers is lower than the maximum expansion temperature of the thermally expandable fine particles, the low-melting-point fibers thermally bonding the fiber web will melt first when the thermally expandable fine particles expand due to heating. The thermally expandable fine particles can expand without being blocked by the fibers.

The low-melting-point fibers may be those normally used in the production of non-woven fabrics, and composite fibers having a core-sheath structure, an eccentric structure, or a side-by-side structure in which a plurality of resins having different melting points are combined; modified polyester fibers; modified polyamides. Fiber: Modified polyolefin fiber such as modified polypropylene fiber can be used. Combinations of resins used for the conjugate fibers include polyolefin-based combinations such as polyethylene-polypropylene and polypropylene-modified polypropylene, as well as polyethylene-polyester, polyester-modified polyester, nylon-modified nylon and the like. In addition, in the case of a composite fiber obtained by combining a plurality of resins, at least one of the plurality of resins may have a melting point within the range of the low melting point fiber. Also, depending on the melting point, a low-melting-point fiber made of a single resin can be used. Among them, conjugate fibers having a core-sheath structure are preferable because of their high productivity and easy availability, but low-melting-point fibers made of a single resin are also acceptable.

The fineness of the low melting point fiber is preferably 1.0 dtex or more, more preferably 1.1 dtex or more, still more preferably 1.2 dtex or more, preferably 20 dtex or less, more preferably 17 dtex or less, and still more preferably 5 dtex or less. When a plurality of low-melting-point fibers having different finenesses are included, the fineness of the low-melting-point fibers is obtained by a weighted average considering the ratio (mass basis) of the low-melting-point fibers of each fineness. If the fineness of the low-melting-point fiber is at least the above lower limit, it is preferable because sufficient strength as a nonwoven fabric base material can be obtained and adhesion and bonding between fibers can be strengthened by thermal bonding. If the fineness of the low-melting-point fiber is equal to or less than the above upper limit, the nonwoven fabric substrate will have low air permeability, which is preferable in terms of sound absorption or heat insulation. Furthermore, if the fineness of the low-melting-point fiber is equal to or less than the above upper limit, the number of fibers in the nonwoven fabric substrate will be appropriately increased, so that the thermally expandable fine particles can be easily distributed uniformly in the nonwoven fabric substrate. Since the fibers can move flexibly when the fine particles expand, the thermal expansion is less likely to be inhibited, which is preferable. Due to these advantages, the nonwoven fabric for sound absorbing material or heat insulating material of the present invention is bulky even though the content of thermally expandable fine particles is small, and furthermore, it is possible to achieve both low bulk density and low air permeability, which are normally contradictory. can be done.

The blending ratio of the low-melting-point fiber is preferably 5% by weight or more, more preferably 10% by weight or more, and still more preferably 15% by weight or more, based on 100% by weight of the nonwoven fabric substrate. The upper limit is, for example, preferably 95% by weight or less, more preferably 80% by weight or less, and even more preferably 60% by weight or less. If the blending ratio of the low-melting-point fiber is less than the above lower limit, it is not preferable because the fibers cannot be firmly adhered or bonded. On the other hand, if the blending ratio of the low-melting-point fiber exceeds the above upper limit, the nonwoven fabric substrate becomes unstable when expanded by the thermally expandable fine particles, making it difficult to control the thickness, which is not preferable.

The fiber length of the low melting point fiber is preferably 200 mm or less, more preferably 100 mm or less, and preferably 20 mm or more, more preferably 40 mm or more.

As the low-melting-point fiber, one type of low-melting-point fiber or a combination of multiple types of low-melting-point fibers can be used.

<Method for producing nonwoven fabric substrate>
The manufacturing method of the nonwoven fabric base material is based on two steps of forming a fibrous web and bonding the fibrous web. The steps of weighing, blending, and laminating the nonwoven fabric substrate fibers and the low-melting-point fibers in the fiber web forming step may be performed using a general manufacturing method. Any method of manufacturing a web can be used. According to the method for producing a short fiber web, the degree of freedom of movement of the fibers can be increased, and the expansibility of the nonwoven fabric due to the thermally expandable fine particles can be increased. As a method for forming the short fiber web, for example, the fibers to be used are weighed and blended, then carded using a carding machine, and then wrapped with a cross wrapper. The obtained short fiber web is thermally bonded by a thermal bonding method using the low-melting-point fibers.

Conditions such as heat treatment temperature and time for thermal bonding (thermal bonding) using low-melting-point fibers may be appropriately selected according to the required strength of the non-woven fabric base material. It may be less than the melting point of the material fiber. The heat treatment time is, for example, preferably 20 seconds to 3 minutes, more preferably 30 seconds to 2 minutes. The heat treatment temperature is preferably 150 to 210°C, more preferably 170 to 200°C.

As for the bonding of the fiber web, the strength necessary for the nonwoven fabric base material can be sufficiently obtained by bonding between the fibers using the low-melting-point fibers. (needle punch method, water punch method, etc.) may be provided. Particularly preferably, the needle punching method and the thermal bonding method are used in combination to entangle and bond the fibers.

When the entangling is performed by the needle punching method, the number of needles punched per unit area in the needle punching process is, for example, preferably 5 needles/cm ² or more, more preferably 10 needles/cm ² or more, and still more preferably 20 needles/cm ^{2 .} 100 lines/cm ² or less, more preferably 70 lines/cm ² or less, and even more preferably 50 lines/cm ² or less. It is preferable that the number of impregnations is within the above range, because an appropriate amount of the resin containing the thermally expandable fine particles can be contained in the nonwoven fabric substrate and expansion of the thermally expandable fine particles is not hindered.

When performing entangling by a needle punching method, the needle depth in the needle punching process is preferably 0 mm or more, more preferably 3 mm or more, still more preferably 5 mm or more, and 20 mm or less, more preferably 15 mm or less, still more preferably 12 mm. It is below.

<Characteristics of nonwoven fabric substrate>
Although the thickness of the nonwoven fabric substrate is not particularly limited, it is preferably 2.5 mm or more, more preferably 3.0 mm or more, and still more preferably 3.2 mm or more.

The basis weight of the nonwoven fabric substrate is preferably 50 g/m ² or more, more preferably 80 g/m ² or more, still more preferably 100 g/m ² or more, and preferably 400 g/m ² or less, more preferably 350 g/m 2 or more. m ² or less, more preferably 300 g/m ² or less. If the fabric weight of the non-woven fabric substrate is within the above range, the content of the thermally expandable fine particles is at least, and due to the expansion of the thermally expandable fine particles, the bulk density is small, the air permeability is small, and the sound absorption has sound absorption properties or heat insulation properties. It is preferable because it is possible to obtain a nonwoven fabric for a material or a heat insulating material.

The bulk density of the nonwoven fabric substrate is preferably 0.020 g/cm ³ or more, more preferably 0.025 g/cm ³ or more, and preferably 0.070 g/cm ³ or less, more preferably 0.065 g/cm ³ . It is below.

<<Coating liquid>>
Next, the coating liquid with which the nonwoven fabric substrate is impregnated will be described. The coating liquid contains thermally expandable fine particles and their dispersion medium, and preferably further contains an adhesive component such as a thermoplastic resin. By impregnating the nonwoven fabric base material with the coating liquid, the thermally expandable fine particles can be attached (preferably adhered) to the nonwoven fabric fibers.

<Thermal expandable particles>
Thermally expandable fine particles are microcapsules in which a vaporizable liquid is encapsulated in a thermoplastic polymer. When heated, the thermoplastic polymer forming the outer shell of the thermally expandable fine particles is softened, and at the same time, the evaporative liquid contained therein is gasified, increasing the internal pressure and expanding the thermally expandable fine particles. This state is sometimes referred to as an internal hollow resin capsule. In the nonwoven fabric for sound absorbing material or heat insulating material of the present invention, the expansion of the thermally expandable fine particles widens the spaces between the fibers of the nonwoven fabric to obtain bulkiness.

As the vaporizable liquid, a liquid that is liquid at room temperature and vaporizes at the expansion start temperature can be appropriately used, and hydrocarbons are preferable.

The coefficient of thermal expansion of the thermally expandable fine particles is preferably 2 or more, more preferably 3 or more when expressed as the ratio of the diameter _D2 after expansion to the diameter _D1 before expansion ( _D2 / _D1 ). It is preferably 3.5 or more, preferably 5.5 or less, more preferably 5 or less, and still more preferably 4.5 or less. By adjusting the coefficient of thermal expansion within the above range, it is possible to obtain a nonwoven fabric for a sound absorbing material or a heat insulating material that achieves both high bulkiness and low air permeability, which normally contradict each other.

The average median particle size of the thermally expandable fine particles in an unexpanded state is 20 µm or more, more preferably 25 µm or more, still more preferably 30 µm or more, and 70 µm or less, more preferably 65 µm or less, and still more preferably 60 µm or less. is. If the average median particle size of the thermally expandable fine particles exceeds the upper limit, there is a risk that the thermally expandable fine particles will not be able to uniformly attach or adhere to the nonwoven fabric base material, or that the thermally expandable fine particles will fall off from the nonwoven fabric for sound absorbing or heat insulating materials. It's likely to get easier. If the average particle size of the heat-expandable fine particles is below the lower limit, the coefficient of expansion of the nonwoven fabric to which the heat-expandable fine particles are adhered or adhered will be small, so there is a risk that the nonwoven fabric will not have a sufficiently low bulk density.

The average median particle size of the thermally expandable fine particles can be measured, for example, with a laser diffraction particle size distribution analyzer (“SALD-2300” manufactured by Shimadzu Corporation).

The expansion start temperature of the thermally expandable fine particles is preferably 70° C. or higher, more preferably 90° C. or higher, and still more preferably 100° C. or higher. Also, the maximum expansion temperature of the thermally expandable fine particles is preferably 200° C. or lower, more preferably 180° C. or lower, and still more preferably 165° C. or lower. If the thermal expansion starting temperature of the thermally expandable fine particles is lower than the above lower limit, the thermally expandable fine particles may further expand under the influence of heat when the nonwoven fabric of the present invention is used as a heat insulating material, or the outer shell may collapse due to excessive expansion. becomes thinner, the vaporizable liquid inside permeates and diffuses, and the tension and external pressure of the thermoplastic polymer forming the outer shell overcome the internal pressure, causing the nonwoven fabric to shrink, and the thickness of the nonwoven fabric may change.

The solvent for dispersing the thermally expandable fine particles may be, for example, an organic solvent system or an aqueous medium, preferably an aqueous medium. The aqueous medium is a medium containing at least water, and may be water only. Water and alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone; may be a mixed solvent of

The concentration of the thermally expandable fine particles to be contained in the coating liquid may be appropriately selected according to the basis weight of the nonwoven fabric substrate to be used. It is preferably 7 g/L or more, preferably 35 g/L or less, more preferably 30 g/L or less, and still more preferably 27 g/L or less. Since the nonwoven fabric for sound absorbing or heat insulating material of the present invention uses a nonwoven fabric base material produced by the thermal bonding method, expansion is not hindered, and even if the content of thermally expandable fine particles in the coating liquid impregnated layer is small, the bulk can be increased. The concentration of the thermally expandable particles contained in the liquid can be reduced to the above range.

<Adhesive component>
Adhesive components in the coating liquid include thermoplastic resins.

The type of thermoplastic resin may be a general-purpose one, for example, acrylic resin containing structural units derived from (meth)acrylic acid and/or (meth)acrylic acid ester; vinyl acetate containing structural units derived from vinyl acetate vinyl chloride resins containing structural units derived from vinyl chloride; synthetic rubber resins such as butadiene-styrene, butadiene-acrylonitrile, and chloroprene resins; polyester resins; urethane resins; These resins can be used alone or in combination of two or more. Among them, vinyl acetate-based resins of copolymers (including tertiary or higher multi-component copolymers) having structural units derived from vinyl acetate and structural units derived from ethylene are preferable from the viewpoint of weldability and flexibility. Acrylic resins are preferred in terms of adhesiveness and availability.

The glass transition temperature of the thermoplastic resin used as the adhesive component in the coating liquid is preferably -30 to 50°C, more preferably -20 to 40°C.

The thermoplastic resin may be contained in the coating liquid as an emulsion.

The thermoplastic resin emulsion may be an organic solvent-based emulsion, but is preferably an aqueous medium emulsion. Even when the resin is composed of a plurality of (co)polymers, a uniform resin emulsion can be easily obtained by mixing and stirring the emulsions. In addition, if the emulsion is an aqueous medium, the resulting resin emulsion can have a low viscosity and is environmentally friendly. In addition, the same solvent as the solvent for dispersing the thermally expandable fine particles may be used.

The content of the thermoplastic resin is preferably 2 to 10% by mass, more preferably 3 to 9% by mass, still more preferably 4 to 7% by mass, based on 100% by mass of the coating liquid.

<Method for preparing coating solution>
The method for preparing the coating liquid of the present invention is not particularly limited, and a general method such as stirring the thermally expandable fine particle solution and the thermoplastic resin emulsion with a stirrer or the like so as to achieve the above-mentioned ratio can be used. It can be prepared by mixing. Moreover, a solvent such as water may be appropriately mixed.

<<Nonwoven fabric for sound absorbing material or heat insulating material>>
The nonwoven fabric for sound absorbing material or heat insulating material of the present invention can be easily reduced in weight, and has properties of achieving both excellent sound absorbing property or heat insulating property and prevention of falling powder.

<Method for producing nonwoven fabric for sound absorbing material or heat insulating material>
The nonwoven fabric for sound absorbing material or heat insulating material of the present invention is prepared by impregnating the thermally bonded nonwoven fabric substrate with a coating liquid containing the thermally expandable fine particles to prepare a thermally bonded nonwoven fabric, and the thermally expandable nonwoven fabric in the thermally bonded nonwoven fabric. It can be manufactured by expanding microparticles.

The impregnation of the nonwoven fabric substrate with the coating liquid may be carried out by a general method such as a so-called dipping method in which the nonwoven fabric substrate is immersed in a container containing the coating liquid. After impregnation with the coating liquid, excess impregnated coating liquid is removed by a method such as squeezing with a moderate pressure using a mangle roll, and then dried. Examples of the drying method include general methods such as air drying and heat treatment, and the conditions for the heat treatment are not particularly limited as long as the conditions are such that the coating liquid can be dried. are carried out at the same time, conditions may be appropriately selected so that the nonwoven fabric base material has a predetermined thickness due to the expansion of the thermally expandable fine particles. When the drying and the expansion of the thermally expandable fine particles in the coating liquid are performed at different timings, the conditions under which the coating liquid is dried and the temperature at which the thermally expandable fine particles begin to expand may be appropriately selected.

The drying temperature is, for example, preferably 80° C. or higher, more preferably 90° C. or higher, still more preferably 120° C. or higher, and preferably 220° C. or lower, more preferably 210° C. or lower, and still more preferably 200° C. ℃ or less. The drying time is, for example, preferably 30 seconds or longer, more preferably 1 minute or longer, still more preferably 2 minutes or longer, preferably 5 minutes or shorter, more preferably 4.5 minutes or shorter, and still more preferably. is less than 4 minutes.

The expansion of the thermally expandable fine particles by heat treatment may be performed simultaneously with the drying of the coating liquid as described above, or may be performed at a different timing. When the drying and the expansion of the thermally expandable fine particles in the coating liquid are performed at different timings, the heat treatment conditions in the expansion step are equal to or higher than the expansion start temperature of the thermally expandable fine particles, and The treatment time may be appropriately selected so that the nonwoven fabric substrate has a predetermined thickness at a temperature below the melting point of the fiber.

The expansion temperature in the nonwoven fabric expansion step is, for example, preferably 20° C. or more higher than the melting point of the low melting point fiber, more preferably 30° C. or more higher than the melting point, and 30° C. higher than the expansion start temperature of the thermally expandable fine particles. It is preferably 40° C. or higher, more preferably 40° C. or higher, and preferably 30° C. or higher, more preferably 40° C. or higher than the melting point of the nonwoven fabric base fiber.

The fixed amount (resin basis weight) of the coating liquid to the nonwoven fabric for sound absorbing material or heat insulating material is preferably 20 g/m ² or more, more preferably 30 g/m ² or more, and still more preferably 40 g/m 2 in terms of solid content. ² or more, preferably 120 g/m ² or less, more preferably 100 g/m ² or less, and still more preferably 90 g/m ² or less. When the resin basis weight is within the above range, the thermally expandable fine particles do not fall off and the expansion of the thermally expandable fine particles is not hindered.

The mass ratio of the thermoplastic resin (solid content) to the thermally expandable fine particles (thermoplastic resin (solid content)/thermally expandable fine particles) fixed to the nonwoven fabric for sound absorbing material or heat insulating material is preferably 1.0 or more, and more It is preferably 1.5 or more, more preferably 2.0 or more, still more preferably 2.3 or more, and although the upper limit is not particularly limited, it is preferably 10.0 or less, more preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less. If the blending ratio of the thermally expandable fine particles is too high, the resin cannot sufficiently fix the thermally expandable fine particles to the nonwoven fabric base material, and the heat expandable fine particles may drop off from the base material. On the other hand, if the blending ratio of the heat-expandable fine particles is too low, the expansion of the nonwoven fabric substrate will be insufficient, and there is a risk that a sound absorbing or heat insulating nonwoven fabric having a predetermined thickness will not be obtained.

<Characteristics of Nonwoven Fabric for Sound Absorbing Material or Heat Insulating Material>
The thickness of the nonwoven fabric for sound absorbing material or heat insulating material is preferably 5 mm or more, more preferably 8 mm or more, still more preferably 10 mm or more, and even more preferably 12 mm or more. A nonwoven fabric having a low bulk density can be obtained by setting the thickness to the above lower limit or more.

The total basis weight of the nonwoven fabric for sound absorbing material or heat insulating material is preferably 110 g/m ² or more, more preferably 120 g/m ² or more, still more preferably 125 g/m ² or more, and preferably 500 g/m ² or less. , more preferably 400 g/m ² or less, still more preferably 350 g/m ² or less. If the total basis weight is below the lower limit, it becomes difficult to maintain the desired thickness. If the total basis weight exceeds the above upper limit, it is not preferable in terms of reducing the weight of the nonwoven fabric.

The bulk density of the nonwoven fabric for sound absorbing material or heat insulating material is preferably 0.001 g/cm ³ or more, more preferably 0.003 g/cm ³ or more, still more preferably 0.005 g/cm ³ or more. It is more preferably 0.010 g/cm ³ or more, preferably 0.050 g/cm ³ or less, more preferably 0.045 g/cm ³ or less, still more preferably 0.035 g/cm ³ or less. More preferably, it is 0.030 g/cm ³ or less. If the bulk density is within the above range, the nonwoven fabric is lightweight, and is therefore advantageous when incorporated in equipment or the like as a sound absorbing material or heat insulating material.

The content of the thermally expandable fine particles after expansion, that is, the content of the internal hollow resin capsules in the nonwoven fabric for sound absorbing material or heat insulating material is 20 g/m ² or less, more preferably 18 g/m ² or less, and still more preferably 18 g/m 2 or less. It is 17 g/m ² or less, preferably 0.5 g/m ² or more, more preferably 1.0 g/m ² or more, still more preferably 1.5 g/m ² or more. Since the nonwoven fabric for sound absorbing or heat insulating material of the present invention uses a nonwoven fabric base material produced by the thermal bonding method, the expansion is not inhibited. It is preferable because it is possible to achieve both low air permeability (that is, high sound absorption or high heat insulation) and bulkiness, which are normally contradictory. In addition, since the content of the thermally expandable fine particles after expansion is as small as in the above range, powder drop does not occur, which is preferable.

The average median particle diameter of the internal hollow resin capsules contained in the nonwoven fabric for sound absorbing material or heat insulating material is 170 μm or more, more preferably 173 μm or more, still more preferably 175 μm or more, and 200 μm or less, more preferably 198 μm. 195 μm or less, more preferably 195 μm or less. By adjusting the average median particle size of the inner hollow resin capsules contained in the nonwoven fabric for sound absorbing or heat insulating materials within the above range, a nonwoven fabric for sound absorbing or heat insulating materials that achieves both high bulkiness and low air permeability, which are usually contradictory. can be done.

The content of internal hollow resin capsules contained in the nonwoven fabric for sound absorbing material or heat insulating material is preferably 1000/cm ² or more, more preferably 1100/cm ² or more, and still more preferably 1200/cm 2 or more per unit area. cm ² or more, more preferably 1300/cm ² or more, 2000/cm ² or less, more preferably 1950/cm ² or less, still more preferably 1900/cm ² or less, More preferably, it is 1800/cm ² or less. If the content of the internal hollow resin capsules contained in the nonwoven fabric for sound absorbing or heat insulating material is within the above range, a nonwoven fabric for sound absorbing or heat insulating material that achieves both high bulkiness and low air permeability, which normally contradict each other, can be obtained.

The air permeability of the nonwoven fabric for sound absorbing material or heat insulating material is preferably 1.0 cc/cm ² ·sec or more, more preferably 1.5 cc/cm ² ·sec or more, still more preferably 2.0 cc/cm ² ·sec. sec or more, more preferably 2.5 cc/cm ² ·sec or more, preferably 50.0 cc/cm ² ·sec or less, more preferably 30.0 cc/cm ² ·sec or less, still more preferably It is 10.0 cc/cm ² ·sec or less, and more preferably 8.0 cc/cm ² ·sec or less. If the air permeability is within the above range, high sound absorption performance or heat insulation performance can be obtained.

The nonwoven fabric for sound absorbing material or heat insulating material of the present invention exhibits excellent sound absorbing performance with a normal incident sound absorption coefficient of 0.300 or more at 1600 to 5000 Hz. In addition, the nonwoven fabric for sound absorbing material or heat insulating material of the present invention exhibits excellent heat insulating performance.
[Sound Absorption Performance] Complies with JIS A1405-2 (vertical incident sound absorption coefficient).

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be modified appropriately within the scope that can conform to the gist of the above and later descriptions. It is of course possible to implement them, and all of them are included in the technical scope of the present invention.

Evaluations adopted in Examples and Comparative Examples are as follows.
1. Metsuke: Conforms to JIS L1913 6.2.
2. Thickness: Measured with vernier calipers.
3. Bulk Density: Convert basis weight/thickness into units.
4. Air permeability: Measured with a Kato Tech Co., Ltd. air permeability tester (type: KES-F8).
5. Sound absorption performance: conforms to JIS A1405-2 (vertical incident sound absorption coefficient).
6. Insulation performance: A box with an open top made of polystyrene foam with bottom and side walls with outer dimensions of 90 x 130 x total height of 110 mm and inner dimensions of 60 x 100 x depth of 95 mm, so as to cover the entire top opening Place the sample nonwoven fabric on the Then, a 125 W infrared light bulb is used as a heat source, and a light intensity of 10,000 lux is applied from 20 cm vertically above the sample nonwoven fabric, and the temperature change over time inside the box is measured. However, the measurement is performed in an atmosphere with a temperature of 25° C. and a relative humidity of 65% RH.

Example 1
70% by weight of polyester fiber with a fineness of 1.3 dtex, a fiber length of 38 mm, and a melting point of 255°C, and a low melting point polyester with a fineness of 2.2 dtex, a fiber length of 51 mm, and a core-sheath structure with a core melting point of 255°C and a sheath melting point of 130°C. After weighing 30% by weight of fibers (core: PET, sheath: denatured PET), the fiber web obtained by blending, carding, and cross-laminating was needle-punched with a needle punching number of 40/cm ² and a needle depth of 6 mm. , and heated for 30 seconds in a heat treatment machine with a set temperature of 170°C to obtain a thermal bond nonwoven fabric base material for nonwoven fabric for sound absorbing material or heat insulating material having a basis weight of 245 g/m ² .
To 70 parts by mass of water, 1 part by mass of thermally expandable fine particles (median particle diameter 50 μm; manufactured by Matsumoto Yushi) having a thermal expansion start temperature of 100° C. and a maximum expansion temperature of 160° C., and 50% by weight of ethylene-vinyl acetate A coating liquid was prepared by dispersing 6 parts by weight of a polymer emulsion (manufactured by Sumika Chemtex) and 4 parts by weight of a 50% by weight acrylic emulsion (manufactured by DIC). The thermal bond nonwoven fabric substrate (basis weight: 245 g/m ² ) for sound absorbing or heat insulating nonwoven fabric was impregnated in the coating liquid, then squeezed with a mangle roll pressure of 3 kg/cm ² , and the temperature inside the dryer was 160°C. A nonwoven fabric for sound absorbing or heat insulating material having a basis weight of 334 g/m ² , a thickness of 15 mm and a bulk density after expansion of 0.022 g/cm ³ was produced by drying with hot air for 3 minutes in an atmosphere of . Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Example 2
A nonwoven fabric for sound absorbing or heat insulating material was produced in the same manner as in Example 1, except that the basis weight of the thermal bond nonwoven fabric substrate for nonwoven fabric for sound absorbing or heat insulating material was changed as shown in Table 1. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Example 3
Example 1 except that the basis weight of the thermal bond nonwoven fabric substrate for nonwoven fabric for sound absorbing material or heat insulating material was changed as shown in Table 1, and the thermally expandable fine particles were changed to 2 parts by mass when preparing the coating solution. A nonwoven fabric for sound absorbing material or heat insulating material was produced in the same manner. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Comparative example 1
A needle-punch spunbond long-fiber nonwoven fabric (“Bolance 4101N” manufactured by Toyobo Co., Ltd.; weight per unit area: 100 g/m ² , thickness: 1.4 mm) was used as the base material instead of the thermal bonded nonwoven fabric base material for nonwoven fabrics for sound absorbing or heat insulating materials. A nonwoven fabric for a sound absorbing material or a heat insulating material was produced in the same manner as in Example 1, except that it was used. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Comparative example 2
70% by weight of polyester fiber with a fineness of 1.8 dtex and a fiber length of 51 mm and 30% by weight of a polyester fiber with a fineness of 3.3 dtex and a fiber length of 51 mm were weighed, blended, and laminated to produce a fiber web with a number of yarns of 250/cm ² . Needle-punched with a needle depth of 8 mm to obtain a needle-punched nonwoven fabric base material for sound absorbing or heat insulating nonwoven fabric having a basis weight of 100 g/m ² .
Example 1, except that the needle-punched nonwoven fabric substrate (basis weight: 100 g/m ² ) for sound absorbing or heat insulating nonwoven fabric was used instead of the thermal bond nonwoven fabric substrate for sound absorbing or heat insulating nonwoven fabric. A nonwoven fabric for a sound absorbing material or a heat insulating material was produced in the same manner as above. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Comparative example 3
A nonwoven fabric for a sound absorbing material or a heat insulating material was produced in the same manner as in Comparative Example 1, except that the amount of thermally expandable fine particles during preparation of the coating liquid was changed to 10 parts by mass. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

Comparative example 4
A nonwoven fabric for a sound absorbing material or a heat insulating material was produced in the same manner as in Comparative Example 2, except that the amount of thermally expandable fine particles during preparation of the coating liquid was changed to 10 parts by mass. Tables 1 and 2 and FIG. 1 show the properties of the produced nonwoven fabric for sound absorbing material or heat insulating material.

The nonwoven fabrics for sound absorbing material or heat insulating material of Examples 1 to 3 all have a small content of thermally expandable fine particles after expansion, ie, internal hollow resin capsules, but have a large thickness expansion and a small bulk density. can be formed, and the sound absorption coefficient at 1600 to 5000 Hz is as high as 0.300 or more, and it also has good sound absorption performance. On the other hand, in the nonwoven fabrics for sound absorbing material or heat insulating material of Comparative Examples 1 and 2, since the nonwoven fabric base material is not produced by the thermal bond manufacturing method, the coating liquids of Examples 1 and 2 having the same concentration of thermally expandable fine particles were used. Compared to nonwoven fabrics for sound absorbing materials or heat insulating materials, the thickness expansion is small, the bulk density is high, and the sound absorbing performance is inferior. In the nonwoven fabrics for sound absorbing material or heat insulating material of Comparative Examples 3 and 4, the concentration of the thermally expandable fine particles in the coating liquid used is about 9.2 times that of Comparative Examples 1 and 2. Although it is slightly better than 1 to 2, it has less thickness expansion than Examples 1 to 3, has a higher bulk density, and is inferior in sound absorption performance.

Example 4
Enlarged photographs of the surface and cross section of the nonwoven fabric for sound absorbing material or heat insulating material produced in Example 3 were taken using a coded stereomicroscope ("M125C" manufactured by Leica). Photographed images are shown in FIGS. In addition, based on the photograph of the surface of the nonwoven fabric for sound absorbing material or heat insulating material, the internal hollow resin capsule content per unit area in the nonwoven fabric for sound absorbing material or heat insulating material was measured. Table 3 shows the measurement results.

Comparative Examples 5 and 6
As in Example 4, photographs of the surfaces and cross sections of the nonwoven fabrics for sound absorbing or heat insulating materials of Comparative Examples 1 and 3 were taken, and the internal hollow resin capsule content was measured. Photographic images are shown in FIGS. 4 to 7, and measurement results are shown in Table 3.

As shown in FIGS. 2 and 3, in the nonwoven fabric for sound absorbing material or heat insulating material of Example 4, internal hollow resin capsules are uniformly dispersed throughout the nonwoven fabric. On the other hand, in the sound absorbing or heat insulating nonwoven fabric of Comparative Example 5 (FIGS. 4 and 5), internal hollow resin capsules are scattered along the entanglement of the nonwoven fabric, and there are many voids. In other words, the sound absorbing or heat insulating nonwoven fabric of Comparative Example 5 has a large number of voids, so it has high air permeability and is inferior in sound absorbing performance or heat insulating performance. In addition, since the nonwoven fabric for sound absorbing material or heat insulating material of Comparative Example 6 (FIGS. 6 and 7) is produced by being impregnated with a coating liquid having a high concentration of thermally expandable fine particles, the fibers are covered so that they cannot be seen. The inner hollow resin capsules are dense. In other words, the nonwoven fabric for sound absorbing material or heat insulating material of Comparative Example 6 may fall off as powder.

Example 5
Using the nonwoven fabric for sound absorbing material or heat insulating material produced in Example 3, the heat insulating performance was measured. The results are shown in Table 4 and FIG.

Comparative example 7
The heat insulating performance was measured in the same manner as in Example 5 using the thermal bond nonwoven fabric base material for the sound absorbing or heat insulating nonwoven fabric of Example 3. The results are shown in Table 4 and FIG.

The nonwoven fabric for sound absorbing material or heat insulating material of Example 5 is impregnated with the thermally expandable fine particles of Comparative Example 7 and thermally bonded nonwoven fabric base for sound absorbing or heat insulating nonwoven fabric without expansion of the thermally expandable fine particles. The temperature rise after 15 minutes of light irradiation is suppressed by 34% compared to the material, and it can be said that the heat insulation performance is good.

Claims (9)

Non-woven fabric base fibers (excluding glass fibers) and fibers having a lower melting point than the non-woven fabric base fibers are mixed and thermally bonded to each other, and a volatile liquid is encapsulated in a thermoplastic polymer to form a microfiber. Thermally expandable fine particles that are capsules and a coating liquid containing a resin are impregnated, and the thermally expandable fine particles are expanded to make the thickness of the nonwoven fabric substrate 5 mm or more. A method for producing a nonwoven fabric for sound absorbing or heat insulating material, characterized in that the content is 20 g/m ² or less and the total basis weight is 400 g/m ² or less. 2. The method for producing a nonwoven fabric for a sound absorbing material or a heat insulating material according to claim 1, wherein the nonwoven fabric for a sound absorbing material or a heat insulating material has a bulk density of 0.001 to 0.050 g/cm ³ by expansion of the thermally expandable fine particles. . 3. The method for producing a sound absorbing or heat insulating nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric substrate fibers are discontinuous fibers having a fineness of 0.8 to 30 dtex. 4. The method for producing a nonwoven fabric for sound absorbing or heat insulating material according to any one of claims 1 to 3, wherein the fibers having a lower melting point than the nonwoven fabric base fibers have a fineness of 1.0 to 20 dtex. 5. The method for producing a nonwoven fabric for sound absorbing or heat insulating material according to claim 1, wherein the thermally expandable fine particles have a median particle diameter of 20 to 70 μm. It contains thermally bonded nonwoven fabric substrate fibers (excluding glass fibers), internal hollow resin capsules dispersed among the nonwoven fabric substrate fibers, and a resin, and has a thickness of 5 mm or more and a total basis weight. 400 g/m ² or less, and a bulk density of 0.001 to 0.050 g/cm ³ for sound absorbing or heat insulating nonwoven fabric. 7. The nonwoven fabric for sound absorbing or heat insulating material according to claim 6, wherein said nonwoven fabric substrate fibers are discontinuous fibers having a fineness of 0.8 to 30 dtex. The inner hollow resin capsules have an average median particle size of 170 to 200 μm, a content of the inner hollow resin capsules per unit area of 2000/cm ² or less, and an air permeability of 50.0 cc/cm ² ·. 8. The nonwoven fabric for sound absorbing material or heat insulating material according to claim 6 or 7, which has a thickness of sec or less. The nonwoven fabric for sound absorbing or heat insulating material according to any one of claims 6 to 8, wherein the nonwoven fabric for sound absorbing or heat insulating material has a normal incident sound absorption coefficient at 1600 to 5000 Hz of 0.300 or more.

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