JP2008231596A - Fiber structure having excellent sound absorbency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing material having excellent shape stability and moldability at a low cost while keeping the balance of the weight and the sound absorbing performance of the structure. <P>SOLUTION: The fiber structure having excellent sound absorbency is produced by an air laid process from (A) a pulp fiber and (B) a synthetic fiber composed mainly of a heat-adhesion synthetic fiber, wherein the mixing ratio of (A) pulp fiber to (B) synthetic fiber (A/B) is (0 to 100)/(85 to 15) by wt.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fiber structure having good sound absorption and also excellent in form stability and formability. More specifically, the present invention relates to home appliances, OA equipment, construction / civil engineering machines, industrial machines, The present invention relates to a fiber structure excellent in sound absorption that can be used to reduce noise in vehicles, houses, and highways.

  Conventionally, as sound absorption for vehicles, houses, highways, etc., glass wool, urethane foam, hard cotton made of synthetic fibers containing thermoplastic fibers (for example, see Patent Document 1) Composites in which spunbond nonwoven fabrics are integrated, nonwoven fabrics in which polyester fibers are mixed in meltblown fibers, and composites in which spunbond nonwoven fabrics are integrated on the surface thereof have been widely used. For example, as a sound-absorbing material for automobiles, in order to prevent engine noise from being emitted outside or inside the vehicle, a composite of hard cotton is used in parts such as ceiling materials, door trims, hood silencers, floor insulators, headlinings, trunk rims, and dash insulators. Body and melt blown composites are used.

  However, hard cotton made of synthetic fibers containing thermoplastic fibers does not have sufficient sound absorbing performance as a single unit. Therefore, the sound absorbing performance is improved as a composite in which the nonwoven fabric of the melt blow method or the spun bond method is integrated on the surface. Yes. On the other hand, the melt blown nonwoven fabric has good sound absorption performance when used alone or in its composite, but its shape stability is poor due to its low rigidity. For the purpose of improving shape stability, composites with embossed and spunbonded nonwoven fabrics integrated on the surface are also used, but the improvement of rigidity is insufficient, and the vehicle manufacturing process, houses, roads It is known that the workability at the construction site is extremely poor, and it takes time for construction.

  Furthermore, the composite of hard cotton made of synthetic fiber or the composite by the melt blow method has insufficient sheet forming characteristics. In composites of hard cotton made of synthetic fibers, most of the synthetic fibers are fixed with heat-adhesive fibers, and the degree of deformation during hot pressing or cold pressing during molding is low, and the level has not reached a practical level. . On the other hand, many composite structures by the melt blow method are mainly composed of polypropylene, so that the processing temperature cannot be raised during molding, and the molding cycle is low and economical production cannot be performed. In addition, the thickness of the fiber is extremely thin, the volume is reduced by molding, and there is a problem that it is difficult to secure a structure that exhibits good sound absorption performance.

  Furthermore, in recent years, soundproofing measures for environmental problems have become particularly important issues for vehicles, houses, highways, and the like. For example, in a vehicle, improvement in comfort in the vehicle is accompanied by a strong social demand in addition to improvement in fuel consumption, and low noise and light weight have become important targets for the vehicle. Therefore, in the above prior art, it is an extremely difficult theme to achieve both improvement in soundproofing performance and weight reduction.

  In the case of hard cotton using a short fiber nonwoven fabric, the weight of the sound absorbing material is reduced in order to reduce the weight, but it is difficult to use fibers having an average fineness of 1 decitex or less in production. Yes, sound absorption characteristics are poor. Further, when using a long-fiber non-woven fabric, the melt blow method makes fine denier in production, so that productivity is poor and it is difficult to produce economically. In addition, in any method for producing nonwoven fabrics, it is difficult to perform composite integration in a normal production line, and a separate composite process is performed, which is not an economically simple method.

Here, the sound absorption by the sound absorbing material of such a fiber structure uses viscous friction of air when sound is transmitted through the air in the fine gap, that is, the pressure in the fine gap (in the pore). It is said that the frictional resistance acts on the vibration of the air particles accompanying the fluctuation and the energy of the pressure fluctuation is converted into thermal energy. Therefore, the fiber diameter of the sound-absorbing material has a very important role. If the fiber diameter is the same, the finer gaps (pores) increase and the sound-absorbing effect is exhibited.
JP-A-7-3599

  The present invention has been found to solve the above problems, and economically provides a sound-absorbing material excellent in form stability and formability while balancing the weight of the structure and sound-absorbing performance. is there.

In the present invention, a fiber structure that satisfies the four elements of sound absorption, light weight, form stability, and moldability by utilizing the sound absorption characteristics of pulp fibers and combining with synthetic fibers mainly composed of heat-bonding synthetic fibers. As a body, the present invention has been achieved.
According to the present invention, “(A) Pulp fiber and (B) a fiber structure manufactured by an air raid method comprising synthetic fibers mainly composed of heat-bonding synthetic fibers, B) A fiber structure excellent in sound-absorbing property in which the mixing ratio with synthetic fibers is (A) pulp fibers / (B) synthetic fibers = 0 to 85/100 to 15% by weight ”is provided.
At that time, the basis weight of the fiber structure is 100 to 2,000 g / m ² , and the density is 0.01 to 0.20, so that the sound absorption, light weight, shape stability, and moldability are four. A fiber structure satisfying the elements can be obtained.
Moreover, the fiber structure of the present invention has an average fineness of 0.01 to 7 dtex, and by further integrating a nonwoven fabric having a basis weight of 8 to 100 g / m ² , further improvement in sound absorption characteristics and moldability can be achieved. .
Furthermore, the fiber structure of the present invention further integrates a film-like material having a basis weight of 5 to 100 g / m ² , a hole having a diameter of 2 mm or less, and a hole area of 15% to 50%. As a result, a further sound absorbing effect is exhibited.

  The fiber structure of the present invention can economically provide a sound-absorbing material excellent in form stability and moldability while balancing the weight and sound-absorbing performance.

Hereinafter, embodiments of the present invention will be described in detail.
The fiber structure of the present invention is a nonwoven fabric produced from (A) pulp fibers and (B) synthetic fibers by an air raid method.
Here, the nonwoven fabric by an air raid method can be obtained as follows.
That is, a predetermined amount of defibrated heat-adhesive synthetic fiber or a mixture mainly composed of pulverized pulp is conveyed while being uniformly dispersed in an air stream, and the fiber blown out from a screen having pores provided in a discharge part The fiber is deposited on the net while dropping into a metal or plastic net installed at the bottom and suctioning air at the bottom of the net. Next, the fiber structure of the present invention can be obtained by heat-treating the whole to a temperature at which the heat-adhesive synthetic fiber in the sheet sufficiently exhibits its adhesive effect. In order to fully exhibit the adhesive effect, heat treatment is required at a temperature 15 to 40 ° C. higher than the melting point of the adhesive component of the thermoadhesive synthetic fiber.

  Thus, the nonwoven fabric manufactured by the air raid method can three-dimensionally orient the fibers randomly in the flow direction, width direction, and thickness direction of the nonwoven fabric. This three-dimensional orientation structure greatly contributes to the development of good sound absorption. And since these are thermally bonded, delamination does not occur. Moreover, since the non-woven fabric manufactured by the air raid method has good uniformity, there is less variation in sound absorption performance. If necessary, chemical bond treatment, calendar treatment and emboss treatment can be further performed.

(A) Pulp fiber used in the present invention refers to natural pulp extracted from wood and other plants. Examples of the type of pulp to be used include wood pulp, hemp pulp, linter pulp, kenaf pulp and the like, and wood pulp is most preferable from the viewpoint of price and the like.
(A) As the pulp fiber, a pulverized pulp having a length of 0.2 mm to 5 mm is preferable. The fiber cross section of the pulverized pulp fiber is an atypical shape mainly having a flat shape, has a large surface area, and has a void inside. Further, the fiber diameter is distributed from several μm to several tens of μm, and plays a large role in forming a minute space. The cross-sectional structure and the minute space of the fiber greatly contribute to the good sound absorption of the fiber structure containing the pulp fiber.

  On the other hand, as the heat-adhesive synthetic fiber which is the main component of the component (B) mixed with the pulp fiber used in the present invention, any fiber may be used as long as it is melted by heat and bonded to each other. Although the pulp is fixed in a network structure by interfiber bonding, fibers using a polymer having a high affinity with the pulp fibers are particularly preferable. For example, polyolefins, polyolefins grafted with unsaturated carboxylic acids, copolymerized polyesters, polyvinyl alcohol and the like can be mentioned.

  Further, as the heat-adhesive synthetic fiber, a heat-adhesive conjugate fiber can also be used. As the heat-adhesive conjugate fiber, a core-sheath type or an eccentric side-by-side type conjugate fiber is suitable. Examples of the polymer constituting the sheath or the outer periphery of the fiber include polyethylene and polypropylene. As the polymer constituting the core component or the fiber inner layer part, a polymer having a melting point higher than that of the sheath and not changing at the heat bonding treatment temperature is preferable. Examples of such combinations include polyethylene / polypropylene, polyethylene / polyester, polypropylene / polyester, and the like. These polymers may be modified as long as they do not impair the action / effect of the present invention.

  When the average fineness of the heat-adhesive synthetic fiber is thin, the number of constituent fibers increases, so that the number of fallen fibers decreases and the texture becomes soft. When it is thick, the gap between the fibers becomes large, resulting in a bulky nonwoven fabric and a sound absorbing effect can be expected. Therefore, the thickness of the fiber may be selected according to the application, but the preferred fineness is 0.5 dtex to 50 dtex, and more preferably 0.8 dtex to 30 dtex. If it exceeds 50 dtex, it is not preferable because the falling of the pulp cannot be suppressed. On the other hand, if it is less than 0.5 dtex, it is not practical because the productivity of the nonwoven fabric is lacking.

  The length of the heat-bonding synthetic fiber is preferably 1 to 15 mm. If the fibers are short, the mixability with the pulp is improved, and a more uniform non-woven fabric tends to be obtained. This is not preferable because the strength as a structure is low and the practicality is lacking. On the other hand, if the length is longer than 15 mm, the strength of the fiber structure increases, but it is not preferable because the fibers tend to be entangled during the pneumatic transportation of the fibers during the production, increasing the fiber mass defects. Particularly preferred is 3 to 10 mm.

  (B) Synthetic fibers constituting the fiber structure include, in addition to the above-mentioned heat-bonding synthetic fibers, as regular fibers, synthetic fibers such as polyester, polypropylene, polyamide and vinylon, regenerated fibers such as rayon, acetates and the like Semi-synthetic fibers and other fibers may be contained in the component (B) in an amount of about 50% by weight or less. Furthermore, a fibrillar fiber can contribute to the improvement of the sound absorption effect. For example, SWP of Mitsui Chemicals, Inc. is mentioned. These polymers may be modified as long as they do not impair the action / effect of the present invention. In addition, various stabilizers, ultraviolet absorbers, thickening and branching agents, matting agents, colorants, other various improving agents, and the like may be blended in the polymer constituting these fibers as necessary.

  In the fiber structure of the present invention, the mixing ratio of (A) pulp fiber and (B) synthetic fiber is 0 to 85/100 to 15% by weight, preferably 0 to 15/100 to (A) / (B). 75% by weight. (A) When the pulp fiber exceeds 85% by weight, the inter-fiber entanglement is reduced, the form stability at the time of molding is reduced, and product defects are likely to occur.

The basis weight of the fiber structure of the present invention is preferably 100 to 2,000 g / m ² , more preferably 100 to 1,000 g / m ² , and the density at that time is preferably 0.01 to 0.00. 20, More preferably, it is 0.01-0.15. If the basis weight is lower than 100 g / m ² , the shape stability and moldability are insufficient, while if it exceeds 2,000 g / m ² , it is inconvenient in terms of weight reduction. On the other hand, if the density is less than 0.01, the shape retention is deteriorated. On the other hand, if the density is more than 0.20, the minute space inside the structure is reduced and the sound absorption performance is lowered. .
In addition, in the fiber structure of the present invention, the density is determined by forming a web mainly composed of the component (A) and the component (B) by an air raid method, followed by hot-pressure calendering, cold pressing, hot air suction, or the like. It can be adjusted easily.

  In the fiber structure of the present invention, the thickness is preferably 5 to 100 mm, more preferably 10 to 60 mm. When this thickness is larger than 100 mm, not only is it difficult to produce the fiber structure, but there is a possibility of increasing the weight and cost, which is not preferable. On the other hand, if the thickness is less than 5 mm, the sound absorption is reduced, which is not preferable.

In the fiber structure of the present invention, by further integrating a synthetic fiber nonwoven fabric having an average fineness of 0.01 to 7 dtex and a basis weight of 8 to 100 g / m ² , sound absorption characteristics and moldability can be further increased. Improvement can be achieved.
Here, the type of fiber constituting the synthetic fiber nonwoven fabric integrated with the fiber structure of the present invention is not particularly limited, and polyester fiber, polyamide fiber, acrylic fiber, polypropylene fiber, aromatic polyamide fiber, flame resistance Known fibers such as fire fibers are used. Of these, polypropylene fibers and polyester fibers are preferable from the viewpoint of handling workability, recyclability, performance, and price. And as a form of these fibers, a long fiber may be sufficient and a short fiber may be sufficient. Furthermore, the short fiber to which crimp was provided may be sufficient.
At that time, the fiber structure may be formed of one type of fiber, or the nonwoven fabric may be formed of a plurality of types of fibers.
In the synthetic fiber nonwoven fabric, when the average fineness is larger than 7 dtex, satisfactory sound absorption which is the main object of the present invention cannot be obtained. On the other hand, if the average fineness is less than 0.01 dtex, not only is it difficult to produce the fiber structure, but the shape stability of the entire sound absorbing structure is lowered, which is not preferable. The average fineness is preferably 0.5 to 4 dtex.
On the other hand, if the basis weight is less than 8 g / m ^2, it is not preferable because breakage of the nonwoven fabric at the time of molding and handling at the time of operation are difficult. On the other hand, when the basis weight is larger than 100 g / m ² , the moldability as the fiber structure is decreased, which is not preferable. The basis weight is preferably 20 to 80 g / m ² .

  The method for producing the above synthetic fiber nonwoven fabric is not particularly limited, and the spunbond method or melt blow method for directly producing the nonwoven fabric from long fibers, or after the short fibers are uniformly dispersed and then entangled between the fibers. Known methods such as a needle punch method for forming a nonwoven fabric, a water needle method, a thermal bond method, and a chemical bond method can be used.

  At this time, the method for integrating the synthetic fiber nonwoven fabric and the fiber structure is not particularly limited, and a known method can be used. For example, a method of laminating a nonwoven fabric and a fiber structure via a thermal adhesive sheet and then thermally bonding, a method of entanglement of the nonwoven fabric and the fiber structure using a needle punch machine, heat in the fiber structure Examples thereof include a method of thermally bonding the heat-adhesive composite short fiber and the nonwoven fabric by including the adhesive composite short fiber, and a method of bonding the nonwoven fabric and the fiber structure with a liquid binder or a powder binder. Most preferably, when the fiber structure is produced by the air raid method, the synthetic fiber nonwoven fabric is used as a carrier sheet and integrated in the same process. By this method, a manufacturing process can be omitted, and a composite fiber structure that is more economical and stable in quality can be obtained.

Next, the fibrous structure of the present invention further integrates a film-like material having a basis weight of 5 to 100 g / m ² , a hole having a diameter of 2 mm or less, and a hole area of 15% to 50%. As a result, a further sound absorbing effect is exhibited.
If the basis weight of the film-like material is lower than 5 g / m ² , the strength and rigidity of the resulting composite will be weak. On the other hand, if it exceeds 100 g / m ² , the cost will increase due to an increase in thickness, which is not practical. . The basis weight of the film is more preferably 10 to 50 g / m ² .
Moreover, it is preferable that a film-like thing has a hole with a diameter of 2 mm or less. When the size of the perforations exceeds 2 mm, the sound absorbing performance is deteriorated, and breakage during molding is likely to occur. The hole diameter of the film-like material is preferably 0.5 to 0.15 mm.
Furthermore, the perforated area of the film-like product is preferably 15% or more and 50% or less. When the perforated area in the film-like material is less than 15%, the sound is reflected on the surface of the film-like material, and the sound absorbing performance is deteriorated. On the other hand, if it exceeds 50%, the film portion is damaged during molding. The perforated area is more preferably 15 to 40%.
At this time, the method of integrating the film-like material and the fiber structure is not particularly limited, and is the same as the integration of the synthetic fiber nonwoven fabric and the fiber structure.
The fiber structure of the present invention may be provided with antibacterial agents, deodorants, antiallergen agents, fragrances, acaricides, fungicides, colorants and the like.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.
In addition, each measurement item in an Example was measured with the following method.
(1) Fabric weight: The fabric weight (g / m ² ) was measured according to JIS L1096.
(2) Thickness: Thickness (mm) was measured according to JIS L1096.
(3) Density: The density (g / cm ³ ) was measured according to JIS L1097.
(4) Sound absorption characteristics: Based on JIS A1405, the normal incident sound absorption coefficient of the building material was measured by the pipe method. In addition, it measured by 1/3 octave center frequency 400Hz, 1,000Hz, 5,000Hz.
(5) Formability: Between a stainless steel circular convex object (bottom diameter 50 mmΦ, top diameter 30 mmΦ, height 30 mm) and circular concave object (bottom diameter 30 mmΦ, top diameter 70 mmΦ, depth 20 mm) Each fiber structure was sandwiched between and the shape was determined from the shape of the molded product after being left for 2 minutes at a temperature of 160 ° C. and a pressure of 100 g / cm ² .
Judgment criteria ○: Molding was possible without forming wrinkles
Δ: Wrinkles slightly on the molded product.
X: Cannot be molded.

Example 1
As heat-adhesive synthetic fibers, a composite fiber having a core of polypropylene and a sheath of copolymer polyethylene (manufactured by Chisso Polypro Fiber Co., Ltd., intac, single yarn fineness 1.7 dtex × length 5 mm) and pulp (manufactured by Weyerhaeuser, NB416 Kraft) A nonwoven fabric was produced by an air raid method using a mixture of 30% by weight and 70% by weight, respectively, at a heating temperature of 145 ° C. The basis weight was 180 g / m ² . The thickness was 8 mm.

Example 2 and Example 4
All the nonwoven fabrics were manufactured by the air raid method in the same manner as in Example 1. The basis weight was 310 g / m ² and 600 g / m ² .

Example 3
Homotype regular fibers that are not heat-adhesive synthetic fibers (polyester short fibers made by Teijin Fibers 2.2 dtex x length 51 mm) and heat-adhesive synthetic fibers mixed in a proportion of 1/2% by weight, A nonwoven fabric was produced by the air raid method in the same manner as in Example 1 except that the basis weight was 310 g / m ² .

Example 5 to Example 6
A melt blown non-woven fabric made of polypropylene (30 g / m ² basis weight, average fineness 0.3 dtex) or a spunbonded non-woven fabric made of polyester (20 g / m ² basis weight, average fineness 1.7 dtex) is used as a carrier sheet. A nonwoven fabric was produced by the air raid method in the same manner as in Example 1.

Example 7
A synthetic fiber nonwoven fabric made of spunlace nonwoven fabric was produced.
That is, PET / PE core-sheath type thermoadhesive conjugate fiber (manufactured by Teijin Fibers Ltd., single yarn fineness 2.2 dtex × length 51 mm) is 50% by weight, PET fiber (manufactured by Teijin Fibers Ltd., single yarn) After mixing 50% by weight (fineness 2.2 dtex x length 51 mm) and forming a web by the carding method, the fiber is entangled by a spun rail method in which a high pressure water flow of 100 kgf / cm ² is sequentially applied to both sides, and hot air at 140 ° C. The spunlace nonwoven fabric (thickness: 1.0 mm) was obtained by drying with heat treatment of the heat-adhesive conjugate fiber. The spunlace nonwoven fabric was used as a carrier sheet, and everything else was produced in the same manner as in Example 1 by the air raid method.

Example 8
A synthetic fiber nonwoven fabric made of a needle punch method nonwoven fabric was produced.
That is, 50% by weight of PET / PE core-sheath type thermoadhesive conjugate fiber (manufactured by Teijin Fibers Ltd., single yarn fineness 2.2 dtex × length 51 mm) and PET fiber (Teijin Fibers Ltd., single yarn fineness) A mixture of 50 wt% (2.2 dtex × 51 mm in length) was mixed and formed into a web by a carding method, and then a felt made of synthetic fibers was produced with a cross wrap weber. This felt was subjected to needle punching at 1,500 pieces / cm ² to obtain a needle punch method nonwoven fabric (thickness 1.8 mm). A nonwoven fabric was produced by the air raid method in the same manner as in Example 1 except that the needle punch method nonwoven fabric was used as a carrier sheet.

Example 9
A polypropylene film having a thickness of 0.35 mm was used. In this film, the diameter of the hole was 0.4 mm and the degree of opening was 25% of the film surface area by a hot needle method (tapered using a taper needle). A nonwoven fabric was produced by the air raid method in the same manner as in Example 1 except that the above film was used as a carrier sheet.

Comparative Example 1
A thermoplastic polyester-based single yarn fineness of 3.3 dtex with a melting point of 150 ° C., a core-sheath type heat-adhesive composite short fiber having a fiber length of 51 mm (core component: sheath component is 60:40 by weight), and single fiber fineness of 3 Polyethylene terephthalate short fibers (melting point: 256 ° C.) having a length of 3 dtex and a fiber length of 51 mm were mixed in a weight ratio of 30:70, and a uniform web was obtained by a roller card. Next, this web was introduced into a hot-air circulating dryer and heat treated at 200 ° C. for 20 minutes to form fixing points by heat fusion, thereby obtaining a fiber structure (hard cotton) (weight per unit: 300 g / m ² , thickness 10 mm). A composite of the above-mentioned hard cotton and polypropylene melt blown nonwoven fabric used a hot melt adhesive (polyolefin system manufactured by Matsumura Oil Research Co., Ltd.). The hot melt adhesive was melted at 200 ° C., and sprayed onto the hard cotton from the nozzle together with compressed air (applied amount: 4 g / m ² ). Immediately, the melt blown nonwoven fabric was laminated and integrated to obtain a fiber structure.

Comparative Examples 2-3
A polypropylene melt-blown nonwoven fabric (170 g / m ² basis weight, 375 g / m ² ) and a spunbond nonwoven fabric (20 g / m ² basis weight) were integrated in the same manner as in Comparative Example 1 using a hot-melt adhesive, and a fiber structure Got the body.

Comparative Example 4
A polypropylene film having a thickness of 0.35 mm and no holes was used.
Other than that, a composite body integrated with the fiber structure manufactured by the air raid method was manufactured in the same manner as in Comparative Example 1.
Tables 1 and 2 show the physical properties and sound absorption characteristics of Examples 1 to 9 and Comparative Examples 1 to 4.

  The fiber structure of the present invention includes home appliances, office automation equipment, construction / civil engineering machinery, industrial machinery, ceiling materials, door trims, hood silencers, floor insulators, head linings, trunk rims, dash insulators and other various vehicle members, houses Or it can be used to reduce noise on highways.

Claims (4)

  (A) Pulp fiber and (B) A fiber structure manufactured by an air raid method composed of synthetic fibers mainly composed of heat-adhesive synthetic fibers, and a mixture of (A) pulp fibers and (B) synthetic fibers A fiber structure excellent in sound absorption, wherein the ratio is (A) pulp fiber / (B) synthetic fiber = 0-85 / 100-15% by weight. The fiber structure excellent in sound absorption according to claim 1, wherein the basis weight of the fiber structure is 100 to 2,000 g / m ² and the density is 0.01 to 0.20. The fiber structure excellent in sound-absorbing property according to claim 1 or 2, wherein a synthetic fiber nonwoven fabric having an average fineness of 0.01 to 7 dtex and a basis weight of 8 to 100 g / m ² is further integrated. 3. A film-like material having a basis weight of 5 to 100 g / m ² , a hole having a diameter of 2 mm or less and a hole area of 15% to 50% is further integrated. A fiber structure with excellent sound absorption.