JPWO2013129298A1 - Nonwoven fabric and method for producing the nonwoven fabric - Google Patents

Abstract

A non-woven fabric that can use rigid natural fibers such as bamboo fiber, is environmentally friendly, and can secure sufficient bending strength and bending rigidity even if the fiber weight is reduced for weight reduction, and It aims at providing the manufacturing method of this nonwoven fabric. A step of mixing natural plant fibers and thermoplastic resin fibers in an entangled state, and a non-woven fabric obtained through a heat press step, wherein the water-soluble polymer having adhesive strength to the natural plant fibers is Supported by natural plant fibers, the entangled portions of the fibers are fixed by the water-soluble polymer and are needle punched.

Description

  The present invention relates to a nonwoven fabric capable of effectively utilizing natural plant fibers and a method for producing the nonwoven fabric.

Non-woven mats are used for automobile interior materials, for example, rear partitions and ceiling materials.
As this kind of non-woven mat, in consideration of the environment such as CO ₂ emission reduction, natural plant fibers such as kenaf and bamboo, and thermoplastic resin fibers that serve as binders such as polypropylene (PP) fibers, etc. There has been proposed a non-woven fabric mat (for example, Patent Document 1).

In other words, in response to an increase in global automobile production, the use of cheap and rigid natural plant fibers such as bamboo fibers is also becoming important as described above. The nonwoven fabric mat to be obtained has not only required strength but also high rigidity, heat resistance, heat insulation and sound insulation, and weight reduction is an urgent issue.

Therefore, as a method for reducing the weight without reducing the rigidity and strength of the nonwoven fabric mat, there is a method using a needle punch.
By performing needle punching as described above, out-of-plane rigidity and entanglement between fibers increase, so that the basis weight (fiber amount) can be reduced without reducing rigidity and strength compared to nonwoven fabrics that do not use needle punching. Weight reduction can be achieved.

JP 2007-160742 A

However, a rigid natural fiber such as a bamboo fiber has a problem that even when needle punching is performed, the entanglement between the fibers is insufficient and high bending rigidity cannot be obtained. Moreover, there is a limit to the weight reduction by the needle punching as described above. That is, if the basis weight is too low, the rigidity will not satisfy the required performance.
On the other hand, using high-rigidity fibers such as carbon fibers instead of natural plant fibers having low rigidity is not practical in terms of cost.

  In view of the above circumstances, the present invention is environmentally friendly because it is possible to use rigid natural fibers such as bamboo fibers, and sufficient bending strength and bending can be achieved even if the fabric weight of the fibers is reduced for weight reduction. It aims at providing the nonwoven fabric which can ensure rigidity, and the manufacturing method of this nonwoven fabric.

  In order to achieve the above object, the nonwoven fabric according to the present invention is a nonwoven fabric obtained through a process of mixing natural plant fibers and thermoplastic resin fibers in an intertwined state, and a hot press process, wherein A water-soluble polymer having adhesion to plant fibers is supported on the natural plant fiber, and the entangled portion between the fibers is fixed by the water-soluble polymer and is needle punched. It is characterized by.

  Although it does not specifically limit as a natural plant fiber used for this invention, For example, hemp type fibers, such as a jute and a kenaf, cotton type fiber, bamboo fiber, etc. are mentioned. Among them, bamboo fiber is stronger and more rigid than other natural plant fibers, and it can be obtained easily and cheaply by taking it out of bamboo, a natural resource that can be continuously regenerated regardless of domestic or overseas. Since it has the advantage of being possible, it is suitable as a reinforcing material for industrial products. The “bamboo fibers” referred to here include bamboo fiber bundles in which a plurality of single fibers are gathered in addition to bamboo single fibers.

  The bamboo used as the raw material of the bamboo fiber is not particularly limited, and examples include bamboo, bamboo shoot, light bamboo, female bamboo, citrus, etc., which are readily available in Japan if cost reduction is to be achieved. Miso bamboo and true bamboo are preferred.

The length and the vertical cross-sectional area (thickness) of the natural plant fiber are not particularly limited as long as the object of the present invention can be achieved. In the case of bamboo fiber, the fiber length is 25 mm or more and 50 mm or less, and the maximum cross-section of the fiber cross section is maximum. It is preferable to use one having a length of 0.05 mm or more and 0.3 mm or less.
In the case of kenaf fiber, it is preferable to use a fiber having a fiber length of 25 mm or more and 50 mm or less and a maximum cross-sectional length of the fiber cross section of 0.05 mm or more and 0.3 mm or less.
That is, if the fiber length is too short, it cannot be made into a non-woven fabric, and if it is too long, it will not only break and shorten as a result, but also may become caught during needle punching or become entangled with thermoplastic resin fibers. There is.
On the other hand, if the maximum passing length of the cross section of the fiber is too short, that is, if the fiber is too thin, the rigidity of the molded product does not increase, and if the maximum passing length is too long, that is, if the fiber is too thick, the needle punch At this time, the needle may break or the entanglement with the thermoplastic resin fibers may be worsened.

  Moreover, the manufacturing method of the bamboo fiber used for this invention is not specifically limited.

  The thermoplastic resin fiber serving as a binder is not particularly limited, but those that are easily entangled with natural plant fibers and easy to thermocompression with natural plant fibers are preferable. For example, polypropylene fibers, polyethylene fibers, polyethylene coating Examples thereof include polyethylene terephthalate (PET) fiber. Further, these thermoplastic resin fibers may be single yarns or twisted yarns.

The water-soluble polymer used in the present invention is not particularly limited as long as it has adhesiveness to natural plant fibers. For example, those having biodegradability such as polyvinyl alcohol, starch, and carboxymethyl cellulose are preferable. Of these, polyvinyl alcohol is more preferred because of its excellent cost reduction and water resistance.
The molecular weight and saponification degree of the polyvinyl alcohol are not particularly limited, but those having a molecular weight of 25 to 50 MPa · s at a concentration of 4% and a viscosity at 20 ° C. can be supplied even by spraying because of easy availability. Those having a saponification degree of 80 or more are preferred. As such polyvinyl alcohol, for example, JF17L manufactured by Nihon Vinegar Poval Co., Ltd. can be used.

The nonwoven fabric of the present invention is formed through a needle punching process, and the punching density (the number of needles pierced per unit area of the nonwoven fabric) is preferably 20 / cm ² or more and 60 / cm ² or less. .
That is, if the density is too small, improvement in both out-of-plane and in-plane rigidity is insufficient, and if the density is too large, the in-plane rigidity may be impaired.

The mixing ratio of the natural plant fiber and the thermoplastic resin fiber is appropriately determined depending on the use of the nonwoven fabric, the type of fiber, and the combination. Natural plant fiber: thermoplastic resin fiber = 50-80: 50- 20 is preferable. That is, if the mixing ratio of the natural plant fiber is too small, sufficient rigidity cannot be obtained, and if it is too large, there is a possibility that a problem in weight reduction occurs.
On the other hand, the method for producing a nonwoven fabric of the present invention comprises a defibrating and mixing step of defibrating and mixing natural plant fibers and thermoplastic resin fibers, and a defibrated mixture obtained in the defibrating and mixing step with respect to natural plant fibers A water-soluble polymer supporting step of obtaining a water-soluble polymer carrier by immersing in a water-soluble polymer aqueous solution having adhesive force or spray-coating the water-soluble polymer aqueous solution on a defibrated mixture; After the mixing step and the water-soluble polymer supporting step, and the needle punch step of needle punching the defibrated mixture at least at any time after the water-soluble polymer supporting step, And a step of hot pressing.

Instead of spraying the water-soluble polymer aqueous solution, the nonwoven fabric may be immersed in the aqueous solution.
Moreover, you may provide the drying process which dries a support body following a water-soluble polymer support process.

In the method for producing a nonwoven fabric of the present invention, the defibrating and mixing step is not particularly limited. For example, a cotton-like or sliver-like body made of thermoplastic resin fibers and bamboo fibers are passed through a defibrating machine or a card machine. A method of defibrating and mixing is mentioned.
Further, the web that is the defibrated mixture obtained through the carding machine may be further passed through the carding machine.

  As the card machine, a card machine (for example, trade name MDKS manufactured by Ikegami Machinery Co., Ltd.) used for manufacturing a normal nonwoven fabric can be used. As the defibrating machine, a defibrating machine (for example, a product name recycle breaker RB-100 manufactured by Ikegami Machinery Co., Ltd.) used for manufacturing a normal nonwoven fabric can be used.

In the water-soluble polymer supporting step, when polyvinyl alcohol is used as the water-soluble polymer, the concentration of polyvinyl alcohol in the aqueous polyvinyl alcohol solution is not particularly limited, but is preferably 2% by weight or more and 10% by weight or less.
That is, if the concentration is too low, the fixing effect is insufficient, and if the concentration is too high, the viscosity becomes too high and the inside of the defibrated mixture may not sufficiently penetrate. Also, spray application becomes difficult.

When the drying step is provided, the drying temperature is not particularly limited, but when polyvinyl alcohol is used, the drying temperature is preferably 50 ° C. or higher and 100 ° C. or lower.
The drying time is appropriately determined depending on the type of fiber, the mixing ratio, the type of water-soluble polymer, the concentration of the aqueous solution, and the like.

The timing of needle punching may be between the defibrating and mixing step and the water-soluble polymer supporting step and after the water-soluble polymer supporting step, but the former is preferable.
In addition, the needle punching may be performed by using the web obtained by the card machine alone or by stacking a plurality of webs.

Although it does not specifically limit as a use of the nonwoven fabric of this invention, For example, since it has the heat insulating property, the interior material of a motor vehicle, the structural material of a medical device, the panel of a house, the interior material for architects, etc. are mentioned. In addition, the natural fiber may be impregnated with a flame retardant or the like, if necessary, and subjected to flame retardant processing or the like.
Moreover, the nonwoven fabric of this invention is good also as a sandwich material laminated | stacked with the other material as needed.

As said sandwich material, what laminated | stacked the nonwoven fabric of this invention on the surface of the core material is mentioned, for example.
Although it does not specifically limit as said core material, Well-known nonwoven fabrics and resin foam other than the nonwoven fabric of this invention are mentioned.

Although it does not specifically limit as said resin foam, For example, a polyurethane resin foam, a polypropylene foam, a polyethylene foam etc. are mentioned.
The method for joining the nonwoven fabric of the present invention and the resin foam is not particularly limited, and examples thereof include a method of interposing an adhesive and a method of heat-sealing.

The non-woven fabric of the present invention is a non-woven fabric obtained through a process of mixing natural vegetable fibers and thermoplastic resin fibers in an entangled state and a hot pressing process, as described above, with respect to the natural plant fibers. The water-soluble polymer having adhesive strength is supported on the natural plant fiber, and the entangled portion of the fiber and the fiber is fixed by the water-soluble polymer and is needle punched, so that bamboo fiber etc. Therefore, sufficient bending strength and bending rigidity can be ensured even if the amount of fiber is reduced for weight reduction.
In particular, by using bamboo fiber, it is possible to effectively use bamboo, which is a natural resource that can be continuously reproduced regardless of whether it is domestic or overseas, and it can be made more environmentally friendly and less expensive.

One example of bamboo fiber and polypropylene fiber used for the nonwoven fabric of the present invention is shown. An example of the first defibrated mixture obtained by defibrating and mixing the bamboo fiber of FIG. 1 and polypropylene fiber is shown. An example of a web as a second defibrating mixture obtained by passing the defibrating mixture of FIG. 2 through a card machine is shown. It is a figure explaining the needle punching process of the manufacturing method of the nonwoven fabric of this invention. It is a figure explaining the hot press molding process of the manufacturing method of the nonwoven fabric of this invention. It is a figure explaining the needle of the needle punch apparatus used for the Example. It is a figure explaining a 4-point bending test method. It is a graph showing the bending strength of the nonwoven fabric obtained in Example 10 and Comparative Example 5 in comparison. It is a graph showing the bending rigidity of the nonwoven fabric obtained in Example 10 and Comparative Example 5 in comparison. It is a graph showing the bending strength of the nonwoven fabric obtained in Reference Examples 1-4. It is a graph showing the bending rigidity of the nonwoven fabric obtained in Reference Examples 1 to 4. It is a graph showing the change of the load with respect to the displacement of the test piece at the time of the four-point bending test of the nonwoven fabric obtained in Reference Example 1 and Reference Example 3.

  Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof.

The nonwoven fabric of this invention is obtained through the following processes (1) to (4), for example.
(1) Defibration mixing step For example, lignin, which is the main component of bamboo material, is obtained by cutting bamboo material such as Soso bamboo, true bamboo, and citrus into a desired length and alkali-treating the crushed material obtained by crushing under pressure. After removing the hemicellulose, it is thoroughly washed with cold water to extract a rigid bamboo fiber bundle.
Then, the obtained rigid bamboo fiber bundle is softened by passing it through a defibrator, and the fiber length shown in FIG. 1 (a) is 25 mm or more and 50 mm or less, and the maximum cross-sectional length of the fiber cross section is 0.05 mm or more. Bamboo fiber 1 that is 0.3 mm or less is obtained.
The obtained bamboo fiber 1 and polypropylene fiber 2 as a thermoplastic or sliver-like thermoplastic fiber having a fiber length of 10 mm to 100 mm and a fineness of 1 dtex to 5 dtex shown in FIG. In a ratio of 50 to 80:50 to 20 by weight in a defibrating machine (for example, product name recycling breaker RB-100 manufactured by Ikegami Machinery Co., Ltd.), and bamboo fiber 1 and polypropylene fiber 2 are disassembled. A first defibrated mixture 3 as shown in FIG. 2 is obtained.
The first defibrated mixture 3 is put into a card machine (for example, trade name MDKS manufactured by Ikegami Machinery Co., Ltd.), and further defibrated and mixed while the web 4 is a second defibrated mixture as shown in FIG. Get.
(2) Water-soluble polymer carrying step The above-described web 4 is immersed in a 2% to 10% by weight aqueous solution of polyvinyl alcohol, which is a water-soluble polymer, and the web is impregnated with the aqueous polyvinyl alcohol solution. A web 41 carrying polyvinyl alcohol as shown in FIG. 5 is obtained by putting in a furnace or the like and drying.
(3) Needle punch processing step As shown in FIG. 5, the web 41 carrying polyvinyl alcohol is sandwiched between the upper die 5a and the lower die 5b of the needle punch device 5, and 20 pieces / cm ^{2 to} 60 pieces. A needle punched web 42 as shown in FIG. 6 is obtained by needle punching at a density of / cm ² .
(4) Heat treatment step As shown in FIG. 6, the needle-punched web 42 is heated at a pressure of 1 to 10 MPa between the upper die 6 a and the lower die 6 b heated to the melting point of polypropylene of the hot press molding device 6. It is sandwiched for several minutes to obtain a sheet-like nonwoven fabric [not shown].

The nonwoven fabric of the present invention thus obtained is excellent in rigidity because polyvinyl alcohol is supported around the bamboo fiber in the nonwoven fabric, and the entangled portion of the fiber and fiber is fixed by polyvinyl alcohol. It will be a thing.
In addition, since the needle punching process is performed, the fibers and the fibers are intertwined with each other and heated and pressed, and the polypropylene fibers are thermally fused with the bamboo fibers, so that the bending strength is excellent.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the heat treatment step is provided, but the heat treatment step may be omitted. Moreover, you may provide a drying process after a heat press process.

  Specific examples of the present invention are described in detail below.

Example 1
Crushing bamboo mulberry that grows naturally on the Doshisha University Kyotanabe Campus, crush it with a press machine, treat the crushed material with alkali to remove lignin and hemicellulose, which are the main components of bamboo, and then wash thoroughly with cold water to extract bamboo fiber bundles did.
The thus-obtained rigid bamboo fiber bundle was softened by passing it through a defibrating machine to obtain bamboo fiber 1 (fiber length 200 mm, cross section maximum maximum length 0.3 mm) 1.
The resulting bamboo fiber 1 and cotton-like polypropylene fiber (made by Chisso Polypro Fiber Co., Ltd., fiber length 50 mm, fineness 2.2 dtex, 2) are superposed on top and bottom at a weight ratio of 7: 3. First, a first defibrated mixture 3 as shown in FIG. 2 was obtained.
The obtained first defibrated mixture 3 was further passed through a card machine to obtain a web 4 as shown in FIG. 3 having a basis weight of 800 g / m ² .
The obtained web 4 was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L, manufactured by Nippon Vinegar Poval Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. A web 41 carrying polyvinyl alcohol as shown in FIG. 4 was obtained.
When the cut surface of the obtained web 41 was magnified with a magnifying glass and visually confirmed, polyvinyl alcohol was supported in a state of covering almost the entire surface of the bamboo fiber, and the entangled portion between the fiber and the fiber was fixed. .
Then, as shown in FIG. 4, the upper die 5 a and the lower die 5 b of the needle punch device 5 provided with needles so that the needle density per unit area is 40 needles / cm ^2. The punched web 42 shown in FIG. 5 was obtained by needle punching.
Thereafter, as shown in FIG. 5, the punched web 42 is press-molded between the upper mold 6a and the lower mold 6b of the hot press molding apparatus 6 at 190 ° C. and 0.5 MPa for 5 minutes. The sheet-like nonwoven fabric A1 having a thickness of 2.8 mm was obtained.
In addition, the used needle has a structure as shown in FIG. 5, and the dimension of each part is as follows.
B = 0.6, J = 0.1, M = 1, T = 2.1, G = 6.3, H = 5 (unit: mm)

(Example 2)
A sheet-like nonwoven fabric B1 was obtained in the same manner as in Example 1 except that the density of the needles was 20 / cm ² .

(Example 3)
A sheet-like non-woven fabric C1 was obtained in the same manner as in Example 1 except that the needle density was 60 / cm ² .

Example 4
Similar to Example 1 except that after punching polyvinyl alcohol, needle punching is performed, and then polyvinyl alcohol is supported and needle punching is not performed after loading, and heat press molding is performed in the same manner as in Example 1. Thus, a sheet-like nonwoven fabric D1 was obtained.

(Example 5)
A sheet-like nonwoven fabric E1 was obtained in the same manner as in Example 1 except that the concentration of the polyvinyl alcohol aqueous solution was 15%.

(Example 6)
A sheet-like nonwoven fabric F1 was obtained in the same manner as in Example 1 except that the concentration of the polyvinyl alcohol aqueous solution was 17%.

(Example 7)
A sheet-like nonwoven fabric G1 was obtained in the same manner as in Example 1 except that the concentration of the polyvinyl alcohol aqueous solution was 3%.

(Example 8)
A sheet-like nonwoven fabric H1 was obtained in the same manner as in Example 1 except that the mixing ratio of bamboo fiber and polypropylene fiber was 8: 2.

(Comparative Example 1)
A sheet-like nonwoven fabric I1 was obtained in the same manner as in Example 1 except that the press molding was not performed.

(Comparative Example 2)
A sheet-like nonwoven fabric J1 was obtained in the same manner as in Example 1 except that needle punching was not performed.

(Comparative Example 3)
A sheet-like nonwoven fabric K1 was obtained in the same manner as in Example 1 except that it was not immersed in polyvinyl alcohol.

(Comparative Example 4)
The web 4 obtained in the same manner as in Example 1 was subjected to needle punching with a needle density per unit area of 40 needles / cm ² to obtain a punched web.
Thereafter, press molding was performed for 5 minutes under the conditions of 190 ° C. and 0.5 MPa to obtain a sheet-like web having a thickness of 5 mm.
The obtained sheet-like web was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L manufactured by Nippon Vinegar Pover Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. Thus, a sheet-like nonwoven fabric L1 carrying polyvinyl alcohol was obtained.

[Evaluation of bending strength and bending rigidity]
About the sheet-like nonwoven fabrics A1 to L1 obtained in Examples 1 to 8 and Comparative Examples 1 to 4, a 4-point bending test is performed as follows, the bending strength and the bending rigidity are evaluated, and the results are shown. It was shown in 1.
[4-point bending test]
Using a table band saw machine from the obtained sheet-like nonwoven fabrics A1 to L1, as shown in FIG. 7, test pieces having a length of 100 mm and a width of 30 mm were cut out, the distance between the outer fulcrums was 81 mm, the distance between the inner indenters was 27 mm, A four-point bending test was performed under the condition of a displacement speed of 30 mm / min. For the test, an AUTOGRAPH universal testing machine (rated 100 kN, manufactured by Shimadzu Corporation) was used. The reaction force and the surface strain generated at the center of the test piece were measured using a load cell and a strain gauge attached to the front and back of the test piece. The number of measurements under each condition was 5.

  As shown in Table 1 above, Examples 1 to 8 show superior properties in both strength and bending rigidity compared to the comparative example (according to the conventional manufacturing method), and the method shown in the present invention is effective. It shows that there is.

Example 9
Bamboo fibers (fiber length 100 mm, delivery maximum length 0.25 mm) were obtained in the same manner as in Example 1 except that Jiso bamboo was used as the bamboo material.
A nonwoven fabric M having a basis weight of 1.3 kg / m ² was obtained in the same manner as in Example 1 except that this bamboo fiber and the same polypropylene fiber 2 as in Example 1 were blended at a weight ratio of 4: 1.

(Comparative Example 5)
A sheet-like nonwoven fabric N was obtained in the same manner as in Example 9 except that it was not immersed in polyvinyl alcohol.
The sheet-like nonwoven fabrics M and N obtained in Example 9 and Comparative Example 5 were subjected to a four-point bending test in the same manner as the sheet-like nonwoven fabrics A1 to L1, and the bending strength obtained from the results was compared with FIG. The bending rigidity is shown in comparison with FIG.

8 and 9, it can be seen that when polyvinyl alcohol is used, the bending strength is increased by 40% and the bending rigidity is increased by 280% as compared with the case where polyvinyl alcohol is not used.
As a result, when polyvinyl alcohol is used as in the present invention, it is understood that a nonwoven fabric having a bending strength and a bending rigidity equivalent to those when polyvinyl alcohol is not used can be obtained even if the fiber weight is reduced by 20%. .

(Reference Example 1)
A web was obtained in the same manner as in Example 1 using only the same bamboo fibers as in Example 1, and then two sheets of this web were stacked and further passed through a card machine to obtain a nonwoven fabric a.

(Reference Example 2)
The nonwoven fabric a obtained in Reference Example 1 was further punched at a punching density of 20 / cm ² using the same needle punch apparatus as in Example 1 to obtain a nonwoven fabric b.

(Reference Example 3)
The nonwoven fabric a obtained in Reference Example 1 was further punched at a punching density of 40 / cm ² using the same needle punch apparatus as in Example 1 to obtain a nonwoven fabric c.

(Reference Example 4)
The nonwoven fabric a obtained in Reference Example 1 was further needle punched at a punching density of 60 / cm ² using the same needle punch apparatus as in Example 1 to obtain a nonwoven fabric d.

The nonwoven fabrics a to d obtained in Reference Examples 1 to 4 were subjected to the above four-point bending test to determine bending strength and bending rigidity, and the results are shown in comparison with FIGS.
10 and 11, it can be seen that the needle punch increases the bending strength but slightly decreases the bending rigidity.

Moreover, about the said nonwoven fabric a and the nonwoven fabric c, the change of the load with respect to the displacement of the test piece at the time of a 4-point bending test was investigated, and the result was shown in FIG.
From FIG. 12, it can be seen that when needle punching is not performed, delamination occurs between the laminated webs, so that the load is almost in equilibrium when the displacement exceeds 10 mm.

(Example 10)
The first defibrated mixture 3 was the same as in Example 1 except that kenaf fiber (fiber length 200 mm, maximum cross-sectional length 0.3 mm) 1 was used instead of the bamboo fiber 1 in Example 1 above. Got.
The obtained first defibrated mixture 3 was further passed through a card machine to obtain a web 4 as shown in FIG. 3 having a basis weight of 800 g / m ² .
The obtained web 4 was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L, manufactured by Nippon Vinegar Poval Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. A web 41 carrying polyvinyl alcohol as shown in FIG. 4 was obtained.
When the cut surface of the obtained web 41 was magnified with a magnifying glass and visually confirmed, polyvinyl alcohol was supported in a state of covering almost the entire surface of the bamboo fiber, and the entangled portion between the fiber and the fiber was fixed. .
Then, as shown in FIG. 4, the upper die 5 a and the lower die 5 b of the needle punch device 5 provided with needles so that the needle density per unit area is 40 needles / cm ^2. The punched web 42 shown in FIG. 5 was obtained by needle punching.
Thereafter, as shown in FIG. 5, the punched web 42 is press-molded between the upper mold 6a and the lower mold 6b of the hot press molding apparatus 6 at 190 ° C. and 0.5 MPa for 5 minutes. The sheet-like nonwoven fabric A2 having a thickness of 2.8 mm was obtained.
In addition, the used needle has a structure as shown in FIG. 5, and the dimension of each part is as follows.
B = 0.6, J = 0.1, M = 1, T = 2.1, G = 6.3, H = 5 (unit: mm)

(Example 11)
A sheet-like non-woven fabric B2 was obtained in the same manner as in Example 10 except that the needle density was 20 / cm ² .

(Example 12)
A sheet-like nonwoven fabric C2 was obtained in the same manner as in Example 10 except that the density of the needles was 60 / cm ² .

(Example 13)
Similar to Example 1 except that after punching polyvinyl alcohol, needle punching is performed, and then polyvinyl alcohol is supported and needle punching is not performed after loading, and heat press molding is performed in the same manner as in Example 10. Thus, a sheet-like nonwoven fabric D2 was obtained.

(Example 14)
A sheet-like nonwoven fabric E2 was obtained in the same manner as in Example 10 except that the concentration of the polyvinyl alcohol aqueous solution was 15%.

(Example 15)
A sheet-like nonwoven fabric F2 was obtained in the same manner as in Example 10 except that the polyvinyl alcohol aqueous solution concentration was 17%.

(Example 16)
A sheet-like nonwoven fabric G2 was obtained in the same manner as in Example 10 except that the concentration of the polyvinyl alcohol aqueous solution was 3%.

(Example 17)
A sheet-like nonwoven fabric H2 was obtained in the same manner as in Example 10 except that the mixing ratio of bamboo fiber and polypropylene fiber was 8: 2.

(Comparative Example 5)
A sheet-shaped nonwoven fabric I2 was obtained in the same manner as in Example 10 except that the press molding was not performed.

(Comparative Example 6)
A sheet-like nonwoven fabric J2 was obtained in the same manner as in Example 10 except that needle punching was not performed.

(Comparative Example 7)
A sheet-like nonwoven fabric K2 was obtained in the same manner as in Example 10 except that it was not immersed in polyvinyl alcohol.

(Comparative Example 8)
The web 4 obtained in the same manner as in Example 10 was subjected to needle punching with a needle density per unit area of 40 / cm ² to obtain a punched web.
Thereafter, press molding was performed for 5 minutes under the conditions of 190 ° C. and 0.5 MPa to obtain a sheet-like web having a thickness of 5 mm.
The obtained sheet-like web was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L manufactured by Nippon Vinegar Pover Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. Thus, a sheet-like nonwoven fabric L2 carrying polyvinyl alcohol was obtained.
The sheet-like nonwoven fabrics A2 to L2 obtained in Examples 10 to 17 and Comparative Examples 5 to 8 are subjected to a 4-point bending test in the same manner as the sheet-like nonwoven fabrics A1 to L1 to evaluate bending strength and bending rigidity. The results are shown in Table 2.

  As shown in Table 2 above, Examples 10 to 17 show excellent properties in both strength and bending rigidity as compared with Comparative Examples (according to the conventional production method), and the method shown in the present invention is effective. It shows that there is.

1 Bamboo fiber (natural fiber)
2 Polypropylene fiber (thermoplastic resin fiber)
3 First defibrated mixture 4 Web (second defibrated mixture)
41 Web carrying polyvinyl alcohol 42 Needle punched web 5 Needle punch device 5a Upper die 5b Lower die 6 Hot press molding device 6a Upper die 6b Lower die

[0011]
Thus, a sheet-like nonwoven fabric G1 was obtained.
[0040]
(Example 8)
A sheet-like nonwoven fabric H1 was obtained in the same manner as in Example 1 except that the mixing ratio of bamboo fiber and polypropylene fiber was 8: 2.
[0041]
(Comparative Example 1)
A sheet-like nonwoven fabric I1 was obtained in the same manner as in Example 1 except that the press molding was not performed.
[0042]
(Comparative Example 2)
A sheet-like nonwoven fabric J1 was obtained in the same manner as in Example 1 except that needle punching was not performed.
[0043]
(Comparative Example 3)
A sheet-like nonwoven fabric K1 was obtained in the same manner as in Example 1 except that it was not immersed in polyvinyl alcohol.
[0044]
(Example a)
The web 4 obtained in the same manner as in Example 1 was subjected to needle punching with a needle density per unit area of 40 needles / cm ² to obtain a punched web.
Thereafter, press molding was performed for 5 minutes under the conditions of 190 ° C. and 0.5 MPa to obtain a sheet-like web having a thickness of 5 mm.
The obtained sheet-like web was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L manufactured by Nippon Vinegar Poval Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. Thus, a sheet-like nonwoven fabric L1 carrying polyvinyl alcohol was obtained.
[0045]
[Evaluation of bending strength and bending rigidity]
For the sheet-like nonwoven fabrics A1 to L1 obtained in Examples 1 to 8, Example a and Comparative Examples 1 to 3, a 4-point bending test is performed as follows, and bending strength and bending rigidity are evaluated. The results are shown in Table 1.
[4-point bending test]

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上記表１に示すように、実施例１〜８は、（従来の製法による）比較例に比べて、強度、曲げ剛性いずれも優れた特性を示しており、本発明で示した方法が有効であることを示している。
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（実施例９）
竹材として孟宗竹に代えて慈竹を用いて実施例１と同様にして竹繊維（繊維長１００ｍｍ、差し渡し最大長さ０．２５ｍｍ）を得た。
この竹繊維と実施例１と同様のポリプロピレン繊維２とを重量比４：１で配合した以外は、実施例１と同様にして目付け量１．３ｋｇ／ｍ^２の不織布Ｍを得た。
［００４９］
（比較例４）
ポリビニルアルコールに浸漬しなかった以外は、上記実施例９と同様にしてシート状不織布Ｎを得た。
上記実施例９及び比較例５で得られたシート状不織布Ｍ，Ｎについて、上[0012]
Using a table band saw machine from the obtained sheet-like non-woven fabrics A1 to L1, as shown in FIG. 7, test pieces each having a length of 100 mm and a width of 30 mm were cut out, an outer fulcrum distance of 81 mm, an inner indenter distance of 27 mm, A 4-point bending test was performed under the condition of a displacement speed of 30 mm / min. For the test, an AUTOGRAPH universal testing machine (rated 100 kN, manufactured by Shimadzu Corporation) was used. The reaction force and the surface strain generated at the center of the test piece were measured using a load cell and a strain gauge attached to the front and back of the test piece. The number of measurements under each condition was 5.
[0046]
[Table 1]

[0047]
As shown in Table 1 above, Examples 1 to 8 show superior properties in both strength and bending rigidity compared to the comparative example (according to the conventional manufacturing method), and the method shown in the present invention is effective. It shows that there is.
[0048]
Example 9
Bamboo fibers (fiber length 100 mm, delivery maximum length 0.25 mm) were obtained in the same manner as in Example 1 using Ji bamboo instead of Miso bamboo as the bamboo material.
A nonwoven fabric M having a basis weight of 1.3 kg / m ² was obtained in the same manner as in Example 1 except that this bamboo fiber and the same polypropylene fiber 2 as in Example 1 were blended at a weight ratio of 4: 1.
[0049]
(Comparative Example 4)
A sheet-like nonwoven fabric N was obtained in the same manner as in Example 9 except that it was not immersed in polyvinyl alcohol.
About the sheet-like nonwoven fabrics M and N obtained in Example 9 and Comparative Example 5,

［００７０］
上記表２に示すように、実施例１０〜１７は、（従来の製法による）比較例に比べて、強度、曲げ剛性いずれも優れた特性を示しており、本発明で示した方法が有効であることを示している。
符号の説明
［００７１］
１ 竹繊維（天然繊維）
２ ポリプロピレン繊維（熱可塑性樹脂繊維）[0016]
A sheet-like nonwoven fabric K2 was obtained in the same manner as in Example 10 except that it was not immersed in polyvinyl alcohol.
[0068]
(Example b)
A web 4 obtained in the same manner as in Example 10 was subjected to needle punching with a needle density per unit area of 40 needles / cm ² to obtain a punched web.
Thereafter, press molding was performed for 5 minutes under the conditions of 190 ° C. and 0.5 MPa to obtain a sheet-like web having a thickness of 5 mm.
The obtained sheet-like web was immersed for 1 minute in a 5% aqueous solution of polyvinyl alcohol (JF17L manufactured by Nippon Vinegar Poval Co., Ltd.) and then dried in an electric furnace maintained at a furnace temperature of 50 ° C. for 3 hours. Thus, a sheet-like nonwoven fabric L2 carrying polyvinyl alcohol was obtained.
About sheet-like nonwoven fabric A2-L2 obtained in the said Example 10- Example 17, Example b, and Comparative Examples 5-7, a 4-point bending test is done similarly to the said sheet-like nonwoven fabric A1-L1, and bending strength and The bending stiffness was evaluated and the results are shown in Table 2.
[0069]
[Table 2]

[0070]
As shown in Table 2 above, Examples 10 to 17 show excellent properties in both strength and bending rigidity as compared with Comparative Examples (according to the conventional production method), and the method shown in the present invention is effective. It shows that there is.
Explanation of symbols [0071]
1 Bamboo fiber (natural fiber)
2 Polypropylene fiber (thermoplastic resin fiber)

Claims (9)

A process of mixing natural vegetable fibers and thermoplastic resin fibers in an intertwined state, and a non-woven fabric obtained through a hot press process,
A water-soluble polymer having an adhesive force to the natural plant fiber is supported on the natural plant fiber, and the entangled portion of the fiber and the fiber is fixed by the water-soluble polymer and is subjected to needle punch processing. A nonwoven fabric characterized by   The nonwoven fabric according to claim 1, wherein the natural plant fiber is any one selected from the group consisting of bamboo fiber, hemp fiber, and cotton fiber.   3. The nonwoven fabric according to claim 2, wherein the bamboo fiber has a fiber length of 25 mm or more and 50 mm or less and a maximum cross-section length of the fiber cross section of 0.05 mm or more and 0.3 mm or less.   The nonwoven fabric according to claim 2 or 3, wherein the hemp fiber is kenaf fiber, the fiber length is 25 mm or more and 50 mm or less, and the maximum cross-sectional length of the fiber is 0.05 mm or more and 0.3 mm or less.   The nonwoven fabric according to any one of claims 1 to 4, wherein the thermoplastic resin fiber is a polypropylene fiber or a low melting point polyethylene-coated polyethylene terephthalate fiber.   The non-woven fabric according to any one of claims 1 to 5, wherein the water-soluble polymer is polyvinyl alcohol. The nonwoven fabric according to any one of claims 1 to 6, wherein the punching density of the needle punch is 20 / cm ² or more and 60 / cm ² or less.   The mixture ratio of natural plant fiber and thermoplastic resin fiber is natural plant fiber: thermoplastic resin fiber = 50-80: 50-20 by weight ratio, The nonwoven fabric in any one of Claims 1-7. A defibrating and mixing step of defibrating and mixing natural plant fibers and thermoplastic resin fibers;
A water-soluble solution in which the defibrated mixture obtained in the defibrating and mixing step is immersed in an aqueous solution of a water-soluble polymer having adhesion to natural plant fibers, or the water-soluble polymer aqueous solution is spray-coated on the defibrated mixture. A water-soluble polymer carrying step for obtaining a polymer carrier;
A needle punching step of needle punching the defibrated mixture between the defibrating and mixing step and the water-soluble polymer supporting step, and at least any time after the water-soluble polymer supporting step;
The method for producing a nonwoven fabric according to any one of claims 1 to 8, further comprising a step of performing hot pressing after each of the above steps.

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